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PeecANOGRAPHY OF PLANTS
ESPECIALLY OF THE
ARCHEGONIATAE AND SPERMOPHYTA
BY
Dee Kk. GOEBEL
PROFESSOR IN THE UNIVERSITY OF MUNICH
AUTHORIZED ENGLISH EDITION
BY
fone BAYLEY BALFOUR, M.A., M.D., F.RS.
KING’S BOTANIST IN SCOTLAND; PROFESSOR OF BOTANY IN THE UNIVERSITY AND
REGIUS KEEPER OF THE ROYAL BOTANIC GARDEN OF EDINBURGH
PART ll
SPECIAL ORGANOGRAPHY
WITH 417 WOODCUTS
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Peerace £O THE GERMAN EDITION
THE aim of the Second Part of this book requires no exposition.
The large space devoted to the Bryophyta receives its justification in the
fact that these plants offer an easily accessible and easily cultivated material
for Experimental Organography, and that they, especially the Hepaticae,
show particularly clearly how by different paths complex configuration has
been reached from simple beginnings. Earlier accounts of these plants!
have dealt with them almost exclusively from the purely formal standpoint,
and in this offer a contrast with the work of the great bryologist of the
eighteenth century, Hedwig, who was untrammelled by the limiting concept
that has attached to the terms ‘Morphology’ and ‘ Physiology”. How
incomplete is our knowledge of the phenomena of life of this group is
everywhere apparent.
To give a comprehensive exposition is always a forbidding task ; I hope
that my readers will not consider the many new results of investigation 3
and the interpretations that are given in this book as a ‘ crambe biscocta,’
and that what I have said may lead to new investigations.
To prevent misunderstanding I may say that teleological expressions
are only used for shortness. My position with regard to the question of
adaptations is fully set forth elsewhere *.
The nomenclature of the Bryophyta is at present in great confusion.
In respect of it I adopt-a conservative attitude, and regard as a nuisance
the practice of changing plant-names which have been long in use and
appear in fundamental works like those of Hofmeister and Leitgeb purely
on the ground of a shadowy priority. Fortunately the practice appears
to have over-reached itself.
K. GOEBEL.
Ambach, 1898°.
1 The most complete account of the Group is that of Douglas Campbell, The Structure and
Development of the Mosses and Ferns, London and New York, 1895. This book is full of details
of minute anatomy obtained by microtome-methods, and is specially valuable because of the records
of the author’s own researches.
? Compare, for example, the Preface of his ‘ Descriptio et adumbratio microscopica-analytica
muscorum frondosorum,’ where he gives free expression to his teleological instincts. Neglecting the
physico-theological tone of the work we find that a separation of form and function was to the
author unthinkable.
$ I wish here to acknowledge my indebtedness for material for these investigations to Dr. E. Levier
of Florence and F. Stephani of Leipzig.
* See an address by me, ‘ Uber Studium und Auffassung der Anfassungserscheinungen bei Pflanzen,’
Miinchen, 1898.
* The year of publication of the First Section of this Second Part. The last section appeared
in Igol.
PREFATORY NOTE TO TH
ENGLISH EDITION
THE reasons for this translation are given in the Preface to the
First Part.
In preparing for English readers this Special Part of Professor Goebel’s
book, which abounds in facts and interesting interpretations, titles have
been prefixed to the paragraphs, and to them a key will be found in the
extended Table of Contents. By this, and by the Index, it is hoped that
reference to the book will be facilitated.
Professor Goebel has read all the proof-sheets, and has modified the
text in several places, and added additional notes. The paragraphs upon
germination of microspores (p. 612) have been rewritten, and new figures
have been introduced.
On the title-page of and throughout the First Part the word Sper-
maphyta was used in conformity with custom. In this Second Part the
word appears in the more correct form of Spermophyta.
I should have preferred in the translation to restrict the term ‘flower’
to its established signification of that sporangiferous shoot which is found
in flowering-plants. The extension of the term in the text to the
Pteridophyta—adopted also by some English writers—is apt to lead to
ambiguity, and encourages other loose expressions such as ‘seed ’ of ferns.
A change in the direction I have indicated would have involved, however,
in default of another general term in use by which to designate the
' sporangiferous shoot of Pteridophyta and Spermophyta, so many modifica-
tions in the text as to have caused me to transgress the guiding principle
of the translation—to produce the work as nearly as possible as minted
by the author.
I. 3. B.
Edinburgh, 1905.
ABLES) OF: CONLENTS
SPECIAL ORGANOGRAPHY
PAGE
INTRODUCTION. : : : ; : “ : : : I
FIRST SECTION.
BRYOPHYTA. 5-167
Sexual Organs of tai ga tae . : ; 3 : , ‘ 9-17
A. The antheridium ‘ : : : - 5 ‘ - 9
1. Structure and position : ; : 3 : 9
2. Opening of antheridium and discharze of Snes oe ; : . : 10
(a) Hepaticae . : C E : : : ; : 10
(6) Musci : : : : 2 : ; ; 11
3. Development of the pniendioen : : , : : : ‘ 12
(a) Hepaticae : ay ; : : 2 , ; . 12
(6) Musci. : é ; : ; : : ‘ 13
RP. The archegonium : ; : ; : ; ; ° : 14
1. Structure and position : ; ; : : ; 5 , 14
2. Opening of the archegoninm . : ; : : ( : ; 15
3. Development of the archegonium . : 2 : : 4 : 15
(a) Hepaticae A : : : : : : : 16
(6) Musci . a A 3 , : 2 ; ; ‘ 17
HEPATICAE. 18-115
I. Vegetative Organs of Hepaticae . : ‘ ‘ : ‘ 18-47
1. Relationships of symmetry . : : : ; ah : 18
2. Vegetative point and arrangement of cells : . : : : : 20
3. Differentiation of organs 21
A, Branching : : d : 5 : é - 21-27
B. Appendages : : é : : 5 4 ‘ : 27-47
1. Mucilage-hairs. Scales 4 . < - 27-34
In Jungermanniaceae . 28
Blasia. 28
In Marchantiaceae 29
Riccieae 29
Marchantieae 30
Dumortiera ‘ 33
2. Leaves 35-45
In thallose feos - 35-38
Anthoceros, Dendroceros . 35
Blyttia, Symphyogyna, Blasia 37
In anacrogynous foliose forms 38-40
Fossombronia, Androcryphia, Petalophyllum 38
Treubia, Calobryaceae , 39
In acrogynous foliose forms 40-45
Concrescence of leaves 42
vi TABLE OF CONTENTS
Reversion to thallus-form
Flagella :
Long shoots and short age :
Tubers :
Branching and the eaves
Resting buds
Endogenetic shoots
3. Rhizoids . :
Monoclea, iaechantiaecae
Transformation of rhizoids
Ii. Asexual Propagation of Hepaticae
1. Separation of special twigs from the vegetative body .
2. Gemmae (brood-buds) formed by gemma-cells (brood- cells)
III, Phenomena of Adaptation of the Vegetative Organs of Hepaticae
I. Relationships to water
1. Arrangements for retention of seis
A. In thallose forms
(a) Jungermanniaceae
Aneura endiviaefolia :
Aneura hymenophylloides, Aneura peeeaee
Metzgeria 2 :
(6) Anthoceroteae
Anthoceros, Dendroceros
B. In foliose forms
A. Paraphyllia < :
Trichocolea, Stephaniella ,
B. Leaves and parts of leaves as water-reservoirs
1. Aggregation of leaves
2. Outgrowths in the form of nea or colbedives eee the ae or the
surface of the leaf
Trichocolea, Lophocolea, Gorethes
3. By transformation of individual portions of the leat Pesos: are
developed :
A. Under and upper lobe form a kee
Lejeunia
Radula
B. Under lobe alone ae a oe
Frullania
Polyotus
C. Water-sacs which are eed by a taseet ae
Colura .
Physiotium
D. Capture of animals by eater ae
2. Arrangements for resisting drought
(a) Involution of parts
(6) Formation of tubers
Historical
Fossombronia fuberifera
Anthoceros dichotomus, A. TREE
(¢) Hypogeous organs for absorption of water
Stephaniella
(d) Anatomical structure in relation fo water
Air-cavities
Water-tissue
Sclerenchyma
TABLE OF CONTENTS Vil
3. Hydrotropism . : : : : : : : 76
II. Relationships to gravity : : ‘ : é ; 76
III. Relationships to light ; : , 76
IV. Relationships to other organisms : 78
IV. Fertile Shoots and Protection of Sewell c Organs of Hépaticas : - 79-93
1. Disposition and protection of the sexual organs or sporogonia : ; 80-93
In anacrogynous Jungermannieae : : . : . 80-84
Monoclea, Aneura : : : 2 5 : 81
Hymenophytum, Metzgeria, Blyttia 82
Symphyogyna, Morkia, Pellia . 2 ; , 83
Sphaerocarpus, Fossombronia, Haplomitrium : é : : : 84
In Marchantiaceae : 3 : : : : : 84-88
1. Diffuse disposition in Riccia ; : ; : : : 84
2. Combination of sexual organs in groups : : ; 84
Corsinia : - : : ; ; ; 84
Plagiochasma : : : : ; 85
3. Special sexual shoots. : : : : 5 : 85
Marchantia, Preissia ; 4 - : ; . 85
Dumortiera . : : : : : ; : 87
In Acrogynous hea : : : : : - 88-93
Trichocolea . : - : : : : : 89
Calypogeia ‘ - ‘ : . : : ; : go
Gymnanthe . : é ‘ : : : ; g ; gI
2. Summary . - : : : : ! 93
V. The Sporogonium of Heputteac : ; : 2 : ; 93-106
1. Structure and life-relationships of the mature sporogonium : : - 93-103
1. Type of the Anthoceroteae . : : : i : : : 94
Notothylas = : : ; : 95
2. Type of the Rear Mantiaceac and faeera tee - 96
I. Sporogonium is differentiated into wall-layers and inner ae filled wae ey
spores . - : 97
2. Cells within the inner ee ae not all Deco pee ceris: ; a Bettion remains
sterile s : : 4 - : 97
A. The sterile cells are oa eee fale : ’ : : : 97
Sphaerocarpus : : : ‘ 97
B. The sterile cells are provided oan penalty cena Gackeninés : : 98
I. Elaters act as organs of ejection . . : : : Z 99
A. There are no elaterophores ‘ : ‘ : z 99
(a) Type of Jungermannia - : ; : : 99
(6) Type of Frullania A : : : : ‘ Ico
B. Elaterophores are present. - : : : 2 1(EOO
(a) Type of Pellia . : . ‘ ‘ : : 100
(6) Type of Aneura . IOI
2. Elaters are not, or not eat organs a the Beion of oe but
serve to hold the mass of spores : ; : : 102
2. Development of the sporogonium : : : ; : : 103-106
Type of the Jungermannieae : : ; 2 : . : 103
Sphaerocarpus, Symphyogyna - 5 : : : : om “EOS
Riccieae and Marchantieae Fe : : : : ; : 104
Type of Anthoceros . : ‘ : ‘ , F : | Fox
VI. Germination of the Spores of Hepaticae : : . 106-115
1. Jungermanniaceae 5 - A : : 2 : 2 Seely
Thallose forms . : : : ; : : ‘ ; 107
Metzgeria . : 3 3 : : : : SLO?
Aneura, Pellia . ‘ : : : z ToS
aii TABLE OF CONTENTS
PAGE
Acrogynous forms : 108
Frullania, Madotheca, Radnla: ne < : : 3 é 108
Lophocolea, Chiloscyphus, Calypogeia, Cephalozia : ‘ ‘ = nro
Alicularia, Trichocolea, Jungermannia, Lepidozia 3 é ; ‘J 110
2. Marchantieae and Riccieae - : : ; ; : ; cae AE
Preissia IO" III
Marchantia, Lunularia : é é : ; : We ath Gy eur)
Plagiochasma . : - 3 : : : : ; 113
MUSCI. 116-167
I. Germination of the Spore of Musci : : : : é 116-130
1. The configuration of the pro-embryo . ; ; : : ‘ . 16-124
Oblique walls in rhizoids . : : . : : : 5.) sty
Shorts shoots and long shoots of protonema_ . : : : : 11g
Rhizoid-strands. : < : = - : S520
Luminous protonema of Scluststena : . : : ; : 120
Concrescence of protonema-threads = : - : : ee LT
Special organs of assimilation of protonema . - . ‘ : 121
The pro-embryo of Andreaea ° : : : : : ot VE2E
The pro-embryo of Sphagnum . - : : : ‘ : 122
Eucamptodon Hampeanum, Dicnemon semicryptum : : : E23
2. Gemmae (brood-buds) on the pro-embryo_. : : : : . 125-127
Funaria hygrometrica : : 5 5 - : - 25
Schistostega, Ephemeropsis. ; : ; : ; : 126
3. Significance of the protonema_ . 5 : - : : 127-130
Buxbaumia : : : ; 3 ° : ; : 127
Phascaceae tte ‘ : : : : ¢ we 026
Schistostega, Fissidens prroltes : : : : : : 130
II. Configuration of the Moss-plant . : : : . : 131-139
1. The configuration of the shoot 6 : : ; - : . 132-138
(a) Radial shoots. : : : : : : Le 3
Leaves on radial shoo = = : = : ; : 134
Hypsophylls” . : : : é : F : Seuss
(2) Bilateral shoots : : 137
Eriopus remotifolius, Drepatopiylaee Gehieroseeel HisileHe 3 = eS 7
(¢) Dorsiventral shoots . : : 2 fs : : : 138
2. Appendages 2 : : - : 3 : : 138-139
III. Asexual Propagation of Musci : , F F : - 139-141
1. Entire shoots : : ; : 3 : : : : = «039
2. Leaves ; : 2 ; é : ; : : : 139
3. Protonemata : 5 : : ; : ; ais:
IV. Vegetative ere of Musci : 3 : 3 , . 141-149
I. Relationship to water : : 2 : : ; : 141-149
1. Arrangements for retention of ates 4 - : : . - 143-148
A. Inthe leaf . ; : : . - : = | 143
(a) In the form of fs feat : “ 3 : : : = 143
(4) In the construction of the leaf. 3 : : : j Sela s
1. By outgrowths of the leaf-surface : ; ; : . 143
(@) Mammillae . - < : é : zs ee ys
(2) Papillae . : : ; < : = F 143
(c) Lamellae 3 a) iad
Polytrichaceae, Herbal: Pottia, Canpylante polyeaaiee F 144
2. By empty cells with perforated walls - eect a
Sphagnum, Leucobryaceae, Dicranum albidum, Poti Syorhopadon
revolutus . - 4 - : < - : 145
TABLE OF CONTENTS
B. Inthe stem . - : .
(a) Paraphyllia
Hypnum splendens .
Thuidium tamariscinum
(2) Other arrangements
2. Arrangements against drought
Silver-glance
Hair-points
II. Relationship to light
V. Sexual Organs of Musci.
1. Position of the sexual organs
Sphagnum
Polytrichaceae :
. Distribution of the sexual: organs
. The antheridial groups and oat ot pone :
Paraphyses
VI. The Sporogonium of Musci
1. Structure and development
The calyptra . ;
Structure and development of the embryo
2. Relationships of nutrition of the sporogonium
Rooting by rhizoids
Assimilation. The apophysis
3. Arrangements for the shedding of the spores .
Cleistocarpous forms . : :
Schizocarpous forms
Stegocarpous forms
1 a peristome alone Gis a part in the shedding of the ods :
. The peristome serves only as a hygroscopic lid to the capsule
Type of Weissia, Barbula, Trichostomum
2. The peristome secures besides the Pi discharge BG the ae
1. Peristome single
(a) Trellis-work of Tone teeth
Dicranaceae, Fissidentaceae, Ceratodon
(6) Permanent union of teeth at the tip
Type of Conostomum .
2. Peristome double
(a) The inner “ersten narrows the ee Beate:
Orthotrichum
Fontinalis, Cinclidium, Peers ieee of Pestana :
1X
PAGE
146
146
146
147
148
148-149
148
149
149
149-152
149
149
150
150
151
I51
(4) The inner peristome serves also for the abjection of the spores 165
Bryaceae, Hypnaceae, Mniaceae
B. The columella also shares in the shedding of the spores
Type of Pottia truncata, PCE a. of ge é
Type of Polytrichaceae . .
SECOND SECTION.
PTERIDOPHYTA AND SPERMOPHYTA.
THE GAMETOPHYTE OF THE PTERIDOPHYTA.
I. Structure and ao of Sexual ne of oe
A. The antheridium . .
The spermatozoid
The structure of the Srtheridinm
165
x TABLE OF “CONTENTS
Embedded antheridia
Opening of the embedded maaberasie
Equisetaceae . .
Lycopodium, Marattiaceae, Onhibeliecieess
Free antheridia
Opening of the free putherdinm
The development of the antheridium
Homosporous Pteridophyta
Equisetum
Osmunda, Pole otracere Antena
Heterosporous Pteridophyta
Marsiliaceae
Isoetes
Selaginella, Sulyinivesse’
B. The archegonium :
Opening of the archegonium
Development of the archegonium
C. Comparison of the antheridia and occa
Within the Pteridophyta
The Pteridophyta and the Bryophyta
D. Abnormal sexual organs
II. The Configuration of the Prothallus of Pteridophyta
1. Duration of life
2. Relationships of symmetry :
3. Gametophyte of the several groups of Picndephyi
A. Gametophyte of the Lycopodineae :
Lycopodium :
Chlorophyllous protuillos
Saprophytic prothallus
Dorsiyentral prothallus .
Phlegmaria-type of prothallus
Development of the prothallus
Selaginella :
B. Gametophyte of the Bguicetscese
Female prothallus :
Male prothallus
Development of the prothallus :
C. Gametophyte of the Filicineae .
1. Eusporangiate Filicineae .
Marattiaceae, Ophioglossaceae, Opkeslesoes Bagchee
2. Homosporous Leptosporangiate Filicineae
Osmunda, Cyatheaceae .
Polypodiaceae . :
Prothallus with heart-like eae
Prothallus without heart-like outline
Anogramme
Vittariaceae, Hymenophylium :
Trichomanes ;
Summary
3- Heterosporous Leptosporangiate eee .
Salviniaceae . 5
Salvinia
Azolla
Marsiliaceae
D. Gametophyte of Isoetaceae
PAGE
174
174
175
176
177
177
177
178
178
179
180
180
181
182
ae -184.
183
184
184-187
184
ae) EOS
187-188
188-213
189
IgI
IgI
TQI-195
IgI
192
Ig2
193
193
194
194
195-197
195
196
197
197-212
198
198
199
199
200
201
205
205
206
207
208
210
211
211
212
a Ue
212-213
TABLE OF CONTENTS XI
PAGE
III. Asexual Propagation of the Prothallus of ae tala : 213-215
Adventitious shoots . : 213
Gemmae : 213
Lycopodium Ehlecnseds Eenenapivilacece, Vi cee : : 214
IV. Phenomena of Adaptation of the Prothallus of Pteridophsta : 215-221
Relationships to water 215
Anogramme chaerophylla 215
Anogramme leptophylla 216
Aquatic prothallus 217
Symbiosis with fungi 218
Polypodiaceae : ; 218
Hymenophyllaceae, Gnioglessaceae) Tyeapadiaceae 219
Distribution of the sexual organs - 220
220
Apogamy
THE SPOROPHYTE OF THE PTERIDOPHYTA AND SPERMOPHYTA. 222-642
Tue Orcans oF VEGETATION. 222-572
I, Introduction 222-226
Tendrils of Smilax . 222
Haustoria of parasites . ; 3 : : , 3) 22g
Pilostyles Ulei, Pilostyles Eaustenechti : : ; ; : 225
II. Root and Shoot : - ; ; ‘ 226-233
A. Transformation of undoubted ont into shoot: : ; : : . 226
227
Filicineae, Spermophyta
B. Organs which are not typical roots 228
The rhizophore of Selaginella 228
The protocorm : : ; ; : : : : : 231
Lycopodium . : ‘ 231
Monocotyledones, Pitcotyledocs Ehpligelosarak: : s ‘ : 232
C. Transformation of shoots into roots : : “ : 2 . <y 233
III. Free-living Roots and Leaves. Transition between Leaf and
Shoot . , : 2 : : : P ; . 233-242
Rootless shoots . : i : : : ‘ : : s 234
Free-living roots. ; : : : : : : 234
Pyrola uniflora, Metalcore 4 F : : : : : a. page:
Free-living ae : : : : : : : : - 235
Streptocarpus, Lemnaceae_ : . = : - . - 235
Transition between leaf and shoot . : : : : . . 236
Lentibulariaceae ‘ ; : : : : : : 2236
Utricularia Hookeri : a : ; é ‘ 237
Utricularia coerulea P A ; ‘ : : =e) E238
Filicineae . : : 241
IV. Conformation of the Vegetative Organs in the Embryo , 242-262
Morphological differentiation of the embryo - : . 242-246
A. Pteridophyta . = : : * : : 2 : - 243
Filicineae : : : , : ‘ : 243
Isoetes, Equisetum, [See s : A : ‘ : ae
B. Spermophyta . : : : ; : : : 244
Orientation of the organs in the embryo : : , : : 246-262
A. Pteridophyta : : : : : : : 246
(a) Forms without a Eepenie: : : . : : i 240
Filicineae : : : : : ; : : 246
Isoetes : : : é : . : . ery;
X1i TABLE OF CONTENTS
PAGE
(6) Forms with a suspensor 247
Lycopodium, Selaginella 247
B. Spermophyta 248
1. Differentiation of the ences 248
I, Incomplete embryos. 249
(a) Embryos temporarily anaied ratte the seed 249
A. Dicotyledones 249
Eranthis hyemalis, evunedan Bieta 249
Anemone, Fumariaceae, Stylidiaceae . 250
B. Monocotyledones 250
Gagea arvensis 250
Paris quadrifolia, Bpyiiconian Dens- ots, Hyenuene sueciced Grsens
vernus, Scilla sibirica . 251
C. Gymnospermae 251
Ginkgo biloba, Gnetum Garment . 251
(2) Embryos incomplete up to the time of germination 253
Juncus glaucus, Orchideae . é 253
Dicotylous saprophytes, parasites, Users 254
II. Embryos of viviparous plants 255
Mangroves 255
Cryptocoryne ciliata 2356
2. Change of configuration of the embryo thrones the fepoaes of pee el 257
A. Dicotyledones é 257
Xanthochymus pictorius 258
Barringtonia Vriesei 259
Bertholletia excelsa 260
B. Monocotyledones . 260
Zannichellia 260
Posidonia, Ruppia, Zostera 261
SPECIAL CHARACTERS OF THE ORGANS OF VEGETATION. 263-572
THE ROOT. 263-290
I. Rootless Plants. 3 ‘ P : : : ; . 263-265
A. Pteridophyta 263
Filices 263
Salvinia, leyceranineee 264
B. Spermophyta . 265
Dicotyledones, Neooentiedones 265
II. Characters of the Root . : : : é é : . 265-272
1. The apex of the root : i 266
Azolla, Lemnaceae, Hydrocharis, Nesenies Hep eee 267
Bromchinese! Cuscuta ; : 268
2. The region of growth of the root 268
3. The region of the root-hairs 269
4. The region in which the short-lived Haire. are dead 269
Arum maculatum 279
Pull-roots 279
III. The Root-system : : ; : : : . 272-275
Monocotyledones 272
Dicotyledones 272
Method of origin of secondary cts 273
Place of origin of lateral roots on the chief roots 273
The origin of roots upon shoots. Adventitious roots
274
—
TABLE OF CONTENTS X1il
PAGE
IV. Different Construction of the Members of the Normal Root-system
of the Soil ; : . : : - : : « 275-277
The production of shoots—adventitious shoots—upon roots. : : - 276
V. Roots adapted to Special Functions . ; ; : 5 . 277-289
a. Pneumatophores or breathing-roots : : : ; 3 we 27s
Mangroves . : : . : ; : 278
Taxodium, aeenes. Gebania pedleats : ; : at 280
6. Assimilation-roots and shoot-forming roots of Eatastemareae é 5 . 280°
Dicraea elongata, D. algaeformis : : ; : : : 250
Oenone leptophylla, Hydrobryum . ; : ; 2 : ; 281
c. Air-roots of the Cycadaceae : : : : : : : vy) 291
ad. Roots of epiphytes. - 4 é ; , : : : 282
(a) Nest-roots . = 5 ; : ; . F : ee zos
(6) Assimilation-roots : ; 5 , : ; . : 284
Phalaenopsis : é : : : : : : a 254
Taeniophyllum : : : : , : : F 285
(¢) Anchoting-roots : ‘ : : : 2 : 2) 8286
e. Anchoring-roots of climbing one ‘ : é ; : : , 286
Root-tendrils ‘ - ‘ , : ‘ * 286
Ff. Roots as mechanical organs of a estan Thorn-roots - : : : 288
Monocotyledones . : ; , 288
Acanthorhiza aculeata, Teiarteas Digceams preheat Meesen ; - 288
Dicotyledones : : : : : : ; : - 288
Myrmecodia . : : 3 : : : : : 288
g. Storage-roots : : 5 : : ‘ : é - 289
h. Mycorthiza . : 2 ‘ 3 289
VI. Period of Pectasment of the Root. : : : F 289-290
THE SHOOT. 291-572
A. THE LEAF. 291-430
I, Introduction . , : ; 3 3 : : : . 291-298
Anatomic construction ; . C : s : : : se) 5202
Vascular bundles 2 : : 3 : : : . : 292
Chlorenchyma : : : : : : ‘ : ; 203
Symmetry of construction : 2 : : : : ° : 293
Leaf-form in Australia. : : ‘ : : ; : . 293
Leaf-form in Europe . 3 : : : ; : : 2 294
Inversion of the leaf é : : : : : : . 296
Monocotyledones. ; . : ; : , : P 296
Pharus brasiliensis . : : : 3 5 : : 206
Alstroemeria, Melica nutans : : : : . ‘ 297
Dicotyledones . A ‘ : : : : } : - 298
Stylidium . ; : ‘ : : : 298
II. Outer Differentiation of the Leaf . ; : : ‘ 298-302
The leaf-base . - : ; ‘ ; : ‘ : : 298
Leucojum, Narcissus ¢ é ‘ ; , : : ‘ - 299
The leaf-stalk . : : F ; : ‘ : : é 299
Monocotyledones . : . : ; ‘ : , - 299
Xerotes longifolia, Phormium aes : : : : : : 300
Dicotyledones : . 3 : : : : . = 1300
III. Development of the Leaf : : 3 : : ‘ . 302-338
A. History . é : : : : 2 , 302-305
B. Growth of the fear i in Peper : ; ; : . » 305-306
X1V TABLE OF CONTENTS
C. Distribution of growth in the leaf
a. Apical growth and intercalary growth.
Leaf-tip in Musci .
Forerunner-tips
Plug-tips .
Measurements
Guarea .
Apical growth in Speronbyia
. The inception of the leaf-surface in Goendoanyes
Basiplastic type “
Pleuroplastic type.
Eucladous type
D. Formation and development of the leaf in fae cue piene sae .
a. Pteridophyta ; :
1. Equisetaceae and cee podinede :
2. Filicineae 5
Marattiaceae, @enindageas
Leptosporangiate Filicineae C
Apical growth in the leaves of Filices
Nephrolepis, Hymenophyllum, Gleicheniaceae
Lygodieae . : :
b, peed
. Gymnospermae .
Cycadaceae, Gieoreaes Convene Guetseere :
2. Monocotyledones
Dorsiventral leaves .
Dactylis glomerata .
Hinge-cells in grasses
Basal laminar growth ;
Perforate and split leaves of Aroidene
Leaves of palms
Leaf of fan-palms
Leaf of feather-palms
Radial and bilateral leaves
Leaf of Iris
3. Dicotyledones
Branching of the leaf
Dichotomy
Monopodium
Sympodium
Interruptedly-pinnate (eaves :
Relation of the pinnate to the ieee leaf
Single branched leaves as apparent whorls
Alchemilla nivalis, Limnophila pices! 7
Peltate leaves é
Kataphylls, stamens, Goiedaue
Peltate foliage-leaves
Short-stalked . : 5 :
Long-stalked : - :
Conditions under which Heltate eae occur
Tubular leaves .
IV. Relationships between Venation and Development of Leaf
Venation of iit = as : : :
Funkia ovata
Xanthosoma Delodivdlact
PAGE
306-312
306
306
308
309
309
310
310
311
312
312
312
313-338
313-321
313
313
315
315
317
318
319
321-338
322
322
323-329
323
323
324
324
325
325
326
327
328
328
329-338
329
329
330
330
331
332
332
333
333
334
334
334
335
335
337
338-344
339
349
341
TABLE OF CONTENTS XV
PAGE
Venation of Dicotyledones : . é : : : , ee ee
Acer platanoides . : : : ; 5 : ; : 6-342
Caltha palustris, Asarum europaeum . ; : : : : : 343
Jussienea salicifolia, Fraxinus excelsior . - 344
V. Connexion between Configuration of bent and melatiodative of Life.
Heterophylly . : : P , ‘ f 3 - 345-358
1, Pteridophyta : : : : = : : : : 346-351
Lycopodium : : : : : : , : : 346
Filicineae . - 346
Asplenium ebtusifolium Gee ecstatic aoe var. inermis, Henican
capensis, mena phe liscene : : : : - 347
Salvinia, Azolla_. : : ; : : ‘ ; 4) 345
Epiphytic Filices : 3 : : : 349
Polypodium (section ieyrares) : : : : ‘ - 349
‘Platycerium . : 2 : : : : - 350
Kataphylls in Peeridophya : ; : ‘ : : ‘ - 350
2. Spermophyta . : ? : ; : : : - 351-358
(a) Land-plants . : ; 351-357
Campanula rotundifolia aad pines Scabies Columbaria sectd allies - ; 351
Scale-like leaves . : ; d : : : 3 od 353
Phyllodia ; : : : 353
Rubus australis, Waciadlaia seardates Granlia metal : ; : a ae
Parkinsonia aculeata, Acacia : : : ; : 355
(4) Marsh-plants and aquatic plants ; ‘ ; . : : 357-358
Monocotyledones : : : : - : : : 357
Dicotyledones : Z ; aso
Limnophila heterophylla, eaomte: Renee malaGdas : 5 358
VI. Stipules. Ligules. Stipels : , : ; : . 359-381
1. Origin and function of stipules ‘ : ; _ : - 359-364
Cobaea scandens as : : : 5» 360
Guilandina, Lotus Porganen Ase sonoleene ehauesns : : 361
Auricles : : : - < 5 : : OL
Adenostyles iifeons F : : 5 : : , : 361
Viburnum : : ; : : : : - 362
Protective function of Sie : : : ; : : ; 363
Assimilation-function of stipules : : : F : : 03
Number of stipules : : - : : : : ; 364
Vascular supply of stipules. - : : : : : out #362
2. Development of stipules - - - ‘ 3 : - 364-365
Arrest of stipules : : : : , “an 364
Distribution of stipules in the Plant- Fic aain : Bc : 365
Pteridophyta : : - : ; ; : 3"), 366
Monocotyledones : : : : 365
3. Relationships of ea of ales aad their eecctqeee en ; : 366-372
Inequality in size . C : : : : ; : 366
Relationships of symmetry ; - : : . 366
Stipular appendages in erence E . ; : : : 366
Concrescence . ; A : ‘ : 3 : a? 20%
of stipules of one ee : : : : : ; ; : 367
of stipules of adjacent leaves : é : : ‘ : - 368
Stipules of the Stellatae : ‘ ; : : 368
Alchemilla galioides, Acacia sesiciiats : ; : : : Sy era
4, Axillary stipules 3 = : ‘ , ; : . - 372-376
Dicotyledones . . ; : : é é ; YE
Caltha palustris, Polygonaceae . 373
Gaertnera, Gunnera. : : : ‘ ‘ : P es 74!
Xvi TABLE OF CONTENTS
Monocotyledones . : : .
Potamogeton
5. Ligules
The ligule of grasses
Function of the ligule of pees
The ligule of palms
6. Stipels :
7. Transformed stipules
Summary .
VII. Transformed Leaves
1. Prophylls
Aristolochia Eiesaa:
Winter-buds
Tilia, Cyperus.
Cucurbitaceae
2. Kataphylls
A. Formed by the whole eee onic
B. Formed by the stipules
C. Formed by the leaf-base
Evidence from development .
Acer Pseudoplatanus .
Prunus Padus :
Evidence from transition-forms .
Evidence from experiment .
Monocotyledones .
8. Hypsophylls
I. Development .
A. Formed by the orale ieeepriecuedanes
B. Formed by the stipules .
C, Formed by the leaf-base
Mulgedium macrophyllum
Astrantia major
Hypsophylls of Monsearledanes
2. Relationships between configuration and function
Lolium, Xeranthemum macrophyllum
4. Storage-leaves
Lathraea Squamaria, Tez Sipe
5. Cotyledons
a. Pteridophyta
b. atelier ‘
. Dicotyledones
Morphology of the poryliedors
Oenothera bistorta
Factors causing configuration of eoeyledon
Narrow and broad cotyledons
Asymmetric cotyledons
Lobed and emarginate cotyledons .
2. Monocotyledones
Stages of differentiation of coty fede
Epigeous cotyledons
Hypogeous cotyledons .
Cyperaceae
Carex . °
Cyperus plenntolias
Scirpus lacustris
382-430
382-384
383
383
383
384
384-389
384
385
386
386
386
387
388
388
389
389-398
eS
392
394
394
394
395
396
396-398
397
398-400
399
400-419
400
401-419
402
402
404
405
406
406
407
408
408
409
410
4II
4II
413
414
TABLE OF CONTENTS XVil
PAGE
Grasses : : : ; : < - - 414
Zea Mais c 5 “ ; A Z 7 416
Zizania aquatica . 3 : : c : See ate7
Development . S : ° < - : 418
The epiblast < : : : . . = 418
¢. Retrospect . é . ° ° : . - : : 419
6. Leaves as climbing-organs : : : “ ° : : 419-428
Hooks 2 ; - 5 ‘ : : : : - 419-421
A. Pteridophyta : : : ° . : ; ° - 419
Lycopodium volubile d : z 2 2 Z : 419
B. Dicotyledones : 3 : > 1420
Stylidium scandens, Bertin Gurquatis sda Biswouia . : : 420
C. Monocotyledones . 5 : 2 : ; : . e420
Asparagus comorensis ~ - : : : - 2 420
Palms). . : ; a : : = Z 2 ARK
Calamus . : : : 4 4 2 : ; 421
Tendrils . : : ; = ‘ - : : : 421-428
A. Dicotyledones . : é : ;: 3 : 421
Corydalis Prapiculstes : : + ; - : Az
Adlumia cirrhosa, Cobaea scandens : c , - F : 422
Cucurbitaceae . : < c : . . 423
Benincasa cerifera, @ucunits aaa 3 : A : 424
Pilogyne suavis : : : = 5 A =) 425
Miiller’s investigations . : : : . : . 425
Cucurbita . : - 5 : A : : - 426
Zanonieae : : : : : 5 427
Teratological preemies - 5 : : : 22 *428
B. Monocotyledones : 5 : 3 c : : : 428
Smilax, Gloriosa, Littonia . : : = - oe AZS
Factors causing transformation into adie ; J : : 428
7. Leaves as thorns . : : A 3 J : : ; 428-430
Astragalus ; ° : : : 428
Carragana, Cicer abephyllne: Beers: Gaciacese : 3 - 20
Gitrus)= . ‘ F 2 : : : Z 5 430
8. Leaves as nectaries 3 ; : A é : 3 = 430
Cactaceae . ‘ : : F : : : 5 : 430
B. BRANCHING OF THE SHOOT. 431-439
Axillary branching and exceptions - - : : wo \agt
Time-relationship in development of axillary eck ad aaillant leaf ~ : . 432
Accessory shoots 3 : : 5 : : 5 ~ - ae 433
Shoot-tendrils of Ampelideae “ 3 : : Bs ‘ : : 435
Foliar origin of shoots . : ; : : . : : . - 435
Epiphyllous inflorescence . : : : - . : . : 436
Adhesion of the bract . F ; ; : x E : = ~. 435
Atropa : é : ; : : : : : : 438
Arrested Buds . : 5 A = : . : : 5 si 439
C. DIFFERENT CONSTRUCTION OF THE SHOOT. DIVISION OF LABOUR. 440-572
Division of labour and duration of shoots - ‘ ; . 2 i : 440
Relationships of shoots to their function : a g B : _ 5 441
THE SHOOT IN VEGETATION. 441-467
I. Epigeous (Photophilous) Shoots . : é z : ; . 442-462
a. Orthotropous radial shoots and their transformations . : 2 - 442-457
1. Arrangement of the leaves and length of internodes . : ‘ - 442-443
Callitriche . . : 2 < - : : Soe!
Gentiana : : - : - : : - 443
GOEBEL 11 b
XVIil TABLE OF CONTENTS
2. Short shoots and long shoots
Double needles of Sciadopitys
Precedence in unfolding of short shoots
Assimilating shoot-axes
Reduction of leaves on assimilating alee -Axes
Increase of surface of assimilating shoot-axes .
Phylloclades and cladodes .
(a) Pteridophyta .
(4) Gymnospermae
(¢) Monocotyledones
Bowiea volubilis
Asparagus, Ruscus .
(2) Dicotyledones :
Carmichaelia, Bossiaea, Collletia; Phyllanthus
Cactus-form
3. Transformed radial shoots
Thorns
Storage-shoots :
4. Transformed radial shoots in lianes
Searcher-shoots
(a) Temporary eelardation of foliaee
(6) Permanent retardation of foliage
Climbing-organs
Shoot-tendrils .
Shoot-hooks
6, Plagiotropous (dorsiventral) shoots
In trees
In herbs
Relationships to conditions BE life
Ajuga reptans
Glechoma hederacea, Siachys
Factors which condition plagiotropous growth
II. Geophilous Shoots.
Perennial geophilous shoots
Paris quadrifolia
Periodic geophilous shoots
Polygonatum multiflorum, Circaea HEE
Depth in soil of geophilous eoor
Polygonatum multiflorum
Photophilous shoots in the soil
THE SHOOT IN THE SERVICE OF REPRODUCTION.
I. Introduction
A. Gemmae .
Lycopodium
Remusatia vivipara
B. The flower
Terminology
If. The Sporophylls and Flower of the Pteridophyta
A. General features of the sporophylls .
Biological relationships of sporophylls
Relationships of sporophylls to foliage-leaves .
Experimental proof in Onoclea, Selaginella
Experimental proof in Botrychium Lunaria
Sporophylls and fertile leaf-parts as new formations
1. Leptosporangiate Filicineae
PAGE
444-452
- 444
445
445
446
448
448
448
448
449
449
450
451
451
452
452-453
452
453
453-457
453
454
454
455
472-511
472-482
474
474
475
476
477
477
TABLE OF CONTENTS
Schizaeaceae
Schizaea rupestris
Polypodiaceae :
Asplenium dimorphum
Marsiliaceae
Marsilia polycarpa .
2. Eusporangiate Filicineae
Ophioglossaceae
B. Special features of the ee
1, Filicineae
1. Eusporangiate Paieinese
Marattiaceae
Ophioglossaceae
Helminthostachys
2. Leptosporangiate Filicineae
(a) Isosporous Leptosporangiate Bilicese
External Form
Anatomy
Acrostichum peleataen
(4) Heterosporous Leptosporangiate Biaaneeee
Salviniaceae . ;
Salvinia
Azolla
Marsiliaceae
Marsilia polycarpa
Hypogeous sporocarps
3. Position and arrangement of the sporangia upon fie Speraphylis and ates pro-
tection
(a) Position of the sporangia .
Dicksonia antarctica
(+) Arrangement of the sporangia
(c) Protective arrangements for the sporangia
By the whole configuration of the en ere 3
By formation of hairs
By indusia
By sinking of the sori in are
4. Conditions for the appearance of the epee
II. Equisetaceae ‘
Protection at base and eee of ee
Equiseta homophyadica .
Equiseta heterophyadica
Ametabola .
Metabola
III. Lycopodineae
Lycopodium annotinum
Psilotaceae
Isophyllous Selasincllcas
Selaginella Preissiana
Anisophyllous Selaginelleae
Tetragonostachyae .
Platystachyae
Distribution of sporangia in Sclanwcliene
Relationships of flower to vegetative shoot in Frc pede
Ill. The Sporophylis and Flower of the PE Sage .
1. Cycadaceae
Megasporophylls ee .
b 2
Xx TABLE OF CONTENTS
PAGE
Cycas . é 2 A : ° y ; : o eer
Dioon, Ceratozamia : ° . . - 4 : 512
Microsporophylls (stamens) . : 2 . : : : ey!
2. Ginkgoaceae and Coniferae . : : : s : : - 514-526
Male flower . : : : : é Ae tiie
Position of the Piriceparands : : : : - : 515
Variation of microsporophylls in one flower . : ; - Gs
Juniperus communis. 5 : : . : ; 516
Female flower - : : : ° : : . > 518
Ginkgo : : : : ; : - : : 518
Taxineae : : ; : : oe Lit)
Cephalotaxus, Doreya, Phyllccladus : : : ; = 519
Podocarpeae, Dacrydium Colensoi, Taxus . : 5 - 520
Araucarieae . : : : : 5 - : 52
Taxodieae, Cupressineae : : : - : : al
Abietineae . : = : . 521
Development of ie faa fener in es fir : : : 522
Pollination in Pinus Pumilio . . c : C ; 522
Position of the female flower in Coniferae : : - : SO IE
Biological relationships. 2 : - : - : 523
Question of flower or inflorescence : : : : : «a4
Argument from anamorphose_ . . - : c : 524
Argument from virescence . : : : ° 5 5 2
Summary : : : “ “ : - < 525
sce : 3 : cS : “ - : 525
8. Gnetaceae . : : : : - : F s oe
IV. The Soseapiallay and Flower of the a : : 527-572
A. The flower in general ; c . 5247-548
1. Arrangement i the parts Ae the flower ; : 6 : 528-546
(a) Relationship of relative size of parts of the flower : : ; 529
Geum, Rosa, Agrimonia . : 3 < : 5 + 529
Potentilla, Rubus é ; : - c 2 : 530
Eschscholtzia californica . > : = : : 2 531
Chorisis : : : : 5 ; 5 532
Branching of the canes 4 : : 3 = 5 » 534
Hypericaceae : : < c : : 5 534
Chorisis of the stamens : ‘ 5 : 2 = se 5S5
Adoxa ¢ . : c 3 : : : 535
Malvaceae : 3 ‘ : : : . s 536
Doubling of the stamens ; ‘ : ; ‘ : 536
Phytolacca, Rumex : : 5 : 5 - gi IES
Double flowers . : : 3 : ; : 536
Branching of the ee : : : : : Gey
Factors determining numerical yelatigaeiies . : 537
(6) Change in numerical relationships of the flower through Sinica : Sgt
Confluence of petals. , 5 5 : c 4 538
Confluence of stamens - : : : : : ae 530.
(c) Suppression of the elongation of torus : ; : - : 540
(d) Limited growth of the torus 3 2 . : , . AT
a. Terminal flower-leaves . 4 5 : : 541
b. Basipetal succession of flower legac c : : = Sat
(e) Dorsiventrality . Z t - : : : : 542
Reseda, Lentibularieae 5 3 : : ° d - 542
Papilionaceae, Cruciferae : 5 ; - : 543
The anatomical method in flow eo rele . : . 545
TABLE OF CONTENTS
2. Concrescence in parts of the flower
3. Arrests
B. Individual organs of the cone ea.
1. The flower-envelopes :
(a) Morphological ee ceanre of the cen er-env hie
Anemoneae = : -
Trollius europaeus .
Factors influencing colour anid size
(6) Differences in configuration due to distribution of ame
2. The androecium
(2) Division of the ae : :
(4) Arrest or suppression of pollen-sacs
(¢) Confluence of pollen-sacs
(@) Division of pollen-sacs by sterile pitta
Transformed stamens E
3. The gynaeceum
Terminology
Ovules on the under- Beer of es
A. The superior ovary
1. The apocarpous poe
Papilionaceae, Rosaceae
Ranunculaceae
Ailanthus, Coriaria
2. The syncarpous gynaeceum
(1) With septal placentation
(a) The flower-axis does not oa
Acer
Solanaceae, ee idee
(4) The flower-axis shares
Oxalis
Caryophylleae
(2) With parietal placentation
Cistus populifolius
3. The paracarpous gynaeceum
Dionaea . :
Primulaceae, Dest dedteiced
B. The inferior ovary.
(2) Vegetative point of the axis is ne a up
Pyrus Malus
(4) Vegetative point of the axis is — =
Umbelliferae, Valerianaceae .
The biology of ripening fruit
C. Transformed flowers
Sesamum indicum, Trifolium Sabicea 5
Tue Orcans or PRopaGATION
I, The Sporangium .
Embedded and free sporangia .
The relationships of symmetry
Arrangements for distribution of spores
‘Elaters’ in Equisetum . :
‘Elaters’ in Polypodium imbricatum
Differences in the structure of the sporangial wall
Division of labour in sporangia
op
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XXIl TABLE OF CONTENTS
II. The Mature Fabio So of the ees
A, Lycopodineae
Psilotaceae, Tmesipteris
Lycopodieae .
Lycopodium
Selaginella
Lycopodium inundatum
B. Equisetineae
C. Filicineae .
1. Eusporangiate
Ophioglossaceae
Marattiaceae
Danaea, Kaulfussia
Marattia, Angiopteris
2. Leptosporangiate : :
. Slit transverse to long axis of seomeeel Renata vance
2. Slit oblique to long axis of sporangium. Annulus oblique
Trichomanes .
Alsophila, Pi sceyae
3. Slit longitudinal to long axis of eos heugine eee or oblique .
Osmundaceae
Gleicheniaceae, Echiaeseede
Mohria, Schizaea, Aneimia
Lygodium .
Ceratopteris
III. Development of the Sporangium
The archesporium :
Microsporangia of the Re ae:
Hyoscyamus, Symphytum officinale, Kneis arvensis .
Sporangia of the Pteridophyta
Eusporangia and leptosporangia
Microsporangia and megasporangia .
The megasporangium of Selaginella
The megasporangium of Isoetes
IV. Phyletic Hypotheses relating to the Formation of Sporangia
V. Apospory
VI. The Sporangium of the Spermophyta
A. Microsporangia
a. Gymnospermae .
6, Angiospermae
Ericaceae
Microspores
Germination of Sena
B. Megasporangia
A. General features
Porogamy and aporogamy 2 : - . :
a. The integuments : , : é - 5 . :
The nature of the integuments
Development of the integuments
Ategminous ovules
A. Monocotyledones
Amaryllideae
Crinum
605-606
607-609
610-642
610-614
610
610
611
611
612
614-642
614-626
615
616
616
617
618
618
618
618
TABLE OF CONTENTS
B, Dicotyledones
Gentianeae .
Voyria
Olacineae, Santalaceae
Loranthaceae - ; : : ;
Loranthus pplgeoeenas: Viscum articulatum, Loranthus pentandrus
Balanophoreae
é. The Nucellus
Developments within the aucellos i in piles to tiraals
Parthenogenetic state
Development of the megaspore
B, Special features of the megasporangium of Gyaudepeetae
Cycadaceae :
Ceratozamia ieaeiatia
Coniferae, Gnetaceae
Female sexual organ of Gy eee
Cycadaceae, Ginkgoaceae, Coniferae, Gnetaceae
c. Special features of the megasporangium of Angiospermae
Origin of the megaspore :
Alchemilla, Casuarina
Germination of the megaspore .
Feeding of the megaspore, endosperm, and noise
Epithelium
Haustoria
Linum, Torenia, Byblis PE
Globularia, Utricularia, Polypompholyx
Development of the fertilized egg
LIST OF THE ILLUSTRATIONS .
INDEX
Page 5,
10,
CORRECTIONS.
PART:
line 12 from bottom, for If vead It.
line 13 from top, for Bilbergia vead Billbergia.
39, Fig. 14, for Mortiziana vead Moritziana.
46, Footnote 1, for lacustre ead palustre.
113;
190,
210,
256,
260,
264,
68,
973
157,
210,
222%
315,
315,
35°,
445,
469,
478,
478,
479,
575)
line 2 from top, for Strobilanthus vead Strobilanthes.
line 19 froin top, for Weigelia read Weigela.
line 5 from top, for stipelles read stipels.
line 18 from top, for moschatellina vead Moschatellina.
lines 12 and 13 from bottom, for Jussiaea vead Jussieuea.
Footnote, line 1, fox pyracantha vead Pyracantha.
PART II.
line 2 from top, for moschatellina vead Moschatellina.
line Io from bottom, for remain ead remains.
Fig. 123, for transverse vead longitudinal.
Footnote, /ov aquatica 7cad aquaticum.
line 3 from bottom, for emergencies read emergences.
line 9 from top, for Amphicosmia Walkerae read Hemitelia (Amphicosmia) Walkerae.
line 4 from bottom, for Amphicosmia Walkerae vead Hemitelia (Amphicosmia) Walkerae.
line 4 from bottom, for O. Struthiopteris vead Onoclea Struthiopteris.
line g from top, for Pumilo vead Pumilio.
line 16 from top, for Vzvipara read vivipara.
line 4 from top, for Rupestris read rupestris.
line 3 from bottom, for Dimorphum read dimorphum.
line 13 from top, for Polycarfa read polycarpa.
line 15 from top, for ARRANGEMENT read ARRANGEMENTS.
624, top line, for megaprothallium read megaprothallus.
SePeciAlL ORGANOGRAPHY
INTRODUCTION
I HAVE endeavoured in the general part of this work to depict in some
examples the general relationships of the formation of organs in plants;
I have now in this special part to describe these relationships in the several
groups with more detail. Various considerations, especially those of space,
compel me to restrict my attention to the groups which fall within the
limited scope of this book, namely, the Archegoniatae and Spermophyta.
In conformity with general usage, I include amongst the Archegoniatae
the Bryophyta and the Pteridophyta. We might directly link on to these
the Gymmnospermae, whose relations to the heterosporous Pteridophyta
have been proved in recent times to be very close by the discovery of
spermatozoids in the Cycadaceae, with which group perhaps other forms will
have to be reckoned ; but the combination of groups between which actual
connecting members are not known must always be a matter of con-
venience, and I have therefore preferred to keep together under the term
Spermophyta the whole of the plants that produce seed. At the same
time we must remember that the chief classes of Spermophyta embrace
lines of development as different as are those of the groups Pteridophyta
and Bryophyta which make up the Archegoniatae.
When we compare any one of the natural series of these groups in their
different members, the first question that arises is, what is the relationship
between formation of organs and adaptation? In other words, are the
specific marks which separate from one another the several species, genera,
and so forth, within one series, of a purely adaptive nature as the extreme
disciples of the ‘natural selection’ school hold, or are the specific and the
adaptive marks separable? In my opinion there can be no doubt that the
latter is the case. The formation of organs must naturally always stand
in conformity with the furtherance of life, but the special stamp it bears in
each group, in spite of all differences in the individual adaptive configura-
tion, shows that the ‘inner constitution, if we may use this expression
which cloaks our ignorance, plays the chief part ; were it not so the pro-
fuseness of the formation of organs could not be understood. What special
GOEBEL II B
2 SPECIAL ORGANOGRAPHY
advantage should it bring to the Anthoceroteae that their chloroplasts
possess pyrenoids which are not seen in other Hepaticae? Or, that the
mucilage which protects their apical region arises in mucilage-slits
instead of in club-shaped papillae? Or, that their sporogonia are not
stalked? Or, that their sporogenous layer is laid down in a way different
from that in other Hepaticae? Or, that their archegonia are always
embedded, and their antheridia are developed in pits? All these are
specific characters which cannot be reckoned as adaptations. On the other
hand, the production of water-sacs by species of Dendroceros, after the
fashion of Metzgeria saccata and other forms, is an adaptation; the same
may be said of the arrangements for collecting water which Anthoceros
exhibits in common with many other Hepaticae; and also of the tubers
which some species of Anthoceros produce, as do the prothalli of Ano-
gramme amongst the Filices. Many other examples in this and in other
series might be given.
Seeing that the phenomena of adaptation repeat themselves in different
groups in like manner, they naturally must appear more conspicuously in
the First Part of this book than they can in this Special Part. The
appearance of characters of adaptation, everywhere or almost everywhere
in a group, in all its members, for example the structure of the thallus
in the Marchantieae, must be considered rather as an accidental concurrence
with the specific marks—a conformity which we can understand if we
assume that the adaptation is a very old one, that is to say, it took place
before the separation of the group into isolated forms which developed in
different directions.
The structure of the sexual organs and an abrupt alternation of genera-
tions are characteristic of the Archegoniatae. The name is based upon the
structure of the female sexual organ, which throughout the whole group
has an essentially similar construction in its mature state. The antheridium
is a cellular body provided with an envelope if it is not sunk in other
tissue, and this envelope almost always consists of one layer of cells. The
archegonium is flask-shaped and encloses a single egg which is fertilized
by the spermatozoids—male elements swimming freely in water, and of
characteristic configuration and special origin. The elongated configuration
of these is probably an adaptation which fits them to penetrate the
mucilage investing the egg!. The peculiar transformation of the cells
which leads to the formation of the spermatozoids finds its counterpart, so
far as is yet known, only in the Characeae. I cannot, however, go further
into that subject here.
Experience has shown us that the nature of the sexual organs is of quite
special importance for the characterization of the groups we are dealing
‘ We find them in Volvocineae. See Part I, p. 28, Fig. 4.
INTRODUCTION 3
with, and we must therefore ask in the first place whether there is to be
found in their structure any indication of a common line of genetic con-
nexion. The more recent investigations into the history of development of
these organs have in the main neglected the mature stage; yet the manner
in which, for example, the antheridia open in the Bryophyta is of no less
importance than is the succession of cell-divisions.
It would be instructive to give a comparative account here of the
structure and of the development of the sexual organs of all the Arche-
goniatae, but for the reasons stated we must discuss these organs separately
in the two archegoniate groups—Bryophyta and Pteridophyta.
In the following pages our subject is dealt with in the two sections :—
I. Bryophyta.
II. Pteridophyta and Spermophyta.
FIRST SECTION
env Or Ta YT A
bun’ ©) PoE Y¥,- EA
IT has been customary from of old to subdivide the Bryophyta or
Muscineae into the two classes of the Hepaticae or liverworts and the
Musci or mosses!. Each class embraces a number of series which are
in part sharply separated from one another; at the same time they have
so much in common that their combination even to-day appears still useful.
Between Hepaticae and Musci there are no transition-forms, as there are
none between Bryophyta and Pteridophyta; and as there never were such
transitions? their absence is not caused by their having died out. If the
development proceeded from very simple nearly related forms in definite
and divergent directions we ought always to find a partial correspondence
only in the simplest forms, and as a matter of fact we find these, as will be
shown in the following pages. All of the speculations upon the relationship
between the Hepaticae and Musci, Bryophyta and Pteridophyta, and other
groups, which are based upon the highly developed Archegoniatae are
therefore products of fancy ; they spring from the tendency of our imagina-
tion to assume connexions even where they are not directly proved, but
they have no sufficient support in the facts of experience, and their sole
value lies in the new points of discussion they create.
The two groups of the Bryophyta behave quite differently in the
formation of their vegetative organs. TEEverywhere in the Musci we find
one and the same type of differentiation of the members of the vegetative
body—that of the leafy stem. In the Hepaticae there is much greater
variety :—starting from simple thallose forms which in their differentiation
of members are far behind many of the Thallophyta, for example
Sargassum, we have a rich variety in the construction of the vegetative
body and its adaptation to external relationships. We gain the impression
that the Hepaticae, apart from the Anthoceroteae, are a younger group,
1 It was Hedwig (Theoria generationis et fructificationis plantarum cryptogamicarum Linnaei,
Lipsiae, 1798) who, I believe, framed this classification. He divided (p. 119) the Musci into
* Frondosi,’ including those whose sporangium usually has a lid, and ‘ Hepatici,’ including those
whose sporangium has no lid, but opens by longitudinal valves. Micheli originally gave the name
‘ Hepatica’ to Fegatella conica on account of a fancied resemblance to the lobes of the liver.
Linnaeus had placed Jungermannia and Marchantia amongst the Algae.
easee Part I, p. 19.
8 BRYOPHYTA
still in a condition of flux, as compared with the older more fixed Musci.
This is, however, a purely subjective representation, as the facts of
Palaeontology leave us completely in the dark. The soft Hepaticae
especially are but little favourable to preservation as fossils, and it is
impossible to say whether many of the impressions which are described
as ‘Algae’ are not to be ascribed to the thallose Hepaticae.
The structure of the sexwal organs on the other hand supplies, as has
been already indicated, a resemblance between the groups, and this, when
we consider it from the standpoint of the theory of descent, appears to
be an inherited portion from common ancestors. In other words, if we
assume a descent in general it follows that the vegetative organs must have
been greatly changed in different directions, whilst the sexual organs have
altered but little. It is clear from this that the endeavours to refer back
the sexual organs to parts of the vegetative body’ must be futile.
Further, the construction of the sexual organs is not the same in all
Archegoniatae, but is rather characteristic in the individual groups, yet
does not always exhibit quite constant differences. The development of the
archegonia in the Bryophyta is everywhere different from that in the Pteri-
dophyta, and the explanation of this is, as I tried to show long ago, that these
two complex groups have from a very early time developed in diverging
directions, and it is therefore impossible to prove a dvect affinity.
An exposition of cytological relationships is not within the plan of this
book. I may merely mention that Farmer? found in the dividing nuclei
of the sexual generation of Blyttia (Pallavicinia) decipiens fowr chromosomes,
whilst in the asexual generation derived from the fertilized egg there are
eight. The sporocytes on the other hand show in division only four
chromosomes—a reduction to one half. It is probable that this difference
in the nuclei of the sexual and asexual generations exists also in other
Bryophyta* and Archegoniatae. From many points of view this is an
important difference, and it is to be wished that it will receive ere long full
elucidation.
In what immediately follows, the grosser relationships of configuration
and the structure of the sexual organs of the Bryophyta are shortly
described.
' With the morphological value of ‘ caulomes’ or ‘ trichomes,’ see Part I, p. 17.
? Farmer, Studies in Hepaticae: On Pallavicinia decipiens, Mitt., in Annals of Botany, viii
(1894), Pp. 35:
$ Farmer has already proved this in Pellia epiphylla. See Annals of Botany, ix (1895), p. 488.
THE ANTHERIDIUM OF BRYOPHYTA 9
SEXUAL ORGANS OF BRYOPHYTA
ee LE MANPAE RTT OM.
I. STRUCTURE AND POSITION. The mature antheridium has the
same essential structure in Hepaticae and Musci. The special body of the
antheridium is seated upon a stalk (Fig. 2), the length of which varies in
evident connexion with the relationships of life of the plant. It is short
in the antheridia of the Hepaticae if they are sunk in pits, and then, as we
shall see, the mouth of the pit supplies frequently a mechanism for the
ejection of the spermatozoids; it is long in Musci, where the antheridia are
not closely enveloped by leaves but stand more or less exposed and pro-
tected only by paraphyses. Relatively long stalks are found in antheridia,
/
vn ey
RR /6\ : }
Sy aie
a
Fic. 1. Marchantia polymorpha. 4, antheridium with Fic. 2. Phascum cuspidatum. Stem in
mucilage-papillae, 4, at its base. 2, spermatozoids. 4, mag- longitudinal section. 4, leaves; #, paraphyses;
nified 90. 8, magnified 600. After Strasburger. ar, archegonium ; a7z,antheridium. Magnified
45. After Hofmeister. Lehrb.
which stand in the axils of leaves as in the acrogynous Hepaticae, and there
they secure that the contents of the antheridium do not remain in the axils
of the leaves when they are discharged. We find similar relationships
amongst the Musci in the antheridia of Buxbaumia (Fig. 105), where they
are enclosed in an envelope like a mussel-shell and superficially resemble the
antheridia of Hepaticae. The configuration of the body of the antheridium
is connected also with the distribution of the spermatozoids. The deeply
sunk antheridia of the series of the Marchantiaceae and those of Monoclea
are club-shaped, whilst they have a more spherical form when they occupy
a more exposed position, as is the case in most of the Musci.
The body of the antheridium is composed of a wall investing a mass
of spermatocytes. The spermatozoids! are always biciliate (Fig. 1). The
' These were first described in Fossombronia pusilla by Schmidel, Icones plantarum, Norim-
bergae, 1747.
10 SEXUAL ORGANS OF BRYOPHYTA
wall, which originally possesses chlorophyll, frequently shows in Hepaticae,
such as Sphaerocarpus, Fossombronia, Anthoceros, and in many Musci
abundant chromoplasts which give it a reddish or -yellow-brown appearance,
and we might with Stahl conjecture that this colouration promotes an
increase of warmth to the antheridium. In support of the view that the
colouration of the wall has a biological significance I-‘may point out that in
Sphaerocarpus the sac-like envelope in which the antheridia are enclosed
has a reddish colour, and in Pellia the walls of the shallow pits in the thallus
in which the antheridia are sunk is coloured frequently violet. The pits for
the antheridia in Marchantia also are coloured violet. The wall of the
antheridium is covered with a cuticle which is thicker in those which are
exposed than in those which are in pits.
2. OPENING OF THE ANTHERIDIUM AND’ DISCHARGE OF THE SPER-
MATOZOIDS. The method in which the antheridia discharge their sper-
matozoids has not been much referred to in recent literature. If a ripe
antheridium be touched with a drop of water it opens instantaneously and
the spermatozoids are at once placed in favourable conditions. It has been
commonly assumed that the wall of the antheridium is gradually ruptured
at the apex through the pressure of its swelling contents! which then issue
from it. I have satisfied myself, however, by the examination of a large
number of antheridia of both Hepaticae and Musci that the wall plays an
active part in the opening of the antheridium ?. In most cases this is brought
about by the same means as are employed in the annulus for the opening
of the capsules of many Musci—a deposition of mucilage takes place in
the cells, and this by its increase in volume through the absorption of water
causes the dehiscence. So far as my investigations show there appear to be
two types of opening in the antheridium of Bryophyta :—
(1) One cell or a sharply limited group of cells at the apex of the
antheridium takes part in the opening; this cell or group of cells may be
called the opening cap. This type occurs in the Musci with the exception
of Sphagnum.
(2) No such limitation of the cells concerned in the opening is found,
but a large number of cells of the wall take part in it. This type is found
in the Hepaticae and in Sphagnum.
I shall now describe shortly a few examples of the opening of
antheridia.
(z) Hepaticae. The opening of the antheridium of the Junger-
manniaceae is brought about in the same way in all cases so far as we
know. A deposition of mucilage takes place in the outside wall of the cells
forming its wall, especially in the upper part of the antheridium. The
’ The wall of the spermatocytes becomes mucilage at a relatively early period.
* Goebel, Uber den Offnungsmechanismus der Moos-antheridien, in Annales du Jardin botanique
de Buitenzorg, Supplement II (1898). The literature is cited here.
THE ANTHERIDIUM II
swelling of this mucilage stretches the cuticle, which finally splits.
Frequently the cells of the wall separate from one another and curve in
a direction the reverse of their original curvature (Fig. 5, 5). I have
never observed that they act as ‘ejaculatores seminis’ as Gottsche sug-
gested!. They may, however, remain in connexion with one another
except at the point of splitting. In the series of Marchantiaceae I noticed
a very great increase in the radial diameter of the cells of the wall of
the ripe antheridium, which is here in a deep pit. In this case we have
not to consider the tension induced by the cuticle of the antheridium,
but that caused by the wall of the pit in which the antheridium is seated.
The mouth of the pit is in many forms of this series raised above the
surface as a projecting point, and this in my opinion has the same use
as the nozzle of a syringe, and the wall of the antheridium acts like that
of the india-rubber ball of a hand-spray. The emptying of the antheridium
Fic. 3. Opening cap of the antheridium in Musci. 1, Funaria hygrometrica. Antheridium in profile; the
opening cap consists of onecell. 2, Polytrichum. Emptied antheridium; the opening isin section. 3, Catharinea
undulata. Apex of an antheridium in longitudinal section; the cells of the opening cap are marked by the
deposition of mucilage in their walls.
may also take place gradually, and drops containing spermatozoids are
then found at the mouth of the pits, whence they can be either washed
away or removed by small animals. The pit has then a definite function
to perform in the ejection of the spermatozoids, and is not merely concerned
with the protection of the antheridium*. We have as yet no certain
knowledge of the method by which water gets from the outside into the
narrow pits of the antheridiophore of Marchantia. Perhaps the mucilage
which is formed in the pits by special mucilage-papillae (Fig. 1, 4, 9),
and which accumulates at the mouth of the pits and so acts as a protection
against dryness, may also act as an absorbent of water.
(4) Musci. Funaria, Mnium, Catharinea, Polytrichum, were examined
(Fig. 3). The process in all cases is the same excepting that the number
1 When an ejection of the contents of the antheridium occurs, as in Frullania, it is the sudden
contraction of the previously stretched wall of the antheridium which causes this.
? In the Anthoceroteae the antheridia are laid down in intercellular spaces of which the covering is
subsequently destroyed; the protection of the antheridia is in this case the only function of the pit.
12 SEXUAL ORGANS OF BRYOPHYTA
of cells in the opening cap differs; in Funaria there may be one or two, in
the others there may be more. The cap appears in water like a clear
vesicle, as it was described and figured by Hedwig. The cuticle becomes
greatly stretched and the cells of the opening cap suddenly burst and their
contents pass either at first inwards to be subsequently discharged with the
contents of the antheridium when the cuticle ruptures at the apex, or are
discharged outwards at once if the cuticle at the apex ruptures earlier. In
all cases a narrow opening only is formed which is bounded by the remains
of the cells of the opening cap (Fig. 3, 2), and through this channel the
slimy contents of the antheridium slowly pass out. There can be no doubt
that the contraction of the previously stretched wall of the antheridium aids
Fic. 4. Monoclea dilatata. 7, 77, young antheridium in a pit of the thallus. /7/, female plant in longi-
tudinal section showing the inception of young archegonia in a pit behind the apex. Drawn by Ruge from material
collected by me on the Cordilleras of the coast of Venezuela.
their passage, but at the same time their swelling into the form of a sausage
is an important factor. The spermatozoids disperse afterwards when the
mucilage in which they are embedded becomes more fluid.
3. DEVELOPMENT OF THE ANTHERIDIUM. As we have such charac-
teristic differences in the structure of the mature antheridium in the two
classes of the Bryophyta it is not surprising that differences show them-
selves also in the manner in which they are built up out of cells. Are these
differences then of systematic significance, and if so to what extent? We
may say generally that they are of importance and the chief facts may be
shortly stated here.
(z) Hepaticae’. Two types are exhibited, but they are connected by
intermediate links :—
* See Leitgeb, Untersuchungen iiber die Lebermoose, i-vi, Graz, 1874-1881; Satter, Beitrige
zur Entwicklungsgeschichte des Lebermoosantheridiums, in Sitzungsberichte der Wiener Akademie,
Ixxxvi (1882); Douglas Campbell, The Structure and Development of the Mosses and Ferns,
London, 1895. In this book the older literature is cited.
THE ANTHERIDIUM 13
1. Construction by formation of transverse disks which is characteristic of the
club-shaped antheridia in Riccieae and Marchantieae and of those of Monoclea.
This is the more primitive type, inasmuch as a separation of the wall from the
inner cells of the antheridium takes place at a late period. Many tiers of cells
arise, the lowermost of which goes to form the stalk (Fig. 4, Z, 77), and each tier
becomes divided into quadrants and then the separation of the wall from the inner
cells appears. We do not know what is the significance of the beak-like prolongation
which is found in the antheridium of Corsinia.
2. Construction through growth in every direction as it is seen in the spherical
antheridia of Jungermanniaceae and Anthoceroteae.
Sphaerocarpus may be first mentioned as it shows a transition from the first to
the second type (Fig. 5, 1, 2). The mother-cell of the antheridium which has become
club-like in form is divided by three cross-walls (1, 2, 3 in Fig. 5, 1, 2); the lowermost
cell forms the stalk, the next lowest forms the under portion of the wall, the upper two
Z
FIG. 5. _1to 3, diagrams illustrative of the cell-division in the formation of the antheridium of Hepaticae.
1 and 2, Sphaerocarpus terrestris. 3, view from above of the apex of a young antheridium of one of the Junger-
manniaceae. 4, diagrammatic representation of an antheridium of an acrogynous Jungermannia in longitudinal
section. 5, Blyttia Lyelli. Cell from the wall of an opened antheridium. The side which is now concave was
originally the convex outer side. Highly magnified.
cells divide into quadrants and make the body of the antheridium. In the other
Jungermanniaceae the body of the antheridium usually is derived from ove transverse
disk. This commonly divides by a first longitudinal wall (1 in Fig. 5, 3) into halves;
two longitudinal walls (2, 3 in Fig. 5, 3) then cut this obliquely; and the manner in
which the inner space is formed is shown in Figure 5, 3. We do not know the
reason for this remarkable deviation’ from the customary formation of quadrants,
but it is not quite constant, and Leitgeb’ found the normal formation of quadrants
in the antheridium of Scapanieae.
(4) Musci. The cellular construction of the antheridia appears to be fairly
uniform in this class so far as we as yet know %, and the body of the antheridium is
built up through the formation of a two-sided apical cell. The divisions through
which the separation of the cells of the wall and the inner cells comes about
correspond with those of the antheridium in Jungermanniaceae (Fig. 5, 3). In
many forms the antheridium has a stalk which is a short cell-row in Nanomitrium
1 Tt is also found in the antheridium of Musci.
? Leitgeb, Untersuchungen iiber die Lebermoose, Graz, ii (1875), p. 43.
$ For an account of the divergent type of Sphagnum see Leitgeb, Wachstum des Stimmchens und
Entwicklung der Antheridien bei Sphagnum, in Sitzungsberichte der Wiener Akademie, lix, 1 (1869).
In my view the case of Sphagnum requires further investigation. Its mature antheridium belongs
to the type of the Hepaticae.
14 SEXUAL ORGANS OF BRYOPHYTA
and other Phascaceae but a very long one in Buxbaumia (Fig. 105); in others the
stalk is a short cell-mass.
29. THE ARCHEGONIUM.
1. STRUCTURE AND POSITION. The form of the archegonium is every-
where uniform in so far as it consists of a neck which provides the path for
the spermatozoids attracted by a substance exuded from its open mouth,
and of a venter which contains the egg (Fig. 6). The Anthoceroteae
(Fig. 83, 1) differ from all
other Bryophyta in having
their archegonia sunk in the
thallus, and this of course in-
volves a modification in the
history of their development
which in Anthoceros itself ap-
proaches in some measure the
type of development which is
exhibited by the Pteridophyta.
The ‘free’ archegonia of
the other Bryophyta have
either no stalk as in Riccia or
a stalk (Fig. 2) which may be
short or long and is longest in
some Musci. The stalk, unlike
that of the antheridium, has not
merely the function of bringing
the neck of the archegonium
into a favourable position, but,
where it is massive, is destined
Fic. 6. Marchantia polymorpha. 4, young arche- to be of use to the embryo,
the fa fe be eetoedies oh tcoinie eens and after fertilization has taken
yD Senos ae) a ‘Mapuitied place it may grow to a con-
540. After Strasburger. i E
siderable extent (see Fig. 119).
The embryo bores in the first instance into the stalk and may go no further,
as in Nanomitrium (Fig. 120), or, as in other forms, it may penetrate into
the tissue beyond the stalk. This subject will be discussed when the rela-
tionships of the embryo in Calypogeia are described ’.
The mature archegonium possesses a neck traversed by a row of cells, the
neck-canal-cells (Fig. 6, A, #’) and a venter enclosing a central cell. This
central cell divides by a transverse wall into an upper cell, the ventral canal-
cell (Fig. 6, A, #”), and an under cell, the egg (Fig. 6, A, 0); these two
1 See p. go.
THE ARCHEGONIUM 15
cells are often equal in size but commonly the egg is the larger. Wedonot
know the significance of this division or whether the ventral canal-cell has
any definite function such as that of the secretion of the attractive substance
for the spermatozoids. Hypothetically we may regard the ventral canal-
cell as the vestige of a second egg, but we know nothing definitely about it,
yet its constant occurrence points to its possession of a physiological role.
The neck-canal-cells furnish the mucilage which fills the canal of the neck
after the opening of the archegonium. Their protoplasm, so far as it
is not employed in the formation of mucilage, dies off, as does that of the
ventral canal-cell. I have no doubt that the mucilage filling the canal
of the neck at first protects the egg against contact with water. This is
a function which very often attaches to mucilage even where it lies within
a cell-membrane!.
2. OPENING OF THE ARCHEGONIUM. The opening of the archegonium
is brought about by the separation of the apical cells of the neck, and perhaps
processes similar to those observed in the case of the antheridium occur
here also.
Fic. 7. Scheme of the development of the archegonium of the Hepaticae. 1, 3, and 4 in longitudinal section.
2,from the top. d, lid-cell; s#, stalk-cell; c, primary central cell; the dotted line from cin 3 and c in 4 should
run to the central cell of the figure ; 4, mother-cell of the neck-canal-cells ; c1, secondary central cell which divides
into ventral canal-cell and egg.
3. DEVELOPMENT OF THE ARCHEGONIUM. Passing now to the
development of the archegonium, it may be asked if this conforms in any
measure with that of the antheridium. I have elsewhere shown? that it is pos-
sible to establish amongst the lower plants homologies in the development
of the male and the female sexual organs, but that the higher the differentia-
tion the more do differences appear from the beginning in the construction of
the two kinds of sexual organs. In the Bryophyta such differences exist, but
they do not make impossible the occasional occurrence of malformations ®
which are half archegonia, half antheridia ; even as amongst the Spermo-
? Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 233. See also Schilling, Anatomisch-
biologische Untersuchungen iiber die Schleimbildung der Wasserpflanzen, in Flora, Ixxviii (1894),
p- 280.
? See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884), p. 416.
$ See Lindberg, Ofverging af honorgan till hanorgan hos en bladmossa, in Ofversigt af Kongl.
Vetenskaps-Akademiens Forhandlingar, Stockholm, 1879, No. 5.
16 SEXUAL ORGANS OF "BRYOPHYTA
phyta the appearance of pollen has been observed in ovules!. The presence
of divisions like those in the antheridium within the mother-cell of the arche-
gonium in the Bryineae is not to be considered as indicating a conformity
of the formation of the archegonium with that of the antheridium, because
they have nothing to do with the construction of the special body of the
archegonium but only with that of its stalk.
How far the development of the archegonium ? is alike in the two series
of the Bryophyta and within each series is a matter in regard to which at
present there is no agreement amongst observers.
(2) Hepaticae. The following is the scheme
of development. The archegonium takes origin from
a single cell here as everywhere else. This divides
into a lower cell (Fig. 7, 1, s/) which limits the arche-
gonium below by forming the usually short stalk, and
an upper cell. The upper cell divides by three
longitudinal walls (Fig. 7, 2) into a central cell
and three peripheral cells; the central cell then
divides by a transverse wall into the lid-cell (Fig. 7,
3,@), and the primary central cell (Fig. 7, 3,¢). The
primary central cell next divides by a transverse wall
into two cells (Fig. 7, 4, 4, ¢,). The cell & is the
mother-cell of the neck-canal-cells and forms them by re-
peated transverse divisions. The cell c, is the secondary
central cell and divides into the ventral canal-cell and
the egg. The peripheral cells form the neck, the
lid-cell d repeatedly dividing *. In the Anthoceroteae
the general scheme is the same, but the mother-cell
is sunk in the tissue and the mother-cell of the neck
is cut off from the lid-cell 2; this cell d has therefore
Fic.8 Mnium undulatum. De. 0 further share in the construction of the neck be-
velopment of the archegonium. J, 17, cause this does not reach above the surface, but it
IIT, IV, show successive stages. The
archegonium, 4, begins to be laid aT - . ;
down'n JZ 'd lid-ccll. sf stalk, not Vides by tranverse walls into four cells lying in one
shown in /V7; * in ZY, the lidcell plane which separate from) One) anotmer sala vater
which acts as an apical cell.
period.
* Compare the case of Begonia: Goebel, Beitriige zur Kenntniss gefiillter Bliiten, in Pringsheim’s
Jahrbiicher, xvii (1886), p. 246.
* Since this was written I have come to the conclusion that the homology between the construction
of the sexual organs in Musci can be traced to their inception and that the archegonium corresponds
to one half of the antheridium. See Goebel, Uber Homologien in der Entwicklung minnlicher
und weiblicher Geschlechtsorgane, in Flora, xc (1902), p. 295.
* See Janczewski, Vergleichende Untersuchungen iiber die Entwicklungsgeschichte des Arche-
goniums, in Botanische Zeitung, xxx (1872), p. 377; Douglas Campbell, The Structure and
Development of Mosses and Ferns, London, 1895; Gayet, Recherches sur le développement de
Varchégone chez les Muscinées, in Annales des sciences naturelles, sér. 8, iii (1897), p. 161, where
details regarding the number of canal-cells and so forth are given.
* Notwithstanding Janczewski’s statement to the contrary. See Gayet, op. cit.
THE ARCHEGONIUM ET
(2) Musci. According to the statements of Janczewski, Kiihn, and
Campbell, the development of the archegonium of Musci differs from that of the
Hepaticae chiefly in this, that the neck-canal-cells do not arise by the division of
one mother-cell but are produced in part by a peculiar growth of the lid-cell.
This lid-cell acts as an apical cell (Fig. 8, ZV, *) and furnishes segments having
walls parallel respectively with the axis and the base of the archegonium, the outer cells
thus formed become cells of the wall of the neck, the inner ones become neck-canal-
cells. Gayet contradicts this. According to him the course of the development
is in essentials like that of the Hepaticae, that is to say, the lid-cell forms new cells
of the wall of the neck but no internal segments. From my examination of Mnium
undulatum (Fig. 8) I cannot confirm what Gayet says: I find in this plant
confirmation throughout of the statements of Janczewski and others, and that the
archegonium of the Musci is distinguished from that of the Hepaticae by its peculiar
apical growth (Fig. 8, ZV, *). The stalk of the archegonium of Mnium undulatum
which I select as an example is very strongly developed. It is furnished with plastic
material which the young embryo uses up, and it contains also a definite nutritive
tissue for the embryo, which after fertilization increases in amount; this feature
which appears to have been hitherto overlooked corresponds to what we find in the
development of the seeds in the Spermophyta. The primordium of the stalk
precedes that of the body of the archegonium. In figure 8, /, the primordium
of the stalk growing by means of a two-sided apical cell is alone visible. Out of its
terminal cell the primordium of the body of the archegonium proceeds (Fig. 8,
IT, A), and this increases by apical growth in the way described.
From what I have said it will be seen that the relationships in the
process of cell-construction, as well as those of the mature structure of the
sexual organs, are characteristic of the large group of the Bryophyta. They
have ‘ varied’ less than has been the case in the vegetative organs.
GOEBEL II G
HEP Avie
I
VEGETATIVE ORGANS OF HEPATICAE
1. RELATIONSHIPS OF SYMMETRY.
THE statement made above!’ regarding the great variety of the forma-
tion of vegetative organs in the Bryophyta requires qualification in so far as
the relationships of symmetry are concerned. Amongst Musci radial and
dorsiventral forms of different construction are found”, but amongst the
Hepaticae the dorsiventral type, and in association therewith plagiotropous
growth, predominates, and the vegetative body either clings to the sub-
stratum * or grows up obliquely from it. The group of Calobryaceae, which
includes Calobryum and Haplomitrium, is however orthotropous; and so
also are the sexual shoots of some forms and the shoots bearing gemmae.
Some species of the remarkable genus Riella are also orthotropous, but they
have only an apparently radial thallus ; in reality the thallus is a modifica-
tion of the dorsiventral®. The species of Riella possess a many-layered
axis bearing a unilateral ‘wing’. In some, for example Riella gallica,
the axis lies upon the substratum, fastened to it by rhizoids on its under
side. Such species diverge from the ordinary forms of Hepaticae merely
in having the wing developed in a profile position, and this is also the case
if the plant is fastened only at its base. In those species of Riella which
grow erect the wing is arranged like a spiral stair round the axis. Its
origin is always unilateral and the subsequent configuration may be attained
to in one of two ways,—either the wing grows more in length than the
thickened axis of the thallus, or a torsion of the whole vegetative body
takes place. In the cases which I have investigated I have only met with
the first of these, the thallus having a more or less strong wndulation
peSee palsy 2 See Part I, p. 100.
* The plagiotropous growth of most Hepaticae is connected, in my opinion, with their rooting.
Their unicellular—usually very short—rhizoids cannot serve so well as anchoring organs and as
absorption organs as the much longer usually pluricellular rhizoids of the Musci; therefore they
make any great extension from the substratum disadvantageous. From this point of view the
possession by the only radial Hepaticae, the Calobryaceae, of root-shoots instead of rhizoids is
no accidental circumstance.
* See Part I, p. 87 and Fig. 41.
RELATIONSHIPS OF SYMMETRY 19
(Fig. 9), and Trabut' also who examined many living plants found the
same in them. On the other hand Leitgeb?, as the result of his study of
dried specimens, describes a torsion extending over the wingless basal portion
of the axis, the surface of which he compares with a strongly twisted cord.
Probably both undulation and torsion occur. At any rate both states have
the same significance in Jdiological relationship—they place the wing not
11. HT.
Fic. 9. Riella Clausonis. Upon one side of the axis is FiG.10. 1, Riella Battandieri. Upper part of
seen the winding wing in which the antheridia are sunk. If plantlet in profile. At ¢ a pit inthe wing in which
these are not developed the wing ismore prominent. Uponthe anow emptied antheridium sat. At ? an arche-
under side large scales containing chlorophyll (leaves) are | gonium surrounded by arenvelope. vw, vegetative
seen, which Be ee in the figure than the wing. Magnified. point. 11, scheme of Riella. 111, scheme of one of
the Marchantiaceae ; the thallus seen in transverse
section. Magnified.
vertically, but transversely or obliquely to the light falling upon it from
above. We may find an explanation of the whole process of the formation
of the wing in the fact that submerged water-plants are sensitive to
light of strong intensity, and in the case of small creeping forms, or even
of those growing erect in shallow water, injury from the light would
' Trabut, Révision des espéces du genre Riella, in Revue de botanique, iii (1891), p. 433.
? Leitgeb, Untersuchungen itiber die Lebermoose, Graz, iv (1879), p. 75.
C2
20 VEGETATIVE ORGANS OF HEPATICAE
be obviated by the development of the wing in the vertical plane.
Larger forms of Riella are able to grow up in deeper water ', and they live
therefore in subdued light which they can use better by the oblique position
of the wing, and this is attained by undulation or torsion. Leitgeb’s con-
jecture that the germ-plants wind round a support after the manner of
a twining plant appears to be extremely improbable, because the undulation
of the wing or the torsion of the whole plant is connected in my opinion
with the relationship to light and not with the fixation of the plant.
In other thallose He-
paticae the ‘wing’ of the
thallus is spread out flat
(see the scheme in Fig. 10,
Ti). “The central jaxis of
the thallus is usually the
thickest, and it serves asa
place of storage of material
as well as for its conduction ;
and it also acts mechani-
cally asa ‘rib, which is par-
ticularly prominent in forms
which possess a wing con-
sisting of one layer of cells;
Metzgeria and Blyttia for
example. The thallus of
Metzgeria and Aneura is a
simple cell-surface in the
Fic. 11. Metzgeria furcata. Apical region of the thallus seen
from above; 4, the apical cell; Ss‘ to s'’4, successive segments; 7, 2, = > aes F 2
portion of segment s// devoted to the formation of the midnis mee juvenile condition ’ the rib
wl, marginal cells of successive grades; #, surface-cell of first grade ;
c, mucilage-hairs upon the under side of the thallus. After Stras- only appears at a_ later
Burger’ -Maguified! 540. period, and in Aneura it is
not sharply marked off from the wing. The wing makes an indentation
at the apex of the thallus in which the vegetative point lies.
2. VEGETATIVE POINT AND ARRANGEMENT OF CELLS.
The arrangement of the cells at the vegetative point has been the
subject of numerous and thorough investigations ; but few facts of importance
from the point of view of the organography of the Hepaticae have resulted
from these, and therefore they do not require to be spoken of here in
any detail.
The vegetative point of most Hepaticae possesses a distinct apical cell which has
been recognized by Leitgeb and others even in cases where the apex is occupied by
' Montagne says that Riella helicophylla grows at a depth of seven decimeters.
* Strasburger, Das botanische Practicum, Jena, 1884, Fig. 112.
BRANCHING Ze
a number of cells like one another in form. In such cases, for example in Anthoceros,
Blasia, Riccia, the apical cell cannot well be distinguished from its segments, and
one might speak of an apical angle.
The configuration of the apical cell appears to be constant at corresponding
stages of development within one genus usually and even within larger groups.
Thus the Aneureae including Aneura, Metzgeria (Fig. 11), and Hymenophytum
possess a two-sided wedge-shaped apical cell. But it may change even within ove
genus ' and in the course of development in oxe f/ant. It is, for example, two-sided
and wedge-shaped in the germ-plants of Preissia and Marchantia polymorpha, but
it is four-sided and pyramidal in the mature plant. The
interest of this lies in this,—it shows that the form of
the apical cell stands in relation to the whole vege-
tative body. Forms of thallus which are thin cell-surfaces,
as in Metzgeria where the midrib alone has many layers
and in the germ-plants of Marchantia, have a two-sided
apical cell which gives off segments only to the right and to
the left. Those, on the other hand, which have a massive pyg 12 Riccia _fluitans.
construction throughout have a four-sided or a three-sided forked | branching thallus.
pyramidal apical cell, which from the beginning gives off {he Branches. Natural size.
segments above and below also. Other factors, however,
have also an influence. We find, for example, that Aneura pinguis with a thick
thallus has a two-sided apical cell, and Cyathodium with its very thin thallus has an
apical cell like Marchantia®. It is evident then that the factor of affinity operates
also.
3. DIFFERENTIATION OF ORGANS.
A. BRANCHING.
The branching of the thallus takes place partly in the plane of its
flattening, partly upon its under side. The latter is predominant in
Hymenophytum and many others; but it is rare elsewhere, for instance in
the Marchantieae, and in Metzgeria it is limited to the sexual shoots,
whilst in Pellia and many others it is wanting altogether *.
Twigs which are not ventral always proceed from a new apical cell laid down in
the vicinity of the old one. An actual bipartition of the apical cell so as to produce
a forking such as the mature condition would suggest does not take place (see
Fig. 15). It is characteristic of the branching that a ‘middle lobe’ shoots out
between the two new apices and is the common basis for the wings of the two
separating lateral shoots (Fig. 14).
1 Pellia epiphylla differs from P. calycina and Blyttia Lyallii from B. decipiens in this respect.
See Leitgeb, Untersuchungen iiber die Lebermoose, iii (1875), pp. 54, 80; Farmer, Studies in
Hepaticae: On Pallavicinia decipiens, Mitt., in Annals of Botany, viii (1894), p. 40.
2 According to Leitgeb’s figure.
$ I have on the other hand met with ventral shoots in Aneura. Why these should be so con-
spicuous in some forms it is difficult to explain at present, but it is easy to see that corsal shoots
would be most disadvantageous.
22 VEGETATIVE ORGANS OF HEPATICAE
The relationship between the configuration of the thallus and the kind
and method of construction of the several branchings is of some interest. In
Fic. 13. Hymenophytum Phyllanthus. The plant seen from below. The thallus has a midrib and is grown out
at the point into a stolon-like process. It bears five ventral shoots, and there is the primordium of a sixth at the
right side of the lower part of the figure. Two of the shoots which remain very short are female sexual shoots, the
one on the left has developed a sporogonium. A, margin of the sexual shoot; /, perichaetium; .S, perianth.
Magnified 5.
the first place, it may be noted that in many thallose Hepaticae the
formation of the wing on the thallus may be suppressed over a portion of its
extent. This is seen at the base of lateral shoots, and also at the point of
Fic. 14. Anthoceros fimbriatus. Surface view of the dividing apical region. There are many vegetative
points, S, between which are the middle lobes which later grow out into crested structures. Highly magnified.
shoots of first order in Hymenophytum (Fig. 13), in Blyttia, and others. It
also occurs in e¢iolated shoots of other Hepaticae through the absence
BRANCHING 23
of light, but here it belongs to the normal course of development, inasmuch as
the shoots which spring from the ventral side of the thallus are those which
are at first wingless in correspondence with the fact that in their first develop-
mental stages they obtain very little light. We observe then on these shoots
a division of labour; the wingless portion serves to bring the assimilating
portion into the light. A sharper division of labour occurs when the wingless
portion serves also as an anchoring organ and as the absorber of nutriment
from the soil, and thus in a measure corresponds with the root of higher
plants. The assimilation-shoot has then no hair-roots; it raises itself above
the substratum. If we imagine the wingless, apparently cylindric, but
often somewhat flattened, portion to bore into the soil, and the winged
=" i
Fic. 15. Metzgeria furcata. Branching; 7’, old Fic. 16. Symphyogyna sinuata, or an allied form
apical cell; 2, new apical cell ; 7”, #2'”, marginal cells from Martinique. The thallus has leaf-like lobes which
of first and second grade; 4, surface-cell of first grade; disappear in its upper part. The growth is sympodial.
¢, mucilage-hairs. After Strasburger!. Magnified 540. The successive shoot-generations are numbered I, I,
III, Iv, V; each begins with a stalk-like portion in the
substratum, and gradually expands into the lobed
portion above the substratum. Magnified 3.
portion to raise itself above that and to be endowed with limited growth,
we obtain a form of thallus which occurs with a varying degree of limitation
in the cycle of affinity of Blyttia, Symphyogyna, and others. Fig. 16 is an
illustration of Symphyogyna sinuata in which the winged lobed thallus
appears*. In it the winged shoots can again decrease at the apex and
become stolons, but usually they conclude their growth after reaching
a definite medium size, and then at their base they form a ventral lateral
shoot which as a stolon continues the growth, subsequently rises above the
substratum, broadens out, and then again forms a ventral shoot, and so on.
In Fig. 16 there is a chain of five such generations, forming a sympodial
1 Strasburger, Das botanische Practicum, Jena, 1884, Fig. 113.
? See what is said afterwards upon the transition to the formation of leaves, p. 37.
24 VEGETATIVE ORGANS OF HEPATICAE
rhizome upon which assimilation-shoots stand as apparently lateral structures.
In foliose forms we find exactly similar features, and the behaviour is
biologically the same as that exhibited by the sympodial rhizome of species
Fic. 17. Symphyogyna sp. I gathered this in 1890
at Tovar in Vehenlae The divided, fan-like sania
of the thallus is the continuation of the nearly cylin-
dric portion on the right. Upon it arise two ventral
lateral shoots of which one, the upper, rises above the
substratum, becomes flattened, and has begun to fork.
Magnified 2.
FiG. 18. Blyttia decipiens. I gathered this in Fic. 19. Hymenophytum flabellatum. Seen
1885 at Nuwara Elyia in Ceylon. Illustration of from the under side. ‘The plant on the right of the
the habit of a male plant with two cylindric ventral figure bears fructification, and a lateral shoot aris-
lateral shoots. Magnified 2. ing to the left has produced two small sexual shoots
appearing as scales upon its under side. Mag-
nified 2.
BRANCHING 25
of Polygonatum. If the assimilation-shoots, which here have limited
growth, possessed a leaf-like habit, and this would be more marked if they
branched by repeated forkings, we should have structures like the leaves of
many ferns!; and, indeed, from the point of view of their function, they
would be exactly the leaves of a small Hymenophyllum. It is of special
interest to note that in no fewer than three genera do we find this form of
the vegetative body—namely, in Symphyogyna (Fig. 17), Blyttia (Fig. 18),
and Hymenophytum (Fig. 19). They are, it is true, allied, but each of them
begins as a creeping, simple thallose form, and independently of the others
attains the configuration— shall we call it hymenophylloid ?—depicted above.
The figures will show how nearly these
parallel forms correspond outwardly
with one another, and we can only
obtain evidence enabling us to say to
which genus any individual plant be-
_longs by an examination of the arrange-
ment of the sexual organs.
Fic. 20. Aneura bogotensis. From the Fic. 21. Aneura eriocaulis. Habit of the
rhizome indicated by dotted shading the forked plant. At the base ‘roots.’ The chief axis
thallus-branches have shot up. Magnified has been broken off above. Magnified 5.
many times.
In the genus Aneura there are many gradations up to the division of
labour of the species with richly branched thallus. There are species like
A. pinguis in which all the vegetative shoots behave alike *, but it is different
especially in epiphytic species, amongst which is Aneura bogotensis.
A portion of a ‘stolon’ of this plant is represented in Fig. 20. Its vegetative
body shows two parts—the one indicated in the figure by dotted shading
lies on the substratum as a creeping rhizome which is not sympodial, the
1 See Farmer, Studies in Hepaticae: On Pallavicinia decipiens, Mitt., in Annals of Botany, vili
(1894), p- 36.
2 Those which bear the sexual organs we leave out of consideration here.
26 VEGETATIVE ‘ORGANS OF HEPATICAE,
other consists of a number of dichotomously branched members which
spring as lateral shoots from the creeping axis, and in a measure perform
the function of leaves. In Aneura (Pseudoneura) eriocaulis (Fig. 21) we
find a much higher division of labour. Its chief axis is differently con-
structed from the lateral axes, especially the terminal branchings of these,
here of the third order. These terminal branches have limited growth, are
organs of assimilation, although some of them also bear reproductive organs,
and in correspondence with their function they are thin plates thickened only
in their middle portion. The chief axis, on the other hand, whose function is
partly a mechanical one, partly that of conveying nourishment ', has almost
a cylindric outline on cross-section, although there is a slight flattening
visible upon the upper and the under sides*. Whereas in Aneura hymeno-
phylloides (Fig. 47) and A.
fucoides stronger mechanical
claims are made upon the
chief axis than upon the
lateral axes, more of its cells
exhibit thickened walls (Fig.
22), and the difference be-
tween the two axes is there-
fore greater. In other words,
starting from a thallus with
throughout similar branch-
ing (Fig. 12), a progressive
differentiation into stem and
leaf appears, and we are
Fic. 22. Aneura fucoides. Upper figure; chief shoot in able clearly bor fellow “its
Sea eens aes figure; lateral shoot in transverse evolution. These species of
Aneura possess also ‘ roots.’
There are forms which no longer lie with the whole under-surface upon the
substratum, but which fasten themselves to it by means of special anchoring-
organs (Figs. 21, 23). These anchoring organs are distinguished from the
4 See Part Wy pii3z4:
* The differences between the chief and lateral shoots in the species of Aneura are brought about
through the suppression from the first of the formation of the wing on the chief axis, and through
the assimilation-shoots in the middle region of the thallus undergoing only few divisions. There are
of course transitions, that is to say, forms in which the difference between the chief axis and the
lateral axis is simply one of the greater thickness of the former. Stephani’s statement, in Hedwigia,
xxii (1893), p. 12, that the thin membranous wing often thickens as it gets older until it becomes
a stalk with a cylindric cross-section is, so far as I have observed, an error. The same author says
(Colenso’s New Zealand Hepaticae, in Journal of the Linnean Society, Botany, xxix (1892), p. 264)
‘in Aneura fucoides, on the contrary, the thickness of the stem, similar to that of our forest trees,
is continually increasing with advancing age.’ Regarding this I may say that I believe a secondary
growth in thickness in Aneura fucoides like that of tree-stems is entirely out of the question, because
of the thickness of the peripheral cells.
APPENDAGES. MUCILAGE-HAIRS. SCALES 27
assimilation-shoots by their direction and their configuration. They are
smaller and lie clinging to the substratum. That they are no ew forma-
tions, but merely transformations of the lower branches of the thallus, is
proved by our finding not infrequently NG
an assimilation-shoot grown out into !
a ‘root’ (Fig. 23), and there can be a
no doubt that assimilation-shoots could
arise upon the ‘roots, although this does
| ee
not usually happen. External influences
probably determine these changes. Un- x
fortunately there has been as yet no
experimental examination of these
forms, of which the organs are not so
sharply limited from one another as
they are in the higher plants, and the
culture of such plants in Botanic Gar-
dens would be of great interest. Fic. 23. Aneura fucoides. Basal part of a plant.
The higher differentiation of the A lateral shoot has become transformed into an
anchoring-organ; it lies in close contact with the
; 1 ‘ surface of the leaf of one of the Spermophyta; on
vegetative body with which we have the branches below it the apices have elongated into
iithero dealt has arisen through > Mesnifed
differences in the construction of the branches of the thallus; but this is
not the only path along which the higher differentiation has been reached.
A second way is that of the appendages of the thallus.
B. APPENDAGES.
1. Mucilage-hairs. Scales.
We find appendages in the lowest members of the Hepaticae taking the
form only of hair-like bodies secreting mucilage which surround the vege-
tative point and often arise in definite order (see Figs. 11, 15),and ought to be
considered as protective organs to the vegetative point. Such mucilage-hairs
are wanting in the Anthoceroteae, where the vegetative point is nevertheless
always covered with a thick pellicle of mucilage because mucilage-slits,
another form of mucilage-organ, are present ; secretion of mucilage is absent
from the Riccieae, from many Marchantieae, and perhaps also from Riella,
and its absence in the last-mentioned plant is the more striking because
water-plants so commonly protect their young parts by copious secretion of
mucilage’. The secretion of mucilage by most of the Hepaticae which live
on moist spots serves not only as a means of protection against drought, but
* At the apex of the ‘leaves’ of Riella which will be described later a papilla is frequently found
which may perhaps secrete mucilage. Small papillae of unknown function are found in various
places upon the thallus of Riella helicophylla.
28 VEGETATIVE ORGANS OF HEPATICAE
also and specially against water. A similar protection, as will be explained
presently, is given to the growing sporogonia by envelopes of different kinds.
Mucilage-organs are also found in the foliose Hepaticae, in exceptional
amount in Anomoclada mucosa ', which is covered with a thick envelope of
mucilage. Mucilage-organs may appear also in the thallose Hepaticae in
the guise of simple papillae. These appendicular organs of the thallus
deserve mention here, the more because their biological significance has
hitherto received little notice, although the relationships between configura-
tion and function are extremely evident. The series of the Marchantiaceae,
of which we shall presently speak, supplies us with instructive illustrations.
All thallose Jungerman-
niaceae and Marchantieae
have at first appendicular
organs for the protection
of the vegetative point.
Leitgeb’s statement that
they are wanting in Mo-
noclea is an error (see
Fig. 4, 7/7), the result of
the examination of un-
favourable material. In
Riccia crystallina? which,
according to Leitgeb, pos-
sesses no scales, I found
them as very delicate
structures, but perhaps
Fic. 24. Blasia pusilla. 1, vegetative point in longitudinal section; - -
#, amphigastrium with mucilage-papilla, e; 0, leaf-auricle with outer there are some forms of
papilla, /, as well as inner papilla, 7; 00, papilla of the upper side of the ‘ H
thallus. 1, similar section through a younger amphigastrium. Letter- this species where the
ing the same. IJ, young leaf-auricle seen from above. After Leitgeb. scales are wanting, be-
cause an observer like Leitgeb would scarcely have overlooked them
were they present.
JUNGERMANNIACEAE. Mucilage-papillae are of common occurrence
in this group. In Blyttia and Morkia they are upon both sides of the thallus,
in Metzgeria only upon the under side. They are simple and club-shaped in
Metzgeria and Aneura, or the mucilage-secreting cell stands at the end of a
cell-row as in Morkia (Fig. 25, 1), and this gives us a transition to the scales.
These mucilage-organs arise in a definite order, for example, in Metzgeria.
Blasia. The relationships in Blasia are somewhat peculiar and com-
plex. Besides the lateral leaves which are inserted horizontally we find—
* See Spruce, Hepaticae amazonicae et andinae, in Transactions of the Botanical Society of
Edinburgh, xv (1884), p. 407.
* I am indebted to Dr. Levier of Florence for the specimens of this species as well as of many
other interesting Hepaticae. Ss Seespye 7a
APPENDAGES OF THE THALLUS. MUCILAGE-HAIRS. SCALES 29
1. Mucilage-hairs: simple papillae springing out of the upper and the
under side of the thallus (Fig. 24, I, 00).
2. Amphigastria: scales containing chlorophyll and standing upon
the under side of the thallus with their under edge growing downwards
beyond the point of insertion (Fig. 24, I, 7); also half-shield-like scales
which are arranged in two longitudinal rows in such a manner that usually
an amphigastrium corresponds to one lateral scale. Each amphigastrium
bears also originally at its apex a mucilage-papilla (Fig. 24, I, e), which is
displaced subsequently to one side, as it is in many Marchantiaceae.
3. Leaf-auricles : spherical bodies (Fig. 24, 111) formed by the incurving
of a cell-surface rising above the surface of the thallus and then coming
into contact again with it (Fig. 24, I, 0). They are usually infested by
a nostoc. They form mucilage, having in their interior a mucilage-papilla
(Fig. 24, I, z), and another near the aperture leading into their cavity
Bic. 24, 3, f).
One might describe the development of these different appendicular
organs of Blasia by saying that they all proceed from mucilage-hairs. The
scales would arise by the supporting cells of definite mucilage-papillae
growing out and thus bringing these still nearer to the apex of the thallus,
as happens also in Sphaerocarpus, Morkia and others where the mucilage-
papillae are borne upon cell-rows. Individual scales would then be trans-
formed into leaf-auricles, perhaps primarily in consequence of external
stimuli. We cannot at present say for what reason so richly membered an
apparatus for the protection of the vegetative point has been produced in
Blasia.
MARCHANTIACEAE. The formation of scales in Blasia may lead us
on to the series of the Marchantiaceae in which we find the vegetative point
almost exclusively protected by scales which appear in very different
number and configuration.
Riccieae. The formation of mucilage is unknown in any Riccia, and
it occurs but seldom in the Marchantieae. In Riccia the scales do not lie
over the vegetative point but they only lean upon its outside. A longitu-
dinal section therefore of the apex of Riccia exhibits an appearance different
from that of the apex of Marchantia. The reason for this is that the vege-
tative point of the Riccieae lies in a cleft formed by the protuberant Jateral
portion of the thallus, and this needs to be closed by the scales only upon
one side ; the surfaces of the protuberant lateral portions of the thallus are
often so closely apposed that their cells are interlocked.
Most of the Riccieae have only one row of scales! standing in the
middle line of the thallus, and these, except in Riccia fluitans, subsequently
* Contradictory statements are not infrequently found in the literature, but without the historical
developmental basis which alone is of value.
30 VEGETATIVE ORGANS OF HEPATICAE
become torn, and protection of the vegetative point against drought is
effected by the air which is held between them, and the entrance of water is
also thus prevented. In Riccia lamellosa the scales reach far beyond the
lateral edges of the thallus; they are indented in the middle, which may
perhaps be recognized as the first indication of the appearance of more than
one row of scales; certainly it is an indication of fission. In Oxymitra
pyramidata we find two rows of scales which, as is shown in Fig. 25, IV,
form an extremely dense plug to the apical cleft by their interlocking one
with the other. As this is a genus of drier habitats than the other
2
si
Fic. 25. 1, Mérkia. Cell-row with a mucilage-papilla at its apex. 11 and 111, Cyathodium cavernarum. Two
point & practically clacedita the ontalde by the incor Ingle Series st tamale ta
Riccieae we can easily understand that the vegetative point requires more
special protection. The features of Riccia natans will be described after the
scales of the aquatic forms are described.
Marchantieae. The Marchantieae, including Corsinia, are distinguished
by having their vegetative point in a flat depression over which the scales
bend (Fig. 26); it is not in a narrow cleft as in the Riccieae. Cyathodium,
a genus which inhabits very feebly illuminated spots, has cell-rows instead
of scales (Fig. 25, 11, 111), evidently because an elaborate protection of the
apex is superfluous ; the germ-plants of Marchantia have a like arrange-
ment. The scales in Marchantia and other genera stand immediately
behind the vegetative apex. The tip of the young scale takes the form of
a Club-like hair, which in Targionia, Sauteria, and Dumortiera remains
inserted upon the edge of the scale usually at the apex of a lobe-like
APPENDAGES OF THE THALLUS. MUCILAGE-HAIRS. SCALES 31
projection. In others, again, there is formed upon the under side of the
scale at its base defore the construction of its apical papilla is completed an
outgrowth which soon overtops the papilla and pushes it to the upper side,
in the same way as the mucilage-papilla of the amphigastrium of Blasia?
is displaced. This outgrowth, consisting at first of a single cell, becomes a
cell-surface and may be called the apical appendage, and it shows beautifully
how its form is conditioned by its function. In Fig. 27 we have an illustra-
tion of the under side of the thallus of Marchantia chenopoda. It bears
two rows of scales, the majority of which still possess the apical appendage
Fic. 26. Plagiochasma Aitonia. Male Fic. 27. Marchantia chenopoda. An Andine species. Apex
plant, with five antheridial groups, seen from of the thallus seen from below. There are two rows of scales.
above. The scales upon the under side bend Towards the upper left side of the figure an additional one is
over the vegetative point. The younger visible. Each scale has an apical appendage which originally
antheridial groups are protected also by arched over the vegetative point and subsequently falls away.
overlapping scales which form their perichae- Magnified 15.
tium. Magnified 8.
which is sharply marked off from the broad scale, is darker in colour than it,
and has at its base a constriction at which its edges are bent downwards.
This constriction corresponds exactly to the width of the apical depression.
Over the apex these apical appendages alone are bent, and they lie upon it
like the leaves of a book ; subsequently they are displaced to the under side
of the thallus and then readily fall off. They have now become functionless,
their work has been done ; but this is not the case with the scales. These have
stillan important duty. The scales lying upon the midrib form a canal within
which the tufts of rhizoids run to penetrate the soil further back under the
U Seep. 29:
32 VEGETATIVE ORGANS OF HEPATICAE
thallus. The tufts of rhizoids are protected from loss of water by the scales,
ana are held together by them so that where they occur in great masses, as
in xerophilous forms, they make wick-like strands and the water then does
not pass merely into the lumen of the rhizoid but passes upwards between
the rhizoids by capillarity. This relationship of the scales to the rhizoids is
particularly striking in Marchantia polymorpha and other species in which
there are not only scales in two rows approaching the midrib, but also over
the surface of the thallus. It will
not be superfluous to say a word here
regarding these relationships. *
Marchantia polymorpha has_ been
figured and described times without
number, but the distribution of the rhi-
zoids has not attracted much attention.
We can recognize three series of scales in
Marchantia polymorpha (Fig. 28). The
median scales, which are provided
with apical appendages like those repre-
sented in Fig. 273; marginal scales,
which partially project over the edge
of the thallus; and between these
there stand scales which we may call
intermediate scales. Underneath the
median scales there runs a strand of
rhizoids, the chief strand. Rhizoids
also spring out both below and from
the marginal and intermediate scales,
wend their way united in thinner
strands to the median scale, and there
! join on to the chief strand. It thus
I comes about that a series of strands is
Fic. 28. Marchantia polymorpha, Thallus seen @@Veloped which we may compare with
from the under side. A dense strand of rhizoidslies 4 system of irrigation. The lateral
along the midrib and the strands of rhizoids which
arise under the outer scales unite with this. Single strands serve to conduct water to the
free rhizoids spring out also from the thallus.
RE Eon, marginal parts of the thallus. The
scales at this point are chiefly organs of protection and direction to the
rhizoid-strands, they are no longer protective organs for the vegetative
point. Marchantia lamellosa, which inhabits the higher parts of the Northern
Andes, has many more scales than M. polymorpha. This plant, notwith-
standing that it lives upon a moist soil, has a xerophilous character, and the
thick covering of scales upon the under side of the thallus between which
the numerous strands of rhizoids run assures a sufficient supply of water
even if the transpiration be profuse. It is further clear that the scales
SS
SS
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aN - ss
SS SW
ee :
ESL
=
4S -
.
Zr
yy f 4 “J i q "Va
oes iy
Y iy’ A J
So pee = _— Zip
S = — =
—— e ) =
SSS
SX
SSN
=
———
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SLL
eS
APPENDAGES OF THE THALLUS. MUCILAGE-HAIRS. SCALES 33
themselves standing close together will retain water by capillarity, as
happens in Aneura endiviaefolia and other species }.
Dumortiera. This genus has experienced a reduction in its anatomical
structure, which is connected with its hygrophilous character” ; it is found
growing upon moist places, under the spray of waterfalls, or upon the banks
of streams. In Dumortiera hirsuta, for example, the scales are represented
by a few ridges upon the thallus, and can serve as no protection to the
rhizoid. There is along the midrib of the thallus a strand of very thin
gee Ree nthe ean Sonics upon the under onde appear at cach vegetative point ta thres
rows. The scales of each lateral row overlap later those of the middle one.
rhizoids, but the remarkable arrangements of Marchantia polymorpha are
not found here.
We observe then that the configuration of the scales, and no less their
number, stand in the closest relationship to the conditions of life, and of
course also to the mass of the thallus. The narrow forms of Riccieae have
one row of scales, the broad Riccia natans has many rows (Fig. 29). The
1 See p. 53.
2 Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 223.
GOEBEL II D
34 VEGETATIVE ORGANS OF HEPATICAE
narrower species of Marchantia have two rows of scales, the broad Mar-
chantia polymorpha has many rows. Originally developed as protective
organs to the vegetative point the scales when they are produced in numbers
find their function in connexion with the supply of water ; they form cavities
within which the strands of rhizoids run in the manner already described in
the case of Marchantia polymorpha and others. We shall see afterwards
that between the scales on the rays of the antheridiophore in Marchantia
run strands of rhizoids to conduct water.
It is probable that these scales took origin out of ce//-rows. The case
of Cyathodium! indicates this as well as that of Corsinia in which the
ventral scales possess a terminal process—the oldest part of the scale—
consisting of a cell-row. In Hepaticae, such as Sphaerocarpus and Riella ”,
which possess no elaters, we observe the same course of development.
Sphaerocarpus possesses mucilage-papillae borne upon a cell-row. We find
in place of these in Riella complete leaf-like scales, containing chlorophyll,
which no longer serve merely as protective organs for the vegetative point,
but are also assimilation-organs (Fig. 9). This no doubt is connected on
the one hand with the direction of the thallus which exposes the scales to
illumination, and on the other hand with the influence of the aquatic life.
That the latter has an effect is shown by Riccia natans, the large water-form
of which has strongly developed ventral scales which contain chlorophyll.
These scales have here evidently the same biological significance as the
water-leaves of Salvinia, they increase the surface by which water is
absorbed ; they give the floating plant more stability ; they protect it by
their secretions against the attacks of water-animals ; and further, on account
of the chlorophyll which they possess, they co-operate in assimilation. They
are much less developed in the /and-form, and are present in it usually
as protective organs to the vegetative point oz/y. Inthe water-form they
construct in front of the vegetative point a tuft which encloses air, and thus
prevents the water from touching the apical region. Riccia fluitans (Fig. 12),
on the other hand, which also lives in water, has scales which are not endowed
with any new function, and are, as in the land-form of Riccia natans, only
protective organs; and this is so apparently because this species is more
adapted to submerged life, as its anatomical structure indicates, and its
delicate, richly-branched thallus can take up water through its zv/ole surface ;
whilst Riccia natans, which swims on the surface of the water, takes up
water through the scales. There is an interesting parallel in the behaviour
of the ventral scales in Riccia natans and in Riella, and these scales may be
designated /eaves *.
Sy SCesp. 140,
* These are in my opinion the lowest members in the series of Marchantiaceae, and approach
Monoclea in some points.
* See p. 35.
BEAVES OF THALLOSE’ FORMS 35
2. Leaves.
Another series of appendicular organs includes those which in configu-
ration and origin so much resemble the leaves of the foliose Hepaticae that
we may designate them also leaves. We term these appendicular organs
leaves if they are laid down in definite regular succession at the vegetative
point and conform in configuration and function with the leaves of forms in
which such organs have from the very oldest times been spoken of as
leaves!. The formation of leaves in the Hepaticae has arisen in a large
number of series zzdependently one of the other, and this is characteristic.
The so-called ‘ foliose’ forms, in the narrower sense of the acrogynous ones,
constitute only ove of these series, and besides those amongst the Junger-
manniaceae there are many others. If we leave out of consideration the
ventral scales of Marchantieae and Riella described above—but as I have
said we may always call them leaves in Riccia natans and Riella*—the
series of Marchantiaceae alone, so far as we know, is wanting in the forma-
tion of leaves.
(a) LEAVES OF THALLOSE FORMS.
Anthoceros. There are a few cases of a like want of leaves amongst the
Anthoceroteae, but these are not quite complete. In the genus Anthoceros
itself we find leaf-like appendages in A. fimbriatus (Fig. 50), a species I found
upon the Cordilleras of Merida. The one-layered crested appendages of the
many-layered thallus are in this species really produced by the middle lobes
which arise in the course of branching (see Fig. 14). There is a frequent
division of the vegetative point with which is associated a corresponding
formation of branches. Many of the vegetative points which are thus
formed are arrested in development, and their apical cell loses its rich
protoplasmic content and takes no further share in growth; but the middle
lobes increase and become crested appendages, which will be mentioned
again when I refer to the absorption of water °.
Dendroceros. Some species of Dendroceros show, in addition to the
leaves, other structures which are also connected with the supply of water.
I have examined Dendroceros foliatus, a species described by Spruce *.
1 See the remarks upon ‘ Formation of Organs and Division of Labour,’ Part I, pp. 21-40. Many
systematists who have studied the Hepaticae have raised objections to the use of the term ‘ leaves’ for
the organs under consideration here. Stephani (Treubia insignis, GOb., in Hedwigia, xxx (1891),
p- 190), for example, made out the leaves of Treubia, Symphyogyna, and others to be no leaves but
‘frond-lobes.’ The altogether superfluous and almost fossil expression ‘frond’ instead of ‘ thallus’
ought to be entirely discarded. But these ‘frond-lobes’ cannot be distinguished by any single
essential character from the ‘leaves’ of the foliose forms. It would be different if they arose
irregularly as outgrowths upon the margin of the thallus. But as Leitgeb has shown in Blasia and
I have proved in the cases of Treubia and Symphyogyna this does not happen. To call the leaves
of Calobryaceae ‘frond-lobes’ would be nonsense.
a See pi 34- S See p. 56.
* Spruce, Hepaticae amazonicae et andinae, in Transactions of the Botanical Society of Edinburgh,
xv (1884), p. 574. Professor Bayley Balfour was so good as to supply me from Edinburgh with
Spruce’s original specimens.
D 2
36 VEGETATIVE ORGANS OF HEPATICAE
The plant (Fig. 51) possesses a number of relatively large hood-like forma-
tions, of which we can distinguish two kinds ; one (Fig. 30, J7) corresponding
Fic. 30. Dendroceros foliatus. Apex ofa thallus; J/, middle lobes of different age, on the one to the left the
formation of holes is seen on the upper right portion. Besides these the somewhat oblique hoods, ‘the leaves,’
appear as lateral shoots on the vegetative point. Magnified.
with the middle lobe developed by branching is recognizable by its deep
emargination which indicates the beginning of a splitting; the other, in the
form of a simple hood, arises as an independent
outgrowth at the vegetative point and becomes
hollowed at a subsequent period upon its
under side. These ‘leaves’ are not attached
to the midrib, but are bound to one another
Fic. 31. Blyttia longispina. Apex of Fic.32. Symphyogyna Brogniartii (Amphibiophytum dioicum,
the thallus. On the edges the first indica- | H. Karsten). A plant with two unripe sporogonia still enclosed
tions of leaves are seen as cell-rows below in their calyptra.
the shallow indentations. Magnified 8.
by the very slight wing-like part of the thallus. Dendroceros inflatus’ and
D. crispus show in their laminar folds an approach to the formation of leaves;
1 G. Karsten, Morphologische und biologische Untersuchungen iiber einige Epiphytenformen der
Molukken, in Annales du Jardin botanique de Buitenzorg, xii (1895), p. 125.
LEAVES OF THALLOSE FORMS 37
if these laminar folds were flat they would be like the leaves of Blasia. From
a biological point of view their origin is easily understood. Leaves with a
horizontal insertion, such as we meet with in different Jungermanniaceae,
link on to them.
We have next to consider the features in the cycle of affinity of Blyttia
and Symphyogyna.
Blyttia. Most of the species of Blyttia possess an unsegmented thallus
(see Fig. go). Blyttia longispina (Fig. 31) has appendicular organs in the
form of cell-threads, which lie directed partly upwards, partly downwards,
about the vegetative point, and so form a kind of protection. They some-
times also appear upon teeth which project from the edge of the thallus.
These are more prominent in other species.
Symphyogyna. The plant represented in Fig. 16 has a thallus with
evident segmentation into separate leaf-like lobes, and the segmentation
may cease, and the thallus can, as the figure
shows, grow on with an entire edge. The seg-
mentation to form ‘leaves’ is more marked in
Symphyogyna Brogniartii (Fig. 32). It reaches
here almost to the midrib. The leaves approach
the horizontal, are one-layered, and end in a short
papilla, or a cell-row of two cells. They arise
like the teeth already mentioned in regular
progressive serial succession from the segments
of the apical cell at the vegetative point*.
Here also the formation of leaf may cease upon
young shoots; and in all these cases it is evi- gcnis'osn: shncde Machined»
dently not yet fixed. The chief point is that ——
the sproutings are laid down in regular succession at the vegetative point.
Whether they are to be regarded as separate leaves or as small appendages
depends upon their own growth and that of the axis of the thallus ; accord-
ing to the strength of the one or the other of these there appears at the
vegetative point, in essentially similar primordia, a leafy stem or a thallus
with appendages like that depicted above in Blyttia longispina.
Blasia. This and its nearly allied genus Cavicularia possess horizon-
tally inserted lateral leaves, and these in Blasia (Fig. 33) are not sharply seg-
- mented from the flat portion which corresponds with the shoot-axis of other
Hepaticae ; usually the formation of leaves appears in slender plantlets.
One advantage the formation of leaves possesses over the unsegmented
thallus is apparent even in forms provided with horizontal leaves: the
development of leaves inserted obliquely or transversely to the long axis
of a shoot provides for the protection of the vegetative point by the forma-
* Goebel, Archegoniatensiudien: II]. Rudimentire Lebermoose, in Flora, lxxvii (1893), p. 98.
2 Goebel, op. cit., p. 100, Figs. 16—20.
38 VEGETATIVE ORGANS OF HEPATICAE
tion of an actual bud, which must of course be a very incomplete one when
the leaves have an insertion parallel with the stem-axis ; and, besides, the
leaves are able also to retain water, and then the regular appearance of
a number of sharply limited organs makes possible their adaptation to definite
functions.
The foliose Hepaticae includes both anacrogynous and acrogynous
forms.
(6) LEAVES AND SHOOTS OF ANACROGYNOUS FOLIOSE FORMS.
These forms belong to the cycle of affinity of the thallose group and
call for attention first.
Fossombronia. The species of this genus (Fig. 34) possess two rows of
obliquely placed lateral leaves which give the plant a crested aspect and
Fic. 34. Fossombronia tuberifera, Goebel. Lateral view of a distichously leaved plant in fructification. The
sporogonium is surrounded by a bell-shaped envelope. The point of the plant begins to penetrate the ground where
it would develop into a new tuber. Magnified 18.
favour greatly the retention of water. The shoot-axis has a two-sided
apical cell and is much flattened upon the upperx side. Upon its ventral side,
which the edges of the leaves scarcely overlap, club-shaped mucilage-papillae
occur which frequently in consequence of the growth and division of their
supporting cells come to stand upon the summit of a leaf-like scale; this
process is interesting because it furnishes a support to the suggestion given
above in regard to the origin of the amphigastria of Blasia and other forms.
Upon the dorsal side the edges of the leaves overlap almost to the middle,
and here are found the sexual organs.
Androcryphia and Petalophyllum. In Androcryphia and Petalophyl-
lum the formation of the leaves is similar, the apical cell is, however,
a three-sided pyramid, as in the acrogynous forms. The leaves overlap the
dorsal side to a very slight extent. Mucilage-papillae occur upon the under
side in Androcryphia.
LEAVES AND SHOOTS OF ANACROGYNOUS FORMS 39
Treubia. The largest of all the Hepaticae in this cycle of affinity is
Treubia insignis, a species found by me in Java. In it there are two rows
of large lateral leaves; the under side has no trace of appendages; the
shoot-axis is not visible usually between the leaves, only on young and
delicate examples are there internodes (Fig. 35, lower portion). The leaves
which are over one centimeter long, are nearly horizontal, and are many-
layered at the base, but one-layered higher up; the fore edge of the leaves
is inserted deeper than the hinder edge, and
when the position of the leaves is very close
the hinder edge of each younger leaf covers
the fore edge of the next older. The leaves
are therefore succubous'. Upon the dorsal
surface of the stem there are two rows of scales
beside the leaves and surrounding the insertion
of each, and their posterior part forms a zigzag
comb (Fig. 36). They cover the sexual organs
and the gemmae where these exist, and con-
tribute also to the protection of the vegetative
point which, however, is also enveloped in
mucilage. The mucilage is derived from
mucilage-papillae, which stand upon a wing-
FIG. 35.
Young plant seen from above. The leaves
Treubia insignis, Goebel.
like growth on the under edge of the leaf, and
thus replace or render superfluous the central
mucilage-papillae which are found in other
Hepaticae *.
Calobryaceae®. The Calobryaceae is the
only group of Hepaticae in which orthotropous
are not numbered according to age. The
hinder edge of leaf 2 evidently embraces
the point of insertion of the fore edge of
leaf 3. Beside and near the fore edge of
each leaf stands a scale whose insertion is
prolonged crestwise backwards. Under
the scales stand the sexual organs if these
are present. At the base of the shoot
where the leaves are smaller the crest is
less visible. The stem upon which the
scales are inserted is quite evident.
shoots occur; it has perhaps some affinity with Mesoined 14.
Treubia. Fig. 37 shows the habit of Calobryum. Tristichous leafy shoots are
borne upona sympodial rhizome. The leaves, like those of Treubia, are many-
1 Stephani (Treubia insignis, Goebel, in Hedwigia, xxx (1891), p. 191) has made a number of
statements which are not altogether in consonance with the developmental history of Treubia insignis.
As our Fig. 35 shows, it is incorrect to say that ‘the overlapping edges of two neighbouring leaves
spring from ove point.’ The arrangement is, as I have satisfied myself by a renewed investigation,
that the anterior edge of each leaf lies deeper than the posterior of the next younger. These are
actual succubous leaves; they are not what Stephani calls them ‘ frond-lobes.’ Stephani also mis-
quotes when he says ‘ Goebel describes the midrib as cylindric in transverse section.’ What I said
was ‘the stem does not usually show between the leaves, but on young and feeble examples, as well
as at the base of the lateral twigs, one finds conspicuous internodes, and /eve the stem has an outline
approaching the cylindric’ ; and what I have said is correct. Stephani is also incorrect in what he
says about the dorsal scales. These are found here and there where there are no sexual organs as
I made clear in my original description. Stephani takes as a basis of his definition of the notion
of leaf exclusively the structure of that name in the foliose acrogynous forms. This is inadmissible.
The formation of leaf has originated repeatedly in the different cycles of affinity in the Hepaticae.
2 Leaf-born mucilage-papillae occur also in Fossombronia caespitiformis.
’ See Goebel, Morphologische und biologische Studien: IV. Uber javanische Lebermoose; 2.
Calobryum Blumii, Nees, in Annales du Jardin botanique de Buitenzorg, ix (1892), p.11. I have
40 VEGETATIVE ORGANS OF HEPATICAE
layered, and like them also bear mucilage-papillae. Such papillae are,
however, also found upon the cylindric shoot-axis. The Calobryaceae ex-
Fic. 36. Treubia insignis, Goebel. A plant seen from above. Natural size. It bears a sporogonium which is
shown somewhat smaller than natural size.
hibit the highest stage of development of the anacrogynous Hepaticae, inas-
much as the shoots which bear the sexual organs possess terminal antheridia
and archegonia, to which I shall refer when I
speak of the position of sexual organs generally.
Further, the cylindric shoot-axis is sharply de-
marcated from the transversely inserted leaves,
and there is throughout a typical leafy shoot. It
is interesting to note that occasionally anisophyl-
lous shoots appear. The leaves of one lateral row
have one side smaller than the other, and may
indeed occasionally almost entirely abort, whilst
the leaves in the other two rows have an oblique
not transverse insertion. The importance of this
case lies in its features being determined by
external factors, and therefore showing that this
stolons united into a cvmpodial construction of the leaves, which is the dominant
Tin tice eben eo ew ‘ates OMe in the acrogynous foliose Hepaticae, may be
sory stolons. Natural size. reached experimentally ile
Fic. 37. Calobryum Blumii, Nees.
Habit of a female plant. Hi, Hn, Hin,
(c) LEAVES AND SHOOTS OF ACROGYNOUS FOLIOSE FORMS.
In this group we have growth usually from a three-sided apical cell ?,
which gives rise to a typical tristichous leafy stem, but the ventral row of
here shown that Calobryum, which until now has been considered to be quite unique, should be
united in one group with Haplomitrium, and I have called the group Calobryaceae. Schiffner’s
(Hepaticae, in Engler and Prantl, Die natiirlichen Pflanzenfamilien, 1893, p. 60) alteration of the
name to Haplomitrioideae is quite arbitrary.
1 See Part I, p. 102. Also Goebel, Morphologische und biologische Studien: IV. Uber javanische
Lebermoose ; 2, Calobryum Blumii, Nees, in Annales du Jardin botanique de Buitenzorg, ix (1891),
p. 16. ; 2 See Part I, p. ror.
a
LEAVES AND SHOOTS OF ACROGYNOUS FORMS 41
leaves consists of the amphigastria, which are smaller than the leaves of the
two lateral rows, and this is connected with the fact that only plagiotropous
shoots occur in the vegetative region, with the exception of shoots which
produce gemmae. The amphigastria are sometimes reduced to hair-like
structures or are entirely wanting, as in Jungermannia bicuspidata, although
there they occasionally if seldom appear. These features are entirely ex-
cluded in the case of Physiotium (Fig. 57, 1), in which the shoot-axis has
a two-sided apical cell from which segments are cut off giving rise to lateral
leaves!. On the orthotropous sexual shoots the amphigastria appear,
although they may be wanting on the vegetative shoots, and the presence
of a similar character upon the orthotropous shoots which bear gemmae in
Calypogeia has been already pointed out”.
In most members of this group the leaves are one-layered, but many-
layered leaves are found in Gottschea pachyphylla, and a few others in
which this character has probably the same significance as the succulence
of the leaves of higher plants. There is commonly no midrib. Where a
trace of this exists, as in Frullania Tamarisci, it is composed of cells with
peculiar content different from that of the other cells of the leaf, and due
perhaps to the accumulation of oil-bodies. This requires further investiga-
tion. An indication of a many-layered rib is found in Scapania, species of
Plagiochila, and in Jungermannia albicans °*.
The early appearance in many forms of a division of the leaf into halves
is very characteristic, but this often disappears as the plant grows; its occur-
rence precludes the apical growth which occurs in the leaves of the Musci.
In consequence of it the mature lateral leaves of many Jungermannieae are
two-lobed and possess an upper lobe and an under lobe which are frequently
very different in form and size. This is never seen in the amphigastria.
This bipartition distinguishes the leaves of the acrogynous species from
those of the anacrogynous ones. The outgrowths which, in the form of
lamellae, papillae, and so forth, are frequently found upon the leaves, will
be spoken of when I discuss the arrangements for the taking up of
water.
It has been already shown * that in many forms there is a displacement
which may go so far that the leaves appear to have a horizontal insertion.
This is by no means generally the case. Where no leaf-surface is formed,
but the leaf consists merely of cell-rows, as in Jungermannia trichophylla,
Lepidozia bicruris, Arachniopsis, there is no displacement. From this we
may conclude that the displacement is connected with the obtaining of
* Goebel, Archegoniatenstudien: V. Die Blattbildung bei den Lebermoosen und ihre biologische
Bedeutung, in Flora, Ixxvii (1893), p. 445.
2 See Part I, p. 102.
* See Morin, Anatomie comparée de la feuille des Muscinées. Thése, Rennes, 1893.
= mee Part-I; p. ror.
42 VEGETATIVE ORGANS OF HEPATICAE
a favourable surface of assimilation, and it may be directly brought about
by tight, as it is in Jungermannia bicuspidata ', or it may be inherited.
Concrescence of the leaves, either of the two upon the upper side, or
of these with the corresponding amphigastrium, is met with in Plagiochila
connexa and P. conjugata, species of Chiloscyphus and others, but we are
unable at present to give any biological explanation of it.
Reversion to thallus-form. Some leafy Jungermannieae exhibit the
remarkable feature of a
reversion of their vegeta-
tive bodies in some degree
to the form of a thallus.
Cephalozia (Pteropsiella)
frondiformis shows. this.
The vegetative body of
this plant is, as its specific
name implies, a flat band-
like thallus from which
leafy shoots bearing the
sexual organs spring ; but
the apparent thallus is a
leafy shoot, the horizon-
tally- placed leaves of
which have united with
one another, or, which
comes to the same thing,
stand upon a wing-like
outgrowth of the stem *.
Transition-forms from the
thallus to the leafy stem
also occur. Zoopsis,which
is a sub-genus of Cepha-
lozia, shows similar fea-
Fic. 38. Lepicolea cavifolia. A plant seen from below. The lateral 5
branches have grown out into flagella which are clad with reduced tures (see Fig. 97). Its
leaves. Magnified 3.
leaves are small appen-
dages of the stem, and the flattened large-celled dorsal surface of the stem
does the work of assimilation; but at the vegetative point the same relation-
ships are found as occur in other foliose forms, and the sexual shoots have
well-developed leaves.
Flagella. The reduction of the leaves on shoots which are constructed as
Jiagella, and as stolons or rhizomes, comes about in another way. Flagella
' Goebel, Uber Jugendformen yon Pflanzen und deren kiinstliche Wiederhervorrufung, in Sitzungs-
berichte der bayerischen Akademie, xxvi (1896).
? Goebel, Archegoniatenstudien : III. Uber rudimentiire Lebermoose, in Flora, Ixxvii (1893), p. 83.
BEAGELLA. LEONG SHOOTS AND SHORT SHOOTS 43
are shoots with thin long axes and reduced leaves. Lepicolea (Fig. 38)
amongst others commonly has lateral shoots developing into flagella.
These are usually richly provided with rhizoids, and apparently serve as
a fixing-apparatus like the anchoring-organs in some species of Aneura?.
In Mastigobryum these flagella arise ventrally. The shoots in this species
do not cling to the substratum but rise obliquely from it, and the flagella
have exactly the function of the rhizophores in Selaginella. They conduct
water and the substances dissolved in it from the substratum to the plant,
and like rhizophoresthey
may be caused to de-
velop as leafy shoots.
Lembidium dendroideum
(Fig. 39) has an oblique
ascending shoot-system
which develops no rhi-
zoids. These are found
upon shoots, bearing re-
duced leaves, which bore
into the substratum, and
penetrate it in all direc-
tions, being externally
quite root-like. In many
species of Plagiochila
and Bryopteris (Fig. 40)
the shoots in their lower
part cling to the sub-
stratum, and raise them-
selves up as free struc-
tures in their upper part.
What outer factors in-
fluence the development ie
Fic. 39. Lembidium dendroideum. An isolated plant. The aerial
of these forms of shoots shoot-system ascends obliquely with incurved ends. A, antheridial branches
at the base of the shoot-system. Root-like subterranean shoots pass down-
we do not yet know. wards on one of which is a tuber, B. The oldest aerial shoot is the broken
stump on the right. Magnified 4.
Long shoots and
short shoots. Of other kinds of division of labour among the branches of
one shoot-system, apart from the supporters of the sexual organs, that of
long shoots and short shoots, which as is known also occurs in the thal-
lose forms, must be mentioned. It is very distinct in Bryopteris filicina
(Fig. 40).
Tubers. The formation of tubers which takes place in some of the
thallose Hepaticae, is unknown as yet in the foliose acrogynous forms (see,
however, Fig. 39, 8).
1 See p. 26-
44 VEGETATIVE ORGANS OF HEPATICAE
Branching and the leaves. There remains to mention relationships of
the branching to the leaves. In no case is branching axillary. The branches
are either lateral or ventral, in correspondence with the dorsiventral character
of the foliose Jungermannieae, just as in the thallose usually dorsiventral
forms. In Anomoclada alone do the branches appear upon the dorsal side
of the shoots, and the branching in this genus requires further investigation.
In the lateral branching the formation of the branch takes place partly
at the cost of one
lateral leaf. A leaf, of
say Frullania dilatata,
from whose base a
lateral shoot springs,
wants its auricle, and
in place of it there
is the shoot. Whilst
usually the whole lat-
eral segment of the
apical cell is claimed
for the formation of
MAMET, LPG
mM nec the leaf, occasionally
ZUR ZDSNO yecees a few of the cells
being devoted to the
construction of a free
stem-surface, here in
the case of the branch-
ing the ventral portion
of the segment is de-
voted to the making
of a branch, and the
upper part of it only
is) left “for the >leaf.
Different in degree
Fic. 40. Bryopteris filicina. Habit. The shoot branches in one plane. At ° .
the base are stolons with reduced leaves which can give rise to new shoot- only 1S the laying
systems and at the same time help in anchoring the plant. Magnified 4. down of the primor-
dium of the branch in the basiscopic basilar portion of the segment, that is
to say, the formation of the leaf out of the segment is complete, but one
cell on the under basiscopic portion of the segment becomes the apical
cell of the primordium of a branch, and when this develops we find,
as in Radula compianata, the branch underneath a completely developed
leaf.
Resting buds. The lateral shoots of many species may become resting
buds. In Lejeunia, for example, the first three leaves of the lateral shoot
coalesce to form an envelope surrounding the primordium of the shoot which
RHIZOIDS 45
rests for an indefinite period. In the further development of the bud the
envelope is broken through.
Endogenetic shoots. This leads us to what Leitgeb has described as
the endogenetic origin of the ventral and lateral shoots of many species.
He says that the flagella of Mastigobryum are formed from cells lying
immediately under the outer cells, and the same is the case with the fructi-
fication-branches of this plant, as well as of Lepidozia, Calypogeia, and
others. The disposition of these endogenetic branches in Lophocolea
bidentata and in Jungermannia bicuspidata is peculiar. They are almost
exclusively ventral, and the branches spread themselves out upon the sub-
stratum to both sides of the chief axis, so that the branch-system has the
same facies as is produced by lateral branching.
3. Rhizoids.
Knowing now the relationships of configuration of the vegetative body,
we have to cast a glance at the organs which anchor it to the substratum
and draw therefrom, at least in many cases, water with the substances dis-
solved in it. These bodies are the rhzzoids, hair-roots. All Hepaticae,
whether thailose or foliose, possess unicellular rhizoids; the Musci, on the
other hand, always have rhizoids composed of a single row of cells. These
rhizoids differ in function. In some Hepaticae, for example epiphytic
foliose forms, they are only anchoring-organs, in others they combine the
work of fixing the plant and of absorbing water. They are absent in
only few forms, and we can usually discover a reason for their absence.
The Calobryaceae, for example, have no rhizoids!, and they possess root-like
shoots creeping in the substratum *, and these render the rhizoids unneces-
sary. Physiotium cochleariforme also has no rhizoids, but it is provided with
large water-sacs, and in this resembles Sphagnum *.
‘The two species of Riccia, R. natans and R. fluitans, each of which
possesses a land-form and a water-form, have no rhizoids in their water-
form, and this because they are as unnecessary here as are the hairs upon
the roots of many water-plants of higher groups, for example, Salvinia,
Utricularia. In R. fluitans the water-form may produce rhizoids if it comes
in contact with a solid body*. In many epiphytic forms, such as species of
Lejeunia, a strong anchoring disk develops out of a bundle of rhizoids”.
A division of labour occurs in the rhizoids of some thallose forms which
attain a considerable stature, and particularly in those in which the upper
' The germination of these Hepaticae is not yet known, and it is probable that as in Sphagnum
the germ-plant has rhizoids.
3 See p. 39, and Fig. 37.
% Trichocolea tomentella has well-developed rhizoids, although Nees thought it had few or none.
* See Part I, p. 269.
5 For an account of this see Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 161, Fig. 66.
46 VEGETATIVE ORGANS OF HEPATICAE
side of the thallus takes in no water, and the care of the water-supply
devolves upon the rhizoids. Amongst such forms we know at present
species of Monoclea' and the members of the series of the Marchantiaceae.
Monoclea. I had the opportunity of examining Monoclea dilatata in a
living condition in Venezuela, and the interest of the species lies in this, that
it foreshadows the peculiar features of the formation of rhizoids which belong
to the Marchantiaceae’. It has two kinds of rhizoids ; some wide and thin-
walled, arising exclusively out of the under side of the thickened midrib of
the thallus (Fig. 4, 111), and at once piercing the substratum; others narrow
and relatively thick-walled, which arise partly upon the edge of the thallus,
partly upon its under side, and grow at first adpressed to the thallus, those
that arise laterally converging to the midrib, beneath which runs a strand of
rhizoids, keeping it moist by capillarity. These lateral rhizoids can irrigate
the lateral parts of the thallus. The
whole arrangement reminds one of
that found in hygrophilous Marchan-
tiaceae, especially in Dumortiera.
Monoclea itself occurs like them in
moist places. The arrangement, which
is indicated in Monoclea, finds perfect
development in the Marchantiaceae.
Marchantiaceae. Here the rhi-
zoids are frequently over two centi-
meters in length, and often form a
thick felt on the under side of the vege-
soniaphore ja temusrerde eect Tio aaae hangman body. The division of labour
rhizoids are sunk in two deep lateral channels. : : :
among them finds its expression in
a difference between ‘smooth’ rhizoids, which have the usual construction,
and ‘trabecular’ rhizoids, which have trabecular thickenings upon the
inside of their wall. Germ-plants of Marchantia and plants which arise
from gemmae possess at first only smooth rhizoids, and they it is which
enter the soil directly from the under side of a mature thallus and anchor
it. The trabecular rhizoids, on the other hand, lie upon the under side
of the thallus in strands, the strongest of these running along the midrib,
and only at some distance behind their point of origin do they enter the
soil®, There is no doubt that these strands, which are also found under
the rays of the disk of the sexual shoot and upon its stalk (Fig. 41),
conduct water by capillarity, although at the same time the movement of
water chiefly takes place through their lumen. The trabeculae within the
* Which, however, can take up water directly from outside.
* See Ruge, Beitrige zur Kenntniss der Vegetationsorgane der Lebermoose, in Flora, lxxvii (1893),
Pp: 279.
$ See p. 32.
RHIZOIDS 47
rhizoids have also, as Kamerling! has recently shown, a connexion with
the conduction of water. If the thallus draws water from the trabecular
rhizoids, and a supply to replace it cannot be sufficiently quickly obtained
from the soil, air-bubbles will be formed within the rhizoids which will
interrupt the current of the water. The presence of the trabeculae
compels the formation of these bubbles in the centre of the cavity of the
rhizoids, and so the current of water can pass the bubble. The trabecular
rhizoids then make possible the maintenance of a more copious supply of water
than do the smooth ones. Concomitantly with this we find that the
trabecular rhizoids are specially developed in forms with relatively great
transpiration, whilst they are subordinated in forms in which this is feeble ;
for instance, in a Venezuelan hygrophilous species of Dumortiera they were
present in extremely small numbers, and were entirely wanting in Cyatho-
dium cavernarium.
Transformation of rhizoids. <A portion of the rhizoids is transformed
into thick-walled bristles in Dumortiera hirsuta, and the
transition-forms to rhizoids show the true nature of the
bristles, which may be considered protective organs for the
thallus, although it is impossible to say precisely wherein
the protection lies*. Change of function and transfor-
mation of rhizoids is otherwise unknown. Lindenberg — ,,F';42., Ricciana-
tans. Land-form, seen
speaks of segmented rhizoids in the land-form of Riccia [omy ses. ane
natans, but this is either an error or a misdescription Pee atlas
of the filiform adventitious shoots which sometimes occur "4 Natural size.
upon old examples of species of Riccia®. So far as we know, the rhizoids
in Hepaticae are incapable of a transformation or further development,
and in this they contrast with their condition in the Musci.
‘
Bh
ASEXUAL PROPAGATION OF HEPATICAE 4
Every asexual multiplication is fundamentally a process of division of
the vegetative body in which the products of division may be very unequal
in size. In creeping Hepaticae, as in many other plants, the branches may
* Kamerling, Zur Biologie und Physiologie der Marchantiaceen, in Flora, Ixxxiv (Ergiinzungsband
zum Jahrgang 1897).
* Compare with these the bristles arising upon the thallus of many species of Metzgeria which may
be considered transformed rhizoids.
* A recent compiler has again mistaken these for rhizoids.
* Nees von Esenbeck, Naturgeschichte der europaischen Lebermoose, i-iv, Berlin and Breslau,
1833-8; Leitgeb, Untersuchungen iiber die Lebermoose, i-vi, Graz, 1874-81; Ruge, Beitrige zur
48 ASEXUAL PROPAGATION OF HEPATICAE
become independent plants through the dying off of the older parts behind
(Fig. 42). Frequently, however, special propagative organs are developed
which have been termed gezzae or brood-buds, and of these some examples
must be given.
I. SEPARATION OF SPECIAL TWIGS FROM THE VEGETATIVE BODY}.
This is the nearest to the ordinary processes of division. In its simplest
form it is observed in Pellia calycina. Towards the close of the vegetative
period of this plant there appear upon sterile plants, through repeated
forking of the vegetative point, short-lived branchings filled with starch and
other reserve-materials, but without rhizoids and frequently standing erect
and overlapping one another. These readily break off, and clearly exhibit
a primitive form of gemma (Fig. 43). If they do not break off they may
fg
Fic. 43. Pellia calycina. Branching of a sterile lobe Fic. 44. Fegatella supradecomposita. Thallus
ofthe thallus in autumn. Seen from below. Magnified. with three gemmae seen from below. Magnified 12.
grow in the succeeding spring as ordinary branches of the thallus. Fegatella
supradecomposita shows a further stage of differentiation of these branches.
In it they are borne upon thin stalks, and can therefore easily separate
(Fig. 44). Superficially they resemble the similar structures in Marchantia
and are nearly circular flat plates with a vegetative point on one side but they
differ altogether in their origin. Whilst the gemmae of Marchantia are uni-
cellular structures, which only before their separation, or it may be at germi-
nation, grow into cell-masses, those of Fegatella supradecomposita are merely
modified branches of the thallus, and possess a series of scales covering the
vegetative point in the manner usual amongst the Marchantieae.
Kenntniss der Vegetationsorgane der Lebermoose, in Flora, Ixxvii (1893); Schostakowitsch, Uber
die Reproduction und Regenerationserscheinungen bei den Lebermoosen, in Flora, lxxix (Erganzungs-
band zum Jahrgang 1894).
1 We leave out of account here the formation of tubers which will be referred to in a subsequent
page. See p. 66.
GEMMAE 49
2. GEMMAE (BROOD-BUDS) FORMED BY GEMMA-CELLS (BROOD-CELLS).
All other forms of gemmae can be traced back to a construction out of
gemma-cells (brood-cells), but these frequently develop so far on the mother-
plant that it is impossible sometimes to draw a sharp limit between them
and adventitious shoots. This is particularly the case within the cycle of
affinity of the Metzgeriae. Many species of Aneura have duplex gemma-cells
which fall away from the thallus. They are discharged from their mother-
cells with a slight jerk’, probably by swelling of the inner layers of the
membranes of these; the outer portion of the membrane remains behind.
They often appear in large numbers. Allied to this is the copious forma-
tion of gemmae in Metzgeria conjugata. In this species some branches of
the thallus become very narrow and develop as supporters of the gemmae.
They ascend from the substratum, and, gradually losing their dorsiventrality,
they become radial, whilst the gemmae, which appear close together at first
and only upon the margin of the branch, are found later upon the upper and
under sides of the thallus as well. The upright position evidently favours
the distribution of the gemmae. The gemmae, at the moment when they
are shed, are in the form of concave cell-plates, with a vegetative point
having a two-sided apical cell, from which a new thallus is formed”, and in
the process of shedding a remnant of the wall of the mother-cell is left
behind as is the case in Aneura. In Metzgeria furcata adventitious shoots
are regularly developed instead of the gemmae, and each of them proceeds
from a single cell of the margin or of the midrib. Gemmae of a more or less
advanced stage of development before shedding are found in other thallose
Hepaticae, for example in Marchantia and Lunularia, in which they have
been so often described, and also in Treubia, Cavicularia, and Blasia.
Bldsia has two kinds of gemmae: the one is a nearly spherical cell-mass
produced in a flask-like receptacle with a long neck, out of which it is
squeezed through the swelling, when moistened, of mucilage formed by the
mucilage-papillae at the base of the receptacle* ; the other is a gemma-scale
at the base of which there is to be seen at a very early period of develop-
ment the cell from which the new thallus proceeds,—this gemma-scale
arises upon the upper side of the thallus, especially upon shoots which bear
neither sexual organs nor receptacles for gemmae*. Cavicularia has gemmae
whose outer cells have thick walls, and each of them has an excrescence
which has perhaps to do with the scattering of the gemmae by animals.
1 See Goebel, Die Muscineen, in Schenk’s Handbuch der Botanik, ii (1882), p. 338; Ruge,
Beitrage zur Kenntniss der Vegetationsorgane der Lebermoose, in Flora, Ixxvii (1893), p. 307.
* In Aneura the gemma is shed before these landmarks are developed.
* This also takes place in Marchantia, but in a less pronounced manner.
* These gemma-scales require investigation especially in their biological relationships. A similar
dimorphism of gemmae appears probably in the genus Tetraphis amongst the Musci.
GOEBEL II E
50 ASEXUAL PROPAGATION OF. HEPATICAE
A description of the formation of the gemmae in the several forms of
Hepaticae would have no general interest. Their appearance is sporadic
within cycles of affinity, and even within genera. Anthoceros glandulosus,
for example, is the only known species of the genus in which they are found,
and in it they take the form of oval cell-masses. Amongst the Marchantieae,
Marchantia and Lunularia alone possess them, and how profusely they are
distributed in these genera is well known to gardeners. They overrun every
pot in cultivation.
The occurrence of gemmae produced from shoots is not unknown in the
foliose Jungermannieae, and they may be either unicellular or before their
Fic. 45. Lejeunia. Formation of gemmae. 1, Lejeunia (Odontolejeunia) mirabilis, Steph. Gemma; 5S, apical
cell; A, point of attachment. Rhizoids in the form of long tubes have developed upon the under side from single
marginal cells. 11, 111, Lejeunia (Cololejeunia) Goebelii. 11, portion of a leaf with three gemmae still attached ;
Ss, 8, indicate the points of attachment of two gemmae which have fallen off. 111, gemma with four anchoring-
organs, s, and two apical cells.
separation grow into cell-masses. The formation of gemmae occurs in many
species, usually upon the edge or upon the tip of leaves, and the gemmae
appear then often as long branched yeast-like chains. The several gemma-
cells separate easily from one another in moisture. In Lophocolea bidentata
aggregates of cells loosely joined together fall from the leaves. According as
the formation of gemmae takes place at an early or late stage, the formation
of the leaf is more or less influenced by it, and variations may be seen upon
one and the same shoot. In Scapania nemorosa, for example, only the
points of the upper lobes of the lower leaves of the shoot are furnished with
gemmae; their formation therefore was relatively late. On the leaves
higher up the under lobes of the leaves are first concerned in the formation
GEMMAE 51
of gemmae, and the further up one goes the more is the development of the
leaf-surface hindered, until finally, in the position of each leaf we find a group
of gemmae issuing directly from the segment of the apical cell. The
leaf-borne gemmae have thus become stem-borne, and we are furnished with
an instructive example of a gradual transposition. The number of the gem-
mae in such cases is very large, as many as a thousand. The shoots which
bear gemmae in many species, for example in Calypogeia Trichomanes, are
orthotropous, as are those of Metzgeria conjugata’?. In the genera Radula’,
Lejeunia*, and Colura*, gemmae in the form of cell-surfaces appear upon the
leaves, and in these genera, which include mostly epiphytic species, they
secure a rapid fixation to the substratum. The gemmae of Lejeunia (Fig. 45)
have two vegetative points out of which shoots may subsequently develop,
and they are furnished with anchoring-organs, which are merely arrested
rhizoids (Fig. 45,1, 11). The example figured in Fig. 45, I is of interest
because there is only one apical cell, probably because the gemma is
anchored not by its middle but excentrically. When the gemmae of
Lejeunia have two apical cells (Fig. 45, 111), a leafy plant may spring out of
each of them, but the apical cell may also grow out into a thallus with
a continued segmentation of a two-sided cell, like the product of a germi-
nating spore. Such a formation of thallus takes place if the conditions are
unfavourable for the formation of a stem, and it is particularly often seen in
the germinating gemmae of Radula*, where it furnishes the young plant
with a firm fixation upon its substratum, which is the leaves of Spermophyta.
These relationships of the development of the gemmae find their counter-
part, both physiological and morphological, in the phenomena of the
germination of the spore*. The germination of the gemma conforms
generally with that of the spore. In Marchantia and Lunularia this is
evidently not the case, but in these genera the profile disposition of the
gemma, as in Riella, makes it impossible.
It is easy to establish that there is often a certain antagonism between
the formation of gemmae and sexual reproduction. Gemmae appear either
exclusively or preferably upon sterile individuals. Leitgeb, however, observed
them upon the tips of the leaves about the antheridia in Scapania nemorosa,
and Nees von Esenbeck recorded the occurrence of ‘Jungermannia Sphagni,’
bearing sporogonia and gemmae at the same time.
When the phenomena of regeneration were discussed, it was shown that
1 See p. 49.
* See Goebel, Morphologische und biologische Studien: I. Uber epiphytische Farne und Musci-
neen, in Annales du Jardin botanique de Buitenzorg, vii (1888), p. 49.
* See Goebel, op. cit., Figs. 60-67.
* Goebel, Die Muscineen, in Schenk’s Handbuch der Botanik, ii (1882), p. 339; Ruge, Beitrage
zur Kenntniss der Vegetationsorgane der Lebermoose, in Flora, Ixxvii (1893); Schostakowitsch,
Uber die Reproduction und Regenerationserscheinungen bei den Lebermoosen, in Flora, Ixxix
(Erganzungsband zum Jahrgang 1894).
E 2
52 VEGETATIVE ADAPTATION IN HEPATICAE
the Hepaticae have a rich capacity of regeneration’, especially by severed
portions, and that there is a difference between them and Musci in this
respect. In the Musci, regeneration always begins by the formation of the
protonema characteristic of the germination of the spore, but in the Hepaticae
cell-masses are produced in regeneration, even although the spore forms
cell-surfaces or cell-threads in germination. I have been led by my inves-
tigations to the view that every cell in the Hepaticae has the latent capacity
to develop further like the spore, but this is only called forth if there is
an enfeeblement of the vegetative body. The proof of this was especially
afforded by Metzgeria furcata?, in which under definite conditions the cells
did not grow out as usual directly into ‘adventitious shoots, but into cell-
rows just as in the germination of the spore; and in support of this is an
observation of Leitgeb that upon old, that is in my view enfeebled, plants
of Jungermannia bicuspidata, cells of the surface of the stem could grow out
into tubes like germ-tubes and form a shoot at their apex. In like manner
on the old leaves of Lophocolea bidentata, and of a tropical species of
Lejeunia which I observed, the same phenomenon may be noted. This
subject cannot be discussed further here, but the facts are of the greatest
importance for our comprehension of the development, although little
attention is given to such phenomena in our times when the microtome is so
popular an instrument.
III
PHENOMENA, OF ADAPTATION OF THE VEGEaArivE
ORGANS OF iE PAGI CA
Il. RELATIONSHIPS LO” WA PEE.
The anatomical structure of the vegetative body of the Hepaticae is
quite different according as it has or has not to take up water directly from
the outside. A high anatomical differentiation is only reached in those
Hepaticae which possess a vegetative body of which the surface cannot be
wet. But such forms may revert again to a simpler relationship. It is
easy to satisfy oneself that a Riccia, excepting Riccia fluitans, or a Mar-
chantia, cannot be directly wet by water like a Pellia or one of the foliose
Hepaticae, and this gives us the clue to their diverse structure which finds
a parallel in the differentiation of tissues of the higher plants.
Most of the Hepaticae are hygrophilous and live in a moist medium, where
they are seldom exposed to the danger of long drought, and therefore, as is
* See Part I, p. 48.
* See Goebel, Archegoniatenstudien: VIII. Riickschlagsbildungen und Sprossung bei Metzgeria, in
Flora, Ixxxv (1898), p. 69.
RETENTION OF WATER IN THALLOSE FORMS 53
the case with the lichens, the number of forms of the Hepaticae is greater
as we approach moist mountainous regions. Epiphytic forms and those in
unsheltered localities are subjected occasionally to a want of water, and they
are endowed partly with the capacity of resisting drought of short duration,
and partly with special contrivances to retain water. These contrivances
also occur in terrestrial forms and in extraordinary abundance in many
species.
I. ARRANGEMENTS FOR THE RETENTION OF WATER.
The arrangements for securing the retention of water imply a copious
absorption of it. Their value to the plant is that even in drought the most
delicately constructed forms are able to carry on the phenomena of their
life, especially assimilation !, and the longer the water is retained the longer
and the more actively will their life-processes be maintained. Hepaticae in
the tropics frequently live upon the leaves of the higher plants from which
water readily flows off, and therefore we find in them arrangements for
retaining water even in species which live in the wettest tropical hill-
regions. Species of Physiotium furnish an example. In these species we
have to deal with a relationship similar to that observed in Sphagnaceae,
which, growing in localities which are always moist, have nevertheless
a most remarkable contrivance for taking and retaining water. Why should
this be so? I find nothing about it in the literature of Botany. The
Sphagna chiefly live upon vrain-water, and they take consequently ash-
constituents from the substratum in only very small amounts’; they must
therefore give off by evaporation a large quantity of water. Similarly the
Hepaticae which live in the wet hill-regions take their necessary water from
clouds and rain which contain but little nutritive matter, so that a large
volume of water is necessary for them.
Although the arrangements for retaining water are essentially the same
in thallose and foliose forms, it will be more instructive if we look at the
two series separately.
A. In Thallose Forms.
a. JUNGERMANNIACEAE. The following are illustrations in this series:—
Aneura endiviaefolia is represented in Fig. 46. As its name indi-
cates the thallus resembles a curled leaf of endive because the branches are
curved inwards and downwards, and they thus provide in the thallus a sort
of spongy construction which is favourable to the retention of water. The
branches of the higher order differ from the chief axes in having a one-
1 Goebel, Archegoniatenstudien: V. Die Blattbildung der Lebermoose und ihre biologische
Bedeutung, in Flora, Ixxvii (1893), p. 439. Air-dried, still living Frullania after eight hours’ exposure
to illumination had decomposed no carbon-dioxide. See also Jonsson, Recherches sur la respiration
et l’assimilation des Muscinées, in Comptes Rendus, cxix (1894). He comes to the same con-
clusion :—‘ the more considerable the proportion of water, the more intense is the gaseous exchange.’
2 This interpretation was first given to me by my deceased friend Sachs.
54 VEGETATIVE ADAPTATION IN HEPATICAE
layered cell-surface except at the midrib. Similar arrangements occur in
some Javanese species of Aneura (Pseudoneura). An investigation of
living plants is required to determine whether the marginal cells of the
thallus in species of Aneura absorb water.
Aneura hymenophylloides
behaves ina similar manner (Figs.
47, 48). Its thallus in some
measure resembles the feather-
branched leaf of a species of
Hymenophyllum, and it possesses
an excellent arrangement for re-
taining water. The tips of the
thallus are all strongly incurved
downwards, and the _ branches,
placed in two rows upon the
chief axis.converge by their under
sides, each branch having its
Fic. 47. Aneura hymenophylloides. Seen in profile.
pene 46. Aneura endiviaefolia. Portion of The vegetative point of the long shoot and all the
thallus seen from below. The twigs are curled branches are curved inwards-and downwards. Mag-
inwards and downwards. Magnified 9. nified 8.
edges concave downwards (Fig. 48, 2, 3). In addition, the thin-walled
cells of the surface of the thallus are frequently convex outwards, and
are excellently arranged for the retention of water. The branch-system
does not lie upon a substratum, and a consideration of Fig. 48 will show
the important difference there is between the cellular construction in the
chief and Jateral axes.
Aneura fuegiensis (Fig. 49) exhibits other arrangements. Upon the
a
REDPENTION OF WATER IN. THALLOSE FORMS 55
under side of the thallus we find lamellae, most numerous upon the chief
axis, becoming always
fewer upon the lateral
axes of higher order.
The margin of these
lamellae is not smooth,
but is provided with
pluricellular ‘hairs,
which increase the ef-
ficiency of the whole
as a sponge. The cell-
walls of the lamellae
are thickened at their
corners as they are in
the cells of the leaves
of many foliose forms.
One may compare the
lamellae with leaves
. inserted longitudinally,
and they arise like the
amphigastria of Fos-
sombronia, each one
behind a_ mucilage-
papilla. They do not,
however, run over the
whole length of the
thallus. In the lateral
shoots ofa higher order
a lamella is not formed
behind each mucilage-
papilla.
Metzgeria. Our
indigenous species of
Metzgeria have no
special arrangements
for retaining water if
we except the papillae
with which the thallus
of Metzgeria pubescens
is covered. On the other
=>
e}
Fic. 48. Aneura hymenophylloides. 1, chief axis. 2, axis of the first
order. 3, axis of the second order. All in transverse section. Highly
magnified.
Fic. 49. Aneura fuegiensis. Thallus in transverse section,
showing the lamellae upon the under side as cell-rows. Between
these lamellae water is held. Highly magnified.
hand Metzgeria saccata', which lives between mosses on the bark of trees in
" See Goebel, Archegoniatenstudien: V. Die Blattbildung der Lebermoose und ihre biologische
Bedeutung, in Flora, Ixxvii (1893), p. 425, Fig. 1.
56 VEGETATIVE ADAPTATION IN HEPATICAE
New Zealand, possesses water-sacs like those on the auricles of the leaves
of Frullania, or like those which have yet to be described in Dendroceros
foliatus (Fig. 51). On the edge of the thallus are found vesicular or hood-
like appendages which are laid down near the apex by the concave
infolding of isolated parts of the thallus. These become larger, fill with
water, and so serve as water-sacs.
6. ANTHOCEROTEAE. Several species of Anthoceroteae repeat the
arrangements which have been described above in thallose Jungermannieae.
Anthoceros. Our indigenous
Anthoceros punctatus has upon
the upper side of the thallus pit-
like depressions which retain
water. A. arachnoideus! has,
instead of these, a net-work of
low intersecting ridges, to which
we must ascribe the same signifi-
cance. On the other hand, A.
fimbriatus (Fig. 50) is provided
with a crisped one-layered cell-
surface at the margin of its many-
layered thallus, giving it a strik-
ing appearance as it grows upon
the Cordilleras of Merida. The
marginal fringe arises out of the
‘middle lobe in the forking of
the thallus*, and it reminds us
of the relationships which have
been described in Aneura endi-
viaefolia *.
Fic. 50. Anthoceros fimbriatus. Portion of a thallus
seen from below; the rhizoids are not shown. The one- Dendroceros. The remark-
layered crisped lobes at the edge hold water. Magnified. r F
able relationships of Dendroceros
foliatus (Fig. 51) were touched upon when speaking of the formation of
leaves, and it was shown that on the edge of the thallus cap-like formations
are found which are partly laid down as special shoots at the vegetative
point and partly proceed from the middle lobes. These structures have
evidently the same significance as the water-sacs of Metzgeria saccata.
The same arrangement is found in Karsten’s Dendroceros inflatus. The
cells in the one-layered surface of the thallus of Dendroceros frequently
separate from one another, and the schizogenetic intercellular spaces
increase the spongy nature of the whole thallus.
' See Stephani, Colenso’s New Zealand Hepaticae, in Journal of the Linnean Society, Botany,
xxix (1892), p. 265. 2 See p. 21 and Fig. 14.
3 See p. 533; adventitious shoots may arise from them.
RETENTION OF WATER. PARAPHYLLIA 57
These examples show that in different cycles of affinity the thallose
Hepaticae exhibit avalogows adaptations. When we deal with formation of
tubers we shall find additional evidence of this.
B. In Foliose Forms.
As has been shown in the description of the formation of leaves,
adaptations appear upon these which make possible the retention of water.
They are indeed abundant, but are almost entirely wanting in plants which
grow in moist localities.
A. PARAPHYLLIA.
The shoot-axis may share
in such adaptations by the for-
mation of outgrowths, which after
the analogy of the Musci we may
name paraphyllia. These are
known in two genera which are
not systematically nearly allied,
Trichocolea and Stephaniella.
Trichocolea. They have
been longest known in Tricho-
colea tomentella’, but nothing
has been said regarding their
function. I find them only upon
the upper side and upon theflanks
a eee a ae
other hood-like structures are the ‘ leaves.’
or branched cell-threads like those
which are found upon the leaf-edges?, and they make the whole plant a
spongy mass. Trichocolea paraphyllina shows the same features. The
paraphyllia without doubt act like the lamellae upon Aneura fuegiensis
and upon the leaves of Polytrichum.
Stephaniella. Stephaniella paraphyllina® is a xerophilous form with
remarkable formation of ‘ roots’ which will be described later*.. The leaves
in this plant are hardly organs of assimilation; they lose very early their
chlorophyll and become mere covers for the stem-bud and for the para-
phyllia which clothe densely the surface of the shoot-axis and are at once
an apparatus for holding water and organs of assimilation °.
* Nees von Esenbeck, Naturgeschichte der europaischen Lebermoose, ili, p. 109, mentions them
in this species, but erroneously calls them ‘ leaf-appendages.’ 2 See p. 58.
$ See Jack, Stephaniella paraphyllina, Jack., nov. gen. Hepaticarum, in Hedwigia, xxxiii (1894),
18h Ao = Weep. 70-
° In Trichocolea the assimilatory activity of the paraphyllia is subordinate because the leaves
retain chlorophyll.
58 VEGETATIVE ADAPTATION IN HEPATICAE
B. LEAVES AND PARTS OF LEAVES AS WATER-RESERVOIRS.
A transformation of the leaves themselves more frequently provides the
mechanism for retaining water than does the formation of paraphyllia.
I. AGGREGATION OF LEAVES. Of the simplest case, where capillary
chambers are formed by the close aggregation of leaves, as is the case in
Musci, we need not say much; only this, that in different genera there are
species which hang in the form of strands from tree-branches, for example
Frullania atrosanguinea, F. atrata, Lejeunia lumbricoides?, in which the
lateral leaves are not expanded flatly, as usual, but are incurved so as to
form with the relatively large amphigastria a system of capillary chambers
around the whole stem.
Of other arrangements the following may be noticed :—
2. OUTGROWTHS IN THE FORM OF CELL-ROWS
Bi OR CELL-SURFACES UPON THE MARGIN OR THE
4 SURFACE OF THE LEAF:
Trichocolea. In Trichocolea tomentosa we find
a number of branched cell-rows springing from the
margin of the leaf, and they also proceed from the
under-surface of the leaf. They spread out in all
directions and thus construct a spongy mass.
Lophocolea. In less degree the same thing is
found in Lophocolea muricata ”.
Gottschea. In species of Gottschea * one or more
Fic. 52. Frullania Tama. lamellae spring from every leaf, and they form in
Baw. una aeeee Gottschea sciurea a remarkable water-apparatus.
fap Water pe ood Ee 3. By TRANSFORMATION OF INDIVIDUAL PoR-
hollowed out larger portion
of the under lobe of the leaf; TIONS OF THE LEAF WATER-RESERVOIRS ARE
Seman Ee Demtonnn, ae
ster A. The under lobe of the leaf is so laid against
the upper lobe that the two form a pocket-like or pitcher-like organ. This
occurs in Radula (Fig. 76), Phragmicoma, Lejeunia, and others. These
organs have been called auricles *.
Lejeunia. Heterophylly, a division of labour amongst the leaves, is
a conspicuous feature in species of Lejeunia (Ceratolejeunia). Upon the
* See Goebel, Archegoniatenstudien: V. Die Blattbildung der Lebermoose und ihre biologische
Bedeutung, in Flora, Ixxvii (1893), p. 431, Plate viii and ix, Figs. 1, 2.
* See Goebel, op. cit., p. 430, Plate viii and ix, Fig. 3.
* See Goebel, op. cit., p. 430, Plate viii and ix, Fig. 18; id. Morphologische und biologische
Studien: I. Uber epiphytische Farne und Muscineen, in Annales du Jardin botanique de Buitenzorg,
vii (1888), Plate v, Fig. 53.
* With regard to their configuration see Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 178,
Figs. 78,79. Although this was published in 1889 it has recently been asserted that these structures
have not been recognized hitherto.
LEAVES AS WATER-RESERVOIRS 59
leaves at the base of the lateral shoots one or two relatively large water-
sacs are formed, and there is almost no free leaf-surface, whilst on the upper
leaves many small sacs occur, and there is a large leaf-surface formed by
the upper lobe.
Radula. Radula pycnolejeunioides! is still more specialized. It has
short shoots, the leaves of which become altogether narrow-mouthed
PIG. 53. Polyotus clavigea. Both on the amphigastria and on the lateral leaves there are water-sacs, one to
two on each amphigastrium, one on each lateral leaf. Magnified.
water-sacs, with no free leaf-surface; whilst on the leaves of the long
shoots the leaf-surface is quite conspicuous.
B. The under lobe of the leaf is laid against the upper lobe, but the under
lobe alone constitutes the water-reservoir ; it is concave upon the morphologic-
ally upper side, not, as in the previous case, upon the under side. Frullania
(Fig. 52) and Polyotus (Fig. 53) supply examples.
Frullania. In Frullania the under lobe of the jieaf is much smaller
than the upper lobe ; it is concave upwards and forms a hood-like structure,
1 See Goebel, Archegoniatenstudien: V. Die Blattbildung der Lebermoose und ihre biologische
Bedeutung, in Flora, lxxvii (1893), p. 433.
60 VEGETATIVE ADAPTATION IN HEPATICAE
beside which stands a shorter body having a tip ending in a mucilage-papilla,
Fic. 54. Colura tortifolia. Beside each lateral leaf is an
amphigastrium at the base of which rhizoids develop. The
sac of the lateral leaves is turned with its point outwards, not
well represented in the figure. At 4 a branch bearing anthe-
tidia. The figure does not show a characteristic development
of Colura, namely that the leaves stand away from the sub-
stratum. Magnified 30.
the so-called ‘stylus auriculae’ !.
Here as in “other ‘cases rie
water-receptacle is so formed
that there is no wide opening to
the outside so that the water can
only slowly evaporate, and is
taken up in great part by the
cells of the leaf ?.
Polyotus. The genus Poly-
otus, as its name indicates, is
richly provided with water-sacs.
We find ‘auriculae’ not only on
the lateral leaves but also on
the amphigastria (Fig. 53), and
the lateral leaves in many
species are provided with mar-
ginal cell-rows which increase
the sponge-like character.
All the species of Radula,
Lejeunia, Frullania,and Polyotus
have water-sacs more or less
developed, but there are some
genera, for instance Plagiochila,
Chiloscyphus, and Jungerman-
nia in which they occur only in
isolated species: in Plagiochila
cucullifolia *, Chiloscyphus de-
cipiens, C. cymbaliferus. Jun-
germannia curvifolia. I have
proved that the formation of
the water-sac is retarded in
Frullania if it be cultivated for
a long time in moisture. The
formation of the water-sac is
therefore an adaptation in direct
relation to external factors. According as these influences affect the genus
1 The secretion of mucilage only takes place in youth, and serves for the protection of the stem-bud.
? With regard to ‘ Frullania’ cornigera and others see Goebel, Pflanzenbiologische Schilderungen,
i (1889), p. 182, Fig. 82; id. Archegoniatenstudien: V. Die Blattbildung der Lebermoose und ihre
biologische Bedeutung, in Flora, Ixxvii (1893), p- 444.
° See Goebel, Morphologische und biologische Studien : IV. Uber javanische Lebermoose ; 4, Eine
javanische Plagiochila mit Wassersacken, in Annales du Jardin botanique de Buitenzorg, ix (1891),
P. 34.
LEAVES AS WATER-SACS WITH VALVE 61
early or late in its history will the character of adaptation be of use or not
as a systematic mark.
C. Water-sacs which are closed by a hinged valve. The genera Colura
(Colurolejeunia) (Figs. 54, 55) and Physiotium (Figs. 56, 57, 58) exhibit the
most highly developed adaptations for retaining water. They have water-sacs
the opening of which is closed by a hinged valve. The valve crumples up
in drought and opens the water-sac, in moisture it spreads out and closes it ;
and the arrangement is like that which occurs in the utricles of Utricularia.
Colura. Colura tortifolia (Fig. 54) isan epiphytic species which grows
in South America’. The number of the amphigastria it is easy to see in
the figure is double? that in the other foliose Hepaticae. The end of each
lateral leaf takes on the form of a club-like sac into which a tube leads.
There are two things to notice in the development of the leaves of Colura.
First of all the under lobe of the leaf is rolled inwards against the upper
lobe as in Lejeunia. It may become concrescent with the upper lobe and
thus form the closed tube leading to the terminal club-shaped sac. The sac
itself, which is not found in Lejeunia, is the result of an increased growth
in surface of that part of the leaf which lies immediately above the tube
just mentioned. The club-shaped sac arises then, not, as previous writers
have assumed, by inrolling, but in exactly the same way as the water-sac of
Frullania ; and it is to be noted that the first sac-forming leaves which
appear upon the germ-plant ® of Colura, after a few flat leaves have been
formed, conform in their configuration with these water-sacs in Frullania,
and especially in the mouth of the sac which is directed downwards being
not yet closed by a lobe. But the club-shaped sac here chiefly proceeds
from the wpper lobe, the inrolled under lobe of the leaf only forms the
narrow tube leading up to the sac. The original apex of the leaf stands
subsequently at the entrance to the club-shaped sac, and at this point the
club-shaped papillae on the under lobe which secrete mucilage are found
chiefly. It is extremely remarkable that the entrance to the sac is closed by
a valve (Fig. 55). This lies upon a frame produced by a special outgrowth
and partial overlapping growth of some cells of the wall of the sac. The
valve is derived from a marginal cell of the under lobe of the leaf. It has
at its base a joint * which provides that the valve can easily be bent inwards
1 For a description of the configuration of the leaf see Goebel, Morphologische und biologische
Studien : I. Uber epiphytische Farne und Muscineen, in Annales du Jardin botanique de Buitenzorg,
vii (1888), p. 33: IV. Uber javanische Lebermoose; 3, Colura ornata, Goeb., ibid. ix (18g), p. 28;
id. Archegoniatenstudien: V. Die Blattbildung der Lebermoose und ihre biologische Bedeutung, in
Fora, Ixxvii (1893), p. 437-
2 This is brought about by the formation of a ventral segment after each lateral segment of the
apical cell.
3 For the germination of Colura ornata see Goebel, Morphologische und biologische Studien: IV.
Uber javanische Lebermoose ; 3, Colura ornata, Goeb., in Annales du Jardin botanique de Buitenzorg,
ix (1891), p. 28.
* The structure of the joint is not alike in all species ; for details see Goebel, Archegoniatenstudien:
V. Die Blattbildung der Lebermoose und ihre biologische Bedeutung, in Flora, Ixxvii (1893).
62 VEGETATIVE ADAPTATION IN HEPATICAE
whilst the frame upon which it lies prevents its opening outwards. When
the sac becomes emptied of water there can be little doubt that as in
Physiotium it is opened by a crumpling up of the valve.
I observed Colura tortifolia in British Guiana living upon the leaves of
trees. The leaves were not, as in other Hepaticae which live upon leaves,
adpressed to the leaf but directed upwards’. The valve has here then not
merely to hinder a free evaporation of water, but also the flowing back of
water, and to this end the capillarity of the narrow sac is favourable. No
animals were found in the sac, but these inhabitants will be referred to
subsequently.
2, 3, and 5, Physiotium
cochleariforme. 1, stem seen from below. Through the water-sacs the
depressions in which the apertures of entrance lie are visible. 2, stem-
apex from above; two young water-sacs visible. 3, young water-sac
Fic. 55. Colura Karsteni. Dia-
grammatic longitudinal section
through the saccate leaf at right
angles to the closing valve. A, valve ;
FIG. 56.
1 and 4, Physiotium giganteum.
W’, the frame upon which the valve
lies. The valve has a joint below
and can only open inwards in the
direction to which the arrow points.
seen from in front; O, upper lobe of the leaf; AZ, upper part of the
under lobe. 4, water-sac in section through the middle. 5, longitudinal
section through the point of origin of the valve. The hinge is indicated
by smaller cells.
Physiotium. The remarkable configuration of the leaves of Physiotium
next require notice.
regions in various parts of the tropics.
Physiotium is a genus inhabiting cool moist hill-
In Europe only one species,
* This is true probably of all species of Colura, at any rate of the beautiful large Colura Karsteni;
see Goebel, Archegoniatenstudien: V. Die Blattbildung der Lebermoose und ihre biologische
Bedeutung, in Flora, Ixxvii (1893), p. 427.
LEAVES AS WATER-SACS WITH VALVE 63
P. cochleariforme, remains as a relic of preglacial times in the same situations
as the Hymenophyllaceae which share with it its history. Rhizoids are not
present in the European species, of which I have examined living specimens
in Norway. The water-
sacs in the genusare very
large, and are complete-
ly closed but for the
special aperture of en-
trance. Their arrange-
ment is shown in the
transverse section repre-
sented in Fig. 57, and
from itwe learn that am-
phigastria are not pre-
sent. This happens be-
cause there isatwo-sided
apical cell and not a
three-sided one, as is the
Ese dmlleBe Eicpatict=) yi- 57 Fhysiotiua conchacfolinm. Stem-bud in transverse section.
which have been men- 1, high up; apical cell visible. 2, lower down. Magnified.
tioned until now ; consequently only two rows of segments forming leaves are
produced!. The development of the water-sac cannot be described here,
but it is noteworthy that the whole of the lower half of
the segment is not used in its formation, and that an out-
growth on the upper side takes a part in its construction,
as is the case in Frullania cornigera. In Physiotium micro-
carpum we find, as in some other species, a very simply
constructed water-sac, the nature of which may be
understood by a reference to Fig. 58,—water-sacs are
usually more complex (see Fig. 56). They have a
narrow mouth which lies in a depression. The special
exit is bounded by two portions of the wall of the sac, — py¢. <8. Physiotium
microcarpum. Dissected
lying upon one another like valves of a mussel, of which gnqSpread-out leaf. To
ae ; ie the left the simply-con-
the one is stiff the other is movable atajoint. Thevalve structed water-sxc. It is
: : ; -, scaphoid and has awid
consists of dead cells with delicate outer walls, and it opening ponthengnes
; : 5 - : si f the leaf a lamell
shrivels when water is withdrawn from it, and thus gives Springs out which em:
braces the point of inser-
a free entrance into the sac. At its base it possesses a tion of the water-sac.
ses : : = : 2 . Magnified.
joint like that in Colura. The water which is contained in
the sac must, excepting a very small fraction of it, before evaporation pass
* The germination of Physiotium is still unknown. It would be interesting to know whether in
course of the individual development there is a transition from the three-sided to the two-sided
apical cell as is the case in some Musci, for example in Fissidens.
64. VEGETATIVE ADAPTATION IN HEPATICAE
through the wall of the sac, and as this wall consists of living cells, these will
not merely make use of the water, but also of all the substances dissolved in
it. Evaporation through the dead cells of the valve is reduced toa minimum,
because the aperture of entrance lies in a depression which itself contains
water, and after the disappearance of this water it contains moist air. Ifthe
supply of water ceases, the water lying upon the surface of the plant evapo-
rates first, the water-sacs by their position upon the under side are protected
against rapid loss of water. They lose at first the water which is in the
chamber in front of the entrance, and then the water in the sac itself. The
air-bubble in its interior becomes greater, the water finally all disappears,
and the valve and the whole sac shrivels, but it fills again with water
in a short time on the addition of moisture, usually, however, one or two
air-bubbles remain.
Capture of animals by water-sacs. Frequently, but not always,
animals are found in the water-sacs of Physiotium, but by no means
only in them. It has been long known that many Hepaticae have
regularly a larger or smaller number of animals in their water-sacs.
Rotifera are found in indigenous and tropical species of Lejeunia and
Frullania, and also in the narrow water-sacs of Radula pycnolejeunioides.
These aquatic animals, which are able to withstand drying up for a long
time, find in the water-sacs favourable habitations, and similarly many
lower forms of animal life inhabit moss-tufts. They are not necessary
for the plant. That they may bring it some advantage is possible, as
does the addition of animal manure to other plants. The conjecture,
first put forward by Spruce and then afterwards by Zelinka, that the
water-sacs have originated in consequence of a stimulus exercised upon
them by the animals has no support. Even in the large wide water-sacs
of Lejeunia (Ceratolejeunia and Lejeunia paradoxa)' zo animals are
usually met with. They seek out preferably the narrow water-sacs in
which the water will naturally remain longer. The arrangement of valves
in species of Colura and Physiotium recalls the utricles in Utricularia, and
as these are traps for animals it was natural to suppose that the sacs of
these Hepaticae were of like character. It is true that in Physiotium coch-
leariforme animals are often found in the sacs, but much seldomer than one
would expect were the plants really carnivorous. Members of the most dif-
ferent affinities of water-animals were found, such as Tardigrada, Anguilluleae,
Crustacea *. Once they have entered the sac, they cannot escape unless
by breaking through its walls. If the water disappears and the valve shrivels
a passage of exit is made, but being water-animals they cannot move in
* Goebel, Archegoniatenstudien: V. Die Blattbildung der Lebermoose und ihre biologische
Bedeutung, in Flora, Ixxvii (1893), p. 435.
* Goebel, op. cit., p. 451.
AXEROPHILOUS ADAPTATIONS 65
the absence of water. No animals were found in the sacs of Physiotium
conchaefolium. It is probable that the rotting bodies of the dead animais
in the sacs may supply soluble substances which can be absorbed by the
plant. But this process must be quite a subordinate one to the chief work
of the sacs as water-reservoirs.
2. ARRANGEMENTS FOR RESISTING DROUGHT FOR A PERIOD.
One must not reckon all Hepaticae as hygrophilous. That would be
an error, for there are xerophilous adaptations. The configuration of Baz-
zania filum +, one of the foliose Hepaticae, is xerophilous. This plant grows
upon red clay soils which often become dry. The leaf-surface is but slightly
developed, and the leaves are closely adpressed to the stem and have greatly
thickened cell-walls. The whole plant has the stiff habit of many desert
plants. The simplest of these xerophilous adaptations is seen in the
capacity of many forms to withstand drying for a considerable period. The
capacity exists in varying degree in different species, and is based upon
the nature of their protoplasm. What interests us here is only the feca-
liarities of the formation of organs the advent of which are concurrent with
resting stages under conditions of dryness. These special features will now
be examined :—
(a) INVOLUTION OF ParTs. Riccia in-
-flexa*, protects its forked thallus in drought
against rapid loss of water by the inbending
of the edges of the delicate assimilation-tissue,
and some Marchantieae do ljkewise *. Species
of Plagiochasma, Reboulia, Grimaldia, Fim- Fic. 59. Plagiochila circinalis. Apex
briaria, Targionia, close up their thallus in Magnified. nee Mindenbags _—
such a way in drought that the assimilation-
tissue is protected. The dark, or in some cases, almost black scales of the
under side which were formerly invisible, now cover the thallus and give it
a most peculiar appearance in its rolled up condition. The addition of
moisture brings about again its expansion. The movements following upon
loss of water, or absorption of water, take place in the membrane of the
cells of the portion of the thallus containing no chlorophyll, and doubtless
bring the assimilation-tissue into a position where it is protected. Grimaldia
dichotoma may remain in the ‘latent’ condition in an absolutely dry atmo-
sphere for seven years without losing its capacity for development, while
* See Stephani, Hepaticarum Species Novarum, iii, in Hedwigia (1893), p. 206.
* Gottsche, Lindenberg et Nees von Esenbeck, Synopsis Hepaticarum, Hamburgi, 1844-7, p. 794-
* Mattirolo, Contribuzione alla biologica delle Epatiche, in Malpighia, ii (1888), p. 181; id.,
Nuove osservazioni sulla reviviscenza della Grimaldia dichotoma, Raddi, in Rendiconti della Acca-
demia dei Lincei, 1894.
GOEBEL II F
66 VEGETATIVE ADAPTATION IN HEPATICAE
shoots of Grimaldia cultivated in a moist chamber soon die when placed in
a drying apparatus.
The same kind of hygroscopic movement is found in the foliose forms.
Fig. 59 shows the end of a shoot of Plagiochila circinalis, which is rolled
up like a crozier in a dry condition, and the vegetative point is thus protected
by an envelope of older tissue !.
(b) FORMATION OF TUBERS. Further progress in the adaptation to
periods of drought is observed in forms which produce in their resting stage
tubers full of reserve-material.
Historical. The formation of tubers in the Hepaticae is a process of so much
biological interest that a short
historical notice of the subject
may be admitted here. Raddi
appears to have been the first
who observed this in Anthoceros
dichotomus. Neessays?: ‘ Raddi
found in the swelling at the end
of the root-strand a white almost
spherical little body which he
considered a germ-bud.’ Nees
conjectured that this species of
Anthoceros multiplied by shoots
from the thickened end of its
stout root-shoots, and Stephani *
subsequeiutly took this view.
Meanwhile the formation of
os tubers was found in other spe-
‘Kr
. cies of Anthoceros. Taylor saw
Ki, old tuber which has given ree to'a leafy shoot the ent otwieh it in the Australian Anthoceros
Monnowabes Rig hackegech caticupmetdcarte des? tuberosus’. Lindenberg? stated,
ieee regarding a species of Riccia
from South Africa, that upon the under side ‘here and there large shoots de-
velop . . . which at their point are thickened into a spherical or elongated head,
and this subsequently becomes a disk and probably ultimately grows into a new
plant.’ It is possible, however, that here ventral stolons only were observed, not
formation of tubers. Regarding Riccia natans he says®: ‘so soon as it approaches
the shore or touches the mud there shoot out from the whole under-surface, and
also out of the shreds belonging to this’, thin, delicate, cylindric, hair-like, very
* This, it must be stated, is concluded from the behaviour of dead plants only. No experiment
relating to this point has been made with the living plant.
* See the account by Nees von Esenbeck, Naturgeschichte der europadischen Lebermoose, iv. p. 347-
* Stephani, Ueber einige Lebermoose Portugals, in Hedwigia, xxvi (1887), p. 6.
* Taylor, Novae Hepaticae, in Hooker’s London Journal of Botany, v (1846), p. 412.
* Lindenberg, Monographie der Riccieen, in Nova Acta Academiae Caesareae leopoldino-carolinae
naturae curiosorum, xviii. I (1836).
® Lindenberg, op. cit., p. 479. 7 By this he meant the scales.
FORMATION OF TUBERS 67
often segmented! root-threads, which are coloured at the junction of the segments
like the under-surface of the thallus but are otherwise hyaline or granular. ‘These
fibres often thicken into a club-like or spherical form in which case the red or brown
colouring-matter accumulates at these thickened ends which subsequently flatten
and develop into new plants.’ This statement by Lindenberg allows us to conjec-
ture that here formation of tubers occurs, but it does not give us any insight into
the matter. Formation of tubers has also been said to occur in Petalophyllum ’.
In a species of Fossombronia growing upon the Cordilleras of Venezuela I observed
a formation of tubers * ; and recently Douglas Campbell has made a careful inves-
tigation of the formation of tubers in a species of Jungermannia which he calls
Geothallus tuberosus, and which is probably very near Petalophyllum *.
Fic. 61. Fossombronia tuberifera. Profile view ofa distichously-leaved plant in fructification. The sporogonium
is surrounded by a bell-shaped envelope. The point of the plant begins to penetrate the ground where it would
develop into a newtuber. Magnified 18.
I shall describe here, upon the basis of my own investigations, the
formation of tubers in one species of Fossombronia and two species of
Anthoceros.
* This is certainly wrong. The phenomenon is evidently one which can be observed in Riccia
glauca, where on older plants single cells grow out as tubes which form at their end a disk like
the germ-disk from the germinating spores. We have in this an example of what rarely occurs in
the Hepaticae, namely, the development of the germ-phase in regeneration. When this is the case
the plant is in unfavourable external conditions, and it is to be observed that the above-mentioned
phenomena were specially seen upon o/d plants which had lasted through the winter. It has been
stated recently that rhizoids might serve for regeneration, but this is certainly not the case. See
Fellner, Keimung der Sporen von Riccia glauca, in Jahresbericht des akademischen naturwissen-
schaftlichen Vereins in Graz, i (1875).
* Gottsche, Lindenberg et Nees von Esenbeck, Synopsis Hepaticarum, Hamburgi, 1844-7, p. 792.
* See Ruge, Beitrage zur Kenntniss der Vegetationsorgane der Lebermoose, in Flora, Ixxvii (1893).
* Douglas Campbell, A new Californian liverwort, in Botanical Gazette, xxi (1896), p. 9; id., The
development of Geothallus tuberosus, in Annals of Botany, x (1896), p. 489.
F 2
68 VEGETATIVE ADAPTATION IN HEPATICAE
Fossombronia tuberifera, as I will name the species’, lives in some
ways like Adoxa moschatellina or Solanum tuberosum, that is to say, it
forms alternately clongated shoots above the ground and tuberous shoots in
the ground, and this alternation may be repeated many times on one and the
same shoot-axis. In Fig. 60, for example, there may be seen at the hinder
end of the plantlet the old tuber, K'; out of it the leafy shoot developed
which appeared above the
ground, and which has upon
its posterior side some ar-
chegonia, A. After the
formation of leaves has
reached the highest point—
and this happens very soon,
as the whole plant is very
small—the shoot in its fur-
ther growth curves very
sharply downwards, the
leaves become reduced and
appear as but slightly pro-
jecting wings, and then
root-hairs develop out of
their edge, a development
always absent from the epi-
geous shoot. The summit
of the shoot then swells up
into a tuber, K,,, the vege-
iG. 62, Anthoceros dichotomus. Portion of the thallus. From pane pou ieese Eomeed
division ofthe sight "Ouallte lobe’ tre caline OF a youup me te ey eee
pale oe dark spots on the left indicate colonies of Nostoc. ordia, the epigeous parts die
off with the advent of the
dry period of the year, whilst the tuber persists. If it shoots out again it
can branch, and so give origin to a small tuft of plants. If a sporogonium
has been developed the plant nevertheless continues itself usually by a
tuber-shoot (see Fig. 61).
The formation of tubers in Geothallus tuberosus is very like that in the Fos-
sombronia just described, but the stalk which ensures the burying of the tuber in
the ground, and which occurs in the species of Anthoceros as well as in Fossom-
bronia tuberifera, is wanting. In Geothallus that portion of the tuber which contains
the reserve-material is bounded by one or two layers of cells with thick, dark walls,
and this is characteristic. The tubers arise both upon fertile and upon sterile shoots.
? I found it along with Anthoceros argentinus, a form which also produces tubers, in a gathering
from Pelegua in Chili. It is very nearly allied to a species I found at Tovar in Venezuela.
FORMATION OF TUBERS 69
Anthoceros dichotomus and A. argentinus. The tubers of the two
species of Anthoceros, A. dichotomus and A. argentinus, which have been
examined, may be regarded as transformed branches of the thallus, whose
ends have become swollen and filled with reserve-material. So far as
material has sufficed for examination of the structure of these tubers, it
corresponds with that of the tubers of Anthoceros tuberosus'. The tubers
are surrounded by some layers of empty cork-like cells ; their inner cells are
filled with fat and small grains like
aleurone. In Anthoceros dichotomus
(Fig. 62) the tubers stand upon the
under side of the thallus both upon
sterile parts and upon fertile parts,
but mostly upon the sterile. They
arise from its thickened midrib-
like portion, which is here not very
sharply differentiated, and they have
long stalks and are provided with
rhizoids. They are laid down close
behind the vegetative point, and are
therefore not adventitious but ventral
shoots. Instead of the stalk, which
-at a later period like the rest of the
thallus dies off, there is sometimes
found a thallus-lobe rich in chloro-
i z Fic. 63. Anthoceros argentinus. Thallus with tubers,
phyll. In Anthoceros argentinus * apparently derived from the germination of a tuber
which is still visible as a slight swelling at the base.
the tuberous shoots are partly lateral, Each tuber arises as a swelling of the end of a marginal
: lobe which bends downwards.
partly ventral. Fig. 63 shows how
lateral lobes of the thallus curve downwards, darken in colour, swell up,
and become tubers.
The method of germination of the tubers is unknown. Those taken
from herbaria have lost their power of germination. If, as appears to be the
case, the vegetative point of the tuber is not retained, we must assume that
cells lying underneath the cork-envelope produce one or more new vegetative
points, which rupturing the envelope grow out into lobes of the thallus.
I have recently observed formation of tubers in a cultivation of Anthoceros
laevis sent to me by Dr. Levier of Florence. The tubers were whitish swellings
upon the under side of the thallus near the vegetative point, and were filled with
reserve-material and provided with rhizoids.
There can be no doubt that formation of tubers also takes place in the Riccieae.
1 See Ashworth, On the structure and contents of the tubers of Anthoceros tuberosus, Taylor, in
Memoirs and Proceedings of the Manchester Literary and Philosophical Society, xli (1896), p. I.
* See Jack and Stephani, Hepaticae Lorentzianeae, in Hedwigia, xxxiv (1895), p. 317.
7o VEGETATIVE ADAPTATION IN HEPATICAE
In an Italian species of Riccia I found whole segments of the thallus developed as
Fic. 64.
paraphyllina.
Stephaniella
Profile view
of ashoot. A lateral shoot
springs from the side. Upon
the under side a hypogeous
rhizome clad with rhizoids
which have been broken off
short.
long tuber-like structures, the margins of the thallus being
turned inwards, and the tissue lying under the chlorophyll-
tissue being richly filled with reserve-material so that the body
appeared white on the outside. Stephani’ has lately de-
scribed tubers in Riccia bulbifera, but the descriptions do
not make clear what their morphological nature is.
The formation of brood-tubers as adventitious shoots
upon the midrib of the thallus of Fegatella conica? may be
mentioned in connexion with the tubers above described.
The contents of these tubers may be drawn upon by others
and they finally die off, but whilst they are undoubtedly
a resting-stage they have no special relation to a period of
drought, because Fegatella affects moist localities. ‘Tubers
dried for seven days were no longer able to form shoots. As
in other cases the capacity to resist drying may sometimes be
increased. It may be noted here that in the prothalli of
ferns, for example species of Anogramme, analogous forma-
tion of tubers takes place *.
(c) HYPOGEOUS ORGANS FOR THE ABSORPTION
OF WATER. A further peculiarity of xerophilous
Hepaticae is that they form organs which bore deeply
into the ground to take up water. We leave out of
account here the hair-roots of the Marchantieae, the
length and bulk of which stand in relation to the fact
that the surface of the thallus takes up no water.
Stephaniella. Here we have specially to mention
the behaviour of species of Stephaniella*. These are
foliose Hepaticae which grow upon clayey soil liable to
great dryness. They are small plants, two to four mil-
limeters long, with a worm-like configuration recalling
the condition under drought of the Marchantieae°.
The position occupied by the scales in those Mar-
chantieae is taken in Stephaniella by leaves closing
together like the shells of a mussel, and these embrace
the stem. Single plants form firm, compact, dry, hard
covers, which provide a protection to the subterranean
parts. These subterranean parts (Fig. 64) bore into
the ground to a length of as much as thirty millimeters,
quite eight times that of the leafy shoot, and this phe-
R. vesicata ; Taylor, Novae Hepaticae, in Hooker’s London Journal of Botany, v (1846), p. 416.
* G. Karsten, Beitrage zur Kenntniss von Fegatella conica, in Botanische Zeitung, liv (1887),
p- 649.
ST SEelpsy2il5.
* See Jack, Stephaniella paraphyllina, Jack, nov. gen. Hepaticarum, in Hedwigia, xxxiii (1894), p.11.
° See p. 65.
AIR-CAVITIES 71
nomenal length enables them to serve much more efficiently as organs for
the taking up of water, than would short small hair-roots alone which are
found upon them, and also upon the under side of the shoot. These hypo-
geous ‘rhizomes’ have greatly reduced leaves, and are the morphological
equivalents of the flagella', which are found in so many Hepaticae, and
they are able to grow out into leafy branches.
(d) ANATOMICAL STRUCTURE IN RELATION TO WATER. The in-
fluence which the kind and method of absorption of water has upon the
anatomical construction of the thallus appears particularly clearly in the
Marchantieae and Riccieae. The anatomical construction and the rooting
of the Marchantieae stand in the most direct relationship to the absorption
of water”. These Hepaticae are by no means all of them adapted to dry
habitats. Many of them, like Dumortiera, have returned to the behaviour
of the majority of the other Hepaticae, and some of them, like Riccia natans
and Riccia fluitans, are floating water-forms. But the typical representa-
tives of this group are distinguished by taking their water through their
rhizoids, which are specially strongly developed, and not through the whole
surface of the thallus. In correspondence with this we find that in warm
sunny areas like the south Tyrol, Jungermannieae have but a few represen-
tatives, but the Marchantieae and the Riccieae are abundant, and of them
Grimaldia fragrans and Riccia ciliata occur in mass upon sunny localities.
_ These forms have, in association with the strongly illuminated habitats they
affect, a well-developed assimilation-tissue. In shaded localities the members
of this cycle ofaffinity exhibit a very marked reduction in this respect.
Air-cavities. The existence of air-cavities in the assimilation-tissue is
characteristic of the Marchantieae and Riccieae. They arise, as Leitgeb
first showed, not schizogenetically like the intercellular spaces of higher
plants, nor by a progressive rupture of the tissue from the outside inwards,
but they are primarily depressions in the surface which result from the
lagging behind in growth of the tissues at certain points, which are always
those where four cells meet, and over these the adjacent parts then grow.
These depressions then: become deep pits, which are very narrow in the
land-forms of Riccieae. It is easy to satisfy oneself that these pits retain
air and do not allow the entrance of water. If a drop of water is placed
upon the thallus, of say Riccia glauca, it does not disperse because the
thallus cannot be wetted, and it does not enter into the pit. Even if the
surface of the thallus be removed by a horizontal cut and laid in water
the air-bubbles remain held between the cells. The uppermost cells of
the dorsal tissue of the thallus have no chlorophyll in the Riccieae, and
= See) Dp, 42.
* See Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 222; Kamerling, Zur Biologie und
Physiologie der Marchantiaceen, in Flora, lxxxiv (Ergiinzungsband zum Jahrgang 1897).
SRSee P45.
72 VEGETATIVE ADAPTATION IN HEPATICAE
in many they are somewhat broadened out, and so increase the difficulty of
entrance of water into the air-canal. If, however, transpiration be arrested
or made difficult, these cells without chlorophyll are able to give out water
in liquid form, at least I have in some circumstances found Riccia lamellosa
covered with small drops of water. They are evidently arranged for the
purpose of the giving off of water-vapour, and they are rich in water and
draw their supply to replace that which they lose from the cells containing
chlorophy!!. The Riccieae which live in dry localities have often many
of the cells from the surface inwards wanting chlorophyll. This is the
primitive form of an epidermis. In Riccia fluitans and Riccia natans the
air-canal is replaced by a wide chamber, a structure the occurrence of which
need not surprise us in plants living upon the surface of water or in moist
localities. These chambers open by only a narrow aperture to the outside,
and this in the water-form of Riccia fluitans is usually closed later. The
chambers are overarched by the growth in surface of the epidermis. The
chambers open to the outside in their whole width only in Riccia crystallina,
a species which grows in moist localities, goes rapidly through its develop-
ment up to the formation of the spores, and then dies. Such an easily
attained to structure can only exist where no serious claim is made upon it.
The type of dorsal air-chambers opening to the outside by few or many
pores, the ‘ breathing-pores,’ is widely spread with a different construction in
the series of the Marchantiaceae. Since Mirbel’s beautiful exposition of the
features of Marchantia polymorpha ' this species has become, in textbooks,
the representative of the Hepaticae. This is unfortunate, because it is
really one of the most highly specialized forms. A detailed description of
it is not necessary here, but an account of the relationships of its structure
to the conditions of its life is required, as these are very instructive. The
lid which roofs over the air-chamber is more or less sharply marked off as
‘epidermis, and consists in xerophilous species, like those of Oxymitra and
Plagiochasma, of cells having no chlorophyll and possessing thickened cuti-
cularized outer walls, but in forms like species of Cyathodium which live in
moist localities, these cells of the epidermis, which are usually in two layers,
contain chlorophyll. The other forms may be grouped, according to their
conditions of life, between these two extremes. The ‘ breathing-pores’ have
a threefold aim, one only of which is expressed in the name: firstly, to give
entrance and exit to carbon dioxide and oxygen ; secondly, to hinder the
entrance of water; thirdly, to regulate the evaporation of water. Whilst
then they differ in their origin from the stomata upon the sporogonia of
Anthoceros and of many Musci within the series of the Bryophyta, and
from the stomata of Vascular Plants, they resemble them in their function.
In the construction of these breathing-pores many cells share and they
‘ Mirbel, Recherches auatemiaeee et Siyel logiques sur le Marchatitie polymorpha, in Memoires
de l’Académie des Sciences de l'Institut de France, 1835.
AIR-CAVITIES AND BREATHING-PORES 73
bound the opening. According as these cells divide by walls at right angles
to the surface or parallel to it, s¢#ple or canal-hke breathing-pores are formed.
The latter are found upon the thallus in Marchantia (Fig. 65) and Preissia,
and upon the sporogoniophore in other species which have simple ones upon
the thallus. The simple breathing-pores are raised above the thallus upon
a wart-like projection, so that water can readily flow away from them, and
as the aperture is narrow water cannot enter. The canal-like openings
also do not allow the entrance of water, and in the water-form of Riccia
fluitans the openings are closed. This is the case also in a water-form of
Marchantia polymorpha which Ruge has accurately described’. In it the
submerged mode of life had hindered the formation of air-chambers in many
parts of the thallus, but where these chambers did exist the breathing-pores
were closed through papilla-like outgrowths of the cells of the lower tier of
FG. 65. Marchantia polymorpha. Breathing-pore. A, in surface view. 4, in vertical section. Magnified.
After Strasburger.
the pore. Finally in Dumortiera, which grows in the spray of waterfalls,
on stones in streams, and other similar spots, there is a remarkable reduction
evidently caused primarily by the conditions of its life*. The layer in which
the air-chamber is formed is laid down at the vegetative point but is soon
destroyed, and Dumortiera therefore behaves subsequently like a Pellia
which usually lives upon land, but can also take up water directly from the
outside. The reduction may go to varying lengths. In most species an
areolation marking the outline of the destroyed air-chambers may be ob-
served, and it is from these areolae that the assimilation-tissue subsequently
shoots out free and exposed from the base of the air-chambers. In one
species which I have examined this does not happen, and its older thallus
' Ruge, Beitrage zur Kenntniss der Vegetationsorgane der Lebermoose, in Flora, Ixxvii _1893),
p- 294.
* See Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 223.
74 VEGETATIVE ADAPTATION IN HEPATICAE
therefore exhibits in section a structure like that of Pellia or Monoclea, that
is to say, the chlorophyll is in its outer cell-layer 1.
With regard to the relationship of the breathing-pore to transpiration,
it is clear that the narrower the opening the slower will be the evaporation
of water. As a matter of fact we find the opening narrower in xerophilous
forms than it is in hygrophilous. In many species a closure of the opening
may take place, as I first showed in Preissia commutata. In Marchantia
there is no power of closure. The lowermost tier of the breathing-pore is
that which brings about its closure or the narrowing of it in Preissia (Fig. 66),
and Kamerling has confirmed this in the case of the breathing-pores of the
sporogoniophores in other species *. Closure takes place when water is with-
drawn, when there is strong turgescence there is opening. In Preissia, which
grows upon stones, walls, and similar places not always moist, the aperture
of the pore is always narrower than in Marchantia; each of the cells of the
lowermost tier—these are three to six in number, usually four—projects in-
wards so that the aperture is four-rayed.
The surface of the cells which bound the canal
of the breathing-pore is coated with wax
granules, as in Marchantia; it cannot there-
fore be wetted by water; moreover, the
breathing-pore is narrower at the outer aper-
ture than it is in the middle. When then a
p drop of water falls upon a thin thallus of
Sree este Preissia, it never can force out the air in the
Hicseh Pedi Ceo ee breathing-pore, and thus the tissue lying
ing-pore seen from below. Highly magni- below is completely protected from wetting.
A complete closure of the pore does not
appear to take place in Preissia, but there can be no doubt that its narrowing
is a provision for the regulation of transpiration. Simple breathing-pores
have but limited capacity of closure. The presence of canal-like breathing-
pores, which are usually capable of closure, upon the sporogoniophores in
species where the vegetative parts have only simple breathing-pores, is no
doubt due to the fact, as Ruge has pointed out, that an increased protection
against transpiration is required in the former positions®. In the genus
It is an open question whether the species I investigated is the same as D. trichocephala in
which Douglas Campbell (The Structure and Development of the Mosses and Ferns, London, 1895,
p- 49) found analogous features.
* See Goebel, Die Muscineen, in Schenk’s Handbuch der Botanik, ii (1882), p. 327, where I say :—
“From what I have seen in Preissia, where the lowermost tier consists of four cells, I believe we
may assume that they have the capacity to close the breathing-pore and thus to function as actual
guard-cells.” Kamerling (Zur Biologie und Physiologie der Marchantiaceen, in Flora, Ixxxiv,
Erganzungsband zum Jahrgang 1897, p. 37) is not justified then in his remark, that the opening
and closing of the breathing-pores in Marchantiaceae has hitherto been unrecognized.
* This is very evident in the case of stalked antheridiophores, but not so in the sessile ones of
Fegatella. The air-chambers are in this genus small, and chiefly serve for respiration. The diminu-
AIR-CAVITIES AND BREATHING-PORES 75
Exormotheca (Fig. 67) there is a peculiar disposition of the breathing-pores’.
The air-chambers of the thallus are so high that seen from above the thallus
appears white, and the breathing-pores are at the end of high chimney-like
processes. The air-layer, which lies here in the thallus above the assimila-
tion-tissue, acts as a kind of insulator against intense heat, in the same way
as do the dead portions of the leaves which enclose air in many Musci, for
example Bryum argenteum.
In Fegatella conica, which inhabits moist localities, there lie under the
breathing-pores beak-like cells containing but little chlorophyll which, acting
as evaporation-cells, increase the transpiration*. The construction of the
assimilation-tissue in these Hepaticae stands otherwise also in evident rela-
tion to the transpiration as well as
to the intensity of the light. In the
simplest cases the side and ground
walls of the air-chamber act as as-
similation-tissue ; in Cyathodium the
roof does so as well. This is also <S. Uk -
the case in the germ-plants of Mar- A uw \ ‘\ \ } a
chantia polymorpha, but subsequent- ~ La, N 4 i ¥
ly confervoid septate cell-threads :
sprout from the bottom, sometimes ~NNYN A
_also from the sides and roof, of the Re x TY} |
chamber; the same features are found Ss Spon hig
in Boschia, Preissia, Lunularia, Fe- YS ffs
gatella, Targionia; on the other hand ‘|
in Reboulia, Grimaldia, Fimbriaria, \\\ | i
Duvalia, and some species of Plagio- ; ay
chasma, the whole of the tissue be- sae Pie ese ace ae “Lower
figure; thallus in vertical section. The assimilation-
neath the upper surface of the thallus _ tissue peices oy shling: Lower less highly mag-
exhibits an apparently irregular
net-work of small and large air-chambers communicating with one another.
This construction is brought about by the development ofcell-plates from the
walls and roofs of the air-chambers, and these project into the chambers
and so divide them incompletely by septa. The narrower the communi-
cation between the several chambers and the breathing-pores the slower
will be the transpiration. The several different conditions of life to which
these forms are adapted have not, however, been thoroughly investigated.
tion of the transpiration may, however, be of use to the antheridia which require water for the
discharge of the spermatozoids.
* See also Solms-Laubach, Uber Exormotheca, Mitten, eine wenig bekannte Marchantiaceen-
gattung, in Botanische Zeitung, xiv (1897), p. 1.
* See Kamerling, Zur Biologie und Physiologie der Marchantiaceen, in Flora, lxxxiv (Erginzungs-
band zum Jahrgang 1897).
76 VEGETATIVE ADAPTATION IN HEPATICAE
Water-tissue. It is of less interest to us that in many Marchantieae
and Riccieae, which possess a thick thallus, a storage-tissue lies under the
assimilation-tissue, and in it water especially can be stored. The formation
of mucilage may also be regarded as serving the purpose of storage of water,
and it is found in many Hepaticae, both amongst Marchantieae and Antho-
ceroteae', The mucilage-cells in the Marchantieae are partly isolated,
partly in groups, as in Fegatella. In many species of Anthoceros, and evi-
dently also in Dendroceros, mucilage-pits are formed in the thallus. They
are present in great numbers in Anthoceros glandulosus, and have been
described, even in recent times, as ‘air-canals.. The formation of mucilage
here is intercellular not intra-cellular as it is in Marchantieae?. We have
no experimental proof of the importance of the formation of mucilage, but
it is striking that it is so abundant in a hygrophilous form like Fegatella.
Its relation, however, to water-storage is much more probable than the purely
mechanical function ascribed to it by Leitgeb.
Sclerenchyma. It is not the plan of this book to deal with anatomical
details, therefore I merely mention here that in many thallose Hepaticae,
for example Preissia, Blyttia, and others, sclerenchyma-fibres are found. In
many forms with strongly thickened cell-membranes the thickening has
clearly not a mechanical function, but is chiefly connected with storage of
water. The membranes are capable of swelling and can retain more water
the thicker they are, and this is probably the reason for the occurrence of
such membranes in the cells of the stem and leaves of Lepicolea ochroleuca.
The differentiation of the tissue in the stems of the foliose forms is other-
wise so simple that it requires no further mention here.
3. HYDROTROPISM.
The influence which their relationships to water have upon the disposi-
tion of the Hepaticae with reference to their substratum requires still more
accurate investigation.
Il. RELATIONSHIPS, HOGG ea la iy:
The relationship to gravity has only been studied in the Marchantieae.
In the forms which live upon the bark and leaves of trees negative geo-
tropism if it exists is only feebly expressed, as they grow clinging to the
surface in all directions.
Ill. RELATIONSHIPS TO LIGHT.
Light has a powerful influence upon the configuration of both the
thallose and the foliose Hepaticae. Etiolated shoots of species of Mar-
* See Goebel, Zur vergleichenden Anatomie der Marchantieen, in Arbeiten des botanischen Instituts
in Wurzburg, ii (1878-82), p. 529; also Prescher, Die Schleimorgane der Marchantieen, in Sitzungs-
berichte der Wiener Akademie, lxxxvi, i (1882). For the Anthoceroteae see Ruge, Beitrage zur
Kenntniss der Vegetationsorgane der Lebermoose, in Flora, lxxvii (1893).
* As in many alpine plants. See Lazniewski, Beitrage zur Biologie der Alpenpflanzen, in Flora,
Ixxxii (1896), p. 224.
RELATIONSHIP TO LIGHT (7 |
chantieae and other thallose forms grow erect! and remain narrow and
folded together ; the development of the thallus as a surface, and with its
characteristic anatomical construction, only takes place in light of sufficient
intensity *. This influence of light upon the growth in surface may be
limited only to one side of the thallus. I found a species of Blyttia upon
the bark of a tree in Venezuela which usually had only one wing, that on
the side away from the substratum ; the other was only indicated or sup-
pressed. Like appearances are presented by foliose Jungermannieae when
they grow clinging to a pot and receive their light from above. One row of
leaves then appears upon the side away from the substratum, that upon the
other side is reduced to the smallest rudiments*. This conforms with what
has been already said*, that the leaves are arrested at an early stage of
development in etiolated shoots of species of Jungermannieae. What is
artificially and occasionally developed here occurs in nature regularly in
some forms. In localities marked by feeble illumination, for example in
hollows or in dark woods, Hepaticae grow with the peculiar habit which
elsewhere is seen in germ-plants or in shoots which are half-etiolated ; the
leaves are feebly developed, chiefly in the form of cell-rows, and the function
of assimilation is taken on mainly by the elongated shoot-axis. These are
partly the’forms which have been referred to as ‘rudimentary.’ In most
of them we have to deal with an arrest at a stage of development which is
passed by others, and this arrest stands probably in relationship to the con-
ditions of the locality, especially those of feeble intensity of light. Experi-
mental investigation of this subject is still wanting.
The peculiar colouration of the vegetative organs of many Hepaticae
has in many cases a relationship to light. Green is the colour of most of
them but not of all. Every one knows the dark copper colour of the tufts
This may take place also in illuminated shoots if they are cultivated in a very moist atmosphere.
See Kamerling, Zur Biologie und Physiologie der Marchantieen, in Flora, lxxxiv (Erganzungsband
zum Jahrgang 1897).
* Plants of Marchantia developing from gemmae in feeble illumination grow very slowly, and
are arrested at an early stage of the formation of their tissue; see Stahl, Uber den Einfluss des
sonnigen und schattigen Standorts, in Jenaische Zeitschrift fiir Naturwissenschaften, xvi. In etiolated
shoots of Fegatella I find the assimilation-tissue only in the form of single cells instead of cell-rows,
and not developed at all in the marginal portions,
* See Frank, Die natiirliche wagerechte Richtung von Pflanzenteilen, Leipzig, 1870, p. 70.
Frank does not express himself regarding the cause of the suppression, but seems to consider it as
the result of want of room, In my opinion it is an effect of light. Let us suppose that the plant
at first grows close upon the pot with the two rows of lateral leaves clinging to the substratum and
equally developed. If the light now should fall directly upon them from above, the transversely
heliotropic leaves as well as the shoot-axis would experience a torsion through go”, and thus a row
of leaves would come to lie between the stem and the pot, and would thus be entirely removed
from light. I have observed the same phenomenon in the distichously-branched Musci, for example
species of Hypnum. If these lie with one of the sides bearing twigs towards the tree-stem, the
formation of twigs is suppressed on that side and appears only upon the other.
* See Part I, p. 241.
78 VEGETATIVE ADAPTATION IN HEPATICAE
of Frullania upon the bark of our trees, and more striking still is the dark
colour of Frullania atrata and F. atrosanguinea, which hang in long strands
from the trees in the moist woods of the mountains of South America. The
dark colouration is particularly striking in several Antarctic species of
Jungermannieae collected by Will in South Georgia. The Gymnomitrieae
which grow upon rocks have a similar dark colour which is only developed
in them as in others on the portions exposed to light, and is brought about
by the deposition in the cell-membranes of the colouring-matter by the
protoplasm. Red colouring-matters are tolerably common, for example in
Physiotium, Scapania undulata, and others; the scales of many of the Mar-
chantiaceae, and also the under side of the thallus in part, have a purple
colouration ; the cell-wall of the rhizoids is violet in many species of Fos-
sombronia. We may agree with Stahl in regarding the dark colouration of
many Hepaticae as well as of many mosses as having a relationship to the
absorption of heat'. But this point requires experimental investigation.
The short statement by Jonnson” that dark-coloured individuals of Frul-
lania Tamarisci respire and transpire more feebly than green ones is not
sufficient basis for the settlement of the question.
We do not know whether the yellow colouring of many species of
Lepicolea has any biological significance *.
IV. RELATIONSHIPS TO OTHERFORG ANS.
Reference has been already made to the animal lodgers of the Hepaticae,
and now we have to consider the symbiosis of Nostoc with Blasia and
Anthoceros, and the protection against animals which the Hepaticae
exhibit.
The mucilage-pits of the Anthoceroteae are regularly inhabited by
colonies of Nostoc. The hormogonia of Nostoc penetrate the mucilage-
slits and grow into. colonies. Their presence has a curious effect upon the
mucilage-pit, it closes and the cells of the wall of the pit grow out into
tubes which branch and enter into such intimate contact with one another
and with the colony of Nostoc that the appearance is produced of a paren-
chyma-tissue within the intercellular space *.
The leaf-auricles of Blasia are similarly inhabited by Nostoc, and other
Cyanophyceae may also be met with in them. These cause an enlargement
of the auricle and the formation of a much-branched tube which, spreading
from a single cell, grows into the colony.
We have no experimental evidence giving us an explanation of this
* Stahl, Uber bunte Laubblatter, in Annales du Jardin botanique de Buitenzorg, xiii (1896),
p- 168.
* Jonnson, Recherches sur la respiration et assimilation des Muscinées, in Comptes Rendus, cxix
(1894).
* See Czapek, Zur Chemie der Zellmembran bei den Laub- und Lebermoosen, in Flora, Ixxxvi
(1899), p. 361.
' Leitgeb, Untersuchungen iiber die Lebermoose, Graz, v (1879), p. 16.
a
RELATIONSHIP TO OTHER ORGANISMS 79
symbiosis. We can only say of it here, as elsewhere in Azolla and Gunnera,
that the Cyanophyceae only enter depressions which form mwcilage, and we
gain the impression that the algae become shut up in them. They find in
them protection and lodging. Whether they benefit the host or not we do
not know ; perhaps the colonies of Nostoc serve as reservoirs of moisture on
account of their mucilage'. Other authors ascribe to them the capacity of
assimilation of free nitrogen like the bacteria of the tubercles of Legumi-
nosae. These are, however, all mere conjectures, and experimental proof
can alone settle the point.
Many Hepaticae are not eaten by snails or other animals” because usually
they possess a definite ‘ protective substance.’ Mechanical protection by thick-
ening of the cell-membrane is only seldom met with. It is easy to prove
by chewing them that many Hepaticae have an unpleasant taste. Their
peculiar smell is also a protection to many against animals, and this odour is
naturally associated with the presence of oil-bodies *. Experimental proof of
this is, however, wanting. The oil-bodies lie isolated in the cells of the
Marchantieae or they may be in numbers in the cells, and they consist of a
ground-substance or stroma in which the drops of fatty matter are embedded ;
and along. with these tannin occurs in the Marchantieae and in other species,
perhaps also small quantities of volatile oil. At any rate these substances
so deposited must be regarded as excreta, and they are found in parts which
are produced in the dark; but we are unable at present to say what is their
significance in metabolism. Kiister, who examined a large number of the
Hepaticae, found them wanting only in Riccia lamellosa, Oxymitra pyra-
midata, two species of Clevia, Metzgeria furcata* and Metzgeria pubescens,
Jungermannia bicuspidata and J. Michauxii, whilst other species of Riccia
possess them. They appear to be altogether wanting in Anthoceroteae.
IV
FERTILE SHOOTS AND PROTECTION OF THE SEXUAL
ORGANS OR THE SPOROGONIA OF HEPATICAE
The structure of the sexual organs and their products has been already
described®. Here we have two points to notice, the disposition of the
sexual organs, and the influence which the appearance of the sexual organs
! Goebel, Die Muscineen, in Schenk’s Handbuch der Botanik, ii (1882), p. 360.
2 Stahl, Pflanzen und Schnecken, Jena, 1888.
° W. y. Kiister, Die Olkérper der Lebermoose und ihr Verhalten zu den Elmioplasten. Inaug.
Dissertation. Pasel, 1894. The literature is cited in this paper. Stahl has designated the oil-
bodies ‘ protective bodies.’
* Whether the refringent bodies described by Stahl in Metzgeria as oil-bodies are really so or not
requires further investigation. 5 See p. 9-
80 FERTILE SHOOTS*IN PHEPATICAE
has upon the vegetative organs, an influence which finds expression in
changes of form of these,and in the development of envelopes for the sexual
organs or the sporogonia.
I. DISPOSITION AND PROTECTION OF THE SEXUAL ORGANS
OR SPOROGONIA.
No reference is required here to monoecious or dioecious conditions
because they occur in one and the same genus, for example in Pellia.
That dioecious forms, in the absence of male plants, are not fertile is
a matter of course, but it may be seen in a very striking manner in Lunu-
laria vulgaris, which for a long time has been known in North Europe in
female examples only!, this form having been introduced probably in orange-
casks from South Europe. It has increased by gemmae, formed groups of
archegonia but no sporogonia.
In the thallose forms the sexual organs always sit upon the dorsal or
upper surface of the thallus. In Riella, where the existence of the wings
gives an appearance of another arrangement, the disposition of the sexual
organs is the same (see Figs. 9, 10); the antheridia are sunk in the many-
layered wing; the archegonia are found on the two sides of it. Leitgeb
has divided the Jungermannieae into the two groups of acrogynous and
anacrogynous according to the point of origin of their archegonium. In
the acrogynous group, to which the majority of the foliose forms belong,
the apex of the stem is used up in the formation of archegonia; in the
anacrogynous group this. does not occur, yet Calobryum approaches the
acrogynous forms inasmuch as there are here terminal groups of archegonia
and antheridia (Fig. 37).
In the anacrogynous Jungermannieae and in the Marchantieae, two
methods of disposition of the sexual organs may be observed ; either they
are disposed irregularly, as for example in Riccia, Fossombronia, the
antheridia of Pellia, and others, or they are arranged in more or less sharply
limited groups. In the former series of cases, and sometimes also in the
latter, the shoots which bear the sexual organs continue their growth after
the formation of these; but if they are constructed as short shoots (see
Fig. 68), they are naturally more sharply marked off from the vegetative,
branches. .
The primitive disposition is the diffuse as it is found in Riccia. Here
the neck of the archegonium reaches beyond the surface of the thallus,
whilst the lower portion is found in a pit. The antheridia are also sunk,
and completely so. The mouth of the pit in which they sit projects more
‘ The statement in books that male plants are rare in the South is incorrect. I found them
everywhere when I looked for them in Florence, Rome, Naples, Sic ly. That Lunularia seldom
fruits in Italy is probably a consequence of its period of fertilization happening in spring when
the requisite moisture for the process is often wanting. Cultivated examples fruit abundantly at
Munich. ’
DISPOSITION OF SEXUAL ORGANS 81
or less beyond the thallus and is pierced by a narrow canal ; in general the
pit-mouth projects beyond the thallus as far as does the neck of the arche-
gonium, but this requires further investigation. When the antheridia
discharge their contents they press their mucilaginous content, including
the spermatozoids, out of the narrow canal
traversing the mouth of the antheridial pit,
and owing to the narrowness of the canal
there may be a gradual emptying of the an-
theridium. The spermatozoids may either
swim freely to the archegonia which usually
stand in a channel of the thallus, or they may
be carried to the neck of the archegonium
by small mites or other animals. As a
matter of fact the Riccieae are usually found
in very moist localities.
Monoclea forms groups of antheridia
which resemble those of many of the Mar-
chantiaceae. The shoot which bears the
antheridial groups does not stop its growth
upon their production, but that bearing the
archegonia does so. Fic. 68. Aneura (Pseudoneura) erio-
In Aneura (Fig. 68) the sexual shoots et nche Mag
lag behind the sterile ones at a very early ;
period in growth, and appear in consequence as lateral appendages
upon the margins of the thallus. These shoots
produce either antheridia or archegonia. and
with their appearance the growth of the shoot
ends. Male and female sexual shoots are found
upon the same plant, for example in Aneura
multifida, but they may be upon different
plants. The antheridia arise in progressive
serial succession and are sunk in the tissue of
the shoot which bears them. As they stand
close together in the greater number of cases
the shoot has a wavy appearance.
About the archegonia of Aneura there are
: : Fic. 69. Aneura sp. Archegonial
arrangements which, whilst they protect the shoot, seen from above. The margin is
: : ° curved upwards and grown out into a
archegonia, are also specially fitted to retain number of scales, Si, Sx, Ss. A scale-
like outgrowth is also visible at the
drops of water which are so important for _ posterior end of the shoot; this is repre-
sented in the figure as directed upwards.
fertilization. This is a point which has been
hitherto overlooked. Fig. 69 shows a group of archegonia from above.
It is surrounded by an envelope, and this is formed from the two
margins of the thallus first of all, and then by a scale-like growth from
GOEBEL II G
82 PERTILE SHOOTS. IN HEPATICAE
the posterior end of the sexual shoot. It is specially noteworthy that
the margins of the thallus of the sexual shoot have grown out into a
series of distinct scales, S,, S,. S,, on the left side of the figure. These
are to be considered as an indication of a formation of leaves and they
appear only wpon the sexual shoots, not upon the sterile ones. The long
drawn-out lobes of this envelope form an apparatus which holds water-
drops.
Whilst in Aneura modified Jateral twigs of the thallus are formed for
the purpose of bearing the sexual organs, in Hymenophytum and Metz-
geria there are ventral shoots which perform this service. The species
of Hymenophytum shown in Figs. 13
and 19, exhibit these short shoots which
bear the sexual organs, in this case
the archegonia, upon their upper side.
ae
ee Fic. 71. Symphyogyna. Group of archegonia
in vertical section. To the left the perichaetium
Fic. 70. Blyttia sp. Group of archegonia in vertical which is composed of one simple scale only. To
section. Surrounding the group is the cup-like peri- the right the thallus. The embryo has burrowed
chaetium and within this the primordium ofthe ‘ perianth’ into the tissue of the stem beneath the arche-
Heth gonium, this tissue has originated by growth
accompanied by cell-multiplication after fertiliza-
tion.
The groups of archegonia are surrounded by a cup-like envelope, the
perichaetium! (Fig. 13, 7), which is split up into different scales, as in
Blyttia (Fig. 70), and this slit perichaetium forms an apparatus for collect-
ing water-drops, like the structure described in Aneura. Within the
perichaetium there is developed after fructification a second envelope, the
perianth (Fig. 13, .S) for the protection of the sporogonium. This perianth
is also seen in Blyttia (Fig. 70, J/, 7). In Metzgeria no special envelope
} We shall, in order to avoid confused nomenclature and the coining of new words, name the
envelope which invests the group of archegonia Jdefore fertilization, and which serves for fixing
the drop of water, the Jerichaetéum, and the envelope which grows out only a/ter fertilization the
perianth. Many Hepaticae have only a perichaetium, cthers, like Hymenophytum, have also a
perianth.
DISPOSITION OF SEXUAL ORGANS 83
exists!, its place is taken by the concave curvature of the sexual shoot
itself. In Symphyogyna (Fig. 71) the group of archegonia is protected by
a single scale-like growth of the thallus which forms a perichaetial scale,
whilst the antheridia stand singly, covered over by a small scale on the
dorsal side of the thallus. This position I assume to be the original one
for the archegonia. The behaviour of Morkia points in this direction. In
it there are, outside the perichaetium, some single scales; whilst in Blyttia
these are united more or less to a scale-like envelope. Such a homology
can only hold, however, within one genus or within a very near cycle of
affinity, and in other Hepaticae the perichaetium arises certainly in another
way than by the union of scales. In Pellia, at least in P. calycina, the
FiG. 72. Sphaerocarpus terrestris. Portion of a female plant seen from above. Many perichaetia, each
surrounding one archegonium, cover almost the whole surface of the thallus. Magnified 12.
perichaetium is like that of Blyttia, only that its mouth inclines towards
the apex of the thallus, as there is formed, not only de/zvd the archegonial
group, reckoned from the vegetative point, but also zz front of it, a growth
which after fertilization grows out strongly and forms with the scales the
envelope of the sporogonium.
The combination of the archegonia in groups increases evidently the
probability of fertilization. Usually only a single embryo develops into
a sporogonium, and this bores into the tissue underneath the archegonium ;
in P. calycina I have occasionally found two sporogonia within one envelope,
but they were unequally developed.
* This is at least the case in Metzgeria furcata. According to Stephani, Hepaticae Australiae,
in Hedwigia, xxviii (1889), p. 268, the perichaetium is present in Metzgeria australis, and there-
fore it is possible that it is a primitive structure in the genus which has been lost in most species
in consequence of the strong incurving of the sexual shoot.
G2
84 FERTILE SHOOTS IN HEPATICAE
In Sphaerocarpus the sinking of the antheridia and archegonia in the
thallus is impossible because this only consists of a few cell-layers. Here
the cells lying around the incipient antheridium grow up afound it, and
this envelope forms the perichaetium which arches over the apex of the
young antheridium and ends in a lobed projection with an opening at its
point. A similar perichaetium surrounds the archegénium (Fig. 72).
These perichaetia contain chlorophyll and evidently perform some work as
organs of assimilation.
In Fossombronia (Fig. 61) and Haplomitrium, the antheridia stand free
upon the surface of the stem ; in youth they are protected by the leaves of
the terminal bud. Occasionally they, as
well as the archegonia, are protected also
by scales which we may, with Leitgeb, con-
sider as the remains of the protecting organ,
no longer constantly formed, which the true
thallose ancestors of Fossombronia pos-
sessed. With the appearance of leaves they
became superfluous and degenerated. But
the case of Treubia! shows that this hypo-
thesis cannot be generally applied. In it
the dorsal scales belong to organs of the
plant which constantly occur, evidently
because they share in the protection of the
vegetative point. Calobryum forms a tran-
sition to, or rather a parallel formation with,
the acrogynous Jungermannieae in so far
as its archegonia and also its antheridia
form terminal groups upon the leafy shoots,
FIG. 73. _Plagiochasma Aitonia. Male and conclude the growth of the latter.
plant with five antheridial groups seen from ‘ :
above. The younger groups, like the vege- MARCHANTIACEAE. The Marchanti-
Ceatce Cihes aah the Sime cent Te aceae are distinguished by the fact that in
antheridial groups. Magnified 8. : é
them the transformation of the vegetative
shoot-axis into sexual shoots reaches its extreme. The sexual shoots
here form the peculiar antheridiophores and archegoniophores which we
know in Marchantia, Preissia, and others. In the series all gradations
from simplest up to the most complex development are found. We may
distinguish three chief stages :—
1. Diffuse disposition of the sexual organs, as in Riccia.
2. Combination of the sexual organs in groups without transformation
of the branches which bear them. This is the case in Corsinia where the
archegonia stand in pits which are developed by the suppression of the
Tees sO:
DISPOSITION OF SEXUAL ORGANS 85
assimilation-tissue ; further, we find it in Plagiochasma (Fig. 73), where
antheridial groups are repeatedly developed upon the back of the thallus
and are protected by enveloping scales. The envelope-scales form the
perichaetium and take origin in the same way as the ventral scales of the
thallus already described’. The archegonial groups are ensheathed in
similar perichaetial scales, which stand erect, and thus can readily hold
water by their apices, and so favour fertilization. In Plagiochasma I found
two groups of archegonia at the base of one papilla and enclosed by an
outgrowth which formed a shell-like envelope. The papilla is constricted
below and rounded above, and then, shortly before ripening of the arche-
gonia, it grows out, so that the constricted part below the archegonia be-
comes elongated into a stalk. There is thus formed a structure very like the
stalk of the archegoniophore in Marchantia and others, but which has quite
another origin. There are in Plagiochasma then very simple means for the
protection of the archegonia, for the
furthering of fertilization, and for the
favouring of the distribution of the
spores. The head of the archegonio-
phore, if it develops chlorophyll-tissue,
which is not always the case, has sto-
mata of the usual canal-like form °.
3. The sexual organs are borne
upon special shoots which are trans-
formed into radiately branched axes
of limited growth. Marchantia and —_Fic.74. Marchantia polymorpha. 4, male plant
A with two antheridiophores of different age; 4, cup for
Preissia furnish well-known illustra- gemmae. B, vertical section of antheridiophore; a,
antheridium sunk in the disk; s, the vertical scales;
Bee etiionanc tie) sexual branches) .% thioids; 4 thallus. 4, natural si: 2; magnified
in them owe their origin to a repeated
forking of the vegetative point of the fertile shoot. The summit of the
antheridiophore is disk-like (Fig. 74), and that of the archegoniophore is
cap-like. These structures have been often described and yet their bio-
logical significance has not yet been explained. Why should male and
female sexual branches have a radiating construction? Why should the
male be differently formed from the female, and why should both be
stalked, although this appears to be useful only for the female in con-
nexion with the distribution of spores? What significance have the
different envelopes of the sexual organs?
This disk is not actually radial but symmetrically divisible by only
one plane. This appears much more conspicuously in species of Marchantia
other than the endemic M. polymorpha. The fact that the disk of the
antheridiophore consists of branches of the thallus each with progressive
1 See p. 30. a See pe 74-
86 FERTILE SHOOTS IN HEPATICAE
formation of antheridia at its vegetative point, may be connected with the
fact that in this way spermatozoids capable of doing the work of fertiliza-
tion become available for
a long period.
As to the difference
between the antheridio-
phore and the archegonio-
phore, it is evident that the
antheridia remain _ per-
manently upon the upper
side as in all other Hepa-
ticae ; the archegonia are
laid down upon the upper
side, but are displaced to
the under side where they
have a protected position.
The disk-form of the
summit of the antheridio-
phore has relation to its
function. Thelieis directed
somewhat upwards. If a
drop of water, say a rain-
drop, fall upon the disk it
spreads out quickly there-
on it, as Strasburger has re-
marked!; and if the an-
theridia are ripe they
empty their contents into
the drop of water, and
when a new drop of water
falls upon the disk, it will
FiG.75. Marchantia polymorpha. .A, female plant with four arche-
goniophores of different ages; 6, cupfor gemmae. Natural size. B, wash off the greater part
cap of an archegoniophore seen from below; s¢, rays of the cap; 4, F
perichaetium ; sf, young sporogonium. Magnified 3. C, vertical section of the previous one con-
of the cap of an archegoniophore; 4%, perichaetium. Magnified 5. a) E
D, young sporogonium still within the archegonial venter in vertical taining the spermatozoids.
section; sf/, the seta; sf, sporogenous tissue; £w, wall of capsule; % = A
aw, wall of venter of archegonium ; #, neck of archegonium; /, ‘peri: The disk being stalked it
anth.’ Magnified 70. 2, ruptured sporogonium from which the spores,
$s, and elaters are issuing ; 2, wall of capsule; c, venter of archegonium; jg enabled to throw the
?, ‘perianth.’ Magnified 10. #, an elater. G, spores. Magnitied 315.
H, germ-plant; s, spore; vs, germ-tube; 4, germ-disk; v, vegetative
point of the young plantlet ; 7A, its first rhizoid. Magnified 100. C, &, water-drop with the Spel
after Bischoff. &, D, F-H, after Kny. Lehrb. matozoids further than it
could were it unstalked*. If such a drop reaches the cap of the
* Strasburger, Die Geschlechtsorgane und die Befruchtung bei Marchantia polymorpha, in
Pringsheim’s Jahrbiicher, vii (1869-70), p. 49.
* Whilst the advantage of the stalk of the archegoniophore in facilitating spore-distribution is
clear, that of the stalk of the antheridiophore is not so evident. Might it be a survival like the nipples
ina male Mammal? The explanation I have given in the text seems to me the true one.
DISPOSITION OF SEXUAL ORGANS 87
archegoniophore from below, the incurved rays of the cap hold it firmly.
If the drop falls upon the upper surface of the cap, and it may do so
easily so long as the cap is unstalked, it does not lie upon the convex
surface of the incurved rays, but flows down in the grooves between them,
carrying the spermatozoids to the groups of archegonia which in the un-
stalked cap have their necks directed upwards’ and are therefore readily
fertilized. The necks of the archegonia are subsequently, when the cap
is raised up on its stalk, directed straight downwards, and fertilization can
then only be brought about by water coming up from below; but such
a movement of spermatozoids between the bundles of rhizoids upon the
stalk appears to me to be highly improbable.
In addition to the incurving of the rays of the cap, which only later spread
out if the sporogonium develops, the perichaetium also supplies a mechanism
for holding drops of water (Fig. 75, 4, 2). This envelope corresponds to
the mussel-shell envelope, which envelops the group of archegonia in
Plagiochasma. In addition, there is around each archegonium a special
envelope, the pertanth (Fig. 75, D, p), which before fertilization appears as
a low ring around the base of the archegonium, and subsequently grows
over it. This envelope is, with reference to other Marchantiaceae, an
entirely new formation, and it seems to be connected with the necessity of
providing a strong protection against drought to the young sporogonia
which are seated upon the stalked archegoniophore. It is absent in forms of
Marchantiaceae, which grow in shaded localities, or in which the sporogonium
is only borne on a long stalk at a late period of development.
We have thus endeavoured to bring the conformation of the antheridio-
phore and archegoniophore of Marchantia into relation with three factors :—
1. The distribution of the spermatozoids and the securing of fertilization.
2. The prolongation of the possibility of fertilization over a long period,
and with this is connected the fact that several sporogonia may
be found in each group of archegonia, and that there may be there-
fore more sporogonia than there are rays to the cap.
3. Protection of the sporogonium and the distribution of spores.
Let us compare now another nearly allied form which has an altogether
different mode of life :—
The genus Dumortiera* develops the stalk of its archegoniophore only
after fertilization has taken place, and from this we might conclude that the
antheridiophore should be unstalked. This is the case. The stalk scarcely
deserves the name, and at most it serves to facilitate the throwing off of water
from the antheridial disk. As the genus is hygrophilous we should not
expect a special envelope to the archegonium, and I have found no trace of
1 Tn response to what ‘stimulus’ ?
* See p. 73. I examined two species which I collected in South America, and the Canary Island
species D. irrigua.
88 PERTILE, SHOOTS IN THEPATICAE
it, and in this I differ from Leitgeb!. The cap of the archegoniophore is
not provided at the time of fertilization with rays, but is only slightly nicked
at the edge. The rays which appear later are a consequence of the strong
development of the perichaetia surrounding the several archegonial groups.
Each perichaetium has a narrow funnel-like mouth out of which the necks
of the archegonia project to a considerable extent, and it is filled with
mucilage*, The numerous scales which are found upon the cap are very
striking; they are partly curved upwards, partly directed downwards,
and they form a net-work for the firm retention of the water contain-
ing the spermatozoids. The entrance of the spermatozoids into the open
Fic. 76. Radula tjibodensis. An archegonial group at the end of thestem. /%, leaves of the perichaetium ;
P?, incipient perianth. Tufts of rhizoids are shown springing forth from the water-sacs.
neck of the archegonium is determined by chemotactic influences, and only
one sporogonium is produced from each archegonial group.- In Dumortiera
the biological relationships, fertilization, distribution of spores, and so
forth, are essentially the same as in Plagiochasma, whilst the morpho-
logical features are different, and we have here an instructive example of
how the same end is reached by different means.
ACROGYNOUS HEPATICAE. In the acrogynous Hepaticae the pro-
tection of the antheridium is effected by the leaves which are often charac-
teristically formed for this purpose, and they have in their axil one or many
antheridia. The archegonia also, which may be solitary as in Lejeunia and
Phragmicoma, or in groups of two to three in Frullania, or of a larger
' Leitgeb, Untersuchungen iiber die Lebermoose, Graz, vi (1881), p. 174.
* The envelope is, as in Plagiochasma, thicker than that in Marchantia.
DISPOSITION OF) SEXUAL ORGANS 89
number in Plagiochila, Jungermannia, of as many as a hundred in Lopho-
colea, are at first surrounded by leaves which form the perichaetium (Fig.
76, Pc). These leaves are distinguished from the vegetative ones mainly by
their great size and by the absence of the adaptations of the latter, such as
the formation of water-sacs. Where the sexual shoots are orthotropous am-
phigastria often appear in the perichactium, even though they be absent from
the vegetative shoots ; but from sexual shoots
which are not orthotropous, for example those
of Radula, amphigastria are absent as com-
pletely as they are from the vegetative shoots.
Further, most forms possess an organ which,
at the time when the archegonia are ripe,
appears as a low annular wall (Fig. 76, Pz) ;
this grows out later as the perianth, and
is commonly considered as being formed
of three concrescent leaves, although I think
the interpretation is doubtful. It appears to
me to be much more likely that the perianth
is the descendant by inheritance of an organ
present in thallose ancestors. It is not
present everywhere ; it is wanting in Tricho-
colea, Gymnomitrium, and in the Junger-
mannieae of the group Geocalyceae.
Trichocolea. In Trichocolea pluma
(Fig. 77), which I collected in Java, an arche-
gonial group is found at the end of a thick roe
branch clothed with leaves and numerous para- _ Fic. 77. Trichocolea pluma. Fertile
phyllia, and from this, as usual, only one sporo- neue. Meera CE the actos och
: : = : A gonium; 4, sterile archegonia. The
gonium is formed. The archegonium in which dotted line gives the outline of an older
eye ° c - “mule embryo. The relationships are not quite
fertilization is effected achieves only an insig- correctly given in the figure because during
nificant growth, but the embryo penetrates at sige SES ect eros eee
an early period into the tissue of the stem aie. a
which furnishes it with the necessary protection, and acts as substitute for the
wanting perianth. If we limit the notion of calyptra to an archegonial venter
which increases in size after fertilization, Trichocolea has no calyptra. Such
a limitation would be, however, alike useless and untenable. It is incorrect to
say of this genus that the ‘ calyptra is woolly on account of the adherent invo-
lucral leaves?.’ There isno concrescence here, and the ‘ wool’ is formed by the
paraphyllia*, which as in the vegetative shoot are organs for holding water.
The significance of the perianth (see also Fig. 85) for the ripening of
" Schiffner, Hepaticae, in Engler und Prantl, Die natiirlichen Pflanzenfamilien, p. 110.
3 See p. 57.
go PERTILE: SHOOTS IN WWEPATICAE
the sporogonium is mainly this, it hinders the entrance of water and
protects from drying up. Only in one form, Anthoceros, do we find water
in the pit which surrounds the young sporogonium, and this water is
secreted by separate cell-threads which project into the pit. Probably
here, as in the case of some Musci in which the dilated calyptra exudes
water, the water is required by the sporogonium; and this recalls the
exudation of water in the flower-bud of many Spermophyta.
Calypogeia. A slimy fluid is also found in the narrow tube at the base
of which sit the archegonia of Calypogeia ericetorum. Calypogeia belongs
——<
sf |; ao
Fic. 78. Calypogeia ericetorum. Plant with fertile root-like shoot at the translucent end of which the fertile
archegonium is visible.
to a group of Jungermannieae which has been designated Geocalyceae,
because the sporogonium is sunk in a hollow branch which in fructification is
to a greater or less extent pushed into the soil. It has been long recognized '
‘that this group is a dzological one, not systematic, that is to say, its special
feature is a character of adaptation which may occur in different groups,
and we shall see that, notwithstanding opinions to the contrary, the
adaptation appears in different forms and in different ways. No member
of this group has a perianth*; other structures do its work and give the
ripening sporogonium protection, especially against drying, a protection the
more necessary because the water-supply available to these plants at the
time of the development of their sporogonium is by no means a certain one.
In Calypogeia ericetorum (Fig. 78) there arises upon the under side of the
plant the hollow fertile branch which penetrates the soil like a root, reaching
‘ See Spruce, On Cephalozia and some Allied Genera, Malton, 1882, p. 92. Spruce dwells upon
the relationship of Acrobolbus (Gymnanthe, Taylor, pro parte) with Alicularia, and of Calypogeia
with Southbya. The history of development he gives of the Geocalyceae is incorrect.
* There is a rudimentary perianth in some species. ;
DISPOSITION OF SEXUAL ORGANS gI
a length of almost one centimeter. It is covered with hair-roots, and comes
ultimately into a position which facilitates the intake of water, but makes
difficult the drying up of the shoot. The inside of the hollow branch is
lined with hair-like cells, and on these there are present special papillae
(Fig. 79, 2), which secrete mucilage and contribute to keeping the growing
sporogonium moist; they are later pushed to one side by the developing
sporogonium. The history of this sac, in which the sporogonium
develops, has been examined by Gottsche and Hofmeister. The arche-
gonia stand primarily upon the upwardly curved apex of a short ventral
branch which is surrounded by some envelope-leaves. The summit of this
branch later becomes concave, owing to the
growth upwards of an annular portion of
cell-tissue under the point of attachment
of the archegonial group, in the same way
as happens in the production of an inferior
ovary, or of an inflorescence like the fig,
and thus the fertile archegonium finally
comes to lie at the bottom of a tube, on
the outside of which are some leaves and
numerous rhizoids. The zone from which
the growth proceeds is recognizable also at
a later period (Fig. 79). If it includes the
points of insertion of leaves, then we find
leaves on the surface of the tube as in , | esd, Ccicren, aan!
Calypogeia Trichomanes; where the inser- gtammatic representation of a fertile sac in
z longitudinal section. , mucilage papilla;
tions are not included leaves are absent, as 4% embryo; &, nutritive tissue of the stalk,
sé, of thearchegonium ; 4, sterile archegonium.
Bee alyposciaericctorum. Ihe: appear- Ths shading te RE
ance of leaves on the outside of the
tube has given rise to the incorrect assumption! that a vegetative point lies
in an umbilicate pit at the base of the tube, and that this produces leaves.
Whence could this vegetative point come? The vegetative point of the
fertile shoot is used up in the formation of the archegonia: it must then
belong to a lateral shoot, and this leads to impossible results. Lateral
shoots occasionally appear on the fertile shoot of Calypogeia ericetorum,
but in quite another position.
Gymnanthe. The method of formation of the tube or sac for the
sporogonium in Gymnanthe saccata is somewhat different from that observed
in Calypogeia, and has hitherto been incorrectly described. In Calypogeia
the calyptra is almost completely concrescent with the tube of the fertile
shoot, but this is not the case in Gymnanthe saccata. Springing from the
under side and near the apex of its obliquely ascending stem (Fig. 80, 1), is
* Schiffner, Hepaticae, in Engler und Prantl, Die natiirlichen Pflanzenfamilien, p. 70.
92 FERTILE SHOOTS IN UGEPALIGAT:
a thick, fleshy, brownish body upon the outer side of which I found but few
rhizoids. It appears to me, from an examination of dried specimens, doubt-
ful if this sporogonial shoot is really pushed into the soil. It is possible
that it bends down the plant by its weight ; this, however, can only be deter-
mined by the examination of living plants, In the juvenile stages there is
no sac only a solid fleshy body upon the
summit of which there are a number, about
twenty, of archegonia. The archegonia are
found, as a comparison of the longitudinal
with the transverse section shows, in a
shallow pit, covered in great measure by
the neighbouring leaves. These stand about
the apex of the shoot, and the tissue of
the shoot has grown out somewhat about
them and forms also underneath the arche-
gonial group a tuber-like outgrowth. The
embryo bores into the tissue which, in the
case examined by me, contained no starch
but inulin, and dissolves the central portion
of it so that an actual sac arises, upon whose
summit the sterile archegonia and the very
slightly developed calyptras are found 1.
But it is remarkable that the tissue which
the embryo has to penetrate here is, at first,
so massively developed, and the embryo
follows it in its growth. Evidently the
tuber is formed only after fertilization and
doubtless furnishes the material at the cost
of which the embryo grows. The fleshy
Fic. 80. Gymnanthe saccata. 1, plant Character of the tuber is evidently connected
bearing a‘sac.’ Magnified 2. 11, ‘sac’ in 3 os
longitudinal section ; ‘the embryo indicated more with the provision of an adequate food-
by dots. 11, the shallow pit upon the upper :
Se Or es AG a en aE eeaconia supply than with that of water, because Gym-
nanthe saccata is adapted to a moist position.
From the biological side then the sac-tissue does not correspond in essen-
tials with the sac of Calypogeia, but with its archegonial foot, which is only
developed after fertilization, and into which the sporogonium penetrates.
* My investigations have led me to a different result from that reached by Stephani, Hepaticae
Australiae, in Hedwigia, xxviii (1889), p. 276, who says ‘ the basal portion of the calyptra is soon con-
crescent with the wall of the sac, and as this elongates progressively the calyptra grows out into a
long tube at whose base the sporogonium sits.’ This description proceeds from the assumption that the
development is originally like that in Calypogeia, and that there is formed an actual sac with which the
calyptra is united. Such a concrescence does not take place, and the process is much more like that
observed in the penetration of the embryo of Blyttia and others into the tissue lying below them. [I
have, since the above was written, seen living specimens in New Zealand, and convinced myself that
the ‘sac’ neyer touches the ground. ]
DISPOSITION OF SEXUAL ORGANS 93
A further obscure notion which is found in the literature of Hepaticae concerns
these geocalycean Jungermannieae, that of the ‘involucel.’ This is said to be
a special ‘second envelope’ which is developed ‘ within the calyptra’ ; but so far as
I see it is only a collar-like outgrowth upon the suctorial swollen base of the sporo-
gonium. To speak of an involucel seems to me superfluous. A similar collar is
found, as Gottsche has shown, in Pellia epiphylla and elsewhere. We have here
only a surface increase of the ‘haustorium’ in connexion with the peculiar con-
figuration of the sac, not an ‘envelope.’
2. SUMMARY.
If now we review the relationships which I have depicted, we see that the
differences which the sexual shoots show as compared with the vegetative
ones can be interpreted, at least mainly, from the Jdolegical standpoint.
We have on the one side the securing of fertilization, and upon the other
side the protection and nutrition of the growing sporogonium. A /phyletic
derivation of the different forms of construction is at the present time
impossible, or only possible in a very limited sense. The several genera
have indeed in many cases reached the present construction of their sexual
shoot by very different ways, and as the result of ‘inner’ causes.
In consequence of this many parallel formations occur. As such we
may note the envelopes which are formed about the single archegonia in
Sphaerocarpus and in the Marchantieae, the perianth of Blyttia, and of
the foliose Jungermannieae and others. It is noteworthy that in the sexual
shoots there is frequently an indication of leaf-formation, even in the
thallose forms, as we see in Aneura and in the covering scales of the
antheridia in Morkia, and elsewhere, and this fact will be referred to again
when the hypothesis of the phyletic origin of the acrogynous Jungerman-
nieae is discussed '.
V
THE SPOROGONIUM: OF HEPATICAE
1. STRUCTURE AND LIFE-RELATIONSHIPS OF THE
MATURE SPOROGOMIUM.
The increased interest which has been shown in the developmental
history of the Hepaticae during the past decades has brought it about
that the structure and the life-relationships of the mature sporogonium
has not received satisfactory consideration. I therefore put this subject
prominently forward, as the mature condition is the ultimate aim of all
development, and is therefore the most important *.
2 See p. 115.
2 See Goebel, Archegoniatenstudien: VI. Uber Function und Anlegung der Lebermoos-Elateren,
in Flora, Ixxx (1895), p. I.
O4 THE SPOROGONIUM IN HEPATICAE
The production of the spores is the common function of all sporogonia,
as the name indicates, and the spores arise by division
into four of mother-cells. The configuration of the
sporogonium, in spite of its uniform function, is very
different, and the function of distribution of the spores
is frequently associated in it with that of the formation
of spores, and both are accomplished in manifold ways.
We have first of all to recognize two chief types, on
the one side that of the series of the Anthoceroteae,
and on the other that of the series of the Marchantiaceae
lacie thallus withepere, and of the Jungermannieae. In both series there are
ee eae unopened parallel formations, for example, the appearance of
opened sporogonium the
prem seteml aig @laters, although these have a different construction in
visible. Natural _ size.
Lehrb. the two groups.
Fic. 81. Anthoceros
1. TYPE OF THE ANTHOCEROTEAE.
Anthoceros. We must start from the genus Anthoceros itself (Fig. 81).
The long cylindric structure, which is not segmented into stalk and capsule,
is here characteristic. The basal portion only is somewhat swollen and
developed as a haustorium from which there pass out many suctorial
tubes into the mother-
plant. The sporogonium
has, however,an abundance
of chlorophyll, and is there-
fore able to assimilate. On
this account the outer cell-
layer is provided with sto-
mata which have the same
structure as those of the
higher plants (Fig. 82).
Stomata are known else-
where amongst the Bryo-
phyta only upon the sporo-
gonia of some Musci, and
they furnish thus a remark-
able example of a parallel
formation.
Fic. 82. Anthoceros punctatus. Immature sporiferous portion of .
sporogonium in anes section. Small-celled columella in the In Fig. 82 we have a
centre, connected with the assimilating wall-layers by sterile cells °
which would become elaters. Between these sterile cells are the spore- transverse section of a spo-
tetrads. The epidermis shows one stoma. :
rogonium of Anthoceros.
The many-layered wall functions as an assimilation-tissue ; in the middle
runs a narrow-celled strand of tissue, which ultimately projects between
IN ANTHOCEROTEAE 95
the two lobes of the opening sporogonium as a bristle, this is the columella.
At first it has a mechanical function in relation to the somewhat pro-
longed development of the sporogonium. It forms, in a certain measure,
the frame-work upon which a net-work of sterile cells is fastened, between
which the sporocytes lie. The columella has, besides, a nutritive function.
It passes below into the basal portion of the sporogonium which is con-
cerned with the taking up of water from the mother-plant. Transpiration
from the surface of the sporogonium is considerable, especially as the
sporogonium continues to elongate for a long time by intercalary growth;
it opens indeed at the apex before the spores are formed in the lower
part. The columella is then comparable with the ‘central strand’ of many
of the Musci in serving as a channel for water. The columella can also
supply to the sporocytes other substances, and this certainly takes place
also through the sterile cells between the spores, as they are in con-
nexion with the peripheral layer of assimilating tissue. These sterile
cells take on another function at a later period. They separate in
great part from the wall of the sporogonium and the columella, and as
they dry exhibit movements of torsion which set the spore-masses in
movement. The single spores, or it may be groups of them, are in this
way thrown out along with these e/azers from the open sporogonium,
and this proceeds much more energetically in sunlight as will appear from
what follows. Occasionally as in Anthoceros laevis, A. punctatus, and
others these elaters exhibit a rudimentary spiral thickening of their cell-
membrane!, but in other species of Anthoceros, such as A. Vincentianus,
A. giganteus, A. multifidus, A. denticulatus, and others, and in Dendroceros,
the spiral thickenings are sharply marked. Elaters with prominent
thickenings act as more energetic exploding organs than do those in which
only rudimentary thickening is present. There seems to me to be no
reason for considering the latter as reduced forms of the others ; rather must
we see in these elaters an illustration within the series of a progressive
formation of one organ. The elaters in the Anthoceroteae are distinguished
from the outwardly similar elaters of the Jungermannieae and Mar-
chantiaceae, which may also show spiral thickening, by the fact that they
are composed of cell-rows.
Notothylas. Douglas Campbell? has recently shown what the con-
dition is in Notothylas (Fig. 83), the third genus of the Anthoceroteae, and
has proved that Leitgeb’s views, which were founded upon unfavourable
material, are incorrect. The differentiation of archesporium and columella
proceeds in exactly the same way as in Anthoceros, only the intercalary
* Usually there are two thickening bands in the longitudinal direction, but they do not run with
a straight course.
* See Douglas Campbell, The Structure and Development of Mosses and Ferns, London, 1895.
96 THE SPOROGONIUM IN HEPATICAE
growth is less marked, and the division of the archesporium proceeds some-
what differently. The structure of the ripe capsule, however, shows remark-
able differences. The sporogonium of Notothylas is wach smaller than that
of Anthoceros and has neither an assimilation-tissue in the capsule nor has
it stomata. Whether the sterile cells share in the scattering of the spores
is unknown!. Further investigation is required to determine whether some
species of Notothylas want the columella, at least in the ripe sporogonium ?.
The Anthoceroteae, in all their characters, appear to be a group sharply
differentiated from the other Hepaticae, and to be of a considerable age.
Fic. 83. Notothylas orbicularis. 1, thallus in longitudinal section; x, apical cell ; to the right of this a young
archegonium, ?, and an older one; Dd, lid-cells; 2, , neck-cells. Magnified 600. 2, young sporogonium in longi-
tudinal section. The shading indicates the archesporium. After Douglas Campbell.
2. TYPE OF THE MARCHANTIACEAE AND
JUNGERMANNIEAE.
The sporogonia of the Anthoceroteae have reached a somewhat higher
stage of differentiation than that of the lowest type of sporogonium in
the Marchantiaceae, for in this there is no special arrangement for the
scattering of the spores. Sporogonia without a distributing mechanism occur
then amongst the Hepaticae as well as amongst Musci, but such sporogonia
are either relatively small or if relatively large contain but few relatively
large spores. Wherever we have numerous small spores there is always a
special arrangement for their distribution and the sporogonium is differenti-
ated into a capsule which contains, besides spores, some sterile cells which
serve for the distribution of the ripe spores, and into a stalk whose basal por-
tion is constructed as a suctorial organ. By the elongation of this stalk the
' Probably they do so because their walls show spiral thickening.
* It may be suppressed early here as it is in the Ephemeraceae amongst the Musci.
IN MARCHANTIACEAE AND JUNGERMANNIEAE 97
venter of the archegonium is ruptured and the capsule protrudes. This
elongation is a rapid one and is due to the great increase in size of the
stalk-cells which use up the starch which lies within them. The wall of the
capsule opens in a characteristic manner, the spores are scattered and the
thin-walled cells of the stalk wither. In contrast with the course of events
in the Anthoceroteae, the sporogonium has but a short existence here outside
the venter of the archegonium. It lives chiefly as a parasite at the cost of
the sexual generation which often forms a special nourishing tissue for it.
The simplest forms of sporogonia are cleistocarpic ; the relatively large spores
escape from them by rotting of the wall, and there is no special means for distribu-
tion. In the more complex sporogonia the wall, at maturity, ruptures by four
valves in the Jungermannieae, and in different ways in the several genera of
Marchantiaceae. According to investigations carried out in the Botanical Institute
at Munich?, a lid-portion always separates, except perhaps in Targionia in
which the wall breaks up into several irregular pieces. ‘This lid is either in one
piece or it breaks up into single cells. The remainder of the capsule forms an urn
in Reboulia, Grimaldia, and others, splits into four lobes which are afterwards
divided in Lunularia, rolls itself together in Fegatella, and, in short, shows many
variations. The illustration and description of the tufts of elaters hanging on the
points of the lobes in Lunularia, which have been again put forth by Schiffner, are
altogether wrong, although such an arrangement is found in Aneura. I cannot,
however, discuss here these relationships, nor give the details of the deviations
from the usual manner of opening that may be observed in the capsule of the
Jungermannieae.
With regard to internal differentiation, we find in the Marchantiaceae
and Jungermannieae the following types :—
1. THE SPOROGONIUM IS DIFFERENTIATED INTO A WALL-LAYER
AND AN INNER SPACE FILLED ONLY BY SPORES; this in Riccia and
Oxymitra. The wall-layer is absorbed early in Riccia and the spores are
then set free by rotting of the thallus.
2. THE CELLS WITHIN THE INNER SPACE DO NOT ALL BECOME
SPOROCYTES ; A PORTION OF THEM REMAIN STERILE.
(A) The sterile cells are only nutritive cells, and the sporogonium has
no stalk, but at the most a short appendage which acts as a sucker; this in
Corsinia, Riella, and Sphaerocarpus.
Sphaerocarpus. The most primitive relationships are those of Sphaero-
carpus, for here the difference between sterile and fertile cells sets in
relatively late. It is remarkable that the wall of the sporogonium at an
early period separates from the content (Fig. 84, 77), which is surrounded
by a slimy fluid comparable with that which is found in the ‘ water-
chambers’ of the calyptra of some Musci?, and which there serves as
* See Andreas, Uber Bau der Wand und die Offnungsweise der Lebermoossporogons, in Flora,
Ixxxvi (1899), p. 161. * See p. 153.
GOEBEL II H
98 THE SPOROGONIUM IN HEPATICAE
a water-reservoir. The sterile cells are distinguished by their starch-
content, whilst the fertile ones contain more proteid, a difference which
appears also in Aneura. The fertile cells are the larger and the dis-
position of the two kinds of cells is such that at first groups of two to three
sporocytes with a few sterile cells attached to them are formed. The fluid
which fills the inside of the spore-capsule renders possible perhaps an
exchange of material, for soluble materials may pass into it from the sterile
cells and’ be again taken out of it into the fertile cells. At any rate the
fertile cells are here chiefly nourished by the chlorophyllous sterile ones and
by the chlorophyllous wall of the capsule ; the short stalk of the sporogonium
disappears so soon that the sporogonium has from an early period to depend
upon itself for its nourishment. The division of the nuclei in the sterile
cells! recalls rather the nuclear fragmentation of the tapetal cells in the
Fic. 84. Sphaerocarpus terrestris. J, three spore-tetrads and two sterile cells from a ripe sporogonium.
Z/, longitudinal section through a sporogonium about half-developed, the sporocytes are not yet divided;
c, calyptra ; & perianth.
anthers than the divisions within the sporocytes. The spores remain in
tetrads (Fig. 84, /); the sterile cells are still visible when the spores are ripe.
The method by which the spores are set free, whether by rotting of
the sporangial wall or otherwise, is unknown in Riella and Sphaerocarpus,
as well as in Corsinia. Probably in them all the spores float away after
the sporogonium has withered. In Corsinia the sterile cells, as in Sphaero-
carpus, are still living at the time of the ripening of the spores, and are pro-
vided with small chloroplasts ; they also serve as nutritive cells, but are
externally much more like elaters than are those in Sphaerocarpus.
(B) The sterile cells are provided with usually spiral thickenings ;
they are spindle-formed and sometimes branched; they are dead at the
time of ripening of the spores and they take a share in the distribution of
the spores. This is effected in different ways; sometimes in the process
1 Frequently nuclear division is followed by a retarded formation of cell-wall (see Fig. 84, 7, to
the left).
ELATERS AND ELATEROPHORES 99
of drying spring-like movements of the sterile cells are induced, and these
are the more energetic the quicker the process of drying’; sometimes after
the opening of the sporogonium hygroscopic movements bring about the forma-
tion of a loose framework which occupies a larger space than in the spore-
capsule and from which the spores are gradually removed by air-currents.
The hygroscopic movements of different strength brought about by
varying rapidity of drying must be kept in view in the following grouping
of forms. The two groups, in one of which
the elaters act as ejecting-organs whilst in the
other they do not, are not sharply separated
from one another, and in both groups there are
different types to be distinguished.
i THe ELATERS, ACT AS ORGANS OF
EJECTION.
A. There are no Elaterophores.
(a) Type of Jungermannia. The elaters
are free ; they are not fastened to the wall of the
sporogonium and have no definite arrangement
inside the capsule. The capsule opens by four
valves, and the moist mass of spores and elaters
is thus exposed to drying. So soon as the wall
of the capsule ruptures the ejection of the spores
begins ; it lasts only a short time usually and is
all over in a few minutes. The existence of the
sporogonium finds in this its end. Different
species of Jungermannia show this method, also
Plagiochila, Chiloscyphus, and others. A modi-
fication of it, leading on to the next type, is }
observed in Jungermannia bicuspidata (Fig. 85), / Hf
J. trichophylla, and others. In them the very lp
long elaters are fastened by their base to the /
wall of the sporogonium ; they convergeinwards yg. Petitiangernannia bien, tdnes
towards a zone free from elaters. In the open Ser,” Ree eat ae has boted
sporogonium the spores are seen invested by “°?¥ ito theste™
the elaters, which with their free end exhibit movements of torsion and
then they jerk themselves off from their point of attachment and thus
* In the Marchantieae, for example, there is usually no marked ejection of spores, but this may
occur if conditions arise which, in the words of the renowned observer of last century, K6lreuter
(Das entdeckte Geheimniss der Kryptogamen, Karlsruhe, 1777, p. 23), whose work contains many
valuable observations, I may describe as follows :—‘If one wishes that the threads of the capsule
should show active movement one must, after the sporogonium has stood in the shade, place it in the
sun, or where the sun’s rays have access, and where there is little moisture. Then as the moisture
H 2
100 THE SPOROGONIUM IN HEPATICAE
throw out the spores which are seated upon them. A few of them usually
remain upon the wall of the capsule.
(6) Type of Frullania. Besides Frullania we have showing this type
the allied genera Lejeunia, Colura, and Phragmicoma. The elaters lie
nearly parallel with one another in the long axis of the sporogonium ; their
broadened ends are united to the inner surface of the capsule. When the
sporogonium opens they rupture at their base and remain with their upper end
seated upon the wall of the sporogonium. The opening of the capsule takes
place very quickly in Frullania; a touch, and the spores are shed. The elaters
are evidently stretched by the bending back of the valves; they break off
from them, quickly spring loose, and throw offthe spores. The hygroscopic
movements which the elaters also exhibit have in this type
only a subsidiary importance.
B. Elaterophores are present.
(a) Type of Pellia'. The large capsules of the
species of Pellia contain spores which exhibit the first
stages of germination within the sporogonium, and there-
fore become cell-masses ; consequently the spores are not
usually thrown out to a distance. The dehisced sporo-
gonium of Pellia calycina (Fig. 86) exhibits a tuft of
many, often a hundred, long, thread-like, spirally-thickened
cells seated upon the base of the capsule. In P. epi-
phylla the threads are fewer in number and are usually
connected one with the other at their base. This tuft is
the elaterophore ; the special free elaters have been shed
Fic. 86. Pellia caly. from it with the spores. A section through an unopened
oie ue cay capsule shows in its centre in the lower part a cell-mass
spowsne ate a with radiating cells which will become the elaterophore.
thread" ™"Y — Sporocytes usually do not exist here. The work of the
elaterophore is determined by the manner in which the
capsule opens. In P. calycina I found the following, which I give in supple-
Bs
a
a5
y
4
el
evaporates from the sporogonium their movement becomes all at once stronger and more vigorous,
and the spores thus loosened are thrown off in a cloud. This effect is most strongly seen if one
focuses the light with a burning-glass upon the yellow woolly tuft. This experiment may be made
with equal success upon the spikes of Equisetum.’ This spring-effect of the elaters has been entirely
overlooked by recent authors.
The mechanism of the movement of the elaters of Hepaticae has recently been the subject of
a searching investigation at the hands of Kamerling (Der Bewegungsmechanismus der Lebermoos-
elateren, in Flora, Ixxxii (1898), p. 157). The mechanism is not the same in all elaters, that in
Anthoceros for example differing from that in most of the Jungermanniaceae. Kamerling sees in this
difference of mechanism a support to my view that the elaters are primarily nutritive cells which have
taken on as a secondary duty the work of distribution of spores.
* See Goebel, Archegoniatenstudien : VI. Uber Funktion und Anlegung der Lebermoos-Elateren,
in Flora, lxxx (1895), p. 1. The literature is cited here. Also Jack, Beitrage zur Kenntniss der
Pellia-Arten, in Flora, Ixxxi (Ergianzungsband zum Jahrgang 1895), p. I.
j
ELATERS AND ELATEROPHORES IOL
ment to my earlier statements. The capsule opens by four valves which
spread out nearly horizontally. Elaters and spores exhibit lively move-
ment, and some spores are occasionally shot out toa short distance. At first
one sees nothing of the elaterophore, because it is spread like a web over the
mass of spores or the four clumps of these. This mass of elaters and spores
increases to a larger volume than it possessed within the capsule and rests
first of all upon the valves, which then bend backwards more and more and
the spores consequently fall off, if they have not been carried away before
by the wind. But this does not happen all at once, because the elaterophore
has still some hold on the mass, and forms a kind
of support to it. Subsequently the elaterophore,
which with the opening of the capsule became
diffuse, again acquires a more erect form, and if
spores are still sticking to it they can then be easily
blown off. The elaterophore thus secures a gradual
sowing of the spores!, and when we know that Jack
counted 4,500 spores in one capsule of Pellia epi-
phylla, it is clear that it is a matter of importance
for the plant that these should not fall out of the
capsule in great numbers together.
(4) Type of Aneura, including Aneura, Metz-
geria, Hymenophytum. The elaterophore in this
type is more specialized than in Pellia, where it
may be considered as a peculiarly developed tuft
of elaters. In Fig. 87 we have a representation of
a longitudinal section through the ripe capsule of
Aneura pinguis. The elaterophore appears as a
tissue-mass projecting downwards from the upper HRA TH
wall of the capsule and the loose elaters are distri- —,,,. Py Bi dateee Ripe
buted in a radiating manner in the space between {APG J2, jongiipdingl section.
the spores. The elaterophore splits later into four Parssintoth spore caniy in which
parts, and the lines of separation are very early ™#¢
recognizable. The cells of the elaterophore have semi-annular thicken-
ings, and the lowermost of the cells frequently grow into pointed cells like
elaters. Between these projections of the elaterophore, as well as in
other places, the ends of a number, not all, of the free elaters lie. The
capsule opens by four valves which assume a nearly horizontal position, and
the mass of spores and elaters divides similarly into four parts. Each one
of the four masses thus formed and lying upon a valve undergoes a torsion
of about go” at its point of attachment to the elaterophore, and thus the
spore-mass upon each valve stands erect. An energetic throwing off of the
Saas to
Ay ri OU bor
a
30 o8
‘ Its nutritive function in the juvenile stage of the sporogonium will be referred to below.
See p. 103.
102 THE SPOROGONIUM IN HEPATICAE
spores now begins, and in about five minutes there is hardly a single elater
left upon the elaterophore. It is evident that two things are achieved by
this arrangement : firstly, the spore-masses being raised above the sporangial
wall can be shot out further into the environment, and secondly, the elon-
gated cylindric form of the sporangium results in a more thorough dis-
charge of the spores ; and in correspondence therewith we see that the
elaterophore is more developed the longer the capsule 1.
II. ELATERS ARE NOT, OR NOT USUALLY 7, ORGANS FOR THE EJEC-
TION OF SPORES, BUT SERVE TO HOLD THE MASS OF SPORES.
Features of this kind seen in Pellia have been already mentioned.
Fossombronia shows the same. The wall of its capsule separates into
single pieces, leaving a lower scutellar portion which acts as a support
Fic. 88. Lophocolea heterophylla. Central figure. Young embryo seen from outside. Figure to the left.
Young embryo in median longitudinal section. Figure tothe right. Older embryo in median longitudinal section.
Central and left figure magnified 300. Right figure magnified 53. After Kienitz-Gerloff.
to the mass of spores and elaters. By the movements of the elaters, which
have little power as organs of ejection, the mass becomes more voluminous
and can be readily gradually removed. The Marchantiaceae which have
been examined behave in exactly the same way. In them there is formed
before the opening of the capsule a voluminous framework, which reminds
one of the capillitium in the sporangium of many of the Myxomycetes.
The function of the elaters just described is only exercised in the
mature condition. I do not doubt that they have also some significance
during the development of the sporogonium. They may by their elongated
form act as channels through which nutritive material may be transported
to the sporocytes, especially in cases where the elaters or elaterophores are
united with the sporangial wall, as in the types of Frullania, of Aneura, of
Pellia, and in Jungermannia bicuspidata. Where the elaters lie scattered
amongst the spores in the cavity of the sporangium they must always act
! For an account of Metzgeria, see Goebel, Archegoniatenstudien : VI. Uber Funktion und Anlegung
der Lebermoos-Elateren, in Flora, lxxx (1895), p. 27.
2 See p. 99.
DEVELOPMENT OF THE SPOROGONIUM 103
as nutritive cells, giving up the greater part of their contents to the sporo-
cytes. This service is facilitated by the wall of the sporocytes, like that of
the incipient elaters, taking on a mucilaginous character at a middle stage
of development. Under the elaterophore also in the young capsule in Pellia
there is an accumulation of starch which we must regard as the surplus of
the carbohydrate after the elaterophore has taken what it requires, and this
starch is used subsequently and evidently not for the construction of the
elaterophore alone.
2. DEVELOPMENT OF THE SPOROGONIUM.
We can recognize more than one type of arrangement of the cells in the earliest
developmental stages of the embryo, but they are not strictly maintained :—
TYPE OF THE JUNGERMANNIEAE (Fig. 88). This is the most common. The
fertilized egg is first of all divided into an upper and an under cell by a wall at right
angles to the long axis of the archegonium. ‘The upper cell gives rise to the capsule
and the stalk of the sporogonium, the under cell appears as an appendage at the foot
of the stalk of the sporogonium and probably serves as a suctorial organ. A somewhat
older embryo shows in its upper part a number of transverse disks, each of which
consists of four cells disposed as the quadrants of a cylinder. The apex is occupied
by four cells disposed as quadrants of a hemisphere. The division-walls of this mark
the four lines of separation along which the capsule subsequently splits. In the
simplest cases? the capsule proceeds from these four quadrants. Four outer cells,
which are the primordium of the wall of the capsule, are separated by periclinal walls
from four inner cells, which are the archesporium or primordium of the sporocytes.
In most cases, however, the four cells of the transverse disk next these quadrants
share in the formation of the capsule, as for example in Radula. We regard as the
most primitive case in the group that in which all the cells of the embryo ® form the
archesporium and therefore the nearer to this the development of a sporogonium is,
the later the differentiation of its archesporium will be completed. Within the
sporogenous mass of cells which arises by the division of the archesporium, there are
formed a number of sterile cells which become the nutritive cells and elaters already
mentioned. This process of sterilization proceeds much further in the forms which
are provided with elaterophores, for example in Aneura palmata® (Fig. 89). It is
characteristic of this species that a separation at a very early period is observable in
the sporogenous mass of cells by which two meristems arise, of which the one with
less capacity forms the elaterophore which occupies the chief part of the capsule,
whilst the other gives rise to the fertile cell-tissue which only subsequently diffe-
rentiates into sporocytes and elaters. The cells within the capsule are primarily all
alike, as in other Hepaticae. The peripheral series of the cells becomes subsequently
marked out by a richer protoplasm-content, by chlorophyll, and by the absence of
starch, and forms the secondary archesporium, whilst the inner cells form the
1 Which are precisely those furthest removed from the original configuration, for example in
Pellia, Frullania, Lejeunia. 2 ‘With the exception of the wall-layer as in Riccia.
8 Goebel, Archegoniatenstudien: WI. Uber Funktion und Anlegung der Lebermoos-Elateren, in
Flora, Ixxx (1895), p. 24.
104 THE SPOROGONIUM IN HEPATICAE
elaterophore. We may assume that the sterile cells serve as stores of food and as
channels of food to the fertile ones, and that this is the reason of their early
differentiation. Apart from the interest which this development possesses it is of
importance because it offers an omdogenous procedure which upon comparative
grounds we believe to be f&yletic in Anthoceros.
Deviations in the cellular construction of the sporogonium within the series of
the Jungermannieae are only known in Sphaerocarpus and Symphyogyna.
In SPHAEROCARPUS the embryo has an elongated form and is therefore divided
at first into transverse disks lying one above the other, and these are later divided
into quadrants.
The embryo of SyMpHyocyNna has, according to Leitgeb, an apical growth like
that in the case of Musci, and a later differentiation of the spore-cavity.
Fic. 89. Aneura palmata. Two sporogonia of different age showing their capsular portion in longitudinal
section. The ‘fertile’ tissue is shaded. 7) line of separation of elaterophore and wall of capsule.
When additional forms have been investigated we shall probably learn of more
divergences oscillating around the type as in other cases.
The RicciEAE and MARCHANTIEAE have a spherical or ovoid embryo, and the
arrangement of the cells, a description of which here would offer no point of interest,
corresponds. It may only be mentioned that Kienitz-Gerloff says of the Marchan-
tieae that the first wall, which is at right angles to the long axis of the archegonium,
separates the capsule and the stalk from one another. There are, however, varia-
tions, for in Targionia * transverse walls appear first of all in the elongated embryo,
and there may be for a short time the formation of a two-sided apical cell, but
later there appears in the upper part formation of quadrants. That the embryo of
Riccia is the most primitive of which we have knowledge has already been stated °.
Type oF ANTHOCEROS. As the mature sporogonium differs from that of
other Hepaticae so also does its development, but the first stages of the development
‘ Goebel, Die Muscineen, in Schenk’s Handbuch der Botanik, ii (1882), p. 355. 7 See pp. 97, 103.
DEVELOPMENT OF THE SPOROGONIUM 105
resemble those of the type of Jungermannieae ; the embryo consists of two to three
tiers of cells arranged in quadrants. From the lower proceeds the ‘foot,’ from the
upper one or two proceeds the capsule. The cells of these tiers are divided by
periclinal walls into inner and outer cells (Fig. 83, 2). But whilst in the other
Hepaticae the outer cells form the wall and the inner cells the archesporium,
here the archesporium is separated off from the outer cells by further periclinal
division, whilst the inner cells form the columella. The archesporium is a cell-
layer in the form of a bell-glass with the mouth downwards, as it is in Sphagnum
and Andreaea, amongst the Musci. Originally the inner cells were fertile, but
sterilization has taken place, as in the case of Aneura, and this along with the
fact that the layers of the wall of the capsule, which function as assimilation-tissue
arise by further periclinal divisions, shows that we have here to do with a new and
later formation. The archesporium gives rise to a net-work of sterile cells as well
. ats
= DS
mh Faeea i __/ NX Ne
mo MS x
‘
\
Fic. Blyttia sp. from Ceylon. A young sporogonium arises from the upper surface of the thallus and is in-
vested by the calyptra, the perianth and the perichaetium. Upon the group of archegonia to the left the perichae-
tium alone is visible and is provided with a tuft of hair-like outgrowths.
as to the sporocytes, which lie in its meshes as they do in Aneura. It has
already been shown that the sporogonium of Anthoceros is an independent assimi-
lating structure’. The embryos of other Hepaticae are usually, at least in the
earlier stages of development, also chlorophyllous but, excepting in the cases of
Sphaerocarpus, Riella, and Corsinia’, this is of little importance for their nutrition,
and they live mainly at the cost of the mother-plant. The basal portion of the
embryo bores deep into it, and there is frequently a meristematic tissue which is
developed after fertilization has taken place in Pellia, Aneura, and others. In
Calypogeia there is a very greatly developed ‘foot’ to the embryo.
The effect of fertilization is not confined to the formation of the embryo alone,
but is often seen in the production or the further development of envelopes to the
ripening sporogonium as has been shown, but I may mention one further example.
1 See p. 94. 2 See p. 9S.
106 GERMINATION OF THE SPORES IN HEPATICAE
In Fig. 90 a young sporogonium of a species of Blyttia is seen to the right. It is
surrounded by a two-fold or three-fold envelope, as well as by a calyptra. In its
uppermost part only is this formed by the archegonial venter, it is in the main
composed of the tissue lying below the archegonium into which the stalk of the
sporogonium has burrowed. It appears indeed as if this ‘calyptra’ were the
remains of the unfertilized archegonium. Outside the calyptra there is a much
longer and wider envelope, the perianth, which when the archegonium is ripe exists
only as a small annular wall, and receives by fertilization the stimulus to further
growth. It is provided above with a tuft which prevents the entrance of water-drops
into the interior. Outside and below this is the perichaetium, which is only
slightly increased after fertilization.
VI
GERMINATION OF THE SPORES OF HEPATICAE
The spores of the Hepaticae are unicellular. Where pluricellular bodies
occur in the sporangium, as in Pellia, Fegatella, and Dendroceros, we have
cases in which germination has proceeded within the sporogonium, and
they are not uncommon in the inhabitants of moist localities'. These
pluricellular bodies, like the relatively large spores of Riccieae, are chiefly
distributed by being washed away from the sporangium; whilst in the
majority of the Hepaticae the spores are distributed by wind.
The size and investiture of the spores are very different even in nearly
allied forms: Marchantia has small thin-walled spores, Preissia has large
thick-walled spores. Formerly the cell-wall was said to be composed of
a cuticularized exine, and a cellulosic intine, but Leitgeb? distinguishes
three membranes: the exosporium, consisting of two different layers, of
which the inner belongs to the spore itself and is the special exine, whilst
the outer, the ferininm, is laid down later upon the exosporium and is
composed of parts of the sporocyte. In Fig. 91, is a representation of
a perinium, which is an outer folded membrane. The function of the
perinium is protective, especially against drought, and it is in general
more strongly developed in xerophilous forms than in hygrophilous. Its
relationships, however, are not clear. Leitgeb puts on one side the
suggestion that the perinium is a protection against drought, and ascribes
this to the exine because the perinium is well developed in Corsinia which
inhabits moist places. But it may be asked if these places are really
constantly moist. Certain is it, especially in the aquatic Riccieae, that the
* See Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 133, where I arrange this phenomenon
with the vivipary observable in higher plants.
? Leitgeb, Ueber Bau und Entwicklung der Sporenhaute, Graz, 1884.
GERMINATION IN JUNGERMANNIACEAE 107
perinium provides a protection against fungi. The perinium can certainly
have nothing to do with a long resting period, because thick-walled spores
like those of Corsinia, Preissia, Anthoceros, and Sphaerocarpus germinate
a few days after they are sown. The vesicular swellings of the perinium,
which are found so markedly in Grimaldia (Fig. g1) may, like the analogous
structures on the pollen-grain of Pinus, be regarded as a_ parachute-
apparatus, but at the time of the bursting of the capsule they contain
no air. Leitgeb thinks their significance lies in this, that they increase
the volume of the spore in germination, and at the same time are also
a protective investiture. I confess that this explanation appears to me
unsatisfactory 1 and that in order to obtain a clear idea of the relationships
of the structure of the envelopes of the spores a thorough investigation
of the conditions of life of the several species is necessary. We particularly
want to know zen in nature the germination of the spores takes place.
As in other groups we find amongst the Hepaticae forms whose spores
are arranged for immediate development, e
and which cannot undergo a long period re oS
of drought, and those which can or must eel
pass through a resting period. The eae ?
germination is heteroblastic*. There
is formed first of all a pro-embryo of
simple configuration on which the plant Enel gw Mi@rinaldes tichotoma: Spore to the
then develops, but pro-embryo and plant [Section Contents indicated by dots. ‘The outer
are less sharply distinguished from one “*" So
another than is the case in the Musci, because in most cases the plant arises
from the terminal cell of the pro-embryo. The configuration of the pro-
embryo varies greatly and is in part the result of externai factors*. As
some interesting questions crop up in connexion with the germination a
few illustrative cases will be described.
1. JUNGERMANNIACEAE.
THALLOSE ForMs. The phenomena of germination in Metzgeria and
Aneura are very simple.
In Metzgeria * the spore divides, after increasing in volume, by a trans-
verse wall into two cells which are usually of unequal size; in the one,
the smaller, a two-sided apical cell is formed by a wall inclined obliquely
to the long axis, and by its division a cell-surface which is one cell thick
arises. Later a mucilage-papilla develops at its vegetative point, a midrib
+ In Corsinia the perinium consists of separate layers, which permit of the expansion of what is
within.
* wee Part I, p. 143. 3 See Part I, p. 145.
* See Goebel, Uber die Jugendzustiinde der Pflanzen, in Flora, Ixxii (1889), p. 153; id. Arche-
goniatenstudien : VIII. Riickschlagsbildungen und Sprossung bei Metzgeria, in Flora, Ixxxv (1898).
108 GERMINATION OF THE SPORES IN HEPATICAE
forms, and thus the characteristic appearance of the thallus of Metzgeria
is produced. The length of the first thread-like portion depends upon the in-
tensity of the light ; the feebler this is the later is the cell-surface produced.
Aneura behaves in the same way, and in it branched germ-threads have
been observed. The germination of its gemmae also corresponds with that
of the spores.
The germination of Blyttia, Morkia, Monoclea, Hymenophytum, and
Symphyogyna is not known.
The spores of Pellia begin their germination within the sporogonium
and form there a chlorophyllous cell-mass at one end of which—its position
in the sporogonium is unknown—is a clear cell which grows out into the
first rhizoid whilst the development of the plantlet commonly starts at
the other end of the cell-mass. The cell-mass may,
however, be so placed that rhizoids arise equally at
both ends of it and the primordium of the plant
appears in the middle of the pro-embryo. External
factors apparently determine the position of the
primordium, and the apparent polarity of the pro-
embryo observable in the inception of the rhizoids
is by no means fixed ; it only appears if the embryo
stands erect and different species of Pellia behave
differently in this respect.
ACROGYNOUS FORMS. The germination of Frul-
lania and Madotheca after the sowing of the spores
? runs the same course as that of Pellia. An ovoid
cell-mass arises out of the spore and becomes fastened
Fic.92. Lejeunia. Germina- to the substratum by rhizoids. An outer cell of this
tion of spore. 1-4, Lejeunia
serpyllifolia. Exosporium, in- becomes an apical cell of the leafy stem. What
dicated by dotted line, is here
ay Stes Jonas a the relationship of this method of germination to
pene Se tea South the conditions of life is we do not yet know.
On the other hand this relationship is quite
evident in the case of Radula and in Lejeunia.
Radula. In Radula a cake-like cell-surface is produced out of the
spore which has quite the same configuration as the gemma of this
plant, only that the gemmae show at their base the point of attachment.
From one cell on the margin of this cake-like pro-embryo the primordium
of the leafy plant arises. It is clear that the configuration of the pro-embryo
and of the gemmae fits them to anchor rapidly upon the rind of a tree or
upon a leaf, and this would be a marked benefit to the epiphytic forms.
Lejeunia. The like is seen in the large genus Lejeunia. In Fig. 92, 1,
we have an illustration of the elongated spore of Lejeunia serpyllifolia. It
divides by a transverse wall, and this may be repeated (Fig. 92, 3) and thus
a short germ-tube arises. Usually, however, shortly after the first division,
%
Fi
COMPARISON OF GEMMAE WITH SPORES 109
the formation of a two-sided apical cell takes place in one of the two cells
whilst the other divides by a longitudinal wall and then there is produced,
according to the species and to the external conditions, a broader or smaller
cell-surface (Fig. 92, 5), which can then multiply by adventitious shoots.
The leafy plant finally proceeds from the apical cell of the pro-embryo.
Comparing the construction of a gemma (Fig. 45, 11), we find that the cell-
surface of the gemma upon its short stalk has usually two wedge-shaped
apical cells out.of each of which a leafy shoot may proceed. Such a gemma
then corresponds with two pro-embryos united with one another at their base
or, what is the same thing, with a pro-embryo which is bipolar. The
difference between the germination
of the spore and of the gemma
consists merely in this: in the
spore there is a polarity which is
not present in the gemma develop-
ing free upon the leaf!. If we
consider these differences we shall
find that there is no essential dif-
ference between the germination
of spores and the germination of
gemmae. We might also show
for Marchantia that the apparently
great difference between germina-
tion of the spore and the develop-
ment of gemmae is conditioned
purely by the lie of the gemmae
as they are formed.
In Lejeunia also if the outer
conditions are not favourable pro- .
embryo and gemma grow into a parc: 93- eee Me apeiopsis Male plant. Descrip-
thallus before the leafy plant is
produced, and this is normally the case in an epiphyllous species of Lejeunia
which I found in Java and named L. Metzgeriopsis (Fig. 93). This remark-
able plant has a thallus which is richly branched and bears appendages at
the margin,—cell-rows which arise in regular serial succession at the vegeta-
tive point and may be considered as rudimentary leaves. This thallus,
fastened firmly to the substratum by its rhizoids, propagates itself by
gemmae. Leafy shoots appear as short appendages upon it, and these
have the sole function of producing sexual organs, and their further vegeta-
tive development is not possible so far as we know. The thallus is then
nothing else than a giant pro-embryo possessing a peculiar vegetative
' It is attached somewhat differently from that in Radula.
T10 GERMINATION OF THE SPORES IN HEPATICAE
body which elsewhere is only a rapidly passed over developmental stage.
In Protocephalozia ephemeroides and amongst the Musci we shall find
similar cases.
In other Hepaticae, such as Lophocolea, Chiloseyphus, Calypogeia,
and Cephalozia, the spores, which have a finely granular exosporium,
produce in germination a tube which becomes a cell-row by the formation
of transverse division-walls. It forms then, as in Aneura and Metzgeria
a cell-thread which may also branch, and it is of interest to note that
in Calypogeia Trichomanes, for example, stages
of germination similar to those of Lejeunia appear
occasionally, that is to say, a cell-surface growing
by means of a two-sided apical cell develops, and
we have here a proof that this is only a modi-
fication or a further development of the fila-
mentous stage. Out of the end-cell ofthe thread
or cell-surface there arises a three-sided pyra-
midal apical cell, and thence the development
of the leafy stem proceeds. Regarding the
primary leaves of this plant I shall say some-
thing below. Here I will only point out that
the amphigastria appear after the lateral leaves.
In the position of amphigastria there frequently
arise at first mucilage-papillae which are after-
wards, by division of their supporting cells,
carried up upon the point of scales. The
germination of the gemmae conforms, so far as
it has been examined, also here with the
germination of the spore.
In Cephalozia (Protocephalozia) epheme-
roides, found by Spruce in South America, the
Fic. 94. Anth paeion! : : -
7 cali iss enced in aerminttion, Vegetative body is constituted by the pro-embryo
Tico icment develosinniaon tHe : . .
cell-mass. ///, further stage of acell. Which consists of branched threads upon which
filament. After Leitgeb. .
Saath ve aaet bea the short leafy shoots! bearing the sexual organs
appear as appendages. The threads of the pro-embryo remind one much of
those in the Musci especially in this that they consist of an epigeous part
containing chlorophyll and a hypogeous part containing no chlorophyll.
A further group of the acrogynous Hepaticae is that in which, according
to the external conditions, either a thread-like pro-embryo or a cell-mass
arises in germination. We have examples in Alicularia, Trichocolea,
Jungermannia trichophylla and J. hyalina, Lepidozia reptans. We do
not know what are the external conditions which determine the point
* Goebel, Archegoniatenstudien : III. Rudimentaére Lebermoose, in Flora, Ixxvii (1893), p. 83.
The literature is cited here,
GERMINATION IN MARCHANTIEAE AND RICCIEAE III
whether a thread-like protonema or a cell-mass is to arise. It is probable
that light plays a chief part, and that in feeble light-intensity the fila-
mentous protonema is formed, whilst in stronger light-intensity we have
a cell-mass. Moisture also may have a share. It has been already
shown’ that like variation occurs also in Anthoceros (Fig. 94) whilst
in Dendroceros a cell-body arises at once. We shall find that the same
problem, and in quite the same form, arises for consideration in the
formation of the prothalli of ferns.
2. MARCHANTIEAE AND RICCIEAE.
Preissia. We may refer to the case of Preissia commutata (Fig. 95)
which has been already mentioned?. The individual differences in the
germination of the Marchantieae, when compared with the other thallose
Hepaticae, depend upon the fact that the young plants are not developed
in the same direction as is their pro-embryo. The pro-embryo is positively
heliotropic. It forms at
its end a flattened cell- 4
mass, the germ-disk, at 6)
right angles to the direc- ae
tion of the light-rays, and [|
out of one quadrant of
this the new plant pro-
ceeds. This plant makes
with the germ-tube pri-
marily a right angle, but FIG. 95. Preissia commutata. Half-diagrammatic representation of
: 5 2 the germination of spores. In figures 1 and 5 the spore is shown below.
the sharpness with which 1, the germ-tube is very short and bears at its end a cell-mass, the germ-
roe : ° disk, the end-cell of which is divided by quadrant-walls. 2, in one quadrant
this is marked varieS 1N ofthe germ-disk seen from above the apical cell, s, of the young Sine has
: 3 been formed, 1, 1 the first segment-wall ; 2, 2 the second segment-wall. 3,
different forms °. By the germ-disk seen from above showing apical cell, s, of the erialant formed
: : from one of the halves resulting from division by the first segment-wall 1, r.
withering of the §ermM- 4, the direction of growth of the young plant forms an are of 90° with
h 1 that of the pro-embryo; seen in optical longitudinal section. 5, the apical
tube the plant reaches cell of the young plant has grown out into a germ-tube. See also Part I,
the soil and the whole “*"*
arrangement is directed to bringing the plant into the light should the spores
germinate lying between stones and in like stations; as the germ-tube
is longer, within of course the limits imposed by conditions of nutrition,
the more feeble the light-intensity, the attaining to the most favourable
light-intensity is the more probable. In the Riccieae we observe similar
germination*. The spores of Fegatella sometimes germinate within the
4
4.
1 See Part I,-p. 240. 2 See Part I, p. 239.
3 For that of Marchantia, see p. 86, Fig. 75, H.
* According to Douglas Campbell (The Structure and Development of the Mosses and Ferns,
London, 1895, p. 38) the axis of growth in the young plant of Riccia hirta is continuous with that
of the germ-tube; but this is not borne out by his Fig. 9. The dorsal side of the thallus does not
coincide with the long axis of the pro-embryo. In this method of germination as compared with
that of other Hepaticae, we have primarily a more or less sharp adaptation; the original behaviour
ne GERMINATION OF THE SPORES IN HEPATICAE
sporogonium and form a cell-mass!', as do those of Pellia. In other Mar-
chantieae also the formation of the germ-tube may be occasionally sup-
pressed, as it is in Anthoceros laevis, and this is the case in Targionia 2.
Let us now compare the behaviour of the gemmae of Marchantia
and Lunularia with the germination of their spores. There are marked
differences. The gemmae (Fig. 96) are lenticular cell-masses with an
indentation on two opposite margins, and in these indentations lie the
vegetative points out of which the new thallus develops. I regard she
whole gemma asa vertical germ-disk developing without a germ-tube*, and
at 7s not dorsiventral because it has a profile position; dorsiventrality is
only ‘induced’ in the germ-disk by light*. From the ordinary germ-disk
the gemma is distinguished by its size and, apart from the structural
peculiarities which are concurrent with this,
by the possession of two vegetative points.
We have this also in Lejeunia.
We therefore arrive at the result, that
an all Hepaticae the method of germination
of the spore conforms essentially with that
of the development of the gemmace.
Is there then in the germination of the
spores a common type? I have hitherto
endeavoured to answer this question by
assuming that the formation of a germ-tube
and its further development to a filiform
F1G.96. Marchantia polymorpha. 4-C,
gemmae in different stages of development; branched protonema must be considered the
sé, stalk-cell. 2, mature gemma in surface
view On cach side is seen a vegetative poiat original chamacter, Im suppor orenis we ind
which can grow out into a new thallus; 2,
point at which stalk was attached; 9, oil-
cells ; 7, cells distinguished by their size and
that in a number of forms the formation of
Ze transverse section or D through he lateral germ-tubes regularly appears; in other forms
e y eae are : ° :
AC, magnilied 273; DE, miganined ion alt appears, at least under definite external
conditions, and we can follow the filiform
stage becoming gradually more limited in duration or we note the formation
of a germ-tube being replaced by that of a cell-surface or a cell-mass.
Further, this assumption, which is entirely a hypothesis, brings into con-
formity the formation of the pro-embryo of Hepaticae with that of Musci,
and also, as we shall see, with that of the leptosporangiate ferns. The most
primitive member of the Hepaticae appears to be one which develops a cell-
is doubtless that which has been already described in Metzgeria. In Marchantia polymorpha the
germ-disk is scarcely developed, but the difference in the direction of germ-tube and thallus is quite
evident. If the germ-tube be laid upon the soil at an early period this difference in direction scarcely
appears. See Kny, Botanische Wandtafeln, Abteilung viii, p. 338. 1 See p. 108.
* According to Douglas Campbell, The Structure and Development of the Mosses and Ferns,
London, 1895, p. 67.
* The germ-disk is also vertical in Riella; see Goebel, Archegoniatenstudien: IV. Zur Kenntniss
der Entwicklung von Riella, in Flora, Ixxvii (1893), p. 104. * See Partilejp. 227.
GERMINATION IN MARCHANTIEAE AND RICCIEAE 113
mass on a simple or branched germ-tube, and this cell-mass bears the
sexual organs. Sphaerocarpus approaches this inasmuch as the very young
plant bears sexual organs, and the thallus is only a structure bearing
these as do the leafy shoots in Lejeunia Metzgeriopsis and in Protoce-
phalozia ephemeroides.
It has been already shown by an example drawn from the Myxo-
mycetes! that’ a higher construction of the vegetative body ensues by
the postponement of the formation of spores. If we apply this considera-
tion to the development of the Hepaticae, their vegetative body has
reached a stage in forms like those mentioned. above in which it is able
only gradually and after a long process of development to reach the
construction which is competent to bring forth sexual organs. In the
thallose Jungermanniaceae the changes which the germ-plant experiences
are simple in correspondence with the simplicity of the structure of the
mature plant 2, whilst in the Marchantiaceae the number of the develop-
mental stages through which it passes is greater in correspondence with
the higher differentiation at maturity. The young plants have at first
a different construction of the vegetative point (as Fig. 95 shows), especi-
ally a wedge-shaped two-sided apical cell which later passes over into
a prismatic four-sided one. The thallus is at first one-layered, and if
it becomes many-layered it has at first no scales upon the under side
and no air-chambers upon the upper side. Instead of the scales we find
unicellular or pluricellular club-like papillae, at first like those of Metz-
geria, and later like those of Mérkia or Cyathodium. With the germ-
plants of the latter genera those of Preissia, Marchantia, and others also
conform, in that their first air-chambers have not the characteristic assimila-
tion-tissue spreading from their base. In other words, we see in the rela-
tively highly differentiated Marchantiaceae the embryo-plant pass through
developmental stages which in the other Hepaticae are present in a perma-
nent condition, and this is a fact of extreme interest. Moreover in Mar-
chantia the air-chambers appear relatively late, and it is also characteristic
of the genus that the young plants at first have only the ‘ median scales,’
and in this show a construction which in other Hepaticae is the permanent
one, whilst in Marchantia itself the further copious development of the
scales, which has been already described, subsequently takes place’. If
we can imagine a germ-plant of Preissia or of Marchantia bringing forth
sexual organs before the appearance of the air-chambers, then we should
have a condition like that in Sphaerocarpus.
The thallus of Plagiochasma Aitonia* shows at first upon its upper
‘see Part I, p. 25. 2 See what is said about Metzgeria on p. 107.
* Seep: 32.
* Schostakowitsch, Uber Reproduktion und Regenerationserscheinungen der Lebermoose, in
Flora, Ixxix (Erganzungsband zum Jahrgang 1894), p. 360.
GOEBEL 11 I
114 GERMINATION OF THE SPORES IN HEPATICAE
side pits with broad mouths, and only subsequently do the air-chambers
appear which have only a narrow breathing aperture towards the outside.
The first construction is, like other peculiarities of the germ-plant, only
possible in a small plant growing in shaded and moist places.
In the anacrogynous foliose forms the germ-plant is remarkable for
two things ; first of all, the configuration of the primary leaves, and secondly,
the appearance of the amphigastria. The lateral leaves appear first and as
short cell-rows. One may cause, as I have shown in Jungermannia bicus-
pidata, the shoots again to form primary leaves if the conditions are unfa-
vourable; these primary leaves are purely arrested formations. Whilst
now most forms produce completely developed leaves more or less quickly,
7
FG. 97. Zoopsis argentea. 1, young plant with stem composed of but three cell-rows. The ‘leaves’ are cell-
shoot with yellcicyeloped leaves Dente the archievoie: ERCIG: anette as ame
and always long before the appearance of the sexual organs, this is not the
case in those which I have termed ‘ rudimentary!.’ In them the formation
of leaf upon the vegetative shoot usually remains stationary at a stage which
in other plants is only found in the germ-plant, and only upon the sexual
shoots are further developed leaves found. This procedure recalls in a
certain measure the fact that the formation of the pro-embryo is prolonged,
only this temporary prolongation reaches here to the stage following the
formation of the pro-embryo.
The Hepaticae which come into consideration here are distinguished,
like Lejeunia Metzgeriopsis and Protocephalozia ephemeroides, from the
great majority of the others in that they are very small. They have thin
stems which give them, living as they do in shaded and moist localities, the
* See page 77.
RUDIMENTARY HEPATICAE 115
appearance of an Alga’. Amongst them are the descendants in the most
different cycles of affinity of the foliose Hepaticae. Some examples may
be given. The genus Zoopsis, a sub-genus of Cephalozia, is widely dis-
tributed, and its lateral leaves are unequally developed in the several
species upon the sterile shoots. In Zoopsis argentea (Fig. 97) and Z. setu-
losa they consist of only two cells, each with an appendage, and they
are laid down as in all other Hepaticae, but are displaced completely
into the horizontal position. The amphigastria do not reach beyond the
condition of primordial papillae, two club-like papillae standing near one
another. The sexual shoots are quite different. They have well-developed
leaves formed as cell-surfaces. The leaves are more developed in Lepidozia
bicruris and Arachniopsis. Here they are composed of two cell-rows, and
on the fertile shoots they form cell-surfaces. The same is the case in Lepi-
dozia goniotricha and some others. Of the relationship of the formation
of organs of these Hepaticae to their habitats mention has already been
made *.
* One form has indeed been described as an Alga under the name Kurzia crenacanthoidea; see
Goebel, Morphologische und biologische Studien: IV. Uber Javanische Lebermoose; 5, ‘ Kurzia
crenacanthoidea,’ in Annales du Jardin botanique de Buitenzorg, ix (1897), p. 37.
a See p. 77:
Mili sed
GERMINATION OF THE SPORE IN MUSGI
IN dealing with the Musci I shall, for reasons which will appear
presently, start from the germination of the spore.
From the time when Hedwig first of all described the germination of
the spores of the Musci the subject has evoked many investigations and
many interpretations, notwithstanding which our knowledge is not yet
without gaps. It is true that we no longer regard the pro-embryo as an
Alga, nor do we consider it with Hedwig as a cotyledon, nor suppose like
Nees von Esenbeck that the buds are formed by the weaving together of
protonema-threads ; nevertheless there is much that is still controversial
and obscure. When we use the word ‘pro-embryo’ we naturally do not
say anything about the morphological or biological significance of this
structure which precedes the leafy shoots.
1. ZHE CONFIGURATION OF THE PRO-EMBRVO.
The pro-embryo in most cases consists of branched cell-threads, and
is distinguished from the filiform pro-embryo of the Hepaticae by the
absence of zmzcellular rhizoids; but it produces segmented cell-threads',
designated also rhizoids, which are not the morphological equivalents of
the rhizoids in the Hepaticae. They are subterranean axes of the pro-
embryo, not appendages of the pro-embryo. The degree of development
reached by the pro-embryo differs in different forms, as is also the case
in the Hepaticae.
Physcomitrium pyriforme? furnishes a very simple case. The ger-
minating spore grows out into a cell-thread segmented by cross-walls and
containing chlorophyll, and this thread branches. Rhizoids also arise which
are thinner than are the protonema-threads exposed to the light, and like
these they are provided with cross-walls which are gutte transverse. Cell-
division takes place as a rule only in the end-cells not in the segment-cells
in all the axes of the pro-embryo. The different construction of these axes
* Protocephalozia ephemeroides alone amongst the Hepaticae approaches the Musci in this
feature ; see p. IIo.
? See Goebel, Uber die Jugendzustiinde der Pflanzen, in Flora, 1xxii (188g), p. 1.
RHIZOIDS OF PRO-EMBRYO 117
of the pro-embryo is evidently conditioned by their different physiological
work.
In pro-embryos of greater bulk we find also at first a similar slightly
marked difference between hypogeous and epigeous axes. The hypogeous
axes, at least the stronger ones, are provided in such cases mostly with
brown outer walls and cross-walls oblique to the long axis. Such rhizoids
are also found upon the leafy moss-plants, but there they are more richly
branched and the several branches exhibit a division of labour:—the
last thin branchings may be compared in their function with the root-
hairs of the higher plants, and they grow round the particles of soil; the
thicker branches become anchoring-organs, and they may also serve for
the conduction of food-
material (Fig. 98).
Oblique walls in
rhizoids. The oblique
direction of the walls
in the rhizoids is a re-
markable fact which
invites an explanation
both from the dzologzcal
and from the smorpho-
logical side.
First of all it may
be noted that we have
illustrations of a like
feature in plants out-
side the group of Musci.
at Ae Fig. 98. Funaria hygrometrica. A, germinating spore; ez, exine. B,
In the rhizoids of Chara _ protonema; 4x, buds; S limorda = ce. Magnilied. Lehrb-
the walls are not simple
transverse walls but are somewhat oblique, yet they always join on
to the walls they intersect at a right angle. This, as Errera’ was the
first to point out, and as de Wildeman® has also shown, is also the case
in Musci. The walls originally are set on to the outer wall of the thread at
a right angle, but they have a double curvature; they are not laid down
as flat plates and then displaced, but from the beginning have this double
curvature. When they, at a later period, appear as placed in an oblique
position, that is due to subsequent growth*. It is in this way, as various
1 Errera, Uber Zellenformen und Seifenblasen, in Biologisches Centralblatt, vii (1888), p. 729.
2 De Wildeman, Etudes sur l’attache des cloisons cellulaires, in Mémoires couronnés, publiés par
l’Académie Royale des Sciences de Belgique, 1893.
$ T have not been able to convince myself in my study of the process of division that the walls are
always set on at right angles to the outer wall. Certain is it that the wall is from the beginning
oblique to the long axis, and on one side I often saw plainly that it was set on at a right angle, but,
that the walls are set on throughout at right angles, I am not satisfied. Moreover, as the example
118 GERMINATION OF THE SPORE IN MUSCI
authers have shown!, that the surface by which two superposed cells touch
is increased, and that a more rapid interchange of material between them is
provided for. The thin lateral branches of the last order of the rhizoids are
abundantly provided with straight cross-walls which, however, may also
occur in the chief axes, especially when intercalary division takes place.
In the efigeous parts oblique walls occasionally occur, but the most of the
walls are transverse.
The ¢eleological ‘ explanation’ of the oblique position gives no clue as
to the conditions under which it arises. One may cause hypogeous rhizoids
to pass over into protonema-threads provided with chlorophyll and having
straight walls ; but this is not a simple effect of light, as might at first be
supposed. My researches with Funaria furnished the proof of this. This
plant, cultivated in the dark upon a sugar-solution, grew out to a relatively
large size; the cross-walls remained transverse and were not oblique, and
the rhizoids which developed in the light upon the moss-plants possessed
oblique walls, although green threads with straight walls might arise upon
them. It is in the highest degree probable that light is a condition for the
development of a rhizoid into a green protonema-filament, but in addition
other factors are operative, and especially the relationships of correlation.
The oblique position of the wall in the rhizoid has also received a mor-
phological explanation. Sachs® first of all expressed the view that the
protonema and its equivalent rhizoids in the Bryineae are only a very
feeble form of the moss-stem. Miiller-Thurgau* has endeavoured to sup-
port this view by showing that the segmentation in the apical cell of
a rhizoid is the same as in that of the stem of a moss, only that the chief
walls of the segments which follow one another are so far apart that they
no longer intersect. This view is altogether untenable, as I showed some
years ago”, and have subsequently again proved. As, however, in a recent
compilation °, showing altogether a want of knowledge both of facts and of
literature the Sachs-Miiller idea has again been brought forward, it is neces-
sary once more to state the grounds which show its futility :—
1. The regularity in the orientation of the oblique walls which Miiller-Thurgau
assumed does not always exist. The walls are not always inclined successively
of Ephemeropsis shows (Fig. 99, 6, where the segment-walls show a double curvature whilst retaining
their attachment at a right angle), the surface-development of the wall is more important for the
plant than to have it in any definite position. That its position is mostly oblique.is only of secondary
importance.
' Haberlandt, Physiologische Pflanzenanatomie, Ed. 2, Leipzig, 1896, p. 196.
2 see Part 1p. 233, fie ee
* See Sachs, Textbook of Botany, 2nd English edition, Oxford, 1882, p. 363.
* H. Miiller-Thurgau, Die Sporenvorkeime und Zweigyorkeime der Laubmoose, in Arbeiten aus
dem Botanischen Institut in Wiirzburg, i (1874), p. 475.
* Goebel, Die Muscineen, in Schenk’s Handbuch der Botanik, ii (1882), p. 385.
® Carl Miiller, Musci, in Engler und Prantl, Die natiirlichen Pflanzenfamilien, 1898.
SHORT SHOOTS AND LONG SHOOTS OF PROTONEMA 119
in three directions in space as are those of the apical cell of the stem. ‘Thus in
Fig. 99 the third wall is parallel with the first, the fifth with the fourth. In the
absence of a regular arrangement of the walls in three directions in space the whole
analogy with the apical cell fails.
2. Even if the regularity claimed by Muiller-Thurgau existed, the walls, which
are curved, have quite another character from those of the apical cell of the stem.
3. The oblique position is found only in the rAzzozds, but not everywhere. But
the rhizoids are only a fart of the protonema, and with that portion of it which has
straight walls the hypothesis does not fit. In Sphagnum its impossibility is quite clear.
4. The hypothesis does not fit the pro-embryo of the Hepaticae. The protonema
is certainly a simpler form of the vegetative body, but the simplification expresses
itself in this, that the cell-divisions proceed in it otherwise than they do later. The
oblique position of the wall in the hypogeous
protonema is simply a modification of the
transverse position, is called forth by the |
change in the requirements in relation to |
environment, and has no more morphological
significance than it has in Chara.
Short shoots and long shoots of pro-
tonema. The epigeous parts of the pro-
tonema frequently exhibit a differentia-
tion into short shoots and long shoots.
This may be illustrated by a moss which
I found in Java and have named Ephe-
meropsis tjibodensis, a very instructive
Z i . a Fic. 99. Arrangement of the segment-walls in
form which is epiphyllous, especially upon protonema-threads. 1 to 5, serially successive
segment-walls in the rhizoid of an undetermined
Monocotyledones 1 It shows clearly how _ species of moss. 6, segment-walls in a protonema-
? thread of Ephemeropsis tjibodensis; the walls
the protonema is adapted to external con- show a double curvature Whilst retaining, their
ditions.and particularly in its relationships
ofsymmetry (Fig. 100). The protonema is strongly dorsiventral. Its chief
axis creeps upon the leaf-surface. Distichously-branched branches of limited
growth arise upon the dorsal side and end in long bristles. Upon the flanks
are formed branched anchoring-organs (Fig. 100, H), which glue themselves
closely to the surface of the leaf and occasionally grow out into lateral
twigs. There is no richly developed system of rhizoids; their place is
taken by the short anchoring-organs, and the dorsal assimilating shoots are
specially fitted by their length and stiffness to retain water-drops, and thus
to make possible the nourishment of this peculiar protonema. The gemmae
also, which appear upon the protonema, are, as will be pointed out below *,
adapted in a special manner to the epiphyllous life.
1 The plant is unfortunately only imperfectly known, and its systematic position can only be
decided when female specimens bearing sporogonia are discovered. They have been found lately,
since the above was written, by M. Fleischer, Diagnose von Ephemeropsis tjibodensis, in Annales du
Jardin botanique de Buitenzorg, sér. 2, II (1gor). ? See p. 126.
120 GERMINATION OF THE SPORE IN MUSCI
Rhizoid-strands. Other adaptations are observed in some geophilous
species, for example amongst the Polytrichaceae, where, especially upon the
plant itself, rhizoid-strands are found, which Koch' compared with a badly
twisted string. The lateral branches of the rhizoids lay themselves along
the chief axis and partially invest it; they are not coloured brown. There
can be little doubt that we have here structures analogous with the rhizoid-
strands of the Marchantieae, and that here also a ‘ wick-mechanism’ comes
Fic. 100. _Ephemeropsis tjibodensis, Goebel, from Java. J, habit of the protonema, seen from above. Anchor-
ing-organs, H, shoot out from the flanks of the chief axis. Assimilating distichously-branched short shoots arise
from its dorsal surface. JZ, male plant which shows an abnormal arrest of the leaves.
into play, and thus the most of the Polytrichaceae, amongst which Atrichum,
however, is an exception, are able to live in relatively dry stations. To many
of the Polytrichaceae which reach a considerable size the rhizoids are also of
mechanical benefit, but this is only a secondary service.
Luminous protonema of Schistostega. Schistostega osmundacea” has
1 H. Koch, Bryologische Beitrage, in Linnaea, xvi, I (1842), p. 69.
2 See particularly Noll, Uber das Leuchten von Schistostega osmundacea, in Arbeiten aus dem
Botanischen Institut in Wiirzburg, iii (1887), p. 477.
SPECIAL ASSIMILATION-ORGANS OF PROTONEMA 12
partly ordinary protonema-threads, partly branches which consist of strongly
convex lens-like cells instead of ordinary cylindric cells. The branches
which consist of these lens-like cells, spread out in one plane at right angles
to the direction of the light (Fig. 101). The peculiar conformation of the
cells of the protonema has a relation to the habitat, for the plant grows
usually in clefts of rocks, which are illuminated only feebly and from one
side. Owing to the lens-form of the cells the light-rays falling upon
them are concentrated upon the chloroplasts which lie at one end of
the cells, and these are consequently subjected to a greater light-
intensity. A portion of the light-rays are reflected after they have
reached the chloroplasts, and thus cause the ‘luminous’ appearance of the
protonema of Schistostega. The lens-like cells may pass over into ordinary
cylindric cells, as I have observed, but we do not know what are the
external conditions which bring this about.
Concrescence of protonema-threads. In the Buxbaumiaceae, which
includes Diphyscium and Buxbaumia, the branches of the protonema, both
those containing chlorophyll and _ those
having none, become concrescent at their
points of contact. The possibility there-
fore is created of a copious passage of food-
material to the places where it is required,
and especially to the points of origin of the
moss-buds.
Special organs of assimilation of pro- Fic. toy, Stisestgs, mepgieey: Em
tonema. Diphyscium! has a peculiar organ
of assimilation on its protonema, usually in the form of an upwardly
concave plate, which sits upon a stalk composed of a cell-mass ; even the end
of the germ-thread itself is commonly constructed in the form of such an
organ of assimilation. From the base of this organ of assimilation rhizoids
proceed. I have usually found the primordia of the moss-buds springing
from the protonema-thread, and not, as one would expect, from the base of
the organ of assimilation, a phenomenon which is less striking in view of the
concrescence of the threads. In Diphyscium the surface of the organ of
assimilation is occasionally not at right angles to the stalk but it passes directly
into this. Such flat leaf-like organs of assimilation are also found in Tetra-
phis *, Oedipodium, and Tetrodontium. All these genera grow in relatively
very shady places, and the organs of assimilation are therefore well developed
in them. They have been described so frequently in recent years that it is
unnecessary for me to say more about them.
' See Berggren, Proembryot hos Diphyscium och Oedipodium, in Botaniska Notiser, 1873, p. 109 ;
Goebel, Uber die Jugendzustiinde der Pflanzen, in Flora, Ixxii (1889), p. 9.
See Part I, p. 249, where is quoted the observation of Correns regarding the development of
protonema-tufts under feeble illumination.
122 GERMINATION OF THE SPORE IN MUSCI
The pro-embryo in Andreaea. The remarkable behaviour of Andreaea!
stands in intimate relationship to its locality, as I have before now pointed
out. In the germination of this plant a cell-thread does not arise, but a cell-
body like that of many Hepaticae, and this is probably a protection against
drought. One to three peripherally-placed cells of this cell-mass grow out
into threads in which both transverse and oblique walls appear, and also
longitudinal walls. Where the protonema lies upon a stone it broadens out
into a much lobed and branched plate of tissue, which evidently forms a very
satisfactory anchoring-organ for this exclusively lithophilous moss. Another
form which is met with in the pro-embryo of Andreaea is that of the tree-
pro-embryo. It is a roundish, radially branched, orthotropous structure
which grows isolated occasionally, but mostly associated with others. Its
outer surface is covered with
a thick cuticle, evidently a
protection against drought in
its station. Leaf-like struc-
tures, like the organs of as-
similation of the pro-embryo
of Tetraphis, are found also in
Andreaea, which belongs to
the most highly developed of
the Musci. The dependence
of its configuration upon ex-
ternal factors requires inves-
tigation.
The pro-embryo in
aol timid! SPapean semis, Peonena te weds OFA oo cmbryo in phage
fx, exosporium.
num is well known, but was
commonly described incorrectly until recent times. Hofmeister? was the
first who found that there is developed here a frilled surface some-
what like that found in Anthoceros instead of a branched filamentous
pro-embryo. Schimper * believed that he had found that when the spores
germinated in water the pro-embryo was thread-like. In 1882 I threw
out the suggestion, and in 1889 I proved‘, although later authors have
entirely overlooked this, that Schimper’s statement rested upon an error.
' Berggren, Studier 6fver mossornas byggnad: I. Andreaeaceae, Lund, 1868; Kiihn, Studien zur
Entwicklungsgeschichte der Andreaeaceen, in Schenk und Liirssen, Mittheilungen aus dem Gesammt-
gebiete der Botanik, i (1874).
* Hofmeister, Zur Morphologie der Moose, in Berichte der sichsischen Gesellschaft der Wissen-
schaften, August 1854.
* Schimper, Histoire naturelle des Sphaignes, in Mémoires présentés par divers savants a
l’Académie des Sciences, xv (1858).
* Goebel, Uber die Jugendzustiinde der Pflanzen, in Flora, Ixxii (1889), p. 11.
THE PRO-EMBRYO 123
It is of course possible, by feeble illumination and other external factors,
to hinder the formation of the flat surface, but in the normal relation-
_ships this arises in germination in water just as it does upon the land. It
has further been shown that the flat pro-embryo is nothing but the broadened
cell-thread ; in germination a chief axis is first of all developed, and this
soon passes over into a cell-surface in which the arrangement of the cells
is varied. In weak pro-embryos one finds not infrequently a two-sided
apical cell ; in pro-embryos which are more strongly nourished most of the
marginal cells show differences in growth which here are evidently quite
subsidiary. In the case represented in Fig. 102, A, the formation of the
surface takes place in the second cell, in Fig. 102, 4, it appears in the third
cell of the germ-thread ; rhizoids in the form of filiform branchings segmented
by oblique walls arise from both the short germ-thread and the cell-surface.
The fact that the flat pro-embryo is derived from a filiform one is also
shown by this, that the rhzzotds are able to pass into cell-surfaces at
their end. What are the external factors which cause this are unknown.
Light is probably favourable to it, as perhaps also is an arrest in the growth
of the chief cell-surface. It must suffice for us that these facts show that “
the pro-embryos of all the Musci can be referred back to the filamentous
form. Sphagnum has this further interest, that occasionally pro-embryos are
met with which resemble the assimilation-organs of the pro-embryo of
Diphyscium.
I have observed remarkable relationships in Eucamptodon Hampeanum
and Dicnemon semicryptum ”, two allied genera of which the development
of the spores differs so much from that of the other Musci that Montagne *
believed that there were no spores in the sporogonium of Eucamptodon but
only gemmae like those of Marchantia.
Eucamptodon Hampeanum. If one examines an as yet unopened
sporogonium of Eucamptodon one finds that the ‘spores’ are not simple
cells, but pluricellular bodies of a flat form and somewhat elongated
irregular outline. A better idea of them can be obtained from Fig. 103
than from a description. Many are cell-surfaces, in others divisions have
taken place parallel with or obliquely to the surface; I have seldom found
more than two cell-layers in any one body.
Dicnemon semicryptum has much larger cell-masses with a roundish
outline within the sporogonium. The ‘spores’ from an as yet unopened
sporogonium are easily visible to the naked eye, and therefore are giant as
1 I cannot here discuss the phenomena of regeneration in the pro-embryo of Sphagnum, or other
subsidiary points.
* I have to thank Dr. Carl Miiller-Halle for specimens of these two mosses.
* Montagne, Plantes exotiques nouvelles, in Annales des sciences naturelles, iv (1845), p. 120.
Montagne examined Eucamptodon perichaetialis, Montag., and when he says ‘one cannot regard
these organs as true spores’ he refers to the spores which germinated in the sporogonium.
Montagne’s species grows in Chili, probably in a moist climate.
124 GERMINATION OF THE SPORE IN MUSCI
compared with the spores of other Musci. They are green pluricellular
bodies flattened upon one side whilst the other is somewhat flatly trigo-
nous (Fig. 103, 7). Here then, as in Pellia and Fegatella amongst the |
Hepaticae, the germination of the spore has taken place within the sporo-
gonium, but the pro-embryo found in Dicnemon semicryptum is composed
of many more cells than is the pro-embryo in the Hepaticae mentioned, and
has not the entirely flattened form it possesses in them. The small brown
spheres which are visible at different positions of the cell-mass, are probably
the remains of the strongly stretched exosporium ; they can also be seen on
the outside of the spores of Eucamptodon. A number of cell-walls, which
oe
LEERY
Fic. 103. Germinated spores taken from sporogonia which had not opened. Z, from Dicnemon semicryptum,
Carl Miiller-Halle. Z/-V, from Eucamptodon Hampeanum. Magnified.
by their colouring appear specially prominent, are the first to arise. How
further development proceeds I do not know, as I had only dead material
to examine. It is most probable that out of the germinated spores a fila-
mentous protonema is formed, just as it is out of the gemmae of Tetraphis.
The habitat of this moss on the south side of the South Island of New
Zealand confirms me in the view I put forward long ago, that its peculiar
vivipary is the result of its living in a moist locality. The appearance of
this peculiar method of germination amongst the Musci, whose spores other-
wise only form a filamentous protonema, speaks again strongly in favour of
the view that other variations also in the form of the pro-embryo, are only
later changes of the primitive filamentous protonema.
es
GEMMAE ON THE PRO-EMBRYO 125
2. GEMMAE (BROOD-BUDS) ON THE PRO-EMBRYO.
The pro-embryos of many Musci possess propagative organs which are
known as gemmae (brood-buds). Here we can only show some of the
manifold ways in which these may arise.
The simplest case is that of the breaking up of the pro-embryo into
simple cells under the stress of unfavourable conditions.
Fic. 104. Funaria hygrometrica. 4, B, C, D, protonema-threads showing colourless separation-cells, 7, be-
tween gemmae which contain chlorophyll, and which subsequently may become cell-masses. Magnified.
Funaria hygrometrica. We find this! in Funaria hygrometrica (Fig.
104) and in Bryum pseudo-triquetrum (?). Separation-cells which have
colourless contents and whose walls swell up are formed by intercalary
divisions. The remaining portions of the pro-embryo which contain chloro-
1 Goebel, Uber die Jugendformen von Pflanzen und deren kiinstliche Wiederhervorrufung, in
Sitzungsberichte der bayerischen Akademie, 1896.
126 GERMINATION OF THE SPORE IN MUSCI
phyl] may then grow out into new protonema. This division of the proto-
nema into single cells, or it may be into cell-masses, is the most primitive
method of the formation of gemmae, and it happens especially when the
external conditions for vegetative growth are unfavourable.
Schistostega. In Schistostega’ the end of the filament, composed of
a row of cells, separates off in quite the same way by a separation-cell, but
there is evidently here a little more specialization of the gemma as such.
Ephemeropsis. The formation of an anchor at the base of the gemma
of Ephemeropsis is remarkable*; the gemma after its separation can fix
Fic. 105. Buxbaumia indusiata. 1, protonema-thread bearing a male plant; A, rhizoid. 2, protonema-
thread with two male plants, one seen from in front, the other from behind. 3, young male plant on a proto-
nema-thread. 4, half-diagrammatic longitudinal section of a male plant. 5, 6, cell-grouping in young leaves.
rand 2, magnified 200. 3, more highly magnified.
itself firmly, by means of the projecting arm of its anchor, to the surface of
the leaf if this should offer a slightly rough surface.
The gemmae of the protonema of many other Musci are cell-bodies
which are adapted to a period of rest and possess thickened, often brown,
outer walls. To describe these structures here would carry me too far. In
many cases, although not in all, they are arrested stages of buds of moss-
plants. Investigation is required to show whether they do not play fre-
1 Noll, Uber das Leuchten der Schizostega osmundacea, in Arbeiten aus dem botanischen Institut
in Wiirzburg, iii (1887), p. 477.
* See Goebel, Morphologische und biologische Studien: I. Uber epiphytische Farne und Muscineen,
in Annales du Jardin botanique de Buitenzorg, vii (1888).
SIGNIFICANCE OF THE PROTONEMA 127
quently the part of reservoirs of reserve-food for the protonema, in which
case all these gemmae would not exhibit further development '.
Se otGNITICANCL OF THE PROTONEMA.
In the life of the moss-plant the formation of the protonema has a
double significance : on the one hand it secures that a large number of moss-
plants may proceed from one spore, and on the other it secures a vegetation
under conditions which would not allow of the development of the leafy
moss-plant?. The relationship of the protonema to the moss-plant is, as in
the Hepaticae, of a varying character. In most cases it is a juvenile stage
rapidly passed through, whilst in others it is the special vegetative body, and
the ‘leafy’ plant is nothing more than the bearer of sexual organs.
Buxbaumia. Buxbaumia, one of the most remarkable of the Musci in
other respects *, shows an extreme in this direction. The male plants are
extremely simple, about the simplest moss-plants we know (Fig.105). At
the end of a branch of the protonema there is found a long-stalked anthe-
ridium, which is surrounded by a chlorophyllous envelope shaped like a
mussel-shell. This envelope is the only ‘leaf’ of the plant. These extremely
small male plants, which cannot be seen by the naked eye, have usually no
rhizoids, although these may appear occasionally upon the envelope
(Fig. 105, 1, ), and the Dlants obtain their food therefore from the green
Protonema. There is no formation of a proper stem here, that is replaced
by a very slightly changed branch of the protonema. The female plant has
a slightly higher organization than the male, consisting as it does of a cell-
body which forms a little stem at the apex of which lies an archegonium.
A number of leaves, which contain no chlorophyll, invest the archegonium as
an envelope. We can understand that the female plant is more differentiated
because it has to provide for the sporogonium which appears later, and like
differences between the supporters of the male and the female sexual organs
will be noticed afterwards in the case of the fern-prothalli also. The question
then arises, Is this simple construction of the plant in Buxbaumia a primitive
one, or is it a reduced one? In considering this question inquiry must first
of all be directed to the point, Are there yet other characters in Buxbaumia
which can be called primitive? There are. In the first place, the leaves of
the plants of Buxbaumia have a different arrangement of cells from that of
all known Musci, with the exception of species of Andreaea. The leaves of
other Musci develop by means of a two-sided apical cell (Fig. 106), whereas
Buxbaumia has no apical cell to the leaves but only a cell-grouping more
or less resembling that of the leaves of the Hepaticae (Fig. 105, 5, 6)*.
* See what is said on p. 216 about the tubers in the Filicineae. 2 See Part I, p. 207.
* Goebel, Archegoniatenstudien: I. Die einfachste Form der Moose, in Flora, Ixxvi (Erganzungs-
band zum Jahrgang 1892), p. 92.
* That acute observer Robert Brown so long ago as 1819, said: ‘I have lately ascertained, however,
128 GERMINATION OF THE SPORE IN MUSCI
Another primitive character of the leaves is their production of many
rhizoids, which occurs but rarely elsewhere in moss-leaves. Further, the build
of the sporogonium, especially the device for the throwing off of the lid,
shows a primitive structure. In support of the view that we have in
Buxbaumia a reduced form it might be advanced that the plant is a sapro-
phyte, and in saprophytes and parasites elsewhere reductions commonly
occur. That Buxbaumia leads a saprophytic life is concluded from the
localities—rotting wood, soil of woods rich in humus—in which it occurs,
as well as from the absence of chlorophyll in its leaves. It is possible that
saprophytism does occur here, yet in other Musci which live on the dead
bodies of animals, their saprophytism has not brought about reduction. But
Fic. 106. Funaria hygrometrica. Young plant. At the base of the shoot protonema-threads spread out. The
two-sided apical cell is visible upon each of the upwardly-directed leaves.
saprophytic life has not been froved for Buxbaumia, and its protonema in
the parts exposed to light, as well as its sporogonium, contain chlorophyll’.
If Buxbaumia is a saprophyte this habit would account at any rate for the
that Buxbaumia aphylla is always furnished with perfect leaves, which more nearly resemble, both in
texture and division, those of a Jungermannia than of any species of moss properly so-called... .’;
see Miscellaneous Botanical Works of Robert Brown, London, 1867, II, p. 351.
* This extends to Splachnum also. I sowed spores of several species of Splachnum (S. sphae-
ricum, S. rubrum, S. luteum) upon fresh cow-dung and obtained quite normal green protonemata,
upon which arose subsequently partially formed sporogonia. That the species of Splachnum which
grow upon dung take organic substances from their substratum is probable, as it is in the case of the
species of Tetraplodon.—T. Wormskjoldi upon the dead bodies of lemmings, see Bryhn, Beobachtungen
ber das Ausstreuen der Sporen bei den Splachnaceen, in Biologisches Centralblatt, 1897, p. 48; T.
augustatus upon dead mice and excrement. Saprophytism can never be proved, however, on purely
morphological grounds (the behaviour of the rhizoids), and up till now we know of no moss (if we
except Buxbaumia) which has experienced reduction in consequence of saprophytic life-relationships.
SIGNIFICANCE OF THE PROTONEMA 129
absence of chlorophyll from the leaves and their small number, but would not
explain its other relationships. I have therefore arrived at the conclusion
that—if one rests mainly upon phyletic hypotheses—Buxbaumia is a form
which has sfood still in a stage which other Musci have passed, and that
it has a primitive character. We might imagine such a form to arise from
a filamentous Alga in which the branches bearing sexual organs have
developed somewhat differently from the vegetative branches, especially in
the direction of providing envelopes for the sexual organs. Ifthe formation
of the sexual organs is postponed to a later stage and the envelopes became
purely vegetative, a leafy moss-stem would then arise.
Phascaceae. Only a little more developed than in Buxbaumia are the
plants of some small Phascaceae. In them the protonema perennates and the
Fic. 107. Ephemerum serratum. Portion of a proto-
nema-thread with two young plants. Three antheridia
are visible in the plant to the left, and one archegonium
in the plant tothe right. The first leaf of the female Fic. 108. Schistostega osmundacea. Social
plant is seen turned to the front and consists of a simple rowth. /, the oldest shoot. J//qa and Z/Js issue
cell-row. Magnified. rom Z/.
moss-plants are mere supporters of the sexual organs. They always exist,
however, from the first as cell-bodies constructed out of the three-sided
pyramidal apical cell which is almost universal in Musci, and the segments
of which are devoted to the formation of leaves. In the simplest Musci the
leaves consist of but owe cell-layer, and they can act as organs of assimila-
tion because they contain chlorophyll, but as a fact they are at first used only
as envelopes to the sexual organs. In this relation it is interesting to
observe that the first ‘leaf’ of Ephemerum serratum (Fig. 107) is sometimes
a simple protonema-thread, so that the primordium of a moss-bud up to a
certain stage of development can be caused to grow out into protonema!.
Goebel, Uber Jugendformen von Pflanzen und deren kiinstliche Wiederhervorrufung, in Sitzungs-
berichte der bayerischen Akademie, 1896.
GOEBEL II k
130 GERMINATION, OF .THE, SPORE IN? MGSGi
Schistostega. The next stage is one where the stem passes on to the
formation of the sexual organs at a later time than in the case of Ephe-
merum. It still, however, has a simple conformation as it remains un-
branched. We see this in Schistostega. The several foliage-shoots of this
plant have limited growth, and, according to the hypothesis above stated, were
originally all supporters of the sexual organs, whilst now only a relatively
small number of them are of this nature; the others remain vegetative. All
are alike incapable of branching’. New shoots arise out of protonema-
threads which are formed at the base of the oldshoots. These protonemata
remain very short, and each at its apex passes at once into the formation of
a moss-bud (Fig. 108), evidently because assimilated material flows into
them from the old shoot, They issue from the leafless under-region of
these old shoots, and in this way arises the social growth of the stems. If
we suppose the protonema-threads which will grow out into shoots to be
still more shortened, the resemblance to an actual branching would be even
more conspicuous.
Fissidens bryoides. An interesting transition in this respect is found in
the male branches of Fissidens bryoides?._ This moss retains in its branching
a primitive character—the chief shoot ends with the formation of archegonia.
In the axils of the leaves numerous bud-like groups of antheridia are found,
and in the position occupied by these in the lower region a protonema-thread
appears. The cell which becomes a male branch projects outwards beyond
the surface of the shoot, as if it were about to grow into a protonema-
thread, but then, zzthout forming a protonema-thread, it passes at once into
the formation of an apical cell of a shoot.
The case of Fissidens bryoides brings us evidently very near to that of
Schistostega, and only one step further is necessary for the complete sup-
pression of the protonema in the origination of the shoot. At all events we
could establish a series from Buxbaumia up to the ordinary type of the
Musci, and we have seen analogies in the Hepaticae. Whether it is really
an ascending series, or perhaps a descending series, and whether what we
have regarded as primitive forms are not really reductions, is not at first to
be determined, and it is therefore superfluous to dispute about it. The chief
point is ¢o establish such series as will bring different forms into relationship
one with another.
* Contrary statements which appear in the Bryologia europaea are based upon incorrect obser-
vation. I have not found a single branched individual amongst hundreds of plants of Schistostega
which I have cultivated and examined. Leitgeb also never found a branched plant ; see Leitgeb, Das
Wachstum von Schistostega, in Mittheilungen des naturwissenschaftlichen Vereines fiir Steiermark,
1874, p. I.
* See Leitgeb, Zur Kenntniss des Wachstums von Fissidens, in Sitzungsberichte der Wiener
Akademie, lxix, 1 (1874).
VEGETATIVE ORGANS OF MUSCI 131
II
CONFIGURATION OF THE MOSS-PLANT
The disposition of the cells, the formation of the leaves, and the
branching of the ‘typical’ moss-stem, are described in the textbooks, and
nothing new has been brought forward within the last twenty years. It will
suffice therefore for me to mention here the chief points. These are :—
1. In all moss-stems which have been examined an apical-cell has been found,
and a leaf arises from each segment of this. The apical cell is usually a three-
sided pyramid (Fig. 109). In Fissidens, Phyllogonium, and perhaps also in other
Fic. 109. Thuidium abietinum. Shoot-apex of a bud Fic. 110. Andreaea rupestris. Young leaf. There
seen in transverse section. After Kienitz-Gerloff. is no two-sided apical cell. Highly magnified.
Musci with distichous leaves it is two-sided. This is a derived condition, as
Fissidens clearly shows.
2. The phyllotaxy is determined by the segmentation of the apical cell. Schwen-
dener’s mechanical hypothesis of position of leaves finds therefore no support in the
Musci. Where the phyllotaxy deviates from one-third there is an ‘encroachment
of the segment-wall in the anodic direction’ (Fig. 109), as Hofmeister proved, and
there is therefore an appearance of a torsion of the stem.
3- Branching is not axillary. Each lateral twig shoots out de/ow the leaf with
which it shares origin from a common segment-cell.
4. The arrangement of the cells in the leaves is characteristic. The leaf grows
chiefly by a two-sided apical cell (see Part I, Fig. 26, to the right) in the great
majority of the cases that have been investigated. We have seen an exception in the
case of Buxbaumia. In other genera which have primitive characters like Andreaea
there are also deviations from the ordinary arrangement’. ‘There are leaves which
* Berggren, Studier Gfver mossornas byggnad : I. Andreaeaceae, Lund, 1868; Kiihn, Studien zur
Entwicklungsgeschichte der Andreaeaceen, in Schenk und Liirssen, Mittheilungen aus dem Gesammt-
gebiete der Botanik, i (1874).
K 2
“
132 CONFIGURATION OF THE MOSS-PLANT
have the ordinary arrangement, and there are leaves which show at first a two-sided
apical cell, and then pass over into a condition of simple anticlinal and periclinal
segmentation, as in A. petrophila; finally, in A. rupestris this latter arrangement is
present from the first. Fig. rro illustrates the arrangement of the cells in a young
leaf of Andreaea rupestris. The earliest stages in the development I have not
examined, and I find no account of them in the authors quoted, and it is possible
that at first an obliquely inclined wall, which would be the first indication of the
formation of a two-sided apical cell, appears, and then the cross-walls. I have noticed
this arrangement in the primary leaves of Schistostega, which not infrequently con-
sist of a cell-row like that which has been described above in the case of Ephe-
merum. At all events in the leaves of Andreaea rupestris we have a construction
which resembles that of the leaf-like structures which appear also upon the protonema
of Andreaea, and this construction appears to me to be more primitive, as it is
in Buxbaumia, than that which occurs in other Musci. Diphyscium, which is
nearly allied to Buxbaumia, shows in the formation of its leaves the same transition
to the ordinary arrangement of the cells of Musci as is observed in the leaves,
especially the broader ones, of Andreaea?.
1. ZHE CONFIGURATION OF TAGE S7OoT
a. RADIAL SHOOTS.
When we consider the configuration of the shoot of the moss-plant we
designate as simplest Musci those which possess radial orthotropous shoots
with only foliage-leaves. Different forms exhibit that dzvzston of labour
to which reference in general terms has already been made’, and especially
in the appearance of shoots with limited growth. The limitation of
growth in the lateral shoot is mainly the result of correlation, but it also
occurs in chief shoots, and here I believe that as in the Hepaticae the con-
ditioning cause is mainly the water-supply. So far as I know the cushion-
like Musci which grow out radially have shoots of unlimited growth, and
these die off below as they grow above. This is not the case in segregate
forms. Climacium dendroides, for example, has, as its specific name indi-
cates, a tree-like stem through which its characteristic habit is acquired, and
it only forms twigs of limited growth at a certain height. But these shoots
are capable of further development if they come to lie upon the moist soil.
The plagiotropous lateral shoots of the radial shoot of Mnium undulatum
show similar features ; if they reach the soil they root and grow as creeping
shoots, and only subsequently when they acquire sufficient strength do they
rise as orthotropous shoots and produce sexual organs*. In support of the
* An oscillation between the two types of cell-arrangement, that is to say with or without a two-
sided apical cell, occurs also in the ‘paraphyses’ ending in cell-surfaces that are found in the
antheridial groups of different species of Polytrichum. Paraphyllia also exhibit like differences, as
will be shown on a subsequent page (see p. 146).
as See Partly ps 20
* See the description in Bryologia europaea.
PHEASHOOTAW “RADTAL SHOOTS 133
view expressed above may be cited the fact that the creeping chief axes of
Thuidium and of many other Hypneae and other Musci have unlimited growth.
In radial Musci which attain large dimensions we find frequently in the
leaves of the epigeous shoots the same division of labour that is observed
in many Spermophyta, namely, the shoot is beset in its lower part with
scale-leaves, which are protective organs merely and are not organs of assimi-
lation or function as such only in a slight degree. The shoot of a bamboo,
for example Dendrocalamus gigan-
teus, which reaches giant-dimensions,
produces at first scale-leaves alone,
and these protect the bud of the
stem ; only when the shoot comes
above the ground are assimilating
lateral shoots produced. If we com-
pare with such a shoot the repre-
sentation in Fig. 111 of Bryum gi-
ganteum we shall see the same
Q
Gf
“ps j
Fic. 112. 1 and 2, Hedwigia ciliata. 1, portion
of a leaf in transverse section. 2, portion of a leaf-
surface, the protuberances shaded. 3, : diate? a
longifrons. Bud-scale in transverse section. Mag-
nified.
Bie ouat Poe eo Showing the habit
features. The shoot of Pterobryella longifrons is clothed at first with scale-
leaves which contain no chlorophyll and glisten like silver. Theyare composed,
with the exception of the basal portion, of elongated sclerenchyma-like fibre-
cells with membranes so thickened that the lumen almost disappears (Fig.112,
3), a remarkable deviation from the soft structure which is characteristic of
most leaves of Musci. These scale-leaves fall off at a later period and the shoot
produces in its upper part branches with foliage-leaves which are plagio-
tropous and distichously branched, and the whole resembles closely the leaf
of a fern with a thick stalk. The production of scale-leaves in this plant is
connected with the struggle in which it engages with its fellows to raise itself
wate CONFIGURATION OF THE MOSS-PLANT
above the substratum. In other cases scale-leaves are produced upon shoots
creeping in the substratum, and then it is the want of light which conditions
their appearance, and they are arrested states of the primordia of foliage-
leaves, as I have previously pointed out is the case in Mnium undulatum !.
These scale-leaves here remain stationary at a somewhat late period of
development after the inception of the midrib, and their cells remain small
and like one another, whilst a division of labour subsequently appears in the
foliage-leaf between the marginal cells and those further in; but in Ptero-
bryella, as we have seen, there is a more far-reaching transformation which
is dependent upon the fact that the scale-leaves appear in it upon epigeous
shoots. True leafless shoots of Musci are unknown to me, although they
have been described in systematic works as occurring, for example in the
stolons of Climacium dendroides, but these have scale-leaves which act as
a protection to the bud of the stem. There would be no object in discussing
the transitions between scale-leaves and foliage-leaves. The genetic relation-
ship between the two naturally leads to the occurrence of transition-forms.
All the moss-shoots which bear scale-leaves produce foliage-leaves if
they reach the light. We know of no forms which persist, as in many
Hepaticae, as rhizome-shoots. Fontinalis, the water-moss, preferring to live
in rapidly flowing water, shows some interesting features. The base of the
shoot is fastened by numerous rhizoids to the substratum. Its upper part
floats. The leaves on the lower part are rudimentary. If, however, Fonti-
nalis be cultivated in still water in the laboratory there are formed, especially
in spring, many curved young shoots which are clad with small tufts of
rhizoids and rudimentary leaves—an indication that adaptation to habitat
has here become hereditary.
Leaves on radial shoots. The configuration of the leaves of the radial
stems of Musci is wonderfully uniform, and their adaptation to external
conditions is expressed more in the anatomical structure than in the external
form. Upon this more will be said hereafter’. Here it may be pointed out
that all the leaves of Musci are simple and unbranched, and are originally
simple cell-plates. In the smallest Musci they remain in this condition, for
example, in Ephemerum, Nanomitrium, and elsewhere. But in others the
primary leaves only are so simple, the later ones have a midrib which is
a subsequently formed thickening of the middle portion of the leaf produced
by cell-divisions parallel to the surface of the original one-layered
primordium. The leaves of some Musci have more than one nerve. The
highest degree of differentiation is that possessed, for example, by the leaves
of Polytrichum, in which one can recognize a lamina and a vagina. <<
Notwithstanding their simple relationships of configuration the leaves of
’ Goebel, Beitrige zur Morphologie und Physiologie des Blaites, in Botanische Zeitung, xxxviii
(1880), p. 787. 4 See p. 143.
AYPSOPHYELS 135
different forms frequently show differences, but we do not know in most
cases whether these are connected with the conditions of life or not. One is
inclined, for example, to consider that the form of the keel-shaped leaves
of Fontinalis antipyretica, which grows in rapidly flowing water, has some
connexion with facilitating the gliding off of the water. But it is unknown
whether, and in what manner, the direction to oe side of the apices of the
curved sickle-like leaves of many species is connected with the life-conditions.
Wichura ! has pointed out that in Hypnum uncinatum, H. aduncum, H. re-
volvens, H. cupressiforme, and others, the leaf-apices are turned towards
the shaded side, whilst in the Dicranaceae, for example D. scoparium and
D. undulatum, they are turned towards the
light, and therefore a kind of secondary j
dorsiventrality comes to pass here as lighted |
and shaded sides are differently constructed. i
One might believe that the retention of
water-drops was favoured by this, but then
we find the same appearances in aquatic
Musci like Dichelyma falcatum and others.
We must therefore regard the question of
the utilitarian side of these configurations as
one that is open, and it has not yet received
sufficient attention *. There are some phe-
nomena of adaptation in the configuration EN
of the leaves which standin relation to the | i
uptake of water, and these will be noticed | : ae
presently ; here I wish to note the occur- | : | ee] |
rence of ‘hypsophylls’ *. eke
Hypsophylis. These are present as | H/ \ | | eal
the envelopes of sexual organs, and they ‘\" a
diverge as do the perichaetial leaves of Fic. 113. Diphyscium foliosum. Leaf on
> ; the left a foliage-leaf. Two leaves to its right
the Hepaticae, from the ordinary form of are froma female shoot ; the middle one from
“ © 2 lower down the shoot than the envelope-leaf
foliage-leaves, especially where the foliage- onthe right, anditforms a transition from the
ergs 4 3 foliage-leaf to the envelope-leaf. Magnified 20.
leaves exhibit definite adaptations to outer
factors, because then these adaptations are absent or are reduced in the
hypsophylls. Thus the leaves of the envelope about the antheridia of
Fissidens bryoides want the characteristic wing of the foliage-leaf; in other
species the wing is present in a reduced condition.
In Polytrichum the leaves which envelop the groups of antheridia
arrive at their condition in quite the same manner as the hypsophylls in
* Wichura, Beitrage zur Physiologie der Laubmoose, in Pringsheim’s Jahrbiicher, ii (1860), p. 194.
* We may say the same of the analogous cases, for instance that of Mastigobryum, amongst the
Hepaticae. Why should the leaves by their curvature (which in Mastigobryum is always towards
the under side of the shoot) assume a kind of profile-position ? 3 See p. 389.
136 CONFIGURATION OF THE MOSS-PLANT
many Spermophyta. The sheath of the leaf enlarges, whilst the lamina is
only slightly developed, and thus it forms a large membranous expansion.
The perichaetial leaves of Diphyscium are also markedly different from the
vegetative ones. The vegetative ones (Fig. 113 to the left) are simple
tongue-like: the leaves of the envelope around the archegonia are much
larger and broader, and they end in a long bristle, such as we find in the
vegetative leaves of many xerophilous Musci, and they have ‘cilia’ on the
Fic. 114. -V, Eriopus remotifolius. 7, plant with fructification, showing habit. 2 and 7/7, gemmae; J, out-
growth of the gemma; 7} separation-cell. /V, ‘hair’ from the calyptra. V, ‘hair’ from the seta. V/, Drepa-
nophyllum fulvum. Portion of shoot to show habit. JZ magnified about 4. JZ/ and J/// highly magnified.
V/, magnified 12.
margin in the upper part (Fig. 113 to the right). These cilia are arrange-
ments for the retention of water, which has the same function in fertilization
here as in the Hepaticae. The bristles, as we shall see, are essentially pro-
tections against drought.
Musci possess also bilateral and dorsiventral shoots besides radial
ones, and, as I have already shown ' :—
1 See Part I, pp. 66 and too.
BILATERAL SHOOTS 137
1. The bilateral or dorsiventral shoots proceed from radial ones.
2. The bilateral or dorsiventral shoots are an adaptation, in varying
degree, to external relationships, especially to feeble illumination.
It will suffice if I here point out a few peculiarities.
6. BILATERAL SHOOTS.
These are flattened upon two opposite sides, and frequently the position
of the leaves has passed over from a tetrastichous into an apparently or
really distichous arrangement. In other cases, however, the tetrastichous
arrangement is maintained, and only the “Ze of the leaves is altered.
Anisophylly is then not infrequently observed, sometimes asymmetry of
the leaves. This disposition of parts which in descriptive bryological
works is commonly referred to as a distichous arrangement of the leaves,
gives to the shoots a flat construction which, in the most cases, has to
do with the utilization of feeble unilateral illumination, and it must not
be forgotten that a sparingly-leaved shoot can much more easily retain
water if its leaves take up a pseudo-distichous lie, than if they stand pointing
in all directions upon a radial shoot. The following are some examples :—
Eriopus remotifolius, C. Mill. (Fig. 114, /—V). I collected this moss in
Java?. It is of interest because the leaves which stand upon the upper side
of the stem, and those which stand upon the under side of the stem are often
only half as large as the lateral ones, and there are at the same time differ-
ences between the upper leaves and the under leaves. This case in some
measure approaches that of Lycopodium complanatum *, although the -
phyllotaxy is different.
Drepanophyllum (Fig. 114, V7). The sickle-like apparently distichous
asymmetric leaves of this genus are remarkable. We have before now seen
how oblique lie and asymmetric conformation go together in the moss-leaves,
and in this genus we have a beautiful example of it. The under half of
the leaf, that which is bent towards the base, is very much narrower than
the other ; the insertion of the leaf remains moreover, so far as I have inves-
tigated it, transverse, but the lamina soon bends into an oblique lie. The
biological significance of this asymmetry is probably the same as that which
was suggested in the case of Begonia *, and it may have come about in the
same way, but at present this is only hypothesis.
Schistostega *. It is only necessary to recall here that the bilateral con-
struction in this genus is the result of displacement of the leaves out of the
radial position and is found only in the vegetative shoots.
Fissidens. The formation of the leaves in the Fissidentaceae is remark-
* Whether this is really Miiller’s species or a nearly allied one is not determined. If it be Miiller's
species then the figure of the habit given by Dozy and Molkenboer, Bryologia javanica, ed. by Bosch
et Sande Lacoste, Lugduni Batavorum, 1855-70, tab. clviii, is hardly successful.
? See Part I, p. 103. $ See Part I, p. 119.
* See Part I, pp. 66 and 235, and Figs. 26 and 116.
138 CONFIGURATION OF THE MOSS-PLANT
able and formerly was incorrectly described. The primary leaves resemble in
configuration those of other Musci. This is true of the subsequent leaves
also in the first developmental stages ; but soon there is formed upon the
under side of the leaf-vein a wing-like outgrowth which afterwards becomes
so large that it looks as if it were the leaf itself, whilst the true leaf appears
as a sheathing portion of the wing. By this means the assimilating surface
is markedly increased, and the leaf of Fissidens offers a remarkable parallel
with that of Iris. The apical cell of the stem of Fissidens is two-sided, as
has been stated above’. The young shoots, which bore through the soil,
have, as Hofmeister first showed, a three-sided apical cell, and only at a later
period do they acquire a two-sided one. The branches too, which arise in
a distichous manner upon the stem, have at first a three-sided apical cell, and
the position of their first leaves corresponds therewith, but the apical cell
is gradually transformed into a two-sided one, and the leaves then become
strongly distichous. The branches of Fissidens bryoides alone have from
the first a two-sided apical cell. This transition from one kind of apical
cell to another which leads to a different phyllotaxy cannot be hindered by
absence of light, at least I could not hinder it in this way, although we may
assume that it was primarily caused by the action of light.
c. DORSIVENTRAL SHOOTS.
Dorsiventrality, as has been shown, finds its expression especially in
anisophylly, and of this there are many degrees*. Hypnum (Hylocomium)
splendens, species of Thuidium, and others are not anisophyllous, but the
direction of their terminal bud and the cross-section of the shoot (see Part
I, Fig. 113) nevertheless show a dorsiventral construction. How Hypnum
splendens, living in a shady wood, raises itself always above the detritus of
the wood by its peculiar tiered growth, and contributes to the layering of
humus, has been already shown ®*.
2. APPENDAGES.
Most of the Musci possess, in addition to the leaves, structures in the
form of cell-rows without chlorophyll, which, on account of their external
similarity to many hairs of higher plants, have been termed ‘hairs’; probably
they are transformed protonema-branches. They are the homologues of
the paraphyses, as will be shown below*. They stand usually in the axils
of the leaves. The simplest forms of Musci, like Ephemerum, want them.
They are also absent from the sterile shoots of Schistostega, whilst each of
the envelope-leaves of the archegonia has one of them in its axil. The
function of these ‘hairs’ is only known in Funaria hygrometrica and Di-
physcium, in which I have shown that they secrete mucilage, and in Diphys-
1 Seep. 131s * See Part I, p. roo.
3 See Part I, p. 69. *: Seeporge:
ASEXUAL PROPAGATION IN MUSCI 139
cium this takes place in a peculiar manner by the splitting of the cuticle
of the hair-cells. These ‘hairs’ then conform in their function with the
mucilage-papillae of the Hepaticae, and their mucilage serves for the pro-
tection of the young soft parts at the vegetative point. Whether this function
is generally distributed requires investigation. Perhaps the ‘hairs’ produce
a secretion in other cases, or they may take a share in the uptake of water ;
the latter function at any rate belongs to the paraphyllia? which will be
described below, but these are readily distinguished both by their containing
chlorophyll and by other characters from the ‘hairs’ we have under
consideration.
III
ASEXUAL PROPAGATION IN MUSCI
The Musci have a much richer vegetative propagation than is found in
the Hepaticae. Almost every living cell of a moss can grow out into pro-
vonema, and many produce gemmae of the most different kinds. I do
not intend to describe these here. I shall only give a glance at the best-
known ones along with a note of the special investigations of Correns 2.
We shall only consider how far the asexual propagation has led to a change
in the formation of organs, and this is not clear in all the forms of gemmae.
We have to distinguish two things :—
(2) The application of parts of the leafy shoot to the formation of
gemmae.
(6) The application of protonematous outgrowths to the formation of
gemmae.
As propagative organs we have :—
1. Entire shoots provided with reserve-material which are thrown
off,— either terminal portions of chief shoots and lateral shoots, as in Cam-
pylopus flexuosus, C. Schimperi, and others, or whole lateral shoots, as in
Bryum argenteum. These shoots form rhizoids and grow subsequently. Ac-
cording to Correns, in some species of Webera the leaves of the gemma-
shoot are reduced, and in Webera prolifera, for example, we find that the
apical cell of the shoot no longer continues its normal growth, but instead
there is the formation of protonema.
2. Leaves. The remarkable gemma-laves of Aulacomnium palustre
have been long known ; they are formed upon special greatly elongated
* See p. 146.
* Correns, Vorlaufige Ubersicht iiber die Vermehrungsweise der Laubmoose durch Brutorgane, in
Berichte der deutschen botanischen Gesellschaft, xv (1897), p. 374; Id. Untersuchungen iiber die
Vermehrung der Laubmoose durch Brutorgane und Stocklinge, Jena, 1899.
140 ASEXUAL PROPAGATION IN MUSCI
shoots, are filled with reserve-material', and in germination they produce
a protonema *.
3. Modified protonemata, proceeding partly out of the leaves, partly
out of the shoot-axes. These do not essentially differ from protonema in
the manner of their multiplication. Sometimes they separate as filaments,
sometimes as cell-masses. I may mention only one example. The Java-
nese moss Eriopus, represented in Fig. 114, has in the axils of its leaves
numerous tufted, branched, brown protonema-threads, which form peculiar
two-armed gemmae at their extremities (Fig. 114, //), and these gemmae
are also distinguished from the brown threads by their uncoloured walls and
probably also by their containing chlorophyll*. The gemma forms the
end of a stem-borne protonema-thread. At the point of attachment of the
gemma to the protonema-thread a short separation-cell is cut off, and as
this cell dies a split, which is not produced merely mechanically, develops
about the middle of its cell-wall. But before this occurs a branch which
grows downwards issues out of the basal cell of the gemma. When the
gemma has fallen off, the cell below the separation-cell grows out through
the remains of the separation-cell into a new gemma, and this may be
repeated often, with the result that there is visible on the outside ofthe cells
the remains of cell-membranes like a ruffle (Fig. 114, ///), recalling very
much the features produced in the filament of Oedogonium in the process
of interpolation of cell-membrane.
I may mention, as illustration of the formation of protonemata which
have developed into cell-masses and which arise by suppression of the
formation of leaves at the end of a shoot, the gemmae of Aulacomnium
androgynum which stand upon leafless elongated portions of shoot compar-
able with the pseudopodia of Sphagnum and Andreaea, and those also of
Tetraphis pellucida. In Aulacomnium androgynum they are not leaves
and they show no transitions to leaves *, as they do in the case of Aulacom-
nium palustre, yet they conform in their position with leaves. In Tetraphis
the gemmae stand within a flat, cup-like envelope formed by widened
leaves at the end of special shoots. These have a certain resemblance to
the cup-like groups of antheridia of many Musci, and this led Schimper ® to
' The midrib has developed at the expense of the lamina as in the leaves of Leucobryum.
* For other cases see Correns, Vorlaufige Ubersicht iiber die Vermehrungsweise der Laubmoose
durch Brutorgane, in Berichte der deutschen botanischen Gesellschaft, xv (1897), p. 3743; Id.
Untersuchungen iiber die Vermehrung der Laubmoose durch Brutorgane und Stocklinge, Jena, 1899.
* T examined material preserved in alcohol.
* Grevillius, Uber den morphologischen Wert der Brutorgane bei Aulacomnium androgynum (L.),
Schwaegr., in Berichte der deutschen botanischen Gesellschaft, xvi (1898), asserts that these exist, and
would therefore regard the gemmae as transformed foliage-leaves. The arrangement of the gemmae
is against this assumption. The ‘ transition-structure’ might arise by the development of gemmae
beginning at the apex of the leaves which are arrested in development, and thence invading the
stem. This is what happens in many Hepaticae (see p. 49), only in them many gemmae arise upon
the leaves not one only as here. ° Schimper, Bryologia europaea, Stuttgartize, vol. iii.
RELATIONSHIP TO WATER OF MUSCI 141
conjecture, although not upon solid grounds, that in these cups of gemmae
we have a ‘ virescence of the antheridial groups.’ The assumption of Correns,
that the gemmae of Tetraphis are modified ‘ paraphyses,’ is also untenable.
When we speak of the sexual organs we shall learn about paraphyses which
only occur with them. Gemmae, quite like those upon the shoots, may also
occur upon the protonema of Tetraphis, as Correns has himself shown.
How can paraphyses occur then upon the protonema? It is a ‘contradictio
in adiecto. The facts clearly show that we have only to do with a special
kind of formation of protonema in some measure like that which is found in
paraphyllia ?.
IV
VEGEPATIVE, ADAPTATION, IN. THE. MUSCI
I. RELATIONSHIP TO WATER.
It has been shown that in the Hepaticae the relationships to water
exercise a dominant influence upon their configuration. In the Musci,
although we have not such multifarious adaptations for the retention of
water as are found in the Hepaticae, yet the relation to water affects their
configuration in a profound degree. More than forty years ago Carl
Schimper recognized the essentials of this relationship, although as a matter
of fact his words evince a restricted appreciation of the uptake of water in
the Musci?. That indeed a movement of water and of dissolved salts takes
place in the stem of a moss-plant is suggested by the immense development
of the rhizoid-system of many Musci, and we may surely conclude therefrom
that this system is not simply an anchoring apparatus, but that its essen-
1 For an account of paraphyllia see p. 146.
? Carl Schimper, one of the founders of the Schimper-Braun hypothesis of phyllotaxy, must not be
taken in this connexion for Wilhelm P. Schimper, the bryologist. In his ‘ Mooslob,’ published in
1857, he says on p. 13 :—
Empfindlich fiir das Feuchie,
Wie fiir des Ortes Leuchte,
Was Wurz und Stengel leisten,
Gleich siehst du bei den meisten;
Was die geheim auch mischen,
Sie konnen nicht erfrischen
Die kargen Wasserfasser —
Moos welkt im Glase Wasser!
Die Blatter sind die Leiter,
Und aussen geht es weiter!
This, if wanting as verse, indicates good observation.
142 VEGETATIVE ADAPTATION OF MUSCI
tial function is rather the uptake of dissolved salts from the soil. Haber-
landt and others have also shown that there is in many Musci an internal
movement of water. In the stalk of the sporogonium the water undoubtedly
moves also, and its evaporation takes place from the assimilating tissue of
the sporogonium. The outer walls of the sporogonium are cuticularized,
and take in usually no water’; the water which is evaporated all comes
from the leafy stem, from which it is drawn through the foot of the sporo-
gonium. But in the leafy stem there is evidently no transpiration-stream *
which could cover the loss of water from the leaves in somewhat dry air—
as Schimper says ‘ moss wilts in a glass of water.’ The leaves have, so far
as they have been examined, no cuticularized walls; they rapidly flag and
rapidly take up water again from outside, and the swelling of their cell-
membranes evidently plays in this a different rdle from that which it does in
the higher plants; even a dead moss-leaf may thereby immediately be made
‘turgescent’ again. The turgescence has, in my opinion, no importance in
the living moss-plant also in relation to the imbibition of water through
the membrane ; the whole construction is quite different from that in the
higher plants. With this is connected in the Musci as in the Hepaticae
the fact that many xerophilous forms, for instance Andreaea, have in
their leaves very strongly thickened membranes which can hold relatively
much water.
The ‘external’ conduction * which is spoken of by Schimper is capil-
lary. It is brought about partly by the close aggregation of the leaves and
lateral shoots, partly by the weft of rhizoids, or by the paraphyllia which
will be mentioned below. In Sphagnum there are entirely different devices
for this purpose. Water-storage in the shoots of Musci, apart from that
in their cell-membranes, is unknown, but there are contrivances for the
retention of water and for the protection of the young parts especially
against too great heating and consequent drying. Amongst the xerophilous
forms there are moreover many which are well able to withstand periodic
droughts, and I have not been able to keep alive Andreaea in a continuously
1 The stalk of the sporogonium in many Javanese Musci, for instance Eriopus, is beset with hairs
which probably take up water (see Fig. 114, 7V and V).
* See Oltmanns, Uber die Wasserbewegung in den Moospflanzen und ihren Einfluss auf die
Wasserbewegung im Boden, in Cohn’s Beitrage, iv (1884); Haberlandt, Beitraige zur Anatomie und
Physiologie der Laubmoose, in Pringsheim’s Jahrbiicher, xvii (1886) ; Vaizey, On the absorption of
water and its relation to the constitution of the cell-wall in Mosses, in Annals of Botany, i (1887).
The anatomical relationships which cannot be dealt with here are fully discussed in the works cited.
* Hedwig, Descriptio et adumbratio microscopico-analytica muscorum frondosorum, Lipsiae
1787, p. 109, describes this in the case of Hedwigia ciliata. He says ‘ Papillis nimirum, seu potius
vesiculis diaphanis omne eorum exterius planum dense obsitum est, quae spongiae in modum, avide
adeo attrahunt humiditatem, ut, si plantulam penitus siccam pollice et indice basi sua surrectam teneas,
et minimam aquae guttulam ibi immittas, haec illico attracta, verticaliter adscendat de folio in
folium, unde amoenissimo spectaculo sensim paulatimque unum post alterum ad cacumina usque
erigatur, expandatur reflectaturque.’ The ‘vesicles’ are really the solid thickenings of the
membrane,
LEAVES AND WATER. MAMMILLAE. PAPILLAE 143
moist state; probably it is, like Metzgeria, adapted to conditions of periodic
drought. Some of the chief adaptations will be now mentioned :-—
1. ARRANGEMENTS FOR THE RETENTION OF WATER.
A. “IN THE LEAP,
(2) IN THE FORM OF THE LEAF.
There is wanting in the Musci the wealth of adaptation in the form of
the leaf in relation to the retention of water that is so manifest in the
Hepaticae. The leaves of the Musci are indeed often boat-shaped 1, and
many are widened at the base like a spoon. In Phyllogonium specio-
sum, a beautiful moss hanging from the branches of trees in Venezuela, the
edges of distichous leaves overlap at the point of insertion, so that a tube
surrounding the stem is formed. In Phyllogonium fulgens, as in many
Neckeraceae, there are at the basal portion of the leaf outgrowths of the
leaves which recall in a measure the auricles of the Hepaticae, but only
those of the most simple form. F urther, the leaf-base in the Musci is often
otherwise specially arranged for the uptake of water, as we shall see pre-
sently *, but constructions which could be placed alongside of the complex
auricles of the Hepaticae are unknown.
(4) IN THE CONSTRUCTION OF THE LEAF.
I. By outgrowths of the leaf-surface :—
(a) MAMMILLAE. The simplest case is that where the cell-membrane
protrudes outwards ? and the leaf-surface becomes provided with mammillae,
as in species of Timmia, Bartramia ityphylla, and others. This construction
recalls that of Aneura hymenophylloides amongst the Hepaticae.
(b) PAPILLAE. The formation of papillae, which in the matured con-
dition appear as centrifugal thickenings of the cell-wall, has probably been
derived from that of mammillae. In Hedwigia ciliata (Fig. 112, 1 and 2)
there appears, as has been already mentioned ¢, an extraordinarily effective
capillary apparatus for water. In other Musci growing in sunny dry places,
such as Encalypta, Barbula, Racomitrium, Grimmia, and Weissia, similar
arrangements are found. They never occur, however, in hygrophilous
forms. As many Musci which are commonly xerophilous become hygro-
philous in moist conditions, the point should be investigated whether these
" The undulations of the surface of the leaves of species of Neckera are also a means for the
retention of water.
2c -
See pp. 145, 147.
* See Lorch, Beitrage zur Anatomie und Biologie der Laubmoose, in Flora, lxxviii (1894).
* See p. 142, footnote 3.
144 VEGETATIVE ADAPTATION OF MUSCI
papillae are formed or not in such hygrophilous states. The analogy of
many Polytrichaceae, which will be mentioned below, makes it probable
that these papillae would entirely disappear in cultivation under moist con-
ditions as well as in the absence of light.
(c) LAMELLAE. More common than mammillae or papillae are
outgrowths of the leaf-surface in the form of cell-rows or cell-plates
containing chlorophyll. Formerly these were considered as merely in-
crements to the apparatus for assimilation, but, as I have elsewhere shown’,
this isincorrect. Assimilation can only go on in the presence of water. The
cell-rows or lamellae stand so close together that they hold water between
them. A comparison of the relationships of the forms to the stations in
which they grow leads also to the same result.
Polytrichaceae. We find the most beautifully developed lamellae upon
the broad nerves of the species of Polytrichum which grow in exposed
stations, but in the nearly allied Catharinea undulata which grows in moister
and more shaded stations, the outgrowths are smaller and less numerous,
mostly four to six. The surface of the leaf itself is in Catharinea still rich in
chlorophyll, and its margins roll inwards over the lamellae in dry conditions ;
in Polytrichum the surface of the leaf is far behind its massively developed
lamellae in importance as an assimilation-organ. It has recently been
affirmed that the lamellae disappear under cultivation in moisture. This is
not correct, they are reduced at the most in Catharinea, where they are
without doubt the smallest. If Polytrichum be cultivated in water the old
leaves die, becoming black, the new ones have lower lamellae, adapted to
water-life.
Barbula. Insome species of Barbula, for instance B. aloides, B. ambigua,
and B. membranaefolia, there are close-set branched cell-rows, the terminal
cell in each of which has often a peculiarly thickened membrane which is
evidently protective. The one-layered leaf-surface is concave, bending over
the portion provided with outgrowths, and thus an effective sponge-like
apparatus is provided.
Pottia. Species of Pottia also there are which have lamellae, for
example P. curvifolia, P. barbuloides.
Here then we have an adaptive character which has arisen indepen-
dently in three cycles of affinity of the Musci—the Polytrichaceae, the
Barbulaceae, and the Pottiaceae.
Campylopus polytrichoides. Campylopus polytrichoides also has lamel-
lae-like outgrowths upon the wzder side of its leaves, they consist of some-
what thick-walled cells; their function requires further investigation. It is
probable that they also serve for holding water.
* Goebel, Archegoniatenstudien: V. Die Blattbildung der Lebermoose und ihre biologische
Bedeutung, in Flora, Ixxvii (1893), p. 430.
LEAVES AND WATER. SPONGE-CONSTRUCTION 145
2. By Empty Cells with Perforated Walls :—
This arrangement is found in many different cycles of affinity, and
in plants which grow in very different stations, both wet and dry.
Sphagnum. The species of Sphagnum are well-known examples of
plants from a wet station. I do not require to describe the structure of the
leaf and the stem, but only to recall that, as has already been shown !, the
meaning of the whole mechanism has not been recognized hitherto. It is
most probable that its explanation lies in the fact that Sphagna grow in
places where the water only contains asmall amount of some of the mineral
substances necessary for their nourishment, so that a profuse water-evapora-
tion is necessary.
Leucobryaceae. The cushions of the Leucobryaceae are found in dry
woods, not in wet marshy places. In them we find a many-layered leaf in
which the chlorenchyma takes up only a small portion of the space as
compared with that occupied by tissue containing no chlorophyll’. The
conspicuous feature in the leaf of the Leucobryaceae is the presence of
a strongly developed midrib with a peculiar construction. Its special charac-
ters stand out clearly when it is compared with the leaf of Dicranum
albidum. The empty cells communicate with one another by numerous
holes. On the outer walls there are relatively few pores, but they are
found specially at the basal part of the leaf, whence the water can easily
pass by capillarity into the upper part of the leaf. In the case of Leuco-
bryaceae the water must not (to speak teleologically),as in Sphagnum,
evaporate rapidly, but be retained for a long time for the chlorenchyma.
The two apparently similar kinds of leaf-structure are thus specially adapted
to different external conditions.
Dicranum albidum. The method of uptake of water in Dicranum
albidum requires further experimental investigation. The plant shows
a transition in the structure of its leaves from the ordinary leaf of the
Dicranaceae to that of Leucobryum.
Pottiaceae. Perforated cells are also found in Calymperes, Syrrho-
podon, and Encalypta, which are genera of the Pottiaceae, but in them
always in one layer and usually only in the lower part of the leaf; they
are also found upon all or nearly all of the outer walls and lateral walls.
Syrrhopodon revolutus. The extent to which the transformation of the
function of the leaf tissue to that of absorbing water can go under suppression
of the work of assimilation is shown by the case of Syrrhopodon revolutus,
Dz. and Mb., which I investigated (see Fig. 115). The chlorophyll-cells,
whose area is indicated by shading (Fig. 115, 7), take but a small share in
the structure of the leaf which is made up mainly of empty cells whose walls,
1 See Part I, p. 279.
* For the details of the structure and development I must refer to Lorch, Beitrige zur Anatomie
und Biologie der Laubmoose, in Flora, lxviii (1894).
GOEBEL Il Ts
146 VEGETATIVE ADAPTATION OF MUSCI
both the outer and the lateral ones, have pores. A transverse section through
the lower part of the leaf (Fig. 115, 77) shows but two kinds of tissue—the
empty water-absorbing cells and the mechanical tissue of the midrib and
margins which form the framework on which the thin-walled empty cells are
stretched and which are necessary to them, for in themselves they have not
sufficient firmness. The chlorophyllous cells possess moreover papillae, so
that a most complete mechanism for the retention of water is provided in
the plant. Then besides the above-mentioned anatomical features the leaf
is also not flat but is strongly concave, and the stems grow thickly crowded
together in tufts. Altogether the construction of a sponge in this moss is
as good as is that in Sphagnum or one of the Leucobryaceae.
B. IN THE STEM.
(a) PARAPHYLLIA.
The stems also of many
Musci possess chlorophyllous
outgrowths which may retain
water and conduct it by
capillarity. These are the so-
called paraphyllia, which are
found in some species of
Thuidium and Hypnum. We
have seen analogous structures
in some of the Hepaticae. In
Fic. 115. Syrrhopodon revolutus. JZ, leaf. The position of the the Musci they are _remark-
chlorenchyma is shaded. /, lower portion of a leaf in transverse able jn that they resemble
section. ///, part of the lower portion of a leaf in surface view.
ape, muechacicel ane ig indicated by shading beeween tend? somewhat leaves: ma fier com-
TED BES A ISS EGE struction,and like leavesappear
as cell-surfaces(Fig.116). We have in them, however, in my view, structures
which have sprung from ce//-¢/ireads and which also have not the characteristic
arrangement of leaves.
Hypnum splendens. In Hypnum splendens the paraphyllia cover with
a thick weft the surface of the strong shoots. They are narrower or broader
cel]l-surfaces and through their branching their long axes spread out in
different directions. The history of the development of the paraphyllia
being unknown, I examined it in Hypnum splendens, and found that they
are laid down very early in the stem-bud. Their number increases in pro-
portion as the surface of the segments increases, and new paraphyllia are
laid down between the old ones. It is interesting that the arrangement of
the cells in the paraphyllia resembles that of the leaves. There is a two-
sided apical cell (Fig. 117, 7, //), from whose segments, right and left,
outgrowths proceed in rapid serial succession, and these repeat the cell-
arrangement described ; finally, the formation of the segment-walls ceases
STEM AND WATER. PARAPHYLLIA 147
in the filiform end of the paraphyllium or its branches (Fig. 117, //Z, LV).
The segment-walls are directed obliquely to the long axis of the thread in
a characteristic fashion, reminding us of what occurs in the protonema.
The paraphyllia are narrower and fewer on the lateral branches of higher
order in Hypnum splendens.
Thuidium tamarascinum. In Thuidium tamarascinum, which I also
investigated, the chief shoot alone has paraphyllia. These are usually only
branched cell-rows (Fig. 117, V), provided with snag-like outgrowths like
the papillae of the leaves, and such paraphyllia
may take origin also out of the base of the
leaves. Many of them are also developed as
cell-surfaces whose origin differs, however, from
that of the paraphyllia in Hypnum splendens.
The origin of the cell-threads is not clear here,
for there is no ‘ growth from an apical cell, but
simple anticlinal and periclinal chambering
like that which is observed in the development
of the leaves of Andreaea (see Fig. 110);
ne
FiG.116. Hypnum splendens. Pa-
raphyllium. At the lower left side of
the figure a recurved branch is shown.
Magnified 210.
Fic. 117. Development of a paraphyllium. 7), Hypnum sp'en-
dens. V7, Thuidium tamarascinum. © Z and ZZ, young paraphyllia.
IH and ZV, apices of older paraphyllia not yet mature; the letters
indicate successive segment-walls. 7, mature paraphyllium.
the leaves of Thuidium have, however, the same disposition of cells as
is found in the leaves of other Musci. The paraphyllia in Thuidium
are therefore transitions to the protonema-threads of limited growth
which spring from the stem-surface of other Musci. The protonema-threads,
which arise upon the stem and bear the gemmae also aid in the uptake of
water—those, for example, figured in Eriopus remotifolius (Fig. 114). In
Drepanophyllum falcatum I found similar structures.
Paraphyllia are then to be regarded as protonema-branches of limited
§rowth which issue from the stem-surface, and which are partly developed
into cell-surfaces and have in part attained to a growth and method of con-
L2
148 VEGETATIVE ADAPTATION OF MUSCI
struction analogous with those of the leaves ; their function is to take up
water and at the same time to increase the surface for assimilation.
(6) OTHER ARRANGEMENTS FOR HOLDING OF WATER.
Special devices upon the axes of the shoots for the uptake or holding of
water, apart from the paraphyllia, are known only in the Sphagna, but they
possibly occur also elsewhere. Brizi 1 describes lens-like groups of cells with
unthickened glistening walls on the surface of the shoot-axis in Cyathophorum
pinnatum. When they are full-grown their content has disappeared. I think
that these are cell-groups like those in other Musci indicating the place where
protonema-filaments or lateral twigs take origin. It is possible, however,
that these cells serve specially for the uptake of water. This can only be
determined by experimental investigation.
2. ARRANGEMENTS AGAINST DROUGHT.
As I have already pointed out, xerophilous Musci experience long
periods of drought without injury. Nevertheless, apart from the nature of
the protoplasm, of which we have no knowledge, there are also in the Musci
arrangements which are to be considered undoubtedly as protections against
drought, partly also as protections against too great heat. This may
perhaps be connected with the fact that, on the one hand, protection is
required chiefly for parts that are not juvenile and enclosed in a bud, and
on the other hand, it will not be a matter of equal importance whether the
loss of water in drying follows slowly or quickly. A retardation of the loss
of water will be the result of the movements which the leaves of many Musci
experience in drying. Thus in Polytrichum the leaves lay themselves against
the stem, others wind and twist themselves together, and in Leucobryaceae
the same object is attained by the living cells becoming enveloped with
a mantle of dead ones which contain air. We find the same thing in other
cases where, however, the dead cells serve only as a protective mantle, and
have nothing to do with the uptake of water.
Silver-glance. Bryum argenteum derives its name from the silver-glance
of its shoots, and this is caused by the dying off of the cell-contents in the
upper part of the leaf. These dead upper parts invest as with a mantle the
bud of the stem and must check the outgo of water. It depends upon
outside circumstances how far this process proceeds. If the plant be culti-
vated in shade and moisture the leaves remaim green *, but on dry places the
silver-glance appears and the point of the leaf is drawn out into a hair.
1 Brizi, Sopra alcune particolarita istologiche e biologiche dei Cyathophorum, in Rendiconti della
R. Accademia dei Lincei, ii (1893).
2 Goebel, Uber den Einfluss des Lichtes auf die Gestaltung der Kakteen und anderer Pflanzen,
in Flora, lxxxii (1896), p. 10. _Leucobryum glaucum, on the contrary, retains its tough leaf-structure
even if cultivated under water.
HAIR-POINTS. RELATIONSHIP TO. LIGHT 149
Other similar cases are met with, for example Grimmia leucophaea, a moss
growing upon sunny rocks, receives its name from the white apices of the
leaves, and Hedwigia ciliata, mentioned above, forms in dry sunny places
a variety leucophaea, whose leaves appear to be composed in the upper third
of dead cells, as in Physcomitrium repens and others.
Hair-points. If we have in these cases to deal with a direct adaptation
to external conditions, the same holds good for the “azr-pozints, which are not
uncommonly found in combination with them. Such diaphanous hair-like
points are only seen in the inhabitants of dry stations. They are formed in
the bud and their dense aggregation closes the end-bud to the outside, and
their thickened cell-membranes sometimes act as water-reservoirs. Many
of our Musci, like species of Racomitrium, Grimmia, Barbula, and others,
which grow upon rocks and walls, show these diaphanous hair-like points,
and it is characteristic that many of these Musci exhibit local forms when
growing in moist localities or in water, which do zo¢ have diaphanous hair-
like points upon the leaves. We see this, for example, in Racomitrium
canescens with its form epilosum?. Musci which live in permanently moist
conditions never produce these hair-points.
iH. BELATIONSHIP TO LIGHT.
The relationships of the configuration of the Musci to light are manifold
and have already been referred to. Let me only recall here that the dark
colour of many Musci is evidently dependent on light, and the red colour of
many species of Sphagnum is apparent on the plants exposed to the sun.
These features can be homologated with what has been already said about
the Hepaticae. The dense cushion-growth, which is characteristic of almost
all high alpine Musci, enables the plant to maintain its heat better.
Vi
SEXUAL ORGANS OF MUSCI
PeeeOStILON OF THE SEXCAL. ORGANS.
All the Musci are acrogynous. The archegonial-groups always form the
end of the axis of a shoot, whether this be a main one, as in acrocarpous
Musci, or a lateral one. The acrocarpous state is the more primitive
condition”. Musci are also acrandrous in their primitive condition. The
first antheridium proceeds from the apical cell; the following ones from the
segment-cells. Only two exceptions to this are known, that of Sphagnum
and that of Polytrichum.
Sphagnum. In Sphagnum the antheridium stands. upon the anodic
* See Limpricht, Die Laubmoose, in Rabenhorst, Kryptogamen-Flora von Deutschland, Ed. 2.
3 See p. 129.
150 SEXUAL ORGANS OF MUSCI
margin of the insertion of a leaf. Leitgeb shows that the antheridia take
the position which otherwise the mother-cell of the lateral shoots would
assume, and one might therefore suppose that the lateral twig passes over
in the unicellular condition into the formation of antheridia, and it is note-
worthy that the formation of leaves on the male twigs is often very small,—
in Fontinalis, for example, we get minute reduced branches. Sphagnum,
however, belongs to quite a different cycle of development from that of the
Bryineae, and it appears questionable how far one can make the comparison,
if there is one.
Polytrichaceae. The Polytrichaceae’ have cup-like antheridial groups
which are regularly transpierced by a vegetative shoot, that is to say, the
apical cell of the chief axis remains, and later it elongates into a leafy shoot
through the antheridial group. Within the group several antheridia stand
clustered in transverse lines, there being two to three of them one above the
other under a leaf. Mixed with the antheridia are the paraphyses. Hof-
meister, and with him Leitgeb, has so interpreted this relationship, that
‘every cluster of antheridia under a leaf represents a shortened lateral twig
whose apex is developed into the first antheridium.’ This explanation
would bring the behaviour of Polytrichum into conformity with other Musci,
and one might find an analogy with it in the species of Campylopus ”, in
which many archegonial groups are united into ‘heads’ resembling the cup
of Polytrichum in some measure. If I then give full weight to Hofmeister’s
interpretation I would point out that the 4zstory of development is yet
wanting. Up till now no one has shown that originally in the place of
a cluster of antheridia the apical cell of the twig is to be found which gives
off segments. Also in the case of Mnium and other genera the develop-
mental history of the antheridial groups is still unknown, and it is questionable
whether all Musci must really be considered as acrandrous.
The monoecious Musci make no exception to the acrandry. In them the anthe-
ridia are found free in the axil of the stem-leaves, or of the perichaetial leaves. As
Satter® has shown in the case of Phascum cuspidatum and Archidium, the foliage-
shoot here ends with an antheridial group, and is then overtopped by one lateral
female shoot or there may be two such shoots, and this may also take place in other
Musci.
2. DISTRIBUTION OF THE SEXUAL ORGANS.
On this subject I shall say nothing more beyond this, that in dioecious
1 See Hofmeister, Uber die Zellenfolge im Achsenscheitel der Laubmoose, in Botanische Zeitung,
xxviii (1870), p. 465; Goebel, Uber die Antheridienstinde von Polytrichum, in Flora, Ixv (1882),
p. 323; Leitgeb, Die Antheridienstainde der Laubmoosé, ibid., p. 467.
* See figures in Dozy und Molkenboer, Bryologia javanica, ed. by Bosch et Sande Lacoste,
Lugduni Batavorum, 1855-70; for example, Tab. Ixviii.
’ Satter, Zur Kenntniss der Antheridienstande einiger Laubmoose, in Berichte der deutschen
botanischen Gesellschaft, ii (1884), p. 13.
ANTHERIDIAL AND ARCHEGONIAL GROUPS. PARAPHYSES 151
Musci the male plants are frequently smaller and have a simpler organization
than the female ones. A striking example of this is offered by Buxbaumia’,
whose extremely small male plant has only one leaf and no stem, whilst the
female plant has a large number of leaves and a stem which is no doubt very
small and has a simple construction. In Ephemerum also the male plants
are smaller and have fewer leaves than the female (see Part I, Fig. 87), and in
varying degree this is repeated in most dioecious Musci. Amongst the most
striking examples are those dwarf males which are found along with larger
male plants in Leucobryum and some species of Dicranum. Evidently in
these Musci, as in the prothalli of the ferns, the male sexual organs can develop
under external conditions that do not suffice for the formation of the female
organs, and it is further clear that the female plant, which subsequently
produces the embryo, must be better equipped than the male.
3. THE ANTHERIDIAL GROUPS AND ARCHEGONIAL GROUPS’.
The sexual organs in Musci are protected on the one hand by the
leaves which surround them, the ferichaetial leaves, and on the other hand
by the paraphyses.
Paraphyses. The paraphyses are cell-threads whose upper cells are
frequently swollen into spheres, and contain chlorophyll. In Polytrichum
the paraphyses end in small cell-surfaces*. With regard to their homology,
there can be no doubt that they are nearly allied to hair-like structures which
one meets with also on the vegetative shoot*. In many cases, as in
Diphyscium, they cannot be distinguished from these ; in other cases, as in
Mnium and Polytrichum, I found all stages of transition between them.
Their function has not been sufficiently dwelt upon. As I have elsewhere
pointed out °*, they are in the first instance protective organs, especially
against drought, and the spherical expansion of the cells that characterizes
many paraphyses fits them better to cover the antheridia. Doubtless this
is not their only function ®. Excretion of mucilage by them is only known
in Diphyscium. It is doubtful whether they also excrete water or slimy
water such as Leitgeb has observed amongst the Hepaticae in Corsinia.
The paraphyses can certainly retain water by capillarity, and this is specially
the case in the disk-shaped or flat cup-like antheridial groups of Polytrichum,
Mnium, and others, which are admirably suited by the disposition of their
perichaetial leaves to retain water. Ifa drop of water be placed upon a dry
1 See also p. 127.
* These are not infrequently referred to as the ‘ flowers’ of the Musci only on the ground of an
external resemblance of the antheridial groups with the flowers of higher plants. Any other
homology does not of course exist. % See footnote on p. 132. * See p. 138.
® Goebel, Die Muscineen, in Schenk’s Handbuch der Botanik, ii (1882).
* See also Kienitz-Gerloff, Uber die Bedeutung der Paraphysen, in Botanische Zeitung, xliv,
(1886), p. 248.
152 SPOROGONIUM OF MUSCI
antheridial group it is absorbed. The closely set paraphyses also furnish
the ripe antheridia with an abutment by means of which the mucilage con-
taining the spermatozoids is pressed out
further from them.
How the distribution of the sper-
matozoids is brought about, whether
fortuitously through raindrops, or
whether small animals are concerned in
it, is as little known as it is in the case
of the Hepaticae.
The archegonial groups are in-
vested by one or more cycles of perichae-
tial leaves (Fig. 118), and have ex-
ternally a bud-like aspect. We have
already shown! that these perichaetial
oS hs Ente ate sm Fees anne leaves are frequently distinguished from
tanaverge gection. The archegonia and clase et Ch0se 0) eee ee
arrangements, such as cz/za which can
retain the water which is so necessary for fertilization.
VI
THE SPOROGONIUSM- OE MUSE
1 STRUCTURE AND DEVELOPMENT.
The vegetative differentiation of the Musci is much more uniform than
that of the Hepaticae, and the same may be said of the construction of their
sporogonium. Different though the sporogonium of Splachnum rubrum,
with its long stalk, its remarkable apophysis, and its peristome-apparatus
for the distribution of the spores, appears to be from the unstalked sporo-
gonium of Ephemerum which is filled at maturity with spores, and wants
altogether arrangements for the distribution of the spores, it is nevertheless
constructed upon the same ‘ plan’—only in one case we have an adaptation
for the distribution of szany small spores, whilst in the other only a small
number of large spores is produced, and therefore a less size and simpler
organization of the sporogonium is sufficient.
The calyptra. The archegonial venter does not behave in the same way
in Musci as it does in the Hepaticae. Sphagnum is most like the Hepaticae
in respect of it because its sporogonium remains enclosed almost until
PVSEG py a5.
mn
bulges out in its lower part
CALYPTRA, VAGINULA 153
maturity within the archegonial venter which is only then ruptured by the
stretching of the sporogonium. In the Phascaceae also we find primitive
relationships. In Archidium the sporogonium, as in Sphagnum, comes out of
the ruptured archegonial venter, and in Nanomitrium (see Fig. 120, //) the
capsular portion of the embryo presses together the cells of the archegonial
venter until they are not recognizable; thereafter the capsule of Nano-
mitrium carries upon its apex the archegonial neck alone. The increase of
the venter after fertilization provides a protective organ to the embryo, whose
lower half bores more or less deeply into the moss-stem, and the ensheathing
portion of the moss-stem—the vagzzula—forms the continuation of the
calyptra. In some Musci the venter forms at the same time a water-
reservoir for the embryo. In
Funaria hygrometrica and other
Funariaceae, as well as in En-
calypta vulgaris, the venter
and separates from the embryo,
a behaviour that was quite un-
intelligible until Ishowed’ that |
between the venter and the em-
bryo there is fluid. The locali- \
ties in which these Musci grow
make it probable that the water
thus excreted is made use of
by the embryo at a later period,
but an experimental research
devised to settle this point gave
no more result than it did in
the analogous case of the exu-
dation of water in the flower- Fic. 119. Polytrichum. Shoot-apex in longitudinal section.
: Leaves are seen on the outside. A sterile archegonium on its
buds of many Sper mophyta. stalk is on the right. At the summit one fertile archegonium
: enclosing an embryo. The embryo has grown down into the
In most Musci the elon- stalk of the archegonium, which stalk increased greatly in
° 4 : size after fertilization took place; how greatly may be seen by
gated spindle-like embryo issues comparison with the stalk of the sterile archegonium. Out
é of the archegonial venter which is forming the calyptra many
out of the archegonial venter cell-rows have developed in basipetal succession. These are the
; ‘hairs’ of the calyptra. The upper ones are thick-walled and are
at an early period. It lifts protective ; the lower are thin-walled and absorb water. Mag-
off the calyptra at its base ree
where frequently a line of separation is early marked, and carries it up as
a cap which invests the end of the sporogonium until shortly before maturity
(Fig. 124,c). In Musci which live in dry places, like Polytrichum, Ortho-
1 Goebel, Archegoniatenstudien: VII. Uber die Sporenausstrenung bei den Laubmoosen, in Flora,
Ixxx (1895), p. 463.
* Goebel, op. cit., p. 474. I there refer to the statements of Hedwig, which have been entirely
overlooked,
154 SPOROGONIUM OF MUSCI
trichum, and others, the calyptra is strengthened by ‘Zazrs’! which are merely
protonema-threads of limited growth which have grown out of it after fer-
tilization. These ‘hairs’ in Polytrichum are branched cell-rows which are
closely interwoven with one another*. The cell-walls of the stronger threads
are thick and cuticularized, clearly showing that they act as a protection
against drought (Fig. 119).
The interpretation of these hair-like outgrowths upon the calyptra as
protonema-threads may at first appear surprising, but a protonema out of
which new plants arise is developed out of the calyptra in Conomitrium as
I have before now shown ®. In Polytrichum, Orthotrichum, and other Musci,
these protonemata which are only formed after fertilization on the calyptra
are very characteristic. They have oblique walls, for example in Poly-
trichum (Fig. 119). In this genus they evidently also serve for the absorption
of water for the embryo so long as it is small and enclosed in the archegonial
venter. The ‘hairs’ are developed in basipetal succession, and whilst
the upper thick-walled ones retain air between them and protect from
drought the archegonial venter enclosing the embryo, the lower, being still
thin, absorb water, and it is through them that the store of water in the
venter in Funaria and Encalypta is renewed.
In many Musci the embryo is surrounded by a hyaline mucilage*
which, in my view, is a protection against the entrance of water, as the
neck-portion of the archegonium is by no means always closed after fertili-
zation.
Structure and development of the embryo. The cellular construction of
the embryo in Sphagnum is like that inmany Hepaticae. A transverse wall appears
in the fertilized egg. The lower half then undergoes a few divisions; the upper
divides into six to eight transverse disks, and each of these again into four quadrants
whose further development will be mentioned below.
In all other Musci the method of division is different. After one or two trans-
verse walls have appeared in the fertilized egg there arises in the upper cell, the
one next the archegonial neck, an oblique wall to which a second wall, inclined to
and opposite to it, follows. A two-sided apical cell is thus produced which gives rise
to a number of segments (Fig. 120, Z), but at a later period it sometimes becomes
replaced by a network of cells, in the same manner as we find it in the apical cell
of many prothalli of ferns, or of the strobilus of Equisetum.
In the cell-mass which constitutes the young embryo a relatively small number
* The name Orthotrichum indicates that these ‘hairs’ are erect. They are narrow cell-surfaces of
similar origin to the paraphyllia in Thuidium, Their cells remain alive for a long time, and may
also share in the uptake of water.
* See Fritsch, Uber einige mechanische Einrichtungen im anatomischen Bau von Polytrichum
juniperinum, Willd., in Berichte der deutschen botanischen Gesellschaft, i (1883), p. 83, Plate 11.
* Goebel, Die Muscineen, in Schenk’s Handbuch der Botanik, ii (1882).
* This is found in Andreaea and Sphagnum. See Waldner, Die Entwicklung der Sporogone von
Andreaea und Sphagnum, Leipzig, 1887.
DEVELOPMENT OF THE EMBRYO 155
of the cells are devoted to the formation of spores. Most of them remain sterile and
serve partly for the nutrition of the fertile ones, partly for the distribution of spores.
We do not find amongst the Musci so primitive a sporogonium as that of Riccia
amongst the Hepaticae, but, apart from Archidium, only such as correspond with
the type represented by Anthoceros.
In the capsular portion of the moss-sporogonium there is differentiated at an
early period a fertile cell-layer—the archesporium. Its evolution may be readily
followed in transverse sections. If we make a transverse section through a young
embryo only two cells can be seen at first, and these are separated by the segment-
wall. Then follows a second wall at right angles to the first, and thus a cyinder of
quadrants arises, but this is not formed in Archidium. In each quadrant there is
formed an inner and an outer cell by the appearance of either an anticlinal or
Fic. 120. Nanomitriumtenerum. Archegonium after fertilization and young sporogonium at different stages
of development in longitudinal section. /, young embryo still within the archegonial venter. JZ/, older embryo;
the endothecium is shaded; the foot, 7, has bored into the stalk of the archegonium: .S, stalk of the sporogonium.
Y7, still older embryo; a, amphithecium divided by periclinal walls. ZV, sporogonium showing the sporocytes in
great part separate around the columella. In most of the sporocytes the contents are indicated, in others they
are absent, having fallen out in process of sectioning. All magnified; Z the most highly magnified.
a periclinal wall (Fig. 122, 1), and thus we have four inner cells which may be called
the exdothecium, and a number of outer ones which may be called the amphithectum
(Fig. 120, ZZ, //7). A primitive sporogonium would be one in which the amphithe-
cium formed the wall of the sporogonium, whilst the endothecium gave rise to the
spores. As a fact there are differences in the cell-contents between these layers in
Nanomitrium, and the endothecium is much more rich in protoplasm. In Archidium
the whole endothecium is an archesporium, but all its cells are not fertile; only a few,
one to seven, become sporecytes ; the others are nutritive cells‘ as in Riella. In the
* Nothing is known regarding the nature of their contents. Leitgeb speaks of them as ‘clear as
water,’ so that possibly there is water-storage.
156
SPOROGONIUM OF MUSCI
In Andreaea and Sphagnum this is dome-shaped (Fig. 121, C, sfo); in the others it
rae We
i wd
7TN\
|
YH \ ‘
B C
Fic. 121. 5, C, &, F, Sphagnum acutifolium. 2, archegonium with
embryo, e7, in longitudinal section; the representation of the arrangement
of cells in the embryo is incorrect. C, young sporogonium in longitudinal
section ; a/#, neck of archegonium; ca, calyptra; 4, capsule; spo, spore-
sac with spores ; co, columella; sf/, foot of the sporogonium; ~s, pseudo-
is pierced both above and
below by sterile tissue, and
thus has the form of a
barrel open at both ends.
The sterile tissue is very
early laid down, and it is
the columella. In Sphag-
num the archesporium
arises out of the amphi-
thecium, the endothecium
forms the columella alone.
In all other Musci the en-
dothecium divides by peri-
clinal walls into an outer
cell-layer, the archespor-
ium, and a central sterile
part, the columella. Both
undergo further divisions ;
in the archesporium spo-
rocytes are produced (Fig.
120, ZV), The amphi-
thecium undergoes cell-
division by which it be-
podium. Z, opened antheridium with escaping spermatozoids.
W. P. Schimper. Lehrb.
FIG. 122.
tation of embryos of different age in transverse section.
embryo ; &, endothecium; 4, amphithecium. 2, older embryo; arche-
sporium shaded. 3, still older embryo; av, archesporium ; 2, intercel-
lular spaces in the amphithecium ; a the cell-layers formed by the
e
Funaria hygrometrica. Slightly diagrammatic represen-
I, young
division of one layer in the amphithecium and which nourish the
archesporium, and out of which, at the top of the capsule, the peri-
stome arises,
F, single
spermatozoid. D, Sphagnum squarrosum ; mature sporogonium. fs, pseudo-
podium; ca, calyptra; %, capsule; d, operculum. All magnified. After
comes many-layered even
before the appearance of
the archesporium. There
is produced within the amphi-
thecium an intercellular space
which separates an _ outer
many-layered capsular wall
from two cell-layers lying
against and _ enclosing the
archesporium (Fig. 122, 3).
Thesetwocell-layersaretermed
the outer spore-sac. ‘The outer-
most cell-layer of the columella
abutting against the inside of
the archesporium is the zzver
Spore-sac. These cell-layers
limiting the archesporium on
the outer and the inner sides
are distinguished by the rich-
ness of their cell-content, and
it is clear that their function
is to provide nourishment to
|
NUTRITION OF THE SPOROGONIUM 157
the archesporium and its sporocytes. The construction of a copious sterile tissue
—columella, wall-layer, and others—in the capsule, is evidently connected with
the formation of the spores. In small capsules which form few spores there are few
sterile cells. There is but a small demand for nutrition made by the fertile cells,
and we find in ripe sporogonia, like those of Nanomitrium (Fig. 123) and Ephe-
merum, almost none left over. ‘The cells of the columella serve only as nutritive
cells, and before the spores are ripe they become used up. Ephemerum and
Nanomitrium were regarded formerly, indeed up to quite recent times, as having
no columella. Its existence in Ephemerum was pointed out long ago by J. N. C.
Miiller, and more recent investigations have shown me that it is present also in
Nanomitrium, but in a very slightly developed condition. The more spores there
are formed the larger is the columella.
It serves as a reservoir of water and of
Jood-material for the fertile cells, and
it is commonly rich in starch.
In speaking further of the
phenomena of life of the sporogo-
nium, we must, first of all, notice
its nutrition and then the manner
in which the spores are scattered.
2. RELATIONSHIPS OF NU-
CRI HIOW -Or THE sSPORO-
GONIUM.
The whole embryo of the
moss is, in its earliest stages of
development, a parasite upon the
moss-plant. The lower, sometimes
swollen, portion—the /oot—serves
as a haustorium, and is therefore in dey
. : FIG. 123. Nanomitrium tenerum. Almost ripe sporo-
many Cases, for example in Diphy- gonium in transverse section ; 4, annulus. The spores are
4 a sl still in tetrads. The cells of the amphithecium have almost
scium 1 and Buxbaumia, provided all disappeared excepting the wall-layer. The columella
4 d has entirely disappeared. Magnified 120.
with special tubular outgrowths
which are chambered by cross-walls and may be so far branched that they
are like rhizoids. With regard to the absorption of water the sporogonium
in most Musci depends permanently upon the mother-plant?, yet there are
forms like Eriopus remotifolius which are able to take up water through the
abundant hair-like outgrowths of the stalk of the sporogonium.
Rooting by rhizoids. Eriopus is also distinguished by this other
1 Goebel, Archegoniatenstudien: I. Die einfachste Form der Moose, in Flora, lxxvi (Ergin-
zungsband zum Jahrgang 1892), p. 103.
? There is frequently in the seta a ventral strand of thin-walled tissue wanting protoplasm, the
leptoxylem of Vaizey, and it is the conducting channel; see Vaizey, The Transpiration of the
Sporophore of the Musci, in Annals of Botany, i (1887), p. 73; id. On the Anatomy and Develop-
ment of the Sporogonium of the Mosses, in Journal of the Linnean Society, Botany, xxiv (1888).
158 SPOROGONIUM OF MUSCI
peculiarity, its sporogonium possesses rhizoids—the only example I know
of a sporogonium rooting by rhizoids. The rhizoids are developed at the
point where the sporogonium sits within the ruffle-like vaginula. They
arise by the outgrowth of superficial cells and are cell-
rows with partly oblique, partly transverse walls. They
form a dense weft, and also in part grow downwards
upon the outside of the vaginula. Rhizoids also force
themselves into the vaginula from above, and they lay
themselves upon the foot of the sporogonium, which is
composed of large cells rich in cell-contents. Whether
they also force themselves between these cells of the
foot, I have been unable to determine from the small
amount of material available for investigation. One might
make these features in Eriopus the foundation of the
most daring phyletic speculation. Such a rooting sporo-
gonium requires only to grow out further at its apex
and to branch and so forth in order to approach the
behaviour of the sporophyte of the Pteridophyta. In
my opinion such a conclusion would be absurd. We
have here only what is indeed a remarkable adaptation,
and it no doubt stands in connexion with the fact that at
the point of junction of foot and seta of the sporo-
gonium the cells become brown at a very early period
and, as it appears, die off. By this the conduction of
food-material is made difficult or interrupted. This
, interruption in the supply will be overcome by the
development of rhizoids in the directions described ;
those to the outside will take up water, and those to
1 the inside will lay claim to the material contained in
\ the foot.
rh Assimilation. The Apophysis. With regard to
: the nutrition of the sporogonium in other forms it has
‘ : been definitely proved within recent times, especially
FIG. 124. olytrichum ps i
commune. rf, a small by Haberlandt!,that the sporogonia of many Musci are
portion of the part of the E ray
stem bearing thizoids; s, Capable of independent assimilation. They are possessed
seta; c¢, calyptra; af, eee 3 : i
apophysis jueeestny, of an assimilating chlorenchyma which is developed
atural size. Lehrb. a 5 4 i
in very unequal quantity in the different forms, but
in some cases approaches palisade-parenchyma. In a sporogonium organ-
ized so simply as that of Nanomitrium, the assimilation by the chloro-
phyllous wall-layer of the sporogonium can only be slight, and the same
must be the case in other Musci, like Eriopus, with little capsules. But
1 Haberlandt, Physiologische Pflanzenanatomie, Ed. 2, Leipzig, 1896.
ASSIMILATION. .THE “APOPHYSIS 159
in others the assimilating tissue is present, partly in the wall of the
capsule, partly in that portion of the sporogonium which lies below the
capsule and at the top of the stalk, and is known as the afophysis’. Upon
this apophysis in many Musci there are stomata of quite the same structure
as those of the higher plants”, and they place the numerous intercellular
spaces of the tissue in communication with the outer air, and so make
possible an exchange of gases and transpiration. Their different method of
formation need not be dwelt on here. It may only be mentioned that they
are rudimentary in Sphagnum, which shows that Sphagnum is derived from
a form whose sporogonium projected out of the archegonial venter and
displayed an assimilation-capacity
like the sporogonia of the ma-
jority of other Musci, and that in
this it was much nearer these other
Musci than is the genus at the
present time. Sphagnum, indeed,
is evidently not a primitive but a
greatly altered form, as we have
already learned when considering
its germination, and as the be-
haviour of its antheridia, if we
accept the statement of Leitgeb,
confirms. However this may be,
at any rate it is remarkable that
in the Bryophyta the formation of
stomata repeatedly appears, as for
example in Anthoceros and in the Fic. 125. Splachnum luteum. JZ, ¢, capsule open; 4,
apophysis. ZZ, unopened capsule in longitudinal section ;
= : ; S, seta; La, leptoxylem; sf, stomata on apophysis; c/,
different series of the Musci, and columella; #, peristome; 4s, archesporium ; yeneecetiilar
: = = space. J//and ZV, diagrams to illustrate the opening of
they In €V ery way correspond with the capsule in Splchaaes ; @a, peristome, snenered in Z77,
recurved in JV; 4,terminal disk of columella. JZ magnified
the stomata of the Spermophyta. 3. After Hedwig. JZ, magnified. After Vaizey. //Zand
The development of the apo- 7” ™2snifed. After Bryhn.
physis in many species of Splachnum is remarkable, especially in S. rubrum
and S. luteum ® (Fig. 125, Z, //), in which the apophysis grows out into an
umbrella-like fringe which in its structure resembles a dorsiventral leaf, and
possesses stomata only upon the upper side. The apophysis also takes a
share indirectly in the scattering of the spores as we shall see later. Other
Splachnaceae also have the tendency to develop large apophyses—a character
which has resulted in the most remarkable constructions.
1 I agree with Haberlandt in reckoning the apophysis as a portion of the seta, not of the capsule.
? See also Vuillemin, Sur les homologies des Mousses, Bulletin de la Société des sciences de Nancy,
xix (1886); Bunger, Beitrage zur Anatomie der Laubmooskapsel, in Botanisches Centralblatt, xlii
(1890).
$ See Vaizey, On the Morpholory of the Sporophyte of Splachnum luteum, in Annals of Botany,
v (18go-1), p. I.
160 SPOROGONIUM OF MUSCI
3. ARRANGEMENTS FOR THE SHEDDING OF THE SPORES".
The whole configuration of the sporogonium has as its aim formation
of spores and then distribution of spores. It has been already shown that
the most simple constructions of the sporogonium are found where few and
relatively large spores are contained in the sporogonium. Where many
spores are formed there are often complex arrangements which have as
their object the gradual discharge of the spores.
CLEISTOCARPOUS FORMS. In most Phascaceae arrangements for distri-
bution of spores are not present. The sporogonium is cleistocarpous: it does
not open; it rots*; as we see in the sporogonia of
Ephemerum and others it can easily be broken off and
carried away as a whole by rain. Whether the bright red
colouring of the sporogonium of E. serratum has anything
to do with attraction to animals requires investigation.
It is remarkable that we have in Nanomitrium amongst
the Phascaceae, a genus whose sporogonium opens by a
lid and where there is an annulus, although indeed only
a rudimentary one (Fig. 123, 4). This shows us that a
sharp distinction between cleistocarpous and stegocarpous
Musci cannot be made. The majority of the Musci are
stegocarpous.
SCHIZOCARPOUS FoRMS. Andreaea, however, is an
exception, and its sporogonia are schizocarpous for no lid
is produced, but four to six lines of dehiscence are laid
down in the middle portion of the wall of the sporogonium
and there it opens in dry air when mature (Fig. 126) ;
if the capsule is moistened the valves close the slits. As
Fic. 126. Andreaea : : oe ets
petrophila. As, pseudo- the mass of spores in the capsule is moist it is glued to the
podium; Sf foot of
Se S valves and the spores as they dry are then gradually re-
ae (oS SEE® moved in clusters by currents of air. ;
STEGOCARPOUS FORMS. In the stegocarpous Musci
the upper part of the capsule falls away asa lid. The line of separation is
characteristically constructed. The processes which condition the separation
have not been investigated from all sides, and they are somewhat different in
the several groups *. In most cases there is an annulus, that is to say, a ring
of one or more cell-layers lying over one another and distinguished by their
1 See Goebel, Archegoniatenstudien: VIJ. Uber die Sporenausstreuung bei den Laubmoosen, in
Flora, xxx (1895), p. 459.
? Regarding Phascum subulatum and Physcomitrella patens, see Goebel, op. cit., p. 464. The
division of the Musci into cleistocarpous and stegocarpous groups is entirely artificial. Cleistocarpous
forms appear in different cycles of affinity.
% See Dihm, Untersuchungen iiber den Annulus der Laubmoose, in Flora, lxxix (Erganzungs-
band zum Jahrgang 1894), p. 286.
SHEDDING OF SPORES 161
mucilaginous contents (Fig. 128). The mucilage acts as a store of water,
and brings it about that the cells of the annulus, as they dry, crumple up less
than the other parts of the capsule, and in this way tensions arise which result
in the splitting of the wall of the capsule. The function of the annulus ends
with this in many Musci. In the species of Hypnum it remains in connexion
with the open capsule, or falls off in small pieces ; but in other Musci it rolls
itself off in one piece through the change in volume which its cells holding
mucilage experience in their swelling in consequence of the moisture which
has penetrated through the opening into the wall of the capsule. With refer-
ence to the many details, especially the
remarkable behaviour of Tetraphis,
Buxbaumia, and others, I must refer
to the special treatises which are cited
in the notes.
The arrangements for shedding of
spores,as theyare met with in the stego-
carpous Musci, are also multifarious.
First of all let it be noted that the cap-
sule is usually raised up above the stem
by means of the stalk or seza, or it
may be by the formation of a psezdo-
podium, as in Sphagnum (Fig. 121, D)
and Andreaea (Fig. 126), that is to say,
by a stalk-like elongation of the axis
of the shoot immediately beneath the
archegonium in which fertilization has
been effected. In Musci which live on
the stems of trees or on bare rocks, the
seta is usually very short; they are ex-
posed to relatively strong currents of air.
The character of the mouth of the yg. px, Mnium hornum. A. plant with young
capsule is of special significance in re- speyogontm still Dearing ts calyptra, 2, plan
gard to the shedding of spores, whether (2257) 4.operoulum. .C ne capsule with operce
it possesses a peristome(Fig.127) or not, of" besistome” |: portion of the faner periatome
A great portion of the aperistomous size; C, magnified 3; D, E, magnified 58. Lehrb.
Musci was formerly grouped together in a special genus, Gymnostomum, but
it was subsequently recognized that forms without a peristome were found
in the most different cycles of affinity. In the most of them we can scarcely
express an opinion as to whether this want of peristome is a primary or
a reduced character, and the phylogeny of the peristome of Musci is one of
the most obscure parts of the natural history of the group !. We may regard
> *y1° A rie . e 3 DO 5
Phillibert, Etudes sur le péristome des Mousses, in Revue bryologique, 1884, 1890, does not clear
up the question.
GOEBEL 1 M
162 SPOROGONIUM OF MUSCI
the want of a peristome in Nanomitrium, for example, as primary, but it
may be a reduction in Orthotrichum gymnostomum, as its allied species
are all provided with a peristome, and even in this species itself a rudimentary
peristome exists’. The want of a peristome can be easily explained
biologically. It is absent mostly in small capsules with narrow mouth, for
example Schistostega, Hymenostomum, Pottia, and the spores are held
together in one mass by means of thickenings of the spore-wall, so that
they are only gradually thrown out.
An isolated case”, so far as we know, is found in the distribution of the
spores in Sphagnum ?. When the ripe capsules of Sphagnum dry they
explode with an audible sound, as indeed Bridel
knew, and the cap and the spores are abjected
for a considerable distance, as much as ten cen-
timeters. This takes place on sunny days, and
as the sun dries the capsule the columella is
dried up and is replaced by air. In the process
of drying the longitudinal diameter of the
capsule is not changed, but the transverse
diameter is considerably shortened, and thus
the previously nearly spherical form of the
capsule becomes more cylindric, and the air
in the capsule underneath the spore-mass is
consequently compressed. The lid of firmer
texture does not shrink, or shrinks less than
the capsule. In this way a difference in tension
arises, which brings it about that the lid, at the
IF position of the annulus, is broken off from the
add = capsule and, together with the spores, is shot
Fic. 128. Mnium hornum. Fortion out by the compressed ait like a puller arom
of wall of capsule in the region of the
annulus, in transverse section; 2, muci- an air-oun, Whe, disclaree Orme weres stakes
Benim atin) hres J, A. Eye alice cone
d',d",d’" partial wall-thickenings of teeth Pp ace ere once an ora ? an wit con
opetting’ cs a menbiane at Me bese, siderable force, which makes perfectly certain
end: the scattering of the spores—not in moist
weather, however, because that hinders the drying of the capsule.
Where a peristome exists it prevents the entrance of moisture into the
capsule, and it takes a share in the distribution of the spores. It arises
always out of the amphithecium and consists, except in Tetraphis and the
Polytrichaceae, always of fragments of cell-membrane, that is to say, the
ke SPA LS
pAb
/
1 See Goebel, Archegoniatenstudien: VII. Uber die Sporenausstreuung bei den Laubmoosen, in
Flora, Ixxx (1895), p. 472.
* With regard to Phascum ephemeroides, see Hedwig, Descriptio et adumbratio microscopico-
analytica muscorum frondosorum, Lipsiae, 1787.
* See Nawaschin, Uber die Sporenausschleuderung bei den Torfmoosen, in Flora, lxxxiii (1897),
os we
SHEDDING OF SPORES 163
thickened portions of the cell-membranes left after the thinner portions are
destroyed. There are different types, of which the chief, from the biolo-
gical standpoint, are mentioned here. It must be remembered, however,
that the several groups are not sharply separated one from the other :—
(A) THE PERISTOME ALONE TAKES A PART IN THE SHEDDING
OF THE SPORES.
I. THE PERISTOME SERVES ONLY AS A HYGROSCOPIC LID TO
THE CAPSULE.
Type of Weissia. The teeth of the peristome, when moistened, bend over
the mouth of the capsule and close it; when dry, they are bent backwards. The
peristome is a simple one.
Barbula. In Barbula there is a slight modification of this type. The
thirty-two teeth of the peristome are spirally twisted, and they fit closely to one
another, and in many species, for example Barbula subulata, are united below
by a membrane. As they dry the teeth twist into a brush; at the base they
separate from one another, and there allow the exit of the spores.
Trichostomum. In the allied genus Trichostomum the hair-like teeth form
a sieve which only allows of a gradual exit of the spores. This is a connecting
link with the next.
II. THE PERISTOME SECURES BESIDES THE GRADUAL DISCHARGE
OF THE SPORES.
I. PERISTOME SINGLE.
(a) Trellis-work of Long Teeth.
Dicranaceae, Fissidentaceae, Ceratodon. ‘There is a development of
long teeth which, in the dry state, remain bent over the mouth of the capsule,
and so form a trellis-work. We find this in a number of Dicranaceae and Fissi-
dentaceae, and in some the long teeth serve for the abjection of the spores;
according to Steinbrinck this is also the case in Ceratodon purpureus. The teeth
curve inwards when dry; the spores readily stick to the processes of the teeth as
they primarily form one moist mass, and they are then easily thrown outwards
as the teeth curve outwards.
(2) Lermanent Union of Teeth at the Tip.
Type of Conostomum. In Conostomum the teeth form a cone which has
sixteen long splits; moistened, these close; in dry air they open. I have often
asked myself whether an arrangement of this kind, that is to say a membrane
provided with holes, might not be a more primitive type of the peristome than
that in which there are single teeth to the peristome. It occurs in different series
of Musci.
2. PERISTOME DOUBLE. IN THIS CASE THE INNER IS USUALLY
NoT HyGRoscopPic.
(a) Zhe Inner Peristome narrows the Capsule-mouth ; the Outer is only a Lid.
Orthotrichum. ‘The inner teeth bend in dry air over the mouth of the
M 2
a?
164 SPOROGONIUM OF MUSCI
capsule ; the outer bend backwards}?. In Orthotrichum callistomum the teeth
of the peristome hang together in the centre, and there is formed a caster.
Fontinalis and Cinclidium. A caster is also produced in Fontinalis, where
the inner peristome makes a delicate trellis-work ; also in Cinclidium, where it
appears as a dome with sixteen holes at its base, which are closed in moist air by
the teeth of the outer peristome.
Funaria. The teeth of the outer peristome in Funaria converge together
at the tip, and they form a sieve there. The teeth of the inner peristome bend so
that they narrow the position where the slits between the teeth of the outer peri-
stome are the widest. In moist air the slits, through movement of the teeth
of the outer peristome, are completely closed.
Type of Buxbaumia. The inner peristome is a funnel, composed of a
folded membrane, and with a narrow mouth. This alone exists in Diphyscium
and Buxbaumia aphylla. In Buxbaumia indusiata there are traces of an outer
Fic. 129. Buxbaumia indusiata. Not quite mature peristome in transverse section; //, peristome-membrane ;
Pa, outer peristome-teeth.
peristome (Fig. 129) in the form of small teeth whose function is unknown. The
folded peristome of the Buxbaumiaceae arises through a special process of
division in a ring-like cell-layer? which we must regard as the original position
of the peristome. Probably in all Musci the origin of the peristome may be
traced back to the innermost cell-layer of the amphithecium, which layer, however,
may itself undergo divisions, as in the Buxbaumiaceae and Polytrichaceae. There
would be then, if this were general, a certain analogy with the archesporium, which
also is laid down in all Musci as ome cel/-layer. This point requires further
investigation. At any rate the difference in the formation of the peristome within
the genus Buxbaumia shows us again, what has been already suggested upon
other grounds, that it is a very old type. The funnel of the peristome brings it
about naturally that the spores only gradually escape, and they would be readily
1 With regard to abnormal species of Orthotrichum, see p. 162.
* It is indicated in Fig. 129 by the bracket.
my
SHEDDING OF SPORES 165
washed away if a rain-drop should fall on the upper surface of the dorsiventral
capsule f Diphyscium*. The separation of the thickened outer membranous
layers in Buxbaumia indusiata, which have given it its name, may possibly pro-
vide parachutes.
(6) The Inner Peristome serves also for the Abjection of the Spores.
This is observed in a number of Bryaceae, Hypnaceae, and Mniaceae
(Fig. 127). The mouth of the capsule is here mostly directed downwards ; the spores
reach the funnel of the peristome, but do not fall directly out of it; they are thrown
out only by the threads of the inner peristome.
(B) THE COLUMELLA ALSO SHARES IN THE SHEDDING
OF THE SPORES,
Type of Pottia truncata. This arrangement is found in many forms without
a peristome, like Pottia truncata, in which the columella narrows the capsule-
mouth and so prolongs the shedding of the spores.
Splachnaceae. ‘The same arrangement occurs also in the species of Splach-
num’? (Fig. 125, Z7Zand ZV). The columella in Splachnum has a disk-like expan-
sion at the top. When the capsule shrinks the peristome curves outwards and
downwards, the disk of the columella is projected beyond the mouth of the capsule,
and at the same time the axis of the columella elongates, according to Bryhn,
and this aids in pressing out the spores, which are here, as in many other mosses
aggregated at first in a sticky mass. In moist air the capsule elongates again °,
and the peristome closes over it. It is now remarkable that the spores in
Splachnum, according to Bryhn’s observations, are spread by flies, which are
attracted probably by the brilliant colour which distinguishes the apophysis, as
the specific nomenclature in the genus indicates, for example in S. luteum and
S. rubrum. We have in the visits of these insects an explanation of the peculiar
habitats of the Splachnaceae—excrement and remains of animals. These stations
are, as is known, visited by flies for oviposition, and they deposit at the same time
the spores of the Splachnaceae. This is, so far as I know, the only case which
has been established of spore-distribution by animals in the Musci, but it is
probable that there are other cases.
Type of Tetraphis. The ripe capsules of Tetraphis pellucida and allied
forms have a peristome of four teeth which have between them in dry air only
relatively small slits. In moist air these slits are closed. The teeth are not
portions of cell-membrane, but the whole upper part of the capsule, excepting
the lid, splits into four pieces, and the columella therefore shares in the formation
See Goebel, Uber Sporenverbreitung durch Regentropfen, in Flora, lxxxii (1896), p. 480.
2 See Goebel, Archegoniatenstudien: VII. Uber die Sporenausstreuung bei den Laubmoosen, in
Flora, Ixxx (1895), p. 481, where I give an account of the behaviour of Splachnum based upon my
examination of dried material. Bryhn (Beobachtungen iiber das Ausstreuen der Sporen bei den
Splachnaceen, in Biologisches Centralblatt, 1897, p. 48) confirms in essentials my observations; he
was evidently unaware of my previous publication.
* The change of volume in the wall of the capsule is of importance in connexion with the shed-
ding of the spores, and this requires further investigation.
166 SPOROGONIUM OF MUSCI
of the peristome. But one finds here also* the characteristically thickened cell-
layer, which elsewhere is alone used for the formation of the peristome, and it is
as usual the innermost cell-layer of the amphithecium.
Type of Polytrichaceae. In all the Polytrichaceae the teeth of the peri-
stome are formed out of
entire dead cells, as has been
mentioned above*. These
cells arise from the mother-
cells of the peristome by
cell-division, which proceeds
further than it does in the
Buxbaumiaceae.
In Dawsonia, a genus
very near Polytrichum in its
vegetative characters, the
peristome is a long brush
of numerous bristles. These
bristles are segmented by
cross-walls, which are usuaily
oblique. I had recently
opportunity in Australia to
examine two species of Daw-
sonia, the beautiful large
Dawsonia superba and the
smaller Dawsonia polytri-
choides, and will here * only
note the following :—The
capsule is in both dorsiven-
tral, as it is in Diphyscium.
It possesses a flat side and
a bulged side. It originally
stands erect ; then it bends
so as to approach nearly
the horizontal. The spores
may become discharged by
the same parachute-arrange-
ment as occurs in Diphys-
Fic. 130. Dawsonia superba. Z portion of the peripheral region cium, each shaking sufficing
of the upper part of the capsule in transverse section; W, wall-layer;
P, peristome; Co, columella. Z/, outline of whole capsule in transverse tO bring out the spores
section, lettering asin Z JJ less highly magnified than Z. through the slits of the
pencil-like peristome. The spores are very small, and with this the construction
1 Goebel, Archegoniatenstudien: VII. Uber die Sporenausstreuung bei den Laubmoosen, in Flora,
lxxx (1895), p. 482. 2 See p. 162.
* With reference to the details I must refer to a communication which will soon appear.
SHEDDING OF SPORES 167
of the peristome corresponds. Whilst it is possible, as is stated 1, that the columella
in Dawsonia takes a share in the building of the peristome, I must against
this point out that my earlier expressed doubt of this has been confirmed by
examination of the history of development. Although an external siarf differen-
tiation between peristome and columella does not exist, yet both can be readily
recognized as separate tissues. The peristome proceeds from a ring-like mass of
tissue (in Fig. 130, Z/, it is shaded), which, on its side, owes its origin evidently
to the tangential splitting of ove or a few cell-layers. From the originally similar
cells smaller cells are cut off (Fig. 130, 7), reminding one of the processes in
Diphyscium and Buxbaumia, and these acquire a stronger thickening of their wall.
These cells, placed over one another, form then the bristles of the peristome,
which become isolated by the disappearance of the soft-walled cells.
In other Polytrichaceae we have the type of the pore-capsule. The mouth
of the capsule is closed by an efzphragm which proceeds out of the columella, and
is a thin membrane which is destroyed at a later period. The teeth of the peri-
stome united with the epiphragm consist of bundles of mostly curved horse-shoe-
shaped cells. The construction and origin of the peristome of the Polytrichaceae
evidently point to their being far removed from the primitive type.
Reviewing what has been so shortly stated regarding the wonder-
fully multifarious arrangements for the distribution of spores, it is clear that
we can now recognize on the whole the method of working of these arrange-
ments, but we cannot explain how they have come to be in the several allied
groups of the Musci, whose connexion is not yet very clear. Although this
problem offers a better prospect of solution, it has stimulated less discussion
than has that of the connexion between the Bryophyta and the next higher
group, that of the Pteridophyta. We shall now proceed to consider, at
least in part, the researches bearing upon this problem, although they have
not led to positive results.
1 Hooker (Musci exotici, Tab. clxii) represents the bristles of the peristome as springing from the
columella in Dawsonia polytrichoides. This I have never seen.
SECOND “SECEION
erie kt OOPHYTA AND
seen NEO) P FY TA
[174]
Pere RIDOPHYTA. AND
See RM UP Y FA
THE Pteridophyta and Spermophyta, like the Bryophyta, exhibit in the
course of their development a sexual generation, the gametophyte, alternating
with an asexual generation, the sporophyte. Inthe Spermophyta the alter-
nation of generations is concealed in the formation of the seed, which is
a special further development of the megasporangium. Therefore the
gametophyte of the Pteridophyta only will be described here ; description
of the gametophyte of the Spermophyta is deferred until the development
of the sporangium has been described.
fre GAME PTOPAHYTE IN THE PTERIDOPHYTA}
It has been shown that the gametophyte in the Bryophyta, starting
from simple relationships, attains to a more complex configuration in dif-
ferent series, and that constructions outwardly alike, as for instance that of
the leaf, may be arrived at in different series quite independently of one
another. On the other hand, the structure of the sexual organs has moved
along a common path, although even here there is no complete uniformity.
Similar features recur in the Pteridophyta. The formation of the organs of
their gametophyte, which in them is termed the prothallus, is by no means
so multifarious as it is in the Bryophyta, and this is connected with the
short duration of life of the gametophyte and with the reduction which it
experiences. Before describing the relationships of configuration the struc-
ture of the sexual organs must be described.
1 References to the general literature are not given here; it is fully set out by Douglas Campbell,
The Structure and Development of the Mosses and Ferns (Archegoniatae), London, 1895, and more
recently by Sadebeck, Pteridophyta, Einleitung, in Engler and Prantl, Die natiirlichen Pflanzenfamilien,
1898.
172 SEXUAL ORGANS OF PTERIDOPHYTA
STRUCTURE, AND DEVELOPMENT OF THE
SEXUAL ORGANS
A. THE ANTHERIDIUM.
THE SPERMATOZOID.
The antheridium is the seat of formation of the spermatozoids, which
in the Bryophyta have uniformly two cilia—they are biciliate’. The Pteri-
dophyta, on the other ,hand, may be divided into two groups according to
the structure of the spermatozoids :—
1. Pluriciliate Pteridophyta ”.
Filicineae.
Equisetaceae.
Isoetaceae.
2. Biciliate Pteridophyta °.
Lycopodiaceae *.
Selaginelleae °.
The structure of the sexual cells is undoubtedly of great systematic
value, for it is essentially constant within groups which we recognize as
natural. We know indeed that the number of the cilia in the swarm-spores
may be different in one and the same species of some Algae, for example
Ulothrix, inasmuch as the megaspores have four cilia, whilst the micro-
spores have only two, yet there the number is almost constant in each of the
See p10:
2 Cycadaceae and Ginkgoaceae are pluriciliate.
° The male gametes of the Coniferae, and perhaps also of the Gnetaceae, which exhibit only passive
movement, are evidently connected with this series.
* The spermatozoids are only known in Lycopodium, not in Phylloglossum and the Psilotaceae,
but it is highly probable that in these latter they are biciliate.
° Isoetes is commonly placed among the Lycopodineae, with which in its sporophyte it has some
common features, such as the early disappearance of the apical growth of the leaf, the position of the
sporangia upon the upper surface of the leaf, the dichotomous branching of the root, the presence of
a ‘ligule.’ But these are not critical points. The position of the sporangia varies in the Filicineae,
THE ANTHERIDIUM 173
categories of megaspores and microspores’. As this is the case in so low
a group we must regard the structure of the spermatozoid as a very old
character and of much significance from a systematic standpoint. It is,
however, probable that different developmental series are to be found
within the pluriciliate Pteridophyta, yet we must regard the whole of them
as having taken origin at an early period from biciliate forms.
The finer structure of the development of the spermatozoids cannot be
described here ; but I may point out that the spermatozoid of Lycopodium *
appears to have the simplest construction, that is to say, it proceeds from
a less fundamental transformation of the spermatocyte than is the case in the
other groups. It has a conformation like that of the swarm-spore of many
Algae—an elongated ovoid energid with a prominent nucleus within evident
protoplasm and bearing two cilia slightly below its apex. Itseems to include
the whole plasm of the spermatocyte, whilst elsewhere in the formation of
the spermatozoids a portion of the plasm of the spermatocyte remains
behind unused, sometimes passing out with the spermatozoid as a vesicular
body and then being cast off.
THE STRUCTURE OF THE ANTHERIDIUM.
The structure of the antheridium exhibits two types in the homo-
sporous Pteridophyta, but these are not sharply differentiated :—
(2) Embedded. The antheridium is either entirely or in part sunk in
tissue. This arrangement is found where the antheridia arise upon ce//-
masses, and this is the case in Lycopodiaceae, Equisetaceae *, Marattiaceae,
and Ophioglossaceae. This type also occurs in all the heterosporous Pteri-
dophyta.
(4) Free. The antheridium stands free, and this is the case when it
arises upon a cell-thread or cell-surface. It then usually projects as a
somewhat spherical body upon the surface of the prothallus, or it may be
for example. The ‘ligule’ does not occur in all Lycopodineae, and is also found elsewhere. Both
the gametophyte and the sporophyte show such fundamental differences from those of the Selaginel-
leae that since I said (Outlines of Classification and Special Morphology, English edition, Oxford,
1887, p. 196), ‘The groups which have been brought together under the name Ligulatae have
scarcely anything in common but the presence of a ligule, and it would be better perhaps to make
separate divisions of them,’ the Isoetaceae have been placed by various authors amongst the
Filicineae. I cannot but think that they would be better considered as a special group #eav the
Filicineae showing at the same time relationships to the Lycopodineae.
1 Variations in the number of the cilia do occur in Lycopodium, where there are occasionally
three; see Bruchmann, Uber die Prothallien und die Keimpflanzen mehrerer europaischer Lycopodien,
Gotha, 1898, p. 32.
? Bruchmann, op. cit.
* In Equisetum the antheridium may also be formed upon a cell-thread or cell-surface, but there
arises then in the formation of the antheridium a cell-mass (see p. 178).
174 SEXUAL ORGANS OF PTERIDOPHYTA
seated on the cushion of tissue on the under side of the prothallus. Only in
abnormal cases is the antheridium embedded. This type is met with in the
leptosporangiate Filicineae.
EMBEDDED ANTHERIDIA. Where the antheridia are embedded we
have to distinguish a limiting opercular layer to the outside, which serves,
not only as a protection to the ripening spermatozoids, but also shares
in the process of opening the antheridium. It consists of one layer in
Equisetum (Fig. 131), and the Marattiaceae, of two layers in the Ophio-
clossaceae, whilst in Lycopodium there is an intermediate condition, for it
is one-layered in the middle but two-layered or many-layered towards the
periphery. In the Marattiaceae and Lycopodium this opercular layer, which
originally starts from one cell, exhibits characteristic divisions resulting in
the formation of a middle cell which is triangular in surface-view ; in the
Marattiaceae the pit around the antheridium is also surrounded by tabular
cells cut off by periclinal walls from their neighbours, and these, like the
tapetal cells of the sporangia or the ‘lid-cells’ of the archegonia of many
Coniferae, regulate the transport
of food-material to the sperma-
tocytes. In other respects the
embedded antheridia proceed, if
we except the mantle just men-
tioned, just like the free antheridia
from ove mother-cell, and an ac-
curate comparison of the history
iii Mant iat of development fat made possible
in the {gure on the right it is completely embedded. d, @ Giscussion of the question of the
epercular layer j Me, meristem, Magnited, the fare ©" correspondence of the two kinds
in their whole construction. It
may be mentioned here that the free antheridia are everywhere surrounded
by a single layer of qwadl-cells, and that many possess a short stalk.
OPENING OF THE EMBEDDED ANTHERIDIUM. It might be thought
that structures which have been so often investigated as the antheridia of
the Pteridophyta would be known in all the details of their structure and
life-processes. I do not, however, think that this is the case. What, for
example, is the work of the antheridial wall? We know that in the Bryo-
phyta it not only serves as a protective envelope to the spermatocytes, but
that it actively shares in the process of opening the antheridium. We know
further that there is a difference in regard to it between Hepaticae and
Musci!, so far as we are acquainted with them, inasmuch as the process of
opening in Musci is brought about by a narrowly limited group of cells,
sometimes only one cell, of the antheridial wall which forms the opening cap,
1 See p. 10,
THE ANTHERIDIUM 175
whereas in Hepaticae there is no such limitation, but many cells take
a share in it. It is now commonly assumed that in the Pteridophyta the
antheridial wall is burst by the swelling of the contents of the antheridium, the
interpretation of the process of opening of the antheridium formerly regarded
as the correct one in the case of the Bryophyta also. Any comparison of
antheridia which is to be of value in its bearing on the question of the
uniformity of their construction
can only be undertaken when
this point is cleared up. In my
opinion, which, however, re-
quires searching proof, it will
be found that here also the wall-
cells, or it may be only one of
them, take an actzve part in
the opening by the swelling of .
mucilage deposited in them or
in it, or perhaps indeed in
some other way. This appears
to me to be most clear in Equi-
setaceae.
Equisetaceae. The an-
theridia of Equisetaceae are, as
in all other cases, invested by
a cuticle which is ruptured
afterwards. The cells of the
opercular layer, marked by
their bright colour, separate
from one another, and thus
leave a wide opening which in
some species, for example
Equisetum limosum}, is en-
circled by the separated cells
of the opercular layer arranged
FiG. 132. Equisetum pratense. Male prothallus from below.
in the form of a ‘coronet 2 ? In A, antheridia; d, di, opercular cells. Between and below the
antheridia there is no formation of lobes. Magnified 25.
other cases the formation of the
coronet is less conspicuous, for instance in Equisetum pratense (Fig. 132).
I find in this species that the opercular layer is usually divided into two cells
only, which then separate from one another in the middle somewhat after
the manner of the guard-cells in a stoma. In other species the opercular
cell divides first of all into two, and the first partition-wall indicates the
* See Thuret, Recherches sur les zoospores des Algues et les anthéridies des Cryptogames, in
Annales des sciences naturelles, sér. 3, xvi (1851).
* This is beautifully shown in Thuret’s figures.
176 SEXUAL ORGANS OF PTERIDOPHYTA
position of the subsequent separation, but each of the two daughter-cells is
again divided by anticlinal walls. It is evident that here all the cells share
in the opening, and this notwithstanding statements to the contrary’, and
their curving outwards may take place as the result of causes similar to
those which operate in the antheridia of the Hepaticae*. In relation to
this we have learned in other examples, for instance amongst the sporangia
of the Hepaticae, that the line of separation is from the first marked out
clearly by the nature of the cell-membrane.
Lycopodium. In Lycopodium the construction of the mature anther-
idium is not everywhere the same. The antheridia are embedded in all
known species, and but little weight is to be attached to the fact that in L.
cernuum, L. inundatum, L. Phlegmaria, and others, the opercular layer consists
of ove cell-layer, whilst Bruchmann found in the species examined by him that
it was many-layered towards the edge. In surface-view there appears in all
species a small triangular cell in the middle of the opercular layer, and this
is broken through, according to Treub, whilst Bruchmann says that some
cells of the opercular layer become mucilaginous, and then the sporocytes
absorbing water rupture the antheridium. It is possible that different
species of Lycopodium behave differently ; that in the first-mentioned case
only one of the cells of the opercular layer is ruptured by the formation of
mucilage, as in many Musci, whilst in the second case many cells are so
ruptured, and this would be a primitive condition.
Marattiaceae. Among the Filicineae the Marattiaceae have antheridia
which approach those of Lycopodium, especially through the structure of
their opercular layer, which shows in the middle a special triangular cell
which is ‘ thrown’ off as an ‘ opercular cell *.’
Ophioglossaceae. The antheridia of the Ophioglossaceae are distin-
guished by an opercular layer two cells thick; at least this is the case in
the few members of the Ophioglossaceae whose gametophyte is known, namely,
in Botrychium Lunaria, B. virginianum, and Ophioglossum pedunculosum.
We have seen above that a periclinal rupture of the opercular layer of the
antheridium occurs also in the Lycopodiaceae, although it is not complete,
nor is it found in all the species. The construction of the wall which leads
to the opening is, however, incompletely known also in the Ophioglossaceae.
Mettenius* says, ‘ The cells of the inner of the two cell-layers which form the
1 Campbell (The Structure and Development of the Mosses and Ferns, London, 1895, p. 427) says
of Equisetum Telmateja, ‘ There is often a triangular opercular cell, recalling the similar cell in these
forms’ (i.e. Marattia, Osmunda). To this I may say that the conformation of the cell is no indication
of whether it is an opercular cell or not. Vo such ce// has yet been found in Equisetum.
> pee paca.
* Jonkman, De geschlachtsgeneratie den Marattiacceen, Utrecht; id., L’embryogénie de
l’Angiopteris et du Marattia, in Archives Néerlandaises, xx (1896), p.213; id., Ueber die Entwick-
lungsgeschichte des Prothalliums der Marattiaceen, in Botanische Zeitung, xxxvi (1878), p. 129.
* Mettenius, Filices horti botanici Lipsiensis, Leipzig, 1856, p. 119.
DEVELOPMENT OF THE ANTHERIDIUM Ly i
outer wall of the antheridium are pushed apart, and soon thereafter one cell
of the outer layer is ruptured.’ Jeffrey’ says of Botrychium, ‘The spermato-
zoids make their way out by means of an aperture formed by the disap-
pearance of two superimposed cells of the outer wall of the antheridium.’
What is the mechanism of the process is unknown, as it is in Ophioglossum.
FREE ANTHERIDIA. The leptosporangiate Filicineae normally possess
antheridia which are free, not embedded. In Doodya caudata there are,
besides the ordinary free antheridia, also embedded ones, but these must be
considered as first indications of pathological changes of the sexual organs
taking place in the prothalli of this fern as they age”. The structure of the
antheridia is essentially the same everywhere, a one-layered wall surrounding
the sporocytes.
OPENING OF THE FREE ANTHERIDIUM. The opening of the anther-
idium takes place in owe cell of the one-layered wall, and this cell is desig-
nated the opercular cell. It lies usually at the apex of the antheridium, but
in the Osmundaceae is somewhat to one side. The details of the working
of the opening mechanism are here also unknown ; all we know is that the
opening may take place in two ways :—
(a) The opercular cell, after rupture of the cuticle, is raised up to allow
of the escape of the spermatozoids. This is the case in the Hymenophy]l-
laceae (so far as they have been examined), Osmundaceae, Cyatheaceae (in
which the opercular cell is mostly divided into two), Gleicheniaceae, and
amongst the Schizaeaceae in Lygodium.
(0) The opercular cell is broken through, and thus the spermatozoids
gain exit. This occurs in the Polypodiaceae and in Aneimia and
Mohria °.
The method of opening of the antheridium is then, so far as investiga-
tion has shown, constant within a large cycle of affinity in the Filicineae,
with the exception of the Schizaeaceae, among which, however, Lygodium
differs from the other genera in this, as also in other features of its gameto-
phyte and sporophyte.
DEVELOPMENT OF THE ANTHERIDIUM.
The history of development of the antheridium shows considerable
variations, and the differences are specially marked between embedded and
free forms. Careful comparison, however, as I shall endeavour to show,
teaches us that the differences are not so great as they appear.
1 Jeffrey, The Gametophyte of Botrychium virginianum, in Studies from the University of Toronto,
Biological Series, 1898, p. 15.
* Heim, Untersuchungen iiber Farnprothallien, in Flora, Ixxxii (1896), p. 333. The marginal
antheridia of Ceratopteris are half-embedded.
* It is characteristic that the cell-structure of the antheridium of these two genera diverges from
that of Lygodium, which conforms with the type of Polypodiaceae.
GOEBEL II N
178 SEXUAL ORGANS OF PTERIDOPHYTA
HOMOSPOROUS PTERIDOPHYTA. In the first place, the spermatocytes
always arise in ove mother-cell in both the embedded and the free anther-
idia. In the embedded antheridia (Fig. 133, VI), the mother-cell of the
antheridium divides by a periclinal wall into an outer cell, d, which forms
the wall, and an inner cell, JZ, from which the spermatozoids are derived.
Equisetum. Now in Equisetum the formation of the antheridium may
take place upon a cell-filament or cell-surface, although it commonly occurs
upon a prothallus which has become a cell-mass. Where the former is the
case a cell-mass must be first of all formed in some measure, and to this
end frequently one cell divides in the manner diagrammatically shown in
1G. 133. Scheme of development of the antheridium. I, Aneimia. II, Polypodiaceae. III, Osmundaceae.
IV, V, Equisetum. Development upon a cell-thread of which the end-cell is seen in IV in longitudinal section, in V
from above. VI, Equisetum. Development upon a cellmass. MM, in all figures, the spermatocytes; ad, the
opercular cell; 1, 2, 3, 4, successive division-walls. Further explanation in the text.
Fig. 133, IV, V, that is to say, division-walls are formed in three different
directions so as to cut off a tetrahedral central cell with curved walls, and
this is the mother-cell of the antheridium ; this mother-cell then divides into
the spermatocyte and the opercular cell, which undergoes further division.
The cells cut off to the outside by the walls 1, 2, and 3, are not distinguished
by any special features from other cells of the prothallus, whilst the oper-
cular cells are so distinguished, markedly by their behaviour in the opening
of the antheridium. We must therefore consider the first as belonging
to the prothallus and not to the antheridium'. These divisions remind us
1 This interpretation I put forward long ago, and Buchtien, Entwicklungsgeschichte des Pro-
thallium von Equisetum, in Bibliotheca Botanica, viii (1887), discusses my views.
DEVELOPMENT OF THE ANTHERIDIUM 179
greatly of what we find in the primordium of the antheridium of the
Osmundaceae (Figs. 133, III; 134).
Osmunda. In Osmunda (Fig. 134) many cell-walls arise, inclined in
three directions in space, which lead to the formation of an antheridial stalk ;
then follows a wall curved in a cap-like manner which corresponds with
that which in Marattia, Equisetum, and Lycopodium, separates the opercular
layer from the cell within, and then, by further division of the outer cell
thus cut off, the opercular cell of the antheridium is formed, as in Marattia.
Polypodiaceae. In the Polypodiaceae there is formed first of all
within the mother-cell of the antheridium a funnel-like wall (Fig. 133, II,
I 1) which divides the cell into an outer one and an inner one; the inner
one is the special antheridial mother-cell, from which, by a periclinal wall,
there is cut off the wall-cell, and in this the opercular cell is then cut off by
¢ d
2a 134. Osmunda. a, 6, c, d, e, several views of an antheridium ; D, the opercular cell lying laterally. After
the ring-like wall 3 3. The ring-cell surrounding the mother-cell of the
antheridium is quite different from the vegetative cells of the prothallus in
conformity with the lie of the antheridium, for its function is to serve as
a protection to the antheridium.
Aneimia. A further simplification is seen in Aneimia (Fig. 133, I) where
first of all a wall, 1 1, curved in a cap-like manner appears, and then the
ring-like one, 2 2, is developed.
If we were to construct a series we might say: It is a primitive
character if the antheridium is laid down relatively late, when the prothallus
is already a cell-mass; in this case it is embedded. If the antheridium is
laid down earlier, when only a cell-thread or a cell-surface exists, then it
is free. This type is also retained in the antheridia standing upon the
cell-cushion which necessitates first of all the establishment of a cell-mass
whereby variations in the direction of the walls take place, as we have seen
N 2
180 SEXUAL ORGANS OF PTERIDOPHYTA
them also in the Hepaticae. These appear to be constant within the natural
groups, although the Hymenophyllaceae are insufficiently known in respect
of this, but fundamentally the differences are really smaller than they appear
to be at first sight, because everywhere we find the mother-cell of the
antheridium dividing into mother-cell of the opercular cell and mother-cell
of the spermatozoids. The cells derived from the former are either all, as
in Equisetum, concerned in the opening of the antheridium, or only one of
them—or it may be a few—takes part in this.
HETEROSPOROUS PTERIDOPHYTA. A knowledge of the history of
development will also enable us to understand the formation of the anthe-
ridia of the heterosporous Pteridophyta. The antheridium of these is
always sunk alike in the Filicineae and in the Lycopodineae. Its construc-
tion is like that in the other Pteridophyta ; there are only some partial sim-
plifications which may be connected with the reduction of the prothallus.
F1G. 135. Germinated microspores. I-III, Marsilia. IV, Isoetes Malinverniana. I, the prothallus consists of
four cells 4, B, C, D, separated by the walls 1, 2, 3. II, the mother-cells, 4Z, of two antheridia have been cut off by
the walls 5, 6. III, the mother-cell of each antheridium is divided into an opercular cell, D, and a pluricellular
inner mass of mother-cells of the spermatozoids; FR, rhizoid-cell cut off from A, showing cell a. IV, shows
lid-cell, D, of the antheridium. After Belajeff. Highly magnified.
After I! had first suggested, in the case of Isoetes, that the two ‘sterile
cells’ described by Millardet should be perhaps considered as the rudimen-
tary zwall-layer of the antheridium, the thorough investigations of Belajeff?
furnished us with a sound basis for the explanation of the relationships.
(2) Marsiliaceae. These are first dealt with because they show the
relationships which are least reduced.’ The microspore (Fig. 135, I) divides
in germination first of all into three cells of a prothallus, d, B, C. From
the uppermost of these the cell, D, is cut off. J and A remain sterile, and
from the latter there is cut off at a later period the small lenticular cell
R (Fig. 135, III), which Belajeff considers as a rudimentary rhizoid. In the
1 Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), p. 426, note 2.
2 See Belajeff, Uber die mannlichen Prothallien der Wasserfarne (Hydropterides), in Botanische
Zeitung, lvi (1898). The literature is cited here.
DEVELOPMENT OF THE ANTHERIDIUM 181
cells 5 and C the antheridial mother-cells 7 are cut out by the walls 5 and
6 (Fig. 135, II). Each of these mother-cells then, just as in the Marat-
tiaceae, Equisetum, and others, divides into an opercular cell, D (Fig. 135,
III), and the mother-cell from which the spermatozoids are formed ; the
opercular cell remains simple, the mother-cell of the spermatozoids produces
sixteen spermatozoids. In other words we have a prothallus consisting of
six sterile cells in which are sunk two antheridia, and it is noteworthy
that the whole prothallus is dorsiventral; the antheridia stand towards
one side.
(2) Isoetes'. There is only one antheridium (Fig. 135, IV). In the
microspore a small cell, 2, is cut off by the wall 1 1; the remainder and
larger portion of the interior is divided by two oblique walls inclined towards
the long axis of the spore into two flat cells, and a third which in optical
longitudinal section is tri-
angular. I consider this last
one alone to be the anthe-
ridial mother-cell?. It divides
by a periclinal wall into an
outer cell, the opercular cell,
XD, and an inner cell, out of
which the four mother-cells
ofthe spermatozoids arise by
division. We should have
then a prothallus consisting
of three sterile cells and
one antheridium, and my
explanation differs from Fic. 136. .4-Z, Selaginella stolonifera. Successive stages in the
* See germination of a microspore. #, cell of the prothallus; w, other
that which I originally sug sterile cells ; s, spermatogenous cells. 4, B, D, side views. C, dorsal
gested, and which Belajeff wnpiasta. Spermatoroids, ‘After Belajel’ 4-2 magnited G40.
and others have adopted, “ ™#snified 780. Lehrb.
in that I do not consider all, but only one of the sterile cells, except-
ing F, as belonging to the antheridial wall. The ground for this is to
be found in the comparative developmental history of the antheridia
stated above, and besides, according to my thinking, the relationships
in all the heterosporous forms are alike. That all the sterile cells, apart
' Belajeff, Antheridien und Spermatozoiden der heterosporen Lycopodinen, in Botanische Zeitung,
xliii (1885).
* According to Belajeff, it divides first by an anticlinal wall (which is not visible in Fig. 135, IV,
as it falls in the plane of the paper) into two cells, and from these then by the wall 4 the two
opercular cells are first cut off. This would be a deviation from the development of all other
antheridia in the Pteridophyta, excepting those of Selaginella in which, according to Belajeff, the
same process occurs. One might save the cause of uniformity by the somewhat forced assumption
that two antheridial mother-cells lie close beside one another; moreover the formation of a separation-
wall at a somewhat later period than usual, would be a primitive condition.
182 SEXUAL ORGANS OF PTERIDOPHYTA
from FR, take a share by the formation of mucilage in the rapture of
the exosporium here, as is the case in Marsilia and others, cannot be brought
forward as a reason for considering them as wall-cells. We have to deal
here with an adaptation to rapid germination within the endosporium, and
this brings it about that the sterile cells of the prothallus have quite other
duties than is usual.
(c) Selaginella. In this genus a single antheridium is formed, and
there is produced at first a small sterile cell (Fig. 136, ) which is considered
by authors as a single cell of a prothallus. In my view, however, all the
cells in Fig. 136, A and D, which are marked w are cells of the prothallus,
with the exception of the one about the middle towards the right ; it is the
wall of the antheridium and forms the operculum. In this way, mztatis
mutandis, there is obtained a tolerably com-
plete conformity with the condition in the
Marsiliaceae, a conformity which must rest
essentially upon an analogy of the whole
relationships under which the germination of
the spore takes place.
(d) Salviniaceae. Salvinia alone is men-
tioned here as in it the reduction reaches an
extreme, inasmuch as no opercular layer is
formed. The microspore divides first of all
into three cells of the prothallus, /, //, and
T/T in Fig: 137, A. From e€ll 7 the small cell
p is cut off; cells 77 and /// produce each an
antheridium, each of them divides by two anti-
Fic. 137. Salvinia natans. Development
of the male prothallus. A, division of the
microspore into three ceils Z 7/7, 777. B,
mature prothallus from the side; C, mature
prothallus from below. Cell Zhas divided
into the cells of the prothallus @ and /.
Cell 77has divided into the two sterile cells
6andc, and the two spermatogenous cells
sj, each of which has formed two mother-
cells of spermatozoids. Cell 777has divided
into the two sterile cells d and e and the
two spermatogenous cells s,. Each pair of
cells s, 5; and sg Ss, represent one antheri-
dium. After Belajeff. d, magnified 860.
B, and C, magnified 640. Lehrb.
ridium.
clinal walls into the two sterile cells respect-
ively 4 and c, d and e, Fig. 137, 4, and the
mother-cell of an antheridium out of which
the two mother-cells of the spermatozoids
are developed. The dorsiventrality of the
prothallus is here very apparent. The cells
b, c, ad, e, which remain sterile, and which in
my view are wrongly designated wall-cells,
take no part in the opening of the anthe-
It is indeed clear that in so small antheridia the opening
mechanism may be very simple.
One might endeavour to interpret this
simple structure as not a reduced, but a primitive rudimentary one, inasmuch
as it conforms somewhat with that of the antheridia of Algae like Oedogo-
nium. But general consideration of the reduction of prothalli makes the
view of it as a reduction the more probable, as does also a comparison with
what is found in the allied (although not very nearly so) Azolla, whose
single antheridium possesses a lid. The proof of either view is wanting.
THE ARCHEGONIUM 183
B. THE ARCHEGONIUM.
The term Archegoniatae used to embrace both the Pteridophyta and
the Bryophyta shows that the structure of the archegonia in both groups is
alike. The archegonium of the Pteridophyta has its venter embedded in the
tissue of the prothallus. In Marattia and such heterosporous forms as
Isoetes and Selaginella, the neck only slightly protrudes, and it thus ap-
proaches the condition of the archegonium in Anthoceroteae and in the
Gymnospermae. The neck consists everywhere primarily of four cell-rows,
and it invests the neck-canal-cells, in which is formed the mucilage which is
concerned in the opening of the archegonium. A row of neck-canal-cells is
always present in the Bryophyta, and we are therefore inclined to regard
those archegonia which have a row of neck-canal-cells as the more primi-
tive amongst the Pteridophyta. We find neck-canal-cells in some species
of Lycopodium. L.clavatum and L. annotinum have six to ten of them,
or there may be more, especially in L. annotinum?!; L. Phlegmaria has
three to five, according to Treub. The number may, however, be reduced to
one, for example in L. cernuum and L. inundatum, although perhaps here
there may be a nuclear division which is not followed by the formation of
cell-wall. This at least is the case in the other Pteridophyta, which possess
only one canal-cell, Marattiaceae, Botrychium, Equisetum, the Filices.
Cell-walls are occasionally observed in the Marattiaceae, Osmunda, and
Equisetum, and this supports the assumption that a reduction has taken
place here. The reduction goes even further in the heterosporous forms.
This neck-canal-cell is extremely small in the Marsiliaceae, and a nuclear
division does not take place, and the same is true it appears in Selaginella.
The nucleus of the single broad neck-canal-cell of Isoetes divides, at least
sometimes, in a transverse direction. This reduction in the formation of
the neck-canal-cells is of interest, inasmuch as the formation of neck-canal-
cells does not generally take place in the archegonia of Gymnospermae.
OPENING OF THE ARCHEGONIUM. Our knowledge of the opening
mechanism in the archegonium of the Pteridophyta is as imperfect as it is
in the case of the antheridium. I have no doubt that the neck of the arche-
gonium is not, as is commonly assumed, passively ruptured, but that it opens
by an active opening movement of the cells at its apex. LEquisetum fur-
nishes us with a striking example in illustration of this. At the apex of the
neck of the archegonium in this genus are four long large cells marked out
by their hyaline, perhaps mucilaginous, content, and between these the neck-
canal-cell is not forced. These cells bend outwards, and they undergo then
a change in conformation which, excepting that they remain united with
the other neck-cells, is exactly like that which I described in the wall-cell of
* See Bruchmann, Uber die Prothallien und ie eeietatees a europaischer Lycopodien,
Gotha, 1898, p. 34.
184 SEXUAL ORGANS OF PTERIDOPHYTA
the antheridia in Hepaticae (see Fig. 5, 5), and which, although less
evidently, is also found in the opercular cells of the antheridia of Equi-
setum. In Selaginella spinulosa also 1, a strong outward curving of the four
uppermost neck-cells takes place, and in the leptosporangiate Filicineae
lower-lying cells in the neck take a share in the opening movement.
DEVELOPMENT OF THE ARCHEGONIUM.
The development of the archegonium in the Pteridophyta (Fig. 138)
runs in all known cases on essentially the same lines. An epidermal cell
divides by a transverse wall into an upper and a lower cell. The upper
cell divides by cross-walls into four cells, and these continue to divide, and
then project usually above the epidermal surface as the neck. In Marattia
this projection is only very slight. In Selaginella (Fig. 138, ///7) the neck
also projects but little, and the division-walls never reach the free surface,
so that the neck of the archegonium appears many-layered, and this is note-
worthy in comparison with the archegonium of many Coniferae which will
be described later. The lowermost cell divides into two daughter-cells, the
neck-canal-cell and the central cell. The former by subsequent divisions
may produce daughter-cells, as
-has been shown above, or there
is only a trace of these. The
latter, after separation of the ven-
tral canal-cell, forms the egg. In
the Marattiaceae, the embedded
onglcidisecton, Tend 1 Coptomperingiate Stimeac: est Cum eee ee
Bis Seen lle pioulers. c, central cell; 4, neck-canal-cell; surrounded by tabular investing
cells; in others, only that cell
which limits the egg upon its under side is marked out by its form as
a basal cell, and it may be assumed that this, like the cells investing the
archegonium of the Gymnospermae, has, although in a minor degree, the
function of conveying nutrition to the egg. The details of the relationships
of cell-division in the neck are, as in the case of the Bryophyta, omitted
here.
C. COMPARISON OF THE DEVELOPMENT OF
ANTHERIDIA AND ARCHEGONTIA.
WITHIN THE PTERIDOPHYTA.
A comparison of the development of the embedded antheridia with that
of the archegonia brings to our notice a fairly far-reaching conformity to
* See Bruchmann, Untersuchungen iiber Selaginella spinulosa, A. Br., Gotha, 1897.
COMPARISON OF ARCHEGONIA 185
which I directed attention some years ago!. We do not, however, know
whether this is original or only accidental. Both in the young antheridium
and the young archegonium a wall-layer is separated from an internal
portion by a periclinal wall; the xeck-cells of the archegonium correspond to
the strongly-grown wall-layer of the antheridium. In the free antheridia
the analogy apparently fails, but it yet can in some measure be followed as,
for example, in Osmunda (Fig. 133, III) where an inner cell is separated
from an outer cell by the wall 4 4. This corresponds in Fig. 133, II, to the
wall 2 2, and in Fig. 133, I, to the wall 1 1, whose curved relationship is
conditioned by the form of the mother-cell.
THE PTERIDOPHYTA AND THE BRYOPHYTA.
A comparison between these two groups is of importance in relation to
the question of the connexion between the series, as will be evident from
what has been said previously”. In such a comparison the Anthoce-
roteae have frequently been brought forward, and its best known and most
widely spread member is the genus Anthoceros.
Anthoceros is certainly an exceptional type. Its cell-structure, show-
ing a single chloroplast with pyrenoid, its anatomical construction with
mucilage-cavities and mucilage-splits, the origin of its sexual organs, the
structure and growth of its sporangium, all show deviations from other
Hepaticae. But a careful examination does o¢ show a resemblance with
peculiarities found in the Pteridophyta. The mature antheridia are con-
structed like those of other Hepaticae with a wall-layer, stalk, and other
parts, and its cellular construction is like what occurs elsewhere amongst
Hepaticae, dut 7s known in none of the Pteridophyta. To homologate the
whole antheridial group, with a single antheridium of another liverwort, or
of a fern, because it proceeds from one cell, I hold to be a purely formal, that
is to say, only superficial, comparison. What can one not trace ultimately
to a single cell? But the endogenetic origin is evidently a secondary pheno-
menon, that is to say, is a consequence of the widely spread feature of the
sinking ina pit. That these pits are closed at the beginning finds an analogy
in the origin of the air-chambers of Marchantia, which are not as they
appear, though in Fegatella they really are, indentations of the surface, but
from the beginning are spaces closed to the outside. When Campbell?
endeavours to find an analogy between an antheridium of Marattia and an
embedded antheridium of Anthoceros, which is covered on the outside by
a double cell-layer, and to do so has to imagine the wall-layer and the stalk
to be absent, the comparison seems to me to be bred of the wish to discover
* Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), pp. 425-6.
3 See p. 8.
* Campbell, The Structure and Development of the Mosses and Ferns, London, 1895, p. 298.
186 SEXUAL ORGANS OF PTERIDOPHYTA
points of relationship between the Bryophyta and Pteridophyta, and not to
be founded on facts ?.
The development of the archegonium of Anthoceros differs also from
that of the Pteridophyta. We recall that the archegonium in all Bryophyta
is primarily laid down in the same manner; the mother-cell divides by
three longitudinal walls into an inner cell and three outer cells which again
are divided by longitudinal walls (Fig. 7). Anthoceros also shows the same
character, only the mother-cell of the archegonium here does not project,
but remains sunk, and the mother-cell of the neck is cut off from the oper-
cular cell (Fig. 7,d). Noarchegonium in the Pteridophyta shows a develop-
ment of this kind*. Even if we assume that the neck-cells of the archego-
nium in the Pteridophyta do not correspond with those of the archegonium
of the Bryophyta, but only with the opercular cells (Fig. 7, d@) which then have
undergone a great further development, Anthoceros would, indeed in the
matter of the development of its archegonia, be further separated from the
Pteridophyta than other Hepaticae by the origin of its neck-canal-cells.
The fact that notwithstanding the sinking of the antheridium in Anthoceros,
its development coincides ot with that of the Filicineae, but with that of
the other Hepaticae, shows, as does also the development of the antheridium,
that in Anthoceros we have to deal with a derived type which at any rate
shows no near relationship to the Pteridophyta. The kinship of Anthoceros
to the Pteridophyta is then, so far as the sexual organs are concerned, a
mistaken one.
The result of our comparison then is: The structure of the sexual organs
within the Pteridophyta is a systematic mark of great significance. That of
the archegonium is more uniform than that of the antheridium, and it is
essentially the number of the neck-canal-cells which is subject to variation,
running from ten to one. The greater number is the more primitive
relationship. The embedded type of antheridium is the more primitive.
The developmental process in Equisetum furnishes valuable points for
the comparative consideration of the formation of the free antheridium.
The number of spermatozoids appears to be greater in the embedded
antheridium than in the free, but free antheridia are more numerous than
' Waldner, Die Entwicklung des Antheridiums von Anthoceros, in Sitzungsberichte der Wiener
Akademie, lxxv (1887), p. 81, rightly says: ‘ The differentiation of a wall-layer so completely
individualized in the antheridia of Anthoceros, and in a certain sense also in the archegonia, and
the circumstance that the formation of this envelope-layer is quite like that of the other Hepaticae,
makes the assumption probable that the sinking of the archegonia and the endogenetic origin of
the antheridia are derived features.’
2 The only cases which could be quoted are those of Isoetes and Marsilia, but there is wanting in
them all proof of a costant arrangement of the cells in the origin of the archegonium resembling that
of the Bryophyta. The mother-cells of the archegonium are cut out of single large cells of the
prothallus and this is connected with the early origin. The process has much more resemblance
with that which occurs when in Equisetum the antheridia are laid down upon a cell-thread, see
Pp. L7s:
ABNORMAL SEXUAL ORGANS 187
embedded ones. The structure of the sexual organs is alike in its outlines
in Bryophyta and Pteridophyta, but shows in the development and in the
ultimate details so many differences that we have evidently here to deal
with two phyletic series of which the higher has not been derived from
the lower, but arising at an early period from simple similar primitive forms
they have followed separate paths. Other considerations lead us to the
same result.
D. ABNORMAL SEXUAL ORGANS.
Abnormal sexual organs are of interest upon many grounds, and may
fittingly be considered here.
In ageing prothalli of Hemionitis palmata and Lygodium japonicum
I have frequently found! a virescence of the neck-portion of the arche-
gonium (Fig. 139). Whilst the neck of archegonia in which fertilization
was not effected commonly died off, in many cases chlorophyll appeared,
Fic. 139. Hemionitis palmata. Virescent arche-
onium. Figure to the left in transverse section.
igure to the right in longitudinal section. A, neck-
canal. Several antheridia, A, are visible. Mag-
nified.
and the cells of the neck grew out into adventitious shoots which ultimately
produced antheridia (Fig. 139, 4), and also effected vegetative propagation.
We may consider this condition as one of senescence. In young vigorous
prothalli the meristem draws all the plastic material to itself, and distributes
this proportionately amongst the primordia of the organs, but in old pro-
thalli the meristem is enfeebled, the division of labour amongst the cells is
less precise, and cells which otherwise have other functions may now take
on a vegetative character.
Hofmeister? also mentions a case of abnormal sexual organs in
Asplenium septentrionale, where the neck was entirely embedded in the
prothallus.
That abnormal sexual organs are found on many prothalli which
exhibit apogamous shoots appears to me to be a point of importance, and it
is natural to assume that the two phenomena stand in causal connexion,
’ Goebel, Uber Jugendformen von Pflanzen, und deren kiinstliche Wiederhervorrufung, in Sitzungs-
berichte der bayerischen Akademie, xxvi (1896), p. 475.
* Hofmeister, Vergleichende Untersuchungen, Leipzig, 1851, p. 83
or
188 CONFIGURATION OF THE PROTHALLUS OF PTERIDOPHYTA
that the apogamous formation of new plants is a consequence of the sexual
organs being functionless. It is not always the case that a functionless
archegonium has the outward appearance of malformation, although this is
the more striking condition. An apparently normal archegonium may be
functionless. Heim? has shown that the prothalli of Doodya caudata pro-
duce first of all normal sexual organs, and that sexually produced embryos
may also arise. But if there is suppression of this, apogamy takes place and
the most varied malformations of the sexual organs appear, often mixed with
normal antheridia. Abnormal archegonia are also found in the apogamous
prothalli of Aspidium falcatum, where there may be three instead of four neck-
cells, the neck-canal-cells may divide into many portions, the archegonium
may not open, and so forth. In Osmunda the neck-cells divide by periclinal
walls in archegonia which do not open, and thus form a papilla which encloses
the archegonium. All these phenomena which in my opinion point to a
degeneration, have as a consequence the asexual production of new plants
on the prothallus. The condition of apogamous prothalli will, however, be
referred to later ”.
II
THE CONFIGURATION OF THEAPROTHA LES
The gametophyte of the Pteridophyta has, as its name indicates, the
configuration of a thallus. Where, as is the case in the prothallus of many
species of Lycopodium and of Equisetum, lobes are developed which
physiologically are in a certain degree comparable with the leaves of
Hepaticae, we do not designate these as leaves because they have neither
a determinate form nor a definite point of origin. A distant approach to
the formation of leaf is only to be found in the formation of lobes upon old
prothalli of Osmunda®. ‘Hairs’ of different kinds, and in,some cases
‘paraphyses’ amongst the sexual organs are known as appendages to the
prothallus just as they occur in thallose Hepaticae.
One-celled rhizoids act chiefly as the rooting-organs of the pro-
thallus as in Hepaticae. But this is not always the case. Bauke* found
rhizoids divided by cross-walls in the prothalli of Cyatheaceae, and they
* Heim, Untersuchungen iiber Farnprothallien, in Flora, 1xxxii (1896).
? See p. 220.
* Goebel, Entwicklungsgeschichte des Prothalliums von Gymnogramme leptophylla, Desv., in
Botanische Zeitung, xxxv (1877), p. 705.
* Bauke, Entwicklungsgeschichte des Prothalliums bei den Cyatheaceen, verglichen mit derselben
bei den anderen Farrenkrautern, in Pringsheim’s Jahrbiicher, x (1876), p. 64.
DURATION OF LIFE OF PROTHALLUS 189
generally exist also in Danaea’. They are probably to be found else-
where, and there can be little doubt that they are derived from unicellular
ones. These pluri-cellular rhizoids have only slight resemblance to those
of the Musci in which the walls are oblique*. Rhizoids are wanting in
the male prothallus of the heterosporous forms*, and also in the female
prothallus of Salvinia and Azolla. As the macrospores germinate in these
genera whilst floating in water, there is no fixing of them to the substratum,
and further, as the development of the prothallus takes place exclusively at
the cost of the reserve-material stored up in the macrospore, it is easy to
understand how the rhizoids are wanting. In Marsilia and Pilularia the
rhizoids arise relatively late, and serve only as temporary fixing-organs
until the root of the embryo-plant has penetrated into the soil. In Isoetes
rhizoids do occur upon the female prothalli, but they appear rarely, at least
in the aquatic forms which have been investigated. We have here evidence
of a reduction in the prothallus about which more will be said.
1, DURATION OF LIFE.
In the first place, however, the question of the duration of life of the
prothallus must be discussed because the structural relationships are connected
therewith. Amongst the Hepaticae only a few monocarpic forms are known,
such for example as Sphaerocarpus terrestris. In it the thallus has a very
simple configuration corresponding to its short duration of life. But in the
gametophyte of the Pteridophyta the general feature is that it dies after
producing an embryo. It is, as has been already explained, absorbed by
the embryo. An exception in which repeated formation of an embryo
takes place is perhaps to be found in the old band-like prothalli of
Osmunda. It will be shown that the formation of the embryo may begin
in many prothalli of Filicineae at so early a stage of development that the
relationships of configuration which are possible to them may remain /a/ewt,
as is the case in an Angiosperm which has been dwarfed through unfavour-
able nutrition, where all the forms of leaf which belong to a ‘normal’ plant
before it flowers may not appear. Prothalli, upon which the act of fertiliza-
tion has not been performed, may grow for a long time, but in them sooner
or later phenomena of senescence appear, showing either in abnormal con-
formation or in the development of adventitious shoots*. It would perhaps
be possible to obtain prothalli of Filices showing unlimited duration of
development if they were cultivated under conditions which favoured active
+ Brebner, On the prothallus and embryo of Danaea simplicifolia, in Annals of Botany, x (1896),
p- 109.
* Seep. 117.
* With reference to the cells which perhaps act as substitutes, see p. 1So.
* See Part I, Fig. 20, p. 49, and the facts there stated.
190 CONFIGURATION OF THE PROTHALLUS OF PTERIDOPHYTA
vegetative growth, but not the formation of sexual organs. Many prothalli
may, in addition to multiplication by adventitious shoots, also form gemmae,
and this feature has appeared independently in many series /.
In the heterosporous Pteridophyta the shortly limited development
of the prothallus is determined from the outset. The whole process
may be passed through in the course of a few hours. The male prothalli
are, from the beginning, incapable of vegetative development, but even
the female, notwithstanding the supply of reserve-material in the mega-
spore which is at their service, show but feeble progress in the way of
further development if the act of fertilization is not performed upon them;
even the chlorophyllous prothalli of Salviniaceae and Marsiliaceae soon die
off. They are in our experience, if one may use an old theological expres-
sion ‘ predestined,’ their lot is once for all determined. As the megaspores
and microspores are sown together, it is possible dzvectly to hit upon the
time of the formation of the embryo for which the megaspore possesses the
necessary food-material. The homosporous Pteridophyta, on the other
hand, can only slowly ripen their prothalli and the material which is
required for the formation of the embryo is only acquired by their own
effort. How independent of external factors are the prothalli of hetero-
sporous forms is shown by the fact that the germination of the spores, the
development of the prothalli, the fertilization, as well as the production of
the embryo take place in the absence of light in Salvinia and Marsilia.
But in the homosporous forms, except in some with chlorophyllous spores,
light is an essential condition for germination, and the configuration and
nutrition of the prothallus is profoundly influenced by it. As a consequence
these prothalli are plastic ; they can adapt themselves to their environment
although in different degree. The most plastic are the prothalli of Filici-
neae, and we find that the leptosporangiate Filicineae at the present day,
both in number of forms and in distribution, are at the head of the
Pteridophyta. Less plastic are the prothalli of many Lycopodiaceae whose
behaviour gives us the impression that they belong to an old family not up
to date; the prothalli of the Equisetaceae also very easily succumb in
nature to their enemies. The gametophyte also has a correlative signifi-
cance in the maintenance of forms. This is most prominent in the Filices
where one finds prothalli and germ-plants in abundance, and some forms,
such as Anogramme chaerophylla and A. leptophylla, Salvinia natans, and
many tree-ferns, are exclusively maintained by their gametophyte. Equi-
setaceae and Lycopodiaceae have long-lived sporophytes capable of
vegetative multiplication, and the sexual reproduction is, although greater
than was formerly believed, relatively subordinate, and these forms would
not disappear from the earth even if their gametophyte were entirely
suppressed.
1 See p. 213.
RELATIONSHIPS OF SYMMETRY OF THE PROTHALLUS igt
2. RELATIONSHIPS OF SYMMETRY.
Radial construction of the prothalli only seldom occurs, and in this
the Pteridophyta resemble the Hepaticae. It is found in Lycopodium,
Ophioglossum pedunculosum, and in the archegoniophore of some species of
Trichomanes. The prothalli of Filicineae and Equisetaceae are markedly
dorsiventral. ‘The relationships to light of the dorsiventrality of the prothalli
of Filicineae has been already explained! ; but dorsiventral construction is
also known in cases where there can be no effect of light, for example in
the male prothalli of Salvinia, Isoetes, Marsilia, and in hypogeous prothalli of
Botrychium virginianum. We cannot say whether in such cases we have to
ie
4
cs
ie
Hay
scape
[22
econ
me
ae
a
wiih
Fic. 140. Lycopodium inundatum. 1, few-celled prothallus ;
R, basilar cell. 2, prothallus with antheridium, 47; U, injured Fic. 141. Lycopo-
cell. 3, older prothallus with antheridia, 47, and meristem, JZ; diuminundatum. Pro-
UV, injured cell; 4, basilar cell. 4, prothallus with archegonia, 4, thallus with arche-
and an embryo showing cotyledon, Co, and‘ protocorm,’ 2. All gonia, 4. Magnified.
magnified ; after De Bary.
deal with an ‘inherited’ character from a primitive chlorophyllous prothallus
or with a condition produced by ‘internal causes.’
3. THE GAMETOPHYTE IN THE SEVERAL GROUPS
OF PTERIDOPHYTA.
We must now shortly describe the formation of the prothallus in the
several groups in order that we may discuss how far we can recognize or
construct relationships between them. We shall begin with the Lyco-
podineae because here the sexual organs show a relatively primitive con-
struction as has been already indicated :—
A. GAMETOPHYTE OF THE LYCOPODINEAE.
Lycopodium’. In recent years the formation of the prothalli in
* See Part I, p. 229.
* Literature: De Bary, Uber die Keimung der Lycopodien, in Berichte der naturforschenden
Gesellschaft zu Freiburg i. Br., 1858 ; Fankhauser, Uber den Vorkeim von Lycopodium, in Botanische
Zeitung, xxxi (1873), p.1; Treub, Etudes sur les Lycopodiacées, in Annales du Jardin botanique de
192 CONFIGURATION OF THE PROTHALLUS-OF PTERIDOPHYda
a number of the species of this genus has been made known. Some of the
prothalli are chlorophyllous, others have no chlorophyll and are saprophy-
tic. It is, however, probable that even in the chlorophyllous forms there is
a partial absorption of organic substance through symbiosis with a fungus 1.
The configuration of the prothallus varies somewhat in the several species.
Chlorophyllous prothalh. Starting from the chlorophyllous prothalli
such as we find in Lycopodium inundatum and L. cernuum we find a body
which is erect in the soil, comparable in form with a miniature beetroot.
It bears a crown of lobes above and
below this there is a meristem which
encircles the prothallus and from which
new lobes may proceed. The portion
in the soil is poor in chlorophyll and
bears rhizoids. Both antheridia and
archegonia occur together upon the
prothallus, and as in most Pteridophyta
the antheridia appear earlier (Figs. 140,
An; 141, A) than the archegonia, and as
regards their point of origin are less
restricted than the archegonia, being
found both upon the lobes and upon
the body of the prothallus. The arche-
gonia are confined to the meristem
immediately under the crown of lobes.
The prothallus of Lycopodium
salakense is similarly chlorophyllous,
but has no crown of lobes or only an
indication of these, and perhaps this is
connected with the fact that the basal
tuberous portion of the prothallus is
richly dranched, and these branches are
the biological representatives of the
Fic. 142. Lycopodium complanatum. Prothal lobes.
lus in longitudinal section. s, base, in oldest part ; - .
PE EA mae one enti eee ee Saprophytic prothalli. \n the sap-
cuiya Miguicd = “After Bichatay 7 TORRY HG Ot es
yo. Mag
absent from the prothallus, and this
should not be unexpected, for in the Spermophyta it is common to find
a reduction of the organs of assimilation where there is saprophytism.
Bruchmann has shown that the prothalli of Lycopodium Selago which
Buitenzorg, iv (1884), v (1886), vii (1888) ; Goebel, Uber Prothallien und Keimpflanzen von Lyco-
podium inundatum, in Botanische Zeitung, xlv (1887), p. 161; Bruchmann, Uber die Prothallien
und die Keimpflanzen mehrerer europaischer Lycopodien, Gotha, 1898.
mySee p- 219;
GAMETOPHYTE OF LYCOPODINEAE 193
are commonly hypogeous and colourless, may also be epigeous and are then
green. This alternation can be artificially brought about, although in less
degree, in Lycopodium clavatum, L. annotinum, and L. complanatum.
Mettenius showed that the hypogeous prothalli of Ophioglossum pedun-
culosum are in like manner capable of the same modification.
Fig. 142 represents a longitudinal section through a prothallus of
Lycopodium complanatum. It conforms, excepting in its remarkable
anatomical structure, with the prothallus of Lycopodium inundatum and
L. cernuum, only the lobes fall off and the sexual organs stand upon
the swollen upper portion of the prothallus, below which there is also a
meristem.
The prothallus of Lycopodium clavatum is similar in essentials, its
upper part being only relatively broader and more hollowed. The same
may be said of the prothallus of L. annotinum.
Dorsiventral prothallus. If one conceives that in such a prothallus
a portion of the marginal zone were to grow out strongly and become
separate from the others, the appearance of a dorstventral prothallus would
be produced. This takes place not infrequently in Lycopodium Selago.
The relationships of configuration are here somewhat manifold, yet are
connected with the forms mentioned above, and the prothallus is markedly
characterized by the presence of segmented hairs (paraphyses) between the
sexual organs. In general it is radial, and may by symmetrical growth
assume a cup-form. Usually, however, single portions of the meristem grow
out into elongated prothalli which then, in consequence of their origin, bear
the sexual organs only upon ove side, whilst the rhizoids are distributed
radially at the base. Such forms arise, according to Bruchmann, where
the prothalli, owing to the firmness of the soil, become aggregated on its
surface.
Phlegmaria-type of prothallus. With these dorsiventral forms, which
can be traced back to the ordinary prothallus, I connect those of the Phleg-
maria-type. Here is included, according to Treub, both Lycopodium
Phlegmaria and L. carinatum, and in the main features also L. Hippuris
and L. nummulariaefolium. These species have filiform thin prothalli, un-
limited in their apical growth, and without chlorophyll, and the sexual organs
are borne on ove side,and this appears to me to be an important fact. They
have, like the prothallus of Lycopodium Selago, paraphyses, and produce
remarkable gemmae which will be described below. The early stage of
the development is not known, but I derive them as unilateral outgrowths
from radial prothalli like those which occur in Lycopodium Selago.
Whether this derivation, and indeed whether the whole concatenation of the
different forms of prothalli as I have stated them, is correct, is open to dis-
cussion. It appears to me, however, in the present state of our knowledge,
to be natural, and I can see no valid ground for regarding the gap between
GOEBEL II Oo
194 CONFIGURATION OF THE PROTHALLUS OF PTERIDOPHYTA
the several forms of prothalli of the Lycopodia to be so great, as Treub
and Bruchmann will have it’.
Development of the prothallus. The development cf the prothallus of
Lycopodium from its germinating in the spore is well known in a few species
only. In Lycopodium inundatum the germinating spore divides first of all by
a cross-wall into a basilar cell (Fig.140,1,) and an upper cell in which two
series of segments arise by inclined walls formed alternately right and left ;
later there develops the body of the prothallus, upon whose apex at first the
prothalli-lobes grow out (Fig. 140, 2). Treub found that in Lycopodium
cernuum and L. inundatum a small cell-body, the ‘tubercule primaire,’
develops out of the spore quite like what is shown in Fig. 140, 1. An
arrest in the development then ensues, and the apical cell grows out into
a cell-row which then is transformed by division into a cell-mass. These
cell-rows become very long in the absence of light, and as in the prothalli of
Filices, this formation may be again caused to develop in feeble light upon
young prothalli, and perhaps also upon enfeebled old ones. They can
produce secondary tubercles if they come in contact with the soil.
In the saprophytic prothalli, where the relationship to light is
wanting, a similar cell-body may grow out from the spore. In Lycopodium
salakense, and occasionally also in L. cernuum, many branches spring out
from the ‘tubercule primaire, and this probably accounts for the fact that
the differentiation of members is less rich than in Lycopodium inundatum.
Features that are analogous in some measure will be described presently in
the case of Anogramme leptophylla.
Selaginella. The formation of the male prothallus has been described
above *, and we have therefore only to refer to the female prothallus. In
it there is little to remark of organographic interest. A cell-mass fills
the megaspore and subsequently ruptures its apex. It bears some arche-
gonia, and forms also rhizoids, but is incapable of further vegetative
development.
In most species of Selaginella which have been examined, the develop-
ment of the prothallus begins whilst the spore is still within the megaspo-
rangium, and proceeds so far that the primordia of the archegonia are laid
down. This is found for instance in Selaginella Mertensii, S. lepidophylla,
S. erythropus, S. serpens, and others—all anisophyllous forms *. In the only
isophyllous species which has been examined, Selaginella spinulosa‘*, the
development of prothallus begins only after the scattering of the spores.
1 W. H. Lang, The prothallus of Lycopodium clavatum, Linn., in Annals of Botany, xiii (1899),
p- 278, has recently arrived at similar conclusions. His paper only became known to me after my
manuscript was completed. The facts stated by Lang confirm those of Bruchmann.
2 See p. 182.
Se Seenbatt L, pylon.
* Bruchmann, Untersuchungen iiber Selaginella spinosa, A. Br., Gotha, 1897, p. 42.
GAMETOPHYTE OF EQUISETACEAE 195
The procedure in the formation of the prothallus’ corresponds in nuclear
division, free cell-formation, and so forth, with that in Isoetes, and the for-
mation of a cell-mass in the apical portion of the spore is rapidly promoted,
because here only are the archegonia laid down. But the sharp limit by
means of a ‘diaphragm’ which earlier investigators like Hofmeister and Pfeffer
described as existing between the first-formed and the later-formed portions
of the prothallus has no existence. The ‘rupture-tubercles’ which Bruch-
mann has discovered in the prothallus of Selaginella spinulosa are remark-
able structures. There are three of these cellular tubercles, one lying under
each of the sutures of the spore, and by their increase in volume they
bring about the rupture of its thick envelope. Upon them arise also the
‘trichomes’ which here occur as long unicellular tubes, and which we must
regard as somewhat modified rhizoids serving the purpose of taking up
water, although they do not enter the soil.
Bit tHE GAMETOPAHVTE: OF BOUTSETACEAE.
The prothalli of all species of Equisetum which have been investigated,
all of them species confined to Europe, agree in being usually dioecious. The
dioecism is, however, not a peculiarity of the spore. Poorly nourished prothalli
are male, well-nourished ones are female, and it is possible, as Buchtien *
has shown, to induce a female prothallus to develop antheridia instead of
archegonia by starving it. The male prothalli are not essentially different
from the female; they are with reference to the female ones arrested
formations and, as elsewhere, the arrest may take place earlier or later.
I have found, moreover, occasionally monoecious prothalli in Equisetum pra-
tense ; one had formed an embryo between the lobes ; another was female in
one longitudinal half, and the meristem was interrupted by an ameristic
zone, after which came the male half. It is noteworthy that in Equisetum
the female prothalli do not first of all produce antheridia °.
The female prothallus. This has some resemblance with a prothallus of
Lycopodium cernuum on account of the coronet of lobes which it possesses
and the meristem which lies underneath the lobes. But there is a funda-
mental difference in symmetry. The prothallus is zot radial but dorsiven-
tral, and, as in the prothallus of Filices, we have an illuminated and a shaded
side. Upon the shaded side there is a meristem beneath the lobes from
* See Arnoldi, Die Entwicklung des weiblichen Vorkeimes bei den heterosporen Lycopodiaceen,
in Botanische Zeitung, liv (1896), p. 159.
* Buchtien, Entwicklungsgeschichte des Prothallium von Equisetum, in Bibliotheca Botanica,
viii (1887),
* In most homosporous Pteridophyta the prothallus produces first of all antheridia. It is probable
that in Equisetum it would be possible by feeding to cause the male prothallus to develop into the
female. It is, however, scarcely to be expected even if one sowed the spores singly in apparently
quite similar conditions that they would all furnish female prothalli, as the reaction to stimuli of the
spores is never quite the same. As to the scattering of the spores, see p. 575.
O 2
196 CONFIGURATION OF THE PROTHALLUS OF PTERIDOPHYTA
which new cells are developed both anteriorly and posteriorly. On the
side of the meristem towards the lobes archegonia and new lobes arise, and
thus the archegonia come to lie between the lobes and appear pushed
towards the upper side of the prothallus. Towards the base of the
Fic. 143. Equisetum pratense. Female prothallus seen from below; 4, 4, archegonia. Magnified 35.
prothallus new rhizoids appear. The meristem, as Fig. 143 shows, is not
uninterrupted. The lobes serve partly as organs of assimilation, and partly
as organs for holding drops of water, and thus facilitate fertilization. The
body of the prothallus stores up, as in Lycopodium and Filices, a reserve-
material which is used by the growing embryo at a later period.
The male prothallus. This is smaller and is provided with smaller and
GAMETOPHVTE OF “FILICINEAE 197
fewer lobes (Fig. 132), it is also less rich in chlorophyll than the female.
It varies, however, in bulk according to the environment and to the period
of its development at which the formation of the antheridia sets in, and this
moment depends also upon the environment. If the antheridia are formed
relatively late, the male prothallus is very like the female ; it has a meristem
which produces new antheridia anteriorly, but the formation of lobes from
the meristem does not take place, and this is specially striking where female
prothalli have been transformed into male ones. If, on the other hand.
formation of antheridia takes place early, we commonly find that the pro-
thalli are ameristic, and then they bear the antheridia at the points of their
lobes. It is manifestly an advantage in the distribution of the spermatozoids
when the antheridia are not interspersed amongst lobes.
Development of the prothallus. The earliest stages of germination of
the spores of Equisetum are strongly influenced by external conditions.
As they contain chlorophyll they are able to germinate right away. The
mother-cell of the rhizoid is first of all cut off from the spore, and the
rhizoids are negatively heliotropic in strong light, but if the atmosphere is
moist they do not pierce the soil, being evidently affected by hydrotropism.
In feebler illumination within a moist chamber, the rhizoids are positively
heliotropic, a phenomenon which can scarcely have much significance for
their life under normal conditions. In favourable conditions of illumination
a cell-row proceeds from the mother-cell of the prothallus, and this row is
developed into a surface which branches by the growing out of single cells.
Upon the shaded side of the prothallus, which is already many cells thick,
there appears then a meristem, and from it new lobes and archegonia are
formed. Strong illumination brings about an earlier formation of a cell-
surface, and where there is a copious supply of food-material a cell-mass
may be formed, but this is not the common course of development. We
shall find quite analogous cases of such plasticity amongst the Filicineae.
C. THE GAMETOPHYTE OF THE FILICINEAE.
The relationships of configuration of the prothalli of Filicineae have
been the subject of many investigations, nevertheless our knowledge of them
is not wanting in gaps, and as yet the prothallus is only known in about
a tenth part of the species. For a long time it was supposed that the pro-
thallus of the Filicineae was very uniformly constructed, and its type is
figured in all text-books in what is indeed a very commonly occurring form,
namely, a small thallus of heart-like outline which bears upon the under
side behind the apical indentation the sexual organs—although the anthe-
ridia may also occur upon the one-layered lateral wings—and rhizoids. It is
clear that even if all the prothalli of Filices appeared alike, this would only
show the incompleteness of our method of investigation, because the pro-
thallus of Gleichenia must have zzwardly quite a different nature from that
198 CONFIGURATION OF THE PROTHALLUS OF PTERIDOPHYTA
of Aspidium, otherwise its fertilized egg could not produce so very different
a plant. The egg-cell is only a specially formed cell of prothallus, and is
not fundamentally different from the other cells. There are, however, in the
external relationships of configuration many more differences than has been
supposed, as I have endeavoured to show in a series of publications. The
prothallus with heart-like outline, far from being typical, is only a single
case, no doubt widely spread, but hardly to be considered as the primary.
1. THE EUSPORANGIATE FILICINEAE.
Marattiaceae!. In the Marattiaceae where the prothallus is known
it appears in the form which has been referred to above as that long con-
sidered ‘typical. It is distinguished amongst prothalli of like outline by
its dark-green colour and by its fleshiness, and this extends to the margins
which are here many-layered. The whole prothallus is usually from the
first a cell-mass. It is also distinguished by the structure of the sexual
organs which have been already described. The prothallus of Danaea has
pluricellular rhizoids *.
Ophioglossaceae. The prothalli of the Ophioglossaceae are still in-
completely known, but they have this in common that they are hypogeous
and saprophytic like those of some of the Lycopodia :—
Ophioglossum. In the genus Ophioglossum the prothallus has only
been found in O. pedunculosum, and this by Mettenius*. The youngest
prothalli are tubers from which a conical projection proceeds and this
elongates considerably, exhibiting unlimited growth at its apex. This
cylindric prothallus may become green and split into two or three small
lobes in the light. Can this be an indication of a coronet of lobes?
Mettenius appears to regard the distribution of the sexual organs on these
prothalli as radial. Doubtless the prothalli are inhabited by a fungus. The
prothallus has a certain resemblance to the prothallus of the Phlegmaria-
type of Lycopodium, but the resemblance is entirely superficial.
Botrychium. With regard to Botrychium we have the older observa-
tions of Hofmeister* on Botrychium Lunaria and the more recent ones of
Jeffrey ® on B. virginianum. The tuberous prothallus of B. virginianum
is dorsiventral and bears the sexual organs upon its upper side, and the
1 Jonkman, in Archives Neéerlandaises, xx (1896); id., Uber die Entwicklungsgeschichte des
Prothallium der Marattiacieen, in Botanische Zeitung, xxxvi (1878), p. 129.
2 Brebner, On the Prothallus and Embryo of Danaea simplicifolia, in Annals of Botany, x (1896).
The first root of the embryo-plant has pluricellular root-hairs, a circumstance which appears to me to
favour the view that we are dealing with a derived character.
3 Mettenius, Filices horti botanici Lipsiensis, Leipzig, 1856, p. 119.
* Hofmeister, The Higher Cryptogamia. English Edition, Ray Society, London, 1862, p. 307.
5 Jeffrey, The Gametophyte of Botrychium virginianum, in Studies from the University of Toronto,
Biological Series, 1898.
PROTHALLUS OF OSMUNDA AND CYATHEACEAE 199
meristem of the prothallus is also pushed upwards. Antheridia first of
all arise on a ridge-like projection, on both sides of which the archegonia
appear. The rhizoids are often pluricellular, especially those upon the
ridge or upon the flanks of the prothallus', but those at the base of the
prothallus are unicellular tubes. The prothallus is always inhabited by an
endophytic fungus. Botrychium Lunaria probably resembles this in its
main features, but from Hofmeister’s observations we learn nothing about
the position of the sexual organs and meristem. In both cases the earliest
developmental stages are unknown and therefore we do not know whether
or no the dorsiventral prothallus of Botrychium arises by a unilateral out-
growth from a primary radial body. The position of the sexual organs
upon the upper side is manifestly more advantageous for fertilization in
these hypogeous prothalli, than would be their position upon the under
side”, as in the Marattiaceae and others; and that the prothailus is not
spread out asa surface is doubtless connected with the fact that it does not
assimilate.
2, THE HOMOSPOROUS LEPTOSPORANGIATE FILICINEAE.
Hypogeous prothalli are, so far, unknown in this group. Chlorophy]l
is always present, except in the male prothalli of Salviniaceae and Mar-
siliaceae. There is one circumstance in their relationships of configuration
that deserves notice as being of general interest, namely, that growth of the
prothallus is often arrested by the production of an embryo at an early period
and before its characteristic peculiarities appear. Two examples may
illustrate this.
Osmunda. The prothallus of Osmunda is evidently heart-like in out-
line like that of the Polypodiaceae. If it is not arrested in its growth by
the early formation of an embryo, it takes on its peculiar and characteristic
growth-form: it grows into a band-like thallus extremely like that of many
Hepaticae, attaining a length of over four centimeters and often perennating
for many years*. The cushion of tissue on the under side which usually
serves for the storing up of food-material is developed as a midrib and the
archegonia are arranged to right and left of it, lobes occasionally shoot out
only at the growing point, and these may be considered a rudimentary leaf-
formation as in Dendroceros*. Formation of ‘hairs’ does not occur in the
prothallus of the Osmundaceae.
Cyatheaceae. The Cyatheaceae furnish a second example. If the
prothallus is arrested in its growth in consequence of the formation of
* May these not rather be paraphyses?
* Compare also a like condition in the tuberous archegoniophore of Anogramme.
* Goebel, Entwicklungsgeschichte des Prothalliums von Gymnogramme leptophylla, Desv., in
Botanische Zeitung, xxxv (1877), p. 704.
* See pp. 36, 56.
200 CONFIGURATION OF THE PROTHALLUS OF PTERIDOPHYTA
embryos at a time when it has not yet formed its peculiar ‘hairs,’ these
hairs appear as bristle-like cell-surfaces on both sides of the prothallus, and
also upon the edge in Balantium antarcticum.
I may conclude this notice of these facts by mentioning some other
peculiarities of the Cyatheaceae, particularly the regular and sometimes
very early branching of the prothallus in some forms. This occurs
occasionally also in Osmunda (see Fig. 20, Part I), and in the old prothalli
of Polypodiaceae, but in Cyatheaceae the prothallus may at a very early
period become forked, as in Hemitelia (Amphicosmia) Walkerae (Fig. 144),
or many vegetative points may be developed through branching, as
in Hemitelia gigantea. These phenomena! are of interest because
they furnish an indication of how the reduction of the prothallus
may be brought about by the shifting of the inception of the sexual
organs to an earlier
period in the develop-
ment of the prothal-
lus. Such reduction
appears in a very
striking manner in the
male prothalli of the
heterosporous Filici-
neae, and in badly-
nourished prothalli of
Filicineae antheridia
may appear when
Fic. 144. Hemitelia (Amphicosmia) Walkerae. Development of pro-
thallus. 1, young prothallus; wf, rhizoid. 2 and 3, older prothalli, each only two cells have
with two vegetative points, v, v. Magnified; 1 more highly so than 2 and 3.
been formed.
Polypodiaceae. In the Polypodiaceae the prothallus has always
unicellular ‘hairs’ if hairs are present. Some of them are ‘glandular hairs,’
some of them are ‘ bristle-hairs’ (Figs. 145,146); both are protective organs
against the gnawing of animals. The Dicksonieae furnish a transition to
the hair-formations of the Cyatheaceae. In them, both upon the upper and
under side, as well as upon the edge of the prothallus, there are gland-hairs
which have a basal foot-cell out of which a cell-row, sometimes branched,
develops. Exceptions to the usual heart-like outline of the prothallus are
found in some epiphytic Polypodiaceae, as well as in the Vittariaceae” and
species of Anogramme. ‘These epiphytic forms have long band-like pro-
thalli with no cushion of tissue upon the under side, and the prothallus has
many layers only at the positions where the archegonia arise (Fig. 145).
This condition may be connected with the epiphytic method of life, inas-
* The analogous condition is found in some heart-like prothalli of the Polypodiaceae and Aneimia,
where, if an archegonium is fertilized at an early period, there is unequal development of the wings
of the prothallus, and one of them may be entirely suppressed. 2 See p. 206.
HEART-SHAPED PROTHALLI OF POLYPODIACEAE 201
much as such epiphytic prothalli evidently can only develop archegonia
in special favourable conditions, and they live vegetatively between times ;
Fic. 145. Polypodium obliquatum. Fic. 146. epee of a band-like prothallus with ‘bristle hairs.’ One
Prothallus seen from below. On the of these bristle hairs shows a spiral line of rupture the result of swelling
margin are ‘bristle hairs’ and rhizoids, in potash solution. Highly magnified.
Wh. On the surface two groups of
archegonia surrounded by rhizoids. It
is only at the points where these groups
are that the prothallus is many-layered.
Magnified.
their free propagation by gemmae which will be presently mentioned 1, may
also be connected with this epiphytism.
FiG. 147. Prothalli of Filicineae at different stages of development. 1, Hymenolepis spicata. Young pro-
thallus. Below the ruptured wall of the spore. s, two-sided apical cell cut off by the oblique walls, 4, Ak. 2, an
older prothallus of a species undetermined. The two-sided apical cell is divided by a periclinal wall which initiates
sibel aad growth. 3 and 4, Asplenium Nidus. 4, end-cell of the prothallus, the meristem arises laterally. All
magnified,
PROTHALLI OF POLYPODIACEAE WITH HEART-LIKE OUTLINE.
The prothallus, with heart-like outline, of the majority of the Polypodia-
ceae does not always develop in the same manner. In germination the
cell-filament is first formed from the spore. Its length depends upon
» See p. 214,
202. CONFIGURATION OF THE PROTHALLUS OF PILERIDOPH a
external factors. I have already pointed out when speaking of the Hepa-
ticae that the form of the germ-plant depends upon external conditions, and
that the filamentous form is always
able to arrive at favourable condi-
tions of illumination, in the same
way as these are attained to often
by the seedlings of Spermophyta
through the elongation of the hypo-
cotyl. Now in the Polypodiaceae
this filamentous stage is not, or only
rarely, missed out even in the most
favourable conditions?. Ifthe spores
germinate closely together this stage
persists longer (Fig. 150, V),and not
whieh spies hive poaed Sane waeitaekey eg Men ye eee ele ead
to the spelen ie The spores have formed only cell may take place; where the spores
germinate isolated in most favour-
able conditions of illumination, surface-growth may begin in the second
cellof the thread *. I
found this to be the
case in all the germ-
plants of Pteris longi-
folia which were ger-
minated singly upon
mud. There can be
little doubt that it
would be possible to
retain the germ-plant
longer in the filamen-
tous condition by sub-
jecting it to other
conditions than that
of feeble illumination®,
and it is further pos-
sible that this stage
donot elec De encoun ean nnfevourable ausitive condiaes i ane ete Ee again called
two-sided apical cell, the segments from which are indicated by stronger lines ;
in the figure, has also grown out into a cell-thread; W, rhizoids; A, antheri- forth Ate later period.
dium. Magnified.
Young = germ - plants
* There can be little doubt, however, that just as in Equisetum this can be artificially achieved by
special conditions of cultivation.
* The first cell also may sometimes undergo division by a longitudinal wall, and it is probable
that by definite methods of culture it would be possible to cause a cell-mass to form directly out of
the spore after the fashion which is sometimes normal in the Marattiaceae.
* In Fig. 148 we have a representation of a sporangium of Acrostichum peltatum in which the
HEART-SHAPED PROTHALLI OF POLYPODIACEAE 203
which have not yet formed typical meristem easily pass over again into the
filamentous stage in feeble illumination (Fig. 149), in the same way as I have
shown this to be the case in Preissia!. In older prothalli this only takes place
if they have lost their meristem* and are enfeebled by an unfavourable
Fic. 150. JV, Pteris longifolia. Development of prothalli. In 7/the first cell of the filamentous part of the
prothallus is concealed in the spore. S, apical cell; A, apical meristem ; v, vegetative point. J’, Acrostichum
peltatum ; a filamentous prothallus from the germination of a spore within the sporangium, as shown in Fig. 148.
All magnified. Further description will be found in the text.
environment. Commonly these conditions result in the production of pluri-
cellular adventitious shoots *. The ‘light-optimum’ for the filamentous forma-
tion is lower than that for surface-growth*. Surface-growth is initiated in
spores have germinated whilst the sporangium is still fastened to the sporophyll. They have all
grown out into dark-green cell-rows, and naturally contain only a very small amount of ash-
elements.
1 See Part I, p. 239.
* Goebel, Uber Jugendformen von Pflanzen und deren kiinstliche Wiederhervorrufung, in Sitzungs-
berichte der bayerischen Akademie, 1896. S See pp. 213, 216.
* Longitudinal divisions may take place in prothalli which under special conditions have developed
in the dark.
204. CONFIGURATION OF THE PROTHALLUS OF PTERIDOPHYTA
the germ-thread by longitudinal division, usually before—and often very
early—the first rhizoid has gone out from the position on the thread
limited by the spore-membrane. Numerous other rhizoids follow the first
one at a later period, and these issue from prothalli growing on the soil in
the normal position always on their under side, but in epiphytic prothalli
the rhizoids grow also from the margin (Fig. 145). It is not my intention
here to depict the relationships of the cell-arrangement; I may merely
point out that at the end of the young cell-surface a two-sided apical cell is
found commonly, but this is subsequently divided by a periclinal wall}, and
thus marginal growth sets in (Fig. 147, 2). The two wings of the pro-
thallus are developed right and left of the vegetative point, the heart-like
outline is attained to, and then begins the formation of the many-layered
cell-cushion. To this often-described construction I must merely add that
the two wings of the prothallus are xot of the same age. The surface of the
prothallus which first develops from the germ-thread becomes at once
the one wing, and the meristem which forms the vegetative point of the
prothallus comes thereby to occupy a lateral position, and underneath it
the second wing of the prothallus shoots out. Fig. 150 exhibits this process
in Pteris longifolia. Here it will be seen that a one-layered cell-surface is
formed first of all from the germ-thread without the aid of an apical cell,
and the anticlinal walls diverge at the apex. It shows also the method in
which the cells become chambered in the older stages (Fig. 150, //). The
intensity of the cell-multiplication remains strongest at a /ateral position on
this cell-surface, and there is the meristem in which often a two-sided apical
cell is visible. Below this meristem then shoots out the second prothallus-
lobe which is at first, naturally, much smaller than the older one, but
gradually reaches its size. In this case the cell-surface which first arises
forms the greater part of the first lobe of the prothallus—in other cases it
forms only a small portion of it. In Fig. 147, 4, for example, the young
prothallus of Asplenium Nidus is represented, in which the meristem lies
laterally in an earlier stage of development than that shown in Pteris
longifolia (Fig. 150). If we compare Fig. 147, 3, we shall see that the
meristem proceeds from the second cell from the apex of the cell-filament
which ends with a papilla. In Platycerium” the meristem proceeds from
one half of the end-cell.
I have here shortly referred to these relationships, not because they are
of any great significance, but because they show us :—
* In Lygodium the two-sided apical cell persists.
* The same is the case often in Aspidium Filix-mas and others. In Platycerium the meristem may
sometimes be terminal, and one could also say, in cases in which a two-sided apical cell arises at the
point of a cell-filament, that it only proceeds out of one half of the terminal cell, Such considerations,
however, carry us no further, although analogous assertions, such as that the embryo of Musci
corresponds only to one half of the embryo of Hepaticae, are even now repeatedly made.
PROTHALLI OF POLYPODIACEAE—NOT HEART-SHAPED 205
(a) That every gradation exists between a terminal and lateral primor-
diumt of a meristem.
(4) That zx different sections of the Filicineae both conditions occur.
Thus all Gymnogrammeae, so far as we know the development of their
prothalli, are characterized by the lateral position of the primordium of
their meristem, and by the late appearance of the two wings of the prothallus.
Among the Schizaeaceae, Lygodium terminale has terminal, Schizaea and
Mohria have lateral meristem. If the formation of ove of the two wings be
suppressed we pass then to the form of prothallus like that of Anogramme
and Vittaria described below. I do not believe that one can construct
a phyletic relationship between apical and
lateral position of meristem. It seems to me GEES
that we have rather before us an instructive f ani
example of two possible developments between ; ;
which one and the same species may oscillate,
and of which, so far as our present knowledge
permits us to judge, sometimes one sometimes
the other is become dominant in more than one
cycle of affinity, although, at the same time, it is
a matter of indifference from the point of view of
the manner of life which of them obtains. That
the heart-like outline of the prothallus is always
finally attained to, although by different ways in
these forms, may find its explanation in this, it
is a beneficial configuration. The wings lie
loose, seeing that they develop no rhizoids, gti; Which wee mt dee baclly ea
upon the surface of the soil, and under them 399 Win aoreal aathendin thes
drops of water collect! (Fig. 151), which then can Tire upper part of the Bgure oe
be readily absorbed by the middle portion of the Whee pend ance Rane aes
prothallus with its numerous rhizoids. The pro- age? pe Soty sateen’ “SF
thallus of Osmunda, shown in Fig. 151, was the
result of a prolonged culture upon a substratum very poor in nutriment.
It was weakly, the wing-formation was almost entirely suppressed, no arche-
gonia appeared, antheridia were numerous and mostly upon the edge.
After feeding it well the wing-formation began and also archegonia were
formed. The prothalli of Osmundaceae revert to the filamentous form much
less easily than do those of other ferns.
PROTHALLI OF POLYPODIACEAE WANTING THE HEART-LIKE OUTLINE.
Anogramme. The prothallus of the genus Anogramme connects with
the forms in which the formation of the two wings takes place at different
* How they arise we shall not stop to inquire.
206 CONFIGURATION OF THE PROTHALLUS OF PTERIDOPHYTA
times. On account of its noteworthy adaptations it will be mentioned
particularly below’. It produces only, if one may so say, one wing with
lateral meristem, behind which there is formed a peculiar tuberous arche-
goniophore. The prothallus with heart-like outline is here never reached.
Vittariaceae. The Vittariaceae also have not prothalli with heart-like
outline in the cases which have been accurately investigated. There arises
in the first instance a simple cell-surface with marginal growth. This
divides into lobes (Fig. 152), through isolated portions of the meristic
=
el
a
ae
Fic. 152. Vittaria. 1-6, Formation of prothallus; Ay, archegonia; Z, embryo; Ar, gemmae. 1, highly
magnified. The others slightly magnified.
margin passing into a permanent condition, and thus there is developed
a highly irregular lobed body in some ways resembling the flat protonema
of Sphagnum, and it forms marginal groups of archegonia which, primarily
arising in the meristem, are separated from it at a later time by the portions
which have passed into the permanent condition.
Hymenophyllum. The form of prothallus of Vittariaceae leads us to
that of Hymenophyllum. Here we have also to do with a richly-branched,
PROTHALLI OF POLYPODIACEAE—NOT HEART-SHAPED 207
one-layered prothallus, upon which in most cases only the many cushions
bearing archegonia are many-layered. The meristem is mainly limited to the
points of the lobes of the prothallus, and the lobes are more band-like than
in Vittaria. The rhizoids arise upon the margin. A portion ofa prothallus
of Hymenophyllum axillare is represented in Fig. 153. Cell-cushions
bearing archegonia, A, are formed at five positions on the margin of the
one-layered prothallus. These cushions are originally in connexion with
the apical meristem, as is shown at the top of the figure to the right, and as
the tissue of the cushion retains for a long time its meristic quality, the
cushion often projects lobe-like beyond the margin of the prothallus. The
prothalli may multiply vegetatively by dying off behind, thus isolating the
twigs; but the prothalli of many species of Hymenophyllaceae possess
special propagative organs
besides, as will be shown
below!. The configuration
of the prothallus is alike in
all the species of Hymeno-
phyllum which have been
examined up to this time—
not many it is true.
Trichomanes. We do
not find this similarity,
however, in Trichomanes.
The prothalli in some forms
of this genus, such as T.
rigidum, T. diffusum (Fig.
154, #), and others, diverge ees Mane portion of a prothallus ;
markedly from those which
have been already described, and recall the habit of the protonema of
the Musci. In Trichomanes rigidum the prothallus forms tufts of branched
cell-threads, most of which are epigeous, but some also run hypogeously.
Single short branches become archegoniophores (Fig. 154, //), and they
develop as cell-masses, whilst the antheridia stand upon the ordinary
cells of the filament, a difference which is easily understandable from
the biological side, and is repeated in essentials in the prothalli of other
Filicineae. The archegoniophores are cell-bodies of limited growth and
the archegonia are distributed radially upon them. Species of Tricho-
manes, like T. sinuosum, in which the prothallus is not merely a cell-
filament, but also a cell-surface which has only limited growth, like the
organs of assimilation in the protonema of Tetraphis and allied Musci’*,
afford a transition from the filamentous prothallus of Trichomanes to
1 See p. 214. 2 See p. rar.
208 CONFIGURATION OF THE PROTHALLUS OF PTERIDOPHYTA
the surface-prothallus of Hymenophyllum. The groundwork of the
whole prothallus, its skeleton so to speak, is formed by the threads, and
these also spring out in numbers from the cell-surface (Fig. 154, ///)'.
The cell-surface here must be considered as a transformation of the cell-fila-
ments, and the distribution of the sexual organsalso confirms this view. The
antheridia stand on the cell-filament, more rarely on the margin of the cell-
surface; the archegonia stand upon the archegoniophores, which are formed
as cell-masses at the end of short filaments, just as in Trichomanes rigidum,
only here frequently, but not always, the archegonia have a dorsiventral
distribution. The archegoniophores can grow out into cell-surfaces if the
formation of the embryo is suppressed ; the cushion of the archegonia
then stands on the margin of the under side of this cell-surface, and the
whole reminds one of the behaviour of the prothallus of Hymenophyllum.
If the transition from cell-filaments to cell-surfaces in the prothallus of
Trichomanes sinuosum takes place at an early period in the germination,
the cell-filament will appear as a juvenile stage rapidly passed through; the
cell-masses which are to be designated archegoniophores with unlimited
growth are formed then directly and without any intervention of a cell-
thread on the margin of the cell-surface. The first stages of germination
suggest such a derivation. These show that from the spore there usually
arise many cell-filaments, frequently three, which I have observed at an early
period becoming branched, although this is not the case in Trichomanes
maximum and T. radicans which germinate like other leptosporangiate
Filicineae. Of the three cell-filaments thus initiated all may develop as
cell-filaments in Trichomanes, but in Hymenophyllum one quickly passes
over into a cell-surface, the others are arrested.
SUMMARY.
When we review the facts which have just been cited regarding
the development of the prothallus in the Filicineae, different questions
force themselves upon us; one is, Is there any connecting-thread between
all these varieties of configuration? Can they be arranged in connected
series which would also link on to the gametophyte of the Musci? I have
before now endeavoured to answer this question, and I have pointed out
that if we seek for such a hypothetical link it is essential to keep in view
the configuration of the gametophyte of the Musci as it appears in the
mature stage, that is to say, at the time of the formation of the sexual
organs, as this is, when we regard it from the standpoint of the theory of
descent, also the result of a long development which started from simple
relationships of configuration. We may, from our knowledge of the con-
figuration of the vegetative body produced in germination in many Bryo-
phyta, conceive these simple primitive forms to have had a configuration of
1 Compare the analogous case of the leaves of Buxbaumia, p. 127.
PROTHALLI OF POLYPODIACEAE. PHYLOGENY 209
branched threads upon which the sexual organs sat!. The portion of the
filaments which bore the archegonia achieved a more massive develop-
ment in correspondence with its ‘need’ of a better nutrition, and it became
a cell-mass as we find it in Trichomanes rigidum—an archegoniophore. In
Trichomanes sinuosum we see this grow out into a surface, and thus the
configuration of the prothalli of other Filicineae is approached. If we
suppose that this assumption of vegetative activity of the archegoniophore.
Fic. 154. Trichomanes. Formation ot prothallus. _ ,T. diffusum. Young filamentous prothallus ; S, spore
which has developed cell-filaments in three directions; Rf, rhizoids. 77, T. rigidum. Portion of filamentous pro-
thallus with two archegoniophores. ///, T. sinuosum. Prothallus showing habit. From the cell-surface filaments
pass out which give origin to new cell-surfaces; A, position of an archegoniophore. JZ), T.sinuosum. Portion of
a ore bearing two archegoniophores which pass over into cell-surfaces. Zand ///, slightly mag-
nified, Zand /V, highly magnified.
which renders possible a rapid nutrition of the embryo, was begun at an
early period of development, the filamentous phase of development of the
prothallus would be shortened. It would appear, as in most of the lepto-
sporangiate Filicineae, only in the first steps of development, and might be
entirely lost. And thus a cell-body might arise in the germination at once
similar to that which is found in many examples both of the Hepaticae and
of the Musci. Finally we see that the different forms of surface-formation—
terminal and lateral meristem, heart-like and simple surface-formation—are
' Compare Buxbaumia, p. 127.
GOEBEL It P
210 CONFIGURATION OF THE PROTHALLUS OF PTERIDOPHYTA
connected with one another by transition. We observe then che connexion
between the forms, but whether this corresponds with a phyletic series
is altogether uncertain. We can also here, as has been already pointed out
in the case of the Musci, invert the series, and may start from forms which
begin with massive prothalli, like those of Lycopodium, and which then from
a radial construction pass over into the dorsiventral, as we have observed it
in Lycopodium Selago, and we may consider the formation of cell-filaments
as merely an adaptation to the environment. There is indeed at the present
time nothing to indicate why within the Hymenophyllaceae, which are
so wide-spread yet occur under similar conditions of life, the species of
Trichomanes should have mainly a filamentous prothallus, whilst species of
Hymenophyllum! have a surface-prothallus. In the present state of our
knowledge we must not reckon upon discovering any certain phyletic
indication in the prothallus ; we must simply content ourselves with recog-
nizing the connexions whose genetic significance remains uncertain. It has
already been shown that the structure of the spermatozoids makes improbable
a monophyletic origin of the Pteridophyta, and the similarities which exist,
for example, between the prothallus of Ophioglossum and that of Lycopo-
dium, do not require us to ascribe to these a gevetic relationship. It is much
more probable that these resemblances have come about like those of the
formation of the thallus of many Hepaticae*, in which we can certainly
trace parallel lines of formation which, starting from different simple forms,
have arrived at s¢mzlar conformations. Within single natural groups also
one may well recognize a conformity in the formation of the prothallus
which is expressed in the possibility of arranging them in series, as we have
endeavoured to do for the Hymenophyllaceae and other Filicineae, but as
soon as we pass beyond this we always reach uncertain ground which
indeed offers a favourable field for hypotheses, but is not one upon which to
raise a surely founded superstructure.
3. THE HETEROSPOROUS LEPTOSPORANGIATE FILICINEAE,
We must now say something regarding the heterosporous lepto-
sporangiate Filicineae. It is only necessary to deal with the female
prothallus °%.
1 Tf the configuration of the prothallus of the Hymenophyllaceae, especially that of Trichomanes,
were an adaptation, one would expect similar phenomena in other forms under similar life-conditions,
and we find in the sporophyte of some of the Polypodiaceae, for example Asplenium obtusatum
f. aquatica, of the Osmundaceae species of Todea, and others, adaptations quite like those in the leaves
of the Hymenophyllaceae. Up till now, however, no case has become known of the prothalli of any
of the above-mentioned forms conforming with those of the Hymenophyllaceae. They all resemble
those of allied forms. ‘This does not mean that such cases may not exist, but the position of the
archegonial cushion in Hymenophyllum could scarcely be considered as an adaptive character, and
it appears to me very doubtful whether adaptation can be proved in the other peculiar features of the
prothallus.
a" Seep. 25; 5 See p. 180.
FEMALE PROTHALLUS OF SALVINIACEAE 2II
SALVINIACEAE. The female prothallus of Salviniaceae resembles that
of Marsiliaceae in so far as it is only formed at the apex of the megaspore
(Fig. 156); the greater portion of the internal space of the megaspore
remains as a reservoir of reserve-material. The prothallus is chlorophyllous
and in varying degree, that of Salvinia has much, that of Azolla caroliniana
very little chlorophyll.
Salvinia. The prothallus of Salvinia possesses meristem, and thus
approaches also most nearly that
of the other ferns. In Fig. 155, //,
is shown a prothallus of Salvinia
natans viewed from the upper side.
It has the shape of an equilateral
triangle with blunt angles!. The
portion ending in the angle turned
towards the lower part of the
figure remains sterile, whilst three
archegonia are produced towards
the opposite subtending side. If
fertilization is affected in one of
Fic. 155. Salvinianatans. 7, megaspore germinat- Fic. 156. Salvinia natans. Germinated megaspore;
ing; @, archegonium; sf, apicalridge. Z/, prothallus prothallus and embryo in longitudinal section in the median
isolated seen from above; three archegonia and the line of the prothallus. spz, portion of wall of sporangium ;
mother-cell, 7, of a fourth are visible; s#, apicalridge , perinium; ¢, exine; s, cavity of the spore; #7, prothal-
of meristem; 7, position whence the wings are de- lus; av, neck of archegonium; ev5r, embryo ; sf, apex of
pecped: Magnified. Z After Pringsheim. 77 After stem; / foot; 6/1,4/2,d7s, the first three leaves. Magnified
Bauke. 100. After Pringsheim. Lehrb.
these archegonia no more are developed, but otherwise new archegonia
arise out of the meristem, sk. We may say that the whole prothallus
corresponds somewhat with the cushion of tissue of the prothallus of one of
the Polypodiaceae, only that the archegonia arise here upon the uppe!
side. Two wings arise at a later period out of the meristem, but they do
not extend forwards but backwards. It is scarcely likely that these wings
correspond with those of the prothallus of the Polypodiaceae; they
probably serve to increase the absorptive surface of the prothallus, and
*-The whole prothallus is, however, curved like a saddle (see Fig. 155, 7).
Pz
“'
212 CONFIGURATION OF THE PROTHALLUS OF PTERIDOPHYTA
take a share in adding to the ash-constituents of the embryo. The
capacity for growth of the apex of the prothallus is limited, just as it is in
the Polypodiaceae. There are formed from it a great number of arche-
gonia, but there is no vegetative development, although this were perhaps
possible if the formation of archegonia were suppressed '. y
Azolla. The female prothallus of Azolla* is smaller and more reduced
than is that of Salvinia, and there appears to be no formation of meri-
stem in it. It produces first of all one archegonium, and if fertilization is
effected in this one no more are produced ; if fertilization does not take place
more archegonia arise up to about ten °.
MARSILIACEAE. In the Marsiliaceae but one archegonium is pro-
duced. The prothallus here develops rhizoids, and if no fertilization takes
place upon it, it exhibits an exuberant growth; but it does not form new
archegonia nor adventitious shoots, and soon withers. The reason for the re-
duction in the number of the archegonia may in some measure be understood,
I think, when we look at it from the biological standpoint. In Marsilia and
Pilularia the megaspores and microspores are always distributed together.
That an archegonium should remain unfertilized is here an occurrence which
is rare relatively when compared with the case of homosporous ferns. In
Salvinia fertilization is less certain, but it is made more probable by the
longer duration of active archegonia through their formation anew. In
Azolla the frothy masses in which the microspores are aggregated possess
the remarkable hooks (glochidia) through which they become anchored, so
to speak, to the megaspores*, and therefore fewer archegonia appear to be
necessary here. We may say then generally that the number of archegonia
varies inversely with the certainty of fertilization. Where fertilization
appears to be certain few archegonia are produced. If, on the other hand,
there is a risk of its failure, many archegonia are produced.
4. ISOETACEAE.
I may conclude this account of the formation of the prothallus by
a short description of that in Isoetes, which occupies so isolated a position.
The very simple formation of the male prothallus I have already men-
tioned ®. The female prothallus fills as a cell-tissue the whole interior of
the megaspore, but it forms no chlorophyll, and projects only slightly out
* This would be very difficult to bring about because the megaspore contains food-material suff-
cient to make the prothallus independent of light.
* The megaspores of Azolla germinate under water, and subsequently rise to the surface of the
water. I observed the same in Marsilia Drummondi ; it is only with the development of the inter-
cellular spaces in the embryo-plant that the whole structure is able to float to the surface. Mega-
spores within which no fertilization has taken place remain submerged; see Goebel, Pflanzen-
biologische Schilde:ungen, iii (1893), p. 272.
* In Salvinia there may be four times this number.
* See p. 218. 5 See p. 181.
ADVENTITIOUS SHOOTS AND GEMMAE 254
of the ruptured wall of the megaspore. The course of its development
accords with that in the megaspore of Selaginella1, and also with the forma-
tion of the prothallus in the megaspore of the Gymnospermae. As in
Selaginella, the prothallus shows to a certain extent a polar differentiation
as its formation begins at the apex of the spore, and there alone the arche-
gonia are formed in limited number. So far as we know the prothallus is
incapable of becoming green or of developing further. There is no doubt that
the female prothallus of Isoetes resembles much more that of the Lycopo-
diaceae than that of the heterosporous Filicineae, but we know only the
heterosporous forms of leptosporangiate Filicineae, and with these Isoetes
has but little in common.
III
oeUAL PROPAGATION OF THE PROTFHALLUS
ADVENTITIOUS SHOOTS.
It has been already pointed out that the prothallus may propagate
itself vegetatively and perennate ; that from the old cells that have already
passed into a permanent condition new formations may start, and these may
grow out into prothalli. These are the so-called adventitious shoots. All
prothalli, however, have not this capacity. Adventitious shoots are unknown
in Lycopodium annotinum, L. clavatum, L. complanatum, whilst from
broken-off portions of the coronet of lobes in Lycopodium inundatum new
prothalli may proceed. Bruchmann also found adventitious shoots on pro-
thalli of Lycopodium Selago? which were either old or had an injured apex,
conditions which, as I have previously shown, have to be considered in
connexion with the prothalli of Filicineae*. The question of the capacity
for regeneration in the Equisetaceae requires new investigation. Buchtien *
denies the possibilities, yet I see no reason why it should not occur. In the
homosporous Filicineae the formation of adventitious shoots is extraordinarily
common, but I do not require to mention the details.
GEMMAE.
The formation of special asexual organs of propagation which are
designated gemmae or brood-buds, occurs in the prothalli of some species
* See Arnoldi, Die Entwicklungsgeschichte des weiblichen Vorkeimes bei den heterosporen Lyco-
podiaceen, in Botanische Zeitung, liv (1896), p. 160.
? Adventitious shoots also appear in Lycopodium Phlegmaria.
* See Part I, p. 49.
* Buchtien, Entwicklungsgeschichte des Prothallium von Equisetum, in Bibliotheca Botanica, viii
(1887), p. 24.
214 ASEXUAL PROPAGATION OF THE PROTHALLUS
of Lycopodium, and also in many Hymenophyllaceae and Vittariaceae, and
thus. as in the Hepaticae, formation of gemmae has arisen frequently and
independently in different series of the Pteridophyta, as a ‘character of
adaptation.’
Lycopodium Phlegmaria. Treub found in Lycopodium Phlegmaria
two kinds of gemmae, ordinary ones, and those with thickened outer wall.
The former are ovoid cell-bodies seated upon a short stalk1, and they grow
out directly into the new cylindric prothallus. Thick-walled gemmae
arise from the prothallus when it finds itself under unfavourable conditions
for vegetation, and they consist of few cells, each of which has a thick
Fic. 157. Hymenophyllaceae. Formation of gemmae on the prothallus. 1, Trichomanes rigidum; B, gemma ;
7. sterigma. From a specimen collected in Venezuela. 2, Hymenophyllum sp.; s/, sterigma; wf, primordium of
rhizoid. From a specimen collected in Java. 3, 4,5, Trichomanes venosum; 4, gemma ; .S\sterigma ; 7, developing
stalk fora gemma. From a specimen collected on the Black Spur Mountains, Australia. 6, Germination of gemma.
outer wall. These gemmae are essentially resting buds, and they secure
the perennation of the prothallus when the conditions are unfavourable.
Hymenophyllaceae. Gemmae are known in the species both of Tricho-
manes and Hymenophyllum. I have already carried back the gemmae of
many Hepaticae ‘to the formation of brood-cells, which frequently develop
further even upon the mother-plant, and this holds also for the gemmae of
the prothalli of Filicineae. It is sufficient to refer to Fig. 157 in order to
make clear the relationships.
Vittariaceae. In Vittariaceae * gemmae are known in Vittaria, Mono-
gramme, Hecistopteris, where they appear in the form of cell-rows. The
two end-cells are distinguished from the others which contain chlorophyll
* Gemmae may also proceed from the paraphyses of the sexual organs.
* Goebel, Morphologische und biologische Studien : II. Zur Keimungsgeschichte einiger Farne, in
Annales du Jardin botanique de Buitenzorg, vii (1888), p. 78; id., Hecistopteris eine verkannte
Farngattung, in Flora, Ixxxii (1896), p. 67.
RELATIONSHIPS TO WATER OF PROTHALLUS 215
and starch by their smaller size, and by the absence of chlorophyll, or by
its small quantity. One of them shows an almost circular brown fleck, the
position at which the gemma was attached to its stalk-cell. These stalk-
cells are, just like those of Trichomanes shown in Fig. 157, not ordinary
cells of the prothallus, but special outgrowths upon the prothallus, and they
may be designated sterzgmata. Many sterigmata may arise upon one
cell of a prothallus, and many gemmae may be formed from each sterigma,
consequently the number of buds produced is immense. The gemmae arise
upon the sterigmata originally as narrow outgrowths which are subse-
quently constricted at their base, at which point they become separated
from the sterigma by a wall, and each outgrowth is the mother-cell of
a gemma. This mother-cell divides then by cross-walls, and the gemma
finally separates and forms a new surface-prothallus. Large gemmae may
give rise to two prothalli.
It appears to me probable that the formation of gemmae has origi-
nated, especially in these prothalli of the Pteridophyta, because the forma-
tion of the embryo is often hindered for a long time by the conditions of life.
At any rate the formation of gemmae furnishes a means for unlimited pro-
pagation of the prothallus independently of the germination of the spore.
IV
PHENOMENA OF ADAPTATION OF THE PROTHALLUS
The reason why we should expect fewer striking and less numerous
phenomena of adaptation in the prothalli of Pteridophyta than in the
Hepaticae has been already stated 1.
RELATIONSHIPS TO WATER.
There are no special contrivances for the holding of water—if we
except the formation of lobes in the prothalli of Lycopodium inundatum
and L. cernuum as well as in the female prothallus of Equisetum *—and up
till now arrangements for the tiding over of a period of drought have been
found only in two species of the genus Anogramme, and these take the
form of the production of tubers which, as we know, occur also in many
Hepaticae *.
Anogramme chaerophylla. It has been already pointed out that
1 See p. 189. 2 See p. 195.
* It appears to me probable that analogous conditions occur in other Filicineae, as the formation
of sclerotia occurs in different cycles of affinity in the Hepaticae. See p. 66.
216 PHENOMENA OF ADAPTATION OF THE PROTHALLUS
Anogramme belongs to that group of Filicineae in which the prothallus
with heart-like outline does not appear, and indeed we might regard the
prothallus of Anogramme chaerophylla’, as it is shown in Fig. 158, as quite
that of Gymnogramme or of Pteris longifolia, on which the second wing
had not yet been developed, and the meristem was lateral. Old prothalli
are funnel-shaped, not flattened as is usually the case elsewhere, and a tuber-
cular archegoniophore * arises behind the meristem instead of the usual flat
cell-cushion bearing archegonia. This archegoniophore pierces the soil.
Its hinder portion elongates mostly into a stalk, the front portion bears
a roundish tubercle within which is much starch and other reserve-food.
The tubercle is thus very like tubercles which we have seen in many
Hepaticae and is in a condition to persist through dry periods, and if it
Fic. 158. Anogramme chaerophylla. 1, young prothallus spread out upon which an archegoniophore, /, is
already laid down. 2, a somewhat older prothallus in profile view; 4, probably original apex of prothallus;
sf, exosporium still sticking to the base of the prothallus; 7, archegoniophore. 3, prothallus issuing from a tuber,
#A,; anewtuber is seen at Ay. 4, tuber from which a new prothallus is shooting. All magnified.
bears an embryo this is in a position to develop rapidly with the advent of
more favourable vegetative conditions. Should the formation of the embryo
be suppressed, there is formed from the tuber a new lobe of a prothallus
which then later will form a tuberous archegoniophore (Fig. 158, 3, 4).
Adventitious shoots may sometimes develop into similar tubers in other
positions upon the prothallus, and these are then simply resting vegetative
sclerotia, and they appear only when the conditions of nutrition are bad.
It is probably the external conditions which determine whether an adventi-
tious shoot of the ordinary kind or one in the form of a sclerotium shall
arise, just as these determine the development of the resting gemmae in
Lycopodium Phlegmaria.
Anogramme leptophylla. The relationships in the widely-spread
' See Goebel, Uber die Jugendzustiinde der Pflanzen, in Flora, xxii (1889), p. 21.
* This term of Bower's is preferable to ‘ fruit-shoot,’ the one I used earlier.
RELATIONSHIPS TO WATER. TUBERS 217
Anogramme leptophylla! are somewhat more complex. Its sporophyte is
annual, as is that of A. chaerophylla. The prothallus, like that of A. chaero-
phylla, is a spathulate cell-surface which is funnel-shaped and not flat
(Fig. 159), and which can branch and form lobes somewhat after the
fashion of that in Vittaria. The tuber-like archegoniophore, however, does
not arise upon the lobes, or does so only in a few exceptional cases ; but the
base of the cell-surface which is many-layered produces a new cell-surface
of limited growth”, and this forms upon its under side a tuberous archegonio-
phore, or at its base brings forth a new
cell-surface, and so on. From one spore
there proceed therefore a great number
of surface-prothalli which are connected
at their base, and the youngest of these
produces the archegoniophore. Their
Fic. 159. Anogramme (Gymnogramme) leptophylla. Two prothalli to show habit. To the left a prothallus
with tuber in profile view. To the right a prothallus seen from above. Magnified about 4.
great assimilating surface enables them to produce larger tubercles than is
the case in A. chaerophylla, and as in that species these form, when no
embryo arises, two or it may be three surface-prothalli. The prothallus in
this species is then pre-eminently fitted to withstand a period of drought.
Aquatic prothalli. In prothalli which are adapted to a water-life we
* See Goebel, Entwicklungsgeschichte des Prothalliums von Gymnogramme leptophylla, Desv., in
Botanische Zeitung, xxxv (1877), p. 697; id., Uber die Jugendzustande der Pflanzen, in Flora, xxii
(1889), p. 25.
* This recalls the behaviour—mutatis mutandis—of Lycopodium salakense, where many prothalli
shoot out from the ‘ tubercule primaire.’ In both cases we have to deal with a derived phenomenon.
T have recently found like appearances in Mohria caffrorum.
218 PHENOMENA OF ADAPTATION OF THE PROTHALLUS
find, as we might expect, arrangements which stand in relation to their
method of life. These will be in part mentioned when dealing with the
sporangia’. Here I merely point out that the microspores of the Salvinia-
ceae are not scattered singly, they would be very easily swept away if this
were the case’. In Salvinia they remain as a frothy mass embedded
within the microsporangium, and burst through the sporangial wall in
germination. In Azolla their relationships are still more remarkable, for
there is formed within the microsporangium, not one mass enclosing the
microspores, but many, the so-called massu/ae, and these reach the water
by the rotting of the sporangial wall. They have numerous stalked hooks
(glochidia) by means of which they are able to anchor to the rough envelope
of a megaspore—one of the most remarkable arrangements for securing
fertilization °,
SYMBIOSIS WITH FUNGI.
We have already referred to the remarkable symbiosis of Cyanophy-
ceae and some Hepaticae*, regarding the biological significance of which it
is only possible to put forward conjectures. In the gametophyte of the
Pteridophyta a symbiosis such as that in the Hepaticae which presupposes
the existence of mucilage-chambers is excluded. It turns up, however, in
the most remarkable manner in the sporophyte of Azolla. On the other
hand, the gametophyte of many Pteridophyta harbours fungi, and there is
not the slightest doubt that they live in a number of cases in a state of
reciprocal symbiosis, and not as simple parasites in the prothallus. Prob-
ably they bring about decomposition of organic remains in the substratum
and thereby contribute to the saprophytic nutrition of the prothallus.
They are found particularly in all prothalli which have no chlorophyll,
those, for example, of the Ophioglossaceae ’, and of many species of Lycopo-
dium in which a remarkable formation of tissue is part of the consequence
of the presence of the fungus. There are probably gradations between
cases in which the fungus inhabits the prothallus as a harmless parasite, and
those in which it is of use to the prothallus. Experimental investigation
can alone clear up this point. In what follows I state shortly the most
important morphological facts, beginning with the simplest cases :—
Polypodiaceae. The prothalli of Polypodium obliquatum ° and some
undetermined allies have the rhizoids almost always infected with fungi, and
the mycelium is found also in the cell from which the rhizoids spring as
1 See p. 494.
* We may compare the bundles of floating pollen in Zostera.
$ See p. 212. * See p. 78.
° The existence of the fungus in Ophioglossum pedunculosum is not mentioned by Mettenius, but
there can be little doubt that it is present there.
® See Goebel, Morphologische und biologische Studien: II. Zur Keimungsgeschichte einiger
Farne, in Annales du Jardin botanique de Buitenzorg, vii (1888), p. 76.
SYMBIOSIS WITH FUNGI 219
a fine coil of hyphae. The fungus here gives the impression of being a
harmless parasite.
Hymenophyllaceae. Infection by fungi through the rhizoids takes
place in the prothallus of Trichomanes. All the tufts of prothalli of
Trichomanes rigidum? which I examined showed the fungus, but always
limited to a relatively small number of the cells near the soil, which were
frequently swollen and poor in contents.
Ophioglossaceae. In Botrychium a considerable number of the cells of
the prothallus are inhabited by an unsegmented mycelium which enters
through the rhizoids, the hyphae swell between the cells and frequently
become vesicular. Jeffrey* found in older prothalli which had produced
embryos that the fungus was dead and shrivelled, but this does not prove
that it was digested by the cells of the prothallus.
Lycopodiaceae. The relationships are not everywhere alike in the
prothalli of species of Lycopodium. Endophytic fungi are found in all,
with the exception of L. nummulariaefolium, B].* I, however, can refer here
only to one most interesting case as an illustration. The one I take is that of
L. complanatum, for the knowledge of which we have to thank Bruchmann.
The fungus in this species has an intimate connexion with the anatomical
construction (see Fig. 142). We can recognize beneath the meristem in the
beetroot-like portion of the prothallus the following tissues: the central
tissue, palisade-like cells surrounding it, and the tissue of the rind, the cells
of which inhabited by the fungus have a darker content. The cells are
filled with fine hyphae-coils which are in contact with the outer world
through individual rhizoids, the fungus in some cases passing throughout
the whole length of a rhizoid. The rhizoids are, as in other prothalli
of Lycopodium, relatively few in number. The fungus is not able to pierce
the palisade-cells, but only runs between them, and as plastic material is
stored up in them it is highly probable that the fungus shares in the process
of storage. The central tissue serves for the transport of food-material and
perhaps also for water-storage. This highly differentiated anatomical
structure gives us, however, no ground for considering that the prothallus
is really a stem reduced by its saprophytic mode of life. We have seen in
the Hepaticae that the thallus of many forms, for instance the Marchan-
tieae, has a much more differentiated construction than the shoot of the
foliaged forms.
* See Goebel, Archegoniatenstudien: I. in Flora, lxxvi (Ergiinzungsband zum Jahrgang 1892),
p. 106.
* Jeffrey, The Gametophyte of Botrychium virginianum, in Studies from the University of Toronto,
Biological Series, 1898.
° Treub, Etudes sur les Lycopodiacées, in Annales du Jardin botanique de Buitenzorg, vii (1888),
Ps 147, says nothing about an endophytic fungus in Lycopodium salakense, but as the prothallus
conforms in every way with that of L. cernuum and L, inundatum I think we may assume it exists.
220 PHENOMENA OF ADAPTATION OF THE PROTHALLUS
DISTRIBUTION OF THE SEXUAL ORGANS.
This subject has been often referred to in the preceding pages, and here
it is only necessary to refer shortly to its biological interest. The prothalli
in most of the Pteridophyta produce first of all antheridia and then arche-
gonia, and then at a later period antheridia again. The formation of male
prothalli is easily induced by unfavourable environment. Such prothalli
are frequently amerzstic. ‘There are, however, amongst the Filicineae cases
in which well-nourished prothalli produce only archegonia, for example in
Lygodium and Mohria caffrorum according to Bauke, in Onoclea Struthio-
pthoris according to Douglas Campbell, and in Gleicheniaceae according
to Rauwenhoff, who calls such prothalli afandrous. But it is questionable
how far we have here to deal with a constant relationship ; it is much more
probable that in most cases definite external conditions yet unrecognized
bring about the passing over of the stage of formation ofantheridia. Ihave
always found both antheridia and archegonia upon the prothallus of Mohria.
Heim’s investigation of Lygodium give different results from those of Bauke,
for he showed that in this genus the antheridia appeared after the arche-
gonia. In Equisetum also the prothalli are, as has been shown above,
dioecious, but the dioecism is cancelled by external factors.
The position of the sexual organs and the rare occurrence amongst them
of ‘paraphyses,’ to which we can ascribe the same function as in the Bryo-
phyta, do not call for detailed treatment here.
APOGAMY.
Farlow was the first to show that the embryo-plant in Pteris cretica
arose by vegetative sprouting, and not from the fertilized egg. De Bary,
Leitgeb, Heim, W. H. Lang, and others have investigated this remarkable
condition, and have proved its occurrence in a great number of Filicineae.
I do not intend to treat this subject with any fullness here*, I wish only
to state some fundamental points.
In the first place one must remember that the egg, while certainly
different from the other cells of the prothallus, is only a special construction-
form of these. Then it has been already shown? that in many apogamous
prothalli normal sexual organs in the first instance appear, and these are
followed by abnormal ones, and that a change in the constitution of the
sexual organs may be considered as probably the cause of the appearance of
apogamous shoots. In Doodya caudata, for example (Fig. 160) °, papillae
are frequently produced from malformed sexual organs upon the under side
' See, for a comprehensive statement, Sadebeck, Pteridophyta, Einleitung, in Engler and Prantl,
Die natiirlichen Pflanzenfamilien, 1898.
2 See p. 188.
* Heim, Untersuchungen iiber Farnprothallien, in Flora, Ixxxii (1896).
APOGAMY 221
of the prothallus, and on these young plants then arise. It is remarkable
that in the formation of these young plants, the single organs—first leaf,
vegetative point of the shoot, root—are laid down independently of one
another as in the true embryo, and it is
the rule that the individual parts of the
sporophyte appear independently of one
another. W. H. Lang has recently ob-
served sporangia upon apogamous pro-
thalli, and if we must assume that these
are placed upon an extremely rudimen-
tary sporophyte we have a very re-
markable shortening of the development
which is of extreme interest for the theory
of inheritance and development. We
might find in these facts a support to the
assumption that for each organ or com-
plex of organs there exists a definite
material carrying the inheritance, which
usually appearing late, may, under ab-
normal relationships, appear early. The
same may be said in a certain sense also
of the anatomical relationships. Tracheids,
for example, which normally belong only
to the sporophyte, may appear also in
the apogamous prothalli of Filicineae, see ae ee eee aay tee
although the formation of the organs of young plants arise. After Heim.
the sporophyte is not reached. It even
appears in apogamy that there is a jumbling together of the different
organs such as has been shown to occur in other malformations?.
See Part I, p. 196.
THE SPOROPHYTE. IN DHE PIER DOERR ee
AND SPERMOPTHY
THERE is so great a resemblance in the formation of the organs of the
sporophyte in the Pteridophyta and in the Spermophyta that we may take
the two groups together. In the ‘typical’ cases we find that the vegetative
organs are roots and leafy shoots, and the reproductive organs are spor-
angia! in both groups or aggregate of groups, and whilst there are many
differences, both in the external configuration and in the inner structure of
these organs in the two groups, yet in essentials they are alike.
THE ORGANS OF VEGETA
I
INTRODUCTION
In the first part of this book I have pointed out the general features
of the vegetative organs. If we distinguish root and shoot as fundamental
organs this is only based upon the fact that they are the most important
and are the most generally distributed. I have also shown ” that all organs
cannot be referred back to transformations of root, shoot-axis, and foliage-
leaf. Anchoring-organs, such as we find in many Podostemaceae, furnish
us with an illustration. They serve to fix to their substratum these plants
which grow in flowing water. In Fig. 161 is shown a portion of the root
of Weddelina squamulosa which has produced on the left a leafy ‘adven-
titious’ shoot. The root is beset upon both sides by outgrowths which
serve as anchoring-organs, and may be designated by Warming’s term
haptera. These haptera resemble in some degree short roots, but they
differ from roots in their structure and origin. They are new formations
developed in response to the requirements of the habitat. Many similar
organs are to be found and formal morphology has grouped them together
as emergencies. There is no reason why such new formations should not,
under certain conditions, attain considerable size.
Tendrils of Smilax. For example, the tendrils which appear upon
The fact that the microsporangia of the Angiospermae are frequently not sharply distinguished
from the microsporophyll has up to recent times led to much confusion.
Zisee Parti. ps3.
. i
NEW FORMATION OF VEGETATIVE ORGANS 223
the leaf of Smilax (Fig. 162) probably take origin in a way quite similar to
that of the haptera of the Podostemaceae, at least no satisfactory reference
of them to parts of the leaf out of which they may have arisen by a change
of function has as yet been advanced.
That they cannot be transformed stipules, as has been often assumed, can be
shown upon various grounds but specially by this—that in some species the upper
LMTNTP MIS cron
aye icin a inmencnt 18
Ore
Fic. 161. Weddelina squamulosa. One of the Podo- FiG. 162. Smilax Sarsaparilla. End of a shoot.
stemaceae. Portion of aroot. To the left above is an The lamina of the leaf is here arrested, it becomes
adventitous shoot. Right and left below are haptera. developed in later-formed leaves. The tendrils are well
Slightly magnified.’ developed. Natural size.
end of the sheath of the leaf can be recognized beneath the tendril, but if the tendril
was, like a stipule, an outgrowth from the base of the leaf it must spring from
this sheath. Celakovsky’s opinion, recently expressed}, that these tendrils are
metamorphosed separate lobes of the lamina of the leaf does not, in my opinion,
t Gelakovsky, L. T., Uber die Homologien des Grasembryos, in Botanische Zeitung, lv (1897),
p- 171.
224 VEGETATIVE ORGANS OF PTERIDOPHYTA AND SPERMOPHYTA
give us any advance. There is no known species of Smilax which really shows
such ‘lobes.’ Ifthe tendrils develop from the beginning as /enzdrifs upon the
primordium of the blade, they can be xo transformations but new formations.
The question seems to me to be one in which change of function is predominant,
it is not the purely formal one of whether the tendril springs from the base of the
leaf or from the lamina of the leaf’.
Haustoria of Parasites. The haustoria of parasites may also be con-
sidered as organs saz generis”. Parasites are of course derived from
non-parasitic plants. There are two ways in which this may have come
about :—
(a) Either organs which previously existed became devoted to the
service of a parasitic life; for instance, a root-primordium might obtain
the capacity to bore into a host-plant ;
(2) Or the plant had recourse to new formations in order to bring it
into union with its host. This appears to me to be that which has been
actually followed.
It has been customary to consider the haustoria of Cuscuta, for example.
as partly transformed roots, and this mainly because they are endogenetic ;
but no really convincing proof in support of this has been brought forward,
and certainly such an assumption finds no application in relation to the
haustoria of the Rhinantheae, Orobanchaceae, Balanophoreae, and others.
The haustoria which arise usually in consequence of a chemical or mechanical
stimulus are indeed not fundamentally different from those which we shall
have to notice in the embryo-sac of many Angiospermae *. In Orobanche’*,
for example, the form of the haustorium which is produced on its root is
different according as this is in touch with the root of the host-plant at one
small point or over an extended area. In the first case a single superficial
cell may grow out and penetrate the root of the host as a filiform hausto-
rium, just like the mycelium of a fungus; in the second case the suctorial
process is a cell-mass which has a much higher anatomical construction,
containing both vessels and sieve-tubes, and these enter into union with
similar elements of the host-plant. It is the same in other cases. We
have to deal with new formations in these haustoria which arise in conse-
quence of a stimulus as does the anchoring-disk on the tendril of an
Ampelopsis *.
1 See, for a vésumé of the different views, Delpino, Contribuzioni alla storia dello sviluppo nel
regno vegetale: I. Smilacee.
* The older literature about parasites is brought together in my Vergleichende Entwicklungs-
geschichte der Pflanzenorgane, in Schenk’s Handbuch der Botanik, iii (1884). The limits of the
present book allow only of a citation of some of the more general and important relationships, but
f no details. 3 See p. 638.
* See Hovelacque, Recherches sur l'appareil végétatif des Bignoniacées, Rhinanthacées, Oroban-
chées, et Utriculariées, Paris, 1888, p. 598. The literature is cited in this work.
> See Part I, p. 268.
HAUSTORIA OF PARASITES 225
It is remarkable that the haustoria of many parasites can exhibit
unlimited growth within the host-plant, whilst the portion of the parasite
outside the host-plant suffers so great a reduction that sometimes only
the flower-shoots remain, and the haustoria then alone represent the vegeta-
tive body. Such a case is that in Fig. 163, which is an illustration of a
species of Pilostyles’.
Pilostyles Ulei. Upon the surface of the shoot of the host-plant only the
small flower of the parasite appears. The vegetative body of this member of the
Rafflesiaceae appears to have
the same nature as that of
Pilostylesaethiopica described
by Solms, a plant which lives
as a parasite upon the twigs
of the caesalpineous Berlinia
paniculata. In the secondary
rind of the host run strands
which have no definite form,
and from which small, plate-
like branches pass off, and
these grow radially against the
wood and gradually become
enclosed by this as sznkers.
Foliage-shoots are wanting
here as in all Rafflesiaceae.
The several shoots which
develop as ‘ adventitious buds’
within the ‘ thalloid vegetative
body,’ and burst through the
rind of the twigs of the host,
are flower-buds. The arrange-
ment is therefore like that of
the mycelium of an endo-
phytic fungus—Peronospora,
for example, the conidiophores
of which burst through the
Fic. 163. Pilostyles Ulei, Solms. Only the small flowers of this
host and appear above the parasite are visible upon the shoot-axis and leaves of an Astragalus,
which is the host-plant.
surface.
Pilostyles Haussknechtii. In another species of Pilostyles, P. Haussknechtit’,
the reduction of the intramatrical vegetative body is carried still further. The
plant lives as a parasite upon species of Astragalus, and the flower-shoots appear
1 The plant was sent to me through the kindness of Dr. Ule, and it has been determined by Count
Solms-Laubach to be a new species. See Endriss, Monographie von Pilostyles ingae, Kant. (P. Ulei,
Solms), in Flora, xci (Ergiinzungsband zum Jahrgang 1902), p. 209.
* Solms-Laubach, Uber den Thallus von Pilostyles Haussknechtii, in Botanische Zeitung, xxxii
(1874), p- 49.
GOEBEL II O
4
a
226 ROOT AND SHOOT IN PTERIDOPHYTA AND SPERMOPHYTA
upon the basal portions of the leaves. Young stages of development show that
the flower-buds sit upon a cushion-like irregularly limited mass of tissue of the
parasite termed the /lozwer-cushion which is in firm union with the tissue of the
leaf of the Astragalus. Two such flower-cushions are regularly found in the leaf of
the host when it has reached its development. After the flowering time these die
away. The intramatrical body of the parasite which produces this flower-cushion
consists of simple cell-strands, which Solms designates mycelium on account of
their resemblance to the mycelium of a fungus. It is chiefly spread in the pith of
the shoot of the Astragalus, but its branches force themselves also into the vascular
bundles, penetrate the medullary rays, and spread in the form of irregular
tangled filaments in the rind and end finally in the young flower-cushions.
It is easy to follow this vegetative body nght up into the vegetative point
—into a region where there is scarcely yet a differentiation of rind and pith—
and there it is richly developed. Solms has definitely traced it to the ultimate
cell-layers of the apex’. The flower-cushion arises from the mycelium which
penetrates into a leaf, immediately after the primordium of the leaf is laid down.
This mycelium swells up in the base of the primordium, and then the ends of its
filaments divide and form a net of irregular polyhedral cells which later swell up
into the flower-cushion. The flower-bud is endogenetic in this cushion.
These examples must suffice to show that besides ‘ root and shoot, as
defined above, other organs are formed with special aims, to use a teleological
expression, and these are not transformations of others, and cannot be
referred back to previously existing ones. Keeping in view the relation-
ships of configuration of root and shoot we must remember that the
plasticity of the vegetative organs is very great, and that consequently it
is impossible to find general far-reaching differences between the single
categories of them. The cases where passage-forms occur between the
categories are of special interest, and they require here fuller description
than could be given to them in the general part of this work.
II
ROOT AND SHOOT?
I do not propose to give here a general account of the characteristics
of root and shoot. My object will be much better accomplished by an
exposition of individual cases, but I must discuss here the question: Can
roots pass over into shoots, and does the converse also happen ?
A. TRANSFORMATION OF UNDOUBTED ROOTS INTO SHOOTS.
Both in Pteridophyta and in Spermophyta there are a number of cases
in which, sometimes regularly sometimes occasionally, roots become trans-
1 Solms-Laubach, Uber den Thallus von Pilostyles Haussknechtii, in Botanische Zeitung, xxxii
(1874), p. 68.
TRANSFORMATION OF ROOTS INTO SHOOTS 227
formed into shoots at the apex by throwing off their root-cap and forming
leaves.
Filicineae. The transformation has been observed with certainty in
Diplazium (Asplenium) esculentum!, and in many species ot Platycerium,
such as P. alcicorne, P. Willinkii, P. Stemmaria, P. Hilli. These are plants
which in their manner of life behave very differently. The species of
Platycerium are epiphytes, and produce spores which germinate freely ;
nevertheless, vegetative propagation by shoots from the roots is profuse in
them. Diplazium esculentum, on the other hand, is a tree-like geophyte
which in cultivation apparently seldom pro-
duces sporangia, but in its natural habitat f
does so abundantly. The formation of
root-shoots cannot then be considered as a
substitution for the usual propagation by
spores. Transformation of the tip of the
root into a shoot may take place in short
roots or in long roots, and indeed every
root appears to have the capacity to become
a shoot, for one can almost always observe
the transformation in healthy separated tips
of roots. The transformation seems to be
favoured in the plant by the position of the
root near the surface of the soil. It is easy
to follow the process by which the apical
cell of the root becomes the apical cell of
the shoot.
Spermophyta. The transformation of
roots into shoots has been observed as yet
only amongst the Monocotyledones in, for Re pe ee
gs Ore Nidus. eer mor airetitcms coon theme
avis*®, Anthurium longifolium*. The observa- rid its base a lobed anchoring-disk.
tions which have been made in Dicotyledones
are altogether wanting in accuracy °.
The transformation of roots into shoots is, in my opinion, only an
NVM NTNNEONY
1 See Lachmann, Contributions 4 Vhistoire naturelle de la racine des Fougéres, in Annales de la
Société botanique de Lyon, xvi (1889), p. 159. They are more accurately described by Rostowzew,
Beitrage zur Kenntniss der Gefasskryptogamen, in Flora, Ixxiii (1890), p. 155.
? Brundin, Uber Wurzelsprosse bei Listera cordata, L., in Bihang till k. Svenska Vetenskap
Akademie Handlingar xxi. 3 (1895).
* Warming, Om redderne hos Neottia Nidus-avis, L., in Videnskabelige Meddelelser fra den
Naturhistoriske Forening i Kjobenhayn, 1874. The literature is cited in this work.
* Goebel, Uber Wurzelsprosse bei Anthurium longifolium, in Botanische Zeitung, xxxvi (1878),
p. 645.
® With regard to this see the literature quoted by Rostowzew.
Q 2
228 ROOTS AND SHOOTS IN PTERIDOPHYTA AND SPERMOPHYTA
individual case of the general phenomenon that shoots arise upon roots.
Root-borne shoots occur quite regularly in many plants, the shoots are laid
down endogenetically in serial succession towards the growing point of
the root ; their endogenetic origin gives their vegetative point, like that of
the lateral roots, the protection which they could not otherwise get upon the
leafless root. This is very strikingly shown in many Podostemaceae’. In
Fig. 164 there is a portion of a root of Marathrum, a podostemaceous plant
which I collected some years ago in the Rio Bocono in Venezuela. It
will be seen that there are two rows of shoot-primordia upon it, and the
youngest of these primordia are evident upon that portion of the root which
is still covered by the root-cap. Suppose now that the formation of the
shoots approaches more nearly the tip of the root. Such a case is found in
Ophioglossum vulgatum, whose multiplication, so far as we know, takes
place exclusively by shoots upon the root, and in it the primordia of the
shoots arise out of the youngest segments of the apical cell of the root,
whilst the tip of the root itself continues its growth”. It is but a short
step from this to the transformation of the tip of the root itself into the tip
of the shoot, in which case the primordium of the shoot would be terminal.
We shall have occasion to describe presently a similar pushing of the
formation of shoot to the apex in the leaves of Filicineae *.
B. ORGANS WHICH ARE“ NOT TYG eee:
THE RHIZOPHORE OF SELAGINELLA.
Many authors have considered as roots the rhzzophores, which are
found in a number of species of Selaginella, and which are confined ex-
clusively to plagiotropous dorsiventral forms such as Selaginella Martensii
and S. cuspidata. The upper portions of the plagiotropous but not creeping
shoots in such species, where they are at some distance from the ground, are
enabled to get into connexion with the soil by means of the rhizophores,
just as in Mastigobryum*, one of the foliose Hepaticae, the flagella, which
are branches provided with reduced leaves and numerous rhizoids, bring the
plant into connexion with the soil.
The rhizophores of Selaginella (Fig. 165) are leafless. They arise
usually in pairs, one above and one below the fork, which is formed by the
branching of the axis of the shoot. They are exogenetic’, and near their
1 Warming, Familien Podostemaceae : I-V in Skrifter af det kgl. danske Videnskabernes Selskab,
1881, 1882, 1888, 1891, 1898, has described this in great detail.
2 See Rostowzew, Beitrage zur Kenntniss der Gefasskryptogamen, in Flora, lxxiii (1890), p. 155.
I had expressed my doubts of the accuracy of Van Tieghem’s statement that the tip of the root was
transformed into the tip of the shoot ; see Vergleichende Entwicklungsgeschichte der Pflanzenorgane,
in Schenk’s Handbuch der Botanik, iii (1884), p. 344.
= See! ps 241. * See p. 43-
° See Treub, Recherches sur les organes de la végétation du Selaginella Martensii, Spring., in Musée
botanique de Leide, ii (1877), p. 11.
RHIZOPHORE OF SELAGINELLA 229
tip they form endogenetically the primordia of one or many roots. The
rhizophores may branch dichotomously, and they attain in many forms
a considerable length which is not brought about, as is sometimes wrongly
supposed, by intercalary growth, but by prolonged apical growth. The
formation or extrusion of roots is caused by moisture. Usually it takes
place in the soil, occasionally also in moist air. Pfeffer has shown that’
these rhizophores may be transformed into leafy shoots ', and he pointed
out that cutting through the two shoot-branches above the fork where the
rhizophores arise, appeared to favour the
transformation of the rhizophores into
shoots. We can certainly cause the
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Fic. 165. Selaginella Martensii. Portion of a shoot with Fic.-166. Selaginella. Seedling. Cvé, cotyle-
don; W#, young rhizophore; 2, hypocotyl ; Afa,
megaspore; M1, chief root; M2, Ws, roots spring-
ing from the hypocotyl. Magnified 2.
thizophores. Natural size.
transformation in young rhizophores if we treat the parent-shoot as a cut-
ting, and make the apex of the rhizophore the vegetative point 2. A case
of the kind is illustrated in Fig. 167. Two rhizophores, 177, upon the
upper side, and W7, on the lower side, are shown here at the point of
forking of the shoot. IZ, has developed into a leafy shoot which, after
* Pfeffer, Die Entwicklung des Keimes der Gattung Selaginella, in Hanstein’s Abhandlungen, |
i (1871),
* Behrens, Uber Regeneration bei den Selaginellen, in Flora, lxxxiv (Erganzungsband zum Jahr-
gang 1897), p. 159; Beijerinck, Beobachtungen und Betrachtungen iiber Wurzelknospen und Neben-
wurzeln, in Natuurkundige Verhandelingen der koningklijke Akademie van Wetenschappen in
Amsterdam xxy (1886), p. 16.
|
230 ROOTS AND SHOOTS IN PTERIDOPHYTA AND SPERMOPHYTA
producing some deformed leaves, bears those of normal Selaginella.
A root, W, or it may be a rhizophore, is already seen upon it. This
simple experiment is one of the most instructive and most easily carried
out that we know of for the purpose of showing change of function.
The question now is: What is the rhizophore? There are three possi-
bilities. It may be a leafless shoot ; it may be a capless root; it may be
neither of these, but an
organ saz generis.
In favour of its being
a shoot there may be ad-
vanced its easy transforma-
tion into a leafy shoot, as
well as the method of its
origin. But wedo not know
any transition-form between
a rhizophore and a leafy
shoot. Even in the germ-
plant the rhizophoreappears
with the same configuration
as it has upon the mature
plant. Fig. 166 shows a
germ-plant which has de-
veloped the first rhizophore
above the two cotyledons.
In favour of its being
a root the anatomical con-
siderations have been spe-
cially advanced, but these
do not appear to be critical.
More recently Bruch-
mann ' has pointed out that
in Selaginella spinulosa, a
species of radial configura-
Fic. 167. Selaginella cuspidata. The apices of the two shoots of a tion which does not produce
forked branching were cut off. One of the two rhizophores of the fork
WT», became transformed into a leafy shoot, the other, W7Zj, did rhizophores the roots do
not develop further; V7 root. Magnified 9. ’
not arise immediately from
the stem, but are produced endogenetically in a cell-body of exogenetic
origin. This body appears in this species as if it were a very short ‘stalk’
to the root, and it is found also in other species. The rhizophores of dor-
siventral species of Selaginella may then be only a further development of
this ‘stall’ in correlation with their life-relationships, and we may compare
! Bruchmann, Untersuchungen iiber Selaginella spinulosa, A. Br., Gotha, 1897.
THE PROTOCORM 23%
re
this stalk with the ‘protocorm’ of other Lycopodineae. If this be so, the
thizophore of Selaginella is neither the result of the transformation of a
shoot nor of that of a root, but is the result of a prolonged growth of an
outgrowth of tissue, which appears in all species, but in the radial forms
exists only in a rudimentary condition. Further investigation of the forma-
tion of the roots of Selaginella is needed before we can say that this ex-
planation is founded upon a right basis. It has, however, the advantage
that it is supported by the comparative consideration of the organs within
the genus itself, and not upon any forced general scheme.
THE PROTOCORM.
The organ which Treub? has designated protocorm is found in the
germination of some species of Lycopodium. It is also known in Phyllo-
glossum, the germination of which has not yet been observed.
Lycopodium. Fig. 140, 4, shows a germ-plant of Lycopodium inun-
datum, which still holds on to its prothallus by means of its foot (hausto-
rium). In addition to the cotyledon, Co, the second leaf has developed, and
at its base there is not, as in other germ-plants, the hypocotyl with the root,
but instead a tuber-like body provided with rhizoids, and it corresponds
morphologically with a hypocotylous segment of a stem in which the
primordium of a root is suppressed”. The plant as it grows further be-
comes dorsiventral, forms some new leaves, and only at a relatively late
period does the first root arise as an endogenetic structure, and then also
is developed for the first time a more complex anatomical construction,
evidenced in the presence of vascular bundles. We can recognize thus in the
germ-plant two stages of development ; the first gives us a parenchymatous
tuber which bears a few leaves; in the second the internal and external
differentiation of the plant appears for the first time. Similar tubers arise
also upon the roots in Lycopodium cernuum, and they may bear leaves and
become each of them a new plant should they be isolated. Treub con-
sidered that the tuber of the germ-plant in the species of Lycopodium
mentioned above was not a reduced organ, but a rudimentary one, and that
it was the forerunner of the leafy shoot of the Pteridophyta of the present
day; he therefore named it the profocorm. I must own that this phyletic
conception does not appeal to me.
We find very similar formations in Spermophyta, both amongst the
1 Treub, Etudes sur les Lycopodiacées: VIII. Considérations théoriques, in Annales du Jardin
botanique de Buitenzorg, viii (1890), p. 30. Bruchmann adopts the earlier view of Treub that the
protocorm is a foot which has become free. I cannot agree with him. The function of the foot
(haustorium) is, in the cases referred to, usurped by the strongly developed suspensor,
2 See Goebel, Uber Prothallium und Keimpflanzen von Lycopodium inundatum, in Botanische
Zeitung, xlv (1887), p. 184.
232 ROOTS AND SHOOTS IN PTERIDOPHYTA AND SPERMOPHYTA
Monocotyledones and the Dicotyledones, if the formation of root is
suppressed temporarily or entirely in the seedling.
Monocotyledones. The Orchideae furnish examples of these ‘ proto-
corms. I have described them in the germination of the epiphytic species
Taeniophyllum Zollingeri?, and Ratiborski* found the same relationships
in a number of other epiphytic orchids. The germ-plant is an elongated
sreen body with a rudimentary cotyledon in front, and below this the
vegetative point of the stem. The chief mass of the seedling is formed of
the ‘protocorm,’ that is to say, of a rudimentary hypocotylous segment
which is not prolonged as the primordium of a root, and which is fastened
to the surface of the tree by numerous anchoring-hairs. Raciborski
observed adventitious shoots upon this ‘ protocorm’ in Aerides pusillum.
In the seedlings of orchids growing in the soil the ‘ protocorm’ is commonly
tuberous.
Dicotyledones. Streptocarpus polyanthus may be mentioned as an
illustration amongst dicotylous plants of this formation of the ‘ proto-
corm. Its rootless hypocotylous segment, which is the ‘ protocorm,’ is
fastened by anchoring-hairs to the soil, according to Hielscher’. On the
embryos of species of Utricularia*, the hypocotylous segment is commonly
an undifferentiated cell-body serving as a reservoir of food-material. The
same is the case in some rootiess species of Podostemaceae.
Phylloglossum. Phylloglossum is an Australian lycopodineous plant
which bears at the base of its leafy stem two parenchymatous tubers, and
these are able to perennate in the same way as do those of many Ophrydeae.
These tubers, which show no infection by fungi in the examples I examined,
are generally regarded as being comparable with the ‘ protocorms’ of the
germ-plants just mentioned. They are swellings of the axis of the shoot
upon which no root is laid down; the root arises exogenetically on the
plant above the new tubers ®.
The appearance of a protocorm in very different cycles of affinity
appears to me to be unfavourable to the hypothesis of its having a phy-
letic significance; I can only see in the protocorm an organ which
corresponds in its development, especially in its formation of roots, to an
arrested hypocotylous segment ; its appearance is probably connected with
external conditions of life. That in plants which generally have given up
the forming of roots, like the Utriculariae, there should be no formation of
1 Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 195.
* Ratiborski, Biologische Mittheilungen aus Java, in Flora, Ixxxv (1898), p. 337. The literature
is cited here.
* Hielscher, Anatomie und Biologie der Gattung Streptocarpus, in Cohn’s Beitrage zur Biologie
der Pflanzen, iii (1883).
* Compare the figure of Genlisea (Fig. 169, 1), which in this respect resembles Utricularia.
5 See Bower, On the Development and Morphology of Phylloglossum Drummondii, in Phil.
Trans., 1885.
INDEPENDENT (LIFE OF ORGANS 233
roots in the seedling, is easily understandable. In other plants, like the
species of Lycopodium and Orchideae mentioned above, the suppression of
the formation of roots may be connected with the prolonged development
of the germ-plant ; perhaps also with the symbiosis with fungi which takes
place in these plants’. At the present time, however, we have no clear view
of these relationships.
C. TRANSFORMATION OF SHOOTS INTO ROOTS.
Shoot-axes which have the form of roots have already been described
in the Hepaticae*.. They are found also in the Pteridophyta, for example
in the Psilotaceae, and also in the Spermophyta, but an actual transforma-
tion of a shoot into a root has, as yet, not been shown. Beijerinck has
described its occurrence in Rumex Acetosella, but I cannot accept his state-
ment as conclusive *.
Ill
PREE-LIVING ROOTS AND LEAVES. TRANSITION
BETWEEN LEAF AND SHOOT
We are accustomed to think of the several organs of the plant-body
always as they occur in connexion one with the other, because this is the
most common condition, corresponding as it does with the ordinary require-
ments of the life of the plant, and we regard it consequently as the ‘ normal.’
We see in the vegetative organs the root and the shoot joined to one
another, and the phenomena of regeneration have shown us that the taking
away of the root-system or of the shoot results frequently in a new formation
of the lost parts. But there is another way of looking at these facts. Under
special life-conditions the organs may also live alone, at least for a time.
* At isolated places in the stem of Lycopodium inundatum, cushion-tissue develops which becomes
infected with fungus-hyphae. In the vicinity of this the new formation of roots is promoted, and
upon the protocorm of Lycopodium inundatum similar cushions of tissue are found. In both cases,
and in the root-tubers of Lycopodium cernuum also, the fungus-infection appears to promote an
increase of plastic material.
2 See p. 45.
* Beijerinck, Beobachtungen und Betrachtungen iiber Wurzelknospen und Nebenwurzeln, in Natuur-
kundige Verhandelingen der koningklijke Akademie van Wetenschappen in Amsterdam, xxv (1886),
p- 41. Beijerinck found at the base of newly formed roots one or two leaflets, and concluded therefrom
that a shoot continued its growth as a root after the primordia of one or two leaves had been laid
down. Neither in the text nor in the figures is it, however, shown that these leaves had vascular
bundles, and therefore there is the possibility that these leaf-like structures were only portions of the
Tuptured rind-tissue.
“=
234 FREE-LIVING ORGANS IN PTERIDOPHYTA AND SPERMOPHYTA
ROOTLESS SHOOTS.
The existence of rootless shoots is generally known. They occur in
some free aquatic plants, for instance in Salvinia, Ceratophyllum, species of
Utricularia ; also in terrestrial plants in which the function of the root has
been taken on by the axis of the shoot, as in Psilotum, Epipogon, Coral-
lorrhiza, or by the leaves, as in Genlisea, Polypompholyx, and species of
Utricularia.
FREE-LIVING ROOTS.
Less known, however, is the occurrence of free-living roots, that is to
say of roots which do not spring from a shoot. They occur in some
saprophytes and parasites. In the former the saprophytic mode of life of
the roots is made possible by symbiosis with fungi. They are rendered
thereby independent to a certain degree of the assimilating shoots, and as
a matter of fact the assimilating shoots no longer exist in many saprophytes,
for example Monotropa.
Pyrola uniflora. If we examine, for example, the growth of Pyrola
(Monesis) uniflora?, we find that the leafy shoots spring from a root-system
in the soil. They are quite dependent upon this because they themselves
develop no roots, and form also no lateral shoots*. There are also root-
systems which evidently exhibit younger stages, and have not developed
any shoot. The germination is unfortunately unknown, but probably there
arises from the unsegmented embryo in the germinating seed, not as else-
where a leafy and rooting shoot*, but, the shoot being arrested, only
a saprophytic root-system upon which shoots subsequently appear as
endogenetic structures.
Monotropa. The condition is quite similar in the allied Monotropa,
which, however, does not produce foliage-leaves. Whilst shoots above-
ground die down after the flowering period, the root-system perennates and
develops new flower-shoots again in the next vegetative period.
I do not consider it necessary to distinguish this root-system, which
thus lives independently, by a special name* as we have doubtless here to
do with a condition correlated with the saprophytic mode of life, and derived
from the normal in which frequently we meet with roots that produce shoots,
but they are xot independent roots being always connected with chloro-
phyllous shoots.
* See Irmisch, Bemerkungen iiber einige Pflanzen der deutschen Flora, in Flora, xxxviii (1855),
p- 628.
* In the neighbourhood of the shoot a lateral root commonly arises from the root-system.
* We may of course suppose, with Irmisch, that in the germination a shoot arises whose chief root,
or one of its lateral branches, then develops into the root-system producing shoots, but the analogy
with the germination of Orobanche leads me to think that the assumption I have made in the text is
the more probable, and that the chief shoot is entirely suppressed in germination.
* As does Velenovsky, Uber die Biologie und Morphologie der Gattung Monesis, in Rozpravy
éeské Akademie, Prag, 1892.
FREE-LIVING LEAVES 235
FREE-LIVING LEAVES.
Streptocarpus. The cotyledons of Streptocarpus polyanthus and
S. Wendlandii can scarcely be considered as of this category, although
they frequently are regarded as of this nature. In the germination of the
seeds of these species two cotyledons unfold as in other species of Strepto-
carpus. One cotyledon is soon outstripped in size by the other, and dis-
appears altogether at a later period ; the other grows into a large foliage-
leaf out of whose base the inflorescence springs subsequently. Hielscher?
considered these inflorescences as adventitious formations. It is, however,
more probable—although an unprejudiced investigation of the develop-
mental history has not been carried out—that the inflorescence proceeds
from the end of the primary axis, which elongates into an internode
between the two cotyledons, and appears later as the stalk of the large
cotyledon.
Lemnaceae. But we can reckon in this category the vegetative body
of the Lemnaceae. The flat members which spring one from the other in
this plant have been considered sometimes as segments of a thallus, some-
times—and this has been far the commonest view—as leafless shoots in most
species. These leaf-like structures are, however, really leaves, as I have
stated elsewhere”. The general conclusion in favour of their shoot-nature
was arrived at because one (in Wolffa) or two new members (Fig. 168)
shoot out from the base of each old member, and morphological dogma
maintained that a leaf could never arise out of another leaf but only out of
the vegetative point of a shoot. This dogma, however, has been overthrown
by the condition in Utricularia and in the embryos of many Monocotyle-
dones, conditions which will be described below *. The first leaves arise in
many monocotylous embryos without any vegetative point being visible, and
there is no necessity to suppose that it is existent although not visible.
The cotyledon, the first leaf, is a portion of the embryo, and is not formed
out of a vegetative body. Subsequent leaves may develop in like manner
out of embryonal tissue remaining over at the base of other leaves. This is
what happens in Lemna and its allies, and in support of this view the follow-
ing points may be advanced :—
1. Plants with leafless shoots are found elsewhere amongst those
which ‘aim at’ reduction of the transpiration. Such a condition in plants
like the Lemnaceae, which live partly on, and partly in the water, is quite
impossible.
2. In germination the cotyledon of Lemna develops into the first
1 Hielscher, Anatomie und Biologie der Gattung Streptocarpus, in Cohn’s Beitrage zur Biologie
der Pflanzen, iii (1883). Against this put Fritsch, Uber die Entwicklung der Gesneriaceen, in
Berichte der deutschen botanischen Gesellschaft (General-Versammlung), xii (1894), p. 96.
* Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 276.
3 See pp. 236, 253.
236 FREE-LIVING ORGANS IN PTERIDOPHYTA AND SPERMOPHYTA
‘member’ of the plant, and all the following members essentially resemble
it; but the cotyledon is the first leaf, and consequently the following
‘members’ must also be leaves if we are to accept the comparative method
as of any value.
3. The structure which has hitherto been regarded, for example in
Spirodela, as a leaf-organ, has scarcely any resemblance to a foliage-leaf.
and can without difficulty be arranged amongst the ‘ligular formations.’
The morphology of these remarkable plants cannot be treated of in
detail here. I will only point out that the new ‘members’ of Lemna
appear in pairs upon the upper side of the old ones, and are enclosed in
pocket-like outgrowths (Fig. 168). A zone of embryonal tissue persists at
the base of each leaf and out of it the new formations proceed. A special
vegetative point is never differen-
tiated. If now we were to regard
as leaf that part of the member of
a Lemna which stands above the
position of formation of the lateral
members and roots (/ in Fig. 168),
and as shoot-axis the portion which
lies behind this (S in Fig. 168), we
should not get rid of the fact that
the two are not differentiated one
Eis, Lag alin > ot opel a race!
above. For the explanation see the text.” Magnified. view, the Lemnaceae retain a con-
dition which is otherwise found only
in seedling-plants, just as Phylloglossum retains in the formation of its
tubers a feature of formation of organs that is limited to the germ-plant
in Lycopodium inundatum and L. cernuum, and to the ‘adventitious
shoots’ resembling those in L. inundatum. This view appears to me to be
at the present time the most natural one, even though it may appear a heresy
to the older morphology.
TRANSITION BETWEEN LEAF AND SHOOT.
I have frequently said that the behaviour of Utricularia is of special
interest in the general consideration of the formation of organs, and I must
now say something about it :—
Lentibulariaceae. Utricularia belongs to the family of the Lentibu-
lariaceae, all the genera of which are insectivorous. Pinguicula shows the
normal differentiation of the vegetative body of Spermophyta, namely, root
and leafy shoot. The other genera are rootless. The function of the root
in Genlisea’ has been usurped by the highly remarkable tubes which at the
! Goebel, Pflanzenbiologische Schilderungen, ii (1893) ; id., Zur Biologie von Genlisea, in Flora,
Ixxvii (1893), p. 208.
TRANSITION BETWEEN LEAF AND SHOOT 239
same time serve as insect-traps, and they pierce the substratum just like
roots (Fig. 169). There can be no doubt that these tubes are transformed
leaves. In Polypompholyx, and some few of the species of Utricularia which
live on land, we find the following formation of organs :—
Utricularia Hookeri. As an
example I shall take the West
Australian Utricularia Hookeri!
(Fig. 170). A radial shoot pro-
ceeds from the seed and ends in
aninflorescence. This shoot, apart
from the leaf-structures of the
flowers and the bracts, bears the
following organs :—
(a) folitage-leaves,
(4) tubes (tubular leaves) which
end in insect-traps (bladders),
(c) elongated, but unbranched
and non-tubular, thin structures
resembling roots, which we shall
call leaf-roots or rhizoids.
The leaf-roots enter the moist
soil like the tubes; the foliage-
leaves raise themselves above this.
Here then the double function of
trapping animals and of anchor-
ing and absorbing water for the
plant, which is performed by the
tubular leaves of Genlisea, is dis-
tributed between two organs, the
tubes and the leaf-roots. These
stand near one another; they are
a aol
Fic. 169. Genlisea violacea.
1 1, seedling with three
leaves ; Fj, first foliage-leaf; S, incipient tubular leaf ;
V, vegetative point; WW, root-hair. 2, older seedling
which has formed a number of foliage-leaves, and two
both transformed leaves. The stalk-
portion of the tubular leaf resembles
very much the leaf-root, and not
tubular leaves, Sj So, which have pierced the soil; Jf
terminal inflorescence. 3, the same seedling older. A
second inflorescence is developing at the base of the first
one. 4, portion of an inflorescence with vegetative shoot,
the young two-armed tubular leaves point downwards.
3, natural size. The others magnified.
infrequently there is found at the
end of the stalk an elongated leaf-structure, which one might at first
mistake for a leaf-root instead of a tube? (Fig. 170). Now the trans-
formation of leaves into tubes is known elsewhere, it is therefore not specially
For the relationships of configuration in Utricularia, see Goebel, Der Aufbau von Utricularia,
in Flora, 1xxii (1889) ; id., Morphologische und biologische Studien: V. Utricularia, in Annales du
Jardin botanique de Buitenzorg, ix (1891); id., Pflanzenbiologische Schilderungen, ii (1893). The
simply organized Utricularia Hookeri was unknown to me at the time of my earlier investigations.
* In Utricularia vulgaris also the tube occasionally appears at the end of the first leaf in the seed-
ling. See Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 141, Fig. 43.
238 FREE-LIVING ORGANS IN PTERIDOPHYTA AND SPERMOPHYTA
remarkable here. Leaf-roots are, however, unknown outside the genus
Utricularia, but they do not always differ very markedly from the /eaves of
Fic. 170. Utricularia Hookeri. Flowering-plant showing the sub-
terranean parts dissected out ; Z, foliage-leaves, all shaded for the sake
of distinction; .S, tubes; #, leaf-roots; S7, young tube at the end of a
leaf-root ; x marks where the ends of these have been cut off. Magnified 3.
A portion, three centimeters long, has been cut out of the scape.
Utricularia Hookeri; they
retain for a much longer
period the apical growth
which is present at first
in the leaves although
only for a short time, and
they remain smaller than
the foliage-leaves, and in
this exhibit a character
seen elsewhere in organs
which do not come to the
light. But in other species
of Utricularia we find the
organs which correspond
to the ieaf-roots in Utri-
cularia Hookeri develop-
ing into stolons with un-
limited growth, upon
which are produced the
bladders, the foliage-
leaves 1, the inflorescence,
and other lateral shoots ;
—they thus lose entirely
the leaf-character.
Utricularia coerulea.
In Fig.171, //, we have an
illustration of this in Utri-
cularia coerulea. At the
base of the inflorescence
there are no foliage-leaves,
but only organs, A, cor-
responding to leaf-roots,
and with ‘them are
branched stolons which
bear leaves, &. The leaf-
roots May pass over into
stolons,and again between
these stolons and the foliage-leaves there are found in many species
all transitions, of which I have before now given many examples.
1 These turn their under-surface to the apex of the stolon, and, consequently, axillary shoots
TRANSITION BETWEEN ORGANS IN UTRICULARIA 239
The leaves in many species are marked by an extraordinary power of
reproduction ; stolons, even new leaves, may spring from the leaves (Fig. 171,
f). The stolons themselves may become claw-like anchoring-organs, as
in Utricularia neottioides, or tuberous water-reservoirs. In brief, we may
say that the ordinary scheme of formation of organs is jumbled here.
Examination of the germination and a comparison of the history
of development have given us the starting-point of all these mar-
vellously varied relationships. The seedling-plants! in most of the inves-
tigated species have retained the behaviour which Utricularia Hookeri
Fic. 171. J, Utricularia affinis. 4, a leaf which has shot out astolon and also a second lear, f. J/, Utricu-
laria coerulea. Habit of a flowering-plant, the flower somewhat withered. .S, remains of seed-coat; foliage-leaves,
6, are not found now at the base of the scape of the inflorescence, //, but only leafy stolons, 4, and leaf-roots, A.
Magnified.
shows throughout its life, that is to say, the tubes stand as transformed
entire leaves on the chief axis, while we find them also in many other
species on the leaves. Further, the stolons which arise on the seedling-
plant resemble at first the leaf-roots, but afterwards they branch in the
way described above.
The reasons for our regarding as leaves these organs which have such
different configuration in the terrestrial species of Utricularia are briefly as
follows :—
I. The bladders. The leaf-nature of the bladders is determined by
of these leaves arise upon the side away from the apex of the stolon, and this is a feature which is
altogether opposed to an interpretation of them as being shoots.
* We shall return to these when speaking of the cotyledons, see p. 254.
7
240 FREE-LIVING ORGANS IN PTERIDOPHYTA AND SPERMOPHYTA
comparison with Genlisea, as well as by the history of development and by
the germination, and there are occasionally forms of transition between
bladders and primary leaves!.
2. We saw that the stolons appear at different stages. We find all
transitions between foliage-leaves and stolons, for instance in Utricularia
longifolia, U. bryophila, U. coerulea, and others.
3. Leaves and stolons are alike in their position on the shoot of the
seedling, and we see, further, that stolons may also appear instead of the
prophylls of the flower and the bracts of
the inflorescence.
It is therefore evident that the way
in which the formation of organs in
these species of Utricularia has come to
pass leaves no room for doubt.
The species of Utricularia which
have been hitherto spoken about are not
found in the European Flora. In it we
only know of forms which live in water and
have long, floating, distichously-leaved
‘shoots. Comparative consideration
leads to the conclusion that these aquatic
species are derived forms in which the
shoot of the embryo does not develop ”,
whilst a stolon grows into the ‘shoot’ of
the plant and produces inflorescences,
lateral shoots, and other parts, that is to
say the same structures as we have seen
to be formed out of the leaf-roots or
Fic. 172. Adiantum Edgeworthi. Habitof leaves in the terrestrial species. The
bud-forming leaf; 4, first leaf of bud, s, arising at < ¢ E
Bie api es fae etn orn ee of Utricularia therefore
furnish us with the most striking example
of a free-living leaf, although it has entirely thrown off the features of the
ordinary leaf.
The remarkable protean organ which we find in Utricularia appears to me to
1 If we start from Genlisea and compare therewith forms, such as Polypompholyx as well as
Utricularia Hookeri, where transitions between bladders and stolons are to be found, we might come
to the conclusion that the steps of the transformation were as follows :—
1. Leafy plants with roots as in Pinguicula.
2. Parts of the leaves are formed as tubes to penetrate the soil. The roots become reduced as
useless organs.
3. The stalk of the tube is partly formed into leaf-root, with arrest of the formation of tube, as
in Utricularia Hookeri and Polypompholyx.
4. The leaf-roots become stolons which form the leaves and tubes.
In the terrestrial form it makes an inflorescence.
TRANSFORMATION OF ORGANS IN FILICINEAE 241
be connected with the relationships of nutrition of the plant. Ido not mean to
say that the manifold variations of the formation of the organ are directly conditioned
by the relationships of nutrition, but Utricularia is, by its carnivorous habit, made
independent of the substratum, and it can therefore, if the expression may be
allowed, indulge its fancy in the same way as a rich man does. ‘The fate of the
poor is just like that of the ordinary plant—to be kept strictly to the iron fate of
the requirements of life. Ona former occasion’ I said that the Podostemaceae is
a group of water-plants whose manifold configuration of vegetative organs cannot
be referred back as an adaptation, but that living as they do in places whence plant-
competitors and many animal-
enemies are excluded, they can
retain in great measure the forms
that may arise through ‘sports of
configuration.’ In Utricularia it
has not been the habitat but the
relationships of nutrition which
have given rein to the ‘sports of
configuration, and adjuvant
thereto are naturally the ‘inner’
factors, especially the prolonged
apical growth of the large leaves
of Utricularia which favoured
their further development.
Spates Fic. 173. Adiantum Edgeworthi. Origin of leaf-borne buds.
Filicineae. The trans- /Z apex of leaf seen from above; the apical cell has divided by a
: Z cross-wall ; x, position at which the first leaf of the bud arises;
formation of leaves into shoots, 4 position of origin of the lateral leaf-series whence usually in a
leaf the pinnules develop. J/, apex of leaf seen from the side;
as we find it in some ferns lettering the same. ///, apex of leaf in optical longitudinal
i aeation s, divided apical cell; 4, first leaf of the bud. TV, some-
whose leaves are characterized what older stage than ///. V, apex of leaf in longitudinal section ;
S, apex of the bud surrounded by scales; 4, first leaf looking like
cee 210th) Tiel aaguaed; Miles kghly nage
must be added to the cases
which have just been described. This transformation is by no means
infrequent. I first showed it in Adiantum Edgeworthi (Fig. 172),
where, as in some species of Aneimia, for example Aneimia rotundifolia,
also species of Asplenium and other genera, we find the upper portion
of the leaf prolonged into a flagellum, and at the end of this a new
fern-plantlet (Fig. 173). It is clear that by this elongation of the leaf the
plantlet produced upon it is widely separated from the mother-plant, in the
same way as happens in the runner of a strawberry, and in the fern the
young plantlet at the tip of the ‘ flagellum’ is, as in the strawberry, already
provided with the primordia of roots. The question now is, Does the new
plantlet really grow out of the tip of the leaf? The formation of buds upon
the leaves of ferns is a wide-spread phenomenon, and therefore we may
* See Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 227. Reinke has recently expressed
similar views regarding the interesting relations of configuration in Caulerpa.
GOEBEL II R
a
242 ORGANS IN EMBRYO OF PTERIDOPHYTA AND SPERMOPHYTA
have here as elsewhere a bud laid down zear the tip1. My investigations.
enable me to answer the question in the affirmative. The leaves of Adi-
antum Edgeworthi show at their apex a two-sided apical cell, like the leaves
of other leptosporangiate Filicineae*, and from it two rows of segments are
formed. Preparations of the tip of the leaf repeatedly showed a stage in
which this apical cell was divided by a wall at right angles to its bent side-
walls (Fig. 173, /, //), and thus two apical cells were produced, each of
which approached in form that of the three-sided pyramid as it is found in
the apical cell of the stem of many ferns, and one of them became the apical
cell of the bud arising at the tip of the leaf (Fig. 173, //7,/V, V). The.
first leaf of the bud, however, does not proceed from the new vegetative
point produced out of the tip of the leaf, but from a position near it upon
the convex side of the mother-leaf'—an unexpected phenomenon, but
one with which we can find a parallel in the formation of the embryo, and
in the apogamous origin of a fern-plant. The young plant soon forms endo-
venetically the primordium of a root and then many leaf-primordia, and so
it develops further ; as its leaves repeat the process through which it arose
there is created quite a small colony of plants through these ‘ wandering
leaves.’ It is noteworthy that the elongation of the parent-leaf into a fla-
gellum begins only after the formation of the bud. The case is analogous
with that of the roots of the Filices, in which, as we have already seen ‘*, the
transformation into a shoot may be supposed to take place, speaking theo-
retically, by the pushing up of the otherwise lateral formation of the bud to
the tip of the root; there would be here also not a zransformation but .
a terminal new formation.
LY,
CONFORMATION OF THE VEGETATIVE ORGANS
IN THE EMBRYO
MORPHOLOGICAL DIFFERENTIATION OF THE EMBRYO.
The egg is originally a simple cell. It becomes the embryo by dividing
into a cell-body. Numerous investigations during the last ten years have
made known the connexion between the arrangement of the division-walls.
1 A consideration of the matured condition gives no clue to the point of origin of the bud.
2 Seep. 3l0e
* The early inception of this leaf which precedes all those borne upon the bud itself may be
explained biologically : it is developed early because it is required to bring food-material to the
bud. An examination of the older stages (Fig. 173, V) might lead one to consider it as a continua-
tion of the leaf upon which the bud sits; it is formed, however, undoubtedly to the side of the
original leaf-tip. * See p. 228.
DIFFERENTIATION OF EMBRYO IN PTERIDOPHYTA 243
and the primordia of organs, and the differentiation of tissues. We may
well say that the results of these investigations have not been proportionate
to the trouble that has been expended upon them, in so far as only little of
general significance has come out of them. On this ground therefore
a discussion of the details will not be attempted here ; I shall only try to
state shortly some general considerations.
In the first place two cases must be distinguished :—
1. Where the whole of the cell-body which is derived from the egg
becomes devoted to the formation of the embryo.
2. Where only a portion of this cell-body is used for the embryo, another
portion serves either as the foot or the suspensor to bring the embryo into
the most favourable conditions for nutrition, and after it has done its work
dies off!. We shall discuss the relationship of the nutrition of the embryo
of the Spermophyta in a special chapter, we shall deal at present only with
the morphological features.
A. PTERIDOPHYTA.
Filicineae. One is often inclined to consider the development of
the embryo in Filicineae as ‘ typical’ of the other Pteridophyta ; it is, how-
ever, not ‘typical.’ In judging of the embryo of Filicineae one must not
forget what is, however, often neglected, namely the biological relationship.
In the prothallus there is but a small amount of reserve-material laid down
relatively to what is the case in the Ophioglossaceae and most species of
Lycopodium, and the capacity for assimilation of the prothallus cannot be
very great on account efits small size. The young fern-plant must there-
fore become independent at an early period. In correspondence with this
the several organs are differentiated from one another at an early period.
YIt is characteristic of the embryo that there arise zudependently of one
another : (1) stem-bud, (2) one cotyledon—so called because it does not
arise like the later leaves out of the stem-bud, (3) first root, and (4) foot—
a suctorial organ or haustorium, by means of which the embryo, when it has
burst through the archegonium, can absorb the food-material that is in the
prothallus, and which also serves to fix the embryo before the root has
bored into the soil. The position in the embryo where these organs are
formed may be early discerned. The embryo (see the scheme in Fig. 175, /)
divides into octants, of which one furnishes the stem-bud, two others the
cotyledon—or a third may give a second cotyledon—one the root, and the
rest are devoted to the foot, It would be an error to assume that with ¥.
the first divisions a material differentiation proceeds in the embryo. The
regular sequence of cell-division permits us only to trace relatively far back
the positions occupied /azer by the primordia of the organs. The embryo is
* Both foot and suspensor may occur in one and the same plant, for example in Selaginella.
R 2
244 ORGANS IN EMBRYO OF PTERIDOPHYTA AND SPERMOPHYTA
at first, even after formation of the octants, still composed of essentially
similar cells in which then gradually a difference in construction appears.
All Filicineae, as it appears, are alike in essentials, but in the Marattiaceae
it is difficult to trace back the single organs even to the octants, and it has
not been achieved yet in Botrychium. |
Isoetes. In this genus a vegetative point to the stem is not recog-
nizable after the differentiation of the root and the cotyledon; it only
becomes conspicuous later, and the feeble formation of leaves in the embryo-
plant is probably connected with this.
Equisetum. The development of the em-
bryo is in essentials like that of the Filicineae,
but the formation of the leaves in the embryo is
delayed. It takes place, as in some Lycopodia
which germinate underground, only to form a
protection to the apex of the shoot.
Lycopodineae. We have in this class both
monocotylous and dicotylous embryos. The former
are found in Lycopodium Selago, L. inundatum
(Fig. 140, 3), and L. cernuum, as well as in allied
forms. The latter are found in L. clavatum and
L. annotinum. The difference may perhaps be
connected with the life-relationships, as hypogeous
germ-plants require to have the apex of their stem
more protected by the formation of leaves than do
the epigeous. Selaginella (Fig. 174, B) has two
cotyledons. The embryo of Selaginella spinulosa
has no haustorium (foot) according to Bruchmann.
Fic. 174. Selaginella denti- ° °
SUES Ee glee The embryos of the Lycopodineae which have been
See ee examined, have a suspensor (Fig. 175, 7/V, Ez), and
eo recall in this the features of Spermophyta. The
reference of the organs back to single cells in
the young embryo is, in most cases, impossible here.
B. SPERMOPHYTA.
It is not my intention to review in this book the well-known facts of
embryogeny. I did this some years ago’, and there is the less necessity to
repeat here what I then said, as there is nothing fundamentally new to
add to it. I shall therefore only shortly touch upon the most important
phenomena :—
1. The embryo of the Spermophyta consists in typical cases of a root
1 Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884).
DIFFERENTIATION OF EMBRYO IN SPERMOPHYTA 245
and shoot. The shoot having one or more cotyledons is divided into the
vegetative point of the shoot, and the hypocotylous segment of the stem
prolonged into the first root. The inception of the root may take place in
some cases, for example in Gramineae, in such a way that practically there
is no hypocotylous segment of the stem.
2. These organs are laid down independently one of the other, and
the cotyledons do not arise at the vegetative point of the shoot. The vege-
tative point of the shoot is not visible in many embryos within the seed,
SSS
Fic. 175. Schemes of orientation of organs inthe embryo of Pteridophyta. In the figures: S, apex of stem; /,
and /, haustorium (foot) ; Co, cotyledon ; w, root ; Z%, suspensor ; A, archegonium ; 4, hypocotyl. / Homosporous
leptosporangiate Filicineae. Young embryo within the archegonial venter. //, Botrychium virginianum. The
whole lower portion of the embryo becomes haustorium, the stem and the root proceed from the upper half. Z/Z,
Lycopodium clavatum. ZV, Selaginella. The schemes have been constructed by the help of figures by Jeffrey in
the case of Z/, by Bruchmann for //Z, and by Pfeffer for 7V.
nor is it yet visible in the formation of the first leaves in many of the
Monocotyledones ?.
3. The differentiation of the organs may at most in some cases be
carried back to definite cell-divisions in the embryo, but here we must
remember what I have already said regarding the Filicineae that the actual
separation of the organs begins only late, even although the arrangement of
the cells allows of the fosz¢ion upon the embryo where they will arise being
recognized at an early period. ‘We know no more than this, that one
portion of the embryo which is turned to the micropyle will become the
* We may, as I have already said (Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in
Schenk’s Handbuch der Botanik, iii (1884)), consider it indeed as existing, and of a few cells not
visible externally. The necessity, however, of such an assumption does not seem to exist. See p. 235.
ee
246 ORGANS IN EMBRYO OF PTERIDOPHYTA AND SPERMOPHYTA
root, whilst the cotyledons in the Dicotyledones and the Gymnospermae are
lateral sproutings of the embryo, and in Monocotyledones the cotyledon is
apical, although not always so!. This tallies with what I have so often
said, that a differentiation of the primarily similar cells of the embryo takes
place only gradually.
ORIENTATION OF THE ORGANS IN THE EMBRVO.
The arrangement of the organs in the embryo, especially the relation-
ships in space of the root, the cotyledon or cotyledons, and apex of the
shoot are not the same in all vascular plants. The question what causes,
external or internal, determine these positions, has often been asked, but
not so far as I can see, the question of how far the arrangements stand in
connexion with the relationships of life. In the first part of this book
I have explained “that external forces do not come into consideration in the
arrangement in space of the parts of the embryos, therefore we have here
only to consider zzzerzal factors, and we may say generally, root, shoot, and
haustorium are laid down in the positions that are the most beneficial for
their function. |!
A. PTERIDOPHYTA.
Amongst the Pteridophyta we have to consider separately the forms in
which there is no suspensor in the embryo, and the forms in which one
exists. When the suspensor is developed there is in consequence of it a
polar differentiation, and the end of the embryo which is turned away from
the suspensor is the shoot-pole.
(z) FORMS WITHOUT A SUSPENSOR, Filicineae. A scheme of the
lie of the parts in the embryo of Filicineae is given in Fig. 175, J.
We find the following organs :—primordium of the vegetative point
of the shoot, S, the haustorium, 7, the cotyledon, Co, the root, W. The
archegonium in which the embryo is formed, stands upon the under
side of the prothallus: it is clear then that the haustorium, /, which
takes the nutrition from the prothallus, must be turned towards the
prothallus ; the root, W, will most easily pierce the venter of the arche-
gonium when it lies towards the downwardly directed side of the embryo ;
the vegetative point of the stem, S, if it were not already upon the upper
side, must reach this position by curvature; the cotyledon, Co, aids in the
breaking through of the accrescent venter and adjacent tissue of the arche-
gonium, and therefore its position must be over against the root. How in
1 Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), p. 171. 2 See Part I, p. 219.
EMBRYOS IN PTERIDOPHYTA 247
the horizontal floating megaspores of the Marsiliaceae these positions are
reached by the ‘torsion’ of the first division-walls of the embryo has been
explained before’. If we compare now the formation of the embryo of
Botrychium? (Fig. 175, //), we find that in it the shoot and root both
proceed from the upper part of the embryo. Were the root to originate
below in this case, it must either undergo curving, or pierce through the
tuberous body of the prothallus.
Isoetes. In Isoetes, whose megaspore germinates, not in the hori-
zontal, but in the upright position, that is to say with the neck of the
archegonium upwards, the root and shoot are laid down in the upper part of
the embryo as in Botrychium.
(0) FORMS WITH A SUSPENSOR. Lycopodium. Lycopodium clavatum
(Fig. 175, 7/7) and L. annotinum *
may be taken as examples. The
embryo is provided with a suspensor,
£t, which gives it therefore a polar
differentiation. The suspensor sub-
mits at an early period to a curvature
which brings the apex of the embryo
upwards (see also Selaginella). In
an old embryo we find on the lower
side a massive haustorium, /, around
which lies the nutritive material. On
the upper side we find the apex of
the stem, S, and laterally the root, W.
The bud of the stem, which must
rise up out of the earth, is here
- covered by the primordia of many Fic. 176. Selaginella Martensii. Female pro-
thallus, 4, projecting from the ruptured wall, sfvz, of
: = the megaspore ; av, sterile archegonium ; ¢7725,, evtbo,
leaves. The inception of the root two em 03 embedded in the tissue of the prothallus ;
ef, ef, suspensors. Magnified 124. Adjusted after
takes place relatively late, because phe. Lenrb.
the tuberous prothallus which is rich
in reserve-material permits of the embryo remaining independent for a
relatively long time.
Selaginella. Fig. 175, /I’, shows a germ-plant which has broken
through the thick wall of the megaspore surrounding the prothallus, both
by its hypocotylous segment, //, and by its root, JV. This has taken place
at the position where the thick episporium has been ruptured by the pro-
thallus. The arrangement resembles somewhat that of Isoetes, but is
*spee Part I, p. 220.
? See Jeffrey, The Gametophyte of Botrychium virginianum, Studies from the University of Toronto,
Biological Series, 1898.
* See Bruchmann, Uber die Prothallien und die Keimpflanzen mehrerer europaischer Lycopodien,
Gotha, 1898.
7
248 ORGANS IN EMBRYO OF PTERIDOPHYTA AND SPERMOPHYTA
brought about really in quite a different way. As Fig. 176 shows, the
embryo is pushed into the prothallus by the suspensor, e¢. The apex of
the embryo forms the shoot-portion which curves, evzb,, so that the point at
which the thick megaspore, sf, is ruptured, is reached. The root, W (Fig.
175, 7V), is laid down relatively late when the embryo is already bent at
nearly a right angle to the suspensor, and then in such a way that it at once
is in the most favourable position for reaching the ruptured portion of the
wall of the megaspore, that is to say, it is laid down in a nearly horizontal
position. Selaginella is also of interest, inasmuch as in it the root, at least
subsequently, falls fairly accurately in the long axis of the hypocotylous
segment of the stem! (Fig. 174, 2), a feature in which it differs from all
other Pteridophyta, and which gives it a striking resemblance in habit to
the seedling of the Dicotyledones.
B. SPERMOPHYTA.
In this group the polar differentiation of the embryo is established
from the beginning, as it is in the Lycopodineae, because the fertilized egg
is fixed in the embryo-sac on one side and usually by a suspensor”. The
end of the embryo-sac to which the embryo is fixed, is that next the
micropyle, and the side turned away from this becomes the shoot-pole of the
embryo. The root arises on the micropylar side. This is of advantage,
as in most Spermophyta the root (including the hypocotyl) passes out
through the micropyle. Water is necessary for this, and the micropyle
serves as one of the points of the seed-coat through which the entrance of
water can be most rapidly effected. The arrangements for the nutrition of
the embryo in the seed will, as I have said, be discussed along with the
details of the formation of the seed, in this place I shall only describe the
configuration of the embryo in the seed.
In the Pteridophyta the development of the fertilized egg proceeds
uninterruptedly ; there is no resting period interposed. But in the Spermo-
phyta the embryo, with only a few exceptions, which will be presently men-
tioned, experiences either sooner or later an interruption of its development
which is only resumed in germination. The degree of development which the
embryo has attained at the moment when the seed is ripe varies, and has
relation both to the amount of differentiation, that is to say, to the kind
and number of the organs in general, and to the transformations which
are associated with the deposition of the reserve-material in the embryo.
I. DIFFERENTIATION OF THE EMBRYO.
A ‘normal’ embryo consists of root and shoot, the shoot exhibiting
It is really laid down laterally. 2 See Part I, p. 220, footnote.
INCOMPLETE EMBRYOS IN SPERMOPHYTA 249
a cotyledon or cotyledons, an axis, and a vegetative point upon which
there may often be found primordia of leaves. In this form the embryo
is ready for germination. But deviations from this naturally raise the
question—Why should these be?
I. Incomplete Embryos. In a number of plants the embryo is an
undifferentiated cell-mass at the moment when the seed falls from the mother-
- plant. We must regard it in this state as a retarded formation, and it is
correspondingly small. We may recognize two groups amongst these
incomplete embryos :—
1. That in which the retardation lasts for a relatively short time and
the embryo develops further in the seed after its fall. ‘We have here a kind
of after-ripening such as takes place when seeds are artificially plucked
from the mother-plant.
2. That in which the incomplete formation of the embryo persists
during the whole period of quiescence of the seed up to the moment of
germination. To this group belong a number of saprophytes and parasites,
as well as a number of other plants.
(a) Embryos temporarily retarded within the seed. In order that we
may see how far this is a biological group we must consider a number of
individual cases :—
A. DICOTYLEDONES.
=e, hyemalis. Baillon' has briefly said regarding this embryo ‘it has
long been known that the mature seeds do not contain an embryo.’ How then
does the plant maintain itself? That no visible embryo exists in a ripe seed is,
however, improbable, and as a matter of fact the embryo in the ripe seed of
Eranthis hyemalis -is a cell-mass like that which we know in other Ranunculaceae
and elsewhere amongst dicotylous plants at the stage of development preceding
the laying down of the cotyledons; that is to say, the embryo is no longer
quite spherical but somewhat flattened at its anterior end. It is so small that it
may be easily overlooked in a casual examination.
Ranunculus Ficaria. Ranunculus Ficaria behaves in exactly the same
manner. It would be superfluous to describe here the embryo of this plant, for
this has been already so well done by Hofmeister* and Hegelmaier*. Hofmeister
says that the embryo in the matured seed has a spherical form, whilst Hegelmaier
states that it is arrested in the stage preceding the laying down of the cotyledons.
* Baillon, Sur l’embryon et la germination des graines de l’Eranthis hiemalis, in Bulletin de la
Société Linnéenne de Paris, No. 2, séance du 3 juin 1874, p. 14.
* Hofmeister, Neuere Beobachtungen iiber Embryobildung der Phanerogamen, in Pringsheim’s
Jahrbiicher, i (1858), p. 83.
* Hegelmaier, Vergleichende Untersuchung iiber Entwicklung dikotyledoner Keime, Stuttgart,
1878.
250 ORGANS IN EMBRYO OF PTERIDOPHYTA AND SPERMOPHYTA
He did not succeed in causing seeds to develop further in a chamber, but this
takes place not infrequently in nature’.
Anemone. The features exhibited in the genus Anemone? are interesting.
The embryo is sometimes dicotylous, sometimes acotylous, as in the sections
Sylvia and Hepatica. The size and degree of development of the embryo varies
even in one and the same plant. In Anemone trifolia the cotyledons are occa-
sionally developed ; usually the embryo is a spherical unsegmented body, as for
example in Anemone nemorosa, A. ranunculoides, and A. Hepatica ; the Pulsatilleae
have a small dicotylous embryo. Germination takes place in them only in the
year following the formation of seed, although the root breaks through the pericarp
commonly in the autumn of the preceding year.
Fumariaceae. In Corydalis cava* and C. solida* it is known® that the
embryo which is only a small undifferentiated cell-body in the seed at the time of
its fall develops further in the course of the summer and autumn, and when
germination takes place the seedling bears, as in the case of Ranunculus Ficaria
and Anemone apennina ", only one cotyledon.
Stylidiaceae. The species of Stylidium“ which have been examined have an
undifferentiated embryo without any indication of cotyledons and root.
B. MONOCOTYLEDONES.
That an undifferentiated embryo without any indication of cotyledons
and root may occur in Monocotyledones was pointed out fifty years ago
by Hofmeister *, but his observation appears to have been overlooked.
Speaking of
Gagea arvensis he says :—‘’The embryo forms an ovoid cell-mass. When its
formation has proceeded so far that it shows in the direction of its longitudinal
axis twenty-four cells and in its small axis twelve cells, the walls of the cells of the
endosperm which for some time have closely invested it . . . begin to show a
thickening, the cells of the embryo become filled with granular material and lose
sap—the period of ripening of the seed is entered upon. Gagea therefore furnishes
‘ See Irmisch, Beitrage zur vergleichenden Morphologie der Pflanzen: I. Ranunculus Ficaria,
Halle, 1854. .
* Janczewski, Etudes morphologiques sur le genre Anemone, in Revue de Botanique, iv (1892),
p. 241.
* Bischoff, Beobachtungen iiber den eigenthiimlichen Gang des Keimens und der Entwicklung der
Knollen bei Corydalis-Arten, in Tiedemann et Treviranus, Zeitschrift fiir Physiologie, iv (1831).
Bischoff could not find an embryo in the ripe seed, it only became evident towards the end of August.
* Irmisch, Uber einige Fumariaceen, in Abhandlungen der naturforschenden Gesellschaft zu
Halle, iv (1860); Hegelmaier, Vergleichende Untersuchungen iiber Entwicklung dikotyledoner
Keime, Stuttgart, 1878.
* Hofmeister, Neuere Beobachtungen iiber Embryobildung der Phanerogamen, in Pringsheim’s
Jahrbiicher, i (1858), p. 83.
° See Janczewski, op. cit., p. 296.
” Burns, Beitrage zur Kenntniss der Stylidiaceen, in Flora, 1xxxvii (1900), p. 354.
* Hofmeister, Die Entstehung des Embryo der Phanerogamen, Leipzig, 1849, p. 43.
INCOMPLETE EMBRYOS IN SPERMOPHYTA 251
the interesting example of a plant of which we can scarcely say that it is nourished
only from organic material ... and whose embryo—like that of Orchis although
composed of more cells, not to mention the embryo of Monotropa which is never
more than 1/100” in diameter—consists of a homogeneous cell-mass and at the
period of ripening of the seed possesses none of the vegetative organs (terminal
bud, rootlet, and cotyledon) which we meet with in the majority of Phanerogams.’
The seeds of Gagea lutea which I examined ripened at the end of May, at which
time the leaves had passed out of the condition of active life. The embryo to
which the upper portion of the suspensor is attached is an ovoid body, which in
one carefully examined case had a length of 0-26 mm. and a breadth of 0-17 mm.
In its lower third a shallow pit was visible marking the position of the vegetative
point of the shoot or that of the very slightly conspicuous cotylar sheath. The
formation of the root was scarcely visible. The embryo was altogether more
differentiated than was to be expected after Hofmeister’s statement, but it was still
incomplete. I did not examine into the question of when its further development
began.
Of other Monocotyledones I may mention :—
Paris quadrifolia. The embryo of this plant is figured by Gaertner as
a small undifferentiated body, but at germination it is normally developed.
Erythronium Dens-canis. The embryo of Erythronium Dens-canis is said
by Irmisch? to be a spherical body pointed at the root-end.
Hymenocallis speciosa. A. Braun” describes the embryo of the amarylli-
daceous Hymenocallis speciosa as spherical and scarcely a third of a millimeter in
diameter.
Crocus vernus. In Crocus vernus I found complete embryos, and in the
cotylar pit was developed the primordium of a second leaf.
Scilla sibirica. Scilla sibirica has an embryo which is further developed
than that of Gagea, and possesses a deeper pit of the cotylar sheath.
There are, as will be seen, all stages of transition from complete to incomplete
embryos, and in the former before the germination a further development of the
organs that are laid down is initiated.
C. GYMNOSPERMAE.
I will only mention here the cases of Ginkgo biloba and Gnetum.
Ginkgo biloba. In Ginkgo fertilization, and consequently the development
of the embryo, takes place in fallen seeds.
Gnetum Gnemon. In Gnetum Gnemon* the primordium of the embryo has
been formed at the time when the seed falls, but it only develops further at a later
period.
‘ Irmisch, Beitrige zur vergleichenden Morphologie der Pflanzen: IV. 2. Erythronium Dens-canis,
Halle, 1863.
2 A. Braun, Uber Polyembryonie und Keimung von Coelebogyne, in Archiv der Berliner
Akademie, 1860, p. 172.
$ Lotsy, Contributions to the life-history of Gnetum Gnemon, in Annales du Jardin botanique de
Buitenzorg, xvi (1899), p. 46. Literature is cited in this paper.
-
252 ORGANS IN EMBRYO OF PTERIDOPHYTA AND SPERMOPHYTA
I mention these two cases here but remark at the same time that I would
urge care in the consideration of what is said regarding them, because the proper
relationships of the formation of the embryo to the life-conditions can only be
obtained in the natural home of the plants.
From the examples which have been cited it may be gathered that the
behaviour of the embryos of which I am speaking is no exceptional one.
About the cawses which bring it about we know really nothing, although
various conjectures may be advanced. The most evident is that the
optimum of temperature for the development of the embryo is higher than
that for the formation of endosperm, and that between the two there is
a consequent correlation. One might also suggest that there was some
correlation in the relationship between the formation of seeds and the de-
position of reserve-material in tubers, bulbs, and rhizomes, and this has been
established in some plants’. But as the seeds are provided in the endo-
sperm with all the necessary material which is subsequently required
for the complete formation of the embryo such a relationship is less
probable.
Another question that arises is, Can we give a dzological explanation of
this embryogeny ?
I have elsewhere * pointed out that perhaps a relationship to external
factors may be recognized. Most of the plants exhibiting the features in
question are ‘ spring-plants which have but a short period of development *,
and this occurs at a time when very few plants are strongly developed and
the foliation of the trees in the wood is not yet thick ; it therefore must
give them an advantage over other plants. Teleologically considered it is
of importance for them that the duration of the development of seed upon
the mother-plant should also be shortened. The mother-plant provides
the seed indeed with endosperm, but the further development which usually
goes on upon the mother-plant during a long period takes place here in the
seed after it has fallen.2 That the slow development of such seeds with
incomplete embryos brings it about that they germinate only at a late
period, and at a time which falls in with the normal period of development
of the plant, favours their obtaining proper conditions for germination
and must not be overlooked*. The seeds of Eranthis, for example,
always germinate, favourable conditions being supposed, in February or
' See the literature cited in Part I, on p. 213.
? Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 118.
’ Spring plants which vegetate far into the summer, like Chrysosplenium alternifolium, Symphytum
bulbosum, Pulmonaria, and others, and form also their seeds slowly, have complete embryos so far
as I know.
* Haberlandt, Schutzeinrichtung der Keimpflanzen, Wien, 1877, p. 50, expresses himself in a like
sense regarding Eranthis.
-
INCOMPLETE EMBEYOS TIN) SPERMOPHYTA 253
March, and therefore it must happen that the stage of development in which
they are capable of germination is reached only after sowing and during the
process of ripening of the seed. The like may be said of the species of
Anemone, the complete embryos of which germinate after some weeks, but
the incomplete ones only in the spring after sowing. I think, however, that
the shortening of the development in relation to evolution of the plant in
spring is the more important. On the one hand we see in not a few plants
that the development of the embryo takes more time really than does that
of the endosperm. On the other hand it is questionable if any injury would
accrue to a plant of Hepatica or of Leucojum if its seeds, in this case
provided with complete embryos, were to germinate in the summer after
their formation.
The Stylidiaceae also have only a short vegetation period before the
dry period in which they rest, and perhaps in other plants of their habitat
and other physiologically analogous districts similar relationships might
be found.
(2) Embryos incomplete up to the Time of Germination.—In this
category we include a number of plants which so far as I can see possess
only one common biological character—they have small seeds :—
Juncus glaucus. Juncus glaucus and perhaps other species of the genus
are illustrations’. Embryos removed by pressure from the ripe seeds show that
the stage of development reached by them, especially with regard to the primordium
of the root, is not the same in every case. The cotylar end is easily distinguished
by its larger cells and greater thickness from the other. A definitely limited
vegetative point of the shoot is not visible, yet the embryo which has already
reached its full length is more developed than is that of most of the Orchideae.
Orchideae. Amongst our endemic Orchideae the embryo is an ovoid cell-mass
in which there is no differentiation of cotyledon, of bud of the stem, or of root, and
the meristem is only present to this extent that a layer of dermatogen which is not
always sharply limited covers the embryo. On the other hand Treub has found
in Sobralia macrantha both the cotyledon and the bud of the stem at least indicated
in the embryo. The primordium of a chief root is never found in the embryo nor
does it appear even in germination’, the lower portion of the embryo which is not
differentiated into hypocotyl and root swells up into a tuber and becomes fastened
to the soil by a number of root-hairs, whilst from the apical part the cotyledon
proceeds. Epiphytic Orchideae which have been examined show like features,
and divergent statements regarding the vegetation of terrestrial Orchideae appear
to me to be untrustworthy, because when the apical cotyledon is relatively small
* Cladium Mariscus behaves in an analogous way, see Didrichsen, Om Cyperaceerns Kim, ii, in
Botanisk Tidsskrift, xxi (1897-8). Schoenus nigricans has a similar embryo.
2 See p. 232.
254 ORGANS IN EMBRYO OF PTERIDOPHYTA AND SPERMOPHYTA
and the lower end of the embryo large and swollen, the appearance may readily
suggest that the origin of the bud of the stem is terminal, as has been often
asserted. The embryo of the Orchideae is then to be regarded as a simple
retarded form of the ordinary monocotylous embryo whose apical portion develops
subsequently into the cotyledon.
Dicotylous saprophytes. Most of the Orchideae are humus-plants, and it is
noteworthy that dicotylous saprophytes, such as the Pyrolaceae, the gentianaceous
Voyria, and others, show a reduction of the embryo like that of the Orchideae.
In Monotropa the embryo has but nine cells'. The germination of the seeds of
these dicotylous saprophytes is unknown. It takes place only in the presence of
very special surroundings. Probably the fungi which are found in the roots in
symbiosis are essential. The smallness of the seeds allows of a large number
being formed, and thus the probability that one of the seeds at least will reach
favourable conditions for germination is increased.
Parasites. Many parasites show exactly the same condition. Incompleteness
in the construction of the embryo is not necessarily associated with parasitism.
The mistletoe, which is a chlorophyllous parasite, develops a large and well-
constructed embryo, and the same is true of Lathraea which has no chlorophyil.
In the parasitic Cuscuta the embryo is not only somewhat large and long, but the
chief root is incompletely formed. It wants a certain portion of the tip of the root
together with the root-cap, so that it appears as if it were unclosed. It does not
require a greater differentiation, as in germination it functions for a short time only
until the embryo-plant has been able to reach the host on which it fastens itself
by means of its haustoria. The root then dies along with the whole lower portion
of the embryo-plant, and the plant then becomes entirely parasitic upon the host. The
embryo of Orobanche’ is even less formed. It is laid down like an ordinary
dicotylous embryo, but it remains stationary at an early stage of development, and
is represented in the ripe seed by an undifferentiated cell-mass. The same is true
of other parasites, such as those of the Balanophoreae and Rafflesiaceae.
Utricularia. Of non-saprophytic plants Utricularia has yet to be mentioned.
The connexion of the differentiation of the embryo in this genus with the relationships
of life of the plants is still unknown. We only know that the equipment of the embryo
in the ripe seed is strikingly different in the different species. Utricularia reniformis *
and U. Humboldti have green leaf-organs developed within the seed, and the embryo
appears to pass through no period of rest in the seed and approaches in that way
the case of the viviparous plants which are mentioned below. The other extreme
is shown by, for instance, Utricularia montana, the embryo of which has no leaf-
primordia within the seed. In others again, like Utricularia orbiculata*, these
leaf-primordia are in the form of very small papillae which develop further in
* Koch, Die Entwicklung des Samens von Monotropa Hypopitys, Linn., in Pringsheim’s Jahr-
biicher, xiii (1882).
* Koch, Uber die Entwicklung des Samens der Orobanchen, in Pringsheim’s Jahrbiicher, xi
(1878).
$ Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 142.
* Goebel, op. cit., p. 146.
,
EMBRYOS OF VIVIPAROUS PLANTS 255
germination, and the embryo resembles so far that of other dicotylous plants in
having only two such papillae ; in some of the aquatic species of Utricularia a large
number of these papillae appear. Utricularia amongst Dicotyledones exhibits
this exceptional feature in its embryo that the cotyledons, if one may speak of
them by this name, differ from the primary leaves only by their position.
II. Embryos of Viviparous Plants!. In those plants which have
been designated viviparous the relationship between the differentiation
which the embryo attains to within the seed and the external conditions of
Fic. 177. Cryptocoryne ciliata. Development ot the seed. 1, ovule with young embryo in longitudinal
section. The outer integument has formed a spongy body, the embryo is still within the embryo-sac which is
shaded in the figure. 2, an older stage of the same. The embryo has now issued from the inner integument by
its root, w, and the vegetative point, v7; /e, outer integument. 3, somewhat older stage similarly seen. 4, seed
in transverse section. The embryo has many leaves.
life is very clear. Strictly speaking we understand by viviparous plants
only those in which the embryo germinates without any period of rest,
and indeed within the fruit as it is attached to the mother-plant :—
Mangroves. This is the case in mangroves, especially species of the genus
Rhizophora, Bruguiera, and Ceriops. The embryo of these Rhizophoreae is
* See Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 113, where the older literature is cited.
Karsten, Uber die Mangrove-Vegetation im malayischen Archipel, in Bibliotheca botanica, xxii (1891),
gives the result of a thorough investigation of the subject.
256 ORGANS IN EMBRYO OF PTERIDOPHYTA AND SPERMOPHYTA
distinguished by the great development of a club-like or pole-like hypocotyl,
reaching in many a length of over half a meter, whilst the embryo is still attached
to the mother-plant. The cotyledons serve only as haustoria, absorbing for the
embryo the plastic material supplied by the mother-plant. The embryo acquires
by its configuration the capacity of fastening itself into the muddy substratum
more rapidly than it could do were it to grow in this from the first, and, as
Karsten rightly says’, this is of special importance for plants of relatively slow
development. Seeds of the species of mangrove which are marked by rapid de-
velopment, for example Sonneratia acida, do not show vivipary, and the rapid
development is favoured by the rich deposit of reserve-material®. The seedling of
the mangrove falls with the tip of the root foremost into the mud %, and there roots
Fic. 178. Cryptocoryne ciliata. Figure to the left: seed, not quite ripe, in longitudinal section. The
cotyledon, C, of the embryo lies within the embryo-sac, the primary root, W, and the bud of the stem have developed
outside it ; /e, outer integument; /2, inner integument. Figure tothe right: older embryo which has broken off
from the cotyledon; C, point of attachment of cotyledon; VW root.
very rapidly by means of a root-system, which spreads out laterally in accordance
with the requirements of the environment, and does not produce a chief root.
Avicennia forms, as it were, the transition amongst mangroves to the viviparous
plants in which the fruit-wall is not bored through on the mother-plant; its
seedlings are set loose, sometimes invested by the fruit-wall, at other times without
it. They have stiff upwardly curved hairs upon their hypocotyl, and these serve
for the first fixation in the mud. The embryos of Aegiceras grow out of the
seed within the curved horn-like fruit, and fill the internal cavity of the fruit with
their large hypocotyl *.
Cryptocoryne ciliata. Amongst Monocotyledones analogous phenomena
' Karsten, Uber die Mangrove-Vegetation im malayischen Archipel, in Bibliotheca botanica, xxii
(1891), p. 38.
* Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 135.
* Many also reach the water by which they are carried away and some of them may develop later.
* Goebel, op. cit., Plate V ; Karsten, op. cit.
EMBRYOS OF SPERMOPHYTA WITH RESERVE-FOOD 257
are observable, for example in Cryptocoryne’, leaving out of consideration Crinum.
The ovule of this aroid has two integuments, of which the outer grows, after
fertilization has been affected, into a spongy mass of tissue (Fig. 177, 1, 2); and
the further development of the embryo takes place in it. The under part of the
embryo, that is to say bud of the stem, hypocotyl, and root, grows out of the inner
integument, and only the cotyledon remains as a haustorium in the endosperm
(Fig. 178). The bud of the stem grows into a large body that produces many
leaves, and is invested by only an extremely thin seed-coat ; the embryo separates
itself readily from the cotyledon (Fig. 178, to the right), and is now rapidly
equipped for further development.
Vivipary in its different states is, as I have before now endeavoured to
show, only a special form of the widely spread feature observable in the
inhabitants of moist localities of the germ proceeding to further develop-
ment without a resting period. We have seen this in the Hepaticae, whose
spores germinate even within the sporangium?”, and in the two analogous
cases of the Musci*. Also in the Filicineae, which inhabit moist localities,
the spores are arranged for continuous germination and, as in the Hymeno-
phyllaceae, the first stages of germination may take place partly within the
sporangium ; on the other hand spores of the inhabitants of dry regions have
always a resting period. The nutrition of the embryo of viviparous plants
is facilitated from the side of the mother-plant by the presence of water.
The peculiar form which the hypocotyl of the Rhizophoreae possesses, the
arrangements for anchoring of the embryos of Avicennia and others, are, as
we have seen, special adaptations to locality, and particularly for securing
rapid fixation in the substratum.
2. CHANGE OF CONFIGURATION OF THE EMBRYO THROUGH THE
DEPOSITION OF RESERVE-MATERIAL.
Characteristic changes take place in the embryo when large masses of
material are stored up in it during the resting of the seed.
A. DICOTYLEDONES,
In dicotylous plants the storage takes place commonly ix the cotyledons,
and the massive development of these relatively to the construction of the
root and shoot is well known in the Papilionaceae, Cupuliferae, and other
families. Both cotyledons are commonly used for the storage, but in Trapa*
only one is so used, and it swells up to a considerable size, whilst the other
remains small. It is of interest to notice that this difference is expressed
too in the inception of the two cotyledons®. The larger one arises as a
* See Goebel, Morphologische und biologische Bemerkungen: 5. Cryptocoryne, eine ‘lebendig
gebarende’ Aroidee, in Flora, Ixxxiii (1897), p. 426.
* See pp. 106, 108. 3 See p. 124.
* See Goebel, Pflanzenbiologische Schilderungen, ii (1893), Plate XXIV.
® See Gibelli e Ferrero, Ricerche di anatomia e di morfologia. Intorno allo sviluppo dell’ ovoloe
seme della Trapa natans, in Malpighia, v (1891), p. 156.
GOEBEL II S
258 ORGANS IN EMBRYO OF PTERIDOPHYTA AND SPERMOPHYTA
terminal structure upon the embryo; the smaller is lateral to the stem-bud.
As I have previously said!, I can only see in this the expression of the
fact that an organ that is earlier used is also earlier laid down—and in this
case also in another position—than is one that remains rudimentary.
In many dicotylous plants the hypocotyl is also used for the storage of
reserve-material, and in such cases the cotyledons may remain so small that
in some cases they appear almost to be wanting. I may quote some
examples, but without mentioning species of Utricularia, which might have
been quoted as illustrations, as I have spoken of them elsewhere.
Our first example is from the family of the Guttiferae :—
Xanthochymus pictorius.
In Fig. 179 the configuration of
the embryo and the germina-
tion of Xanthochymus picto-
rius, Roxb., is illustrated”. The
longitudinal section (Fig. 179,
II) shows the two very small
cotyledons, Co, but upon the
surface-view (Fig. 179, III) they
are more conspicuous. They
do not appear right at the point
of the embryo but are pushed
to the side by an outgrowth
(Fig. 179, I, II, a) of the hypo-
cotyl?, which in germina-
tion rises above the ground
and becomes green but dries
up later. The primordium of
FiG. 179. Xanthochymus pictorius, Roxb. I, seedling; the
shoot directed upwards has produced a pair of foliage-leaves the root is small but develops
after some scale-leaves ; Z, tuberous hypocotyl; a, outgrowth from . . :
hypocotyl; 7, primaryroot; 71, adventitious root. II, embryo further in germination. The
isolated from a ripe seed and in longitudinal section; Co, cotyle- S : °
dons ; 4, hypocotyl; @, outgrowth from hypocotyl becoming sub- Primary root is surpassed in
sequently epigeous and green. III, embryo isolated, the two
cotyledons, Co, in surface view. IV, upper part of embryo in 1S development by an adven-
longitudinal section, not quite median; Co, cotyledons. I, one- Bes
third natural size. II, two-thirds natural size. titious root formed at the base
of the shoot of the embryo, and
this elongates with the elongation of the shoot of the seedling and gives
origin to the permanent root-system. In this way a more direct and
* Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 374.
* See Planchon et Triana, Mémoire sur la famille des Guttiféres, in Annales des sciences naturelles,
sér. 4, xvi (1861). The older literature will be found in this paper.
* This appears even more strikingly in the Lecythidaceae. See the figure of the seedling of
Eschweilera obtecta given by Miers, On the Lecythidaceae, in Transactions of the Linnaean Society,
xxx (1875), where the axis of the shoot springs evidently out of the middle of the side of the
hypocotyl.
—"
EMBRYOS OF SPERMOPHYTA WITH RESERVE-FOOD 259
more simple connexion of the shoot with the soil is established than
would be the case if the path of transport through the hypocotyl, which
serves as a reservoir of food-material and which is later pushed aside, were
to persist.
In the family of the Lecythidaceae there are relationships which are
analogous with those of the Guttiferae, and the following are illustrations :—
Col
Fic. 180. Bertholletia excelsa. 7, embryo in longitudinal section ; Co/, cotyledons; w, root-end. J/, apical
portion of an embryo in longitudinal section. The cotyledons are still cavered by a thin layer of endosperm.
/T/, the overlapping cotyledons seen from above. Z magnified 3}. JZ and ///, more highly magnified.
Barringtonia Vriesei. Treub has investigated carefully the forms of
the embryo in Barringtonia Vriesei!. Barringtonia differs in its embryo
from Xanthochymus chiefly in this, that not only is the hypocoty] thick and
fleshy but also its continuation upwards, which is, however, elongated in
germination. This portion of the axis of the shoot bears some irregularly
placed scales?, the lowermost two of which are not opposite one another, so
' Treub, Notes sur l’embryon, le sac embryonnaire et l’ovule: 5. L’embryon du Barringtonia
Vriesei, T. et B., in Annales du Jardin botanique de Buitenzorg, iv (1884), p. Ior.
® TI have found in another species of Barringtonia axillary shoots to these scales when the end of
the shoot of the embryo was injured,
$2
260 ORGANS IN EMBRYO OF PTERIDOPHYTA AND SPERMOPHYTA
that we could scarcely call them cotyledons; they are neither by their
position nor in other respects different from the other scales. According to
Treub the chief root does not develop. As in Xanthochymus the reserve-
food-material is deposited in the strongly swollen central portion of the axis
of the shoot of the embryo-plant.
Bertholletia excelsa. The embryo of Bertholletia excelsa is ‘ undiffe-
rentiated, according to the most recent observations upon the Lecythidaceae},
and this probably means the same as the description of that of Lecythis,
of which it is said that it consists only of stem, that is to say it is a leafless
body whose vegetative point only later elongates into the axis of a shoot.
Investigation of the embryo shows, however, that it pos-
sesses primordia of leaves which cover the vegetative
point. They are indeed very small and have hitherto
been overlooked, but in the longitudinal section they are
clear enough (Fig. 180)”. There are two small scales
(Coz, Fig. 180, 7) which closely cover the vegetative point
_\y of the embryo ; whether they are placed directly opposite
one another or not I cannot say. Other primordia of leaves
were not found, apart from small papillae at the vegetative
NYS
WY
Yy i} point. The massive hypocotyl stores the food-material
Y, I in the pith which is separated from the rind by a tissue *
Yy 3 which is composed of small elongated cells in which
if ff, conducting bundles are subsequently differentiated. The
q If } primordium of the root, W, is but little developed but
Ur Us
/ is recognizable by the arrangement of the cells according
to the figures. It develops afterwards in germination
into a chief root.
In the embryos which have been mentioned there
a ano ce oe exists a relationship, a correlation, between the small de-
Mhoge so’ Magnited velopment of the cotyledons and the massive develop-
ment of the hypocotyl, a relation which appears also
in many Cacteae*, whose hypocotyl is specially developed as a seat of
water-storage.
Ss
B. MONOCOTYLEDONES.
The deposition of reserve-material in the embryos of monocotylous
plants is marked in those forms which have macropodous embryos :—
Zannicheilia. Amongst them we have specially the Potamogetonaceae, and
1 See Niedenzu, Lecythidaceae, in Engler und Prantl, Die natiirlichen Pflanzenfamilien, iii, 7
(1892).
* The embryo lies in a thin layer of endosperm two cells thick.
* The limit is indicated in the figure by the line running parallel with the contour line.
* Goebel, Pflanzenbiologische Schilderungen, i (1889).
MACROPODOUS EMBRYOS OF MONOCOTYLEDONES 261
of these Zannichellia shows a thickened hypocotyi at the end of which the
primordium of the chief root is commonly visible.
Posidonia. fig. 181 shows another case in the embryo of a Posidonia, whose
fruit I have found in quantity on the shores of West Australia. The lower end of
the massive swollen hypocotyl does not develop a root; the root is a lateral one at
the base of the cotyledon (WV, Fig. 181). One would be inclined to consider it as
an adventitious root, and that the chief root was wanting, but it is much more prob-
able that the chief root has been pushed aside by a lateral growth of the hypocotyl.
Bornet’s account of the history of development of the embryo of Phucagrostis,
and the behaviour of Zostera which I have described below, support this view.
Ruppia. The question which arose in connexion with Posidonia recurs in
Ruppia* where, according to Wille, the primordium of the chief root is indicated
at the lower end of the hypocotyl by a few cell-divisions, whilst at the base of the
cotyledonary sheath there is
laid down at a later period a
lateral root which Ascherson ?
held to be the chief root shoved
to one side.
Zostera. ‘hat lateral out-
growths of the hypocotyl ® occur
in macropodous embryos is
shown in the remarkable con-
struction of the embryo in the
genus Zostera. Here the portion
of the embryo which exhibits
further development in germi-
nation apparently springs out Fic. 182. {Zostera marina. I, fruit in transverse section. LI,
young embryo i in optical longitudinal section. The arrow indicates
of a shield-like body which _ the duection in which the apex of the embryo is displaced. III,
older but not mature embryo in profile. IV, embryo seen from in
is folded in the fruit and en- front. In all figures; Co, cotyledon; Ay hypocotyl ; M mantle-like
outgrowth of pee cele Zt, unicellular vesicular suspensor.
closes the upper portion of the
embryo (Fig. 182, III). This makes a strong S-shaped curvature, the lower leg
of which is formed by the cotyledons, Co; the upper, lying against the shield,
corresponds to the upper portion of the hypocotyl (4, Fig. 182, I), whose lower
part has developed into the shield-like growth above mentioned, in which the
reserve-material is stored. There takes place in the embryo at a very early
period through the development of the outgrowth, a torsion of the hypocotyl
like that which has been described above in Lycopodium and others. In Fig,
182, II, a curvature of the point of the embryo by the outgrowth, J/, through
about go° has taken place, and the cotyledon no longer appears to be terminal.
Hofmeister*, who was the first to investigate the developmental history of the
* Wille, Om Kimens Udviklingshistorie hos Ruppia rostellata og Zannichellia palustris, in
Videnskabelige Meddelelser fra den naturhistoriske Forening i Kjobenhavn, 1882.
* Ascherson, Potamogetonaceae, in Engler und Prantl, Die natiirlichen Pflanzenfamilien, ii, r (1889),
Pp. 199. Subsequent investigations did not bear out the correctness of Ascherson’s views.
* These occur also in dicotylous embryos. See p. 258.
* Hofmeister, Zur Entwicklungsgeschichte der Zostera, in Botanische Zeitung, x (1852), p. 121.
\
=
262 ORGANS IN EMBRYO OF PTERIDOPHYTA AND SPERMOPHYTA
embryo of Zostera, interpreted the embryo somewhat differently. What we call
the shield-like outgrowth of the hypocotyl he considered the ‘axis of the embryo
of the first order.’ In this no one now will follow him, but it is much to be
wished that one of the modern microtomists would follow accurately the develop-
ment of the embryo of Zostera’. In Hofmeister’s Fig. 28, the curvature of the
embryonal axis is probably shown.
These examples will suffice to show how far-reaching are the changes
in form which are brought about in the embryos of different plants by the
deposition of reserve-food-material. Fundamentally nothing else takes
place but what is found in many shoots at a later period of development.
The deposition of reserve-material in cotyledons corresponds to that in the
leaves of a bulb; the deposition in the hypocotyl to that in the axis of
a tuber; the deposition in a lateral outgrowth of the hypocotyl finds its
parallel in the axes of many shoots.
1 Since the above was written this has been done by Rosenberg, Uber die Embryologie von
Zostera marina, Linn., in Bihang till kongl. svenska Vetenskaps Akademien, Handlingar, 2, iii
(1901). Rosenberg confirms the view given in the text about the ‘ mantle’ of the embryo of Zostera.
Of special interest is the embryo of Halophila, whose close relation to the embryo of Zostera was
pointed out long ago by Balfour, On the genus Halophila, in Transactions of the Botanical Society,
Edinburgh, xiii (1879).
meee lAlL’ CHARACTERS OF THE ORGANS
OF VEGETAEION
TIE, ROO
Originally all subterranean parts of plants were termed ‘root.’ As our
knowledge increased comparisons showed that under this collective name
organs of different structure and different function were grouped together.
As ‘typical’ roots, that is to say, those which are the most common because
they correspond with the most widely distributed conditions of life, we may
recognize the sozl-roots, which act as nutritive organs and as anchoring-
organs. Organs with analogous function, in which, however, the anchoring
function tends to predominate, occur also in the lower plants!, but they are
essentially of more simple configuration, a difference of which we shall have
an explanation if we remember that vascular plants alone appear as the
typical /and-plants of any significant size. In the vascular plants therefore the
subterranean organs have to satisfy quite different claims from those which
are laid upon the rhizoids of one of the Musci, for these have not to support
a transpiration-current, and have not reached beyond the stage of develop-
ment of branched threads*. At the same time we must remember that in
the vascular plants the functions we have mentioned may be taken over by
organs other than the roots *, and then we find generally that the roots are
not developed. A few illustrative cases may be cited here :—
U!
ROOTLESS PEANTS
RS PLERIDOPA VTA,
Filices. In a number of small epiphytic Hymenophyllaceae, whose
embryogeny we do not yet know, roots are not to be found. They are
forms which are distinguished almost always by their small size. The
species represented in Fig. 183 is much less complex than many of the
Musci, and the work which its vegetative body has to do is correspondingly
1 See Part I, p. 38 and Fig. 14, also pp. 26, 119 of this Part.
2 Compare the rhizoid-strands in Polytrichum and elsewhere,
8 See p. 237.
264 THE ROOT IN PTERIDOPHYTA AND SPERMOPHYTA
4
inconsiderable. The uptake of water is maintained by the one-layered
leaves. ‘ Hair-roots, which are unicellular tubes on the axis of the shoot
and frequently also on the leaves, serve as anchoring-organs. Where the
leaves of rootless forms attain to relatively large size, as in Trichomanes
Hildebrandti?, there are special arrangements—in this case the apposition
of the leaves to the substratum—on account of which the formation of the
roots can be easily spared. Many forms, for example T. membranaceum,
have developed instead of roots leafless shoots, which perform the function
of roots. Mettenius” gives a list of the rootless species of Trichomanes
which he had found, and to it I may refer the reader. There are probably
other rootless forms amongst the small species of Hymenophyllum, and
there can be little doubt from a comparison of the behaviour of a number
of species that we have before us
in them not primary, but reduced
forms. The larger ground-species
of Trichomanes have a well-deve-
loped root-system. Some which
live epiphytically among the
Musci of tree-stems have relatively
few roots. Mettenius states that he
only once found an adventitious
root amongst hundreds of examples
which he examined of T. pedicel-
The plant rootless and has unicelislar hair coom cere | LEU, “By -Ailceered peter elle eretis
Seisce ab anchorigorgans, “Bigare to night aawal COldes: | Whcther @negecemplancs
ase of the rootless species of Tricho-
manes possess a root or not we do not know. Perhaps the different
species behave differently in this respect.
Salvinia. All the species of Salvinia which have been examined
are rootless, and the primordium of the root is suppressed in the embryo.
What for a long time were considered as the roots of these floating species
of water-plants are peculiarly formed submerged water-leaves, which are
divided into numerous segments, and in this respect contrast with the entire
floating leaves.
Lycopodineae. Psilotum and Tmesipteris are both rootless. The
function of the root is performed by a leafless rhizome. In both genera the
superficial development and manifestly the area of transpiration of the shoot
are very small. In Tmesipteris, which possesses the larger leaves of the
two, these are vertical.
1 See Giesenhagen, Die Hymenophyllaceen, in Flora, lxxiii (1890), Plate XIV.
? Mettenius, Uber die Hymenophyllaceae, in Abhandlungen der kGniglich-sichsischen Gesellschaft
der Wissenschaften, xi (1864).
ea
ROOTLESS PEANTS 265
Bs: SLE RMOPH VEA.
Dicotyledones. We have already seen some examples of rootless
forms of Spermophyta amongst the Lentibulariaceae. The genera Genlisea,
Polypompholyx, Utricularia, are entirely rootless. The position of roots is
occupied in the land-form of these genera by peculiar transformed leaf-
organs; in the submerged free-swimming water-form the absence of roots
is easily understandable, inasmuch as the uptake of dissolved food-material
can take place through the whole plant-body, and the function of anchoring-
organs is of course done away with. Other water-plants living under
similar conditions have no roots, for example species of Ceratophyllum and
Aldrovanda!, as well as the submerged lemnaceous plant Wolffia Welwit-
schii”. Some small floating species of Wolffia, such as W. arrhiza, have
also no roots. It is remarkable that in some fixed water-plants the roots
are wanting. We find this, for example, in some though not in all the
Podostemaceae *, especially those of considerable size like Rhyncholacis
macrocarpa. The arrest of tiie roots is here made possible by the develop-
ment of other anchoring-organs—the haptera*. Where roots are present
on forms of Podostemaceae, which possess haptera, they are devoted partly
to purposes other than those of the typical root—to asexual propagation
for example, and to other purposes which will be mentioned below ®.
Monocotyledones. Two rootless saprophytic orchids are known—
Corallorhiza innata and Epipogon Gmelini. They possess only scale-leaves,
and the intake of water is effected by the rhizome-shoot. The reduction of
the assimilating and transpiring leaf-surface characteristic of saprophytic
life has made possible here the reduction also of the roots. Examples of
rootless plants amongst the epiphytes are known—Tillandsia usneoides
takes up water, and with it dissolved food-material through the surface of
the shoot, and fixes itself by twisting its base round the branch of a tree ;
roots are therefore not required. They appear, however, in the germination,
but soon die off.
II
CHARACTERS OF THE ROOT
There are four organographical regions in a typical soil-root :—
1. The apex, that is to say, the vegetative point covered by the
root-cap.
1 The statement, frequently repeated, that Myriophyllum is rootless, is erroneous. The winter-buds,
when they shoot out, form long roots.
* Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 279.
* See Goebel, op. cit., p. 331; Warming, Familien Podostemaceae (Afhandl. I (1881), II (1882),
III (1888), IV (1891), V (1899), VI (1901), in Skrifter af det kongelige danske videnskabernes
Selskab, Reekke 6, ii (1881-6), iv (1886-8), vii (1890-94), ix (1898-1901), xi (1901).
“WOEE P.. 222. 5 See p. 280.
266 THE ROOT IN PTERIDOPHYTA AND SPERMOPAYS
2. The very short region of growth.
3. The region covered by root-hairs.
4. The region in which the short-lived hairs are dead.
This holds for the single nearly cylindric root-threads. The construction of
the root-system will be mentioned below. I shall now pass in review these
several regions.
tT. THE APEX OF THE ROOT.
The biological significance of the root-cap requires no explanation here.
Every one knows that it protects the soft tissue of the vegetative point in
its passage through the soil, and that it makes this passage easier by the
mucilaginous degradation of its outer cell-membranes!. It is also clear that
the possession of the root-cap makes up for absence of leaves upon the
root. Hypogeous shoots protect their vegetative point almost exclusively
by scale-leaves, and they are often markedly developed as boring-organs,
as in Equisetum and Triticum repens. Where this is not the case, as for
example in the rhizomes of Psilotum and Tmesipteris, the shoot lives under
special life-conditions: the plants are epiphytes, whose rhizomes are not
growing in firm soil but between the aerial-roots of tree-ferns, or are living a
-half-saprophytic life in loose pulpy humus?. It is noteworthy that in the
two known cases where the vegetative point of the primordium of a shoot
is provided with a cap of tissue which serves as a boring- and protecting-
organ, and which we can compare in function with a root-cap, this happens
before the appearance of the leaves. Strasburger has shown that in
Cephalotaxus Fortuni and Araucaria brasiliensis the apex of the primor-
dium of the embryo is not developed into the vegetative point of the
embryo. The vegetative point is formed within the primordium of the em-
bryo whilst the original apex which served only as a boring- and protecting-
organ is thrown off. Cases which might lead up to these of leafless shoots
provided with root-caps have been described, but their anatomical dif-
ferentiation has not been made clear. The significance of the root-cap is
also shown by the behaviour of some water-plants, in which the roots hang
free in the water. The root-cap can then no longer be considered as a pro-
tective organ, although one must not forget that we have to deal in such
cases with roots of limited growth whose apex soon loses the embryonal
character. A root-cap constantly regenerating itself by the formation of
new cells must be more or less superfluous in a case of this kind, and
therefore it submits to a reduction of a varying degree, and such roots
* Concerning the significance otherwise of this mucilage, see Goebel, Pflanzenbiologische Schilder-
ungen, ii (1893).
* Solms-Laubach has shown that in Psilotum triquetrum when the apex of a rhizome-shoot has
suffered injury, either a lateral primordium grows out or new shoot-primordia are formed in the
periphery of the apical meristem. See Annales du Jardin botanique de Buitenzorg, iv (1884),
p- 160.
APEX OF THE ROOT 267
are so intimately adapted to the life in water that they have frequently lost
their power of normal growth in the soil. The roots of Lemna minor and
L. trisulca, Azolla filiculoides and Hydrocharis Morsus-ranae, all swimming
water-plants, show for example in a normally moist garden-soil hardly any
growth?. Other water-plants, which are not so exclusively adapted to a
swimming life, are probably more plastic. In conformity with this are the
morphological states, which supply a transition to the cases of complete
suppression mentioned above*. I must now mention some examples :—
Azolla. In contrast with the allied Salvinia this genus possesses two
rows of roots upon the under side of its stem. The apical growth of these
roots is limited. The apical cell of the root produces but oe cap-segment
instead of many, as in other Pteridophyta. If the root grows out the cap is
thrown off. The superficial cells, including the apical cell, grow out into
hairs so that the root resembles the hairy lobes of the water-leaf of Sal-
vinia.
Lemnaceae. Other swimming water-plants like the Lemnaceae pos-
sess an evident root-cap, but it is distinguished by the history of its
development from a true root-cap, inasmuch as it does not arise like the
ordinary root-cap of monocotylous plants from the epidermis of the root,
and it does not show periodic renovation. This cap, in form like the finger
of a glove, protects the root-apex against the attacks of small animals, the
effect of currents of water, and the like. But it does not correspond to a
root-cap, but to the envelope which in other roots only exists for a short
time, and which has been called by Van Tieghem? ‘la poche digestive’
(Fig. 185).
Hydrocharis, probably also the allied Trianea bogotensis, and Pistia
Stratiotes show similar features. The root-envelope is in them, as in Azolla,
lost if the roots continue their growth. In these plants also the differenti-
ation of epidermis from rind is not visible, and their roots are in the nar-
rower sense of the idea quite capless.
Aesculus Hippocastanum. The roots of land-plants are only capless
in rare cases. Aesculus Hippocastanum furnishes an example*. There
arise periodically upon the roots of this plant, in addition to the ordinary
lateral rootlets, small tuber-like roots, about 2mm. long, which have no
root-cap ; these are in addition to the normally formed lateral roots. These
rootlets, whose function is unknown, we may designate arrested formations,
* See Wakker, Die Beeinflussung des Wachsthums der Wurzeln durch das umgebende Medium, in
Pringsheim’s Jahrbiicher, xxxii (1898), p. 71.
2 See Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 280. The literature is cited here.
* Van Tieghem et Douliot, Recherches comparatives sur l’origine des membres endogénes dans
les plantes vasculaires, in Annales des sciences naturelles, sér. 7, viii (1888).
* See Klein und Szabo, Zur Kenntniss der Wurzeln von Aesculus Hippocastanum, L., in Flora,
Ixiii (1880), p. 146.
268 THE ROOT IN PTERIDOPHYTA AND SPERMOPHYTA
whose loss of root-cap stands in relation to their short existence and their
small size. This explanation is rendered probable by the fact that there
are transition-stages between the capless and the normal rootlets.
Bromeliaceae. A peculiar condition which requires further investi-
gation has been shown by Jgrgensen ' to occur in the roots produced by the
shoots of the Bromeliaceae. These commonly grow for a long period in
the tissue of the shoot-axis, and there they have a well-developed cap. But
when the root-tip has bored through the surface of the axis the cap consists
of only a thin layer of dead, more or less compressed, cells. Perhaps we
have to deal here with roots of limited growth—merely anchoring-roots.
Cuscuta. The chief root of the seedling of the parasite Cuscuta *, which
discharges its function for only a very short time, is capless throughout its
life. It has only the duty of fixing the seedling-plant in the soil, and of
taking up water for it during its first developmental stages. Two days
after germination has taken place it usually begins to wither, and with it
naturally the whole plant also, unless it has found a host-plant through which
it can be nourished *.
Like other organs which have become useless under definite life-
conditions the root-cap in some cases is thrown off in course of the develop-
ment; in others it shows no further development. That the root-cap is
lost when transformation of the root takes place has already been pointed
out*. Other cases will be mentioned hereafter.
2. THE REGION OF GROWTH OF THE ROOT.
The distribution of growth in the root will not be spoken of in detail
here, but it may be pointed out that as Sachs has shown it is an advantage
for the penetration of the root-tip into the soil that the growing region lies
immediately behind the root-tip and is relatively very short—only two to
ten millimeters; the shorter in relation to its cross-section the axis of a nail
is, the less easily does the nail bend when one drives it into a board. In
this connexion we may also note that in air-roots the growth-relationships
are altogether different. That otherwise the growth of the root is best
under the conditions in which it normally grows, and to which it is ‘ attuned’
need not surprise us. The roots of some land-plants, Vicia Faba, Lupinus
albus and others, when they were cultivated in water, showed, as might be
expected, a retardation of their growth in length®.
? Jorgensen, Bidrag til Rodens Naturhistorie, in Botanisk Tidsskrift, Rekke 3, ii (1877-9),
p- 144.
* Koch, Untersuchungen iiber die Entwicklung der Cuscuteen, in Hanstein’s Botanische Abhand-
lungen, ii, 3 (1874). The roots of Orobanche have at first no cap, a feeble one develops at a sub-
sequent period. See Koch, Die Entwicklungsgeschichte der Orobanchen, Heidelberg, 1887.
S Seep. 254. = Seep. 2275
° See Wakker, Die Beeinflussung des Wachsthums der Wurzeln durch das umgebende Medium, in
Pringsheim’s Jahrbiicher, xxxii (1898).
ROOT-HAIR REGION OF ROOT 269
3- THE REGION OF THE ROOT-HAIRS.
The root-hairs! arise as outgrowths of the superficial cells of the root.
They have a great significance because by their appearance the absarbing
surface of the root is very greatly increased, and besides in land-plants they
grow firmly around the particles of soil, and so not only strengthen the hold
of the roots in the soil, but also are able to make use of the water-envelope
which adheres to each particle of soil. They are not, however, present in
all plants. They are markedly absent from a number of water-plants and
marsh-plants, as for example Butomus umbellatus, Hippuris vulgaris, species
of Lemna, Menyanthes trifoliata, Pistia Stratiotes, and also from a number
of Coniferae, for example Picea excelsa, Pinus sylvestris, Biota orientalis,
Thuja occidentalis. From some monocotylous plants which produce tubers
like Crocus sativus, and from some parasites and humus-plants like Mono-
tropa, Neottia, and Orobanche ramosa, they are also absent. The plants
just mentioned are all of a kind which either have water in quantity at their
disposal, as is the case with water-plants and marsh-plants ; or they do not
exhibit intense transpiration from their epigeous parts, as the Coniferae
which have leathery leaves—although others like Taxus have numerous
root-hairs ; or they have roots which are inhabited by fungi, as Monotropa
and Coniferae ; or the epigeous parts are only slightly developed and have
a short life, as in Crocus; or the leaves are mostly reduced to small scales,
as in the parasites and humus-plants. In the greater number of plants
which produce hairs normally their formation is suppressed if the roots are
grown in water. We see this in Allium Cepa, Hyacinthus orientalis, Zea
Mais, Cucurbita Pepo, Phaseolus communis, Pisum sativum, and others.
This is, however, not the case in all plants, and many swimming water-
plants like Trianea bogotensis possess very large root-hairs. The possession
of root-hairs by Azolla, Hydrocharis, and other plants, has been already
mentioned. The case of air-roots will be discussed hereafter °.
4. THE REGION IN WHICH THE SHORT-LIVED HAIRS ARE DEAD.
The inner character of that portion of the root which is no longer
concerned with the taking up of nutrition lies in the domain of anatomy.
The point of organographical and biological interest in it is the shortening
which takes place in many roots subsequently to the cessation of growth
in length. There are formed in many plants roots which differ from the
others in their configuration, and whose chief significance consists in their
contractility. Rimbach® has fittingly termed them fuw//-roots. They are
* See Schwarz, Die Wurzelhaare der Pflanzen, in Untersuchungen aus dem botanischen Institut
zu Tiibingen, i (1881-5), p. 135. ? See p. 283.
* Rimbach, Die kontraktilen Wurzeln und ihre Thitigkeit, in Fiinfstiick’s Beitrage zur wissen-
schaftlichen Botanik, ii (1898), p. 1. The literature is cited here.
270 «1HE ROOT IN PTERIDOPHYTA. AND \SPERKMORAYIA
distinguished by the relatively strong development of their thin-walled
cortical parenchyma, whilst the thick-walled cells of the mechanical system
of tissue are entirely, or almost entirely, wanting. These pull-roots have
often the subsidiary function of storing reserve-material, but their chief
work is that of shortening, and in so doing they exercise a pull upon
the portion of the plant out of which they arise. When we consider the
use of this arrangement we must distinguish cases in which the pull-
roots draw down the shoot into the soil from those in which they do not
do so.
In the latter, for example in Polygonatum multiflorum, Canna indica,
and Asparagus officinalis, the shortening of the root only brings about a
firmer anchoring of the plant in the soil, and this is of great importance in
plants with richly developed epigeous organs seeing that they expose to the
wind and other agencies a relatively large surface.
In other plants the shortening of the root is one of the means by which
the hypogeous shoots are brought to a definite depth. The following
example will illustrate this :—
Arum maculatum. In the germination of Arum maculatum the
elongating cotyledon, which is negatively geotropic, pushes the bud of the
seedling vertically downwards into the soil to a depth of fifteen millimeters.
The tuber which develops out of this bud lies therefore at first about two
centimeters from the surface. Full-grown tubers of Arum lie, however, at
a depth of about ten centimeters, and this change in position is brought
about by the power of the pull-roots. The roots arise in a zone which
surrounds the terminal bud of the tuber like a somewhat obliquely lying
ring. Those upon the under side are thick and very contractile, those upon
the upper side are thin and only slightly or not contractile. As a con-
sequence of this the tuber is pulled downward at its apex usually about
one centimeter in each vegetative period, but only during about two or
three months from September to November. Once the xormal depth is
attained the contractility of the roots is diminished, and they grow no longer
directly downwards, but horizontally outwards. If one takes such a tuber
and plants it higher strong contractile roots are again developed. We know
nothing of the causes which bring about this remarkable regulation which
recurs in the growth of many rhizomes.
Pull-roots are widely spread and are best developed among perennial
and herbaceous Spermophyta. Incryptogamous plants and phanerogamous
woody plants they have not yet been observed. The shortening is some-
times very considerable. Rimbach found that for a stretch of root five
millimeters long the contraction in some Amaryllideae, for example Phae-
dranassa chloracea and in Oxalis elegans, was seventy per cent., in Agave
americana and Arum maculatum fifty per cent., in Allium ursinum thirty
per cent., in Asparagus officinalis ten per cent. These high figures are only
PULL-ROOTS 271
applicable to one portion of the shortening stretch of root. Taking the root
as a whole the percentages are somewhat smaller. For Phaedranassa chlo-
_racea, for example, the shortening was only thirty to forty per cent. In
many persistent roots, for example the chief roots and lateral roots of
Taraxacum, Heracleum, Phyteuma, the contraction goes on throughout the
whole year. In other short-lived roots, as in the example of Arum quoted
above, the shortening takes place only during a limited period. In many
plants all the roots of one order are contractile, in others there is distribution
of labour, as has been
already mentioned in
the case of Arum, and
this is seen more strik-
ingly in many other
Monocotyledones and
some Dicotyledones.
Thus it has been long
known that Tigridia,
Gladiolus, Crocus, and /
Scilla possess two L
kinds of roots which
arise in different posi- i,
tions and at different
times. Crocus longi- (
florus, for example
5 Fic. 184. I, Crocus longiflorus. II, Oxalis sp. (marked as pentaphylla).
(Fig. d 84, I), produces Z, pull-roots ; S, stem. Half natural size. P
at the beginning of
the vegetative period on the under side of its tuber numerous thin
filiform non-contractile roots, but later upon one side of the new tuber
there are produced a few—in the figure only two are shown—thick roots
which are strongly contractile and which draw down into the soil the
tuber to which they belong, After doing this they soon die. These
roots are considered by Daniel!, who has overlooked the shortening, as
a transitory compensating system which develops with the need of the
plant when from any cause, internal or external, the general nutrition is
hindered. This conclusion is supported by the fact that the tubers in
Gladiolus, from which evident buds were removed, produced these roots
specially strong, and after two months they were reabsorbed, they were
built anew as well as the new tuber, and they contained large masses of glucose
which disappeared afterwards. It is not impossible that these fleshy roots
at the same time serve as short-lived reservoirs of food-material and also
+ Daniel, Sur les racines napiformes transitoires des Monocotylédones, in Revue générale de
Botanique, iii (1891), p. 455.
272 THE ROOT IN PTERIDOPHYTA AND SPERMOPHYTA
for water. Their substance can then be taken up by the permanent reser-
voirs, tubers, and the like ; at the same time their significance as pull-roots
is none the less evident. :
In Dicotyledones analogous cases are known. We have one repre-
sented in Fig. 184, II, which shows a species of Oxalis.
III
THE ROOT-SYSTEM
The seedling possesses in most cases at first only a simple unbranched
root. Later a root-system develops which is formed either exclusively
from the chief root or by the new formation of roots on the shoot-axis. If
the latter is the case the primary root soon dies. It is well known that this
takes place commonly in the Monocotyledones, but a number of Dicotyle-
dones show it also, and it may be asked if this different behaviour in the
formation of the root-system has biological relationships. Inner structural
relationships are first of all concerned, and then the conditions of life come
into consideration.
Monocotyledones. Monocotyledones show, with few exceptions, no
secondary growth in thickness. This means that the primitive conduct-
ing-channels for water and other plastic material as they lie in the vascular
cylinder of the chief root must remain the same. The demands which
the epigeous parts of the plant make upon the roots are, however, always
becoming greater with the increasing development in their surface by the
multiplication in the number and size of the leaves, and the capacity of the
chief root, even if it were ever so much branched, would no longer suffice,
therefore it is replaced by the formation of new roots on the shoot-axis,
and these appear in great numbers, and in many quickly developing plants,
as, for example, a number of grasses, are developed even upon the embryo.
Dicotyledones. We have already learnt, when considering the ger-
mination of the plants of the mangroves!, of a case amongst the Dicotyle-
dones in which the development of a root-system proceeding from the chief
root was so evidently unsatisfactory in the sticky mud, poor in oxygen, that
it has become suppressed *. Were I to describe here the relationships of the
duration of development of the chief root to the manner of life of its plant,
I should exceed the limits imposed upon this book, for the many-sided
subject of the ‘ succession of shoots *’ would have to be dealt with. It must
* Some swamp-plants with superficial root-system probably behave in like manner, for instance
Taxodium distichum. 2 See p. 256.
* See Warming, Om Skudbygning, Overvintring og Foryngelse. Den naturhistoriske Forenings
Festskrift, Kjgbenhavn, 1884.
—— ir
ORIGIN OF SECONDARY ROOTS 273
suffice that I have indicated merely that it depends on the whole economy
of the plant. The relationships in individual cases frequently still require
explanation.
Methods of Origin of Secondary Roots. New roots are usually endogenetic.
They have to burst through the peripheral tissue of the mother-organ, and this only
happens if the young root which is laid down under the protection of the older tissue
is sufficiently strong. The endogenetic formation is, however, not without exception.
Exogenetic roots are formed, according to Bower, in Phylloglossum Drummondii ;
Treub says that the first roots of the germ-plants of some species of Lycopodium
are endogenetic ; and according to Warming’ this is the case in the roots upon the
stem of Neottia Nidus-avis. They are laid down in the third and fourth periblem-
layer whilst the first and second layers form the root-cap. The epidermis functions
for some time as the outermost layer of this and then dies off*. According to
Hansen * the roots at the base of the adventitious shoots and the adventitious roots
in the leaf-axils of Cardamine pratensis, Nasturtium officinale, and N. sylvestre are
also exogenetic, whilst the adventitious roots of other water-plants and marsh-plants,
for example Veronica Beccabunga, Polygonum amphibium, and Ranunculus fluitans,
are commonly laid down as endogenetic structures.
Place of origin of the Lateral Roots on the Chief Roots. This is definite.
If we leave out of consideration the dichotomy of roots as it occurs in Lycopodiaceae
the primordia of lateral roots are always found at the circumference of the axil vascular
bundle-cylinder of the root, the so-called ‘plerome.’ This is surrounded by a simple
layer of tissue, the pericycle, which is limited on the outside by the innermost layer
of the rind usually designated the endodermis and which has a peculiar structure.
In Spermophyta the lateral roots are laid down in the pericycle, in the Pteridophyta
in the endodermis. In the Pteridophyta the root-primordium proceeds from a
single cell, whilst in Spermophyta several cells always share in the formation of the
lateral root. This cell-group of the pericycle lies opposite one of the xylem-groups
of the axil-strand in plants which have more than two groups of vasa (Fig. 185),
hence the lateral roots are commonly found arranged in as many longitudinal rows
as the vascular cylinder of the root has got xylem-groups. In roots with diarch
bundles there are four rows of lateral roots according to Van Tieghem, and they
arise in the intervals which separate the xylem-bundles from the two adjacent sieve-
groups. I must pass over here the history of the origin, and merely state that the
lateral roots burst through the rind-layers of the chief root at a relatively late period.
The roots of Nuphar for example, leave a stretch of ten or more centimeters above
the tip free from lateral roots. The first formation of the primordia of the roots
1 Warming, Om Redderne hos Neottia Nidus-avis, L., in Videnskabelige Meddelelser fra den
Naturhistoriske Forening i Kjobenhavn, 1874.
2 This takes place so early, as is shown in Warming’s figures, see Plate IV, Fig. 9 and others,
that it occurs when the root is still only a papilla, and one might here assume an endogenetic origin
of the root by holding that the epidermis takes no share in the formation of the root, but is only
stretched by the root-primordium until it dies or is broken through.
* Hansen, Vergleichende Untersuchungen iiber Adventivbildungen bei Pflanzen, in Abhandlungen
der Senckenbergischen naturforschenden Gesellschaft, xii (1881), p. 159.
GOEBEL If A Is
274 THE ROOT IN PTERIDOPHYTA. AND SPERMOPAYTa
was found by Nageli and Leitgeb, in the cases which were examined, close to the
apical region of the root at a point where the first vasa were not yet differentiated
from the surrounding cells. Janczewski says that in Polygonum Fagopyrum the
lateral roots are laid down in the tissue of the vegetative point which is still covered
by the root-cap, and which has not yet lignified vessels; also in Pistia these lateral
roots arise opposite vessels which have not yet become lignified. Still at the time
when the primordia of these lateral roots are laid down the cells of the rind of the
root have already in many cases passed into the permanent condition and inter-
cellular spaces already exist between them. ‘The cells which give origin to the
lateral roots are evidently derived from the terminal embryonal tissue.
The late appearance of the lateral roots has from my point of view to be con-
sidered as a phenomenon standing in relation to the conditions of life. The early
formation of lateral roots must hinder the
passage of the primary root into the soil.
The chief root makes first of all the path
and fastens itself with its root-hairs, and only
when the normal further development of
the root-system is required do the lateral
roots burst forth. In many plants, especially
those which grow in moist soil or whose
roots function for a relatively short time, the
branching may be altogether suppressed.
We see this in Ophioglossum and especially
in a number of Monocotyledones, for example
Arum maculatum, Colchicum autumnale,
Gagea lutea, Leucojum vernum, Opbhry-
deae?; similarly the ‘anchoring-roots’ which
FiG. 185. Young lateral root of a monocotylous
plant in diagrammatic longitudinal section. G, Will be described below are usually un-
xylem of chief root; S, phloem of chief root; 2
pericycle of chief root; MW, root-cap of lateral branched.
root; W%, digestive pocket formed from the en- A iis
dedecmis OfchELaoe ; The Origin of Roots upon Shoots.
Adventitious Roots. The behaviour of
shoots in the matter of the capacity to bring forth roots is extremely varied. Many
annual herbaceous species of Spermophyta do not possess the capacity at all, whilst
others, which have creeping as well as upright shoots, lay down roots quite close
to the vegetative point. According to Van Tieghem and Douliot the roots which
are developed on the shoots in the Spermophyta arise in the pericycle, and thus the
relationships observed in the branching of the root are repeated; but where the
roots are exogenetic this is not the case. The tissue of the rind contributes nothing
to their formation ; it surrounds them with a root-pocket (Fig. 185) which is of use
to them in boring through the tissue, although there is not everywhere a ‘ digestion’
of its tissue. ‘There are differences according as primordia appear earlier or later,
but these have little organographical interest. All the primordia of the roots which
1 See Rimbach Beitrige zur Physiologie der Wurzeln, in Berichte der deutschen botanischen
Gesellschaft, xvii (1899), p: 29.
.
MEMBERS OF ONE ROOT-SYSTEM 275
are formed upon shoots do not develop into roots, but many may remain for a long
time, or indeed always, as ‘latent’ primordia. Wecan scarcely reckon amongst these
the arrested developments of normal root-primordia which take place under unfavour-
able external conditions, for instance in Hedera, when the plant is cultivated
without any substratum for its shoots. On the other hand we find in Salix latent
root-primordia under the cortex, either singly on both sides of the axillary bud or in
numbers as in Salix vitellina, S. pruinosa, and others. These primordia of roots
develop on cuttings of Salix whilst in the normal vegetation they do so only seldom.
Nothing is known about the time of their appearance, but they probably arise pretty
early, at least Vochting mentions them upon the twigs of Salix viminalis, S. pruinosa,
and others, which were only three to four months old. No doubt they exist also in
other woody plants, and they are also found in Equisetum where an adventitious
root is laid down upon every lateral bud, but these do not develop usually in the
epigeous parts. They can, however, be forced into development in moisture and
darkness.
IV
DIFFERENT CONSTRUCTION OF THE MEMBERS OF
THE NORMAL ROOT-SYSTEM OF THE SOIL!
The construction of the members of the root-system and their relation-
ship to external factors vary according to their position in the system.
The morphological differences are like those which have been already
mentioned as occurring in the long and short shoots of the lower plants.
If we turned downwards the apex of the shoot represented in Fig. 12 of
Part I, and imagine the cell-walls removed, we should obtain a picture
corresponding in some measure with a root-system in which, however, as we
know, branching would not come quite so close to the apex. The members
are usually less strong the higher their order, and this finds explanation in
their anatomical structure, in perennial plants also in the shorter duration
of life? of the ‘absorbing rootlets’ about which, however, we have few
exact investigations.
The classical investigations of Sachs have shown us that the regular
spreading of the root-system in the soil is conditioned by the different
capacity of reaction to gravity in the roots of different orders. The primary
roots are positively geotropic; the lateral roots of the first order possess
a ‘special geotropic angle*,’ which is different according to their point of
origin. In the upper roots which stand nearest the root-base it is commonly
a right angle, but in those standing below this it is smaller. The lateral
1 See Sachs, Uber das Wachsthum der Haupt- und: Nebenwurzeln, Gesammelte Abhandlungen,
ii (1893), xxxi and xxxii,
? All the roots of the first order do not have a long life, for instance those on a chief root of
Taraxacum. A number of them die off. But I know of no investigation of this phenomenon.
* Sachs investigated the roots of seedling-plants. The relationships of matured roots deeper in
the soil may be different.
T 2
276 THE ROOT IN PTERIDOPHYTA AND SPERMOPHYTA
roots of the second order which spring from those of the first order are, on the
other hand, not geotropic. They grow from their mother-roots in a straight
line and show no geotropic curvature. That a number of them under usual
conditions do not grow out on the surface of the soil is the result of the fact
that the air is too dry for them. If the air is artificially kept moist many
thin rootlets, especially in the Monocotyledones, will grow out on the surface
of the soil', a fact which is of special interest in connexion with the develop-
ment of the breathing-roots, of which mention will be made below, when it
will be shown that under definite conditions negatively geotropic roots are
formed, and also roots which have entirely lost their geotropic sensitiveness.
I may add that such negatively geotropic roots are not yet known amongst
soil-roots, yet possibly normal negatively geotropic roots occur also
amongst them, but their existence has not yet been brought to light. At
any rate we see in the soil-roots that geotropic sensitiveness is, to speak
teleologically, regulated by the need of it, and this is also the case in
transformed roots. The roots which spring out of the base of the shoot in
Monocotyledones appear to behave like lateral roots of the first order,
but their geotropic sensitiveness is very small in many monocotylous water-
plants. The lateral roots of these roots grow in Pontederia, Pistia, and
others in every direction, and are plainly not geotropic. It is important,
when considering the ‘transformed’ non-geotropic roots, to remember the
fact pointed out by Sachs that geotropic roots if they grow zz the air
without being wetted lose their geotropism either entirely or in part.
The negative heliotropism and positive hydrotropism which are
observed in many soil-roots play a great part evidently in the formation of
the air-roots, which will be subsequently mentioned, and the same may be
said of contact-stimuli, to which also air-roots, like soil-roots, appear to be
sensitive. To what extent ‘exotropy’ is concerned in the direction of the
lateral roots requires further investigation. According to Noll? the lateral
roots which radiate in the direction of the four points of the compass from
the primary root in Lupinus or Vicia Faba, if they are artificially moved
out of their position, assume again the radial position to the primary root
when the distorting force is removed, making a sharp bend to do so. This
power may be of considerable significance for their uniform distribution in
the soil.
The Production of Shoots by Roots. Adventitious Shoots. This
appears to be a subsidiary function of many roots, but in some cases,
as, for example, in the Podostemaceae, it has become the chief function.
Amongst Dicotyledones particularly we find a large number of plants whose
1 See Sachs, Physiologische Notizen: V. Uber latente Reizbarkeiten, in Flora, Ixxvii (1893), p. I.
2 Noll, Uber eine neue entdeckte Eigenschaft des Wurzelsystems (Exotropie), in Sitzungsberichte
der Niederrheinischen Gesellschaft fiir Natur- und Heilkunde zu Bonn, 1894.
pha
ROOTS ADAPTED TO SPECIAL FUNCTIONS 277
roots produce shoots, and these normally arise as endogenetic structures at
the positions whence the lateral roots take origin. Frequently the position
of the lateral shoots has some relationship to that of the lateral roots.
They arise sometimes in the vicinity of the point of origin of a lateral root’,
as in Linaria vulgaris, Solanum Dulcamara, Pyrola, and Dioscorea, and this
position secures that the shoot shall obtain water from the soil by the
shortest way, just as the position of the bud in the axil of the foliage-leaf
of a shoot secures not only its protection but also gives it the advantage of
the materials formed by the assimilation of its axillant leaf. In other cases
the adventitious roots are formed at least in the vicinity of lateral roots.
They arise independently of these, however, when they appear upon older
root-parts which have already developed a woody character. In Pyrus
japonica, Rubus, Prunus, and others, their seat of origin is in the primary
medullary rays; in Ailanthus they are distributed over the general surface
of the mother-root. The exact point of origin too is not constant. In
Aristolochia Clematitis? this is not in the pericycle but in the outer layers
of the primary rind, as it is in the Podostemaceae, only in the somewhat
deeper layers. The root-buds of Linaria* are moreover exogenetic struc-
tures. It appears then that the method of origin of the primordia of root-
shoots is as various as is that of the root itself.
V
BOOt> ADAPTED TO SPECIAL, FUNCTIONS
In a number of plants a portion of the root-system, or it may be the
whole of one of the ordinary soil-roots, is adapted to a special function, and
consequently exhibits a more or less marked change in its inner and outer
configuration. A series of transitions, for example, leads us from the soil-
roots to those which spring from the base of the stem of many Monoco-
tyledones, and which soon entering the soil serve as prop-roots. They appear
in slight degree in, for example, Zea Mais. They are more conspicuous in
the Pandaneae and in many Palmae, for example Iriartea and others. But
their most remarkable formation is found in the Rhizophoreae and many
species of Ficus, in which they have been frequently confounded with stems.
' Beijerinck, Beobachtungen und Betrachtungen iiber Wurzelknospen und Nebenwurzeln, in
Natuurkundige Verhandelingen der Koningklijke Akademie van Wetenschappen in Amsterdam,
xxv (1886).
? Beijerinck, op. cit., p. 109, says the epidermis of the root is usually bored through by the bud,
but in the buds laid down very early the epidermis of the rind of the mother-root is an integral part
of the new formation. There is here a transition from endogenetic to exogenetic inception.
* Beijerinck gives no certain developmental account of this, and his story of the inception of
the lateral roots does not conform with that of Van Tieghem and Douliot for other species of
Linaria.
278 THE ROOT IN PTERIDOPHYTA: AND SPERMOPERG2
A classification of ¢vransformed roots according to their function is
difficult, inasmuch as a root which is constructed as an assimilation-organ
may at the same time serve as an anchoring one. It will therefore be better
to deal with the several forms in the biological groups of plants in which
they occur :—
(2) PNEUMATOPHORES OR BREATHING-ROOTS OF MARSH-PLANTS.
It has been already pointed out that the roots of marsh-plants live in
a substratum which is poor in oxygen and unfavourable to their respiration’,
and it is through the intercellular spaces of the epigeous parts that they
obtain their oxygen*. Some marsh-plants have, however, special arrange-
ments for drawing in air.
Mangroves. Fig. 186 is a portion of Laguncularia racemosa, one of
the plants of the mangrove of South America. All round it upon the
muddy ground washed by the sea there rise hundreds of asparagus-like
breathing-roots or pueumatophores. We find the same in species of Avi-
cennia and Sonneratia. These negatively geotropic roots are commonly
unbranched, but if their tip is injured they may branch and then arise two
or more negatively geotropic roots. The pneumatophores have their in-
ternal structure, which I cannot describe here, arranged specially for intense
gas-exchange. They spring from the roots which are horizontally stretched
in the mud. Similar roots appear in other plants, for example sugar-cane
and some palms, if they are grown in wet soil. The features of Lagun-
cularia, Avicennia, and Sonneratia, are only an exaggerated condition of
a feature that is found elsewhere.
Westermaier * has recently thrown doubt upon the generally accepted morpho-
logical nature of the pneumatophores. He considers that they are organs, swz
generis on account of their anatomical relationship. The vegetative point also is
not covered by a special root-cap, but is protected by a cork-mantle which has come
about evidently as an adaptation to their life in air. This mode of life possibly
may have brought about also the anatomical differences from the normal root-
structure*. We do not, however, know anything about the primordia of these
pneumatophores, and until we do know this we can say little certainly about their
‘morphological significance.’ It is quite possible that the pneumatophores have
arisen in quite the same way as, only probably earlier than, the structures which we
find in Carapa moluccensis doing the work of pneumatophores. In this species
* See Part di; p::260%
2 Goebel, Pflanzenbiologische Schilderungen, ii (1893). Prior to this these intercellular spaces.
were regarded as reservoirs of air which hardly explained their occurrence in the epigeous parts of
marsh-plants.
° Westermaier, Zur Kenntniss der Pneumatophoren; Botanische Untersuchungen im Anschluss.
an eine Tropenreise, Heft 1; Freiburg, Schweiz, 1900.
* Besides, there is no far-reaching anatomical difference between root and shoot. The usual
scheme of shoot-structure is, for instance, in abeyance in many species of Utricularia and Stylidium.
PNEUMATOPHORES 279
horn-like or finger-like outgrowths arise * by inequalities in the secondary growth in
thickness in the upper part of the roots which creep near the surface of the mud.
From a photograph I took in October, 1890, in the island of Curagao.
above the water.
5
Laguncularia racemosa with pneumatophores rising
186.
Fic.
In my view it is most probable that these pneumatophores are roots. In Bruguiera
knee-like curved portions of the root rising above the mud perform the same
+ See Karsten, Uber die Mangrove-Vegetation im Malayischen Archipel, in Bibliotheca Botanica,
xxii (1891), p. 51.
280 THE ROOT IN PTERIDOPHYTA. AND SPERMOPHAa
function. In Lumnitzera numerous lateral roots ascend in a negatively geotropic
manner from the horizontal roots and then bend downwards with a sharp curvature.
At the point of bending special large lenticels are developed, often a centimeter
in diameter, and these perform the work of gas-exchange.
Taxodium. I can dono more than mention here the ‘root-knees’ of Taxo-
dium which discharge a similar function.
The biological significance of the air-roots first of all suggested upon the ground
of their anatomical relationships, and the localities in which they were found ', was
experimentally supported by Karsten and Greschoff. Westermaier’s hypothesis
that they act as ‘ pumps’ is very improbable, and has no experimental foundation.
Jussieuea. The peculiar roots which are developed in some species of
Jussieuea belong to this category”. These roots have large intercellular
spaces, and their apex is directed upwards. They were formerly considered
as swimming-organs, an explanation which it is easy to see is inappropriate.
They have limited growth, are usually unbranched, and may reach twenty
centimeters in length, as in the case of J. salicifolia. They evidently serve
the purpose of gas-exchange.
Sesbania aculeata, one of the Papilionaceae, possesses similar roots °.
(4) ASSIMILATION-ROOTS AND SHOOT-FORMING ROOTS OF THE
PODOSTEMACEAE 4,
The Podostemaceae is a group of water-plants distinguished by many
remarkable adaptations. They grow upon stones in rapidly flowing water.
The roots, when these are present, cannot therefore enter into a substratum,
and therefore they have been adapted to many other functions. Owing to
their position the roots are exposed to light and contain chlorophyll. The
formation of chlorophyll may take place in many roots which are usually
not green if they grow in the light, for example in those of Menyanthes
trifoliata, Mirabilis Jalapa, whilst at the same time other roots of the plant
are not in a position in which this can occur. The roots of the Podo-
stemaceae are, however, all chlorophyllous, and many are constructed as
assimilation-organs. I quote the following examples from Warming :—
Dicraea elongata and D. algaeformis. Dicraea elongata and D. algaeformis
have two kinds of roots. One of these spreads itself over the substratum to which it
1 See Goebel, Uber die Rhizophorenvegetation, in Sitzungsberichte der naturforschenden Gesell-
schaft zu Rostock, 1886; .id., Uber die Luftwurzeln von Sonneratia, in Berichte der deutschen
botanischen Gesellschaft, iv (1886), p. 249; id., Pflanzenbiologische Schilderungen, i (1889),
pss cuss
2 See Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 259, where the literature is cited.
* See Scott and Wager, On the floating-roots of Sesbania aculeata, Pers., in Annals of Botany,
i (1887), p. 307. In this plant the roots are, in my view, not swimming-roots but breathing-roots.
* See Warming, Familien Podostemaceae: I-V, in Skrifter af det kg]. danske videnskaberne Selskab,
1881, 1882, 1888, 1891, 1899; Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 331. The
literature is cited in the last-mentioned work. Also Willis, Studies in the Morphology and Geology of
the Podostemaceae of Ceylon and India, in Annals of the Royal Botanic Gardens, Peradeniya, 1901.
ROOTS OF PODOSTEMACEAE 281
is fastened by root-hairs and haptera*. The other kind floats free in the water like
so many algae anchored at their base. There is evidently no geotropic sensitive-
ness in them, and this may be noted in most algae. These free-floating roots produce
in progressive acropetal succession the primordia of foliage-shoots which are endo-
genetic, but are laid down far from the central cylinder of the root with which they
only come into connexion at a later period, and they attain to only a slight con-
struction and are far behind the roots which are rich in chlorophyll in their power
of assimilation. The free roots evidently have a limited growth, and in this they
contrast with the non-metamorphosed roots which are spread out over the substratum.
In D. elongata they are round, in D. algaeformis they are band-like and have the
appearance of a foliage-leaf. The root-cap is but little developed and rudimentary.
The likeness to a leaf of these remarkable roots of D. algaeformis is heightened
sometimes by the fact that on one side of them there is developed a palisade-like
parenchyma, and in this they exhibit, indeed, an analogy with phylloclades. The
roots of these plants diverge then in conformation, direction of growth, and function
altogether from the common condition, and this deviation is evidently brought
about under the influence of light.
We find also elsewhere amongst the Podostemaceae that roots are flattened
sometimes upon the side to the light and sometimes upon the side to the substratum.
Oenone leptophylla. In the root of Oenone leptophylla, the transverse
section of which is represented in Fig. 122 of Part I, its dorsiventral character is
well shown, and we observe how here, as in the aerial roots of the orchids which
will be mentioned presently, a form may be only indicated in one plant while it
appears as a conspicuous feature in a nearly allied one.
Hydrobryum. ‘The flattening reaches its extreme in Hydrobryum, a small
podostemaceous plant in which the roots form a flat crust upon the stones
and the shoots spring out from its upper side—a most remarkable construction
in which we naturally do not find any special root-cap. In this plant the roots
are anchoring-organs, but they are also of importance for assimilation and for
the production of shoots. This latter function is met with also in other Podo-
stemaceae in which the transformation of the roots has not gone so far (see Fig. 164).
Altogether the roots of the Podostemaceae give us one of the most striking examples
of how change of configuration goes hand in hand with change of function.
(c) AIR-ROOTS OF THE CYCADACEAE.
Remarkable root-formations which require further investigation are
found in many, perhaps all, Cycadaceae :—
These are roots which appear above the soil or near its surface, and by repeated
forkings give rise to coral-like structures. They are shown in Fig. 187, IJ, where
in Macrozamia Fraseri from each side of the thick beetroot-like hypocotyl there
spring near the surface of the soil some roots which grow upwards and perhaps may
be negatively geotropic. The swelling at their points indicates the beginning of
* These arise only on the side next the substratum. Whether light hinders their formation on the
exposed side and contact-stimulus induces them on the other is unknown.
* See pp. 222, 265.
282 THE ROOT IN PTERIDOPHYTA-AND SPERMOPHAYTA
branching. The lateral roots are much shorter, and branch earlier. ‘They are
represented in Fig. 187, I, in a rootlet of Ceratozamia robusta. In this plant the
coral-roots appear, as in Cycas, often in great numbers. They differ from the
ordinary soil-roots by their forked branching. As we find a like abnormal construc-
tion of the roots following upon an infection of lower organisms in other plants, for
instance in the mycorrhiza of many Coniferae and the mycodomatia of Alnus, it is
possible that micro-organisms are also the cause of the condition in Cycadaceae.
Janczewski ' considers the dichotomy in Cycas as a ‘ pathological process,’ brought
about by an ‘endophytic’ Nostoc. Reinke* was the first who showed that in the
cortex of the roots of such Cycadaceae an Anabaena is found. That these Cyano-
phyceae cannot be the cause of the forking in
the roots, as Janczewski would have it, and is
still less the cause of the appearance of the re-
markable breathing-roots*, is evident inasmuch
as the presence of the Anabaena is by no
means a constant occurrence. Other lower
organisms, such as fungi and bacteria, are
not constant inhabitants—according to some
slight investigations which I myself made—
and inducers of the air-roots of the Cycadaceae.
I must therefore assume that we have here to
deal with normal vegetative organs, whose
peculiarity consists in this that they come in
contact with the atmosphere, and that they
are probably to be considered as pneumato-
phores. At any rate we gain nothing by
supposing, as some authors do, that they are
Fic. 187. I, Ceratozamia robusta. Root ‘atavistic.’ The Cycadaceae are allied to the
with normal lateral roots below and coral-like on 8 ; :
branched air-roots. II, Macrozamia Fraseri. Filicineae, but dichotomous branching of the
Seedling with erect air-roots, A, springing from 5 F ees :
the hypocotyl, #, close to the insertion of the YOOt 1s unknown in the Filicineae, if we do
corytedons, cI, natural size, IT, halfnatural ot reckon Isoetes with them. We shall only
gain a knowledge regarding the significance
of the air-roots of Cycadaceae by experimental investigation. It must be remem-
bered that the air-roots need not always have to do with the absorption of oxygen.
(qd) ROOTS OF EPIPHYTES.
The assemblage of epiphytes which is so richly developed in the
tropics finds itself in the matter of nutrition and anchoring frequently under
conditions altogether different from those of plants rooting in the soil,
* Janczewski, Das Spitzenwachsthum der Phanerogamenwurzeln, in Botanische Zeitung, xxxii
(1874), p. 116.
2 Reinke, Uber die anatomischen Verhiltnisse einiger Arten von Gunnera, Linn., in Gottinger
gelehrte Nachrichten, 1872, p. 107; id., Zwei parasitische Algen, in Botanische Zeitung, xxvii
(1879), Pp. 473
* A. Schneider, Mutualistic Symbiosis of Algae and Bacteria with Cycas revoluta, in Botanical
ROOTS” OF -EPIPHYLES 283
and this has led to a divergence in the anatomical and morphological
construction of the root-system in many cases. Epiphytes have been
repeatedly and comprehensively described in botanical literature in recent
times 1, and I need therefore give here only a short exposition of their most
important relationships of an organographical character.
With reference to the anatomical structure the remarkabie apparatus
for the uptake of water which is visible in the velamen of the air-roots of
many orchids and of some aroids may be recalled. Further it may be
pointed out that the root-hairs have in many cases taken on qualities other
than those found in soil-roots. The root-hairs of soil-roots are extremely
sensitive to dryness. Many of the root-hairs of epiphytes are by no means
so sensitive. The older root-hairs, especially in many epiphytic Filicineae,
have a brown colour; their walls behind the point are ‘ encrusted’ with a
substance which resists the action of sulphuric acid and boiling potash, and
this makes them very resistent to drying. The root-hairs also partly serve
here to fix water by capillarity. In Antrophyum cayennense”*, for example,
the shoot-axis is entirely enveloped by a dense reddish root-felt which is
formed by the numerous exposed root-hairs, and it forms a kind of root-
sponge for the taking up of water. In many epiphytic orchids also the
root-hairs are peculiarly constructed °.
The geotropic behaviour of these roots is interesting. Many aerial
roots of orchids have lost their geotropic sensitiveness in great measure, in
others it appears in a peculiar form. Some of the more remarkable con-
structions are these :—
a. NEST-ROOTS OF EPIPHYTES.
By this name we designate negatively geotropic roots which grow
up out of the substratum and form nest-like masses within which humus
accumulates. They are found in some species of Aroideae, for example
Anthurium Hugelii and others, and amongst Orchideae in Grammato-
phyllum speciosum, species of Cymbidium, Aeriopsis javanica*, and others.
Gazette, xix (1894), p. 25, found bacteria in the outer cells of the coral-roots of Cycas revoluta, but
it does not follow that this is either a ‘ symbiosis’ or a cause of the appearance of the roots.
1 See Schimper, Die epiphytische Vegetation Amerikas, in Botanische Mittheilungen aus den
Tropen, i, Jena, 1888; Goebel, Pflanzenbiologische Schilderungen, i (1889).
2 Goebel, Archegoniatenstudien: VIII. Hecistopteris, eine verkannte Farngattung, in Flora, lxxxii
(1896), p. 73. z
3 They may be ‘ lignified,’ according to Molisch, Uber Wurzelausscheidungen und deren Einwirkung
auf organische Substanzen, in Sitzungsberichte der Wiener Akademie, xcvi, I (1887), p. 107, footnote.
Free hanging aerial roots of orchids form usually no root-hairs, but this is not always so. They
appear in moist air upon the air-roots, usually adherent, of Vanilla, Phalaenopsis, and others, even
if these do not touch a substratum.
* The numerous close-set, negatively geotropic, thin roots are covered with short, spreading, lateral
rootlets. AJl water flowing down from the upper surface of the tree will filter through this weft of
roots, but it cannot retain large objects. See Ratiborski, Biologische Mittheilungen aus Java, in
Flora, Ixxxv (1898), p. 352.
284 THE ROOT IN: PTERIDOPHYTA’ AND-SPERMOPHYIs
6. ASSIMILATION-ROOTS OF EPIPHYTES.
The roots of epiphytes which are exposed to the light usually contain
chlorophyll, but where there are numerous and well-developed leaves then
chlorophyll is only present in relatively small amount. In some Orchideae,
however, the roots are essentially the assimilation-organs and even may be
the exclusive ones, and then they show corresponding changes in their anato-
mical structure and their configuration—they are conspicuously dorsiventral ?.
Phalaenopsis. I shall first of all speak shortly of the formation of
the roots in the genus Phalaenopsis. In Fig. 188 there are portions, in
transverse section, of the root of three species. Ph. Esmeralda (Fig. 188, I)
has roots which we cannot designate as dorsiventral, but they function only
to a small extent as assimilation-organs ; they are rather to be regarded,
apart from their capacity to absorb water, as seats of water-storage in the
dry period during which the plant has lost its leaves. Ph. Lueddemanniana
(Fig. 188, II) shows conspicuously flattened and
ae dorsiventral roots. The root-hairs are produced
e | rate upon the under side and only along the middle
See “ ~y¥@® line of the roots which lie close upon the branch
ee an ante ae of the tree*. The’ long roots, oftena meter
long, of Ph. Schilleriana (Fig. 188, III) show
Fic. 188 Phalaenopsis. Roots this flattening in an extreme degree. These
Mlda, TL Ph. Lucddemannisna it, roots are firmly adherent to the stem of the
IV, V, Ph. Schilleriana. Mature 2 F 1
root in Ill; youngroot, thatistosay tree (Pig. 189).) Dhestissuesoneaiewicastes en
lose behind vegetative point in IV : . i :
Boe a Isic ieee palestine both sides of the central cylinder is massively
okt macnifeation “1 of same developed—an arrangement which may be of
advantage by enabling the root to retain by
capillarity the water upon the under side. The flattening begins very
early; probably the transverse section of the vegetative point of the root is
not circular but elliptic®. The uptake of water chiefly takes place by the
under side whilst the upper side is constructed to protect the root against
strong transpiration. The anatomical structure (Fig. 190) shows this clearly.
On both sides there is a two-layered velamen, under which lies the
exodermis. The outer walls of the cells of the exodermis are greatly
thickened in those of the upper side, but only slightly thickened in those
of the under side. The velamen is developed upon the upper side only as
? See Janczewski, Organisation dorsiventrale dans les racines des Orchidées, in Annales des
sciences naturelles, sér. 7, ii (1885); also Goebel, PAanzenbiologische Schilderungen, i (1889), p. 197,
and ii (1893), p. 344. :
* The factors which determine the localization of the root-hairs upon the under side require
investigation. The substratum is not the effective influence because /rze roots in moist air have
hairs only upon the under side. Possibly the dorsiventrality originally induced by light is the
critical factor.
* I have only examined one root-tip. Fig. 188, IV, represents a transverse section near
the tip.
ROOTS: OF EPIPHYTES 285
an apparatus for taking up water, and is composed of empty thin-walled cells
with fibre-thickening. The outer thin-walled layer of the velamen is hardly
visible upon the upper side, but the inner is transformed into thick-walled
cells. In correspondence with this the characteristic ‘aeration-striae’ of
the velamen of the aerial roots of the Orchideae are to be found here
only upon the under side. It has been already pointed out! that the
flattening of the aerial roots of many Orchideae is brought about by light ?,
whilst in other cases it is ‘ fixed by
inheritance. Phalaenopsis Schil-
leriana furnishes us with a case
where the flattening is not due to
light. A portion of the root many
Fic. 189. Phalaenopsis Schilleriana. Roots Fic. 190. PhalaenopsisSchilleriana. Portion
flattened and adpressed to bark of a tree. The of root in transverse section. I, through the
notches on two of the roots are a consequence of upper side. II, through the under side. Zx,
interruption of growth. One-half natural size. exodermis; v, velamen.
centimeters long which was grown ina non-translucent tube was quite devoid
of chlorophyll, and yet as flat as a portion which was developed in light.
On the other hand, thickening of the walls of the cells, especially of the
exodermis, was markedly less*. In many species of Phalaenopsis the
leaves die away in the annual dry season, and only the green roots,
which are well protected against loss of water, and the vegetative point of
the shoot persist.
Taeniophyllum. This behaviour leads us on to the cases in which the
1 See Part I, p. 246.
The anatomical structure also through transpiration-relationships.
I pass over other anatomical differences.
to
286 THE ROOT IN PTERIDOPHYTA AND SPERMOPHYTA
leaves are reduced to scales without chlorophyll, and in which the roots are
the special assimilation-organs. We find this in species of Taeniophyllum,
and also in Angraecum fasciola and others ; foliage-leaves do not arise even
in the germination in Taeniophyllum', and as the roots are frequently
adapted to living in light the foliage-leaves do not appear, according to
Wiesner, even if Taeniophyllum be grown in the absence of light.
c. ANCHORING-ROOTS OF EPIPHYTES.
In some epiphytic plants which are able to take up through their leaves
large quantities of water, with the substances that are dissolved in it, the
roots serve only as anchoring-organs. They cannot take up water to cover
the needs of the plant, their conducting channels are small, and their
mechanical tissues are strongly developed. Such anchoring-roots are found
in some species of Tillandsia, for example T. bulbosa and others, and in
some (not all!) other epiphytic Bromeliaceae. That Tillandsia usneoides
has lost its roots has been stated above ~.
(¢) ANCHORING-ROOTS OF CLIMBING PLANTS.
Root-climbers possess anchoring-roots, and are not sharply distin-
guished from the epiphytes. We frequently find in them a division of
labour in the roots such as has been so long known in the case of Hedera—
we have anchoring-roots and nourishing-roots. As anchoring-roots we
understand here those which serve purely as anchoring-organs ; their func-
tion as nourishing-roots having been given up either entirely or in great
measure. One can easily satisfy oneself in the case of Hedera, for example,
anchored to a wall by means of its anchoring-roots, that if its connexion
with the nourishing-roots which are in the soil is cut through the plant
withers. The nourishing-roots on the other hand are only for the purpose
of acquiring and bringing nutrition. Anchoring-roots* are distinguished
from nourishing-roots not only by their shorter length and thickness, their
shorter duration of life and different anatomical structure, but also by dif-
ferent physiological peculiarities. They have lost entirely or in great measure
geotropic sensitiveness, and therefore their negative heliotropism and their
sensitiveness to contact-stimuli are often much stronger than in soil-roots *.
As regards relationship to contact-stimulus we may specially bring
under notice the roots which Von Mohl?® designated root-tendrils because
* With regard to the relationships of configuration see Goebel, Pilanzenbiologische Schilderungen,
i (1889), p. 194; the species of Taeniophyllum figured there (Fig. 86) is not T. Zollingeri, but
a mountain form in which the assimilation-roots are only partially pendent.
a'See'p: 205,
* See Went, Uber Haft- und Nahrwurzeln bei Kletterpflanzen und Epiphyten, in Annales du Jardin
botanique de Buitenzorg, xii (1895).
* How far positive hydrotropism has to be considered as I formerly supposed it was, demands
experimental inquiry. See Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 160.
® Mohl, Uber den Bau und.das Winden der Ranken- und Schlingpflanzen, Tiibingen, 1827, p. 493
ANCHORING-ROOTS OF CLIMBING PLANTS 287
they can twine round thin supports just like a tendril. These root-
tendrils, however, are not always only anchoring-roots. Von Mohl
specially observed them in Vanilla aromatica, in which species they hang
straight towards the soil if the twig from which they spring hangs free in
the air, but force themselves into the splits on the surface of a tree-stem
should they reach it, and twine round any thin support with which they
come in contact, in the same manner as do tendrils. The melastomaceous
plants Medinilla radicans, Dissochaeta, and
others, show the same features, but in them
the root-tendrils are exclusively anchoring-
organs.
The difference in behaviour between
anchoring-roots and nourishing-roots may
be depicted in one single example. The
anchoring-roots of Philodendron melano-
chrysum (Fig. 191) twine round thick tree-
stems like horizontal thongs; they are not
geotropic, but they are negatively helio-
tropic and extremely sensitive to contact-
stimuli, the cylinder of conducting bundles
has few and narrow vasa and much scleren-
chyma. The nourishing-roots are thicker
than the anchoring-roots ; they do not arise
like them from the side of the shoot-axis
of Philodendron which is turned to the
substratum, but upon the opposite side;
they grow downwards towards the ground,
and usually in contact with the support
on which the plant is climbing, but in
other Aroideae they pass down freely
through the air; the cylinder of conduct- Sees SD een Ene
ing bundles is larger, and has many vasa Homecneal ee eronts. Half natural
and little sclerenchyma. It is clear that
the nourishing-roots can only be formed after the plant has reached a
certain size and has already obtained material for the formation of these
roots, and development of the nourishing-roots is rendered necessary
because so many of these climbing plants reach so great a size. In
climbing plants which soon lose their connexion with the ground and
thus throw off their original root-system, or which from the beginning
grow upon the trees and not in the soil, it may be assumed that anchoring-
also Treub, Sur une nouvelle catégorie de plantes grimpantes, in Annales cu Jardin botanique de
Buitenzorg, iii (1883); Went, Uber Haft- und Nahrwurzeln bei Kletterpflanzen und Epiphyten, in
Annales du Jardin botanique de Buitenzorg, xii (1895).
4
288 THE ROOT IN. PTERIDOPHYTA AND. SPERMOPHYTA
roots first of all develop out of soil-roots, and then nourishing-roots form
from these—an explanation which is supported by the interesting occurrence
in the Aroideae of intermediate transition-forms between anchoring-roots
and nourishing-roots '.
What has been said applies equally well to other climbing plants.
Freycinetia imbricata, one of the Pandaneae, has no nourishing-roots but
only anchoring-roots, but in Fr. javanica anchoring-roots may develop into
nourishing-roots. Fr. Bennettii has well-developed nourishing-roots. Anchor-
ing-roots are elsewhere known in a large number of climbing plants of the
Clusiaceae, Artocarpeae, Bignoniaceae, Asclepiadaceae, and other families.
(7) Roots As MECHANICAL ORGANS OF PROTECTION. THORN-ROOTS.
Roots may develop into thorns just as do leaves and shoots. Examples
are known both amongst the Monocotyledones and Dicotyledones.
MONOCOTYLEDONES.
Amongst Monocotyledones the case of the palms Acanthorhiza *
and Iriartea have been long known :—
Acanthorhiza aculeata. Acanthorhiza aculeata possesses in its lower
stem-region normal soil-roots, but in the upper region there are formed
feebler roots which lose their root-cap, whilst the cell-membranes, with the
exception of the sieve-tubes, become lignified, and the cells of the outer
cortex take on a strongly sclerenchymatous character.
Iriartea. In Iriartea it is the lateral roots which become small thorns.
Dioscorea prehensilis. Dioscorea prehensilis® furnishes a further
example. This remarkable plant possesses tubers which are enclosed in
a sheath of thorn-roots. These are in the soil not above it as in the case
just mentioned. There can be little doubt that these thorns are an effective
mechanical protection against animals, perhaps also against the pressure of
the dried-up soil. Similar relationships are found perhaps in D. spinosa.
Moraea. A South American species of Moraea*, one of the Irideae,
has at the base of its stem a dense net-work of thorn-roots which recalls the
skin of a hedgehog. The thorn-root-system is here hypogeous.
DICOTYLEDONES.
Myrmecodia. Only one case of thorn-roots is known, that of the
remarkable rubiaceous genus Myrmecodia, which Treub * has investigated.
The thorns which appear upon the outer side of the tuber and the
1 See Went, Uber Haft- und Nahrwurzeln bei Kletterpflanzen und Epiphyten, in Annales du
Jardin botanique de Buitenzorg, xii (1895).
2 Friedrich, Uber eine Eigenthiimlichkeit der Luftwurzeln von Acanthorhiza aculeata, Wendl., in
Acta Horti Petropolitani, vii (1880), p. 537; see also Russow, Uber Pandanus odoratissimus,
Untersuchungen, p. 537.
* Scott, On Two New Instances of Spinous Roots, in Annals of Botany, xi (1897), p- 327-
* Treub, Sur le Myrmecodia echinata, Gaud., in Annales du Jardin botanique de Buitenzorg, iii
(1883), p. 129. The literature is cited here.
STORAGE-ROOTS. MYCORRHIZA 289
shield-like projections of the stem bearing the leaves are metamorphosed
roots which have lost their root-caps.
(¢) STORAGE-ROOTS.
These are roots which are used for the storage of reserve-material.
According to the amount of this they diverge more or less from the con-
figuration of the ordinary soil-root. Where considerable masses of reserve-
material have to be deposited they develop parenchyma for its reception,
and frequently therefore become fleshy. The whole root may thus become
a tuber, or only portions of it, and these are then separated from one
another by regions showing the common root-character. We find this in
the cucurbitaceous Thladiantha dubia, and in it the tuberous portions of the
root persist whilst the intermediate portions die away. Where the whole
root forms one tuber the root-cap usually disappears, as for example in the
tubers of Ranunculus Ficaria and of the Ophrydeae. A description of these
tuberous roots belongs, however, more to the province of anatomy. All
fleshy roots do not, however, serve as storage-roots; at least this does not
appear to be the case!, or is so only in a slight degree, in the fleshy roots
of Oxalis tetraphylla previously mentioned as pull-roots?.
(4) Mycorruiza.
I pass over here the formation of mycorrhiza, as any account of this would
involve the description of a number of details of an anatomical and physiological
experimental character, which is beyond the scope of this book. The examples
which I have already given will show how in a number of cases function and the
formation of organs hang together.
VI
EEO OF DEVELOPMENT OF THE ROOT
In plants whose vegetation is periodically interrupted the development
of the root naturally shares in this, and we may say generally that the
development of the root precedes in time the epigeous parts, a fact which
is easily observable in most seedlings, and the biological significance of
which requires no explanation. The periodicity of root-development is
very sharply marked in bulbous and tuberous plants, because in them the
formation of the root is limited to a very short period. Supposing that
the moisture and other conditions are favourable the development of the
roots takes place in Ranunculus Ficaria at the end of June, in the bulbs of
Fritillaria imperialis in August, whilst the majority of other bulbous plants
develop their roots commonly in the autumn before the bud begins to
* See Rimbach, Beitrage zur Physiologie der Wurzeln, in Berichte der deutschen botanischen
Gesellschaft, xvii (1899), p. 28. * See p. 272.
GOEBEL II U
290 THE ROOT IN PTERIDOPHYTA AND SPERMOPHYTA
shoot. Tulipa sylvestris, for example', forms in September twenty to thirty
thread-like roots without root-hairs, and these die in June as well as the
epigeous parts. A longer duration of the roots in bulbous plants may,
however, take place; for example in Leucojum vernum, which inhabits
moist places, the roots live from two to three years. Roots which have
different functions in these bulbous and tuberous plants develop at different
times?. Thus the nutritive roots of Crocus longiflorus (Fig. 184, I) arise in
the autumn, the pull-roots in the spring when the new tuber is ready.
In trees? we can as a rule distinguish two periods of development of
roots, one in autumn, the other in spring before the shooting out of the
leaves. These periods are separated by the winter's rest, which is here not,
as in the case of the shoots, a resting period caused directly by external
factors, but must be regarded as only a retardation caused by the sinking
of the temperature. In a mild winter development and growth of the
roots takes place in the winter. In Tilia europaea, for example, a copious
formation of the root-system occurs in August, September, and October,
and this the cold interrupts. In one special case in a mild winter the new
roots were formed again in December; the period of greatest growth fell
in April before the shooting out of the buds. All trees do not, however,
behave alike in this respect. Quercus, for example, has no strong root-
growth in spring. Its new rootlets only begin to show in June, and the
period of greatest growth falls in October. The differences, so far as they
may be considered constant, evidently have the closest connexion with
the whole economy of each plant. We are, however, very incompletely
acquainted with the co-operation between the several organs.
' See Rimbach, Beitrage zur Physiologie der Wurzeln, in Berichte der deutschen botanischen
Gesellschaft, xvii (1899), p. 28. 2 "Seerp.) 270:
3 See Resa, Uber die Periode der Wurzelbildung. Inang. Dissertation, Bonn, 1877.
[291]
THE. SHOOF
The general features of shoot-formation have been described already '.
The conformation of the leaves is in most cases so important for the con-
figuration of the shoot, that it appears advisable first of all to speak of the
leaves and then to pass on to consider the different forms of the shoot.
A. THE LEAF
|
INTRODUCTION
The characteristics of leaves have been already described ?, and it has
been shown ® also that in the Bryophyta, starting from leafless forms, the for-
mation of leaves has been frequently repeated along different paths. We do
not know how the formation of leaves in the Pteridophyta and Spermo-
phyta has phyletically come about. The leaves in these groups have nothing
whatever to do with the formation of the leaves in the Musci, for there the
leaves belong to the sexual generation, and we have no room here to discuss
the purely hypothetic view which derives the leafy plant of the Pteri-
dophyta and Spermophyta from the sporogonium of a moss. The recently
repeated attempts also which have been made to explain the leaves of ferns
as shoots are based upon entirely false suppositions, and have no longer even
a historical interest, and therefore we shall say nothing about them.
That the chlorophyllous assimilating foliage-leaf, whose capacity alone
renders possible further development in the autotrophic plants, is the leaf-
form out of which the others have been derived by change of function,
follows from what has been already said*+. Moreover there is scarcely one
foliage-leaf which has not some other function in addition to assimilation.
Apart from transpiration, we may point out the importance of the leaves as
protective organs to the buds, whether these be terminal or axillary—a work
which is sometimes taken up by different parts of the leaf. In Aristolochia
Sipho, for example, the leaf-lamina is folded about the end-bud, the leaf-
base encloses the axillary buds. Analogous relationships are found in other
plants with small leaves placed in many rows.
1 See Part I, section I, chap. ii. 2 See Part I, p. 13.
Ss See p. 35. * See Part I, p. 6.
292 THE LEAF IN PTERIDOPHYTA AND SPERMOPHYTA
No organ of the plant-body appears in so many forms as does the leaf,
and this is so because the relationships of the leaf to the outer world are
by far the most manifold. In correspondence with this there are great
differences in the azatomic and symmetric construction of the leaf.
ANATOMIC CONSTRUCTION.
Vascular Bundles. We must specially mention the behaviour of the
vascular bundle, as it has been used partly for solution of the question
whether the organ is a leaf or not.
The majority of leaves are traversed by one or many vascular bundles which
are often copiously branched, and are arranged, as will be shown hereafter’, in
definite relation to the growth of the leaves, whose function we must suppose to be
known. ‘There are, however, leaves without vascular bundles, and this simplifi-
cation of structure must be regarded as a veduction. Leaving out of consideration
the numerous cases in which the primordium of the leaf remains stationary at an
early period of its development and differentiation’, as well as those of the outer
bud-scales of many plants which show a rudimentary primordium of a vascular
bundle, we find leaves without vascular bundles in the bracts of the flower of
Utricularia orbiculata*; in the scale-leaves on the rhizome of the saprophytic
orchid Epipogon Gmelini where there is no chlorophyll, and according to Schacht *
the leaves consist of three cell-layers, possess neither vascular bundle nor stomata,
serve only as protective organs of the vegetative point, and have evidently only
a short existence ; in the scale-like leaves also of the parasitic Cuscuta there is only
a trace of vascular bundles, and similar cases can readily be found in other
saprophytes and parasites’.
That leaf-structures without vascular bundles occur in the flower-region should
not surprise us. ‘Thus they are wanting, for example, in the sepals of Gaiadendron
punctatum (Loranthaceae), the stamens of some Arceuthobiaceae, the carpels of
Balanophoreae. In all these cases we have to deal with a small delicate leaf-
structure whose differentiation is correspondingly simplified.
Hymenophyllaceae furnish also a striking proof of this. The small sterile
leaves of Trichomanes Motleyi® have no trace of a vascular bundle in their leaf-
nerves, the reduction of the conducting channels for water being possible here
because the leaves can take up water directly from the outside, as is the case
1 See p. 338. * Not proceeding beyond the stage of a papilla.
* Goebel, Morphologische und biologische Studien : V. Utricularia, in Annales du Jardin botanique
de Buitenzorg, ix (1891), p. 55.
* Schacht, Beitrige zur Anatomie und Physiologie der Gewachse, Berlin, 1854, p. 115.
° It appears to me not superfluous to refer to these details here, although they are mentioned in
Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der Botanik, iii
(1884). Van Tieghem, Sur l’existence de feuilles sans méristéles dans la fleur de certaines Phanéro-
games, in Revue de botanique, viii (1896), p. 482, has asserted: ‘ Happily such roots, stems, or leaves
[that is without vascular bundles] have not yet been met with in the vegetative apparatus of
Phanerogams.’
° G. Karsten, Morphologische und biologische Untersuchungen iiber einige Mpiphytenformen der
Molukken, in Annales du Jardin botanique de Buitenzorg, xii (1895), p. 135.
SYMMETRY OF CONSTRUCTION OF LEAF 293
amongst Musci. The fertile leaves, however, have in the leaf-nerves a bundle
provided with tracheids—usually only with one.
Similarly the water-channels in the submerged Ceratophyllum are entirely
reduced.
The same holds for the leaves of the podostemaceous Terniola longipes,
Tristicha trifaria, and Tr. hypnoides*. Weddellina squamulosa has leaves upon
the lateral twigs, in which all trace of even the most rudimentary vascular bundle is
wanting.
The possession of vascular bundles cannot therefore be considered as
a general feature of the leaves in Pteridophyta and Spermophyta.
Chlorenchyma. The formation of chlorophyllous leaf-tissue is in the
same position. As will be shown briefly in the following pages, chlor-
enchyma is extremely variable as a tissue in the leaves themselves, and is
found also in phylloclades, which are shoot-axes, in the same state as has
been considered to be typical of the leaves.
SYMMETRY OF CONSTRUCTION.
We are accustomed to consider as typical leaves those which are dorsi-
ventral (bifacial), and which possess usually a leaf-lamina in the form of
a thin plate of tissue. Had botany started in West Australia instead of in
Europe, this leaf-form would have been considered as a not altogether rare,
but yet by no means typical form.
LEAF-FORM IN AUSTRALIA.
Radial and bilateral \eaves are very common in Australia, and are
found in the most different families, and there are also ‘transitions between
dorsiventral and bilateral leaves*. The bilateral leaves are usually not
spread out horizontally like dorsiventral ones ; much more commonly they
adopt a ‘ profile-position ’ like the sickle-leaves of the Eucalypti, the phyl-
lodes of the Acaciae, the leaves of many Proteaceae, or possess entirely or
nearly vertically placed surfaces, or diverge in their form from the usual.
Cylindric leaves are not uncommon. Fig. 192 represents a twig of
Hakea trifurcata, one of the Proteaceae, which at the beginning of the vege-
tative period produces simple flat leaves, but the leaves which are produced
later on are branched, and have nearly a circular outline on transverse
section °.
_ The flat leaves have the upper and under sides essentially differently
constructed, but they are less strongly protected against loss of water.
1 See Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 340, where there are figures.
? See the facts stated by Reinke, Untersuchungen iiber die Assimilationsorgane der Leguminoseen, in
Pringsheim’s Jahrbiicher, xxx (1897).
* The palisade-parenchyma here goes entirely round the leaf, but is interrupted by many rod-
cells; it is also characterized by smaller cells for a short distance upon the under side, and thereby
there is always a slight difference visible between the upper and under side.
294 THE LEAF IN PTERIDOPHYTA AND SPERMOPHYTA
Their epidermis is not so thick as in the cylindric leaves, and the stomata
are not sunk in pits. The surface which is exposed to light in the hori-
zontal leaves is larger than the whole surface of the cylindric branched
leaves. It is well known, however, that light increases transpiration.
Whilst I have not observed in Hakea trifurcata any transition between
entire and divided leaves, such gradations are found in abundance in other
species of Hakea, for example H. pectinata. It is not possible, however, to
bring all the manifold leaf-forms of the Proteaceae severally into relation-
ship with their life-conditions ; to do this would require not only full know-
ledge of the conditions
of life, but also of the
whole organization of
the plants in question.
Under the same ex-
ternal conditions the
leaf of one plant, which
through the activity of
its root-system obtains
less water, may be xero-
philous, that of another,
which through the
activity of its similar
organs receives more
water, is not xerophi-
lous. I specially draw
attention to this because
in recent times ques-
tions of adaptations
Fic. 192. Hakea trifurcata, R.Br. Lower leavessimple flat ; upperleaves .
branched cylindric. : Be have been frequently
treated in a one-sided
manner on the basis of an investigation of a szzgle organ.
LEAF-FORM IN EUROPE.
In Europe comparatively few plants possess bilateral or radial leaves.
Amongst plants with dzlateral ones, however, we must notice the so-
called ‘ compass-plants ', which bring their leaves, which have a similar leaf-
construction on both sides, into the profile-position under intense insolation,
and also a number of marsh-plants—the sword-like leaves of Iris, whose
different species, but by no means all, live in wet places, and those of Acorus
* See Stahl, Uber sogenannte Kompasspflanzen, in Jenaische Zeitschrift fiir Naturwissenschaften,
xv (1881) ; Heinricher, Uber isolateralen Blattbau mit besonderer Beriicksichtigung der europiischen,
speciell der deutschen Flora, in Pringsheim’s Jahrbiicher, xv (1884). Further literature is cited by
Haberlandt, Physiologische Pflanzenanatomie, ed. 2, Leipzig, 1896, p. 260.
LEAF-FORM IN EUROPE 295
Calamus, have markedly from the outset a profile-position’; in Typha
this position is attained by a slight torsion of the blade.
Amongst plants with radial leaves we have our species of Juncus, in
which the leaf has a circular transverse section, and internally is a tubular
leaf, that is to say, it contains numerous air-canals which conduct oxygen to
the subterranean parts. It is clear that such leaves, which we only meet
with in plants growing in the light and therefore freely exposed to the
wind and rain, offer a very small surface to mechanical
influences. The leaf-form of Juncus finds a parallel in
the cylindric leaves of Pilularia which too grows in moist
places, and in those of Crantzia and Ottoa two genera of
Umbelliferae in which the leaves are quite like those of
the species of Juncus that are partitioned by diaphragms.
In these Umbelliferae probably we have to do with a
leaf-form which has arisen by reduction from compound
leaves. In an investigation of Crantzia linearis (Fig.
193), a plant which I collected in New Zealand, I noticed
on the young leaves the primordia of lateral organs which
one might indeed consider as arrested pinnules, although
they only appeared to be in onze row, and not, as one
would expect, in two rows. The features of Oenanthe
fistulosa support this conclusion. On its tube-like leaf-
spindle the leaflets appear in reduced form. In Ottoa ”
I found at the end of the leaves only a small depression
or flattening which perhaps corresponds to the remains
of a rudimentary blade.
In the same biological category I would also place
the leaves of some species of Eryngium which are so like
those of Monocotyledones. They are not phyllodes, as — ,,,226:,19%,,Ct2qtz?
linearis. Young leaf.
At the base, the narrow
is shown by the transition-forms and by the history of dit cfthe open vagine.
Above, the dotted trans-
development, but consist of leaves whose blade has ‘ersetines indicate the
become greatly elongated, whilst there has been reduction L222", 379. SM
or suppression of the leaflets and of the leaf-stalk. I ovaho.2usssh ate
find in species of Eryngium, for instance E. bromeliae- 9 ““S™*°¢ “P07
folium, E. pandanifolium, and others, which are such beautiful marsh-plants,
that the narrow grass-like leaves undergo the torsion of the blade that is
characteristic of Typha and Sparganium, and thereby they take up the
profile-position. By this means they are protected from great transpiration
as fitly as a number of marsh-plants are by their xerophilous character®.
We need not be surprised that in those plants, growing as they do in
1 See p. 328.
2 Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 45.
* See what is said later, p. 447, about the shoot-formation of some Cyperaceae and Restiaceae.
296 THE LEAF IN PTERIDOPHYTA AND SPERMOPHYTA
positions openly exposed to the wind, the earlier differentiation of the
leaf-blade has been lost, and the torsion of the leaf-blade is of advantage
from a mechanical point of view.
We are justified by the facts which have just been stated in saying that
in the ordinary plagiotropous leaves their dorsiventral construction is caused
by their lie, although so far as we know it has become usually an inherited
character ; and in support of this it may also be pointed out that a similar
dorsiventral construction is marked in shoot-axes and roots which have
become leaf-like. The behaviour of a number of scale-like leaves bears also
upon the causal relationship of lie to leaf-structure. In the xerophilous Com-
positae Lepidophyllum quadrangulare and Phoenocoma prolifera ' the leaves
lie with their upper side closely pressed against the axis of the shoot; the
under side, which is turned outwards, is the most important for assimilation,
and it has palisade-parenchyma, whilst the upper side has spongy paren-
chyma. We thus have the normal conditions of leaf-structure reversed.
As here a change of the anatomical structure has come about in connexion
with the change from the usual lie, it follows that the dorsiventral differen-
tiation in the ordinary leaf was originally caused by the lie.
INVERSION OF THE LEAF.
The cases just mentioned lead us on to speak of the special pheno-
menon that in some plants the morphologically upper side of the leaf has
the structure of the under side, and the reverse is also the case. In plants
which exhibit this, a torsion takes place after the unfolding of the leaves
which brings the anatomically upper side upwards, and the anatomically
under side downwards. A number of Monocotyledones show this, for
example Alstroemeria *, Allium ursinum, Pharus brasiliensis, and some
other grasses. Amongst Dicotyledones analogous cases are found, for
instance, in the composite genus Metalesia, and in Stylidium.
A. MONOCOTYLEDONES.
Pharus brasiliensis. In this plant I find the following. The morpho-
logically upper side of the leaf is brighter green than is the under side. This
comes about in this way: the epidermal cells of the upper side are higher than
those of the under side, and the chlorophyllous cells, which in the greenhouse-
plant I examined were in two layers, one under the upper side and one under the
lower side, are higher upon the under side than upon the upper side. The upper
1 See Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 32, Plate XXIII, Fig.12. Passerina
hirsuta, one of the Thymelaeaceae, resembles those Compositae. On the seedling-plant the decussate
leaves have essentially the ordinary structure, but later, where the alternate leaf-position occurs, the
leaves stand pressed to the stem, and upon the very hairy upper side there is spongy parenchyma
and stomata, whilst the under side does not possess these but has palisade-parenchyma. See Caruel,
Struttura delle foglie della Passerina hirsuta, in Nuovo giornale botanico italiano, i (1869), p. 194.
2 Czapek, Studien iiber die Wirkung dusserer Reizkrifte auf die Pflanzengestalt, 1, in Flora,
Ixxxv (1898), p. 429. The literature is cited here.
—_
INVERTED LEAVES OF MONOCOTYLEDONES 297
side is by a torsion of the leaf-base directed downwards. In the leaf standing
immediately below the inflorescence the torsion is only through go”.
Alstroemeria. Czapek' has carefully examined the process in Alstroemeria.
The leaves after the first ones submit as they unfold to a torsion through 180°
(Fig. 194) which may take place, although tardily, in darkness. Czapek comes to
the same conclusion regarding the origin of this peculiar inversion of the leaf-
surfaces as I have done. He holds that the inverted leaves of Alstroemeria have
arisen in the course of the phyletic development of the genus out of leaves which
first of all took up a profile-position, and in consequence of this had a similar
construction on 40th sides. Such leaves occur in some species of Alstroemeria,
and in species also which have leaves exhibiting torsion the
first leaves of the shoot have a profile-position*. This profile- JAS
position which has to be regarded as a protection against in- f
tense insolation and transpiration, was changed again under |
altered external conditions into a horizontal position, not
by a reversion of the torsion through go’, but by a further
torsion through go°, and thus the leaf came to have an in-
verted dorsiventral construction in correspondence with its
changed lie. I think, however, it is probable that the inversion
of the leaf-surface took place in different ways in different E:
groups. | |
Melica nutans. Among endemic grasses Melica nutans =|
shows inversion of the leaf-lamina*. The basal leaves show no = ee re
torsion usually, and turn therefore the brighter green upper side —meriz psittacina. Leaf.
: - Torsion of the stalik-
upwards. On the leaves which stand higher up on the shoot like lower _ portion
the lamina becomes either vertical with a bending over of its aay ato Natural
upper part or it undergoes a torsion whereby the under side ~~
is brought upwards. As now xerophilous forms such as Melica ciliata are found
with rolled leaves, we may suppose that the changes proceeded as follows :—
Starting from a leaf having the ordinary lie, there followed first of all either an
erect leaf lying against the haulm ora rolled leaf whose under side took on the
structure of the upper side *, as in the scale-leaves mentioned above. If such forms
again adapt themselves to moister conditions the structural changes which have
been induced cannot be made to revert. The leaf indeed becomes again hori-
zontal, and exhibits now the movements which result in its lie as described
above. That the lower smaller leaves which are situated in a moister environ-
ment do not share in this, is from the biological standpoint readily understood.
Stahl® has advanced another explanation which does not appear to me to be
a fertile one, and he has given no experimental proof. He finds in the inversion
ee
* See Czapek, Studien iiber die Wirkung ‘usserer Reizkrafte auf die Pflanzengestalt, 1, in Flora,
lexxy (1898), p. 429.
? With reference to their behaviour on the clinostat, see Czapek, op. cit.
* The stomata are found only upon the upper side which bears also hairs. The ‘unfolding cells”
lie as usual upon the upper side.
* Especially limitation of the stomata to the upper side, as this is the rule in this kind of leaf
* Stahl, Regenfall und Blattgestalt, in Annales du Jardin botanique de Buitenzorg, xi (18g3), p-15!-
298 LEAF-DIFFERENTIATION, PTERIDOPHYTA AND SPERMOPHYTA
of the leaf-lamina ‘a means for lessening the effect of the impact of rain.’ The
leaf-blade according to him is made less stiff by the torsion. But the plants in
question, at least our endemic ones, do not grow under conditions which would
render a special protection against raindrops as of much importance, and the
leaves are by their conformation no more set out for protection against raindrops
than are those of other monocotylous plants growing in the same locality, for
example Convallaria majalis. The leaf-lamina of Melica nutans is moreover no
broader than that of many other grasses with leaves which are not inverted.
Pharus brasiliensis possesses a stalk-like narrowed portion of the leaf-surface which
can throw off the raindrops from the leaf without any inversion of it. We find
further in other grasses that the leaf-blade is often only vertical or, as is often the
case in Brachypodium pinnatum, is only twisted in its upper part. According to
Stahl’s hypothesis it would be difficult to understand how these leaves can change
their structure. That in Alstroemeria, for example, the flat leaf-stalk, which is
nothing else than the lower narrowed portion of the blade, should attain by the
torsion a greater mechanical capacity cannot be denied.
B. DICOTYLEDONES.
Among Dicotyledones, apart from the above-mentioned Compositae,
I know of a torsion of the leaves only in some Australian species of
Stylidium—S. pilosum and S. reduplicatum 1.
Stylidium. The stomata here lie upon the morphologically upper side, the
lower side is covered by a many-layered thick-walled epidermis, a construction
which is favourable to the protection of the bud. After unfolding a torsion takes
place somewhat early in S. reduplicatum, later in S. pilosum. ‘There are species
of Stylidium with bilateral as well as with rolled leaves, and the explanation
advanced above for the grasses would appear here also to be the most natural.
Stahl’s hypothesis is evidently inapplicable to this case.
II
OUTER DIFFERENTIATION OF THE LEAF
The configuration of small scale-like leaves is very simple; the leaf
exhibits no segmentation, and there may be only a leaf-surface. Usually,
however, we find the leaf is composed of a /eaf-blade—the lamina, a /eaf-
stalk—the petiole, and a /eaf-base. In the leaf of Juncus there is only the
cylindric leaf-lamina and the short sheath-like leaf-base which serves as
a protection to the bud.
THE LEAF-BASE.
In Monocotyledones, such as grasses, which have a long persistent
intercalary growth of their internodes, the leaf-base is developed into a
long skeath investing the internode of the shoot-axis, and giving the
* Burns, Beitrige zur Kenntniss der Stylidiaceen, in Flora, lxxxvii (1900), p. 337.
LEAF-BASE AND LEAF-STALK 299
necessary support to the still soft plastic tissue of the internode which has
not yet grown out. In Dicotyledones also we find the leaf-base is the
more developed the more it has a protective function. We may recall here
the massive development of the leaf-sheath which covers the dense inflor-
escence-buds of such Umbelliferae as species of Archangelica, Heracleum,
and others which possess large umbels. When hypsophylls and stipules are
described this subject will be referred to again. In this place I shall only
mention one case which shows an apparent exception.
Leucojum. Narcissus. The leaves of Leucojum, Narcissus, and
other like genera have a closed leaf-sheath, that is to say, it completely
surrounds the shoot-axis ; only the leaf in whose axil the flower develops
possesses an open one—a behaviour quite different from that which one would
expect. Any transverse section of a bulb (Fig.
195), however, shows that the construction of
the foliage-leaf, which is axillant to a flower,
is conditioned by considerations of space. The
bulb consists of leaves which are packed ex-
tremely closely one upon the other. In order
to provide room for the flower-bud, the base
of its axillant leaf is not amplexicaul; if, how-
ever, no flower-bud comes to development, then — yg. ios. Narcissus _poeticus.
the leaf forms a closed sheath. Between the Bulb in transverse sections Surat
formation of the axillary bud and this diverse jnigresensyazsghfuins an open
conformation of its axillant leaf, there is evidently
a causal connexion. Whether it is caused oly by a mechanical relation-
ship of space ?, or in other ways, can only be settled by experiments, but
the processes which go on inside the bulb are very difficult to test.
THE LEAF-STALK.
The J/eaf-stalk is an arrangement for bringing the leaf into the most
favourable lie in regard to light, besides it enables the leaf-lamina to lessen
the effect of the impact of wind and rain. The function which in many
plants is assigned to the cushion, which is formed at the base of the leaflets, is
so fully treated of in physiological textbooks, that I may pass over it here.
The origin of the leaf-stalk out of the basal portion of the leaf-lamina,
by the narrowing of its surface-development, is easily followed in mono-
cotylous plants.
A leaf-stalk is a feature in only a few families of Monocotyledones—
Palmae, Aroideae, Scitamineae, and Dioscoreaceae. In other families it
* Otherwise developed as a foliage-leaf.
* In that the early development of the axillary bud hinders the primordium of the axillant leaf
from developing itself round about the shoot-axis.
300 LEAF-DIFFERENTIATION, PTERIDOPHYTA AND SPERMOPHYTA
occurs only in individual forms. In not a few, however, we can recognize
that the dase of the lamina is differently organized from its upper part, and
in many grasses this is strikingly seen, for the ear-like base of the lamina
evidently offers stronger mechanical resistance than it would do were it
flat 1, and its anatomical construction also appears to be different.
Xerotes longifolia. In Xerotes longifolia, one of the Liliaceae, the
lower portion of the leaf-lamina is bent into the form of a channel (Fig.
196, 4, 5), the upper portion is flat. In this way there arises a kind of stalk
without the form-change essential to the stalk, and it is easy to satisfy
oneself that this stalk-like portion is stiffer than the upper portion of leaf-
lamina to which it serves as a stalk.
Phormium tenax. The leaves of Phormium tenax and other species of
the genus have a much nearer approach to the formation of leaf-stalk (Fig.
196,1-3). The lamina is in the
upper portion flat, lower down
it is narrowed and retains as
is a stiffening aid a keel-like pro-
~ jection (Fig. 196, 2, #), which
——— O) is scarcely visible in the upper
4. 3 part (Fig. 196, 1, /), and inthe
1 710,196, 1-3, Phormium tonax. 4. 5, Xerotes logiaia, Orton OF the teal close to the
under side of the leaf. Explanation in the text. Natural size. leaf-base the keel diminishes
again (Fig. 196, 3, F).
Numerous other examples link on with these :—
In Alstroemeria psittacina (Fig. 194), Funkia (Fig. 220), and others, the
leaf-stalk appears as the narrowed leaf-base, and in correspondence with the
claims of greater mechanical resistance is thicker than the lamina, and also
has a slightly different arrangement of its tissue.
Amongst Dicotyledones analogous examples may be mentioned, for
example, in species of Plantago.
The existence of a leaf-stalk and the length which it reaches has always
a relationship to the structure and size of the leaves”, and also to external
factors. When hypsophylls are discussed it will be shown that in many
plants the length of the leaf-stalk in the upper regions of the stem is very
much diminished, and when we consider the behaviour of the species within
one genus, we shall not infrequently find that those which grow in shady
localities are provided with leaves having leaf-stalks, whilst those which
occur in sunny localities have no leaf-stalks. The relationships of size,
* In Bambusa the base of the lamina is so narrowed that it can easily twist. In Pharus,
Anomochloa, and others, there is formation of a conspicuous stalk.
* A very thick leathery leaf of a considerable size can do without a stalk better than a soft one,
for example in Coccoloba pubescens.
LEAF-STALK 301
however, must always be borne in mind ; a small leaf can do without a leaf-
stalk better than a large one—compare for example Saxifraga rotundifolia
and S. granulata, both of which have stalked leaves, with S. Aizoon
and S. longifolia which have unstalked leaves; or the rock-species of
Edraianthus, which have unstalked leaves, with Campanula rotundifolia,
C. latifolia, and others which have stalked leaves. One must not expect
to find here strong far-reaching relationships, because
that unknown quantity —the ‘ specific constitu- Pe
tion —always enters into the problem. Aposeris YAS
foetida, for example, although a very marked shade-
plant, has unstalked or very shortly stalked leaves ; He
the pinnatifid lamina is narrowed downwards, and
one might consider this lower portion of the leaf-
lamina as a kind of expanded stalk, but in general it AY Ye
appears to me that the leaf-stalk is ‘attuned’ to a TNE
less light-intensity than is the lamina’, as it always SS 7
tends to elongate considerably in etiolated plants. ss
In such etiolated plants the formation of a stalk ae
takes place, and the several lobes of the lamina are \ ss
separated by the elongation of the intermediate | ass
portions, and thus the leaf takes altogether a different PAS
habit (Fig. 197). | iS
If now we consider the leaf-rosettes of Trapa aS
and other plants which swim on the surface of the | Peis
water, we shall see that the formation of leaf-stalk i
in the inner strongly illuminated leaves is restricted,
but in the older ones, which are shaded by the
others, formation of leaf-stalk is favoured, so that
the relationship of the formation of leaf-stalk to
light becomes very clear.
In the larger leaf-surfaces of land-plants the 5, tiS)i024 GPR Nn aS
basal part is greatly elon-
greater mechanical demands made upon the leaf- citea, enathe leat has become
stalk bring about its stronger construction, and there- 20 SS
with comes a greater deviation from the configuration 8, prom ea Malt
of the leaf-lamina.
For the view that the leaf-stalk of the leaves of Spermophyta is
nothing else than a narrowed and greatly elongated portion of the
leaf-lamina, we have not only the support of the cases amongst the
Monocotyledones described above and the fact that the formation of
leaf-stalks sometimes also takes place in the leaflets of a compound leaf,
and they then arise as lateral outgrowths of the leaf-lamina, but also this,
—
+ See Part I, p. 238.
302 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
that the leaf-stalk attains its significant thickness, and thereby the form by
which it differs markedly from the lamina in most cases only by the longer
duration of secondary cell-divisions in its ground-tissue?. The arrange-
ment of the vascular bundles in the leaf-stalk is closely connected with this
divergent conformation. This point is involved in the consideration of the
development of the whole leaf, and will therefore be referred to on a subse-
quent page”.
III
DEVELOPMENT OF THE LEAT
AG AIS TORY:
So early as in the pages of Malpighi (1686)* we find some account of the
history of development of the leaf. After depicting in characteristic fashion the
form-changes exhibited by the bud-scales which follow one another in an opening
bud—the ‘ folia caduca,—he examines the development of the foliage-leaves—the
‘folia stabilia.’ He does not distinguish the vegetative point from the youngest
primordium of a leaf*.
The investigations of Kaspar Friedrich Wolff (1759) were more far-reaching.
He recognized that the leaves arise upon the projecting point of the stem above
the youngest primordium, and that on this point there is no differentiation of tissue
visible. Here at the vegetative point®, the leaves arise by the exudation of the
‘succus nutritivus ’ whose outflow is not restrained by the epidermis or rind. He
recognized the ‘acropetal’ arrangement of the leaves, distinguished between
primordial stages and stages of permanent construction, and knew further that
divided leaves arise through the branching of originally simple primordia. The
midrib according to him appears first. Upon it there arises by exudation a clear
margin, the leaf-lamina, on which then by further exudation the foliola spring.
The investigators who followed Wolff at a much later time occupied them-
selves primarily with the question whether the growth of the leaf was from above
downwards, basipetal, or from below upwards, acropetal. At first, however, no sharp
distinction was drawn between the different phases of growth as they were later
established by Sachs, especially between the embryonal phase, in which the tissue
is meristic but increases little in volume, and the phase of elongation. Amongst
the older works upon this subject—putting aside speculation unsupported by
1 See Deinega, Beitrage zur Kenntniss der Entwicklungsgeschichte des Blattes und der Anlage der
Gefassbiindel, in Flora, 1xxxy (1898), p. 439.
2 See p. 338. ’ Malpighi, Opera omnia, Londini, 1686.
* He sums up his investigations thus :—‘ Naturae pariter methodus in producendis stabilibus foliis
mirabilis est. Primo enim costula seu petiolus, carinae instar humore turgidus cum appensis fibrulis
manifestatur e quibus probabiliter sacculorum seu utriculorum transversalium membranulae pendent
(i.e. the secondary veins with the leaf-lamina) ut in animalium primaeva delineatione observatur.
Patent autem deducto novo alimento, quia complicata sacculoram moles, subintrante succo, turget
et ita folii latitudinem et laxitatem conciliat.’ Malpighi, op. cit., p. 30.
5 ‘Ne omni momento opus sit largam descriptionem instituere, liceat vocare haec loca generatim
puncta vegetationis vel superficies vegetationis.” K. F. Wolff, Theoria generationis, Halae, 1759.
AISTORY OF INVESTIGATION 303
investigation such as that of de Candolle' and others—we find those of Steinheil,
Mercklin, Schleiden, Trécul, and others.
Steinheil (1837)? found that the leaf grows from above downwards. The
point is then the oldest part but in the compound leaf the upper leaflets are the
youngest.
Schleiden (1843)* maintained that the leaf shoots out as it were from the axis,
that the point is the oldest, and the base the youngest, and this led to a lively
discussion.
Mercklin (1846) * supported Schleiden’s view by a series of investigations.
Nageli (1846) * took up the opposite side, and in order to realize Schleiden’s
idea of tracing the history of the formation of the leaf in that of its single cells he
commenced his investigations into the lower plants, the Algae and the Musci,
whose simple organization allowed of an examination of the succession of cells.
That the leaf is here not thrust out of the axis, but arises from a single superficial
cell, showed Schleiden’s theory, at least for the cases which had been examined,
to be untenable. Nageli proved :—
(1) that the peripheral cell-formation, that is to say formation at the apex
and at the margin, proceeds from above downwards, and that the base of the leaf
is laid down first, the apex last.
‘(2) that the intercalary cell-formation which follows upon the peripheral
cell-formation ceases sometimes first at the base, sometimes first at the apex, some-
times all at once throughout the whole leaf.
*(3) that the elongation of the cells may proceed either from above down-
wards, or from below upwards, or may take place equally all over.’
Amongst Phanerogamae the leaves of Utricularia, Astragalus, and Myriophyllum
were examined, and it was shown that in Astragalus and Myriophyllum the lateral
leaflets are laid down in éasipefal succession. According to this the leaf then
possesses originally an apical vegetative point (embryonal tissue), but it may be the
first to pass over into permanent tissue, whilst at the base of the leaf cell-formation
takes place freely, inasmuch as the tissue there retains its embryonal character
(vegetative point-tissue). In a later work upon Aralia spinosa® Nigeli explained in
detail the leaf-growth of the Phanerogamae.
Trécul (1853)7 by his extended investigations, although they did not concern
* De Candolle, Organographie végétale, i, Paris, 1854, p. 354. 2nd English edition by Kingdon,
London, 1841.
? Steinheil, Observations sur le mode d’accroissement des feuilles, in Annales des sciences naturelles,
S€r. 2, viii (1837), p. 289.
* Schleiden, Principles of Scientific Botany, English edition by Lankester, London, 1849, p. 261.
In a special form we find the same thought expressed by Naudin, Résumé de quelques observations
sur le développement des organes appendiculaires, in Annales des sciences naturelles, sér. 2, xviii
(1842), p. 360.
* C. E. von Mercklin, Zur Entwickelungsgeschichte der Blattgestalten, Jena, 1846.
5 Nageli, Uber Wachsthum und Begriff des Blattes, in Zeitschrift fiir wissenschaftliche Botanik,
Hefte 3 and 4 (1846), p. 153.
* Nageli, Wachsthumsgeschichte des Blattes von Aralia spinosa, in Pflanzenphysiologische Unter-
suchungen, i (1855), p. 88.
* Trécul, Mémoire sur Ja formation des feuilles, in Annales des sciences naturelles, sér. 3, xx
(1853), p. 235.
304 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
this cell-formation, brought to light a large number of valuable facts, of which we
may note here that the process of leaf-formation in different plants, even those nearly
allied, may be very different. ‘That, for example, the development of the lateral
members takes place sometimes in acropetal manner, sometimes in basipetal manner,
or from the middle both upwards and downwards. His error in considering that the
leaf-sheath was the first to arise was later corrected by Eichler. The leaf-sheath
is only differentiated at a late period from the leaf-primordium, as one can readily
see in the leaf of any grass; the base of the leaf does not at once take on the
character of the leaf-sheath, but the leaf-sheath is only formed by intercalary
growth out of the basal portion of the leaf.
Eichler (1861)* gave a clear account of these relationships, along with a cor-
rection and an extension of Trécul’s investigations.
Hofmeister (1868)° explained in detail the distribution of growth in the leaf,
and also gave a summary of the development, although this is not very far-reaching.
At a later date I applied the facts of historical development to the general
morphology of the leaf, and especially to its metamorphoses*. I showed that
a genetic connexion exists between the different leaves—foliage-leaves in different
forms, hypsophylls, kataphylls—which in the matured condition diverge very widely
JSrom one another, in other words, the path of development is originally the same
for all leaves, but in many leaves at an earlier or later period the development may
proceed along different paths. If we start from the highest differentiated form of
leaves the less differentiated appear as retarded formation. With the retardation
there may also be associated a transformation‘, which is all the more far-reaching
the earlier in the stage of development it appears.
An outline of the development of leaves will be found exhibited in the works
I have referred to, and I shall only further cite here some of the more recent
investigations.
With regard to terminology it may be pointed out that Bower’ has proposed
a different terminology from that of Eichler which is made use of in the following
pages. He calls the whole chief axis of the leaf excluding its branches phyZ/o-
podium. ‘This phyllopodium may be differentiated by the varying distribution of
growth, alike in the transverse and in the longitudinal direction, into different parts
which behave differently, namely into Zypopodium which corresponds with Eichler’s
leaf-base, a middle elongated portion *esopodium which corresponds with the leaf-
stalk, and an upper portion epipodium.
The history of development of the leaf is of course conditioned by
the form of the mature leaf, as has been said already :—‘ What we call
1 Eichler, Zur Entwickelungsgeschichte des Blattes, mit besonderer Beriicksichtigung der Neben-
blattbildungen. Inaug. Dissertation, Marburg, 1861.
? Hofmeister, Allgemeine Morphologie der Gewichse, Leipzig, 1868, p. 519.
° Goebel, Beitrage zur Morphologie und Physiologie des Blattes, in Botanische Zeitung, xxxviii
(1880), p. 753; id., Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Hand-
buch der Botanik, iii (1884).
* See Part I, p. 6.
5 Bower, On the Comparative Morphology of the Leaf in the Vascular Cryptogams and Gymno-
sperms, in Phil. Trans., 1884.
GROWTH OF THE: LEAF 305
the mature condition is only the terminal one of a series of stages of develop-
ment which follow one on the other’.’ We may say in general that parts
which have the earlier functions to perform appear the earliest, and in con-
nexion with this we must remember that the foliage-leaves are not only
organs of assimilation, transpiration, and so forth, but have also to act as
protective organs for the bud.
Massart* has stated that those parts of a compound leaf which in the
expanded condition are smallest, are also the last to appear. This is frequently
true, but not always. Thus in Acer platanoides (Part I, Fig. 1) the lowermost of
the five lobes of the leaf are the smallest, and as the development of the leaf is
basipetal they arise last; but in Fraxinus excelsior the lowermost pair of leaflets,
which are smaller than the others, arise first. Retardation relatively to the growth
of the rest of the leaf-stalk may indeed appear at all stages of development.
B. GROWTH OF THE LEAF IN GENERAL.
The primordia of the leaves arise as lateral outgrowths on the vegeta-
tive point of a shoot-axis, an arrangement which ensures the rapid develop-
ment of numerous \eaf-primordia. We have already seen exceptions to this
rule in the behaviour of some monocotylous embryos where the leaf-
development is relatively slow, and of the embryo in Lemnaceae where one
leaf only is developed, and where the origin of the cotyledon itself* might be
cited in illustration, for it arises independently of a vegetative point. We
shall see hereafter, when discussing the development of the flower, that its
vegetative point is frequently used up entirely for the flower-leaves *, and if
there be but one of these we arrive at zerminal leaves. If, then, the state-
ment ‘that the leaves always arise as lateral outgrowths ona vegetative point’
is not altogether true, yet this is true that the leaf-primordia always proceed
from embryonal tissue. There is no case known in which a leaf-primordium
has proceeded from permanent tissue, although vegetative points of a shoot
may arise from this in regeneration®. So far as we know also there are no
such things as adventitious leaves" or parts of leaves, although many authors
speak of them, for example, in Filicineae. In the Musci the leaf-primordia
proceed from one cell which is a segment of the apical cell. In the Pteri-
dophyta this is the case in the Filicineae alone *. In all the other groups
1 See Part I, p. 9.
? Massart, La récapitulation et l'innovation en embryogénie végétale, in Bulletins de la Societe
royale de botanique de Belgique, xxiii (1894).
3 The first leaves of the fern-embryos which arise apogamously and are formed independently of the
vegetative point of the shoot are also examples.
* This probably holds also for the development of the tendrils of some Cucurbitaceae. See
p- 426. “"oeeybart lL, p. 41. © See Part I, p. 43.
7 See Part I, p. 42. Regarding adventitious leaves see Goebel, Uber Regeneration im Pflanzen-
reich, in Biologisches Centralblatt, xxii (1902).
* At least in the leptosporangiate Filicineae where, however, a leaf Coes not proceed from every
GOEBEL II Xx
306 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
of Pteridophyta, as well as in the Spermophyta, the leaf-primordium grows
out always from a group of cells. These primordia only gradually attain
their full size, and there arises at first usually only the primordium of that
portion of the leaf which will later become the apex, and after this the leaf-
primordium broadens out laterally because further portions of the vegetative
point are drawn into its formation, and this may proceed so far that the
leaf-primordium finally extends completely round the vegetative point like
aring. This happens, for example, in the grasses which have a closed leaf-
sheath and in other cases (Fig. 198).
As to the longitudinal extension
of the primordium of the leaf, we find,
in vegetative points with close-set prim-
ordia of leaves, that not infrequently
there is no free surface of the vegeta-
tive point left over between them, and
in such cases the lower portion of the
leaf-primordium remains frequently united
with the surface of the shoot, and appears
in the mature shoot as a leaf-cushion.
This process is important for the under-
Fic. 198. Dactylis glomerata. 4, vegeta standing of the inferior ovary, and the
tive point with leaf primordia; @, a, apices of
primordia; 2, margin of leafprimordium same process is found also amongst lower
around the vegetation-point. 2, young leaf
differentiated into leaf-lamina, Sf, and leaf- plants for example in Chara
base, s. After Deinega. 2
C. DISTRIBUTION OF GROWTH IN THE LEAF.
(2) APICAL GROWTH AND INTERCALARY GROWTH.
The primordia of leaves, whether they spring from a single cell or from
a group of cells, are primarily composed throughout of embryonal tissue.
Soon, however, there appears within this a differentiation which in different
plants runs a different course. Let us, in the first place, recall what takes
place in the Musci.
Leaf-tip in Musci. In them the leaf’, apart from many exceptions, is
composed at its apex at first of a two-sided apical cell, from which right
and left two rows of segments are cut off”, and thus the foundation is laid
for the construction of the primordium of the leaf. The capacity of this
apical cell is, however, limited. In Schistostega (Part I, Fig. 26) its capacity
segment, nor is the whole surface of the segment, as in the Musci, devoted to the formation of the
primordium of the leaf. In the eusporangiate Filicineae pluricellular origin of the leaf-primordium
must take place. 7 See Pp. P3i.
* We must remember that the leaves of all Musci primarily consist of ome cell-layer, and that
where many layers are present, as is the case when nerves and the like are laid down, these are
subsequent formations.
APICAL AND INTERCALARY GROWTH 307
disappears early, but the cell itself retains its form for some time. We see in
Fig. 26 of Part I, on the right, that already the apical cell of the leaf-primor-
dium, which consists of thirteen cells, has grown out to some extent—an
indication that it has expended its capacity for d/vészon, and that its phase
of elongation has now set in;
but in the basal portion of the
primordium, which is still
small, as we may see by acom-
parison with the figure stand-
ing on the left, the cell-division
FG. 200. Gonolobus sp. Leaves of different age in op-
posite sequence of numbers I, IJ, III. V, forerunner-tip;
£, lamina with mucilage-hairs at base; sf, leaf-stalk. The
Fic. 199. Gonolobus sp. I, end of a venation indicated in the forerunner-tip in I and II is not
shoot. II, youngleaf. V, V,_forerunner- seen in fresh leaves. Magnified 23.
tips. I, magnified 5. II, magnified 10.
and growth are still in progress. The growth and the differentiation of
tissue which is very simple in Schistostega is ended sooner at the apex
than the base. Is this a meaningless phenomenon? In my view this
phenomenon, which as we shall see is widely spread elsewhere, is connected
with the fact that the leaf-apices have first to serve as protection to the bud,
because they reach furthest outwards, and we have seen in the Musci that
the leaf-tips in plants inhabiting dry places are prolonged into diaphanous
x2
308 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
hair-points, which form a little tuft above the stem-bud. The growing
portions are, however, covered over and protected within the bud.
Forerunner-tips. This precedence of the leaf-apex appears specially
prominent in a number of climbing plants, and Ratiborski' has recently
shown the biological significance of it to them. It lightens at first the
weight of the shoot, which is in search of a support in its revolving nutation,
and consequently makes possible a much stronger growth in length of this
shoot out of an equal amount of available material. Raéiborski designates
the early developed apical portion of the leaf the forerunner-tip (Figs. 199,
Fic. 201. Benincasa cerifera. I, young leaf: the orerunner-tip, Y, precedes markedly the development of the
lamina. II, mature leaf: the distinction of the forerunner-tip hardly visible. III, branched tendril in juvenile
state: no vegetative point of a shoot is visible between the two tendrils, even at the apex of the larger tendril
the tissue is still embryonal ; ¢/ vascular bundle. I, magnified 9. II, natural size.
200, V). On the young leaf (Fig. 200, III) the forerunner-tip is essen-
tially complete in development, and is almost twice as long as the primor-
dium of the leaf-lamina Z, which is still very small, but this, as a comparison
with the older leaves shows, grows afterwards, whilst the forerunner-tip
exhibits only an insignificant elongation at its base. The leaf-apex in
a compound leaf shows the same features. In Fig. 201, which illustrates
the development of the leaf in Benincasa cerifera the precedence in develop-
ment of the leaf-apex over the leaf-surface is very strikingly shown, and by
this the leaf in its young condition has quite a different appearance from that
which it has when mature. Rhodochiton volubile shows similar features.
We must look for the significance of the forerunner-tip in the protec-
tion of the vegetative point apart from considerations of the importance of
reduction of the leaf-development for the rotating shoots of climbers ; and
1 Raviborski, Uber die Vorlauferspitze, in Flora, lxxxvii (1900), p. 1. The statements of Criiger
and others are dealt with here.
FORERUNNER-TIPS AND PLUG-TIPS 309
then when the forerunner-tip contains chlorophyll it can carry on the func-
tion of assimilation as well as those of respiration and of transpiration until
the leaf-surface has attained a sufficient extent to take up the work.
Plug-tips. The rapidly drying-up leaf-apices of the unfolded leaves
of Musa which may sometimes be as much as ten centimeters long, and
which were formerly erroneously described as a kind of tendril, as well as the
smaller similar structures which are to be found in the Zingiberaceae, in some
Aroideae, and elsewhere, are in my view structures which serve to close the
éud, and which may be termed p/ug-zips. With them we may reckon the
stipules and ligules which will be mentioned below’. The leaves of all
these Monocotyledones have a lamina which is convolute in the bud. The
somewhat cylindric apical prolongation on the one hand closes each convo-
lute lamina above, and on the other hand fills up the space formed by the
convolution of the leaf which stands immediately above it, and in this way
there is produced a long thin plug which, growing proportionately with the
space, pushes itself upwards. In correspondence with this we find in
Hedychium Gardnerianum, for example, that this closing body is provided
with somewhat long hairs, and in some Aroideae, for example Colocasia,
there are at the leaf-apex water-slits from which drops of water exude.
Where the apices of the leaf-tips in toothed or otherwise segmented leaves
pour out a secretion within the bud %, it is open to us to suppose that this is
not merely the excretion of superfluous by-products, but that there is here
a provision of a special protection for the young parts. The precedence in
growth of the leaf-apex becomes frequently evident also through the fact
that the first hairs appear upon it, and these have evidently to do with
its protective function.
Measurements. Sonntag * has given some measurements from which I extract
a few figures. They give the length which the primordium of the leaf has reached
when the apex has completed its growth, whilst embryonal tissue is still visible at
the base :—
Amongst Gymnospermae we have—
Eaxodiumidistichum . ....., ... °0:2.mm.
PieeaesCelsa :. “i, 5. s. . 6x26)Inm.
mbiespectinata . . . . .,; O32 mm.
Pinus silvestris... . . . O35 mm.
Similar figures have been obtained from a number of JA/onocotyledones. In
Phragmitis communis, whose leaves reach a length of as much as half a meter, the
primordium of the leaf at the end of its apical growth is only half a millimeter long,
1 See p. 359. For illustrations of plug-tips see Goebel, in Flora, Ixxxvili (1901), p. 470.
* See Reinke, Beitrige zur Anatomie der an Laubblattern, besonders an den Zahnen derselben
vorkommenden Sekretionsorgane, in Pringsheim’s Jahrbiicher, x (1876), p. 119.
* Sonntag, Uber Dauer des Scheitelwachsthums und Entwicklungsgeschichte des Blattes, in
Pringsheim’s Jahrbiicher, xviii (1887).
310 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
and from this we may conclude that the leaf attains its size mainly through inter-
calary growth and stretching of the cells.
Amongst Dicotyledones the relationships are more manifold, as is also the
construction of the leaves. The following figures are instructive—
Ruta graveolens’... : ...4.. -* (70-53,
juslans cimeres 2.2 nage ee o-6 mm.
Geranium Robertianum . . . 1-75 mm.
Ailanthus glandulosa . . . . 2-91 mm.
Amthriscus silvesttis i. 9) ee 4-5 mm.
Archangelica officinalis . . . 15:0 mm.
Still larger numbers could be obtained if the Droseraceae, about which we
shall speak presently, were taken into consideration.
Guarea. We shall hereafter deal with the sequence of origin of the lateral
members of the leaf. The peculiar features of Guarea, one of the Meliaceae,
which was formerly considered to be in a line with many ferns, will only be
mentioned here. Its pinnate leaf unfolds at first only a portion of its pinnae—the
lower ones; in the next vegetative period new pinnae appear at the leaf-apex.
According to Sonntag this is not a case of long-lasting apical growth of the leaf.
The leaf, as in other cases, is laid down zz f¢ofo, and its capacity for development is
closed therewith. It is only the time of unfolding which is periodic. The basal
three to four pairs of pinnae unfold in the first vegetative period, whilst the rest
unfold in the succeeding one. How far these peculiarities are connected with the
conditions of the life of the plant is at present unknown.
The behaviour of the leaves of the Spermophyta', about which we have
just spoken, is in marked contrast with that of the leaves of Filicineae in
which the embryonal tissue occupies the apex during the whole duration of
the development of the leaf, and only zz ¢he end passes over into permanent
tissue. It would be an error, however, were one to ascribe apical growth to
the leaves in Filicineae alone.
Apical growth in Spermophyta. In some Spermophyta the leaf is
marked by its apical growth, inasmuch as the apical portion during the
whole period of the building up of the leaf retains its embryonal char-
acter. In such cases we find, just as in the Filices, a ptyxis different
from that which is otherwise usual in the Spermophyta. The leaf is
circinate, and the embryonal portions are thus brought into a position in
which they are protected by the older and more resistant parts. We see
this in Drosophyllum (Fig. 202), in which genus the leaf is revolute, and
also in some other Droseraceae, for instance Drosera binata and D. dicho-
toma”, in which the leaf-apex is involute. The like may be observed in
a number of Utricularieae. That the distribution of the growth-area is not
’ As well as of the Lycopodineae and Equisetaceae.
* In other Droseraceae the duration of apical growth is much shorter. In the Filices also like
cases are found.
APICAL GROWTH IN SPERMOPHYTA 311
determinant of the leaf-form is shown for example by the fact that in Byblis
gigantea—which has hitherto been erroneously reckoned by the systematists
amongst the Droseraceae—the leaves are quite like those of Drosophyllum,
but possess a very marked intercalary growth, and in correspondence there-
with have no circinate ptyxis'. The ptyxis of the leaves depends in my
view partly upon the distribution of the growth in the leaf-development,
and partly upon the amount of space available in the bud. A superficial
examination of some leaves which
have laterally involute ptyxis shows
that they are always leaves which re-
tain for a long time embryonal tissue
and grow at the margin—snufatis
mutandis—we have here the same
relationships as are found in leaves
which are involute at the apex. But
the influence of space-relationships
appears in this, that a leaf in whose
axil at a very early period a bud
arises is hindered by the bud from
assuming the ptyxis which it would
otherwise do by its growth. The
ordinary foliage-leaves of Caltha
palustris, for example, are in the _Fic. 202. Drosophyllum Iusitanicum. Leaf showing
z circinate ptyxis. The tentacular glands are laid down
bud laterally involute 5 those, how- in serial succession, but later ones are also intercalated.
: Magnified.
ever, which subtend a flower-bud
are spread out flat”.
(6) THE INCEPTION OF THE LEAF-SURFACE IN SPERMOPHYTA.
In what we have said above we have dealt with the distribution of
growth in the primordium of the leaf in general. We must now briefly
deal with the laying down of the leaf-surface. The process is relatively
simple where the leaf is from the first laid down as a flat structure which
attains its mature configuration by a uniform stretching of the embryonal
tissue in the transverse direction. Where, however, at a very early period
a portion thickens into a midrib, and is thus separated from a thinner part
which is devoted to the making of the lamina, most complex relationships
ensue between embryonal growth and stretching. The types which have
been created around which to group the forms that are exhibited show
‘By this character young plants of Byblis gigantea can be readily recognized at first sight from
those of Drosophyllum. See F. X. Lang, Untersuchungen iiber Morphologie, Anatomie und Samen-
entwicklung von Polypompholyx und Byblis gigantea, in Flora, Ixxxviii (1901), p. 149.
? See Arnoldi, Uber die Ursache der Knospenlage der Blitter, in Flora, Ixxxvii (1900), p. 453.
312 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
many transitions, and their limitation is consequently more or less arbitrary.
The categories framed by Prantl’ are quoted here in illustration.
He distinguishes :—
(1) Basiplastic type. The stretching takes place at the apex of the primarily
uniform embryonal primordium, and proceeds downwards therein until nearly the
whole of the active meristem disappears. ‘This is found in the Musci, Lycopo-
dineae, Coniferae, with the exception of the genus Ginkgo *, most Monocotyledones,
a number of Dicotyledones with simple leaves, such as Sempervivum, Erica
Tetralix, Gentiana asclepiadea, and the Asclepiadeae. Where, as in Dicotyledones,
feathered veins occur, a strong midrib is first of all differentiated, and this is
accompanied (Fig. 199, II) both right and left by meristic tissue, which passes
over into stretching-tissue successively in a basipetal direction, and at the same
time simultaneously in a transverse direction. In other leaves which may be
assigned to this type there appear basipetally in the meristem branchings which
become leaf-teeth as in Salix, Celtis, and Prunus avium, or pinnules as in Cepha-
laria leucantha, or lobes as in Bryonia and others (see also Fig. 201).
(2) Pleuroplastic type. Where the meristem is marginal the leaf-apex does
not pass into the permanent condition so rapidly as it does in the basiplastic type.
Of simple leaves may be mentioned those of Aristolochia tomentosa, Rhamnus
Frangula, and Syringa vulgaris. The transition into the stretching-tissue takes place
in the whole tissue arising out of the meristem at nearly the same moment, only
at the margin some cells remain for a longer time in the meristic condition. Where
branchings take place these proceed in acropetal succession as in Quercus, Corylus,
Tilia, and others, but in Ulmus from the middle upwards and downwards.
(3) Eucladous type. The branchings here do not proceed, as in the two former
types, only when a portion of the meristem has begun to stretch, but appear at a
time when the leaf is still one uniform mass of embryonal tissue. This is seen in
Ginkgo, Juglans, Papilionaceae.
A sharp limit is not to be drawn between these types, especially
between the first and second, and the advantage of such a grouping appears
to me very doubtful. Upon the question of the distribution of the growth
more will be said in subsequent pages when the leaf-formation in the several
large groups receives special consideration, and when the relationship of the
development of the leaf to the course of the leaf-nerves is discussed.
We find in other parts of plants with /zmzted growth, for example in
placentas, quite similar differences in the distribution of the growth?, and
far too much weight has been attached to these processes of growth in the
leaves.
* Prantl, Studien itiber Wachsthum, Verzweigung und Nervatur der Laubblatter, insbesondere der
Dikotylen, in Berichte der deutschen botanischen Gesellschaft, i (1883), p. 280.
* Now no longer to be reckoned amongst Coniferae.
* See also Part I, p. 41.
DEVELOPMENT OF LEAF IN FILICINEAE 313
D. FORMATION AND DEVELOPMENT OF THE LEAF
N= PHE CHIEL, PLANI-GROOPLS.
(a) PTERIDOPHYTA:
1, EQUISETACEAE AND LYCOPODINEAE.
The simple relationships of the formation of the leaf in the Equisetaceae
and Lycopodineae, where all the leaves are basiplastic, require no further
mention here. But the formation of the leaf of the Filicineae demands
notice as it is marked by many characteristic features, although none of
them, apart from the arrangement of the cells, is limited to the class.
2. FILICINEAE.
The formation of the leaf is in the different forms of this class externally
very different. One need only recall the contrast between the small leaves
of some Hymenophyllaceae, where they are less in size than those of some
Hepaticae and Musci (compare, for example, Fig. 183), and the massive
leaves of Angiopteris with their stout leaf-stalks. Nevertheless we cannot
ignore the fact that there is a common path in their development, and this
appears particularly when we compare not the fully formed but the primary
leaves of the different forms with one another, and with the pinnate leaves.
On these primary leaves we see a conspicuous marginal growth, that is to
say, the meristic tissue occupies the margin of the leaf, and in association
therewith a forked branching of the leaf-nerves appears—this only being
possible where there is marginal growth. Another extreme is seen where
the primordium of the leaf appears as a structure with conspicuous apical
growth, and on it, when branching takes place, the lateral pinnules arise in
monopodial series. There are not wanting transition-stages between these
two, especially do we find, for example in Botrychium, that the apex of the
primordium of the leaf frequently, after it has produced pinnules, passes
over by lateral shooting into marginal growth and dichotomous branching,
and in many leptosporangiate ferns we find the dichotomously branched
leaf is built up sympodially?. This latter process is often considered
as typical of the ferns, but as opposed to this it may be pointed out that
within the series of the ferns is to be found a type of leaf-development
with lateral origination of the leaf-pinnules like that which is observed in
the fern-like Archegoniatae—the Cycadaceae; and when this occurs, as we
shall presently see, it is associated with a gradual reduction of the apical
growth of the leaf-primordium.
It is evident then that alike in the distribution of the growth and in
the branching, the development is determined here by the configuration
1 See p. 316.
314 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
which, to speak teleologically, mast be reached in the mature condition,
and we find the same in the relationship between the leaf-spindle or midrib
and the lamina. The more massively developed the leaf-spindle is, the
earlier is it in general laid down, and therefore the more does the lamina
appear upon it as a wing-like outgrowth originating at a /azer period.
Bower! has attached special importance to the fact that the fern-leaf is
typically provided with a wing even where, as in the almost cylindrical
leaf-stalk of Angiopteris and others, this does not appear externally. The
wings on the lower region of the stalk-like portion of the leaves are shorter
and thicker than they are above, and may in Osmunda, the Marattiaceae,
and others, broaden at the base into a sheath-like form. If now, as indeed
cannot be denied, most of these wing-formations appear in correspondence
with the dorsiventral character and the flattening of the fern-leaf, yet we
must not forget that all transitions may be formed from the cylindric wing-
less leaves of Pilularia right up to the leaves of the Hymenophyllaceae, which
are from the very first laid down as flat structures. In Pteris serrulata, for
example (Fig. 207, II), the primordium of the leaf is somewhat flattened at
the apex, but it is almost cylindric. On each side there shoots out upon
the rhachis, which is first of all laid down, a lamina which is provided with
wedge-like marginal cells, and these divide by walls inclined alternately
upwards and downwards. At first the cells, which proceed from this
division of the marginal apical cells, are devoted to the construction of the
rhachis, and only at a later period does the further growth of the thinner
lamina proceed. <A leaf which had a thin rhachis would allow the marginal
cells to pass over earlier to the formation of a lamina. In the Hymeno-
phyliaceae, where the lamina is only one-layered*, the marginal growth of
the lamina is naturally somewhat different, and the same may be said
of the thicker, more massive leaf-lamina of the Osmundaceae* and of the
Marattiaceae. In the relationships of the arrangement of cells, however,
we find, just as in the case of the thallus of the Hepaticae*, the expression
of the working of inner factors which have no direct connexion with the
grosser relationships. We have also seen when examining the Hepaticae
that in the thallose forms the thallus has a thinner lateral surface and a
thicker middle part, and that in the larger forms of Aneura, for example, the
wing-formation may be practically suppressed in the chief axis. Fig. 22 in
its lower part might, «tatzs mutandis, correspond to a transverse section
through a young leaf of Hymenophyllum; the upper portion of the figure
‘ Bower, On the Comparative Morphology of the Leaf in the Vascular Cryptogams and Gymno-
sperms, in Phil. Trans., 1884; id., The Comparative Examination of the Meristems of Ferns as
a Phylogenetic Study, in Annals of Botany, iii (1889), p. 305.
2 Where the lamina is many-layered, as in Trichomanes reniforme, it is not so from the beginning,
but the layers are the result of subsequent division parallel with the surfaces.
* With the exception of the species which resemble some of the Hymenophyllaceae.
Seep si2 ie
DEVELOPMENT OF LEAF IN FILICINEAE 315
might be the transverse section of a thick fern-leaf. In the development of
the fern-leaf we meet with the two factors which everywhere confront us:
on the one hand the relationships to ower factors which find their expres-
sion, especially in the size which the leaves reach, and this supposes again
definite relationships of organization which determine the developmental
history; and on the other hand incidents which spring out of an zxmer
influence on configuration, and which, if we consider the end-result, might
be brought about equally well in other ways. Thus the leaves of the tree-
fern Amphicosmia Walkerae have just as good a two-sided apical cell’ as
the small leaves of the Hymenophyllaceae up to a certain stage in their
development; they have not, as has been supposed, a three-sided apical cell
like the Osmundaceae.
Marattiaceae. The leaves of the Marattiaceae ® are relatively massive, at least
in the case of Marattia and Angiopteris. The development of the leaf has only
been examined in these two genera, but we may assume that its course is the same
in the other genera. At the base of the leaf of the Marattiaceae as is well
known there are stipular formations *, which are met with elsewhere amongst the
ferns in Todea only where one ‘axillary stipule’ occurs. The primordium of the
leaf is circinate at the apex‘ as in other ferns, and the lateral pinnules arise in
acropetal succession. ‘The laying down of the leaf-surface is from the first more
massive than in the leptosporangiate forms, and the leaf-apex is in Angiopteris
frequently, perhaps always, not involved in the leaf-formation.
Osmundaceae. The Osmundaceae conform with this type in so far as all
the parts of their leaf appear in acropetal succession, and the marginal growth, so
_ characteristic of the leaves of other ferns, appears only relatively late at the apex of
the leaf and of the pinnules which are further divided. The presence of a three-
sided pyramidal apical cell may, as in the case of the thallose Hepaticae,® be con-
nected with the more massive construction of the leaf. But as the leaves of the
tree-fern Amphicosmia Walkerae have a two-sided apical cell and those of Todea
superba, which are not very large and are of delicate construction, have a three-
sided one, the character is evidently racial.
Leptosporangiate Filicineae. In the leptosporangiate ferns® which have
1 Bower, The Comparative Examination of the Meristem of Ferns as a Phylogenetic Study, in
Annals of Botany, iii (1889), p. 305.
2 Bower, On the Comparative Morphology of the Leaf in the Vascular Cryptogams and Gymno-
sperms, in Phil. Trans., 1884.
8 The ‘stipular scales’ which occur one upon each side of the leaf-base in Ceratopteris thalictroides
are really scale-hairs of special construction, and are found also upon the stalk and lamina of older
leaves. See Kny, Die Entwicklung der Parkeriaceae, in Nova acta der kaiser]. Leop.-Carol. deutschen
Akademie der Naturforscher, xxxvii (1875), p. 29.
* The arrangement of the cells at the apex is like that at the apex of the root of the Marattiaceae,
that is to say, there are many initials, but in Marattia there is often, although not always, a three-
sided apical cell. For further details see Bower, op. cit.
5 See p. 21.
® The works of Hofmeister, Kny, Sadebeck, and Prantl, which are mentioned in all textbooks,
316 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
been carefully examined, we find that the leaf-primordia which proceed from one
cell, have at first a two-sided apical cell (see Fig. 173), which, in ferns like Pilularia,
remains for a somewhat long period because the leaf has a cylindric configuration
and is unsegmented. Pilularia has leaves which are traversed by only ove conduct-
ing bundle. In ferns whose leaves are developed as flat expansions the course of
the nerves of the leaf, and the branching of the leaf itself which is connected with
these are of special interest. When speaking of the primary leaves of the ferns? it
was shown that the nerves of the leaf are dichotomously branched and Fig. ga, 5,
Part I, which represents the leaf of
Asplenium viride, shows clearly that
its pinnules are the result of repeated
dichotomous branching. In the leaf
represented in Fig. 92, 4, Part I, on
the other hand, only one dichotomy
has taken place. Fig. 203, which
represents a leaflet of Allosorus
crispus, shows clearly also the di-
chotomous branching. This dicho-
tomous branching may likewise be
found by careful developmental in-
vestigation in many cases. ‘The
meristem is on the margin, andretains
its embryonal character over the cells
arranged in longitudinal rows which
are to give rise to the leaf-nerves,
whilst the cells which lie between
these pass over at an early period into
permanent tissue. We do not, how-
Fic. 203. Allosorus crispus. Outline of a leaflet. The
branching is clearly dichotomous. The apex has divided into
lobes 1 and 2 of which 1 is the stronger and continues the
growth, 2 forms a lateral lobe. Below we have lobes 3 and 4
which have been similarly formed. The leaf-spindle (rhachis),
S\ isonly a slightly broader portion of the lamina which is
ever, find this in every case. Where
we have to deal with e/ongated leaves
provided with numerous lateral parts
subsequently mechanically strengthened. Magnified.
there is developed a uniform, con-
tinuously growing apical meristem. Fig. 204 shows the leaf-tip of Adiantum Edge-
worthi. At the apex is a two-sided apical cell which is not visible in the figure owing
to its small size. The leaflets are laid down as /azeral outgrowths beneath the apex
which continues its growth. They branch dichotomously and finally in feeble
leaves the leaf-apex itself passes over into the same conformation as that exhibited
by the pinnules. We observe, then, that in this characteristic marginal growth we
have, as in many prothalli of ferns, the wedge-shaped apical cell replaced later by a
group of meristic marginal cells. If we conclude? from these and from other facts
—for instance the frequently ‘abnormal’ forked division of the leaf of different
ferns which do not show the ‘normal’ features—that the branching of the fern-leaf
give particulars of these, as do also the memoirs of Bower. Here the details of the arrangement of
the cells cannot be discussed. 1 See Part I, p. 151.
* Goebel, Uber die Jugendzustande der Pflanzen, in Flora, lxxii (1889), p. 26.
"—'
DEVELOPMENT OF LEAF IN FILICINEAE 217
exhibits the primary and now partly lost type we must remember that this is in the
meanwhile nothing more than a hypothesis against which many other facts might
be quoted. What appears to be more important is that we have the relation-
ship above mentioned between lateral branching and dichotomy, from which we
learn that in all ferns the /ateral primordia of the pinnae appear on the primordium
of the leaf, and that tf the leaf ts a greatly elongated one the lateral parts are laid
down in rapid succession, but where surface-growth predominates then there ts dichoto-
mous branching, and there is no formation of a strong leaf-spindle or midrib, In some
cases, as, for example, the Gleicheniaceae
where dichotomy has been assumed, it is
in error.
In ferns where the leaves show a
strong rhachis developing for a long
time by monopodial growth the la-
teral leaflets frequently have a relation
in their configuration to the circinate
ptyxis of the apex of the bud. This
is the case in Nephrolepis exaltata
(Fig. 205). Each pinnule of the sim-
ply pinnate leaf has here at its base a
lobe-like outgrowth which is directed
towards the leaf-apex. A considera-
tion of the leaf-tip will easily convince
one that it is these lobes which at
first cover, on the outside, the circi-
nate apex, whilst the tip of the young
pinnule itself is concealed beneath
’ Fic. 204. Adiantum Edgeworthi. Leaf-apex exposed.
Meememeg de encore the sever Sanaa Eon
development of these lobes! a better Bye) vane Seceinat: a: later per
protection to the young parts is made
possible, as is the case in many Spermophyta where the stipules perform
a like function®. We may say the same for the special configuration of
the leaflets of many species of Adiantum, for example A. trapeziforme. It
will be shown below that even more peculiar relationships are observed in
many of the Gleicheniaceae, relationships which have been erroneously inter-
preted, through want of consideration, to the standpoint of function.
Apical Growth in the Leaves of Filices. The apical growth of the
leaves of many ferns is prolonged over several periods of vegetation. The
growth of the apex is periodically arrested, and then again resumed at
a later period.
1 In the mature leaf each lobe is in great part covered by the base of the one above it, and they
are therefore of little moment in assimilation.
eee bait I, p. 125.
318 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
WNephrolepis. Some but not all species of Nephrolepis! show this, but
it is not observable in their primary leaves. In at least many species, as
I have satisfied myself is the case in Nephrolepis exaltata, it is possible to
recognize the limits of the several yearly growths by the diminution in size
of the pinnules. In old leaves I found the leaf-apex, which is still circinate,
finally dried up.
Hymenophyllum. Many species of Hymenophyllum, for example
H. interruptum, H. Karstenianum, and H. plumosum, show similar features.
Gleicheniaceae. The Gleicheniaceae behave strikingly in a like manner,
and their circinate leaf-tips which are found in the successive resting periods
have been confounded with adventitious buds. The
Gleicheniaceae also exhibit some remarkable adaptations
which have hitherto not received the attention they de-
serve. Of these the most remarkable is the adjustment
of several pinnules as a protection to the resting apex of
the leaf so as to form a kind of bud-scales. These pin-
nules have been quite superfluously named ‘adventitious’
and ‘aphleboid’” formations, and Potonié? has conjec-
tured that they are ‘vestiges of the originally laminar
expansion of the chief spindle of the leaf’ But we
have here neither ‘ adventitious’ structures nor ‘ vestiges,
but only pinnules which, standing next to the resting
leaf-apex, are constructed as protective organs to it.
exniG,,205: Nephrol’ As is shown in Fig. 206, they lie primarily like two
eve gear ypaardy mussel-shells over it. They are, at least in the relatively
Seeuneiee one lobe.’ small leaf which is represented, scarcely divided, but in
other species of Gleichenia they are lobed or cut. The
larger the resting-apex which they have to protect the larger are these
protecting pinnules, and they may be absent if it is very small, whilst
many species of Gleichenia, especially those with a dense covering of scales
or hairs, want them altogether. The figure shows that the portion of the
leaf which is directed outwards is furthered *. Where, as in Gleichenia bifida,
leaflets appear upon the primary axis of the leaf, at first only upon the
inner side, we have perhaps to deal with pinnules which are effective as
protective structures during the period of unfolding’. We do not know
1 Mettenius, Filices horti botanici Lipsiensis, Leipzig, pp. 99 and tor. With regard to the
Hymenophyllaceae, see Mettenius, Uber die Hymenophyllaceae, Leipzig, 1864.
? For instance by Sadebeck, Pteridophyten, Einleitung, in Engler and Prantl, Die natiirlichen
Pflanzenfamilien, 1898.
% Potonié, Lehrbuch der Pflanzenpalaeontologie, Berlin, 1899, p. 119.
*“See Part J; p, 124.
° In one example which I have before me the chief pinnule begins with five lateral pinnules
standing only upon the inner side, and thereafter follows the usual formation of pinnules upon both
sides,
APICAL GROWTH OF LEAF‘ IN FILICINEAE 319
what is the connexion between the periodic growth! of these leaves of ferns
and their relationships of life, yet we may conjecture that the further de-
velopment proceeds in moist periods of the year, and that the arrest
takes place in the dry periods.
Lygodieae. The leaves of species of the Lygodieae are those which
exhibit the most prolonged growth in length, and they twine around
supports. Further investigation is required before we can say that we have
an ‘unlimited’ growth here, and that the leaf only dies down finally by, as
Fic. 206. Gleichenia dichotoma. I, fork of leaf in which is a ‘ bud’ covered by the protecting pinna; 4 and
B, Ay and Aj, pairs of pinnae of very unequal size ; A and Aj, smaller protecting pinnae; Band A, pinnae turned
outwards, larger and more segmented. IJ, the same. III, protecting pinnae. I and II, two-thirds natural size.
III, natural size.
it were, an accident through, it may be, unfavourable external conditions,
difficulties of water-transport, and so forth *.
From what has been said we can recognize in the Filicineae the
following stages :—
"The formation of the leaves is incorrectly described in the most recent account of the
Gleicheniaceae by Diels, in Engler and Prantl, Die natiirlichen Pflanzenfamilien, 1898—* adven-
titious shoots’ do not exist in the ‘forkings’ of the leaf-axis. The structure found in these
positions is the continuously growing leaf-apex. The ‘forking’ is the consequence of the two
pinnules below the circinate persistent leaf-tip developing equally. No species of Gleichenia has
a dichotomous leaf.
? The primary leaves, like those of other ferns, have limited growth.
320 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
(1) The germ-plant begins with a cotyledon, which has marginal
growth from the outset, and it as well as the primary leaves—which only
for a short time have apical growth from a two-sided apical cell—show
dichotomous branching or evident dichotomous venation.
(2) The leaf-apex grows at first monopodially, but after a shorter or
longer time it passes over into marginal growth, and dichotomous branching
follows.
(3) The apical growth persists during many periods of vegetation.
The leaf forms to a certain extent long growths and short growths, and
these latter are the branchings of the higher order, which from the outset
have limited growth.
Whether this series forms an ascending or
descending one, or whether we must recognize
it as simply one construction cannot certainly
be determined. What is certain is that the
configuration of the primordium of the leaf is
connected with that of the mature condition
in the manner that has been indicated above.
The relationship that has been pointed
out ' between apical growth of the leaves of the
ferns and their circinate ptyxis is not alto-
gether without exception. The apical growth
FIG. 207. Pteris serrulata. I, young
leaf. The leaf-stalk is incurved, the
lamina is already divided but is not in-
curved. II, young leaf in transverse
section near the tip of a leaflet. It is
almost circular. he lamina arises
later from the marginal cells, Z, Z.
The upper side, in correspondence with
its lie in the bud, is turned downwards.
III, older leaflet in transverse section.
The precedence in development of the
thick rhachis over the lamina, Z, Z, is.
shown. The upper side is in this figure
turned upwards. I, natural size. II
of the leaf is also not necessarily bound up
with circinate ptyxis. In Pteris serrulata (Fig.
207), P. cretica, and P. umbrosa I found the
laminar portion of the leaf to be straight from
the beginning, the stalk alone showed a sharp
curvature so that the leaf-apices of the leaflets
were all directed downwards’. Nevertheless
and III, magnified.
the normal apical growth exists here. I must
confess that I was astonished to find this, but I believe that we may
obtain the biological explanation in the consideration of two facts—
first of all there are a number of segmented hairs developed at a very
early period, and these cover over the leaf-apex and protect it, and
secondly the leaf-spindle precedes in development the lamina to a very
creat extent, and the lamina attains even later no very marked breadth ;
* See p. 310.
2 It is remarkable that no one has mentioned the facts, although they appear in the cultivation of
one of the commonest ferns, but I may add that Leszcyc-Suminski says of the leaves of Pteris
serrulata that the primary leaves appear to be circinate. His figures, however, show there is only
an incurving of the stalk, not of the lamina, and the statement of Kaulfuss that there is no circinate
ptyxis in Pteris serrulata is correct, although Leszcyc-Suminski endeavoured to controvert it. See
Leszcyc-Suminski, Zur Entwicklungsgeschichte der Farrnkrauter, Berlin, 1848, p. 16.
FORMATION AND DEVELOPMEMT OF LEAF OF SPERMOPHYTA 321
it shoots out to both sides of the almost cylindric leaf-stalk, and retains for
a relatively long period its embryonal character throughout (Fig. 207), and to
its protection the hairs are devoted. A leaf-bud of this kind appears only
in ferns which grow in specially moist shaded stations, as is the case with
these species ; possibly also the character is of importance from a systematic
standpoint.
The case is different in ferns which at an early period lose their apical
growth, and in which therefore the circinate ptyxis is wanting. We see this
in some small-leaved species of Hymenophyllaceae, as, for example, the
species of Trichomanes represented in Fig. 183, and some other forms with
similar leaves. We also find it in T. peltatum and T. Motleyi, which have
small peltate leaves that pass over at an early period into marginal growth’.
The leaves of Ophioglossum and Botrychium also have no circinate ptyxis *.
These examples amongst the Pteridophyta, as well as those amongst the
Dicotyledones 2, show that circinate ptyxis is not a systematic character, but ~
is one connected with apical growth, although not necessarily so, and that
it may be constant, more or less, in one series.
(4) SPERMOPHYTA.
In simply constructed leaves, especially those which have no leaf-stalk,
there appears to be no segmentation of the leaf-primordium as it develops.
It is different, however, in more highly membered leaves. The first thing
that strikes us here is that the leaf-stallk arises relatively late, with which
corresponds the fact that its work has to be done during and after the
unfolding of the leaf. The primordium of the leaf appears at first with the
configuration of a ridge or papilla, and in this condition it is designated
a primordial leaf. The primordial leaf next segments into two portions
which, however, are not separated sharply one from the other, but are only
distinguished by the share which they take in the further growth of the
primordium. That portion which sits upon the vegetative point of the shoot,
the /eaf-base, takes no share in the further differentiation of the leaf-primor-
dium, or at least only in so far as in many plants an outgrowth develops at
each side of the primordium, and these outgrowths of the leaf-base are
designated s¢zpules. In many cases the leaf-base acquires a sheath-like
form, leaf-sheath, especially in the grasses and the Umbelliferae. The
portion of the leaf-primordium which lies above the leaf-base is the upper
leaf, and it is from this that the leaf-lamina proceeds. If in the mature
condition the lamina is segmented, pinnate for example, or otherwise
* Compare what is said under peltate leaves, p. 335.
? The example of some species of Pteris mentioned above shows that even where there is prolonged
apical growth circinate ptyxis of the bud is not necessary.
8 See p. 310.
GOEBEL II ¥
322 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
divided, the divisions come about, apart from the case of palms, by branch-
ing of the upper leaf. The leaf-stalk is everywhere of late origin, and it is
intercalated between leaf-base and upper leaf, that is to say, it arises from
that portion of the leaf-primordium which lies between these two, and which
retains the peculiarity of an embryonal tissue for a longer time. That
a leaf-stalk is absent in many cases requires as little explanation as the fact
that there is no sharp limit between the leaf-stalk and the leaf-sheath. In
what follows the development of the leaf of the larger systematic groups
will be described :—
I. GYMNOSPERMAE.
Cycadaceae!. The leaves of the Cycadaceae externally resemble in their pin-
nation those of many Filices, especially in the fact that the pinnules are circinate in the
bud; but the whole leaf is not circinate because the leaf-apex passes at a relatively
early period into the permanent condition, sometimes even before the appearance
of the pinnules. The pinnules proceed from two wing-like growths of the primor-
dium which remains embryonal, and in this we have a difference in the development
of the leaf as compared with that of the Marattiaceae. The available statements do
not, however, give us a satisfactory view of the duration of the apical growth.
Sonntag * observed a leaf of Cycas Thouarsii which had a length of about fifty
centimeters and possessed a circinate leaf-apex with completely embryonal apex,
whilst in the cases examined by Bower®* this apical growth which was never very
marked ceased with the appearance of the pinnules. The pinnules appear in
acropetal succession in C. Seemanni, but in other species they appear almost
simultaneously, or those in the middle regions of the leaf appear before the upper
and the under ones, as in C. Jenkinsiana, whilst in Macrozamia Miqueli and
Encephalartos Barteri the succession of development is basipetal.
Ginkgoaceae. The apical growth in Ginkgo persists longer than it does in the
Cycadaceae. The division of the leaves takes place by actual branching, and there
is an apical marginal meristem, as in the leaves of many Filices, and the branching
is clearly dichotomous.
Coniferae. The simple configuration of the leaves of the Coniferae makes
it unnecessary to discuss here the development of the leaf.
Gnetaceae. The apical growth of the leaf-primordium ceases very early amongst
the Gnetaceae. This is specially evident in the remarkable Welwitschia mirabilis
which possesses during its life only two leaves, placed at right angles to the
cotyledons, and these grow perennially by means of a persistent basal zone *.
* See Warming, Undersggelser og Betragtninger over Cycaderne, in Oversigt over det kongelige
danske videnskabernes Selskabs Forhandlinger, 1877 ; Bower, On the Comparative Morphology of
the Leaf in the Vascular Cryptogams and Gymnosperms, in Phil. Trans., 1884.
? Sonntag, Uber Dauer des Scheitelwachsthums und Entwicklungsgeschichte des Blattes, in
Pringsheim’s Jahrbiicher, xviii (1887), p. 241.
* In part seedlings; perhaps older plants behave differently. * Bower, op. cit., p. 600.
-
DORSIVENTRAL LEAVES OF MONOCOTYLEDONES 323
2. MONOCOTYLEDONES.
DORSIVENTRAL LEAVES.
The simple construction and the predominance of intercalary growth in
the leaves of most Monocotyledones has been already mentioned !, but we
may here take as an illustration the formation of the leaf of Dactylis
glomerata (Fig. 198).
Dactylis glomerata. The leaf is composed of a closed sheath and
alamina. At the point where these join is the membranous ligule. The
function of the leaf-sheath is to support the internode which has long
intercalary growth. If one holds horizontally the haulm of a grass which is
still in a condition of growth, and from which the leaf-sheath has been
removed, it is unable to support its own weight. The ring-like swelling
upon the leaf-sheath above its point of attachment may at first serve to
give a firmer support to the haulm, because it is formed at the point where
the tissue of the internode is softest. The importance of these nodes for
Fic. 208. Bambusa verticillata. Leaf in transverse section; I, hinge-cell. II, convolute lamina. III, hinge-
cell after unfolding of leaf. All magnified.
the erecting of the haulm is well known and need not be further spoken
of here.
The youngest primordium of a leaf on the massive vegetative cone has the form
of a ridge which does not entirely surround the vegetative point. It is only in the
second youngest leaf that the primordium takes on the form ofa circular wall from
one side of which the lamina springs, and this side is marked out from the first by
being somewhat higher than the adjacent part. This side grows more strongly,
whilst the amplexicaul leaf-base, which at first is very small, develops by inter-
calary growth gradually into the leaf-sheath. The laminar portion only appears as
sharply separated from the leaf-base after the appearance of the ligule. It is clear
that this development cannot be crisply interpreted as Trécul would have it—that
the leaf-sheath is first formed. ‘The primordium of the leaf at the beginning shows
rather neither lamina nor sheath. The former does not grow out of the latter, but
both differentiate only in the further course of development. As to the leaf-sheath
which subsequently becomes the tube, we cannot say that this results from the
*concrescence’ of the margins of an originally open primordium of a sheath, as was
1 See p. 298.
Y¥ 2
324 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
formerly supposed, but only that a ring-like zone of the vegetative point of the shoot
takes a share in the formation of the leaf.
Hinge-cells in grasses. A peculiarity of the leaves of grasses may be mentioned
here because often it is interpreted incorrectly. ‘The lamina in Bambusa has con-
volute ptyxis (Fig. 208), and it remains in this condition for a relatively long time
until the tissue-formation in the leaf is nearly completed. The expansion of the
leaf is provided for by special Azmge-ce//s—epidermal cells which remain at first
small, but in the process of unfolding of the leaf grow rapidly and attain a volume
which is considerably larger than that of the other epidermal cells. These hinge-
cells are found also in some other Monocotyledones’.
FIG. 209. Helicodiceros muscivorus. Leaf seen obliquely from above; WA, the leaf surface; 1 and 1a, two
oe Bier Nokes which branch sympodially in the respective series 2, 3, 4, 5, 6, 7 and 2a, 3a, 4a, 5a, 6a, 7a, 8a.
BASAL LAMINAR GROWTH. The leaves of some Monocotyledones have
a lamina in which growth persists at its lower end. In this way there arises
a sagittate leaf, such as we find in Sagittaria and some Aroideae. This
growth is particularly striking in cases where a branching appears, as it does
in Helicodiceros, Helicophyllum, Dracunculus, Sauromatum, and others. In
Fig. 209 we have a representation of the remarkable formation of the leaf
in Helicodiceros. At first sight it would appear as if two radial leafy shoots
were springing from the base of the leaf. In reality the leaf-lamina has
* Their significance was first recognized by Duval-Jouve, Histotaxie des familles des Graminées,
in Annales des sciences naturelles, sér. 6, i (1875).
PERFORATE AND SPLIT LEAVES OF. AROIDEAE 325
two lobes, 1 and 1a, which would make it a sagittate leaf, as in many other
Aroideae, were they to remain simple. But they branch sympodially, that
is to say a branch, 2, arises out of the base of branch 1, branch 3 arises out
of branch 2, and so on. But these branches are not spread out, as in Sauro-
matum, in one plane, but are twisted in a ladder-like spiral, so that the leaf-
lobes appear as if they were arranged around a central axis. But this
apparent axis is only the thickened outer margin of the base of the suc-
cessive lobes—an interesting example of how definite parts of the leaf
become more strongly constructed in proportion as they have stronger
mechanical claims made upon them. There can be little doubt that such
a special leaf-configuration has some biological significance if we could only
discover it. This much is clear, that the whole leaf-surface occupies
a smaller area than would be the case if the leaf-branches were spread out
in one plane, and that the spiral arrangement prevents shading by the
leaf-lobes as they rise above the original leaf-surface. The small space
which the leaf-surface occupies may be connected with the denser arrange-
ment of the leaves and the shorter length of the leaf-stalk compared with
other forms like Sauromatum. At least I have found that other Aroideae
with a sympodially branching leaf form only one or few leaves, which are
raised free upon long leaf-stalks, whilst in Helicodiceros the leaves stand
close together and have relatively short stalks.
PERFORATE AND SPLIT LEAVES OF AROIDEAE. Many other Aroideae
are distinguished by remarkable formation of their leaves. The leaves of
Anadendrum medium (Part I, Fig. 97) are distinguished by the formation
of holes in the lamina, and also by the development of lobes which are like
pinnules. The construction of the leaf here may be reached in much the
same way as in Monstera deliciosa! and its allies, where the tissue lying
between the nerves lags behind in growth and dries up. If this dying-off
tissue lies near the laminar margin, and this be thin, it splits outwards into
limited strips of tissue, and thus arises a feather-like lobed leaf; if the splits
take place further within the laminar margin there is a hole. The bio-
logical significance of this splitting of the leaf-lamina will be noticed below.
In the pinnatifid or pinnate leaves of species of Philodendron there is no
formation of holes, but only of lobes through the stronger growth of single
marginal portions of the lamina, and in those species of Anthurium which,
like A. digitatum, have compound digitate leaves, the leaflets arise as
branchings from the leaf-primordium in basipetal succession.
LEAVES OF PALMS. The leaves of palms require special notice.
Many of them are the largest leaves which we know of. The segmentation
of the leaves is no doubt connected with their size, and so also is their
possession of a strong leaf-stalk, and in many cases of a massive midrib.
1 See Engler, Araceae, in Engler and Prantl, Die natiirlichen Pflanzenfamilien, ii. 3, p. 104.
326 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
Where the leaf-lamina is membered this is not the result, as is usual, of the
branching of an originally simple primordium, but is a consequence of the
splitting of an originally entire leaf-surface. We have cases analogous with
this amongst other Monocotyledones, for example in Musa, whose leaves are
easily torn into isolated lobes fastened to the thick midrib. In Musa
external factors, especially the wind, bring about the partition, but in other
Monocotyledones, as, for example, Cyclanthus bipartitus, the splitting is a
consequence of the tensions arising in the process of the unfolding of the
leaf. Formerly the division of the palm-leaves also was considered to be
the consequence of mechanical splitting, but investigation of the history ot
development has shown that this is incorrect. The splitting in the palm-
leaves is due to the death, at a more or less early period, always defore the
unfolding of the leaf, of definite portions of the tissue, or it may be that it is
mucilaginous degeneration of the cell-walls of the tissue which brings about
the separation. The splitting of the leaf-surface is therefore from the first
prepared for. Two types of palm are commonly distinguished by the form
of the leaf, the faz-palms and the feather-palms ; in both the leaf diverges
from the usual type of Monocotyledones, and it is easily shown that the
deviation stands in relation to the increase in size.
LEAF OF FAN-PALMS. Let us start with the leaf in fan-palms, because
it is much nearer the primary form of leaf in the Monocotyledones. The
fan-like folding of the leaves has the same mechanical significance as the
folded paper of a fan, that is to say, the leaf-surface is kept expanded
without much expenditure of material’. Were it flat it would be ruptured
by its weight, or very strong ribs would be required. The same principle of
construction is repeated in the pinnules of the feather-palms, which, at least
at their base, are often folded into channels. The folding of the leaf-lamina
begins at a very early period in the leaf-primordium, and this has led to
some misunderstanding ”.
If a fan-leaf is to reach a considerable size, the several rays of the fan
must diverge from one another at their apex ; at the base this is not well
possible on mechanical grounds. The construction is reached thus :—The
upper portion of the primordium of the leaf which has not taken a share in
the folding dies off; thereby room is provided for the divergence of the
folds, and the points of the several rays also separate from one another more
or less far. The separation takes place at a varyingly early period in
different palms. In Pritchardia filifera the upper angles of the folds which
1 The same, although less noticed, is the case in the liliaceous Curculigo, which has thin not
flatly expanded leaves.
* Naumann’s statements, in Beitrage zur Entwickelungsgeschichte der Palmenblatter, in Flora,
Ixx (1887), are for example erroneous. See Deinega, Beitrage zur Kenntniss der Entwicklungs-
geschichte der Blatter und der Anlage der Gefassbiindel, in Flora, 1xxxvy (1898). The literature is
cited here.
LEAVES OF PALMS 327
are already provided with vascular bundles die off, and one can see the
ruptured strips of tissue as long brown threads hanging on the unfolded
leaves. In Chamaerops the separation takes place much earlier, whilst the
tissue of the leaf has still somewhat of an embryonal character, and it is
brought about by the mucilaginous degeneration of the cell-walls just as
it is in Rhaphis and the feather-leaved Cocos. Archontophoenix which has
feather-leaves furnishes, as it were, a transition between these two methods
of separation, for in it the strips of leaf-tissue, which die off in the process
of unfolding of the leaf, are from the
first laid down as thinner layers than
the rest of the leaf-tissue. The seed-
lings of almost all fan-palms' have
the ordinary leaf-form of monocotylous
plants, the veins running with a curved
course and not diverging at the tip
(Fig. 210).
LEAF OF FEATHER-PALMS. We
must next speak of the feather-palms.
The pinnation here is likewise the result
of a splitting, not of a branching, of the
leaf-surface. Let us consider first of
all the primary leaves of Phoenix.
Here we find leaves which resemble the
ordinary ones of Monocotyledones, ex-
cept in having slightly expressed folding
of the lamina (Fig. 210). At the base,
Fic. 210. I and JI, Phoenix canariensis.
and at first limited to the base, of the Primary leaves. III and IV, Chamaerops excelsa.
Primary leaves. One-sixth natural size.
leaf there is formed a stronger middle
portion, which gradually involves a larger portion of the primordium of the
leafand becomesa strong midrib. The leaf-surface separates then into single
segments. That this procedure begins at the base of the primary leaves
is a consequence of the intercalary growth of the leaf (Fig. 210).
Thus, starting from the ordinary leaf of Monocotyledones, we obtain an
altogether different form of leaf, and we may recognize the following stages
of development which lead from an entire leaf-surface to a divided
one :—
(1) The splitting takes place in expanded leaves under the influence of
external factors, such as wind and rain. We find this in Musa, and the
function of the leaf is not interfered with by the splitting. In Heliconia
1 In many palms the first leaf is divided. See Pfitzer, Uber Friichte, Keimung, und Jugendzustiinde
einiger Palmen, in Berichte der deutschen botanischen Gesellschaft, iii (1885), p. 32. The literature
is cited here.
328 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
dasyantha Karsten ' found that there is a special arrangement which brings
about a splitting of the leaf-lamina under the influence of raindrops.
A marginal strip of the leaf-tissue dies away before the middle portion has
reached its complete growth, and in this way tensions arise which cause
the splitting of the lamina when rain falls upon it.
(2) The splitting takes place during the unfolding of the leaf by tensions
within it, as in Cyclanthus bipartitus.
(3) The points of separation are prepared in the bud by the dying-off
or by the mucilaginous degeneration of cells. This is found in palms.
RADIAL AND BILATERAL LEAVES.
In the preceding cases we have dealt with the leaves of monocotylous
plants in which the ordinary horizontal expansion is observed. A number
of leaves, however, in Monocotyledones, have a profile or vertical position,
and they are then either radial or bilateral. Species of Juncus, for example,
have radial leaves which were formerly considered to be shoots because of
their external resemblance to shoots, and because their internal structure
is like that of shoots’. We find radial leaves also in some species of
Allium. Iris supplies a specially good illustration of bilateral leaves, yet
they have frequently given rise to controversy, and even in works of the
most recent date we may read that ‘the leaves of the Iris have taken
their present form by concrescence of the two leaf-surfaces upwards */—
and this on the ground of anatomical investigation.
Leaf of Iris. The developmental history of the sword-like leaves of
Iris is as follows :—
The primordium of the leaf has the normal form, and when it first appears does
not embrace the stem (Fig. 211, 4, 4,) ; but this it soon does (Fig. 211, 4, 4,). The
primordial leaf grows now like an ordinary primordium. Its apex (Fig. 211, A, a)
should become the apex of the leaf-lamina, but it is found to be subsequently at
the position where the leaf-lamina passes over into the leaf-sheath (Fig. 211, B, a).
This ‘ displacement’ is explained by the developmental history. The primordium
acquires soon a growth in surface, and retains therefore a cap-like configuration
(Fig. 211, A,4,). Upon its back the growth in surface is the strongest, and here at
one position the character of the vegetative point is retained (Fig. 211, A, s in the
fourth unnumbered primordium), and the keel of the leaf-primordium grows out
into the primerdium of its ‘sword-like’ lamina. This lamina is hollow only where
it passes into the sheath, in its other part it is from the beginning a solid plate
of tissue. There are on the primordium of the leaf then now two apices—the
' Mentioned by Stahl, Regenfall und Blattgestalt, in Annales du Jardin botanique de Buitenzorg,
xi (1893).
* They have an evident, although small, leaf-sheath, and arise laterally on the vegetative point.
* Massart, La récapitulation et l’innovation en embryogénie végétale, in Bulletins de la Société
Royale de Botanique de Belgique, xxiii (1894), p. 252: ‘La feuille d’Iris ... doit étre considérée
phylogéniquement comme le produit de la soudure des deux moitiés de la feuille par leur face supé-
rieure.’ I hold this to be an impossible view.
BILATERAL LEAVES OF MONOCOTYLEDONES 329
original one, 2, and the new one, s._ The laminar primordium, s, soon acquires an
actual terminal position, and the transition to this is shown in the larger leaf
represented in Fig. 211, 4, where the leaf-base which develops later into the leaf-
sheath is marked off from the laminar primordium by a dotted line. The laminar
primordium has indeed still a lateral position, but its middle line is raised up
already about 45°, and the original apex, a, has assumed a lateral position..
This kind of leaf-development finds an interesting parallel in that of the genus
Fissidens amongst the Musci’.
In this genus the leaf-lamina arises eo | 5
also as a wing-like outgrowth of oo es
the original leaf-primordium, and
as in Iris this formation of wing *
proceeds in Fissidens from the
back of the keel of the leaf-prim-
ordium. The two sides of the
leaf-primordium share equally in
this from the first, so that we need ,£'S, 21%, Ty variggata. Development of leat. vegeta.
pot wonder that in the anatomical #4’s,ar;nambered; (1/6 the youngest, The point marked ¢
Bemeomerepecially inthe course of te Tatsneath he point become the of the min
of the vascular bundles, these sides
are both indicated. Neither in the ontogenetic nor phylogenetic sense can we
speak of the ‘concrescence’ of two leaf-surfaces here, as a comparison with the
radial leaves of Juncus and Allium will readily show, for their origin resembles in
all essentials that of the leaves of Iris.
The few cases of peltate leaves in Monocotyledones will be spoken
of when other peltate leaves are discussed below.
3. DICOTYLEDONES.
BRANCHING OF THE LEAF.
In Dicotyledones the segmentation of the leaf always depends upon
a branching of the primordium, and this always starts from its margins,
which, however, are often bent upwards, so that it looks as if the inception
of the lateral members was upon the upper side. The origin of lateral
members takes place after the following chief types :—
I. Dichotomy :—A division of the vegetative point of the leaf, such as we find
in Filices, relatively seldom takes place, but is found in Utricularia “, Ceratophyllum
demersum *, and also in Drosera binata and D. pedata, which have dichotomously
eee p, 137.
* See also what is said about the formation of a wing on the back of the leaf of Phormium (p. 390).
Tf these wing-like growths arise very early we should get the form of Iris. Perhaps there are
transitions between the form of Iris and of Phormium.
* Goebel, Morphologische und biologische Studien: V. Utricularia, in Annales du Jardin botanique
de Buitenzorg, ix (1891).
* Massart, La récapitulation et l'innovation en embryogénie végétale, in Bulletins de la Société
Royale de Botanique de Belgique, xxiii (1894).
4
330 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
branched leaves. This method of branching is only possible in leaves with
prolonged apical growth.
2. Monopodium :—Lateral branching occurs after the following types :—
(a) Acropetal Development. All the branches of the leaves arise in serial acropetal
succession, as in the Umbelliferae, Papilionaceae, Mimoseae, Caesalpinieae, Sam-
bucus Ebulus, and others. The leaf-apex itself passes at an early period into the
permanent condition, but below this there remains an embryonal zone on which
in acropetal succession the lateral parts appear. On this account Sonntag reckons
them as belonging to an intercalary type, but as a matter of fact the several types
are not sharply limited.
(6) Basipetal Development. The youngest leaf-segments are the lowermost,
as in Myriophyllum, Hot-
tonia, Rosa, Potentilla
anserina, Sambucus nigra
of pinnate forms, Hel-
leborus foetidus and all
digitate forms.
(c) Divergent Deve-
lopment. ‘The branching
here proceeds from one
position of the primor-
dium upwards and down-
wards, as in Achillea Mil-
lefolium, the leaf-teeth of
Ulmus, and others.
The course of deve-
lopment in nearly allied
plants varies, for example
in pinnate leaves it is
sometimes acropetal,
sometimes basipetal, so
that this difference is not
of very great importance.
FiG. 212. Acer platanoides. -4, bud dissected out, showing two young ane BueevoR a
leaves; s¢, stem; sf, lamina with five segments. JZ, older leaf from the Sympodium :—-In some
side, showing the course of the conducting bundles. C, scheme of the course a s
of the conducting bundles in the mature leaf. 2, basal portion of a bud in Dicotyledones a partially
Rese ae eccrine Soon ane ques aa aie sympodial construction
mone all the figures indicate the bundles of successive age. After of the leaf has been as-
sumed, of the same cha-
racter as that which we have observed in the Aroideae, but most of these cases
are ‘palmatifid’ leaves, with basipetal evolution of the leaf-lobes. In the leaf of
Acer platanoides, which is shown in Fig. 212, C, there are, for example, five chief
lobes present, one in the middle and two at each side. Fig. 212, 4, shows how
the lobes arise in basipetal succession, but one may interpret the procedure as that
only two lateral lobes exist, from which then the two lower ones shoot out as
‘
SYMPODIAL LEAVES IN DICOTYLEDONES 331
members of the second order!. It is extremely difficult to follow here the history
of development, and to say whether these lobes arise directly out of the leaf-
primordium as members of the first order or not. That leaflobes branch frequently
only upon their outer side is very common. If the leaf of Chelidonium, shown
in Part I, Fig. 73, were cut through beneath the upper pinnule a five-lobed leaf
would result, but its two lower lobes are outgrowths of the lateral ones. I do
not see, however, why one should call such a leaf cymose, because the several
members of the leaves are not at all separated from one another and the
notion of ‘cymose branching’ is, therefore, not really applicable. The whole
question may be of importance if we are dealing with the derivation of the leafforms
within one cycle of affinity. For the general organography it appears to me to be of
little importance. Prantl certainly goes too far when he says* of Achillea Mille-
folium that the segments arising basipetally in the leaf may be regarded as ‘ shoot-
ing from one another,’ and that the leaf in its under portion is cymose. Here the
history of development shows that the pinnules arising basipetally shoot out from a
marginal zone which remains meristic, whilst in the inner portion of the leaf
differentiation of the tissue has already begun as the appearance of intercellular
spaces first indicates. The pinnules are as elsewhere outgrowths of the margin of
the leaf bent somewhat upwards. I have found no indication that would suggest a
genetic relationship of these one to another.
INTERRUPTEDLY PINNATE LEAVES. Interruptedly pinnate leaves,
that is to say, leaves in which the pinnules are alternately of a very
different size, may also be considered to be sympodial. Examples of these
we find amongst the Solanaceae, as in Solanum tuberosum, Rosaceae, as
in Spiraea Filipendula, species of Geum, Potentilla anserina, and others *.
It has been shown‘ that the small pinnules fill up the spaces between the
larger, and an analogy may be found within the class of Algae. Here we
have only to notice the origin of these small pinnules. They might be
regarded as lateral leaflets of the leaflets of the first order which have been
displaced upon the leaf-spindle. But the history of the development, so far
as it is known, is in the direction of showing that they are independent
formations. Their inception takes place /a/er than that of the larger leaf-
lets, and in this we have an interesting parallel case with that of the
alga Euptilota Harveyi (Part I, Figs. 46, 80). It is easy to convince oneself
that the larger pinnules also arise earlier than the small ones standing oppo-
1 In support of this one might appeal to the course of the vascular bundles. Three chief veins
enter the leaf; one, 7, in the middle, and one upon each side of it, 77 and 7/7. The vascular bundles
ZV.and V unite in the leaf-base with 7/ into one strand, and we may suppose that the leaf-lobes
behave likewise.
* Prantl, Studien iiber Wachsthum, Verzweigung und Nervatur der Laubblitter, insbesondere der
Dicotylen, in Berichte der deutschen botanischen Gesellschaft, i (1883), p. 280.
® Also Reseda alba according to Sonntag, Uber Dauer des Scheitelwachsthums und Entwicklungs-
geschichte des Blattes, in Pringsheim’s Jahrbiicher, xviii (1887), p. 247.
* See Part I, p. 127.
332 LEAF DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
site to them. I regard the small pinnules as reduced leaflets of the first
order, probably the result of correlation, but not as zztercalated new forma-
tions as has been assumed. For this interpretation’ we have support in
the fact that these interposed leaflets may be entirely absent in feebly
developed leaves, for example those of the potato.
RELATION OF THE PINNATE TO THE DIGITATE LEAF. Relatively
small differences in the distribution of the growth upon one and the same
primordium may bring about leaf-forms which are outwardly very different.
Let us suppose, for example, that on one leaf-primordium there are produced
upon each side five lateral primordia. From this would develop a leaf
with five marginal projections if the lamina itself is strong in growth and the
Fic. 213. 1, Limnophila heterophylla. Apex of shoot seen from above. 2, Alchemilla nivalis. Apex of shoot
seen from above; a young primordium of a leaf seen to the left upper side of apex, the older leaves are deeply
divided into leaflets, in the outer two the ring-like sheath-portion is formed. Magnified.
lateral primordia grow less strongly. If now the laminar portion between
the lateral primordia grows strongly in length and less in breadth 2, and the
base of each lateral primordium grows similarly, a pinnate leaf will result,
but if the laminar portion scarcely grows further between the lateral
primordia then the leaf will be digitate. As a matter of fact pinnate and
digitate leaves do not differ essentially one from the other. In Aesculus
Hippocastanum, for example, we usually find digitate leaves, but occasionally
they are pinnate.
SINGLE BRANCHED LEAVES AS APPARENT WHORLS. Segmented
leaves which have no stalks and are deeply divided have a somewhat
peculiar aspect. The single leaf-lobes then take on the appearance of
independent leaves and are partly also described as such. These cases have
some biological interest and therefore two examples are referred to here :—
* It has to be proved whether in cases like Spiraea Filipendula the first view—that these small
leaflets are displaced lateral leaflets—which seems to me to have been hitherto lost sight of, is correct.
A drawing by Massart, La récapitulation et l'innovation en embryogénie végétale, in Bulletins de
la Société Royale de Botanique de Belgique, Pl. II, Fig. 33, supports it. Possibly both cases occur.
* The transition-forms between toothed and pinnatifid and pinnate leaves as they occur, for
instance, in Scabiosa Columbaria, tell the same story (Fig. 228).
SINGLE BRANCHED LEAVES AS APPARENT WHORLS 333
Alchemilla nivalis. Alchemilla nivalis is a plant of the high Andes. It
possesses apparently whorled leaves which are concrescent below into a sheath. In
reality the whorl of leaves is a single leaf, as may be concluded from the fact that
the leaves of the false whorl do not alternate (Fig. 213, 2). Each leaf-primordium
is at first laid down singly on the side of the vegetative point, which it soon
surrounds as aring. ‘This primordial ring itself re-
mains in an arrested state, while the leaf-lobes which
shoot out of it appear in descending serial succes-
sion, and these all attaining to about the same size
they appear as a false leaf-whorl. ‘The foliage-leaves
of this species of Alchemilla are produced in quite
the same way as the hypsophylls of other species
of Alchemilla which have stalked leaves with usually
a well-formed leaf-lamina’. The stalk remains
unformed, the sheath is strongly developed, and it
grasps round the vegetative point. We may un-
derstand the biological significance of this leaf-
formation in some measure if we reflect that the
young portions of the shoot are perfectly protected
by the leaf-sheaths, which are inserted one into the
other, and the small leaf-pinnules are in response
to the physiologically xerophilous station.
Limnophila heterophylla. The second ex-
ample is that of a marsh-plant, Limnophila hetero
phylla. Its swbmerged shoot-portions bear leaves
in an apparent whorl (Fig. 214), whilst the ends of
the shoots above water have the leaves arranged in
decussate dimerous whorls. The history of develop-
ment (Fig. 213, 1) shows that the water-leaves also
appear in dimerous whorls, the leaves in each whorl
soon uniting together into a ring-wall. Each leaf
forms in descending succession numerous leaf-lobes PPh Te ie bee opksliae
which again may branch. As we pass upwards on — Water-leaves and air-leaves and (ran-
Sition-forms. One-half natural size.
the shoot the middle lobe of each leaf is at first
larger than the lateral ones, and then the formation of the lateral ones is gradually
entirely suppressed or reduced to mere marginal leaf-teeth in the aerial leaves. We
shall refer to this plant again when speaking of the biological significance of leaf-
forms.
PELTATE LEAVES”.
By peltate leaves we understand those in which the lamina does not
expand directly out of and in line with the leaf-stalk, but grows out over
the stalk. Where this form is developed we always find upon the fer
* See Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 33- Alchemilla is figured.
* See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884), p. 234. A picture of the peltate leaves, without reference to the recent
»
334 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
(dorsal) side of the leaf, close to the position where the stalk is originally
fixed to the lamina, a zone of the young leaf, which shares in the formation
of the lamina. It is only in cotyledons and some kataphylls, hypsophylls,
and stamens! that we find upon the wzder (ventral) side of the leaf an
outgrowth which prolongs the lamina. De Candolle has in accordance with
these facts divided such leaves into epfipeltate and hypopeltate
forms. Inthe hypopeltate forms the construction is mainly
(leaving out of account the case of‘ versatile ’ anthers) directed
to the provision of means of protection.
PELTATE KATAPHYLLS. The kataphylls of some
species of Asparagus are peltate, and furnish an efficient
protection to the shoot-bud. In most cases of this kind
these kataphylls fall away later ; they are merely protective
organs. But in Asparagus comorensis (Fig. 215), the out-
growth of the under side of the leaf becomes a hard thorn
or hook projecting from the shoot-axis, and is used as a
climbing-organ.
PELTATE STAMENS. The pollen-sacs of Juniperus are
protected by an outgrowth of the scale-like lamina of the
covering leaf, and this I have compared with an indusium *.
PELTATE COTYLEDONS. Where we find peltate coty-
ledons, as in the grasses, the object is to provide a contact-
surface with the endosperm. The short ‘ radicle’ of the oak
is invested by the cotyledons, which grow out below and
protect it.
PELTATE FOLIAGE-LEAVES. The biological signifi-
cance of the peltate foliage-leaves is less clear. We have
first of all to recognize two groups—the short-stalked and
Fic. 215. Aspara- the long-stalked :—
gus comorensis. Tu- -
rio with peltate ka- Short-stalked peltate foliage-leaves. 1 only know of
taphylis ; the lower 3 - “ : 3
part of cach kata. such leaves in some epiphytic species of Trichomanes,
phyll stands out later : Boo} : :
from the shoot, T. Hildebrandtii*, T. peltatum, and T. Motleyi*, but in
nardens, an De-
comes a climbing- the last-named all the leaves are not always peltate. When
10rn. : : :
we recollect that in other species of Trichomanes, for
literature of development, is given by C. de Candolle, Sur les feuilles peltées, in Bulletin des travaux
de la Société botanique de Genéve, 1898-99.
1 IT have pointed ont, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s
Handbuch der Botanik, iii (1884), that stamens with versatile anthers conform with peltate leaves
in their method of formation.
* Goebel, Beitrage zur vergleichenden Entwicklungsgeschichte der Sporangien, in Botanische
Zeitung, xxxix (1881), p. 703; C. de Candolle, Sur les phyllomes hypopeltées, in Bulletin des
travaux de la Société botanique de Genéve, 1895-7.
* See Giesenhagen, Die Hymenophyllaceen, in Flora, 1xxiii (1890), p. 452.
* G. Karsten, Morphologische und biologische Untersuchungen iiber einige Epiphytenformen der
PEETATE LEAVES 335
example T. brachypus, the leaves are closely adpressed to the tree-bark,
to which they are fastened by rhizoids, and that many of the Acrosticheae
have the same kind of leaves, we may assume that the peltate form is of
special advantage in a given size of leaf-surface, both for the retention of
water and for the protection of the delicate stem, which in the cases under
notice is rootless.
Long-stalked peltate foliage-leaves. In the case of these leaves other
considerations have to be looked to. In the first place the size of the peltate
lamina is very different. The ‘ideal’ peltate leaf would be one with a stalk
attached in the middle of an almost circular leaf-surface. This is approached
in, for example, Nelumbium. In others, like many species of Caladium, the
anterior portion of the leaf-surface, which has grown out over the stalk, is
much smaller than the posterior. Possibly the peltate form has appeared
in these later than it has done in cases like Nelumbium.
CONDITIONS UNDER WHICH PELTATE LEAVES OCCUR. Peltate leaves
appear in plants which occur under very different conditions of life, in both
water-plants and land-plants, and amongst the latter in succulents like
Umbilicus, climbers like Tropaeolum majus, trees like Sterculia platanifolia.
These leaves are sometimes small, as in Utricularia peltata where they are
only half a centimeter in diameter, sometimes relatively very large, as in
Victoria regia where they may attain a diameter of two-and-a-half meters.
They are almost exclusively found in plants with alternate phyllotaxy, only
in a few plants with opposite leaves are they known. It is easy to understand
this from the biological standpoint. The peltate lamina requires in its
unfolding more room than others; frequently the laminae are supported
upon orthotropous stalks, and would cover one another if they were to stand
close together!. In plants with creeping rhizomes, or in climbing plants,
the peltate leaf appears to be a particularly advantageous method of placing
the leaf-surface by the shortest way in a transverse position to the light, and
of shading the adjacent plants which appear as competitors for the light-
supply. But although this explanation fits many peltate leaves, it is not
possible to give any plausible causal explanation of their origin. We can
only say that the factors mentioned above favour their origin. Further,
a leaf like that of Geum bulgaricum (Fig. 81, Part I), whose lower part is far
overshadowed by the terminal lobe, is biologically like a peltate one. A
relationship of the peltate form of the lamina to the length of the stalk and
to the position of the leaves, may be recognized in many cases. Whilst, as
in Utricularia peltata, the peltate leaves are relatively small and have not
Molukken, in Annales du Jardin botanique de Buitenzorg, xii (1895), p. 127. The developmental
history of the leaves is given, and it is shown that as the apical growth of these species ceases early
they never have circinate ptyxis.
* See Part I, p. 114.
3
336 LEAF-DEVELOPMENT IN PTERIDOPHYTA AND SPERMOPHYTA
very long stalks, we find allied forms, such as Utricularia nelumbifolia, with
long-stalked larger peltate leaves, and we may conclude that the former are
perhaps derived from originally long-stalked forms. The relation between
the length of the leaf-stalk and the peltate form of lamina appears also in
the individual development of many plants. In Umbilicus (Fig. 216) the
basal leaves are long-stalked and peltate and somewhat concave above,
whilst those upon the flowering shoot, especially the bracts, are not peltate,
and appear usually as ordinary leaves with short stalks. We find the like
in the berberidaceous Di-
phylleia cymosa, where
the upper short-stalked
leaves have frequently,
but not always, lost, or
nearly lost, the peltate
ee
' form. In seedlings also
Ne \ the peltate form appears
usually in the primary
I. leaves, for example in
Tropaeolum majus, T.
minus, and Nelumbium,
yet I have found fre-
quently the primary
leaves in Umbilicus
pendulinus to have the
se Ai
t EE usual form, and in
FIG. 216. Umbilicus pendulinas. JZ, basal foliage-leaf. 7/, foliageleaf species of Drosera with
higher up. //7and /l’, hypsophylls. Natural size. ;
peltate leaves, there is
always developed first of all a rosette of leaves of the ordinary drosera-
ceous form.
It is characteristic of the history of development of peltate leaves that they all
belong to the basipetal type. We may find an explanation of this in that the
peltate form owes its origin to a process of development at the base of the leaf-
lamina. Moreover, the history of development of the peltate leaves shows funda-
mentally no other growth-processes than are to be observed in the peltate hairs,
which occur, for example, in ferns, in the Elaeagnaceae, and elsewhere. The old
explanation that the peltate leaves were the result of a concrescence of the leaf-
edges projecting above the leaf-stalk is erroneous. Only in the biological sense has
it any pretensions to correctness in so far as peltate leaves conform essentially in
their behaviour with cordate leaves and other forms in which the lower leaf-edge
projects over the point of insertion of the leaf-stalk.
Many peltate leaves are evidently derived from ordinary leaves which originally
possessed a richer segmentation of the leaf-lamina. Segmentation is more con-
spicuous in the leaves of Hydrocotyle vulgaris when they are in a juvenile state
TUBULAR LEAVES 337
than when they are adult}, and the same is the case in Tropaeolum majus and
T. minus whose leaves in the unfolded condition are apparently entire, whilst in their
juvenile stages they recall the cut leaves of Tropaeolum aduncum and others. To
this Massart 2 raises the objection that these facts are found also in Umbilicus, whilst
its allied genera possess leaves which in all stages of their development are entire.
He overlooks, however, that Bryophyllum possesses segmented /eaves and that one
species of Bryophyllum has passed over to the formation of peltate leaves. This
species is the Bryophyllum crenatum of Baker which only forms leaves that are
indented at the edge high up on the shoot-axis *, and possesses at the base of this
somewhat short-lived outgrowths which are directed upwards, and whose biological
significance requires investigation.
TUBULAR LEAVES.
Tubular leaves conform with the peltate leaves in the history of their
development up to a certain stage. These tubular leaves are found in
a number of insectivorous plants. I do not mean that
phyletically they are derived from peltate leaves, at
any rate I know of no facts in support of such a view.
In Cephalotus follicularis alone, outside the Utricularieae,
are there, besides the tubular leaves, others of a different
form, and these are not peltate but of the normal flat-
form. Occasionally intermediate states are produced be-
tween these leaf-forms (Fig. 217). They are leaves with
an excavation upon the upper side, but they do not
approach the peltate form and are easily explained, when Fic. 217. Cephalo-
. tus foilicularis. Leaf
one knows the history of development of the tubular Showing a stage be-
C 5 : tw tubular leaf
leaves, as retarded formations, without the necessity of and an ordinary leat.
: ar ° On the upper side of
looking upon them as azavéstic. We meet with tubular the tear is a depres-
: = 4 sion, the leaf having
leaves also especially amongst the Hepaticae*, where no apparently reached the
: stage shown in ig.
peltate leaves are known. If we follow the history of 215,1, has continued
its growth without
development *, we find that an indentation appears upon farther change in com
the upper side of the leaf, and it gradually deepens (Fig. el ca
218). The lower edge of the depression (Fig. 218, 2) —this edge corresponds
to the new formation in a peltate leaf—is in its upper part made into
a lid, and at the same time forms a portion of the collar-like thickened
entrance. The upper portion of the leaf-primordium forms the special
1 Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), p. 234.
2 Massart, La récapitulation et l'innovation en embryogénie végétale, in Bulletins de la Societé
royale de botanique de Belgique, xxiii (1894), p. 81.
* At least in the single living example before me.
* See p. 58.
5 See Eichler, Uber die Schlauchblatter von Cephalotus follicularis, Labill., in Jahrbuch des
’ kGniglichen botanischen Gartens zu Berlin, i (1881), p. 193.
GOEBEL IL Z.
.
338 VENATION AND DEVELOPMENT OF LEAF
tube which is later so bent back upon the stalk that the lid comes to lie on
the top.
If we compare with these the tubular leaves in Nepenthes, Sarracenia, Utricularia
and its allies, all of which genera are carnivorous like Cephalotus, we find that the
history of the development is very similar, only the resulting configuration is some-
what different. I have elsewhere! given so full a description of these that I shall
here only briefly refer to them. The portion marked with d, in Fig. 218, and which,
as has been shown, is devoted in Cephalotus to the formation of the lid, serves
in these other genera for the construction of a portion of the wall of the tube.
The upper portion of the tube-wall corresponding to the leaf-apex forms the lid in
Sarracenia, it grows out in Utricularia and Polypompholyx to the remarkable
valve which closes the entrance of the tube, and in Genlisea two lateral portions of
the margin of the mouth of the tube grow out into long arms which subsequently
become twisted. In Nepenthes the lid arises as an outgrowth underneath the leaf-
apex *, and the leaves are here further remarkable in that the leaf-base develops later
into a laminar surface, whilst between it and the pitcher a stalk-like portion, which
frequently acts as a tendril, is intercalated.
Tubular leaves are only known outside insectivorous plants, passing over of course
abnormal formations, in the epiphytic Dischidia Rafflesiana*, and in the bracts of
the Margraviaceae. In Dischidia Rafflesiana the inner side of the tube corresponds
to the under side of the leaf, not to the upper side as in the cases first mentioned,
and leaves which are concave upon the under side of another asclepiadaceous
plant, Conchophyllum imbricatum, form a kind of transition to the tubular leaves
of Dischidia. In the bracts also of many Margraviaceae the inner side of the
tubular leaf corresponds to the under side of the leaf.
IV
RELATIONSHIPS BETWEEN VENATION- AND
DEVELOPMENT OF LEAF*
The relationships between the venation of the leaf and the growth of
the leaf already described in the case of the Filicineae, are found also amongst
the Angiospermae, although in somewhat different form.
The function of the veins of the leaf is two-fold, mechanical and nutritive.
It is well known that between the leaves of Monocotyledones with
striate venation, and those of Dicotyledones with veziculate venation, there
are differences which, however, are not very far-reaching. On the one hand
there are amongst Monocotyledones not a few, especially of the Aroideae,
* Goebel, PAanzenbiologische Schilderungen, ii (1893), p. 53.
* Goebel, op. cit., Plate XXI.
° Treub, Sur les urnes du Dischidia Raffesiana, Wall., in Annales du Jardin botanique de
3uitenzorg, iii (1883), p. 13.
* See Deinega, Beitrage zur Kenntniss der Entwicklungsgeschichte des Blattes und der Anlage
der Gefassbiindel, in Flora, lxxxv (1898).
VENATION OF MONOCOTYLEDONES 339
which have the venation common in Dicotyledones, and on the other hand
there are amongst the Dicotyledones many in which the venation of the
leaves is that most commonly observed in Monocotyledones, for example
Eryngium pandanifolium, E. agavaefolium, Plantago media, and others.
We find too, in one and the same plant, differences in the venation in
the different leaf-forms, and this is a point which is apt to be overlooked.
The hypsophylls, sepals, petals, and so on, when they diverge considerably
in form from the foliage-leaves, have a venation different from that of the
foliage-leaves, and this raises therefore the question :— What is the relation-
ship between conformation of leaf and course of the veins ?
The investigations which have hitherto been made on the subject of
venations, have dealt mainly with the relationships of the veins in the
matured leaf, when the original arrangement of the conducting bundles is
7, A, 3.
Fic. 218. Cephalotus follicularis. Development of the pitcher-leaves. The numbers show the succession. The
plcios formed bya growing out of the upper side of the leaf, whose lower margin becomes the lid d. After
ichler, but modified.
frequently no longer correctly recognizable, because branching, anastomosis,
formation of strong midrib, and so forth, conceal the primary arrangement.
Besides, such simple technical terms as ‘striate’ and ‘reticulate, give us no
information regarding the connexion between venation and growth of leaf
in a large cycle of affinity.
We shall deal first of all with this connexion, as it is seen in Monoco-
tyledones, for there it can be proved that the apparently great differences
which the venation exhibits, are all modifications of one ‘type,’ just as we
can refer the flowers of all Monocotyledones to one type.
VENATION OF MONOCOTYLEDONES. The typical venation of Mono-
cotyledones arises when a primordium of a leaf, attached by a broad base
to the stem, grows nearly uniformly in length and breadth in all its parts
(but at different times!). The conducting bundles which enter the leaf, and
out of which the median is formed, traverse its whole length nearly
uniformly from the base to the apex. The veins do not project, or only
slightly, upon the leaf-surface. This type occurs in the foliage-leaves of the
grasses, and amongst the Dicotyledones in the species of Eryngium, which
have leaves like Monocotyledones ; and it also occurs, but with some marked
deviations however, in many hypsophylls.
Z 2
340 VENATION AND DEVELOPMENT OF LEAF
When the upper portion of the primordium of the leaf spreads out by
erowth in diameter into a leaf-surface, it receives, from the not very different
leaf-stalk, veins with a more curved course, and we get but a slight modifi-
cation of the preceding venation. This happens in Eichhornia crassipes
(Fig. 219). In the stalk, that is the portion of the leaf-lamina which is
narrow, the conducting bundles retain their parallel arrangement, but in
the lamina they are strongly curved. A like arrangement is found in the
later primary leaves of Sagittaria and other plants.
A lamina constructed after this method cannot, without considerable
demand upon the building-material to make it firmer, or without special
arrangements, such as the folding which
has been mentioned in the case of Cur-
culigo! and other plants, attain any con-
siderable development of surface, and the
method is limited therefore to the rela-
tively small primary leaves of plants,
which produce adult leaves that are large
or are adapted to special purposes. An
instructive illustration of this is afforded
by the seedling-plants of Phoenix and
other palms mentioned above ? (Fig. 210).
In other Monocotyledones we find
that the enlargement of the leaf-surface
Roac siiticae eee ee is made possible ® by the formation of a
leaf. a, leaf-lamina; 4, leaf-base; c, zone out thick middle portion, on which the thin
of which the leaf-stalk'is developed later. 2,
upper part of an older leaf showing the course lateral parts are, as it were, suspended.
of the conducting bundles which are numbered
sh cereal 2a, HELGA) Gyno ol It is interesting to observe by what vary-
eae in the fully formed leaf. After ing gradations this comes about, until
the extreme is reached, in the species of
Musa, where there is a lamina many meters long, and a thick midrib. This
form is, however, only a terminal member of a series which we see begin-
ning in, for example, Funkia ovata (Fig. 220).
Funkia ovata. In this plant the leaf-lamina has nearly an oval outline
and is continued into a channelled leaf-stalk—the portion of the primordium
which has been only slightly widened, and which differs from the leaf-lamina,
in respect of the course of its vascular bundles, only to the slight extent of
having them arranged in one row. In the lower part of the leaf-lamina we
1 See p. 326. + TSEC. 927
* I use this expression intentionally. I do not base this upon the fact that we find large leaf-
surfaces, for instance, in the Aroideae, and that they have the ‘ venation’ about to be described, but
I say :—This venation makes fossible the acquisition of a more significant size of leaf, but we may
meet with it also in small leaves brought about there by the internal peculiarities of the family
which beget the Josszbility of development of larger leaf-surfaces.
VENATION OF MONOCOTYLEDONES 341
see already an indication of a ‘mid-vein, and at this point the bundles
appear to be clustered together, for they run at first parallel, and then bend
out into the leaf-surface which is thicker also at this position than it is
higher up and at the sides. Let us assume now that the vascular bundles
are originally all nearly parallel in the leaf-primordium, and that the growth
in surface of the leaf proceeds from above downwards, first of all nearly
uniformly and then chiefly at the margins because it is in the lower part
that the thicker middle portion is first
formed ; then the course of the bundles
in the upper part must be that which is
diagrammatically represented in Fig.
220, B. The first bundles laid down
have the ordinary course, and further
downwards in the leaf, progressively,
more bundles were present in the middle
FIG. 221. Xanthosoma belophyllum, one of the
Aroideae. A, leaf-stalk in transverse section the
_ Fic. 220. Funkia ovata. 4, primor- upper side turned downwards, and showing at 03
dium of leaf enclosing the vegetative point stronger ‘secondary growth in thickness’; zzz/,
and differentiated into leaf-base, sch ; leaf- under side with less marked secondary growth. JS,
lamina, sf; and the zone out of which the scheme of the course of the vascular bundles in the
leaf-stalk develops, sf. &, scheme of the leaf; they apparently diverge from the monocotylous
course of the veins in the adult leaf. The type. JZ, we ITT indicate successive bundles; 7, the
numbers J, //, Z//, 7V, V, VZ, indicate the youngest vascular bundles which bend out into the
succession. After Deinega. lower part of the leaf. After Deinega.
leaf-portion before the growth in breadth began which caused them to
bend out into the younger portion of the leaf. This appearance of a mid-vein?
at the leaf-base is related to the intercalary growth of the leaf and the
strong mechanical claims of the leaf-base, as in the case of the palms.
Xanthosoma belophyllum. Aroids show exactly the same relationship.
In Fig. 221 we have the scheme of Xanthosoma, and the only difference
from Funkia ovata is that there is a much stronger ‘ midrib’ traversed by
numerous bundles, and disappearing towards the apex. Here also the
oldest bundles, that is to say those which are most early differentiated,
? Which is, however, only the result of the clustering together of the ordinary veins.
342 VENATION AND DEVELOPMENT OF LEAF
reach the highest point in the leaf. The bundles bend out from the midrib
in the leaf-surface in correspondence with the fact that this grows out, if one
may so say, as a wing from each side of the thick middle portion. This
growth takes place, however, earlier above than de/ow, and the course of the
bundles conforms with this. The bundles are not disposed in one row in
the leaf-stalk as they are in the Monocotyledones in which lamina and stalk
are only relatively slightly differentiated from one another, but they are
distributed over the transverse section, and this may be explained by the
fact that the stalk has acquired more of a cylindric form in response to
greater mechanical claims, and exhibits a subsequent increase of growth in
the ground-tissue (Fig. 221, A). The arrangement of the bundles is also
different ; the younger ones, which on account of their origin are found in
the lateral portion of the leaf-sheath, bend upwards in the leaf-stalk, and
they it is which bend out in the lower portion of the leaf-surface. The
hypsophyll of the Aroideae, which corresponds to the vagina of a foliage-leaf,
has on the other hand the ordinary monocotylous venation, and there is
from the beginning, except at the tip, a uniformly distributed growth, as in
the case of grasses.
In this account of the venation in Monocotyledones, I have endeavoured
to show two things:
1. That morphologically, as well as in the distribution of its vascular
bundles, the leaf of Aroideae—and the same holds also for the Scitamineae,
Musacae, Cannacae!, and others—can be derived from a grass-leaf, and that
the vascular distribution has relation to the whole leaf-growth.
2. That the organization of the leaf—especially the appearance of a
midrib—stands in relation to the leaf-size.
VENATION OF DICOTYLEDONES. From what has been said it will be
gathered that there is no specific venation which can be called dicotylous,
but the distribution of the conducting bundles in the leaves of the Dicoty-
ledones also is determined by the relationships of growth. The following
will serve as illustrations :—
Acer platanoides. In the leaves of Acer platanoides (Fig. 212) the
divergent course of the veins is a consequence of the basipetal development
of the leaf, by which the single leaf-lobes are not produced one from another
but the leaf in all its parts is tolerably uniformly expanded. The middle
nerve arises first and then the veins for the two upper leaf-lobes, and so
forth. Finally the chief veins appear to radiate from one point ?.
1 Canna indica is very instructive. The large foliage-leaves have a mid-nerve, and whilst the
upper hypsophylls have no lamina the reduced small laminae of the lower hypsophylls show the
normal monocotylous venation such as is found only at the tops of the foliage-leaves. The con-
formation of the lamina in these hypsophylls is very varied; sometimes it is like that in Funkia
(Fig..220, 4), at other times it is that of the fully developed leaf of Canna.
* See the details in Deinega, Beitrage zur Kenntniss der Entwicklungsgeschichte des Blattes und
der Anlage der Gefassbiindel, in Flora, lxxxv (1898).
VENATION OF DICOTYLEDONES 343
Caltha palustris. We may compare with the case of Acer platanoides
that of the unsegmented leaf of Caltha palustris. The chief veins radiate
outwards here also from the base of the lamina (Fig. 222), and on the
margin of the lamina there are insignificant projections. These arise rela-
tively much later than the lobes in the leaves of Acer. The course of the
veins depends upon the fact that the lamina which comes off from the thick
leaf-stalk at a very early period develops, uniformly and without preference
for any definite direction of growth, into a surface with its margins inrolled.
In Fig. 246 the leaf is still entirely embryonal, only at the position which
corresponds to the base of the lamina intercellular spaces appear. Its con-
figuration, however, has in essentials
been reached. The veins appear
relatively late and radiate from the
leaf-base in correspondence with the
nearly uniform growth of the surface!.
Fic. 222. Caltha palustris. Leaf. One-half natural FiG. 223. Jussieuea salicifolia. Petal to the left.
size. Sepal to the right. Magnified 1}.
If an undivided leaf with ‘feather-venation’ had arisen from such a prim-
ordium, all that would have happened further would have been that the
primordium would have elongated ; the middle part would have developed
strongly ; the leaf-lamina would have appeared as a lateral outgrowth
on each side of this; and thus a middle nerve would have been formed
from which the lateral veins would have proceeded. Of course there are
here also all transitions between the forms of growth and the corresponding
distribution of the veins.
Asarum europaeum. In Asarum europaeum, whose leaf resembles
that of Caltha in all essentials, the elongation is not uniform, is more basi-
petal, and the middle nerve is stronger.
1 The margin remains longer meristic and produces then the leaf-teeth, and the apex of the leaf
appears in the process of elongation to precede the base. These details cannot, however, be
discussed here. It may be pointed out only that the mid-nerve develops somewhat more strongly
than the others and also precedes them somewhat in inception. A monocotylous venation does not
come about here on account of the early inception of a massive cylindric leaf-stalk (see Fig. 246,
to the left).
344 VENATION AND DEVELOPMENT OF LEAF
Jussieuea salicifolia. The relationships in the formation of the leaves
of the flower are very instructive. Fig. 223, for example, shows a petal of
Jussieuea salicifolia upon the left and a sepal to the right. The sepal has
monocotylous venation. From the first its base is broader and it is elon-
gated with uniform growth in surface. The petal arises as a much smaller
papilla, which then widens out in the direction indicated by the course of
the nerves.
Fraxinus excelsior. Fraxinus gives us an example of a pinnate leaf
(Fig.224). The pinnules are
laid down in acropetal suc-
cession, and there appears
in the broad base of the leaf-
primordium a large num-
ber of conducting bundles
(Fig. 224, C), which radiate
from one another in corre-
spondence with the growth
of the pinnules. As the
pinnules separate from one
another at a later period,
there is formed from a por-
tion of the upper leaf be-
tween each pair a stalk-like
leaf-spindle or rhachis, and
the original arrangement of
the bundles is lost. The
leaf-stalk here exhibits also
a growth in thickness, and
the bundles are arranged
nearly in a circle.
Fic. 224. Fraxinus excelsior. 4, tip of the shoot from the out- Amongst the Dicotyle-
side. Right and left of the apex the primordia of pinnate leaves dones there are also cases
already show the acropetal pinnules. &, bud in transverse section.
2, initial strand in base of young leaves; c, vascular bundle in mons Aa
basal part of leaf-stalk of next older leaf } c, vascular bundle in where the leaf-stalk is dis
upper part of leaf-stalk. C, young leafshowing the pinnules a, ¢, d@, : ‘ 5)
and the conducting bundles 7, UTIL Dd, echene of the course of tinguished from the lamina
Dae bundles in the adult leaf, lettering asin C. After only by its small size. It
arises then relatively late
and has the vascular bundles arranged in one row, as, for example, in
Plantago media, whose leaf-lamina has the primary veins arranged quite
like that of the ‘type’ of Monocotyledones.
ae;
ADAPTATIONS - OF THE LEAF 345
V
CONNEXION BETWEEN CONFIGURATION OF LEAF AND
RELATIONSHIPS OF LIFE. HETEROPHYLLY
Frequent reference has been made to the connexion between configura-
tion of leaves and the relationships of life, and a comprehensive treatment
of this subject is scarcely possible without a pretty full account of anatomical
structure, and this is beyond the scheme of this book. We know, too, in
many cases nothing at all about the meaning of the configuration of the
leaves, and I do not think that the configuration of the leaf is everywhere
to be regarded as a direct adaptation. It is quite clear in xerophilous
plants, in which so often there is reduction of the
leaf-surface, that when rolled leaves appear in the
most different families they have relation to the
external conditions. Similarly the divided leaf-
surface which occurs in submerged water-plants
of most different cycles of affinity, whether it
arise by branching, as is usual, or by the formation
of holes, as in Ouvirandra ’, has clearly a relation-
ship to the conditions of life, just as have the gills
in animals. The long drawn-out tips of the leaves
of many plants which grow in wet regions serve as
drip-tips*, and are therefore adapted to the rapid
drying of the leaf-surface. On the other hand, we
find that many forms of leaves appear through , 24° 273, Poppodinm wuleare
Svariation, and stand only in’ very-indirect rela- S8o%s™orecopiousbranching than
tionship *, and cannot at any rate be regarded as
direct adaptations, to environment*. The fern-leaved ‘varieties’ of beech
and other plants and the remarkable crested and other so-called ‘ mon-
strous ’ leaves in ferns are of this character (Fig. 225).
In these circumstances it will be more satisfactory in dealing with this
part of the subject if a few examples be described, drawn from plants in
which the configuration of the foliage-leaves is strikingly different at different
periods of their life.
* See Goebel, Pflanzenbiologische Schilderungen, ii (1893), Pp- 320.
# Jungner, Anpassungen der Pflanzen an das Klima in den Gegenden der regenreichen Kamerun-
gebirge, in Botanisches Centralblatt, xlvii (1891), p. 353; Stahl, Regenfall und Blattgestalt, in
Annales du Jardin botanique de Buitenzorg, xi (1893), p. 00.
* See Goebel, op. cit., ii (1893), p. 320, where I show that the Podostemaceae may under
like external conditions exhibit »anzfold relationships of configuration. See also Goebel, op. Git
i (1889), Introduction ; id., Uber Studium und Auffassung der Anpassungserscheinungen bei Pflanzen,
Akademie-Rede, Miinchen, 1898.
* See Part I, p. 185.
346 CONFIGURATION OF LEAF AND ENVIRONMENT
(3) PLERTD OPA YLAE
Where the configuration of the leaf is so simple, as it is in the Lyco-
podineae and Equisetaceae!', it is hardly to be expected that there will
be any or, at least, any considerable division of labour between the leaves.
Lycopodium. The difference in the conformation of the leaves in the
dorsiventral shoots of Lycopodium has been already explained *. Excep-
tional cases like the formation of hooks on the leaves of the chief shoots of
Lycopodium volubile are evidently modifications for the purpose of climbing.
Filicineae. The Filicineae, as is well known, show a marvellously
varied configuration in leaf. The great division of the leaf-lamina renders
it more resistant to the effect of wind and rain, an effect which can only be
overcome in an undivided leaf by greater strength of construction. The
Hymenophyllaceae are particularly instructive in this respect. One of the few
forms with /arge undivided leaves is Trichomanes reniforme, and it is pro-
vided with kidney-shaped leaves. It grows on tree-stems on the wet west
coast of New Zealand *. Its leaf-lamina is many-layered, in contrast with
the case of other Hymenophyllaceae, where the lamina is almost without
exception one-layered. A similar comparison may be instituted between
the construction of the leaves in Adiantum reniforme, where they are entire
and kidney-shaped, and those in other species of Adiantum, where they are
greatly divided and have delicate leaflets. These examples show that
external form and internal structure are most intimately connected.
Of this anatomical construction I can say but little here. The leaves
of most Filicineae have essentially the same structure as the leaves of other
land-plants, that is to say they possess an epidermis which is often very
little different from the tissue immediately below it; there are stomata
upon the epidermis ; the mesophyll is traversed by conducting bundles and
intercellular spaces, and the whole structure is such that the leaf is not able
to take up water in any quantity from the outside. But there are a number
of ferns which live in moist shady localities whose leaf-structure is simplified
in much the same way as we find it in the leaves of many water-plants ; they
have no stomata, and in the physiological sense no epidermis ; of intercel-
lular spaces there are none; the leaf-surface, apart from the veins, is
frequently one-layered, and the whole differentiation of tissue is quite like
that in one of the Musci. This modification appears in different groups of
the Filicineae and independently in each, a fact of so much interest that
a few examples will be given in illustration :—
* The leaves are here essentially protective organs, in hypogeous shoots also boring organs. The
concrescent sheath-like leaves of the fertile shoots are more strongly developed than those of the
sterile shoots because the bud of thé fertile shoot is more massive. See Goebel, Uber die Frucht-
sprosse der Equiseten, in Berichte der deutschen botanischen Gesellschaft, iv (1886), p. 184.
* See Part I, pp. 103 and 252.
* On rainless days the leaves are rolled up, and if the drought does not last long they expand
again when moistened and continue active life.
LEAF-ADAPTATIONS IN FILICINEAE 347
Asplenium obtusifolium. Asplenium obtusifolium, Linn.’, is a fern which
grows in moist shady localities. The leaves have no stomata and no intercellular
spaces, and can take water directly from outside. That we have here to deal with
a reduced form is evident, inasmuch as forms so nearly allied as to be regarded as
belonging to the same ‘ species’ have both stomata and intercellular spaces.
Todea. Amongst the Osmundaceae some species of the genus Todea—T.
pellucida, T. superba, and their allies which form the section Leptopteris, often
isolated as a special genus—have been long known by their thin translucent leaves
and their life in moist shady localities. ‘T. superba is, however, as I have satisfied
myself in New Zealand, much less sensitive than one would suppose to drought that
is not too prolonged.
Teratophyllum aculeatum, var. inermis, Mett. Amongst the Acrosticheae
Karsten *® has noticed some remarkable examples of analogous adaptation. Terato-
phyllum aculeatum, var. inermis, Mett., is a climbing fern with two kinds of leaves,
those which lie against the tree-stem and those which stand off from it. The latter
are the special assimilation-organs and have the ordinary structure of the leaves of
ferns. The former have an anatomical structure which recalls by its translucency
and colour the leaves of the Hymenophyllaceae, but they have upon their under
side stomata, they can be wetted, and they serve to retain water, and probably
also take up water. It is much to be wished that we knew the configuration of the
leaves of the germ-plant.
Hemitelia capensis. In this category we may place those remarkable forma-
tions upon the leaf-stalk of Hemitelia capensis, which were of old regarded as
Hymenophylleae*, and have in literature the senseless name of ‘adventitious
pinnules.’ Judging from their appearance and the anatomical structure of dried
material * they are merely formations of the basal pinnules of the leaf adapted to
the absorption of water. The plant grows in moist hollows in the vicinity of water-
falls; and as in the Hymenophyllaceae and in Dumortiera amongst Hepaticae, a
change has been brought about in the plant by the conditions of the locality, but it
is limited to a portion only of the leaf. The basal pinnules are finely divided, and
the lamina is much less developed than it is in the ‘normal’ leaf-pinnules and is
only unilateral along the veins. It is thin, probably wettable, and resembles the
leaves of Teratophyllum in having stomata only upon one side. The interceliular
spaces are very small.
Hymenophyllaceae. In the Hymenophyllaceae adaptations like those just
mentioned are very common. We know of no species of Hymenophyllum provided
1 See Giesenhagen, Uber hygrophile Farne, in Flora, Ixxvi (Erganzungsband zum Jahrgang 1892),
Pp. 157-
* Karsten, Morphologische und biologische Untersuchungen iiber einige Epiphytenformen der
Molukken, in Annales du Jardin botanique de Buitenzorg, xii (1895), p. 117. Christ, Die Farn-
krauter der Erde, p. 39, unites this fern with Acrostichum (Lomariopsis) sorbifolium, an identification
that appears to me very doubtful. I cannot discuss systematic questions here, and will only remark
further that Christ’s term ‘adventitious leaves,’ for water-absorbing leaves, is an impossible one, as
there are no adventitious leaves here.
3 In the Munich Herbarium some pinnules are named Trichomanes incisum, Th.; another had
the equally erroneous label ‘palearum Hemiteliae ripariae, R. Br., metamorphosis.’
* T unfortunately had no fresh material.
348 CONFIGURATION OF LEAF AND ENVIRONMENT
with stomata. In many of them—for instance Trichomanes brachypus whose leaves,
lying close upon the stem of the tree, give the impression of a gigantic richly
branched thallose liverwort, T. Hildebrandti, and others—the leaves are fastened
to the substratum by hair-roots evidently in order that they may retain the water
which runs down the stem.
Giesenhagen has shown that arrangements for holding water similar to those
found in some thallose Hepaticae are also known amongst the Filices.
Salvinia. Salvinia possesses leaves which are adapted to a life in water. Every
text-book explains that this plant has two kinds of leaves, float-leaves and water-
leaves, the former are simple, the latter, apparently branched in a tufted manner },
hang in the water and have no stomata. A peculiar divergent form of construction
is described for the float-leaves. Whilst the float-leaves of S. natans are in the
unfolded condition flat those of S. auriculata have a peculiar canoe-form (Fig.
226). This upfolding of the lamina protects the plant from too strong illumi-
nation, but it particularly
affords the leaf-surface pro-
tection against wetting, for it
bears many stalked tuftedly
branched hairs which do not
allow water-drops to reach
the leaf-surface, and even if
the leaf be submerged the air
between the hairs is held so
firmly that the water cannot
touch the leaf-surface. Other
Fic. 226. Salvinia auriculata. On the left: leat seen obliquely float leayesae meee Ce
per eROre On the right: leaf seen from point of insertion. Magni- wettable by the nature of their
surface and not by hairs.
Azolla. In Azolla there is only one kind of leaf. The leaves which stand upon
one leaf-axis have a similar construction, but there is a different construction in the
parts of one and the same leaf, and in this way biological relationships like those in
Salvinia are established. ‘The remarkable construction of the leaf of this floating
water-fern has been described, so far as I know, from the purely morphological
side only, not from that of its biological significance®. Each leaf consists of two
lobes, an upper and an under, and these both in structure and function are very
different. The upper and upwardly directed leaf-lobe serves as an assimilation-
organ, its morphologically lower side is directed upwards, and has an arrangement of
the tissue in correspondence thereto—there are palisade-like cells (Fig. 227, II, 0,, 0,)
and numerous papillae which contribute to making this side unwettable. Upon the
morphologically upper side, here turned downwards, of the upper lobe, there occur the
peculiar pits secreting mucilage* which are inhabited by one of the Nostocaceae,
* See for the history of development, Gliick, Die Sporophyllmetamorphose, in Flora, Ixxx (1895),
p- 368. 2 See Strasburger, Uber Azolla, Jena, 1873.
* I pointed out many years ago that these pits are organs for the secretion of mucilage. The
significance of the symbiosis with Anabaena can only be understood when the metabolism within
the Cyanophyceae is better known.
LEAF-ADAPTATIONS IN FILICINEAE 349
and which are the feature in the leaf of Azolla that commonly attracts notice. The
under lobe is constructed in an altogether different way (Fig. 227,II,z,,,). It consists
throughout its greater part of owe cell-layer, only a middle portion lying somewhat
towards the top is many-layered. In this many-layered area some chlorenchyma and
stomata are present upon the upper side, and it is evidently the position which, as the
transverse section shows, is least covered by the upper lobe and receives the most light.
What is the meaning of this remarkable leaf-structure? It is clear that the juvenile
portions are aptly protected in this infolding, formation of lobes, and covering, and
investigation shows that the lower leaf-lobe is wettable on its outer side and takes
up water’. If one lays root-
less portions upon the surface
of a weak solution of methyl-
blue, the cell-contents soon
become partly coloured blue.
The uptake of water occurs
not only through the roots
but also through the lower
lobe of the leaf, which there-
fore has the double function
of protection of the bud and
uptake of water, besides that
of assimilation which seems
to me to be only secondary. FIG. 227. Azolla filiculoides. I, habit of a shoot, seen from above.
The upper lobe, rich in chlo- The pits inhabited by Anabaena are indicated by circles of dots. II,
bud in transverse section. 0; 741, 02 tt, 03 U3, 04 u#4 are respectively
i the upper and under lobes of four leaves. The shading lines on 9; and
rophyll, is on the other hand 02 indicate the palisade-parenchyma. Magnified.
essentially an assimilation-
organ, and as it nowhere comes in contact with the water, stomata are formed on
both sides, instead of on the upper side only as in float-leaves generally, whilst its
oblique position protects it, as is the case in Salvinia auriculata, against too strong
insolation. Further, the leaves of Azolla by theif peculiar configuration and posi-
tion form many air-spaces between their lobes, and these are of service not merely
in the gas-exchange of the plant but also in enabling the plant to float. Azolla is
thus an instructive plant because it shows how the formation of the leaf is influenced
by its “e—it has palisade-parenchyma upon the under side, and a different con-
struction of the upper and under lobes—and also how the conformation of the leaf
is bound up with the manner of life.
Epiphytic Filices. Remarkable heterophylly also is found in many
epiphytic ferns”, and this was formerly confounded with the differences in
configuration of sterile and fertile leaves which occur in many ferns :—
Polypodium (section Drynaria). In Polypodium quercifolium, P. propin-
1 This is also the case in a land-plant, Pinguicula.
2 See Goebel, Morphologische und biologische Studien: I. Uber epiphytische Farne und
Muscineen, in Annales du Jardin botanique de Buitenzorg, vii (1888), p. 1; id., Pflanzenbiologische
Schilderungen, i (1889), p. 216.
a
350 CONFIGURATION OF LEAF AND ENVIRONMENT
quuin, and other species of the section Drynaria, there are stalked pinnate foliage-
leaves which serve as assimilation-organs and also bear the sporangia ; but besides
there are unstalked west#/eaves, possessing broad heart-like bases which soon lose
their chlorenchyma, and being provided with thick ribs act as accumulators of
humus which the fern then uses as a ‘soil.’ Both leaf-forms appear in regular
alternation, at least in the cultivated examples which I have observed for many
years ; they are not mixed up irregularly one with the other. The formation of the
leaves as it is described in the germ-plants, as well as a comparison with allied
forms, for example P. Heracleum, make it probable that the species which have
nest-leaves have been derived from those possessing at first stalked-leaves, all of
which were assimilation-organs only ; then, a shortening of the stalk and a broaden-
ing of the base of the lamina having taken place, only one kind of foliage-leaf with
broad base was produced, serving both for assimilation and for the accumulation of .
humus; following this a division of labour occurred, and one leaf lost almost
entirely the function of assimilation, whilst another became constructed as an
assimilation-organ alone.
Platycerium. Like features are to be found in the genus Platycerium?. This
fern has two kinds of leaves: one is that of the maztle-leaf, wholly spread out close
upon the substratum, or with its posterior part erect, and thus able to act as a nest-
leaf; the other is that of the ordinary foliage-leaf. The mantle-leaves form layers
closely placed one above the other, and as they die their humus is taken up by the
roots. The erect portion collects humus just like the nest-leaves of the species of
Polypodium mentioned above. The relationship between size and organization
appears in these ferns very markedly ; only by the construction of a special adapta-
tion are they able to reach the giant size often attained by Piatycerium grande and
P. biforme, and which makes them amongst the most bizarre constructions in the
plant kingdom.
KATAPHYLLS IN PTERIDOPHYTA. The formation of kataphylls will
be treated of in a special section, but I may mention here their occurrence
in the Pteridophyta. They are known in only a few species of Filices, for
instance in Onoclea Struthiopteris and some species of Osmunda, O. regalis
and O. cinnamomea. In Cystopteris bulbifera they occur as storage-organs
on the bulb-like leaf-borne ‘adventitious shoots”. They arise in this way :
the leaf-lamina at a relatively late stage of development—a stage quite
visible to the naked eye—becomes arrested, whilst the leaf-base acts as
a protection to the bud. In O. Struthiopteris, moreover, there are transi-
tions also from the foliage-leaves to the kataphylls, they are leaves with
a reduced lamina. The following remark of Stenzel* upon the kataphylls
of O. Struthiopteris illustrates well the earlier dominant idealistic morpho-
1 See Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 224.
* Also in the first leaves of the adventitious buds which arise upon the fleshy s¢zpzles of the
Marattiaceae the lamina is usually arrested.
* Stenzel, Untersuchungen iiber Bau und Wachsthum der Farne, in Nova Acta der Kaiserl. Leop.-
Carol. Akademie der Naturforscher, xxviii (1861).
EI
AMETEROPHYEEY IN: DICOTYLEDONES 351
logy which is even now not without influence. ‘ Their apex bears a circi-
nate leaf-lamina which, although it is very reduced, prevents me from
recognizing them as kataphylls.’ This remark shows very clearly how the
genetic relationship of the foliage-leaves to the kataphylls ' was ignored in
idealistic morphology. Characteristic kataphylls are found in the species of
Isoetes which grow upon land and whose stem during the resting period is
covered by a sheath of hard brown scales. These are the basal portions of
leaves whose arrested lamina is still visible as a small point.
(2) SPERMOPHYTA.
We leave out of consideration for the moment the cotyledons, hypso-
phylls, and kataphylls, although we shall see that there is no sharp limit
between them and the foliage-leaves, and we shall pass over also the primary
leaves, which have been already treated of, and only deal with a few examples
which may show how the appearance of different forms of leaf in one and
the same plant can be explained from the biological standpoint.
(a) LAND-PLANTS.
Campanula rotundifolia and other Campanulaceae. It has been already
shown” that these plants possess two leaf-forms which are connected with one
another by transitions. On the basal part of the plant there occur stalked leaves
with roundish reniform laminae, the so-called rownd leaves (Fig. 121, Part I). Further
up there are leaves which are either unstalked or shortly stalked, and have long
narrower leaf-laminae. These are the /oxg /eaves. The absence of the stalk in the
long leaves can be so far explained by the position of these leaves upon an elongated
shoot-axis, which rises up over the adjacent parts. The narrowing of the leaf-
laminae may make them more resistant to mechanical injuries in their more exposed
position. The round leaves also, as has been shown, are ‘attuned’ to a less light-
intensity than are the long leaves, and this may also explain why such species of
Campanula as C-. latifolia, C. Trachelium, and others, which grow in stations of
a different degree of shadiness, for instance in shrubberies, on the margin of woods,
have no long leaves in their upper part, but leaves which are distinguished from the
lower ones only by the absence of leaf-stalk and their smaller size. In such
localities the leaves are also more protected against wind and rain than they are in
the open. On the other hand we find in species of Edraianthus, for example
E. Pumilio, which grows on sunny rocks, alike in the upper and in the basal part,
leaves which correspond oy with the long leaves of C. rotundifolia.
Scabiosa Columbaria and allies. We have a similar relationship in many
Dipsaceae. In Scabiosa Columbaria there is a striking difference between the
lower and the upper leaves (Fig. 228). The lower are stalked and have a simple
leaf-lamina with toothed margin. As we pass upwards the stalk disappears and the
leaf becomes pinnatipartite, at first at its base and then later above, and in the
Eesee Part I, p: 7. 2 See Part I, p. 242.
352 CONFIGURATION OF LEAF AND ENVIRONMENT
upper leaves branches are formed upon each lobe. The plant grows in sunny
stations and the basal ieaves are more fitted to contend with the environment? as
entire leaves than as divided ones, whilst divided leaves on the other hand, by their
division, are better able to withstand wind and rain”. Putting aside this teleological
explanation it would appear that these undivided leaves are ‘ attuned’ to a smaller
light-intensity than are the divided ones, just as are the round leaves of Campanula
rotundifolia. At least I have found that plants growing in shady places produce
more undivided leaves than do plants in the sun, and Knautia sylvatica which
naturally grows in the shade, has all its leaves, in the neighbourhood of Munich,
undivided. Knautia arvensis has pinnatifid leaves, but there is a ‘ variety ’—integri-
folia—in which the leaves are not pinnatifid, and I conjecture that the variety is
merely a shade-form. Culture
experiments are indeed neces-
sary for the solution of this
question, but that in plants
which first of all bring forth
undivided leaves, and then later
leaves which are more or less
divided, we can finder the
formation of the less divided
leaves by external conditions
is shown by the behaviour of
many arctic plants. Regard-
ing them Pansch ® says, ‘Some
Fic. 228. Scabiosa Columbaria. Leaves, in the succession I, II,
Pe eo SOM ares from different regions of the shoot. One plants, which in the temperate
zone possess mostly divided or
cut leaves, for example Saxifraga caespitosa, Linn., and Taraxacum, produce in the
far north chiefly simple leaves.’ This, however, does not enable us to decide how
far the difference is the result of drec¢t influence of external factors. That the
segmentation of the leaf in Taraxacum is much richer in well-nourished examples
can be easily established by the comparison of the starved form of our meadow-
moors—the Taraxacum palustre, DC.—with the well-nourished examples of our
glens; and it is likewise known that in Symphoricarpus racemosus segmented
leaves appear upon the luxuriant water-shoots whilst they are undivided commonly.
A direct connexion of the segmentation of the leaf with the external conditions of
life is not perceptible.
Cases which are the converse of those which have just been described in
which then the differentiation of the foliage-leaves in course of development
? Which suppresses them through withdrawal of light like the leaves pressed to the ground of
Plantago media.
? See Stahl, Regenfall und Blattgestalt, in Annales du Jardin botanique de Buitenzorg, xi (1893),
p: 168.
’ Pansch, Klima und Pflanzenleben in Ostgrénland, in Zweite deutsche Nordpolfahrt, Botanik,
p- 18. See also what is said about nanism in Part I, p. 259.
/
PHYLLODIA 353
may become simpler than it was at the beginning, are met with especially
in many plants with xerophilous adaptations !.
SCALE-LIKE LEAVES. So far as morphology is concerned I may
mention here, because of the analogy they show with many kataphylls, that
the scale-like leaves of the chief axis, for instance, of Veronica lycopodioides
(Fig. 106, Part I), correspond to the /eaf-base of the more highly segmented
leaves which appear in ger-
mination, and occasionallyalso
later as reversions. The la-
mina is only indicated by a
short point. In this category
we may also include—
PHYLLODIA. Here there
is an alternation of function
between the parts of ove leaf-
primordium. The leaf-stalk,
in many cases also the leaf-
spindle or rhachis, is con-
structed as an assimilation-
organ, whilst the leaf-lamina
is more or less reduced. The
expression phyllodium has
been frequently used, in an
indefinite and wrong manner,
for leaves which diverge from
the forms in their alliance by
being simple and unsegment-
ed ; for example, for the leaves
of the species of Eryngium
which are like Monocotyle-
dones, the leaves of Ranun-
culus Lingua and R. Flam-
mula, and the riband-like FIG. 229. Rubus australis var. cissoides. Seedlingplant. The
primary este oes Sagittaria, foliage-leaves have well-developed laminae. A. 1}
and ‘the leaves of some species of Lathyrus*. As we have learnt from the
account of the history of development of the leaf above given, the notion
of phyllodium involves that az arrested primordium of a lamina is present,
although the arrest may take place at a very early period. But in those
cases where the term phyllodium has been wrongly used, a leaf-stalk has
not generally been laid down, and we must keep the two cases entirely
separate, as they have nothing whatever to do with one another.
See what is said regarding juvenile stages, Part I, p. 165. 2 See Part I, p. 162.
GOEBEL II Aa
354 CONFIGURATION OF LEAF AND ENVIRONMENT
The arrest of the leaf-lamina may take place at various ages, and there
are therefore transitions between phyllodia and foliage-leaves.
Rubus australis. The first example to be quoted is of a plant whose
leaf-stalk serves as an assimilation-organ, but without suffering any striking
change in its outer conformation, whilst the size of the lamina is reduced.
It is Rubus australis. This plant occurs in different forms, which are par-
ticularly marked by the different degree of develop-
ment of the leaf-surface. The plant depicted in Fig.
230 has branched leaves with very small lamina, and
the long stalks of the leaflets serve as assimilation-
organs. The seedling (Fig. 229), on the other
hand, bears leaves with well-developed lamina.
We can hardly speak here of phyllodia because
Fic. 231. Oxalis
ruscifolia. Two leaves.
That to the right has
a well-developed ter-
natelamina. That to
the left shows only the
three points from
which the leaflets,
|
|
Fic. 230. Rubus australis var. cissoides. Portion of an older leaf. which were early ar-
Laminae of the leaflets reduced. The stalk serves as an assimilating and rested, have fallen off.
scrambling-organ. After A. Mann. Natural size.
the leaf-stalk has not the flattened form which is characteristic of most
leaves. Such a limit is, however, scarcely to be drawn, as we know of
cylindric leaves.
Viminaria denudata. Viminaria denudata, one of the Leguminosae,
behaves like Rubus australis. The phyllodia are cylindric, and whilst no
apparent leaf-lamina is present, yet in a careful investigation of the history
of development it could easily be shown. On seedling-plants it is regularly
present.
Oxalis ruscifolia. Fortuitous formation of the leaf-lamina, at least in
the plants cultivated in greenhouses, appears in Oxalis ruscifolia (Fig. 231).
Here the leaves have a leaf-stalk which is broadened out like a lamina.
The leaf-lamina consists of three delicate leaflets, and is in many leaves
fully developed and falls away later, whilst in others it never unfolds. We
_—
PHYLLODIA 355
have then here from the beginning a typical phyllode with arrested lamina.
The event would be quite the same if it took place at a still earlier period’,
at a stage when the primordia of the three leaflets of the lamina are visible as
small rudiments, or at a stage when the leaf-lamina is still undifferentiated.
When speaking of leaf-tendrils hereafter we shall see what a stumbling-block
the notion of a ‘transition’ has always been to many authors. Such cases
as that above explained are therefore worthy of mention here.
Parkinsonia aculeata. Parkinsonia aculeata behaves in a similar
manner in so far as the leaf-spindle is here widened, and the leaflets sitting
upon it fall away later.
Before discussing other examples it must be mentioned that in the
formation of phyllodes
we have always an
adaptation against loss
through intense tran-
spiration. We may as-
sume that in the cases
which have been de-
scribed, the tissue of the
leaf-lamina was not in
a condition in which it
could change in response
to the requirements of
the environment, whilst €.
the leaf-stalk, which
arises as we know at a FIG. 232. Acacia ae ee B, C, stages in the development of a
: : phyllode. 7,the laminar primordium in process of arrest ; #, the leaf-base
later period inthe course Hevelopineraes the eames Beside ak leaf one of its two stipules is
of the development, Hen EEE Magnified. After A. Mann.
mains more plastic. That we must regard the outer conditions asa stimulus
only, which brings about a varying reaction according to the peculiarity of
the individual species, does not require any further exposition ?.
Acacia. The best known examples of the formation of phyllodes are
to be found in a number of Australian species of Acacia. It is usually said
that in the phyllode of Acacia the lamina is entirely wanting*. This
is incorrect, for the lamina can always be seen upon the primordium ‘.
* The behaviour of the Australian species of Cassia is instructive. Cassia eremophila has a leaf-
stalk expanded vertically, but which bears pinnules in pinnate fashion; in C. phyllodina those
pinnules are suppressed. 3 See Part I, p. 217.
* Hildebrand, Uber die Jugendzustinde solcher Pflanzen, welche im Alter vom vegetativen
Character ihrer Verwandten abweichen, in Flora, lviii (1875), p. 322; Frank, Lehrbuch der Botanik,
ii. p. 260.
* See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884), p. 241. A. Mann, Was bedeutet ‘Metamorphose’ in der Botanik? Inaug.
Dissertation, Miinchen, 1894.
Aa2
356 CONFIGURATION OF LEAF AND ENVIRONMENT
The lamina is relatively large in Acacia calamifolia (Fig. 232,7), and the
whole history of development of the phyllode conforms throughout to
the normal development of a leaf, only the lamina soon becomes stationary
and arrested, the leaf-stalk develops into the phyllode. A study of the
history of germination leads to the same result (Fig. 102, Part I). The
lamina is visible in Fig. 233 representing a shoot of Acacia alata.
In some species of Acacia, for example A. floribunda, A. melanoxylon,
and A. uncinata, there are transition-forms which show that the rhachis may
have a share in the formation of the phyllode. .
The configuration of the phyllodes varies greatly in the genus Acacia !.
We may consider as ‘typical’ the phyllode which is
developed in a vertical direction and has a leathery
texture, but the phyllodes may be needle-like, as in
A. juniperina and A. verticillata, or cylindric and
stalk-like, as in A. teretifolia, A. juncifolia, A. scirpi-
folia, and others. We do not know what is the
relation between the configuration of the phyllode
and the habitat in individual cases, and we must
therefore, in framing an explanation of the forms,
draw upon the whole behaviour of the plants. It is
clear that, in one and the same place, a plant which
possesses a deep widely spread root-system requires
the formation of its leaves to be less adapted to the
lessening of transpiration than does one in which the
root-formation is less developed’. It is also scarcely
open to doubt that the profile position of the leaves
Fic. 233. Acacia alata. which is so common in Australian plants, and which
Apex of shoot winged by phyl- ? 2
lodes.. Beside each phyllode js also observed in the formation of phyllodes, is an
feat ts seen 2 the acres arrangement for the lessening of transpiration. The
degree to which this control is developed varies
greatly in the different species of Acacia which have phyliodes. Many
have their phyllodes constructed as relatively thin plates of tissue of
considerable size, resembling in their configuration very markedly the
leaves of many species of Eucalyptus, and these will naturally transpire
more than the forms with small needle-like phyllodes. Of species possess-
ing such needle-like forms A. verticillata (Fig. 245) is worthy of mention
? See Reinke, Untersuchungen iiber die Assimilationsorgane der Leguminoseen: VI. Mimosaceen,
in Pringsheim’s Jahrbiicher, xxx (1897), p. 563.
* The relationships of the root-system to the epigeous part, especially to the leaf-formation, is
generally little regarded. These relationships are evidently different in the seedling and in the
adult ; and that in good soil many thorny plants do not have their twigs developing into thorns is
essentially connected with the development of the root-system. The effect of the relationship
must be more marked in bad soil than in good soil, and must be specially influenced by the water-
supply.
LEAF-ADAPTATIONS IN MARSH AND AQUATIC PLANTS — 357
because in it we find a division of labour amongst the leaves. Only a few
of its phyllodes have axillary shoots, and it is such phyllodes only which
commonly are provided with stipules’ and they precede the others in
development. This has given rise to the zzcorrect hypothesis that the
phenomena here are similar to those observable in the Stellatae, that is to
say, that the phyllodes which have no stipules and no axillary shoots are not
independent leaves, but the stipules of the others.
In some species of Acacia we find an alternation between the formation
of phyllodes and of foliage-leaves, even after the plant has long passed the
seedling state. This happens in A. heterophylla, A. melanoxylon, and
others. We have here possibly a case like that which has been described
above in Hakea trifurcata*, and which is also known elsewhere, namely,
that the severa] shoots which develop periodically repeat the alternation of
the configuration of the leaf which is found in the seedling, and that at the
beginning of the vegetative period, when water is abundant, the juvenile form
of leaf is formed, and then later the formation of phyllodes sets in. In
plants grown in the botanic garden such a periodicity is unrecognizable,
but then such plants are not under natural conditions. It is easy to see
that the formation of phyllodes is no longer under the direct influence
of outer conditions, for seedling-plants of Acacia which I examined formed
phyllodes even though they were cultivated in a very moist chamber. On
the other hand it has happened? in young plants of A. verticillata, which
had reached the stage of the formation of phyllodes, that when they were
retained for a very long time in a very dry chamber and were thus ‘en-
feebled,’ the formation of phyllodes was again called forth by cultivation in
a moist chamber. All these phenomena will find their explanation if we
remember the important fact of development, that the primordium of the
lamina is always present in the phyllode, although in most cases its capacity
for development is limited only to the seedling-plant.
(6) MARSH AND AQUATIC PLANTS.
Differences in the leaf-forms are frequently met with in plants in which
the vegetative organs are placed partly under, partly above the surface of
the water. We shall pass over the differences in anatomical structure and
consider only the differences of form*. There are two groups of phenomena
to be noticed here.
MONOCOTYLEDONES. In monocotylous aquatic and marsh plants the
submerged leaves are essentially more simple than are those above the
water. The submerged leaves have frequently a riband-form, the aerial
leaves have frequently a segmentation into lamina, stalk, and sheath. That
? Other species occasionally have stipules.
2 See p. 294. 3 See Part I, p. 172.
* See Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 217, for details.
358 CONFIGURATION OF LEAF AND ENVIRONMENT
this latter conformation will be more advantageous in enabling the leaves to
rise above the water or to float upon its surface requires no demonstration,
and it is also clear that leaves living submerged in water do not require seg-
mentation into stalk and lamina!.
DICOTYLEDONES. A second kind of heterophylly, which resembles
that in Salvinia mentioned above, is found in a number of dicotylous plants
which possess leaves appearing above the water-surface and leaves re-
maining submerged. The leaves appearing above the water-surface have
either entire margins, for instance the float-leaves of Cabomba, or have
a surface which is only slightly divided at the margin as in Ranunculus
aquatilis, Bidens Beckii, and Limnophila heterophylla*. The submerged
leaves, on the other hand, are divided into numerous filaments, so that they
expose a relatively large surface to the water out of which they take the
material for their food. The biological utility of the difference in the form
of leaf is also clear, although as has been already stated*, there are but
few cases where a direct influence of the water-life upon the leaf-form can be
established.
Limnophila heterophylla. I had expected to find an illustration of this
influence in Limnophila heterophylla* because in this plant all transitions may
be readily observed from the much cut apparently verticillate water-leaves to the
undivided leaves which stand upon the shoot above the surface of the water. The
observations which I was able to make on living plants*® showed, however, that no
such direct influence occurs. The seedling produces divided leaves whether germina-
tion takes place in water or upon the land, although in water the leaves are
more elongated and show a different anatomical structure. Cuttings also from
the upper portion of the plant, where the leaves are undivided, if cultivated as
/and-plants, produce not only side shoots with divided leaves, but themselves grow
partly at the tip into shoots producing this form of leaf.
Cabomba. ‘The relationships in Cabomba where the water-leaves are divided
are similar. The simple peltate float-leaves are only produced at the flowering
period. Although it is natural to assume that the form of the water-leaves is the
result of a direct adaptation, there is no proof of it up to the present.
Ranunculus multifidus. Ranunculus multifidus which is a form only slightly
adapted to life in water °, shows when growing in the water a much richer branching
of the leaf-lamina (Fig. 128, Part I), and it is very probable that a similar direct
influence took place originally in other similar leaves, although it cannot now be
proved.
‘ See also Part I, p. 165.
? In Bidens Beckii and Limnophila heterophylla there are no float-leaves.
* See Part I, p. 260. * See p. 333-
* Plants I brought from Ceylon grew easily and luxuriantly under cultivation.
® See Goebel, Pilanzenbiologische Schilderungen, ii (1893), p. 313.
ORIGIN AND FUNCTION OF STIPULES 359
VI
STIPULES; LIGULES STIRELS
1. ORIGIN AND FUNCTION OF THE STIPULES.
The expression stipule was made use of by the older authors in no
very sharply limited sense. They understood by it any small leaves or
leaf-parts, as for example hypsophylls, or prophylls, or the intravaginal
squamules in the axil of
the leaf-base of many
water-plants!. As stipules,
however, we can only de-
signate appendages of the
leaf-base, which spring
right and left from the leaf-
base, as do the pinnules
and leaf-teeth from the
upper part of the primor-
dium of the leaf. Phe-
nomena of growth appear
later, and in many cases
conceal the original fea-
tures.
In the simplest case
the leaf-base continues to
elongate after the laying
down of the stipules and
raises the stipules some- FIG. 234. Cobaea scandens. Portion of a shoot seen obliquely from
the side. The lowermost pair of pinnules of the leaf that is shown cut
what. These are then off to the left have each an auricled base, and these cover the axillary
bud.
‘adnate stipules.’ Fre-
quently more far-reaching changes ensue which, however, as will be
shown, can be elucidated by a comparison with allied forms and by the
history of the development—take, for example, the axillary stipule of
Ficus and other plants. The recognition of this frequently led also to
the derivation of other outgrowths of the leaf-base from the formation of
free stipules. Free stipules were taken as the ‘type’ because they occur
in a number of plants and suffer definite modifications, and to it even
structures, like the ligule of grasses, were referred by the assumption of
1 See Caspary, Die Hydrilleen (Anacharideen, Endl.), in Pringsheim’s Jahrbiicher, i (1858),
p- 394. The intravaginal squamules are organs which secrete mucilage for the protection of the
bud, as I showed, and as was confirmed by Schilling, Anatomisch-biologische Untersuchungen tuber
die Schleimbildung der Wasserpflanzen, in Flora, Ixxviii (1894), p. 280.
360 SITPULES, LIGUEES, Siiiees
a ‘concrescence’ or other change. This retracing assumption, which up to
the most recent times has been dominant, I hold and shall endeavour
in what follows to show is altogether an incorrect generalization. Out-
growths of the leaf-base, even of the leaf-surface—in the form of the ligule
of Selaginella and Isoetes which secretes slime, as well as of stipels or of
transformations of the basal parts of the leaf-lamina—are developed in
different families ‘for the purpose’ of protecting the bud. That this fre-
quently takes place to the right and left of the leaf-base is easily under-
standable because here the
axillary bud is chiefly exposed.
I must, in the first instance,
bring forward a few examples
about which there has been
some doubt as to whether they
are really stipules, or only
the lowermost leaf-pinnules.
Cobaea scandens. In
Cobaea scandens the lower-
most pinnules of the foliage-
leaf have a different configu-
ration from the others (Figs.
234, 235). Whilst the upper
pinnules, as is usual, are
asymmetric with their basi-
scopic half the larger, in the
lowermost leaf-pair the acro-
scopic half, that is to say the
side turned away from the
FG. 235. Cobaeascandens. Leat seen rom above. A por- shoot-axis, is the broader, and
ton only ofthe tcominal ail shows. | Each Pnanle ot) a shea eae et a
ear-like excrescence. Careful
examination shows that the axillary bud is formed beneath the ‘auricles’ of
the lowermost pinnules which form a roof over it and so protect it against
rain and sun. The position here is quite different from the usual one that is
found when the stipules protect a bud, because commonly the stipules have
their upper side turned to the bud, whilst these lowermost pinnules of Cobaea
turn their wzder side towards it. In the light of these observations we can,
however, readily understand what is the teleological meaning of this divergent
configuration of the pinnules. It is possible that something else has to be
considered, but one can scarcely ascribe a special significance to the circum-
stance that raindrops can collect in the narrow depression formed by the
1 See Part I, p. 122.
ORIGIN’ AND: FUNCTION: OF STIPULES 361
lowermost pinnules, although of course one may suppose that this might
also prevent the access of ‘unbidden guests’ to the flowers. The case
shows us at any rate how leaf-pinnules can be transformed into protective
organs resembling stipules, and one might conjecture that elsewhere—but
not everywhere !—stipules have taken origin in a similar way.
Guilandina. A striking example of the employment of the lower
pinnules as stipules is supplied by a species of Guilandina from Ceram,
which is cultivated in the garden at Buitenzorg (Fig. 236). The leaf is
bipinnate ; the lowermost pinnules have a peculiar form and are developed
to serve as_ stipules.
Possibly we have the
same thing in other
Leguminosae.
Lotus cornicula-
tus. The leaves, again,
of Lotus corniculatus
are ternate and have
two persistent stipules,
but below these there
is found on each side
a small tooth which
by many is considered
the proper stipule. If
this is right, which can
only be determined by
comparative investigation, the lowermost pinnules here are developed in
the place of the arrested stipules, and have taken on quite a stipular form.
Tetragonolobus siliquosus. In this plant we have the same features
as in Lotus corniculatus.
AURICLES. It is not possible in many cases to separate sharply the
pinnules from the stipules, and we find in many plants outgrowths at the
base of the leaf-lamina which are described as auricles, and these have
grown out into stipular formations. One example of this will suffice.
Adenostyles albifrons. The leaves on the under portion of the stem of
Adenostyles albifrons have a sheath-like leaf-base (Fig. 237, 7). This appears
in the leaves which stand higher up as two lobe-like expansions, and these,
in the stage represented in Fig. 237, ///, have become quite stipule-like
structures. The only reason why they are not called stipules is that they
are not present on the lower leaves; but we can easily find a biological
reason for this. The lower leaves have only the stem-bud to protect, whilst
the upper leaves have to protect the massive primordium of the inflores-
cence, and the wing-like expansion of the leaf-base, which has led to the
formation of the stipules, corresponds to this duty.
Fic. 236. Guilandina sp.(Ceram). Stipules.
362 SIIPULES, (LIGUER Syst leita)
In most of the other plants which have got stipules these have arisen
in much the same way only they are present in all leaves. In many cases,
however, their origin has been different.
Viburnum. Lubbock! has in connexion with this pointed out that
in the genus Viburnum only V. Opulus possesses stipules, and he supposes
that these ‘stipules’ are so placed in the intervals between the leaf-bases
that they protect the stem-bud. It must be noted, however, that the
stipules here bear almost always glands at their apex, and further that
they appear often in pairs at the base of a leaf (Fig. 238). Now
below the lamina there appear a number of disk-like glands—which are
much sought after by ants, and their secretion may also take a share
in the protection of the bud, a point to which Lubbock gives too little
Fic. 237. Adenostyles albifrons. Appearance of the leaf-sheath. Z a lower leaf; 7/7 and ///, from higher up
the shoot.
attention—and there are transitions between these sessile glands and
the stipules. These ‘stipules, then, are nothing more than stalked leaf-
glands ; on account of their position they may be named ‘stipules ’ because,
as I have endeavoured to show above, stipules have no uniformity in origin.
In deciding, then, the question what parts that occur at the base
1 Lubbock, On Buds and Stipules, London, 1899.
* Impatiens glandulosa behaves in a like manner. The lower teeth of the leaves are transformed
into glands. Such stalked glands are found also in pairs or in greater number upon the expansion
which unites the bases of the opposite leaves. One may regard them as ‘stipules.’ Sambucus
nigra also shows on strong shoots formations corresponding to those of Viburnum Opulus. Between
its two opposite pinnate leaves there occur two or three nearly cylindric or somewhat flattened
‘ stipules,’ bearing at their apex a gland. Similar structures are found also singly at the base of
each of the leaves of the lowermost two pairs of pinnules, and they are often constructed like leaves,
and indeed considered as lateral leaflets of the second degree. They often, however, are not
developed. In many plants the capacity for a higher leaf-development remains latent. The lower-
most pinnules of the potato, for example, also show frequently an indication of the formation of
pinnules of the second order, and in very strong examples these may be fully developed.
FUNCTION JOE, STIPULES 363
of a leaf are to be considered as stipules, fuction must be taken into
consideration. That this function, in the first place, is that of protecting
the bud has been already stated, and it is performed in two ways :—
(a) Some stipules protect the lamina of the leaf upon which they
spring, along with the portion of the shoot which lies above it, for example
in Cunonia capensis, Castanea vesca, Amicia Zygomeris, and others ;
(4) Other stipules protect the next higher leaves, for example in species
of Cinchona, Magnolia, Ficus, Liriodendron, and others.
PROTECTIVE FUNCTION OF STIPULES. Frequently the work of pro-
tection is the only function of stipules. In trees with marked periodic
development as, for example, Quercus and Fagus, the stipules fall after
the unfolding of the winter-bud. They are caducous. In the buds of
these plants the lamina of the outermost leaves is arrested at an early
period, and then the stip-
ules alone discharge the
function of protection ;
in the inner leaves, how-
ever, the primordium of
the foliage-leaf attains its
normal size. An arrest
of the lamina on the
leaves whose _ stipules
serve as protective organs
during the resting period
is exhibited in very un-
equal degree, as other
plants show. Sometimes
the arrest is early, some-
times itislate. In Lirio-
dendron tulipifera at the
end of the vegetative Fic. 238. Viburnum Opulus. Portion of a shoot. Two pairs of
B geseeeoutemnesiles® tee dctanna Magtatz | Pr Sands om thepetioles
is already laid down in a
complete condition with lamina, stalk, and two stipules, but only the stipules
remain as bud-scales, the lamina and stalk—the leaf itself—are arrested and
fall away ; on the next leaf also, which will be the first to unfold in the
spring, the stipules alone develop further. In this case the primordium of
the leaf becomes arrested only at a late stage of development, yet the process
is fundamentally the same as that which is found in Quercus and Fagus
and like plants. The tendency thereto is undoubtedly transmitted by the
shoot-axis, whose internodes remain extremely short between the bud-
scales.
ASSIMILATIVE FUNCTION OF STIPULES. In other cases the stipules
364 STIPULES, LIGULES, STIPELS
take a share in the assimilation-work of the foliage-leaves and live as long
as these do. Such stipules are persistent.
NUMBER OF STIPULES. As to the number of the stipules we
commonly find that there is one stipule upon each side of the leaf-base,
apart from concrescences and splittings. In Viburnum Opulus (Fig. 238)
we have not infrequently a pair, as is the case also in Sambucus Ebulus, in
which plant the number and construction of the stipules is very variable—
sometimes there are two structures completely formed like pinnate leaves,
sometimes there are four, and especially upon the upper leaves and on
the first strong lateral shoots the stipules are much smaller and reduced
to stalked glands like those in Sambucus nigra’.
VASCULAR SUPPLY OF STIPULES. That the stipules are basal out-
growths of the primordium of the leaf is also shown by the course of the
vascular bundles, although I do not think that this is a point of great
importance in the notion of ‘stipule’ As is pointed out by De Bary’,
the bundles which enter into the stipules are mostly branches from the
leaf-bundles. Colomb? found this to be the case in all the plants he
investigated. I would, however, call an organ a stipule which had other-
wise all the characters of a stipule, even if it had independent vascular
bundles, and Colomb’s derivation of the stipules from ligular formations
I hold to be quite unsupported and I shall advance further proof of this
presently.
2, DEVELOPMENT OF STIPULES.
It has been shown above that the stipules are outgrowths of the leaf-
base. The time of their origin is not fixed. In general it may be said
with Massart* that the szzpules arise the earlier, the earlier their work
as protective organs begins. In Hydrocotyle, for example, where they
enclose the leaf upon which they arise, they appear very early before the
indication of any segmentation of the primordium of the leaf®. But most
stipules have only to protect the younger leaves of the bud, and then they
arise after or before ° the appearance of the differentiation of the upper leaf ;
if their function is an insignificant one or they are inclined to arrest then
they arise relatively late.
ARREST OF STIPULES. Such an arrest of the stipules takes place
1 See footnote 2 on p. 362.
2 De Bary, Comparative Anatomy of the Vegetative Organs in the Phanerogams and Ferns
(English Edition), Oxford, 1884, p. 297.
8’ Colomb, Recherches sur les stipules, in Annales des sciences naturelles, sér. 7, vi (1887).
* Massart, La récapitulation et innovation en embryogénie végétale, in Bulletins de la Société
Royale de Botanique de Belgique, xxiii (1894).
° Massart’s figure is very unsatisfactory.
® According to Massart they arise, in Cunonia capensis, before the primordium of the lamina
appears. ‘This exception to an otherwise general rule requires further investigation.
BEVELOPMENT OF *STIPULES 365
frequently, so that the stipules may appear as small teeth or may be
entirely wanting. Their absence is teleologically explained when the pro-
tection of the bud is otherwise provided for. Such a case has already been
described? in the leaves of Lathyrus Clymenum, which have extremely
reduced stipules, sometimes invisible. The increase in breadth of the
whole leaf-primordium has made superfluous the development of the
stipules as protective organs. We find the same in other cases, for example
in Tropaeolum majus, where the stipules arise only upon the first two
leaves as small pointlets and the broadened leaf-stalk itself protects the
axillary bud. The case of Helianthemum described by Lubbock? is
instructive. A number of species like H. vulgare and H. tomentosum
have stipules; others like H. oelandicum and H. lasianthum have none.
The former possess a narrow leaf-stalk, the latter have a broadened sheath-
like leaf-stalk, and in the former the stipules act as a protection to the
bud, in the latter the leaf-sheath. In H. guttatum the leaves in the lower
part of the shoot have no stipules; stipules appear in the vicinity of the
flower-region, occasionally one of them is more or less arrested. A
comparison with the case of Adenostyles * gives us a biological explanation
of this.
DISTRIBUTION OF STIPULES IN THE PLANT KINGDOM. It would
carry me too far here to give the story of the distribution of stipules in
the different families, and the few illustrations I have mentioned show that
the appearance of these organs within the genera, even within the course
of development of one plant, may vary. I will only say :—
Pteridophyta. Stipules are found in the Marattiaceae of the group
of the Pteridophyta, and their thick fleshy appearance is extremely
characteristic *. The structures which were frequently considered to be
stipules in the Ophioglossaceae are not of this nature.
Monocotyledones. In Monocotyledones, whose ligular formations will
be presently mentioned, typical stipules are unknown, and this is con-
nected with the wide-spread existence of the strongly developed leaf-
sheath in this group. The interpretation of the structures which stand
in the axil of the leaves of Tamus europaeus and of the tendrils of Smilax
as stipules is certainly incorrect °.
1 See Part I, p. 162.
? Lubbock, On Buds and Stipules, London, 1899, p. 203, thinks that the time of origin of
stipules distinguishes them from pinnules, and that in a compound leaf with basipetal development
they appear not last but relatively first. But this entirely overlooks the biological point that early
otigin is connected with earliness of functional activity.
8 See p. 361.
* These are axillary stipules. They appear in the same manner in Todea.
° With regard to Smilax see p. 223.
366 STIPULES, LIGUEES, «SEES
3. RELATIONSHIPS OF CONFIGURATION OF THE STIPULES
AND THEIR TRANSFORMATION.
Stipules do not stand in such varied relationships to the outer world
as do the leaves, and therefore their configuration is simpler than is that
of leaves. The size and form of the stipules is closely connected with their
function as protections to the bud. Where, as in Vicia Cracca (Part I,
Fig. 78), they have only to fill the space between the leaf-pinnules in the
bud, they are naturally smaller than where they have to cover the whole
bud, as in Bauhinia and Lathyrus Aphaca (Part I, Figs. 72 and 77). The
form and size of the stipules often change in the course of the individual
development, during which of course the size of the bud which is being
protected increases, and it is clear that buds of an inflorescence require
more room than a vegetative bud. The primary leaves of Viola tricolor
have, for example, no stipules, then follow leaves with simple stipules, and
further up the stem come leaves with large pinnatifid stipules. The lobes
of these stipules bear glands which secrete mucilage and serve markedly
in this relationship for the protection of the bud. Whether this is the
case in all fringed stipules requires further investigation.
INEQUALITY IN SIZE. Not infrequently the two stipules of a leaf
differ from one another. In the dorsiventral shoots of many Leguminosae ?
the stipule which stands upon the illuminated side is greater than that
upon the shaded side, and in Ervum monanthos the smaller stipule is
simple whilst the larger has its margin divided into lobes. Perhaps this
is connected with the fact that the axillary shoot of the Leguminosae
is displaced towards the illuminated* side and requires here more perfect
protection.
RELATIONSHIPS OF SYMMETRY. With regard to the symmetry-
relationships of the stipules nothing will be said here as the subject has
been already discussed *. Their peculiar construction in many Legumi-
nosae only requires here a short notice :-—
Stipular Appendages in Leguminosae. We have here to deal with
appendages which are found at the base of many stipules and which make
these sagittate or half-sagittate. The relationships are not so simple as
might appear from Lubbock’s description *, because the significance of
the stipular lobe is evidently not the same in all cases. In Aeschynomene
indica the stipules are unilaterally prolonged outwards at the base, and
this prolongation invests the outer side of the young internode whilst the
stipule itself covers the bud. The meaning of the appendage is here quite
clear. Lathyrus pratensis has usually two stipular lobes of which one
+ See Part I, p. 121. 2 See Part I, pp. 121 and 126.
©) See Part 1, p. 1265: * Lubbock, On Buds and Stipules, London, 1899, p. 175.
CONCRESCENCE: OF STIPULES 367
is not infrequently arrested or only indicated by a small tooth, whilst the
larger lobe is on the outside. In the primordium of the bud these stipular
lobes cover, as in some other species of Lathyrus, only so small a portion
of the surface of the internode that they can scarcely be considered as
protective organs to this as they are in Aeschynomene, rather might one
say that, where they lie nearly horizontally against the stem-surface
(Fig. 239, to the left), they serve to hold the stipules in their right position.
After their exit from the bud-condition they enlarge considerably, and
this would seem to indicate that they have in the unfolded condition a
definite function to perform. In Lathyrus latifolius (Fig. 239, to the right)
they appear to serve the function of ‘drip-tips.’ The unilateral elongation
of the stipule is here very great, and the appendages are not flat but
so bent that rain must run out
easily along them from the leaf-
axils, instead of trickling down
from one leaf to another as it would
otherwise do.
CONCRESCENCE OF STI-
PULES. ‘Concrescence’ of stipules
appears regularly in many plants
and there are two cases :—
(a) Concrescence of stipules
of one and the same leaf ;
(2) Concrescence of stipules
of adjacent leaves. This can only
take place, of course, where there
is a cyclic phyllotaxy, and it oc- — yg. 239. To the left: Lathyrus heterophyllus: end of
: ashoot. To the right: Lathyrus latifolius: node. The
curs especially where there are unilateral stipular outgrowths are horizontal in the young
dimerous whorls !. ie ee gee wine Nau
Concrescence of stipules of
one leaf. Fig. 241 shows an example of the concrescence of the stipules
of one and the same leaf. Here instead of two separate stipules we find one
scale-like structure * which is the result of the union of two stipules, as the
apical division in two indicates. How effective is the protection of the bud
thus provided is shown in the transverse section (Fig. 242). In Diptero-
carpus alatus (Fig. 240) the stipules join across the upper side of the leaf-
stalk, forming in this way a sheath enveloping the bud, and the formation
of the sheath by the concrescence of two stipules can be easily recognized
by the presence of two stipular apices.
Cube
ae a
Ma
EARLE AERA A
/
US
ee
dl!
Saale a tA RIAY!
. » wh . ~ Sac
IAAUTtpaetehy Cae uLLeUWusAN heya UITN TUTE ANT)
: \
RL \
X
\
\
Pre La
on
ae
is 74
=:
a
1 The opposite primary leaves of Phaseolus multiflorus furnish an example. The subsequent
leaves are alternate, and there is naturally no concrescence.
? In Onobrychis the concrescent stipules form a dry membranous structure.
368 STIPULES, LIGULES, Stes
Concrescence of stipules of adjacent leaves. Concrescence of stipules
belonging to two separate leaves is frequently observable in the opposite-
leaved species of Urticaceae, for example in Humulus Lupulus and in
a less degree also in Urtica dioica. Here I have found the two neigh-
bouring stipules of one leaf-pair sometimes quite free, sometimes united
more or less, and they may form an apparent single leaflet whose nature,
however, is made clear by the two lobes at the apex. The whole arrange-
ment suggests that instead of four only two stipules are present which
enclose like mus-
sel-shells the bud.
In this way pro-
tection of the bud
is provided for by
the expenditure of
less material than
would be the case
were the stipules to
remain free. Such
stipules formed by
the concrescence of
two belonging to
different leaves are
called interpetiolar
stipules,and they are
specially character-
istic of the Rubia-
ceae. Fig. 243
shows a_ bud of
Cinchona with this
construction. There
can be no doubt we
have here to do
with the ‘concres-
cence’ of two pairs
of stipules, even
Fic. 240. Dipterocarpus alatus. Apex of the shoot of a young plant. The an 5
stipules of the erect leaf are concrescent over the face of the leaf and originally although this is not
formed a sheath enclosing the bud of the stem. to be traced‘in the
history of development, that is to say, the interpetiolar stipule appears
from the first as a single primordium. It is clear that such a concres-
cence in whorled and opposite leaves could readily ensue.
Stipules of the Stellatae. Much attention has been given to the develop-
ment of the leaf in the Stellatae, a tribe of the Rubiaceae. The leaves are
apparently arranged in four to eight-membered whorls, but these leaves are not
WUIRULES (OF! THE STELLATA 369
of equal value as is shown by the fact that in every leaf-whorl at most two leaves,
which stand opposite one another, have an axillary shoot. These axillant leaves
were considered by de Candolle* to be the true leaves, the others were regarded
as stipules which have become leaf-like and which have undergone a ‘chorisis’
if there be more than six leaves present in the whorl, or a ‘concrescence’ if there
be less than six. The history of development supports this interpretation. In
Fig. 244 an axillary shoot of the leaf 77 is shown in surface-view. It has two
leaves 4, and 4,, each of which has a primordium of an axillary shoot 4, and each
has two stipules S,S, and S,S, At the
vegetative point the primordium of a ‘ leaf-
whorl’ appears as a ring-wall whose growth
at two opposite points is taking place and
these points mark the apices of the two
chief leaves of the whorl. The stipules
appear after the primordium of the leaves
and they arise from the margin of the ring-
like primordium between the foliage-leaves
and then gradually grow out into a form
Fic. 241. Astragalus adscendens. Fic. 242. Hedysarum obscurum. Bud
6, stalk of a leaf, the stipules of which in transverse section. J, oldest leaf with
have become concrescent around the its stipular sheath sZ7; 77, second leaf
axis into a sheath s4 at the top of with its stipular sheath s/7; s¢Z/Z, free
which its composition out of the two upper parts of the stipule of the third leaf.
stipules is indicated. Magnified.
and size like that of the proper leaf-primordium. Sometimes, and this regularly
takes place in certain species, there arise between the two primordia of the leaves
more than two stipules so that the ‘whorl’ is then more than six-membered.
On the other hand there sometimes occurs a less number. In Galium palustre,
for example, we find in the false whorl four similarly constructed one-nerved
leaves which are distinguished only from one another by the fact that
* De Candolle, Vegetable Organography. English Edition by Kingdon, London, 1841, ii. p. 286;
also M. Franke, Beitrage zur Morphologie und Entwicklungsgeschichte der Stellaten, in Botanische
Zeitung, liv (1896), p. 33. The literature is cited by Franke.
GOEBEL I Bb
370° STIPOLES, (LIGULES, SITPELS
two cf them, which are opposite to one another, have axillary shoots. Accord-
ing to Eichler we have here a ¢vwe concrescence of originally separate members,
each of the two stipules being formed out of originally separate primordia. I have
found, however, that in Galium palustre this is not or only seldom the case, but
that sometimes the margin of the primordium of the stipule is swollen up or at
least expanded or obliquely projected’, and certainly we may consider this to be
an indication of the primordia of two stipules; more often, however, I found
no such indication, but the stipular primordium appeared uniformly single. There
is as a fact, in the position of the two stipular primordia here, a new formation
which presents the appearance of one single leaflet. Comparative morphology
would here speak of a ‘congenital concrescence,’ which is only a clumsy way
of stating the fact that where other species of Galium have two stipules here there
is only one present from the
beginning. Massart says that
in Sherardia arvensis all the
Fic. 244. Galium Mollugo. Axis of the shoot H
in transverse section; /7, axillant leaf of a bud, which
Fic. 243. _Cinchona succirubra. has laid down the first leaf-primordia of a ‘whorl’;
Terminal bud enclosed by the mussel- V, vegetative point of the axiallry bud ; 41, 2, the first
like interpetiolar stipules of the pair leaves with stipules S}.Sj, S2S2; 4, 4, axillary shoots
of leaves of which the stalks only are of these leaves. The stipules are less developed upon
shown. the side next the axis.
leaves of a whorl arise at the same time. One may bring forward in further
support of the interpretation adopted above, which is also borne out by com-
parison with other Rubiaceae, that in most of the species of Galium the primary
leaves do not differ from those which follow, but in Sherardia arvensis and Galium
peregrinum the ‘stipules’ in the first leaf-whorl are narrower and somewhat shorter
than the ‘leaves’®. From the standpoint of the history of development there
is possible, however, another interpretation which would bring the facts into con-
formity with those of the formation of the leaf of Limnophila heterophylla * :—
That we have here leaves which stand in a two-membered whorl but are very
1 See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884), p. 231, Fig. 48 B. Franke has confirmed my observations. Occasionally
the number of the leaves in following whorls changes. Ina species of Galium growing as a weed
in a plant-house I found successive numbers to be 4, 5, 4, 6.
2 Massart, La récapitulation et l'innovation en embryogénie végétale, in Bulletins de la Société
royale de botanique de Belgique, xxiii (1894), p. 200. 3 See pp. 333, 359.
STIPULES OF STELLATAE AND ALCHEMILLA 371
deeply divided and perhaps have never possessed stipules. To such an inter-
pretation, however, the frequent occurrence of four-membered whorls is altogether
unfavourable. The question here, as in all other like cases, is what weight should
we attach to the comparison with allied forms in framing our explanation.
Amongst the Stellatae there is a form, Didymaea mexicana, which possesses
opposite leaves with two or three small interpetiolar stipules that are not like
foliage-leaves. The plant conforms in all respects with the other Rubiaceae and
may be considered as standing near the original type’. In the flower-region
of the Stellatae simple leaves without stipules appear and the same is the case
in the vegetative region of some species of Asperula?. Asperula scutellaris has
upon the seedling-plant above the cotyledon first of all a four-membered ‘false
whorl,’ but the stipules in it alternating with the chief leaves appear to be already
reduced and in the following whorls gradually they disappear almost entirely.
Alchemilla galioides. Whilst in the Stellatae the manner in which the
peculiar formation of the leaf has come about does not appear to be quite certain
from the phyletic side, the derivation of an analogous configuration of leaf in
another cycle of affinity is quite clear*. The leaf-whorl of Alchemilla galioides *
consists of six almost equal leaves which are united with one another below into
a sheath. Really we have here to do not with a dimerous leaf-whorl as in the
Stellatae, but with a single leaf whose lamina is deeply divided and to such an
extent that the single segments are constructed quite like stipules. A _ similar
feature is found in allied species’ which, in the region of the hypsophylls, are
provided with stalkless leaf-laminae markedly different from the stipules. Not
only is the formation of the stalk suppressed, but the size of the leaf is diminished,
and the several equally large leaf-segments spring apparently directly from the
leaf-sheath,
It was previously stated ® that in species of Alchemilla, which have apparently
whorled leaves, we might recognize in some measure a use for the configuration
of the leaf. We cannot do so yet in the case of the Stellatae. We might suggest
that, the Stellatae being plants with mostly long, thin shoot-axes, a nearly equal
distribution of leaf-substance in a ring about the node involves, for the production
of an equal surface of assimilation, a less expenditure of material in the strengthen-
ing of leaf and stem than would be the case if there were only two opposite leaf-
surfaces, which would need of course to be provided each with its own ribs, stalks,
and so forth. It seems to me that with this suggestion in one’s mind it is of
interest to note that Didymaea mexicana mentioned above is a climbing plant
and uses as climbing hooks the recurved stipules and that its shoot-internodes
have experienced no strengthening although the leaves are stalked.
Acacia verticillata. Hofmeister’ supposed that he discovered in Acacia
1 See Schumann, Rubiaceae, in Engler and Prantl, Die natiirlichen Pfanzenfamilien, p. 147,
Fig. 47 N, O.
2 M. Franke, Beitrage zur Morphologie und Entwicklungsgeschichte der Stellaten, in Botanische
Zeitung, liv (1896), p. 33.
3 Goebel, Pflanzenbiologische Schilderungen, ii (1893), p. 32.
* See Goebel, op. cit., p. 35, Fig. 9. 5 See p. 333- 6 See p.
7 Hofmeister, Allgemeine Morphologie der Gewachse, Leipzig, i 5
Bb 2
392 STIPULES, LIGULES,\ SUE ES
verticiilata a case like that of the Stellatae because in the apparently whorled
phyllodes only single ones have axillary shoots—the others therefore he took to
be leaf-like stipules (Fig. 245). A. Mann and I have shown that Hofmeister’s
supposition was incorrect because at the base of the phyllodes, which have axillary
shoots, there always occur very reduced stipules and these also occasionally occur
upon the other phyllodes. The axillant phyllodes precede the others in the
development. We have here then only a case of peculiar division of labour
amongst the leaves, and it has only a superficial resemblance to the relationships in
the Stellatae.
4. AXILLARY STIPULES.
We designate as axillary stipules, structures which stand in the leaf-axil,
and sometimes are attached to the leaf-base
NW over a longer or shorter extent. In some cases
\\ Ze we find that the axillary stipules have proceeded
. VA from lateral stipules, which have become united
Wy is to one another by a new formation across the
SN eo- upper side of the primordium of the leaf. In
ae Melianthus, for example, there is formed at the
upper limit of the leaf-base, a transverse cushion
WN: which unites the two lateral expansions of the
leaf-base with one another, and then grows
NS _-® along with them, so that one may say that
, be ee the stipular formation here encroaches over the
eau upper surface of the leaf. In species of Ficus,
many transitions are observable between free
stipules and a stipular sheath, which appears
as an independent leaf investing the bud, and
which may be considered as a giant axillary
stipule deciduous from its base. This deciduous
op 245, Acacia verticillata’ End axillary stipular (sheath) jie jiounegameiieus
hyllodes, @, %, have axillary shoots. elastica. In Ficus Pseude-Camcattiererare mice
stipules, whose insertion, however, extends so far
upon each side along the upper side of the leaf-base, that if we imagine this
zone-insertion to be raised up upon a common base, we should have an axillary
stipule with free upper ends, and open upon the outer side as is the case in
Artocarpus; in seedlings of Artocarpus integrifolia I found, moreover, an
incision upon the sheath above, showing its composition out of two stipules.
The earlier the union by the transverse cushion takes place, the more will
the axillary stipule appear as a single structure, and if the stipules become
united also upon the side opposite to the point of insertion of the leaf,
a closed sheath must be formed. Whilst in many cases axillary stipules are
derived in this way from free lateral ones, I do not think that this is the case
ox.
AXILEARY. SPPULES, OF DICOTYLEDONES 373
always. An axillary stipule may appear where there were never any free
lateral stipules laid down, and where we have no ground for assuming them.
DICOTYLEDONES.
Caltha palustris. As an example I take Caltha palustris, of which
Fig. 246 shows in the figure to the left, a dissected-out bud. This bud
(turned to the left) is surrounded by a structure, which is somewhat conical
and open at the top. This is the axillary stipule of the foliage-leaf on its
right. In the figure to the right, which is a bud (turned to the right)
developing into an inflorescence, the axillary stipule which served as a
protection to the bud is developed more massively, corresponding to the
Fic. 246. Caltha palustris. Young leaves dissected out. To the left : leaf with axillary stipule which invests
the bud. To the right: leaf with axillary stipule investing a young inflorescence.
more massive construction of the bud. In older conditions we find the
upper part produced as a kind of horn, or the one margin of the mouth is
cap-like, projecting over the other, and thus the mouth is closed to the
outside. The leaf arises primarily as a ridge-like projection of the vege-
tative point. At an early period there appears on the upper side at the
base of the leaf, an outgrowth which is united with the lateral parts of the
leaf-base. The leaf-base itself extends round sometimes the whole shoot-
axis, and grows out with the outgrowth of the upper leaf-surface over the
vegetative point, and so forms the axillary stipule. How can we see in
this two stipules? These are not even present in other Ranunculaceae.
Polygonaceae. The ochrea of the Polygonaceae arises in the same
manner. Here the derivation of the axillary stipule from lateral ones is not
probable, although at first in Rumex there appears to the right and left on
the leaf an enlargement of the leaf-sheath, which one might regard as an
indication of stipules!, but one does not require to ‘consider it as such,
1 The free lateral stipules which I described in the flower region of Rheum undulatum (see
Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), p. 232) are apparently the result of the splitting of the ochrea into two lobes.
374 STIPULES, LIGULES, STIPELS
for it is easy to understand that the formation of the protecting organs of
the bud is direct in this case. There appears upon the upper side of the
leaf an outgrowth, which connects the lateral parts. The ochrea also
protects the bud by the mucilage-glands which it possesses.
Gaertnera. Such axillary stipules may also appear combined with
interpetiolar stipules, and then there is a very peculiar construction, because
the interpetiolar stipules unite with one another to form a sheath-like body,
which then serves as a protection to the bud. We find this in a species of
Gaertnera which I collected in Ceylon (Fig. 247). The origin of the con-
struction is shown in Fig. 247, I, where between the leaves of the youngest
leaf-pair, the interpetiolar stipules are visible. If now we suppose that the
upper side of the base of each leaf shares in the stipular formation, the
ae 247. Gaertnera sp. (Ceylon). Bud intransverse section. I, higherup; II, lower down. The stipules are
shaded.
interpetiolar stipules would in a certain degree be united across the surface
of their leaves, and thus would arise the peculiar condition which we have
in this plant. The stipular sheaths are provided with numerous glands, and
these it may be assumed aid in the protection of the bud.
Gunnera. Some species of Gunnera possess remarkable axillary stipules.
This genus contains forms of very different dimensions, and the axillary
stipules are only found in those which possess a thick tuberous stem, and
whose terminal bud is therefore very massive. For its protection, organs are
developed which are absent in the species with more slender stem, like G.
macrophylla and the small New Zealand species. We have in this one of
the most striking relationships between size and formation of organs within
one genus. The axillary stipules which are found in Gunnera chilensis',
1 See Reinke, Untersuchungen tiber die Morphologie der Vegetationsorgane von Gunnera, in
Morphologische Abhandlungen, Leipzig, 1873, p. 78.
AXILLARY STIPULES OF MONOCOTYLEDONES 375
and G. manicata are of considerable size, as much as six or seven centi-
meters long. They are traversed by conducting bundles, and serve to store
up food-material as well as to protect the bud in the resting period. The
protection which they offer is increased by the fact that they are glued
together by a mucilage. One may perhaps best derive them from
mucilage-glands which appear as outgrowths of the leaf-base as well as
elsewhere, but are here adapted to other functions and have reached
a giant size.
¢
Fic. 249. Oryza sativa. 7, ligule in the bud-
Fic. 248. A grass. Stem and condition dissected out. 4, portion of the leaf to
portion ofleaf: 4, haulm; yz, leaf- which it belongs. The ligule closes up the bud, the
sheath; 4, swelling of the leaf- two hairy ‘Sickles of the leaf’ act as aids in strengthen-
sheath above the node; s, portion ing this closure by the ligule; they are erect, one out-
of lamina; 4, ligule. Natural size. aide, one inside. JZ/7, ‘sickles of the leaf‘ are ex-
Lehrb. panded, the ligule has been grown through by the
next younger leaf.
MONOCOTYLEDONES |.
Axillary stipules like those of Caltha are found in a number of Mono-
cotyledones :—
Potamogeton. The leaf in Potamogeton possesses at first only a leaf-
sheath sharply marked off from the lamina and very nearly amplexi-
caul. Subsequently an outgrowth appears upon the inner side of the
leaf, at the point where the margins of the leaf-sheath meet, and this
grows inwards from both sides of the leaf-sheath and unites them together.
The sheath which is thus built up, and which afterwards grows out to
1 See Gliick, Die Stipulargebilde der Monocotyledonen, Heidelberg, 1got.
376 STIPULES, “LIGULES, oli S)
a considerable extent, acts as a protection to the bud, and it is distinguished
from that of the Polygonaceae, in all cases which have been examined,
only by being open on one side.
5. LIGULES.
THE LIGULE OF GRASSES. The ligule of grasses appears in the form
of a membranous outgrowth at the limit between the leaf-sheath and the
leaf-lamina (Fig. 248). It usually contains no chlorophyll. Its size varies
greatly in different grasses. In
Psamma arenaria it may be as long
as four centimeters, and in this
species it is traversed by veins which
are accompanied by tissue contain-
ing chlorophyll, and provided with
stomata. In other species with a
well-developed ligule, such as Oryza
& fo) i) D
Fic. 250. Oryza sativa. Leaf in transverse
section above the point of origin of the ligule ;
this is still convolute and closes the bud, and is Fic. 251. Alpinia nutans. Portion of a leaf.
strengthened by the erect ‘sickles’ and their The leaf-sheath ends above in a convolute ligule
hairs. The ‘sickles’ are shaded in the figure. which closes the bud. Natural size.
sativa and Arundinaria japonica, a conducting bundle is present’, but the
ligule usually consists of parenchymatous tissue alone.
FUNCTION OF THE LIGULE OF GRASSES. Widely spread though the
ligule is, we know as yet little about its meaning; the only conjecture
regarding it which has been put forward is, that it prevents rain-water from
' Regarding the course of this, see Colomb, Recherches sur les stipules, in Annales des sciences
naturelles, sér. 7, vi (1887).
LIGULE OF GRASSES STE
penetrating into the space between the leaf-sheath and the stem. This
interpretation of the function of the ligule, first propounded by Schlechten-
dahl, does not appear to me to be very illuminating. It is easy to prove
that the well-developed ligule in Oryza does not hinder the entrance of
water in the way suggested, for water-drops which reach the leaf-surface do
not roll towards the ligule, but fall to the ground from the tip of the
unwettable, downwardly curved leaf.
The ligule has unquestionably the function of protecting the bud. The
terminal bud is invested by the leaf-sheath, and in its further growth only
gradually projects from the sheath, and if one removes the unfolded leaves,
one comes to a point where the bud is closed over by the ligule. As
Fig. 249, / shows, the ligule is rolled up into a conical point, through which
the bud subsequently penetrates. This view is strengthened by the fact that,
at the base of the leaf-lamina, there are found two sickle-like outgrowths,
which in the unfolded leaf stand nearly horizontally (Fig. 249, 7/7), but in the
bud are directed upwards and in such a way that one of the ‘sickles’ lies
outside and the other inside, as is shown in Figs. 249, /, 250. The long
stiff hairs, which clothe the outer edge of the sickle, are in the bud similarly
directed upwards, and contribute to the strengthening of the protective cap,
which is formed above the bud by the convolute ligule.
Even more easily seen, that is to say no removal of the older parts is
necessary, is the significance of the ligule in the uppermost leaf which invests
the inflorescence of Dactylis glomerata and of many Zingiberaceae, for
example Hedychium Gardnerianum and Alpinia nutans (Fig. 251). In
these also the sheath elongates as a ligule beyond the point of insertion of
the lamina, and the ligule of the uppermost foliage-leaf serves as a cover to
close the bud on the top, and it remains as an outgrowth at the base of the
lamina in just the same way as does the ligule in a grass after the bud has
grown through it. It contains many conducting bundles.
In grass-spikelets, where through the formation of the ligule the awz,
which corresponds to a lamina, is often apparently dorsal, we cannot speak
of a protection against the entrance of water; but the ligular outgrowth at
the base of the awn, brings about a close overlapping of the glumes
covering the spikelet, and this is intensified in Bromus and other cases
where the sheathing portion of the glume is elongated right and left into an
outgrowth which may be designated a stipule by those who find pleasure in
giving names to things.
The ligule of grasses is not always as it is in Oryza, an organ which
closes in the terminal bud. It may act elsewhere as a temporary protective
organ. Fig. 252 shows a transverse section through a bud of Alopecurus
pratensis. The ligule is found as usual at the point where the leaf-sheath
passes into the leaf-lamina. As the leaf-lamina subsequently spreads out as
a flat structure and the leaf-sheath remains as a hollow cylinder, there is
378 STIPULES, TIGULES, SiEeLIES
o
formed at this poift of union an open space. The free margins of the
ligule overlap in front as the figure shows, cover the open space, and surround
the next younger leaf at its base. This younger leaf gradually pushes itself
by intercalary growth out of the ligule, and its tissues have time gradually
to change in response to the claims of the outer world. In other words,
I consider the ligule here as an organ which is also able to give a certain
amount of cover to the bud, during the elongation of the next youngest leaf
through the ligule. In Hordeum, Lolium, and others, the protective function
of the ligule is increased by the sickle-like outgrowth on both sides of the
base of the lamina.
According to my view, the ligule in grasses only performs its function
at a somewhat late period, whether it serves as a ‘bud-cap’ or in some other
way aids in the protection of the bud. The
time of its origin corresponds to this, for it
is only formed at the limit of the leaf-sheath
and the leaf-lamina as an outgrowth on the
upper side of the leaf when the sheath has
been already differentiated, whilst axillary
stipules, whose function is performed much
earlier, are laid down at the leaf-base near its
insertion. It would, however, be a mistake to
Fic. 252. Alopecurus pratensis, . COnSider, as was formerly done*, that the ligule
at ean en above of the grasses was derived from an axillary
lea. Siivitly oon! second stipule, which is concrescent by its outer side with
the leaf-sheath. There is no concrescence here,
but only a later inception in correspondence with the later claims made upon
the organ, and this conforms with what we have seen in the axillary stipule
of Caltha and elsewhere. The relatively short time during which the ligule
has to perform its function, explains also its usually delicate construction,
about which, however, we cannot say much here. Whether besides this one
function in relation to the bud the ligule has some other function after
unfolding, I cannot say. It must suffice that I have shown the conjecture
hitherto accepted regarding the function of the ligule to be certainly
incorrect in the case of Oryza, and in the case of other grasses, at least to
be not proved, and this without reference to the consideration that it may be
more ‘harmful’ if the water-drops remain lying upon the base of the lamina,
rather than at the bottom of the sheath—a position indeed, in most Biases:
that could be reached by them only in a very limited amount.
THE LIGULE OF PALMS. Ligular formations are formed also in the
palms. The leaf of Chamaerops®, and of Rhaphis, is in the juvenile
' See A. de St-Hilaire, Legons de botanique, comprenant principalement la morphologie végétale,
Paris, 1840, p. 193, and other later writers.
* Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
LIGULE OF PALMS 379
condition covered by an envelope composed of many layers of cells. This
envelope (Fig. 253) proceeds from a scale which is formed at the limit
between the leaf-stalk and the leaf-lamina, and grows up over the anterior
side of the leaf, and from two scales, or it may be one which is bulged in
the middle, which develop out of the fosterior side of the leaf-primordium.
In the matured leaf, this structure appears as a brown membrane, but in the
young condition it forms a very effective protection to the bud. In
accordance with this
function, it develops
somewhat early, and ra pies
the ligule serves at 2
A
. me
Bb
first as a protection
to the leaf-surface
which it covers, but
later it is bent for-
ward and forms with
theleaf-sheath, which
is now developed, an
almost closed cy-
linder, in which the
next younger leaf is
found. These ligular
formations are un-
doubtedly new for- d
mations upon the
leaf - surface, and
serve as protections (€
to the bud. At the FIG. 253. Chamaerops humilis. Bevelcpioest oe ina ae of siaer eee
7 ‘+9 sections. A, upper part of the young leaf; 4, membrane. , the same lower
same time, it is clear down. The middle apical fold no longer covered by the = = G middle
1 : art of leaf-lamina; /, ligule. 2, basal part of leaf-lamina, the ligule, 4 runs
that in a case like eto the lamina. Z, ieee lain of older leaf; 4 separation cells. F, cells of
r angles in mucilaginous degeneration bringing about the separation.
that of Chamaerops, Wier pefiega.
where these out-
growths are formed upon the anterior avd upon the posterior side, they
cannot be reckoned as similar to the lateral stipules of other plants. There
is as little ground also for such an opinion in the case of the ligule of
grasses.
6. STIPELS.
The ligular formations of these palms lead us on to the stipels of some
Dicotyledones.
Under the term szpel formal morphology has brought together
Botanik, iii (1884), p. 221. Deinega, Beitrage zur Kenntniss der Entwicklungsgeschichte des Blattes
und der Anlage der Gefiassbiindel, in Flora, Ixxxv (1898), p. 488. Deinega gives the literature.
380 STIPULES, (LIGULES; S1iELLs
structures of very different origin’. On the one hand we have independent
outgrowths, which, as will now be pointed out, may serve as protections to
the bud, on the other hand we have reduced pinnules.
The best known example of independent outgrowths is seen in a number
of (although not all) species of Thalictrum. In Thalictrum the leaf is
composed of ternately branched leaflets, and the stipels arise in pairs, one
upon the dorsal side, and one upon the ventral side of the leaf, at the point
where the lateral leaflets of the
first order proceed from the
rhachis (Fig. 254). As the leaf-
lets stand nearly opposite one
another, there are four stipels
at the points of branching, and
not infrequently they unite with
one another. These stipels
cover the leaf-parts in the bud,
as is shown in Fig. 255, and
Fic. 254. Thalictrum aquilegiaefolium. Portion ofa Fic. 255. | Thalictrum aquilegiaefolium. Sy,
foliage-leaf. S, S, the stipels sick are also visible upon young leaf-sheath in transverse section, showing
the stalk of the leaflets of higher order. Reduced. an enclosed?young leaf with stipels, s¢z.
this is their meaning ; they have nothing to do with the retention of drops
of water. What value could a pair of rain-drops be to a large leaf of
Thalictrum ?
The stipels which occur in species of Phaseolus, Robinia, Desmodium,
and other Leguminosae, are found at the base of the leaflets, and are rudi-
mentary pinnules. They appear usually in the form of small teeth, but
occasionally they are developed as leaves upon sucker-shoots, for example
in Robinia. That we have here to do with reduced organs, is not very
probable, nevertheless, not infrequently we have arrested structures in leaves
1 Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), p. 233.
STIPELS. TRANSFORMED STIPULES 381
of other Leguminosae to which stipels are not assigned. For example, in
Acacia lophantha, I find that the lowermost pair of pinnules standing close to
the pulvinus, are either entirely aborted or appear in the form of one or two
small pointlets. It is open to question whether these reduced structures
in Leguminosae ever discharge a function. They arise at a relatively late
period, as is frequently the case with reduced organs.
7. TRANSFORMED STIPULES.
The chief function of the stipules is the protection of the bud, and it
has been shown that in this work organs which secrete mucilage may take
a share, so that the stipules may be considered also as organs of secretion.
Honey-glands also are found upon the stipules in many plants, for
example in species of Vicia, and in some cases, as in Sambucus nigra, the
whole stipule according to the common interpretation is devoted to the
formation of glands and appears only in its original form upon luxuriant
shoots. The converse is, however, also possible, as the case of Viburnum
Opulus shows 1, for there the stipules have developed out of glands of the
leaf-margin. Only by a careful comparison of all the relationships con-
cerned, can we make a distinction.
Ratiborski? found one of the two stipules in Pterospermum javanicum,
transformed into a small cup standing upon the under side of the twig with
its inner surface covered by pearl-glands. These were eagerly sought after
by ants which removed them.
The stipules are transformed into thorns in Robinia Pseudacacia, the
succulent species of Euphorbia, Paliurus australis, and others.
SUMMARY.
Comparison of the different formations of stipules, from the two stand-
points of how they arise and of what is the relationship in them between
configuration and function, shows many gaps in our knowledge. Neverthe-
less it is clear that we have to do with structures which serve as protection
to the bud, a function otherwise accomplished by the broadening out of the
leaf-base, by the sinking of the bud in the tissue of the shoot, and in other
ways. We see that in correspondence with this function there appears
frequently to right and left of the leaf-base an outgrowth, but other parts
of the leaf also can produce analogous protecting organs, and therefore
formal morphology, which everywhere assumes two /7ee stipules as a starting-
point, has arrived very often at untenable constructions.
1 See p. 362. 2 Ratiborski, Uber myrmecophile Pflanzen, in Flora, lxxxvii (1900), p. 40.
382 TRANSFORMED LEAVES
Vil
TRANSFORMED LEAVES
By transformed leaves we mean leaves which have taken on a function
different from that of ordinary foliage-leaves, and have therefore experienced
a more or less far-reaching change in conformation. There is of course no
limit between normal foliage-leaves and transformed leaves as the trans-
formations appear in different degrees and have set in at very different
stages of the development of the leaf. The earlier the transformation sets
in the greater is the change. The treatment of the subject here is not con-
sistent ; sometimes it is approached from the formal side, that is to say that
of positions, sometimes from that of function. I have, however, selected the
Fic. 256. Aristolochia elegans. I and II, portions of shoot with leaves and axillary shoots; v, prophyll which
has reached a considerable size. III, shoot in transverse section: 4, stem of mother-axis; v, prophyll of lateral
axillary bud ; 4, bract.
examples as far as possible to give illustrations from different directions of
the manifold relationships between form and function. This seems to me
to be more instructive than would be the treatment from a single point of
view. We limit ourselves just now entirely to the vegetative region.
Sporophylls will be discussed when the flowers are spoken of.
1: PROPHYLLS.
Prophylls are characterized first of all by their position. We find them
where they occur in the Dicotyledones usually in pairs at the base of the
lateral shoots. In Monocotyledones there is commonly only one which is
placed upon the side of the daughter-shoot next the mother-axis. There
is no doubt, however, in many Monocotyledones that the prophyll is formed
PROPHYLLS 383
by the concrescence of two leaves ', whilst in others the prophyll is ‘reckoned’
to be only a single leaf, as the appearance of one axillary shoot opposite its
median indicates. In relation to their position prophylls, except in cases
where they are adapted to special functions, are usually small and simple,
so that frequently, even in recent times*, they have been confounded with
stipules, from which, however, they are distinguished at once by their origin.
Their function, is, however, like that of stipules, the protection to the bud.
Aristolochia elegans. Aristolochia elegans (Fig. 256) gives us a simple
case. Oxe prophyll only is present here, and it at first surrounds the bud
of the axillary shoot, and is distinguished from the later leaves by its small
size, the less intense green colour of its lamina, and the almost complete
suppression of its stalk—an interesting example of a feature which has
already been mentioned, and will be illustrated again* as appearing in
many hypsophylls, namely, that the stalk is suppressed in leaves whose
function is specially that of protecting a bud. Superficial examination
here might readily lead to the confusion of this prophyll with an axillary
stipule of the subtending leaf*. Where there are two prophylls their
position filling up the gap between the mother-axis and the stalk of the
subtending leaf is particularly favourable for the protection of the young
bud in its first stages of development.
Winter-buds. In overwintering buds the prophylls are usually indis-
tinguishable from the other bud-scales. Sometimes the whole ‘ bud-
covering’ is furnished by the prophylls alone, as in species of Salix, where
they are ‘concrescent’ into a thick scale. In other plants they are dis-
tinguished by their early development, which precedes that of the rest of
the axillary bud. This is seen in Solanum tuberosum, where the prophylls
are asymmetric and their posterior half is scarcely developed, and conse-
quently they are bent in the direction towards the axis of the chief shoot.
Tilia. Of prophylls which are adapted to special functions the wing-
leaf of the inflorescence of Tilia may be mentioned. It first of all acts
as a protective covering to the downwardly bent inflorescence during the
unfolding of this, and thereafter when full grown forms a kind of parachute,
although not a very complete one to the fruits. It has moreover, during
the ripening of the fruit, a physiological significance which will be described
when the formation of the fruit is dealt with.
Cyperus. The prophylls of some species of Cyperus play a part which
has been until now overlooked. They act as expanding bodies which force
1 See Goebel, Morphologische und biologische Studien : ITI. Uber den Bau der Archen und Bliiten
einiger javanischer Cyperaceen, in Annales du Jardin botanique de Buitenzorg, vii (1888), p. 120;
id., Ein Beitrag zur Morphologie der Graser, in Flora, lxxxi (Erganzungsband zum Jahrgang 189s),
p. 28. 2 By Lubbock, On Buds and Stipules, London, 1899. S See p. 392.
* In species of Aristolochia in which the axillary bud is protected by the base of the subtending
leaf, the formation of the prophyll is suppressed.
384 TRANSFORMED LEAVES
the leaves after their unfolding to stand away horizontally from the axis.
This is most clearly seen in shoots of Cyperus alternifolius, which do not
attain to the formation of flower (Fig. 299). In the axil of the foliage-
leaves fleshy bodies pointed at the top are visible, and these have brought
the leaf into its horizontal position. In the formation of these swollen
bodies the fleshy prophyll of the axillary shoot has taken almost the whole
part (see Fig. 299, ///), at the same time the base of the foliage-leaf is
swollen somewhat and becomes fleshy at both sides, but this is not clearly
shown in the figure.
Cucurbitaceae. In the Cucurbitaceae the prophylls are transformed
into tendrils, and these will be described when the tendrils are spoken of.
2, KATAPHY LIES:
The expression kataphyll, as first used by C. F. Schimper, referred to the
formation of leaves on hypogeous shoots. On such shoots the leaves, where
they cannot function as assimilation-organs, are more simply constructed
than they are on epigeous parts, and appear mostly in the form of simple
scales, whose function it is to protect the vegetative point. In many plants
they are used for the storing up of reserve-material, and of this something
will be said later!. To these leaf-formations, both in their construction
and function, all those epigeous parts which have been called bud-scales
(tegmenta) conform, and so closely that they have received the same name,
which is not altogether wrong, inasmuch as these leaf-formations upon an
upright growing shoot stand upon the ‘lower’ region of the shoot and are
followed by the foliage-leaves.
That the kataphylls arise from a transformation of the primordia of
foliage-leaves can be certainly proved? by the history of development, by
transition-forms, and by experiment, and therefore the formation of these
kataphylls has been made use of in this book as a simple example of the
transformation of the primordium of an organ*. This transformation may
take place in three ways :—
(A) The primordium as a whole becomes a kataphyll, undergoing more
or less far-reaching changes.
(B) The lamina is arrested and the stipules form kataphylls.
(C) The leaf-base develops into the kataphyll, the primordium of the
leaf-lamina is arrested, and the leaf-stalk is not developed.
A. KATAPHYLLS FORMED BY THE WHOLE LEAF-PRIMORDIUM.
A very instructive example of this is furnished by Talisia princeps, Oliv.
(Fig. 257), because in it the kataphylls are but little different from the
t See p. 398.
2 Goebel, Beitraige zur Morphologie und Physiologie des Blattes, in Botanische Zeitung, xxxviii
(1880). See also Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s
Handbuch der Botanik, iii (1884), p. 243. * See sbartale pao:
——————————— OO
KATAPHYLLS 385
foliage-leaves. The foliage-leaves are pinnate, and we find the same
segmentation also in the kataphylls, but these, before they reach the size of
ordinary foliage-leaves and before they develop in breadth, dry up, and so
form an envelope to the bud. The protection afforded by this envelope is
not very great. In plants whose buds are more liable to the danger of
drying and freezing we find that the protection to the bud is correspondingly
increased, as, for example, in Syringa and some other Oleaceae, such as
ae
FZ=
ea nf 5
Fic. 257. Talisia princeps, Oliv. End of a shoot with foliage-leaves and erect pinnate kataphylls, Reduced.
Ligustrum and Forsythia; one might also reckon here Salix, whose bud-
cover is formed by the concrescence of two prophylls.
B. KATAPHYLLS FORMED BY THE STIPULES. Here also we find
transitions to the ordinary condition. In Alnus the protection of the bud
is commonly! furnished by three scales. These are stipules, two belonging
1 Occasionally on the outside a still folded foliage-leaf is formed.
GOEBEL II Gc c
386 TRANSFORMED LEAVES
to the outermost leaf of the bud and one to the second. The primordia of
the foliage-leaves to which these stipules belong are well developed and
unfold later. In Magnolia the different species behave differently. The
buds are always protected by stipules. In Magnolia fuscata the leaf itself
to which the stipules belong is arrested usually, but sometimes it is developed ;
in other species, such as Magnolia Campbelli’ and M. Umbrella, the pro-
tective stipules belong to a leaf which discharges its function. In other
woody plants, especially in Quercus and Fagus, the buds are protected by
pairs of stipules, according to the statements of the descriptive botanists,
but the laminar primordia of these are not developed in the outer ones.
I have shown? that the history of development is opposed to this, and that
as a fact the laminar primordium stands as a small unstalked pointlet
between the two stipules which belong to it, and only the first two leaves
of the bud, the prophylls, are simple structures. Beijerinck * subsequently
confirmed this, whilst E. Schmidt? could not find the rudiment of the leaf
probably because it had fallen away at the time of his examination. I have
recently by a series of microtome-sections confirmed my old statement, and
we see therefore that in these genera there is an arrest of the primordium
of the foliage-leaf and a somewhat divergent formation of the stipules.
Analogous processes are found also in herbaceous plants, for example in
the hypogeous shoots of Humulus Lupulus.
C. KATAPHYLLS FORMED BY THE LEAF-BASE. The kataphylls of
the third category show but little fundamental divergence from those last
described, and I repeat here the account of them I have given elsewhere,
in which the evidence in support of their relation to foliage-leaves is
discussed ° :—
EVIDENCE FROM DEVELOPMENT. If an expanding bud of Acer Pseudopla-
tanus be examined in the spring, it will be found that the lowest kataphylls are small
bodies with a broad base narrowing upwards and bearing at the tip a small black
pointlet (Fig. 258, 7 A, Z), which appears upon investigation to be an arrested leaf-
lamina (Fig. 258, 7 B,Z). These leathery scales are traversed by feebly developed
vascular bundles. The bud-scales immediately above them are larger, sappy, and
sometimes have at their apex a small leaf-lamina. If we compare the bud-scales
1 Hooker, J. D., and Thomson, T., Flora Indica, London, 1855, p. 77.
2 Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), p. 244.
° Beijerinck, Beobachtungen iiber die ersten Entwicklungsphasen einiger Cynipidengallen, in
Natuurkundige Verhandelingen der Koninklijke Akademie van Wetenschappen in Amsterdam, xxii
(1883), p. 17.
* E. Schmidt, Beitrag zur Kenntniss der Hochblatter, as Wissenschaftliche Beilage zum Programm
der Friedrichs-Werder’schen Oberrealschule in Berlin, Ostern 1889. Also Lubbock, On Buds and
Stipules, London, 1899, p. 138, says of the stipules ‘there are sometimes more than forty, or twenty
pairs, before those containing the first leaf’ In these pairs the laminar primordium is early
arrested.
° Goebel, op. cit., p. 246.
5
KATAPHYLLS 387
shown in Fig. 258, 7 with a young primordium of a foliage-leaf immediately before
the formation of the stalk, the resemblance between the two structures is evident.
The bud-scale is evidently the leaf-base which is more strongly developed than
it is in the foliage-leaf, whilst the leaf-lamina is arrested ; it has, however, produced
two lateral segments (Fig. 258, 7 8) whose development in the foliage-leaf is in
basipetal succession. If the primordium of the foliage-leaf should develop further
into a foliage-leaf, the laying down of the lateral members of the leaflamina
proceeds further, and between the lamina and the leaf-base there is also inter- .
calated a leaf-stalk by
elongation of the upper
part of the _ leaf-base.
The transition from the
kataphylls or bud-scales
to the foliage-leaves is
sudden; the first foliage-
leaf follows directly the
last large kataphyll.
Prunus Padus.
Prunus Padus possesses
stipules like other mem-
bers of the cycle of
affinity of the Rosaceae,
but these are not, as has
been erroneously sup-
posed, constructed as Fic. 258. 1-6, Prunus Padus. 1 and 2, bud-scales formed of the broadened
¢ leaf-base; Z, arrested primordium ofthe lamina; s/, primordia of the stipules
bud-scales in the bud. seated on the leaf-base. 3, one of the uppermost scales of an unfolding bud,
the three vascular bundles traversing the leaf-base have branched; sv,
The bud-scales are here stipules; Z, lamina; A, gland at base of lamina. The central portion
G between the cross-strokes becomes the petiole, the portion below the lower
ormed out of the leaf- stroke is that represented in the bud-scale. 4, young leaf; s¢, stipules; Z,
ae ets : lamina. The cross-stroke marks the limit ofthe leaf-sheath represented in the
b I
ase. t 1s interesting — budscale. 5 and 6, middle stages between bud-scale and foliage-leaf; B/,
: leaf-base; s¢, stipules. See the text for further explanation. 74 and 78,
to notice the gradual Acer Pseudoplatanus. Bud-scales; Z, lamina. The arrested lamina in 7 4 is
transition = from! the "stows tural size
outer small bud-scales in the lateral buds to the inner larger ones. The middle
line of the scale is traversed by a strand of elongated cells in which there are
neither vasa nor tracheids. These are only found, small and few in number,
in the scales higher up, forming three strands, a middle and two lateral ones
(Fig. 258, 2, 3). The scales end as do those of Acer in a pointlet, Z, which
is the arrested primordium of the lamina. Im scales such as those shown in
Fig. 258, 2 there is observed to right and left of the pointlet a projection, and
this is the first indication of the stipules. These are absent from the lowest
scale-leaves because they proceeded from the transformation of the primordia
of foliage-leaves whose leaf-base had not yet laid down stipules. The later
formed primordia standing higher up undergo the transformation only at a later
stage, when the stipules are already laid down and more or less developed.
Fig. 258, 3 shows a bud-scale in which this is the case. The leaf-base which
forms the bud-scale is here well developed, and branches proceed into the widened
Ges
388 TRANSFORMED LEAVES
leaf-base from the three vascular bundles traversing it. These branches are not
found in the slightly developed leaf-base of the foliage-leaf, a fact which is of
fundamental importance as it shows that the appearance of vascular bundles
is always of secondary importance in morphological questions. Where an organ
is developed so as to have a somewhat extensive outline vascular bundles appear
in it in correspondence therewith. It would be a mistake, yet it is often made, to
endeavour to base a conclusion regarding the nature of an organ upon its vascular
bundles. In Fig. 258, 4 a young foliage-leaf whose stalk is still short is shown
for the sake of comparison with the bud-scale. Three vascular bundles are
observed passing into the leaf-base from the stem and from each of the lateral
ones a branch passes over into the stipules; the cross-stroke indicates the limit
of the portion which is represented in the bud-scale.
EVIDENCE FROM TRANSITION-FORMS. In those woody plants which possess
terminal buds the transition from the foliage-leaves to the kataphylls (bud-scales)
is commonly a gradual one. In Aesculus Hippocastanum, for example, the lamina
of the last leaf before the scaly bud is often reduced to one leaflet and the
rudiments of two others. ‘The same is the case in Juglans regia’, and in species
of Acer. In Prunus Padus also the laminar primordium is greater, the leaf-base
smaller, in the first bud-scales than in those which follow. I mention these
circumstances here because they appear in like manner in plants which have
no bud-scales, such as species of Lycopodium, Juniperus, and Araucaria. Also
in the broad-leaved trees which have been mentioned the leaves which are formed
towards the end of the vegetative period are smaller, and resemble in this way the
middle form between foliage leaves and bud-scales. We may assert that originally
all plants possessed no bud-scales, but arrested or degraded foliage-leaves only
appeared as the vigour of vegetation decreased, and that by a very simple process
of growth the bud-scales took origin from these arrested forms. As a matter of
fact we have seen a thoroughly illustrative case in Talisia princeps ?.
EVIDENCE FROM EXPERIMENT. That the bud-scales have proceeded from
the primordia of foliage-leaves is proved not only by a comparison of the history
of development but also by experiment. It is possible to cause the primordia
which in the normal course of development would develop into bud-scales to
grow into foliage-leaves. This takes place if one causes a bud which has been
laid down and which would normally shoot in a succeeding year, to develop in
the same year as that in which it is formed, at the time when the bud-scales are
still at the stage of inception. This may be done by removing the leaves of
the apex from a young shoot. The lateral buds are then induced to shoot out
and do not form scale-leaves but only foliage-leaves with complete well-developed
lamina and leaf-stalk as well as a leaf-base which is exactly like that of the
ordinary foliage-leaf*.
Middle stages between foliage-leaves and kataphylls are not wanting. They
are shown in Fig. 258, 5 and 6. Fig. 258, 6 shows a broad leaf-base with
* See for further details Goebel, Beitrage zur Morphologie und Physiologie des Blattes, in
Botanische Zeitung, xxxviii (1880), p. 775.
2 See p. 385, Fig. 257. 3 See Goebel, op. cit., for details.
KATAPHYLLS 389
small stipules, s¢, no leaf-stalk, and a normal although very small leaf-lamina.
Fig. 258, 5 approaches much more a normal foliage-leaf, from which it differs
mainly by the great development of the leaf-base. These two leaves would in
undisturbed vegetation have formed small bud-scales as in Fig. 258, 1. They
were caused to develop into foliage-leaves at a time when the primordium of
the foliage-leaf had only begun to develop and to form itself into a bud-scale
by widening of its leaf-base; a relationship which if once started cannot be
reversed but through the increased addition of food-material which the shooting-
out of the bud brings about, must go on still increasing. The same is the case
in the leaf shown in Fig. 258, 6, where the leaf-base resembles entirely the bud-
scale in Fig. 258, 3, although this was one of the wfpermost bud-scales of a
normally elongated shoot, whilst the leaf in Fig. 258, 6 was the Jowermost leaf
of a bud which had been artificially forced into elongation. The causes of the
configuration must indeed be considered to be the same in both cases. The
first bud-scales are laid down very early, about the beginning of April, at a time
when the reserve-material is chiefly required for processes of growth which find
their expression in the shooting-out of the bud completely laid down in the
preceding year. The bud-scales which arise later and the foliage-leaves which
they invest are laid down at a time when the unfolded foliage-leaves of the shoot
to which they belong are still doing assimilation-work. Of course this circum-
stance is only ove fact of importance which has to be considered in the
investigation of the configuration-relationships in question. It is no explanation
of them.
The features which have been described in the case of Prunus Padus are
observable also in other plants, for example in Aesculus and Acer, and also in
plants whose bud-scales are formed from the stipules of arrested foliage-leaves, such
as Quercus, Fagus, and others.
Monocotyledones. In Monocotyledones also we find frequently kataphylls
and transitions from them to foliage-leaves. On such intermediate forms we
observe the lamina reduced and the leaf-base developed—the leaf-base being very
strong on the chief shoots of the Bambuseae which send up giant epigeous turios
upon which kataphylls alone are produced at first. In many cases the lamina
is altogether wanting. The kataphyll has developed into a sheath before any
differentiation of the lamina and the leaf-base had taken place. ‘This subject
will be referred to again, when speaking of the hypsophylls, which arise in the
same way as do the kataphylls, indeed the only distinction between the two is
their place in the plant’s construction.
3. HYPSOPHYLLS.
We owe the term hypsophyll to Schimper. Originally the distinguished,
besides the foliage-leaves of the plant, the forms of sheathing-leaves in which
1 Schimper, C. F., Description du Symphytum Zeyheri, et de deux espéces voisines précédemment
connues, in Bull. Sci. Nat. Férussac, xxi (1830), p. 442; id., in Verhandlungen der schweizerischen
naturforschenden Gesellschaft zu Solothurn, 1836, p. 113.
390 TRANSFORMED LEAVES
there is no leaf-lamina, and which are found upon the lower regions of the
shoots of a plant and upon the upper regions. The latter leaves he subse-
quently! called the hypsophylls ; the former are the kataphylls. Schimper’s
terms were established mainly through the influence of A. Braun, who gives
the following account of the hypsophylls*. ‘To the formation of the
hypsophylls belong the leaves of the involucre and the common calyx of
the inflorescence, the bracts, the bracteoles or prophylls,the glumes and paleae
which accompany the flowers. They are like kataphylls in that the stalk
and lamina as well as the green colour are almost or entirely absent. They
are distinguished from kataphylls chiefly by the narrowness of their base,
their more delicate structure, their rapid formation and equally rapid decay.’
This explanation does not fit a very large number of the structures
which belong to this category. It is based like that of the kataphylls upon
the conception of construction founded by the idealistic morphology and
not upon the real processes of development, and it leaves out of considera-
tion entirely the relationships of the hypsophylls to the foliage-leaves.
I have shown ? that the hypsophylls, like the kataphylls, are developed out
of the primordia of foliage-leaves, and that they may come into existence
in different ways, and of this some examples will be mentioned below.
It may be asked, is there any advantage in retaining Schimper’s
terminology ? The leaves have only this in common, that they occur in the
flower-region, whilst in respect of their function they have very different
significance. Sometimes they are still assimilation-organs ; usually they
are protective organs for the flower-buds or inflorescence ; not infrequently
they act as a flag, or they may combine this with protection ; sometimes
their service is claimed for the distribution of the seeds or of the fruits, as
in Tilia ; whilst again they may be greatly reduced or even aborted. It has
always appeared to me of use to have a common name for the leaves which
occur in the flower-region, and which do not belong to the flower itself,
although the only common link between them may be that of their position.
It is also probable that between the formation of the flower and the con-
figuration of the hypsophylls, which deviates from the typical form of the
foliage-leaf, there exists a correlative connexion, because often, although not
' See also Wydler, Morphologische Mittheilungen, in Botanische Zeitung, ii (1844), p. 626.
* A. Braun, On the Phenomenon of Rejuvenescence in Nature. English Translation by A. Henfrey,
published by the Ray Society, 1853, p. 63.
* Goebel, Beitrage zur Morphologie und Physiologie des Blattes, in Botanische Zeitung, xxxviii
(1880); id., Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), p. 250. The objections which E. Schmidt, Beitrag zur Kenntniss der
Hochblatter, as Wissenschaftliche Beilage zum Programm der Friedrichs-Werder’schen Oberrealschule
in Berlin, Ostern 1889, has raised against single points in my explanation are only of a formal
nature. Schmidt starts from the assumption that I have declared the differentiation of the primordial
leaf into leaf-base and upper leaf to be a wszversal phenomenon. This is an error. I have shown
that in wasegmented leaves also the development is simplified. See Goebel, Vergleichende Entwick-
lungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der Botanik, iii (1884), p. 215.
HYPSOPHYLLS ~— 391
always, if the inflorescence grows further vegetatively the ordinary leaf-form
again appears. The configuration of the hypsophylls therefore has a causal
connexion with the place of their occurrence, and the name, upon this
ground, should be maintained. The causal relationships are here, as in most
other cases, at the present time obscure.
There are, however, two questions which we can answer :—
How do the hypsophylls arise? Does the law hold for them that
the course of development of all leaves of a plant is originally the same,
but that at different stages of development different paths may be assumed ?
In what relation do configuration and function stand in them ?
A. THE DEVELOPMENT OF HYPSOPHYLLS.
We may first of all note that on the one hand graded transitions are
found in many plants between foliage-leaves and hypsophylls, and also it is
impossible to draw any sharp limit between foliage-leaves and hypsophylls
in many cases, although the hypsophylls are very different from the foliage-
leaves. On the other hand, the difference between foliage-leaves and hyp-
sophylls may sometimes be very great, whilst in other cases it sinks to
nothing. This is the more the case the less segmented the typical leaves
are. In Epilobium parvifolium and in Edraianthus Pumilio, a campanula-
ceous plant with linear leaves, the hypsophylls differ little from the foliage-
leaves ; they are only smaller, and those which stand further up upon the
stem and have to protect the flowers in their bud-state have a somewhat
broader leaf-base. In many Monocotyledones also, for example Cypripe-
dium Calceolus, the bracts of the flowers are only distinguished from the
foliage-leaves by being shorter and smaller. But even in simple leaf-forms
amongst the hypsophylls there may be far-reaching transformation. Thus
in Rhinanthus major the foliage-leaves show no evident distinction between
leaf-base and lamina externally, nevertheless such differences exist in the
course of the vascular bundles. The leaf has three vascular bundles, and
the middle one runs as a strong mid-vein from which the lateral nerves
pass out into the depressions between the leaf-teeth (Fig. 259, /). The two
lateral bundles extend only into the lower third of the foliage-leaf, bend then
into one of the marginal depressions (Fig. 259, /, a), and send off twigs
which pass out into the other marginal depressions. If we designate the
upper portion of the leaf, that, namely, which lies above a in Fig. 259, as the
lamina, although it is only distinguished from the lower part by this distri-
bution of the vascular bundles, and if we call the lower portion the leaf-
sheath, then we should find that amongst the hypsophylls the lamina
becomes shortened and the sheath becomes wider (Fig. 259, // and ///),
evidently because it is required for the better protection of the flower-bud.
In Fig. 259, JV and V, the lamina is reduced to a very small portion,
barely one-fifth or one-sixth of the whole length of the leaf, the sheath which
302 TRANSFORMED LEAVES
serves. specially as a flag-apparatus has a white colour, and upon it the
lamina appears at last as only a small green tip.
On plants with stalked and branched, that is to say, segmented leaves,
we observe the following differences usually in the formation of the hypso-
phylls as compared with the foliage-leaves :
(a) Diminution and final disappearance of the leaf-stalks. Teleo-
logically this is easily understandable because :—
1. The hypsophylls are developed in the upper region of the shoot
above all the other leaves.
2. Owing to the diminution of the leaf-surface which will be presently
described, the necessity of a leaf-stalk either as a mechanical support
or for the placing of
the leaf in a favour-
able lie in relation to
light is less than in
the typical foliage-
leaf.
3. The suppres-
sion of the leaf-stalk
enables the _leaf-
lamina more readily
Aa ASS AD BEX to protect the axil-
Wee NZ VE Wipes lary bud.
i (6) Diminution
of the leaf - surface
Fic. 259. Rhinanthus major. Transition, in the sequence 7 to V, from . , yi
foliage-leaf to hypsophyll. a@ indicates the upper limit of the leaf-base. along with a simpli
fication of its seg-
mentation. The work of assimilation is but slightly or not at all per-
formed by hypsophylls.
(c) The widening and often elongation of the leaf-base. This takes place
because its protective function is the chief one.
We find in the development of hypsophylls the same variety of pro-
cesses as in the formation of the kataphylls :—
A. HYPSOPHYLLS FORMED BY THE WHOLE LEAF-PRIMORDIUM. The
hypsophylls are produced by transformation of the leaf-lamina or of the
whole primordium of the leaf in leaves where there is no marked difference
between lamina and sheath. We find illustrations of this in cases where
the hypsophylls are but little different from the foliage-leaves. In Caltha
palustris, for example, the hypsophylls have usually a shorter stalk than
have the foliage-leaves, and in the uppermost hypsophylls the stalk may be
wanting altogether. Apart from the fact that the lamina is smaller than
is that of foliage-leaves, such hypsophylls resemble foliage-leaves in every
respect. From a simplification of this kind there are all transitions to the
HYPSOPHYLIES 393
most characteristic hypsophyils. In Epilobium angustifolium, for example,
the lowermost flowers of the inflorescence stand in the axils of ordinary
foliage-leaves, and the higher one goes the smaller become the bract-leaves,
their breadth sinking to about half a millimeter, and they consist then only
of a midrib and a narrow green wing upon each side of it. Circaea inter-
media, a member of the same family, has all its bracts in the form of
delicate scales which have no vascular bundle, and they form a transition
to the complete arrest of the hypsophylls which will be mentioned below.
In the origin of the hypsophylls we have to deal with an arresz in the
development of the primordium of the foliage-leaf; the extent of this
varies, reaching sometimes complete suppression, and it always begins with
a simplification of the configuration of the leaf.
In some plants, for example Ranunculus acris, Saxifraga rotundifolia,
Heuchera Menziesii, and others, there is a peculiarity, the biological sig-
nificance of which appears to me to be:still doubtful:—The hypsophylls,
at least a portion of them, are relatively more divided than are the foliage-
leaves, whilst commonly the converse occurs. The recognized features of
the formation of hypsophylls are visible in these cases, namely, shortening
or suppression of the leaf-stalk, diminution of the leaf-surface, and to this
end deeper division of the leaf-surface, but the causes of this divergent
configuration are unknown, although a functional as well as a developmental
relationship appears to exist. So far as I know, the occurrence of such
divided hypsophylls is limited to many-flowered inflorescences, which even
in the bud-condition have a somewhat elongated conformation. The long
lobes of the lower hypsophylls lie against the outside of the inflorescence,
and thus form an envelope about it which resembles an envelope
formed out of many narrow separate hypsophylls of which we have an
illustration in the involucre of the Compositae. The formation of these
lobes would be in harmony with the explanation of the hypsophylls as
arrested states of the foliage-leaves if, in the development of the foliage-
leaves, the formation of the lobes preceded the development of the lamina.
We have already seen some cases of this kind. If, for example, the young
leaf of Benincasa cerifera (Fig. 201, 7) remained at this developmental
stage, with elongation of the three upper leaf-lobes, and no further develop-
ment of the lamina took place, a deeply ‘divided’ hypsophyll would be
formed which apparently would deviate far from the foliage-leaf, but would
be only, after all, a product of the arrest of this. Whether this is true of all
cases of hypsophylls which are more deeply divided than are the foliage-
leaves of the same plant requires further investigation. In Heuchera
Menziesii the leaf-development conforms with the theoretical derivation
above given. In its hypsophylls there are fewer lobes laid down than in
the foliage-leaves, but these experience a greater enlargement, especially
elongation. ,
394
B. HYPSOPHYLLS FORMED BY THE STIPULES.
consist of stipules whose leaf-lamina is arrested.
Fic. 260. Mulgedium macrophyllum. Transition, in
the sequence Z to JV, from foliage-leaf to hypsophyll.
Reduced.
TRANSFORMED LEAVES
Hypsophylls may
We find these in the in-
florescence of Humulus Lupulus for
example. The leaves in the axil of
which the catkins of female flowers
arise, show from below upwards a
gradual diminution of the lamina,
until in the uppermost portion of
the inflorescence this is arrested at
so early a period that it apparently
no longer exists. We may, however,
cause its evolution artificially by
removing, for example, the leaves
from the shoot, and occasionally it
may develop without such external
interference because its primordium
is always visible between the sti-
pules. A corresponding case is only
known to me in the inflorescence of
AmiciaZygomeris where thestipules
of the bract-leaves of the flowers are
developed as protective organs whilst
the lamina itself is arrested.
C. HYPSOPHYLLS FORMED
BY THE LEAF-BASE OR MAINLY
so. Where this happens the seg-
mentation of the leaf-primordium
into leaf-base and upper leaf pro-
ceeds gradually, and finally the leaf-
primordium without reaching the
stage of expansion as a leaf-lamina
becomes shéath-like. This process
is found especially in plants with
well-developed leaf-base. In Rhi-
nanthus we have, as has been above
shown, an analogous example in the
case of leaves which are very slightly
segmented. A few examples from
plants with highly segmented leaves
must now be cited :—
Mulgedium macrophyllum. Mulgedium macrophyllum, represented
in Fig. 260, 7, possesses at first a foliage-leaf whose lamina is plainly de-
limited from the leaf-stalk, and the latter is ‘winged’ in its upper part.
|
|
)
|
AYPSOPHYEES 395
The leaf in Fig. 260, // is one from the lower region of the hypsophylls,
and in it the leaf-stalk is scarcely indicated, but the leaf-base is enlarged
evidently in correspondence with its function of protecting the inflorescence-
bud which is thicker than an ordinary foliage-leaf-bud. The leaf in Fig.
260, J/7 has the limit between leaf-lamina and leaf-base still marked
by a deep constriction. No leaf-stalk is present. Fig. 260, 7V shows
a leaf in which the limit between lamina and leaf-base is scarcely at all
shown, and in leaves standing higher up the distinction disappears alto-
gether. This transformation is easily understandable when the history of
the development of the leaf is followed. All these leaf-forms resemble one
another in their primordial stage, and the hypsophylls arise by the arrest of
Cha
ith
ss
Sabon
Fic. 261.__ Astrantia major. Hypsophylls of different degrees of configuration, showing a reduction series
from Zto YZ. Chlorophyllous parts are shaded darker.
the primordium of the foliage-leaf accompanied by an increase of its leaf-
base at an earlier or later stage of its development.
Astrantia major. Astrantia major shows similar features (Fig. 261).
If we pass upwards from the region of the stalked foliage-leaves we observe
that the leaf-stalk and the leaf-surface gradually become smaller. The
leaf-stalk gradually vanishes and the leaf-lamina sits directly upon a widened
leaf-base (Fig. 261, /). The sheathing leaf-base retains at first at the margin
a whitish colour, and the differentiation of the lamina decreases step by
step (Fig. 261, //, Z/7). The white colour of the leaf-base becomes more
conspicuous as we pass upwards, and the lamina can ultimately only be
recognized as a dark green tip upon the top of the otherwise undifferentiated
hypsophyll (Fig. 261, 7V). The hypsophylls (Fig. 261, V7) which form
the zzvolucre have in contrast with the preceding ones a narrow base, and
396 TRANSFORMED LEAVES
this is connected with their ring-like arrangement around the axis: here the
protective function is taken over by numerous small leaves, whilst it is else-
where performed by single relatively large leaves.
The processes in the history of development which led to the formation
of hypsophylls can be readily understood from what we know of the
development of kataphylls from foliage-leaves, and therefore I do not
require here to set them forth in detail. We have to deal with an
external ¢rvansformation of the primordium of the foliage-leaf; it is often
marked by transition-forms, and it may begin sometimes later and some-
times earlier, even before the appearance of any differentiation of the leaf-
primordium, and then we obtain a sheath-like structure without any indication
ofa lamina. That we have really to deal with a structure homologous with
the leaf-sheath is shown by its whole nature, especially often by the course
of the vascular bundles, and by comparison with transition-forms. The
course of the bundles in the hypsophylls of Dicotyledones recalls frequently
that in the ordinary monocotylous leaves (see Fig. 261, ///). That the
whole as yet unsegmented leaf-primordium can be made use of in a con-
struction to which otherwise only a part is devoted, need not surprise us
when we assume Sach’s hypothesis of ‘ material and form. The difference
between lamina and sheath then appears to depend upon definite material
processes—upon the appearance of definite ‘growth-enzymes, or whatever
one chooses to call the unknown material used in the formation of the
organs. Let us name the material which is necessary for the formation of
the lamina x, and that for the leaf-sheath (leaf-base) y, then in the primordium
of the foliage-leaf + + must appear, and the same will happen in many
hypsophylls, but in many only y will be present.
HYPSOPHYLLS IN MONOCOTYLEDONES. The hypsophylls in many
Monocotyledones may be specially mentioned here, for they also show
transition-forms. In Carludovica plicata the spadix is surrounded by
a number of hypsophylls. In one case which was investigated the outermost
of these had still an evident lamina, smaller indeed than that of the
foliage-leaf, but it possessed a stalk, and this was shorter than that of
the foliage-leaf. The following hypsophyll had no stalk but only the
rudiment of a lamina, with the ptyxis characteristic of the genus. In the
third the lamina was still more reduced, and finally the hypsophylls showed
only a sheath without any laminar portion. The paleae and glumes of the
grasses belong also here, and the awn which occurs in many of them has
for long been considered rightly as a rudimentary lamina.
B. RELATIONSHIPS BETWEEN CONFIGURATION AND FUNCTION
IN HYPSOPHYLLS.
It has been already shown several times that we can recognize, usually
very easily, the relationships between the form and the function of the
HYPSOPHYLLS 307
hypsophyl!, because the leaf-base from which it is developed serves habitually
as a protection to the bud, and thus directly points to the chief function
of the hypsophyll.
The recognition of the relationships is no less easy in cases of the arrest
of hypsophylls'. Let us in the first place confine our attention to the
bracts. We may say of them that wherever these are arrested the flowers
have some other method of protection, either by being placed close together
or by special protective arrangements. We need only recall here the
behaviour of most Cruciferae, many Umbelliferae and Compositae, in which
the bracts of the flowers are arrested, because the whole inflorescence is
protected otherwise in the bud-condition, either by special envelopes of
hypsophylls, by the sheathing portion of the foliage-leaves, or in other
ways.
Many arrested hypsophylls exhibit the peculiar phenomenon of division
about which I have before spoken”. Some examples, however, may be
mentioned :—
Lolium. The grass-spikelets are enveloped by two glumes. In Lolium
these are developed upon the terminal free spikelet, but in the lateral
spikelets, which lie with one side in a depression of the axis of inflorescence,
the glume next this axis is absent, because it would be superfluous as a pro-
tective organ*®. In Lolium temulentum, especially in the lower flowers of
the inflorescence, it is frequently developed, seldom as an entire leaf but
usually replaced by two small leaflets, which are separated from one another
by a broad intervening space. These are connected with the undivided
glume by transitional forms of glumes with a deep indentation. The like
is found upon the axis of inflorescence of Typha.
Xeranthemum macrophyllum. Division of the hypsophylls is also
seen in the Compositae. Thus in Xeranthemum macrophyllum* the hyp-
sophylls of the involucre pass, as in other cases, quite gradually into the
bracts of the flowers, the outer bracts are undivided, those further in show
a tendency to divide into two, many being split almost to the middle,
whilst others are split nearly to the base, so that two apparently completely
independent leaves stand before each flower. Each one of these may again
divide, and so instead of one bract there may be a number of small linear,
frequently almost bristle-like, leaf-lobes.
We have here, as it appears to me, the beginning of a new formation.
In the fosztion of the hypsophylls in process of arrest appear bristles which
subsequently act as substitutes for the pappus in the scattering of the fruit,
1 See Nauhaus, Die Verkiimmerung der Hochblatter. Inaug. Dissertation, Gottingen, 187o.
* See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884), p. 299. $ See Part I, p. 57.
* See Warming, Die Bliithe der Compositen, in Hanstein’s Botanische Abhandlungen, iii, 2
(1876).
398 TRANSFORMED LEAVES
and these bristles, as in other Cynareae, such as Cirsium, Carduus, and
Centaurea, cover the receptacle in great number and without transition to
bracts. I put the process thus :—In hypsophylls in process of arrest there
is uniform growth, and to a certain extent a ‘ discipline’ amongst the cells
no longer exists; therefore single parts grow out and these may appear
very early, even on the shoot-axis itself single cell-groups may shoot out
instead of the whole primordium of the hypsophyll. Where now instead of
single parts of a hypsophyll we see ‘ bristle-scales,’ a gualitative change has
taken place which may have begun with a ¢ransformation of the single parts
of the hypsophyll, but I see no ground even then, if the hypsophyll no
longer exists, for keeping its ghost hovering above, or rather below, these
bristle-scales ; to assume that it still exists is an ‘idea, and this ‘idea’ is
stuck somewhere in the axis and only allows the bristle-scales to appear.
Such ‘ideas, however, are to be found in botanical literature even
recent !
4. STORAGE-LEAVES.
The function of storing reserve-material can be undertaken along with
the ordinary function of the foliage-leaves. We find this, for example, in
the leaves of succulent plants which store water as reserve-material in their
foliage-leaves. Other reserve-materials may be similarly stored. Andro-
sace sarmentosa (Fig. 305) forms towards the end of the vegetative period
leaf-rosettes of which the single leaves are thicker and shorter than the
foliage-leaves of the active period of vegetation. Pinguicula caudata and
others behave in like manner. They have green epigeous leaf-tubers. In
the winter-buds of Utricularia and Myriophyllum processes which are
fundamentally the same are to be observed. These leaves do little work as
assimilating organs, and do not develop further in the shooting out of the
bud, but give up their reserve-material into the new shoot.
The two functions of assimilation and storage may also be taken on at
different times by a leaf. Dicentra Cucullaria’ forms tubers on its rhizome.
These are the bases of leaves which are swollen as reservoirs of reserve-food,
and transformation takes place partly at the base of ordinary foliage-leaves,
partly at the base of leaves whose lamina is arrested and which we can
consider as kataphylls acting as reservoirs of reserve-food. Here we have
a case showing that change of function and also change of form may take
place sometimes at a relatively late period of development, sometimes at an
early period*. Similar cases are found amongst Monocotyledones. For
example, the outer scale-leaves of a bulb of Lilium candidum are the basal
+ See Holm, Notes upon Uvularia, Oakeria, Diclytra, and Krigia, in Bulletin of the Torrey
Botanical Club, xviii (1891), p. 5.
? See also Part I, p. 9, and the case of Oxalis rusciformis described on p. 354.
STORAGE-LEAVES 399
portions of foliage-leaves whose lamina has fallen off, the inner ones are
Rataphylls such as are found elsewhere commonly in scaly bulbs, and they
are leaf-structures in which the transformation has taken place at a much
earlier period.
There is no necessity to describe here the different features of storage-
leaves, which from an organographical standpoint are usually very
simple. There is, however, one case of special interest to which I must
refer :—
Lathraea Squamaria. Lathraea Squamaria is a root-parasite, hypogeous
except in its inflorescence. Its rhizomes are
provided with thick fleshy decussate scales,
which serve as reservoirs of reserve-material
and have a peculiar structure! (Fig. 262).
Externally they appear as simple scales, but
really the margin of the scale is not the true
leaf-margin, nor is its point the true leaf-tip.
The upper side of the leaf is so curved down-
wards that a cavity is formed which only com-
municates with the outside by a narrow slit
at its base, and from it canal-like extensions
extend deeper into the fleshy leaf-tissue.
Tozzia alpina. The allied genus Tozzia
has simpler scale-leaves ; besides it possesses
foliage-leaves. Its scale-leaves are therefore
of special interest because they show to a
certain extent the structure ofthose ofLathraea —_ Fic. 262. Lathraea Squamaria. Upper
ina more rudimentary form. In its scale-leaves esi ees genes Fre Rees
> = Si, apparent tip; 7, entrance to leaf-pit £.
the leaf-margin alone is bent over, and only Lower figure: young kataphyll in surface.
a . 5 : : section showing the pits. Magnified.
in the protective cavity which is thus made 5
are water-glands found (Figs. 263, 264, 265). We can easily imagine how
the special form of leaf of Lathraea has sprung from the simple structure of
Tozzia, and if this conformation is the result of a biological need the case in
Lathraea where scale-leaves alone are present, satisfies higher claims than
that of Tozzia, which subsequently sends a shoot bearing foliage-leaves above
the soil. What now is the meaning of this peculiar formation of leaves? The
object is the protection of the water-glands which are found in large num-
bers in these hypogeous leaf-organs, and the activity of which replaces
partially that of transpiration. These water-glands are by the form of the
* It has been frequently described, but I do not cite the literature, as the plant is so widely spread.
I will only say that Irmisch, Zur Morphologie der monokotylischen Knollen- und Zwiebelgewachse,
Berlin, 1850, p. 188, was the first who rightly described the morphology of the leaf of Lathraea,
and refer to Stenzel, Uber die Blatter des Schuppenwurz (Lathraea Squamaria), in Botanische
Zeitung, xxix (1871), p. 241.
400 TRANSFORMED LEAVES
leaf brought into protected cavities. It is possible that, especially in the
juvenile stages, these cavities serve also for aeration }.
5. COTYLEDONS?
The cotyledons demand a special description here, as in more than one
way they exhibit peculiarities which
go so far as to have led some authors
to doubt their leaf-nature. They are
distinguished by their position. We
designate as cotyledon the first leaf or
the first leaves which appear upon the
embryo, and they do not, as do the
later leaves *, proceed out of the vege-
tative point of a shoot, but proceed from
the unsegmented primordium of the
Fic. 263. Tozzia alpina. Storage-kataphyll of embryo. Leitgeb has established the
the rhizome. To the left: seen from above. To
the right: seen from below so as to exhibit the use of the term ‘ cotyledon “also for
revolute margin of the leaf.
the one or two leaves of the embryo
of Pteridophyta, which arise independently of the vegetative point of the shoot.
A. PTERIDOPHYTA.
The cotyledons of the Pteridophyta require hardly any special descrip-
tion. They are so like the primary leaves* that they really may be con-
sidered as the first members of these. They are without exception arrested
Sorms of foliage-leaves, and
they show this more clearly
than do the cotyledons of
Spermophyta, inasmuch as
they do not discharge the
Fic. 264. Tozzia alpina. Kataphyll in transverse section. Water- function which is so com-
glands are seen within the revolute margins of the leaf. 2
mon in the Spermophyta
of suctorial organs. This work is in the Pteridophyta taken on by the
‘foot’ of the embryo. They also do not act as storage-organs. Their
1 See Goebel, Morphologische und biologische Bemerkungen: 7. Uber die biologische Bedeutung
der Blatthohlen bei Tozzia und Lathraea, in Flora, lxxxiii (1897), p. 444; Haberlandt, Zur Kenntniss
der Hydathoden, in Pringsheim’s Jahrbiicher, xxx (1897), p. 511. Darwin observed the exudation
of water in Lathraea.
* Du Petit Thouars proposed many years ago to replace the inexpressive term ‘cotyledon’ by the
term ‘protophyll.’ No one seems to have supported him in this excepting Turpin (see Annales
des sciences naturelles, sér. I, xxiii (1831), p. Io footnote). The name therefore remains, and is
crystallized in the group-names ‘ Monocotyledones’ and ‘ Dicotyledones.’ The leafy cotyledons
developed in germination have also been called ‘feuilles seminales’ by, for instance, A. P. De
Candolle.
* See, however, the development of the embryo in Monocotyledones.
* See Part I, p. 152, Fig. 93.
COTYLEDONS 401
resemblance to the other foliage-leaves is therefore very evident, because
they have no other function but that of these. Only in the floating forms of
Salvinia and Azolla has the cotyledon different conformation from the first
foliage-leaves. It is peltate in Salvinia and turbinate in Azolla, so that
an air-bubble can be retained upon the deepened upper side‘, and the
construction of the cotyledon makes more certain the normal floating
position of the embryo upon the surface of the water.
B. SPERMOPHYTA.
The embryo of the Spermophyta occupies quite a different position
from that of the Pteridophyta. It submits in the seed to an interruption
in its development, except in the case
of viviparous plants, and is during this
invested by stout envelopes. The di-
vergence in form of the cotyledon from
that of the foliage-leaves is usually
very great. The question is, how can
we explain morphologically and _ bio-
logically this divergence? Can we
furnish utilitarian explanations and
satisfactory causes? With respect to
explanations We TSE: forget that Fic. 265. Tozzia alpina. Upper part of a kata-
even in the foliage-leaves the con-_ phyll in transverse section. The water-glands are
> shown. Magnified.
nexion between configuration and life-
relationships are still obscure, and therefore in the case of the cotyledons
also we must use teleological considerations with caution. As regards the
causes, it is evident that there are many factors which have to be considered
beyond those which affect the foliage-leaves, and this, apart from what is
involved in inclusion within the seed and the probably consequent relation-
ships of correlation.
Cotyledons may serve as—
1. Protective Structures. They act in this way to the stem-bud, not
only during its rest in the bud but frequently also during the germination
(Fig. 266). In this connexion we have in many dicotylous plants the forma-
tion of a long cotylar sheath, at the base of which sits a stem-bud;
regarding this we shall say no more here, but the many remarkable and
somewhat similar relationships of monocotylous embryos will be discussed
below.
2. Reservoirs of Reserve-material. In many cases.
3. Haustoria—for the absorption of the endosperm. In this connexion
it may be noted that there are only two genera of Spermophyta—Gnetum
1 See Goebel, Pflanzenbiologische Schilderungen, i (1889) and ii (1893).
GOEBEL I Dd
402
TRANSFORMED LEAVES
and Welwitschia—in which the suctorial organ is developed as an outgrowth
of the hypocotylar segment, independently of the cotyledons. In other
Fic. 266. Leucoden-
dron argenteum. Seed-
ling plant. Cj, cotyledon,
the other cotyledon has
been removed at line C».
The bud of the stem is
seen in a depression of
the base of the cotyledon.
Wh, root-collar, limit be-
tween hypocotyl and root.
cases where we have a suctorial organ the cotyledons
act as this, and in most cases within the seed-coat,
yet it sometimes happens that, in germination after the
embryo has left the seed-coat, a portion of the endo-
sperm is taken along with it and is used ozéstde the
seed. I found this, for example, in a species of Ster-
culia (Fig. 267) in Java, whose cotyledons are usually
separated by an internode.
4. Pzstons—to push the seedling deeper into the
soil in germination. This occurs especially in some
Monocotyledones, for example Phoenix, whose cotyle-
dons are positively geotropic. |
(1) Dicotyledones.
MORPHOLOGY OF THE COTYLEDONS. I shall
suppose that the external relationships of configura-
tion which are usually very simple are known; some
of the more interesting cases only will be noticed. The
first general question that arises is—Are the cotyledons
to be considered as structures swz generis, or are they
only developmental forms of foliage-leaves? The
answer is affirmative to the last question, and for the
following reasons :—
(a) Analogy with the Pteridophyta whose coty-
ledons, apart from their inception, resemble the primary
leaves.
(6) The fact that 2 many Spermophyta the cotyledons
vesemble the foliage-leaves. ‘Thus the single cotyledon
of Cyclamen resembles in form the foliage-leaves
(Fig. 268). Utricularia, Pinguicula, Viscum, Spergula,
all show the same features as do the exalbuminous
Monocotyledones hereafter mentioned. In many plants
which possess tubers, such as species of Corydalis,
Carum Bulbocastanum, Bunium petraeum, Aconitum
Anthora, and others, the cotyledons in the first year of
the seedling are the only assimilation-organs, but
usually they quickly die away—lasting only for a few
weeks in many plants, as in Claytonia perfoliata,
Nolana atriplicifolia, and others. We can easily understand that such
short-lived leaves will be more simply constructed than will be the ‘typical’
COTYLEDONS OF DICOTYLEDONES 403
foliage-leaves. In some annual plants! the cotyledons may persist until
flowering, as in Adonis aestivalis, Fumaria officinalis, Veronica hederae-
folia, Melampyrum pratense, Urtica urens, Euphorbia helioscopia ; but,
owing to their position at the base of the plant, they are unfavourably
placed for assimilation and can
do little in this way. The small
size of the cotyledons, compared
with the foliage-leaves, is a
matter of correlation’. We
observe that the cotyledons
are largest in plants like Strep-
tocarpus, in which the chief
shoot which commonly arises
between the cotyledons is sup-
pressed, and we may express
this otherwise by saying that Fic. 267. Sterculia sp. in Buitenzorg Garden. 1, portion
of embryo and endosperm in longitudinal section ; Cv, cotyle-
merece cotylerions ate Spe- fore. 4, these is tansveieé section. Leticting the came,
cially constructed to be like x 3
foliage-leaves, they precede in development the stem-bud. In many cases
also, if the stem-bud be removed, the cotyledons exhibit an increase in
size beyond the usual.
The simpler configuration of epigeous cotyledons
is thus easily understandable from the biological side.
There are transitions, however, between epigeous and
hypogeous cotyledons, and the fact that different species
of one genus may have epigeous and hypogeous coty-
ledons, for example Rhamnus Frangula and R. cath-
artica, Mercurialis perennis and M. annua, shows that
in the hypogeous cotyledons the functioning as assimi-
lation-organs has only been given up at a late period
in connexion with the deposition within them of reserve-
material, and that in consequence of this they no longer
reach the light.
The simplicity of the configuration ofthe cotyledons, ng x6g. Cyclamen
j ; 1 ersicum. Seedling
compared with the foliage-leaves, we may consider as a Pre as oF the
cotyledon is a haus-
phenomenon of arrest, as it is in the Pteridophyta. This (Ron the hypocotyl ss
arrest is usually persistent, but in many cases, as a few yyoucg.g’® * “er
examples will show, it is only temporary. These
temporary cases are especially interesting, because they throw light upon
the persistent forms, and establish directly the transition of the cotyledons
to the foliage-leaves.
? See Winkler, Uber die Keimblitter der deutschen Dicotylen, in Verhandlungen des botanischen
Vereins der Provinz Brandenburg, xvi (1874), p. 16. 2 See Part I, p. 206.
Dd2
404, TRANSFORMED LEAVES
(c) The existence of all stages of transition-forms between cotyledons
and foliage-leaves. Many cotyledons experience in the process of germina-
tion only an increase in size’, Others exhibit a change im configuration,
which in extreme cases like that of Streptocarpus polyanthus? and other
species, and also in Monophyllea, results in the formation of a massive
foliage-leaf, often over thirty centimeters long, whilst in the embryo it only
possessed a length of about half a millimeter. It need hardly be men-
tioned that this takes place by ‘intercalary’ growth, and we have here, as
in the case of Oenothera mentioned below, only an extreme illustration of
the fact ° that the leaf-apex in most Dicotyledones passes over into the per-
manent condition at an early period, whilst at its base continued growth
proceeds—it is the apex which appears first as the cotyledon. This
remarkable condition in Streptocarpus and other plants is connected with
the fact that in them the cotyledon is the ovly foliage-leaf, and therefore it
has a much longer period of life than usually is the case where the coty-
ledons rapidly die away and are replaced by foliage-leaves.
Even, however, in plants in which foliage-leaves appear later there are
not wanting examples of post-embryonal further development of the coty-
ledons. The Onagrarieae furnish some very instructive examples of this.
In this family * we find a varying behaviour of the cotyledons. In some
plants the cotyledons show the ordinary construction, they are small, with
entire margins and a feeble venation, for example in Epilobium angusti-
folium, Oenothera pumila, O. glauca, O. rosea. In others the cotyledons
show after germination further intercalary growth as it is seen in Strep-
tocarpus, and a portion of foliage-leaf is, as it were, intercalated in the
cotyledon, and carries at its end the original cotyledon; we find this,
and naturally in various degrees, in Clarkia pulchella, Oenothera stricta,
O. bistorta, O. macrantha, and others.
Oenothera bistorta. Let us take Oenothera bistorta as an example.
After the germination the cotyledons are sessile, and they have only a few
long glandular hairs especially at their base. Six days afterwards this base
is elongated into the form of a stalk. Fig. 269, I, shows a seedling eight
days old, and the cotyledons are seen in their surface-view but otherwise
unchanged. The new intercalated portion visible beneath them grows sub-
sequently into a narrow leaf-surface, provided with a mid-rib and a short
leaf-stalk (Fig. 269, II). In this condition it differs from the primary leaves
only by having at its tip the original cotyledon.
1 Compare, for example, Ampelopsis, Part I, p. 145.
* See Hielscher, Anatomie und Biologie der Gattung Streptocarpus, in Cohn’s Beitrage, iii (1879),
p. 1. As regards the cotyledons in germination, see specially Klebs, Beitrage zur Morphologie ‘und
3iologie der Keimung, in Untersuchungen aus dem botanischen Institut zu Tiibingen, i (1881-5),
p- 536. * See p. 308.
* See Lubbock, A Contribution to our Knowledge of Seedlings, London, 1892, i. p. 553-
COTYLEDONS OF DICOTYLEDONES 405
Oenothera shows that in one genus we may have partly persistent
partly temporary arrest of the development of the cotyledon, and we cannot
doubt from this as to the way in which the simpler construction of the
cotyledons, compared with the foliage-leaves, has come about.
THE FACTORS CAUSING THE CONFIGURATION OF COTYLEDONS.
It has been already shown that we must in the first instance consider in
respect of this the enclosure of the cotyledons in the seed; further, it is
probable that relationships of correlation operate here as they do so often.
A limit is put to the growth of the embryo by that of the embryo-sac in
seeheeen “Aner Lathe, I, younger, II, older seedling-plant. Cy, the original cotyledon ; /, the inter-
which it is enclosed, and the history of the development of the seed shows
that the growth of the embryo-sac is primary, that of the embryo itself is
secondary, and therefore we come to the question :—How far is the form
of the cotyledon dependent upon the relationships of space within the seed ?
We have relatively few investigations bearing upon this point. Hof-
meister 1 was the first who took up the question of the relationship of the
lie of the embryo to the space available for it in the embryo-sac. Lubbock *,
starting from the relationships in the matured seed, has endeavoured to
1 Hofmeister, Allgemeine Morphologie der Gewichse, Leipzig, 1868, i. p. 620.
2 Lubbock, A Contribution to our Knowledge of Seedlings, London, 18g2, i. p. 8.
406 TRANSFORMED LEAVES
bring the form of the cotyledons into relationship with the conditions of
space, and he has thereby arrived at certain suggestive interpretations
which, however, can only be placed upon a sound basis by investigation of
the history of development, because he has, for example in the Caryophylleae,
altogether overlooked the difference between endosperm and perisperm, and
it is clear that the conformation of the latter can exercise no influence upon
that of the embryo. The most important of Lubbock’s statements will be
noticed below, but here I may only remark that a consideration of the
mature seed shows that the space-relationships do not operate everywhere
directly in determining the form—for example, in embryos which nowhere
come into contact with the seed-coat. We should expect to find the
influence of such relationships therefore especially in seeds which have no
endosperm. Also if the history of development should show that the space-
relationships are not the direct causal factors of the configuration of the
cotyledons, one might nevertheless maintain that a relation exists between
them, as it might be that an original causal connexion existed, but that in
course of time its effects have become hereditary and therefore we have no
longer to deal with direct causal phenomena’. The resuits of investiga-
tions of the history of development bearing upon this question have been
published by Hegelmaier alone *. They show, for example, that in the
Geraniaceae, whose cotyledons are convolute * and from an early period
asymmetric the ptyxis begins in them at a time when the embryo lies still
free within the embryo-sac, and therefore when no considerations of pressure
are operative, and the asymmetric construction of the cotyledons cannot be
regarded as the effect of pressure. I must refer for details on the subject
to Hegelmaier’s exposition of it, and here I only quote some of Lubbock’s
results amongst the Dicotyledones :—
1. Narrow and broad cotyledons. In many cases the narrow cotyledons
correspond exactly with the form of the embryo-sac, for instance in Platanus
and the Chenopodiaceae‘. The broad ones may do the same, for example, in
Ruellia, Phaseolus, Quercus. This is not the case however, everywhere and
Lubbock, in speaking of the narrowness of the cotyledons in Galium saccharatum,
says that their form enables them to be more easily withdrawn from the hard
testa.
2. Asymmetric cotyledons. These are found in a number of Geraniaceae,
for example, Geranium pratense, G. cicutarium, G. Robertianum, species of Ero-
dium, in the Leguminosae, and in the Polygonaceae, for example Polygonum
1 See what is said Part I, p. 217.
2 Hegelmaier, Uber Orientirung des Keimes im Angiospermensamen, in Botanische Zeitung,
liii (1895), p. 143; id., Uber convolutive Cotyledonen, in Berichte der deutschen botanischen
Gesellschaft, xvii (1899), p. 121.
> See Part I, Fig. 67.
* Lubbock does not recognize the presence of perisperm in this family.
COTYLEDONS OF DICOTYLEDONES 407
Fagopyrum, P. emarginatum, and others. Lubbock refers the asymmetry of the
Geraniaceae to the folding within one another of the cotyledons. The smaller half
of each cotyledon is the inner one. But Hegelmaier’s investigations quoted above
show that the influence here is not a direct one. In Polygonum Fagopyrum 4, also,
the asymmetry of the cotyledons begins early at a time when their margins are
still far away from the seed-coat and the furthered lateral half, which may either
be the right or the left—using these words in a like sense for each cotyledon—
one is always involute and over-lapping whilst the smaller is always revolute
and overlapped. What takes
place in the Leguminosae re-
quires furtherinyestigation,at
any rate the asymmetric form
of the cotyledon corresponds
here with that of the seed.
3. Lobed and emar-
ginate cotyledons. The
emargination of the cotyle-
dons at their anterior end
corresponds in many cases
to the thickening of the
seed-coat, or it may be of
the fruit-wall, for instance, in
Quercus, Impatiens, Urtica.
In many Cruciferae, such as
Raphanus and Sinapis, the
terminal depression of the
cotyledon facilitates their
ptyxis*, and so also may
the lobing of the cotyledons 7 A
of Tilia (Fig. 270) facilitate Wisse Tilia parvifolia. Embryo dissected out of the seed.
their packing in the seed, as
Lubbock explains. But in my view we must also consider here that by the develop-
ment of the lobes the absorptive power of the cotyledons as haustoria is increased.
They have the somewhat hard endosperm to dissolve and to bring the material it
contains into the embryo. The case of Myristica fragrans shows that as a matter of
fact the division of cotyledons stands in relation to their haustorial function *. In this
plant the endosperm is, as is well known, zi nate, that is to say infoldings of the seed-
coat produce a brown marbling 'in it. The cotyledons of the somewhat small embryo
increase in germination considerably, divide in correspondence with the infoldings
of the seed-coat, and when dissected out appear to be lobed like a coronet. The
single lobes which have apical growth force themselves into the endosperm. It
* Lubbock, A Contribution to our Knowledge of Seedlings, London, 1892, i. p.134.
* With regard to Convolvulus and others, see Lubbock, op. cit.
* See Tschirch, Physiologische Studien iiber die Samen, insbesondere die Saugorgane derselben,
in Annales du Jardin botanique de Buitenzorg, ix (1891), p. 143.
408 TRANSFORMED LEAVES
is quite evident that here the lobes, which are only formed in germination, have
a relation to their function as suctorial organs. Similar cases will be described in
Monocotyledones.
(2) Monocotyledones '.
STAGES OF DIFFERENTIATION OF
COTYLEDON. The simplest case of the
cotylar configuration is to be found in
the embryos of exalbuminous Mono-
cotyledones. It has been stated above ”
that the leaf of Monocotyledones is usually
only differentiated into lamina and sheath,
and this we find also in the cotyledon, for
example in the Juncagineae, Butomeae,
Alismaceae, and elsewhere. The coty-
ledon becomes green, and does not differ
in form and structure essentially from the
first foliage-leaves, although its anatomical
differentiation is usually somewhat sim-
pler*. The lamina as in ordinary leaves
appears as the direct continuation of the
sheath. This degree of differentiation of
the cotyledon we may designate as the
first and most primitive *. We distinguish
in the cotyledon the /amzna and the sheath
which invests the but slightly developed
SS stem-bud.
\ From the first stage a second is dis-
tinguished by the further development of
Fic. 271. Dracaena indivisa. Seedling the sheath. There is now developed not
plant. The cotylar tip, which acts as a ‘
haustorium, and js enclosed in the seed in the only the lateral parts of the lamina, but
figure to the left, is marked by a dotted line in 2 r
the figure to the right of an older seedling. It more particularly there is also an out-
becomes more or less green. Natural size. :
growth upon the upper side of the primor-
dium of the leaf, such as we have seen in the development of many axillary
stipules and ligules ; and further the completely ensheathing sheath has grown
up at its base as an outgrowth, so that the stem-bud is surrounded by an
oblique upwardly directed ringwall formed by the cotyledon.
1 See Klebs, Beitrige zur Morphologie und Biologie der Keimung, in Untersuchungen aus dem
botanischen Institut zu Tiibingen, i (1881-5), p. 536. ? See p. 299.
* Anatomical details are given by Schlickum, Morphologischer und anatomischer Vergleich der
Kotyledonen und ersten Laubblatter der Keimpflanzen der Monokotylen, in Bibliotheca Botanica,
XxXxvV (1896).
* See Klebs, op. cit.; Tschirch, Physiologische Studien iiber die Samen, insbesondere die Saug-
organe derselben, in Annales du Jardin botanique de Buitenzorg, ix (1891); Celakovsky, Uber die
Homologien des Grasembryos, in Botanische Zeitung, lv (1897), p. 141.
EPIGEOUS COTYLEDONS OF MONOCOTYLEDONES 409
In the zext stage we see the sheath still more developed and further
separated from the upper part of the cotyledon which in some degree appears
as its appendage.
These three stages are connected, on the one hand, with the size which
the stem-bud reaches before or during the germination, and, on the other hand,
with the changes which the cotyledon passes through in losing gradually its
leaf-nature and finally becoming entirely a haustorium, functionally, but not
morphologically, resembling the suctorial organ of the embryo of Gnetum
and Welwitschia. The stronger development which the cotyledon as a
haustorium has already attained in the seed is connected, on the one hand,
with the richness of development of the endosperm, and,
on the other, with the relative rapidity with which the
process of germination has to be passed through. That
the cotylar sheath may take on, besides its protec-
tive work, other functions also, will be shown in the
examples cited below. It must be remembered, how-
ever, that there are many transitions between the
different types, and they are especially conditioned by
the varying strength of the claims upon the cotyledon
as a haustorium in endospermous seeds.
EPIGEOUS COTYLEDONS. Fic. 272. Seedling of
unknown monocotylous
i i i 1 lant (Allium sp.?). The
We shall consider in the first instance cases in Pim Gee A only
which the epigeous cotyledon becomes green. It then Bee nee paneodie
behaves as it does in seeds which have got no endo- green Shayne rem
sperm, only that its tip serves as a suctorial organ in Soe neha nak ea ae
varying degree, either temporary or permanent. In Pett of is Sgnre) which
Dracaena (Fig. 271) the end of the cotyledon remains
enclosed in the seed as a haustorium. [If it is set free from the seed-coat
it becomes green less intensively, no doubt, than the rest of the cotyledon,
from which it also differs in anatomical structure. Other Liliaceae, like
Allium and Hyacinthus, also Agave and other plants, behave in this manner.
The seedling represented in Fig. 272, which belonged to an unknown
monocotylous plant, probably a species of Allium, shows an interesting
case ':—The whole cotyledon is not devoted to the formation of a foliage-
leaf; its upper part, the thin portion on the right of the figure, the tip of
which functions as a suctorial organ, remains thin and thread-like and dies
away later, whilst the lower portion, the thicker portion on the left of the
figure, becomes an almost cylindric foliage-leaf, whose relatively short sheath
invests the stem-bud. It is very striking to note that the persistent part of
' The seedlings appeared in a pot in which Australian seeds were growing, but they all died off
early, and a certain determination of their affinity could not be made.
410 TRANSFORMED LEAVES
the cotyledon has grown out slightly beyond the thread-like transitory portion
from the point where they are joined in a knee-like bend. This outgrown
portion, directed downwards in the figure, forms subsequently the ‘tip’ of
the cotyledon, and acts as a boring-
organ; the thread-like portion, the
real upper part, appears in conse-
quence to be lateral.
HYPOGEOUS COTYLEDONS,
In hypogeous cotyledons the
qwhole cotylar lamina, excepting the
swollen haustorial tip, not infre-
quently develops into a thread-like
body like that in the embryo just
described, and it serves chiefly as a
conducting-path for the food-material
taken up by the haustorium ; at the
same time, by its great elongation, it
facilitates the changes of position of
the seedling plant.
The cotyledon is thus differen-
tiated into three parts of different
form and different function: — (1)
the haustorium, (2) the middle por-
tion, (3) the sheath.
These parts appear, for example,
in the seedling of Tradescantia
virginica, which is shown in Fig. 273,
III. The haustorium is still within
WS
i) .
Fic. 273. Tradescantia virginica. Seedling plant in three stagesI, II, III. Co, cotyledon; \S, cot lar sheath ;
M, middle portion; Z, first foliage-leaf; W’, first root; #, hypocotyl. In II the endosperm is enclosed in a dotted
line. Magnified 6. I and II after Gravis.
the seed-coat, MZ is the middle portion, and S is the sheath. The sheath
has, during the germination, grown out to a considerable extent, and has
elongated above its point of attachment to the middle portion ; it protects
' Klebs uses this term. There is no necessity for Schlickum’s later expression, ‘ conductor.’
COTYLEDON OF CYPERACEAE 41I
the stem-bud during its passage through the soil, and later it is ruptured.
The process of development of the sheath will be quite clear without further
remark if we consider the younger embryos. In the resting seed shown in
Fig. 273, I, the sheath, S, surrounding the stem-bud, is plainly visible on the
cotyledon; in the young seedling shown in Fig. 273, II, the sheath, .S, has
grown out a little beyond the point of its attachment to the middle portion,
M, which has elongated; in the older seedling shown in Fig. 273, III, the
sheath, .S, has elongated to a considerable extent, and is directed upwards in
a negatively geotropic manner.
In some cases the form of the cotyledon which acts as a haustorium cor-
responds evidently with the space-relation-
ships in the seed. This is seen in Alpinia
nutans?, where the cotyledon is two-lobed,
the lobes extending as two processes into
the sickle-like endosperm, as well asin Areca
Catechu, where the cotyledon, as in Myris-
tica, forms many lobe-like outgrowths which
penetrate between the folds of the ruminate
endosperm *.
COTYLEDON OF CYPERACEAE, The
development of the sheath in the direction
indicated above is especially well seen in
Cyperaceae. There are two cases :— _Fic. 274. Carex Grayana. Basal por-
5 tion of the endosperm enclosing the embryo,
(a) In some of them it takes place only __ in longitudinal section. Co, cotyledon ; 4,
during the germination, as is the case in abligne Geot Soul Tie cabaocaeoedel
Tradescantia. Beentae nen oF sede aay nome is
ante indicated by shading.
(4) In others it occurs earlier and zvzthan
the seed itself.
Carex. Carex may be taken as an example of the first case. The
embryo lies at the base of the endosperm. It is surrounded (Fig. 274) by
the many-layered nitrogenous-layer of this, and the flatly conical summit of
its turbinate cotyledon touches the copious starch-bearing portion of the
endosperm. The configuration of the cotyledon is from its lie and its function
as a suctorial organ—the upper part swells up in germination—easily under-
stood. The stem-bud on which the primordia of two leaves are visible (Fig. 275)
in the figure, is enclosed by the cotylar sheath, s s, the narrow slit of which
is almost closed. This sheath develops considerably in germination, and it
serves evidently, as in the grasses, as a protective investment to the stem-
bud during its boring through the soil ; subsequently it is burst at the apex
by the developing first leaves. The base of the cotyledon above the sheath
? Tschirch, Physiologische Studien iiber die Samen, insbesondere die Saugorgane derselben, in
Annales du Jardin botanique de Buitenzorg, ix (1891).
2 See the chapter upon the development of seeds.
412 TRANSFORMED LEAVES
develops into a very short middle portion. It is noteworthy and of
significance for the explanation of the formation of the organs in the embryo
of grasses, that between the point of attachment of the sheath and that of
the middle portion, a piece appears to be interpolated on the seedling so
that the sheath and the rest of the cotyledon are separated from one another
by an apparent internode (Fig. 275, Me). This piece is neither the hypocoty]
nor an zzzternode, but a greatly elongated
node which may reach a length of from six to
ten millimeters. Celakovsky 1 has named it
ob the mesocotyl. It is certainly an unusual
occurrence that two portions of one leaf-
S primordium should be separated one from
another so that they appear to spring from
different parts of the axis, but the process
can be followed here in its development, and
we may explain it so far biologically that
it facilitates the boring through the earth of
the sheath with the stem-bud which it en-
closes.
FIG. 275. Carex.
Embryo in germina-
tion. Diagrammatic. J, in longitudinal
section. 7, haustorium ; 44/2, middle por-
tion of cotyledon; Me, mesocotyl; S,
cotylar sheath; JZ, foliage-leaves. J/,
part of the cotylar sheath in transverse
section to show the conducting bundle.
The vascular part is indicated by wavy
lines on each side of the sieve-part indicated
by a straight line. J//, cotylar sheath in
transverse section. Conducting bundle,
black.
The anatomical relationships suit this ex-
planation, and I shall very shortly refer to
them here (see Fig. 275)”. The conducting
bundle which passes out from the haustorium
and upper part of the cotyledon does not
attach itself directly to the vascular bundle-
cylinder of the mesocotyl but runs upwards in
the cortex of the mesocotyl. Consequently on
tranverse section the vascular portion of this
bundle, which is represented in the diagrammatic
Fig. 275, Z, by a wavy line, appears in an inverted
position, that is to say it is turned outwards.
At the point where the cotylar sheath joins on
to the mesocotyl there is a conducting vascular
bundle in which the vascular portion has the
normal position; this bundle bends up through
the sheath to its apex then descends again through
the sheath, and is continued downwards, as the bundle with inverted xylem
mentioned above, through the cortex of the mesocotyl into the upper part of the
cotyledon ending in the haustorium. Upon the transverse section of the sheath
(Fig. 275, ZZ) there appears to be but one vascular bundle which has two sieve-
portions almost touching one another and two vascular portions lying over against
: Celakovsky, Uber die Homologien des Grasembryos, in Botanische Zeitung, lv (1897), p. 141.
* See Van Tieghem, Morphologie de l’embryon et de la plantule chez les Graminées et les
Cypéracées, in Annales des sciences naturelles, sér. 8, iii (1897), p. 259.
COTYLEDON OF CYPERACEAE 413
one another. ‘This course of the conducting bundles shows that the bundle which
enters the cotylar sheath be-
longs peculiarly to the coty-
ledon and that the cotylar base,
in a certain measure, forms a
cortical investment of the me-
socotyl.
Cyperus alternifolius.
In illustration of the second
case the germination of
Cyperus alternifolius may
be quoted. “Fis. 276, I,
shows a longitudinal section
through the embryo in the
seed. The root, VW, is only
feebly indicated, and upon
it there is observed the re-
mains of the suspensor £7.
The massive cotyledon
shows at its suctorial end
the cells already ina papilla-
form, and its long axis does
not fall,as in Carex,in nearly
the same plane with the
root, but makes a right
angle with that organ. This
is due to the strong de-
velopment of the cotylar
sheath, S, which completely
invests the stem-bud, and
only opens to the outside
by a narrow slit above the
point of the first foliage-
leaf. As the young seedling
shows (Fig. 276, II), the
sheath develops in germina-
tion also very greatly in
the first instance, and the
elongation of its zone of
insertion, which in Fig. 276,
I, is indicated by the dotted
line, forms the mesocotyl
which brings the stem-bud
f}
}
/
Fic. 276. Cyperus alternifolius. Embryo and germination. I.
embryo in longitudinal section. Co, cotyledon ; S, cotylar sheath ;
L, first foliage-leaf; WW, primordium of a root upon which at £7
is the remains of the suspensor. The zone between the dotted lines is
that which forms the mesocotyl. II, and III, young and older
seedling plants. Lettering as inI. The seed-coat is still attached
to the seedling. In II thecotylar sheath is not yet ruptured. Z1,
second leaf; Afe, mesocotyl. All magnified.
414 TRANSFORMED LEAVES
above the soil, where finally the cotylar sheath is ruptured at its tip
(Fig. 276, III).
Scirpus lacustris. A further example of this second case amongst the
Cyperaceae is furnished by Scirpus lacustris (Fig. 277). In general, we may
say that the cotylar sheath is the more developed in the seed, the earlier and
the more massively it has to be developed in the germination. In Scirpus
lacustris this is seen in marked degree. The sheath becomes green at the
tip, and forms there, apparently, a second lamina—the first being the broad
shield-like portion forming the hypogeous haustorium, and lying apparently
over against the stem-bud. The great development of the sheath in the
seed has given rise to misinterpretation. The portion marked a, in Fig. 277,
is by most authors called the ‘radicle. The root, 7, here, as in other
FiG. 277. Scirpus lacustris. A, embryo. B, seedling plant. C, Cyperus decompositus. Embryo in longi-
tudinal section. Inall figures: a, a, cotylar sheath; /1, 72, first leaves; » primary root; .S, suspensor.
magnified 75. After Didrichsen.
similarly constituted Cyperaceae, occupies a lateral position’, as is shown
also clearly in the embryo of Carex (Fig. 274, Wh). That in the germina-
tion at first the stem-bud, as well as the cotylar sheath develops, is shown
in Fig. 277, B, and there also we observe the strong development of the
cotylar sheath before germination. This bears out what has been said above
about the development of the foliage-leaves?, that in general, the parts
which are most developed in the matured condition, are the first laid down
as primordia.
THE COTYLEDON OF GRASSES. These cases lead us on to an
explanation of the much discussed formation of organs, in the embryo of
grasses. As will be shown, we find nothing new when we compare the
grass-embryo with that of the Cyperaceae just described.
Didrichsen, Om Cyperaceernes Kim, in Botanisk Tidsskrift, xix (1894), xxi (1897).
—Seeip: 3311.
COTYLEDON OF GRASSES 415
Let us see first of all what are the actual relationships’. In Fig. 278,
we have a longitudinal section through the basal portion of a grain of wheat.
The embryo lies at the base of the endosperm ?, and it turns towards the
endosperm a broad shield-like portion, which since the time of Gartner has
been termed the scutellum, sc; this acts as a suctorial organ, and remains
within the seed in germination. Opposite it is a small scale with no vascular
bundles, which is termed the efzd/ast, /. Above it there follows a sheathing
leaf, with a narrow slit, which appears above the ground in germination,
but never becomes green; this is the colcoptile or pileole,c. The endo-
genetic primary root, 7, which in germination breaks through the peripheral
layer of tissue, coleorrhiza, cl, requires here no further description. I may
only say that the hypocotyl, hp, is
scarcely formed in the grasses, as the
body of the embryo is almost entirely
used for the laying down of root.
The morphological explanations
that have been given of these organs
may be grouped as follows :—
1. The cotyledon is not a leaf-
organ. We may put on one side the
quite untenable view of Nageli, that
the cotyledon is a_ thallus-lobe.
Hofmeister and others consider the
scutellum as an outgrowth ofthe axis
of the embryo. But the history of
development shows clearly that the
scutellum arises as a terminal struc- FIG. 278. Portion ot grain of wheat in median
ture on the embryo, like the cotyledon longitudinal section. To the left the embryo. Sv,
scutellum ; 7’, ligule; vs, vascular supply ofscutellum ;
in other Monocotyledones (Fig. 282). ce, cylindric epithelium of scutellum; ¢, cotylar
sheath ; fv, vegetative point of stem; 44, hypocotyl;
5 Z, epiblast ; 7, root; c/, root-sheath; cf, calyptra; 72,
2. The scutellum is the coty- Hane of exit of root; /, fruit-stalk ; vf, vascular supply
ledon, and the epiblast which lies over Secubed feos as SS oe
against it, but is not present in all
grasses, is an arrested second leaf, and the coleoptile is the third leaf.
This view is supported by the following :—
(2) Between the coleoptile and the scutellum, there is in many grasses
a strongly developed ‘ internode.’
(6) In the axil of the coleoptile an axillary bud is often found.
(c) The basal part of the scutellum in many grasses, for example Oryza
(Fig. 281, V), Leersia, and others (Fig. 281, I) develops like the sheath of
1 These are most fully depicted by E. Bruns, Der Grasembryo, in Flora, Ixxvi (Erganzungsband
zum Jahrgang 1892). The literature is cited there.
2 Van Tieghem’s statement that the embryo is completely surrounded by the nitrogenous layer of the
endosperm is not true for Triticum vulgare. See Van Tieghem, Morphologie de l'embryon et de la plan-
tule chez les Graminées et les Cypéracées, in Annales des sciences naturelles, sér. 8, iii (1897), p. 260.
416 TRANSFORMED LEAVES
the foliage-leaves of many Monocotyledones. It would therefore be extra-
ordinary were there the formation of a second sheath in the coleoptile!.
3. Scutellum and coleoptile form together the cotyledon, the epiblast
is not a leaf.
This view would bring the formation of the organs in the embryo of
the grasses into conformity with that of the Monocotyledones mentioned
above, and it has therefore upon comparative grounds great probability.
Let us now pass in review the relationships
\ between the embryo-plant and its functions.
| Zea Mais. Fig. 279 is the representation
of a seedling plant of Zea Mais, seen from in
front. It has a chief root, HW, and two upwardly
directed lateral roots, V. The stem-bud is still
invested by the coleoptile, S, which at its apex
is split by the leaves unfolding within it. On
the transverse section shown in Fig. 280, we
observe that a large number of leaves already
exist, which are thinner than is the coleoptile,
and are also distinguished from it by having a
large number of veins, whilst the coleoptile has
only two vascular bundles. The coleoptile,
which by its want of chlorophyll is very
Me
Fic. 279. Zea Mais. Seed-
ling. H, primary root; G,
coleorrhiza; Sc, scutellum ;
F, fruit; Me, mesocotyl; A,
first node; So cotylar sheath
(coleoptile); |, secondary Fic. 280. Zea Mais. Seedling plant in transverse section.
roots. Magnified 14. S, cotylar sheath.
markedly distinguished from the foliage-leaves*, has no sclerenchyma,
1 These arguments were to me conclusive at the time of the appearance of Bruns’ work. But the
comparative standpoint appears to me to be now all the more strengthened by the proof that in
Streptochaete we have a grass which has entirely the conformation of the flower that is ‘typical’
in Monocotyledones. See Goebel, Ein Beitrag zur Morphologie der Graser, in Flora, Ixxxi (Ergan-
zungsband zum Jahrgang 1895), p. 17, also Celakovsky, as cited there.
2 It may become green in many grasses if light of no great intensity has access to it.
COTYLEDON IN GRASSES 417
but its strong turgescent tissue enables it, in a very perfect manner, to protect
the stem-bud it invests as this bores through the soil. Toa certain extent
it prepares the way, and gives to the leaves and the shoot-nodes, which have
intercalary growth, the first necessary start. This coleoptile sits upon the
node, marked K, which is indicated externally by a slight swelling, and
below this is an ‘internode, J/e, which is negatively geotropic. One sees
further the scutellum, Sc,
upon the surface of the fruit,
fF, and at G we have the
coleorrhiza. The anatomical
relationships here favour the
view that the scutellum and
coleoptile are independent
leaves. The scutellum con-
tains at its point of insertion
on the internode, one vascular
bundle which branches in the
scutellum ; the coleoptile con-
tains two of these which are
derived from the node KX.
The ‘internode, Je, has a
quite different structure from
the later internodes. It has,
not like them scattered vas-
cular bundles, but a vascular
cylinder enclosed by an en-
dodermis. In other grasses
the anatomical relationships
correspond, on the other hand,
with those of Carex.
Zizania aquatica. In Fic. 281. I, Berchtoldia bromoides. Embryo from outside.
Bieiteem Mel have the 1h catcyo fom onesie IV. emboyo tu Gensverse ‘ccction
representation of a longitu- patie fae pe eatiga reer oe Le ermal ts ee
dinal section, through the She ae ue penta = pee oon epee ves:
embryo of Zizania aquatica. z See EL in oeknice a a era iv gio
- fied 22, I, II, IV, V, after Bruns. III, after Schlickum.
In the seed there is a structure
which can be directly compared with the features observed in the germina-
tion of Carex. Between the coleoptile and the scutellum, a mesocotyl
is developed. In this there run two vascular strands, 7, of which the one
forms the conducting cylinder of the mesocoty]l, the other coming out of the
scutellum runs upwards in the mesocotyl!, and there giving off two
> 4a
Cac el Nan ea
PRATS
. SO S--- W
Z =
~ S39
USee p. 412.
GOEBEL II E e
418 TRANSFORMED LEAVES
branches which pass into the coleoptile it itself joins on to the bundle of
the mesocoty].
We find the same in Oryza sativa, Phalaris canariensis, and other cases.
Where no mesocoty! exists, the relationships of the vascular cylinder
in its course are essentially the same, that is to say, the scutellum and
sheath stand in direct connexion with one another. The bundles of the
coleoptile may be considered as branches of that which enters the scutellum.
If the coleoptile is greatly elongated the arrangements described in Zizania
are developed. The mesocotyl is, as in Carex, no internode, but a node.
Where, as in Zea, the anatomical relationships diverge, it may be asked if
this is not only apparently the case. But even if in this species the
anatomical relationships are really different, and they have been referred to
particularly here because they are important, yet
we cannot come to any other conclusion than that
which is valid in the other grasses.
Development. The history of development,
owing to the peculiar relationships which are found
in the embryos, cannot be here of so much general
significance as elsewhere, yet it does not contradict
the explanation that the coleoptile is an outgrowth
of the scutellum, which is the upper part of the coty-
ledon, and that it corresponds to the cotylar sheath
Be anes oe of other monocotylous plants. In Fig. 282, a half-
Mesueee S, cotylar sheath. ripe embryo of Hordeum hexastichum is shown.
The coleoptile, S, arises at the base of the scutellum,
Sc, grasps right round as an amplexicaul structure, and now forms a cup
with a narrow mouth above, like the structure shown in Fig. 246, in the case
of Caltha palustris. Like the axillary stipule of Caltha, it serves as a pro-
tection to the bud, and aids it also in germination, and is therefore strongly
developed. That the basal portion of the cotyledon is also frequently con-
structed in the sheath-form (Fig. 281, I, V) may be connected with the
fact that the coleoptile has here taken on a further function. Axillary
stipules may, as we have seen above!, stand also on the sheath-like leaf-base.
Unlike the ligular formations which are found elsewhere in the grasses, the
coleoptile is laid down early, and the place of its inception is associated
with the fact that the end of the cotyledon remains as a haustorium in the
seed.
The Epiblast. If the explanation I adopt is correct the epiblast cannot
be a rudimentary leaf. It is undoubtedly a protecting arrangement for the
embryo like the ligule of palm-leaves and of grasses, but whether we desig-
nate it as a growth from the sheathing-base of the cotyledon (and to this
FSSC Ds gii2.
LEAVES AS CLIMBING-ORGANS. HOOK-LEAVES 419
view the condition in Oryza represented in Fig. 281, V, gives support) or
explain it as an independent formation, appears to me to be of little moment.
At any rate it fills the gap left upon the outer side by the cotylar sheath.
C. RETROSPECT.
It follows from the preceding description that we fairly understand the
relationship between form and function in the cotyledons. On the other
hand we are entirely in the dark as to the conditions for their configuration.
6. LEAVES AS CLIMBING-ORGANS.
Leaves may be devoted to the purposes of climbing in many ways, some-
times with, sometimes without, a change in their original form. We find in
Europe amongst plants which are leaf-climbers almost only those with /eaf-
tendrils; elsewhere the leaf-forms are more manifold. It is interesting to
see how, in many plants, the leaf-organs become devoted to climbing which
were originally formed for quite other ‘purposes.’ Drosera macrantha,
which I found in West Australia, possesses a thin stem almost a meter in
length. Systematic works describe it as ‘twining, but this is incorrect.
The leaves have very long stalks and cling to shrubs by their outer ten-
tacles, which are bent back specially as traps for insects, and the leaf-surfaces
lie with their under side upon the upper surface of the twig, a sticky secre-
tion of the recurved tentacles gluing them firmly to it. We shall leave out
of consideration plants in which the leaves are useful in ‘scrambling,’ and
direct our attention only to those whose leaves exhibit a more or less far-
reaching transformation either into hooks or into tendrils.
LEAVES AS HOOKS.
Here we have leaves or parts of leaves with a curved hook-like form,
and these after they have grasped a support show no further change.
A. PTERIDOPHYTA.
Lycopodium volubile. Lycopodium volubile, a species which climbs
high up in the trees in Java, gives us an example. The chief shoots have
a radial arrangement of the leaves, and each of the leaves grows out at its
base over the point of attachment. It is thus somewhat peltate. The blunt
basal continuation standing out from the surface of the shoot serves as
a hook for climbing, although not a very complete one. The formation of
the leaves conforms in all essentials with what we have seen in Asparagus
comorensis (Fig. 215). The branches of higher order do not form these
hooks and climb ; they are dorsiventral shoots like those of Lycopodium
complanatum }.
1 See Part I, p. 103.
Beg
420 TRANSFORMED LEAVES
B. DICOTYLEDONES.
Stylidium scandens. Stylidium scandens climbs by means of leaves
with hook-like ends.
Pereskia. Many species of Pereskia develop single thorn-leaves as
hooks for climbing.
Quisqualis indica. The features of Quisqualis indica have already
been referred to’. Upon the long shoots the stalks of well-developed foliage-
leaves, whose lamina has functioned as a leaf, are transformed into hooks
Fic. 283. Bignonia albo-lutea. Portion of shoot. The two lower leaves are ternate, the two upper have a trifid
tendril instead of the end leaflet. After A. Mann.
which remain after the lamina has fallen, and thus offer an instructive
example of seasonal change of function.
Other Dicotyledones show a transition from formation of hooks to
formation of tendrils: the lamina, which forms a curved hook, serves as an
anchoring-organ, whilst the stalk is a tendril.
Bignonia. Many Bignoniaceae have strong claw-hooks, for example
Bignonia unguis. These are less developed in, for example Bignonia albo-
lutea (Figs. 283, 284), where the history of development, as in Cobaea,
shows that the hooks proceed from the lamina which is in a rudimentary
condition visible on young tendrils (Fig. 284).
C. MONOCOTYLEDONES.
Asparagus comorensis. The climbing-hooks of Asparagus comorensis,
formed from the under portion of the peltate leaves, have been described ”.
1 See Part I, p. 9. 3 See p. 334.
LEAVES AS TENDRILS 421
PALMS. The climbing-hooks of the leaves of many Palms are larger.
In Chamaedorea desmoncoides the pinnules of the leaf are so bent back that
they form with the rhachis a very obtuse angle upwards, and these leaves
act as hooks. They are, however, still assimilation-organs. But in the
leaves of Desmoncus (Fig. 285) the upper leaf-pinnules are transformed into
hooks which are climbing-organs oz/y. We can recognize that they have
taken origin from leaf-pinnules by the transition-forms that occur. We
have again an illustration here of the oft-recurring series of transformations
which ends with complete change of function and earlier transformation.
Calamus. The climbing-organs of species of Calamus, the well-known
rotang palm, must not be confounded with the climbing-
organs above mentioned. This palm, which has climb- ) \\
ing-organs as much as ten meters long, is beset with
claw-like, strongly silicified hooks, which are not formed rat) f
by a transformation of leaf-pinnules but are highly de- as) } LE
veloped prickles such as occur in species of Rubus and (a ee /
elsewhere. The long axis which bears these claws is | hae ae
either a transformed inflorescence or springs from the | /
elongated rhachis of the leaf. /
LEAVES AS TENDRILS.
A. DICOTYLEDONES.
Only in relatively few cases do we find leaves Ps]
combining the function of assimilation-organs and of
5 b 2 a s Z Fic. 284. _Bignonia_al-
tendrils without a change in their conformation, that is bo-lutea. “Young tendril.
At the end of each branch
to say, there are parts of the leaf—the leaf-stalk of of the (eadil a radians
Solanum jasminoides, species of Tropaeolum, Maurandia, ed Oe Fa
the leaf-spindle of species of Clematis—which are sensi-
tive to contact, and in consequence of this are able to twine round a support.
We usually find that a division of labour occurs here, and that one part of
the leaf—in compound leaves the leaflets—only is constructed as a tendril,
whilst its original function has entirely disappeared. There are not wanting
examples where we can observe this process developing zz a single plant.
Corydalis claviculata. Of special interest in this respect is Corydalis
claviculata, which has been described by Darwin}, and in which we observe
a gradual transformation of the leaf into a tendril. In the juvenile condi-
tion the plant bears ordinary leaves, and all the leaflets of the bipinnate
leaf are also formed as leaves. In the following leaves the upper part of the
leaf, or leaf-spindle, becomes thinner and longer than the lower part, and
the pinnules of the leaflets which sit on this portion which is elongated
like a tendril become reduced in size, often so far as to be no longer
* Darwin, The Movements and Habits of Climbing Plants, 5th thousand, London, 1891, p. 121.
422 TRANSFORMED LEAVES
visible, and we thus have all stages between them and normal leaves. Not
infrequently on all the terminal leaflets of the leaf every trace of pinnule
disappears, and leaflets appear then as complete tendrils.
Adlumia cirrhosa. We find the
same thing in Adlumia cirrhosa. In it
the leaf is constructed as a tendril only
inits upper part; below it is not sensitive
to contact. In the tendril-portion of the
leaf the lamina of the leaflets is greatly
reduced although it is still visible. It
is the sza/k of the leaflets which serves as
the climbing-organ.
Cobaea scandens. What is visible
in these plants to the naked eye may
be seen in others if we follow the
developmental history as it was first
traced in Cobaea scandens!'. The effec-
tive tendrils of this plant are formed
out of the end-portion of the pinnate
leaves. The tendril-branches are at
their end provided with small curved
claws, by means of which the shoot of
Cobaea is able to climb for great dis-
tances over tree-stems, rocks, and like
objects. The history of development (see
Figs. 286, 287) shows that these claws,
which are very small, are vestiges of
reduced or transformed laminae of leaf-
lets, and the tendrils are the leaf-stalks.
The development of the arms of the
tendrils entirely conforms to that of
the leaflets in the earliest stages, only
in the formation of the tendrils in the
upper part of the leaf a richer branch-
ing sets in, and the laminar primordia of
the leaflets is arrested very early. The
Fic. 285. Desmoncus sp. Leaf. Transition : : : : : :
of leaf-pinnules into hagke: Much reduced. same thing 1S seen in Species of Bignonia
(Figs. 283, 284) and of Eccremocarpus.
The tendrils do not, however, in all cases proceed from leaf-stalks
or the stalks of leaflets. They may be formed by the early elongation of
1 See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884), p. 431; A. Mann, Was bedeutet ‘Metamorphose’ in der Botanik? Inaug.
Dissertation, Miinchen, 1894.
TENDRILS OF CUCURBITACEAE 423
the primordium of the whole leaf, or of a portion of a leaf, and then the
inception of a blade may no longer be visible. This is what takes place, so
far as my investigations extend, in the Leguminosae, Cucurbitaceae, and
Tropaéolum tricolorum?. In the Leguminosae, as in other cases, it is the
end of the leaf which is transformed into the tendril ?,and in Pisum the prim-
ordium of a tendril may be caused to develop partially as a foliage-leaf
(Fig. 289)* by separation of all other leaves and leaflets of the plant, and
this is in correspondence with what has been said above* in regard to the
behaviour of kataphylls.
Cucurbitaceae. The for-
mation of tendrils in the Cucur-
bitaceae demands special de-
scription, as it has been for long
a matter of dispute. It would
be of no interest to discuss the
literature of the subject, espe-
cially as, according to my view,
the questions at issue are now
settled®. We find in the Cu-
curbitaceae both simple and
branched tendrils. The simple
tendrils are the transformed
prophylis of axillary shoots.
For a long time these were
Fic. 287. Cobaea
scandens. Young ten-
dril formed from upper
part of leaf. Branches
of tendril are laid down
not recognized as such, because like leaf-pinnules. The
- Fic. 286. Cobaea scandens. stalks of the leaf-pinnules,
there usually appears beside Young leaf. The upper part, R, is which are hardly visible
being formed asatendril. a, 4, ¢, in the figure, elongate
each axillary shoot only omé _leaf-pinnules; x, primordium of into arms of the tendril.
- i lowermost branch of tendril. Magni- Magnified less than Fig.
tendril, and the prophylls in fied. After A. Mann. 286. After A. Mann.
Dicotyledones are normally
paired right and left of the axillary shoot. But we find the pair
of prophylls, not infrequently, in the seedling-plant of the Cucurbitaceae,
especially in Benincasa cerifera, where they are also visible in older plants ;
in other Cucurbitaceae ® they seem to be confined to the seedling-plant, for
example in Coccinia indica, where, however, they are retained for a some-
what long period, and where there are, as also in Momordica balsamina,
transitions between the prophylls and the tendrils. The seedling-plants
in one and the same species may show some variation; sometimes they
have prophylls, sometimes there are none.
1 See Part I, p. 163. 2 See Part I, p. 162.
3 As A, Mann has shown, Was bedeutet ‘Metamorphose’ in der Botanik? Inaug. Dissertation,
Miinchen, 1894. * See p. 388.
5 Nevertheless, erroneous statements are still repeated, for example by Lubbock, On Buds and
Stipules, London, 1899, p. 214.
§ T have found, not infrequently, two prophylls on the seedling-plants of Cyclanthera.
424. TRANSFORMED LEAVES
Benincasa cerifera. If one follows the development of the embryo of Benin-
casa, one sees on the first axillary shoots one or two, on subsequent ones always two,
prophylls of which one is transformed into a tendril which is at first rudimentary ;
occasionally this transformation does not take place. There may be observed some-
times? in the juvenile stages of these tendrils a trace of the primordium of a leaf-
Jamina, but, through the stretching in the formation of the tendril, this is no longer
visible upon the mature tendril. The other prophyll is seldom developed into a
form like the foliage-leaves (Fig. 288, 1), it mostly remains unsegmented (although
traces of segmentation may be proved in the history of development), is scaphoid
é. 3. 4
Fic. 288. Benincasa cerifera. 1-4, prophylls. 5s, prophyll showing transition to a tendril. 6, portion of an
axillant leaf, 7:2, with two-armed tendril. All magnified. After A. Mann.
(Fig. 288, 4), deep green, and occasionally has an axillary shoot. Branched
tendrils appear at a later period. ‘They may arise in a similar way to those that
will be presently described in Cucurbita *.
Cucumis sativa. I shall take next the case of Cucumis sativa. In the axil
of a leaf we find a flower, beside it a vegetative shoot, and beside this a tendril.
As the history of development shows, the flower is an axillary shoot of the foliage-
leaf, and it bears only one prophyll which is transformed into the tendril. This
position is determined by the fact that generally the anodic side of the leaf, that
is to say, the side which is turned to the vegetative point, if one imagines the leaves
disposed in a spiral *, is furthered.
1 This, as I formerly showed, can be often seen in the Cucurbitaceae.
2 Occasionally one tendril-arm takes the form of a foliage-leaf or a flower is formed upon the
tendril. In that case the vegetative point of the axillary shoot usually is entirely used up in the
formation of the second tendril-arm (see Fig. 201, III), which develops into flower.
® This assumes that the leaves are not inserted quite transversely but have the anodic margin
inserted somewhat higher. The axillary shoot is not quite median.
TENDRILS OF .CUCURBITACEAE 425
Pilogyne suavis. In Pilogyne suavis we find that upon the kathodic side
of the leaf-axil a tendril also arises which, however, is smaller than that upon the
anodic side (see Fig. 290) ; evidently ove axillary tendril is sufficient for climbing,
and the plant raises itself up on its support like a gymnast who, freely suspended,
climbs up a ladder using alternately the right and the left arm—just as in the
shoot-tendrils of Ampelopsis the tendril-arms are placed alternately right and left.
We must assume that in other Cucurbitaceae the tendrils are transformed
leaves—that the szmple tendrils are the prophylls of axillary shoots of which only
one prophyll is commonly developed, the other is wanting, but the dvranched tendrils
are shoots which bear leaves
transformed into tendrils.
The reasons for this expla-
nation are developmental
and as follows :— SiS}
(a) We see that the a\
tendrils belong to the axil-
lary shoot beside which they
stand. &
(4) In the seedlings we
can follow frequently the >. | E.
appearance of the prophylls,
and in Benincasa a prophyll 5. og, pisumsativam. A, B,C, D, E, F, G, artificial foliation of
is often present beside the thetendrils. In G the stipules are shown. After A. Mann.
Fal
tendril in the mature plant.
(c) The developmental history of the individual tendril shows in many cases
clearly the direct transformation of the primordium of the foliage-leaf into a tendril:
the leaf-lamina is still laid down but only in a rudimentary condition ; it does not
develop in breadth; the whole tendril grows markedly in length because there
is often an embryonal apical growth which lasts much longer than it does in
the foliage-leaves.
Miller’s Investigations. This explanation of the tendril of the Cucurbita-
ceae does not quite agree with that which has been recently given by O. Miiller’
as the result of his anatomical investigations. According to him in some Cucurbi-
taceae which bear both simple and branched tendrils, for example Cyclanthera
pedata, C. explodens, Thladiantha, as well as in some which have simple tendrils
only, for example species of Bryonia, Coccinia, and Momordica, the non-sensitive
base of the tendril is a shoot-axis, the upper portion is a ‘leaf-spindle*’; whilst
in Cucumis the lower part of the tendril also has the structure of a leaf-spindle.
Upon this I may remark :—
1. Anatomical relationship a/oze can never solve a morphological problem.
1 ©. Miiller, Untersuchungen iiber die Ranken der Cucurbitaceen, in Cohn’s Beitrage zur Biologie,
v (1887), p. 97. The literature is faultily quoted in this work, for instance it is an error to say that
Eichler considered the cucurbitaceous tendril to be a transformed stipule.
2 The author does not say what he means by this term. The new anatomical school is not fond
of giving clear morphological definitions.
426 TRANSFORMED LEAVES
There are shoots like, for example, the phylloclades of Asparagus medeoloides,
which have entirely the structure of leaves, and there are leaves which have quite
the structure of shoot-axes.
2. In many of the plants mentioned, for example Momordica balsamina, there
are undoubtedly transitions between prophylls and tendrils.
3. It is indeed conceivable that in the formation of tendrils ‘terminal leaves’
may arise, that is to say the vegetative point of a shoot may be used for the
formation of a tendril, and as a matter of fact such a condition appears to occur
Fic. 290. Pilogyne suavis. Portionof shoot. Beside each leaf stand a developed and an arrested tendril.
in the formation of the branched tendrils of Benincasa cerifera. But this process
can only be determined for certain upon a basis of careful developmental and
comparative investigation, which is indeed less easy than the popular riband-
sectioning anatomy.
An experimental ‘foliation’ of the tendrils of the Cucurbitaceae has not yet
been achieved.
Cucurbita. We find spirally branched tendrils in Cucurbita. Here we have
to do with an axillary shoot of the simple tendril, which itself is concrescent
with its axillary shoot, and this axillary shoot brings forth a number of leaves
which are developed as tendrils.
TENDRILS OF CUCURBITACEAE 427
The tendrils of the garden cucumber consist of a stalk and a series of arms
radiating from its apex. We may call them compound tendrils. The arms are
really arranged in a spiral upon the stalk, and not infrequently this spiral position
is exposed by the elongation of the internodes of the stalk, and one finds then
single tendrils at the base of the stalk. In the seedling the elongation of the
stalk from which the tendrils spring is suppressed at first, and it is clear that
the stalk is of advantage in order to raise up the tendrils as far as possible
and thus facilitate their getting hold of the support. Each tendril-arm is a trans-
formed leaf, but the stalk which bears the tendrils is a shoot-axis. On the
compound tendrils which I have studied, each tendril-arm has an axillary bud
which not infrequently develops into flower, and in individual cases the stalk
of the compound tendril
became ashoot on which
the tendrils in its upper
part passed into leaves
—often in such a way
that only one-half of
the leaf-lamina was de-
veloped, whilst the other
part was wanting and
the middle portion of the
leaf was elongated be-
yond the leaf-surface in
the form of a small ten-
dril. Usually, however,
the vegetative point of
the shoot-axis, on which
the tendrils are inserted, FIG. 291. Zanoniamacrocarpa. I, portion ofa shoot with axillary tendrils,
zi : The axillant leaves have fallen off. II, portion of shoot of a seedling plant,
is arrested after their showing a tendril and a bud in the axil of the leaf. 1, reduced.
inception and they grow
out apparently radiating from one point. That the stalk of the tendrils together
with the tendrils is not to be considered as a single leaf is clear. We do not
know of spirally arranged shoots upon a leaf, and besides the construction of
the perfect tendril, as we know it in the cases described above, shows that it
has nothing to do with such a configuration.
Zanonieae. The relationships in the Zanonieae are not at all clear. In
the year 1885 I concluded, from investigations previously made in Java, that
dichotomously branched tendrils occur here and that the two arms become
anchoring-disks (Fig. 291, 1), whilst the lower part becomes coiled subsequently.
On the seedling the primary leaves are reduced to small scales. In the axil of
each of the two lowermost leaves there is found, at least at first, a resting-bud
with two prophylls. Further up a two-armed tendril occurs in each leaf-axil, and
its arms swell out without any stimulus of contact into anchoring-disks (Fig. 291).
Beside the tendril is an axillary bud. Between the two arms of the tendril no
vegetative point is visible.
428 TRANSFORMED LEAVES
Veratological phenomena. ‘Teratological phenomena, which are not in-
frequent, especially in cultivated Cucurbitaceae, must be interpreted with care.
Darwin mentions a case from Holland in which one of the short prickles of
the fruit had apparently grown out into a tendril. In reality a tendril was here
concrescent with the fruit.
B. MONOCOTYLEDONES.
In Monocotyledones tendrils are rare.
Smilax. The tendrils of Smilax have been already mentioned 1.
Gloriosa and Littonia. In Gloriosa and Littonia the narrow apex of
the simple leaf acts as a tendril*. It is laid down at a very early period,
and one might consider it as a transformed forerunner-tip. As for the con-
jecture which has been advanced that the leaf-lamina here is transformed
into a tendril, and the leaf-base which gradually passes into the tendril is
grown out in the same way as has that in Nepenthes, there is neither
evidence in the history of the germination, nor, so far as I know, any other
ground whatever for it.
THE FACTORS CAUSING TRANSFORMATION INTO TENDRILS. The
manner in which the transformation into tendrils of leaves or parts of leaves
takes place is evident from what I have said. What we want to know now
is what factors come into consideration in the formation of tendrils and cause
a strong transformation of the leaves. That the leaf-surface should be
the more reduced the longer the tendril, is quite clear, as is also the advan-
tage which accrues from the elongated form in the way of facilitating the
tendril to find a support ; for it gives a wider surface of grasping and a longer
sensitive area. In tendrils which are formed out of the stalk of a leaf in
process of arrest, one might refer back the abortion of the lamina to corre-
lation, but that there is little probability in this we have seen, for the whole
leaf-primordium can stretch into a tendril. Perhaps one of the influential
factors to be considered in formation of tendrils is this, that in leaves,
which were in the first instance sensitive to contact-stimuli but were not
transformed even by their employment as climbing-organs, destruction of
their other capacities, assimilation and the like, took place, and this
resulted in a reduction in the formation of the lamina, and the consequent
elongation of the leaf-parts into a tendril.
7. LEAVES AS THORNS.
The transformation of leaves into thorns may take place in different
ways and in different degrees.
Astragalus. One instance in which it takes place relatively late has
1 See p. 223.
* The leaf thus resembles the primary leaf of Lathyrus Clymenum (Part I, Fig. 99, Z/).
LEAF-THORNS 429
been already mentioned in the case of some Leguminosae. Species of
Astragalus, for example A. horridus, A. Tragacantha, and others, and of
Carragana, which live in dry localities, have pinnate leaves. The pinnules,
which possess bilateral construction and have usually a profile position in
nature, fall away, but the leaf-spindle remains behind and becomes a thorn.
Cicer subaphyllum. In Cicer subaphyllum, another leguminous plant,
the leaf-spindle runs out into a hooked thorn, and the pinnules are also
transformed into thorns ”.
Simple undivided leaves may also be transformed into branched thorns
in another way :—
Berberis. Thus in Berberis the leaves of the long shoots are thorns.
Transition-stages, which are known, show that the leaf-lamina becomes
gradually more deeply cut at the edge as it diminishes in breadth, whilst
several of the marginal teeth, which are fewer in number than appear in the
foliage-leaves, develop considerably, and instead of the assimilation-paren-
chyma there is a dominance of sclerenchyma. The earlier in the develop-
mental stages the formation of the thorn sets in, the more is the assimilating
tissue reduced, and the more does the sclerenchyma predominate.
Cactaceae. The transformation of leaves into thorns is seen in greater
degree in many cacti whose thorns * have a varying ‘ morphological value.’
The thorns are here usually arranged in tufts on very short shoots. The
view, which I have expressed elsewhere *, that the thorns are transformed
leaves, has been confirmed by the investigations of Ganong*®. We must
restrict our attention here to an exposition of the formation of the thorns in
some of the Opuntieae. In Opuntia arborescens, for example, the arrange-
ment of the thorns is peculiar, as they are all on the outer side of the
vegetative point from which they shoot out, and therefore are disposed
dorsiventrally. The foliar nature of the thorns is evident because one finds
all transitions between thorns and leaves, and they can even be artificially
produced. When a vegetative point of Opuntia ceases to produce thorns
and begins to produce leaves, the transition is not a sudden one but gradual.
After the last thorn there comes a structure which is leaf-like at the base,
and then after that there is one which is more like a leaf. In the next
there appears a trace of a vascular bundle and of an axillary shoot, and then
comes a structure in which only the apex is thorn-like, and which possesses
1 See Part I, p.g; also Goebel, Beitrage zur Morphologie und Physiologie des Blattes, in
Botanische Zeitung, xxxviii (1880).
2 See the figure given by Keinke, Untersuchungen iiber die Assimilationsorgane der Leguminoseen,
in Pringsheim’s Jahrbiicher, xxx (1897), p. 538.
8 Stout spinose structures which are the result of the transformation of shoots or leaves are thorns
not frickles, which are ‘ emergences.’
* See Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 36.
5 W. F. Ganong, Beitrage zur Kenntniss der Morphologie und Biologie der Cakteen, in Flora,
Ixxix (Erganzungsband zum Jahrgang 1894), p. 49, where the older literature is cited.
430 TRANSFORMED LEAVES
a well-developed axillary bud. Finally there follows a typical leaf. This
development can be artificially induced if one causes the vegetative point of
the short shoot, which produces thorns, to shoot out by cutting off the chief
shoot. That the base of the incompletely transformed thorn retains its
leaf-character is easily explained by the basipetal development of the leaf.
The tissue in this region is embryonal, whilst at the apex it is already
converted into a thorn. With regard to the function of the thorns there
can be no doubt that they are protections against animals. I do not mean
by that that the thorns have been produced by natural selection, they may
have been induced by the dryness of the locality. Animals and men avoid
most carefully an opuntia-bush because the small thorns especially are
extremely irritating—they are beset with recurved hooks, and break off
very easily because the tissue at the base is, with the exception of the
fragile epidermis, disorganized.
Citrus. The thorns of Citrus and other genera of Aurantieae are also
leaf-thorns. Owing to their position they were formerly considered as
branch-thorns. They are found more or less accurately in the axil of the
foliage-leaves, either singly or in pairs, and beside or between them lies
a bud sometimes latent, sometimes active. In reality the bud is the axillary
shoot, and its first leaf, or first pair of leaves, becomes thorny ?.
8. LEAVES AS NECTARIES.
The petals or stamens are transformed into nectaries in many flowers,
for instance in the Ranunculaceae’. The transformation in the vegetative
region of stipules into nectaries has been mentioned °.
Cactaceae. The transformation of the whole primordium of a leaf into
a nectary is as yet only known in the case of the Cactaceae. In a number
of species of Opuntia*, in which all transitions from thorns to nectaries
occur, the nectaries are distinguished from the thorns, apart from their secre-
tion, by their thickness and the possession of a vascular bundle. The same
may be observed in some Mammillarieae. One would not consider the
turbinate structure which secretes honey in the axil of the mammilla of
Mammillaria macrothele and other species as a transformed leaf if the com-
parative history of development did not show that it was of this nature.
1 See Urban, Uber die morphologische Bedeutung der Stacheln bei den Aurantieen, in Berichte
der deutschen botanischen Gesellschaft, i (1883), p. 313.
2 See p. 550. 3 See p. 381.
* See Ganong, Beitrage zur Kenntniss der Morphologie und Biologie der Cakteen, in Flora, lxxix
(Erganzungsband zum Jahrgang 1894), p. 56.
BRANCHING OF THE SHOOT 431
B. BRANCHING OF THE SHOOT
The shoot develops out of the dvd in which the internodes are still short
and the leaves closely pressed together. Here, under the protection of
the older parts, are the primordia of the
new organs upon the vegetative point,
in the first place those of the leaves, and
next those of the lateral shoots. The
formation of lateral shoots at the apex of
the stem is suppressed entirely in only a
few plants. We find this amongst the
Pteridophyta in Ceratopteris, where an
abundant formation of leaf-borne buds
replaces them ; in Ophioglossum, where
there is a profuse formation of root-
buds; in Isoetes, where leaf-borne buds
appear exceptionally (Fig. 292)'; and
in the Marattiaceae with tuberous stem.
In many forms which are commonly
unbranched the capacity for branching
remains ‘latent,’ probably because the
primordia of lateral shoots are present,
but commonly are undeveloped. This
is the case in tree-ferns. I saw Dicksonia
antarctica frequently in Australia with
many ‘heads, and the development of
these was probably caused by damage
done to the chief axis. Also in palms,
which except in the inflorescences do not
produce,asa rule, lateral shoots, vegetative
branching sometimes, although perhaps, f1G,20%.,,jsgetes eustris, | Lowes portion of
farely, appears. Such branching is en- Zisrtomeshos. bamiea’
tirely excluded in Welwitschia mirabilis.
AXILLARY BRANCHING AND EXCEPTIONS. The method of the branch-
ing in the Pteridophyta and Spermophyta varies with the space-relationships
of the leaves. In the Spermophyta axillary branching is the rule, that is
to say, a lateral shoot arises out of the axil of a subtending leaf. This is,
however, not without exception. In the Pteridophyta, as in the Musci, this
* See Goebel, Ueber Sprossbildung auf Isoetes-Blattern, in Botanische Zeitung, xxxvii (1879).
432 BRANCHING OF THE SHOOT
relationship does not exist. In the Lycopodineae, for example, we have all
transitions, from a dichotomous division of the shoot-apex to the formation
of lateral shoots which are laid down indeed near the apex but are smaller
than the shoot-apex of the chief axis. The primordia of the twigs do not,
however, stand in the axil of the primordium of a leaf; as they far exceed
these in size each twig-primordium stands over a great number of the leaf-
primordia'. The lateral shoots in Equisetum too do not spring out of the
axil of the leaves, but they alternate with the teeth of the leaf-sheath. With
regard to the branching of the ferns nothing more can be said here. In the
Spermophyta it is specially dorsiventral shoots which show a divergence in
position of the lateral buds *. “Formal morphology has made many efforts
to refer back the branching of the Spermophyta to one definite scheme.
Pringsheim *, for example, as the result of insufficient observations, made out
the branching to bea division of the vegetative point ofthe shoot. Hofmeister*
believed that the lateral shoots always stood higher on the vegetative point
than the youngest leaves. Nageli® distinguished between ‘acrogenous’
and ‘phyllogenous’ (axillary) branching, and ascribed the latter to the
Equisetaceae and the Spermophyta. There is really no such scheme as
any one of these. The branching is indeed usually axillary but the
relationship between leaf and axillary shoot is not the same everywhere#
TIME-RELATIONSHIP IN DEVELOPMENT OF AXILLARY SHOOT AND
AXILLANT LEAF. Let us first of all consider the relationships in time.
We may, so far as I can see, say generally, as was said in the case of the
development of the leaf, that the organs which are earliest unfolded are also
earliest laid down. Thus the leaf arises in the vegetative region usually
much earlier than its axillary bud®. The winter-buds of Syringa, for
example, consist of the leaves laid down in the preceding year, and the
axillary buds of these leaves are only laid down in their axils as the bud
wnfolds; above the leaves in whose axil the first primordium of a bud is
visible one finds three to four pairs of leaves without buds. The leaves
then are laid down in one vegetative period, the axillary shoots are laid
down in the next’. The axillary shoots proceed from groups of cells of the
axis of the shoot immediately above the insertion of a leaf, and these groups
derived from the embryonal tissue of the vegetative point have retained their
embryonal character, but only at a late period, are stimulated to a new
’ As is shown by an examination of Lycopodium clavatum. 2 See Part I, p. 90.
§ Pringsheim, Uber die Bildungsvorgange am Vegetationskegel von Utricularia vulgaris, in Monats-
berichte der Berliner Akademie, 1869.
* Hofmeister, Allgemeine Morphologie der Gewachse, Leipzig, 1868, p. 408.
° Nageli, Theorie der Abstammungslehre, p. 478.
6 See Warming, Forgreningsforhold hos Fanerogamerne, in Kongelige danske Videnskabernes
Selskabs Skrifter, Reekke 5, x (1872); Koch, Die vegetative Verzweigung der héhern Gewachse, in
Pringsheim’s Jahrbiicher, xxv (1893). The older literature will be found in these works.
7 Tn other trees, for instance Fagus, axillary buds are already laid down in the winter-bud.
AXILLARY BRANCHING. ACCESSORY SHOOTS 433
formation, into which also lower and already more differentiated cells
can be brought. We see the same thing in other cases amongst trees
and shrubs and in the seedlings of herbs where, if one may so say, the plant
at first produces the necessary leaf-apparatus whose formation is later on
lessened. Where, as in long shoots of Berberis, the lateral shoots, which
are leafy short shoots, are unfolded rapidly, they also appear very near the
apex. This also holds for many water-plants.
In the inflorescence also of many plants, for example Amorpha and Salix,
the leaves nearest to the vegetative point have still no axillary bud, but it
is more common to find in the flower-region the axillary buds developing
so early that they are the lateral outgrowths of the axis nearest to
the vegetative point and there are no primordia of leaves above them,
and this independently of whether the axillary bud arises immediately
after its subtending leaf as in Plantago, Orchis, and Epipactis, or at
the same time with it as inthe Gramineae, Cytisus Laburnum, Trifolium,
Orchis mascula and Plantago, or before it as in Brassica oleracea var. botrytis
and other Cruciferae, Umbelliferae. Lastly it may happen that lateral buds
are developed without any trace whatever of a subtending leaf and this
takes place in many Cruciferae, Compositae like Inula, Gramineae like
Secale cereale in the upper part of its inflorescence. There is then in the
flower-region a hastening in the formation of the lateral shoots which is
often associated with a reduction in the development of the subtending
leaves and which may go so far that these may disappear altogether. This
reduction in some cases, as in the Gramineae, may be followed from below
upwards upon one and the same inflorescence. The bracts of the twigs
of the inflorescence are most developed in this family in the lower part of
the inflorescence, where however they have but the form of short sheath-like
primordial leaves or of cushions, whilst in the upper part they are only
visible at the very first inception of the lateral twigs and do not reach any
further development or as in the case of Secale cereale are wanting altogether.
We find the same in Sisymbrium where the formation of the bract is still
visible at the base of the inflorescence, but further up there is no trace of
one. Similarly the outer flowers in the umbel of many Umbelliferae have
bracts but the inner ones have none. In these, as in other cases, protection
of the flower-bud is attained in other ways, in the Umbelliferae for instance
by the concentrated position of the flowers and their envelopment by leaf-
sheaths?. The lateral shoots, to which bracts fail, have the same origin as if
these were present. They do not arise, as was at one time in a measure
supposed, by division of the vegetative point of the chief axis. This only
happens in flowering plants occasionally ”.
ACCESSORY SHOOTS. That the lateral shoots are products of the shoot-
1 See Part I, p. 59. * See below, p. 435, for the case of Vitis.
GOEBEL II F f
434 BRANCHING OF THE SHOOT
axis and become displaced subsequently more upon the leaf-base can be
clearly seen in the examples just mentioned, especially also in those cases in
which out of one leaf-axil mazy shoots arise. This may either result from
the early branching of an axillary bud or from the development of many
independent shoots out of the embryonal tissue of the shoot-axis. In the
leaf-axils of Aristolochia Clematitis we find a number of flowers arranged in
two zigzag rows. The oldest is furthest from the leaf-axil. In Aristolochia
Sipho and Menispermum canadense, above the cotyledons of Juglans regia,
and in other cases, such lateral buds stand in a simple row above the axil.
The history of development ! of Aristolochia Sipho and A. Clematitis as well
as of Menispermum canadense shows that the buds in these rows arise
independently one from another out of the stem-tissue. ‘The fact is simply
this, that in a leaf-axil where otherwise one shoot occurs the tissue of the
vegetative point of the stem remains long in the condition of a vegetative
point and forms a number of buds in progressive serial succession.’ These
shoots then spring out of a tissue-cushion formed by the intercalary vegetative
point of the stem above the leaf-base. Putting on one side the case of
Aristolochia Clematitis—in which the upper of these serial buds form flowers
whilst the under form leaf-shoots—it may be noted that most of these buds
usually do not unfold; it is only the uppermost one which develops,
whilst the others become resting-buds and only develop if the chief bud is
injured. In Juglans regia, for example, there may be above the axil of the
cotyledons as many as eight primordia of shoots and of these the uppermost
is the strongest. Not one of all these primordia usually grows out but they
gradually dry up and after some years, when the axis has become thicker and
the outermost layer ofthe rind has died off and split, there is visible no trace
whatever of them. But if in the course of the first or second year of the
existence of the plant the end-shoot is destroyed then one or more of these
primordia begin to grow. Gymnocladus canadensis behaves in a like
manner. In Gleditschia sinensis the primordia of the shoots which occur in
numbers in a row in the leaf-axils behave in such a way that the uppermost
develops into a thorn, the next into a foliage-shoot, and those lower down
either into foliage-leaf-buds or if they first shoot out on older portions of
the stem they become thorns*. Many attempts have been made to refer
these cases to a repeated branching of one axillary shoot *, and sharp limits
between the two interpretations can scarcely be drawn. If one supposes
that the tissue of the first axillary shoot has with its inner (upper) side
1 Goebel, Uber die Verzweigung dorsiventraler Sprosse, in Arbeiten des botanischen Instituts in
Wiirzburg, ii (1882), p. 391. Koch, Die vegetative Verzweigung der hohern Gewiichse, in Prings-
heim’s Jahrbiicher, xxv (1893), came to the same results.
* See A. Hansen, Vergleichende Untersuchungen iiber Adventivbildungen bei Pflanzen, in Abhand-
lungen der Senckenbergischen naturforschenden Gesellschaft, xii (1881), p. 169.
* See Russell, Recherches sur les bourgeons multiples, in Annales des sciences naturelles, sér. 7,
xv (1892).
SHOOT-TENDRILS OF AMPELIDEAE 435
united with the tissue of the chief axis and produces upon its embryonal
outer side a series of shoots, this construction would give in a certain measure
the scheme of the axillary branching.
SHOOT-TENDRILS OF AMPELIDEAE. The shoot-tendrils of the
Ampelideae have given rise to much discussion. They stand laterally on
the primary axis without a subtending leaf in their developed condition.
Phyletically these tendrils are derived from terminal inflorescences.
They are pushed to the side by the formation of vegetative lateral shoots
and the whole construction is then sympodial!. The history of development
(see Fig. 293) has been examined by many observers and shows that the
tendrils are not, as one would expect according to the theory just stated,
formed as the evident continuation of the internode immediately below them
‘ve.
Pash TO :
ee fare
Fic. 293. A, Vitis vulpina(‘odoratissima’). £, Vitis cinerea. A, tendrils; 5, eaves. After A. Mann.
and then only gradually pushed to the side by the stronger growth of their
uppermost axillary shoot, but that they either from the first have the leaf-
opposed position of the mature condition? or, that they proceed from the
apex of the axis itself through its unequal division, and in this way the other
portion of the vine is formed *. There occurs in the plant a rapid continua-
tion of the vegetative skeleton which finds its expression in the behaviour of
the vegetative point ; whether we speak of a sympodium or a monopodium
depends entirely upon what one chooses to express by these terms *.
FOLIAR ORIGIN OF SHOOTS. The axillary shoot is,as has been said °,
the product of the shoot-axis in many cases and becomes displaced upon the
base of the leaf. Koch is inclined to take this as the general rule but this
1 As this explanation is found in all textbooks I need not dwell upon it further.
2 As Nageli, Schwendener, and Warming have shown in Ampelopsis.
$ As Prillieux and Warming have shown in Vitis vulpina.
* According as one gives preference to the phyletic (comparative) or the developmental stand-
point. The assumption that a branch-system originally laid down as a sympodium may become
monopodial is probable in more than one case—fern-leaf, inflorescence of Boragineae, Hyoscyamus.
The biological significance of these phenomena has been discussed above, see p. 316.
5 See p. 432.
Ff 2
436 BRANCHING OF THE SHOOT
appears to me to be a by no means well-founded generalization. There is no
good reason why the primordia of shoots should not arise upon the /eaf-dase.
We see them in this position in many ferns and in Isoetes (Fig. 292). In
Bryophylium calycinum also and other plants they occur even upon the
leaf-surface and there they always develop out of stz// embryonal leaf-tissue.
Formation of adventitious shoots upon cut mature leaves is an extremely
common phenomenon. As has been already stated a sharp limit between
leaf-base and shoot-axis does not really occur. There isat any rate in many
cases an intimate connexion between subtending leaf and axillary shoot
which finds expression especially in this, that the axillary shoot ‘grows up
upon’ its subtending leaf—that is to say, the common base of the two is
elongated. We find this in many Cactaceae! especially in Mammillarieae.
Fleshy outgrowths appear in these plants
upon the shoot-axis and bear at their apex
a tuft of thorns and in their axils there
are frequently flowers. These fleshy out-
growths were formerly regarded as leaves ;
but the mammilla consists of two parts”:
first the lower strong-grown part of the leaf
which may be called the ‘leaf-cushion’ ;
second the axillary shoot which is united
throughout its length with the upper part
of the leaf-cushion. The vegetative point
of the axillary shoot frequently divides
Fic. 294. Mammillaria. Diagrammatic repre- into two pales wilichiare latemsepatarea by
sentation of a vegetative point with forked mam-
millae in longitudinal section. VP vegetative H thi
point, the young mammilla to the right Donets permanent tissue—an upper part which
ofleaf, 4, anditsaxillary shoot, VY, grownup upon as *
it. The vegetative point of the axillary shoot only br Ings forth leaf-thorns, and an under
will eae ve aa alawen Wi eee part which becomes a flower or a vegetative
permanent tissue, # &. Syst, leaf-bundles; : : :
P. Syst, axillary shootbundles,’S. Sys/, main @Xillary shoot. In many Mammnillarieae
mene ard frre fo" pag the flowers arise also upon the apex of the
mammillae and then we have quite similar relationships to those in other
plants where the flowers or inflorescences are leaf-borne. We must not
confuse with these the cases where the flowers are falsely described as
leaf-borne, as for example in species of Limnanthemum ? or in the case of
phylloclades *.
EPIPHYLLOUS INFLORESCENCE. We find the inflorescence of some
Dicotyledones on the leaves ® for example in Helwingia japonica, Dulongia
1 See Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 79; Ganong, Beitraége zur Kenntniss
der Morphologie und Biologie der Cakteen, in Flora, xxix (Erginzungsband zum Jahrgang 1894), p. 48.
2 See Goebel, op. cit.
* See Goebel, Morphologische und biologische Studien : VI. Limnanthemum, in Annales du jardin
botanique de Buitenzorg, ix (1891).
* See p. 449.
® See C. de Candolle, Recherches sur les inflorescences épiphylles, in Mémoires de la Société de
-_
EPIPHYLELOUS INFLORESCENCE 437
acuminata (Phyllonoma), species of Chailletia, Stephanodium _ peru-
vianum, Polycardia phyllanthoides, Begonia sinuata, B. prolifera, and
others. In the most of these instances we might have to deal with
a ‘displacement’ of the bud from the leaf-axil and a ‘concrescence’ of it
with the leaf, taking place in exactly the same way as was described in the
case of the Cactaceae and of Spathiphyllum platyspatha?. Such a con-
crescence occurs in Helwingia ruscifolia,
where the inflorescence is laid down
in the leaf-axil. But in other cases the
axillary bud may from the first be produced
rather upon the surface of the subtending
leaf near its base. We find this in Du-
longia which is shown in Fig. 295. The
inflorescence arises here upon the upper
side of the leaf below its ‘ forerunner tip’
which differs from that of the other leaves.
There is no reason for regarding the leaf
as a leaf-like twig; it has stipules at its
base; it had in the few cases I examined
an axillary bud just like the mammilla of
the Mammillarieae; and it has also the
usual origin of a leaf. That the primor-
dium of the inflorescence appears first of
all near the base of the leaf corresponds
to the intercalary growth of the leaf;
the anatomical character of the ‘sterile’
leaves examined by C. de Candolle does
not differ essentially from that of the
‘fertile’ leaves, and this may be so be-
cause the conducting system of the midrib
of the leaf is sufficient for the care of the
small-flowered inflorescence, from which
Say Ou Gesrwariimtts arise, sa far as her- 11-295. Dalongiaacuminats, H-B.K. I, leaf
with inflorescence. II, young leaf seen from the
barium-specimens enable me to judge. the sipaits with stalked marginal glands come
Whether the peculiar phenomenon of epi- {i Norchishlymaguitcd 1? Tasnified 2.
phyllous inflorescences stands in relation-
ship to the conditions of life or only illustrates what has been designated
by the beautiful name of ‘ construction-variation’ is unknown.
physique et @histoire naturelles de Geneve, Volume supplémentaire, 1891. De Candolle’s investi-
gations are inadequate for the solution of the question where the first inception takes place. He
trusts chiefly to anatomy which is only of secondary importance in such problems. There are many
transformations in configuration which find no expression in anatomy. De Candolle does not notice
the instructive features in the Cactaceae.
wee Part I, p. 55, Figs. 23, 24.
438 BRANCHING OF THE SHOOT
ADHESION OF THE BRACT. In the cases just mentioned the dract zs
predominant ; it is the most conspicuous part of the construction and we there-
fore commonly speak of the ‘adhesion of the axillary shoot’ to its bract.
Quite the same process only with predominance of the shoot is seen in the
very abundant cases of ‘adhesion of the bract’ to its axillary shoot. We
cannot however here discuss this condition ; its biological significance has
not been investigated. That it has such a significance I do not doubt as
the result of casual examination of the Solanaceae.
Atropa. In Atropa the sympodially constructed flower-bearing shoots
are, as has been already pointed out}, dorsiventral and the position and
Fic. 296. Atropa Belladonna. Bud of inflorescence in transverse section. Z 7/7, 77/7, IV, flowers. Ty, Tv, Tyiz,
flower Z'balong Vir and 717i, toflower 227 belong Via an iy, tose: Op belae eee eg
formation of the leaves stand in connexion therewith ; but in the peculiar
‘displacement’ which the leaves obtain by the ‘adhesion of the bract to ‘its
axillary shoot’ we have, in my view, an arrangement for the protection of
the flower-buds. If we examine a transverse section through a bud of the
inflorescence of Atropa as we see it in Fig. 296, we shall find that each
flower-bud is protected by two leaves turned towards the outer side of
the whole inflorescence much more so than is shown in the figure which is
taken through the lower portion of the older leaves where the lamina has
only a narrow surface. One of these leaves is the bract, 7, adherent to the
flower-stalk, the other is one of the two prophylls, V, of the flower.
Seeing that the bract stands at about the same height as the prophyll the
tr Seenbart Ups fi.
ADHESION: OF “BRACTS. * ARRESTED, BUDS 439
closure round the flower towards the outside is made possible and this not
only affects the individual flower but also all the parts which lie inside}.
I believe that in this way it is possible to interpret, upon biological grounds,
relationships which have hitherto only been treated from the side of formal
morphology. At any rate, in the flower-bud, which is marked ///, it appears
that the first sepal arises in the position which is least protected by other
parts, an incident which is self-explanatory. We shall speak of analogous
cases when considering the development of the flower.
ARRESTED Bubs. Of the lateral buds which are laid down it is only
seldom that all develop further. Some are arrested either at once if they
are flower-buds or if they are vegetative buds they remain for some time
capable of development and may under special conditions such as loss of
other shoots enter into activity. The branching renders easy also the
division of labour amongst the several shoots, the more important different
forms of which I must now refer to.
' Other Solanaceae show the same features. In Datura the adhesion of the bracts closes the bud
on the outside. The leaves have in Datura, as in Atropa, a large ‘forerunner-tip.’
2 See Part I, pp. 58 and 208.
440 DIVISION OF “LABOUR GIN: THEY SHCOe
C. DIFFERENT CONSTRUCTION OF THE SHOOT.
DIVISION OF LABOUR
Just as we consider the foliage-leaf to be the typical leaf by the trans-
formation of which the other leaf-forms arise so we take the foliage-shoot or
assimilation-shoot to be the typical shoot, and we can show that there may
be also a change of function in it, and that therewith is bound up a change
in conformation. The transformation may take place here also early or late.
A shoot of Prunus spinosa, for example, bears at first a number of foliage-
leaves decreasing in size upwards and then it becomesa thorn. It is first of
all foliage-shoot and then thorn, and it is easy to cause its further develop-
ment as a foliage-shoot if one cuts off sufficiently early the apex of the shoot
from which it arises—that is to say before the determination of the character
of the twig as a thorn. The stolons of Circaea lutetiana and C. alpina
arise in the ground, are stolons from the beginning, and produce only small
scale-leaves, but by definite influences referred to below, we can induce
a plant, which has already produced a number of leaf-pairs, to grow out
at its apex—that normally would become an inflorescence—into a stolon
below the soil. Even shoots, which are changed to the great extent
observable in the flower-shoots, may in their earliest stages grow out
further as foliage-shoots, for example the female flowers of Cycas. In other
cases this takes place only exceptionally where pathological changes occur.
The plant takes the organs which are necessary first of all for its existence,
and these are the assimilation-organs, and adapts them to other functions.
We speak of the most important shoot-forms shortly in relation to their
function, and this depends upon the manner of life of the plants, using this
expression in its widest sense. Two factors have specially to be con-
sidered :—
(a) The relationship of the reproductive organs to the vegetative
organs.
(2) The influencing of the vegetative organs by the external conditions
of life.
DIVISION OF LABOUR AND DURATION OF SHOOTS. In the Spermo-
phyta the division of labour amongst the shoots is the less marked the more
rapidly they proceed to the formation of seeds, and it is plants which last
during many vegetative periods interrupted by periodic stages of rest
before they produce flower that have shoot-forms adapted to very different
functions,
In annual Spermophyta there is no division of labour between the vege-
THE SHOOT IN VEGETATION 441
tative shoots. All these shoots are attuned toa life in light and pass finally
all of them to the formation of flower. The primordia of shoots in the under
region of the plants remain however often undeveloped or only develop if
the nutrition is particularly abundant or if there is injury to the chief shoot.
The complex shoot-formations have sprung from that of the annual plants.
The later in the developmental stages the formation of the reproductive
organs is undertaken, the more opportunity is there, as has already been
remarked 1, for the vegetative body to increase in mass and to experience
that division of labour which is bound up with this.
Among the Pteridophyta there are relatively few annual forms, for
instance Anogramme leptophylla and A. chaerophylla, Salvinia natans, and
Selaginella Drummondi?. These are all adapted to localities in which there
is a periodic interruption in vegetation, in the resting period the spores are the
only things which are left over. Where more uniform conditions of life
exist annual Pteridophyta are not present. The tropical species of Salvinia,
for example, known to me have all an unlimited existence. The peren-
nating Pteridophyta conform with the Spermophyta in the configuration
of their shoots although they show in general a less varied adaptation than
these do.
RELATIONSHIPS OF THE SHOOTS TO THEIR FUNCTION. The doctrine
of the ‘ succession of shoots,’ that is to say the construction of the plant-body
out of shoots with different function and of different conformation, cannot be
stated shortly here*. We can only speak in general of the relationships of
the shoots to their function. This will be done in two sections, the first one
dealing with the shoot as a vegetative organ and the second with the shoot
in the service of reproduction.
SHESSHOOT IN VEGETATION
The most striking differences observable in vegetative shoots are those
between efigeous and hypogeous shoots; but there is really no sharp dis-
tinction to be made between them. Yet it appears to me better to treat
of them separately because there are a number of biological characters which
are different in each.
1 See Part I, p. 141.
? Ceratopteris thalictroides can hardly be included. It propagates freely by leaf-borne shoots, it
is like many other marsh and water-plants adapted to rapid changes in environment expressed in the
short limit of existence imposed upon single shoots. It is not adapted however to periodic changes
in environment.
$ Raunkizr, De Danske Blomsterplanters Naturhistorie, Bd. 1, Kjgbenhavn, 1895-9, gives an
excellent account of these relationships so far as European monocotylous plants are concerned. The
literature is fully cited.
442 EPIGEOUS SHOCTS
I
EPIGEOUS (PHOTOPHILOUS) SHOOTS
(a) ORTHOTROPOUS RADIAL SHOOTS AND THEIR TRANSFORMATIONS.
Ie ARRANGEMENT OF THE LEAVES AND LENGTH OF INTERNODES,
There are two important features in this configuration—
1. The arrangement of the leaves,
2. The length of the internodes.
In shoot-axes with elongated internodes the method of arrangement of
the leaves within somewhat wide limits is of clearly little biological
importance. Whether the leaves on an elongated shoot are in whorls or are
distributed in the phyllotaxy of 4, 2, 3, and
so on, is of little moment for the function of
the leaves, because they cannot cover one
another or shade one another for long.
It is different in plants with short con-
tracted internodes, and here there are fre-
quently arrangements by which the over-
lapping of the leaves is prevented. Some
examples of these may now be given :—
Callitriche. Callitriche (Fig. 297) has leaves
in decussate pairs. The internodes are at first
elongated. If the apex of the shoot of this water-
FIG. 297. Callitriche verna. Leaf-rosette plant reaches the surface of the water an arrest
from above. Magnified 3. G
takes place in the elongation of the internodes.
They remain short but one can cause them to elongate by submerging the plant’.
If now the leaf-pairs were strictly decussate they would so cover one another that only
the two uppermost pairs would be exposed to direct light. ‘This is avoided by torsion of
the internode (Fig. 297)° and the well-known ‘ water-star’ is formed, the older leaves
in which are brought beyond the younger ones by the stalk-like elongation of their
bases.
Similar features are observed in some species of Cyperus which have a one-third
spiral phyllotaxy. Figs. 298 and 299 show the torsion of the leaf-rows. It is well
known that in Pandanus also and some species of distichous Aloe like features are
observed.
It is clear that the same result would be obtained if the leaves were from the
first spirally arranged with a higher divergence, and we find this in many species of
Sempervivum and Sedum and in the floating leaf-rosettes of Trapa, Pistia, and others.
' The plant at first endeavours by elongating the internodes to bring the leaf-rosette to the surface
of the water, if this does not suffice then the internodes which normally would be short elongate.
? I leave on one side the question whether there is not a divergence from the decussate position in
the inception of the primordia on the vegetative point.
LEAF-ARRANGEMENT ON RADIAL SHOOTS 443
Gentiana. Plants such as Gentiana acaulis, G. verna, Arnica montana
which have decussate leaves in a basal leaf-rosette, are no exception. It
Fic. 298. Cyperus alternifolius.
Bud invested by kataphylls shown in transverse section. The tristichous
arrangement of the leaves is evident but is already somewhat distorted in the lower ones.
can be readily observed in Gentiana acaulis, for example, that the number of
leaf-pairs at the base is very small, I have usually found here only four assimilating
leaves in the rosette4, so
that there can be no cover-
ing by the individual leaves.
The species of Gentiana
which form a greater num-
ber of leaf-pairs, like Gen-
tiana lutea, G. asclepiadea,
and others, have elongated
internodes. Shoots with
contracted internodes are
found in plants of the most
different cycles of affinity, and
living under the most differ-
ent conditions, so that no
general explanation of this
arrangement can be given.
Fic. 299. Cyperus alternifolius. I, shoot from above, the leaves are
clipped. The tristichous arrangement slightly distorted is indicated by
the figures 1, 2, 3. II, leaf with axillary bud. III,axillary bud in trans-
verse section. .S, prophyliswollenup. I, half naturalsize. III, magnified.
1 If it were six the uppermost pair was very small and could only cover the lower part poor in
chlorophyll of the leaf-pair below.
I found the same in G. verna. The older etiolated leaves,
which are still retained, are of course not considered.
444 EPIGEOUS SHOOTS
2. SHORT SHOOTS AND LONG SHOOTS.
One of the most frequent divisions of labour observed upon the
vegetative shoots, is that into short shoots and long shoots. This terminology
is hardly fitting, because the diagnosis of the two shoot-forms lies less in their
length than in their significance in the construction of the woody plants in
which they are almost exclusively found. The short shoots take no share
in the construction of the permanent skeleton of the plant. They die after
a comparatively short time. Their shoot-axis does not branch vegetatively
or form any mass of wood. Yet the short shoots are frequently those which
produce the flowers, and this conforms entirely with the fact that restriction
of vegetative growth favours the formation of flower’. It is impossible to
draw a sharp limit between long shoots and short shoots. In many plants,
for instance Larix europaea, short shoots may spontaneously grow out into
long shoots, and under unfavourable conditions the formation of long shoots
may be suppressed for years. In other cases the same result is brought
about by the cutting off of the long shoots, even in cases where the short
shoots are so sharply distinguished from the long ones as they are in species
of Pinus. In Pinus, after the first few years of life, the long shoots produce
the scale-leaves only, the assimilation-leaves are limited to the short shoots
on which they appear in pairs, as in P. sylvestris, or in greater numbers,
five for instance in P. Strobus. In Pinus also the short shoots may be
caused to grow out into long shoots; they are only quantitatively, not
qualitatively, different from them.
Double needles of Sciadopitys. In the remarkable short shoots of Sciado-
pitys there is occasionally observed a ‘ continuation of growth*’ These short shoots
are commonly called double needles. As a matter of fact one sees upon young just
elongated shoots the combination of two ‘ concrescent’ needles between which a
longitudinal furrow is very conspicuous. These double needles stand in the axil of
small scales upon the stem and have therefore the same position as the short shoots
of Pinus. They are traversed by two completely separate vascular bundles which are
enclosed by the peculiar /ransfuston-tissue of the coniferous leaf, and von Mohl * upon
this basis suggested that they were the result of the concrescence of the two first leaves
of an axillary shoot which was otherwise arrested. The history of development as
published by Strasburger® is very peculiar and requires, I think, further proof.
There arises in the axil of the scale the primordium of an axillary bud which shows
very early an evident median indentation at the apex, and this is still recognizable on
the mature double needle. According to Strasburger this whole structure is the
15See Part I,\p. ara:
* Regarding juvenile stages see Part I, p. 153.
* See Carriére’s figure in Gardeners’ Chronicle, March 1, 1884, p. 282.
* Von Mohl, Morphologische Betrachtungen der Blatter von Sciadopitys, in Botanische Zeitung,
xxix (1871), p. Tor.
* Strasburger, Die Coniferen und die Gnetaceen, Jena, 1872, p. 382.
ORTHOTROPOUS SHORT SHOOTS AND LONG SHOOTS 445
primordium of the double needle. It grows at its base like other needles after apical
growth has ceased at an early period. The apex then of the axillary shoot is here
used up in the formation of the needles, but the individual needles of the combined
body do not grow separately but by intercalary growth at theircommon base. There
can be no doubt that the structure corresponds to the primordium of a short shoot
of Pinus, in which only two leaf-primordia are laid down, but the interpretation of the
double needle as being formed out of two concrescent ‘leaves ’ appears to me ! to be
by no means devoid of doubt although Strasburger has found double needles both in
Pinus sylvestris and in Pinus Pumilo. We do not know the mode of origin of these
needles in Pinus. They might be the result of an actual concrescence of two needles
whereby the vegelative point of the short shoot remains behind at the base and the needles
are joined together by their contiguous sides; but in Sciadopitys the chief portion of
the needle proceeds from the part of the axillary bud which lies below its vegetative
point. Sciadopitys affords in the vegetative region an example which has no parallel
elsewhere, and according to the ordinary terminology we must regard the double
needle rather as leaf-like twig—a phylloclade—bearing on its primordium the tips
of two needles as small points, notwithstanding the anatomical fact, which however
is not after all of much importance, that we know elsewhere also phylloclades which in
their structure resemble leaves. The actual name we use is of less importance ; the
fact remains that out of the axillary shoot there proceeds a structure which in its
construction resembles two leaves united by their edges.
PRECEDENCE IN UNFOLDING OF SHORT SHOOTS. The short shoots
precede in their unfolding the long shoots in most instances and this we can
understand upon biological grounds, because less energy and less material is
required for them than for the long shoots. The capacity for assimilation also
of the short shoots partly comes into consideration. In Larix, for example,
they have to furnish the material for the formation of the long shoots, and
in plants like Pyrus and Prunus, which have entomophilous flowers, their
development before the long shoots is of marked advantage for the exposure
of the ‘flag-apparatus’ of the flowers. That the short shoots of Pinus and
Berberis unfold at the same time as their subtending leaves, is a consequence
of the transformation of these leaves into kataphylls and thorns.
ASSIMILATING SHOOT-AXES. Shoot-axes whose internodes are elon-
gated may share in the work of assimilation if they contain chlorophyll, but
the amount of this is small and much behind that in the leaves. In numerous
plants we find, however, that there is a reduction of the leaves accompanied
by an increased assimilation-capacity of the shoot-axes. That we have here
1 As I have shown, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Hand-
buch der Botanik, iii (1884), p. 216, whence this passage is taken. Dickson, The phylloid shoots of
Sciadopitys, in Journal of Botany, iv (1866), regarded the ‘double needles’ as phylloclades. See
also Bower, in Gardeners’ Chronicle, March 15, 1884, p. 346. Also Bertrand, Anatomie comparée
des tiges et des feuilles chez les Gnétacées et Coniféres, in Annales des sciences naturelles, sér. 5,
xx (1874).
446 EPIGEOUS SHOOTS
a correlation has been proved by the investigations of Boirivant! who found
in anumber of plants that the shoot-axis became richer in chlorophyll if the
leaves were removed. In Sarothamnus vulgaris shoot-axes which are thus
treated have a palisade-parenchyma much more developed than that of the
untouched shoot-axes. The connexion between the removal of leaves
and the increase of chlorophyll in the shoot-
axes is not explained by this. We have yet
to find out, for example, whether the shoot-axis
would be constructed as a stronger assimila-
tion-organ if the leaves were not removed but
were merely prevented doing their assimilation
work. We may, however, assume that there
is a direct connexion between the reduction of
the leaves and the formation of the shoot-axis
as an assimilation-organ. —
REDUCTION OF LEAVES ON ASSIMILA-
TING SHOOT-AXES. Arrest of the leaves on
assimilating shoot-axes appears very markedly
in xerophilous plants in which there is a gene-
ral reduction of the transpiring surface. We
find examples of this in the most different
cycles of affinity, as in the Casuarineae, many
Leguminosae, such as Spartium junceum and
others, amongst the Ranunculaceae in Clematis
afoliata, in most of the Cactaceae, and so on.
But in marsh-plants also we have the same
phenomenon, for example in the composite,
shown in Fig. 300, which I found in a very
moist marsh in West Australia. It is well
known that many although not all marsh-
plants have xerophilous features, but their
relationships to life-conditions I cannot enter
into here. Where there is copious branching
. of the shoot-axis with reduced leaves we get
aoe ates West Aus- the same result in the matter of development
. of surface as we do when the leaves are pre-
sent with less branching, and amongst our endemic species of Equisetum,
E. hyemale may be designated xerophilous, but E. sylvaticum, E.
pratense, and E. arvense are not so. We must here, as everywhere
else, consider, besides the adaptation to external relationships, an ‘internal’
* Boirivant, Recherches sur les organes de remplacement chez les plantes, in Annales des sciences
naturelles, sér. 8, vi (1897). The literature is cited here, but very imperfectly.
7
ASSIMILATING SHOOT-AXES 447
factor which conditions the formation of the organs but which does not allow
us to regard them as purely adaptations. Thus amongst submerged plants
also there are some which belong to this category—Scirpus submersus,
C. Wright, for example, which I found in large masses in the Tapacooma
lake. The shoot-axes of this plant are tuftedly branched, each produces
some kataphylls and assumes, what is a character of the short shoots, the
form of a cylindric leaf with a layer of assimilating cells under the small-
celled epidermis (Fig. 301).
Assimilating shoot-axes with reduction of the leaves are very abundant
in Monocotyledones, for example in Heleocharis, Scirpus lacustris, the Res-
tiaceae, and elsewhere. The juvenile stages of
these plants, so far as we know them, have
foliage-leaves and it is only upon the elongated
assimilating shoot-axes that the leaves are re-
duced to scale-leaves. Perhaps these assimi-
lating shoot-axes are really zzflorescence-axes
—upon which, however, the flowers often abort.
We shall have opportunity to return to this
subject again when dealing with phylloclades.
The striking similarity observable between the
sterile shoot-axes of plants like Heleocharis!
and Scirpus lacustris and the cylindric leaves Tee ee ar
of Juncus—these were formerly therefore desig-
nated ‘sterile culms ’—and the fact that all these plants live under essentially
the same conditions have led to the supposition that the conformation of the
assimilation-organs is utilitarian in both cases. The leaves of the species of
Scirpus were perhaps not in a condition to take on the cylindric form and
experienced, in consequence, a reduction in formation with a corresponding
diminution in function’. In many of these Monocotyledones it can be shown
that the leaf-formation may again set in under conditions which are unfavour-
able to the formation of assimilating shoots, and we have here then essentially
a reversion to the juvenile stage*. Scirpus lacustris* forexample forms long
These consist of one long shoot-internode at the end of which a couple of scales is found if no
flowers develop. On the rhizomes there are kataphylls only. In Cyperus alternifolius the elongated
shoot-axis bears foliage-leaves. Here also perhaps originally there were inflorescences which in the
first developmental stages of the plant suppressed their flower-formation and appeared as strengthening
shoots. From the same standpoint we may regard the first still flowerless shoots that appear above
ground in Polygonatum, Paris, and like plants, and it seems to me this gives us a more comprehensive
view of the construction of these plants in which a process similar to that in the Cladonia amongst
the lichens (Part I, p. 72) may have taken place—first of all the fructification was raised upon a stalk
and then vegetative activity set in within it.
? See what is said about the formation of phyllodes, p. 353.
musee arth, p..t7I.
* In this plant the formation of foliage-leaves is not so completely limited to the seedling-stage
as it is in Heleocharis, where, so far as I know, it is unknown in older plants, though perhaps
448 EPIGEOUS SHOOTS
bana-like leaves in deep or rapidly running water, and also if the plant is
‘weakened’ by repeated removal of the haulms. In Eriophorum alpinum also
I saw leafy foliage-shoots develop as solitary vegetative organs like those
of the young plants, upon plants ‘enfeebled’ by unfavourable conditions of
cultivation.
INCREASE OF SURFACE OF ASSIMILATING SHOOT-AXES. The assimilat-
ing shoot-axis may experience an increase in surface in the most different
cycles of affinity. This may be brought about in two ways which however
are scarcely separable from one another :—
(2) By the flattening of the shoot-axis. Opuntia illustrates this.
(2) By the formation of wings. This is a consequence of ‘decurrent
leaf-bases.’ These are found on the shoots of some plants, like species of
Symphytum, Carduus, which have not reduced leaves. But in Genista sagit-
talis! the green membranous surface which is formed by the wing of the
stem-internode far exceeds the total surface of the small unsegmented
leaves. The stem in this species is still sharply segmented into internodes,
and the nodes upon which the leaves arise are not ‘winged.’ Below each
leaf the internode is widened by two ‘wings’ which are continuous with the
leaf-surface. The leaves do not yet stand in two rows.
PHYLLOCLADES AND CLADODES. The more the segmentation of the
nodes and internodes disappears, and the distichously arranged leaves become
reduced, the more does the shoot-axis diverge from its ordinary habit, and
if at the same time it assumes limited growth it acquires a striking resem-
blance to a leaf, and is designated a piylloclade. This name is best reserved
for such leaf-like shoot-axes of limited growth, whilst other widened axes
may be called cladodes. ‘The following are some illustrations :—
Pteridophyta.
The Equisetaceae and some Lycopodineae especially the family of the Psilotaceae
supply examples. The two epiphytic genera, Psilotum and Tmesipteris, have no roots
but root-like shoot-axes and live in stations where temporary want of water can readily
occur. In the two species of Psilotum the leaves are reduced to small scales for the
protection of the vegetative point, whilst in Tmesipteris they are better developed, but
by their vertical position approach xerophilous construction. It is noteworthy that _
in one species of Psilotum, Ps. complanatum, the shoot-axis is no longer nearly |
cylindric but is flattened in the way that we frequently find it in Spermophyta.
Gymnospermae ’.
The species of Phyllocladus are low trees or shrubs which are endemic in
New Zealand and Tasmania. They have cylindric chief axes with spirally placed
leaves, and these are small and scale-like soon dry and fall away. In their axils flat
it might be artificially induced. The leaves at the base of the ‘haulm’ often have a very short
lamina.
+ See Part I, Fig: 124:
2 Regarding Sciadopitys see p. 444.
PHYLLOCLADES AND CLADODES 449
leaf-like twigs, which in their outline resemble the leaves of ferns, are developed, and
these are again branched but always in ove plane. Individual branches of this form
produce flowers. There is a difference
in these leaf-like twigs between the struc-
ture of the upper side and of the under
side as in most leaves. The under side
has far more stomata than the upper,
whilst the upper side has sub-epidermal
palisade-tissue which is wanting on the
under side’. The phylloclade-nature
of these twigs is not yet fixed here,
because the stronger ones may again
grow out at the tip into radial cylindric
shoots, whilst those in which this does
not take place doubtless soon fall from
the stem like the short shoots of Pinus,
or those short shoots of Larix which are
not developed into long shoots.
Monocotyledones.
Bowiea volubilis. The first
example to be noted here is Bowiea
volubilis. The shoot-axis produces long
narrow foliage-leaves only in the seedling-
stage, that is to say until the bulb is
strongly developed. Subsequently there
develops out of the bulb a very long—
as much as two meters in cultivated
examples — twining chief axis whose
straggling lateral cylindric shoots may
be recognized as scramblers. The
elongated axis on which these cylindric
shoots which are of limited growth arise
forms only scale-like kataphylls; the
cylindric shoot-axes themselves act as
the assimilation-organs. In the upper
part flowers appear whose stalks (Fig.
302) have exactly the same form as the
assimilating short shoots. It appears to
me that the whole shoot which springs
from the bulb has arisen from az in-
florescence whose branchings have par-
tially lost the capacity of forming flowers,
Fic. 302. Bowiea volubilis. The flower-stalks contain
chlorophyll and act as assimilation-organs. In the lower
region rile plant, and upon young plants, the flowers are
arrested. Natural size.
1 Resembling both in habit and in structure these phylloclades is the twig-system of Thuja,
in which, however, leaves are present but closely pressed_to the twigs.
GOEBEL II
Gg
450 EPIGEOUS SHOOTS
and that in conjunction with the formation of assimilation-shoots the formation
of foliage-leaves dwindled. I have been led to speak of this liliaceous plant because
it shows in a somewhat more primary form the same relationships as we meet with
in the genus Asparagus.
Asparagus. The phylloclades here have somewhat varying forms. In
Asparagus officinalis, for example, they are needle-like leafless shoot-axes standing in
tufts in a double scorpioid cyme in the axils of the kataphylls. In Asparagus
Sprengeri they are flattened’, very leaf-like, but constructed alike upon both sides.
In Asparagus (Myrsiphyllum) medeoloides the resemblance in appearance to a leaf
is very marked, the anatomical structure is also dorsiventral, and the course of the
vascular bundles conforms to that of the leaves. The conjecture, first put forward
by Kunth’, that the phylloclades of Asparagus proceed from the stalks of arrested
flowers seems to me plausible, and it gives an explanation also of their deciduous
character. Such a sterilization of the flower-stalks and inflorescence-axes takes place
frequently in the formation of tendrils.
Ruscus. Ruscus from which the genera Semele and Danaé are separated * has,
on account of its phylloclades, caused much discussion, and at all times, up to the most
recent, there have not been wanting those who declared these to be leaves, and
especially upon anatomical grounds: the vascular bundles form a cylinder only at
the base of the phylloclade; they spread out in the leaf-like surface. That this fact
is of no moment as against the morphological facts which stand as clear as day is
evident. The species of Ruscus with leaf-like twigs, such as Ruscus aculeatus,
R. Hypoglossum, R. Hypophyllum, possess a subterranean rhizome out of which
annually in the spring turios appear above ground. These shoots bear in their
lowermost part a number of sheath-like relatively considerable leaves which are
usually green at the tip*. These leaves are reduced foliage-leaves as is shown by the
fact that Semele androgyna possesses well-developed foliage-leaves upon the seedling-
plant’. Askenasy® has also observed in Danaé racemosa the interesting anomaly
that some leaves with a long stalk and oval green lamina, like the leaves of Convallaria,
sometimes follow upon these sheathing-kataphylls—an appearance which may be
considered a reversion to the leaf-form possessed originally by Ruscus before it had
phylloclades. The stem, however, usually elongates above the sheathing-leaves and
1 See Reinke, Die Assimilationsorgane der Asparageen, in Pringsheim’s Jahrbiicher, xxxi (1898) ;
where are figures, and the literature is cited. It may be noted here that the flower-stalk in Asparagus
Sprengeri is not flattened but cylindric.
* See Kunth, Enumeratio plantarum, Stutgardiae et Tubingae, v (1850). Regarding Asparagus
(Myrsiphyllum) medeoloides he says, p. 105, ‘ folia squamaeformia, pedunculos 1-3 fertiles, unifloros,
basi bracteolatos, superne noduloso-articulatos et unum sterilem foliiformem, magis minusve
inaequilaterum (cladodium) stipantia, saepissime nonnisi hunc.’
5 In Semele the inflorescences arise on the margin of the phylloclade, in Ruscus on the upper side,
in Danaé they are separate from the phylloclade.
* See Schacht, Beitrag zur Entwicklungsgeschichte flachenartiger Stammorgane, in Flora, xxxvi
(1853), Pp. 457; Askenasy, Botanische morphologische Studien, Frankfurt, 1872, p. 3; Celakovsky,
Uber die Kladodien der Asparageen, in Denkschriften der Bohmischen Akademie, 1893 ; see also
résumé by the author in Engler’s Jahrbiicher, xviii (1894), Litteraturbericht, p. 30; Reinke, op. cit.
See Part leap. 100;
§ Askenasy, op. cit., p. 22.
PHYLLOCLADES AND CLADODES 451
produces then a number of small membranous scales which fall off early and in the
axils of which the phylloclades stand*. The apex of the shoot itself commonly
becomes. leaf-like. The whole of the parts of a shoot of Ruscus are already laid
down when its apex appears above ground in spring. ‘The flowers, or rather the few-
flowered inflorescences, arise out of the phylloclades, upon the upper side in Ruscus
aculeatus (see Part I, Fig. 101) and Ruscus Hypoglossum, upon the under side in
Ruscus Hypophyllum. They stand in the axil of a leaf, the only one which the
phylloclade possesses ; it shoots out early upon the phylloclade which is laid down
like other twigs. The bract dries up in Ruscus aculeatus usually early, but in Ruscus
Hypoglossum it is larger and leathery and takes the form and structure of the phyllo-
clade itself, and this has given rise to erroneous interpretations. The phylloclades of
Ruscus aculeatus place themselves in such a position that they do not have one surface
directed upwards and another directed downwards but undergo a torsion through go’,
so that their edges are directed upwards and downwards as is the case in the phyllodes
of Acacia. These relationships may, however, be changed by illumination.
Dicotyledones.
‘Phylloclades or cladodes occur in different families of this class, and the following
are a few instances only of the manifold variations they exhibit.
Carmichaelia. In this, chiefly New Zealand, genus of Leguminosae? the
reduction of the leaves and the consequent flattening of the shoot-axis are phenomena
of adaptation. Some species have cylindric leafy shoots, for example C. Exsul, they are
also found in C. flagelliformis, in which the leaves are arrested in sunny situations but
are developed in shady positions*. Most species after the first juvenile stage have
flattened shoot-axes whose leaf-development appears to be in great measure dependent
upon external conditions. In cultivation the young shoots especially still bear foliage-
leaves whilst the older ones only produce reduced leaves.
Bossiaea. Similar features to those in Carmichaelia are found in this legu-
minous genus.
Colletia. This genus of the Rhamnaceae has in one species, Colletia spinosa,
cylindric shoots with reduced formation of leaves. Colletia cruciata, on the other hand,
possesses short shoots flattened in the vertical plane, but seedling-plants have the form
which appears during its whole life upon Colletia spinosa. Shoots showing a reversion
to the juvenile state also appear on adu// plants‘.
Phyllanthus. Features of some species of this genus of Euphorbiaceae have
been already referred to®. There are dorsiventral lateral shoots bearing at their base
a bud—just as a leaf has an axillary bud—out of which may proceed a long shoot.
1 In Ruscus aculeatus and Danaé they stand on the lateral axes; only in the seedling, for instance
of R. aculeatus, are they on the chief axes.
See Reinke, Untersuchungen iiber die Assimilationsorgane der Leguminoseen : I-VII. in Prings-
heim’s Jahrbiicher, xxx (1897). The literature is cited here.
° See L. Cockayne, An Inquiry into the Seedling Forms of New Zealand Phanerogams and their
Development, in Transactions of the New Zealand Institute, xxxi (1898).
* See Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 17, Fig. 8.
5 See Part I, p. 97
Gg2
452 EPIGEOUS SHOOTS
It is probable that as Dingler’* conjectures the construction of these leaf-like short
shoots was the cause of the reduction of the foliage-leaves of the chief shoot to kata-
phylls. On the seedling-plant foliage-leaves still appear. Still further goes the
transformation of the shoot in that section of the genus termed Xylophylla where the
shoot-axes are transformed into leaf-like phylloclades? which bear kataphylls only
in the mature plant but have still foliage-leaves in the seedling-plant. These
phylloclades are laid down as normal cylindric axes, but they broaden later and
become flat.
Other examples, like Muhlenbeckia platyclados one of the Polygonaceae, and
Siebera compressa one of the Umbelliferae, do not require further explanation. We
must, however, mention the—
Cactus-form. By this we understand assimilating shoot-axes with fleshy tissue
acting as a water-reservoir. Storage of water appears also in other assimilating shoot-
axes for example amongst the Leguminosae in Carmichaelia crassicaulis, Notospartium
and others, in Kleinia and other Compositae, in Geraniaceae ; but the cactus-form of
the Cactaceae—a form which is repeated in the succulent species of Euphorbia and in
the Stapelieae—has special characteristics. The formation of shoots of the Cactaceae
has been already described *, and further information may be obtained from the
sources cited below ¢.
3. TRANSFORMED RADIAL SHOOTS.
We must consider as transformed shoots all those in which the work of
assimilation has been exchanged entirely or in great part for other functions.
THORNS. In the transformation of shoots into zhorus as it takes place
in species of Prunus, Rhamnus cathartica, Ononis spinosa, and others, we
have features resembling those of the shoots mentioned above whose axis
serves as an assimilation-organ, in so far as in the thorn-shoots the leaves
are suppressed, and there are not wanting middle stages between shoots
which have taken over the function of foliage-leaves and those which have
been constructed as thorns. In many shoots both features appear together.
Thus the phylloclade of Ruscus aculeatus ends in a thorn, and the same is
the case in the flat shoots of Colletia cruciata. Transition-forms from normal
foliage-shoots to thorns are also found, for instance, in the Pomaceae and
Amygdaleae’. The thorn-twigs of Crataegus Oxyacantha, for example,.
before they close their growth at the apex by producing a thorn, form a
? Dingler, Die Flachsprosse der Phanerogamen, Heft i: Phyllanthus, Miinchen, 1885.
? Dingler conjectures that the ‘ phanerogamous leaf’ has arisen in the same way, that it is a
flattened shoot. Against this it may be said (1) the development of the phylloclade in Phyllanthus
itself evidently points to an origin from a /eafy shoot, (2) in the Hepaticae the ‘leaf’ has developed
in different series from different starting-points.
8 See Part I, p. 168.
* Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 67; Ganong, Beitrage zur Kenntniss
der Morphologie und Biologie der Cakteen, in Flora, lxxix (Erganzungsband zum Jahrgang 1894).
° See Delbrouck, Die Pflanzen-Stacheln, in Hanstein’s Botanische Abhandlungen, ii (1875), p. 17;
Areschoug, Beitrage zur Biologie der Holzgewachse, in Acta Universitatis Lundensis, xii (1875-6).
TRANSFORMED RADIAL SHOOTS 453
number of rudimentary foliage-leaves which soon fall off, and have at their
base a pair of buds which in the next year grow out into short twigs. Also
other twigs become converted into thorns? after having produced some
foliage-leaves whose axillary buds grow out in the next year. If in
Crataegus one cuts off at the right moment a long foliage-shoot above
the point where stands a normal lateral short shoot which would become
a thorn, one may compel this short thorn-shoot to become a long foliage-
shoot instead of a thorn-shoot. This same effect has, as is well known,
been produced by cultivation in Pyrus Malus and other Pomaceae. As on
the phylloclades so on the thorn-shoots the formation of foliage-leaf is
rudimentary. In many thorn-shoots the leaf-formation is as entirely absent
as in the needle-like twigs of Asparagus.
' STORAGE-SHOOTS. I donot require to say anything further here about
the shoots which are used as storage-organs. The configuration of bulbs
and tubers is explained in every textbook, and we know nothing about the
conditions which have brought about the appearance of these organs. Most
of these storage-shoots proceed out of hypogeous (geophilous) shoots, yet the
cactus-form—which must be reckoned amongst these—shows that epigeous
(photophilous) shoots may be devoted to the same useful function, and many
other plants form epigeous tubers or bulbs. Vitis pterophora shows this in
remarkable degree, for at the end of its vegetative period the tips of the shoot
are arrested and one or two internodes below it swell out, then they fall off
with the buds, one or more, that are upon them, and after a period of rest—
which probably enables the plant to live through a dry period—they again
shoot out into active life *.
4. TRANSFORMED RADIAL SHOOTS IN LIANES.
When speaking of the transformation of leaves into climbing-organs
such as hooks and tendrils, as well as when discussing the formation of roots,
reference was made to some species of liane. Here therefore we have only
to note the formation of the shoot in some other lianes. The phenomena of
growth of the shoots of lianes, such as circumnutation and the like, dealt with
in physiological textbooks, will not be discussed here, and I shall refer only
to a few cases illustrative of the formation of the shoot in relation to the
conditions of life :—
SEARCHER-SHOOTS. In European lianes—plants which do not reach
any great height, except in the case of Lonicera Periclymenum and Clematis
Vitalba—the usual vegetative shoot-formation takes place. In tropical lianes.
on the other hand, we find often shoots developed which may be termed
* Areschoug’s ‘ false short twigs.’
? See Lynch, On Branch Tubers and Tendrils in Vitis gongyloides, in Journal of the Linnean
Society, xvii (1878), p. 306, plate 15.
454 EPIGEOUS SHOOTS
searcher-shoots. They have the power of rapid growth and elongation in
order to enable them to search for a support. They can grow for a long
time in a vertical direction without a support, and thus their apex moves
through a comparatively wide area. They will reach a greater length the
less the weight’ of leaves they have to carry’, and we find therefore a
retardation in the formation of their leaves which is either (a) temporary, or
(2) permanent. These searcher-shoots arise only if the plant is a strong
srower and is living in favourable conditions. |
(2) Temporary retardation of foliage. Here we have the cases of the
plants whose leaves form ‘forerunner-tips’.’ In other cases the stipules
are formed whilst the leaf-primordium itself is still undeveloped, as, for
example, in Buettneria pilosa and Leguminosae. Specially interesting is the
fact that often a further development of the leaves only takes place if the
searcher-shoots have reached a support, as, for example, in Banisteria aurea
and Beaumontia grandiflora, and this condition may go so far that the
searcher-shoots, which do not reach a support, throw off the young leaves, as
in Combretum, many of the Apocynaceae, Derris elliptica, and finally even
the whole shoot dies. There is here a special phenomenon of sensitiveness,
the use of which to the plant is evident, and it spares the plastic material
for the development of leaves and shoots for those shoots which can make
use of it best. Its origin, however, is still obscure. It is not connected with
‘contact-stimulus.’ We may recall here that Sachs? pointed out that in
European twiners ‘ vigorous shoots when they grow out beyond their support,
or meet with none at all, become moribund; it is easy to observe that a
shoot which has been growing for some time without a support, on being
afforded opportunity to twine round a support obtains after a few days a new
lease of life, so to speak, and grows out much more actively.’ This sensitive-
ness—the dependence of vigorous life upon the exercise of a function, the
reaching of a support in the case before us—is developed in special degree
in these searcher-shoots. The searcher-shoots which throw off their leaves
form in some measure a transition to the next group.
(6) Permanent retardation of foliage. Here the division of labour is
of such a kind that the shoots which serve as searcher-shoots and subse-
quently anchor the plant have only kataphylls. The foliage-leaves are
restricted to the short shoots which are not climbing-organs. We see this in, for
instance, Gnetum funiculare, Melodorum bancanum, Myxopyrum nervosum.
The same features are observed in tendrillous lianes in which the tendrils
1 Ratiborski, Ueber die Vorlauferspitze, in Flora, lxxxvii (1900), p. 1; Treub, Sur une nouvelle
catégorie de plantes grimpantes, in Annales du Jardin botanique de Buitenzorg, iii (1883), p. 44; id.,
Observations sur les plantes grimpantes du Jardin botanique de Buitenzorg, ibid., p. 160.
2 See p. 308.
® Sachs, Lectures on the Physiology of Plants, English edition by Marshall Ward, Oxford,
1887, p. 674.
SHOOT-TENDRILS 455
are placed upon the short shoots. The division of labour between short
shoots and long shoots may, however, be of varying sharpness’. In Hiptage
obtusifolia and other Malpighiaceae the long shoots, for example, have still
foliage-leaves at their base and above that kataphylls, but the foliaged short
shoots can grow out into long shoots which if they have not reached a sup-
port pass over at the apex again into the formation of foliage-leaves; they
submit then to a retardation which is less strong than that of the searcher-
shoots in the other plants mentioned above”.
In other plants every bud by its position is, on the other hand, unalter-
ably fixed as either a long
shoot or a short shoot.
There is then, even if the
long shoots are removed,
no transformation of the
short shoots®.
SHOOTS AS CLIMB-
ING-ORGANS*. We can
scarcely speak of a trans-
formation in the case of
‘scramblers’ which simply
hold on to other plants by
their straggling branches.
The formation of shoots in
twining plants has been ;
already described. Here ‘Ni
we have to deal with—
Shoot-tendrils. When
Ft ‘ Fic. 303. Securidaca Sellowiana, Klotzsch. Shoot with tendrillous
speaking of leaf-tendrils lateral twigs. Two-thirds of natural size. After H. Schenck.
it was shown that in many
plants, leaves, which are sensitive to contact-stimulus and are unchanged
in their configuration, may function as tendrils; similarly we find that in
many ‘twig-climbers, as Fr. Miiller first of all pointed out, the ordinary
twigs are capable of acting as climbing-organs. As an example of this we
have Securidaca Sellowiana (Fig. 303), a Brasilian polygalaceous plant. It
possesses long shoots with non-irritable elongated internodes, and on these
Ct
Ny
1 See Massart, Sur la morphologie du Bourgeon, in Annales du Jardin botanique de Buitenzorg,
xiii (1896).
2 See also Ratiborski, Ueber die Vorlauferspitze, in Flora, lxxxvii (1900), p. 36.
3 See, for example, Massart, op. cit.
* See what is said about root-climbers and leaf-tendrils, pp. 286, 421. A comprehensive exposition
of the features of lianes—not altogether above criticism from the morphological standpoint—is that
of H. Schenck, Beitrage zur Biologie und Anatomie der Lianen, im Besonderen der in Brasilien
einheimischen Arten, in Botanische Mittheilungen aus den Tropen, Jena, Heft iv (1892), Heft v
(1893). The literature is cited.
456 EPIGEOUS SHOOTS
there are foliaged lateral twigs which, like the twigs of higher order, are
very sensitive to friction. In other plants we find upon the shoots which
act as tendrils, a reduction of the leaves, as in species of Salacia. This
reduction takes place in varying degree in different species of the genus,
and its final result is a twig-tendril which has its leaves arrested at a very
early period of development,
and so appears at maturity to
be leafless, as is also the case
in Acacia lacerans, A. velutina,
and others.
Shoot-hooks. The hook-
climbers possess as climbing-
organs hooks which after they
grasp the support experience
a thickening. They have in
most cases taken origin from
the stalks of inflorescences? in
which the flowers have been
suppressed. Inflorescences fre-
quently become climbing-or-
gans. The greatly elongated
axis of the inflorescence twines
in Utricularia reticulata, for
example, whilst the vegetative
shoot-axes remain in the
ground. Were we to imagine
that in other inflorescences an
irritability of the axis or of a
part of it were to set in, that
then a division of labour be-
tween an irritable and a non-
irritable part followed, and that
then this appeared at a quite
early stage in the development,
we should obtain a picture of
spring disc heetdseataralaee Anerit Scieace | HOW Osea eee
have come about. Moreover
transition-forms between tendrils and inflorescences are abundant enough,
sometimes of the nature of watch-spring-tendrils, which are thin and spirally
inrolled tendrils, and do not become firmly fixed to the support, but through
contact-stimulus become thicker and harder (Fig. 304), sometimes of
1 The sensitiveness of the twig-thorns in Olaceae described by Schenck appears to me doubtful.
a a ea —
PLAGIOTROPOUS SHOOTS 457
filiform tendrils, as in Passiflora, Vitis, and other plants—structures which
do not require further notice in this place.
I may recall here those cases in which the shoot-axes which originally
served for the formation of flowers have again turned back to a vegetative
function!, and that in such shoot-axes we may note—
1, the formation of flower is absolutely suppressed ;
2, consequently the appearance of these shoot-axes may be relegated
to an earlier stage of the development than that at which the inflorescences
appear.
(6) PLAGIOTROPOUS SHOOTS.
The general relationships between orthotropous and plagiotropous
shoots have already been described?. It has been shown that one and the
same shoot at different stages of development may be orthotropous or
plagiotropous, and that in many cases external factors, especially the
intensity of light, exercise an influence upon the growth and determine it
as orthotropous or plagiotropous.
In trees. To the relationships as they are found in trees, which have
orthotropous chief axes and plagiotropous lateral axes, reference was made
when speaking of the relationships of symmetry, of correlation*, of
anisophylly®, and also when mention was made of the plagiotropous shoots
in root-climbers®. I have therefore to mention here only the configuration
of the plagiotropous shoot of herbaceous plants.
In herbs. In many herbaceous perennials the flower-bearing shoot is
orthotropous, the vegetative shoot is plagiotropous. These plagiotropous
shoots are chiefly distinguished from the flowering orthotropous shoots by
the elongation of one or all of the internodes, by which process they provide
for vegetative spreading. The plagiotropous shoot can behave in this way
with some variation: the shoot at first orthotropous may subsequently bend,
become plagiotropous, and as a creeping shoot root if it reach the soil; then
it may raise itself again in the next year under favourable conditions and
form an orthotropous shoot. We find this, for example, in Galeobdolon luteum.
In other plants the shoot is from the beginning directed obliquely, as in Ajuga
reptans and Glechoma hederacea, or it may be creeping, as in Potentilla
anserina. In Potentilla anserina and P. reptans, as well as in Duchesnea
(Fragaria) indica, the ‘stolons’ are properly the lateral flower-stems which end
in one flower’; in the axil of the lowermost prophyll of the flower there arises
a new rooting foliage-shoot which again produces lateral flowers and so on.
In Fragaria there are also transitions between inflorescences and stolons, and
' See pp. 447, 450. # See Part I, p. 67. S See Part I, p. 93.
4 See Part I, p. 214. 5 See Part I, p. 250. 6 See Part I, p. 157.
7 Irmisch, Einige Bemerkungen iiber die krautartigen Rosaceen, in Botanische Zeitung, viii (1850),
p. 292. See also Maige, Recherches biologiques sur les plantes rampantes, in Annales des sciences
naturelles, sér. 8, xi (1900), p. 249.
458 EPIGEOUS SHOOTS
we may expect to find them elsewhere, especially in plants whose vegetative
shoots are ‘contracted,’ that is to say, consist of internodes which remain short.
In such plants the inflorescences are shoots which by the elongation of one
or many internodes are raised above the leaf-rosettes. If in these inflore-
scences the formation of flower is suppressed, or is postponed to a later time,
they may at once give rise to ‘stolons.’ Such a vegetative activity of the
inflorescences has been several times mentioned in preceding pages ', and it
>
aX AS, =
>a Jr aD,
<a Hmemy)
omy o fC
Fic. 305. Androsace sarmentosa. Z, storage-leaves; JV, foliage-leaves; 41—A4, stolons. The flowering-plant
is itself the product of a stolon, of which a small portion is seen below. One-half natural size.
is found in some water and marsh-plants* which produce within the inflore-
scences vegetative buds which then spread out upon the surface of the water
and become organs of vegetative multiplication for which they are most
favourably constructed. We might imagine that the plant of Androsace
sarmentosa, depicted in Fig. 305, was originally an annual plant which
besides the termina] inflorescence produced also at a later period axillary
ones; that in these axillary inflorescence-shoots the formation of flowers was
postponed to the next vegetative period ; then there would develop upon
each of them, instead of the flower-umbel, a vegetative leaf-rosette upon
* See pp. 447, 449.
? See the cases of Alisma natans, Limnanthemum Humboldtii, in Goebel, Pflanzenbiologische
Schilderungen, ii (1893), p. 329.
PLAGIOTROPOUS SHOOTS AND ENVIRONMENT 459
which in the following season the flowering-shoot would elongate and bear
flowers. This of course is a purely arbitrary assumption. We have,
however, every ground for the assumption that in the Labiatae mentioned
below the plagiotropous shoots proceed out of orthotropous ones, which
have experienced a retardation in the formation of their flower. The
plagiotropous shoots in these cases serve also specially as vegetative propa-
gating-organs—‘wandering shoots’ (Fig. 305)—which are of importance for
the spread of the plant and the utilization of new stations.
Other plants show throughout the whole of their shoot-system a plagio-
tropous growth. They are glued to the ground and have frequently taken
on the dorsiventral character. This is the case in Anthyllis tetraphylla, the
leaf-formation of which has been previously described’. The direction is
here certainly caused by light. In light of feeble intensity the shoots are
erect, as cultivated plants have shown, and it may be that the plagiotropous
growth is of importance for this kind of plant which grows in strong
illumination, in that it hinders evaporation of water and that it facilitates
the obtaining of water, as is the case in Hepaticae?. These relationships,
however, as well as the factors which in alpine and polar regions, for
example, cause plagiotropous growth, cannot be discussed further here.
RELATIONSHIPS TO CONDITIONS OF LIFE. I shall only now briefly
refer to the relationship between the formation of plagiotropous shoots with
elongated internodes and the conditions of life. This may be illustrated by
examples from the Labiatae. So far as I can see such plagiotropous shoots
do not appear in species which grow in dry sunny spots*. Plants in such
stations form a woody framework of orthotropous shoots. Compare, for
example, the small shrubby Thymus vulgaris of south Europe, growing
on dry sunny localities, with the widely spread-out Thymus Serpyllum,
which indeed grows upon relatively bright sunny dry areas but only between
other plants which shade the shoots. The vegetative shoots are here
plagiotropous. The shorter vegetative period of course must be taken into
consideration also as it is less favourable to the construction of a woody
framework of shoots, and there is also the question of exposure to cold.
Lavender, rosemary, and other plants of sunny dry localities have no
marked plagiotropous shoots, but we find in general these are the more
developed the more shaded and moist are the localities, such as meadows
1 See Part I, p. 121. ar SEG py 15.
$ In other plants this is different as is well known, for instance, apart from those mentioned above,
in many creeping plants of the sea-shore like Ipomaea Pes-Caprae. Research is required to show
how the plagiotropous growth comes about here. It may have started more than once and in
relation to different external stimuli. We have seen that the plagiotropous Hepaticae on tree-stems
are never orthotropous, and that the plagiotropous growth has special relations to water. Temperature
is influential in mountain and polar plants. Ican only see in the above a sfecéa/ case of plants
with radial flower-shoots and plagiotropous stolons, but this does not by any means give us a scheme
for all.
460
EPIGEOUS SHOOTS
and valleys, in which the plant grows. In such places the construction
of vegetative orthotropous shoots which will rise up high into the light
demands a consider-
able amount of mate-
rial. The diminished
light can be better
used by plagiotropous
shoots to which the
moist soil offers at the
same time an opportu-
nity to root. We find
therefore that as has
been mentioned for
other plants a trans-
formation has taken
place in the Labiatae
of the orthotropous
shoots—these alone are
found in annual species
— into plagiotropous
ones, and of this the
following plants offer
illustrations :—
Ajuga reptans?’
(Fig. 306). The shoot
of the seedling is ortho-
tropous and it forms inthe
first year a rosette of de-
cussate foliage-leaves, and
in the second year bears
the terminal inflorescence.
The lateral buds become
plagiotropous stolons with
elongated internodes, they
root later and form attheir
apex a new leaf-rosette
with contracted inter-
nodes which can, in a
plant growing in the sun,
form flowers in its first year.
Fic. 306. Ajuga reptans. The flowering-shoot has developed from the stolon, 4, and has given rise to plagiotropous lateral shoots. Reduced.
Usually, however, this takes place only in the second
year. Orthotropous shoots which produce only few flowers, and which occasionally
1 See Irmisch, Beitrage zur vergleichenden Morphologie der Pflanzen, Abth. ii, Labiatae, Halle,
1856, p. 29.
PLAGIOTROPOUS SHOOTS AND ENVIRONMENT 461
arise as lateral shoots, may after flowering time become plagiotropous stolons *, and
these stolons have taken origin from orthotropous flower-shoots by adaptation.
Glechoma hederacea. We have in this plant a case which we may compare
with that of Hedera Helix®. In that plant we have seen that the juvenile form is adapted
to plagiotropous growth, that the formation of orthotropous shoots only begins later, and
that this behaviour is a derived one. In Glechoma hederacea the juvenile and adult
forms are not markedly different in their configuration, but they show a different
growth. The axis of the seedling-shoot is at once plagiotropous and it roots from its
stem-segments which attain a length of thirty centimeters or thereabouts. In the next
year under favourable conditions it forms * an orthotropous flowering-shoot, at whose
base plagiotropous lateral twigs subsequently arise. But the orthotropous flower-shoot
may pass over again at its apex into a plagiotropous shoot, as Irmisch and others* have
observed, and this happens especially in plants which grow in deeply shaded habitats.
These form but few flowers whilst the orthotropous shoots in stronger illumination pro-
duce many flowers, and do not as a rule grow out further as vegetative plagiotropous
shoots. The tendency here to the formation of plagiotropous shoots is then much more
deeply engrained, for not only is the seedling-axis plagiotropous, but also the ortho-
tropous shoots pass over relatively easily into plagiotropous ones, and this may be con-
nected with the relationships to the locality as Glechoma grows in more shaded places.
Stachys. The genus Stachys may be mentioned here because it shows a tran-
sition from plagiotropous light-shoots into hypogeous shoots. Stachys sylvatica has
plagiotropous shoots which grow sometimes upon, sometimes beneath the surface of
the soil. In the first case they have throughout foliage-leaves and come into flower
often in October; in the second case they have kataphylls ° and appear above the soil
in the autumn usually with the apex covered with foliage-leaves ®. According to Maige’
these plagiotropous shoots may become orthotropous in direct sunlight, whilst, as might
be expected, in feeble illumination the flower-bearing lateral shoots of the ortho-
tropous inflorescence discontinue the formation of flower and become plagiotropous—
a transformation which never happens in the chief axis. Stachys palustris, on the other
hand, has stolons which force themselves into the soil and are therefore geophilous.
FACTORS WHICH CONDITION PLAGIOTROPOUS GROWTH. We do not
learn from the above what factors condition the plagiotropous growth.
1 This has not yet been observed in the case of the terminal inflorescence. Moquin Tandon, who
has been cited as the authority for such a change, only speaks of a foliation of the bracts which need
not be connected with plagiotropous growth. See his Eléments de tératologie végétale, Paris, 1841,
p. 205. Important results of expetimental research are given by Klebs, Willkiihrliche Entwicklungs-
anderungen bei Pflanzen, Jena, 1903.
3 See Part I, p. 160. 3 The method of branching need not be described.
* As A. de St. Hilaire, Lecons de Botanique comprenant principalement la morphologie végétale,
Paris, 1840, p. 104. He believes, however, that the shoots ‘ entrainés par leur poids’ sink to earth,
5 The stolons of other plants show also the formation of kataphylls in the light—Fragaria vesca,
Saxifraga sarmentosa. The retardation of the development of the leaves here may have relation
to the rapid elongation of the shoot-axis as in the shoots of many lianes. Experimental evidence is
entirely wanting.
® See Irmisch, Beitrage zur vergleichenden Morphologie der Pflanzen, Abth. ii, Labiatae, Halle,
1856, p. 15.
7 Maige, Recherches biologiques sur les plantes rampantes, in Annales des sciences naturelles,
sér. 8, xi (1900).
462 EPIGEOUS SHOOTS
A discussion of this question belongs to experimental physiology, and here
I shall therefore only say this :—
Frank and others formerly thought that the plagiotropous shoots above mentioned
were negatively geotropic and negatively heliotropic, because many of them although
not all became erect in darkness. This erecting of the shoot I consider as an adapta-
tion by which the plagiotropous shoot is protected from being smothered by other plants
or by a covering of leaves and the like. Oltmanns? found, moreover, that the shoots of
Glechoma became orthotropous in darkness only in the spring. Later in the summer
the stolons grew out, even in darkness, to a considerable horizontal length. Negative
heliotropism therefore does not play a part in directing the plagiotropism of these shoots
but there is ‘re-attuning’ of the geotropism by the influence of light”. The working
of the light is here evidently somewhat complex and we must distinguish two things—
(a) the influence upon the direction of the shoot; and
(2) the influence upon the processes of ripening.
Let us consider the latter first. We find that the shoots grow out at different
stages of development at which they react differently to the influence of directing
forces. ‘The external forces which are necessary for this development are in part
those which affect the direction. ‘The terminal stage is that of flower-formation, the
shoot therewith reaches its ‘ripeness.’ Every shoot of Glechoma begins as a plagio-
tropous foliage-shoot and ripens then into an orthotropous one. ‘This happens under
the influence of light and its ripening process goes on in general more quickly the
higher—within of course certain limits—the intensity of the light is. The coming of
the orthotropy is then zzdvrectly a consequence of the influence of light which causes
a change in the inner peculiarities of the shoot. ‘This has as a consequence that the
shoot, so far as its direction is concerned, reacts differently to light in the different
developmental stages. In the first unripe condition light causes a ‘ re-attuning’ of
the positive to transversal geotropism—using this word in its most general sense—and
the stronger the light, other things being equal, the more marked is the plagiotropous
growth. The influence of light may gradually reach a climax in the summer, the
shoot can, as we saw in Glechoma, be so ‘induced’ that it is no longer orthotropous
in darkness. If we separate these points of view the behaviour of the plagiotropous
shoots is as it appears to me much more easily understood. The ripening process
does not of necessity lead to the cessation of the growth of the shoot. We have seen
that in Campanula rotundifolia the growth can be interrupted, and that the juvenile-
form can again be brought forth. The same is the case in many of the Labiatae
mentioned above. If we designate a shoot with the properties of the plagiotropous shoot
of Glechoma by ~, it will be orthotropous if it has been formed under the influence of
the light y. The shoot + +y is orthotropous, but y is not always present in large
amounts. If now there be only little of y present, and x is not exhausted, the shoot
grows as x, that is to say, grows further as a plagiotropous shoot, but the plagiotropous
growth also makes possible to it, as we have indicated, the better utilization of the
light, and at the same time vegetative propagation in stations with less intense light.
} Oltmanns, Uber positiven und negativen Heliotropismus, in Flora, Ixxxiii (1897), p. 24.
* See Czapek, Uber die Richtungsursachen der Seitenwurzeln und einiger anderer plagiotroper
Pflanzenteile, in Sitzungsberichte der Wiener Akademie, civ, i (1895).
GEOPHILOUS SHOOTS 463
II
GEOPHILOUS SHOOTS
With Areschoug ' we may designate by the term geophilous such shoots
as produce their renovation-buds under the surface of the earth. They
occur especiallyin regions where vegetative activity is periodically interrupted,
whether this is by cold or by drought, and they are united by many intermediate
stages with ‘ photophilous ”’ shoots.
We have to distinguish two categories :—
PERENNIAL GEOPHILOUS SHOOTS. In this category we have shoots
which are persistently hypogeous.
Paris quadrifolia. The rhizome of Parissuppliesanexample. It has un-
limited monopodial growth in the soil,and sends up lateral shoots into the light.
PERIODIC GEOPHILOUS SHOOTS. By these we understand shoots which
in the different vegetative periods
of thet “existence ate {at first
geophilous and then photophilous,
or the reverse.
Polygonatum multifiorum.
This is the case in sympodial
rhizomes such as that of Polygo-
natum (Fig. 307). The shoots are
here geophilous,and they remain in
the soil and bear only kataphylls sort epigel shoot ofthe next year Fear ots Cat
there. In the next year they are of preceding Se ae eee esl toe
photophilous, and appear above the
soil and produce assimilating foliage-leaves as well as flowers. The means
which the plant adopts to bring its shoots into the soil or above it are evi-
dently governed in the first place by changes in its geotropic sensitiveness,
and this itself is most probably conditioned by processes of metabolism.
Circaea intermedia. The case of Circaea intermedia offers an illustration
to which I have called attention before now*. The photophilous shoots
of this plant are negatively geotropic and end in an inflorescence. Beneath
the soil the plant develops stolons which subsequently swell up at the end,
and in the next year become photophilous orthotropous shoots. If now
these overwintering shoots are stimulated to further development in the
1 Areschoug, Beitrage zur Biologie der Scales Pflanzen, in ae nivs Lundensis, xxxi (1896).
? This name seems more suitable than Areschoug’s term ‘aerophilous,’ which does not apply to
the shoots of water-plants. The essential point is that a shoot sometimes or always is adapted to
darkness or to light. ‘Skotophilous’ might be used for geophilous shoofs, and more appropriately,
because as has been shown (Part I, p. 232) darkness has a favourable influence upon the formation
of the geophilous potato-tuber, and also upon many stolons.
* Goebel, Ueber den Einfluss des Lichtes auf die Gestaltung der Kakteen und anderer Pflanzen, in
Flora, Ixxxii (1896), p. 11. The plant there called Circaea alpina is C, intermedia.
464 GEOPHILOUS SHOOTS
winter, by cultivation in a higher temperature, certain peculiar phenomena are
observed. The point of the shoot which ought to be an inflorescence
becomes a stolon which again pierces the soil, and this may take place after
the shoot has attained a height of many centimeters and formed a number
of well-developed leaves (Fig. 308, II). The appearance of the shoots above
the ground also may be quite suppressed, and the shoot, instead of forming
a photophilous shoot with foliage and flower, may continue its growth as
a stolon (Fig. 308, I). This depends in general upon the time at which the
plant has been caused to ‘shoot out.’ The later this happens the longer time
elapses before the formation of the stolon
begins, and one might believe that one had
completely normal plants under examination
which were prepared to form flower, until
one sees the tip of the shoot begin to bend
downwards, and the formation of stolons
is entered upon—this being recognized not
only by the changes of direction, but also by
the elongation of internodes and the like. So
long as these stolons remain above ground
they produce foliage-leaves only which are
merely smaller than usual, but when they
pierce the soil kataphylls are produced?;
_ in the axil of the foliage-leaves stolons arise,
which are commonly produced only in the
seedling-plant.
These facts will bear it seems to me
but one interpretation: In the resting geophi-
ee en ene ery ot lous shoot, processes of metabolism take place
pore et enter whose shoot- which cause it to become negatively geotropic
when it shoots out. These processes require
a low temperature amongst other conditions. If one raises the temperature
prematurely, that is to say before the metabolic changes about which we
know nothing are completed, the stolons will at first be photophilous, but as
they contain a certain amount of geophilous substance which has not been
used up—if one may use this expression for brevity—after a certain time
they bend down again to the soil. There appears thus an inversion of that
order of shoots which is usual in plants with geophilous shoots—the geophilous
shoots arise at the dase of the photophilous ones, an arrangement the
advantage of which does not require any explanation?. The transformation
of primordia of photophilous shoots into geophilous ones may, moreover, as
has been proved in some cases %, be caused also by the early removal of the
1 See Part I, p. 256. ? See also Part I, pp. 215, 221.
* This is easily proved by water-cultures of Circaea.
DEPTH IN’ SOIL) OF, GEOPHILOUS SHOOTS 465
primordia of the geophilous shoots, just as on the other hand a removal of
the photophilous chief shoot causes 1 in many cases the geophilous primordia
in the year of their formation to grow out into photophilous foliage-shoots.
DEPTH IN SOIL OF GEOPHILOUS SHOOTS. It is the alternation in the
relationships between the geophilous and photophilous shoots or parts of
shoots which evidently regulates the depth at which the geophilousshoots grow’.
Many plants have indeed
no definite depth in the
soil at which they live best
because their geophilous
parts possess no power of
movement, for example, the
tubers of Corydalis cava.
But most of them have the
capacity to take up a higher
or a deeper position in the
soil, whether this is brought
about by pull-roots or by
a change in their geotropic
sensitiveness.
Polygonatum wmulti-
florum. Let us follow, for
example,the development of
Polygonatum multiflorum.
The short fleshy shoot which
i h ing-
s formed by Ae seedling FIG. 309. Felyeons tai malicram. A, rhizome placed artificially
i i higher in the soil than the normal depth; its continuation-shoot has
plant is at first erect (Fig. aoe downwards. J, rhizome placed deeper than the normal depth ;
its continuation-shoot has grown upwards. The dotted lines indicate
She, to the left). It has the from # in 4 and Z point to the annual growths inthe rhizome. C, seed-
i i ling plant. To the right the seed enclosing the haustorial end of the
duty, which = performed Sony edon ; #, primary root; 7, lateral rootlet arising within the axis
sual in the second’ te Soet; rerenor se of solar sheath: amterioe se of
year, of bringing into the After Rimbach. C, magnified. After Irmisch.
light the foliage-leaf which follows upon the kataphylls. In this way is made
possible the further development through the assimilative activity of the
foliage-leaf. Subsequently the shoot, which is at first monopodial, penetrates
the soil? and grows there in a horizontal direction (transversely geotropic),
1 Goebel, Beitrage zur Morphologie und Physiologie des Blattes, in Botanische Zeitung, xxxviii
(1880). The placing in darkness of the orthotropous chief shoot in Circaea sufficed to cause the
shoot next the apex, which would otherwise have been plagiotropous, to become orthotropous.
2 See Royer, Flore de la Cote dor, p. xx; Rimbach, Das Tiefenwachstum der Rhizome, in
Fiinfstiick’s Beitrage zur wissenschaftlichen Botanik, iii (1898), p. 178. P. E. Miiller’s view of the
importance of earth-worms in bringing about the sinking of rhizomes in the soil is, to my thinking,
exaggerated. The worm will only sometimes bring the rhizome a little quicker into its definite depth.
* Investigation is required as to whether shortening of a pull-root does not take the germ-shoot
into the soil.
GOEBEL I Hh
466 GEOPHILOUS SHOOTS
and as it strengthens it turns upwards, forms foliage-leaves! and becomes
photophilous, whilst a geophilous lateral shoot continues the rhizome. If
one changes the depth by bringing the rhizome nearer the surface the
continuation-shoot grows downwards (Fig. 309, 4) and the converse is the
case (Fig. 309, B).
Similar relationships are found as the investigations of A. Braun, Irmisch,
Warming, and others, have shown in other tubers and rhizomes. For a de-
tailed account of these relationships I cannot find space here. It must suffice
if I merely mention this remarkable fact that the depth of geophilous shoots
is regulated in this way :—during the strengthening period there is an en-
deavour through apical growth directed downwards to secure a definite
‘normal depth,’ the retention of which is striven for amongst higher or lower
plants by changes in depth either upwards or downwards; the action of pull-
roots, as they have been described in the case of Arum”, is also important in
relationtothis. The regulation of the depth is effected through the influence
of the processes of metabolism, as has been shown to be probable in the case of
Circaea. All geophilous shoots must, so far as they are not saprophytes or
parasites, send assimilating portions into the light, either single leaves or
foliaged shoots. Between these and the geophilous shoots, or parts of shoots,
there exists an exact regulating correlating relationship which, however, we
cannot penetrate. We name the neutral line between the two that which is
exhibited in the normal depth. If the lie is deepened there must be, as
Rimbach has shown, more material used up for the formation of photophilous
parts than otherwise, and this disturbance of the balance finds its expression
in a change of geotropic sensitiveness. One might elaborate the picture
further, in that one might consider that the bearers of the positive and geo-
tropic sensitiveness are separate and distinct entities which by the capacity of
their metabolism can increase or diminish and so sometimes hold the balance
even, whilst at other times they might give a preference to one side or the
other. But even then one would only arrive at an incomplete picture of
phenomena requiring further investigation.
PHOTOPHILOUS SHOOTS IN THE SOIL. The photophilous shoots which
are laid down under the soil show different adaptations which enable them
to bore through the soil®. These are essentially the same as those which
are found in many seedling-plants, for example :—convex bending upwards of
the axis or of the leaf-stalk, which facilitates the boring through the soil and
the drawing out of the leaves ; protection by a kataphyll, like the coleoptile
of the grasses, in erect shoots and so on. Where the leaves bore through the
* It is characteristic that the foliage-leaves arising directly upon the rhizome are here stalked as in
Paris. Those on the photophilous shoots are sessile. Another example of the phenomena referred
to on pp. 300, 390. 2 See p. 270.
* See Areschoug, Beitrige zur Biologie der geophilen Pflanzen, in Acta Universitatis Lundensis, xxxi
(1896).
GEMMAE 467
soil in the erect position we find the parts that are in front in the movement
especially arranged to facilitate the passage throughthe earth. This is seen
in the leaf-tips of many monocotylous plants, for instance in Gagea arvensis,
where the apex of the leaf is conical and is somewhat horny at the tip, whilst
the rest of the leaf is flat. But I have no room for a description of these
phenomena.
THE SHOOT IN THE SERVICE OF REPRODUCTION
I
INTRODUCTION
A. GEMMAE.
‘Space forbids the discussion of the different arrangements which we find
in connexion with the formation of gemmae, but there are two illustrations
which may be quoted to show the connexion between form and function.
One of them is from the domain of the Pteridophyta, the other from the
Spermophyta.
Lycopodium. Lycopodium Selago and some other species of the genus,
for example, L. lucidulum and L. reflexum, form short deciduous shoots or gemmae,
around which considerable literature has collected’. They fall off as small leafy shoots
provided with the primordium of aroot. ‘They are not, as is usually the case, abscised
at their point of origin from the chief shoot, but separate above their base, and the lower-
most part of the shoot remains with some leaves. The point at which they fall off
(Fig. 310, IV at A) is prepared—the axis of the shoot is here thinner, so that it
easily breaks through. What then is the significance of the leaves that remain
behind? Formal morphology has considered it sufficient to assume that the anterior
of these (Fig. 310, II A) is the ‘axillant leaf, which is ‘ concrescent’ with the bud-
shoot developed in its axil. But this explanation is not very illuminating because the
Lycopodineae do not generally possess axillary branches, and this leaf is inserted
higher up upon the axis of the lateral shoot than the two lateral leaves. To me it
appears that the lowermost leaves of the gemma can be nothing else than its Jud-sca/es.
We see that the leaf which stands on the outer side is the most strongly developed.
It is concave inwards, and forms with the adjacent leaves of the mother-shoot of the
bud a protective cover to this on the outside, and the other bud-scales fit in with it.
By the elongation of the shoot-axis below the bud-scales the gemma is raised up
beyond the foliage-leaves, and can thus be easily distributed; and indeed the bud-
scales evidently help in this distribution, for it is probable that an adjection of the
gemma takes place here, brought about by the pressure which its first two leaves
* See Hegelmaier, Zur Kenntniss der Gattung Lycopodium, in Botanische Zeitung, xxxii (1874),
p-. 481. As regards history—Dillenius, Historia muscorum, p. 436, tab. 56, gave a good description
of the gemmae, as also did Hedwig, Theoria generationis et fructificationis plantarum cryptogamicarum
Linnaei, Lipsiae, 1797, p. 112, who took them to be male flowers.
Hh2
468 THE SHOOT IN REPRODUCTION
exercise upon the adjacent leaves. These leaves experience a certain tension, and
when this is released the gemma can be cast out for some distance’.
The first leaves of the gemma possess a peculiar conformation. They are at
first filled with reserve-material, and facilitate therefore rapid further development in
the germination. Then the first two lateral leaves, whose surface is originally vertical,
experience a torsion whereby their flat sides are turned upwards (Fig. 310, III) *.
At the same time these leaves are asymmetric, as the course of their mid-nerve, which
is but slightly developed, shows. The
asymmetry evidently depends upon the
almost horizontal position of the gemma,
which diverges greatly from the erect
growth which all other shoots of Lyco-
podium Selago have. The torsion of
the leaves enables them to make use
of the light better *. Evidently a part of
the food-material accumulated in the
bud is produced by its own activity.
It is interesting to see here how
under definite conditionsaconfiguration
appears which is found generally in the
plagiotropous shoots in another species
ofthe same genus. The large flat leaves
of the gemma may further serve also
as a kind of parachute, and thus aid the
distribution. Altogether the gemmae
exhibit marked, and in more than one
relationship, excellently constructed
organs for spreading; the special fea-
Fic. 310. Lycopodium Selago. I, view from above of E
the saree of a eno Br, gemmae standing all on tures are:
the outer sides of the shoots only. II, portion of the apex .
of a shoot in transverse section. yThe leaves of the gemmae 1. The construction of the shoot-
in ransver est ction the storage eaves are shaded, axis—basal portion to raise up the gem-
oy onior Pieiieh eae eet: ana P * ma, point of rupture higher up.
2. The leaf-formation—bud-scales
which persist and serve as agents in the abjection; storage-leaves; torsion of the
first two leaves.
With regard to the origin of the gemmae, according to Hegelmaier they arise
at the position where otherwise a leaf would have developed. ‘The morphological
explanation of this behaviour must be passed over here. I would only say that it
appears easy to understand that the slender gemma from the outset would take up
a smaller space on the apex of the shoot than the strong dichotomous shoot. The
? In favour of this it may be noted that the two bud-scales right and left of the gemma curl
inwards concavely after the gemma has been set free. Mr. F. Lloyd informs me orally that he has
seen the abjection.
2 See Part I, p. 105, where a like phenomenon is described in Lycopodium alpinum.
’ See also what has been said above about the effect of pressure.
GEMMAE 469
gemmae are not disposed all round the shoots, but are arranged unilaterally (see
Fig. 310, 1). The side upon which the gemmae stand appears to me to be always
the ouser side with regard to the whole stock (see Fig. 310, 1). In two shoots of
a fork which bear gemmae the gemmae will not, or will only exceptionally * stand
upon the sides of the shoots which are turned towards one another. We have here,
it seems to me, one of those frequent cases of furthering of the outer side.to which
I have several times referred.
Finally it may be mentioned that the formation of the gemmae takes place under
conditions other than those under which the sporangia appear. We find them chiefly
on the upper* part of the year’s shoot. The leaves in this part have no sporangia,
or only aborted ones, in their axils. Subsequently sporangiferous leaves are formed.
The conditions under which the two kinds of organs develop have yet to be deter-
mined experimentally. Adaptations like those which have been so briefly depicted
are found in many Spermophyta. The gemmae of Lycopodium are distinguished by
no very great characters from the du/éz/s of many species of Allium and Lilium.
Remusatia Vivipara. ‘This aroid bears, as has long been known, a mis-
leading descriptive specific name. ‘There is no ‘vivipary,’ that is to say, continuous
development of the seed, without a resting period; there is only the formation of
gemmae. The gemmae arise characteristically on kataphyllary shoots* which are
orthotropous and stand up from the far-creeping stolons. The gemmae are small
tuberous shoots which easily fall off. Their outer leaves are kataphylls and have
hooked incurved leaf-tips, so that the gemmae can be easily distributed by animals,
which their position on orthotropous shoots makes easier than it would be were they
to spring from shoots on the surface of the soil. It appears that the propagation of
this plant by gemmae far outstrips that by seed, at least under certain conditions *.
The relationships of configuration of the gemmae to their function as
organs of distribution is evident without further comment in the cases men-
tioned above, but we do not know the conditions for their formation.
Whilst I pass over with this brief mention these gemma-shoots, I
must give a very full account of the formation of the ffower.
B. THE FLOWER.
I understand here by the term ‘flower’ a shoot beset with sporophylls °,
that is to say, leaves bearing sporangia. Such a shoot consists, as do all
shoots, of two parts: an axis—here the fower-axis—and the leaves of which
in the flower there are two kinds, the essential ones which are the sporophylls—
* I found such an exception in a shoot whose twin, that is the other one belonging to the same
dichotomy, was arrested at an early period. Upon it the gemmae were disposed radially.
? Using the ordinary expression ; to me, however, this part seems rather the under.
* These are distinguished anatomically by an early development of cork.
* Wight, Icones Plantarum Indiae Orientalis, iii, Pl. 900, says that the seed-bearing form is
‘exceedingly rare’ at Courtallum, where the form-bearing gemmae is abundant. Probably seed-
bearing takes place under other conditions than that of gemma-formation. In plants cultivated
in plant-houses the formation of gemmae takes place regularly.
° This expression was originally used by Schleiden, but has only come into general use within
recent years.
470 THE SHOOT IN REPRODUCTION
sometimes only one in number—and the wnessential ones, which are frequently
absent, and are the leaves which form the ezvelope of the flower.
The flower is a shoot of limited growth in a number of Pterido-
phyta, and in all Spermophyta with the exception of the female flower of
Cycas!. Consequently in many the flower-axis is only slightly visible. It
is sometimes entirely used up in the formation of the one or many sporo-
phylls in the case of the Angiospermae, a fact the neglect of which has led
to many false deductions. From this definition of the flower, which is based
upon the results of Hofmeister’s comparative investigations into the history
of development, it follows that the old Linnean conception of the ‘Crypto-
gsamae’ as flowerless plants is untenable, because we must speak of the flower
of the Pteridophyta if the portion of the shoot which bears the sporophylls
is different from the vegetative shoot, as is the case when the sporophylls are
not mixed up with the foliage-leaves, but are confined to definite regions of
the axis of the shoot. As in the case of all groupings and definitions, how-
ever, it is a matter of subjective opinion where one will draw the limit. It
will be hardly necessary, for example, to designate as ‘flower’ the sporiferous
portion of the shoot which is developed in regular alternation with the
foliage-leaves in the fern Onoclea Struthiopteris. If we do this in the case
of the genus Cycas, where quite similar relationships occur, it is only
because in the other Cycadaceae the flower is sharply marked off from the
vegetative shoot, and also upon comparative grounds. Moreover we find in
the rudimentary” flower of the Pteridophyta all stages from the ordinary
configuration of vegetative shoots* up to flowers which, like those of Equise-
tum, are large, and have for long been recognized as having a resemblance
to the male flowers of many Gymnospermae‘.
If one wishes to construct a picture of the origin and development of
the flower one must start from the flower of the Pteridophyta. Such a con-
struction can only be a probable one for evident reasons. I shall here only
indicate some general points which must be taken into consideration in
regard to this.
1. The arrangement of the sporophylls on the shoot differs in many
Pteridophyta from the arrangement of the foliage-leaves upon the shoot.
Both evidently were alike to begin with. Two possibilities are offered to us:
(a) The arrangement of the sporophylls is the original one, that of the
foliage-leaves has been derived ;
(4) The converse is the case.
It is commonly held that the second alternative is the correct one.
I shall recur to this subject when I speak of the flower of Selaginella.
1 Also Dacrydium Colensoi (?), see Fig. 348.
* Using this term in Sachs’ sense.
* The sporophylls frequently resemble the foliage-leaves in this group.
* See Von Mohi, Vermischte Schriften botanischen Inhalts, Tiibingen, 1845, p. 96.
THE FLOWER 471
2. In any comparison of the flower of Pteridophyta with that of Sper-
mophyta the heterosporous Lycopodineae and Isoetaceae must be taken
account of, especially because in them, more than in the heterosporous
Filicineae, we can speak of flower. In them:
(z) The microsporophylls and megasporophylls of the flower appear
in relatively large ‘indefinite’ number.
(6) The megasporophylls are less numerous, for instance, in Selaginella!.
(c) A separation between male and female flowers has not been
discovered in any living Pteridophyta. We meet with only an occasional
indication of it in Selaginella. Herma-
phrodite flowers, at least in the morpho-
logical sense, are therefore the primitive
type. But if, for example, we tried to
derive by arrest the unisexual flowers
of the Gymnospermae from hermaphro-
dite flowers because Welwitschia shows
in the male flowers the rudiment of a
female organ, or if we tried the converse,
we should be speculating upon very
insecure foundation, because, in the first
place, the Gymnospermae certainly are
no single group, and secondly, the separa-
tion of the flowers into male and female
may have taken place in their pterido-
phytous-like azcestors. One must not
judge of all forms by one.
Hermaphrodite flowers occur now occa-
sionally as a ‘ variation’ in the Gymnospermae.
I found them in hundreds in an example of ees Teteenah Getioes ms eee
Pinus, probably P. maritima®. The male pit aS a ae ee as
flowers standing near the apex of the twig -
in this example were transformed into female ones. At the point of transition
I found not infrequently a stamen with a rudimentary ovuliferous scale in its axil
(Fig. 311, x). Such a flower might serve in phyletic speculation as the type
of a very simply constructed hermaphrodite spermophytous flower from which
by reduction, concrescence, and transformation of single parts pretty well every-
thing might come. But as regards this I will only point out briefly here that
the separation of the flowers into male and female has in the case of some plants
resulted in their different arrangement upon the plant. In Pinus the male flowers
stand in the position of short shoots, the female in the position of long shoots,
The biological reason for this is clear. The short shoots, as we have already seen,
are retarded formations compared with the long shoots; they are worse nourished
1 The reason for this isobvious. * At Majori. Analogous cases are often described in the literature.
472 THE SPOROPHYEILS OF PIERIDCGPHYTA
than are the long shoots, which occur at the most favourable position for nutrition
at the end of the shoots. That the female shoots should occupy this position is
of importance in view of their long-continued further development in connexion
with formation of seed, whilst the male flowers soon fall away. Similar relation-
ships are found in Juglans, Fagus, Quercus, Corylus, and elsewhere. The different
position occupied by the male and female flowers in the system of shoots in these
genera may, I think, be explained in this way: she female flowers appear in the
region of the shoot which is best nourished. In herbaceous plants such differences do
not appear, and there is absent amongst them also the polar differentiation of the
annual shoots. We can understand therefore why the formation of the herma-
phrodite flowers in Pinus described above appeared in the upper male flowers, and
similarly that there is no reason why in the Pteridophyta the male and female
flowers should have a different place of origin.
In the following pages we shall first of all deal with the formation of
flowers and sporophylls in the Pteridophyta, and I may point out now that
the conformity in habit of the male flowers of the Gymnospermae with the
flowers of Selaginella and Equisetum is clearly connected with the fact that
in all of them distribution of the spores takes place by the wind, whilst the
configuration of the sporophylls is readily understood when it is regarded
as having a special relation to the construction of the bud of the flower.
Regarding Terminology. ‘The place upon the sporophyll at which the
sporangia arise, especially if these are in numbers, differs frequently from the rest
of the sporophyll. We designate this spot the placen/a, and its function is to enable
the sporangia to obtain a larger amount of nourishment’. We can understand
therefore why solitary sporangia do not sit upon a placenta. They are found in
Ceratopteris, the Schizaeaceae, Osmundaceae. The expression ‘receptacle,’ which
is often used for the point of origin of the sporangia, is, I think, unnecessary. The
designation placenta, which comes from the Spermophyta and took origin in a false
comparison with the animal kingdom, is now so commonly used that it can
scarcely be ousted. We use it according to the above definition in a biological,
that is to say a functional, sense, and its use simplifies the nomenclature.
II
THE:SPOROPHY LES AND FLOWER:
THE, PTERIDOPHYA
A. GENERAL FEATURES OF THE SPOROPHYELS.
We have assumed that the spore-bearing organs of the Pteridophyta
and Spermophyta are produced by the leaf-organs which are designated
sporophylls. In how far the microsporangia or megasporangia of the Sper-
mophyta take their origin always from microsporophyll or megasporophyll
will be explained when speaking of the formation of their flower.
* Especially by storing up food-material, which afterwards can be used in the development of the
sporangia.
ORIGIN AND FUNCTION OF SPOROPHYLLS 473
In the Pteridophyta the origin of the sporangia from leaf-organs is
almost everywhere conspicuous. They stand in the Filicineae mostly upon
the under side or upon the margin of the leaf, in the Lycopodineae upon
the upper side of the sporophyll, in Equisetum uniformly around it.
In Selaginella alone do the sporangia arise upon the vegetative point
of the shoot immediately above the primordium of the sporophyll, and this
is the case also in Selaginella spinulosa, although some authors have said
that the sporangia are leaf-borne in this species'. Hypothetically the leaf-
borne origin of the sporangia might be explained either by supposing a
‘displacement,’ or that in consequence of the
relatively early appearance of the primordia
of the sporangia the cell-layers out of which
they arise (Fig. 312, 5,6, 7, 8) would be drawn
into the formation of the leaf ifthe formation
of the sporangia did not begin, but this picture
must remain purely conjectural until it is
proved that the primordia of the sterile leaves
of Selaginella do really extend gradually
upwards. The whole question has lost inter-
est since we have recognized that the place
of origin of an organ is not critical for its
‘morphological ’ significance.
The function of the sporophyll is not
only to produce the sporangia but also to LE org Be Saree il cement a
protect them in their youth, to aid in the _ in, longitudinal ‘section. Magnified’ 460.
scattering of the ripe spores—in seed-plants
to promote pollination and fertilization. It is easy to prove in many cases
that the conformation of the sporophyll has a relationship to these functions,
and this is evidently the reason why frequently its configuration differs so
markedly from that of the foliage-leaves. In considering therefore the
sporophylls from the organographical standpoint we have to seek for an
answer to two distinct questions:
1. The biological one—in what relationship does configuration stand to
function ?
2. The purely morphological one—in what genetic relationship do the
sporophylls stand to the foliage-leaves ?
We might add a third question, namely—what are the efficient causes
of the configuration, especially in cases where the sporophylls diverge far
from the foliage-leaves ?
To answer this third question we have not at present the necessary
* Goebel, Beitrage zur vergleichenden Entwicklungsgeschichte der Sporangien, in Botanische
Zeitung, xxxviii (1880), p. 561; Gliick, Die Sporophyllmetamorphose, in Flora, Ixxx (1895), p. 355.
474 THE SPOROPAYELS (OF \PTERIDOPA YT
foundation. The answer to the other two is possible, although here also we
have not yet the insight which is to be desired.
Biological relationships scarcely give us the cause of differences ; and
indeed only the arrangements which serve for the protection of the sporangia
are the biological ones which have been mainly considered, although, as we
now know, there are relationships of configuration which are connected with
the distribution of the spores.
BIOLOGICAL RELATIONSHIPS OF SPOROPHYLLS. Amongst the Pteri-
dophyta the sporophylls present striking differences according as the
distribution of the spores takes place by water or through the air. The dis-
tribution through water occurs in the case of the sporophylls of the Mar-
siliaceae, and these externally are very like the fruits of many Spermophyta.
They owe their conformation to the circumstance that they are adapted to
pass through a resting period’. They have the sporangia sunk within the
sporocarp, and the tissue of the sporocarp is so arranged that it is only upon
the entrance of a quantity of water that the opening of the sporocarp is
effected by the swelling of the tissue whose function it is to do so. The
advent of water is also necessary for the germination of the spores. Sporo-
phylls which produce spores that are scattered by the wind facilitate the
process of shedding by their fosztion ; for example, in Aneimia, Onoclea
Struthiopteris, Helminthostachys (Fig. 319), and others, the sporophylls are
erect and projected beyond the vegetative parts, an arrangement which is
repeated in the strobili of the Lycopodineae and other forms. The diminu-
tion in the amount of the assimilating tissue in many sporophylls relatively
to the foliage-leaves—and in some cases this goes so far that the assimilation-
tissue disappears altogether—will also make more easy the scattering of the
spores. In the configuration of the sporophyll too less specialized arrange-
ments for the distribution of spores are needed the more spores there are
formed, or the easier these can acquire favourable conditions of germination *.
Whilst there can be no fundamental difference of opinion regarding
these relationships, it is. otherwise with regard to the interpretation of
morphological points involved in the relationship of the sporophylls to the
foliage-leaves.
RELATIONSHIP OF SPOROPHYLLS AND FERTILE LEAF-PARTS TO
FOLIAGE-LEAVES. The close relationship of the two is clear. In many
cases they are entirely alike in their configuration, for example, in Aspidium
Filix-mas, and many other Leptosporangiate Filicineae. In others there are
gradual ¢ransitions from ordinary foliage-leaves, which are at the same time
sporophylls, to leaves which are sporophylls alone—transitions which we
know also to occur between foliage-leaves and hypsophylls, and tendrils,
’ In this period protection against drought is what is required.
* A like relationship mtatis mutandis has been already pointed out in the case of the archegonia.
See p. 212.
ORIGIN AND FUNCTION OF SPOROPHYLLS 475
and-bud scales, and storage-leaves. After the analogy of these it seems fair
to conclude that the sporophylls also are merely more or less transformed
foliage-leaves, and we have seen further that the Azstory of the development
of the sporophyll conforms often during a long period with that of the foliage-
leaves ; besides, we can experimentally cause the primordia of sporophylls to
develop into foliage-leaves if we destroy or suppress the formationof sporangia.
This happened in the cases of Onoclea Struthiopteris’ and Selaginella
mentioned above”.
Experimental Proof in Onoclea Struthiopteris. The mature sporophylls
of Onoclea are very different from
the foliage-leaves; they are much
smaller, quite erect, their differen-
tiation of tissue and their external
segmentation come to maturity
much more rapidly than in the
foliage-leaves. The plant is especially
favourable for research because the
sporophylls alternate regularly with
foliage-leaves. Every year there
arises at the beginning of the vege-
tative period a number of foliage-
leaves, and at its end, so soon as the
plant is strong enough, a number of
sporophylls. If now all the foliage- iN
leaves be removed from a plant whose gen
sporophylls are not yet mature, folia- a4,
tion of the sporophylls may be caused,
that is to say, the primordia of the
foliage-leaves are checked in their
development to sporophylls and de-
velop further as foliage-leaves. The
most various intermediate stages be- 016. 31},,tand2, Botryehinm Lanara, Pinna o
tween sporophylls and foliage-leaves 35 Poet Sosa aroduced eoperimentally,
are thereby produced, and one of one SE yp have become sterile in different
these is represented in Fig. 313. It
might be said teleologically that the plant sacrifices its propagative organs
in order to preserve its vegetative condition.
Experimental proof in Selaginella. Selaginella offers a second case
in which a correlation between the formation of sporangia and the configura-
tion of the sporophyll diverging from that of the foliage-leaf has been
Let MLLILMLEL
Ld
GS
ae iad
c
1 Goebel, Uber kiinstliche Vergriinung der Sporophylle yon Onoclea Struthiopteris, Hoffm., in
Berichte der deutschen botanischen Gesellschaft, v (1887), p. lxix.. Atkinson repeated this research
with the same results in the case of Onoclea sensibilis. 2 See Part I, p. 216.
476 THE SPOROPHYLLS OF PTERIDOPHYTA
experimentally proved’. The sporangia in this genus are arranged in spike-
like strobili. If these are cut off and used as cuttings they grow out vegeta-
tively, and the contrast between the two forms is very marked because the
strobili in most species of Selaginella are isophyllous, whilst the vegetative
shoots are anisophyllous*» The sporangia abort in the upper part of the
strobilus which is used as a cutting, and the leaves upon the newly formed
portion of the shoot take on the ordinary form of the foliage-leaf.
The features thus artificially produced appear spontaneously in nature.
Sometimes sporophylls show a partial virescence, that is to say, may appear
to have a vegetative formation, sometimes parts of foliage-leaves which nor-
mally bear no sporangia occasionally produce these and assume then quite
the configuration of sporophylls. We may quote as an example:
Botrychium Lunaria. The sporophyll arises upon the upper side of
the sterile leaf in this plant. It is richly branched, and the sporangia arise
at the end of a vein on its margin somewhat approaching the upper side. If
we compare a large number of examples we shall find that the difference
between the sterile and fertile portion of the leaf is not constant, although
in the majority of cases it is sharply marked. The variations, however, take
different directions. The normally fertile portion of the leaf, the sporophyll,
may become entirely or partially sterile, or the sterile portion of the leaf may
become entirely or partially fertile. In both cases there are intermediate
forms such as are shown in Fig. 313, 1and 2. Onthese it may be clearly seen
that the more the sporangia appear the more is there a division of the leaf
into single segments, and the more do the leaf-lobes elongate and narrow.
The sporangia are in these cases normal, and one cannot therefore speak of
a malformation associated with a destruction of the function, as is the case
in the phyllody of ovules.
These facts furnish irrefragable proof that there is a causal connexion,
which we call correlation, between the formation of the sporangia and the
divergent configuration of the sporophyll ; and if we read into this further
and say that the sporophyll arises from an earlier or later transformation of
the primordium ofa foliage-leaf, this is founded upon the fact that in all known
Pteridophyta and Spermophyta the foliage-leaves appear first in the course
of the development and are followed by the sporophylls. It by no means
follows that we must interpret this process as also phyletic®. The reasons
" See Goebel, Beitrage zur Morphologie und Physiologie des Blattes, in Botanische Zeitung,
xxxviii (1880), p. 821; Behrens, Uber Regeneration bei den Selaginellen, in Flora, Ixxxiv (Erganzungs-
band zum Jahrgang 1897), p. 163. The literature is cited here.
2 See p. 506.
* Many authors who have dealt with these questions do not separate these two sides of the
question. What I have been speaking of above is based upon the relationships as we see them
now. It does not touch questions of phyletic speculation. So long as we know so little about the
things that surround us, it will be more profitable to go more into ¢hezr life-conditions before exorcising
the shades of the past. There is nothing in the way of the assumption that originally all leaves were
sporophylls, and that the formation of sporangia was introduced at a stage in the life which was
SPOROPHYLLS AS NEW FORMATIONS 477
which have made it probable that the sporophylls are phyletically the older
will be spoken of when the sporangia are discussed’.
The interpretation of the sporophylls as transformed foliage-leaves sup-
poses that they conform to foliage-leaves or parts of foliage-leaves in their
position and their origin. This appears in many cases but not in all. That
the sporophylls conform to the foliage-leaves in their position requires
no illustration here. It is well known and seen everywhere. But the con-
formation of the sporophylls to the foliage-leaves or
parts of foliage-leaves in respect of their origin is of special
importance for the theoretical interpretation of the sporo-
phyll.
In the Lycopodineae, Equisetineae, the Marattiaceae,
Poly podiaceae, Gleicheniaceae, most Schizaeaceae, Osmun-
daceae, the sporophylls do not differ in position and origin
from the foliage-leaves.
FIG. 314. Schizaea
ec Sporophyll. FIG. 315. Schizaea rupestris. Apex of =o ale profile; Si-S4, primordia
Natural size. of fertile pinnules. Magnified.
SPOROPHYLLS AND FERTILE LEAF-PARTS AS NEW FORMATIONS. In
Schizaea, the Marsiliaceae and Ophioglossaceae we find that they do differ ;
the sporophylls or the fertile leaf-part cannot be traced back to a transfor-
mation of a sterile portion of a leaf, but they are really ew formations,
which have no representation on the sterile leaves. The following examples
will illustrate this :—
(I) LEPTOSPORANGIATE FILICINEAE.
SCHIZAEACEAE. In this family the relationships are the simplest in so
later the larger the dimensions attained by the sporophyte. We have indeed before now seen that
even in the seedling-plant the configuration may be changed by adaptation. As in plagiotropous
seedlings of ivy the orthotropous shoots proceed from the plagiotropous ones, although it is in the
highest degree probable that the orthotropous are phyletically the older, so also at the present day
the sporophylls proceed from the foliage-leaves. 1 See p. 510.
478 THE SPOROPHYELS OF) FIPRIDCCR Ya
far as the sporophylls although new formations appear in the same position
as do sterile leaf-parts elsewhere. We may first of all discuss the case of
Schizaea.
Schizaea Rupestris. I have examined Schizaea rupestris which I
collectedin Australia. The sterile leaf is here elongated, linear, and traversed
by asingle nerve. It grows by means of a two-sided apical cell. No branch-
ings are laid down. The fertile leaf (Fig. 314) bears at its apex a number
of pinnules which produce sporangia in two rows, and the terminal part of
the leafis likewise fertile 1. The history of development shows (Fig. 315) that
these fertile portions of the leaf develop as outgrowths of the margin beneath
the continually growing apex (Fig. 315, S,S;, S3, S,). There is formed
in each of these outgrowths a two-sided apical cell, and thus the sporiferous
pinnules grow like the whole leaf. One would have the sterile leaf if one
removed the fertile
upper portion as it is
shown in Fig. 315.
The appearance of the
fertile parts here as
new formations only
supplies a_ specially
instructive example of
the fact that the deve-
lopment of sporangia
occasions a richer seg-
mentation than exists
in the sterile leaf.
Fic. 316. Asplenium dimorphum. I, sterile pinna. II, fertile pinna. imilar i
III, transition-form. All hea : - Similar behaviour
is found in other genera
of the Schizaeaceae, for instance in Aneimia and Lygodium. In Mohria
there is no essential difference between the sporophylls and foliage-leaves.
That the striking conformation and disposition in Aneimia facilitates the
distribution of the spores will be shown later ”.
POLYPODIACEAE. This family furnishes another example of like fea-
tures :——
Asplenium Dimorphum. Fig. 316, I and II, show two pinnae of the
first order of Asplenium dimorphum. The sterile pinna, I, is strikingly
different from the fertile one ; its pinnules of the second order are broad, only
1 The sporangia are marginal on the pinnules of the sporophyll. The same is the case with the
sporangia of the Marsiliaceae, although the relationships are evidently quite different. In both
cases it is noteworthy that the fertile pinnules and sporangia conform to one another as regards
their place of origin, and this is of value in relation to the hypothesis which derives the vegetative.
formation of the leaf from sporangia which have become sterile.
2 See p. 592.
—
SPOROPHYLLS AS NEW FORMATIONS 479
indented at the margin, whilst in the fertile leaf the pinnules of the second
order are again pinnatifidly cut with narrow pinnules of the third order!. The
case of Schizaea does not differ essentially from this.
MARSILIACEAE. In the Marsiliaceae we find relationships which
conform essentially to those of the Schizaeaceae. It is evident that the
peculiarly formed sforocarps in the species of Marsilia are outgrowths of the
sterile leaves. To the solitary sporocarps in Pilularia another origin was
formerly in part assigned, but they also arise from a foliage-leaf* as I have
stated, and as the thorough investigations of Campbell, Gliick, and
D. S. Johnson have confirmed. The relationships in the species of Marsilia,
whose leaves bear a large number of sporocarps, are specially peculiar, for
instance in M. polycarpa:—
Marsilia Polycarpa®. The sporocarps arise in acropetal serial succession
upon the part of the leaf-primordium which becomes stalk (Fig. 317). The
Fic. 317. Marsilia polycarpa: I, lower part of a sporophyll with eight sporocarps in profile. II, young
Spocop yt seen from above. III, younger sporophyll in profile. , primordium ofa pinnule; Sf, young sporocarp.
agnified.
first are laid down before the vegetative pinnules are present upon the leaf-
primordium. As we have here a large number of sporocarps the plant is
particularly suited for an accurate investigation of their position. The fertile
segments spring from the »argzn of the sterile leaf. They arise, however,
only on ove margin ina series one above the other, although at the same time
the serial arrangement is not always very strongly maintained, being probably
affected by relationships of space. Fig. 317, III, shows clearly that the
sporocarps assume upon the leaf-primordium the same position in space as
do the sterile pinnules; the lowermost pair particularly* clearly appears as
1 This case differs somewhat from that of Schizaea because on the sterile leaf also the apex of
each nerve corresponds to the vegetative point of a leaf (see p. 313), which in the fertile leaf
develops further, but in the one-nerved sterile leaves of Schizaea pusilla the leaf is ‘ potentially’
also quite simple. There is however only a graded difference. There are moreover species of
Schizaea with dichotomously branched sterile leaves.
2 See Goebel, Beitrage zur vergleichenden Entwicklungsgeschichte der Sporangien: Uber die
‘Frucht’ von Pilularia globulifera, in Botanische Zeitung, xl (1882), p. 771.
$ I gathered the material for investigation some years ago in South America. As to the specific
name :—Marsilia polycarpa I consider as an ‘ aggregate’ species, especially as A. Braun himself was
doubtful whether his Marsilia subangulata was actually different from Marsilia polycarpa.
* In the profile view only one pinnule is naturally visible.
480 THE SPOROPHYLES OF PTERIPCOPHYT
a marginal outgrowth quite as the pinnules already described in Adiantum
Edgeworthi!. The arrangement of the cells is different: the sporophylls
srow for a long time by a two-sided apical cell, just like the apex of the
sterile leaf; the sterile pinnules show from the beginning a marginal growth
with diverging anticlines at the apex. I must not, however, attach much
weight to this difference. We have already seen? that the arrangement of the
cells at the apex of the leaf in ferns has a connexion with the configuration
which will be reached; we need not therefore wonder that the sporocarps
which develop into greatly elongated bodies show a cell-arrangement different
from that of the flat leaflets. We have besides seen in Schizaea rupestris
fertile leaf-pinnules growing with a two-sided apical cell, and these are marked
out in like manner by an elongated conformation and absence of development
in surface. The branching of the fertile leaves in Marsilia is, however, uni-
lateral, and in this they show a difference from the sporophylls of Schizaea.
The leaf of Marsilia stands obliquely upon the dorsiventral rhizome, the
anterior leafmargin being deeper than the posterior one. It is from the
anterior one that the sporocarps spring, and this disposition is still visible
even in the mature condition, as the leaf-stalk has a channel upon its upper
side*®. This unilateral position of the fertile leaf-portion is a striking one,
and may be connected with the dorsiventral character of the whole shoot.
Also the lateral buds stand upon the anterior margin of the leaves, and they
find here at first just as do the sporocarps a specially protected position
between the shoot-axis and the leaf-primordium. Unilateral formation of
pinnules is found also elsewhere amongst the ferns, for example in the leaves
of Pteris semipinnata. We may also compare the unilateral development of
the fertile leaf-portions with the cases already described* of unilateral pinna-
tions, for example of Anthyllis tetraphylla and other Leguminosae, only we
saw there that we had to deal with a phenomenon of vegetative adapiation
standing in relation to the dorsiventral construction of the whole plant.
Putting aside phyletic speculation, such an adaptation can scarcely be admitted
in the Marsiliaceae; but it is striking that a similar development is re-
peated in the Marsiliaceae, which are likewise dorsiventral. The important
point is, however, the proof that the fertile leaf-portions, even where they
appear in relation to the sterile leaves as mew formations®, yet conform im
position and origin to the leaf-pinnules.
1 See p. 316, Fig. 204. The last two pinnules arise when the apex of the leaf-primordium has
already expanded. It forks in more feeble primordia.
2 See p. 316.
* See A. Braun, Neuere Untersuchungen iiber die Gattungen Marsilia und Pilularia, in
Monatsberichte der Berliner Akademie, aus dem Jahre 1870, p. 653.
* See Part I, p. 121. Also the facts mentioned Part I, p. 88. In Fig. 228, IV, the pinnate leaves
are partly unilaterally developed, so that the phenomenon is not at all rare.
° In many species of Marsilia many sporocarps are seated upon one stalk, for instance often
in Marsilia quadrifolia. Usually we have a branching of the sporocarp, of which Johnson has
SPOROPHYLLS AS NEW FORMATIONS 481
(II) EUSPORANGIATE FILICINEAE.
OPHIOGLOSSACEAE. In this family, at least in the large majority of
species, the condition is somewhat different. The sporophyll does not arise
upon the margin, but upon the wffer side of the sterile leaf-portion. In
Ophioglossum palmatum the marginal position is also found, but in most
cases the sporophyll arises here also from the upper side of the sterile leaf,
but more or less near its margin’. The history of development is unfortu-
nately unknown. It is possible, although indeed not very probable, that the
sporophyll originally marginal has become displaced upon the upper side.
As it is we can give some ‘ reasons, or rather hint at some relationships, which
account for the divergent position of the sporophyll even in the Ophioglos-
Fic. 318. Helminthostachys zeylanica. I, young leaf in profile. The sterile pinnules cover the sporophyll, the
point of which, S, is seen projecting, but at alater period would be covered. II, leaf in transverse section; Zs, leaf-
stalk; Sf, sporophyll invested Bi the pinnules of the sterile leaf-part. III, sporophyll in transverse section;
S, sporangiophore. IV, young foliage-leaf in transverse section; Z, primordium of lamina; 0, upper side;
uw, under side; J, primordium of mid-vein. Magnified.
saceae. It is laid down very early, and in correspondence with its
later construction is relatively very thick. The young leaf is firmly
ensheathed in envelopes, and the position of the sporophyll upon the upper
side of such a primordium would take up less room than it would were it
placed right and left; its median position secures that the sporophyll is
enveloped and protected by the sterile leaf (Fig. 318, II), and this, in a case
where there is such very slow development of the leaf as occurs here, must
traced the history of development in one species. It may be that in other cases an elevation of the
common base takes place. See D.S. Johnson, On the Development of the Leaf and Sporocarp in
Marsilia quadrifolia, L., in Annals of Botany, xii (1898), p. 119; id., On the Leaf and Sporocarp
of Pilularia, in Botanical Gazette, xxvi (1898).
* Bower, Studies in the Morphology of Spore-producing Members: II. Ophioglossaceae, London,
1896.
GOEBEL II li
482 THE SPOROPHYLLS OF PTERIDOPHYTA
be of great importance. We shall return below to the phyletic explanations
which have been given of the divergent position of the sporophyll in the
Ophioglossaceae. At present I wish only to indicate that the normal branch-
ing of the foliage-leaf in one plane is connected with the provision of an
assimilation-surface exposed to the light, and that therefore in the biological
connexion the divergent position of a non-assimilating leaf-segment is of no
importance. Asa matter of fact we find the same phenomenon in the leaf-
structures of the flowers of higher plants!, for example in the formation of
the corona in Narcissus, Sileneae, and elsewhere, and in the multiplication
of petals by splitting in double flowers. All these phenomena conform to that
of the position of the sporophyll in Ophioglossum which has xothing or only
little to do as an assimilating portion of the leaf. This resemblance of the
sporophyll of the Ophioglossaceae to a leaf-segment expresses itself also in
its remarkably dorsiventral character’.
There is, therefore, no necessity, so far as living plants show us, for con-
sidering the sporophyll as anything else but a foliage-leaf which experiences
soon or late, sometimes not at all, a transformation; otherwise the relation-
ships of configuration of the sporophylls and of the flowers of the Pterido-
phyta are so manifold and so important for a consideration of the flowers in
the higher plants that it will be useful to select here from the larger groups
some illustrations. The arrangements for the protection of the sporangia
will be spoken of separately °.
B. SPECIAL FEATURES OF THE SPOROPHYLLS.
I. FILICINEAE,
I. EUSPORANGIATE FILICINEAE.
MARATTIACEAE. In the Marattiaceae the sporophylls are the ordin-
ary foliage-leaves.
OPHIOGLOSSACEAE. In the Ophioglossaceae the fertile leaf-portion
springs from the sterile, which is very different in appearance. It has no
special assimilation-tissue, and is erect and stalked. The features are
apparently strictly fixed inOphioglossum*; in Botrychium we find frequently
1 The position of the ovules should be specially considered here. These, for example, in the
Ranunculaceae are originally marginal on a megasporophyll. Where this forms a basal sac the
ovule springs from a median position, and in Ranunculus and other genera frequently this is the
only ovule that remains. Its position is originally like that of the sperophyll of the Ophioglossa-
ceae to the sterile leaf-part.
* See especially the sporophylls in Helminthostachys, p. 483.
3 See p. 496.
* The vegetative transformation of the sporophyll is very rare in Ophioglossum. Apart from the
branching at the apex of many sporophylls, which for our purpose is of the same kind, I only know
of one record of it, that of Presl, Supplementum tentaminis Pteridographiae, in Abhandlungen der
Konig]. Bohmischen Gesellschaft der Wissensch. in Prag, Folge 5, iv (1845-6), who says: ‘ vidi
specimen Ophioglossi vulgati, cuius spica marginem foliaceum utrinque duas lineas latum eviden-
tissime yenosum habuit.’
SPOROPHYLLS OF OPHIOGLOSSACEAE 483
intermediate forms!. The configuration of the sporophyll of Ophioglossum
and Botrychium is described in every text-book, and need not be further
spoken of here beyond the statement that the sporangia
in both genera are marginal.
Helminthostachys *. The relationships of configura-
tion are peculiar and remarkable in this third genus of
the Ophioglossaceae. The sporophyll differs most of all
amongst the Pteridophyta from the configuration of the
foliage-leaves, at the same time the construction offers
interesting points of comparison with features that are
observed frequently in the formation of the stamens of
many dicotylous plants. The sporophyll arises as in
other Ophioglossaceae in the form of an outgrowth upon
the upper side of the foliage-leaf, which is here divided
many times into a somewhat palmate form. The lobes
of the sterile leaf-part are in their juvenile condition
projected beyond the sporophyll (Fig. 318, I), so that
the sporophyll is protected upon the one side by the
downwardly curved sterile leaf-part, and upon the other
by the massive leaf-stalk (Fig. 318, II). The whole leaf
is originally covered in a cap-like manner by an out-
growth of tissue of the shoot-axis. The fertile sporophyl]
is evidently negatively geotropic (Fig. 319), is apparently
radial, and its surface is densely occupied by supporters
of the sporangia, which Bower has designated sforangio-
phores. These sporangiophores, simple or branched, only
rarely bear one, more usually many, sporangia, and these
are then most frequently disposed in two tiers one above
another and in a radial manner (Fig. 320). The lower
Fic. 319. Helmintho-
stachyszeylanica. Sporo- FIG. 320. Helminthostachys zeylanica. Sporangiophore.
phyll. Magnified. I, I, simple ; III, IV, branched. Magnified.
portion of the sporangiophore is usually narrowed to astalk-like form. The
upper part is broadened out and has grown out into lobes, so that the whole
tSee p. 446. a, Se ipracim pre
* See Prantl, Helminthostachys zeylanica und ihre Beziehungen zu Ophioglossum und Botrychium,
in Berichte der deutschen botanischen Gesellschaft, i (1883), p. 155; Bower, Studies in the
Morphology of Spore-producing Members: II, Ophioglossaceae, London, 1896. The account
given in the text is based upon investigations carried out on material collected by me in Ceylon and
Java in 1886, and which I have lately re-examined.
Ii2
484 THE. SPOROPHYLILS OF) PILRIDPOrA Via
sporangiophore has some resemblance to a sporophyll of Equisetum. The
upper broad portion forms a roof above the young sporangia and must be
considered as a protective apparatus for them. Examination of the young
sporophyll (Fig. 321) shows that its radial disposition is only apparent ; it
is really bilateral or dorsiventral, for there remains upon its upper side and
upon its under side a strip free of sporangia, and these strips are still visible
in many mature sporophylls. These free strips correspond to the middle
nerve of the sterile leaf-portion. The sterile leaf-lamina is here, as in the case
of some leptosporangiate ferns 1, laid down relatively late
(Fig. 318, Z). The development of the massive middle
nerve (Fig. 318, J7) precedes that of the lamina, which
shoots out right and left from a zone of embryonal tissue
remaining about the middle nerve (Fig. 318, IV, LZ)’.
In the case of the sporophyll there is no laying down of
one leaf-lamina. This is toa certain extent from the very
first divided into a number of small papillae (Fig. 318,
ITI, S~) which indicate the sporangiophores*. The re-
markable thing then is that the ‘ division’ of the lamina
takes place so very early, and that it does not as else-
where proceed in the plane of the leaf-surface which is
here undeveloped, but in directions which lie oblique to
this. We speak figuratively of a division here because
evidently a leaf-surface to the sporophyll is usually not
developed, but in its place the sporangiophores appear.
The leaf-surface may, however, develop in abnormal
i cases, such as I observed in Java in 18854. The sporo-
FIG. 321. Helmintho- = :
stachys zeylanica. Young phyll had in these examples repeatedly divided at its end
sporophyl! in oblique pro- E is e :
file. The primordia of —thus approaching in its behaviour the sterile leaf-part
the sporangiophores are <i : ;
densely clustered on the —agnd the single portions of the leaf contained chloro-
margin. Magnified. oe es
phyll were flattened and were divided at the margin
into lobes which bore the sporangia. In this case then the sporangiophore
appeared as a segment of a foliage-leaf. Upon these general grounds then
I regard the sporophyll of Helminthostachys as a portion of a foliage-leaf
which has become modified at an early period and in a peculiar manner.
The lamina is replaced by a sporangiophore which appears in its position.
That the virescence should proceed most easily at the evd of the sporophyll
can be easily understood from the history of development. Fig. 321 shows
1 See p. 320, and Fig. 207 of Pteris serrulata.
* The arrangement of the cells is different from that in Pteris serrulata.
* In many cases there is evidently a common base which one might recognize as the rudimentary
primordium of the lamina. In rare cases in Java I found this developed as a wing.
* See also Bower, Studies in the Morphology of Spore-producing Members: II. Ophioglossaceae,
London, 1896, Pl. ix, Figs. 138 and 139.
SPOROPHYLLS OF ISOSPOROUS FILICINEAE 485
that the formation of the sporangiophores decreases towards the end of the
sporophyll, and there they arise partly in a szmgle row, which means that
the lamina of the sporophyll approaches more the ordinary form ?.
We can, therefore, trace back the sporophyll to a specially far-reaching
transformation of the vegetative leaf, and at the same time see that the
sporophyll of Helminthostachys in its dorsiventral construction conforms
with that of Ophioglossum and Botrychium. The hypothesis, which will be
subsequently mentioned, that the sporophylls have proceeded from a further
vegetative development of the sporangia, would assume that upon a sporo-
phyll of Ophioglossum the sporangia were chambered by sterile plates of
tissue nearly parallel with the leaf-surface, and that then these partial
FiG. 322. Drymoglossum subcordatum, Fee. Habit.
The sterile leaves are broad and shortly stalked. The
sporophylls are erect, have long stalks, and a narrow Fic. 323. Elaphoglossum spathulatum. Habit.
lamina. After Christ. After Christ. Natural size.
sporangia grew out vegetatively into sporangiophores. We content ourselves
here with proving the fact that the sporophylls of Helminthostachys conform
in their primordia to the foliage-leaves, although the two leaf-forms
appear so very markedly different when we only regard their mature con-
dition.
2. LEPTOSPORANGIATE FILICINEAE ~,
(a) ISOSPOROUS LEPTOSPORANGIATE FILICINEAE.
The manifold construction of the sporophyll in this group has been
already mentioned ?, and it would take me too far were I to give a thorough
account of it. Only a few points may be noted.
EXTERNAL FORM. The sporophylls often are distinguished from the
foliage-leaves by having a different conformation of the stalk and the
lamina. The stalk in many of the sporophylls is longer than that of the
foliage-leaves, and thus facilitates the distribution of the spores (Figs. 322,
323).
1 Where the transformation has proceeded less far, there the vegetative formation can most easily
enter in.
? See Gliick, Die Sporophyllmetamorphose, in Flora, lxxx (1895). 3 See p. 482.
486 THE SPOROPHYLLS (OP PIEBIDOLA Yaa
In the segmentation of the lamina we have to recognize two cases :—
(a) The sporophylls have the segmentation of their lamina reduced as
compared with that of the foliage-leaves’. This occurs in Onoclea Stru-
thiopteris, Allosurus crispus (Fig. 324), Acrostichum peltatum, and it is the
more common.
(4) The sporophylls have their lamina more richly segmented than is
that of the foliage-leaves. This occurs in Asplenium dimorphum (Fig. 316),
and also in Osmunda regalis, Aneimia, and elsewhere.
ANATOMY. The existence of anatomical differences, such as the
reduction of the assimilating leaf-tissue and so on, in the sporophylls, can
only be mentioned here.
It seems to me improbable—at any rate it is not yet proved—that the
difference in the configuration of the sporophylls when compared with the
®
r7)
A fry
Vi
b
Fic. 324. Allosorus crispus. 1, sterile pinnule. 2, 3, 4, transition-stages between sterile and fertile pinnules.
5, fertile pinnule with the margin rolled back. After Gliick.
foliage-leaves can be always explained teleologically®. More probably it
is determined by the metabolic processes connected with the formation of
sporangia, and these cannot always be brought into close relationship with
the conditions of life. The endeavour to find such connexions is neverthe-
less a sound one. It must have as a starting-point a review of the relation-
ships of life. I may here briefly refer to one illustration :—
Acrostichum (Rhipidopteris) peltatum. This fern owes its name
to the configuration of the sporophylls, which indeed are not peltate, but
which by their undivided lamina, in contrast with the richly segmented
and frequently forked sterile leaf, are very striking *. The original resem-
blance of the two often shows itself, however, in the sporophyll by indenta-
1 That is to say the primordium of the leaf has remained stationary at a certain definite stage of
segmentation. For the protection of the juvenile sporangia such sporophylls are much better suited
than are those which are much divided.
2 We must always remember that the configuration of the sporophyll has not only to do with the
distribution of the spores, but also with the protection of the sporangium in its juvenile state.
° In systematic works, for example Christ’s Die Farnkrauter, it is assumed that the sporangiferous
side of the leaf is the under side, and this undoubtedly is in accordance with the usual behaviour and
the lie. Moreover, the stomata are also limited, as in the sterile leaves, to the under side. The
ptyxis, however, suggests that the sporangia stand upon the wffer side. At least we find the
marginal portion incurved towards this side—especially clearly is this seen in transition-forms
between sterile and fertile leaves where the lamina is still more divided—but the incurving takes
place in the sterile leaves as elsewhere towards the wffer side. There is here then much that is
still enigmatical.
SPOROPHYLLS OF HETEROSPOROUS FILICINEAE 487
tions at its margin which correspond to a division which has not proceeded
very far. Probably the species has been derived from forms with slightly
divided leaves’, and the sporophylls approach more nearly the primitive
leaf-configuration than do the foliage-leaves. The conformation of the
sporophyll has moreover probably also a biological significance. The bright
margin of the sporophyll is free of sporangia and is bent backwards. It is
easy to observe that the sporophylls retain water-drops, which then will be
carried to its sporangiferous side. Now the species grows in moist mountain-
ous woods’, but the leathery texture of the sterile leaves, their sharply
differentiated epidermis bearing stomata only upon the under side, indicate
that the plant is arranged to withstand temporary want of water. The
sporophylls by their conformation hold water-drops for a time and pass it
on directly to the young sporangia, which in other ferns are protected against
wetting but here evidently are not injured by this.
(6) HETEROSPOROUS LEPTOSPORANGIATE FILICINEAE.
SALVINIACEAE. Inthe Salviniaceae* we may speak of microsporophylls
and megasporophylls and of parts of these, because the microsporangia
and megasporangia appear in separate sori, and these stand upon leaves‘.
There is a difference in the construction and conformation of the micro-
sporophyll and megasporophyll respectively in the Salviniaceae *®, and a short
explanation of this is necessary because the difference between micro-
sporophylls and megasporophylls is much greater in the Spermophyta, and
if we assume that the Spermophyta have sprung from pteridophytous
ancestors a consideration of the sporophylls of the Pteridophyta offers us
the best prospect of a basis for a satisfactory interpretation of the sporo-
phyll of the Spermophyta.
Salvinia. In Salvinia the difference to which I have referred is
essentially this: the number of the microsporangia is larger than that of
the megasporangia®. The significance of this is of course that the number
of the microspores is greater than that of the megaspores.
As a matter of fact the nearly allied Acrostichum flabellatum has such leaves. By some authors
Acrostichum flabellatum is united with Acrostichum peltatum. In Acrostichum flabellatum there
are sterile leaves also which are only indented at the margin and otherwise are undivided. This
whole cycle of forms, whether we call it a species or a group of nearly allied species, is allied to the
species of Elaphoglossum, whose leaves are almost throughout undivided. That the bearers of the
organs of reproduction retain primitive relationships of configuration more than the vegetative organs
which have been changed subsequently through adaptation is seen elsewhere, for example in
Schistostega and others amongst the Musci, and also in the Cactaceae.
2 JT gathered it some years ago, for example, in the Cumbre de San Hilario in Venezuela.
3 As in the heterosporous Lycopodineae.
* Both kinds may occur upon different lobes of the same leaf. That the two kinds of sporangia stand
upon separate leaves in the Lycopodineae is easily understood because the sporangia arise singly.
° A difference in the structure and the conformation of the microsporophyll and megasporophyll
in the Lycopodineae and Isoeteae is not known.
6 We have no reason for supposing that Salvinia originally had sori composed of both micro-
488 THE SPOROPHYLES OF “PIE RIDOLAYTA
Azolla. In Azolla the difference between the two kinds of sori is ex-
aggerated by the appearance of only one megasporangium in the megasorus.
The two kinds of sori can, however, be traced back to one type—to a sorus
which consists of a placenta corresponding to a leaf-lobe round about
which microsporangia are distributed, whilst the point is occupied by a mega-
sporangium. In the microsori this megasporangium early aborts’. In the
megasori, on the other hand, only the megasporangium develops, but there
are found at later stages of development (Fig. 325) primordia of micro-
sporangia which abort. The indusium
appears as an annular wall, and thus the
whole structure acquires a resemblance
to the ovule of one of the Spermophyta.
Azolla shows then a reduction of the
number of megasporangia in relation
to the number of microsporangia, and
probably also a separation of the original
hermaphrodite sori into male and female
ones.
I was not able to form a definite
picture of the sporophylls of Azolla from
the statements of Strasburger? and of
Campbell®, and I have therefore ex-
amined the relationships in Azolla
filiculoides, which some twelve years
ago fruited freely in the Botanic Garden
at Marburg. Each foliage-leaf very
early divides,as we know‘, into an upper
lobe and an under lobe, whose position
arevislbleabove the megasporanginm. Frimortia is indicated im Fig. 927) HOw now
themegasporangium Mapes do these two leaf-parts behave in the
fertile leaf? We know that the sori enclosed by the indusium stand in
pairs®, and they are besides covered by a one-layered cap-like envelope.
Fic. 325. Aczolla filiculoides. Megasorus in
longitudinal section. /d@, indusium; Za, mega-
plains St P, placenta. Threads of Anabaena
sporangia and megasporangia, yet the behaviour of Azolla suggests such a supposition. It is evident
that the separation of the microsporangia and megasporangia favours cross-fertilization. Moreover
Heinricher, Die naheren Vorgange bei der Sporenbildung der Salvinia natans verglichen mit der
der iibrigen Rhizocarpeen, in Sitzungsberichte der Wiener Akademie, lxxxv (1882), found on one
occasion in Salvinia natans a sporocarp which contained some megasporangia among a number of
microsporangia.
1 See Strasburger, Histologische Beitrige, Heft 2, Jena, 1889, p. 8. _ Campbell, On the Develop-
ment of Azolla filiculoides, Lam., in Annals of Botany, vii (1893), found no primordium of
a megasporangium in the microsori. Both exist in Azolla filiculoides according to my experience.
? See Strasburger, Uber Azolla, Jena, 1873, p. 52.
See Campbell, op. cit.
* See p. 348.
° Occasionally I found three upon the under side of the stem.
3
SPOROPHYLLS OF AZOLLA 489
Strasburger maintains that the sori are transformed leaf-lobes and speaks
of the envelope as the under lobe of the leaf, whilst Campbell came to
the conclusion ‘that the whole of the ventral lobe goes to form the sori,
and that the involucre is derived from the whole of the dorsal lobe
Fic. 326. Azolla filiculoides. I, sporophyll dissected out in surface view; O, upper lobe; /, primordium of
wing of upper lobe; S,, S2, primordia of megasporangia; /d, /d2, the indusium. II, two leaves in transverse
section. To the left a sterile leaf; O1, upper lobe; Oj, under lobe. To the right a fertile leaf shown in two
sections, one lower down in the leaf by dotted lines, the other higher up; O, upper lobe; F, wing of the upper lobe
covering two megasori. III, under lobe dissected out and seen from the surface; it is wholly used in the formation
of two megasori, and the indusium appears as an annular wall. All magnified.
of the leaf1.’ Neither of these authors is altogether correct so far as my
investigations show. I agree with Campbell that the sori proceed from
one portion of the under lobe of the leaf which very early develops, but
the upper lobe is by no means devoted to the formation of the involucre.
This upper lobe is pre-
sent as elsewhere, and
contains also a branched
vascular bundle and a
pit inhabited by Ana-
baena. It produces at
its base a wing-like one-
layered outgrowth which
partially covers the sori,
and this is the origin of
the ‘involucre’ (Figs. 326 gee he
: Fic. 327. Azolla filiculoides. Sporophyll spread out flat. To the left
and no LF ); which I need two megasori. To the right the upper lobe. , Wing-like outgrowth of the
E upper lobe, the mucilage-pit is visible below.
not say contains no
conducting bundle. The under leaf-lobe, which is used for the formation
of the sori, contains as elsewhere its conducting bundle. That Strasburger
ascribed the involucre to the under lobe of the leaf is due to the fact that it
is separated from the upper lobe by a somewhat deep depression. Com-
ig ie?
? Campbell, On the Development of Azolla filiculoides, Lam., in Annals of Botany, vii (1893), p. 158.
490 THE SPOROPHYLLS OF. PYIERIDOPAYIA
paring then the fertile leaf with the sterile the following changes in
configuration are found :—
(1) The under lobe, which is elsewhere undivided, divides into two lobes,
more seldom three, and even into four in Azolla nilotica according to Stras-
burger, from the apex of these the single megasporangium proceeds in the
megasorus?. Beneath this there rises up as an annular wall the indusium,
which, being favoured upon the outer side, grows round the megasporangium
like an integument ”.
(2) From the portion of the margin of the upper lobe which touches upon
the under lobe a wing-like outgrowth at first proceeds, and one might
designate it as an indusium if each of the two sori had not already its own
indusium.
MARSILIACEAE. The microsporangia and megasporangia are found to-
gether in the same sorus in the Marsiliaceae. The sporocarps diverge in
their configuration more than those of any other group from the sporophylls
met with elsewhere. The sporangia apparently are enclosed within a body
of tissue which is surrounded by a usually hard shell, and this, when it is
ripe, is opened in a remarkable manner by the swelling up of mucilaginous
tissue within it—an arrangement which makes possible the withstanding of
a dry period, and as a matter of fact the sporocarp exhibits a resting period—
and thus the germination of the spores can only begin if such a quantity of
water is present as is necessary for the further development. It has been
already shown® that the sporocarps are always leaf-borne, and like the
pinnule of Marsilia they take rise upon the flanks of the foliage-leaf
(Fig. 317). The history of development has also explained the rest of the
structure of this remarkable body. The sporocarps are always dorsiventral,
even where, as in Pilularia, this is not externally marked. The ‘ fruit’ con-
sists in Pilularia globulifera of four chambers, in which megasporangia and
microsporangia lie. In Marsilia the chambers are more numerous and are
arranged in two rows. Ihave pointed out* in opposition to the assumption,
based upon the consideration of the mature condition only, that the sporangia
arise actually within closed spaces, and also in opposition to Russow’s state-
ment, based upon beautiful but incomplete developmental investigations,
that the ‘sorus-canal’ arises by a splitting of the tissue, and that the sori
here are formed, as in other Leptosporangiate Filicineae, from superficial cells
of the primordium of the sporophyll, and are only gradually sunk subsequently
into the tissue. Biisgen, Meunier, Campbell, and Johnson have confirmed
this, and supplemented it by showing that the placenta arises upon the
1 The division of the under lobe is specially plainly seen in Fig. 326, III.
* See the section upon the development of the sporangium, p. 595.
Ss See p. 470:
* See Goebel, Beitrige zur vergleichenden Entwicklungsgeschichte der Sporangien : III. Ueber
die ‘ Frucht’ von Pilularia globulifera, in Botanische Zeitung, xl (1882), p. 771.
SPOROPHYLLS OF MARSILIA 491
margin of the leaf. The processes which are thus brought about recall in
more than one sense the features which will be depicted below in other ferns,
for example in the cyatheaceous Balantium antarcticum, only that the sori
do not appear in Azolla as they do there upon the under side of the leaf, but
are displaced to the ~pper szde whenever the formation of the pit sets in.
The diagrammatic representation of cross-sections shown in Fig. 328, I-III,
will illustrate this. The youngest stage, Fig. 328, I, recalls the transverse section
of a leaf of a young fern such as is shown in Fig. 207, II. We saw there a lamina,
L, L, springing from marginal cells. In the sporocarp of the Marsiliaceae we find
quite similar marginal cells, X, which, however, are displaced somewhat more towards
the upper side. In some parts of the margin corresponding to the later-formed
fruit-chambers an increased growth takes
place, accompanied by characteristic divi- 0D 5 J s
sions of the marginal cells. In Fig. 328, II, oF Ns
the marginal cells, from each of which a
sorus springs, are marked with the letter S.
They are already sunk in a shallow pit,
and are pushed upwards by the growth of
a portion of the under side of the leaf. FIG. 328. Marsilia. Three sporocarps of different
: ; : age in diagrammatic transverse section. 1, youngest;
At the same time the deepening of the pits ©, upper side; U, under side; R, marginal cells:
5 : : D, segment-wall. II, older; 7, primordium of indu-
begins. The portions which are marked sium; S, S, primordia of sorus; y, y, lateral out-
Wy and /, ff grow up and cause the sinking poet oe still older. Lettering
of the leaf-margin more and more in a
deep pit which has a narrow mouth to the outside, and this subsequently forms
by concrescence a closed canal. If now we compare the process with that of
Dicksonia, which will be mentioned presently’, we see quite analogous® processes
if we only consider one-half of the Fig. 331, I]. The portion of tissue marked
Jy, ¥ in Fig. 328, which, however, remains united with the rest of the sporocarp-tissue,
corresponds to the outer indusium (Fig. 331, I, /o), whilst the part marked /, / in Fig.
328 corresponds to the inner indusium (Fig. 331, I, /z). As amatter of fact one may
consider usually the tissue marked /, / as an indusium in the Marsiliaceae, especially
because in the process of emptying of the sori in Marsilia each of these is surrounded
by a sac-like envelope (Fig. 329, II). These indusia, however, are not laid down as
separate tissue, but are raised as one tissue-mass common to all the sori, and in it
the lines along which they will subsequently be separated one from the other can
be recognized at an early age. If then these are to be regarded as individual indusia
one must assume a ‘congenital concrescence,’ but even now I know of no ground
for such an assumption.
The question may be asked now—how are we to interpret the sporocarp as
a whole? I may state, in the first place, that I have nowhere said what Johnson
ascribes to me, ‘that it represents a simple leaflet or pinna with its edges folded in
to meet at the ventral side of the capsule’ My view is that the sori are sunk in
the upper side of the sporophylls. This upper side is, however, extremely narrow,
ES
S
¥ IH
1 See p. 494. ? Not homologous. * This is A. Braun’s interpretation, not mine.
492 THE SPOROPHYLLS OF ' PTERIDOPHYTA
represented essentially only by the indusium. In Fig. 328, III, the limits are
marked by the letter O. Everything else, apart from the margin, is strongly
developed wnder side; an infolding does not take place. Johnson’s statement
that the sporocarp is homologous with the ‘petiole only of the sterile branch of
a leaf,’ does not correspond with the facts. What is the ‘petiole’ of a fern-leaf?
The portion of the leaf-primordium on which the formation of the lamina is sup-
pressed entirely or in great part, and where the formation of mechanical tissue is
conspicuous instead! The sporocarp is not homologous with this differentiated
part of a leaf, but with a leaf-primordium on which the
differentiation of the lamina is zof_ye/ begun, as is shown
for Petris (Fig. 207, II). Thatisa difference! Biisgen’s
in
ep ate
; Oa
2S
indy
iL
Fic. 329. I, Marsilia polycarpa. Very young sporocarps from the
upper side: \S¥, stalk; 2, 21, mother-cells of the sori which proceed from
marginal cells, but appear to be displaced to the upper side. II, Marsilia
Brownii. Older sporocarp in section parallel with the surface. Eight sori
are seen. III, Marsilia polycarpa. Sporocarp like that of I in optical
longitudinal section. The large cells are the mother-cells of the sori.
I and III magnified.
Fic. 330. Pilularia Novae-Hollandiae.
Anterior portion of a plant in profile. Two
rows of leaves are visible upon the dorsi-
ventral shoot-axis. .S,, Sz, Ss, sporocarps;
W, W, roots; Wa, broken-off root. Two
roots arise beside each leaf. Magnified.
observations of monstrosities show also that in rare cases pinnules of Marsilia may
develop to sporocarp-like structures, and A. Braun found a pinnule with narrow
lamina instead of the sporocarp in Marsilia. Now, as heretofore, 1 regard the
sporocarp as homologous with a leaf-segment, just as it is in Schizaea. The only
point in doubt is whether one should consider the marginal portion which is
devoted to the formation of the sorus as indication of a further pinnation which,
however, remains fused with the leaf. In support of this I know of no weighty
grounds at the present time.
Marsilia polycarpa. In order to explain the relationships still further I
would refer to a very instructive preparation of Marsilia polycarpa which is repre-
sented in Fig. 329 :—In I we have a view of the upper surface of an entire sporocarp
which has been dissected out. It is extremely small and still straight. It is a club-like
body whose lower part, SZ, develops subsequently into stalk. The two-sided apical
cell is still visible at the apex. The primordia of the sori, 7, «,, are evident, and are
clearly superficial cells, and indeed, as a transverse section shows, are marginal cells
POSITION OF SPORANGIA ON SPOROPHYLLS OF FILICINEAE 493
which bulge up by their size. They are mostly divided by a cross-wall into two
cells, and these cells it is which in the manner described above become subsequently
sunk in pits. Fig. 329, III, gives a side-view of the margin, and already there are
upon the upper side of the sporocarp three shallow longitudinal pits which are
separated from one another by an intermediate elevation.
I need not go into details further here. It must suffice that we have
determined that the remarkable relationships of configuration of the sporo-
carp of the Marsiliaceae can be referred back to the formation of the
sporophylls in other leptosporangiate ferns, and that they only exhibit a
special case in relation to the life-relationships.
HYPOGEOUS SPOROCARPS. A few words must be said about the Mar-
siliaceae which bury their sporocarps in the soil. In West Australia I
gathered Pilularia Novae-Hollandiae, which is shown in Fig. 330. The stalk
of the sporocarp in this plant bends very early downwards, and the sporocarp
itself is directed with the mouth of the pit obliquely upwards. There is no
doubt that we have here a phenomenon quite like that of the formation of
tubers! in the Hepaticae, and that we have especially a protection against
rapid and extreme drying. Quite similar relationships are apparently
found in Marsilia subterranea, but I do not know this plant from my own
observation. Amongst the Spermophyta there are a number of cases in
which the ripening fruits are buried in the soil. The examples here men-
tioned show us anew how analogous adaptations are repeated in the most
different cycles of affinity.
3. POSITION AND ARRANGEMENT OF THE SPORANGIA UPON THE
SPOROPHYLLS AND THEIR PROTECTION IN FILICINEAE.
These relationships are amply explained in systematic works. Here only
some general connexions will be set forth, in order that a comparison may
be made with Spermophyta.
(z) POSITION OF THE SPORANGIA.
If we keep in view the relationships in a// the Pteridophyta it would
appear as if nearly all possibilities were realized. The sporangia are upon
the upper side of the sporophyll in the Lycopodineae ; upon the under side
in most of the Leptosporangiate Filicineae and in the Marattiaceae ; upon
the leaf-edges in the Schizaeaceae where there is a slight displacement
downwards, in the Marsiliaceae where there is a slight displacement upwards,
and in the Ophioglossaceae where in the mature condition of the leaf they
appear displaced upwards; uniformly distributed all round in Osmunda%, in
the Equisetaceae, and in Salvinia; on the placenta (‘receptacle’) in the
1 See p. 66.
? See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884), p. 387. In the allied Todea they stand upon the under side.
494 THE SPOROPHYELS: OF PTERIDOPHYTA
Hymenophyllaceae. This variability we shall also meet with in the sporo-
phylls of the Spermophyta.
General connexions in this variety will not be easy to find without the
help of some more or less bold hypotheses. These will be of most service
within narrow cycles of affinity, for example that of the Filicineae. We may
here, as it appears to me, establish the fact that the sporangia in general
‘ strive’ for a position upon the under side of the leaf the more the portion of
the sporophyll bearing the sporangia 1s constructed like a foliage-leaf. The
position of the sporangia upon the under side will be of advantage in many
ways :—
(a) The capacity of assimilation of the side of the leaf turned towards
the light will not be interfered with ;
(4) The sporangia which in the land-forms only scatter their spores
when they dry will be protected from wetting ;
(c) The distribution of spores will be favoured because the spores will
fall away from, and not upon, the surface of the leaf.
Only rarely do the sporangia occur upon the upper surface of sporo-
phylls which are like foliage-leaves!.
The following examples will illustrate what has just been said :—
The difference between Osmunda and Todea is very striking. In Osmunda
the sporophylls are sharply distinguished from the foliage-leaves. In Todea
they are not so. If in Osmunda only a few sporangia were to be found upon
the leaf, they would stand as in Todea upon the under side. We have then
here in one and the same plant the connexion mentioned above.
In the same way the marginal position is mostly found where the fertile
leaf-part is not, or only seldom, assimilating, as in Ophioglossum, Botry-
chium, Aneimia (Section Euaneimia). The attempt has been made®* to
establish this position as the primary, and the position upon the under side
as a displacement. Such a displacement has been observed in the history
of development of many cases, for example amongst the Schizaeaceae, in
Schizaea, Lygodium, Mohria, and in many species of Aneimia. In all these
the sporangium is laid down as a marginal structure, and is displaced upon
the under side by the development of the ‘ indusium.’
Dicksonia antarctica. A simple example of this is shown in Dicksonia
antarctica (Fig. 331, III). The tufts of sporangia, which apparently spring from
1 For example, in Aspidium anomalum of Ceylon, which may be only a form of Aspidium
aculeatum, and regarding which therefore it is questionable whether it is constantly reproduced by
spores, and the more so, because in other ferns which normally bear sporangia upon the under side
the position upon the upper side occasionally is found, as in Polypodium lepidotum, P. proliferum,
and Asplenium Trichomanes. See Kunze, Uber abnorme Fruchtbildung auf der Oberflache der
Wedel von Farm aus den Polypodiaceen, in Botanische Zeitung, vi (1848), p. 687. It should be
tried whether by sowing the spores of Asplenium anomalum the offspring may not in some cases
produce also sporangia upon the under side. With regard to Acrostichum peltatum, see p. 486.
? Prantl, Untersuchungen zur Morphologie der Gefasskryptogamen: II. Die Schizaeaceen,
Leipzig, 1881.
a
POSITION OF SPORANGIA ON SPOROPHYLLS OF FILICINEAE 495
the under side of the leaf are enclosed by an envelope or indusium of two flaps.
The upper overlapping flap, /o, has the structure of the leaf-surface apart from its
hairy margin; the under overlapped flap, /z, is composed of cells without chlorophyll,
and serves at first for water-storage, but later experiences a movement? which lays
bare the sorus and so brings about the distribution of the spores. The history of
development shows that the cushion of tissue—the placenta—upon which the spor-
angia sit, proceeds from the leaf-margin, which was, however, at an early period
displaced upon the under side of the leaf. This process is begun in the stage shown
in Fig. 331, I, where the wedge-shaped cell, A, which occupies the leaf-margin, is
conspicuous; the under indusial flap, /z, is also seen to be laid down as an out-
growth of the under side of the leaf, and the position at which the upper flap, /o,
takes origin is clearly visible. /w is then an outgrowth of the under leaf-surface ;
Fic. 331. Dicksonia antarctica. I, pinnule preparing for the inception of a sorus, in transverse section; R,
marginal ccll. II, the same in an older stage. S%, primordium of spon ance III, sorus almost ripe, in
transverse section; P, placenta. In all figures: /o, primordium of the upper indusial flap ; _/#, primordium of the
under indusial flap.
Jo an outgrowth of the upper surface of the leaf. The first sporangia proceed from
the marginal cells of the broadened leaf-margin itself, and there they follow one
another in irregular serial succession.
Essentially the same processes are observed in Davallia and in other cases.
If now we imagine this process to be shortened so that the upper indusial flap from
the very first occupies the margin of the leaf instead of subsequently attaining this
position in course of elongation, then in other words we have it that the sporangia
appear upon the under side of the leaf®. They arise here often quite close to the
leaf-margin, for example in Allosurus, Fig. 332, where the youngest sporangia—
the outermost ones *—are only separated by one cell from the leaf-margin. Whether
1 How this takes place requires investigation, as does the movement of the indusium-lobes in
many species of Hymenophyllum, but there can be little doubt that drying is the cause of the
movement.
* We may constitute the following series :—
(1) Single marginal sporangia in the Schizaeaceae and Ophioglossaceae.
(2) In addition to these there are some which are further up on the upper side of the leaf,
and upon the under side of the leaf.
(3) The formation of the marginal sporangia is suppressed, the margin grows vegetatively,
and the sporangia on the upper side are usually suppressed in the Polypodiaceae and others.
$ New ones also arise towards the inside.
496 THE SPOROPAYVELS OF (PRELRIDGE Rae
this displacement corresponds with a phyletic process is at present beyond our
knowledge.
(2) ARRANGEMENT OF THE SPORANGIA.
The sporangia stand upon the sporophylls either singly or in groups. If
they arise upon a placenta into which a continuation of a vein enters, either
directly or through a tracheid-group, we get the sorws. There is, however, no
sharp limitation of the sorus in many cases, and Bower? has recently grouped
succinctly the distribution of sporangia as follows :—
(1) Szmplices: Sporangia solitary, or if in groups developed synchro-
nously: in’ Marsiliaceae, Osmundaceae, Schizaeaceae, Gleicheniaceae,
Matoniaceae.
Fic. 333. I. Hymenolepis spicata.
3
II. Elaphoglossum (Acrostichum) spa-
Fic. 332. Allosorus crispus. Apex of the pinnule of a sporo- thulatum. Still folded sporophyll in
phyll seen from the under side. Highly magnified. transverse section, underside upwards.
When unfolded and mature the sporo-
phyll is flat.
(2) Gradatae: Sporangia arising in basipetal succession upon a more
or less elongated placenta: in Loxsomaceae, Hymenophyllaceae, Cyathe-
aceae, Dicksonieae, Dennstedtineae.
(3) Mixtae: Sporangia of different ages mixed together: in all the
rest of the leptosporangiate ferns.
(c) THE PROTECTIVE ARRANGEMENTS FOR THE SPORANGIA.
BY THE WHOLE CONFIGURATION OF THE SPOROPHYLL. In many
ferns the sporangia are protected by the ptyxis of the sporophyll, for ex-
ample in Ophioglossaceae*, or the margin of the sporophyll bends over the
sporangium, just as the margin of the carpel of Angiospermae bends over the
ovule. The resemblance is conspicuous in many Acrostichaceae. The
sporophylls of Elaphoglossum (Fig. 333, II) have in their young condition a
1 Bower, Studies in the Morphology of Spore-producing Members: IV. The Leptosporangiate
Ferns, in Phil. Trans., 1899, should be consulted regarding this point. I cannot go here into
characters taken from the structure of the sporangia.
2 See p. 481.
PROTECTION OF SPORANGIA OF FILICINEAE 497
pod-like appearance. They have their margins bent downwards'. Hymeno-
lepis spicata shows the same features only that a larger part of the leaf-surface
is free from sporangia (Fig. 333, I). It is clear that such an arrangement
will have relation to the age of the sporangia at the time when the sporo-
phyll unfolds. If the sporangia at the time of unfolding of the sporophyll
are already mature or provided with thick walls, they will require less pro-
tection than would young sporangia standing upon an unfolded leaf. Per-
haps this is the reason why in the Gradatae and Mixtae protective arrange-
ments are developed in profusion.
By HAIRS UPON THE SPORANGIA. These occur in. Gymnogramme
villosa, G. Totta, Polypodium
crenatum,and others”. These
hairs may also occur between
sporangia. Peltate hairs form
a specially effective protec-
tion.
By INDusIA. These are
outgrowths of the margin of
the leaf, of the under side
of the leaf, of the placenta’.
The importance of the indu-
sium was established long
ago experimentally by Koel-
reuter* who found in different
ferns that the sporangia dried Fic. 334. Polypodium obliquatum. Sorus in somewhat diagram-
= é ; matic longitudinal section: Sf, sporangia; Z, elevation on the
up if the indusium was re- sporophyll; G, vascular supply. Magnified.
moved from young sori. In
young sori of Scolopendrium vulgare he found an exudation of drops
which according to his view proceeded from the indusium, a proof therefore
that the indusia in the juvenile conditions are very rich in water. The
indusia dry later and so allow of the distribution of the spores?.
By SINKING OF THE SORI IN PITS. This may be combined with
the formation of an indusium, for instance in Scolopendrium. Polypodium
obliquatum offers a simpler condition (Fig. 334). The sori are placed in
depressions of the leaf-tissue which are surrounded by an annular growth
(Fig. 334, Z). The sporangia according to their age reach the mouth of
1 The sporangia here arise upon the whole surface excepting upon the margins and the midrib.
? See Gliick, Die Sporophyllmetamorphose, in Flora, xxx (1895).
3 See Burck, Over de ontwikkelings geschiedenis en den aard van het Indusium der Varens,
Academisch Proefschrift, Haarlem, 1874; Gliick, op. cit.
* See Koelreuter, Das entdeckte Geheimniss der Kryptogamie, Karlsruhe, 1777.
5 When speaking of the sporangia the specially peculiar formation of indusia in Lygodium will
be described (see p. 592). Further investigation is required before we can say whether in many ferns
the indusium when ripe experiences any other movements than those due to shrinking.
GOEBEL II Kk
498 THE SPOROPHYLLS OF PTERIDOPHYTA
the pit by an elongation of their stalk, and then they discharge their spores.
The young sporangia are protected by the old ones. In other ferns, for
example Polypodium jubaeforme, P. saccatum, there are hairs between the
sporangia which originally close the mouth of the pit. The sinking of the
sporangia in the Marsiliaceae is not essentially different from this, only that
there the mouth of the sorus-pit is closed subsequently.
4. CONDITIONS FOR THE APPEARANCE OF THE SPOROPHYLL.
The sporophyll does not appear in germination but only after a definite
age has been reached by the plant—earlier naturally in annual ferns like
Anogramme leptophylla, than in perennial forms which develop slower.
There can be no doubt that the formation of the sporangium and the
sporophyll are dependent upon definite external factors—intensity of light,
relationships of nutrition—and upon inner relationships (correlation). That
correlation exists here has been experimentally shown where we get a
transformation of the primordia of sporophylls into foliage-leaves’, and it is
quite evident that the plants only proceed to the formation of sporangia
when they have accumulated a sufficient amount of plastic material. Besides
these conditions, which we may designate shortly as the reaching of a certain
stage of ‘ripeness, some special stimuli appear to be concerned in
isolated cases.
The dependence of the formation of sporophylls upon external factors
has not been much examined. Raciborski? has proved a remarkable case
in a fern allied to Acrostichum Blumeanum. This fern formed as it grew
upon the ground very luxuriant leaves but no sporophylls, but the latter
appeared when the plant was given the possibility of climbing upon a vertical
support. What changes in the life-condition ‘set free’ the formation of
sporophylls here is not known. I may, however, conjecture that a pre-eminent
factor was the restriction in growth of the rhizome after a preceding period
of good nourishment. The case would be analogous to that of Marsilia
quadrifolia. If this plant grows in water it forms long, very luxuriant
shoots but produces no sporophylls, whilst the sporophylls appear in quantity
if it grows upon land*. If the plant be cultivated upon persistently dry
soil then usually sporophylls do not appear*. The plant is then evidently
enfeebled and under-nourished. In the fructifying shoots we may, how-
ever, observe that the internodes of the shoot-axis are shorter and more
contracted than in the luxuriant water-shoots, and it might be possible
* See p. 474.
? Ratiborski, Morphogenetische Versuche: I. Beeinflussung der Sporophyllbildung bei dem
Acrostichum Blumeano affine, in Flora, Ixxxvii (1900), p. 25.
* The relationships of adaptation to moist and dry soils also are operative here.
* See A. Braun, Nachtragliche Mittheilungen iiber die Gattungen Marsilia und Pilularia, in
Monatsberichte der Berliner Akademie aus dem Jahre 1872, p. 650.
SPOROPHYLLS OF EQUISETUM 499
experimentally to compel the formation of sporophylls here also by
restricting the growth. We must therefore in every species consider with
care the life-conditions to which it is adapted as these are of importance
for the appearance of the sporophylls.
Il. EQUISETACEAE.
The sporophylls of Equisetum are stalked disks which bear the sporangia
distributed around the under side of their peltate surface. The divergence in
form from the sterile leaf is great: the sterile leaves are concrescent in a
sheath and form the single teeth of it; the sporophylls are free and peltate.
The greatness of the differences between the two constructions shows that
they appear early. The questions that we have to ask here are
(a) What is the biological significance of the conformation of the
sporophyll ?
(5) What connexion is there between the sporophylls and the sterile
leaves?
(2) The sporophylls form a close-set spike-like flower. They lie with
their disk-like margins at first close against one another and to a certain
extent interlocked, and in this way the young sporangia upon the under
side of the disks are completely protected, so that there is no need for an
indusium or any other protective apparatus. The internodes between the
whorls of sporophylls are primarily very short ; they elongate later as do
the stalks of the sporophylls, and then the sporangia when they are ripe
open by drying and scatter the spores’. We find quite the same configura-
tion of sporophy]l in the male flowers of many Coniferae, for example Taxus.
In Equisetum then the conformation of the sporophyll—the peltate form,
and the possession of a stalk—is connected with the protection of the
sporangia and with the dissemination of the spores.
(2) The vegetative leaves act as a protective apparatus to the stem and
its still-growing internodes. It is probable that they are reduced, although
it is difficult to speak with certainty in the absence of allied living forms.
The primordia of the leaves arise as papillae projecting upon the vegetative
point. The upper portion of the papilla is, however, in the vegetative leaves
only applied to the formation of the leaf?, whilst the lower portion of the
primordium serves as an envelope to the internode of the shoot. But
the cells of the primordium of the sporophyll are all drawn into the
1 This is facilitated in some species by the bending upwards of the stalk of the sporophyll which
is evidently negatively geotropic. This is the case in Equisetum Telmateia ; see Goebel, Outlines
of Classification and Special Morphology of Plants, English Edition, Oxford, 1887, Fig. 221.
The surface of the sporophyll is placed obliquely or almost horizontally, and this prevents the spore-
masses from coming to lie in quantity between the sporophylls. There is certainly no chance of
this happening in this species which possesses the largest sporophylls.
2 Connected with the slight development of the leaf.
Kk2
500 THE “SPOROPAYLES: OF \PTERIDOPAY 1A
formation of the sporophyll, and we have a correspondingly more massive
development of the sporophyll’. The difference of the development,
apart from the relationship of volume, consists fundamentally in this,
that at a very early period, even before the appearance of the stalk of
the sporophyll, which arises by intercalary growth, that distribution of
growth sets in which leads to ahypopeltate form of leaf?, and by which
a reduction of the leaf-surface constituting the wpper part of the leaf takes
place, at the same time the marginal growth which elsewhere results in the
formation of a thin leaf-lamina is suppressed. The occasional occurrence
of intermediate forms between sporophylls and vegetative leaves is quite in
accordance with the development*. In these intermediate states a lamina
is often more developed and it corresponds then always to the upper part
of the sporophyll; the lower part of the sporophyll is, in relation to the
sterile leaf, a new formation such as is found in the stamens of many
Cupressineae, or in the kataphylls of Asparagus comorensis (Fig. 215). The
fact that the first developed stages of vegetative leaf and sporophyll conform
to one another, and that the primordium of the vegetative leaf only
partially grows out, whilst that of the sporophyll grows out entirely, is to
my thinking not an argument in favour of the view that the configuration of
the sporophylls in the Equisetaceae is phyletically the original one*; it
rather shows that here as always the development is in harmony with the
condition arrived at in the adult. A thin organ demands less cell-material
than a thick organ. At most one could find in the development of the
primordia of the vegetative leaves a reason for saying that they were at one
time more massively developed than they are now. But we see that even
now we can derive without difficulty the sporophyll from the foliage-leaves.
Assimilation-organs of the conformation of the sporophylls of Equisetum
would be very wonderful constructions.
PROTECTION AT BASE AND APEX OF FLOWER. At the base of the
flower of Equisetum there is one whorl® of leaves which differ both from the
vegetative leaves and from the sporophylls. This whorl is called the aznzlus,
and it is occasionally drawn into the formation of sporophylls. The question
whether any functional significance attaches to this structure appears so far
as I know to have been overlooked. Yet that it does possess such a signifi-
cance in the bud-condition of the flower is indubitable. The sporangia are
so crowded together that they are concealed under the peltate expansions
of the sporophylls. The lower sporangia of the lowermost whorl of sporo-
phylls would be exposed but that the annulus protects them, and is so
1 Goebel, Beitrige zur vergleichenden Entwicklungsgeschichte der Sporangien, in Botanische
Zeitung, xxxviii (1880), p. 549. Gliick, Die Sporophyllmetamorphose, in Flora, Ixxx (1895), confirmed
this later.
? See p. 334. 3 See Gliick, op. cit.
* Whether there are othev grounds for this may be left untouched here.
° In Equisetum arvense there are sometimes two.
PROTECTION OF SPORANGIA OF EQUISETUM 501
constructed that it fits accurately into the projections of the sporophylls,
like a bit of moulding wax, and closes the base of the flower. We may
compare it in respect of this function with the calyx of the Spermophyta.
In this function the arrest which this leaf-whorl has experienced may find a
teleological, but not a causalexplanation. At the top of the flower an analo-
gous protective device is provided inasmuch as the sporophylls which stand at
the tip are incompletely developed, and remain concrescent partially with
the flower-axis'.. Their configuration is, however, somewhat different from
that of the annulus, and gives no support to the conjecture that the annulus
is the result of the sterilization of sporophylls. The annulus is clearly an
arrested formation of the vegetative leaves.
The flowers of the Equiseta are shoots of limited growth. This finds
expression in the arrangement of the cells: the apical cell of the vegeta-
tive shoot is replaced by a cell-group. The formation of the flower is then
not merely a consequence of a change in the configuration in the leaves but
also involves a change in the axis of the shoot. In support of this we have
also the fact that the leaf-sheaths enveloping the flower-buds are larger than
those in the vegetative shoots, evidently in correspondence with the larger
circumference of the flower-bud.
The production of the sporophylls in many species of Equisetum
effects a change in the external configuration of the whole shoot whose end
becomes the flower. In other species we do not find this. A. Braun has
in consequence of this difference divided the species of Equisetum into two
series :-—
(2) EQUISETA HOMOPHYADICA, in which the sterile and fertile shoots
are alike, as in Equisetum palustre, E. limosum, E. hyemale.
(6) EQUISETA HETEROPHYADICA, in which the sterile and fertile
shoots are different, and the fertile shoots are distinguished by having no
branches ; they cannot assimilate because they have no chlorophyll, and their
chromatophores contain a reddish colouring substance instead of chloro-
phyll. It may well be that in this way the fertile shoot obtains a greater
amount of heat. The heterophyadic forms in turn fall into two series :—
(z) Equiseta heterophyadica ametabola, as in Equisetum arvense
and E. Telemateia, where the fertile shoots remain in this stage of develop-
ment, and after the shedding of the spores die away.
(2) Equiseta heterophyadica metabola, as in Equisetum pratense
and E. sylvaticum, where the fertile shoot subsequently forms whorls of
branches and becomes green—the process taking place in different ways*.
In Equisetum sylvaticum the tissue of the internode of the fertile shoots
1 In Equisetum arvense the uppermost incompletely developed sporophylls are not infrequently
concrescent into one, apparently terminal, peltate sporophyll.
2 See Goebel, Uber die Fruchtsprosse der Equiseten, in Berichte der deutschen botanischen
Gesellschaft, iv (1886), p. 184.
502 THE SPOROPHYLES OF PIERIDOPHYVIA
remains at first embryonal, and is protected by the specially long leaf-sheaths.
Subsequently this develops like that of the sterile shoot. In Equisetum
pratense the persistence of embryonal tissue and the subsequent develop-
ment only affects the /ower portion of the internode; the upper portion has
passed into permanent tissue, and does not change.
The fertile shoots appear then, when they are compared with the
sterile shoots, as formations arrested’ at a simpler stage of their configuration
and of their anatomical structure. In the Equiseta heterophyadica ametabola
this arrest is permanent ; in the others it is temporary. Experiment shows
us that the fertile shoots of the ametabolous species may be induced to pro-
ceed to at least a partial vegetative development?. If they are submerged
some of them die away but a large number of them send out lateral shoots
from the lowest up to the sixth internode, and the internodes themselves
become green*. These shoots also appear to us as arrested formations,
and it is probable that the arrest stands in connexion with both external
and internal conditions.
With regard to the external conditions we may recall that the ametabo-
lous Equiseta are those which develop their fertile shoots in the early spring.
The soil, especially that of the moist stations in which the Equiseta are
found, is at this time still cold, and their intake of water is correspondingly
hindered. The degree of temperature suffices for the elongation of the fertile
shoots which were already almost completely formed in the autumn. The
vegetative development only begins later, and the vegetative shoots probably
withdraw from the fertile shoots material—water and other substances—
which these might use for vegetative development. The homophyadic
Equiseta develop their fertile shoots later at a time when the conditions for
the intake of water are more favourable. The metabolous Equiseta stand
intermediate to the other groups—that is to say they grow, so far as my
experience goes, upon soil that is less cold and wet.
Whilst the fertile shoots of the Equiseta as of the Filicineae appear to
be the result of transformation of the sterile ones, experience also allows us
to conclude that the differences in the behaviour of the fertile shoots can be
brought into connexion with the relationships of life*. Further experi-
" Compare the temporary and persistent arrest in the cotyledons. See p- 403.
* See Goebel, Uber die Fruchtsprosse der Equiseten, in Berichte der deutschen botanischen
Gesellschaft, iv (1886), p. 187.
* This phenomenon is seen also in nature in meadows which are under water in the early spring.
See further descriptions of the different forms of construction of the fertile shoots of Equisetum
given by Luerssen, Die Farnpflanzen oder Gefassbiindelkryptogamen Deutschlands, Osterreichs und
der Schweiz, in Rabenhorst’s Kryptogamen-Flora, Leipzig, iii (1889).
* We must not, however, forget that in the ametabolous Equiseta the influence of the conditions
of life has evidently worked a change upon the whole organization. If the conditions for the uptake
of water from the soil are favourable a vegetative development does not require to take place in them,
because they are no longer adapted to the uptake of water and nourishment like the sterile shoots.
In the upper portion of the fertile shoot a vegetative further development can no longer take place.
SPOROPHYLLS OF LYCOPODIUM 503
mental investigation must, however, prove still more definitely these con-
nexions,
The remarkable fossil formations of the Equisetineae must be left
undescribed here as in other groups. The result of phytopalaeontological
investigation in recent years has been of the utmost importance. But it is
evident that in the nature of the case the morphological interpretation of the
flower-formation of the extinct forms is often very uncertain, and on the
other hand the discovery of relationships between configuration and inner and
outer conditions at the time when the plant
lived is impossible 1.
III. LYCOPODINEAE.
Whilst in the Equiseta the sporophylls
and foliage-leaves are always different, apart
of course from teratological phenomena, we
find in the Lycopodineae as in the Filicineae
cases in which the foliage-leaves and the
sporophylls are alike, for example in Lyco-
podium Selago’, and cases in which they ‘
are different, as in Lycopodium annotinum. eee cece The sere. stand
: < in a tetramerous whorl. Two sporangia are
The case of Lycopodium annotinum may apparently attached to each sporophyll, but
be described :— Se oe ey
base of the sporophyll of the next succeeding
LYCOPODIUM ANNOTINUM. Bans qt sets lesa razor blade. After Ginck
sporophylls of this species are no longer
assimilation-organs, and they have a yellowish, not a green, colour. The
leaf-base is widened, and this fits the leaf better to embrace the large
sporangium seated upon its base. The margin of the leaf is spread out ina
wing-like manner. When the spores are ripe the membranous margins of
the sporophyll, like its upper portion, bend backwards and thus facilitate the
distribution of the spores*. A leaf-cushion* (Fig. 335, B) which has the
form on transverse section of the blade of a razor also runs downwards
from each sporophyll and fills up the spaces between the sporangia. The
sporangia are carefully protected as is shown in Fig. 335, and it is easy to
understand teleologically the deviation from the foliage-leaves in the con-
figuration of the sporophyll °.
' The reader is referred for the description of fossil forms to the palaeophytological text-books,
of which may be mentioned the following: H. Potonié, Lehrbuch der Pflanzenpaliontologie,
Berlin, 1899; Zeiller, Eléments de paléo-botanique, Paris, 1900; Scott, Studies in Fossil Botany,
London, 1900. Scott’s book givesa particularly clear and concise account to the beginner.
2 See also in the species of Isoetes, about which no further mention will be made here.
* There can be no doubt that this movement of the sporophyll is a consequence of its drying.
On the edges of the forests the movement always begins upon the side of the flower directed outwards.
* In many Lycopodia, for example Lycopodium cernuum, the sporophyll is hypopeltate as it is
in Selaginella Preissiana. See p. 506.
5 With regard to the formation of mucilage in Lycopodium inundatum see the figures given by
Gliick, Die Sporophyllmetamorphose, in Flora, Ixxx (1895).
504 THE’ SPOROPHYLLS OF PTERIDOPHYTA
The sporangia are laid down in the Lycopodineae as in the Equiseta when
the sporophylls are still relatively small (see Fig. 312). I do not, however,
see in this a point of phyletic importance, but only that the formation of the
leaves in both of these cycles of affinity is reduced in comparison with
that of the Filicineae. Very small-leaved ferns would show quite the same
phenomena in their sporophylls as do the Equiseta and Lycopodineae.
PSILOTACEAE. The Psilotaceae, Psilotum and Tmesipteris, demand
special mention because the sporophylls in them deviate further from the
sterile leaves than do those of other Lycopodineae. The sporophyll is bifid,
but the whole structure was formerly considered—and I shared the view—
as a small branch bearing two leaves and a plurilocular sporangium. This
interpretation has, however, been shown to be impossible by the investigations
FIG. 336. Tmesipteris truncata. I, simple sporophyll with one sporangium. II, portion of a shoot bearing
a sterile and a fertile leaf. In the sterile leaf the profile-position of the lamina is evident. Both magnified.
of Solms-Laubach! and Bower”. In support of the modern and accepted
view that we have here a bifid sporophyll I may mention that I have often
observed on simple undivided foliage-leaves in Tmesipteris one sporangium
(Fig. 336, I), which in the cases I investigated was simple, although the spor-
angium is usually divided into two or more, rarely three, chambers, and there
was no trace visible of a second somewhat reduced lobe of a sporophyll.
Transverse sections show that a simple conducting bundle runs into the lower
simple portion of the sporophyll, whence a branch proceeds towards the
sporangium, and one finds tracheids proceeding even into the wall of the
sporangium.
In Fig. 337 the end of a shoot of Psilotum complanatum (P. flaccidum)
is shown. ‘The shoot is flattened and provided with small distichous leaves.
A conducting bundle does not enter the leaves, but a vascular bundle branches
* H. Graf zu Solms-Laubach, Der Aufbau des Stockes von Psilotum triquetrum und dessen
Entwicklung aus der Brutknospe, in Annales du Jardin botanique de Buitenzorg, iv (1884), p. 139.
* Bower, Studies in the Morphology of Spore-producing Members: Equisetineae and Lyco-
podineae, in Phil. Trans., 1894.
SPOROPHYLLS OF PSILOTACEAE 505
off towards the sporangium from the strand of the shoot-axis, and we have
here a case which shows us that the distribution of the vascular bundles can-
not always be trusted for a decision as to the mor- x
phological value of an organ :—the sporangium is leaf- fit Ts
borne, but is nevertheless supplied with a vascular strand / & j
from the shoot-axis ; moreover the sporangia frequently bt ME |
are arrested, and then one finds apparently sterile bifid | ; |
leaves, into which a strand of vascular bundles runs?. i By
That the forking of the sporophylls in the Psilo- 2 @ \ j/
taceae is a ‘morphological’ character is supported by pe
the fact that the plants in which it is found diverge so | ins
much in habit as do Tmesipteris and Psilotum. But | ?
we must not forget that the forking is at the same time :
‘useful. It is evident that in Psilotum the young
sporangium is invested and protected right and left
by the two tips of the leaf (Fig. 337), whilst the
undivided base of the leaf gives a protection to the
outside. This feature is less marked in Tmesipteris ?.
The fork in the sporophyll in which the old sporangium
sits in Psilotum serves besides as a mechanical support. — yg, 437. Psilotum com.
Regarding the comparison which is frequently made of sean Bia aah perio
the sporangial group of the Psilotaceae with a sporo- ‘“POroPnylls: Magnified.
phyll of the Ophioglossaceae,
something will be said when
the subject of sporangia is
dealt with *.
The flowers of Selaginella
are of special importance for
comparison with the flowers of
the Spermophyta :—
ISOPHYLLOUS SELAGI-
NELLEAE. We shall first of
all deal with the isophyllous
Selaginelleae and take as an
illustration
Selaginella Preissiana. Se-
laginella Preissiana, which I
collected in West Australia, is Magee Selaginella Preissiana. Lower portion of a flower.
—_—
? It is upon these cases that Solms has based the statement that the leaves have a well-developed
conducting bundle. As a matter of fact the leaves I investigated showed no trace of a bundle.
? One may imagine that its leaves have arisen from those of Psilotum by the strong outgrowth of
a basal part whilst the small apex keeps pace with it, this apex corresponding to the leaf of
Psilotum. 5 See p. 605.
506 THE SPOROPHYLILS OF (PYERIDOPAVTA
very instructive. The leaves are in decussate pairs. Fig. 338 shows
the base of the spike of sporangia. The lowermost leaf, which bears
a microsporangium, is constructed like a sterile one. Those which follow
it have grown out downwards beyond their point of insertion. These out-
growths are clearly protections not to the sporangium which is axillant to
their sporophyll, but to the sporangium which lies immediately below each
sporophyll. Analogous arrangements we have seen appearing in the vege-
tative region, as was stated when we considered the sporophylls of Equisetum,
and exactly the same arrangements are met with in the stamens of many
Coniferae and Angiospermae. At the same time the formative stimulus given
by the appearance of the sporangia, and which leads to an external configura-
tion of the sporophyll different from the vegetative leaf-form, evidently
affects not the single sporophyll—for otherwise the lowermost sporophyll
must also have the conformation of the others—but the vegetative point
itself of the sporangial spike, and this then acts upon the primordia of the
sporophylls !.
ANISOPHYLLOUS SELAGINELLEAE. We must distinguish two groups
of the anisophyllous Selaginelleae in respect of their formation of flowers—
the Zetragonostachyae and the Platystachyae.
Tetragonostachyae. These are distinguished by the anisophylly of the
vegetative shoot stopping short of the flower. The sporophylls are all of
nearly equal size in contrast with the condition that is found in the vegeta-
tive leaves, and the leaf-pairs do not cross obliquely as in the vegetative shoot
but nearly at a right angle®. When we remember that the vegetative shoots
of the anisophyllous Selaginelleae owe the configuration of their leaves evi-
dently to an adaptation to definite external factors *, we may assume that
the configuration and position of the sporophylls exhibit a retention of a
phyletically primitive stage*. Why this should be is at any rate biologi-
cally or teleologically easily understandable, for in the flowers where all the
leaves have the same function, which is essentially that of protecting the
sporangium, it is natural that their configuration should be also the same.
Moreover the flowers are frequently although not always orthotropous in
contrast with the plagiotropous vegetative shoots.
1 In other words the transformation of the vegetative shoot into flower proceeds gradually, and
expresses itself only plainly if the formative stimulus, of which we know nothing, has reached
a definite intensity. That the lowermost sporangia in the flowers of many Selaginelleae and
Lycopodia do not reach complete development, as will be more particularly shown hereafter (see
P- 510), is probably connected with this.
* I examined the case of Selaginella erythropus.
= See Part I, p. 105;
* We must, however, point out that several isophyllous Selaginelleae, like Selaginella Preissiana,
have also decussate leaf-pairs on the vegetative shoots, and that in the isophyllous Selaginella
rupestris the flowers have likewise decussating sporophylls, although the foliage-leaves have a
spiral position.
SPOROPHYLLS OF SELAGINELLA 507
Platystachyae. There are also dorsiventral flowers in Selaginella ! and
these have a special interest in view of the presence of dorsiventral flowers
amongst the higher plants. We find indeed two kinds of these :—
(2) The one continues the anisophylly of the vegetative shoots, that is
to say the sporophylls upon the upper-surface of the flower are smaller than
those upon the under-surface or flanks. This is, however, a rare condition,
and it is only known in two species of very limited distribution, namely,
Selaginella pallidissima and S. ciliaris, Spr.
FIG. 339. Selaginella chrysocaulos. I, flower seen from above. _ II, flower seen from below: S, S, vegetative
lateral leaves corresponding to the small sporophylls; O, upper leaf Soe pOnGne to the larger sporophylls;
sp, sporangium, III, larger sporophyll. I and II slightly magnified. III highly magnified.
(4) The other which I have termed the zxverse-dorsiventral flower is
the more frequent *. In it the dorsiventrality is the reverse of that in the
vegetative shoots. The sporophylls on the two surfaces of the flower are of
unequal size, but the larger stand upon the upper-surface, and they form the
continuation of the smaller leaves of the vegetative shoot. Selaginella
chrysocaulos (Fig. 339) furnishes an example ofthis. The larger sporophylls
which stand upon the upper-surface of the axis form a protecting cover to
the whole flower, and this—as well as the increased capacity of assimilation
established by these leaves—is, to speak teleologically, the reason why the
1 See Goebel, Archegoniatenstudien: IX. Sporangien, Sporenverbreitung und Bliithenbildung
bei Selaginella, in Flora, lxxxviii (1901), p. 207. The older literature will be found here.
? The earlier expression for these flowers, »esupimate, involves an erroneous statement, for here
there is no torsion of the flower-axis.
508 THE SPOROPHYLLS OF PTERIDOPHYTA
sporophylls of the upper-surface are different from the foliage-leaves of the
upper-surface. The sporophyll has also a wing-like appendage recalling the
leaftof Fissidens (Fig. 339, III; Fig. 340, /); indeed the development of the leaf
shows that it follows the same course as that of Fissidens, and the wing is an
outgrowth of its back, and is the structure which specially forms with the
under-surface a protecting cover for the sporangia’. The inverse-dorsiventral
flowers appear so much more utilitarian than do those which are not inverted
that we need not be surprised at the rarity of the latter, and they furnish at the
same time a remarkable proof of the fact that in the formation of flower
a complete change of the whole shoot takes place. Ifan inverse-dorsiventral
flower should growout vegetatively * the outgrowth assumes the dorsiventrality
of the orzgznal vegeta-
hea tive shoot, so that the
‘inversion’ of the dor-
siventrality was only
caused by the forma-
tion of flower. No
such inversion has yet
been experimentally
producedinthesterzle
FiG. 340. Selaginella suberosa. Flower in transverse section near the shoots of Selaginella,
vegetative point: /, wing. Z é
yet it might be pos-
sible if we were in the position to ‘disattune’ the shoot in the same way
as this is effected by inner processes in the formation of the inverse-dorsi-
ventral flower.
DISTRIBUTION OF SPORANGIA IN SELAGINELLEAE. In regard to the
distribution of the two forms of sporangia in the flowers of Selaginella it is
clear that everywhere originally there is hermaphroditism. The number
of the megasporangia varies in the different species. In some only one or
a few are found at the base of the flowers; in others they are mixed with the
microsporangia, as in Selaginella rupestris and S. chrysocaulos. Only in
a few species, so far as we know at present, are there occasionally—not
exclusively—entirely male flowers, in for example Selaginella Martensii,
or female flowers, as for example in Selaginella pectinata.
Fertilization of the megaspores by the microspores of the same flower,
even in the hermaphrodite flowers of the Selaginelleae, only seldom occurs
because :—
1. The megasporangia precede in their development the microsporangia,
1 With regard to the anatomical differences of the upper and under-surface of the flower see Goebel,
Archegoniatenstudien: IX. Sporangien, Sporenverbreitung und Bliithenbildung bei Selaginella, in
Flora, lxxxviii (1901).
? J have observed this in Selaginella Belangeri growing wild in Java, and in Selaginella suberosa
in which it was artificially produced.
SPOROPHYLLS OF LYCOPODINEAE 509
and the megaspores are mostly thrown out before the microsporangia have
opened.
2. The megaspores are thrown out further than the microspores as I
have noticed.
3. A simultaneous sowing of microspores and megaspores, in the few
cases that have been investigated for this point, has resulted in the formation
of no embryo, because the microspores discharged their spermatozoids before
the archegonia of the megaprothalli were ripe.
In all these points the flowers of Selaginella remind us of those of much
higher plants which have to be considered as only morphologically, not
physiologically, hermaphrodite.
If we endeavour to arrange the flowers of Selaginella in series the
radial ones appear to be the most primitive, and they also still appear in
" many species where the vegetative shoots have become by adaptation dorsi-
ventral. In a number of species the dorsiventral construction has also
extended to the flowers, but the attempt to continue here the usual vegetative
dorsiventrality is of little utility and has soon been given up, being retained
only in two species. In the large majority inverse-dorsiventral flowers have
been developed.
RELATIONSHIPS OF FLOWER TO VEGETATIVE SHOOT IN LYCOPO-
DINEAE. If, finally, we consider the flowers of the Lycopodineae in their
relationship to the vegetative shoot-system we find frequently that when
the flowers are shoots of limited growth the sporophylls diverge markedly
from the foliage-leaves, but when there is no limited spike of sporangia then
the sporophylls are like the foliage-leaves, for example in Lycopodium
Selago and its allies. We cannot, however, establish this as a general rule.
We have only now to mention some general biological relationships :—
_1. Where the vegetative shoots are dorsiventral the flowers, apart from
the Selaginelleae Platystachyae, are radial, as in Lycopodium complanatum
and other similar species. It is probable that here the flowers have retained
the original arrangement and configuration of the leaves whilst the con-
figuration of the vegetative shoot has become changed by subsequent
adaptations’.
2. Orthotropous position is not necessarily associated with the radial
construction of the flowers. Orthotropy appears rather only where the
vegetative shoot grows more prostrate upon the soil, and it is therefore
of advantage for the scattering of the spores that the flowers should be
raised up above the substratum. In these cases, for example in Lycopodium
inundatum, L. clavatum, L. carolinianum, Selaginella denticulata, S. helvetica,
and others, a portion of the shoot-axis under the flower is elongated more or
less, and at the same time is orthotropous and not infrequently beset with
1 See Part I, p. 102.
510 THE SPOROPHYLLS OF PTERIDOPHYTA
reduced leaves. This portion is named the fodiwm and, in correspondence
with what has been said, is everywhere wanting where
(2) The sporangia stand on a sufficiently long radial shoot-axis, as in
Lycopodium Selago and L. annotinum, where it is orthotropous and erect,
and as in Lycopodium Phlegmaria and L. linifolium, where it is orthotropous
and pendent ;
(4) The plagiotropous shoot-axes raise themselves well above the
substratum '.
Here as everywhere in regard to such rules we find examples which do
not conform to what has been said because in them other relationships
bring about a divergent construction, but on the whole, so far as I know,
the relationships I have mentioned are valid.
It has then been shown that the sporophylls of Selaginella still exhibit
frequently in their construction and arrangement relationships which appear
to be primitive in comparison with the foliage-leaves which have been
changed by adaptation. This does not controvert the assumption that the
leaves of the Pteridophyta were originally all sporophylls which at the same
time assimilated’, and that then a division of labour set in by which some
became sterile whilst others remained as sporophylls and now frequently in
their construction differ more or less from the foliage-leaves. In support of
this one may also adduce the fact that where foliage-leaves and sporophylls
are formed alternately, as for example in Lycopodium Selago and other
species, and in Isoetes, we frequently find sporophylls with aborted sporan-
gia at the limits between the two kinds of leaf*. We know, however, that
such an arrest of the sporangia may result from other causes if the formation
of sporangia begins but does not proceed sufficiently vigorously, for example
in Onoclea Struthiopteris whose sporophylls have been already mentioned *.
Its germ-plant produces at first only foliage-leaves, then transitions between
foliage-leaves and sporophylls the sporangia of which are generally in great
part arrested at different stages of development. Later, when the plant
becomes stronger, such an oscillation is normally no longer visible, yet it
may be artificially called forth if the sporophylls are caused to become
virescent. Vegetative organs and reproductive organs stand also otherwise
in a certain opposition, that is to say their formation is dependent upon
different outer and inner conditions, At any rate we will have to trace back
the arrest of the sporangia at the upper end of the flowers of many Lyco-
1 Compare, for example, Selaginella Martensii, with apodial radial but not orthotropous flowers,
with Selaginella denticulata (Fig. 174, A), S. helvetica, and others, in which the flowers have a
podium and are orthotropous.
? With Potonié we may designate them tropho-sporophylis,
° See also Bower, Studies in the Morphology of Spore-producing Members: Equisetineae and
Lycopodineae, in Phil. Trans., 1894. Also at the end of the flower in Selaginella and elsewhere
aborted sporangia occur.
* See p. 475.
SPOROPHYLLS OF CYCADACEAE 511
podineae? to other causes than those that are operative at the base. At
the apex we have to deal chiefly with a general want of tone in the whole
flower-development, not only are the sporangia arrested but also the
development of the sporophyll; at the base we have to deal witha trans-
formation of the vegetative shoot into a flower.
III
THE SPOROPHYLLS OF THE GYMNOSPERMAE
I. CYCADACEAE.
In this family not only are the relationships of configuration of the flower
especially simple, but the configuration of the sporophyll enables us to
recognize very clearly in what relationship it stands to the foliage-leaf and
also how form and function hang together.
As regards the whole configuration of the flowers they have the form
of cones, frequently of giant dimension, except in the case of the female
flowers of Cycas where a sharply limited flower is not formed ?, but the
carpels appear upon the shoot-axis which subsequently again forms foliage-
leaves and kataphylls—the arrangement being comparable with that of
Onoclea Struthiopteris amongst the ferns*. As will be shown presently,
the configuration of the sporophyll has the closest connexion with this
arrangement.
In the flowers which form cones it is noteworthy that the uppermost
and lowermost sporophylls are frequently sterile. They are, however, not
functionless, but close in the flower in the bud-condition both above and
below after the method in the spike of Equisetum. It is a wide-spread
phenomenon that the middle portion of an organ of limited growth is the
best nourished; even in the leaves of many Cycadaceae the lowermost pin-
nules are aborted, the middle ones being the most developed, and there
are all transitions from sterile to fertile sporophylls in the male flowers of
Ceratozamia.
The configuration of the sporophylls will first of all be noticed, and
then some general questions will be dealt with :—
MEGASPOROPHYLLS (CARPELS). We have before us in these an
almost uninterrupted series. At its beginning there stand those which still
resemble most closely in their form the pinnate foliage-leaves; at the other
end stand those which are most widely separated from them. The mega-
sporangia (ovules) are everywhere marginal.
Cycas. Thecarpels of Cycas revoluta are smaller than the foliage-leaves
but they show still at their extremity somewhat long rudiments of pinnules,
and resemble the pinnate leaves otherwise, especially in their flat and
elongated form (Fig. 341). Only in Cycas circinalis are the pinnules indi-
1 And also in the case of Equisetum. 2 See p. 470. S See p. 475.
512 THE SPOROPHYLLS OF GYMNOSPERMAE
cated merely as teeth. Whether each of the ovules, which are here larger
than those which appear elsewhere in pairs, stands in the place of a pinnule
can only be determined by an examination of the history of development
which is still unknown. The wall which surrounds on the outside the
ovule at its base I consider for the reasons specified below to be no
‘rudimentary pinnule, but an outgrowth arising subsequently. In Cycas
Normanbyana the number of the megasporangia has become reduced to two.
Interesting as is the leaf-like construction of the sporophyll of Cycas,
and diverging as the sporophyll does from those of the other Cycadaceae, yet
it offers little in its external form alone to detain us.
Much more important is it to inquire whether we
can discover any relationships by which to explain
its deviation. It appears to me that there are
such, and they are the following :—
1. The sporophylls do not stand as in the
cone-flowers on an axis which, compared with the
vegetative one, is relatively thin, but upon the thick
vegetative axis itself. They form a much more
massive tuft, and by their considerable development
in length are in a position to protect the young
ovules by covering them. It is quite clear then
AI why in the upper part of the sporophyll there are
Pe A eiecnin no ovules—these upper parts form a protecting
Megasporapliyil ot carpe) ters (Covering. amid close in the massive flower-bud above.
2. The seeds attain the most significant size
in the genus Cycas. To protect them in the same manner as the seeds
are protected in other Cycadaceae, where a change in form of the scale-like
sporophylls takes place, would be scarcely possible with the megasporophylls
arranged as they are. In the other Cycadaceae the megasporophylls
experience in the course of their development a special change in form
corresponding to the enlargement of the ovule.
Dioon. The flower of Dioon comes nearest in outer configuration
to that of Cycas. The carpels are still flat, and show the rudiment of
a lamina (Fig. 342, Z), and at their base also a rudimentary pinnule, some-
times two.
Ceratozamia. In the other genera of Cycadaceae the lamina of the
megasporophyll is very much reduced, yet in Ceratozamia there are still
rudiments of two pinnules! in the two ‘horns’ of the sporophyll. These
are originally soft and lie upon the outer surface of the sporophyll in the
young flower. Later they diverge and begin to harden into spiky structures,
which may perhaps be considered as a mechanical protection of the flower.
1 Sometimes more than two.
FEMALE FLOWER OF CYCADACEAE 513
The sporophylls themselves are originally flat (Fig. 343, I), and have scarcely
any indication of a stalk. Subsequently when the megasporangia become
larger changes ensue which bring it about that the sporophylls form
a protecting roof. The first thing that takes place is a stalk appears
(Fig. 343, II), and then there develops upon the upper side and upon the
under side a thickening (Z, Fig. 343, II) which gives the sporophyll
a somewhat peltate conformation. Thus a process which occurs in Equi-
setum and elsewhere before the formation of the
sporangium begins here at a much later moment
in the development. Fig. 343, III, shows us how
the peltate expansion of the sporophyll forms a
mail-covering to the outside, and the ‘horns’
Fic. 342. Dioonedule. Megasporo-
phyll: Z, lamina; RF, RF, reduced Fic. 343. Ceratozamia robusta. I, young megasporophyll, still flat;
pinnules; 4, 4, swelling of the sporo- right and left of its still very short stalk is a megasporangium (ovule).
phyll below the megasporangium rig older megasporophyll which is become shield-like through the out-
whose micropyle is turned downwards __ growth, &, Stich appears both above and below; A, swelling under the
in the figure. Reduced. ovule. III, three sporophylls seen from outside the cone.
which have not hitherto been considered, so far as I know, as rudimentary
pinnules appear displaced upon the outer surface of the shield.
What the relationship of the configuration of the sporophyll is to
pollination is not known. The question when the normal pollination takes
place can only be certainly solved in the home of the plants, and up till now
nothing definite is known about the pollination. The observations of Kraus
seem to indicate that not all the Cycadaceae are wind-pollinated as is
commonly supposed}.
The other genera have megasporophylls which are distinguished
essentially from those of Ceratozamia by the last traces of rudimentary
pinnules having fallen away. Lang? found the megasporangia of Stangeria
* G. Kraus, Physiologisches aus den Tropen, in Annales du Jardin botanique de Buitenzorg,
xiii (1896), p. 273.
? W. H. Lang, Studies in the Development and Morphology of Cycadean Sporangia: II. The
ovule of Stangeria paradoxa, in Annals of Botany, xiv (1900), p. 281.
GOEBEL 11 al
514 THE SPOROPHYLLS OF GYMNOSPERMAE
paradoxa upon the under side of the sporophyll, which is of interest in
so far as here a displacement has evidently taken place in the course of
the development}, a displacement which is no longer directly perceptible
in the microsporangia.
MICROSPOROPHYLLS (STAMENS). These have a more uniform con-
figuration in the Cycadaceae than have the megasporophylls. They are
everywhere broad scales, in Zamia approaching the
peltate form, and in Ceratozamia still showing rudi-
mentary pinnules like the megasporophylls. The
microsporangia stand upon the under side arranged
in many evident sori (Fig. 344).
The difference in the configuration of the
microsporophylls and megasporophylls shows itself
also in the number and position of the sporangia.
It is clear that upon the under side of the micro-
sporophyll many more sporangia will find room
than upon the edges. One might then upon the
ground of the assumption that the megasporophylls
and microsporophylls must have been originally
constructed alike take as a starting-point sporo-
phylls constructed with marginal sporangia. In
the case of megasporangia there has been reduction
usually to two. In the case of the microsporangia
ee ene a there has been an increase in the number, and a
Stamen seen from below. After displacement upon the under side. Whether—and
Richard. Lehrb. s
regarding this I have no first-hand knowledge—the
formation of the stamens of Zamia Skinneri, whose pollen-sacs are almost
entirely pushed to the margins”, may be considered as giving support to
this conjecture is a matter for further examination. It may be pointed out,
however, that these differences repeat themselves in other cycles of affinity.
II. GINKGOACEAE AND CONIFERAE.
MALE FLOWER. Relationships are here very simple and clear. It
has been already pointed out * that the male flowers resemble very closely
the spikes of sporangia of many Pteridophyta. Like them they consist of
sporophylls and flower-axis. The scales which invest the male flowers in
* Similar to that which takes place in Schizaea and other ferns.
* A. Braun, Die Frage nach der Gymnospermie der Cycadeen erlautert durch die Stellung dieser
Familie im Stufengang des Gewachsreichs, in Monatsberichte der Berliner Akademie aus dem Jahre
1875, p. 357. On p. 351 he says that on the stamens frequently only two microsporangia are present,
and they are placed so near the margin of the stamen that they may be said almost to have the same
position, exactly as the megasporangia on the megasporophylls.
* See pp. 470, 472.
MALE FLOWER OF GINKGOACEAE AND CONIFERAE 515
the bud-condition must be considered as bud-scales analogous with those of
the vegetative buds, they are not sterile sporophylls.
The conformation of the stamens stands in the closest connexion with
the protection of the microsporangia in the bud, and as in the case of the
carpels of the Cycadaceae we meet with two chief relationships of configura-
tion of the sporophylls, although they are united by many transitions :-—
(az) Stamens which have more or less developed flat scale-like lamina.
(5) Stamens with a peltate lamina.
Where the stamens are scale-like the upper part of each is in the bud
laid over the sporiferous lower part of the higher-placed sporophylls. The
scale-like stamens of many Cupressineae and other
groups show upon their under side an outgrowth
which I regarded formerly as the analogue of an
indusium, because it serves for the protection of
the microsporangia. Through this outgrowth these
stamens have become hypopeltate. Should this
outgrowth arise in a still earlier stage the leaf
would from the first be peltate, as it is in Taxus
whose microsporophylls closely resemble the sporo-
phylls of Equisetum in general form and likewise
in having the sporangia distributed radially upon
them. The significance of the configuration of the
microsporophylls for the protection of the sporan-
gium is conspicuous also where the sporophyll in yg 345, Ginkgo biloba. Por-
the mature state appears very reduced, as in Ginkgo 9", 012, male flower in longita-
(Fig. 347, 4, 6) and Phyllocladus. Fig. 345 shows involved, Te sporogenous col
that the lamina, Z, of the sporophyll of Ginkgo pag ae ate wie eee
forms also in the bud-condition a closing structure
towards the outside. It possesses many secretion-reservoirs, 7, and there
is abundance of calcium oxalate in the tissue of its upper part. Evidently
it serves as a seat of deposit of the by-products of metabolism which
arise in the formation of the sporangia. That the microsporangia of
Ginkgo require at a later period, as they unfold, less protection may be
connected with the fact that their wall is constructed out of relatively
many cell-layers. We shall see that in the female flower of Ginkgo the
sporophylls are likewise very reduced.
POSITION OF THE MICROSPORANGIA. The position of the microspo-
rangia upon the microsporophylls is not everywhere the same. In Ginkgo,
Phyllocladus, the Abietineae, two sporangia are normally present and we
may call them ‘marginal.’ The number is sometimes greater in Ginkgo, and
the additional ones stand then upon the under side which is the normal
position in the Araucarieae, Cupressineae, and other groups. The radial
distribution in Taxus has been referred to above.
Lia
516 THE SPOROPHYLLS OF GYMNOSPERMAE
VARIATION OF MICROSPOROPHYLLS IN ONE FLOWER. The construc-
tion of the microsporophylls of many Coniferae varies somewhat in one and
the same flower. In illustration we may consider the case of
Juniperus communis. Its stamens are of the very greatest interest on
account of their variations, although hitherto this matter appears to have
been overlooked!. The ‘typical’ form of the stamen is well known: it has
a scale-like lamina, and bears upon its under side three or four pollen-sacs ;
the lamina has the function as it is describedabove. In the upper portion of
the flower we see two phenomena :—
(a) The lamina of the sporophyll is reduced.
(2) The number of pollen-sacs is reduced.
The reduction of the lamina can be easily understood biologically.
In the upper part of the flower-bud the area which has to be protected is
Fic. 346. Juniperus communis. I, summit of a male flower seen from above; sé, the uppermost staminal
whorl of three stamens; s/2, the second staminal whorl, shows on each stamen two pollen-sacs and the indication
of a lamina, 7; s¢3, the third staminal whorl, of which only the tips of the laminae of two stamens are seen; each
of the stamens of this whorl had three pollen-sacs not shown in the figure. II, the same in longitudinal section.
III, the same in transverse section.
much smaller than is that of the wider part below, and the protection is shared
with the lamina by the staminal primordia standing lower down. The cause of
the phenomenon is that the processes which finally lead to the stoppage of the
growth of the whole flower do not set in all at once but gradually—we have
a developmental arrest. Fig. 346, 1, gives a view from above of a flower
very near the time of its unfolding and provided with perfect pollen-sacs.
The sporophylls stand in a trimerous whorl, the stamens of the second whorl
from the top, s¢,, have each only two pollen-sacs which are evidently /ateral
upon the stamen, as we find them in Abies, Pinus, and others. The lamina, /, is
1 Celakovsky, Nachtrag zu meiner Schrift iiber die Gymnospermen, in Engler’s Jahrbiicher, xxiv
(1898), for example, expressly states that all the stamens of the Coniferae still possess above the
pollen-chambers a vegetative end-portion which disappears in the stamens of the Gnetaceae. The
same author, Die Gymnospermen, eine morphologisch-phylogenetische Studie, in Abhandlungen der
koniglich-bohmischen Gesellschaft der Wissenschaften, Folge 7, iv (1890), further declares that
the anthers of the Coniferae ‘do not have their pollen-sacs terminal but sub-lateral, and there is
always a vegetative terminal portion developed above the pollen-sacs, the crésta or shzeld, which
indeed may be much reduced, as it is in Ginkgo, and still more in Torreya, without, however,
the pollen-sacs thereby being made terminal.’ I believe that I show in the text that the pollen-sacs
are often terminal in Juniperus.
MALE FLOWER OF GINKGOACEAE AND CONIFERAE 517
greatly reduced. As the stamens become broader a third and then a fourth
sporangium appear. Thus the hypothetical procedure premised above for the
stamens of the Cycadaceae here actually takes place within one and the same
flower. Further, it is clear that between the configuration of the stamens of
the Cupressineae and those of the Abietineae there is much less difference
than one would be disposed to admit at first. The two sporangia of such a
stamen are sometimes found united with one another, a condition evidently
connected with the reduction of the lamina. Higher up upon the flower-axis
are found instead of the sporophylls single sporangia at the end of the flower
(sz,, Fig. 346, I, II). There can be no doubt that this is a consequence of
a reduction of the sporophyll, as indeed the transition-forms show. But this
reduction is often so fundamental that nothing but the sporangium remains.
The history of development would doubtless show that the sporophyll has not
entirely disappeared. To it evidently belongs the lower stalk-like part of
the sporangium which, did we not know of the transition-forms, might well
be regarded as the stalk of the sporangium. Such astalk is not found upon
microsporangia arising upon the under side ofthe stamens. The proof which
we have here, without any application of hypotheses, that a sporophy]l may
be reduced to one sporangium appears to me of momentous interest, and it
supplies us with a sound ground for the assumption of far-reaching reduction
in the case of the megasporophyll which will be presently mentioned, for in
the case before us it is based upon observation, and not merely upon com-
parison. Those who would have it that the sporophylls have arisen from a
partial sterilization of sporangia will be able to use Juniperus as an example
of the occurrence of the process they assume—if they do not read the writ-
ing from below upwards but inversely. When speaking of the formation of
sporangia I shall deal briefly with this question’. Here I may only point
out that in all such comparisons one is treading upon uncertain ground.
This is shown, for example, by the fact that in Juniperus two of the last
sporangia occasionally unite with one another. _ Fig. 346, III, shows a trans-
verse section through the apex of a male flower which has only two sporangia
of unequal size at itsend. At the base of the larger of the sporangia I found,
however, as the following section in the series showed, a rudimentary, very
short partition-wall indicating that the structure was the result of the con-
crescence of two sporangia. One might then in fancy derive the three
sporangia from the splitting of one single one, and finally the whole flower
from oe sporangium by ‘progressive sterilization, ‘amplification,’ and so
forth! Here, as in other cases, the first thing that has to be sought is not
the phyletic value of the phenomenon depicted, but the determination of the
conditions under which they occur.
1 See p. 606.
518 THE SPOROPHYLLS OF GYMNOSPERMAE
FEMALE FLOWER!. The female flowers are much more variously
constructed than are the male flowers, so much so that the questions what is
carpel? what is flower? what is inflorescence? have been much discussed.
We proceed from the cone-like flower as it is found in many Coniferae, and
name as sporophylls or carpels the leaves which are sessile on the axis of the
cone which has some resemblance in habit with the female flower of the
Cycadaceae. The ovules stand in the axil of these leaves, sometimes as in
the Abietineae upon a special scale—the semzniferous scale.
Fic. 347. Ginkgo biloba. 6, portion of a branch with a short shoot bearing a male flower; a, 5, stamens ;
c, female flower; d@, the same with seed; e¢, stone of the seed; _# seed in transverse section; g, seed in longitudinal
section; /, flower with many ovules. After Richard. Lehrb.
We may first of all point out that the carpels at the period of flowering
are in general the less developed the less they are required for the protection
of the ripening seed. We see this particularly in Ginkgo.
GINKGO. The female flowers of Ginkgo (Fig. 347, c) are small axillary
shoots on which normally two ovules are found (Fig. 347, 2)? The sporo-
phylls are usually not visible here as separate formations, and it is highly
probable that an entire reduction has taken place, as we have seen it in
the male flowers of Juniperus, that is to say the sporophylls are reduced to
single megasporangia. Only if these appear stalked, as in Fig. 347, %, the
' A detailed description of the relationships of the female flower is more within the province of
systematic botany. There are, however, a few facts which must be stated on account of their organo-
graphical bearing. Of the literature see specially Strasburger, Die Coniferen und die Gnetaceen,
Jena, 1872; id., Die Angiospermen und die Gymnospermen, Jena, 1879; Celakovsky, Die
Gymnospermen, eine morphologisch-phylogenetische Studie, in Abhandlungen der koniglich-
bohmischen Gesellschaft der Wissenschaften, Folge 7, iv (1890); id., Nachtrag zu meiner Schrift ber
die Gymnospermen, in Engler’s Jahrbiicher, xxiv (1898). The further literature is cited in these works.
* This figure shows a great number, and thus the ovules appear stalked.
FEMALE FLOWER OF GINKGOACEAE AND CONIFERAE 519
stalk, as in the megasporangia of Juniperus, is the lower portion of a carpel
upon which the megasporangium is terminal. The sporophyll is indeed
also very reduced in the male flower of Ginkgo, but in abnormal cases, as
Fuji has observed, megasporangia can also appear upon the foliage-leaves.
The seeds are specially
large (Fig. 347, d) and
have as in Cycadaceae a
fleshy outer coat and hard
inner one. The hook-like
swelling at one side of the
base of the megasporangium
may be compared with the
outgrowth of the sporophyll
arising in a similar position
in the Cycadaceae.
TAXINEAE. In_ this
family likewise the ovules
ripen without the protection
of carpels, and the seeds like
those of Ginkgo have a hard
inner coat and a succulent
outer coat, and are thus
adapted for distribution by
animals, especially birds.
Cephalotaxus and Tor-
reya. In Cephalotaxus and
Torreya the ovules stand in
pairs in the axils of one leaf,
the sporophyll (Fig. 348, V).
In Cephalotaxus these sporo-
phylls are united into small — Fic. 348. I-III, Dacrydium Seiad Tjiilower willl ant uedlen
cones, and of the ovules usually erence foal e OF ie age handles ar a oe.
only one develops further. inccieceae Sarak ee eae a eer pai ta ae
Between the ovules there is 37 eats, i cepbelptanns Roane roi ot eee
a flat enlargement which has cladus alpinus. Young fruit in longitudinal section; 4”, aril,
been interpreted as the vegetative point of the axillary shoot which bears the ovule },
or as a third sterile carpel.
Phyllocladus. In Phyllocladus (Fig. 348, VI) the ovules are solitary in the
axil of a carpel. They are provided with an aril and are protected, at least in the
cases which have been examined, by the sterile carpel standing above them. Formal
morphology takes the ovule in this genus to be the single carpel of an axillary
carpellary shoot that is no longer perceptible.
1 By this explanation we should have here as in Ginkgo a carpel reduced to an ovule.
520 THE SPOROPHYLLS Of GYMNOSPERMAE
In the illustrations that have been given the ‘ flowers?’ consist of a large number
of carpels which bear one or many ovules in their axils.
Podocarpeae. A reduction in the number of the ovules takes place also in the
Podocarpeae, where we have sometimes flowers in which there are many sporophylls
each bearing one anatropous bitegminous ovule (Fig. 349, IV), sometimes flowers
in which only one sporophyll is fertile, or, it may be, only one sporophyll exists.
In Podocarpus ensifolius? (Fig. 349, I-III) the flowers begin with two sterile
prophylls which are frequently like foliage-leaves, whilst the sporophylls thicken
fleshily at their base (Fig. 349, I). In Fig. 349, I, two sporophylls are fertile,
that is to say, bear ovules. In Fig. 349, III, only one sporophyll is fertile notwith-
standing the number of leaves which are combined together in the cone.
a
ie,
Ar
\e
FiG. 349. Podocarpus ensifolius. I-III, female flower-cone in different stages of construction. IV, apex of
a cone-scale with ovule in longitudinal section; A», aril. V, point of insertion of ovule in transverse section ;
vascular portion of the conducting bundle shaded, sieve-portion dotted.
Dacrydium Colensoi*® (Fig. 348, I-III) has flowers which are no longer
sharply limited. On a branch which may subsequently elongate vegetatively * some
leaves develop bearing one or two sporangia (Fig. 348, I, Il). This is the flower.
We can imagine that such a flower has arisen out of one like that of Podocarpus
ensifolius by the flower-axis forming vegetative leaves above the carpels, and in
connexion therewith showing no limited growth but growing forth further as a
vegetative shoot.
Taxus. In the genus Taxus (Fig. 350) the female flower is composed of a
single ovule which forms the end of a small shoot, and below the ovule there are
a number of small scales. It is a form of flower which differs much more from the
sporangial grouping in the Pteridophyta than do the forms which have been mentioned
above.
1 According to other interpretations really inflorescences.
? I gathered this in West Australia.
? I collected this in New Zealand thinking it was Podocarpus, but Dr. Pilger of Berlin has been
good enough to identify it for me.
* One sees then on the twig a scar indicating the place where the seed sat.
FEMALE FLOWER OF CONIFERAE 521
With regard to the female flowers of the other Coniferae :—
ARAUCARIEAE. We have a simple construction in the Araucarieae.
The ovules are solitary or many upon the upper side of the sporophylls
which stand on an axis and compose with it the female cone. We should
obtain the relationships of position of the female flower of Dammara rightly
enough if we replaced
by ovules the sporangia
of a spike of Lycopo-
dium.
TAXODIEAE. CU-
PRESSINEAE. A com-
plication appears in
other forms where an
outgrowth arises upon
the sporophyll above
the primordium of the
ovule and becomes only
a membranous wing, as
in Cunninghamia; or
a scale-like formation,
as in Cryptomeria japo-
nica, where it ends
above in several leaf-
point-like teeth which
are also indicated in
Sequoia sempervirens
ic. 346; TV)? ;. ora
massive outgrowth not
segmented off from the x
ee Fic. 350. Taxus baccata. 4, twig with female flowers; * two ovules on
sporophyll Or S@mini- thesameshoot. JB, leaf with fertile axillary shoot. C, shoot in longitudinal
fe ee reed crc picncacly a, cuceluns.¢ raepacpore; & integument; on micropyle
. After Strasburger. Lehrb. 4, naturalsize. 2, magnified 2. C, magnified 48.
Cupressineae, where in
most cases it is unmembered but in Cupressus Lawsoniana such teeth are
also seen. The ovule stands here upon a small growth in the axil of the
scale of the cone. The scale itself develops after fertilization in the same
way as does the megasporophyl! of Ceratozamia ®.
ABIETINEAE. The Abietineae show the most peculiar formations.
The ovules are placed upon a body called the seminiferous scale which
covers and reaches beyond the scale of the cone. The cone is composed of
a spindle on which scales, the sporophylls *, are inserted, and in their axils
the seminiferous scales arise. Each seminiferous scale bears two ovules upon
' Where, however, the teeth do not fall over the ovules.
2 See p. 512. % The ‘ bract-scales’ of authors.
522 THE SPOROPHYLLS* OF (GYMNOSPERMAE
its upper-surface. The history of development makes clear the relationships,
and I may describe them briefly as they are known in the silver fir ?:—
Development of the female flower in silver fir. The bud out of which
the female flower proceeds is distinguished at first only slightly from a foliage-bud.
It stands in the axil of a foliage-leaf or needle upon the upper side of a twig, and is,
like the buds which will unfold as new shoots in the following spring, covered with
bud-scales. Its thick vegetative cone which is enclosed by the bud-scales produces
a number of primordia of leaves as does the foliage-bud. These primordia which in
their young condition quite conform to those of the foliage-leaves do not, however,
develop into foliage-leaves but into the sporophylls mentioned above, and they
remain somewhat small. After some time, at the beginning of October, there is
found at the base of each sporophyll a hemispheric swelling. This is the primordium
of the seminiferous scale upon which later the ovules arise. Were the seminiferous
scale in this stage to be arrested it would appear as an ordinary placenta, like the
placental cushions of many ferns, or those upon which the microsporangia of the
Cycadaceae arise. But instead of doing this when the further development begins
in May of the succeeding year this cushion begins to grow into the form of a scale,
becomes much larger than the sporophyll, and quite covers it. At the base of this
seminiferous scale the ovules arise; they are at first erect, and later become inverted
so that their micropyle is directed downwards towards the spindle of the cone.
This peculiar construction has a connexion with pollination ?, which is somewhat
different in the different species because the seminiferous scale at the time of
pollination does not show everywhere the same relationship to the sporophyll.
Everywhere in the cone-flower the scales open out at the time of pollination and
subsequently lie close together upon one another. The separation of the scales is
occasioned by a stretching of the internode of the axis of the flower. The closing
is the result of the strong growth upwards of the seminiferous scale.
Pollination in Pinus Pumilio. As regards pollination, we may describe it
in Pinus Pumilio. The seminiferous scales, as in the other species of Pinus, are much
larger at this time than the sporophylls. They have a bright red colour, and possess
upon their middle a keel-like elevation (Fig. 351, A), and the pollen-grains slide along
the erect seminiferous scale on both sides of this median keel (Fig. 351, a, 4) and so
reach the micropyle of the ovule (Fig. 351, 47) which is drawn out into two long
lobes. This, however, is not the only path for the pollen-grains. The margins of the
sporophyll are bent back so as to produce four channels (Fig. 351, ¢, d, e, £), and
these all lead finally to the micropyle.
In Abies excelsa, Larix, and elsewhere, where the seminiferous scales at the
time of flowering are still smaller than the sporophylls, it is the sporophylls which
form the passage for the pollen-grains, and the seminiferous scales take only a
secondary share in it, inasmuch as they cause the pollen-grain in the last portion of
* See Schacht, Grundriss der Anatomie und Physiologie der Gewichse, Berlin, 1859, pp. 182 ff. ;
also Strasburger, Die Coniferen und die Gnetaceen, Jena, 1872.
* See Vaucher, Histoire physiologique des plantes d’Europe, Paris, 1841, tome iv; Strasburger,
op. cit., p. 268.
FEMALE FLOWER OF CONIFERAE 523
its way to slide downwards to the ovule. After fertilization the seminiferous scale
enlarges considerably and encloses the seed closely. It fulfils now the same function
as does the outgrowth which appears only after fertilization upon the sporophyll of
Cupressus. In the two functions—the protection of the ovule and the conduction
of the pollen-grain to the ovule—the seminiferous scale conforms to the ovary of
the Angiospermae. The important part played by the exudation of a drop at the
micropyle of the megasporangium has long been known in the fertilization of all
the Coniferae 7.
POSITION OF THE FEMALE FLOWER IN CONIFERAE. As regards the
position of the flowers: the female flower in the majority of the Coniferae
is so placed that the pollina-
tion takes place from adove.
Where they are not erect they
curve negatively geotropically
upwards, as is especially seen
in the case of Larix. It ap-
pears to me to be significant
that this takes place specially
in the coniferous flowers which
possess ovules whose micro-
pyle by a subsequent growth
is turned downwards, as in the
Abietineae and Podocarpus.
BIOLOGICAL RELATION-
SHIPS. Regarding the bio-
logical relationships of the — Fic.351. Pinus Pumilio. Portion of a tangential section through
female flower there is little fue Se eae ee a a
a, 6, c, d, e, 7, channels along which the pollen-grains slide to the
of a general character to re- _ micropyle.
late. There is, however, the
question of the pollination of the ovules and the protection of the ripening
seed.
This problem can be solved in different ways. In many cases the aid of
carpels is entirely got rid of, as in Ginkgo and Taxus, and the flowers then
appear to be extremely reduced. The outgrowth of the carpels appears the
earlier, the earlier its function is performed ; where its work is only that
of protecting the seed, as in the Cupressineae, it arises late ; where it aids in
the conduction of the pollen-grain, as in the Abietineae, it appears earlier.
The lie of the megasporangium within the flower may be connected with
its size or with that which the seed will reach. So far as I see, the ovules of
flowers where there are numerous ovules retain the upright position only if
they are relatively small and belong to cones of small dimensions. Where
1 Vaucher, Histoire physiologique des plantes d’Europe, Paris, 1841, tome iv.
524 THE SPOROPHYLLS OF GYMNOSPERMAE
the seeds are larger and are arranged in larger cones they can be better
looked after if their longer axis falls in with that of the cone-scales!.
Nevertheless in the Abietineae the ovules are inverted. What significance
the anatropous configuration in the ovules of the Podocarpeae has we do
not know.
THE QUESTION OF FLOWER OR INFLORESCENCE. The relationships of
configuration of the female flowers of the Ginkgoaceae and of the Coniferae
have received very different morphological explanations. Worsdell has
given recently an historical account of these to which I may refer”. I would
only refer to one point. What has been spoken of above as a female flower
in the Abietineae, Podocarpeae, and Cupres-
sineae, is by others regarded as an inflorescence.
This interpretation is with great ingenuity de-
fended by Celakovsky, who bases it chiefly
upon two grounds :—
(a) the structure of the female flower of
Ginkgo ;
(2) the ‘anamorphose’ which has been fre-
quently observed especially in the Abietineae.
The argument from anamorphose. In this
FIG. 352. Pinus maritima. Malformde : :
seminiferous scale. Explanation in the We have to deal with malformations—when compared
text. The ‘bract-scale’ lying behind tl : : : - :
seminiferous scale is partly indicated by | With the normal—in which a shoot appears in the posi-
ee aeeaute see eee from are tion of the seminiferous scale, and various intermediate
states between normal seminiferous scales and vegeta-
tive shoots arise—a consequence of the vegetative transformation setting in at an earlier
or later stage. We may meet with, for example, a shoot which begins with two leaves
bearing upon their under-surface rudimentary ovules. From this it has been concluded
that the seminiferous scale is an axillary shoot producing two leaves which twist through
about 90°, become concrescent by their edges, and bear each of them one ovule upon
the under-surface which is turned to the axis of the cone. In Pinus a third rudimentary
leaf is added, which is constructed as a ‘keel.’ Fig. 352 will help to explain this.
It shows a malformed seminiferous scale from an androgynous cone*. Instead of
the normal seminiferous scale there are three leaf-like structures, a, 4, c, united at
their base and each bearing upon its under-surface one malformed ovule recognizable
by the abnormal micropyle, mz. a@and 6 correspond to the first two leaves of the
axillary shoot of the bract-scale. They have not, however, undergone complete
torsion and they bear the ovular primordia evidently still upon their outer side.
Whether ¢ is a new formation or corresponds to the keel, which might also be
' We have seen the same features in the Cycadaceae; one may compare the lie of the megaspo-
rangia of Ceratozamia (Fig. 343) with that of Cycas.
* Worsdell, The Structure of the Female ‘ Flower’ in Coniferae. An Historical Study, in Annals
of Botany, xiv (1900).
* See the account of this cone on page 471 where it is figured (Fig. 311). Malformed scales
frequently appear here as well as normal seminiferous scales.
FEMALE FLOWER OF CONIFERAE 525
represented by d, is not of importance. That we have to do here with a check of
the development is shown by the arrest of the ovules. If we regard the occurrence
from the ‘ purely morphological’ side the whole structure corresponds to an axillary
shoot of the bract-scale which usually is reduced to two leaves; in Araucaria and
Podocarpus there would be only one present, in Cryptomeria and others there would
be many laterally confluent with one another. If these leaves be the sporophylls,
the covering scales are the bracts of the flower.
Argument from virescence. Similar phenomena appear when virescence takes
place. There can be no doubt that in virescence we have a vegetative transformation
of the seminiferous scale, but it does not follow that we must endeavour to make out
that the observed phenomena are those of the ‘normal’ course of development.
The plant devotes to the construction of the ovules and to the protection of these an
axillary outgrowth of the bract-scale which can appear in vegetative development as
a shoot. This transformation is brought about by external influences, at least in
many cases’. We find virescent cones on pruned spruce-hedges, and on trees
growing at the upper limit of tree-growth where they easily lose their top. Naturally
other factors can act also.
Summary. Putting on one side, however, the causes which bring about the
virescence and other checks, we may sum up as follows :—
If the development of the primordium of the seminiferous scale of the Abietineae
is stopped at an early enough period it can grow out into an axillary shoot whose
first leaves bear the arrested ovules on their under-surface. It is possible to construct
a series which, starting from the seminiferous scale of the Abietineae, passes to the
dorsal outgrowth of the cone-scale of the Cupressineae. This does not require the
primordium of the seminiferous scale to have been a shoot with developed leaves. It may
have experienced its transformation into seminiferous scale before such a segmentation
set in, and in phyletic relationship I see no necessity for the assumption that the
seminiferous scale corresponds to a small greatly reduced flower. There are wanting
transition-forms which would demonstrate any such history. The analogy with
Ginkgo is of less value as an argument because a common origin of the Coniferae
and Ginkgoaceae is extremely improbable.
Hypothesis. We may, however, if we wish to construct hypotheses suggest
others. Starting from a carpel like that of Ceratozamia which bears two lateral
ovules, if these are displaced upon the upper-surface of the carpel they may assume an
axillary position to it. If their number increases then we at once have the relationship
in many Cupressineae ; if it diminishes we have that of Podocarpus. For the pro-
tection of the seeds the carpel develops into the peltate form of the Cupressineae,
and soon there arises a more or less independent axillary outgrowth of this, which
in its extreme form exhibits the construction asit occurs in the Abietineae. Virescence
and other malformations seem to me only to show that the primordium of the semini-
ferous scale has the capacity, although this usually remains latent, to develop into
an axillary shoot, but not that it ever was a functionally active one. The mycelium
of a fungus induces the leaf of Pteris quadriaurita to produce shoots—a capacity
* See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884), p. 123.
526 THE SPOROPHYLLS OF GYMNOSPERMAE
which usually remains latent—which are then provided with leaves. The galls caused in
Aspidium aristatum? by Taphrina cornu cervi may be termed a rudimentary attempt
at the formation of shoots. The unfolding of a latent primordium does not of
necessity require us to conclude that it is a ‘reduction.’
The foregoing hypothesis, which of course is only ove of the many that might
be suggested to bring the facts into union one with another, appears to me, however,
to lead to greater simplification. Whilst there is something to be said for the hypo-
thesis which traces the construction from Ginkgo, yet I must state that it seems to
me to be a ‘purely formal’ one, and that it has not as yet explained to us in its
teleological connexion why the female coniferous flower should have experienced
such far-reaching transformations whilst the relation-
ships to pollination at least are nearly alike in all.
III. GNETACEAE.
The third group of the Gymnospermae—
or, if one makes the Ginkgoaceae a separate
group, the fourth—is the Gnetaceae, and it does
not require here any elaborate description.
The flower is surrounded by a perianth, indi-
cations of which are also found in the flowers
of other Gymnospermae, and in Welwitschia we
meet with for the first time a hermaphrodite
flower, which, however, becomes unisexual by
Fié. 364. Welvitechia mirabilis. ‘Male tH€ -aifesh jer the stamens or of the female
flower after removal of the flower-enve-
lope; WV, stigmaclike apex of the integu. @pparatus. It is possible that Welwitschia
rae hevclogeeat en C088 not attain (Fig, 353) originally possessed hermaphrodite
flowers. That consequently all gymnospermous
flowers must be considered as primarily hermaphrodite does not appear to
me to be a consequence *. The stamens of Welwitschia are concrescent below
into a cup-like structure, and each bears at its apex three microsporangia
arranged radially, and opening by splits. In Ephedra there stands in the
middle of the flower which is invested by two envelope-leaves a stalk-like
column on which two or more bilocular sporangia are seated, and these may
well be regarded as reduced stamens. The function of the filaments which
are absent is performed here by the elongation of the flower-axis which thus
raises up the sporangia for the proper distribution of the spores °.
The essential thing here is that the conformation of the stamens stands
in relation to the presence of a flower-envelope which encloses the stamens
until a short time before their unfolding. Inthe other Gymnospermae it has
* See Giesenhagen, Die Entwicklungsreihen der parasitischen Exoasceen, in Flora, Ixxxi
(Erganzungsband zum Jahrgang 1895), p. 330.
? See in this relation what has already been said, p. 471, and Part I, p. 60.
* It is therefore of little moment whether one derives the column from the flower-axis or from
a congenital union of leaf-structures in whose formation the flower-axis is quite used up.
FLOWER OF GNETACEAE 527
been shown that the conformation of the stamens has the closest connexion
with the protection of the microsporangia in the bud, and that the special
‘aim’ of the configuration of the lamina of the stamens is the protection
of the microsporangia during their ripening and there is no question of an
envelope of the male flower for this purpose. But in the Gnetaceae where
the envelope itself encloses the microsporangia the configuration of the
stamens is correspondingly simplified. The majority of Angiospermae
behave in exactly the same way.
The construction of the female flower will be briefly referred to when
megasporangia are described !.
The flower-envelope of the Gnetaceae may be considered as being
constructed out of hypsophylls. When speaking of the envelopes in the
Angiospermae reference will be made to this again ”.
An approach to the Angiospermae is also found in this—the ovule is
invested by an outer envelope. This may be regarded as composed of two
concrescent leaves, and it is present, for example, in Ephedra, even when the
seed is ripe, forming a thick outer shell like a pericarp in an angiospermous
fruit. This structure may be regarded as a rudimentary ovary which has
not reached the stage of forming a stigma; the stigma-like organ of the
Gnetaceae belongs rather to the integument of the ovule.
IV
THE SPOROPHYLLS OF THE ANGIOSPERMAE
A. THE FLOWER IN GENERAL.
The flowers of the Angiospermae are much more varied than are those
of the Gymnospermae*. They differ from those of the Gymnospermae
particularly in this, that the ovu/es (megasporangia) are enclosed before
pollination in an ovary which has developed a special organ—the stigma—
for the reception of the follen-grains (microspores). The carpels (mega-
sporophylls) are therefore differently constructed from those of the Gymno-
spermae. The stamens (microsporophylls) have in almost all Angiospermae
an essentially similar construction about which more will be said later on.
The flower-envelopes which in the Gymnospermae only give protection in
the bud, are much more conspicuously developed in the Angiospermae. In
many forms, especially those in which pollination is effected by the agency
1 See p. 629. 2 See p. 549.
° I can only briefly refer in this book to some general relationships and to some of the chief pecu-
liar organographical features. Valuable material from the morphological side will be found in Payer,
Traité d’organogénie comparée de la fleur, Paris, 1857; Eichler, Bliithendiagramme, Leipzig,
1875; Engler und Prantl, Die natiirlichen Pflanzenfamilien; Goebel, Vergleichende Entwicklungs-
geschichte der Pflanzenorgane, in Schenk’s Handbuch der Botanik, iii (1894). As regards the
configuration of the flower in relation to pollination see Knuth, Handbuch der Bliitenbiologie,
Leipzig, 1898-1904.
528 THE SPOROPHYLLS OF ANGIOSPERMAE
of animals, this envelope is entirely or partially developed as a flag-apparatus.
And we may mention as a further peculiarity of the angiospermous flower
that it is predominantly hermaphrodite, and unisexual flowers can be proved
to be frequently the result of arrest of either the microsporophylls or the
megasporophylls.
The great importance of the construction of the flower in systematic
botany has led to extended investigation of it, and its innumerable variations
have received very full treatment in systematic works. I can therefore pass
over these here, as well as the consideration of the relationships of the flower
to pollination1, and confine myself only to an account of some of the chief
peculiarities by which flowers are distinguished from vegetative shoots. Apart
from the construction of its several leaf-organs, which is bound up with their
function, and the special features of its axis which have been shortly mentioned
above ?, we may say that the flower of the Angiospermae chiefly differs from
the vegetative shoot by features which can be traced back to
(1) changes in the arrangement of the parts,
(2) concrescences,
(3) arrests.
I propose now to give some illustrations showing only the general
relationships °.
(1) ARRANGEMENT OF THE PARTS OF THE FLOWER.
It has been already shown * that the flower in Selaginella possesses an
arrangement of the leaves which is in part different from that in the foliage-
shoots. This is repeated in the flower of the Gymnospermae and the Angio-
spermae, and not only in the flower but also in the inflorescence, very
strikingly, for example, in many Orchideae. This evidently isa consequence
of the changed relationships of space at the vegetative point of the inflorescence
and of the flower. This change can be brought about in different ways.
Some of the processes are as follow :—
1 It is incorrect to speak of this subject as ‘ flower-biology,’ a term which has a much wider signi-
ficance.
3 See p. 470.
3 The account I give is based essentially upon what I have already published in Vergleichende
Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der Botanik, iii (1884). I here
once and for all make reference to Hofmeister’s Allgemeine Morphologie der Gewichse, Leipzig,
1868. With regard tothe mechanical theory of leaf-position I may refer to Schwendener, Mecha-
nische Theorie der Blattstellungen, Leipzig, 1868, and to Schumann, Bliithenmorphologische Studien,
in Pringsheim’s Jahrbiicher, xx (1889) ; id., Neue Untersuchungen iiber den Bliithenanschluss, Leip-
zig, 1890; id., Morphologische Studien, Heft 1, Leipzig, 1892. A criticism of the researches
which have been made to establish a mechanical explanation of the relationships of configuration in
flowers is here impossible, but I must state that my view of the results to which the mechanical
theory of leaf-position leads in the domain of flower-morphology differs altogether from that given
by Weisse, Die Zahl der Randbliithen am Compositenképfchen in ihrer Beziehung zur Blattstellung
und Ermahrung, in Pringsheim’s Jahrbiicher, xxx (1897) ; see also Part I, p. 84.
* See p. 509.
RELATIVE SIZE OF PARTS OF FLOWER 529
(a) RELATIONSHIP OF RELATIVE SIZE OF PARTS IN THE FLOWER.
If the vegetative point of the flower or inflorescence retains the dimen-
sions of that of the vegetative shoot, whilst the size of the primordia of the
leaves—whether these be leaves within the flower or bracts upon the inflor-
escence—decreases, then we shall find numerous primordia of leaves with
a different arrangement from that in the vegetative shoot. Again, ifthe vege-
tative point of the flower or inflorescence broadens relatively to the foliage-
shoot this likewise occasions a change in the arrangement of the primordia
of the leaves. Changes in arrangement are all the more prominent if the
two processes mentioned are combined together as they are in the capitulum
of Compositae. This connexion between relationship of size and arrange-
ment becomes specially conspicuous if there are changes in the numerical
relationships of the parts within the flower itself. The microsporophylls in
particular furnish us with examples. They are almost never leaf-like in the
Angiospermae, but commonly possess a narrow thread-like filament, conse-
quently each of the stamens occupies at its origin a smaller area of the torus
than does, for example, the sepal. Whilst then in the case of foliage-leaves
if their arrangement is cyclic the number of members in the several succeed-
ing whorls normally remains the same, this is not generally the case in
flowers. The disposition of the stamens in many Rosaeflorae supplies us
with a striking illustration of this '.
Geum. Rosa. The young flower-bud of a species of Geum or of Rosa shows
the usual form of this organ :—there is a broad convex vegetative point, upon which
the sepals arise in the usual successive series. Then before the inception of the
five alternisepalous petals there develops upon the peripheral zone of the torus an
annular ring or cup which surrounds the central portion of the torus upon which the
carpels arise. The primordia of the stamens shoot out upon the inner margin of this
cup, appearing in basipetal serial succession as the toral cup grows by means of its
intercalary vegetative point. The number of the staminal primordia is very variable,
not only in the different genera and species but also in one and the same individual
—and this in accord with the size of the staminal primordia and also with the
relationships of growth of the torus shortly before their origin. The number
increases if either the size of the primordia diminishes or that of the zone of the torus
upon which they arise increases immediately before their inception. According to the
earlier or later entrance into the development of either of the two factors just
mentioned we find at first five alternipetalous staminal primordia, or ten stamens
appear after the pentamerous corolla.
Agrimonia. Agrimonia gives us an illustration of the five alternipetalous
staminal primordia. Here, after the inception of the five petals, there appear five
strikingly large alternipetalous staminal primordia which fill up the space between the
primordia of the five petals. In Agrimonia pilosa a second pentamerous staminal
1 See Goebel, Beitrige zur Morphologie und Physiologie des Blattes, in Botanische Zeitung,
xl (1882), p. 353.
GOEBEL 1 Mm
530 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
whorl follows and alternates with the first’, but in other species of the same genus the
size of the staminal primordia decreases after the inception of the first whorl, and a
second staminal whorl which is decamerous follows the first pentamerous one. The
members of this decamerous second whorl link themselves in pairs to those of the
first. This construction is not the result of chorisis*. In consequence there is
a variation in the number of the stamens: Agrimonia Eupatoria, for example, has some
flowers which have twenty stamens and some flowers which have only five stamens,
and in numerous cases the number of stamens oscillates between these extremes.
The whole condition depends upon relationships of nutrition. We have no reason for
assuming that the most completely furnished flowers are the typical ones, that is to say,
are to be considered as phyletically the older ; and this is shown by a comparison with
other species. We can only conclude from what has been said that there is here no
constancy in the number of the stamens from the beginning.
Fic. 354. Scheme of staminal arrangements in Rosaceae. 1, species of Potentilla; a, cd, ef, pairs of
stamens of the outermost whorl. 2, Rubus Idaeus, only the outer stamens indicated ; a, 4, ¢, d, e, sepals; 1, 2, 3, 4, 5,
petals. 3, Potentilla fruticosa ; 1, 2, 3, successive staminal whorls.
Similar relationships occur in other Rosaceae, but the diminution of growth in
the organs, and the consequent multiplication of the number of stamens, appears
in the first staminal whorl. Following upon the five petals there are therefore ten
stamens which in general are so distributed that the pairs are separated from one
another by an equal distance (Fig. 354).
Potentilla. These relationships of space are retained in a number of flowers,
for example in many species of Potentilla, and then a second decamerous staminal
whorl (Fig. 354, 1)—in many cases even a third (Fig. 354, 2)—alternates with the first.
“Rubus. It is otherwise in Rubus of which Rubus Idaeus may be taken as an
example. Here the first ten stamens arise at almost equal distances from one another,
but very early this arrangement is changed, inasmuch as the zone of the torus
opposite the sepals (Fig. 354, 2, a, 4, c, d, e) experiences a considerable growth, so that
the separation of the antisepalous stamens is greater than is that of the antipetalous
ones. On account of the extent of this growth there are usually two—seldom
one—staminal primordia opposite each sepal. These again by further growth of
the torus may be pushed aside from one another, and between them one stamen or,
should the size of the space and of the staminal primordia permit of it, two stamens
may be interposed. Thus there is no uniformity even within one and the same
flower, as the diagram shows. Likewise in front of each of the petals (Fig. 354, 2, 1,
* It is frequently, however, incompletely formed. * See p. 532.
RELATIVE ‘SIZE OF PARTS OF FEOWER 531
2, 3, 4, 5) there may appear two—seldom only one—stamens, usually synchronously
but often one before the other, and in that case the earlier is placed somewhat higher
than the other, so that we can suppose that there has been chorisis. The further
staminal primordia place themselves in the gaps between those that precede them.
In other Rosaceae! there are found like variations in the number of the
staminal primordia according to the relationships of space and the relationships of
position which in one form occasionally vary in another appear to be nearly constant ;
thus Potentilla nepalensis has usually two antipetalous staminal primordia instead of
one, a relationship which is almost constant in Rubus.
Fic. 355. Eschscholtzia californica. Flower-bud in transverse section. I, the two carpels removed; a, bract;
a, 6, prophylls; c, calyx; #, petals; then follows one tetramerous staminal whorl, 1, and four hexamerous staminal
whorls, 2-5. II, shows thirty-one stamens. III, shows twenty-eight stamens. The anthers in II and III almost all
extrorse through the medianly convex curvature of the connectives.
Relationships of position like those of the stamens of the flowers of the
Rosaceae are found also in the primordia of other organs, for example in
the bristles which stand upon the outer side of the receptacle of Agrimonia,
the body of pappus of many Compositae, and I have found the same in the
androecium of a number of flowers in other families, for example Mimoseae,
some Anonaceae, Clematis, Papaveraceae. I shall give one more example
taken from the Papaveraceae.
Eschscholtzia californica. In Fig. 355, I] and III, we have representations
of two transverse sections of the flower of Eschscholtzia californica. The stamens are
1 See the treatises that have been cited.
Mm 2
532. THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
numerous ; their connective shows later a strong convex curvature upon the inner side
so that the ex/rorse position is assumed. The number of the stamens is here, as
in Rosaceae, by no means constant. There are, for example, twenty-eight in
Fig. 355, I, thirty-one in Fig. 355, II, and twenty-eight in Fig. 355, III. How these
are arranged is shown in the young flower-bud (Fig. 355, I). Following upon the
dimerous calyx comes the corolla of two dimerous whorls f,~, and the petals are set
on the torus with a broad base. With these four petals there alternates a tetra-
merous staminal whorl? whose members are marked with 1. Now the conformation
of the flower-bud is not circular but transversely oval in cross-section, and the
narrower sides are turned to the prophylls a and 4. Upon the broad sides? of
the flower there is more room for the insertion of the stamens with narrow base on
the flower-axis, and as a matter of fact we find here two, whilst upon the narrower
side there is only one. A hexamerous whorl follows the tetramerous one and its
members are marked with 2, and in turn it is succeeded by two other hexamerous
whorls until finally what is left unoccupied of the torus is used up by two carpels.
In the flower represented in Fig. 355, II, the last leaf-whorl is not complete.
In other Papaveraceae the relationships are the same*. In Bocconia the
cyclic arrangement of the stamens is somewhat confused.
CHORISIS. The examples which have been quoted show that there is a
connexion between the number of the stamens and the relationships of space
in the primordium of the flower, and this explains why we have changes in the
numerical relationships in the several whorls. The old morphology gave a
much simpler explanation in these cases, namely, the word ‘ chorisis.’ Even
in the latest text-books* this notion is still brought forward as an ‘explana-
tion. I must repeat what I said about it twenty years ago.
Moquin-Tandon was the founder of the theory of ‘dédoublement®.’ Later the
same notion was designated ‘chorisis, a name introduced indeed by Dunal, who
* It is a not uncommon occurrence that the change of the numerical relationships in cyclic flowers
does not take place abruptly but only gradually. Thus we see in the first staminal whorl still a
tetramery.
* The transverse position of the carpels is no doubt connected with this also. Elsewhere, if two
carpels are present, they are usually median.
* See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884), p. 300. It is there shown that in the Cruciferae, where usually the two pairs
of longer stamens are interpreted as a chorisis of two primordia, the analogy with the Papaveraceae
speaks strongly in favour of the independence of each staminal leaf. The relationships of space are
quite the same. Before the broad side of the carpel there is more room than before the narrow
side.
* In Strasburger’s Text-book of Botany, 2nd English Edition, London, 1903, it is said (p. 526)
that in the Rhoeadinae to which the Papaveraceae belong the androecium consists often of more than
two whorls on account of the splitting of its members, and again (p. 561) that in the Rosaceae a
‘ splitting of the whorls and of the individual members of the androecium’” has taken place phyleti-
cally. Neither statement corresponds with facts; they are hypotheses which long ago have been shown
to be untenable.
° Or perhaps we should say Dunal. See Moquin-Tandon, Essai sur les dédoublements ou multi-
plications des végétaux, Paris and Montpellier, 1826.
CHORISIS "533
also is the author of the term ‘carpel’.’ German authors distinguish between
‘splitting,’ in the narrower sense, and ‘dédoublement’ or ‘chorisis’ proper. If the
portions proceeding out of a common primordium appear as halves of one whole
then one speaks of ‘splitting,’ but if each of these parts has the nature of a whole
leaf-organ then one speaks of ‘dédoublement’ or ‘chorisis?.’ Moquin-Tandon’s
original definition ran* ‘when in the place of one stamen, which ordinarily exists
in an organic symmetry‘, one finds many stamens, these have become many by
dédoublement or by multiplication.’ Have we now a right to make any such assumption?
It is clearly based upon a comparison. We might just as well say that if a woman
bears twins there is a dédoublement because in place of one child one finds two, It
may be asked, if the expression has a palpable meaning—do the twins arise through
the splitting of an embryonal primordium or through fertilization and further develop-
ment of two independent separate eggs? It is clear that only the history of
development and the comparison with allied forms can give information as to which is
the actual process. In dédoublement Moquin-Tandon included also cases in which
later botanists spoke of ‘branched stamens, for example in Hypericum; moreover
he enumerated amongst the cases in which dédoublement occurred those of the
Ranunculaceae, Anonaceae, and indeed all plants with many stamens. That
dédoublement which corresponds with the present-day meaning of this word is his
‘dédoublement complete but simple’—in which the organs arising by dédouble-
ment stand either in one line beside one another, or in many phalanges around the
gynaeceum, asin Hypericum. The first is the case, for example, in Alisma Plantago :
‘six stamens opposite in pairs to each of the three petals, and produced by the dé-
doublement of three stamens each intotwo.’ More particular examination of this case
tells us that the history of development’ by no means bears out that two staminal
primordia have proceeded from the splitting of an originally simple one, but on the
contrary the two supposed split portions are wholly independent and arise upon the
torus completely separated from one another by an angle of it. Yes! But this is
‘congenital dédoublement.’ In other words we quiet our minds regarding the fact
that in the position of the primordium of an organ two completely independent ones
arise in this way: we write down the fact in two words, which indeed say no more
than that nothing of a splitting or branching is to be seen here from the very first.
Yet many see in this an ‘explanation’! More consequently it might be maintained
that the ‘ congenital dédoublement’ may be an actual one, as our methods of investi-
gation—and this is doubtless true—are imperfect, and the splitting takes place very
early. But in many cases as is shown by the whole configuration of the flowers
concerned, those, for example, of Alisma, as well as those of Rosaeflorae and
1 See regarding this terminology Moquin-Tandon, Eléments de tératologie végétale, Paris, 1841,
P- 335-
? See Eichler, Bliithendiagramme, i, p. 5.
3 See Moquin-Tandon, op. cit., p. 8.
* By this he understands with de Candolle what one now expresses by the word ‘type’ or ‘ plan of
structure,’
5 See Buchenan, Uber die Bliithenentwickelung von Alisma und Butomus, in Flora, xl (1857),
p- 241; Goebel, Beitrage zur Morphologie und Physiologie des Blattes, in Botanische Zeitung,
xl (1882).
534 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
Papaveraceae above described, this contention is quite untenable, and the general
conception out of which it has sprung is certainly not one that need be maintained
at all hazards. It is possible to show in a number of cases that the replacement
of one stamen by two or more is not the result of a splitting, but depends upon
the relationships of growth in the torus, and variations in the size of the primordia of
the organs, An ‘explanation’ is indeed not given by this, but only one of the con-
ditions or accompanying circumstances in which the phenomena in question appear
is made clear’. An explanation of the causes of
these relationships of growth we do not possess.
That usually alternation takes place is moreover only
a fact of experience for which we cannot adduce a
causal but at the most a teleological connexion.
That a splitting and branching of staminal primordia
takes place should not surprise us. We have indeed
seen in the sporophylls of the Filicineae that these
are often richly branched like the foliage-leaves.
But there is no doubt that comparative morphology
has landed itself frequently in a misuse of this notion.
In recent times, however, even amongst morpho-
logists a reaction has begun to make itself felt in
the direction of the view early pleaded for by me,
but naturally then ignored by the ‘ morphologists ’—
a reaction which has led to the notion, to be men-
tioned below, of ‘ negative chorisis.’ I must, however,
next deal with the question of the occurrence of
branching or splitting of stamens and carpels in
general.
BRANCHING OF THE STAMENS. We
start from a special case :—
Fic. 356. Hypericum aegyptiacum,
Linn. (H. heterostylum, Parl.). Staminal
phalange. Magnified 20.
Hypericaceae. The stamens in the flower
of Hypericum aegyptiacum are arranged in bundles, one of which is shown in
Fig. 356: a number of perfect stamens spring both from the edge and from the
outer side of a common flat column. ‘This structure has been recognized as one
branching leaf for the following reasons :—
1. The history of development shows that each bundle of stamens arises out
of a specially limited part of the torus upon which the staminal primordia are laid
down.
2. The staminal primordia are laid down in descending serial succession, an
* If we see in a flower that the primordia of the organs appear in greater number where there is
more room at the vegetative point of the flower, this does not necessarily mean that we can say
that the relationships of space are those conditioning the numerical relationships ; just as well can
we assume that there is more space provided where the vegetative point of the flower is disposed
most to the building of primordia of organs. All ‘ mechanical’ explanations are excluded in these
relationships.
BRANCHING OF STAMENS 535
arrangement which in ‘ comparative’ morphology is not permitted for the parts of a
leaf or for the inception of leaves upon a shoot.
Against this I have already shown! that the comparison of the different forms of
flower and their development makes possible another suggestion, namely, derivation
from a flower which forms numerous stamens in descending serial succession uniformly
distributed on the torus®. Such forms are found in the Hypericaceae. In Brathys
prolifica * the torus forms five antipetalous primordia separated from one another by
depressions, and the stamens arise preferably—that is to say appear first of all—upon
these elevations of the flower-axis, but not exclusively there for staminal formation also
takes place in the depressions of the torus. Loasaceae show like features. It is not
necessary to regard these antipetalous primordia as basipetally branching staminal
primordia the branchings of which become partial stamens, but we may recognize in
them merely areas of the torus on which the staminal formation in many Hypericaceae
is localized, especially in forms which we may designate as impoverished when com-
pared with Brathys where the whole torus is still covered with stamens. In the species
of Hypericum in which five such antipetalous primordia are present this method of
origin shows itself in the perfect flower mainly in the assemblage of the stamens in
five groups; in Hypericum aegyptiacum the antipetalous primordia grow out into long
columns. It will be evident that the two explanations differ in their starting-point ;
the old one proceeds from a pentamerous androecium; the other from a polymerous
androecium* which breaks up into single groups—a segregation which is also
expressed at an early time in the parcelling of the torus, and is correlated with an
arrest of the staminal primordia lying between the antipetalous primordia. It appears
to me that this last explanation gives us a better picture of the facts®, and I see no
reason why we should not extend it to the Loasaceae, Myrtaceae, and other families.
Of course only careful comparison within a cycle of affinity can show in any case
what explanation is the best.
CHORISIS OF STAMENS. It is indeed possible that in many cases a
complete splitting of the staminal primordia takes place, and there are
certainly constant examples of an incomplete splitting.
Adoxa. In the lateral pentamerous flowers of Adoxa, for example, there are
apparently ten stamens which alternate in pairs with the petals and possess in the ripe
1 Goebel, Beitrage zur Morphologie und Physiologie des Blattes, in Botanische Zeitung, xl (1882),
p- 378; id., Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, ili (1884), p. 302.
4 See Part I, p. 41.
3 See Payer, Traité d’organogénie comparée de la fleur, Paris, 1857, p. 8, pl. 1, Figs. 19-25.
* I have searched recently many authors without finding any mention of this which was published
in 1882 and 1883.
5 Schumann, Beitrige zur vergleichenden Bliithenmorphologie, in Pringsheim’s Jahrbiicher, xviii
(1887), p. 151, says that my explanation is not mecessary. agree. Every explanation or theory is
only of value in so far as it gives the most satisfactory picture of the phenomena according to the pre-
sent state of our knowledge. As to the causes of the parcelling of the torus, it appears to me
probable that the trimery of the primordia of many species of Hypericum is connected with the
trimery of the carpels, and this relationship may be not merely one of space but differences of
physiological nutrition may come into consideration.
536 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
condition only unilocular anthers. The history of development shows that as a matter
of fact we have here a splitting of an originally simple staminal primordium’; each
half develops certainly into a half stamen possessing one loculus.
Malvaceae. We know also of other cases, for example in the Malvaceae,
where each single stamen splits likewise into halves, each bearing a unilocular anther.
DOUBLING OF STAMENS. With this we may link on cases in which
an actual doubling, and not a splitting, takes place, in so far as the halves
become complete, each usually having a bilocular anther. According to
Payer we find this in Phytolacca and Rumex.
Phytolacea. In Phytolacca there appear at first simple papillae alternating with
the leaves of the perianth, and they then divide into two parts each of which develops
into a complete stamen, and this process is repeated in Phytolacca icosandra once
more in a second staminal whorl.
Rumex. In Rumex where the androecium is composed of six outer and three
inner stamens the outer ones are derived in pairs from the division of an originally
simple primordium. We leave untouched the question whether one could explain
this process otherwise in the phyletic sense.
DOUBLE FLOWERS. Specially evident examples of the multiplication
of flower-organs by splitting or branching are supplied by double flowers *.
Splitting or branching may occur here in the petaline primordia, as in some
Onagrarieae like Fuchsia, Clarkia pulchella, and in the staminal primordia,
as in Petunia, Primula sinensis, all the Caryophylleae which have been ex-
amined, the Cruciferae. The large number of petals in ‘ perfectly’ doubled
- carnations is well known; in one not very strongly doubled flower I counted
forty-eight. These are all, with the exception of the five normal petals, the
result of a splitting of the ten staminal primordia. This splitting takes place
in different directions, and to a greater or less degree. In slightly doubled
flowers of Dianthus barbatus for example, there is no chorisis—the outer
stamens are transformed into petals, and the others show middle stages
between stamens and petals; but in more fully doubled flowers the splitting
takes place (Fig. 357).
It is difficult to see why such a process should not also occur in the ‘normal’
development of the flower, and therefore the number of the stamens be increased. We
usually assume a diminution of these. | We are always too much inclined to reduce
the processes of configuration which occur in nature to ‘single’ schemes, because
these make easy for us their orientation in the midst of their manifoldness, and we forget
that to nature, if we may be allowed the expression, there are offered many ways of
reaching one ‘ goal’ from which she selects the most practicable in the several cases.
1 Payer, Traité d’organogénie comparée de la fleur, Paris, 1857, p. 414, pl. Ixxxvi.
* See Goebel, Beitrage zur Kenntniss gefiillter Bliithen, in Pringsheim’s Jahrbiicher, xvii (1886),
p- 207.
BRANCHING OF CARPELS 537
Of this the double flowers furnish an instructive example. The excess of the petals
in such flowers can be reached in very different ways: by transformation into petals
of the organs which in the normal flower are devoted to other purposes, usually the
stamens or more rarely the carpels; through splitting or branching of the primordia of
organs and the petaloid construction of the new primordia which so arise ; by formation
of primordia of organs which did not exist in the normal flower, as, for example,
by the origin of new whorls in cyclic flowers’. We learn from these facts that the
inner nature of the vegetative point of the flower is proportioned to the formation of
organs. If the vegetative point is ‘induced’ to bring forth more petals than
usual it offers for these the necessary conditions of development. It is in it likewise
that the changes first of all take place. Such considerations make us from the outset
very sceptical regarding great mechanical influences such as have been used frequently
in morphology as ‘ explanations.’
Fic. 357. Figure to the left: Dianthus Caryophyllus. Bud of a double flower dissected out; ca/, calyx; fer,
petals. The ten staminal primordia fork and so produce a great number of organs which develop as petals.
Figure to the right: Nerium Oleander. Bud of a double flower in transverse section. Between calyx and
androecium there are four pentamerous corolline whorls instead of one.
BRANCHING OF THE CARPELS. The number of the carpels may also
increase by branching, for example in many Malvaceae. Payer found in
Kitaibelia vitifolia five carpellary primordia” out of which by branching and
the formation of false septa numerous monospermous ovaries are developed.
In Malva and others the numerous carpels appear to be separated from the
first. The process is in any case a rare one, and it is undoubtedly connected
here with the development of the monospermous mericarps in place of the
capsule. More common is it to find a diminution in the number of the
carpels, as will be pointed out below.
FACTORS DETERMINING NUMERICAL RELATIONSHIPS IN THE
FLOWER. The numerical relationships in the flower are in most cases
1 For examples see Goebel, Beitrige zur Kenntniss gefiillter Bliithen, in Pringsheim’s Jahrbiicher,
xvii (1886), p. 207. Compare also Fig. 357, figure to the right. I may specially note the fact
that the primordia of petals, which in the ‘normal’ flower are arrested, are developed in double
flowers. This happens, for example, in Delphinium which gives us an illustration of the development
of ‘latent’ primordia under definite stimuli. The latent primordia are not, however, always to
be traced to those which formerly were developed, as is shown by the behaviour of other
double flowers.
2 See Payer, Traité d’organogénie comparée de la fleur, Paris, 1857, p. 35, pl. viii. I have
convinced myself by examination of the correctness of his figures of Kitaibelia vitifolia.
538 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
determined by ‘inner’ causes, and in their variations we cannot usually trace
the operation of outer factors. Yet as has been shown above in the Rosa-
ceae the number of the stamens is often dependent upon relationships of
nutrition, and the like occurs elsewhere. Thus the first flowers of some
Caryophylleae are hexamerous, the following ones are pentamerous; the
terminal flower of the cyme of Ruta graveolens is pentamerous, the others
tetramerous; and we find the same thing in Lythrum Salicaria. The
carpels of Nigella damascena furnish another example. Normally, that is
to say in well-nourished flowers, they are five; in later flowers they are
partly four and partly three, and it may be noted that this last number is
the normal one in the allied genus Aconitum. Such cases are interesting
because they lead us to the conjecture that what in one plant is directly
caused by external conditions is determined by the internal economy of the
plant from the beginning in another allied plant constructed after the same
‘type. Such cases will perhaps furnish a clue for our determining by
further experimental research what are the factors which condition the
numerical relationships in the flower.
(2) CHANGE (IN THE NUMERICAL RELATIONSHIPS OF THE FLOWER THROUGH
CONFLUENCE.
We have dealt above with the appearance of higher numbers in the leaf-
whorl. We have now to look at cases where dzmznution in number of parts
takes place.
We refer here not to the absence of single leaf-organs of the flower, but
to the changes in the numerical relationships dependent upon confluence of
parts which may take place at different stages, and there are all transitions from
the separate inception of two leaf-structures to the appearance of one instead
of the two—a phenomenon of which we have seen also examples amongst the
vegetative organs’. The phenomenon is observed in the calyx, corolla, and
androecium. It is best known and most easily proved in the corolla.
Confluence of petals. The corolla of the Labiatae is composed of five
leaf-organs which are quite separate from one another as primordia. Of these two
form the upper lip, three the lower lip. Those of the upper lip become confluent at
a very early period, so that they appear as if they were a single leaf?, and in the
perfect condition the upper lip shows in consequence only a slight indentation, as in
Lamium, or this is scarcely visible as in Betonica officinalis. It is possible that the
upper lip appears from the beginning as ove leaf in these cases; this happens at any
1 See page 370.
* Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), where I have shown that this union stands in connexion with the fact that the
fifth stamen (which falls opposite the upper lip) has entirely disappeared, and that the four other
stamens arrange themselves into a tetramerous whorl with nearly equal intervals. This would affect
the construction of the corolla, that is to say the confluence of the two upper leaves.
CONFLUENCE OF STAMENS 539
rate in Veronica where in the mature condition, apart from the presence of the fifth
sepal which is found in many species, the larger size of one petal alone suggests that
it is to be considered as replacing two. The upper lip of the calyx of Utricularia is
similarly never laid down in three parts’; the lower lip consists of two separate
primordia. In the nearly allied genus Polypompholyx the calyx is laid down as five
primordia’: it is evidently quite immaterial for the function of the organs in question
whether the original segmentation is abolished or not.
Confluence of stamens, We find similar features in the androecium. In the
Cucurbitaceae, for example, there are visible in the male flower frequently three
stamens, two perfect, that is to say each with four pollen-sacs, and one a half-stamen.
Fic. 358. Cucurbitaceae. Androecium. 4, Fevillea trilobata; male flower in vertical section, showing five
free stamens, each with a bilocular anther opening independently. &, Thladiantha dubia; male flower in vertical
section ; one stamen free, two others of the five close together as a pair. C, Sicydium gracile; male flower in
vertical section ; one staminal pair visible, filaments coherent below only. J, Bryonia dioica; male flower in ver-
tical section; the filaments of this one staminal pair visible are completely coherent. Z, the same in transverse
section showing corolla and androecium. , Sechium edule; male flower in vertical section; five stamens con-
crescent. G, Cyclanthera pedata ; synandrium in profile. 4, the same in vertical section. After E.G. O. Miller
and Pax from Flora Brasiliensis.
Comparative consideration shows that in this family, starting from an androecium com-
posed of five half-stamens such as is found in Fevillea (Fig. 358, A) ; there are in Thladi-
antha (Fig. 358, 2) four stamens approached in pairs ; in Sicydium (358, C) the filaments
of these pairs are confluent with one another to a greater or less extent, in Bryonia
the anthers only are still free (Fig. 358, D); in the majority of the Cucurbitaceae the
anthers also are confluent; in forms like Sechium (Fig. 358, /’) the confluence
involves the whole five stamens, but the anthers are separated from one another; in
Cyclanthera (Fig. 358, G, /Z) there is in the middle of the flower a structure provided
with two pollen-sacs which runs right round it and which shows ontogenetically no
longer any trace whatever to indicate that it takes the place of five stamens which are
1 See Buchenau, Morphologische Studien an deutschen Lentibularieen, in Botanische Zeitung,
xxiii (1865), p. 94.
2 See F. X. Lang, Untersuchungen iiber Morphologie, Anatomie und Samenentwicklung von Poly-
pompholyx und Byblis gigantea, in Flora, lxxxviii (I1g01), p. 167.
540 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
confluent with one another. This example is of interest on different grounds, for the
problem takes its first start in the establishment of such a series. Those who main-
tain that all ‘morphological’ characters are adaptations find in the flower of the
Cucurbitaceae ‘hic Rhodus, hic salta’! To those who like myself do not share this
view the question arises whether there is any other causal factor for the special
confluence. Researches in the comparative history of its development from this
standpoint are unknown to me, but it appears to be probable that the trimery of the
stamens produced here by confluence has a relationship to the trimery of the carpels,
whose rudiments are visible in the male flower and reach a considerable size in
the mature flower of Cucurbita. A process analogous with that which has been
described in the Cucurbitaceae is found likewise in Hypecoum?. I need hardly recall
that this process of concrescence may come about in different ways*. _ We may find
staminal primordia, for example, so closely pressed together that they appear as
a single primordium (Part I, Fig. 22, III) and then in later stages grow out separate.
Celakovsky has lately designated this process ‘negative chorisis’—a somewhat
unhappy term.
(c) SUPPRESSION OF THE ELONGATION OF THE TORUS.
It is in consequence of this that we so often find a cyclic arrangement
in the flowers of plants which have alternate phyllotaxy on the vegetative
shoots. As the single leaves which compose, for example, the corolla dis-
charge their function together, their syzchronous origin is easily understand-
able; on the other hand, it will be a distinct advantage to the vegetative shoot
that the foliage-leaves unfold in a gradual serial succession, and with this
their spzral arrangement is consonant. The alternation of the foliage-leaves
secures their efficient disposition without overlapping *, but this consideration
does not count in the leaves of the flower which do not assimilate, and we
find that the alternation of whorls is not always retained. It is a matter
therefore of no moment whether superposition, for instance of the stamens
and petals of the Primulaceae, is phyletic and brought about by the arrest
of a previously existing leaf-whorl, or is primitive. We can only assert that
the relationships are of a kind other than those of the vegetative shoot.
If comparative morphology makes the assumption in the case of the Primulaceae
—and indeed correctly—that the position of the stamens opposite the petals is
‘explained’ by the abortion of an alternipetalous staminal whorl, only the historical
side of the question is kept in view. From the standpoint of what has been said
above such a superposition requires no explanation if the space-relationships in the
vegetative point of the flower are favourable to it. It is from the point of view of
1 See Payer, Traité d’organogénie comparée de la fleur, Paris, 1857, p. 229; Hichler, Uber
den Bliithenbau der Fumariaceae, Crucifereen und einiger Capparideen, in Flora, xlviii (1865),
P- 433-
2 See the scheme, Part I, p. 53, Fig. 22.
’ The unfolding of a whole leaf-whorl when the leaves are of equal size makes a greater demand
upon the rvot-system than does a single leaf, and we have already seen that the shoot-axis must
stretch out in order to avoid the shading of one leaf by the other. See p. 442.
GROWTH OF THE TORUS 541
efficiency quite as correct as is the alternation of the whorls. Schumann’ has pointed
out that such a superposition of stamens and petals is found in particular if the petals
are very small? and their development remains behind at first that of the stamens, a
phenomenon which is partially responsible for the earlier view that the petals of
Primula arise as dorsal outgrowths of the stamens—a view which nowadays hardly
finds a supporter.
(Z) LIMITED GROWTH OF THE TORUS.
Two special features of the flower are connected with this * :—
1. The fact that in the flower terminal leaves are not uncommon.
2. The serial succession of the parts of the flower not infrequently
deviates from the acropetal succession of the vegetative shoot.
Fic. 359. Acer Pseudoplatanus. Flower-buds dissected and seen from above. I, bicarpellary. II, tricar-
pellary ; Ze, petals. 1, earliest formed stamens; 2, interposed stamens. Magnified.
(a) Terminal flower-leaves. These arise if the vegetative point which is the
embryonal region of the shoot is entirely used up in the formation of leaves. It is
easy to understand that this may readily occur in a shoot of limited growth. Many
leaves may share in a certain proportion in the vegetative point, or only one may
be produced. The process in each case is essentially the same. The former is
frequent in the formation of the gynaeceum, and this is a matter of importance for
the ‘explanation’ of the ovary*. Acer furnishes an example (Fig. 359). The car-
pels in Acer form the termination of-the flower-bud. Whether there be two or three
carpels s/he whole area of the vegetative point of the flower ts used up by these, and what
holds for two or three leaves is likewise true in other cases for one. In this narrower
sense single stamens or carpels are terminal on the flower-axis, and we have such
stamens in Callitriche, Casuarina, Najas, and such carpels in Typha and elsewhere.
1 Schumann, Neue Untersuchungen iiber den Bliithenanschluss, Leipzig, 1890, p. 479.
2 In Urticaceae and elsewhere other relationships have to be considered.
5 See Part I, p. 41.
* See Goebel, Zur Entwicklungsgeschichte des unterstandigen Fruchtknotens, in Botanische Zeitung,
xliv (1886).
542 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
(6) Basipetal succession of flower-leaves. The general rule for the succes-
sion or origin of lateral organs is that they appear in progressive serial succession ’,
that is to say the youngest stand next the embryonal region whether this lies next to
the apex or elsewhere. It has been already shown” that in organs of limited growth
the apex often takes precedence in the development whilst zones lower down continue
to bring forth new formations. This is frequently seen in the flower *°. The stamens
in particular arise frequently in descending progressive series, for example in the
Cistineae (Fig. 369), Malvaceae, and others. This is also the case with the hook-like
structures upon the outer side of the calyx of Agrimonia. It is also frequent in the
case of the ovules. Nowhere do we know what the biological relationship of this
order is.
(ec) DORSIVENTRALITY.
A deviation in the succession of origin of the parts of the flower is
found in many dorsiventral flowers *+—repeated also in many inflorescences
—and in particular in those in which the dorsiventrality expresses
itself in a conformation of the vegetative point different from the
ordinary radial one, which is uniform on all sides before the primordia of
the Jeaf-structures appear, and upon which the primordia of the organs arise
upon all sides in progressive series towards the apex. One side of the
vegetative point of the flower is furthered—either the side next the chief
axis, as in Reseda, or the side farther away from this—there is a sym-
metric configuration °.
Reseda. In Reseda the side of the vegetative point thai is turned towards the
inflorescence-axis is higher than that which is turned away from it, and the develop-
ment of the sepals and petals corresponds to this construction®. The first sepal
appears upon the side next the inflorescence-axis, and then in progression anteriorly
the subsequent sepaline primordia. The petals and stamens follow suit, and the first
stamen is showing before all the petals are formed.
Lentibularieae. This method of development is known also in the Lenti-
bularieae’. Before the appearance of the leaf-organs a furthering occurs of one side
of the vegetative point, and upon this side in Pinguicula vulgaris the sepals, petals,
and stamens first appear before the sepaline primordia are visible on the other side.
In Utricularia also the upper part of the corolla arises only @/fer the inception of the
1 This expression is more comprehensive than that of the ‘ acropetal’ and ‘basipetal’ origin. See
Goebel, Uber die Verzweigung dorsiventraler Sprosse, in Arbeiten des botanischen Instituts in Wiirz-
burg, ii (1882). De Bary has also used it in connexion with the Fungi.
2 See p. 330, also Part I, p. 41.
3 Without, however, our being able to discover teleological connexions as can be done in the case
of the foliage-leaves.
* The phenomenon is also repeated in many inflorescences. See Goebel, op. cit.
5 In the case of dorsiventral inflorescences also the dorsiventrality appears in the conformation of
the vegetative point, and this is a fact of great importance in all attempts to give an explanation.
® See Payer, Traité d’organogénie comparée de la fleur, p. 193, pl. xxxix; Goebel, Beitrage zur
Morphologie und Physiologie des Blattes, in Botanische Zeitung, xl (1882), p. 388.
7 See Buchenau, Morphologische Studien an deutschen Lentibularieen, in Botanische Zeitung,
xxiii (1865).
DORSIVENTRALITY 543
stamens which are two in number and are formed upon the favoured side of
the axis.
Papilionaceae. A similar symmetrical succession of development is found in
the flower of the Papilionaceae’, only the progression is towards the posterior side,
that is to say towards the inflorescence-axis.
There is in these cases only an unequally-sided development by which the lower
standing flower-whorls always arise earlier than those which stand higher, yet there
may well be exceptions to this behaviour.
That the succession of development of the leaf-organs in these dorsiventral
flowers has been derived from that in radial flowers is probable for more than one
reason 2; on the other hand, the method in which the deviation has come about is not
at all clear. Payer’s investigations show that there are attempts at unequal-sided
development even in radial flowers *.
Cruciferae. The Cruciferae, for example, have two dimerous calyx-whorls,
one median and one transverse. In many, for example Cochlearia, the median
appears first—its sepals synchronously—in consequence of the radial construction
of the flower, and then the transverse. In Cheiranthus, on the other hand, the
anterior (outer) leaf of the first whorl arises first, and then two transverse ones, and
last the posterior leaf of the first whorl. Such deviations may be connected with,
to speak teleologically, the great need for protection of the flower-bud upon the
outer side, but more accurate investigation will perhaps show why Cochlearia differs
in this relation from Cheiranthus. ‘The difference is not one of habitat but the whole
behaviour of the inflorescence to the rest of the plant must be considered.
It is possible that these relationships have given the occasion for the
construction of the dorsiventral flower as we find it in Resedaceae and the
Papilionaceae. Another possibility is that, as we have already said, these
flowers which are dorsiventral from the first have been derived from those
which are only dorsiventral after unfolding *. Whether now the two kinds
of dorsiventral flowers have arisen in different ways or not we may at any
rate see that the dorsiventral construction of the flower has set in in different
developmental stages. In Hyoscyamus, for example, the calyx, corolla, and
androecium are laid down as in a radial flower®, only after this does the
extension of the torus begin which brings about the oblique insertion of the
1 See Payer, Traité d’organogénie comparée de la fleur, p. 517; Hofmeister, Allgemeine
Morphologie der Gewachse, p. 464; Frank, Uber die Entwicklung einiger Bliithen, mit besonderer
Beriicksichtigung der Theorie der Interponiring, in Pringsheim’s Jahrbiicher, x (1876), p. 205.
Ba See PLATeslGspamiacs
$ For example in the development of the calyx of Symphoricarpus. Payer, op. cit., p. 617.
According to Payer’s figures, Plate cxxviii, Figs. 3, 4,5, which are opposed to what he says in the text, the
serial succession starts from the sepal over against the bract, and then proceeds laterally. Buchenau
gives a like account of the involucre of Lagascea. Further, in species of Begonia, for example
Begonia xanthina, Hooker (see in Hofmeister, Allgemeine Morphologie der Gewachse, Fig. 87), the
staminal primordia appear earlier upon one side of the flower-axis than upon the other, but here
the vegetative point of the flower is not uniform all round.
* See Part I, p. 128.
5 Schumann, Neue Untersuchungen iiber den Bliithenanschluss, Leipzig, 1890, p. 317.
544 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
carpels to the median plane of the flower, and the other changes in the flower-
construction set in.
Schwendener ! has conjectured that the oblique position of the flowers in
the Solanaceae depends upon relationships of pressure. The flower-shoot,
ITT, in Fig. 296, for example, is exposed at the time of the inception of the
carpels to the pressure of the leaves marked Vz and 77, because these
are inserted at the same height. These behave like ove leaf, and the plane
of symmetry undergoes on account of the pressure a torsion which brings
it nearer to the median of this one leaf?. The history of development of
Atropa showed me nothing in support of Schwendener’s hypothesis. The
position of the carpels stands indeed in the nearest relationship to the
whole symmetry of the inflorescence, but is certainly not affected by
pressure. Such pressure would at first make itself felt upon the calyx; but
it is laid down as in radial flowers*. The first sepal (in Fig. 296, ///, that
turned upwards) falls upon the outside and appears then in the widest gap,
where therefore the protective need of the flower-bud is the greatest. The
factors which condition its appearance in this place we do not know*. We
can only see that it is of advantage that the protection of the bud begins on
the most exposed side. A plane through the middle of this first sepal and
the centre of the flower-bud marks the median plane of the carpels. The
whole of the median planes of the flowers of an inflorescence fall in this
direction if one considers them as vertical. The flowers are intrinsically
all dorsiventral, but in the whole of them the dorsiventrality is not clearly
seen apart from the oblique position of the carpels. In the construction of
the flower in this sympodial inflorescence the outer side is differently
organized from the inner side°.
We may say in general that in flowers which are laid down dorsi-
ventrally the succession of origin which deviates from the radial, and the
arrangement of the leaf-organs, depends upon an earlier or later setting
in of the change of configuration of the vegetative point, but we do not
know why a furthering of the outer side or of the inner side begins. One
might indeed be inclined to assume ® that those leaf-structures in the flower
which attain the most conspicuous size are most furthered in the time of
their appearance. This may well be the case in for example the calyx
of the Papilionaceae, as well as in the corolla and the ‘disk’ in the
1 See Schwendener, Mechanische Theorie der Blattstellung, Leipzig, 1878, p. 124.
? Otherwise the plane of symmetry of the carpels falls in with that of the bract.
* See also Schumann, Neue Untersuchungen iiber den Bliithenanschluss, Leipzig, 1890, p. 315.
* The numerous other cases in which a mechanical influence has been assumed are quite analogous.
Fig. 296 shows also that the first sepal does not fall over the median between Vir and Zz but
is nearer 7y7 and over the median between this leaf and the flower /.
° In this the dorsiventral flowers of the Solanaceae conform with those of other plants, but in other
plants the outer side is mostly marked by the bract.
° As has been stated in the case of the vegetative organs. See pp. 305 and 364.
THE ANATOMICAL METHOD IN MORPHOLOGY 545
Resedaceae—the calyx of the Resedaceae is more strongly developed in the
mature condition upon the owfer sede than upon the inner side.
We arrive therefore at two conclusions :—
(a) the furthered organs are laid down earliest ;
(4) after the inception an unequally strong construction may ensue
even within the leaves of one whorl’.
The anatomical method in flower-morphology. It hardly needs to be
pointed out that where there is limited growth of the flower-axis, the distinction
between what is axis and what is flower-leaf is much more difficult than in
vegetative shoots. We shall recur to this point later, but here I would only
comment upon an aid which has been used frequently in the solution of this and all
other questions of flower-morphology. The so-called ‘anatomical method’ is based
upon the claim’ that it can say better than anything else what is an axis and what is
a leaf. The axis is quite generally radial, the leaf has a dorsiventrally arranged vascular
bundle-system. That this behaviour is as little constant as other marks has long been
proved. Dorsiventral shoot-axes have the dorsiventrality abundantly expressed in the
arrangement of their vascular bundles, for example the inflorescences of Urtica dioica *.
The phylloclades of some Asparagineae show this also very strikingly and the
anatomical method has consequently declared them to be leaves in opposition to the
facts which are as clear as day! It is nothing less than the old idealistic morphology
in anatomical dress which asserts that the distribution of the vascular bundles as it
occurs in radial vegetative shoots and assimilating leaves must also be found in the
' flowers. Where the axis stops its growth and its further development this fact will be
expressed in its completed anatomical structure, and the formation of the conducting
bundles will gradually recede in the leaves which are remaining rudimentary and will
finally entirely cease. In such cases the anatomical method is useless. It has the ad-
vantage of easy handling and of course its results must be considered. But these can
never be regarded alone as critical and as determining interpretations within the flower.
They are in their nature essentially of less importance than are those which are ob-
tained by the comparative history of development. If Payer and other phyletic
researchers have come to untenable results regarding the formation of the placenta
through their investigations by the comparative historical method, these were not due to
faults in the method but rather to the omission of one weighty consideration from their
survey, namely, that of ‘what area of the torus—that is to say of the vegetative point
—the carpels occupy at the time of their appestance *” Payer’s investigations gave
1 Tt is to be noted that the TEES, inception of leaf-organs at the vegetative point is not
limited to the flower-region. It takes place also in the vegetative shoots, in which, however, it has
been much less considered. See, for example, Ganong, Beitrage zur Kenntniss der Morphologie und
Biologie der Cacteen, in Flora, ]xxix (Erganzungsband zum Jahrgang 1894), p. 52. The comparison
of this vegetative shoot, which is laid down dorsiventrally, with the dorsiventral flowers is all the more
apt, inasmuch as there can be no doubt that they are both derived from originally radial shoots.
* See Van Tieghem, Recherches sur la structure du pistil, in Annales des sciences naturelles, série 5,
ix (1868).
* See Goebel, Uber die Verzweigung dorsiventraler Sprossen, in Arbeiten des botanischen Instituts
in Wiirzburg, ii (1882), p. 430. in
* Goebel, Zur Entwicklungsgeschichte des unterstandigen Fruchtknote1 —_ , Botanische Zeitung, xliv
GOEBEL II Nn
546 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
frequently no ground for a conclusion upon this point, and consequently the distinc-
tion between the share of leaf and axis in the construction was not correctly expressed.
The history of development when more accurately used leads to results which conform
with those which have been obtained in other ways, as will be pointed out more fully
when the development of the ovary is considered.
(2) CONCRESCENCE IN PARTS OF THE FLOWER.
Concrescences are frequent in flowers, both of flower-leaf with flower-
leaf and with flower-axis. The cases of confluence which were discussed
above ! may be reckoned here, but we shall only speak of the cases in cyclic
flowers where all the members are concrescent with one another or with
the other members. It only rarely happens that there is an actual con-
crescence or growing together—the latter, for example, in the anthers of the
Compositae. More commonly the concrescence is ‘congenital.’ What
takes place has been already explained *, and one need only repeat that the
concrescence occurs in different degrees. We may regard as the original
condition that in which there is no concrescence and the several neighbouring
primordia of leaves develop free from one another. A concrescence begins
if they are raised upon a common usually annular base. The last stage
is that where, for example in the corolla of Cucurbita, the single primordia
are no longer separate. It has been a matter of dispute with regard to the
concrescence of the leaf-whorls in many cyclic flowers how far the flower-
axis shares in the construction. I may therefore here recall that the
differentiation of leaf and axis is usually not prominent in the flower; it
would therefore be incorrect to apply a scheme derived from the vegetative
organs to the interpretation of the flowers and to imagine that axis and leaf
must be separated sharply in the flower, and that one must accurately
recognize what belongs to the one and what belongs to the other. This
will be illustrated below, especially when speaking of the formation of the
ovary. Here I may only remark that one can the more speak of the axis
sharing in the concrescence of different leaf-whorls with one another the
earlier this takes place.
(3) ARRESTS.
A flower may be reduced to a simple sporophyll terminal on the flower-
axis °, and in every large cycle of affinity we find the numerical relationships
changed by arrests, especially in the staminal whorl in which there is no
lack of transitions from complete construction to abortion. The series
which have been constructed regarding flower-formation in the Angiosperms
are exclusively reduction-series*. Here a few examples will be given of
(1886). See also the detailed work of my pupil Schaefer, Beitrage zur Entwicklungsgeschichte des
Fruchtknotens und der Placenta, in Flora, lxxiii (1890), p. 62.
TTSeelps 1530: Ba 7 ee Part, p.c52. 3 See Part I, p. 52.
* See Part I, p. 60. © ,jA particular Celakovsk¥, Das Reductionsgesetz der Bliithen, das Dédou-
ARRESTS 547
the more or less probable reductions which can only be regarded as correct
of we can give biological reasons for the reduction’. Hitherto botanists have
limited themselves almost exclusively to the purely formal side. If we put
on one side the causal standpoint into which it is quite impossible to enter,
there remains the dzo/ogical, that is to say, the question of the connexion of
the arrests with the function of the flower, and without doubt this is a very
complex one. We are concerned with not only the number of the stamens,
but also with that of the microspores and the relation of the number of these
to that of the ovules in which fertilization is to be effected as well as to the
method in which pollination is carried out. We have tried to show when
speaking of the Pteridophyta that the number of the archegonia is the
smaller the more the fertilization appears to be secured. A similar relation-
ship can certainly be often proved in the flowers of the Spermophyta.
In the anemophilous flowers of Monocotyledones the number of the
stamens is specially reduced in those which have by reduction only one
ovule in the ovary, for example most Gramineae and Cyperaceae. The
case of the Irideae where there are numerous ovules in the ovary, and one
staminal whorl is arrested, cannot be brought forward against this connexion
for there quite other relationships have to be considered—the whole flower
is specialized and adapted preferably to definite insect-visitations, the pollina-
tion is also made certain, and the formation of the inner staminal whorl
would be superfluous in view of the whole scheme of the flower. The same
holds for the Orchideae and others. Flowers which are less sharply adapted
to special insect-visitors have more stamens than the specialized ones.
Amongst the Dicotyledones a comparison of the flower of Eschscholtzia
with that of the Cruciferae may be made in order to illustrate the numerical
relationships of the stamens just spoken of. In Eschscholtzia there are
numerous stamens; in the Cruciferae there are only six; similar relation-
ships of position obtain in both cases. The Papaveraceae, to which
Eschscholtzia belongs, have pollen-flowers. The number of the stamens
is therefore caeteris paribus easily understandable because the pollen-
production will be all the greater the more stamens there are. The flowers
of the Cruciferae on the other hand have honey-glands, and as they do
not require to furnish pollen to the insect they produce less pollen than
Eschscholtzia. This relationship is clear; whether it is phyletic or not we
cannot say~. We should have ground for such an assumption in regard
blement und die Obdiplostemonie, in Sitzungsberichte der kéniglich béhmischen Gesellschaft der
Wissenschaften, 1894.
* This is a subject which the text-books of flower-morphology say nothing about.
* Cruciferae with more than six stamens are known, for example Megacarpaea, and there are
some which have less than six. The biological behaviour, especially in the first case, is unknown.
Perhaps they are in part pollen-flowers. In the Fumariaceae we can directly prove the reduction of
the ovules, and following upon this is the probability of a reduction in the androecium. See Goebel.
Nn2
548 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
to it if we could establish the probability that the forefathers of the
Cruciferae had pollen-flowers, and then along with reduction of the
staminal whorl passed over to the formation of honey-flowers. Such an
assumption will offer no difficulty to those who can see that nectaries simply
arise through the prodding of the insects into the flower. These, however,
are mere fancies which we leave out of consideration".
In the simple formal construction of arrests we must not rely upon
reductions, we have rather to seek to prove on the basis of biological
relationships the reductions which are assumed in consequence of the
morphological evidence. For this at present there are only small data.
In general too we have a somewhat safe basis for the assumption of arrest
only within families; the more we go beyond these the more insecure
becomes the ground for this.
Phenomena of reduction are abundant in the gynaeceum, and this has
been already pointed out, and it has been shown? that the object, namely
the diminution in the number of the ovules, is partly brought about by the
diminution in the number of carpels, partly by that of the ovules themselves;
in many cases both phenomena appear together.
B. INDIVIDUAL ORGANS OF THE FLOWER.
In what follows the several organs of the flower will be shortly considered,
all details which can be read of in systematic works being omitted.
(1) THE FLOWER-ENVELOPES.
The conformation and biological significance of the flower-envelope
are supposed to be familiar. So far as we know the biological significance
of the envelope is of a double character :—
(a) it protects the flower in the bud-stage ° ;
(2) it secures pollination.
The strengthening which the flower-envelope frequently receives through
an epicalyx, envelope of hypsophylls, and so forth, will be left untouched
upon. A few points only require notice :—
(a) MORPHOLOGICAL SIGNIFICANCE OF THE FLOWER-ENVELOPES.
The question of the origin of the parts of the flower-envelope has
exercised botanists from early times. When we proceed from the flowers
Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der Botanik,
iii (1884), p. 318.
‘ The case would be different if it could be shown that such glands in any one case developed
more in consequence of mechanical stimulus than without the stimulus, but such a case is at present
unknown.
2 Part Ioapeisoe
* See Ratiborski, Die Schutzvorrichtungen der Bliithenknospen, in Flora, Ixxxi (Erganzungs-
band zum Jahrgang 1895).
THE FLOWER-ENVELOPES 549
of the Pteridophyta and many Gymnospermae which have no special flower-
envelope, there are evidently two possibilities for the origin of the flower-
envelope of the Angiospermae :—
(1) Either it has arisen from the hypsophylls in the vicinity of the flower ;
(2) It has been formed either entirely or partially by the transforma-
tion of the sporophylls.
The latter view is supported by A. P. de Candolle, especially for the
corolla ', and many later authors have followed * him mostly without quoting
him. This explanation appears to me to be well founded in a number of
cases, as is also the view that the outer portion of the flower-envelope, the
calyx, has proceeded from hypsophylls. The conclusion is arrived at, as
de Candolle showed, from the fosition of both structures, not from the
colour; the calyx can, as is known, be petaloid. One must never forget,
however, that here as elsewhere in the plant kingdom the same result may
come about in different ways.
It must suffice to put forward as examples some cases from one family
—that of the Ranunculaceae*—-which on account of their instructive
relationships have been frequently used for illustration of the question under
discussion :—
Anemoneae. As a starting-point we may consider a flower which has a simple
petaloid flower-envelope and numerous stamens and carpels. Such a flower occurs,
for example, in the Anemoneae. In them the number of the leaves which form the
flag-apparatus is not constant, because frequently the outermost stamens are trans-
formed into petaloid leaves*. The simple petaloid envelope of the Anemoneae we
consider to be the result of the transformation of stamens, but within the same group
other organs may be formed out of the stamens. The outer stamens are transformed
into nectaries in Anemone Pulsatilla where there are all transitions between the
normally constructed stamens and the nectaries at the base of the androecium, which
nectaries still have the conformation of the stamens: normal stamens with four
pollen-sacs*® whose filament is shortened ; stamens with only three or two pollen-sacs ;
1 A. P. de Candolle, Théorie élémentaire de la botanique, Paris, Ed. 1, 1823, Ed. 3, 1844.
See also Considérations générales sur les fleurs doubles et en particulier sur celles de la famille des
Renonculacées, in Mémoires de Physique et de Chimie dela Société d’Arcueil, iii (1817), p. 394. ‘As
I have shown in my ‘“‘ Théorie élémentaire ” the petals are merely the outer stamens which in the
natural state of things are transformed into plates or into horns.’
2 In recent times Celakovsky, Uber den phylogenetischen Entwicklungsgang der Bliite und iiber
den Ursprung der Blumenkrone, I und II, in Sitzungsberichte der kéniglich bodhmischen Gesell-
schaft der Wissenschaften, 1896, 1900, has in an extreme manner supported this. He derives all
perianth-leaves as well as the foliage-leaves from transformed sporophylls. How plants with non-
assimilating sporophylls can exist is difficult to understand.
3 The following account conforms in all essential points with that which I gave in 1886. See Goebel;
Beitrage zur Kenntniss gefiillter Bliithen, in Pringsheim’s Jahrbiicher, xvii (1886). Subsequently
other authors have also expressed the same view.
* See what is said about Anemone Hepatica, Part I, p. 177.
5 See also Familler, Biogenetische Untersuchungen iiber verkiimmerte oder umgebildete Sexual-
organe, in Flora, Ixxxii (189€), p. 149.
550 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
and as a final stage stamens in which the pollen-sacs are entirely suppressed. If we
imagine that these nectariferous staminodes have a pit upon their upper surface
we are on the road to forms such as are found in Trollius, Helleborus, and elsewhere,
and finally to the nectariferous petals of Ranunculus. But in some forms of the
Anemoneae another series of transitions runs alongside of this one. In the Pulsa-
tilleae, Anemone nemorosa, and others, the flower-bud is surrounded by three foliage-
leaves which elsewhere pass over into hypsophylls, experiencing at the same time a
reduction of their segmentation’. In Anemone Hepatica the internode between these
entirely calyx-like leaves and the flower is not elongated as it is in the other species
of Anemone mentioned, and the zzvolucre has become actually a calyx. This calyx
may now itself become petaloid, but it shows through many interesting transitions its
relationship with hypsophylls.
Trollius europaeus. The same is the case in Trollius europaeus. Its flower
is surrounded by a number of yellow-coloured leaves which are mostly unsegmented,
and are distinguished in that way from preceding
hypsophylls. An examination of a large number
: of flowers brings to light transition-forms which
mae show that the outer flower-envelope consists of only
) specially constructed hypsophylls, the whole having
1. Ze. Eis
come to pass in the same way as in Astrantia*. These
transition-forms * have still at their apex indications
Fic. 360. Trollius europaeus. Three 5 3 i
leaves Showing transition from hypso- Of the segmentation of the foliage-leaves (Fig. 360),
phyll to outer flower-envelope. They 2 0
are yellow, with the exception of the aS well as a tinge of green colour whilst the greater
lottéd area which contains chlorophyll. ;
ess ares ec a ae ee part of the leaf has become yellow. We shall con-
sider them as hypsophylls which have become an element of the flower and serve
thus both as a flag-apparatus and as a protection to the bud. Following them
we have the nectaries consisting of transformed stamens which correspond to the
corolla of Ranunculus, then we have the stamens, and then the carpels.
A flower-axis then which possessed originally sporophylls can attain to richer
endowment by :—
(1) The hypsophylls in the vicinity of the flower entering into its service,
forming themselves into a ca/yx, as in Anemone Hepatica, and at the same time be-
coming a flag-apparatus.
(2) The outermost stamens either forming only a flag-apparatus, as in many
Clematideae, for example Atragene alpina, or becoming nectaries, as in Anemone
Pulsatilla, or becoming structures which serve both as a flag-apparatus and as
‘ See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884), p. 288, Fig. 61, of Anemone stellata.
* See p. 395-
* These are also found in the terminal flower of Gentiana asclepiadea. We can there follow how
the two uppermost foliage-leaves are, as it were. drawn into the formation of the calyx. Not infre-
quently one of them is only partially united with the calyx-tube, and shows then a widened sheath-like
basal portion, whilst the apex of the calyx-tube corresponds to the lamina of a foliage-leaf.
There are to be found, if one examines a large number of plants, all transition-stages from
flowers which are sharply shut off from the vegetative shoot to those which ‘gradually pass
into it.
THE FLOWER-ENVELOPES 551
nectaries, as in Ranunculus and also in Trollius, where, however, the relatively small
nectaries in spite of their orange colour can scarcely be considered as a flag-
apparatus.
That in many other families, especially the Nymphaeaceae, Mesembry-
anthemum, the Zingiberaceae, the Candollean view fits well; and without
forcing of the morphological facts appears to me incontestable. In many
flowers indeed the stamens clearly act as a flag-apparatus with or without
loss of function, and our knowledge of double flowers tells us that the stamens
are transformed specially easily into petals. That this transformation can
take place in foliage-leaves also follows, not only from what has been said
about Trollius but also from what was said before about Nidularium |.
FACTORS INFLUENCING COLOUR AND SIZE. The colour ofthe flag-
apparatus of the flower, by which it differs so markedly from the vegetative
part, is purely an arrangement in relation to pollination. We find male and
female flowers which have a lively red colour in many Coniferae, for example
the spruce, although here the pollination takes place by the wind, and in
Musci frequently the same phenomenon is observed in the sexual organs.
It is therefore very probable that the feature of colour which so often
appears when the propagative organs are being brought forth has some
connexion with definite metabolic processes, although up till now we cannot
recognize what these are. It has been shown ” that the capacity for respira-
tion of the flower is greater than that of the green leaf-organs, whilst its
transpiration is less, but we do not know yet how this functional behaviour
affects the whole economy of the flower, nor what is the reason from the
purely physiological standpoint why in many flowers, for example those of
the Urticaceae, corolline organs are entirely wanting.
That the size of the corolla, and in many cases also the intensity of its
colouring *, is dependent upon external factors, especially upon the intensity
of light *, has been already pointed out, and it was shown that this is only an
individual illustration of the fact that the different developmental stages of
the plant are bound up with different external conditions, and that other
factors besides light have an influence upon the formation of flower®. Here
we shall only further say that the ‘unessentially zygomorphous’ flowers
1 See Part I, p. 10.
* Curtel, Recherches physiologiques sur la fleur, in Annales des sciences naturelles, sér. 8, vi (1897).
* The dependence of the intensity of the colouration upon light is not equally expressed in all
plants. Askenasy, Uber den Einfluss des Lichtes auf die Farbe der Bliithen, in Botanische Zeitung,
xxxiv (1876), has moreover shown that flowers of Antirrhinum majus and Digitalis purpurea, which
had developed on the shoots of plants deprived of their leaves remained white, and that therefore the
disturbance of nutrition affects the formation of colour.
* See Part I, p. 243.
5 G. Klebs, Einige Ergebnisse der Fortpflanzungsphysiologie, in Berichte der deutschen botanischen
Gesellschaft, xvii (Generalversammlungs-Heft Ig00), p. 201, has confirmed this. He found, amongst
other things, that the size of the corolla of Myosotis palustris was changed not only by feeble light
but also by too moist air or by too strong nutrition.
552 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
which we formerly described’ as they are found on the margin of many
inflorescences, that is to say those with unilaterally—outwardly—furthered
corollas, owe their conformation perhaps to the fact that the outer part of
the corolla has been the more intensely illuminated side in a long series of
generations, and therefore we have to deal most probably with an inherited
influence. It is at any rate of interest to note that we can produce quite
similar phenomena experimentally *. In Fig. 341 is shown an inflorescence
of Helianthus annuus. On it the ray-florets are developed unequally in
consequence of unequally strong illumination. If now we substitute for the
capitulum figured in Fig. 361, II, a single marginal flower of Scabiosa we
Fic. 361. Helianthus annuus. Capitulum grown in feeble unilateral illumination. The ray-florets on the feebly
illuminated side are smaller than on the side under stronger illumination. I, capitulum in vertical section. II, the
same seen from above. After N. J. C. Miiller.
obtain fundamentally quite similar configuration. Whether the analogy
here assumed is actual or only apparent can only be shown by experimental
investigation of the plants which from this standpoint possess ‘ plastic’
flowers.
(0) DIFFERENCES IN CONFIGURATION DUE TO DIFFERENCES IN DISTRIBUTION
OF GROWTH.
An account of the numberless differences in configuration of the flower-
envelope could only be given along with a discussion of their function and
will not be attempted, but there is one point of general importance which
may be briefly referred to, namely, that marked changes in form may
appear in the mature condition through relatively small differences in the
distribution of growth. This is a generally effective cause. I have
endeavoured to explain it in an example of the grass-inflorescence *, and
= bartles pens:
* See also N. J. C. Miiller, Handbuch der Botanik, i, p. 269. Curtel, Recherches physiologiques
sur la fleur, in Annales des sciences naturelles, gives us nothing essentially new. I may here recall
what was said about the unilateral construction of Hepaticae and Musci; see p. 77, note 4. In the
prophylls of some Dicotyledones I have recently found relationships of construction.
* Goebel, Beitrige zur Entwicklungsgeschichte einiger Inflorescenzen, in Pringsheim’s Jahrbicher,
xiv (1884).
THE ANDROECIUM 553
Sachs! has subsequently in his instructive manner illustrated it in the
development of the foliage-leaves.
With regard to the corolla, we may start from the primordium of
a radial pentamerous corolla of concrescent primordia as it occurs in many
dicotylous flowers. The concrescence depends, as we have seen, upon a dis-
placement of the growth. If each of the five leaf-primordia were to grow
into a free part, then we should have a choripetalous corolla. But the free
parts grow only insignificantly, the zone of insertion of the five primordia
grows strongly, and there arises the tube with the five teeth with which
we started. This develops further into a radial corolla such as we find in
Campanula, or into the tubular flower of some of the Compositae, if the sub-
sequent growth is chiefly upon the cup-like or tube-like basal portion, whether
this grows uniformly throughout or only retains a zone
of embryonal tissue, which is then usually at the base.
If, however, the zone below the teeth grows strongly,
then according to the course of this zone of growth
other relationships of configuration appear. Let us
suppose that the growing zone is below 1 and 2 in
Fig. 362 in the position of the dotted line there. This ;
runs left from 1 and right from 2 up to the indenta- sieage ser ecdepuration
: - . in a sympetalous corolla
tions which separate the two corolla-lobes, but it runs _ in consequence of differ-
: ‘ ent distribution of growth.
between I and 2 under the separating depression. If
now such a zone of growth occurred also below the lobes 3, 4, 5,a two-lipped
corolla must arise if the lobes 1 and 2 were early checked in their growth
—the conformation which the marginal flowers of the tubulifloral Com-
positae show; if the zone of growth touch only at one position upon the
separating depression, then we obtain the ‘ unilaterally split *’ corolla, which
is subsequently spread out flat, of the ligulifloral Compositae.
(2) THE ANDROECIUM.
The conformation ofthe microsporophyll is much more uniform amongst
the Angiospermae than amongst the Gymnospermae. In the Gymnospermae
the number of microsporangia is somewhat variable, even within one and
the same flower, for example in Juniperus, but in the Angiospermae the
number four predominates.
The pollen-sacs in the majority of cases run parallel with the length
of the staminal leaf, so that they correspond to the four angles of the
anther. By the growth of the connective the pollen-sacs may be pushed
towards the inner side (zz¢rorse) or to the outer side (extrorse) of the flower—
1 See Sachs, Lectures on the Physiology of Plants, English edition by Marshall Ward, Oxford,
1887, p. 506.
2 That this expression is not literally correct is clear from the description that is given.
554 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
changes which have an intimate relationship to the manner in which
pollination is effected. There are, however, cases in which the anthers have
two pollen-sacs above and two below, as in the Laurineae, but I do not
know whether this is the result of a displacement taking place in the course
of the development. Where there are deviations from the number four in
the microsporangia we can refer them back to this type by the following
assumptions :—
(a) Division of the anther.
(2) Arrest or suppression of pollen-sacs.
(c) Confluence of pollen-sacs.
(Zz) Division of pollen-sacs by sterile plates of tissue.
The following are illustrations of these :—
(2) Division of the anther. This scarcely requires an explanation. It is
found in Betula, Althaea and other Malvaceae, and in Salvia along with sterilization
and transformation of one anther-lobe.
(2) Arrest or suppression of the pollen-sacs. In the case of the
Asclepiadeae ' only the pair of anterior sporangia are developed. The arrest of the
posterior pollen-sacs is evidently connected with the peculiar construction of the
stamens. Arrest also occurs in the Marantaceae, where one-half of the stamen has
become petaloid.
(c) Confluence of pollen-sacs. We have seen confluence in Juniperus
amongst the Gymnospermae, and its occurrence in the Angiospermae is less striking
because the microsporangia are less independent than they are in the Gymnospermae.
This confluence may take place by the subsequent breaking down of sterile tissue,
or by the development of fertile tissue in places where otherwise sterile tissue
should be.
Which process takes place in the Orchideae where confluence occurs, for instance
in Stanhopea, Gongora, Trichopilia, I do not know, but it seems to me probable that
it is the second one. This can only be determined by an examination of the
development. It is probable that the body possessing two annular pollen-chambers in
the middle of the flower of Cyclanthera has arisen by simplification of an androecium
which consisted of five stamens, each having two horizontal chambers between which
sterile tissue was no longer formed '.
(2) Division of pollen-saes by plates of sterile tissue. This process isa more
frequent one and will be referred to again when the formation of sporangia is discussed
“ See Engler, Beitrage zur Kenntniss der Antherenbildung der Metaspermen, in Pringsheim’s
Jahrbiicher, x (1876). With regard to the Cucurbitaceae see the description in the text on p. 539.
The convolution of the pollen-sacs makes possible an abundant formation of pollen, notwithstanding
the halving of the anther. The convolution is greatest where the need of pollen is greatest, that is
to say, where there are many ovules.
* Whether one should consider these anthers as affendicuday and arising out of concrescent leaves,
or as axza/, seems to me little more than a matter of words. The question only is how they have
been derived. It is clear that in their inception there can be no separation into axis and leaf.
THE ANDROECIUM 555
It is found along with the ‘normal’ formation of anthers in different families, for
example, amongst the Onagrarieae, in Clarkia where there are four to five chambers,
in Gaura biennis where there are six chambers, whilst in Epilobium and Oenothera
and others there is only a single chamber. The occurrence of chambering in
different cycles of affinity appears to me important, because here a derived, not an
original, character lies before us, and its biological significance corresponds evidently
to that of the ‘trabeculae’ in the sporangia of Isoetes'—by the formation of these
sterile plates of tissue the nourishment of the sporogenous cell-complex is facilitated.
We find this construction therefore, as might be expected, especially in massive broad
and long anthers, for example in Rhizophora (Fig. 363).
TRANSFORMED STAMENS. That the stamens of many flowers expe-
rience a transformation along with a
change in function will be evident from
what has been said regarding the Ra-
nunculaceae?, with which many others
might be associated. In many cases
the function of the transformed or de-
formed stamen is not known, as for
example in Boronia and Cassia. At
any rate there is between transformed
stamens and stamens which are de-
formed * in the course of their normal
development no sharp limit.
(3) THE GYNAECEUM.
The enclosure of the megasporan-
gium within a chamber—the ovary—
is a characteristic feature of Angio-
peeeeeg ihe manner im which this +; 3m 7c¢, Risener mucronate. | Flower in
comes about has given rise to much spofangia.f, in she anther; s, spongy tsaue under
discussion. The differences of inter-
pretation are a consequence partly of the peculiarities in the development
of this organ, which have not been always clearly appreciated, and to which
reference will be made presently, but they are also in great part purely
differences in the use of words. The essential points in dispute are to
what extent the carpel (megasporophyll) and the flower-axis (torus) share
respectively in the construction of the gynaeceum, and in particular what
is the correct interpretation of the placenta. Comparative morphology,
starting from the behaviour of the Cycadaceae, where the foliar origin of
See p. 604. 2 See p. 549.
* See Familler, Biogenetische Untersuchungen iiber verkiimmerte oder umgebildete Sexualorgane,
in Flora, Ixxxii (1896).
556 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
the ovules is evident, as well as from other cases, and particularly from
conditions of phyllody, endeavoured to prove that the placenta and there-
fore the ovules were everywhere the products of the carpels’, and to maintain
this it was necessary to assume concrescence and unions which were
altogether hypothetical. The history of development appeared to lead to
quite other results. Payer, for example, believed that the placenta should
be interpreted always as an axial organ’. There were no less differences in
the views upon the nature of the inferior ovary and other questions.
An attempt has been made above to show that the flowers are indeed
derived from vegetative shoots, but that in consequence of their whole con-
struction a number of deviations from the behaviour of purely vegetative
shoots show themselves. It would be, therefore, incorrect to endeavour
to find the scheme of segmentation of the vegetative shoots without
modification in all the relationships of configuration of the flower, and to
consider the flower—at least in idea—as being based upon this scheme.
Every explanation must, in the first instance, closely fit the individual
facts. We have here, as in other cases, to construct a picture after com-
parison of all the observed phenomena as they actually occur, or, to speak
more accurately, to arrange the manifold phenomena in series, but we shall
gain little if we still read into the terminal member of a series its beginning
stages. We shall do better if we admit that nature steers straight forward
to its end, and in consequence takes short cuts, the evolution of which we
can to a certain extent follow by comparison. We may recall the instructive
case of the microsporangia of Juniperus amongst the Gymnospermae,
which, originally clearly leaf-borne, finally become axis-borne by reduction
of the sporophylls at the end of the flower. There is, indeed, still a remnant
of the sporophylls existing, but things would be little changed were it too
to disappear and the sporangium were to spring directly from the flower-
axis. The interesting point in this is not the fact that the sporangium,
which arises in the ordinary case on a sporophyll, has here at last taken
up a position on the flower-axis, but the tracing of the path by which this
axial position has been acquired. Hitherto morphologists have considered
leaf-borne and axis-borne organs as having a different ‘ morphological
value,’ and have therefore endeavoured to avoid tracing to the same place
of origin organs which in their other peculiarities appear as evidently
similar. To me the place of origin is more or less a subordinate point,
as I have several times said—everything else can change, so also can this.
What we should endeavour to find out is the method and manner of oz
the change has taken place, and—what is a much more difficult but also
1 See especially Celakovsky, Vergleichende Darstellung der Placenten in den Fruchtknoten der
Phanerogamen, in Abhandlungen der kéniglich bohmischen Gesellschaft der Wissenschaften, Folge
6, viii (1876).
* Payer, Traité d’organogénie comparée de la fleur, Paris, 1857, p. 728.
THE GYNAECEUM 557
a much more stimulating question—the covditions under which it has been
completed. In Juniperus, as we have seen, we had to deal with a shorten-
ing in the development. Such shortenings are found in predominant degree
in the construction of the gynaeceum of the Angiospermae. Whilst we may
in regard to it start from cases where the phenomena as we know them of
the vegetative shoot and the flower of the Gymnospermae are still perceptible,
the carpels are sharply marked off from the axis and produce the ovules
either on their concrescent margins or on their surface; at the end of the
series we shall find cases in which the differentiation not only of the carpels
from the flower-axis, but also of the ovules from the carpels, is entirely
suppressed. Such a case will be mentioned when speaking of the ovules
in Balanophora. Should we endeavour to read into them our scheme? Are
we to expect nature to adjust itself to our abstractions, or is it not rather
the right way to adapt our opinions to its innumerable changes ?
: 5
ax ie) |
h\, @
Nea t e
FiG. 364. Scheme of the development of the ovary in many Angiospermae with formation of the sole. 1-5 in
longitudinal section. 6-7 in transverse section. a, apex of the carpel; 4, the sole.
a.
The shortenings which we can recognize in the formation of the ovary
are specially the following :—
(a) The differentiation of axis and leaf is at different stages only slightly
marked, because the area of the vegetative point of the flower is often
entirely used up by the carpels.
(2) Concrescent parts appear from the beginning i in combination with
one another, instead of subsequently uniting.
(c) This is not only true of the combination of many carpels with one
another, but also for each single carpel itself. The chamber which a single
carpel has to build is relatively seldom formed by the union of originally
free margins; much more frequent is it that the carpel develops like
a peltate leaf, only without a stalk; that is to say, there appears upon the
upper side of the carpel a depression very like what is found in the forma-
tion of a tubular leaf of a Sarracenia, and then this deepens. One part
corresponding to the apex of the carpel (Fig. 364) grows most strongly ;
it forms the style where that exists, and the stigma. The other may be
called the sole of the carpel. It is continued upwards on the margin of
the carpels, and is so placed that the margins have not separated here from
558 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
one another. At this point, especially where their number is reduced, the
ovules are by preference formed—a phenomenon which may be connected
with the fact that the most protected place to be found is in this basal pit.
If only one ovule is found here, it takes up a median position, whilst higher
up the margins of the carpel are the positions of origin}.
The gynaeceum forms originally the terminal structure of the flower.
Its position is more or less early changed in perigynous and particularly in
epigynous flowers. The history of development and comparison show us
how this process comes about, and that there is no essential difference
between the structure of the gynaeceum in hypogynous and epigynous
flowers. Transition-forms between these are also known. It will, however,
be more instructive to deal with these two kinds of flower separately.
Terminology. The expressions monomerous, dimerous, polymerous, referring
to the number of the carpels, explain themselves. By afocarpous we designate a
gynaeceum in which the several carpels
are not concrescent with one another,
and by syncarpous one in which two
or more carpels are united to form
one ovary. I think it is useful to add
the expression paracarpous to indicate
ovaries whose carpels are joined to-
gether by the margins only —their
position corresponding to that of the
leaves in valvate aestivation—as in
FiG. 365. Erythraea pulchella. 1, flower-bud in trans- Dionaea and Primula ; the term a dae
verse section. The two carpels of the gynaeceum in the carpous would then be retained for
middle touch by their edges, but ovules are not yet formed.
II and III, older gynaecea in transverse section. The gynaecea in which the carpels are
carpels have curved inwards more conspicuously and have =)
produced ovules on their zzderx surface. Magnified. united by their outer surfaces.
OVULES ON THE UNDER-SURFACE OF CARPELS. The ovules may
arise at different positions upon the carpels, chiefly on their margins, which
are often greatly swollen, but they also occur upon the upper-surface, as in
Butomus and Cabomba, and also upon the under-surface. Their occurrence
upon the under-surface is really not a rare phenomenon, and yet Celakovsky
has recently expressly denied it, and therefore I must say something about
it. There are syncarpous ovaries in which the margins of the carpel are
strongly bent inwards, but are only united over a relatively small surface °,
for example in Erythraea, where the ovary is composed of two carpels
1 See Ophioglossum, p. 481.
* Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), p. 432. Chauveaud, Sur l’insertion dorsale des ovules chez les Angiospermes,
in Comptes Rendus de Académie des Sciences de Paris, cxiv (1892), p. 142, subsequently came to
the same result for the Asclepiadeae and Apocynaceae. See alsozA. Braun, Die Frage nach der
Gymnospermie der Cycadeen erlautert durch die Stellung dieser Familie im Stufengang des
Gewachsreichs, in Monatsberichte der Berliner Akademie aus dem Jahre 1875, p. 352.
THE SUPERIOR OVARY... APOCARPY 559
which become concrescent at a relatively late period. Their inturned
margins bear the ovules upon the under-surface, and upon the margin
(Fig. 365, I] and III). It is evident in the figure that the incurving of the
margins of the carpel increases in course of the development, and analogous
cases are found elsewhere. With regard to the question which position of
the ovules—whether marginal or surface—is to be considered the primitive
one, I can only refer to what has been said in the case of the sporophylls of
the Filicineae and Gymnospermae. These are questions which at the
/present time we cannot expect to solve with certainty.
(2) THE SUPERIOR OVARY.
l. The Apocarpous Gynaeceum.
The simplest case is that of an ovary formed from a single carpel
which, originally open, grows together later at the margins, and bears the
ovule on the concrescent margin.
Papilionaceae. We have this in the Papilionaceae. In them the
single carpel arises in the form of a horse-shoe shaped primordium in-
vesting one side of the flower-axis before the whole of the stamens are laid
down, and gradually the primordium encloses the whole apex of the axis in
the same way as does the primordium of the leaf of a grass. The growth
is always furthered upon the side where originally there was the most
prominent part of the primordium. Ata later stage! the carpel appears in
a form which Payer aptly compares with a sack slit upon one side; the slit
is formed by the margins which have approached one another, but are not
yet concrescent. The ovules sprout from these leaf-margins and form then
two rows opposite the middle line of the carpel; and as the edges later
become completely united, the pod of the Papilionaceae is produced, which
primarily is unilocular, and only in a few species is divided by growths
from the inside of the carpel throughout its length in Astragalus, or at right
angles to its axis in Cassia Fistula—a phenomenon which is not uncommon
in other ovaries.
Numerous monomerous ovaries are found in many Rosaceae and
Ranunculaceae.
Rosaceae. Amongst the Rosaceae, of which the tribe Dryadeae will
be specially kept in view, the flowers are perigynous, that is to say, sepals,
petals, and stamens stand upon a cup-like zone of the flower-axis, which
invests the terminal conical portion of the same axis which bears the
carpels. The carpels arise from this conical portion of the flower-axis in
numbers, and the first of them appears, for example in species of Rubus.
always before the stamens are all laid down upon the cup-like zone.
? Vicia Faba was used as a subject of investigation.
560 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
A single carpel of Geum! or of Rosa has at first the form of a hemi-
spherical papilla, which becomes flattened in its further growth, and takes
on the form of an ordinary leaf-primordium. The surface then becomes
concave, the margins approach one another, a considerable elongation takes
place, and the margins close together as in the cases already described ”.
But at the same time the basal part of the leaf—the sole—is raised
upwards*, With this we observe here, as in other cases, a reduction in the
number of the ovules: the Spiraeeae have still numerous margin-borne
ovules ; in Rosa there are two ovules, which spring immediately above the
lower sack-like portion of the carpel; in Geum one of the two ovules
regularly aborts very early, or its formation may be entirely suppressed,
and then the one that is left assumes a nearly median position, and stands
then immediately above the lower sack-like portion of the ovary, which
develops par? passu with its further development.
Ranunculaceae. A similar process—reduction of the ovules to
one and its adoption of a median position—may be observed in the
Ranunculaceae. The carpels of Ranunculus and Myosurus are spirally
placed upon the conical vegetative point of the flower. Each produces
one ovule. The carpel is concave upon its upper surface as it is in Rosa
(Fig. 364, 2), then it becomes cap-like, and the originally free margins
approach one another and subsequently coalesce. Immediately below the
position where the concrescence begins the ovule arises, in Ranunculus
apparently in the axil of the carpel*, but really, as‘the case of Anemone
specially shows, it arises upon the surface of the carpel, from indeed its sole,
immediately below the middle of the split limited by the two concrescent
carpel-margins. If the ovule is not clearly limited from the sole of the
carpel it appears in longitudinal section as the direct prolongation of
this, and therefore gives the impression of being axillary, and was formerly
partly so described. Other Ranunculaceae, like Clematis calycina °, possess
besides this median ovule two others upon each carpel-margin—a transition
to the behaviour of Helleborus, where, as in the Papilionaceae and
Spiraeeae, there are numerous marginal ovules in each carpel. The
cap-like hollowing out or formation of the sole of the carpel follows
exactly the same course as that in the construction of the horned petals
of Delphinium ®, where a concave excavation of the upper side takes place
along with the appearance of a transverse cushion at the base of the petal,
quite as in the formation of the tubes of Utricularia or of the petals
transformed to nectaries of Helleborus.
' See Payer, Traité d’organogénie comparée de la fleur, Paris, 1857, p. 502, pl. c; also Warming,
De Vovule, in Annales des sciences naturelles, sér. 6, v (1878), p. 181.
* See also Payer, op. cit., pl. c, Fig. 15. 3 See the definition upon p. 557.
* As seen in longitudinal section. 5 See Payer, op. cit., p. 253, pl. lviii, Figs. 18 and 19.
6 See Payer, op. cit., pl: lv, Figs. 20-27.
THE SUPERIOR OVARY,. -APOGARPY 561
More correctly than in the Ranunculaceae we can speak in some
other apocarpous gynaecea of ovules which apparently spring from the
flower-axis and are axillary to the carpel’. Fig. 366 furnishes us with
an instructive example. Both in Ailanthus and in Coriaria five carpels
are laid down beneath the broad flattened vegetative point.
Ailanthus. The carpels of Ailanthus show the formation of a cap
as do those of Ranunculus (Fig. 366, 2). At s we have the carpellary
sole, above this a broad quadrangular split which is closed subsequently
by the concrescence of its edges (Fig. 366, 3). That the split, as
in the Papilionaceae, is not prolonged to the point of the carpels does
not depend upon the fact that a process analogous with the formation
of a sole takes place, but upon the strong development of the surface
Fic. 366. 1-3, Ailanthus glandulosa: development of ovary; s, sole of the carpel; s%, ovule. 4-5, Coriaria
myrtifolia; za, sepal; ~, petal; sa, stamen; cf, carpel; the ovules arise as in Ailanthus in front of the middle of
the carpel, but no sole is perceptible.
underneath the carpellary apex. The carpel sits here upon the flower-axis
with a broad base, as in Ranunculus, and consequently in longitudinal
section it has the appearance as if the carpellary sole (s in Fig. 366, 3)
is itself a sprout from the flower-axis, but the process is, as accurate
tracing of the history of development shows”, quite like that in Ranunculus,
only the separation between carpel and vegetative point of the flower-axis
is less sharp.
Coriaria. In Coriaria, on the other hand, this process proceeds still
further. The carpellary sole is not differentiated in longitudinal section
1 That Payer’s view is also here untenable I have already shown. See Goebel, Vergleichende
Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der Botanik, iii (1884), p. 432.
2 See Schaefer, Beitrag zur Entwicklungsgeschichte des Fruchtknotens und der Placenten, in Flora,
Ixxiii (1890), p. 69.
GOEBEL II re) oO
562 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
from the vegetative point of the flower, yet the investigation of the history
of development would doubtless show here also that it arises as a portion of
the carpel in the same way as in Ailanthus, but it grows up together with
the vegetative point of the flower so that a separation of the two does not
appear. We can of course imagine a purely ideal limit running up between
them, as is shown in Fig. 366, 5, by shading of the carpel to the left’. The
origin of the ovule is here the same as in the cases mentioned above.
The same origination is valid in cases where only one carpel exists and
in its origin uses up the substance at the vegetative point at the apex.
This is the case in Gramineae where, however, the ovule has been considered,
though incorrectly, as springing out of the vegetative point of the flower ;
the formation of the carpel and the fact that the ovule is displaced later
upon the lateral wall of the ovary both point to its belonging to the carpel
in this family.
2. The Syncarpous Gynaeceum.
In different families we find not only forms with apocarpous ovaries,
but also those in which the ovaries are syncarpous, and there are transitions
between them. We must first of all distinguish two categories of the
development of the syncarpous ovary :—
(2) That where the apex of the flower-axis does not share in the
development ;
(2) that in which the apex of the flower-axis does share.
The two categories are not sharply separable, as we see in those ovaries
where the lower part belongs to the first category, the upper to the
second category. In the following a few examples only will be given to
illustrate some of the great variations in the processes concerned here.
According to the area of the torus which is occupied by the carpels
the placentation is different :-—
1. If the carpels in their origin from the torus use it all up amongst
them we obtain a bilocular or plurilocular ovary which bears the placentas
upon the septa.
2. If a middle zone of torus is left over which remains behind in
esrowth there arises a unilocular ovary with parietal placentation.
We shall speak of the first case to begin with because the latter
one connects better with cases where the axis shares in the formation
of the ovary.
(1) THE SYNCARPOUS SUPERIOR OVARY WITH SEPTAL PLACENTATION.
(a) The Flower-axis does not share in the Formation.
Acer. We may start from a case like that of Acer which has been
already mentioned and figured*. The carpels use up entirely the vegetative
* Payer’s figures tell us nothing on this point. 2 See p. 541.
THE SUPERIOR OVARY. SYNCARPY 563
point of the flower, and upon the upper side of each arises the depression
already spoken of. Thus from the first there is a bilocular ovary whose
septum is produced by the non-separation of the two carpels at their base,
or rather by their common growth together upwards. This behaviour can
be seen, mutatis mutandis, in other plants such as the Boragineae and
Labiatae. In each chamber two ovules only arise.
Solanaceae. Scrophularineae. The process is exactly the same where
we have in each loculus a many-ovuled placenta developed, as in Solanaceae
and Scrophularineae!. The ovary in its upper part is unilocular with two
parietal placentas, and the process of development is quite the same as that
in Acer*; the carpels use up entirely the torus, and form to a certain extent
a double sole, the septal wall. The margin of the cup of the ovary shows
an increased growth at the points corresponding to the apices of the carpels,
and the lateral parts raise themselves somewhat at the position of con-
crescence, and there form the parietal part of the placenta.
Beyond this the question of how far the flower-axis is drawn into the
Fic. 367. Ovaries in transverse section. 4, Lobelia. 2B, Diapensia. C, Rhododendron. J, Passiflora. pA,
placenta; sa, ovule. After Le Maout et Decaisne. Lehrb.
formation of the ovary is of quite subordinate importance *, yet there are
some examples of septal placentation in which the axis shares which deserve
notice.
(6) The Flower-axis shares in the Formation.
We shall specially refer to the cases of Oxalideae and Caryophylleae.
Oxalis. In Oxalis stricta (Fig. 368) the five carpels arise in a whorl
around the broad flattened apex of the flower-axis, but they do not use this
up entirely. Each carpel shows also here the formation of the sole, but the
flower-axis from which the sole is not separated grows up with it. In this
way there is produced a quinquelocular ovary to which the upper free
* See Fig. 367, A, which, although it represents the transverse section of an inferior ovary,
shows the same placentation. I formerly supposed that there was a sharing of the axis in these
families, misled by the incomplete and therefore incorrect statements of Payer.
* Schaefer has proved by the history of development that this, which I had conjectured, is the case.
* Even allied forms may, as it appears, behave differently, as we see, for example, in the
Caryophylleae.
O02
564 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
portion of the carpels forms the style. A transverse section through the
lower part—the ovary itself—shows then a central axis on which the
margins of the carpel are set, and they remain united with this central axis,
and at the position of the union there run in each loculus two longitudinal
cushions, the placentas. Doubtless these latter correspond each to a
marginal part of a carpel which has, however, not separated itself from
the tissue of the vegetative point of the flower’. The process in Impatiens
and elsewhere is similar.
Caryophylleae. In Caryophylleae, like Lychnis, Malachium, Silene,
and others, we have the same. The so-called ‘free central placenta’ of
these forms arises because the septa are early broken down. As Van
Tieghem says*, ‘one sees then how great is the mistake of the organo-
grapher who recognizes in this complex column only a simple axis which
will produce the ovules on its surface. Much more correct is the view,
which is supported by the history of development *, that the placentas
correspond to the margins of the carpels united with the axis. In this large
family, however, there
are transitions from
the condition in which
the vegetative point of
the flower is entirely
used up for the forma-
tion of the carpels to
those where the flower-
coerce ehteeg eae ee ae ee eed
on the flower-axis, aa, to which they are subsequently united. ively large portion,
and is distinguished
anatomically by special vascular bundles. It is easy to understand that a
long massive column in the middle of the ovary which stores up material
for the development of the seeds must be specially constructed anatomically.
At the same time the question whether the flower-axis shares in the forma-
tion of the ovary or not is by no means of first-class importance.
(2) THE SYNCARPOUS SUPERIOR OVARY WITH PARIETAL PLACENTATION.
Here the vegetative point of the flower remains at the base of the cup
of the ovary; the placentas do not reach it (Fig. 367, D), and they appear
1 Anatomically speaking, the axial tissue in Oxalis stricta does not appear. The bundles which
run in the central column of the ovary belong to the margins of the carpel in the sense given above.
* Van Tieghem, Recherches sur la structure du pistil, in Annales des sciences naturelles, sér. 5,
ix (1868), p. 181.
* See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884), p. 372; G. Lister, On the Origin of the Placentas in the Tribe Alsineae of the
Order Caryophylleae, in Journal of the Linnean Society, xx (1883), p. 442; Schaefer, Beitrag zur
Entwicklungsgeschichte des Fruchtknotens und der Placenten, in Flora, lxxiii (1890).
THE SUPERIOR OVARY. SYNCARPY 565
therefore as projections from the wall of the ovary. One example will
suffice :—
Cistus populifolius. The carpels of this species (Fig. 369) are laid
down in the form of transverse cushions which approach one another some-
what, but at first are not connected together. In Fig. 369, 1, the ovary is
shown already in the form of a cup with five angles, whose points indicate
the middle of the carpellary primordia, which have become raised up early
upon a common annular base. At those places which correspond to the
lines of separation between the several carpellary primordia upon the open
cup of the ovary, a thick longitudinal cushion appears upon the inner wall
of the cup; these are the placentas. The free margins of the several carpels
ending above at the angles of the cup of the ovary grow in many cases,
for example in Reseda and species of Hypericum, into as many styles,
in that the margins lay themselves together and so form the tubes of the
styles, and we thus have an ovarian cavity which is continued into many
FIG. 369. Cistus populifolius. 1, young flower seen obliquely from above: the ovarian cup is laid down with
five placentas; numerous stamens around it. 2, ovarian cup in vertical section: five placental cushions before
the inception of ovules. 3, older ovary in oblique profile: the upper part will become subsequently the style.
After Payer.
distinct styles. In Cistus this is not the case. The style-tube is formed by
the elongation of the upper part of the ovarian cup, and that it took origin
at the time of the formation of the five distinct carpellary leaves is shown
by the appearance upon its outside of the five stigmas (Fig. 369). The
placentas project inwards as cushions into the middle of the ovary, and
bear upon each side two rows of ovules. The ovary thereby becomes
incompletely quinquelocular.
An ovary which is laid down in this way as a unilocular one may
become plurilocular by different processes: in most Cruciferae by the
formation of a false septum through the union of two outgrowths from
the placentas; in the Geraniaceae the placentas bear ovules only in the
lower part of the ovary, in the upper part they grow together into a column
occupying the canal of the style from which the wall of the ovary is
subsequently thrown off in five valves, a process which is closely connected
with the distribution of the seeds.
566 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
3. The Paracarpous Gynaeceum.
Dionaea. Fig. 370 shows a transverse section of the lower part of the
ovary of this droseraceous genus from which we may start. There are five
carpels which are concrescent, and in such a way that their margins only are
in contact. Within this ovary we find an annular swelling which produces
ovules in serial succession from within outwards. As the longitudinal
section in Fig. 370, II, shows, this swelling belongs evidently to the carpels.
It represents the basal portions of the carpels which are xot separated from
one another. It is no longer possible to assign the ovules to the several
carpels to which they belong. The excavation in the middle (Fig. 370, A)
represents the remains
of the vegetative point
of the flower - mass
which is not devoted
to the formation of the
ovary. We can easily
derive this case from
the common one: no
infolding of the car-
pellary leaves takes
place here, but a para-
FiG. 370. Dionaea muscipula. I, young flower in transverse section- :
II, the ovary of a similar flower in longitudinal section. A, vegetative point CarpOus carpellary ring
rate False is produced in which
the united carpels raise up their base and bear the ovules.
Primulaceae. Lentibularieae. From this it is easy to derive the free
central placenta which we find in the Primulaceae, Lentibularieae, and others.
In them the differentiation of the placental portion of the carpels is sup-
pressed. The whole of the portion of the vegetative point of the flower
which is not used for the formation of the wall of the ovary is pro-
longed in the middle of the ovary. What now is this central placenta?
‘Orthodox morphology’ considers the central placenta as formed out of the
axis on which run up the basal portions—the soles—of the carpels, and
defends this interpretation very well against those who have declared the
placenta to be the continuation of the flower-axis alone. The anatomical
school, on the other hand, regards the placenta as formed from the carpellary
soles alone, because it is pierced by a system of conducting bundles, which
have their vascular portion turned outwards, and are connected with the
conducting bundle-system of the carpels. This condition, however, is by
no means general; where the placenta is weak, the supply of vascular
bundles is simplified. In Primula farinosa, for example, there is a simple
concentric strand in the middle of the placenta, and the same is the case in
THE SUPERION OVARY. PARACARPY 567
Androsace villosa and others’. From this we learn that the anatomical
structure gets its direction after the formation of the placenta, and is not
inverted ; in other words, the relationships of the vascular bundles are
determined by the claims of physiology, not by those of morphological
behaviour, and they require an explanation based upon the whole con-
figuration ; they themselves cannot give an explanation.
The view which has been put forward here may be stated in the
following way: in the free central placenta we should distinguish neither
appendicular nor axial parts. We have to do with a placenta which has
probably come about by a process like that which has been shown above
in the case of Dionaea, but which now exhibits a peculiar new formation
of the flower. Can orthodox morphology say where the axis begins and
where the carpellary sole ends? Must it still sing the old song that in
every development nothing really new occurs, but that there is only a
congenital union of the old? This gives us no insight into the processes
themselves. That in abnormal cases the placenta itself can elongate into
a shoot depends in our view upon the fact that the transformation of the
primordium of a foliage-shoot into a flower is a gradually completed
process, and if it be disturbed then the apex of the flower-axis can grow
further as a shoot. It is peculiar that in many Primulaceae, especially in
Soldanella, a process of the placenta stretches up into the style. Possibly
it shares in the conduction or nourishment of the pollen-tube. Biological
relationships which might make understandable the appearance of the free
central placenta are as yet unknown. That the free central placenta
contains as elsewhere substances which are used for the development of
the seed scarcely requires to be mentioned, as these are found in other
placentas.
(2) THE INFERIOR OVARY.
There are repeated here all the relationships of configuration which we
have learnt in connexion with the superior ovary, and in particular the
different kinds of placentation, as well as the condition that the vegetative
point of the flower is either entirely used up by the carpels, or that
a portion of it remains behind. On account of deficient historical investi-
gation, the view was formerly advanced that the ovary in the epigynous
flower is formed from the cup-like flower-axis, and the carpellary leaves
only produce the styles and stigmas. Comparative morphology has rightly
contradicted this interpretation, which, however, is still found in many books.
As the history of development shows *, the carpels share in the construction
1 Vidal, Recherches sur le sommet de l’axe dans la fleur des Gamopétales, These de Paris,
Grenoble, 1900.
2 Goebel, Zur Entwicklungsgeschichte des unterstandigen Fruchtknotens, in Botanische Zeitung,
xliv (1816), p. 729; Schaefer, Beitrag zur Entwicklungsgeschichte des Fruchtknotens und der
Placenten, in Flora, Ixxiii (1890).
568 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
of the ovarian cavity, and the ovules have no other origin than that which
is found in the superior ovary. It is common in all inferior ovaries that
the .vegetative point becomes at an early period more or less concavely
hollowed out, and that the leaf-structures of the flower sprout out partly
from the margins, partly from the inner surface of this depression. Whether
one describe the marginal part of the flower-axis as a ‘congenital con-
crescence’ of the different leaf-whorls of the flower is an arbitrary matter,
because the flower-axis ends its active existence with the bringing forth of
the leaf-structures of the flower’. The earlier the flower-axis assumes the
cup-like form, the more will we in general ascribe its character to the
flower-axis; the later this form is assumed, the more will its features
approach the more primitive condition as we find it in hypogynous
flowers. Where, as for example in many Cactaceae, the outer surface of
the inferior ovary is able to produce leaves and lateral shoots, we can have
no doubt about its axial nature; the flower-axis has here become drawn
into the formation of the ovary at a late period. In other cases, however,
this takes place very early, and then the axis appears, as has been said, to
pass right back into the leaf-structures of the flower.
(a) The Vegetative Point of the Flower-axis is not used up.
In the flowers of many Rosaeflorae we find transitions from perigynous
to hypogynous flowers, and amongst these we have the flowers of some
Pomeae.
Pyrus Malus. Fig. 371, 1-6, exhibits the development of the ovary of
Pyrus Malus. The flower-axis has already become cup-like in Fig. 371, I,
and the five carpels appear as papillae upon the hollowed-out inner surface.
They take up the whole zzzer margin of the cavity, but at the base there is
visible—and even at later stages it is so—the flattened vegetative point of
the flower, v. From now onwards we should have an ordinary perigynous
flower in which the carpels a/owe produce the ovary, if the shaded zone,
Fig. 371, 4, in one carpel to the right exhibited a strong intercalary growth
corresponding with the distribution of growth in the leaves of most angio-
spermous plants. But this is not the case. What happens is that the
ovarian cavity is formed by the growth of the zone, Fig. 371, 4, which is
shaded to the left?. This, however, involves both the flower-axis and the
base of the carpels which quite cover its inside. The ovarian cavity, which
is produced by the growth of the zone, is then clothed on the inside by the
carpellary leaves, and we need not be surprised therefore that the placentation
is quite the same as in the superior ovary. We have to deal here with
a common growth of the torus and the carpels*, and this is a widely-spread
+ And this is naturally expressed also in the anatomical structure.
* This is a further illustration of the fact that relatively small displacements of a zone of growth
may lead to great results. 5 See p. 5506.
THE INFERIOR OVARY 569
phenomenon in the vegetative shoots also, for example in the encrusting of
the shoot-axis in Chara, and in the formation of the leaf-cushions of many
Coniferae. We find the same in other investigated cases, and it is clear
therefore that the view that the carpels only form the styles is quite
untenable.
(0) The Vegetative Point of the Flower-axis is used up.
Umbelliferae. We may cite as an illustration of this the case of the
Umbelliferae (Fig. 371, 7-9).
The features that we have
seen in Acer are repeated
here, but they are complicated
by the fact that the carpels
are not free, but are united
on their outer surface with the
vegetative point of the flower.
The two soles of the carpels
upon which the ovules arise
are united with one another,
and they forma septum. In
each chamber are two ovules,
of which one—that turned up-
wards—is regularly aborted,
whilst the other develops
further. The ovules were
originally laid down at the
base of the ovary, but there-
after, by the further growth
in the young ovarian cavity,
were pushed upwards.
Valerianaceae. This
process takes place also else-
where, for example in the
Valerianaceae. In them we
find three carpels, and a tri-
locular ovary is laid down,
but there is an ovule in only
one chamber, and this cham-
ber is always much larger
than the others.
the style and the stigma.
,
pas ~
ste ls
Fic. 371. 1-6, Pyrus Malus. 1, young flower in longitudinal
section; v, vegetative point of the flower; 4 carpel. 2-5, older
stages of the same. 6, ovary in transverse section; 7, vegeta-
tive point of the flower; sa, ovule. 7, Eryngium maritimum.
Young flower in longitudinal section; S, vegetative point of the
flower ; sf, stamen; cf, carpel. 8, 9, Angelica sylvestris. 8,
Young flower in longitudinal section; s4:, sg, two ovules in
an ovarian loculus of which one directed upwards (sf: in right
loculus) aborts; sf incipient stamen; 4, axis. 9, young ovary
in transverse section; the ovules are parietal and arise in the
position which corresponds with the concrescent margins of the
carpels. They are subsequently carried upwards.
The two other carpels share only in the formation of
In Fig. 372, 7, a young flower of Valeriana
Phu is shown in longitudinal section.
A comparison of 7 and //7 shows
570 THE SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
at once how the stamens are concrescent with the tube of the corolla by
the further development of the zone which is marked x. The ovule,
s, is visible as a papilla at the base of the ovary. The flower-axis is
entirely used up by the carpels. In //7 the ovule appears to be pushed
somewhat upon the right side by a unilateral broadening of the base of the
ovarian cavity. Now the portion of the ovarian cavity lying below the
ovule grows. It is the portion between the dotted lines in Fig. 372, //, and
is marked y. The ovule must therefore be pushed up within the ovary, and
it hangs later downwards from the upper part of the ovarian cavity. Here
also we do not recognize the biological significance of this displacement,
but it is a step forward to have
se attained to this, that the different
Jie = forms of ovarian formation can be
(Ean A referred back to the different dis-
| i \ tribution of growth in the primor-
Nae Gl Ly dium of the flower, as this must be
SS y the point whence further investiga-
tion must take its start.
In what has been said only a
es brief indication of the construction
\ of the gynaeceum in the Angio-
9) spermae has been attempted. It
/ does not seem to be necessary to
iM enter here into the details of the
FiG. 372. Valeriana Phu. Flower in different develop formation of the style and Bema,
mental stages in longitudinal section. /, s, ovule still especially as these are expressly
very young; , primordium of style; c, calyx, rudi- 5 : :
mentary ; x zone in which corolla and stamens arise connected with the relationships of
together. J//, older flower; s, ovule; y, zone of growth A ‘ Se
pip eesti Aa into the ovary. 7/7 still pollination. A description also of
the changes which take place in
consequence of the fertilization in the flower and the formation of the
fruit must be passed over here, and a description of forms of fruit is beyond
the scope of this book. The relationships of the configuration of the ripe
fruits and seeds to their distribution have in the last ten years so often been
described comprehensively that there is no need for a further description.
BIOLOGY OF RIPENING FRuIT. Another problem, the biology of
the ripening fruit, that is to say the relationship between the formation of
the fruit and the life-conditions in their widest sense, has hitherto scarcely
received attention. I may say of it here only that in dry fruits frequently
arrangements arise which make possible a rapid transpiration, and conse-
quently a more rapid ripening. The great surface-development which
appears in these fruits is in marked contrast with the relatively small more
or less spherical form which is found in most fleshy fruits. Many arrange-
ments which have hitherto been considered merely as a parachute-apparatus
TRANSFORMED FLOWERS 571
on the ripe fruit are in my view to be considered as a transpiration-
apparatus for the ripening fruit, and these subsequently can be used for distri-
bution, but are not necessarily for this. Thus we have winged fruits which
open and do not fall, for example in Sophora tetraptera ; the lively red
and brown colour in many ripening pods of Leguminosae may facilitate
also the outgo of the water-vapour; and the same may be said of the
exposed lie of these fruits through which many become easily dried as
they hang down. Investigation of the anatomical relationships, and
experiment, can alone give us information upon these points.
C. TRANSFORMED FLOWERS.
It is a remarkable fact that a structure which is so peculiarly con-
structed and which is so markediy different from the vegetative shoot as
is the flower, should yet submit itself to certain transformations again.
As transformed flowers we consider all those which show a departure from
the function of producing at least a single sporophyll. Amongst them we
can reckon flowers which are only flags, and which no longer take any share
in sexual reproduction, such as we find in Compositae, Viburnum Opulus,
species of Hydrangea, Muscari botryoides, some Orchideae ; also the double
flowers mentioned above may be reckoned at least partly here. It has
been said! that probably phenomena of correlation have to be considered
here. The transformation mostly affects the corolla, but the flower-stalk
is involved in Muscari botryoides and Rhus Cotinus*. More peculiar are
the following cases :—
Sesamum indicum. In the flower-region below the normal flowers of
Sesamum indicum some flowers are transformed into glands. The primordia of
sepals, petals, and stamens are to be found usually still in them. The sepals are
small and inconspicuous; the petals have become secretion-organs, and appear
as thick, yellow, cylindric bodies*; the stamens have also become thick, club-like
secretion-organs. The primordium of the gynaeceum is usually entirely suppressed
or is only seen in the earliest developmental stages.
Trifolium subterraneum. In Trifolium subterraneum* the inflorescence
bores into the soil. It is protected against detachment by the primordia of the upper
flowers of the inflorescence being transformed into organs which anchor the
inflorescence. On the uppermost of the transformed flowers all the calyx-lobes are
present, whilst the other flower-parts are aborted. The further up the flowers stand
1 See Part I, p. 211.
2 For an account of the stages of development at which the transformation takes place, see Familler,
Biogenetische Untersuchungen iiber verkiimmerte oder umgebildete Sexualorgane, in Flora, lxxxii
(1896).
% See Familler, op. cit.
* See Warming, in Botanisches Centralblatt, xiv (1883), p. 157.
572 SPOROPHYLLS AND FLOWER OF ANGIOSPERMAE
the less are the calyx-lobes developed, and the uppermost flowers are only short,
thick, spherical, somewhat crumpled bodies, without a trace of leaves. But whilst
normal flowers possess almost no stalk these transformed ones have stalks as much as
two to four millimetres long. It is clear that we have here an instructive example of
a gradual transformation. An arrest of the flower-primordia at different stages of
development has taken place, and then a transformation in other directions. The
conditions of the new formation require experimental investigation.
|
|
THE ORGANS OF PROPAGATION
Our account of the sporophyte of the Pteridophyta and Spermophyta
has hitherto been concerned with the vegetative organs only, which as bearers
of organs of propagation may experience peculiar transformations—a pheno-
menon which we have also observed in the gametophyte of the Bryophyta.
The sforangia are the organs of propagation of the sporophyte.
Whilst in the Bryophyta the whole sporophyte is made use of in the
formation of spores, and with reference to its function therefore can be
designated as ove sporangium, the other Archegoniatae and the Spermo-
phyta devote only a relatively small portion of the whole plant to the
formation of spores, which arise in the special structures—the sporangia.
The possession of more or less large vegetative organs which may repeat
the spore-formation, often one year after another for a considerable time,
permits of the formation of a large number of spores. In the tree-ferns
there may be millions. That the pollen-sac and ovule (nucellus) in the
Spermophyta are merely sporangia is now generally recognized.
I propose to give here a short comparative account of the construction
of the sporangium, with special reference to the connexion between its
structure and its function.
I
THE SPORANGIUM
The function of the sporangium is twofold.
(a) to produce the spores ;
(2) to scatter the spores?.
Other organs of the plant besides the sporangia are involved in these
functions inasmuch as they furnish the necessary building-material to the
sporangia, and they bring them into a position which facilitates the sowing
of the spores. When speaking of the sporophyll this was pointed out.
Now in considering these functions we have to look at
(a) the construction of the sporangium in the mature condition ;
(4) the course of the development of the sporangia.
EMBEDDED AND FREE SPORANGIA. Sporangia may be embedded
or may be free”. Embedded sporangia are enclosed in the tissue of the
1 The sowing of the spores is not a function of the megasporangia in the Marsiliaceae, Salviniaceae,
and Spermophyta, nor of the microsporangia in the Salviniaceae and Marsiliaceae.
? As is the case with antheridia and archegonia, see p. 173.
574. SPORANGIA OF PTERIDOPHYTA AND SPERMOPHYTA
sporophyll. Free sporangia project beyond this, and are therefore provided
usually with a shorter or longer stalk, which during their youth conducts
the nutritive material and in the adult gives the sporangium a favourable
lie for the sowing of the spores. As transitions between embedded and
free sporangia, we have the unstalked sporangia of the Equiseta which,
with a broad base, sit on the sporophyll. Sporangia in Ophioglossum are
embedded; so also are the microsporangia of most Spermophyta. In the
Coniferae both types appear, as well as forms which may be considered as
transitions '. The embedding of the sporangia favours their nutrition. The
free position and the existence of a stalk favours the scattering of spores.
The tissue of a young sporophyll of Ophioglossum pedunculosum within
which the sporangia are sunk will be found to be gorged with starch, and
probably also other reserve-materials which are used up by the ripening
sporangia. Sporangia which throw out their spores are, so far as I know,
never embedded. The transition-forms between embedded and stalked
sporangia, as we shall presently see them in Botrychium, offer a subject for
our special attention, as they enable us to obtain some insight into the
origin of the stalk. We may ascribe it either to the sporangium itself or
to the sporophyll ; the question—to which of them—appears of itself to be
somewhat unimportant, but is of significance for a critical judgement on the
connexion between the several forms of sporangia, especially also for the
interpretation of the megasporangium of the Spermophyta. An attempt
will be made below to show that the history of the stalk is not the same
in all sporangia, but that the leptosporangiate Filicineae are specially dis-
tinguished from the eusporangiate Filicineae and the other Pteridophyta by
the formation of the stalk of their sporangium.
THE RELATIONSHIPS OF SYMMETRY OF SPORANGIA. The sporogonia
of the Bryophyta are constructed radially in by far the greater number
of instances. Where a dorsiventral form appears, as, for example, in
Diphyscium and some other Musci, we are able to trace it to a change
from the radial construction which begins earlier or later, and which
stands in relationship to the distribution of the spores, and is caused by
external factors, especially unilateral illumination. The sporangia of the
Pteridophyta are never radial, apart from those of the Salviniaceae and
Marsiliaceae, where, however, we must consider them as reduced structures.
Most sporangia are dorsiventral, as for example in Equiseta, Polypodiaceae,
Schizaeaceae, Osmundaceae, Lycopodium inundatum ; others are bilateral
or at least nearly so, as in most of the Ophioglossaceae and Lycopodineae.
We must inquire how far the relationships of symmetry of the sporangia
are related to the distribution of spores, and we shall show that such
relationships are very clearly visible in a number of cases where the
1 Embedded in Abietineae ; free in Cupressineae ; Equisetum-like in Araucaria and others.
B= )
SPORANGIA AND SPORE-DISTRIBUTION 575
conformation of the sporangium is asymmetric, as in the Hymenophyllaceae.
The direction in which the sporangium opens is specially dependent upon
its conformation and lie, a relationship about which more must be said as
it has hitherto received far too little attention.
We can clearly recognize in some cases that the outer conformation
of the sporangium stands in relation to the place of its appearance. If
a sporangium of Botrychium standing free upon a sporophyll approaches
the spherical form, if the sporangium of a Lycopodium lying parallel to the
surface of the leaf in whose axil it stands possesses the greatest extension,
we scarcely require to point out the relationship between the conformation
and the lie. The sac-like sporangia of Equisetum are also so formed
that they fit under the space which is made by the peltate sporophyll.
Analogous cases are found in the Hymenophyllaceae. In other cases,
however, such simple relationships are not probable.
ARRANGEMENT FOR DISTRIBUTION OF SPORES. The arrangement
for the distribution of spores consists, in the first instance, in a characteristic
structure of the wall of the sporangium, just as the structure of the wall of
the antheridium of the Bryophyta and Pteridophyta is arranged for the
distribution of the spermatocytes, only that by far the greater number of
the spores are adapted to distribution by air-currents, not by water, as is
the case with the spermatocytes. In the relatively small number of cases
in which the spores are spread by the water, as in the Marsiliaceae,
Salviniaceae, and Isoetaceae, the sporangial wall, so far as we know, does
not take an active share in the opening; it has a very simple construction
probably as the result of reduction, and it finally withers. We thus have
in them phenomena which recall the aquatic Bryophyta, such as Riella,
which ripen their sporogonia under water. In the sporangia which discharge
their spores into the air we find arrangements in the wall-structure for its
opening, and frequently also for the scattering of the spores. A point of
opening which we may designate the s¢omdzaum occurs ix all sporangia which
discharge their spores into the air!. The cells of the sporangial wall
condition by their characteristic structure the emptying of the sporangium
of the spores, whether these be only exposed, be slowly pressed out, or be
ejected. Other arrangements for distribution, that is to say arrangements
not conditioned by the construction of the wall of the sporangium, are
found only in Equisetum and Polypodium imbricatum in the conformation
of the organs which have been erroneously named ‘elaters,’ although
neither in structure nor in function are they like the elaters of the
sporangia of Hepaticae.
‘Elaters’ in Equisetum. It is well known that the spores of Equisetum are
provided with two membranous bands which are formed by splitting of the episporium,
* Notwithstanding what is said in the latest literature.
576 SPORANGIA OF PTERIDOPHYTA AND SPERMOPHYTA
and which when dried spread out but when moistened coil up round the spore.
They have been considered as means for spreading the spores as these, when they are
shed, if they come in contact with alternating moist and dry air, undergo movements
in space. As the spores could in this way approach one another as well as move
apart no scattering of them is associated with this movement. ‘The question therefore
is, How do the ‘elaters’ behave in the opening of the sporangium? De Bary has
made an incidental communication upon this subject which I here quote!: ‘If one
leaves a dehiscing spike of sporangia quiet in dry air the spores are pressed slowly
out of their receptacles in consequence of the progressive crumpling through drying
of the wall of the sporangium. ‘The “elaters”’ of each spore at the same time stretch
themselves. As, however, they never can become guz/e stratghi, and as also on account
of the roughness of their outer surface they hook and interlock one with another, after
a time there come in this way large, loose, woolly flocks together which are easily
broken up into small flocks.’ These flocks consist always of many spores which are
therefore sown together—an arrangement which receives its explanation in the fact
that the prothalli of Equisetum are normally dioecious*. The ‘elaters’ then hinder
a segregation of the spores. I would, however, add to what De Bary says that I think
this is not the only function of the ‘elaters,’ but that they also serve as a parachute,
for the spores embedded in the loose flocks offer a larger surface to the wind. If the
spore-flocks reach moist ground they become smaller by the coiling up of the ‘ elaters,’
and heavier by the taking up of water. The ‘elaters’ also act to a certain extent in
temporarily fastening the spores to the substratum by their roughness, whilst from
a dry place the flocks are again easily blown away. ‘The spores, however, are not
arranged for long flight in the air as they quickly lose their capacity for germination.
‘Elaters’ in Polypodium imbricatum. Within the sporangium of this
epiphytic fern are found besides the spores fine hygroscopic fibres which are slightly
cuticularized and which arise out of the plasm of the degenerated tapetal cells*. The
function of these ‘elaters’ is here unknown. Karsten thinks that they contribute to
the loosening of the spore-mass after the rupture of the sporangia, but this could
scarcely be the case, seeing that in the sporangia of the Polypodiaceae, which are
provided with an annulus, the spores are not gradually pressed out as in Equisetum
but are thrown out all at once‘. I think Karsten’s further suggestion is better
founded, ‘that by their not inconsiderable length they favour the fixation in moist
weather of the relatively large spores to the tree-stems,’ in the same way as Beccari
has shown that tufts of hairs on the seeds of Asclepiadeae act. At any rate these
structures have no more right to be called ‘elaters’ than have the structures so-called
in the Equiseta. Further investigation must show whether or not they are found
elsewhere amongst the ferns.
DIFFERENCES IN STRUCTURE OF THE SPORANGIAL WALL. The
wall of the sporangium is specially adapted to the distribution of the spores
1 De Bary, Notiz iiber Elateren von Equisetum, in Botanische Zeitung, xxxii (1881), p. 782.
2 See p. 195. 8 See p. 590.
* Karsten, Die Elateren von Polypodium imbricatum, in Flora, lxxix (Erganzungsband zum
Jahrgang 1894), p. 87.
DIVISION OF LABOUR IN SPORANGIA 577
by a special structure of the cells, in particular by peculiar thickenings of
the cell-membrane. There is a great multiplicity of details, but there is
one feature that must be specially mentioned as I do not find that it has
hitherto been carefully considered. Wherever in the Pteridophyta and
Gymnospermae there are specially thickened cells—actzve cells—of the wall
of the sporangium serving as an opening or scattering mechanism, these
always belong to the outermost cell-layer of the sporangial wall’, which in
many cases is the only one present in the ripe sporangium. In Angio-
spermae this is never the case”. Even where apparently the active cells, as
they may be called, belong to the outermost layer this is not really so.
This is a difference which we cannot well say is of great functional
significance, yet it is of great interest from the comparative morphological
standpoint, because we have regarded for long, and rightly so, the structure
of the wall of the sporangium as an important systematic mark. We shall
presently speak about the genetic relationships of the sporangium, and
endeavour to answer by individual instances the question of the relationship
between conformation and function in the sporangia of the several groups.
DIVISION OF LABOUR IN SPORANGIA. The division of labour
between microsporangia and megasporangia that is found in the three
classes of the Pteridophyta which now possess living representatives
furnishes us with one of the most remarkable illustrations of ‘parallel
formations’ in the plant kingdom. We start in the group from isosporous
forms, but we have not yet succeeded in tracing back the division of labour
to an ‘adaptation. We have already seen, when speaking of the germination
of spores*, that in the heterosporous forms the spores as they leave the
mother-plant are ‘induced’ to a definite limited development which is little
dependent upon external conditions. In Equisetum there is so far biologi-
cally an approach to this behaviour inasmuch as the ‘ induction’ is practically
a consequence of the manner of the distribution of the spores. The spores
are indeed all potentially alike, but through the scattering of many together
it follows that the conditions of nutrition are not equally alike for all, and
the worst nourished will give male prothalli. When the development of
the sporangia is considered, it will be shown that the separation of micro-
sporangia and megasporangia appears at different stages in the development
of the Filicineae and Lycopodineae ; the most extreme case is again offered
by the Spermophyta. Our short account of the mature sporangium will follow
the same sequence of groups as that adopted when the construction of the
gametophyte was described, because in the Lycopodineae, with the exception
of Selaginella, and in Equisetineae less specialized arrangements are to be
found than in the Filicineae, especially the Leptosporangiate Filicineae.
1 With the exception of Ginkgo. See Goebel, Morphologische und biologische Bemerkungen ;
13. Uber die Pollenentleerung bei einigen Gymnospermen, in Flora, xci (1902), p. 253.
2 Some Ericaceae are an exception. See Artopoeus, Uber den Bau und die Offnungsweise der
Antheren und die Entwicklung der Samen der Ericaceen, in Flora, xcii (1903), p. 309. 3 See p. 189.
GOEBEL II P p
578 MATURE SPORANGIUM OF PTERIDOPHYTA
II
THE MATURE SPORANGIUM OF THE PTERIDOPHYTA
A. LYVCOLODINEALE®
We have in this group two kinds of sporangia to consider.
1. Lycopodium, and Phylloglossum which is perhaps not generically
separated from it, as well as Selaginella, possess solitary sporangia sessile
upon the sporophylls.
2. In the Psilotaceae there are two sporangia on the sporophylls, as in
Tmesipteris (Fig. 336), or three to four.
We shall leave unanswered the question whether the sporangia of the
second group are the result of the ‘concrescence’ of separate sporangia, or
of the division of a single sporangium? by the development of plates of
sterile tissue. At any rate they are so far independent that each opens by
a special longitudinal split. It may be also stated that in Tmesipteris the
formation of one of the two sporangia may be entirely suppressed. The
single sporangia of Lycopodium and Selaginella also open by a longitudinal
split, but this does not reach the stalk. The line of opening is always
prepared for. The opening is brought about by the structure of the cells
of the outermost cell-layer of the wall of the sporangium. The side-walls
of these cells are thickened equally in Psilotaceae and Selaginella, unequally
in Lycopodium and Phylloglossum, and show the lignin-reaction with
phloroglucin *, whilst the outer wall, if it is thickened apart from the cuticle,
shows a cellulose-reaction. This is the common character of the structure
of the sporangial wall in Lycopodineae. As regards individual cases we
may remark * :—
PSILOTACEAE.
The Psilotaceae have, besides the outer layer of the sporangial wall,
many inner ones which furnish material for the formation of the relatively
numerous and large spores, and of course also act as an effective protection
to the ripening spores.
Tmesipteris. [mesipteris is a remarkable exception, according to
Leclerc du Sablon®, because its outer layer also consists of cells with
lignified outer walls, and in consequence the usual causes of dehiscence
1 We exclude Isoetes from this class for the reasons already stated. See p. 172, footnote 5.
? I observed in Lycopodium clavatum the occasional division of the sporangium, which reached
either only up to the stalk or also into this.
$ In Psilotum the lignified layer also still shows a cellulose-reaction.
* Tn the following I do not deal with the mechanism of the opening of the sporangium, but only
with the question how far the different forms of sporangia in a group can be referred to a common
fundamental ‘ type.’
° Leclere du Sablon, Recherches sur la dissémination des spores dans les Cryptogames vasculaires,
in Annales des sciences naturelles, sér. 7, ii (1885), p. 24.
MATURE SPORANGIUM OF LYCOPODIUM 579
have disappeared ; on the other hand the sub-epidermal cells are lignified.
But I find the following: the middle lamella of the lateral cell-walls is
lignified, and the lignin-reaction is also stronger at the point where the cells
stand in contact. The inner layer of the cell-wall is present in exceptional
amount only under the position of opening, which is quite the same as what
we find in Lycopodium clavatum which will be mentioned below. In the
outer cell-wall a subcuticular layer more often colours red, but a complete
lignification of the outer cell-wall I never found, nor can I discover that in
Tmesipteris there is an essentially different construction from that in the
other Lycopodineae.
LYCOPODIEAE.
Lycopodium. Here, as in Selaginella, the wall of the sporangium
apart from the tapetal cells consists usually of two cell-layers when ripe}.
The majority of cells of the
outer layer of the wall, for * iN
example in Lycopodium cla- Ses ae)
vatum, have an _ undulated San PXe Ry cas
outline, and possess thickened aay Z nee Se
ridges at the points of bending us ASN NO: WS
of the cell-wall (Fig. 373, 1). Se ea |
They recall the nature of the CONS Ta at
same cell-layer in the wall of \ eX . \ aes
the microsporangia of many ys ac & a)
Coniferae, for example some a \ (ar
Cupressineae. In the lower 5 SX \_J>
portion of the sporangium the Qe PN Se Vea
cells are elongated, the thick- Ik \
: St
ned ridges frequently extend
< dg et y FiG. 373. Lycopodium clavatum. I, portion of the wall of
and join into half-hoops and sporangium in surface view; s/, stomium. II, portion of wall
2 of sporangium in longitudinal section; s¢, stomium-cells sepa-
thus lead on to the character rated from one another by the cut, the thickenings of the wall-
: : cells are shaded.
of the wall-cells in Lycopodium
inundatum, for example, where the half-hoop-thickening is specially evident.
The cells which limit the line of separation approach more nearly rect-
angular form. The statement of a recent author that there is in the
Lycopodiales ‘positively no contrivance for dehiscence, and no vestige of
an annulus or stomium?’ is incorrect. The stomium is quite evident,
not only through the cells in the line of opening being differently con-
structed—usually lower than are the others—but also by their behaviour
* In many the lower portion of the sporangium has an increased number, for example in Lycopodium
inundatum,
? See R. Wilson Smith, The Structure and Development of the Sporophylls and Sporangia of
Isoetes, in Botanical Gazette, xxix (1900), p. 331. The error is probably the result of the examination
of longitudinal sections only.
Pp2
580 MATURE SPORANGIUM OF PTERIDOPHYTA
otherwise. I may shortly describe this in Lycopodium clavatum. If one
adds phloroglucin to a surface-section such as that shown in Fig. 373, I',
the opening cells will appear as a red band which is easily visible to the
naked eye. In the ordinary wall-cells here? it is the side-walls only which
are lignified, especially at the thickened portions. At the stomium® the
inner wall, to which the thickening may have spread, is also lignified.
Doubtless this is of importance for the opening mechanism. An annulus
is at any rate not specially formed. Almost all the cells of the wall of the
sporangium by their structure bring it about that as they dry they cause
movements which lead to the opening.
The ejection of the spores has not been observed in isosporous
Lycopodineae. I could only see in Lycopodium annotinum that in the
wide-open sporangium when the sporangial wall dried the spores lay
in a loose mass which projected somewhat, and the spores could then be
carried away by the wind. This would be facilitated by the rolling back
of the margins and the apices of the sporophylls.
Selaginella. There are remarkable
phenomena in this genus*. In the first
place there is a difference in structure be-
tween microsporangia and megasporangia
which is of importance for the physiology of
propagation. Both kinds of sporangia open
(Fig. 374). The megaspores as well as the
microspores are ejected in the process of
opening of the sporangium, the megaspores
_Fic. 374. Selaginella erythropus. I; me- much futther than the mierespors.. in
iat foaeonol mre ieee eee ee ee
She Teeed elite im g. 374 a megasporangium and a micro-
sporangium are shown from the narrow side,
both with the same slight magnification. They have split in two valves which
do not reach to the base, and they also show two lateral lines of splitting
(Fig. 374, 7,7). In the alveolar lower portion of the megasporangium there
appears very evidently a stripe of cells passing out on each side from the
stalk. This is the hinge, and it is composed of low thin-walled cells (Figs.
375, 376) very different from the other cells of the wall. When the
sporangium opens the two valves bend out from one another with such
force that the sporophyll is bent downwards, and then the four spores are
This was taken from a sporangium which was not quite ripe but possessed well-developed spores.
It is different, for example, in Lycopodium Selago.
That is to say the nearly rectangular cells, frequently also those at their sides.
See Goebel, Archegoniatenstudien: IX. Sporangien, Sporenverbreitung und Bliithenbildung bei
Selaginella, in Flora, lxxxviii (1901), p. 207. I treat here in some detail of the relatively far-
reaching adaptations in the structure of the spores of the Selaginella, especially in relation to the spore-
distribution, because these have been expressly denied by R. Wilson Smith, The Structure and
Development of the Sporophylls and Sporangia of Isoetes, in Botanical Gazette, xxix (1900),
1
2
3
4
MATURE SPORANGIUM OF SELAGINELLA 581
suddenly thrown out. A surface-view of the sporangium shows that when
this has taken place the whole sporangium has experienced a change in
form. In this the lower portion of the sporangium plays an important role.
As the process of drying proceeds it becomes narrower and longer, the
convex outer walls endeavour to straighten themselves and approach one
another (Fig. 377, to the right), and this movement is rendered possible
through the thin hinge-cells which are in consequence pushed outwards.
During this movement the megaspores are thrown out suddenly by it. In
the microsporangium the formation of the hinge is only slight. A com-
parison of the two forms of sporangia shows very clearly how structure and
function are connected, and that this mechanism is much more developed
in the megasporangium of Selaginella as compared with Lycopodium. In
the outlines of their structure
the microsporangium of Sela-
ginella and the sporangium of
Lycopodium conform with
one another, but the mega-
sporangia of Selaginella show
a much greater specialization
which is evidently of advan-
tage and requires no further
demonstration.
Having in view the mul-
tiplicity of forms in the spo-
rangia of the Filicineae and Fic. 375. Selaginella erythropus. Surface-view of a portion of
z the wall of the sporangium; G, position of the hinge, the more
their not always clear rela- thickened cells of the wall are the ‘atresia.’ Magnified.
tionships, it may be asked
whether there is any relation G ae
between the manner of open- yp ee
ee ee eee
Lycopodineae and the con-
formation which it presents. This may be answered in the affirmative.
The sporangia of the Lycopodineae are either dorsiventral or bilateral,
and the opening takes place in such a way that the spore-masses can be
most easily and most completely cleared out. We may compare the form
of a sporangium in Lycopodium, if we leave out of account the stalk,
with a gold-purse: the opening runs along the length of the broad side,
not across it. In the Psilotaceae, mutatis mutandis, we have the same.
It is clear that if the sporangia stand nearly upright the opening will be
best along the apical line of the sporangium, for there it will best serve
for the distribution of the spores. Where we find exceptions to this they
demand an explanation. Two cases seem to be possible: either the de-
viation is a consequence of inner causes, that is to say without connexions
582 MATURE SPORANGIUM OF PTERIDOPHYTA
perceptible to us with the other relationships of configuration and life, or
these connexions do exist. We find such exceptions, for example, in
Lycopodium inundatum and L. cernuum?.
Lycopodium inundatum. I think this plant shows that the deviation
in the lie of the position of rupture is connected with the lie and conforma-
tion of the sporangium—a result which is of special interest on account of the
relationships which will be described in connexion with the sporangia of
the Filicineae. The sporangia in Lycopodium inundatum are markedly
dorsiventral. Their upper side, which is turned to the flower-axis, is larger
than the under side turned to the sporophyll. The upper side is not flat
but has in the middle a projection, and is flattened from there towards the
G ? 0
Fic. 377. Selaginella erythropus. Empty megasporangium; moist in figure to the left, dry in figure to the
right; A, A, the two valves; G, G, hinge; %, ”, lines of split.
sides. This conformation, as well as the lie, depends upon the pressure’
to which the sporangium is subjected by the sides of the two sporophylls
which stand immediately above it. In consequence of this the sporangium
comes to occupy a nearly horizontal position, and its upper side is closely
covered by two indusium-like curtains, as each sporophyll has upon its
under side an elongation which shows right and left a pit-like depression
into which one half of a sporangium fits, and which is modelled in corre-
1 Kaulfuss, Das Wesen der Farrenkriuter, Leipzig, 1827, p. 19, has remarked this. I do not
find, however, that the sporangium is spherical as Kaulfuss has it, or transversely oval as Luerssen
(Die Farnpflanzen oder Gefassbiindelkryptogamen Deutschlands, Osterreichs und der Schweiz, in
Rabenhorst’s Kryptogamen-Flora, Leipzig, 1890, iii, p. 800) has it, but as it is represented in the text.
MATURE SPORANGIUM OF EQUISETINEAE 583
spondence with the upper surface of the sporangium. The line of rupture
lies now not along the apical edge of the sporangium! but upon its wader
side (Fig. 378), and this corresponds with the conformation and lie of the
sporangium, which, as has been shown, departs from the nearly erect position
of those in the other Lycopodineae and has a nearly horizontal lie. If the
sporophyll curves back towards the outside the wzder side of the sporangium
will be left free, and the sporan-
gium opens here nearly in the
middle of the free side, so that
out of the longitudina! opening of
the other Lycopodineae a cross-
opening has been reached here.
The upper side of the sporangium
zs at the period of opening still
covered by the curtains of the two
sporophylls standing over it, for
the emptying of the sporangia
proceeds gradually from below
upwards. We see then why it is
that the sporangium is not opened
by a longitudinal slit but by a lj %7%,,Lveqpodiam inundatum, Sporangium in long
es wodes Mealy this cross-clit aai att haat ee
is only a long slit pushed down-
wards. The displacement is an actual one, not merely a fancy, if we
consider as the original the behaviour of the great majority of the Ly-
copodineae, including Selaginella2. We shall have to discuss the same
problem in the case of the Filicineae, but whilst in the Lycopodineae,
so far as we know, there is only a divergence in regard to the opening of
the sporangia in two species, there is amongst the Filicineae a much greater
variation.
t
B. EQUISETINEAE.
The distribution of the spores has been already described *. The wall
of the ripe sporangium is commonly but incorrectly represented as one-
layered. I find it is—at least in Equisetum Telmateia, and less strikingly
in Equisetum arvense—many-layered at the angles, but over large stretches
the cell-layers have disappeared with the exception of the outermost. This
outermost layer shows very characteristic thickenings in the formation of
1 That is the one over against the stalk. We do not discuss here the question whether the apical
edge does not here coincide originally with the position of rupture which is subsequently displaced
upon the under side, because this is of no significance for the point under discussion.
2 The reason for this I will not give here. The gametophyte of Lycopodium inundatum and
L. cernuum is rather a primitive than a derived one. See p. 192.
> See p. 576.
584. MATURE SPORANGIUM OF PTERIDOPHYTA
‘lignified’ spirals or rings, which are occasionally double. The sporangium
always opens upon the inner side by a longitudinal slit, and subsequently
gapes widely. The opening is effected by an arrangement of cells! which
are shorter than others of the wall, and have their long axis placed nearly
at right angles to the line of opening. As these cells dry, they shorten in
the direction of their long
axis*, so that a slit must
occur. The formation of
the slit upon the inner
side makes possible the
free movement of the
sporangial wall outwards °,
and it experiences besides
a curvature making it con-
cave upwards, so that the
widely gaping opening is
turned more downwards’.
C. HILICINEAE.
I. EUSPORANGIATE FILI-
CINEAE.
OPHIOGLOSSACEAE.
Although the spo-
rangia of Ophioglossum
and Botrychium are out-
wardly somewhat differ-
Fic. 379. Botrychium Lunaria. Sporangium in longitudinal sec- :
tion, showing the sporogenous mass of cells surrounded by the tapetal ent, those of Ophioglossum
cells and the many-layered wall. From a photograph.
being embedded in the
tissue of the sporophyll, whilst those of Botrychium project freely beyond
it, they are in structure and development essentially alike. In Botrychium
the outermost cell-layer of the wall of the sporangia runs directly into the
epidermis of the sporophyll. The sporangia project at their origin only
1 See Leclerc du Sablon, Recherches sur la dissémination des spores dans les Cryptogames
vasculaires, in Annales des sciences naturelles, sér. 7, ii (1885). The description of the sporangia
of Selaginella in this paper is incorrect.
* We cannot discuss the peculiar mechanism of the opening of this and other sporangia, especially
as views regarding it are not very definite. That the arrangement of the thickenings of the cell-wall,
whether these be spiral or ring-like, the elongated form of the wall-cells, and in particular the
shortening of the wall-cells in their long axis are connected with the opening is clear. It appears to
be a common feature in the ‘active’ cells of the sporangia of all Pteridophyta that the thickenings
are so arranged that in drying a stronger deformation takes place in the tangential direction than in
the radial.
* Analogous cases will be mentioned in the Filicineae.
* Particularly well seen in Equisetum arvense.
— a a
MATURE SPORANGIUM OF MARATTIACEAE 585
slightly above the surface of the sporophyll. The cells which lie under-
neath the sporogenous tissue and which belong peculiarly to the sporophyll
push the sporangium, whose wall-layer also experiences a considerable
increase of growth, beyond the sporophyll! (Fig. 379). A branch of a
conducting bundle runs to each sporangium, and we may say that each of
the sporangia of Botrychium is embedded in a branch of the sporophyll.
The similarity with Ophioglossum is seen also in the method of opening,
which takes place by a longitudinal slit in the wall of the sporangium in
a definitely determined position. As in Ophioglossum there are two series
of small cells, between which the separation occurs*. An ejection of
the spores is impossible in Ophioglossum on account of the lie of the
sporangium. Whether it happens in Botrychium and Helminthostachys
is not known, and is, I think, improbable. In Helminthostachys the
sporangia open outwards, and their conformation approaches the dorsi-
ventral, inasmuch as the slit extends deeper downwards on the side of the
sporangium which is turned away from the apex of the sporangiophore.
The lie of the sporangium resembles—but in a slight degree only—the
hanging lie of the sporangium in Equisetum. That this lie is not more
expressed depends upon the looser position of the sporangiophores com-
pared with the close-set sporophylls of Equisetum.
MARATTIACEAE.,
In this group the sporangia always project above the surface of the
sporophyll. In Angiopteris and Archangiopteris they are free single
sporangia which are united together in a sorus. In the other genera we
find syzangia—structures with several sporiferous chambers. We can
regard the synangium either as the result of the concrescence of single
sporangia, if we consider forms like Angiopteris as primitive, or as a single
sporangium which has become chambered by the formation of sterile
isolated portions between many sporogenous cell-masses. In speaking of
the development of the sporangia we shall revert to this question, and
now will only shortly refer to the relationships of the configuration of the
~ synangium or sporangium to the function of distribution of spores.
Danaea. Kaulfussia. The synangia of Danaea and Kaulfussia are
built upon the principle of the pore-capsule, that is to say, each of the
single chambers opens by a single pore, through which the spores are
1 With this corresponds the fact that stomata are found at the base of the sporangium even in that
part of the ‘ wall ‘ which lies above the spore-bearing inner space. It is a matter of moment for the
interpretation of the funicle of the ovule whether the lower part of the sporangium in Botrychium
belongs to the sporangium or to the sporophyll.
2 The slit lies at right angles to the long axis of the sporophyll. In Helminthostachys it is in
the long axis of the sporangiophore, which stands at nearly a right angle to the long axis of the
sporophyll.
586 MATURE SPORANGIUM OF PTERIDOPHYTA
gradually shaken out. Considering the whole structure of the synangium,
any other arrangement is scarcely possible !.
Marattia. The chambers of the synangium in Marattia are not nearly
circular, as in Kaulfussia, or connected together all round, as in Danaea, but
are in two rows separated from one another by a groove (Fig. 380). This
gives the possibility that the whole synangium when ripe can break up
into halves?, whilst each single chamber opens inwards. The position of
opening is laid down beforehand.
Angiopteris. In Angiopteris we find
separate single sporangia, which are arranged
in two rows as they are in the synangium
(Fig. 381). Not infrequently a sporangium
stands at the end of the sorus before the
two rows, and this gives us a transition to
the arrangement in Kaulfussia. Each spo-
rangium opens for itself, and the spores—
according to observations upon Angiopteris
evecta—are ejected, although not very ener-
getically. The emptied sporangia gape
widely. The mechanism of the valvular open-
ing requires further explanation *. Doubtless
the antagonism between the cells whose inner
and outer walls are thickened and ‘lignified’
and those whose walls remain unthickened
plays a part. The thick-walled cells are
found particularly at the apex and on the
flanks of the sporangium, which is constructed
as a markedly dorsiventral structure, as in
all Marattiaceae. Whether now the opening
Fic. 380. Marattia fraxinea. Synan. is effected by the disappearance of the un-
gium. Uppermost figure, closed and
viewed obliquely from above. Middle thickened cells has to be determined. At
figure, Open and viewed from above. : i xm
Lowermost figure, in transverse section. any rate one sporangium of Angiopteris
Magnified. After Hooker. i
corresponds to ove chamber of the synangium
of Marattia and Kaulfussia. Whether we are to reckon Angiopteris at the
end or at the beginning of the series is at the present time a mere matter
of opinion. Still, Angiopteris shows us the most specialized structure of
the sporangial wall, and approaches in that feature the behaviour of the
Leptosporangiate Filicineae, the Osmundaceae in particular, which other-
wise stand nearest to the Eusporangiate Filicineae.
* See the systematic works. Also Bower, Studies in the Morphology of Spore-producing Members :
III. Marattiaceae, in Phil. Trans., 1897.
* The chambers extend deeper than the groove.
* See Bower, op. cit.
eee
MATURE SPORANGIUM OF LEPTOSPORANGIATE FILICINEAE 587
As regards the relationship of the direction of the opening of the
sporangia to their lie, we observe that in all the Marattiaceae the point of
opening lies upon the side of the sporangium turned away from the
sporophyll. The sporangia stand upon the under side of the sporophyll,
and the strong dorsiventral conformation of the sporangium, which deviates
very greatly from that of the sporangium in Botrychium, is evidently
closely connected with the ‘endeavour’ of the sporangium to bring the
point of opening into such a position.
Il. LEPTOSPORANGIATE FILICINEAE!.
The structure of the sporangia in this group is characteristic by the
fact that the thickened cells which effect the opening of the sporangium
and the scattering of the spores are localized
upon one part of the sporangial wall. They
constitute an aznziulus, even where it has not the
form of a ring, and they bring about, as the
sporangium dries, movements which have as a
result an energetic ejection of the spores. The
arrangement of the cells of the annulus deter-
mines not only the manner and method of the
rupture of the sporangia, but is, as is well known,
of systematic importance. For the details the
systematic text-books may be consulted, and the
elaborate exposition of the subject by Bower.
Here I shall only bring forward a few examples
bearing upon the question of whether the con- Warr
struction and lie of the annulus is one which is Gigpes foae garter ala leat pin.
: ; nule with sori, one has fallen off.
purely the result of ‘internal’ factors, or whether See fore ae
we can discover relationships between its form
and function. There are such relationships. It can be shown, at least in
the cases which have been investigated, that the arrangement of the annulus
is ‘purposeful, that is, stands in connexion with the form and lie of the
sporangium. The annulus is so arranged that the slit by which the sporan-
gium opens is always towards the side whence the distribution of the spores
can proceed unhindered, to speak generally, to the outside—the ‘ outside’
being differently placed according to the lie of the sporangium. There
are three chief methods of opening to be distinguished :—
1. By a slit transverse to the long axis of the sporangium. The
annulus is vertical. In the great majority of Leptosporangiate Filicineae.
1 Excluding the Salviniaceae and Marsiliaceae. See Bower, Studies in the Morphology of Spore-
producing Members: IV. The Leptosporangiate Ferns, in Phil. Trans., 1899.
588 MATURE SPORANGIUM OF PTERIDOPHYTA
2. By a slit oblique to the long axis of the sporangium. The annulus
is oblique. Hymenophylleae, Cyatheaceae, and allies.
3. By a slit parallel with the long axis of the sporangium, The
annulus is transverse or oblique. Gleicheniaceae, Schizaeaceae, Osmunda-
ceae, Loxsoma.
(1) SLIT TRANSVERSE TO THE LONG AXIS OF THE SPORANGIUM.
ANNULUS VERTICAL.
The sporangia are always zxdependent of one another even if they stand
in dense groups. They have usually long stalks! (Fig. 382, I), and they do
not ripen together*. The
vertical annulus has there-
fore free room for play.
It stretches itself at first
straight, bends then so that
it is concave outwards—
even so far that the two
ends of the ring touch—
springs back, and throws out
the spores. Frequently on
account of this the sporan-
gium splits off at its base,
as in Platycerium grande
and others. A definite posi-
tion of rupture, the stomzum,
is present. Frequently at
this point there are flat cells
with thickened walls, which
Fic. 382°. I, Platycerium grande. Ruptured sporangium; /, /, may be designated as the
seam-cells. IJ, Aneimia fraxinifolia. Upper portion of a sporan- Z
gium; R, annulus; S\ seam-cells; S¢, stomium. III, Osmunda seam-cells (Fig. 382, rp. Wh II
regalis. Sporangium, not quite ripe, in transverse section; .S, sto- 5 Z
raiai: Iv. aici eaten. Sporangium seen from above; &, and LEY: 5). Their function
annulus; S%, stomium. All magnified. : z
is to secure that the split
takes place in a definite position, and in a definite direction. Once the split
has begun then the thin-walled cells behind the seam split through also.
Through alternations of moisture and dryness this spring-like mechanism
can be brought into operation more than once.
1 This is not the case in Ceratoptenis.
2 See the striking example in Polypodium obliquatum in Fig. 334.
8 Professor Giesenhagen has been so good as to supply the figures 382, 386, and 388, which are
drawn from his own investigations.
'
SPORANGIAL RUPTURE OF LEPTOSPORANGIATE FILICINEAE 589
(2) SLIT OBLIQUE TO THE LONG AXIS OF THE SPORANGIUM.
ANNULUS OBLIQUE.
Trichomanes. We may take as an example of this Trichomanes. Its
sporangia are distributed radially on an elongated placenta, upon which they
Fic. 383. Trichomanes_ tenerum.
Sorus in surface-view; the placenta
bearing radially distributed eta Ae
issues from the two-lobed beaker-like
indusium. The annulus is visible on the
several sporangia. Slightly magnified.
arise in basipetal serial succession (Fig. 383).
The sporangia have only a very short stalk
(Fig. 384), their long axis is oblique to the
placenta, and they cover one another imbri-
cately. A glance at Fig. 383 shows that the
annulus lies in such a position that it has free
room for play, because it runs obliquely to the
long axis of the sporangium. The position of
the slit is found near the base of the sporan-
gium, and the annulus becomes detached
at this point and takes with it the greater part
of the sporangial wall, and the spores also.
The annulus bends first of all to the side of
the sporangium which lies over against the
Fic. 384. Trichomanes tenerum. I, sporangium seen from
the side. II, portion of the placenta in longitudinal section
with two sporangia; the annulus is visible above and below
each. I, magnified.
position of rupture, and this tears off the sporangial wall right and left of
the annulus, then it springs back, the whole sporangium is torn off, and the
spores are thrown out.
This is what occurs in Trichomanes tenerum.
Atkinson’s statement ‘that the spores in the Hymenophyllaceae are not
very effectively dispersed’ is incorrect’. We have here one of the most
1 Atkinson, The Biology of Ferns, p. 72. The lie of the annulus of the Hymenophyllaceae is
incorrectly given there. It is not horizontal but oblique. Bower shows it correctly. The ring
590 MATURE SPORANGIUM OF PTERIDOPHYTA
perfect mechanisms amongst the Filicineae, for the sporangia seated on the
long placenta, where moisture can be retained between them, are shot free
one after another at short intervals until finally the placenta is quite freed
from them or only solitary sporangia remain occasionally upon it. The
spores of the Hymenophyllaceae often germinate within the sporangia, but .
this is by no means the normal behaviour, and only occurs apparently if
during long periods of rain there has been no opportunity for their drying’.
So soon, however, as a short dry period begins the numerous ripe sporangia
shoot out their spores in all the greater number.
Alsophila. The cyatheaceous Alsophila shows the same connexion
of the lie of the annulus with that of the sporangium in the sorus. The
species examined was Alsophila Leichardtiana.
Plagiogyria. The genus Plagiogyria, which up till now has been placed
amongst the Polypodiaceae, but which at the same time has an oblique
annulus, does not show the same imbrication of the sporangia as the
Hymenophyllaceae and Also-
phila. The sporangium is from
the first unilateral and shortly
stalked, and the sporangia stand
close together. ’
(3) SLIT LONGITUDINAL. ANNULUS
TRANSVERSE OR OBLIQUE.
Fic. 385. Osmunda regalis. I, sporangia 27 sz/ze seen from OSMUNDACEAE. (Figs. 382,
above; J, leaf-nerve. The annulus is indicated by a black Ihe 385, lL. ik 386 II TIT.)
spot. II, one of the dorsiventral sporangia in profile; a, annulus. ? ? - a 2 2
IfI, Gleichenia circinata. Sorus seen from above. The dotted The sporangia stand all round
lines indicate the lines of rupture. : -
the sporophyll in a somewhat
loose manner in Osmunda. A surface view of a group of sporangia shows
(Fig. 385, I) that the place of rupture is here everywhere upon the side of
the sporangium turned away from the sporophyll?, so that in those which
are found upon the under side it is directed downwards, in those which stand
upon the edge it is directed outwards*, The annulus, on the other hand,
shows no different orientation. It is formed by a plate of cells which lie
extends upon the one side (Fig. 384, I, to the right below) over the point of the insertion of the
sporangium, but not upon the other which is the side of the opening. In consequence of this we
have the movement described.
1 That the sporangia are able, owing to their density, to retain between them water on the exposed
placenta is of importance for the spores which do not bear a long drought; besides this brings it
about that the sporangia dry from above downwards, and their spores are gradually thrown out, not
all at once. In the moist stations which are inhabited by the Hymenophyllaceae it is important that
every dry period should be used for copious spore-distribution. Evidently the arrangement of the
sporangia is connected with this.
* This is true also for the microsporangia of the Cycadaceae.
* None of these marginal sporangia is represented in the figure.
SPORANGIAL RUPTURE OF LEPTOSPORANGIATE FILICINEAE 591
upon one side of the dorsiventral sporangium. In my view this annulus lies
immediately under the apex of the sporangium, but is displaced on account
of the unilateral development of the sporangium (Fig. 385, II, a), and lies
then not over against the stalk but laterally. There is a similar displace-
ment in Lygodium. The place of opening is marked by lower cells, as is
shown by a section taken at right angles to the stalk (Figs. 382, III, s; 386,
II). The plate of the annulus in drying ‘endeavours’ to become concave
outwardly, and this is facilitated by the conformation of the cells, by the
oblique position of their cross-walls, or by their cross-walls being somewhat
thin in the middle—an arrangement which brings about an approach of the
thickened longitudinal walls!. By the throwing back of the sporangia]
valves the spores are thrown out.
GLEICHENIACEAE. In the Gleicheniaceae also the lie of the sporangium
is connected with that of the annulus (Fig. 385, III), and the line of rupture
is upon the side of the sporangium turned away from the sporophyll, as it
is in Osmundaceae. The annulus has really the form of an incomplete
ring which has a somewhat oblique, nearly transverse, direction to the
long axis of the sporangium below its apex. It is very evident here that
the lie of the annulus is only a ‘ means to an end, that is to say, it hinges
upon the lie of the line of rupture. The annulus would have freer play if
the position of rupture were to lie turned towards the sporophyll, but such
a lie would prejudice the distribution of the spores.
SCHIZAEACEAE. (Figs. 382, II, IV; 386, I; 387; 388; 389; 390.)
The Schizaeaceae show analogous cases. The annulus is generally trans-
verse beneath the apex of the sporangium, and the sporangium opens by
a longitudinal slit which is turned outwards. ‘QOutwards’ has here, as
elsewhere, a different significance in different cases, as will be pointed out
in the several genera.
Mohria. In this genus the sporangia have a short stalk and sit upon
the under side of the sporophyll at nearly a right angle. They are con-
sequently less markedly dorsiventral than in other genera, and the point of
rupture I found to be directed always towards the margin of the leaf.
Schizaea. Aneimia. The sporangia in these genera are oblique to
the sporophyll, and the point of rupture looks outwards (Fig. 387), conse-
quently the sporangia are on this outer side somewhat swollen, and in their
1 Luerssen, Die Farnpflanzen oder Gefassbiindelkryptogamen Deutschlands, Osterreichs und der
Schweiz, in Rabenhorst’s Kryptogamen-Flora, Leipzig, 1890, iii, Figs. 35, 36, represents almost all
the cross-walls as actually transverse. I have not seen such cases. Only occasionally were the walls
transverse in the sporangia investigated. In Osmunda there is formed in the vicinity of the annulus,
right and left of it, and before the slit of dehiscence, a short transverse slit, somewhat like that in
Selaginella, and this facilitates the outward movement of the valves. This fact is not shown in any
of the published figures. These transverse slits are prepared for in the structure of the sporangial
wall, but have been entirely overlooked.
592 MATURE SPORANGIUM OF PTERIDOPHYTA
whole external conformation markedly dorsiventral. The point of rupture
is very clearly constructed (Fig. 386, I).
Lygodium. The most interesting relationships in the Schizaeaceae
are, however, found in Lygodium, where the sporangia stand singly enclosed
in pockets (Fig. 388), and directed so that the annulus is oblique towards
the under side’. Does this change in conformation of the sporangium,
when compared with the other genera, have any connexion with the
scattering of the spores? It is most remarkable that this question has
nowhere been discussed in descriptions of Lygodium. Even the method
of rupturing is often incorrectly given*. In reality this conformation
secures under the given conditions the best distribution of the spores. Given
the position of the annulus, longitudinal dehiscence, and the indusial pocket
a
Fig. 386. I, Aneimia rotundi-
folia. Line of rupture of the spo- Fic. 387. Aneimia to- Fic. 388. Lygodium microphyllum.
rangium in transverse section. mentosa. Upper figure: Portion of a fertile leaf-lobe seen from
II, Osmunda regalis. Cells ofthe tip of a sporangiferous below. Four sporangia. The indusium
annulus in transverse section. pinnule. Lower figure: removed from the two lower ones. The
III, Todea barbara. Cells of the sporangium seen from two upper ones seen through the indusium,
annulus in surface-view. All the side of rupture. Mag- Jd; F, position of annulus; J, under-sur-
magnified. nified. After Prantl. face of indusial pocket.
in which the sporangium lies. This pocket consists of two parts *, one, the
indusium proper springing from the under side of the leaf, and one the leaf-
1 The long axis of the sporangium, however, does not lie as it is figured by Prantl, and in many
other figures, in the plane of the sporophyll, but it forms with the short stalk an angle of go”.
? Thus Luerssen, Handbuch der systematischen Botanik, Leipzig, 1879, p. 570, Fig. 146, A, says
that the sporangium opens by a longitudinal slit turned towards the wzder half of the indusium.
’ Prantl has represented the whole indusial pocket as a single indusium, because it arises as
a crescentic wall beneath the sporangium which is laid down on the margin. I do not think that
we have here anything but what is found in Schizaea and a number of species of Aneimia where the
sporangia laid’down upon the margin are displaced to the under side by a growth of the upper surface
of the leaf. Coincident with this outgrowth the indusium is formed upon the under side. Prantl’s
explanation, influenced evidently by a desire to find an analogy with the formation of the integument
of the ovule, must assume a complex concrescence of the indusium, whilst the explanation given
above seems to me to find the relationship without any strain.
MATURE SPORANGIUM OF LYGODIUM 593
surface into which the indusium passes over. The free margin of the
indusial pocket lies directed obliquely downwards, and so does the point
of rupture of the sporangium (Fig. 388). The annulus opens wide when
ripe, and in that way presses outwards the under half of the indusial pocket,
and this is made possible by the annulus occupying the position where the
indusium projects freely beyond the leaf-surface and where a movement can
proceed unrestrained (Fig. 388, #). The configuration of the sporangium
has therefore the most intimate connexion with its lie. Were the annulus
to lie above instead of below in the indusial pocket the exit of the spores
would be essentially hindered, as a twisting or movement of the indusium
at this point where it joins the leaf-surface is scarcely possible. The great
elongation of the outer side of the sporangium (Fig. 389), which leads to
a bending of the sporangium through go’, brings the annulus, according
to our explanation, into the most suitable place for
its function; at the same time we must point out
that the peculiar growth of the sporangium is only
an exaggeration of the behaviour which is found in
Aneimia, and that here also the outer side of the
sporangium is more strongly developed than is the
inner side. The ‘disposition’ to dorsiventral de-
velopment of the sporangia which exists in the Sat Seoraagien Magid.
whole group reaches an extreme in Lygodium. “"**"*
The great protection afforded to the sporangium in this genus by its
inclusion within an indusial pocket evidently is connected with the climbing
habit of the plant. The leaves climb far up into the shrubs?. The fertile
leaf-pinnae (Fig. 390) are only formed in the wffermost part. Climbing-
leaves are relatively very much exposed, and with this the marked pro-
tection of the sporangia corresponds.
The different lie of the annulus of the sporangia of the Filicineae which has just
been depicted may give rise to phyletic speculations. Has a ‘displacement’ of the
annulus taken place or not in the several groups? I do not think that at the present
time we have a sufficient number of facts to warrant an answer to the question. We
should have this if we could prove that starting from a definite wel/-déffereniiated form
others have arisen by its transformation. Such a transformation is found in many
cases where there has been a change of function, but more frequently it would seem
that the ‘capacity for development’ belonging to the construction of the protoplasm
has under the influence of external or internal formative stimuli unfolded /rom the
outset tn different directions. If we assume a ‘ primitive sporangium’ we do not require
1 This is effected in two ways:—(1) by twining leaf-spindles, (2) by scrambling-pinnae. Jn
Lygodium japonicum, for example (Fig. 390), the apex of the leaf-pinnae of the first order is usually
undeveloped, whilst the two lower pinnae of the second order are well developed, stand out far, and
act as scrambling-organs. ‘The circinate persistent vegetative point of the pinnae of the first order
may, however, resume its growth. The case resembles that of the Gleicheniaceae (see p. 318).
GOEBEL Ul Q g
594
MATURE SPORANGIUM OF PTERIDOPHYTA
to ascribe to it a definite lie of the annulus, but only the capacity of thickening the
FIG. 390. Cen-
tral figure shows habit. The leaves arise
from a horizontal creeping rhizome. Only
a portion of one leaf is shown. On the
thachis is a branched pinna of the first
order. It has two pinnae of the second
order between which is the undeveloped
persistent apex. The pinna to the left is
represented complete, that to the right has
only its rhachis. Figure to the right below
shows a fertile leaflet. It is much more
branched than the sterile leaflet of the same
order and shows the indusial pockets.
Reduced. After Christ.
Lygodium japonicum.
wall-cells in greater or less number in relation to
the lie of the sporangium and so to construct an
opening apparatus. Whether one therefore will
start from sporangia which still want a thickening
of their wall, as, for example, those sometimes oc-
curring in Ceratopteris, or from a form of spo-
rangium like that of Lycopodium in which the
majority of the wall-cells are ‘active,’ appears to
be of no great moment. What should be here
laid stress upon is that a sporangium of Hymeno-
phyllum, for example, never required to have pos-
sessed another lie of its annulus than that which
we now find. To assume a displacement of it
would only be justified if we had ground for the
further assumption that the lie and configuration
of the sporangium were different at an early period.
A displacement of the point of rupture of the
sporangia is probable as we have seen in Lyco-
podium inundatum, but in Lygodium we have a
case which shows how within one cycle of affinity
after the lie of the annulus is once fixed the whole
configuration of the sporangium is adapted to the
work of distribution of the spores. We could
prove that the divergences in the conformation of
its sporangium from the allied forms is conditioned
on the one hand by its pocket-like envelope, and
on the other hand by the once given lie of the
annulus. Lygodium appears to be not a primitive
but a greatly changed form of the Schizaeaceae.
There is still another side of the question as
to the significance of the lie of the annulus in
the Filicineae which must be touched upon here.
I have elsewhere briefly shown? that the lie of the
annulus in the fern-sporangium should not be re-
garded as a character of adaptation. This view
I still hold although it appears to stand in oppo-
sition to what has been brought forward above.
It is evident that the arrangement of the annulus
has the closest connexion with the whole con-
figuration of the sporangium on the one hand and
with its lie upon the other, and that under the
1 Goebel, Uber Studium und Auffassung der Anpassungserscheinungen bei Pflanzen, Miinchen,
1898, p. 23.
i
MATURE SPORANGIUM OF CERATOPTERIS 595
given relationships it is a purposeful one. But the purpose cannot of itself explain why
the work of opening of the sporangium and the distribution of the spores is performed
in such different ways. The sporangium of Osmunda would function well with an
annulus of the Gleicheniaceae or of the Schizaeaceae. We have here as everywhere
to consider the ‘inner constitution’ of the plant on the one hand and its aim on the
other. What we can prove sometimes in a number of sporangia is the connexion of
the lie and the conformation of the sporangium with its manner of opening. In all
other questions we have only to do with hypotheses.
The structure of the sporangial wall is extremely constant in the different
forms of Pteridophyta, yet there are species where there are variations.
Ceratopteris. The most striking example is Ceratopteris, in which
all stages occur, from that of a complete vertical annulus to that of entire
absence of annulus?. In an example which I gathered in British Guiana *
the annulus consisted of usually five or six cells, but in the rest of the
sporangial wall it was not developed. Such a rudimentary annulus can
scarcely be of importance in the distribution of the spores. The cause of
this variation is unknown, but biologically we can understand that the
annulus might disappear in a fern which floats upon the water, and which
would not need to scatter its spores as these would be readily carried by
currents in the water. Besides Ceratopteris, on account of its rich asexual
propagation, is less dependent upon the distribution of spores than most
other ferns. This phenomenon requires, however, a more close investiga-
tion, because the connexion of the lie of the annulus with the configuration
of the spores is somewhat obscure in the sporangia of Ceratopteris. In its
structure also the annulus diverges from that of the Polypodiaceae—it
consists of very many low and broad cells. When the sporangium opens
only few spores are thrown out, most of the spores remain behind in the
sporangium *, and this fact again leads us to the view that the spore-
distribution proceeds here in a manner somewhat different from that which
is observed in ordinary land-ferns.
ItI
DEVELOPMENT OF THE SPORANGIUM
The history of development has shown us that sporangia run through
a course of development which in its main features is much alike in all.
1 See Hooker, Species Filicum, London, 1858, ii, p. 236.
* This form, which was described by Hooker and Greville, Icones Filicum, Taf. 97, as Parkeria
pteridioides, is very different from the plant cultivated in our plant-houses, at least I have never been
able to obtain from the latter the floating form with massive swollen leaf-stalks which I gathered in
British Guiana. Whether or no there is a connexion has still to be proved experimentally. I do
not know that similar forms have been described from other tropical countries, and perhaps in South
America a special ‘ physiological race’ of this fern has developed.
$ Readily seen on examining a sporophyll in the inverted position.
Qq2
596 DEVELOPMENT OF THE SPORANGIUM
In the first place it is characteristic that all the spores, as in the Bryophyta,
proceed from sporocytes which, with reduction of the number of chromo-
somes, divide into four daughter-cells. This is also the case in the
microsporangia of the Spermophyta, whose development therefore can be
treated of in this place also. In the megasporangia of the Spermophyta
peculiar relationships arise which demand a special treatment.
The sporangium at a middle stage of development consists of a zvad/
composed of a number of cell-layers, the number varying in different
cases!; of an inner tissue whose cells are densely filled with protoplasm and
later form the sporocytes—the sporogenous cell-mass; and of one or more
cell-layers of characteristic aspect which envelop the sporogenous cell-mass
and lie below the wall—the
tapetal cells which together
constitute the ¢apetum.
The significance of the ta-
petum is nutritive. It furnishes
the sporocytes with plastic
material, especially what is re-
quired at a later period for the
construction of the outer spore-
membranes. It appears that
we may distinguish two kinds
of tapeturn between which.
however, there are a number
of transitions :—
FiG. 391. Symphytum officinale. Portion of anther with
microsporangium in transverse section. Sporogenous cell-mass 1. Plasmodial lapetum in
in the middle, its cells having large nuclei: 7, tapetum; e, epi- < :
dermis ; 7%, outer parietal layer which forms endothecium ; =, which the wall of the tapetal
compressed inner parietal layer.
cells is broken down; its plasm
along with the nuclei, which are often fragmented, wanders between the
isolated sporocytes, or their daughter-cells, and is by them used up. The
Filicineae (Fig. 379), Equisetum, and the microsporangia of the Spermo-
phyta (Figs. 391, 392) have typically a plasmodial tapetum.
2. Secretion-tapetum, in which the tapetal cells remain until the
ripening of the spores, but they excrete evidently soluble substances which
are used by the sporocytes, and they have, as elsewhere, the function of
supplying the sporangium-wall with plastic material in an available form.
The sporangia of the Lycopodineae, and especially that of Selaginella
(Fig. 394) and Isoetes*, have a secretion-tapetum.
* If the sporangial wall is many-layered, we designate in what follows the cells which lie under the
outermost layer and outside the tapetum as the parietal /ayer.
* See Fitting, Bau- und Entwicklungsgeschichte der Makrosporen von Isoetes und Selaginella, in
Botanische Zeitung, lviii (1900), p. 107.
RHE TAPELUM.” THE ARCHESFORION 597
Apart from the case of Isoetes this grouping conforms with the
arrangement in the Pteridophyta'.
The idea of the tapetal cells is not morphological’, but is only
functional*. In correspondence with this the origin of the tapetum is
not uniform. Where the sporogenous cell-mass reaches a larger size there
are frequently arrangements which make possible a more profuse supply of
food-material. These are—
(z) an increase in surface of the sporogenous cell-mass. This is the
case in the sporangia of Lycopodium clavatum and L. annotinum, for
example, as well as in the microsporangia of many Angiospermae, where
_the sporogenous cell-mass becomes curved, and thus comes in contact with
many sterile cells, especially at its base (Fig. 393, A/) ;
(6) individual cells, or in extreme cases many cells, or a cell-complex
of the cell-mass, become sterile and serve to supply food-material to the
fertile ones*. Isoetes supplies the most striking case of this. Its large
broad sporangia are traversed by ¢rabeculae of sterile tissue. Their appear-
ance is easily understandable on account of the size of the sporangium.
They serve to bring nourishment to the sporogenous cells, and they also
facilitate by their intercellular spaces the exchange of gases. Bower has
shown that similar arrangements exist in Lepidodendron. He also found
irregularly arranged sterile cells in the sporogenous tissue of Equisetum,
Tmesipteris, and Psilotum, as well as in Ophioglossum, where Rostowzew
had also found it®. These cases recall that of the Hepaticae. The micro-
sporangia of many Spermophyta show similar arrangements®. In some of
the Onagrarieae the microsporangia are penetrated by plates of tissue; in
Viscum, Rhizophora (Fig. 363), and others, the fertile cells in the anthers
are limited to isolated groups.
THE ARCHESPORIUM. The origin of the sporogenous cell-mass has
given rise in recent years to a series of investigations especially directed to
the solution of the question whether this could be traced back to a single
cell, cell-row, or cell-layer, which in the very young stages of the sporangial
development is marked out by a rich protoplasmic content, and which
produces by divisions the sporogenous cells. These primitive sporocytes
have been called the archesporium.
1 See p. 172, footnote 5.
2 As recent authors like Kérnicke have maintained in the ovule of the Angiospermae.
3 Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
3otanik, iii (1884), p. 384.
‘ With regard to the connexion between configuration of this sporogenous cell-mass and its
nutrition, see Goebel, On the Simplest Form of Moss, in‘Annals of Botany, vi (1892), p. 356.
5 In Ophioglossum pedunculosum and Equisetum arvense I could only find a plasmodial tapetum,
no sterilized sporogenous cells.
® See p. 554.
™ Goebel, Beitrige zur vergleichenden Entwicklungsgeschichte der Sporangien, in Botanische Zeitung,
598 DEVELOPMENT OF THE SPORANGIUM
Strasburger’? has recently pointed out that the centre of gravity of the process of
development which takes place in the sporangium does not lie in the archesporium,
but that the new generation starts from the sporocytes, as in their division a reduction
of chromosomes takes place which is accompanied by the separation of these cells from
their condition of a tissue. Certain is it, however, that the centre of gravity of the
development does not lie in any one stage, and on this ground one cannot speak of
a ‘centre of gravity’ in the process of development. We have before us a series of
definite processes following one upon the other which in the case under consideration
lead up to the formation of spores. That in these the changes in the nuclear division
appear to us to be the most striking is in part certainly a consequence only of the
imperfection of our methods of investigation. We may with truth say that in the
protoplasm itself there are changes occurring, and indeed not suddenly but gradually,
and these express themselves in my view in the development of the sporogenous tissue
Fic. 392. Knautia arvensis. Anther in transverse section. 1, younger stage. 2, older stage at which one of
the microsporocytes, #, has already divided into four daughter-cells. 4, tapetal cells which in 2 have many nuclei,
2%; i, 2, parietal layers, of which z becomes compressed, and 2 forms the fibrous parietal layer or endothecium ;
&/, vascular cylinder.
out of the archesporium. That the archesporium has a different quality from the rest of
the tissue will be shown when we speak of apospory. Moreover the aim of comparative
investigation of the sporangia is the ‘proof’ of the homology of the development
in the whole series of sporangia?’—a proof which remains established even if the
differentiation of the archesporium is not everywhere so early as it is in some’ cases.
xxxvili (1880); xxxix (1881); id., Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in
Schenk’s Handbuch der Botanik, iii (1884), p. 384.
1 Strasburger, The Periodic Reduction of the Number of Chromosomes in the Life-history of
Living Organisms, in Annals of Botany, viii (1894).
* Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), p. 384, footnote 2.
MICROSPORANGIA OF ANGIOSPERMAE 599
(2) MICROSPORANGIA OF THE ANGIOSPERMAE.
Warming ' has shown that the archesporium, as well as the wall-layers
which subsequently surround the sporogenous tissue, proceed from a
hypodermal cell-row or cell-layer. At each of the four angles of the
anther a hypodermal cell-row or cell-layer divides by periclinal walls
(Fig. 393, 2). Of the cells thus produced the inner give rise to the
archesporium, the outer form the primary tapetal layer, the cells of which
now divide further by periclinal walls, and the innermost layer of cells so
formed becomes later ¢apfetum (Figs. 391, ¢, 392, 2), its cells are s¢apetal
cells, and this layer is completed on the inner side of the archesporium by
other tapetum-cells which are furnished by the cells limiting it there. The
process which in all details corresponds to that in the sporangia in the
Pteridophyta is made clear by a comparison of the figures.
FiG. 393. Hyoscyamus albus. 1, anther in transverse section; o7/, vascular bundle of the connective, co. The
Fee pee ts Otentere pie yeuuy aatier ws Concreue aeutans a archcsoden, s pricy ape
layer ; 7, epidermis.
Hyoscyamus. In Hyoscyamus (Fig. 393, 2) the archesporium shows on
transverse section a cell-row. The sporogenous tissue which proceeds from
this is not very large. It is composed only of two cell-layers, and is curved
in a horse-shoe shape, so that the tissue of the stamen is pushed into the
pollen-sac. These portions of staminal tissue have been called by Chatin
placentoids, but they have really nothing in common with the placenta.
Symphytum officinale. In Symphytum (Fig. 391) the sporogenous
tissue is much greater in amount. It proceeds here from a cell-layer which
in transverse section consists of only a few cells”.
Knautia arvensis. There are also cases in which the archesporial cells
become directly sporocytes. We find this in Knautia arvensis (Fig. 392).
The archesporium is here a cell-row. The cells double themselves in some
1 Warming, Uber pollenbildende Phyllome und Kaulome, in Hanstein’s Botanische Abhandlung,
ii (1873).
2 See Warming, op. cit., Taf. iii, Figs. 1-8, representing Symphytum orientale.
600 DEVELOPMENT OF THE SPORANGIUM
pollen-sacs by one—seldom two—longitudinal walls (Fig. 392, 1, below),
and the cells of the two rows which thus arise become now sporocytes.
In other cases (Fig. 392, 2) this division does not take place, and the
archesporial cells directly become the sporocytes.
The outer envelope of the pollen-sac is formed of four cell-rows in
Fig. 392, 1—the tapetal cells, ¢, two parietal layers, #, z, and the epidermis.
The outer tapetal cells and parietal cells have proceeded from the division
of one layer of cells—the primary tapetal layer—and this origin is still
evident. The inner of the two parietal layers, z, after sharing at first in
the conduction of plastic material to the sporogenous cell-mass, is sub-
sequently compressed by the tapetal cells, which, as Fig. 392, 2, shows,
enlarge greatly. The outer parietal layer forms here as in many other
pollen-sacs the fibrous cell-layer of the anther—the exdothecium. The
walls of the cells of the endothecium have fibrous thickening upon their
inner side. They are the ‘active’ cells, and in the process of drying
a tension arises which ruptures the anther-wall at its weakest position,
which is opposite the septum separating the two pollen-sacs of one anther-
half. The separation-wall consisting of many cell-layers has been destroyed
earlier either entirely or only in its lower part. The tapetal cells are also
here dissolved about the same time that the young pollen-grains become
isolated. First of all there is usually a multiplication of the cell-nuclei
within them (Fig. 392, 2) which is the result of fragmentation, according to
Strasburger. The protoplasm of the tapetal cells is used up by the growing
pollen-grains.
A doubt remains as to the first differentiation of the archesporium in some of the
plants investigated by Warming, for example Zannichellia, Gladiolus, Ornithogalum,
Funkia ovata, Eschscholtzia californica, Tropaeolum. It is possible that sometimes
more than one cell-layer is employed in forming the archesporium, at least Warming
gives this behaviour in the case of Tropaeolum. Yet it seems to me that according
to his figures this case also can be traced back to the ordinary scheme, especially if one
assumes that in the archesporium very irregularly directed division-walls appear.
(6) SPORANGIA OF THE PTERIDOPHYTA.
Like differences with regard to the sharp differentiation of the arche-
sporium are found amongst the Pteridophyta. A sporangium of a medium
development in Selaginella, such as is represented in Fig. 394, shows clearly
that it corresponds throughout with the like stage of development of a
microsporangium in Angiospermae. Above and to the left is a longitudinal
section through a young sporangium; @ is an archesporial cell’; ¢ is the
first tapetal cell which is given off from the archesporium. The wall of
the sporangium becomes later two-layered by division.
1 As a matter of fact there are many archesporial cells side by side owing to the flat conformation
of the sporangium, and this can be seen in a tangential section.
SPORANGIUM OF PTERIDOPHYTA 601
According to Bower’ the separation of the wall from the archesporium does not
take place so early as I had assumed’, but the cell, 4 proceeds from the division
of the outer cell, and it itself shares in the formation of the sporogenous cell-mass.
He also says the limitation of the archesporium is frequently less sharp than I sup-
posed. He thinks that in Equisetum arvense and Isoetes, for example, sporogenous
cells can be furnished by those which I had considered as the primordium of the
wall of the sporangium. That the wall can be differentiated at a relatively late
period from the sporogenous cells I had already shown in the case of Ophioglossum,
and according to Bower’s investigations this occurs elsewhere. A variation in the
formation of the sporogenous cells is found also in the Musci; cells of the columella
may occasionally be fertile even in the Musci which have a sharply differentiated
archesporium, and it seems to me
that the question whether the arche-
sporium may be differentiated earlier
or later has no fundamental import-
ance, evidently both cases may occur.
Absolute rules are never found in
relation to organisms.
So far as I can see the simplest
expression of the facts regarding the
first inception of the sporangia is
this: the essential content of the
sporangium—the sporogenous cell-
mass + sporangial wall—can be
Fic. 394. A and B, Selaginella spinulosa. Young and
traced back to a superficial cell, cell- old sporangium in longitudinal section. a@, archesporium,
¥ shaded in all figures; 4, tapetum; ¢, ligule. C, Cuphea Zim-
row, or cell-mass. This divides by Cs Nucellus of ovule in longitudinal section. C, after
hnsson.
periclinal walls. In this way the pri- ie
mordia of the wall and sporogenous cell-mass are separated, but the outer cells or
cell-layer may also share in the increase of the sporogenous mass, and the wall then is
only later differentiated. One might then designate as archesporium that superficial
cell-row or cell-layer which earlier or later gives off sterile cells, whilst in the sporangia
of the Angiospermae the archesporium is a layer lying under the already differentiated
epidermis, and upon this would depend the above-mentioned differences in the
structure of the wall within the Pteridophyta and the Gymnospermae on the one
hand and the Angiospermae on the other *.
1 Bower, Studies in the Morphology of Spore-producing Members: I. Equisetineae and Lyco-
podineae, in Phil. Trans., 1894; II. Ophioglossaceae, London, 1896; III. Marattiaceae, in Phil.
Trans., 1897; IV. Leptosporangiate Ferns, in Phil. Trans., 1899.
2 Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884). I have not myself examined into this question anew, and therefore refer only
to the very thorough investigations of Bower, which have frequently completed and partly corrected
my investigations made before the time of microtome-work.
$ I do not regard as well founded the statement of R. Wilson Smith, The Structure and Develop-
ment of the Sporophylls and Sporangia of Isoetes, in Botanical Gazette, xxix (1900), p. 255. ‘* The
origin of the sporogenous tissue from a hypodermal layer, separated from the beginning from the
epidermis, is a spermatophyte character.’ The microsporangia of the Gymnospermae behave quite
like those of the Pteridophyta.
602 DEVELOPMENT OF THE SPORANGIUM
All sporangia zz the outline of their process of development are the
same. The differences in details are more a question for systematists, and
may be omitted here’. I must, however, refer to the difference between
eusporangiate and leptosporangiate forms :—
EUSPORANGIA AND LEPTOSPORANGIA. Eusporangia are sporangia
which proceed from many cells and have, at least in the primordium,
a many-layered wall. Leptosporangia are sporangia which proceed from
one cell and have a one-layered wall. There are transitions in the
Osmundaceae.
It probably may be also added as a distinction that the stalk in the
eusporangium consists of a portion of the tissue of the sporophyll?; the
stalk in the leptosporangium proceeds from the archesporium, so that if
the mother-cell of the sporangium of the Leptosporangiatae is designated
as the ‘archesporium °,” the archesporium would appear to be here in most
cases a derived structure in that only after formation of a number of sterile
cells it proceeds to the formation of the fertile ones. Leptosporangia occur
only in Leptosporangiate Filicineae; all other Pteridophyta, as well as
Spermophyta, have eusporangia. This distinction is, however, not absolute,
as may be expected from what has been already said *, and the sporangia
of the Osmundaceae are probably a connecting link between the two
forms of sporangia.
One other question must be dealt with here, namely, that of the
origin of the distinction between microsporangia and megasporangia :—
MICROSPORANGIA AND MEGASPORANGIA. When we compare the
development of the megasporangia in the heterosporous Pteridophyta with
that of their microsporangia, two facts of general interest appear :-—
1. The development of the two kinds of sporangia proceeds for a long
time in the same way, and the whole development of the microsporangia
corresponds with that of sporangia which have only one kind of spore ; but
in the megasporangia an abortion of a number of the sporocytes takes
place. The megasporangia show in their development also that they
are derived from sporangia which have possessed a larger number of spores
than is now the case, and, as a matter of fact, in fossil forms a larger
number of megaspores are present °.
* For these details see the thorough investigation of Bower, Studies in the Morphology of Spore-
producing Members: I. Equisetineae and Lycopodineae, in Phil. Trans., 1894; JI. Ophioglossa-
ceae, London, 1896; III. Marattiaceae, in Phil. Trans., 1897; IV. Leptosporangiate Ferns, in Phil.
Trans., 1899.
? See p. 476, Botrychium.
* Not, as has been customary up to now, the tetrahedral inner cell from which the sporocytes
proceed.
* See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, ili (1884).
° In Calamostachys Casheana—a fossil equisetineous plant—numerous spores are present in the
megasporangium, although they are fewer in number than in the microsporangia. See Scott, Studies
MEGASPORANGIUM OF SELAGINELLA 603
2. Amongst the heterosporous forms which have now living repre-
sentatives, a reduction takes place which we can follow. Tetrad-formation
goes on in all the sporogenous cells together of the megasporangia of
Salvinia and the Marsiliaceae, but it is only in one of the tetrads that one of
the four daughter-cells forms a megaspore. Whilst then only one megaspore
is found in each megasporangium, the heterospory has proceeded less far
than it has in Selaginella, where four megaspores arise from one tetrad.
The Megasporangium of Selaginella. In Selaginella the development
of the megasporangium is characterized throughout by the fact that usually
only one cell of the sporogenous mass’ arrives at the formation of tetrads.
Fig. 395 shows a megasporangium in which the cells of the sporogenous
cell-mass have degenerated. One is larger and richer in content than the
others, and this is the megasporocyte which
will divide into four daughter-cells. There
can be no doubt that the sterile and un-
divided? spororytes are used up as nutrition,
although their remains may long be retained.
We may well assume that each one of the
sporogenous cells was in the condition to
become fertile, and that the relationships
here are somewhat like those in the case of
bees, whose female larvae have all the po-
tentiality of developing into queens, whilst
in reality this usually only happens in one
Special one that is well fed. Anyhow it sic. sos. Selaginellaerythropus. Mega
appears in Selaginella, so far as my observa- SPorangium ih longitndna dss central
tions reach, that the most favoured cell is ome js larger,than the others, and is the
one which lies about the middle of the spo-
rangium. Even if it should take up no material from the sporocytes which
remain sterile*, it would be still favoured in its nutrition, as to it alone
all material would stream from the tapetal cells. It is recognizable even
before the breaking up of the sporogenous cell-mass*.
The Megasporangium of Isoetes. The differentiation of the mega-
in Fossil Botany, London, 1900, p. 53. Also in Lepidostrobus Veltheimianus more than four spores
(8 to 16?) are found in each megasporangium, ibid., p. 173-
1 In Selaginella erythropus I found, not infrequently, two.
2 As Sachs rightly showed. The statement of Campbell, The Structure and Development of the
Mosses and Ferns, London, 1895, p. 504, that the differentiation of the megasporocyte takes place only
after the tetrad-division in all the sporocytes, is erroneous—at least for the species examined by me.
8 In Selaginella helvetica and S. denticulata the sporocytes degenerate in the microsporangia. See
Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), p. 389. This shows also that the difference between microsporangia and
megasporangia is only one of degree.
* See also Fitting, Bau- und Entwicklungsgeschichte der Makrosporen von Isoetes und Selaginella,
in Botanische Zeitung, lvili (1900).
604. DEVELOPMENT OF -THE*SPORANGIOM
sporocytes in Selaginella takes place always at an earlier stage in the
development than it does in Isoetes, where both in the microsporangia and
megasporangia there is a further approach to the behaviour of the Spermo-
phyta. This view, which I published long ago, I still maintain after
renewed investigation of both Isoetes lacustris and I. Hystrix'.
The contradiction which my statement has met with at the hands of Fitting *
and of Smith* relates to subsidiary points, such as the arrangement of the cells, the
question when the separation of wall and content takes place, and the like. I have
said* that from the archesporium a cell-mass proceeds, composed at first of similar
cells arranged zearly at right angles to the surface of the sporangium; isolated
cell-rows of the mass lose their rich protoplasmic content, remain also in their growth
behind the others, and become the trabeculae. I do not find that Smith’s account
deviates from this in any essential point. He finds the arrangement of the cells less
regular ; doubtless it varies. In Isoetes Hystrix, for example, they run nearly in rows
which are directed obliquely towards the base of the sporangium. I have never
designated the sporangia as ‘ chambered’ or as ‘compound,’ although Smith thinks
this to be a consequence of my work, and the trabeculae are expressly designated as
‘ sporogenous tissue which has become sterile.’ The tapetal cells are, as in Selaginella,
not broken down. With regard to the megasporangia I stated® that at a medium
stage of development there is one large sporocyte lying in the middle of the sporan-
gium. This is the case; but I was wrong, as the investigations of Fitting and Smith
have shown, in the statement that the megasporocyte exercises a destructive influence
upon the surrounding cells. I still find stages in which the megasporocytes are
separated from the surface by two or three cells which I had considered as proceeding
from the division of an archesporial cell out of which the megasporocyte also came,
and I see nothing to lead me to regard this interpretation as wrong. This point is,
however, quite subordinate. What is more important is the fact that in the mega-
sporangia of Isoetes the cells which do not become megasporocytes divide further,
although no further than do megasporocytes, and take on a much more vegetative
character than do those of Selaginella. In the megasporangium of Isoetes Hystrix
there appears moreover, as I find in conformity with Smith, at the beginning a number
of cells marked out by their size, all of which, however, do not become megasporocytes.
Those which remain sterile evidently divide later. In this and not in the relationships
of the arrangement of the cells lies as it appears to me the interest of the development
of the sporangium in Isoetes, for we have in it a further approach to the behaviour
of the megasporangium of the Spermophyta—an approach which is also expressed
in the differentiation of the microsporangia and megasporangia at an earlier period
in Selaginella than in Isoetes.
* From material kindly supplied by Graf zu Solms-Laubach.
’ Fitting, Bau- und Entwicklungsgeschichte der Makrosporen von Isoetes und Selaginella, in
Botanische Zeitung, lviii (1900).
° R. Wilson Smith, The Structure and Development of the Sporophylls and Sporangia of Isoetes,
in Botanical Gazette, xxix (1900), pp. 225, 323.
* Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884), a work which Smith has not referred to. 5 Goebel, op. cit.
605
IV
roe iG sy POTHESES. RELATING TO. THE
FORMATION OF SPORANGIA
I propose to deal briefly here with the hypotheses to which origin has
been given by the necessity for the endeavour to connect the different
forms of sporangial formation one with another, and at the same time to
connect the relationships of propagation of the Pteridophyta and Spermo-
phyta with those of the Bryophyta. I cannot pretend to give an account
of the different views, more or less well founded, of different authors;
I must content myself in this respect with specially calling attention to
Bower’s views, because they are founded upon a number of exact historical
developmental investigations. All I can do here is to put forward some
general thoughts lying at the base of this research.
The principle from which we start is that first formulated by Nageli’. In the
year 1853 Nageli wrote ‘One of the first laws is that a higher species or group
repeats the phenomena of the lower, but proceeds therefrom to a new phenomenon.
This first law finds its explanation and its origin in a second which to me appears to
be of the highest significance for the succession of the groups in the Plant Kingdom :—
the reproductive phenomenon of one stage is at a higher stage vegetative’ In 1884
Nageli more fully set forth this view? and assumed that the sporophyte-generation
of the Pteridophyta has arisen by the branching of a sporophyte like that of the moss;
it formed a spike-like strobilus in which the terminal sporangium disappeared, and
the lateral ones ‘by adaptation’ became constructed in a leaf-like form. That
Nageli’s ‘law ’—apart altogether from the hypothesis just mentioned—is one of great
importance admits of no doubt. In Part I of this book it was shown in examples of
the construction of colonies, for example in the Myxomycetes, how a ‘higher’
construction of the vegetative body comes about by the postponement of the propaga-
tion to a later stage of development, and this is really the essence of Nageli’s law.
We see further that the sporogonia of the Bryophyta arrange themselves in a series
which begins with forms in which all the cells are devoted to spore-formation, as in
Riccia—with the exception of a peripheral layer—and ends with forms in which the
majority of the cells of the sporogonium have become sterile. Also in the sporangia
of the Pteridophyta such a sterilization appears as we see in the trabeculae in Isoetes®,
and in the chambering of the sporangia of Psilotum, the synangia of Marattia, and
elsewhere as interpreted by Bower. Further in the shoots.a sterilization of those which
originally were flower-shoots or inflorescences is a wide-spread phenomenon. The
question then is how far do the facts that are before us warrant our extending the
principle? Let us look at a special case.
1 Nageli, Systematische Ubersicht der Erscheinungen im Pflanzenreich, Freiburg i. B., 1853, p. 35-
? Nageli, Mechanisch-physiologische Theorie der Abstammungslehre, see specially p. 472.
* Goebel, Beitrige zur vergleichenden Entwicklungsgeschichte der Sporangien, in Botanische Zeitung,
Xxxvili (1880), p. 565.
606 PHYLETIC HYPOTHESES OF SPORANGIAL FORMATION t
When speaking of the sporophyll the peculiar position of the sporophyll of the
Ophioglossaceae was pointed out : how it arises upon the upper side of a foliage-leaf.
The whole sporophyll is now regarded by many authors as a sporangium of equal
value to that of Lycopodium’. Now the sporangia of Lycopodium arise in the
leaf-axils (Fig. 396, 1). If we suppose such a sporangium is gradually increased in
size, a large number of sterile cells will be necessary for the nourishment of the
spores. We might then suppose that as in Anthoceros or Sphagnum the archesporium
surrounds like a dome the inner sterile mass (Fig. 396, IT), and that further as in the
Musci also the upper part of the archesporium was sterilized (Fig. 396, III). Upon
the transverse section of such a construction we might find the archesporium no
longer annular but at two places only—right and left (Fig. 396, IV). If
now further sterilization throughout its length breaks it up into single sections
(Fig. 396, V), we could thus obtain the sporangia of Ophioglossum, and if these
were to project slightly
those of Botrychium
(Fig. 396, VII)?. Were
these sporangia now
partly sterilized we
should obtain a lateral
sporangiophore - sterile
at the “4p. as,-it is
found in Helmintho-
Fic. 396. Scheme of the transformation ot a sporangium, say of Lyco- stachys (Fig. 396,
podium, into a sporophyll like that of Helminthostachys. The stages follow VIII) and eventually
the numbers I to VIII. VIII represents the sporophyll of Helminthostachys. : es
IV represents a transverse section of the sporophyll of Ophioglossum with by complete steriliza-
enveloping sterile leaf-portion.
tion a sterile leaf.
It has been shown ® that if we read backwards the history of development of the
microsporangia of Juniperus we find there the transition from a sporangium into
a sporangiferous leaf. The sporangia were then primary, the foliation of these
secondary. That such a process is possible cannot be denied, but the facts which
have been used as a starting-point do not form a sure foundation for it. According
to the present state of our knowledge, far-carrying phyletic constructions which deal
with processes which were in progress in the very earliest periods of the earth’s
history, of which the vegetation is known to us now only by some straggling remains,
for instance that of the Carboniferous Period, are certainly stimulating, especially if
they are founded with sagacity, but there are numerous problems which offer more
prospect of a certain solution than these. In this connexion I may refer to what
I have said regarding the sporophyll.
|
;
|
' We must not forget that the selection ‘of a single organ without reference to others must often
lead to untenable conclusions. The Ophioglossaceae are undoubtedly Filicineae by their structure,
the development of their leaves, shoot-axes, roots, and sporangia. One must therefore compare
them with Filicineae not with Lycopodineae.
* This figure corresponds more with the sporangial spike of Botrychium simplex. In most species
of Botrychium we find that the portion bearing the sporangia is branched. One must therefore
suppose that a division by branching of a marginal sporangium has taken place.
$ See p. 516.
ae. Te
607
V
APOSPORY
By apospory is meant the remarkable phenomena which are expressed
in the suppression of the formation of the spores. To a certain extent it
is the converse of the apogamy! of the prothallus, and it appears in two
different forms :—
(z) The sporangia are replaced by a vegetative propagation of the
sporophyte, the gametophyte is, as it were, entirely kept out.
This case is as yet only known in Isoetes, and here only from the
single station, Lake Longemer in the Vosges”. It is, however, probable
that it will be found elsewhere. The phenomenon comes about probably
under the direct influence of externa! factors. The facts are shortly these:
There are plants of Isoetes which bear neither megasporangia nor
microsporangia, but, in place of these, young plants are developed upon
the leaves. In some cases sporangia are found as well. In Fig. 292 a case
is represented in which a leaf bears a reduced sporangium, and below it
a shoot*. There are also intermediate stages between the normal con-
struction and complete suppression of the sporangia, coupled with their
replacement by the formation of shoots. That the suppression of the
sporangia takes place under conditions which are unfavourable for the
development of sporangia—be these failure of illumination or the nature of
the soil—is very probable, but exact information upon this can only be
obtained by experimental cultures—observations in the natural habitat
alone are insufficient. I have already compared this case with that of the
formation of the gemmae in Lycopodium Selago, in which species it is
characteristic to find the gemmae appearing in the region of the shoot
where the formation of the sporangia is suppressed*. The conditions for
this in Lycopodium Selago are in the first place given by periodicity,
probably induced primarily by external factors; in Isoetes it is a con-
sequence probably directly of the environmental conditions of the station.
The general interest of the case lies in this, that, apart from the remarkable
morphological fact, a rich shoot-development takes place in a plant which
otherwise usually remains unbranched.
(4) The gametophyte is formed directly from the sporophyte, without
the intervention of spores.
1 See p. 220.
2 Goebel, Uber Sprossbildung auf Isoétesblittern, in Botanische Zeitung, xxxvii (1879), p. 1;
xxxviii (1878), p. 413; also Mer, De l’influence exercée par le milieu sur la forme, la structure et le
mode de reproduction de l’Isoetes lacustris, in Comptes-rendus de l’Académie des sciences, xcii (1881).
* It may be remarked that also amongst the normal plants the sporangium often keeps only to the
upper part of the leaf-base on leaves which have restricted formation of sporangia.
* See p. 467.
608 APOSPORY
Druery was the first who found in Athyrium Filix foemina clarissima
(Fig. 397) an arrest of the spore-formation and development of the
prothalli out of the sporangium without the intervention of spores. Bower
made a thorough investigation of the phenomenon, and named it apospory!.
He found that the arrest of the development of the sporangia may take
place at different stages, and an aposporous further development of the
sporangia, from which prothalli grow out, ensues all the more completely
the earlier this arrest takes place. In the sporangia which have proceeded
furthest in their ‘normal’ development, no further development takes place,
or this goes on only in the stalk, and it is of special interest that the
archesporium” takes no share in the further
vegetative development. We may in this see
an indication that the archesporium is dis-
tinguished from the other cells of the sporan-
gial primordium, just as we saw that a further
development can proceed in the wall-layers
il of the antheridium or the archegonium, but
| not in the spermatocytes* The prothalli
Ca which grow out from this sporangium pro-
eas duce normal sexual organs.
In Polystichum angulare, var. pulcherri-
mum, the apospory goes further. Prothalli
here arise from the arrested sporangia, from
the base of the sorus, from the surface of the
pinnules, or from the leaf-tip. The develop-
ment of the sporangium is thus entirely cut
out.
The same thing is observed in Scolopen-
I I V. drium vulgare, var. crispum Drummondiae.
In Lastraea pseudomas, var. cristata,
«Ei64p7. Athyrium Filistoeminaclaris, Druery found” the leaf tip of a germ-plant
optical section. Ill and IV, similar spor. Owing out into prothalli, and he described
a es eae germ-plants in which the primary leaves
consisted of erect prothalli standing upon stalks which corresponded well
with leaf-stalks.
The causes of these remarkable phenomena are unknown to us. We
only know that they have nothing to do with the influence of cultivation.
ae e
° ele
7 le
6
b
? Bower, On Apospory and Allied Phenomena, Transactions of the Linnean Society, London, 1889.
* Using this term in its ordinary sense, that is, for the tetrahedral cell out of which the tapetal cell
and the sporogenous cell-mass proceed.
3 See p. 187.
* Druery, Notes upon Apospory in a Form of Scolopendrium vulgare, var. crispum, and a new
Aposporous Athyrium ; also An Additional Phase of Aposporous Development in Lastraea pseudomas,
var. cristata, in Journal of the Linnean Society, xxx (1894).
APOSPORY 609
Speculations innumerable may, however, be based upon them, but they do
not give us much insight. We may, for example, derive the Pteridophyta
from a plant which had no alternation of generations, but somewhat the
conformation of a prothallus of Lycopodium inundatum ; whose lobes bore
partly sexual organs and partly spores, and only later its development
divided into a gamophytic and sporophytic section, which originally were
constructed alike; then the gametophyte experienced a regression and the
sporophyte a progression. This may be spun out further, but it is mere
fancy, which does not help us forward. We do, however, see here that the
cells of the sporophyte can furnish the gametophyte without the reduction
of the chromosomes to one half, as it takes place in the division of the
sporocytes. Moreover, apospory also can be combined with apogamy!.
The transitions which lead from the normal behaviour to apospory
appear to me to show that apospory is not an original but a derived con-
dition in which two factors are concerned :—
1. The arrest of the development of the sporangia ;
2, The introduction of a new vegetative development leading to
formation of prothalli.
Favourable objects for experimental investigation would be furnished
by the Hymenophyllaceae with their basipetal development of the sorus.
That apospory is found frequently in forms of fern in which the configura-
tion of the leaf deviates from the normal type, shows us that the formation
of the organs has connexions about which at present we know nothing.
A slight change in the whole constellation can effect a destruction in
another place. We have to do with a system of connexions where ‘one
thread holds thousands.’ An insight into these connexions can only be
obtained experimentally, and a work of Atkinson? is of interest, who,
repeating my research into the virescence of Onoclea*, found apospory in
virescent sporophylls of Onoclea sensibilis which were produced experi-
mentally. Here the influence is certainly one from the outside, but up till
now we only know the external jog which brings it about, not the chain
which conditions
1. the destruction ofthe sporangial development, which also takes
place in Onoclea Struthiopteris under like conditions ;
2. the development of the prothalli.
The examination into these connexions, and not the creation of phyletic
pictures, will be the work of the future.
1 See Bower, On some Normal and Abnormal Developments of the Oophyte in Trichomanes, in
Annals of Botany, i (1888),
? Only known to me by a reference in Just’s Botanischer Jahresbericht, Jahrgang xxiv (1896), p. 433.
3 See p. 475.
GOEBEL II Rr
610 THE SPORANGIUM OF SPERMOPHYTA
VI
THE SPORANGIUM OF THE SPERMOPHY i
A. MICROSPORANGIA.
(2) MICROSPORANGIA OF THE GYMNOSPERMAE.
The structure of the microsporangia of the Gymnospermae links on
closely to that of the sporangia of the Pteridophyta, in that the outermost
layer of their sporangial wall shows the same characteristic thickenings of
the active cells of the opening mechanism—at least this is the case in all
the Cycadaceae, Coniferae, and Gnetaceae which I have examined!. The
development of the microsporangia also” is so like that of the sporangia
of the Pteridophyta that it does not appear necessary to enter into this
question here, and the relationships of arrangement and of number have
already been spoken of when the sporophyll was described *. I will only
state that in the arrangement of the microsporangia, especially if these are
few in a sorus, we can readily see that they are uniformly distributed in the
space available—for instance, if there be three they stand at about 120°
from one another—and that they also have a marked dorsiventral structure,
and in correspondence therewith they open by a longitudinal slit which is
directed downwards—reckoned from the stamen. In the Coniferae there
occur both longitudinal and transverse slits, the latter, for example, in
Abies, and doubtless the difference in the method of opening is connected
with the conformation and lie of the sporangia*: elongated nearly cylindric
sporangia, like those of Pinus, best open along their long axis; those of
Abies are more spherical. In a more spherical sporangium the direction
of opening is a matter of little moment, yet in such a case it is influenced
by the position, for instance in Juniperus and other Cupressineae the
opening takes place on the side which is turned away from the sporophyl—
an arrangement regarding the advantage of which it is unnecessary to
speak, especially as it has been shown how in the Pteridophyta there is
a connexion between the lie and the manner of opening of the sporangia.
(0) MICROSPORANGIA OF THE ANGIOSPERMAE.
The microsporangia of the Angiospermae differ from those of the
Gymnospermae in this that their active cells where such exist are always
1 Regarding Ginkgo see p. 515.
? See concerning the Cycadaceae: Warming, Bidrag til Cycadernes Naturhistorie, Afdryk af Overs.
over d. K. D. Vidensk Selsk. Forhandl., 1879; Treub, Recherches sur les Cycadées, in Annales du
Jardin botanique de Buitenzorg, ii (1881); W. H. Lang, Studies in the Development and Morphology
of Cycadean Sporangia : The Microsporangia of Stangeria paradoxa, in Annals of Botany, xi (1897).
Concerning the Coniferae: Strasburger, Die Coniferen und Gnetaceen, Jena, 1872; Goebel, Beitrage
zur vergleichenden Entwicklungsgeschichte der Sporangien, in Botanische Zeitung, xl (1882), p. 771.
8 See p. 511-
* Compare Goebel, Uber die Pollenentleerung bei einigen Gymnospermen, in Flora, xcii (Ergin-
zungsband zum Jahrgang 1902).
-
MICROSPORANGIA AND MICROSPORES 611
hypodermal. Even where in the mature condition the active cells apparently
form the outermost layer, for example in Casuarina, the history of develop-
ment nevertheless shows that there is an epidermis over them, but its cells
soon become inconspicuous, and in the examination of the mature anthers
can be readily overlooked. In many cases the formation of active cells is
suppressed entirely, for example in the parasitic Pilostyles Ulei and in the
Ericaceae, or partly as in many plants like Berberis, which have valvular
dehiscence of the microsporangia and in which the active cells only occur at
the valvest. The epidermis of the microsporangia in the Angiospermae may
also have a characteristic construction, but we never see in its cells, so far
as I know, the peculiar construction of the cell-wall, especially the charac-
teristic thickening which is found in the cells that lie immediately under
the epidermis * and constitute the hypodermal enxdothecium.
Ericaceae °. Fig. 398 shows certain relationships which are found in
the Ericaceae and which require further investigation. The epidermal cells
of the microsporangia are large, and possess
as it appearsa slimy content. At the position
where dehiscence will occur they are much
smaller, and probably the opening which takes
place usually in the flower-bud is brought
about by the drying up of these cells. At
any rate, there are no thickenings in the cell-
walls of the endothecium.
It is then evidently a weighty sys-
3 é Fic. 398. Erica carnea. Half of an
tematic character of the Angiospermae that anther in transverse section beyond the
‘ FE 3 : point of opening. No endothecium is
the active cells of the microsporangium, if present, although’ the pollen-tetrads are
¥ js already formed. Magnified.
they are present, are in the endothecium,
whilst in the Pteridophyta and Gymnospermae they are in the exothecium*.
As to the lie of the point of opening of the sporangium in the
Angiospermae there are many variations. The-significance of this depends
specially upon the relationships to pollination by insects and must remain
here unexplained. It lies within the province of the biology of pollination.
MICROSPORES.
Space forbids us a discussion of the construction of the microspores.
I will only briefly recall the differences in the pollen in wind-pollinated and
insect-pollinated flowers, the remarkable thread-like pollen of Zostera and
Halophila, the pollen-tetrads and pollinia as they occur in different cycles
of affinity.
1 See Chatin, De l’anthére, Paris, 1870. 2 These extend often over the connective.
* See Artopoeus, Uber Bau und Offnungsweise der Antheren und die Entwicklung der Samen der
Ericaceaen, in Flora, xcii (1903).
* Whether this is without exception further investigation alone can tell. See p. 577.
Rra2
612 THE SPORANGIUM OF SPERMOPHYTA
The gametophyte in the Spermophyta is so dependent that it appears
best to deal with it along with the sporophyte. We must therefore speak
here of the germination of the microspores.
GERMINATION OF THE MICROSFPORES.
The development of the microspores in germination has been made
known to us specially by the investigations of Strasburger, Belajeff, Ikeno,
Hirase, and Webber. It shows us so far a parallel formation with that in
the megaspore, as we find in both a vegetative development which is always
very much shortened.
The form of the microspores varies ; sometimes it is tetrahedral, some-
times bean-like (dorsiventral), sometimes more spherical. The rounded
in the Coustrnction, TLE Ablerineas:. TV, Anptesse tae Messe ot tela ae eee Mina eres aie
sheridian: ; Som, mother.cell of the male scxaalicelisy (99, qpenetnerceae 07 oe alee eee ener
basal surface of the tetrahedral microspore may be designated the dase ;
the portion over against it the afex; and, similarly, in the dorsiventral
microspore the convex outer surface is the base.
Amongst the Cycadaceae' the germination of the microspore of
Zamia has been made known to us through the researches of Webber. In
the ripe microspore we find three cells? (, A, Sch, in Fig. 399, I). Cell p
lies at the apex of the microspore and is a cell of the prothallus; cell A is
the mother-cell of the antheridium; cell ScZ is the tube-cell which, developing
in the pollen-chamber, at first acts as a haustorium to bring nourishing
material out of the nucellar tissue to the germinating microspore; only
1 See Ikeno, Untersuchungen iiber die Entwicklung der Geschlechtsorgane und den Vorgang der
Befruchtung bei Cycas revoluta, in Pringsheim’s Jahrbiicher, xxxii (1898) ; H. J. Webber, Spermato-
genesis and Fecundation of Zamia, in U.S. Department of Agriculture, Bureau of Plant-Industry,
Bulletin No. 2, Washington, 1901. Webber gives the literature.
? Whether occasionally a fourth appears is of no significance here.
a
GERMINATION OF THE MICROSPORE 613
later does the tube-cell bring the apex of the microspore into contact with
the archegonia by the formation through intercalary growth of a sac-like
outgrowth (Fig. 399, II). Such pollen-tubes I call acrogamous. Acro-
gamous pollen-tubes are only found in the Cycadaceae and Ginkgo, and
this fact has no doubt the closest connexion with the existence of a pollen-
chamber.
At the apical end of the pollen-tube the following changes take
place:—The mother-cell of the antheridium is divided by a wall oblique
to the long axis of the pollen-tube into two cells, an upper and an
under. The upper cell is the central cell of the antheridium out of which
by division two spermatocytes proceed, and these give origin to two giant
spermatozoids. The under cell has received the unfortunate name of
‘stalk-cell’ which is inapplicable upon the two grounds that the anthe-
ridium is sunk and can therefore have no true stalk-cell, and that we never
see that a stalk-cell is separated from a spermatocyte, but there is a separa-
tion of the wadl-cell'.
The first cell of the prothallus at the apex of the microspore (Fig. 399,
I, f) swells up and surrounds the stalk-cell like a ring. Both are limited
to the outside only by a membrane, not by a wall. Nevertheless these
cells may reach a considerable size, and it is remarkable that no function
has yet been ascribed to them. One might suppose, as they contain starch,
that they aid in the nourishment of the strongly growing spermatocyte,
but I think that they constitute an apparatus for the opening of the pollen-
tube at its point. The pollen-tube is cuticularized. Both in the pollen-
tube and in the cells which are found under the spermatozoids the osmotic
pressure gradually increases. The prothallus-cell, , presses upon the stalk-
cell it encircles, and this again is under the pressure of the content of the
pollen-tube. The pressure so acts that the membrane of the pollen-tube
bursts at its least stretchable place—that is, at the point of attachment to
the cells of the prothallus—the spermatozoids are pressed out and are able
then to force themselves into the egg.
The tube-cell has been also considered as the wall of the antheridium.
I see no ground for this. We know of no case in which the antheridial
wall functions as a haustorium, but we have many cases, on the other hand,
in the megaspores of the Angiosperms where the cells of the prothallus
are converted into haustoria 2.
We have then in the microspore of the Cycadaceae the following
structure :—
1. Two cells of the prothallus, of which one becomes a pollen-tube
* See p. 180. Wettstein, Handbuch der systematischen Botanik, ii (1904), has recently called the
stalk-cell a ‘ wall-cell.’
* The whole orientation of the antheridium is against the view also.
614 THE SPORANGIUM OF SPERMOPHYTA
which originally is a haustorium, and later conducts the spermatozoids to the
archegonium, whilst the second one effects the opening of the pollen-tube.
2. The antheridium, consisting of wall and spermatocytes.
In the other Gymnospermae and in the Angiospermae the pollen-tubes
are basigamous. They serve indeed at first as haustoria, and later as
canals, which here conduct the massive male gametes to the egg. As
the opening of the pollen-tube takes place at the basal end the cells of the
prothallus have become, with the exception of the tube-cell, functionless.
They are indeed in many still formed—two, for example, in Larix, Picea
vulgaris, Pinus silvestris, P. Pumilio—although in such cases they usually
collapse soon, but in the Cupressineae and Taxodium their formation is
entirely suppressed, as it is in all Angiospermae. We have, therefore, in
these cases only the tube-cell and the mother-cell of the antheridium.
This mother-cell in the Gymnospermae divides into two cells—one corre-
sponding to the spermatocyte, which furnishes the two spermatozoids ;
the other is the wall-cell which we prefer to designate the dzslocator-cell.
Its function is to set loose the spermatocyte from its point of attachment,
as is particularly evident in Juniperus, where the dislocator-cell is very
large. Perhaps it bursts and in that way promotes the passage of the
spermatocytes into the pollen-tube, but in other cases the simple swelling
of the dislocator-cell may effect this. Only in some Gymnospermae is it
suppressed, but in Angiospermae its formation is always suppressed, because
there it would be unnecessary, seeing that the spermatocytes from the first
are not firmly fixed and have no attachment to the wall of the microspore.
The views that have been here expressed require to be proved by
investigation, but it seems to me hardly to admit of doubt that we shall
obtain a proper understanding of the germination of the microspore only
when we obtain more information about the fazction of the cells which are
found in the pollen-tube. If what has been said above be correct there is
in the microspore of the Spermophyta clear connexion between structure
and function, and functionless parts are evidently reductions.
B. MEGASPORANGIA.
(a2) GENERAL FEATURES.
Hofmeister’s epoch-making investigations determined once and for all
that the ovule in the Spermophyta is the homologue of the megasporangium
in the Pteridophyta. A thorough comparison of these sporangia only is
possible, however, if the historical development of their relationships are
discussed. Here we shall deal first of all with the grosser configuration of
the ovule.
We distinguish usually in it a stalk or funicle, one or more zntegu-
ments, and the zucellus enveloped by the integuments. The nucellus
THE MEGASPORANGIUM 615
is the megasporangium!. This is undoubted. On the other hand the
views upon the morphological significance of the integuments are various,
So far as functional importance is concerned we have to consider the
following :—The integuments act as a protective envelope to the ovule,
and then later they form the seed-coat. Where, as in Sympetalae, the
ovule consists of a thin nucellus and one thick integument, the integument
has to provide nutrition to the embryo-sac which grows out into it*. The
micropyle in all porogamous plants evidently conducts the pollen-tube. In
the germination of the seed the most rapid uptake of water also takes place
at this point.
Porogamy and aporogamy. In a number of Dicotyledones the micropyle
does not function as a conductor of the pollen-tube, and the plants are therefore
designated apforogamous. In Cynomorium * coccineum the micropyle withers very
rapidly and forms no longer an open canal. The same thing happens in the genus
Gunnera‘*, which stands so isolated in the plant kingdom; also in the Cannabineae®
and in Alchemilla arvensis®. This aporogamous condition has evidently appeared
independently in different dicotylous plants. In Cynomorium the pollen-tube forces
its way through the apex of the ovule. This method is acrogamous. Gunnera ripens
its seeds most probably parthogenetically. Pollen-tubes have never been proved
here. In Alchemilla the pollen-tubes force themselves in between the cells, and
grow up from the chalazal region to the egg-apparatus. This method is Jdaszgamous.
It also happens in Casuarina” as well as in the Corylaceae and Juglandeae,
notwithstanding that they possess a micropyle. These variations have evidently
no importance for the systematic grouping within the plant kingdom, but an
explanation is still required of why they should appear so frequently in plants which
have specially simply constructed flowers*. An intermediate position is taken by
the ovules in which a pollen-tube partly grows through the tissue of the ovule.
We see this in the Ulmaceae® and in the Cannabineae. It may well be assumed
that in all these plants special reasons exist, either in the structure of the cells or in
the conditions of nutrition of the pollen-tube, which cause it to take the path it does.
1 I may mention here that the nucellus may sometimes be abnormally developed as a micro-
sporangium. I observed such a case in Begonia; see Goebel, Beitrage zur Kenntnis gefiillter Bliithen,
in Pringsheim’s Jahrbiicher, xvii (1886), p. 246, Figs. 48 and 49. The literature is cited.
2 See p. 638.
3 Pirotta e Longo, Osservazioni e ricerche sulle Cynomoriaceae, in Annuario del R. Istituto
Botanico di Roma, ix (1900), Fasc. 2.
* Schnegg, Beitrage zur Kenntnis der Gattung Gunnera, in Flora, xl (1902).
5 Zinger, Beitrage zur Kenntnis der weiblichen Bliithen und Inflorescenzen bei Cannabineen, in
Flora, Ixxxv (1898), p. 189.
6 Murbeck, Uber das Verhalten des Pollenschlauches bei Alchemilla arvensis, (L.) Scop., und das
Wesen der Chalazogamie, Acta Universitatis Lundensis, xxxvi (1900).
7 Treub first discovered the process in this plant and called it chalazogamy.
* Vet the Fagaceae have porogamous fertilization. How do Sagina and like forms behave?
9 Nawaschin, Uber das Verhalten des Pollenschlauches bei der Ulme, Nachrichten der Kaiser).
Akad. der Wissenschaften in St. Petersburg, 1897. The pollen-tube here pushes ont of the tissue of
the funiculus through the integuments to the apex of the nucellus.
616 THE SPORANGIUM OF SPERMOPHYTA
THE INTEGUMENTS.
THE NATURE OF THE INTEGUMENT. From the morphological
standpoint there are two possible explanations of the formation of the
integument :—
(z) We may consider it as a new formation which finds no analogy in
the Pteridophyta.
(2) We may link it on to the indusial formation of the Pteridophyta,
finding an analogue in the megasporangia of Azolla (Figs. 325-327), which
are invested by an indusium laid down like an annular wall.
The second interpretation was mainly founded by Warming. Under it
it is most natural to consider the nucellus only as the megasporangium,
to regard the funiculus as a portion of the sporophyll on which the mega-
sporangium arises as
a terminal new forma-
tion, just as a mega-
sporangium of Azolla
aes arises on a placenta
\ which is formed from
| if a transformed _leaf-
/ ; lobe. This view may
| {L find confirmation in
/ the remarkable con-
is struction of Lepido-
carpon, a fossil ly-
x \ ioe copodiaceous _ plant
Ng
\
recently described by
Scott!. The sporo-
Fic. 400. Ceratozamia robusta. I, surface-section through the basal phyll of Lepidocar-
ortion of a carpel. One ovule is cut through longitudinally ; W, swelling =
elow the integument. II, the same ina younger stage. The swelling below pon bears at its base
the integument is not yet visible. : -
a megasporangium, in
which one only of four spores that are laid down develops, and the mega-
sporangium is surrounded by a thick integument which proceeds from the
sporophyll. The microsporangia too have a similar integument. The
assumption then that the integument of the ovule in Spermophyta took
origin from the sporophyll is not altogether unsupported by analogy, and
the known cases of virescent malformation” are conformable also with
this. We may also recall in this connexion that the outgrowth beneath
the ovule in the Cycadaceae (Fig. 400, WV) certainly belongs to the carpel,
1 Scott, Note on the Occurrence of a Seed-like Fructification in Certain Palaeozoic Lycopods,
Proceedings of the Royal Society, Ixvii (1900).
? Part I, p. 182.
INTEGUMENTS OF THE MEGASPORANGIUM 617
and may be considered as an approach in some measure to a second
integument, and that in the Eusporangiate Pteridophyta the stalk of the
sporangium has been explained as arising through an outgrowth of the
tissue of the sporophyll'.
DEVELOPMENT OF THE INTEGUMENTS. To enter into a description
of the development of the integuments here is unnecessary as no new point
of departure or facts has been brought forward during the last twenty
years. I will mention therefore only shortly the following :—
1. The integuments arise always as lateral outgrowths on the ovule below the
nucellus, which is laid down everywhere as a terminal structure, even in cases where
in its Jater stages, on account of the massive development of the integuments, its
terminal position is not apparent, as in many Sympetalae, whose ovules have a thin
nucellus and ove massive integument.
2. In afropous? ovules the integuments arise as a circular wall.
3. In anatropous and campylotropous ovules the development of the integument,
if only one is present, is arrested on the side turned towards the funicle, or forms
there only the portion of the integument devoted to the micropyle.
4. Where two integuments arise, in the majority of cases, the inner is the one
first formed, then the outer—Euphorbia is an exception. In anatropous ovules the
outer integument then shows the arrest above mentioned, that is to say, is not
developed upon the side next the funicle.
5. In small ovules the integuments proceed from the outermost cell-layer.
Where there is more massive construction of the integument deeper cell-layers
also share.
6. The number of the integuments is generally within one large cycle of
affinity constant: two in most Monocotyledones and choripetalous Dicotyledones *
also in the Primulaceae; one in most sympetalous Dicotyledones, the Cupres-
sineae, Abietineae, and elsewhere. Yet there are within one family varia-
tions which more accurate investigation may show perhaps to be derived. For
example, Aconitum has two integuments to its ovule, whilst the nearly allied
Delphinium. has only one. But ovules of Delphinium* at a middle stage of
development show clearly at the micropylar end—especially if they be looked at
whole and not in section—that the integument is double, and we may regard the
integument of Delphinium as the result of a concrescence of two. ‘The phenomenon
is quite like that of the origin of a sympetalous corolla. In the cycle of affinity
of the Ranunculaceae one might, upon the basis of the facts above mentioned,
conjecture that the ovules provided with two integuments were a more primitive type
1 See p. 602.
2 The expression orthotropous for straight ovules should be avoided, as it is used now of shoots in
a definite sense, which does not fit most atropous ovules.
* One integument is possessed by the Umbelliflorae and many Ranunculaceae.
* Delphinium cashmirianum was examined. See also Strasburger, Die Coniferen und die Gnetaceen,
Jena, 1872, p. 415. The indentation of the outer integuments often appears slight, or not at all, upon
sections, even where a study of the inception of an outer integument shows that, as usual in anatropous
ovules, it is only developed upon the side turned away from the funiculus.
618 THE SPORANGIUM OF SPERMOPHYTA
from which that with one integument has been derived. We might see the like also
in other cycles of affinity, especially in the Rosaceae. Spiraea Lindleyana? has two
separate integuments; in Spiraea Fortunei and others they hang together, except at
the micropylar region; in Spiraea Aruncus, S. Ulmaria, and S. Filipendula there
is only one. Also in Hippuris Van Tieghem considered that the integument is
the result of the fusion of two which are quite separate from one another in
Myriophyllum.
ATEGMINOUS OVULES. Naked ovules—that is to say ovules with no
integument—occur both in Monocotyledones and Dicotyledones, but the
question arises whether this behaviour is a reduction or a primitive one, and
with what biological relationships it stands in connexion. Some examples
therefore of it will be given :—
MONOCOTYLEDONES.
AMARYLLIDEAE. In this family we find ategminy of the ovules in
Crinum. The ovules of this amaryllidaceous plant, which is neither a parasite
nor a saprophyte, have no integument*. The ovules appear on the placenta as
slightly differentiated swellings provided with a funiculus, and they contain, not
infrequently, more than one embryo-sac. This rudimentary construction may be
connected with the fact that no seed-coat is formed*. The seeds are arranged for
immediate germination, and are protected only by some layers of cork-cells which
are formed from the endosperm. As a matter of fact the endosperm develops here, in
the main, independently of the nucellus. It contains chlorophyll also and forms, in
a certain measure, a passage to a development independent of the megasporangium.
The other Amaryllideae have mostly two integuments. Amaryllis Belladonna
has only one. Although we have no comparative history of the development of the
seeds of this family, such as is necessary in order to form a secure basis for phyletic
conclusions, it appears to me that the facts, so far as we know them, are in favour of
a reduction.
DICOTYLEDONES.
Amongst these we find ategminous ovules chiefly in some parasites and
saprophytes, but also in other plants.
GENTIANEAE. Whilst other gentianaceous plants possess ovules with one integu-
ment the saprophytic Voyria has an ovule which is described as naked *.
Voyria. The ovules in this genus occur in large numbers within the ovary.
They are elongated but have a normally constructed and normally arising embryo-
‘ Van Tieghem, Structure de queiques ovules, Journal de Botanique, xii (1898), p. 213.
* See Goebel, Pflanzenbiologische Schilderungen, i (1889), p. 129, confirming the statements of
Prillieux and of A. Braun. See also the literature cited by A. Braun, Uber Polyembryonie und
Keimung von Coelebogyne, in Abhandlungen der Berliner Akademie (1859).
* That is to say, the laying down of an integument may be suppressed because the whole economy
of the seed is of such a kind that the seed-coat, which would protect it otherwise during the resting
period, is not required.
* Johow, Die chlorophyllfreien Humusbewohner West-Indiens, in Pringsheim’s Jahrbiicher, xvi
(1885), p. 442.
ATEGMINY 619
sac}. Some years ago I had the opportunity of gathering in Venezuela, on the
slopes of the Cumbre de San Hilario, plants of Voyria azurea, which decked with its
blue flowers the soil of the shady woods and grew along with a number of mono-
cotylous saprophytes. After examination of, I must admit, only a small amount
of material, there seemed to me to be an indication of an integument, and of a
micropyle as a shallow, easily overlooked indentation (Fig. 401, JZ). Johow has
remarked that the ovule, after the formation of the embryo-sac, corresponds essen-
tially with an anatropous one. I would consider the terminal outgrowth of the ovule
as belonging to the integument, which here in other respects remains stationary at an
early stage of development. The extremely rudimentary nucellus experiences no
curvature, as in anatropous ovules elsewhere, but it develops from the first in an
inverted position, so that, to speak in comparative morphological terms, we have
a ‘congenital curvature.’ I have shortly referred to this case because it appears to
me to support clearly the assumption of a reduction. Why this condition should be
brought about we do not know. It is probable that it is teleologically? connected
with the great number of ovules, perhaps
causally with the saprophytic, in others the
parasitic, mode of life, But then against
this we have the fact that ategminous ovules
occur also in a number of autotrophic plants.
It is then very possible that the want of the
integuments of the ovule has really nothing
whatever to do with parasitism and sapro-
phytism, but that amongst plants with this
kind of ovule a certain number have re-
tained a parasitic type.
OLACINEAE. Valeton and Van Tie- Fic. 401. Voyria azurea. I and II, ovule of
x middle development in longitudinal section. III,
ghem ° have shown that ategminous ovules the same in transverse section. Megasporocyte
A 2 shown ; 442, rudimentary micropyle.
occur in some plants which are commonly
reckoned in the family of the Olacineae—in Olax, Liriosma, Schoepfia—whilst other
plants belonging to this family, in the old sense, have ovules with one or two
integuments. A parasitic or saprophytic mode of life of those Olacineae which are
provided with ategminous ovules, has not yet been shown.
Regarding Van Tieghem’s peculiar systematic views I do not require to say
anything after what has been said above about the Amaryllideae and Gentianeae ;
I may add only that the rubiaceous plant Houstonia, which is autotrophic, has
ategminous ovules *,
SANTALACEAE. In this family we find, for example in Thesium ‘, three naked
ovules upon a free central placenta. Each of them stands opposite one of the three
Z By tetrad-division. 2 See p- 254.
* Van Tieghem, Sur les phanérogames 4 ovules sans nucelle, formant le groupe des Innucellées ou
Santalinées, in Bulletin de la Société Botanique de France, xliii (1896), p. 543. See also Engler, in
Engler und Prantl, Die natiirlichen Pflanzenfamilien, Nachtrage zu III, i, p. 144.
* According to a communication in a letter from F. E. Lloyd.
5 See Guignard, Observations sur les Santalacées, in Annales des sciences naturelles, sér. 7, ii
(1885), p. 181. The literature is cited here.
620 THE -SPORANGIUM OF SPERMOPRHY TA
carpels. A small depression can be seen at the apex of this ovule, as in Voyria, and
may be considered as the remains of a micropyle, so that the Santalaceae possess the
indication of ove thick integument. The formation by the embryo-sac at its basal
end of a haustorium, which bores deeply into the placenta, is a feature which is
widely spread in the Sympetalae. The growing out from the ovule of the embryo-
sac at its apex, where the formation of endosperm takes place, is seen also in Crinum,
and is probably connected with the rudimentary construction of the whole ovule.
That no relationship exists between this rudimentary construction and the number
of the ovules is clear. Of the three ovules only one becomes perfect, and the
envelope of this is supplied by the ovarian wall, as there is no seed-coat present.
Such rudimentary ovules are found in particular in parasites which form rich
endosperm and a complete embryo—at least this is true for
LoranTHACEAE’. We owe our knowledge of the ovules in this family to the
investigations of Treub °.
Loranthus sphaerocarpus. In Loranthus sphaerocarpus a free central placenta
rises up at the base of the ovarian cavity, which bears some very rudimentary
ategminous ovules, and later becomes concrescent completely with the inner surface of
the ovary, so that the embryo-sacs then are embedded apparently in a tissue filling the
ovary. ‘The reduction goes further in Viscum articulatum and Loranthus pentandrus,
where there is a central placenta, and ovules are no longer formed upon it.
Viscum articulatum. Viscum articulatum * possesses an ovary formed of two
carpels which so closely unite with one another that only a narrow slit remains
between them. Where this slit ceases at the base of the ovary many embryo-sacs
proceed out of some cells rich in protoplasm, which lie near one another or are
separated by parenchymatous cells; of these embryo-sacs, however, only one
experiences a further development.
Loranthus pentandrus. A similar development appears in Loranthus pentan-
drus. If we compare it with that found in Loranthus sphaerocarpus we can have no
doubt whatever that we have to deal with a reduction. The placenta and the ovule
are then not ‘congenitally concrescent’ with the tissue of the ovary, but have not
come into existence—like the pollen-mother-cells of Cyclanthera*, which do not
differentiate in a specially constructed pollen-sac, but in a ring-like swelling of the
flower-axis ; the mother-cells of the embryo-sacs of the Loranthaceae do not develop
in the ovule, but in the flower-tissue beneath the ovary. The megasporangium then
is suppressed in its differentiation, only the megaspores develop, and, as in the
Santalaceae, they show often peculiar phenomena of growth which have a most
* Van Tieghem’s more recent work is set forth by Engler, in Engler und Prantl, Die natiirlichen
Pflanzenfamilien, Nachtrage zu III, i, p. 124.
2 Treub, Observations sur les Loranthacées, in Annales du Jardin botanique de Buitenzorg, ii
(1881), p. 543 iii (1883), p. 1. Treub’s results completed and corrected the older work of Hof-
meister, Neue Beitrage zur Kenntniss der Embryobildung der Phanerogamen : I. Dikotyledonen, in
Abhandlungen der Koniglich sachsischen Gesellschaft der Wissenschaften, vi (1859).
* The same is the case in Viscum album, see Jost, Zur Kenntniss der Bliithenentwicklung der Mistel,
n Botanische Zeitung, xl (1888), p. 357. The mother-cell of the embryo-sac divides here into two
daughter-cells, the lower of which soon forms upwards an outgrowth, this I consider as an early
haustorial formation. * See p. 554.
a
~
7
REDUCTION OF THE MEGASPORANGIUM 621
intimate connexion with the nutrition of the megaspores—a connexion which of
course is different from what it would be were the megaspore in a well-formed
megasporangium. Other cases, which will be presently mentioned, show us that the
embryo-sac lives as a parasite, and that it derives its nourishment from wherever it
best can.
BaLanopHorEAE. ‘The reduction goes furthest in the Balanophoreae, whose
behaviour Treub? has made clear. There is neither a flower-envelope nor carpels
visible in the female flower here. ‘The whole flower consists of a cell-body, of which
a hypodermal cell (Fig. 402) becomes an archesporium *, whilst the outer cell-layer
grows out into a long pointed process; the whole structure has a certain resemblance
to an archegonium, but there is
no neck-canal. As other Balano-
phoreae* possess usually two
carpels with a central placenta,
and two very slightly differenti-
ated ategminous ovules, it appears
most natural to derive Balano-
phora from them by assuming
that
1. The formation of the
carpels is suppressed.
2. The number of the ovules
is reduced to one.
3. The formation of the
ovules takes place out of the
primordium of the flower itself‘,
in which one can no longer speak
of an ‘axis,’ as this expression
has a meaning only when we
understand a structure that pos- Fic. 402. Balanophora elongata. I, young female organ in
longitudinal section. II, older female organ in similar section
sesses at least the possibility of showing the archesporium, which is shaded. III, female organ
3 nearly mature in like section ; embryo-sac developed. I magnified
bringing forth organs aS appen- 230 II and III magnified 300. After Treub.
dages.
The case is quite like what occurs in the vegetative organs of many parasites.
We know from the researches of Solms-Laubach that, for example in species of
Pilostyles °, the vegetative body of the parasite which bores into the host may be
1 Treub, L’organe femelle et l’apogamie du Balanophora elongata, Bl., in Annales du Jardin
botanique de Buitenzorg, xv (1898), p. 1.
3 Sometimes this divides once, sometimes it does not divide at all, and then at once becomes
a megaspore.
8 See Lotsy, Rhopalocnemis phalloides, in Annales du Jardin botanique de Buitenzorg, sér. 2,
ii (1901), p. 73. Lotsy thinks that the Helosideae, to which Rhopalocnemis phalloides belongs,
are better separated from the Balanophoreae; even if one does so their near relationship would not
be doubtful.
* An analogous case would arise if the male flower of Juniperus were reduced to one of its
microsporangia. See p. 516. 5 See p. 225.
622 THE SPORANGIUM OF SPERMOPHYTA
reduced to a single hypha-like strand of tissue. In this there is no possibility
of applying the ordinary morphological schemes. The same is the case in the
flowers of Balanophora. We do not know here, as elsewhere, in what connexion
the reduction stands to the parasitic mode of life. If such a connexion exists it may
be of two kinds,—
(a) direct—that is to say, conditioned by the parasitic mode of life itself ;
(2) zndirect—that is to say, the parasitic mode of life permits of the retention of
variations in structure which may also appear in non-parasitic plants, but are there
incapable of persistence. An indirect connexion of this kind—of reduction with
mode of life—has been already shown to be probable in Utricularia and the Podo-
stomaceae }.
From what has been said we gather that in the ovule, and partly also
in the whole gynaeceum of the Angiospermae, considerable reductions may
take place. We can hardly designate as a reduction the limitation of the
integument to one, but we may certainly call it a reduction if the formation
of the integuments is entirely suppressed, although we may not be able to
give the reason for this. At the same time it is easy to understand that
where the integument plays no longer any part in the formation of the
seed-coat—and this is the case in many plants in which the envelope of
the seed is formed by the pericarp, the seed-coat being at the same time
destroyed, for instance in Gunnera, the grasses—the formation of the
integument may from the first be suppressed. We must assume that
the ‘tendency to disappear’ may show itself in all organs in individual
forms, and that this then leads to an abortion if this can take place
without injury to the whole economy of the plant. It would be of course
quite absurd to endeavour to group plant-forms which have naked ovules
into ove systematic group. It is quite clear that this condition is developed
in different cycles of affinity.
A further stage of reduction is that in which the ovules and placenta
no longer appear as definite organs within the gynaeceum, as in Viscum,
but the megasporangia are sunk in the tissue of the megasporophyll.
Finally, in Balanophora the differentiation of the megasporophylls them-
selves is suppressed, the whole flower is evidently reduced to one mega-
sporangium. It has been shown’ how this example specially illustrates
the fact that we cannot deny the occurrence of far-reaching changes in the
formation of organs, and that our work at first must be to make a picture
of how they have come about, but not to endeavour to read into a terminal
member of a series its first beginnings.
THE NUCELLUS.
DEVELOPMENTS WITHIN THE NUCELLUS IN RELATION TO STIMULI.
The megasporangium of Spermophyta is distinguished from that of the
1 See p. 241. 3 See p. 557-
it
GERMINATION OF THE MEGASPORE 623
Pteridophyta by the fact that the megaspores germinate within the
sporangium, and that the megasporangium with its envelope or envelopes
develops, after fertilization, into a seed. Approaches to this behaviour
are found in some Pteridophyta. In Salvinia the megaspores germinate
within the megasporangium!. The megaspores in many species of Sela-
ginella® undergo the first stages of germination within the megasporangium,
are then emptied out of the megasporangium, and only later resume their
germination. An actual transition to seed-formation does not appear in
any living forms; such a transition would not even exist if, for example
in Selaginella, there were found forms in which the megaspores were not
shed from the sporangia, but remained enclosed in the megasporangium
until germination of the embryo of the sporophyte*®. From the teleological
side one might consider it a step forward were the megaspores, which
represent a considerable expenditure of plastic material, no longer shed
from the mother-plant, away from which it is uncertain whether they find
favourable conditions for germination and fertilization, but from which
when they separate they carry usually reserve-material sufficient for the
first development of the embryo which proceeds from the fertilized egg.
Asa matter of fact we observe that the plant is, so to speak, always more
sparing with material the higher we rise in the series of the Spermophyta:
the Cycadaceae form in their megaspores large prothalli even without
pollination *; the Coniferae allow of the germination of the megaspore within
the megasporangium only after the stimulus of a pollen-tube ; upon this
stimulus is dependent in some Angiospermae the laying down of the ovules, in
others their further development at least. Some examples may be quoted.
The female flowers of Quercus and Fagus, also Corylus, show no trace
of ovule at the time of pollination. So far as I know it has not been
experimentally proved, but it appears probable that the stimulus exercised
by the pollen-tube starts a further development ®. It is certain that this is
the case in the Orchideae whose ovules are quite rudimentary at the time
of pollination, and also in some Dicotyledones, for example in Fraxinus,
Forsythia, and Syringa dubia ; whilst in other Oleaceae®, such as Syringa
vulgaris, Fontanesia Fortunei, and species of Ligustrum, there are well-
developed ovules at the time of pollination.
} This may be connected with the aquatic life.
* Bruchmann says that Selaginella spinulosa is an exception.
* Compare F. M. Lyon, A study of the Sporangia and Gametophytes of Selaginella apus and
Selaginella rupestris, in Botanical Gazette, xxxii (1901), p. 124.
* How far the several genera differ in this character requires investigation. In Cycas, as it grows
in our plant-houses, the formation of archegonia takes place in the prothallium of some, usually not
all, of the unpollinated ovules.
®° The further development of the ovary is suppressed in Corylus if the male catkins discharge their
pollen before the development of the stigmas, and this happens in many springs and may be considered
an experimental proof of the connexion mentioned above.
® See Billings, Beitrage zur Kenntniss der Samenentwicklung, in Flora, Ixxxviii (1901).
624 THE SPORANGIUM OF SPERMOPHYTA
In the Coniferae the development of the megaprothallium depends
upon the pollination but not upon the fertilization!; the Angiospermae
go one step further. Out of the germ-tube of the microspore two nuclei
pass into the megaspore in fertilization, as has been shown by the investiga-
tions of Nawaschin, Guignard, and others*. One of these stirs up the egg
to a further development. It effects the fertilization. The second one
stimulates the formation of endosperm. Whether we speak of this as
a ‘double fertilization’ or not is to my mind non-essential. I have always
seen in the process, since it became known, only an arrangement which
secures the further development of the endosperm in those cases where
formation of an embryo takes place.
PARTHENOGENETIC STATE. This feature too is not without exception.
We have come to know of, in recent times, many examples of partheno-
genetic formation of embryo, and these are being multiplied. In these
cases the formation of the endosperm proceeds at the same time without
the stimulus which is given in other plants in the way described, whether
the embryo proceed from an unfertilized egg, as in Antennaria alpina and
most of the species of Alchemilla that have been examined, or from a cell
of the endosperm, as in Balanophora. We have learnt to distinguish in
sexual reproduction two processes :—
1. the taking over of paternal and maternal qualities into the germ ;
2. the stirring up of this germ to further development.
The stirring of the germ to further development may result through
factors other than the union of the male and female cells. What is the
development-stimulus in the seeds produced parthenogenetically we do
not know, but it appears to me very probable that in many cases it is
the pollen-tube which without causing fertilization stimulates the further
development and the formation of embryo. Where as in Balanophora
and Alchemilla, with the exception of Alchemilla arvensis, usually no
pollen-tube is formed, we naturally cannot speak of this, but in the
formation of the adventitious embryos out of the nucellus, as they occur
in Funkia, Citrus, and elsewhere, and also in Casuarina, as will be men-
tioned below, we have analogous cases. I do not see why the pollen-tube
should not in many cases stir up the egg also to further development
without effecting fertilization.
1 Hofmeister, Allgemeine Morphologie der Gewachse, p. 637, showed that, for example, in
orchids the further development of the ovules can also be brought about by foreign pollen, which can
cause no fertilization.
* I pointed out, in 1883, that the effect of fertilization also reached the secondary embryo-sac-
nucleus :—‘ In all the cases examined by me this (nucleus) is connected with the egg by means of
a plasma-strand, so that a material influence upon this from the egg or pollen-tube can take place.’
This material influence consists in a union of nuclei as the beautiful investigations of the various
authors mentioned have shown. Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane,
in Schenk’s Handbuch der Botanik, iii (1884), p. 429. See also Strasburger, in Botanische Zeitung,
lii (1900), p. 293.
DEVELOPMENT OF THE MEGASPORE 625
DEVELOPMENT OF THE MEGASPORE. The most important part of
the nucellus is the megaspore or embryo-sac, and we may ask now how far
the megaspore in its origination conforms with that of the Pteridophyta 1.
In the Pteridophyta it arises everywhere by a division into four of the
sporocyte. The megaspore of the Spermophyta proceeds also from a
sporocyte, but the daughter-cells of this do not all become megaspores,
although all have the potentiality of so doing ?. The number of cells into
which the megasporocyte divides is in many Spermophyta likewise four,
and in recent times it has been many a time shown that this behaviour
is far more general than was earlier supposed, when the number of the
daughter-cells was considered as variable*. That the division into tetrads
is a generally spread phenomenon seems very probable, since Overton’s
investigation of the relationship of nuclear division, directed to establish
the homology of the megasporocyte and microsporocyte, showed that in
both cases the number of the chromosomes in each is one-half that of the
other cells*. Four daughter-cells have been found in Gymnospermae ®,
as well as in a number of Monocotyledones and Dicotyledones. That
a reduction of the divisions can take place is shown by the fact that in
many plants the megasporocyte passes directly into the embryo-sac
without division, for instance in Tulipa and other Liliaceae. I do not
see why if in these cases the division is generally suppressed there should
not also occur a reduction in the two or three divisions.
In the arrangement of the walls of the division the tetrad-formation
varies from that which is usual in sporocytes, because the daughter-cells
are usually arranged in one longitudinal series. Seldom do they lie through
longitudinal division two beside one another. This variation often occurs
also in pollen-tetrads. The lie of the division-walls in the pollen-tetrads
is determined by the conformation of the pollen-mother-cells®. I may
illustrate this shortly in one example. Fig. 403 shows pollen-tetrads of’
Typha Shuttleworthii. The most usual arrangement is that of Fig. 403, 1
b
1 I do not require to quote any literature, for it is found in all text-books.
2 See Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch
der Botanik, iii (1884).
* See Juel, Beitrage zur Kenntniss der Tetradenteilung, in Pringsheim’s Jahrbiicher, xxxv (1900),
p- 626; Komicke, Studien an Embryosackmutterzellen, in Sitzungsberichte der Niederrhein. Gesell-
schaft fiir Natur- und Heilkunde, 1901. The literature is cited here.
* See Strasburger, Histologische Beitrige, Heft vi; id., Uber periodische Reduktion der Chromo-
somenzahl im Entwicklungsgang der Organismen, in Biologisches Centralblatt, xiv (1894).
5 In Larix, by Juel, op. cit. In Pinus Laricio, Coulter and Chamberlain, Morphology of Spermato-
phytes, New York and London, i, p. 161.
§ Goebel, Zur Embryologie der Archegoniatae, in Arbeiten des botanischen Instituts in Wiirzburg,
ii (1880), p. 441. The assumption there made regarding the succession of the division-walls was
incorrect. There evidently takes place, as Wille later pointed out, a repeated bipartition of the
mother-cell. This is, however, of subordinate importance as against the general connexion, that
is now also accepted by later authors, between the conformation of the mother-cell and the direction
of division.
GOEBEL II Ss
626 THE SPORANGIUM OF SPERMOPHYTA
where the pollen-mother-cell has divided into four in one plane of division.
In Fig. 403, 2, the two planes of division have crossed. In Fig. 403, 3, they
have an oblique position to one another, and the arrangement approaches
that of the tetrad. More rare are the forms which are shown in Fig. 403, 4
and 5, which, however, are of especial interest for a comparison with the
megasporocyte. We may well assume that the elongated conformation of
the pollen-mother-cells, which determines the arrangement of the daughter-
cells, is connected with the relationships of space within the microsporangium.
Further, in the megasporangium it is of the first importance to remember
that the megaspores do not lose touch one with another, and therefore
cannot acquire the spherical form, which for the ordinary tetrad-arrange-
ment is the most suitable. The division by transverse walls suits much
better their position in the long axis of the megasporangium ?.
The phenomenon that only one of the four daughter-cells normally
develops further into a megaspore may be connected with the reduction
in the number of spores in the megasporangium, a reduction which finds its
extreme expression in the suppression of
the tetrad-formation altogether in cases like
Tulipa. Moreover, there are analogies with
this in the megasporangia of Salviniaceae
and Marsiliaceae, and in the formation of
the microspores of some Monocotyledones?.
The megaspores of the Cycadaceae and of
many Coniferae have still an evident -cuti-
cularized exosporium which, as a reminis-
Fic. 403. Typha Shuttleworthii. Pollen- < Ase
tetrads. Magnified. cence of the behaviour of free-living mega-
spores, is of interest.
We must now speak shortly of the structure and the development
of the megasporangia in Gymnospermae and in Angiospermae.
(6) SPECIAL FEATURES OF THE MEGASPORANGIUM OF
GYMNOSPERMAE.
CYCADACEAE. Owing to the difficulty of obtaining material, the
development of the megasporangia in none of the Cycadaceae is completely
known, yet we do know that the ovule has a primitive character, that is to
say, it is allied to that of the sporangia of the Pteridophyta. This con-
clusion is based upon the following :—
(1) The existence of a somewhat copious sporogenous tissue (Fig. 404,
1 That in an arrangement of tetrads, as is shown in Fig. 403, only three cells may easily be
visible upon the section is evident, and Johow has figured a case like this for Voyria.
2 See regarding Carex, Juel, Beitrage zur Kenntniss der Tetradenteilung, in Pringsheim’s Jahr-
biicher, xxxv (1900), and Wille’s work cited there.
THE MEGASPORANGIUM OF GYMNOSPERMAE 627
S~), from which, however, so far as we know, only one cell develops
further as the megasporocyte.
(2) The funicle arises by a sabseguent elongation of the tissue of the
sporophyll.
(3) The nucellus arises evidently by a further development of the wad/
of the sporangium.
To these may be added that the development of a pollen-chamber in
the nucellus may be considered, as in Ginkgo, a primitive character.
Our knowledge rests upon the investigations of Warming’, of Treub?,
and of W. H. Lang*. We shall take Treub’s investigations of Ceratozamia
longifolia as our starting-point, as they deal with the earliest stages, and
confirm and complete Warming’s work.
Ceratozamia longifolia. An ovule springs from the edge of the sporophyll
where it passes over into its
zone ofinsertion. The tissue
at this point has a meristic
character, and produces two
outgrowths, which may be
recognized as the primordia
of two ovules. If a longi-
tudinal section be made
through this we obtain a
picture which is quite like
that observed in the trans-
verse section of a young
sporangium of Ophioglos- 0
sum: under the epidermis is Fic. 404. I, Ceratozamia longifolia. Ovule in longitudinal! section ;
a group of sporogenous cells Znz, integument; 477, micropyle ; Nu, nucellus ; Sf, sporogenous tissue.
which have clearly arisen by me eed ge ecience Gens. 1 sightly ungetied
es after Treub. II after W. H. Lang.
the division of one or some
few archesporial cells. Their appearance is then the first differentiation within the
primordium of the ovule, which at this period is essentially like the primordium of
the sporangium of Ophioglossum. Between the epidermis and the sporogenous
cell-mass there lies one or it may be more cell-layers which have a different destiny ;
they do not share in the formation of the sporogenous cell-mass, but they become
cells which are designated /ayer-cells. ‘Two changes proceed in the older stages:
by the growth and splitting of the layer-cells an outgrowth is formed covering the
sporogenous cell-mass (Fig. 404, Vz), and simultaneously there rises up around the
1 Warming, Undersggelser og Betragtninger over Cycaderne, in Oversigt over de kongelige
Danske Videnskabermes Selskabs Forhandlinger, 1877; id., Bidrag til Cycadeernes Naturhistorie,
ibid., 1879.
* Treub, Recherches sur les Cycadées, in Annales du Jardin botanique de Buitenzorg, iv (1884).
®* W. H. Lang, Studies in the Development and Morphology of Cycadean Sporangia: II. The
Ovules of Stangeria paradoxa, in Annals of Botany, xiv (1900).
Ss2
628 THE SPORANGIUM OF SPERMOPHYTA
sporogenous mass an annular wall which is the primordium of the integument.
The outgrowth referred to is the primordium of the nucellus which now like the
integument continues to grow. The number of the cells of the sporogenous cell-
mass increases, and the whole cell-mass becomes more sharply delimited, and is
surrounded by narrow cells stretched in the longitudinal direction, regarding which
it is questionable whether they may be considered as tapetal cells. Somewhere in
the middle of the sporogenous mass there is found a large cell—the mother-cell
of the embryo-sac (Fig. 404, II, Sp). It divides into usually three cells, but it is
possible that the formation of tetrads also occurs here. At any rate one of the
daughter-cells grows into the megaspore, and overwhelms the others. It becomes
filled subsequently with the prothallus which produces the archegonia. In Stangeria
the formation of the prothallus appears to be dependent upon pollination. The
differentiation of the megaspore is completed here in quite the same way as is that
in Isoetes?, and we may assume that the tapetal cells also proceed from the sporo-
genous cell-mass. At the apex of the nucellus the pollen-chamber arises by re-
sorption in the nucellar tissue (Fig. 400, I).
CONIFERAE. The ovules have sometimes two integuments, some-
times only one. The integument develops into a wing in some forms
when they are ripe, for example in Dammara; in the Abietineae the wing
appears to unite with the seminiferous scale, but evidently is derived
originally from the integument. The relationships otherwise conform
essentially with those of the Cycadaceae, yet, so far as investigation enables
us to judge, the sterilization of the sporogenous cell-mass appears to have
proceeded a stage further in many cases; nevertheless it is fairly developed
in the Cupressineae, where its origin, as shown in the young stages which
have been observed in Cupressus, can be traced back to a few-celled hypo-
dermal archesporium?. The material is laid down in the nucellus, for use
later by the megaspore.
Strasburger found in Larix one megasporocyte as is the case in other
Abietineae. In Thuya and Taxus he found many. The earlier the sterilization of
the sporogenous cells begins the less do they differ from the other cells of the
nucellus, so that it is often merely a matter of opinion what one will designate
as ‘sporogenous cell-mass.’ This is a consequence of the nature of the course
of development which has been briefly sketched.
GNETACEAE. Space forbids our entering into an account of the
interpretations of the much-discussed relationships of the ovule, especially
1 See p. 212.
2 This gives off, however, numerous cells also for the construction of the nucellus. At the moment
of pollination I find in the Cupressineae that have been examined a more or less developed sporogenous
cell-mass, which is overlain by a copious nucellar tissue which serves later for the nutrition of the
megaspores, just as nutritive material which is laid down in the many-celled wall in the young
sporangium of Botrychium serves chiefly for the construction of the spores. The sporogenous
cell-mass in Juniperus, where it consists of only few cells, lies about the place where the integument
is inserted. In Callitris it is somewhat deeper. The megasporocyte appears in Juniperus at this
time often clearly marked ont by its size and richness of content.
FEMALE SEXUAL ORGAN OF GYMNOSPERMAE 629
of the formation of the integument in this family +, and a short exposition
would not serve to make clear the relationships of the several forms”.
FEMALE SEXUAL ORGAN OF GYMNOSPERMAE.
The formation of the female sexual organ, however, may be noticed here :—
Cycadaceae, Ginkgoaceae, Coniferae. These families possess archegonia
which are embedded deeply in the prothallus, and there is an egg which reaches
giant dimensions in the Cycadaceae. In consequence of the size of the egg there
is always a special cell-layer around it which plays an important part in its nutrition *.
The neck of the archegonium, except perhaps in Cycas, does not project beyond the
surface of the prothallus, and as it does not open no neck-canal-cell is formed. The
formation of the neck-portion is strikingly variable. In the Cycadaceae, Ginkgo,
Cephalotaxus Fortunei, Sequoia sempervirens, Tsuga canadensis, there are only two
neck-cells, but in the most of the Coniferae there are four—the so-called roseffe—
which may divide by periclinal walls into one or more tiers, each composed of four
or eight cells, as in Abies. We do not know whether this varying behaviour of the
neck-portion has any biological significance.
Gnetaceae. The Gnetaceae exhibit peculiar and remarkable relationships.
According to Strasburger * Ephedra possesses a typical coniferous archegonium with
a long neck which appears to be but little different from the surrounding cells
of the prothallus. In Welwitschia® Strasburger found a considerable simplification
in the formation of archegonia. The twenty to sixty initials lying at the apex of the
prothallus do not divide further, but form only outgrowths which grow into the
nucellar tissue and against the pollen-tubes. Each archegonium is then reduced
to a single cell surrounded by a membrane.
The behaviour of the megaspore in Gnetum, which has recently been studied by
Karsten® and Lotsy’, has special interest. In Gnetum Gnemon (Fig. 405) free
nuclear division at first takes place in the embryo-sac and leads to the formation of
the prothallus, as in the Coniferae, but the formation of cell-tissue only follows at the
lower end of the embryo-sac. At the upper end the nuclei remain free, embedded in
1 I may only mention that Ephedra possesses one integument, the outer integument-like envelope
is evidently formed by the concrescence of two leaves, as it is in Welwitschia, whose integument often
forms a stigma-like structure above (Fig. 353). Gnetum has evidently three integuments. I may
refer to Lotsy’s interpretation according to which there is here only one integument, and the outer
envelopes constitute a peculiar perianth. With regard to Ephedra, see Jaccard, Recherches embryo-
logiques sur l’Ephedra helvetica, Diss. inaug., Lausanne, 1894.
2 See Coulter and Chamberlain, Morphology of Spermatophytes, New York and London,
p- 119, where more recent literature is cited although not fully.
5 Arnoldi, Beitrige zur Morphologie der Gymnospermen : IV. Was sind die ‘ Keimb)aschen’ oder
‘ Hofmeisters-Korperchen’ in der Eizelle der Abietineen? in Flora, Ixxxvii (1900), p. 194. The
literature is cited here.
* See also Jaccard, op. cit.
° The relationships here require renewed investigation. It is questionable whether the archegonia
are really functional.
® Karsten, Untersuchungen tiber die Gattung Gnetum, in Annales du Jardin botanique de Buitenzorg,
xi (1893); id., in Cohn’s Beitrige zur Biologie der Pflanzen, vi.
7 Lotsy, Contributions to the Life-history of the Genus Gnetum, in Annales du Jardin botanique de
Buitenzorg, xiv (1899).
630 THE SPORANGIUM OF SPERMOPHYTA
the protoplasm, and they may be regarded as free cells, although a definitely limited
portion of the protoplasm around each single nucleus cannot be proved. These cells
or nuclei are egg-cells. They can all be fertilized, although only one embryo develops
further. The germinated megaspore then has two regions, which, at least in the
beginning, are marked out by a slight constriction: the upper generative region and
lower vegetative region. The vegetative region has the duty of bringing up the plastic
material for the further growth of the megaspore at the cost of the nucellar tissue, in
the same way as happens in the Angiospermae. The formation of the cell-tissue
Fic. 405. Gnetum Gnemon.
Megaspore. To the right,
above, another megaspore
compressed and pushed to Fic. 406. Gnetum. Upper part of a megaspore in longitudinal section ;
one side. Magnified 37. After gs, apex of pollen-tube; 7%, #zk, male nuclei; PA, tubenucleus; wé,
Lotsy. female nuclei. After Karsten. Lehrb.
in the antipodal region of the megaspore did not occur in the species of Gnetum
(Fig. 406) examined by Karsten, but the zwhole émbryo-sac behaved like the upper
end of that of Gnetum Gnemon.
Although our knowledge of the development of Welwitschia presents many
gaps, and that of Ephedra requires careful reinvestigation, yet we can arrange the
behaviour of the megaspores of the Gymnospermae evidently in one series, of which
the following are the members? :—
1 Apart altogether from the réle which the pollen-tube exercises as a developmental stimulus.
THE MEGASPORANGIUM OF ANGIOSPERMAE 631
(a) The megaspore becomes filled completely with prothallus which bears
normal archegonia: Cycadaceae, Coniferae, Ephedra.
(4) The megaspore forms a prothallus whose uppermost cells no longer unite
together, but become unicellular fertilization-cells: Welwitschia.
(c) This process takes place still earlier, whilst the growth of the reduced
archegonia is suppressed, there are still evidently distinguishable two regions in the
megaspore, but in the generative region the cells are not sharply limited from
one another: Gnetum Gnemon.
(d) The formation of a cell-tissue before fertilization is entirely suppressed :
other species of Gnetum.
In other words, we observe here that the course of development which was
visible in the heterosporous Pteridophyta has proceeded a step further, and the
vegetative development of the prothallus has become always more shortened, and
consequently the fertilization takes place at an always earlier stage.
It must, however, be remembered that it is doubtful whether the series above
constructed is a phyletic one, for a polyphyletic origin of the Gymnospermae is more
probable than a monophyletic one. At the same time we may conclude that the
development is not a fortuitous one, but has proceeded progressively in a definite
and regular manner.
(c) SPECIAL FEATURES OF THE MEGASPORANGIUM OF
ANGIOSPERMAE,
The development of the megasporangium in the Angiospermae
diverges in no essential point from that in the Gymnospermae, different
though the external appearance of the ovule in the different families of
Angiospermae is’. In general we may say that the structure of the ovule
stands in relation to that of the perfect seed. Small seeds without endo-
sperm, like those of the Orchideae, or seeds which have only small endo-
sperm and small embryo, like those of the Begoniaceae, Rafflesiaceae, and
others, proceed from ovules which have both the integuments and the
nucellus very slightly developed. Seeds whose construction makes larger
demands are provided from the first with a greater development of the
integument or nucellus ; as special adaptations are to be noted the formation
of an epithelium in not a few cases, and the development of the austorium
1 We know, unfortunately, very little about the biological significance of this difference.
Why is it that the ovules are atropous, anatropous, epitropous, apotropous, and so on? Is the
course of the pollen-tube a specially important factor—the path along which it must pass, the
rapidity with which the fertilization must take place, the material of which it stands in need,
the arrangement of the conducting tissue—or is it only the ‘internal’ factors which determine the
configuration? Regarding these we know nothing, but I have no doubt that definite relationships
will be discovered, as in so many other cases, between the conformation and functions of the ovule.
That the frequency of the anatropous and campylotropous states, as compared with the atropous,
is connected with the fact that in the former the micropyle, cefer?s Partdus, always comes nearer to
the conducting tissue appears to me to be beyond doubt.
632 _ THE SPORANGIUM OF SPERMOPHYTA
in the embryo-sacs, about which more will be said immediately. We have
first of all to consider the origin and construction of fhe megaspore !.
Fic. 407. I-III, Alchemilla alpina. 1V, Alchemilla pubescens. Nucellus in longitudinal section, showing
development of megasporangium. In I, five archesporial cells are shown. In IV, sporogenous tissue, with six
ripe megaspores and some tapetal cells. After Murbeck.
ORIGIN OF THE MEGASPORE.
The archesporium is frequently unicellular, even in megasporangia with
massively constructed nucellus, and this is evidently the case because other
cells have been early sterilized. There are, however, not wanting cases of
1 Strasburger, Die Angiospermen und die Gymnospermen, Jena, 1879; Fischer, Zar Embryo-
sackentwicklung einiger Angiospermen, in Jenaische Zeitschrift fiir Naturwissenschaft, xiv (1880) ;
Jonsson, Om embryosackens utveckling hos Angiospermerna, in Acta Universitatis Lundensis, xvi
(1879-80); Guignard, Recherches sur le sac embryonnaire des phanérogames angiospermes, in
Annales des sciences naturelles, sér. 6, xiii (1888); Nawaschin, Uber die gemeine Birke (Betula
alba, L.), in Mémoires de Académie Impériale de St-Pétersbourg, sér. vii, xlii (1894); id.,
Zur Entwicklungsgeschichte der Chalazogamen, Corylus Avellana, in Bulletin de lAcadémie
Impériale de St-Pétersbourg, x (1899) ; Benson, Contributions to the Embryology of Amentiferae,
in Transactions of the Linnean Society, series 2, iii (1894).
ee a 7 ee
be]
THE MEGASPORE OF ANGIOSPERMAE 633
pluricellular archesporia. We find them especially in Rosaceae, Aesculus
Hippocastanum, Paeonia arborescens. Sometimes also many embryo-sacs
are developed, as in Alchemilla (Fig. 407).
Alchemilla. Fig. 407 shows the development of the primordium of the ovule
in Alchemilla?. The behaviour of the nucellus recalls the development of the micro-
sporangia. The archesporium is a cell-plate, from which layer-cells are given off to
the outside, and the epidermis itself experiences periclinal divisions (Fig. 407, II).
It is peculiar that a central cell is not devoted here, as elsewhere, to the formation of
a megasporocyte, but it lies somewhat to one side, and then it divides into three or
four—most commonly four—daughter-cells, of which more than one may become an
embryo-sac. The superfluous embryo-sacs, which are later pushed to one side,
evidently help in the draining of the nucellar tissue. The longitudinal section
(Fig. 407, III) will enable a comparison to be made readily with a sporangium such
as is shown in Figs. 379 and 391, whilst in other ovules of Angiospermae, in which
the sporogenous tissue remains less developed, the outer differences in relation to the
sporangia are much greater. }
Casuarina. ‘The structure of the megasporangia in Casuarina is very peculiar.
We owe our knowledge of it to Treub*. Copious sporogenous tissue is developed,
and the sterile tissue of the nucellus conspicuously corresponds in general features
to the wall of the sporangia of the Pteridophyta (Fig. 408,1). The cells of the
sporogenous tissue divide all in the same manner as the sporocytes of other Angio-
spermae, yet the number of the daughter-cells cannot be certainly determined from
Treub’s account. The daughter-cells which do not function as megaspores evidently
serve for a long time as nutritive cells. Many megaspores are laid down, but the
most of them remain sterile, and only bring the nutritive material to the favoured
megaspore. They elongate into a tube-like form and become haustoria, which force
themselves into the funiculus (Fig. 408, III). Biologically this repeats the case of the
embryos of the Abietineae, where, of the many embryos which arise from one egg,
only one develops, and the others function as haustoria for it*. The favoured mega-
spore in Casuarina lays down no antipodal cells, for these would be functionless,
the megasporial haustoria having taken their place. -At the apex of the favoured
megaspore there will be found two to three—seldom only one—cells, which appear
to proceed from one mother-cell, and are usually provided with cell-walls. They are
formed before fertilization. The egg has the thickest membrane. Besides there is
one nucleus present which later divides, and initiates the formation of the endosperm.
Whether this takes place before or after fertilization—if a fertilization takes place—is
doubtful. Many circumstances appear to me to point to the conclusion that the
1 See Murbeck, Parthenogenetische Embryobildung in der Gattung Alchemilla, in Acta Universi-
tatis Lundensis, xxxvi (1900). 2 See p. 599.
° Treub, Sur les Casuarinées et leur place dans le systéme naturel, in Annales du Jardin botanique
de Buitenzorg, x (1891), p. 145. Fujii, The embryo-sac of Casuarina stricta, in Botanical Gazette,
Xxxvi (1903), has pointed out that the embryo-sac of Casuarina stricta shows the normal behaviour
of the embryo-sac of Angiospermae; there is no parthenogenesis : results confirming my view that
Casuarina is not a ‘ primitive’ form. * See Part I, p. 208.
634 THE SPORANGIUM OF SPERMOPHYTA
pollen-tube, which forces its way through the chalaza’, stirs up the megaspore to
further development, but does not effect a fertilization, and that Casuarina really
exhibits parthenogenesis. The reasons for this conjecture are as follows :—
1. The egg forms before fertilization a somewhat thick cellulose-membrane.
This might, of course, be somewhat softened or absorbed.
ae
Fic. 408. I, Casuarina Rumphii. Megasporangium in lon itudinal section. Sporogenous tissue dotted.
II, Casuarina tuberosa. Portion of an old dial section. Three megaspores visible in the
sporogenous tissue which is dotted. III, Casuarin a glauca. Older stage of a megaspore grown out into
ahaustorium. A tracheid is visible in the sporogenous tissue. After Treub. I magnified 100.
2. The pollen-tube does not here reach the sexual apparatus, but implants
itself on the embryo-sac at a point separated from this.
3. There is no fusion of two polar nuclei.
1 Casuarina was the first example known of chalazogamy. See p. 615.
~~
GERMINATION OF MEGASPORE OF ANGIOSPERMAE 635
This is, of course, only a conjecture, but it seems to me to be not unwarranted.
The investigation of the fertilization in this genus is attended with great technical
difficulties, and only when they are overcome shall we obtain a settlement of the
question.
In speaking of Casuarina, I have considered it from the biological and not from
the phyletic standpoint. Isee in it a plant which shows interesting arrangements
for the nourishment of the megaspores, which are not known in other Angiospermae
in the same degree of completeness, but I can see little that is ‘primitive’ in its
behaviour apart from the existence of a copious sporogenous cell-tissue, which,
however, is found also in a similar condition in other different cycles of affinity of the
Angiospermae. The processes within the megaspore seem to me to point rather to
a reduction. Apparently the nucleus divides in two—the endosperm-nucleus and
that which forms the egg-apparatus and the two cells which accompany it. Every-
thing else is uncertain’, and we must restrain ourselves from indulging the natural
desire to find here a ‘ missing link’ with the Gymnospermae, for this is an interpre-
tation which the facts, as we know them at present, do not support. The whole
economy of the plant, too, must be kept in mind, for it will perhaps give us the
explanation of why the reserve-material is here laid down at first partly in the
sporogenous cell-mass, partly in the funiculus, and then subsequently is apparently
quickly used up by the megasporial haustoria. The case of Alchemilla, moreover,
shows us in the nucellus remarkable links with that of Casuarina.
Most of the Angiospermae have a sporogenous tissue which is much
less developed than in the plants mentioned above, and often consists of
only one cell. The terminal result—usually only one megaspore—is the
same.
GERMINATION OF THE MEGASPORE.
The processes of germination in the megaspore are not always the
same, but they group themselves about one centre which we may consider
the most usual and the most typical. It was first made clear by Stras-
burger, and is as follows :— |
The young embryo-sac possesses ove nucleus—the primary nucleus
of the embryo-sac. This divides in further growth. The two daughter-
nuclei pass one to each end of the embryo-sac, and there each divides,
so that four nuclei are found at each pole of the embryo-sac. Two of
these nuclei—one from each pole, the folar nuclei—move back again to
the middle of the embryo-sac, and they are united sooner or later to form
the secondary nucleus of the embryo-sac. Thus at each end of the
embryo-sac are found three naked cells; those at the micropylar end
1 Engler, in Engler und Prantl, Die natiirlichen Pflanzenfamilien, Nachtrage, LI, i, p. 113, is
quite unjustified when, in referring to Treub’s investigations, he says, ‘ There arises defore fertiitzation
a rudimentary prothallus consisting of twenty or more cell-nuclei.’ Treub has mentioned this only
as possible and eventually probable. As we know nothing, however, of where and when fertilization
takes place we can naturally say nothing whatever about it.
636 THE SPORANGIUM OF SPERMOPHYTA
forming the egg-apparatus, those at the lower end the azzipodal cells. This
behaviour stands nearest to that of Gnetaceae, where we have seen that the
fertilization takes place at a stage in which the germination of the mega-
spore has not yet proceeded to the formation of a cell-tissue, and the cells
are all potentially alike, although there is a more or less expressed polar
differentiation, which is deter-
mined by the lie of the micro-
pyle, into an upper generative
and a lower vegetative portion
of the megaspore. We have the
same polar differentiation in the
Angiospermae?. The antipodal
cells, at least in many cases, have
certainly an important function in
the nutrition of the megaspore ?,
and this we can quite well con-
ceive of as being like that of
the epithelium; which will be
described below—it secretes an
enzyme which brings about the
solution of the nucellar tissue,
and thus shares in the carrying
over of the plastic material into
the embryo-sac. This function
will naturally be specially as-
signed to the antipodal cells where
Fic. 409. Aconitum Napellus. 1, embryo-sac shortly they remain for a relatively long
before fertilization. 2, embryo-sac with giant antipodal cells 1 { j j
at ee time of free formation of Sndosre mmanelen 3, anti- time and reach a significant ote,
podal cells from above. 4,5, one of the synergidae and one 6 j
Eheya Ager Decal ypete as, for example, in Asarum, many
Helleboreae (Fig. 409); in other
cases they lose their function very early and disappear. The egg-apparatus
’ I consider then the whole content of the megaspore as a slightly differentiated prothallus with
a vegetative and a generative part. The union of the two polar nuclei is a purely vegetative process,
and stands in relation to the fact that the formation of endosperm proceeds from ome nucleus,
strengthened here by union with another, and is only started by the act of fertilization. Whether we
consider the endosperm of the Angiospermae, in contrast with that of the Gymnospermae, as a zew
JSormation or as a consequence of a further development following upon fertilization of the prothallus
existing before fertilization, appears to me to have no essential significance. From what I have said
upon the course of development of the Spermophyta I hold the latter connexion to be the more
correct. In other words the endosperm of the Angiospermae is the same as that of the Gymno-
spermae, only it develops first of all in consequence of the stimulus given by fertilization, whilst this
stage of development of the megaspore in the Coniferae is set going by the pollination.
* As was first shown by Westermaier, Zur Embryologie der Phanerogamen, insbesondere iiber die
sogenannten Antipoden, in Nova Acta der kgl. Leop.-Carol. Deutschen Akademie der Naturforscher,
lvii (1890); id., Historische Bemerkungen zur Lehre von der Bedeutung der Antipodenzellen, in
Berichte der deutschen botanischen Gesellschaft, xvi (1898), p. 215.
See a it oe tha eis a.
os
cite See
ERAS SS
es
NUTRITION OF MEGASPORE OF ANGIOSPERMAE 637
consists of the egg and the two sywergidae. The function of the synergidae
is unknown. The most probabie conjecture regarding them is that, prob-
ably by the extrusion of soluble substances, they determine the pollen-tube
to grow to an egg. Occasionally the synergidae as well as the antipodal-
cells may form embryos', which will surprise us the less as Treub’s
investigations have shown that the embryo of Balanophora arises from an
endosperm-cell, and in plants which have marked polyembryony, like
Citrus, Mangifera indica, Clusia alba, Opuntia Ficus indica, Funkia coerulea,
the adventitious embryos, as Strasburger has shown, proceed from the
nucellar tissue—a condition which may be compared with the phenomena
of apospory in some of the Pteridophyta.
There would be little interest in enumerating here the cases in which relation-
ships in the megaspore different from the ‘normal’ have been observed. So far as
we know at present they have no significance, either in the way of leading to phyletic
conclusions or in giving us a deeper insight into the processes of germination of the
megaspore. The number of the nuclei arising by division of the nucleus of the
megaspore is sixteen in Peperomia?, but in the ripe embryo-sac a behaviour quite
like the normal results, for a larger number of these nuclei, usually eight, unite to
form the secondary nucleus of the embryo-sac. Similar variations occur also else-
where. ‘The number of the antipodal cells is more than three in many Monocoty-
ledones, for example Zea Mais, and in many Dicotyledones, for example Stack-
housia*. In Sparganium and Lysichiton* they are stirred up in fertilization to
further development and multiplication; they may increase up to one hundred and
fifty, and they remain for a long time. Biologically this process might be scarcely
different from the enlargement of the antipodals after fertilization in other plants. In
both cases they have that function which is elsewhere performed by the epithelium.
THE FEEDING OF THE MEGASPORE, ENDOSPERM, AND EMBRYO.
The arrangements which make possible the nutrition of the megaspore
and the endosperm and embryo arising within it in the ripening seeds are
very different, and only in recent times have they begun to receive
attention. The most simple case is that where the megaspore increases,
and, without the help of any structural relationships apart from the anti-
podal cells, gradually absorbs and displaces the surrounding cells. We
find this particularly in many Monocotyledones, but also in not a few
Dicotyledones.
Epithelium. Ina number of cases the ovule possesses a layer of cells
1 See Ernst, Beitrage zur Kenntnis der Entwicklung des Embryosackes und des Embryo (Poly-
embryonie) von Tulipa Gesneriana, L., in Flora, 1xxxviii (1901). The literature is given here.
? See Johnson, On the Endosperm and Embryo of Peperomia pellucida, in Botanical Gazette,
Xxx (1900); Campbell, The Embryo-sac of Peperomia, in Annals of Botany, xv (1901).
$ See Billings, Beitrage zur Kenntniss der Samenentwicklung, in Flora, lxxxviii (1901).
* Campbell, Notes on the Structure of the Embryo-sac in Sparganium and Lysichiton, in Botanical
Gazette, xxvii (1899), p. 153.
638 THE SPORANGIUM OF SPERMOPHYTA
marked out by a rich protoplasmic content, and evidently also by the
nature of the substances within its cells, as well as by its behaviour; this
layer we designate the cfzthelium'. Its signification can only at present be
concluded from external considerations, which point to the fact that it has
the duty in a certain degree of dissolving the tissue which serves for the
nutrition of the growing megaspore, and of transferring this plastic material
to the macrospore. The indications for this, besides the nature of the
contents, which have been already pointed out, are in particular the long
duration of this layer—_in Linum it is still present in the ripe seed, in other
cases it remains at least longer than the other layers—and the fact that
where the embryo-sac forms haustoria the epithelium is wanting in the
parts that form the haustoria. Where it exists it belongs usually to the
inner integument. In Drosera, however, it belongs to the nucellus. It
forms the innermost layer of the single integument in many Sympetalae.
An epithelium has been shown in the Choripetalae, for example in the
Geraniaceae, as well as in many Sympetalae; yet it is even within one
family, according to the usual limitations, not present everywhere. It is
wanting in the species of Gentiana, but it is present in Menyanthes, which is
usually considered as belonging to the Gentianaceae (Fig. 410).
Haustoria. An epithelium may be combined with the presence of
haustoria (Fig. 411). These occur in manifold forms. They grow out in
most cases through the tissue of the nucellus or the integuments, in
extreme cases appearing even outside the micropyle, and they are dis-
tinguished from the other part of the embryo-sac usually by this, that they
1 Frequently this is also designated the ¢ape¢twm, which can certainly, in a purely functional sense,
be correctly applied. I have elsewhere (Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in
Schenk’s Handbuch der Botanik, iii (1884), p. 407) referred to this, and shown that the designation
tapetum is a functional, not a formal, historical-developmental term (see also p. 597 of this book), and
that it is therefore incorrect to give the name tapetal cells to the sterile cells that are separated from
the archesporium, because they contribute to the wall of the megasporangium ; further, that a tapetum
does exist and has an epithelium-like construction in the ovule and has a definite nutritive importance.
This explanation found at first no attention, but it has been confirmed by later research, and has been
better substantiated. M. Goldfuss has also accepted my expression and designated the tapetum-like
absorbing layer as ‘assise épithéliale.’ The expression tapetum might here lead to a misunderstand-
ing, as it must be used in a different sense from the ordinary. The epithelium of the ovule is
morphologically different from the tapetum of the sporangia. The activity of the tapetum of the
sporangium falls in the time dJefore the complete construction of the spore; the activity of the
epithelium falls during the period of germination of the spore, but as we could speak in many ovules
also of tapetal cells around the megaspore during the development, in the same way as in the case
of the megasporangium of Isoetes, so it has come about that if the epithelium be called tapetum,
as is done by my pupils who have investigated the development of the seed—see Merz, Unter-
suchungen iiber die Samenentwicklung der Utricularieen, in Flora, Ixxxiv (Erganzungsband zum
Jahrgang 1897); Balicka Iwanowna, Contribution 4 l’étude du sac embryonnaire chez certains
Gamopeétales, in Flora, lxxxvi (1899); F. X. Lang, Untersuchungen iiber Morphologie, Anatomie
und Samenentwicklung von Polypompholyx und Byblis gigantea, in Flora, Ixxxvili (1901);
Billings, Beitrage zur Kenntniss der Samenentwicklung, in Flora, lxxxviii (1901)—a double
terminology is introduced which is better avoided.
HAUSTORIA OF MEGASPORE OF ANGIOSPERMAE 639
do not share in the permanent construction of the seed, at least in those
which are not—or only slightly—filled with endosperm. The following
are some illustrations :—
Linum. The megaspore enlarges in this genus considerably after fertilization.
Only one part of it is, however, filled with endosperm; the other serves as haustorium,
and is later separated from it’.
- Yorenia. In Torenia the apical portion of the embryo-sac grows as a hausto-
rium out of the micropyle before fertilization.
Torenia belongs to the Sympetalae, and the
formation of haustoria is widely spread? in this
group.
Byblis gigantea. Fig. 412 shows a longi-
tudinal section of Byblis gigantea. Only the
middle part of the embryo-sac is filled with endo-
sperm, within which the young embryo lies. The
Fic. 411. Myoporum serratum.
Fic. 410. Menyanthes trifoliata. Ovule in Embryo-sac in longitudinal section.
longitudinal section. There is a thick integument It is surrounded by an epithelium
in which a conducting bundle runs to near the excepting in the upper (antipodal)
downwardly directed micropyle. The embryo-sac and the lower (egg-apparatus)
fills the nucellus. It is surrounded by an epi- regions, where haustoria are sub-
thelium. After Billings. sequently formed. After Billings.
embryo-sac at the upper micropylar end, as well as at the chalazal end, has become
a haustorium. These haustoria are filled with cell-tissue, and are apparently
structures which have only a temporary function. The haustorium experiences a
large increase in surface by outgrowths which spread like a fungus-mycelium into
the thick integument *. Subsequently the upper and lower portions of the embryo-sac
* See Billings, Beitrage zur Kenntniss der Samenentwicklung, in Flora, 1xxxviii (1g01), and the
works of Hegelmaier and others cited there.
* See Balicka Iwanowna, Contribution 4 1’étude du sac embryonnaire chez certains Gamopétales, in
Flora, Ixxxvi (1899) ; Billings, op. cit.
* In plants we find frequently the phenomenon of autoparasitism, that is to say, that an organ lives
at the cost of another belonging to the same plant. The phenomenon is very strikingly seen,
especially in the development of the seed and fruit. That this parasitism is essentially different
from alloparasitism, where a foreign organism is used as a host, as some people say, I do not believe.
640 THE SPORANGIUM OF SPERMOPHYTA
are cut off from the remaining portion of the endosperm by tabular endosperm-cells
with cuticularized walls.
Globularia. The haustoria are even more developed in Globularia (Fig. 413),
where they also grow out of the micropyle.
Utricularia and Polypompholyx. The behaviour in these genera is also
remarkable. The nutritive materials for the haustoria are laid down before their
appearance, and are only later sought out by the haustoria and absorbed by them.
The phenomenon probably occurs elsewhere, although it is usually less visible. The
ee :
TRE |
rk SOS leas
VRE ie Mpa
Nore — ae
<I Ne f te
NN =u
TERN V i
p ee
Te
| va
Mf LLU ih
IS? oN
Ib Ya eh =
\ iN
te _ : 4 f
NX . TK eae i
Y ay a)
Fic. 413. Globularia cordifolia.
< Portion of a young seed in longitudinal
A section. The haustorium has grown
out of the micropyle and has branched,
Fic. 412. Byblis gigantea. Young seed in longitudinal section; the branches lying against the ovarian
E, embryo embedded in the endosperm, 2xzd; A, H, haustoria at the wall, , and against the funicle, /
end of the seed, and showing hypha-like outgrowths. After F. X. Lang. After Billings.
points of deposition of nutritive material may be designated as nutritive tissue. They
are found in these plants in two places :—
1. Internal in the chalazal region (Figs. 414 Dr above; 415, oDr; 417 41).
2. External within the funiculus. In Polypompholyx the external position is
clearly in the funiculus (Fig. 417, 4V), in Utricularia it is at the place where the
funiculus passes into the placenta (Figs. 414 Dr below, 415 uDr); but even here, as
the behaviour in Polypompholyx shows, the nutritive tissue should be reckoned
as funicular. ‘The megaspore sends out at both ends a haustorium; the micropylar
haustorium grows out of the micropyle and into the external funicular nutritive
tissue ; the chalazal one pierces the internal chalazal nutritive tissue. Both haustoria
ee ee ee
—_—
HAUSTORIA OF MEGASPORE OF ANGIOSPERMAE 641
Fic. 415. Utricularia stel-
laris. Ovule in longitudinal
section; oDyr, chalazal nu-
tritive tissue for the embryo
sac; «Dr, funicular nutritive
tissue for the embryo-sac,
which has quite used up the
nucellus and is protruded
Fic. 414. Utricularia inflata. Ovule in longi- from the micropyle; ¢f, epi-
tudinal section; Dr, nutritive tissue; 7, nucellus; thelium ; 4, young embryo.
esm, Megasporocyte. Magnified 500. After Merz. After Merz.
Fic. 416. Polypompholyx multi-
fida. Young ovule in longitudinal Fic. 417. Polypompholyx multifida. Older ovule in longitudinal
section: #, nucellus composed of section. The micropyle, from which the megaspore has grown out, is
an axile row of cells. The lower- turned obliquely upwards: 4%, egg-apparatus; #, antipodal cells;
most cell is the megasporocyte. #N, chalazal nutritive tissue; 62, funicular nutritive tissue; 4 epi-
The outer cell-layer is shaded. thelium. After F. X. Lang.
GOEBEL I! TE
642 THE SPORANGIUM OF SPERMOPHYTA
are, as in Byblis, cut off later from the middle portion of the embryo-sac carrying the
endosperm.
Fundamentally we have here only special cases of the general behaviour that in
the ovule or outside of it material is stored up which can be absorbed by the mega-
spore in its further growth.
Similar relationships repeat themselves in the development of the
embryo.
DEVELOPMENT OF THE FERTILIZED EGG.
With regard to the development of the fertilized egg I must refer to
what I have said elsewhere!, and also to Areschoug’, for nothing funda-
mentally new has been added to the subject. I will only here indicate
the following points :—
1. The fertilized egg does not usually become zz fofo the embryo,
but the embryo develops only out of the distal portion of the embryonal
primordia—the so-called pro-embryo. The proximal portion becomes the
suspensor.
2. The function of the suspensor ? is a double one :—
(2) The uptake of nutritive material, and in connexion therewith
we often observe a considerable increase in its surface. In many plants
haustorial outgrowths appear, as in Stellatae, Ribesiaceae, and Orchideae.
(2) To bring the embryo into the most favourable position for its
nutrition, especially during germination, and we have seen this function
very markedly in the species of Lycopodium and Selaginella as well as in
most Gymnospermae.
The functioning of the suspensor as a haustorium finds analogy in the
megasporial haustoria which have been mentioned above. Treub’s investiga-
tions of the Orchideae have in this respect a special interest, and have
supplied a number of remarkable examples. Also the case of Tropaeolum,
which has been so frequently described, may be placed in the same
category. If in this and like cases we are satisfied with giving as an
‘explanation ’ that the ‘need acts as a stimulus, we do not seem to get any
further than a paraphrase of the fact that this phenomenon is one which
is evidently advantageous.
The processes which lead to the formation of the seed-coat and its
appendages, as well as the appearance of the aril and caruncule, must
be left untouched. They belong to the question of the distribution of the
seed which does not require a new exposition at this time.
* Goebel, Vergleichende Entwicklungsgeschichte der Pflanzenorgane, in Schenk’s Handbuch der
Botanik, iii (1884).
2 Areschoug, Om de Phanerogames Embryo Nutrition, in Lunds Universitets Arsskrift, xxx (1894).
* See Goebel, op. cit., p. 172.
LIST OF THE ILLUSTRATIONS
(I and II respectively refer to Parts I and II.)
Abietineae. Scheme of germination of the microspore. Fig. 399: 1 ps6122
Acacia. Seedling-plant. Transition to phyllodes. Fig. 102. I, p.1 66.
Acacia alata. Apex of shoot winged by phyllodes. Fig. 233. Il, p- 356.
Acacia calamifolia, Stages in development of phyllode. Fig. 232. II, p. 355
Acacia verticillata. Young plant showing reversion. Fig. 105. I, p. 173.
x 5 End of a shoot bearing phyllodes. Fig. 245. II, p. 372.
Acer platanoides. Metamorphosis of leaf. Fig. 1. I, p. 7.
Venation and development of leaf. Fig. 212. II, p. 330.
Acer Pseudoplatanus. Development of bud-scale. Fig. 258. II, p. 387.
3 3h eee, dissected showing development of gynaeceum. Fig. 359.
P- 54!-
Achimenes Haageana. Adventitious flowering-shoot developed on leaf. Fig. 19. I, p. 47.
Aconitum Napellus. Embryo-sac. Fig. 409. II, p. 636.
Acrostichum peltatum. Sporangium with internal spore-germination. Fig. 148. II, p. 202.
3: Filamentous prothallus. Fig. 150. II, p. 203.
Acrostichum scandens. Dorsiventral stem in transverse section. Fig. 48. I, p. g2.
Adenostyles albifrons. Appearance of leaf-sheath in different regions. Fig. 237. II, p. 362.
Adiantum Edgeworthi. Bud-forming leaf. Fig. 172. II, p. 240.
5 5 Origin of leaf-borne buds. Fig. 173. II, p. 241.
FS a Leaf-apex exposed. Fig. 204. II, p. 317.
Ailanthus glandulosa. Development of superior apocarpous gynaeceum. Fig. 366. II, p. 561.
Ajuga reptans. Flowering-plant with stolons. Fig. 306. II, p. 460.
Alchemilla alpina. Development of megaspores. Fig. 407. I, p. 632.
Alchemilla nivalis. Apparent leaf-whorl. Fig. 213. II, p. 332.
Alchemilla pubescens. Development of megaspores. Fig. 407. II, p. 632.
Alliaria patente. Phyllody of ovule. Fig. 107. I, p. 182.
Allium sp. ? Displaced cotylar tip. Fig. 272. II, p. 409.
Allosorus crispus. Branching of leaf. Fig. 203. II, p. 316.
2 es Transition between sterile and fertile pinnules. Fig. 324. II, p. 486.
Apex of pinnule of a sporophyll. Fig. 332. II, p. - 496.
Alopecurus pratensis, Leaf above insertion of ligule in transverse section. Fig. 252. II,
P- 378.
Alpinia nutans. Convolute ligule. Fig. 251. II, p. 376.
Alsophila australis. Prothallus showing reversion to cell-threads. Fig. 149. II, p. 20
Alstroemeria psittacina. Resupination through torsion of leaf-stalk. “Fig. 194. II, p. —
Ampelopsis. Tendrils with anchoring-disks. Fig. 130. I, p. 267.
Amphibiophytum dioicum. See Symphyogyna Brogniartii.
Anadendrum medium (Pothos flexuosus). Forms of leaf. Fig. 97. I, p- 158.
Andreaea petrophila. Plant with dehiscing capsule. Fig. 126. II, p. 160.
Andreaea rupestris. Apex of young leaf. ” Fig. Bio.” Ty pi: 231:
Androsace sarmentosa. Flowering-plant with stolon and storage- -leaves. Fig. 305. II, p. 458.
Aneimia. Scheme of development of the antheridium. Fig. 133. II, p. 178.
Aneimia fraxinifolia. Upper portion of sporangium. Fig. 382. I, p- 588.
Aneimia rotundifolia. Line of dehiscence of sporangium in transverse section. Fig. 386. II,
P- §92-
Aneimia tomentosa. Sporangiferous pinnule on sporangium. Fig. 387. II, p. 592.
Aneura bogotensis. Branched thallus. Fig. 20. II, p. 25.
Aneura endiviaefolia. Thallus with curled Braniticn which retain water. Fig. 46. II, p. 54
Aneura eriocaulis. Habit. Fig. 21. II, p. 25,
5 Shoot bearing antheridial branches. Fig. 68. II, p. 81.
Aneura fucoides, Terminal and lateral shoots in transverse section. Fig. 22. II, p. 26.
is ; Basal part of plant with anchoring-organ. Fig. 23. II, p. 27.
Aneura fuegiensis. Thallus in transverse section showing lamellae. Fi ig. 49. Il, p. §5.
Aneura hymenophylloides. Thallus with curled branches which retain water. Fig. 47.
Il, p. 54.
- Chief and lateral axes in transverse section. Fig. 48. II, p. 55.
Aneura palmata. ” Capsule in longitudinal section showing fertile and sterile tissue. Fig. 89.
II, p. 104.
T-e2
644. LIST (OF THE ALLUSTRATIONS
Aneura pinguis. Ripe capsule in longitudinal section. Fig. 87. I, p. ror.
Aneura sp. Shoot bearing archegonia. Fig. 69. I, p. 81.
Angelica sylvestris. Development of inferior ovary. Fig. 371. II, p. 569.
Angiopteris evecta. Sori and sporangia. Fig. 381. II, p. 587.
Angiospermae. Scheme of change in configuration of sympetalous corolla in consequence of
different distribution of growth. Fig. 362. II, p. 553.
$3 Scheme of development of the ovary with formation of the sole. Fig. 364.
UL, p. 557
5 Scheme of germination of the microspore. Fig. 399. II, p. 612.
Anogramme chaerophylla, Tuber-formation on prothalli. Fig. 158. II, p. 216.
Anogramme (Gymnogramme) leptophylla. Tuber-formation on prothalli. Fig. 159. II,
p. 217.
Antheridium. Scheme of cell-division in its formation in Hepaticae. Fig. 5. II, p. 13.
Antheridium. Scheme of development in Homosporous Pteridophyta. Fig. 133. II, p. 178.
Anthoceros. Germination of spore. Fig. 119. I, p. 240. Fig. 94. I, p. Ilo.
Anthoceros argentinus. Thallus with tubers. Fig. 63. II, p. 60.
Anthoceros dichotomus. Thallus with bers. Fig. 62. I, p. 68.
Anthoceros fimbriatus. Apical region of thallus. Fig. 14. II, p. 22.
iS i Thallus with crisped marginal lobes. Fig. 50. II, p. 56.
Anthoceros laevis. Thallus with sporogonia. Fig. 81. II, p. 94.
Anthoceros punctatus. Sporiferous region, immature sporogonium in transverse section. Fig. 82.
II, p. 94.
Anthyllis tetraphylla. Neaneee of leaves. Fig. 71. I, p. 121.
Antithamnion (Pterothamnion) Plumula. Branching of thallus. Fig. 43. I, p. 87.
Aposeris foetida. Etiolated and normal leaf. Fig.197. I, p. 301.
Archegonium. Scheme of development in Hepaticae. Fig. 7. II, p. 15.
05 Scheme of development in Leptosporangiate Filicineae. Fig. 138. II, p. 184.
- Scheme of development in Selaginella spinulosa. Fig. 138. II, p. 184.
Aristolochia elegans. Prophyll; shoot in transverse section. Fig. 256. II, p. 382.
Aroid. Young plant of a climbing species. Fig. 95. I, p. 157-
Asparagus comorensis. ‘Turio with peltate kataphylls. Fig. 215. II, p. 334.
Asplenium dimorphum. Sterile and fertile pinnae and transition-form. Fig. 316. II, p. 478.
Asplienium Nidus. Developing prothallus. Fig. 147. II, p. 201.
Asplenium Ruta-muraria. Primary leaves. Fig. 92. I, p. 151.
Asplenium viride. Oldleaf. Fig.g92. I, p. 151.
Astragalus adscendens. Concrescent stipules. Fig. 241. II, p. 369.
Astrantia major. Reduction-series of hypsophyll. Fig. 261. II, p. 395.
Athyrium Filix-foemina clarissima. Apospory. Fig. 397. I, p. 608.
Atropa Belladonna. Bud of inflorescence in transverse section. Fig. 296. II, p. 438.
Azolla filiculoides. Habit of shoot; bud in transverse section. Fig. 227. I, p. 349.
of Fp Megasorus in longitudinal section. Fig. 325. II, p. 488.
> ES Sporophyll dissected out. Fig. 326. II, p. 489.
3 eS Sporophyll spread out. Fig. 327. II, p. 489.
Balanophora elongata. Development of female organ. Fig. 402. II, p. 621.
Bambusa verticillata. Leaf in transverse section showing hinge-cells. Fig. 208. II, p. 323.
Bauhinia sp. Shoot-apex with asymmetric leaves. Fig. 72. I, p. 123.
Bauhinia sp. Watch-spring tendrils. Fig. 304. II, p. 456.
Begonia incarnata. Scheme of leaf-arrangement and branching. Fig. 7o. I, p. 118.
Begonia Rex. Scheme of leaf-arrangement and branching. Fig. 69. I, p. 118.
Benincasa cerifera, Development of forerunner-tip and tendril. Fig. 201. II, p. 308.
“5 0 Prophylls and development of tendril. Fig. 288. II, p. 424.
Berchtoldia bromoides. Embryo from outside. Fig. 281. II, p. 417.
Bertholletia excelsa. Embryo. Fig. 180. II, p. 259.
Bignonia albo-lutea. Trifid tendrillar hooks. Fig. 283. II, p. 420.
As Fp Young tendril. Fig. 284. II, p. 421.
Blasia pusilla. Vegetative point with developing organs. Fig. 24. II, p. 28.
3 4S Plant with sporogonia and lateral segmentation of thallus. Fig. 33. II, p. 37.
Blyttia decipiens. Male plant. Fig. 18. II, p. 24.
Blyttia longispina. Apex of thallus with marginal cell-rows. Fig. 31. I, p. 36.
Blyttia Lyelli. Wall-cell of opened antheridium. Fig. 5. II, p. 13.
Blyttia sp. Archegonial group in vertical section. Fig. 70. II, p. 82.
Blyttia sp. Thallus with archegonia and young sporogonium. Fig. go. Il, p. 105.
Bostrychia Moritziana. Branching and root-formation. Fig. 14. I, p. 39.
Botrychium Lunaria. Transition between sterile and fertile pinnae. Fig. 313. II, p. 475.
» on Sporangium in longitudinal section showing sporogenous mass and tapetum.
Fig. 379. II, p. 584.
Botrychium virginianum. Scheme of orientation of organs in embryo. Fig.175. HU, p. 245.
LIST OF THE TLEUSTRATIONS 645
Bowiea volubilis, Climbing assimilating inflorescence. Fig. 302. II, p. 449.
Bryonia dioica. Androecium. Fig. 358. II, p. 539.
Bryopteris filicina. Stoloniferous plant. Fig. 40. II, p. 44.
Bryum giganteum. Habit of plant. Fig. 111. II, p. 133.
Bryum pseudotriquetrum ? Protonema-cushion. Fig. go. I, p. 148.
Buxbaumia indusiata. nee male plants and showing leaf-development. Fig. 105.
i ps £2
Structure of peristome. Fig. 129. II, p. 164.
Byblis gigantea. Young seed in longitudinal section. Chalazal and micropylar haustoria.
Fig. 412. II, p. 640.
Callitriche verna. Leaf-rosette. Fig. 297. II, p. 442.
Calobryum Blumii. Female plant. Fig. 37. Il, p. 40.
Caltha palustris. Venation cf leaf. Fig. 222. II, p. 343.
5 Development of axillary stipule. Fig. 246. II, p. 373.
Calypogeia ericetorum. ei with fertile root-like shoot enclosing sporogonium. Fig. 78.
I, p. 90.
3 x Fertile sac enclosing archegonia and embryo. Fig. 79. Il, p. 91.
Campanula rotundifolia. Shoot showing reversion of leaves. Fig. 121. I, p. 243.
Carex. Scheme of embryo in germination. Fig. 275. II, p. 412.
Carex Grayana. Base of endosperm enclosing embryo in longitudinal section. Fig. 274. TI,
SALT.
Casuarina glauca. Megasporangium in longitudinal section with megasporial haustorium.
Fig. 408. II, p. 634.
Casuarina Rumphii. Young megasporangium in longitudinal section. Fig. 408. II, p. 634.
Casuarina torulosa. Seedling-plant. Fig. 84. I, p. 144.
Casuarina tuberosa. Megasporangium with three megaspores in longitudinal section. Fig. 408.
II, p. 634.
Catharinea undulata. Opening cap of antheridium in longitudinal section. Fig. 3. II, p. 11.
Caulerpa prolifera. Creeping shoot. Fig. 47. I, p. gI.
Centradenia inaequalateralis. Shoot with asymmetric leaves. Fig. 65. I, p. 111.
Cephalotaxus Fortunei. Portion of female flower in longitudinal section. Fig. 348. II, p. 519.
Cephalotus follicularis. Transition-stage from ordinary foliage-leaf to tubular leaf. Fig. Zi.
II, p. 337-
as Development of pitcher-leaves. Fig. 218. II, p. 339.
Ceratozamia longifolia. Ovule in longitudinal section. Fig. 404. II, p. 627
Ceratozamia robusta. Coral-like branched air-roots. Fig. 187. II, p. 282.
4 AB Megasporophylls, young and older. Fig. 343. II, p. 513.
‘ Development of ovule. Fig. 400. II, p. 616.
Chamaerops (Trachycarpus) excelsa. Primary leaves. Fig. 210. II, p. 327.
Chamaerops humilis. Development of leaf in a series of transverse sections, Fi ig. 253. II, p. 379.
Chara fragilis. Shoot showing habit. Fig. 10. I, p. 35.
Chelidonium majus. Asymmetric leaf-lobes. Fig. your ep. r2s.
Chondrioderma difforme. Germination and formation of plasmodium. Fig. 2. I, p. 25.
Cinchona succirubra. Interpetiolar stipules. Fig. 243. II, p. 370.
Circaea intermedia. Stoloniferous plants with geophilous shoot-apices. Fig. 308. II, p. 464.
Cistus populifolius. Development of syncarpous superior gynaeceum. Fig. 369. II, p. 565.
Cladonia coccifera. Thallus with podetia. Fig. 31. I, p. 72.
Cladonia verticillata. Tiered growth. Fig. 32. I, p. 72.
Cladophora glomerata. Branching. Fig.g. I, p. 34.
Cladostephus verticillatus. Long shoot, with short shoots, in longitudinal section. Fig. 13.
: I, p- 37-
Cliftonaea pectinata. Branching of dorsiventral shoot. Fig. 16. I, p. 40; Fig. 40. I, p. 86.
Cobaea scandens.~ Portion of shoot showing leaf-base. Fig. 234. II, p. 350.
Leaf with auriculate lower pinnules. Fig. 235. LI, p. 360.
Development of tendril. Fig. 286. II, p. 423.
a 9 Development of tendril. Fig. 287. II, p. 423.
Colura Karsteni. Saccular leaf with valve in longitudinal section. Fig. 55. II, p. 62.
Colura tortifolia. Shoots with amphigastria. Fig. 54. II, p. 60.
Commelina coelestis. Scheme of an inflorescence. Fig. 82. I, p. 129.
Composite. Nearly aphyllous plant. Fig. 300. II, p. 446.
Concrescence and free development.—Scheme of. Fig. 22. I, p. 53.
Coriaria myrtifolia. Development of superior apocarpous gynaeceum. Fig. 366. II, p. 561.
Crantzia linearis. Young cylindric leaf. Fig. 193. II, p. 295.
Crocus longiflorus. Pull-roots. Fig. 184. Il, p. 271.
Cryptocoryne ciliata. Development of the seed and embryo. Fig. 177. Il, p. 255.
Seed in longitudinal section. Embryo detached from cotyledon. Fig. 178.
Dip. 250%
»” ?
” ”?
”? ”?
646 LIST OF THE TELUST RATIONS
Cucurbitaceae. Androecium in several genera. Fig. 358. II. p. 530.
Cuphea Zimpani. Young nucellus in longitudinal section. Fig. 394. II, p. 601.
Cyathodium cavernarum. Two cell-rows forming scales on underside of thallus. Fig. 25. II,
: Pp. 30.
Cyathophorum pennatum. Plant showing anisophylly. Fig. 54. I, p. 100.
Cycadaceae. Scheme of germination of the microspore. Fig. 399. II, p. 612.
Cycas circinalis. Microsporophyll. Fig. 344. II, p. 514.
Cycas revoluta. Megasporophyll. Fig. 341. II, p. 512.
Cyclamen persicum. Seedling-plant with tuberous hypocotyl. Fig. 268. II, p. 403.
Cyclanthera pedata. Androecium. Fig. 358. II, p. 539.
Cyperus alternifolius. Stages of germination and formation of seedling-plant. Fig. 276. II,
Pp. 413.
% . Bud in transverse section. Fig. 298. II, p. 443.
5 Shoot with distorted leaves and fleshy prophylls. Fig. 299. II, p. 443.
Cyperus decompositus. Embryo in longitudinal section. Fig. 277. II, p. 414.
Dacrydium Colensoi? Flower and ovules in section. Fig. 348. II, p. 519.
Dactylis glomerata. Development of leaf. Fig. 198. II, p. 306.
Dawsonia superba. Structure of wall of capsule. Fig. 130. II, p. 166.
Dendroceros foliatus. Apex of thallus. Fig. 30. II, p. 36.
3 Thallus with hood-like structures. Fig. 51. II, p. 57.
Desmoncus sp. Transition of leaf-pinnules to hooks. Fig. 285. II, p. 422.
Dianthus Caryophyllus. Bud of a double flower dissected out. Fig. 357. II, p. 537.
Diapensia. Syncarpous superior ovary in transverse section. Fig. 367. II, p. 563.
Dicksonia antarctica. Development of sorus and sporangia. Fig. 331. II, p. 495.
Dicnemon semicryptum. Germinated spore from unopened sporogonium. Fig. 103. II, p. 124.
Dionaea muscipula. Development of paracarpous superior gynaeceum. Fig. 370. II, p. 566.
Dioon edule. Megasporophyll. Fig. 342. I, p. 513.
Diphyscium foliosum. Forms of leaf. Fig. 113. II, p. 135.
s5 Stem in longitudinal section, bearing sporogonium. Fig. 117. I, p. 237-
Dipterocarpus alatus. Concrescent stipules. Fig. 240. II, p. 368.
Doodya caudata. Germ-plant with primary leaves. Fig. 93. I, p. 152.
Apogamous prothallus. Fig. 160. II, p. 221.
Dracaena indivisa. Seedling-plant with cotylar haustorium. Fig. 271. II, p. 408.
Drepanophyllum fulvum. Distichously-leaved shoot. Fig. 114. II, p. 136.
Drosophyllum lusitanicum. Circinate ptyxis of leaf. Fig. 202. II, p. 311
Drymoglossum subcordatum. Plant with sterile and fertile leaves. Fig. 322. II, p. 485.
Dulongia acuminata. Epiphyllous inflorescence. Fig. 295. IJ, p. 437.
Eichhornia crassipes. Development of venation of leaf. Fig. 219. II, p. 340.
Elaphoglossum (Acrostichum) spathulatum. Sterile and fertile leaves. Fig. 323. II, p. 485.
Sporophyll still folded in transverse section.
us » Fig. 333. HL, p. 496.
Elatostemma sessile. Bud in transverse section. Hic lOAw Vp: suo:
Embryo. Scheme illustrating orientation of organs in Homosporous Leptosporangiate Filicineae,
Botrychium virginianum, Lycopodium clavatum, Selaginella. Fig. 175. I, p. 245.
Ephemeropsis tjibodensis. Segment-walls of protonema. Fig. 99. II, p. 119.
an Habit of protonema. Fig. roo. II, p. 120.
Ephemerum serratum. Protonema with male and female plants. Fig. 87. I, p. 147.
7 - Protonema with two young plants. Fig. 88. I, p.147; Fig. 107. II,
p- 129.
Equisetum. Scheme of development of the antheridium. Fig. 133. II, p. 178.
Equisetum pratense. “Antheridia in longitudinal section. Fig. 131. II, p. 174.
cs ; Male prothallus. Fig.132. II, p. 175.
i Female prothallus. Fig. 143. II, p. 196.
Erica carnea, Half-anther in transverse section. Fig. 398. II, p. 611.
Eriopus remotifolius. Plant in fructification showing gemmae with separation-cell. Fig. 114.
I; om 136:
Eryngium maritimum. Development of inferior ovary. Fig. 371. II, p. 569.
Erythraea pulchella. Flower-bud in transverse section, development of ovary. Fig. 365.) Il)
. 558.
Eschscholtzia californica, lower-bud in transverse section. Fig. 355. II, p. 531.
Eucamptodon Hampeanum. Germinated spores from unopened sporogonium. Fig. 103. II,
Pp. 124,
Euptilota Harveyi. Branching, long shoots and short shoots. Fig. 46. I, p. 89; Fig. 80. I,
Potays
Exormotheca Holstii. Thallus. Fig. 67. II, p. 75.
LIST OF THE. ILLUSTRATIONS 647
Fagus. Scheme of position of lateral buds. Fig. 49. I, p. 93.
Fegatella supradecomposita. Separable propagative twigs. Fig. 44. II, p. 48.
Filices. Primary leaves. Fig. 92. I, p. 151.
Fevillea trilobata. Androecium. Fig. 358. II, p. 539.
Filicineae. Prothalli at different stages of development. Fig. 147. II, p. 201.
Fossombronia tuberifera. Plant with fructification and developing tuber. Fig. 34. II, p. 38;
Fig. 61. II, p. 67.
3 . Thallus with subterranean tuber. Fig. 60. II, p. 66.
Fraxinus excelsior. Development of leaf and venation. Fig. 224. II, p. 344.
Free-development and concrescence. Scheme of. Fig. 22. I, p. 53.
Frullania Tamarisci. Shoot showing amphigastria and water-sacs. Fig. 52. II, p. 58.
Funaria hygrometrica. Opening cap of antheridium. Fig. 3. II, p. 11.
Germination of spore. Protonema. Fig, 89. I, p. 147; Fig. 98. II,
EL Ge
Peolsnenna with separation-cells, Fig. 104. II, p. 125.
Young plant attached to protonema. Fig. 106. II, p. 128.
Protonema produced in darkness. Fig. 114. I, p. 233.
3 5S Scheme of cell-divisions in development of capsule. Fig. 122. II, p. 156.
Funkia ovata. Development of leaf. Venation. Fig. 220. II, p. 341.
Gaertnera sp. Bud in transverse section. Fig. 247. II, p. 374.
Galium Mollugo. Shoot in transverse section showing axillary bud. Fig. 244. II, p. 370.
Genista sagittalis. Showing shoot produced in darkness. Fig. 124. I, p. 248.
Genlisea violacea. Seedling, older plant, portion of inflorescence. Fig. 169. II, p. 237.
Geranium pratense. Seed in transverse section. Fig. 67. I, p. 116.
Geum bulgaricum. Leaf. Fig. 81. I, p. 127. _
Ginkgo biloba. Portion of male flower in longitudinal section. Fig. 345. II, p. 515.
a - Male and female flowers. Fig. 347. II, p. 518.
Gleichenia circinata. Sorus. Fig. 385. II, p. 590.
Gleichenia dichotoma. Forked leaf with bud and protecting pinnae. Fig. 206. II, p. 319.
Globularia cordifolia. Portion of young seed in longitudinal section. Micropylar haustorium.
Fig. 413. II, p. 640.
Gnetum. Upper part of megaspore in longitudinal section at time of fertilization. Fig. 406. II,
p- 630.
Gnetum Gnemon. Megaspore. Fig. 405. II, p. 630.
Goldfussia glomerata. Scheme of phyllotaxy and leaf-symmetry. Fig. 66. I, p. 112; Fig. 127.
I, p. 254.
Gonolobus sp. Forerunner-tip of leaf. Fig. 199. II, p. 307.
ms », Development of forerunner-tip of leaf. Fig. 200. II, p. 307.
Grass. Stem and portion of leaf. Fig. 248. II, p. 375.
Grimaldia dichotoma. Spores. Fig. g1. II, p. 107.
Guilandina sp. Stipules. Fig. 236. II, p. 361.
Gymnanthe saccata. Plant and fertile sacs. Fig. 80. II, p. 92.
Gymnogramme leptophylla. See Anogramme leptophylla.
Hakea trifurcata. Twig with simple flat and branched cylindric leaves. Fig. 192. II, p. 294.
Halopteris filicina. Shoot-system. Fig. 11. I, p. 36.
» a End of long shoot. Fig. 12. I, p. 37; Fig. 44. I, p. 88.
Hedera Helix. Leaf-forms. Fig. 98. I, p. 160.
Hedwigia ciliata. Leaf-structure. Fig.112. II, p. 133.
Hedysarum capitatum. Asymmetry of leaves. Fig. 71. I, p. 121.
Hedysarum obscurum. Bud in transverse section showing stipules. Fig. 242. II, p. 369.
Helianthus annuus. Capitula showing size of ray-florets affected by light. Fig. 361. II, p. 552.
Helicodiceros muscivorus. Branching of leaf. Fig. 209. II, p. 324.
Helminthostachys zeylanica. Development of sporophyll. Fig. 318. II, p. 481.
‘5 S53 Mature sporophyll. Fig. 319. II, p. 483.
a = Mature sporangiophore. Fig. 320. II, p. 483.
3 » Young sporangiophores on sporophyll. Fig. 321. II, p. 484.
Hemionitis palmata. Virescent archegonium. Fig. 139. I, p. 187.
Hemitelia (Amphicosmia) Walkerae. Development of prothallus. Fig. 144. II, p. 200.
Hepaticae. Scheme of cell-division in the formation of the antheridium. Fig. 5. II, p. 13.
as Scheme of development of archegonium. Fig. 7. II, p. 15.
Hesperis matronalis. Phyllody of ovule. Fig. 107. I, p. 182.
Heteranthera reniformis. Seedling-plant showing reversion. Fig. 104. I, p. 172.
Hordeum hexastichum. Half-ripe embryo. Fig. 282. II, p. 418.
Hydrurus foetidus. Coenobium. Fig. i Incpe St:
Hymenocarpus circinnatus. Asymmetry of leaves. Fig. 71. I, p. 121.
Hymenolepis spicata. Young prothallus. Fig. 147. IJ, p. 20.
6438 LIST. OF THE JELOSERATIONS
Hymenolepis spicata. Sporophyll still folded in transverse section. Fig. 333. II, p. 496.
Hymenophyllaceae. Formation of gemmae on prothallus. Fig. 157. II, p. 214.
Hymenophyllum axillare. Portion of prothallus. Fig. 153. II, p. 207.
Hymenophyllum sp. Gemmaeon prothallus. Fig. 157. II, p. 214.
Hymenophytum flabellatum. Habit of plant. Fig. 19. II, p. 24.
Hymenophytum Phyllanthus. Habit of plant. Fig.13. II, p. 22
Hyoscyamus albus. Anther in transverse section and scheme of cell-layers in young anther. Fig.
393-_ II, p. 599.
Hypericum aegyptiacum, Linn. (H. heterostylum, Parl.). Staminal phalange. Fig. 356. II,
534+
Hypericum heterostylum, Parl. See Hypericum aegyptiacum.
Hypnum (Hylocomium) splendens. Tiered growth. Fig. 27. I, p. 68.
Fe 55 5 Paraphyllium. Fig. 116. II, p. 147.
PY 7 ¥. Development of a paraphyllium. Fig. 117. I, p. 147.
Indigofera diphylla. Asymmetry of leaves. Fig. 71. I, p. 121.
Iris variegata. Development of leaf. Fig. 211. II, p. 329.
Isoetes lacustris. Leaf-borne shoot. Fig. 292. II, p. 431.
Isoetes Malinverniana. Germinated microspore. Fig. 135. II, p. 180.
Juncus lamprocarpus. Shoot transformed by attack of Livia juncorum. Fig. 109. I, p. 196.
Jungermannia bicuspidata. Portion of stem grown in feeble light. Fig. 120. I, p. 241.
Ms 3 Stem with sporogonium in longitudinal section. Fig. 85. II, p. go.
Jungermanniaceae. Development of antheridium. Fig. 5. II, p. 13.
Juniperus communis. Male flower. Fig. 346. II, p. 516
Jussieuea salicifolia. Venation of sepal and petal. Fig. 223. II, p. 343.
Knautia arvensis. Anther, younger and older, in transverse section. Fig. 392. II, p. 598.
Laguncularia racemosa. Pneumatophores rising above the water. Fig. 186. II, p. 279.
Lathraea Squamaria. Storage-scale-leaves in section. Fig. 262. II, p. 399.
Lathyrus Aphaca. Seedling-plant. Fig. 76. I, p.126; Fig. 110. I, p. 211.
Shoot-bud in transverse section. Fig. 77. I, p. 126.
Lathyrus Clymenum. Leaf-form. Fig. 99. I, p. 162.
Lathyrus heterophyllus. End of a shoot showing erect stipules. Fig. 239. II, p. 367.
Lathyrus latifolius. Node showing horizontal stipules. Fig. 239. I, p. 367.
Leguminosae. Unequally-sided leaves. Fig. 71. I, p. 121.
Lejeunia (Cololejeunia) Goebelii. Gemmae. Fig. 45. II, p. 50.
Lejeunia Metzgeriopsis. Habit of male plant. Fig. 86. I, p. 146; Fig. 93. II, p. 109.
Lejeunia (Odontolejeunia) mirabilis. Gemmae. Fig. 45. II, p. 50.
Lejeunia serpyllifolia. Germination of spore. Fig. 85. I, p. 146; Fig. 92. II, p. 108.
Lejeunia sp. Pro-embryo. Fig. 85. I, p. 146; Fig. 92. II, p. 108.
Lemanea torulosa?. Pro-embryo with young plant. Fig. gr. I, p. 149.
Lembidium dendroideum. Plant with antheridial branches and tuber. Fig. 39. II, p. 43.
Lemna trisuleca. Isolated segments of plant. Fig. 168. II, p. 236.
Lepicolea cavifolia. Plant with incipient flagella. Fig. 38. II, p. 42.
Leptosporangiate Filicineae. Scheme of development of archegonia. Fig. 138. II, p. 184.
Leptosporangiate Filicineae (Homosporous). Schemes illustrating the orientation of the organs
in the embryo. Fig. 175. II, p. 245.
Leucodendron argenteum. Seedling plant. Fig. 266. II, p. 402.
Licmophora flabellata. Coenobium. Fig. 5. I, p. 30.
Limnophila heterophylla. Apparent leaf-whorl. Fig. 213. II, p. 332.
nA - Water-leaves, land-leaves, transition-forms. Fig. 214. II, p. 333.
Lobelia. Syncarpous superior ovary in transverse section. Fig. 367. II, p. 563.
Lophocolea heterophylla. Young embryo entire and in longitudinal section. Fig. 88. II, p. 102.
Lycopodium alpinum. Shoot in transverse section at different levels. Fig. 57. I, p. 105.
Lycopodium annotinum. Sporiferous spike in transverse section. Fig. 335. I, p. 503.
Lycopodium clavatum. Scheme of orientation of organs in embryo. Fig. 175. II, p. 245.
56 Wall of sporangium and stomium. Fig. 373. II, p. 579.
Lycopodium complanatum. Dorsiventral shoots. Fig. 55. I, p. 103.
9 » Dorsiventral shoots in transverse section. Fig. 56. I, p. 103.
a cf Showing shoot developed in darkness. Fig. 125. I, p. 252.
» oF Shoot-axes in transverse section. Fig. 126. I, p. 253.
Prothallus in longitudinal section. Fig. 142. II, p. 192.
Lycopodium inundatum. Development of prothallus. Fig. 140. II, p. rgI.
» . Prothallus with archegonia. Fig. 141. II, p. Ig1.
» a Sporangium #7 sz¢z in longitudinal section. Fig. 378. II, p. 583.
Lycopodium Selago. Gemma-formation. Fig. 310. II, p. 468.
LIST OF THE ILLUSTRATIONS 649
Lygodium japonicum. Sporangium. Fig. 389. II, p. 593.
- a Fertile leaflet and portion of rhizome with sterile leaf. Fig. 390. II,
P- 594-
Lygodium microphyllum. Fertile leaf-lobe with four sporangia. Fig. 388. II, p. 592.
Macrozamia Fraseri. Seedling with erect air-roots. Fig. 187. II, p. 282.
Mammillaria. Scheme of vegetative point with forked mammillae. Fig. 294. II, p. 436.
Marathrum utile. Root with two rows of adventitious shoots. Fig. 164. II, p. 227.
Marattia fraxinea. Synangia. Fig. 380. II, p. 586.
Marchantia chenopoda. Apex of thallus from below. Fig. 27. II, p. 31.
Marchantia polymorpha. Development of gemmae. Fig. 112. I, p. 227; Fig. 96. II, p. 112.
Antheridium and spermatozoids. Fig.1. II, p. 9.
a a Archegonia. Fig. 6. II, p. 14.
Rhizoids on under-surface of thallus. Fig. 28. II, p. 32.
Breathing-pore of thallus. Fig. 65. II, p. 73.
oe Ar Male plant with antheridiophores. Fig. 74. II, p. 85.
Female plant with archegoniophores and sporangia. Germination of
spore. Fig. 75. II, p. 86.
Marchantiaceae. Scheme of thallus-symmetry in. Fig. 41. I, p. 86; Fig. 10. Ul, p. Ig.
Marsilia. Germinated megaspore in longitudinal section. Fig. 111. I, p. 220.
Germinated microspores. Fig. 135. II, p. 180.
Ds Scheme of sporocarp in transverse section. Fig. 328. II, p. 491.
Marsilia Brownii. Sporocarp in section parallel with surface. Fig. 329. II, p. 492.
Marsilia polycarpa. Development of sporocarps on sporophyll. Fig. 317. II, p. 479.
; Very young sporocarp and portion in transverse section. Fig. 329. II,
2?
1) ”?
Pp- 492- :
Menyanthes trifoliata. Ovule in longitudinal section with embryo-sac and epithelium. Fig. 410.
Il, Pp: 39-
Metzgeria furcata. Apical region of thallus. Fig.11. TI, p. 20.
5 Branching at apex of thallus. Fig.15. I, p. 23
Microspore. "Scheme of germination in Cycadaceae, “Abietineae, eee Bcrades Fig. 399. II,
p- 612,
Mimosa sensitiva. Asymmetric leaflets. Fig. 74. I, p. 124.
Mnium hornum. Plant with sporogonia. Structure of capsule and peristome. Fig. 127. I,
p- 16.
Structure of wall of capsule. Fig. 128. II, p. 162.
Mnium undulatum. Vegetative shoot, orthotropous and plagiotropous. Fig. 28. I, p. 69.
FF a5 regu shoot bearing antheridia and plagiotropous shoots. Fig. 29.
p- 9.
3 5 Development of the archegonium. Fig. 8. II, p. 16.
Young archegonial group in transverse section. Fig. 118. II, p. 152
Mohria caffrorum. Sporangium seen from above. Fig. 382. II, p. 588.
Monoclea dilatata. Young antheridium, development of archegonium. Fig. 4. II, p. 12.
Monocotyledones. Scheme of young lateral root in longitudinal section. Fig. 185. II, p. 274.
Morkia. Cell-row with mucilage-papilla. Fig. 25. II, p. 30.
Mucor Mucedo. Origin and germination of zygospore. Fig. 129. I, p. 267.
Mulgedium macrophyllum. Transition from foliage-leaf to hypsophy yll. Fig. 260. II, p. 394.
Musci. Opening ofthe antheridium. Fig. 3. II, p. 11.
se Oblique segment-walls in rhizoid. Fig. 99. II, p. 119.
= Segment-walls of protonema-threads. Fig. 99. II, p. 119.
Myoporum serratum. Embryo-sac in longitudinal section with epithelium and chalazal and
micropylar haustoria. Fig. 411. II, p. 639.
Nanomitrium tenerum. Development of sporogonium. Fig. 120. I], p. 155.
Sporogonium i in longitudinal section. Fig. 123. II, p. 157.
Narcissus poeticus, Bulb in transverse section. Fig. 195. II, p. 299.
Nephrolepis exaltata. Leaf-tip. Fig. 205. II, p. 318.
Nerium Oleander. Bud of a double flower in transverse section. Fig. 357. I, p. 537-
Notothylas orbicularis. Sporogonium and thallus with young archegonia in longitudinal section.
Fig. 83. II, p. 96.
Oenone leptophylla. Dorsiventral root in transverse section. Fig, 122. I, p. 246.
Oenothera bistorta, Seedling-plant showing intercalary growth of cotyledons. Fig. 269. I,
p. 405.
Onoclea Struthiopteris. Transition between sterile and fertile pinnae. Fig. 313. Il, p. 475.
Opuntia leucotricha. Showing shoots produced in darkness. Fig. 123. 1, p. 247.
Oryza sativa. Ligule and sickles of the leaf. Fig. 249. Il, p. 375.
35 9 Leaf above origin of ligule in transverse section. Fig. 250. II, p. 376.
650 LIST (OF (THE ILLUSTRATIONS
Oryza sativa. Embryo from outside. Fig. 281. II, p. 417.
Osmunda. Antheridium. Fig. 134. II, p. 179.
Osmundaceae. Scheme of development of the antheridium. Fig. 133. II, p. 178.
Osmunda regalis. Prothallus with adventitious shoots. Fig. 20. I, p. 49
5) a Prothallus under different conditions of nutrition. Fig. I 51. II, p. 205.
Ms . Unripe sporangium in transverse section. Fig. 382. Il, p. 588
5 m Sporangia showing position of annulus, Fig. 385. II, p. 590.
- Cells of annulus in transverse section. Fig. 386. II, p. 592.
Oxalis ruscifolia. Leaf and phyllode. Fig. 231. II, p. 354.
Oxalis sp. Pull-roots. Fig. 184. II, p. 271.
Oxalis stricta. Development of syncarpous superior gynaeceum. Fig. 368. II, p. 564.
Oxymitra pyramidata. Vegetative point of thallus in surface-section. Fig. 25. Il, p. 30.
Passiflora. Syncarpous superior ovary in transverse section. Fig. 367. II, p. 563.
Pediastrum granulatum. Formation of coenobium. Fig. 3. I, p. 26.
Pellia calycina. Autumnal propagative twigs. Fig. 43. II, p. 48.
+r Emptied capsule showing elaterophore. Fig. 86. II, p. 100.
Pellionia Daveauana. Shoot with asymmetric leaves. Fig. 62. I, p. 109.
53 Bud in transverse section. Fig. 63. I, p. 110.
Phalaenopsis Esmeralda. Root in transverse section. Fig. 188. II, p. 284.
Phalaenopsis Luddemanniana. Root in transverse section. Fig. 188. II, p. 284.
Phalaenopsis Schilleriana. Root in transverse section. Fig. 188. II, p. 284.
9 + Roots flattened and adpressed to bark ofatree. Fig. 189. II, p. 285.
” » Exodermis and velamen of root in transverse section. Fig. Igo.
II, p. 285.
Phascum cuspidatum. Stem in ‘longitudinal section with antheridia and archegonia. Fig. 2.
II, p. 9.
Philodendron melanochrysum. Vertical nourishing and horizontal anchoring-roots. Fig. Igt.
II, p. 287.
Phoenix canariensis. Primary leaves. ; Fig. ikon ANE) SVE
Phormium tenax. Keeled leaves in transverse section. Fig. 196. II, p. 300.
Phyllanthus mimosoides. Habit. Fig. 53. I, p. 98.
Phyllocactus phyllanthoides. Seedling plant. Fig. 103. I, p. 169.
Phyliccladus alpinus. Young fruit in longitudinal section. Fig. 348. II, p. 510.
Phyllody of the ovule. Fig. 107. I, p. 182.
Phyllotaxy. Schemes of. Fig. 33. I, p. 75.
” ” Fig. 34- I, P- 75-
” Fig. 35. I, p. 79.
S 3 Fig. 36. I, p. 80.
53 Pigs 37155, ps0:
Fig. 38. I, p. 80
Physiotium cochleariforme. Valved water-sacs. Fig. 56. II, p. 62.
Physiotium conchaefolium. Shoot-bud in transverse section. F ig. 37 7. ld, p.i63.
Physiotium giganteum. Shoot with water-sacs. Fig. 56. II, p. 6
Physiotium microcarpum. Dissected leaf showing water-sac. Fig. Tee II, p. 63.
Pilogyne suavis. Portion of shoot with developed and arrested tendril. Fig. 290. UL, p. 426.
Pilostyles Ulei. On Astragalus, only its flowers appearing. Fig. 163. II, p. 225.
Pilularia Novae-Hollandiae. Anterior portion of a plant with sporocarps. Fig. 330. Il, p. 492.
Pinus maritima. Androgynous flower in longitudinal section. Fig. 311. II, p. 471.
5 Malformed seminiferous scale. Fig. 352. II, p. 524.
Pinus Pumilio. Portion of tangential section of female flower. Fig. 351. II, p. 523.
Pisum sativum. Asymmetric stipules. Fig. 75. I, p. 124.
53 Artificial foliation of tendrils. Fig. 289. II, p. 425.
Plagiochasma Aitonia. Male plant with antheridial groups. Fig. 26. II, p. 31; Fig. 73. UL,
. 84.
Plagiochila asplenioides. Habit, Higet153 oly p.) 234s
Plagiochila circinalis. Circinate shoot-apex. Fig. 59. II, p. 65.
Platycerium grande. Dehisced sporangium. Fig. 382. II, p. 588.
Plocamium coccineum. Adhesive disks. Fig. 15. I, p. 40; Fig. 45. I, p. 88.
Podocarpus ensifolius. Female flower in different stages of construction. Fig. 349. II, p. 520.
Polygonatum multiflorum. Rhizome. Fig. 307. II, p. 463.
9 + Rhizome and seedling-plant in relation to depth in soil. Fig. 309.
Il, p. 465.
Polyotus claviger. Shoots with arnionens and water-sacs. Fig. 53. II, p. 590.
Polypodiaceae. Scheme of development of the antheridium. Fig. 133. Il, p. 178.
Apex of a band-like prothallus with ‘ bristle-hairs.’ Fig. 146. II, p. 201.
Polypodium obliquatum. Prothallus from below. Fig. 145. II, p. 201.
oe ne Scheme of sorus in longitudinal section. Fig. 334. II, p. 497.
LIST OF THE ILLUSTRATIONS 651
Polypodium Schomburgkianum. Dorsiventral stem in transverse section. Fig. 48. I, p. 92.
Polypodium vulgare. Leaf with variation in degree of branching. Fig. 225. II, p. 345.
Polypompholyx multifida. Young ovule in longitudinal section. Fig. 416. II, p. 641.
an a Older ovule in longitudinal section. Chalazal and funicular nutritive
tissue. Fig. 417. II, p. 641.
Polytrichum. Apex of emptied antheridium., Fig. 3. II, p. 11.
=p Shoot-apex with sunk embryo in longitudinal section. Fig. 119. II, p. 153.
Polytrichum commune. Plant with sporogonia. Fig. 124. II, p. 158.
Polyzonia jungermannioides. Branching. Fig. 17. I, p. 40.
Posidonia sp. Embryo. Fig. 181. II, p. 260.
Potentilla. Scheme of staminal arrangement. Fig. 354. I, p. 530.
Potentilla fruticosa. Scheme of staminal arrangement. Fig. 354. I, p. 530.
Pothos celatocaulis. Juvenileform. Fig. 96. I, p. 157.
Pothos flexuosus. See Anadendrum medium.
Preissia commutata. Germination of spore. Fig. 118. I, p. 239; Fig. 95. Il, p. 111.
ss “p Stalk 3 archegoniophore in transverse section showing rhizoids. Fig. 41. II,
Pp. 40.
2 + Breathing-pore of thallus. Fig. 66. II, p. 74.
Prunus Padus. Development of bud-scales. Fig. 258. I, p. 387.
Psilotum complanatum. End ofa shoot with axillary sporangia. Fig. 337. II, p. 505.
Pteris longifolia. Development of prothallus. Fig. 150. II, p. 203.
Pteris quadriaurita. Leaf-pinnule with Witches’ broom. Fig. 108. I, p. 194.
Pteris serrulata. Young leaf in profile and in transverse section. Fig. 207. II, p. 320.
Pterobryella longifrons. Bud-scale in transverse section. Fig. 112. II, p. 133
Pyrus Malus. Development of inferior ovary. Fig. 371. II, p. 569.
Radula tjibodensis. Shoot with archegonial group. Fig. 76. II, p. 88.
Ranunculus multifidus. Water-leaf and land-leaf. Fig. 128. I, p. 261.
Rhinanthus major. Transition from foliage-leafto hypsophyll. Fig. 259. II, p. 392.
Rhizophora mucronata. Flower in longitudinal section. Fig. 363. II, p. 555.
Rhododendron. Syncarpous superior ovary in transverse section. Fig. 367. I
Riccia fluitans. Forked branching thallus. Fig. 12. Il, p. 21.
Riccia natans. Apex of thallus which has forked in transverse section. Fig. 29. II, p. 33.
55 Land-form showing isolation of branches by dying off. Fig. 42S p47
Riella Battandieri. Habit with schemes of thallus-symmetry. Fig. 41. I, p. 86; Fig. 1o. II, p. Ig.
Riella Clausonis. Male plant. Fig. 9. I, p. ro.
Rochea falcata. Bud in transverse section. ‘Fig. GS ipa trz.
Root. Scheme of young monocotylous lateral root. Fig. 185. Il, p. 274.
Rosaceae. Scheme of staminal arrangements. Fig. 354. IL, p. 530.
Rubus australis, var. cissoides. Seedling plant. Fig. 229. II, p. 353.
“ “0 ‘ Older leat with reduced leaflets. Fig. 230. II, p. 354.
Rubus idaeus. Scheme of staminal arrangement. Fig. 354. II, p. 530.
Ruscus aculeatus. Shoot. Fig. 101. I, p. 166.
Salvinia auriculata. Leaf. Fig. 226. II, p. 348.
Salvinia natans. Development of male prothallus. Fig. 137. II, p. 182.
op Bs Germinating megaspore and prothallus. Fig. 155. Il, p. 211.
= 5 oe megaspore, prothallus, embryo in longitudinal section. Fig. 156.
p. 211.
Scabiosa Columbaria. Leaves from different regions of the shoot. Fig. 228. II, p. 352.
Scheme of free-development and concrescence. Fig. 220) ep: : 3.
Schemes of Phyllotaxy. Fig. 33. I, p. 75.
” ”? Fig. 34- is p- 75-
” » Fig. 35. I, p. 79.
”? ”? Fig. 306. a Pp. 80.
” ” Fig. 37. I p- 8o.
Fig. 38. I, p. 80.
Scheme of thallus- -symmetry in Marchantiaceae. Fig. 41. I, p. 86; Fig. 10. II, p. 19.
Scheme of thallus-symmetry in Riella. Fig. 41. I, p. 86; Fig. 10. WH, p. 19.
Scheme of branching in Thuya occidentalis. Fi ipaoy Ep. Sr.
Scheme of the insertion of leaves and lateral shoots on the dorsiventral branches of Tilia, Fa: gus, and
others. Fig. 49. I, p. 93.
Scheme of phyllotaxy and leaf-symmetry in Goldfussia glomerata. Fig. 66. I, p. 112; Fig. 127.
I, p. 254
ee of leaf-arrangement and branching in Begonia Rex. Fig. 69. I, p. 118.
Scheme of leaf-arrangement and branching in Begonia incarnata. Fig. 7o. I, p. 118.
Scheme of inflorescence of Commelina coelestis. Fig. 82. I, p. 129.
Scheme of cell-division in the formation of the antheridium of Hepaticae. Fig. 5. Il, p. 13.
>°
652 LIST OF» THE ALLOSTRATIONS
Scheme of the development of the archegonium of the Hepaticae. Fig. 7. II, p. 15.
Scheme of development of antheridium in Homosporous Pteridophyta (Aneimia, Polypodiaceae,
Osmundaceae, Equisetum). Fig. 133. II, p. 178.
Scheme of development of the archegonium in Selaginella spinulosa. Fig. 138. II, p. 184.
Scheme of development of the archegonium in Leptosporangiate Filicineae. Fig. 138. II, p. 184.
Schemes illustrating the orientation of the organs in the embryo of Homosporous Leptosporangiate
Filicineae, Botrychium virginianum, Lycopodium clavatum, Selaginella. Fig. 175. II, p. 245.
Scheme of young lateral root of a monocotylous plant in longitudinal section. Fig. 185. II, p. 274.
Scheme of embryo of Carex in germination. Fig. 275. II, p. 412.
Scheme of vegetative point of Mammillaria with forked mammillae. Fig. 294. II, p. 436.
Scheme of sporocarp of Marsilia in transverse section. Fig. 328. II, p. 491.
Scheme of sorus of Polypodium obliquatum in longitudinal section. Fig. 334. II, p. 497.
Scheme of staminal arrangement in Rosaceae. Fig. 354. II, p. 530.
Scheme of staminal arrangement in Rubus Idaeus, Fig. 354. II, p. 530.
Scheme of staminal arrangement in species of Potentilla. Fig. 354. II, p. 530.
Scheme of staminal arrangement in Potentilla fruticosa. Fig. 354. II, p. 530.
Scheme of change in configuration in a sympetalous corolla of Angiospermae in consequence of
different distribution of growth. Fig. 362. I, p. 553.
Scheme of the development of the ovary in many Angiospermae with formation of the sole.
Fig. 364. II, p. 557.
Scheme of cell- -layers i in young anther of Hyoscyamus albus. Fig. 393. II, p. 599.
Scheme of the transformation of a sporangium, say of Lycopodium, into a sporophyll like that of
Helminthostachys. Fig. 396. II, p. 606.
Scheme ea of the microspore in Cycadaceae, Abietineae, Angiospermae. Fig. 399.
II, p. 612
Schistostega osmundacea. Bilateral construction. Fig. 25. I, p. 67.
5) 3 Leaf-position. Fig. 26. I, p. 67.
23 33 Plants cultivated in feeble light. Fig.116. I, p. 235.
5 Ae Protonema. Fig. 101. II, p. 121.
: x, Social growth from protonema. Fig. 108, II, p. 129.
Schizaea rupestris. Sporophyll. Fig. 314. II, p. 477.
» Apex of sporophyll. Fig. 315. II, p. 477.
Scirpodendron costatum. Construction of spikelet. Fig. 21. I, p. 51.
Scirpus lacustris. Embryo and seedling in longitudinal section. Fig. 277. II, p. 414.
Scirpus submersus. Axis of long shoot in transverse section. Fig. 301. II, p. 447.
Scolopendrium officinale. Primary leaves. Fig.g2. I, p. 151.
Sechium edule. Androecium. Fig. 358. II, p. 539.
Securidaca Sellowiana. Shoot with tendrillous lateral twigs. Fig. 303. II, p. 455.
Selaginella. Germ-plant. Fig. 166. II, p. 229.
5 Scheme of orientation of organs in embryo. Fig. 175. II, p. 245.
Selaginella chrysocaulos. Sporiferous spikes and sporophyll. Fig. 339. II, p. 507.
F 5S Hinge of sporangial wall. Fig. 376. TI, p. 581.
Selaginella cuspidata. Spermatozoids. Fig. 136. II, p. 181.
. 5 Transformation of rhizophore into leafy shoot. Fig. 167. II, p. 230.
Selaginella denticulata. Mature plant and germ-plant. Fig. 174. II, p. 244.
Selaginella erythropus. Dehiscence of megasporanginm and microsporangium. Fig. 374.
II, p. 580.
39 ¥ Wall of sporangium with hinge. Fig. 375. I, p. 581.
39 5 Empty sporangia illustrating dehiscence. Fig. 377. II, p. 582.
pe » Megasporangium in longitudinal section. Fig. 395. II, p. 603.
Selaginella haematodes. Dorsiventral anisophyllous shoot. Fig. 60. I, p. 106.
» + Dorsiventral shoot-bud in transverse section. Fig. 61. I, p. 107.
Selaginella Martensii. Shoot with rhizophores. Fig. 165. II, p. 229.
» 35 Germinated megaspore, prothallus and embryos in longitudinal section.
Fig. 176. II, p. 247.
Selaginella Preissiana. Lower portion of sporiferous spike. Fig. 338. II, p. 505.
Selaginella sanguinolenta. Isophyllous shoot-apex. Fig. 58. I, p. 106.
» a Dorsiventral anisophyllous shoot. Fig. 59. I, p. 106.
Selaginella spinulosa. Scheme of development of archegonium. Fig. 138. II, p. 184.
5: 3 Young sporophyll with primordia of sporangia in longitudinal section.
Fig. 312. II, p. 473.
3 + Young and old sporangia in longitudinal section. Fig. 394. II, p. 601.
Selaginella stolonifera. Stages in germination of microspore. Fig. 136. II, p. 181.
Selaginella suberosa. Sporiferous spike in transverse section near apex. Fig. 340. II, p. 508.
Sequoia sempervirens, Cone-scale and ovule in longitudinal section. Fig. 348. I, p. 519.
Sicydium gracile. Androecium. Fig. 358. II, p. 539.
Smilax Sarsaparilla. End of shoot with tendrils. Fig. 162. II, p. 223.
Solidago canadensis. Axillary bud and axillant leaf in transverse section. Fig. 39. I, p. 82.
LIST OF THE ILLUSTRATIONS 653
Spathiphyllum platyspatha. Inflorescence concrescent with spathe. Fig. 23. I, p. 54.
ss 4 Development of inflorescence. Fig. 24. I, p. 55.
Sphaerocarpus terrestris. Development of antheridium. Fig. 5. I, p. 13.
5 3 Female plant with many perichaetia. Fig. 72. I, p. 83.
” re Spore-tetrads and spores. Half-developed sporogonium in longitudinal
section. Fig. 84. II, p. 98.
Sphagnum acutifolium. Protonema. Fig. 102. II, p. 122.
op F Sporogonium and spermatozoid. Fig. 121. I, p. 156.
Sphagnum cuspidatum. Protonema. Fig. 102. II, p. 122.
Sphagnum squarrosum. Sporogonium with pseudopodium. Fig. 121. II, p. 156.
Splachnum luteum. Capsule and apophysis. Mechanism of opening. Fig.125. UL, p. 159.
Sporangium. Scheme of transformation of sporangium into sporophyll. Fig. 396. HU, p. 606.
Stangeria paradoxa. Nucellus in longitudinal section. Fig. 404. HU, p. 627.
Stephaniella paraphyllina. Shoot with hypogeous rhizoid-clad rhizome. Fig.64. Ul, p. 7o.
Sterculia sp. Portion of cotyledon and endosperm in section. Fig. 267. II, p. 403.
Symphyogyna Brogniartii (Amphibiophytum dioicum). Plant with lateral segmentation of
thallus. Fig. 32. I, p. 36.
Symphyogyna sinuata. Sympodial growth of thallus. Fig. 16. II, p. 23.
Symphyogyna sp. Habit. Fig.17. II, p. 24.
oe rs Archegonial group in vertical section. Fig. 71. HU, p. 82.
Symphytum officinale. Portion of anther with microsporangium in transverse section. Fig. 391.
II, p. 596.
Syrrhopodon revolutus. Leaf-structure. Fig. 115. UH, p. 146.
Talisia princeps. End of shoot with pinnate foliage-leaves and pinnate kataphylls. Fig. 257. U,
p- 385.
Taxus baccata. Twigs with female flowers. Fig. 350. II, p. 521.
Thalictrum aquilegiaefolium. Portion of leaf showing stipels. Fig. 254. Il, p. 380.
» ”» Young leaf in transverse section. Fig. 255. I, p. 380.
Thladiantha dubia. Androecium. Fig. 358. II, p. 539.
Thuidium abietinum. Shoot in transverse section. Fig. 113. I, p. 232.
” 3 Shoot-apex in bud in transverse section. Fig. 109. HU, p. 131.
Thuidium tamarascinum. Paraphyllium. Fig.117. II, p. 147.
Thuya occidentalis. Scheme of branching. Fig. 42. I, p. 87.
Tilia. Scheme of position of lateral buds. Fig. 49. I, p. 93.
Tilia parvifolia. Bud of shoot-axis in transverse section. Fig. 30. I, p. 70; Fig. 52. I, p. 96.
a5 or Embryo with lobed cotyledons dissected out. Fig. 270. II, p. 407.
Tmesipteris truncata. Sterile leaf and sporophyll. Fig. 336. I, p. 504.
Todea barbara. Cells of annulus in surface-view. Fig. 386. II, p. 592.
Tozzia alpina. Storage-kataphyll. Fig. 263. I, p. 400.
of = Storage-kataphyll in transverse section. Fig. 264. Il, p. 400.
” ” Upper part of storage-kataphyll in transverse section showing water-glands.
Fig. 265. II, p. gor.
Tradescantia virginica. Seedling plant in three stages. Fig. 273. II, p. 410.
Treubia insignis. Young plant. Fig. 35. II, p. 30.
af 5 Plant with sporogonium. Fig. 36. II, p. 40.
Trichocolea pluma. Fertile shoot in longitudinal section, showing sunk embryo. Fig. 77. UU,
8
p- 89.
Trichomanes. Formation of prothallus. Fig. 154. II, p. 209.
Trichomanes diffusum. Young filamentous prothallus. Fig. 154. II, p. 209.
Trichomanes Goebelianum. Rootless plant. Fig. 183. II, p. 264.
Trichomanes rigidum. Portion of filamentous prothallus with archegoniophores. Fig. 154. U,
Pp. 209.
ee * Gemma on prothallus. Fig. 157. II, p. 214.
Trichomanes sinuosum. Prothalli with archegoniophores. Fig. 154. I, p. 209.
Trichomanes tenerum. Sorus. Fig. 383. II, p. 580.
- - Sporangia attached to placenta. Fig. 384. Il, p. 589.
Trichomanes venosum. Gemma of prothallus. Fig. 157. WU, p. 214.
Triticum. Base of grain in median longitudinal section. Fig. 278. II, p. 415.
Trollius europaeus. Transition from hypsophyll to flower-envelope. Fig. 360. II, p. 55°.
Typha Shuttleworthii. Cell-division in pollen-tetrads. Fig. 403. II, p. 626.
Ulothrix zonata. Anchoring-organ. Fig. 7. I, p. 32.
Ulva lactuca. Germ-plant with anchoring-organ. Fig. 8. I, p. 32.
Umbilicus pendulinus. Foliage-leaves and hypsophylls. Fig. 216. LI, p. 336.
Utricularia affinis. Stolon-formation from leaf. Fig. 171. II, p. 230.
Utricularia coerulea. Flowering-plant with leafy stolon and leaf-roots. Fig. 171. LI, p. 239.
654. LIST (OF THE SLEUSTRATIONS
Utricularia Hookeri. Flowering-plant with hypogeous parts spread out. Fig. 170. II, p. 238.
Utricularia inflata. Ovule in longitudinal section. Chalazal and funicular nutritive tissue.
Fig. 414. II, p. 641.
Utricularia stellaris. Ovule in longitudinal section. Chalazal and funicular nutritive tissue.
Fign4ry. WL) p. 640:
Vaccinium Myrtiilus. Bud in transverse section. Fig. 50. I, p. 94; Fig. 51. I, p. 95.
Valeriana Phu. Development of inferior ovary. Fig. 372. II, p. 570.
Vallisneria (Lagarosiphon) alternifolia. Apex of. young inflorescence in longitudinal section.
Fig. 18. I, p. 41.
Veronica lycopodioides. Shoot with tevecsiontlentes. Fig. 106,: I, p.' 173.
Viburnum Opulus. Base of a leaf-pair showing stipules and petiolar glands. Fig. 238. II, p. 363.
Vicia Cracca. Shoot-bud in transverse section. Fig. 78. I, p. 126; Fig. 83. I, p. 135.
ss 36 Shoot with axillary bud in transverse section. Fig. 79. I, p. 126.
Vicia Faba. Primary leaves, stages of transformation. Fig. 94. I, p. 156.
Victoria regia. Seedling plant. Fig. 100. I, p. 165.
Vitis cinerea. Development of tendrils. Fig. 293. II, p. 435.
Vitis vulpina. Development of tendrils. Fig. 293. Il, p. 435.
Vittaria. Prothallus. Fig. 152. II, p. 206.
Volvox aureus. Coenobium. Fig. 4. I, p. 28.
Voyria azurea. Development of ovule. Fig. 401. II, p. 619.
Weddelina squamulosa. Root, adventitious shoot, haptera. Fig. 161. II, 223.
Welwitschia mirabilis. Male flower from which flower-envelope has been removed. Fig. 353.
Il, p.526.
Wheat. Base of grain in median longitudinal section. Fig. 278. II, p. 415.
Xanthochymus pictorius. Embryo and seedling. Fig. 179. II, p. 258.
Xanthosoma belophyllum. Venation. Secondary growth in leaf-stalk. Fig. 221. II, p. 341.
Xerotes longifolia. Leaf in transverse section. Fig. 196. II, p. 300.
Zanonia macrocarpa. Axillary tendrils. Fig.291. II, p. 427.
Zea Mais. Seedling plant. Fig. 279. II, p. 410.
Behe Seedling plant in transverse section. Fig. 280. II, p. 416.
Zizania aquatica. Embryo from outside and in section. Fig. 281. II, p. 417.
Zoopsis argentea. Portions of a young and older plant. Fig. 97. II, p. 114.
Zostera marina. Construction ofembryo. Fig. 182. II, p. 261.
INDEX
(i and ii respectively refer to Parts I and II.)
A.
Abies, anisophylly, lateral i 108;
archegonium ii 629; arrest of
organs and light i 232; leaf-
insertion i 94; pollen-sac,
lateral 11 516, opening ii 610;
shoot, correlation and direction
i 214, substitution of lateral for
lost terminal i 50.
A. canadensis, anisophylly and
light i 255. |
A. pectinata, anisophylly and
light i 250; flower, female,
development ii 522; leaf-apex,
precedence in growth ii 309 ;
leaf, insertion i 94; pollina-
tion ii 522; shoot, dorsi-
ventral lateral i 94.
Abietineae, anamorphose and
flower ii 524; bract-scale ii
521; flower, female ii 521,
morphology ii 524 ; megaspo-
rocyte ii 628; ovule, anatro-
pous ii 524, integumentary
wing ii 628, unitegminous ii
617 ; pollen-grain, germination
ii 612; pollen-sacii 515; seed,
protection of ripening li 523;
seminiferous scale ii 518, 521.
Abnormality, meaning i 177.
See also Malformation.
Abortion, meaning i 56. See
also Arrest.
Absorption of water, by leaf
of Pinguicula ii 349; by leaf
and leaflet of Pteridophyta ii
347, 349; by Musci ii 142.
Absorptive organs of Stepha-
niella ii 70.
Acacia, alternation of phyllo-
dium and foliage-leaf ii 357 ;
development, heteroblastic i
144 ; juvenile form i 166, 167;
phyllodium ii 355, independent
of environment ii 357, profile- |
position ii 293; reversion-
shoot i 172 ; xerophilous adap-
tation i 165.
A. alata, calamifolia, floribunda,
juncifolia, Juniperina, scirpi- |
folia, teretifolia, uncinata ii
35
A. heterophylla 1tO7, ashy.
A. lacerans, velutina, shoot-
tendril ii 456.
A. lophantha, reduction of pin-
nule i 155, ii 381.
A, melanoxylon ii 356, 357.
A. verticillata, leaf, division of
labour ii 357; phyllodium ii |
356, apparently whorledii 372 ;
reversion to juvenile form i172.
Acanthaceae, anisophylly, ha- |
bitual i 112.
Acanthorhiza aculeata, root, |
transformation i 12; thorn-root
li 288.
Accessory, axillary bud ii 434 ;
cotyledonary bud of /ug/ans |
regia ii 4343 shoot ii 433.
Acer, flower-leaf, terminal ii 541;
ovary, syncarpous ii 562 ; pla-
centation, septal ii 563.
A. campestre, anisophylly, lateral
i 108.
A. obtusatum, anisophylly and |
light i 255. |
A. platanotdes, anisophylly and |
light i 254, laterali 108; leaf,
branching ii 330, development
ii 305, transformation i 6,
venation ii 342.
A. Pseudoplatanus, anisophylly,
lateral i 108; flower-bud ii
541; kataphyll ii 386.
A. striatum, inheritance
variegation i 184.
Achimenes, leaf, asymmetry i
120; leaf-cutting, age-varia- |
tion i 47.
A. grandiflora, peloria i 189.
A. Haageana, leaf, asymmetry |
i 120.
Achnanthes, fixed colony i 29.
Aconitum, carpel, number ii 538;
ovule, bitegminous ii 617.
A. Anthora, cotyledon, assimi- |
lating ii 402. |
A. Napellus, embryo-sac ii 636. . |
of |
| Acorus, dorsiventrality i go.
A. Calamus, bilateral leaf, profile
position ii 294.
Acotylous embryo ii 280.
Acrandrous Musci, primitive |
character ii 149.
Acrasieae,
25. |
Acrobolbus, related to Alicularta
ii go.
Acrocarpous Musci,
character ii 149.
Acrogamous, entrance’ of |
pollen-tube into ovule ii 615;
pollen-tube ii 613.
Acrogamy in Cynomorium ii
615. |
Acrogenous branching ii 432.
Acrogynous Hepaticae, ani-|
sophylly i ror; leaf ii 40;}
primitive |
| Adaptation,
spore-formation i |
sexual organs, protection ii
88 ; shoot ii 40.
Acropetal leaf-branching of
Dicotyledones ii 330.
Acrosticheae, leaf-structure and
environment li 347; leaf, ad-
pressed ii 335; sporangium,
protection ii 496.
Acrostichum Bliumeanum, sporo-
phyll and external factors ii
498.
A. peltatum,
trasporangial iil 202;
phyll ii 486.
A. scandens, stem, flattening i 92.
Active cells of sporangial wall
ii 577, 600, 610, 611.
anisophylly
character of i 99.
Adenostyles albifrons, auricle ii
361.
germination in-
sporo-
a
| Adhesion of bract and shoot ii
438.
Adhesive disk, and contact in
Plocamium i 40, 269; on
tendril i 268, ii 224.
Adiantum, leaf-form, biological
significance ii 346.
| A. Edgeworth, flagellum ii 241 ;
leaf, branching ii 316 ; leaf-
borne shoot ii 241 ; transfor-
mation of leaf into shoot ii
241.
| 4. reniforme, \eaf-form,
logical significance ii 346.
bio-
| A. trapesiforme, leaf, develop-
ment ii 317.
Adlumia cirrhosa, tendril ii
422; transition from leaf to
tendril i 161.
| Adnate stipule ii 359.
Adonis aestivalis, cotyledon,
persistent ji 403.
Adoxa, chorisis of stamen ii
535.
A. Moschatellina, habit ii 68;
light and leaf-formation i 256.
Adpressed leaf ii 335.
Adult, features i 174;
arrested i 167.
Adventitious, definition i 42;
embryo ii 624, from nucellar
tissue 1i 637 ; leaf, non-existent
ii 305; pinnule in Hemitelta
capensis ii 347}; root ii 264,
274; shoot i 17 7 42, A, a
932; 276, of ‘prothallus ii
213, phyllotaxy i 83.
Accidium elatinum and witches’
broom i 192.
leaf,
656
Aegiceras, viviparous embryo ii
256.
Aeration-stria3 on
Orchideae ii 285.
Aerides pusillum, protocorm ii
232.
Aeriopsis javanica, nest-root ii
283.
ren shoot ii 463.
Aeschynomene indica, stipular
appendage ii 366.
Aesculus, anisophylly, lateral i
108; flower, oblique symmetry
1-128:
A. Hippocastanum, anisophylly
determined in bud i 251;
archesporium, pluricellular ii
633; kataphyll ii 388; leaf,
digitate and pinnate ii 332;
leaflet, asymmetry i 122, un-
equally-sized i 128 ; root, cap-
less ii 267.
Agaricus campestris, growth in
darkness i 257.
root of
Agave, cotyledon, epigeous ii
409. :
A. americana, root, shortening
ii 270.
Aggregate species, Marsilia
polycarpa ii 479.
Agrimonia, calycine hook ii
542; flower, arrangement of
parts il 529; stipule, asym-
metry i125.
A. Eufpatoria, flower, arrange-
ment of parts ii 530.
Ailanthus, adventitious shoot
ii 277; carpel and ovule,
development ii 561.
A. glandulosa, \eaf-apex, prece-
dence in growth li 310.
Air-cavities in Hepaticae ii 71.
Air-layer of dead leaves in
Bryum argenteum ii 75.
Air-moisture, influence upon
organs i 260.
Air-root, function ii 280; geo-
tropic ii 283; and light ii
285; of Podostemaceae i 246;
velamen ii 283.
Ajuga reptans, plagiotropous
shoot ii 457, 460.
Alchemilia, basigamy ii 615;
ovule, development ii 633;
parthenogenesis ii 624 ; pollen-
tube, none ii 624.
A. alpina, pubescens,
development ii 632.
A, arvensis, aporogamy ii 615;
pollen-tube formed in par-
thenogenesis ii 624.
A. galiotdes, \eaf-whorl, con-
struction ii 371; stipule, con-
crescent ii 371.
A. nivalis, leaf, branching ii
333-
Aldrovanda, rootless ii 265.
Algae, development, hetero-
ovule,
-
INDEX
blastic i144; germ-plant and
light i 238; malformation,
experimental 1 188; pro-em-
bryo i 148, independent pro-
pagationi 149 ; polar differen-
tiation i 229; shoot and light
i 256; thallus and gravity i
224.
Alicularza, germ-plant and light
i 240; related to Acrobolbus
ii 90; spore, germination ii
IIo.
Alisma Plantago, dédoublement
il 533-
Alismaceae, cotyledon, differen-
tiation ii 408; juvenile form
i 164.
Alliaria officinalis, phyllody of
flower i 181.
Allium, bulbil ii 469 ; cotyledon,
epigeous ii 409; leaf, radial ii
328.
A. Cepa, root-hair, suppressed
in water ii 269.
ursinum, leaf, inversion ii
296 ; root, shortening ii 270.
Alloparasitism ii 639.
Allosorus, sporangium, develop-
ment and displacement ii 495.
A. crispus, \eaf, branching ii
316; sporophyll ii 486.
Alnus, kataphyll, stipular ii
385; ovule, formed through
stimulus of pollen-tube i 269.
A. viridis, shoot, dorsiventral
lateral i 96 ; phyllotaxy, varia-
tion i 96.
Aloe, phyllotaxy ii 442.
Alopecurus pratensis, ligule ii
377:
Alpinia nutans, cotyledon, two-
lobed ii 411 ; ligule ii 377.
Alsophila australis, prothallus,
Teversion li 202.
A. Leichardtiana, sporangium,
annulus and opening ii 590.
Alstroemeria, \eaf, inversion ii
296.
A. psittacina, leaf-stalk ii 300.
Alternation of gametophyte
and sporophyte ii 171.
Althaea, pollen-sac, reduction
of number ii 554.
Amaryllideae, ovule, ategminy
ii 618, bitegminy ii 618 ; root,
shortening li 270.
Amaryllis Belladonna,
unitegminy ii 618.
Ameristic, male prothallus, of
Pteridophyta ii 220; pro-
thallus of Lguzsetum ii 197.
Ametabolous Equiseta ii 502.
Amicitia Zygomeris, hypsophyll,
stipular ii 394; stipule, pro-
tective ii 363.
Amorpha, branching, axillary ii
433: :
Ampelideae, shoot-tendril ii
A.
ovule,
435; and contact-stimulus i
268.
Ampelopsis, cotyledon i 145;
disk, adhesive, on tendril i
268, ii 224.
A. hederacea, guinguefolia, Veit-
chit i. 268.
Amphibiophytum diotcum, thal-
lus li 36.
sae se plants, organs i
260.
Amphigastrium, of Alasia ii
29; of Jungermannia bicuspi-
data ii 41; origin i Iot.
Amphithecium,of moss-capsule
11155; peristome derived from
ii 162.
Amplexicaul state, origin ii
306.
Amygdaleae, transition from
foliage-shoot to thorn ii 452.
Anabaena, in leaf of Azolla ii
348 ; inroot of Cycadaceae ii
282.
Anacrogynous foliose Hepa-
ticae, leafii 38 ; shoot ii 38.
Anadendrum marginatum, mon-
tanum, juvenile form absent
1159.
A. medium, adult form of Pothos
Jlexuosus 1 158 ; perforated leaf
ii 325.
Analogous organsalike in adap-
tation i 19.
Analogy and homology i 5.
Anamorphose in flower
Abietineae ii 524.
Anatomie, construction of leaf
ii 292, 486; method in
flower-morphology ii 545;
structure, and water in Hepa-
ticae ii 71; of homologous
organs differs i 14.
Anatropous ovule ii 631; in-
teguments, development ii 617;
significance in Coniferae ii
524. 5
Anchoring-disk, i 40,
268, li 45, 224.
Anchoring-organ, and contact
stimuli i 269; of Axeura ii
26; of Podostemaceae ii 222,
265, 281; of Utricularia neot-
tioides ii 239.
Anchoring-root ii 286; and
nourishing-root, transition ii
288 ; unbranched ii 274.
Andreaea, archesporium ii 156;
leaf, apical segmentation ii
132; pro-embryo ii 122;
pseudopodium ii 161 ; sporo-
gonium, opening ii 160.
A. petrophila, capsule, dehiscence
ii 160.
A. rupestris, leaf ii 131.
Androcryphia, \eaf ii 38; muci-
lage-papilla ii 38.
Androecium, of Angiospermae
of
150,
ii 535, 539, 5533 of Cucurbi-
i ii 539 ; origin in Salvia
i 60.
Androgynous cone of Pinus
li 524.
Androsace sarmentosa, shoot,
plagiotropous ii 458; storage-
leaf ii 398.
A. villosa, placentation ii 567.
Aneimia, antheridium, develop-
ment ii 179, opening of free ii
177; sporangium, annulus ii
591, position ii 494; sporo-
phyll ii 486, and wind-distri-
bution of spores, ii 474, de-
velopment ii 478.
A. fraxinifolium, sporangium ii
88.
A psdeeclifetdi transformation
of leaf into shoot ii 241.
A. tomentosa, sporophyll and
sporangium ii 592.
Anemone, embryo, acotylous
retarded ii 250; germination
ii 253 ; involucreii 550; ovule,
position in ovary ii 560.
A. Hepatica ii 250, 550; flower,
malformed i 177.
A. nemorosa ii 250, 550.
A. Pulsatil/a, staminal nectary
li 550.
A. ranunculoides, trifolia ii
250.
Anemoneaze, flower-envelope,
evolution ii549; ovule, arrest
i 59.
Moneta piations: flower of Mo-
nocotyledones ii 547 ; plants,
dorsiventral inflorescence i
134.
Aneura, anchoring-organ ii 26;
apical cell ii 21; branching
ii 21, 26; embryo, nutrition
ii 105; gemma-cell ii 49;
mucilage-papilla ii 28 ; spore,
ejection ii 101, germination ii
108 ; sporogonium, develop-
ment ii 103, with elatero-
phore ii 101; sexual organs,
disposition and protection ii
81; stolon ii 25; thallus,
development ii 314, winged ii
20.
A. bogotensis, thallus ii 25.
A. endiviaefolia, adventitious
shoot ii 56; retention of
water ii 33, 53.
A, (Pseudaneura) eriocaulis, an-
theridial shoot ii 8; division
of labour in ii 26.
A. fucotdes, shoot ii 26; an-
choring-organ ii 27.
A. fuegiensis, lamella ii 54,| Angraecum fasciola,
57-
A. hymenophylloides, chief axis
INDEX
A. palmata, capsule, sterilization
ii 103.
A. pinguis, capsule ii Io.
Angelica sylvestris, bract, sup-
pression i 59; gynaeceum, in-
ferior ii 569.
Angiopteris, leaf, development ii
315; leaf-stalk ii 314; spo-
rangium ii 585; sorus ii 586.
A, evecta, sorus and sporangium
ii 587.
Angiospermae, androecium ii
553; antipodal cells ii 636;
aporogamy ii 615; archespo-
rium ii 599, 601, pluricellular
ii 633, unicellular ii 632; basi-
gamy ii 614; carpel ii 527,
sole ii 557; chalazogamy ii
615; corolla, development of
sympetalous ii 553; dislocator-
cell suppressed ii 614; egg,
development of fertilized ii
642; egg-apparatus ii 636;
embryo-sac, intrasporangial
germination ii 623, segmenta-
tion of nucleus ii 635, signifi-
cance of contents ii 636; en-
dosperm, significance ii 636;
endothecium ii 611; flag-
apparatus ii 528; fertilization,
double ii 624; flower ii 527,
and vegetative shoot, differ-
ence ii 528, arrangement of
parts ii 528, dorsiventrality ii
542, double ii 536, envelopes
ii 548, relative size of parts
ii 529; gynaeceum ii 555,
reduction ii 622, suppres-
sion in construction ii 557;
hyponasty i 85 ; leaf, auricle
ii 361 ; microsporophyll, uni-
formity ii 553; ovule ii
527, 614, 631, development
after pollination ii 623, hau-
storium ii 638, reduction ii
622; parthenogenesis ii 624;
placentation, ii 562; pollen-
grain ii 527, 611, germination
ii 612 ; pollen-sac ii 553, 610,
archesporium and tapetum ii
599, arrest and reduction ii
554; pollen-tube, basigamous
ii 614, function ii 614 ; poro-
gamy ii 615; pro-embryo ii
642; prothallus, female ii 636;
sporangium, active cells in
wall ii 577, 610, 611 ; sporo-
phyll ii 527; stamen ii 527,
filament ii 529, transformation
ii 555; stigmaiis527; suspensor
and its function ii 642; syner-
gidae ii 637.
air-root,
dorsiventral i 246; root, as-
similating ii 286.
and lateral axes ii 26; reten-| Animal, lodgers in Hepaticae
tion of water ii 54; shoot ii
55:
GOEBEL II
ii 64; spore-distribution in
Splachnaceaze ii 164.
Uu
657
Anisophylly, adaptative char-
acter in plagiotropous shoot
199; cause i 113; determined
in bud i 251; and extemal
factors i 106, 255; of flower
of Selaginelleae ii 506; and
gravity i 226; habitual i 107—
13; Herbert Spencer on i 99;
history i 99; and internal sym-
metry i 254; inversion, arti-
ficial i 255; of Hepaticae i
101; of Muscii 100; of Pteri-
dophyta i 102, ii 506; of
Spermophyta i 107; lateral i
108; and light i 250, 252;
meaning of i gg; retardation,
i 107; Wiesner on i roo.
Annual plant, early flowering
of well-nourished i 212; in
Pteridophyta rare ii 441; in
Spermophyta, shoot ii 440.
Annulus, function in Musci ii
160; lie in Filicineae ii 594;
of Zguzsetum ii 500; of Fili-
cineae il 587 ; rudimentary ii
595-
Anogramme, prothallus ii 205.
A. chaerophylia, leptophylla, an-
nualii 441; annual sporophyte
ii 217; archegoniophore ii
216; prothallus, tubers ii 217,
water - relationships ii
water-storing tuber ii 216.
A. leptophylia, sporophyll, time
of appearance ii 498.
Anomaly, Moquin-Tandon’s de-
finition i 178.
Anomociada, branch in relation
to leaf ii 44.
A. mucosa, mucilage-organ ii
28.
Anonaceae, flower, arrangement
of parts ii 531 ; dédoublement,
ii 533:
Antagonism, of reproductive
organs and vegetative growth
i 142, 212, ii 212, 605; of
sexual and vegetative propaga-
tion i 45, 213, li 51, 215,
469.
Antennaria alpina, partheno-
genesis ii 624.
Anther ii 553.
Antheridial groups of Musci
ii 151.
Antheridiophore of Hepaticae
ii 84.
Antheridium, of Angiospermae
ii 614; of Cycadaceae 1i 612;
development in Hepaticaeiir2,
in Musci ii 13, in Pteridophyta
ii 177; embedded ii 174; free
ii 84, 177; homology i 17;
opening in Hepaticae li 10, in
Musci ii 11, in Pteridophyta
li 174; origin varied in Musci
i 18; position in Hepaticae ii
So, in Musci ii 149; structure
215,
658
and position in Bryophyta ii 9,
in Pteridophyta ii 172.
Anthoceros, antheridium i 17, ii |
186, chromoplasts ii 10;
apical angle ii 21; arche-
gonium ii 186; archesporium
ii 606; elater ii 95; germ-
plant and light i
kinship with Pteridophyta ii
186; leaf ii 355; spore, ger-
mination ii 107 ; sporogonium,
chlorophyllous ii 105, develop-
ment ii 104, pit around, ii go,
sterilization ii 105, structure ii
94; symbiosis with MVostoc ii
78; water-retention ii 56;
water-storage ii 76.
A. arachnoideus, water-retention
by ridges ii 56.
A. argentinus, dichotomus, tuber
ii 69.
A. jfimbriatus, \eaf-like appen-
dages ii 35; thallus li 22;
water-retention by fringe ii 56.
A. giganteus multifidus, denti-
culatus, Vincenttanus, elater
spirally thickened 11 95.
A. glandulosus, gemma ii 50;
mucilage-pit ii 76.
A. laevis, germ-tube suppressed
ii 112; sporogonium 1i 94.
A. punctatus, sporogonium ii 94;
water-pit ii 56.
A. tuberosus, tuber ii 66.
Anthoceroteae, antheridium,
development ii 13; arche-
gonium ii 14, development
ii 16 ; oil-bodies, absent ii 79;
old group ii 96; mucilage-slit
ii 27; water-retention ii 56.
Anthriscus sylvestris, leaf-apex,
precedence in growth ii 310.
Anthurium digitatum, digitate
leaf by branching ii 325.
A. Hugeliz, nest-root ii 283.
A. longifolium, transformation
of root into shoot ii 227.
Anthyllis tetraphylla, growth,
plagiotropous ii 459; leaf, uni-
laterally pinnate i 121, ii
480 ; leaflet, asymmetry i 121.
Antipodal cells ii 636 ; fertiliza-
tion-effect ii 637.
Antirrhinum magus, colour of
flower in light ii 551.
Antithamnion cruciatum, di-
rective influence of light on
branching i 237.
A. Plumuta, branching of shoot,
i 89, 237.
Antitropic leaves of Rochea fal-
cata i 116.
Antrophyum cayennense, felt of |
root-hairs ii 283.
Apandrous prothallus ii 220.
Apex of root ii 266.
Aphis causes phyllody in Avadzs
i 194.
240 5 |
INDEX
Aphlebia of Gleicheniaceae ii
318.
Apical cell, of Hepaticae ii 21;
of Musci ii 131, 138.
Apical closure of bud ii 309.
Apical growth, of cotyledonary
lobes of Myristica fragrans
ii 407; of Hepaticae ii 20;
of leaf, of Gymnospermae ii
322; of leaf of Filices ii 317,
periodic ii 318, with circinate
ptyxis ii 320; of leaf of
Filicineae ii 310, 313; of leaf
of Lygodieae, prolonged 1i 319;
of leaf of Spermophyta ii 310.
Afpiocytis, colony i 29.
Apocarpous gynaeceum ii 558.
Apocynaceae, searcher-shoot
il 454-
Apodial flower of Lycopodineae
ii 510.
Apogamy, with apospory ii 609;
of Pteridophyta ii 187, 220;
shoot formed in, and light i
229.
Apophysis of Musci ii 158.
Aporogamy ii 615.
A poseris foetida, development of
leaf-stalk and light ii 30r.
Aposporous fern budding i 46:
Apospory ii 607; with apo-
gamy ii 609.
Apotropous ovule ii 631.
Aquatic, Bryophyta, sporogo-
nium ii 575; leaf of Salvinza
ii 348 ; plants, heterophylly ii
357,juvenile formi 164, organs
i 260, riband-form of monoco-
tylous leaf ii 357; prothallus
ii 217.
Aquilegia vulgaris, phyllody of
flower i 181.
Arabis, phyllody produced by
aphis i 194.
Arachniopsis, anisophylly i 101 ;
leaf ii 41; rudimentary forms
i DEE.
Araliaceae, shoot, direction i
160.
Arawcaria correlation and di-
rection of shoot i 214.
A. brasiliensis, endogenetic shoot
with protective cap ii 266.
Araucarieae, flower, female ii
521; pollen-sac, position ii
BIS.
Arceuthobiaceae, stamen with-
out vascular bundle ii 292.
Archangelica, \eaf-base, function
li 299.
A, officinalis, leaf-apex, prece-
dence in growth ii 310.
Archangiopteris, sporangium
ii 585.
Archegonial, group of Musci ii
152; venter of Musci ii 153.
Archegoniatae defined ii I.
Archegoniophore of Hepaticae
ii S45 of Pteridophyta ii 207,
216.
Archegonium, abnormal of
Pteridophyta ii 188 ; develop-
ment, in Hepaticae ii 15, in
Musci ii 17, in Pteridophyta
ii 184; of Gymnospermae ii
629; of Pteridophyta ii 183 ;
opening, in Bryophyta ii 15, in
Pteridophyta ii 183 ; position,
in Hepaticae ii 88; relation of
number to fertilization in Pteri-
dophyta ii 547; structure and
position in Bryophyta ii 14;
of unpollinated ovule of Cycas
ii623 ; venter in Musci ii 153;
virescence ii 187.
Archesporium ii 597; of An-
giospermae ii 601 ; of Antho-
ceros ii 606; of Gymnospermae
ii 601; of Musci ii 155, 601 ;
of ovule of Cuphea Zimpant
ii 601; of pollen-sac of Angio-
spermae ii 599; of Pterido-
phyta ii 601 ; of Sphagnum ii
606.
Archidium, archegonial venter
ii 153; capsule, development
ii 155.
Archontophoenitx, \eaf-form, de- .
velopment ii 327.
Areca Catechu, cotyledon, lobed
ii 411; endosperm, ruminate
Pe ts
Areschoug, aerophilous shoot
of ii 463; false short twig of
pig oe)
Aristolochia Clematitis,accessory
axillary bud ii 434; adven-
titious shoot, position ii 277.
A. elegans, prophyll and function
li 383.
A. Sipho, accessory axillary bud
ii 434; leaf-base, protective
function ii 291.
A. tomentosa, laminar growth,
pleuroplastic ii 312.
Aristolochiaceae, dorsiventral
flower i 133.
Arnica montana, phyllotaxy ii
443-
Aroideae, concrescence ofspadix
and spathei55 ; displacement,
in members of spadix i 80,
through diminution in size of
organ i 81; growth of juvenile
form, direction i 143; hypso-
phyll a leaf-sheath ii 342;
juvenile form i 157, mistaken
for Marcgravia i 159; leaf,
perforated ii 325, sagittate ii
324, split ii 325; leaf-forms,
development i 158; leaf-stalk
ji 299; nest-root ii 283;
plug-tip ii 309; Pothos-form
i 159; Rhaphidophora-form,
i 159; transition from anchor-
ing-root to nourishing-root ii
288 ; velamen ii 283; venation
ii 342, reticulate ii 338.
Arrest, of bract,i57,59, ii 397,
433; of branching of root ii
274; of bud ii 439; of latent
buds in deciduous trees i 58 ;
of corolla i 59; in cotyledon
ii 400, 403 ; of development i
6; of flower i 52, 57, ii 546;
in flower and function ii 547;
of gametophyte in apospory ii
607 ; of gynaeceum ii 557,621 ;
in juvenile form i 145, 152,
ii 400; of leaf, adult i 167,
on assimilating shoot-axes ii
446; of ovule i158, 59, ii 560;
of pinnule ii 511; of pollen-sac
of Angiospermae ii 554; of
prothallus by embryo-forma-
tion ii 199 ; of shoot, lateral at
apex of stem ii 431,apexin trees
i 209; inspikelet i 56; of spor-
angium ii 510, 554; of stipule
ii 364; of torus-elongation ii
540; rarer in Thallophyta than
in higher plants i 56; through
correlation i58, through loss of
function i 58, through feeble
illumination i 232, through
want of nutrition i 60.
Arrested, formations in /alo-
pleris filicina i 37; organs,
morphological importance i6o.
Artanthe jamaicensts, arrest in
flower 157.
Artocarpeae, anchoring-root ii
288.
Artocarpus, stipule, axillary ii
372-
A. integrifolia, stipule, concre-
scence ii 372.
Arum, depth in soil of tuber
ii 460.
A. maculatum, root, branching
suppressed ii 274; pull-root,
shortening ii 270.
wale Mea Japonica, ligule ii
379.
Asarum, antipodal cells, per-
sistent ii 636; flower, dorsi-
ventral i 133.
A. europacum, venation ii 343.
Asclepiadease, anchoring-root ii
288; laminar growth, basi-
plastic ii 312; pollen-sac, ar-
rest ii 554, suppressed ii
554- Pees a
Ascobolus, directive influence of
light i 258.
Ascomycetes, growth in dark-
ness i 257.
Ascophyllum nodosum, light and
spore-germination i 230.
Asexual propagation, of Fungi
i 49; of Hepaticae ii 47; of
Musci ii 139; of Pteridophyta
ii 213, 467; of Spermophyta
ii 469; antagonistic to seed-
INDEX
formation i 45, 213, ii 51, 469;
from old prothalli of Osmunda
i 49.
Asparagineae,
structure ii 545.
Asparagus, phylloclade i 15, 20,
ii 450.
A. comorensis, climbing-hook ii
419; kataphyll, peltate ii 334,
500.
A. (Myrsiphyllum) medeoloides,
phylloclade ii 426, 450.
A. officinalis, phylloclade ii 450;
root, shortening ii 270.
A. Sprengert, phylloclade ii 450.
Asperula, stipule ii 371.
A. scutellaris, stipule ii 371.
Aspidium aristatum, gall, by
Taphrina cornu cervi ii 526.
A, falcatum, archegonium, ab-
normal ii 188.
A. Filix-mas, sporophyll and
foliage-leaf alike ii 474.
Asplenium, transformation of
leaf into shoot ii 241.
A. bulbiferum, \eaf-borne bud
i 42.
A. dimorphum, sporophyll, form
ii 486, as new formation ii
478.
A. Nidus, prothallus, develop-
ment ii 204.
A. obtusatum aquaticum, pro-
thallus ii 210,
A. obtusifolium, leaf, water-ab-
sorbing ii 347.
A. Ruta-muraria, juvenile form
1151.
A. septentrionale, abnormal or-
gans ii 187.
A. viride, leaf, branching ii 316.
Assimilation-axis, a _ trans-
formed inflorescence-axis in
Monocotyledones ii 447.
Assimilation-cotyledon ii 402.
Assimilation-root ii 280, 284.
Assimilation-shoot, the typical
shoot li 4403 of Codiuwm and
light i 249.
Assimilation-shoot-axisii 445;
arrest of leaf ii 446; with in-
creased surface ii 448.
Assimilation-sporogonium ii
105, 158.
Assimilation-stipule ii 363.
Astragalus, carpel, longitudinal
septum ii 559; cotyledon,
asymmetry i 115; host of
Pilostyles ii 225 ; leaf, change
of function ig; thorn ii 428 ;
thorn-leaf i 9.
A, adscendens, stipule, concres-
cent ii 369.
A. horridus, Tragacantha, thorn
il 429.
Astrantia, flower-envelope, de-
rived from hypsophyll
55°.
phylloclade,
UU 2
ii |
659
A. major, hypsophyll, reduced
foliage-leaf ii 395.
Asymmetry, of cotyledon i115,
ii 406, cause ii 407; of flower
i 129; of leaf i 106, 115, 116;
of leaflet i 121-4, and gravity i
123; of sporangium ii 575 ; of
stipule i 121, 125.
Ategminy of ovule ii 618, and
autotrophism and _heterotro-
phism ii 619.
Athyrium Filix-foemina claris-
Stma, apospory ii 608.
Atragene alpina, staminal flag-
apparatus li 550-
Atrichum, rhizoid-strand ii 120.
Atriplex rosea, halophyte i
266.
Atropa, adhesion of bract and
shoot ii 438; inflorescence ii
438.
A. Belladonna, anisophylly, habi-
tual i 113.
Atropous ovule ii 631.
Aulacomnium androgynum,
gemma ii 140.
A. palustre, gemma-leaf ii 139;
gemma, protonemoid ii 4o.
Aurantieae, thorn-leaf ii 430.
Auricle of Angiospermae ii 361;
of Hepaticae ii 29, 58.
Autoparasitism ii 639.
Autotrophism and ategminy of
ovule ii 619.
Avicennia, germination ii 256 ;
pneumatophore ii 278.
Awn of Gramineae ii 377.
Axial placenta ii 556.
Axillary, branching ii 431, in
flower-region ii 433, and phyl-
lotaxy i 81, time-relationship
li 432; ovule ii 561; shoot
and axillant leaf, concrescence
ili 436, development ii 432,
displacement ii 434; stipule
ii 315, 359, 372.
Axis, nodes i 35; share in
gynaeceum ii 556, 557, 562,
566, 568.
Azo/lla, foliage-leaf, segmentation
ii 488 ; glochidia ii 212, 218 ;
involution, dorsiventral i 86;
juvenile form i 164; leaf ii
348; leaf-float ii 349; mas-
sulae ii 218; megasorus ii 488;
megasporangium, analogy
with ovule ii 616; megaspore,
germination ii 212; mega-
sporophyll ii 488 ; microsorus
ii 488; microspore, germina-
tion ii 218; microsporophyll
ii 488 ; mucilage in leaf ii 348 ;
prothallus, female ii 212, rhi-
zoids absent ii 189; root-apex
ii 267; root-hairs on water-
root ii 269; symbiosis with
Nostocaceae ii 348; water-
absorption by leaf ii 349.
660
A. filiculoides, growth of aquatic
root in soil ii 267; habit il
438; megasorus ii 488; sporo-
phyll ii 489.
B.
Balanophora, embryo formed
from endosperm ii 637; flower,
reduction ii 557, 621; par-
thenogenesis ii 624; pollen-
tube not formed ii 624.
B. elongata,embryo-sac, develop-
ment ii 621.
Balanophoreae, carpel with-
out vascular bundle ii 292;
embryo, reduced ii 254; em-
bryo-sac, development ii 621 ;
flower, reduction ii 621 ; hau-
storium ii 224; organ-forma-
tion in absence of light i 257;
ovule, ategminous reduced
ii 621.
Balantium antarcticum, pro-
thallus ii 200; sporangium,
position ii 491.
Bambusa, hinge-cell ii 324.
B. verticillata, hinge-cell ii 323.
Bambuseae, kataphyll ii 389.
Banana, correlation of growth
in fruit i 212.
Banisteria aurea,
shoot ii 454.
Barbuila, hair-point ii 149 ; leaf,
lamella ii 144, papilla ii 143 ;
peristome ii 163; spore, shed-
ding ii 163.
B. aloides, ambigua, membranae-
Solia ii 144.
B. subulata, dorsiventral sporo-
gonium and light i 236.
Barringtonia Vrieset,
cotylar storage ii 259.
Bartramia ityphylia, \eaf-sur-
face, mammilla ii 143.
Basal cell of archegonium of
Pteridophyta ii 184.
Basal, and terminal growth i
41; growth of leaf ii 306;
laminar growth of Aroideae
li 324.
Bastdiobolus, malformation, arti-
ficially produced i 188.
B. ranarum, gonidia-formation
in light and darkness i 257.
Basidiomycetes, growth
darkness i 257.
Basigamous pollen-tube ii 614.
Basigamy ii 615.
Basipetal, development of pel-
tate leaf ii 336, of pinnule of
Cycadaceae ii 322, of spo-
rangia ii 496; leaf-branching
of Dicotyledones ii 330; suc-
cession in flower ii 542.
‘Basiplastie type of laminar
growth ii 312.
Batrachospermum, Chantransia
searcher-
hypo-
in
INDEX
its pro-embryo i 149, and
light i 238; juvenile form i
148.
Battarea, elater i 19.
Battersia mirabilis, anchoring
disk as vegetative body i 150.
Bauhinia, leaflet, asymmetry
i 1233 stipule and function ii
366; watch-spring-climber ii
450.
Bazzania filum,
adaptation ii 65.
Beaumontia grandiflora, search-
er-shoot ii 454.
Begonia, adventitious shoot,
origin i 17; leaf, asymmetry i
118; lieaf-borne bud i 42;
leaf-cutting i 45, varies with
age i 46; leaf, form and
branching i 11g, and gravity
i 2109.
B. fagifolia,
climber i 120.
B. hydrocotylifolia, tncarnata,
maculata, manicata, Rex,
scandens, leaf,asymmetryit19.
B. prolifera, stnuata, inflore-
scence, epiphyllous ii 437.
B. Rex, rhizome, thick i 120.
B. xanthina, flower, develop-
ment ii 543.
Begoniaceae, seed with small
embryo and endosperm ii 631.
Benincasa cerifera, forerunner-
tip 11 308; leaf-primordium,
division in formation of hypso-
phyll ii 393 ; tendril, develop-
ment ii 423 ; transition between
leaf-forms i 10.
Berberis, branching ii 433 ; cor-
relation in arrest of shoot i
209; leaf-thorn ii 429 ; pollen-
sac, partial suppression of
active opening cells ii 611;
short shoot precedes long in
unfolding ii 445.
B. vulgaris, axis, radial with
plagiotropy i 85.
Berchtoldia bromoides, embryo ii
417.
Berlinia paniculata,
Pilostyles ii 225.
Bertholletia excelsa, hypocotylar
storage li 260.
Betonica officinalis, corolla, con-
fluence of parts ii 538.
Betula, pollen-sacs, reduction of
number ii 554; phyllotaxy,
spirali 96; shoot, dorsiventral
lateral i 96; witches’ broom i
192. i
B. lenta, nigra, shoot, dorsi-
ventral lateral i 96; phyllo-
taxy, variation i 96.
Beyerinck on gall-formation i
202.
Biciliate | spermatozoid
Pteridophyta ii 172.
xerophilous
scandens, root-
host of
of
Bidens Beckti, divided sub-
merged leaf ii 358.
Bifacial leaf ii 293.
ignonia, transformation of leaf
into tendril ii 422.
B. albo-lutea, claw-hook ii 420;
tendril ii 42T.
BL. capreolata, littoralis, adhesive
disk of tendril i 268.
B. unguis, claw-hook ii 420.
Bignoniaceae, adhesive disk
of tendril i 268; anchoring-
root ii 288 ; claw-hook ii 420.
Bijugate system of phyllotaxy
of Bravais i 80.
Bilateral, leaf ii 293, 328, pro-
file-position ii 293 ; organ, de-
finition i 66; shoot, of Musci
i 66, ii 137; shoot with dis-
tichous phyllotaxy in Monstera
deliciosa 1 90; sporangium ii
574, 581.
Billbergia, transition from fo-
liage-leaf to bract i Io.
Bilocular ovary ii 562.
Biota orientalis, root, hairless ii
269.
Bipartite leaf of Hepaticae ii
41.
eat organ, definition
i 66.
Bitegminy of ovule ii 617,
628.
Bladder of Utricularia Hookeri
il 237%
Biasia, amphigastrium ii 299;
apical angle ii 21; gemma,
dimorphous ii 49 ; leaf ii 37;
leaf-auricle ii 29 ; mucilage-
hair ii 29; symbiosis, with
LNostoc ii 78.
B. pusilla, germ-plant i 240;
thallus, segmentation ii 37 ;
vegetative point ii 28,
Blind flower, result of high
temperature i 213.
Blitum polymorphum, halophyte
i 266.
Blyttia, apical cell ii 21 ; branch-
ing ii 22; leaf ii 37; light and
growth ii 77; mucilage-papil-
la ii 28; perichaetium ii 82;
thizome, sympodial ii 25;
sclerenchyma-fibres ii 76;
shoot, etiolated i 249; sub-
archegonial _ tissue-develop-
ment after fertilization ii 106;
thallus, hymenophylloid ii 25,
winged ii 20.
B. decipiens, apical cell ii 21;
chromosomes ii 8 ; habit ii 24.
B. longispina, \eaf ii 37.
B. Lyelizi,antheridium, develop-
ment ii 133; apical cell ii
at.
Bocconia, flower, arrangement of
parts ii 532.
Boragineae, branching ii 435;
flower, suppression of upper i
58; inflorescence, compensa-
tion of growth 1 208, dorsi-
ventral circinate i 1365 ovary
and placentation ii 563.
Soronia, stamen, transformation
Il 555- ;
Boschia, ait-cavities ii 75.
Bossiaea, cladode ii 451 ; tran-
sition-forms of shoot i 168.
B. heterophylla, microphylla i
168.
B. rufa, arrest of adult leaf i
168 ; juvenile form i 168.
Bostrychia callipteris, long shoot
and short shoot i 39. —
B. Moritziana, long shoot and
short shoot i 38.
Botrychium, antheridium, open-
ing il 177; embryo, differen-
tiation ii 244, position of
organs in ii 247; leaf, develop-
ment ii 313, prothallus, dor-
siventrality ii 199, hypogeous
ii 199, symbiotic ii 199, 219;
ptyxis, not circinate ii 321;
sporangium ii 606, dehiscence
ii 585, free ii 574, 584, posi-
tion li 494; spore, nutrition ii
628 ; sporophyll ii 482.
i. Lunaria, prothallus ii 198;
relationship of sporophyll and
foliage-leaf ii 476; sporan-
gium ii 584.
B. simplex, sporangial spike ii
606.
B. virginianum, orientation of
organs of embryo ii 245; pro-
thallus, tuberous ii 198.
Botrydium granulatum, resting
state i 261.
Bower, on grouping of distribu-
tion of sporangia ii 496; on
leaf-development ii 304.
Bowitea volubilis, cladode ii 449.
Brachypodium pinnatum, involu-
tion of leaf ii 298.
Bract, adhesion to shoot ii 438 ;
arrest ii 397; of Daucus
Carota 1 59; as_ protective
organ ii 391, 397; without
vascular bundle ii 292.
Bract-leaf, transition from foli-
age-leaf i 10, ii 391, 551.
Bract-scale of Abietineae i 521.
Branch-system of Cupressineae
and light i 230.
Branch-thorn, correlation and
formation i 215; and medium
i 263.
Branching, absent in lVe/wit-
schia mirabilis ii 431; acrogen-
ous ii 432; of Algae and light
i237; axillary ii 431; capacity,
latent ii 431; of carpel ii 537;
of inflorescence, of Boragineae
ii 537, of Hyoscyamus ii 435 ;
of leaf of Dicotyledones ii 329,
INDEX
forming apparent leaf-whorl ii
333, of leaf of Filicineae ii 316,
of leaf of Ophioglossaceae, in
one plane ii 482 ; of upper-leaf
ii 3.22 ; of petaline primordia ii
530; and phyllotaxy i 82; of
protonema and light i 234; of
root, suppressed ii 274; of sta-
men ii533; of staminal primor-
dium ii 536; of shooti 88, ii 21,
132, 431, and leafof Hepaticae
ii 44, non-axillary of Musci ii
131; of thallus of Algae i 34,
of Aneura ii 26; variation in
place of in Pteridophyta ii 431;
and vegetative point 132; with-
out axillant leaf ii 433.
Brand-fungus modifying flower
i 193.
Brassica, flower-buds do not un-
fold in darkness i 243.
B. oleracea var. botrytis, axillary
branching ii 433.
Brathys prolifica, androecium ii
535-
Bravais, bijugate and trijugate
phyllotaxy i 80.
Breathing outgrowth on root ii
278.
Breathing-pore of Hepaticae ii
4
Breathing-root ii 278 ; in rela-
tion to dry soil i 260; in moist
soil ii 278.
Bristle of Compositae ii 398 ; of
inflorescence in Gramineae i 20.
Bromeliaceae, root, anchoring
ii 286, intracortical ii 268;
transition from foliage-leaf to
bract i To, ii 551.
Bromus, awn ii 377.
Brood-bud. See Gemma.
Brood-gemma, See Gemma.
Brownea erecta, protection of
bud i 7.
Bruguiera, embryo, viviparous
ii 255; root, breathing out-
growth ii 270.
Bryaceae,archegonium,develop-
ment ii 16; spore, shedding ti
165.
Bryonia, laminar growth, basi-
plastic ii 312; leaf-lamina,
branching ii 312; tendril ii
425.
B. dioica, androecium ii 539.
Bryophylium, leaf ii 337
B. calycinum, leaf-borne bud i
42, li 436.
B. crenaium, leaf, indented ii 337.
Bryophyta, comparison of sex-
ual organs with those in Pteri-
dophyta ii 185 ; development,
heteroblastic i 144; directive
influence of light i 234; extent
of ii 7; involution, dorsiventral
186; juvenile formi 151; mois-
ture and organsi 261; phyletic
661
relationship with Pteridophyta
ii 187; protonema and light i
239 ; reversion to juvenile form
i 171; sporogonium, radial
ii 574; sterilization ii 605.
Lryopsts, light and vegetative
organs i 256; reaction of shoot
to external stimulii 217; thal-
lus, bilateral i 66.
Lryopteris, long shoot and short
shoot ii 43; reaction of shoot
to external stimuli i 217.
B. filicina, flagellum ii 44.
Bryum argenteum, air-layer of
dead leaves ii 75 ; dorsiventral
sporogonium and light i 236;
propagative shootii 139; silver-
glance ii 148 ; silver-sheen and
medium i 261.
B. giganteum, shoot ii 132.
B. pseudo-triguetrum, asexual
propagation ii 125 ; protonema-
cushion ii 148; separation-cell
of protonema ii 125.
Bud ii 431; apical closure ii 309;
arises direct in Hepaticae i 48 ;
arrested li 439; convolute lami-
na of in Monocotyledones ii
309; leaf-borne i 42, ii 241,
431, 436, 441, 595; resting i
174, 218, ii 44, 398; root-
borne i 42, 46, ii 228, 276,
280, 431.
Budding of aposporous Filices
i 46.
Bud-protection. See Protec-
tive organ.
Bud-scales, correlation i 216.
Buetineria pilosa, searcher-shoot
i 454-
Bulbil, i 45, ii 469.
Bunium petraeum, cotyledon,
assimilating ii 402.
Butomeae, cotyledon, differen-
tiation ii 408.
Butomus, ovule on under-surface
of carpel ii 558.
umbellatus, creeping shoot
with distichous phyllotaxy i
90; dorsiventrality i go ; hair-
less root ii 269.
Buxbaumia, antheridium, de-
velopment ii 14; haustorium
of embryo ii 157; simplest
moss-plant ii 127, 208 ; proto-
nema ii 127, threads, concre-
scence ii 121; male and female
plants ii 151.
B.aphylla,spore,shedding ii 164.
Be: Pe NS peristome ii 164;
protonema ii 126 ; spore, shed-
ding ii 164.
Buxbaumiaceae, dorsiventral
sporogonium and light i 236;
origin of peristome ii 164.
Byblis gigantea, ovular hausto-
rium li 639 ; intercalary growth
ii 311.
B.
662
Cc
abomba, divided submerged leaf
ii 358; ovule on upper surface
of carpel ii 558.
Cactaceae, arrest of leaf on
assimilating shoot-axis ii 446 ;
Cereus-form i 169; concre-
scence of axillary shoot and
axillant leaf ii 436; leaf-thorn
i 168, 264, ii 429; leaf trans-
formed into nettary li 430;
hypocotylar water-storage ii
260; juvenile form i 166, 168;
ovary, inferior ii 429 ; phyletic-
ally recent i170; phyllotaxy
i 78; reversion-shoot i 173;
shoot as water-reservoir il 452;
long shoot and short shoot i
353 increase of shoot-surface
and light i 247; succulent
form i 19.
Cactus-form of shoot ii 452.
Caducous stipule ii 363.
Caesalpineae, branching of leaf
ii 330.
Caesalpinia Sappan,
asymmetry i 122.
Caladium, foliage-leaf, peltate ii
leaflet,
335-
Calamostachys Casheana, mega-
sporangium ii 602; micro-
sporangium ii 602.
Calamus, climbing-hook ii 421.
Calathea, flower, asymmetry i
129; inflorescence, dorsiventral
i 129.
Calcarate flower i 131.
Callista delicatula, leaf, asym-
metry i 117.
Callithammion, vegetative organs
and light i 256.
C. corymbosum, branching and
light i 237.
Callitriche, flower-leaf, terminal
il 541; phyllotaxy ii 442.
C. verna, leaf-rosette il 442.
Calhtris, juvenile form i 154;
reversion-shoot i 1733 sporo-
genous cell-massin ovuleii 628.
Callus-formation, on root-tip i
43; and gravity i 222.
Callus-root in seedling i 44.
Callus-shoot i 44.
Calobryaceae, growth, ortho-
tropous 1118; mucilage-papilla
ii 40; rhizoid, absent ii 45;
shoot ii 40, orthotropous ii 39.
Calobryum, anisophylly, occa-
sional 1 102; growth, ortho-
tropous i 102, ii 18; isophylly
i 102; sexual organs, protec-
pon ii 84, terminal groups of ii
oO.
C. Blumez, female plant ii 40.
Caltha palustris, ptyxis and
space-relationship ii 311; hyp-
sophyll of whole leaf-primor-
INDEX
dium ii 392; stipule, axillary
li 373, 418; venation ii 343.
Calycanthemy through Phyto-
plus i 195.
Calymperes, perforated water-
cell ii 145.
Calypogeta, endogenetic shoot ii
45; fluid around young sporo-
gonium ii 90; foot of embryo
ii 105; hypogeous fruit-branch
ii 90; orthotropous sexual
shoot ii 41; related to Southbya
ii 90; spore, germination ii I Io.
C. ertcetorum, fertile sac enclos-
ing embryo li gI ; sporogonium
ii go.
C. Trichomanes, anisophylly and
dorsiventral shoot i 102; fertile
sac leafy ii 91; gemma ii 51 ;
spore, germination ii 110.
Calyptra of Musci ii 152; of
Trichocolea ii 89.
Calycine hook of Agrimonia
li 542.
Calyx, development in Sym-
Pphoricarpus ii 543.
Campanula, evolution of radial
corolla ii 553.
C. latifolia, heterophylly absent
li 351; stalked leaf ii 301.
C. rotundifolia, heterophylly ii
351 ; reversion to juvenile form
and light i 242; stalked leaf ii
or.
C. Trachelium,
absent ii 351.
Campanulaceae, heterophylly,
explanation ii 351.
Campylopus, archegonial groups
in head ii I50.
C. flexuosus, propagative shoot
ii 139.
C. polytrichoides, lamella on
under-side of leaf ii 144.
C. Schimper, propagative shoot
li 139.
Cannabineae, aporogamyii615.
Cannaceae, venation in relation
to whole leaf-growth ii 342.
Canna indica, root, shortening
ii 270; venation ii 342.
Capillarity between rhizoids of
Hepaticae ii 32.
Capillary,water-chamberformed
by leaf of Hepaticae ii 58;
water-reservoir of /rullania
dilatata i 261.
Capitulum of Compositae, reci-
procal pressure changing form
177
Capless root ii 230, 267.
Caprifoliaceae, double leafi Igo.
Capsella Bursa-pastoris, \eaf-
form in dwarfing conditions i
heterophylly
259.
Capsule of Musci, development
ii 155; of Sphagnum, explo-
sive li 162.
Caragana, change of function in
leaf i g; thorn-leaf i 9, ii
429.
Carapa moluccensis, breathing
outgrowth on root ii 278.
Cardamine pratensis, double
flower i 213; exogenetic root
ii 273; vegetative develop-
ment and suppression of repro-
ductive organs i 213.
Carduus, bristle ii 398; de-
current leaf-base ii 448.
Carex, embryo ii 411 ; seed, ger-
mination ii 412.
C. Grayana, embryo ii 411.
Carludovica plicata, hypsophyll
ii 396.
Carmichaelia, cladode ii 451.
C. crassicaulis, shoot as water-
reservoir li 452.
C. Engsiz, juvenile form i 168;
transition from heteroblastic
to homoblastic germination i
168.
C. Exsul, flagelliformis ii 451.
C. stricta, arrest of adult leaf i
167 ; juvenile form i 167.
Carpel, of Angiospermae ii 527,
"555; branching ii 537; of
Cycadaceaeii511; of Coniferae
ii 518; of Ginkgoaceae ii 518;
of Gymnospermae ii 511; in
inferior ovary ii 567 ; number
in Aconitum ii 538; ovule on
uncer side ii 558; septation
ii 559; sole ii 557; in syn-
carpous gynaeceum ii 562;
terminal ii 541 ; without vas-
cular bundle ii 292.
Carpellary, ovule ii 560; pla-
centa ii 556.
Carpinus, juvenile form, direc-
tion of growth i 143; leaf-
position i 96; shoot, abortion
of apex of annual i 209;
shoot, dorsiventral lateral i 96.
Carun Bulbocastanum, cotyle-
don, assimilating ii 402.
Caryophylleae, embryo, lie in
seed, Lubbock’s statement ii
406 ; gynaeceum, superior syn-
carpous ii 563 ; hexamery and
pentamery in same plant ii
538; placenta, free central ii
564; staminal primordium,
branching ii 536.
Cassia, transformation of stamen
il 555:
C. Fistula, carpel, transverse
septum ii 559.
Castanea vesca, phyllotaxy,
variation i 96; shoot, dorsi-
ventral lateral i 96; stipule,
protective function ii 363.
Caster of peristome of Musci ii
164.
Casuarina, basigamy ii 615 ;
development homoblastic i
ity
an
143; embryo, adventitious ii
624; flower-leaf, terminal ii
541; juvenile form i 166;
ovule, development ii 633,
haustorium ii 633; partheno-
genesis ii 633; pollen-sac,
active opening cells ii 611;
phyletic position ii 633, 635.
Casuarina glauca, ovular hau-
storium ii 634.
C. Rumphii, ovule ii 634.
C. stricta, embryo-sac ii 633.
C. torulosa, seedling - plant i
144.
C. tuberosa, nucellus ii 634.
Casuarineae, arrest of leaf on
assimilating shoot-axis ii 446.
Catalfa syringaefolia, aniso-
phylly, lateral i 108.
Catharinea, antheridium, open
ing ii II.
C. undulata, leaf, lamella ii 144;
sporogonium, dorsiventral and
light i 236.
Caulerpa, \eaf-like organs and
light i 249 ; light andregenera-
tion i 237.
C. prolifera, position of organs i
0.
elcudineds, correlation of
growth in flag-apparatus i 211.
Caulome, definition i 16.
Cavicularia, gemma ii 49; leaf
1G 3 7
Cecidomyia Poae, gall i 200.
Cecidotes Eremita, gall i 199.
Cedrela amara, leaflet, asym-
metry i 122.
Cedrus, juvenile form i 154.
Cell, use of term i 22.
Cell-colony of Thallophyta i
22.
Cell-dominion, of Thallophyta
i 22; with vegetative point i 33.
Cell-mass, sporogenous ii 596.
Cellular structure of land-plants
i 24.
Cellulose in sporangial wall of
Lycopodium ii 578.
Celosta cristata, correlation of
growthin flag-apparatus i 211;
inherited fasciation i 184.
Celtis, laminar growth, basi-
plastic ii 312; leaf-lamina,
branching ii 312.
Cenchrus, inflorescence, bristle i
20.
Centaurea, bristle ii 398.
Centradenia, anisophylly, ha-
bitual i 111; leaf, asymmetry
1116.
C. floribunda, anisophylly, arti-
ficial inversion i 255, habitual
i11t.
C. inaequilateralis, anisophylly,
habitual i 111.
Central cell of archegonium of
Pteridophyta ii 184.
INDEX
Centranthus Calcitrapa, enation
i 195.
Cephalaria leucantha, \aminar
growth, basiplastic ii 312; leaf-
lamina, branching ii 312.
Cephalotaxus, flower, female ii
519; ovule ii 519.
C. Fortunet, archegonium ii 629 ;
endogenetic vegetative point
of shoot ii 266.
Cephalotus follicularis, \eaf,
tubular ii 337, development ii
339+
Cephalozia, spore, germination ii
Iol.
C. (Protocephalozia) epheme-
vowdes, pro-embryo persistent ii
110, 113; rhizoid as in Musci
ii 116; rudimentary formii 114.
C. (Pteropsiella) frondiformis,
reversion of leaf to thallus-
form ii 42.
Ceratodon purpureus,
shedding ii 163.
Ceratophyllum, rootless ii 234,
265; vascular bundle ii 293.
C. demersum, \eaf, dichotomy ii
spore,
329.
Ceratopteris, leaf-borne bud ii
431, 441, 595; placenta,
absent ii 472; prothallus and
gravity i 221 ; shoot, suppres-
sion of lateral ii 431 ; sporan-
gium ii 588, 595.
C. thalictroides, juvenile form i
152; propagation by leaf-
borne shoot ii 441; stipular
scale ii 315.
Ceratozamia, flower ii 512,
spike as protection to ii 512;
pollination ii 513 ; sporophyll,
development ii 513, transition
from sterile to fertile ii 511;
stamen il 514.
C. longifolia, ovule, develop-
ment ii 627, sterilization ii 627.
C. robusta, air-root ii 282;
carpel ii 513 ; ovule ii 616, in-
tegument ii 616.
Cereus-form in Cactaceae i169.
Ceriops, viviparous embryo ii
255-
Ceropegia, concrescence in corolla
1 53+
Cetraria tslandica, symmetry
and direction i 72.
Chaetophora, chief axis and
lateral axes i 34.
Chailletia, epiphyllous inflore-
scence ii 437.
Chalazal nutritive tissue ii 640.
Chalazogamy ii 615.
Chamaecyparis, juvenile form i
154.
Chamaedorea desmioncoides,
climbing-hook ii 421.
Chamaerops, leaf, development
ii 327; ligule ii 378.
663
Chamaerops ( Trachycarpus) ex-
celsa, primary leaf ii 327.
C. humilis, leaf, development
1 379.
Change of function, in leaf ig,
ii 398; in organsi 8; in root
i 12; through light i 255.
Chantransia a pro-embryo il49.
Chara, \eaf i 153 node and in-
ternode i 35; pro-embryo i
150; rhizoid ii 117; rhizoid-
formation and light i 231.
C. fragilis, habit i 35.
Chasmogamy and light i 245.
Cheiranthus, flower, develop-
ment il 543.
Chelidonium, leaf, branching ii
331; leaflet, asymmetry i 122.
C. majus, \eaflet, asymmetry i
124.
Chenopodiaceae, cotyledon ii
406.
Chief axis and lateral shoot i
34-
Chiloscyphus, elater ii 99; leaf,
concrescence ii 42 ; spore, ger-
mination ii 110 ; sporogonium
without elaterophore ii gg.
C.cymbaliferus, decipiens, water-
sac ii 60.
Chlamydomonas, monergic form
277.
C. Browniz, monergic organiza-
tion i 27.
Chlorenchyma of leaf ii 293.
Chloris, dorsiventral inflore-
scence i 134.
Chlorophyceae, anchoring-or-
gan developed through con-
tact-stimulus i 269.
Chlorophyllous, embryo of
Hepaticae ii 105 ; foliage-leaf
the primitive leaf-form ii 291 ;
prothallus of Filicineae ii 199,
of Lycopodium ii 192, of Sal-
winia ii 211; root of Podo-
stemaceaeii 280 ; sporogonium
li 105, 158.
Chondrioderma difforme, plas-
modium i 25.
Choripetalae, ovule, biteg-
minous ii 617, epithelium ii
638.
Chorisis ii 532; negative 533,
ii 540; of stamen ii 535.
Chromosome - reduction, in
formation of megaspore ii 625;
in gametophyte of Alyttia ii 8;
in pollen-sac ii 598; in spore-
development ii 596.
Cicer, cotyledon, asymmetry i
115.
C. subaphyllum,
420.
Cinchona, stipule, concrescent ii
368, protective function ii 363.
C. succtruéra, stipule, concrescent
ii 370.
leaf-thorm ii
664.
Cinclidium, spore, shedding ii
164.
Circaea, light and leaf-formation
i 256.
C. alpina, lutetiana, stolon, de-
velopment ii 440.
C. intermedia, hypsophyll ii
393; shoot, persistent geo-
philous ii 463, transformation
ii 464.
Circinate, dorsiventral inflore-
scence in Boragineae i 136;
leaf-apex in Cycas Thouarsit
ii 322; ptyxis, absent in some
Pteridophyta ii 321, in leaf
with apical growth ii 310. See
also Involution.
Cirsiunt, bristle 11 398.
Cistineae, stamen,
succession ii 542.
Cistus populifolius, gynaeceum
ii 565; style, formation ii 565.
Citrus, adventitious embryo ii
624; leaf-thorn ii 430; poly-
embryony ii 637.
Cladode. See Phylloclade.
Cladonia,symmetry and direction
2s
G3 cocnifona, thallus and podetium
172s
basipetal
GS ensieclicia symmetry and
direction i 73.
Cladophora, filament, branched
i 33; rhizoid, development
i 269.
C. fracta, vegetative point i 33.
C. glomerata, prolifera, branch-
ing i 34.
Cladosporium, spore, limited
growth through starvation i
142.
Cladostephus verticillatus, long
shoot and short shoot i 37.
Clarkia, pollen-sac, sterilization
Il §55-
C. pulchella, cotyledon, inter-
calary growth ii 404; petaline
primordium, branching ii 536.
Claw-hook ii 420.
Claytonia perfoliata, cotyledon,
assimilating ii 402.
Cleistocarpous Musci ii 160.
Cleistogamy, arrest of corolla
through loss of function i 59;
and external factors i 245; and
light 1 245.
Clematideae, staminal flag-
apparatus ii 550; ovule, arrest
i 59.
(Gj ae flower, arrangement of
parts ii 531; leaf-spindle-
climber ii 421.
C. afoliata, arrest of adult leaf
i 167, of leaf of assimilating
shoot-axis ii 446; juvenile
form i 167.
C. calycina, ovary, pluriovular
ii 560.
INDEX
Clematis Vitalba, liane-growth
ii 453.
Cliftonaea pectinata, dorsiventral
involutioni86; dorsiventrality,
significance of i 87; shoot, di-
vision of labour i 40.
Climacium dendroides, branch-
ing ii 132. 7
Climbing, Aroideaei 157 ; Cac-
taceae, reversible dorsiventral-
ity ini 231; Filices ii 346, 593;
figs i 159; hook i 9, ii 334,
346,419, stipularii371; Marc-
gvavia i159; organ, leaf as ii
419, peltate kataphyll as ii334,
shoot as ii 455,stipule asii 371,
tentacle as ii 419; plants i157,
with anchoring-root ii 286;
shoot, symmetry i 90, flattening
of i 92; by tendril i 161.
Clusia alba, polyembryony ii
Clusiaceae, anchoring-root ii
288.
Coéaea, tendril i 161.
C. scandens, auricle, ii 360; leaf-
form i 10; stipule ii 360;
transformation of leaf into
tendril ii 422.
Coccinza, tendril, nature ii 425.
C. indica, tendril, development
ii 423.
Cochlearia, flower, succession of
development ii 543.
Cocos, leaf-form, development ii
3247.
Codium, assimilation-shoot and
light i 249.
Coenobium, definition i 21, 24,
25.
C ehanen autumnale, branching
of root suppressed ii 274.
Coleochaete, sporangium i 19.
Coleoptile of Gramineae ii 415.
Coleorrhiza of Gramineae ii
415.
Colletza, cladode ii 451 ; juvenile
form i 168; reversion to ju-
venile state ii 451.
C. cructata, cladode ii 451 ; ju-
venile form i 168 ; reversion-
shoot i173; shoot-thorn i 168,
ii 452.
C. spinosa, cladode ii 451.
Colocasza, water-slit at leaf-apex
ii 309.
Colony i 25.
Colour, of flower ii 522, 551,
and light ii 551; of Hepaticae
and heat ii 78, and light ii 77,
and transpiration ii 78; and
sexual organ ii 10; and trans-
piration of fruit ii 571.
Columella, of Anthoceroteae ii
94; of Musci ii 156; function
ii 157.
Columnea, anisophylly, habitual |"
rip tp
Columnea Kalbreyeri, Schiede-
ana, leaf, asymmetry i 116;
anisophylly, habitual i 113.
Colura, elater ii 100; gemma ii
51 5; sporogonium without ela-
terophore ii 100; water-sac
ii 61.
C. Karsteni, water-sac ii 62.
C. ornata, germination ii 61.
a amphigastrium ii
Ee
Combretum, searcher -shoot ii
4.
Commelina, flower,
trality i 131.
C. coelestis, flower, oblique dor-
siventral i 128.
Commelinaceae, flower, oblique
symmetry i 128; leaf, asym-
metry i Ir.
Compass-plant, profile position
il 294.
Compensation of growthi 207,
208,
Competition between vegetative
points i 42.
Compositae, bract, arrested ii
397, suppression i 59; bristle-
scale, relationship to hypso-
phyll ii 398; capitulum, rela-
tionship ofsizef partsii 529,re-
ciprocal pressureini77; corolla
ii 553, unilaterally split ii 553;
flag-apparatus, correlation of
growth i 211; flag-flower ii
574; flower, arrangement of
parts ii 531, concrescence in ii
546, evolution of tubular ii
553, retardation i 57, unessen-
tial zygomorphy i130; hypso-
phyllii 393, 397; leaf, inversion
by torsion ii 296; shoot as
water-reservoir ii 452.
Compound leaf, correlation of
growth i IIo.
Conchophylium tmbricatum,tran-
sition to tubular leaf ii 338.
Concrescence, actual ii 546; of
axillary shoot and axillant
leaf ii 436; congenital i 53,
in flower ii 546; in corolla of
Gamopetalae i 52; in false
septum of fruit of Cruciferae
i53; in flower of Sc¢vpodendron
costatum: i 51; in gynaeceum
ii 557; of hair-root of Flori-
deae i 54; of leaves of Hepa-
ticae ii 42; of nucellus and
integuments ii 618; of organs
i 51; of ovule and ovary ii
620; of prophylls of Mono-
cotyledones ii 382; of pro-
tonema-threads ii 121; of
spadix and spathe of Aroideae
i 55; in staminal tube of
Lobelia i 53; of stipules of
adjacent leaves ii 368; of
stipules of one leaf ii 367.
dorsiven-
ew
Conducting-bundle, function ii
Conduction of water in Mar-
chantia ii 34.
Cone, reciprocal pressure in,
changing form of organsi 77.
Configuration, influence of ex-
ternal stimuli upon i 217; of
flower and distribution of
growth ii 552; of halophytes
and environment i 265; of leaf
and relationships of life ii 345 ;
of organs and mechanical
stimuli i 268; of sporophylls,
cause ii 473.
Confluence, of flower parts ii
538; of pollen-sacs ii 554.
Conformity in development of
antheridia and archegonia in
Pteridophyta ii 185.
Congenital, concrescence i 53 ;
concrescence of flower ii 546.
Coniferae, anther, crista ii 516,
shield ii 516; archegonium
ii 629; basiplastic laminar
growth ii 312; branching and
phyllotaxy i 82; carpelii 518;
cone, reciprocal pressure i 77;
cuttings root feebly i 51; dis-
locator-cell ii 614; embryo-
gely i 208; embryo-sac-ger-
mination ii 631, and stimulus
of pollen-tube ii 623; epinasty
i 85 ; exosporium cuticularized
and embryo-sac ii 626; flower,
colourii 522,551; flower female
ii 518, biological relationships
li 523, formation and restricted
growth i 212, hypothesis of
evolution ii 525, or inflore-
scence ii 524, malformation ii
524, morphology ii 524,
position ii 523, virescence ii
5255 flower male ii 499, 514;
hyponasty i 85; inflorescence ii
518; juvenile form i 153,sexual
organs i 146; leaf-cushion ii
569; leaf-insertion i 93; mega-
prothallus depends upon pol-
lination ii 624; ovule ii 628,
bitegminous ii 628, lie in the
flower ii 523, sterilization ii
628; pollen-grain, germination
ii 614; pollen-sac ii 610, open-
‘ing ii 610; pollination ii 523;
prothallus, male ii 614; re-
production, capacity i 143;
root, hairless ii 269; rosette
of archegonium ii 629; seed,
correlation in development i
208; shoot, correlation and
direction i 214, dorsiventral
lateral i 93 ; short shoot and
long shoot ii 444; spermato-
cyte ii 614; spermatozoid ii
614; sporangium, embedded
and free ii 574; sporophyll as
sterilized sporangium ii 517;
‘INDEX
stamen, variation in one flower
ii 516.
Connective of anther ii 553.
Conomitrium, hair-protonema
from calyptra ii 154.
a eee spore, shedding ii
163.
Contact-stimulus, and disks on
tendrils i 268 ; and hair-roots
and anchoring-organs i 269.
Convallaria, leaf ii 450.
C. majalis, leaf and environ-
ment ii 298.
C. Polygonatum, inflorescence,
unilateral i 137.
Coprinus ephemerus, plicatzlis,
stercorarius, sporophore mal-
formed in darkness i 258.
C. niveus, nycthemerus, sterile
in darkness i 259.
C. stercorarius, regeneration of
cortex of sclerotium i 50.
Corallorrhiza, rootless shoot ii
234.
C. innata, rootless ii 265.
Cordyline, gravity and formation
of organs i 224.
Cortandrum, flower, unessential
zygomorphy i 130.
Coriaria, carpel and ovule, de-
velopment ii 561; ovule, axil-
lary to carpel ii 561.
C. myrtifolia, gynaeceum ii 561.
Corolla, confluence of parts ii
538; of Compositae ii 553;
radial, evolution of ii 553 ; size
and light ii 551.
Correlationi 205; arrestthrough
158, 208; bract and leaf-sheath
of Umbelliferae i 59; in bud-
scalesi216; in budsoftreesi58,
208; inaxillary buds of Jzg/azs
regia 1 209; carpel and ovule
i 59; cotyledon and hypocotyl
ii 260, of Stveptocarpusi 210; in
direction of root i 214; in em-
bryogenyi 208; infloweri 211,
flag-apparatus i 211; in fruit i
208, 212; in leafi 209, com-
poundi 210; inleaf-formi 215;
leaf-lamina and stipule i 210;
leaf-size and shoot-axis i 211;
leaf-stalk and lamina ii 300;
in organs, direction i 214,
reproductive and vegetative
i 142, 212; in prothallus, and
embryo i 142, and sexual or-
gansi58 ; qualitative influence
i 214; quantitative influence
i 207; rhizoid and water-sac
ii 45 ; in root-system, direction
i a14; seed and flower i 58,
208 ; in shoot, leaf and bud i
209; in shoot-system, direc-
tion i 214, of potato i 215;
sporangium and leaf of Se/a-
ginella i 216; in sporophyll-
form of Pteridophyta i 215;
665
in stipule i 210; in tendril,
formation i 216; in thorn,
formation i 215; of growth,
interpretationi 209 ; vegetation
and reproduction i 212.
Corsinia, antheridium, develop-
ment li 13; embryo, chloro-
phyllous ii 105; scale ii 30;
sexual organs, grouping ii 84 ;
spore, cell-wall ii 106, rapid
germination ii 107; sporo-
gonium contains spores and
nutritive cells ii 98.
Corydalis ,cotyledon,assimilating
ii 402; flower, transverse dorsi-
ventral i 128.
C. cava, embryo, retarded ii 250 ;
geophilous shoot, depth in soil
li 465.
C. claviculata, transformation of
leaf into tendril ii 421 ; transi-
tion from leaf to tendril i Io,
161.
C. solida, embryo, retarded ii 250;
inheritance of peloria i 184.
Corylaceae, basigamy ii 615.
Corylus, flower, position of male
and female ii 472; laminar
growth, pleuroplastic ii 312;
leaf-lamina, branching ii 312;
ovular development after pol-
lination ii 623; ovule formed
by stimulus of pollen-tube i
269.
C. Avellana, phyllotaxy, varia-
tion i 96; shoot, dorsiventral
lateral i 96.
C. Colurna, shoot, dorsiventral
lateral i 97.
Cotylar storage ii 257, 401.
Cotyledon Umbilicus relationship
of leaf to shoot-axis i 114.
Cotyledon ii 400; arrested form
of foliage-leaf ii 400, 403;
assimilation-organ ii 402; a-
symmetry i I15, ii 406, cause
ii 407; broad ii 406; convolute
ii 406 ; developmental stage of
foliage-leaf ii 402 ; differentia-
tion in Monocotyledonesii 408 ;
of Dicotyledones ii 402 ; emar-
ginate ii 407 ; epigeous, simple
configuration ii 403; factors
of configuration ii 405; feuilles
seminales of A. P. De Candolle
ii 400 ; haustorium il 401, 410;
intercalary growth ii 404;
lobed ii 407, 411 ; mesocotyl
ii 412; middle portion in
Monocotyledones ii 410; nar-
row ii 406; peltate ii 334;
persistent ii 235, 403; piston
11402; post-embryonaldevelop-
ment ii 404; protective li 401 ;
protophyll of Du Petit Thouars
ii 400; of Pteridophyta ii 400;
resembling foliage-leaf ii 402 ;
reservoir of reserve-material
666
ii 257,401; sheath in Monoco-
tyledones ii 408, 410; of Sper-
mophyta ii 401 ; transition be-
tween epigeous and hypogeous
ii 403; transition to foliage-
leaf ii 404; tuber ii 257; and
hypocotyl, correlation in size
ii 260.
Crantzia linearis, cylindric leaf
by reduction ii 295.
Crassulaceae, branching and
phyllotaxy i 82.
Crataegus, reversion of thorn-
shoot to foliage-shoot ii 453.
C. Oxyacantha, thorn-twig ii
452.
C. Pyracantha, thorn-develop-
ment i 264.
Creeping shoot, symmetry i 90;
flattening i g2; with distichous
phyllotaxy i go.
Crepis biennis, inheritance of
fasciation i 185.
Crested leaf ii 345.
Crinum, embryo-sac, haustorium
ii 620, many ii 618; endo-
sperm, development ii 618;
ovule, ategminy ii 618, rudi-
mentary ii 620.
Crista of anther of Coniferae ii
516.
Crocus, root, dimorphism ii 271.
C. longtfiorus, pull-root ii 271;
root, dimorphism ii 271 ; root-
development, periodic ii 290.
C. vernus, embryo, retarded ii
"yee
Cruciferae, bract, arrested i 57,
i 39075 _bract; developed
through Phytoptus i 195;
branching, axillary ii 433, with-
out axillant leaf ii 433 ; cotyle-
don, emarginate ii 407; flower,
arrangement of parts ii 531,
structure ii 543, structure in
relation to pollination ii 547,
unessential zygomorphy i 130;
fruit, concrescence in false sep-
tum i 53; hypsophyll ii 397;
ovary, false septum ii 565, uni-
locular becoming plurilocular
ii 565; staminal primordium,
branching ii 536.
Cryptocoryne ciliata, viviparous
germination ii 256.
Cryptomeria japonica,
female ii 521.
Cucumis sativa, tendril, develop-
ment ii 424.
Cucurbita, flower-buds do not
unfold in darkness i 243; root,
experimental malformation i
191; tendril, spirally-branched
ii 426.
C. Pepo, root-hair, suppressed in
water ii 269; seedling, etio-
lated, flowering i 243.
Cucurbitaceae, stamen,
flower,
con-
INDEX
fluence ii 539; tendril i 164,
development ii 423, Miiller’s
investigations ii 425, prophyl-
lar ii 384, teratological pheno-
mena ii 428,
Cunninghamia, flower, female ii
521.
Cunonia capensis, stipule, de-
velopment ii 364, protective
function ii 363.
Cuphea Zimpani, archesporium
of ovule ii 601.
Cupressineae, branch-system
and light i 230; flower, female
li 521, morphology ii 524;
juvenile form i 153, cutting i
45; ovule, sterilization ii 628,
unitegminous il 617; pollen.
sac, opening ii 610, position
11515; prothallus, male ii 614;
reversion, its cause i 173,
shoot i 172; seed, protection
of ripening ii 523; stamen ii
500, 515.
Cupressus, juvenile form i 154.
C. Lawsoniana, flower, female ii
521.
Cupuliferae, cotylar storage ii
57
Curculigo, significance of fan-
shaped leaves ii 326; venation
ii 340.
Cuscuta, embryo, reduced ii 254;
haustorium ii 224, development
through contact-stimuli 1 268;
root, capless chief ii 268; scale-
leaf without vascular bundle ii
292.
Cuticularized exosporium and
embryo-sac in Gymnospermae
ii 626.
Cutting, of Coniferae roots feebly
151; of leaf i 46; gravity and
formation of organs in i 223;
interpretation of position i 45 ;
of Gesneraceaei 46; of juvenile
form of Cupressineae i 45; of
Klugia Notoniana i 46; of
Phyllanthus lathyroides i 51 ;
propagation by i 45; of stro-
bilus of Selaginella ii 476.
Cyanophyceae, in leaf of Azol/a
ii 348; in root of Cycadaceae
ii 282.
Cyatheaceae, antheridium, free,
opening ii 177; prothallus ii
199, branching ii 200, hair ii
199, septate rhizoid ii 188;
sporangia, _ basipetally de-
veloped ii 496; sporangium,
opening ii 588.
Cyathodium, air-cavitiesii 72,75;
apical cell ii 21; protective
cell-rows ii 30.
C. cavernarium, suppression of
trabecular rhizoids ii 47.
Cyathophorum ,anisophyllyitoo.
C. pennatum, anisophylly i 101.
C. pinnatum, cell for uptake of
water ii 148.
Cycadaceae, air-root ii 281;
Anabaena in root ii 282; an-
theridium ii 612; archegonium
ii 612, 629; carpel ii 511, 555;
Cyanophyceae in root ii 282;
embryo-sac, germination il
631 ; exosporium cuticularized
and embryo-sac ii 626; hau-
storium in germinating pollen-
grain ii 612; leaf, develop-
ment ii 313, 322, abortion of
pinnule ii 511 ; ovule, develop-
ment ii 626, foliar origin ii 556,
integument ii 616, marginal ii
511, position ii 514, primitive
character ii 626, and sporan-
gium of Pteridophyta 11 626;
pollen-chamber ii 612 ; pollen-
grain, germination ii 612;
pollen-sac ii 610; pollen-tube
ii 613, acrogamous 1i 613, rup-
ture ii 613; pollen-tube-cell,
nature ii 613; pollination ii
513; prothallus, male ii 613;
prothallus without pollination
ii 623; spermatozoid ii 613;
spermatocyte ii 613; sporo-
phyll ii 511; stamen ii 514.
Cycas, archegonium ii 629, in
unpollinated ovule ii 623;
flower, female ii 511, explana-
tion of form ii 512, unlimited
growth ii 470; flower, relation-
ships ii 512; root, symbiosis ii
282; seed, large ii 512; shoot-
transformation ii 440; sporo-
phyll, sterile ii 511.
C. ctrcinalis, carpel ii 511; sta-
men ii 514.
C. Jenkinsiana, leaf, succession
of pinnules ii 322.
C. Normanbyana, ovules reduced
to two ii 512.
C. revoluta, carpel ii 511.
C. Seemanni, leaf, acropetal suc-
cession of pinnules ii 322.
C. Thouarsii, apical growth,
prolonged ii 322; leaf-apex
circinate ii 322.
Cyclamen, cotyledon resembles
foliage-leaf ii 402.
Cyclanthera, pollen-mother-cell
ii 620; pollen-sac, confluence
Il 554- E:
C. explodens, tendril, nature ii
425.
C. pedata, androecium ii 539;
tendril, nature ii 425.
Cyclanthus bipartitus, split-leaf,
development ii 326; splitting
of lamina through tensions ii
328.
Cylic position in phyllotaxy i 80.
Cylindric leaf, by reduction ii
295; in Australia ii 293; of
Juncus ii 447.
i
er
Cymbidium, nest-root ii 283.
Cymose branching of leaf in
Dicotyledones ii 331.
Cynareae, hypsophyll as bristle
li 398.
Cynips-gall, origin i 198.
Cynips Rosae, efiect upon oak i
198.
Cynomorium, acrogamy li 615.
C. coccineum, aporogamy ii 615.
Cyperaceae, cotyledon ii 411;
flower-structure and pollina-
tion ii 547; mesocotyl ii 412.
Cyperus, expanding prophyll ii
383; phyllotaxy ii 442.
C; alternifolius, cotyledon ii 413;
' fleshy expanding prophyll ii
384,443; foliage-leaf on shoot-
axis 11 447 ; ; germination ii 41 3:
& Pier as germination ii
Cypripedium Catceolus, hypso-
phyll ii 391
Cystopteris bulbifera, kataphyll
as storage-organ ii 350.
Cytisus Laburnum, branching,
axillary ii 433; leaflet, asym-
metry i 122.
D.
Dacrydium Colensoz, flower,
female ii 520.
Dactylis, inflorescence, dorsi-
ventral i 134.
D. glomerata, leaf, development
ii 323, function of closed sheath
ii 323; ligule, significance ii
377:
Daedalea quercina, light, direc-
tive influence i 257.
Danaé, inflorescence, position ii
450.
D.racemosa, \eaf and phylloclade
ii 450.
Danaea, prothallus ii 198, sep-
tate rhizoid ii 198; synangium
ii 585.
Dammara, flower, female ii 521 ;
ovule, integumentary wing ii
628.
Darkness and, cleistogamy of
Tropacolum i243; dorsiventral
aerial root i 246; flower, pro-
duction i 243; flower-buds not
unfolding i 243; fructifica-
tion of Fungi i 258; growth
of Fungi i 257; sterility of
Fungi i 258.
Darwin, definition of a monstro-
sity i178.
Datura, adhesion of bract ii 439.
Daucus Carota, bract i 59.
Davaliia, sporangium, develop-
ment and displacement ii 495.
Dawsonia superba, spore, shed-
ding ii 166.
De Candolle, definition of ‘plan
INDEX
of structure’ ii 533; definition
of ‘type’ ii 533.
Deciduous tree, arrest of latent
buds i 58.
Decurrent leaf-base as wing ii
488.
Dédoublement ii 532 ; negative
ll §34-
Dehiscence. See Opening.
Delesseria Leprieuriz, division
of labour amongst shoots i 39.
Delphinium, flower, double ii
537; horned petal, develop-
ment ii 560; ovule, unitegmi-
nous li 617.
D. cashmirianum, ovule, uniteg-
minous ii 617.
Dematium pullulans, malforma-
tion, experimental i 187.
Demodium gyrans, cotyledon,
asymmetry 1 I15.
Dendroceros, leaf ii 35 ; retention
of water ii 56; sporogonial
germination ii 106; water-
storage il 76.
D. crispus, \eaf ii 36.
D. foliatus, leaf ii 35; hood on
thallus ii 56.
D. inflatus, \eaf ii 36; sponge-
tissue of thallus ii 56.
Denunstedtineae, sporangia,
basipetally developed ii 496.
Depth in soil, of geophilous shoot
ii 465; of tuber of Arum ii
Derangement of organs in mal-
formation i 196.
Derris elliptica, searcher-shoot ii
454- fe
Desmodium, stipel ii 380.
Desmoncus, climbing-hookii 421.
Deutzia, ieaf-insertion ig3; shoot,
dorsiventral lateral i 93.
Development of leaf, Massart’s
views ii 305; sterilizationasa
factor ii 517, 605.
Developmental, history of or-.
gans i 11; series of antheri-
dium of Pteridophyta ii 180;
stages in relation to light i 238.
Dianthus barbatus, staminal pri-
mordium, branching ii 536.
D. Caryophyllus, double flower
ii 537. ;
Diapensia, syncarpous superior
ovary ii 563.
Diatomaceae, colony i 29.
Dicentra Cucullaria, leaf, dual
function ii 398 ; storage-leaf ii
398.
Dichelyma falcatum, symmetry
and environment ii 135.
Dichotomy of leaf in Dicotyle-
dones ii 329.
Dicksonia antarctica, branching,
latent capacity ii 431; sporan-
gium, development and dis-
placement ii 494.
667
Dicksonieae, prothallus ii 200 ;
sporangia, basipetally deve-
loped i1 496.
Dicnemon semicryptum, intra-
sporangial spore-germination
ii 123.
Dicotyledones, antipodal cells,
increase in number ii 637;
cladodeii 451; cotyledonii257,
402; embryo, storage of food-
material ii 257, retarded ii 249,
of saprophyte, reduced ii 254;
embryo - sac, absorption of
ovileveaita ii1637; flower-struc-
ture in relation to pollination
ii 547; heterophylly1i 351, 358;
hook -leaf ii 420; laminar
growth, basiplasticii 312 ; leaf-
apex, precedence in growth ii
310; leaf, of aquatic and
marsh plants ii 358, base ii
299, branching ii 329, in-
terruptedly-pinnate ii 331, in-
version by torsion ii 296,
peltate ii 333, stalk ii 301,
tendril ii 421, tubular ii 337;
megasporocyte, tetrad-division
ii 625; ovule, ategminous ii
618 ; ovular development after
pollination ii 623 ; phylloclade
11451; prophyll, positionii 382;
protocorm ii 232; root, short-
lived primary ii 272; rootless
ii 265; shoot, adventitious ii
276; stipel ii 379; stipule,
axillary ii 373; thorn-root ii
288; venation, reticulate ii
338.
Dicotylous venation li 338, 34
Dicraea algaeformts, bepters ii ii
281; root, dimorphism ii 280,
flattened, in relation to light
1 247.
D. elongata, haptera ii 281;
root, dimorphism ii 280.
Dicranaceae, spore, shedding ii
163.
aarcwube. dwarf male plant ii
I5I.
D. albidum, uptake of water by
leaf ii 145.
D. scoparium, undulatum, \eaf-
apex photophilous i ii 135.
Dictyostelium mucoroides, life-
history i 26.
Didymaca mexicana, climbs by
recurved stipule ii 371.
Dielytra, change of function of
leaf i 9.
Different galls produced by one
gall-wasp i 199.
Differentiation, of plant body i
3; theory i 6.
Digitalis, inflorescence unilate-
ral i 137.
D, purpurea, colour of flower in
light ii 551; peloria i 190; in-
florescence unilateral i 136.
668
Digitate leaf, by branching in
Anthurium digitatum ii 325 ;
of Dicotyledones, basipetal
branching ii 330; relation to
pinnate leaf ii 332.
Dimerous gynaeceum ii 558.
Dimorphism, of gemma ii 49;
of root ii 271, 280, 286.
Dingler on origin of leaf from
flattened shoot ii 452.
Dioecism and monoecism, of
Hepaticae ii 80; of Musci ii
150; of gametophyte of Equise-
taceae il 195.
Dionaea, gynaeceum, paracar-
pous li 558; placentation ii
506.
D. muscipula, gynaeceum para-
carpous ii 566.
Dioon, flower ii 512.
D. edute, carpel ii 513.
Dioscorea, adventitious shoot,
position ii 277.
D. prehensilis, spinosa, thorn-
root ii 288.
Dioscoreaceae, leaf-stalk ii 299.
Diphylleia cymosa, leaf, peltate
and non-peltate ii 336.
Diphyscium, haustorium of em-
bryo ii 157; hypsophyllii 136 ;
leaf, apical segmentation ii
132; mucilage-hair ii 138;
paraphyses ii 151 ; protonema,
special organs of assimilation
ii 121, threads, concrescence ii
121; spore, shedding ii 164;
sporogonium, dorsiventral ii
574-
D. foliosum, flattening of surface
in light i 249,; leaf-form ii 135;
sporogonium, dorsiventral and
light i 237.
Diplazium ( Asplenium) esculen-
tum, transformation of root
into shoot ii 227.
Dipsaceae, flower, unessential
zygomorphy i 130; hetero-
phylly ii 351, explanation ii
352.
Dipterocarpus alatus,
concrescence ii 367.
Directive influence of external
factors i 218, 227, 257.
Dischidia Rafflesiana, tubular
leaf ii 338.
Disease, definition i 178.
Disk, anchoring i 40, 150, 268,
ii 45, 224.
Dislocator-cell, of Coniferae ii
614; suppressed, in Angio-
spermae ii 614, in Gymno-
spermae ii 614.
Displacement, of axillary shoot
stipule,
INDEX
Dissochaeta, root-tendril ii 287.
Divided submerged leaf ii 358.
Division of anther ii 554.
Division of labour i 213; in
leaves in Acacia verticillata ii
3573 in shootii 440; in spo-
Trangia ii 577; in Thallophyta
13.2)
Doodya caudata, antheridium,
free and embedded ii 177;
apogamy ii 220; juvenile form
and reversion i 152; vegetative
developmentincreased through
suppression of reproductive
organs i 214,
Dorsal leaf-rows in Filices i gt.
Dorsiventral, bilateral shoot of
Musci i 68; branching of or-
thotropous shoot i 71; con-
struction due to lie ii 296;
flower derived from radial i
129, 1333; involution i 85;
organ, definition i 67; and
radial flower, relationship ii
544; shoot, relationships of
position ini 85; structure, of
shoot-axis of Urtica dioica ii
545, of Hepaticae i 84; type
in Musci and Hepaticae ii 18.
Dorsiventrality, and conditions
of life i 86; of flower i 128,
an adaptation i 132, of An-
giospermae ii 542, cause i
133, development ii 542,
and external factors i 129,
lateral i 133, origin ii 543,
pressure as a factor ii 544, of
Selaginella ii 507 ; of inflore-
scence i 67, 129, 134, in-
fluenced by external factors i
138; of leaf ii 293, of Mono-
cotyledones ii 323; and light
i 227, in Lycopodium i 104;
of prothallus, of Filicineae and
light i 227, 228, of Lyco-
podineae ii 193, of Pterido-
phyta and light ii 191, of
Pteridophyta, inheritance ii
I91; reversible i 228, 231;
of root and light i 246; of
aerial root ii 2843; of shoot i
84, of Lycopodium conplana-
tumii 419, of Hedera i gg, and
light i 230, lateral i 92, of
Musci ii 138, sexual, of Radula
ii 8g, and radial flower of
Lycopodium complanatum ii
509; of stem igI; of sporan-
gium ii 574, 581; of sporo-
gonium of Dzphyscium ii 574 ;
of sporophyll of Ophioglos-
saceae li 482; significance in
Algae i 87.
ii 434; of lateral organi 74 ; of | Dovstenta, inflorescence, dorsi-
leaf in Hepaticae ii 41; of
sporangium in Schizaeaceae ii
494; through diminution in
size of organ i 80,
ventral i 134.
Double, fertilization of Angio-
spermae ii 624; flower ii 536,
artificial production of i 194,
transmissible by seed i 184;
leaf of Caprifoliaceae i 190;
needle of Pinus Pumilio ii
445, of Sctadopitys ii 444.
Doubling, of flowers, Peyritsch
i 195; of flower through
Phytoptus i 195; of stamen ii
530.
Dracaena, cotyledon, epigeous
ii 409.
D. indivisa, haustorial cotylar
tip ii 408.
Dracunculus, basal laminar
growth ii 324.
Draparnaldia, chief axis and
lateral axes i 34.
D. glomerata, rhizoid, develop-
ment i 269.
Drepanophyllum, bilateral shoot
ee
D. falcatum, protonema-thread
on stem ii 147.
D. fulvum, distichous shoot ii
136,
Drip-tip, biological significance
li 345. 4
Drosera, dorsiventral involution
i 85; epithelium of ovule ii
638; primary leaf non-peltate .
ii 336.
D. binata, \eaf, dichotomy ii
329; involute ptyxis li 310.
D. dichotoma, involute ptyxis ii
310.
D. macrantha, stem, climbing
by tentacles ii 419.
D. pedata, \eaf, dichotomy ii 329.
Droseraceae, leaf-apex, prece-
dence in growth ii 310.
Drosophyllum, revolute ptyxis 1i
310.
D. lusitanicum, circinate ptyxis
ii 311.
Drought, resting state and i
261.
Dryadeae, monomerous ovary
ll 559.
Drymoglossum subcordatum, ste-
rile and fertile leaf ii 485.
Dryophanta folit, gall upon
oak-leaf i 199.
Duchesnea indica, shoot, pla-
giotropous ii 457.
Dulongia acuminata, epiphyl-
lous inflorescence ii 437.
Dumontia filiformis, pro-embryo
i 149.
Dumortiera, air-cavities il 73;
antheridiophore and arche-
goniophore ii 87; rhizoid,
division of labour ii 47; scale
li 30.
D. hirsuta, thizoid-bristle ii 47 ;
scale ii 33.
Duplex gemma-cell of Axeura
ii 49.
Duration, of apical growth of
Ginkgo ii 322; of juvenile
form i 145 ; of life of prothallus
of Pteridophyta ii 189; of
shoot of Spermophyta ii 440.
Duvalia, air-cavities ii 75.
Duvaua, gall i 199.
Dwarf male plant of Musci ii
I5I.
E.
Earlier functioning parts appear
earliest ii 305, 314, 414.
Eccremocarpus, transformation
of leaf into tendril ii 422.
Echinocereus cinerascens, gravity
and shoot i 221.
Ectocarpeae, juvenile form i
150.
LEctocarpus, light and vegetative
organs i 256.
Ldraianthus, \eaf, linear ii 351,
unstalked ii 301.
£.. Pumtlio, hypsophyll ii 391;
leaf, linear ii 351.
Egg-apparatus of Angiosper-
mae ii 636.
Egg of Pteridophyta ii 184.
Lichhornia azurea, reversion-
shoot i 172.
LE. crasstpfes, venation ii 340.
Eichler on leaf-development ii
304.
Ejection, of gemmae ii 49, 467 ;
of spores ii Ior, 162, 580.
Elaeagnaceae, hair, peltate ii
336.
Elaphoglossum, sporangium, pro-
tection ii 496.
E. (Acrostichum) spathulatum,
sterile and fertile leaf ii 485 ;
sporophyll ii 496.
Elaterophore, sporogonium
with ii 100, without ii 99.
Elater, of Anthoceros ii 95,
100; of Battareai 19; attached
to surface of capsule ii 100 ;
free ii 99 ; holding the mass of
spores ii Iol; mechanism of
movement ii 100.
‘Elaters,’ of Zgutsetum ii 575 ;
of Polypodium imbricatum ii
Elatostemma, anisophylly i 99,
i 108, habitual i 109; hypo-
nasty and epinasty i 85.
E. sessile, anisophylly, habitual
i IIo.
Emarginate, cotyledon ii 407.
Embedded, antheridium of
Pteridophyta ii 173 ; embryo-
sac in torus of Loranthaceae
ii 620; sporangium ii 573,
574, 584; and free sporan-
gium, transitions ii 574.
Embryo, acotylous ii 250;
adventitious ii 624; after-
ripening in Spermophyta ii
Embryo-sac,
429.
Empusa
INDEX
249; chlorophyllous of Utricu-
laria ii 254; of Cyperaceae ii
411; development interrupted
in seed ii 248, 401; of Musci
ii 154; dicotylous, of Pulsa-
tilleae ii 250; differentiation,
morphological ii 242, in Pteri-
dophyta ii 243,in Spermophyta
ii 244; differentiation, polar, of
Lycopodineae ii 247, of Sper-
mophyta ii 248; feeding, in
Angiospermae ii 637 ; formed,
from antipodal cellsii637,from
endosperm ii 624, from syner-
gidae ii 637, from unfertilized
egg ii 624 ; of Gramineae ii
415; gravity and, in Pterido-
phyta i 219; incomplete ii
249; lie in relation to space
in embryo-sac ii 405; macro-
podous li 260 ; of Monocotyle-
dones and exalbuminy ii 408;
orientation of organs, of Pteri-
dophyta ii 246 ,of Spermophyta
ii 248; parthenogenetic ii 624 ;
of parasites ii 254; reduced ii
254; retarded ii 249, cause ii
252;ofsaprophytesii254;small,
of Begoniaceae ii 631 ; storage,
hypocotylar ii 258, in Dicotyle-
dones ii 257, in Monocotyle-
dones ii 260; unsegmented ii
250; viviparous ii 256.
Embryonal tissue, in regenera-
tion i 43; originating leaf-
primordia ii 305.
absorption of
ovular cells in Angiospermae
ii 637; of Aconztum Napellus
ii 636; of Casuarina stricta
ii 633; changes within, in
Gnetum ii 629 ; development,
in Balanophoreae ii 621, in
Spermophyta ii 625;embedded,
in Loranthaceae ii 620; feed-
ing, in Angiospermae ii 637;
germination, in Angiospermae
ii 635, intranucellar ii 622;
haustorium ii 620; many, of
Alchemilla ii 633, of Crinum
ii 618, of Viscum articulatum
ii 620; nucleus ii 635 ; origin
ii 632 ; significance of contents
in Angiospermae ii 636 ; varia-
tions within ii 637.
Emergence, anchoring-organ in
Podostemaceae ii 222; defini-
tion i 13, ii 222; prickle ii
Muscae, limited
growth in starvation i 142.
Enation in Centranthus Calei-
trapa i 195.
Encalypta, leaf-surface, papilla
ii 143; water-cell, perforated
ii 145.
£. vulgaris, archegonial venter
a water-sac li 153.
Epidendrum
669
Encephalartos Barteri, basipetal
development of pinnules ii 322.
Encrustation of shoot-axis of
Chara ii 569,
Endogenetic, adventitious root
of marsh and water-plants ii
273; first root of Lycopodium
ii 273; flower-bud of Pilo-
styles ii 226 ; secondary root ii
273; shoot of Hepaticae ii
45; stem-root of Weottia
Nidus-avis ii 273; vegetative
point of shoot of some Gym-
nospermae li 266.
Endosperm, absorption, extra-
seminal and intraseminal ii
402; embryogenic of Balano-
Phora ii 637 ; feeding, in An-
giospermae ii 637; ruminate
of Aveca Catechu ii 411;
significance in Angiospermae ii
636; small in Begoniaceae ii
631; of Triticum vulgare ii
415.
Endothecium ii 600; active
cells ii 600, 611 ; of moss-cap-
sule ii 155.
Energid, definition i 23; of
Siphonieae i 23.
Energid-colony i 24; of Proto-
coccaceae i 26; of Pediastrum
i 27; dominion i 24.
Entomophilous plant, dorsiven-
tral inflorescence i 135.
Environment, Fungi and their
i 266; and fertile shoots of
LEquisetum ii 502; apospory
a consequence of ii 607; and
configuration i 217.
Ephedra, archegonium ii 629;
embryo-sac, germination ii631;
flower ii 526; perianth-leaf,
origin from dermatogen i 17;
unitegminy ii 629.
Ephemeropsts,protonema, branch-
ing and light i 234; pro-em-
bryonal gemma ii 126.
E. tjibodensis, protonema ii 120,
segment-walls ii IIg.
Ephemerum, columella ii 157 ;
juvenile form, extended life i
147; male and female plants,
relative size ii 151.; protonema,
persistent i 58.
£. serratum, ‘leaf’ of proto-
nema ii 129; protonemai 147,
li 129; spore, shedding ii
160.
Epiblast of Gramineae ii 415,
418.
nocturnum, flat-
tening of root in light i 246.
Epigeous, green cotyledon of
Monocotyledones ii 409; co-
tyledon, simple configuration
ii 403; (photophilous) shoot
ii 442.
Epigyny ii 558.
670
LE pilobtum, pollen-sac, steriliza-
tion ii 555.
£. angustifolium, cotyledon ii
404; flower becomes dorsi-
ventral in development i 129 ;
hypsophyll of whole leaf-pri-
mordium ii 393.
E. parvifolium, hypsophyll ii
Soka e
Epinasty i 84.
Epipactis, axillary branching ii
433- a
Epipeltate leaf ii 334.
Epiphragm of Musci ii 166.
Epiphyllous inflorescence ii
36.
Epishyllum, juvenile form i 169;
Phyllocactus-form i 169.
E. truncatum, flower becomes
dorsiventral in development i
129.
Epiphyte, anchoring-disk ii 45;
heterophyllous ii 349; rootless
ii 265; root ii 282; and water
ii 53.
Epipodium ii 304.
Epipogon, rootless shoot ii 234.
E. Gmelini, rootless il 265;
scale-leaf without vascular
bundle ii 292.
Epithelium, of ovule ii 631,637,
function ii 638.
Epitropous ovule ii 631.
Equiseta, ametabola ii 502;
heterophyadica ii 501 ; homo-
phyadica ii 501; metabola ii
501.
Equisetaceae, anisophylly, ab-
sent i 102; antheridium, open-
ing ii 175; branching, phyllo-
genous ii 432; cladode ii 448;
development, homoblastic i
151; flower, protection ii 500;
gametophyte ii 195; laminar
growth, basiplastic ii 313;
prothallus, dorsiventral ii 191;
spermatozoid, pluriciliate i
172; sporangium, dehiscence
ii §84, position il 493 ; sporo-
phyll and foliage-leaf alike in
position and origin ii 477.
Equisetum, annulus ii 500; an-
theridium, development ii 178;
archegonium, opening ii 183;
branching ii 432; ‘elaters,’
ii 100, 575; embryo, differ-
entiation ii 244; fertile shoot,
arrested formation ii 502, and
conditions of development ii
502, transformed sterile leaf
ii 502; flower ii 499, apical
plug ii 500; foliage-leaf
and fertile leaf ii 499; leaf,
vegetative, and function ii
499; prothallus, ameristic
ii 197, dorsiventral ii 195,
heliotropism ii 197, hydro-
tropism ii 197, male ii 196,
INDEX
water-relationshipii 215; root-
primordia on stem, latent ii
275; shoot, hypogeous, as
boring-organ ii 266; sporan-
gium, dorsiventral ii 574,
origin from leaf-organ ii 473,
and peltate sporophyll ii 575,
wall ii 582; spore-germina-
tion and light 1 299; spore,
shedding ii 100, 575; sporo-
genous tissue, sterile cells ii
597; sporophyll, development
ii 500, and sporangium ii 499;
tapetum, plasmodial ii 596;
transition, embedded and free
sporangia ii 574.
E. arvense, archesporium ii 601;
special fertile shoot ii 501;
sporangial wall ii 583; steri-
lized sporogenous cells, absent
ii 597; not xerophilous ii
446.
E. hyemale, sterile and fertile
shoot alike ii 501; xerophilous
ii 446.
E. limosum, antheridium, open-
ing ii 175; sterile and fertile
shoot alike ii 501.
E. palustre, sterile and fertile
shoot alike ii 501.
E. pratense, antheridium opening
ii 175; fertile shoot subse-
quently vegetative ii 501; not
xerophilous ii 446; prothallus,
male ii 175, female ii 196.
E. sylvaticum, fertile shoot sub-
sequently vegetative ii 501;
not xerophilous ii 446.
E. Telemateia, special fertile
shoot ii 501; sporangial wall
ii 583.
Evranthis, germination ii 252.
E.. hyemaiis, embryo, retarded ii
249.
Reewedioee monergic spheri-
cal body i 65.
Erica carnea, endothecium ii
611.
£. Tetralix, laminar growth,
basiplastic ii 312.
Ericaceae, pollen-sac, active
opening cells suppressed ii
577, 611.
Erineum-gall caused by mites
i 196.
Eriophorum alpinum, reversion
li 448.
Eviopus, protonemoid gemma ii
140; rhizoid on sporogonium
il 142, 057
E. remotifolius, absorption of
water by sporogonium ii 157 ;
bilateral shoot ii 137; gemma
with separation-cell ii 136;
protonema-threads on stem ii
147.
Evodium, cotyledon, asymmetry
i 115, ii 406.
Ervum monanthos, stipule, in-
equality in size ii 366.
Eryngium, leaf, monocotylous
form ii 295.
LE. agavaefolium, pandanifolium,
striate venation ii 339.
E. bromeliaefolium, pandani-
folium, leaf, monocotylous
form ii 95; profile-position by
torsion ii 295.
E.. maritimum, inferior ovary ii
560.
Erythraea pulchella, ovule on
under side of carpel ii 558.
Erythronitum Dens-canis, em-
bryo, retarded ii 251.
Eschscholizia, flower-structure
and pollination ii 547.
£. californica, flower, arrange-
ment of parts ii 531; pollen-
sac, differentiation of arche-
sporium ii 600.
Essential zygomorphy of flower
i 130.
Etiolated, seedling flowering i
243 shoot in Hepaticae i 249,
ii 22.
Etiology, of peloria i 188; of
malformation i 184.
Eucalyptus, bilateral leaf, pro- -
file-position ii 293; juvenile
form i 167; reversion-shoot i
173; xerophilous adaptation
i 165.
£. globulus, foliage-leaf, asym-
metry i 116.
Eucamptodon Hampeanum, pert-
chaetialis, spore, germination
intrasporangial ii 123.
Eucladous type of laminar
growth li 312.
Ludorina, colony i 27.
Euphorbia, ovular integuments,
development ii 617; shoot, as
water-reservoir ii 452, sterile
when attacked by Uvomyces
pist i 192; thorn-stipule ii
381.
E. alcicornis, chief and lateral
shoots and gravity i 226.
£. helioscopia, cotyledon per-
sistent ii 403.
Euphorbiaceae, phylloclade ii
451; succulent form i Ig.
Luptzlota, shoot, branching i 88.
£. Harveyt, branching compared
with that of dicotylous leaves
li 331; shoot, branching i 89.
Euryale ferox, prickle i 264.
Eusporangiate Filicineae, spo-
rangium, mature ii 584, un-
stalked ii 574; sporophyll as
new formation ii 481.
Eusporangiate Pteridophyta,
stalk of sporangium an ont-
growth of the sporophyll ii617.
Eusporangium ii 602.
Evolution, of differentiation of
.*
embryo in Spermophyta ii 245 ;
of tubular flowerin Compositae
ii 553; of radial corolla ii 553.
Exalbuminy, of Dicotyledones
ii 257; of Monocotyledones ii
260, 402.
Bxine of spore of Hepaticae
ii 106.
Lxoascus causing witches’
broom i 192.
Exodermis of Phalaenopsis
Schilleriana ii 284.
Exogenetic, root ii 273; root-
borne bud of Zzuarza ii 277;
secondary root of Phylloglos-
sum Drummond ii 273.
Exormotheca, breathing-pore ii
75-
E. Holstiz, thallus ii 75.
Exosporium of Hepaticae ii
106,
Exothecium, active cells ii 611.
Exotropy i 109; of lateral root
ii 276.
Experimental organography,
importance i 52.
Exstipulate Monocotyledones
ii 365; Ophioglossaceae ii
365. '
External, factors condition
gemma-formation ii 607; for-
mative stimuli, influence of i
205; stimuli, directive in-
fluence of i 218, and configura-
tion i 217,reaction of organs to
i 217, reaction of plasmodium
in Myxomycetes to i 218,
and reversion-shoot i 218.
Extraseminal absorption of en-
dosperm ii 402.
Extrorse anther ii 553.
F.
Factors influencing, colour and
size of flower-envelope ii 551 ;
configuration of cotyledon
ii 405; growth of searcher-
shoot ii 454; numerical re-
lationships of flower ii 537;
plagiotropous growth ii 461;
position of sporangium in
Pteridophyta ii 494 ; reduction
of leaf in Monocotyledones ii
447; leaf-transformation into
tendril ii 428.
Fagaceae, aporogamy ii 615.
Fagus, callus-shoot i 44; fermn-
leaved variety ii 345; flower,
position of male and female ii
472; fruit, compensation of
growth i 207; juvenile form,
direction of growth i 143;
kataphyll, stipular ii 386;
leaf-insertion i 93; ovule, de-
velopment after pollination ii
623; seedling i 70; shoot,
abortion of apex of annual i
209, concatenation of plagio-
INDEX
tropous i 70, dorsiventral
lateral i 93; stipule, caducous
ii 363, protective function ii
363; winter-bud, structure ii
32.
False, septum in ovary of Cruci-
ferae, ii 565; short twig of
Areschoug ii 453.
Fan-palm, leaf-form, signifi-
cance ii 326, of seedling ii 327.
Fasciated shoot and double leaf
i 190,
Fasciation i Igo; artificial pro-
duction i 190; inherited i 184.
Feather-palm, leaf-form, de-
velopment ii 327.
Feeding, of embryo, embryo-
sac, endosperm ii 637.
Fegatella, air-cavities ii 74, 75;
spore- germination ii I11;
sporogonium, development ii
105.
Ff. conica, air-cavities li 75;
brood-tuber ii 70.
f supradecomposita, propagative
shoot ii 48.
Female flower. See Flower.
Female prothallus. See Mega-
prothallus.
Female sexual organ.
Archegonium.
Ferns. See Filices.
Fern-leaved variation ii 345.
Fertile shoot, of Lguzsetum,
arrested formation ii 502; of
Hepaticae ii 79.
Fertilization, double ii 624;
effect upon antipodal cells ii
637; of Angiospermae, stimuli
concerned in i 269; induces
envelope-formation in Hepa-
ticae ii 105; of Selaginelleae
ii 508.
Feuilles seminales, A. P. De
Candolle’s name for leafy
cotyledons ii 400.
Fevillea trilobata, androecium ii
539-
See
Ficus, prop-root ii 277; stipule,
axillary li 359, 372, protective
function ii 363.
F.. Pseudo-Carica, stipular sheath,
deciduous axillary ii 372; sti-
pule, free ii 372.
FF. pumila, scandens, juvenile
form i 159.
F. stipularis, foliage-leaf, asym-
metry i 116.
Figs, climbing i 159.
Filament of stamen of Angio-
spermae ii 529.
Filaments, branched in C/a-
dophora i 33.
Filices, hair, peltate ii 336;
heterophylly in epiphytic ii
349; leaf, apical growth ii
317, with circinate ptyxis ii
320, primary i 151, with
671
unlimited growth i 15;
leaf-cutting, unknown i 46;
prothallus, arrest through
correlation i 58, regeneration
i 43, reversible dorsiventrality
i 228; reversion to juvenile
form i 171.
Filicineae, annulus ii 587, lie,
not an adaptation ii 594; an-
theridium, free ii 177; embryo,
differentiation, ii 243, and
gravity i 219, orientation of
organs ii 246; gametophyte ii
197, relation to that of Musci
ii 208 ; leaf, apical growth ii
310, 313, marginal growth
ii 313; leaf-borne shoot ii
436; leaf-form, factors in-
fluencing ii 315, series ii 320;
leaf-primordium arises from
one cell ii 305; leaf-structure,
biological significance ii 346;
leaf-wing ii 314; propagative
adventitious shoot on pro-
thallus ii 213; prothallus ii
197, 201, chlorophyllous ii
199, dorsiventral ii 191, evolu-
tion ii 208, hastening of em-
bryogeny ii 189; spermato-
zoid, pluriciliate ii 172; spor-
angium, mature ii 584, origin
from leaf-organ ii 473; sporo-
phyll, condition for its appear-
ance ii 498; tapetum, plas-
modial ii 596; transformation
of leaf into shoot ii 241, of
root into shoot ii 227.
Filiform tendril ii 457.
Fimbriaria, air-cavities ii 75;
involution of parts to resist
drought ii 65.
Fissidens, apical cell of stem,
two-sided ii 131; directive
influence of light i 236; ju-
venile form i 151; leaf i 103,
ii 5¢8, development like that
of /7zs ii 329, iris-likeii 137,
surface i 87; shoot, bilateral
i 66, dorsiventral bilateral i 68.
F. adianiotdes, directive influence
of light i 236.
F. bryoides, hypsophyll ii 135 ;
protonema, significance ii 130;
shoot, branching ii 130.
Fissidentaceae, peristome ii
163 ; spore, shedding ii 163.
Fixed colony of Thallophyta i
29.
Mlcct Nensnedin: of Angiosper-
mae ii §28; staminal ii 550.
Flagellum, of Hepaticae ii 42;
use in AMastigobryum ii 228;
of Adiantum Edgeworthi ii
241.
Flag-flower ii 571.
Flattened shoot, the origin of
spermophytous leaf, Dingler’s
view il 452.
672
Flattening of, organs and light
i 245; organs and light in
Hepaticae i 249, in Musci i
249, in Pteridophyta i 249;
shoot and light in Dicotyle-
dones i 247; creeping shoots
i g2; climbing shoots i 92;
shoot-axis in Opuntia ii 448;
root and light i 246; aerial
root i 92.
Float-leaf of Sa/vinza ii 34,348.
Florideae, concrescence of hair-
roots i 54.
Flower, of Angiospermae ii 527;
apodial ii 510; arrangement
of parts ii 528-31; asym-
metry i 129; arrest i152, 57,
ii 546; arrest and function ii
547; blind and high tempera-
ture i 213; bud, endogenetic
ii 226; buds, do not unfold
in darkness i 243, of Acer
Pseudoplatanus ii 541; cushion
of Pilostyles ii 226; calcarate
i131; colour ii 522, 551, and
light ii 551; concrescence of
parts ii 546; confluence of parts
ii 538; correlation of growth
i 211; cushionii 226; definition
ii 469; development ii 542-5,
of Adzes pectinata ii 522; dor-
siventrality i 128, ii 542,
developmenti 129, and external
factors i 129, an adaptation i
132; of Equisetaceae ii 499;
envelope of Angiospermae ii
548, evolution ii 549, factors
influencing size and colour
ii 551, function ii 548, of
developed hypsophylls ii 549,
morphological significance ii
548, of transformed sporo-
phylls ii 549 ; female, of Coni-
ferae ii 518, of Cycas ii 511, of
Cycas with unlimited growth ii
470, of Selagznella ii 508 ; fur-
thered organs laid down earliest
in ii 545 ; of Gnetaceae ii 526 ;
hermaphrodite, primitive in
Gymnospermae i 60 ; and in-
florescence in Coniferae ii 524;
inverse-dorsiventral ii 508;
irregular i 128; labiate i 131;
leaf, basipetal succession of ii
542, terminal ii 541; and
light i 244; ligulate i 131;
male, of Coniferae ii 499, 514,
of Gzxkgo ii 515, of Selaginella
Martensit ii 508, of Wel-
witschta i 60, ii 526; male
and female, separation ii 471 ;
nectary ii 430; number in rela-
tion to pollination ii 547 ; and
nutrition i I91; origin in
Gymnospermae i 60; ortho-
tropy ii 509 ; personate i 131;
position of male and female ii
472; of Pteridophyta ii 472;
INDEX
radial i 128, and dorsiventral ii
544; reduction in Balanophora
li 622; regular i 128; of Sela-
ginelleae ii 505; separation into
male and femaleii 471 ; shoot
of limited growth ii 470; size
and light ii 551 ; structure and
pollination ii 547; suppression,
in Boragineae i 58, of torus
ii 540; symmetry i 128, ii
509, 537; transformed ii 571 ;
and vegetative shoot, relation-
ship in Lycopodineae ii 509 ;
zygomorphy, essential i 130,
unessential i 130; use of
term in Pteridophyta ii 470.
Flower-morphology, anato-
mic method in ii 545.
Flowering and rays of the
spectrum i 244.
Foliage-leaf, asymmetry i 116;
absent in some epiphytes ii
286 ; cotyledon, arrested form
of i. 145, developmental stage
toii402; hypsophyll developed
from ii 390; relation to spo-
rophyll 1 11, ii 473, 499,
503, 509, 510; transforma-
tion i ro, 161, 168, 178, 181,
11 394,421,477.
Foliage-shoot, the typical shoot
ii 440; transition to thom ii
452.
Foliar, gland ii 362; origin of
ovules ii 556 ; placenta ii 556;
spine i 168, ii 429.
Foliose,Jungermanniaceae, light
and growth ii 77; lichens,
usually dorsiventral i 71.
Fontanesia Fortunet, ovule and
pollination ii 623.
Fontinalis, adaptation to habitat
ii 134; spore, shedding il
164; peristome ii 164.
Ff. antipyretica, adaptation to
flowing water ii 135.
Foot of embryo in Musci ii 157.
Forerunner-tip ii 308.
Form, and function, Herbert
Spencer on i 4, interdependent
i5, relationi4; of hypsophyll
and function ii 396; of sporo-
phyll and sporangium ii 499 ;
of stipule and function ii
366.
Formation of flower and light
i 242; of organs at vegetative
point i 41; ofovary ii 555; of
root and light i 231; of spo-
rangium and light i 245.
Formative stimulus, gravity as
i 219.
Forsythia, kataphyll ii 385;
ovular development after pol-
lination ii 623.
Ffossombronia, antheridium ii 84 ;
chromoplasts in antheridium ii
10; colour and light ii 78;
leaf ii 38; sexual organs,
diffuse disposition ii 80;
elaters holding mass of spores
ii 102.
F. caespitiformis, leaf-borne mu-
cilage papilla ii 29.
£. ene leaf ii 38 ; tuber ii
8.
Fragaria, shoot, plagiotropous ii
457-
F. vesca, stolon ii 461.
Fraxinus, anisophylly, lateral
i 108; leaflet, asymmetry i
122; ovular development after
pollination ii 623.
F. excelsior, leaf, development ii
305, venation ii 344.
Free, antheridium of Pterido-
phyta ii 177 ; central placenta-
tion ii 564, 567; sporangium
li 573, 584; Stipule ii 359.
Free-living, leaf ii 235; root ii
234.
Freesia, unilateral inflorescence i
136.
Freycinetia Bennettit,
ing-root ii 288.
F.. imbricata, anchoring-root ii
288.
F javanica, anchoring-root de- -
veloped into nourishing-root
ii 288.
Fritillaria imperialis, periodi-
city of root-development ii 289.
Fruit, biology of ripening li
50; compensation of growth
i 207; correlation of growth i
212; parachute-apparatus ii
nourish-
570.
Frullania, archegonial groups ii
88.; colour and light ii 78;
elater attached to surface of
capsule ii 100; spore-germina-
tion ii 108 ; sporogonium with-
out elaterophore ii 100;
stylus auriculae ii 60; water-
chamber, capillary ii 58;
water-reservoir ii 59.
F. atrata, atrosanguinea, capil-
lary water-chamber ii 58;
copper-colour ii 78.
F. cornigera, water-reservoir ii
60, 63.
F, dilaiata, branching in relation’
to leaf ii 44; water-reservoir,
capillary i 261.
F. Tamarisci, colour and trans-
piration ii 78; leaf ii 41;
water-reservoir ii 58.
Fruticulose lichens
radial i 71.
Fucaceae, higher differentiation
i 21; light and spore- germi-
nation 1 230.
Fuchsia, branching of petaline
primordium i ii 536.
Fucus, absence of juvenile form i
148.
usually
INDEX
Fucus serratus, \ight and spore- | G. peregrinum, stipule ii 370.
germination i 230.
Fumaria, transverse dorsiventral
flower i 128.
F. officinalis, cotyledon persis-
tent ii 403.
Fumariaceae, embryo, retarded
ii 250; flower-structure and
pollination ii 547; transition
from foliage-leaf totendril i ro.
Funarvia, antheridium, opening
ii 11 ; peristome ii 164 ; spore,
shedding ii 164.
F. hygrometrica, archegonial
venter a water-sac ii 153;
archesporium ii 156; asexual
propagation ii 125 ; mucilage-
hair ii 138; protonema-branch-
ing and light i 234; resting
state i 262; separation-cell of
protonema ii 125; spore-
germination i 147, il 117.
Function, change of, and light
i 255, in organs i 8, in rooti
I2; in determination of im-
portance of organsi5; dual,
of leaf i 8, ii 398; multiple, of
leaf i 161, ii 291.
Fungi, and their environment i
266; configuration and light i
257; causing malformation i
192; causing transformation
of organs i II; causing sex-
change i 193; mechanical
stimuli affecting i 269; mal-
formation in, experimentally
evoked i 187; nutrition and
form i266; vegetative propaga-
tion i 49.
Fungus-gall in Polygonum chi-
nense i 196.
Funicle of ovule ii 614.
Funicular nutritive tissue ii
640.
— adventitious embryo ii
24.
F.. coerulea, polyembryony ii 637.
f. ovata, archesporium of pollen-
sac, differentiation ii 600;
venation ii 340.
Furthered organs in flower
laid down earliest ii 545.
G
Gabler of Vitis vinifera i 186.
Gaertnera, stipule axillary and
interpetiolar ii 374.
Gagea arvensis, embryo,
tarded ii 250.
G. lutea, embryo, retarded ii 251;
root-branching suppressed ii
re-
274.
Gaiadendron punctatum, sepal
without vascular bundle ii 292.
Galeobdolon luteum, peloria i
189; transition from ortho-
tropy to plagiotropy ii 457.
Galium palustre, stipule ii 368.
GOEBEL Il
G. saccharatum, cotyledon nar-
row ii 406.
Gall, of Asfidium aristatum
caused by TZaphrina cornu
cervvé ii 526; Beyerinck’s views
i 202; of capitulum in Hera-
cium umbellatum i 197;
from Cecidomyia Poae i 200;
from Ceczdotes Eremita i 199 ;
from Dryophanta foltt upon
oak-leaves i199; of Duvaua
i 199; growth-enzyme as
stimulus i 202 ; of inflorescence
of Cruciferae i 197; material
influence of the parasite i 196 ;
from Nematus Capreae i 200;
origin of i 198; of Polygonum
chinense; of Pteris quadriau-
ritai 198; of Quercus i 199; of
Selaginella pentagona 1 193;
and stimuli i 198.
Gall-bulbil of Selagznella pen-
tagona i 197.
Gall-insect, root-development
through stimulus of i 200.
Gall-production in relation to
formation of organs i 202.
Gall-wasp, different galls pro-
duced by one i 199; of oak,
Spathegaster Taschenbergt i
199.
Gametophyte, male, of An-
giospermeae ii 614, of Gymno-
spermeae ii 612, of Jsoefes ii
181, of Marsiliaceae ii 180,
of Salvinia ii 182, of Sela-
ginellaii 182; of Equisetaceae
ii 195; of Filicineae ii 197,
connexion with that of Musci
ii 208; of Lycopodineae ii
191 ; primitive in Lycopodium
ii 583; of Pteridophyta ii
171, configuration ii 188 ; and
sporophyte, alternation ii 171,
homology i 20 ; suppression in
apospory ii 607.
Gamopetalae, concrescence in
corolla i 52.
Gaura biennis, pollen-sac, steri-
lization ii 555.
Gemma, antagonistic to sexual
reproduction ii 51; conditioned
by external factors ii 607;
dorsiventral and light i 227 ;
dimorphism in Hepaticae ii
49; distribution by animals ii
49; ejection ii 49, 467; of
Lycopodium ii 467, 607; pro-
embryonal ii 125; prothallial
ii 213, origin ii 215; proto-
nemoid ii 140; of Nemusatia
vivipara ii 469.
Gemma-cell ii 49.
Gemma-leaf ii 139.
Gemma-scale ii 49.
Gemma-shoot ii 139.
Genetic relationship of sporo-
X X
7)
673
phyll and foliage-leaf ii 470,
473-
Genista sagittalis, leaf-base, de-
current, as wing ii 448 ; shoot,
flattened and light i 249.
Genisteae, juvenile form i 168.
Genlisea, insect-trap ii 237; leaf-
root ii 237; leaf, tubular ii 237,
338; rootless ii 265; root-
less shoot ii 234; transition
between leaf and shoot ii 236.
Gentiana, phyllotaxy ii 443.
G. acaulis, verna ii 443.
G. asclepiadea, \aminar-growth,
basiplastic ii 312; leaf-inser-
tion i 93; shoot, dorsiventral
lateral i 93, orthotropous or
plagiotropous i 68; transition
from hypsophyll to flower-
envelope ii 550.
Gentianeae, ovule, absence of
eae ii 638, ategminy ii
18.
Geocalyceae, perianth wanting
ii 89; sporogonial sac ii go.
Geophilous shoot ii 463 ; depth
in soil ii 465; pull-root of ii
ees perennial and periodic ii
463.
Geothallus tuberosus, tuber ii
7, 68.
Geotropism, of aerial root ii
283 ;of rootand moistureii 276.
Geraniaceae, cotyledon con-
volute, asymmetry ii 406;
embryo, lie in seed ii 406;
gynaeceum ii 565; ovule,
epithelium ii 638; shoot as
water-reservoir li 452.
Geranium,cotyledon, asymmetry
i 115, li 406.
G. cicutarium ii 406.
G. pratense i 115, ii 406.
G. Robertianum 11406 ; leaf-apex,
precedence of growth ii 310.
Germination, of embryo-sac of
Angiospermae ii 635, of Coni-
ferae ii 631, of Cycadaceae ii
631, of Gnetaceae ii 629, after
stimulus of pollen-tube in
Coniferae ii 623; of gemma
and spore compared in Hepa-
ticae ii 112; intrasporangial,
of Angiospermae ii 623, of
Hymenophyllaceae ii 590, of
megaspore of Heterosporous
Pteridophytaii 623; intrasporo-
gonial, of Hepaticae ii 106, of
Musci ii 123; of microspore of
Heterosporous Pteridophyta ii
180; of pollen-grain, of Coni-
ferae ii 614, of Cycadaceae ii
612, of Spermophyta ii 612; of
seed, of Cyperaceaeii 412, 413,
414, and embryogeny in An-
giospermae ii 253, of Oro-
banche i 205, of Streptocarpus
ii 235, viviparous ii 255; of
674
spore, of Equisetaceae ii 197,
heteroblastic of Hepaticae
li 107, 108, of Homosporous
Leptosporangiate Filicineae ii
202, of Musci ii 116.
Germ-plant and light i 238.
Gesneraceaze, anisophylly, habi-
tual i 113; cutting i 46; leaf,
asymmetry i 120.
Geum, flower, arrangement of
parts ii 529; leaf, interrupted-
ly pinnatei 127, ii 331; ovary,
uniovular, development ii 560 ;
ovule, abortion ii 560.
G. bulgaricum, \eaf, biological
relationship ii 335,interrupted-
ly pinnate 1 127.
Ginkgo, anther, shield ii 523;
apical growth, duration ii 322;
archegonium ii 629; laminar
growth, eucladous ii 312;
flower, female ii 518; pollen-
chamber ii 627; pollen-sac ii
515; pollen-tube, acrogamous
ii 613; seed, protection of
ripening il 523; stamen li 515.
G. biloba, embryo, retarded ii
251; flower, female ii 518,
male ii 515
Ginkgoaceae, archegonium ii
629; flower, male ii 514,
morphology ii 524; leaf, de-
velopment ii 322.
Gladiolus, archesporium of pol-
len-sac ii 600; inflorescence,
unilateral i 136; root, dimor-
phism ii 271.
Gland, petiolar ii 362; mucilage
ii 374; stipular ii 362, 381.
Glechoma hederacea, growth,
plagiotropous ii 461; shoot,
plagiotropous ii 457.
Gleditschia horrida, leaflet asym-
metry i 122.
G. sinensis, accessory axillary
bud ii 434
Gletchenia, \eaf-apex,
protection of ii 318.
G. bifida, leaf, apical growth,
periodic ii 318.
Gleicheniaceae, antheridium,
opening of free 11177; aphlebia
ii 318; leaf, branching ii 317,
periodic apical growth ii 318;
pinnule ii 593; protection of
leaf-apex ii 318; prothallus,
apandrous ii 220 ; sporangium,
opening ii 588; sporangia,
disposition ii 496; sporophyll
and foliage-leaf alike in posi-
tion and origin ii 477.
Globularia, haustorium of ovule
ii 640.
G. cordifolia ii 640.
Glochidia of Azo//a ii 212, 218.
Gloriosa, tendril ii 428.
Glossodium, symmetry and direc-
tion i 72.
Testing,
INDEX
Gloxinia speciosa, peloria i 189.
Gnetaceae, archegonium ii 629 ;
flower ii 526; flower-envelope
of hypsophylls ii 527; leaf,
limited apical growth ii 322;
ovule ii 628; pollen-chamber
ii 516; pollen-sac ii 610.
Gnetum, embryo, suctorial organ
ii 409 ; embryo-sac, changes in
ii 629 ; hypocotylarhaustorium
li 402; ovule, three integu-
ments ii 629.
G. funiculare, searcher-shoot ii
454-
G. Gnemon, embryo, retarded ii
251; embryo-sac, changes in il
629, germination ii 629, 631.
Goebel, on leaf-development ii
304.
Goethe, definition ofmorphology
ih Sy
Goldfussia, anisophylly habitual
ek os
G. antsophylla, anisophylly i 99,
and light i 253; hyponasty
and epinasty i 85.
G. glomerata, anisophylly, habi-
tual i 112.
Gongora, pollen-sac, confluence
li 554.
Gonidia-formation in light and
darkness in Fungi i 257.
Gonium pectorale, colony i 27.
Gottschea, leaf ii 41 ; water-reser-
voir ii 58.
G. pachyphylla, \eaf ii 41.
G. scturea, lamella ii 58.
Gradatae, grouping of sporangia
in Pteridophyta ii 496.
Gramineae, awn ii 377; branch-
ing, axillary ii 433; coleoptile
ii 415; coleorrhiza ii 415;
cotyledon ii 414, peltate ii 334;
embryo, development ii 418,
differentiation ii 245, interpre-
tation ii 416, structure li 415;
epiblast ii 415, 418; flower-
structure and pollination ii 547 ;
hinge-cell ii 324; hypocotyl ii
415; inflorescence, dorsiventral
i 134, radial i 135; lamina,
differentiation ii 300; leaf,
asymmetry i 116; leaf-inver-
sion by torsion ii 296; leaf-
sheath ii 321; ligule ii 376, a
bud-cap ii 378, formation ii
418, function 11376, 377, sickle
ii 377; ovule, reduction ii 622;
pileole ii 415 ; scutellum ii 415.
Grammatophyllum speciosum,
nest-root ii 283.
Gravity, and anisophylly i 226;
and asymmetry of leaflet i
123; and chief and lateral
shoots i 225; and cutting i
223; and disposition of organs
i 219; and embryo of Pterido-
phyta i 219; and formative
stimulus i 219; and leaf of
Begonia i 219; and organ-
formation i 222, 224; and
prothallus of Filices i 221;
qualitative influence i 226;
and regeneration i 221; and
root-formation i 222; and
shoot, of Cactaceae i 221,
of trees i 224; and thallus,
of Algae i 224, of Hepaticae
i 2245 and tuber of 7h/ladi-
antha i 221.
Grimaldia, air-cavities ii 75;
involution of parts to resist
drought ii 65; perinium, vesi-
cular swelling ii 107.
G. dichotoma, \atent condition ii
65; spore ii 107.
G. fragrans, habitat ii 71.
Grimmia, hair-point ii 149 ; leaf-
surface, papilla ii 143; sporo-
gonium, radial i 236.
G. leucophaea, silver-glance ii 149.
Growth, apical, of Hepaticae ii
20, of leaf ii 131, 310, 313,
B17, \g2eebesal, of leat
ii 306, laminar ii 325, and
terminal i 41; compensation
of i 207, 208; in darkness, of
Basidiomycetes i 257; distri- -
bution in flower ii 552; inter-
calary i 41, of cotyledon ii
404, of leaf of Byd/zs ii 311, pre-
dominant in Monocotyledones
ii 298; in land and in water of
iMarsilia quadrifolia ii 498;
limited, and unlimited i 15, ii
132, 144, and causes i 142, li
190; organs of limited have
mid-portion best nourished ii
511; of torus, limited ii 541.
Growth-enzyme as stimulus of
gall-formation i 202.
Guarea, pinnae, sequence of ori-
gin ii 310.
Guilandina, pinnule as stipule ii
361.
Gunnera, aporogamy ii 615;
ovule, reduction ii 622; par-
thenogenesis ii 615; stipule,
axillary ii 374, origin ii 375.
G.chilensis,stipule, axillaryii 374.
G. macrophylla, stipule, absent
ii 374.
G.manicata,stipule,axillaryii375.
Guttiferae, hypocotylar storage
li 258.
Guttulina, spore-formation i 25.
Gymnanthe, sporogonial, sac ii
gi, tuberous shoot ii 92.
G. saccata, sporogonial sac ii gI.
Gymnocladus canadensis, acces-
sory axillary bud ii 434.
Gymnogrammeae, prothallus,
development ii 205.
Gymnogramme Totta, villosa,
sporangium protected by hairs,
ii 497.
ale Paige
eC te 8
a
Gymnomitrieae, colour and
light ii 78.
Gymnomitrium, perianth absent
ii 89.
Gymnospermae, antheridium,
mother-cell ii 614; arche-
gonium ii 629; archespo-
rium ii 601; cladode ii 448;
dislocator-cell suppressed ii
614; embryo, retarded ii
251; epidermal active cells in
pollen-sac ii 610; exothecium,
active cells ii 611; flower,
hermaphrodite ii 471, question
of origin i 60; juvenile form,
configuration i 153; leaf,
development ii 322, primary i
153, li 154, 155; leaf-apex,
precedence in growth ii 309;
megasporocyte, tetrad-division
ii 625; pollen-sac ii 610,
confluence ii 554, variation
in number ii 553; pollen-tube,
basigamous ii 614, reduction
ii 614; polyphyletic origin ii
31; sporangium, active cells
inwallii577; sporophyllii srr.
Gymnostomum, old genus of
Musci ii 161.
Gynaeceum, of Angiospermae
ii 555, suppressions in con-
struction il 557; apocarpous
ii 558, 559; comcrescence ii
557; dimerons ii 558; in epi-
gynous flower ii 558; in hypo-
gynous flower ii 558; mono-
merous ii 558; paracarpous ii
558,566; in perigynous flower
li 558; polymerous ii 558;
reduction ii 548, 557, 621;
syncarpous ii 558, 562; termi-
nal structure of flower ii 558.
H
Habitual anisophylly, defined i
108.
Hair, definition i 13, 16; of
calyptra ii 153; of Musci ii
138; of prothallus, of Cyathea-
ceae ii 199, of Osmunda, absent
ii 199, of Polypodiaceae ii 200,
of Pteridophyta ii 188 ; of root
and transpiration ii 269; as
sporangial protection ii 497.
Hairless root ii 269.
Hair-point of Muscii 261, ii14g.
Hair-root of Hymenophylla-
ceaeii 264. See also Rhizoid.
Hakea pectinata, transition from
entire to divided leaf ii 294.
Hf. trifurcata, heterophylly ii
357; leaf, cylindric ii 283, di-
morphism ii 293.
Halogeton sativus, halophyte i
266.
Halophila, macropodous embryo
ii 262; pollen ii 611.
Halophilous plants i 265.
INDEX
Halophyte, configuration and
environment i 265.
Halopteris, arrested formations i
37:
f1. filicina, branching of shoot i
88, and light i 237; long
shoot and short shoot i 36.
Hanburya mexicana, adhesive
disk on tendril i 268.
flaplolophium, adhesive disk on
tendril i 268.
Haplomitrium, free antheridium
ii 84; isophylly i r0oz; ortho-
tropy ii 18.
Haptera of Podostemaceae ii
222, 265, 281.
Hastening of embryogeny of
prothallus of Filicineae ii 189.
Haustorium, cotylarii 401, 410;
cotyledon, lobed ii 407; of
Cuscuta developed through
contact-stimuli i 268; of em-
bryo in Musci ii 157; of Fungi,
result of mechanical stimulus
i 269; of germinating pollen-
grain of Cycadaceae ii 612;
as new formation ii 224, 226;
of ovule ii 631; ovular, of
Angiospermae ii 638, of Casua-
rina ii 633; of parasite ii 224,
unlimited growth of ii 225;
pollen-tube, a ii 614; of seedi
208.
Hlecistopteris, prothallial gemma
ii 214.
Hedera, anchoring-root ii 286;
juvenile state an adaptation i
170; nourishing-root ii 286;
root, dimorphism ii 286 ; root-
primordia on stem ii 275;
shoot, dorsiventral i 99, plagio-
tropous and orthotropousi 160;
reversible dorsiventrality i 231.
Hi. Helix, \eaf-forms ii 160.
Hedwigia ciliata, \eaf-surface,
papilla ii 143; silver-glance
ii 149. :
Hedychium Gardnerianum,
plug-tip ii 309; ligule, signifi-
cance li 377.
Hedysarum capitatum, \eaflet,
asymmetry i 121.
H. obscurum, stipule ii 369.
H. sibiricum, inflorescence, uni-
lateral i 136.
Heleocharis, assimilating shoot-
axis with arrested leaf ii 447.
Helianthemum, stipule, arrest ii
2 & guttatum, leaf, stipulate and
exstipulate ii 365.
H. lasianthum, oelandtcum,
tomentosum, vulgare, stipule
ii 365.
Helianthus annuus, size of flower
and light ii 552.
Helicodiceros muscivorus, laminar
growth basal ii 324.
XX 2
675
Heliconia dasyantha, \eaf-lamina
split through rain-drops ii
328.
Flelicophyllum, \aminar growth
basal ii 324.
Heliotropism, of prothallus of
Equisetum ii 197; of soil-
root ii 276.
Helleboreae, antipodal cells,
persistent ii 636; few carpels
and many ovules i 59.
Helleborus, nectary ii 550, 560 ;
ovary, pluriovular ii 560.
Hf. foetidus, leaf, basipetal
branching ii 330.
Lelminthostachys, sporangio -
phore ii 483, sterile at tip
ii 606; sporangium, dehiscence
ii 585 ; sporophyll, configura-
tion ii 483, a transformed
vegetative leaf ii 485, and
wind-distribution of spore ii
474-
ff. zeylanica, sporangiophore ii
483.
Helwingia japonica, inflore-
scence, epiphyllous ii 436.
H. ruscifolia, inflorescence,
epiphyllous ii 437.
Hemionitis palmata, virescent
archegonium ii 187.
Hemttelta, basal pinnule ii 347.
H. (Amphicosmia) Walkerae,
leaf, development ii 315; pro-
thallus, branching ii 200.
H. capensis, adventitious pinnule
ii 347 ; water-absorbing leaflet
ii 347.
H. gigantea, prothallus, branch-
ing ii 200.
Hepatica, acotylous embryo ii
250; time of germination of
seed ii 253.
Hepaticae, absorptive hypo-
geous organ li 70; air-cavities
li 71; anatomic structure and
water ii 71 ; anisophyllyi tor;
antheridium, development ii
I2, opening ii Io; archego-
nium, development ii 16;
branching ii 21, in relation to
leaf ii 44; breathing-pore ii
72; bud, direct origin i 48;
colour, and heat ii 78, and light
ii 77; dioecism ii 80; dorsiven-
tral structure i 84; dorsiven-
trality dominant ii 18; elater,
organ of ejection ii 99; em-
bryo, chlorophyllousii 105 ; en-
dogenetic shoot ii 45 ; epiphy-
tism, and rhizoidal anchoring-
disk ii 45, and water ii 53;
exosporium ii 106; fertile
shoot ii 79; flagellum ii 42;
gemma ii 49; germ-phase
in regeneration ii 67; germ-
plant, and external stimuli i
217, and light i 239 ; germina-
676
tion, of gemma and spore
compared ii 109, of spore
heteroblastic ii 107, of spore
and formation of pro-embryo
compared ii 113; hydrotro-
pism ii 76; hygrophily ii
52; involucel ii 93; involu-
tion of parts to resist drought
ii 65; juvenile form, retention
ii 146; lamella on thallus
it” 55,57 salear eas he abi
partite ii 41, forming capil-
lary chambers ii 58, concre-
scence ii 42, displacement ii 41,
tubular ii 337 ; long shoot and
short shoot ii 43; and light ii
76; monoecism ii 80; muci-
lage-hair ii 27; mucilage-
secretion ii 27; paraphyllium ii
57; perianth, function ii 89;
propagation, vegetative i 48 ;
propagative capacity i 47;
protective, odour ii 79, taste-
substance ii 79; regeneration
ii 51; resting bud ii 44; re-
tention of water ii 53 ; rhizoid
ii 45; rudimentary ii 114;
scale ii 27, biological signifi-
cance of ii 34; sclerenchyma-
fibre ii 76; sexual organs,
diffuse and limited disposition
ii 80, dorsal in thallose ii 80,
protection ii 81, 88; sexual
shoot, construction ii 89, poly-
phyletic origin ii 93; spore ii
106, exine ii 106, perinium ii
106 ; sporogonium ii 93, de-
velopment ii 103, function ii
94; sterile cells of sporogen-
ous tissue 11597; stolon ii 23 ;
symbiosis ii 78; symmetry of
organs ii 18; tannin-body ii
79; thallus and gravity i 224;
transformation, of leaf to
water-reservoir ii 58, of rhi-
zoids ii 47; tuber ii 43, 66,
history of discovery ii 66:
vegetative body, variety ii 7;
vegetative organs 11 18; and
waterii 52; water-sac, as insect-
trap ii 64, with hinged valve
ii 61; xerophilous adaptation
ii 65; younger group than
Musci ii 7.
Heracleum, flower, unessential
zygomorphy i 130 ; leaf-base,
function ii 299; leaflet, asym-
metry i 122; root, periodic
shortening ii 271.
Herb, plagiotropous shoot ii
457-
Herbert Spencer on aniso-
phylly i 99, 250; on relation
of form and function i 4.
Hermaphrodite, flower of
Gymnospermae i 60, ii 471;
flower of Selaginelleae, original
ii 508.
INDEX
Herposiphonia, organs, position
i go.
Besgeris matronalts ,
of ovule i 182.
LHeteranthera zosteracfolia, juve-
nile form i 164.
fH. veniformts, reversion i 172.
Heteroblastic development i
144; spore-germination in He-
paticae ii 107.
Heteroblasty in juvenile forms i
143.
Fleterocentron diversifolia, gra-
vity and cuttings i 223.
Heterodromy in phyllotaxy of
Pteridophyta i 78.
Heterophyadiec Equiseta ii
5ol.
Heterophylly, i 102, ii 345,
351; of dicotylous aquatic
and marsh plants ii 358; of
epiphytic Filices ii 349; of
monocotylous aquatic and
marsh plants ii 357; of Pteri-
dophyta ii 346, 350; of Sper-
mophyta ii 351.
Heterosporous, Leptosporan-
giate Filicineae, sporophyll ii
487; Pteridophyta, antheri-
dium, development ii 180, spo-
rangium, development ii 602.
Heterospory of Pteridophyta ii
577, 603.
Heuchera Menziesii,
hypsophyll ii 393.
Hexamery and pentamery in
Caryophylleae ii 535.
Hieractum, \eaf-formation and
light i 256.
Hieracium umbellatum, gall-
formations of capitulum i 197.
Hinge of valve of sporangium
of Selaginella ii 580.
Hinge-cell, leaf of Mona
ledones ii 324.
flippuris, unitegminy by con-
crescence of ovule and integu-
ment ii 618.
H. vulgaris, hairless root ii 269.
fliptage obtustfolia, searcher-
shoot ii 455.
Hoffmann, experiment in pelo-
Tia 1 189.
Hofmeister, on development
of leaf ii 304; on directive in-
phyllody
divided
fluence of light in Bryophyta
MOVE
Homoblastic development i
143; of Equisetineae i 151; of
Lycopodineae i 151.
Homoblasty in juvenile forms i
143.
Homodromy in phyllotaxy of
Pteridophyta i 78.
Homology i 14; and analogy i
5; of gametophyte and sporo-
phyte i 20; of megasporocyte
and microsporocyte of Angio-
spermae ii 625; not based on
one character i 14; varying
use of term i 18.
Homophyadie Equiseta deve-
loped through fertile shoots in
summer ii 502.
Homosporous Pteridophyta,
antheridium, development ii
178.
Honey-gland, stipular ii 381.
Hook, climbing ii 324, 371, 419;
calycine of Agrimonia ii 452;
leaf ii 419.
Hordeum, ligule,
function ii 378.
HT, hexastichum, embryo, deve-
lopment ii 418.
forminum pyrenaicum, inflo-
rescence, unilateral ii 136.
Horn of sporophyll of Cevato-
cama ii 512.
Horned petal, development ii
560.
Hosackia subpinnata, leaflet,
asymmetry i 121; leaf, uni-
laterally pinnate i 121.
Host of parasite ii 225.
FHfottonia, leaf, basipetal branch -
ing ii 330.
Hloustonia, ovule, ategminy ii
619.
Humulus Lupulus, stipular, by-
psophyll ii 394; stipules of
adjacent leaves, concrescent ii
368, kataphyll of hypogeous
shoot ii 386.
Humus-plant, hairless root ii
269.
Hyacinthus, cotyledon, epigeous
green ii 409; flower in dark-
ness i 243.
HZ, orientalis, bulbil in regenera-
tion i 45 ; root-hair suppressed
in water ii 269; vegetative
propagation and seed-forma-
tion i 45.
Hydrangea, flag-apparatus, cor-
relation of growth i 211 ; flag-
flower ii 571.
Hydrobryum, root, dorsiventral
ii 281 ; flattened in relation to
light i "247.
Hydrocharis, hair on water-root
ii 269 ; root-apex ii 267.
H. Morsus-ranae, growth of
aquatic root in soil ii 267.
Hydrocleis Humboldti, rever-
sion-shoot i 172.
Hydrocotyle, stipule, develop-
ment ii 364.
H. vulgaris, \eaf, segmentation
ii 336.
Hydrophylleae, inflorescence,
dorsiventral i 136.
Hydrotropism, of Hepaticae li
76; of prothallus of Zguzse-
tum ii 197; of soil-root ii
276.
protective
Hydrurus, branching i
colony i 30.
Hi. foetidus, vegetative point i
343
31.
Hygrophily of Hepaticae ii 52.
Hymenocallis speciosa, embryo,
retarded ii 251.
Hymenocarpus circinatus, leaf,
asymmetry i 121.
Hymenolepis spicata, prothallus
ii 20 ; sporophyll ii 496.
Hymenomycetes, abnormal fructi-
fication in darkness i 258;
fructification and light i 257.
Hymenophyllaceae, antheri-
dium, opening of free ii 177 ;
and apospory ii 609; gemma,
prothallial ii 214; hair-root ii
264; leaf, adaptation to en-
vironment ii 347, develop-
ment ii 313; leaf-form, bio-
logical significance ii 346;
prothallus, surface and fila-
mentous ii 210; ptyxis, cir-
cinate absent ii 321; rootless ii
263, teduced form ii 264 ;
sporangium, asymmetry ii
575, basipetally developed ii
496, opening ii 588, position
ii 494, and peltate sporophyll
ii 575; spore, intrasporangial
germination ii 590; symbiosis
with fungi ii 219.
Hymenophyllum, leaf, apical
growth periodic ii 318; pro-
thallus ii 206.
HI, axillare, prothallus ii 207.
HZ. interruptum, Karstenianum,
plumosum, leaf, apical growth
periodic ii 318.
Hymenophytum, apical cell ii
21; branching ii 21; peri-
chaetium ii 82 ; rhizome, sym-
podial ii 25; shoot, ventral,
bearing sexual organs ii 82;
spore, ejection ii IoI ; sporo-
gonium with elaterophore ii
Iol.
H. flabellatum, hymenophyl-
loid habit ii 24.
HT. Phyllanthus, thallus ii 22.
HHyoscyamus, branching ii 435;
flower, dorsiventrality ii 543;
inflorescence, dorsiventral i
136; placentoid ii 599.
ff, albus, archesporium ii 599 ;
pollen-sac, development ii 599.
Hypecoum, androecium ii 540.
Hypericaceae, stamen, brancli-
ing ii 534.
Hypericum, dédoublement ii
5333; gynaeceum, develop-
ment ii 565; stamen, branched
ii 533; style, formation ii 565.
Hi, aegyptiacum, staminal pha-
lange ii 534.
| so Sinaia spore, shedding ii
165.
INDEX
Hypnum, annulus, function ii
101.
Hl. aduncum, cupressiforme,
revolvens, uncinatum, \eaf-
apex, photophobous ii 135.
Hf, crista-castrensis, involution,
dorsiventral i 86.
HI, splendens, axis, dorsiventral i
84; paraphyllium ii 146;
shoot, dorsiventral ii 138, pla-
giotropous and light i 233;
tiered growth i 68; transition
from orthotropy to plagio-
tropy i 69.
Hypocotyl, of Gramineae ii 415;
tuber ii 258, 260.
Hypocotylar, food-storage of
Dicotyledones ii 258, of Mono-
cotyledonesii 260; haustorizrm
of Gnetum ii 402, 0f Welwit-
schia ii 402; water-storage of
Cactaceae ii 260.
Hypogaeae, growth in dark-
ness i 257.
Hypogeous, absorptive organs
of Hepaticae ii 70; cotyledon
ii 410; fruit ii 493; inflores-
cence ii 571; prothallus ii
798 ; shoot as boring-organ ii
266; sporocarp ii 493; stipular
kataphyll ii 386.
Hypogynous flower ii 558.
Hyponasty i 84, 85.
Hypopeltate, leaf ii 334; sporo-
phyll in Lycopodineae ii
503.
Hypopodium ii 304.
Hypopterygium, anisophylly i
100.
H. fuscolimbatum, anisophylly i
Iol.
Hypothesis, of development of
leafy sporophyte from moss-
sporogonium ii 291; of evolu-
tion, of flower of Coniferae ii
525; of hypsophyll! of Mono-
cotyledones ii 396; phyletic,
regarding sporangium ii 605.
Hypsophyll ii 389; bristle in
Cynareae ii 398; development
ii 391; division and arrest ii
393, 397; flower-envelope de-
veloped from ii 549; form in
relation to function ii 396;
formed, by leaf-base ii 342,
394, by whole leaf-primor-
dium ii 392; originates from
foliage-leaf ii 390; of Musci
ii 135; position ii 390; pro-
tective organ ii 397; stipular ii
394-
..
Iberis, flower, unessential zygo-
morphy i 130.
Idealistic morphology i 5.
flex Aquifolium, leat of young
plant, prickly i 264.
677
Impatiens, cotyledon, emargi-
nate ii 407; gynaeceum and
placentation ii 564.
I. glandulosa, foliar gland ii
362.
I. parviflora, flowering and light
i 244.
Indented leaf of Bryophyllum
crenatum ii 337.
Indigofera diphylla, leaf, uni-
laterally pinnate i 121 ; leaflet,
asymmetry i 121.
Indusium, homology with in-
tegument of ovule ii 616; use
ll 497, 592.
Inferior ovary ii 567.
Inflorescence i 128; bristle-
shoot of Gramineae i 20; com-
pensation of growth in i 208;
climbing organ ii 456; of
Coniferae ii 518 ; of Cruciferae
i 197; dorsiventral i 134, cir-
cinate i 136; epiphyllous ii
436; phyllocladous ii 450;
radial i 134; symmetry i134;
unilateral, origin of i 1338.
Inflorescence-axis transform-
ed into assimilation-axis li
447-
Inheritance of malformation i
184.
Insect inducing phyllody i 181.
Insect-trap ii 64, 237..
Insectivorous plants, tubular
leaf ii 338.
Insertion of leaf on dorsiventral
shoot i 93.
Integument,ofmegasporangium
ii 614; of ovule ii 616, develop-
ment 617, significance ii 615 ;
of sporangium of Lepidocarpon
ii 616.
Integumentary wing of ovule
of Coniferae ii 628.
Intercalary § growth. See
Growth.
Intercellular mucilageof Hepa-
ticae li 76.
Internal symmetry and aniso-
phylly i 254.
Internode i 35; length and
phyllotaxy ii 442; torsion in
plagiotropous shoot i 93, in
radial shoot il 442.
Interpetiolar stipule ii 368.
Interruptedly pinnate leaf,
cause i 127; of Dicotyledones
ii 331; interpretation il 332.
Intracellular mucilage of Hepa-
ticae ii 76.
Intramatrical vegetative body
of parasite ii 225.
Intranucellar germination of
embryo-sac ii 622.
Intraseminal absorption of en-
dosperm ii 402.
Intrasporangial germination.
See Germination.
678
INDEX
Intrasporogonial germination. | 7. AMalinverniana, microspore,
See Germination.
Intravaginal squamule ii 359.
Introrse anther ii 553.
Inula, branching without axil-
lant leaf ii 433.
Inverse-dorsiventral flower of
Selaginella ii 507; growing
out vegetatively ii 508,
Inversion of leaf ii 296; ex-
planation of ii 297.
Involucel, of Hepaticae ii 93;
of Spermophyta i 59.
Involucre, arrest through loss
of function i 59, ii 397; de-
velopment in Lagascea ii 543;
of Pulsatilleae ii 550.
Involution of leafi 85, ii 298,
Stahl’s hypothesis of ii 298 ; of
parts to resist drought in
Hepaticae ii 65.
Lpomoea Pes-Caprae, plagiotropy
11 459.
Irregular flower i 128.
germination ii 180.
Isophyllous Selaginelleae,
flower ii 505.
Isophylly, of Hepaticae i 102;
of Selaginella i 105, ii 505.
Isosporous, Leptosporangiate
Filicineae, sporophyll ii 485 ;
Lycopodineae, spore-ejection
ii 580; Pteridophyta ii 577.
J:
Juglandeae, basigamy ii 615.
Juglans, laminar growth eucla-
dous ii 312; leaflet, asymmetry
i 122; flower, male and female,
position ii 472.
J. cinerea, \eaf-apex, precedence
in growth ii 310.
J. vegia, accessory cotyledonary
bud i 434; correlation in axil-
lary bud i 209; kataphyll ii
388.
colour and light ii 78; gemma
of foliose ii 50; germ-plant
and light i 240; leaf, displace-
ment and light ii 41, two-lobed
ii 41; Leitgeb’s divisions of
acrogynous and anacrogynous
ii 80; light and foliose ii 77 ;
mucilage-papilla ii 28; reten-
tion of water ii 53; reversion
of leaf to thallus-form ii 42;
spore-germination ii 107;
sporogonium, development ii
97, 103, mature ii 96, opening
ii 97, without elaterophore ii
99, contains spores and elaters
li 99, sterilization ii 103.
Juniperus, dislocator-cell ii 614;
megasporocyte ii 628; pollen-
sac, confluence ii 554, develop-
ment ii 556, number varies ii
553, Opening ii 610, terminal
ii 516; stamen, peltate ii 334;
transition from sporangium to
sporangiferous leaf ii 606.
friartea, prop-root ii 277; thorn- | Juncagineae, cotyledon, differ- |7. chinensis, virginianum, juve-
root ii 288.
entiation ii 408.
nile form i 154.
Irideae, flower-structure and | /zscus, leaf, cylindric ii 447, |/. communis, juvenile form i 154;
pollination ii 547; thorn-root
li 288.
Tris, inheritance of staminal varia-
differentiation ii 298, radial
ii 295, 328, orthotropous i
68.
tion i187; leaf, bilateral, i68,| 7. dzfonzus, flower, malformed
li 294, 325, development ii 328,
dorsal wing i 87.
I. variegata, leaf, development ii
320.
Isoetaceae, spermatozoid, pluri-
ciliate ii 172; spore, water-
distribution ii 575; systematic
position ii 173.
Lsoetes, antheridium, develop-
ment ii 181; apospory ii,607 ;
archesporium 1i 601 ; embryo,
differentiation il 243, position
of organs ii 247 ; gametophyte,
male ii 181 ; kataphyll ii 351;
leaf, terminal i 16; leaf-borne
bud ii 431, 436; ligule ii
360; megaspore, differentia-
tion ii 628; microspore, ger-
mination 11 181; prothallus ii
212, development ii 213; rhi-
zoid rare on female prothallus
ii 189; sporangium, develop-
ment ii 604, sterilization ii 555,
605; stem-apex, suppression
of lateral shoots ii 431; sys-
tematic position ii 172; tape-
tum, secretion ii 596; trabecu-
lae of sporangium ii 555, 597,
605; transition from sporo-
phyll to foliage-leaf ii 510.
I. Hystrix, sporangium, develop-
ment ii 604.
J. lacustris,aposporyi 214, ii 607 ;
sporangium, development ii
604; vegetative development
increased through suppression
of reproductive organs i 214.
by starvation i 191.
J. capitatus, flower, not mal-
formed by starvation i rgI.
J. glaucus, embryo, incomplete
ll 253.
J. lamprocarpus, malformation
caused by Livia juncorum i
195.
J. supinus, malformation caused
by Livia juncorum i 195;
tuber i 262.
Jungermannia, archegonia in
groups with perichaetiumii 89;
elater free ii 99.
J. albicans, leaf ii 41.
J. bicuspidata, amphigastrium ii
41; elater ii 99, 102 ; etiolated
plant and light i 241; leaf-
displacement through light ii
42; light, directive influence of
i 234 ; oil-bodies absent ii 79;
regeneration ii 52; shoot, en-
dogenetic ii 45 ; sporogonium
li 99.
J. curvifolia, water-sac ii 60.
J. hyalina, spore-germination ii
110.
J- Michauxiz, oil-bodies absent
ii 79.
J. Sphagni, sporogonium and
gemma together ii 51.
/. trichophylla, anisophylly itor;
elater ii 99 ; leaf ii 41; spore-
germination ii IIo.
Jungermanniaceae, anisophyl-
stamen, variation in one flower
ii 516.
Jussteued, ait-root ii 280; influ-
ence of medium i 260.
J. grandifiora, breathing-root
absent in dry soil i 260.
J. salicifolia, ait-root ii 280;
sepal and petal, venation ii
344- t
Juvenile form i141; absent, in
some Algae i 148, in some An-
giospermae i 159; of Angio-
spermae i 155; of aquatic
plants i 164; with arrest of
adult leaves i 166, ii 447, 450;
arrested formations in i 145 ;
of Bryophyta i 151 ; described
as distinct species i 149, 159,
ii 115; differences in con-
figuration i 145; direction of
growth i143; distinguished by
different phyllotaxy i 161;
duration i 145; of Gymno-
spermaei 153 ; heteroblasty in
i143; homoblasty in i 143; of
marsh-plants i 164; of Pteri-
dophyta i151; result ofadapta-
tioni170; retention, in Algae
i 149, in Hepaticae i 146, in
Lemnaceae ii 236, in Musci i
147, 151, in Passerina i 167,
in Phylioglossum ii 236; re-
version to i 145, 171, li 447,
in feeble light i 242, in
Monocotyledones ii 447; sex-
ual organs on in Coniferae i
146; tendril absent in i161 ; of
Thallophyta i 148; of xero-
philous plants i 165.
ly i 100; antheridium, develop- | Juvenile stage, difference from
ment ii 13, opening ii 10;
adult i 143.
K.
Kataphyll ii 384; from leaf-base
ii 386 ; from leaf-primordium ii
384; of Monocotyledones i
389; origin ii 384; peltate ii
334, 500; protective ii 385; of
Pteridophyta ii 350; stipular ii
385 ; storage-organ li 350, 398.
Kaulfussia, synangium ii 585.
Kennedya rubicunda, juvenile
form i 155.
Kitaibelia _vittfolia,
branching ii 537.
Kleinia, shoot as water-reservoir
ll 45.
Klinotropism i 116,
Klugia, anisophylly, habitual i
Et 3
K. Notoniana, cutting of inflo-
rescence-axis i 46,
Knautia arvensis, archesporium
of pollen-sac ii 599; doubling
caused by /eronospora viola-
cea i 192; fungus-attack and
staminal primordium i I1;
heterophylly ii 352.
K. arvensis, var. integrifolia,
shade-form li 352.
&. sylvatica, heterophylly ii 352.
Knee-root ii 280; absent from
Taxodium distichum in dry soil
i 260.
Kny, experiment, silver fir and
light i 250.
Kurzia crenacanthotdea, juvenile
form of liverwort ii 115.
L.
Labiatae, corolla, confluence of
parts ii 538; flower, dorsi-
ventral and radial i 133, sup-
pression of organs i 57; hair
116 ; inflorescence, unilateral i
136; ovary and placentation
ii 563; shoot, plagiotropous
il 459-
Labiate flower i 131.
Lachenalia, antagonism of seed-
formation and vegetative pro-
pagation i 45.
L. luteola, antagonism of seed-
formation and vegetative pro-
pagationi 45, 213; bulbili 45.
Lagascea, involucre, development
1 §43-
Laguncularia racemosa, pneu-
matophore ii 278.
Lamella, of leaf, of Musci ii 144,
of Hepaticae ii 58 ; of thallus
of Hepaticae ii 55.
Laminar growth, apical ii 310;
basal ii 324; types ii 312.
Laminariaceae, higher differ-
entiation i 21.
Lamium maculatum, peloria i
189.
Piaststeatcn of Riccia i 269, ii
34> 45>
carpel,
INDEX
Land-plants, cellular structure
i 24.
Larix, flower female, position ii
523; juvenile form i 154;
megasporocyte, solitary li 628;
pollination ii 522; prothallus,
male ii 614; short shoot
precedes long shoot in unfold-
Ing ii 445.
L. europaea, short shoot and long
shoot ii 444.
Lastraea pseudomas, var. cri-
stata, apospory ii 608.
Latent, capacity of branching ii
431; primordium i 97, of
root on shoot ii 275.
Lateral, anisophylly defined i
108; flower, dorsiventrality i
133; organ, displacement i
74, development in serial suc-
cession li 542; root, exotropy
ii 276, not geotropic ii 276;
shoot, and chief axis i 34, dor-
siventral i g2, suppression at
stem-apex ii 431.
Lathraea, embryo, reduced ii
254; organ-formation in ab-
sence of light i 257.
L. Squamaria, storage-kataphyll
11 399-
Lathyrus Aphaca, correlation i
210; malformation i 178;
seedling i 126, 211; stipule,
asymmetry i 125, function
ii 366; tendril i 161; transi-
tion-form of leaf i 161.
L. A. unifoliatus, malformation
et Se
L. Clymenum, \eaf-form ii 162 ;
stipule arrested, meaning ii
365.
L. heterophyllus, stipular out-
growth ii 367.
L. latifolius, stipular drip-tip ii
367.
LZ. Nissolia, transition-form of
leaf i 163.
LZ. Ochrus, transition-form of
leaf, i 161.
L. pratensis, stipular appendage
ii 366.
Laurineae, pollen-sac, position
Ml §54-
Lavender, shoot, plagiotropous
development ii 459.
Leaf, an abstract idea i 8;
adaptation in Filicineae ii
346; adventitious, non-exist-
ent li 305; anatomic construc-
tion il 292; apical growth, of
Filices, ii 317, of Filicineae ii
310, 313, of Musci ii 131, of
Spermophyta, ii 310; apical
segmentation in Musci ii 132;
of aquatic Filices ii 348;
arrest, of adult i 167, on assimi-
lating shoot-axisii 446; asym-
metry i115, ofentirei 116; basal
679
growth ii 306 ; bifacial ii 293;
bilateral ii 293, 328, profile-
position ii 293; bipartite of
Hepaticae ii 41 ; branching, of
Dicotyledones ii 329, forming
false whorl ii 333, of Gymno-
spermae ii 322, of Ophio-
glossaceae ii 482, of Pterido-
phytaii 316; change, offunction
i 8, 9, of position in Vaccinium
Myrtillus i 94; of Charaits;
chlorenchyma ii 293; crested
ii 345; configuration and rela-
tionships of life ii 345; corre-
lation, and form i 215, of
growth i 209; cylindric ii
293; development ii 302, his-
tory ii 302-4, of Pteridophyta
ii 327, of Spermophyta ii 321,
and venation, ii 338; dimor-
phism of Hakea trifurcata ii
293; distinction from stem i
16; distribution of growth in
ii 306 ; divided submerged ii
358; dorsiventrality ii 293;
drip-tip ii 345; dual function
ii 8, 398; earlier functioning
parts appear earliest ii 305;
epipeltate ii 334; of epiphytic
Filices ii 350; of Filices with
unlimited growth i 15; fore-
runner-tip ii 308; free-living
ii 235; growth limited i 15;
growth-area and form ii 311;
of Hepaticae ii 35, 38, 40;
hypopeltate ii 334; inception
of leaf-surface in Spermophyta
ii 311; insertion on dorsi-
ventral lateral shoots i 93; in-
terruptedly pinnate i127; in-
version li 296; inverted struc-
ture ii 296; lamella ii 144;
monocotylous form in Dicoty-
ledones ii 295; of Mausci,
simple and unbranched ii
134; origin independent of
vegetative point il 253, 305;
outgrowth as water-reservoir
ii 58; peltate ii 333, long-
stalked ii 335, short-stalked
ii 334, biological relation-
ships ii 335; and phyllo-
clade ii 450; plug-tip ii 309;
position, in deciduous trees i
96, mechanical hypothesis of
i 74; profile-position of radial
ii 293, 328, by torsion ii
295; ptyxis and growth ii
311; radial ii 293, 295, 328,
construction of, how brought
about i I1I4; segmentation
of primordial ii 321 ; sequence
from entire to divided in
Monocotyledones ii 327; size,
and correlation of growth i
211, and venation ii 342;
splitting ii 325; stalked and
unstalked compared ii 301 ;
680
submerged divided ii 358;
symmetry i 114, of construc-
tion li 293 ; terminali 16, 41,
ii 305, 541; tuber ii 398;
upper il 321; vascular bun-
dle ii 292, without vascular
bundle ii 292; water-absorb-
ing ii 347, 349; water-relation
in Musci ii 143; wing, dorsal
i 87.
Leaf-apex, precedence ingrowth
ii 309.
Leaf-auricle, of Angiospermae
ii 361; of Hepaticae ii 29, 58.
Leaf-base, forming hypsophyll
ii 394, kataphyll i 11 386; func-
tion ii 299; of Dicotyledones
li 299; of Monocotyledones ii
298; of Spermophyta ii 321.
Leaf-borne, bud i 42, ii 241, 431,
436; flower, falsely described
ii 436; inflorescence ii 436;
shoot ii 241, 435; sporangium
becoming axis-borne ii 556.
Leaf-bud and light i 232.
Leaf-climber ii 419, 593.
Leaf-cushion, of Lycopodium i
103; origin ii 306 ; of Coni-
ferae ii 569.
Leaf-cutting i 45, 46; differ-
ences according to age i 46.
Leaf-differentiation ii 298; of
Musci ii 134.
Leaf-form, in Australia ii 293;
of Dicotyledones ii 329; in
dwarf-conditions of Cruciferae
i 259; in Europe ii 294; evolu-
tion in Aroideae i 158; of
Gymnospermae ii 322; modi-
fied, on renovation-shoots i
190; of Monocotyledones ii
323; and nutrition ii 352; of
Pteridophyta, ii 313; in rela-
tion to shoot-axis of Cotyledox
umbilicus i114, ii 336; series
in Filicineae ii 320; signifi-
cance in fan-palm ii 326;
transitions i 10.
Leaf-formation and light i 256.
Leaf-hook ii 419.
Leaf-lamina, branching ii 312.
Leaf-nectary, ii 430.
Leaf-organs, terminal i 41.
Leaf-prickle of Victoria regia
i 264.
Leaf-primordium, arrest pro-
duces hypsophyll ii 393;
division in Benincasa cerifera
ii 393; growth, method ii
306; origin in embryonal
tissue ii 305, in one cell in
Filicineae ii 305, in cell-group
in most Pteridophyta ii 306,
in cell-group in Spermophyta
ii 306.
Leaf-root ii 237.
Leaf-sheath ii 298; and axillary
structure ii 299; closed ii
INDEX
323; of Dicotyledones ii 299 ;
of Monocotyledones ii 2098,
323; of Spermophyta ii 321;
storage-organ i 8, ii 398.
Leaf-spindle-climber ii 421.
Leaf-stalk, correlation with la-
mina ii 300; developed from
leaf-lamina, ii 299; develop-
ment, cause ii 300, and en-
vironment ii 301 ; of Dicotyle-
dones ii 300; function ii 299;
of Monocotyledones ii 299;
origin late in Spermophyta ii
321; of Pteridophyta ii 314.
Leaf-stalk-climber ii 421.
Leaf-structure, in relation to
environment in Pteridophyta ii
347; and water in Musci, ii143.
Leaf-structures, epidermal
origin in £phedrai 17.
Leaf-tendril i 161, ii 419, 421.
Leaf-tentacle ii 419.
Leaf-thorn, ii 428; of U/ex and
medium i 263.
Leaf-tip, of Musci, development
i 131, ii 306; precedence in
growth ii 308.
Leaf - transformation. See
Transformation, Trans-
formed.
Leaf-transition forms. See
Transition.
Leaf-tuber ii 308.
Leaf-vagina. Secaoataneatil
Leaf-whorl, false ii 333, 371.
Leafless shoot, functions as root
in Trichomanes membrana-
ceum ii 264; of limited growth
i 20, ii 450.
Leaflet, asymmetry i 124; of
unequal size i 126.
Lecythidaceae, hypocotylar
storage li 259.
Lecythis, hypocotylar storage ii
260.
Leersta, scutellum ii 415.
Leguminosae, cladode ii 451 ;
cotyledon, asymmetry ii 406;
flower, dorsiventral from the
outset i 129; fruit, colour and
transpiration ii 571; inflo-
rescence, unilateral i 136; leaf-
arrest on assimilating shoot-
axis ii 446; leaf, asymmetry i
121 ; shoot as water-reservoir
ii 452; stipel ii 380; stipular
appendage ii 366; stipule,
asymmetry i 121, 125, ine-
quality in size ii 366; tendril,
development ii 423.
Leitgeb, groups of Acrogynous
and AnacrogynousJungerman-
nieae ii 80.
Lejeunza, anchoring-disk ii 45 ;
archegonium, solitary ii 88;
auricle ii 58; elater attached
to surface of capsule ii 100;
gemma ii 51; pro-embryo i
146, ii 108; regeneration ii
52 resting-bud ii 44; spore,
germination ii 108; sporo-
gonium without elaterophore
ii 100.
L.( Cololejeunia) Goebeliz,( Odon-
tolejeunta) metrabilis, gemma
ii 50.
L. lumbricoides, capillary water-
chamber ii 58.
L. Metzgeriopsis, juvenile form,
retention i 146, ii 113; male
plant ii 109 ; gemma, limited
growth i 142; rudimentary
form li IT4.
L. paradoxa, water-sac ii 64.
L. serpyllifolia, spore, germina-
tion i 146, ii 108.
Lemanea, juvenile form i 148 ;
pro-embryo, i 148
Lembidium dendroideum, fla-
gellum ii 43.
Lemna, free-living leaf i 16, ii
235; root, hairless ii 269;
vegetative body, development
ii 236.
L. minor, growth of aquatic root
in soil ii 267.
L. trisulca, growth of aquatic
Toot in soil ii 267 ; pects of
plant ii 236.
Lemnaceae, free-living leaf ii
235; juvenile form, retention
ii 236;
tative body, morphology ii
235; vegetative point, absent
i4t.
Lentibularieae, flower, de-
velopment ii 542, dorsiven-
tral ii 542; gynaeceum, para-
carpous ii 566; placenta-
tion ii 566; rootless ii 265;
transition, from root to leaf ii
240, from leaf to shoot ii 236.
Lenticel on root of Lumnitzera
li 280.
Lentinus, abnormal sporophore
in darkness i 258.
Leonurus Cardiaca, peloria igo.
Lepicolea, colour and environ-
ment ii 78; flagellum ii 43.
L. cavifolia, flagellum ii 42.
L. ochroleuca, thickened wall-
membrane ii 76.
Lepidium sativum, succulence of
leaf depending upon salt i 266.
Lepidocarpon, sporangium, inte-
gument ii 616.
Lepidodendron, sporangium, tra-
beculae il 597.
Lepidophyllum quadrangulare,
leaf, inverted structure ii 296.
Lepidozia, rudimentary forms ii
115; shoot, endogenetic ii 45 ;
spore, germination ii 110.
L. bicruris, leafii 41.
Lepismium radicans, dorsiven-
trality of shoot, reversible i231.
root-cap ii 267; vege-
Leptosporangiate Filicineae,
antheridium, free ii 177;
archegonium, development ii
184; embryo, orientation of
organs ii 245; leaf, develop-
ment ii 316; sporangia of
different age, mixed ii 496;
Sporangium, opening ii 387,
position ii 493, seam-cells ii
588, stalked ii 574, stomium
ii 588.
Leptosporangium ii 602.
Leptoxylem, ii 157.
Leucobryaceae, leaf-structure
ii 145; water-cell, perforated
ii 145.
Leucobyyum, dwarf male plant
ii 151.
L. glaucum, xerophilous structure
maintained in water ii 148.
Leucodendron argenteum, coty-
ledon ii 402.
Leucojum, \eaf-sheath and axil-
lary structure ii 299; seed-
germination, time of ii 253.
L. vernum, root, duration of
life ii 290, branching sup-
pressed ii 274.
Liane, i 159, 1i 389, 419, 421,
453, 593; foliage, permanent
retardation ii 454, temporary
retardation ii 454; shoot,
transformed radial ii 453.
Liane-growth, temperate and
tropical ii 453.
Lichenes, foliose, usually dor-
siventral i 71; fruticulose,
usually radial, i 71; podetium,
function i 72; symmetry and
direction i 71.
Licmophora flabellata,
i 30.
L. vadicans, colony i 30.
Light, and anisophylly i 250;
and apogamy i 229; and
arrest of organs i 232; and
branching of marine Algae i
237, of protonema i 234; and
branch-system of Cupressineae
i 230; and change of function
i255; and chasmogamy i 245;
and cleistogamy i 245; and
colour, of flower ii 551, of fruc-
tification in Sphaeriaceaei 258,
of Hepaticae ii 77; and con-
figuration, of Algae i 256, of
Bryophyta i 234, of Fungi i
257, of Hepaticae ii 77, of
plants i 227; and develop-
mental stages i 238; and
direction of shoots i 71;
directive influence i 227, 257 ;
and dorsiventral, inflorescence
i 136, shoot i 230; and dorsi-
ventrality i227; and flattening,
of aerial root ii 285, of organs
i 245; and flower i 245, ii 551;
and flower-formation i 242,
colony
INDEX
Vochting’s experiments i 244 ;
and germ-plant, of Algaei238,
of Hepaticae i 239, of Musci i
241 ; and gonidium-formation
i 257; and leaf-formation i
256; and opening, and closing
of flower i 245, of sporangium
ii 575; and organs of dicoty-
lous parasite i 257; and pla-
giotropous shoot of Musci i
232; and polar differentiation
i 229; and pro-embryo of
Batrachospermum i 238; and
prothallus of Pteridophyta i
241 ; and protonema of Bryo-
phyta i 239; qualitative in-
fluence i 238; and regenera-
tion of Algae i 237; and root-
formation i 231 ; and seedling-
plant of Spermophyta i 242;
and size, of corolla ii 551, of
flower ii 551; and sporangium
of Pteridophyta i 245; and
spore-germination i 229; and
sporogonium of Musci i 236 ;
and surface-increase of organs
i 245; and unilateral inflo-
rescence i 137; and zygo-
morphy ii 552.
Lignin in sporangial wall of
Lycopodium ii 578.
Ligulatae, systematic value li
173.
Ligulate flower i 131.
Ligule, ii 376; of Gramineae ii
376, 418; of Jsoetes ii 360; of
Palmae ii 378, 418; of Se/a-
ginella ii 360; of Spirodela ii
236; of Zingiberaceae ii 377.
Ligustrum, kataphyll ii 385;
ovular development ii 623.
Liliaceae, cotyledon, epigeous
green ii 409; leaf-lamina,
differentiation ii 300; mega-
sporocyte becomes embryo-sac
ii 625.
Lilium, bulbil ii 269.
L. auratum, lancifolium, flower
becomes dorsiventral in de-
velopment i 129.
candidum, antagonism of
vegetative propagation and
seed-formation i 45, 213; leaf,
change of function i 8, ii 398;
storage-leaf of bulb ii 398.
Limitation of development of
organs i142; of organsi 14.
See also Growth.
Limnanthemum,
flower
436.
Limnophila heterophylla, false
leaf-whorl ii 333, 370; hetero-
phylly ii 358.
Linaria, root-bud, exogenetic ii
277.
L. spuria, cleistogamy and light
1245.
L.
leaf-borne
faisely described ii
681
L. vulgaris, adventitious shoot,
position ii 277.
Linum, ovule, epithelium ii 638,
haustorium ii 638.
Liparis latifolia, ovule-forma-
tion induced by stimulus of
insect i 270.
Liriodendron, stipule, protective
function ii 363.
L. tulipifera, phyliotaxy i 953
stipule, protective function ii
363.
Liriosma, ategminy ii
619.
Listera cordata, transformation
of root into shoot ii 227.
Littonia, leaf-tendril ii 428.
Livia juncorum, malformation
caused by i 195.
Loasaceae, androecium ii 535.
Lobelia, ovary syncarpous ii 563 ; ;
staminal tube, concrescence i
ovule,
53-
L. Erinus, flowering and rays
of spectrum i 244.
Lolium, glume, suppression
through loss of function i 58;
hypsophyll, divided arrested
li 397 ; ligule, protective func-
tion li 378.
L. temulentum, glume, suppres-
sion i 57; hypsophy ll, divided
ii 397.
Lomentaria impudica, division
of labour amongst shoots i 39.
Long shoot and short shoot i
35,11 444; of Hepaticae ii 43;
of Musci ii Ig.
Lonzcera, leaf, double i Igo,
insertion i 93; shoot, dorsi-
ventral lateral i 93, orthotro-
pous or plagiotropous i 68.
L. Periclymenum, \iane-growth
ii 453.
Lophocolea, archegonia in groups
with perichaetium ii 8g; spore-
germination ii 110; water-
reservoir li 58.
L. bidentata, endogeneticshoot ii
45; gemma ii 50 ; regeneration
ii 52.
L. heterophylla, embryo ii 102.
L. muritcata, foliar water-reser-
voir ii 58.
Loranthaceae, embryo-sac em-
bedded in torus ii 620; ovule,
reduction ii 621, rudimentary
ii 620.
Loranthus pentandrus, sphaero-
carpus ii 620.
Lotus corniculatus, a halophyte
i 266; stipule ii 361.
Loxsoma, sporangium, opening
ii 588.
Loxsomaceae, sporangia basi-
petally developed ii 496.
Lubbock, on lie of embryo in
seed i IIs, ii 406.
682
Lumnitzera, \enticel on root ii
280.
Lunularia, air-cavities ii 75;
gemma ii 49, and light i 227;
sporogonium, opening ii 97.
L. vulgaris, dioecism ii 80.
Lupinus, cotyledon, asymmetry i
115; leaflet, unequally sized i
128; root, movement in soil ii
276.
Luzula flavescens, Forsteri, flower
modified by attack of brand-
fungus i 193.
Lychnts, gynaeceum and placen-
tation ii 564.
L. vespertina, sex-change due to
Usitlago antherarumt i 193.
Lyctum barbarum, axis, radial i
85.
Lycopodineae, anisophylly i
102 ; branching ii 432; cladode
ii 448; development, homo-
blastic ii51; embryo, differen-
tiation ii 244, polar dif-
ferentiation ii 247; flower,
podium ii 510, and vegetative
shoot li 509; gametophyte ii
191; laminar growth, basi-
plastic ii 312; phyllotaxy in
dichotomous branching i 81;
rootless ii 264; spermatozoid,
biciliate ii 172; sporangium,
arrest 11 510, bilateral ii 574,
581, dorsiventral ii 581, open-
ing ii 578, origin from leaf-
organ il 473, position ii 493,
time of origin ii 504; sporo-
phyll ii 503, and foliage-leaf
alike in position and origin ii
477, and wind-distribution of
spore ii 474; tapetum, secre-
tion ii 596; transition from
sporophyll to foliage-leaf ii
510; tropo-sporophyll ii 510.
Lycopodium, antheridium, em-
bedded ii 174, opening ii 176;
cellulose in sporangial wall ii
578 ; dorsiventrality and light
i 104; embryo, position of
organs ii 247; endogenetic
first root ii 273; gemma,
abjection ii 467 ; heterophylly
ii 346; leaf-cushion i 103;
lignin in sporangial wall ii
578; protocorm ii 231; pro-
thallus, development ii 194,
dorsiventral ii 193, radial ii
191; shoot, hypogeous i 104 ;
spermatozoid-structure sim-
plest ii 173; sporangium,
mature ii 578, position ii 575,
phyletic hypothesis of trans-
formation ii 606, wall and
dehiscence ii 579; stomium ii
579; symbiosis with fungi ii
218 ; transformation of sporan-
gium into sporophyll ii 606;
‘tubercule primaire’ ii 194.
INDEX
L. alpinum, anisophylly i 103.
L. annotinum, embryo, differen-
tiation li 244, position of
organs li 247; flower, apodial
orthotropous erect li 510;
prothallus, saprophytic li 193 ;
sporangium, position ii 510;
spore, discharge ii 580 ; sporo-
genous cell-mass, nutrition
ii 597 ; sporophyll differs from
foliage-leaf ii 503.
L. carinatum, prothallus filiform
ii 193.
L. carolinianum, flower, ortho-
tropy li 509.
L. cernuum, embryo, differen-
tiation ii 244; gametophyte,
primitive ii 583; prothallus,
chlorophyllous ii 192, develop-
ment ii 194, water-relation-
ship ii 215; protocorm ii 231 ;
sporangium, dehiscence ii 582;
sporophyll, hypopeltate ii 503.
L. Chamaecyparissus, anisophyl-
ly and external factors i 255.
L. clavatum, not anisophyllous
i 102; branching ii 432; em-
bryo, differentiation ii 244,
position of organs ii 247;
flower, orthotropy ii 509;
prothallus, development ii
194, saprophytic ii 193; spo-
rangium-wall, lignin ii 579;
sporogenous cell-mass, nutri-
tion ii 597 ; stomium ii 579.
L. complanatum, anisophylly i
100, 103, caused by light i
252; prothallus, saprophytic
ii 193; shoot, dorsiventral ii
419, dotsiventral and flower,
radial ii 509, flattened and
light i 249; symbiosis with
fungi ii 219.
L. Hippuris, prothallus filiform
li 193.
L. tnundatum, not anisophyllous
i 102; embryo, differentiation
ii 244; flower, orthotropy
li 509 ; gametophyte, primitive
ii 583; mucilage-formation ii
503; a primitive type ii 609 ;
prothallus, chlorophyllous ii
192, developmentii 194, water-
relationships ii215; protocorm
ii 231 ; reproduction, capacity
i143; shoot, adventitious, of
embryo-plant i 46; sporan-
gium, dehiscence ii 582, dorsi-
ventral ii 574, position, and
leaf ii 582, wall and dehi-
scence ii 579.
L. lintfolium, flower, podial or-
thotropous and pendent ii 510;
sporangium, position ii 510.
L. lucitdulum, gemma ii 467.
L.nummutlariaefolium, prothal-
lus, filiform ii 193 ; symbiosis
with fungi li 219.
L. Phiegmaria, flower, podial
orthotropous pendent ii 510;
prothallial gemma ii 214;
prothallus ii 193 ; sporangium,
position ii 510.
L. reflexum, gemma ii 467.
L. salakense, prothallus, chloro-
phyllous ii 192, development ii
194; ‘tubercule primaire’ ii 217.
LZ. Selago, not anisophyllous i
103; embryo, differentiation ii
244; flower, apodial ortho-
tropous erect ili 510; gemma
ii 467, 607; paraphyses on
prothallus ii 193 ; propagative
adventitious shoot on pro-
thallus ii 213 ; prothallus, dor-
siventral ii 193, saprophytic ii
193; sporangium, position ii
510; sporophyll and foliage-
leaf alike ii 503, 509; transi-
tion between sporophyll and
foliage leaf ii 510.
L. volubile, climbing leaf ii 419;
hook on leaf ii 346.
Lygodieaze, apical growth of
leaf, prolonged ii 319.
Lygodium, antheridium free,
opening ii177; climbing-organ
ii 593; indusium ii 497; pro-
thallus apandrous ii 220; spo-
rangium, and annulus ii 592,
displacement ii 494, mature
ii 591; sporophyll, develop-
ment ii 478.
L. japonicum, archegonium, vire-
scentii 187; leaf-climberii 593;
sporangium, position ii 593.
L. microphyllum, sporangium
and opening ii 592.
L. palmatum, \eaf, dorsal row i
gi; stem, dorsiventrality i 91.
ZL. terminale, prothallus, ter-
minal meristem ii 205.
Lysichiton, antipodal cells, in-
crease in number ii 637.
Lythrum Salicaria, flower, nu-
merical symmetry il 538.
M.
Macropodous embryo ii 260.
Macrozamia Frasert, coral-like
air-root ii 281.
M. Migueli, pinnule, basipetal
development ii 322.
Madotheca, spore-germination ii
108.
Magnolia, kataphyll ii 386;
stipule, protective ii 363.
M. Campbelli, Umbrella, stipule,
protective ii 386.
M. fuscata, kataphyll, stipular
ii 386.
Maize, inherited sterility i 186.
See also Zea Mais.
Malachium, gynaeceum and pla-
centation ii 564.
Male flower. See Flower.
Male gametophyte. See Game-
tophyte.
Male prothallus.
prothallus.
Male sexual organ. See Anthe-
ridium.
Malformation, of archegoninm
ii 15 ; of bud i 178; definition
i177; derangement of organs
1196; of fungii 187; caused,
by fungi i 192, ii 526, by in-
sects i 178, 194, by over-
nutrition i 190, by wunder-
nutrition i Ig1; etiology i
184; experimentally evoked
i 187; of flower i 177, 181,
189, in Coniferae ii 524;
galls i 196; inherited i 185,
190; of leaf i 191 ; question of
new formation in i 196; of
ovule i 180; of roots 1 I9I;
significance i 177; of sexual
organ of Pteridophyta ii 187;
spontaneous i 184, transmis-
sible by seed i 184 ; of stamen
i 180; of stem i 190; value in
organography i 179.
Malpighi, on leaf-development
li 302.
Malpighiaceae, searcher-shoot
i 459°
Maiva, carpel, branching ii 537.
See Micro-
M. vulgaris, flowering and light |_
i 244.
Malvaceae, carpel, branching
ii 537; chorisis of stamen ii
530; flower, radial lateral i
INDEX
archegonium, development ii
184; embryo, differentiation
ii 244; kataphyll of adventi-
tious bud ii 350; leaf, develop-
ment ii 315; leaf-stalk ii 314;
leaf-structure ii 315; prothal-
lus ii 198; shoot, lateral, at
apex of stem, suppressed ii
431; sporangium, mature ii
585, opening ii 587, position
ii 493; sporophyll, and foliage-
leaf alike in position and origin
ii 477, the ordinary foliage-
leaf ii 482; stem, tuberous ii
431; stipular bud i 46; stipule
li 315, 365; synangium ii 585.
Marcgravia, juvenile form mis-
taken for aroid i 159; juvenile
state, result of adaptation i170;
liane i 159.
Marcgraviaceae, bract, tubular
li 338 ; juvenile form, direction
of growth i 143.
Marchantta, antheridiophore and
archegoniophore ii 85; apical
cell ii 21; branching ii 21;
breathing-pore in transpiration
ii 74; cell-row, protective ii
30; colour, violet of antheridial
pit ii 10; dorsiventrality and
light i 227; gemma i 227, ii
49; germination of spore and
gemma compared ii 112; re-
generation i 48; spore, thin-
walled ii 106.
M. chenopoda, scale with apical
appendage ii 30.
133; pollen-sac, reduction of | JZ. /amellosa, scale and rhizoid ii
number ii 554; stamen, basi-
petal succession ii 542.
Mammilla on leaf-surface of
Musci ii 143.
Mammillaria macrothele, \eaf-
nectary il 430.
Mammillarieae, concrescence
of axillary shoot and axillant
leaf ii 436; inflorescence, leaf-
borne ii 436; transition from
thorn to nectary ii 430.
Mangifera indica, polyembryony
ii 637.
Mangrove, embryo, viviparous
ji 255; pneumatophore ii
278; root-system from chief
root, suppressed ii 272.
Mantle-leaf of Platycerium ii
350.
Marantaceae, petaloid half-
stamen ii 554; pollen-sac,
arrest ii 554.
Marathrum, root-borne shoot ii
228.
M. utile, root with shoot ii 227.
Marattia, synangium ii 586,
sterilization li 605.
M. fraxinea, synangium ii 586,
Marattiaceae, antheridium, em-
bedded ii 174, opening ii 176;
aps
M. polymorpha, air-cavities ii
72; antheridium and sperma-
tozoid ii 9; female plant ii
86; gemma, developmenti 227,
ii 112; germ-disk, small ii 112;
male plant ii 85; rhizoid, dis-
tribution ii 32; symmetry of
gonophore ii 85.
Marchantiaceae, air-cavities ii
72; antheridiophore ii 84;
antheridium, development li
13, opening ii 11; archegonio-
phore ii 84; colour and light
ii 78; embryo-plant and light
i 239; gravity, relationships ii
76 ; involution of parts to resist
drought ii 65 ; light and growth
ii 77; mucilage-cell ii 76;
oil-body ii 79; reversion to
juvenile form i 171; rhizoid,
division of labour ii 46; scale,
protective ii 29; shoot, form
of etiolated i 249; spore-
germination ii ITI ; sporogo-
nium, development ii 97, 104,
mature ii 96, opening ii97, con-
tains spores and elaters ii 99 ;
thallus, symmetry i 86, ii 19;
water-storage tissue ii 76,
683
Marginal, growth of leaf of Fili-
cineae ii 313; ovule ii 558, of
Cycadaceae ii 511.
Marine Algae, branching in
relation to light i 237.
Marsh-plant, endogenetic ad-
ventitious root ii 273; leaf,
arrest on assimilating shoot-
axis ii 446; heterophylly ii
357; juvenile form i 164;
riband-form of leaf in mono-
cotylous ii 357.
Marstlia, antagonism between
reproductive and vegetative
organs i 213; dorsiventrality
i g1; embryo and gravity i
220; megaspore i 220, ii 212;
microspore ii 180; radial leaf
i114; rhizoid of female pro-
thallus ii 189; spore-distribu-
tion il 212 ; spore-germination
in absence of light ii 190;
sporocarp ii 491, outgrowth of
sterile leaf ii 479 ; stem, creep-
ing igl.
M. Brownit, sporocarp ii 492.
M. Drummondi, wmegaspore,
germination ii 212.
M. polycarpa, an aggregate
species il 479; sporocarp,
development ii 492, marginal
formation ii 479, origin ii
479-
M. pedinsfolia, effect of land
and water on formation of
sporophyll ii 498; growth in
land and in water ii 498.
M, subangulata, specific value ii
479-
M. si etume hypogeous sporo-
carp ii 493.
Marsiliaceae, antheridium, de-
velopment ii 180; dorsiventra-
lity ii 480; embryo, position
of organs ii 247; gametophyte,
male ii 180; megasporangium,
tetrad-formation ii 603 ; mega-
spore, reduction in number ii
626; microspore, germination
ii 180; pinnule, unilateral
formation ii 480; prothallus,
female ii 212, limited develop-
ment i 142, male ii 180;
sporangium, arrangement i
490, position ii 492, protected
in pit ii 498, reduced not
radial ii 574, sunk in sporocarp
ii 474; spore-distribution, not
a function of sporangium ii
573, in water ili 474, 5753
sporocarp ii 474, development
ii 490, hypogeous ii 493;
sporophyll as new formation
477, 479-
Massart on leaf-development ii
3°5-
Massulae of Ase//a ii 218.
| Mastigobryum, anisophyllyi1o1 ;
684.
endogenetic shoot ii 45; in-
volution, dorsiventral i 86;
flagellum ii 43, use ii 228 ; pro-
file-position of leaf ii 135.
M. trilobatum, anisophylly i 102.
Material and form, Sachs’ hy-
pothesis i 200.
Matoniaceae, sporangium, dis-
position ii 496.
Maturity, terminal stage of a
series 1 Q, ll 304.
Maurandia, \eaf-stalk-climber ii
421.
Mechanical, hypothesis of leaf-
position i 74; stimulus and
configuration of organs i 268.
Medicago sativa, pressure and
development of inflorescence i
138.
Medinilla radicans, root-tendril
ii 287.
Medium, and amphibious plants
i 260; and aquatic plants i
260; and Fungi i 266; and
hair-points of Musci i 261 ;
and halophily i 265 ; and leaf-
succulence i 264; and organs
i 259; and prickle-formation
1 263; and resting states i 261 ;
and thorn-formation i 263;
and tuber-formation i 262.
Megacarpaea, flower-structure
and pollination ii 547.
Megaprothallus, of Angio-
spermae ii 636; of Coniferae
developed after pollination ii
624; of Gymnospermae ii 629;
of Heterosporous Filicineae i
220, li 211; of Jsoetes ii 212;
of Selaginella ii 194.
Megasorus of Azol/a ii 488.
Megasporangium, of Calamo-
stachys Casheana ii 602; of
Isoetes, development ii 603;
of Pteridophytaii 578, develop-
ment ii 602; of Se/agznella ii
580, development ii 508, 603,
disposition ii 508. See also
Ovule.
Megaspore, of Heterosporous
Filicineae, germination i 220;
ii 211; of /soetes, differentia-
tion ii 628; ejection in Selagi-
nelleae ii 509. See also Em-
bryo-sac.
Megasporocyte, and microspo-
rocyte of Angiospermae, homo-
logy ii 625; of Coniferae ii
628; becomes embryo-sac in
Liliaceae ii625 ; tetrad-division
in Spermophyta ii 625.
Megasporophyll, of Hetero-
sporous Filicineae ii 487; of
Selaginella ii 471. See also
Carpel.
Melaleuca micromera, reversion-
phenomena i 167; reversion-
shoot i 172,
INDEX
Melampyrum, inflorescence, uni-
lateral i 136.
M. pratense, cotyledon, persistent
ii 403; inflorescence, unilateral
Wa
M. sylvaticum, inflorescence, uni-
lateral i 137.
Melandrium album, rubrum,
flower and light i 245.
Melastomaceae ,anisophylly, habi-
tual i 111.
Melianthus, stipule, axillary ii
372.
Melica ciliata, nutans, \eaf-in-
version, explained ii 297.
Melocactus, adult feature i 174.
Melodorum bancanum, searcher-
shoot ii 454.
Menispermum canadense, acces-
sory axillary bud ii 434.
Menyanthes, ovule, epithelium
ii 638.
M. trifoliata, root, chlorophyl-
lous ii 280; hairless ii 269.
Mercklin on leaf-development
ii 303.
Mercurialis perennis, transition
between epigeous and hypo-
geous cotyledon ii 403.
Meristem, apical and lateral,
phyletic relationship in pro-
thallus ii 205.
Myrmecodia, thorn-root ii 288.
Mesembryanthemum, transform-
ation of stamen into petal ii
55I-
Mesocotyl of Cyperaceae ii 412.
Mesopodium ii 304.
Metalesia, \eaf-inversion by tor-
sion ii 296.
Metamorphosis, doctrine i 5 ;
is ontogenetic i I1.
Metzgeria, apical cell ii 21;
branching ii 21; ejection of
spore il IOI; gemma ii 49;
mucilage-papilla ii 28; reten-
tion of water ii 55; spore-
germination il 107; sporogo-
nium with elaterophore ii Iot ;
thallus, winged ii 20; ventral
shoot bearing sexual organs ii
82.
M. australis, perichaetium ii 83.
M. conjugata, gemma ii 49.
M. furcata, adventitious shoot as
gemma ii 49 ; petianth absent
ii 82; oil-bodies absent ii 79 ;
regeneration ii 52; vegetative
point ii 20, 23.
M. pubescens, oil-bodies absent
li 79; water-retention ii 55.
M. saccata, water-sac ii 56.
Microprothallus, of Angio-
spermae ii 614; of Gymno-
spermae ii 612; of Hetero-
sporous Filicineae ii 180, 182;
of Zsoetes 11 181 ; of Selaginella
ii 182.
Micropyle, function ii 615.
Microsorus of Azol/a ii 488.
Microsporangium, of Calamo-
stachys Casheana ii 602; of
Heterosporous Pteridophyta ii
487,602; of Selaginella ii 580,
development ii 600. See also
Pollen-sac.
Microspore, of Heterosporous
Pteridophyta, germination ii
180; of Salviniaceae, distribu-
tion li 218. See also Pollen-
grain.
Microsporophyll, of Hetero-
sporous Filicineae ii 487. See
also Stamen.
Mimosa sensitiva, leaflet, asym-
metry i 124, unequally-sized
i 126.
Mimoseae, flower, arrangement
‘of parts ii 531; leaf, acropetal
branching ii 330.
Mimulus Tlingit, flower and
light i 245.
Mirabilis Jalapa, root, chloro-
phyllous ii 280.
Mistletoe, embryo, reduced ii 25 4.
Mites cause Erineum-galls i 196.
Mniaceae, spore, shedding ii
165.
Mnium, antheridium, opening ii
I1; paraphyses ii 151.
M. hornum, sporogonium ii 161;
capsule, wall ii 162.
M, undulatum, anisophylly i
100; archegonial group li 152;
archegonium, development ii
17; scale-leaf ii 134; shoot,
radialand plagiotropous ii 132;
vegetative shoot plagiotropous,
propagative shoot orthotro-
pous i 69.
Modification, of flower by over-
nutrition i 190, by starvation i
191; of host by parasitic
Fungi i1g2; of sex by external
conditions i 191.
Morkia, mucilage-papilla ii 28 ;
perichaetium ii 83.
Mohria, annulus and mature spor-
angium ii 591; antheridium
free, opening ii 177; prothal-
lus, lateral meristem i1 205;
sporangium, displacement ii
494; sporophyll and foliage-
leaf alike ii 478.
M. caffrorum, prothallus, apan-
drous ii 220; sporangium ii
588.
Momordica, tendril, morphology
ii 425.
M. balsamina, tendril, develop-
ment ii 423; transition from
prophyll to tendril ii 426.
Monergic, and polyergic cells
of Siphonocladiaceae i 24;
organization of Chlamydomo-
mas i 27; plant-body i 24;
plants i 23 ; spherical body of
Lremosphaera i 65; transition
to polyergic forms i 24,
Monocarpic, gametophyte of
Pteridophyta ii 189.
Monoclea, antheridium, develop-
ment ii 13; rhizoid, division
of labour ii 46 ; sexual organs,
disposition ii 80; vegetative
point, mucilage protection of
ii 28.
M. dilatata, thizoid ii 46 ; sexual
organs ii 12.
Monocotyledones, antipodal
cells, increase in number ii
637; assimilating axis a trans-
formed inflorescence-axis ii
447; cladode ii 449; cotyle-
don, differentiation ii 408, epi-
geous li 409, hypogeous ii 410,
sheath ii 408, 410, terminal i
16; embryo, differentiation ii
245, retarded ii 250, vegetative
point absent ii 245, storage of
food ii 260; exalbuminy ii
402, 408; exstipulate ii 365;
flower, anemophilous ii 547;
germination, viviparous ii 256;
growth, intercalary predomi-
nant ii 298, 323; hook-leaf ii
420; hypsophyll, hypothesis
regarding evolution ii 396;
inflorescence, unilateral i 136 ;
kataphyll ii 389; lamina con-
volute in bud ii 309; laminar
growth, basal ii 324, basi-
plastic ii 312; leaf, apex,
precedence in growth of ii 309,
arrest in assimilating shoot-
axeSii 447, base ii 298, bilateral
11328, development ii 323, dor-
siventral ii 323, hinge-cell ii
324, inversion by torsion ii 298,
peltate ii 329, profile-position
ii 328, radial ii 328, reduction,
factors causing ii 447, sequence
from entire to divided ii 327,
sheath ii 298, stalk, rare ii 299,
terminal i 16; megaspore, ab-
sorption of ovular cells ii 637;
megasporocyte, tetrad-division
ii 625; microspore, reduc-
tion in number ii 626; ovule,
ategminy ii 618, bitegminy ii
617; phylloclade ii 449; pro-
phyll, concrescenceii 382, posi-
tion ii 382; prop-root ii 277 ;
protocorm ii 232; root, branch-
ing, suppressed ii 274, lateral
origin ii 274,system ii 272; root-
less ii 265; stipule, axillary
ii 375; tendril ii 428; thom-
root ii 288; transformation of
root into shoot ii 227; vena-
tion ii 339, striate ii 338;
wind-pollination ii 547.
Monoecism and dioecism of
Hepaticae ii 80.
INDEX
685
Monogramme, prothallial gemma | Musaceae, venation and leaf-
li 214.
growth ii 342.
Monomerous, gynaeceumii558; | Muscarz botryoides, flag-flower
ovary of Dryadeae ii 559.
Monophyliea, cotyledon, persis- | JZ.
tent 404.
li 571.
comosum, flag-apparatus,
correlation of growth i 211.
Monopodial leaf-branching of | Musci, acrandrous, more primi-
Dicotyledones ii 330.
Monotropa, embryo, reduced ii
254; root, free-living ii 234,
hairless ii 269.
Monstera, juvenile form i 157.
M. deliciosa, dorsiventrality i go;
leaf, perforated ii 325; shoot,
bilateral with distichous phyl-
lotaxy i go.
Monstrosity, Darwin’s defini-
tion i 178.
Moquin-Tandon on dédouble-
ment li 533; definition of ano-
maly i178.
Moraea, thorn-root ii 288.
Morphological, categories of
organs i 13; importance of
arrested organs i 60.
Morphology, and physiology,
relation i 4; definition i 3;
first based on the study of
higher plants i 13; Goethe’s
definition i 3; idealistic i 5;
Sachs’ definition i 4.
Moss-capsule, ampithecium ii
155; archesporium ii 155;
endothecium ii 155.
Moss-plant, configurationii 131.
Moss-stem, apical cell, three-
sided ii 131, two-sided ii 131.
Mucilage, round embryo of
Musci ii 154; of Lycopodium
tnundatum ii 503; gland on
ochrea ii 374; hair of He-
paticae ii 27, of Musci ii 138;
and opening of antheridium
of Bryophyta ii 11; papilla
of Hepaticae ii 28, 60; pit of
Azolla ii 348; secretion of
Hepaticae ii 27, 76; slit of
Hepaticae ii 27 ; stipule secret-
ing ii 381.
Mucor,regeneration of germ-tube
i 49.
M. Mucedo, germination of zygo-
spore in varying nutrition i
266.
M. racemosus, growth of myce-
lium, limited i 142; nutrition
and form i 267.
M. stolonifer, rhizoid developed
through contact-stimuli i 269.
Muhlenbeckia platyclados, cla-
dode ii 452.
Mulgedium macrophyllum, tran-
sition from foliage-leaf to
hypsophyll ii 391.
Musa, fruit, correlation of growth
i 212; leaf-form ii 327, split-
ting by wind ii 326; venation
ii 340.
tive il 149 ; acrocarpous, more
primitive ii 149; adaptation,
vegetative ii 141; all acrogy-
nous 11149 ; anisophyllyi1oo;
annulus of capsule ii 160,
function ii 161; antheridial
groups ii 151; antheridium
il 9, 149, varying origin i 18;
apophysis ii 158, organ of
assimilation ii 159; arche-
gonial groups ii 151 ; arche-
gonium ii 1I4, 149; arche-
sporium il 155, 601, steriliza-
tion ii 606; branching not
axillary ii 131; calyptra ii
152; caster formed by peri-
stome ii 164; cleistocarpous
ii 160; colour in sexual
organs ii 551; columella,
function ii 157; dioecism ii
150; embryo, ‘foot,’ ii 157,
haustorium ii structure
and development ii 154;
gametophyte and that of Fili-
cineae ii 208; germ-plant and
light i 241; hair ii 138;
hair-points ii 149, and medium
i 261; hypsophyll ii 135;
laminar growth, basiplastic ii
312; leaf, adaptation ii 135,
apical cell two-sided ii 131,
function ii 134, on radial shoot
ii 134, simple unbranched ii
134, tip, development ii 306 ;
mucilage ii 27, 76, around
embryo ii 154; older than
Hepaticae ii8 ; paraphyllium ii
146; paraphyses ii 151; peri-
chaetial leaf ii 152; peristome
ii 161; phyllotaxy i 78, ii
131; propagation asexual ii
139; propagative capacity,
great i 47; protonema, and
light i 234, and correlation i
58, long shoot and short shoot
ii 119, precedes bud-formation
i 48; radial and dorsiventral
ii 18; regeneration ii 52, from
severed leaf i 50; relationship
to light ii 149; retention of
water ii 143; rhizoid ii 45,
segmented ii 116, strand ii
120; schizocarpous ii 160;
seta li 161; sexual organs ii
9, 14, 149; silver-glance i
261, ii 148; shoot, dorsi-
ventral ii 138, plagiotropous,
and light i 232, radial ii 132;
spermatozoid, distribution un-
known ii 152; spore, distribu-
tion ii 160, germination ii 116;
157;
686
spore-sac ii 156 ; sporogoninm
ii 152, and stomata ii 159;
stegocarpous ii 160; uni-
formity of vegetative body ii
7; water-absorption ii 142.
Mussaenda, calycine flag-appara-
tus i 130; flower, unessential
zygomorphy i 130.
Mycorrhiza ii 289.
Myoporum serratum, ovule, epi-
thelium ii 639, haustorium ii
Myosotis alpestris, inheritance of
malformation i 186.
M. palustris, size of corolla and
light ii 551.
Myosurus, ovary, development ii
560; ovule, reduction in ovary
ii 560.
Myriophyllum, bitegminy ii 618;
leaf - branching, basipetal ii
330; reaction of organs to
external stimulii 218; reversion
and its cause i 174; storage-
leaf ii 398; winter-bud i174,
218, ii 398.
Myristica’ fragrans, apical
growth of cotyledonary lobes
li 407; cotyledon, lobed ii
407; endosperm, ruminate ii
407.
Myrmecodia echinata, transfor-
mation of root i 12.
Myrtaceae, androecium ii 535.
Myxomycetes, organization i
25; polyergic i 23; reaction
of plasmodium to external
stimulii 218; sclerotium i 262.
Myxopyrum nervosum, searcher-
shoot ii 454.
N.
WNageli on leaf-development ii
303; on origin of sporophyte
of Pteridophyta ii 605; phy-
tome i 21.
Najas, flower-leaf, terminal ii
bar
Nanism 1 259.
Nanomitrium, antheridium, de-
velopment ii 13; archegonial
venter ii 153; capsule, de-
velopment ii 155; columella
ii 157; embryo ii 14; sporo-
gonium, opening ii 160.
JV. tenerum, sporogonium ii 155,
157.
Narcissus, \eaf-sheath and axil-
lary structure ii 299.
LV. poeticus, bulb ii 299.
Nassovia, thorn-plant of Andes
i 264.
Nasturtium lacustre, \eaf-cut- |
ting i 46.
NV. offictnale, sylvestre,
exogenetic ii 273.
root,
Neck-canal-cells of archego- |
nium ii 14, 184.
INDEX
Neckera, \eaf-undulation retains
water ii 143.
Neckeraceae, leaf-base, out-
growth retains water ii 143.
Nectary, leaf ii 430; of Helle-
borus ii 560; petaline ii 550,
551; staminal ii 549, 550;
stipular ii 381.
Negative chorisis ii 533, 540.
Nelumbium, foliage-leaf, peltate
ii 335; leaf, primary, peltate
ii 336, radial i 114.
Nematus Capreae, forming galls
i 200.
Neottia, root, hairless ii 269.
NV. Nidus-avis, endogenetic stem-
root ii 273; transformation of
root into shoot ii 227.
Nepenthes, leaf, tubular ii 338,
tendril ii 428; transition from
leaf to climbing organ i 161.
Nephrolepis, \eaf, periodic apical
growth ii 318.
JV. exaltata, leaf, development
ii 317, periodic apical growth
ii 318.
Nerium Oleander, flower, double
Il 537+
Nest-leaf of Polypodium ii 350.
Nest-root of epiphytes ii 283.
New formation, integument of
ovule as, ii 616; in flower,
free central placenta as ii
567; in malformation i 196;
sporophyll in Pteridophyta as
Ml 477-
New formation of organs, from
wound-callus i 44 ; in regenera-
tion i 44.
Nidularium splendens, transi-
tion of foliage-leaf to hypso-
phylli fo, ii 551.
Nigella damascena, flower, varia-
tion in numerical symmetry ii
583.
Nodes and internodes, of Chara
i 35; of axis 1 35.
Nolana atriplicifolia, cotyledon
as assimilation-organ ii 402.
Norantea guianensis, juvenile
form, absent i 159.
iVostoc symbiotic, with <Aztho-
ceros i178, with Blasza ii 78.
Notospartium, shoot as water-
reservoir ii 452.
Notothylas, sporogonium ii 95.
J. orbicularis,sporogonium ii 96.
Nourishing root of climbing
plants ii 286, 288.
Nucellar tissue, adventitious
embryo formed from ii 637.
| Nucellus ii 573, 614, 622;
development in large ovules ii
631; stimulation affecting
development in ii 622.
Numerical relationships of
flowers, factors determining ii
537-
Nuphar, juvenile form i 164;
root, lateral, origin ii 273.
LV. luteum, dorsiventrality i 85,
and light i 231 ; juvenile form,
i 165.
Nutrition, and configuration of
Fungi, i 266; effect on an-
droecium of Rosaceae ii 538 ;
and malformation i 187, ii
190, 191; and prothallus of
Equisetum ii 195; of spore of
Coniferae ii 628; of spores in
sporogonium of Hepaticae ii
97; of sporogenous cell-mass,
of Lycopodium ii 597, of pollen-
sac of Angiospermae ii 597.
Nutritive, cell in sporogonium
of Hepaticae ii 97; function
of integument of ovule ii 615 ;
tissue, chalazal ii 640, funicu-
lar ii 640.
Nymphaea rubra, juvenile form
i 165.
Nymphaeaceae, juvenile form i
164; petal a transformed sta-
men ii 551.
O.
Oak, Cynifs rosae upon i 198.
Obligate torsion i 186. ;
Oblique, dorsiventral flower i
128; plane of symmetry of
flower i128; wall in rhizoid
of Musci ii 117.
Ochrea ii 373.
Oedipodium, protonema, special
organs of assimilation ii 121.
Oedocladium, protonema, shoot
and light i 256.
Oedogonium, juvenile form ab-
sent i 148.
Oenanthe fistulosa, leaf, cylindric
by reduction ii 295.
Oenone leptophylia, root, dorsi-
ventral li 281.
Oenothera, cotyledon, transiently
arrested foliage-leaf i 145;
flower, suppression of upper i
58.
O. btennis, inflorescence, com-
pensation of growth i 208.
O. bistorta, macrantha, stricta,
cotyledon, intercalary growth
ii 404.
O. glauca, pumila, rosea, cotyle-
don ii 404.
Oil-body of Marchantieae ii 79.
Olacineae, ovule, ategminy ii
619.
Olax, ovule ategminy ii 619.
Oleaceae, ovular development
ii 623 ; twig-thorn ii 456.
Onagrarieae, cotyledon, post-
embryonal development ii 404;
petaline primordium, branch-
ing ii 536; sporogenous
tissue, sterile cells ii 597;
sterilization in pollen-sac ii
5552 597- ;
Onoclea sensibilis, apospory in
virescent sporophyll ii 609.
O. Struthiopteris, apospory ii
609 ; artificial modification of
transmission of organs i IT;
correlation and configuration
of sporophyll i 216; develop-
ment of sporophyll into foliage-
leaf ii 475; kataphyll ii 350;
leaf, succession ii 511; pro-
thallus, apandrous ii 220;
sporangium, arrest li 510;
sporophyll ii 486, and wind-
distribution of spores ii 474;
transition from foliage-leaf to
kataphyll ii 350.
Ononis, juvenile form i155.
O. Natrix, juvenile form i 155.
O. spinosa, shoot-thorn ii 452.
Opening, of antheridium of
Bryophyta ii 10; of embedded
antheridium of Pteridophyta
ii 174; of free antheridium of
Pteridophyta ii 177; of arche-
gonium of Bryophyta ii 15,
of Pteridophyta ii 183; cap
of antheridium of Bryophyta
ii 10; cells of sporangium ii
577, 600, 610, 611; and clos-
ing of flower in relation to
light i 245; of pollen-sac of
Angiospermae il 600, 611,
of Gymnospermae ii 610; of
sporangium il 509, 575, 577-
95, 600, 610, o u-
sporangiate Filicineae ii 584,
of Equisetineae ii 585, of Lep-
tosporangiate Filicineae ii
587, in relation to light ii 575,
of Lycopodineae ii 578; of
sporogonium ii 95, 160.
Ophioglossaceae, antheridium,
embedded ii 174, opening ii
176 ; exstipulate ii 365; leaf,
branching in one plane ii 482 ;
prothallus, hypogeous ii 198,
saprophytic ii 198; sporan-
gium, bilateral ii 574, position,
11 493, protected by ptyxis of
sporophyll ii 496 ; sporophyll,
dorsiventral ii 482, as new
formation ii 477, 481, posi-
tion ii 606 ; symbiosis of pro-
thallus with Fungi ii 198, 218.
Ophioglossum, prothallus, sym-
biotic ii 198; ptyxis, circinate
absent ii 321; regeneration i
46; root, branching suppressed
li 274; root-borne bud i 46,
ii 431 ; sporangium ii 584, 626,
dehiscence ii 585, embedded
ii 574, 584, position ii 494;
sporogenous tissue, sterile
cells ii 597; sporophyll ii
482; stem-apex, suppression of
lateral shoot ii 431.
INDEX
O. palmatum, sporophyll, mar-
ginal and surface formation ii
481.
O. pedunculosum, prothallus ii
198, radial ii 191, saprophytic
ii 193 ; sporangium embedded
ii 574; sterilized sporogenous
cells, absent ii 597.
O. vulgatum, root-borne shoot ii
228.
Ophrydeae, toot, branching sup-
pressed ii 274; root-tuber ii
289.
Opuntia, flattening of shoot-axis
ii 448, and light i247 ; gravity
and shoot i 221; transition
from thorn to nectary ii 430.
O. arborescens, \eaf-thorn ii 429 ;
papillose surface and light i
248.
O. brastliensis, gravity and chief
and lateral shoots i 226.
O. Ficus-indica, gravity and
shoot i 221; polyembryony ii
37:
O. leucotricha, flattening of shoot
and light i 247.
Orchideae, assimilation-root ii
284; difference between flower
and vegetative shoot ii 528 ;
embryo incomplete at germi-
nation ii 253; epiphytic ger-
mination ii 232; flag-flower ii
571 ; flattening of aerial root i
92 ; flower-structure and polli-
nation ii 547; nest-root ii 283 ;
pollen-sac, confluence ii 554 ;
root, aeration-striae ii 285,
chlorophyllous aerial i 246,
dorsiventral aerial i 246, dorsi-
ventral and light i 246; proto-
corm ii 232; seed, small ii 631 ;
stimulus of pollen-tube induc-
ing formation of ovule i 269,
ii 623; reaction of aerial root
to external stimuli i 217; sus-
pensor-haustorium ii 642;
velamen ii 283.
Orchis, axillary branching ii 433.
O. mascula, axillary branching ii
433-
Organs, of amphibious plants i
260 ; of aquatic plants i 260 ;
bisymmetric i 66; changed
form through reciprocal pres-
sure 1 77; at different stages
of development i 141 ; differen-
tiation in Spermophyta i 13;
dorsiventral i 67; formation
and adaptation i 21, ii 1;
formed in absence of light i
257; of limited growth have
mid-portion best nourished ii
511; malformed and their
significance i 177}; new forma-
tion of i 44; normal formation
at vegetative point i 41; of
plants, nature of i 5; position,
687
on radial axes i 73, in em-
bryo ii 243 ; progressive serial
succession i 33; of propaga-
tion of Spermophyta ii 573;
protean ii 240; radial i 66;
symmetry i 65.
Organography and formal mor-
phology i 4.
Origin of dorsiventral flower ii
543; of embryo-sac ii 632; of
kataphyll ii 384; of lateral
root ii 273; of megaspore ii
632 ; of peltate hair ii 336; of
root on shoot ii 274; of scale
of Hepaticae ii 34.
Ornithogalum, differentiation of
archesporium in pollen-sac ii
600.
Orobanchaceae, haustorium ii
224; organ-formation in ab-
sence of light i 257.
Orobanche, embryo, reduced ii
254; germinationi 205; hau-
storium ii 224.
O. ramosa, root, hairless ii 269.
Orobus, stipule, asymmetry i125.
Orthotrichum, calyptra, hairs ii
154; Sporogonium, radial i
236; spore, shedding ii 163.
O. callistomum, spore, shedding
ii 164.
O. gymnostomum, peristome ab-
sent, a reduction ii 162.
Orthotropy and bilateral organs
i 68; of Calobryaceae ii 18,
39; definition i 67; of flower
of Lycopodineae ii 509; of
ovule ii 617 ; and plagiotropy,
transitions i 68, ii 457, 459;
of radial shoot ii442 ; of sexual
shoots of Hepaticae ii 41; of
chief shoots i 93, 214; of shoot
and conditions of life ii 459.
Oryza, ligule closing terminal
bud ii 377 ; scutellum ii 415.
O. sativa, embryo ii 417 ; ligular
sickle ii 375 ; ligule ii 376.
Osmunda, antheridium, develop-
ment ii 179; archegonium,
malformed ii 188; kataphyll
ii 350; leaf-stalk ii 314; pro-
thallus ii 199, branching ii
200, hairs absent ii Ig9,
perennating ii 189, reversion
ii 205 ; sporangium, position ii
493 ; vegetative propagation
of old prothallus i 49.
O. cinnamomea, kataphyll ii 350.
O. regalis, kataphyll ii 350;
regeneration i 49 ; sporangium
and annulus ii 588, 590, 592;
sporophyll ii 486.
Osmundaceae, annulus ii 590 ;
antheridium free, opening ii
177; leaf, development ii
315, structure and environment
ii 347 ; placenta, absent ii 472 ;
sporangium, disposition ii 496,
688
INDEX
dorsiventral ii 574, opening | O. tetraphylla, root, fleshy ii 289.
588; sporophyll and foliage- | Oxymztra, air-cavities li 72;
leaf alike in position and
origin ii 477; transition from
eusporangium to leptosporan-
gium ii 602.
Ottoa, leaf cylindric ii 295.
Ouvirandra, leaf, biological re-
lationships ii 345.
Ovary, bilocular ii 562, 563;
biovular ii 560; development
ii 559; formation ii 555; in-
ferior ii 567; monocarpellary
ii 559; monomerous il 559;
plurilocular ii 565; plurio-
vular ii 560; superior li 549 ;
unilocular ii 565; uniovular ii
560.
Ovular development after polli-
nation in Angiospermae i
269, ii 623.
Ovule, acrogamous entrance of
pollen-tube ii 615; anatropy
ii 631; of Angiospermae il
527, 614, archesporium ii 601,
632, development ii 631;
apotropy ii 631; ategminy ii
618; atropy ii 631; axillary
ii 561; basigamous entrance
of pollen-tube ii 615; basi-
petal succession ii 542; bi-
tegminy ii 617, 628 ; concres-
cent with ovary ii 620; of
Coniferae ii 519, development
ii 628; of Cycadaceae ii 511,
616, development ii 626, foliar
origin ii 555, primitive charac-
ter ii 626; development ii
625; epithelium ii 631, 637;
epitropy ii 631; funicle ii
614; of Ginkgoaceae ii 519;
of Gnetaceae 11 628; of Gym-
nospermae ii 511, 626; hau-
storium ii 631 ; integument ii
614, 616, nutritive function ii
615, three in Gnetum ii 629 ;
marginal ii 558; nucellus ii
622; nutritive tissue 11 640;
orthotropy 11 617 ; of parasites
ii 618; phyllody i 181;
rudimentary construction ii
620; of saprophytes ii 618;
sterilization ii 632; structure
in relation to perfect seed ii
631; a sporangium ii 573;
tapetum ii 638; on under side
of carpel ii 558.
Oxalideae, gynaeceum and pla-
centation ii 563.
Oxalis, gynaeceum, superior
syncarpous ii 563; placenta-
tion ii 564, septal ii 563 ; root,
dimorphism ii 272.
O. elegans, root, shortening i
270.
O. ruscifolia, phyllodium ii 354.
O. stricta, gynaeceum and pla-
centation 11 563.
sporogonium, internal differen-
tiation ii 97.
O. pyramidata, oil-bodies absent
ii 79; scales at vegetative
point ii 30.
184
Paconia arborescens, archespo-
rium, pluricellular ii 633.
Paliurus australis, thorn-stipule
ii 381.
Palmae, branching, latent capa-
city ii 431; breathing-root in
moist soil ii 278; climbing
hook ii 421; leaf, lamina split-
ting by degeneration ii 328,
segmentation by splitting il
326, stalk ii 299; ligule ii 378,
a new formation ii 379 ; prop-
root ii 277 ; thorn-root ii 288.
Pallavicinia, chromosomes ii 8.
Pandaneae, prop-root ii 277.
Pandanus, phyllotaxy ii 442.
Pandorina, colony i 27.
Panicum ztalicum, malforma-
tion i 178.
Papaver, capsule porose i 16;
flower-bud does not unfold in
darkness i 243.
Papaveraceae, flower, arrange-
ment of parts ii 531, structure
and pollination ii 547.
Papilionaceae, cotylarstorageii
257; flower, symmetric succes-
sion in development ii 543;
laminar growth, eucladous ii
312; gynaeceum, development
ii 559; leaf, branching acro-
petal ii 330.
Papilla, on leaf-surface of Musci
li 143.
ae sacs oe gynaeceum ii 558,
566.
Paraphyllium, of Hepaticae ii
57; of Musci ii 146, nature ii
147.
Paraphyses, of Musci ii 151;
upon prothallus of Pterido-
phyta ii 188, 193, 220.
Parachute-apparatus of fruit ii
570.
Parasitic Fungi, anchoring-
organ developed through con-
tact-stimuli i 269; modifica-
tion of host by i 192.
Parasitism, embryo, reduced inii
254; flower, reduction inii622;
haustorium in ii 224, unlimited
growth ii 225; ovule in, ateg-
miny ii 618, rudimentary ii
620 ; root in, free-living ii 234,
hairless ii 269; vegetative
body in, intramatrical ii 225,
reduction ii 225, thalloid ii 225.
Parietal, layer of sporangium ii
590; placentation ii 564.
Paris, inflorescence-axis trans-
formed into assimilation-axis
It 447-
P. quadrifolia, embryo, retarded
ii 251; rhizome, persistent
geophilous ii 463.
Parkeria pteridioides, physiolo-
gical race ii 595.
Parkinsonia aculeata, phyllo-
dium ii 355.
Parthenogenesis of Angio-
spermae ii 615, 624, 634.
Passertna, javenile form, reten-
tion of i 167.
P. hirsuta, javenile form i 167.
Passiflora, ovary, syncearpous in-
ferior ii 563 ; tendril ii 457.
Pavia macrostachya, \eaflet,
asymmetry 1 122.
Payer on placentation ii 556.
Pearl-gland ii 381.
Pediastrum, ~energid-colony i
24.
P. Boryanum, experimental mal-
formation i 188.
P. granulatum, colony i 26.
Pellia, branching ii 21; colour
of antheridial pits ii 10; di-
oecism ii 80; elaters holding
mass of spores ii 102 ; germina-
tion intrasporogonial ii 106;
monoecism ii 80; nutritive
meristem for embryo li 105;
perichaetium ii 83; sexual
organs, diffuse disposition ii
8c; spore-germination li 108 ;
spores, gradual exit ii 101;
sporogonium with elatero-
phore ii 100.
P. calycina, apical cell ii 21;
elaterophore ii 100 ; perichae-
tium ii 83 ; propagative shoot
ii 48.
L.. epiphylia, apical cell ii 21;
involucellar collar 11 93.
Pellionia, anisophylly i 108;
leaf, asymmetry i 118,
P. Daveauana, anisophylly,
habituali 109 ; leaf,asymmetry
i 116.
Peloria, etiology i 188; Hoff-
mann’s experiments i 189; of
Angiospermae i 189; Pey-
ritsch’s experiments i 188;
transmissible by seed i 184,
190.
Peltate, cotyledon ii 334; hair,
growth processes in li 336;
kataphyll ii 334, climbing
organ ii 334; leaf ii 334, and
alternate phyllotaxy ii 335,
basipetal in development ii
336, biological relationships
ii 335, conditions of develop-
ment ii 335, of Dicotyledones
ii 333, of Monocotyledones ii
329, origin ii 337, protective
function ii 334 ; sporophyll of
Pteridophyta ii 499,
stamen ii 334.
Pelvetia canaliculata, spore-ger-
mination and light i 230.
Peperomia, embryo-sac, pluri-
nucleate ii 637.
se cael spikelet, arrest i
56.
Pentamery, and hexamery in
same plant of Carophylleae ii
538; and tetramery in same
plant of Ruta graveolens ii
538.
Perennating, geophilous shoot
ii 463; prothallus of Osmunda
ii 189.
Pereskia, hook-leaf ii 420.
Perforated, leaf in Aroideae ii
325; water-cells of Musci ii
145.
Perianth, of Zphedra derived
from dermatogen i 17; of
Hepaticae ii 89.
Perichaetial, leaf of Musci ii
152; scale to archegonium of
Symphyogyna ii 83.
Perichaetium of Hepaticae ii
82.
Perigynous gynaeceum ii 558.
Perinium of spore, of Hepaticae
ii 106; vesicular swellings in
Grimaldia ii 107.
Periodic, apical growth of leaf
in Filices ii 318 ; development
of root ii 289, 290 ; geophilous
shoot ii 463; shortening of
root ii 271.
Peristome, absent in narrow-
mouthed capsule of Musci ii
162; derived from amphi-
thecium ii 162; of Musci ii
161, 167.
Permanent retardation of foli-
age of liane ii 454.
Peronospora violacea, doubling of
flower in Anautia arvensis
caused by i 192.
Persistent, cotyledon ii 403;
stipule ii 364.
Personate flower i 131.
Petalophyllum, \eaf ii 38.
Petal, absence in Urticaceae un-
explained ii 551; flag-appara-
tus in Ranunculus ii 551 ;
confluence ii 538; nectary ii
§50, 5513 transformed stamen
il 551.
Petiolar gland ii 362.
Petunia, branching of staminal
primordium ii 5306.
Peyritsch, artificial doubling of
flower i 194; experiments in
peloria i 188.
Pesiza, directive
light i 258.
P. sclerotiorum, tubzrosa, an-
choring - organ developed
through contact-stimuli i 269.
GOEBEL Il
5753
influence of
INDEX
Phaedranassa chloracea,
shortening ii 270.
Phaeophyceae, higher differen-
tiation i 21; long shoot and
short shoot i 35.
Phalaenopsis, assimilation-root
li 284.
P. amabilis, root, flattening and
light i 246.
P. Esmeralda, assimilation-root
ii 284; water-storage root ii 284.
LP. Lueddemanniana, root, dor-
siventral aerial ii 284.
P. Schilleriana, exodermis ii
284; velamen ii 284.
Phalange, staminal ii 533, 534-
Phalaris canartensis, embryo ii
418,
Pharus brasiliensis, leaf, inver-
sion by torsion ii 296.
Phaseaceae, antheridium, de-
velopment ii 14; archegonial
venter ii 153; calyptra ii
153; cleistocarpous ii 160;
protonema ii 129; sporogo-
nium, radial i 236.
Phascum cuspidatum, antheridial
group ii150; shoot with sexual
organs ii 9.
P. ephemeroides, spore, shedding
ii 162.
LP, subulatum, spore, shedding ii
160.
Phaseolus, cotyledon, broad ii
400 ; leaflet, asymmetry i 122;
root-formation and light i 231 ;
stipel ii 380.
communis, root-hair sup-
pressed in water ii 269.
P. multifiorus, fasciation i 190;
leaf-size and correlation of
growth i 211 ; stipule, correla-
tion of growth i 210.
P. vulgaris, etiolated seedling
flowering i 243.
Philadelphus, \eaf-insertion i 93 ;
shoot, dorsiventral lateral i 93.
Philodendron, leaf, pinnatifid by
branching ii 325.
LP. melanochrysum, root, dimor-
phism ii 287.
Philoxerus vermiculatus, \eaf-
succulence and environment i
265.
Phlegmaria-type of prothallus
ii 193.
Phoenix, leaf, development ii
327; piston-cotyledon ii 402 ;
venation ii 340.
P. canariensis, primary leaf ii
327.
Phoenocoma prolifera, leaf with
inverted structure ii 296.
Phormium tenax, \eaf-lamina,
differentiation ii 300.
Photo-plagiotropy i 100.
Photophilous shoot in the soil
ii 466.
root,
12.
bs
689
Phragmicoma, archegonium soli-
tary ii 88 ; auricle ii 58; elater
attached to surface of capsule
il 100; sporogonium without
elaterophore ii 100,
Phragmitis communts, \eaf-apex,
precedence in growth i ii 309.
Phucagrostis, macropodous em-
bryo ii 261.
Phyletic, hypothesis regarding
sporangium ii 605; position
of Casuarina ii 635 ; relation-
ship of Bryophyta and Pteri-
dophyta ii 187; series in pro-
thallus of Pteridophyta ii 210;
significance of protocorm ii 232.
Phyllanthus, correlation i 207,
and direction of shoot i 214;
phylloclade i 20, ii 451; shoot,
dorsiventral lateral i 97.
P. lathyroides i 97; cutting i 51;
dorsiv entrality 1 84.
P. mimosoides i 97.
Phyllocactus, shoot,
and light i 248.
L. latifrons i 248.
LP. phyllanthoides i 248; juvenile
form i 169.
Phyllocactus-form i 169.
Phylloclade i 20, ii 448; of
Asparagineae, structure li 545;
of Dicotyledones i 168, ii
451; of Gymnospermae ii 448;
of Monocotyledones ii 449; of
Pteridophyta ii 448 ; and light
in Ruscus aculeatus i 249; of
Sciadopitys ii 445.
Phyllocladus, juvenile form i 155;
ovule ii 519; phylloclade ii
448 ; pollen-sacii 515; stamen
il 515.
£. alpinus, young fruit ii 519.
Phyllode-formation of Acacia,
independent of environment ii
357-
Phyllodium ii 353; of Acacia
vertictllata,apparentlywhorled
ii 372; of <dcacza, profile-
position ii 293; erroneous use
of term ii 353; transition from
leaf ii 354.
Phyllody, induced by insects i
181 ; of bract ii 197; of carpel
in Trifolium repens i 181 ; of
flower i181, ii 525; of ovule
i ISI, not a reversion i 183,
significance i 182; of pappus
i197; of sporophyll ii 475 ; of
stameni 180; of tendrili 19.
Phyllogenous branching, of
Equisetaceae ii 432; of Sper-
mophyta ii 432.
Phylloglossum, javenile form, re-
tention ii 236; protocorm ii
231, 232; sporangium, mature
ii 578.
P, Drummondi, root, exogenetic
secondary ii 273.
flattening
690
Phyllogontum, apical cell of
stem, two-sided ii 131.
P. fulgens, speciosum, \eaf and
water ii 143.
Phyllome, definition impossible
i 16.
Phyllopodium ii 304.
Phyllotaxy i 74; ofadventitious
twig i 83; and asymmetry of
seedling i 83; and axillary
branching i 81; of bilateral
shoot i 90; cyclic position i
80 ; in dichotomous branching
i 81; and dorsiventrality of
shoot i 93, 94, 96, 160, 161; he-
terodromy i 78; homodromy
i 78; juvenile form distin-
guished by different i 161;
mechanical hypothesis of i 74 ;
of Musci i 78, ii 131; and
peltate leaf ii 335; of shoot,
with contracted internode ii
442, with elongated internode
ii 442; and symmetry i 70;
transition-figure in i 79 ; varia-
tion in deciduous trees i 96.
Physcomitrella patens, spore,
shedding ii 160.
Physcomitrium pyriforme, rhi-
zoid li 116.
P. repens, silver-glance ii 149.
Physiology, and morphology,
relation i 4; Sachs’ definition
i 4.
Phystotium, apical cell of shoot
two-sided ii 41; colour and
light ii 78; shoot ii 41; and
water ii 53; water-sac li 62,
as insect-trap ii 64.
P. cochleariforme, rhizoid, absent
ii 45; valved water-sac ii 63.
£. conchaefolium, water-sac ii
63, 65.
P. giganteum,
water-sac ii 62.
Phyteuma, root, periodic shorten-
ing li 271.
Phytolacca icosandra, doubling of
stamen ii 536.
Phytome of Nageli i 21.
Phytoptus causing malformation
i 195.
Picea, hyponasty and spinasty
i 85; leaf, insertion i 94;
shoot, dorsiventral lateral i 94;
substitution of lateral for lost
terminal shoot i 50.
P. excelsa, hairless root ii 269;
leaf-apex, precedencein growth
ii 309; male prothallus ii
614.
Pileole of Gramineae li 415.
Pilobolus microsporus, sporan-
gium and light i 258.
Pilogyne suaves, tendril, develop-
ment il 425.
Pilostyles, on Astragalus ii 225 ;
29
microcarpum,
on Lerlinia paniculata ii 2
INDEX
flower-bud endogenetic ii 226;
flower-cushion ii 226; sinker
ii 225 ; vegetative body ii 621.
Pilostylesa ethtopica, haustorium
ii 225.
P. Haussknechtiz, parasite ii
225.
f. Ulei, haustorium ii 225;
pollen-sac, opening celis sup-
pressed ii 611.
Pilularia, dorsiventrality i gt ;
leaf, cylindric ii 295, develop-
ment ii 316, wingless ii 314;
rhizoid as temporary fixing-
organ of female prothallus ii
189 ; spore-distribution ii 212;
sporocarp, outgrowth of sterile
leafii 479; stem, creeping i 91.
P. Novae-Hollandiae, sporocarp
hypogeous ii 493.
Pineapple, correlation of growth
in fruit i 212; reciprocal pres-
sure of carpels i 77.
Pinguicula, cotyledon resembles
leaf ii 402; transition between
leaf and shoot ii 236; water-
absorption by leaf ii 349.
P. caudata, storage-leaf ii 398.
P. vulgarzs, flower, development
of dorsiventral ii 542.
Pinnae, sequence of origin in
Guarea ii 310.
Pinnate leaf, relation to digitate
leaf ii 332.
Pinnatifid leaf formed by
branching, not in Palmae ii
326; in Philodendromn ii 325.
Pinnule, acropetal succession in
Cycas Seemannz ii 322; basi-
petal development in Cycada-
ceae ii 322; of Cobaeascandens,
stipular ii 360; of Gleichenia-
ceae ii 593; of Guzlandina,
stipular ii 361; reduction in
Acacia lophantha i 155, ii
381.
Pinus, androgynous cone ii 524;
correlation, of growth of twig
i 209, and direction of shoot
i 214; flower, position ii 472;
juvenile form i 153; ortho-
tropy and plagiotropy 1 69;
pollen-sac, lateral ii 516, open-
ing, longitudinal ii 610; short
shoot and long shoot i 35, ii
444.
P. maritima, flower, androgy-
nousii 471;*seminiferous scale,
malformed ii 524.
P. monophylla, Pinea, juvenile
form i 153.
LP. Pumitio, double needle ii 445 ;
prothallus, male ii 614; pol-
lination ii 522.
P. Strobus, short shoot and long
shoot ii 444.
P. sylvestris, double needle ii
445; juvenile form i 153;
leaf-apex, precedencein growth
ii 309; prothallus, male ii
614; root, hairless ii 269;
short shoot and long shoot ii
444.
Pistia, phyllotaxy ii 442; root
lateral, not geotropic ii 276,
place of origin ii 274.
P.. Stratiotes, root-apex ii 267;
root, hairless ii 269.
Piston-cotyledon ii 402.
Pisum, correlation and formation
of tendril i 216; stipule,
asymmetry i 125; tendril, de-
velopment ii 423.
P. sativum, foliation of tendril,
artificial ii 425; leaf, experi-
mental malformation i 191;
root-hair suppressed in water
li 269.
Placenta, absent in some Pteri-
dophyta ii 472; of Angio-
spermae, foliar origin ii 556,
interpretation ii 556; axial ii
556; carpellary ii 556; defi-
nition ii 472; Payer’s views ii
556.
Placentation central ii 564;
free-central ii 564, 566; of
inferior ovary ii 567; parietal
ii 564; septal ii 562.
Placentoid of Hyoscyamus ii
599-
Placophora, pro-embryo i 150.
Plagiochasma, air-cavities ii 72,
75; involution of parts to
resist drought ii 65; sexual
organs, grouping ii 85.
P. Aitonia, antheridial groups ii
31, 843; germ-plant ii 113, and
light i 240.
Plagiochtla, archegonia in groups
with perichaetium ii 89 ; elater
free iigg; flagellum ii 43 ; leaf
ii 41,concrescence ii 42; sporo-
gonium without elaterophore
li 99.
P. asplentoides, directive influ-
ence of light i 234.
LP. circinalis, involution of parts
to resist drought ii 66.
P. connexa, conjugata, concre-
scence of leaf ii 42.
P. cucullifolia, water-sac ii 60.
Plagiogyria, sporangium and
annulus ii 590.
Plagiotropy, and anisophylly i
99, 113; definition i 67; often
antecedent to dorsiventrality i
68; dominant in Hepaticae ii
18 ; of juvenile formi1ms59; of
leafi68; of lateral shoot i 69,
94, 95, 2143; of shoot ii 457,
and conditions of life ii 459,
concatenation in trees i 70,
and correlation i 214, with
elongated internodes ii 459,
factors causing ii 461, of He-
ee ©
a al Oe al a
—
ee Te Se oe
paticae i 101, of Muscii 100,
and orthotropy i 68, 94, 160,
214, ii 457, of Pteridophyta i
102, of Spermophyta i 111, of
trees ii 457, transition to ortho-
tropy i 69, ii 457, 459; and
thizophores ii 228; of subter-
ranean organ i 68 ; of vegeta-
tive shoot in herb ii 457. ©
Plan of structure of De Candolle
ll §33- MAR
Plantago, axillary branching ii
433; leaf-stalk ii 300.
P. major, a halophyte i 266.
P. media, venation ii 344, striate
ll 339-
Plant-body, differentiation i 3.
Plasmodial tapetum ii 596.
Plasmodium of Myxomycetes
i 25.
Plastic material, direction of in
regeneration i 45.
Plasticity, of potato i 215; of
prothallus of Pteridophyta ii
190.
Platanus, cotyledon, narrow ii
406.
Platycerium,heterophylly ii 350;
mantle-leaf ii 350; prothallus,
development ii 204; root,
transformation into shoot i 12,
il, 2272
P. alcicorne, Hilli, Stemmaria,
Willinckiz ii 227.
P. biforme ii 350.
P. grande ii 350; sporangium,
opening ii 588.
Platystachyae -Selaginelleae,
anisophylly ii 506; flower ii
507.
Pleuroplastic type of laminar
growth ii 312.
Plocamium, adhesive disk and
contact i 269; division of
labour amongst shoots i 39.
IP. mee adhesive disk i 40,
8.
Plug of flower of Zyzzsetum ii
500.
Plug-tip ii 309.
Pluricellular, archesporium of
Angiospermae ii 633; plant of
Thallophyta i 22.
Pluriciliate spermatozoid of
Pteridophyta ii 172.
Plurilocular, ovary of syncar-
pous gynaeceum ii 562; uni-
locular ovary becoming ii
565.
Plurinucleate embryo-sac of
Peperomia ii 637.
Pluriovular ovary of Ranuncu-
laceae ii 560.
Pneumatophore ii 278; mor-
phological significance ii 278.
Poa, malformation i 178; vivi-
pary, transmission i 184.
| £. alpina, vivipary i 179, 185.
INDEX
P. bulbosa, tuber-formation i 263;
vivipary i179.
P. nemoralis, gall formed by
Cectdomyia Poae i 200.
Podetium of lichens, function
Aries.
Podium in flower of Lycopodi-
neae ii 510.
Podocarpeae, flower, female ii
520, morphology ii 524; ovule,
anatropy ii 524.
Podocarpus, flower, female, posi-
tion ii 523.
P. enstfolius, flower, female ii
520; ovule, reduced in number
ii 520.
Podostemaceae, anchoring-
organ ii 222; assimilation-root
ii 280; dorsiventrality i gi;
haptera ii 222, 265; leaf,
without vascular bundle ii 293;
protocorm ii 232; reduction
of form and mode of life ii
622; root, aerial, flattening i
246, dorsiventral and light i
246, flattened i 247; root
transformed to shoot ii 228;
root-borne shoot i 42, ii 228,
276, 280; rootless ii 265;
shoot, adventitious ii 276, its
position ii 277.
Pogonopus Ottonts, flower, un-
essential zygomorphy i 131.
Polar, construction i 66; differ-
entiation, and light i 229, of
Algae i 229, in germination of
radial spores i 229; nuclei of
embryo-sac of Angiospermae
ii 635.
Polarity of plants i 44, 65.
Pollen, filamentous, of marine
Angiospermae ii 611.
Pollen-chamber,of Cycadaceae
ii 612; of Gnetaceae ii 516;
of Ginkgo ii 627.
Pollen-grain, of Angiospermae
ii 527, germination ii 614; of
Gymnospermae, germination
ii 612; of Spermophyta ii 611.
Pollen-mother-cell of Cyclan-
thera ii 620.
Pollen-sac, a sporangium li 573;
of Angiospermae ii 597, 610,
active opening cells ii 577, 600,
610, and their suppression ii
611, archesporium ii 599, arrest
ii 554, confluence ii 554, de-
velopment ii 599, endothecium
ii 600, four ii 553, nutrition of
sporogenous cell-mass ii 597,
position li 553, primary tapetal
layer ii 600, reduction by di-
vision of anther ii 554, sup-
pression ii 554, variation in
number ii 554; of Coniferae
ii 610, lateral ii 516, position
ii 515; of Cycadaceae ii 610
position ii 514; of Ginkgoa-
Yy2
691
ceae, position ii515; of Gneta-
ceae ii 610, position ii 526; of
Gymnospermae ii 610, active
opening cells ii 577, 611,
number varies ii 553, position
11514, 526; of Juniperus, ter-
minal ii 516; reduction of
chromosomes within ii 598;
of Spermophyta ii 610, plas-
modial tapetum ii 596; steri-
lization ii 554, 597-
Pollen-tetrad ii 611, 626.
Pollen-tube, acrogamous ii613;
of Angiospermae, function ii
614; basigamous ii 614; of
Cycadaceae ii 613: of Gymno-
spermae ii 612; haustorium ii
612, 614; a non-fertilizing
stimulus ii 624; and partheno-
genesis ii 624.
Pollen-tube-cell of Cycadaceae,
nature ii 613.
Pollination, anemophily of
Monocotyledones ii 547; of
Abietineae ii 522 ; and flower-
structure of Angiospermae ii
547; of Cycadaceae ii 513;
and number of flowers in Sper-
mophyta ii 547.
Polycardia phyllanthoides, in-
florescence epiphyllous ii 437.
Polyembryony ii 637.
Polyergic plants i 23.
Polygonaceae, cladode ii 452;
cotyledon, asymmetry ii 406;
ochrea ii 373; stipule, axillary
li 373.
Polygonatum, inflorescence-axis
transformed into assimilation-
axisii 447; sympodial rhizome
ii 24.
P. muitifiorum,geophilousshoot,
depth in soil ii 465, periodic
ii 463; root, shortening ii
270.
Polygonum, cotyledon, asymme-
try i IIs.
P. amphibium, root, endogenetic
adventitious ii 273.
P. chinense, fungus-gall i 196.
P. emarginatum, cotyledon,
asymmetry ii 407.
P. Fagopyrum, cotyledon, asym-
metry i I15, ii 407; root,
lateral, place of origin ii 274.
Polymerous gynaeceum ii 558.
Polyotus, water-reservoir ii 60.
P. claviger, amphigastrium and
water-sac ii 50.
Polyphyletic, development of
gametophyte of Pteridophyta
ii 210; originsi1g; origin, of
construction of sexual shoots
of Hepaticae ii 93, of Gymno-
spermae ii 631.
Polypodiaceae, antheridium,
development ii 179, opening
of free ii 177; prothallus ii
692
200, configuration and light
ii 202, dorsiventrality rever-
sible i 227, hair ii 200, heart-
like ii 201%, meristem ii 204,
not heart-like ii 205, regenera-
tion i 43; sporangium, dorsi-
ventral ii 574 ; spore-germina-
tion ii 413; sporophyll, and
foliage-leaf alike in position
and origin ii 477, as new for-
mation ii 478.
Polypodium crenatum, sporan-
gium protected by hairs ii
ve
pags ee ees dorsal rows of
leaves igi; dorsiventrality of
stem i 91; leaf ii 350.
P. imbricatum, ‘elaters’ ii 576.
LP. jubaeforme, sporangium pro-
tected in pit ii 498.
P. obliguatum,prothallus, bristle-
hairs ii 201; sporangium, pro-
tection ii 497 ; symbiosis with
fungi ii 218.
P. propinquum, heterophylly ii
350; nest-leaf ii 350.
P. querctfolium, dorsal rows of
leaves i 91; dorsiventrality of
stem ig1; heterophylly ii 349;
nest-leaf ii 350.
P. saccatum, sporangium pro-
tected in pit ii 498.
P. Schomburgkianum,
axis, flattening i 92.
P. taeniosum, dorsiventrality of
stem i gI.
£. vulgare, fern-leaved ii 345;
juvenile form i 152; reversion
1185.
P. vulgare, var. cambricum, mal-
formation of leaf i 185.
Polypompholyx, leaf, transition
to shoot ii 237; tubular ii 338,
ovule, haustorium ii 640, nu-
tritive tissue ii 640; rootless
ii 234, 265; sepal, confluence
11 §39-
P. muiltifida, chalazal funicular
nutritive tissue ii 641; ovule,
epithelium ii 641.
Polyporus fomentarius, directive
influence of light i 257.
Polysiphonia Binderi, pro-em-
bryoi 150.
LPolysphondylium violaceum, life-
history i 26.
Polystichum angulare, var. pul-
cherrimum., apospory ii 608.
Polytrichaceae, antheridium,
position ii 150; epiphragm ii
166; rhizoid-strand ii 120;
spore, shedding ii 166.
Polytrichum, antheridium, open-
ing ii 11; calyptra, hairs ii
154; capsule, porose i 19;
embryo, protection ii- 153;
hypsophyll ii 135; juvenile
form i 151; leaf, differentia-
shoot-
INDEX
tion ii 134; leaf-lamella ii
144; paraphyses ii 151.
Polytrichum commune,
gonium ii 158.
Polyzonia jungermannioides,
concrescence of hair-roots i
54; differentiation i 21; divi-
sion of labour amongst shoots
139; dorsiventral involution i
86.
sporo-
Pomaceae, reversion of thorn-
shoot to foliage-shoot ii 453 ;
transition from foliage-shoot
to thorn, ii 452.
Pontederia, lateral
geotropic ii 276,
Pontederiaceae, juvenile form
i 164.
Populus, callus-root i 44;
gravity and regeneration i 222.
P. nigra i 222.
P. pyramidalis i 222; arrest of
leaf-bud and light i 232.
Porogamy ii 615.
Porose, capsule of Papaveriig;
of Polytrichum i 19.
Posidonia, macropodous embryo
ii 261.
Position, of leaf in relation to
stem-branch i 81; of new
organs in regeneration i 45;
of organs on radial axes i 73.
Post-embryonal development
of cotyledon ii 404.
Potamogeton, stipule, axillary ii
375:
P. natans, reversion-shoot i 172.
Potamogetonaceae, juvenile
form i 164; macropodous
embryo ii 260.
Potato, correlation and shoot
system i215; plasticity i215;
tuber-formation retarded by
light i 232.
Potentilla, flower, arrangement
of parts ii 530.
P. anserina, leaf, interruptedly
pinnate, i 127, ii 331; leaf-
branching, basipetal ii 330;
plagiotropous shoot ii 457.
P. fruticosa ii 530.
P. nepalensis, flower, arrange-
ment of parts ii 531.
P. reptans, plagiotropous shoot
ii 457. :
Pothos celatocaulis, juvenile form
of aroid i 157.
P. flexuosus, yavenile form of
Anadendrum medium i 158.
Pothos-form of Aroideae i 159.
Pottia, \eaf-lamella ii 144.
P. barbuloides, curvifolia ii 144.
£. truncata, spore, shedding ii
165.
Pretssia, air-cavities ii 73, 75;
antheridiophore ii 85; apical
cell ii 21; archegoniophore
ii 85; breathing-pore and
root not
transpiration ii 74; scleren-
chyma-fibres ii 76; spore,
germination ii 107, 111, thick-
walled, ii 106.
Preissia, commutata, breathing-
pore ii 74; germ-plant and
light i 239; rhizoid ii 46.
Pressure, and leaf-position i
74; and development of in-
florescence of Leguminosae i
138 ; cause of oblique flower of
Solanaceae ii 544; reciprocal,
changing form of organs i 77.
Prickle, an emergence ii 429;
a juvenile form i 264.
Prickle-formation and medium
i 263.
Primary leaf, of Angiospermae
i155, ii 336; of aquatic plants
i 164; of Bryophyta i 151,
of climbing plants i 157; of
Gymnospermae i 153; of
marsh plants i 164; of Pteri-
dophyta i151; of xerophilous
plants i 166; and regeneration
i 46; reversion to i 172.
Primary tapetal layer of pollen-
sac of Angiospermae ii 600.
Primitive type, Casuarina, not
ii 633; Lycopodium inundatum
ii 609.
Primordium, of organ not
indifferent i 8; of root on
shoot, latent ii 275; trans-
formation hindered i 11.
Primula, gynaeceum paracar-
pous ii 558.
P. farinosa, placentation ii 566.
P. sinensis, branching of staminal
primordium ii 536.
Primulaceae, flower, structure
ii 540; gynaeceum, paracar-
pous ii566; ovule, bitegminous
ii 617 ; placentation ii 566.
Pritchardia filifera, \eaf-form,
development ii 326.
Pro-embryo, of Algae i148; of
Angiospermae ii 642; Chan-
transia,ait49; of Hepaticae
ii 107; of Musci ii 116.
Pro-embryonal gemma of
Musci ii 125.
Profile-position of leaf ii 135,
293, 328.
Progressive serial succession
of lateral organs i 41, ii 542.
Propagation, asexual, of He-
paticae i 48, ii 47, of Musci i
47, li 138, of Pteridophyta,
gametophyte ii 213, of Pteri-
dophyta, sporophyte ii 441,
467, of Spermophyta ii 469;
by cutting i 45; organs of ii
5733; sporangium an organ of
ii 573-
Propagative, adventitious pro-
thalloid shoots ii 213; capacity
of organs, variation i 46;
.
7
.
organs, cannot be referred back
to vegetative organs i 18, of
higher plants i 20.
Prophyll ii 382; asymmetry,
ii 383; fleshy expanding, of
Cyperus alternifolius ii 384,
443; function ii 383; trans-
formation to tendril ii 384,
426; in winter-buds ii 383.
Prophyllar, parachute of fruit
of Tila ii 383 ; tendril of Cu-
curbitaceae ii 384, 426.
Prop-root ii 277.
Proteaceae, leaf, cylindric ii
293, profile-position ii 293;
leaf-form and life-conditions
ii 294.
Protean vegetative organ of
Utricularia ii 240.
Protection, of bud of Lrownea
erectai7; against drought i
261, ii 65, 148; of ripening
seed, of Ginkgo ii 523, of Co-
niferae ii 523 ; of seed of Cycas
ii 512; of sporangium ii 474,
496, 497-
Protective, cell-rows and scales
in Hepaticae ii 30; mucilage
ii 27, 139, 154, 359) 374, 381;
our of Hepaticae ii 79;
organ, bract, ii 391, 397, coty-
ledon ii 401, hypsophyll ii
397, kataphyll ii 334, 385,
ligule ii 377, peltate leaf ii
334, pinnule of Gleicheniaceae
ii 318, stipule ii 359, 363,
386, stipel ii 380; ptyxis i
85, ii 310; taste-substance of
Hepaticae ii 79.
Prothallus, adaptations ii 215,
and phylogeny ii 210; adven-
titious shoots ii 213 ; ameristic
ii 220; of Angiospermae ii
614, 636; apandrous ii 220;
apogamy ii 220; aquatic ii
217 ; arrested through correla-
tion i 58; branching ii 200;
correlation of growth and
sexual organs i 142; distribu-
tion of sexual organs ii 220;
dorsiventrality i 227, 229, 231,
ii 191, 193; duration of life
ii 189 ; of Equisetaceae ii 195 ;
filamentous and surface growth
and light ii 202; of Filicineae
ii 197, Eusporangiate ii 198,
Heterosporous Leptosporan-
giate i 220, ii 180, 210,
Homosporous _Leptosporan-
giate ii 199, evolution ii 208 ;
of Gymnospermae ii 612, 627 ;
heart-like ii 205 ; influence of
gravity i 219; of Isoetaceae ii
181, 212; of Lycopodineae ii
182, I91; and pollination in
Spermophyta ii 623, 628;
propagation, asexual ii 213 ;
of Pteridophyta, rhizoid one-
INDEX
celled ii 188; radial ii ig1;
reaction to external stimuli i
218; reversion ii 205; sapro-
phytic ii 193, 198; symbiosis
with fungiii 198, 218; terminal
and lateral meristem i 231, ii
205; and tubercule primaire
ii 194, 217; tuberous ii 198;
tubers on ii 217; water-rela-
tionships ii 215. See also
Megaprothallus, Micro-
prothallus.
ee oe nic eokay
i 26.
Protocorm, of Dicotyledones ii
232; of Lycopodium ii 231;
of Monocotyledones ii 232;
phyletic significance ii 232; of
Phylloglossum ii 232; tuber-
ous ii 231.
Protonema, arrest through
correlation i 58; branching
and light i 234; from calyptra
in Conomitrium ii 154; and
external factors ii 234 ; gemma
ii 140; ‘leaf, in Ephemerum
serratum ii 129; and light ii
241; luminous, of Schistostega
ii 120; persistent in Lphe-
merum 1 58, 147; precedes
bud-formation in Musci i 48;
resting state i 262; saprophytic
life ii 128; separation-cell ii
125; short shoot and long
shoot ii I1g; significance ii
127; special organs of assimi-
lation 1i 121.
Protonema -thread,
scence ii 121.
Protophyll, Du Petit Thouars’
name for cotyledon ii 400.
Prunus, adventitious shoot ii
277; shoot-thom ii 452;
short shoot precedes long
shoot in unfolding ii 445;
witches’ broom i 192.
P. avium, \aminar growth, basi-
plastic ii 312; leaf-lamina,
branching i 312.
P. Padus, kataphyll, develop-
ment ii 387.
P. spinosa, transformation of
shoot to thorn il 440.
Psamma arenaria, ligule ii 376.
Pseudo-midrib of Hepaticae ii
xa
Pimhideindd beeen of Musciii 161.
Psilotaceae, cladode, ii 448;
sporangium and spore-distri-
bution ii 578; sporophyll and
sterile leaf compared ii 504.
Psilotum, cladode ii 448; root-
less ii 264; shoot, rootless ii
234; shoot-apex, unprotected
hypogeous ii 266; sporangium,
relationship ii 505 ; sporophyll
and sterile leaf compared ii
504; sterile cells of sporogen-
concre-
693
ous tissue ii §97 ; sterilization
in sporangium ii 605.
Psilotum complanatum, cladode
ii 448.
P. complanatum (P. flaccidum),
sporangium, origin and posi-
tion ii 504.
Ptelea trifoliata, leaflet, asym-
metry i 122.
Pteridophyta, annual, rare ii
441; antheridium ii 172, de-
velopment ii 177, develop-
mental series ii 180, embedded
ii 174, free ii 177, structure ii
173; apogamy ii 187, 220;
archegonium ii 183, develop-
ment ii 184, number and fertil-
ization ii 547; archesporium
ii 601; branching, variation
in place of ii 431; cladode ii
448; conformity in develop-
ment of antheridium and
archegonium ii 185 ; cotyledon
ii 400, arrested foliage-leaf ii
400, not storage-organ ii 400,
not suctorial organ ii 400,
resembles primary leaf ii 402 ;
egg ii 184; embryo, and
gravity i 219, organs ii 242;
flower ii 472, use of term ii
47°; gametophyte, configura-
tion ii 188, monocarpic ii 189,
polyphyletic development ii
210, significance in mainten-
ance of forms ii 190, symmetry
ii I91; gemma ii 213, 467,
origin of formation ii 215;
Heterosporous ii 577, 603,
antheridium of, development ii
180, prothallus of, limited de-
velopment i 142, ii 190;
Homosporous, antheridium of,
development ii 178; hook-
leaf, ii 419; induction of
limited growth ii 577; involu-
tion, dorsiventral i 86; iso-
spory ii 577; juvenile form,
configuration i151; kataphyll
ii 350; leaf-primordium, origin
from group of cells ii 306,
origin from one cell ii 305 ;
megasporangium ii 602; micro-
sporangium ii 602; paraphyses,
rare ii 220, of prothallus ii
188 ; phyletic relationship with
Bryophyta ii 187; phyllotaxy,
heterodromy i 78, homodromy
i 78; prothallus, adaptation
ii 215, ameristic male li 220,
asexual propagation of ii 213,
dorsiventral and light ii 191,
dorsiventral and radial ii
210, dorsiventrality inherited
character ii 191, duration
of life ii 189, hairs ii 188,
and light i 241, phyletic
questions ii 210, plasticity ii
190, one-celled rhizoid ii 188,
694
water-relationship ii 215; root,
bud i 46, ii 431, lateral, origin
in endodermis ii 273; root-
less ii 263; sexual organs ii
172, abnormal ii 187, com-
pared with those of Bryophyta
ii 185, distribution ii 220,
systematic importance ii 186;
spermatozoid ii 172; spor-
angium, active cells of exo-
thecium ii 611, active cells
in wall ii 577, development
ii 600, inception ii 601, and
light i 245, mature ii 578,
origin from leaf-organ ii
473, position ii 493, radial
ii 574, resembles ovule of
Cycadaceae ii 626, stalked and
unstalked ii 574; sporophyll
ii 472, function ii 473, as new
formation ii 477; stipule rare
ii 365 ; subterranean parts have
no chlorophyll i 103; stem-
apex, suppression of lateral
shoot ii 431; symbiosis with
fungi ii 218.
Pteris cretica, apogamous shoot
and light i 229; circinate
ptyxis, absent ii 320; leaf,
development ii 320.
P. longifolia, prothallus and
light ii 202; spore-germina-
tion li 203.
P. quadriaurita, gall-formation
i 198; malformation caused
by fungus ii 526; witches’
broom i 193.
P. semipinnata, pinnule, lateral
formation ii 480.
P. serrulata, leaf, development
ii 314, 320.
P. umbrosa, circinate ptyxis
absent ii 320; leaf, develop-
ment ii 320.
Pterobryella longifrons, scale-
leaf ii 133.
Prerocarya caucasica,
asymmetry i 122.
LPierospermum javanicum, sti-
pule with pearl-gland ii 381.
Ptyxis, and growth-relationship
in leaf ii 311; circinate, in
leaf with apical growth ii 310,
321; influence on of space-re-
lationships in Caltha palustris
ii 311; involutei 85, ii 310; re-
volute of Drosophyllum ii 310.
Pull-root ii 269 ; and geophilous
shoot ii 466; regulates depth
of shoot in soil ii 270.
Pulsatilleae, dicotylous embryo
ii 250; involucre ii 550.
leaflet,
Pycnothelia, symmetry and
direction i 72.
Pyrola, adventitious shoot,
position ii 277.
Pyrola (Monesis) uniflora, free-
living root ii 234.
INDEX
Pyrolaceae, embryo, reduced
ii 254; inflorescence, unilateral
i136.
Pyrus, short shoot precedes long
shoot in unfolding ii 445.
P. japonica, adventitious shoot,
position ii 277.
LP. Malus, ovary, development
ii 568; reversion of thorn-
shoot to foliage-shoot ii 453.
Quadrants of moss-capsule ii
155.
Garttatiee influence, of corre-
lation i 2143; of gravity i 224;
of light i 238.
Quantitative influence of cor-
relation i 207.
Quercus, affected by Cynips
vosae i 198; anisophylly of
lateral shoot i 93; compensa-
tion of growth in fruit i 207;
cotyledon, broad ii 406, emar-
ginate ii 407, peltate ii 334;
flower, position of male and
female ii 472; gall-formation
i 199; kataphyll, stipular ii
386; laminar growth, pleuro-
plastic ii 312; leaf-lamina,
branching ii 312; leaf-insertion
on lateral shoot i 93; ovule,
formed through stimulus of
pollen-tube i 269, ii 263, sup-
pression of i 58 ; root-develop-
ment, periodicity ii 290; sti-
pule caducous ii 363, protec-
tive function ii 363.
O.pedunculata, sesstliflora, shoot,
dorsiventral lateral i 93.
Quisgualis chinensts, change of
function of leafig; climbing
organ i 9.
Q. indica, hook for climbing ii
420.
R.
Raciborski induces _ experi-
mental malformation i 187.
Racomttriun, hair-point ii 149 ;
papilla on leaf-surface ii 143.
Racopilum, anisophylly i 100.
Radial, axis, position of organs
i 73, with plagiotropy i 85;
construction, definition i 66,
of leaf, how brought about
i114, of prothallus of Pterido-
phyta ii 191; corolla, evolution
ii 553; and dorsiventral, flower
i 128, 129, ii 544, forms in
Hepaticae ii 18, forms in Musci
ii 18, inflorescence i 134, pro-
thallus of Pteridophyta ii 210,
lateral shoot, transition i 98;
flower of Selaginella primitive
ii 509; lateral flower i 133;
leaf, in Australia ii 293, of
Monocotyledones ii 328 ; shoot
of Musci ii 132; spore, polar;
differentiation in germination
i 229; sporangium of Pterido-
phyta ii 574; sporogonium of
Bryophyta i 236, ii 574.
Radula, auricle ii 58; gemmae ii
51; sexual shoot, dorsiventral
ii 89; spore-germination ii
' 108; sporogonium, develop-
ment ii 103.
R. complanata, branching in rela-
tion to leaf ii 44.
R. pycnolejeuniordes, water-sac
ii 59, as animal-trap ii 64.
R.tjtbodensis, archegonial groups
ii 88.
Rafflesiaceae, embryo, reduced
11254; parasitism ii 225; seed
with small embryo and endo-
sperm ii 631.
Ranunculaceae, assimilating
shoot-axis, arrest of leafii 446;
correlation, carpel and ovule
i 59; dédoublement ii 533;
flower-envelope, evolution ii
549; flower-nectary ii 430;
ovary, monomerous ii 559,
reduction of ovules ii 560;
ovule, arrest i 59, carpellary ii
560, position in ovary ii 560,
variation in number of integu-
ments ii 617; sole of carpel,
development ii 560; trans-
formation of stamen il 555.
Ranunculus, ovary, development
ii 560, reduction of ovules ii
560; ovule, position ii 482;
petal, nectariferous ii 550;
petaline flag-apparatus ii 551.
R.acris bypsophyll,dividediiz93.
R. aguatilts, leaf, divided sub-
merged ii 358.
Rk. Ficaria, antagonism between
vegetative propagation and
seed-formation i 213 ; embryo,
retarded ii 249; root-develop-
ment, periodicity ii 289 ; root-
tuber ii 289.
R. fluitans, root, endogenetic
adventitious ii 273; water-leaf
and land-leaf i 260.
R. multifidus, leaf, divided sub-
merged ii 358; water-leaf and
land-leaf i 261.
Raphanus, cotyledon emarginate
li 407.
Reaction of organs to external
stimuli i 217.
Reboulia, air-cavities ii 75; invo-
lution of parts to resist drought
ii 65.
Receptacle ii 472.
Reciprocal, influence of organs
i 206; pressure changing form
of organs i 77.
Reduced, form of Filices ii 264;
leaf in juvenile stage ii 447;
sporangium of Heterosporous
Filicineae ii 574.
ee
ee a
Loe ey eT Ie Ee tee ee ee
Reduction, of chromosomes, in
Bryophyta ii 8; and spore-
development ii 596, 598, 625;
of form and mode of life i 225,
241, 622; in gynaeceum of
Angiospermae ii 548, 622; in
number, of megaspores ii 626,
of parts of flower by arrest
ii 546, of parts of flower by
confluence ii 538, of pollen-
grains ii 626, of pollen-sacs
ii 554, of ovules in ovary ii
560, 621; in ovule, of Angio-
spermae ii 622, and parasitism
and saprophytism ii 618; in
pollen-tube of Gymnospermae
ii 614; of prothallus, method
ii 200; series i 61; of water-
channels in leaf ii 293.
Regeneration, bulbils in i 45;
and callus i 44, 222; direction
of plastic material ini 45; em-
bryonal tissue first formed i 43;
in Fungi i 49; and gravity i
45, 221; in Hepaticae i 48,
ii 52, 67; from leaf i 45, 50;
and light, in Algae i 237; in
Muscii48,ii52; new formation
of organs in i 44; and polarity
i 44; position of new organs in,
definite i 45; of prothallus of
ferns i 43; of root-apex i 43;
from shoot i 46; at vegetative
point i 41; of vegetative point
1 43.
Regular flower i 128.
Relationships, of correlation i
206 ; of foliage leaf and sporo-
phyll i 11, ii 474, 498, 509;
of juvenile and adult form i
143; of organs, to external
stimulus i 217, to gravity i 219,
ii 76, to light i 227, ii 76, 149,
to mechanical stimulus i 260,
to water i 260, ii 52, 141, 215;
of shoot to function ii 441; of
symmetry i 65, of flower i 128,
ii 528, 544, of flower, Spren-
gel’s interpretation i 132, of
inflorescence i 128, 134, of
leaf i114, ii 293, of prothallus
ii1g1, of shoot i 84, 11 18, 131,
442, 459, of sporangium ii 475,
574, of sporogonium ii 93, 157,
of stipule ii 366.
Remusatia vivipara, gemma ii
469.
Renovation-shoot,
leaf-form i Igo.
Reproduction, shoot in the ser-
vice of ii 467.
Reproductive, capacity varying
with age i 143; organs and
vegetative growth, antagonism
between i 142, 212, ii 212,
605.
Reseda, flower, development ii
542, dorsiventral i 129, ii 542;
modified
INDEX
gynaeceum, development ii
565; style, formation ii 565.
Reseda odorata, phyllody i 181.
Resedaceae, flower, develop-
ment ii 545.
Reserve-material, cotyledon as
reservoir ii 401; hypocotyl as
reservoir ii 258.
Restiaceae, assimilating shoot-
axis with arrested leaf ii 447.
Resting, bud i 174, 218, ii 44,
398; state, and drought i 261,
sclerotium, a i 262.
Retardation in development i
57-
Retarded, embryo ii 252; forma-
tion, tubular leaf as ii 337.
Retention of water, in Hepaticae
ii 53; in Musci ii 143.
Reticulate venation ii 338.
Retinispora, juvenile form of
Cupressineae i 154.
Reversible dorsiventrality of
prothallus of Filices i 228.
Reversion, causes inducing i
173, 185, 218, 242, 260, ii 205,
448; to juvenile form i 145,
171, 218, 242, 260, ii 447, 451;
of leaf to thallus-form in Jun-
germannieae ii 42; and malfor-
mation i 183, 185; of thorn-
shoot to foliage-shoot ii 453.
Rhamnaceae, cladode ii 451.
Rhamnus cathartica, shoot-thom
ii 452; transition between epi-
geous and hypogeous cotyle-
don ii 403.
R. Frangula, laminar growth,
pleuroplastic ii 312; transition
between epigeous and hypoge-
ous cotyledon ii 403.
Rhaphidophora-form of Aroi-
deae i 159.
Rhaphis, \eaf-form, development
ii 327; ligule ii 378.
Rheum undulatum, ochrea, split-
ting ii 373.
Rhinantheae, haustoriumii 224.
Rhinanthus, hypsophyll formed
by leaf-base ii 394.
R. major, hypsophyll ii 391;
transition from foliage-leaf to
hypsophyll ii 392.
Rhipsalis, juvenile form i 170;
Phyllocactus-form i 169.
R. Cassytha, paradoxa, juvenile
form i170.
Rhizoid, of Algae i269; absent
in aquatic Hepaticae i 269,
ii 45; absent in prothallus
of aquatic Pteridophyta ii
189; anchoring-disk on ii
45; of Chara ii 117, and
light i 231; developed through
contact-stimuli i 269; of He-
paticae ii 45, division of labour
ii 45; of Musci ii 45, 116; of
Pteridophyta ii 188 ; smooth ii
695
47; symbiosis with fungi ii
218; trabecular ii 47; trans-
formation in Hepaticae ii 47;
unicellular and pluricellular in
Pteridophyta ii 189; of Utrz-
cularia ii 23,7; and water-sac,
correlation in Hepaticae ii 45.
Rhizoid-bristle of Dumortiera
hirsuta ii 47.
Rhizoid-disk of epiphytic He-
paticae li 45.
Rhizoid-strand, of Hepaticae
ii 32; of Musci ii 120.
Rhizome of Begonia Rexii20;
of Hepaticae, sympodial ii 25;
perennating geophilous ii 463;
of Polygonatum i 24.
Rhizophora, embryo, viviparous
ii 255; sterilization in pollen-
sac li 555, 597.
R. mucronata, septate pollen-
sac il 555.
Rhizophore of Selaginella ii
228 ; a further development of
stalk of root ii 231; develop-
ment ii 229; morphological
nature ii 230; transformed into
leafy shoot ii 229.
Rhizophoreae, prop-root ii 277.
Rhodochiton volubile, forerunner-
tip li 308.
Rhododendron, ovary, syncar-
pous superior ii 563.
Rhoeadinae, flower, arrange-
ment of parts ii 532.
Rhus Cotinus, correlation of
growth in flag-apparatus i
212; flag-flower ii 571.
Rhynchoglossum, anisophylly,
habitual i 113.
Rhyncholacis macrocarpa, root-
less ii 265.
Riband-form of leaf in mono-
cotylous aquatic plants ii 357.
Ribesiaceae, suspensor-hausto-
rium li 642.
Riccia, apical angle ii 21 ; arche-
gonium, free ii 14; oil-bodies ii
79; rhizoid, absent in water-
form ii 45, present in land-
form ii 45; scale ii 28 ; sexual
organs, diffuse disposition ii
80,84; sporogonium, internal
differentiation ii 97.
R. bulbifera, tuber ii 7°.
R. ciliata, habitat ii 71.
R. crystailina, air-chamber ii 72;
scale ii 28.
R. glauca, regeneration ii 67;
unwettable thallus ii 70.
R. fluitans, air-chamber ii 72;
antagonism between repro-
ductive and vegetative organs
i 213; land-form and water-
form i 269, ii 34; protective
scale ii 29; relationship to
water ii 52; rhizoid and con-
tact stimulusi 269; thallus ii21.
696
Riccta hirta, pro-embryo ii 111.
R. inflexa, involution of parts to
resist drought ii 65.
R. lamellosa, oil-bodies ii 79 ;
scale ii 30; water-excretion ii
a
Rr! natans, air-chamber ii 72;
forked thallus ii 33; land-
form ii 34, 47; scale ii 30, 33;
tuber ii 67; water-form ii 34.
Riccieae, air-cavities ii 71;
antheridium, development ii
13; scale ii 29; spore-germi-
nation ii 111; spores large ii
106; sporogonium, develop-
ment ii 104; tuber ii 70; water-
storage-tissue ii 76.
Riella, chlorophyllous embryo ii
105; dorsiventrality i 87;
mucilage-papilla ii 27 ; sexual
organs, position ii 80; sporo-
gonium ii 575, contains spores
and nutritive cells ii 98; scale
ii 34, 35; thallus, symmetry ii
18.
R. Battandieri, thallus, sym-
metry i 86, ii 19.
R. Clausonis, male plant ii 19.
R. helicophylla, depth in water
ii 20,
Ripening fruit, biology of ii
570; transpiration in li 570.
Robinia, stipel ii 380; thorn-
formation and moisture i 263.
R. Pseudacacia, stipular thorn ii
381 ; stool-shoot i 210.
k. viscosa, leaflet, asymmetry i
122.
Rochea falcata, leaf, antitropic i
116, asymmetry i 116.
Root ii 263 ; adaptation ii 277 ;
adventitious ii 264, 274; aera-
tion-striae ii 285; air ii 281;
anchoring ii 286, usually un-
branched ii 274; aquatic,
growth in soil ii 267; assimi-
lation i 246, ii 280, 284;
branching, suppressed ii 274;
breathing ii 278; capless ii
267, 268; characters ii 265 ;
chlorophyllous i 246, ii 280,
284; cuttings, feeble in Coni-
ferae i 51; dimorphism ii 271 ;
dorsiventrality i 246, ii 281,
284; duration of life ii 290; of
epiphytes i 246, ii 282; and
exotropy ii 276 ; free-living ii
234; function ii 263, change
of, rare i 12; and gravity i
222, ii 276; hairless ii 269;
intracortical, in Bromeliaceae
ii 268; and light i 217, 219,
231, 246, ii 276; malforma-
tion, experimental i IgI;
mechanical organ of protec-
tion, ii 288; mycorrhiza ii
289; nest ii 283; period of
development ii 289; pull ii
INDEX
269, 465; region of growth ii
268 ; region of root-hairs ii 269 ;
secondary, endogenetic forma-
tion ii 273 ; shoot transformed
into ii 233; shortening ii 269 ;
stalk in Selaginella spinulosa
ii 230; storage ii 289; sym-
biosis with Thallophyta ii 282,
289; tendril ii 286; thorn ii
288 ; transformation into shoot
explained ii 228; transformed
i 12, ii 278, into shoot i 12,
ii 226; and water ii 276.
Root-apex ii 266 ; regeneration
i 43.
Root-borne, bud, exogenetic ii
276, of Ophioglossum i 46, ii
431, of Spermophyta ii 276;
shoot, endogenetic ii 288, of
Ophioglossum vulgatum ii 228,
origin ii 274, of Podostemaceae
i 42, li 228, 276, 280.
Root-cap, of aquatic plants ii
267; function ii 266; signifi-
cance ii 266.
Root-climber i 120, 157.
Root-development, _ periodi-
city ii 289 ; through stimulus
of gall-insect i 200.
Root-formation and light i
231.
Root-hair ii 269; absent in
Coniferae ii 269, in water-
plants ii 269; of epiphytes ii
283; and epigeous parts ii
269; in Taxus ii 269; on
water-roots ii 269 ; suppression
in water ii 269.
Root-knee of Zaxodium i 260,
ii 280.
,Root-primordium, latent on
stem li 275.
Root-spread in the soil ii 275.
Root-system ii 272; correla-
tion, and direction i 214, ii
275, and gravity ii 275; of
Monocotyledones ii 272; sup-
pression in mangrove ii 272.
Root-tendril ii 286.
Root-tip, callus-formation i 43.
Root-tuber ii 289.
Rootless, Pteridophyta ii 263 ;
shoot ii 234; Spermophyta ii
265.
Rosa, flower, arrangement of
parts ii 529; leaf-branching,
basipetal ii 330; ovary, de-
velopment ii 560; ovule, re-
duction in number ii 560.
R. gallica, pomifera, \eafiet,
asymmetry i 122.
Rosaceae, archesporium, pluri-
cellular ii 633; flower, arrange-
ment of parts ii 530; leaf, in-
terruptedly pinnate ii 331;
effect of nutrition on number
of stamens ii 538; ovary,
monomerous ii 559; ovule,
carpellary ii 559, variation in
number of integuments ii 618 ;
stipule, asymmetry i 125.
Rosaeflorae, ovary, inferior ii
568; stamen, disposition ii
520.
Rosemary, plagiotropous shoot,
conditions for development ii
459-
Rosette of archegonium of Coni-
ferae ii 629.
Rubiaceae, flower, unessential
zygomorphy i 130; ovule,
ategminy ii 619; stipular
whorl ii 369; stipule concre-
scent ii 368.
Rubus, adventitious shoot, posi-
tion ii 277; flower, arrange-
ment of parts ii 530; leaflet,
asymmetry i 122; ovary,
monomerous ii 559.
R. australis, transition from
foliage-leaf to phyllodium ii
354-
R. australis, var. cissoides, seed-
ling ii 353.
R. fruticosus, leaflet, asymmetry
i 122.
R. Ldaeus, flower, arrangement
of parts ii 530; leaflet, asym-
metry i 122. :
Rudimentary Hepaticae ii 114.
Ruellia, cotyledon, broad ii 406.
gaa stamen, doubling ii
530.
R. Acetosella, transformation of
shoot into root ii 233.
Ruminate, endosperm ii 407.
ee macropodous embryo ii
261.
Rupture of pollen-tube in
Cycadaceae ii 613.
Rupture-tubercles of prothal-
lus of Se/aginella spinulosa ii
195.
Ruscus, phylloclade i 15, ii 450.
R. aculeatus, etiolated shoot i
249 ; inflorescence upon upper
side of phylloclade ii 451;
juvenile form i 166; phyllo-
clade ii 451, and light i 249;
shoot-thorn ii 452.
R. androgynus, juvenile form i
166.
R. Hypoglossum, inflorescence
upon upper side of phylloclade
ii 451; juvenile form i 166;
phylloclade ii 450.
R. Hypophyllum, inflorescence
upon under side of phyllo-
clade ii 451; phylloclade ii
450.
Ruta graveolens, pentamery and
tetramery in same plant ii
538; leaf-apex, precedence in
growth ii 310.
Rytiphloea pinastroides, dorsi-
ventrality, significance i 87.
eo
Ss.
Sachs, definition of morphology
i 4, of physiology i 4; experi-
ment on flowering and light i
244; hypothesis of material
and form i 200.
Sagittaria, leaf, sagittate ii 324;
reversion to juvenile form and
light i 242; reversion-shoot i
172 ; venation ii 340.
S. cordifolia, juvenile form i 164.
S. natans, juvenile form i 164;
reversion i 260; reversion-
shoot i 172, 218.
Sagittate leaf, development ii
324.
Salacia, shoot-tendril ii 456.
Salicornia, halophyte i 265.
Salix, axillary branching ii 433 ;
gravity and cutting i 223;
gravity and formation of new
shoot i 222; kataphyll ii 395;
laminar growth, basiplastic ii
312; latent root-primordium
on stem ii 275; leaf-lamina,
branching ii 312; prophyll of
bud ii 383.
S. Caprea, repens, modification
of sex by external conditions i
Igi.
S. incana, arrest of leaf-bud and
light i 232.
S. pruinosa, vitellina, latent
root-primordium on stem ii 275.
Salsola Kali, halophyte i 266.
Salvia, origin of androecium i
- 60; reduction of number of
pollen-sacs ii 554.
S. Horminum, peloria i 189.
Salvinia, antheridium, develop-
ment ii 182; gametophyte,
male ii 182; heterophylly ii
348; juvenile, formi164, state,
result of adaptation i 170;
leaf, water ii 348, float ii 34,
348; megasporangium, tetrad-
formation ii 603 ; megaspore,
intrasporangial germination ii
623; megasporophyll ii 487;
microsporophyll ii 487;
microspore, germination ii
182, 218; prothallus, chloro-
phyllous ii 211 ; rhizoid absent
from female prothallus ii
189; rootless ii 264, shoot ii
234 ; Sporangium, position ii
493; Spore-germination in ab-
sence of light ii 190; tropical
species with unlimited life ii
44I.
S. auriculata, float-leaf ii 348.
S. natans, annual ii 441; float-
leaf ii 348; germination of
megaspore ii 211.
Salviniaceae, megaspore, re-
duction in number of ii 626;
microspore, distribution ii 218 ;
INDEX
prothallus, female ii 211;
sporangium reduced, not radial
11574 ; spore-distribution not a
function of sporangium ii 573;
sporophyll ii 487 ; water-dis-
tribution of spores ii 575.
Sambucus Ebulus, \eaf, acro-
petal branching ii 330; stipule,
number ii 364.
S. nigra, anisophylly, lateral i
108 ; leaf-branching, basipetal
ii 330; petiolar gland ii 362;
stipule, as honey-gland ii 381,
of sucker-shoot i Ig1, variable
number ii 364; stool-shoot i
210.
Santalaceae, embryo-sac-hau-
storium ii620; ovule,ategminy
ii 619.
Saponaria officinalis, doubling of
flower caused by Ustz/ago an-
therarum i 192.
Saprophytism, assimilating and
transpiring leaf-surface, re-
duced in ii 265; embryo, re-
duced in ii 254 ; of free-living
root ii 234; of Musci ii 128;
ovule, ategminy in ii 618; of
prothallus, of Lycopodium ii
193, of Ophioglossaceae ii 198,
of Ophioglossum pedunculosum
ii 193; of protonema ii 128;
scale-leaf and vascular bundle,
reduced in ii 292.
Sarcanthus Partshii, rostratus,
flattening of root in light i
246.
Sarothamnus vulgaris, assimi-
lating shoot-axis ii 446.
Sarracenia, leaf, tubular ii 338,
557-
Sarraceniaceae, juvenile form
i 164.
Sauromatum, laminar growth,
basal ii 324.
Sauterta, scale ii 30.
Saxifraga <Atzoon, longifolia,
leaf, unstalked ii 301.
S. caespitosa, heterophylly ii 352.
S. granulata, leaf, stalked ii 301.
S. rotundifolia, hypsophyll,
divided ii 393; leaf, stalked
ii 301.
S. sarmentosa, stolon ii 461.
S. stellaris, flower becomes dor-
siventral in development i 129.
Scabiosa, size of flower and light
ii 552.
S. Columbaria, heterophylly ii
351; transition between pin-
natifid and pinnate leaf ii 332.
Scale, of Hepaticae ii 27, biolo-
gical significance ii 34; semi-
niferous, of Abietineae ii 518,
521.
Scale-leaf, of bulb ii 399; of
Musci ii 133; without rudi-
mentary vascular bundle in
697
saprophytes ii 292. See also
Kataphyll.
Scapania, leaf ii 41.
S. nemorosa, gemma ii 50, on
leaf near antheridia ii 51.
S. undulata, colour in relation
to light ii 78.
Scapanieae, antheridium, de-
velopment ii 13.
Schistostega, adult features i174;
branching ii 130; gemma of
pro-embryo ii 126; light,
directive influence i 234; leaf,
apical segmentation ii 132,
development ii 307 ; protone-
ma, luminous ii 120, signifi-
cance ii 130; shoot, bilateral
i 66, ii 137, dorsiventral i 68.
S. osmundacea, protonema, lu-
minous ii 120; reversion to
juvenile form i 172; social
growth ii 129.
Schizaea, prothallus, lateral
meristem ii 205 ; sporangium,
annulus ii 591, displacement ii
494; sporophyll as new for-
mation ll 477.
S. pustlla, leaf, fertile, develop-
ment li 479.
S. rupestris, sporophyll, develop-
ment 11 478.
Schizaeaceae, antheridium, free
opening ii 177; placenta, ab-
sent ii 472; prothallus, de-
velopment ii 205; sporangium,
annulus ii 591, arrangement ii
496, displacement ii 494, dor-
siventral ii 574, opening 1i 588,
position ii 493; sporophyll
and foliage-leaf alike in posi-
tion and origin ii 477.
Schizocarpous Musci ii 160.
Schleiden on leaf-development
il 303.
Schoepfia, ovule, ategminy ii 619.
Sctadopitys, double needle ii 444;
juvenile form i 155; phyllo-
clade ii 445.
Scilla, root, dimorphism ii 271.
S. sibirica, embryo, retarded ii
251.
Scirpodendron costatum, flower,
arrest 1 52, concrescence 1 51.
Scirpus lacustris, assimilating
shoot-axis with arrested leaf ii
447; cotyledon ii 414; ger-
mination ii 414.
S. submersus, vegetative charac-
ters ii 447.
Scitamineae, leaf-stalk ii 299;
venation and whole leaf-growth
ii 342.
Sclerenchyma-fibres of Hepa-
ticae ii 76.
Sclerotium of Myxomycetes i
262.
Scolopendrium, sporangium, pro-
tected in pit il 497.
698
Scolopendrium officinale, juvenile
form i 151.
S. vulgare, sporangium, pro-
tected by indusium ii 497.
S. vulgare, var. cambricum, re-
version from malformation i
185.
S. vulvare, var. crispum Drum-
mondiae, apospory ii 608.
Scrophularia, anisophylly, lateral
i 108.
S. frutescens, halophyte i 266.
S. officinalis, anisophylly i 254.
Scrophularineae, inflorescence,
unilateral i 136; ovary and
placentation ii 563.
Scutellaria peregrina, inflore-
scence, unilateral i 136.
Scutellum of Gramineae ii 415.
Seam-cells of sporangium of
Leptosporangiate Filicineae ii
588.
Searcher-shoot ii 453; factors
influencing growth ii 454.
Secale cereale, branching without
axillant leaf ii 433.
Sechium edule, androecium ii
539.
Secretion-tapetum ii 596.
Securidaca Sellowtana, tendril-
lous lateral twig ii 455.
Sedum, phyllotaxy ii 442.
S. Clusianum, Magnoliz, rubens,
stellatum, tuberosum, succu-
lence of leaf and environment
i 265.
Seed, compensation of growth
i 208; haustorium i 208; pro-
tection of ripening li 512, 523,
of Cycas ii 512; and ovule ii
631.
Seed-coat ii 642.
Seed-formation and vegetative
propagation antagonistic i 45,
213, ii 460.
Seedling, callus-root i 44; etio-
lated, flowering i 243; of
Gramineae ii 416; of Hedera
i160; of Palmae, leaf ii 327;
phyllotaxy and asymmetry i
83; of Spermophyta and light
i 242. See also Juvenile
form.
Segmentation, of foliage-leaf
of Azolla ii 488; of leaf by
splitting ii 326; of nucleus of
embryo-sac of Angiospermae
ii 635; of peltate leaf ii 336;
of primordial leaf of Spermo-
phyta ii 321.
Selaginella, anisophylly i 99,
104, 105, ii 506, habitual, an
adaptation i107; antheridium,
development ii 182; arche-
gonium, development ii 184;
archesporium ii 601; correla-
tion of sporangium and leaf
i 216; embryo, differentiation
INDEX
ii 244, position of organs ii
247; foliage-leaf changed by
adaptation ii 510; flower ii
505, dorsiventral ii 507, in-
verse-dorsiventral ii 507, 508,
hermaphroditism ii 509, radial,
is primitive ii 509; gameto-
phyte, male ii 182; germ-
plant ii 229; leaf, asymmetry
i 106; ligule ii 360; mega-
sporangium ii 580, develop-
ment ii 603; megaspore, in-
trasporangial germination ii
623; megasporocyte ii 603;
microsporangium ii 580, de-
velopment ii 600; microspore
ii 182; prothallus, develop-
ment i 142, ii 194, trichome
ii I95; rhizophore ii 228, de-
velopment ii 229, a form of
root-stalk ii 231, transforma-
tion to foliage shoot ii 229;
secretion-tapetum ii 596; spor-
angium, opening ii 580, mature
ii 578, origin from vegetative
point ii 473; sporophyll, de-
velopment into foliage-leaf ii
475, primitive ii 510 ; strobilus
as cutting ii 476.
S. Belanger ,inverse-dorsiventral
flower grows out vegetatively
li 508.
S. caulescens, anisophylly and
external factors i 106.
S. chrysocaulos, inverse-dorsiven-
tral flower ii 507; megaspor-
angia and microsporangia,
mixed ii 508 ; sporangial wall,
structure ii 581; vegetative
shoot ii 507.
S. ciliaris, flower, dorsiventral
ii 507.
S. cuspedata, rhizophore ii 228 ;
spermatozoid ii 181.
S. denticulata, flower, orthotropy
ii 509, podial orthotropous ii
510; germ-plant ii 244.
S. Drummondi, annual ii 441.
S.erythropus, prothallus,develop-
ment ii 194; megasporangium
ii 580, 603 ; microsporangium
ii 580; sporangium-wall ii
581.
S. haematodes , dorsiventral shoot
i 107.
S. helvetica, anisophylly, retarded
i 107; flower, orthotropy ii
509, podial orthotropous ii
510.
S. lepidophylla, anisophylly i
105; prothallus, development
ii 194.
S. Lyaliz, correlation of sporan-
gium and leafi 216.
S. Martensiz, embryo ii 247;
flower, apodial radial not
orthotropous ii 510, female ii
508, male ii 508; prothallus,
development ii 194; rhizo-
phore ii 228.
Selaginella pallidissima, flower,
dorsiventral ii 507.
S. pectinata, flower, female ii
508.
S. pentagona, gall-bulbil i 197;
gall i 193.
S. Pretssiana, flower ii 5053
sporophyll, hypopeltate ii 503.
S. rupestris, isophylly i 105 ;
megasporangia and micro-
sporangia, mixed ii 508.
S. sangutnolenta, isophylly and
anisophylly i 105.
S. serpens, prothallus, develop-
ment ii 194.
S. spinulosa, archegonium, open-
ing ii 183; archesporium ii
601; embryo, differentiation
ii 244 ; isophylly i105; mega-
spore, time of germination ii
623; prothallus, development
ii 194; root-stalkii 230; rup-
ture-tubercle of spore ii 195 ;
sporangium, origin from vege-
tative point ii 473.
S. stolonifera, germination of
microspore ii 181.
S. suberosa, inverse-dorsiventral
flower grows out vegetatively
ii 508.
Selaginelleae, fertilization ii
508; flower, originally her-
maphrodite ii 508; isophylly
ii 505; megasporangium pre-
cedes microsporangium in de-
velopment ii 508; megaspore
thrown out further than micro-
spore ii 509; Platystachyae ii
506; sowing of megaspore
and microspore, simultaneous
ii 509; spermatozoid, biciliate
ii 172; sporangium, distribu-
tion ii508 ; Tetragonostachyae
ii 506.
Semele androgyna, phylloclade ii
450; seedling with foliage-leaf
ii 450.
Seminiferous scale of Abieti-
neae ii 518, 521.
Sempervivum, laminar growth,
basiplastic ii 312 ; phyllotaxy
ii 442.
Sepal ii 321; venation ii 344;
without vascular bundle ii 292.
Septal placentation ii 562-4.
Septate, carpel ii 559; pollen-
sac ii 555, 597; rthizoid, of
Musci ii 45, 116, of prothallus
ii 188; sporangium ii 555,
597- }
Sequoia sempervirens, archego-
nium ii 629; flower, female
ii 519, 521; sexual organ,
female ii 629.
Sesamum indicum, transforma-
tion of flower to gland ii 571.
Sesbania aculeata, air-root ii 280.
Seta of Musci ii 161.
Setaria, arrest in spikelet i 56;
bristle of inflorescence i 20.
Sex-change due to fungus-attack
i 193.
Sbecpediseation by external
conditions i 19!.
Sexual organs, colour ii 551;
constancy in Bryophyta ii 8;
of Hepaticae ii 79, disposition
- ii 80, protection ii 81, 84, 88 ;
of Musci ii 149; phyletic im-
portance ii 2; of Pteridophyta
ii 172, abnormal ii 187, distri-
bution ii 220, systematic im-
portance ii 186.
Sexual shoot of Hepaticae ii
82, 85.
Shade-form of Knautia arvensis
L352:
Sherardia arvensis, stipule ii
370-
Shield of anther, of Coniferae ii
516, of Gzmhgo ii 516.
Shoot, accessory ii 433; adven-
titious 117, 42, 46, 83, li 212,
232, 276; annual, of Spermo-
phyta ii 440; assimilation-
shoot the typical ii 440; axil-
lary, and axillant leaf ii 432;
axis, assimilating ii 445, as-
similating and light i 245,
internodes, contracted ii 442,
internodes, elongated ii 442,
winged ii 448; bilateral i 66,
90, 137; branching ii 431;
Cactus-form ii 452 ; cladode,
i 20, 168, 249, ii 445, 448, 451,
545; climbing i go, organ ii
455 ;correlation ofgrowthi 207,
creeping i 90; differentiation,
various methods i 16; dorsi-
ventral i 84, ii 138, 457, lateral
i 92, and anisophylly i 99, and
correlation i 214, and gravity
i 219, 225, and light i 230;
endogenetic apex ii 266; epi-
geous (photophilous) ii 442;
etiolated i 249; flattened i 92,
247; foliage-shoot, typical ii
440; and function, relation-
ships ii 441; geophilous ii 463;
of limited growth, flower is ii
470; organ of unlimited growth
i115; hook ii 456; hypogeous,
with unprotected apex ii 266;
involution i 85; juvenile and
adult differ i 144; and leaf i
13; leaf-borne i 42, ii 241,
431, 435) 441; long and short
i 35, il 43, 119, 444; ortho-
tropy and plagiotropy i 68, ii
39, 41, and correlation ii 215,
and gravity ii 223, 225, and
lightii 231, 232, 247; orthotro-
pous radial ii 442; photophi-
lous, in the soil ii 466° phyl-
INDEX
loclade i 20, 168, 249, ii 445,
448, 451, 5453 plagiotropy li
457, andanisophyllyi113; with
protective apical cap ii 266;
radiali 73, ii 132; reproductive
ii 467; root-borne i 42, 46,
ii 228, 276, 280, 431; rootless
ii 234; searcher li 453; sexual
ii 82, 85; skotophilous ii
463 ; storage ii 453; substitu-
tion of lateral for lost terminal
150; tendril ii 435, 456; thorn
i 168, 264, ii 440, 452, 456;
transformation i 20, ii 168,
233, 264, 435, 449, 452, 456,
464 ; transformed root ii 226;
vegetative ii 441 ; water-reser-
voir ii 452.
Shortening, of axillary branch-
ing in flower-region ii 433 ;
of root ii 269, periodic or con-
tinuous ii 271.
Short-lived primary root ii 272.
Short-stalked peltate foliage-
leaf ii 334.
Sickle of ligule of Gramineae
i 377-
Sicydium gracile, androecium ii
539-
Stebera compressa, cladode ii 452.
Stlene, gynaeceum and placenta-
tion ii 564.
S. noctiflora, flower and light
1 245.
Silver fir, anisophylly and light
i 250; and light, Kny’s experi-
ment i 250; flower, female,
development ii 522; shoot and
gravity i 225.
Silver-glance in Musci ii 148.
Silver-sheen of Bryum argen-
teum in relation to medium
i 261.
Simplices, grouping ofsporangia
of Pteridophyta ii 496.
Sinapis, cotyledon emarginate ii
407.
Sinker of P2/ostyles ii 225.
Siphonieae, energid i 23 ; light
and regeneration i 237; poly-
ergic i 23.
Siphonocladiaceae, monergic
and polyergic cells i 24.
Sisymbrium, suppression of up-
per bracts il 433.
Size, and colour of flower and
light ii 551; of parts of flower
and intensity of light i 245.
Skotophilous shoot ii 463.
Smilax, exstipulate ii 365 ; ten-
dril ii 223, 428, as new forma-
tion ii 224.
S. Sarsapariila, tendril ii 223.
Sobralia macrantha, embryo in-
complete at germination ii 253.
Soil-root ii 263; heliotropism
ii 276; hydrotropism ii 276.
Solanaceae, adhesion of bract
699
and shoot ii 438; flower, ob-
liquity and pressure ii 544;
leaf, interruptedly pinnate ii
331; ovary and placentation
ii 563.
Solanum Dulcamara, adventi-
tious shoot ii 277.
S. jasminiotdes,
climber ii 421.
S. tuberosum, correlation and
tuber-formation i 215; habit ii
‘68; leaf, interruptedly pinnate
i127,ii331; prophyll of bud,
asymmetry ii 383; tuber-for-
mation and light i 232.
Soldanelia, placentation ii 567.
S. pusilla, flower becomes dorsi-
ventral in development i 130.
Sole of carpel ii 557; develop-
ment in Ranunculaceae ii 560.
Solidago canadensis, axillary
branching and phyllotaxy i 82.
Sonneratia, pneumatophore ii
278.
S. acida, embryo, non-viviparous
ii 256.
leaf - stalk -
| Sophora japonica, leafiet, asym-
metry i 123.
S. tetraptera, transpiration-ap-
paratus in fruit ii 571.
Sorbus Aucuparia, leaflet, asym-
metry i 122.
Sorus, of Angiopteris ii 586; of
Pteridophyta ii 496, 590; sunk
in pit ii 497.
Southbya, related to Calypogeta
ii go.
Sparganium, antipodal cells, in-
crease in number ii 637 ; leaf,
profile-position, by torsion ii
295.
Spartium junceum, assimilating
shoot-axis, arrest of leaf ii 446.
Spathegaster Taschenbergi, gall-
wasp of oak i 199.
Spathiphyllum platyspatha, con-
crescence of spadix and spathe
i535; inflorescence, epiphyllous
ii 437- _
Species, aggregate ll 479.
Spergula, cotyledon resembles
foliage-leaf ii 402.
Spermatocyte, of Coniferae ii
614; of Cycadaceae ii 613.
Spermatozoid, biciliate ii 9,
172; of Coniferae ii 614; of
Cycadacene ii 613 ; distribution
unknown in Musci ii 152; of
Pteridophyta ii 172; pluricili-
ate ii 172; structure, an old
character ii 173, simplest in
Lycopodium ii 173.
Spermophyta, anisophylly i
107; branching, axillary the
rule ii 431, phyllogenous ii 432;
cotyledon ii 401; embryo ii
244, 248; flower ii 470; fruit,
hypogeous ii 493; gameto-
700
phyte and sporophyte ii 171;
gemma ii 469; heterophylly ii
351; involution, dorsiventral i
86; juvenile form i 153; leaf,
apical growth ii 310, formation
and development ii 321, pri-
mordium originates from group
of cells ii 306, surface, inception
ii 311; light, qualitative influ-
ence i 242; malformation arti-
ficial i 187; ovule ii 614; pol-
len-sac ii 574, 599, 610; pro-
tocorm ii 230; regeneration i
45; reproductive organs and
lighti 242; reversion tojuvenile
form i 172; root, origin of
lateral, from several cells ii
273; rootless ii 264; seedling-
plant and light i 242; shoot,
division of labour ii 440; spor-
angium ii 573,596, 610; spore-
distribution not a function of
megasporangium ii §73; sporo-
phyte ii 222; transformation
of root into shoot ii 227;
vegetative organs and light i
242.
Sphacelarieae, long shoot and
short shoot i 36; pro-embryo
i I50.
Sphaeria velata, influence of light
i 258.
Sphaeriaceae, influence of light
on colour and consistence of
fructification i 258.
Sphaerobolus steliatus, sterile in
darkness i 258.
Sphaerocarpus, antheridium,
chromoplasts ii ro, develop-
ment ii 13; chlorophyllous
embryo ii 105; sinking of
archegonium and antheridium
in thallus ii 84; spore-germina-
tion, rapid ii 107; sporogonium,
contains spores and nutritive
cells ii 97, development ii 104.
S. terrestris, antheridium ii 13;
archegonium, distribution ii
83; spore-tetrad ii 98.
Sphagnum, antheridium, develop-
ment ii 13, position ii 149;
archegonial venter ii 153;
archesporium ii 156, 606 ; cap-
sule, explosive ii 162 ; embryo,
structure and development ii
154; flattening of protonema-
formation in light i 249 ; juve-
nile form i 151; nota primitive
form ii 159; pro-embryo ii
122; pseudopodium ii 161;
relationship to water ii 53;
sporogonium, radial i 236;
water-cells, perforated ii 145.
S. acutifolium, protonema ii 122;
sporogonium ii 156.
S. cuspidatum, protonema ii 122.
S. pei ga sporogonium ii
156.
INDEX
Spike protecting flower of Ceva-
tozamia ii 512.
Spiraea, leaf-insertion i 93; shoot,
dorsiventral lateral i 93.
S. Aruncus, ovule, unitegminy
ii 618.
S, Filipendula, leaf, interruptedly
pinnate i 127, ii 331; ovule,
unitegminy ii 618.
S. Fortunet, Lindleyana, ovule,
bitegminy ii 618.
S. Ulmaria, ovule, unitegminy ii
618; stipule, asymmetry 1125.
Spiraeeae, ovary, pluriovular ii
560.
Spiral phyllotaxy i 73; in Betula
i 96.
Spirodela, ligular formation ii
236.
Spirogyra, rhizoid, development
i 26
S. fluviatilis, anchoring rhizoid
developed through contact-
stimuli i 269.
Splachnaceae, spore, distribu-
tion by animals ii 165, shed-
ding ii 165.
Splachnum, apophysis ii 159.
S. luteum, rubrum, capsule and
apophysis ii 159; protonema
ii 128.
S. sphaericum,
128,
Split leaf, of Aroideae ii 325;
development in Cyclanthus
bipartitus ii 326; of Palmae
ii 326.
Splitting of leaf, by wind, in
Musa ii 326; by degenera-
tion in Palmae ii328; a method
of leaf-segmentation ii 325 ;
protonema ii
ceae ii 499, in Lycopodineae ii
503, in sorus of Pteridophyta
ii 496; and distribution of
spores ii 575, in one flower of
Selaginelleae ii 508; division
of labour ii 577 ; embedded ii
573, 584; eusporangium ii602;
factors determining position in
Pteridophyta ii 494; foliar,
marginal in Filicineae ii 473,
peripheral in Equisetineae ii
473, superior in Lycopodineae
ii 473; free ii 573, 584; func-
tion ii 573; homology i 17;
inception in Pteridophyta ii
601; leaf-borne, in Pterido-
phyta ii 473, becoming axis-
borne ii 517, 556; leptosporan-
gium ii 602; and light i 245 ;
mature, of Equisetineae ii 583,
of Filicineae ii 584, of Lyco-
podineae ii 578, of Spermo-
phyta ii 610; opening li 509,
575, 577, 578, 583, 587, 595,
00, 610; organ of propaga-
tion i 20, ii 573; ovule, a ii
5733 pollen-sac, a 11573 ; posi-
tion, in sporocarp ii 479, 487,
on sporophyll in Filicineae ii
493; protective arrangement
ii 474, 496; phyletic hypothe-
sis regarding ii 605; stalk, its
origin ii 574; stalked and un-
stalked in Pteridophyta ii 574 ;
stomium ii §75, 579, 588; sym-
metry ii 574; tapetum ii 596,
599, 638; wall-structure ii 576,
578, 583, 584, 595, 596, 598,
610. See also Ovule, Mega-
sporangium, Microsporan-
gium, Pollen-sac.
through rain-dropsin He/iconia | Spore, of Hepaticae ii 106;
dasyantha i ii 328 ; through ten-
sions in Cyclanthus bipartitus
ii 328.
Spontaneous malformation i
184; transmissible by seed i
184.
Sporangial spike of Botrychium
simplex ii 606.
Sporangiophore in Helmintho-
stachys ii 483, 606.
Sporangium, active opening-
cells, endothecial and exothe-
cial ii 577, 611 ; annulusii 587,
variable in Ceratopteris ii 595;
on apogamous prothallus ii
221; arrest of ii 510, 554; axis-
borne in Selaginella ii 473;
Bower’s grouping of disposition
ii 496; of Ceratopteris ii 588,
5953 of Coleochaete i Ig; con-
figuration in relation to place
of appearance ii 575; correla-
tion with sporophyll i 216; de-
velopment ii 595, 599,601,625;
displacement of marginal ii
494; disposition, in Equiseta-
formation in Myxomycetes i
25; of Musciiir52; and sporo-
cyte ii 596.
Spore-distribution, by animals
in Splachnaceae ii 165; in
aquatic Pteridophyta ii 212;
218, 474, 575, in Hepaticae ii
95,97; simultaneous in hetero-
sporous Pteridophyta ii 212,
509; not a function of mega-
sporangium ii 573; in Musci ii
160; and sporangium ii 575,
580; and sporophy]ll in Pteri-
dophytaii474; by water ii 98,
212, 218, 474, 575:
Spore-germination, in aquatic
Filicineae ii 211; in Hepaticae
ii106; intrasporangial li 202 ;
intrasporogonial ii 106, 123;
in Musci ii 116; rapid in
Hepaticae ii 107. See also
Embryo-sac, Megaspore,
Microspore, Pollen-grain.
Spore-sac of Musci ii 156.
Sporocarp ii 474, 479, 4903
hypogeous ii 493.
ee eae eS hf le
7"
Re a a ee
j
4
Sporocyte and spore ii 596. See
also Megasporocyte.
Sporogenous cell-mass ii 596.
Sporogonial, sac ii 90; tuber-
shoot ii 92.
Sporogonium, absorption of
water ii 157; of aquatic Bryo-
phyta ii 575; assimilation ii
158 ; containing spores ii 97,
and elaters ii 99, and nutritive
cells ii g8; with elaterophore
ii 100; without elaterophore
ii 99; and gemma produced
together ii 51 ; of Hepaticae ii
93, development ii 103, fluid
around young ii go, function
li 94, opening ii 95, 97, 99;
of Musci ii 152, and light i
236, opening ii 160; rhizoid in
Eriopus ii 157.
Sporophyll, anatomy in Pteri-
dophyta ii 486; biological re-
lationship in Pteridophyta ii
474; cause of configuration ii
473; condition for appearance
in Filicineae ii 498 ; configura-
tion protects sporangium ii 496;
correlation and form i 215;
developed into foliage-leaf ii
475; and foliage-leaf, alike ii
474, 478, 503, 509, conform
in position and origin ii 477,
genetic relationship ii 470; is
foliage-leaf ii 482; form in
relation to sporangium ii 499;
formation and medium ii 498;
function in Pteridophyta ii
473; malformation i 179;
new formation in Eusporan-
giate Filicineae ii 481, in Lep-
tosporangiate Filicineaeii 477;
primitive in relation to foliage-
leaf ii 510; sterilized sporan-
gium in Coniferae ii 517; and
spore-distribution in Pterido-
phyta ii 474; time of appear-
anceii 498; transformed foliage-
leaf i 8, 216, ii 477; transition
to foliage-leaf in Pteridophyta
ii 474; of Angiospermae ii
527; of Coniferae ii 515; of
Cycadaceae ii 511; of Equi-
setaceae ii 499; of Eusporan-
giate Filicineae ii 482; of
Heterosporous Leptosporan-
giate Filicineae ii 487; of Iso-
sporous Leptosporangiate Fili-
cineae ii 485; of Ginkgoaceae
ii 515; of Isoetaceae ii 471;
of Lycopodineae ii 471, 503;
of Pteridophyta ii 472. See
also Carpel, Megasporo-
phyll, Microsporophyll,
Stamen.
Sporophyte, and gametophyte,
alternation ii 17%, connexion
ii 598, homology i 20; an-
nual, Anogramme leptophylla
INDEX
ii 217, 498; of Pteridophyta,
Nageli’s view of origin ii 605.
Sprengel on symmetry of flower
i132.
Spruce, bud malformed by
Chermes Abtetis i 178; early
flowering of transplanted i 212.
Squamule, intravaginal ii 359.
Stachys, plagiotropy ii 461.
S. palustris, sylvatica ii 461.
Stackhousia, antipodal cells, in-
creased number ii 637.
Stahl, hypothesis of leaf-involu-
tion ii 298.
Stalk-cell of antheridium of
Cycadaceae ii 613.
Stalk, of leaf ii 299; of sporan-
gium, origin ii 574, outgrowth
of sporophyll ii 602, 617.
Stalked and unstalked leaf, com-
pared ii 301.
Stamen, basipetal succession ii
542; branching ii 533; cho-
risis ii 535; compared with
sporophyll of Helminthosta-
chys \i 483; confluence ii 539;
disposition in flower ii 529;
doublingii 536; flag-apparatus
ii 550; homology i 181, ii
500; malformation i 180, in-
herited i 187; peltate ii 334;
phyllody i 180; transformation
1 11, ii 551, 555; uniformity ii
553; without vascular bundles
ji 292; of Angiospermae ii
527; of Coniferae ii 515; of
Cycadaceae ii 514; of Gink-
goaceae li 515; of Gnetaceae
ii 526.
Staminal, phalange in Hyferi-
cum aegyptiacum ii 534; pri-
mordium, branching ii 536.
Staminode, nectariferous ii 550.
Stangeria, ovule li 513, develop-
ment ii 628 ; prothallus a con-
sequence of pollination ii 628.
S. paradoxa, ovule ii 627.
Stanhopea, pollen-sac, confluence
il 554-
Stapelieae, shoot as water-re-
servoir ii 452.
Staphylea pinnata, anisophylly,
lateral i 10S.
S. trifoliata, leaflet, asymmetry
eta
Stegocarpous Musci ii 160.
Steinheil on leaf-development
li 303.
Stellaria media, cleistogamy and
light i 245.
Stellatae, stipule ii 368, foliar
ii 369; suspensor-haustorium
ii 642.
Stem, and leaf, distinction i 16;
tuberous i 232, 262, 263, ii
269, 431, 453, 463. :
Stephaniella, paraphyllium ii §7;
water-absorptive organ ii 70.
qo
S. paraphyllina, hypogeous rhi-
zome ii 70; xerophily ii 57.
Stephanodium peruvianum, in-
florescence, epiphyllous ii 437.
Sterculia, cotyledon ii 402; ex-
traseminal absorption of endo-
sperm ii 402.
S. platantfolia, leaf, peltate ii 335.
Stereocaulon, symmetry and di-
rection i 72.
Stereum sanguinolentum, sporo-
phore abnormal in darkness i
258.
Sterigmata of Vittariaceae ii
215.
Sterile, and fertile shoot alike in
Lquisetum ii 501; sporophyll
of Cycas ii 511.
Sterility, inherited i 186.
Sterilization, a factor in de-
velopment ii 605; in ovule ii
627, 628, 632; in pollen-sac
ii 554, 597; in sporangium ii
555, 597, 604; of sporangium
into sporophyll ii 517; in
sporogonium ii 97, 103, 605,
606 ; in synangium ii 585, 605.
Stigma of Angiospermae ii 527.
Stimuli, concerned in fertiliza-
tion in Angiospermae i 269,
ii 622; external formative and
configuration i 205.
Stimulus, of insect inducing
formation of ovule i 270; of
pollen-tube inducing formation
of ovule i 269, ii 623; pollen-
tube a non-fertilizing ii 624.
Stipel i 210, ii 379; protective
function ii 380.
Stipular,appendage ii 366; drip-
tip ii 367; formation of Marat-
tiaceae ii 315 ; hypsophyll ii
394; kataphyll ii 386; pro-
pagation in Marattiaceae i 46;
scale of Ceratopteris thalic-
troides ii 315; sheath, deci-
duous axillary, in Ficus Pseudo-
Carica ii 372.
Stipule ii 359; adnate ii 359;
arrest ii 364; assimilative
function ii 363; asymmetry i
125; axillary ii 315, 3590, 372,
418; climbing hook ii 371;
concrescence, ofadjacent leaves
ii 368, of one leaf ii 367;
correlation of growth i 210;
developed on sucker-shoot i
Igt; development ii 364;
fleshy ii 365; foliar ii 369;
form and function ii 366; free
ii 359, 372; gland ii 362, 381;
inequality in size ii 366 ; inter-
petiolar ii 368, 374; juvenile
form in Zropacolum majyus i
163; number ii 364; persistent
ii 364; protective function ii
359, 363, 386; rare in Pteri-
dophyta ii 365; reduced ii
702
365; secreting mucilage ii
381; symmetry-relationships
i 125, li 366; transformed ii
381; vascular supply ii 364.
Stolon, and condition of life, of
Fragaria vesca ii 460; de-
velopment in Czrcaea ii 440;
of Hepaticae ii 23; of Utrz-
cularia ii 238; water-tuber ii
239. : :
Stoma on sporogonium of Musci
ii 159.
Stomium ii 575, 579, 588.
Stool-shoot i 210.
Storage, of food-material in em-
bryo ii 257; hypocotylar ii
258, 260; kataphyll ii 399;
leaf ii 398; root ii 289; shoot
Il 453-
Streptocarpus, correlation of
growth in cotyledon i 210;
cotyledon, persistent ii 235,
403; free-living leaf ii 235;
germination ii 235; intercalary
growth of cotyledon ii 404.
5S. polyanthus, cotyledon ii 404;
free-living leaf ii 235; proto-
corm ii 232.
S. Wendlandit, free-living leaf
li 235.
Striate venation ii 338.
Strobilanthus, anisophylly, habi-
tual i 113.
Strobilus of Se/aginella ii 476,
505.
Struthiopterts germanica, phyllo-
taxy i 78.
Style, formation ii 565.
Stylidiaceae, embryo, retarded
ii 250; seed, time of germina-
tion ii 253. Me
Stylidium, embryo, retarded ii
250; leaf inversion by torsion
ii 296, 298.
S. pilosum, reduplicatum, leaf
inversion by torsion ii 298.
S. scandens, hook-leaf ii 420.
Stylus auriculae, of /72/lania
ii 60.
Submerged leaf, divided ii 358,
riband-form li 357.
Subterranean organ plagiotro-
pous i 68; shoot i 104, 1i 463.
Succubous leaves ii 39.
Succulence, of leaf, and environ-
ment i 265, and salt i 266; in
Cactaceae i 1g; in Euphorbia-
ceae i 19.
Superior ovary ii 559; syncar-
pous gynaeceum ii 562.
Suppression, meaning of i 56;
of active opening cells in
pollen-sac ii 611. See also
Arrest.
Surface and filamentous pro-
thallus of Hymenophyllaceae
ii 210.
Suspensor, and function in An-
INDEX
giospermae ii 642; haustorium
ii 642.
Symbiosis, in Hepaticae ii 78;
in Pteridophyta ii 198, 218,
348; in root of Cycas ii 282;
and saprophytism ii 218, 234.
Symmetry. See Relationships.
Sympetalae, ovule, epithelium
ii 638, unitegminy ii 617.
Symphoricarpus, calyx, develop-
ment il 543.
S.vacemosus ,heterophylly ii 352;
leaf-form on renovation-shoot
i 190.
Symphyogyna, branching ii 23;
hymenophylloid thallus ii 25 ;
leaf ii 35; perichaetial scale to
archegonium ii 83; rhizome,
sympodial ii 25 ; sporogonium,
development ii 104.
S. Brogniartiz, leaf ii 36.
Symphytum, \eaf-base decurrent
as wing ii 448.
S. officinale, orientale, arche-
sporium of pollen-sac ii 599.
Sympodial, branching, of Am-
pelideae ii 435, of leaf in
Dicotyledones ii 330; rhizome
of Hepaticae ii 25.
Synangium of Marattiaceae ii
585.
Syncarpous gynaeceum ii 558,
562-4.
Synergidae, embryo-formation
ii 637; function ii 637.
Syringa, kataphyll ii 385; win-
ter-bud, structure li 432.
S. dubia, ovular development
after pollination ii 623.
S. vulgaris, \aminar growth,
pleuroplastic ii 312.
Syrrhopodon, water-cell,
forated ii 145.
S. vevolutus, \eaf-structure ii 145.
Swarm-spore of Vazcheria i
23.
per-
Ap
Taeniophylium, foliage-leaf, ab-
sent ii 286; root, assimilation
ii 286.
T. Zollingert, protocorm ii 232.
Talisia princeps, kataphyll ii
384, from leaf-primordium ii
385.
Tamarindus indica,
asymmetry i 122.
Tamus europaeus, exstipulate ii
365.
Tannin-body of Hepaticae ii
leaflet,
79:
Tapetum ii 596; functional not
morphological layer ii 597,
638; of ovule ii 638; plas-
modial ii 596; of pollen-sac
of Angiospermae ii 599; se-
cretion ii 596; varying origin
1 §97-
Taphrina cornu cervi, causing
gall ii 526.
T. Lauvencia, causing witches’
broom i 193.
Taraxacum, heterophylly ii 352;
root, periodic shortening ii
571.
T. officinale, inheritance of fascia-
tion i 186.
T. palustre, \eaf-form ii 352.
Targionia, air-cavities ii 75; in-
volution of parts to resist
drought ii 65; scale ii 30;
spore-germination ii 112; spo-
rogonium, development ii 104.
Taxineae, flower, female ii 519.
Taxodieae, flower, female ii
521.
Taxodium, prothallus, male ii
614; root, knee ii 280.
T. distichum, absence of knee-
root in dry soil i 260; leaf-
apex, precedence in growth ii
309.
Taxus, flower, female ii 520,
male ii 499; hyponasty and
epinasty i 85 ; megasporocyte,
many ii 628; protection of
ripening seed ii 523; root-
hair ii 269; stamen ii 515.
T. baccata, flower, female ii 521.
Teesdalia nudicaulis, \eaf-form
in dwarf-conditions i 259.
Temperature, and blind flower
Lange
Temporary, and persistent arrest
of cotyledon ii 403; retarda-
tion of foliage in liane ii 454.
Tendril, absent in juvenile form
i 161; adhesive disk i 268,
ii 224, and contact-stimulus
i 268; correlation and forma-
tion i 216; factors causing
transformation into ii 428;
filiform ii 457; and inflore-
scence ii 435, 450; leafi161,
ii 421, of Dicotyledones ii 421,
of Monocotyledones ii 428;
Miiller’s investigations ii 425 ;
as new formation ii 224; root
ii 286; shoot ii 435, 455;
spirally-branched ii 426 ; tran-
sition, from leaf i 163, to leaf
i 161 ; transformed leaf ii 421;
watch-spring ii 456.
Teratological phenomena in
tendril of Cucurbitaceae ii
428.
Teratophylium aculeatum, var.
inermis, leaf, adaptation to
environment ii 347.
Terminal, and basal growth i
413 cotyledon of Monocotyle-
‘dones i 16; leaf i 16, 41, ii
305, 541; new formation at
leaf-apex ii 242.
Terniola longipes, leaf without
vascular bundle ii 293.
Tetrad-division, of megaspo-
rangium of aquatic Filices ii
603; of megasporocyte of
Spermophyta ii 625 ; of micro-
sporocyte of Zypha Shuttle-
worthiz ii 625; of sporocyte
of Hepaticae ii 98.
Tetragonolobus, cotyledon, asym-
metry i 115; leaflet, asymme-
try i 122.
T. stliquosus, stipule ii 361.
Tetragonostachyae, anisophylly
ii 506; flower ii 506.
Tetraphis, gemma ii 140, dimor-
phism ii 49 ; protonema, special
organs of assimilation ii 121 ;
virescence ofantheridial groups
ii 141.
T. pellucida, flattened surface and
light i 249; gemma, origin 1i
140; spore, shedding ii 165.
Tetraplodon Wormskjoldt,sapro-
phytism ii 128.
Tetrodontium,protonema,special
organs of assimilation ii 121.
Thalictrum, stipel ii 380.
T. aquilegiaefolium ii 380.
Thalloid vegetative body of
parasite ii 225.
Thalloidima vesiculare, symme-
try and direction i 72.
Thallophyta, arrest rarer than
in higher plants i 56; cell-
colony i 22; cell-dominion i
22; colony, fixed i 29; con-
figuration of juvenile form i
148 ; division of labour i 21,
32; pluricellular plant i 22 ;
resting state i 261 ; trichome
i 21; unicellular plant i 22.
Thallose Hepaticae leaf ii 35.
Thallus, bilateral, of Avyopszs
i 66; definition i 21.
Thestum, ovule, ategminy ii
619.
Thladiantha, tendril, nature ii
425; tuber and gravity i
221.
TZ. dubia, androecium ii 289;
root-tuber ii 289.
Thorn, formation, and medium
i 263, an adult character i
168; leaf ii428; root ii 288;
shoot ii 452, 456, reversion to
foliage-shoot ii 453; stipule
ii 381 ; transformed shoot i 9,
ii 429.
Thuidium, shoot, dorsiventral
ii 138, plagiotropous, and light
1/293;
T. tamarascinum, paraphyllium
ii 147.
Thuya, javenile form i 154;
megasporocyte, many ii 628;
shoot-system ii 449.
TZ. occidentalis, branch-system
and light i 230; hairless root
ii 269; shoot, branching i 88 ;
INDEX
transplanted, early flowering
i 212:
Thuyopsis dolabrata, branch-
system and light i 230.
Thymus Serpyllum, plagiotro-
pous shoot in shade ii 459.
T. vulgaris, orthotropous shoot
in sunny localities ii 459.
Tigridia, root, dimorphism ii
271.
Tilia, cotyledon, lobed ii 407;
fruit, compensation of growth
i 207, prophyllar parachute ii
383; juvenile form, direction
of growth i 143; laminar
growth, pleuroplastic ii 312;
leaf, asymmetry i 117, branch-
ing of lamina ii 312, insertion
i 93, position i 96; shoot,
abortion of apex of annual i
209, concatenation of plagio-
tropous i 70, 96, dorsiventral
lateral i 93, 96.
T. europaea, root, development
periodic ii 290.
TI. parvifolia, cotyledon, lobed
il 407 ; symmetry i 96.
Tillandsia, anchoring-root
286,
T. bulbosa ii 286.
T. usneotdes, rootless ii 265.
Time-relationship in axillary
branching ii 432.
Timmia, mammilla on
surface ii 143.
Tissue -development below
archegonium after fertilization
in Hepaticae ii 106.
Tmestpterts, cladode ii 448; hy-
pogeous shoot-apex unpro-
tected ii 266; rootless ii 264;
sporangial wall and distribu-
tion of spores ii 578; sporan-
gium, mature ii 578, relation-
ships,ii 505; sporophyll ii504,
and sterile leaf ii 504; sterile
cells of sporogenous tissue ii
207.
T. truncata, sporophyll ii 504.
Todea, leaf, structure and envi-
ronment ii 347; prothallus,
adaptation ii 210; sporangium,
position ii 494; stipule, axillary
ii 315.
T. barbata, annulus ii 592.
T. pellucida, leaf, structure and
environment ii 347.
T. superba, \eaf, development ii
315, structure and environ-
ment ii 347.
Torenta, haustorium of ovule ii
630. f
Torreya, anther, shield ii 516;
flower, female ii 519; ovule
ii 510. P
Torsion, causing leaf-insertion
ii 296; changing leaf-insertion
i 93; obligate i 186, inherited
i
leaf-
193
i186; unilateral inflorescence
through i 136.
Torus, limited growth in Angio-
spermae ii 541; suppression
ii 540.
Tozzia alpina, storage-kataphyll
ii 399.
Trabeculae, of sporangium, of
Lsoetes ii 555, 597, of Lepido-
dendron ii 597.
Tradescantia virginica, embryo,
differentiation ii 410.
Transformation, actual i 6;
carpel to foliage-leaf, i 181;
flower to anchoring-organ ii
571; flower to gland ii 571;
foliage-leaf, to hypsophyll i
Io, 161, ii 394, to sporophyll
i 11, 181, ii 477, to tendril i
178, ii 421, to thorn i 168;
hypsophyll to sepal ii 549;
inflorescence, to assimilation-
shoot ii 447, to climbing-or-
gan ii 435, 456, to tendril ii
435; inflorescence-shoot, to
geophilous shoot ii 440, 464;
of leaf i 6-11, to insect-trap
ii 237, to nectary ii 430, to
Toot 1 161, ii 237, to shoot
ii 241, to water-reservoir in
Hepaticae ii 58; of organsi5,°
actual i 6, conditioned by
change of function i 12, 256,
by fungus-attacki11; of ovule
to foliage-leaflet i 181; petal
to nectary ii 430, 560; of pri-
mordiai8; of rhizoid in Hepa-
ticae ii 47; rhizophore to leafy
shoot ii 229; of root i 12, to
assimilation-organ ii 246, 280,
284, to pneumatophore ii 278,
to shoot i 12, ii 227, and its in-
terpretation ii 228, to tendril ii
286, to thorn ii 288, to tuber
ii 289; of shoot, photophilous
to geophilous ii 464, to hook ii
456, to phylloclade i 20, 168,
ii 445, 448, 545, to root ii 233,
to tendril ii 455, to thorni 168,
264, ii 440, 452, to tuber ii
453; of sporangium and sporo-
phyll, phyletic hypothesis ii
606; stamen,to carpeli17g, to
flag-apparatusii 550, to foliage-
leaf i 180, to nectary ii 449,
to petal i 11, 177, 179, 192, il
449, 551; and temporary re-
tardation in development i 57.
See also Malformation,Phyl-
lody.
Transformed, flower ii 571;
leaf ii 382; radial shoot ii
452, of liane ii 453; root ii
278; shoot ii 4444 sporophyll,
flower-envelope and ii 549;
stamen ii 555; stipule ii 381.
Transition between, bract, and
bristle-scale i 197, and petal i
704
197; cotyledon and foliage-leaf
1145, ii 404; embedded and
free sporangium ii 574; epi-
geousand hypogeous cotyledon
ii 403 ; eusporangium and lep-
tosporangium ii 602; foliage-
leaf, and hypsophylli 10,11 391,
551, and kataphyll i 9, ii 350,
and phyllodium ii 354, and
tendril i 10, 161, and tubular
leaf ii 338; foliage-shoot and
thorn ii 452; gemma and leaf,
ii140; heteroblasticandhomo-
blastic germination i 168;
hypsophyll and flower - en -
velope ii 549, 550; inflore-
scence and stolon ii 457; leaf,
and climbing-organ i 161, and
root ii 237, 240, and shoot ii
236; leaf-form i 6, 10, 163;
leaf, entire and divided ii 294;
monergic and polyergic forms
i 24; organs i 9, of different
symmetry i 67; peltate and
ordinary leaf ii 336; pinnatifid
and pinnate leaf ii 332; plagio-
tropy and orthotropy of shoot
i 69, ii 457, 459; prophyll
and tendril ii 384, 426; radial
and dorsiventral lateral shoot
ig8; rootsi12, anchoring and
nourishing ii 288 ; sporangium
and sporangiferous leaf ii 606 ;
sporophyll and foliage-leaf ii
474,510; stamen, and nectary
ii 449, and petal ii 449, 550;
sterile and fertile sporophyll
ii 511; thorn and nectary ii
430.
Transition-figure in phyllotaxy
i 79.
sDemeeataetn through seed of
malformation i 184.
Transpiration and ripening of
fruit ii 570.
Transplanted tree, early flower-
ing i 212.
Transverse dorsiventral flower
i128.
Trapa, cotylar storage ii 257;
leaf-stalk and light ii gor ;
phyllotaxy ii 442.
Trecul, on leaf-development ii
303.
Tree, concatenation of plagio-
tropous shoots i 70, li 457;
correlation of growth in bud
i 208; gravity and shoot i 224;
root, periodicity of develop-
ment ii 290.
Tree-ivy i 160.
Treubia, gemmaii 49 ; leafii 39;
sexual organs, protection ii 84.
T. insignis, leaf, arrangement ii
39; habit ii 40.
Trianea bogotensis, root-apex ii
267; root-hair of water-root
ii 269.
INDEX
Trichocolea, calyptra ii 89; para-
phyllium ii 57; perianth want-
ing ii 89; spore, germination
ii 110; water-reservoir ii 58.
T. paraphyllina, paraphyllium
ii 57.
T. pluma, fertile shoot ii 89.
T. tomentella, paraphyllium ii
57; rhizoid ii 45.
ZT. tomentosa, foliar water-reser-
voir ii 58.
Trichomanes, archegoniophore,
radial ii 191; leaf, short-
stalked peltate ii 334, water-
holding ii 348; prothallus ii
207, archegoniophore ii 207,
formation ii 209, gemma ii
214, radial ii I91; ptyxis,
circinate, absent ii 321.
T. Ankersti, muscordes, pedt-
cellatum, root, adventitious ii
264.
T. brachypus, leaf, adaptation to
environment ii 348, adpressed
Nl 335-
T. diffusum, prothallus ii 207.
T. Goebelianum, rootless ii 264.
T. Hildebrandtz, leaf, adapta-
tion to environment ii 348,
form and external factors i
117, short-stalked peltate ii
334; rootless ii 264.
7. incisum, pinnule, basal ii
347-
T. maximum, radicans, prothal-
lus, development ii 208.
T. membranaceum, leafless shoot
functions as root ii 264,
T. Motleyi, \eaf, short-stalked
peltate ii 334; ptyxis, circinate,
absent ii 321; sterile leaf
without vascular bundle ii 292.
T. peltatum, leaf, short-stalked
peltate ii 334; ptyxis, circinate
absent ii 32T.
T. ventforme, \eaf-form, bio-
logical significance ii 346;
leaf, lamina many-layered ii
314.
7. rigidum, prothallus ii 207,
gemma ii 214; symbiosis with
fungi ii 219.
T. tenerum, sorus ii 589; spo- |
rangium, opening ii 589.
T. venosum, prothallus, gemma
ii 214.
Trichome, definition impossible
i 16; of prothallus of Sela-
ginella ii 195; of Thallo-
phyta i 21.
Trichopilia, pollen-sac, conflu-
ence ii 554.
Trichostomum, spore, shedding
ii 163.
Trifolium, branching, axillary
ii 433; juvenile form i 155.
T. repens, phyllody of carpel i
181.
T. rubens, pressure and develop-
ment of inflorescence i 138.
T. subterraneum, inflorescence,
hypogeous ii 571; transforma-
tion of flower into anchoring-
organ ii 571.
Trijugate system of phyllotaxy
of Bravais i 80.
Tristichahypnotdes, trifaria, leaf
without vascular bundle ii 293.
Triticum repens, hypogeous
shoot as boring-organ ii 266.
T. vulgare, embryo ii 415.
Trollius, nectariferous staminode
ii 550; petal as flag-apparatus
and nectary ii 551.
T. europaeus, flower - envelope
derived from hypsophyll ii
550-
Tropacolum, archesporium of
pollen-sac ii600; cleistogamy
in darkness i 243; flower-bud
not unfolding in darkness i
243; haustorium of ovule ii
642; leaf-stalk-climber ii 421;
Sachs’ experiments on flower-
ing i 244.
T. aduncum, cut leaf ii 337.
T. majus, gravity and root-for-
mation i 222; juvenile leaf,
segmentation ii 337; leaf,
peltate ii 335, primary peltate
ii 336; stipule, a juvenile form
i 163, reduced ii 365.
T. minus, leaf, juvenile, segmen-
tation ii 337, primary peltate
ii 336.
T. tricolorum, tendril, develop-
ment i 163, ii 423, a juvenile
form i 163.
Trophic pole of Volvox i 28.
Tropical, plants, anisophylly,
lateral i 108; species of Sa/-
vinta have unlimited life ii
441.
Tropo-sporophyll of Lycopodi-
neae ii 510.
Tsuga canadensis, archegonium
ii 629.
Tuber, of Hepaticae ii 43, 66,
history of discovery ii 66; of
Juncus supinus i 262; of Poa
bulbosa i 263; of potato, re-
tarded by. light i 232; on
prothallus of Anogramme ii
217. .
‘Tubercule primaire’ of Zyco-
podium ii194; of Lycopodium
salakense ii 217.
Tuberous, cotyledon ii 257;
hypocotyl ii 258, 260; leaf ii
398; monocotylous plants,
hairless root of ii 269; prothal-
lus of Botrychiumvirginianum
ii 198; protocorm ii 231 ; root
ii 289; stem ii 269, 431, 453,
463; stolon as water-reservoir
of Utricularia ii 239.
sl ae Ss A lea
ee
Tubular, bract of Marcgravia-
ceae li 338; leafii 58, 237, 337,
557, 500, characteristic of in-
sectivorous plants ii 237, 338,
development ii 237, 337, as
retarded formation ii 337.
Tulipa, embryo-sac, reduction in
number ii 262; flower in dark-
ness i 243; megasporocyte be-
comes embryo-sac ii 625.
T. sylvestris, root-development,
periodicity ii 290.
Twig, correlation of growth i
209.
Twig-thorns in Olaceae ii 456.
‘Type’ as defined by de Can-
dolle ii 533.
Typha, hypsophyll ii 397; leaf,
bilateralii 295, profile-position
by torsion ii 295; terminal
flower-leaf ii 541.
T. Shuttleworthzz, tetrad-division
of microsporocyte ii 625.
Typical root ii 263.
U.
Ulex, branch-thorn and medium
i 263; leaf-thorn and medium
i 263.
U. europaeus, juvenile form i
168 ; thorn i 168.
Ulmaceae, aporogamy ii 615.
Ulmus, laminar growth, pleuro-
plastic ii 312 ; leaf, asymmetry
i 117, branching ii 312, posi-
tion i 96; seedling i 70;
shoot, abortion of apex of an-
nual i 209, concatenation of
plagiotropousi 70, dorsiventral
lateral i 96.
U. campestris, effusa, phyllotaxy
i 70.
Ulothrix zonata, colony i 31.
Ultra-violet rays and flower i
244.
Ulva lactuca, anchoring-organ i
ad.
Umbelliferae, bract, arrest i
89, ii 397, 4333; branching,
axillary ii 433; cladode ii
452; correlation, bract and
leaf-sheath i 59; flower, un-
essential zygomorphy i 130;
hypsophyll ii 397; leaf,
acropetal branching ii 330,
cylindric ii 295; leaf-base,
function ii 299 ; leaf-sheath ii
321; ovary, inferior, develop-
ment ii 569 ; ovule, unitegminy
ii 617.
Umobilicus, leaf, peltate ii 335,
origin of peltate ii 337, transi-
tion from peltate to ordinary
ii 336.
U. pendulinus, primary leaf,non-
peltate ii 336.
Unequally-sized leaflet i i22, |.
126.
GOEBEL Ut
INDEX
Unessential
flower i 130.
Unfolding of long shoot and
short shoot ii 445.
Unicellular, archesporium of
Angiospermae ii 632; plant |
of Thallophyta i 22.
Uniformity of stamen of An- |
giospermae ii 553.
Unilateral, formation of pin-
nules ii 480; inflorescence i
zygomorphy of
136, and light i 137, and ex-
ternal factors i 137, origin i
138, through torsion i 136;
pinnation i 121, ii 480.
Unilaterally split corolla of
Compositae ii y53.
Unilocular ovary, becoming
plurilocular ii 565; of syncar-
pous gynaeceum ii 562.
Unitegminy of ovule ii 617,
618, 629; by concrescence ii
Si, 618; and sympetaly ii
17.
Unstalked, leafandenvironment
ii 301 ; sporangium of Euspor-
angiate Filicineae ii 574.
Uromyces pist, causing malfor-
mation in Euphorbia i 192.
Urtica, anisophylly,
108 ; cotyledon, emarginate ii
407.
VU. dioica, anisophylly i 254 ; in-
florescence, dorsiventral i 134 ;
shoot-axis, structure of dorsi-
ventral ii 545; stipule, con-
crescence ii 368.
U. urens, cotyledon, persistent
ii 403; inflorescence, radial
i 134.
Urticaceae, anisophylly i 108,
habitual i 109; absence of
petal unexplained ii 551 ; leaf,
asymmetry i 116; stipule,
concrescence ii 368
Ustilago, causes sex-change i
193.
U. antherarum, causes doubling
of flower i 192.
U. Treubiz, produces gall i 196.
|
lateral i |
7°5
shoot, rootless ii 234; storage-
leaf ii 298 ; transition between
leaf and shoot ii 236; tuberous
water-reservoir ii 239; vege-
tative organ, protean, origin ii
240; winter-bud ii 398.
U. affints, stolon-formation ii
239.
U. bryophila, longifolia, stolon
and foliage-leaf ii 240.
U. coerulea, \eaf-root ii 238;
stolon ii 238, and foliage-leaf
| ii 240.
U. Hookert, bladders ii 237;
insect-trap ii 237; rhizoid ii
237; seedling, development ii
239; tubular leaf@mi 237;
vegeta-tive organs ii aoe
| U. Humboldti, renifoemis, em-
| bryo, chlorophyllous in seed ii
254.
U. inflata, stellaris, chalazal and
funicular nutritive tissue ii
641.
U. montana, capacity for repro-
duction i 143; embryo, reduced
ii 254.
U. nelumbifolia, leaf, peltate ii
336.
U. neottioides, anchoring-organ
ii 239.
UY. orbiculata, bract without
vascular bundle ii 292; em-
bryo, reduced ii 254.
U. peltata, \eaf, peltate ii 335.
U. reticulata, inflorescence a
climbing-organ ii 456.
Utricularieae, ptyxis ii 310;
tubular leaf ii 337.
we
| Vaccintune Myrtilius, shoot,
dorsiventral lateral i 94; phyl-
lotaxy i 161.
Vaginal outer storage-leaf of
bulb of Lilium candidum ii
398.
Valeriana, flower, asymmetry i
129; intermediate formations
between organs i 197.
Utricularia, calyx, confluence of | V. Phu, inferior ovary, develop-
parts ii 539; cotyledon re-
sembles foliage-leaf ii 402;
embryo, reduced ii 264; flower,
development of dorsiventral ii
542; form reduced in relation
to mode of life ii 622; haus-
torium of ovule ii 640 ; involu-
tion, dorsiventral i 86 ; juve-
nile form i 164; leaf, dicho-
tomy ii 329; leaf-root ii 237 ;
leaf-tuber ii 398 ; leaf, tubular
ii 338, 560; morphological
categories, abolished i 15, ii
239; nutritive tissue of ovule
ii 640; organs, categories not
sharply separated i 8; proto-
corm li 232; rootless ii 265 ;
ZZ
ment ii 569.
V. ¢tripteris, bud degenerate
through Phytopius i 195.
Valerianacease, inferior ovary,
development ii 569; malfor-
mation due to PAytopius i
194.
Vallisneria (Lagarosiphon) alte
nifolia, vegetative point of
flower-axis i 41.
Value, in organography of mal-
formation 1 179; of colour in
flower ii 551.
Valvate vernation
crescence I 53.
Vanilla aromatica, root-tendril
ii 287.
and con-
706
Variation, in number of pollen-
sacs in Angiospermae ii 554; in
numerical symmetry of flower
ii 538; in propagative capacity
of organs i 46; of stamen in
one flower of Coniferae ii 516;
within embryo-sac ii 637.
Variations inherited i 185.
Variegation, inheritance of i
184.
Varying origin, of similar or-
gansi18; of tapetum ii 597.
Vascular bundle, of leaf ii 292;
leaf without ii 292 ; supply of
stipule ii 364.
Vaucheria, absence of juvenile
form i 148 ; swarm-spore i 23.
V. clavata, anchoring rhizoid
developed through contact-
stimuli i 269; rhizoid, a ju-
venile character i 269.
V. geminata, resting state in
drought i 262.
Vegetative, adaptation of Musci
ii 141; body, of Lemna i
16, ii 236, of Pélostyles
ii 225, 621; development,
through postponement of pro-
pagation ii 605, increased
through suppression of repro-
ductive organs i 142, 212, ii
212; organs, liable to change of |
function i 14, of higher plants
i 20, propagative organs
cannot be referred back to i |
18; point, absent in Lemnaceae
1 41, absent in embryo of Mo-
nocotyledones ii 245, approach |
to in Thallophyta i 31, and
branching i 32, formation of or-
gans ati 41, regeneration at i
41, regeneration of i 43, Wolff's
term i33; points, cell-dominion
with i 33, competition between
i 42; propagation antagonistic
to seed-formation i 45, 213, ii |
51, 215, 469, in regeneration |
i 48; and reproductive shoots,
symmetry i 69, ii 507.
Velamen of air-roots ii 283,
284.
Venation, dicotylous ii 342;
and leaf-size ii 342; and whole
leaf-growth ii 342; monoco-
tylous ii 339; of petal ii 344;
of sepal ii 344; variation in
one plant ii 339.
Ventral canal-cell of archego- |
nium of Pteridophyta ii 184.
Vernation, concrescence in val-
vate i 53.
Veronica, confluence of petals ii
539; juvenile form i 167; re- |
version-shoot i 172.
V. Beccabunga, endogenetic ad- |
ventitious root ii 273.
V. cupressotdes, yavenile form i
167; reversion-shoot i 218.
INDEX
V. hederacfolia, cotyledon per-
sistent ii 403.
V. lycopodioides, heterophylly ii
353; juvenile form i 167; re-
version i 173.
Viburnum, petiolar gland ii
question of stipule ii
V. Opulus, correlation of growth
in flag-apparatus i 211; flag-
flower ii 571 ; honey-gland be-
coming stipule ii 381; stipule
ii 362, number ii 364.
Vicia, stipule, asymmetry i 125,
honey-gland ii 381.
V. Cracca, inflorescence, dorsi-
ventral i 67, 1353 stipule,
asymmetry i 121, 125, func-
tion ii 366.
V. faba, etiolated seedling
flowering i 243; fasciation i
190 ; juvenile form i 156; leaf,
malformation i 178, experi-
mental i 191; root, formation
and light i 231, movement
in soil ii 276; shoot, orthotro-
pous, dorsiventral branching
Be
Victoria vegia, juvenile form i
165; leaf, peltate ii 335,
prickle i 264.
Viminartadenudata,phyllodium
Il 354-
Viola, flower, opening and clos-
ing and light i 245.
V. tricolor, stipule and function
ii 366.
Virescence, of antheridial group
in Zetraphis ii 141; of arche-
gonium ii 187; of sporophyll
ii 609.
Viscum, cotyledon resembles foli-
age-leaf ii 402; flower, reduc-
tion ii 622; sterilization of
sporogenons tissue in pollen-
sac ii 597.
V. album, embryo-sac embedded
in torus ii 620.
V. articulatum, many embryo-
sacs embedded ii 620.
Vitex Agnus-castus,
asymmetry i 123.
Vitis, tendril ii 457.
V. cinerea, vulpina, tendril ii
leaflet,
435- ;
V. pterophorva, storage-shoot ii
453:
V. vinifera, gabler i 186.
| Vittarza, prothallial gemma ii
214 ; prothallus ii 205.
Vittariaceae, prothallial gemma
ii 214; prothallus ii 206;
sterigmata ii 215.
Viviparous, plants, embryo ii
255; race, of Poa alpina i
179, of Poa bulbosai 179.
Vivipary, and moisture ii 257;
transmission in Poa i 184.
Vochting, experiments upon
flower and light i 244.
Volvocineae, colony, configu-
ration i 27.
Volvox, colony i27; division of
labour i 28 ; trophic pole i 28.
V. aureus, coenobium i 28.
Voyria, embryo, reduced ii 254;
ovule, ategminy ii 618.
V. azurvea, ovule, ategminy ii
619, development ii 619.
We
Wachendorfiia thyrstfiova, flower,
transverse dorsiventral i 128.
Wall-cell of antheridium of
Cycadaceae ii 613.
Watch-spring-tendril ii 456.
Water, absorption by Musci ii
141; influence upon organs i
260 ; relationship of Sphagua
to ii 53; root has arrested hairs
ii 269; and spore-distribution
ii 575; storage-root ii 284;
storage-tissue of Hepaticae ii
76; storage-tuber of <Azo-
gramme ii 216; uptake by
leaf, of Hepaticae ii 52, of
Musci ii 145, of Pzngudcula ii
349, of Pteridophyta ii 347,
349- *:
Water-chamber, capillary in
Hepaticae ii 58.
Water-excretion of Réccza ii
Wa:
Water-form of Ricca i 269, ii
34) 45: :
Water-leaf i 260, ii 34, 348;
and medium i 260.
Water-pit in Anthoceros ii 56.
Water-plant, endogenetic ad-
ventitious roots ii 273; root-
hairs absent ii 269; rootless ii
265.
Water-reservoir, capillary in
Hepaticae i 261; leaf as, in
Hepaticae ii 58; shoot as ii
452; stolon as ii 239.
Water-sac, archegonial, of
Musci ii 153; insect-trap in
Hepaticae ii 64.
Water-slit at leaf-apex ii 309.
Water-storage in mucilage ii
Wobora prolifera, propagative
shoot ii 139.
Weddelina squamilosa, anchor-
ing-organ ii 222; haptera ii
222; leaf without vascular
bundle ii 293.
Weigela, double leaf i 190.
Wetssia, papilla on leaf-surface
ii 143 ; spore, shedding ii 163.
Welwitschia, archegonium ii
629; embryo, suctorial organ
ii 409; embryo-sac, ger-
mination ii 629; flower, male
i 60; hermaphroditism i 60, ii
|
~~
526; hypocotylar haustorium
ii 402 ; sexual organ, female ii
629; ovule, unitegminy ii 629.
W. mirabilis, branching, power
absent ii 431; flower, male ii
526; leaf, persistent basal
growth ii 322.
Wheat, embryo ii 415.
Whorl, false ii 332.
Wiesner, on anisophylly i 100;
on internal symmetry-relations
and anisophylly i 254.
Wind-distribution of spores
ii 575, sporophyll and ii 474.
Wind-pollination, in Cycada-
ceae not universal ii 513; in
Monocotyledones ii 547.
Wing, decurrent leaf-base ii
448; of leaf of Filicineae ii
314; of shoot-axis ii 448.
Winged thallus of Hepaticae
ii 18, 20.
Wingless leaf of Prlularia ii
314.
Winter-bud, of ALyriophyllum
1174, 218, ii 398; prophyll ii
383; structure in Syrvinga li
432; of Utricularia ii 398.
Witches’ broom, caused by
Accidium elatinum i 192,
Exoascus i 192, Taphrina
Laurencia i 193; develop-
ment i 192; shoot always
sterile i 192.
INDEX
Wolff, Kaspar Friedrich, ser-
vice to history of develop-
ment i 6; on leaf-development
ii 302.
Wolffia, free-living leaf, ii 235.
W. arrhiza, Welwitschit, root-
less ii 265.
Wound-callus, new formation
of organs on i 44.
2
Xanthochymus pictorius, hypo-
cotylar storage ii 258.
Xanthosoma belophyllum, vena-
tion ii 341.
Xeranthemum macrophyllum,
hypsophyll, division ii 397.
Xerophilous, adaptation i 165,
in Eguzsetum hyemale ii 446,
in Hepaticae ii 57, 65, in
Musci ii 142, 148; marsh-
plants ii 446; plant, juvenile
form i 165.
Xerotes longifolia, \eaf-lamina,
differentiation ii 300.
Xylophylla, phyllociade ii 452.
pe
Yucea, formation of organs and
gravity 1 224.
Z.
Zama, pollen-grain, germina-
tion ii 612; stamen ii 514.
/
Fiat
Z. Skinnert, stamen ii 514.
Zamioculcas, leaf, cutting i 46.
Zannichellia, archesporium of
pollen-sac ii 600; macropo-
dous embryo ii 260.
Zanonieae, tendril ii 427.
Zanonia macrocarpa, tendril,
axillary ii 427.
Zea Mais, antipodal cells,
number ii 637; prop-root ii
277; root-hair arrested in
water ii 269; seedling ii 416;
sterility inherited i 186.
Zilla myagroides, leaf, adult,
arrest i 167; juvenile form i
167.
Zingiberaceae, ligule ii 377;
petal, transformed stamen ii
551: plug-tip ii 309.
Zizania aquatica, seedling ii
417.
Zoopsis, reversion of leaf to thal-
lus-form ii 42; rudimentary
form ii 115.
2. argentea, rudimentary form ii
114.
Zostera, macropodous embryo ii
261; pollen ii 611.
Z. marina, macropodous embryo
ii 262.
Zygospore of Mucor, germina-
tion in varying nutrition i
266.
OXFORD ;
PRINTED AT THE CLARENDON PRESS
BY HORACE HART, M.A.
PRINTER TO THE UNIVERSITY
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