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Full text of "A manual of botany: being an introduction to the study of the structure, physiology, and classification of plants"

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MANUAL OF BOTANY: 



INTRODUCTION TO THE STUDY 



STRUCTURE, PHYSIOLOGY, AND CLASSIFICATION OF PLANTS. 



JOHN HUTTON BALFOUE, M.D., F.L.S, F.R.S.E., 

PBOPBSSOR OP MEDICIXE ASD BOTANY IX THE fXIVEBSITY OP ED1XBUBGH, 



ILLUSTRATED BY NUMEROUS WOOD-CUTS. 



SECOND EDITION. 



LONDON: 

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53 BAKER-STREET, PORTMAN SQUARE ; 

AND RICHARD GRIFFIN & CO. GLASGOW. 
1851. 



GLASGOW: 
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ENCYCLOPEDIA METROPOLITAN 



OR, 



Astern of SHntoersal 



ON A METHODICAL PLAN 



PROJECTED BY SAMUEL TAYLOR COLERIDGE. 



SECOND EDITION, REVISED. 



tonnii Itaura. Ipplbfr Irirarcs. 



BOTANY. 



LONDON: 

PUBLISHED BY JOHN JOSEPH GRIFFIN AND CO. 

S3 BAKER-STREET, PORTHAX SQUARE ; 

AND RICHARD GRIFFIN & CO., GLASGOW. 
1851. 



20S1200 



BOTANY. 



JOHN BUTTON BALFOUK, M.D., F.L.S., F.R.S.E., 

PKOFESSOK OF MEDICINE AND BOTANY IN THE UNIVERSITY OF EDINBURGH. 



SECOND EDITION. 



TABLE OF CONTENTS. 



PAGE 

PREFACE xi 

INTRODUCTORY REMARKS xiii 

PART I. VEGETABLE ANATOMY, ORGANOGRAPHY, AND PHYSIOLOGY 1 

CHAPTER I. ELEMENTARY ORGANS, OR VEGETABLE TISSUES 1 

SECTION I. CELLULAR TISSUE 2 

1. Form and Arrangement of Cells 2 

2. Contents of Cells. 6 

3. Development and Functions of Cells 10 

SECTION II. VASCULAR TISSUE , 11 

1. Form and Arrangement of Vessels lo 

2. Development and Functions of Vessels 1! 

Tabular Arrangement of Vegetable Tissues 21 

CHAPTER II. COMPOUND ORGANS FORMED BY THE TISSUES 22 

SECTION I. ORGANS OF NUTRITION OR VEGETATION 22 

Structure, Arrangement, and Special Functions 22 

General Integument 28 

Stomata 25 

Hairs 27 

Stem or Ascending Axis 33 

Forms of Stems 33 

Internal Structure of Stems 36 

Exogenous or Dicotyledonous Stem 37 

Anomalies in its Structure 47 

Endogenous or Monocotyledonous Stem 50 

Acrogenous or Acotyledonous Stem 55 

Formation of the different parts of Stems, and their special Functions 58 

Root or Descending Axis 62 

Structure of Roots 62 

Forms of Roots.. 63 

Functions of Roots 66 

Leaves and their Appendages 67 

Structure of Leaves 67 

Venation of Leaves 71 

Forms of Simple Leaves 73 

Forms of Compound Leaves 77 

Petiole or Leaf-stalk 80 

Stipules 83 

Anomalous Forms of Leaves and Petioles 85 

Structure and Form of Leaves in the Great Divisions of the Vegetable 

Kingdom V 86 

Phyllotaxis, or the Arrangement of Leaves on the Axis 87 

Leaf-buds 93 

Vernation 95 

Special Functions of Leaves 105 



TABLE OF CONTENTS. 



SECTIOX II. GENERAL VIEW OF THE FUNCTIONS OF THE NUTRITIVE ORGANS 106 

1. Food of Plants, and Sources whence they derive their Nourishment 106 

Chemical Composition of Plants. 106 

Organic Constituents and their Sources. 108 

Inorganic Constituents and their Sources Ill 

Chemical Composition of Soils 116 

Application of Manure 118 

Various kinds of Manure 118 

Epiphytic and Parasitic Plants. 123 

2. Absorption and Circulation of Fluids 124 

3. Respiration of Plants 134 

Effects of Certain Gases on Living Plants. 137 

4. Products and Secretions of Plants 140 

SECTION III OKGANS OF REPRODUCTION 150 

Structure, Arrangement, and Functions. 150 

1. Inflorescence or the arrangement of the flowers on the axis 150 

Tabular View of Inflorescence or Anthotaxis. 164 

2. Bracts or Floral leaves 165 

3. The Flower and its Appendages. 167 

External Floral Whorls, or the Floral Envelopes; ;:-.. 171 

Calyx 171 

Corolla 176 

Inner Floral Whorls, or the Essential Organs of Reproduction 186 

Stamens. 186 

Pistil 207 

Ovule 224 

4. Functions of the Floral Envelopes 230 

5. Functions of the Stamens and Pistil ; Fertilization or Fecundation. 235 

Embryology. 241 

6. Fruit or the Pistil arrived at maturity. 249 

Fruits which are the produce of a single flower 259 

Fruits which are the produce of several flowers united. 266 

Tabular arrangement of Fruits. 267 

7. Maturation of the Pericarp 268 

Ripening of Fruits 271 

Grafting. 272 

x. Seed or Fertilized Ovule arrived at Maturity 274 

Embryo 283 

9. Functions of the Seed 291 

Germination. 292 

Vitality of Seeds. 295 

Direction of Plumule and Radicle 298 

Proliferous Plants 303 

Duration of the Life of Plants 303 

10. General Observations on the Organs of Plants, and on the mode in which they 

are arranged 305 

Tabular View of the Organs 305 

Symmetry of Organs 308 

Teratology 310 

SECTION IV. SOME GENERAL PHENOMENA CONNECTED WITH VEGETATION 317 

1. Vegetable Irritability 317 

2. Temperature of Plants 322 

3. Luminosity of Plants 323 

4. Colours of Plants 324 

5. Odours of Plants 329 

6. Diseases of Plants 330 

PART II. SYSTEMATIC BOTANY, TAXONOMY, OR THE CLASSIFICATION OF 

PLANTS. 337 

CHAPTER I. SYSTEMS OF CLASSIFICATION. 337 

Nomenclature and Symbols. 341 

Linnsean System t 342 

Natural System 344 

System of Jussieu. 347 

System of DeCandolle 347 

System of Endlicher 348 

System of Lindley 349 



TABLE OF CONTENTS. 



CHAPTER II. ARRANGEMENT AND CHARACTERS OF THE CLASSES AND 







.. 352 


Class I. Dicotyl 
Subclass 1. 






.. 352 






.. 353 






.. 380 


2. Dilleniaceag. 355 
3. Magnoliaceae 355 


22. Tamaricaceae .... 
23. Frankeniaceae ... . 


.... 367 
.... 368 
.... 368 




.. 381 




.. 381 




.. 382 


5. Menispermaceae 356 




368 




.. 383 


26. Vivianaceaa 


.... 370 

. . . 370 




.. 383 






.. 384 




28 Sterculiaceae. . . 


.... 372 




. 385 


9 Nelumbiaceae 358 




. .. 373 




.. 385 




30 Tiliaceae 


373 




.. 386 




31. Dipterocarpaceas.. 


.... 374 
375 




.. 387 






.. 387 


13 Crucifer*^ . 360 


33. Ternstreemiaceae. . 


.... 375 

. . 376 




.. 388 






.. 388 


15. Resedacefe 364 


35. Aurantiaceae 


.... 377 

. . 378 




.. 388 




.. 389 


17. Cistace* 365 
18. Violaceae 365 


37. Guttiferae 


.... 378 
379 


57. Xanthoxylaceae .... 


.. 390 
.. 891 


19. Droseraceaj 366 
''0 Polygalaceae 366 


39. Hippocrateacese. . 


.... 380 

380 


59. Ochnaceje 


.. 392 
.. 392 


Subclass 2. 
61. Stackhousiacese 393 






.. 392 


74. Vochysiaceae .... 


409 
.... 409 


87. Turneracese 


.. 418 
.. 419 


62 Celastraceae 393 


63. Staphyleacea? 394 
64. Rhanmaceas 394 
65. Anacardiaceaa 395 
66. Amyridaceae 396 


76. Melastomacese.. 
77. Alangiacca? 
78. Philadelphacese .. 


.... 410 
.... 410 
.... 410 
411 


89. Paronychiacese 


.. 419 
.. 420 




. 420 




.. 421 


67. Conaraceae 397 




412 




.. 423 


68. Leguminosas 398 




414 




.. 423 






. 414 




.. 424 






. . 414 


96. Hamamelidaceae .. . . 
97 Uinbelliferas 


.. 424 
.. 424 






... 416 


72. Lythraceae 408 




.. 417 




.. 428 


73. Rhizophoraceae 408 




417 




.. 428 






.. 429 


100. Loranthaceaa 429 
101. Caprifoliaceae 430 
102 Rubiaceae 430 


115. Epacridaceae .... 
116. Columelliaceaa... 
117. Styracaceaa 


447 
447 
448 
449 


130 Hydrophyllaceae . . . 


...460 


131 Convolvulacea? 


...460 


13 9 Cordiaceas 


..462 






..462 


104. Dipsacaceas 435 


119. Aquifoliaceae .... 
120. Sapotaceae 
121 Myrsinaceae 


449 
450 
451 
. ..451 




..464 


135. Orobanchaceas 
136. Scrophulariaceai . . 


..467 
..468 
. 469 


106. Compositae 435 






123 Oleaceag 


....451 




. 472 


109 Stylidiaceae 442 




... 453 




..472 


110. Campanulacese 443 




. . . 455 




..473 




456 




..474 






457 




..475 


113. Ericaceae 445 




458 




..476 


114. Vacciniaceae 446 

Subclass 4. 


129. Polemoniaceae . . . 
Monochlamydeae 


459 




.. 476 


A. Angiospernife . . . 




...476 




.... 486 160 Santelarpjp 


.. 489 






... 486 


161. Aristolochiacea? 


.. 489 
.. 491 


146. Chenopodiaceaj 478 
147. Phytolaccaceae 479 




...487 


155. Thymelreaceae . . . 


.... 487 
488 


163. Datiscaceaa 


..491 




..492 


149. Begoniaceae. 482 
150 Lauracese 482 


157. Chailletiacea;.... 


.... 488 
.... 488 




..492 


166 Urticacea? 


..496 


101. Mvristicaceae 485 




.. 4*9 


167. CeratODhrllaceaj.. . . 


.. 500 



TABLE OF CONTENTS. 



168. Pqdostemacea? 5001 172. Lacistemaceaa 

169. Stilaginaceae 500 | 173. Chloranthaceae 



PAGE 

17fi. Amentacese 503 

177. Juglandacese 507 

178. Garryaceas 507 



170. Monimiaoeas 500 I 174. Saururaceaa... 

171. Atherospermacea? .... 501 ' 175. Piperaceas 502 

B. Gymnospermae 508 

179. Conifera.., 508 | 180. Cycadaceae 511 

Class II. Monocotyledones or Endogense 512 

Subclass 1. Dictyogena? 512 

181. Dioscoreaceae 512 | 182. Smilaceae 513 | 183. TrilliaceaB 514 

Subclass 2. Petaloideaa 514 

a. Perianth adherent, Ovary inferior, Flowers usually hermaphrodite. 514 



184. Hydrocharidaceae.... 514 

185. Orchidaceae 515 

186. Zingiberaceae 517 

187. Marantaceae. 519 



8. Musacea? 520 192 Amaryllidacea? 522 

193. Hypoxidacea? 523 

190. Burmanniaceae 5221194. Bromeliaceae 524 



191. Haemodoraceje 



522 



6. Perianth free, Ovary superior, Flowers usually hermaphrodite 524 



199. Xyridacese 528 I 202. Commelynaceae 532 



528 



204. Butomaceae 532 



646 

540 



216. Musci 546 

217. Hepatica; 548 



195. Liliaceae 524 

196. Melanthaceae 526 

197. Gilliesiaceae 527 j 201. Palmae. 

198. Pontederiacese 528 | 

c. Flowers incomplete, often unisexual, without a proper perianth, or with a few 

verticillate scales 533 

205. Pandanaceae 533 | 207. Naiadacea? 535 

206. Aracea 533 | 208. Restiaceae 535 

Subclass 3. Glumacess 536 

209. Cyperaceas 536 211. Rhizanthea? 541 

210. Gramineas 537 

SECTION II. CETPTOGAMOUS PLANTS 542 

Class III. Acotyledones. 542 

Subclass 1. Acrogense or Cormogense 542 

212. Equisetaceas 5421 214. Marsileaceae.. 

213. Filices 5431 215. Lycopodiacea 

Subclass 2. Thallogenaj or Cellulares. 549 

218. Lichenes 549 | 219. Fungi 551 | 220. Algse 555 

PART III. GEOGRAPHICAL BOTANY, OR THE DISTRIBUTION OF PLANTS OVER 

THE GLOBE 559 

L EPIRRHEOLOGY, OR THE INFLUENCE OF VARIOUS EXTERNAL AGENTS ON PLANTS. . . 559 

1. Effects of Temperature 560 

2. Effects of Moisture 563 

3. Effects of Soil, Light, and other Agents. 563 

IL DISSEMINATION OF PLANTS 566 

1. Agents employed in their Dissemination 566 

2. General and Endemic Distribution of Plants 568 

3. Conjectures as to the mode in which the Earth was originally clothed with 

Plants 569 

4. Distribution of Plants considered Physiognomically and Statistically 572 

Physiognomy of Vegetation 572 | Statistics of Vegetation 573 

5. Phyto-geographical Division of the Globe 575 

" Vertical Range of Vegetation 583 

Distribution of Plants in Britain 585 

Acclimatizing of Plants 590 

PART IV. FOSSIL BOTANY.... 591 



Horizontal Range of Vegetation 575 

Schouw's Phyto-geographic Regiona 575 

Meyen's Phyto-geographical Zones 581 



Character and arrangement of Fossil Plants 591 

Fossiliferous Rocks 593 

Fossil Plants of different Strata 594 



Fossil Plants of the Carboniferous system . . 596 

Fossil Plants of the Secondary Strata 603 

Fossil Plants of the Tertiary Strata 607 



APPENDIX 611 

I. ON THE USE OF THE MICROSCOPE IN BOTANICAL RESEARCHES 611 

Simple and Compound Microscope 612 Histology 616 

Microscopical Apparatus 613 Microscopical Preparations 617 

II. ON COLLECTING AND EXAMINING PLANTS, AND ON THE FORMATION OF A HERBARIUM, 618 

Preservation of specimens in a moist state.. 621 

Preservation of Seeds 621 

623 



Instruments and Apparatus required 618 

Process of Drying Plants. 620 

INDEX AND GLOSSARY 



PREFACE. 



IN the compilation of this Manual of Botany, the object has been 
to give a comprehensive, and, at the same time, condensed view of 
all departments of the science. Attention is directed, first, to the 
Elementary structure of plants, and the functions of the simplest 
tissues, and then to the Compound organs, and the functions which 
they perform. In the consideration of these subjects, the works of 
Jussieu and Henfrey have served as a model. The application of 
Physiology to Agriculture, both as regards the cultivation of plants 
and their diseases, is brought under notice; the works of Liebig, 
Miilder, and Johnston having been consulted. In the important 
subject of Classification, much aid has been derived from the standard 
work of Lindley. The system adopted is that of De Candolle, but 
in the arrangement and definition of the natural orders, Walker 
Arnott has been chiefly followed. Many important hints have been 
derived from Henslow's excellent Syllabus, as well as from the sys- 
tematic work of Endlicher. In detailing the properties of plants, 
care has been taken to notice all those which are important in a 
medical and economical point of view Christison, Royle, Burnett, 
and Lindley, supplying valuable data. In the chapter on the Geo- 
graphical distribution of plants, a very general view is given of the 
principal facts brought forward by Meyen, Schouw, Humboldt, Berg- 



Xll PREFACE. 

haus, Watson, and Forbes; and in Fossil Botany, the labours of 
Brongniart, Ansted, and Hooker have been made available. The 
Publishers placed at the Author's disposal, the wood-cuts of Jussieu's 
Cours Elementaire, and some from Beudant's Geology , and, in addi- 
tion to these, there are others taken from Raspail, St. Hilaire, 
Schleiden, Amici, and Maout. By combining together in the Manual, 
information which the student has to acquire by the consultation of 
several volumes, it is hoped that the work may be a useful text-book. 



INTRODUCTORY REMARKS. 



IT has too often been supposed that the principal object of Botany is to give 
names to the vegetable productions of the globe, and to arrange them in such a 
way that these names may be easily found out. This is a most erroneous view 
of the science, and one which was perhaps fostered by some of the advocates of 
the Linnjean system. The number of species collected by a botanist is not con- 
sidered now-a-days as a measure of his acquirements, and names and classifica- 
tions are only the mechanism by means of which the true principles of the science 
are elicited. The views in regard to a natural system proposed by Ray and 
Jussieu did much to emancipate botany from the trammels of artificial methods, 
and to place it in its proper rank as a science. Their labours have been ably 
carried out by De Candolle, Brown, Endlicher, Lindley, Hooker, Arnott, and 
many others. The relative importance of the different organs of plants, their 
structure, development, and metamorphoses, are now studied upon philosophical 
principles. The researches of Gaudichaud, Mirbel, and others, as to the struc- 
ture and formation of wood; the observations of Schleiden and Mohl on cell 
development; the investigations of Brown, Schleiden, Fritzsche, Amici, Meyen, 
Griffith, and others, into the functions of the pollen, the development of the ovule, 
and the formation of the embryo; the experiments of Schultz, Decaisne, and 
Thuret, on the movements observed in the cells, vessels, and spores of plants, 
and various other physiological inquiries, have promoted much our knowledge 
of the alliances and affinities of plants. Thus the labours of vegetable anatomists 
and physiologists all tend to give correct views of the relation which plants bear 
to each other, and of the great plan on which they were formed by the All-wise 
Creator. 

The Botanist, in accomplishing the ends he has in view, takes an enlarged 
and comprehensive view of the vegetation with which the earth is clothed. He 
considers the varied aspects under which plants appear in the different quarters 
of the globe, from the Lichen on the Alpine summits, or on the Coral reef, to 



XIV INTRODUCTORY REMARKS. 

the majestic Palms, the Bananas and Baobabs of tropical climes from the 
minute aquatics of our northern pools to the gigantic Victoria of the South 
American waters from the parasitic fungus, only visible by the aid of the 
microscope, to the enormous parasite discovered by Raffles in the Indian Archi- 
pelago. 

It is interesting to trace the relation which all these plants bear to each other, 
and the mode in which they are adapted to different climates and situations. 
The lichens are propagated by spores (seeds) so minute as to appear like thin 
dust, and so easily carried by the wind that we can scarcely conceive any place 
which they cannot reach. They are the first occupants of the sterile rock and 
the coral-formed island being fitted to derive the greater part of their nourish- 
ment from the atmosphere and the moisture suspended in it. By degrees they 
act on the rocks to which they are attached, and cause their disintegration. By 
their decay a portion of vegetable mould is formed, and in progress of time a 
sufficient quantity of soil is produced to serve for the germination of the seeds of 
higher plants. In this way the coral island is, in the course of years, covered 
with a forest of coco-nut trees. Thus it is that the most despised weeds lay the 
foundation for the denizens of the wood; and thus, in the progress of time, the 
sterile rock presents all the varieties of meadow, thicket, and forest. 

The Creator has distributed bis floral gifts over every part of the globe, from 
the poles to the equator. Every climate has its peculiar vegetation, and the 
surface of the earth may be divided into regions characterized by certain pre- 
dominating tribes of plants. The same thing takes place on the lofty mountains 
of warm climates, which may be said to present an epitome of the horizontal 
distribution of plants. Again, if we descend into the bowels of the earth, we 
find there traces of vegetation a vegetation, however, which flourished at dis- 
tant epochs of the earth's history, and the traces of which are seen in the coal, 
and in the fossil plants which are met with in different strata. By the labours 
of Brongniart especially, these fossil remains have been rendered available for 
the purposes of science. Many points have been determined relative to their 
structure, as well as in regard to the climate and soil in which they grew, and 
much aid has been afforded to the Geologist in his investigations. 

The bearings which Botany has on Zoology are seen when we consider the 
lowest tribe of plants, such as Diatomacese. These bear a striking resemblance 
to the lowest animals, and have been figured as such by Ehrenberg and others. 
The observations of Thwaites on Conjugation have confirmed the view of the 
vegetable nature of many of these bodies. There appear, however, to be many 
productions which occupy a sort of intermediate territory between the animal 
and vegetable kingdom, and for the time being the Botanist and Zoologist must 
consent to joint occupancy. 

The application of botanical science to Agriculture and Horticulture has of late 



INTRODUCTORY REMARKS. XV 

attracted much attention, and the chemistry of plants has been carefully examined 
by Liebig, Miilder, and Johnston. The consideration of the phenomena con- 
nected with germination, and the nutrition of plants, has led to important con- 
clusions as to sowing, draining, ploughing, the rotation of crops, and the use of 
manures. 

The relation which Botany bears to Medicine has often been misunderstood. 
The medical student is apt to suppose that all he is to acquire by his botanical 
pursuits, is a knowledge of the names and orders of medicinal plants. The 
object of the connection between scientific and mere professional studies is here 
lost sight of. It ought ever to be borne in mind by the medical man, that the 
use of the collateral sciences, as they are termed, is not only to give him a great 
amount of general information, which will be of value to him in his after career, 
but to train his mind to that kind of research which is essential to the student of 
medicine, and to impart to it a tone and a vigour which will be of the highest 
moment in all his future investigations. What can be more necessary for a 
medical man, than the power of making accurate observations, and of forming 
correct distinctions and diagnoses? These are the qualities which are brought 
into constant exercise in the prosecution of the botanical investigations, to which 
the student ought to turn his attention, as preliminary to the study of practical 
medicine. In the prosecution of his physiological researches, it is of the highest 
importance that the medical man should be conversant with the phenomena 
exhibited by plants. For no one can be reckoned a scientific physiologist who 
does not embrace within the range of his inquiries all classes of animated beings ; 
and the more extended his views, the more certain and comprehensive will be 
his generalizations. 

To those who prosecute science for amusement, Botany presents many points 
of interest and attraction. Though relating to living and organized beings, the 
prosecution of it calls for no painful experiments nor forbidding dissections. It 
adds pleasure to every walk, and affords an endless source of gratification, which 
can be rendered available alike in the closet and in the field. The prosecution 
of it combines healthful and spirit-stirring recreation with scientific study ; and 
its votaries are united by associations of no ordinary kind. He who has visited 
the Scottish Highlands with a botanical party, knows well the feelings of delight 
connected with such a ramble feelings by no means of an evanescent nature, 
but lasting during life, and at once recalled by the sight of the specimens which 
were collected. These apparently insignificant remnants of vegetation recall 
many a tale of adventure, and are associated with the delightful recollection of 
many a friend. It is not indeed a matter of surprise, that those who have lived 
and walked for weeks together in a Highland ramble, who have met in sunshine 
and in tempest, who have climbed together the misty summits, and have slept 
in the miserable shieling should have such scenes indelibly impressed on their 



XVI INTRODUCTORY REMARKS. 

memory. There is, moreover, something peculiarly attractive in the collecting 
of alpine plants. Their comparative rarity, the localities in which they grow, 
and frequently their beautiful hues, conspire in shedding around them a halo of 
interest far exceeding that connected with lowland productions. The alpine 
Veronica displaying its lovely blue corolla on the verge of dissolving snows ; the 
Forget-me-not of the mountain summit, whose tints far excel those of its name- 
sake of the brooks; the Woodsia, with its tufted fronds, adorning the clefts of 
the rocks ; the snowy Gentian concealing its eye of blue in the ledges of the steep 
crags; the alpine Astragalus enlivening the turf with its purple clusters; the 
Lychnis choosing the stony and dry knoll for the evolution of its pink petals ; the 
Sonchus raising its stately stalk and azure heads in spots which try the enthu- 
siasm of the adventurous collector; the pale-flowered Oxytropis confining itself 
to a single British cliff; the Azalea forming a carpet of the richest crimson ; the 
Saxifrages, with their white, yellow, and pink blossoms, clothing the sides of 
the streams ; the Saussurea and Erigeron crowning the rocks with their purple 
and pink capitula; the pendent Cinquefoil blending its yellow flowers with the 
white of the alpine Cerastiums and the bright blue of the stony Veronica ; the 
stemless Silene giving a pink and velvety covering to the decomposing granite ; 
the yellow Hieracia, whose varied transition forms have been such a fertile cause 
of dispute among botanists ; the slender and delicate grasses, the duckweeds, the 
carices, and the rushes, which spring up on the moist alpine summits; the grace- 
ful ferns, the tiny mosses, with their urn-like theca?, the crustaceous dry lichens, 
with their spore-bearing apothecia ; all these add such a charm to highland 
botany, as to throw a comparative shade over the vegetation of the plains. 

Many are the important lessons which may be drawn from the study of plants, 
when prosecuted in the true spirit of Wisdom. The volume of Creation is then 
made the handmaid of the volume of Inspiration, and the more that each is 
studied, the more shall we find occasion to observe the harmony that subsists 
between them. It is only Science, falsely so called, which is in any way opposed 
to Scripture. Never, in a single instance, remarks Gaussen, do we find the 
Bible in opposition to the just ideas which Science has given us regarding the 
form of our globe, its magnitude, its geology, and the productions which cover 
the surface. "The invisible things of God from the creation of the world are 
clearly seen, being understood by the things that are made, even his eternal 
power and Godhead." The more minutely we examine the phenomena of the 
material world, and the more fully we compare the facts of Science with Revealed 
Truth, the more reason shall we have to exclaim, in adoring wonder, with the 
Psalmist of old, " Lord! how manifold are thy works! in wisdom hast thou 
made them all ; the earth is full of thy riches." 



BOTANY. 



PART I. 

VEGETABLE ANATOMY, OKGANOGRAPHY, AND 
PHYSIOLOGY. 



1. BOTANY is that branch of science which comprehends the know- 
ledge of all that relates to the Vegetable Kingdom. It embraces a con- 
sideration of the external configuration of plants, their structure, the 
functions which they perform, the relations which they bear to each 
other, and the uses to which they are subservient. It has been 
divided into the following departments : 1. Structural Botany, or 
Organography, which has reference to the textures of which plants are 
composed, and to the forms of their various organs. 2. Physiological 
Botany, in which plants are considered in their living or active, state, 
and while performing certain vital functions. 3. Systematical Botany, 
or Taxonomy, the arrangement and classification of plants. 4. Geogra- 
phical Botany, or the distribution of plants over the globe. And, 5. 
Fossil Botany, or the nature of the plants found in a fossil state in the 
various geological formations. 






CHAPTER I. 
ELEMENTARY ORGANS, OR VEGETABLE TISSUES. 

2. In their earnest and simplest state, plants consist of minute vesicles, 
formed by an elastic transparent membrane, which is composed of a 
substance called Cellulose. This substance is of general occurrence, 

B 



CELLULAR TISSUE. 



and constitutes the basis of vegetable tissues. The chemical formula 
representing it is C 24 H 21 O 21 , or 2 (C 12 H 10 O 10 ) + HO.* It is allied 
to starch, becomes yellow on the addition of iodine, and when acted 
upon by iodine and sulphuric acid assumes a blue colour. The mem- 
brane formed by it is permeable by fluids, and becomes altered in the 
progress of growth, so as to acquire various degrees of consistence. In 
the advanced stages of growth, plants consist of two kinds of tissue, 
Cellular and Vascular, which, under various modifications, constitute 
their Elementary organs. These, by their union, form the Compound 
organs, by which the different functions of plants are carried on. 
3. The elementary organs consist of vesicles and tubes, varying in 
/-WW, form and size, and united in different ways. The vesicles 
\Jl are cavities surrounded by a membrane, their length not 
much exceeding their breadth (fig. 1) ; while the tubes are 
similar cavities more or less elongated (figs. 3, 4). 



SECTION I. CELLULAR TISSUE. 
1. FORM AND ARRANGEMENT OF CELLS. 

4. Cellular Tissue- is formed by the union of minute vesicles or blad- 
ders, called cells, cellules, or 'utricles. This tissue is often called Parenchyma 
(TT, beside or between, and #tYa, any thing effused or 
spread out, tissue). The derivation of Parenchyma is, by some 
given waj, through, and fy^ea, I infuse. The individual 
cells of which it is composed, when allowed to develop them- 
selves equally in all parts of their circumference, are usually 
of a more or less rounded form (fig. 5, 6, 7) ; but, when 
pressed upon during the progress of development, they be- 
come more elongated in one direction than in another (fig. 2), 
and often assume angular or polyhedral forms (fig. 8). 




234 




5. The following names have been applied by Morren, and other 
authors, to the tissue made up of variously-formed cells: 1. Paren- 
chyma, a general name for cellular tissue, but often applied to that 
consisting of dodecahedral cells (fig. 8, 12, 13), which, when cut in 



* For the meaning of these and other chemical symbols, see Chap. II. Sect. I. Div. 2, on the 
Food of Plants. Figs. 1, 5, 6, 7, 8. Cells, vesicles, or utricles, separate and combined. 

Fig. 2. Fusiform or spindle-shaped cell. Figs. 3, 4. Tubes or vessels. 



FORM AND ARRANGEMENT OF CELLS. 3 

one direction, exhibit an hexagonal form (figs. 14, 15), and hence the 
tissue is sometimes called heocagonienchyma (t^ofyuvios, six-angled); it is 




seen in the pith of the Elder, and in young palm stems. 2. Sphceren- 
chyma (yQatget, a sphere), spheroidal cells (fig. 5). 3. Merenchyma 
(fiYigva, to revolve), ellipsoidal cells (fig. 6). 4. Ovenchyma (&POI/, an egg), 
oval cells. Round, elliptical, and oval cells, are common in herbaceous 
plants. 5. Conenchyma (x.avo$, a cone), conical cells, as hairs. 6. Columnar 
cellular tissue, divided into Cylindrenchyma (xt^/i/Sjo?, a cylinder), cylin- 
drical cells, as in Chara (fig. 17 a), and Piismenchyma (naia^a,, a prism), 
prismatical cells, seen in the bark of some plants (fig. 10). When 
compressed, prismatical cells form the muriform (murus, a wall, like 
bricks of a building) tissue of the medullary rays of woody stems, and 
when much shortened they assume a tabular form, constituting Pinen- 
chyma (vivu.%, a table), tabular cells (fig. 11), or square cells (fig. 9). 
7. Prosenchyma (^[ 29), or Atractenchyma (oiT^atxros, a spindle), fusi- 
form or spindle-shaped cells, seen in bark and wood (fig. 2). 8. 
Colpenchyma (x.favo$, a sinus or fold), sinuous or waved cells, as in the 
cuticle of leaves. 9. Cladenchyma (x^xlog, a branch), branched cells, 
as in some hairs. 10. Actinenchyma (CCX.TH/, a ray), stellate or radiat- 
ing cells, as in Juncus and Musa (fig. 16). 11. Dcedalenchyma (B/JXof, 
entangled), entangled cells, as in some Fungi. 






15 

6. The size of cells varies not less than their figure in different 
plants, and in different parts of the same plant. They are frequently 
seen from 5 ^o to ^Jo of an inch in diameter. In cork, which is cellu- 
lar, Hooke found more than a thousand in the length of an inch. 

7. Each cell consists originally of a separate membrane, but in the 
progress of growth the walls of contiguous cells may become united. 
When cells are united by their extremities (fig. 17), their partitions 



Figs. 9, 10, 11, 12, 13. Figures representing the forms of cells. Figs. 14, 15. Hexagonal cells. 
Fig. 16. Brandling cells of Vicia Faba. 1 1, Intercellular lacuna;. 



FORM AND ARRANGEMENT OF CELLS. 



are occasionally absorbed so as to form continuous tubes. When 
cells are united in a rectilinear manner, those in contiguous rows are 
either directly opposite to each other, that is, are placed at the same 
height (fig. 18), or are alternate, from being placed at different heights 
(fig. 19); cells sometimes communicate with each other laterally (fig. 
20 a a). Isolated cells, as spores of sea-weeds, occasionally have free 
filaments, or cilia (cilium, an eyelash) developed on their surface. 





18 



19 




8. The simplest kinds of plants, as mushrooms and sea-weeds, are 
composed entirely of cellular tissue, and are called Cellulares. The 
pulpy and succulent parts of all plants contain much cellular tissue, 
and the object of horticultural operations is to increase the quantity of 
this tissue in ordinary fruits and vegetables. The pith of trees and 
plants during their early development is cellular ; so also are cotton 
and rice-paper. 

9. In general, no visible openings can be detected in cells, although 
fluids pass readily into and out of them. Harting and Mulder, however, 
state, that they have observed perforations in the cells of Hoya carnosa, 
Asclepias syriaca, Cycas revoluta, Virginian spiderwort, and Traveller's 
joy. In one cell (from a Euphorbia), having a transverse diameter of 
0.03777 millimetres,* they counted 45 minute holes. In some mosses, 
also, openings have been found in the cells. 

10. Porous ceils are those in which the membrane has been thick- 

ened at certain parts, leaving thin rounded spots, which, 
when viewed by transmitted light, appear like perfora- 
tions or pores (figs. 21, 28). The pores of contiguous 
cells usually correspond as regards position, and some- 
times the membrane becomes absorbed between them, so 
as to allow a direct communication by means of lateral 
canals, as is seen in the cells from the root of the Date 

Figs. 17, 18, 19. Cells united together by their extremities. 

Fig. 20. Elongated thickened cells, from the root of the Date palm, o a, Canals of communi- 
cation. 

Fig. 21. Porous cell, from the Elder (Sambucus nigra). 

Fig. 22. Articulated Bothrenchyma, or Taphrenchyma, from Misletoe, having a inoniliform 
appearance. * A millimetre is about l-25th of an English inch. 




FORM AND ARRANGEMENT OF CELLS. 5 

(fig. 20 a a). When porous cells are united end to end, so as to 
form tubes, they have been denominated articulated Bothrenchyma 
(/3o0go;-, a pit), on account of the pits or depressions in their thickened 
walls (fig. 22). 

11. Fibrous OP Spiral cells are those in which there is a spiral 
elastic fibre coiled up in the inside of the membrane (fig. 23). When 
united, they form fibro-cellular tissue, or Inenchyma (his, fibres). These 







cells generally consist of membrane and fibre combined, but the 
former appears to be sometimes absorbed wholly or partially during 
the progress of growth. The membrane, in some instances, is easily dis- 
solved by water, and then the elastic close convolutions of the fibre spring 
out with considerable force, as in the outer covering of the seeds of 
Collomia and Salvia. Spiral cells abound in many of the Orchidaceous 
plants, and in the Cactus tribe. They are also found in the inner 
covering of anthers, in the spore-cases of many of the lower tribes of 
plants, and in the coats of the seed of Acanthodium spicatum. The 
spiral filaments sometimes exhibit peculiar movements when placed 
in water. The fibre varies from about 55 ^o to 10,000 f an mcn m 
diameter; it is solid, and presents either a circular, an elliptic, or a 
quadrangular section. The coils of the fibre sometimes separate from 
-each other, and become broken up and united in various ways, so as 
to appear in the form of rings, bars, or dots, thus giving rise to annular 
(fig. 24), reticulated (fig. 25), scalariform and dotted cells (fig. 26), which 
constitute the spurious or imperfect Inenchyma of authors. 

12. In certain parts of plants cells are placed closely together, and 
compressed so as to touch each other by flat surfaces, filling up space 
completely, and leaving no intervals; they then form the perfect Paren- 
chyma of Schleiden (figs. 8, 27). In lax tissues, however, the cells retain 
a rounded shape, and then touch each other at certain points only, 
leaving intervals of various sizes and shapes, and forming the imperfect 
Parenchyma of Schleiden (figs. 7, 28). These intervals, when of moder- 
ate size and continuous, are called intercellular passages or canals; when 
large, irregular, and circumscribed, intercellular spaces, or Lacunae (fig. 
16 1 1). 

13. A difference of opinion prevails as to the mode in which cells 

Figs. 23, 24, 25. Spiral, annular, and reticulated cells, from Misletoe (] 7 iscitm album). 
F'g. Id.' Scalarifbrm and dotted cells, from Elder (Sanibucus niyra). 



CONTENTS OF CELLS. 



are united together. Some maintain that the cell-walls in the young 
state unite together directly, and become agglutinated, more or less, 





27 

according to their places of contact. Others, as Mohl and Henfrey, 
hold that there is an intercellular matter which acts as a sort of 
cement, or Collenchyma (x&'?a, glutinous matter). In sea-weeds, the 
cells, of which the entire plant is composed, are placed at a distance 
from each other (fig. 29 a a), and the intervals are filled up by this 
intercellular substance (fig. 29 ft), which thus forms a large part of 
their bulk. In the higher classes of plants, when the cells touch 
each other, the layer of intercellular matter must be very thin, except 
in the intercellular canals or spaces. Mirbel looks upon it as the re- 








mains of the mucilaginous fluid in which the cells were originally deve- 
loped, and which has become thickened to a greater or less degree, as 
in the root of the Date (fig. 30), where a a a indicate the cells, and 
b b b the interposed substance. 



2. CONTENTS OF CELLS. 

14. The external membrane of cells is composed of the unazotised 
substance called Cellulose, and in their interior a mucilaginous matter 
is contained, which undergoes changes in the progress of growth. 

Fig. 27. Cellular tissue, from pith of Elder. 

Fig. 28. Porous Merenchyma, from Houseleek (Sempermvum tectorumi). a, Intercellular canal. 
Fig. 29. Cellular tissue of Sea-weed (Himanihalia lorea). a a, Cells. 6, Intercellular matter. 
Fig. 30. Central portion of young root of Date, a a a, Thickened cells, bbb, Intercellular 
substance of Mirbel. 



CONTENTS OF CELLS. 



This matter is the Protoplasm (K^UTO;, first, and ^-Aa^a, formative 
matter) of Mohl, the Cytoblastema (XVTOJ, a cell, and /SAaar^a, a germ) 
of some authors. It is at first homogeneous, but ultimately assumes 
a granular form. It contains nitrogen in its composition, or is azotised, 
and it assumes a brownish colour when acted upon by iodine. It 
forms a mucilaginous layer on the inner surface of the cell-wall, and 
thus gives rise to the internal utricle of Harting and Mulder, the prim- 
ordial utricle of Mirbel. This inner membrane is visible in the young 
state of the cell, and under the action of tincture of iodine may be 
made to contract and separate from the outer cell-wall. It may also 
be rendered distinct by the action of strong hydrochloric acid, and by 
diluted sulphuric acid. When the process of lignification or thicken- 
ing has advanced, this utricle disappears, in consequence of becoming 
incorporated with the cell-wall. 

15. In certain cells the membrane continues throughout to be formed 
of a thin layer of cellulose, while in others it becomes thickened by the 
deposition of matter on its inner side. These secondary deposits, or in- 
crustations, are sometimes of a gelatinous consistence; at other times they 
are hard. In the latter case, the incrusting matter is looked upon as a 
modification of cellulose, and has received the name of li<jnine (lignum, 
wood), or sclerogen (o-xXfoV, hard, and ytwu.tiv, to generate). On mak- 
ing sections of such cells, in a transverse (fig. 31) or longitudinal di- 
rection (fig. 32), the successive layers may 

be seen either continuous all round, or leav- 
ing parts of the membrane uncovered. Cells 
of this kind are well seen under the micro- 
scope in thin sections of the hard shell of the 
Coco-nut, or of Attalea funifera, and of the 
hard seed of the Ivory Palm. In all cell- 
deposits there is a tendency to a spiral ar- si 
rangement. When the deposition is uniform over the whole surface, 
this arrangement may not be detected ; but when interruptions take 
place, then the continued coil becomes evident. In spiral cells the 
fibre seems to be formed before the full development of the cell, the coils 
of the fibre being at first in contact, and afterwards 
separated, whereas the secondary thickening layers are 
deposited after the cell is fully formed. 

16. Each cell is found to contain, at some period of \__// j-j 0; 
its existence, a small body, called a nucleus (fig. 33 nn ri), 

in which there are often one or two, rarely more, min- 
ute spots, called nucleoli. The nucleus is of a round 
or oval shape, granular and dark, or homogeneous 
and transparent, bearing some resemblance to a smaller internal cell. 

Fig. 31. Transverse section of cells from pulp of Pear. 

Fig. 32. Longitudinal section of the same. Fig. 33. Nucleated cells from the Beet. 





8 



CONTENTS OP CELLS. 



Nucleoli are not always present. They are either vesicles and 
granules contained in the nucleus, or minute cavities in its substance. 
The latter view is supported by Barry, who holds that a peculiar sub- 
stance, called hyaline (JAoj, glass), is developed there, which, accord- 
ing to him, is the origin of the nucleus. The nucleus is situated at 
different parts of the cell. It is either free in its cavity, or connected 
with its wall by mucilaginous threads, or imbedded in the substance of 
the membrane. The addition of acetic acid often renders the nucleus 
distinct. 

17. Starchy matter is found in cells, which constitute the tissue 
called, by Morren, Perenchyma (vi\^a. y a sac.) Starch exists in the 
form of granules, which are minute cells, (perhaps nuclei, as Mulder 
states,) in which nutritious matter is stored up. This matter may be 
deposited in such a way as to give the appearance of stria? surrounding 
a point or hilum, which is considered as an opening into the cell. 
The grains of starch are well seen in the cells of the potato (fig. 34). 
In wheat (fig. 35), and in maize (fig. 36), the form of the granules, 






and the successive layers of deposit, are also seen. The grains in the 
stem of Nuphar luteum show the centripetal formation, that is, the 
increase by layers deposited within each other. The addition of iodine 
causes the grains of starch to assume a blue colour, and marks the 
difference between them and the walls of the cell containing them. 
18. Crystals are found in the interior of cells. They probably 
owe their origin to the union between the acids pro- 
duced or taken up by plants, as oxalic, phosphoric, 
malic and carbonic, and the alkaline matter, as lime 
and potash, absorbed from the soil and circulating in the 
sap. The crystals usually lie loose in the cells (figs. 37, 
38) ; but, according to Pay en, they are sometimes found 
in a distinct tissue, and suspended from the wall of a 
large cell (fig. 39) filling what some have supposed to 
be the base of an undeveloped hair. The crystals are 
of different sizes and forms. Occasionally, a single large 
crystal nearly fills a cell, but in general there are numerous crys- 
tals united together. Sometimes the crystals radiate from a common 
point (figs. 40, 41), and form a conglomerate mass; at other times they 

Fig. 34. Cell of Potato, containing striated starch grains. 
Fig. 35. Grains of starch of Wheat. Fig. 36. Grains of starch of Maize. 

Fig. 37. Cellular tissue of Arum maculatum. c, Cells containing chlorophylle. r r, Raphidian 
cells. 




CONTENTS OF CELLS. 



lie parallel, and have the appearance of bundles of fine needles (figs. 
37, 38). To the latter, the name of Raphides (pxQis, a needle), or 





acicular crystals (acws, a needle), was originally given. It has been 
said that these crystals exist also in the intercellular spaces ; but this 
seems to depend on the mode in which the section of the plant is made, 
for when raphidian cells (fig. 42 r r r r) are situated close to a lacuna, 
the crystals may easily be pushed into it accidentally by the knife. 
Raphides consist principally of phosphate and oxalate of lime. They 
abound in some plants, especially Cacti, and they 
are common in Squill, and in the officinal Tur- 
key Rhubarb, which owes its grittiness to their 
presence. One hundred grains of rhubarb root 
contain about 30 or 40 grains of oxalate of lime 
crystals. Acicular crystals may be easily seen by 
making a section of any Liliaceous plant, as the 
hyacinth, and spreading the thick mucilaginous 
matter of the cells on the field of the micro- 
scope. Radiating raphides are seen in the sepals of Geranium robertia- 
num and lucidum; the crystals, consisting of oxalate of lime, fill the 
whole of the cells in the middle of the sepal, their size varying from 
Woo to T 3oo f an inch. Quekett found them in all the species of 
Pelargonium and Morisonia that he examined, and he thinks that they 
are as general as the beautiful markings in the cuticle of the petals of 
these plants. Clustered crystals have been detected in Malvaceous 
plants, and in the sepals of the strawberry; numerous acicular crystals 
have been observed in Fuchsias, and solitary cubical crystals in the 
superficial cells of the sepals of Prunella vulgaris and Dianthus Caryo- 
phyllus. In the outer covering of the seed of Ulmus campestris, the 
sinuous boundaries of the compressed cells are traced out completely 

Fig. 38. Cells of Aurum maculatum. Clusters of raphides in a large oval cell surrounded by 
smaller cells. 

Fig. 39. Cellular tissue, from leaf of Flcus elastica. c, A large cell, r, An agglomeration of 
crystals suspended in a sac by a tube, t. u, Utricles filled with grains of chloropliylle. 

Fig. 40. Cells of Beet with conglomerate radiating crystals, a. b, Separate crystals of different 
forms. 

Fig. 41. Conglomerate crystals of oxalate of lime from Rhubarb. 

Fig. 42. Cellular tissue of Colocasia odora. c c, Cells with grains of chlorophylle. rrrr, Ra- 
phidian cells projecting into a lacuna or intercellular space. 



10 DEVELOPMENT OF CELLS. 

by minute rectangular crystals adhering to each other. Unger detected 
oxalate of limp crystals in Ficus bengalensis and Calathea zebrina. 

19. Chlorophyll*- (^Xagoj, green, and <p^Xo(/, a leaf), or the green 
colouring matter of plants, floats in the fluid of cells, accompanied by 
starch grains. It has a granular form (fig. 39 w, 42 c), is soluble in alcohol, 
appears to be analogous to wax in its composition, and is developed 
under the agency of light. Its granules are usually separate, but some- 
times they unite in masses (fig. 37 c). Other kinds of colouring matter 
are also produced during vegetation, and occur in the form of fluids or 
of granules in the interior of cells. 

20. Oils and Resinous matter are found in the interior of cells, as 
well as in intercellular spaces. The cavities containing them are deno- 
minated cysts, reservoirs of oil, and receptacles of secretions. They are 
easily detected in the rind of the orange and lemon, in the myrtle tribe, 
and in Hypericum. When small portions of the fresh leaf of Schinus 
mollis are thrown on water, the resinous matter, by its rapid escape, 
causes them to move by jerks, and the surface of the fluid is covered 
with the exudation. In the bark of the Fir tribe there are cavities 
with thick walls containing turpentine. In the fruit of UmbelliferEe, 
canals occur called vittce \vitta, a head-band, from surrounding the 
fruit), containing oil. 

21. Air ceils, or cavities containing air, consist either of circum- 

scribed spaces surrounded by cells (fig. 43), or of lacunae 
formed by the rupture or disappearance of the septa be- 
tween a number of contiguous cells, as in grasses, Equise- 
turn, Umbelliferous plants, and pith of Walnut. They 
are often large in aquatic plants, and serve the purpose of 
43 floating them, as in Pontederia, Trapa, Aldrovanda, and 
sea-weeds. 

3. DEVELOPMENT AND FUNCTIONS OF CELLS. 




22. The subject of Cell-development, or Cytogenesis (XVTOS, a cell, and 
yfviai;. origin), which has given rise to great diversity of opinion among 
physiologists, is still involved in much obscurity. By some it is 
affirmed that the first appearance of vegetable tissue is in the form of 
a mucilaginous fluid, which, gradually thickening, becomes hollowed 
into a number of small cavities constituting the future cells. Schleiden 
believes that the cell is formed from the nucleus, to which he gave 
the name of Cytoblast (XJ/TO?, a cell, and /sxewroV, a germ), or cell-germ, 
from its supposed generative function. This cytoblast, according 
to him, is the part first formed. It acts by attracting the mucilagi- 
nous matter in which it lies, and forming around itself a sort of gela- 
tinous covering. There is thus produced round the nucleus a closed 

Fig. 43. Air-cells in Ranunculus aquatilis. 



DEVELOPMENT OF CELLS. 1 1 

utricle, which increases in size by the assimilation of the fluid in which 
it is placed. The development usually takes place on one side, the new 
cell appearing in the form of a transparent vesicle rising from the 
surface, and leaving the nucleus attached to the other side of the 
utricle (fig. 33). The cytoblast is thus enclosed in the utricle, and may 
ultimately disappear by absorption, leaving a non-nucleated cell. The 
membrane surrounding the nucleus is converted gradually into cellu- 
lose, and thus the perfect cell is formed. According to Mohl, the 
nucleus is at first retained in the centre of the cell by means of mucous 
threads, and afterwards becomes fixed to the sides. Occasionally, the 
nucleus becomes imbedded in a duplication of the cell-wall. This 
process of cell-development, according to Ascherson, is similar to what 
takes place when oil is mingled with a mucilaginous or albuminous 
fluid, each minute molecule of oil becoming surrounded by a thin 
film of membrane. In this view the cell is originally of a more or less 
globular form, and all the varieties of shape afterwards seen are due 
to changes in the progress of growth. 

Barry affirms that a minute pellucid globule (hyaline) is first seen in 
the formative matter. This absorbs and assimilates new matter, enlarges 
and becomes granular, thus forming the cytoblast of Schleiden, after it 
has prepared a nucleolus for itself. The outer part of the cytoblast rises 
in the form of a membrane to produce a cell; another portion of it is 
concerned in the formation of the contents of the cell; and what is left of 
the cytoblast in the cell-wall becomes the nucleus of the cell. This nu- 
cleus (not the cytoblast of Schleiden) remaining on the cell-waE, is not 
absorbed, but becomes the source whence cytoblasts are formed. Tims, 
according to Barry, the substance of the larger body is not deposited 
around the smaller, but the smaller is transformed into the larger; the 
nucleolus becomes the cytoblast, and the cytoblast becomes a nucleated 
cell. 

As regards the development of cells from nuclei, the present state of 
our knowledge does not warrant us in stating more than that there is 
a protoplasm, or soft organizable matter, which is contained in cells, or 
in the spaces between them ; that in this matter a nucleus is produced, 
either around previously existing nucleoli, or from the granules of the 
protoplasm; and that the nucleus has the power of developing new 
cells, which become nucleated, increase in size, and escape from the 
parent cell, by rupture or absorption. In the production of young 
cells, the nucleus of the parent cell sometimes divides into two, each 
part having the power of giving rise to a new cell. There is thus a 
constant multiplication of cells by an intra-cellular or endogenous 
(svftov, within, and yewativ, to generate) process. 

23. It is supposed by some that cells may arise without a nucleus, 
by the simple aggregation of granular matter, which becomes enve- 
loped in a membrane, and thus forms a cell with granular contents. 



12 FUNCTIONS OF CELLS. 

In such cells, a body similar to a nucleus may be afterwards formed, 
and may assume the function of the cytoblast of Schleiden, as far as the 
subsequent endogenous development of new cells is concerned. Some 
physiologists maintain that the cytoblast is never concerned in cyto- 
genesis, but only takes part in the various chemical and other changes 
which occur in the contents of the cell during its growth and nutrition. 
Mohl and Henfrey state that new cells are produced by the division of 
the primordial utricle (T 14), which gradually folds inwards about 
the middle, forming an annular constriction, and ultimately a complete 
separation of the utricle into two parts. Each of these afterwards be- 
comes covered by a permanent cell-wall. Henfrey has supported this 
view by observations made on the hairs of Tradescantia and of Achimenes 
grandiflora, in which he has traced the gradual formation of a septum. 

24. Naegeli maintains that new cells are produced by the division 
of the primordial utricle, or mucilaginous sac, as he calls it, and its 
contents into two or four portions, each of which encloses a free nu- 
cleus. From each of these portions, a cell, with its outer layer of 
cellulose, originates, while the parent cell becomes dissolved and disap- 
pears. The outer layer of the new cells is formed, according to him, 
round, and by the separate portion of the divided utricle. The mode 
of division he does not explain. This view does not appear to differ 
much from that adopted by Unger, who traces in Alge the develop- 
ment of new cells, by ajissiparous (Jissus, split, andjoano, I produce), 
or merismatic (^gj/o-^of, division) separation of the old ones into four 
divisions, in the same way as occurs in pollen grains. In some of the 
most simple plants, multiplication takes place by a sort of sprouting of 
new cells from old ones, like buds from a stalk. 

25. The various theories of cell-development may be therefore re- 
duced to the following: 1. The Endogenous formation within a parent 
cell; 2. the Exogenous (<!%&>, without), without, or on the outside of 
the cell; 3. Merismatic, or by division of cells; and, 4. Isolated, or 
the independent formation of cells in a protoplasm.* 

26. The formation of cells from nuclei, and their fissiparous division, 
are by some attributed to different electrical currents excited by the 
chemical actions going on in the cell. Cells are produced with great 
rapidity, especially in the case of fungi. Lindley calculates that the 
cells of Bovista gigantea have been produced at the rate of more than 
sixty-six millions in a minute, and Ward has noticed a similar occur- 
rence in Phallus impudicus. In warm climates, at the commencement 
of the wet season, the production of cells in the higher classes of plants 
proceeds with astonishing rapidity. 

* For a full view of the subject of the development and growth of cells, the following works 
maybe consulted: Schleiden on Phylogenesis, and Mohl on the Structure of the Vegetable 
Cefi, translated in Taylor's Scientific Memoirs, Vols. II. and IV. ; Naegeli on Vegetable Cells, 
Ray Society's Reports, 1846; Sharpey, Anatomy; M. Barry, Physiology of Cells, &c., in Philo- 
sophical Transactions, 1840 ; and on Nucleus of Cells, in Jameson's New Philosophical Journal for 
September, 1847; Carpenter's Physiology. 



FORM AND ARRANGE MENT OF VESSELS. 13 

27. The organized cells of plants appear to be the more immediate 
seats of the various changes which constitute the functions of nutrition 
and reproduction. In cellular plants they are the only form of elemen- 
tary tissue produced throughout the whole of life. They absorb nour- 
ishment through their walls, elaborate secretions, and give rise to new 
individuals. In the newly-formed tissue of vascular plants, cells alone 
at first exist. Fluid matters are absorbed by them, and are transmitted 
from cell to cell by a process of transudation. The name of Endosmose 
(ti/Soi/, inwards, p,ec.u, pa, I seek), and Exosmose (e|<a, outwards), were 
given by Dutrochet to the process of transudation, which leads to the 
motions of fluids of different densities placed on opposite sides df 
animal and vegetable membranes. This process appears to be of uni- 
versal occurrence in plants, being concerned in the movements of the 
sap, the opening of seed-vessels, and many other phenomena. The 
capsule of the Elaterium, for instance, opens with great force by a pro- 
cess of endosmose going on in the cells, and such is also the case with 
that of the Balsam. The power which cells possess of absorbing fluids 
is well seen in sea-weeds, which, after being dried, can easily be made 
to assume their natural appearance by immersion in fluids. It is also 
observable in the spores of the Equisetum, the teeth of Mosses, the 
seed-vessels of some Fig-marygolds, the Rose of Jericho (Anastatica), 
and some Lycopodiums. 

Various organic secretions, which are necessary for growth and nour- 
ishment, are formed by the internal membrane of cells. It is m cells 
that the azotised and unazotised matters .ire deposited, which are after- 
wards applied to the purposes of vegetable lit e. In them we meet with 
the proteine compounds, albumen, fibrine, and caseine, consisting of 
carbon, oxygen, hydrogen, and nitrogen, with proportions of sulphur 
and phosphorus; as well as starch, gum, sugar, oil, and colouring mat- 
ters, in which no nitrogen occurs. Some of the organic matters found 
in plants have been artificially formed by chemical means, while others 
have only as yet been met with in the living organism. Spiral cells 
sometimes contain air. 



SECTION II. VASCULAR TISSUE. 
1. FORM AND ARRANGEMENT OF VESSELS. 

28. Vascular Tissue, or AngiencJiyma (yyo?, a vessel), consists of 
tubes whose length greatly exceeds their breadth. These may be 
formed of membrane only, or of membrane altered in various ways 
by deposits of fibre, or thickening matter in the interior. 

29. Woody Fibre, or Ligneous Tissue, Pleurenc/tyma (TT^IV j, a rib, 
from its firmness), (fig. 44,) consists of tubes, or, according to some, 
elongated cells, of a fusiform (fusus, a spindle) or spindle-like shape 
(fig. 3), having their walls thickened so as to give great firmness. Some 



14 



FORM AND ARRANGEMENT OF VESSELS. 



have called this tissue Prosenchyma (K&, close to, in reference to the 
close apposition of the tubes), a term, however, generally 
applied to shortened fusiform cells only. Pleurenchyma- 
tous vessels lie close together, overlap each other, and, by 
their union, give strength and solidity to the plant. Their 
membrane becomes thickened by successive deposits of 
layers of cellulose and sclerogen, and in a transverse sec- 
tion the tubes present tHe appearance of concentric circles, 
occasionally with intervals, where the ligneous matter is 
deficient (fig. 45). The wood of trees is made up of fibres 
or tubes of this kind, and they are found in the inner 
bark, and in the veins of leaves. The woody fibres may 
be separated from the cellular parts of plants by macera- 
tion. In this way Flax and Hemp are procured, as Avell 
as the Bast used for mats. The strength of the woody 
fibres of different plants varies. Thus, New Zealand Flax, 
the produce of Phormium tenax, is superior in tenacity to 
Common Hemp; while the latter, in its turn, excels Com- 
mon Flax, as well as Pita Flax, which is the produce of 
Agave americana. Linen is formed from woody tissue. 
Cotton, on the other hand, consists of elongated cells or 
hairs, the membrane of which becomes contracted in the 
process of drying, so as to appear twisted when viewed 
under the microscope. By this character mummy cloth 
was shown to be composed of linen. Woody fibres, in 
fabric, form muslin, lace, &c., some fine India muslins 
only are formed from woody fibre ; other muslins are 
made of cotton ; when reduced to small fragments, they constitute the 
pulp whence paper is made. 

30. In its ordinary form, Pleurenchyma has no definite markings 
on its walls; but in some instances these pre- 
sent themselves in the form of simple discs (fig. 
46), or of discs with smaller circles in the 
centre (fig. 47). The latter occurs in the wood 
of Firs, Pines, and "Winter's bark, and has re- 
ceived the name of glandular or punctated woody 
tissue. These markings are formed by concave 
depressions on the outside of the Avails of .conti- 
guous tubes, which are closely applied to each 
other, forming lenticular cavities between the 
vessels, like two watch-glasses in apposition, 
and when viewed by transmitted light they ap- 

Fig. 44. Woody fibres (Pleurendiyma,) from Clematis vitalba. 
Fig. 45. Transverse section of the same. 

Fig. 46. Woody fibres with circular spots where the membrane is thin (Rignonia). 
Fig. 47. Punctated woody tissue, with a double circle or disc, from common Scotch fir. 
Fig. 48. Longitudinal section of the same, showing the union between the fibres and the mode 
in which the circles are formed. 





FORM AND ARRANGEMENT OF VESSELS. 



pear like discs (fig. 46). In the centre of the depression there is a 
canal, often funnel-shaped, and the part of the tube corresponding to it 
being thus thinner than the surrounding texture, gives the aspect of a 
smaller circle in the centre (fig. 47). When a thin section is made 
through two parallel lines of punctations, the slits or fissures are seen 
which give rise to the appearances mentioned (fig. 48). That these mark- 
ings are cavities between the fibres was proved by Quekett 
in the case of fossil pine wood, where he separated lenticu- 
lar masses of solid matter from the discs. There is some- 
times observed a thickening layer, in the form of a spiral 
fibre, surrounding the discs more or less completely. The 
discs are usually arranged in single rows, but they occur 
also in double and triple rows, more particularly in Arau- 
caria and Altingia. 

31. Fibre- Vascular Tissue, or Trachenchyma (trachea, 
windpipe ; rpet^vg, rough), is formed of membranous tubes 
tapering at each end, less firm than Pleurenchyma, and 
either having a fibre coiled up spirally in their interior, or 1 
having the membrane marked with rings, bars, or dots, I 
arranged in a more or less spiral form. 

32. True Spiral Teasel* (spiroidea, trachece), constituting | 
the typical form, present themselves as elongated tubes | 
clustered together, overlapping each other at their conical j 
extremities, and having a spiral fibre or fibres surrounding ; 
the interior of the cy Under (fig. 49). Their outer mem- 
brane is thin, and consists of pure cellulose. At the point \ 
where they overlap, it is sometimes absorbed so as to i 
allow direct communication between the vessels. The 
fibre or spiral filament is generally single, forming simple 49 
trachece (fig. 50); but sometimes numerous fibres, varying from two to 
more than twenty, are united together, assuming the aspect of a broad 
ribband (fig. 51), and constituting Pleiotrachece (^M'IUI>, more). The 
fibre is elastic, and can be unrolled. This can be seen by taking the 
leaf of a Pelargonium, and after making a superficial cut round the 
stalk, pulling the parts gently asunder, when the fibres will appear like 
the threads of a cobweb. 

33'. Spiral vessels were first noticed as early as 1661, by Henshaw. 
They occur principally in the higher classes of plants, and are well seen 
in annual shoots, as in Asparagus; in the stems of Bananas and Plan- 
tains, where the fibres may be pulled out in handfuls, and used as tin- 
der ; in many aquatics, as Nelumbium and Nymphasa, and in Liliaceous 
plants. In hard woody stems, they are principally found in the sheath 



Fig. 49. Two spiral vessels united. 

Fig. 50. Simple trachea. 

Fig. 51. Spiral vessel with a ribband of united fibres (Pleiotrachea,) from the Banana. 



16 



FORM AND ARRANGEMENT OF VESSELS. 




surrounding the pith, and they are traced from it into the leaves. 
They are rarely found in the wood, bark, 
or pith. Spiral vessels occasionally exhi- 
bit a branched appearance. This may 
arise from the union of separate vessels in 
an angular or jointed manner, as where a 
leaf or branch is given off (fig. 52 a a), or 
it may depend on a regular division of the 
fibres, as is seen in the Misletoe, Long- 
leek, and Gourd (fig. 53). 

34. The fibre is on the inside of the mem- 
brane. Quekett has shown this in silicified 
spiral vessels, where the mark of the spiral 
was on the outside of the mineral matter 
filling the tube. The fibre usually turns 
from left to right, if we suppose the observer placed in the axis of 
the tube (fig. 54), or from right to left, if we suppose him looking 
at the vessel in its natural position. The fibre retains its direction 
throughout the length of the vessel. When examined under the micro- 
scope, there is often the appearance of the crossing of fibres (fig. 54), in 
consequence of the transparency of the membrane, and the 
observer seeing the fibre on each side of the vessel at the 
same time. In twining plants, the direction of the fibre 
does not always correspond with that of the stem. The 
coils of the spiral fibre may be close together (fig. 50), or 
be separated (fig. 55). Sometimes they become united 
together, and to the membrane of the tube, so that they 
cannot be unrolled. Such vessels are called closed trachea?, 
or closed ducts. 

35. False or Spurious Tracheae, the ducts of some authors, are ves- 
sels in which the internal fibre does not form a complete spiral coil. 
The chief varieties are annular, reticulated, and scalariform vessels, or 
ducts. In annular vessels (annulus, a ring), the fibres form complete 
rings round the tubes (fig. 56). They resemble the trachea? of animals 
more than spiral vessels do. The rings are by no means regular ; 
they may be horizontal or inclined, simple, or forked (fig. 57), placed 
near to each other or separated by considerable intervals, the inter- 
mediate spaces being sometimes occupied by a fibre of an elongated 
spiral form, which is continuous with the rings or distinct from them 
(fig. 58). All these forms are easily recognized in the common Bal- 
sam. Occasionally, the ring becomes very much thickened in a direc- 
tion perpendicular to the walls of the vessel, so as to leave only a 

Fig. 52. Spiral vessels, united so as to have a branched appearance. 
Fig. 53. Branching fibre, from spiral vessels of Gourd (Cucurbita fepo). 
Fig. 54. Spiral vessels. Coils seen on both side.s. 
Fig. 55. Coils of fibre, much separated in trachea of Gourd. 



FOBM AND ARRANGEMENT OF VESSELS. 



17 



small space in the centre, as in some of the Cactus tribe. When 
separate fibres cross each other, forming a kind of net- work on the walls 
of the tubes (fig. 59), the vessels become reticulated (reticulum, a net); 
and the name dotted is sometimes applied when the fibre is so broken 
up as to leave small isolated portions adhering to the membrane 
(fig. 60). In scalariform vessels (scala, a ladder), there are short 
horizontal lines or bars, composed of fibre, arranged along the sides 
of the tubes, at nearly equal distances, like the steps of a ladder, and 
presenting a striated appearance. In some cases, as in the Vine (fig. 
61), they are composed of tubes united to each other by thin, broad, 
oblique extremities; at other tunes they taper like spiral vessels. 
They generally assume a prismatic form, the angles being unmarked 
by lines, as is seen in Ferns (fig. 62). 







67 



58 



62 



36. Porous Vessels. Another kind of vessel common in plants is the 
porous vessel, so called from the appearance of pores on its surface. 
The tissue formed by porous vessels has received the name of Vasiform 
tissue, Pitted tissue, Bothrenchyma, or Taphrenchyma (Soffpeg or Ta<pjso?, 
a pit). The vessels are of large size, and are easily observed in the 
Vine (fig. 63), Sugar Cane, Bamboo, Gourd (fig. 98 ter), and other 

Figs. 56, 57, 58. Annular vessels from the stem of the Common Balsam. 
Fig. 59. Spiral vessel. Wide coil, and fibre dividing. 
Fig. 60. Vessel showing rings of fibre and dots. 
Fig. 61. Scalariform vessel from the Vine. 

Fig. 62. Prismatic scalariform vessel from Eoyal Fern (Osmunda reyalis). 
C 



18 



FORM AND ARRANGEMENT OF VESSELS. 



plants, in which the sap circulates rapidly. They consist of cylinders 
more or less elongated, in which the thickening matter is so deposited 
as to leave part of the membrane uncovered, thus giving rise to the 
porous or pitted appearance. The uncovered portions of membrane are 
sometimes absorbed in old vessels, and a direct com- 
munication is established between them. The pores 
have sometimes a bordered aspect, which, according 
to Schleiden, depends on air contained in the cavities 
between contiguous vessels. Porous vessels are usually 
united to each other by a broad and often oblique 
septum. 

37. This kind of vessel occa- 
sionally presents a beaded appear- 
ance, as if formed by porous cells, 
with distinct constrictions at their 
point of union (figs. 64, 65). This 
articulated Bothrenchyma is by 
some considered as a form of cel- 
lular tissue (f 10, fig. 22). To 
vessels exhibiting contractions of 
this kind, whether spiral or porous, 
the terms moniliform (monile, a 
necklace), or vermiform (vermis, a 
worm), have been applied; and the tissue composed of spiral, annular, 
or porous moniliform vessels, has been denominated phleboidal (<pxtif , 
<pA/3oV, a vein). 

38. Kiaticiferons vessels form the tissue called Cinenchyma (nivta, I 
move, from certain movements of their contents, to be afterwards 
noticed). They are the Milk-vessels, and the Proper vessels of old 
authors ; and of late years they have been particularly examined and 
described by Schultz. They consist of long, branched, homogeneous 
tubes, which unite or anastomose freely (fig. 66), thus resembling the 
vessels of animals. At first the tubes are very slender and uniformly 
cylindrical (fig. 67 a), but afterwards they enlarge and present irregular 
distensions at different parts of their course (figs. 67 b, 68), so as to give 
rise to an articulated appearance. Their walls vary in thickness, and 
are not marked by any depressions or fibres. These vessels are met with 
in the inner bark, and they contain a granular fluid called latex, which 
is at first transparent, but often becomes of a white, yellow, or reddish 
colour. Endlicher and Unger state that they are formed by cells 
united in a linear series, their septa being obliterated; while Meyen 





Fig. 63. Porous vessel (Bothrenchyma) from the Vine, showing its connection with woody 
fibres, and the broad septa or partitions of the vessel itself. 
Fig. 64. Porous vessel from Traveller's joy (Clematis vitalba). 
Fig. 65. Moniliform porous vessels from the Common Balsam. 



DEVELOPMENT OF VESSELS. 



19 



and Schleiden maintain, that at a very early period the currents of 
latex may be seen in the intercellular canals, and that ultimately a 





66 67 68 

separate membrane is developed to form the vessels. The tissue can 
be easily examined hi the India-rubber tree, in Dandelion, Lettuce, 
and Celandine, and in various species of Ficus and Euphorbia. 

2. DEVELOPMENT AND FUNCTIONS OF VESSELS. 

39. The simple cell is the state in which vegetable tissue first 
makes its appearance. It is the primary form of all the textures sub- 
sequently produced in vascular plants. To the elongation of cells, and 
the deposition of thickening layers and fibres hi their interior, the 
various vessels owe their origin. Thus when cells are developed as 
continuous branching tubes, which anastomose freely, Cinenchyma is 
formed; when they are elongated, as spindle-shaped tubes, and their 
walls are thickened and hardened by depositions of ligneous matter, 
they give rise to Pleurenchyma; and when elongated membranous tubes 
are strengthened by spiral fibres, the different kinds of Fibro-vascular 
tissue are produced. The spiral vessel may be considered as the type 
of the last-mentioned tissue, and all its varieties may be traced to 
changes taking place in the development of the fibre. The coil may 
be broken hi consequence of the fibre adhering to the membrane, and 
the latter increasing rapidly hi growth ; or the fibre may be deposited 
irregularly, in consequence of interruptions hi growth. This view of 
the formation of vessels is confirmed by finding hi the same tube a com- 

Fig. 66. Laticiferous vessels (Cimnchyma) from Euphorbia dulcis. 
Figs. 67, 68. Vessels of Latex from Celandine (Chelidonium nwjus). 



20 FUNCTIONS OF VESSELS. 

plete spiral fibre in one part, annular fibres, either complete or with their 
ends overlapping, at another, and bars or dots at a third portion. In the 
case of some vessels, their formation can be distinctly traced to cells 
placed end to end, the partitions between which have been absorbed. 
The moniliform or beaded appearance often presented by the different 
kinds of vessels, more especially the Porous, plainly indicates this mode 
of formation. 

40. As in cells, so in vessels, the walls are composed of cellulose, and 
there are usually no visible perforations; the communication between 
them taking place by imbibition or endosmose. In some instances, 
when vessels are closely applied to each other, especially when they 
overlap, the membrane becomes absorbed, and direct communication 
takes place. This has been seen in spiral and porous vessels. The pits 
or depressions on the walls of vessels, and the thinning of the tissue 
at particular points, appear to serve the purpose of allowing the rapid 
transmission of fluids ; and, according to some, they permit the passage 
of small cells from the interior, which become developed as tubes, and 
form branching vessels. 

41. Pleurenchyma, in its early state, contains fluids, and conveys 
them from one part of the plant to another. In the progress of growth, 
the secondary deposits obliterate the vessels, as in the perfect or 
heart wood of ordinary trees. These deposits are often of a very 
hard nature, and assume particular colours in different kinds of trees. 
From the firmness of this tissue, it is well fitted to give solidity to 
the stems and to strengthen the leaves of plants. In Spiral vessels, 
the fibre adds to their elasticity, and keeps the tubes always pervious. 
The fibre, when once formed, does not increase much in thickness, and 
the secondary deposits do not obliterate the canal. Various opinions 
have prevailed regarding the contents of these vessels. The name 
Trachea;, given by Grew and others, was partly from their structure, 
and partly from the idea that they contained air. The accurate experi- 
ments of Bischoff lead to the conclusion that the perfect spiral vessels 
convey air, which often contains a large amount of oxygen in its com- 
position. Hales showed that air was evolved from the vessels of the 
Vine when cut, and Decandolle thought that part of the air in these 
vessels was derived from the pores of the leaves. Other authors look 
upon these vessels as conveying fluids/while a third set maintains that 
both air and fluids are present, the air being derived in part from 
decompositions going on in the interior of the plant. The other kinds 
of vascular tissue, and especially the porous vessels, are the means 
by which the fluids taken up by the roots of plants are conveyed to 
the leaves, and to all parts of the plants. Laticiferous vessels contain, 
according to Schultz, the elaborated sap or latex on its return from 
the leaves to the bark. This latex is either transparent or opaque, 
colourless or coloured. These vessels, when examined with the micro- 



FUNCTIONS OF VESSELS. 21 

scope in the living plant, exhibit movements in their fluid contents of 
a peculiar kind, which will be considered under Cyclosis. 

42. The cell has been already shown to be the type of all the tissues 
of plants, and to be the basis of all vegetable structure. It is of equal 
importance as regards function. In the lowest plants, as the Protococ- 
cus nivalis, or the Alga found in red snow, and the various species of 
Palmella, Nostoc, and Hsematococcus, cells constitute the whole sub- 
stance, and perform all the functions of life ; they absorb and assimi- 
late, thus performing the functions of nutrition and secretion, and they 
form new cells, thus reproducing individuals like themselves. When 
a more complex structure exists, as in the higher tribes of plants, 
certain cells are appropriated for absorption, others are concerned in 
assimilation, and others in forming and receiving secretions. When a 
certain degree of solidity appears to be required to support the stem, 
leaves, and flowers, ligneous matter is deposited, and woody fibre 
formed. When the transmission of fluids and air is carried on rapidly, 
the elastic fibres of the fibro-vascular tissue seem to keep the elongated 
cells and vessels pervious, and when the elaborated sap is conveyed 
continuously without interruption, anastomosing tubes occur in the 
form of laticiferous vessels. 

TABULAR ARRANGEMENT OF VEGETABLE TISSUES. 

A. Cellular Tissue (Parenchyma), composed of membrane, or of membrane and 
fibre, having the form of vesicles whose length does not greatly ex- 
ceed their breadth. 

1. Membranous Cellular Tissue; cells formed by membrane alone, of various 

thickness, but without markings on it. 

2. Porous Cellular Tissue; cells formed by membrane, which has been une- 

qually thickened in such a way as to leave rounded depressions at 
regular intervals. 

3. Fibrous Cellular Tissue (Inenchyma); cells formed by membrane and fibre; 

occasionally formed by fibre alone. 

a. Spiral Cells, with a complete spiral fibre inside. 

b. Dotted Cells, with opaque spots, which are isolated portions of fibre. 

B. Vascular or Tubular Tissue (Angienchyma), composed of cylindrical tubes, 
which are more or less continuous, and usually overlap each other, 
or are united by broad oblique extremities. 

I. Membranous Vascular Tissue; tubes formed by membrane alone, of vari- 

ous thickness, but without markings on it. 

1. Ligneous Tissue (Pleurenchyma), composed of fusiform tubes with 

thickened walls. 

2. Laticiferous Tissue (Cinenchyma), composed of tubes which anastomose, 

often present irregular dilatations, and convey a peculiar fluid, called 
Latex. 

II. Porous Vascular Tissue; tubes formed by membrane, which becomes 

thickened by spiral deposits, in such a way as to leave rounded de- 
pressions at regular intervals. 

1. Vasiform Tissue, or Porous vessels (Bothrenchyma or Taphrenchyma); 
large tubes, usually ending in broad extremities, with pits or circular 
markings on their walls. This tissue sometimes exhibits contractions 



22 ARRANGEMENT OF VEGETABLE TISSUES. 

at regular intervals, as if formed of porous cells laid end to end, and 
then is called Moniliform, or Beaded (Articulated Bothrenchyma). 
2. Punctated Tissue (Glandular Woody Tissue) ; fusiform woody tubes, 
with depressions and markings on their walls, presenting the appear- 
ance either of a single or double circular disc. 

III. Fibro- Vascular Tissue, composed of tubes in which the thickening mat- 
ter is deposited in the form of spiral fibres, rings, bars, or dots. 

a. Perfect Fibro- Vascular Tissue, composed of tubes, in which there is a 

complete spiral fibre. 

1. Spiral Vessels (Tracheae, Trachenchyma), in which the spiral fibre is 

elastic, and may be unrolled. 

2. Closed Spiral vessels, or closed Trachea, in which the spiral fibre is 

brittle, or its coils so united to each other, and to the membrane, 
that they cannot be unrolled. 

b. Imperfect Fibro- Vascular Tissue, composed of tubes marked by rings, 

lines, or dots, but without a complete fibre inside. 

1. Annular Vessels or Ducts, having fibres in the form of detached rings, 

which are occasionally united by portions of fibre. 

2. Reticulated Vessels, having fibres which cross each other, or are dis- 

posed so irregularly as to form a net-work. 

3. Scalariform Vessels, having their walls marked by isolated portions 

of fibre, in the form of ladder-like bars. 

4. Dotted Vessels, having their walls marked by isolated portions of 

fibi-e in the form of opaque dots or points. 

Any of the vessels included under the Fibro-vascular tissue, may exhibit con- 
tractions at regular intervals, so as to become moniliform. 



CHAPTER II. 

COMPOUND ORGANS FORMED BY THE TISSUES. 

43. Some plants consist of cells only, which continue throughout 
life to produce new cells, and to perform all the vital functions. The 
great mass of flowering plants, however, although originally cellular, 
produces organs composed of cells and vessels variously arranged, and 
covered by an epidermis. These Compound Organs may be divided 
into Nutritive, or those concerned in the nourishment of the plant; and 
Reproductive, or those which are employed in the production of new 
individuals. The former consist of the stem, root, and leaves ; the 
latter, of the flower and fruit. 

SECTION I. ORGANS OF NUTRITION OR VEGETATION. 
1. STRUCTURE, ARRANGEMENT, AND SPECIAL FUNCTIONS. 

44. Under this head will be considered the tissues of which the 
various nutritive organs are composed, the mode in which the parts 
are arranged, and the particular function which each of the organs 
performs. 



ORGANS OF NUTRITION OR VEGETATION. 



23 




-Jt 



GENERAL INTEGUMENT. 

45. General integnment is the name given to the external cellular 
covering of plants. It can be 

easily detached from young 
leaves and stems, usually in 
the form of a colourless trans- 
parent membrane. By pro- 
longed maceration it has been 
shown to consist frequently of 
two layers ; a superficial, called 
Cuticle or Pellicle (fig. 69 p p), 
and a deep layer, usually called s - 
the Epidermis (fig. 69 e e). 

46. The Superficial Pellicle 

(pdlis, skin) is a very thin con- 
tinuous membrane, which is 
spread over all parts except the 
openings of the stomata; in some 
cases entering these openings, 
and lining the cavities beneath 

them. It is formed from the epidermal cells below it ; Treviranus, 
Schleiden, and Payen, considering it as a secretion on the outside 
of the cells, while Mohl and Henfrey look upon it as composed of the 
altered primary walls of the cells. In fig. 70, it A h 
is represented as detached from the leaf of the ; '^/i 
cabbage, forming a sheath over the hairs, hhhh, and IL 

leaving slits, s s, corresponding to the openings of 
the stomata. This pellicle appears to be similar to /A\ / 'V 
the intercellular substance surrounding cells, and \ vA 
to the definite mucus which is conspicuous in some I 1{=1 
sea- weeds (fig. 29 V). It is possible that this / I'll /j 
matter, in place of being produced on the outside ( /" ? 
of cells, may be formed within them, and ulti- 
mately deposited externally by passing through 
their parietes. On the inner surface of the pel- 
licle the impressions of the epidermal cells are 
sometimes observed (fig. 69 p). The pellicle is h 

the only layer of integument which is present in 70 

aquatic plants, and in some of the lower tribes. 

47. The Epidermis (tvl, upon, and li^et, skin), (fig. 69 e e,) is 



C 



Fig. 69. General integument of a leaf of Iris germanica. pp. The Cuticular pellicle with slits, 
/, lying upon the proper epidermis, e e, formed of hexagonal cells, and furnished with stomata, ts. 

Fig. 70. Pellicle of Cabbage detached by maceration, covering the hairs, hhhh, and having 
openings, ss, corresponding to the stomata. 



24 



EPIDERMIS. 



extended over all the parts of plants exposed to the air, except the 
stigma. On the extremities of newly-formed roots, the integument 
consists of loose cells, which are considered either as being the ordinary 
cellular tissue of the plant, or as being an imperfectly-formed epider- 
mis, which has received the name of Epiblema (tvl, upon, and phy/ax, 
wound, as being the tissue which first covers wounds). This latter 
kind of tissue occupies the place of the epidermis, in the parts of plants 
which are always under water. On the aerial roots of Orchidaceous 
plants, there is an epidermal layer consisting of spiral cells (fig. 23), 
containing air. 

48. The epidermis is usually formed by a layer or layers of com- 
pressed cells, which assume a more 
or less flattened tabular shape, 
and have their walls bounded by 
straight or by flexuous lines. Fig. 
69 e e, represents an epidermis 
formed of regular hexagonal cells ; 
fig. 72, one composed of irregular 
hexagons ; while in fig. 71, the 
boundaries of the cells, e, are flexu- 
ous and wavy. The cells of the epi- 
dermis are so intimately united 
together, as to leave no intercel- 
lular spaces (fig. 74 e e). 

49. The epidermis is sometimes 
thin and soft, at other times dense 
and hard. In the former case it 
may be easily detached from the 
subjacent cells ; in the latter, the cells become thickened by deposits, 
and sometimes the layers are so produced as to leave uncovered spots, 





fig. 71. Epidermis, from lower surface of the leaf of Madder (Rubia tinctorum). e, Cull of the 
Epidermis. s, Stoma. 

Fig. 72. Epidermal layer, from upper surface of a leaf of Ranunculus aquatilts when growing 
out of water, e e, Epidermal cells, ssss, Stomata. 

Fig. 73. Vertical section of lower epidermis of the leaf of Rochea fakata. e , Double epider- 
mal layer, with very large external cells, small internal ones pierced by a stoma, s, which com- 
municates with a lacuna, I. p, Parenchyma of the leaf. 



STOMATA. 25 

which communicate with the interior of the cell by canals passing 
through the thickening layers, as in Cycas. In Eochea falcata (fig. 
73), the epidermis, e e, consists of two layers of cells the outer ones 
large, the inner small. The cells of epidermis are usually filled with 
colourless fluid, but they sometimes contain resinous and other sub- 
stances. Waxy matter is occasionally found in the epidermis, silica is 
met with in the integument of grasses and Equisetums, and carbonate 
of lime in that of Chara. The colour of the epidermis generally 
depends on that of the subjacent parenchymatous cells. The epider- 
mal cells are usually larger than those of the tissue below them; but 
sometimes, for instance in Ficus elastica, they are smaller. 

50. Stomata (a-ropa, a mouth) are openings existing between some 
of the cells of the epidermis on parts exposed to the air. They consist 
usually of two semilunar cells surrounding an oval slit or orifice (figs. 
69 s s, 71 s), which have been considered as resembling the lips and the 
orifice of the mouth. Stomata open or close according to the state 
of moisture or dryness in the atmosphere. By examining, under the 
microscope, thin strips of epidermis in a moist and dry state, it will 
be seen that in the former case the lips are distended, they assume a 
crescentic or arched form, and leave a marked opening between them ; 
while in the latter, they approach each other, and close the orifice. 

51. The cells surrounding the openings of stomata are sometimes more 
numerous, as in Marchantia. In Ceratopteris thalictroides, Alhnan 
observed stomata formed by three cells ; two of which, in their open 
condition, are crescentic and concave inside, while the third surrounds 
them, except at a small space at the end of the long axis of the stoma, 
and has on this account been called peristomatic (vt^l, around). In 
Equisetum, the stomata, which are about 5 | 5 of an inch in their great- 
est diameter, consist of four pieces ; two of which are arched and thick 
at their outer convex margin, becoming thin at their inner concave 
edge, where two other bodies occur, having numerous processes like 
the teeth of a comb, hence called pectinate (pecten, a comb). Occa- 
sionally the stomatic cells become united, so as to appear in the form 
of an uninterrupted rim; and at other times the stoma is a minute 
orifice in the walls of a cavity. 

52. Stomata communicate with intercellular spaces (figs. 73 s, 74 s), 
the connection being sometimes kept up by means of a funnel-shaped 
prolongation of the cuticle, called, by Gasparrini, a cistoma (wry, a 
cyst or bag, and trrof^a,, a mouth). They are scattered over the surface 
of the epidermis in a variable manner. Sometimes they are placed at 
regular intervals corresponding to the union of the epidermal cells 
(fig. 69 s); at other times they are scattered without any apparent 
order (figs. 71, 72) ; and in other instances they are united in sets of two 
or three, or in clusters at particular points, as may be seen in Begonia, 
Saxifraga (fig. 75 s s), and Proteacese. 



26 



STOMATA. 



53. Stomata occur on the green parts of plants, especially on the 
leaves and their appendages. They are not usually found in cel- 
lular plants, nor in plants always submerged, nor in pale parasites. 





74 75 

This is not, however, a universal rule, for stomata have been de- 
tected in Marchantia and some other Cellulares; also in the sub- 
merged leaves of Eriocaulon setaceum, according to Griffith, and in the 
pale parasite Orobanche Eryngii, according to Duchartre. They do 
not exist in roots, nor in plants kept long in darkness so as to be 
blanched or etiolated, and they are rare or imperfectly developed in 
succulent plants. 

54. Stomata vary in their form. 

* The oval form is very common, 

and may be easily seen in Lili- 
aceous plants ; the spherical oc- 
curs in Oncidium altissimum and 
the Primrose, the quadrangular in 
Yucca and Agave. In the Ole- 
ander, in place of stomata there 
are cavities in the epidermis pro- 
tected by hairs (fig. 76 s). 
55. The development of stomata has been traced by Mirbel and 
Mohl. In the Hyacinthus orientalis, they appear first between the 
epidermal cells in the form of quadrangular spaces containing gra- 
nular matter, which gradually collects towards the centre, where a 
septum or partition is formed. This septum ultimately splits, leaving 
a slit or opening which constitutes the stoma. Mohl has traced this 

Fig. 74. Vertical section of epidermis, from the lower surface of the leaf of Madder, show-ing 
the intimate union of the epidermal cells, e e, the loose subjacent parenchyma, p, with intercel- 
lular canals, TO, and lacuna, 1. s, Stoma. 

Fig. 75. Epidermis of leaf of Saxifraga sarmentosa, showing clusters of stomata, s s, surrounded 
by large epidermal cells, e e. The cells among which the stomata occur are very small. 

Fig. 76. Vertical section of lower epidermis of the leaf of A'erium Oleander, e, Epidermis 
composed of several layers of cells, p. Parenchyma of the leaf. , Cavity filled with hairs, which 
may represent a stoma. 




STOMATA. 27 

process throughout the same leaf in different stages of growth. In 
Marchantia, Mirbel found several tiers of cells forming the stoma, and 
he supposed that the opening was produced by the absorption of a 
central cell, leaving the others to form the rim or border. 

56. The number of stomata varies in different parts of plants. They 
are most abundant on the under surface of leaves exposed to the air, 
and are often entirely wanting on the upper surface, more especially 
when it has a dense shining cuticle. In floating leaves the stomata, 
when present, are on the upper surface only. When plants usually 
under water are made to grow for some time in the air, their 
leaves exhibit stomata. When leaves grow vertically, the stomata are 
often equal in number on both sides. The number of stomata varies 
from a few hundreds to many thousands on a surface of one inch square. 
The following table exhibits the number of stomata in the leaves of a 
few plants : 

STOMATA IN ONE INCH SQUARE. 

Upper side. Under side. 

Misletoe, 200 200 

Tradescantia, 2,000 2,000 

Rheum palmatum, 1,000 40,000 

Crinum amabile, 20,000 20,000 

Aloe, 25,000 20,000 

Clove-pink, 38,500 38,500 

Yucca, 40,000 40,000 

Mezereon, None 4,000 

Paeony, None 13,000 

Vine, None 13,600 

Holly, None 63,600 

Cherry-laurel, None 90,000 

Lilac, Tew 160,000 

57. Appendages of the Epidermis, or Appendicnlar Organs. 

The epidermis frequently exhibits projections or papilke on its surface, 
in consequence of some cells being enlarged in an outward direction 
(fig. 73 e e). When these assume an elongated or conical form they 
constitute hairs (pili or villi), as seen in (fig. 77 h h K). 

Hairs, then, are composed of one or more transparent delicate cells 
proceeding from the epidermis, and covered with the cuticle (fig. 
70). They are erect (fig. 78 a), or oblique, or they lie parallel to 
the surface, and are adpressed. Sometimes they are formed of a 
single cell, which is simple and undivided, (fig. 78 a), or forked (fig. 
78 >), or branched (fig. 78 c); at other times they are composed 
of many cells either placed end to end, as in moniliform or neck- 
lace-like hairs (fig. 79), or united together laterally, and gradually 
forming a cone, as in compound hairs (fig. 80), or branched (fig. 81). 
When several hairs proceed from a common centre, they become stellate 
(stella, a star), or radiated (fig. 82). The latter arrangement occurs in 



28 



EPIDERMAL APPENDAGES. HAIRS. 



the hairs of the Mallow tribe, and is well seen in those of Deutzia 
scabra. When stellate hairs are placed closely together, so as to form a 




sort of membranous expansion (fig. 83), a scale or scurf is produced. 
To such expansions of the epidermis the name lepis (xez-*?. a scale), 
is applied, and the surface is said to be lepidote. These scales have 
sometimes a beautiful silvery appearance, as in Elseagnus. Sur- 
rounding the base of the leaves of Ferns, a brown chaffy substance 

Fig. 77. Young root of Madder, showing cellular processes, hhh, equivalent to hairs, e. The 
epidermal cells which are not elongated. 

Fig. 78. Hairs formed by single cells of the epidermis, e. a, Simple hair. 6, Bifurcated hair 
of Slsymbrium Sophia, c, Branched hair of Arabis alpina. 

Figs. 79 82. Compound hairs formed by the union of several cells, e, Epidermis, 79. MoniU- 
form hair, from Lychnis chalcedonica. 80. Partitioned, unbranched hair, from stem of Bryonia 
alba. 81. Partitioned, branched hair, from flower of Nicandra anomala. 82. Stellate, a star-like 
hair, from leaf of Althaea rosea. 




EPIDERMAL APPENDAGES. HAIRS. 29 

occurs, consisting of elongated cells, to which the name of ramenta- 
ceous hairs, or, ramenta (ramentum, a 
shaving), has been given. In Palms 
also a similar substance occurs, called 
reticulum (reticulum, a net), or mattulla, 
(matta, a mat). Prickles or aculei, as in 
the Rose, (fig. 191 a), are hardened hairs 
connected with the epidermis, and differ 
from spines or thorns, which have a 
deeper origin. Setae are bristles or 
stiff hairs, and the surfaces on which 
they occur are said to be setose or seta- 
ceous. Some hairs, as those of Drosera, 
or sundew, have one or more spiral fibres in their interior. 

58. Various names have been given to the different forms of hairs: 
they are clavate or club-shaped (clava, a club), gradually expanding from 
the base to their apex; capitate, having a distinct rounded head; rough 
or scabrous, with slight projections on their surface; hooked or uncinate 
(uncus, a hook), with a hook at their apex pointing downwards and to 
one side; barbed or glochidiate (yX^/V, a barb), with two or more 
hooks around the apex; shield-like or 'peltate (pelta, a buckler), when 
attached by their middle, and projecting horizontally on either side (fig. 
84), as in many cruciferous plants; 

ciliated (cilium, an eye-lash), when 

surrounding the margin of leaves. 

On the pod of the Cowitch (Mucuna 

pruriens), hairs are produced with 

projections on their surface, which cause great irritation when applied 

to the skin. In Venus' Fly-trap (Dioncea muscipula), stiff hairs exist on 

the blades of the leaf (fig. 186 e), which, when touched, cause their closure. 

59. Hairs occur on various parts of plants; as the stem, leaves, 
flowers, seed-vessels and seeds, and even in the interior of vessels. 
Cotton is the hair surrounding the seeds of Gossypium herbaceum. 
Hairs are developed occasionally to a great extent on plants exposed to 
elevated temperatures, as well as on those growing on lofty mountains. 
When occurring on the organs of reproduction, they seem to be con- 
nected with fertilization, as the hairs on the style of Goldfussia or 
Ruellia, and the retractile hairs of Campanula. Different parts of plants 
are transformed into hairs; as may be seen in the flowering stalks of 
Rhus Cotinus, and in the calyx of Composite. 

60. Names are given to the surfaces of plants according to the 
presence or absence of hairs, as well as the nature of the hairs which 

Fig. 83. Scale or scaly hair, from leaf of Hippophae rhamnoides. 

Fig. 84. Peltate hair' of Malpighia, pp, arising from epidermis, e. y, The gland which com- 
municates with the hair. 




30 



EPIDERMAL APPENDAGES. GLAKDS. 



cover them. The following are the more important terms: Glabrous, 
smooth, having no hairs; hairy (pilosus), furnished with hairs; 
pubescent, covered with soft, short, downy hairs ; villous, having long, 
weak, often oblique hairs; sericeous, covered with long, closely ap- 
pressed hairs, having a silky lustre; hispid (hispidus, hirtus), covered 
with long stiff hairs not appressed; hirsute, having long tolerably dis- 
tinct hairs, not stiff nor appressed; (velvety velutinus), with a dense 
covering of short down, like velvet; tomentose, covered with crisp, 
rather rigid, entangled hairs like cotton, which form a sort of felt 
(tomentum); woolly, with long curled and matted hairs like wool; 
bearded or stupose, (VTVKYI, tow), when hairs occur hi small tufts. 

61. The hairs which are most frequently met with in plants are called 
lymphatic, from their not being connected with any peculiar secretion. 
Those, on the other hand, which have secreting cells at their base or apex, 
are denominated glandular, and are not to be distinguished from glands, 
under which therefore they will be considered. Lymphatic hairs occur 
on parts exposed to the air, and are wanting in blanched plants. On 
young roots, cellular projections of the cuticle are seen (fig. 77), which 
may be called radical hairs. Young leaves and buds are frequently 
thickly covered with protecting hairs. In this instance the hairs arise 
chiefly from the veins; and as the leaves increase hi size, and the veins 
are separated, the hairs become scattered, and apparently less abun- 
dant. On the parts of the flower, coloured hairs occur which have 
been called coralline. 

62. Gland* are collections of cells forming secretions. The term 
has been vaguely applied to all excrescences occurring on the surfaces 
of plants. They are either stalked (petiolate, stipitate) or not stalked 

abed (sessile). The former 
f ^ may be called glandular 

hairs, having the secret- 
ing cells at the apex. 
Stalked glands, or glan- 
dular hairs, are either 
composed of a single cell, 
with a dilatation at the 
apex (fig. 85 a), or of 
several cells united to- 
gether, the upper one 
being the secreting or- 
gan (fig. 85 ft). In place 
of a single terminating 

Fig. 85. Glandular hairs, e, Epidermis, a, Hair formed by a single cell from Sisymbrium 
chilense. 6, Hairs formed of several cells terminated by a secreting cell, from flower-stalk of 
Antirrhinum majus. c, Hair composed of several cells, terminated by two secreting cells 
united laterally, from flower-stalk of Lysimaehia vulgaris. d, Compound hair, terminated 
by several secreting cells united end to end, from Geum urbanum. 




EPIDERMAL APPENDAGES. GLANDS. 



31 



secreting cell, there are occasionally two (fig. 85 c) or more (fig. 85 d). 
Hairs sometimes serve as ducts through which the secretion of glands is 
discharged; these are glandular hairs, with the secreting cells at the base. 
Such hairs are seen in the nettle (fig. 86), in Loasa or 
Chili nettle, and in Malpighia (fig. 84), and are commonly 
called stings. In the nettle they are formed of a single 
conical cell, dilated at its base (fig. 86 >), and closed at first 
at the apex, by a small globular button placed obliquely 
(fig. 86 s). This button breaks off on the slightest touch, 
when the sharp extremity of the hair enters the skin, and 
pours into the wound the irritating fluid which has been 
pressed out from the elastic epidermal cells at the base. 
When a nettle is grasped with violence, the sting is frac- 
tured, and hence no injury is done to the skin. The 
globular apex of glandular hairs sometimes forms a viscid 
secretion, as in the Chinese primrose and sundew. The 
hairs of the latter plant, by this secretion, detain insects 
which happen to light on them. 

63. When glands are sessile, they consist of epider- 
mal cells either surrounding a cavity, or enclosing small 
secreting cells. In fig. 87, is represented a gland taken 
from the flower-stalk of Dictamnus albus, cut vertically to 
show the cavity surrounded by cells, and filled with a 6 

greenish oil; while in fig. 88, there is a gland with a short thick 
stalk, full of cells, taken from Rosa centifolia. 
These figures show the transition from sessile 
to stalked glands. Some of the superficial cells 
of the epidermis are sometimes slightly elevated 
above the rest, and contain peculiar fluids. In 
the Ice-plant, the appearance of small pieces of 
ice on the surface is produced by cells contain- 
ing a clear fluid, which is said to have an alka- 
line reaction, while that of the tissue around 
the vesicles is acid; in the Chick-pea, similar 
superficial cells contain a subacid fluid. Glandular depressions or pits 
occur, surrounded by secreting cells. At the base of the petals of 
the Crown-imperial, for instance, cavities are seen containing a honey- 
like fluid, secreted by what are called nectariferous glands. Cavities 
containing saccharine matter, surrounded by small thin-walled cells, 
are met with in the leaves of Acacia longifolia, also in Viburnum 

Fig. 86. Conical hair of Urtica dioica, or common nettle, ending in a button or swelling s, 
with a dilatation or bulb at its base 6, which is surrounded by epidermal cells u e. In the hair 
are currents of granular matter//. 

Fig. 87. Gland from flower-stalk of Dictamnus albus, cut vertically, showing central cavity I, 
filled with greenish oil, and surrounded by a layer of cells c, which contain a red juice and are 
connected with the epidermis e. 

Fig. 88. Gland from Rosa centifolia e, The epidermis. 








32 FUNCTIONS OF EPIDERMIS. 

tinus, and Clerodendron fragrans. The cavities communicate with the 
surface of the leaves by means of canals. 

Glands are occasionally sunk in the epidermis, so as merely to have 
the apex projecting; at other times they lie below the epidermal cells, 
as in the Myrtle, Orange, St. John's-wort, and Rue. 
In the latter case they are sometimes called vesicular, 
and are formed by cells surrounding cavities contain- 
ing oil (fig. 89). When they occur in the leaves, 
they give rise, when viewed by transmitted light, to 
the appearance of transparent points or dots. Ver- 
rucce, or warts, are collections of thickened cells on 
the surface of plants, assuming a rounded form, and 
containing starch or other matters. Lenticels, or Lenticular glands, are 
cellular projections on the surface of the bark, arising from its inner 
part. 

64. The Special Function* of the Epidermis and its appen- 
dages, are to protect the parts beneath from various atmospheric 
and meteorological influences. In plants growing in dry climates, 
the epidermis is often very thick, and coated with a waxy secre- 
tion, to prevent too great transpiration or exudation of fluids. In 
those which inhabit humid places, the epidermis is thin and absorbent; 
while in submerged aquatics, there is no proper epidermal cover- 
ing. The stomata regulate the transpiration, opening and closing 
according to the state of humidity and dryness of the atmosphere, 
surrounding them. When a plant is growing vigorously, the constant 
passage of fluids keeps the regulating cells around the stomata in a 
distended state, and thus opens the orifice; whereas, when the circulation 
is languid and the fluids are exhausted, the cells collapse and close 
the opening. The opinion that the succulency of plants is a sort of 
dropsical condition, caused by the absence of stomata to carry off the 
fluids, has not been confirmed by observation. Hairs, according to 
their structure, serve various purposes. Lymphatic hairs protect the 
surface, and regulate evaporation. Plants thickly covered with 
hairs, as Verbascum thapsus, have been knoAvn to resist well an 
extended period of drought. Glandular hairs, and glands in general, 
form secretions which are employed in the economy of vegetation, or 
are thrown off" as excretions no longer fitted for the use of the plant 
itself. Many of these secretions constitute important articles of materia 
medica. Lenticels keep up a connection between the air and the inner 
bark, and probably perform the function of stomata in the advanced 
period of the growth of the plant. They are considered, by Decan- 
dolle and others, as being the points where young roots are produced 

Fig. 89. Vesicular gland from Ruta graveolens, or Common Rue. gr, Gland formed by large 
transparent cells, surrounding a central lacuna, I. e, Epidermis from upper surface of the taf 
c, u c, Cells filled with Chlorophylle. 



FORMS OF STEMS. 33 

in certain circumstances, and on that account they have been called 
Rhizogens (p<ct, a root, and yiwdiiv, to produce). They are conspi- 
cuous in Willows, the young branches of which form roots very 
readily when placed in moist soil. Some hairs occurring on the style 
of plants are called collecting hairs, from the functions which they per- 
form in taking up the pollen. In the species of Campanula, these hairs 
are so formed, that after the pollen has been discharged, their upper 
part is drawn within the lower. In many hairs a circulation of fluids 
takes place, connected apparently with their nutrition and develop- 
ment (fig. 86). In the monuiform purple hairs on the stamens of Trades- 
cantia, or Spiderwort, this movement may be easily seen under the 
microscope. The subject of the circulation in hairs will be considered 
under Rotation. 

STEM OR ASCENDING AXIS. 

Forms of Stems. 

65. The stem is that part of a plant which bears the leaves 
and flowers. It receives the name of Caulis in ordinary herbaceous 
plants which do not form a woody stem, Truncus in trees, Caudex 
in shrubs, Culm in grasses, and Stipe in Palms and Ferns. It is not 
always conspicuous. Plants with a distinct stem are called caules- 
cent; those in which it is inconspicuous are acaules. Some plants are 
truly stemless, and consist only of expansions of cellular tissue, called 
a Thalha, and hence are denominated Thallogens, or Thallophytes (da^og, 
a frond, yswa.ziv, to produce, QVTOV, a plant). They have no true vas- 
cular system, but are composed of cells of various sizes, which some- 
times assume an elongated tubular form, as in Chara. The cells are 
sometimes united in one or several rows, forming simple filaments, 
as in Confervas ; or branched and interlaced filaments, as in some 
Fungi ; or membranous expansions, as in Lichens and sea- weeds. 

66. Stems have usually considerable firmness and solidity, but 
sometimes they are weak, and either he prostrate on the ground, thus 
becoming procumbent, or climb on plants and rocks by means of suckers 
like the Ivy, being then called scandent, or twist round other plants in 
a spiral manner like Woodbine, becoming volubile. Twining plants turn 
either from right to left, as the French bean, Convolvulus, Passion- 
flower, and Dodder; or from left to right, as Honeysuckle, Hop, and 
Tamus. Bryonia alba twines from right to left, and from left to right, 
alternately. In warm climates, twining plants (lianas) often form 
thick woody stems ; while in temperate regions they are generally 
herbaceous. Exceptions, however, occur in the case of the Clematis, 
Honeysuckle, and Vine, the woody stems of which have received the 
name ofSarmentum (sarmentum, a twig, or cutting of a vine). Some stems 

D 



34 FORMS OP STEMS. 

are developed more in diameter than in height, and present a peculiar 
shortened and thickened aspect, as Testudinaria, or Tortoise-plant, and 
Cyclamen. 

67. Stems have a provision for a symmetrical arrangement of leaves 
and branches ; nodes (nodus, a knot), or points whence leaf-buds are 
produced, being placed at regular intervals. No such provision occurs 
in roots which ramify irregularly, according to the nature of the soil. 
The intervals between nodes are called internodes. The mode in which 
branches come off from the nodes, gives rise to various forms of trees, 
such as pyramidal, spreading, or weeping ; the angles formed with 
the stem being more or less acute or oblique. In the Italian Poplar 
and Cypress the branches are erect, forming acute angles with the 
upper part of the stem ; in the Oak and Cedar they are spreading or 
patent, forming nearly a right angle ; in the weeping Ash and Elm 
they come off at an oblique angle ; while in the weeping Willow and 
Birch, they are pendulous from their flexibility. The comparative 
length of the upper and under branches, also gives rise to differences 
in the contour of trees, as seen in the conical form of Spruce, and the 
umbrella-like form of the Italian Pine (Pinus Pinea). 

68. Plants which form permanent Avoody stems above ground, are 
denominated trees and shrubs, while those in which the stems die 
down to the ground, and are not persistent, are called herbs. The 
term tree (arbor) is applied to those plants which have woody stems 
many times exceeding the height of a man, the lower part free from 
branches being the trunk : a shrub (frutex) has a stem about three 
times taller than a man, and branches from near the base: an under- 
shrub (suffrutex) does not exceed the length of the arm ; while a bush 
(dumus) is a low diminutive shrub, with numerous branches near the 
base. The terms arborescent, fruticose, suffruticose, and dumose, are 
derived from these. 

69. Stems have usually a round form; but they are sometimes com- 
pressed or flattened laterally, while at other times they are angular : 
being triangular, with three angles and three flat faces; trigonous 
(r^iif, three, and yavlcc, an angle), with three convex faces; triquetrous 
(triquetrum, a triangle), with three concave faces ; quadrangular, or 
square; quinquangular, or five-angled; octangular, or eight-angled, &c. 

70. The stem has been called the ascending axis, from being devel- 
oped in an upward direction. It does not, however, ahvays ascend 
into the air; and hence stems have been divided into aerial, or stems 
which appear wholly or partially above ground ; and subterranean, or 
those which are entirely under ground. The latter are often called roots, 
but they are distinguished by producing leaf-buds at regular intervals. 
The following are some of the more important modifications of stems: 
The Crown of the root is a shortened stem, often partially under ground, 
which remains in some plants after the leaves, branches, and flower- 



FORMS OF STEMS. 



35 



stalks have withered. In this case the internodes are very short, and 
the nodes are crowded together, so that the plant appears to be stem- 
less. It is seen in perennial 
plants, the leaves of which die 
down to the ground annually. 
A Rhizome or root-stock (fig. 90), 
is a stem which runs along 
the surface of the ground, be- 
ing partially covered by the 
soil, sending out roots from its 
lower side, and leaf-buds from 
its upper. It occurs in Ferns, 
Iris, Hedychium, &c. By many 
the term rhizome is applied to stems creeping horizontally, whether 
they are altogether or only partially subterranean. A Pseudo-bulb is 
an enlarged bulbous-like aerial stem, common in Orchidaceous 
plants. It is succulent, often contains numerous spiral cells and 
vessels, and is covered with a thick epidermis. In the Kohl-rabi, 
a peculiar thickened turnip-like stem is met with. A Soboles is a 






t 



creeping under-ground stem, sending roots from one part and 
leaf-buds from another, as in Couch grass, Carex arenaria, and Scir- 
pus lacustris (fig. 91). It is often called a creeping root. A Tuber 

Fig. 90. Portion of Rhizome, r, of Convallaria Polygonatvun. a, A bud in the progress of de- 
velopment. 6, A bud developed as a branch at the extremity of the rhizome, c c, Cicatrices or 
scars, indicating the situation of old branches which have decayed. 

Fig. 91. Soboles, or Creeping subterranean stem, r, of Scirpus lacustris. fe,fe, Scales on the 
stem, p a, Aerial portion of the plant. 1 1, Level of the earth. 

Fig. 92. Lower portion of a potato plant s s, Level of earth, pa, pa, Aerial portion bearing 
leaves, t, Subterranean portion of stem or tubers. T, tuber showing eyes or leaf-buds, covered 
by scales, 6, which are equivalent to leaves. 



36 



STRUCTURE OF STEMS. 




is a thickened stem produced by the approximation of the nodes 
and the swelling of the internodes, as in the potato (fig 92 i). 
Tubers are sometimes aerial, occupying the place of branches, more 
especially when the potato has been made to grow in darkness. The 
eyes of the potato are leaf-buds. The ordinary herbaceous stem of the 
potato, when cut into slips and planted, some- 
tunes forms branches from its base which 
assume the form of tubers. These tubers 
occasionally become nodulated, or elongated, 
or curved in various ways. Arrow-root is 
derived from the scaly tubers of Maranta 
arundinacea. A Corm is a solid under- 
ground stem which does not spread by 
sending out shoots, but remains of a rounded 
form, and is covered by thin scales on the 
outside (fig. 93). It occurs hi Colchicum, 
Tulip, Crocus, and Gladiolus. It is distin- 
guished from a root by sending off annually 
buds in the form of small conns or thick- 
ened branches, either from the apex as in 
Gladiolus, or from the side as Colchicum 
(fig. 93 a"). These buds feed on the ori- 
ginal conn a', and destroy it. It will be noticed afterwards, when leaf- 
buds and bulbs are considered. 

Internal Structure of Stems. 

71. Stems, according to their structure, have been divided into three 
classes: Exogenous (!|<a, outward, and ytwiitiv, to produce), when the 
bundles of vascular tissue are produced regularly in succession exter- 
nally, and go on increasing indefinitely in an outward direction. Endo - 
genous (1*800, within), when the bundles of vascular tissue are produced 
hi definite bundles and converge towards the interior, additions being 
thus hi the first instance made internally. Acrogenous (x.(>of, summit), 
when the vascular bundles are developed at the same time and not hi 
succession, the addition to the stem depending on the union of the base 
of the leaves and extension of the growing point or summit. The plants 
which exhibit these three kinds of stem, are distinguished also by the 
structure of their embryo. Thus exogenous stems are met with in plants 
having an embryo or germ which has two cotyledons or seed-lobes, 
hence they are called Dicotyledonous (8<V> twice, and noTv^nluii, a seed- 
lobe) ; plants with endogenous stems have only one cotyledon, and are 
called Monocotyledonous (ftovos, one); while plants with acrogenous stems 

Fig. 93. Corm or under-ground stem of Colchicum autumnale. r. Roots. /, Leal a', Ascend- 
ing axis of preceding year, withered, a", Axis of the year, a"'. Point where axis of next year 
would be formed. 



EXOGENOUS OK DICOTYLEDONOUS STEM. 



37 




have no cotyledons, and are called Acotyledonmis (*, privative). The 
terms connected with the embryo will be afterwards fully explained. 

Exogenous or Dicotyledonous Stem. 

72. The Exogenous or Dicotyledonous stem characterizes the trees 
of this country. It consists of a cellular and vascular system : the former 
including the outer bark, medullary rays, and pith ; the latter, the 
inner bark, woody layers, and medullary sheath. In the early stage 
of growth, the young dicotyledonous stem is entirely cellular; but 
ere long fusiform tubes appear, forming bundles, having the appear- 
ance of wedges (fig. 94 w w) 

arranged in a circle round 
a central cellular mass of 
pith (fig. 94 p\ which is 
connected to the outer part 
or bark, by means of cellu- r\ 
lar processes called medul- 
lary rays (fig. 94 r r r). At 
first, the cellular portion is 
large, the pith, bark, and 
rays occupying a large por- 
tion of the stem ; but by degrees new vascular bundles are formed, which 
are deposited between the previous ones (fig. 95 n n n). By this means 
the pith is more circumscribed, the medullary rays become narrow, and 
the bark more defined. Such is the structure presented by an annual 
herbaceous dicotyledonous stem, consisting of pith, a circle of fibro- 
vascular and woody tissue, medullary rays, bark, and epidermis. 

73. The stems of trees and shrubs in their young state exhibit an 
arrangement similar to that represented as occurring in the herbaceous 
stem (fig. 95), with this difference, that the vascular circle is more 
firm and solid. As ligneous stems continue to grow, further changes 
take place by which their diameter is increased, and they are rendered 
more dense. The shoots or young branches given out annually, how- 
ever, are similar in structure to annual herbaceous stems ; and in 
making successive sections from the apex of a branch, which is succu- 
lent and green, to the base of a trunk, which is comparatively dry 
and hard, the various changes which take place can be easily traced. 
Fig. 96 represents a thin horizontal or transverse section of the upper 
part of a young branch of Acer campestre. In the centre, TO, is the 
pith, very large at this period of growth, and occupying at least one- 
half of the whole diameter, its cells diminishing in size as they approach 

Fig, 94. Young Dicotyledonous or Exogenous stem, w w, Vascular bundles in the form of 
wedges, p, Pith, rrr, Medullary rays. 

Fig. 95. -Same stem further advanced ; the letters as in fig. 94, n n n, new vascular wedges 
interposed between those first formed. 



38 



EXOGENOUS OB DICOTYLEDONOUS STEM. 




the circumference. Immediately surrounding the pith is a layer of a 
greenish hue, the medullary sheath, e m, from which the medullary 

rays, r m, proceed towards the cir- 
cumference, dividing the vascular 
circle into numerous compact seg- 
ments, which consist of woody ves- 
.'yp sels,/>, and of porous vessels, v p. 
These are surrounded by a moist 
layer of greenish cellular tissue, c, 
J7 called the cambium layer, which 
is covered by three layers of bark, 

ff^S^^P9^, ; -&%?" :x \i%fiP- P J c i e c i anc * Pi wrtn laticilerous 
* ^ - vessels, v I, the whole being en- 

closed by the epidermis, e p. On 
making a thin vertical section of a 
96 portion of the same branch, and 

viewing it under the microscope, the parts composing the different por- 
tions become more obvious 
(fig. 9 7). The pith, m, with its 
hexagonal cells decreasing 
in size outwards, surrounded 
by a narrow fibro- vascular 
zone; the medullary sheath, 
consisting chiefly of spiral 
vessels, t; the medullary 
ray, r m; the vascular zone, 
consisting of porous vessels, 
v p, of large diameter, and 
, forming the large round 

fl fl & W apertures seen in a trans- 
97 verse section; the woody 

fibres, //, with their thick walls and smaller apertures; the inner bark 
or liber, f c, with the layer of cambium cells, c; the second layer 
of bark, or the cellular envelope, e c, with the laticiferous vessels, v I; 
the outer or suberous layer of bark, p, with the thin layer of epider- 
mis, e p, having hairs scattered over its surface. 

74. Such is the structure of a young shoot during the first year of 
its growth. At the end of a second year the shoot is found to have 
increased in diameter by the formation of a zone of vessels consisting 
of porous and woody tissue, and a zone of fibrous bark, the medullary 




\vl\c 



/* 



rr 



Fig. 96. Horizontal section of young stem of Acer campestre, magnified twenty-six diameters- 
m. Pith, em, em, Medullary sheath. fb,fb. Woody bundles, v p, Porous vessels, r m, Medul- 
lary rays, c, Cambium, /c, Fibres of Endophloeum. v I, Laticiferous vessels, e c, Cellular envel- 
ope, Mesophlffium. p, Corky envelope, Epiphlceum. e p. Epidermis. 

Fig. 97. Vertical section of the same stem more highly magnified. /, Tracheze or spiral 
fl,fl,fl, Woody fibres. The other letters as in fig. 96. 



EXOGENOUS STEM. PITH. 



39 



rays being at the same time continued from within outwards. This is 
represented in fig. 98, where (1, 1) indicates the section of the stem of 




98 ter. 



the first year's growth (the letters referring to the same part as in figs. 
96, 97); and (2) shows the interposed zones of the second year, by 
which the diameter of the stem is increased. 

75. The Pith, or the central part of a dicotyledonous stem, is com- 
posed of cellular tissue, which is developed in an upward direction, 
the cells diminishing in size towards the circumference, and being often 
hexagonal. In the young plant it occupies a large portion of the stem, 
and sends cellular processes outwards at regular intervals to join the 
medullary rays (figs. 94, 95, p). The pith has at first a greenish hue, 
and is full of fluid, but in process of time it becomes pale-coloured, 
dry, and full of air. These changes take place first in the central cells. 
Sometimes the pith is broken up into cavities, which have a regular 
arrangement, as in the Walnut and the Jessamine; it is then called dis- 
coid or disciform (S<Wo?, a disc, from the circular partitions). At 
other times, by the rapid growth of the outer part of the stem, the 

Fig. 98. Vertical section of a branch of Acer campestre, two years old, where (1, 1) indicates 
the portion formed the first year, and (2) that formed the second. The letters as in figs. 96 and 97. 

Fig. 98 bis.- Certain parts of the preceding magnified in order to show the structure of the 
vessels and cells, as well as their form and direction. Fig. 98 ter. A portion of a porous vessel 
magnified. 



40 EXOGENOUS STEM. WOOD. 

pith is ruptured irregularly, and forms large cavities, as in the fistular 
stem of Umbelliferous plants. Circumscribed cavities in the internal 
cellular portions of stems are by no means unfrequent, arising either 
from rupture or absorption of the cells. In some rare instances, ves- 
sels occur in pith, as in Elder, Pitcher-plant, and Ferula; and occa- 
sionally its cells are marked by pores indicating the formation of 
secondary deposits. The extent of pith varies in different plants, and 
in different parts of the same plant. In Ebony it is small, while in 
the Elder it is large. In the Eice-paper plant, a species of _<Eschyno- 
mene, the interior of the stem is occupied almost entirely by cellular 
tissue, which may be called pith; from this the paper is made by 
cutting thin sections in a circular manner. The same kind of tissue 
occurs in the Papyrus of the Nile. When the woody circle of the 
first year is completed, the pith remains stationary as regards its size, 
retaining its dimensions even in old trunks, and never becoming oblit- 
erated. 

76. The Medullary Sheath, is the fibro-vascular layer immediately 
surrounding the pith. It forms the inner layer of the vascular bundle 
of the first year (fig. 97 i), and consists chiefly of true spiral vessels, 
which continue to exercise their functions during the life of the plant, 
and which extend into the leaves. With the spiral vessels there are a 
few woody fibres intermingled. The processes from the pith are pro- 
longed into the medullary rays between the vessels of the sheath. 

77. Woody Layers. During the first year, the vascular circle con- 
sists of an internal layer of spiral vessels forming the medullary sheath, 
and external bundles of porous and ligneous vessels. In subsequent 
years the layer of spiral vessels is not repeated, but concentric zones 
of porous vessels (fig. 98 ter.), and pleurenchyma are formed, consti- 
tuting what are commonly called the woody circles of trees. The 
vascular bundles, from their mode of development in an indefinite 
manner externally, have been called Exogenous; and, for the same 
reason, Schleiden has denominated them Indefinite. Exogenous plants 
have sometimes received the name of Cydogens (xvx^os, a circle), 
in consequence of exhibiting concentric circles in their stems. On 
a transverse section, each zone or circle is usually seen to be separ- 
ated from that next to it by a well-marked line of demarcation. This 
line, as in the Oak (figs. 99, 100), and in the Ash, is indicated by 
holes which are the openings of large porous vessels; the remainder 
of the tissue in the circle being formed by pleurenchyma, with 
thickened walls and of smaller calibre. In some trees, as the 
Lime, Hornbeam, and Maple, the line is by no means so well marked, 
as the openings are smaller and more generally diffused; but there 
is usually a deficiency of porous vessels towards the outer part of the 
circle. In cone-bearing plants, as the Fir, in which the woody layers 
consist entirely of punctated woody tissue (fig 47), without any 



EXOGENOUS STEM. WOOD. 




large porous vessels, the line of separation is marked by the pleuren- 
chyma becoming dense and often 
coloured. In some kinds of wood, 
as Sumach, the zones are separated 
by a marked development of cellular 
tissue. The separation between the 
zones is said to be owing to the 
interruption in the growth of the 
tree during autumn and winter, and 
hence it is well defined in trees of 
temperate and cold climates. But 
even in tropical trees, the lines, al- 
though often inconspicuous, are still 
visible; the dry season, during which 99 

many of them lose their leaves, being their season of repose. 

78. The woody layers vary in their texture at different periods. At 
first the vessels are pervious and full of fluid, but by degrees thicken- 
ing layers are deposited which contract their canal, and sometimes 
obliterate it. The first- 
formed layers are those 
which soonest become thus 
altered. In old trees, there 
is a marked division be- 
tween the central Heart - 
wood or Duramen (durus, 
hard), and the external 
Sap-wood or Alburnum 
(albus, white); the former 
being hard and dense, and 
often coloured, with its 
tubes dry and thickened; while the latter is less dense, is of a pale 
colour, and has its tubes permeable by fluids. The difference of colour 
between these two kinds of woods is often very visible. In the Ebony 
tree, the duramen, or perfect- wood, is black, and is the part used for 
furniture, &c.; the alburnum is pale: in the Beech, the heart- woodis light- 
brown; in the Oak, deep-brown: in Judas tree, yellow: in Guaiacum, 
greenish. The alteration in colour is frequent in tropical trees. In 
those of temperate climates, called white-wood, as the Willow and Pop- 




Fig. 99. Horizontal section of the stem of an oak eight years old. 6, Wood, showing con- 
centric circles or zones, separated by points which correspond to the opening of the large porous 
vessels, or Bothrenchyma. e, Bark, showing also eight concentric circles, thinner and less 
distinct. The wood and bark are traversed by medullary rays, some of which extend from the 
bark to the pith, and others reach only a certain way inwards. 

Fig. 100. Horizontal section of two woody bundles of Cork-oak, separated from each other 
by the medullary ray, r m'. The two primary bundles are divided by secondary rays, r m" 
r ml", r m'"', which vary in extent according to the period when they originated, m, Pith, e c, 
Cellular envelope, y, Corky envelope, which is highly developed and exhibits several layers. 



42 EXOGENOUS STEM. WOOD. 

lar, no change in colour takes place; this is also the case in the Chest- 
nut and Bombax. The relative proportion of alburnum and duramen 
differs in different trees. Duhamel says that in the oak, six inches in 
diameter, the alburnum and duramen are of equal extent; in a trunk 
one foot in diameter, they are as two to seven; in a trunk two feet in 
diameter, as one to nine. The heart-wood is more useful than the sap- 
wood, and less liable to decay. The wood of different trees varies much 
in its durability. Pieces of wood, 2f- inches square, were buried to the 
depth of one inch in the ground, and decayed in the following order: 
Lime, American Birch, Alder, and Aspen, in three years; Willow, 
Horse-chestnut, and Plane, in four years; Maple, Red Beech, and Birch, 
in five years; Elm, Ash, Hornbeam, and Lombardy Poplar, in seven 
years; Robinia, Oak, Scotch Fir, Weymouth Pine, Silver Fir, were 
decayed to the depth of half an inch in seven years; while Larch, 
common Juniper, Virginian Juniper, and Arbor Vitas, were uninjured 
at the end of that time. 

79. From the mode in which the woody layers are formed, it is 
obvious that each vascular zone is moulded upon that which precedes 
it; and as in ordinary cases each woody circle is completed in the 
course of one year, it follows, that, by counting the concentric circles, 
the age of a tree may be ascertained. Thus fig, 99 represents an oak eight 
years old having eight woody layers, b. This computation can only be 
made in trees having marked separations between the circles. There 
are, however, many sources of fallacy. In some instances, by interrup- 
tion to growth, several circles may be formed in one year, and thus lead 
to an erroneous estimate. Care must be taken to have a complete section 
from the bark to the pith, for the circles sometimes vary hi diameter 
at different parts of their course, and a great error might occur from 
taking only a few rings or circles, and then estimating for the whole dia- 
meter of the tree. When by the action of severe frost, and other 
causes, injury has been done to the tender cells from which the young 
wood is developed, while, at the same time, the tree continues to live, 
so as to form perfect woody layers in subsequent years; the date of 
the injury may be ascertained by counting the number of layers which 
intervene between the imperfectly formed circle and the bark. In 
1800, a Juniper was cut down in the forest of Fountainbleau, exhibiting 
near its centre a layer which had been affected by frost, and which was 
covered by ninety-one woody layers, showing that this had taken place 
in the winter of 1709. Inscriptions made in the wood become 
covered, and may be detected hi after years when a tree is cut down; 
so also wires or nails driven into the wood. As the same develop- 
ment of woody layers takes place in the branches as hi the stem 
of an Exogenous tree, the time when a branch was first given off 
may be computed by counting the circles on the stem and branch 
respectively. If there are fifty circles for instance in the trunk, thirty 



EXOGENOUS STEM. BARK. 43 

in one branch, and ten in another, then the tree must have been 
twenty years old when it produced the first, and forty when it formed 
the other. 

80. In Exogenous stems the pith is not always in the centre. The 
layers of wood on one side of a tree may be larger than those on the 
other, in consequence of more full exposure to light and air, or the nature 
of the nourishment conveyed, and thus the pith may become excentric. 
Zones vary in size in different kinds of trees, and at different periods 
of a plant's life. Soft wooded trees have usually broad zones, and old 
trees form smaller zones than young ones. There are certain periods 
of a plant's life when it seems to grow most vigorously, and to form the 
largest zones. This is said to occur in the oak between twenty and 
thirty years of age. 

81. Cambium. External to the woody layers, and between them 
and the bark, there is a layer of mucilaginous semifluid matter, which 
is particularly copious in spring, and to which the name of Cambium 
(cambio, to change, from the alterations that take place in it) has been 
given (figs. 96, 97 c). In this are afterwards formed cells, called cam- 
bium cells, of a delicate texture, in which the protoplasm and primary 
utricle are conspicuous. These cells undergo changes, so as to assume 
an elongated fusiform shape, and ultimately become thickened pleuren- 
chyma. So long as the primary utricle can be detected, they appear 
to be in an active state, and capable of developing new cells. This 
cambium layer marks the separation between the wood and the bark. 

82. Bark or Cortical (cortex, bark) System, lies external to the wood, 
and, like it, consists of several layers. In the early state it is entirely 
cellular, and is in every respect similar to the pith; but, as the vascular 
bundles are developed, the bark and pith are separated, and the former 
gradually becomes altered by the formation of secondary deposits. 
The bark consists of a cellular and vascular system. In this respect 
it resembles the wood, but the position and relative proportion of these 
two systems is reversed. In the bark the cellular system is external, 
and is much developed; while the vascular is internal, and occupies 
comparatively a small space. The cellular portion of the bark con- 
sists of an external layer, or Epiphlceum (Ivi, upon, on the outside, and 
<pWof, bark), and the cellular envelope, or Mesophloeum (ftioo;, middle); 
while the vascular system forms the internal portion called Liber, or 
Endophlceum (iv^ov, within). 

83. The inner bark, or endophlceum (fig. 98 /c), is composed of elon- 
gated pleurenchyma mixed with laticiferous vessels and some cellular 
tissue. It is separated from the wood by the cambium layer. The pleu- 
renchymatous tubes are thickened by concentric deposits in their 
interior, and thus they acquire a great degree of tenacity. The liber 
of the Lime tree and of Lepurandra saccidora (a species of Antiaris?), are 
used to form mats, cordage, and sacks; and the toughness of the fibres 



44 



EXOGENOUS STEM. BA.RK. 



of the inner bark of flax, hemp, and of many of the nettle and mallow 
tribe, render them fit for various manufacturing purposes. The liber 
is sometimes called the bast-layer, from its uses. Occasionally it is 
continuous and uninterrupted, as in the Vine and Horse-chestnut ; at 
other times, as in the Oak, Ash, and Lime, the fibres are separated during 
the progress of growth, and form a sort of net-work, in the interstices 
of which the medullary rays are seen. The fibres of the lace-bark 
tree (Lagetta lintearia) are thus formed. In fig. 
101, is represented the bark of Daphne Lau- 
reola;/ indicating the woody fibres of liber, and 
r the medullary rays. The endophlosum in- 
creases by layers on its inside, which are thin, 
and may be separated like the leaves of a book, 
and hence the application of the name liber. The 
term liber may be derived from the fact of the 
inner bark being used for writing upon. 

84. The cellular envelope, or mesophlceum, lies 
immediately on the outside of the liber. It con- 
sists of polyhedral, often prismatical cells (fig. 
fWOinjWUl 98 bis, e c), usually having chlorophylle, or green 
r ttJmMxMi^S colouring matter, in their interior, but some- 
times being colourless and containing raphides. 
They are distinguished from those of the epi- 
phloaum by their form and direction, by their 
thicker walls, their green colour, and the inter- 
cellular spaces which occur among them. This covering is usually less 
developed than the outer suberous layer, but sometimes, as in the 
Larch and common Fir, it becomes very thick, and separates like the 
epiphloeum. In the cellular envelope laticiferous vessels occur. 

85. The Epiphloeum is the outer covering of the bark, consisting of 
cells which usually assume a cubical or flattened tabular form (fig. 98 
bis, p). The cells have no chlorophylle in their interior, are placed 
close together, and are elongated in a horizontal direction ; and thus 
they are distinguished from the cells of mesophlceum. In the progress 
of growth they become often of a brown colour. This covering may be 
composed of a single layer of tabular cells; but in some trees it consists 
of numerous layers, forming the substance called cork, which is Avell seen 
in Quercus suber, the Cork-oak (fig. 100 p); hence the name suberous, 
or corky layer, which is given to it. The form of its cells varies in 
some instances, being cubical at one part, and more compressed or tabu- 
lar at another, thus giving rise to the appearance of separate layers. 
After a certain period (sometimes eight or nine years), the corky portion 
becomes dead, and is thrown off in the form of thickish plates, leaving 




Fig. 101. Network formed by liber of Daphne Laureola. //, Fibrous bundles, r r, Medullary 
rays. 



EXOGENOUS STEM. BARK. 45 

a layer of tabular cells or periderm below. On the exterior of the epi- 
phloeum is situated the epidermis, which has already been described 
(f 47). It is formed of a layer of cells, which in woody stems serve 
only a temporary purpose, becoming ultimately dry, and being thrown 
off in the form of plates or shreds. 

86. The bark, in its increase, follows an order exactly the reverse of 
that which occurs in the woody layers. Its three portions increase by 
additions to their inside. The layers of liber owe their increase to the 
cambium cells, which, by their constant reproduction, mark the separ- 
ation between the vascular bundles of the wood, and the fibres of the 
endophloeum. These layers are often so compressed and united together 
as to be counted with difficulty, while at other tunes they are separated by 
rings of cellular tissue, and thus remain conspicuous. In the case of the 
cellular portions of the bark, there are also successive additions, sometimes 
to a great extent, but they do not usually exhibit any marked divisions. 

87. As the additions are made to the woody layers on the outside, 
and to the bark on the inside, there is a constant distension going on, 
by which the bark becomes compressed, its layers of liber are con- 
densed, the fibres are often separated so as to form meshes (as in the 
lace-bark), its epidermis is thrown off, and the epiphlceum is either 
detached along with it, or, when thick, is ruptured in various ways, so 
as to give rise to the rugged appearance presented by such trees as the 
Elm and Cork-oak. In some instances the bark is very distensible, 
and its outer cellular covering is not much developed, so that the 
surface remains smooth, as in the Beech. The outer suberous layer 
sometimes separates with the epidermis, in thin plates or scales. In 
the Birch, these have a white and silvery aspect. There is thus a 
continual destruction and separation of different portions of the bark. 
The cellular envelope and liber may remain while the epiphlreum 
separates, or they also may be gradually pushed off the parts which 
were at first internal becoming external. In the case of some Australian 
trees, both the cellular and fibrous portions are detached in the form 
of thin flakes, and occasionally each annual layer of liber throws off 
that which preceded it. The epidermis separates early, and no renewal 
of it takes place. There is, however, an internal covering, which is 
formed of various portions of the bark. To this covering the name 
Periderm (ve^l, around, and Sc^a, skin) has been given by Mohl. 

88. From the mode in which the outer layers of bark separate, it 
follows that inscriptions made on them, and not extending to the wood, 
gradually fall off and disappear. A nail driven into these layers 
ultimately falls out. In consequence of the continued distension of an 
exogenous stem, it is found that woody twining plants cause injury, by 
interrupting the passage of their fluids. A spiral groove may thus be 
formed on the surface of the stem, by the compression exercised by a 
twining plant, such as honeysuckle. From what has been stated rela- 



46 



EXOGENOUS STEM. RAYS. 



tive to the changes which take place in the bark, it will be understood 
that it is often difficult to count its annual layers, so as to estimate the 
age of the tree by means of them. This may, however, be done in 
some cases, as shown at fig. 99, where there are eight layers of bark, 
e, corresponding to eight woody layers, b. 

89. Medullary Rays or Plates. While the bark and pith become 
gradually separated by the intervention of vascular bundles, the con- 
nection between them is kept up by means of processes called medul- 
lary rays (figs. 94, 95 r). These form the silver grain of carpenters ; 
they communicate with the pith and the cellular envelope of the bark, 
and they consist of cellular tissue, which becomes compressed and flat- 
tened so as to assume a muriform appearance (fig. 1 02 m r). At first 
they occupy a large space (fig. 94 r) ; but as the vascular bundles in- 
crease, they become more and more narrow, forming thin laminae or 
plates, which separate the woody layers. On making a transverse or hori- 
zontal section of a woody stem, the medullary rays present the aspect of 
narrow lines running from the centre to the circumference (figs. 99, 100 
r TO); and in making a vertical section of a similar stem through one 
of the rays, the appearance represented in fig. 102 will be observed, 
where a medullary ray, m r, composed of flattened muriform cells 



QQQQOCEggc 

lob 








ce cf ce 



passes from the pith, p, to the cellular envelope, c e, crossing the 
tracheae of the medullary sheath, t, the ligneous tissue, , the porous 
vessels of the wood, b, and the fibres of the liber, cf. The lamina do 
not by any means preserve an uninterrupted course from the apex to 

Fig. 102. Vertical section of a one-year old branch of Acer campestre highly magnified, and 
extending from the pith to the bark, parallel to the medullary rays, m r, A medullary ray or 
plate extending from the pith, p, to the bark, c e, crossing trachea, t, woody fibres, I, porous 
vessels, 6, and cortical fibres, cf. 

Fig. 103. Vertical section of the same branch perpendicular to medullary rays. 1 1, Woody 
fibres which interlace, leaving spaces, mr,mr,mr, where the medullary rays pass. 



ANOMALOUS EXOGENOUS STEMS. 47 

the base of the tree. They are broken up by the intervention of woody 
fibres, as seen in a vertical section of a woody stem (fig. 103), perpen- 
dicular to the medullary rays m r, m r, m r, which are separated by 
interlacing woody fibres, 1 1. The medullary rays are usually continu- 
ous from the pith to the bark, additions being made to them as they 
proceed outwards. But, occasionally, secondary rays arise from the 
outer cells, which pass only to a certain depth between the vascular 
bundles, as in the Cork-oak (fig. 100, r m'", r m", r m""). Medul- 
lary rays are conspicuous in the Cork-oak, Hazel, Beech, Ivy, Clematis, 
Vine. They are not so well marked in the Lime, Chestnut, Birch, 
Yew. 

Anomalies in the Structure of the Exogenous Stem. 

90. The stems of Dicotyledonous plants occasionally present anomalous 
appearances in the structure and arrangement of their wood, bark, and 
medullary rays. In place of concentric circles, there are sometimes only 
a few rows of wedge-shaped vascular bundles produced during the life of 
the plant, additions being made by the interposition of bundles of a simi- 
lar kind annually, resembling in this respect the formation of woody 
bundles in the early growth of herbaceous plants (fig. 95). In the 
Pepper tribe, Aristolochiacea?, and Menispermaceas, these anomalous 
stems occur. In Gnetum (fig. 104), the vascular bundles, b b b b b b b, 
form zones, which are each the produce of several years' growth, and 
are separated by layers, 1 1 1 1 1 1, which may be considered as repre- 
senting different zones of liber. 

In some of the Menisper- 
mum tribe, the separating lay- 
ers are of a cellular and not 
of a fibrous nature. In Banis- 
teria nigrescens (fig. 105), the 
young stem (1) presents a 
four-lobed surface; the lobes 
gradually deepen (2), and ulti- 
mately (3) the stem is divided 
into a number of separate por- 
tions, the central one of which 
alone exhibits pith and medul- 
lary rays. The portions are 
separated by interposed cortical layers. 

Many of the Malpighiacea?, Sapindaceas, and Bignoniacese of Brazil, 
exhibit stems in which the woody layers are arranged in a very irregu- 
lar manner. In the stem of Calycanthus floridus, and of some Bra- 
Fig. 104. Horizontal section of stem of Gnetum. m, Pith, e m, Medullary sheath, b b b 
6666, Woody bundles forming seven concentric zones, each of which is the produce of several 
years. I II II ?, Fibres of liber forming interposed circles, equal in number to the woody zones. 




48 



ANOMALOUS EXOGENOUS STEMS. 



zilian Sapindacese, such as Paullinia pinnata (fig. 106), Serjania tri- 
ternata, and Selloviana, there is a central woody mass with from three 
to ten small secondary ones around it. Each of the masses contains 
true pith, apparently derived from the cortical cellular tissue, or from 
the original medullary centre. Gaudichaud and Jussieu state that 
around these separate collections of pith, there is a medullary sheath 
and spiral vessels. No annual rings have been detected in the 
secondary masses, but medullary rays exist, usually in their outer 
portion (fig. 106). In these anomalous Sapindaceag, the central and 
lateral woody masses are enclosed in a common bark, with a continu- 
ous layer of liber. Some have supposed that the lateral masses are 
undeveloped branches united together under the bark; but Treviranus 
considers them as connected with the formation of leaves, and as de- 
pending on a peculiar tendency of the vascular bundles to be devel- 
oped independently of each other round several centres. 






In some Bignoniacese (fig. 107), the layers of wood are divided in 
a crucial manner into four wedge-shaped portions by the intervention 
of plates differing in texture from the ordinary wood of the plant, and 
probably formed by introversion, or growing inwards of the liber. In 
some Guayaquil Bignonias, Gaudichaud perceived first four of these 
plates, next eight, then sixteen, and finally thirty-two. In Aspido- 
spermum excelsum of Guiana, and in Heteropterys anomala (fig. 108), 



Fig. 105. Horizontal section of stem of Banisteria nigrescens at different ages. 1. Stem 
presenting four superficial lobes. 2. Showing six deeper lobes, with intermediate divisions. 3. 
The lobes separated by cellular tissue, the middle one alone having pith and medullary sheath . 
The points indicate the orifices of porous vessels. 



ANOMALOUS EXOGENOUS STEMS. 



49 



the stem assumes a peculiar lobed and sinuous aspect, and in some woody 
climbing plants, pressure causes the stems to become flattened on the 
side next the tree on which they are supported, while from being 
twisted alternately in different directions, they present a remarkable 






zigzag form, having the woody layers developed only on one side (fig. 
109). In Firs, the wood is occasionally produced in an oblique in 
place of a perpendicular manner, thus injuring the timber, and causing 
it to split in an unusual way. The young plants produced from the seed 
of such twisted- wooded firs, are said to inherit the peculiarity of their 
parents. 

Fig. IOC. Horizontal section of the stem of Paullinia pinnata, one of the Sapindaceae of 
Brazil, showing numerous secondary woody masses, surrounding a central one. Each of the 
separate masses has pith, often excentric, with a medullary sheath, containing spiral vessels, 
and a few medullary rays chiefly towards the circumference of the stem. 

Fig. 107. Horizontal section of the stem of Bignonia capreolata, showing the crucial division 
of the woody layers. 

Fig. 108. Horizontal section of stem of Heteropterys anornala, one of the Brazilian Mal- 
pighiacea?, showing an irregularly lobed surface. The dots indicate porous vessels. 

Fig. 109. Fragment of a stem of a climbing species of Banistcria (B. scandens) showing the 
effects of compression^ 

E 



ENDOGEXOUS OR MONOCOTYLEDONOUS STEM. 



Endogenous or Monocotyledonous Stem. 

91. This kind of stem is composed of cells and vessels which are 
differently arranged from those of the Exogenous stem. The vascular 
bundles are scattered through the cellular tissue, and there is no dis- 
tinction of pith, wood, bark, and medullary rays (fig. 110). In the 
young state, the centre of the stem is occupied 
entirely by cells, which may be said to represent 
pith, and around this the vessels are seen increas- 
ing in number towards the circumference. The 
central cellular mass has no medullary sheath. In 
some cases its cells are ruptured, and disappear dur- 
ing the progress of growth, leaving a hollow cavity 
(fig. Ill); but in general it remains permanent, 
and is gradually encroached upon by the develop- 
ment of the vascular system. The latter consists 
of vessels arranged in definite bundles, which do 
not increase by additions to their outside after 
being once formed, although they are developed 
in a progressive manner. These bundles may be 
considered as representing the vascular wedges, 
produced during the first year of an exogenous 
stem's growth (fig. 94). They consist of woody 
vessels enclosing some cellular tissue between 
them, spiral, and porous vessels. The outer part 
of the stem is not formed by a separable bark, but consists of a dense 
mass of fibrous tissue, mixed with laticiferous vessels and cells. It is 
intimately connected to the inner part of the stem, without the inter- 
vention of medullary rays. 

92. On making a transverse section of a young endogenous stem (fig. 
112), there is observed a mass of cells or utricles, w, of various sizes, 
often small in the vicinity of the vascular bundles, spiral vessels or 
tracheae, t, large porous vessels, v p, laticiferous vessels, I, and woody 
fibres, f, resembling those of liber, thickened by internal deposits. A 
similar section of a further advanced endogenous stem, as of a Palm 
(fig. 113), shows numerous bundles of vessels dispersed irregularly in 
cellular tissue; those near the centre, m, being scattered at a distance 
from each other, while those towards the outside are densely aggre- 
gated, so as to form a darkish zone, b, and are succeeded at the circum- 
ference by a paler circle of less compact vessels, /, with some compressed 

Fig 
tribut 

Fig. 111. iransverse section 01 stem ot rnragmites commums, or common reed me cellu- 
lar tissue in the centre has disappeared, leaving a ristular or hollow stem, with a ring of cells 
and vessels, the latter indicated by dots, n, Node where the fibres cross, so as to form a solid 
partition. 




ENDOGENOUS OR MONOCOTTLEDONOUS STEM. 51 

cells, covered by an epidermis, e. The peripherical portion, /, differs 
from true bark, in not being separable from the rest of the tissue. It 
has received the name of false bark, and consists of the epidermal cells, 



/ 



v/i M. 





e, and what has been called the cortical integument, I. This portion 
of the stem is often very inconspicuous, but sometimes it is much 
developed as in Testudinaria elephantipes, in which it is rugged, and 
is formed of a substance resembling cork in many respects. 

93. Mohl states that, in the stem of a Palm, there may be distin- 
guished a central region, a fibrous layer, and a cortical region; and 
the same divisions are pointed out by Henfrey in the stem of Spar- 
ganiiun ramosum and other monocotyledons. The central portion, 
representing the pith of dicotyledons, consists in Sparganium of 
spherical cells containing starch, while the cortical or outer portion is 
formed by irregular cells, which are usually destitute of starch. 

94. It was at one time supposed that the woody portion of these 
stems was increased by additions to the centre, so that the first-formed 
fibres were gradually pushed towards the circumference by those which 
succeeded them, in the manner represented in fig. 114, 1: hence 
the term Endogenous (bSov, within, and ygj/i/aa, I produce), meaning 
internal growth. But Mohl showed that this was not strictly correct. 
For although the fibres connected with the leaves, in the first instance, 
are directed towards the centre, and are therefore always internal to 
those previously formed, yet, when they are traced downwards, they are 

Fig. 112. Horizontal section of a vascular bundle from the stem of a Palm (Coryphafl-igida). 
t, Tracheae, or spiral vessels, v p, Large porous vessels. , Cells or utricles of various kinds 
surrounding the vessels, and forming the parenchyma. I, Laticiferous vessels. /, Fibres analo- 
gous to those of liber, thickened by concentric deposits. 

Fig. 113. Transverse section of part of the stem of a Palm (Astrocaryum Murumura). m, 
Central or medullary portion in which the woody bundles are distant and scattered, b, External 
woody portion, where the fibres are numerous and densely aggregated, so as to form a dark 
zone. /, Paler circle of more slender and less compact fibres, which may be considered as analo- 
gous to liber, e, Cellular epidermal portion. 



52 



ENDOGENOUS OR MONOCOTYLEDONOUS STEM. 



found not to continue in a parallel direction, but to arch outwards, so 
as ultimately to reach the circumference. Hence, the newly-formed 
fibres really become external at the base, although internal above. 
On making a vertical section of an endogenous stem, as of a Palm, 
there is observed an interlacing of fibres, similar to what is represented 

in fig. 114, 2, where the four vas- 
cular bundles, abed, are first 
directed towards the centre, and 
<* r^ '' d then curve outwards towards the 

circumference, so that those last 
formed ultimately become external. 
The term Endogenous, will, there- 
fore, only apply strictly to the 
fibres at the early part of their 
course. On this account, the terms 



a 



\ 






\ 



r/U 



(' Endogenous and Exogenous have 



been recently discarded by many 
writers, the terms Monocotyledon- 
ous and Dicotyledonous being sub- 
stituted. The true distinction 
between Exogenous and Endogen- 
ous stems consists in this, that in 
the former, the woody or vascular 

\ / \1 I I y bundles increase indefinitely at 

their periphery, while in the latter, 
they are arrested in their transverse 
growth at a definite epoch. 

95. The composition of the vas- 
cular bundles, in different parts of 
then* course, varies. Thus, at the 
11 upper part, where they proceed 
from the leaves towards the centre, 
they contain spiral vessels, porous 
vessels with some cellular tissue, a 
few laticiferous vessels, and woody 
fibres resembling those of liber (fig. 
112). As the bundles descend, the 
spiral vessels disappear, then the 
porous vessels, and when they have 
reached the periphery, and have become incorporated with it, nothing 
but fibrous tissue, or pleurenchyma, remains, forming by its division a 
complicated anastomosis, or net-work. Thus, at the commencement 



ENDOGENOUS OR MONOCOTYLEDONOUS STEM. 53 

the bundles are large, but as they descend they usually become more 
and more attenuated. In some instances, however, as in Ceroxylon 
andicola, they increase at different parts of their course, probably by 
interstitial growth, and give rise to irregular swellings of the stem. 
This distension takes place occasionally at the base of the stem, as in 
Euterpe montana. 

96. There are many herbaceous plants in this country, as Lilies, 
Grasses, &c., having endogenous stems, in which the course of the 
vascular bundles may occasionally be traced, but there are no British 
endogenous plants with permanent aerial woody stems. All the British 
trees are exogenous. Illustrations of endogenous stems must therefore 
be taken from trees of foreign countries. Palms furnish the best exam- 
ples. In them the stem forms a cylinder of nearly uniform diameter 
throughout. The leaves are produced from a single terminal and cen- 
tral bud, called a Phyllophor, or Pkyllogen, (tpv^ov, a leaf, and q>i%u, I 
bear, or */tvvx.u, I produce). Connected with the leaves are the vascu- 
lar bundles, and the bases of the leaves remain attached to the outer 
part of the stem, surrounded by the mattulla or reticulum (^[ 57). 
While the leaves produced by one bud decay, another bud is developed 
in the centre in a similar manner. As the definite vascular bundles 
are produced, the stem acquires increased thickness, but it is arrested 
in its transverse diameter at a certain epoch. The bundles, although 
developed progressively, do not multiply indefinitely ; and thus a 
Palm-stem seldom becomes of great diameter. 

97. In consequence of this mode of formation, the outer part of a 
Palm-stem is the hardest and densest, and after acquiring a certain 
degree of solidity, it resists all further distension, and frequently be- 
comes so hard as to resist the blow of a hatchet It has been already 
stated, that in the exogenous stem, provision is made for unlimited 
extension laterally, by the development of indefinite bundles of woody 
fibres and vessels, and the formation of a separable bark which can be 
thrown off; but in the endogenous stem there is no such provision. 
Hence, when the first-formed part of the stem has increased to a cer- 
tain amount, its progress is stopped by the hard mdistensible outer 
fibrous covering ; and the same thing takes place with the other parts 
in succession, till at length all have acquired a comparatively uniform 
size, as is seen in the coco-nut palm (fig. 115, 1). In consequence of 
the small lateral increase of Palm-stems, a woody twining plant does 
less injury to them than to trees of exogenous growth. 

98. The growth of endogenous stems may be said to resemble the 
upward growth of Exogens by terminal buds only, for there is no cam- 
bium layer, and no peripherical increase. Hence, in Palms, the ter- 
minal shoot is developed, but there are no annual rings. The harden- 
ing of the stem depends, in all probability, partly on internal changes 
in the woody fibres, similar to what takes place in the heart- wood of 



54 



ENDOGENOUS OR MONOCOTYLEDONOTJS STEM. 



Exogens. Occasionally, at the upper part of a palm-stem there is an 
appearance of zones, but it does not continue throughout the stem. 
From the absence of concentric circles, the age of a Palm cannot be 
estimated hi the same way as an exogenous tree. The elongation, 

however, of each species of Palm 
is pretty regular, and by it an 
opinion may be formed of the 
age. The rings on the surface 
of the stem are not indicative of 
yearly growth. 

99. In Palms, there is in gen- 
eral no provision for lateral buds, 
and no branches are formed. 
Hence, destroying the central 
bud will kill the tree. In some 
Palms> however, as the Doom 
palm of Egypt (Cucifera thebaica\ 
the stem divides in a forked or 
dichotomous (/#, two ways, 
and Ttpvu, I cut,) manner. 
Gardner, in his travels in Brazil, 
noticed a Palm in which the cen- 
tre bud had been destroyed, and 
two side ones had been produced, 
so as to- give it a forked appear- 
ance. Other plants with endo- 
genous stems, also produce lateral 
buds, In fig. 115, 2, there is 
a representation of such a stem, 
in the case of the Screw-pine, 
(Pandanus odoratissimus), and examples are seen in Grasses, as the 
Bamboo, in Asparagus, Asphodels, and Dracaenas. In these cases, the 
stem is conical, like that of Exogens, and the destruction of the ter- 
minal bud is not necessarily followed by the death of the plant. The 
development of lateral buds is accompanied often by an increased 
diameter of the stem. A Draeasna in the Canary Islands, has a hollow 
stem capable of holding several men; and the fact of its living in this 
state, is marked by Jussieu as an argument against the strict endoge- 
nous formation ; for, if the centre were the youngest and newest part, 
its destruction would put an end to the existence of the tree, in the 

Fig. 115. Two endogenous or monocotyledonous trees, belonging- to two different families. 
1. Cocos nucifera, or coco-nut, belonging to the Palm family. 2. Pandanus odoratissimus, or 
screw-pine, belonging to Pandanacea?. The first has a simple unbranched stem, with a cluster 
of leaves at the summit; the second has a branched stem, with numerous leafy clusters, and 
peculiar aerial roots, proceeding from different parts of the stem. Two human figures are given 
to indicate the height of the trees. 




ACROGENO1JS OR ACOTYLEDOXOUS STEM. 55 

same way as the removal of the outer part of the wood Avould destroy 
an exogenous stem. The branches in such plants are formed on the 
same principle as the stems ; but their fibres, when reaching the stem, 
dp not proceed to the centre, but extend outside the previous layers, 
between them and the outer false bark (fig. 113 I e), and thus it 
is that they give rise to lateral increase. In Grasses, the stem 
or culm is usually hollow or fistular (fig. Ill), in consequence of 
the outer part, by its rapid increase, causing the rupture and ulti- 
mate disappearance of the internal cellular portion. The fibres in 
some Grasses cross from one side to the other, forming partitions, as 
in Bamboo. 

100. In many Endogenous or Monocotyledonous plants, the stem 
remains below ground, developing shoots which are simple, as in 
Banana and Plantain, or branched, as in Asparagus. In the former, 
the stem above ground is an herbaceous shoot, composed of the 
sheaths of the leaves. It dies after fruiting, and is succeeded by 
other shoots from the subterranean stem. The shoots or buds from 
such stems occasionally remain below ground in the form of bulbs, 
as in Lilies. 

101. In some instances, the aerial stem has the usual endogenous 
structure, while the under-ground stem has the vascular bundles 
developed in the form of wedges, with cellular tissue in the centre, 
thus resembling some Exogens. The structure has been remarked in 
the Smilax or Sarsaparilla family. Lindley calls these plants Dictyogens 
(bixrvov, a net), from their netted leaves, a character by which they 
differ from other Endogens. Henfrey holds that the ring of woody 
fibres in Tamus and Smilax, is merely an alteration of the parenchy- 
matous cells of the periphery, and is not produced, as some have sup- 
posed, in the same way as the zones of Dicotyledons. He considers 
this ring as probably analogous to the liber, and not to the indefinite 
vascular bundles of Exogenous stems. 

Acrogenous or Acotyledonous Stem. 

102. This stem, in its general external aspect, resembles that of 
Endogens. It is unbranched, usually of small, nearly uniform diameter, 
and produces leaves at its summit. It is easily distinguished by its 
internal structure. Tree Ferns furnish the best example of this kind of 
stem. In them it is denominated a Stipe, or a Rachis, and often attains 
the height of 120 feet (fig. 116). A transverse section of the stem 
(fig. 117) exhibits a circle of vascular tissue composed of masses, z, I, 
of various forms and sizes, situated near the circumference; the centre, 
m, being either hollow or formed of cellular tissue. On the outside 
of the vascular circle, cells exist, p, covered by an epidermal layer or 
cellular integument, e, often of hard and dense consistence, formed 



56 



ACROGENOUS OB ACOTYLEDONOUS STEM. 



originally by the bases of the leaves, which remain for a long time 

attached to the stem. 

103. The vascular bundles are formed 
simultaneously, and not progressively 
as in the stem already noticed; and 
additions are always made in an up- 
ward direction. The stem then is 
formed by additions to the summit,, 
and by the elongation of vessels already 
formed; hence the name Acrogenous, 
(oLx.^, summit). The leaves unite by 
their bases to form the stem, and the 
arrangement of their vessels is traced 
into it. The vascular system is of 
greater density than the rest of the 
tissue, and is usually distinguished by 
the dark colour of the pleurenchyma 
(fig. 117 /), which surrounds the paler 
vessels in the centre (fig. 117 v v). 
The vascular bundles do not follow a 
straight course, but unite and separate, 
leaving spaces between them, similar 
to those seen in the liber of Exogens 
(fig. 101). 





Fig. 116. Tree fern (Alsophilaperrotetiana), of the East Indies. Stem or stipe is cylindrical, 
unbranched, and presents at its base, r a, a conical enlargement, formed by a mass of adventi- 
tious roots. The leaves are terminal, and in the young state are rolled up in a circinate 
manner. 

Fig. 117. Transverse section of the stem of a Tree fern (Cyathea). m, Cellular tissue, corre- 
sponding to pith, occupying the central part, z I, Vascular circle composed of numerous irregu- 
larly-formed masses. /, Dark-coloured woody or prosenchymatous fibres, forming the borders 
of the vascular masses, v v, Pale-coloured vessels, chiefly scalariform, occupying the centre of 
the masses, p, Parenchymatous or cellular external zone, often communicating with the central 
portion, e, Hard epidermal envelope, occupying the place of the bark. 



ACROGENOUS OR ACOTYLEDONOUS STEM. 



57 



104. The acrogenous stem in the young state is solid, but it fre- 
quently becomes hollow in the progress of growth, by the rupture and 
absorption of the walls of the cells in the centre. The bases of the 
leaves remain long attached, but ultimately fall off, leaving marked 
scars which are at first close together, but often separate afterwards 
by interstitial growth. On these scars or cicatrices (cicatrix, a wound), 
the markings of the vessels are easily seen, arranged in the same man- 
ner as those of the stem with which they are continuous. The vascu- 
lar system of ferns consists chiefly of scalariform vessels (fig. 62), 
mixed with annular (fig. 57), and porous vessels (fig. 98 ter). There 
are no true trachea with fibres which can be unrolled. In the stems 
of Lycopodiaceae, closed tracheae or ducts (If 34) occur; and in Equi- 
setaceae, the rings of the annular vessels are closely united. 

105. The stem of Ferns is generally of small diameter ; it does not 
increase much laterally, after having been once formed, and it does not 
produce lateral buds. Sometimes it divides into 

two (fig. 118), by the formation of two buds at its 
growing point. This, however, is an actual divi- 
sion of the stem itself, and differs from the branch- 
ing of Exogenous and Endogenous stems. In the 
Ferns of this country, the stems usually creep 
along and under the ground, and the leaves which 
they produce die annually without giving origin 
to an .elevated trunk. In the common Brake 
(Pteris aquilina), the arrangement of the vascular 
system may be seen by making a transverse section 
of the under-ground stem. The plant has received 
its name aquilina, from a supposed resemblance to 
a spread eagle, presented by the vessels when thus 
cut across. 

106. In some Thallogens, which have been noticed as being stem- 
less, the thallus or frond is supported by a stalk, in which there are 
concentric circles, with divisions in the form of rays, and a sort of 
pith. These are all forms of cellular tissue, however, without any 
woody fibres. These appearances are presented by some large antarc- 
tic sea- weeds, species of D'Urvillea, and by some lichens, as Usnea. 

107. There are thus three kinds of stems in the vegetable king- 
dom: 

1. Exogenous or Dicotyledonous, having a separable bark; distinct 
concentric circles, composed of progressive indefinite vascular bundles, 
increasing at their periphery, the solidity diminishing from the centre 
towards the circumference ; pith, enclosed in a longitudinal canal or 




Fig. 118. Vertical section of part of the forked stem or stipe of Alsophila perrotetiana. m, 
Cellular central portion, z I, z I, Vascular zone, consisting of woody fibres and scalarifonn 
vessels. The forking is caused by an actual division of the stipe. 



58 DEVELOPMENT AND FUNCTIONS OP STEM. 

medullary sheath, with cellular prolongations in the form of medullary 
rays. 

2. Endogenous or Monocotyledonous, having no separable bark; no 
distinct concentric circles ; vascular bundles progressive and definite, 
not increasing at their periphery, the solidity diminishing from the 
circumference to the centre; no distinct pith, no medullary sheath nor 
medullary rays, the cellular tissue being interposed between the vas- 
cular bundles. 

3. Acrogenous or Acotyledonous, having no separable bark; no con- 
centric circles; vascular bundles simultaneous, forming an irregular 
circle; additions being made to the summit; no distinct pith, no medul- 
lary sheath nor medullary rays; conspicuous scars left by the bases of 
the leaves. 

Formation of the different parts of Stems, and their special Functions. 

108. The stem bears the leaves and flowers, exposes them to the 
atmosphere and light, conveys fluids and air, and receives secretions. 
Stems vary much in their size, both as regards height and diameter. 
Some oaks in Britain have a height of nearly 120 feet ; forest trees in 
France have attained to 120 and 130 feet, and in America even to 
150 feet; while palms are frequently still higher. The trunks of 
some Baobabs in Senegal (Adansonia digitatd), are said to be 30 feet 
in diameter. 

109. The pith, in its early state (fig. 94 p), is of a greenish colour, 
and contains much fluid, which is employed in the nourishment of 
the young plant. After serving a temporary nutritive purpose, it 
becomes dry, or disappears by rupture and absorption of the walls of 
the cells which enter into its composition. The medullary sheath (fig. 
96 e TO), keeps up a connection between the central parts of the stem 
and the leaves, by means of spiral vessels, which seem to be concerned 
partly in the conveyance of air. The medullary rays (fig. 97 r m), 
preserve a communication between the bark and the pith. The cells 
of which they are composed, are concerned in the production of leaf 
buds, and they assist in the elaboration and conveyance of secretions. 
They have a direct connection with the cambium cells (fig. 97 c), or 
the cells between the wood and bark, whose function is to aid in the 
formation of new wood. The bark (fig. 97 fc, e c, p), protects the 
tender wood, conveys the elaborated sap downwards from the leaves, 
and is the part in which many valuable products, such as gum, tan- 
nin, and bitter principles, are formed and deposited. The vascular 
bundles (fig. 97 f I, v p), convey the sap from the root to the leaves. 
This function is carried on during the life of the plant by the annular 
vessels and the porous vessels, as well as other kinds of spurious fibro- 
vascular tissue ; but in the woody fibres it ceases at a certain epoch, 



FORMATION OF WOOD. 59 

in consequence of the tubes being filled up by secondary deposits, so 
as to form the perfect wood, which gives strength and stability to the 
stem. 

110. Considerable differences of opinion have arisen on the subject 
of the formation of wood. All agree that it cannot be properly formed 
unless the leaves are exposed to air and light, but physiologists differ 
as to its mode of deposition. Some say that it is deposited in a hori- 
zontal, others, in a vertical direction. There seems to be no doubt, 
that the cambium cells perform an important part in the formation of 
wood, and that their activity depends on the proper development of 
leaves. These formative cells, although most easily detected in exo- 
genous stems, appear also to be present in the other forms of stems 
which have been described. 

111. The early physiologists made experiments on exogenous stems, 
as being most easily procured. They espoused the horizontal theory 
of deposition, and disputed as to the formation of cambium ; some 
maintaining that it was formed by the cells of the bark ; others, by 
the central cells of the stem ; and others, by both united. Duhamel, 
by putting silver plates between the bark and wood, and Dr. Hope, 
by detaching portions of bark, endeavoured to show that the bark 
alone was concerned in the formation of wood ; while Decandolle 
and others were led to the conclusion, that both were concerned in 
the process of forming cambium, by means of which a layer of liber 
and a layer of wood was annually produced. 

112. Knight espoused what is called the vertical theory, considering 
the wood as developed in a downward direction by the leaves, and in 
this view he is supported by Petit-Thouars and Gaudichaud. These 
physiologists maintain that there are two vascular systems in plants, 
an ascending and descending ; the one connected with the leaf forma- 
tion, or the spiral vessels ; the other connected with the production 
of roots, or the woody fibres the cellular tissue being more especially 
concerned in horizontal development. Every bud is thus, according 
to them, an embryo plant fixed on the stem, sending leaves upwards, 
and roots downwards. In Palms, Dracaenas, and other Endogenous 
stems, the peculiar manner in which the woody fibres interlace (fig. 
114, 2), favours the opinion that they are developed like roots, by 
additions to their extremities ; and this is also strengthened by the 
formation of adventitious or aerial roots, which burst through different 
parts of the stem in Screw-pines (fig. 115, 2), in the Banyan, and in the 
Fig tribe in general. In Vellozias and Tree Ferns, the surface of the 
stem is often covered with thin roots, protruding at various parts, and 
becoming so incorporated with the stem as to appear to be a part of 
it. In the Tree Fern, represented hi fig. 116, the lower part of the 
stem is enlarged in a remarkable degree by these fibres, so as to give 
it a conical form. In Exogenous stems, when ligatures are put round 



60 FORMATION OF WOOD. 

the stem, and when portions of bark are removed, a swelling takes 
place above the parts where the injury has been inflicted, thus appa- 
rently proving that the new matter is developed from above down- 
wards. 

113. Gaudichaud endeavours to account for various anomalous 
forms of stems (figs. 105-108), by considering them as depending on 
the arrangement of the leaves, and on the mode in which the woody 
fibres are sent down from them. Thus, the four secondary masses 
surrounding the central one in the stem of Calycanthus floridus, are 
traced to four vascular bundles from the leaves, penetrating the cellu- 
lar tissue of the bark, distinct from the central wood and from each 
other, except at the nodes, where the cross bundles unite them so as 
to form a ring round the central mass. New fibres are formed on the 
inner side of these bundles, and by degrees they assume a crescentic 
shape, while the horns of the crescent ultimately unite on the outer 
side (centrifugally), and enclose a portion of the bark, which thus forms 
a kind of spurious excentric pith, with numerous woody layers on the 
inside, and a smaller number on the outside. Again, in Brazilian 
Sapindaceae (fig. 106), with five, seven, nine, or ten woody masses, 
the same thing is said to occur, with this difference, that the pith of 
each of the masses is derived from the original medullary centre, 
portions of which are enclosed by the vascular bundles in a centripetal 
manner, or from without, inwards. 

114. Treviranus states that the fibrous and vascular bundles de- 
scending from the leaves, are destined in general to unite around a 
common centre, but that they retain a certain degree of independence, 
and may be developed separately in some instances, giving rise to 
anomalous fasciculated stems. 

115. Gardner, from an examination of Brazilian Palms, adopts the 
vertical theory, and Lindley also supports it. It is strongly opposed 
by Schleiden, Mirbel, Naudrn, Henfrey, and others, who consider the 
development of the vascular bundles, as proceeding from below up- 
wards; in Dicotyledons, by peripherical production of woody and vas- 
cular tissue from cambium cells ; and in Monocotyledons, by a definite 
formation of woody and vascular bundles by means of terminal buds ; 
the hardening of the stem depending on the interstitial changes which 
take place afterwards in the woody fibres. 

116. A consideration of all the observations made on the formation 
of woody stems, leads apparently to the conclusion, that there is an 
ascending and descending axis in plants, and that each plant consists 
of one or more individuals, or phytons (tpvrov, a plant), as they are 
called by Gaudichaud and others, having both axes developed ; the 
Exogenous stem being formed by the original formation of two oppo- 
site phytons, the Endogenous by one : and that woody fibres are 
produced from cells, which, in Exogens, are formed annually between 



FORMATION OF WOOD. 61 

the wood and bark, as cambium cells; and, in Endogens, are developed 
in the internal parts of the stem. Proof seems, however, still wanting 
of the direction in which the development of wood takes place in the 
former; while, in the latter, observations seem to be in favour of a 
vertical formation, or of additions of woody fibre being made in a 
downward direction, as in roots, thus following the course of the 
descending elaborated sap.* 

117. The formation of wood depends mainly on the functions of the 
leaves being carried on properly, and this can only be effected by ex- 
posure to air and light. The more vigorously the plant grows, the 
better is the wood produced. Experiments made in the British dock- 
yards proved that those oaks which had formed the thickest zones, 
yielded the best timber. Barlow's experiments at "Woolwich, showed 
that a plank of quick-grown oak, bore a greater weight than a similar 
plank of slow- grown oak. 

118. In order that trees may grow well, and that timber may be 
properly formed, great care should be taken in planting at proper 
distances and in soil fitted for the trees. Firs ought to be planted 
from 6 to 8 feet apart, and hardwood trees for a permanent plantation, 
28 feet distant, the spaces being filled up with larch, spruce, or Scotch 
fir, according to soil and situation. Hardwood is of no value till it has 
attained some age, while larch and spruce may be applied to use in ten 
or twelve years; and thus judicious thinning may be practised. 
When trees are set too close, their leaves are interrupted in their 
functions; many of them fall off, leaving the stems bare; the wood is 
imperfectly formed, and the roots are not sent out vigorously. When 
such plantations are allowed to grow without being thinned, the trees 
are drawn up without having a hold of the ground; and when a por- 
tion of them is subsequently removed, the remainder is easily blown 
over by the wind. In thick plantations, it is only on the trees next 
the outside, where the leaves and branches are freely formed, that the 
wood and roots are properly developed. When a tree is fully exposed 
to air and light on one side only, it is frequently found that the woody 
zones on that side are largest. When trees are judiciously planted, 
there is a great saving both in the original outlay and in the subse- 
quent treatment. Pruning or the shortening of branches, and the 
removal of superfluous ones ought to be cautiously practised. It is 
only applicable to young branches and twigs, and is had recourse to 
chiefly in the case of fruit-trees when the object is to make the plants 
produce flowers and fruit. If forest trees are properly planted and 
thinned, little pruning is required. 

* For full details relative to the formation of wood, see Gaudichaud, Recherches sur 1'Organo- 
graphie, &c., Paris, 1841 ; Mirbel, Annales des Sciences Naturelles, 3d series, torn, xx., &c. ; Nau- 
din, do., 3d series, torn. i. ; Henfrey, Annals of Natural History, 2d series, vol. i. 



62 



STKUCTURE OF ROOTS. 



ROOT OR DESCENDING AXIS. 

Structure of Roots. 

119. In the young state there is no distinction between stem and 
root, as regards structure; both being cellular, and an extension of 
each other in opposite directions. In stemless plants, as Thallogens, 
the root remains in a cellular state throughout the life of the plants. 
The root is afterwards distinguished from the stem, by the want of 
a provision for the development of leaf-buds, and by increasing from 
above downwards. Some plants, however, as the Moutan Pasony, the 
Plum-tree, Pyrus japonica, and especially Anemone japonica, have a 
power of forming buds on their roots. The last-mentioned plant 
developes these buds on every part of its extensively ramifying roots, 
which may be chopped into numerous pieces, each capable of giving 
rise to a new plant. The part where the stem and root unite is the 
collum or neck. In woody plants, the fibres of the stem descend into 
the roots, and there is a similar internal arrangement of woody layers, 
as is seen in the stem itself. 

120. Roots are usually subterranean and colourless. Externally, 
they have a cellular epidermal covering of a delicate texture, some- 
times called epiblema (^[ 47), in which no stomata exist. Their in- 
ternal structure consists partly of cells, and partly of vascular bundles, 

in which there are no vessels with fibres 
which can be unrolled. Roots do not ex- 
hibit true pith, nor a medullary sheath. 
The axis of the root gives off branches 
which divide into radicles or fibrils (fig. 119), 
the extremities of which are composed of 
loose sponge-like cellular tissue, and are 
called spongioles or spongelets. Over these 
a very thin layer of cells is extended, 
called, by Trecul, a Pileorhiza (y/xo?, a 
cup, and ^, a root). This sometimes 
becomes thickened, and separates in the 
form of a cup, as in Screw-pines (fig. 115, 
2), and in Lycopodiums. Occasionally 
the extremities of roots are enclosed in a 
sheath, or ampulla, as in Lemna. Cellular 
papillae and hairs are often seen in roots 
(fig. 77), but no true leaves. Roots do not 
grow throughout the whole length like stems, but by additions to their 




119 



Fig. 119. Tapering root of Malva rotumlifolia, giving off branches and fibrils. 



FORMS OF ROOTS. 63 

extremities, which are constantly renewed, so that the minute fibrils 
serve only a temporary purpose, and represent deciduous leaves. 

121. Roots, in some instances, in place of being subterranean, be- 
come aerial. Such roots occur in plants called Epiphytes, or air- 
plants (gV/, upon, and tpvrov, a plant, from growing on other plants), 
as Orchidaceee; also in the Screw-pine (fig. 115, 2), the Banyan (Fi- 
cus indica), and many other species of Ficus, where they assist in 
supporting the stem and branches, and have been called adventitious or 
abnormal. In Screw-pines, these aerial roots follow a spiral order 
of development. In Mangrove trees, they often form the entire 
support of the stem, which has decayed at its lower part. The name 
of adventitious has also been applied to those roots which are formed 
where portions of stems and branches, as of the Willow and Poplar, 
are planted in moist soil. They appear first as cellular projections, 
into which the fibres of the stem are prolonged, and by some are said 
to proceed from lenticels (*([ 63). They frequently arise from points 
where the epidermis has been injured. A Screw-pine in the palm- 
house of the Edinburgh Botanic Garden, had one of its branches in- 
jured close to its union with the stem. This branch was at the 
distance of several feet above the part where the aerial roots were in 
the course of formation. At the part, however, where the injury had 
been inflicted, a root soon appeared, which extended rapidly to the 
earth, and now the branch is firmly supported. 

122. Green-coloured aerial roots are frequently met with in endo- 
genous plants. Such roots possess stomata. In the Ivy, root-like 
processes are produced from the stem, by means of which it attaches 
itself to trees, rocks, and walls. In parasites, or plants which derive 
nourishment from other plants, such as Dodder (Cuscuta), roots are 
sometimes produced in the form of suckers, which enter into the cellu- 
lar tissue of the plant preyed upon. 

123. When roots have been exposed to the air for some time, they 
occasionally assume the functions of stems, losing their fibrils, and 
developing abnormal buds. Duhamel proved this experimentally, 
by causing the branches of a willow to take root while attached to 
the stem, and ultimately raising the natural roots into the air. 

Forms of Roots. 

124. The forms of roots depend upon the mode in which the axis 
descends and branches. When the central axis goes deep into the 
ground in a tapering manner, without dividing, a tap-root is pro- 
duced (fig. 119). This kind of root is sometimes shortened, and 
becomes succulent, forming the conical root of carrot, or the fusiform, 
or spindle-shaped root of radish, or the napiform root of turnip; or it 
ends abruptly, thus constituting the prcemorse (prcemorsus, bitten) root 
of Scabiosa succisa; or is twisted, as in the contorted root of Bistort. 



64 



FORMS OF ROOTS. 



125. When the descending axis is very short, and at once divides 
into thin, nearly equal fibrils, the root is called fibrous, as in many 
grasses; when the fibrils become short and succulent, the root is fasci- 
culated, as in Ranunculus Ficaria and Asphodelus luteus (fig. 120); when 
the succulent fibrils are of uniform size, and arranged like coral, the 
root is coralline, as in Corallorhiza innata; when some of the fibrils 
are developed in the form of tubercules containing starchy matter, as 
in Orchis, the root is tubercular (fig. 121); when the fibrils enlarge in 
certain parts only, the root is nodulose, as in Spiraea Filipendula (fig. 
122), or moniliform, as in Pelargonium triste (fig. 123), or annulated, as 
in Ipecacuanha. 




120 



126. Root of Dicotyledonous or Exogenous Plants. In these plants 

the root in its early state, or the radicle as it is then called, is a pro- 
longation of the stem, and elongates directly by its extremity. It then 
continues to grow in a simple or branched state (fig. 119). From this 
mode of root development, these plants have been called Exorhizal 
(lg<a, outwards, and pict, a root), by Eichard. In their after progress, 
these roots follow the arrangement seen in the woody part of the stem. 
In some cases, as in the Walnut and Horse-chestnut, there is a pro- 
longation of the pith into the root to a certain extent. 

127. Root of Monocotyledonons or Endogenous Plants. In these 

Fig. 120. Fasciculated root of Asphodelus luteus. 

Fig. 121. Tubercular root of Orchis. Several of the radical fibres retain their cylindrical form, 
while two are tubercules containing starchy matter. 
Fig. 122. Nodulose root of Spiraea Filipendula. 
Fig. 123. Moniliform root of Pelargonium triste. 



FORMS OF ROOTS. 



65 



plants, the young root or radicle pierces the lower part of the axis 
(fig. 124 r), is covered with a cellular sheath, c, and gives rise to 
numerous fibrils, r' r' r' r', which are similarly developed. These 
plants are therefore called by Eichard, Endorhizal (svlov, within); 
and the sheath is denominated Coleorhiza (xoheos, a sheath). In their 
after progress, they usually retain their compound character, con- 
sisting of fibrils, most of which often remain unbranched (figs. 120, 121). 
The first-formed roots which surround the axis, if the plant is peren- 
nial, gradually die, and others are produced in succession farther 
from the central axis. In Endogenous roots, the same structure is 
observed as in the stem. Thus, fig. 125 represents a section of a 





Palm root, composed of cellular tissue, porous vessels, v p, scalari- 
form vessels, v s, fibrous or woody tissue, f, and laticiferous vessels, I. 
Eoots are pushed out from various parts of the stems of many Palms, 
and ultimately appear as part of the external integument. 

128. Root of Acolj Icdonous or Acrogenous Plants. In these plants, 

the young root is a development of superficial cells from no fixed 
point, and they have been called Heterorhizal (er^os, diverse). In 
their subsequent progress, these roots present appearances similar to 
those seen in the stem. They frequently appear in the form of fibres 
on the outer part of the stem, giving rise, by their accumulation at the 
base, to the conical appearance represented in fig. 116 r a. 



Fig. 124. Grain of wheat germinating. <7, The mass of the grain, t, The young stem begin- 
ning to shoot upwards, r, The principal root of axis. i j r 1 r 1 r 1 , Lateral roots, covered like the 
preceding, with small hairs or threads, c c c, Coleorhiza or sheath, with which each of the roots 
is covered at its base, while piercing the superficial layer of the embryo. 

Fig. 125. Transverse section of part of the root of a Palm (Diplothemimn maritimum), to show 
the mode in which the cells and vessels are arranged, v p, Large porous vessels situated in the 
interior, v s, Scalariform vessels more external, and becoming smaller the farther they are from 
the centre. /, Fibrous tissue, or elongated cells, accompanying the vessels. I, Groups of latici- 
ferous vessels of different sizes, the larger being inside. 

F 



66 FUNCTIONS OF EOOTS. 

Functions of Boots. 

129. Roots fix the plant, either in the soil or by attachment to 
other bodies. They absorb nourishment by a process of imbibition 
or endosmose (^[ 27), through their spongioles or cellular extremities. 
The experiment of Duhamel and Senebier, conducted by inserting at one 
time the minute fibrils alone into fluid, and at another, the axis of the 
root alone, showed clearly that the cellular extremities were the chief 
absorbing parts of the roots. Hence the importance, in transplanting 
large trees, of cutting the roots some time before, in order that they 
may form young fibrils and spongelets, which are then easily taken 
up in an uninjured condition, ready to absorb nourishment. 

130. The elongation of the roots by their extremities, enables them 
to accommodate themselves to the soil, and allows the spongioles to 
extend deeply without being injured. Eoots in their lateral extension, 
bear usually a relation to the horizontal spreading of the branches, so 
as to fix the plant firmly, and to allow fluid nutritive substances to 
reach the spongioles more easily. It is of importance to permit the 
roots to extend easily in all directions. By restricting or cutting the 
roots, the growth of the plant is to a certain degree prevented, although 
it is sometimes made to flower and bear fruit sooner than it would 
otherwise have done. The system of restrictive potting, formerly 
practised in green-houses, often destroyed the natural appearance of 
the plants. The roots filled the pots completely, and even raised the 
plants in such a way as to make the upper part of the root appear above 
the soil. 

131. To roots there are sometimes attached reservoirs of nourish- 
ment, in the form of tubercules, containing starch and gum (fig. 121), 
which are applied to the nourishment of the young plant. These are 
seen in the Dahlia and in terrestrial Orchids. In epiphytic Orchids, 
on the other hand, the roots are aerial, and the stems are much 
developed, forming pseudo-bulbs. Upon the roots of Spondias tuberosa 
there exist round black-coloured tubercules, about eight inches in 
diameter, consisting internally of a white cellular substance, which is 
full of water. These tubercules seem to be intended to supply water 
to the tree during the dry season. They are often dug by travellers, 
each of them yielding about a pint of fluid of excellent quality. 

132. Roots also give off" certain excretions, which differ in different 
species. These are given off by -a process of exosmose (^[ 27), and 
consist both of organic and inorganic matter. They were examined 
by Macaire and Decandolle, and at one time they were thought to be 
injurious to the plant, and by their accumulation to cause its deterio- 
ration. It was also supposed, that while they were prejudicial to the 
species of plant which yielded them, they were not so to others, and 
that hence a rotation of crops was necessary. Daubeny and Gyde 



STRUCTURE OF LEAVES. 



67 



have found by experiment, that these excretions are not injurious, 
and it is now shown, that the necessity for rotation depends on the 
want of certain nutritive matters in the soil.* In very rich and fertile 
land, the same crop may be grown successively for many years. 



LEAVES AND THEIK APPENDAGES. 

Structure of Leaves. 

133. Leaves are expansions of the bark, developed in a symmetrical 
manner, as lateral appendages of the stem, and having a connection 
with the internal part of the ascending axis. They appear at first as 
small projections of cellular tissue, continuous with the bark, and 
closely applied to each other. These gradually expand in various 
ways, acquire vascular tissue, and ultimately assume their permanent 
form and position on the axis. They may be divided into aerial and 
submerged leaves, the former being produced in the air, and the latter 
under water. 

134. Aerial Leaves. These leaves consist of vascular tissue in the 
form of veins, ribs, or nerves, of cellular tissue or parenchyma filling up 
the interstices between the veins, and of an epidermal covering. 

135. The Vascular System of the leaf is continuous with that of the 
stem, those vessels which occupy the internal part of the stem becoming 
superior in the leaf, while the more external become inferior. Thus, in 
the upper part of the leaf, which may re- 
present the woody layers, there are spiral 

vessels (fig. 126 t), annular reticulated or 
porous vessels, v, and woody fibres, f; 
whilst in the lower side, which may repre- 
sent the bark, there are laticiferous ves- 
sels and fibres, resembling those of liber, I. 
There are usually two layers of fibro- 
vascular tissue in the leaf, which may be 
separated by maceration. They may be 
seen in what are called skeleton leaves, in 
which the cellular part is removed, and 
the fibro-vascular left. The vascular 
system of the leaf is distributed through 
the cellular tissue in the form of simple 
or branching veins. 

* This subject is considered when the sources whence plants derive their nourishment are 
treated of. 

Fig. 126. Bundle of fibro-vascular tissue, passing from a branch, 6, into a petiole, p. The 
vessels are first vertical, then nearly horizontal, but they continue to retain their relative posi- 
tion. Changes take place in the size of the cells at the articulation a. 1 1, Tracheae, in which 
the fibre can be unrolled, v v, Annular vessels. //, Woody fibres. 1 1, Cortical fibres, or fibres 
of liber. 




68 



STRUCTURE OF LEAVES. 



136. The Epidermis (fig. 127 e s, ei), composed of cells more or 
less compressed, has usually a different structure and aspect on the two 
surfaces of the leaf. It is chiefly on the epidermis of the lower sur- 
face (fig. 128 ez), that stomata, s s, are produced, occupying spaces 





between the veins, and it is there also that hairs usually occur. In 
these respects, the lower epidermis resembles the outer bark of 
young stems, with which it may be said to correspond. The lower 
epidermis is often of a dull or pale-green colour, soft, and easily de- 
tached. The upper epidermis (figs. 127 and 128 e s) is frequently 
smooth and shining, and sometimes becomes very hard and dense. In 
leaves which float upon the surface of water, as those of the water- 
lily, the upper epidermis alone possesses stomata (^[ 56). On removing 
a strip of epidermis, part of the parietes of the cells below is often 
detached in the form of a green net- work (fig. 129 p p), and on 

examination under the microscope, the 
stomata, s s, are seen communicating 
with colourless spaces, III, surrounded 
by green matter. 

137. The Parenchyma of the leaf IS 

the cellular tissue surrounding the ves- 
sels, and enclosed within the epidermis 
(fig. 127 PS, pi). It has sometimes re- 
ceived the names of Diachyma (S/, in 
the midst, and xvpa., tissue), or Meso- 

phyllum (pwos, middle, and (pv^ov, a leaf), or Diploe (S/TrXo??, a cov- 
ering). It is formed of two distinct series of cells, each containing 
chlorophylle or green-coloured granules, but differing in their form 

Fig. 127. Thin vertical section of the leaf of a Lily, highly magnified, ef, Epidermis of upper 
pagina or surface, e i, Epidermis of lower surface, p s. Parenchyma of upper portion of the leaf, 
composed of close vertically-placed cells, p i, Parenchyma of lower portion, composed of loose 
horizontal cells, in, Intercellular passages. 1 1, Lacuna;. 

Fig. 128. Similar section of the leaf of Balsam. The letters denote the same parts as in fig. 
127. s s, Stomata. 

Fig. 129. Strip of the lower epidermis, e e, of the leaf of Balsam, showing a net-work formed 
by a portion of the parenchyma below, p p, being detached. The spaces of the net are lacunae, 
III, often corresponding to stomata, s s. 




STRUCTURE OF LEAVES. 



69 



and arrangement. This may be seen on making a vertical section 
of a leaf, as in fig. 127. Below the epidermis of the upper side of 
the leaf, there are one or two layers of oblong blunt cells, placed 
perpendicularly to the surface (fig. 127 p s), and applied so closely 
to each other as to leave only small intercellular spaces (fig. 127 TO), 
except when stomata happen to be present. On the under side of 
the leaf, the cells are irregular, often branched, and are arranged 
more or less horizontally (fig. 127 p i), leaving cavities between them, 
I , which often communicate with stomata (fig. 128 s s). On this ac- 
count the tissue has received the name of cavernous. The form and 
arrangement of the cells, however, depend much on the nature of the 
plant, and its exposure to light and air. Sometimes the arrangement 
of the cells on both sides of the leaf is similar, as occurs in leaves which 
have their edges presented to the sky. In very succulent plants, the 
cells form a compact mass, and those in the centre are often colour- 
less. In some cases the cellular tissue is deficient at certain points, 
giving rise to distinct holes in the leaf, as in Dracontium pertusum. 

138. Submerged Leaves. Leaves which are developed under 
water differ in many points of structure from aerial leaves. They 
have no fibro- vascular system, but consist of a congeries of cells which 
sometimes become elongated and compressed so as to resemble veins. 
They have a layer of compact cells on their surface (fig. 130 j>), but no 
true epidermis, and no stomata. The internal structure consists of 
cells, disposed irregularly, and sometimes leaving spaces which are filled 
with air for the purpose of floating the leaf (fig. 130 /). When ex- 
posed to the air, these leaves easily part with their moisture, and be- 
come shrivelled and dry. In some instances there is only a net-work 





of filamentous-like cells formed, the spaces between which are not 
filled with parenchyma, giving a peculiar skeleton appearance to the 
leaf, as in Hydrogeton or Ouvirandra fenestralis (fig. 131). Such a 
leaf has been called fenestrate (fenestra, a window). 

Fig. 130. Perpendicular section through a small portion of the submerged leaf of Potamogeton 
perfoliatus. p. Parenchyma. J, Lacunae. 

Fig. 13L Fenestrate leaf of Ouvirandra fenestralis, composed of vascular tissue, without inter- 
vening cellular tissue or diachyma. 




70 STRUCTURE OP LEAVES. 

139. A leaf, in general, whether aerial or submerged, consists of a 
flat expanded portion (fig. 132 I), called the blade, limb, or laminar 
menthal (fttyos, a part, and 0XAoV, a frond), of a narrower portion 
called thepetiole (petiolus, a little foot or stalk), stalk, orpetiolary merithal 

(fig. 132 p), and sometimes of a portion 
at the base of the petiole, which forms a 
sheath or vagina (fig. 132 #), or is de- 
veloped in the form of leaflets, called 
stipules (fig. 191 s). The sheathing por- 
tion or vagina merithal is sometimes 
incorporated with the stem, and has 
been called Tigellary (tige, Fr., a stem 
or stalk), by Gaudichaud. These por- 
tions are not always present. The 
sheathing, or stipulary portion, is fre- 
quently awanting, and occasionally only 
one of the other two is developed. 
When a leaf has a distinct stalk it is called petiolate; when it has none, 
it is sessile (sessilis, from sedeo, I sit). When sessile leaves embrace 
the stem, they are called amplexicaul (amplector, I embrace, and caulis, 
a stem). The part of the leaf next the petiole or the axis is its base, 
while the opposite extremity is the apex. The surfaces of the leaf are 
called the pagince (pagina, a flat page), and its edges or margins form 
the circumscription of the leaf. The leaf is usually horizontal, so that 
the upper pagina is directed towards the heavens, and the lower pagina 
towards the earth ; but in many cases leaves are placed vertically, as 
in some Australian Acacias, Eucalypti, &c. ; in other instances, as ia 
Alstromeria, the leaf becomes twisted in its course, so that what is 
superior at one part becomes inferior at another. 

140. The upper angle formed by the leaf with the stem is called its 
axil (axilla, arm-pit), and every thing arising at that point is called 
axillary. It is there that leaf-buds (* 178) are usually developed. 
The leaf is sometimes articulated with the stem, and when it falls off" 
a scar or cicatricula remains ; at other times it is continuous with it, 
and then decays gradually, while still attached to the axis. In their 
early state all leaves are continuous with the stem, and it is only in 
their after-growth that articulations are formed. When leaves fall 
off annually, they are called deciduous; when they remain for two 
or more years, they are evergreen. The laminar portion of a leaf is 
occasionally articulated with the petiole, as in the Orange (fig. 185), 
and a joint at times exists between the vaginal or stipulary portion 
and the petiole. 

Fig. 132. Leaf of Polygonum Hydropiper, with a portion of the stem bearing it ?, Limb 
lamina, or blade, p, Petiole or leaf-stalk, g. Sheath or vagina, embracing the stem, and ter- 
minated by a fringe. 



STRUCTURE OF LEAVES. 



71 



Distribution of the Veins, or Venation of Leaves. 

141. The distribution of the veins has been called Venation, some- 
times Nervation. In most leaves this can be easily traced, but in 
the case of succulent plants, as Hoya, Agave, and Mesembryanthemum, 
the veins are obscure, and the leaves are said to be Hidden-veined 
(figs. 171, 172). In the lower tribes of plants, as sea- weeds, and in 
submerged leaves, there are no true veins, but only condensations of 
elongated cellular tissue, and the term Veinless (avenid) is applied. 
In an ordinary leaf, as that of Lilac or Chestnut, there is observed a 
central vein larger than the rest, called the midrib (fig. 133 TO); this 
gives off veins laterally (primary veins), ns ns ns, which either end in a 
curvature within the margin, as in Lilac (fig. 133), or go directly to 
the edge of the leaf, as in Oak and Chestnut (fig. 134). If they are 
curved, then external veins and marginal veinlets are 
interspersed through the parenchyma external to the 
curvature. There are also other veins of less extent 
(costal veins) given off by the midrib, and these give 
origin to small veinlets. In some cases, as Sycamore and 
Cinnamon, in place of there being only a single central 
rib, there are several which diverge from the part where 





Fig. 133. Leaf of Belladonna, p, Petiole or leaf-stalk, nm, Midrib, nsnsns. Primary 
veins, ending in curvatures at their extremities. 

Fig. 134. Leaf of Oak, pinnatifld or divided into lobes in a pinnate manner ; feather-veined, 
the veins going directly to the margin. 

Fig. 135. Leaf of Banana, showing midrib and primary veins running parallel and in a curved 
manner to the margin. No reticulation. Plant monocotyledonous. 



72 STRUCTURE OP LEAVES. 

the blade joins the petiole or stem. Thus, the primary veins give off 
secondary veins, and these in their turn give off tertiary veins, and so 
on, until a complete net-work of vessels is produced. To such a dis- 
tribution of veins, the name of Reticulated or Netted venation has 
been applied. 

142. In the leaves of some plants there exists a central rib or mid- 
rib, with veins running nearly parallel to it from the base to the apex 
of the leaf, as in grasses (fig. 194) and Fan palms; or with veins com- 
ing off from it throughout its whole course, and running parallel to 
each other in a straight or curved direction towards the margin of the 
leaf, as in Plantain and Banana (fig. 135). In these cases the veins 
are often united by cross veinlets, which do not, however, form an 
angular net-work. These are called Parallel-veined. 

143. Leaves may thus be divided into two great classes, according 
to their venation Reticulated or netted leaves, in which there is an 
angular net-work of vessels, as occurs generally in the leaves of exo- 
genous or dicotyledonous plants; and Parallel-veined, in which the 
veins run in a straight or curved manner from base to apex, or from 
the midrib to the margin of leaf, and in which, if there is a union, 
it is effected by transverse veins which do not form an angular net- 
work. This kind of leaf occurs commonly in endogenous or monocotyle- 
donous plants. 

144 TABULAR ARRANGEMENT OP VENATION. 

A. Reticulated Venation. 
L Unicostate (unus, one). A single rib or costa in the middle (midrib). 

1. Primary veins coming off at different points of the midrib. 

a. Veins ending in curvatures within the margin (fig. 133), and forming 
what have been called true netted leaves (Lilac). 

6. Veins going directly to the margin (fig. 134), and forming feather- 
veined leaves (Oak and Chestnut). 

2. Primary veins coming off along with the midrib (fig. 143) from the base 

of the leaf. 

II. Midticostate (multus, many). More than one rib. In such cases there 
are frequently three (tricostate), as in fig. 162 ; or five (quinquecos- 
tate), as in fig. 158. Authors usually give to these leaves the 
general name of costate, or ribbed. 

1. Concostate (con, together, costa, a rib). Ribs converging, running from 

base to apex in a curved manner, as in Cinnamon, Laurus Cinna- 
momum(fig. 158). There is occasionally an obscure rib running close 
to the edge of the leaf, and called intramarginal, as in the Myrtle. 

2. Discostate (dis, separate). Ribs diverging or proceeding in a radiating 

manner; this is called radiating venation, and is seen in Sycamore, 
Vine, Geranium (figs. 144, 146). 

B. Parallel Venation. The term parallel is not strictly applicable, for the veins 
often proceed in aradiating manner, but it is difficult to find a compre- 
hensive term. This venation may be characterised as not reticulated. 
L Veins proceeding from midrib to margin, usually with convexity towards 
the midrib, as in Musa and Canna (fig. 135). 



FOKMS OF SIMPLE LEAVES. 



73 



II. Veins proceeding from base to apex. 

1 . Veins more or less convergent (fig. 1 73), as in Iris, Lilies, Grasses (fig. 194 ). 

2. Veins more or less divergent, as in Fan Palms. 

To this may be added the venation common in Ferns where the veins divide 
in a forked manner. This venation has been called Furcate (furca, a fork). 

Forms of Leaves. 

145. Leaves have been divided into simple and compound. The 
former have no articulation beyond the point of their insertion on the 
stem, or consist of one piece only, which, however, may be variously 
divided (figs. 136, 137, 138, &c.). The latter have one or more artic- 






ulations beyond the point of their insertion on the stem, or consist of 
one or more leaflets (foliola) separately attached to the petiole or leaf- 
stalk (fig. 141). In the earliest stage of growth all leaves are simple 
and undivided, and it is only during the subsequent development 
that divisions appear. The forms which the different kinds of simple 
and compound leaves assume, are traced to the character of the 
venation, and to the amount of parenchyma produced. 

146. Simple Leaves. When the parenchyma is developed symme- 
trically on each side of the midrib or stalk, the leaf is equal (fig. 149); 
if otherwise, the leaf is unequal or oblique (fig. 136), as in Begonia. If 
the margins are even and present no divisions, the leaf is entire (in- 

Fig. 136. Leaf of Ulmus effusa. Reticulated venation ; primary veins going to the margin, 
which is serrated, Leaf unequal at the base. 
Fig. 137. Pinnatifld leaf of Valeriana dioica. 
Fig. 138. Bipinnatifld leaf of Papaver Argemone. Feather-veined. 



74 



teger), as in figs. 149 and 150; if there are slight projections of cellular 
or vascular tissue beyond the margin, the leaf is not entire (fig. 136); 
when the projections are irregular and more or less pom ted, the leaf 
is dentate or toothed (fig. 155); when they lie regularly over each 
other, like the teeth of a saw, the leaf is serrate (figs. 136, 154); when 
they are rounded, the leaf is crenate (fig. 159). If the divisions extend 
more deeply than the margin, the leaf receives different names accord- 
ing to the nature of the segments: thus, when the divisions extend 
about halfway down (figs. 134, 144), it is cleft (Jissus), and its segments 




139 



140 



141 



are called fissures (fissura, a cleft); when the divisions extend nearly 
to the base or to the midrib (fig. 170), the leaf is partite, and its 
segments are called partitions. 

147. These divisions take place in simple leaves exhibiting differ- 
ent kinds of venation, and thus give rise to marked forms. Thus, if 
they occur hi a feather-veined leaf (fig. 137), it becomes either pin- 
natifid (pinna, a wing or leaflet, and Jissus, cleft), when the segments 
extend to about the middle and are broad; or pectinate (pecten, a 
comb), when they are narrow; or pinnatipartite, when the divisions ex- 
tend nearly to the midrib. These primary divisions may be again sub- 
divided in a similar manner, and thus a feather-veined leaf will become 
lipinnatifid (fig. 138), or bipinnatipartite ; and still further subdivisions 
give origin to tripinnatifid and laciniated leaves. If the divisions of a 
pinnatifid leaf are more or less triangular, and are pointed downwards 
towards the base, the extremity of the leaf being undivided and tri- 
angular, the leaf is rundnate (runcina, a large saw), as in the Dande- 
lion. When the apex consists of a large rounded lobe, and the divi- 
sions, which are also more or less rounded, become gradually smaller 
towards the base (fig. 139), as in Barbarea, the leaf is called lyrate, 
from its resemblance to an ancient lyre.* When there is a concavity 

Fig. 139. Lyrate leaf of Barbarea. 

Fig. 140. Panduriform, a fiddle-shaped leaf of Rumex pulcher. 

Fig. 141. Compound leaf; ternate, the leaflets being obcordate. 

Fig. 142. Compound leaf; quaternate, the leaflets being rotundate-cuneiform, or wedge- 
shaped with rounded apices. 

Fig. 143. Two-lobed leaf, somewhat cordate at the base, emarginate, and mucronate. 

Fig. 144. Palmate leaf, the divisions acute and serrated at their margins. Radiating vena- 
tion. 

* Under the term lyrate, some include compound pinnate leaves in which the several pinnse 
are united at the apex of the leaf, and the others become gradually smaller towards the base. 



FORMS OF SIMPLE LEAVES. 



75 



on each side of a leaf, so as to make it resemble a violin, as in Rumex 
pulcher (fig. 140), it is called panduriform (^roe,v^w^x, fiddle). 

148. The same kind of divisions taking place in a simple leaf 
with radiating venation, gives origin to the terms lobed or cleft 
(figs. 174, 146), when the divisions extend about half-way through 
the leaves : and thus they may be three-lobed, five-lobed, seven- 
lobed, many-lobed; or, trifid, quinquefid, septemfid, multifid, according 
to the number of divisions. The name of palmate, or palmatifid 
(fig. 144), is applied to leaves with radiating venation, in which 
there are several fissures united by a broad expansion of parenchyma, 
like the palm of the hand, as in Passion-flower and Rheum palma- 
tum ; while digitate (digitus, a finger), or digitipartite, includes leaves 
in which there are deeper partitions, five in number, like the fingers, 
as in Janipha ; and dissected applies to leaves with radiating venation, 
having numerous narrow divisions, as in Geranium dissectum. When 
in a radiating leaf there are three primary partitions and two lateral 
ones spreading and forming divisions on their inner margin only, as 
in Helleborus (fig. 170), the leaf is called ^jeJate or pedatifid (pes, a 
foot), from a fancied resemblance to the claw of a bird. 

149. In all the instances already alluded to, the leaves have been 
considered as flat expansions in which the ribs or veins spread out on 
the same planes with the stalk. In some cases, however, the veins 
spread at right angles to the stalk. If they do so equally on all sides, 
and are united by parenchyma, so that the stalk occupies the centre 
(fig. 145), the leaf becomes orbicular (orbis, a circle), as in Hydrocotyle; 
if unequally, so that the stalk is not in the centre, the leaf is peltate 
(pelta, a buckler), as in the 

Castor oil plant (fig. 146). 
The edges or margins of or- 
bicular and peltate leaves 
are often variously divided. 

150. It is impossible to 
notice all the forms of 
leaves without exceeding 
due limits. The following 
are enumerated as the 
most important. When 
the veins do not spread 
out, but run from the base 
to the apex with a narrow 

strip of parenchyma, the leaf is linear or acicular (fig. 147), as in 

Fig. 145. Orbicular leaf of Hydrocotyle vulgaris. Radiating venation, p, Petiole. /, La- 
mina. 

Fig. 146. Peltate leaf of Ricinus communis, or Castor oil plant. Radiating venation, p, Petiole 
or leaf-stalk. I, Lamina or blade. 

Fig. 147. Linear, or acicular leaf of Fir. 




(I 



140 



147 



76 



FORMS OF SIMPLE LEAVES. 



Pines and Firs. When the veins diverge, those in the middle 
being longest, and the leaf tapering at each end (fig. 166), it becomes 
lanceolate (lancea, a spear). If the middle veins only exceed the others 
slightly, and the ends are convex, the leaf is either rounded (rotun- 
datus), as in fig. 164, elliptical (fig. 162), oval (fig. 149), or oblong (fig. 
150). If the veins at the base are longest, the leaf is ovate or egg- 
shaped, as in Chick-weed (fig. 152), and if those at the apex are 
longest, the leaf is obovate, or inversely egg-shaped. Leaves are cuneate 
(cuneus, a wedge) or wedge-shaped, in Saxifraga (fig. 155); spathulate, 
or spatula-like, having a broad rounded apex, and tapering down to 
the stalk in the Daisy (fig. 148); subulate (fig. 167), 
or narrow and tapering like an awl (subula); acu- 
minate, or drawn out into a long point, as in Ficus 
religiosa (fig. 159), mucronate, with a hard stiff point 
or mucro at the apex (figs. 160 and 143). When the 





102 



153 



parenchyma is deficient at the apex so as to form two rounded lobes, 
the leaf is obcordate or inversely heart-shaped ; when the deficiency 
is very slight, the leaf is called emarginate (fig. 143) as having a por- 
tion taken out of the margin ; when the apex is merely flattened or 




150 



159 



160 



Fig. 148. Spathulate leaf of Daisy. Fig. 149. Oval leaf. Fig. 150. Oblong leaf. 

Fig. 151. Petiolated, reticulated, somewhat oblong leaf, truncate at the base. 

Fig. 152, Ovate pointed leaf. Fig. 153. Cordate pointed leaf. 

Fig. 154. Ovato-lanceolate leaf, i. e. lanceolate in its general contour, but ovate at the base 
doubly serrated, or having large and small serratures alternately at the margin. 

Fig. 155. Cuneate or wedge-shaped leaf of Saxifraga, ending in an abrupt or truncate manner, 
and toothed or dentate at the apex. 

Fig. 156. Perfoliate leaf of Bupleurum, formed by lobes uniting at the base on the opposite 
side of the stem from that to which the leaf is attached. 

Fig. 157. Retuse leaf, i. e. slightly depressed at the apex. Margin slightly waved. 

Fig. 158. Ovate, five-ribbed leaf. 

Fig. 159. Rounded acuminated leaf of Ficus religiosa, with the margin crenate or slightly 
sinuous. 

Fig. 160. Sub-ovate, retuse, mucronate leaf 



FORMS OF SIMPLE LEAVES. 



77 




slightly depressed (fig. 157), the leaf is refuse (retusus, blunt) ; and 
when the apex ends abruptly in a straight margin, as in the Tulip 
tree (fig. 163), the leaf is 
truncate. When the vena- 
tion is prolonged down- 
wards at an obtuse angle 
with the midrib, and round- 
ed globes are formed, as in 
Dog-violet, the leaf is cor- 
date or heart-shaped (fig. 
153), or kidney-shaped (reniform} when the apex is rounded (fig. 
161), as in Asanun. When the lobes are prolonged downwards 
and acute (fig. 165), the leaf is sagittate (sagitta, an arrow); when 
they proceed at right angles, as in Eumex Acetosella, the leaf is hastate 
(hasta, a halbert) or halbert-shaped. When a simple leaf is divided 
at the base into two leaf-like appendages (fig. 169), it is called auricu- 
late (auricula, the ear). When the veins spread out in various planes, 
and there is a large development of cellular tissue, so as to produce a 
succulent leaf, such forms occur as conical, prismatical, ensiform or 
sword-like (ensis, a sword), acinaciform (acinaces, a scimitar) or scimitar- 
shaped (fig. 172), and dolabrifoi~m (dolabra, an axe) or axe-shaped 
(fig. 171). When the development of cells is such that they more than 
fill up the spaces between the veins, the margins become wavy, crisp, 




164 



165 



or undulated, as in Rumex crispus and Eheum undulatum (fig. 1 74). 
By cultivation the cellular tissue is often much increased, giving rise 
to the curled leaves of Greens, Savoys, Cresses, Lettuce, &c. 

151. Compound Leaves are those in which the divisions extend to 

Fig. 161. Reniform or kidney-shaped entire leaf of Asarum. Radiating venation. 

Fig. 102. Elliptical and somewhat lanceolate leaf; three-ribbed. 

Fig. 163. Three-lobed, truncate, or abrupt leaf of Liriodendron tnlipifera. 

Fig. 164. Rounded entire leaf, ending in a short point 

Fig. 165. Sagittate or arrow-shaped leaf of Sagittaria. 

Fig. 166. Lanceolate, acute leaf, with minute teeth or dentations at the margin. 

Fig. 167. Subulate or awl-shaped leaf. 

Fig. 168. Whorl or verticil of linear-obovate leaves. 

Fig. 169. Auriculate lanceolate leaf, oblique at the base, with minute toothings at the margin. 



78 



FOKMS OF COMPOUND LEAVES. 



the midrib, or petiole (fig. 175), and receive the name of foliola or 
leaflets. The midrib, or petiole, has thus the appearance of a branch 




170 171 172 173 174 

with separate leaves attached to it, but it is considered properly as 
one leaf, because in its earliest state it arises from the axis as a single 
piece, and its subsequent divisions in the form of leaflets are all in 
one plane. When a compound leaf dies, it usually separates as one 
piece. The leaflets are either sessile (fig. 176), or have stalks, called 





petiolules (fig. 175), according as the vascular bundles of the veins 
spread out or divaricate at once, or remain united for a certain length. 

Fig. 170. Pedate or pedatifid leaf of Hellebore. Radiating venation. 

Fig. 171. Dolabriform or axe-shaped fleshy succulent leaf. Hidden-veined. 

Fig. 172. Acinaciform or scimitar-shaped succulent leaf. Hidden-veined. 

Fig. 173. Oval leaf with converging veins ; not reticulated. 

Fig. 174. Palmately-lpbed leaf, crisp or undulated at the margin. Radiating venation. 

Fig. 175. Leaf of Robinia pseudo-acacia, often called Acacia. The leaf is impari-pinnate, or 
alternately pinnate. The pinna are supported on stalks or petiolules. p, Petiole or leaf-stalk. 
I, Lamina or blade divided into separate leaflets or pinnae. 

Fig. 176. Septenate leaf of jEsculus Hippocastanum or Horse Chestnut, p, Petiole. I, Lamina, 
divided into seven separate leaflets. 



FORMS OF COMPOUND LEAVES. 



79 



152. Compound leaves have been classified according to the nature 
of the venation, and the development of parenchyma. In a feather- 
veined leaf, if the divisions extend to the midrib, and each of the 
primary veins spreads out or branches so as to become covered with 
parenchyma, and thus form separate leaflets, which are usually articu- 
lated to the petiole or midrib (fig. 177), the leaf is pinnate (pinna, a 
wing or feather). If the midrib and primary veins are not covered 
with parenchyma, while the secondary (or those coming off in a feather- 
like manner from the primary veins) are, and separate leaflets are 
thus formed which are usually articulated with the veins, the leaf is 
bipinnate (fig. 178). In this case the secondary veins form as it were 
partial petioles. A farther sub-division, in which the tertiary veins 
only are covered with parenchyma and have separate leaflets, gives tri- 
pinnate or decompound, in which case, the tertiary veins form the partial 
petioles; and a leaf divided still more is called supradecompound (fig. 
179). 

153. When a pinnate leaf has one pair of leaflets, it is unijugate 




(unurn, one, and jugum, a yoke); when it has two pairs, it is bijugate; 
many pairs, multijugate (fig. 175). When a pinnate leaf ends in a 
pair of pinnae (fig. 177), it is equally or abruptly pinnate (pari-pinnate); 
when there is a single terminal leaflet (fig. 175), the leaf is unequally 
pinnate (impari-pinnate) ; when the leaflets or pinna? are placed alter- 
nately on either side of the midrib, and not directly opposite to each 

Fig. 177. Pari-pinnate leaf with six pairs of pinnae (sexjugate). 

V\K. 178. Bipinnate leaf, with sessile foliola or leaflets. 

Fig. 179. Part of the supradecompound leaf of Laserpitium hirsutum. 



80 



FORMS OP COMPOUND LEAVES. 



other, the leaf is alternately pinnate (fig. 175); and when the pinna? 
are of different sizes, the leaf is interruptedly pinnate (fig. 180). 

154. In the case of a leaf with radiating venation, if the ribs are 
separately covered with parenchyma, and each leaflet is articulated to 
the petiole, the leaf becomes ternate (figs. 141, 181)if there are three 
divisions; quaternate, if four (fig. 142); quinate, if five; septenate, if 
seven (fig. 176), and so on.* If the three ribs of a ternate leaf sub- 
divide each into three primary veins, which become covered with 
parenchyma so as to be separate articulated leaflets, the leaf is biternate; 
and if another three-fold division takes place, it is triternate (fig. 182). 




.1S2 



155. Petiole OP Leaf-stnlk. This is the part which unites the limb 
or blade of the leaf to the stem (figs. 132 and 175 p). It consists of one 
or more bundles of vascular tissue, with a varying amount of paren- 
chyma. The vessels are, spiral- vessels connected with the medullary 
sheath in Exogens and with the fibro-vascular bundles in Endogens, 
porous vessels and other forms of fibro-vascular tissue, woody tissue, 
and laticiferous vessels. These vessels are enclosed in an epider- 
mal covering, with few stomata, and are more or less compressed. 
When the vascular bundles reach the base of the lamina, they separate 
and spread out in various ways, as already described under venation. 
A large vascular bundle is continued through the lamina to form the 
midrib (fig. 133, n m), and sometimes several large bundles form 
separate ribs (figs. 146, 162), whilst the ramifications of the smaller 
bundles constitute the veins. 

156. At the place where the petiole joins the stem, there is fre- 

* Some apply the term digitate to radiating compound leaves with five or seven leaflets. 

Fig. 180. Impart -and alternately pinnate leaf. Leaflets or pinnas sessile, and serrated at the 
margin. 

Fig. 181. Ternate leaf of Strawberry. Margin of leaflets, toothed or dentate, p, Petiole with 
projecting hairs. I, Lamina divided into three leaflets. 

Fig. 182. Tritemate leaf. Leaflets cordate. 



FORMS OF PETIOLES OB LEAF-STALKS. 



81 



quently an articulation or a constriction with a tendency to disunion, 
and at the same time there exists a swelling (fig. 203 JP), called pulvmus 
(pulvmw, a cushion), formed by a mass of cellular tissue. At other 
times the petiole is not articulated, but is either continuous with the 
stem, or forms a sheath around it. At the point where the petiole 
is united to the lamina, or where the midrib joins the leaflets of a 
compound leaf, there is occasionally a cellular dilatation called struma 
(struma, a swelling), with an articulation. This articulation or joint is 
by many considered as indicating a compound leaf, and hence the leaf of 
the orange is considered as such, although it consists of one undivided 
lamina (fig. 185). In articulated leaves, the pulvinus may be attached 
either to the petiole or to the axis, and may fall with the leaf, or remain, 
attached to the stem. When articulated leaves drop, their place is marked 
by a cicatrix or scar, seen below the bud in fig. 203. In this scar, the re- 
mains of the vascular bundles, c, are seen; and its form furnishes charac- 
ters by which particular kinds of trees may be known when not in leaf. 
157. The petiole varies in length, being usually shorter than the lamina, 
but sometimes much longer. In some palms it is fifteen or twenty 
feet long, and is so firm as to be used for poles or walking-sticks. 
In general, the petiole is more or less rounded in its form, the upper 
surface being flattened or grooved. Sometimes it is compressed later- 
ally, as in the Aspen, and to this peculiarity the trembling of the leaves 
of this tree is attributed. In aquatic plants, the leaf-stalk is sometimes 
distended with air 
(fig. 183 />), as in 
Pontederia and Tra- 
pa, so as to float 
the leaf. At other 
times it is winged, 
or has a leaf-like ap- 
pearance, as in the 





183 184 185 

pitcher plant (fig. 184 p), orange (fig. 185 p), lemon, and Dionsea 

Fig. 183. Leaf with a quadrangular toothed lamina or blade, /, and an inflated petiole, p, con- 
taining air cells. 

Fig. 184. Ascidium or pitcher of Nepenthes, p, Winged petiole which becomes narrowed, and 
then expands so as to form the pitcher by being folded on itself. , The operculum or lid, formed 
by the blade of the leaf, and articulated to the pitcher. 

Fig. 18-5. Leaf of Orange, which some call compound, p, Dilated or winged petiole, united by 
an articulation to the blade. In such a leaf, if the vessels of the petiole were developed in a cir- 
cular manner, so as to form a pitcher, the lamina or blade would form the jointed lid. 

G 



82 



FORMS OF PETIOLES OK LEAF-STALKS. 



(fig. 186 p). In some Australian Acacias, and in some species of 
Oxalis, Bupleurum, &c., the petiole is flattened in a vertical direc- 
tion, the vascular bundles separating immediately after quitting the 




stem, and running nearly parallel from base to apex. This kind 
of petiole (fig. 188 p), has been called Phyllodium (<p^xxo, a leaf, 
and ?8o? , form). In these plants the lamina? or blades of the leaves 
are pinnate, bipmnate, or ternate, and are produced at the extre- 
mities of the phyllodia in a horizontal direction (fig. 188 I) ; but in 
many instances they are not developed, and the phyllodium serves 
the purpose of a leaf. Hence, some Acacias are called leafless. These 
phyllodia, by their vertical position, and their peculiar form, give a 
remarkable aspect to vegetation. On the same Acacia, there occur 
leaves with the petiole and lamina perfect ; others having the petiole 
slightly broadened or winged, and the lamina imperfectly developed ; 
and others in which there is no lamina, and the petiole becomes large 

Fig, 186. Leaf of Dioiuea muscipnla, or Venus' Fly-trap, p. Dilated or winged petiole, 
e, Jointed blade, the two fringed halves of which fold on each other, when certain hairs on the 
upper surface are touched. 

Fig. 187. Ascidium, or Pitcher of Sarracenia, formed by the petiole of the leaf. The lid is not 
articulated to the pitcher as hi Nepenthes (fig. 184). 

Fig. 188. Leaf of Acacia heterophylla. p, Phyllodium or enlarged petiole, with straight 
venation. / /, Lamina or blade which is bipinnate. The blade is frequently awanting, and the 
phyllodium is the only part produced. 



STRUCTURE AND FORMS OF STIPULES. 83 

and broad. Some petioles, in place of ending in a lamina, form a 
tendril or cirrhus (If 201), so as to enable the plant to climb. 

Stipules. 

158. At the place where the petiole joins the axis, a sheath 
(vagina) is sometimes produced, which embraces the whole or part of 
the circumference of the stem (fig. 182 g). This sheath is formed by 
the divergence of the vascular bundles which separate so as to form a 
hollow cavity towards the stem. The sheath is occasionally developed 
to such a degree as to give a character to the plants. Thus, in the 
Khubarb tribe, it is large and membranous, and has received the name 
of ochrea or boot (fig. 132 #); while in Palms it forms a kind of net- 
work, to which the name of reticulum has been given (^[ 57) ; and in 
umbelliferous plants, it constitutes the pericladiwn (vtpl, around, and 
xA<jf, a branch). In place of a sheath, leaves are occasionally pro- 
duced at the base of the petiole (fig. 189 s s), 

which have been denominated stipules (stipula, 
straw or husk). These stipules are often two 
in number, and they are important as sup- 
plying characters in certain natiu-al orders. 
Thus they occur in the Pea and Bean family, 
in Rosaceous plants, and the Cinchona bark 
family. They are rarely met with in Endo- 
gens, or in Exogens with sheathing petioles, 
and they are not common in Exogens with 

opposite leaves. Plants having stipules, are stipulate; those having 
none, are exstipulate. 

159. Stipules are formed by some of the vascular bundles diverg- 
ing as they leave the stem, and becoming covered with parenchyma, 
so as to resemble true leaves. Like leaves they are large or 
small, entire or divided, deciduous or persistent, articulated or non- 
articulated. Their lateral position at the base of the petiole, distin- 
guishes them from true leaves. In the Pansy, the true leaves are 
stalked and crenate, while the stipules are large, sessile, and pinnatifid. 
In Lathyrus aphaca, and some other plants, the true pinnate leaves 
are abortive, the petiole forms a tendril, and the stipules alone are 
developed, performing the office of leaves. 

160. When stipules are attached separately to the stem at the base 
of the leaf, they are called caulinary. Thus, in fig. 189, r is a branch 
of Salix aurita, with a leaf, f, having a bud, &, in its axil, and two 
caulinary stipules, s s. When stipulate leaves are opposite to each 

Fig. 189. Portion of a branch, r, of Salix aurita, bearing a single petiolate leaf,/, which has 
been cnt across, s s, Stipules, b, Bud in the axil of the leaf. 




84 



FORMS OP STIPULES. 



other at the same height on the stem, it occasionally happens that the 
stipules at either side unite wholly or partially, so as to form an inter- 
petiolary or interfoliar (inter, between) stipule, as in Cinchona (fig. 

190 s). In the case of alternate leaves, the stipules at the base of 
each leaf are sometimes united to the petiole and to each other, so as 
to form an adnate, adherent, or petioldry stipule, as in the Rose (fig. 

191 s), or an axillary stipule, as in Houttuynia cordata (fig. 192 s}. 




190 





In other instances, the stipules unite together on the side of the stem 
opposite the leaf, and become synochreate (avv, together), as in Astragalus 
(fig. 193 s). The union or adhesion of stipules is not an accidental 

Fig. 190. Branch, r, and two leaves, //, of Cephalanthus occidental's, s, Interpetiolary or 
interfoliav stipule, formed by the partial union of two. 



., formed by the union of two. 

Fig. 193. Branch, r, and portion of the leaf, /, of Astragalus Onobrychis, with a synochreate 
stipule, formed by the union of two stipules on the opposite side of the branch from that to which 
the leaf is attached. The leaf is pinnate, and in the figure three pairs of leaflets or pinnae are 
left 



ANOMALOUS LEAVES AND PETIOLES. 



85 




occurrence taking place after they have been developed; but is in- 
timately connected with the general law, in accordance with which the 
parts of the plants are formed. 

161. Stipules are sometimes large, envelop- 
ing the leaves in the young state, and falling 
off in the progress of growth, as in Ficus, 
Magnolia, and Potamogeton; at other tunes 
they are so minute as to be scarcely distin- 
guishable without the aid of a lens, and so 
fugaceous as to be visible only in the very- 
young state of the leaf. In grasses, the sheath 
or sheathing petiole (fig. 194^rv) has a prolon- 
gation or folding of the epidermis * at its upper 
part, distinct from the leaf, to which the name of 
ligule (ligula, a small slip) has been given (fig. 
194 g I). Some consider it as equivalent to a 
stipule. It is either long or short, acute or 
blunt, entire or divided, and thus gives rise to 
various characters. At the base of the leaf- 
lets or foliola of a compound leaf, small stipules 
are occasionally produced, to which some have 
given the name of stipels. 

Anomalous Forms of Leaves and Petioles. 

162. Variations in the structure and forms of leaves and leaf- 
stalks are produced by the increased development of cellular tissue, by 
the abortion or degeneration of parts, by the multiplication or repeti- 
tion of parts, and by adhesion. When cellular tissue is developed to 
a great extent, leaves become succulent, and occasionally assume a 
crisp or curled appearance. Such changes take place naturally, but 
they are often increased by the art of the gardener; and the object of 
many horticultural operations is to increase the bulk and succulence of 
leaves. It is in this way that Cabbages and Greens are rendered more 
delicate and nutritious. 

163. In some plants true leaves are not produced, their place being 
occupied by dilated petioles or phyllodia (^[ 157), or by stipules 
(^f 159). In other instances scales are formed instead of leaves, as in 
Orobanche, Lathrsea, and young Asparagus (fig. 110 I). Divisions 
take place in leaves when there is a multiplication of their parts; 
and a union of two or more leaves, or of parts of leaves, occurs in many 

* See Deduplieation, under the head of Corolla. 

Fig. 194. Portion of a leaf of Phalaris arundinacea, one of the grasses. /, Laminar merithal 
or blade of the leaf, with straight parallel venation, g r. Vaginal, or sheathing portion repre- 
senting the petif-if, ending in a membranous process or ligule, g I. 



ASCIDIA OE PITCHERS. 



When two lobes at the base of a leaf are prolonged beyond 
the stem and unite (fig. 156), the leaf is pafoKate (per, through, and 
fofatm, leaf), the stem appearing to pass through it, as in Bupleurum 
perfoliatum, and Chlora perfohata: when two leaves unite by their 
bases they became ammatt (eon, together, and notes, born), as in 
Lonioera OmETrC^f"'"; an ^ '*hen leaves adhere to the stem, forming 
a sort of winged or leafy appendage, they are decurrtnt (efecurrt), to 
ran down or along), as in Thistles. 

164. The vascular bundles and cellular tissue are sometimes devel- 
oped in such a way as to form a circle, with a hollow in the centre, and 
thus give rise to what are called jittxlar (jiftula, a pipe) or hollow leaves, 
and to asddia (n2m*, a small bag) or pitchers. Hollow leaves are 
well seen in the Onion. Pitchers are formed either by petioles or by 
lamina*) and they are composed of one or more leaves. In some Con- 
vallarias, two leaves unite to form a cavity. In Sarracenia (fig. 187) 
and Heliamphora, the pitcher is composed apparently of the petiole of 
the leaf. In Xephentes (fig. 181), and perhaps in Cephalotus. while 
the folding of a winged petiole,/), forms the pitcher, a, the lid, e, which 
is united by an articulation, corresponds to the lamina. This kind of 
asridiiim is called calyptrimorphovs (zjcArcrf*, a covering, and p**Zr., 
form), and may be considered as formed by a leaf such as that of the 
Orange (fig. 185); the lamina, , being articulated to the petiole, />, 
which, when folded, forms the pitcher. In Dischidia Raffiesiana. a 
daubing plant of India, the pitchers, according to Griffith, are formed 
by the lamina of the leaf, and have an open orifice into which the 
rootlets at the upper part of the plant enter. These pitchers would 
seem therefore to contain a supply of fluid for the nourishment of the 
upper branches of the plant. In Utricularia, the leaves form sacs 
called ampullae. 

Structure and Farm cf Leaves in the Great Dirwiwu cf the Vegetable 

Kingdom. 



165. KxgaMM r iiMjit. " !>**. In Ifra^gw, the vena- 
tion is reticulated, the veins coming off at acute angles and forming 
an angular network of vessels (fig. 136), and the trachea? communi- 
cating with the medullary sheath. They are frequently articulated, ex- 
hibit divisions at their margin, and become truly compound. There 
are no doubt instances in which the veins proceed in a parallel man- 
ner, but this win be found to occur chiefly in cases where the petiole 
may be considered as occupying the place of the leaf. Examples of 
this kind are seen in Acacias (fig. 188), as weQ as in Ranunculus 
gramineus, and I-inon* 

' Edge r Tona-f otrledonou. t.-eaTe- Ir. E:_ :; : _-.:_>, '..- 

leaves do not present an angular network of vessels, nor do they er- 



EXOGENOUS, ENDOGENOUS. AND ACROGENOUS LEAVES. 87 

hibit divisions on their margin. Their venation is generally parallel, 
and their margin entire (figs. 135, 194). Exceptions to this rule 
occur hi some plants, as Tamus and Dioscorea, which have been called 
Dictyogens by Lindley, on account of their somewhat netted venation; 
and in Palms, ha which although the leaves are entire at first, they 
afterwards become split into various lobes. Endogenous leaves are 
rarely stipulate, unless the ligule of grasses be considered as being a 
stipule. Their leaves are often sheathing, continuous with the stem 
(forming a spurious stem hi Bananas), and do not fell off by an artic- 
ulation. When there is only a slight divergence of then- veins, they 
may be looked upon more as enlarged and flattened petioles than as 
true lamina?. This remark is illustrated by the leaves of Typha and 
Iris. In some Endogens, as in Sagittaria sagittifolia, the submerged 
and floating leaves are narrow, like petioles, while those growing erect 
above the water expand and assume an arrow-like shape (fig. 165). 

167. AcrogenoM or AcolTledonous I-eare*. In AcTOgens, the leaves 

vary much ; being entire or divided, petiolated or sessile, often feather- 
veined, occasionally with radiating venation, the extremities of the 
veins being forked. The fibre- vascular bundles of the leaves resemble 
those of the stem both in structure and arrangement In Thallogens. 
the leaves when present have no vascular venation. In many of 
them, as Lichens, Fungi, and Algae, there are no true leaves. 

Phyllotaxis, or the Arrangement of the Leaves on the Axis. 

168. Leaves occupy various positions on the stem and branches, 
and have received different names according to their situation. Thus, 
leaves arising from the crown of the root, as in the Primrose, are 
called radical; those on the stem are cauline; on the branches, ramal: 
on flower-stalks, floral leaves. The first leaves developed are deno- 
minated seminal (semen, a seed), or cotyledons (wre/AuS**, a name given 
to a plant); and those which succeed are primordial (primus, first, 
and ordo, rank). 

169. The arrangement of the leaves on the axis and its appendages 
is called phyllotaxis (0t/xxo, a leaf, and ri;, order). In their 
arrangement, leaves follow a definite order. It has been stated 
already (^[ 67) that there are regular nodes or points on the stem 
(fig. 195 H) at which leaves appear, and that the part of the stem 
between the nodes is the internode or menthol (fig. 195 m). Each 
node is capable of giving origin to a leaf. Occasionally several nodes 
are approximated so as to form as it were one, and then several leaves 
may be produced at the same height on the stem. When two leaves 
are thus produced, one on each side of the stem or axis, and at the 
same level, they are called opposite (fig. 196); when more than two 



88 



PHYLLOTAXIS OR LEAF- ARRANGEMENT. 



are produced (figs. 1C8, 197), they are verticillate (verto, I turn), and 
the circle of leaves is then called a verticil or whorl. When leaves are 






196 

opposite, the pairs which are next each other, but separated by an in- 
ternode, often cross at right angles (fig. 196 a J), or decussate (decusso, I 
cut crosswise), following thus a law of alter- 
nation. The same occurs in verticils, the 
leaves of each whorl being alternate with 
those of the whorl next to it; or, in other 
words, each leaf in a whorl occupying the 
space between two leaves of the whorl next 
to it. There are considerable irregularities, 
however, in this respect, and the number 
of leaves in different whorls is not always 
uniform, as may be seen in Lysimachia 
vulgaris. 

170. When a single leaf is produced at a 
node, and the nodes are separated so that 
each leaf occurs at a different height on the 
stem, the leaves are alternate (fig. 198). 
The relative position of alternate leaves 
varies in different plants, although it is 
tolerably uniform in each species. In fig. 195, leaf 1 arises from a 

Fig. 195. Portion of a branch of a Lime tree, with four leaves arranged in a distichous manner, 




the spiral and two leaves. 

Fig. 196. Opposite, decussate leaves of Pimelea decussata. a, A pair of opposite leaves, b, 
Another pair placed at right angles. 

Fig. 197. Leaves of Lysimachia vulgaris, in verticils or whorls of three. The leaves of each 
verticil alternate with those of the verticils next it. In this plant the number of the leaves in a 
verticil often varies. 



PHYIXOTAXIS OR LEAF-ARRANGEMENT. 



89 



node, n; leaf 2 is separated by an internode or merithal, m, and is 
placed to the right or left ; while leaf 3 is situated directly above 
leaf 1. The arrangement in this case is distichous (S<j, twice, and 
ffT/%o?, order), or the leaves are arranged in two rows. In fig. 199, on 
the other hand, the fourth leaf is that directly above the first, and the 
arrangement is tristichous (f^e^ three, and (tripos, order). The same 
arrangement continues throughout the stems, so that in fig. 199 the 
7th leaf is above the 4th, the 10th 
above the 7th ; also the 5th above 
the 2nd, the 6th above the 3rd, 
and so on. There is thus through- 
out a tendency to a spiral arrange- 
ment, the number of leaves in the 
spire or spiral cycle, and the num- 
ber of turns varying in different 
plants. In plants whose leaves 
are close to each other, the spiral 
tendency is easily seen. In the 
ScreAv pine (Pandanus odoratis- 
simus), in the Pine-apple family, 
and in some Palms, as Corypha 
cerifera, the screw-like arrange- 
ment of the leaves is obvious. This 
mode of development prevails in all 
parts of plants, and may be con- 
sidered as depending on then- man- 
ner of growth in an upward and at 
the same time in a lateral direction, 
the normal arrangement of all parts of plants. 

171. In a regularly-formed straight branch covered with leaves, if 
a thread is passed from one to the other, turning always in the same 
direction, a spiral is described, and a certain number of leaves and of 
complete turns occur before reaching the leaf directly above that from 
which the enumeration commenced. This arrangement has been 
reduced to mathematical precision,* and Braun has expressed it 
by a fraction, the numerator of which indicates the number of 
turns, and the denominator the number of leaves in the spiral cycle. 
Thus, in fig. 198 a J, the cycle consists of five leaves, the Gth leaf 
being placed vertically over the first, the 7th over the 2nd, and so 
on ; while the number of turns between the 1st and Gth leaf is two : 

Fig. 198. Part of a branch of a Cherry with six leaves, the sixth being placed vertically over 
the first, after two turns of the spiral. This is expressed by -J or the quincimx. a, The branch, 
with the leaves numbered in order. 6, A magnified representation of the branch, showing the 
cicatrices of the leaves or their points of insertion, and their spiral arrangement 

* For a full account of .Phyllotaxis, see Bravais Mem. snr la Disposition Ge"ometrique di-s 
Feuilles. Annales des Sciences Naturelles. Jan. and Feb. 1837. 




198 



Alternation is looked upon as 



90 



PHYLLOTAXIS OR LEAF- ARRANGEMENT. 




hence, this arrangement is indicated by the fraction f. In other 
words, the distance or divergence between, the first and second leaf, 
expressed in parts of a circle, is ^ of a circle, or 360 -f- j = 144. 
In fig. 195, a b, the spiral is ^, i.e. 
one turn and two leaves; the third leaf 
being placed vertically over the first, 
and the divergence between the first 
and second leaf being one-half the cir- 
6 cumference of a circle, 360-f-^, = 180. 
Again, in fig. 199, a >, the number is ^, 
or one turn and three leaves, the an- 
gular divergence being 120. 

172. In cases where the internodes 
are very short, and the leaves are closely 
applied to each other, as in the House- 
leek, it is difficult to trace what has 
been called the generating spiral, or 
that which passes through every leaf 
of the cluster. Thus, in fig. 200, there 
are thirteen leaves which are numbered 
in their order, and five turns of the 
spiral marked by circles in the centre (fa indicating the arrange- 
ment); but this could not be detected at once. So also in Fir cones 
(fig. 201), which are composed of scales or modified leaves, the gener- 
ating spiral cannot be determined easily. In such cases, however, 
there are secondary spirals running parallel to each other, as is seen 
in fig. 201, where spiral lines pass through scales numbered 1, 6, 11, 
16, &c., and 1, 9, 17, &c., and by counting those which run parallel 
in different directions, the number of scales intervening between 
every two in the same parallel coil may be ascertained. Thus, in fig. 
201, it will be found that there are five secondary spirals running 
towards the right and parallel to each other, the first passing through 
the scales 1, 6, 11, 16, &c.; the second through 9, 14, 19, 24, &c.; 
the third through 17, 22, 27, 32, 37, &c.; the fourth through 30, 35, 
40, 45, &c ; the fifth through 43, 48, 53, &c. The number of these 
secondary spirals indicates the number of scales intervening between 
every two scales in each of these spirals the common difference being 
five. Again, it will be found on examination that there is a number 
of secondary spirals running to the left, in which the common difference 
between every two scales is eight, and that this corresponds to the 
number of secondary spirals, the first of which passes through the 
scales 1, 9, 17, &c.; the second through 6, 14, 22, 30, &c.; the third 

Fig. 199. Young plant of Cyperus esculentus. with leaves in three rows, or tristichous. ex- 
pressed by the fraction J, or one turn and three leaves, a, The plant, with its leaves numbered 
in their order. 6, Magnified representation of the stem, showing the insertion of the leaves and 
their spiral arrangement 



PHYLLOTAXIS OR LEAF- ARRANGEMENT. 



91 



through 3, 11, 19, 27, 35, 43, and so on. Thus it is that, by counting 
the secondary spirals, all the scales may be numbered, and, by this 
means, the generating spiral may be discovered. 





173. The primitive or generating spiral may pass either from right 
to left or from left to right. It sometimes follows a different direction 
in the branches from that pursued in the stem. When it follows the 
same course in the stem and branches, they are homodromous (oftoi'o?, 
similar, and dj&^oj, a course) ; when the direction differs, they are 
heterodromous (trigo;, another). In different species of the same genus 
the phyllotaxis frequently varies. 

174. Considering alternation as the usual leaf-arrangement, some 
have supposed that opposite leaves are owing to the development of 
two spirals in opposite directions, while others look upon them as pro- 
duced by two nodes coming close together without an internode. A 
verticil, in the latter view, will be the result of the non-development of 
more than one internode. Thus, in fig. 195, if the space between 1 
and 2 were obliterated, or the internode, m, not developed, the leaves 
would be opposite. In fig. 198, if the spaces between each of the 
leaves were obliterated, there would be a verticil of five leaves. In 
many plants there is a law of arrestment of development, by which 
opposite and verticillate leaves are naturally produced : but in such 

Fig. 200. Cycle of thirteen leaves placed closely together so as to form a rosette, as in Sem- 
pervivum. A, is the very short axis to which the leaves are attached. The leaves are numbered 
in their order, from below upwards. The circles in the centre indicate the five turns of the 
spiral, and show the insertion of each of the leaves. The divergence is expressed by the fraction 

T%- 

Fig. 201. Cone of Pinus alba, with the scales or modified leaves numbered in the order of their 
arrangement on the axis of the cone. The lines indicate a rectilinear series of scales, and two 
lateral secondary spirals, one turning from left to right, the other from right to left. 



92 I'HYLLOTAXIS OR LEAF-ARRANGEMENT. 

cases the alternation is still seen in the arrangement of the different 
clusters of leaves. 

175. In some cases the effect of interruption of growth, in causing 
alternate leaves to become opposite and verticillate, can be distinctly 
shoAvn, as for instance in Rhododendron ponticum. In other cases, 
parts which are usually opposite or verticillate, become alternate by 
the vigorous development of the axis: and on different parts of the same 
stem, as in Lysimachia vulgaris, there may be seen alternate, opposite, 
and verticillate leaves. When the interruption to development takes 
place at the end of a branch, the leaves become fasciculate (fasciculus, 
a bundle) or clustered, as in the Larch. A remarkable instance of the 
shortening of internodes, and the clustering of leaves, occurred in the 
Palm house of the Botanic Garden of Edinburgh, in the case of a 
Bamboo which was exposed for many months to a low temperature, 
during the time that the roof of the house was being renewed. The 
plant had been growing rapidly, with its internodes of the usual 
length, but it was suddenly arrested near the summit, the internodes 
became gradually shortened, till the nodes were close to each other, 
and the leaves came off in bunches. All modifications of leaves follow 
the same laws of arrangement as true leaves a fact which is of im- 
portance in a morphological point of view. 

176. In Exogenous plants, the first leaves produced, or the 
cotyledons, are opposite. This arrangement often continues during 
the life of the plant, but at other times it changes. Some tribes of 
plants are distinguished by their opposite or verticillate, others by 
their alternate, leaves. Labiate plants have decussate leaves, while 
Boraginacese have alternate leaves, and Tiliaceaj have distichous leaves 
in general ; Cinchonacea? have opposite leaves ; Galiacea3, verticillate. 
Such arrangements as f, f , / 4 , and ,f T , are common in Exogens. The 
first of these, called quincunx (quincunx, an arrangement of five), is met 
with in the Apple, Pear, and Cherry (fig. 198); the second, in the Bay, 
Holly, Plantago media; the third, in the cones of Pinus alba (fig. 201); 
and the fourth, in those of the Pinus Picea. In Endogenous plants, 
there is only one seed-leaf or cotyledon produced, and hence the 
arrangement is at first alternate ; and it generally continues so more or 
less. Such arrangements as \ \ (fig. 199), and f, are common in 
Endogens, as in Grasses, Sedges, and Lilies. In Acrogens, the leaves 
assume all kinds of arrangement, being opposite, alternate, and ver- 
ticillate. It has been found in general that, while the number 5 
occurs in the phyllotaxis of Exogens, 3 is common in that of Endogens. 

_ 177. Although there is thus, in the great divisions of the vegetable 
kingdom, a, tendency to certain definite numerical arrangements, yet 
therearemany exceptions. Inspeaking of Palms, which are endogenous 
plants, Martius states that the leaves of different species exhibit the 
following spirals , j, f, g, |, ^, ^ }i . ^ tne spe cies of the genus 



LEAF-BUDS AND BRANCHES. 



93 



Pinus, , f<s, ^f, 7f T , f, occur. Thus, while it has been shown that the 
phylloplastic ((Zst/XAov, a leaf, and -x(7T/xoV, formative), or leaf-formative 
power, moves in a spiral round the axis, it has been found impossible 
to apply phyllotaxis satisfactorily to the purposes of classification. 

178. The spiral arrangement of the leaves allows all of them to be 
equally exposed to air and light, and thus enables them to carry on 
their iunclions with vigour. The form of the stem is also probably 
connected with the leaf arrangement. When leaves are opposite and 
decussate, the stems are often square, as in Labiate plants. The ordi- 
nary rounded stem appears to be associated with a certain degree of 
alternation in the separate leaves, or in the different pairs of leaves 
when they are opposite. 

179. The study of the structure, forms, and arrangement of leaves, 
is of great importance, when it is considered that all parts of plants are 
to be looked upon as leaf-formations variously modified, in order to 
serve special purposes in the economy of vegetation. The morphological 
relations of leaves, or the varied forms which they assume, will be 
illustrated during the consideration of the organs of reproduction, and 
of the doctrine of metamorphosis, as propounded by Goethe and others. 
It is only by looking upon all the organs of plants in their relation to 
the leaf as a type, that a philosophical view can be given of the great 
plan on which they have been formed. 

Leaf-buds. 

180. Leaf-buds contain the rudiments of branches, and are found 
in the axil of previously-formed leaves (fig. 202 ba, ba, ba) ; or, in 
other words, in the angle formed between the 

stem and leaf. They are hence called axillary, 
and may be either terminal, b t, or lateral, b a. 
In their commencement, they are cellular pro- 
longations from the medullary rays bursting 
through the bark. The central cellular por- 
tion is surrounded by spiral vessels, and is 
covered with rudimentary leaves. In the pro- 
gress of growth, vascular bundles are formed 
continuous with those of the stem ; and, ulti- bf[ \ 
mately, branches are produced which hi every 
respect resemble the axis whence the buds first 
spnmg. The cellular portion in the centre 
remains as pith with its medullary sheath, which 
is closed and not continuous with that of the 
parent stem. Thus, in the stem and branch, this sheath forms a 




-ba 



202 



Fig. 202. Upper portion of a branch of Lonicera nigra in a state of hibernation, that is to say, 
after the fall of the leaves ; covered with leaf-buds, b t , A terminal bud. ba, b a, b a, Axillary 
lateral buds. Below the buds, the cicatrix or scar left by the fallen leaves is seen. 



94 LEAF-BUDS AND BRANCHES. 

canal which is closed at both extremities, and which sends prolonga- 
tions of spiral vessels to the leaves. As the axis or central portion of 
the leaf-bud increases, cellular projections appear at regular intervals, 
which are the rudimentary leaves. 

181. A leaf-bud may be removed in a young state from one plant 
and grafted upon another, by the process of budding, so as to continue 
to form its different parts; and it may even be made to grow in the soil, 
in some instances, immediately after removal. In certain cases, leaf- 
buds are naturally detached during the life of the parent, so as to 
form independent plants, and thus propagate the individual. Leaf- 
buds have on this account been called fixed embryos, by Petit-Thouars 
and others. They are embryo plants fixed to the axis, capable of send- 
ing stems and leaves in an upward direction, and woody fibres down- 
wards, which, according to some, may be considered as roots. A tree 
may be said to consist of a series of leaf-buds, orphytons (Qv-rov, a plant), 
attached to a common axis or trunk. In ordinary trees, in which there 
is provision made for the formation of numerous lateral leaf-buds, any 
injury done to a few branches is easily repaired ; but in Palms, which 
only form central leaf-buds, and have no provision for a lateral forma- 
tion of them, an injury inflicted on the bud in the axis is more likely 
to have a prejudicial effect on the future life of the plant. 

182. In the trees of temperate and cold climates, the buds which 
are developed during one season lie dormant during the whiter, ready 
to burst out under the genial warmth of spring. They are generally 
protected by external modified leaves in the form of scales, tegmenta or 
perulce (tegmenta, coverings, peruke, small bags), which are of a firmer 
and coarser texture than the leaves themselves. These scales or pro- 
tective appendages of the bud, consist either of the altered lamina, or 
of the enlarged petiolary sheath, or of stipules, as in the Fig and Mag- 
nolia, or of one or two of these parts combined. They serve a tempo- 
rary purpose, and usually fall off sooner or later after the leaves are 
expanded. The bud is often protected by a coating of resinous mat- 
ter, as in the Horse-chestnut and Balsam poplar, or by 
a thick downy covering, as in the Willow. Linnajus 
called leaf-buds hibernacula, or the winter quarters of the 
young branch. 

183. In the bud of a common tree, as the Syca- 
more (fig. 203), there is seen the cicatrix left by the 
leaf of the previous year, c, with the pulvinus or 
swelling, p, then the scales, e e, arranged alternately 
in a spiral manner, and overlying each other in what 
203 is called an imbricated (imbrex, a roof tile) manner. 

nr^w a i^'J"^ f "^ ud of ^ c ^ r Pscudo-platanus covered with scales, r, The branch, p, Pulvinus 
or swelling at the base of the leaf which has fallen, leaving a scar or cicatricula, c, in which the 
remams of three vascular bundles are seen, e, e, Imbricated scales of the bud. 




VERNATION OK PR^EFOLIATION. 



95 



On making a transverse section of the bud (fig. 204), the over-lying 
scales, e e e e, are distinctly seen surrounding the leaves, f, which are 
plaited or folded round the axis or 
growing point. In plants of warm 
climates, the buds are often formed by 
the ordinary leaves without any pro- 
tecting appendages; such leaf-buds are 
called naked. 

184. Vernation. The arrangement of 
the leaves in the bud has been deno- 
minated vernation (ver, spring), orprce- 
foUation (prce, before, and folium, leaf), 
or gemmation (gemma, a bud). This 
differs in different plants, but in each 
species it follows a regular law. The e 

leaves in the bud are either placed 

simply in apposition, as in the Misletoe, or they are folded or rolled 
up longitudinally or laterally, giving rise to different kinds of verna- 
tion, as delineated in fig. 205 a , where the dot represents the axis, 





and the folded or curved lines, the leaves Avith the thickened part indi- 
cating the midrib ; figs, a and g, being vertical sections ; h n, horizontal. 
185. The leaf taken individually, is either folded longitudinally from 
apex to base (fig. 205 a), as in the Tulip-tree, and called reclinate; 
or rolled up in a circular manner from apex to base, as in Ferns 

Fig. 204. Transverse section of the same leaf-trad e e e e, The scales arranged in an imbri- 
cated manner, like the tiles on a house. /, The leaves folded in a plaited manner, exhibiting 
plicate vernation. 

Fig. 205. Figures to show the different kinds of vernation, a g, The folding of individual 
leaves; a and g being vertical sections, b c d e and/, being horizontal a, Reclinate. 6, Con- 
duplicate, c, Plicate, d, Convolute. , Involute. /, Revolute. g, Circinate. h n, Folding of 
leaves when united together in the leaf-bud. The sections are horizontal or transverse, and 
show the relative position of the leaves, and the mode in which each of them is folded. A, Val- 
vate. i, Twisted or spiral k I, Induplicate. m, Equitant. n, Obvolute or half-equitant In all 
the figures, the thickened portion indicates the midrib of the leaf, and the dot marks the position 
of the axis. 



96 VERNATION OR PR^FOLIATIOX. 

(fig. 205 g), and called circinate (circino, I turn round); or folded later- 
ally, conduplicate, as in Oak (fig. 205 b); or it lias several folds like a 
fan, plicate or plaited, as in Vine and Sycamore (figs. 204/ 205 c), and 
in leaves with radiating vernation, where the ribs mark the foldings ; 
or it is rolled upon itself, convolute or supervolute, as in Banana and 
Apricot (fig. 205 d) ; or its edges are rolled inwards, involute, as in 
Violet (fig. 205 e); or outwards, revolute, as in Rosemary (fig. 205 /). 
The different divisions of a cut leaf may be folded or rolled up separ- 
ately, as in Ferns, while the entire leaf may have either the same or 
a different kind of vernation. 

186. Other kinds of vernation receive their names from the arrange- 
ment of the leaves in the bud, taken as a whole. Leaves in the 
bud are opposite, alternate, or verticillate ; and thus different kinds of 
vernation are produced. Sometimes they are nearly in a circle at 
the same level, remaining flat, or only slightly convex externally, and 
placed so as to touch each other by their edges ; thus giving rise to 
valvate vernation (fig. 205 h). At other times they are at different 
levels, and are applied over each other, so as to be imbricated, as in 
Lilac, and in the outer scales of Sycamore (figs. 203, 204) ; and occa- 
sionally the margin of one leaf overlaps that of another, while it, in its 
turn, is overlapped by a third, so as to be twisted or spiral (fig. 205 i). 
When the leaves are more completely folded, they either touch at their 
extremities (fig. 205 &), or are folded inwards by their margin, and 
become induplicate (fig. 205 1) ; or a conduplicate leaf covers another 
similarly folded, while it covers a third, and thus the vernation is 
equitant (riding), as in Privet (fig. 205 m) ; or conduplicate leaves are 
placed, so that the half of the one covers the half of another, and thus 
they become half-equitant or obvolute, as in Sage (fig 205 n). The 
scales of a bud sometimes exhibit one kind of vernation, and the 
leaves another (fig. 204). The same modes of arrangement occur in 
the flower-buds, as will be afterwards shown. 

187. Leaf-buds, as has been stated, are either terminal or lateral. 
By the production of the former (fig. 202 b t), stems increase in length, 
while the latter (fig. 202 ba,ba,ba) give rise to branches, and add to 
the diameter of the stem. The terminal leaf-bud, after producing 
leaves, sometimes dies at the end of one season, and the whole plant, 
as in annuals, perishes; or part of the axis is persistent, and remains for 
two or more years, each of the leaves before its decay producing a 
leaf-bud in its axil. This leat : bud continues the growth in spring. 

188. In some trees of warm climates, as Cycas, Papaw-tree, Palms, 
and Tree ferns, the production of terminal buds is well seen. In these 
plants, the elongation of the stem is generally regular and uniform, so 
that the age of the plant may be estimated by its height. Such stems 
(often endogenous) may thus be considered as formed by a series of 
terminal buds, placed one over the other. From this mode of growth 



LEAF-BUDS AND BRANCHES. 97 

they do not attain a great diameter (fig. 115, 1). In other trees, 
especially Exogens, besides the terminal bud, there are also lateral 
ones. These, by their development, give rise to branches (ramz), from 
which others called bmnchlets or twigs (ramuli) arise. Such buds 
being always produced in the axils of leaves, are of course arranged 
in the same manner as the leaves are. By the continual production 
of lateral leaf-buds, the stem of exogenous plants acquires a great 
diameter. 

189. Although provision is thus made for the regular formation of 
leaf-buds, there are often great irregularities in consequence of many 
being abortive, or remaining in a dormant state. Such buds are 
called latent, and are capable of being developed in cases where the 
terminal bud, or any of the branches, have been injured or destroyed. 
In some instances, as in Firs, the latent buds follow a regular system 
of alternation ; and in plants with opposite leaves, it frequently hap- 
pens that the bud in the axil of one of the leaves only is developed, 
and the different buds so produced are situated alternately on opposite 
sides of the stem. 

190. When the terminal leaf is injured or arrested in its growth, the 
elongation of the main axis stops, and the lateral branches often acquire 
increased activity. By continually cutting off the terminal buds, a woody 
plant is made to assume a bushy appearance, and thus pollard trees are 
produced. Priming has the effect of checking the growth of terminal 
buds, and of causing lateral Qnes to push forth. The peculiar bird-nest 
appearance often presented by the branches of the common Birch, 
depends on an arrestment in the terminal buds, a shortening of the 
internodes, and a consequent clustering or fasciculation of the twigs. 
In some plants there is a natural arrestment of the main axis after a 
certain time, giving rise to peculiar shortened stems. Thus the crown 
of the root (^[ 70) is a stem of this nature, forming buds and roots. 
Such is also the case in the stem of Cyclamen, Testudinaria elephan- 
tipes, and hi the tuber of the potato. The production of lateral in 
place of terminal buds, sometimes gives the stem a remarkable zigzag 
aspect. 

191. In many plants with a shortened axis, the lateral buds produce 
long branches. Thus the Jiagellum (flagellum, a whip or twig), or 
nmner of the Strawberry and Ranunculus, is an elongated branch, 
developing buds as it runs along the ground ; the propagulum (pro- 
pago, a shoot), or offset, is a short thick, branch produced laterally in 
tleshy plants from a shortened axis, and developing a bud at its ex- 
tremity, which is capable of living when detached, as in Houseleek. 
Fig. 206 represents a strawberiy plant in which a' is the primary 
axis, ending in a cluster of green leaves, r, and some rudimentary leaves, 
f, and not elongating ; from the axil of one of the leaves proceeds a 

branch or runner, a", with a rudimentary leaf, f, about the middle, 

H 




98 AERIAL AND SUBTERRANEAN LEAF-BUDS. 

and another cluster of leaves,/and r, forming a young plant with roots; 

from this a third axis comes off, a'", and so on. In many instances 

the runner decays, and the 
young plant assumes an inde- 
pendent existence. Gardeners 

imitate this ** tlie Propaga- 
tion of plants by the process 
of layering, which consists in 
bending a twig, fixing the 
central part of it into the 
ground, and, after the pro- 
duction of adventitious roots, 
cutting off its connection with 
the parent. 

192. When the stem creeps along the surface of the ground, as in 
the Rhizome (fig. 90), or completely under ground, as in the Soboles 
or creeping stem (fig. 91), the terminal bud continues to elongate 
year after year, thus making additions to the axis in a horizontal 
manner. At the same time buds are annually produced on one side 
which send shoots upwards and roots downwards. Thus, in fig. 91 
(soboles of a Rush), r is the extremity of the axis or terminal bud, / e 
the leaves in the form of scales, p a the aerial shoots or branches, 1 1 
being the level of the ground. Again, in fig. 90 (rhizome of Solomon's 
seal), a is the terminal bud which has been formed subsequently to b, 
1) the bud which has sent up leaves, and which has decayed, c c being 
the scars left by the similar buds of previous seasons. 

193. Aerial and Nnblerrniiean Lent-bud*. According to the nature 

of the stems, leaf-buds are either aerial or subterranean; the former 
occurring in plants which have the stems above ground, the latter 
in those in which the stems are covered. In the case of Asparagus 
and other plants which have a perennial stem below ground, sub- 
terranean buds are annually produced, which appear above ground 
as shoots or branches covered with scales at first (fig. 110 /), and 
ultimately with true leaves. The young shoot is called a Turio (turio, 
a young branch). These branches are herbaceous and perish an- 
nually, while the true stem remains below ground ready to send up 
fresh shoots next season. In Bananas and Plantains, the apparent 
aerial stem is a shoot or leaf-bud sent up by an underground stem, and 
perishes after ripening fruit. In some plants, several branches are sent 
up at once from the underground stem, in consequence of a rapid 
development of lateral as well as terminal buds; and in such cases the 

Fig. 206.- -Flagellum, or Eunner of the Strawberry, a', One axis which has produced a cluster 
of leaves, the upper, r, green, the lower, /, rudimentary. From the axil of one of the latter, a 
second axis, a", arises, bearing about the middle a rudimentary leaf,/, and a cluster of leaves, 
r, partly green, and partly rudimentary, at its extremity. From the axil of one of the leaves of 
this cluster, a third axis, a'", proceeds. 



SUBTERRANEAN LEAF -BUDS, BULB, AND CORil. 



99 



lateral ones may be separated as distinct plants in the form of suckers 
(surculi). The potato is a thickened stem or branch capable of 
developing leaf-buds, which in their turn form aerial and subterranean 
branches, the former of which decay annually, while the latter remain 
as tubers to propagate the plant. Thus, in fig. 92, s s is the surface of 
the soil, p a is the aerial portion of the potato covered with leaves, t is 
the subterranean stem or tuber covered with small scales or projections, 
as represented at T b, from the axil of which leaf-buds are produced. 
This provision for a symmetrical development of axillary leaf-buds at 
once distinguishes the tuber of the potato from fleshy roots, like those 
of the Dahlia. 

194. Bulb. A good example of a subterranean bud occurs in the 
Bulb, as seen in the Hyacinth, Lily, and Onion. This is a subterranean 
leaf-bud covered with scales, arising from a shortened axis. From the 
centre of the bulb a shoot or herbaceous stem is produced which dies 
down. New bulbs, or cloves as they are called, are produced from 
the subterranean axis. At the base of, the scales there is a flat- 
tened disc, varying in thickness, which is formed by the base of the 
buds, and which has sometimes been called the stem. The parts of 
the bulb are seen hi fig. 207, where p marks the disc or round flat 
portion formed by the bases of the lateral buds from which the fasci- 
culated roots, r, proceed, e the scales or modified leaves, and /the true 
leaves. In the vertical section (fig. 208), b is the new bulb formed like 




207 208 209 

a bud in the axil of a scale. The new bulb sometimes remains attached 
to the parent bulb, and sends up an axis and leaves; at other times it 

Fig. 207. Tunicated bulb of Allium Porrum, or the Leek, r. Roots, p, A circular disc, or 
shortened stem intervening between the roots and the bulbous swelling, e e. Scales, or subter- 
ranean modified leaves. /, Upper leaves which become green. 

Fig. 208. Vertical section of the tunicated bulb of the Leek. The letters indicate the same 
parts as in the last figure. 6, Bud situated in the axil of a scale, which, by its development, forms 
a new bnlb. 

Fig. 209. Scaly or naked bulb of Lilium album, r, Roots, eee. Scales or modified under- 
ground leaves, t, The stem cut. 



100 ANOMALIES AND TRANSFORMATIONS OF LEAF-BUDS. 

is detached in the course of growth, and forms an independent plant. 
The new bulbs feed on the parent one, and ultimately cause its 
absorption. The scales are sometimes all fleshy, as in the scaly or naked 
bulb of the white lily (fig. 209 e e e), or the outer ones are thin and 
membranous, overlapping the internal fleshy ones, and forming a 
tunicated bulb, as in the Onion, Squill, and Leek (fig. 207). 

195. The form (x,oofin s a stump) has already been noticed under 
the head of subterranean stems (^[ 70, fig. 93). It may be considered 
as a bulb in which the central portion or axis is much enlarged, 
while the scales are reduced to thin membranes. Some have called it u 
solid bulb. It is seen in the Tulip, Colchicum, Crocus, and Gladiolus. 
It produces either terminal buds, as in Gladiolus and Crocus, in which 
several annual additions to the corm remain attached together, and 
the newly produced corms come gradually nearer and nearer to the 
surface of the soil ; or lateral buds, as in Colchicum, represented at fig. 
03, where r indicates the roots, / the leaf, a 1 the stem or axis of the 
preceding year withered, a" the secondary axis, or the stem developed 
during the year, and taking the place of the old one, and which, in 
its turn, will give origin to a new axis, a'", on the opposite side, 
according to the law of alternation. The new axes or corms being 
thus produced alternately at either side, there is very little change in 
the actual position of the plant from year to year. Bulbs and corms 
contain a store of starch and of other substances, for the nourishment 
of the young plants. 

196. Anomalies and Tranaformations of I-caf-buds. Leaf-buds arise 

from the medullary system of the plant, and in some instances thev 
are found among the cellular tissue, without being in the axil of leaves. 
In this case they are extra-axillary, and have been called adventitious 
or abnormal. Such buds are produced after the stem and leaves have 
been formed, and in particular circumstances they are developed like 
normal buds. What have been called embryo-buds, are woody nodules 
seen in the bark of the Beech, Elm, and other trees. They are looked 
upon as partially developed abnormal buds, in which the woody matter 
is pressed upon by the surrounding tissue, and thus acquires a very 
hard and firm texture. When a section is made, 
they present woody circles arranged around a 
central pith, and traversed by medullary rays 
(fig. 210). The nodules sometimes form knots 
on the surface of the stem, at other times they 
appear as large excrescences, and in some cases 
twigs and leaves are produced by them. Some 
consider embryo-buds as formed by layers of 
woody matter, which originate in the sap con- 

Fig. 210. Vertical section of a nodule, , or embryo-bud embedded in the bark of the Cedar 
forms a projection on the surface. The woody layers form zones round a kind of pith. 




ANOMALIES AND TRANSFORMATION'S OF LEAF-BrDS. 



101 



veyed downward by the bark and cambium cells, and are deposited 
round a nucleus or central mass. 

197. Leaf-buds sometimes become extra-axillary (fig. 211 5), in 
consequence of the non-appearance or abortion of one or more leaves, 
or on account of the adhesion of the young branch to the parent stem. 
In place of one leaf-bud, there are occasionally several accessory ones 
produced in the axil, giving origin to numerous branches (fig. 212 b). 





Such an occurrence is traced to the presence of latent or adventitious 
buds. Fig. 211 represents a branch, r, of walnut, p the cut petiole, 
and b tAvo buds, of which the upper is most developed, while fig. 212 
exhibits a branch of Lonicera tartarica, with numerous buds, b, in the 
axil of the leaves, the lowest of Avhich are most advanced. By the 
union of several such leaf-buds, branches are produced having a 
thickened or flattened appearance, as is seen in the Fir, Ash, and 
other trees. These fasciated (fascia, a band) branches, in some cases 
however, are owing to the abnormal de- 
velopment of a single bud. 

198. In the axil of the leaves of Lilium 
bulbiferum, Dentaria bulbifera, and some 
other plants, small conical or rounded bodies 
are produced called bulbils or bulblets (fig. 
213 b b b). They resemble bulbs in their 
aspect, and consist of a small number of 
thickened scales enclosing a growing point. 
These scales are frequently united closely 
together so as to form a solid mass. Bulbils 
are therefore transformed leaf-buds, which 

Fig. 211. Portion of a branch, r, of the walnut, bearing the petiole, p, of a leaf which has 
been cut In the axil of the leaf, several buds, 6, are produced, the highest of which are most 
developed. 

Fig. 212. Portion of a branch, r, of Lonicera tartarica, bearing two opposite leaves, one of 
which has been cut, the other, /, being preserved. In the axil of the leaves, clusters of buds, 6, 
ure seen, the lowest of which are most developed. 

Fig. 213. Portion of the stem of Lilium bulbiferum with three alternate leaves,///, and three 
bulbils or bulblets, b b b, in their axils. 




102 



SPINES OR THORNS. 




are easily detached, and are capable of producing young plants when 
placed in favourable circumstances. 

199. Occasionally leaf-buds are produced naturally on the edges 
of leaves, as in Bryophyllum calycinum and Malaxis paludosa (fig. 
214), and on the surface of leaves, as in Ornithogalum thyrsoideum 
(fig. 215). These are capable of forming independent plants. Similar 

buds are also made to ap- 
b ~ * > ., pear on the leaves of Gesne- 

ra, Gloxinia, and Achime- 
nes, by wounding various 
parts of them, and placing 
them in moist soil ; this 
is the method often pur- 
6 sued by gardeners in their 
propagation. The cellular 
tissue near the surface of 
plants, seems therefore to 
214 215 have the power of develop- 

ing abnormal leaf-buds in certain circumstances. Even roots, when 
long exposed to the air, may thus assume the functions of stems. 
Leaves bearing buds on their margin, are called proliferous (proles, 
offspring, and jfero, I bear). 

200. Spines or Thorns. Branches are sometimes arrested in their 
development, and, in place of forming leaves, become transformed into 
spines and tendrils. Spines or thorns are undeveloped branches, ending 

in more or less pointed extremi- 
ties, as in the Hawthorn. Plants 
which have spines in a wild state, 
as the Apple and Pear, often lose 
them when cultivated, in conse- 
quence of their being changed 
into branches; in some cases, as 
in Prunus spinosa, or the Sloe (fig. 
217), a branch bears leaves at 
its lower portions, and terminates 
in a spine. Leaves themselves 
often become spiny by the har- 
dening of their midrib or primary 
21? veins, and the diminution or 
absence of parenchyma, as in Astragalus massiliensis (fig. 217 r), 

Fig. 214. Extremity of a leaf, !, of Malaxis paludosa, the margin of which is covered with 
adventitious buds, 6 b; thus becoming proliferous. 

Fig. 215. Portion of the blade of a leaf, /, of Ornithogalum thyrsoideum, on the surface of 
which are developed adventitious or abnormal buds, 6666, some of which are large. 

Fi<r. 216. Branch of Prunus spinosa, or Sloe, with alternate leaves, and ending in a spine or 
thorn. 

Fig. 217. Pinnate leaf of Astragalus massiliensis, the midrib of which, r, ends in a spine .< 
Petiolary stipules. /, Nine pairs of leaflets. 




SPINES OR THORNS, AND TENDRILS. 



103 



where the midrib becomes spiny after the fall of some of the leaflets; in 
the Holly, where all the veins are so; and in the Barberry (fig. 218), 
where some of the leaves, fff, are produced in the form of spiny 
branches, with scarcely any parenchyma. In place of producing a lamina 
or blade at its extremity, the petiole sometimes terminates in a spine. 
Stipules are occasionally transformed into spines, as in Robinia pseudo- 
acacia (fig. 219, ss), and such is also the case with the swelling or pulvinus 
at the base of the leaf, as in Ribes Uva-crispa (fig. 220, ccc). Branches 




are sometimes arrested in their progress at an early state of their de- 
velopment, and do not appear beyond the surface of the stem; at 
other times, after having grown to a considerable size, they undergo 
decay. In both instances, the lower part of the branch becomes 
embedded and hardened among the woody layers of the stem, and 
forms a knot. 

201. Tendrils. A leaf-bud is sometimes developed as a slender spiral 
or twisted branch, called a tendril or cirrhus (cirrus, a curl), as in the Pas- 
sion-flower, in which the lateral buds are thus altered with the view of 
enabling the plant to climb. When tendrils occupy the place of leaves, 
and appear as a continuation of the leaf-stalk, they are called petiolary, 
as in Lathyrus Aphaca, in which the stipules perform the function of 
true leaves. In Flagellaria indica, Methonica superba, Anthericum 

Fig. 21S. Branch of Berberis vulgaris, or Barberry, the leaves of which, ///, are transformed 
into branching spines. In the axil of each, a cluster, r r r, of regularly formed leaves is de- 
veloped. 

Fig. 219. Base of the pinnate leaf of Robinia pseudo-acacia, the stipules of which, s s, are 
converted into spines or thorns, b, Branch, r, Petiole. 

Fig. 220. Branch of Ribes Uva-crispa, in which the pulvinus or swelling, ccc, at the base 
of each of the leaves, ///, is changed into a spine, which is either simple, or double, or tripk-. 
b 6, Leaf-buds arising from the axil of the leaves. 



104 



TENDRIL OR CIRRHUS. 



cirrhatum, and Albuca cirrhata, the midrib of the leaf ends in a ten- 
dril; and hi Vetches, the terminal leaflet, and some of the lateral ones 
at the extremity of their pinnate leaves, are changed, so as to form a 
branching tendril. In the Vine, the tendrils are looked upon as the 
terminations of separate axes, or as transformed terminal buds. In this 
plant there are no young buds seen in the angle between the stem and 
leaves, nor between the stem and tendrils; and the latter are not axillary. 
Fig. 221 represents the branch of a Vine, hi which a! is the primary or 

first formed axis, ending inv', 
a tendril, or altered terminal 
bud, and having a leaf, f,' on 
one side. Between this leaf 
and the tendril which repre- 
sents the axis, a leaf-bud was 
formed at an early date pro- 
ducing the secondary axis, 
or branch, a", ending in a 
tendril, v", with a lateral leaf, 
f", from which a tertiary axis 
or branch, a'" was developed, 
ending in a tendril, v'", and 
so on. 

202. Tendrils twist in a 
spiral manner, and enable the 
plants to rise into the air by 
twining round other plants. 
The direction of the spiral 
frequently differs from that 
of the climbing stem, pro- 
ducing the tendril. In the Vine, the lower part of the stem is strong, 
and needs no additional support; the tendrils therefore occur only 
in the upper part where the branches are soft, and require aid to 
enable them to support the clusters of fruit. In Vanilla aromatica, 
the vanille plant, tendrils are produced opposite the leaves, until the 
plant gains the top of the trees by which it is supported; the upper ten- 
drils being then developed as leaves. The midrib is sometimes prolonged 
in a cup-like form: this is occasionally seen in the common cabbage, 
arid seems to depend on the vascular bundles of the midrib spreading 
out at their extremity in a radiating manner, and becoming covered 
with parenchyma in such a way as to form a hollow cavity in the centre. 




Fig. 221. Portion of a branch of the Vine (Vita viniferd). a', First axis, terminated by a 
tendril or cirrhus, -', which assumes a lateral position, and bears a leaf, /'. From the axil of this 

also by a ten _ 
terminated by 
arises. 



cirrhus, t', which assumes a lateral position, arid bears a leaf, /'. From the axil of this 
ond axis, a", comes off, which seems to be a continuation of the first, and is terminated 
tendril, v', bearing a leaf,/''. From the axil of this second leaf, a third axis, "', arises 
d by a tendril, v"', and bearing a leaf, /'", from the axil of which a fourth axis a '", 



EXHALATION OR TRANSPIRATION. 105 



Special Functions of Leaves. 

203. Leaves expose the fluids of the plant to the influence of air 
and light, and their spiral arrangement enables them to do so effectu- 
ally. They are concerned in the elaboration of the various vegetable 
secretions, in the formation of wood, and in the absorption of fluid and 
gaseous matters. A plant, by being constantly deprived of its leaves, 
will ultimately be destroyed. On this principle, weeds, with creeping 
stems and vigorous roots, which are with difficulty eradicated, may be 
killed. In the cells of the leaves changes take place under the agency 
of light, by which oxygen is given off and carbon fixed. These will 
be considered under the subject of vegetable respiration. The absorp- 
tion of carbonic acid and of fluids is carried on by the leaves, chiefly 
through their stomata, according to Bonnet. Some physiologists have 
expressed doubts as to absorption being carried on by the leaves in 
ordinary circumstances. Leaves also give off gases and fluids by a 
process of exhalation or transpiration. Carbonic acid, to a moderate 
extent, is exhaled during darkness, and a large quantity of fluid is 
given off by transpiration. The number and size of the stomata regulate 
the transpiration of fluids, and it is modified by the nature of the 
epidermis. In plants with a thick and hard epidermal covering, ex- 
halation is less vigorous than in those where it is thin and soft. Some 
succulent plants of warm climates have a very thick covering. The 
peculiar character of the leaves or phyllodia of Australian plants, is 
probably connected with the dry nature of the climate. While heat acts 
in promoting evaporation, the process of transpiration is more under 
the influence of light. It assists the process of endosmose, by rendering 
the fluid in the cells thicker, and thus promotes the circulation of sap. 

204. The quantity of fluid exhaled varies in amount in different plants. 
A Sunflower, three feet high, gave off twenty ounces of watery fluid 
daily. Hales found that a Cabbage, with a suface of 2,736 square 
inches, transpired at an average nineteen ounces; a Vine, of 1,820 square 
inches, from five to six ounces. Experiments on exhalation maybe made 
by taking a fresh leaf with a long petiole, putting it through a hole in 
a card which it exactly fits, and applying the card firmly and closely 
to a glass tumbler, about two-thirds full of water, so that the petiole 
is inserted into the water, then inverting an empty tumbler over the 
leaf, and exposing the whole to the sun, the fluid exhaled will be seen on 
the inside of the upper tumbler. The experiment may be varied by 
putting the apparatus in darkness, when no exhalation takes place, or 
in diffuse daylight, when it is less than in the sun's rays. This process 
of exhalation imparts moisture to the atmosphere, and hence the dif- 
ference between the air of a wooded country and that of a country 
deprived of forests. The cells in the lower side of a leaf where stomata 



106 FUNCTIONS OF NUTRITIVE ORGANS. 

exist, are chiefly concerned in the aeration of the sap, whilst other 
assimilative processes go on in the upper cells. 

205. Leaves, after performing their functions for a certain time, 
wither and die. In doing so, they frequently change colour, and hence 
arise the beautiful and varied tints of. the autumnal foliage. Leaves 
which are articulated with the stem, as in the Walnut and Horse- 
chestnut, fall and leave a scar, while those which are continuous with 
it remain attached for some time after they have lost their vitality, as 
in the Beech. Most of the trees of this country have deciduous leaves, 
their duration not extending over more than a few months; while in 
trees of warm climates, the leaves often remain for two or more years. 
In tropical countries, however, many trees lose their leaves in the dry 
season. This is seen in the forests of Brazil, called Catingas. Trees 
which are called evergreen, as Pines and Evergreen oak, are always 
deprived of a certain number of leaves at intervals, sufficient being 
left, however, to preserve their green appearance. Various causes 
have been assigned for the fall of the leaf. . In cold climates, the de- 
ficiency of light and heat in winter causes a cessation in the functions 
of the cells of the leaf; its fluid disappears by evaporation; its cells and 
vessels become contracted and diminished in their calibre; various 
inorganic matters accumulate in the texture; the whole leaf becomes 
dry; its parts lose their adherence; and it either falls by its own weight 
or is detached by the wind. In warm climates, the dry season gives 
rise to similar phenomena. 



SECTION II. GENERAL VIEW OF THE FUNCTIONS OF 
THE NUTRITIVE ORGANS. 

206. In order that plants may be nourished, food is required. This 
food, in a crude state, enters the roots by a process of absorption or 
imbibition; it is then transmitted from one part of the plant to another, 
by means of the circulation or progressive movement of the sap; it reaches 
the leaves, and is there submitted to the action of light and air, which 
constitutes the function of respiration; and thus the fluids are finally 
fitted for the process of assimilation, and form various vegetable pro- 
ducts and secretions. 

1. FOOD OF PLANTS, AND SOURCES WHENCE THEY DERIVE THEIR NOURISHMENT. 
CHEMICAL COMPOSITION OF PLANTS. 

207. The nutriment of plants can only be ascertained when their 
chemical composition has been determined. The physiologist and chemist 
must unite in this inquiry, in order to arrive at satisfactory conclu- 
sions. Much has been done of late by Liebig, Mulder, Dumas, Bous- 



CHEMICAL COMPOSITION OF PLANTS. 



107 



singault, and other chemists, to aid the botanist in his investigations, 
and to place physiological science on a sound and firm basis. It is true 
that many processes take place in plants which cannot as yet be ex- 
plained by the chemist, and to these the name of vital has been applied. 
This term, however, must be considered as implying nothing more 
than that the function so called occurs in living bodies, and in the 
present state of our knowledge is not reducible to ordinary chemical 
or physical laws. A greater advance in science may clear up many 
difficulties in regard to some of the vital functions, while others may 
ever remain obscure. 

208. Plants are composed of certain chemical elements, which are 
necessary for their growth. These are combined in various ways, so 
as to form what have been called organic and inorganic compounds. 
The former are composed of carbon, oxygen, hydrogen, and nitrogen 
or azote, with a certain proportion of sulphur and phosphorus ; while 
the latter consist of various metallic bases, combined with oxygen, 
metalloids, and acids. In all plants there is a greater or less propor- 
tion of water, the quantity of which is ascertained by drying at a 
temperature a little above that of boiling water. By burning the 
dried plant the organic constituents disappear, and the inorganic part 
or the ash is left. The relative proportion of these constituents varies 
in different species, as seen in the following table by Solly, in which 
the proportions are given in 10,000 parts of the fresh plants: 

Water. Organic Matter. Inorganic. 

Potato, 7713 2173 . 114 

Turnip, 9308 588 . 104 

Sea Kale 9238 705 . 57 

French Beans 9317 619 . 64 

lied Beet 8501 1390 . 10'J 

Asparagus, 9210 735 . 55 

WaterCress, 9260 633 . 107 

Sorrel, 9207 702 . 91 

Parsley 8430 1299 . 271 

Fennel, 8761 1048 . 191 

Salsafy 7951 1929 . 120 

Mustard, 9462 436 102 

209. The analysis of 100 parts of Fruits gives the following results: 

Water. Organic. Inorganic. 

Strawberry 90-22 9'37 .... 0-41 

Green Gage, whole fruit 83'77 .. 15-83 .... 0'40 

Cherry, do., 82'48 .. 17'09 .... 0'43 

Pear, do,, 83'55 .. 16-04 .... 0'41 

Apple, do., 84-01 .. 15-72 .... 0'27 

Gooseberry, 90-26 .. 9'35 .... 0'39 

210. The following table, by Johnston, represents the constitution in 
1000 parts of plants and seeds, taken in the state in which they are 



1 08 ORGANIC CONSTITUENTS OF PLANTS. 

given to cattle, or laid up for preservation, and dried at 230 Fahren- 
heit; the organic matter being indicated by the carbon, oxygen, 
hydrogen, and nitrogen ; the inorganic by the ash : 

Wheat. Oats. Peas. Hay. Turnips. Potatoes. 

Carbon 455 507 465 458 429 441 

Hydrogen, 57 64 61 50 56 58 

Oxygen, 430 367 401 387 422 439 

Nitrogen, 35 22 42 15 17 12 

Ash, 23 40 31 90 76 50 

By the process of drying, the 1000 parts of these substances lost water 
in the following proportions : 

Wheat, 166 Peas, 86 Turnips, 925 

Oats, 151 Hay, 158 . Potatoes, 722 

211. As plants have no power of locomotion, it follows that their 
food must be universally distributed. The atmosphere and the soil 
accordingly contain all the materials requisite for their nutrition. 
These materials must be supplied either in a gaseous or a fluid form, 
and hence the necessity for the various changes which are constantly 
going on in the soil, and which are aided by the efforts of man. 
Plants are capable of deriving all their nourishment from the mineral 
kingdom. The first created plants in all probability did so, but in the 
present day the decaying remains of other plants and of animals are 
also concerned hi the support of vegetation. 

Organic Constituents and their Sources. 

212. Carbon (C) is the most abundant element hi plants. It forms 
from 40 to 50 per cent, of all the plants usually cultivated for food. When 
plants are charred the carbon is left, and as it enters into all the tissues, 
although the weight of the plants is diminished by the process, their form 
still remains. When converted into coal (a form of carbon), plants are 
frequently so much altered by pressure as to lose their structure, but 
occasionally it can be detected under the microscope. Carbon is insoluble, 
and therefore cannot be absorbed in its uncombined state. When 
united to oxygen, however, hi the form of carbonic acid, it is readily 
taken up either hi its gaseous state by the leaves, or hi combination with 
water by the roots. The soil contains carbon (humus), and in some soils, 
as those of a peaty nature, it exists in very large quantity. The carbon 
in the soil is converted into carbonic acid in order to be made avail- 
able for the purpose of plant-growth. Carbon has the power of absorb- 
ing gases, and in this way, by enabling certain combinations to go on, it 
assists in the nourishment of plants. In the atmosphere, carbonic acid 
is always present, averaging about ^^ part, arising from the respir- 
ation of man and animals, combustion, and other processes. 



ORGANIC CONSTITUENTS OF PLANTS. 109 

213. Oxygen (0) is another element of plants. Air contains about 
21 per cent, of it. Every 9 Ibs. of water contain 8 of oxygen, and it 
is combined with various elements, so as to form a great part of the 
solid rocks of the globe, as well as of the bodies of animals and man. 

214. It is chiefly in its state of combination with Hydrogen (H), so 
us to form water (HO), that oxygen is taken up by plants. Hydrogen 
is not found in a free state in nature, and with the exception of coal, 
it does not enter into the composition of the mineral masses of the 
globe. It forms ^ of the weight of water, and it is present in the 
atmosphere in combination with nitrogen. Hydrogen is also furnished 
by sulphuretted hydrogen, and some compounds of carbon. 

215. Nitrogen (N) is another element found in plants. It forms 79 
per cent, of the atmosphere, and abounds in animal tissues. The latter, 
during their decay, give off nitrogen, combined with hydrogen, in the 
form of ammonia (NH 3 ), which is absorbed in large quantities by 
carbon, is very soluble in water, and seems to be the chief source 
whence plants derive nitrogen. In tropical countries where thunder 
storms are frequent, the nitrogen and oxygen of the air are sometimes 
made to combine, so as to produce nitric acid, (NO 5 ) which, either in 
this state, or in combination with alkaline matters, furnishes a supply 
of nitrogen. Daubeny thinks that the ammonia and carbonic acid in 
the atmosphere are derived in part from volcanic actions going on in the 
interior of the globe. The continued fertility of the Terra del Lavoro, 
and other parts of Italy, is attributed by him to the disengagement of 
ammoniacal salts and carbonic acid by volcanic processes going on un- 
derneath ; and to the same source he traces the abundance of gluten 
in the crops, as evidenced by the excellence of Italian macaroni. 

216. Mulder maintains that the ammonia is not carried down from 
the atmosphere, but is produced in the soil by the combination between 
the nitrogen of the air, and the hydrogen of decomposing matters. The 
same thing takes place, as in natural saltpetre caverns of Ceylon, with 
this exception, that, by the subsequent action of oxygen, ulmic, humic, 
geic, apocrenic, and crenic acids, are formed in place of nitric acid. 
These acids consist of carbon, oxygen, and hydrogen, in different pro- 
portions, and they form soluble salts with ammonia. By all porotis 
substances like the soil, ammonia is produced, provided they are 
moist, and filled with atmospheric air, and are exposed to a certain 
temperature. It is thus, he states, that moist charcoal and hunms 
become impregnated with ammonia. 

217. These four elementary bodies then are supplied to plants, chiefly 
in the form of carbonic acid (CO 2 ), water (HO), and ammonia (NH 3 ). 
In these states of combination they exist in the atmosphere, and hence 
some plants can live suspended in the air, without any attachment to 
the soil. When a volcanic or a coral island appears above the waters 
of the ocean, the lichens which are developed on it are nourished 



110 ORGANIC CONSTITUENTS OF PLANTS. 

in a great measure by the atmosphere, although they subsequently 
derive inorganic matter from the rocks, to which they are attached. 
Air plants, as Bromelias, Tillandsias, and Orchidacese, and many species 
of Ficus, can grow for a long time in the air. In the Botanic Gar- 
den of Edinburgh, a specimen of Ficus australis has lived in this con- 
dition for upwards of twenty years, receiving no supply of nourishment 
except that afforded by the atmosphere and common rain water, con- 
taining, of course, a certain quantity of inorganic matter. The follow- 
ing analysis was made of the leaves of this plant, in 1847, by my 
pupil, Mr. John Macadam : 

Organic. Inorganic. 
In 100 -parts. In 100 parts. 

Petiole of former year's growth, including midrib, 82'98 ... 17 - 02 

Three leaves of former year's growth, 86 - 24 ... 13'76 

Petiole of present year's growth, with midrib, 92'65 ... 7'35 

Seven leaves of present year's growth, 92-28 ... 7*72 

All were dried at 212 Fahrenheit. 

In the experimental Garden of Edinburgh, Mr. James M'Nab has 
cultivated various plants, as Strelitzia augusta, currants, gooseberries, 
&c., without any addition of soil, and simply suspended in the air, with 
a supply of water kept up by the capillary action of a worsted thread. 
Some of the plants have flowered and ripened fruit. These experiments 
show that the atmosphere and rain water contain all the ingredients 
requisite for the life of some plants. Boussingault, from observations 
made on the cultivation of Trefoil, was led to the conclusion, that under 
the influence of air and water, in a soil absolutely devoid of organic 
matter, some plants acquire all the organic elements requisite for growth. 
Messrs. Wiegman and Polstorf took tine quartz sand, burnt it to destroy 
any organic matter, digested it for sixteen hours in strong nitro-muriatic 
acid, and then washed it with distilled water. Various kinds of seeds, 
as barley, oats, vetch, clover, and tobacco, were then sown in it, and 
watered with distilled water, and all grew more or less. 

218. The elementary bodies already mentioned, in various states of 
combination, constitute the great bulk of plants. They occur in the 
form of binary compounds, as water and oily matters ; ternary, as 
starch, gum, sugar, and cellulose ; quaternary, as gluten, albumen, 
caseine, and fibrine. The latter compounds seem to require for their 
composition, not merely the elements already noticed, in the form of a 
basis, called Proteine (C 40 H 31 N 5 O 12 according to Mulder, or C 48 
H 36 N 6 O 14 according to Liebig), but certain proportions of sulphur and 
phosphorus in addition ; thus, albumen = 10 Pr. + IP-f IS; fibrine 
= 10 Pr. + 1 P + 2 S; caseine = 10 Pr. + 2 S. The tissues into the 
composition of which these proteine compounds enter, are tinged of a 
deep orange-yellow, by strong nitric acid. These compounds are highly 
important in an agricultural point of view, and the consideration of 
them will be resumed when treating of the application of manures. 



INORGANIC CONSTITUENTS OF PLANTS. Ill 

Inorganic Constituents, and their Sources. 

219. The consideration of the inorganic constituents of plants is no 
less important than the study of their organic elements. The organic 
substances formed by plants are decomposed by a moderately high 
temperature ; they easily undergo putrefaction, especially when ex- 
posed to a moist and warm atmosphere, and they have not been formed 
by human art. Their inorganic constituents, on the other hand, are 
not so easily decomposed ; they do not undergo putrefaction, and they 
have been formed artificially by the chemist. 

220. The combustible or organic part of plants, even in a dried 
state, forms from 88 to 99 per cent, of their whole weight. Conse- 
quently, the ash or inorganic matter frequently constitutes a very small 
proportion of the vegetable tissue. It is not, however, on this account 
to be neglected, for it is found to be of great importance in the 
economy of vegetation, not merely on account of its entering directly 
into the constitution of various organs, but also from assisting in the 
production of certain organic compounds. Some of the lower tribes of 
cellular plants can exist apparently without any inorganic matter. 
Thus Mulder could not detect a particle of ash in Mycoderma vini, 
nor in moulds produced in large qiiantity by milk siigar. Deficiency of 
inorganic matters, however, in general injures the vigour of plants, and 
it will be found that, in an agricultural point of view, they require 
particular attention a distinct relation siibsisting between the kind and 
quality of the crop, and the nature and chemical composition of the 
soil in which it grows. It has been shown by careful and repeated 
experiments, that, when a plant is healthy and fairly ripens its seeds, 
the quantity and quality of the ash is nearly the same in whatever 
soil it is grown ; and that, when two different species are grown in the 
same soil, the quantity and quality of the ash varies the difference 
being greater the more remote the natural affinities of the plants are. 

221. The inorganic elements of plants and their combinations, are 
thus given by Johnston: 

Chlorine (Cl.) combined with metals forming chlorides. 
Iodine (I.) ... ... metals ... iodides. 

Bromine (Br.) ...... metals ... bromides. 

f ...... metals ... sulphurets. 



[_ ...... oxygen ... sulphuric acid. 

Phosphorus (P.) ... ... oxygen ... phosphoric acid. 

p . , , f ...... oxygen ... potassa. 

*> \ ...... chlorine ... chloride of potassium. 

( ...... oxygen ... soda. 

Sodium (Na.) < ,, (chloride of sodium. 

j ... ... chlorine -< / , , 

( ( (common salt. ) 

p ol , fr < -, \... ... oxygen ... lime. 

Calcium (L/a.) ,,- . ,, . -, e , . 

(... ... chlorine ... chloride of calcium. 



112 



INORGANIC CONSTITUENTS OF PLANTS. 



Magnesium (Mg.) combined with oxygen forming magnesia. 
Aluminum (AL) ...... oxygen ... alumina. 

Silica (Si.) ...... oxygen ... silica. 

Iron (Fe.) ) (oxides 

Manganese (Mn.)> ...... S^ '" 1 and 

Copper (Cu.) j sulphur - (sulphurets. 

222. The quantity of inorganic matter or ash left by plants, varies 
in different species, and in different parts of the same plant. The 
dried leaves usually contain a large quantity. Saussure found that 

Dried bark of Oak gave ...................................... 60 of ash in 1000 

Dried leaves ............................................... 53 

Dried Alburnum ............................................... 4 ...... 

Dried duramen ................................................. 2 

The dried leaves of Elm contain more than 11 per cent, of inorganic 
matter, while the wood contains less than 2 per cent. ; the leaves of 
the Willow, 8 per cent., wood, 0*45 ; leaves of Beech, 6'69, wood, 
0'36; leaves of Pitch-pine, 3'5, wood, 0*25. Thus, the decaying 
leaves of trees restore a large quantity of inorganic matter to the soil. 

223. The following tables show the relative proportion of inorganic 
compounds present in the ash of plants: 

According to Sprengel, 1000 Ibs. of wheat leave 11 '77 Ibs., and of wheat 
straw 35-18 Ibs. of ash, consisting of 

Grain. Straw. 

Potash .......................................... 2-25 ......... 0"20 

Soda ............................................. 2-40 ......... 0-29 

Lime .......................................... 0-96 ......... 2-40 

Magnesia ..................................... 0'90 ......... 0*32 

Alumina with trace of iron ............... 0-26 ......... 0'90 

Silica ............................................. 4-00 ......... 28-70 

Sulphuric acid ................................. 0-50 ......... 0'37 

Phosphoric acid ............................. 0-40 ......... 1-70 

Chlorine ........................................ 0-10 ......... 0-30 

11-77 Ibs. 35-1 8 Ibs. 

In 1000 Ibs. of the grain of the Oat, are contained 25 - 80 Ibs., and of the dry 

straw 57 '40 Ibs. of inorganic matter, consisting of 

Grain. Straw. 

Potash ......................................... 1-50 ......... 8-70 

Soda ........................................... 1-32 ......... 0-02 

Lime ............................................. 0'86 ......... 1-52 

Magnesia ....................................... - 67 ......... 0-22 

Alumina ...................................... . 0'14 ......... 0'06 

Oxide of iron .................................. 0-40 ......... 0'02 

Oxide of manganese ........................ O'OO ......... 0-02 

Silica ............................................. 19-76 ......... 45-8S 

Sulphuric acid ................................ 0'35 ......... 079 

Phosphoric acid ............................... 0'70 ......... 0'12 

Chlorine ........................................ 0-10 ......... 0-05 



57-40 Ibs. 



INORGANIC CONSTITUENTS OF PLANTS. 



113 



In 1000 Ibs. of the field Bean, field Pea, and Rye-grass hay, after being dried in 
the air, the following is the amount of ash, and its composition : 



Potash 


Field I 
Seed, 

..4-15 ... 


Jean. 
Straw, 

16-56 
0-50 
6"24 
2-09 

o-io 

0-07 
0-05 
2-20 
0-34 
2-26 
0.80 


Field 
Seed. 

8-10 ... 
7-39 ... 


Pea. 

Straw. 

2-35 . 


Rye-gras 
Hay. 

8'81 


Soda 


.8-16 ... 




3-94 


Lime 


. 1'65 ... 


0-58 ... 
1-36 . 
0-20 ... 

o-io ... 

4-10 ... 
053 ... 
1-90 ... 
0-38 ... 


27-30 . 
3-42 . 


7-34 
0-90 


Magnesia 


..1-58 ... 


Alumina 
Oxide of Iron 


..0-34 ... 


0-60 . 
0-20 
0-07 . 
9'96 . 


0-31 


Oxide of Manganese., 
Silica 


,.1'26 ... 


27'72 


Sulphuric acid 
Phosphoric acid , 
Chlorine 


..0-89 ... 
,.2'92 ... 

..0-41 ... 


3 37 . 
2-40 . 
0-04 . 


353 
025 
0-06 



2136 31-21 



24-64 



49-71 



52-86 



224, Dr. R. D. Thomson gives the following analysis of the inorganic 
matter in the stem and seeds of Lolium perenne : 



Stem. 

Silica 64-57 

Phosphoric acid 12-51 

Sulphuric acid 

Chlorine 

Carbonic acid 

Magnesia 4-01 

Lime 6-50 

Peroxide of Iron 0'36 

Potash 8-03 

Soda... .. 2.17 



Seed. 

42-28 

18-89 

3-12 

trace. 

3-61 

5-31 

18-55 

2-10 

4-80 

1-38 



225. These substances are variously combined in plants, in the form 
of sulphates, phosphates, silicates, and chlorides. Some plants, as 
Wheat, Oats, Barley, and Eye, contain a large quantity of Silica in 
their straw; others, such as Tobacco, Pea-straw, Meadow-clover, Potato- 
haulm, and Sainfoin, contain much lime ; while Turnips, Beet-root, 
Potatoes, Jerusalem-artichoke, and Maize-straw, have a large proportion 
of salts of potash and soda in their composition. Sulphates and phos- 
phates are required to supply part of the material necessary for the 
composition of the nutritritive proteine compounds found in grain. 

226. Silica abounds in Grasses, in Equisitem, and other plants, 
giving firmness to their stems. The quantity contained in the Bam- 
boo is very large, and it is occasionally found in the joints in the form 
of Tabasheer. Eeeds, from the quantity of siliceous matter they con- 
tain, are said, during hurricanes in warm climates, to have actually 
caused conflagrations by striking against each other. In the species 
of Equisetum, the silica in the ash is as follows : 



114 INORGANIC CONSTITUENTS OF PLANTS. 

Ash. Silica. 

Equisetum arvense 13-84 6'38 

limosnm 15'50 

hvemale H-81 8'75 

Telroateia 23'61 12-00 



The third of these furnishes Dutch Rush, used for polishing mahogany. 
The silica is deposited in a regular manner, forming an integral part 
of the structure of the plant. Many insoluble matters, as silica, seem 
to be deposited in cells by a process of decomposition. Thus, silicate 
of potash in a vegetable sap may be mixed with oxalic acid, by which 
oxalate of potash, and silicic acid will be produced, as in the cells of 
Grasses and Equisetum. Chara translucens has a covering of silicic 
acid, while C. vulgaris has one composed of silicic acid and carbo- 
nate of limp ; and Chara hispida has a covering of carbonate of lime 
alone. 

227. JLime is found in all plants, and in some it exists in large 
quantity. It occurs sometimes in the form of carbonate on the sur- 
face of plants. Thus, many of the Characeas have a calcareous encrus- 
tation. The crystals or raphides (^ 18) found in the cells of plants, 
have lime in their composition. 

228. Soda and Potash occur abundantly in plants. Those grow- 
ing near the sea have a large proportion of soda in their composition, 
while those growing inland contain potash. Various species of Salsola. 
Salicornia, Halimocnemum, and Kochia, yield soda for commercial pur 
poses, and are called Halophytes AJ, salt, and Qvroy, plant). The 
young plants, according to Gobel, furnish more soda than the old ones 
There are certain species, as Armeria maritima, Cochlearia officinalis, 
and Plantago maritima, which are found both on the sea-shore, and 
high on the mountains removed from the sea. In the former situation 
they contain much soda and some iodine ; while in the latter, accord- 
to Dr. Dickie, potash prevails, and iodine disappears. 

229. iron, manganese, and Copper, especially the two last, exist 
in small quantity in plants. Copper was detected, by Sarzean, in 
coffee. 

230. All these inorganic matters are derived in a state of solution 
from the soil, and plants are said to have, as it were, a power of selec- 
tion, certain matters being taken up by their roots in preference to 
others. Saussure made a series of experiments on this subject, and 
stated that when the roots of plants were put into solutions contain- 
ing various saline matters in equal proportions, some substances were 
taken up by imbibition in larger proportion than others. Bouchardat 
doubts the accuracy of Saussure's conclusions on this point. He thinks 
that errors arose from the excretions of the plants and other causes. 
He performed similar experiments with plants of Mint, which had been 
growing for six months in water previous to experiment, and he found 



ROTATION OP CROPS. 



115 



that in cases of mixed salts in water, the plant absorbed all in equal 
proportions. Daubeny states, that if a particular salt is not present, 
the plant frequently takes up an isomorphous one. 

231. The differences in the absorption of solutions depend, per- 
haps, on the relative densities alone, and not on any peculiar selecting 
power in roots, for it is well known that poisonous matters are absorbed 
as well as those which are wholesome. The following experiments show 
that poisonous matters in solutions, varying from half a grain to five 
grains to the ounce of water, are taken up by roots, and that some 
substances which are poisonous to animals do not appear to act ener- 
getically upon plants : 



Chloride of zinc, 
Sulphate of zinc. 
Sulphate of copper, 
Nitrate of copper, 
Acetate of copper, 

Bichloride of mercury, 

Arsenious acid, 
Arseniate of potash, 
Acetate of lead, 

Bichromate of potash, 

Nitrate fe sulphate of iron, 
Chloride of barium, 
Nitrate of baryta, 

Nitrate of strontia, 

Muriate, sulphate, and) 
nitrate of lime, ) 

Sulphate and muriate) 
of magnesia, / 

Phosphate of soda, 

Chloride of sodium, 



Growing Plants. . 
i beans, 

. cabbages, and wheat, 
, beans, 
. beans, 
cabbages, 
(beans, 
< wheat, 
(cabbages, 
cabbages and wheat, 
barley and cabbages, 
beans, 

cabbages, beans, barley 

beans, 
beans, 
cabbages and wheat, 

beans, 
beans, 

beans and cabbages, 

beans and cabbages, 
beans and cabbages, 



J- quickly destroyed. 



"I weak solutions did not 
/ destroy. 

destroyed in a few days. 
f destroyed unless much 
"| diluted. 

destroyed in a few days. 

V quickly destroyed. 

J plants uninjured, except 
( solution strong. 
< improved when very di- 

luted, 
injured, and if strong 

destroyed. 



v 

} no injury when diluted. 



232. Rotation of Crops. As the inorganic materials which enter 
into the composition of plants vary much in their nature and relative 
proportions, it is evident that a soil may contain those necessary for 
the growth of certain species, while it may be deficient in those 
required by others. It is on this principle that the rotation of crops 
proceeds ; those plants succeeding each other in rotation which require 
different inorganic compounds for their growth. In ordinary cases, 
except in the case of very fertile virgin soil, a crop, by being constantly 
grown in successive years on the same field, will deteriorate in a 
marked degree. Dr. Daubeny has put this to the test of experiment, 
by causing plants to grow on the same and different plots in successive 
years, and noting the results : 



116 COMPOSITION OF SOILS. 

Average of 5 years. 

(in the same plot 72-9 Ibs. tubers. 

Potatoes, -J in differem 1 ot8 92 . 8 - 

/same I 5 ' olbs - 

Flax {different * 



(same. 



Tfc 1 1 OtllllO.. ******** 

Barley, j different 46-5 

. . /same 104>0 

Turnips, | different 173-0 

~ t /same 28 ' 

Oat8 ' \different 32-4 

1 his shows a manifest advantage in shifting crops, varying from 1 to 
75 per cent. ; the deficiency of inorganic matter being the chief cause 
of difference. As this matter is shown to be of great importance to 
plants, it follows that the composition of soil is a subject requiring 
special notice. 

CHEMICAL COMPOSITON OF SOILS. 

233. Soils have been divided in the following way, according to the 
proportion of clay, sand, and lime, which they possess : 

1. Argillaceous soils, possessing little or no calcareous matter, and above 

50 per cent, of clay. 

2. Loamy soils, containing from 20 to 50 per cent, of clay. 

3. Sandy soils, not more than 10 per cent, of clay. 

4. Marly soils, 5 to 20 per cent, of calcareous matter. 

5. Calcareous soils, more than 20 per cent, of carbonate of lime. 

6. Humus soils, in which vegetable mould abounds. 

Below the superficial soil there exists what is called subsoil, which 
varies in its composition, and often differs much from that on the 
surface. Into it the rain carries down various soluble inorganic mat- 
ters, which, when brought to the surface by agricultural operations, as 
trenching and subsoil ploughing, may materially promote the growth 
of crops. 

234. Hamas, or decaying woody fibre, exists in soils to a certain 
amount. This has been called also ulmine, or coal of humus. In a 
soluble state it forms humic and ulmic acid. Humus absorbs ammo- 
nia, and it is slowly acted upon by the atmosphere, so as to form car- 
bonic acid by combination with oxygen. Peaty soils contain much of 
this substance. When peroxide of iron is present in such soils, it 
loses part of its oxygen, and is converted into the protoxide. 

235. Silica in greater or less quantity, is found in all soils ; but it 
abounds in sandy soils. In its ordinary state it is insoluble, and it is 
only when acted iipon by alkaline matter in the soil that it forms com- 
pounds which can be absorbed by plants. Silica, in a soluble state, 



COMPOSITION OF SOILS. 



117 



exists in minute quantities in soils; the proportion, according to John- 
ston, varying from 0'16 to 0"84 in 100 parts, while the insoluble 
siliceous matter varies from 60'47 to 83'31 in 100 parts. Wiegman 
and Polstorf found that plants took up the silica from a soil composed 
entirely of quartz sand, from which every thing organic and soluble 
had been removed. The following table shows the plants which ger- 
minated, the height to which they grew previously to being analysed, 
the quantity of silica they contained when planted, and the increase : 



Barley 


Height 
....15 inches 


Silica 
Seed. 

0-034 
0-064 


in the ash. 
Plant 

0-355 
0-354 
0-075 
0-135 
0-091 
. 0-549 


Silica had 
increased. 

10 times. 

18 
10 
10 
500 


Oats 


....18 


Buckwheat ... 


....18 


0-004 


Vetch 


....10 


0-013 


Clover 


... 34 


0-009 


Tobacco... 


... 5 


. 0.001 



236. Alumina exists abundantly in clayey soils, but it does not enter 
largely into the composition of plants. It has the power of absorbing 
ammonia, and may prove beneficial in this way. 

237. Lime is an essential ingredient in all fertile soils. In 1000 
Ibs. of such soil, there are, according to Johnston, 56 Ibs of lime; 
Avhile barren soil contains only 4 Ibs. The presence of phosphoric 
acid in soils, in the form of phosphates of potass, soda, and lime, is 
essential for the production of certain azotised compounds in plants ; 
and sulphuric acid, similarly combined, is required for the formation 
of others. 

238. A rough way of estimating the general nature of a soil, is thus 
given by professor Johnston : 

1. Weigh a given portion of soil, heat it and dry it. The loss is water. 

2. Burn what remains. The loss is chiefly vegetable matter. 

3. Add muriatic acid to residue, and thus the quantity of lime may be 

determined. 

4. Wash a fresh portion of soil to determine the quantity of insoluble 

siliceous sand. 

Such an analysis, however, is by no means sufficient for the pur- 
poses of the farmer. 

239. The chemical composition of a plant being known, conclusions 
can be drawn as to the soil most suitable for its growth. This is a 
matter of great importance both to the farmer and to the planter. In 
order that a plant may thrive, even in a suitable soil, exposure and 
altitude must also be taken into account. It is only by attention to 
these particulars that agricultural and foresting operations can be 
successfuL As regards trees, the following practical observations are 
given as an illustration of what has been stated. The Scotch Fir 



118 APPLICATION* OF MANURE. 

thrives best in a healthy soil, incumbent on a pervious subsoil, and at 
a high altitude ; Larch in loam, with a dry subsoil, in a high situa- 
tion, and on sloping banks ; Spruce and silver firs, in soft loam or 
peaty soil, in a low moist situation, but they will also grow in a dry 
soil, and in a pretty high altitude; Oak in any soil and situation under 
800 feet above the level of the sea, but it thrives best in clayey loam, 
on a rather retentive subsoil, and on gently sloping ground ; Ash and 
Elm, on a gravelly loam, on gravel or sand, at an altitude under 
500 feet above the level of the sea; Sycamore, at 100 feet higher 
than the ash or elm, and in a more retentive soil and subsoil ; Beech, 
on a dry gravelly soil, and in a rather high situation, but it is often 
luxuriant on strong retentive clay, and in a low damp situation. 



APPLICATION OF MANURE. 

240. If the soil does not contain the ingredients required for a 
crop, they must be added in the form of manure. The principle of 
manuring is to supply what the plant cannot obtain from the soil, and 
to render certain matters already in the soil available for nutrition. 
In order that this may be properly practised, there must be an 
analysis of the soil, of the plant, and of the manure. Hence the im- 
portance of agricultural chemistry to the farmer. 

Various kinds of Manure. 

241. Natural Manures, as farm-yard dung, are more valuable than 
simple manures; inasmuch as the former furnish all the substances 
required for the growth of plants, while the latter only supply a 
particular ingredient. The plant itself, in a soluble state, would be 
the best manure. In ordinary farm-yard manure, the straw is again 
made available for the purpose of the plant. The whole crop of wheat 
and oats, however, cannot be returned to the soil, as part must be 
retained for food. A substitute, therefore, must be found for the 
portion thus taken away. This contains both azotised and unazotised 
matters, the former consisting of proteine compounds which supply 
nitrogen for the muscular tissue of man and animals ; the latter of 
starchy, mucilaginous and saccharine matters, which furnish carbon as 
a material for respiration and fat. The object of manuring is chiefly 
to increase the former, and hence those manures are most valuable 
which contain soluble nitrogenous compounds. 

242. The value of manures is often estimated by the quantity of 
gluten which is produced by their application. Hermbstaedt sowed 
equal quantities of the same wheat on equal plots of the same ground, 
and manured them with equal weights of different manures, and from 



VARIOUS KINDS OF MANURE. 119 

100 parts of each sample of grain produced, lie obtained gluten and 
starch in the following proportions : 

Gluten. Starch. 

Without manure 9'2 66'7 

Cow dung 12-0 623 

Pigeons' do 12-2 63'2 

Horse do 137 61'6 

Goats' do 32-9 42-4 

Sheep do 32-9 42'8 

Dried night soil 33-1 41-4 

Dried Ox blood 34-2 41'3 

243. Manures containing ammonia, owe their excellent qualities to 
the nitrogen which enters into their composition ; hence the value of 
sulphate of ammonia, ammoniacal liquor of gas-works, and urine. The 
value of guano, or the dung of sea-fowl, depends chiefly on the ammo- 
niacal salts, and the phosphates which it contains; thus supplying the 
nitrogen and phosphorus requisite for the proteine compounds which 
contain the elements of flesh and blood. The guano, which is 
imported, is the excrement of numerous sea-fowl which frequent the 
shores of South America and Africa. It often contains beautiful 
specimens of infusoria, as Campylodiscus, Coscinodiscus, &c. The 
guano found in caves on the coasts of Malacca and Cochin-China, is the 
produce of frugivorous and insectivorous bats, and of a species of 
swallow the last being the best. 

244. The following analyses by Dr. Colquhoun of Glasgow, which 
are the result of an examination of a large number of samples, give a 
general idea of the composition of guano. The term ammoniacal 
matter includes urate of ammonia and other ammoniacal salts, as 
oxalate, phosphate, and muriate, as well as decayed organic matter of 
animal origin. The term bone earth, includes posphate of lime 
(always the principal ingredient), phosphate of magnesia (always in 
small amount), oxalate of lime ; and in African guano, a minute 
quantity of carbonate of lime, and from ^ to 2 per cent, of fragments 
of sea shells. The fixed alkaline salts, are various salts of soda, as 
muriate, phosphate, and sulphate ; a little of a potash salt has been 
detected. 

South American Guano. 

Fine Chiiicha. Middling. Inferior. Low Qualities. 

Ammoniacal matter G2 42 '28 12 , 15 



Bone earth 20 24 30 50 

Fixed alkaline salts 10 14 21 10 

Rock, sand, earth 0'5 5 3 15 

Water.... , 7-5 .. 15 . 18 . 13 



37 
5 

34 
9 



100-0 100 100 100 100 



120 VARIOUS KIXDS OF MANURE. 



African Guano. 

Best Ichaboe. Inferior. Low Quality. 

Ammoniaeal matter 45 ...... 28 20 

Boneearth 20 21 17 

Fixed alkaline salts 12 16 14 

Rock, sand, earth 1 3 25 

Water 22 32 24 



100 100 100 

245. The guano from the islands on the British coasts, contains the 
same ingredients, but the soluble salts are generally washed out by 
the action of rain. The following is the analysis, by Dr. R. D. 
Thomson, of guano gathered on Ailsa Craig : 

Water 50'30 

Organic matter and ammoniacal salts, containing 3 '47 per 

cent, of ammonia 12 '50 

Phosphates of lime and magnesia 12'10 

Oxalate of lime 1'50 

Snlphate and phosphate of potash, and chloride of potassium 1 -00 

Earthy matter and sand 15.00 

246. simple Mannres supply only one or two of the materials re- 
quired for the growth and nourishment of plants. The ammoniacal 
liquor of gas-works, in a very diluted state, has been advantageously 
applied to the soil, on account of the nitrogen which it supplies. Soot 
has also been used, from furnishing salts of ammonia. Nitrates of 
potash and soda have been recommended not only on account of the 
alkalies, but also on account of the nitrogen which they contain, in the 
form of nitric acid. The quantity of gluten is said to be increased by 
the use of nitrates. Carbonate of potash and soda, and chloride of 
sodium, are frequently used as manures. The latter is especially use- 
ful in the case of plants cultivated inland, which were originally 
natives of the sea-shore, as Cabbage, Asparagus, and Sea-kale. As 
lime is found in all plants, the salts containing it are of great import- 
ance. It may be used in the caustic state with the view of decom- 
posing vegetable matter, and aiding in the formation of carbonic acid. 
It also neutralizes any acid previously in the soil, as is said to occur 
occasionally in boggy and marshy land, abounding in species of Juncus, 
Carex, and Eriophorum, with some Calluna vulgaris. Lime also 
combines with certain elements of the soil, and sets potash free, which 
reacts on the silica, and renders it soluble. Lime is sometimes washed 
down into the subsoil; and, in such cases, trenching improves the land. 
Phosphate of lime is a valuable manure, both on account of the lime, 
and of the phosphorus which it contains. Without the presence of 
phosphates, gluten, and the proteine compounds of plants, cannot be 



VAKIOUS KINDS OF MANURE. 121 

formed. Phosphate of lime exists abundantly in animal tissues ; and 
hence it must be furnished by plants. The use of bone-dust as a 
manure, depends in a great measure on the phosphate of lime which 
it contains. Besides phosphate of lime, bones contain about 3 per 
cent, of phosphate of magnesia, carbonate of lime, and salts of soda. 
The gelatine of bones also seems to act beneficially, by forming car- 
bonic acid and ammonia. Bones are best applied mixed with sulphuric 
acid, so as to give rise to the formation of soluble phosphates by de- 
composition. They are broken into pieces, and mixed with half their 
weight of boiling water, and then with half their weight of sulphuric 
acid. The mixture is applied to the soil, either in a dry state by 
the drill, with saw-dust and charcoal added, or in a liquid state diluted 
with 100 to 200 waters. Phosphates and other inorganic matters, 
sometimes exist potentially in the soil, but in a dormant state, re- 
quiring the addition of something to render them soluble. Allowing 
the ground to lie fallow, and stirring and pulverizing it, are methods 
by which air and moisture are admitted, and time is allowed for the 
decomposition of the materials, which are thus rendered available for 
plants. Sulphur exists in considerable quantity in some plants, as 
Cruciferse, and it forms an element in albumen ; hence the use of 
sulphuric acid and of sulphates as manures. Sulphate of lime or 
gypsum, is well fitted as a manure for clover. It acts in supplying 
sulphur and lime, and in absorbing ammonia. Charcoal in a solid 
state, has been applied with advantage as a manure. It acts partly 
by taking up ammonia in large quantities, and partly in combining 
slowly with oxygen, so as to form carbonic acid. The effects of car- 
bonic acid on vegetation are said to be remarkably conspicuous in 
some volcanic countries, in which this gas is evolved from the bottom 
of lakes. When it accumulates in large qxiantities, however, it destroys 
plants as well as animals. 

247. manuring with Oreen Crops is sometimes practised. The 
mode adopted is to sow certain green crops, the roots of which extend 
deeply into the soil; and when the plants have advanced considerably 
in growth, to plough them in, and sow a crop of some kind of grain. 
In this way the nutritive matter from the deeper part of the soil is 
brought within reach of the roots of the grain crop. Manuring with 
sea-weeds is also resorted to in cases where they are accessible. They 
supply abundance of carbonate, phosphate, and sulphate of lime, besides 
chloride of sodium. There are considerable differences in their chemical 
composition; thus, while in Laminaria saccharina, alkaline carbonates, 
potash, and iodine, predominate ; in Fucus vesiculosus and serratus, 
sulphates and soda are in excess, and iodine is less abundant. In the 
cultivation of the Coco-nut Palm, Mr. M'Nab finds that sea-weeds act 
very beneficially. 

248. Liquid manures have of late years been much employed, and 



] 22 VARIOUS KINDS OF MANURE. 

the formation of tanks for their reception has been strongly recom- 
mended, in which the ammonia is fixed by the addition of sulphuric 
acid or charcoal They can be applied after vegetation has advanced, 
and they are in a state to be made at once available to the crop. More 
recently some have advocated a system of steeping seeds and grains in 
certain solutions before sowing them. Professor Johnston suggests 
a mixture of phosphate of soda, sulphate of magnesia, nitrate of potash, 
common salt, and sulphate of ammonia (1 Ib. of each), in ten gallons 
of water, to steep 300 Ibs. of seeds, which are to be afterwards dried 
with gypsum or quicklime. 

249. The following experiment, conducted by Mr. Wilson, at Knock, 
near Largs, shows the mode of estimating the effects of manures. The 
land was a piece of three-year old pasture, of uniform quality. It was 
divided into ten lots, and these were treated with different kinds of 
manure. The quantity of well-made hay is given in Ibs. : 

Produce Rate 
per Lot per Acre, 

Lot 1 .Left untouched 420 3360 

2. 2 barrels Irish quicklime ... 602 4816 

3 20" cwt. Lime of pas-works, 651 5208 

4. 4| cwt. Wood charcoal powder, 665 5320 

52 bushels Bone-dust 893 5544 

618 Ibs. Nitrate of potash, 742 5936 

720 Ibs. Nitrate of soda, 784 6272 

8 2 1 bolls Soot, 819 6552 

9 28" Ibs. Sulphate of ammonia 874 6776 

10. 100 gallons Ammoniacal liquor of gas-works. \ Q 

5 Tweddell's hydrometer,.../ 

The value of each application was the same, all were applied at the 
same time, and the grass also was cut at the same time. 

250. Plants are thus employed to form from the atmosphere and 
soil those organic products which are requisite for the nourishment of 
man and animals. While an animal consumes carbon so as to form 
carbonic acid, gives off ammonia in various excretions, transforms 
organized into mineral matters, and restores its elements to air and 
earth ; a plant, on the other hand, fixes carbon in its substance and 
gives off oxygen, forms from ammonia solid compounds, transforms 
mineral into organized matters, and derives its elements from the air 
and earth. Thus, says Dumas, what the atmosphere and soil yield to 
plants, plants yield to animals, and animals return to the air and earth, 
a constant round in which matter merely changes its place and form.* 

* For fuller particulars as to the food of plants, analyses of plants, soils, manures, and rota- 
tion of crops, see Johnston's Lectures on Agricultural Chemistry; Liebig's Works; Dumas on 
Organic Nature; Davy's Agricultural Chemistry, by Shier; Mulder's Chemistry of Organic 
Bodies, translated by Fromberg ; and various Papers in the Quarterly Journal of Agriculture 
1844-46 ; Saussure's Works ; Daubeny on Rotation of Crops, Phil Trans. 1845 ; Boussingault, 
Economic Rurale. 



EPIPHYTES AND PARASITES. 123 

EPIPHYTIC AND PARASITIC PLANTS. 

251. Some plants grow without any attachment to the soil, and are 
able to derive in a great measure, from the atmosphere, all the ma- 
terials required for their growth. Such plants are called Epiphytes (gV/, 
upon, and QVTM, a plant), or air-plants, and may be illustrated by the 
Tillandsias, Bromelias, and Orchids of warm climates. Such plants, 
when attached to the surface of trees, may perhaps derive some nourish- 
ment from the inorganic matter in the decaying bark; but they do not 
become incorporated, so to speak, with the trees. 

252. There are other plants, however, which are true Parasites (KU.^K., 
beside, and airo;, food, deriving food from another), sending prolonga- 
tions of their tissue into other plants, and preying upon them. Many 
Fungi, for instance, develop their spores (seeds) and spawn (mycelium) 
in the interior of living or dead plants, and thus cause rapid decay. 
The disease of corn, called smut and rust, and the dry rot in wood, are 
due to the attacks of these parasitic Fungi. The minute dust or powder 
produced by these plants, consists of millions of germs which are easily 
carried about in the atmosphere, ready to fix themselves on any plants 
where they can find a nidus. There are also flowering plants which 
grow parasitically, and they may be divided into two classes; 1. Those 
which are of a pale or brownish colour, and have scales in place of 
leaves ; and 2. Those which are of a green colour, and have leaves. 
The former, including Orobanche or broom-rapes, Lathra?a or tooth- 
wort, Cuscuta or dodder, derive their nourishment entirely from the 
plant to which they are united, and seem to have little power of elabor- 
ating a peculiar sap ; while the latter, as Loranthus, Viscum or misle- 
toe, Myzodendron, Thesium, Euphrasia, Melampyrum, and Buchnera, 
expose the sap to the action of air and light in their leaves, and thus 
allow certain changes to take place in it. The Misletoe, from its power 
of elaboration, is able to grow on different species of plants, as on the 
apple, beech, oak, &c. Some of these parasites are attached to the roots 
of plants by means of suckers, as in the case of Broom-rapes, Tooth- 
wort, and Thesium ; while others, as Dodder, Misletoe, &c., feed upon 
the stems. The plants to which the parasites are attached give origin 
frequently to their specific names. The species of Cuscuta or dodder, 
inhabit all the temperate and warm parts of the globe, and are peculiarly 
destructive to clover and lint. They are produced from seed which at 
first germinates in the soil like other plants ; but after the stem has coiled 
closely round another plant, and becomes attached to it by means of 
suckers, then ah 1 connection with the soil ceases, and the Dodder con- 
tinues its life as a parasite. A remarkable tribe of parasites, called 
Raffiesias, has been found in Sumatra and Java. They are leafless, and 
produce brown- coloured flowers, which are sometimes three feet in 
diameter. On account of their only producing a flower and root, 
they are denominated Rhizanths (*, a root, and v0o;, a flower). 



124 



CIRULAT1ON OP THE SAP. 



2. ABSORPTION AND CIRCULATION OF FLUIDS. 

253. While the leaves and other aerial organs of plants have the 
power of absorbing fluids, it is chiefly in the roots that this process takes 
place. The cells of the spongioles or fibrils of the roots, are covered 
by a very delicate membrane (*f[ 120), which allows the imbibition of 
fluids to proceed rapidly ; and as additions are made to their extremi- 
ties, they are constantly placed in circumstances favourable for the re- 
ception of fresh nutriment. The nutritive materials in the soil, partly 
derived from the decomposition of organic and inorganic materials, 
and partly from the atmosphere, are supplied to the roots in a state of 
solution; and as the substances in the cells of plants are usually denser 
than the external fluid matters, a process of endosmose takes place by 
which the latter pass through the cell-membrane in large quantities, 
while a small portion of the former is given off or excreted by exosmose. 
These movements have already been alluded to as taking place be- 
tween fluids of different densities, when separated by an animal or 
vegetable membrane (^[ 27). They are referred by some to electrical 
agency, and they perform an important part in the motions of vege- 
table fluids. 

254. Endosmose and Exosmose, then, are the names given to the 
phenomena of mixture through a membrane accompanied with change 

of volume. The former being given when the volume 
increases by an in-going strong current, the latter when 
the volume diminishes by an out- going weak current. 
In most cases, but not all, the dense fluid increases. 
The rapidity of the mixture depends on the position 
which the denser fluid occupies being quicker when it 
is uppermost. In fig. 222 is represented the mode 
of showing endosmose by means of a bladder full 
of syrup, which is attached to the end of a tube and 
immersed in water. In this case the water passes 
rapidly into the bladder by endosmose, so that the fluid 
rises in the tube, while a portion of the thicker fluid 
passes out by exosmose. The force of this endosmose 
may be measured by a graduated tube, as ha the figure, 
or by a tube with a double curvature, as fig. 224, the 
lower part of which is filled with mercury. In the 
latter case, the mercury is pushed upwards into a 
graduated tube, and thus an endosmosmeter (/AETJ ov, a 
measure), or measure of the force of endosmose, is formed. 

255. Dutrochet found that with a membrane of 40 millimetres* in 

* A millimetre is about l-25th of an English inch. 

Fig. 222. Instrument to show Endosmose and Exosmose, consisting of a bladder containing 
syrup attached to a tube, and plunged in a vessel of water. The inward motion of the water 
(endosmose) exceeds the outward movement of the syrup (exosmose). 




CIRCULATION OF THE SAP. 125 

diameter, a tube of 2 millimetres, and a solution of sugar, the density of 
Avhich was 1'083, the fluid rose 39 millimetres in the space of an 
hour and a hah"; with syrup, of density 1'145, the rise was 68 milli- 
metres; and with syrup, of density 1'228, the rise was 106 milli- 
metres. Syrup of density 1'3, produced a current capable of raising 
a column of mercury of 127 inches, which is equal to a pressure of 
4\ atmospheres. Thus the velocity and force of the rise depends 
on the excess of density of the interior liquor over that of the water 
outside. Different substances act with various intensity hi pro- 
ducing endosmose. The following ratio expresses the variable in- 
tensity of endosmose, in different cases in which the density of the 
solution was the same: Solution of gelatine, 3; of gum, 5*17; of 
sugar, 11; of albumen, 12. In order that endosmose and exosmose 
may take place, the liquids must have an affinity for the interposed 
membrane, and an affinity for each other, and be miscible. Accord- 
ing to Matteucci and Cima, the interposed membrane, whether animal 
or vegetable, is very actively concerned hi the intensity and direction 
of the endosmotic current. The different surfaces of membranes also 
act variously, and it is probable that the physiological condition of the 
membrane has an important effect. 

256. The fluid matters absorbed by the roots are carried upwards 
through the cells and vessels of the stem, under the form of ascending 
or crude sap ; they pass into the leaves, where they are exposed to the 
influence of air and fight, and afterwards return through the bark hi the 
form of descending or elaborated sap, and a portion of them ultimately 
reaches the root, where it is either excreted or mixed with the new 
fluid entering from the soil. 

257. Ascending or Crude Sap. In order to show the course of the 
fluids in exogenous stems, numerous experiments have been performed 
by Walker, De la Baisse, Burnett, Schultz, and others. These consisted 
in making incisions or notches in the bark and wood of trees at dif- 
ferent heights, and noting the points where the sap made its appearance 
at different periods of the year, more especially in spring; also in 
plunging plants with their roots entire into certain coloured solutions, 
and marking the course of the coloured fluids. These experiments 
led to the conclusion that the sap ascends chiefly through the alburnum 
or newer wood, proceeds along the upper side of the leaves, and re- 
turns by their lower side to the bark and root. If incisions are 
made into the trunk of a tree at different heights early in spring, it is 
found that the discharge of sap takes place, first from the lower parts 
of the incisions, and chiefly from the alburnum ; while at a later period 
of the year the discharge, or the bleeding, occurs on both sides of the 
incision, chiefly from the new wood on the lower side, and from the 
bark on the upper side. If a plant be plunged into a Aveak solution 
of acetate of lead (Avhich is capable of being absorbed), the metal may 



126 CIRCULATION OF THE SAP. 

be detected, first in the new wood, next in the leaves, and then in the 
bark. 

258. From the minuteness of the tissue, and the difficulty of ex- 
amining the circulation in a living plant, it is not easy to determine 
the vessels through which the sap moves. In its upward course, it 
appears to pass through the recent woody tissue and the porous vessels, 
and in its downward course through the laticiferous vessels and cellular 
tissue of the bark, being also transmitted laterally through the cells of 
the medullary rays. In some cases, when the bark has been removed, 
and the tree continues to live, the descent or fall of the sap takes place 
by the cells of the medullary rays. In the course of this circulation, 
the sap nourishes the different organs, its carbonic acid and water are 
partly decomposed, combinations take place with nitrogen, protoplasm 
or formative matter is produced, and various secretions are formed in 
the cells and intercellular passages. 

259. Gaseous matters are taken up by the roots of plants and cir- 
culated along with the sap, as well as in the spiral vessels. These 
usually consist of common air, carbonic acid, and oxygen. Hales 
showed the existence of a large quantity of air in the vessels of the 
Vine, and Geiger and Proust have proved that the sap of this plant 
contains much carbonic acid. In some aquatic plants, as Pontederia 
and Trapa, there is a quantity of air contained in the vessels or inter- 
cellular spaces, with the view of floating them. In Vallisneria, the 
large cells in the centre of the leaves are surrounded by air cavities, 
which are seen as dark lines under the microscope. When cut, the air 
comes out in bubbles, and this escape will continue under water for 
several days, from the part of the leaf attached to the plant, when ex- 
posed to the light. An ounce of air has been collected from two 
leaves of the plant in six days. This air, as well as that contained in 
sea-weeds, does not enter by stomata, for none exist, but must be taken 
up by the cells probably in solution. 

260. Changes take place in the composition and density of the sap 
in its upward course, but the chief alterations take place in the leaves. 
There it is exposed to the influence of light and air, by means of which, 
as will afterwards be seen, carbon and hydrogen are fixed, oxygen is 
given off, and an exhalation of watery fluids takes place. The sap 
becomes denser, and consequently the process of endosmose is pro- 
moted, so that the fluids pass from cell to cell along the upper surface 
of the leaf, and are gradually propelled into the lower cells, where 
they are acted upon by the air through the stomata, and are ulti- 
mately sent into the vascular and cellular tissue of the bark, where 
further changes take place. 

261. Elaborated or Descending Sap. The elaborated sap is some- 
times clear and transparent, at other times it is milky or variously 
coloured and opaque. By Schultz it has been called latex, and the 



CYCLOSIS. 127 

vessels transmitting it have been denominated laticifwous (^f 38). The 
latex contains granules, which exhibit certain movements under the 
microscope. These were first noticed by Schultz, who has written a 
very elaborate treatise on the subject.* On account of these move- 
ments in the latex, the laticiferous vessels have been denominated 
Cinenchymatom (x.ivia, I move), and the movements themselves are in- 
cluded under the name Cyclosis (x.vx.*ot, a circle.) Schultz looks upon 
the latex as a fluid of vital importance, and similar to the blood in 
animals. His views are opposed by Mohl, Tristan, and Treviranus, 
who consider the latex as a granular fluid containing oil, resin, and 
caoutchouc, which exhibits molecular movements only when injury is 
done to the vessels containing it. 

262. The plants in which the movements are best observed, are those 
in which the latex is milky or coloured, such as various species of 
Ficus, Euphorbia, and Chelidonium. In fig. 223 there is represented 
A small fragment of a leaf of 
Chelidoniummajus(ce/aftc?ee), 
which shows the currents of 
orange granules in the lati- 
ciferous vessels, their direction 
being indicated by arrows. 
From observations made last 
summer, I am disposed to agree 
with Schultz's statements. It 
is true, as Mohl remarks, that 
any injury done to the part 
examined causes peculiar os- 
cillatory movements, which 
speedily cease. Thus if the 
young unexpanded sepal of 
the Celandine is removed from 
the plant, and put under the 
microscope, or if the inner 
lining of the young stipule of 
Ficus elastica be treated in a 
similar manner, very obvious 

motion is seen in the granular contents of the vessels, and this motion 
is affected by pricking the vessels or by pressure. In order to avoid 
fallacy, however, I applied the microscope to the stipules of Ficus 
elastica, Avhile still attached to the plant and uninjured; and I remarked 
that, while pressure with any blunt object on the stipule caused a 

* Xova acta Acatlemire Ca;sar. Leopold-Carol. Natune Curios, torn, xviii. 

Fig. 223. Small portion of the leaf of Chelidonium majus or Celandine, (highly magnified), 
showing a network of laticiferous vessels. The direction of the currents in the vessels is indi 
cuted by the arrows. 




128 CIRCULATION OF THE SAP. 

marked oscillation in the vessels showing their continuity, there could, 
nevertheless, be observed a regular movement from the apex towards 
the base, independent of external influences, when the stipule was 
simply allowed to lie on the field of the microscope without any pres- 
sure or injury whatever. This movement continued for at least twenty 
minutes during one of the experiments, and I have no doubt might have 
been observed longer. It is of importance to distinguish between 
those molecular movements which are caused by injury and pressure, 
and those which depend on processes going on in the interior of the 
living plant. My experiments are by no means complete, but they 
lead at present to the adoption of Schultz's opinion relative to the 
existence of cyclosis. 

263. The elaborated sap descends partly by the vessels of latex, and 
partly by those of the liber. It has been said that there is sometimes 
a difference in the sap contained in these two kinds of vessels. Occasion- 
ally, as in Euphorbia canariensis, the elaborated sap has acrid properties, 
while the ascending sap is bland and wholesome. The elaborated sap 
contributes to the formation of the cambium, which is produced be- 
tween the bark and wood of exogens. 

264. It appears, then, that in the case of Exogenous plants, the 
fluid matter in the soil, containing different substances in solution, is 
absorbed by the extremities of the roots, ascends to the stem, passes 
through the woody tissue, porous vessels and cells, dissolving and ap- 
propriating various new substances. Proceeding upwards and out- 
wards, this sap reaches the leaves and the bark, where it is exposed to 
the air, and is elaborated by the function of respiration. It then 
returns, or descends chiefly through the bark, either directly or in a 
circuitous manner, communicating with the central parts by the 
medullary rays, depositing various secretions, more especially in the 
bark, and giving origin to substances which are destined to nourish 
and form new tissues. Finally, it reaches the extremity of the root, 
where absorption had commenced ; a small portion is there excreted, 
while the remainder mixes with the newly-absorbed fluids, and again 
circulates in the sap. 

265. In the case of Endogenous plants, observations are still wanting 
by which to determine the exact course of their fluids. The vascular 
bundles contain woody vessels, which probably are concerned in the 
ascent of the sap, and vessels equivalent to those of the bark and of the 
latex, which serve for the descent of it. The cellular tissue is also proba- 
bly concerned hi the movements. Cambium is produced in these plants 
in the neighbourhood of the vascular bundles, and is thus generally 
diffused through the texture of the stem. In acrogenous stems, it is 
likely that the sap follows the same course as in Endogens, although, 
in regard to both, experiments are still wanting. In cellular plants, 
transmission of the sap takes place from one cell to another ; and, as 



PROGRESSION OF THE SAP. 129 

their texture is often delicate, the movements are rapid. Many of 
these, as sea-weeds, when plunged into water, after having been dried 
by evaporation, imbibe the fluid with very great rapidity. 

266. The Cause of the Progression of the Sap has been investigated 
by Malpighi, Hales, Dutrochet, Draper, Briicke, and Liebig. While 
the capillarity of the vessels in the higher plants operates to a certain 
degree, it would appear that the process of endosmose is that by which 
the continued imbibition and movement of fluids is chiefly carried on. 
From the loss of its watery contents, by exhalation, and the meta- 
morphoses going on during the process of nutrition and secretion, the 
sap becomes gradually more and more dense, and thus, throughout 
the whole plant there is a forcible endosmotic transmission of the 
thinner fluids, and a constant change in the contents of the cells and 
vessels. These movements will of course take place with greater 
vigour and rapidity according to the activity of the processes going on 
in the leaves, which thus tend to keep up the circulation. 

267. Draper attributes the movement of the sap to capillary attrac- 
tion, which he considers as an electrical phenomenon. This attraction 
takes place when a fluid moistens a capillary tube, and there can be 
no flow unless a portion of this fluid is removed from the upper ex- 
tremity ; for capillarity will not of itself raise a fluid beyond the end 
of the tube. Evaporation and transpiration, which take place in the 
leaves, remove a portion of the vegetable fluids, and thus they promote 
the capillary action of the vessels. When two fluids of different kinds 
come into contact in a tube on different sides of a membrane, (which 
membrane being porous, may be considered as made up of numerous 
short capillary tubes), that will pass the fastest which wets it most 
completely, or has the greatest affinity for it. Hence, Draper ex- 
plains the phenomena of endosmose and exosmose by referring them to 
capillary attraction, aided by transpiration. 

268. Liebig adopts a somewhat similar view of the phenomena. He 
states that the accurate experiments of Hales have shown the effects 
of evaporation and transpiration on the movements of sap. Transpira- 
tion takes place chiefly in clear and dry weather, and consequently is 
regulated by the hygrometric state of the atmosphere. When the 
weather is cloudy and the atmosphere moist, transpiration is checked, 
and stagnation of the juices takes place. The greater the transpira- 
tion, the greater the supply of fluid necessary. Hence, plants kept in the 
dry atmosphere of rooms fade from want of a due supply to compensate 
for transpiration ; and hence the importance of pruning plants before 
transplanting them, so as to diminish the evaporating surface, and of 
performing the operation in dull and moist weather, so as to allow the 
absorption of fluids to keep pace with the transpiration. This pro- 
cess of transpiration, therefore, by forming a vacuum, assists capillary 
attraction and the atmospheric pressure, and thus the fluids rise. As 

K 



130 PROGRESSION OF THE SAP. 

the process of endosmose and exosmose depends on the chemical affinity 
between the fluids on each side of a membrane, the porosity of the 
membrane, "and the attraction existing between it and either of the fluids, 
it follows that the nature of the parietes of the cells and vessels of plants 
must have a marked effect on their contents and secretions. 

269. The observations of physiologists and chemists thus lead to the 
conclusion, that the movement of the sap in plants is due partly to the 
changes effected in the leaves and other green parts, by light and air ; 
partly to capillary attraction, the continuous influence of which is kept 
up by the constant loss of fluids ; and partly to endosmose and exos- 
mose. It may be said that there is a vis a tergo, without the presence 
of leaves, as shown by the experiments of Hales (fig. 224), combined 
with vis afronte, depending on the suction-power of the leaves. 

270. When cut twigs or flowers are put into water, their functions 
are kept up for some time by endosmose and capillarity. The latter 
power has great influence in such a case, and hence the cleaner the 
cut the better, so that no lacerated or ragged edge may interrupt its 
operation. In these circumstances also small solid particles and colour- 
ing matters will enter the tubes. Boucherie found that felled trees, 
the extremities of which were immediately immersed in various solu- 
tions, continued to imbibe them with great force and rapidity for many 
days. A Poplar, 92 feet high, absorbed in six days nearly sixty-six 
gallons of a solution of pyroMgnite of iron. 

271. Heat and light have a powerful influence on the movements of 
the sap, by promoting transpiration and the action of the cells. After 
the winter's repose, the first genial sunshine of spring stimulates the sap 
to activity, and after the leaves are expanded, the circulation goes on 
with vigour. The effect of leaf-buds in promoting the movement of 
sap, may be exhibited by introducing a single branch of a vine growing 
in the open air into a hot-house during winter, thus exposing it to heat 
and light. In this case the leaves are developed, and the fluids are 
set in motion from the roots upwards, so as to supply this single 
branch, although in the other branches there is no circulation. 

272. In spring, the first effect of light and warmth is to stimulate 
the leaf-buds. These enlarge, and the endosmotic process commences 
in their cells. This is communicated to other cells, and gradually 
extends to the root, which draws up a continued supply of fluids from 
the soil. The matter stored up during the winter undergoes changes ; 
certain substances are dissolved, and thus the sap is thickened, so that 
the endosmotic process is powerfully increased, and the whole plant 
exhibits an active and vigorous circulation. Towards the latter part 
of the season, when the heat and light decrease, the leaves perform 
their functions more languidly, and there is a near approach to equili- 
brium in the density of the fluids, and ultimately there is a cessation 
of the circulation. 



PROGRESSION OF THE SAP. 



131 



273. Liebig thinks that in the case of the vine, in which, according 
to Briicke, the specific gravity of the sap in spring is very little 
more than that of water, the rise of 

the sap does not at this season depend 
on endosmose, but on the disengage- 
ment of gas, which was shown by 
Hales to be given off in large quanti- 
ties, when the vessels were cut. The 
gas is conjectured to be carbonic acid 
gas, judging from the experiments of 
Geiger and Proust, who showed that 
the sap of the vine contains much of 
this acid. 

274. The height to which the sap 
rises hi the case of lofty trees, with 
spreading roots, is very great. The 
force with which it ascends has been 
measured by Hales, and is found to 
vary according to the state of the 
weather and the vigour of the plant. 
By fastening a bent tube, containing 
mercury, on the stem of the vine, he 
found in one of his experiments, that 
the sap raised the mercury upwards of 
thirty inches. The apparatus used 
by Hales, is similar to that used 
by Dutrochet, to measure endosmose, 
as is represented at fig. 224, where 
c is the stem of a vine cut, t is a 
bent glass tube fitted to the cut ex- 
tremity of the vine by a copper ring, 
v, carefully luted and secured by a bit 
of bladder, m; n n represents the level 
of the mercury in the two branches 
of the lower curvature, before the 
experiment, and n' n' the level at the 
conclusion of it. He calculated that 
the force of the sap in the vine, in 
some of his experiments, was five times 
greater than that of the blood in the 
crural artery of the horse. 




Fig. 224, 



Fig. 224. Experiment by Hales, to show the force of ascent of the sap. c, Stock of a vine cut. 
t, A glass tube with a double curvature attached to the upper part of the vine-stock, by means 
of a copper cap, r, which is secured by means of a lute and piece of a bladder, m. n n Level of 
the column of mercury in the two branches of the tube at the commencement of the experiment. 
ri n', Level at the conclusion of the experiment. 



132 MOVEMENTS IN CELLS. ROTATION. 

275. Special Movements of Fluids. Besides this general circulation 
of the sap, special movements have been observed in the cells of 
plants, which have been included under the name of Rotation (rota, a 
wheel), or Gyration (gyms, a circuit or circle). These motions have 
been detected in the cells of many aquatic plants, especially species of 
Chara and Vallisneria, and in the hairs of Tradescantia. The currents 
proceed in a more or less spiral direction, and are rendered visible 
by the granules of chlorophylle which they carry along with them. 
There exist also other granules in the fluids, which are coloured 
yellow by iodine, and are probably of a nitrogenous nature. 

276. The species of Chara, in which rotation has been observed, 
are aquatic plants growing in stagnant ponds, and are composed of a 
series of cylindrical cells, placed end to end. Sometimes the plant con- 
sists of a single central cell ; at other times there are several smaller 
ones surrounding it, which require to be scraped off in order to see 
the movements. Many of the species are incrusted with calcareous 
matter, so as become opaque, while others, as Chara flexilis, included 
under the division Nitella, have no incrustation, and are transparent. 
In these plants the movements take place between the two membranes 
of which the cell- wall is composed. Some granules, of a green colour, 
are attached to the cell- wall, while others are carried with the current, 
which passes along one side and returns by the other, following an 
elongated spiral direction. The descending current in the branches 
is next to the axis. 

277. In Vallisneria spiralis (which includes V. Micheliana and 
Jacquiniana), the cells in all parts of the plant, as in the leaf, root, 
flower-stalk, and calyx, contain numerous green granules, and an 
occasional cytoblast or nucleus, which, under certain circumstances, 
are carried, with the juices of the plant, in continual revolution round 
the walls of each cell. Although in different cells the currents pro- 
ceed often in different directions, still, in any given cell the rotation is 
uniform; for if stopped by cold it resumes the same direction. Rota- 
tion will continue in detached portions of the plant for several days, or 
even for three or four weeks. The best way of showing these motions 
is to take a small portion of a young leaf and divide it in halves, by 
making a very oblique section on the plane of the leaf, by which means 
a transparent end is obtained. This should be done at least an hour 
before it is put under the microscope. The part is to be viewed in 
water, between two pieces of glass ; and a little heat is sometimes use- 
ful in causing the movements to commence. 

278. A similar intra-cellular circulation, is seen in species of Potamo- 
geton, Hydrocharis, and many aquatics, as well as in the moniliform 
purple hairs on the filaments, and in the calycine hairs of Trade- 
scantia virginica. In the examination of these hairs a higher micro- 
scopic power is required than in the case of the plants previously 



MOVEMENTS IN CELLS. ROTATION. 133 

mentioned. The nucleus in the cells of these hairs is usually fixed to 
the walls, and the movements take place to and from it, and appear to 
be confined between a double cell-wall. Fig. 225 shows a calycine 
hair,/), of Tradescantia virginica, 
with a small portion of the epi- 
dermis, e e, on which a stoma, s, 
is seen. In each of the cells, 
both of the epidermis and the 
hair, there is a nucleus, n, and 
rotatory currents, the direction 
of which is indicated by that of 
the arrows. In each cell, as 
seen in a, there are several cur- 
rents, which cross each other 
at the point where the nucleus is 
situated, thus giving rise to the 
appearance of an irregular net- 
work. The hairs of many other 
flowering plants exhibit rotation 
(fig. 86), and it is probable that 
in all young cells there are cur- 
rents or streams radiating from 
the nucleus. The fluid circulating 
is a mucilaginous protoplasm or 
formative matter, and in Chara 
and VaUisneria it forms a uniform 
investing layer on the inner sur- 
face of the cell. The motions 
would appear to be connected in 
some way with the nutrition of 
cells and the formation of new 225 

ones; and, while they continue throughout life in aquatics, they often 
cease in plants living in air, after they have attained a certain develop- 
ment. 

279. Some of these movements, especially in hairs, were looked 
upon by Schultz as occurring in minute vessels, and therefore he 
included them under cyclosis. Schleiden maintains that in the Val- 
lisneria cells it is not the cellular sap that is in motion, but a mucila- 
ginous fluid, with which the chlorophylle granules and the nucleus are 
connected, and which flows in an uninterrupted manner along the cell- 
walls, but on account of its transparency and slight thickness, is not 

Fig. 255. Hair, p, taken from the calyx of Tradescantia virginica, with a small portion of the 
epidermis, e , on which there is a stoma s. In each of the epidermal cells there is a nucleus, n, 
and currents (rotation), the direction of which are indicated by the arrows. In each cell there 
are several currents moving to and from the nucleus, as is well seen at a. In the elongated cells 
of the hair, the nucleus, n, is carried along with the currents. 




134 MOVEMENTS IN CELLS. - ROTATION. 

easily seen. In Chara, also, he states it is not the cell-sap which moves, 
but a denser fluid, present in large quantity, and occupying the outer 
parts of the cell-cavity. Mold thinks that a homogeneous protoplasm 
fills these cells at first completely, but that during growth it becomes 
hollowed out into one or more cavities, and that around these the 
mucilaginous matter circulates. In Vallisneria, there is only one 
cavity, while in other plants there are several, giving rise to the 
appearance of mucilaginous streams or lines running from the nucleus 
to the cell-wall These mucilaginous lines, he says, occasionally after 
the circulation has ceased, remain permanently on the cell-walL The 
existence of spiral fibres in cells has been traced to currents of this 
kind. 

280. The velocity of the currents in various plants, at 66 to 68 
Fahrenheit, is thus given by Mohl: 



Filamental hairs of Tradescantia virginica, ^ to ^j of a Parisian line in a 

second; mean, -5^. 
Leaves of Vallisneria spiralis quickest, -5-^-5 ; slowest, -^^ ; mean, -j-Lg- of a 

line in a second. 

Stinging hairs of Urtica baccifera quickest, g^ T ; slowest, -g^ ; mean, yi^. 
Cellular tissue of young shoot of Sagittaria sagittifolia, j^, to 1 ^ 56 ; mean, -g^. 

leaf of do., y^, to -j-jVtj ; mean, 
Hairs of Cucurbita Pepo quickest, ^4^; slowest, 



The measurements were made by noting the passage of the globules 
across the field of a micrometer, fixed in the ocular of the microscope, 
and counting the strokes of a second's pendulum. These movements 
appear more rapid to the observer; but then it must be recollected 
that the parts are seen in a highly magnified state. 

281. The Cause of Rotation has not been satisfactorily explained. 
Some attribute it to electrical or magnetic currents causing attrac- 
tion and repulsion of the granular contents of cells. The different 
contents of the cells, according to them, mutually act and react on 
each other, and thus give rise to movements similar to those which 
take place on the surface of water when oily or resinous matters are 
added, and which have been called epipolic (liriK&qs, on the surface). 
Recent observations, by Dutrochet, seem to show that the magnetic force 
exercises no influence over the movements in Chara. Others believe 
that while heat, and electricity, and physical agents, stimulate these 
movements, they are not the cause of them. Some trace the move- 
ments to the presence of the nucleus, and look upon them as connected 
with the period of growth when new cells are being formed, and 
as ceasing after the nucleus has disappeared. 

3 RESPIRATION OF PLANTS. 

282. The changes which are produced in the atmosphere by living 
plants have been included under the title of Vegetable Respiration. 



RESPIRATION OF PLANTS. 13 

The experiments of Priestley, in 1771, showed that plants when put 
into an atmosphere containing a considerable proportion of carbonic 
acid, and exposed to light, purified the air by removing carbon and 
producing oxygen. Air in which animals had died, was thus rendered 
again fit for breathing. Scheele made a series of experiments with 
nitrogen in place of carbonic acid, and he found that plants did not 
purify an atmosphere composed of nitrogen alone. The foul air, then, 
in his experiments, differed completely from that in Priestley's experi- 
ments, and hence the difference of results. Ingenhouz and Senebier 
performed numerous experiments, which proved that during the day, 
plants gave out oxygen gas, while during darkness, this process was 
suspended. Saussure stated, that during the night, oxygen gas was 
absorbed in different quantities by plants. Fleshy plants absorbed 
least; next came evergreen trees, and then deciduous trees and 
shrubs. This absorption of oxygen is attended with the formation of 
carbonic and other acids. It has been said that some leaves, on 
account of this process of oxidation, are acid in the morning, and 
become tasteless during the day. Decandolle, Ellis, Daubeny, and 
numerous other observers, have confirmed the conclusions drawn by 
the early experimenters. The results of all these observations are, 
that plants, more especially their leaves and green parts, have the 
power of decomposing carbonic acid under the influence of solar 
light, and of evolving oxygen. While in darkness, no such decom- 
position takes place, oxygen is absorbed in moderate quantity, and 
some carbonic acid is given off". The former process caused by the 
deoxidizing power of plants, much exceeds the latter in amount. 

283. Burnett endeavoured to show that there are two processes 
constantly going on in plants, one being what he calls digestion, con- 
sisting in the fixation of carbon and the evolution of oxygen, and 
only carried on during the day; the other being what he calls proper 
respiration, consisting in the evolution of carbonic acid gas, and 
carried on at all periods of a plant's growth. He thinks that his 
experiments prove the disengagement of carbonic acid from the leaves 
of plants, both during night and during day. These opinions are not 
confirmed by other experimenters. What is generally called vege- 
table respiration, may be regarded as equivalent to digestion, con- 
sisting, as it does, of the decomposition of certain matters, and the 
fixation of others by a process of assimilation; but there is no evidence 
of the constant elimination of carbonic acid, in the same way as occurs 
in animal respiration. It would appear to be more correct to con- 
sider the processes in animals and vegetables as opposed. Eespiration 
in the former being the elimination of carbon, while in the latter it is 
the elimination of oxygen. 

284. The changes produced in the atmosphere, are caused chiefly 
by the superficial green parts of plants. It was ^long ago supposed 



136 KESPIEATION OF PLANTS. 

that the spiral vessels from their structure were to be looked upon as 
true wind-pipes or tracheae, conveying air from the stomata or pores 
in the leaves. But although they contain aeriform matters, they have 
been shown to be not directly concerned with the changes in the 
atmosphere, and to have no immediate connection with the stomata. 
The oxygen evolved by plants, appears to be derived from the carbonic 
acid (CO 2 ), the carbon of which is appropriated, and from water 
(HO), the hydrogen of which is assimilated. Light is necessary for 
these decompositions, and it is probable that the alkalies taken up by 
the roots aid the process. 

285. If the leaves of a plant are bent under an inverted tumbler of 
water, in a pneumatic trough, and exposed to the sun, bubbles of gas 
will soon be given off, which are found to be pure oxygen; and if the 
water contains carbonic acid, there will be a diminution in its quantity. 
The same leaves in darkness will not evolve any oxygen, light being 
essential for the process. The oxygen derived from the carbonic 
acid may be all evolved, or part of it may in its nascent state enter 
into certain combinations within the plant. The brighter and longer 
continued the light, the more oxygen is given off, and the greater the 
quantity of carbon added to the plant. If a healthy plant is covered by 
a bell jar, and exposed to light for twelve hours, oxygen will be formed, 
and if carbonic acid be added to the air, it will gradually diminish, 
while the oxygen will increase. During the night the action is 
reversed, and if the plant is ieft twelve hours in darkness, the oxygen 
will decrease, while carbonic acid will increase. 

286. The fixation of carbon probably takes place gradually, giving 
rise at different stages to the formation of various organized com- 
pounds. Thus, two atoms of carbonic acid, by losing one of oxygen, 
become oxalic acid; this oxalic acid, with the aid of water, may yield 
other acids, from which by the elimination of oxygen, and the addition 
of the elements of water, various unazotised matters, as starch, gum, 
and sugar, may be derived; these changes being promoted by the 
presence of alkalies. The fixation of carbon and hydrogen from the 
decomposition of carbonic acid and water, gives rise to the formation 
of the various secretions found in the bark and external cells, as 
chlorophylle, resins, oils, caoutchouc, and wax. 

287. Carbonic acid, as has been already noticed, is taken up in large 
quantity by the roots of plants from the soil, and it is also probably 
absorbed from the atmosphere by the leaves. In the ulterior of plants 
it is changed in various ways, but it is in the leaves more especially 
that its decomposition takes place. At night it is given off unchanged, 
by what Liebig considers as a mere process of exosmose, in conse- 
quence of the dissolved acid being no longer assimilated by the action 
of light. Others say that carbonic acid is not produced by exhalation 
only, but is also derived from the direct union between the oxygen of 



RESPIRATION OF PLANTS. 137 

the air and the carbon of the plant. This may occur in some plants 
without leaves, as Fungi, where a direct process of oxidation takes 
place in the organic matters which have been assimilated. The 
quantity of this acid given off during night, is by no means equal to 
that which is absorbed by the plant during the day. 

288. The parts of plants which are not green, seem to absorb oxygen. 
Thus, roots and subterranean organs act in this way, and the presence 
of oxygen seems to be necessary for their growth. There are also 
certain periods in the life of a plant when carbonic acid is given off 
in large quantity, even during the day, depending on a chemical 
change taking place in the starch of the plant, by which it is con- 
verted into sugar. These periods are germination, flowering, and 
fruiting. The changes produced will be alluded to when these 
subjects are considered. When plants are decaying, or are hi an 
unhealthy state, they undergo chemical changes, by which carbonic 
acid is formed. This was found by Burnett to have effected the 
results of some of Mr. EUis's early experiments. 

289. Certain plants have a great power of decomposing carbonic 
acid under the action of light. This is particularly the case with 
aquatics. It is thus that they keep up the purity of the pools and 
ponds in which they grow. Pistia Stratiotes has this effect in the 
Batavian ponds, and Sir H. Davy notices the great vigour of aquatic 
plants in the lake Solfatara, where carbonic acid was constantly 
bubbling up on the surface. The oxygenation of the water by aquatics 
has also been observed by Morren of Geneva. 

290. Experiments have been made as to the effect of the different 
rays of the spectrum in aiding the decomposition of carbonic acid, by 
the green parts of plants. Draper states that the light-giving rays, or 
those nearest the yellow, have the greatest effect; while the heat-giving 
and the tithonic, or chemical rays, had scarcely any influence. The 
experiments of Hunt also lead to the conclusion, that the yellow rays 
have most effect in the fixation of carbon, and in the production of 
woody matter. 

291. While the breathing of man and animals, and the various 
processes of combustion, are constantly abstracting oxygen from the 
atmosphere, and substituting carbonic acid, plants are decomposing 
this noxious gas, and restoring the oxygen. In tropical countries, 
where the vegetation is luxuriant and the light intense, the fixation of 
carbon and evolution of oxygen goes on with great vigour, thus fur- 
nishing a supply to those regions where, during certain periods of the 
year, both vegetation and heat are deficient. 

Effects of certain Gases on living Plants. 

292. It has been already stated that plants can live in an atmos- 
phere containing a considerable proportion of carbonic acid, provided 



138 EFFECTS OF GASES ON PLANTS. 

they are exposed to the light. Thus, an atmosphere which could not 
be breathed by man and animals is capable of supporting vegetable 
life. The experiments of Priestley, Percival, and Saussure, show, 
however, that plants will not continue to exercise their functions in 
pure carbonic acid gas, but that in all cases a certain quantity of free 
oxygen must be present. It has been found that plants do not thrive 
in pure nitrogen, nor in hydrogen gas. These gases seem to have no 
directly injurious effects, but to act chiefly by depriving the plants of 
carbon and oxygen. 

293. There are certain gases which have very prejudicial effects on 
plants, as proved by the experiments of Turner and Christison.* 
Some of them act as irritant poisons, causing local disorganization; 
others as narcotic poisons, inducing a drooping and decay of the entire 
plant. To the former class belong sulphurous acid gas, hydrochloric 
or muriatic acid gas, chlorine and nitrous acid gas; while under the 
latter are classed sulphuretted hydrogen, cyanogen, carbonic, oxide, 
and ammoniacal gas. 

294. Sulphurous Acid Ga is highly injurious to plants. It pro- 
duces greyish-yellow dry-looking spots on the leaves, which gradually 
extend until the leaves are destroyed and fall. The effect resembles 
much the ordinary decay of the leaves in autumn. The proportion of 
gas, in some experiments, was only 1 in 9,000 or 10,000 parts of air, 
and the quantity $ of a cubic inch; and yet the whole unfolded leaves 
of a mignionette plant were destroyed in forty-eight hours. This pro- 
portion of the gas is hardly or not at all discoverable by the smell. 

295. muriatic Acid Gas produced effects similar and scarcely inferior 
to those of the last-mentioned gas. When | of an inch was diluted 
with 10,000 parts of air, it acted destructively on Laburnum, and 
Larch, destroying the whole vegetation in less than two days. Even 
when in quantity not perceptible by the smell, it still acts as an irritant 
poison. 

296. Sulphuretted Hydrogen acted in a different way from the acid 
gases. The latter attacked the leaves at the tips first, and gradually 
extended their operation to the leaf-stalks. When in considerable 
proportion, their effects began in a few minutes; and, if diluted, the 
parts not attacked generally survived if the plants were removed into 
the air. But in the case of sulphuretted hydrogen, the leaves, with- 
out being injured in texture or colour, became flaccid and drooping, 
and the plant did not recover when removed into the air. It 
required a larger quantity of this gas to produce the effects stated. 
When six inches were added to sixty tunes their volume of air, the 
drooping began in ten hours. This gas then acts like a narcotic 
poison, by destroying vegetable life throughout the whole plant at 
once. 

* See Edinburgh Medical and Surgical Journal, vol. xxviii. p. 356. 



GROWTH OF PLANTS IN WARD'S CASES. 139 

297. These observations point out the great injury which is caused 
to plants by the gases given off during the combustion of coal, and 
more especially by certain chemical works. In the vicinity of the 
latter, the vegetation, for a considerable distance around, is often 
destroyed, particularly in the direction of the prevailing winds of the 
locality. The atmosphere of large manufacturing towns, in which 
fuliginous matter and sulphurous gases abound, is peculiarly hurtful 
to vegetable life. In order to protect plants from such prejudicial 
influences, Mr. N. B. Ward has invented close glass Cases, in which 
plants can be made to grow independently of the noxious atmosphere 
around.* These Cases consist of a trough containing soil, and a frame 
of glass, which is accurately fitted upon it. The soil is well supplied 
with water at first, and after the plants are put in they are kept exposed 
to the light. In these circumstances, they will continue to thrive for 
a long time, even for years, without any fresh supply of moisture or 
any direct exposure to the air. They are peculiarly fitted for rooms 
where the dryness of the atmosphere interferes with the vigour of 
plants, by causing greater exhalation than can be compensated by 
the absorption of moisture by the roots. Some tribes of plants, as 
Ferns, requiring a humid atmosphere, thrive well in such Cases. The 
windows of houses may be converted by this means into conservatories. 
Those who wish to see the effects thus produced, ought to visit Mr, 
Ward's house, in Wellclose square, London. Nothing can exceed 
the beauty and luxuriance of his Ferns. 

298. But it is not merely as matters of luxury and curiosity that 
these Cases deserve notice. They serve as a most important means of 
transporting plants, in a living state, to and from foreign climates; and 
they are in constant use for that purpose. Plants have thus been brought 
to this country which could not have retained their vitality in the form 
of seed, and which would have been destroyed by exposure to the 
sea-breeze and to the vicissitudes of climate experienced during their 
transport. The stillness of the atmosphere in the Case contributes 
materially to prevent injurious consequences. In June 1833, Mr. 
Ward filled two Cases with Ferns, Grasses, &c., and sent them to 
Sydney, where they arrived in January 1834. The plants were 
taken out in good condition, and the Cases were refilled at Sydney, 
in February 1834, the thermometer then being between 90 and 
100 Fahrenheit. In their passage to England, they encountered 
very varying temperatures. The thermometer fell to 20 on round- 
ing Cape Horn, and the decks were covered a foot with snow. In 
crossing the line, the thermometer rose to 120, and fell to 40 on 
their arrival in the British channel in the beginning of November, 
eight months after they had been enclosed. The plants were not once 

* See Ward on the growth of plants in closed Cases. 



140 PRODUCTS AND SECRETIONS OF PLANTS. 

watered during the voyage, and received no protection by day or by 
night, but were taken out at Loddiges in a most healthy and vigorous 
condition. 

299. It is a mistake to suppose that the air in the Cases is not changed. 
They are not henneticaly sealed; and by the law of diffusion of gases 
there is a constant although gradual mixture of the external air, free 
however from many impurities, with that inside. Plants will con- 
tinue to grow for a long time, even in Cases hermetically sealed, if 
supplied at first with abundance of good soil and water. By the united 
action of the plant and light, the air undergoes constant changes, and 
thus continues fit for vegetable life. 

4. PRODUCTS AND SECRETIONS or PLANTS. 

300. The sap, in its progress through the cells and vessels, and espe- 
cially in its passage through the leaves, is converted into organizable 
products, from which the vegetable tissues and the secretions contained 
in them are ekborated. Light, by enabling plants to fix carbon, has 
an important influence over these secretions. When plants are kept 
in darkness they become etiolated or blanched, and do not form their 
proper secretions. Gardeners resort to the practice of blanching when 
they wish to diminish or destroy certain secretions, and to render 
plants fit for food. In speaking of the contents of cells and vessels, 
allusion has already been made to some of the more important 
organizable products. It is proposed in this place to take a general 
view of those vegetable secretions which are connected with the 
nutrition of plants, or which are important on account of their medical 
or commercial uses. Some of these occur in small quantity, and 
are limited to certain plants only; others are abundant, and more 
universal in their distribution. Thus, while quinine and morphine, the 
active ingredients of Peruvian bark and opium, are circumscribed, 
both as regards quantity and distribution, starch, gum, sugar, woody 
matter, and certain nitrogenous compounds are more abundant, and 
more generally diffused over the vegetable kingdom. The latter 
substances therefore demand especial attention. If a plant is macer- 
ated in water, and all its soluble parts removed, lignine or woody 
fibre is left, and the water in which it has been macerated, gradually 
deposits starch. If the liquid is boiled, a scum coagulates, formed of 
albumen and some azotised matters, while gum and sugar remain in 
solution. 

301. Starch is a general product, being laid up as a store of nourish- 
ment, and undergoing changes at certain periods of a plant's life, which 
fit it for further uses in the economy of vegetation. It is not found in 
animal cells. It consists of C 12 H 10 O 10 , and occurs in the form of 
grains of various sizes and forms, having an external membrane, en- 



VEGETABLE PRODUCTS. STARCH. 141 

closing a soluble substance. By boiling in water, the pellicle bursts, 
and the contents are dissolved, becoming gelatinous on cooling. The 
circular markings and strias seen on the grains, and the part called the 
hilum, have already been noticed (If 17). Some plants, such as 
potato, arrow-root, and wheat, contain a large quantity of starch, 
which varies, however, in quantity according to the period of growth. 
Thus, while starch abounds towards the latter part of the season in the 
potato, it decreases when the tubers begin to germinate in spring. 
It was found that 240 Ibs. of potatoes, left in the ground, contained 
of starch : 

In August, 23 to 25 Ibs., or 9 '6 to 10'4 per cent. 



September, 32 

October 32 

November, 38 

April, 38 

May, 28 



38 " " 13-3 " 16 

40 " " 13-3 " 16-6 

45 " " 16 " 187 

28 " " 16 " 11-6 

20 " " 11-6 " 8-3 



The quantity of starch remained the same during the dormant state 
hi winter, but decreased whenever the plant began to grow, and to 
require a supply of nourishment. 

302. Starch is stored up hi many seeds. It exists hi roots, especially 
hi those which are fleshy; hi stems; hi the receptacles of flowers; and 
hi pulpy fruits. The seed-lobes of the Bean and Pea, and many other 
leguminous plants; the roots and the under-ground stem of Maranta 
arundinacea or Arrow-root, and of Canna coccinea or Tous-les-mois, 
Canna Achiras and C. edulis; the stem of the Sago Palm (Sagus 
Rumphii and farmifera), and of the Cycas tribe; the receptacle of the 
artichoke, and the pulp of the apple, are familiar instances of parts 
in which starch abounds. The grains of potato-starch are pearly 
or sparkling hi their appearance, of large size, having one or more 
hila, and often cracks on the surface. Those of arrow-root are dull, 
white, and small, while those of Tous-les-mois, present a glistening 
appearance like potato-starch, and are larger. In some cases, starch 
is associated with poisonous or acrid juices, as in Jatropha Manihot, 
which yields Cassava and Tapioca, and hi Arum maculatum, the under- 
ground stem of which furnishes Portland sago. Inuline is a substance 
analogous to starch, found hi the roots and tubers of Inula Helenium 
(Elecampane), Dahlia variabilis, and Helianthus tuberosus (Jerusalem 
artichoke); while Lichenin is a variety of starch occurring hi Cetraria 
islandica (Iceland moss). Lichenin or lichen starch consists of C 12 H 10 
O 10 , and is deposited hi the primary cell- wall of the plant, hi the form 
of an incrusting layer. By the action of malt or of sulphuric acid 
upon starch, or by long boiling in water, a gummy matter is pro- 
duced called dextrin* or soluble starch composed of C 12 H 10 O 10 . Some 

* Dextrin is so called from possessing the property of effecting the right-handed rotation of the 
plane of polarization of a ray of light. 



142 VEGETABLE PRODUCTS. GUM. 

consider this to be the substance contained in the interior of the 
starch grains. When dried, it constitutes British gum. It is one 
of the steps in the process of the conversion of starch into sugar. 

303. Gum is one of the substances which are produced abundantly 
in the vegetable kingdom. Its composition is C 12 H u O 11 , the same 
as that of Cane-sugar. It exists in many seeds, exudes from the 
stems and twigs of many trees, and is contained in the juices of others 
from which it does not exude. It is one of the forms through which 
organic matter passes during the growth of plants. The different 
kinds of gums have been divided into those which are soluble in cold 
water (Arabine, mucilage), and those which only swell up into a gela- 
tinous matter (Bassorine or Tragacanth, Cerasine and Pectine). Ara- 
bine is familiarly known by the name of gum-arabic or gum-senegal, 
and is the produce of various species of Acacia, chiefly natives of Arabia, 
Egypt, Nubia, and Senegambia, such as Acacia Ehrenbergii, tortilis, 
Seyal, arabica, vera, and albida. From the bark of these plants it 
exudes in the form of a thick juice, which afterwards concretes into 
tears. Old stunted trees, in hot and dry seasons, yield the most gum. 
Arabine exists with cerasine in the gum of the Cherry and Plum. 
Mucilage is present in many of the Mallow tribe, as Malva sylvestris, 
Althaea officinalis or marsh mallow, and in Linseed. In Sphserococcus 
crispus, mucilage is present, of which the formula is C 24 H 19 O 19 . 
Bassorine forms the chief part of gum-tragacanth, the produce of several 
species of Astragalus, and of gum-bassora. It exists in Salep, procured 
from the tubercules of Orchis mascula. Cerasine is that part of the 
gum of the Cherry (Cerosws), Plum, and Almond trees, which is 
insoluble in cold water. Pectine is a substance procured from pulpy 
fruits, as the apple and pear. It forms a jelly with water, and when 
dried, resembles gum or isinglass. It is changed by alkalies into 
pectic acid, which is found in many fruits and esculent roots. 

304. Sugar. This substance which forms an important article of 
diet, exists in many species of plants. Sugars have been divided into 
those which undergo vinous fermentation, as Cane and Grape sugar, 
and those which are not fermentescible as Mannite. Cane sugar, C 12 H 9 
O 9 -\- 2 HO, is procured from Saccharum officinarum (sugar-cane), 
Beta vulgaris (beet-root), Acer saccharinum (sugar-maple), and many 
other plants. It has been conjectured that the Calamus or sweet 
cane mentioned in the Old Testament, may be the sugar cane. At 
all events, the plant was known as early as the commencement of the 
Christian era. In the East and West Indies, at the present time, 
numerous varieties of cane are cultivated, such as Country cane, Ribbon 
cane, Bourbon cane, Violet or Batavian cane, which are distinguished 
by their size, form, the position and colour of their joints, their 
foliage, and their glumes. Bourbon cane is richest in saccharine 
matter. Canes demand a fertile soil, and for their perfect maturation 



VEGETABLE PRODUCTS. SUGAR. 143 

they require from twelve to fourteen months. Those which are 
grown from planted slips, are plant-canes, those which sprout up from 
the old stems, are rattoons. After being cut, the canes are crushed 
(the pressed canes being called begass), the saccharine juice is ex- 
tracted, evaporated, and crystallized, as Eaw or Muscovado sugar, 
which is afterwards refined in vacuo, so as to form loaf sugar. 

305. In 1844, the gross amount of sugar entered for consumption 
in the United Kingdom was 4,139,994 cwt. The quantity of sugar 
produced from the sugar cane in different parts of the world, in 1839, 
has been thus estimated : 

British Sugar Colonies, 3,571,378 cwt. 

British India 519,126 

Danish West Indies, 450,000 

Dutch West Indies, 260,000 

French Sugar Colonies, 2,160,000 

United States of America, 900,000 

Brazil, 2,400,000 

Java, 4,481,342 

306. Maple Sugar is much used in America. It is procured from 
the sugar maple by making perforations in the stem, and allowing the 
sweet sap to flow out. Two or three holes, at the height of eighteen 
or twenty inches from the ground, are said to be sufficient for an 
ordinary tree. The season of collecting is from the beginning of Feb- 
ruary to the middle of April. Beet sugar is the produce of the root 
of Beta vulgaris, and is extensively manufactured in many parts of the 
continent. In the year 1841, there were 142,518 acres in France 
planted with beet-root for sugar, and the quantity of sugar produced 
was 31,621,923 kilogrammes, (one killogramme being equal to about 
2 1 Ibs.). Manna sugar, or Mannite, differs from the others in not being 
fermentescible. Its composition is, C 6 H 7 O 6 . It is the chief ingre- 
dient of Manna, which exudes from the Ornus europasa and rotundi- 
folia. From Sicily and Calabria it is exported under the name of 
flake-manna. Mannite is found in the juices of Mushroom, in Celery, 
and in Laminaria saccharina, and Eucalyptus mannifera. Dr. Sten- 
house has determined the quantity of Mannite in some sea- weeds as 
follows : 

Laminaria saccharina, 12 to 15 per cent, of Mannite. 

Halydris siliquosa, 5 to 6 per cent. 

Laminaria digitata, 4 to 5 per cent. 

Fucus serratus, rather less 

Alaria esculenta, about the same 

Khodomenia palmata, 2 to 3 per cent. 

Fucus vesiculosus, 1 to 2 per cent. 

Fucus nodosus nearly same. 

Knop and Schnederman have detected Mannite in Agaricus piperatus, 
and other chemists have found it in Cantharellus esculentus, and 
Clavaria coralloides. 



144 VEGETABLE PRODUCTS. LIGNINE. 

307. Grape sugar, called also Starch sugar, or Glucose, is composed 
of C 12 H 1 * O u . It occurs in the juices of many plants, and is a pro- 
duct of the metamorphoses of starch, cane sugar, and woody fibre. It 
may be extracted from dried grapes, and may be prepared from starch 
by the action of an infusion of malt, or of a substance called Diastase 
(If 310). It is less soluble and less sweet than cane-sugar." It gives 
sweetness to gooseberries, currants, apples, pears, plums, apricots, and 
most other fruits. It is also the sweet substance of the chestnut, of 
the brewer's wort, and of all fermented liquors. 

308. Lignine is the substance which gives hardness and solidity to 
the cells and vessels of plants. It exists abundantly in woody fibre, 
which may be said to be composed of cellulose forming the parietes, 
and lignine forming the incrusting matter in the ulterior or the Sclero- 
gen of Payen. The latter dissolves in strong nitric acid, forming oxalic 
acid, while the former is left undissolved. Lignine is said to be com- 
posed of C 34 H 2 * O 20 . According to Mulder, the formula for the lig- 
neous matter of ordinary wood is C 40 H 28 O 26 . When a portion of the 
stem of a herbaceous plant, or of newly cut wood, is reduced to small 
pieces and boiled in successive portions of water, alcohol, ether, diluted 
acids and alkalies, until every thing soluble in these menstrua is 
removed, a white fibrous mass remains, to which the name of woody 
fibre is given. It varies slightly in its composition in different trees, 
thus: 

Oak. Beech. Pine. Willow. 

Carbon, 5-2-53 51-45 50- 49-8 

Hydrogen, 5'69 5'82 5'55 5-58 

Oxygen 41-78 42-73 44-45 44'62 

Iron wood contains 53-44 per cent, of carbon. 

This woody fibre exists in linen and paper; and these substances, when 
subjected to the action of sulphuric acid, are converted into grape 
sugar. Lignine gives support to the vegetable texture, and is often 
deposited in concentric layers. It occurs in large quantity in the 
wood of trees, and is also present in the stem of herbaceous plants. 
In some cellular plants it is absent, and the object of many horticul- 
tural operations, as blanching, is to prevent its formation. Beet-root 
and white turnips contain only 3 per cent. 

309. All these organic substances, consisting of carbon united with 
the elements of water, are easily convertible into each other by the 
action of sulphuric acid and heat. Similar changes are induced during 
the growth and development of plants, as will be noticed under the 
head of flowering, fruiting, and germination. In many unazotised 
matters ths proportion of the elements is the same, or they are 
isomeric. Thus, cellulose and starch have the same composition, and 
the difference in their qualities seems to depend on the mode in which 
the elements are united. Their form is altered by a change in the 



AZOTISED VEGETABLE PRODUCTS. 145 

molecular arrangement. The unazotised products which have been 
noticed, supply carbon for the respiration of man and animals, and 
probably assist in the formation of fat. It is impossible to notice all 
the compounds of carbon, oxygen, and hydrogen, found in plants. 
Some of these exist in small quantity in particular plants. For 
example, Salicine, a bitter neutral crystalline substance, is procured 
from the bark of Salix alba, Helix, purpurea, viminalis, pentandra, 
&c.; and Phloridzine, an analogous substance, occurs in the bark of 
the roots of the apple, pear, and plum. 

310. Azotised Products. There are certain azotised products which 
exist in greater or less quantity in plants, and which are particularly 
abundant in grains and seeds. The nutritive matter of wheat consists 
of starch or unazotised matter, separable by washing, and of azotised 
matter or gluten. Gluten is composed of certain proteine compounds 
(Fibrine, Caseine, Albumen, Emulsine), containing carbon, oxygen, 
hydrogen, and nitrogen, with some phosphorus and sulphur. Vegetable 
fibrine is the essential part of the gluten of wheat, and of the cereal 
grams. It may be procured by treating with ether the glutinous mass left 
after kneading wheat flour in linen bags under water. Vegetable caseine 
or legumine is an essential part of the seeds of Leguminous plants, and 
also of oily seeds. It may be procured in solution from kidney beans 
and peas, by bruising them in a mortar with cold water, and straining. 
Vegetable albumen occurs in a soluble form associated with caseine. It 
forms a small proportion of cereal grains. Wheat is said to contain 
to 1^ per cent.; Eye, 2 to 3f per cent.; Barley, J 5 to per cent.; 
jind Oats, ^ to J per cent. It is distinguished by its coagulation at 
a temperature of 140 to 160, and by not being precipitated by 
acetic acid. These three compounds dissolve in a solution of caustic 
potash ; and if to the solution acetic acid is added, the same precipitate 
is obtained whichever of the three is employed. This precipitate is 
called Proteine (WQUTWU, I have the first place). Its formula is C 48 
H 36 N 6 O u . Fibrine is proteine -j- S. + Ph. Albumen is proteine + 
S 2 -J- Ph. Caseine is proteine + S. Emulsine, or synaptase, is a nitro- 
genous compound found in certain oily seeds, as in almonds. It 
exists in the milky emulsion which these seeds form in water, and it is 
coagulated by acetic acid, and by heat. In bitter almonds, it is 
associated with a substance called amygdaline, on which it acts in a 
peculiar manner, producing hydrocyanic acid. Diastase is an azotised 
substance procured from malt, and developed during the germination 
of plants. It is probably fibrine in an altered state, and it has the power 
of promoting the conversion of starch into sugar. 

311. The azotised products of plants have a similar composition 
with blood and muscular fibre, and hence their value in the food of 
man and animals. The following table gives a general view of the 

L 



146 VEGETABLE OILS. 

quantity of azotised and unazotised matters occurring in certain plants, 
with the amount of water and inorganic matter : 

Azotised Carbonaceous 
Water. matter. matter. Ashes. 

Peas 16 29 52 3 

Beans H -31 52 i 

Lentils 16 33 48 i 

Oats 18 11 68 3 

Barley 16 14 69 2 

Potatoes 72 2 25 1 

Turnips 89 1 ' 

312. The following arrangement is given by Fromberg of the com- 
parative value of various plants as articles of food, taking into account 
the proteine compounds, and the starch, gum, and saccharine matter 
which they contain, the highest value being 100 : 



Beans 100 

Peas 80 

Oats 75 

Wheat 70 

Maize 60 



Eye 55 

Barley ....50 

Potatoes 45 

Rice... ....35 



313. As regards the produce of different crops per acse, Johnston 
gives the following estimate of the nutritive products which they 
yield : 

Average produce per No. of Ibs. of true 

acre of tubers and nutriment in pro- 

grain, duce of an acre. 

Beet, Mangel-wurzel, and Turnip 30 tons 672 Ibs. 

Beans 30 bushels, or 1980 Ibs. 594 

Potatoes 8 tons 358 

Peas 20 bushels, or 1 1 60 Ibs. 348 

Barley 36 bushels, or 1872 Ibs. 243 

Jerusalem Artichokes, 10 tons 224 

Wheat 25 bushels, or 1500 Ibs. 180 

Oats. 30 bushels, or 1200 Ibs. 132 

314. Fixed Oils are found in the cells and intercellular spaces of 
the fruit, leaves, and other parts. Some of these are drying oils, as 
Linseed oil, from Linum usitatissimum; others are fat oils, as that from 
Olives (fruit of Olea europaea) ; while others are solid, as Palm oil. 
The solid oils or fats procured from plants, are Butter of Cacao, from 
Theobroma Cacao ; of Cinnamon, from Cinnamomum zeylanicum ; of 
Nutmeg, from Myristica moschata ; of Coco-nut, from Cocos nucifera ; 
of Laurel, from Lauras nobilis ; Palm oil, from Elais guineensis ; Shea 
butter, from Bassia Parkii; Galam butter, from Bassia butyracea; 
and Vegetable tallow, from Stillingia sebifera in China, from Vateria 
indica in India, and from Pentadesma butyracea in Sierra Leone. 
These oils contain a large amount of stearine, and are used as substi- 



VEGETABLE OILS. 147 

tutes for fat. Castor Oil, from the seeds of Ricinus coinmunis, differs 
from other fixed oils in its composition. 

315. Decandolle gives the following table to show the quantity of 
oils got from seeds: 



Hazel-nut 60 per cent, in weight. 

Garden Cress ...57 

Olive 50 _ 

Walnut 50 

Poppy 48 

Almond 46 

Euphorbia Lath- 

yris 41 

Colza 39 



White Mustard ..36 per cent, in weight. 

Tobacco 34 

Plum 33 

Woad 30 

Hemp 25 

Flax 22 

Sunflower 15 

Buckwheat 14 

Grapes 12 



316. Tegeiabie Wax is a peculiar fatty matter sometimes found in 
the stem and fruit of plants. It is procured from several species of 
Palms, as Ceroxylon andicola, and Corypha cerifera, and from the 
fruit of Myrica cerifera or candle-berry myrtle, and Myrica cordifolia. 
Waxy matter also occurs on the exterior of fruits, giving rise to the 
bloom of grapes, plums, &c., on the outer surface of the bracts of Musa 
paradisiaca, and on the leaves of many species of Encephalartos. In 
Cork there exists a fatty body which, when acted upon by nitric acid, 
yields suberic acid. Chlorophylle, or the green colouring matter of 
leaves, is allied to wax in its nature, being soluble in ether and alcohol, 
but insoluble in water. 

317. Volatile or Essential Oils occur in the stem, leaves, flowers, 
and fruit of many odoriferous plants, and are procured by distillation 
along with water. They are called essences, and contain the concen- 
trated odour of the plant. They usually exist ready-formed, but 
occasionally they are formed by a kind of fermentation, as oil of bitter 
almonds, and oil of mustard. Some of them consist of carbon and 
hydrogen only, as oil of turpentine, procured from various species of 
Pinus and Abies; oil of juniper, from Juniperus communis; oil of 
Savin, from Juniperus Sabina; oil of lemons and oranges, from the 
rind of the fruit; and oil of neroli, from orange flowers. A second 
series contain oxygen in addition, as oil of cinnamon, from Cinnamo- 
mum zeylanicum; otto or attar of roses, from various species of 
Eose, especially Rosa centifolia; oil of peppermint, from Mentha 
viridis; oil of caraway, from Carum carui; oil of cloves, from Caryo- 
phyllus aromaticus. Oils of this kind are procured from many Labiate, 
as species of Lavandula, Origanum, Rosmarinus, Thymus; and from 
the fruit of Umbellifera3, as species of Anethum, Fceniculum, Corian- 
drurn, Cuminum, Petroselinum, Pimpinella ; and from some Compositae, 
as species of Anthemis, Pyrethrum, and Artemisia. A third series have 
also sulphur in their composition, and have a peculiar pungent, often 
alliaceous smell, with an acrid burning taste, as oil of garlic, and of 
onion, procured from the bulbs of Alhum sativum and Cepa; oil of 



148 RESINOUS PRODUCTS. CAOUTCHOUC. 

assafoetida, from Narthex Assafoetida; and oil of Mustard, which is 
obtained from the seeds of Sinapis nigra, by a kind of fermentation 
induced by the action of a nitrogenous body, myrosine, on a substance 
called myronic acid, or myronate of potash, when macerated in water. 
A similar oil exists in many Cruciferae, as in Erysimum AUiaria, 
Armoracia rusticana, and Cochlearia officinalis, and in several Umbel- 
liferse, yielding gum-resin, as Opoponax, Ferula, Galbanum, &c. Many 
of the essential oils deposit a solid crystalline matter, called Stearop- 
tene, allied to camphor. This latter substance, which consists of carbon, 
oxygen, and hydrogen, is procured from Camphora officinarum, a 
native of Japan and India. There is also another kind of camphor, 
produced hi Borneo, by Dryobalanops Camphora. 

318. Resinous Products. The milky and coloured juices of plants 
contain frequently resins mixed with volatile oils, in the form of 
balsams, besides a quantity of caoutchouc. The resinous substances 
found in plants, are either fluid or solid. The former may be illus- 
trated by Balsam of Tolu, procured from Myrospermum toluiferum; 
Balsam of Peru, from Myrospermum peruiferum; Balsam of Copaiva, 
from various species of Copaifera, especially Copaifera officinalis ; 
Carpathian Balsam, from Pinus Pinea; Strasburg turpentine, from 
Abies pectinata, or silver fir; Bourdeaux turpentine, from Pinus pin- 
aster; Canada Balsam, from Abies balsamea, or Balm of Gilead fir; 
Chian turpentine, from Pistacia Terebinthus, &c. The latter may be 
illustrated by common resin or Colophony, and Burgundy pitch, from 
Pinus sylvestris ; Mastich, from Pistacia Lentiscus; Sandarach, from 
Callitris quadrivalvis ; Elemi, from several species of Amyris ; Guaiac, 
from Guaiacum officmale ; Dragon's-blood, from Dracaena Draco, and 
Calamus Draco ; Dammar, from Dammara australis and orientalis ; 
Labdanum, from Cistus creticus, and others ; Tacamahaca, from Calo- 
phyllum Cadaba, and from Elaphrium tomentosum ; Resin of Jalap, 
from Exogonium Purga ; Storax, from Styrax officinale ; Benzoin, 
from Styrax Benzoin ; Copal, from Vateria indica, &c. ; Lac, from 
various species of Ficus, as Ficus indica, and benghalensis, after attacks 
of Cocci, and from Aleurites laccifera, and Erythrina monosperma ; Eu- 
phorbium, from Euphorbia officinarum, antiquorum, and canariensis. 

319. Caoutchouc is in some respects analogous to essential oils. It 
is found associated with them and resinous matters, in the milky juice 
of plants. It is procured from various species of Ficus, as Ficus 
elastica, Eadula, elfiptica, and prinoides, from Urceola elastica, Siphonia 
elastica, and Vahea gummifera, by wounding the plants. A kind of 
caoutchouc, called gutta percha, imported from Singapore and Borneo, 
is procured from Isonandra Gutta, one of the Sapotacese. The milky 
juice of many plants, as of Euphorbiaceae, Asclepiadaceae, Apocynaceae, 
Artocarpacea?, and Papayaceae, contain caoutchouc or gum elastic. 
Some of these coloured juices are bland, as that produced by the Cow- 



ACIDS, ALKALOIDS, AND COLOURING MATTERS. 149 

tree (Galactodendron utile); others are narcotic, as those of Poppy 
and Chelidonium ; others are purgative, as Gamboge; others diuretic, 
as Taraxacum. 

320. Organic Acids are produced by processes going on in living 
plants, and exist in vegetable juices combined often with peculiar 
bases and alkaloids. Thus, Citric acid occurs in the fruit of the orange, 
lemon, lime, red currant, &c. ; Tartaric acid, in the juice of the grape, 
and in combination with potash in tamarinds ; Malic acid, in the fruit 
of the apple, gooseberry, mountain ash ; Tannic acid or Tannine, in 
oak bark and nut-galls ; Gallic acid, in the seeds of Mango ; Meconic 
acid, in the juice of Papaver somniferum ; Kinic acid, in the bark of 
various species of Cinchona. Besides these, there are numerous others, 
which are characteristic of certain species or genera. To these may 
be added Hydrocyanic acid, as found hi Prunus Laurocerasus, &c., 
and Oxalic acid, which exists in combination with potash in Rumex 
acetosa, and Acetosella, Oxyria reniformis, Oxalis Acetosella, in the 
fluid in the pitcher of Nepenthes distillatoria; and in combination with 
lime in Rhubarb, and many species of Parmelia and Variolaria. 

321. Alkaloids or Organic bases are azotised compounds found in 
living plants, and generally containing their active principles. They 
occur usually in combination with organic acids. Quinine and Cincho- 
nine exist in the bark of Cinchona, the former predominating in yellow 
bark, the latter in pale bark; Morphine, Narcotine, Codeine, Thebaine, 
and Narceine, occur in the juice of Papaver somniferum ; Solanine is 
an alkaloid found in many species of Solanum, as Solanum tuberosum, 
nigrum, and Dulcamara ; Veratrine exists in Veratrum Sabadilla and 
album ; Aconitine in Aconitum Napellus ; Strychnine in Strychnos 
Nux-vomica, Sancti Ignatii, Colubrina and Tieute ; Brucine also in 
Nux-vomica, or False Angustura bark ; Atropine in Atropa Bella- 
donna ; Bebeerine in Nectandra Rodiei ; Pipeline in Piper longum 
and nigrum ; Emetine in Cephaelis Ipecacuanha ; Caffeine (Theine 
and Guaranine) in Coffea arabica, Thea Bohea and viridis, Paullinia 
sorbilis, and Ilex paraguayensis ; Theobromine in the seeds of Theo- 
broma Cacao or chocolate ; besides numerous others of less import- 
ance. These Alkaloids are often found in plants having poisonous 
properties. 

322. Colouring matters are furnished by many plants, either directly 
or by a process of fermentation. Yellow colouring matters are pro- 
cured from the roots of Curcuma longa or Turmeric, from the pulp 
surrounding the seeds of Bixa orellana (arnotto), from the stem of the 
Gamboge plant (Hebradendron Cambogioides), and various species of 
Garcinia,as Garcinia Cambogia and elliptica, from the flowers of Cartha- 
mus tinctorius (safflower), from the stigmata of Crocus sativus (saffron), 
from a kind of Mulberry (Morns tinctoria), from Reseda Luteola (weld), 
and from some Lichens, as Parmelia parietina (parietin or chryso- 



1 50 ORGANS OF REPRODUCTION. 

phanic acid). Red colouring matters are procured from the root of 
Anchusa tinctoria (alkanet), from Pterocarpus santalinus, Dracaena 
Draco (Dragon's-blood), the root of Eubia tinctorum or madder (aliza- 
rine), the root of Morinda citrifolia (Sooranjee), Haematoxylon campe- 
chianum (logwood), Csesalpinia braziliana (Brazil wood), from Cam- 
wood, also from Carthamus tinctorius (Carthamine), and from some 
Lichens, as Roccella tinctoria (Archil and Litmus). Blue colouring 
matters are furnished by the flowers and fruits of many plants, and 
from the leaves of some, by chemical action. Indigo, a most valuable 
dye, is procured by fermentation from various species of Indigofera, as 
Indigofera tinctoria, Anil, coerulea and argentea, as well as from 
Wrightia tinctoria, Marsdenia tinctoria, Nerium tinctorium, and Gym- 
nema tingens, &c. The plants in full flower are cut and put into A-ats 
with water, fermentation takes place, and a peculiar substance is formed, 
which, by absorption of oxygen, becomes blue. The best and the 
largest quantity of Indigo is produced in the Delta of the Ganges. 
Several Lichens yield nitrogenous colouring matters, which give blue 
and purple colours with alkalies, &c. Lecanora tartarea yields Cud- 
bear. 

SECTION III. ORGANS OF REPRODUCTION. 

STRUCTURE, ARRANGEMENT, AND FUNCTIONS. 

323. The reproductive organs consist of the flower and its appen- 
dages, the essential parts being the stamens and pistil. When the 
flower, or at least the essential organs, are conspicuous, the plants are 
called Phanerogamous (tfetvi^o;, conspicuous, and ya^o?, union or mar- 
riage), or Flowering plants ; when they are inconspicuous, the plants 
are Gryptogamous (K^TTTOS, concealed, and y^o?, union or marriage), 
or Flowerless plants. The former include Exogens and Endogens, the 
latter Acrogens and Cellular plants. On careful examination, it will be 
found that the organs of reproduction and nutrition are modifications 
of each other. The parts of the flower, as regards their development, 
structure, and arrangement, may all be referred to the leaf as a type. 
They commence like leaves in cellular projections, in which fibre-vas- 
cular tissue is ultimately formed; they are arranged in a more or less 
spiral manner, and they are often partially or entirely converted into 
leaves. 

1. INFLORESCENCE, OR THE ARRANGEMENT OF THE FLOWERS ON THE AXIS. 

324. The arrangement of the flowers on the axis, or the ramification 
of the floral axis, is called Inflorescence or Anthotaods (oivdos, a flower, 
and T |/f, order). Flower-buds, like leaf-buds, are produced in the axil 



INFLORESCENCE OR ANTHOTAXIS. 



151 



of leaves, which are called floral leaves or bracts. A flower-bud has 
not in ordinary circumstances any power of extension by the develop- 
ment of its central cellular portion. 
In this respect it differs from a leaf- 
bud. In some cases, however, of 
monstrosity, especially seen in the Eose 
(fig. 226) and Geum, the central part, 
A, is prolonged, and bears leaves 
or flowers. In such cases the flowers 
are usually abortive, the essential or- 
gans being so altered as to unfit them 
for their functions. Such metamor- 
phoses confirm Goethe's doctrine, that 
all the parts of the flower are altered 
leaves. 

325. The general axis of inflor- 
escence, is sometimes called rachis 
(fax's, the spine); the stalk support- 
ing a flower, or a cluster of flowers, 
is a peduncle (pes, a foot) (fig. 231 a'); 
and if small branches are given off by 
it, they are called pedicels (fig. 231 
a"). A flower having a stalk is called 
pedunculate or pedicellate (fig. 231); 
one having no stalk is sessile (fig. 237). 
In describing a branching inflores- 
cence, it is common to speak of the 

Rachis as the primary floral axis, its branches as the secondary floral 
axes, their divisions as the tertiary floral axes, and so on; thus avoid- 
ing any confusion that might arise from the use of the terms rachis, 
peduncle, and pedicel. 

326. The Peduncle assumes various forms. It is 
cylindrical, compressed, and grooved; simple, bear- 
ing a single flower, as in Primrose; and branched, 
as in London-pride. It is sometimes large and suc- 
culent, as in the Cashew (fig. 227 p\ in which the 
peduncle forms the large coloured expansion sup- 
porting the nut; spiral, as in Cyclamen and Vallis- 
neria (fig. 228); spiny, as in Alyssum spinosum. 
Sometimes the floral axis is shortened, assuming a 
flattened, convex, or concave form, and bearing 327 

Fig. 226, Proliferous or monstrous Rose, showing the prolongation of the axis beyond the 
flowers, c, Calyx transformed into leaves, p, Petals multiplied at the expense of the stamens, 
which are reduced in number. /, Coloured leaves representing abortive carpels, a, Axis pro - 
longed, bearing an imperfect flower at its apex. 

Fig. 237. Fruit of Cashew (Anacardium occidental), p. Enlarged peduncle, a, Fruit or nut. 





152 



INFLORESCENCE OR ANTHOTAXIS. 



numerous flowers, as in the Artichoke, Daisy, and Fig. In these cases 
it is called a Receptacle or Phoranthium ((popa, I bear, and udog, 
flower), or Clinanthium (xx/i/w, a bed, and &>?, flower). 

327. The Floral axis sometimes assumes a leaf-like arphyHoid(9fa*or, 
a leaf, and i'/So?, form) appearance, bearing numerous flowers at its 
margin, as in Xylophylla longifolia (fig. 229), and in Ruscus; or it 
appears as if formed by several peduncles united together so as to be- 
come a fasciated axis, as in the Cockscomb (fig. 230), in which the 

flowers form a pecu- 
liar crest at the apex 
of the flattened pe- 
duncles. Adhesions 
take place between 
the peduncle and the 
bracts or leaves of 
the plant, as in the 
Lime tree, Helwingia, 
Chailletia, several 
species of Hibiscus, 
and in Zostera. The 
adhesion of the pe- 
duncles to the stem 
accounts for the 
extra-axillary posi- 
tion of flowers, as 
in many Solanaceae ; 
when this union ex- 
tends for a consider- 
able length along the 
stem, several leaves 
may be interposed 
between the part 
where the peduncle 
becomes free, and the 
leaf whence it ori- 
ginated, and it maybe 
difficult to trace the 
connection. 

328. The peduncle occasionally becomes abortive, and in place of 
bearing a flower, is transformed into a tendril (^f 201); at other times 




Fig. 228. Wstilliferous plant of Vallisneria spiralis, shewing spiral peduncles or flower-stalks, 
l>y the uncoiling of which the flowers reach the surface of the water previous to fertilization. 

Fig. 229. Leaf-like (phylloid) flattened peduncle, r, of Xylophylla longifolia. ///, Clusters 
of flowers developed in a centrifugal or cymose manner. 

Fig. 230. Upper part of flattened or fasciated flowering stem of Celosia cristata (Cockscomb), 
having the form of a crest, covered with pointed bracts, and supporting flowers on its summit. 



INFLORESCENCE OK ANTHOTAXIS. 



153 



it is hollowed at the apex, so as apparently to form the lower part of 
the outer floral envelope, as in Eschscholtzia. 

329. The termination of the peduncle, or the part on which the 
whorls of the flowers are arranged, is called the Thalamus or Torus. 
It is the termination of the floral axis. The term receptacle is also 
sometimes applied to this, whether expanded so as to bear several 
flowers, or narrowed so as to bear one. It may be considered as the 
growing point of the axis, which usually is arrested by the production 
of the flowers, but which sometimes becomes enlarged and expanded. 
Thus, in the Geranium, it is prolonged beyond the flower in the form 
of a beak; in the Arum, it is a club-shaped fleshy column (fig. 239, 
2, a) ; in the Strawberry, it becomes succulent and enlarged, bearing 
the seed-vessels; while in Nelumbium it envelops them in the form of 
a truncated tabular expansion. In some cases it bears the seeds. In 
some monstrous flowers, as in Eose and Geum, it is prolonged as a 
branch bearing leaves (fig. 226). 

330. There are two kinds of inflorescence one in which flowers are 
produced in the axil of leaves, while the axis continues to be elongated 
beyond them, and to bear other leaves and flowers; the other in which 
the axis ends in a single terminal flower. In the former, the flowers 
are axillary, the axis extends in an indefinite manner, and the flowers, 
as they successively expand, spring from floral leaves placed higher on 
the axis than the leaf from which the first flower was developed. In 
the latter, the single solitary flower terminates and defines the axis, 
and the flowers developed subsequently, arise from floral leaves below 
this central flower, and therefore further re- ( ^v 

moved from the centre. 

331. The first is Indeterminate, Indefinite, or 
Axillary inflorescence, in which the axis is either 
elongated, continuing to produce flower-buds 
as it grows, the lowermost expanding first ; or 
it is flattened and depressed, and the outermost 
flowers expand first. The expansion of the 
flowers is thus centripetal, that is, from base to 
apex, or from circumference to centre. When 
this kind of inflorescence produces many flowers, 
it is simple, and proceeds from the development 
of the flower-buds of a single branch. This 
kind of inflorescence is shown in fig. 231, where 
the leaf from which the cluster of flowers is 

Fig. 231. Raceme of Barberry (Herberts vulgaris), produced in the axil of a leaf or bract,/, 
which has been transformed into a spine, with two stipules, s, at its base, of. Primary floral 
axis, bearing small alternate bracts, 6, in the axil of which the secondary axes, a" a" are pro- 
duced, each terminated by a flower. The expansion of the flowers is centripetal, or from base to 
apex ; the lower flowers have passed into the state of fruit, the middle are fully expanded, and 
those at the top are still in bud. Indeterminate simple inflorescence. 




154 



rNTLORESCENCE OR ANTHOTAXIS. 




produced, / represents the bract or floral leaf. The rachis, or primary 
axis of the flower, is of; this produces small leaflets, b, which bear 

smaller flower-leaves or bractlets, from 
which peduncles or secondary axes 
spring, bearing each single flowers. 
The whole inflorescence is the product 
of one branch, the lower flowers having 
expanded first, and bearing fruit, while 
the upper are in bud, and the middle 
are in full bloom. In fig. 232, the same 
232 kind of inflorescence is shown on a 

shortened axis, the outer flowers expanding first, and those in the 
centre last. 

332. The second is Determinate, Definite, or T'ermznaZ inflorescence, in 
which the axis is either elongated and ends in a solitary flower, which 
thus terminates the axis, and if other flowers are produced, they are 

secondary, and farther from the centre ; 
or the axis is shortened, and produces 
at once a number of flower-buds, but of 
these the central flower expands first, 
being in fact the termination of the 
axis, while the other flowers are develop- 
ed in succession further from the centre. 
The expansion of the flowers is in this 
case centrifugal, that is, from apex to 
base, or from centre to circumference. 
When this inflorescence produces many 
flowers, it is compound, and proceeds 
from the development of the buds of 
several branches. It is illustrated in 
fig. 233, where a representation is given 
of a plant of Ranunculus bulbosus; a' is 
the primary axis swollen at the base in a 
bulb-like manner, ft, and with roots pro- 
ceeding from it. From the leaves which 
are radical proceeds the axis ending in 
a solitary terminal flower,/'. About 
the middle of this axis there is a leaf 

Fig. 232. Head of flowers or glomerulus of Scabiosa atro-purpnrea. The inflorescence is sim- 
ple and indeterminate, and the expansion of the flowers centripetal, those at the circumference 
opening first 

Fig. 233. Plant of Ranunculus bulbosus, showing determinate compound inflorescence, a*, 
Primary fioral axis dilated at its base, so as to form a sort of bulb, 6, whence the roots and radical 
leaves proceed, f, Solitary flower, terminating the primary axis. About the middle of the axis 
a leaf is developed which gives origin to a secondary axis, a'', ending in a solitary flower, _/", 
which is not so advanced as/. On the secondary axis a leaf is formed, from the axil of which a 
tertiary axis, a"', proceeds, ending in a flower, /", which is still in bud. On this axis another 
floral leaf and bud is in the progress of formation. 




IXDEFIN-ITE IXFLORESCENCE. 



155 



or bract from which a secondary floral axis, a", is produced, ending in 
a single flower, f", less advanced than the flower, /'. This secondary 
axis bears a leaf also from which a tertiary floral axis is produced, a'", 
bearing an unexpanded solitary flower, f". From this tertiary axis 
a fourth is in progress of formation. Here f' is the real termination 
of the axis, and this flower then expands first, the other flowers being 
developed centrifugally on separate axes. It is a compound inflores- 
cence. 

333. indefinite inflorescence. The simplest form of this inflores- 
cence is when single flowers are produced in the axils of the ordinary 
leaves of the plant, the axis of the plant elongating beyond them, as 
in Veronica hederifolia, Vinca minor, and Lysimachia nemorum. The 
ordinary leaves in this case become floral leaves, by producing flower- 
buds in place of leaf-buds. In place of solitary flowers there is 
often an elongated floral axis or peduncle arising from a more or less 
altered leaf or bract, and bearing numerous leaflets, called bracteoles or 
bractkts, from which smaller peduncles 
are produced, and those in their turn 
may be branched in a similar way. 
According to the nature of the sub- 
division, and the origin and length of 
the flower-stalks, there arise numerous 
varieties of floral arrangements. When 
the primary peduncle or floral axis, as 
in fig. 231 a, is elongated, and gives 
off pedicels, a", of nearly equal length 
ending in single flowers, a raceme or 
cluster is produced, as in Currant, 
Hyacinth, and Barberry. If the sec- 
ondary floral axis gives rise to ter- 
tiary ones, the raceme is branching, 
and forms a panicle. In fig. 234 is 
represented a panicle of Yucca gloriosa, 
of being the primary axis or rachis with 
bracts, giving off numerous secondary 
axes, a", which in their turn develop 
tertiary axes, a"', the development in 

each of the secondary axes being centripetal, and b b b b being the bracts 
from which the separate axes are produced. If the peduncles in the 
middle of a dense panicle are longer than those at the extremities, 

Fig. 234. Panicle or branching raceme of Yucca gloriosa. a', Primary axis or rachis. a", 
Secondary axes or smaller peduncles, a"', Tertiary axes or pedicels bearing flowers, bbbb, 
Bracts and bracelets, in the axil of which the axes are produced. The inflorescence is indeter- 
minate, and consists of a series of racemes on a common axis. a'. The expansion of the whole 
inflorescence is centripetal, and such is also the case with each of the racemes forming it, the 
flowers at the base of the axes opening first. 




156 



INDEFINITE INFLORESCENCE. 



a thyrsus is produced, as in Like. If in a raceme the lower flower- 
stalks are elongated, and come to nearly a level with the upper, a 
corymb is formed, which may be simple, as in fig. 235, where the pri- 





mary axis, a', divides into secondary axes, a" a", which end in single 
flowers; or compound, as in fig. 236, where the secondary axes again 
subdivide. 

334. If the peduncles or secondary axes are very short 
or awanting, so that the flowers are sessile, a spike is pro- 
duced, as in Plantago and Verbena officinalis (fig. 237). 
The spike sometimes bears unisexual flowers, usually stami- 
niferous, the whole falling off by an articulation, as in Wil- 
low or Hazel (fig. 238), and then it is called an amentum 
or catkin; at other tunes it becomes succulent, bearing 
numerous flowers surrounded by a sheathing bract or spatha, 
and then it constitutes a spadix, which may be simple, as in 
Arum maculatum (fig. 239), or branching, as in Palms. 
A spike bearing female flowers only, and covered with 
C^ scales, is either a strobilus, as in the Hop; or a cone, as in 
Y the Fir (fig. 201). In grasses, there are usually numerous 
037 sessile flowers arranged in small spikes, called Locustce or 

Fig. 235. Corymb of Cerasus Mahaleb, produced in the axil of a leaf which has fallen, and ter- 
minating an abortive branch, at the base of which are modified leaves in the form of scales, f. 
a 1 . Primary axis, or peduncle, or rachis, producing alternate bracts, 6 6, from the axil of which 
secondary axes or pedicels, a" a", arise, each bearing a single flower. The evolution or expansion 
of the flowers is centripetal 

Fig. 236. Compound or branching corymb of Pyrus torminalis. of, Primary axis. a" a", 
Secondary axes, a!" a'". Tertiary axes or pedicels bearing the flowers directly. 666, Bracts. 

Fig. 237. Spike of Verbena offlcinalis, showing sessile flowers on a common rachis; the in- 
florescence indeterminate, and the evolution of the flower centripetal. The flowers at the lower 
part of the spike have passed into fruit, those towards the middle are in full bloom, and those at 
the top are only in bud. 




INDEFINITE INFLORESCENCE. 



157 



spikelets, and these clusters are either set closely along a central axis 
or rachis, or they are produced on a branched panicle. 




335. If the primary axis, in place of being elongated, is depressed 
or flattened, it gives rise to other forms of indefinite inflorescence. 
When the axis is so shortened that the secondary axes or peduncles 
arise from a common point, and spread out like radii of nearly equal 
length, each ending in a single flower, or dividing again in a similar 
radiating manner, an Umbel is produced, as in figs. 240 and 241. In 
fig. 240 the floral axes, a', a', a', end in simple umbels, o', o', </, and the 
umbels are called stipitate or stalked; while in fig. 241 the primary 
floral axis, a', is very short, and the secondary axes, a' a', come off" from 

Fig 238. Amentum or catkin of Hazel (Corylus Avellana), consisting of an axis or rachis 
covered with bracts in the form of scales (squamce), each of which covers a male flower, the 
stamens of which are seen projecting beyond the scale. The catkin falls off in a mass, 'separat- 
ing from the branch by an articulation. 

Fig. 239. Spadix or succulent spike of Arum maculatum. 1 Exhibits the sagittate leaf, the 
spatha or sheathing bract, 6, rolled round the spadix, the apex of which, a, is seen projecting. 
2. Shows the spatha, 6, cut longitudinally, so as to display the spadix, a. f. Female flowers at 
the base, m, Male flowers. On the spadix there are numerous abortive flowers indicated by 
hair-like projections. 

Fig. -240. Several umbels, c/ o 1 <x </, of Aralia racemosa. a, General axis or the apex of the 
branch terminated by a single umbel farther advanced than the rest a' a' a' a', Axes arising 
from it, which are secondary as respects the general axis, a; each of them bears an umbel, and 
as regards this inflorescence they are primary, a" a" a", Secondary axes, or the radii of the 
umbel. 666, Bracts placed alternately on the general axis, d, Shows a double bud proceeding 
from the axil of one of these bracts, and thus giving rise to two-stalked or stipitate umbels, 
* e, Verticillate bracts, forming involucres at the base of the radii of the umbels. 



158 



INDEFINITE INFLORESCENCE. 



it in a radiating or umbrella-like manner, and end in small umbels, o', 
which are called partial umbels or umbellules, to distinguish them from 
the general umbel arising from the primary axis. This inflorescence is 
seen in Hemlock, and other allied plants, which are hence called 
Umbelliferous. 





336. If there are numerous flowers on a 
flattened convex or slightly concave recep- 
tacle, having either very short pedicels or 
none, a capitulum (a head) or anthodium 
oLv6o$, a flower, &<>;, a way or method), or 
calathium (xx^oidtov, a small cup), is formed 
as in Dandelion, Daisy, and other composite 
plants, (figs. 242 and 243); or a glomerulus* 
(a ball), as in Scabiosa (fig. 232), and in 
Dipsacus (fig. 244). Such a receptacle or 
flattened peduncle may sometimes be folded 
so as to enclose partially or completely a 
number of flowers (generally unisexual), 

* By some this term Is applied to the centrifugal inflorescence of certain Urticacece, Chenopo- 
diacea?, and Juncaceae. 

Fig. 241. Compound umbel of Carrot (Daucus Carota). of, Primary axis shortened and 
depressed, so as to present a convex surface, a" a", Secondary axes or radii of the general um- 
bel, each ending in a partial umbel or umbellule, o" o" o" o". a'" a"', Tertiary axes or radii of 
the partial umbels or umbellules. i', Pinnatipartite bracts, forming the general involucre, t" if, 
Simple bracts, forming the partial involucre or involucel. 

Fig. 242. Capitulum, Anthodium, or Head of flowers of Scorzonera hispanica. 6, Imbricated 
bracts, forming an involucre. /, Florets or small flowers on the receptacle, having a centripetal 
evolution. 

Fig. 243. The same Capitulum cut vertically, r, The Receptacle, Phoranthium, or the- flat- 
tened and depressed apex of the peduncle, bearing the florets, /, which are surrounded by bracts, (>. 




DEFINITE INFLORESCENCE. 



159 



giving rise to the peculiar inflorescence of Dorstenia (fig. 245), or to 
that of the Fig (fig. 246), where/ indicates the flowers placed on the 
inner surface of the receptacle, and provided with bracteoles. This 
inflorescence has been called Hypanthodium (tiro, under, and ay do;, a 
flower). 




337. On reviewing these different kinds of inflorescence, it will be 
observed that the elongation or shortening of the axis, and the presence 
or absence of stalks to the flowers, determine the different varieties. 
Thus, a spike is a raceme in which the flowers are not stalked, the 
umbel a raceme in which the primary axis is shortened, the capitulum 
or head a spike in which the same shortening has taken place. 

338. Definite inflorescence. The simplest form of this inflorescence 
is seen in Anemone nemorosa (fig. 247), or in Gentiana acaulis (Gen- 
tianella) where the axis terminates in a single flower; and if other 
flowers are produced, they arise from the leaves below the first-formed 
flower. When numerous flowers are produced, and the axes are much 
shortened, it is sometimes difficult to understand this mode of in- 
florescence. It may be distinctly traced, however, in plants with 
opposite leaves, in which the different axes are clearly developed. In 
fig. 248 is represented the flowering branch of Erythrasa Centaurium. 
Here the primary axis, ', ends in a flower, /", which has passed 
into the state of fruit. At its base two leaves are produced, each 
of which is capable of developing buds. In the Gentiana acaulis 

Fig. 2-14. Inflorescence of Dipsacus sylvestris. Glomerulns, or head of flowers, each of 
which is separated by long pointed bracts. The flowers are evolved in a centripetal manner. 
e i, The first expanded, followed by those at e m, while those at the apex, e s, are in bud. 

Fig. 245. Inflorescence of Dorstenia Contrayerva, consisting of a broad slightly concave 
receptacle, r, on which numerous male and female flowers, f, are placed. 

Fig. 246. Inflorescence of Fig (Fiats Carica). showing the hofiow receptacle, r, or peduncle, 
which forms the fruit covered with flowers, /, of various kinds. 



160 



DEFINITE INFLORESCENCE. 



these leaves rarely produce buds, but in the present plant they 
generally do. The buds so produced are flower-buds, and constitute 
secondary axes, a" a", ending in single flowers, f" f", which thus are 
terminal and solitary ; and at the base of these axes a pair of opposite 
leaves is produced, giving rise to tertiary axes, a'" a!" a'", ending in 
single flowers, f" f" f", and so on. The divisions in this case 
always take place by two, or in a dichotomous (otxa, in two ways, and 
ispi/a, I cut) manner. Had there been a whorl of three leaves in 
place of two, the division would have been by three, or trichotomous 
(*/, in three ways). 




>, R l' ^~' v ^ADemone nemorosa. a, Subterranean stem. /, Leaf rf, Horal axis producine 
nracts, o, wnich form a three-leaved involucre, c, Solitary flower terminating the axis. Inflor- 



DEFINITE INFLORESCENCE. 



161 



339. When the leaves become very small, and are transformed 
into true bracts, this whole system forms a single inflorescence, and 
has received the name of cyme. As 
the definite inflorescence occurs in a 
marked degree in the cyme, it has 
hence been called cymose; and the 
cyme itself, according to its divisions, 
has been characterized as dichotomous 
or trichotomous. In figs. 249 and 
250, the cyme is represented hi two 
species of Cerastium, belonging to the 
natural order Caryophyllaceas, in 
which cymose inflorescence is of 
general occurrence. The leaves in 
the figures are small bracts giving 
origin to flower-buds in the same 
way as in fig. 248; the flowers at a' 
a' being the termination of the pri- 
mary axis and expanding first, the 





Fig. 248. Flowering branch of Erythra?a centaurium. \ Primary axis, a" a", Two secon- 
dary axes, u"' '" a'", Tertiary axes, four in number, a"" a"" <<"", Quaternary axes, eight in 
number. /, The flower in various stages of development. /', Solitary flower which has passed 
into fruit, terminating the primary axis. /", Flowers less advanced, terminating the secondary 
axes. /'". Flowers in bud at the extremity of the tertiary axes, and so on. Inflorescence 
definite or determinate. Evolution of flowers centrifugal. 

Fig. '249. Inflorescence of Cerastium grandiflorum. b b l>, Opposite bracts produced at each 
of the branchings; The axes are indicated as in last figure. The primary axis, a', ends in u 
flower which has passed into fruit. Inflorescence determinate. Evolution of flowers centrifugal. 

Fig. 250. Inflorescence of Cerastium tetrandrum. Letters have the same meaning as in the 
last two figures. In the quaternary axes, a"", the inflorescence becomes lateral by the non- 
development of the flower-buds on one side. 

M 



162 



DEFINITE INFLORESCENCE. 



others being subsequently developed in a centrifugal order. In some of 
the Pink tribe, as Dianthus barbatus, Carthusianorum, &c., in which 
the peduncles are short, and the flowers closely approximated, with a 
centrifugal expansion, the inflorescence has received the name of fascicle. 
A similar inflorescence is seen in such plants as Xylophylla longifolia 
(fig. 229). When the axes become very much shortened, the arrange- 
ment is more complicated in appearance, and the nature of the inflores- 
cence is indicated by the order of opening of the flowers. In Labiatas, 
as in the Dead nettle (Lamium), the flowers are produced at the axil 
of each of the leaves, and might be looked upon as ordinary whorls, 
but on examination it is found that the central flower expands first, 
and that the expansion is thus centrifugal. The inflorescence is there- 
fore truly cymose, the flowers being sessile, or nearly so, and the clusters 
are called verticillasters (verticilltis, a kind of screw). 

340. Sometimes the bract on one side of a dichotomous cyme, 
especially towards the summit of the inflorescence, does not give 
origin to buds, as seen in the upper flower of fig. 250. When a 
single bract only is produced, in place of two, there is often an anoma- 
lous cymose inflorescence produced, resembling a raceme. Thus, in 
Alstromeria, as represented at fig. 251, the axis, ', ends in a flower, 
which has been cut off, and a leaf. From the axil of this leaf, that is, 
between it and the primary axis, ', a secondary axis, a", is formed, 
ending in a flower/", and producing a leaf about 
the middle. From the axil of this leaf, a tertiary 
floral axis, a"', endingin aflower,/'", isdeveloped, 
and so on. Sometimes the bract on the opposite 
side shows itself, as at a. This inflorescence 
therefore, although it appears simple and race- 
mose is truly compound and cymose, consisting 
of a series of separate axes, with a 
centrifugal expansion. The flower- 
ing branch often exhibits, in such 
cases, a series of curvations. In cer- 
tain orders of plants, especially 
Boraginacea?, the bracts being alter- 
nate, give rise to an inflorescence 
of this kind. Thus, in fig. 252, a 
is a primary axis, ending in a flower, producing another, ft, and that, 
a third, c, a fourth, d, &c., ah 1 on the same side. In such a case there 
is usually a remarkable curvature resembling the tail of a scorpion, 

Fig. 251.- -False raceme of a species of Alstromeria, a' a" a'" a"", Separate axes successively 
developed, .vhich appear to form a simple continuous raceme, of which the axes form the inter- 
nodes. It is a eompound determinate inflorescence, however, with centrifngal evolution. Each 
of the axes is produced in the axil of a leaf, and is terminated by a flower,/'/"/'"/"", opposite 
to that leaf. 

Fig. 252. Figure to show the formation of a scorpioidal or helicoid cyme, consisting of separate 
axes, a b c d e. 





MIXED INFLORESCENCE. 



163 



and the cyme is called scorpioidal or helicoidal (&/!, a spiral, and 
lllog, form) or gyrate.* It is seen in the forget-me-not (fig. 253). 

341. Instances of both kinds of floral expansion occur occasionally 
on the same plant. Thus, in Compositse, the heads of flowers taken 
as a whole, are developed centrifugally, the terminal head first; while 
the florets, or small flowers on the receptacle, open centripetally, those 
at the circumference first. So also in Labiata?, the different whorls of 
inflorescence are developed centripetally, while the florets of the verti- 
cillaster are centrifugal. Sometimes this mixed character presents 
difficulties in cases such as Labiatae, where the leaves, in place of 
retaining their ordinary form, become bracts, and thus might lead to 
the supposition of all being a single inflorescence. In such cases, the 
cymes are described as spiked, racemose, or panicled, according to 
circumstances. Fig. 254 represents a panicled cyme of Privet, in 





* Schleiden says that this inflorescence is simply a unilateral raceme, having centripetal ex- 
pansion. 



164 



TABULAR VIEW OF INFLORESCENCE. 



V 



which the primary axis, a', gives of secondary axes, a" a", whence arise 
tertiary, a!" a'", ending dichotomously, and producing three-flowered 
cymes, c c, in which the central flower expands first. Fig. 255 is a 

racemose cyme of Campanula, de- 
veloped in a very irregular manner, 
and giving rise to a peculiar mixed 
inflorescence ; a' of is the primary 
axis, ending in a flower, /', which 
has withered, and giving off secon- 
dary axes, a" a" each terminated by a 
flower, and developed centripetally, 
the lowest being most expanded. 
These are anomalous cases and not 
easily explained. Such mixed in- 
florescences, partly definite and 
partly indefinite, are by no means 
uncommon. 

342. Sometimes flowers proceed 
from what are called radical leaves ; 
that is, from an axis which is so 
shortened, as to bring the leaves 
close together in the form of a clus- 
ter. From such stems, floral axes 
are pushed upwards occasionally, 
bearing single flowers, or flowers 
in umbels and racemes, as hi Primrose, Auricula, Hyacinth, &c. In 
these cases, the name of scape is applied to the flowering stem. 




343 TABULAE ARRANGEMENT OF INFLORESCENCE oa AXTHOTAXIS. 

A. Flowers Sessile. 

I. Floral Axis elongated. 
1. Axis permanent. 

Spike (Plantago), Locusta or Spikelet (Lolium), Spadix (Arum), 

Cone (Fir), Strobilus (Hop). 
2 Axis deciduous. 

Catkin or Amentum (Willow), Compound Catkin (Male flowers of 
some Palms). 

II. Floral Axis shortened or depressed (a Receptacle). 

Capitulum, Anthodium or Calathium (Dandelion). 

B. Flowers Pedicellate. 

I. Floral Axis elongated. 



Fig. 255. Racemose cyme, or Cymose raceme of Campanula, ' a'. Primary axis, terminated 
by a flower, /, which has already withered, and is beginning to pass into the state of fruit. 
a" a" a", Secondary axes, each terminated by flowers, /", which are more advanced the lower 
they are in their position. 



BRACTS OR FLORAL LEAVES. 165 

1 Peduncles simple. 

a. of equal or nearly equal length. 

Raceme (Currant, Hyacinth). 

b. lowermost longest. 

Centripetal expansion Corymb (Ornithogalum) 
Centrifugal expansion Fascicle (Pink). 
2. Peduncles branched. 

Panicle (Poa), Thyrsus (Lilac), Anthela (Luzula), Compound Ra- 
ceme (Plane-tree), Compound Corymb (Milfoil). 
II. Floral Axis shortened or depressed. 

1. Expansion centripetal. 

a. Peduncles very short, Flowers forming a close head. 

Glomerulus (Armerin, Scabious). 

b. Peduncles nearly equal, radiating from a common centre. 

Peduncles simple Simple Umbel (Astrantia, Ramsons). 
Peduncles branched Compound Umbel (Hemlock). 

2. Expansion centrifugal. 

a. Peduncles simple Verticillaster (Lamium). 

b. Peduncles branched Cyme (Elder). 

2. BRACTS OR FLORAL LEAVES. 

344. Flowers, with the exception of the terminal flower, arise from 
the axil of leaves, called Bractece, bracts or floral leaves. The term 
bract is properly applied to the leaf, from which the primary floral 
axis, whether simple or branched, arises, while the leaves which arise 
on the axis between the bract and the outer envelope of the flower 
are bracteoles or bractlets. The two are distinct, but are often used 
indiscriminately in ordinary descriptions. Bracts sometimes do not 
differ from the ordinary leaves, and are then called leafy, as in Ajuga. 
Like leaves, they are either entire or divided. In general, as regards 
their form and appearance, they differ from the ordinary leaves of the 
plants, this difference being greater in the upper than in the lower 
branches of an inflorescence. They are distinguished by their position 
at the base of the flower or flower-stalk. When the flower is sessile, 
the bracts are often applied closely to the calyx, and may thus be con- 
founded with it. 

345. When bracts become coloured as in Amherstia nobilis, Eu- 
phorbia splendens, and Salvia splendens, they may be mistaken for 
parts of the corolla. They are sometimes mere scales or threads, and 
at other times they are abortive, and remain undeveloped, giving rise 
to the ebracteated inflorescence of Cruciferae and some Boraginacea?. 
Sometimes flower-buds are not produced in their axil, and then they 
are empty. A series of empty coloured bracts terminates the inflores- 
cence in Salvia Horminum. The smaller bracts or bracteoles, which 
occur among the subdivisions of a branching inflorescence, often produce 
no flower-buds, and thus anomalies occur in the floral arrangements. 

346. Bracts are occasionally persistent, remaining long attached to 



166 



BRACTS OB FLORAL LEAVES. 




the base of the peduncles, but more usually they are deciduous, falling 
off early by an articulation. In some instances they form part of the 
fruit, becoming incorporated with other 
organs. Thus, the cones of Firs (fig. 201) 
and the strobili of the Hop, are composed 
of a series of bracts arranged in a spiral 
manner, and covering fertile flowers ; and 
the scales on the fruit of the Pine-apple 
(fig. 256 a), are of the same nature. In 
Amenta or catkins (fig. 238), the bracts 
are called squamce or scales. As regards 
their arrangement, they follow the same 
law as leaves ; being alternate, opposite, or 
verticillate. 

347. At the base of the general umbel 
in umbelliferous plants, a whorl of bracts 
often exists called a general involucre (fig. 
241 i f ), and at the base of the smaller umbels 
or umbellules, there is a similar leafy whorl 
called involuceloT partial involucre (fig. 241 i"). 
In the case of Composite, the name involucre 
is also applied to the leaves or scales surrounding the head of flowers (fig. 
242 J), as in Dandelion, Daisy, and Artichoke. This involucre is often 
composed of several rows of leaflets, which are either of the same or dif- 
ferent forms and lengths, and often lie over each other in an imbricated 
manner. When the bracts are arranged in two rows, and the outer row 
is perceptibly smaller than the inner, the involucre is sometimes said 
to be caliculate as in Senecio. The leaves of the involucre are spiny in 
Thistles and in Dipsacus (fig. 244 e z), and hooked in Burdock. Such 
whorled or verticillate bracts may either remain 
separate (polyphyllotis), or be united by adhesion 
(gamophyllotis), as in many species of Bupleurum, 
and in Lavatera. In the acorn they form the cupula 
or cup (fig. 257 c), and they also form the husky 
covering of the Hazel-nut. 

348. When bracts become united together, and 
overlie each other in several rows, it often happens 
that the outer ones do not produce flowers or be- 
come empty or sterile. In the artichoke, the outer 
imbricated scales or bracts are in this condition, 

Fig. 256. Fruit of Pine-apple (Ananatsa satira), composed of numerous flowers united into one 
mass; the scales, a, being modified bracts or floral leaves. The crown, b, consists of a prolonga- 
tion of the axis bearing leaves, which may be considered as a series of empty bracts, i. e. bracts 
not producing flowers in their axil. 

Fig. 257. Acorn, or Fruit of the Oak. f, Cupula or cup, formed by the union of numerous 
bracts or floral leaves, the free points of which are seen arranged in a spiral manner. 




THE PARTS OF THE FLOWER. 167 

and it is from the membranous white scales or bracts (palece) forming 
the choke attached to the edible receptacle, that the flowers are pro- 
duced. The sterile bracts of the Daisy occasionally produce capitula, 
and give rise to the Hen-and-Chicken Daisy. In place of developing 
flower-buds, bracts may, in certain circumstances, as in proliferous or 
viviparous flowers, produce leaf-buds. 

349. A sheathing bract enclosing one or several flowers, is called 
a spatha or spathe. It is common among Endogens, as Narcissus, Arum 
(fig. 239 b), and Palms. It is often associated with the spadix, and may 
be coloured as in Calla or Richardia ajthiopica. When the spadix is 
compound or branching, as in Palms, there are smaller spathes sur- 
rounding separate parts of the inflorescence, to which the name spa- 
thellce has sometimes been given. The spathe protects the flowers in 
their young state, and often falls off after they are developed, or hangs 
down in a withered form, as in some Palms, Typha, and Pothos. In 
grasses, the outer scales have been considered as sterile bracts, and 
have received the name of glumes, and in Cyperaceas bracts enclose 
the organs of reproduction. 

3. THE FLOWER AND ITS APPENDAGES. 

350. The Flower consists of whorled leaves placed on an axis, the 
internodes of which are not developed. This shortened axis is the 
Thalamus or torus. There are usually four of these whorls or ver- 
ticils : 1. The outer one called the calyx. 2. The corolla. 3. The 
stamens. 4. The most internal one, tine pistil. Each of these consist nor- 
mally of several parts, which, like leaves, follow a law of alternation. 
Thus, the flower of Crassula rubens (fig. 258) presents a calyx, c c, 
composed of five equal pieces arranged in a whorl ; a corolla, p p, 
also five parts, placed in a whorl Avithin the e t 

former, and occupying the intervals between 

the five parts of the calyx ; five stamens, e e e, 

in the spaces between the parts of the corolla, 

and consequently opposite those of the calyx; 

and five parts of the pistil, o o, which follow 

the same law of arrangement. Again, in 

Scilla italica, the parts are arranged in sets of 

three in place of five, as shown in fig. 259, 

where p' p' p' are three parts of the external 

whorl ; p" p" p", three of the next whorl ; 258 

e 7 , an outer row of stamens ; e", an inner row ; o, the pistil formed 

of three parts. It is distinctly seen in these instances, that the parts of 

the flower are to be regarded as leaves arranged on a depressed or 

shortened axis. 

Fiff. 258. Flower of Crassula rubens. c c, Foliola of calyx or sepals, p p. Petals, e e, Stamens. 
o o. Carpels, each of them having a small scale-like appendage, a, at their base. 




168 



FLORAL ENVELOPES. 



351. When all the parts of the flower axe separate, and normally 
developed, there is no difficulty in tracing this arrangement ; but in 

many cases it is by no means an easy mat- 
ter to do so, on account of changes pro- 
duced by the union of one part to another, 
by degeneration, by the abortion or non- 
development of some portions, and by the 
multiplication or folding of others.* Of 
the four whorls noticed, the two outer (calyx 
and corolla), are called floral envelopes ; the 
two inner (stamens and pistil), are called 
essential organs. When both calyx and 
corolla are present, the plants are Dichlamy- 
deous (S<j, twice, and ^at/uvs, a covering) ; 
occasionally one or both become abortive, 
and then the flower is either Monochlamydeous (povos, single), having 
a calyx only, or Achlamydeous ( privative) or naked, having only 
the essential organs, and no floral envelope. 

352. The Floral Envelopes consist of the calyx and corolla. In 
most cases, especially in Exogens, these two whorls are easily dis- 
tinguishable, the first being external and green, the latter internal, 
and more or less highly coloured. If there is only one Avhorl, then, 
whatever its colour or degree of development, it is the calyx. Some- 
times, as in many Endogens, the calyx and corolla both display rich 
colouring, and are apt to be confounded. In such cases, the term 
Perianth (irigt, around, and itdo { , flower), or Perigone 1 and <-wv, 





pistil), has been applied to avoid 
ambiguity. Thus, in the Tulip, 
Crocus, Lily, Hyacinth, in place 
of calyx and corolla, authors 
speak of the parts of the peri- 
anth, although in these plants, 
an outer whorl (calyx), may be 
detected, of three parts, and an 
inner (corolla), of a similar 
number arranged alternately. 
Thus, the perianth of the White 
Lily (fig. 260 p), consists of 
three outer parts, p e, alternating 

* At the conclusion of the remarks on the organs of reproduction, notice is taken of various 
metamorphoses produced in flowers by the causes above specified. 

Fig. 259. Flower of Scilla italiea. p' p' //, Three external leaflets, or divisions of the perianth 
or Perigone. p" p"p", The three internal leaflets, e', Stamens, opposite to the first or external 
leaflets, e', Stamens, opposite the second or internal leaflets, o, Ovaries united together into 
one. *, Three styles, consolidated so as to form one. 

Fig. 260. Flower of White Lily (Lilium album), p, Perianth or Perigone, having three parts 
exterior, p e, alternating with three interior, p i. e. Stamens, having versatile anthers attached 
to the top of the filaments, s, Stigma at the apex of the style. 



FLOWER-BUD. ^STIVATIOX. 



169 



with three internal parts, p z, surrounding the essential organs, e, 
the stamens, and, s, the pistil. 

353. The term perianth then is usually confined to the flowers of 
Endogens, whatever colour they present, whether green, as in Aspa- 
ragus, or coloured, as in Tulip. Some use the term perianth as a 
general one, and restrict the use of perigone to cases where a pistil is 
present, not applying it to unisexual flowers, in which stamens only 
are produced. In some plants, as Nymphaea alba (fig. 310), it is not 
easy to say where the calyx ends, and the corolla begins; as these two 
whorls pass insensibly into each other. 

354. Flower-bud. To the flower-bud, the name alabastrus (mean- 
ing rose-bud) is sometimes given, and its period of opening has been 
called anthesis (oiv9wtf, flower opening), whilst the manner in which 
the parts are arranged with respect to each other before opening, is 
the (estivation (cestivus, belonging to summer), or prcefloration (prce, 
before, andyfos, flower). The latter terms bear the same relation to 
the flower-bud, that vernation does to the leaf-bud, and distinctive 
names have also been given to the different arrangements which it 
exhibits. When the parts of a whorl are placed in an exact circle, 
and are applied to each other by their edges only, without overlapping 
or being folded, thus resembling the valves of a seed-vessel, the aesti- 
vation is valvate, as in Calyx of Guazuma ulmifolia (fig. 261 c). The 
edges of each of the parts may be turned either inwards or outwards ; 
in the former case, the aestivation is induplicate, as in corolla of Gua- 
zuma ulmifolia (fig. 261 p), in the latter reduplicate, as in calyx of 
Althaea rosea (figs, 262 c, 263 c). When the parts of a single whorl 
are placed in a circle, but each of them exhibits a torsion of its 
axis, so that by one of its sides it overlaps its neighbour, whilst its 




Fig. 261. Diagram of calyx, c, and corolla, p, in the bud of Guazuma ulmifolia. ^Estivation 
of calyx valvate, of petals induplicate. 

Fig. 262. Diagram of calyx, c, and corolla, p, in the flower-bud of Althaea rosea. ^Estivation 
of calyx reduplicate, of petals contorted or twisted. 

Fig. 263. Flower-bud of Altha;a rosea in a young state, showing calyx, c, still completely 
enveloping the other parts, and the edges of its divisions touching each other. 

Fig. 264. The same in a more advanced state, where the calycine divisions, c, are separated 
so as to allow the expansion of the corolla, the petals of which, p, are contorted in aestivation. 



170 



FLOWER-BUD. AESTIVATION. 



side is overlapped in like manner by that standing next to it, the 
aestivation is twisted or contorted, as hi corolla of Althaea rosea (figs. 
262 p, 264 p). This arrangement is characteristic of the flower-buds 
of the Malvaceae and Apocynaceae, and it is also seen in the Convolvu- 
lacea? and some CaryophyDaceae. When the flower expands, the traces 
of twisting often disappear, but sometimes, as in Apocynaceae, it 
remains. 

355. In these instances of aestivation, the parts of the verticils are 
considered as being placed regularly in a circle, and about the same 
height, and they are included under circular aestivation. But there 
are other cases in which there is a slight difference of level, and then 
the true spiral arrangement exhibits itself. This is well seen in the 
leaves of the calyx of Camellia japonica (fig. 
265 c), which cover each other partially like 
tiles on a house. This aestivation is imbricated. 
At other times, as in the petals of Camelh'a 
(fig. 265 p), the parts envelop each other com- 
pletely, so as to become convolute. This is 
also seen in a transverse section of the calyx 
of Magnolia grandiflora (fig. 267), where 
each of the three leaves embraces that within 
it. When the parts of a whorl are five, as 
occurs in many Exogens, and the imbrication 
is such, that there are two parts external, two 
internal, and a fifth which partially covers one 

of the internal parts by its margin, and is in its turu partially covered 
by one of the external parts, the aestivation is quincunxial (fig. 266). 
This quincunx is common in the corolla of Rosaceae. Fig. 266 is a 
horizontal section of the calyx in the flower-bud of Convolvulus 

sepium, in which the parts are 
numbered according to their 
arrangement in the spiral 
cycle, and the course of the 
spiral is indicated by a line of 
points. In fig. 268, a section 
is given of the bud of Antirr- 
hinum majus, showing the 
imbricated spiral arrangement. In this case it will be seen, when 

Fig. 265. Flower-bud of Camellia japonica. c, Imbricated sepals of the calyx, p, Petals with 
convolute aestivation. 

Fig. 266. Horizontal section of calyx in flower-bud of Convolvulus sepium. Calyx consists 
of five sepals corresponding to the numbers in the figure, and the line of points indicates the 
direction of the spiral according to which they are arranged. 

Fig. 267. Arrangement of the three outer leaflets (calyx) in the bud of Magnolia grandiflora, 
cut transversely ; aestivation convolute. 

Fig. 268. Arrangement of the parts of the calyx in the flower of Frogsmouth (Antirrhinum 
majtu). The arrangement differs from that in fig. 266, on account of a slight twisting and over- 
lapping of the parts. 





FLORAL ENVELOPES. CALYX. 171 

contrasted with. fig. 266, that the part marked 2, by a slight change 
in position, has become overlapped by 4. In flowers, such as those 
of the Pea (^[ 379, fig. 292), one of the parts, the vexillum, is often 
large and folded over the others, giving rise to vexittary aestivation, 
or the carina may perform a similar part, and then the aestivation 
is carinal. 

356. The different verticils often differ in their mode of aestivation. 
Thus, in Malvaceae, the corolla is contorted, and the calyx valvate, or 
reduplicate (fig. 264). In Convolvulaceae, while the corolla is twisted, 
and has its parts arranged in a circle, the calyx is imbricated and 
exhibits a spiral arrangement (fig. 266). In Guazuma (fig. 261), the 
calyx is valvate, and the corolla induplicate. The circular aestivation 
is generally associated with a regular calyx and corolla ; while the 
spiral aestivations are connected with irregular as well as regular forms. 

357. The different parts of the flower, besides having a certain 
position as regards each other, bear also definite relations with respect 
to the floral axis whence they arise. An individual part of a flower 
may be turned to the one or the other side of the axis, to the right or 
to the left, in its normal state, and the same will be the case with the 
corresponding parts of the other flowers. This law often holds good 
with whole groups of plants, and a means is thus given of character- 
izing them. If a whorl of the flower consists of four parts, that which 
is turned towards the floral axis is called superior or posterior, that 
next the bract whence the pedicel arises is inferior or anterior, while 
the other two are lateral. If again, there are five parts of the whorl, 
then two are inferior, two lateral, and one superior. In plants having 
blossoms like the Pea, the vexillum, or odd petal, is the superior part; 
whilst in the calyx, the odd part, by the law of alternation, is inferior. 
Sometimes the twisting of parts makes an apparent change in their 
position. 

External Floral Whorls, or Floral Envelopes. 

358. Calyx. The calyx is the external envelope of the flower, and 
consists of verticillate leaves, called sepals, foliola, or phylla (folium, and 
(jt/AXov, a leaf). These calycine leaves are sometimes separate from each 
other, at other times they are united to a greater or less extent ; in 
the former case, the calyx is polysepalous or polyphyllous (TTOX<>?, many), 
in the latter gamosepalous or gamophyllous, monosepalous or monophyl- 
lous (-/dpo;, union, or pt,c,vog, one). The divisions of the calyx present 
usually all the characters of leaves, and in some cases of monstrosity 
they are converted into the ordinary leaves of the plant. This is 
frequently seen in the Rose (fig. 226 c), Paeony, &c. Their structure 
consists of cellular tissue or parenchyma, traversed by vascular bundles, 
in the form of ribs and veins, containing spiral vessels, which can be 



172 



FLORAL ENVELOPES. CALYX. 



unrolled, delicate woody fibres, and other vessels, the whole being 
enclosed in an epidermal covering, having stomata, and often hairs on 
its outer surface, which corresponds to the under side of the leaf. 

359. _The venation of the calyx in the great divisions of the vege- 
table kingdom, is similar to that of their leaves; parallel in Endogens, 
reticulated in Exogens. The leaves of the calyx are usually entire 
(fig. 269), but occasionally they are cut in various ways, as in the 
Rose (fig. 270 c/), and they are sometimes hooked at their margins, as 
in Rumex uncatus (fig. 271 c i). In the last-named plant, there are IWD 




whorls of calycine leaves, the outer of which, c e, are entire, and there 
are also swellings, g, in the form of grains or tubercles on the back 
of the inner hooked sepals. The outer leaves, c e, may be looked upon 
in such cases as bracts occupying an intermediate place between leaves 
and sepals. It is rare to find the leaves of the calyx stalked. They 
usually consist of sessile leaves, in which the laminar portion is only 
slightly developed, and frequently the vaginal part is alone present. 
Sepals are generally of a more or less oval, elliptical, or oblong form, 
with the extremity either blunt or acute. In their direction they 
are erect or reflexed (with their apices downwards), spreading out- 
wards (divergent or patulous), or arched inwards (connivent). They 
are usually of a greenish colour, and are called foliaceous or herbaceous ; 
but sometimes they are coloured, as in the Fuchsia, Tropoeolum, and 
Pomegranate, and they are then called petaloid. Whatever be its 
colour, the external envelope of the flower must be considered as the 
calyx. 

Fig. 269.--Pentaphyllous or pentasepalous calyx of Stellaria Holostea; sepals entire. 

Fig. 270.- -Flower of the Rose, cut vertically, c t, Tube of the calyx, c/, Limb of calyx divided 
into leaflets, e e, Stamens, o o, Ovaries, each having a style which reaches beyond the tube of 
the calyx, and ending in a stigma, *. 

Fig. 271. Calyx of Rumex uncatus, composed of two verticils or whorls; the outer, c e, having 
short and entire divisions; the inner, c t, having larger divisions, which exhibit at the margin 
narrow hooked projections, and have at their base a granular swelling, g. 



FLORAL ENVELOPES. CALYX. 



173 




360. The nature of the hairs on the calyx gives rise to terms simi- 
lar to those already mentioned as applied to the surfaces of plants 
(^[ 60). The vascular bundles 

sometimes form a prominent rib 
(figs. 272, 273), which indi- 
cates the middle of the sepal, at 
other times they form several (fig. 
274). The venation is useful in 
pointing out the number of leaves 
which form a gamosepalous calyx. 
At the part where two sepals 
unite, there is occasionally a pro- 
minent line, formed by the union 
of the vessels of each (fig. 274), which divides near the apex into two 
branches, each following the course of their respective sepals. 

361. In a polysepalous calyx, the number of the parts is marked by 
Greek numerals prefixed. Thus, a trisepalons calyx has three sepals, 
pentasepalous or pentaphyllous, five, as in Stellaria Holostea (fig. 269), 
and so on. The sepals occasionally are of different forms and sizes. 
Thus, in Aconite, one of them has a peculiar helmet shape, and has 
been called galeate (galea, a helmet); some authors regard this as a 
petal, but it seems to belong to the outer whorl, and is consequently 
a part of the calyx. In Calcophyllum, one of the sepals enlarges after 
the corolla falls, and becomes of a fine pink colour. 

362. In a monophyllous or gamosepalous calyx, the sepals adhere 
in various ways, sometimes very slightly, as in CEnothera; and their 
number is marked by the divisions at the apex. These divisions are 
either simple projections in the form of acute or obtuse teeth (fig. 273), 
or they extend about hah way, as fissures, the calyx being trifid (three- 
cleft), quinquefid (five-cleft), as in Primula elatior (fig. 272), according 
to circumstances; or they reach to near the base in the form of parti- 
tions, the calyx being tripartite, quadripartite, quinquepartite, &c. The 
adhesion or union of the parts may be complete, and the calyx may 
be quite entire or truncate, as, in some Correas, the venation being 
the chief indication of the different parts. The adhesion is sometimes 
irregular, some parts uniting to a greater extent than others, thus 
forming a two-lipped or labiate calyx, which, when the upper lip is 
arched, becomes ringent. The upper lip is often composed of three 
parts, which are thus posterior or next the axis, while the lower has 
two, which are anterior. The part formed by the union of the sepals 
is called the tube of the calyx; the upper portion where the sepals 
are free is the limb. Sometimes a monophyllous calyx assumes an 



Fig. 279. Quinquefid or five-cleft calyx of Primula elatior or the oxlip. 

Fig. -/7o. Five-toothed calyx of Silene inflata. 

Fig. 274. Calyx, c, of Hibiscus, with its caliculus or epicalyx, b. 



174 



FLORAL ENVELOPES. CALYX. 




angular or prismatic form, as in Lamium and Primula, and then the 
angles are marked by the midribs of the sepals which form it. 
Occasionally the calyx has a globular form, at other tunes it is bell 
shaped, funnel-shaped, turbinate (like a top), or inflated. 

363. Occasionally, certain parts of the 
sepals undergo marked enlargement. In the 
Violet, the calycine segments (lacinice) are pro- 
longed downwards beyond then 1 insertions, 
and in the Indian Cress (Tropoeolum) this 
prolongation is in the form of a spur (calcar), 
formed by three sepals (fig. 275, e); in Del- 
phinium it is formed by one. When one or 
more sepals are thus enlarged, the calyx is 
calcarate or spurred. In the Pelargonium, the 
spur from one of the sepals is adherent to the 
flower-stalk. 

364. In some plants as the Mallow tribe, the flower appears to be 
provided with a double calyx, which has been denominated caliculate 
the outer calyx being the epicalyx. In fig. 274, c represents the calyx 
of Hibiscus, and b the smaller calyx or epicalyx outside; and in fig. 

276, the same thing is shown in Potentilla verna. 
Many authors look upon the outer calyx as a col- 
lection of whorled bractlets, or an involucre placed 
immediately below the flower. In some cases the 
projecting teeth between the divisions of the calyx, 
as in Kosaceae, are to be traced to the transformed 
stipules of the calycine leaves. Degenerations take 
276 place in the calyx, so that it becomes dry, scaly, and 

glumaceous (like the glumes of grasses), as in the Rush tribe; hairy as 
in Composite; and a mere rim, as in some Umbellifera and Acanthaceae, 
when it is called obsolete or marginate. 

365. In Compositae, Dipsaceaa, and Valerianaceas, the tube of the 
calyx adheres to the pistil, and the limb is developed in the form of 
hairs, called pappus. This pappus is either simple (pilose) (fig. 278), 
or feathery (plumose) (fig. 279). In cases where, to the naked eye, the 
hairs appear to be simple, the application of a lens sometimes exhibits 
distinct tooth -like projections often irregularly scattered. In figs. 
277, 278, and 279, there are examples of calyces, c, the tubes of 
which, t, are united to the pistil, while the limbs, I, show a transition 
from the narrowed thread-like form in Catananche caarulea (fig. 277), 
to the pilose in Scabiosa atro-purpurea (fig. 278), and thence to the 
plumose in Pterocephalus paltestinus (fig. 279). In Valeriana, the 
limb of the calyx at first seems to be an obsolete rim, but as the fruit 

Fig. 275. Calcarate calyx of Tropoeolum or Indian cress, e, Spur or calcar. p, Pedicel. 
Fig. 276. Calyx, c c, of Potentilla verna, with its epicalyx or caliculus, b 6. 




FLORAL ENVELOPES. CALYX. 



175 



ripens, it is shown to consist of hairs rolled inwards, which expand so 
as to waft the fruit. 






366. The calyx sometimes falls off before the flower expands, as in 
Poppies, and is caducous ; or along with the corolla, as in Ranunculus, 
and is deciduous ; or it remains after flowering, as in Labiatae, Scrophu- 
lariaceas, and Boraginacese ; or its base only is persistent, as in Datura 
Stramonium. In Eschscholtzia and Eucalyptus, the parts of the calyx 
remain united at the upper part, and become disarticulated at the base 
or middle, so as to come off in the form of a lid or funnel. Such a 
calyx is operculate (operculum, a lid), or calyptrate (x.*i/7rToe., a cover- 
ing). The existence or non-existence of an articulation determines 
the deciduous or persistent nature of the calyx. In the case of Esch- 
scholtzia, the axis seems to be prolonged so as to form a sort of tube, 
from which the calyx separates. In Eucalyp- 
tus, the calyx consists of leaves, the laminae or 

petioles of which are articulated like those of 
the Orange, and the separation between the 
parts occurs at this articulation. 

367. The tube of the calyx is sometimes 
united to the pistil, and enlarges subsequently, 
so as to form a part of the fruit, as in the Apple, 
Pear, Pomegranate, Gooseberry, &c. In these 
fruits the limb of the calyx is seen at the apex. 
Sometimes a persistent calyx increases much 
after flowering, without being incorporated with 
the fruit, becoming accrescent (accresco, to in- 
crease), as in various species of Physalis (fig. 280); 

Figs. 277279.- 
hairs or pappus. 

column above it, in ngs. 440, tiy, mu nmu, t, irons 
i Involucre or gamosepalous bracts cut vertically. 

Fig. 277. Calyx of Catananche coerulea. 

Fig. 278. Calyx of Scabiosa atro-purpurea. 

Fig. 279. Calyx of Pterocephalus palffiStlmu, 

Fig. 280. Accrescent calyx, c, connected with the fruit of Physalis alkekengi. 




1 76 FLORAL ENVELOPES. COROLLA. 

at other times it remains in a withered or marcescent (marcesco I 
decay) form ; sometimes it becomes inflated or vesicular. In Trifolium 
fragiferum, the union of the inflated calyces causes the strawberry-like 
appearance of the head of flowers when in fruit. 

368. Corolla. The corolla is the more or less coloured inner floral 
envelope, forming the whorl of leaves between the calyx and the 
stamens. It is generally the most conspicuous whorl. The gay colours 
and fragrant odours of flowers are resident in it. It is present in the 
greater number of Exogens. It is composed of parts which are usually 
disposed in one or more verticillate rows, and which are called petals 
(viTathoit, a leaf). The petals sometimes form a continuous spiral with 
the calycine segments, but in general they are disposed in a circle, and 
alternate with the sepals. 

369. Petals differ more from leaves than sepals do, and are much 
more nearly allied to the next whorl or the stamens. In some cases, 
however, they are transformed into leaves like the calyx, and occa- 
sionally leaf-buds are developed in their axil. They are seldom green, 
although occasionally this colour is met with, as in some Coba?as, 
Hoya viridiflora, Gonolobus viridiflorus, and Pentatropis spiralis. 
They are generally white, red, blue, or yellow, or exhibit some colour 
produced by an intermixture of these. The colouring matter is con- 
tained in cells, and differs in its nature from the chlorophylle of the 
leaves. As regards their structure, petals consist of cellular tissue 
traversed by true spiral vessels, and thin-walled tubes. In delicate 
flowers, as Convolvulus and Anagallis, these vessels are easily seen 
under the microscope. Petals do not usually present numerous layers 
of cells like the leaves, neither is the epidermis always distinct although 
in some instances it may be detached, especially from the surface next 
the calyx. The cuticle of the petal of a Pelargonium, when viewed 
with a \ or inch object glass, shows beautiful hexagons, the boun- 
daries of which are ornamented with several inflected loops in the 
sides of the cells. 

370. On the outer surface of petals, corresponding to the lower side 
of leaves, stomata are sometimes found. Petals are generally glabrous 
or smooth ; but, in some instances, hairs are produced on then: sur- 
face. Petaline hairs, though sparse and scattered, present occasionally 
the same arrangement as those which occur on the leaves : thus, in 
Bombaceaj they are stellate. Coloured hairs are seen on the petals 
of Menyanthes, and on the segments of the perianth of the Iris. 
Although petals are usually very thin and delicate in their texture, 
they occasionally become thick and fleshy, as in Stapelia and Eaf- 
flesia ; or dry, as in Heaths ; or hard and stiff, as in Xylopia. A petal 
often consists of two portions the lower narrow, resembling the 
petiole of a leaf, and called the unguis or clatv ; the upper broader, like 
the blade of a leaf, and called the lamina or limb. These parts are 




FLORAL ENVELOPES. COROLLA. 177 

seen in the petals of the Pink (fig. 281), where o is the claw, and I 
the limb. The claw is often wanting, as in the Rose, and the petals 
are then sessile. Those having a claw are ungui- 
culate. 

371. Petals, properly so called, belong to Exo- 
genous plants, for in Endogens the flowers consist of 
a perianth or perigone, which is referred to the caly- 
cine envelope. Hence the venation of petals resem- 
bles that of exogenous leaves. In the claw the 
vessels are approximated, as in the petiole, and in 
the limb they expand. There may be a median 
vein whence lateral veins go off, at the same or dif- 
ferent heights, forming reticulations; or there may 
be several primary veins diverging from the base 
of the limb, and forming a sort of fan-shaped vena- 
tion. At other times the median vein divides into two. 

372. According to the development of veins, and the growth of 
cellular tissue, petals present varieties similar to those already noticed 
in the case of leaves. Thus the margin is either entire or divided 
into lobes or teeth. These teeth sometimes form a regular fringe 
round the margin, and the petal becomes fimbriated^fimbria?, a fringe), as 
in the Pink (fig. 281); or laciniated, as in Lychnis Flos cuculi ; or crested. 
as in Polygala. The median vein is occasionally prolonged beyond 
the summit of the petals in the form of a long process, as in Strophan- 
thus hispidus, where it extends for seven inches; and at other times it 
ends in a free point or cuspis, and thus becomes cuspidate ; or the pro- 
longed extremity is folded downwards or inflexed, as in Umbellifera? 
(fig. 282), so that the point approaches to the base. If the median 
vein divides into two, the space between 

the divisions may be filled up so as to leave 
only a slight deficiency, and thus the petal 
becomes emarginate; or the deficiency may 
be greater, while the limb gradually expands 
from below upwards, and its extremity 
becomes two-lobed, so that the petal be- 
comes obcordate. If the separation extends 
to the middle, it is bifid; if to near the 
base, bipartite, as in Chickweed (fig. 283 I). 282 
In the same way as in leaves, the venation of the petals is sometimes 
unequal, and the cellular tissue is developed more on one side than 
on the other, thus giving rise to an oblique petal. 

Fig. 281. An unguiculate petal of Dianthus monspessulanus. o, Unguis or claw. I, Limb 
which is nmbriated, or has a fringed margin. 

Fig. 282. A petal of Eryngium campestre, with the apex inflected or turned down towards 
the base. 

Fig. 283. A bipartite petal of Alsine Media, or common Chickweed. I, The limb split into two 
o, The claw. 

N 




178 



FLORAL ENVELOPES. COROLLA. 



373. According as the veins proceed in a straight or curved direc- 
tion, so may the limb of the petal be flat or concave, or hollowed like 
a boat, cymbiform or navicular (cyrnba, a boat, and navis, a ship), or 
like a spoon, cochleariform (cochleare, a spoon). In the case of the 
navicular petal, the median vein forms a marked keel. In Hellebore, 
the petals become folded in a tubular form, resembling a horn ; in 

Aconite (fig. 284), some of the 
petals, p, resemble a hollow 
curved horn, supported on a 
grooved stalk, while in Colum- 
bine (fig. 285), Violet, Snap- 
dragon, and Centranthus, one 
or all of them are prolonged 
in the form of a spur, and are 
calcarate (calcar, a spur). In 
Valeriana, Antirrhinum, and 
Corydalis, the spur is very 
short, and the corolla or petal 
is said to be gibbous (gibbus, a 
bunch or swelling), or saccate 
at the base. In some Bora- 
ginacea? (fig. 297), there are 
foldings at the upper part of 
the tube of the corolla, r, caus- 
ing hollow projections, open 
on the outside, which might be considered as small internal spurs. 

374. When a petal continues narrow, as if formed by a prolonga- 
tion of the claw, it is called linear; when the limb is prolonged below, 
so as to form two rounded lobes, it is cordate, as in the petal of Genista 
candicans (fig. 286), and when the lobes are acute, it may be sagittate 
or hastate. The meaning of the epithets applied to the forms of petals, 
will be understood by considering those applied to leaves. In general, 
it may be stated, that the terms refer to the limb of the petal, which is 
frequently the only portion developed. In the Poppy, the petals have 
a puckered or corrugated appearance, arising from their delicacy, and 
the mode in which they are folded in aestivation. Other petals have 
a crisp or wavy margin. 

375. A corolla rarely consists of one petal, and when this occurs, 
as in Amorpha, it depends on the abortion or non-development of 
others. Such a corolla is unipetalous (unus, one), a term quite distinct 

Fig. 284. Part of the flower of Aconitum Napellus, showing two irregular horn-like petals, p, 
supported on grooved stalks, o. These used to be called nectaries, s, The whorl of stamens 
inserted on the thalamus, and surrounding the pistil. 

Fig. 285. Single spurred petal of Aquilegia vulgaris, or common Columbine, formed by a 
folding of the margins. 

Kg. 2S:>. Cordate or cordiform petal of Genista candicans. o, The claw. I, The limb. 




FLORAL ENVELOPES. COROLLA. 



179 



from monopetalous (^f 376). In general, the corolla consists of several 
petals, equalling the sepals in number, or being some multiple of 
them. When this is the case, the floral envelopes are said to be sym- 
metrical; when, however, by the abortion of some of the petals the 
numbers do not correspond, then the flower becomes unsymmetrical. 
When alluding to the general symmetry of the flower, the various 
changes produced by some petals being undeveloped will be considered. 
A corolla is dipetalous, tripetalous, tetrapetalous, or pentapetaloits, 
according as it has two, three, four, or five separate petals. 

376. The general name of polypetalous (vohv;, many), is given to 
corollas having separate petals, while monopetalous or gamopetalous 
(ftwof, one, and ya^o?, union) is applied to those in which the petals 
are united. This union generally takes place at the base, and extends 
more or less towards the apex ; in Phyteuma, the petals are united at 
their apices also. In some polypetalous corollas, as that of the Vine, 
in which the petals are separate at the base, they adhere by their 
apices. That a monopetalous corolla consists of several petals united, 
is shown in such cases as Phlox amcena, some specimens of which have 
the petals more or less completely disunited, while others exhibit the 
normal form of coherent petals. When the petals are equal as regards 
their development and size, the corolla is regular ; when unequal it is 
irregular. Even although the separate petals are oblique, still, if they 
are all equally so, as in many Malvaceaa with twisted aestivation, the 
corolla is regular. The size of the corolla as compared with the 
calyx, the number, direction, and form of its parts, and their relation 
to the axis of the plant, require attention. * 

377. When a corolla is monopetalous, it 
usually happens that the claws, or the lower 
parts of the petals, are united into a tube 
(figs. 287 t, 288 i), while the upper parts are 
either free or partially united, so as to form a 
commom limb (fig. 287 I), the two portions 
being separated by the faux or throat, which 
often exhibits a distinct contraction or ex- 
pansion. The number of parts forming 
such a corolla can be determined by the 
divisions, as by the number of teeth, 
crenations, fissures, or partitions ; or if, as 
rarely happens, the corolla is entire, by the 
venation. The union may be equal among 
the parts, or some may unite more than 




Fig. 287. Regular monopetalous or gamopetalous tubular corolla of Spigelia marylandica. 
c, Calyx, t, Tube of the corolla, /, Limb of the corolla, *, Summit of style and stigma. 

Fig. 288. Irregular gamopetalous or monopetalous corolla of Digitalis purpurea, or Foxglove, 
c, Calyx. /), Corolla, t, Tube. I, Limb. 



180 



POLYPETALOUS COROLLAS. 



others, leaving gaps between the united portions. Sometimes the 
tubular portion is bent, as in Lycopsis ; at other times the limb is 
curved at its apex, as hi Lamium. 

378. Regular Polypetaiou* Corollas. Among them may be noticed 
the rosaceous corolla, hi which there are five spreading petals, having 





no claws, and arranged as in the single Eose (fig. 289) and Potentilla; 
the caryophyllaceous corolla, hi which there are five petals with long 

narrow tapering claws, as hi many 
of the Pink tribe (figs. 290, 281); 
the alsinaceous, where the claw is 
less narrow, and there are distinct 
spaces between the petals, as hi some 
species of Chickweed; cruciform, 
having four petals, often unguiculate, 
placed opposite hi the form of a 
cross, as seen hi Wallflower (fig. 
291), and other plants called cruci- 
ferous (crux, a cross, andfero, to bear). 
379. irregular Polypetalous Corollas. The most marked of these 
is the papilionaceous (fig. 292), hi which there are five petals; one 
superior (or posterior), turned next to the axis, usually larger than the 
rest, e, and folded over them in estivation, called the vexillum or stan- 
dard; two lateral, a, the alee or wings; two inferior (or anterior), partially 

Fig. 989. Polypetaloiis flower of Rosa rubiginosa, or the Sweet-brier. 6, Bract or floral leaf, 
e t, Tube of calyx, which forms the conspicuous part of what is commonly called the fruit 
/, c/, cf, cf, Sepals or foliola of the calyx, pppp, Petals, without a claw, e, Stamens attached 
to the calyx. 

Fig. 290. Polypetalous flower of Dianthus monspessulanus. 6, Bracts, c, Calyx, p p, Petals 
with their claws, o, approximated so as to form a tube. 

Fig. 291. Cruciferous flower of Cherianthus Cheiri, or Wallflower, e, Lobes of the sepals ; the 
two external sepals being prolonged inferiorly, so as to form a sort of spur or swelling, p p, The 
four petals arranged like a cross, e, The four longer stamens, the summits of the anthers being 
visible. 




MONOPETALOUS COROLLAS. 



181 



or completely covered by the alae, and often united slightly by their 
lower margins, so as to form a single keel-like piece, b, called carina, 
or keel, which embraces the essential organs. This 
corolla occurs in the Leguminous plants of Bri- 
tain, or those plants which have flowers like the 
pea. Among the irregular polypetalous corollas 
might be included the orchidaceous, although it is, 
properly speaking, the perianth of an Endogen. 
This perianth consists of three outer portions 
equivalent to the calyx, and three inner alternat- 
ing with them, constituting the petals. The latter 
are often very irregular, some being spurred, 
others hooded, &c. ; and there is always one, called the labellum or lip, 
which presents a remarkable development, and gives rise to many of 
the anomalous forms exhibited by these flowers. 

380. Regular Moiiopetiilous or Gamopetalons Corollas. These are 

sometimes campanulate or bell-shaped, as hi Campanula rotundifolia (fig. 
293); infundibuliform or funnel-shaped, when the tube is like an inverted 
cone, and the limb becomes more expanded at the apex, as in Tobacco 
(fig. 294 ;) hypocrateriform or salver-shaped, when there is a straight 
tube surmounted by a flat spreading limb, as in Primula (fig. 295) ; 





293 294 295 296 

tubular, having a long cylindrical tube, appearing continuous with the 
limb, as in Spigelia (fig. 287), and Comfrey (fig. 296); rotate or wheel- 
Fig. 292. Irregular polypetalous corolla in the papilionaceous flower of Lathyrus odoratns, or 
Sweet-pea, c, Calyx, e, Vexillum or standard, a, Two alae or wings, b, Carina or keel, formed 
of two petals. 

Fig. 293. Regular monopetalous or gamopetalous campanulate or bell-shaped corolla of Cam- 
panula rotundifolia. c, Calyx. I, Limb of corolla, s, Stigma. 

Fig. 294. Regular monopetalous or gamopetalous infundibuliform corolla of Nicotiana Taba- 
cum, or Tobacco. The letters as in tig. 293. 

Fig. 295. Regular monopetalous or gamopetalous hypocrateriform corolla of Primula elatior, 
or Oxlip. c, Calyx, p, Corolla, t, Tube. I, Limb, a, Anthers. 

Fig. 296. Regular gamopetalous tubular corolla of Symphytum officinale, or common Comfrey. 
c, Calyx, t, Tube of corolla. I, Limb. *, Stigma, r. External depressed surface of folds which 
project into the tube of the corolla. 



182 



MONOPETALOUS COROLLAS. 



shaped, when the tube is very short, and the limb flat and spreading, 
as in Myosotis (fig. 297); when the divisions of the rotate corolla are 
very acute, as in Galium, it is sometimes called stellate or star-like ; 
urceolate or urn-shaped, when there is scarcely any limb, and the tube 
is narrow at both ends, and expanded in the middle, as in Erica 
cinerea (fig. 298). Some of these forms may become irregular in 
consequence of certain parts being more developed than others. Thus, 
in Veronica, the rotate corolla has one division much smaller than the 
rest, and in Digitalis there is a slightly irregular campanulate corolla 
(fig. 288), which some have called digitaliform. 




381. Irregular Nonopctalous or Gamopetalous Corollas. Among 

these may be remarked the labiate or lipped (fig. 299), having two 
divisions of the limb in the form of what are called labia or lips 
(from a fancied resemblance to a mouth), the upper one composed 
usually of two pieces, and the lower of three, separated by a hiatus or 
gap, I. In such cases the tube varies in length, and the parts of the 
calyx follow the reverse order in their union, two sepals being united 
in the lower lip, and three in the upper. When the upper lip of a 
labiate corolla is much arched, and the lips separated by a distinct 
gap, it is called ringent (ringor, to grin). The Labiate corolla charac- 
terizes the natural order Labiatse. In Lobelia, there is a Labiate corolla, 
the upper lip of which becomes convex superiorly, and is split to near 
the base. When the lower lip is pressed against the upper, so as to 
leave only a chink or rictus between them, the corolla is said to be 
personate or masked (persona, a mask), as in Frogsmouth, Snapdragon, 
and some other Scrophulariaceae (fig. 300), and the projecting portion, 

Fig. 297. Regular gamopetalous rotate corolla of Myosotis palustris, or Forget-me-not c, 
Calyx, p. Corolla, r. Folds of the corolla, forming projections at the upper part of the tube, 
which are opposite to the lobes of the corolla. 

Fig. 298. Regular gamopetalous urceolate or urn-shaped corolla of Erica cinerea, or cross- 
leaved Heath. Letters as in fig. 295. 

Fig. 299. Irregular gamopetalous labiate or lipped corolla of Salvia pratensis. c, Calyx. <, 
Tube of corolla. /, Limb, forming two lips, having a gap or hiatus between them, s, Summit of 
style. 

Fig. 300. Irregular gamopetalous personate or masked corolla of Antirrhinum majus, or 
Frogsmouth. c, Calyx, t, Tube of corolla, having a gibbosity or swelling, a, at its base. /, Limb 
of corolla, g, The faux or mouth closed by a projection of the lower lip, p. 



COROLLINE APPENDAGES. 



183 



./>, of the lower lip is called the palate. In some corollas the two lips 
become hollowed out in a remarkable manner, as in Calceolaria, assum- 
ing a slipper-like appearance, similar to what occurs in the labellum 
of some Orchids, as Cypripedium. Such calceolate (calceolus, a slipper) 
corollas, may be considered as consisting of two slipper-like lips. 

382. When a tubular corolla is split in such a way as to form a strap- 
like process on one side with several tooth-like projections at its apex, 
it becomes ligulate (ligula, a little tongue), or strap- 
shaped (fig. 301). This corolla occurs in many 

composite plants, as in the florets of Dandelion, 
Daisy, and Chiccory. The number of divisions 
at the apex indicates the number of united petals, 
some of which, however, may be abortive. Occa- 
sionally, some of the petals become more united than 
others, and then this corolla assumes a bilabiate or 
two-lipped form. In Compositor there are often 
two kinds of florets associated in the same head. 
Thus, in the Daisy, there are irregular ligulate 
white florets on the outside or in the ray, while 
there are regular tubular yellow florets in the centre 
or disc. In Sc&vola and in Honeysuckle, the corolla 
is split down to its base, so as to resemble somewhat 
the ligulate form. 

383. Nectaries and Anomalies in Petals. Certain 

abnormal appearances occur in the petals of some 
flowers, which received in former days the name of nectaries. The 
term nectary was very vaguely applied by Linnaeus to any part of 
the flower which presented an unusual aspect, as the 
crown of Narcissus, the processes of the Passion-flower, 
&c. If the name is retained, it ought properly to in- 
clude only those portions which secrete a honey- like 
matter, as the glandular depression at the base of the 
perianth of the Fritillary (fig. 302 r), or on the petal of 
Ranunculus, or on the stamens of Rutaceaj. Some say that 
in all flowers there is an apparatus for secreting honey 
connected with the essential organs of the flower, and 
in some way concerned in fertilization, and the nouris- 
ment of the young seeds. This opinion is particularly 
supported by Vaucher and Bravais. The sap of Zea 
Mais is said to contain much saccharine matter before 
flowering, which ultimately passes to the flower, and 

Fig. 301. Irregular gamopetalous ligulate floret of Catananche caerulea, c, Calyx, with a 
quinquefid limb united inferiorly with the ovar}', o. e, Stamens with united anthers, a, (synan- 
tlierous or syngenesiov-s), surrounding the style, s, with its bifid stigma. 

Fig. 302. One of the segments, s, of the perianth of Fritillaria imperialis, or Crown Imperial, 
with a pit or depression, r, at its base, containing honey-like matter. The cavity is coloured 
differently from the rest of the segment, and it is often called a nectary, or a nectariferous gland. 





184 



COROLLINE APPENDAGES. 



disappears from the rest of the plant. What have usually, however, 
been called Nectaries, are mere modifications of some part of the flower, 
produced either by degeneration, or by a process of dilamination (dis, 
separate, and lamina, a blade), or chorization (%u^<a, I separate). 
This process, called unlining by Lindley, and deduplicatwn by Henfrey, 
consists in the separation of a layer from the inner side of a petal, 
either presenting a peculiar form, or resembling the part from which 
it is derived. The parts thus produced are not alternate with the 
petals or the segments of the corolla, but opposite to them. In these 
cases, the petals at the lower part consist of one piece, but where 
the limb and claw separate, or where the tube ends, 
the vascular layer splits into two, and thus two 
laminae are formed, posteriorly and anteriorly, one 
of which is generally less developed than the other. 
These dilaminated scales are well seen in Lychnis (fig. 
303 a), Silene, Cynoglossum, and Ranunculus, and 
may be considered as formed in the same way as the 
ligule of grasses (^[ 161). Corollas having these scaly 
appendages, are sometimes denominated appendiculate. 
In other cases, as in Cuscuta, the scales are alternate with 
the petals, and are not traced to dilamination. This 
system of dilamination has been applied by the French 
botanists to all cases in which the parts of whorls be- 
come opposite in place of alternate. Lindley and others, 
however, believing that the law of alternation is the 
normal one, refer such cases in general to an abortion 
of a whorl, or to some peculiar arrestment in development, as will be 
shown under the section of Morphology and Symmetry. 

384. In general, the parts called Nectaries, are to be 
considered as merely modifications of the corolla or 
stamens. Thus, the horn-like nectaries under the 
galeate sepal of Aconite (fig. 284 p), are modified 
petals, so also the tubular nectaries of Hellebore. The 
nectaries of Menyanthes and of Iris, consist of hairs 
developed on the petals. Those of Parnassia (fig. 304 
/i), and of the Passion-flower, Stapelia, Asclepias, and 
Canna, are fringes, rays, and processes, which are ap- 
parently modifications of stamens, and some consider 
the crown of Narcissus as consisting of a membrane 
similar to that which unites the stamens in Pancratium. 
It is sometimes difficult to say whether these nectaries 





Fig. 303. Petal of Lychnis fulgens, seen on its inner side, o, Claw. I, Limb, a, An appen- 
dage formed by dilamination or chorization. This appendage has been called a nectary. 

Fig. 304. Petal, p, of Parnassia palustris, or grass of Parnassus, with a nectary, n, which ap- 
pears to be an abortive state of some of the stamens. 



DEVELOPMENT OF FLORAL ENVELOPES. 185 

are to be referred to the row of the corolla or of the stamens. The 
paraphyses of the Passion-flower, the crown of Narcissus, and the 
coronet of Stapelia, are referred sometimes to the one and sometimes 
to the other. In general, they may be said to belong to that series 
with which they are immediately connected. Some have attempted 
to give names according to the parts of which they are modifications, 
by prefixing the term para (vet^ot, beside, or close to), and speaking 
of paracorolla and parastemones. 

385. Petals are attached to the axis usually by a narrow base, but 
occasionally the base is larger than the limb, as in the Orange flower. 
When this attachment takes place by an articulation, the petals fall off 
either immediately after expansion (caducous), or after fertilization 
(deciduous). A corolla or petals which are continuous with the axis 
and not articulated, as Campanula, Heaths, &c., may be persistent, and 
remain in a withered or marcescent state while the fruit is forming, 
A gamopetalous corolla always falls off in one piece. Sometimes the 
base of the corolla remains persistent, as in Ehinanthus and Oro- 
banche. 

386. Development of Floral Envelopes. The floral envelopes, when 
monosepalous and monopetalous, first appear in the form of a ring, 
whence various cellular projections arise, constituting the sepals and 
petals ; when they are polysepalous and polypetalous, the ring is 
wanting. Even when the parts become ultimately 

unequal, as in Digitalis (fig. 288), they form equal 
cellular papilla? when first developed (fig. 305). 
Barneoud has shown this in the irregular Ranun- 
culaceaa, Violacese, Orchidacese, Labiatae, Scrophu- 
lariacea?, Leguminosae, and Polygalaceae. 

387. In Begoniacese, the floral envelope at first 
appears as a continuous ring, having five very equal 
small segments ; some of these, especially in the 

male flowers, disappear entirely or become atrophied. All the obser- 
vations of Barneoud confirm Decandolle's statement, that irregular 
flowers are to be referred to regular types, from which they seem to 
have degenerated. There appear to be three principal kinds of irre- 
gularity among corollas : 1. Irregularity by simple inequality of 
development of the several segments, often along with adhesion or 
atrophy, or arrest of growth : this is the most common kind. 2. Irre- 
gularity of deviation, when the segments, though equal, turn all to 
the same side, as in ligulate florets. 3. Irregularity by simple meta- 
morphosis of stamina, as in Canna. The irregular corollas of Acan- 
thacese, Bignoniaceas, Gesneracese, Lobeliaceae, and Scrophulariaceae, are 
formed at first in a regular manner by equal projections from a sort of 

Fig. 305. Bud of the irregular gamopetalous flower of Digitalis purpurea. c c, Calyx, p. Corolla, 
which in its early development is regular. , The stamens at first projecting beyond the corolla. 




186 ESSENTIAL ORGANS. STAMENS. 

cup or ring. Even in Calceolaria, there is at first a scooped-otit cup, 
with four regular and very minute teeth, which are ultimately developed 
as the corolla ; the nascent calyx having also four divisions. 

Inner Floral Whorls, or the Essential Organs of Reproduction. 

388. These organs are the stamens and the pistil, the latter contain- 
ing the seeds or germs of yoking plants, and corresponding to the 
female, while the former produces a powder necessary for fecundation, 
and is looked upon as performing the part of the male. The presence 
of both is required in order that perfect seed may be produced. A 
flower may have a calyx and corolla, and yet be imperfect if the essen- 
tial organs are not present. The name of hermaphrodite is given to 
flowers in which both these organs are found ; that of unisexual (one 
sex), or diclinous) 3<V, twice, and x^ivn, a bed), to those in which 
only one of these organs appears, those bearing stamens only, being 
staminiferous (stamen, a stamen, and fero, I bear), or male ; those 
having the pistil only, pistilliferous (pistillum, a pistil, and fero, I bear), 
or female. 

389. The absence of one of the organs is due to abortion or non- 
development. When in the same plant there are unisexual flowers, 
both male and female, the plant is said to be monoecious (p,6vo$, one, and 
oix.io, habitation), as in the Hazel and Castor oil plant; when the male 
and female flowers of a species are found on separate plants, the term 
dioecious (o<V, twice) is applied, as in Mercurialis and Hemp ; and when 
a species has male, female, and hermaphrodite flowers on the same or 
different plants, it is polygamous (vo^vg, many, and ya^oj, marriage). 
The term agamous ( privative, and yafto$, marriage) has sometimes 
been applied to Cryptogamic plants, from the supposed absence of any 
bodies truly representing the stamens and pistil. 

390. Stamens. The stamens (stamina) arise from the thalamus or 
torus within the petals, forming one or more verticils or whorls, which 
collectively constitute the androecium (dv^, a male, and omiov, habita- 
tion), or the male organs of the plant. Their normal position is below 
the inner whorl or the pistil, and when they are so placed (fig. 306 e), 
they are hypogynous (ilwo, under, and yvvvi, female or pistil). Some- 
tunes they become united to the petals or epipetalous (Ivl, upon, and 
Kt-TttKM, a leaf), and the insertion of both is looked upon as similar, 
so that they are still hypogynous, provided they are independent of 
the calyx and the pistil. In fig. 307, the stamens, e, and the petals, p, 
are both below the pistil or ovary, o, and separate both from it and 
the calyx, c, and are therefore hypogynous; when the stamens are 
inserted on the calyx, that is, become united to it to a greater or less 
height above the base of the pistil, then they become lateral as it were 
in regard to it, and are perigynous (OT? /, around). This is shown in the 



ESSENTIAL ORGANS. STAMENS. 



187 



flower of almond (fig. 308), in which the petals, p, and the stamens, e, 
are united to the calyx, c, while the pistil is free. When the union 
of the parts of the flower is such that the stamens are inserted upon 




307 308 

the ovary, they are epigynous (i^i, upon or above). In this case, the 

whorls are usually so incorporated, that the stamens appear also to 

come from the calyx. In Aralia spinosa (fig. 309), all the whorls, 

calyx, c, petals, p, and stamens, e, are united to the pistil, and the two 

latter whorls appear to arise from the point 

where the calyx joins the upper part of the 

pistil. These arrangements of parts have 

given rise to certain divisions in classification, 

to be afterwards particularly noticed. De- 

candolle, for instance, applies the term thala- 

miflorce, to plants having the parts of the 

corolla and androecium independent of each 

other, and all the whorls inserted immediately 

into the torus or thalamus ; calyciflorce, to those where the petals are 

separate, and the stamens are inserted directly on the calyx ; corolli- 

florce, to those in which the united petals bear the stamens. 

Fig. 306. Central part of the flower of Liriodendron tulipifera, the tulip-tree, composed of 
carpels, c c, which together form the pistil. They cover the upper part of the axis, a, and below 
them are inserted numerous stamens, some of which are seen, e e. These stamens are hypogy- 
nous and extrorse. 

Fig. 307. Section of a flower of Geranium robertianum. c c, Calyx, p, Petals, e, Stamens. 
Pistil composed of ovary, o, and style and stigmata, s. t, Torus or thalamus. The petals and 
stamens are hypogynous, and the latter are monadelphous. 

Fig. 308. Section of the flower of the Almond-tree. The letters indicate the same parts as in 
the last figure. The petals and stamens are perigynous. The pistil is free. 

Fig. 309. Section of the flower of Aralia spinosa. Letters as in last figure. The petals and 
stamens are epigynous, attached to a large disk, rf, which covers the summit of the ovary. The 
ovary is adherent to the calyx, and has been laid open to show its loculaments and pendulous 
ovules. 




188 



ESSENTIAL ORGANS. STAMENS. 



391. The stamens vary in number, from one to many hundred. 
Like the other parts of the flower, they are modified leaves resembling 
them in their structure, development, and arrangement. They consist 
of cellular and vascular tissue. They appear at first in the form of 
cellular projections, and are arranged in a more or less spiral form. 
In their general aspect they have a greater resemblance to petals than 
to the leaves, and there is often seen a gradual transition from petals 
to stamens. Thus, in Nymphaea alba, or the White Water-lily (fig. 
310, 2), c represents a sepal, which gradually passes into the petals, J9, 





310,1 

and these in their turn become modified so as to form the stamens, e, 
which are more or less perfect as we proceed from without inwards, 
or from 1 to 5. When flowers become double by cultivation, the 
stamens are converted iuto petals, as in the Pasony, Camellia, Rose, 
Anemone, and Tulip ; and in these instances, the changes from one 
to the other may be traced in the same way as in the Water-lily. 

392. When there is only one whorl, the stamens are usually equal 
in number to the sepals or petals, and are arranged opposite to the 
former, and alternate with the latter. The flower is then isostemonous 
(fro?, equal, and arviftuv, a stamen). When the stamens are not equal 
in number to the sepals or petals, the flower is anisostemonous (oiviaos, 
unequal). When there is more than one whorl of stamens, then the 
parts of each successive whorl are alternate with those preceding it. 
The stamina! row is more liable to multiplication of parts than the 
outer whorls. If the stamens are double the sepals or petals as regards 
number, the flower is diplostemonous (liif^oog, double) ; if more than 
double, polystemonous (woXvj, many). In general, when the stamens 



Fig. 310, 1, Flower of Nymphsea alba, or White Water-lily, cccc, The four foliola of the 
calyx or sepals, p p p p, Petals, e, Stamens, s, Pistil. 

Fig. 310, <?. Parts of the flower separated to show the transition from the green sepals of the 
calyx, c, and the white petals of the corolla, p, to the stamens, e. The latter present changes 
from their perfect state, 5, through intermediate fonns, 4, 3, 2, and 1, which gradually resemble 
the petals. 



ESSENTIAL ORGANS. STAMENS. 189 

are normally developed, and are more numerous than the sepals and 
petals, they will be found arranged in several whorls, and their parts 
multiples of the floral envelopes. Thus, if a flower has five sepals, five 
petals, and twenty stamens, the latter are arranged in four alternate 
rows, having five in each. Although this is the usual law, yet various 
changes take place by abortion and arrestment of development. In 
this way the stamens may neither be equal to, nor a multiple of, the 
floral envelopes, and they may even be less numerous, so that the flower 
is miostemonous (/uiiav, less). 

393. In certain cases, as in Primula, the row of stamens is opposite 
to the petals forming the gamopetalous corolla. This opposition is by 
many looked xipon as caused by the non-appearance of an outer row 
of stamens; by others it is considered as produced by chorization or 
separation of lamina? from the petals, which become altered so as to 
form stamens, a view which is thought to be confirmed by their de- 
velopment taking place before the petals; by a third party, each petal 
is looked upon when fully developed as formed by the halves of two 
contiguous petals, and thus the stamens are considered as being really 
alternate with the original petals. 

394. When the stamens are under twenty, they are called definite, 
and the flower is oligandrous (o'A/yo?, few, and eivyp, male or stamen); 
when above twenty, they are indefinite or polyandrous (VoAi)f, many), 
and are marked ><>. The number of stamens is indicated by the Greek 
numerals prefixed to the term androus: a flower with one stamen be- 
ing monandrous (povog, one); with two, diandrous (S/V, twice); with 
three, triandrous (r^i7;, three); with four, tetrandrous (rsr^x;, four); 
with five, pentandrous (vivrs, five); with six, hexandrom (I|, six); with 
seven, heptandrous (kvr*, seven); with eight, octandroits (6x.ru, eight); 
with nine, enneandrous (sweat, nine); with ten, decandrous (btx.*., ten); 
with twelve, dodecandrous (3<y3gK, twelve). These terms will be 
referred to when treating of the Linnasan system of classification. 

395. A stamen consists of two parts a contracted portion, usually 
thread-like, equivalent to the petiole of the leaf, and termed the fila- 
ment (jilum, a thread); and a broader portion, representing the folded 
blade of the leaf, termed the anther (dvfagci;, belonging to a flower), 
which contains a powdery matter, called pollen. The filament is no 
more essential to the stamen than the petiole is to the leaf, or the claw 
to the petal. If the anther is absent, the stamen is abortive, and can- 
not perform its functions. The anther is developed before the fila- 
ment, and when the latter is not produced the anther is sessile (sessilis, 
sitting), or has no stalk, as in the Misletoe. 

396. The Filament, when structurally considered, is found to consist 
of a thin epidermis, on which occasionally stomata and hairs occur, 
and of a layer of cellular tissue enclosing a bundle of spiral vessels, 




190 ESSENTIAL ORGANS. STAMENS. 

the filament and the anther. The filaments of Callitriche verna are 
said to have no vessels. The filament is usually, as its name imports, 
filiform or thread-like, cylindrical, or slightly tapering towards its 
summit. It is often, however, thickened, compressed, and flattened 
in various ways. It sometimes assumes the appearance of a petal, or 
becomes petaloid (7rsTKov, a leaf or petal, and g<oj, form), as in Canna, 
Maranta, Nymphasa alba (fig. 310, 2); occasionally it is subulate 
(subula, an awl), or slightly broadened at the base, and drawn out into 
a point like an awl, as in Butomus umbellatus; and at 
other times it is clavate (clava, a club), or narrow below 
and broad above, like the club of Hercules, as in Thalic- 
trmn. In place of tapering, it happens, in some in- 
stances, as in Tamarix gallica (fig. 311), Peganum 
Harmala, and Campanula, that the base of the filament 
is dilated much, and ends suddenly in a narrow thread- 
like portion. In these cases, the base may represent 
the sheath or vagina of the petiole, and, like it, may 
give off stipulary processes in a lateral direction. Some- 
times the filament is forked, or divided at the apex into 
branches or teeth. In Allium there are three teeth, the central one 
of which bears the anther. 

397. The filament varies much in length and in firmness. The 
length bears a relation to that of the pistil, and to the position of the 
flower, whether erect or drooping; the object being to bring the an- 
ther into more or less immediate contact with the upper part of the 
pistil, so as to allow the pollen to be scattered on it. The filament is 
usually of sufficient solidity to support the anther in an erect position; 
but sometimes, as in Grasses, Littorella, and Plantago, it is very deli- 
cate and capillary (capillus, a hair), or hair-like, so that the anther is 
pendulous. The filament is usually continuous from one end to the 
other, but in some cases it is bent or jointed, becoming geniculate 
(genu, a knee); at other times, as in the Pellitory, it is spiral. It is 
frequently colourless ; but, in many instances, it exhibits different 
colours. In Fuchsia and Poinciana, it is red; in Adamia and Trades- 
cantia virginica, blue; in (Enothera and Eanunculus acris, yellow. 

398. Hairs, scales, teeth, or processes of different kinds are some- 
times developed on the filament. In Tradescantia virginica, or Spider- 
wort, the hairs are beautifully coloured, and moniliform (monile, a 
necklace) or necklace-like. These hairs exhibit movements of rotation 
(IF 278). Such a filament is bearded or stupose (stiipa, tow). At the 
base of the filament, certain glandular or scaly appendages are occa- 
sionally produced, either on its internal or external surface. These 
may be either parts of a whorl, to be afterwards noticed under the 

Fig, 311. Three out of the ten stamens of Tamarix gallica, united together by the dilated 
basc-s of their filaments. 



ESSENTIAL ORGANS. STAMENS. 



191 




name of the Disk, or separate prolongations from the filament itself. 
In fig. 313, a represents such a staminiferous appendage found 011 
the inner side of the base of the filament, f, 
which is hence called appendiculate, or some- 
times strumose (struma, a swelling). The pro- 
cesses noticed in the Boraginaceas as modified 
petals (fig. 312 a), may be considered external 
appendages of the filaments, the stamen being 
regarded as the lamina of a petal. 

399. Filaments are usually articulated to 
the torus, and the stamen falls off after fertili- 
zation; but in Campanula and other plants, 
they are continuous with the torus, and the 
stamen remains persistent, although in a 
withered state. Certain changes are pro- 
duced in the whorl of stamens by adhesion 
of the filaments to a greater or less extent, 
while_ the anthers remain free; thus, all the filaments of the An- 
droecium may unite, forming a tube round the pistil (fig. 307 e), or 
a central bundle 
when the pistil is 
abortive (fig. 314, 
1), the stamens be- 
coming monadelphous 
(povo;, one, and aSsX- 
<poV, brother), as oc- 
curs in Geranium (fig. 
307), Malva, Hibis- 
cus, and Jatropha 
Curcas (fig. 314, 1); 
or they may unite so 
as to form two bun- 
dles, the stamens be- 
ing diadelphous (d<?, 
twice), as in Poly gala, 
Fumaria, and Pea; 
in this case the bun- 




314,1 



314,2 



Fig. 312. Stamen of Borago officinalis. /, Appendiculate filament, o, Appendage prolonged 
in the form of a horn-like process. I, Lohes of the anther. 

Fig. 313. Stamen of Zygophyllum fabago. /, Filament, connected with a broad scaly ap- 
pendage, a. 

Fig. 314. Male or staminiferous flower (1), and female or pistilliferous flower (2), of Jatropha 
Curcas. c, Calyx, p, Corolla, , Stamens united by filaments occupying the centre in flower 1, 
in consequence of the suppression of the pistil, p, Pistil in flower 2, composed of ovary, o, with 
three bifid styles at its summit, a, Small glandular appendages alternating with the divisions 
of the corolla. Above each of the flowers is a diagram representing the order In which the dif- 
ferent parts of the flower are arranged. In diagram 1 are represented five parts of the calyx, 
five of the corolla, two rows of stamens, five in each. In diagram 2, the staminal rows arc abor- 
tive, and there are three carpels, forming the pistil, in the centre. 



192 



ESSENTIAL ORGANS. STAMENS. 



dies may be equal or unequal. It frequently happens, especially in 
Papilionaceous flowers, that out of ten stamens, nine are united by 
their filaments, while one (the posterior one) is 
free. When filaments form three or more bun- 
dles, the stamens are triadelphous (TJ<?, three), 
as in Hypericum segyptiacum (fig. 315), or polya- 
delphous (-s-oXiyf, many), as in Luhea paniculata 
(fig. 316, 1), or in Ricinus communis (fig. 317, 
1). The union of the filaments takes place some- 
times at the base only, as in Tamarix gallica (fig. 
311); at other times it extends throughout their 
Avhole length, so that the bundles assume a 
columnar form. In certain cases, the cohesion 
extends to near the apex, forming what Mirbel 
calls an androphore (K.V/JQ, male or stamen, and 
(?>o(>fa, I bear), or a column which divides into terminal branches, each 
bearing an anther (fig. 315, fe). Occasionally some filaments are 
united higher up than others, and thus a kind of compound branching 
is produced (fig. 317, 2). In Pancratium, the filaments are united by 
a membrane, which may be considered as corresponding to the crown 
of Narcissus. 





316, 1 



316, 2 



317, 2 



317, 1 



400. Filaments sometimes are united with the pistil, forming a 
columna or column, as in Stylidium, Asclepiadacea?, Eafflesia, and Or- 
chidaceae. The column is called gynostemium ("/My, pistil, and ar^av, 
stamen), and the flowers are denominated gynandrous (yt/j/jj, pistil, and 
male or stamen). 



Fig. 315. Triadelphons stamens of Hypericum aegyptiacutn surrounding the pistil, o. //, 
United filaments forming columns, e e, Anthers, free. The outer envelope .of the flower has 
been removed, the essential organs alone heing left 

Fig. 316. 1. Flower of Luhea paniculata. c c c c, Segments of calyx, p p, Petals, e e, Sta- 
mens grouped in bundles, which alternate with the petals, s, Stigma, composed of five parts, 
indicating the union of five carpels. 2. One of the staminal bundles magnified, showing all the 
filaments united into a single mass at the base, but separating superiorly, fa, The larger in- 
ternal filaments, each ending in an anther. /, The shorter outer ones, sterile and abortive. 

Fig. 317. 1. Male flower of Ricinus communis, or Castor oil plant, consisting of a calyx, r, 
composed of five reflexed sepals, and of stamens, e, united by their filaments so as to form many 
bundles, thus being polyadelphous. 2. One of the stamiual bundles, /, branching above, so as to 
leave the anthers free and separate. 



ESSENTIAL ORGANS. STAMENS. 193 

401. In the case of certain Achlamydeous (^[ 351) flowers, as 
Euphorbia, with only one stamen developed, there is the appearance 
of a jointed filament bearing one anther. This, however, is not a true 
filament, but a peduncle with a single stamen attached to it, as proved 
by the fact, that in some species of Euphorbia one or more verticils are 
produced at the joint. Thus the so-called anther is in reality a single 
flower supported on a stalk, all the parts being abortive, except a 
solitary stamen. 

402. The Amber corresponds to the blade of the leaf, and consists 
of lobes or cavities containing minute powdery matter, called pollen, 
Avhich, when mature, is discharged by a fissure or opening of some 
sort. The anther-lobes may be considered as formed by the two halves 
of the lamina, their back corresponding to the under surface, and their 
face to the upper surface, united by the midrib, the pollen being cellular 
tissue, and the fissure of the anther taking place at the margin, which, 
however, is often turned towards the face. In this view, the two 
cavities which are found to exist in each lobe, may correspond with 
the upper and under layer of cells, separated by a septum equivalent 
to the fibro-vascular layer of the leaf. Others view the anther as 
formed by each half of the lamina being folded upon itself, so that the 
outer surface of both face and back corresponds to the lower side of 
the leaf, and the septum dividing each cavity into two is formed by 
the upper surfaces of the folded half united. 

403. There is a double covering of the anther the outer, or exo- 
thecium (i%-a, outwards, and 6-tix.iov, a covering), resembles the epider- 
mis, and often presents stomata and projections of different kinds (fig. 
318 c e); the inner, or endothecium (s^ov, 

within), is formed by a layer or layers of 
fibro-cellular tissue (fig. 318 c /), the cells 
of which have a spiral (fig. 23), annular (fig. 
24), or reticulated (fig. 25) fibre in their in- 
terior. This internal lining varies in thick- 
ness, generally becoming thinner towards the 

part where the anther opens, and there disappears entirely. The 
membrane of the cells is frequently absorbed, so that when the anther 
attains maturity the fibres are alone left, and these by their elasticity 
assist in discharging the pollen. 

404. The anther is developed before the filament, and is always 
sessile in the first instance. It appears in the form of a small cellular 
projection, containing a mass of mucilaginous CPUS (fig. 319). In the 
progress of growth, certain grooves and markings appear on its sur- 
face, and its interior becomes hollowed out into two marked cavities, 

Fig. 318. Transverse section of a portion of the covering of the anther of Cotea scandens at 
the period of dehiscence. c e, Exothecium, or external layer, consisting of epidermal cells, c/, 
Endothecium, or inner layer, composed of spiral cells or inenchyma. 

O 




194 



ESSENTIAL ORGANS. STAMENS. 



containing a mucilaginous matter (figs. 320, 321). In these cavities 
cells make their appearance the outer small (figs. 320, 321, c p), 
forming ultimately the endothecium (fig. 318 c/); the interior layer 
forming cells in which the pollen is produced (figs. 320, 321, up,). 





As the cavities become larger, the layer of cells (figs. 320, 321, c t), 
between the endothecium, c p, and exothecium, c e, is gradually 
absorbed more or less completely, forming at first septa in the cavities : 
and ultimately the anther assumes its mature form, consisting of two 
lobes with their membranous coverings (fig. 322, /). 





405. In the young state there are usually four cavities produced, 
two for each anther-lobe, separated by the connective, and each divided 
by the septum, which sometimes remains permanently complete, and 
thus forms a quadrilocular (quatuor, four, and loculus, a pouch or box), 
or tetrathecal (rlT^us, four, and Sti**, a sac) anther. The four cavities 
are sometimes placed in apposition, as in Poranthera (fig. 323) and 
Tetratheca juncea (fig. 324), and at other tunes two are placed above 

Fig. 319. Transverse section of an anther of Cucurbita Pepo, or Gourd, taken from a bud 
about two millimetres, or l-12th of an English inch, in length. 

Fie 320. Similar horizontal section from a bud in a more advanced state, c e, Outer layer 
of cellules (Exothecium) forming the epidermis, c t, Intermediate layer of cellules in several 
layers, most of which are ultimately absorbed, cp, Internal layer of cells (Endothecium), up, 
Anther-cavities filled with large cells, which constitute the first state of the pollen-utricles. 

Fig. 321. Similar section in a still more advanced state. The letters have the same meaning 
as in the last figure. 

Fip. 322. Anther of the Almond-tree. ', Seen in front ", Seen behind. //, Filament at- 
tached to the connective, c, by a point 1 1, Anther-lobes containing pollen. 



ESSENTIAL ORGANS. STAMENS. 



195 



and two below, as in Persea gratissima (fig. 325 I I). In general, 
however, only two cavities remain in the anther, in consequence of the 
more or less complete removal of the septum, in which case the anther 
is said to be bilocular (bis, twice), or dithecal (3i?, twice), as seen in 
figs. 322, 326. Sometimes the anther has a single cavity, and becomes 
unilocular (unus, one), or morwthecal (pottos, one), by the abortion of 




one of its lobes, as in Styphelia Ia3ta (fig. 327), and Althaea officinalis 
(fig. 328). Occasionally, there are numerous cavities in the anther, as 
in Viscum and Eafflesia. The number of loculi or cavities is only seen 
when the anther opens. 

406. The form of the anther-lobes varies. They are generally of 
a more or less oval or elliptical form (figs. 322, 329 I). Sometimes 
they are globular, as in Mercurialis annua (fig. 326) ; at other times 
linear or clavate (fig. 330), curved (fig. 331), flexuose, sinuose, or 
anfractuose (anfractus, winding), as in Bryony and Gourd (fig. 332). 
The lobes of the anther are sometimes in contact throughout their 
whole length (fig. 329), at other times they are separate (figs. 326, 
333). In the former case their extremities may be rounded, forming 
a cordate anther (fig. 322), or the apex may be acute (figs. 312, 

Fig. 323 Quadrilocular anther, /, of Poranthera, attached to the filament,/, and opening at 
the summit by four pores, p. 

Fig. 324. Quadrilocular anther of Terratheca juncea. 1. The anther entire, with its four 
loculaments ending in one opening. 2. Anther cut transversely, showing the four loculaments. 

Fig. 325. Anther of Persea gratissima, composed of four cavities or loculaments, / /, united 
in pairs, one above the other, and opening each by a valve, v. At the base of the filament, /, 
are two glands, g g, which seem to be abortive stamens. 

Fig. 326. Pendulous anther lobes, I f, of Mercurialis annua, supported on the filament, /, and 
united by the connective, c. 

Fig. 327. Unilocular or monothecal anther of Styphelia ijBta, one of the Epacridacese, seen in 
front, ', and behind, ". /, Filament /, Anther. 

Fig. 328. Unilocular anther of Althasa officinalis, or Marsh mallow. One of the lobes of the 
anther, Z, abortive. /, Filament 



196 



ESSENTIAL ORGANS. STAMENS. 



313); in the latter case the lobes may divide at the base only, and 
end in a sagittate or arrow-like mariner (fig. 334 I) ; or at the apex, 
so as to be bifurcate or forked (fig. 335 p) ; or quadrifurcate, doubly 
forked (fig. 336 I) ; or at both base and apex, so as to be forked at 




33.-, 



each extremity, as in Grasses (fig. 337). The cavities of the anther 
are occasionally elongated so as to end in points (fig. 336 V). Some- 
times the lower part of the antherine cavities is obliterated, and they 
degenerate into flattened appendages (fig. 338 a). It happens at 



Fig. 329. Adnate or adherent anther of Begonia manicata, opening by longitudinal dehiscence. 
7, Anther lobes. /, Filament. 

Fig. 330 Forked or bifurcate anther, I, of Acalypha alopecuroidea, in the expanded flower. 

Fig. 331. Same anther in the bud, exhibiting a curved form. 

Fig. 33?. Sinuous anther, I, of Bryonia dioica. /, Filament. 

Fig. 333. Anther of Salvia officinalis. If, Fertile lobe full of pollen. I s, Barren lobe without 
pollen, c, Distraetile connective. 

Fig. 334. Anther of Nerium Oleander, with its lobes, 1 1, sagittate at the base, and ending at 
the apex in a long feathery prolongation. 

Fig. 335. Anther, I, of Vaccinium uliginosum. I, Lobes ending in two pointed extremities, 
which open by pores, a, Appendages to the lobes. 

Fig. 3.36. Quadrifurcate anther of Gualtheria procumbens. I, Lobes ending in four points. 

Fig. 337. Versatile anther of Poa compressa. /, Filament. I, Lobes separating at each end. 

Fig. 338. Anther, I, of Erica cinerea. /, Filament, r, Lobes split partially downwards, a, 
Scale-like prolongations at the base. 

Fig. 339. Anther of Pterandra pyroidea. 1. Entire anther, seen laterally 2. Lower half 
after having been cut transversely, a a', a, Antherine appendages. II, Anther-lobes, c e, Con- 
nective. 



ESSENTIAL ORGANS. STAMENS. 197 

times that the surface of the anther presents excrescences in the 
form of warts, awl-shaped pointed bodies (fig. 335 a), or crests (fig. 
339 a). 

407. That part of the anther to which the filament is attached, and 
which is generally towards the petals, is the back, the opposite being 
thejface. The division between the lobes is marked on the face of the 
anther by a groove or furrow, and there is usually on the face, a 
suture, indicating the line where the membranous coverings open to 
discharge the pollen. The suture is often towards one side in con- 
sequence of the valves being unequal. 

408. The anther-lobes are united either by a direct prolongation of 
the filament, or more generally by a body called the connective, con- 
sisting of a mass of cellular tissue different from that contained in the 
filament. In this tissue the spiral vessels of the latter terminate. 
From the connective a partition or septum extends across each antherine 
loculus, dividing it either partially or completely. The septum some- 
times reaches the suture. When the filament is continuous with the 
connective, and is prolonged so that the anther-lobes appear to be 
united to it throughout their whole length, and lie in apposition and 
on either side of it, the anther is said to be adnate or adherent (fig. 
329); when the filament ends at the base of the anther, 

then the latter is innate or erect. In these cases the anther 
is to a greater or less degree fixed. When, however, 
the attachment is very narrow, and an articulation exists, 
the anthers are then moveable, and easily turned by the 
wind. This is well seen in what are called versatile (verto, 
I turn) anthers, as in Tritonia, Grasses, &c. (figs. 260, 
337), where the filament is attached only to the middle 
of the connective ; and it may occur also in cases where 
it is attached to the apex, as in pendulous anthers (fig. 
340). 34 

409. The connective may unite the anther-lobes completely, or only 
partially. It is sometimes very short, and is reduced to a mere point 
(fig. 326), so that the lobes are separate or free. At other times it is 
prolonged upwards beyond the lobes in the form of a point, as in 
Acalypha (fig. 331 c); or of a feathery awn, as in Nerium, Oleander 
(fig. 334) ; or of a conical or tongue-like process (figs. 341, 342 c) ; or 
of a membranous expansion (fig. 343 c) ; or it is extended back- 
wards and downwards, in the form of a spur, as in fig. 343 a; or 
downwards, as in the case of the flaky appendage in Ticorea febrifuga. 
In Salvia officinalis (fig. 333), the connective is attached to the fila- 
ment in a horizontal manner, so as to separate the two anther-lobes, 
and then it is called distractile (dis, separate, and traho, I draw). 

Fig. 340. Pendulous anther, I, of Pyrola rotundifolia. The anther is suspended from the 
summit of the filament, /, and opens at its apex by two pores, p. 




198 



ESSENTIAL ORGANS. STAMENS. 



In Stachys, the connective is expanded laterally, so as to unite the 
bases of the antherine lobes, and bring them into a horizontal line. 






410. The opening of the anthers to discharge their contents is 
denominated dehiscence (dehisco, I open). This takes place either by 
clefts, by hinges, or by pores. When the anther-lobes are erect, the 
cleft takes place lengthwise along the line of the suture, constituting 
longitudinal dehiscence (figs. 322, 329, 342). At other times, the slit 
takes place in a horizontal manner, from the connective to the side, as 
in Alchemilla arvensis, and in Lemna, where the dehiscence is trans- 
verse. When the anther-lobes are rendered horizontal by the enlarge- 
ment of the connective (figs. 328, 344 a<?), then what is really longitudinal 
dehiscence may appear to be transverse. In other 
cases (fig. 344 a #), when the lobes are united 
at the base, the fissure in each of them may be 
continuous, and the two lobes may appear as one. 
411. The cleft does not always proceed the 
whole length of the anther-lobe at once, but often 
for a time it extends only partially (figs. 343, 2, 
338). In other instances the opening is confined 
to the base or apex, each loculament (loculus) 
opening by a single pore, as in Pyrola (fig. 340), 
Vaccinium (fig. 335), and Solanum, where there 
are two, and Poranthera (fig. 323), where there 
344 are four. In Tetratheca juncea, the four cavities 

(fig. 324, 2) open into a single pore at the apex (fig. 334, 1) ; and in 

Fig. 341. Anther of Hnmiria balsamifera 1 1, Anther lobes. /, Filament, ciliated or fringed 
with glandular teeth, c, Conical appendage, which seems to be a prolongation of the connective. 

Fig. 3*2. Anther of Byrsonima bicorniculata, /, Filament. I, Anther-lobes. The empty 
lobes at the summit are detached in the form of two small horn-like projections, c, A lingui- 
form or tongue-like appendage prolonged from the connective. 

Fig. 343. Sessile anther of Viola odorata, or sweet violet. 1. Seen in front. 2. Seen behind. 
I, Anther-lobes, a, Spur-like appendage from the connective, c, Membranous expansion at 
the apex of anther-lobes. 

Fig. 344. Corolla of Digitalis purpurea, cut in order to show the didynamous stamens (two 
long and two short) which are attached to it. t, Tube. /, Filaments which are united to the 
corolla at i, and run along its inner surface, having formed a marked adhesion, a g, Anthers 
of the long stamens, a q, Anthers of the short stamens. 




ESSENTIAL ORGANS. STAMENS. 199 

the Misletoe, the anther has numerous pores for the discharge of the 
pollen. Another mode of dehiscence is called hinged. In the Barberry, 
each lobe opens by a valve on the outer side of the suture, separately 
rolling up from base to apex ; while in some of the Laurel tribe (fig. 
325 t>), there are two such separating valves for each lobe, or four 
in all. This may be called a combination of transverse and hinged 
dehiscence. In some Guttiferge, as Hebradendron cambogioides (the 
Gamboge plant), the anther opens by a lid separating from the apex, 
or by what is called circumsctssile (circum, around, and scindo, to cut) 
dehiscence. In the last-mentioned dehiscence, the anther may be 
considered as formed of jointed leaves like those of the Orange, the 
blades of which separate at the joint. 

412. The anthers open at various periods of flowering; sometimes 
in the bud, but more commonly when the pistil is fully developed, and 
the flower is expanded. They either open simultaneously or in suc- 
cession. In the latter case, individual stamens may move towards the 
pistil and discharge their contents, as in Parnassia palustris, or the 
outer or the inner stamens may open first, following thus a centri- 
petal or centrifugal order. The anthers are called introrse (introrsum, 
inwardly), or anticce (anticus, the fore part), when 

they open on the surface next to the centre of the flower 
(fig. 345); they are extrorse (outwardly), or posticce 
(posticus, behind), when they open on the outer surface ; 
when they open on the sides, as in Iris, and some 
grasses, they are called laterally dehiscent (fig. 337). 
Sometimes anthers originally introrse, from their versa- 
tile nature, become extrorse, as in the Passion-flower 
and Oxalis. The attachment of the filament either on 
the outer or inner side, and the position of the anther 
in the young state, assist in determining the direction 
of the dehiscence when the anthers open by pores, or are versatile. 

413. The usual colour of anthers is yellow, but they present a great 
variety in this respect. They are red in the Peach, dark purple in the 
Poppy and Tulip, orange in Eschscholtzia, &c. The colour and appear- 
ance of the anthers often change after they have discharged their 
functions. 

414. Sometimes a flower consists of a single stamen, as already 
stated in regard to Euphorbia (^[ 401). It is said also, that in the 
Coniferge, as in the Fir, and in the Cycadacese, the stamens are to be 
regarded as single male flowers, supported on scales ; being either a 
single stamen with bilocular anthers, as in Pinus, or uniloctdar, as in 
Abies, or several stamens united in an androphore, as in Taxus. 

Fig. 345. Tetradynamous stamens (two long and two short) of Cheiranthus Cheiri. p, Top 
of the peduncle, c, Cicatrices left by the sepals of calyx which have been removed, e g, Two 
pairs of long stamens, e p, The short stamens, t, Torus or thalamus to which the stamens are 
attached. 





200 ESSENTIAL ORGANS. STAMENS. 

415. Stamens occasionally become sterile by the degeneration or 
non-development of the anthers, which, in consequence of containing 
pollen, are essential for fertilization ; such stamens receive the name of 

staminodia, or rudimentary stamens. In Scrophularia 
(fig. 346), the fifth stamen, s, appears in the form of a 
scale ; and in many Pentstemons it is reduced to a fila- 
ment with hairs, or a shrivelled membrane at the apex. 
In other cases, as in double flowers, the stamens are 
converted into petals. In Persea gratissima (fig. 325), 
two glands, g, are produced at the base of the filament 
in the form of stamens, the anthers of which are abor- 
tive. Sometimes only one of the anther-lobes becomes 
abortive. In many unilocular anthers, the non- 
development of one lobe is indicated by the lateral 
346 production of a cellular mass resembling the connec- 

tive. In Salvias, where the connective is distractile, one of the lobes 
only is perfect or fertile (fig. 333 lf\ containing pollen, the other (fig. 
333 / s) is imperfectly developed and sterile. In Canna, in place of 
one of the lobes, a petaloid appendage is produced. 

416. It has been already stated, that the term nectary has been 
sometimes applied to modified stamens presenting abnormal appear- 
ances. Thus, in Parnassia palustris, the so-called nectaries are clusters 

of abnormal stamens (fig. 304 ), united by a mem- 
brane at the base, and ending in glandular bodies 
like anthers. Staminodia were also called nectaries 
(fig. 346 s). When treating of the disk, other modi- 
fications of stamens will be considered. 

417. The stamens, in place of being free and sepa- 
rate, may become united by their filaments (^[ 399). 
They may also unite by their anthers, and become 
syngenesious or synantherous (avv, together, and ym<7/?, 
origin, or dvd^K, anther). This union occurs in 
Composite flowers, and in Lobelia, Jasione, Viola, &c. 
418. Stamens vary in length as regards the corolla. Some are 
enclosed within the tube of the flower, as in Cinchona, and are called 
included (figs. 287, 288, 344); others are exserted, or extend beyond 
the flower, as in Littorella, Plantago, and Exostemma. Sometimes 
the stamens in the early state of the flower project beyond the petals, 
and in the progress of growth become included, as in Geranium stria- 
turn (fig. 347). Stamens also vary in their relative lengths as respects 
each other. When there is more than one row or whorl of stamens 
in a flower, those on the outside are sometimes longest, as in Eosacea? 

Fig. 346. Irregular corolla of Scrophularia with a staminodium, s, or abortive stamen in the 
form of a scale. 

Fig. 347. Bud of polypetalous corolla of Geranium striatum, exhibiting the stamens, e e, at 
first longer than the petals, p p. 




ESSENTIAL ORGANS. POLLEN. 201 

(fig. 308); at other times those in the ulterior, as in Luhea (fig. 316, 
2 fa). When the stamens are in two rows, those opposite the petals 
are usually shorter than those which alternate with the petals. 

419. It sometimes happens that a single stamen is longer than all 
the rest. In some cases there exists a definite relation, as regards 
number, between the long and the short stamens. Thus, some flowers 
are didynamous (3<?, twice, and StW^/f, power or superiority), having 
only four out of five stamens developed, and the two corresponding to 
the upper part of the flower longer than the two lateral ones. This 
occurs in Labiate and Scrophulariacese (figs. 344, 346.) Again, in 
other cases there are six stamens, whereof four long ones are arranged 
in pairs opposite to each other, and alternate with two isolated short 
ones (fig. 345), and give rise to tetradynamous (rsr^tisj four, and BtW^/f, 
power or superiority) flowers, as in Crucifera3. 

420. Stamens, as regards their direction, may be erect, turned in- 
wards, outwards, or to one side. In the last-mentioned case they are 
called declinate (declino, I bend to one side), as in Amaryllis, Horse- 
chestnut, and Fraxinella. 

421. The Pollen. The Pollen or powdery matter contained in 
the'anther, consists of small cells 

developed in the interior of 
other cells. The cavities formed 
in the anther (fig. 321), are sur- 
rounded by a fibro-cellular en- 
velope, c PI and within this are 
produced larger cells, u p, con- 
taining a granular mass (fig. 348, 
1), which divides into four min- 
ute cells (fig. 348, 2), around 
which a membrane is developed, 
so that the original cell, or the 
parent pollen-utricle, becomes re- 
solved by a merismatic division 
(f 24) into four parts (fig. 348, 
3), each of which forms a granule 
of pollen. The four cells continue 
to increase (fig. 348, 4), distend- 
ing the parent cell, and ulti- 
mately causingits absorption and 348 
disappearance. They then assume the form of perfect pollen-grains, 

Fig. 348. Development of the pollen of Viscum album, or the Misletoe. 1. Two pollen-cells 
or pollinary utricles filled with granular matter. 2. Four nuclei produced in this matter. 3. 
Separation into four masses, each corresponding to a nucleus or a new utricle. 4. Pollenic or 
pollinary utricle containing three separate vesicles in its interior. 5. Two of the latter, or the 
young pollen-grains, removed from the mother-cell or utricle. 6. The grains of pollen in their 
perfect state. 




202 



ESSENTIAL ORGANS. POLLEN. 



and either remain united in fours or multiples of four, as in some 
Acacias, Periploca greeca (fig. 349), and Inga anomala (fig. 354), or 
separate into individual grains (fig. 348, 5), which by degrees be- 
come mature pollen, (figs. 348, 6, 351, 352). In Acacia ringens, there 





are eight pollen-grains united; in Acacia decipiens, twelve; and in 
Acacia linearis, sixteen. Occasionally the membrane of the parent 
pollen-cell is not completely absorbed, and traces of it are detected in 
a viscous matter surrounding the pollen-grains, as in Onagrariacea?. 
In Orchidaceous plants, the pollen-grains are united into masses or 
pollinia, by means of viscid matter. In Asclepiadacese (fig. 353), the 
pollinia, p, seems to have a special cellular covering, 
derived from a layer of reproductive pollen- cells, 
or from the endothecium. Pollinia in different 
plants vary from two to eight. Thus, there are 
usually two in Orchis, four in Cattleya, and eight in 
Lselia. The two pollinia in Orchis Morio, accord- 
ing to Amici, contain each about 200 secondary 
smaller masses. These small masses, when bruised, 
divide into grains which are united in fours. In 
Orchids, each of the pollen-masses has a prolonga- 
tion or stalk, called a caudicle (cauda, a tail,) which 
often adheres to a prolongation at the base of the 
anther, called rostellum (rostellum, a beak), by 
means of a viscid tenacious matter secreted by cells, and denominated 
retinacula, (retinaculum, a band or rein). Lindley considers the cau- 
dicle as derived from the stigma, and not from the pollinary tissue. 
The term clinandrum (*x/, a bed, and yyp, a stamen), is sometimes 
applied to the part of the column in Orchids, where the stamens are 
situated. 

422. When mature, the pollen-grain is a cellular body having an ex- 
ternal covering, extine (exto, to stand out, or on the outside), and an in- 

Fig. 349. Pollen of Periploca graeca, showing four grains agglutinated together. 
Fig. 350. Pollen of Inga anomala. The grains united in multiples of four. 
Fig. 351. Pollen-grain showing the extine covered with small punctuations. 
Fig. 352. Pollen-grain with the extine covered with granulations. 

Fig. 353. Flower of Asclepias, showing the pollinia or pollen-masses, p, attached to the 
stigma. 




ESSENTIAL ORGANS. POLLEN. 203 

ternal, inline (intus, within). Fritzsche states that he has detected, in 
some cases, other two coverings, which he calls intextine and exintine. 
They occur between the extine and intine, and are probably formed by 
foldings of these membranes. In some aquatics, as Zostera marina, 
Zannichellia pedunculata, Naias minor, &c., only one covering exists, 
and that is said to be the intine. The extine is a firm membrane, which 
defines the figure of the pollen-grain, and gives colour to it. It is either 
smooth or covered with numerous projections, granules, points, minute 
hairs, or crested reticulations (fig. 356). The colour is generally 





yellow, and the surface is often covered with a viscid or oily matter. 
The intine is uniform in different kinds of pollen, thin and transparent, 
and possesses great power of extension. It is said to be the first 
envelope formed, the other being subsequently deposited while en- 
closed in the parent cell. 

423. Within these coverings a granular semifluid matter, called 
fovilla, is contained, along with some oily particles, and occasionally 
starch. The fovilla contains small sphe- 
rical granules, sometimes the ^^^0 ^ 

an inch in diameter (fig. 357), andlarger 
ellipsoidal or elongated corpuscles (fig. 
358), which are said to exhibit move- 
ments under the microscope similar to 
those seen in some Infusoria, and in 
some Algas, to be afterwards noticed. 
These movements generally cease long 
before maturation, except in Zostera marina and some other plants. 

424. Pollen-grains vary from 5 J 5 to 7 i g of an inch or less in dia- 

Fig. 354. Pollen-grain of Passiflora before bursting, o o o, Opercula or lids formed by the 
extine, which open to allow the protrusion of the intine in the form of pollen-tubes. 

Fig. 355. Pollen-grain of Cucurbita Pepo, or Gourd, at the moment of its dehiscence or rup- 
ture, o o, Opercula or lids separated from the extine by the protrusion of the pollen-tubes, 1 1. 

Fig. 356. Pollen-grain of Ipomoea, with a reticulated extine. 

Fig. 357. Pollen-grain of Amygdalus nana, the intine or internal membrane of which is pro- 
truding at three pores under the form of as many ampullae or sacs, tt t. One of these is open at 
the extremity, and from it is discharged the foviUa, /, composed of variously-sized granules. 

Fig. 358. Large granules of fovilla of Hibiscus palustris. 




204 



FORMS OF POLLEN-GRAINS. 



meter. Their form is much diversified. The most common form is 
ellipsoidal (figs. 358, 359), more or less narrow at the extremities, 
which are called its poles, in contradistinction to a line at e, equidistant 
from either extremity, and which is its equator. In figs. 359, 360, 
1 and 2, the two surfaces of the pollen-grains of Alh'um fistulo- 
surn and Convolvulus tricolor are represented with their poles, p, 
their equator, e, and the longitudinal folds in their membrane; 





360 






362 363 

while at 3, are shown transverse sections at the equators, with a 
single fold in one case, and three folds in the other. Pollen-grains 
are also of a spherical, triangular, trigonal (fig. 362), or polyhedral 
figure (fig. 364). In the latter case, when there are markings on their 
surface, those at the poles, p, sometimes differ from those at the equa- 
tor, e. In Tradescantia virginica, the pollen is cylindrical, and becomes 
curved ; it is polyhedral in Dipsacea? and Compositae ; nearly trian- 
gular in Proteacese and Onagrariaceae. The surface of the pollen- 
grain is either uniform and homogeneous, or it is marked by folds 
dipping in towards the centre, and formed by thinnings of the mem- 
brane. In Endogenous plants there is usually a single fold (fig. 359); 



Fig. 359. Pollen of Allium fistulosum. p, Pole, e, Equator. 1. Pollen-grain seen on the face. 
2. On the opposite side or back. 3. Transverse section through its equatorial line. 

Fig. 360. Pollen of Convolvulus tricolor. The letters and numbers have the same signification 
as in fig. 359. 

Fig. 361. Grain of pollen of Cannabls sativa, or common Hemp. , Eqiiator. p p, Poles. 

Fig. 362. Pollen-grain of O3nothera biennis entire, with three angles, where tubes are pro- 
duced. 

Fig. 363. The same, with one of its angles giving origin to a pollen-tube, which is formed by 
the intine. When the tube protrudes, the extine is ruptured. 

fig. 364. Polyhedral pollen-grain of Cichorium Intybus, or Chiceory. 




FORMS OF POLLEN-GRAINS. 205 

in Exogens, ofteii three (fig. 360). Two, four, six, and even twelve 
folds are also met with. 

425. There are also pores or rounded portions of the membrane 
visible in the pollen -grain. These vary in number from one to fifty. 
In Endogeus, as in Grasses, there is often only 

one (fig. 365); while in Exogens, they number 

from three upwards. When numerous, the 

pores are either scattered irregularly (fig. 366), 

or in a regular order, frequently forming a 

circle round the equatorial surface (fig. 361). 

Sometimes at the place where the pores exist, 

the outer membrane, in place of being thin and 

transparent, is separated in the form of a lid, 

thus becoming operculate (operculum, a lid), as 

in the Passion-flower (fig. 354) and Gourd (fig. 

355). Grains of pollen have sometimes both 

folds and pores. There may be a single pore 

in each fold, either in the middle (fig. 367), or 

at the extremities; or folds with pores may 

alternate with others without pores; or finally, the pores and folds 

may be separate. 

426. The form of the pollen-grains is much altered by the applica- 
tion of moisture. Thus, in fig. 367, 1, the pollen-grain of Lythrum 
Salicaria, when dry, has an ellipsoidal form, but when swollen by the 
application of water, it assumes a globular form (fig. 367, 2). This 
change of form is due to endosmose, and depends on the fovilla being 
denser than the water. If the grains are retained in water, the disten- 
sion becomes so great as to rupture the extine irregularly if it is 
homogenous, or to cause projections and final rupture at the folds or 
pores when they exist. The intine, from its distensibility, is not so 
liable to rupture, and it is often forced through the ruptured extine, 
or through the pores, in the form of small sac-like projections (figs. 
367, 2, 362). This effect is produced more fully by adding a little nitric 
acid to the water. The internal membrane ultimately gives way, and 
allows the granular fovilla to escape (fig. 357 /). If the fluid is ap- 
plied only to one side of the pollen-grain, as when the pollen is applied 
to the pistil, the distension goes on more slowly, and the intine is pro- 
longed outwards like a hernia, and forms an elongated tube called a 
pollen-tube (fig. 363). This tube, at its base, is often covered by the 



Fig. 36-3. Pollen -grain of Dactylis glomerata, or Cocks-foot grass. 

Fig. 366. Pollen-grain of Fumaria capreolata. 

Fig. 367. Grain of pollen of Lythrum Salicaria, showing six folds, three of which are per- 
forated by a pore in their middle, "and three alternating with them have no pores, p p, Poles. 
e e, Equator. 1. The grain in a dry state. 2. The grain swollen in water, so as to take a globular 
form and display its folds. The intine or internal membrane begins to protrude through the 
pores. 



206 



FORMS OP POLLEN- GRAINS. 



ruptured extine, and probably also by some of the coverings mentioned 
by Fritzsche as intervening between it and the intine. It contains in its 
interior fovilla-granules, and its functions will be particularly noticed 
under fertilization. The number of pollen-tubes which may be pro-: 
duced depends on the number of pores. In some pollinia, the number 
of tubes which are found is enormous. Thus, Amici calculates that 
the two pollen-masses of Orchis Morio may give out 120,000 tubes. 

427. in Cryptogamic Plants there are certain organs which are sup- 
posed by some to be equivalent to stamens. On that account they 
were denominated by Hedwig antheridia, by others pollinaria. They 
consist of closed sacs of different forms, rounded, ovate, oblong, clavate, 
flask-like, &c., developed in different parts of the plants, containing a 
number of corpuscles immersed in a mucilaginous fluid, which at a 
certain period of growth are discharged through an opening at the sur- 
face. Sometimes the antheridium is a simple cell, at other times it is 
composed of a number of cells, as in Hypnum triquetrum (fig. 368, 1). 





It either appears on the surface of the plant, or is concealed within its 
tissue. Antheridia are sometimes confined to particular parts of the 
plant, at other times they are more generally diffused. Their contents 
are small utricles or cellules, varying, like pollen -grains, La the different 

Fig. 368. 1. Antheridium or pollinarium, a, of a moss called Hypnum triquetrum, at the 
moment when its apex is rupturing to discharge the contents, /. 2. Four utricles of the contents, 
containing each a phytozoon or moving corpuscle rolled up in a circular manner. 3. Single 
phytozoon separated. 

Fig. 369. 1. Portion of antheridium or globule of Chara vulgaris. Several septate or par- 
titioned tubes, t, attached to a utricle or vesicle. A mass of similar utricles, forming the bases 
of a large number of tubes, fills the cavity of the antheridium. 2. Extremity of one of these 
tubes, composed of several cellules, in each of which is a phytozoon. One of the phytozoa is 
represented half detached from the cellule. 3. Extremity of a tube from which the phytozoa 
have escaped, with the exception of the terminal cellule. 4. One of the phytozoa separated. 



ESSENTIAL ORGANS. THE PISTIL. 



207 



orders of cryptogamic plants, and enclosing in place of fovilla, peculiar 
bodies called phytozoa (QVTOV, a plant, and ao, an animal) (fig. 368, 2), 
which are often rolled up in a circular or spiral manner, as in Hepa- 
tica3 and Mosses (fig. 368, 3). These exhibit active movements at 
certain periods of their existence, and resemble in this respect animal- 
cules. In Chara vulgaris (fig. 369), the antheridium or globule, as it is 
called, contains cells, 1, from which proceed numerous septate (septum, 
a division) tubes, t. In each of the divisions of these tubes, 2, there 
is a phytozoon which escapes in a spiral form, leaving the division 
empty, 3, and ultimately becomes unrolled, 4, exhibiting two vibra- 
tile cilia (ciltum, an eyelash), to which the movements are referred. 

428. The Dish. The term disk is applied to whatever intervenes 
between the stamens and the pistil, and is one of these organs to 
which the name of nectary was applied by old authors. It presents 
great varieties of form, such as scales, glands, hairs, petaloid appen- 
dages, fec., and in the progress of growth it often contains saccharine 
matter, thus becoming truly nectariferous. The degeneration and trans- 
formation of the stamens frequently form the disk. It may consist of 
processes rising from the torus, alternating with the stamens, and thus 
representing an abortive whorl; or it may be opposite to the stamens, 
and then formed by chorization (^[ 383), as 

in Crassula rubens (fig. 258 a). In some 
flowers, as Jatropha Curcas, in which the sta- 
mens are not developed, their place is occu- 
pied by glandular bodies forming the disk 
(fig. 314, 2, a). In Gesneraceae and Cruci- 
ferse the disk consists of tooth-like scales at 
the base of the stamens (fig. 345, t). The 
parts forming the disk sometimes unite and 
form a glandular ring, as in the Orange ; 
or a dark-red lamina covering the pistil, as 
in Paeonia Moutan (fig. 370 rf); or a waxy 
lining of the calyx tube, as in the Rose 
(fig. 270 c i); or a swelling at the top of the 
ovary, as in Umbelliferas. 

429. The Pistil. The pistil occupies the centre or axis of the 
flower, and is surrounded by the stamens and floral envelopes, when 
these are present. It constitutes the innermost whorl, and is the 
female organ of the plant, which after flowering is changed into the 
fruit, and contains the seeds. It sometimes receives the name of 
gyncecium (yvvy, pistil, and cmlov, habitation). It consists essentially 
of two parts, the ovary or germen, containing ovules or young seeds, 
and the stigma, a cellular secreting body, which is either seated im- 

Fig. 370. Disk, d, of Paeonia Moutan, or Tree Paeony, covering the ovary, and interposed be- 
tween the whorl of stamens, s, and the pistil, />. 




208 



ESSENTIAL ORGANS. THE PISTIL. 



mediately on the ovary, and is then called sessile, as in the Tulip and 
Poppy, (fig. 409), or is elevated on a stalk called the style, interposed 
between the ovary and stigma. The style is not neccessary for the per- 
fection of the pistil. Sometimes it becomes blended with other parts, 
as with the filaments of the anthers in the column of Orchidacese. 

430. Like the other organs, the pistil consists of one or more modi- 
fied leaves, which in this instance are called carpels ^x^6;, fruit). 
The analogy of carpels to leaves may be deduced from their similarity 
in texture, and in venation, from the presence of stomata, hairs, and 
glands; from their resemblance to leaves in their nascent state ; from 
then- occasional conversion into true leaves, as in Lathyrus latifolius ; 
and from the ovules corresponding in situation to the germs or buds 
found in some leaves, as those of Bryophyllum calycinum. When a 
pistil consists of a single carpel it is simple, a state usually depending 
on the non-development of other carpels; when it is composed of 
several carpels, more or less united, it is compound. In the first- 
mentioned case, the terms carpel and pistil are synonymous. Each 
carpel has its own ovary, style (when present), and stigma, and is 
formed by a folded leaf, the upper surface of which is turned inwards 
towards the axis, and the lower outwards; while at its margins are 
developed one or more buds called ovules. That this is the true nature 
of the pistil may be seen by examining the flower of the double- 
flowering Cherry. In it no fruit 
is produced, and the pistil con- 
sists usually of sessile leaves (fig. 
371), the limb of each being 
green and folded, with a narrow 
prolongation upwards, s, as if 
from the midrib, n, and ending 
in a thickened portion. When 
the single-flowering Cherry is 
examined, it is found that, in 
place of folded leaves, there is 
//* a single body (figs. 372, 373), 
the lower part of which is 
enlarged, forming the ovary, o, 
and containing a single ovule, 
<7, attached to its walls, with a bundle of vessels, fn, entering it, a 




Fig. 371. Carpellary leaf of the double-flowering Cherry. In this plant the pistil is composed 
distinctly of one or more leaves folded inwards. I, Lamina or blade of the leaf or carpel, s, 
Prolongation of the midrib, n, representing the style, and ending in a circular thickened portion 
equivalent to the stigma. 

Fig. 37:!. Pistil or carpel of the single-flowering Cherry in its normal state, o, Ovary. 
t, Style, s, Stigma, 

Fig. 373. The same cut vertically, to show the central cavity of the ovary, o, with the ovule, 
g, suspended from its wall at a point where a bundle of nourishing vessels, / n, terminates. 
t, Style traversed by a canal, c, which runs from the stigma, s, to the cavity of the ovary. 



ESSENTIAL ORGAXS. THE PISTIL. 



209 



cylindrical prolongation, 2, forming the style, and a terminal expansion, 
s, the stigma. It will be seen that in this case two carpellary leaves 
have become succulent and have united together, so as to form a com- 
pound pistil, with a single cavity containing one young seed. 

431. The ovary then represents the limb or lamina of the leaf, and 
is composed of cellular tissue with fibro-vascular bundles, and an 
epidermal covering. The cellular tissue, or parenchyma, often be- 
comes much developed, as will be seen particularly when fleshy fruits 
are considered. The outer epidermis corresponds to the lower side of 
the leaf, exhibiting stomata, and sometimes hairs ; the inner surface 
represents the upper side of the leaf, being usually very delicate and 
pale, and forming a layer called sometimes epithelium (ivl, upon, and 
dfav;, tender), which does not exhibit stomata. The vascular bundles 
correspond with the veins of the leaf, and consist of spiral, annular, 
and other vessels. 

432. The Style has usually a cylindrical form, consists of cellular 
and vascular tissue, and when carefully examined is found to be 
traversed by a narrow canal (fig. 373 c), in which there are some 
loose projecting cells (figs. 374, 375), forming what is called the con- 





ducting tissue. A transverse section of the style of Crown Imperial 
(fig. 374), shows three vascular bundles, v v v, corresponding to three 
styles which are united into one, and, p, loose cells in the canal of the 
style. This canal is bounded by cellular tissue (fig. 375 c c) traversed by 
spiral vessels, v v, and in its ulterior, besides the loose cells, pp, there are, 

Fig. 374. Transverse section of the style of Fritillaria imperially or Crown Imperial The 
style is composed of three united together, vvv, Three vascular bundles, each corresponding 
to one of the three styles, p, Papillae or cellular bodies projecting into the cavity of the canal 

Fig. 375. Structure of the canal in the centre of the style of a Campanula, c c, Cellular tis- 
sue forming its parietes traversed by tracheae, v. p p, Variously formed cells, displaced as it 
were, and along with other elongated and filamentous ones, //, obstructing the canal 



210 



ESSENTIAL ORGANS. THE PISTIL. 



especially at the period of fecundation, elongated tubes, ff, which in 
part fill up the canal The name, conducting tissue, is given to that 
found in the canal of the style, on account of the part which it plays 
in conveying the influence of the pollen to the ovules, as will be ex- 
plained under fertilization. 

433. The Stigma is a continuation of the cellular tissue in the centre 
of the style, and it may be either terminal, when the canal opens at 
the top only (figs. 373 s, 376, 1), or lateral, when the splitting of the 
canal takes place on one side (fig. 377 s), or on both sides (fig. 378 s s). 
The stigma sometimes extends along the whole length of the style. 
In Orchidaceous plants, it is placed on a part of the column called the 
gynizus (yt>), pistil, and Zga, I sit). It is composed of cellular tissue 
more or less lax, and often having projecting cellules in the form of 




papilla? (fig. 376, 2), or of hairs (figs. 379, 3, 410 s), and at the 
period of fertilization exuding a viscous fluid, which retains the grams 
of pollen, and causes the protrusion of tubes. 

434. A pistil is xisually formed by more than one carpel. The 
carpels may be arranged like leaves, either at the same or nearly the 
same height in a verticil (figs. 380, 381), or at different heights in a 
spiral cycle (fig. 306 c). When they remain separate and distinct, thus 
showing at once the composition of the pistil, as in Caltha, Kanun- 
culus, Hellebore, and Butomus (fig. 381), the term apocarpus (a., 
separate, and Ketovos, fruit) is applied. Thus, hi Crassula rubens 
(fig. 258), the pistil consists of five verticillate carpels, o, alternating 
with the stamens, e ; and the same arrangement is seen hi Zanthoxylon 

Fig. 376. L Stigma, *, of Daphne Laureola, terminating the style, t, o, Summit of the 
ovary. ?. A small portion of the surface of the stigma, much magnified to show its papillae. 

Fig. 377. Unilateral stigma, s, of Asimina triloba. t, Style. 

Fig. 378 Bilateral stigma, s s, of Plantago saxatilis. o, Ovary. , Style. 

Fig. 379. 1. Summit of the style, t, of Hibiscus palustris, dividing into five branches, which 
are each terminated by a stigma, s. 2. One of these branches highly magnified. 3. Portion 
of the surface of the stigma still more magnified to show its papillae, which are elongated like 
hairs. 



ESSENTIAL ORGANS. THE PISTIL. 



211 



fraxineum (fig. 380). In the Tulip-tree (fig. 306), the separate car- 
pels, c c, are numerous, and arranged in a spiral cycle, upon an elon- 
gated axis or receptacle. In the Raspberry, the carpels are on a 
conical receptacle ; in the Strawberry, on a swollen succulent one ; and 
in the Rose (fig. 270 o o), on a concave one, r r, covered by the tube 
of the calyx, c t. 




435. When the fruit consists of several rows of carpels on a flat 
receptacle, the innermost have their margins directed to the centre, 
while those of the outer rows are arranged on the back of the inner 
ones ; if the receptacle is convex, the outer carpels are lowest, as in the 
Strawberry ; if concave, the outer ones are uppermost, as in the Rose. 
At other tunes the carpels are united, as in the Pear, Arbutus, and 
Chickweed, so that the pistil becomes syncarpous (avv, together or 
united). In Dictamnus Fraxinella (fig. 382), five carpels unite to form 
a compound pistil. In Scilla italica (fig. 259), the three carpels form 
only one apparently ; but on examination it will be found that the 
pistil consists of three carpels alternating with the three inner stamens. 
The union, however, is not always complete ; it may take place by the 
ovaries alone, while the styles and stigmata remain free, the pistil being 
then gamogastrous (ya.pos, union, and "/etar^, ovary) ; and in this case, 
when the ovaries form apparently a single body, this organ receives the 

Fig. 380. Pistil of Zanthoxylon fraxineum, consisting of five distinct carpels, supported on a 
gynophore, g. Each of the ovaries, o, bears a terminal style dilated at its extremity into a 
stigma, s. The five stigmata remain for a long time adherent by their sides. 

Fig. 381. 1. Carpels of Butomus umbellatus, consisting of folded leaves arranged in different 
verticils. 2. Section of the same, showing the alternation of the parts of the flower. Three 
outer leaves of the perianth, o', alternating with three inner ones, p i, three rows of stamens, e o 
and e i, and the carpels, c e anil c i. 

Fig. 382. Portion of the pistil of Dictamnus Fraxinella. Two of the five carpels have been 
removed in order to show how the styles, s, produced on the inner side of the carpels, and at 
first distinct, approximate and become united into one. o, Ovaries, two of which in front show 
their dorsal surface, d, and their lateral surface, I. At the base of the gynophore, g, are seen 
the cicatrices, c, marking the insertion of the calyx, the petals, and the stamens. 



212 ESSENTIAL ORGANS. THE PISTIL. 

name of compound ovary ; or the union may take place by the ovaries 
and styles, while the stigmata are disunited ; or by the stigmata and the 
summit of the style only (fig. 380). Various intermediate states exist, 
such as partial union of the ovaries, as in the Eue, where they coalesce 
at their base ; and partial union of the styles, as in Malvaceae (fig. 383). 
The union is usually most complete at the base ; but in Labiatae the 
styles are united throughout their length, and in Apocynacea3 and 
Asclepiadaceae, the stigmata only. 

436. When the union is incomplete, the number of the parts of 
a compound pistil may be determined by the number of styles and 
stigmata (fig. 383 s) ; when complete, the external venation, the 

grooves on the surface, and the 
internal divisions of the ovary, indi- 
cate the number. When the grooves 
between the carpels are deep, the 
ovary is denominated lobed, being 
one, two, three, four, or five-lobed, 
according to circumstances. In fig. 
383, the nine carpels forming the 
ovary, o, are divided by grooves; 
and in fig. 384, a transverse section 
c of the ovary of Fuchsia coccinea, 
shows the four carpels which form 
it. The changes which take place 

in the pistil by adhesion, degeneration, and abortion, are frequently so 
great as to obscure its composition, and to lead to anomalies in the 
alternation of parts. The pistil is more liable to changes of this kind 
than any other part of the flower. 

437. The carpels are usually sessile leaves, but sometimes they are 
petiolate, and then are elevated above the external whorls. This 
elevation of the pistil may in general, however, be traced to an elon- 
gation of the axis itself, in such a way that the carpels, in place of 
being dispersed over it, arise only from its summit. A monstrosity 
often occurs in the Rose (fig. 385), by which the axis is prolonged, 
and bears the carpels,^ in the form of alternate leaves. Thus, by 
the union of the petioles of the carpels, or by lengthening of the axis, 
the pistil becomes stipitate (stipes, a trunk), or supported, as in the 
Passion-flower, on a stalk (figs. 380, 382 g), called a gynophore (yvvvi, 
pistil, and <pog!a, I bear), or thecaphore (6yx.ii, a case). Sometimes the 



Fig. 383. --Pistil of Malva Alcea. o, Nine ovaries, united so as to form one. t, Column formed 
by nine styles united to near their summit, where they diverge and separate . Each of the divi- 
sions of the style is terminated by a stigma, *. 

Fig. 384. Horizontal section of the four-celled (quadrilocular or tetrathecal) ovary of Fuchsia 
coccinea. c c c c, Wall of the ovary, which is formed by four carpellary leaves, a, Quadran- 
gular axis to which the carpels are united, o, Ovules attached to the inner margin of the 
carpels. 




ESSENTIAL ORGANS. THE PISTIL. 



213 



axis is produced beyond the ovaries, and the styles become united to 
it, as in Geraniaceae and Umbellifera. In this case the prolongation 
is called a carpophore (*g7ro$, fruit, and Qogsu, I 
bear). 

438. The ovules are developed on the inner side 
of the carpel where the two edges of the carpellary 
leaves unite, and they are connected to it by vas- 
cular bundles which proceed from below upwards, 
traverse the carpel, and send a branch to each of 
the ovules. At the same place there is a develop- 
ment of cellular tissue in connection with the con- 
ducting tissue of the style and with the stigma. By 
the union of these tissues is formed the placenta, 
or projection to which the ovules are attached. 
Some restrict the term placenta to the point of 
attachment of a single ovule, and call the union of 
placentas, bearing several ovules, placentaries or 
pistillary cords. The part of the carpel where the 
placenta is formed, is the inner or ventral suture, cor- 
responding to the margin of the folded carpellary 385 
leaf, while the outer or dorsal suture corresponds to the midrib of the 
carpellary leaf The placenta is hence sometimes called marginal. 
The placenta is formed on each margin of the carpel, and hence is 
essentially double. This is seen in cases where the margins of the 
carpel do not unite, but remain separate, and consequently two pla- 
centas are formed in place of one. In fig. 386, the two carpels are 
folded, so that their margins meet, and the placenta is apparently 
single; whereas in fig. 387 the margins of each carpel do not meet, 







and the placenta of each is double. Again, in fig. 388, the two carpels, 
after meeting in the centre or axis, a, are reflected outwards towards 
the dorsal suture, s d, and their margins separate slightly, each being 
placentary and bearing ovules, o. 

439. When the pistil is formed by one carpel, the inner margins 
unite in the axis, and form usually a common marginal placenta. 

Fig. 385. Section of monstrous Rose, as figured at section 324, the axis of which is prolonged 
beyond the flower, and the envelopes removed to show the abortivei stamens, r. The carpels 
are attached alternately along the axis in the form of leaves, p, Abortive floral envelopes, 
c, Stamens in imperfect flower at the apex. 

Figs. 386, 387, 388. Horizontal sections of ovaries, composed of two carpellary leaves, the edges 
of which are folded so as to meet in the axis, a, in fig. 387 ; are reflected inwards into the locu- 
laments after meeting in the axis in fig. 388 ; and do not reach the axis in fig. 387. 



214 FORMATION OP THE PLACENTA. 

This placenta may extend along the whole margin of the ovary as far 
as the base of the style, or it may be confined to the base or apex 
only. When the pistil is composed of several separate carpels, or, in 
other words, is apocarpous, there are generally separate placentas at 
each of their margins. In a syncarpous pistil, on the other hand, the 
carpels are so united that the edges of each of the contiguous ones by 
their union form a septum (septum, a fence or enclosure), or dissepiment, 
(ctissepio, I separate), and the number of these septa consequently in- 
dicates the number of carpels in the compound pistil. It is obvious 
then that each dissepiment is formed by a double wall or two laminae; 
that the presence of a septum implies the presence of more than one 
carpel; and that, when carpels are placed side by side, true dissepi- 
ments must be vertical, and not horizontal. 

440. When the dissepiments extend to the centre or axis, the 
ovary is divided into cavities, cells or loculaments (loculus, a box), and 
it may be bilocular, trilocular, quadrilocular, quinquelocular, or multi- 
locular, according as it is formed by two, three, four, five, or many 
carpels, each corresponding to a single cell or loculament (fig. 381, 2, 
c e, c i). In these cases the marginal placentas meet in the axis, and 
unite so as to form a single central one (fig. 386 a). Some call this 
placentation axile (belonging to the axis), but this term is perhaps pro- 
perly restricted to cases where the placenta is an actual prolongation 
of the axis. The number of loculaments is equal to that of the dis- 
sepiments. In fig. 384, there is shown a transverse section of the ovary 
of Fuchsia coccinea, c c c c being its parietes formed by the union of 
four carpellary leaves, a the axis united to the parietes by dissepiments, 
and o the ovules attached to the placentas at the margin of each carpel. 
When the carpels in a syncarpous pistil do not fold inwards completely 
so as to meet in the centre, but only partially, so that 
the dissepiments appear as projections on the walls 
of the ovary, then the ovary is unilocular (fig. 387), 
and the placentas are parietal (paries, a wall). A 
horizontal section of the ovary of ErythraeaCentaurium 
'7> (fig- 389), exhibits a unilocular ovary with parietal 
placentas, p, formed at each of the margins of the 
carpels which do not meet in the centre. In these 
instances the placentas may be formed at the margin 
of the united contiguous leaves, so as to appear single, 
or the margins may not be united, each developing a placenta. From 
this it will be seen that dissepiments are opposite to placentas, formed 
by the union of the margins of two contiguous carpels, but alternate 
with those formed by the margins of the same carpel. 

Fig. 389. Horizontal section of the ovary of Erythraa Centaurinm. c, Wall or paries of the 
ovary or carpellary leaf, p, The edge on which the placenta is formed, bearing the ovules, o. 
I, Cell or loculament. 




FORMATION OP THE PLACENTA. 



215 



441. The carpellary leaves may fold inwards very slightly, or they 
may be applied in a valvate manner, merely touching at their margins, 
the placentas then being parietal, and appearing as lines or thicken- 
ings along the walls. In fig. 390, the pistil of Viola tricolor is repre- 
sented, 1, cut vertically, and, 2, cut transversely, the ovules being 
attached to the walls of the ovary, and the placentas, p, being merely 
thickened portions of the walls. Cases occur, however, in which the 
placentas are not connected with the walls of the ovary, and form what 
is called a free central placenta. This is seen in many of the Caryo- 




392 



phyllacese. Thus, in Cerastium hirsutum (figs. 391, 392), the ovary, 
o, is composed of five carpels, indicated by the styles, s, but there is 
only one loculament, the placenta, p, being free in the centre, and the 
ovules, <?, attached to it. 

442. In Caryophyllacese, however, while the placenta is free in the 
centre, there are often traces found at the base of the ovary of the 
remains of septa, as if rupture had taken place; and, in rare instances, 
ovules are found on the margins. But examples occur of this kind 
of placentation, as in Primulaceae, Myrsinaceae, Santalaceas, and Theo- 
phrasteas, in which no vestiges of septa or marginal ovules can be 
perceived at any period of growth. Duchartre states that the free 
placenta of Primulacese, is totally different from that of Caryophyl- 
laceas. It is always free, and rises in the centre of the ovary, and the 
part uncovered by ovules gradually extends into the style. It is not 
first continuous with the style, and then free; neither is it originally 
marginal, and then free; but it is, according to him, wholly through- 
Pig. 390. Pistil of Viola tricolor, or Pansy, cut vertically to show the ovules, o, attached to the 
parietes. Two rows of ovules are seen, one in front, and the other in profile, p, A thickened 
line on the walls forming the placenta, c, Calyx, d, Ovary. 1. Hooded stigma terminating the 
short style. 2. Horizontal section of the same, p, Placenta, o, Ovules, s, Suture. 

Fig. 391. Pistil of Cerastium hirsutum cut vertically, o, Unilocular or monothecal ovary, p, 
Free central placenta, g, Ovules, s, Styles. 

Fig. 392. The same cut horizontally, and the halves separated so as to show the interior of the 
cavity of the ovary, o, with the free central placenta, p, covered with ovules, g. 



216 



FORMATION OF THE PLACENTA. 



out its organogeny (6'pyctvov, organ, and yivioig, production or develop- 
ment) separate and axile. 

443. This placentation, therefore, has been accounted for in two 
ways, either by supposing that the placentas in the early state were 
formed on the margins of carpellary leaves, and that in the progress of 
development these leaves separated from them, leaving the placentas 
and ovules free in the centre; or by supposing that the placentas are 
not marginal but axile formations, produced by an elongation of the 
axis, the ovules being lateral buds, and the carpels verticillate leaves, 
united together around the axis. The latter view has been sup- 
ported by many botanists, and is confirmed by the fact, that in some 
cases the placenta is actually prolonged beyond the carpels. The 
first of these views would apply well to Caryophyllaceae, the second 
to Primulaceae. In the latter case, the only way of explaining the 
appearance on the marginal hypothesis, will be by considering the 
placentas as formed from the carpels by a process of chorization (^[ 383), 
and united together in the centre. 

444. Some indeed, as Schleiden and Endlicher, consider the axile 
view of placentation as applicable to all cases, the axis in some cases 
remaining free and independent, at other tunes sending prolongations 
along the margins of the carpellary leaves, and thus forming the mar- 
ginal placentas. The occurrence of placentas 
over the whole inner surface of the carpels 
or of the dissepiments, as in Nymphsa and 
in Butomus umbellatus (figs. 393, 394); 
also, though very rarely, along the dorsal 
suture, as in Cabomba, or on lines within 
the margin, as in Orobanche, has been 
supposed to confirm this view. Schleiden 
argues in favour of it, from the case of Ar- 
meria, where there axe five carpels and 
a single ovule attached to a cord, which 
arises from the axis, and becomes curved at 
the apex so as to suspend the ovule ; also, 

from cases, such as Taxus, where the ovule appears to be naked and 
terminates a branch. 

445. This theory of placentation, however, cannot be easily applied 
to all cases; and Gray says that it is disproved in cases of monstrosity, 
in which the anther is changed into a carpel, or where one part of 
the anther is thus transformed and bears ovules, while the other, 
as well as the filament, remain unchanged. In the case of Luffa 
foetida, the entangled fibres of the carpeUary leaves, even in the young 




Figs. 393, 394. One of the carpels of Butomus umbellatus, or flowering Rush, cut trans- 
versely in 393, and longitudinally in 394-. I, Loculament or cavity of the carpel, o, Ovules. 
s, Stigmata. 



DIVISIONS IN OVAKIES. 217 

state, seem to be connected with perpendicular lines forming the pla- 
centa. Brongniart mentions a case where the marginal placenta was 
entire, while the axis was prolonged separately, and totally uncon- 
nected with the placenta; he also notices peculiar monstrosities, which 
seem to prove that, in some cases at least, marginal placentation must 
take place. 

446. Upon the whole, then, it appears that marginal, or, as it is 
often called, carpellary placentation generally prevails; that axile 
placentation explains easily cases such as Primulaceae, while such in- 
stances as Caryophyllacese are explicable on either view. 

447. Occasionally, divisions take place in ovaries which are not 
formed by the edges of contiguous carpels. These are called spurious 
dissepiments. They are often horizontal, and are then 

called phragmata (<pj Hypo,, a separation), as in Catharto- 
carpus Fistula (fig. 395), where they consist of transverse 
cellular prolongations from the walls of the ovary, only 
developed after fertilization, and therefore more properly 
noticed under fruit. At other times they are vertical, as 
in Datura, where the ovary, in place of being two-celled, 
is thus rendered four-celled; in Crucifera?, where the pro- 
longation of the placentas forms a replum (replum, leaf of a 
door) or partition; in Astragalus and Thespesia, where the 
dorsal suture is folded inwards ; and in Diplophractum, 
where the inner margin of the carpels is reflexed (fig. 388). 
In Cucurbitaceae, divisions are formed in the ovary, appa- 
rently by peculiar projections sent inwards from curved parietal pla- 
centas. In some cases, horizontal dissepiments are supposed to be formed 
by the union of carpels situated at different heights, so that the base 
of one becomes united to the apex of another. In such cases, the 
divisions are true dissepiments formed by carpellary leaves. The 
anomalous divisions in the ovary of the Pomegranate have been thus 
explained. 

448. The ovary is usually of a more or less spherical or curved form, 
sometimes smooth and uniform on its surface, at other times hairy and 
grooved. The grooves, especially when deep, indicate the divisions 
between the carpels, and correspond to the dissepiments. The dorsal 
suture may be marked by a slight projection, or by a superficial groove. 

449. The ovary is either free in the centre of the flower, or it is 
united to the surrounding parts, more especially to the calyx. The 
union may take place completely, so that the calyx is adherent through- 
out, and becomes superior while the ovary is inferior, as in the Melon 
(fig. 396, o being the ovary, I the upper part of the adherent calyx); 
or it may take place partially, as in Saxifragaceae (figs. 397, 398), where 

Fig. 395. Pistil of Cassia, or Cathartocarpus Fistula, in an advanced state, cut longitudinally 
to show the spurious transverse dissepiments, or phragmata. 




218 



ADHESIONS BETWEEN THE CALYX AND OVARY. 



the ovary, o, becomes half-inferior, the calyx being half-superior. These 
adhesions between the calyx and the ovary will be found to be of 
importance, as determining the epigynous and perigynous (tvl, upon or 



above, and 



pistil) condition of the stamens. 




Cases of adhesion between the ovary and the calyx, as occurin the Apple, 
Pear, Gooseberry, and Fuchsia (fig. 399), must not be confounded with 
cases such as the Eose (fig. 270), where the tube of the calyx becomes 
enlarged and hollowed so as to cover the carpels. In the former 
case, a transverse section (fig. 399) shows one or several closed locula- 

Fig. 396. Flower of Cucumis Melo, or Melon, o, Inferior ovary covered by the adherent calyx. 
Z, Limb of the calyx appearing above the ovary, p. Corolla. 

Fig. 397. Flower of Saxifraga Geum, cnt vertically to show the ovary, o, adherent for half its 
height to the calyx, c, The calyx, which is called half-superior, p, Petals. , Stamens, s, Styles 
and stigmas. 

Fig. 398. Pistil of Hoteia japonica, one of the Saxifragacese, cut vertically in order to show the 
interior of ite two cavities or loculaments. It is a bilocular or dithecal ovary, o, Two ovaries 
consolidated into one, and adherent for half their height to the calyx, c. t, Styles, s, Stigmas. 
p, Placentas covered with ovules, p e, Base of the petals. 

Fig. 399. Flower of Fuchsia coccinea divided horizontally into two halves through the middle 
of the ovary, o. The lower hal 2, of the ovary has been left untouched, to show its four cavities 
or loculi, with the ovules attached to their internal angles. Fig. 384 shows the same section more 
highly magnified. The upper half, 1, has been cut vertically, to show the ovules, g, arranged in 
a row in each loculament. The calyx, incorporated with the ovary below, is prolonged above it 
in the form of a tube, t, and divides at its summit into four segments, 1 1. p, Petals inserted on 
the tube of the calyx at the place where it divides into segments, e, Stamens inserted also on the 
tube, alternately large and small. The style rising from the summit of the ovary, and terminated 
by an ovoid stigma, s. 



ESSENTIAL ORGANS. THE STYLE. 219 

merits containing ovules ; while in the latter, it exhibits one cavity 
open at the top, and separate carpels scattered over the surface, each 
having a style and stigma. 

450. Peculiar views have been advocated by Schleiden, who con- 
siders the ovary in some cases as not formed by carpels, but by a 
hollowing out of the axis, at other times by these two modes combined. 
Thus the superior ovary, according to him, is formed of carpeUary leaves, 
while the inferior ovary of the Apple and Pomegranate is composed of 
the expanded summit of the axis, bearing the carpels in its interior ; 
that of Epilobium is formed from the stem alone, and that of Saxi- 
frage partly by the peduncle and partly by carpels. 

451. The Style proceeds from the summit of the carpel, and may 
be looked upon as a prolongation of it in an upward direction (fig. 
372 t). It is hence called apicilar (apex, top). It consists not merely of 
the midrib, but of the vascular and cellular tissue of the carpel, along 
with a continuation of the placenta or conducting tissue, which ends 
in the stigma. In some cases, the carpellary leaf is folded from above 
downwards, in a hooded manner, so that its apex (as in reclinate ver- 
nation, fig. 205 a) approaches more or less to the base. When the 
folding is slight, the style becomes lateral (fig. 382); when to a greater 
extent, the style appears to arise from near the base, as in the Straw- 
berry (fig. 400), or from the base, as in Chrysobalanus Icaco (fig. 401), 
when it is basilar. In all these cases the style still indicates the organic 
apex of the ovary, although it may not be the apparent apex. 






452. The carpel sometimes becomes imbedded in the torus or tha- 
lamus, so as to have a projection of the latter on one side; and then, if 
the style is basilar or lateral, it may adhere to this portion of the torus, 
and appear to arise from it. This is seen in Labiatae (fig. 402), and 

Fig. 400. Carpel of Strawberry, o, Ovary, t, Style arising from near the base, and becoming 
basilar by the mode in which the ovary is developed ; the style, however, still indicating the 
organic apex of the ovary. 

Fig. 401. Carpel of Chrysobalanus Icaco. o, Ovary, t, Basilar style, s. Stigma. 

Fig. 402. Pistil of Lamitun album, shown by a vertical section of part of the flower. Two of 
the four ovaries have been removed to exhibit the connection of the style with the torus, r, by 
adhesion, o, The two remaining ovaries, d, Glandular disk placed below the pistil c, Part of 
calyx, p, Corolla. 




220 ESSENTIAL ORGANS. THE STYLE. 

Boraginacese (fig. 403), where the four carpels, o, are sunk in the 
torus, r, in such a way that the common style, s, formed by the union 
of four basilar styles, seems to be actually a prolonga- 
tion of the torus. When ovaries are thus attached 
round a central prolongation of the torus, continuous 
with a united columnar style, the arrangement is 
called a gynobase (yvvvi, pistil, and /3<r/?, base). It is 
well developed in Ochnaceae. In Geraniums there is 
a carpophore or prolongation of the torus in the 
form of a long beak, to which the styles are at- 
tached. 

453. The form of the style is usually cylindrical, more or less filiform 
and simple ; sometimes it is grooved on one side, at other times it is 

flat, thick, angular, compressed, and even petaloid, as in 
Iris and Canna. In Goodeniaceae it ends in a cup-like ex- 
pansion enclosing the stigma. It may be smooth and covered 
with glands and hairs. These hairs occasionally aid in scat- 
tering the pollen, and are called collecting hairs, as in Gold- 
fussia or Ruellia. In Campanula they appear double and 
retractile. In Aster and other Composite (fig. 404), there 
are hairs produced on parts of the style, p c, prolonged 
beyond the stigma, s; these hairs, while the part is being 
developed, come into contact with the pollen and carry 
it up along with them. In Vicia and Lobelia, the hairs 
form often a tuft below the stigma. 

454. The styles of a syncarpous pistil may be either separate or 
united ; when separate, they alternate with the septa. When united 
completely, it is usual to call the style simple (fig. 399) ; when the 
union is partial, then the style is said to be bifid, trifid, multifid, accord- 
ing as it is two-cleft, three-cleft, many-cleft; or, to speak more correctly, 
according to the mode and extent of the union of two, three, or many 
styles. The style is said to be bipartite, tripartite, or multipartite, when 
the union of two, three, or many styles only extends a short way above 
the apex of the ovary. The style from a single carpel, or from each 
carpel of a compound pistil, may also be divided. In fig. 314, 2, each 
division of the tricarpellary ovary of Jatropha Curcas, has a bifurcate 
or forked style, s, and in fig. 405, the ovary of Emblica officinalis has 
three styles, each of which is divided twice in a bifurcate manner, ex- 
hibiting thus a dichotomous division. 

455. The length of the style is determined by the relation which 

Fig. 403. Pistil of Erithricium Jacquemontianum, with one of the ovaries removed in front, 
to show the manner in which the ovaries are inserted obliquely on a pyramidal torus, r, whence 
the style appears to arise, ending in a stigma, s. 

Fig. 404. Summit of the style, t, of an Aster, separating into two branches, s, each terminated 
by an inverted cone of collecting hairs, p c. The stigma, s, is seen below in the form of a band 
or line on the inner curvature of the branches. 




ESSENTIAL ORGANS. THE STIGMA. 



221 




ought to subsist between the position of the stigma and that of the 
anthers, so as to allow the proper application of the pollen. In some 
cases the ovary passes directly into the style, 
as in Digitalis, in other instances there is a 
marked transition from one to the other. 
The style may remain persistent, or it may 
fall off after fertilization is accomplished, and 
thus be deciduous. 

456. The stigma is the termination of 
the conducting tissue of the style, and is 
usually in direct communication with the 
placenta. It may, therefore, in most in- 
stances, be considered as the placentiferous 
portion of the carpel prolonged upwards. In 
Armeria and some other plants, this connec- 
tion with the placenta cannot be traced. * 05 

Its position may be either terminal or lateral. The latter is seen in 
some cases, as Asimina triloba, where it is unilateral (fig. 377), and in 
Plantago saxatilis (fig. 378), where it is bilateral. Occasionally, as in 
Tasmannia, it is prolonged along the whole inner surface of the style. 
In Iris, it is situated on a cleft on the back of the petaloid divisions of 
the style. It consists of loose cellular tissue, and secretes a viscid 
matter which detains the pollen, and causes it to protrude tubes. 
This secreting portion is, strictly speaking, the true stigma, but the 
name is generally applied to all the divisions of the style on which the 
stigmatic apparatus is situated, as in Labiatae. The stigma usually 
alternates with the dissepiments of a syncarpous pistil, or corresponds 
with the cells ; but in some cases, it would appear, that half the stigma 
of one carpel unites with half that of the contiguous carpel, and thus 
the stigma is opposite the dissepiments, or alternates with the cells. 
This appears to be the case in the Poppy, where the stigma of a single 
carpel is two-lobed, and the lobes are opposite the septa. 

457. If the stigma is viewed as essentially a prolongation of the 
placenta, then there is no necessary alternation between it and the 
placenta, both being formed by the margins of carpellary leaves, which 
in the one case are ovuliferous, in the other stigmatiferous. There is 
often a notch in one side of a stigma (as in some Rosace*), indicating 
apparently that it is a double organ like the placenta. To the division 
of a compound stigma the terms bifid, trifid, &c., are applied according 
to the number of the divisions. Thus, in Labiataj (fig. 299) and in 
Composite (figs. 301, 404 s), the stigma is bifid ; in Polemonium, trifid. 
When the divisions are large, they are called lobes, and when flattened 



Fig. 405. Female flower of Emblica officinalis, one of the Euphorbiaceae. c, Calyx, p p 
Petals, t, Membranous tube surrounding the ovary, o, Ovary crowned by three styles, s, each 
being twice bifurcate. 



222 



ESSENTIAL ORGANS. THE STIGMA. 



like bands, lamella ; so that stigmas may be bilobate, trilobate, bilamel- 
lar, trilamellar, &c. 

458. It has already been stated, that the divisions of the stigma 
mark the number of carpels which are united together. Thus, in Cam- 
panula (fig. 405 bis), the quinquefid or five-cleft stigma indicates five 
carpels, the stigmata of which are separate, although the other parts 
are united. In Bignoniaceae (fig. 406), as well as in Scrophulariacese 
and Acanthacese, the two-lobed or bilamellar stigma indicates a bilo- 
cular ovary. Sometimes, however, as in the case of the styles, the 
stigma of a single carpel may divide. It is probable that, in many in- 
stances, what is called bifurcation of the style, is only the division of the 
stigma. In Gramineae and Composite (figs. 301, 404), there is a bifid 
stigma and only one cavity in the ovary. This, however, may be pro- 
bably traced to subsequent abortion of the ovary of one of the carpels. 
The stigma presents various forms. It may be globular, as in Mirabilis 
Jalapa (figs. 376, 407) ; orbicular, as in Arbutus Andrachne (fig. 408); 
umbrella-like, as in Sarracenia, where, however, the proper stigmatic 
surface is below the points of the large expansion of the apex of the 
style; ovoid, as in Fuchsia (fig. 399); hemispherical; polyhedral; 




405 bis 



407 408 



radiating, as in the Poppy (fig. 409), where the true stigmatic rays 
are attached to a sort of peltate or shield-like body, which may repre- 
sent depressed or flattened styles. The lobes of which a stigma con- 
sists may be flat or pointed, as in Mimulus and Bignonia (fig. 406); or 
fleshy and blunt, smooth, granular, feathery, as in many Grasses (fig. 
410). In OrchidaceaB, the stigma is placed on the column formed by 
the union of the styles and filaments. The situation where it occurs 
has been called gynizus (^[ 433). In Asclepiadacese the stigmas are 

Fig. 405, bis. Stigmas, s, of Campanula rotundifolia. I, Style. 

Fig. 406. Bilamellar stigmas of Bignonia pandorea. The two lamella; are applied naturally 
against each other in 1, while in -i they are artificially separated. 

Fig. 407. Globular stigma of Mirabilis Jalapa, t. Style. *, Stigma. 

Fig. 408. Circular stigma, s, and t, style of Arbutus Andrachne. 

Fig. 409. Pistil of Papaver somniferum, or opium Poppy, o, Ovary, s, Radiating stigmas 
on its summit. 

Fig. 410. Pistil of Cynodon Dactylon, a Grass, o, Ovary, s, Feathery Stigmas. 



PISTILLIDIA IN CRYPTOGAMIC PLANTS. 



223 



united to the face of the anthers, and along with them form a solid 
mass (fig. 353). 

459. in Cryptoganiic Plants there exist organs called pistillidia, 
which have been supposed to perform the function of pistils. They 
consist of hollow cavities, like ovaries, to which the names of sporangia 
(airo^*, a spore or seed, and yyo?, a vessel), and thecce (tiqxii, a sac), 
have been given, containing bodies called spores, equivalent to ovules. 
The sporangia or spore-cases are sometimes immersed hi the substance 
of the plant, as in Riccia glauca (fig. 411, 1); at other times they are 
supported on stalks or setce (seta, a bristle), as in Mosses. In Mar- 
chantia polymorpha, they consist of distinct and separate expansions, 
having a bottle-like form (fig. 412), the lower part, o, being enlarged, 
containing the spores, and being surrounded by a cellular tube resem- 
bling a calyx, c. From this ovary-like body there is a prolongation 
which may be eonsidered as a style, t, terminated by a cellular enlarge- 






ment, s, which has been compared to a stigma. The styloid prolonga- 
tion withers and disappears when the spores are mature. Sometimes 
the thecse, as in Lichens, consist of a club-shaped elongated cell or 
ascus (fig. 413, 1), containing nuclei or cells hi its interior, which form 



Fig. 411. L Perpendicular section of the frond, / of Riccia glauca, and of the sporangium 
or spore-case, o, which is imbedded in it s, Narrow process or style by which the sporangium 
communicates with the external surface. L, Its cavity or loculus. f, Young spores still united 
in sets of four in the parent cells, r, Cells elongated like roots. 2 One of the cells more highly 
magnified, with the four spores which it contains. Three of the spores are seen, the fourth 
being concealed by them. 

Fig. 41<?. Sporangium or spore-case of Marchantia polymorpha. o, Hollow swelling contain- 
ing spores, and which has been compared to the ovary, t, Narrow process prolonged upwards, 
and resembling a style, s, Termination of this cellular process, compared to the stigma, c, 
Cellular covering of the sporangium or spore-case, surrounding it like a calyx. 

Fig. 4ia 1. Theca or ascus of Solorina saccata, a species 'of Lichen, containing eight spores, 
united in sets of two. 2. Two of these double spores highly magnified. 



224 ESSENTIAL ORGANS. THE OYULE. 

the spores. Sometimes these are single, at other times united in sets 
of two (fig. 413, 2), or of four (fig. 411, 2), or of some multiple 
of four. There are various modifications of sporangia in other 
Cryptogamic tribes. Thus, in Ferns, they are often surrounded by 
an annular ring, or by elastic bands, which cause their dehiscence ; 
while in the Chara they are called nucules, and present an oval form 
with a spiral arrangement of tubes. 

460. The Ovule. The ovule is the body attached to the placenta, 
and destined to become the seed. It bears the same relation to the 
carpel that marginal buds do to leaves, and when produced on a free 
central placenta, it may be considered as a bud developed on a branch 
formed by the elongated axis. The single ovule contained in the 
ovaries of Composite and Grasses, may be called a terminal bud 
surrounded by a whorl of adhering leaves or carpels, in the axil of 
one of which it is produced. In Delphinium elatum, Brongniart 
noticed carpels bearing ovules, which were sometimes normal, at other 
times mere lobes of the carpellary leaf; and in Aquilegia, Lindley saw 
ovules transformed into true leaves, produced on either margin of the 
carpel. Henslow has seen the ovules of Mignonette become leaves. 
In such cases the vascular bundles of the placenta (pistillary cords) 
are formed by the lateral veins of the carpellary leaf. These veins 
pass into the marginal lobes or leaflets which represent ovules, and 
seem to prove that the placenta in such cases must be truly a 
carpellary, and not an axile, formation. Godron, from observing 
monstrosities, says, that in Leguminosag, the pericarp or seed-vessel is 
formed by the common petiole dilated, the style is probably the 
terminal leaflet, or tendril, or apiculum, while the ovules represent 
lateral leaflets of the leaf, and are modifications of it. 

461. The ovule is usually contained in an ovary, but in Coniferas 
and Cyadacese it has no proper ovarian covering, and is called naked. 
In these orders the ovule is produced on the edges, or in the axil of 
altered leaves, which do not present a trace of style or stigma. The 
carpellary leaves are sometimes so folded as to leave the ovules exposed 
or seminude, as in Mignonette. In Leontice thalictroides (blue cohosh), 
the ovules rupture the ovary immediately after flowering, and the 
seeds are exposed. So also in species of Ophiopogon, Peliosanthes, 
and Stateria. In the species of Cuphea, the placenta ultimately bursts 
through the ovary and corolla, becoming erect, and bearing the 
exposed ovules. 

462. The ovule is attached to the placenta either directly, when it 
is called sessile, or by means of a prolongation called afuniculus (funis, 
a cord), umbilical cord, or podosperm (woDj, afoot, and onl^a, a seed). 
This cord sometimes becomes much elongated after fertilization. The 
placenta is sometimes called the trophosperm (T^U, I nourish). The 
part by which the ovule is attached to the placenta or cord, is its base 



ESSENTIAL ORGANS. THE OVULE. 



225 




or hilum, the opposite extremity being its apex. The latter is fre- 
quently turned round in such a way as to approach the base. The 
ovule is sometimes imbedded in the placenta. 

463. In its simplest form, as in the Misletoe, the ovule presents itself 
as a small cellular projection, which enlarges, assumes an ovoid form 
(fig. 414), and ultimately becomes 

hollowed at the apex (fig. 415 c). 
The cavity thus produced is sur- 
rounded by a mass of cells called the 
nucleus, n, and is destined to contain 
the embryo plant after the process of 
fertilization has been completed. In 
this embryonal cavity the young plant 
is suspended by a thread-like cellular 
process called suspensor, attached to the summit of the nucleus. This 
cavity in some plants is surrounded by the cells of the nucleus ; but, 
in other cases, it becomes lined with a regular epithelial (^[ 431), or thin 
cellular covering, and constitutes the embryo-sac, which is produced 
before fecundation, and contains amnios or mucilaginous matter in 
which the embryo is formed. 

464. The nucleus (fig. 421 n) may remain naked, and form the ovule, 
as in the Misletoe, Veronica hederifolia, Asclepias, &c.; but in most 
plants it becomes surrounded by certain coverings during the progress 
of development. These appear first in the form of one or more cellular 
rings at the base, which gradually spread over the surface. In some 
cases only one covering is formed, as in Composite, Campanulaceas, 
Walnut &c. Thus, in the latter (fig. 416), the nucleus, n, is covered 
by a single envelope, t, which, in the first instance, extends over the 
base, and then spreads over the 

whole surface (fig. 417), leaving only 
an opening at the apex. In other 
instances (fig. 418), the nucleus, n, 
besides the single covering (fig. 418, 
2, fe'), has another developed sub- 
sequently (fig. 418, 3, te), which 
gradually extends over the first, 
and ultimately covers it completely. 
There are thus two integuments, an 

outer and an inner the latter, according to Schleiden, being first pro- 
duced. Mirbel considers the outer as the first formed, and hence has 
called it primine, te, while the inner is denominated secundine, ti. The 

Fig. 414. Ovule of the Misletoe entire. 

Fig. 415. Ovule of Misletoe cut to show the embryo-sac, c. and the whole of the rest of the 
mass, n, composed of uniform tissue, and forming a nucleus without integuments. 

Fig. 416 Ovule of Juglans regia, the Walnut, t, Simple integument. , Nucleus, the base of 
which only is covered with integument at the early period of development. 

Fig 417. The same ovule more advanced, in which the nucleus is nearly completely covered. 




226 



ESSENTIAL ORGANS. THE OVULE. 




418,1 



418,2 



418,3 



latter names are in the present day used by botanists as denominating 
the outer and inner covering, witho u t reference to their order of 

development. At the apex 
of the nucleus these integu- 
ments leave an opening or 
foramen composed of two 
apertures; that in the pri- 
mine (fig. 418, 3, ex), called 
exostome (i%a, outside, and 
tnof^a., mouth), that in the 
secundine (fig. 418, 3, e,d\ 
endostome (st/^ov, within). The 
foramen of the ovule is also called micropyle (^/xg&r, small, and vfa-n, a 
gate) ; but this name is often restricted to its appearance in the seed after 
fecundation. The length of the canal of the foramen depends on the 
development of the nucleus, as well as the thickness of the integuments. 
The embryo-sac is sometimes prolonged beyond the apex of the nucleus, 
as noticed by Meyen in Phaseolus and Alsine media, and by Griffith in 
Santalum album and Loranthus. Some authors, as Mirbel, consider 
the ovule in reference to the embryo, and speak of five coverings of 
the latter, viz., 1. primine ; 2. secundine ; 3. tercine, or the nucleus ; 
4. quartine, a temporary cellular layer, which is occasionally formed 
at an after period around 5. quintine, or the embryo-sac. By most 
botanists the nucleus and sac with its two integuments, are mentioned 
as the ordinary structure of the ovule. 

465. All these parts are originally cellular. The nucleus and in- 
teguments are united at the base of the ovule by a cellulo-vascular 
membrane, called the chalaza (fig. 421 ch). This is often coloured, of 
a denser texture than the surrounding tissue, and is traversed by fibro- 
vascular bundles, which come from the placenta, in order to nourish 
the ovule. The hilum indicates the organic base of the ovule, while the 
foramen marks its apex. When the ovule is so developed that the 
union between the primine, secundine, and nucleus with the chalaza, 
is at the hilum or base (next the placenta), and the foramen is at the 
opposite extremity (figs. 417, 418), the ovule is orihotropal, orthotro- 
pous or atropous (6^60;, straight, and rjoVo?, mode, or , privative, and 
Tf7T6), I turn). This is the state of an ovule when it first makes its 
appearance, and occasionally, as in Polygonacese, it remains permanent. 
In such ovules, a straight fine drawn from the hilum to the foramen 
passes through their axes. 



ESSENTIAL ORGANS. THE OVULE. 



227 



466. In general however, changes take place on the ovule, so that it 
deviates from the straight line. Thus it may be curved upon itself, so 
that the foramen approaches to the hilum or placenta, and ultimately is 
placed close to it, while the chalaza is only slightly removed from the 
hilum. This change depends apparently on the ovule increasing more on 
one side than on the other, and as it were drawing the chalaza slightly 
to one side of the hilum opposite to that where the foramen is applied. 
Such ovules are called campylotropal or campylotropous (x.aft.'jrfaog, 
curved), when the portions on either side of the line of curvation are 
unequal (fig. 419) ; or camptotropal (KX^^TOS, curved), when they are 





equal (fig. 420). Curved ovules are found in Leguminoste, Cruciferas, 
and Caryophyllaceae. The union between the parts of the curved por- 
tion usually becomes complete, but in some cases there is no union, 
and the ovules are lecotropal, or horse-shoe shaped (>,kx.og, a hollow 
disk, and TgoVoj, mode or form). 




467. When in consequence of the increase on one side, the ovule is 
so changed that its apex or foramen (fig. 421, 4, n,) is in close apposition 

Fig. 419. Campylotropal or Campylotropous ovule of the Stock. 1. Ovule entire. 2. Ovule 
cut lengthwise. /, Funiculus or umbilical cord, c, Chalaza, n, Nucleus, te, Primine or outer 
covering, ti, Secundine or inner covering, ex, Exostome. eel, Endostome. 

Fig. 420. Carpel of Menispermum canadense, with a curved or camptotropal ovule, o. f, 
Funiculus. s, The base of the style. 

Fig. 4-21. Ovule of Chelidonium majus at different stages of development, h, Hilum or um - 
bilicus. ch, Chalaza, /, Funiculus or umbilical cord, r, Raphe. n, Nucleus, ti, Secundine. 
te, Primine. ed, Endostome. ex, Exostome. 1. First stage: nucleus still naked. 2. Second 
stage: nucleus covered at its base by the secundine. 3. Third stage: the primine developed 
and covering the secundine at its base. 4. Fourth stage : the ovule completely reflected, and 
its point turned downwards. 5. The same cut longitudinally, to show the relation of its different 
parts. 




228 ESSKNTIAL ORGAXS. THE OVULE. 

to the hilum (fig. 421, 5, h) and the chalaza is also earned round so 
as to be at the opposite extremity (fig. 421, 5, c), then the ovule 
becomes inverted, anatropal or anatropous (d,va,-r^a, I subvert). 
In this case (fig. 422), the union of the chalaza, ck, with the nucleus, 
n, is removed from the hilum, and the connection 
between the chalaza and placenta is kept up by a vas- 
cular cord, r, passing through the funiculus, and called 
the raphe (ZK<PYI, a line). The raphe often forms u 
ridge along one side of the ovule, and it is usually 
on the side of the ovule next the placenta. Some 
look upon this kind of ovule as formed by an elongated 
funiculus (fig. 421, 5, /) folded along the side of the 
ovule, and becoming adherent to it compeletely ; and 
support this view by the case of semi-anatropal ovules, 
where the funiculus is only, as it were, partially 
attached along one side, becoming free in the middle; and also by cases 
where an anatropal ovule, by the separation of the funiculus from its 
side, becomes an orthotropal seed. 

468. The anatropous form of the ovule is of very common occurrence, 
and may probably aid in the process of fertilization. Ovules which are 
at first orthotropous, as in Chelidonium majus (fig. 421, 2), become 
often anatropous in the progress of development (fig. 421, 4). When 
the ovule is attached to the placenta, so that the hilum is in the middle, 
and the foramen and chalaza at opposite ends, it becomes transverse, 
amphitropal or heterotropal (dp,}, around, erhof, diverse). 

469. The nucleus of the ovule becomes hollowed at a particular part 
(fig. 415 c), so as to form a cavity. Mirbel states that the whole nucleus 
is transformed into a membrane called the tercine, lining the secundine, 
and that in its interior another covering, the quartine, and finally, the 
embryo-sac, are produced. The view, however, generally adopted, is 
that the embryo-sac is formed within the nucleus, assuming a greater 
or less size according to circumstances, and in some instances reducing 
the nucleus to a mere external sac. In the interior of the embryo- 
sac, cellular layers are deposited from without inwards, the earlier 
ones probably forming the fugacious quartine of Mirbel. 

470. In the Misletoe there are two or three embryo-sacs. The neck 
of the embryo-sac in Veronica and Euphrasia becomes elongated and 
swollen, and from it are developed certain cellular or filamentous 
appendages, which are probably connected with the nutrition of the 
embryo. 

471. The position of the ovule relative to the ovary varies. When 
there is a single ovule, it may be attached to the placenta at the base 
of the ovary (basal placenta), following a straight direction, and being 

Fig 122. Anatropous ovule of Dandelion, cut vertically, ch, Chalaza. r, Raplie. , Nucleus. 



ESSENTIAL ORGANS. THE OVULE. 



229 



erect, as in Polygonacea? and Composite (fig. 423); or it may be inserted a 
little above the base, on a parietal placenta, with the apex upwards (fig. 
424), and then is called ascending, as in Parietaria. It may hang from 
an apicilar placenta at the summit of the ovary, the apex being down- 







wards, and be inverted or pendulous, as in Hippuris vulgaris (fig. 425), 
or from a parietal placenta near the summit, and be suspended, as in 
Daphne Mezereum (fig. 426), Polygalacea?, and EuphorbiaceaB. Some- 
times a long funiculus arises from a basal placenta, reaches the sum- 
mit of the ovary, and suspends the ovule, as in Armeria; at other 
times the hilum or true organic base appears to be in the middle, and 
the ovule becomes horizontal, peltate (pelta, a shield), or peritropom 
(vipl, around, and Tpevu, I turn). All these modifications are influenced 
by the relative position of the hilum and foramen, the length of the 
funiculus, and its adhesion, as well 
as the position of the placenta. 

472. When there are two ovules 
in the same cell, they may be 
either collateral, that is, placed side 
by side (fig. 427), or the one may 
be erect and the other inverted, 
as in some species of Spiraea and 
vEsculus (fig. 428), or they may be 
placed one above another, each 
folloAving the same direction. Such is also the case with ovaries con- 
Fig. 423 426. Carpels belonging to different flowers, cut vertically to show the different 
directions of the solitary ovule, o, contained in them. /, Funiculus. r, Raphe. c, Chalaza. 
.1, Base of the style. 

Fig. 423. Carpel of Senecio vulgaris, with a straight or erect anatropous ovule. 

Fie. 424. Carpel of Parietaria officinalis, pellitorv, with an ascending orthotropous ovule. 

Fig. 425. Carpel of Hippuris vulgaris, Mare's-tail, with a reversed or pendulous anatropous 
ovule. 

Fig. 426. Carpel of Daphne Mezereum, with a suspended anatropous ovule. 

Fig. 427. Carpel of Nuttallia cerasoides, with two suspended collateral ovules, o, One of the 
ovules. /, Funiculus. s, The base of the style. 

Fig. 428. One of the loculaments of the ovary of ^Esculus hybrida, laid open to show two 
ovules, o o, inserted at the same height, but turned in different directions, m m, Micropyle in- 
dicating their apex s, Base of the style. 





230 



FUNCTIONS OF FLORAL ENVELOPES. 



taining a moderate or definite number of ovules. Thus, in the ovary 
of Leguminous plants (fig. 429), the ovules o, are attached to the 
extended marginal placenta, one above the other, forming usually two 

parallel rows corresponding to each 
margin of the carpel. When the 
ovules are definite (uniform and 
can be counted), it is usual to find 
their attachment so constant as to 
afford good characters for natural 
orders. When the ovules are very 
numerous or indefinite, while at 
the same time the placenta is not 
much developed, their position ex- 
hibits great variety, some being 
directed upwards, others downwards, 

others transversely (fig. 430), and their form is altered by pressure 
into various polyhedral shapes. In such cases it frequently happens 
that some of the ovules are arrested in their development and become 
abortive. In Cryptogamous plants, in place of ovules there are cellu- 
lar bodies called spores, to which allusion will be made when the seed 
is considered. 




4. FUNCTIONS OF THE FIX5RAL ENVELOPES. 

473. The bracts and calyx, when of a green colour, perform the 
same functions as leaves, giving off oxygen under the influence of light, 
and producing the carbonized substance caUed chlorophylle. They 
are consequently concerned in the assimilation of matters fitted for the 
nutrition of the flower, and they aid in protecting the central organs. 
The corolla, along with the thalamus and disk, is concerned rather 
with development than with respiration. Hence it does not in general 
produce chlorophylle, nor does it give off oxygen. It protects the 
essential organs, and eliminates carbonic acid by a process of oxidation. 
The starch granules contained in it, as well as in the thalamus and 
disk, are not altered by the respiratory process, so as to become more 
highly carbonized, but are oxidized, so as to be converted into saccha- 
rine matter. The quantity of oxygen absorbed was determined by 
Saussure. He found that double flowers absorbed less in proportion 
to their volume than single flowers; that the essential organs contained 
more oxygen than the floral envelopes; and that the greatest absorp- 
tion took place when the stamens and pistil were mature. 



Fig. 429. Carpel or legume of Ononis rotundifolia, with several campylotropous ovules, o, 
placed one above the other. /, Funiculi. a, Base of the style. 

Fip. 430. - Loculament of the ovary of Peganum Harmala, with numerous ovules, o, attached 
to a projecting placenta, p, and pointing in different directions, s, Base of style. 



FUNCTIONS OF FLOEAL ENVELOPES. 



231 



474. The following are some of Saussure's experiments: 



Name. 



Duration of 
Experiment. 

Stock, single, 24 hours. 

Stock, double 

Tuberose, single 

Tuberose, double, 

Indian Cress, single,... 
Indian Cress, double,.. 
Brugmansia arborea,... 
Passiflora serratifolia,. 

Gourd, male flower 10 

Gourd, female, 24 

Hibiscus speciosus, 12 

Hypericum calycinum, ...24 

Cob?ea scandens, 

Arum italicum, 

Typha latifolia, 

White lily, 

Castanea vulgaris, 



Oxygen Consumed 



By Flowers entire. 

11-5 times their voL 

7-7 

9- 

7-4 

8-5 

7-25 



18-5 
7-6 
3-5 
5-4 
7'5 
6-5 



By Essential Organs 
only. 

18' times their vol. 



9-8 

5- 

9-1 



16-3 



16- 

6'3 
8-5 

7-5 
30- 



475. While this oxidation is going on, carbon is given off in the 
form of carbonic acid, and heat is developed by the combination between 
the oxygen and carbon. Experiments have been performed by La- 
marck, Schultz, Huber, Saussure, Brongniart, Vrolik, and De Vriese, 
as to the amount of heat produced during flowering, especially by 
species of Arum, Caladium, and Colocasia. These are plants in which 
the floral envelopes are nearly absent, while the essential organs, the 
torus and growing point, attain a high degree of development, forming 
a spadix enclosed in a large spatha. No heat could be detected when 
the contact of oxygen was prevented, either by putting the plants into 
other gases, or by covering the surface of the spadix with oil. The 
surface of the spadix is the part whence the heat was chiefly evolved. 
The Arum cordifolium occasionally had a temperature 20 or 30 above 
that of the surrounding air; Arum maculatum 17 to 20; and Arum 
Dracunculus and other species still higher. The following observations 
were made by Brongniart on the spadix of Colocasia odora. The spathe 
opened on the 14th of March; the discharge of pollen commenced on 
the 16th, and continued till the 18th. The maximum temperature 
occurred at different hours. 



M . Temperature 

Maximum. above p the Air , 



14th March. 
15th 
16th 



3 P.M. 

4 

5 



4-5 Cent. 

10-0 

10-2 



Maximum. 



Temperature 
above the Air. 



17th March, 5 P.M. 1 1-0 Cent. 
18th 11 A.M. 8-2 
19th 10 2-5 



476. Vrolik and De Vriese made a series of observations on the 



232 FUNCTIONS OF FLORAL ENVELOPES. 

same plant, and have given the results for every half hour. The fol- 
lowing are some of these results: 



Hour. 


Temperature 
of Plant. 


Temperature 
of Air. 


Hour. 


Temperature 
of Plant. 


Temperature 
of Air. 


11-30 


20-6 Cent. 


18-3 Cent. 


3 


25-Qo Cent. 


15-6 Cent. 


12 


21-1 


18-7 


3-30 


24-4 


15-0 


12-30 


23-3 


19-4 - 


4 


23-3 


15-0 


1 


24-4 - 


19-4 


5 


22-2 


18'7 


1-30 


24-4 


18-9 


6 


21-0 


18-7 


^ 


25-6 


17-2 7 


200 


IS'" 



2-30 26-5 15-6 i 

The greatest amount of heat observed was at 2-30 P.M., when it was 
10 '9 above the temperature of the air. On the previous day the maxi- 
mum occurred at 3 P.M., and on the following day at 1, but then it 
was only 8 '2 above that of the air. Decandolle states that at Mont- 
pelier, Arum italicum attained the maximum of temperature about f> 
P.M. Saussure observed similar phenomena, but to a less extent, in 
the Gourd, where the temperature varied from 1'8 to 3 '6; also in 
Bignonia radicans, from 0*9 to 3. From all these experiments, it 
would appear that in the Araceas and some other plants, especially at 
the period when the essential organs reach maturity, there is a produc- 
tion of heat, which increases during the performance of their functions, 
attaining a daily maximum, and ultimately declining. 

477. While these changes are taking place, the starch is converted 
into dextrine, and ultimately into grape-sugar, which, being soluble, 
can be immediately applied to the purposes of the plant. The honey- 
like matter thus formed is stored up frequently at the base of the 
petals, in little pits or nectaries, as in Fritillary, Asarum, &c. It is 
considered by Vaucher and others as performing an important office in 
fertilization, covering the stigma, and aiding in the dispersion and rup- 
ture of the pollen-grains. Bees and other insects, in collecting the 
saccharine matter, also scatter the pollen. 

478. Flowering takes place usually at a definite period of the plant's 
existence. It requires a considerable amount of nutrient matter, and 
its occurrence is accompanied with a greater or less exhaustion of the 
assimilated products. Hence, a certain degree of accumulation of sap 
seems necessary in order that flowering may proceed. Annual plants 
are so exhausted after flowering as to die; but, by retarding the epoch 
for two or more years, as by nipping off the flower-buds, tune is 
allowed for accumulating sap; the stems, from being herbaceous, be- 
come shrubby, and sometimes, as in the Tree-Mignonette, they may be 
made to live and flower for several years. Perennial plants, by the 
retardation of flowering, are enabled to accumulate a greater amount 
of nutritive matter, and thus to withstand the exhaustion. Many cul- 
tivated plants, which lay up a large store of nutriment in the form of 



PERIODS OF FLOWERING. 233 

starch, lose it when the plants shoot out a flowering stem. This is 
seen in the case of Carrots and Turnips, in which the succulent roots 
become fibrous and unfit for food when the plants are allowed to run 
to seed. The receptacle of the Artichoke, and many Compositse, which 
is succulent before the expansion of the flowers, becomes dry as the 
process of flowering proceeds. The juices of plants then, when re- 
quired for the purpose either of food or medicine, ought in general to 
be collected immediately before flowering. 

479. By cutting a ring out of the bark of trees, and thus retarding 
the descent of the sap, the period of flowering is sometimes hastened. 
Again, when the period of flowering is long delayed, either naturally, 
as in Agave and several palms, or artificially, the process, when it does 
begin, proceeds with amazing rapidity and vigour. In such cases this 
vigorous flowering is often followed by the death of the plant. Richard 
mentions, that a plant of Agave, which had not flowered for nearly a 
century, sent out a flowering stem of 22^ feet in 87 days, increasing at 
one period at the rate of one foot a day. Common fruit trees, when 
they begin to flower, often do so luxuriantly ; but if, from the season 
being bad, there is a deficiency in flowering, it frequently happens that, 
from the accumulation of sap, the next year's produce is abundant. 

480. If plants are allowed to send out their roots very extensively 
in highly nutritive soil, the tendency is to produce branches and leaves 
rather than flowers. In such cases, cutting the roots or pruning the 
young twigs may act beneficially in checking the vegetative functions. 
In pruning, the young shoot is removed, and the buds connected with 
the branch of the previous year are left, which thus receive accumu- 
lated nourishment. Grafting, by giving an increase of assimilated 
matter to the scion or graft (see section on Fruiting), and at the same 
time checking luxuriant brandling, contributes to the hastening of the 
flowering. 

481. The period of flowering of the same plant varies at different 
seasons, and in different countries. During the winter in temperate 
climates, and during the dry season in the tropics, the vegetative pro- 
cess is checked, more especially by the diminished supply of moisture, 
and the arrestment of the circulation of the sap. The assimilated 
matter remains in a state of repose, ready to be applied to the purposes 
of the plant when the moisture and heat again stimulate the vegetable 
functions. This stimulation occurs at different periods of the year, 
according to the nature of the climate. By observing the mode of 
flowering of the same species of plant in successive years, conclusions 
may be drawn as to the nature of the seasons in a country; and by 
contrasting these periods in different countries, comparisons may be 
instituted as to the nature of their climate. Thus valuable floral 
calendars may be constructed. 

482. Plants are accommodated to the climate in which they grow, 



234 PERIODS OF FLOWERING. 

and flower at certain seasons ; and even when transferred to other 
climates where the seasons are reversed, they still have a tendency to 
flower at their accustomed period of the year. Again, in the same 
climate, some individuals of a species, from a peculiar idiosyncrasy, 
regularly flower earlier than others. Decandolle mentions a horse- 
chestnut at Geneva, which flowered always a month before the rest in 
the neighbourhood. From such individuals, by propagation, gardeners 
are able to produce early-flowering varieties. 

483. There is a periodicity in the hours of the day at which some 
species open their flowers. Some expand early, some at mid-day, 
others in the evening. The flowers of Succory open at 8 A.M., and 
close at 4 P.M. ; those of Tragopogon porrifolius, or Salsafy, close about 
mid-day. Linnasus constructed a floral clock or watch, in which the 
different hours were marked by the expansion of certain flowers. The 
periods, however, do not seem to be always so regular as he remarked 
them at Upsal. The following are a few of these horological flowers, 
with their hours of opening : 

Ipomcea Nil, 3 to 4A.M. 

Tragopogon pratense, 4 ... 5 

Papaver nudicaule 5 

Hypochseris maculata, 6 

Various species of Sonchus and Hieracium, 6 ... 7 

Lactuca sativa, 7 

Specularia Speculum, \ _ _ 

Calendula pluvialis / 

Anagallis arvensis 8 

Nolana prostrata, 8 ... 9 

Calendula arvensis, 9 

Arenaria rubra, 9 ...10 

Mesembryanthemum nodiflorum, 10 ...11 

Ornithogalum umbellatum (Damed'onze heures\ 11 

Various Ficoideous plants 12 

Scilla pomeridiana, 2 P.M. 

Silene noctiflora,.. 5 ... 6 

CEnothera biennis, 6 

Mirabilis Jalapa, 6... 7 

Cereus grandiflorus, 7 ... 8 

484. Plants which expand their flowers in the evening, as some 
species of Hesperis, Pelargonium, &c., were called by Linnaeus plantce 
tristes on that account. Several species of Cooperia and of Cereus, also 
Sceptranthus Drummondii, are nocturnal flowers. Some flowers open 
and decay in a day, and are called ephemeral, others continue to open and 
close for several days before withering. The corolla usually begins to 
fade after fecundation has been effected. Many flowers, or heads of 
flowers, do not open during cloudy or rainy weather, and have been 
called meteoric. Composite plants frequently exhibit this phenomenon, 
and it has been remarked in Anagallis arvensis, which has hence been 



FERTILIZATION OR FECUNDATION. 235 

denominated the " poor man's weather-glass." The closing of many 
flowers in such circumstances protects the pollen from the injurious 
effects of moisture. 

485. The expansion and closing of flowers is regulated by light and 
moisture, and also by a certain law of periodicity. A plant accustomed 
to flower in day-light at a certain time, will continue to expand its 
flowers at the wonted period, even when kept hi a dark room. De- 
candolle made a series of experiments on the flowering of plants kept 
in darkness, and in a cellar lighted by lamps. He found that the law 
of periodicity continued to operate for a considerable time, and that 
in artificial light some flowers opened, while others, such as species 
of Convolvulus, still followed the clock hours in their opening and 
closing. 

486. Light has been said also to have an effect on the direction which 
flowers assume. Some Compositor, as Hypochasris radicata and Apar- 
gia autumnalis, are stated by Henslow to have been seen in meadows, 
where they abound, inclining their flowers towards the quarter of the 
heavens in which the sun is shining. A similar statement has been 
made regarding the Sun-flower, but it has not been confirmed in this 
country at least. Perhaps in its native clime, where the effect of the 
sun's rays is greater, the phenomenon alluded to may be observable. 
Vaucher mentions the effects of light on the direction of the flowers of 
many plants, as Narcissuses and certain species of Melampyrum. 

487. It is of importance, both as regards meteorology and botanical 
geography, that observations should be made carefully on what are 
called the annual and diurnal periods of plants : the former being the 
space of time computed between two successive returns of the leaves, 
the flowers, and the fruit; and the latter, the return of the hour of the 
day at which certain species of flowers open. The same species should 
be selected in different localities, and care should be taken that the 
plants are such as have determinate periods of flowering. Rules as 
to the mode of observing periodical phenomena in plants have been 
drawn up by the British Association, and a committee has been ap- 
pointed to carry this into effect. The committee has published (1.) a 
list of plants to be observed for the periods of foliation and defolia- 
tion ; (2.) a list of plants to be noticed for flowering and ripening of 
the fruit; (3.) a list of plants to be observed at the vernal and autum- 
nal equinoxes, and summer solstice, for the hours of opening and closing 
then: flowers. 

5. FUNCTIONS OF THE STAMENS AND PISTIL FERTILIZATION OR FECUNDATION. 

488. The stamens and pistil are called the Essential Organs of 
flowering plants, inasmuch as without them reproduction cannot be 
effected. The stamens, considered as the male organs, prepare the 



236 FERTILIZATION OR FECUNDATION. 

pollen, which is discharged by the dehiscence of the anther. The 
pistil, or the female organ, is provided with a secreting surface or 
stigma, to which the pollen is applied in order that the ovules con- 
tained in the ovary may be fertilized. 

489. The existence of separate sexes in plants appears to have been 
conjectured in early times, as shown by the means taken for perfecting 
the fruit of the Date Palm. In this palm, the stamens and pistils are 
on separate plants; and the Egyptians were in the habit of applying 
the sterile flowers to those in whicn the rudiments of the fruit appeared, 
in order that perfect dates might be produced. This practice appears 
to have been empirical, and not founded on correct notions as to the 
parts of the plant concerned in the process. In the case of the Fig, 
they were in the habit of bringing wild figs in contact with the culti- 
vated ones, on the erroneous supposition that a similar result was pro- 
duced as in the case of the Date, proving that they were not aware of 
the fact, that in the Fig there are stamens and pistils present on the 
same receptacle. The effect produced by the wild figs, or the process 
of caprification (caprificus, a wild fig-tree), as it was called, seems to 
depend on the presence of a species of Cynips, which punctures the 
fruit, and causes an acceleration in ripening. The presence of sexual 
organs in plants was first shown in 1676, by Sir Thomas Millington, 
and it was afterwards confirmed by Grew, Malpighi, and Ray. Lin- 
naeus made it the basis of his artificial system of classification. 

490. Numerous proofs have been given of the functions of the sta- 
mens and pistils, especially in the case of plants where these organs are 
in separate flowers, either on the same or on different plants. Thus, a 
pistilliferous specimen of Palm (Chamaerops humilis), in the Leyden 
Botanic Garden, which had long been unproductive, was made to pro- 
duce fruit by shaking over it the pollen from a staminiferous specimen. 
The same experiment has on several occasions been performed in the 
Botanic Garden at Edinburgh, and the fruit thus ripened has furnished 
seeds which have germinated. Similar results were observed in the 
case of the Pitcher plant. In Cucumbers, when the staminiferous 
flowers are removed, no perfect fruit is formed. Removing the sta- 
mens in the very early state of the flower, before the pollen is perfectly 
formed, prevents fertilization. Care must be taken, in all such experi- 
ments, that pollen is not wafted to the pistil from other plants in the 
neighbourhood, and the result must be put to the test by the germina- 
tion of the seed; in some instances, the fruit enlarges independently of 
the application of the pollen, without, however, containing perfect seed. 
Thus, a species of Carica was fertilized by the application of pollen, and 
produced perfect fruit and seed, and it continued for at least one year 
afterwards to have large and apparently perfect fruit, but the ovules 
were abortive. 

491. Some authors maintain, that in the case of Hemp, Lychnis 



FERTILIZATION OR FECUNDATION. 237 

dioica, and a plant called Coelebogyne, perfect seeds have been pro- 
duced without the influence of any substance equivalent to pollen ; but 
these statements have not as yet been confirmed. On the contrary, 
in Phanerogamus or flowering plants, all experiments lead to the con- 
clusion that there are distinct sexual organs. 

492. In Cryptogamous or flowerless plants, considerable doubts have 
been entertained as to the existence of such organs. There seem 
to be in this case cells of different kinds, which require to be brought 
into contact in order that spores (which are equivalent to seeds) may 
be produced. These reproductive cells are of two kinds, and they 
are situated either together or apart, on the same or on different 
individuals. One of these is the AnthericUum, a cellular body contain- 
ing granular matter, and Phytozoa (tpvTo*, a plant, and ioY, living), 
or minute bodies which exhibit movements ; the other is the Pistilli- 
dium or Archegonium (n%,'/j, beginning, and yovo;, offspring), containing 
spores which germinate, and which are some- 
times provided with cilia (figs. 431 434), 

so as to become Zoospores (00;, living, and 
(j~oox, a seed or spore), or moving spores. The 
contact of the Antheridium and PistiUidium 
is by many considered as necessary for the fer- 
tilization of the spore. In other cases, as in 
Conferva? and Diatomacese, there is a union of 
the cells of the plant by conjugation, so as to 
produce germinating bodies. In these cases, 
the contents of one cell pass, by the formation 
of a tube, into the other. In Zygnema, this 
conjugation gives rise to germinating bodies in 
the interior of one of the cells of the plant ; in Diatomaceas, on the 
outide of the cells. 

493. The union of two lands of endochrome (f^o, within, and ^^*, 
colour), or of two kinds of coloured particles, appears in these plants 
to give rise to the sporangium or spore-case, and the spore. Some- 
times the two kinds of endochrome are in separate plants, as already 
noticed, and then conjugation unites them, and causes a mixture of the 
endochrome; while in Meloseira, &c., the different kinds are apparently 
situated in different parts of the same cell, and movements take place 
towards the centre, by which their union is effected and a spore pro- 
duced. In Ferns, Mosses, &c., there have been detected separate cel- 
lular bodies, the union of which is considered necessary for the perfec- 
tion of the spores. In many Cryptogamic plants, besides this kind of 

Fig. 431 434. Spores of different fresh-water Alga. 
Fig. 431. Spores of a Conferva, with two vibratile cilia. 
Fig. 432. Spore of a Quetophora. with four cilia. 
Fig. 433. Spore of a Prolifera, with a circle of cilia. 
Fig. 434. Spore of a Vaucheria, covered with cilia. 




238 FERTILIZATION OR FECUNDATION. 

reproduction, there is also a formation of new cells by a constant 
process of fissiparous or merismatic division (f 24), which may be 
considered as analogous to the formation of buds, and which per- 
haps depends on certain changes similar to fecundation going on in 
the interior. 

494. In flowering plants, various provisions are made for insuring 
the application of the pollen to the stigma. The comparative length 
of the stamens and pistils, their position, and the dehiscence of the 
anthers, are all regulated with this view. The existence of spiral cells 
in the endothecium has reference apparently to the bursting of the 
anther, and the scattering of the pollen. The number of pollen-grains 
produced is also very great. Hassall says that a single head of Dande- 
lion produces upwards of 240,000, each stamen of a Pa3ony 21,000, a 
Bulrush 144 grams by weight. It has been stated, that a single plant 
of Wisteria sinensis produced 6,750,000 stamens, and these, if perfect, 
would have contained 27,000,000,000 pollen-grains.* In the case 
of Evergreens, such as Firs, the quantity of pollen is enormous, 
apparently to insure its application notwithstanding the presence of 
leaves. The pollen from pine forests has been wafted by the winds 
to a great distance, and is said to have fallen on the ground like a 
shower of sulphur. 

495. The quantity of pollen required for impregnation varies. 
Koelreuter says, that from fifty to sixty grains of the pollen of Hibiscus 
Trionum are required to fecundate the fruit completely, containing 
about thirty ovules. The ovary of Nicotiana, Datura, Lychnis, and 
Dianthus, according to Gartner, may be completely fertilized by the 
pollen of a single perfect anther. In Geum, from eight to ten 
anthers, out of eighty-four to ninety-six contained in each flower, are 
sufficient to fertilize from eighty to one hundred and thirty ovules 
contained in the ovary. 

496. In many trees in which the organs of reproduction are in 
separate flowers (as Hazel and Willow), the leaves are not produced 
until fertilization has been effected. The protection of the pollen from 
the direct influence of moisture, is effected by the closing of the flow- 
ers, by the elasticity of the anther-coat only coming into play in dry 
weather; and in aquatics, either by a peculiar covering, as in Zostera, 
or by the flowers being developed above water, as in Nymphaea, Lo- 
belia, Stratiotes, and Hottonia. In VaUisneria spiralis, a plant growing 

* The following estimate was made of the amount of flowers, stamens, &c., in a single specimen 
of Wisteria sinensis: 

Number of clusters of Flowers, 9,000 

individual Flowers, 675,000 

Petals, 3,375,000 

Stamens, 6,750,000 

Ovules, 4,050,000 

For the purpose of fertilizing these ovules, the anthers, if perfect, would have contained about 

27,000,000,000 pollen-grains, or about 7000 grains to each ovule. 



FERTILIZATION OE FECUNDATION. 239 

in the mud of ditches, the staminiferous plants are detached from the 
soil, float on the surface of the water, and produce there flowers and 
pollen ; while the pistilliferous plants send up a long peduncle (fig. 
228), which accommodates itself to the depth of the water by being 
spiral, and bears on its summit the flower with the pistil. By this 
means the two organs are brought into contact, and fertilization is 
effected. Lagarosiphon muscoides, an aquatic plant from Africa, shows 
similar phenomena in regard to impregnation as are seen in Vallis- 
neria. When continued wet weather comes on after the pollen has 
been matured, and has begun to be discharged, it often happens that 
little or no fruit is produced. In flowers where the anthers burst in 
succession, the injury done by moisture is less likely to extend to all. 

497. In some plants the stamens, at a certain period of their develop- 
ment, move towards the pistil, so as to scatter the contents of the anther. 
In Parnassia palustris and Rue, they do so in succession. In Kalmia, 
the anthers are contained in little sacs or pouches of the corolla, until 
the pollen is mature, and when the expansion of the corolla, and the 
elasticity of the filament, combine to liberate them, they spring towards 
the pistil with a jerk. In Parietaria officinalis, and in the Nettle, the 
spiral filament is kept in a folded state until the sepals expand, and 
then it rises with elastic force and scatters the pollen. Similar pheno- 
mena are observed in the Cornus canadensis. In the various species 
of Barberry, the inner and lower part of the filament is irritable, and 
when touched it causes the stamen to move towards the pistil. This 
takes place naturally when the anther is ripe, and the recurved valves 
covered with pollen are ready to be applied to the stigma. The species 
of Stylidium have their anthers and stigma seated on a column, the 
base of which is slightly swollen and irritable. When a stimulus is 
applied, this column passes with considerable force from one side of 
the flower to the other, rupturing the anther-lobes, and thus aiding in 
fertilization. 

498. In certain plants the agency of insects is employed to ensure 
fecundation. In species of Aristolochia, the tube of the calyx com- 
pletely encloses the organs of reproduction, and the stamens are placed 
below the stigma, so that the pollen can neither be applied directly, 
nor be carried by the winds. These plants are said to be frequented 
by insects, which enter the tubes and reach the little chamber at the 
base, with the view of collecting saccharine matter. The deflexed 
hairs in the interior of the tube prevent their escape, and in their 
movements they apply the pollen to the stigma. When this is accom- 
plished, the flower withers, and the insects escape. Orchidaceous 
plants have remarkable flowers, which resemble bees, flies, spiders, 
and in general the insects of the country in which they grow. They 
also contain a large quantity of honey-like matter connected with the 
essential organs, which attract insects. These insects, in searching for 



Z-1U FERTILIZATION OR FECUNDATION. 

food, detach the pollen masses, which are easily removed from the 
clinandrium, or the part of the column on which they are placed, and 
then naturally fall on the stigmatic surface. Bees and aphides may, 
in many instances, contribute to the process of fertilization. 

499. While the pollen is being elaborated, the stigma is also under- 
going changes. It secretes a viscid matter ready to detain the pollen- 
grains when they are discharged. This secretion was represented by 
Dr. Aldridge to be, in some cases, acid ; but it seems more generally 
to be of a mucilaginous or saccharine nature. Vaucher thinks that 
the nectariferous fluid usually found in the flower spreads itself over 
the stigma, and that it is sometimes instrumental in conveying the 
pollen-grains. In Goldfussia or Ruellia anisophylla, and the species 
of Campanula, as media, Eapunculoides, and Trachelium, the style is 
covered with collecting hairs, which appear to aid in the application 
of the pollen. In the first-mentioned plant, a remarkable curvation of 
the style takes place, so as to make the stigma come into contact with 
the hairs. In Campanula, the hairs on the upper part of the style 
seem to collect the pollen, and allow it to be applied to the revolute 
branches of the stigma. In this genus the style is at first slightly 
longer than the stamens, but it soon becomes twice their length, and 
during its elongation, the hairs xipon it brush the pollen-grains out of 
the anther cases, and thus raise them into a position where they can 
be applied ultimately to the stigmatic surface. The stigma consists of 
two branches, which are at first erect, but afterwards, by changes in 
the cells, become completely revolute, so as to come into contact with 
the hairs. After the hairs have performed their office, their fine inner 
membrane collapses by a process of endosmose, and the stiff outer 
membrane is drawn inwards, so as to retire within its cell. After the 
pollen reaches the stigma, changes take place in it, by which the fovilla 
contained in the intine of the grains is allowed to escape. This fovilla 
consists of minute molecules exhibiting certain movements, which by 
some have been considered analogous to those of phytozoa in Crypto- 
gamic plants, or spermatozoa in the animal kingdom. Others look 
upon these motions as entirely molecular. 

500. The length of time during which the pollen retains its vitality, 
or power of effecting fertilization, varies in different plants. Accord- 
ing to Gzertner and others, the pollen of some species of Nicotiana 
retains its vitality only for forty-eight hours ; pollen of various species 
of Datura, two days ; pollen of Dianthus Caryophyllus, three days ; 
pollen of Lobelia splendens, eight or nine days ; pollen of Cheiranthus 
Cheiri, fourteen days ; pollen of Orchis abortiva, two months ; pollen of 
Candollea, one year; pollen of Date Palm, one year or more. Michaux 
says, that in some Palms, as Date and Chamaarops humilis, the pollen 
may be applied successfully after having been carefully kept for 
eighteen years. The pollen retains its vitality longer when not removed 



THEORIES OF EMBRYOLOGY. 241 

from the anthers; and the finer it is, the more quickly it loses its 
fecundating property. 

501. Theories of Embryology. So far as the application of the pollen 
to the stigma is concerned, the process of fertilization can be easily 
traced, but the changes which are subsequently produced on the pollen- 
grain and the ovule are very obscure, require minute microscopic 
research, and have led to numerous conflicting theories of Embryology. 
It has been already stated, that some physiologists, especially Bernhardi, 
believe, that in the case of Hemp, Lychnis dioica, and some other 
plants, an embryo, or young plant, can be produced without the in- 
fluence of the pollen. These views have not been confirmed. It has 
been supposed that ha such plants as Hemp, where the stamens and 
pistil are generally on separate individuals, there may occasionally occur 
instances in which they are developed on the same plant. It is known 
that this takes place in other cases. Thus, a specimen of Chamserops 
humilis, or European Fan-palm, in the Botanic Garden of Edinburgh, 
which had for upwards of twenty years shown pistilliferous flowers only, 
exhibited, in 1847, both pistilKferous and staminiferous clusters,* and 
produced perfect fruit without an artificial application of pollen. Again, 
in Dioecious plants growing in the open air, the pollen may be carried 
from other plants by the wind, and thus produce perfect seed. There 
are thus numerous sources of fallacy in Bernhardi's observations ; and 
Gartner's recent experiments seem to prove that Hemp is no exception 
to the ordinary rule. Some, on the supposition of the correctness of 
Bernhardi's views, have thought that the case might be analogous to that 
of some Aphides, where one impregnation is sufficient to produce several 
generations. Mr. Smith has recently stated, that a female plant of 
Coelebogyne, belonging to the natural order of Euphorbiaccas, produced 
perfect seeds in the garden at Kew, without any apparent contact of 
pollen ; and Gasparrini maintains, that in the case of the cultivated 
Fig, the seeds are the product of pistillate flowers only. Such cases, 
if proved, will modify the views entertained relative to the action of 
pollen. Can it be that, as in the case of some Cryptogamics, there are 
in these anomalous cases two lands of cells present in the same organ, 
some with fertilizing matter, and others containing the rudiments of 
ovules, or of the embryo ? 

502. The subject of Embryology, or the development of the embryo 
in the seed, has attracted much attention of late, and numerous opinions 
have been advanced. There are many discrepancies as to the contents 
of the ovule before impregnation ; some maintaining that the cavity of 
the nucleus, or the embryo-sac alone, is developed before the pollen 
is applied ; others, that besides it there is a utricle, or vesicle, in its 
interior, which forms the first embryonic cell. The tubes in contact 

* It has clone so also in 1848. 
R 



242 THEORIES OF EMBRYOLOGY. 

with the ovule, are by some said to be derived from the pollen ; by 
others, from the ovule itself; and by a third set, from the conducting 
tissue of the style. 

503. Some maintain that the pollen-grains burst on the stigma, and 
scatter the fovilla directly upon it, the influence of which is conveyed by 
the conducting tissue to the ovule. Hartig seems to adopt this view 
in some cases, as well as Gasparrini, who, from observations on the 
Orange-tree and Cytinus, thinks that, as the result of this influence, 
a filament or cellular prolongation is sent from the lower extremity of 

the style into the ovule. Almost all 
modern physiologists discard this view, 
and believe in the formation of pollen- 
tubes, which were so ably demonstrated 
by Brown in Orchidaceas and Ascle- 
piadacea?, and have subsequently been 
shown by Schleiden, Amici, Brongniart, 
Meyen, Mohl, Mulder, Griffith, and 
others. These tubes, which vary in 
size, being often about 5 J U5 inch in 
diameter, may be easily traced in many 
instances, after the pollen has lain for a 
few hours on the stigma ; for instance, 
in Crocus, Salvia, Colocasia odora, Ges- 
nera, (Enothera and Antirrhinum (fig. 
434 bis). When an ovary, style, and 
stigma are present, the tubes pass into 
the conducting tissue, while in the case 
of naked ovules, as in Conifer se and 
Cycadaceae, the pollen comes into 
434 bis direct contact with the foramen. 

504. The extent to which the tubes penetrate, and the mode in 
which they give rise to the embryo, are matters of dispute. It is 
maintained by some, that the tubes formed by the intine proceed only 
to a certain extent down the style before rupturing to discharge the 
fovilla, so that the influence of the latter is subsequently conveyed to 
the ovule by the conducting tissue, and thus causes the formation of 
an embryo. Mirbel and Spach, from observations made on Gramineaj, 
as Zea Mais, and on the Yew and other Coniferae, have been led to 
support this view. They believe that the tube does not reach the 
ovule, that a primary utricle or vesicle (the first part of the embryo) 
exists in the embryo-sac, or cavity of the nucleus, before fertilization, 

Fig. 434 bis. Portion of the stigma of Antirrhinum majus at the time of fecundation. ps,ps, 
Superficial cells forming the papillse. tc, <c. Deep elongated cylindrical cells forming the con- 
ducting tissue. </]), Grains of pollen attached to the surface of the stigma, the extine having 
been ruptured, and the intine protruded in the form of tubes, tp, tp, which pierce the interstices 
between the superficial stigmatic cells. 




THEORIES OP EMBRYOLOGY. 243 

and that the fovilla is the means of determining the future development 
of an embryo in it. This utricle is attached to the embryo by a cellular 
process, or suspensor. Giraud entertains the same opinion, founded 
on an examination of the ovule of Tropaeolum majus. In this plant 
he traces the formation of the amniotic or embryo-sac, and primary 
utricle or germinal vesicle of the embryo, before impregnation, the 
latter being at first distinct from the sac, but subsequently attached to 
it by a suspensor ; the fovilla is brought into contact with the outer 
surface of the embryo-sac, and the first trace of the embryo appears in 
the formation of a spherical body at the inferior extremity of the pri- 
mary utricle, this spherical body resulting from a peculiar process of 
nutrition, determined by the dynamic influence of the fovilla. Giraud 
also observed a lengthening of the primary utricle and of its suspensor, 
so as to protrude through the apex of the embryo-sac the nucleus and 
the foramen, forming cells which partly communicate with the conduct- 
ing tissue, and partly passed round the ovule within the carpellary 
cavity. By slight traction of this cellular process, the suspensor with 
the embryo may be drawn from the embryo-sac through the exos- 
tome. 

505. Hartig thinks that in some cases, where the pollen-tube 
cannot be traced directly downwards to the ovule, there is a series 
of cells which, from their continuity, might be mistaken for it. In 
some recent observations on Campanula rotundifolia, Wilson appears 
to think that the pollen- tube is prolonged into the foramen of the 
ovule. Dickie has noticed, in Xarthecium ossifragum, and Euphrasia 
officinalis and Odontites, a cellular process proceeding upwards from 
the ovule into the style, which he thinks may unite with the pollen- 
tube. Through Dr. Dickie's kindness, I have had an opportunity of 
seeing these ovule tubes, which appear to end in shut extremities, and 
not to have a direct communication with the pollen-tubes. These tubes 
(less than ^ J 55 of an inch in diameter) have been traced by him from 
the interior of the embryo-sac. They are probably derived from the 
embryo itself, which, in its early state, may send out tubular prolonga- 
tions similar to those of the spores of Cryptogamic plants. Tubular 
prolongations from the ovule were long ago noticed by Mirbel, and of 
late years by Griffith and Hartig. These authors, however, seem to 
differ from Dickie, in supposing that the tubes are derived from the 
embryo-sac, or some of the coverings of the ovule. 

506. Another, or what may be called a third view of impregnation, 
is, that the pollen-tube does not stop short in the style, but proceeds 
as far as the foramen of the ovule, enters it, and is applied to the 
embryo-sac. In the case of the Misletoe, where there are no coverings 
of the ovule, and consequently no foramen, the pollen reaches the 
nucleus directly. Meyen, Amici, Mohl, Mulder, and Hofineister, are 
in favour of this theory. Meyen states, that after the pollen-tube 



244 THEORIES OF EMBRYOLOGY. 

becomes united to the ovule, in the form of a cul de sac, the process of 
absorption goes on so as to allow the fovilla to reach the embryo-sac. 
Immediately thereafter, a development of cells takes place in the form 
of a beaded prolongation or suspensor, at the extremity of which the 
embryo, in the form of a globular cell, is developed. The free com- 
munication between the pollen-tube and the embryo-sac ceases after 
a time ; a constriction takes place by the formation of a diagonal sep- 
tum, and the pollen-tube either shrivels or continues for some tune 
adherent to the sac. 

507. Amici also believes that the pollen-tube is applied to the sac 
of the embryo. He observes in the nucleus a large cavity, which he 
has called the embryonic vesicle (fig. 435 c). In Cucurbita Pepo and 
Orchidacese, he traces the tube to a certain depth into the nucleus, 
and he believes that the granular contents of the tube, which are 
accumulated at the extremity, are absorbed by the embryonic vesicle, 
so as to effect impregnation. Cells are then produced hi the vesicle, 

commencing at the base, i.e. opposite to the 
part where the pollen-tube exerts its influence. 
The vesicle becomes full of granular matter ; it 
then exhibits a contraction in the middle, the 
lower part becoming appropriated to the em- 
bryo, and forming the true embryo-sac, while 
the upper part, in such plants as Orchis Mono 
and mascula, elongates upwards (fig. 435 e), 
| forming a compound filament, composed of cells 
with fluid contents. This filament traverses 
in an inverse manner the course followed by the 
pollen-tube, and passes into the ulterior of the 
placenta, being quite distinct from the pollen- 
435 tube, and probably connected in some way 

with the nutrition of the embryo. Sometimes the pollen-tube re- 
mains after the embryo has multiplied its cells. Hartig thinks that, in 
different instances, the mode of impregnation is different. Thus he 
admits that the true pollen-tube comes into contact with the ovule 
in Coniferae, that in some Cruciferse the tubes in connection with the 
ovule are derived from the conducting tissue of the style, as main- 
tained by Gasparrini, while, in certain Cupuliferse, tubes proceed 
from some part of the ovule itself. 

508. A fourth theory is, that the pollen-tube (fig. 436 p f), after 
reaching the ovule, enters the foramen, ex and en, and then penetrates 
the embryo-sac, es, or pushes the sac before it, becoming thus en- 
closed in a reflection of it. This view is supported by Schleiden, 

Fig. 435. Ovule of Orchis mascnla, illustrating Amici's view of fertilization, a, Primine. 6, 
Secundine. c, Embryo. , Confervoid filament .which proceeds from the embryo towards the 
placenta, and is independent of the pollen-tube. 




THEORIES OF EMBRYOLOGY. 



245 




Wydler, Tulasne, Gelesnow, and Wilson. Schleiden, who has made 
a very elaborate series of observations on the embryo, is in favour of 
this view. According to him, the 
extremity of the pollen-tube does not 
enter the embryo-sac, but continues 
on the outside of it, pressing in the 
sac before it, and thus becoming sur- 
rounded by a double layer of it. The 
end of the pollen-tube (fig. 436 e) 
forms the germinal vesicle, in the 
interior of which nuclei and cells are 
produced, which ultimately give origin 
to the embryo. All the portion of 
the pollen-tube within the embryo-sac 
may be developed as the embryo, or 
a portion may remain in the form of 
a suspensor, or suspensory filament, 
attached to the upper part of the sac. 

509. Wydler, Gelesnow, and Tulasne, maintain that there is no 
indentation of the sac, but that the tube enters it directly. Schleiden 
thinks that this may be true in certain cases where the embryo-sac 
becomes elongated upwards, and then the membrane is absorbed so as 
to allow the pollen-tube to penetrate into the interior. Schleiden thus 
looks upon the embryo as a foreign body entering from without, and 
supports his views by cases of polyembryony in Coniferse, Cycadaceae, 
Misletoe, Onion, &c., where the plurality of embryos, according to him, 
depends on more than one pollen-tube having entered the foramen of 
the ovule. Wilson has adopted Schleiden's views, from observations 
made on Campanula rotundifolia. Tulasne, from examining the 
embryogeny of Veronica hederifolia, triphyllos, and prsecox, concurs 
in Wydler's views. Endlicher supports similar views with Schleiden, 
considering the stigma, however, as an organ, the peculiar secretion of 
which acts on the pollen-grain so as to render it capable of penetrating 
to the ovule, and developing an embryo. Unger's opinion nearly cor- 
responds with this. Griffith, from his researches on Viscum, Santalum, 
Osyris, and Loranthus, concludes, that the pollen-tube penetrates the 
embryo-sac or cavity, and passes through it longitudinally ; and he 
seems to think that, in some cases, the embryo proceeds from cells 
developed from the end of the tube. Klotszch states that pollen-tubes 
may be seen entering the embryo-sac in Lavatera tremestris, Tobacco, 
and some Orchidaceag, after the pollen has lain from twenty-four to 
thirty-six hours on the stigma. Hofmeister admits that the pollen- 



Fig. 436. Section of ovule to illustrate Schleiden's view of fertilization, r, Raphe. c *, 
Chalaza. p, Primine. s, Secundine. e x, Exostome. n, Endostome. n, Nucleus, e *, Em- 
bryo-sac, p t. Pollen-tube, e, The embryo formed by the extremity of the pollen-tube 



246 THEORIES OF EMBRYOLOGY. 

tube, in some cases where the embryo-sac is very delicate, pushes it 
inwards to a certain extent. 

510. Those who object to Schleiden's views, think that he has 
mistaken the primary utricle, or germinal vesicle, which exists in the 
embryo-sac before impregnation, for the end of the pollen-tube, and 
that the cellular filament attaching this to the embryo-sac is totally 
independent of the pollen-tube. Brown finds that, in the seed of 
Coniferous plants which have several embryos, there are semicylindrical 
corpuscles, three to six in number, which are arranged in a circle near 
the apex. In each of these is a distinct embryonal filament. These 
filaments frequently ramify, each of the ramifications terminating in an 
embryo. He believes that these corpuscles are not formed by the 
pollen-tubes, and that the fact of the ramifications giving rise to rudi- 
mentary embryos is opposed to Schleiden's views. The corpuscles lie 
dormant for at least twelve months before being developed. In a 
female plant belonging to Cycadaceae, another polyembryonous Order 
of plants, Brown has noted the formation of corpuscles at a time when 
no male flowers were known to exist in the country. These cor- 
puscles may probably be considered as analogous to embryo-sacs, or 
embryonal cavities, such as those in the Misletoe. 

oil. Some of the supporters of Schleiden's views institute a fanciful 
comparison between the spores of Cryptogamous, and the pollen of 
Phanerogamous plants. In the former, the cellular germinating body 
or spore is contained in a case or theca, just as the pollen-grains are 
in the anther of the latter. In the first instance, the body when dis- 
charged is at once fit for germination ; hi the second it requires to be 
transmitted to an ovary, and then to be matured within an ovule, and 
supplied with a store of nutritious matter, so as to be fitted for inde- 
pendent existence. These views are theoretical, and do not seem to 
be borne out by facts. 

512. It will thus be seen that physiologists are much divided in 
their views relative to this obscure subject ; and when we consider the 
minuteness of the observations, and the high microscopic powers re- 
quired, it is not a matter of surprise that there are numerous sources 
of fallacy. Nearly all agree in the formation of pollen-tubes ; these, 
according to some, end hi the cellular tissue of the style ; according 
to others, they reach the ovule ; the influence of the fovilla is com- 
municated to the ovule either directly or indirectly ; the first cells of 
the embryo, some maintain, are formed by the end of the pollen-tube 
directly, while others say indirectly ; and a third party consider them 
as the result of changes induced by the action of the fovilla. 

513. The opinions which have been recently supported by Amici, 
Mohl, Karl Mulder, and Hofmeister, are those which seem to rest on 
the best foundation, viz., that at the tune of the opening of the flower 
the embryo-sac exists, and that, at its upper or micropyle end, one or 



THEORIES OF EMBRYOLOGY. 247 

more cells or germinal vesicles are produced from cytoblasts ; that the 
pollen-tubes pass down the style to the ovary into the foramen of the 
ovule, and come into contact with the embryo-sac, either at its apex 
or a little below it; then an imbibition of fluids takes place, the 
embryo-sac begins to increase, and the embryo is produced. The 
chief point to be determined, is the existence or not of the germinal 
vesicle before impregnation. 

514. The formation of the process called the suspensor is variously 
accounted for. Schleiden considers it as a part of the pollen-tube ; 
Amici thinks that it is part of the embryo-sac prolonged upwards, 
forming a confervoid filament (fig. 435 e); Mohl, Mirbel, and Spach 
maintain that the suspensor is produced from the germinal vesicle, and 
therefore intimately united to the embryo, which is developed from 
the lowest cells of that vesicle ; Dickie thinks that the suspensor may 
be a cord-like process sent out from the cellular embryo, reaching a 
certain degree of development, and sometimes sending off tubular 
prolongations or filaments, as in Euphrasia and Orchidacea?. The 
suspensor is usually directed to the apex of the nucleus or the micro- 
pyle, and it is sometimes of great length. In Draba verna (fig. 485, 2), 
Dickie says he observed in an embryo, ^n f an mcn ^ on g' a suspensor 
three times that length. In Gnetum, Griffith mentions a tortuous 
suspensor 3 J to 5 inches long, the whole seed being only one inch long. 

515. Taking a comprehensive view of the whole subject, it may be 
said that the union of two kinds of cells appears to be necessary for 
fertilization. In Cryptogamic plants this has been traced, particularly 
in certain cases of conjugation ; where the two cells come into contact, 
a tube is formed between them, and the contents of the one unites 
with those of the other, giving rise to a germinating body. In Phane- 
rogamic plants, also, there are two cells with different contents the 
pollen-grain with its granular fovilla, and the ovule with its muci- 
laginous fluid. These are brought into connection by means of the 
pollen-tube, formed from the intine, which either enters the embryo- 
sac, or comes into contact with it, the union taking place either 
directly by its extremity, or indirectly by cellular prolongations from 
the conducting tissue, or from the ovule. By this means the forma- 
tion of the embryo is determined, which commences as a cellular body 
or germinal vesicle, in the interior of which other cells are subse- 
quently formed in a definite order of succession.* 

* For opinions as to Embryology, see Schleiden's paper in Nova acta Academ. C:vsar. Leppold- 
Corol. Naturae Curios.; Brown on the Fecundation of Orchidaceie and Asclepiadaceze, in the 
Transactions of the Linnaean Society for 18:J3 ; Brongniart on the same subject, in Annales des 
Sciences Natnrelles, 1st series, torn, xxiv., 1831; Meyen on the Act of Impregnation, translated in 
Taylor's Scientific Memoirs, vol. iii. ; Amici sur la Fe"eondation des Orchide'es, in Annales des 
Sciences Naturelles, 3d series, torn. vii. ; Wilson on Tropseolum majus, and Hairs of Campanula, 
London Journal of Botany, voL ii. ; Giraud on Embryology, in the Transactions of the Edinburgh 
Botanical Society, and in the Annals of Natural History, vol. v. ; and on the Ovule of Tropa:o- 
lum, in Linnseau Transactions, vol. xlx. ; Henfrey and Dickie on Embryology, in the Annals of 
Natural History for 1848; Griffith on the Ovule of Santalum, Osyris, &c., in Linnsean Trans- 
actions, vol. xix. ; also Notulae ad Plantas Asiaticas, Calcutta, 1847. 



248 PRODUCTION OF HYBRIDS. 

516. The Production of Hybrids. If the pollen of one species is 
employed to fertilize the ovules of another, the seed will often produce 
plants strictly intermediate between the two parents. These are termed 
hybrids, and are analogous to mules in the animal kingdom. As a 
general rule, hybrids can only be produced between plants which are 
very nearly allied, as between different species of the same genus. 
Thus, different species of Heath, Fuchsia, Cereus, Rhododendron, and 
Azalea, readily inoculate each other, and produce intermediate forms. 
It is found, however, that species which seem to be nearly related do 
not hybridize. Thus, hybrids are not met with between the Apple 
and Pear, between the Goosberry and Currant, nor between the Rasp- 
berry and Strawberry. The ovules of Fuchsia coccinea, fertilized 
with the pollen of Fuchsia fulgens, produce plants having intermediate 
forms between these two species. Some of the seedling plants closely 
resemble the one parent, and some the other, but they all partake more 
or less of the characters of each. By the examination of the foliage, 
conclusions may be drawn as to what will be the character of the flower. 
Mr. Thwaites mentions a case in which a seed produced two plants 
extremely different in appearance and character ; one partaking rather 
of the character of Fuchsia fulgens, and the other of Fuchsia coccinea. 

517. In the case of hybridization, there appears to be a mixture of 
matters derived from the pollen-grain and the ovule, just like the 
mixture of two endochromes in flowerless plants ; and the nature of 
the hybrid depends on the preponderance of the one or other. Some 
have supposed that the pollen-grains require to be of the same form 
and dimension, in order to admit of artificial union taking place ; but 
this is a mere conjecture. Hybrids perform the same functions as 
their parents, but they do not perpetuate themselves by seed. If not 
absolutely sterile, at first, they usually become so in the course of the 
second or third generation. Herbert mentions instances of hybrid 
Narcissuses, from which he attempted in vain to obtain seed. The 
cause of this sterility has not been determined. Some have referred it 
to an alteration in the pollen. Hybrids may be fertilized, however, 
by the pollen taken from one of the parents, and then the offspring 
assumes the characters of that parent. 

518. Hybrids are rarely produced naturally, as the stigma is more 
likely to be affected by the pollen of its own stamens than by that 
of other plants. In dioecious plants, however, this is not the case, 
and hence the reason probably of the numerous so-called species 
of Willows. Hybrids are constantly produced artificially, with the 
view of obtaining choice flowers and fruits, the plants being propa- 
gated afterwards by cuttings. In this way many beautiful Roses, 
Azaleas, Rhododendrons, Pansies, Cactuses, Pelargoniums, Fuchsias, 
Calceolarias, Narcissuses, &c., have been obtained. By this process of 
inoculation, and carefully selecting the parents, gardeners are enabled 



FRUIT OR MATURE PISTIL. 249 

to increase the size of the flowers, to improve their colour, to render 
tender plants hardy, and to heighten the flavour of fruits. Herbert 
thinks, from what he saw in Amaryllides, that in hybrids the flowers 
and organs of reproduction partake of the characters of the female 
parent, while the foliage and habit, or the organs of vegetation, resem- 
ble the male. 

519. This subject is important as connected with the origin and 
limitation of species. If, as some of the old authors believed, there 
were only a few species originally formed, and all the rest are the result 
of hybridization, there appears to be no limit to species, and no perma- 
nence in their characters. This, however, is not borne out by facts ; 
the generally received opinion being, that types of all the species now 
in existence were originally placed on the globe, and that these have 
given origin to an offspring like themselves, capable of reproducing 
the species. Hybrids, on the other hand, are rare in a wild state, and 
they are seldom permanent and fertile. Even where they are so, there 
seems to be a tendency in the offspring to return to one or other of 
the original types from which they sprung. 

6. FRUIT, OR THE PISTIL, ARRIVED AT MATURITY. 

520. After fertilization, various changes take place in the parts of 
the flower. Those more immediately concerned in the process, the 
anther and stigma, rapidly wither and decay, while the filaments and 
style often remain for some time ; the floral envelopes also become dry, 
the petals fall, and the sepals are either deciduous or remain persistent 
in an altered form ; the ovary becomes enlarged, forming the pericarp 
(-7ft $, around, and KX^OS, fruit) ; and the ovules are developed as the 
seeds containing the embryo-plant. The term fruit is strictly applied 
to the mature pistil or ovary, with the seeds in its interior. But it 
often includes other parts of the flower, such as the bracts and floral 
envelopes. Thus, the fruit of the Hazel and Oak consists of the ovary 
and bracts and calyx combined ; that of the Apple, Pear, and Goose- 
berry, of the ovary and calyx; and that of the Pine-apple, of the ovaries 
and floral envelopes of several flowers combined. Fruits formed by 
the ovaries alone, as the Plum and the Grape, seem to be more liable 
to drop off and suffer from iuifavourable weather, than those which have 
the calyx entering into their composition, as the Gooseberry, the Melon, 
and the Apple. 

521. In general, the fruit is not ripened unless fertilization has been 
effected ; but cases occur in which the fruit swells, and becomes to all 
appearance perfect, while no seeds are produced. Thus, there are 
seedless Oranges, Grapes, and Pine-apples. "When the seeds are abor- 
tive, it is common to see the fruit wither and not come to maturity; but 
in the case of Bananas, Plantains, and Bread-fruit, the non-develop- 



250' FRUIT OR MATURE PISTIL. 

raent of seeds seems to lead to a larger growth, and a greater succu- 
lence of the fruit. 

522. In order to comprehend the structure of the fruit, it is of great 
importance to study that of the ovary in the young state. It is in this 
way only that the changes occurring in the progress of growth can be 
determined. The fruit, like the ovary, may be formed of a single 
carpel, or of several It may have one cell or cavity, then being uni- 
locular (MWWS, one, and loculus, box or cavity) ; or many, multilocular 
(multus, many), &c. The number and nature of the divisions depend 
on the number of carpels, and the extent to which their edges are 
folded inwards. The appearances presented by the ovary do not, how- 
ever, always remain permanent in the fruit. Great changes are ob- 
served to take place, not merely as regards the increased size of the 
ovary, its softening and hardening, but also in its internal structure, 
owing to the suppression, enlargement, or union of parts. In this way 
the parts of the fruit often become unsymmetrical, that is, not equal to, 
or some multiple of, the parts of the flower ; and at times they are 
developed more in one direction than another, so as to assume an irre- 
j gular appearance. In the Ash (fig. 437), an ovary with two 
cells, each containing an ovule attached to a central placenta, 
is changed into a unilocular fruit with one seed ; one ovule, 
I, having become abortive, and the other, g, gradually extend- 
ing until the septum is pushed to one side, becoming united 
to the walls of the cell, and the placenta appearing to be parietal. 
In the Oak and Hazel, an ovary with three cells, and two ovules 
in each, changes into a one-celled fruit with one seed. Simi- 
lar changes take place in the Horse-chestnut, in 
which the remains of the abortive ovules are often 
seen in the ripe fruit. In the Coco-nut, a trilocular 
and triovular ovary is changed into a one-celled, 
one-seeded fruit. This abortion may depend on the 
pressure caused by the development of certain ovules, 
or it may proceed from the influence of the pollen 
not being communicated to all the ovules. Again, 
by the growth of the placenta, or the folding inwards 
of parts of the ovary, divisions may take place in the fruit which did not 
exist in the ovary. In Pretrea Zanguebarica, a one-celled ovary is 
changed into a four-celled fruit by the extension of the placenta. In 
Cathartocarpus Fistula (fig. 395), a one-celled ovary is changed into a 
fruit having each of its seeds in a separate cell, in consequence of spu- 
rious dissepiments being produced in a horizontal manner from the inner 





FRUIT OR MATURE PISTIL. 



251 




wall of the ovary after fertilization. In Tribulus terrestris, each cell of 
the ovary (fig. 438) has slight projections, c, on its walls, interposed 
between the ovules, o, which, when the fruit is 
ripe, are seen to have formed distinct transverse 
divisions (fig. 439 c), or spurious dissepiments, 
separating the seeds, g. In Astragalus, the 
folding of the dorsal suture inwards converts a 
one-celled ovary into a two-celled fruit. 

523. The development of cellular or pulpy 
matter frequently makes great changes in the 
fruit, and renders it difficult to discover its for- 
mation. In the Strawberry, the axis becomes succulent, and bears 
the carpels on its convex surface; in the Rose, there is a fleshy lining 
of the calyx (sometimes called a disk), which bears the carpels on its 
concave surface. In the Gooseberry, Grape, Guava, Tomato, and 
Pomegranate, the seeds nestle in pulp formed apparently by the 
placentas. In the Orange, the pulpy matter surrounding the seeds is 
formed by succulent cells, which are produced from the inner lining 
of the pericarp. 

524. The pistil, in its simplest state, consists of a carpel or folded 
leaf, with ovules at its margin; and the same thing will be found in the 
fruit, where the pericarp, as in the Bean (fig. 440), 

represents the carpellary leaf, and the seeds corre- 
spond to the ovules. The pericarp consists usually 
of three layers: the external (fig. 440 e), or epicarp 
(tTTi, upon, or on the outside, xajTro?, fruit), cor- * ' 
responding to the lower epidermis of the leaf; the 
middle (fig. 440 TO), or mesocarp (f^saof, middle), 
representing the parenchyma of the leaf; and the 
internal (fig. 440 ), or eridocarp (ivlw, within), 
equivalent to the upper epidermis of the leaf, or 
the epithelium of the ovary. In some plants, as 
Colutea arborescens, the pericarp retains its leaf- 
like appearance, but in most cases it becomes al- 
tered both in consistence and in colour. Sometimes the three parts 
become blended together, as in the Nut ; at other times, as in the 
Peach, they remain separable. In the latter fruit, the epicarp is thick- 
ened by the addition of cells, and can be taken off in the form of what 
is called the skin; the mesocarp becomes much developed, forming the 

Fig. 438. Cell or loculament of the ovary of Tribulus terrestris, out vertically, to show the 
commencement of the projections, c, from the paries, which are interposed between the ovules, o. 

Fig. 439. The same in a mature state, showing the transverse partitions, c, dividing the fruit 
into cavities, in one of which a seed, g, is left. 

Fig. 440. Lower portion of the carpel or legume of the Bean, Faba sativa, cut transversely, to 
show the structure of the pericarp, e, Epicarp, or external epidermis, m, Mesocarp. n, Endo- 
carp. s d, Dorsal suture, s v, Ventral suture, g, A seed situated at the upper part of the sec- 
tion, and cut also transversely. 



e -- 

7H-- 

n 




252 FKUTT OR MATURE PISTIL. 

flesh, or pulp, and hence has sometimes been called sarcocarp (Wj , 
flesh), while the endocarp becomes hardened by the production of 
woody cells, and forms the stone or putamen (putamen, a shell), imme- 
diately covering the kernel or the seed. The same arrangement is 
seen in the fruit of the Cherry, Apricot, and Plum. In these cases, 
the mesocarp is the part of the fruit which is eaten. In the Almond, 
on the other hand, the seed is used as food, while the shell or endo- 
carp, with its leathery covering or mesocarp, and its greenish epicarp, 
are rejected. The pulpy matter found in the interior of fruits, such as 
the Gooseberry, Grape, and Cathartocarpus Fistula (fig. 395), is formed 
from the placentas, and must not be confounded with the sarcocarp. 

525. In the Date, the epicarp is the outer brownish skin, the pulpy 
matter is the mesocarp or sarcocarp, and the thin papery-like lining is 
the endocarp covering the hard seed. In the Pear and Apple, the outer 
skin or epicarp is composed of the epidermis of the calyx, combined with 
the ovary ; the fleshy portion is the mesocarp, formed by the cellular 
portion of the calyx and ovary 5 while the scaly layer, forming the 
walls of the seed-bearing cavities in the centre, is the endocarp. In 
the Medlar (fig. 472), the endocarp becomes of a stony hardness. In 
the Melon, the epicarp and endocarp are very thin, while the mesocarp 
forms the bulk of the fruit, varying in its texture and taste in the ex- 
ternal and internal part. The rind of the Orange consists of epicarp 
and mesocarp, while the endocarp forms partitions in the interior, filled 
with pulpy cells. 

526. Thus, while normally the divisions of the fruit ought to indi- 
cate the number of the carpels composing it, and these carpels should 
each have three layers forming the walls, it is found that frequently the 
divisions of a multilocular fruit are atrophied or absorbed, in whole or 
in part, and the layers become confounded together, so that they 
appear to be one. Again, in fruits formed of several carpels, the 
endocarp and mesocarp are occasionally so much developed as to leave 
the epicarp only on the free dorsal face of the fruit, forming a covering 
which is wholly external, as in the Castor-oil plant, Euphorbia, and 
Mallow. Occasionally, the endocarp remains attached to the centre, 
forming cells, in which the seeds are placed, while the outer layer 
separates from it at certain points, and leaves a row of cavities in the 
substance of the pericarp itself. 

527. While in many fruits the calyx becomes incorporated with the 
pericarp, there are others in which it is closely applied to the ovary, 
but still separable from it. Thus, in the fruit of Mirabilis Jalapa 
(fig. 441, 1), when a section is made longitudinally (fig. 441, 2), the 
hardened calyx, c c, is observed distinct from the fruit, f, which is in 
this instance incorporated with the seed, but at once distinguished by 
its style, s. The same thing occurs in Spinacia or Spinach. Again, 
in Hippophae rhamnoides, and in the Yew (fig. 442), there is an exter- 



FRUIT OR MATURE PISTIL. 



253 



nal succulent covering, zc, formed by modified bracts, which here occupy 
the place of a pericarp, and display the seed, <?, which is naked, because 
not contained in a true ovary with a style and stigma. 






441, 1 



441, 2 



528. The part of the pericarp attached to the peduncle is called its 
base, and the part where the style or stigma existed is the apex. This 
latter is not always the mathematical apex. In AlchemiUa, Labiata?, 
and Boraginaceas, it is at the base or side (figs. 400, 401, 402). The 
style sometimes remains in a hardened form, rendering the fruit apicu- 
late; at other times it falls off, leaving only traces of its existence. The 
presence of the style or stigma serves to distinguish certain single- 
seeded pericarps from seeds. 

529. As in the case of the carpel, so in the mature ovary formed 
of it, the edges unite towards the axis, and constitute the ventral 
suture (fig. 443 s v), while the back, corresponding 

with the midrib, is the dorsal suture (fig. 443 s d). The 
inner suture, in some fruits formed of a single carpel, as 
the Apricot and Bladder senna, is marked by a distinct 
furrow or depression, consequent on the folding in- 
wards of the carpellary edges; and occasionally the 
outer or dorsal suture is also thus rendered distinctly 
visible. When the fruit consists of several mature 
carpels, all meeting in the centre, and united together, 
then the dorsal suture is also visible externally; but 
in cases where the placentation is parietal or free cen- 
tral, then the edges of the separate carpels, being near the surface, may 
present also externally the marks of the ventral sutures. 




Fig. 441. Fruit of Mirabilis Jalapa. 1. Entire. 2. Cut longitudinally, to show its composi- 
tion, c c, Lower part of calyx hardened, and forming an outer envelope. /, The true fruit, 
covered by the calyx. The integuments of the fruit are incorporated with those of the seed, 
which has been also cut. The fruit is distinguished by the remains of the style, s, at the api- 
culus or summit 

Fig. 442. Fruit of Taxus baccata, the Yew. 6, Imbricated bracts at its base, i c, Fleshy 
envelope taking the place of the pericarp. This envelope covers the seed, g, partially, leaving 
its apex naked. 

Fig. 443. A single carpel of Helleborns foetidus after dehiscence. s rf, Dorsal suture. v, 
Ventral suture. The carpel, when mature, opens on the ventral suture, and forms the fruit 
denominated a follicle. 




254 DfDEHISCENT AND DEHISCENT FRUITS. 

530. Where the sutures are formed, there are usually two bundles 
of fibro-vascular tissue (fig. 443), one on each edge. The edges of the 
sutures are often so ultimately united, as not to give way when the fruit 
is ripe. In this case it is called indehiscent (in, used in the sense 

of not, and dehisco, I open), as in the Acorn and Nut; at 
other times the fruit opens between the two vascular bundles, 
either at the ventral or dorsal suture, so as to allow the 
seeds to escape, and then it is dehiscent (dehisco, I open). 
By this dehiscence the pericarp becomes divided into dif- 
ferent pieces, which are denominated valves, the fruit being 
univalvular, Uvalvular, or multivalvular, &c., according as 
there are one, two, or many valves. These valves separate 
either completely or partially. In the latter case, the divi- 
sions may open in the form of teeth at the apex of the fruit, 
the dehiscence being apicular, as in Caryophyllacece (fig. 
444 v), or as partial slits of the ventral suture, when the 
carpels are only free at the apex, as in Saxifrages. 

531. indchiscent Fruits are either dry, as the Nut, or fleshy, as the 
Cherry and Apple. They may be formed by one or several carpels ; 
and in the former case they usually contain only a single seed, which 
may become so incorporated with the pericarp as to appear to be naked. 
Such fruits are called pseudo-spermous (\^iv^f, false, and aTri^x, seed), 
or false-seeded, and are well seen in the gram of Wheat. In such 
cases the presence of the style or stigma determines their true nature. 

532. i>< iii. ni Fruits, when composed of single carpels, may open 
by the ventral suture only, as in the follicles of Pseony; by the dorsal 
suture only; or by both together, as in the legume of the Pea and 
Bean; in which cases the dehiscence is called sutural. When composed 
of several united carpels, the valves may separate through the dissepi- 
ments, so that the fruit will be resolved into its original carpels, as in 
Rhododendron, Colchicum, &c. This dehiscence, in consequence of 
taking place through the lamella of the septum, is called septicidal 
(septum and ccedo, I cut) (figs. 445, 446). The valves may separate 
from their commissure, or central line of union, carrying the placentas 
with them, or they may leave the latter in the centre, so as to form 
with the axis a column of a cylindrical, conical, or prismatic shape, 
which has received the designation of columella (fig. 447 c). The 
union between the edges of the carpels may be persistent, and they 
may dehisce by the dorsal suture, or through the back of the locula- 
ments, as in the Lily and Iris (fig. 448). In this case the valves are 
formed by the halves of the cells, and the septa either remain united 
to the axis, or they separate from it, carrying the placentas with them 

Fig. 444. Capsule or dry seed-vessel of Cerastium viscosum after dehiscence. c, Persistent 
calyx, p, Pericarp dividing at the apex, r, into ten teeth, which indicate the summits of as 
many valves united below. 



DEHISCENT FRUITS. 



255 



(fig. 449), or leaving them in the centre. This dehiscence is loculicidal 
(locuhtfj cell, and ccedo, I cut). Sometimes the fruit opens by the 
dorsal suture, and at the same time the valves or walls of the ovaries 
separate from the septa (fig. 450), leaving them attached to the centre, 




as in Datura. This is called septifragal dehiscence (septum and frango, 
I break), and may be looked upon as a modification of the loculicidal. 
The separation of the valves takes place either from above downwards 
(fig. 450), or from below upwards (fig. 451). 

Fig. 445. Capsule of Digitalis purpurea at the moment of dehiscence, when the two cavities, 
c c, separate by division of the septum, d d, so as to have the appearance of distinct carpels. At 
the apex are seen the seeds, y. 

Fig. 446. Inferior portion of the same capsule cut transversely, to show the formation of the 
septum, d, formed by the two inner faces of the carpels, c c. pp, Placentaries reflected and pro- 
jecting into the interior of the cavities, g, Seeds. 

Fig. 447. Capsule (tricoccous regma) of Kieinus communis, Castor-oil plant, at the moment of 
dehiscence. The three carpels or cocci, c c c, are separated from the axis, a, by which they were 
at first united (see fig. 453), and which remains in a columnar fora. These cocci begin to open 
by their dorsal suture, s d. 

Fig. 448. Capsule of Iris opening by loculicidal dehiscence. 

Fig. 449. Capsule of Hibiscus esculcntus, showing also loculicidal dehiscence. v v v, Valves of 
the seed-vessel, <, Septum or partition. </, Seeds. 

Fig. 450. Capsule of Cedrela angustifolia, the valves of which, v v v, separate from the septa, 
c c, by septifragal dehiscence. The separation takes place from above downwards, in such a 
manner that the axis, a, remains in the centre, with five projecting angles, corresponding to the 
septa, ff, The seeds contained in the loculaments. 



256 



DEHISCENT FRUITS. 



533. Sometimes the axis is prolonged as far as the base of the styles, 
as in the Mallow (fig. 452), and Castor-oil plant (fig. 453), the carpels 
being united to it by their faces, and separating 
from it without opening. In the Umbelliferae 
(fig. 454), the two carpels separate from the lower 
part of the axis, and remain attached to a pro- 
longation of it, called a carpophore (xtt^vo;, fruit, 
and &&>, I bear), or podocarp (-noii;, foot, and 
x^os, fruit), which splits into two (fig. 454 a). 
and suspends them. Hence the name cremocarp 
(x.^/ndu, I suspend), applied to this fruit. In 
4? Geraniaceae, the axis is prolonged beyond the 
carpels, forming a carpophore, to which the styles 
are attached, and the pericarps separate from 
below upwards, before dehiscing by their dorsal 
suture (fig. 455). Carpels of this kind are 
called cocci (X.OXX.GS, seed, berry), and the fruit is said to be tncoccous, 
&c., according to the number of separate carpels. In the case of many 
Euphorbiaceae, as Hura crepitans, the cocci separate with great force 
and elasticity, the cells being called dissilient (dissilio, I burst). 





1.-.3 



534. In the Siliqua or fruit of Cruciferse, as Wallflower (fig. 456), 
the valves separate from the base of the fruit, leaving a central repluin 
or frame, r. The repluin is considered as being formed by parietal 
placentas, which remain attached to the fibro- vascular line of the 
suture, the valves giving way on either side of the suture. In Orchi- 
daceae (fig. 457), the pericarp, when ripe, separates into three valves, 

Fig, 45L Capsule of Swietenia Slahagoni, opening by valves from below upwards. The letters 
have the same signification as in fig. 450. 

Fig. 452. Fruit of Malva rotundifolia, with half the carpels comprising it removed, to show 
the axis, a, to which they are attached. This axis ends at the point where the style, s, is pro- 
duced, c <, The carpels which are left attached to the axis, around which they are arranged in 
a verticillate manner. The lateral surface of the two carpels in front, f, is exposed. 

Fig. 453. Tricoccous capsule of Kicinus communis, Castor-oil plant, cut vertically, to show 
the axis, a, prolonged between the carpels, and terminating by small cords or funicuU, /, which 
project into the loculaments, and are attached to seeds, g g, Seeds exposed, each surmounted by 
a fleshy caruncula, c . p p, Pericarp. 

Fig. 454. Fruit or cremocarp of Prangos uloptera, an umbelliferous plant. The carpels, 
meriearps, or achsenia, c c, separate from the axis, a, and are each suspended by a carpophore. 
* , Persistent styles with swollen bases, forming an epigynous disk. 



DEHISCENT FRUITS. 



257 



by giving way only on the margins within the sutures, where the 
placentas are united ; and when the valves fall off, the placentas are 
left in the form of three arched repla or frames, to which the seeds 
are attached. In the case of a free central placenta, when the valves 






separate, it is sometimes difficult to tell whether the dehiscence is 
septicidal or loculicidal, inasmuch as there are no dissepiments, and 
the placentas and seeds form a column in the axis. Their number, 
as well as their alternation or opposition, as compared with the sepals, 
will aid in determining whether the valves are the entire carpeUary 
leaves, as in septicidal dehiscence, or only halves united, as in loculi- 
cidal. In some instances, as in Linum catharticum, the fruit opens 
first by loculicidal dehiscence, and afterwards the carpels separate in 
a septicidal manner. 

535. Another mode in which fruits open is transversely, the dehis- 
cence in this case being called circumscissile (circum, around, and 
stindo, I cut). In such cases, the fruit or seed-vessel may be supposed 
to be formed by a number of articulated leaves like those of the 
Orange, the division taking place where the laminae join the petioles. 
In this dehiscence, the upper part of the united valves falls off in the 
form of a lid or operculum, as in Anagallis (fig. 458), and in Hyos- 
cyamus (fig. 459), and hence the fruit is often denominated operculate 
(operculum, a lid). In some instances the axis seems to be prolonged 

Fig. 455. Fruit or mature carpel of Geranium sanguineum. c, Persistent calyx, o, Axis 
prolonged as a beak. 1 1, The styles, at first united to the beak, and afterwards separating from 
below upwards, along with the carpels, o o, which dehisce by their dorsal suture, s. Stigmas. 
The fruit is sometimes called gynobasic. 

Fig. 456. Siliqua of Cheiranthus Cheiri, Wallflower, dehiscing by two valves, v v, which 
separate from a frame or replum, r. gr, Seeds arranged on either margin, s, Two-lobed stigma. 

Fig. 457. Capsule of Orchis maculata at the period of dehiscence. c, Remains of the limb of 
the calyx crowning the fruit v v, Segments of the pericarp which are detached in the form ot 
valves, p p, Arched repla or placentas which remain persistent, and bear the seeds. 

S 



258 



DEHISCENT FRUITS. 




in the form of a hollow cup, and the valves appear as leaves united to 
it by articulation, similar to what occurs in the calyx of Eschscholtzia. 

In Lecythis, or the Monkey -pot, and 
in Couratari, the calyx is adherent 
to the seed-vessel, and the lid is 
formed at the place where the tube 
of the calyx ceases to be adherent. 

536. Transverse divisions take 
place occasionally in fruits formed 
by a single carpel, as in the pods 
of some leguminous plants. Exam- 
ples are met with in Ornithopus, Hedysarum (fig. 460), Coronilla, &c., 
in which each seed is contained in a separate division, the partitions 
being formed by the folding in of the sides of the pericarp, and distinct 
separations taking place at these partitions, by what has been termed 
solubility. Some look upon these pods as formed by pinnate leaves 

folded, and the divi- 
sions as indicating the 
points where the dif- 
ferent pairs of pinnre 
are united. Others 
do not admit this ex- 
planation, but regard 
the legume or pod 
as formed by the ex- 
-F W^ii^.l^i. panded midrib or pe- 
tiole, and the pimue 
as represented by the 
seeds. Dehiscence may 
also be effected by partial openings in the pericarp, called pores, 
which are situated either at the apex, base or side. In the Poppy (fig, 
409), the opening takes place by numerous pores under the peltate 
processes bearing the stigmas. In Campanulas, there are irregular 

Fig. 458. Pyxidium or capsule of Anagallis arvensis, opening by circumscissile dehiscence. 
c, Persistent calyx, p, Pericarp divided into two, the upper part, o, separating in the form of a 
lid or operculum. On the capsule are seen three lines passing from the base to the apex, and 
marking the true valves, g, Seeds forming a globular mass round a central placenta. 

Fig. 459. Operculate capsule or Pyxidium of Hyoscyamus niger. Henbane, o, Operculum or 
lid separating and allowing the seeds to appear. 

Fig. 460. Lomentaceous legume or lomentum of Hedysarum coronarium. 1. Entire, the 
upper division being nearly detached from the rest. 2. Two of the joints cut longitudinally to 
show the spurious loculaments, each containing a seed. This seed-vessel divides into separate 
single-seeded portions by solubility. 

Fig. 461. Capsule of Campanula persicifolia, opening by holes or pores, 1 1, above the middle, 
c, Persistent calyx, incorporated below with the pericarp, p, and separating above into five 
acute segments, in the midst of which is seen the withered and plaited corolla in the form of 
induvias, e. The holes perforate the walls of the pericarp and the calyx. 

Fig. 462. Capsule of Antirrhinum majus, Frogsmouth, after dehiscence. c c, Persistent 
calyx, p, Pericarp perforated near the summit by three holes, 1 1, two of which correspond to 
one of the loculaments, and one to the other. The apex of the capsule is acuminated by the 
remains of the persistent style *. 




APOCARPOUS FRUITS. 259 

openings towards the middle or base (fig. 461 i), which pierce both 
the pericarp and the adherent calyx. In Frogsmouth (fig. 462) or 
Snapdragon, the pericarp gives way at certain fixed points, forming 
two or three orifices, one of which corresponds to the upper carpel, 
and the other to the lower. These orifices have a ragged appearance 
at the margins, which has given rise to the name rupturing, as applied 
to this mode of dehiscence. 

537. Carpology. Much has been done of late in the study of car- 
pology (xajxof, fruit, and Aoyo?, discourse), or the formation of the 
fruit ; but much still remains to be done ere the terminology of this 
department is complete. Many classifications of fruits have been 
given, but they are confessedly imperfect, and unfortunately much 
confusion has arisen in consequence of the same names having been 
applied to different kinds of fruit. In many cases, therefore, it is 
necessary to give a description of a fruit in place of using any single 
term. There are, however, some names in general use, and others 
which have been carefully defined, to which it is necessary to direct 
attention. 

538. Fruits may be formed by one flower, or they may be the 
product of several flowers combined. In the former case, they are 
either apocarpous (xo, separate, and xag^oV, fruit) or dialycarpous 
(<Wxv<w, I dissolve or separate), that is, composed of one mature 
carpel, or of several separate free carpels ; or syncarpous avv, together), 
that is, composed of several carpels, more or less completely united. 
These different kinds of fruits may be indehiscent (not opening), or 
dehiscent (opening). When the fruit is composed of the ovaries of 
several flowers united, it is usual to find the bracts and floral envelopes 
also joined with them, so as to form one mass ; hence such fruits are 
called multiple or anthocarpous (olvOos, flower, and XX^TTOS fruit). The 
term simple is perhaps properly applied to fruits, which, when mature, 
appear to be formed of one carpel only ; but it has been also given to 
those which, when mature, are formed by several separate carpels; 
while the term compound is applied to cases where several carpels are 
combined. The name aggregate is by some made synonymous with 
anthocarpous, while multiple is applied to apocarpous fruits formed by 
several free carpels. 

Fruits which are the Produce of a Single Flower. 

539. Apocarpous Fruit*. These fruits are formed out of one or 
several free carpels. They are either dry or succulent ; the pericarp, 
in the former instance, remaining more or less foliaceous in its struc- 
ture, and sometimes becoming incorporated with the seed; in the 
latter, becoming thick and fleshy, or pulpy. Some of these do not 
open when ripe, but fall entire, the pericarp either decaying, and thus 




260 INDEHISCENT APOCARPOUS FRUITS. 

allowing the seeds ultimately to escape, as is common in fleshy fruits, 
or remaining united to the seed, and being ruptured irregularly when 
the young plant begins to grow ; such fruits are indehiscent. Other 
apocarpous fruits, when mature, open spontaneously to discharge the 
seeds, and are dehiscent. 

540. indehiscent Apocarpous Fruits, when formed of a single mature 
carpel, frequently contain only one seed, or are monospermous (1*61*0$, 
one, and ani^a,, seed). In some instances there may have been only 
one ovule originally, in others two, one of which has become abortive. 

541. The Achcenium (, privative, and -^a-ivu, I open) is a dry 
monospermous fruit, the pericarp of which is closely applied to the 

seed, but separable from it (fig. 
463). It may be solitary, form- 
ing a single fruit, as in the 
Cashew (fig. 227 a), where it 
is supported on a fleshy pedun- 
cle, p; or aggregate, as in 
Ranunculus (fig. 464), where 
several achasnia are placed on 

~fr;3* 464 a common elevated receptacle. 

In the Strawberry, the achtenia 

are placed on a convex succulent receptacle. In the Eose, they are 
supported on a concave receptacle, covered by the calycine tube (fig. 
270), and in the Fig, they are placed inside the hollow peduncle or 
receptacle (fig. 246), which ultimately forms what is commonly caEed 
the fruit. In the Eose, the aggregate achsenia, with their general 
covering, are sometimes collectively called Cynarrhodum (KVUV, a dog, 
and go'Soi/, a rose, seen in the dog-rose). It will thus be remarked, 
that what in common language are called the seeds of the Strawberry, 
Eose, and Fig, are in reality carpels, which are distinguished from 
seeds by the presence of styles and stigmas. The styles occasionally 
remain attached to the achaania, in the form of feathery appendages, 
as in Clematis, where they are called caudate (cauda, a tail). 

542. In Composite, the fruit which is sometimes called Cypsela 
(KV^&D, a box), when ripe, is an achasnium united with the tube of 
the calyx (fig. 279 t). The limb of the calyx hi the Compositas, some- 
times becomes pappose, and remains attached to the fruit, as in 
Dandelion, Thistles, &c. (fig. 279 t). When the pericarp is thin, 
and appears like a bladder surrounding the seed, the achasnium be- 
comes a Utricle, as in Amaranthacea3. This name is often given to fruits 
which differ from the achsenium, in being composed of more than one 

Fig. 463. Achaenium or indehiscent monospermous carpel from the pistil of a Ranunculus. 

Fig. 464. 1. Similar achsenium, with rough points on the pericarp, from the pistil of Ranun- 
culus muricatus. 2. Achsenium cut transversely to show the seed, g, not adherent to the 
parietes. 



INDEI1ISCENT APOCARPOUS FRUITS. 



261 



carpel When the pericarp is extended in the form of a winged 
appendage, a Samara (samera, seed of Elm) or samaroid achcenium is 
produced, as in the Ash (fig. 437), common Sycamore (fig. 465), and 
Hirasa (fig. 466). In these cases, there are usually two achasnia 
united, one of which, however, as in Fraxinus oxyphylla (fig. 437), 
may be abortive. The Wing (fig. 465 a) is formed by the carpel, and 
is either dorsal, i.e. a prolongation from the median vein (fig. 465 a), 
or marginal, that is, formed by the lateral veins (fig. 466 a). It sur- 
rounds the fruit longitudinally in the Elm. When the pericarp be- 
comes so incorporated with the seed, as to be inseparable from it, as 




in Grains of Wheat, Maize, Rye (fig. 467), and other grasses, then the 
name Caryopsis or Cariopsis (xx^vx, a nut, and &]/is t appearance) is 
given. 

543. There are some fruits which consist of two or more achaania, at 
first united together, but which separate when ripe. Of this nature 
is the fruit of the Tropaaolum or Indian Cress, also that of Labiatae 
and Boraginacese, which is formed of four achaenia attached to the 
axis (fig. 402), whence the common style appears to proceed. Some 
of these are occasionally abortive. In the ripe state the pericarp 
separates from the seed in these cases ; and thus there is a transition 
from indehiscent achasnia to single seeded dehiscent pericarps. So 
also the Cremocarp (K^^XU, to suspend), or the fruit of Umbellifera3 
(fig. 454), which is composed of two achsenia united by a commissure 



Fig. 465. Seed-vessel of Acer Pseudo-platanus, composed of two samaras or winged raono- 
spermous carpels united, a, Upper part forming a dorsal wing. I, Lower portion corresponding 
to the loculaments. 

Fig. 466. Samara taken from the fruit of Hiraea. s, Persistent style. I, Part corresponding to 
the loculament a a, Marginal wing or ala. 

Fig. 467. Caryopsis of Secale cereale, Rye. 1. Entire. 2. Cut transversely to show the seed 
adherent to the parietes of the pericarp. 



262 DEHISCENT APOCAEPOUS FBTJITS. 



to a common axis or carpophore (KX^TTO;, fruit, and (pogea, I bear), 
from which they are suspended at maturity. It is sometimes deno- 
minated diachcenium (3< f , twice), from the union of two achaenia, which 
in this instance receive the name of mericarps (fify oj , part), or hemicarps 
(vfticrvs, half, and xx^vog, fruit). 

544. The Nut or Glans. This is a one-celled fruit with a hardened 
pericarp, surrounded by bracts at the base, and, when mature, con- 
taining only one seed. In the young state, the ovary contains two or 
more ovules, but only one comes to maturity. It is illustrated by the 
fruit of the Hazel and Chestnut, which are covered by leafy appendages, 
in the form of a husk, and by the Acorn, in which the leaves or bracts 
are united so as to form a cupola or cup (fig. 257). The parts of the 
pericarp of the Nut are united so as to appear one. In Sagus, or the 
Sago Palm, it is covered by peculiar closely applied scales, giving the 
appearance of a cone. 

545. The Drupe (drupce, unripe olives). This is a succulent fruit 
covered by a pericarp, consisting of epicarp, mesocarp, and endocarp; 
and when mature, containing a single seed. This term is applied to 
such fruits as the Cherry, Peach, Plum, Apricot, Mango, Walnut, 
Nutmeg, and Date. The endocarp is usually hard, forming the stone 
of the fruit, which encloses the kernel or seed. The mesocarp is 
generally pulpy and succulent, so as to be truly a sarcocarp (Peach), 
but it is sometimes of a tough texture, as in the Almond, and at other 
times more or less fibrous. There is thus a transition from the Drupe 
to the Nut. Moreover, in the Almond, there are often two ovules 
formed, only one of which comes to perfection. In the Walnut, the 
endocarp, which is easily separable into two, forms prolongations which 
enter into the interior, and cause a remarkable division in the seed. 
It has been sometimes called Tryma. In the Easpberry and Bramble, 
several small drupes or drupels are aggregated so as to constitute an 
Etcerio (tratlpos, a companion). 

546. Dehiscent Apocarpous Fruits. These open in various 
ways, and usually contain more than one seed, being either 
few-seeded, oligospermous (o'A/yo?, few, and wi^pa,, a seed), or 
many-seeded, polyspermous (vo^t);, many). 

547. Follicle (folliculus, a little bag). This is a mature 
carpel, containing several seeds, and opening by the ventral 
suture (figs. 443, 468). It is rare to meet with a solitary 
follicle forming the fruit. There are usually several aggre- 
gated together, either in a circular manner on a shortened 
receptacle, as in Hellebore, Aconite, Delphinium, and Ascle- 

piadaceae; or in a spiral manner on an elongated receptacle, as in 



Fig. 468. Follicle or dehiscent many-seeded carpel of Aquilegia vulgaris, Columbine. The 
follicle dehisces by the ventral suture only. 



DEHISCENT APOCARPOUS FRUITS. 



263 



Magnolias, Banksias, and Liriodendron (fig. 306). Occasionally in 
Magnolia grandiflora, some of the follicles open by the dorsal suture. 

548. The Legume or Pod (legumen, pulse) is a solitary, simple, ma- 
ture carpel, dehiscing by the ventral and dorsal suture, and bearing 
seeds on the former. It characterizes leguminous plants, and is seen 
in the Bean and Pea (fig. 469). In the Bladder-senna (fig. 470) 
it retains its leaf-like appearance, and forms an inflated legume. In 
some Leguminosse, as Arachis, the fruit must be considered a legume, 
although it does not dehisce. In place of opening at the sutures, some 
legumes are contracted at intervals, so as to include each seed in a 




separate cell, and when ripe, the different divisions of the pod separate 
from each other. This constitutes theLomentum(lomentum, bean-meal), 
or lomentaceous legume of Hedysarum coronarium (fig. 460), Coronillas, 
Ornithopus, &c. In Medicago, the legume is twisted like a snail (fig. 
471), and in Csesalpinia coriaria, or Divi-divi, it is vermiform or curved 
like a worm ; in Carmichaelia, the valves give way close to the suture, 
and separate from it, leaving a division. 

549. Syncarpous Fruits are formed by several carpels, which are 

Fig. 469. Legume of Pisum sativum, common Pea, opened. It is formed by a single carpel, 
and dehisces by the ventral and dorsal suture, v v. Valves formed by the two parts of thi 
pericarp, p, The epicarp or external layer of the pericarp, f/, Endocarp or internal layer. 
Between these the mesocarp is situated g, Seeds placed one over the other, attached to the 
placenta by short funiculi or cords, //. The placenta forms a narrow line along the ventral 
suture, v. s d, The dorsal suture corresponding to the midrib of the carpellary leaf. 

Fig. 470. Legume of Bladder-senna (C'olutea arbor escens), showing an inflated, foliaceous 
pericarp. 

Fig. 47L Twisted or spiral legume of Medicago. 



264 INDEHISCENT SYNCARPOUS FRUITS. 

so united together as to appear one in their mature state. These 
fruits are either dry or succulent : in the former case, being usually 
dehiscent, in the latter, indehiscent. 

550. Indehiscent ttyncarpona Fruits. The Berry (baCCO) IS a SUCCU- 

lent fruit, in which the seeds are immersed in a pulpy mass, formed 
by the placentas. The name is usually given to such fruits as the 
Gooseberry and Currant, in which the calyx is adherent to the ovary, 
and the placentas are parietal, the seeds being ultimately detached 
from the placenta, and lying loose in the pulp. Others have applied 
it also to those in which the ovary is free, as in the Grape, Potato, and 
Ardisia, and the placentas central or free central. The latter might be 
separated under the name Uva (grape). In general, the name of baccate 
or berried is applied to all pulpy fruits. In the Pomegranate there is 
a peculiar baccate many-celled fruit, having a tough rind formed by 
the calyx, enclosing two rows of carpels placed above each other. The 
seeds are immersed in pulp, and are attached irregularly to the parietes r 
base, and centre. The fruit has been called Balausta (balawtium, 
flower of pomegranate), and the tough rind is called malicorium (a 
name applied to it by Pliny). 

551. The Pepo or Peponida (-KIKUV, a pumpkin), is illustrated by the 
fruit of the Gourd, Melon, aud other Cucurbitaeese, where the calyx 
is adherent, the rind is thick and fleshy, and there are three or more 
seed-bearing parietal placentas, either surrounding a central cavity, 
or sending prolongations inwards. The fruit of the Papaw resembles 
the Pepo, but the ovary is not adherent to the calyx. 

552. The Hesperidium (golden fruit in the garden of Hesperides) is 
the name given to the fruit of the Orange, &c., in which the epicarp 
and mesocarp form a separable rind, and the endocarp sends prolonga- 
tions inwards, forming triangular divisions, in which pulpy cells are 
developed so as to surround the seeds which are attached to the inner 

n angle. Both Pepo and Hesperidium may be 

considered as modifications of the Berry. 

553. The Pome (pomum, an apple) seen in 
the Apple, Pear, Quince, &c., is a fleshy fruit 
with the calyx adherent, and forming along 
with the epicarp and mesocarp a thick cellular 
mass, which is eatable, while the endocarp is 
scaly or horny, and forms separate cells enclos- 
ing the seeds. The covering of the cells is 
472 sometimes stony, as in the Medlar (fig. 472), 

and the Holly, forming what has been called a Nuculanium (nucula, a 
nut). In the Medlar, the stony endocarps are called pyr&twe 




Fig. 472. Fruit of common Medlar (Mespilus gtrmanica). Transverse section showing, e, epi- 
carp. s, Sarcocarp. n, Endocarp ;forming stony coverings of the seeds. The fruit has been 
called nuculanium, and the hard central cells pyrense. 




DEHISCENT SYNCAKPOUS FRUITS. 265 

the stone of the fruit). In Cornus mas (fig. 473), there are two stony 
cells, n, surrounded by the fleshy epicarp and mesocarp, and as they 
are close together, and one is often abortive 
(fig. 473, 2, I), there is a direct transition 
to the Drupe. 

554. Dehiscent Syncarpons Fruits. 

The Capsule (capsula, a little chest). This 
name is applied generally to all dry syn- 
carpous fruits, which open by valves or 
pores. The valvular capsule is observed in 
Digitalis (fig. 445), Hibiscus esculentus (fig. 449), Cedrela angustifolia 
(fig. 450), Mahogany (fig. 451), and Cerastium viscosum (fig. 444). 
The porous capsule is seen in the Poppy, Antirrhinum majus (fig. 462), 
and Campanula persicifolia (fig. 461). Sometimes the capsule opens 
by a lid, or by circumscissile dehiscence, and it is then called a 
Pyxidium (pyxis, a box), as in AnagaUis arvensis (fig, 458), Henbane 
(fig. 459), and Lecythis. The capsule assumes a spiral form in the 
Helicteres and a star-like or stellate form in Illicium anisatum. In 
certain instances, the cells of the capsule separate from each other, and 
open with elasticity to scatter the seeds. This kind of capsule is met 
with in Hura crepitans, and other Euphorbiacea;, where the cocci, con- 
taining each a single seed, burst asunder with force (fig. 453); and in 
Geraniacea?, where the cocci containing more than one seed,* separate 
from the carpophore, and. become curved upwards by their adherent 
styles (fig. 455). In the former case, the fruit collectively has been 
called JKegma (ptj-yftu, a rupture). 

555. The Siliqua (siliqua, a husk or pod) (fig. 456), may be con- 
sidered as a variety of the capsule, opening by two valves ; these are 
detached from below upwards, close to the sutures, bearing thin parie- 
tal placentas, which are united together by a prolongation called a 
replum, or spurious dissepiment, dividing the fruit into two. The 
seeds are attached on either side of the replum, either in one row 
or in two. When the fruit is long and narrow, it is called Siliqua; 
when broad and short, it is called Silicula. It occurs in cruciferous 
plants, as Wallflower, Cabbages, Cresses, &c. The siliqua may be 
considered as formed of two carpels, and two parietal placentas united 
together so as to form a two- celled seed-vessel. Some say that in its 
normal state it consists of four carpels, and that two of these are abor- 
tive. There are four bundles of vessels in it, one corresponding to 
each valve, which may be called valvular or pericarpial, and others 
running along the edge called placental. The replum consists of two 

Fig. 473. Cruit of Cornus mas, common Cornel. 1. Transverse section detaching the tipper 
half of the fleshy portion, s, so as to show the central kernel, n. 2. Transverse section of the 
fruit through the central portion, n, showing that it consisted of two loculaments. I, One of the 
loculaments empty, the other containing a seed, g. 

* The individual cocci of Geraniaceoe contain only one seed each. 



266 ANTHOCABPOUS FRUITS 

lamellae. It sometimes exhibits perforations, becoming fenestrate (fenes- 
tra, a window). At other times its central portion is absorbed, so 
that the fruit becomes one-celled. 

Fruits which are the produce of several Flowers united. 

556. It sometimes happens that the ovaries of two flowers unite so 
as to form a double fruit. This may be seen in many species of 
Honeysuckle. But the fruits which are now to be considered, consist 
usually of the floral envelopes, as well as the ovaries of several flowers 
united into one, and are called Multiple or Anihocarpous. 

557. The Sorosis (<ra(>os, a congeries or cluster) is a multiple fruit 
formed by a united spike of flowers, which becomes succulent. The 
fruit of the Pine-apple (fig. 474) is composed of numerous ovaries, floral 
envelopes, and bracts combined so as to form a succulent mass. The 
scales outside, c c, are the modified bracts and floral leaves, which, 
when the development of the fruit-bearing spike terminates, appear in 
the form of ordinary leaves, and constitute the crown, f. Other in- 
stances of a sorosis are the Bread- 
fruit and Jack-fruit. Sometimes a 
fruit of this kind resembles that 
formed by a single flower, and a 
superficial observer might have some 
difficulty in marking the difference. 
Thus, the Strawberry, Mulberry, and 
Easpberry appear to be very like 
each other, but they differ totally in 
their structure. The Strawberry and 
Easpberry are each the produce of a 
single flower, the former being a 
succulent edible receptacle bearing 

achaenia on its convex surface; the latter being a collection of drupes 
placed on a conical unpalatable receptacle; while the Mulberry (fig. 
475) is a sorosis formed by numerous flowers united together, the 
calyces becoming succulent, and investing the pericarps. 

558. Syconus (<rvxo, a fig,) is an anthocarpous fruit, in which the 
axis, or the extremity of the peduncle, is hollowed, so as to bear 
numerous flowers, all of which are united in one mass to form the 
fruit. The Fig (fig. 246) is of this nature, and what are called its 
seeds are the achsenia or seed-vessels of the numerous flowers scattered 
through the pulpy hollowed axis. In Dorstenia (fig. 245), the axis is 

Fig. 474. Anthocarpous fruit of Ananassa sativa, Pine-appla Axis bearing numerous 
flowers, the ovaries of which are combined with the bracts, c c, to form the fruit /, Crown of 
the Pine-apple consisting of empty bracts or floral leaves. 

Fig. 475. Anthocarpous fruit of the Mulberry, formed by the union of several flowers. 




ANTHOCARPOUS FRUITS. 



267 



less deeply hollowed, and of a harder texture, the fruit exhibiting often 
very anomalous forms. 

559. Strobiha (oTpofifoo;, fir-cone,) is a fruit-bearing spike more or 
less elongated, covered with scales, each of which represents separate 
flowers, and has two seeds at its 
base (fig. 476). The scales may be 
considered as bracts, or as flattened 
carpellary leaves, and the seeds are 
naked, as there is no true ovary 
present with its style or stigma. 
This fruit is seen in the cones of 
Firs, Spruces, Larches, Cedars, &c., 
which have received the name of 
Coniferae, or cone- bearing, on this 
account. The scales of the strobilus 
are sometimes membranous and thin, 
as in the Hop; at other times they 
are thick and closely united, so as 
to form a more or less angular and 
rounded mass, as in the Cypress 
(fig. 477); while in the Juniper 
they become fleshy, and are so in- 

corporated as to form a globular fruit like a berry (fig. 478), which 
has received the name of Galbulus (galbulw, nut of the cypress). 

560 TABULAR ARRANGEMENT OF FRUITS. 

A. Fruits formed from a single flower, and consisting of one or more Carpels, 
either separate or combined ; thus including Apocarpous, Aggregate, and 
Syncarpous Fruits. 

I. Indehiscent Pericarps. 
1. Usually containing a single seed : 

(Achrenium (Lithospermum). 
Separable from the seed ..... <Mericarp and Cremocurp in Umbelliferae, 

{ and Cypsela in Composite). 

Achsenia enclosed in fleshy tube of Calyx, Cynarrhodum (Rose). 
Inseparable from the seed, ...... Caryopsis (Grasses). 

Inflated ...... Utricle (Chenopodium). 

Having a cupulate involucrum, Glans (Acorn). 
(^Having winged appendages ..... Samara (Sycamore). 




o.S 



Fig. 476. Cone of Pimis sylvestris, Scotch Fir, consisting of numerous bracts or floral leavt s, 
each of which covers two winged seeds. These seeds are called naked, in consequence of not 
being contained in an ovary, with a style or stigma. 

Fig. 477. Cone of Cupressus sempervirens, Cypress; one of the Gymnospermous or naked- 
seeded plants, like the Pine. 

Fig. 478. Succulent cone or Galbulus of Juniperus macrocarpa. e K e e, The different scales or 
bracts united so as to enclose the seeds. 



268 TABULAR VIEW OP CARPOLOGT. 

Covered by a Pericarp, consisting of Epi-) -p. , n . .. 

carp, Sarcocarp, and Endocarp, ..} Drupa (Cherry). 

Drupe, with a two-valved Endocarp, having divisions extending from its 

inner surface, Tryma (Walnut). 
Aggregate Drupes, Etcerio (Kaspberry). 

2. Containing two or more seeds : 

t*> fOvary adherent to Calyx, Placenta parietal,) fr . , N ' 
S attachment, nf 8ft d Int. whn rinL ' \ Bacca (Gooseberry.) 



cs e 



attachment of seeds lost when ripe, ........ . 

- --- -- attachment perma-) -n ff ^ JN 

nent, rind thick and hard, ............ . ....... [ Pe P (Gourd). 



o ^ I Peculiar berried many-celled fruit, with two) , , fT> 

Jf 1 or more rows of Carpels, } Balausta (Pomegranate). 

' Ovary notadherenttoCalyx, Placentacentral,...Uva (Grape). 



Placenta parietal,. Papaw fruit. 



Having a spongy separable rind, and separable f TT -j- //-. 
pulpy cells,.. L... } Hespenehum (Orange). 

"S S . f Walls f cells or Endocarp horny, covered by) -p. ^ f . ,^ 

||3 J a fleshy Mesocarp and Epicarp ..} Pomum ( A PP le >- 

"w ^ ^ ', Walls of cells or Endocarp stony, covered by) XT , . ,* T ,, ^ 
( a fleshy Mesocarp and Epicarp, ..[ Nuculamum (Medlar). 



II. Dehiscent Pericarps. 

["Opening by Ventral Suture only Follicle (Pasony). 

Opening by Ventral and Dorsal Suture Legume (Pea). 

Lomentum, a Legume separating into distinct pieces, each containing a 

seed (Ornithopus). 
Opening by two valves which separate from a Gen-) Siliqua (Cabbage). 

tral Eeplum or Frame, ) Silicula (Capsella). 

Opening by Transverse or Circumscissile Dehiscence,.Pyxidium (Henbane). 
Opening by several valves or pores, without Ventral) n , ,--p,v,^ 

n , or Dorsal Suture or Keplum, | ^apsu 

"j3 I Capsule adherent to Calyx, Diplotegia (Campanula). 

jg J A long pod-like Capsule, Ceratium (Glaucium). 

^Opening by separation of elastic Cocci, Eegma (Hura). 

B. Fruits formed by the union of several Flowers, and consisting of Floral En- 
velopes, as well as Ovaries ; these are Multiple or Anthocarpous. 

Hollow Anthocarpous Fruit Syconus (Fig). 

["formed by Indurated Catkin Strobilus (Fir 

ConvexAnthocarpousFruit,] J^ 6 ^ Succulent Spike.-Sorosis (Bread- 
(_ fruit. 

7. MATURATION OF THE PERICARP. 

561. After fertilization, the parts of the ovary begin to swell, the 
foramen of the ovule is more or less closed, the stigma becomes dry, 
and the style either withers and falls off, or remains attached as a 
hardened process or apiculum; while the embryo plant is developed 
in the ovule. It has been stated that fruits, such as Oranges and 
Grapes, are sometimes produced without seeds. It does not appear, 
therefore, necessary for the production of fruit in all cases, that the 



MATURATION OF THE PERICAP. 269 

process of fertilization should be complete. In speaking of seedless 
Oranges, Dr. Bullar states that the thinness of the rind of a St. Michael 
Orange, and its freedom from pips, depend on the age of the tree. 
The young trees, when in full vigour, bear fruit with a thick pulpy 
rind and abundance of seeds ; but, as the vigour of the plant declines, 
the peel becomes thinner, and the seeds gradually diminish in number, 
till they disappear altogether. 

562. While the fruit enlarges, the sap is drawn towards it, and a great 
exhaustion of the juices of the plant takes place. In Annuals, this ex- 
haustion is such as to destroy the plants; but if they are prevented from 
bearing fruit, they may be made to live for two or more years. Peren- 
nials, by acquiring increased vigour, are able better to bear the demand 
made upon them during fruiting. If large and highly-flavoured fruit 
is desired, it i^f importance to allow an accumulation of sap to take 
place before the plant flowers. When a very young plant is permitted 
to do so, it seldom brings fruit to perfection. When a plant produces 
fruit in very large quantities, gardeners are in the habit of thinning it 
early, in order that there may be an increased supply of sap to that 
which remains. In this way, Peaches, Nectarines, Apricots, &c., are 
rendered larger and better flavoured. When the fruiting is checked 
for one season, there is an accumulation of nutritive matter, which 
has a beneficial effect on the subsequent crop. 

563. The pericarp is at first of a green colour, and performs the 
same functions as the other green parts of plants, decomposing car- 
bonic acid under the agency of light, and liberating oxygen. As it 
advances to maturity, it either becomes dry or succulent. In the for- 
mer case, it changes into a brown or a white colour and has a quantity 
of ligneous matter deposited in its substance, so as to acquire some- 
times great hardness ; in the latter, it becomes fleshy in its texture, 
and assumes various bright tints, as red, yellow, &c. In fleshy fruits 
however, there is frequently a deposition of ligneous cells in the endo- 
carp, forming the stone of the fruit ; and even in the substance of the 
pulpy matter or sarcocarp, there are found isolated cells of a similar 
nature, as in some varieties of Pear, where they cause a peculiar 
grittiness. The contents of the cells near the circumference of succu- 
lent fruits are thickened by exhalation, and a process of endosmose 
goes on, by which the thiner contents of the inner cells pass out- 
wards, and thus cause swelling of the fruit. As the fruit advances to 
maturity, however, this exhalation diminishes, the water becoming 
free, and entering into new combinations. In all pulpy fruits which 
are not green, there are changes going on by which carbon is separ- 
ated in combination with oxygen. 

564. Dry fruits may remain attached to the tree for some tune 
before they are fully ripe, and ultimately separate by disarticulation. 
Occasionally, when the pericarp is thick, it separates in layers like 



270 MATURATION OF THE PERICARP. 

the bark. Succulent fruits contain a large quantity of water, along 
with cellulose or lignine, sugar, gummy matter or dextrine, albumen, 
colouring matter, various organic acids, as citric, malic, and tartaric, 
combined with lime and alkaline substances, besides a pulpy gelatinous 
matter, which is converted by acids into pectine or pectose, whence 
pectic acid is formed by the action of albumen. Pectine is soluble 
in water, and exists in the pulp of fruits, as Apples, Pears, Goose- 
berries, Currants, Raspberries, Strawberries, &c. Pectic acid is said 
to consist of C u H s O 12 + HO. It absorbs water, and is changed 
into a jelly-like matter; hence its use in making preserves. Each kind 
of fruit is flavoured with a peculiar aromatic substance. Starch is 
rarely present in the pericarp of the fruit, although it occurs commonly 
in the seed. In Plantains, Bananas, and Bread-fruit, however, 
especially when seedless, there is a considerable quantity of starchy 
matter, giving rise to mealiness when these fruits are prepared as 
fritters. Oily matters are also found in the cellular tissue of many 
fruits. Thus, a fixed oil occurs hi the Olive, and essential oils in the 
Orange, Lemon, Lime, Rue, Dictamnus, &c. 

565. During ripening, much of the water disappears, while the 
cellulose or lignine, and the dextrine, are converted into sugar. The 
acids also combine with alkalies, and thus the acidity of the fruit 
diminishes, while its sweetness increases. In the Grape, when young, 
there is abundance of tartaric acid; but as the fruit advances to matu- 
rity, this combines with potash, so as to diminish the acidity. Certain 
fruits owe their aperient qualities to the saline matter which they 
contain. In seasons when there is little sun, and a great abundance 
of moisture, succulent fruits become watery, and lose their flavour. 
The same thing frequently takes place in young trees with abundance 
of sap, and in cases where a large supply of water has been given 
artificially. 

566. The following analysis of the Cherry in its unripe and ripe state, 
as given by Berard, exhibits generally the chemical composition of 
succulent fruits : 

Unripe. Ripe. 

Chlorophylle 0-05 

Sugar 1-12 18-12 

Gum or dextrine 6'01 3'23 

Cellulose 2-44 1'12 

Albumen 0-21 0.57 

Malic acid 1-75 2'01 

Lime 0-14 0-10 

Water.... ....88-28 74-85 



100-00 100-00 



The following table shows the changes produced on the water, sugar, 
and cellulose, in 100 parts of unripe and ripe fruits : 



RIPENING OF FRUITS. 271 

Water. Sugar. Cellulose. 

Unripe. Ripe. Unripe. Ripe. Unripe. Ripe. 

Apricot 89-39 74'87 .. 6'64 16'48 .. 3'61 1'86 



Peach 90-31 80-24 

Cherries 88'28 74-85 

Plums 74-87 71-10 

Pears 86-28 83'88 



0-63 11-61 

1-12 18-12 

17-71 24-81 

6-45 11-52 



3.01 1-21 

2-44 1-12 

126 1-11 

3-80 2-19 



567. It is not easy in all cases to determine the exact time when 
the fruit is ripe. In dry fruits, the period immediately before dehis- 
cence is considered as that of maturation ; but, in pulpy fruits, there 
is much uncertainty. It is usual to say that edible fruts are ripe, when 
their ingredients are in such a state of combination as to give the most 
agreeable flavour. This occurs at different periods hi different fruits. 
After succulent fruits are ripe in the ordinary sense, so as to be capable 
of being used for food, they undergo further changes, by the oxidation 
of their tissues, even after being separated from the plant. In some 
cases, these changes improve the quality of the fruit, as in the case of 
the Medlar, the austerity of which is thus still further diminished. In 
the Pear, this process, called by Lindley bletting (from the French, 
blessi), renders it soft, but still fit for food ; while in the Apple, it 
causes a decay which acts injuriously on its qualities. By this process 
of oxidation, the whole fruit is ultimately reduced to a putrefactive 
mass, which probably acts beneficially in promoting the germination 
of the seeds when the fruit drops on the ground. 

568. The period of time required for ripening the fruit, varies in 
different plants. Most plants ripen their fruit within a year from the 
time of the expansion of the flower. Some come to maturity in a few 
days, others require some months. Certain plants, as some Conifera?, 
require more than a year, and in the Metrosideros, the fruit remains 
attached to the branch for several years. The following is a general 
statement of the usual tune required for the maturation of different 
kinds of fruit : 

Grasses 13 to 45 days 

Raspberry, Strawberry, Cherry ....2 months. 

Bird-cherry, Lime-tree 3 

Eoses, White-thorn, Horse-chestnut 4 

Vine, Pear, Apple, Walnut, Beech, Plum, Nut, Almond, 5 to 6 

Olive, Savin 7 

Colchicum, Misletoe 8 to 9 

Many Coniferae, 10 to 12 

Some Coniferag, certain species of Oak, Metrosideros, above 1 2 

The ripening of fruits may be accelerated by the application of heat, 
by placing dark-coloured bricks below it, and by removing a ring of 
bark so as to lead to an accumulation of sap. Trees are sometimes 
made to produce fruit, by checking their roots when too luxuriant, 
and by preventing the excessive development of branches. 



272 EFFECT OF GKAFT1XG ON FRUITS. 

569. Crafting. A very important benefit is produced, both as re- 
gards the period of fruiting and the quality of the fruit, by the process 
of grafting. This is accomplished by taking a young twig or scion, 
called a graft, and causing it to unite to a vigorous stem or stock, thus 
enabling it to derive a larger supply of nutritive matter than it could 
otherwise obtain, and checking its vegetative powers. In place of a 
slip or cutting, a bud is sometimes taken. In order that grafting 
may be successfully performed, there must be an affinity between the 
graft and the stock as regards their sap, &c. It has often been sup- 
posed that any kinds of plants may be grafted together, and instances are 
mentioned by Virgil and Pliny, where different fruits are said to have 
been borne on the same stock. This was probably produced by what 
the French call Greffe des charlatans, cutting down a tree within a 
short distance of the ground, and then hollowing out the stump, and 
planting within it several young trees of different species ; in a few 
years they grow up together so as to fill up the cavity and appear to 
be one. The deception is kept up better, if some buds of the parent 
stock have been kept alive. 

570. The object which gardeners wish to secure by grafting, is the 
improvement of the kinds of fruit, the perpetuation of good varieties, 
which could not be procured from seed, and the hastening of the period 
of the fruit-bearing. Grafting a young twig on an older stock, has the 
effect of making it flower earlier than it would otherwise do. The 
accumulation of sap in the old stock is made beneficial to the twig, and 
a check is given at the same tune to its tendency to produce leaves. 

571. Mr. Knight did much to improve fruits by grafting. He 
believed, however, that a graft would not live longer than the natural 
limit of life allowed to the tree from which it has been taken. In this 
way he endeavoured to account for the supposed extinction of some 
valuable varieties of fruits, such as the Golden pippin, and many cider 
apples of the seventeenth century.* He conceived that the only natural 
method of propagating plants was by seed. His views have not been 
confirmed by physiologists. Many plants are undoubtedly propagated 
naturally by shoots, buds, tubers, &c., as well as by seed ; and it is 
certain that the life of slips may be prolonged by various means, much 
beyond the usual limit of the life of the parent stock. The Sugar-cane 
is propagated naturally by the stem, the Strawberry by runners, the 
Couch-grass by creeping stems, Potatoes and Jerusalem Artichokes by 
tubers, the Tiger-lily by bulblets, and Ap.himp.nes by scaly bodies, like 
tubers. The fruits, moreover, which Mr. Knight thought had disap- 
peared, such as Red streak, Golden pippin, and Golden Harvey, still 
exist, and any feebleness that they exhibit does not appear to proceed 
from old age, but seems to be owing to other causes, such as the nature 
of the soil, cold, violence, and mutilation. Vines have been transmitted 

* See Knight's Horticultural Papers, 8vo, London, 1841, p. 8L 



DIFFERENT MODES OF GRAFTING. 273 

by perpetual division from the time of the Eomans. A slip taken 
from a Willow in Mr. Knight's garden, pronounced by him as dying 
from old age, was planted in the Edinburgh Botanic Garden about 
thirty years ago, and is now a vigorous tree, although the original stock 
has long since undergone decay. It is true, however, that a cutting 
taken from a specimen already exhausted by excessive development 
of its parts, will partake of the impaired vigour of its parent, and will 
possess less constitutional energy than that taken from a vigorous stock. 

572. In grafting, various methods have been adopted. One of these 
is grafting by approach, or inarching, when two growing plants are 
united together, and after adhesion one is severed from its own stock, 
and left to grow on the other. This kind of adhesion sometimes takes 
place naturally in trees growing close together. It is well seen in a 
iir-tree in the burying-ground at Killin. The branch of the same tree 
may also be bent, so as to become united to the stem at two points. 
This is often seen in the Ivy. The roots of contiguous trees occasion- 
ally unite by a process of grafting, and to this is attributed the 
continued vigour of the stump of Sprace-trees cut down on the Swiss 
mountains. This natural grafting of roots has been observed in the 
White Pine (Abies pectinata), and sometimes in the Red Pine (Abies 
excelsa), as well as in the Scotch Fir (Pinus sylvestris). 

573. The usual method of grafting is by scions or slips, which are 
applied to the stock by a sloping surface, or are inserted into slits 
in it by cleft-grafting, or into perforations by wimble or peg-grafting. 
Sometimes several slips are placed in a circular manner, round the 
inside of the bark of the stock, by crown-grafting; or the bark of a 
portion of the stock is removed, and that of the scion is hollowed out, 
so as to be applied over it like the parts of a flute, hence called flute- 
grafting. Budding is practised by the removal of a bud from one 
plant, along with the portion of the bark and new wood, and applying it 
to another plant, in which a similar wound has been made. Grafting 
is usually performed between the woody parts of plants, but herba- 
ceous parts may also be united in this way. The graft and stock are 
secured together by means of clay, or a mixture of bees'-wax and 
tallow, or by bits of Indian rubber. 

574. By grafting, all our good varieties of apples have been pro- 
duced from the Crab Apple. The seeds of the cultivated apples, when 
sown, produce plants which have a tendency to revert to the original 
sour Crab. Grafted varieties can only be propagated by cuttings. 
The influence exercised by the stock is very marked, and it is of great 
importance to select good stocks on which to graft slips. In this way 
the fruit is often much improved by a process of ennobling, as it is 
called. The scion also seems in some cases to exercise a remarkable 
eflect on the stock. Slips taken from varieties with variegated leaves, 
grafted on non-variegated, have caused the leaves of the latter to 



274 SEED OR MATURE OVULE. 

assume variegation, and the effect, when once established, has con- 
tinued even after the slip was removed. The effects of grafting are 
well seen in the case of the Eed Laburnum, when united to the Yellow 
species. The Red Laburnum is a hybrid between the common Yellow 
Laburnum and Cytisus purpureus, or the Purple Laburnum. The 
branches below the graft produce the ordinary yellow laburnum 
flowers of large size ; those above exhibit often the small purple 
laburnum flowers, as well as reddish flowers intermediate between the 
two in size and colour. Occasionally, the same cluster has some 
flowers yellow and some purplish. 

8. SEED OR FERTILIZED OVULE ARRIVED AT MATURITY. 

575. While the pistil undergoes changes consequent on the dis- 
charge of the pollen on the stigma, and ultimately becomes the fruit, 
the ovule also is transformed, and, when fully developed, constitutes 
the seed. After fertilization, the foramen of the ovule contracts, the 
embryo or young plant gradually increases in its interior, by the 
absorption of the fluid matter contained in the sac of the amnios, 
solid nutritive matter is deposited, and a greater or less degree of 
hardness is acquired. The seed then is the fecundated mature ovule 
containing the embryo, with certain nutritive and protective appen- 
dages. When ripe, the seed contains usually a quantity of starchy 
and ligneous matter, various azotised compounds, as caseine, vegetable 
albumen, oily and saline matters. It sometimes acquires a stony 
hardness, as in the case of vegetable ivory, the seed of Phytelephas 
macrocarpa. Care must be taken not to confound it with single- 
seeded pericarps, such as the Achaenium and Caryopsis, in which a 
style and stigma are present; nor with bulbils or bulblets, as in 
Lilium bulbiferum, and Pentaria bulbifera, which are germs or separ- 
able buds developed without fecundation. 

576. Seeds are usually enclosed in a seed-vessel or pericarp, and 
hence the great mass of flowering plants are called angiospermous 
xyyo?, or dyyeiot/, a vessel, and ani^a, a seed). In Coniferas and 
Cycadaceae however, the seeds have no true pericarpial covering, and 

fertilization takes place by the direct application of the 
pollen to the seed, without the intervention of stigma or 
style. Hence the seeds, although sometimes protected by 
scales, are truly naked, and the plants are called gyrnnos- 
permous (yvpvos, naked, and avin/nx, a seed). Occasion- 
ally, by the early rupture of the pericarp, seeds originally 
covered become exposed. This is seen in Leontice, 

Cuphea, &c. In Mignonette, the seed-vessel (fig. 479) opens early, 

so as to expose the seeds, which are called seminude. 

Fig. 479. Fruit or capsule of Reseda opening early, so that the ovules become seminude. 




SEED OR MATURE OVULE. 275 

577. Besides being contained in a pericarp, the seed has its own 
peculiar coverings. Like the ovule, it consists of a nucleus or kernel, 
and integuments. In some instances, although 
rarely, all the parts of the ovule are visible 
in the seed, viz., the embryo- sac, or quintine, 
the quartine, the tercine formed from the 
nucleus, the secundine, and the primine. 
In fig. 480, there is a representation of the 
seed of Nymphaea alba, in which s e indicates 
the embryo-sac, containing the embryo, e; 
v the cellular farinaceous covering (quar- 
tine), formed round the embryo-sac ; m t, 
membrane formed from the nucleus (tercine); 
m i, the secundine; t, the primine. In general, 
however, great changes take place by the 
development of the embryo; the embryo -sac 
is often absorbed, or becomes incorporated 
with the cellular tissue of the nucleus ; the 
"same thing occasionally takes place in the 
secundine, so that in the ripe seed, all that 
can be detected is the embryo and two 
coverings. The general covering of the 
seed is called spermoderm (aveppu, seed, 48 

and tiepftu, covering). In order to correspond with the name applied 
to the covering of the fruit, it ought more properly to be denominated 
perisperm (wtpl, around, and o-z-g^a, seed). This latter term, however, 
has been appropriated to a certain portion of the seed, to be afterwards 
noticed under the name of albumen. 

578. The Spciinoderm usually consists of two parts, an external 
membrane, called the episperm or testa (sirl, upon, or on the outside, 
and ovigftK, a seed, or testa, a shell), and an internal membrane, called 
endopleura (Ii/Sov, within, and TT^SV^X, side). The former may consist 
of a union of the primine and secundine, or of the primine only, when 
as occasionally happens, the secundine is absorbed ; the latter, of a 
combination between the membrane of the nucleus and the embryo - 
sac, or of one of these parts alone. Sometimes the secundine remains 
distinct in the seed, forming what has been called a mesosperm (/twos, 
middle) ; and when it assumes a fleshy character, it has received the 
name of sarcosperm or sarcoderm (?P|, flesh). 

579. The .Episperm consists of cellular tissue, which often assumes 

Fig. 480. Young seed of Nymphsea alba cut vertically. /, Fnniculus or umbilical cord. 
a, Arillus derived from the placenta, r, Kaphe. e, Chalaza or eotyledonary end of the seed. 
h, Hilum or base of the seed, m, Micropyle or foramen, t, Testa or Primine. mi, Secundine. 
mt, Tercine or membrane of the nucleus, n, Farinaceous external perisperm or albumen formed 
by the nucleus, and probably constituting the quartine of Mirbel. s e, s e, Internal perisperm 
or endosperm formed by the embryo-sac, e, The embryo. 




276 SEED OR MATURE OVULE. 

various colours, and becomes more or less hardened by depositions in 
its interior. In Abrus precatorius, and Adenanthera pavonina, it is 
of a bright red colour; in French beans, it is beautifully mottled; in 
the Almond, it is veined ; in the Tulip and Primrose, it is rough ; in 
the Snapdragon, it is marked with depressions; in Cotton and Ascle- 
pias, it has hairs attached to it ; and in Mahogany and Bignonia, it is 
expanded in the form of wing- like appendages. In Salvia, Collomia, 
Acanthodium, and other seeds, it contains spiral cells, from which, 
when moistened with water, the fibres uncoil in a beautiful manner, 
having a membranous covering. In the episperm of the seed of 
Ulmus campestris, the cells are compressed, and their sinuous bound- 
aries are traced out by minute rectangular crystals adhering to their 
walls. 

580. The Endopleura is also cellular. It is often thin and trans- 
parent, but it sometimes becomes thickened. It is applied more or 
less closely to the embryo, and sometimes follows a sinuous course, 
forming folds on its internal surface, and separating from the episperm. 

When the embryo-sac remains distinct from the nucleus in the seeds, 
as in Nymphaea, Zingiber, Piper, &c., it forms a covering to which 
the name of vitellus (vitellus, yolk of an egg) was given by Gaertner. 

581. Arillus. Sometimes there is an additional covering to the 
seed, derived from an expansion of the funiculus or placenta after 
fertilization, to which the name arillus has been given. This is seen 
in the Passion-flower, where the covering commences at the base, and 
proceeds towards the apex, leaving the foramen uncovered. In the 
Nutmeg and Spindle-tree, this additional coat is said to commence at 
the side of the exostome, and to proceed from above downwards, con- 
stituting, in the former case, the substance called mace ; and in the 







481 

latter, the bright scarlet covering of the seeds (figs. 481, 482). In 
such instances, it has been called by some an arillode. This arillode, 
after growing downwards, may be reflected upwards, so as to cover 
the foramen. 

Fig. 481. 1, 2, 3, and 4, Various states of the arillus of Euonymus, the Spindle-tree. The 
figures show the mode in which it is developed from the edges of the foramen, a a a a, Arillode. 
ffffi Foramen or exostome. 



SEED OR MATURE OVULE. 



277 



582. On the testa, at various points, there are produced at times 
cellular bodies, which are not dependent on fertilization, to which the 






name of strophioles (strophiolum, a little garland), or caruncuks (carun- 
cula, a little piece of flesh), has been given, the seeds being strophio- 
late or carunculate. These tumours may occur 
near the base or apex of the seed, they may be 
swellings of the exostome, as in Eicinus (fig. 483 c), 
or they may occur in the course of the raphe. 

583. Seeds are attached to the placenta by 
means of a funiculus or umbilical cord, which 
varies much in length. In Magnolias it attains a 
great length, and when the seed is ripe it appears 
like a cord suspending it from the follicle. The 
point of the seed by which it is united to the cord 
or the scar left on its separation, is called the hilum or umbilicus, and 
represents its base. It frequently exhibits marked colours, being 
black in the Bean, white in many species of Phaseolus, &c. It may 
occupy a small or large surface, according to the nature of the attach- 
ment. What constitutes the foramen of the ovule, becomes the 
micropyle (fiixgo;, small, and Z-J/AH, gate) of the seed, with its exostome 
and endostome. This may be recognizable by the naked eye, as in 
the Pea and Bean tribe, Iris, &c , or it may be very minute and 
microscopic. It indicates the true apex of the seed, and is important 
as marking the part to which the root of the embryo is directed. At 
the micropyle in the Bean, is observed a small process of integument, 
which, when the young plant sprouts, is pushed up like a lid, and is 

Fi^. 482. Development of the same arillus, or, around the ovule, o, exhibited in a different 
position. 1, 2, 3, 4, are four succesive stages of development. In fig. 4, the arillus has been cut 
vertically, to show its relation to the ovule, which it surrounds completely. 

Fig. 483. Vertical section of a carpel of Ricinus communis, and of the seed which it contains, 
n, Pericarp. Z, Loculament /, Funiculus or umbilical cord, t, Integuments of the seed, having 
at their apex a caruncula, c, which is traversed by the small canal of the exostome. The exos- 
tome does not correspond exactly with the endostome, which is immediately above the radicle. 
r, Raphe. c h, Chalaza. ft Perisperm or albumen, the upper portion of which only is seen 
e, Embryo, with its radicle, e r, and its cotyledons, c. 




278 SKED OR MATUKE OVULE. 

called embryotega (tego, I cover.) The fibro- vascular bundles, from 
the placenta pass through the funiculus and reach the seed, either 
entering it directly at a point called the omphalode (o'^oAo?, navel,) 
which forms part of the hilum, or being prolonged between the outer 
and inner integument in the form of a raphe, and reaching the chalaza 
or organic base of the nucleus, where a swelling or peculiar expansion 
may often be detected, as in Crocus. In fig. 480, the spiral vessels, 
r, are seen entering the cord, f, passing through the hilum, A, forming 
the raphe, r, between the testa, t, and endopleura, m z, and ending in 
the chalazal expansion, c. So also in fig. 484, where f is the funi- 
culus, r the raphe united to the hilum and chalaza, c, whence vessels, 
v, penetrate the seed. In some seeds, as Narthecium ossifragum, the 
vessels are said not to appear till after fertilization, and in Habenaria 
viridis, none have been detected. The chalaza is often 
of a different colour from the rest of the integuments. 
In the Orange, it is of a reddish-brown colour. Some- 
times, however, its structure can only be recognized 
by careful dissection. It indicates the cotyledonary 
extremity of the embryo. The hilum and chalaza 
may correspond, or they may be separated from each 
other and united by the raphe (fig. 484). The raphe 
is generally on the side of the seed next the ventral suture. 

584. The positions of the hilum, micropyle, and chalaza, are of 
importance in determining the nature of the seed. The hilum is the 
base of the seed, and the micropyle its apex, while the chalaza is the 
organic base of the nucleus. The hilum and chalaza may correspond, 
the micropyle being at the opposite extremity, and then the seed is 
orthotropal (ojdoj, straight). The seed may be curved so that the 
micropyle is close to the hilum, and the chalaza, by the growth of the 
seed on one side, may be slightly removed from the hilum, then the 
seed is campylotropal (xa^Tiixo?, curved). The micropyle may be 
close to the hilum, and the chalaza in the progress of development 
may be removed to the opposite end, then the seed is anatropal 
(Tg7na, I reverse).* 

585. The position of the seed as regards the pericarp, resembles 
that of the ovule in the ovary, and the same terms are applied erect, 
ascending, pendulous, suspended, curved, &c. (figs. 423, 424, 425, 
426, 420.) These terms have no reference to the mode in which the 
fruit is attached to the axis. Thus the seed may be erect while the 
fruit itself is pendent, in the ordinary meaning of that term. The part 
of the seed next the axis or the ventral suture is its face, the opposite 
side being the back. Seeds exhibit great varieties of forms. They 

* See T 467, where these terms are more fully explained when treating of the ovule. 
Fig. 484. Seed of the Hazel. /, Funiculus. r, Raphe. c, Chalaza. n. Veins spreading in a 
radiating manner over the integuments of the seed. 



SEED OR MATURE OVULE. 



279 



may be flattened laterally, compressed; or from above downwards, 
depressed. They may be round, oval, triangular, polygonal, rolled up 
like a snail, as in Physostemon ; or coiled up like a snake, as in Ophio- 
caryon paradoxum. 

586. The great object of fertilization is the formation of the embryo 
in the interior of the seed. In general, one embryo is produced, con- 
stituting what is denominated monembryony (jx-dvo^ one) ; but in Coni- 
ferse, Cycadacese, Misletoe, &c., there are frequently several embryos, 
giving rise to what is called polyembryony (VoAwf, many). Sometimes 
two embryos become united together in the same seed. In the coni- 
ferous seeds, numerous corpuscles are seen whence the embryos pro- 
ceed. The process of fertilization has already been traced until the 
embryo appears as a rounded cellular body, enclosed in the embryo- 
sac, and attached to a suspensor. In fig. 480, e is the embryo, and 
a e the embryo-sac. In this sac there is at first a mucilaginous fluid, 
the amnios, in which cells are speedily developed, commencing on its 
inner surface, and extending towards the interior. The embryonic 
cell (fig. 485 v), still attached to the sac by its suspensor, s, contains 
in the early state semifluid granular matter, which becomes organized, 
producing distinct nucleated cells (fig. 485, 2, e). These gradually 
multiply, and form at length a cellular mass, at first undivided (fig. 
485, 3, e), but afterwards showing a separation of parts, so that the 




axis and lateral projections or rudiments of leaves can be distinguished. 
In figs. 486 to 491, all the stages of the formation of embryo can be 

Fig. 485.- First development of the embryo of Draba verna. o. Suspensor, which in this plant 
is very long, v, Embryonic or germinal vesicle, e, Embryo. 1. First stage, in which the 
embryonic vesicle only is seen. 2. Second stage, showing several cells formed in the embryonic 
vesicle. 3. Third stage, in which the embryo becomes more conspicuous in consequence of the 
formation of numerous small cells. 

Fig. 486. Monocotyledonous embryo of Potamogeton perfoliatus in its early stage, appearing 
as a vesicle or simple cell. 

Fig. 487. The same farther advanced, showing radicle, >, gemmule or plumule, g, and the 
cotyledon, c. 

Fig. 488. Dicotyledonous embryo of (Enothera crassipes in its early stage, appearing as a 
vesicle or cell. 

Fig. 489. The same further advanced, showing three united utricles or cells. 

Fig. 490. -The same more developed, showing numerous cells. 

Fig. 491. The same in a more developed state, showing radicle, r, gemmule, </, and cotyle- 
dons, cc. 



280 



PERISPERLM OR ALBUMEN OF THE SEED. 



traced ; appearing first as a simple cell (figs. 486, 488), forming others 
in its interior (figs. 489, 490) ; and finally, the parts of the embryo 
becoming visible, as in fig. 491, where g r is the axis representing the 
stem and roots, and c c are the lateral projections, which are developed 
as leaf-like bodies, called cotyledons {norv^nluv, the name of a plant, 
having leaves like seed-lobes). 

587. Perisperm or Albumen. As the embryo increases in size, it 
gradually causes absorption of the cellular tissue in the embryo-sac, and 
it is sometimes developed to such a degree as to reduce the nucleus and 
embryo-sac to a thin integument. In such a case the seed consists of 
integuments and embryo alone. In Santalum, Osyris, and Loranthus, 
Griffith says the ovule is sometimes reduced entirely to a sort of embryo- 
nary sac. In Avicennia, the embryo, at its maturity, is on the outside of 
the nucleus and body of the ovule. In other cases it enlarges to a certain 
extent, filling the embryo-sac completely or partially, and only encroach- 
ing slightly on the cells of the nucleus. The cells surrounding the em- 
bryo then become filled with a deposit of solid matter called albumen, 
consisting of starchy, oily matter, and nitrogenous compounds. To 
this matter some have applied the term perisperm (<KI% \, around, and 
avi^f*,*, seed) ; others, that of endosperm (IvSo*, within). The name 
perispermic albumen, or perisperm, is often restricted to that found in 
the cells of the nucleus alone (fig. 480 ) ; endospermic albumen, or 
endosperm, to that found within the embryo-sac alone (fig. 480 s e), as 
in Chelidonium majus, Kanunculaceae, Umbelliferse, &c. Sometimes 
both kinds of albumen occur in the same seed, as in Nymphaeacea? 






and Piperaceae. Schleiden states, that in some instances the albumen 
is produced in the region of the chalaza. He also remarks, that endo- 
spermic albumen is common in Endogens. In some Scrophularias, the 

Fig. 49?. AnatTOpal mature seed of HeUeboms niger cut vertically. The embryo, e, is small 
as compared with the perisperm or albumen, p. t, Spermoderm or coverings of the seed. 
/, Funiculus. h, Hilum. c, Chalaza. 

Fig. 493. Mature seed of Diphylleia peltata, showing an embryo, e, which occupies a larger 
portion of the seed than in fig. 494. Letters indicate the same parts as in the previous figure. 

Fig. 494. Ripe seed of Berberis vulgaris, exhibiting a larger embryo, ?, as compared with the 
perisperm, p. Letters as in figs. 492 and 493. 



PERISPEEM OR ALBUMEN OF THE SEED. 281 

embryo-sac forms little cavities or bags, which in the ripe seed remain 
as appendages to the albumen. Seeds in which the embryo occupies 
the entire seed, are called exalbuminous (ex, without), as Composite, 
Cruciferae, and most Leguminosae, while others having separate albumen 
are albuminous. The larger the quantity of albumen in a seed, the 
smaller the embryo. In figs. 492 to 494, the relative proportion which 
the embryo bears to the albumen or perisperm in different seeds is 
shown; e being the embryo with its cotyledons and young root, p 
the perisperm, t the coverings of the seed, / the funiculus or cord, 
h the hilum, and c the chalaza. In fig. 492, the embryo is minute, 
and occupies only a small part of the apex of the albumen ; in fig. 

493, it is larger, and has encroached on the perisperm ; while in fig. 

494, it is still more developed, much of the albumen having been 
absorbed. 

588. The albumen varies much in its nature and consistence, and 
furnishes important characters. It may be farinaceous or mealy, con- 
sisting chiefly of cells filled with starch (fig. 495), as in Cereal grains, 
where it is abundant ; fleshy or cartilaginous, consisting of thicker ceUs 
which are still soft, as in the Coco-nut, and which sometimes contain 
oil, as in the oily albumen of Croton (fig. 496), Bicinus, and Poppy; 
horny, when the matter in the cells is of a hard consistence, and often 
arranged in a concentric manner, so as nearly to fill the entire cavity, 
as hi Date, Ivory-Palm, and Coffee. The albumen may be uniform 
throughout, or it may present a mottled appearance, as in the Nutmeg, 
the seeds of Anonaceae, and some Palms (fig. 497), where it is called 






ruminated. This mottled appearance depends on the endopleura or 
inner integument forming folds on which the albumen is deposited, 
and when the seed is ripe, these foldings of the membrane divide the 
albumen in a sinuous or convoluted manner. 

Fig. 495. - Section of a small portion of the farinaceous perisperm or albumen of Zea Mais, 
Indian corn, c c c, Cells. // f, Grains of starch in the cells. 

Fig. 496. Section of a small portion of the oily perisperm or albumen of Croton Tiglium. 
c c c c, Cells, hhh, Drops of oil contained in the cells. 

Fig. 497. Vertical section of the fruit of Areca Catechu, c, Perianth. /, Pericarp, p, Rumi- 
nated perisperm or albumen, e, Embryo. 



282 



PARTS OF THE EMBRYO PLANT. 



589. The albumen is a store of matter laid up for the nourishment 
of the embryo. In the Coco-nut and double Coco-nut, it forms the 
great bulk of the seed, weighing many ounces, while the embryo is 
minute, weighing a few grains, and lies in a cavity at one extremity. 
In Coffee, the albumen is the horny portion, the infusion of which is 
used for a beverage. In Phytelephas it is called vegetable ivory from 
its hardness, and is used for the same purposes as ivory. In the horny 
albumen of this Pahn, as well as in that of the Attalea funifera, the 
Date and the Doom Pahn, the concentric deposition of secondary 
layers, leaving a small cavity in the centre of the cells, and radiating 
spaces uncovered with thickening matter, is well seen under the 
microscope. 

590. The embryo consists of cotyledons or rudimentary leaves, the 
plumule (plumula, a little feather), or gemmule (gemma, a bud), repre- 
senting the ascending axis, the radicle (radix, root), or the descending 
axis, and their point of union the collum, collar or neck ; that part 

of the axis which intervenes between the collar and cotyledons 

being the caulicule (cauliculus, a little stalk), or tigelle (tigellus a 
little stalk). The embryo varies in its structure in the different 
498 divisions of the vegetable kingdom. In acrogenous and thallo- 
genous plants, it continues as a cell or spore, with granular, 
matter in its ulterior (fig. 498), without any separation of parts or 




the production of cotyledons. 
donous ( privative xorv^r^av). 



Hence these plants are called acotyle- 
Endogenous and Exogenous plants, 



Fig. 498. Acotyledonous embryo of Marchantia polymorpha. Such embryos bear the name 
of spores. 

Fig. 499. Monocotyledonous embryo of Potamogeton perfoliatus nearly mature, r, Kadicle. 
/, Caulicule or tigellus. c, Cotyledon, g, Gemmule or plumule. 

Fig. 500. Mature dicotyledonous embryo of the common Almond, r, Radicle or young root. 

Fig. 501. The same, with one of the cotyledons removed, r, Radicle, t, Tigelle or caulicule. 
f, One of the cotyledons left, ic, Cicatrix left at the place where the other cotyledon was at- 
tached, g, Gemmule composed of several small leaves. 



PARTS OF THE EMBRYO PLANT. 283 

on the other hand, exhibit a marked separation of parts in their 
embryo, the former having one cotyledon, and hence being mono- 
cotyledonous (/to'oj, one); the latter two, and hence dicotyledonous (5u, 
twice). Thus, the whole vegetable kingdom is divided into three 
grand classes by the nature of the embryo. Fig. 499 represents a 
monocotyledonous embryo, with its cotyledon, c ; while figs. 500 and 
501, exhibit a dicotyledonous embryo, with its cotyledons, c c. 

591. The Spore of acotyledonous plants (fig. 498) is a cellular 
body, from which a new plant is produced. Germination takes place 
in any part of its surface, and not from fixed points. Some consider 
it as produced independent of any process of fertilization, others con- 
sider the union of two kinds of cells as necessary for its formation. 
When formed, it sometimes presents filaments or vibratile cilia on its 
surface (figs. 431-434), by means of which it moves about in fluids like 
some of the Infusoria. When it germinates, these cilia disappear. 
Sometimes spores are united in definite numbers, as in fours, sur- 
rounded by a cellular covering, or perispore (vs^l, around, and avo^d, 
a spore), or sporidium, and thus forming the reproductive body called 
a tetraspore (rg^a?, four), which is common in Algas. 

592. Embryo. In the embryo or corculum (corculum, a little heart), 
the first part formed is the axis, having one of its extremities turned 
towards the suspensor, and the other in the opposite direction ; the for- 
mer indicating the point whence the young root or radicle is to pro- 
ceed, and the latter that whence the leafy stem is to arise. As the 
first leaves produced are the cotyledons, this stem is called the cotyle- 
donary extremity of the embryo, while the other is the radicular. 
The radicular is thus continuous with the suspensor, and consequently 
points towards the micropyle (fig. 494 A), or the summit of the nu- 
cleus, an important fact in practical botany; while the cotyledonary, 
being opposite, is pointed towards the base of the nucleus or the 
chalaza (fig. 494 c). Hence, by ascertaining the position of the micro- 
pyle and chalaza, the two extremities of the embryo can in general 
be discovered. In some rare instances, in consequence of a thicken- 
ing taking place in the coats of the seed, as in Ricinus (fig. 483), 
and some Euphorbiacese, there is an alteration in the micropyle, so 
that the radicle does not point directly to it. 

593. The part of the axis which unites the radicle and the cotyle- 
don or cotyledons, is denominated caulicule or tigelle (figs. 499 t, 
501 t). This is sometimes very short. From the point where the 
cotyledons are united to the axis, a bud is developed (in the same 
way as from the axil of leaves); this bud contains the rudiments of 
the true or primordial (primus, first, and or do, rank) leaves of the plant, 
and has been called plumule or gemmule. This bud may be seen 
usually lying within the cotyledons. Thus, in fig. 501, the embryo 
of the Almond exhibits the gemmule, g, lying on one of the cotyle- 




284 MONOCOTYLEDONOTJS EMBRYO. 

dons, the other having been removed and leaving a cicatrix, i c ; while 
in fig. 499, the gemmule, ^, of Potamogeton perfoliatus, is covered by 
the single cotyledon, c. 

594. The gemmule as well as the cotyledon are sometimes obscurely 
seen. Thus, in Cuscuta (fig. 502), the embryo appears as an elon- 
gated axis without divisions ; and in Pekea 
butyrosa (fig. 503), the mass of the em- 
bryo is made up by the radicular extremity 
and tigelle, , in a grove of which, s, the 
cotyledonary extremity lies embedded, which 
when separated, as in the figure, shows only 
very small cotyledons. In some monocotyle- 
donous embryos, as Orchidaceae, it requires 
a microscopic examination to detect the 

cotyledonary leaf. 

595. irionocotyledonous Embryo* In this embryo, the single cotyle- 
don in general encloses the gemmule at its lower portion, and exhibits 
on one side a small slit (fig. 504/), which indicates the edges of the 

vaginal, or sheathing portion of the cotyledonary leaf. The 
embryo presents commonly a cylindrical form, rounded at the 
extremities, or a more or less elongated ovoid (fig. 504). At 
first sight there seems to be no distinction of parts ; but on 
careful examination, by moistening the embryo, and making 
a vertical section, there will be detected, at a variable height, 
a small projecting mammilla, buried a little below the surface. 
This is the gemmule which marks the termination of the axis. 
From the lower extremity proceeds the radicular portion (figs. 
499 t r, 504 r), which may be said to represent both the tigelle 
and radicle. The upper portion or chalazal end of the em- 
bryo, is the cotyledon (figs. 499, 504 c), which is sheathing at 
its base, so as to enclose the gemmule. The length of the radicular 
portion, or that below the gemmule, varies. It is usually shorter than 
the cotyledon, and is denser in structure ; but in some instances it 
becomes much larger, giving rise to what has been called a macra- 
podous embryo (potx.^;, long, and vwc., a foot). Thus, in fig. 505, 
t represents the long radicular portion in the young state, whence 
ultimately the root, r, proceeds. Occasionally, the radicular portion 
becomes very thick and large, so as to form a considerable portion 
of the embryo; and in all monocotyledons, it may be considered as 



Fig. 502. Spiral embryo of Cuscuta or Dodder. 

Fig. 503. Embryo of Pekea, butyrosa. t. Thick tigelle or caulicule, forming nearly the whole 
mass, becoming narrowed and curved at its extremity, and applied to the groove", s. In the 
figure this narrowed portion is slightly separated from the groove, c, Two rudimentary 
cotyledons. 

Fig. 504. Embryo of Triglochin Barrelieri. r. Radicle. /, Slit corresponding to the gemmule. 
e. Cotyledon. 



DICOTYLEDONOUS EMBRYO. 



285 



an enlarged mammillary projection, whence the rootlets proceed by 
bursting through it, and carrying with them a covering or sheath 
(f 127, fig. 124.) 

596. When considering endogenous or 
monocotyledonous stems, it was shown that 
the leaves are produced singly and alter- 
nately, in a sheathing manner, each em- 
bracing the subsequently developed bud. 
So it is in the monocotyledonous embryo. 
There is a single leaf or cotyledon pro- 
duced, and if in any instance there is more 
than one, it is alternate with the first 
formed. The cotyledon (fig. 504 c) is 
folded either partially, as in Dioscorea, or 
completely. Its sheathing portion (vagina) 
embraces the bud or gemmule, which - 
appears as a mammillary projection ; its 
position being indicated by a cleft or slit 
(fig. 504/), where the edges of the sheath 
unite. All the portion of the embryo above 
the gemmule, is the cotyledon ; all below, 
the radicle. 

597. Dicotyledonous Embryo. The form 

of this embryo varies much ; and although 
sometimes resembling in its general aspect 
that of monocotyledons, yet it is always 
distinguished by a division taking place at 
the cotyledonary extremity, by which it is 
separated into two, more or less evident, 
lobes. The parts of this embryo are easily 
traced in the Bean, Pea, Acorn, and Almond. 
In the latter (fig. 500), the embryo has an 
oval form, consisting of two thick cotyle- 
dons, c c, and a radicle, r. When one of 
the cotyledons is removed (fig. 501), leaving . 
scars, i c, the gemmule or plumule, g, is 
seen included between them, with its cauli- 
cule or tigelle, t. 

598. The cotyledons, are not always, 

however, of the same size. Thus, in a 505 

species of Hirsea (fig. 506), one of them, c', is smaller than the other; 

and in Carapa guianensis (fig. 507), there appears to be only one, 

Fig. 505. Monocotyledonous embryo of Zannichellia palustris germinating, m, Collum or 
neck, the point intermediate between the stem or tigelle, t, and the radicle or root, r. c, Cotyle- 
don, g, Gemmule or plumule. 



286 



DICOTYLEDONOUS EMBIIYO. 



in consequence of the intimate union which takes place between 
the two as indicated by the dotted line, c. The union between the 
cotyledonary leaves may continue after the young plant begins to 
germinate. Such embryos have been called pseudo-monocotyledonous 
(\]/fvlvjs, false.) When there are two cotyledons, they are opposite to 
each other. In some cases there are more than two present, and then 
they become verticillate. This occurs in Coniferas, especially in the 
Fir (fig. 508), Spruce, and Larch, in which six, nine, twelve, and even 

2 





506 507 508 

fifteen have been observed. They are linear, and resemble in their 
form and mode of development the clustered or fasciculated leaves of 
the Larch. Plants having numerous cotyledons are occasionally deno- 
minated polycotyledonous. Duchartre thinks that the multiple cotyle- 
dons of the Firs are not verticillate, but occur in two opposite groups, 
placed like two ordinary cotyledons. Hence he considers the plants 
to be truly dicotyledonous, with the cotyledons deeply divided into a 
number of segments. Between the two cotyledons there is a slit which 
is well seen in Pinus Pinaster and excelsa. Thus, the arrange- 
ment of the cotyledons follows the same law as that of the leaves in 
dicotyledonous or exogenous plants, being opposite or verticillate 
according to the mode of formation of the axis. 

599. The texture of the cotyledons varies. They may be thick, as 
in the Bean, exhibiting only slight traces of venation, with their flat 
internal surfaces in contact, and their backs more or less convex; or 
they may be in the form of thin and delicate laminae, flattened on both 
sides, and having distinct venation, as in Kicinus (fig. 509), Jatropha, 
Euonymus, &c. In the former case they are called fleshy, or seminal 
lobes ; in the latter, foliaceous, or seminal leaves. 

600. Cotyledons are usually entire and sessile. But they occasionally 

Fig. 506. Embryo of Hiraea Salzmanniana, cut vertically, to show the inequality of the two 
cotyledons, one of which, c, forms almost the whole mass of the embryo, d, The small cotyle- 
don, g, Gemmule or plumule, r, Radicle. 

Fig. 507. F " 
the distinctioi 

c, Cotyledons, which are numerous; the plant being polycotyledonous. 



DICOTYLEDONOUS EMHKYO. 



287 



become lobed, as in the Walnut and the Lime (fig. 510), where the 
cotyledon, c, has five lobes; or petiolate, as in Geranium molle (fig. 
oil p) ; or auriculate, as in the Ash (fig. 512 6). Like leaves in the 
bud (see Vernation, ^[ 184), cotyledons may be either applied directly 
to each other (fig. 509), or may be folded in various ways. In the 
Almond (fig. 500) they lie in the direction of the axis. In other cases 
they are folded laterally, condupKcate (fig. 513); or from apex to base, 




reclmate (fig. 205 a); or rolled up laterally, so as partially to embrace 
each other, convolute (fig. 514); or rolled up like the young fronds of 
ferns, drcinate (fig. 515). In these cases, both cotyledons follow the 
same direction in their foldings or convolutions; but, in other in- 
stances, they are folded in opposite directions, resembling the equitant 
(fig. 205 m) and semi-equitant (fig. 205 n) vernation. 

601. The radicle may be either straight or curved, and, in particular 
instances, it gives a marked character to the seed. Thus, the divisions 
of the order Cruciferae are founded on the relative position and folding 
of the radicle and cotyledons. In the division Pleurorhizece (?r?i svod, side, 



Fig. 509. Embryo of Ricinus communis taken out of the seed (see fig. 48-3), and cut trans- 
versely. The two halves are separated so as to show the two cotyledons, e, applied to each other. 
r, Radicle. 

Fig. 510. Embryo of the Lime, r, Radicle, c. One of the divided or palmate cotyledons. 

Fig. 511. Embryo of Geranium molle. r. Radicle, c, Cotyledons attached to the collar by 
a stalk or petiole, p. 

Fig. 512. Embryo of the Ash. r. Radicle, c, One of the cotyledons, o o, Auricular appen- 
dages to the cotyledon. 

Fig. 513. Embryo of Brassica oleracea, Cabbage, r, Radicle, c, Cotyledon. 1. Entire embryo, 
2. Embryo cut transversely, showing the cotyledons folded on the radicle or conduplicate. The 
radicle is dorsal, or on the back of the cotyledons. 

Fig. 514. Embryo of Punica Granatum, Pomegranate, cut into two halves. The upper half 
removed to show the convolute cotyledons, r, Radicle. 

Fig. 515. Circulate embryo of Bunias oiientalis. 



288 



DICOTYLEDONOUS EMBRYO. 



and /, root), the cotyledons are applied by their faces, and the 
radicle (figs. 516, 517 r) is folded on their edges, so as to be lateral, 
while the cotyledons, c, are decumbent (accumbo, I lie at the side). In 
Notorhizece (varov, back), the cotyledons (fig. 518 c) are applied to each 






other by their faces, and the radicle r, is folded on their back, so as 
to be dorsal, and the cotyledons are incumbent (ineumbo, I lie upon or 
on the back). In Orihoploceoe (otfog, straight, and SS-AO'KO?, a plait), the 
cotyledons are conduplicate (fig. 513, 1, 2, c), while the radicle, r, is 
dorsal, and enclosed between their folds. In other divisions, the radicle 
is folded in a spiral manner (fig. 515), and the cotyledons follow the 
same course. In the Dodder (fig. 502), the embryo appears as an 
axis without divisions, having several turns of the spiral on different 
planes. 

602. The seed sometimes is composed of the embryo and integu- 
ments alone, the former being either straight or folded in various ways, 
as already shown. In other cases there is an addition of perisperm or 
nutritive matter, in greater or less quantity, according to the state of 
development which the embryo attains (figs. 492, 493, 494). When 
the embryo is surrounded by the perisperm on all sides except its 
radicular extremity (fig. 494), it becomes internal or intrarius (infra, 
within); when lying outside the perisperm, and only coming into con- 
tact with it at certain points, it is external or extrarius (extra, without). 
When the embryo follows the direction of the axis of the seed, it is 
axile or axial, and it may be either external, so as to come into contact 
with the perisperm only by its cotyledonary apex (fig. 519), or internal 
(figs. 492, 493, 494). In the latter case, the radicular extremity may, 
as in some Coniferae, become incorporated with the perisperm appa- 
rently by means of a thickened suspensor. When the embryo is not 
in the direction of the axis, it becomes abaxile or abaxial (fig. 520 e); 

Fig. 516. Embryo of a Pea, cut transversely. Upper half separated to show the fleshy accum- 
bent cotyledons, c. r, Radicle applied laterally. 

Fig. 517. Embryo of Isatis tinctoria. c, Accumbent cotyledons, r, Radicle. 1. Embryo 
entire. 2. Transverse section of the embryo. 

Fig. 518. Embryo of Cheiranthus Cheiri, Wallflower, c, Incumbent cotyledons, r, Radicle. 
L Embryo entire. 2. Transverse section of the embryo. 



POSITION AND FORM OF THE EMBRYO. 



289 



and in this case it may be either straight or curved (fig. 521), internal 
or external. In the straight seed of Grasses, the perisperm is abun- 
dant, and the embryo lies at a point on its surface, immediately below 




the integuments, being straight and external. In Campylotropous 
ovules, the embryo is curved, and in place of being imbedded in peri- 
sperm, is frequently external to it, following the concavity of the seed 
(fig. 522), and becoming peripherical (vs^Kfs^a, I carry round), with 
the chalaza situated in the curvature of the embryo. 

603. It has been already stated, that the radicle of the embryo is 
directed to the micropyle, and the cotyledons to the chalaza. In some 
cases, by the growth of the integuments, the former is turned round 
so as not to correspond with the apex of the nucleus, and then the 
embryo has the radicle directed to one side, and is called excentric, as 
is seen in PrimulaceaB, Plantaginacese, and many Palms, especially the 
Date (fig. 520). The position of the embryo in different kinds of seeds 
varies. In all cases the radicle or base of the embryo points more or 
less directly to the micropyle, while the cotyledonary extremity is 
directed towards the chalaza. In an orthotropal seed, then, the em- 
bryo is inverted or antitropal vrt, opposite, r^ina, I turn), the radicle 
pointing to the apex of the seed, or to the part opposite the hilum 
(fig. 521). Thus, fig. 523 represents an orthotropal seed of Sterculia 
Balanghas, attached to the pericarp, p c, by the funiculus, f. The 
chalaza and hilum are confounded together at c h, the micropyle being 
at the opposite end. The integuments of the seed, i, cover the embryo 
with its perisperm, ps; the cotyledons, c, point to the hilum and 
chalaza ; while the radicle, r, points to the micropyle, and the embryo 

Fig. 519. Grain of Carex depauperata, cut vertically, t, Integuments, p, Perisperm. e, 
Embryo. 

Fig. 520. Seed or kernel of the Date, p, Perisperm or horny albumen, e, Embryo. 1. En- 
tire seed. 2. Seed cut transversely at the point where the embryo, e, is situated. 

Fig. 521. Winged fruit of Ruinex, cut vertically, to show the abaxile or abaxial slightly 
curved embryo. 

Fig. 522. Carpel of Mirabilis Jalapa, cut vertically, with the seed which it contains, , Peri- 
carp crowned with the remains of the style, . t, Integuments of the seed or spermoderm. 
e, Peripherical embryo with its radicle, r, and its cotyledons, c. p, Perisperm or Albumen sur- 
rounded by the embryo. 

U 



290 



POSITION AND FORM OF THE EMBRYO. 




is thus reversed or inverted. Again, in an anatropal seed (figs. 493, 
494), where the micropyle is close to the hilum, and the chalaza at 

the opposite extremity, 
the embryo is erect or 
homotropal (Spoto;, like, 
and T^iTru, I turn), the 
radicle or base of the 
embryo being directed to 
the base of the seed. In 
some anatropal ovules, as 
in Castor oil (fig. 483), 
the exostome is thickened 
or carunculate, c, and the 
endostome does not correspond exactly to it, so that the radicle, e r, 
of the embryo is directed to a point a little removed from the exostome. 
In curved or campy lotropal seeds (fig. 419), the embryo is folded so 
that its radicular and cotyledonary extremities are approximated, and 
it becomes amphitropal (xp(pl, around, and Tpeira, I turn). In this 
instance the seed may be exalbuminous, and the embryo may be 
folded on itself (fig. 524) ; or albuminous, the embryo surrounding 
more or less completely the perisperm, and being peripherical (fig. 
522). In fig. 524, the seed of Erysimum cheiranthoides 
is shown, with the chalaza, c A, and the hilum, A, nearly 
confounded together, the micropyle, m, the embryo occu- 
pying the entire seed, with the radicle, r, folded on the 
cotyledons, c, which enclose the plumule, g. Thus, by 
determining the position of the hilum, chalaza, and 
micropyle, the direction of the embryo may be known. 

604. According to the mode in which the seed is at- 
tached to the pericarp, the radicle may be directed up- 
wards, or downwards, or laterally, as regards the ovary, 
In an orthotropal ovule attached to the base of the peri- 
carp, it is superior (fig. 521). So also in a suspended 
525 anatropal ovule, as in fig. 483. In other anatropal ovules, 

as in figs. 492, 504, 525, the radicle is inferior. When the ovule is 
horizontal as regards the pericarp, (fig. 523), the radicle, r, is either 





inverted. 

Fig. 524. Campylotropal seed of Erysimum cheiranthoides, cut longitudinally, m, Micropyle. 
c ft, Chalaza not far removed from the hilum, h. t, Testa or episperm. m i, Inner covering of 
the seed or endopleura. r, Radicle, c, Cotyledons, g, Gemmule. The embryo is curved or 
amphitropal. 

Fig. 525. Vertical section of the carpel of Triglochin Barrelieri. p. Pericarp crowned by 
the sessile stigma, s. g, Seed. /, Funiculus. r, Raphe. c, Chalaza. 



FUNCTIONS OF THE SEED. 291 

centrifugal, when it points to the outer wall of the ovary; or centrip- 
etal, when it points to the axis or inner wall of the ovary. 

9. FUNCTIONS OF THE SEED. 

605. The seed contains the embryo or germ, which, when placed in 
favourable circumstances, is developed as a new plant. The embryo 
is usually of a whitish or pale colour, resembling the perisperm when 
present, and sometimes scarcely distinguishable from it at first sight. 
Occasionally, however, it is of a greenish or yellow hue. Instances 
of this occur in the perispermic or albuminous seed of Euonymous, and 
the aperispermic or exalbuminous seeds of most Cruciferae. The 
changes which take place in the composition of the seed, and in its 
coats, are with the view of protecting the embryo from vicissitudes of 
temperature, moisture, &c., and of laying up a store of nourishment 
for its after growth. The coats become thickened and hardened by 
the deposition of lignine; and in its interior, starch, nitrogenous 
compounds, phosphates, and sulphates, besides oily and fatty matters, 
various organic acids, tannin, and resins, are found. The specific 
gravity of the seed is much increased, so that it usually sinks in water, 
and it becomes more capable of resisting decomposition, and preserving 
the vitality of the embryo. 

606. When seeds are matured, they are detached from the plant in 
various ways. They separate from the funiculus at the hilum, and 
remain free in the cavity of the pericap, which either falls along with 
them, or opens in various ways so as to scatter them. The elasticity 
with which some seed-vessels open during the process of desiccation is 
very great. It may be seen in Hura crepitans, Common Broom, and 
Cardamine. In the Geranium (fig. 455), the seed vessels are coiled 
upwards on the elongated beak, and in this way the seeds are dropped. 
In the succulent fruit of Momordica Elaterium, or squirting Cucum- 
ber, the cells vary in their size and contents in different parts; some 
containing thick matter become distended at the expense of others 
with thinner contents, and the force of endosmose ultimately causes 
rupture of the valves at their weakest point, viz., where they are 
united to the peduncle. When this takes place, the elasticity of the 
valves sends out the seeds and fluid contents with great force through 
the opening left by the separation of the peduncle. In the Impatiens 
or Balsam, the seed-vessel opens with force by a similar process, the 
five valves curving inwards in a spiral manner, in consequence of 
the distension of the outer large cells. The seeds are discharged be- 
fore they are dry. In the case of Mignonette (fig. 479), the seed- 
vessel opens early, so as to expose the seeds ; and in Cuphea, the 
placenta pierces the ovary and floral coverings early, so as to render 
the seeds naked. 



292 GERMINATION REQUISITES FOR IT. 

607. Wind, water, animals, and man, are instrumental in the dis- 
semination of seeds. Some seeds, as those of Mahogany, Bignonia, 
Tecoma, Pine, Asclepias, Epilobium, and the Cotton plant, have winged 
or feathery appendages, by means of which they are wafted to a dis- 
tance. The same thing occurs in some indehiscent seed-vessels, as 
the samara of the Sycamore and Ash, and the achaenia of Dandelion, 
Thistles, &c. Moisture, as well as dryness, operates in the bursting of 
seed-vessels. The pod of the Anastatica, or Rose of Jericho, and the 
capsule of some Mesembryanthemums, exhibit the effects of moisture 
in a remarkable degree. Animals, by feeding on fleshy fruits, the 
kernels of which resist the action of the juice of the stomach, dis- 
seminate seeds ; and man has been the means of transporting seeds 
from one country to another. In some cases, the pericarps ripen their 
seeds under ground, and are called hypocarpogean (Wo, under, xm^o;, 
fruit, and yia,, earth). This is seen in the Arachis hypogaea, or 
Ground-nut. Others, as Vicia amphicarpos, have both aerial and 
subterranean fruit. Many seeds are used for food by animals, and a 
great destruction of them takes place from decay ; but this is compen- 
sated for by the vast number produced, so as to secure the continuance 
of the species. The quantity of seeds produced by many plants is 
very great. In single capsules of Poppy and Tobacco, upwards of 
40,000 have been counted. 

608. Germination. The act by which the embryo of a seed leaves 
its state of torpidity, and becomes developed as a new plant, is called 
germination (germmatio, springing). In order that this process may go 
on, a certain combination of circumstances is necessary. The chiei 
requisites are moisture, air, and a certain temperature. Exclusion 
from light is also beneficial. 

609. Moisture is necessary in order that the nutritive matters may 
be taken up in a state of solution, and that certain changes may take 
place in the seed. Dry seeds will not germinate. The quantity of 
water absorbed by seeds is often very large. Decandolle found that 
a French bean, weighing 544 milligrammes, absorbed 756 of water. 
The swelling of Pease by absorption of water is familiar to all. The 
kernels or seeds by this means are enabled to burst their stony coverings. 

610. The temperature required for germination varies in different 
seeds. Some demand a tropical heat, others are satisfied with the 
warmth of our spring. In general, the requisite temperature may be 
said to vary from 60 to 80 F. Some seeds can bear a temperature 
which would kill others. Some have been known to germinate after 
exposure for a short time to the heat of boiling syrup ; others after 
exposure to a cold of 39 F. Many plants grow in the immediate 
vicinity of very hot springs, others in cold regions. Edwards and 
Colin, from their experiments, were led to fix 95 F. as the highest 
limit of prolonged temperature which cereal grains can bear in water; 



GERM1XATION REQUISITES FOR IT. 293 

and 113 F. as the highest they can bear in sand or earth. Wheat, 
Oats, and Barley, are said to thrive in any country where the mean 
temperature exceeds 65 F. The spores of certain cryptogamic plants 
are especially fitted for cold countries. Edwards and Colin found that 
seeds in a dry air bore a higher temperature than in water or steam. 

611. Air, or rather oxygen, was shown by Scheele to be necessary 
for germination. Seeds deeply buried in the soil, and excluded from 
air, do not spring. The depth at which seeds should be sown, varies 
from half an inch to two inches, according to the nature of the soil. 
The following experiments were made by Petri : 

Seed sown to the Came above ground No. of plants that 
depth of in came up. 
inch 11 days 7-8ths. 

1 12 all. 

2 .18 7-8ths. 

3 20 6-8ths. 

4 21 4-8ths. 

5 22 3-8ths. 

6 23 l-8th. 

Shallow sowing is thus proved to be the best. 

612. Seeds, when buried deep in the soil sometimes lie dormant 
for a long time, and only germinate when the air is admitted by 
the process of subsoil ploughing, or other agricultural operations. 
When ground is turned up for the first time, it is common to see a 
crop of white clover and other plants spring up, which had not been 
previously seen in the locality. After the great fire in London, plants 
sprung up, the seeds of which must have long lain dormant ; and the 
same thing is observed after the burning of forests, and the draining 
of marshes. Gardner says that the name capoeira is given in Brazil, 
to the trees which spring up after the burning of the virgin forests 
(matos virgens and capoes), and that they are always very distinct 
from those which constituted the original vegetation. Mr. Vernon 
Harcourt mentions a case where turnip seeds lay in a dormant state 
for seven or eight years, in consequence of being carried down to a 
great depth in the soil. On the Calton Hill, at Edinburgh, when 
new soil was turned up some years ago for building, a large crop of 
Fumaria micrantha sprung up ; and seeds gathered from under six 
feet of peat-moss in Stirlingshire have been known to germinate. Mr. 
Kemp mentions the germination of seeds found at the bottom of a 
sand-pit 25 feet deep, which he concludes from various circumstances, 
to have been deposited more than 2000 years ago. The seeds were 
farinaceous, belonging to the natural order Polygonacese. A weak 
solution of chlorine is said to accelerate germination, probably by the 
decomposition of water, and the liberation of oxygen. 

613. Darkness is favourable to germination. Seeds germinate best 
when excluded from light. M. Boitard showed this by experiments 



294 GERMINATION KEQUISITES FOR IT. 

on Auricula seeds, some of which were covered by a transparent bell- 
jar, others by a jar of ground glass, and a third set by a jar enveloped 
in black cloth. The last germinated most rapidly. Mr. Hunt says 
that the luminous or light-giving rays, and those nearest the yellow, 
have a marked effect in impeding germination ; the red or heat-giving 
rays are favourable to the process, if abundance of water is present ; 
while the blue rays, or those concerned in chemical action or actinism, 
accelerate the process and cause rapid growth. His experiments were 
performed by making the sun's rays pass through different kinds of 
coloured glass. He believes that the scorching effect of the sun on 
leaves may be prevented by the use of blue glass, and that a high 
temperature might be obtained by red glass. He has suggested a 
pale-green glass made with oxide of copper, as that best fitted for con- 
servatories. By this means he expects that the scorching rays of 
light will be excluded, while no hinderance is given to the passage of 
the others ; the green colour being a compound of yellow or luminous, 
and of blue or chemical rays. A delicate emerald-green glass has 
been employed lately at his suggestion, in glazing the large Palm- 
house at Kew. 

614. Some have said that electricity prevents germination, but facts 
are wanting to confirm this. The experiments of Dr. Fyfe,* Mechi, 
Coventry, and others, have shown that the statements made in regard 
to the efficacy of electro-culture are erroneous. 

615. In order that plants may germinate vigorously, moisture, heat, 
and air must be supplied in due proportion. If any of them are de- 
ficient, or in excess, injury may be done. It is of great importance, 
therefore, in agricultural operations, that the ground should be well 
pulverized, the seeds regularly sown at a proper and equal depth, and 
the soil drained. Pulverized soil, when examined, is found to consist 
of small particles having cavities in their interior, and separated from 
each other by interstitial spaces. In a very dry soil, all these cavities 
are full of air ; in a very wet undrained soil, they are full of moisture ; 
while in a perfectly drained soil, the interstices are full of air, while 
the particles themselves are moist. The seed in such a soil is under 
the influence of heat, air, and moisture, and is excluded from light. 
Hence it is in very favourable circumstances for germination. Frost 
has an important effect in pulverizing the soil, by the expansion of the 
water contained in the particles, when it is converted into ice. Snow, 
again, acts in giving a covering to the young plant, protecting it from 
intense frost and sudden alternations of temperature, and by its slow 
"melting allows the plant to accommodate itself to the mild atmosphere. 
Snow contains often much oxygen. 

616. If a field is not equally planted, the seeds will sink to different 
depths, and will spring up very irregularly. The seeds should be 

* See Trans, of Soc. of Arts, voL iii. part ii. p. 109. 



VITALITY OP SEEDS ITS DURATION. 295 

placed at a depth not greater than two inches. Draining acts not 
merely in removing superfluous moisture, but in allowing a constant 
renewal of nutritive matter, more especially of ammonia and carbonic 
acid from the atmosphere, in giving a supply of air, and in keeping 
up a proper temperature in the soil. In an undrained soil the water 
is stagnant, and there is little supply of fresh nutriment, and much 
cold is produced. Of late there has been a discussion as to whether 
shallow or deep draining is the best. Much depends on the nature of 
the soil, and it is impossible to lay down any fixed rule applicable to 
all cases. Mr. Smith says that drains in very stiff soils should be 
fifteen feet apart, and in very light soils thirty or forty ; the depth 
being from thirty to thirty-six inches, and the main drains six inches 
deeper than the parallel ones. In extremely stiff clays, he makes 
drains two and a half feet deep. He was the first to advocate the 
system of parallel drains, or what is called thorough-draining. 

617. vitality of Seeds. Some seeds lose their vitality soon, others 
retain it for a long time. Coffee seeds, in order to grow, require to be 
sown immediately after ripening. On the other hand, Melon seeds have 
been known to retain their vitality for upwards of forty years, and those 
of the Sensitive plant for more than sixty years Oily seeds in general, 
lose their vitality quickly, probably from their power of absorbing oxy- 
gen, and the chemical changes thus induced. Considerable discussions 
have taken place as to the length of time during which seeds will retain 
their germinating powers. Lindley mentions a case in which young 
plants were raised from seeds found in an ancient barrow in Devon- 
shire, along with some coins of the Emperor Hadrian ; and M. des 
Moulins relates an instance of seeds capable of germinating, which 
were discovered in a Roman tomb, supposed to be fifteen or sixteen 
centuries old. In these instances, it is to be remarked, that the seeds 
were protected from the influences required for growth, and were pre- 
served in circumstances which cannot be easily imitated. There seems 
to be great doubts as to the seeds found in the catacombs of Egypt, 
and in mummy cases, having actually produced living plants. The 
statements relative to Mummy Wheat are not fully confirmed, and 
there are many sources of fallacy. 

618. With the view of preserving seeds, it is of importance that 
they should be thoroughly ripened, kept in a uniform temperature, 
and in a dry state, and not directly exposed to the oxygen of the air. 
They are often best kept in their seed-vessels. The hard coverings of 
many foreign legumes, and of the cones of Firs, &c., seem to be of im- 
portance in preserving the germinating power of seeds. Seeds not 
fully ripened are very apt to decay, and are easily affected by moisture. 
Seeds, although fit for food, may have lost their germinating power. 
Corn, pulse, and farinaceous seeds generally will live for a long time 
if gathered ripe, and preserved quite dry. In sending seeds from 



296 VITALITY OF SEEDS ITS DURATION. 

foreign countries, they should be put into dry papers, and exposed to 
free ventilation in a cool place ; as, for instance, in a coarse bag sus- 
pended in a cabin. Oily seeds and those containing much tannin, as 
beech-mast, acorns, and nuts, must not only be ripe and dry, but also 
must be excluded from the air. When transported, they are often put 
into dry earth and sand, and pressed hard, or preserved in charcoal 
powder, the whole being covered with tin, and put into a stout box. 
Some have suggested their preservation in hermetically-sealed bottles 
full of carbonic acid gas. Seeds enveloped in wax sent from India 
germinated well. They had been kept for three months, and were 
quite firm and fresh. They did not sprout for a month, but afterwards 
grew strong and healthy. Seeds sent in cotton and brown paper had 
grown considerably in their transit, and, when potted, grew fast, but 
soon displayed symptoms of debility. Spanish chestnuts and filberts 
have been sent enveloped in wax to the Himalayahs, and are now 
growing there. Cuttings of fruit trees, with their ends enveloped in 
wax, were also sent, and arrived in a living state. In this way also, 
apples, pears, and plums have been sent. 

619. M. Alphonse Decandolle made experiments on the vitality of 
seeds. He took 368 species of seed, fifteen years old, collected in the 
same garden, and sowed them at the same time, and in the same 
circumstances as nearly as possible. Of the 368, only seventeen ger- 
minated, and comparatively few of the species came up. The following 
are the results : 

Percent 

Malvaceae 5 came up out of. 10 species - 50 

Leguminosse 9 45 0'20 

Labiatse 1 30 0'OS 

Scrophulariaceae 10 O'OO 

Umbelliferse 10 O'OO 

Caryophyllaceas 16 O'OO 

Graminese 32 0-00 

Cruciferas 34 O'OO 

Composite 45 O'OO 

In 357 species, of which the duration of life was known, the results were: 

Per cent. 

Annuals 9 came up out of. 180 species 5'0 

Biennials 28 O'O 

Perennials 4 105 3'8 

Ligneous 3 44 6'7 

16 357 4-4 

or it may be thus given 

Per cent 

Monocarpic 9 came up out of. 208 species 4'3 

Polycarpic* 7 149 4-7 

16 357 4-4 

* For an explanation of these terms, see ^f 634. 



CHANGES IN THE SEED DURING- GERMINATION. 297 

620. Woody species thus seem to preserve the power of germinat- 
ing longer than others, while biennials are at the opposite end of the 
scale ; perennials would appear to lose their vitality sooner than an- 
nuals. Large seeds were found to retain the germinating power longer 
than small ones, and the presence or absence of separate albumen or 
perisperm did not seem to make any difference. Composite and Um- 
belliferae lost their germinating power very early. From these experi- 
ments, Decandolle concludes that the duration of vitality is frequently 
in an inverse proportion to the rapidity of the germination. This 
subject is now being investigated by a committee of the British Asso- 
ciation, under the direction of Professor Daubeny. 

621. <) IM-III ifl changes daring Germination. During the process 
of germination, certain changes take place in the contents of the seed, by 
which they are rendered fit for the nourishment of the embryo. In 
exalbuminous or aperispermic seeds, where the embryo alone occupies 
the interior, these changes are effected principally in the matters stored 
up in the cotyledons. In albuminous or perispermic seeds, on the 
other hand, the changes occur in the substance of the perisperm. One 
of the most remarkable of these changes is the conversion of starch into 
dextrine and grape sugar by a process of oxidation, the object being 
the conversion of an insoluble into a soluble substance. A nitrogenous 
compound, called Diastase (^[ 310), is developed during germination, 
and is said to act on the starch. This diastase may be probably a por- 
tion of gluten passing into a state of decomposition, and acting as a 
ferment. The change of starch into dextrine and sugar is referred 
by chemists to catalytic action, or the action of contact, and to the 
influence exercised by diastase and other matters in making a new 
arrangement of the molecules. While this conversion of starch into 
sugar proceeds, oxygen is absorbed, carbonic acid is given off, and 
heat is produced. These phenomena are well seen in the malting of 
barley. The changes produced in the air by germinating seeds have 
been investigated by Saussure, who showed that in all cases carbonic 
acid was evolved at the expense of the carbon of the seed. 

622. When all the requisites for germination are supplied, the seed, 
by the absorption of moisture, becomes softened and swollen. When 
albumen or the perisperm is present, it undergoes certain chemical 
changes by the action of the air and water, so as to be rendered fit for 
the nutrition of the embryo. These changes consist partly in the con- 
version of starch into sugar, and are accompanied with the evolution 
of carbonic acid, and the production of heat. As the fluid matters are 
absorbed by the cells of the embryo, the latter continues to increase 
until it fills the cavity of the seed, and ultimately bursts through the 
softened integuments. In cases where there is no perisperm, the exal- 
buminous embryo occupies the entire seed, and the process of germi- 
nation goes on with greater rapidity. The embryo speedily swells, 



298 STAGES OF GERMINATION. 

ruptures the integument, and is nourished at the expense of the 
cotyledons, which are often fleshy, containing much starchy matter, as 
in the Bean and Pea, along with oily matter, as in the Nut and Rape 
seed. There are thus two stages of germination that in which the 
embryo undergoes certain changes within the seed itself, and that in 
which it protrudes through the integuments and becomes an indepen- 
dent plant. 

623. The embryo then, nourished at the expense of its perisperm 
and cotyledons, continues to grow, and usually protrudes its radicular 
extremity (fig. 526, 1) in the first instance, which is nearest the sur- 
face, and next the micropyle. This, which in the embryo is very short, 
and confounded with the cauliculus so as to form the first internode, 
becomes thickened by addition to its extremity (fig. 526, 2), and the 
division between the ascending and descending axis becomes more 
marked. The caulicule or axis also elongates, bearing at its summit 
the plumule, which now appears outside the integuments (fig. 526, 3, 

g), forming the second internode, either 
accompanied by the cotyledons, or 
leaving them still within the seed coats. 
In the latter case, the cotyledons are 
usually fleshy and of a pale colour, 
and become gradually absorbed like 
the perisperm. In the former they 
assume a more or less leafy aspect, 
exercising the functions of leaves for a 
certain period, and ultimately decaying. While the radicle descends 
towards the centre of the earth, producing roots of a pale colour, the 
plumule has a tendency to ascend, forming the leafy axis, and assum- 
ing a green colour under the influence of light and air. 

624. Direction of Plumule and Radicle. Various attempts have been 
made to explain the ascent of the plumule, and the descent of the radicle, 
but none of them are satisfactory. Physiologists have not been able 
to detect any law to which they can refer the phenomena, although cer- 
tain agencies are obviously concerned hi the effects. Some have said 
that the root is especially influenced by the attraction of the earth, while 
the stem is influenced by light. Experiments have shown that the 
direction of the root is not owing to the moisture of the soil, and that 
the ascent of the stem is not due to the action of light and air ; for roots 
descend, and stems ascend, even when the latter are placed in contact 
with the earth, and the former submitted to the action of light. Knight 

Fig. 526. Germination of the dicotyledonous aperispermic seed of Acacia Julibrissin. , 
Spermoderm or testa, r, Radicle of the embryo, t, Tigellus or cauliculus. c, Cotyledons, g, 
Gemmule or plumule. L First stage: in which the radicle ruptures the envelope or spermoderm, 
and appears externally at the micropyle. 2. Second stage: where the parts of the embryo are 
further disengaged from the covering, the summit of the cotyledons only being retained by the 
spermoderm. 3. Third stage : where the embryo is entirely disengaged from the envelope or 
spermoderm, and the cotyledons, c c, are separated so as to exhibit the plumule, g. 




DIRECTION OF PLUMULE AND RADICLE. 299 

thinks that the direction of stem and roots may be traced to the state of 
the tissues. When a branch is horizontal, the fluids gravitate towards 
the lower side ; a vigorous growth takes place there; the tissues enlarge, 
and, by increasing more than those on the upper side, an incurvation 
is produced, the convexity of which looks downwards, and thus the 
extremity of the branch is directed upwards. Again, in the root the 
increase takes place by the extremity, and the fluids by their gravity 
cause this to retain always a descending direction. A similar explana- 
tion is given by Dodart. Dutrochet refers the phenomena to endos- 
mose, which varies in its effects according to the comparative size of 
the cells in the centre and circumference of an axis. In young stems 
with large pith, the central cells are larger, and they diminish towards 
the circumference ; whereas in roots, accordiag to him, the diminution 
takes place in the reverse manner. Large cells distend more rapidly 
than small ones ; and, according to their position in the axis, will thus, 
cause curvature outwards or inwards, the largest occupying the con- 
vexity of the arch, the smallest the concavity. When a branch or root 
is laid horizontally, the force of endosmose is weakened on the lower 
side, and, consequently, will cease to neutralize the tendency to incur- 
vation on the upper side, which will therefore be directed either up- 
wards or downwards, according to the position of its layers of small 
cells, in the case of a branch with large central cells, curving upwards ; 
and in the case of a root with larger hemispherical cells, downwards. 

625. These explanations do not appear, however, to be altogether 
satisfactory. It is known that the stem is directed upwards, the root 
downwards, but, as yet, physiologists have not been able to ascertain 
the laws which regulate them. The tendencies of the root and stem 
are not easily counteracted. When a seed is planted in moist earth, 
and suspended in the air, the root will, in the progress of growth, leave 
the earth and descend into the air in a perpendicular direction, while 
the stem will pass through a quantity of moist earth in an upward 
direction. If their positions are reversed they will become twisted, so 
as to recover their natural positions. 

626. The effect of light on the stem may be illustrated by the 
growth of plants in circumstances where a pencil of light only is 
admitted on one side. Experiments on this subject have been made 
by Payen, Dutrochet, and Gardner. They consider the blue rays as 
those which have the greatest effect on the plumule. Hunter observed, 
that if a barrel filled with earth, in the centre of which are some 
beans, be rotated for several days horizontally, the roots pointed in a 
direction parallel to the axis of rotation. Knight* put Mustard seeds 
and French beans on the circumference of two wheels, which were 
put in rapid motion, the one in a horizontal, and the other in a vertical 
manner; and he found that, in the former, the roots took a direction 

* See Knight's Horticultural Papers, London, 1841, p. 124. 



300 MONOCOTYLEDONOUS GERMINATION. 

intermediate between that impressed by gravitation and by the centri- 
fugal force, viz., down wards and outwards ; while the stems were 
inclined upwards and inwards. In the latter, where the force of gravi- 
tation was neutralized by the constant change of position, the centri- 
fugal force acted alone, by which the roots were directed outwards, at 
the same time that the stem grew inwards. To explain these results, 
there must be allowed 1. A more or less liquid condition of the new 
parts of the young plant. 2. A different density in the different parts 
of the latter. 3. A tendency of the denser parts of new plants, during 
germination, towards the root. On the vertical wheel, the parts of the 
young plants submitted to the centrifugal force only, had their roots 
or densest parts at the circumference. On the horizontal, the effect 
was intermediate between centrifugal force and gravity. The upper 
side of leaves is under the influence of light in a marked degree, 
for, when placed in the reverse position by the turning of a branch, 
they twist round so as to resume their natural exposure. During 
darkness, on the contrary, many leaves fold in such a Avay that their 
lower surface is exposed. Some plants grow indifferently in all direc- 
tions at the period of germination. The Misletoe and other parasites 
direct their radicles towards the centre of the tree or plants to which 
they are attached, while the plumule grows perpendicularly to the 
surface. 

627. Monocoiyiedonons Germination. In Monocotyledons, there is 
generally a perisperm present, often in large quantity, and in them 
the cotyledon remains more or less within the seed at the period of 
germination. The intra-seminal portion of the cotyledons, as in Canna, 
and especially in the Coco-nut, becomes developed as a pale cellular 
mass, which increases much, and absorbs the nutriment required for 
the embryo. In some Monocotyledons the perisperm disappears en- 
tirely ; in others, as in the Phytelephas or Ivory Palm, while certain 
soluble matters are removed, the perisperm still retains its original 
form. The intra-seminal part may be said to correspond to the limb 
or lamina of the cotyledonary leaf. The extra-seminal portion, corre- 
sponding to the petiole, becomes often much elongated, as in the 
double Coco-nut, and ends hi a sheath which envelopes the axis or 
cauliculus, and the plumule. Sometimes, however, there is no marked 
elongation of the cotyledon, the sheath being at once formed on the 
outside of the seed, so that the plumule and radicle are, as it were, 
sessile on its surface. These phenomena are well seen in Canna 
indica (fig. 527), where e is the envelope of the seed ; p the perisperm 
or albumen; c the intra-seminal portion of the cotyledon, which 
absorbs the nourishment ; p c the petiolary or extra-seminal portion 
of the cotyledon, which varies in length, and may be wanting ; v the 
sheathing portion of the cotyledon, from a slit in which, f, the plumule, 
g, protrudes, supported on the axis or cauliculus, t ; while the radicles, 



DICOTYLEDONOUS GERMINATION. 



301 



r and r', pierce the integument at the base, and are each covered with 
a separate sheath, c o, called coleorhiza (fig. 124). In aperispermic 
Monocotyledons, as Alismacea? and Potameae (fig. 505), the cotyledon 
does not remain within the seed, but is raised above the ground, c, 
giving origin to the plumule, <7, which is at first enclosed in its sheath. 






628. Thus the cotyledon follows the development of leaves. Its 
limb is first produced, and is either pushed above ground, or is con- 
fined within the seed. In the latter case it is arrested in its progress; 
subsequently, a sheath is formed which may either be a direct con- 
tinuation of the limb, or may be separated from it by a petiolary 
portion. When the limb is confined in the seed, and ceases to be 
developed, the sheath often continues to grow, forming a marked 
covering of the axis. The roots in Monocotyledons during germina- 
tion (fig. 124 r r), pierce the radicular extremity of the embryo, and 
become covered with sheaths or coleorhizas, c c, formed by a super- 
ficial layer of cellular tissue. As the radicular extremity thus remains 
within the embryo, and sends out radicles from its surface, the plants are 
said to be endorhizal (sv^oy, within, and /$/, a root). See ^[ 127. 

629. Dicotyledonous Germination. In Dicotyledons, the cotyledons 
generally separate from the integuments, and either appear above 
ground in the form of temporary leaves (figs. 528, 529 c c), which differ 
in form from the permanent leaves of the plant (fig. 529 g\ or remain 
below as fleshy lobes. In the former case they are epigeal (tiri, upon or 
above, and ye, the earth); in the latter case (as in Beans, Arachis, 
&c.), they are hypogeal (tiro, under). The cotyledons usually separate, 
but sometimes they are united, and appear as one. In all cases, the 

Fig. 527. Germination of the monocotyledonous perispermic seed of Canna indica. The seed 
is cut to show the relation between the perisperm and the embryo at different stages, the for- 
mer diminishing, while the latter increases, e. Envelope or spermoderm. o, Its upper part, 
which is separated like a lid or operculum, to allow the passage of the radicle, p, Perisperm or 
albumen, c, Cotyledon, r. Radicle or young root, r 1 r 1 , Secondary radicles, c p, Coleorhiza or 
sheath of the roots. /, Slit indicating the position of the gemmulc; at this slit an elongated 
sheath, r, is protrude! p c, Narrow portion of the cotyledon (corresponding to the petiolary 
portion), intermediate between its enlarged portion, c (corresponding to the lamina or limb of 
the leaf), and its sheathing or vaginal portion, r. t, Tigellns or cauliculus. g, Gemmule or 
plumule. 1. First stage, in which the radicle, r, begins to appear throilgh the integuments or 
spermoderm. 2. Second stage, where the slit, /, is seen also on the outer surface, indicating the 
situation of the gemmule. The true radicle, r, has pierced the envelope of the seed, and at its 
base shows a small sheath or coleorhiza. One of the small radicles, r 1 is also seen with a coleo- 
rhiza. 3. Third stage, when all the parts are more developed, and the gemmule, <7, appears on 
the outside of the slit, /, the edges of which are prolonged in the form of a sheath or vagina, e. 



302 



DICOTYLEDONOUS GERMINATION. 



plumule (figs. 528, 529 g) proceeds from between the two cotyledons, 
and does not pierce through a sheath as in monocotyledons. The 
root (fig. 528 r) is a direct prolongation of the axis, f, in a downward 





direction, separating from it at the collar, m, and the embryo is here 
exorhizal (||, outwards). See ^[ 126. 

In Acotyledons, the spore (fig. 530) has no separate embryo in its 
interior, but germinates from any part of the surface; hence it is called 
heterorhizal (irepos, diverse). See ^[ 128. The spore may be considered 
as a cellular embryo rather than a seed. 

630. Some seeds commence the process of germination before being 
detached from the plant. This occurs in a remarkable degree in the 
Mangrove trees, or Ehizophoras, which grow at the muddy mouths of 
rivers in warm climates. Coco-nuts often begin to germinate during 
a voyage from the tropics to Britain, and germinating seeds have 

Fig. 528. Germination of the dicotyledonous embryo of Acer Negundo. m, Collum, collar or 
neck, r, Root (, Caulicule or stem, c c, Cotyledons, g. Gemmule or plumule. 

Fig. 529. Upper parfrof the same embryo more developed, c c, Cotyledons, g, Gemmule, 
the first leaves of which are already expanded, t, Caulicule or stem. 

Fig. 530 Acotyledonous embryos or spores of Marchantia polymorpha, germinating. 1. Spore 
in the early stage of germination. 2. In a more advanced stage. The spores are simple cells, 
which elongate during germination at some point of their surface. They are heterorhizal. 
They may be compared to naked embryos rather than to seeds. 



PROLIFEROUS OR VIVIPAROUS PLANTS. 303 

been found in the interior of Gourds, as well as the fruit of Carica 
Papaya, the Papaw. 

631. Proliferous Plants. In place of seeds, some plants produce 
buds which can be detached and produce separate individuals. Flowers 
which are thus changed into separable buds, are called proliferous 
(proles, offspring, and fero, I bear), or viviparous (vivus, alive, and 
pario, I produce). They are met with in many alpine grasses, as 
Festuca ovina, var. vivipara, Aira casspitosa, var. alpina, Poa alpina, &c., 
as well as in Alliums, Trifoliums, &c. Buds of a similar kind may be 
produced on the edges, or in the axil of leaves, as in Byrophyllum 
calycinum, Malaxis paludosa, many species of Gesnera, Gloxinia, and 
Achimenes ; and the bulbils of Lilium, Ixia, and Dentaria, seem to be 
peculiar forms of buds, capable of being detached, and of assuming 
independent growth. Buds, however, differ from embryos of seeds 
in the direction of the roots being towards the axis of the plant. 

632. The length of time required for the protrusion of the radicle 
varies in different plants. Some seeds, as garden cresses, germinate in 
the course of twenty-four hours, others require many days or many 
months. Seeds with hard coverings, or a stony perisperm, may lie 
dormant in the soil for a year or more. The following experiments 
were made in the Geneva garden, on seeds similarly watered, and ex- 
posed to a medium temperature of 53 F. It was ascertained that 
one half of the species of the following families germinated after the 
lapse of the number of days here mentioned : 

Amaranthacese, 9 days. 

Cruciferse, 10 

Boraginaceze, Caryophyllacese, Chenopodiacece, Malvaceae, ...11 

Compositse, Convolvulaceae, Plantaginacese, 12 

Polygonacea?, , 13 

Campanulacese, Leguminosae, Valerianacese, 14 

Graminese, Labiatse, Solanacea?, 15 

Rosacese, 17 

Ranunculaceae 20 

Antirrhinums, Onagrariaceae 22 

Umbelliferae, 23 

Temperature has a great effect in accelerating germination. Thus, 
Erigeron caucasicum, at a temperature varying from 49 to 53, ger- 
minated in ten days; at a temperature from 66 to 72, in two days ; 
Dolichos abyssinicus, at the former temperature, in ten days, at the 
latter, in three; Zinnia coccinea, in twenty-two, and five days respec- 
tively. 

633. Duration of the Life of Plants. Plants, according to the 
duration of their existence, have been divided into annual, biennial, 
and perennial The first of these terms imports that the seed germinates, 
and that the plant produces leaves and flowers, ripens its seed, and 
perishes within twelve months; the second, that a plant germinates 



304 DURATION OP THE LIFE OF PLANTS. 

and produces leaves the first year, but does not produce a flowering 
stem, nor ripen its seed, till the second, after which it perishes ; 
while the third intimates, that the process of flowering and fruiting may 
be postponed till the third year, or any indefinite period. The first 
two exercise the function of flowering in general only once, while 
the last may do so several tunes before dying. Under different 
climates, however, and under different modes of management, the 
same species may be annual, biennial, or even perennial. Thus, 
Wheat in this country is annual if sown early in spring, but biennial 
if sown in autumn; in hot climates, Lolium perenne proves annual; 
the Castor-oil plant in this country is annual, while in Italy it is a 
shrub of several year's duration; the annual Mignonette, by removing 
its flower-buds the first year, and keeping it in a proper temperature 
during the winter, may be rendered perennial and shrubby. Many 
flowering garden plants, as Neapolitan Violet and Lily of the Valley, 
may be brought into flower at a late period of the year, by pinching 
off the blossoms in the early part of the season. 

634. Plants, as regards their flowering and fruiting, have also been 
divided into monocarpic (ftovos. one, and gago-oV, fruit), or those which 
flower once only and then die; and polycarpic (TOAI)?, many), or those 
which flower and fruit several times before the entire plant dies. Thus, 
annuals and biennials, which flower the first or second year and die, 
as well as the Agave, and some Palms which flower only once in forty 
or fifty years, and perish, are monocarpic; while perennials are poly- 
carpic. Some perennial woody plants live to a great age. Some 
specimens of Adansonia digitata, the Baobab of Senegal, are said to be 
more than 5000 years old. The Yew, the Oak, the Lime, the Cypress, 
the Olive, the Orange, Banyan, and Chestnut, often attain great 
longevity. 

635. The following is a notice of the size and age of some trees: 

Height to which forest trees grow in France, 120 to 130 feet. 

Height to which forest trees grow in America, 150 

Trunks of some Baobabs have a girth of 90 

Trunk of Dracaena of the Canaries has a girth of 45 

That of an Acer in South Carolina has a girth of. 62 

In France, trees have often a girth of 25 to 30 

Oaks in Britain planted before the Conquest, more than 800 years old. 

Yew at Fountain's Abbey, Ripon, 1200 

Yews in churchyard of Crowhurst, Surrey, 1450 

Yew at Fortingal, Perthshire, , 2500 to 2600 

Yew at Brabourn churchyard, Kent 3000 

Yew at Hedsor, Bucks, 27 feet diameter 3200 

A specimen of Ficus indica, or the Banyan, on an island in the river 
Nerbudda, is believed to be identical with one that existed in the time 
of Alexander the Great, and which, according to Nearchus, was then 
capable of overshadowing 10,000 men. Parts of it have been carried 



TABULAR ARRANGEMENT OF ORGANS. 305 

away by floods, but it can shade 7000 men, and its circumference, 
measuring its principal trunk only, is 2000 feet. The chief trunks of 
this tree greatly exceed our English Oaks and Elms in thickness, and 
are above 350 in number. The smaller stems are more than 3000 
in number. 

636. The Maronites believe that some Cedars near the village of 
Eden in Lebanon, are the remains of the forest which furnished Solo- 
mon with timber for the temple, full 3000 years ago. These Cedars 
were visited by Belonius in 1550, who found them twenty-eight in 
number ; Rawolf, in 1575, makes them twenty-four ; Dandini, in 
1660, and Thevenot, about fifty years after, make them twenty-three; 
Maundrell, in 1696, found them reduced to sixteen; Pococke, in 
1736, found fifteen standing; in 1810, Burckhardt counted eleven or 
twelve ; and Dr. Eichardson, in 1818, states them to be no more than 
seven. They must be of great antiquity, seeing they were counted 
old 300 years ago. Maundrell mentions the size of some of the 
Cedars. The largest he measured was 36 feet 6 inches in circumfer- 
ence, and 117 feet in the spread of its boughs. 

637 Decandolle gives a list of the ascertained ages of certain trees : 

Elm, 335 years. 

Cypress, about 350 

Cheirostemon (Hand-tree), about 400 

Ivy 450 

Larch, 576 

Sweet Chestnut, about 600 

Orange, 630 

Olive, 700 

Platanus Orientalis, 720 

Cedar, 800 

Many tropical trees, according to Humboldt, about.. ..1000 

Lime, 1076, 1147 

Oak, 810, 1080, 1500 

Yew 1214, 1458, 2588, 2820 

Taxodium, upwards of 4000 

Adansonia, 5000 

10. GENERA! OBSERVATIONS ON THE ORGANS OF PLANTS, AND ON THE MODE IN WHICH THEY 
ARE ARRANGED. 

638. Before concluding the consideration of the elementary and 
compound organs of plants, it is proposed to make some general 
observations on their arrangement and development. The following 
is a tabular view of the various organs to which attention has been 
directed : 

GENERAL ARRANGEMENT OF THE ORGANS OF PHANEROGAMOUS PLANTS. 
I. Elementary Organs. 

( Vesicles or Cellules, Cellular Tissue. 



306 TABULAR ARRANGEMENT OF ORGANS. 

II. Compound Organs. 

1. General Integument. 
Cuticle or Pellicle,... 1 T, ., 

Stomata, !...} Epidermis. 

Hairs, Prickles or Aculei, Stings, Glands. 
2. Nutritive Compound Organs. 

Spongioles,...\T> . 

Fibrils I 1 * 00 ' 8 ' 

Pith "I Rhizome. 



Medullary Sheath, 
Heartwood or Duramen, 



Tuber. 
Stem Runner. 

Sapwood or Alburnum, j- and Sucker. 

Medullary Rays or Plates, I Branches. Conn. 

Liber or Endophlceum, | Bulb. 

Cortical Layers or Epi- and Mesophloeum, ... J Thorn. 

Petiole, ) r - Phyllodia. 

Limb or Lamina, ../ Tendrils. 

Stipules. Ascidia. 

3. Reproductive Compound Organs. 
Bract. Involucre. 

Sepals-Calyx, ) *" th 1 



Petals-Corolla, 



" 



Fovilla \ Pollen ) . , 1 

granules,...) grains, ) "*> Stamens, .................. j- Fl 

Filament,..) 



4. Composition of Ripe Fruit. 

Pericarp, ~) 
Radicle, ...... ) 1 

Cotyledon,.. A Embryo, ............................... I _.. 

Plumule, ..... ) I Seed, ..... f ff 

Spermoderm, .......................... | 

Albumen or Perisperm, ............. J 

639. Plants may be said to be composed of numerous individuals, 
each having a sort of independent existence, and all contributing to 
the general growth of the compound individual formed by their union. 
In the case of a tree there are a vast number of buds, each of which 
is capable of being removed, and made to grow on another tree by 
grafting ; and although each has thus a vitality of its own, it is never- 
theless dependent on the general vitality of the tree, so long as it is 
attached to it. The same thing is seen in Sertularian Zoophytes. Each 
of the individuals forming a compound plant is called by Gaudichaud 
a phyton (tpvTev, a plant), and in it he recognizes three parts or meri- 
ihalli (^fgoj, a part, and tfaAAoj, a frond), the radicular inerithal corres- 
ponding to the root, the cauline to the stem, and the foliar to the leaf. 

640. In the Acotyledonous plants, the embryo or spore consists of 



VEGETABLE METAMORPHOSIS. 307 

cells united together, and it is only during germination that it exhibits 
these different parts. In Monocotyledons, the embryo consists of a 
single phyton, with a radicular merithal or radicle, a cauline or tigellus, 
and a foliar or cotyledon. In Dicotyledons, the embryo consists of two 
or more phytons united, with their foliar merithals (cotyledons) distinct, 
while their cauline and radicular merithals form each a single organ. 

641. In tracing the various parts of plants, it has been shown that 
all may be referred to the leaf as a type. This morphological law was 
propounded by Linnaeus and Wolff, but it is to Goethe we owe the full 
enunciation of it. Vegetable morphology, the study of forms, or the 
reference of the forms of the parts of plants to the leaf, is now the 
basis of organography ; and it will be observed, that in considering the 
various organs, this has been kept constantly in view. The calyx, 
corolla, stamens, and pistil, are only modifications of the leaf adapted 
for peculiar functions. It is not meant that they were originally leaves, 
and were afterwards transformed; but that they are formed of the 
same elements, and arranged upon the same plan, and that in the 
changes which they undergo, and the relation which they bear to each 
other, they follow the same laws as leaves do. The different parts 
of the flower may be changed into each other, or into true leaves ; or, 
in other words, the cellular papilla? from which they are formed are 
capable of being developed in different ways, according to laws which 
are still unknown. These changes may take place from without in- 
wards, by an ascending or direct metamorphosis, as in the case of petals 
becoming stamens ; or from within outwards, by descending or retro- 
grade metamorphosis, as when stamens become petals. 

642. Bracts are very evidently allied to leaves, both in their colour 
and form. Like leaves, too, they produce buds in their axil. The 
monstrosity called Hen and Chicken Daisy, depends on the develop- 
ment of buds in the axil of the leaves of the involucre. The sepals 
frequently present the appearance of true leaves, as in the Eose. The 
petals sometimes become green like leaves, as in a variety of Ranun- 
culus Philonotis, mentioned by Decandolle, and in a variety of Cam- 
panula rapunculoides, noticed by Dumas. At other times they are 
changed into stamens. Decandolle mentions a variety of Capsella 
Bursa-pastoris, in which there were ten stamens produced in conse- 
quence of a transformation of petals. The stamens in double flowers 
are changed into petals, and in Nymphsea alba there is a gradual 
transition from the one to the other. Sometimes the stamens are 
changed into carpels, and bear ovules. This has been seen in Wall- 
flower, some Willows, Poppy, &c. Petit-Thouars noticed a plant of 
Houseleek, in which the one half of the anthers bore ovules, and the 
other half pollen. The carpels, as in the double Cherry, may be seen 
in the form of folded leaves ; in double flowers they are transformed 
into petals, and in other cases they are developed as stamens. It is 



308 



SYMMETRY OF ORGANS. 



said that increase of temperature, and luxuriance of growth, sometimes 
make flowers produce stamens only. In plants having unisexual 
flowers, this is more liable to take place, as in Melon, Cucumber, &c. 
Increased vigour seems to be required for the development of stamens, 
for some fir trees in their young state bear cones, and produce male 
flowers only when they reach the prime of life. 

643. Symmetry of Organs. In the progress of growth, the plants 
belonging to the different divisions of the vegetable kingdom follow 
certain organogenic laws (S^yavov, an organ, and ysymifiv, to produce), 
the operation of which is seen in the definite arrangement of their 
organs. The flower consists sometimes of three, at other times of four 
or five equal sets of organs, similarly and regularly disposed. Thus, 
the Iris has three straight parts of its perianth, and three reflexed ones 
alternately disposed, while the Fuchsia has four parts of the calyx 
alternating with four petals, and the Rose has five alternating portions. 
This orderly and similar distribution of a certain number of parts is 
called symmetry, and flowers are thus said to be symmetrical with vari- 
ous numbers of members. When the number of parts is two, the 

flower is dimerous (Sif, twice, 
and ftfos, a part) (fig. 531), 
and the symmetry two-mem- 
bered. When the number of 
parts is three, the flower is 
trimerous (T^S, three), and 
when the parts are arranged 
in an alternating manner (fig. 
532), the symmetry is trigonal 
or triangular (TJ?, three, and 
yaviet,, an angle), as in the Lily. 
When there are four parts, the 
flower is tetramerous (rer^eis, 
four, and the symmetry is 
tetragonal or square (figs. 533, 
534), as in Gah'um and Paris. 
When there are five parts, the 

flower is pentamerous (vivrt, five), and the symmetry pentagonal (fig. 
535), as in Ranunculus. The number of parts in the flower is indi- 
cated by the following symbols: Dimerous $ Trimerous $ Tetra- 
merous /<y Pentamerous \/. 

Fig. 531. Diagram of the dimerous flower of Circaea Lntetiana, Enchanter's Nightshade. 
There are two carpels, two stamens, two divisions of the corolla, and two of the calyx. The 
flower is Isostemonous. 

Fig. 532. Diagram of the rrimerous Isostemonous flower of Cneorum tricoccum. The floral 
envelopes are arranged in sets of three, and so are the essential organs. 

Fig. 533. Diagram of the tetramerous Isostemonous flower of Zieria. The organs are ar- 
ranged in verticils of four parts each. 

Fig. 534. Diagram of the tetramerous Diplostemonous flower of Ruta graveolens. There are 
four carpels, eight stamens, or four in each verticil, four folioles of the calyx, and four petals. 




SYMMETRY OF ORGANS. 309 

644. There are also other kinds of arrangements in flowers, which 
may be referred to certain modifications in the organogenic law. Thus, 
what is called oblong or two and two-membered symmetry, occurs in 
cases where the opposite ends are similar, and the opposite sides as hi 
the arrangement of the stamens of Cruciferse. Again, simple symmetry is 
that in which the two sides of the object are exactly alike, without any 
further repetition, as in papilionaceous, personate, and labiate flowers, 
as well as in most leaves. The term symmetry, however, is properly 
confined to cases where the parts are arranged alternately, and are 
either equal or some multiple of each other, and has no reference to 
the forms of the different parts. In the very young state, the parts of the 
flower appear as a shallow rim, from which the petals and sepals arise 
as mammilla?., in a symmetrical manner. In the case of irregular 
corollas, the parts at first appear regular, as shown by Barneoud.* In 
speaking of flowers, it is usual to call them symmetrical when the 
sepals, petals, and stamens follow the law mentioned, even although the 
pistil may be abnormal. Thus, many Solanacea? are pentamerous, and 
have a dimerous ovary, yet they are called symmetrical. In Cruciferaa, 
the flowers are, properly speaking, unsymmetrical, for while there are 
four sepals and four petals, there are six stamens in place of four. 
This depends apparently on the long stamens being in reality composed 
only of two, the filament of each of which is split by a process of chori- 
zation (^[ 383), and each division forms for itself by multiplication a 
perfect anther. In Papilionaceous flowers, the parts are usually sym- 
metrical, there being five divisions of the calyx, five petals, and ten 
stamens in two rows. 




645. It will be seen that flowers constituting trigonal or pentagonal 
symmetry, may present what has been called simple symmetry, when one 

* Annales des Sciences Xaturelles, November, 1846. 

Fig. 535. Diagram of the pentamerous Isostemonous flower of Crassula rubens. cccc c. Parts 
of the calyx, p p p p p. Petals alternating with the leaves of the calyx e e e e e, Stamens alter- 
nating with the petals, a, Accessory bodies in the form of scales, or a disk alternating with the 
stamens. These scales are often an abortive row of stamens, o. Carpels alternating with the 
stamens, and opposite to the scales. 

Fig. 536. Diagram of the pentamerous flower of Sedum Telephium. The stamens are ten, 
arranged in two alternating verticils. The flower is Diplostemonous. 

Fig. 537. Diagram of the pentamerous Diplostemonons flower of Coriaria myrtifolia; the 
parts of the four whorls alternating, the verticil of stamens being double. 

Fig. 538. Diagram of the trimerous Diplostemonous flower of Ornithogalnm pyrenaicum. 
Stamens six in two alternating verticils. 



310 TERATOLOGY. SUPPRESSION OF ORGANS. 

of the petals or sepals becomes more developed than the others. In Di- 
cotyledonous plants, it is common to meet with pentagonal (figs. 535, 
536, 537) and tetragonal (figs. 533, 534), symmetry, the parts being 
arranged in fives and fours, or in multiples of these numbers. It is 
common to find the stamens more numerous than the petals, and in that 
case they are arranged in different verticils, each alternating with that 
next it. Thus if there are five sepals, five petals, and twenty stamens, 
the latter are considered as forming four verticils. No doubt the verticils 
are often traced with difficulty, more especially when adhesions take 
place. In Monocotyledons (fig. 538), the parts are usually in sets of 
three, or in some multiple of that number, exhibiting trigonal symme- 
try. In Acotyledons, when any definite number can be traced, it is 
found to be two, or some multiple of two. The teeth of Mosses are in 
sets of four, or some multiple of four. The spores of many Acotyle- 
dons are also arranged in fours. 

646. Teratology. There has thus been traced a tendency to sym- 
metrical arrangement in plants. But the parts of plants are often 
modified by natural causes which cannot be explained. It is assumed 
that each of the similar members of a flower have the same organiza- 
tion, and a similar power of development; and hence, if among these 
similar parts some are less developed than others, they are considered 
as abortive, and these abnormal states are traced to changes which 
take place in the earlier stages of growth. Such changes often inter- 
fere with the symmetry of the flower. Alteration in the symmetrical 
arrangement, as well as in the forms of the different parts of plants, 
have been traced to suppression or the non-development of organs, degen- 
eration or imperfect formation, adhesion or union of one part to another, 
multiplication of parts, and unlining or chorization. The study of 
Teratology (r^og, a monstrosity, and Xoyo?, treatise), or of the mon- 
strosities occurring in plants, has led to many important conclusions 
relative to the development of organs, and it is only by tracing the 
parts of plants through all their stages and transformations, that correct 
ideas can be formed as to their relations and forms. 

647. By suppression is meant the non-appearance of an organ at the 
place where it ought to appear if the structure was normal; the organ 
being wanting to complete the symmetry. This suppression is liable 
to occur in all the parts of plants, and gives rise to various abnor- 
malities. Suppression may consist in the non-appearance of one or more 
parts of certain verticils, or of one or more entire verticils. In the 
flowers of Staphylea (fig. 539), there are five parts of the calyx, five 
petals, five stamens, and only two carpels; in many Caryophyllacete, 
as Polycarpon and Holosteum (fig. 540), while the calyx and corolla 
are pentamerous, there are only three or four stamens and three car- 
pels; in Irnpatiens noli-me-tangere (fig. 541), the calyx is composed of 
three parts, while the other verticils have five; in Labiate flowers, there 



TERATOLOGY. SUPPRESSION OF ORGANS. 



311 



are five parts of the calyx and corolla, and only four stamens; and in 
Tropaeolum pentaphyllum (fig. 542), there are five sepals, two petals, 
eight stamens, and three carpels. In all these cases, the want of sym- 
metry is traced to the suppression of certain parts. In the last men- 
tioned plant, the normal number is five; hence it is said that there 





are three petals suppressed, as shown by the position of the two 

remaining ones (fig. 542); there are two rows of stamens, hi each of 

which one is awanting, and there are two carpels suppressed. In many 

instances the parts which are afterwards suppressed can be seen in the 

early stages of growth, and occasionally some vestiges of them remain 

in the fully developed flower. Sometimes 

the whorl of the petals is awanting, the 

llowers being apetalous (, privative, and 

3-TXo, a leaf) (fig. 543), and in such cases 

it is common to see the stamens opposite to 

the segments of the calyx, as in Chenopo- 

diacese (fig. 544). That this suppression of the petals takes place is 

shown in the case of certain allied plants, as in the natural orders 

Caryophyllaceae and Paronychiacese, where some species have petals 

and others want them. 

648. By the suppression of the verticil of the stamens or of the 

Fig. 539. Diagram of the flower of Staphylea pinnata. The parts of the calyx, corolla, arid 
stamens are pentamerous, while the pistil, in consequence of the suppression of three carpels, is 
dimerous. 

Fig. 510. Diagram of the flower of Holosteum umbellatum. There are five calycine divisions, 
and five petals; but the stamens, by the suppression of one, are only four in number; while the 
carpels are, by suppression, reduced to three. Thus, the flower is unsymmetrical. 

Fig. 541. Diagram of the flower of Impatiens parviflora, with one of the calycine leaves 
spurred. There are five carpels, five stamens, five petals, one of which is larger than the rest, 
but only three parts of the calyx, in consequence of suppression. 

Fig. 542. Diagram of the flower of Tropaeolum pentaphyllum, with a spurred or calcarate 
calycine leaf. The petals, by suppression, are reduced to two ; the stamens are eight in place of 
ten, and the carpels three in place of five. 

Fig. 543. Diagram of the flower of Glaux maritima, showing the suppression of the verticil of 
the corolla. There are five divisions of the calyx, five stamens alternating with them, and five 
divisions of the ovary, with a central placentation. 

Fig. 544. Diagram of the flower of Chenopodium album, showing the suppression of the ver- 
ticil of the corolla. The five stamens, in this case, are opposite to the divisions of the calyx, thus 
exhibiting the arrangement which might be expected from a non-development of the corolla. 
The divisions of the ovary are not easily seen, the placentation being central. 



312 TERATOLOGY. SUPPRESSION OP ORGANS. 

carpels, flowers become unisexual (unus, one and sexu$, sex), or diclin- 
ous (big, twice, and x^ivn, a bed), and are marked thus, $ $ ; the 
first of these symbols indicating the male, and the second the female 
flower. Thus, in Jatropha Curcas (fig. 314), the flowers have five 
segments of the calyx, and five petals, while in some (fig. 314, 1) the 
pistil is awanting; in others (fig. 314, 2), the stamens. In the genus 
Lychnis, there are usually stamens and pistil present, or the flower is 
hermaphrodite, or monoclinous (^o'j/oj, one, and x^tvn, a bed); but in 
Lychnis dioica, some flowers have stamens only; others pistils only. 
Thus it is that monoecious and dioecious (ftovo;, one, Si;, twice, and 
OIKIOV, a habitation) plants are produced by the suppression of the essen- 
tial organs of the flowers, either of the same or of different individuals 
of the same species; while polygamous (oroAv?, many, and ya/tto?, mar- 
riage) plants are those in which, besides unisexual, there are also her- 
maphrodite or perfect flowers. 

649. Some parts of the pistil are generally suppressed hi the pro- 
gress of growth, and hence it is rare to find it symmetrical with the 
other whorls. When the fruit was treated of (^[ 522), it was shown 
that carpels and ovules often become abortive by pressure and 
absorption, so that the pericarp and seeds differ in their divisions 
and number from the ovary and ovules. If the whorls of the calyx 
and corolla are awanting, the flower becomes naked or achlamydeous 
(If 351). It may still, however, be fitted for the functions of producing 
seed; but if the essential organs, viz., the verticils of stamens and 
pistils, are suppressed, then the flower, however showy as regards its 
envelopes, is unfit for its functions, and is called neuter. Flowers hav- 
ing stamens only, are staminiferous, staminal, sterile; or those having 
pistils only, are pistilliferous, pistillate, or fertile. The suppression of 



54-3 546 547 548 549 550 

various verticils, and parts of them, is well seen in the family of the 
Euphorbiacea3 (figs. 545 550). Thus, in fig. 545 is delineated an 

Figs. 545 550. Diagrams of flowers of Euphorbiaceous plants, becoming more and more 
simple. (L) The calyx is the only envelope, and consists of three parts in figs. 545, 546, and 547. 
It is completely suppressed in figs. 548, 549, and 550, and its place is occupied by a bract, in the 
axil of which the flower is produced; this bract being accompanied in figs. 548 and 549 with two 
small bractlets. (2.) The male flowers in fig. 545 have three stamens, in figs. 546 and 548 they 
have two, in figs. 547 and 549 one stamen only is developed, and in fig. 550, 1, the solitary stamen 
has only one anther-lobe. (3.) The female flower in fig. 550, 2, is reduced to a single carpel, with 
a bract in the axil of which it is produced. 

Fig. 545. Diagram of a staminiferous flower of Tragia cannabina. 

Fig. 546. Diagram of a staminiferous flower of Tragia volubilis. 

Fig. 647. Diagram of a staminiferous flower of Anthostema senegalense. 

Fig. 548. Diagram of a staminiferous flower of Adenopeltis colliguaya. 

Fig. 549. Diagram of a staminiferous flower of a Euphorbia. 

Fig. 550. L Diagram of a staminiferous flower of Naias minor. 2. Of a pistilliferous flower of 
Xaias major. 



TERATOLOGY. DEGENERATION. 313 

apetalous trimerous staminal flower ; in fig. 546 one of the stamens is 
suppressed and in fig. 547 two of them are awanting. Again in figs. 
548, 549, 550, the calyx is suppressed, and its place occupied by one, 
two, or three bracts (so that the flower is, properly speaking, achla- 
mydeous), and only one or two stamens produced. In fig. 550, 1, 
there is a sterile flower, consisting of a single stamen with a bract ; and 
in fig. 550, 2, a fertile flower, consisting of a single carpel with a bract. 
There is thus traced a degradation, as it is called, from a flower with 
three stamens and three divisions of the calyx, to one with a single 
bract and a single stamen or carpel. 

650. It is common to find some of the buds of a plant suppressed, 
thus altering the spiral arrangement. Such, buds, however, are often 
capable of being developed, if any accident occurs, or if the plant is 
pruned. Deficiency of light and of air, and want of proper nourish- 
ment, are capable of producing abortions of various kinds. The non- 
development of a branch gives rise to clustered or fascicled (fastis, a 
bundle of twigs) leaves, as in the Larch, and to fascicled twigs, as 
in a common bird-nest-like monstrosity of the Birch. When the 
true leaves of a plant are suppressed, their place may be occupied 
by a tendril, as in Lathyrus Aphaca, in which the stipules perform the 
functions of leaves (^[ 201) ; or the petiole may be developed in a 
peculiar way, as in the phyllodia (^[ 157) of some Acacias. 

651. Degeneration, or the transformation of parts, often give rise 
either to an apparent want of symmetry, or to irregularity in form. 
Branches, when not properly developed, may assume the form of thorns 
or spines (^[ 200), as in the Hawthorn and Wild-plum ; and by cul- 
ture these spines may be converted into leaf-bearing branches. Leaves 
often become mere scales, as in Lathrasa, Orobanche, and in Bulbs. 
The limb of the calyx may appear as a rim, as in some Umbelliferse ; 
or as pappus, in Composite and Valeriana. In Scrophularia, the 
fifth stamen appears as a scale-like body, called staminodium (fig. 346); 
in many other plants belonging to the Scrophulariacese, it assumes the 
form of a filament, with hairs at its apex in place of an anther. In 
unisexual flowers, it is not uncommon to find vestiges of the un- 
developed stamens in the form of filiform bodies or scales. To many 
of these staminal degenerations, Linnreus gave the name of nectaries. 
In double flowers, transformations of the stamens and pistils take place, 
so that they appear as petals. In Canna?, what are called petals are 
in reality metamorphosed stamens. Allusion has already been made 
to the various changes which the different parts of the flower thus 
undergo. The object of the florist is to produce such monstrosities ; 
and flowers, which by him are considered perfect, are looked upon by 
the botanist as imperfect, from the want of the essential organs. 

652. Adhesion, or the growing together of parts, is a very common 
cause of changes both as regards form and symmetry. The union of 



314 



TERATOLOGY. ADHESION. 



stems gives rise occasionally to anomalies, as in the fasdated stalk of 
Cockscomb (fig. 230), and the flattened stems of some Conifers (^[ 197), 
and probably also the peculiar stems of certain Sapindaceaa and Meni- 
spermacea? of Brazil (^[ 90). Some of these, however, may perhaps 
be traced not to adhesion, but to an abnornal development of buds, 
producing wood only in one direction in place of all round. Natural 
grafts occasionally occur from one branch of a tree uniting to another. 
Boots also sometimes become grafted, and to this has been attributed 
the vitality occasionally preserved by the stumps of Spruce-firs which 
have been felled on the Swiss Alps. The union of two leaves by their 
base, forms a connate leaf, and the adhesion of the lobes of a single 
leaf on the opposite side of the stalk, gives rise to perfoliate leaves 
(fig. 156). The union of the edges of a folded leaf forms Ascidia, or 
pitchers (figs. 184, 187). The different parts of the same verticil of 
the flower unite often more or less completely, giving rise to a mono- 
phyllous or gamophyllous involucre (^[ 347); a monosepalous or 
gamosepalous calyx (fig. 273); a monopetalous or gamopetalous corolla 
(figs. 293, 294, &c.) ; monadelphous (figs. 307, 314, 1), diadelphous 
(^[ 399), and polyadelphous (figs. 315, 551), stamens; syngenesious 
anthers (^[417); a gynandrous column (^[ 400); and a syncarpous 
ovary (fig. 383). The different verticils of the flower are frequently 





adherent. The calyx is often united to the corolla or to the stamens, 
or both (fig. 308) ; the stamens may adhere to the corolla (fig. 552) ; 
or there may be a union of the four verticils of the flower, so that the 
calyx becomes superior (fig. 309). In some instances, when the axis 
is elongated, adhesions take place between it and certain whorls of the 
flower. Thus, in some Caryophyllaceae (fig. 553), the calyx, c, bear- 
Fig. 551. One of the five bundles of stamens taken from the polyadelphous flower of Malva 
miniata. Stamens are united by their filaments. 

Fig. 55-2. Portion of the gamopetalous or monopetalous corolla, p, of a Collomia, showing part 
of the tube t. terminated by two lobes of the limb, I, and having the stamen, e, inserted into it, 
and united to it, so that the upper part of the filament, i, only is free. 



TERATOLOGY. MULTIPLICATION AND CHOKIZATION. 



315 



ing the stamens, e, and petals, p, becomes united to the axis, </, which 
supports the ovary, o. In Capparidaceae (fig. 554), the calyx, c, and 
petals, p, occupy their usual position, but the axis is prolonged in the 
form of a gynophore, ag, to which the stamens, e, are united. Occa- 
sionally, contiguous flowers may unite, giving rise to double fruits, as 
is sometimes seen in Apples, Grapes, and Cucumbers. 





653. Multiplication, or an increase of the number of parts, gives rise 
to changes in plants. It is often found, that in plants belonging to the 
same natural order, the number of stamens in one is greater than that 
in another, either in consequence of additional stamens being developed 
in the verticil, or on account of the production of additional verticils. 
The same thing is met with in the case of the other whorls, and is 
well illustrated in the formation of the disk (If 428). Multiplication 
causes a repetition of successive whorls, which still follow the law of 
alternation. 

654. Parts of the flower are often increased by a process of dedupli- 
cation, unlining, dilamination, or chorization, i.e. the separation of a 
lamina from organs already formed (^[ 383). This is believed to take 
place in a remarkable degree in the case of appendages to petals. 
Thus, in Ranunculus, the petal (fig. 555) has a scale at its base, a, 
which is looked upon as a mere fold of it. This fold may in some 

Fig. 553. Flower of Lychnis viscaria, one of the Caryophyllacese, cut lengthwise, to show the 
relation of its different parts, c, Gamosepalous calyx, p, Petals with their elongated unguis or 
claw, u , their limb, 1 1, and the appendages, a a, in the form of dilaminated scales of the petals. 
e e, Stamens. Pistil consists of the ovary, o, and five styles, *. g, Prolongation of the axis in the 
form of a gynophore, or anthophore bearing the petals, the stamens, and the pistil. 

Fig. 554. Flower of Gynandropsis palmipes, one of the Capparidacea. c, Calyx. p t Petals, 
e, Stamens, a y, Gynophore or elongated internode or axis bearing the stamens, a </", Gyno- 
phore or elongated internode bearing the pistil, of, Pistil composed of an ovary, o, a style and 
a stigma, /. 




316 EFFECTS OF CULTIVATION ON ORGANS. 

cases be more highly developed, as in Caryophyllaceae, and in Cras- 
sula rubens (fig. 258 a), and it may even assume the characters of 
a stamen, which will therefore be opposite the petal, as in 
Primulaceaj. Some do not consider the production of scales 
or stamens opposite to the petals, as the result of choriza- 
tion. Lindley argues against it from what is observed in 
Camellia japonica, in which the petals are usually alternate ; 
but, by cultivation, the law of alternation is interfered 
with, and the parts are so developed that the petals are 
opposite, and run in several regular lines, from the centre 
to the circumference. Again, by this process of chorization, 
one stamen may give rise to several. Thus, in Luliea pani- 
culata (fig. 316, 1), in place of five stamens there are five 
000 bundles (fig. 316, 2), composed partly of sterile filaments, fs, 
and partly of filaments bearing anthers, fa\ and each of these bundles 
is traced to a deduplication of a single stamen, inasmuch as they arise 
from one point, and do not follow the law of alternation. Thus, dilami- 
nation repeats the single organs, and causes opposition of parts. In 
the case of the four long stamens of Cruciferse (^[ 644), chorization is 
said to take place by a splitting of the filaments of two stamens ; and 
thus the two stamens on each side are, by gemination (gemini, twins), 
normally one. This view is confirmed by cases in which the fila- 
ments of the long stamens are more or less united ; also, by cases in 
which the shorter filaments exhibit tooth-like processes on either side, 
while the longer ones have them only on the outer side. In such 
cases, the two long filaments, if united, would present the same appear- 
ance as the shorter ones, and occupy their usual position of alternation 
with the petals. In some instances, by pelorization (vfruoios, mon- 
strous), it is found that tetradynamous plants become tetrandrous 
with equal stamens alternating with the petals. 

655. Cultivation has a great effect in causing changes in the various 
parts of plants. Many alterations in form, size, number, and adhesion 
of parts, are due to the art of the horticulturist. The development 
of cellular tissue and of starchy matter is often thus much increased, 
as may be seen in the case of Turnips, Carrots, and Potato. The 
succulence of the leaves of the Cabbage and Lettuce, and the forma- 
tion of a heart, as it is called, is due to cultivation ; so also the curled 
leaves of Savoys, Cress, Endive, &c. The changes in the colour and 
forms of flowers thus produced are endless. In the Dahlia, the 
florets are rendered quilled, and are made to assume many glowing 
colours. In Pelargonium, the flowers have been rendered larger and 
more showy ; and such is also the case with the Ranunculus, the Au- 



Fig. 555. Petal of Ranunculus Ficaria, viewed on the Inside. I, The limb, a, Small scaly 
appendage at its base formed by chorization or dilamination. 



VEGETABLE IRRITABILITY. 317 

ricula, and the Carnation. Some flowers, with spurred petals in their 
usual state, as Columbine, are changed so that the spurs disappear ; 
and others, as Linaria, in which one petal only is usually spurred, are 
altered so as to have all the petals spurred. 



SECTION IV. SOME GENERAL PHENOMENA CONNECTED ; 
WITH VEGETATION. 

1 . VEGETABLE IRRITABILITY. 

656. Under this head are included certain sensible movements of 
living plants, exercised without any direct application of mechanical 
force, and not referable to mere elasticity, or the hygroscopic nature 
of the tissues. These motions are influenced chiefly by light and heat, 
and, like many phenomena occurring in organized beings, they cannot 
at present be explained by chemical or mere mechanical laws. They 
may, however, be excited by stimuli of a chemical or mechanical 
nature. Although the cause of them is obscure, still, in some instances, 
their use is obvious. 

657. Among the lowest classes of plants there are some peculiar 
movements of this kind. The simplest members of the Sea- weed tribe 
occasionally move throughout their whole substance. Oscillatorias, 
which are filaments composed of cells placed end to end, containing 
fluid and granular matter, have an undulating movement, by means of 
which they advance. When placed in fluids under the field of the 
microscope, some of them may thus be seen to pass from one side to 
the other. The filaments sometimes twist up in a spiral manner, and 
then project themselves forward by straightening again. The motions 
are influenced by temperature and light, and by some are considered as 
being connected Avith the production of new cells. The spores of many 
Cryptogamic plants, especially species of Vaucheria, Conferva, and Proli- 
fera, exhibit motions which, according to Thuret and Decaisne, depend 
on the presence of cellular hair-like processes, called cilia or tentacula. 
These motive organs are in a state of constant agitation, which lasts for 
some hours, becoming slower, and finally ceasing after germination has 
commenced. In the spores of Conferva glomerata and rivularis (fig. 
431), there are two of these cilia or filiform tentacula, which project 
from a colourless rostrum. In Chajtophora elegans, var. fusiformis, 
four have been seen (fig. 432) ; in Prolifera (fig. 433), there is a circle 
of cilia, and in Vaucheria (fig. 434), the spore is entirely covered with 
very short cilia, the vibration of which determines their forward move- 
ment. These spores, from their movements, have received the name of 
Zoospores (^[ 492). Mr. Thwaites accounts for the rhythmical move- 
ments of cilia by electrical currents. In certain cells of Cryptogamic 



318 VEGETABLE IRRITABILITY. 

plants, especially in what are called Antheridia, bodies are met with 
called Phytozoa (^[ 492), which also exhibit movements during a part 
of their existence. 

658. Kemarkable movements have also been observed in the higher 
classes of plants. The fovilla contained in the pollen-gram in a young 
state, when moistened with water, exhibits movements when viewed 
under the microscope. These movements have by some been referred 
to irritability, but by Brown and other accurate observers, they are con- 
sidered as merely molecular, and similar to what takes place between the 
minute particles of inorganic matter as, for instance, finely powdered 
Gamboge suspended in water. These fovilla movements are easily seen 
in the very young pollen of Antirrhinum majus. Certain movements 
also take place in the floral envelopes. Thus many flowers open and 
close at particular periods (^[ 483 485) ; these phenomena depending 
on light, temperature, and moisture. Leaves also, especially those 
which are compound, are folded at certain periods in a distinct and 
uniform manner. What was called by Linna3us the sleep of plants, is 
the change produced on leaves by the absence of light. It is by no 
means analagous to the sleep of animals. During darkness some are 
slightly twisted and hang down ; others, such as pinnate and ternate 
leaves, have the leaflets folded together, and frequently the common 
petiole depressed. The youngest leaflets first exhibit these changes ; 
and when the plants become old, and their tissues hardened, the 
irritability is often much diminished, as is seen in Oxalises. The fold- 
ing of the leaflets of compound leaves usually takes place from below 
upwards, but sometimes in the reverse manner, as in Tephrosia 
Caribsea ; so also with the common petiole, which is directed upwards 
during sleep in the Cassias, and downwards in Amorpha. When be- 
sides the common petiole there are partial petioles, as in the Sensitive 
plant, they may be bent inwards towards each other, while the former 
is bent downwards. 

659. Mimosa sensitiva and pudica, commonly called sensitive plants, 
display these movements of their leaves in a remarkable degree, not 
only under the influence of light and darkness, but also under mechani- 
cal and other stimuli. They have bipinnate leaves with four partial 
petioles proceeding from a common rachis, and each of the petioles is 
furnished with numerous pairs (about twenty) of leaflets, which are 
expanded horizontally during the day. During darkness, or when 
touched or irritated in any way, each leaflet moves upwards towards 
its fellow of the opposite side, which in its turn rises up, so that their 
upper surfaces come into contact. When the movement commences 
at the apex of the leaf, it usually proceeds downwards to the base, and 
thence may be communicated to the leaflets of the next partial petiole, 
and ultimately to the common petiole, which falls down towards the 
stem. The partial petioles then converge towards each other, and 



VEGETABLE IRRITABILITY. 319 

have a tendency to become parallel to the common petiole, at the ex- 
tremity of which they are suspended. When the plant is shaken as 
by the wind, all the leaflets close simultaneously, and the petioles drop 
together. If, however, the agitation is long continued, the plant seems 
as it were to become accustomed to the shock, and the leaflets will 
expand again. The stem itself is not concerned in the movements. 
It may be cut and wounded cautiously without causing any change in 
the leaves, and a portion of it may be removed with a leaf attached, 
and still remaining expanded. If, however, a mineral acid is applied 
to the stem, after some time the petioles will fall and the leaflets 
collapse the leaves perishing with the stem which has been moistened. 
The chemical action of the acid and absorption cause these phenomena. 
When a sensitive plant is exposed to artificial light during the night, 
Decandolle found that its leaves expanded, and that they closed when 
put into a dark room during the day, showing the influence which 
light has on these phenomena. It is to be remarked, however, that if 
the plant is kept for a long period of time in darkness, it will ultimately 
expand its leaves, and the phenomenon of folding and opening will go 
on, although at very irregular intervals. 

660. The ternate leaves of many species of Oxalis fold not merely dur- 
ing darkness, but also when agitated or struck lightly and repeatedly. 
Each of the leaflets folds iipon itself, and then bends downwards upon 
the common petiole. The plant caUed Desmodium gyrans, the moving 
plant of India, has compound leaves consisting of a large terminal 
leaflet, and usually two smaller lateral ones. The latter are in con- 
stant movement, being elevated by a succession of little jerks, until 
they come into contact, and sometimes even slightly cross each other ; 
after remaining in this position for a short time, they separate from 
each other, and move downwards by rapid jerks on opposite sides of 
the petiole. This process is constantly repeated, and goes on in a 
greater or less degree, both during day and night, but is most vigorous 
during warm moist weather. The large terminal leaflet undergoes 
movements also, oscillating very gradually from one side to the other, 
and becoming horizontal or depressed. By the lateral oscillatory 
movement, the leaf becomes inclined in various ways, often assuming 
a remarkable oblique direction. The upward and downward move- 
ments seem to depend on the influence of light and darkness. During 
the day the leaf becomes more or less horizontal, while during dark- 
ness it hangs down. Similar movements are seen in other species of 
Desmodium, as D. gyroides and vespertilionis. 

661. The movements in these cases have, by Martius and Meyen, 
been referred to the presence of some structure analogous to the 
nervous system in animals. There is, however, no evidence of such a 
structure in plants, and these authors have not pretended to prove its 
existence. It is to be remarked, that the movements differ in many 



320 VEGETABLE IRRITABILITY. 

respects from animal contractility. They are usually hinge movements, 
and may be referred to certain changes in the organs, causing dis- 
tention or contraction of these tissues. Dutrochet and Morren refer 
them to alterations in the circulation of fluids and air in the vessels 
and cells. In plants with irritable leaves, there are frequently 
swellings where the leaflets join the stalk, as well as where the stalk 
joins the stem. These swellings contain cells which differ in their 
dimensions and their contents, and the movements are considered as 
being produced by changes in the contents of the cells, some of which 
become more distended than others, and thus cause incurvation or 
folding. In these swellings the vascular bundles are disposed in a 
circle near the periphery, and may be concerned in the movements. 
Mechanical and chemical stimuli are supposed to act by inducing 
alterations in the contents of the vessels and cells. 

662. In the case of the sensitive plant, if the swelling at the base of 
the common petiole is touched even slightly on its lower side, it is 
followed by instant depression of the whole leaf, but no such effect is 
produced if the upper portion of the swelling is lightly touched. 
Again, touching the little swelling at the base of each leaflet on its 
upper side, causes the upward movement of the leaflet, but no such 
effect follows cautious touching of the lower part of the swelling only. 
If a pair of leaflets is touched at the extremity of a petiole, the irritation 
is usually continued downwards from apex to base ; but if a pair at the 
base are touched, the progress of folding is reversed. Clear warm 
weather, with a certain degree of moisture, seem to be the conditions 
most favourable for these movements. They are seen best in young 
plants. The leaves of the sensitive plant contract under the action of 
electricity and galvanism. Some suppose, that in the sensitive plant 
there are two kinds of cells connected with the upper and lower sides 
of the leaves and petioles; the one set being contractile, and causing 
the closing of the leaflet and the fall of the petiole, the other being 
acted on chiefly through the circulation. In the case of the petiole, 
it is conceived that the tissue on the lower side of the swellings is 
contractile, while that in the upper is distensible. The turgescence 
of the latter, which is kept up by light, counteracts the contractility of 
the former, and maintains an equilibrium, so as to keep the petiole 
erect; but when acted on by cold, mechanical irritation, &c., the 
equilibrium is disturbed, and the contractility operates in depressing 
the petiole. A careful microscopic dissection of the swelngs, shows 
peculiar cells in some pars, which seem to differ in theircontents 
from others in their vicinity. 

663. In the sensitive species of the Desmodium and Oxalis, the 
movements are not so evidently influenced by mechanical irritation. 
In the former, the little leaflets are supported on swollen petiolules, 
and it is to the curvation and twisting of these in different directions, 



VEGETABLE IRRITABILITY. 321 

that the movement seemed to be owing. The leaflets remain flat and 
do not fold on themselves. It is said that by arresting the vital 
actions going on in the leaflets, by giving them a coating of gum, and 
thus preventing transpiration and respiration, the movements are 
stopped, and that they recommence when the gum is removed by 
water. Cutting a leaflet across, and only leaving a small portion of its 
lamina attached to the petiolule, does not immediately stop the move- 
ment of gyration. In such a case, however, the motion ultimately 
ceases, while it continues in the uncut leaflet. So also, if a leaflet is 
divided longitudinally into two parts, each of them continues to move 
for a time, but the motions cease as the process of desiccation goes on. 

664. There are occasionally cellular prolongations from the leaf, 
which, when touched, cause folding. Thus, in Dionaea muscipula, 
or Venus's fly-trap, the lamina is articulated to the petiole, and consists 
of two free portions which are united together, by a joint along the 
midrib. On the upper side of each part of the lamina are situated 
three hairs with swellings at the base, and when these hairs are 
touched, the halves approach each other from below upwards, so as 
to enclose any object, as a fly, which may happen to light on them. 
Similar movements, but in a much less obvious manner, are said to 
take place in the leaves of Droseras or Sun-dews. The movements 
are attributed to the same causes as those already mentioned, but 
the ultimate object is not known. 

665. Movements take place in some parts of the flower, occasionally 
with the view of scattering the pollen on the stigma. The stamens 
of various species of Berberis and Mahonia, are articulated to the torus 
or thalamus, and when touched at their inner and lower part, move 
towards the pistil. In Parnassia palustris, the stamens move towards 
the pistil in succession to discharge their contents. The Helianthe- 
mum vulgare or common Kock-rose, exhibits staminal movements 
also connected with the bursting of the anthers. Morren has noticed 
sensitiveness in the androacium of Sparmannia africana and Cereus 
grandiflorus. In the Nettle and Pellltory, the filaments are confined 
in a peculiar way by the perianth, and at a certain period of growth 
they are released so as to allow their elasticity to come into play, by 
means of which the pollen is forcibly scattered (^[ 497). In Goldfussia 
or Ruellia anisophylla, the style has a curved stigmatic apex, which 
gradually becomes straightened, so as to come into contact with the 
hairs of the corolla, upon which the pollen has been scattered ; and in 
Mimulus and Bignonia (fig. 406), the stigma has two expanded lobes 
which close when touched, a movement apparently in some way con- 
nected with fertilization. In the Passion-flower, and some Cacti, the 
styles move towards the stamens. The species of Stylidium have the 
filaments and styles united in a common column, at the upper part of 
which the anther-lobes and stigma are placed. The column often 



322 TEMPERATURE OF PLANTS. 

projects beyond the flower, and is jointed. At the articulation an 
irritable swelling occurs, which when touched or acted upon by heat 
and light, causes a sudden incurvation by which the column is thrown 
to the opposite side of the flower, bursting the anthers and scattering 
the pollen on the central stigma. After a time the column recovers 
its position. These movements take place in the flower for some time 
after it has been removed from the plant and kept in water (^[ 497). 
Certain petals in some flowers, as in Orchidacese, are said to move. 
Morren notices this in the case of species of Megaclinium and Pteros- 
tylis. Gentiana sedifolia closes its petals when touched. Draksea 
elastica, a Swan River terrestrial Orchid, is remarkable for the irrita- 
bility of the stalk of the labellum. This stalk exhibits a moveable 
joint like an elbow. 

666. Chemical agents have an effect on the movements of plants. 
Some act by causing irritation, others by destroying irritability. Nar- 
cotic poisons, as opium, belladonna, and hydrocyanic acid, either 
taken up by the roots or applied externally, destroy the irritability of 
plants. They cause closure of the leaves of the sensitive plant, and 
render it insensible to the action of stimuli. Their prolonged action 
causes death, but if they are applied in moderate quantity, the plant 
may recover, and again unfold its leaflets. It frequently happens, 
however, that the irritability continues for some time much impaired ; 
so that mechanical stimuli do not act in the same rapid and energetic 
manner as at first. Similar effects are produced by ether and chloro- 
form when sensitive plants are introduced into an atmosphere through 
which these substances are diffused. The effects may be produced 
locally by applying the vapour only to certain parts of the plant. 
Experiments on the action of poisonous agents, both in the fluid and 
gaseous state, have been performed by Marcet, Christison, Turner, 
and others (IT 292296).* 

2. TEMPERATURE OF PLANTS. 

667. The heat developed during the expansion of flowers and the pre- 
paration of the pollen, especially in the case of Aroideas, and also at the 
period of germination, has been already considered (^f 475, 476, &c.) 
These phenomena appear to be strictly of a chemical nature, and may 
be traced to the absorption of oxygen, and its combination with the 
carbon of the starch, the latter being converted into dextrine and 
grape sugar. It is now proposed to consider the observations which 
have been made relative to the general temperature of plants. 



LUMINOSITY OF PLANTS. 323 

668. Great differences of opinion have prevailed as to the existence 
of a, proper heat in plants. Hunter examined the heat of the inter- 
nal parts of the trunks of trees by boring holes of different depths in 
them, and inserting thermometers; and similar experiments were made 
by Schubler at Tubingen. The results of these experiments were, 
1st. That the temperature of trees is higher than that of the air in 
winter, and lower in summer ; 2d. That the temperature corresponds 
to the depth in the soil to which the roots penetrate ; and, 3d. That 
it depends on the temperature of the fluid matters taken up by the 
roots, as well as the bad conducting power of the wood of the trees. 
Dutrochet instituted a series of experiments to determine the tempera- 
ture of the growing parts of plants. He found, by means of a thermo- 
electric apparatus, that this varied from two or three-tenths of a 
degree, to one degree above that of the air. This generation of heat 
only takes place when the plant is active and vigorous, and seems to 
be connected with processes going on in the interior of the cells. It 
reaches a daily maximum, the period of which varies in different plants, 
according to their vigour. Rameaux has confirmed Dutrochet's ob- 
servations. There appear, therefore, to be two sources of heat in 
plants, one depending on organic actions carried on in the growing 
parts, and the other on meteorological influences, which either act 
directly through the air, or indirectly through the fluid matters 
brought up from a certain depth in the earth.* 



3. LUMINOSITY OF PLANTS. 

669. Luminous appearances have been observed in certain plants. 
These have been long noticed in the lower classes of plants, such as 
Fungi. Decaying wood, in which Fungi are developed, is sometimes 
luminous. Mr. James Drummond describes some species of Agaric, 
near the Swan River, growing on the trunks of Banksias and other 
trees, which emitted at night a phosphorescent light sufficient to 
enable him to read. A phosphorescent Agaric, with the upper sur- 
face of the pileus black, while the centre and gills were white, was 
noticed by him on the trunk of a dead Eucalyptus occidentalis. The 
Agaricus Gardneri, found in Brazil, gives out a light of a pale greenish 
hue, similar to that of fire-flies. It is found growing on a Palm, and 
is called Flor de Coco. Delile found luminosity in the Agaricus 
olearius, near Montpelier. In the coal mines of Dresden, certain 
Rhizomorphous fungi have long been celebrated for the light which they 
emit. The spawn of the Truffle (Tuber cibarium) is said to present 

* For further remarks on the Subject of Vegetable Heat, see Rameaux's papers in the Annales 
<Tes Sciences Naturelles, January, 1843. Schubler's experiments in Poggendorff Annalcn, x. 092; 
translated in Thomson's Chemistry of Vegetables, p. 959. Dutrochet, Ann. des Sc. Nat. (n. s.) 
torn. xii. Gardner in Linn. Trans, for Dec. 1841, and in Philosoph. Mag. for July, 1812. 



324 COLOTJKS OF PLANTS. 

similar appearances. Some have said that the luminosity of these fungi, 
as well as of decaying wood, is increased by exposure to oxygen gas. 
Some consider it as connected with the absorption of oxygen, being 
in reality a slow spontaneous combustion ; while, according to others, 
it is referable to the liberation of phosphorus from some of its com- 
binations in the plant. 

670. These luminous appearances are said not to be confined to fungi. 
The younger Linnaeus states, that the flowers of Nasturtium, Orange 
Lily, and African Marigold, at the end of a hot summer day, give out 
intermittent light. Mr. Dowden and Mr. James confirmed this by 
observations on the common Marigold and Papaver pilosum ; while 
other observers have noticed the phenomena in the Sun-flower, French 
Marigold, species of (Enothera, and Arum. It is to be remarked, that 
the flowers said to be thus luminous, are all of a more or less orange 
colour, and that the phenomenon takes place in still warm summer 
evenings, towards twilight. Hence, Professor Allman is disposed to 
attribute them to optical illusions, depending on a peculiar intermit- 
tent effect on the retina. Some authors mention the occurrence of 
luminous sap in plants with milky juices, as the Euphorbia phosphorea 
of Brazil. A rhizome of an endogenous plant from India, is said, when 
moistened, to acquire a phosphorescent appearance, and to lose this 
property when dry. 

4. COLOURS OF PLANTS. 

671. Colour is not of much importance in botany as regards classi- 
fication and arrangement. It is chiefly in the case of Fungi that it is 
employed as a means of diagnosis. Perhaps the want of an accurate 
nomenclature of colours in botany may have in part led to this. Mir- 
bel and Henslow have proposed a nomenclature, which consists in 
referring all natural colours to certain absolute tints and shades, deter- 
mined according to fixed laws. Thus, the latter assumes three prim- 
aries, as red, blue, and yellow, which together give white light, and 
derives all others from admixtures of these in definite proportions. 
On this principle he has constructed a chromatometer (^u^a,, colour, 
and ftir^ov, a measure), or measure of colour, the employment of which 
would lead to an accurate nomenclature. 

672. It has already been remarked, that the green colour of the 
leaves, young bark, calyx, and carpels, depends on the presence of 
chlorophylle (^[ 19). This waxy substance is contained in the deep 
cells or mesophyllum of leaves, and depends on the action of light for 
its elaboration. When leaves are grown in darkness, they become 
colourless from the absence of chlorophylle. Light acts by the fixation 
of carbon. The different rays of the spectrum appear to differ in their 
power of developing the green colour. Senebier performed experiments 



GREEN COLOUR OF PLANTS. 325 

on the subject, by making the light pass through coloured media, and 
he was led to the conclusion, that while the yellow rays had the 
greatest effect on the growth of the plant, the blue and chemical rays 
were those chiefly concerned in the production of the green colour. 
Hunt seems to agree with Senebier. Other experimenters, however, 
as Morren, Daubeny, Draper, and Gardner, think the yellow rays are 
the most active in producing the green colour. The following table 
shows the result of some of Gardner's experiments. The rays are 
denominated active or inactive in relation to their power of producing 
a green colour, and the figures under each of them show their power 
in this respect, 1 being the highest value. The sign indicates that 
the effect was not satisfactorily tested : 

T? PI nf Hours of Total. Active rays. Inactive. 

sunshine. time. Red. Or. Yel. Gr. Bl. In. Vio. 

1. Turnips 22 ... 109 .. 4 2 1 3 .. 

2. Beans 14 ... 95 ... 2 1 3 .. 

3. Turnips 8 ... 69 ... 4 2 1 3 .. 

4. Turnips 23 ... 101 ...__ 1 .. 

5. Turnips 175 ... 52 ... 2 1 3 .. 4 

6. Turnips 5'5 ... 6 ... 4 2 1 3 . 

673. The ray producing the green colour is found to be that which 
acts most efficiently on the decomposition of carbonic acid, as shown 
by the following table : 

Places of spectrum Production of Decomp. of Illuminating 

examined. chlorophylle. CO 2. power. 

Extreme Red 0-000 0-0000 .. 00000 

Commencement of Urange '5500 .. 

Centre of Orange '777 .. 

Centre of Yellow 1-000 1-0000 .. I'OOOO 

Centre of Green, -583 . .. 

Centre of Blue, -100 .. 

674. The green colour becomes lighter or deeper according to the 
quantity of chlorophylle and the aggregation of the cells. It is usually 
paler on the lower sides of leaves. The dark shades of green in the 
Yew, Bay, and Holly, are the effect of an immense crowding together 
of green cells. 

675. As light decreases in Autumn, the chlorophylle, in many cases, 
diminishes, and is probably altered by the loss of a portion of carbon. 
Thus, Evergreen leaves become of a paler colour, and deciduous leaves 
assume various hues, commonly called autumnal tints. The leaves of 
the Poplar, Ash, and Beech, before falling, become yellow ; those of 
some species of Rhus, bright red ; those of Cornus sanguinea, dull red ; 
those of the Vine, yellow and purple. Berzelius states, that the leaves 
become red in plants having red fruits. Robinet and Guibourt main- 
tain that the Vines which produce bluish grapes, have red leaves 



326 COLOURS OF PLANTS. 

in autumn, while such as produce white grapes have yellow leaves 
These yellow and red colours by some are said to depend on changes, 
in the state of oxidation of the chlorophylle, and have been traced by 
others to the production of peculiar waxy substances, one red, called 
crythrophylle, the other yellow, xanthophylle. Marquart believes that 
the action of water on chlorophylle, in different proportions, gives rise 
to yellow and blue matters. Ellis supposed the change of hues to be 
due to the prevalence of acid and alkaline matters. 

676. Dr. Hope endeavoured to show that there is in plants a 
colourable principle, chromogen (^uf**, colour, and yewu.u t I generate), 
consisting of two separate principles, one of which forms a red com- 
pound with acids, while the other forms a yellow with alkalies, and he 
attributes the green colour produced by the latter to the mixture of 
the yellow matter with the blue infusion. The two principles, 
according to him, may exist together, or separate, in different parts of 
the same plant. In some very fleshy leaves, as Agave, the central 
cells are pale, while those of the cuticle are coloured and much 
thickened. Although leaves are usually of a green colour, still they 
frequently assume various tints. In certain varieties of Beech and 
Beet, they become of a uniform red or copper colour. In some cases, 
only one of the surfaces of the leaf is coloured, as in many species of 
Begonia, Saxifraga, Cyclamen, and Tradescantia, in which they are 
green above and red or brown below ; while in others there is a vari- 
ation of colour, giving rise to variegation, as in Acuba japonica, 
Carduus marianus, and Calathea zebrina, where there are yellowish 
spots, or in many Arums, where they are of a red colour. The whitish 
or brown spots which occur on leaves, are often produced by thickened 
cells containing peculiar colouring matter, underlying the chlorophylle 
cells. In such cases, variegation might be traced to an alteration in 
the epidermal cells, and the same is true of certain bright colours 
assumed by the surfaces of some leaves. The juices of many plants 
are colourless when contained in the vessels, but become milky or 
coloured by exposure to the ah*. Thus, the sap of (Enanthe crocata 
becomes yellow, that of Chelidonium orange, that of Madder changes 
from yellow to red, and that of some Boletuses becomes blue or bluish- 
green. In some instances, the changes have been prevented by keeping 
the cut or broken surfaces in nitrogen or hydrogen, or carbonic acid, 
and thus preventing their exposure to oxygen. It is said, however, that 
the change of colour in the Madder does not take place in pure oxygen. 

677. The bark, at first green, becomes often of a brown colour from 
the thickening of the cell-walls, as well as the deposition of brown 
matter. Similar changes take place in the woody fibres, giving rise 
to the coloured duramen of many trees, as the Laburnum, Guaiac, 
Ebony, &c. Such changes, however, depend on chemical actions going 
on in the interior of stems, and are not due to the direct influence of 



COLOURS OF PLANTS. 327 

the air. The colour of wood, however, is generally deepened when 
exposed to the atmosphere. 

678. The red, blue, and yellow colours of flowers depend on fluid or 
semifluid matters contained in superficial cells, which can be detached with 
the cuticle. This coloured cellular tissue is called by Nourse the Rete, 
and lies immediately below the epidermis. In this respect these colours 
differ from the green colour hi the leaf which is confined to the central 
cells, and which, as already stated, owes its origin to a granular matter of 
a peculiar nature. In petals, different cells frequently contain different 
kinds of colouring matter, thus giving rise to variegation. By the 
juxta-position and mechanical mixture of various cells, different tints 
are produced ; and the colours are also modified by the nature of the 
cuticle through which they are seen. In the interior of petals, the 
colour is generally more or less yellow, but it is modified when seen 
through superficial cells. Along with the colouring matter, there is a 
colourless substance present, the relative quantity of which varies, and 
hence the colour may be deeper or fainter. In flowers as well as in 
leaves, the colours appear to depend on the action, of light. It has been 
said, however, that the powerful action of solar light, in some cases, 
tends to decolorize flowers. Hence, tulips are screened by floriculturists 
from the direct rays of the sun. The leaves of herbaceous plants 
also, when exposed to the direct rays of the sun, do not acquire so 
deep a green as when they are subjected merely to a bright daylight. 

679. The colours of flowers have been arranged in two series : 
1st. The xanihic (^otvSog, yellow) or yellow; and 2d. The cyanic (xt/oez/oj, 
blue) or blue; and it has been shown that plants in general may be 
referred to one or other of these series, while red is common to both 
series, and green, as composed of blue and yellow, is intermediate be- 
tween them. White is considered as depending on absence or extreme 
dilution of the colouring principles, whue brown or black depends on 
their accumulation or concentration. Even in white flowers there will 
be seen a slight admixture of a yellowish or bluish tint. 

Green, 



\ 



Greenish-blue. 
Blue. 



Cyanic j Violet-blue, 
series. 1 Violet. 

Violet-red. 
[Bed. 



Yellowish-green. ~) 

Yellow. 

Orange-yellow. I Xanthic 

Orange. ( series. 

Orange-red. 

Bed. 



680. Some starting from greenness, as a state of equilibrium between 
the two series, pass through the blue and violet to red, by a process of 
oxidation, while the transition from red to orange and yellow has been 
traced to deoxidation. As illustrations of the cyanic series may be 
mentioned, all, or nearly all, the species of Campanula, Phlox, Epilo- 
bium, Hyacinth, Geranium, Anagallis ; of the xanthic series, Cactus, 



328 COLOURS OF FLOWERS. 

Aloe, Cytisus, Oxalis, Rose, Verbascum, Potentilla, (Enothera, Ranun- 
culus, Adonis, Tulip, Dahlia. 

681. Plants belonging to either series, vary in colour usually by 
rising or falling in the series to which they belong, and not by passing 
from one to the other. Thus, a plant belonging to the blue series 
does not usually become yellow, nor does one in the yellow series 
change into a pure blue. This remark will not apply in all cases, 
although it is generally true. It cannot be said to hold good in 
regard to genera, as at present determined; thus, in the genus Gentian, 
there are blue and yellow species. It seems, however, to be applicable 
to individual species; thus, the Dahlia belonging to the yellow series 
has been made to pass to all varieties of that series, but has never 
been produced of a blue colour; so also with the Tulip, the Rose, &c. 
Even in the case of species, however, there are anomalies. Thus, the 
rule does not apply to such plants as Myosotis versicolor and Dendro- 
bium sanguinolentum, where there are different yellow and blue colours 
on the corolla. Notwithstanding, however, all the exceptions, the 
general law already mentioned as to the variation of colour in flowers, 
seems to be founded on correct observations. 

682. Changes are produced in the colour of flowers, by bruising and 
injuring the petals. The pure white flowers of Camellia easily become 
brown, while those of Calanthe veratrifolia and Bletia Tankervillae 
assume a deep blue. By drying, many flowers become of a brown or 
black colour: this is particularly the case with Orchidaceae, Melam- 
pyrum, and Orobus niger. It would appear to depend on the com- 
bination between the colouring principle and the oxygen of the air, 
and may in some cases be traced to the existence of tannin, gallic acid, 
and iron. Blue flowers, under the process of desiccation, are often 
whitened. Ipomcea Learii, in drying, changes from blue to red. 

683. Remarkable changes take place in the colour of some flowers 
during the course of the day. The flowers of the common pink Phlox, 
early in the morning, have a lightish blue colour, which alters as the 
sun advances, and becomes bright pink. The CEnothera tetraflora has 
white flowers which change to red. Hibiscus variabilis has its flowers 
white in the morning, pink at noon, and bright red at sunset. The 
colour of many flowers of Boraginaceae, before expansion, are red; after 
expansion, blue. The bracts of Hakea Victoria are yellowish-white in 
the centre the first year; the second year, what was white becomes a 
rich golden yellow; the third year, the yellow becomes rich orange; 
the fourth year, the colour becomes blood-red; the green portion of 
the bracts becomes annually darker. It has been stated that soils 
have an effect on the colour of flowers. The flower of the common 
Hydrangea hortensis may be changed from pink and rose-coloured to 
blue, by growing the plant in certain kinds of loam and peat earth. 
Alum in the soil is said to produce a similar effect. 



ODOURS OF FLOWERS. 



329 



684. Kb'hler and Schubler have endeavoured to determine the 
relative proportions between the different colours met with in flowers. 
They examined upwards of 4000 species, belonging to twenty-seven 
natural orders, of which twenty were dicotyledonous, and seven mono- 
cotyledonous. The following are some of their conclusions : 



1. White 1193 

2. Yellow 951 

3. Red 923 

4. Blue 594 

5. Violet... .. 307 



6. Green 153 

7. Orange 50 

8. Brown 18 

9. Nearly Black 8 



685. The proportion of white, cyanic, and xanthic flowers varies in 
different quarters of the globe, and at different elevations. The fol- 
lowing are the proportions of colour in different natural orders, deduced 
from the examination of about 120 species of each: 



Ked. Violet. Blue. Green. Yel. Orange. White. 



Nymphaeacea; 11 14 

Rosacese 52 1 

PrimulaceiE 41 7 6 2 

Boraginaceaj 10 9 28 3 

Convolvulacese 39 10 12 

Ranunculacese 16 4 15 2 

Papaveracese 38 9 

Campanulaceas 5 21 58 



28 
52 
15 
13 

7 

42 
36 

3 



10 
1 
2 
1 



46 
40 
27 
35 
27 
19 
7 
10 



Thus, Nymphasaceaj and Eosacea?, according to Schubler and Kohler's 
observations, contain a large number of white flowering species; Primu- 
lacese and Convolvulaceas, red; Companulaceaj, blue; Ranunculaceae, 
yellow. 

686. In arranging flowers in a garden, it is of importance to place 
the complementary colours together, in order to produce the best effect. 
The complementary colour of red, or that which is required to make 
white light, is green ; of orange, blue ; of yellow, violet ; consequently 
blue and orange coloured flowers, yellow and violet, may be placed 
together ; while red and rose-coloured flowers harmonize well with their 
own green leaves. When the colours do not agree, the interposition 
of white often restores harmony. 

5. ODOURS OF FLOWERS. 

687. The peculiar odours of plants depend on various secreted 
volatile matters, which are often so subtle as to be incapable of detec- 
tion by ordinary chemical means. Nothing is known of the causes 
which render one flower odoriferous and another scentless. In some 
cases the odours of plants remain after being dried, but in general they 
disappear. Some leaves, as of the Woodruff, become scented only 



330 DISEASES OF PLANTS. 

after drying; and certain woods, as Teneriffe rosewood, give out their 
odour only when heated by friction. Meteorological causes have a 
great influence on the odours of living plants. Dew, or gentle rain 
with intervals of sunshine, seems to be the circumstances best fitted for 
eliciting vegetable perfumes. Light has a powerful effect on the odour 
as well as the colour of flowers. Plants, when etiolated by being kept 
in darkness, generally lose their odour. In certain cases, the perfumes 
of flowers are developed in the evening. Some of these plants were 
called tristes by Linnasus, as Hesperis tristis, or night-scented stock. 
Many orchidaceous plants are fragrant at night only, as some Catase- 
tutns and Cymbidiums. Cestrum nocturnum and the white flowers of 
Lychnis vespertina are also night-scented. The odours of some plants 
are peculiarly offensive. This is the case with Phallus impudicus, and 
with the flowers of many Stapelias. 

688. Schubler and Kb'hler, whose investigations in regard to colour 
have been noticed, have also made observations on the odours of 
plants in the same monocotyledonous and dicotyledonous orders. The 
following tables show some of their results : 



Colour. 
White 


Xo. of 

species. 

1193 


Odoriferous. 
187 


Agreeable. 
. .. 175 .... 


Disagreeable. 
12 


Yellow 


951 


75 


61 .... 


.... 14 


Red 


923 


85 


76 .... 


9 


Blue 


594 


31 .... 


23 .... 


7 


Violet 


307 


.. .. 23 


17 .... 


6 


Green 


153 


12 


10 .... 


2 


Orange 


50 


3 


1 .... 


2 


Brown.... 


18 


1 


. 


1 



Thus, of the plants examined, those having white flowers presented 
the larger proportion of odoriferous species. The orange and brown 
coloured flowers often gave a disagreeable odour. In examining 
numerous species from various natural orders, they found that out of 
100 species of 

Nymphseaceae 22 were odoriferous. 

Rosacese 13 

Primulaceae 12 

Boraginacese 6 

Convolvulacese 4 

Ranunculaceae. 4 

Papaveraceae 2 

Campanulaceae 1 

6. DISEASES OF PLANTS. 

689. Great obscurity attends this department of botany, and much 
remains to be done ere a system of vegetable nosology (Wo-of, disease) 



DISEASES OF PLANTS. 331 

can be completed. It is, however, of great importance, whether we 
regard its bearing on the productions of the garden or the field. Some 
have divided the diseases of plants into general, or those affecting the 
whole plant, and local, or those affecting a part only. A better 
arrangement seems to be founded on their apparent causes, and in 
this way they have been divided by Lankester into four groups. 1. 
Diseases produced by changes in the external conditions of life ; as 
by redundancy or deficiency of the ingredients of the soil, of light, 
heat, air, and moisture. 2. Diseases produced by poisonous agents, 
as by injurious gases, or miasmata in the atmosphere, or poisonous 
matter in the soil. 3. Diseases arising from the growth of parasitic 
plants, as Fungi, Dodder, &c. 4. Diseases arising from mechanical 
injuries, as wounds and attacks of insects. 

690. Plants are often rendered liable to the attacks of disease by 
the state of their growth. Thus, cultivated plants, especially such as 
become succulent by the increase of cellular tissue, appear to be 
more predisposed to certain diseases than others. Concerning the 
first two causes of disease very little is known. Absence of light 
causes blanching, which may be looked upon as a diseased state of the 
tissues. Excess of light may cause disease in plants whose natural 
habitat is shady places. Excess of heat is sometimes the occasion 
of a barren or diseased state of some of the organs of the flowers, and 
frost acts prejudicially on the leaves, stem, and flowers. By excess 
of moisture, a dropsical state of the tissue is induced. 

691. Concerning the influence of atmospheric changes on plants, 
very little has been determined. Many extensive epidemics seem to 
depend on this cause. Thus, the late potato disease must be traced, 
apparently, to some unknown miasma conveyed by the air, and 
operating over large tracts of country ; the disease probably affecting 
some plants more than others, according to their state of predisposition, 
and in its progress leading to disorganization of the textures, alteration 
in the contents of the cells and vessels, and the production of Fungi, 
&c. In the early stage of the disease, a brown granular matter was 
deposited in the interior of the cells, beginning with those near the 
surface. For some time the cell- walls and starch-grains remained 
uninjured, but were ultimately attacked, the former losing their trans- 
parency, and the latter becoming agglomerated in masses. Subse- 
quently to this, parasitic organisms of various kinds make their appear- 
ance, cavities were formed, and rapid decay took place. Among the 
vegetable parasites, were detected species of Fusisporium, Oidium, 
Botrytis, Capillaria, Polyactis, &c. The prevalence of hot or cold 
weather, the amount of light and moisture, changes in the atmosphere, 
and electrical conditions of the air and earth, are in all probability 
connected with epidemic diseases. By some, the late potato disease 
is attributed to suppressed evaporation and transpiration, depending 



332 DISEASES OF PLANTS. 

on the hygrometric state of the atmosphere. The vessels and cells are 
said to become charged with fluids, stagnation of the circulation takes 
place, and thus disease and death are induced.* 

692. Gangrene in plants, is caused by alterations in the contents of the 
cells, leading to death of a part. In succulent plants, as Cactuses, 
this disease is apt to occur. Sometimes excision of the diseased part 
checks the progress of the gangrene. Canker, which attacks Apple 
and Pear trees, is a kind of gangrene. Some of the most important 
diseases of corn and other agricultural crops, are owing to the pro- 
duction of Fungi. These have been divided into 1. Those attacking 
the grain, as Uredo fcetida, or pepper-brand. 2. Those attacking the 
flower, as Uredo segetum, or smut. 3. Those attacking the leaves and 
chaff", as Uredo Kubigo, or rust. 4. Those attacking the straw, as 
Puccinia graminis, or corn mildew. 

693. Smut-balls, pepper-brand, or blight, is a powdery matter, occu- 
pying the interior of the grain of wheat, &c. When examined under 
the microscope, it consists of minute balls, four millions of which may 
exist in a single grain, and each of these contains numerous excessively 
minute sporules. It is caused by the attack of Uredo Caries, or 
fcetida. In this disease the seed retains its form and appearance, 
and the parasitic fungus has a peculiarly foetid odour, hence called 
stinking rust. 

694. Smut or dust-brand is a sooty powder, having no odour, found 
in Oats and Barley, and produced by Uredo segetum. The disease 
shows itself conspicuously before the ripening of the crop. Bauer 
says that in TWooo P art of a square inch he counted 49 spores of the 
uredo. 

695. Rust is an orange powder, exuding from the inner chaff" scales, 
and forming yellow or brown spots and blotches in various parts of 
corn plants. It owes its presence to the attack of Uredo Rubigo. It 
is sometimes caUed red gum, red robin, red rust, and red rag. Some 
consider Mildew (Uredo linearis) as another state of the same disease. 

696. Those Fungi which are developed in the interior of plants, and 
appear afterwards on the surface, are called entophytic (ivrog, within, 
and QVTOV, a plant). Their minute sporules are either directly applied 
to the plants entering by their stomata, or they are taken up from the 
soil. Many other Fungi grow parasitically on plants, and either give 
rise to disease ; or modify it in a peculiar way. Among them may be 
mentioned species of Botrytis, Fusisporium, Depazia, Sclerotium, Fu- 
sarium, and Erysiphe. Fusisporium solani is considered by Martius 
as the cause of a certain disease in the Potato. In the recent potato 
disease, the Botrytis infestans, a species of Fusarium and other Fungi, 
committed great ravages, spreading their mycelium or spawn through 

* See remarks on this subject by Klotzsch, translated by Gregory, in the Appendix to Liebig's 
work on the Motion of the Juices. London, 1848. 



DISEASES OF PLANTS. 333 

the cells of the leaves and the tubers, and thus accelerating their de- 
struction. Berkeley, Morren, and Townley, consider the Botrytis as 
the cause of the disease. Various species of Botrytis also attack the 
Tomato, Beet, Turnip, and Carrot. A species of Depazia sometimes 
causes disease in the knots of Wheat. A diseased state of Rye and 
other grasses, called ergot, owes its production to the presence of a 
species of Spermoedia. By the action of the fungus, the ovary becomes 
diseased and altered in its appearance, so as to be dark-coloured, and 
project from the chaff in the form of a spur. Hence the name spurred 
rye. The nutritious part of the grain is destroyed, and it acquires 
certain qualities of an injurious nature. Spontaneous gangrene is the 
consequence of living for some time on diseased rye. Ergot has been 
seen in Lolium perenne and arvense, Festuca pratensis, Phleum pra- 
tense, Dactylis glomerata, Anthoxanthum odoratum, Phalaris arun- 
dinacea, &c. 

697. Fruits when over-ripe are liable to attacks of Fungi, which 
cause rapid decay; wood also, especially Alburn virn or sap-wood, is 
injured by the production of Fungi. Dry rot is the result of the 
attack of Merulius lacrymans, which in the progress of growth de- 
stroys its texture, and makes it crumble to pieces. Some kinds of 
wood are much more liable to decay than others. 

698. The diseases caused by attacks of Fungi may be propagated 
by direct contact, or by the diffusion of the minute spores through the 
atmosphere. When we reflect on the smallness of the spores, the 
millions produced by a single plant, and the facility with which they 
are wafted by the wind in the form of the most impalpable powder, 
we can easily understand that they may be universally diffused and 
ready to be developed in any place where a nidus is afforded. Perhaps 
some of the diseases affecting man and animals may be traced to such 
a source. Quekett found that he could propagate the ergot by mix- 
ing the sporules with water, and applying this to the roots. 

699. In order to prevent these diseases, it has been proposed to steep 
the grains in various solutions previously to being sown. For this 
purpose, alkaline matters and sulphate of copper have been used. In 
all cases, the seed should be thoroughly cleansed. Smut and pepper- 
brand have been averted by these means. In the case of the latter, 
diseased grains are easily removed by being allowed to float in water, 
and the grains that remain are washed with a solution of lime, com- 
mon potash, or substances containing ammonia, which form a soapy 
matter with the oil in the fungus. A weak solution of sulphate of 
copper acts by destroying the fungus. To prevent wood from dry rot, 
the processes of kyanizing and burnetizing have been adopted: the 
former consists in making a solution of corrosive sublimate enter into 
the cells and vessels; the latter, in impregnating the wood with a 
solution of chloride of zinc. Creosote has also been used to preserve 



334 DISEASES OF PLANTS. 

wood. Boucherie proposed that a solution of pyrolignite of iron 
should be introduced into trees before being felled, by making perfora- 
tions at the base of the trunk, and allowing the absorbing power of the 
cells and vessels to operate. This plan does not appear to have been 
successful, although reported favourably to the French Academy, and 
also recommended by Mr. Hyett. 

700. Other diseases in plants owe their origin to insects. Earcockles, 
purples, or pepper- corn, is a disease affecting especially the grams of 
wheat. The infected grains become first of a dark green, and ulti- 
mately of a black colour. They become rounded like a small pepper- 
corn, but with one or more deep furrows on their surface. The glumes 
spread open, and the awns become twisted. The blighted grains are 
full of a moist white cottony matter, which, when moistened, and put 
under the microscope, is seen to consist of a multitude of minute in- 
dividuals of the Vibrio triciti, or eel of the wheat. The animalcules 
deposit their eggs in the ovary, and their young are hatched in eight 
or ten days. Henslow calculates that 50,000 of the young might be 
packed in a moderately sized grain of wheat. The Vibrio retains its 
vitality long. It will remain in a dry state for six or seven years, and 
when moistened with water will revive. The Wheat-fly, or Cecidomyia 
tritici, is another destructive insect. It deposits its eggs by means of 
a very long retractile ovipositor, and is seen abundantly in warm even- 
ings. The Cecidomyia destructor, or Hessian fly, also causes injury, 
and is said to be very destructive to wheat in America. These insects 
are destroyed in numbers by the Ichneumons, which deposit their ova 
in their bodies. The Apple-tree mussel, or dry-scale, Aspidotus con- 
chiformis, attacks the bark of Apples, Pears, Plums, Apricots, and 
Peaches. Many of the Coccus tribe are highly injurious to plants. 
One of this tribe, in 1843, destroyed the whole orange trees in the island 
of Fayal, one of the Azores. Many insects cause the rolling up of leaves. 
Tortricida viridana acts thus on the leaves of the Oak, and various 
species of Losotgenia do so with other trees. Sacchiphantes abietis is 
the aphis which causes the leaves of the Spruce-fir to be united together, 
so as to have the appearance of a cone. 

701. Many insects, called miners, make their way into the interior 
of leaves, and hollow out tortuous galleries, sometimes causing an 
alteration in the colour of the leaves. Galls are caused by the attacks 
of species of Cynips, which are provided with ovipositors, by means of 
which they pierce the bark or leaves with the view of having a nidus 
for their ova. These galls are very common on the Oak, and are 
called oak-apples. Sometimes they have one cavity, at other times 
they are divided into numerous chambers, each containing a grub, 
pupo, or perfect fly, according to the season. 'Galls are produced on 
the twigs, catkins, and leaves of the Oak. The artichoke gall of the 
Oak depends on an irregular development of a bud, caused by the 



DISEASES OF PLANTS. 



335 



I 



attack of insects, and consists of a number of leafy imbricated scales 
resembling a young cone. On examining the galls of commerce, the 

"lour, containing 
nth a perfora- 
are committed 
he presence of 
fs them. Mr. 
ig off the sub- 
d of getting rid 
eaves, and burst 
jrenate borders 
.e galls resemble 
. They are at- 
3 leaf, the inner 
Each contains 
i, long after the 

the insects which 
cts peculiar to it, 
use great injury, 
mses, have called 
rious means have 
Lmong them may 
quor of gas-works, 
er ; vapour of tur- 
ives, for the white 








r in the Journal of the 



334 DISEASES OF PLANTS. 

wood. Boucherie proposed that a solution of pyrolignite of iron 
should be introduced into trees before being felled, by making perfora- 
tions at the base^^" tTmnV nr.^1 ni.in^r.n.11 1.1- ------ ' 

cells and vesse 1 
successful, alth 
also recommen 

700. Other. 
purples, or pep d 
wheat. The ii 
rnately of a blac 
corn, but with o 
spread open, am 
full of a moist ~s\ 
under the micro 
dividuals of the 
deposit their eggs 

or ten days. He . 

packed in a mode 

vitality long. It 

when moistened w 

tritici, is another c 

a very long retract: 

ings. The Cecido 

and is said to be ve 

are destroyed in nu 

in their bodies. Tl X 

chiformis, attacks 

Peaches. Many oi 

One of this tribe, IE 

of Fayal, one of the 

Tortricida viridan: 

species of Losotae 

the aphis which ct 

so as to have the 

701. Many insects, caiieu 

of leaves, and hollow out tortuous galleries, 



alteration in the colour of the leaves. Galls are caused bylEe~al 
of species of Cynips, which are provided with ovipositors, by means of 
which they pierce the bark or leaves with the view of having a nidus 
for their ova. These galls are very common on the Oak, and are 
called oak-apples. Sometimes they have one cavity, at other tunes 
they are divided into numerous chambers, each containing a grub, 
pupo, or perfect fly, according to the season. Galls are produced on 
the twigs, catkins, and leaves of the Oak. The artichoke gall of the 
Oak depends on an irregular development of a bud, caused by the 



DISEASES OF PLANTS. 335 

attack of insects, and consists of a number of leafy imbricated scales 
resembling a young cone. On examining the galls of commerce, the 
produce of the Quercus infectoria, some are of a blue colour, containing 
the larva of the insect; others are pale, and are marked with a perfora- 
tion by which the insect has escaped. Extensive ravages are committed 
in Elms and other trees by the attacks of Scolyti. The presence of 
much moisture, such as the rapid flow of sap, destroys them. Mr. 
Robert found that the flow might be promoted by taking off" the sub- 
erous layer of the bark, and he proposes this as a method of getting rid 
of the insects. Some galls are formed in the substance of leaves, and burst 
through the cuticle in the form of ovate bodies, with crenate borders 
and opercula, which are perforated in the centre. These galls resemble 
parasitic fungi. Oak-spangles are galls of this nature. They are at- 
tached by a central point to the under surface of the leaf, the inner 
side being smooth the outer red, hairy, and fringed. Each contains 
a single insect, which retains its habitation till March, long after the 
leaves have fallen to the ground. 

702. It is impossible in this place to enumerate all the insects which 
attack plants. Almost every species has certain insects peculiar to it, 
which feed on its leaves, juices, &c., and often cause great injury. 
Those which are common to hothouses and greenhouses, have called 
for the special attention of horticulturists, and various means have 
been suggested for their removal or prevention. Among them may 
be enumerated, vapour of tobacco and ammoniacal liquor of gas-works, 
to kill aphides; vapour of sulphur, for the red spider; vapour of tur- 
pentine, for the wasp; vapour of crushed laurel leaves, for the white 
bug; coal-tar, for the wire-worm, &c.* 

* For further remarks on the Diseases of Plants, see Henslow's paper in the Journal of the 
Royal Agricultural Society of England. 



PART II. 

SYSTEMATIC BOTANY, TAXONOMY, OE THE 
CLASSIFICATION OF PLANTS. 



CHAPTER I. 
SYSTEMS OF CLASSIFICATION. 

703. THIS department of Botany may be considered as a combina- 
tion of all the observations made on the structure and physiology of 
plants, with the view of forming a scientific arrangement. It can only, 
therefore, be prosecuted successfully after the student has acquired a 
complete knowledge of Organography. In every branch of science, 
arrangement is necessary in order that the facts may be rendered avail- 
able, and this is more especially the case when a knowledge of species 
is to be acquired. When it is considered that there are upwards of 
100,000 known species of plants, it is obvious that there must be a 
definite nomenclature and classification, were it only to facilitate refer- 
ence and communication. Taxonomy has sometimes been pursued 
with no higher aim than that of knowing the names of plants. When 
prosecuted in such a spirit, it does not lead to an enlarged and philoso- 
phical view of the vegetable kingdom. In all truly scientific systems, 
regard is paid, not merely to the determination of the names of the 
species, but to their relations and affinities, so as to give some concep- 
tion of the order which has been followed in the plan of creation. 

704. In Classificatory Sciences, the arrangements are founded upon 
an idea of likeness an idea, however, which is applied in a more exact 
and rigorous manner than in its common and popular employment. 
The resemblances of the objects must rest, not on vague generalities, but 
upon an accurate scientific basis. In order that an arrangement may be 
constructed on philosophical principles, and that it may be rendered 
useful for the purpose of science, the following steps are required: 
1. A Technical (rt-^vi^, artificial or conventional) language, rigorously 



338 DEFINITION OF SPECIES. 



defined, or what is termed Glossology (yAaWa, a tongue or language, 
and Ao'yo?, a discourse), and Termonology (rlytuv, 'oo?, a termination). 
The meaning of the terms in this descriptive language must not depend 
on fancied resemblances, but must have a precise definition, and be 
constant. In acquiring a knowledge of the conventional terms, or of 
the vocabulary of the science, the student at the same time fixes in 
his mind the perceptions and notions which these terms convey, and 
thus, in reality, becomes acquainted with important elementary facts. 
2. A Plan of the system, or the principles on which the divisions and 
subdivisions of the system are made, Diataxis (d/arai/?, orderly arrange- 
ment), or what is properly called Taxonomy (rdfa, order, and j/o^o?, 
law). There have been two great plans proposed in Botany, one 
denominated artificial, the other natural. The first is founded on 
characters taken from certain parts of plants only, without reference 
to others; while the second takes into account all the parts of plants, 
and involves the idea of affinity in essential organs. 3. There must be 
also the means of detecting the position of a plant in a system by short 
diagnostic marks. In doing so, a few essential characters are selected 
in accordance with natural affinities. The division into genera is a 
most valuable help in determining plants. Linnaeus did great service 
to science by his generic divisions, and by adopting a binomial (bis, 
twice, and nomen, a name) system of nomenclature, in which the genus 
and species are included in the name of the plant. 

705. Species. No classification can be made unless the meaning of the 
term species is defined. By species, then, are meant so many individuals 
as are presumed to have been formed at the creation of the world, and 
to have been perpetuated ever since. A species embraces individuals 
which resemble each other more closely than they do any other plant, 
so that they are considered as originating from a common parent; and 
their seeds produce similar individuals. There may be differences in 
size, colour, and other unimportant respects; and thus varieties may 
exist, exhibiting minor differences, which are not, however, incom- 
patible with a common origin. Varieties owe their origin to soil, expo- 
sure, and other causes, and have a constant tendency to return to the 
original type. They are rarely propagated by seed, but can be per- 
petuated by cuttings and grafts. By cultivation, permanent varieties 
or races have been produced, the seeds of which give rise to individuals 
varying much from the original specific type. Such races are kept up 
entirely by the art of the gardener, and may be illustrated in the case 
of the Cereal grains, and of culinary vegetables, such as Cabbages, 
Cauliflower, Brocoli, Turnips, Radishes, Peas. It is only after a 
series of years that these permanent varieties have been established, 
and there is still a tendency in their seeds, when sown in poor soil and 
neglected, to produce the original wild form. Permanent varieties in 
the animal kingdom may be illustrated by the different races of man- 



SPECIES AND VARIETIES. 



339 



kind. By scattering the pollen of one plant on the pistil of an allied 
species, seeds are formed, which, when sown, produce intermediate 
forms or hybrids (^[ 516). Hybrids, however, are rarely perpetuated 
by seed. 

706. Many species vary in a remarkable manner, without any ex- 
ternal influences to account for it. Thus, a plant of Fuchsia has pro- 
duced, in successive years, flowers differing so much in form and 
shape, that, if they had not been known to be produced by the same 
plant, they would have been considered as belonging to distinct species. 
Such is also the case with Calceolarias, some species of Amaryllis, and 
many Orchids. Hence there is sometimes considerable difficulty in 
determining what are true species, and what are only varieties, more 
especially when these varieties are permanent and reproduce themselves. 
To this must in part be attributed the disputes which have arisen among 
botanists as to the species of many British genera, such as Roses, Rubi, 
Salices, and Hieracia. The following table shows the number of British 
species in some of the British genera, as given by different authors, 
and exhibits the uncertainty which still exists as to the limits of 
species: 

Salix. 

Hudson (1798) 16 

Smith (1824-28) 64 

Lindley (1835) 29 

Hooker (1842) 70 

Babington (1843) 57 

"Watson (1844) 38 

Babington (1847).. ..58 

707. It is only after a careful study of such forms during a series 
of years, that any conclusion can be drawn in regard to them. It is 
important to record all the varieties which occur, but great care is 
necessary not to raise to the rank of species what are mere accidental 
aberrant forms. Some have of late years advocated the doctrine of the 
transmutation of species, or the conversion of one species into another. 
It has been said, that Oats may be changed into Rye, by being con- 
stantly cut down for a series of years before flowering. Such state- 
ments are not founded on correct data, and have led to very erroneous 
views and doctrines, which have been recently promulgated with much 
apparent plausibility. All that has been observed in the vegetable 
kingdom leads to the conclusion, that there are distinct species which 
continue to be perpetuated by seed, and that, although these may vary 
within certain limits, there is always a typical form to which the 
varieties have a tendency to revert. By grafting and other horticultural 
operations, changes of a marked kind may be produced in fruits; but 
the seeds of such fruit, when sown, give rise to individuals resembling 
the original stock they perpetuate the typical form, not the artificially- 
produced variety. 



racium. Mentha. 
8 . 10 


Rosa. 
5 


Rubus. 
5 


Saxifraga. 
9 


18 


13 


22 


14 


25 


19 


9 


17 


21 


24 


13 


13 


19 


14 


16 


19 


8 


19 


24 


20 


17 


8 


7 


34 


16 


21 


9 


19 


36 


20 



340 GENERA, ORDERS, AND CLASSES. 

708. Genera. Certain species are more nearly allied than others, and 
are conveniently grouped together so as to form a distinct kind or genus. 
A genus then is an assemblage of nearly related species, agreeing with 
one another in general structure and appearance more closely than 
they accord with any other species. Thus, the various species of Roses 
compose one genus, which is distinguished by marked characters. 
Occasionally, a subgenus is formed by grouping certain species, which 
agree more nearly with each other in some important particulars than 
the other species of the genus. The characters of the genera are taken 
exclusively from the parts of fructification, while all parts of the plant 
furnish specific characters. In the name of a plant, the genus is given 
as well as that of the species. The latter was called by Linnaeus the 
trivial name. Thus, a particular species of Rose is called Rosa spino- 
sissima; the first being the genus, and the second the specific or trivial 
name. As regards the definition of genera and species, and nomen- 
clature in general, no one has conferred so much benefit on science as 
the great Linnaeus. This may be considered as among his highest 
titles to fame. 

709. Orders. Several genera agreeing in more general characters, 
although differing in their special conformation, are grouped together 
so as to form an order or family. As genera include allied species, so 
orders embrace allied genera. Subdivisions are also made to facilitate 
reference, so that suborders and tribes are formed consisting of cer- 
tain genera, more nearly related in particular characters than others. 
Thus, the order Rosaceae, or the Rose family, includes the genera 
Rosa, Rubus, Potentilla, Fragaria, Prunus, &c., which all agree in 
certain general characters; and the order is divided into various sub- 
orders, such as the true Roses, the Amygdalese, comprehending the 
Plum, Almond, Peach, &c. ; the Potentilleae, embracing the Cinquefoil, 
Strawberry, Raspberry, &c. (1[ 854). 

710. Classes. Orders having some general characters in common, 
are united together in classes, and subclasses are formed in the same 
way as suborders. This is the general plan upon which botanical 
classification proceeds. With the exception of the individual species, 
all the divisions are more or less arbitrary. In making them, however, 
the object of the enlightened botanist is to follow what he considers 
to be the natural affinities, and thus to trace, as far as possible, the 
order which pervades the vegetable creation. 

711. Essential Characters. Each of the divisions of a system is 
accurately defined, the characters being as short as is consistent with 
precise diagnosis. Such characters are called essential, and they em- 
brace only those points by which the group is distinguished from the 
others in the same section. The complete description of an individual 
species, from the root to the flower and fruit, is called the natural 
character, and embraces many particulars which are not requisite for 



NOMENCLATURE AND SYMBOLS. 341 

the purpose of diagnosis. The essential characters of genera, when in 
Latin, are put in the nominative case, while those of species are in the 
ablative. 

712. Nomenclature. The names of genera are variously derived, 
from the. structure or qualities of the group, from the name of some 
eminent botanist, &c. ; while specific names have reference also to the 
country where the plant is found, the locality in which it grows, the 
form of the leaves, root, stem, or the colour of the flowers, &c. When 
a species is named in honour of its discoverer or describer, his name is 
put in the genitive, as Carex Vahlii, or the Carex detected by Vahl; 
but if it is merely in compliment to a botanist, his name is added in 
an adjective form, as Jungermannia Doniana, or a Jungermannia named 
in honour of Don, as a botanist. Sometimes two nouns are united in 
a specific name, as Dictamnus Fraxinella. In such cases, the specific 
name is often an old generic one, has a capital letter prefixed, and 
does not necessarily agree in gender with the name of the genus. The 
name of the orders in what is called the natural system, are derived 
from one of the typical genera included under them. 

713. Abbreviations and Symbols. It is of great importance that 
correct descriptions should be given of species, for without them it is 
impossible to form the groups accurately. The difficulties of the 
taxonomist are often greatly increased by imperfect and careless 
descriptions. Valuable directions are given in Lindley's Introduction 
to Botany, as to the proper method of describing plants. There are 
certain abbreviations in constant use among botanists, which it may 
be of importance to notice here. The authorities for genera and 
species are given by adding the abbreviated name of the botanist who 
described them. Thus, Veronica L., is the genus Veronica as defined 
by Linnaeus; Veronica arvensis L., is a certain species of Veronica, de- 
fined by the same author; Oscytropis DC., is the genus as defined by 
De Candolle. It is usual in descriptive works to give a list of the 
authors, and the symbols for their names. The abbreviation v. s. sp., 
means vidi siccam spontaneam, or that the author has seen a dried wild 
specimen of the plant; v. s. c., means vidi siccam cultam, or that he 
has seen a dried cultivated specimen; v. v. s., means vidi vivam spon- 
taneam, or that he has seen a living wild specimen; while v. v. c., 
means vidi vivam cultam, or that the author has seen a living cultivated 
specimen. The asterisk prefixed to a name (* L.), indicates that there 
is a good description at the reference given to the work; while the 
dagger (fL.), implies some doubt or uncertainty. The point of admira- 
tion (! DC.), marks that an authentic specimen has been seen, from 
the author named; and the point of interrogation (?) indicates doubts 
as to the correctness of genus, species, &c., according as it is placed 
after the name of the one or other. , Q > > or A, annual ; <J , O Q , 
0, or B, biennial; 1{, A, or P, perennial; \\ , 5, or Sh, shrub; 



342 SYSTEMS OF CLASSIFICATION. 

(, twining to the right; ), twining to the left; $ , hermaphrodite; 
J , male; ? , female; 5 $ , monoecious, or the male and female on 
one plant; J : ? , dioecious, or the male and female on different plants; 
00 or oo, means indefinite in number. After the description of a 
plant, its habitat, or the country and locality in which it grows, is 
given. If the plant has been described by others, reference is given 
to the work in which the description may be found. If it has re- 
ceived different names, the synonymes must be carefully detailed, and 
ought to be arranged in chronological order. 

714. Systems. Various attempts have been made at different times 
to classify plants. One of the earliest methodical arrangements was 
that of CaBsalpinus, in 1583. It was entirely artificial, and the same 
thing may be affirmed of those of Gesner, Morison, Rivinus, and Tour- 
nefort. The system propounded by Tournefort, was for a long time 
adopted by the French school, but was ultimately displaced by that 
of Linnaeus, who must be looked upon as the great promulgator of the 
artificial method. In 1682, Ray published a system which laid the 
foundation of the natural method of classification. It was long 
neglected, and did not receive the attention it deserved, until Jussieu 
entered the field, and developed his views. Since that tune, the 
natural method has been advanced by the labours of De Candolle, 
Brown, Endlicher, Lindley, and many others. 

715. Kiinnaean System. Although the Linnasan system is not in 
conformity with natural affinities, and does not tend to comprehen- 
sive views of structure, still it is useful to the student as an index. 
LinnaBus himself did not consider it as occupying a higher position, 
and he stated distinctly that a natural method was the great object of 
scientific inquiry. "When not elevated to a rank which its author 
never meant it to occupy, this system may, with all its imperfections, 
be employed as a useful artificial key, and as such may be combined 
with the natural system. In many works of the present day, as in 
Babington's Manual of British Botany, the Linnaean system is used 
as an index to the genera. In the Lmnsean or sexual system, twenty- 
three classes are founded on the number, position, relative lengths, and 
connection of the stamens; while the orders in these classes depend 
on the number of the styles, the nature of the fruit, the number of 
stamens in the classes where this character is not used for distinguish- 
ing them, and the perfection of the flowers. The twenty-fourth class 
includes plants having inconspicuous flowers, and in it the orders are 
formed according to natural affinities. Under these classes and 
orders, all the known genera and species were arranged. It is in the 
higher divisions that the system is artificial, for, as regards genera, 
the Linnsean rules are followed even in the natural systems of the 
present day. 



ARTIFICIAL SYSTEM. 



343 



nine. 

ten. 

, twelve. 
, twenty. 
, many. 



., 
" 1 "*'"''' pov 



716. TABULAR VIEW OF THE CLASSES OF THE LINN^AN SYSTEM. 

A. Flowers present (Phanerogamia). 

I. Stamens and Pistil in every flower. 

1. Stamens Free. 

a. Stamens of equal length, or not differing in certain propor- 

tions ; :?, male or stamen. 

in Number 1, ........................ Class I. Monandria ..... /*'*. ona 

2, ........................ II. Diandria ....... Sif, two. 

3, ........................ in. Triandria ....... T^r?, three. 

4, ........................ IV. Tetrandria.....r; f , four. 

5, ........................ V. Pen tandria,... '>", five. 

6, ........................ VI. Hexandria ..... If, six. 

7, ........................ VII. Heptandria....s!TT*, seven. 

8, ........................ VIII. Octandria ...... <f*, eight. 

9, ........................ IX. Enneandria....lv, 

10, ....................... X. Decandria ...... Ss* 

12-19, ........................ XL Dodecandria... &"? 

20) Inserted on Calyx XII. Icosandria ..... iixo 
or more,) onReceptacle XIII. Polyandria, ..... x 

6. Stamens of different lengths ; 

two long and two short, ....... XIV. Didynamia.. ..\ . 

four long and two short, ....... XV. Tetradynamia 

2. Stamens United ; 

by Filaments in one bundle, ..... XVI. Monadelphia") 

- in two bundles, ............... XVII. Diadelphi 

- in more than two bundles, XVIII. Polyadelphi 

by Anthers (Compound flowers), XlX.Syngenesia../ 

J e \ 

with Pistil on a Column .......... XX. Gynandria ....... ? 

II. Stamens and Pistil in different 

flowers ; on the same Plant, ..... XXI. Moncecia ...... ) 

on different Plants, ................ XXILDicecia ........ 

III. Stamens and Pistil in the same") 

or in different flowers on the > XXIII. Polygamia ...... yA"?, marriage. 

same or on different plants,...) 

B. Flowers Absent, ........................... XXIV. Cryptogamia.*;uTT6 f , concealed. 

717. TABULAE VIEW OF THE ORDERS OF THE LINNJEAN SYSTEM. 

ym*i, female or pistil. 
Class I.) Monogynia ................. 1 Free Style ..................... A*, one. 

n. Digynia, ..................... 2 Free Styles .................... S/?, two. 

III. Trigynia, .................... 3 .................... r ? t7s, three. 

IV. Tetragynia, .................. 4 .................... Tj f , four. 

V. Pentagynia, ................. 5 ............ . ....... =>, five. 

VI. Hexagynia, .................. 6 ................... e{. six. 

VII. \ Heptagynia, ........ , ...... 7 .................... |TT, seven. 

VIII. Octogynia, ................... 8 .................... <j*rir, eight. 

IX. Enneagynia, ................ 9 ..................... im, nine. 

X. Decagynia, .................. 10 ..................... Jl*, ten. 

XI. Dodecagynia, ............... 12-19 ..................... SaSixa, twelve. 

XII. Polygynia, .................. 20 and upwards .................. roxif, many. 

XHL 



phia") 
ia... > 
phia) 



^o?, brother. 
to S et . her - 

rif, origin. 

, female. 

-. , 
"** house ' 



344 LINN^EUS'S ARTIFICIAL SYSTEM. 

(Gymnospermia Fruit formed by four Achainia) yu^o;, naked. 

XIV. -(Angiospermia Fruit, a two-celled Capsule, > .yycs, a vessel. 

( with many seeds ) <r'^, a seed. 

-y (Siliculosa, Fruit, a Silicula. 

' (Siliquosa, Fruit, a Siliqua. 

XVI.) 

XVII. > Triandria, Decandria, &c. (number of Stamens), as in the Classes. 
XVIII.) 

fPolygamia JEqualis, Florets all hermaphrodite. 

Superflua,... Florets of the disk hermaphrodite, those of the 

ray pistilliferous and fertile. 

Frustranea,..Florets of the disk hermaphrodite, those of the 

XIX. \ ray neuter. 

Necessaria,.. Florets of the disk staminiferous, those of the 

ray pistilliferous. 

Segregata,...Each floret having a separate involucre. 

f Monogamia, Anthers united, flowers not compound. 

XX.) 

XXI. > Monandria, Diandria, &c. (number of Stamens), as in the Classes. 
XXII.) 

fMonoecia, 1... Hermaphrodite, staminiferous, and pistillifer- 

XXITI J ous fl wers on tne same plant. 

' j Dicecia, on two plants. 

l/rricecia, on three plants. 

f Filices, Ferns. 

1 Musci Mosses. 

j Hepaticss Liverworts, 

iv - ) Lichenes, Lichens. 

I Algae, Sea-weeds. 

^ Fungi, Mushrooms. 

718. Even as an artificial method, this system has many imperfec- 
tions. If plants are not in full flower, with all the stamens and styles 
perfect, it is impossible to determine their class and order. In many 
instances, the different flowers on the same plant vary as regards the 
number of the stamens. Again, if carried out rigidly, it would separ- 
ate in many instances the species of the same genus ; but as Linnaeus 
did not wish to break up his genera, which were founded on natural 
affinities, he adopted an artifice by which he kept all the species of 
a genus together. Thus, if in a genus nearly all the species had both 
stamens and pistils in every flower, while one or two were monoecious 
or dioecious, he put the name of the latter in italics, in the classes and 
orders to which they belonged according to his method, and referred 
the student to the proper genus for the description. 

719. Natural System. It has been already stated, that a natural 
system endeavours to bring together plants which are allied in all 
essential points of structure. It purposes to ascertain the system of 
nature, and the affinities of plants; and, in doing so, it takes into 
account all their organs. Every natural method, however, is, to a 
certain extent, artificial, and is likely to be so. It is impossible to 
show the affinities of plants in a lineal series; many orders pass insen- 



PLAN OP THE NATURAL SYSTEM. 3-15 

sibly into others, so that their limits cannot be accurately defined; and 
no perfect system can be constituted until all the plants of the globe 
are known. Moreover, many artificial means are avowedly used in 
all natural systems to aid the student. 

720. The early natural systems were very imperfect, being founded 
on comparatively vague views of structure and affinity. Such were 
the systems of Magnolius and Adanson. The sketch of a natural sys- 
tem by Linnaeus was very incomplete, and even that of the celebrated 
Eay was imperfect. It was not until the knowledge of structural 
botany had advanced, that the affinities of plants were ascertained, and 
the relative importance of the different characters discovered. The 
natural systems of the present day recognize a certain subordination of 
characters, founded on the fact that some organs are of more impor- 
tance to the life of plants than others. The relative values of these 
characters are determined by the study of organization, and are not 
fixed by arbitrary rules. The following table will illustrate this 
subordination of character: 

721 SUBORDINATION IN VALUE OF THE OEGANS or THE SAME CLASS. 

Relative Values. Elementary. Nutritive. Reproductive. 

1. Cellular Tissue. 

("Vascular Tissue f Embryo or Spore. 

Q J a. Spiral Vessels. J a. Cotyledon. 

] b. Ducts ] b. Radicle. 

^Stomata I c. Plumule. 

[ fl. Stamens and 

I T> T r \ Pistil, 

a j Root, Stem, Leaf, I 9 v . 

Frond, Thallus.] 2 '^ 

L t. Theca. 

/'Perianth. 

4. < a. Corolla. 

I b. Calyx, 
flnflorescence, 

' J Torus, Nectary, 

1 Bract, Invo- 
L lucre. 

722. Thus, cellular tissue occupies the highest place, as being most 
universally diffused, and capable of carrying on all the functions; next 
comes vascular tissue. By the consideration of these, the two great 
divisions of cellular and vascular plants are determined. There is 
nothing in the nutritive and reproductive systems of the same value as 
cellular tissue. The embryo and its parts are reckoned as occupying 
the highest place in the nutritive system, and as corresponding in value 
with the vascular among the elementary tissues. In the same way 
the other values are determined. In examining organs, it is essential 



346 PRIMARY DIVISIONS OF THE NATURAL SYSTEM. 

to compare those which belong to the same series; for an organ which 
occupies the highest place in one series, may be inferior in value to a 
second-rate organ in another. The comparative importance of the 
different series must be taken into account also. Thus, the nutritive 
may be considered as of more importance than the reproductive func- 
tion, as being more essential for the life of the individual; and an 
organ of first-rate value in the one, will therefore assume a higher func- 
tion than one of the same value in the other. The changes which take 
place in any one set of organs are often accompanied with changes in 
others; and thus it is found that natural divisions may be arrived at 
by different routes for instance, by the elementary, nutritive, and re- 
productive functions. This gives the true notion of affinity; and clas- 
sifications formed on such principles will obviously be more valuable, 
in a practical and physiological point of view, than those which adopt 
characters in an arbitrary manner. 

723. Primary Divisions of the Vegetable Kingdom. In taking a 

survey of the Vegetable Kingdom, some plants are found to be com- 
posed of cells only, and are called Cellular (*H 8); while others consist of 
cells and vessels, especially spiral vessels, and are denominated Vascular 
(^[ 28). If the embryo is examined, it is found in some cases to have 
cotyledons or seed-lobes, in other cases to want them; and thus some 
plants are cotyledonous, others acotyledonous (^[ 590); the former being 
divisible into monocotyledonous, having one cotyledon, and dicotyledo- 
nous, having two cotyledons. The radicle, or young root of acotyle- 
dons, is heterorhizal(^ 629), that of monocotyledons is endorhizal(^ 628), 
that of dicotyledons, exorhizal (*([ 629). When the stems are taken 
into consideration, it is seen that marked differences occur here also, 
acotyledons being acrogenous, monocotyledons endogenous, and dicoty- 
ledons exogenous (^[ 107). The venation of the leaves, whether parallel 
or reticulated (^[ 143), establishes the same great natural divisions; and 
similar results are obtained from a consideration of the flowers, mono- 
cotyledons and dicotyledons being phanerogamous, and acotyledons 
cryptogamous (^ 323). 

724. Thus, the following grand natural divisions are arrived at: 

1 . Cellular.. . Acotyledonous. Heterorhizal. Acrogenous. Cryptogamous. 

2 Vascular /Monocotyledon ous. Endorhizal. Endogenous. > p hanero , amous 
lar " \Dicotyledonous. ExorhizaL Exogenous. / 

These larger groups are, on similar principles, subdivided, until at 
length genera and species are reached by a process of analysis. 
Similar results will be obtained by a synthetical process, conducted 
on the same principles, and proceeding from species upwards. 

725. Henslow illustrates the divisions and subdivisions of a natural 
system by reference to Anihyllis Vulneraria, thus: 



SYSTEMS OF JUSSIEU AND DE CANDOLLE. 



347 



I. Class 

Subclass 
II. Order 
Suborder .. 
Tribe 
Subtribe 

III. Genus 

Subgenus or Section 

IV. Species . 
Variety . 
Eace 
Variation 



Dicotyledones. 

Calyciflorae. 

LeguminosaB. 

Papilionacese. 

Loteas. 

Genisteae. 

Anthyllis. 

Vulneraria. 

Vulneraria. 

Dillenii. 

Floribus coccineis. 

Foliis hirsutissimis. 



726. The most important natural systems are those of Jussieu, De 
Candolle, Endlicher, and Lindley. The larger divisions of each of them 
are given in a tabular form. 

727. CLASSES OF JUSSIEU'S SYSTEM. 

Acotyledones, Class I. 

( Mono-hypogynae, (Stamens hypogynous,) II. 

Monocotyledones,... <Mono-perigyna3,..( perigynous,) III. 

{Mono-epigyna3....( . epigynous), IV. 

f Monoclines, Flowers hermaphrodite. 

(Epistaminese, (Stamens epigynous,) V. 

Apetalse -jPeristamineaj, ( - perigynous VI. 

(No Petals.) (Hypostaminese, .( hypogynous, VII. 

f Hypocorollas, (Corolla hypogynous,) VIII. 

I Pericorollaa ( perigynous,) IX. 

lj I j f Synantheras, X. 

Monopetalte, 1 /(Corolla j (anthers united.) 

(Petals united. ) EpicorollaB, ... \ epigynous,) 1 Corisantheras,.... XL 

( (anthers free.) 

(Epipetalaa, (Petals epigynous,) XII. 

Polypetala3, .... < Peripetalas, ( perigynous,) XIII. 

(Petals distinct) (Hypopetalae, ....( hypogynous,) XIV. 

I^Diclines, Flowers unisexual, or without a perianth, XV. 

Under these Classes Jussieu included 100 Natural Orders, or Groups of Genera. 

728 CLASSES OF THE NATURAL SYSTEM OF DE CANDOLLE. 
A. VASCULARES OR COTYLEDONE^:. 

Class I. Dicotyledones or Exogense. 

f Subclass 1. Thalamiflora3, Petals distinct, stamens hypo- 
gynous. 

2. Calyciflorae, Petals distinct or united, sta- 

mens perigynous. 

3. Corolliflorse, Petals united, hypogynous, 

bearing the stamens. 



Dichlamydeaj, j 
having calyx -[ 
and corolla. 



Having a single 
perianth. / 



4. Monochlamydea3,...A calyx only, or none. 

Class II. Monocotyledones or Endogenae, 



Subclass 1. Mon-Phanerogamse, Having floral envelopes. 

2. Mon-Cryptogamee, Having no floral envelopes. 



348 SYSTEM OF ENDLICHER. 

B, CELLULARES OR ACOTYLEDONE^E. 

Class III. Acotyledones. 

Subclass 1. Foliosse, Having leaves. 

2. Aphyllas, Leafless. 

729. By some recent authors, this system has been modified, so as 
to include, under CorolliflorEe, all Dicotyledons with united petals, whe- 
ther hypogynous or not, and to exclude from Class II. all plants 
Avithout flowers. It is then presented in the following form : 

MODIFICATION OF DE CANDOLLE'S SYSTEM. 
Class I. Dicotyledones or Exogenaj. 

Dichlamydeae, (Subclass 1 . Thalamiflorse,...Petals distinct, stamens hypogynous. 

having calyx < 2. CalyciflorsE, Petals distinct, stamens perigynous. 

and corolla. (_ 3. Corollifloraj, Petals united, bearing the stamens. 

a\ ing a sing e i ^ Monochlamydea3,.A Calyx only, or none. 

Class II. Monocotyledones or Endogense. 

Subclass 1. Petaloideae or Florida} Floral envelopes verticillate. 

2. Glumaceaj, Floral envelopes imbricated. 

Class III. Acotyledones or Acrogenas. 

Subclass 1. JEtheogamai, Having vascular tissue. 

2. Amphigamaj or Cellulares,.Entirely cellular. 

730. SYSTEM OF ENDLICHER. 

REGION L THALLOPHYTA (fexxfc, frond $**,, a plant). No opposition 
of stem and root. No spiral vessels, and no sexual organs. Pro- 
pagated by spores. 

SECTION i. PROTOPHYTA fax, first or originating). Developed without 

soil; deriving nourishment all around; fructification indefinite. 
SECTION n. HYSTEROPHYTA (srn^of, posterior or derivative). Developed 

on decaying organisms ; nourished internally from a matrix ; 

all the organs appearing at once, and perishing in a definite 

manner. 

KEGION H CORMOPHYTA (*. ?/1 *, a stalk or trunk). Opposition of stem 
and root. Spiral vessels and sexual organs distinct in the more 
perfect. 

SECTION in. ACROBRYA (*?, summit, and 0$tu, to germinate). Stem 
increasing by the apex, the lower part being unchanged, and 
only conveying fluids. 

Cohort 1. Anophyta (,>*>, above). No spiral vessels. Both sexes pre- 
sent. Spores free within spore-cases. 

Cohort 2. Protophyta. Bundles of vessels more or less perfect. No male 

organs. Spores free within one- or many-celled spore-cases. 

Cohort 3. Hysterophyta. Both sexes perfect. Seeds without an 

embryo, consisting of many spores. Parasitic. 

SECTION iv. AMPHIBRYA (^i, around). Stem increasing at the circum- 
ference. Vegetation peripherical. 



NATURAL SYSTEM OF LINDLET. 349 

SECTION v. ACEAMPHIBETA (*{, /*?/, and fyvu). Stem increasing both 
by apex and circumference. Vegetation peripherico-terminal. 

Cohort 1. Gymnospermffi (yu^os, naked, and <r<ri ? ^, seed). Ovules naked, 
receiving the fecundating matter directly at the micropyle. 

Cohort 2. Apetalse (, privative or without and STX, a petal). Perigone 
either wanting or rudimentary or simple, calycine or coloured, 
free or adherent to the ovary. 

Cohort 3. Gamopetalse (J<M. union). Perigone double ; outer calycine, 
inner corolline ; gamopetalous, rarely wanting by abortion. 

Cohort 4. Dialypetalas (s/zXya, I separate). Perigone double; outer 
calycine, parts distinct or united, free or attached to the ovary ; 
inner corolline, parts distinct or very rarely cohering by means 
of the base of the stamens ; insertion hypogynous, perigynous, 
or epigynous ; sometimes abortive. 

Under these sections, Endlicher enumerates 279 natural orders, which 
are grouped under 61 classes. 

731. DIVISION OF THE VEGETABLE KINGDOM BY LINDLEY. 1839. 

(Cyclogens, /Class I. Exogens (proper). 

Exogens < (Wood in circles,) \ II. Gymnogens (naked seeds). 

(.Wood in wedges, III. Homogens. 

fSpermogens, / IV. Dictyogens (leaves reticulated). 

Endogens < (Bearing seeds), \ V. Endogens (proper). 

(Bearing spores, VI. Sporogens or Khizanths. 

Arrnwns /Distinct Stem, VII. Cormogens. 

\0nly a Thallus, VIII. Thallogens. 

In the Exogens and Endogens, the following subordinate series of sub- 
classes are formed: 

1. Consolidated. Floral envelopes are united both with each other and the 

stamens, and with the ovary. 

2. Separated. Floral envelopes and stamens are united to each other, but the 

ovary is consolidated and free. 

3. Adherent. Petals and sepals adhere to each other and the stamens and 

ovary, but have their parts disunited. 

4. Disunited. Petals and sepals adhere to each other and the stamens, but 

have their parts disunited, and do not adhere to the consolidated ovary. 

5. Dissolved. Petals and sepals are distinct from the stamens, and also from 

the ovary, whose carpels are disunited, either wholly or by the styles. 

In each of these subdivisions, the orders are arranged in two series, 
the one Albuminous, the other Exalbuminous. 

732. LINDLEY'S DIVISION OF THE VEGETABLE KINGDOM. 1846. 

ASEXUAL OR FLOWEELESS PLANTS. 

Stem and leaves undistinguishable, Class L Thallogens. 

Stem and leaves distinguishable, II. Acrogens. 



350 NATURAL SYSTEM OF LINDLET. 

SEXUAL OR FLOWERING PLANTS. 

Fructification springing from a thallus,.. in. Khizogens. 

Fructification springing from a stem, 
Wood of stem youngest in the centre, cotyledon single. 
Leaves parallel-veined, permanent, wood of stem al- 
ways confused, IV. Endogens. 

Leaves net-veined, deciduous, wood of stem, when 

perennial, arranged in a circle with a central pith, V. Dictyogens. 
Wood of stem youngest at the circumference, always 
concentric, cotyledons two or more. 

Seeds quite naked, VI. Gymnogens. 

Seeds enclosed in seed-vessels, VII. Exogens. 

The following are the subclasses of Endogens and Exogens adopted by 
Lindley: 

ENDOGENS. 

Subclass I . Glumaceous. Floral envelopes imbricated. 
2. Petaloid Floral envelopes verticillate. 

a. Unisexual, often achlamydeous. 

6. Hermaphrodite, ovary adherent. 

c. Hermaphrodite, ovary free. 

EXOGENS. 

Subclass 1. Diclinous. Flowers unisexual. 

2. Hypogynous. Flowers usually hermaphrodite, stamens completely 

hypogynons, free from the calyx or corolla. 
3. Perigynous. Flowers usually hermaphrodite, stamens growing to the 

side of either the calyx or corolla; ovary superior, or nearly so. 
4. Epigynous Flowers usually hermaphrodite, stamens growing to 

the side of either the calyx or corolla ; ovary inferior, or nearly so- 

Under the classes, Lindley enumerates 303 natural orders, which are 
grouped together under 56 alliances. In this system of Lindley, the 
divisions of Asexual and Sexual plants correspond to Endlicher's 2 
Eegions ; the 7 classes represent Endlicher's 5 sections ; and the 56 
alliances are equivalent to the 61 classes in Endlicher's system. 
733. This division may be presented thus: 



Classes. Wood. Leaves. ttmSaL* Sexes - Embryo. 



Floral 
Envelopes. 

l.Exogenae Exogenous-Netted Quinary-Perfect Dicotyledonous. 

2. Gymnospermse Exogenous..Parallel or forked.None Imperfect-Dicotyledonous. 

3. Endogense Endogenous.Parallel Ternary. .Perfect Monocotyledonous. 

4. Dictyogense Endogenous.Netted. Ternary-Perfect Monocotyledonous. 

5. Khizauthae None None Variable.Imperfect.Acotyledonous? 

6. Acrogenae Acrogenous.Forked or none. .None None Acotyledonous. 

7. Thallogenae None None None None Acotyledonous. 

734. Henslow has given a comparative view of all these systems, 
pointing out, in a tabular form, the corresponding divisions in each of 
them: 





















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352 CHARACTERS OF CLASSES AND ORDERS. 

735. In the succeeding pages the natural orders will be grouped 
under the following divisions : 

A. PHANEROGAMOUS, OB VASCULAR FLOWERING PLANTS. 
Class I. Dicotyledones or Exogense. 

f Subclass 1 .Thalamiflorse, Petals distinct, ~| 

TV T.I., A* stamens hypogynous I Polypetalse of Jus- 

Dichlamydeie ' 2 Calyciflor Je ,:....?.Petal S distinct, f sieu. 

having calyx { stamens perigynous J 

and corolla. 3 Corolliflore) Petals un i t ed,< Monopetala; of 

I bearing the stamens / Jussieu. 

[ 4. Monochlamydese,.A calyx only,^ 

Having a sin- 1 or none I Apetalae and partly 

gle perianth, j a. Angiospermse, seeds in an ovary. [Diclines of Jussieu. 

6. Gymnospermae, seeds naked, j 

Class II. Monocotyledones or Endogense. 

Subclass 1. Dictyogense, Floral envelopes verticillate, leaves reticulated. 

2. PetaloideasorFloridffijFloral envelopes verticillate, leaves parallel- 
veined. 

a. Hermaphrodite, ovary adherent. 

b. Hermaphrodite, ovary free. 

c. Unisexual, often achlamydeous. 

3. Glumacese, Floral envelopes imbricated, leaves parallel-veined. 

B. CRTPTOGAMOUS, OR CELLULAR FLOWERLESS PLANTS. 
Class III. Acotyledones or Acrogenae. 

Subclass 1. .JDtheogamse or Cormogense Having vascular tissue. 

2. Amphigamae, Thallogense, or Cellulares, Entirely cellular. 



CHAPTER II. 

ARRANGEMENT AND CHARACTERS OF THE CLASSES 
AND NATURAL ORDERS. 

SECTION I. PHANEROGAMOUS PLANTS. 
CLASS I. DICOTYLEDONES AND EXOGEN.E, Juss. and DC. ACRAMPHIBRYA, Endl. 

736. This is the largest class in the vegetable kingdom. The plants 
included under it have a cellular and vascular system, the latter con- 
sisting partly of elastic spiral vessels (fig. 49). The stem is more or 
less conical, and exhibits wood and true bark. The wood is exogenous, 
i. e. increases by additions at the periphery, the hardest part being 
internal (^[ 72, &c.) It is arranged in concentric circles. Pith exists 
in the centre, and from it diverge medullary rays. The bark is separ- 



EANUNCULACE.E. 



353 



able, and increases by additions on the inside. The epidermis is furnished 
with stomata (^[ 50). The leaves are reticulated (^[ 143), usually 
articulated to the stem. The flowers are formed upon a quinary 
or quaternary type, and have stamens and pistils. The ovules are 
either enclosed in a pericarp, and fertilized by the application of the 
pollen to the stigma, or they are naked, and fertilized by the direct 
action of the pollen. The embryo has two or more opposite cotyle- 
dons, and is exorhizal in germination (^[ 629). 

Subclass 1 THALAMIFLOE^;.* 

737. Calyx and corolla present; petals distinct,! inserted into the thala- 
mus or receptacle ; stamens hypogynous. This includes the hypogynous 
polypetalous orders of Jussieu, and a diclinous order (Menispermaceae). 

738. Order 1. Ranuncuiacece, the Crowfoot Family. (Polypetalce 
Hypogynce.) Sepals 3-6, frequently 5, deciduous 

(fig. 556 c). Petals 5-15 (fig. 556 p e), rarely 
abortive, sometimes anomalous in form (figs. 
284 p, 285), occasionally with scales at the 
base (fig. 555 a). Stamens usually indefinite, 
hypogynous (fig. 556 e) ; anthers adnate (figs. 
558, 559) ; carpels numerous, 1 -celled (fig. 
556 p i), distinct, or united into a single many- 
celled pistil ; ovary containing one anatropal 
ovule (figs. 492, 560 g), or several united to 





561 560 559 556 558 

the inner edge. Fruit various, either dry achamia (figs. 463, 561), 

* Thalamu.i, receptacle, and_/7o.s, flower. 

t Sometimes the petals are abortive, and it is then difficult to determine whether the plant 
belongs to this subclass or to Monochlamydese. 

Figs. 556 561. Exhibit the organs of fructification of Ranunculus acris, to illustrate the 
natural order Ranunculacese. 

Fig. 556. Flower cut vertically, c, Calyx, pe, Petals. , Stamens, pi, Pistil composed of 
several carpels on an elongated receptacle or axis. 

Fig. 557. Diagram of the flower, showing 5 imbricated sepals, 5 petals alternating with the 
sepals, indefinite stamens in several whorls, multiples of the petals, and numerous carpels or 
achsenia in the centre. 

Fig. 558. Adnate anther seen on the outer side. The anther is in this instance extrorse. In 
Pawnia and other Ranunculaceoe it is introrse. 

Fig. 559. Adnate anther viewed on the inside. 

Fig. 560. Vertical section of the ovary, o, showing the ovule, g. s, Stigma. 

Fig. 561. Fruit or achamium cut vertically. /, Pericarp, t, Spermoderm or integument of the 
anatropal seed, p, Perisperm or albumen, between fleshy and horny, e, Minute embryo. 

2 A 



354 RANUNCULACE^E. 

or baccate or follicular (figs. 443, 468). Seeds albuminous, erect, or 
pendulous; albumen horny (fig. 561 p) ; embryo minute (fig. 561 e). 
Herbaceous, suffruticose, or rarely shrubby plants, having alter- 
nate or opposite, simple, much-divided leaves, with dilated sheathing 
petioles (fig. 233). Juice watery. Hairs, if present, simple. 

739. The plants of the order are found in cold damp climates, and 
in the elevated regions of warm countries. Europe contains one-fifth 
of the order, and North America about one-seventh. The order is 
divided into five suborders: 1. Clematidege; 2. Anemones (fig. 247) ; 
3. Ranunculea? (fig. 233) ; 4. Helleboreae (fig. 443) ; 5. Actsea?, or 
Pseoniae (fig. 370), according to the .aestivation of the calyx, the nature 
of the fruit, &c. Henslow gives the following analysis of these sub- 
orders, with the number of British species in each : 

Spec. Brit Anther. Carpel Seed. ^Estiv. 

1. Clematideae, 1^| "i -. valvate. 

2. Anemone*, 9 j^^ ' } pendulous imbricate. 

3. Banunculeaj, 20 { ) * ' erect. 

4. Helleboreae, 9j poly sperm. 

5. Paeoniaj 2 introrse 

Lindley enumerates 41 known genera, comprising 1000 species. 
Examples of the genera Clematis, Anemone, Ranunculus, Helleborus, 
Delphinium, Aconitum, Actasa, Paaonia, PodophyUum. 

740. The order has narcotico-acrid properties, and the plants are 
usually more or less poisonous. The acridity is frequently volatile, 
and disappears when the plants are dried or heated. It varies in dif- 
ferent parts of the plants, and at different seasons. Ranunculus (the 
genus whence the order is named) contains many acrid species, such 
as R. sceleratus, alpestris, bulbosus, gramineus, acris, and Flammula; 
while others, such as R. repens, aquatilis, Lingua, and Ficaria, are 
bland. The acridity is entirely lost by drying, and it disappears in the 
pericarps as the seeds, which are themselves bland, ripen. The leaves 
of Aconitum Napellus, Monkshood, contain a narcotic alkaloid, called 
aconita or aconitina. They are used as an anodyne in neuralgic affec- 
tions, in the form of extract and tincture. The root of Aconitum ferox 
furnishes the powerful East Indian poison, called Bikh or Nabee. The 
leaves of Clematis recta and Flammula have been used as vesicants. 
The seeds of Delphinium Staphisagria, Stavesacre, are irritant and 
narcotic, and are used for destroying vermin. They owe their activity 
to an alkaloid principle, called delphinia. The Hellebores have been 
long noted for their irritant qualities. Helleborus officinalis, niger, 
fcetidus, and viridis, act as drastic purgatives ; hence the use of some 

of them in ancient times in cases of mania. The rhizome of Podophyl- 
lum peltatum, May-apple, is employed hi America as a purgative. 
Some of the Ranunculaceae are chiefly marked by bitter tonic pro- 
perties. 



DILLENIACE.E MAGNOLIACEJE. 355 

741. Order 2. Dilieniacetc, the Dillenia Family. (Polypet. Hypog.) 
Sepals 5, persistent. Petals 5, deciduous, in a single row. Stamens 
indefinite, hypogynous, either distinct or combined into bundles ; fila- 
ments dilated at the base or apex ; anthers adnate, introrse, with 
longitudinal dehiscence. Ovaries definite, more or less distinct, with a 
terminal style and simple stigma; ovules ascending. Fruit of 2-5 cap- 
sular or baccate unilocular carpels, which are either distinct or coherent. 
Seeds arillate, several in each carpel, or only two, or one by abortion ; 
testa (spermoderm) hard; embryo straight, minute, at the base of 
fleshy albumen. The plants of the order are trees, shrubs, or under- 
shrubs, having alternate, exstipulate, coriaceous, or rough leaves. 
They are found chiefly in Australasia, Asia, and the warm parts of 
America. They have astringent properties, and some of the species 
afford excellent timber. Lindley enumerates 26 genera, including 200 
species. Examples Dillenia, Delirna. 

742. Order 3. Tiagnoiiacefe, the Magnolia Family. (Polypet. 
Hypog.} Sepals 2-6, usually deciduous. Petals 2-30, hypogynous, 
often in several rows. Stamens indefinite, distinct, hypogynous ; an- 
thers adnate, long, dehiscing longitudinally. Carpels numerous, 1- celled, 
arranged upon a more or less elevated receptacle ; ovules anatropal, 
suspended or ascending ; styles short. Fruit consisting of numerous 
distinct or partially coherent carpels, which are either dehiscent or 
indehiscent, sometimes sainaroid. Seeds, when ripe, often hang sus- 
pended from the carpels by a long slender cord ; embryo minute, at 
the base of a fleshy perisperm. Trees and shrubs, with alternate 
coriaceous leaves, and deciduous convolute stipules. They abound in 
North America, and some species occur in South America, China, 
Japan, New Holland, and New Zealand. The order has been divided 
into two suborders : 1. Winterese ; aromatic plants, in which the 
leaves are dotted, the carpels are in a single verticil, and the wood 
often consists of punctated tissue (fig. 47). 2. Magnoliete ; bitter plants 
with fragrant flowers, in which the carpels are arranged in several 
rows on an elevated receptacle (fig. 306), and the leaves are not 
dotted. Lindley mentions 11 known genera, comprising 65 species. 
Examples Illicium, Drimys, Magnolia, Liriodendron. 

743. The properties of the order are bitter, tonic, and often 
aromatic. Illicium anisatum, Star-anise, is so called from its carpels 
being arranged in a star-like manner, and having the taste and odour 
of anise. Its fruit is employed as a carminative. Drimys Winteri or 
(iromatica, brought by Captain Winter from the Straits of Magellan hi 
1579, yield's Winter's bark, which has been employed medicinally as 
an aromatic stimulant. It somewhat resembles Canella bark. Magnolias 
are remarkable for their large odoriferous flowers, and their tonic 
qualities. The bark of Magnolia glauca, Swamp Sassafras or 
Beaver-tree, is used as a substitute for Peruvian bark. Liriodendron 



356 ANONACE.E MENISPERMACEJE. 

tulipifera, the Tulip-tree, marked by its truncate leaves, has similar 
properties. 

744. Order 4. Anonacere, the Custard-apple Family. (Polypet. 
Hypog.) Sepals 3-4, persistent, often partially cohering. Petals 6, 
hypogynous, in two rows, coriaceous, with a valvate aestivation. Sta- 
mens indefinite (very rarely definite); anthers adnate, extrorse, with 
a large 4-cornered connective. Carpels usually numerous, separate 
or cohering slightly, rarely definite; ovules anatropal, solitary or several, 
erect or ascending. Fruit succulent or dry, the carpels being one or 
many-seeded, and either distinct or united into a fleshy mass ; spermo- 
derm brittle; embryo minute, at the base of a ruminated perisperm. 
Trees or shrubs, with alternate, simple, exstipulate leaves, found usually 
in tropical countries. Lindley enumerates 20 genera, including 300 
species. Examples Anona, Uvaria, Guatteria. 

745. Their properties are generally aromatic and fragrant. Some 
of the plants are bitter and tonic, others yield edible fruits. The Cus- 
tard-apples, Sweetsops, and Soursops of the East and West Indies, are 
furnished by various species of Anona, such as A. squamosa, reticulafa, 
and muricata. Anona cherimolia furnishes the Cherimoyer, a well- 
known Peruvian fruit. The fruit of Xylopia aromatica is commonly 
called Ethiopian Pepper, from being used as pepper in Africa. Xylopia 
glabra is called Bitter-wood in the West Indies. The Lancewood 
of coachmakers appears to be furnished by a plant belonging to this 
order, called by Schomburgk Duguetia quitarensis. 

746. Order 5. menispermacete, the Moon-seed Family. (Polypet. 
Hypog.) Flowers usually unisexual (often dioecious). Sepals and petals 
similar in appearance, in one or several rows, 3 or 4 in each row, 
hypogynous, deciduous. Stamens monadelphous, or occasionally free ; 
anthers adnate, extrorse. Carpels solitary or numerous, distinct or 
partially coherent, unilocular; ovule solitary, curved (fig. 420). Fruit 
a succulent 1 -seeded oblique or lunate drupe. Embryo curved or 
peripherical; radicle superior; albumen fleshy, sometimes wanting. 
The plants of this order are sarmentaceous or twining shrubs, with 
alternate leaves, and very small flowers. The wood is frequently 
arranged in wedges, and hence the order was at one time put under 
the division called Homogens by Lindley (IT 90 and 731). The order 
is common in the tropical parts of Asia and America. There are 
23 known genera, including 202 species. Examples Menispermum, 
Cissampelos, Cocculus, Lardizabala, Schizandra. 

747. The species are bitter and narcotic. Some are employed as 
tonics, others have poisonous properties. The root of Cocculus pal- 
matus, a plant found in the eastern part of Africa, is known as Calumba- 
root, and is used as a pure bitter tonic in cases of dyspepsia, in the 
form of infusion or tincture. It contains a bitter crystalhzable prin- 
ciple called Calumbin. Cocculus indicus is the fruit of Anamirta 



BERBERIDACE^: CABOMBACE.E NYMPH^EACE^E. 357 

Coceulus. It is extremely bitter, and contains a crystalline poisonous 
narcotic principle, Picrotoxin, which is its active ingredient. It has 
been used externally in some cutaneous affections. At one time it 
was employed, most prejudicially, to give bitterness to porter. Cis- 
sampelos Pareira, Wild-vine or Velvet-leaf, furnishes Pareira-brava- 
root, which is employed as a tonic and diuretic, and has been recom- 
mended in chronic inflammation of the bladder. 

748. Order 6. Berberidacere, the Berberry Family. (Polypet. 
Hypog.) Sepals 3-4-6, deciduous, in a double row. Petals hypogyn- 
ous, equal in number to the sepals, and opposite to them, or twice as 
many, often having an appendage at the base on the inside. Stamens 
equal in number to the petals, and opposite to them; anthers adnate, 
bilocular (dithecal), each of the loculi opening by a valve from the 
bottom to the top. Carpel solitary, unilocular, containing 2-12 
anatropal ovules; style sometimes lateral; stigma orbicular. Fruit 
baccate or capsular, in dehiscent. Albumen fleshy or horny; embryo 
straight, sometimes large (fig. 494). Shrubs or herbaceous perennial 
plants, with alternate, compound, exstipulate leaves. The true leaves 
are often changed into spines (fig. 231 /). Found chiefly in the moun- 
tainous parts of the temperate regions of the northern hemisphere. 
The plants of the order have bitter and acid properties. The bark 
and stem of Berberis vulgaris, common Berberry, are astringent, and 
yield a yellow dye; the fruit contains oxalic acid, and is used as a 
preserve. Lindley enumerates 12 genera, including 100 species. 
Examples Berberis, Epimedium, Leontice. 

749. Order 7. Cabombacere, the Watershield Family. (Polypet. 
Hypog.) Sepals 3-4. Petals 3-4, alternate with the sepals. Stamens 
hypogynous, arising from an inconspicuous torus, two or three times 
the number of the petals; anthers linear, introrse, continuous with the 
filament. Carpels 2 or more; stigmas simple; ovules orthotropal. 
Fruit indehiscent, tipped with the indurated styles, containing one 
or two pendulous seeds. Embryo minute, enclosed in a vitellus (the 
sac of the amnios), and placed at the base of a fleshy perisperm. 
American aquatic plants, with floating peltate leaves. Lindley men- 
tions 2 genera, including 3 species. Examples Hydropeltis, Cabomba. 

750. Order 8. .\ymphreaceu-, the Water-lily Family (fig. 562). 
(Polypet. Hypog.) Sepals usually 4, sometimes confounded with the 
petals. Petals numerous, often passing gradually into stamens (fig. 
310, 2). Stamens indefinite, inserted above the petals into the torus 
(fig. 562 c); filaments petaloid; anthers adnate, introrse, opening by 
two longitudinal clefts. Torus large, fleshy, surrounding the ovary 
more or less (fig. 562 t). Ovary multilocular, many-seeded, with 
radiating stigmas (fig. 562 s); numerous anatropal ovules. Fruit 
many-celled, indehiscent. Seeds very numerous, attached to spongy 
dissepiments; albumen farinaceous; embryo small, enclosed in a fleshy 



358 



NELUMBI ACE.E S ARRA C ENI AC EJE. 




vitellus, and situated at the base of the perisperm (fig. 480). Aquatic 
plants, with peltate or cordate fleshy leaves, and a rootstock or stem 

which extends itself into the mud at 
the bottom of the water. Lindley 
enumerates 5 genera, comprehend- 
ing 50 species. Examples Nym- 
phasa, Nuphar, Victoria, Euryale. 

751. The plants of this order are 
found throughout the northern 
hemisphere, and are generally rare 
in the southern hemisphere. Little 
is known in regard to their proper- 
ties. Some of them are astringent 
and bitter, while others are said 
to be sedative. They have showy 
flowers, and their petioles and 

peduncles contain numerous air-tubes. Victoria regia, is one of the 
largest known aquatics. It is found in the waters of South America, 
and is said to range over 35 degrees of longitude. The flowers have 
a fine odour. When expanded they are a foot in diameter. The 
leaves are from four to six and a half feet in diameter. The seeds and 
rootstocks of many plants of this order contain much starch, and are 
used for food. 

752. Order 9. Nelumbiaceie, the Water-bean Family. (Polypet. 
Hypog.) Sepals 4-5. Petals numerous, in many rows. Stamens in- 
definite, in several rows; filaments petaloid; anthers adnate, introrse, 
opening by a double longitudinal cleft. Torus large, fleshy, elevated, 
enclosing in hollows of its surface numerous carpels. Nuts numerous, 
inserted, but loose, into the depressions of the torus. Seeds 1-2; 
perisperm none; embryo enclosed in a vitellus, large, with 2 fleshy 
cotyledons. Aquatic herbs, with showy flowers, peltate floating leaves, 
and prostrate rootstocks, found in the temperate and tropical regions 
of the old and new world. Lindley enumerates 1 genus, including 3 
species. Example Nelumbium. 

753. The flower of Nelumbium spedosum is supposed to be the Lotus 
figured on Egyptian and Indian monuments, and the fruit is said to be 
the Pythagorean Bean. The plant is said to have disappeared from 
the Nile, where it used to abound. The petioles and peduncles contain 
numerous spiral vessels, which have been used for wicks of candles. 

754. Order 10. Sarraeeniacetc, the Sidesaddle-flower Family. 
(Polypet. Hypog.) Sepals 5, persistent, imbricated in aestivation, 
often with coherent bracts outside. Petals 5, hypogynous, concave; 



Fig. 562. Section of a flower of Nymphsea alba, white Water-lily, showing the pistils and the 
receptacle or torus bearing the stamens and petals, p. Peduncle or flower-stalk, t, Elevated torus 
or receptacle, s, Radiating stigmas, a, Sepal. 6, Petal, c, Stamens. 



PAPAVEKACE^E. 359 

occasionally, the corolla is absent, and the calyx consists of 4-6 
segments. Stamens 00; anthers adnate, dithecal, introrse, with longi- 
tudinal dehiscence. Ovary free, tri-quinquelocular; style single; 
stigma persistent, either a truncated point, or large and peltate with 
5 angles ; ovules anatropal. Capsule 3-5-celled, with loculicidal 
dehiscence. Seeds very numerous, small, attached to large placentas 
which project from the axis into the cavity of the cells ; albumen 
copious ; embryo cylindrical, lying at the base of the seed ; radicle 
pointing to the hilum. Herbaceous plants, found in boggy places, 
having radical leaves, the petioles of which are folded, and cohere so 
as to form ascidia or hollow tubes (fig. 187). Scapes one or more 
flowered. The plants are found in North America and Guiana. Their 
properties are not known. Lindley enumerates 2 genera, including 7 
species. Examples Sarracenia, Heliamphora. 

755. Order 11. Pnpaveracwe, the Poppy Family. (Polypet. 
Hypog.) Sepals 2, deciduous. Petals hypogynous, usually 4, cruciate, 
sometimes a multiple of 4, regular, rarely wanting. Stamens hypo- 
gynous, usually 00, sometimes a multiple of 4 ; anthers dithecal, in- 
nate. Ovary solitary; style short or none; stigmas 2, or many and 
radiating (fig. 409); ovules 00, anatropal (fig. 421). Fruit unilocu- 
lar, either siliquseform with two, or capsular with several parietal 
placentas. Seeds numerous; albumen between fleshy and oily; 
embryo minute, at the base of the albumen, with plano-convex coty- 
ledons. Herbs or shrubs, usually with milky or coloured juice, 
having alternate exstipulate leaves, and long one-flowered peduncles. 
The plants belonging to this order are chiefly European. The species, 
however, are found scattered over tropical America, Asia, China, New 
Holland, Cape of Good Hope, &c. Lindley mentions 18 known 
genera, and 130 species. Examples Papaver, Meconopsis, Esch- 
scholtzia, Glaucium, Chelidonium. 

756. The order possesses well-marked narcotic properties. Opium 
is the concrete milky juice procured from the unripe capsules of 
Papaver somniferum, and its varieties. The plant is a native of Western 
Asia, and probably also of the south of Europe; but it has been dis- 
tributed over various countries. There are five kinds of opium known, 
viz. Turkey, Egyptian, East Indian, European, and Persian ; of which 
the first is the kind chiefly used in Britain. The most important 
active principle in opium is the alkaloid called morphia. There are 
other crystalline principles found in it, such as codeia and narcotine ; 
and an acid called meconic acid, which constitutes with sulphuric acid 
the solvent of the active principles. According to various circum- 
stances, opium may act as a stimulant, a narcotic, anodyne, or diapho- 
retic. The seeds of the Opium Poppy yield a bland, wholesome oil. 
Chelidonium majitSj Celandine, yields an orange-coloured juice, which 
is said to have acrid properties. In this plant, observations were made 



360 



FUMARIACE^E CRUCIFER^E. 



by Schultz on Cyclosis (^[261, and fig. 223). Eschscholtzia is remark- 
able for the dilated apex of the peduncle, from which the calyx 
separates in the form of a calyptra, resembling an extinguisher of a 
candle. Sanguinaria canadensis, Blood-root or Puccoon, has emetic 
and purgative properties. 

757. Order 12. Fnmariaceze, the Fumitory Family. (Polypet. 
Hypog.) Sepals 2, deciduous. Petals 4, cruciate; one or both of the 
two outer gibbous at the base, the two inner cohering at the apex. 
Stamens hypogynous, usually 6, diadelphous; anther of middle stamen 
of each parcel bilocular, outer ones unilocular. Ovary free, 1-celled; 
style filiform ; stigma with 2 or more points ; ovules amphitropal. 
Fruit either an achasnium, or a 2-valved 2-seeded capsule, or a many- 
seeded siliqua. Seeds crested; albumen fleshy; embryo minute, 
excentric. Herbaceous plants, with a watery juice, and alternate 
multifid leaves. Although at first sight very unlike the Poppy family, 
the Fumitories resemble this order in their deciduous sepals, in their 
seeds, and, in many cases, in their fruit. The two outer unilocular 
stamens of each parcel may be considered as forming one perfect 
stamen, thus making the whole number four. They are found chiefly 
in northern temperate latitudes. They are said to be bitter and 
diaphoretic in their properties. Lindley notices 15 genera, including 
110 species. Examples Fumaria, Corydalis, Diclytra. 

758. Order 13. Cruciferee, the Cruciferous or Cresswort Family. 
Brassicacese of Lindley. (Polypet. Hypog.) Sepals 4, deciduous, the 
two lateral ones gibbous at the base. Petals 4, hypogynous, alternat- 
ing with the sepals, deciduous, cruciate (fig. 291). Stamens 6, tetra- 
dynamous (figs. 345, 565), two shorter solitary (fig. 565 e'), opposite 




r,\;\ 



5C5 



Figs. 563 570. Organs of fructification of Erysimum lanceolatum. one of the Cruciferse. 

Fig. 563. Diagram of the flower, showing the arrangement of four sepals, four petals alter- 
nating with them, six tetradynamous stamens, and a siliqua with replum. 

Fig. 564. Vertical section of the flower, c, Calyx, p, Petals. , Stamens, o. Ovary laid 
open, s, Stigma. 

Fig. 565. Flower deprived of its envelopes, c c, Cicatrices left by the fall of the sepals, 
<7, Glands which are situated at the base of the stamens. tf, Two short stamens opposite lateral 
sepals, e", Four long stamens opposite anterior and posterior sepals, p, Pistil. 

Fig. 566. Horizontal section of the ovary, g, Ovules, c. Spurious dissepiment or replum, 
which divides the ovary into two cavities. This replum is formed by the placentas. 



C11DCIFER.E. 




the lateral sepals, occasionally toothed; four longer (fig. 565 e"), 
opposite the anterior and posterior sepals, generally free, sometimes 
partially united and furnished with a tooth on the inside ; anthers 
bilocular, introrse (fig. 564). Torus with green glands between the 
petals and stamens and ovary (fig. 565 g). Ovary superior, with 
parietal placentas, which meet in the middle, forming a spurious 
dissepiment or replum (fig. 566 c); stigmas 2, opposite the placentas, 
or anterior and posterior (fig. 456 s). Fruit 
a siliqua (figs. 567, 568), or a silicula, rarely 
1 -celled and indehiscent, usually spuriously 
2-celled and dehiscing by two valves, which 
separate from the replum (figs. 456, 568), 
one or many-seeded. Seeds campylotro- 
pous (figs. 419, 524), pendulous, attached in 
a single row by a funiculus to each side of 
the placentas (fig. 568) ; perisperm none ; 
embryo with the radicle folded upon the 
cotyledons which are next the placenta (figs. 
524, 569 r). Herbaceous plants, seldom 
undershrubs, with alternate leaves, and yel- 
low or white, rarely purple, flowers, without 
bracts. This order is well distinguished by 
having tetradynamous stamens. Most of the plants belonging to the 
order are European. The species, however, are found scattered all 
over the world. De Candolle, in 1821, calculated that the species 
then known were distributed as follows: 

In the frigid zone of the northern hemisphere, 205 

In all the tropics (chiefly mountainous parts), 30 

f of northern hemisphere, 548 ) 

In the temperate zone, | of southern hemis j; here ; 86 ; 634 

Lindley enumerates 173 genera, including 1600 species. Examples 
Draba, Lepidium, Isatis, Brassica, Sinapis, Bunias, Senebiera, Schizo- 
petalon. 

759. The order has been subdivided into sections, according to the 
mode in which the radicle of the embryo is folded on the cotyledons, 
as well as according to the nature of the fruit. The suborders founded 
on the embryo are 1. Pleurorhizeas (wAewf, side, arid pigu, root), = 
cotyledons accumbent, radicle lateral, i.e. applied to their edge (fig. 
517). 2. Notorhizea3 (VUTOV, back), || cotyledons incumbent, 
radicle dorsal, i.e. applied to their back (fig. 518). 3. Orthoplocea? 

Fig. 5C7. Siliqua or long pod. 

Fig. 568. Siliqua with one of its valves removed, in order to show the seeds attached to the 
replum. 

Fig. 569. Vertical section of the seed. /, Funiculus or umbilical cord, t, Spermodenn or 
testa swollen at the chalaza, c. r. Radicle, c, Cotyledons. 

Fig. 570. Horizontal section of the seed, t, Spermodenn or testa, r, Radicle, c, Incumbent 
cotyledons. 



362 CRUCIFER^E. 



(flftfd?, straight, and wXo'xo?, a plait or fold), 077 cotyledons condupli- 
cate (folded), radicle dorsal (figs. 513, 570). 4. Spirolobeaj (c-z-eija, a 
coil, and Ao/3oV, a lobe), || || cotyledons twice folded, radicle dorsal 
(fig. 515). 5. Diplecolobeae (Sij, twice, v^ina, I fold or plait, and 
A.i,3oV, a lobe), || || || cotyledons three times folded, radicle dorsal. 

760. The divisions founded on the seed-vessel, are 1. Siliquosaa, 
a siliqua, linear or linear-lanceolate, valves opening longitudinally. 2. 
Latiseptse (latus, broad, and septum, partition), a silicula, partition in 
its broadest diameter, oval or oblong, valves flat or convex, opening 
longitudinally. 3. Angustiseptae (angustus, narrow), a silictua, parti- 
tion in its narrow diameter, linear or lanceolate, valves opening longi- 
tudinally, folded and keeled. 4. Nucumentaceae (nucumentum, a nut), 
silicula, valves indistinct or indehiscent, often 1 -celled, from the 
absence of the replum or partition. 5. Septulatae (septa, partitions), 
valves opening longitudinally, furnished with transverse partitions in 
their interior. 6. Lomentaceae (lomentum, an articulate legume), sili- 
qua or silicula, dividing transversely into single-seeded cells, the true 
siliqua being often barren and all the seeds placed in the beak. 

761. In this order there is a want of symmetry as regards the 
number of stamens, compared with the floral envelopes. The two long 
stamens placed close together may, however, be looked upon as one 
divided by a process of deduplication, so that the actual number will 
thus be reduced to four. This view is confirmed by the shorter stamens 
having teeth on each side, while the longer ones are toothed on one 
side only. By pelorization, too, some Cruciferae become tetrandrous. 
While there is a splitting of the filaments, there is also the production 
of two additional anther-lobes. In regard to the fruit, it has been 
stated, that normally there are four carpidia or carpels, two of which 
are constantly abortive. In some species of Iberis there have been 
seen four sepals, four petals, four stamens, and four carpels. Thus the 
floral type of Cruciferae is quaternary: calyx having four sepals, corolla 
four petals, receptacle four staminiferous glands, androecium four 
stamens, gynoecium four phyllidia, fruit four carpidia. 

762. There are no truly poisonous plants in the order. In general, 
it possesses antiscorbutic and stimulant qualities, with a certain degree 
of acridity. Many of the most common culinary vegetables belong to 
the order, such as Cabbages, Cauliflower, Turnip, Radish, Cress, Horse- 
radish, &c. They contain much sulphur and nitrogen, and, on this 
account, when decaying, give off a disagreeable odour. Many garden 
flowers, such as Wall-flower, Stock, Rocket, and Honesty, are found in 
this order. Brassica oleracea is the original species whence all the 
varieties of Cabbage, Cauliflower, Brocoli and Savoys have been obtained 
by the art of the gardener. The part of the Cauliflower used as food 
is the deformed flower stalks. Brassica Rapa is the common Turnip, 
while Brassica campestris is the source of the Swedish Turnip. Brassica 



CAPPARIDACE^E. 363 

chinensis yields Shanghse oil. Lepidium sativum is the common Cress, 
and Raphanus sativus the Eadish. Crambe maritima is the Sea-kale. 
The seeds of Sinapis nigra (Brassica nigra of some), furnish table 
mustard. These contain a bland fixed oil, a peculiar bitter prin- 
ciple, myronic acid, and another principle analogous to albumen or 
emulsin, called myrosine. When water is added, the myronic acid 
and myrosine, by their combination, form a pungent volatile oil, 
containing sulphur and nitrogen, which gives to mustard its peculiar 
properties as a physiological agent. Sinapis alba furnishes white 
mustard, which contains more fixed oil than black mustard. It does 
not, however, contain myronic acid, but an analogous principle called 
sinapin, or sinapisin, which, by combination with another principle, 
forms an acrid compound, but not a volatile oil. The mustard of 
Scripture is not a species of Sinapis, but Salvadora persica, according 
to Royle, belonging to the natural order Chenopodiacece. Many other 
Cruciferous plants yield volatile oils containing sulphur, and the seeds 
of many yield by expression a bland fixed oil, such as Kape-seed oil. 
Cochlearia officinalis, common Scurvy-grass, is used as a stimulant. 
Cochlearia Armor acia, or Armor acia rusticana, the Horse-radish, has 
irritant and even vesicant qualities. Anastatica hierochuntina, Rose 
of Jericho, is remarkable for the hygrometric property of the old 
withered annual stems, which are rolled up like a ball in dry weather, 
and drifted about by the winds in the deserts of Syria and Egypt. If 
rain falls, they resume their original direction. They thus continue 
for many years to curl up and expand, according to the state of the 
atmosphere. The genus Scliizopetalon is remarkable on account of its 
tetracotyledonous (having four cotyledons) embryo. Isatis tinctoria, 
Woad, when treated like Indigo, yields a blue dye. Isatis indigotica 
is the Tein-Ching, or Chinese Indigo. 

763. Order 14. Capparidaee, the Caper Family. (Polypet. Hypog.} 
Sepals 4, often more or less cohering (fig. 554 c). Petals 4, some- 
times 0, cruciate (fig. 554 p], usually unguiculate and unequal. Sta- 
mens hypogynous, 4, 6 (fig. 554 e), or 00, but in general some high 
multiple of four, placed on an elongated hemispherical and often 
glandular torus (fig. 554 a g'}. Ovary usually stalked (fig. 554 o) ; 
style filiform, sometimes 0; ovules curved. Fruit unilocular, siliquse- 
form and dehiscent, or fleshy and indehiscent, rarely monospermous, 
usually with two polyspermous placentas. Seeds generally reniform 
and exalbuminous; embryo curved; cotyledons foliaceous, flattish. 
Herbs, shrubs, sometimes trees, with alternate, stalked, undivided, or 
palmate leaves, which are either exstipulate or have spines at their 
base. They are found chiefly in warm countries, and are abundant in 
Africa. There are 28 genera, and 340 species. The order is divided 
into two suborders: 1. Cleomeae, with capsular fruit. 2. Capparese, 
with baccate fruit. Examples Cleome, Capparis. 



304 EESEDACE^E FLACOUKTIACE^E. 

764. The plants of this order have stimulant qualities. The flower- 
buds of Capparis spinosa furnish capers. The plant is a native of 
the south of Europe, and, according to Royle, is the Hyssop (mw) of 
Scripture. Some species of Cleome and Polanisia are very pungent, 
and are used as substitutes for mustard. The pungency of some is so 
great that they act as blisters. The root of Cleome dodecandra is used 
as an anthelmintic. 

765. Order 15. Resedacere, the Mignonette Family. (Polypel.Hypog.) 
Calyx many-parted. Petals 4-6, unequal, entire, or lacerated, in the 
latter case consisting of a broad scale-like claw with a much-divided limb. 
Stamens 10-24, hypogynous, attached to a glandular torus; filaments 
variously united; anthers bilocular, innate, with longitudinal dehis- 
cence. Ovary sessile, 3-lobed, 1-celled, multiovular, with 3-6 parietal 
placentas; stigmas 3. Fruit either a unilocular many-seeded capsule, 
opening at the apex so as to render the seeds seminude (fig. 479), or 
3-6 few-seeded follicles. Seeds reniform, usually exalbuminous; em- 
bryo curved; radicle superior; cotyledons fleshy. Herbaceous plants, 
rarely shrubs, with alternate, entire, or divided leaves, having gland- 
like stipules. They inhabit chiefly Europe and the adjoining parts of 
Asia. A few are found in the north of India and south of Africa. 
The uses of the order are unimportant. Reseda Luteola, Weld, yields 
a yellow dye. Reseda odorata is the fragrant Mignonette. The Mig- 
nonette is rendered suflruticose, by preventing the development of its 
blossoms. This is the origin of the tree Mignonette, which is much 
cultivated in France. There are 6 known genera, and 41 species, 
according to Lindley. Example Reseda. 

766. Order 16. Flacourtinccte, the Arnotto Family. (Polypet.Hypog.} 
Sepals 4-7, slightly cohering. Petals equal to and alternating with 
the sepals, or wanting. Stamens hypogynous, equal in number to the 
petals, or some multiple of them. Ovary roundish, sessile, or slightly 
stalked; style either none or filiform; stigmas several, more or less 
distinct; ovules attached to parietal placentas, which sometimes branch 
all over the inner surface of the valves. Fruit 1-celled, containing a 
thin pulp, either fleshy and indehiscent, or capsular with 4 or 5 valves. 
Seeds numerous, enveloped in a covering formed by the withered 
pulp; albumen fleshy, somewhat oily; embryo axile, straight; radicle 
turned towards the hilum; cotyledons flat, fohaceous. Shrubs or small 
trees, with alternate, simple, usually exstipulate leaves, which are 
often dotted. The plants are chiefly natives of the warmest parts 
of the East and West Indies, and of Africa. The order is divided 
into two sections: 1. Flacourtieas, having the placentas ramifying 
over the inner surface of the fruit. 2. Bixeas, placentas narrow, and 
running in lines along the parietes. Many of the plants yield edible 
fruits. The pulp is often sweet and wholesome. Some are astringent, 
others purgative. The reddish pulp surrounding the seeds of Bixa 



CISTACE^E VIOLACE^E. 3(55 

orellana supplies the substance called arnotto, which is used for yield- 
ing a red colour, and for staining cheese. There are 31 genera, and 
85 species, according to Lindley. Examples Patrisia, Flacourtia, 
Prockia, Erythrospermum, Bixa. 

767. Order 17. eistacete, the Rock-Rose Family. (Polypet. Hypog.) 
Sepals usually 5, persistent, unequal, the three inner with contorted 
aestivation. Petals 5, caducous, hypogynous, aestivation corrugated, and 
twisted in an opposite direction to that of the sepals. Stamens usually 
00, free, hypogynous ; anthers 2-celled, adnate. Ovary syncarpous, 
1- or many-celled ; style single ; stigma simple. Fruit capsular, 3-5- 
10-valved, either 1-celled or imperfectly 5-10-celled, with loculicidal 
dehiscence. Seeds usually indefinite ; embryo inverted, either spiral 
or curved, in the midst of mealy albumen; radicle remote from the hilum. 
Shrubs or herbaceous plants with entire, opposite or alternate, stipu- 
late or exstipulate leaves. They inhabit chiefly the southern regions 
of Europe, and the north of Africa. Some of the species are remark- 
able for the irritability of their stamens (^[ 665). Many of them 
yield a resinous balsamic juice, which imparts viscidity to the branches. 
The resinous matter called ladanum or labdanum, is yielded by Cistus 
creticus. There are 7 known genera, and 185 species, according to 
Lindley. Examples Cistus, Helianthemum, Lechea. 

768. Order 18. vioiaccte, The Violet Family. (Polypet. Hypog.} 
Sepals 5, persistent, usually elongated at the base, aestivation imbri- 
cated. Petals 5, hypogynous, equal or unequal, generally withering, 
aestivation obliquely convolute. Stamens 5, alternate with the petals, 
sometimes opposite to them, inserted on a hypogynous torus ; anthers 
dithecal, introrse, often cohering, with a prolonged connective some- 
times spurred (fig. 343); filaments dilated, two of them in the irregular 
flowers having an appendage at their base. Ovary unilocular, with 
many (rarely one) anatropal ovules ; style single, usually declinate, with 
an oblique hooded stigma (fig. 390, 1 s). Fruit a 3-valved capsule, 
dehiscence loculicidal, placentas on the middle of the valves (fig. 390.) 
Seeds 00 or definite ; embryo straight, erect, in the axis of a fleshy 
perisperm. Herbs or shrubs, with alternate, rarely opposite, leaves, 
having persistent stipules, and an involute vernation. They are 
natives of Europe, Asia, and America. The herbaceous species 
inhabit chiefly the temperate parts of the northern hemisphere, 
while the shrubby species are found in South America and India. 
They have been divided into two suborders: 1. Violeas, with irregular 
flowers. 2. Alsodeiea3, with regular flowers. There are 14 known 
genera, and 315 species. Examples Viola, lonidium, Alsodeia. 

769. They are distinguished by the emetic properties of their roots, 
which contain an active principle called violine, similar in its qualities 
to emetin. The roots of Viola odorata have been used medicinally as 
emetics. Some species of lonidium are used in South America as substi- 



366 DROSERACEuE. POLYGALACE-E. 

tutes for Ipecacuanha. The petals of the Sweet or March Violet, the Jot, 
of the Greeks, are laxative, and are used in the form of infusion mixed 
with sugar ; and a violet or purple coluring matter is procured from 
them, which is employed as a test for acids and alkalies, being changed 
into red by the former, and into green by the latter. Viola tricolor, 
Heart's-ease, and other species, have been used as demulcent expecto- 
rants. V. tricolor is the origin of all the cultivated varieties of pansy. 

770. Order 19. roeraceie, the Sundew Family. (Polypet. Hypog.) 
Sepals 5, persistent, equal; aestivation imbricated. Petals 5, hypo- 
gynous. Stamens free, withering, alternate with the petals, or 10 or 
more ; anthers bilocular, with longitudinal dehiscence. Ovary single ; 
styles usually 3-5, sometimes 1 or wanting. Fruit a unilocular or 
spuriously trilocular capsule, 3- 5-valved, with loculicidal dehiscence, 
occasionally indehiscent. Seeds numerous, either albuminous or ex- 
albuminous; embryo minute and erect. Herbaceous plants with 
alternate leaves, usually inhabiting marshy places. They are found in 
various parts of the world, in Europe, North and South America, 
China, East Indies, &c. The order has been divided into two sections ; 
1. Drosereae, styles 3-5, albumen present, leaves with a circulate 
vernation, and furnished with glandular hairs ; stipules in the form of 
fringes. 2. Parnassieas, some of the stamens sterile ; style 1 or none ; 
no albumen nor glandular hairs. There are 8 known genera, and 
upwards of 90 species. Examples Drosera, Aldrovanda, Dionaea, 
Parnassia. 

771. The Droseras have a more or less acid taste, combined with 
slight acridity. Some of them are said to be poisonous to cattle. 
Their leaves are furnished with glandular capitate hairs, which are 
covered with drops of fluid in sunshine ; hence the name Sundew or Eos 
solis. An Italian liqueur, called Rossoli derives its name from a Drosera 
used in its manufacture. Some of the Droseras have dyeing properties. 
Dioncea muscipula, Venus's fly-trap, is a North American plant, having 
the lamina} of the leaves in two halves, each furnished with three 
irritable hairs, which, on being touched, cause the folding of the divi- 
sions in an upward direction (figs. 186, 664). Aldrovanda vesiculosa, 
an aquatic found in the south of Europe, is distinguished by its 
whorled, cellular leaves, or floating bladders. Parnassia palustris, 
Grass of Parnassus, has remarkable gland-like bodies between the 
stamens (fig. 304). These are probably an abortive state of the 
stamina! organs. Lindley looks upon them as bundles of stamens, and 
places the genus among Hypericacese. The stamens of Parnassia are 
irritable, and move towards the pistil in succession (*f 665). 

772. Order 20. Poiygalacete, the Milkwort Family. (Polypet. 
Hypog.) Sepals 5, very irregular, distinct; 3 exterior, of which 1 
is superior, and 2 inferior ; 2 interior, usually petaloid, lateral ; aesti- 
vation imbricated. Petals hypogynous, unequal, usually 3, of which 



TREMANDRACE^E TAMARICACE.E. 367 

1 is anterior, and larger than the rest, and 2 are alternate with the 
upper and lateral sepals ; sometimes there are 5 petals, 2 of them very 
minute ; the anterior petal, called the keel, is often crested. Stamens 
hypogynous, 8, monadelphous or diadelphous ; anthers clavate, usually 
1 -celled, and having porous dehiscence. Ovary mostly bilocular; 
ovules solitary, rarely 2 ; style simple, curved ; stigma simple. Fruit 
dehiscing in a loculicidal manner, or indehiscent. Seeds pendu- 
lous, anatropal, strophiolate at the hilum ; albumen fleshy ; embryo 
straight. Shrubs or herbs with alternate or opposite exstipulate leaves. 
They are found in all quarters of the globe. Lindley mentions 19 
genera, including 495 species. Examples Polygala, Securidaca, 
Krameria. 

773. In the appearance of their flowers, the plants of this order 
have a resemblance to Papilionaceae. They are distinguished, however, 
by the odd petal being inferior, and the sepal superior. They are 
generally bitter, and their roots yield a milky juice. Polygala Senega, 
Snake-root, is a North American species, the root of which is used 
medicinally in large doses as emetic and cathartic ; and in small doses 
as a stimulant, sudorific, expectorant, and sialagogue. It contains an 
acrid principle, called polygalin, senegin, and polygalic acid. The 
name of Snake-root was given from its supposed use as an antidote to 
the bite of the rattle-snake. Krameria triandra, a Peruvian plant, 
furnishes Rhatany-root, which is employed as a powerful and pure 
astringent in cases of haemorrhage, and chronic mucous discharges. 

774. Order 21. Tremandracete, the Porewort Family. (Polypet. 
Hypog.} Sepals 4-5, slightly coherent, deciduous with a valvate aesti- 
vation. Petals 4-5, deciduous, with an