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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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arV19069 

A Manual of botan' 




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MANUAL OF BOTANY. 



By the same. 

In one volume, royal 8vo, pp. III7> price 2is. 

CLASS-BOOK OF BOTANY, 

Illustrated with 1800 Wood Engravings. 



Uniterm with above, price 7s. 6d. 
PAL^ONTOLOGICAL BOTANY. 



In foolscap 8vo, illustrated, price 3s. 6d. 
ELEMENTS OF BOTANY. 



In fcap. 8vo, second Edition, with Map, 3s. 6d. 
THE FLORA OF EDINBURGH. 



MANUAL OP BOTANY 



AN INTEODUCTION" 

TO THE 

STUDY OF THE STRUCTUEE, PHYSIOLOGY, AND 
CLASSIFICATION OF PLANTS 



BT 

JOHN HUTTON BALFOUR, A.M., M.D. Edin., 

F.B.sT, See. E.S.B., F.L.S., 

PROFESSOR OF MEDICINE AND BOTANY AND DEAN OF THE MEDICAL FACULTY IN THE 

UNIVERSITY OF EDINBURGH, HER MAJESTY'S BOTANIST FOR SCOTLAND, 

AND REGIUS KEEPER OF THE ROYAL BOTANIC GARDEN. 



FIFTH EDITION 



WITH UPWARDS OF NINE HUNDRED ILLUSTRATIONS 



EDINBURGH 
ADAM AND CHARLES BLACK 

1875 

9 



Pnnted by R. & R. Clark, Edinburgh, 



ORIGINAL DEDICATION IN 1849. 



TO 
EOBEET KAYE GEEVILLE, LL.D. 

AS A SMALL BUT SINCERE 

MAKE OF REGAED FOE HIS EMINENCE AS A BOTANIST, 

OF GRATITUDE 

FOR HIS KIND BOTANICAL SERVICES, 

AND OF ESTEEM 

FOR HIS CHARACTER AS A CHRISTIAN FRIEND, 

THE FOLLOWING PAGES ARE 

DEDICATED BY 

J. H. BALEOUE. 



PEEFAOE. 



In drawing up this Manual of Botany, tlie object has been to 
give a comprehensive, and, at the same time, a condensed view 
of all departments of the science, including the microscopical 
structure of plants and their morphology, the functions of 
their various organs, their classification and distribution over 
the globe, and their condition at various geological epochs. 
Care has been taken to notice the plants used for commercial 
and economical purposes, and particularly those having 
medicinal properties. The principles of adaptation and order 
which prevail in the vegetable kingdom have been promi- 
nently brought into view, with their bearings on symmetry 
and arrangement. 

The physiology of plants has been considered in connec- 
tion with the anatomical structure of their different organs, 
and the recent views in regard to the embryogenic process 
in flowering and flowerless plants have been brought under 
notice. In the department of classification, the system of 
De CandoUe has been more or less completely followed, and 
the characters of the Natural Orders have been briefly given. 
It has been shown that the great object of classification is to 
arrange plants according to their affinities in aU important 
particulars, and thus to trace, what may be considered to be, 



Vm PKEFACE. 

the plan of the Almighty and all-wise Creator. At the same 
time, in all systems it is necessary to have artificial means to 
aid in the study- of genera and species. Such means, like an 
index, must be easily applied so as to assist the beginner in 
his studies. It is only the Botanist, who has an extended 
knowledge of the vegetation of the globe, who has examined 
the effects produced on vegetation by climate and other cir- 
cumstances of existence, and who has studied aberrant forms 
in connection with natural orders, that can take a correct 
view of the alliances of plants. 

The divisions of geographical and palseontological Botany 
are still in an imperfect state, and are undergoing constant 
changes from the discoveries of naturalists in various parts of 
the world. All that has been attempted in this volume is to 
give a very general outline of these subjects, and to call the 
attention of the student to the points which still require 
elucidation. In the Appendix will be found a description of 
the microscope, of its use as an instrument of research in 
histological Botany, and of the mode of making vegetable 
preparations. There are also added directions as to the col- 
lecting of plants and the formation of a herbarium, with hints 
as to alpine travelling, and as to the examination of a country 
in a botanical point of view. A full glossary of the ordinary 
botanical terms is likewise given. 

The study of Botany is well fitted to call the observant 
faculties into active exercise. It teaches the student to mark 
the differences and resemblances between objects, and leads 
to habits of correct observation and diagnosis. In the present 
day there is a growing feeling of its importance in mental 



PEEFACE. IX 

culture, and a tendency to include it as a subject of study in 
the curriculum of Arts, as well as in that of Medicine. It is 
now also taking a place in our school-books, and thus becom- 
ing part of the education of the young. It is a science fitted 
for all ages, for all ranks, and for aU seasons. " In youth, 
when the affections are warm and the imagination vivid ; in 
more advanced life, when sober judgment assumes the reins ; 
in the sunshine of fortune and the obscurity of poverty, it 
can be equally enjoyed. The opening buds of spring ; the 
warm luxuriant blossoms of summer ; the yeUow bower of 
autumn ; and the leafless desolate groves of winter, equally 
afford a supply of mental amusement and gratification to the 
Botanist." It is hoped that the present Manual may aid in 
the promotion of a science the study of which is so well cal- 
culated to contribute to the enjoyment and wellbeing of 
mankind. The examination of the plants which clothe the 
surface of the globe, of the lilies of the field, and of the 
meanest moss or lichen in our path, is well fitted to call forth 
exalted views of the eternal power and Godhead of Him who 
hath made aU these for His own glory, and whose providential 
care extends to the clothing of the grass of the field, which 
to-day is, and to-morrow is cast into the oven. 

27 Inveeleith Row, Edinbubgh, 
April 1875. 



INTRODUCTOET EEMARKS. 



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 Linnsean 
system. The number of species collected by a botanist is not 
considered now-a-days as a measure of his acquirements, and 
names and classifications 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 Eay 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 CandoUe, Brown, End- 
Hcher, Lindley, Hooker, Arnott, Bentham, and others. The 
relative importance of the different organs of plants, their 
structure, development, and metamorphoses, are now studied 
upon philosophical principles. The researches of G-audichaud, 
Mirbel, and Trecul, as to the structure and formation of wood ; 
the observations of Schleiden, Schwann, and Mohl on cell-develop- 
ment ; the investigations of Brown, Schleiden, Fritzsche, Amioi, 
Hofmeister, Tulasne, Darwin, Strasburger, Pringsheim, Cohn, Her- 
mann Miiller, and others, into the functions of the pollen, the 
fertilisation of plants, both phanerogamous and cryptogamous, the 
development of the ovule and spore, 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 



xii INTEODUCTOET EEMABKS. 

correct views of the relation whicli plants bear to each other, of 
the lavs which regulate their development, and of the great plan 
on which they were formed by the Creator. 

There is a tendency, however, to speak of the laws of nature 
as if they were in themselves executive, and this has led to 
erroneous views of the system of the universe. Some there are 
who attempt to shut out God from His works by this means. The 
Creator is regarded as looking at the development of His plan, 
and watching its progress, but not requiring to exercise constant 
and unwearied superintendence of the minutest event. Nay, 
even when He creates animals with certain instincts, and plants 
with certain functions, He is represented like an imperfect work- 
man taking a lesson from the operations of the beings which He 
has made, and which, by their own efforts of selection, or by their 
own struggles for existence, complete what the Creator had set 
on foot. A certain mechanism is set agoing in some unknown 
way, and it continues to work according to definite laws. But 
what are laws unless there is some one to carry them out ? The 
great Author of these laws must be always working in them and 
by them, and upholding them in their integrity and efficiency. 
No doubt the Creator is a God of order and method, and the 
operations of His wisdom and power are displayed in what we 
call laws. The execution of these laws, however, is just as won- 
derful and miraculous as is a fiat of creation, and requires equally 
the exercise of Almighty power. The uniformity of nature de- 
pends on the wisdom that made these laws and adapted them 
to aU the varying conditions of the universe. In the course 
of Providence, however, there are every now and then marked 
events which seem to be at variance with this uniformity, as 
when a deluge overwhelms mankind, or when a sudden convulsion 
destroys the cities of the plain. Such events show that all things 
do not continue as they were from the beginning of the creation. 
Those who look for a progressive development and a gradual and 
eternal advance towards perfection in the living beings which 
cover the earth, without further creative fiats or movements mr 
saltum, forget, in their speculations, that a time is coming when, 
as the Apostle says, " the earth and the works that are therein 



INTEODUCTOEY EEMAEKS. Xui 

shall be burned up," and then shall there be ushered in " a new 
earth," wherein righteousness shall dwell. We cannot but honour 
the man, who, by his genius and talent, has been enabled to 
develop one of the great laws of nature, and who feels and ac- 
knowledges that he has been the humble instrument to Uft the 
veil to a certain extent which conceals the workings of the 
Almighty; but we have no sympathy with that discoverer in 
science, who, puffed up with intellectual superiority, puts the laws 
which he has elucidated in the place of the Creator, whose per- 
sonality and ever-working omnipresence he ignores. 

In studying, therefore, the laws which are exhibited in the 
economy of living beings, let us never, in the pride of science 
and philosophy, forget Him who not only created all things but 
upholds all things, and by whom all things consist. While 
we apply ourselves with the earnestness of zealous students to 
examine those wondrous works which are sought out of all that 
have pleasure therein, let us take everything in connection with 
that Word which is the sole record of Truth, and which, as coming 
from the God of nature, must be in perfect harmony with the 
laws of nature. 

The Botanist, in prosecuting his researches, takes an en- 
larged 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 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 EafSes in the Indian Archipelago. 

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 or germs 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 reacL They are the first occupants of the 
sterile rock and the coral-formed island — ^being fitted to derive 



XIV INTEODUCTOET EEMAEKS. 

the greater part of their nourishment 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 pro- 
gress 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 pro- 
gress of time, the sterile rock presents all the varieties of meadow, 
thicket, and forest. 

The Creator has distributed His 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 characterised by certain predominating 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 
latitudinal distribution of plants. Again, if we descend into the 
bowels of the earth, we find there traces of vegetation — a vegeta- 
tion, however, which flourished at distant 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 difi'erent strata. By the 
labours of Brongniart, Goeppert, Schimper, and others, 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 afi'orded 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 Horti- 



INTEODUCTOET EEMAEKS. XV 

culture has of late attracted mucli attention, and the chemistry 
of plants has been carefully examined by Liebig, Mulder, and 
Johnston. The consideration of the phenomena connected with 
germination and the nutrition of plants has led to important 
conclusions 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 connec- 
tion 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 1 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 generalisations. 

To those who prosecute science for amusement, Botany pre- 
sents many points of interest and attraction. Though , relating 
to living and organised beings, the prosecution of it calls for no 
painful experiments nor forbidding dissections. It adds pleasure 
to every walk, affords an endless source of gratification, and it 
can be rendered available alike in the closet and in the field. 
The prosecution of it combines healthful and spirit-stirring recrea^ 



xvi INTRODUCTORY REMARKS. 

tion 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 dehghtful 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 indehbly impressed on their 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 shed- 
ding 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 namesake of the brooks ; the Woodsia, with its tufted fronds, 
adorning the clefts of the rocks ; the nival Gentian concealing its 
eye of blue in the ledges of the steep crags ; the alpine Astragalus 
enlivening the turf with its purple clusters ; the dwarf mountain 
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 enthusiasm 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 deli- 



INTEODUCTOEY EEMARKS. Xvii 

cate grasses, the chickweeds, the carices, and the rushes, which 
spring up on the moist alpine summits ; the graceful ferns, the 
tiny mosses, with their urn- like thecse, the crustaceous dry lichens, 
with their spore-hearing 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 Gaus- 
sen, do we find the Bible in opposition to the just ideas which 
Science has given us regarding the form of our globe, its magni- 
tude, 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 Eevealed 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." 



TABLE OF CONTENTS. 



Page 
£ Aiiii) AOfi >•••...,, vii 

INTEODUCTOEY EEMAEKS ...... xi 

PAET I.— VEGETABLE ANATOMY, OEGANOGEAPHY, AND PHY- 
SIOLOGY 1 

CHAPTEE I.— ELEMENTAEY OEGANS, OE VEGETABLE TISSUES 1 
Sbctioh I. — Cellulab Tissue. 

1. Form and Arrangement of Cells . 



2. Contents of Cells 

3. Development and Functions of Cells 

Sbction II.— Vascdiab Tissue 

1. Form and Arrangement of Vessels 

2. Development and Functions of Vessels 
Tatular Arrangement of Vegetable tissues 



8 
13 

16 

16 
21 
23 



CHAPTEE II.— COMPOUND OEGANS FOEMED BY THE TISSUES 25 



Section I. — Oegajss of Nutkition oe Vegetation 



1. structure, Arrangement, and Special Functions 


25 


General Integument .... 


25 


Stomata 




28 


Hairs 




30 


Glands 




34 


Functions of the Epidermis 




36 


Eoot or Descending Axis . 




37 


Structure of Eoots 




37 


Forms of Eoots 




40 


Functions of Eoots 




43 


Stem or Ascending Axis 




44 


Forms of Stems 




44 


Internal Structure of Stems 




49 


Exogenous or Dicotyledonous Stem 


49 


Anomalies in its Structure 


60 


Endogenous or Monoootyledonons Stem 


64 


Acrogenous or Acotyledonous Stem 


70 


Formation of the different parts of Stems, and thei 




special Functions 


75 


Leaves and their Appendages 


79 


Structure of Leaves . 




79 



25 



XX 



TABLE OF CONTENTS. 



Venation of Leaves . ' . 

Forms of Simple Leaves 

Forms of Compound Leaves 

Petiole or Leaf-Stalk . 

Stipules 

Anomalous Forms of Leaves and Petioles 

Structure and Form of Leaves in the Great Divisions of 

the Vegetahle Kingdom . 
Phyllotaris, or the Arrangement of Leaves on the Axis 
Leaf-buds ..... 
Vernation ..... 
Aerial and Subterranean Leaf-buds 
Anomalies and Transformations of Leaf-buds . 
Tendrils ..... 

Special Functions of Leaves . 



83 
85 
91 
94 
97 
99 

100 
101 
108 
110 
114 
116 
120 
121 



Section II. — Generai. View of the Functions oe the Nutri- 
tive Oroans .... 124 

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

NouiTshment . . . . .124 

Chemical Composition of Plants . . . 124 

Organic Constituents and their Sources . . 126 

Inorganic Constituents and their Sources . . 128 

Chemical Composition of Soils . . 134 

Application -of Manure ' . . . . 136 

Various kinds of Manure . . . 136 

Epiphytic and Parasitic Plants . . .141 

2. Absorption and Circulation of Fluids . . . 142 

3. Respiration of Plants . . . . .155 

Effects of Certain Gases on Living Plants . 159 

4. Products and Secretions of Plants . . . 161 

Section III. — Organs oe Ebpeoduction . . . 171 

Structure, Arrangement, and Functions . . 171 

1. Inflorescence or the arrangement of the flowers on the 

axis ...... 172 

Tabular View of Inflorescence or Anthotazis . . 188 

2. Bracts or Floral leaves .... 189 

3. The Flower and its Appendages . . . 191 
Flower-bud, aestivation .... 193 
External Floral Whorls, or the Floral Envelopes . 195 

Calyx ...... 195 

Corolla ...... 200 

Nectaries and Anomalies of the Petals . . 209 
Inner Floral Whorls, or the Essential Organs of Repro- 
duction ...... 211 

Stamens ..... 212 

Pollen ...... 228 

Disk . . . . . .234 

Pistil, Carpels, and Placenta . . . 235 

Ovule ...... 251 

4. Functions of the Floral Envelopes . . . 258 

5. Functions of the Stamens and Pistil ; Fertilisation or 

Fecundation • . . . . 264 



TABLE OF CONTENTS, 



XXI. 



Fertilisation in Cryptogamoua or Flowerless Plants 
Fertilisation in Phanerogamous or Flowering Plants 

Embryogenic process in Gymnospermons Flower- 
ing Plants ..... 
Embryogenic process in Angiospermous Flower- 
ing Plants . . 

6. Fruit or the Pistil arrived at maturity 

Fruits which are the produce of a single flower 
Fruits which are the produce of several flowers 

united .... 
Tabular arrangement of Fruits . 

7. Maturation of the Pericarp 

Eipening of Fruits 

Grafting .... 

8. Seed or Fertilised Oyule arrived at Maturity . 

Embryo . 

9. Functions of the Seed .... 

Germination .... 
Vitality of Seeds 
Transportation of Seeds 
Direction of Plumule and Radicle 
Proliferous Plants 
Duration of the Life of Plants . 
10. General Observations on the Organs of Plants, and on 
the mode in which they are arranged 
Symmetry of Organs 
Teratology .... 



Section IV. — Some Genbeal Phenomena connected with 
Vegetation .... 



1. Vegetable Irritability , 

2. Temperature of Plants 

3. Luminosity of Plants . 

4. Colours of Plants 

5. Odours of Flowers 

6. Diseases of Plants 



PART n.— SYSTEMATIC BOTANY, TAXONOMY, OR THE CLASS- 
IFICATION OP PLANTS .... 

CHAPTER L— SYSTEMS OF CLASSIFICATION 



Nomenclature and Symbols 

Linnaean System 

Natural System 

System of Jussieu 

System of De Candolle 

System of Bndlieher . 

System of Lindley 

Henslow's Comparison of Systems 

Natural arrangement by Hooker 



•xxn 



TABLE OF CONTENTS. 



CHAPTER II.— CHARACTERS OF THE CLASSES AND NATURAL 
ORDERS ...... 

SuB-KnrGDOM I. — Phaudkoqamous Plants . 



Class I. — Dicotyledones or Exogense 



Sub-class l.^Thalamiflorse 



1. Ranimculacese . 426 

2. DilleniaoeaB . . 428 

3. Magnoliaceae . 428 

4. Anonaceae . . 429 

5. Menispermacese 430 

6. Berberidacese . 430 

7. Nymphseaceae . 431 

8. Sarraceniacese . 432 

9. Papaveraoese . 433 

10. Fumariacese . 434 

11. Craoiferae . . 434 

12. Capparidacese . 437 

13. Resedaceae . . 438 

14. Cistaoeae . . 439 

15. Canellaoeae . . 439 

16. Bixaceffi. . . 439 

17. Violaceae . . 440 

18. Droseraoese . . 441 

19. Polygalacese . 441 



20. 
21. 
22. 
23. 
24. 
25. 
26. 
27. 
28. 
29. 
30. 
31. 
32. 
33. 
34. 
35. 
36. 
37. 
38. 



Tremandraceae . 
Tamarioaceae . 
Frankeniaceae . ' 
Elatinaceae . . 
Caryophyllaoese 
Portulacaceae . 
Malvaceae . 
Sterculiacese . 
Byttneriaoeae . 
Tiliaceee 
Dipterocarpacese 
Chlaenaceae . . 
Temstroemiaoeffi 
Olacaceae . . 
Aurantiaceae . 
Hypeiicaceae . 
Guttiferae . . 
Brythroxylaoeae 
MalpigHaceae . 



442 
442 
443 
443 
444 
445 
446 
448 
449 
450 
451 
451 
452 
453 
453 
455 
456 
457 
457 



423 

425 

425 

425 

Aceraceae . . 458 

Sapindaceae . 458 

Meliaoeae . . 459 

Cedrelaceae . . 460 

Ampelideae . . 460 

Geraniaceae . . 462 

Vivianaceae . 463 

Linaceae . . . 463 

Balsaminaceae . 464 

Oxalidaceae . . 464 

Tropaeolacese . 465 

Pittosporaceae . 465 

Zygophyllaceae . 466 

Rutaceae . . 467 

Xanthoxylaceae 468 

Simarubaceae . 468 

Ochnaceae . . 469 

Coriariaceae . 470 



Sub-class 2. — Calyciflorae. Section 1. — Polypetelce, 



470 



57. Stackhousiaceae 470 

58. Celastracese . 471 

59. Staphyleaceae . 472 

60. Rhanmaceae . 472 

61. Anacardiaceae . 473 

62. Burseraceae. . 475 

63. Connaraceae . 476 

64. Legumiliosae . 476 
65. -Morlngaceae . 482 

66. Rosaceae . . 483 

67. Calycanthaoeae . 487 

68. Lythraoeae . . 487 

Sub-class 2.- 

93. Caprlfoliaceae . 510 

94. Rubiaceae . . 511 

95. Valerianacese . 514 

96. Dipsacaceae. . 515 



105. Ericaceae . . 526 

106. Epacridaceas . 527 

107. Ebenaceae . . 628 

108. Styracaceae. . 629 

109. Aquifoliaces . 529 

110. Sapotaceae . . 630 

111. Myrsinaceae . 631 



69. Rhizopboraceae 488 

70. Vochysiaceae . 488 

71. Combretaceae . 488 

72. Melastomaceae . 489 

73. Philadelphaceae 489 

74. Myrtaoeae . . 490 

75. Onagraceae . . 492 

76. Halorageaoeae . 493 

77. Loasaceae . . 493 

78. Cucurbitaceae . 494 

79. Papayaceae . . 496 

80. Passifloraceae . 497 



81. Turneraceae. . 498 

82. Paronyohiaoeae . 498 

83. Crassulaceae . 499 

84. Ficoideae . . 500 

85. Cactaceffi . . 500 

86. Grossulariaceae 502 

87. Saxifragaceae . 502 

88. Bruniacese . . 504 

89. Hamamelidacefe 504 

90. Umbelliferse . 505 

91. AraUaceae . . 609 

92. Comaceae . . 509 



■Calyciflorae. Section 2. — QamopetalcR. . 510 

101. Stylidiaces. . 523 

102. Campanulaceae . 524 

103. Lobeliace*. . 525 



97. Calyceraceae . 515 

98. Compositae . . 517 

99. Bninoniaceae . 522 
100. Goodeniaceae . 522 

Sab-class 3. — Corolliflorae 

112. Jasminaceas . 531 

113. ColumelUaceEe . 532 

114. Oleaceffi. . . 532 

115. Salvadovaoeae . 534 

116. Asclepiadaceae . 534 

117. Apocynaceae . 536 

118. Loganiaceffi . 537 



104. Vacciniaoeae . 525 

526 

119. Gentianaceae . 539 

120. Bignoniaceffi . 540 

121. Gesneraoeae^ . 541 

122. Polemoniacese . 541 

123. HydropbyUaceae 542 

124. Convolvulaoeae . 542 

125. Cordiaoeae . . 545 



TABLE OF CONTENTS. 



XXIU 



126. 
127. 
128. 
129. 



137. 
138. 
139. 
140. 
141. 
142. 
143. 
144. 
145. 
146. 
147. 
148. 
149. 
150. 
151. 
152. 

183. 



185. 
186. 
187. 
188. 

197. 
198. 
199. 
200. 

209. 
210. 

213. 



Boraginaeese . 545 
Solanacese . . 547 
Orotenchacese . 550 
Scroplmlariaoese 651 



130. Latiatse . . 552 

131. Vertienaceae . 555 

132. Aoanthaceae . 556 

133. Lentibulariacese 557 



Sub-class 4. — MonooMamydese. Section A. 



Nyctaginacese . 
Araaranthaceae 
Chenopodiaoese 
Phytolaocacese 
Polygonaceae . 
Begoniacese 
Lauraceae . . 
Myristioacese . 
Proteaoeae . . 
Elasagnaceae . 
Penseaceffi . . 
Thymelaeaceae . 
Aquilariaceaa . 
Chailletiaceae . 
Samydaceae 
HomaUacese . 



560 
562 
562 
563 
563 
566 
566 
569 
570 
570 
571 
571 
572 
572 
573 
573 



153. 
154. 
155. 
156. 
157. 
158. 
159. 
160. 
161. 
162. 
163. 
164. 
165. 
166. 
167. 



Santalaceae . . 574 
Loranthaceae . 574 
Aristolochiacese 575 
BalanophoraceSB 577 
Cytinaceae . . 577 
Bafflesiaceae 
Nepenthaceae 
Datiscaceae . 
Empetraceae 
Buphorbiaceae 
Urticaoese . 
CannabinaoesE . 584 
Ulmaceae . . 585 
Moraceae . . 586 
Ceratophyllaceae 588 



577 
578 
578 
579 
579 
583 



Page 

134. Primtdaceae . 557 

135. Plumbaginacese 559 

136. Plantaginacese . 559 

—AngiospermcB . 560 

168. Podostemaceae . 588 

169. Stilaginaceae . 588 

170. Monimiaoeae . 588 

171. Atherosperinaceae589 

172. Laojstemaceae . 589 

173. Ghlorantbaoes 590 

174. SaumraceaB . 590 

175. Piperaceas . . 590 

176. Salicafsese . . 591 

177. Myricaceae . . 592 

178. Casuarinaceae . 593 

179. Bettdaceie . . 593 

180. Platanaceae. . 593 

181. Corylaoeae . . 594 

182. Juglandaceae . 595 



Section B. — Gfymnospermce 
Coniferae . . . 596 | 184. Cycadaceae 
Class II. — Monocotyledones or Endogenae 
Sub-class 1.— -Petaloideae 

a. — Epigynae 
Hydroobaridaceae601 
Orchidaceae . 602 
Zingiberacese . 605 
Marantacese . 606 



189. Musaceas . . 607 

190. Iridaceae . . 608 

191. Burmanniaceae . 610 

192. Haemodoraceae . 610 



529 
600 
601 
601 

601 

193. Diosooreaoeae . 610 

194. Amaryllidaceae 611 

195. Hypoxidacese 612 

196. Bromeliaceae . 612 



6. — Hypogynse 
Liliaceas . . 613 
Melanthaceae . 616 
Smilaceae . . 617 
TriUiacese . . 617 

c. — Incompletse 
Pandanaceae 
Ara«eae 



201. Gilliesiaceae . 618 

202. Pontederiaceae . 618 

203. Xyridacese . . 618 

204. Juncaceae . . 619 



205. Palmae 

206. Commelynace 

207. Alismaceae 

208. Butomaceae 



624] I 211. Naiadaoeae 
625 I 212. Eestiaceae 



-Glumiferse i 

, 627 214. GramineK 



Sub-cjass 2.- 
Cyperaceae 

Sob-Kingdom: II.— Ceyptogamous Plaijts 
Class III. — Acotyledons 

Sub-class 1. — Acrogenae 
Equisetace» . 636 I 217. Marsileaceae . 640 I 219. Musci 

. 637 218. Lycopodiacese 640 | 220. Hepaticae 



215. 

216. Fiiices 



Sub-class 2. — ThaUogense 
221.Liclienes . . 644 | 222. Fungi . . . 647 | 223. Cbaraceae 
224. Algsa .... 652 
Additional Bemarlcs on Fertilisation of Gramlneae 



613 
619 
i622 
623 
623 

624 
626 
627 

627 
628 

635 
635 

635 
641 
643 

644 
651 

656 



XXIV 



TABLE OF CONTENTS. 



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

i. — epikrheoloa's', ob the ihtlubnoe of vabious extebnal 
Agents on Plahts 

1. Effects of Temperature . 

2. Effects of Moisture 

3. Effects of Soil, Light, and other Agents 

II. — ^DissBMnrATiow of Plants 

1. Agents employed in their Dissemination 

2. General and Endemic Distribution of Plants 

3. Conjectures as to the mode in which the Earth was origin- 

ally clothed with Plants .... 

4. Distribution of Plants considered Physiognomically and 

Statistically ...... 

Physiognomy of Vegetation . 675 | Statistics of Vegetation 

5. Phyto-geographical Division of the Globe . ' . 



Latitudinal Range of Vegetation 678 
Schouw's Phyto-geographic Re- 
gions 679 

Meyen's Phyto-geographical Zones 692 



Altitudinal Range of Vegetation 
jZones of Marine Vegetation . 
Distribution of Plants in Britain 
Acclimatising of Plants . 



Page 
657 

657 
658 
662 
662 

668 
668 
670 

671 

675 
677 
678 

695 
699 
702 
716 



PART IV.— FOSSIL BOTANY . . . . .718 

Character and arrangement of Fossil I Fossiliferous Rocks . . 723 

Plants . . . . 719 I FossU Plants of different Strata 724 

1. Flora of the Primary or Palaeozoic Period . . . 728 

Reign of Acrogens ..... 728 

2. Flora of the Secondary or Mesozoic Period . . . 745 

Reign of Gymnosperms ..... 745 

3. Flora of the Tertiary or Cainozoic Period . . . 750 

Reign of Angiosperms ..... 750 

APPENDIX ........ 761 

I. — On the Use oe the Microboope in Botamioai, Reseaeches 761 

II. — On CoLLEOTma and Examtning Plakts, and on the Forma- 
tion OE a Herbabioti ..... 795 

GLOSSARY 809 

ABBREVIATIONS AND SYMBOLS 830 

INDEX .•••■-.. 831 



PAET I. 

VEGETABLE ANATOMY, ORGANOGEAPHY, AND 
PHYSIOLOGY. 



Botany is that brancli of Biological science which comprehends the 
knowledge of aU that relates to the Vegetable kingdom. It embraces 
a consideration 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 takes a 
comprehensive view of the vegetation with which the earth is clothed 
at the present day, and of that which covered it at former epochs. 
It has been' divided into the following departments : — 1. Structural 
Botany, or Organography/, having reference to the anatomical structure 
and the forms of the various parts of plants, including vegetable 
histology, or the microscopical examination of tissues ; and morpho- 
logy, or the transformations which the organs undergo. 2. Physiological 
Botany, the consideration of the functions performed by the living 
plant, or the phenomena of life as exhibited by its various organs 
during the processes of development, growth, and multiplication. 
3. Systematical, or Taxological Botany, the arrangement and classifica- 
tion of plants. 4. Geographical Botany, the distribution of plants 
in space. 5. Fossil, or Palceontological Botany, the distribution of 
plants in time, with a description of the form and - structure of the 
plants found in a fossil state in the various geological formations. 



CHAPTER I. 

ELEMENTAEY OEGANS, OE VEGETABLE TISSUES. 

In their earliest and simplest state plants consist of minute vesicles, 
each of them bounded by a transparent membrane, which is composed 
of a substance called Cellulose. This, substance is of general occurrence, 
and constitutes the basis of vegetable tissues. It "is composed of 
carbon, hydrogen, and oxygen, and the chemical formula representing 

B 



2 ELEMENTAET OEGANS. 

it is Cj Hi„ O5.* It was long considered as essentially a vegetable 
product, not found in animal structures ; but it has now been de- 
tected in the tissues of the ascidia, and other molluscous animals. 
It is a white substance, insoluble in water, alcohol, or ether, 
but soluble ia an ammoniacal solution of cupric oxide. It is aUied 
to starch, into which it is convertible by the action of heat, the 
addition of sulphuric acid, or caustic potash. It becomes yeUow on 
the addition of iodine, and when acted upon by iodine and sidphuric 
acid, a blue colour, like that of iodide of starch, is produced. The 
acid appears to convert the cellulose into starch. When cellulose is 
acted on by a mixture of equal volumes of strong sulphuric and nitric 
acid it forms gun-cotton (pyroxylin), (tDj, fire, and f uXok, wood), and 
this when dissolved in a mixture of ether and alcohol yields a solution 
called collodion. The membrane formed by ceUulose is permeable by 
fluids, and becomes altered in the progress of growth, so as to acquire 
various degrees of consistence. A modification of cellulose occurs in 
the form of woody matter or lignin. The hard cells in the stone of 
the peach, in the shells of other fruits, and in the coats of seeds, 
consist of cellulose, with deposits of lignin. In the advanced stages 
of growth, plants consist of two 'kinds of tissue, Cellular and Vascular, 
which, under various modifications, constitute their Elementary organs ; 
and these, by their union, form the Compound organs, by which the 
different functions of plants are carried on. 

The elementary organs are vesicles and tubes, which vary in form 
and size, and, when united in different ways, constitute the tissues. 
Vesicles or cells may be defined as closed sacs, composed of 
r% solid membrane, containing fluid or semifluid matter, and 
^^ having a diameter nearly equal in every direction (fig. 1); 
Fig- 1- while tubes or vessels are similar sacs with the longitudinal 
much exceeding the transverse diameter (figs. 3, 4). Cellular tissue 
is formed by a combination of these cells or vesicles ; a similar union 
of vessels constitutes vascular tissue. 

Fig. 1. Vesicles or small cells, each of them enclosed hy a membrane of cellulose. 

* These symbols indicate the equivalents of Carbon (C), Hydrogen (H), and Oxygen (O), 
which enter into the composition of cellulose. For the meaning of these and other chemical 
symbols, see Chap. II. Sect. I. Div. 2, on the Food of Plants. 



CELLULAR TISSUE. 



Sectioni I. — Oellulae Tissue. 
1. — Form and Arrangement of Cells. 



Celiulae Tissue is formed by the union of minute vesicles or 
bladders, called cells, cellules, or utricles. This tissue is often called 
Parenchyma {'Tta.^d, through, and lyyyiJja, an infusion). The terms 
Parenchymatous, Areolar, Utricular, and Vesicular, when 
1 applied to vegetable tissues, may be considered as synony- 

mous. The individual cells of which this tissue is com- 
posed, when allowed to develop equally in all directions, 
are usually of a more or less rounded form (figs. 5, 6, 7) ; 
but during the progress of development they frequently 
become more elongated in one direction than in another 
(fig. 2), and often assume angular or polyhedral forms 
(%■ 8). 






Figs. 
'2. 3. 4. 




Fig. 5. 



Fig. S. 



Fig. r. 




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 (figs. 8, 12, 13), which, when cut in 
any direction, exhibit a hexagonal form (figs. 14, 15), and hence the 
• tissue is sometimes called hexagonenchyma (i^dyavog, six-angled) ; it is . 






Fig. 9. 



Fig. 10. 




Fig. 11. 



Fig. 12. 




seen in the pith of the Elder, and in young palm stems. 2. Sphceren- 
chyma {^(l(pa,7^a, a sphere), spheroidal cells (fig. 5). 3. Merenchyma 



Fig.. 2. Fusiform or spindle-shaped cell. 
8, CeUs, or utricles, separate and combined, 
the forma of cells. 



'igs. 3, 4. Tubes or vessels. Figs. 5, 6, 1 
Figs. 9, 10, 11, 12, 13. Figures representing 



4 FORM AND ABKANGEMENT OF CELLS. 

(^»;giw, to revolve), ellipsoidal cells (fig. 6). 4. Ovenchyma (oiov, an 
egg), oval cells. Eound, elliptical, and oval cells, are common in 
herbaceous plants. 5. Gonenchyma (xSvos, a cone), conical cells, as 
hairs. 6. Columnar cellular tissue, divided into Cylindrenchyma 
(xvXivS^og, a cylinder), cylindrical cells (fig. 17 a), as in Ohara, and 
Prismenchyma (-ir^ie/jija,, a prism), prismatical cells, seen in the bark of 
some plants (fig. 10). When flattened, 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 Pinakenehyma (mva^, a table), 
tabular cells (fig. 11), or square cells (fig. 9). 7. Prosenchyma (•ffgos, 
indicating addition), or Atraetenchyma (argaxros, a spindle), fusi- 
form or spindle-shaped cells, seen in woody structures (fig. 2). 8. 
Golpenchyma (xoX-rog, a sinus or fold), sinuous or waved cells, as in 
the cuticle of leaves. 9. Cladmchyma (xXdSog, a branch), branched cells, 
as in some hairs. 10. Actinenchyma (^axTig, a ray), stellate or radiat- 
ing cells, as in Juncus and Musa (fig. 16). 11. DcBdalenchyma [baibcCkog, 
entangled), entangled cells, as in some Fungi. 






Fig. 14. Fig. 16. Fig. 16. 

The size of cells varies not less than their figure in difierent plants, 
and in dififerent parts of the same plant. They are frequently seen 
from shs, rhi, to -nnnr of an inch in diameter. In cork, which is 
cellular, there are about a thousand in the length of an inch. In' 
the pith of Elder cells tw of an inch in diameter are seen. In 
many succulent vegetables, and in the pith of some aquatic plants, 
large cells ranging from t* to A of an inch in diameter occur ; 
while the cells in spores of Fungi have been computed at Tt^ST of an 
inch in diameter. In a cubic inch of the leaf of a carnation, there 
are said to be upwards of three millions of cells. 

Each cell has originally a separate membranous wall, 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 
are occasionally absorbed so as to form continuous tubes. .W,hen 
cells are united in a rectilinear manner, those in contiguous rows are 

Figs. 14, 15. Hexagonal cells, cut longitudinally and transversely. Fig. 16. Branching, 
stellate, or radiating ceUs of Vicia Faba, the common bean. 1 1, Intercellular lacunffi, or 
air-spaces between tlie cells. 



FOEM AND AEEANGEMENT OK CELLS. 



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 later- 
ally (fig. 20 a a). Isolated cells, as spores of sea-weeds, occasionally 
have free filaments, or cilia (cilium, an eyelash), developed on their 
surface. 






Fig. 17. 



Fig. 18. 



Fig. 19. 



Fig. 20. 



The simplest kinds of plants, as mushrobms and searweeds, 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 are cellular; so also are cotton 
and rice-paper. The cell may be considered as the ultimate struc- 
tural element of all organisms. In the simplest vegetable forms, as in 
imicellular algse, it is adequate to aU the purposes of plant life. Vital 
operations are carried on in all plants by means of cells, the constitu- 
tion and functions of which vary according to the nature of the plants 
and the position in the scale of organisation which they occupy. In 
the higher classes of plants, certain cells are concerned in the secre- 
tion ^of organisable products, which are elaborated by others into new 
tissues. The life of the higher species of plants results from the 
regular action of cells, which are of unequal value as regards the for- 
mation of new organs and new products. In cells there are observed 
the albsorption and movements of fluids, the elaboration of these by 
exposure to air and light, and the formation of new cells. Schacht 
remarks that a plant is composed of one or more cells, and that it is 
only in the lowest species that the cells are of the same value ; in other 
words, are of the same chemical and physical nature, and of the same 
physiological importance. Even amongst the mushroom and sea- 
weed orders, it is only the lowest plants which have cells concerned 
alike in the processes of vegetation and reproduction. The higher 
plaitts of these orders are composed of parts having different values. 

Figs. 17, 18, 19. Cells united together by their extremities. Fig. 20. Elongated 

thickened cells from the root of the Date Palm, a a. Canals of communication. 



6 FORM AND AEEANGEMENT OF CELLS. 

In general, no visible openings can be detected in cells, although 
fluids pass readily into and out of them. Harting and Mulder, how- 
ever, state, that they have observed perforations in the cells of Hoya 
carnosa, Asclepias syriaca, Oycas 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, as in 
Sphagnum and Leucobryum glaucum. 

PoEOUS OR Pitted Cells are those in which the membrane is 
thickenedatcertainparts,leavingthinrounded spots intervening, which, 
when viewed by transmitted light, appear like perforations or pores 
(figs. 21, 28). The unequal deposit of the internal en- 
crusting cellulose or woody matter, is the cause of this 
condition. The pores of contiguous " cells usually corre- 
spond as regards position, and sometimes 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 (fig. 20, aa). When 
porous cells are united end to end, so as to form tubes, 
the tissue is denominated articulated Bothrenchyma or 
Taphrmchyma (jSo'^jos and rapjos, a pit), on account of their bead- 
like appearance, and the pits or depressions in their thickened walls 
(fig. 22). Pitted cells are seen in Elder pith. 

PiBEOiTS OR 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 toim fibro-cellular tissue, or Inenchyma (ivig, fibres). These 







Fig. 23. 



Kg. 24. 



Fig. 25. 



Fig. 26. 



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 menibrane, in some instances, is easily 
dissolved 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 linearis, and in the pericarp of Salvia. Spiral cells 

Fig. 21. Porous cell, from the Elder (Samhucus nigra). Fig. 22. ArtictQated Both- 

renchyma, or Taphrenchyma, from Mistleto, having a moniliform appearance. Figs. 23, 
24, 25. Spiral, annular, and reticulated ceUs, from Mistleto (Vis(mm albmn). Fig. 26. 

Scalariform and dotted cell, from Elder {Sambuetts nigra). 



■ A millimetre is about l-25th of an English inch. 



FORM AND ARRANGEMENT OF CELLS. 7 

abound in many of the Orchidaceous plants, as Oncidium and 
Pleurothallis ruscifolia, also in the garden Balsam, in the leaf of the 
moss called Sphagnum, 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 seeds of Acanthodium spica- 
tum, Sphenogyne speoiosa, Calempelis scaber, and Oobsea. The spiral 
filaments sometimes exhibit peculiar movements when placed in water. 
The fibre in these cells varies from about twu-u to -mhr^ of an inch 
in 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), sealariform and dotted cells 
(fig. 26), which constitute the spurious or imperfect Inenchyma of 
authors. Annular cells are met with hi Opuntia, and in the endothe- 
cium of Cardamine pratensis ; reticulated cells, caused by fibres forming 
a sort of mesh or network, are seen in the wing of the seed of Swietenia, 
the pericarp of Picridium tingitanum, the leaf of Sanseviera guineensis, 
and the pith of Eubus odoratus and Erythrina Corallodendron, as well 
as in the endothecium of the sea-pink and the butterwort. 

In certaia parts of plants cells are placed closely together, and 
touch each other by flat surfaces, filling up space completely, and 
leaving no intervals ; they then form the .perfect Parenchyma 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 imper- 
fect Parenchyma of Schleiden (figs. 7, 28). These intervals, when of 
moderate size and continuous, are called intercellular passages or canals ; 
when large, irregular, and circumscribed, intercellular spaces, or Lacunm 

(fig. 16,Z0- 





Fig. 2T. Kg. 28. 

A difference of opinion prevails as to the mode in which cells 
are united together. Some maintain that the cell-walls in the young 

Fig. 27. CelluJar tissue, from pith of Elder. Fig. 28. Porous merenciyma, from 
Houseleelc ifim^ermAywm, tectonm). a, Intercellular canal. 



8 CONTENTS OF CELLS. 

state unite together directly, and become agglutinated, more or less, 
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 Collmchyma {xoXKa, glutinous matter). In sear-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 fiUed up by this 
interceUular substance (fig. 29, h), 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 thm, except 
in the interceUular canals or spaces. Mirbel looks upon it as the 





Pig. 29. Pig. 30. 

remains of the mucilaginous fluid in which the cells were originally 
developed, and which has become thickened to a greater or less de- 
gree, as in the root of the Date (fig. 30), where aaa indicate the 
cells, and hhh the interposed substance. 

2. — Contents of Cells. 

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. 
This mucilaginous matter is the Protoplasm (•yjairos, first, and TXatf/ia, 
formative matter) of Mohl, the Cytdblastema {xvrog, a cell, and 
ffXasTiyj^a, growth) of some authors. It is at first homogeneous, but 
ultimately assumes a granular form. The appearance of granules may be 
regarded as the earKest evidence of the formative process. Protoplasm 
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 primordial 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 thickening has advanced, this utricle dis- 
appears, in consequence of becoming incorporated with the cell- wall. 

Fig. 29. CeUular tissue of Sea-weed {EvmaMhalia lorea). a a, Cells. 6, Intercellular 
matter. Fig. 80. Central portion of young root of Date, aaa, Thickened cells. 6 6 ft, 
ntercellular substance of Mirbel. 




CONTENTS OF CELLS. 9 

When small portions of vegetable tissue are soated in Beale's Car- 
mine solution, only those ceUs containing protoplasm appear stained. 
The nuclei and granules in the protoplasm seem alone to he affected. 
The depth of colouring depends on the number of granules in the 
protoplasm and the size of the nuclei. 

In certain cells the membranous wall consists throughout life 
of a thin layer .of cellulose, while in others it becomes thickened by 
the deposition of matter on its inner side. These secondary deposits 
are sometimes of a gelatmous consistence; at other times they are 
hard. In the latter case, the matter is looked upon as a modification 
of cellulose, and has received the name of lignin (lignum, wood), or 
scUrogm (sxXri^hg, hard, and ymaeiv, to generate). On making sec- 
tions of such cells, in a transverse (fig. 31) or longitudmal direction 
(fig. 32), the successive layers may be seen 
either continuous all round, or leaving parts 
of the membrane uncovered. Cells of this 
kind are well seen under the microscope in 
thin sections of the hard shell of the Coco-nut, 
and Attalea funifera, and of the hard seed 
of the- Ivory Palm. In all cell deposits there 
is a tendency to a spiral arrangement. When ^- • 

the deposition is uniform over the whole surface, this arrangement 
may not' be detected; but when interruptions take place, thep the 
continued coil becomes evident. In spiral cells the fibre seems to be 
formed before the fuU development of the cell, the coils of the fibre 
being at first in contact, and afterwards separated, whereas the second- 
ary thickening layers are deposited after the cell is fully formed. Ac- 
cording to the observations of Barry, Agardh, and others, the filamentous 
origin of fibrous structures is recognisable in the earliest stage of cell 
growth, and the interweaving of these filaments constitutes the cell- walls. 

Each cell is found to contain at some period of its existence a 
small body called a nucleus (fig. 33, n n n), in which 
there are often one or two, rarely more, minute spots /~\__i*'\ » 
called nucleoli. The nucleus is of a round or oval ( '^ /LA/^ 
shape, granular and dark, or homogeneous and trans- )~\__i~Lv " 
parent, bearing some resemblance to a smaller in- f® ji /~j 
ternalcell. -Nucleoli are not always present. They are ^~{_/~w " 
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 substance called hyaline 
(uaXog, glass) is developed there, which, according to him, is the origin 
of the nucleus. The nucleus is situated at difierent parts of the cell. 
It is either free in its cavity, or connected with its walls by mucilaginous 

Fig. 31. Transverse section of cells from pulp of Pear. Fig. 32. Longitudinal section 
of the same. Fig. 33. Nucleated cells from the Beet. 



10 CONTENTS OF CELLS. 

threads, or embedded in the substance of the membrane. The addi- 
tion of acetic acid often renders the nucleus distinct. 

Starchy matter is found in cells, which constitute the tissue 
called by Morren, Perenchyma (•ff^fa, a sac). Starch exists in the 
form of granules, which are minute cells (perhaps nuclei, as Miilder 
states), in which nutritious matter is stored up. This matter may be 
deposited in such a way as to give the appearance of striae surrounding 
a point or hUum, which is considered as an opening into the cell. 
Allman says the starch granule consists of a series of lamellae, in the 
form of closed hollow shells, included one within another, the most 
internal inclosing a minute cavity filled with amorphous amylum. 
The concentric striae visible on the granule indicate the surface of 
contact of these lamellse, and the so-called nucleus of Fritsche corre- 
sponds to the central cavity. The external and internal lamellse differ 
in consistency, and in other conditions of integration. The lamellse are 
deposited centripetally. The starch granule differs from a true vege- 
table cell in the absence of a proper nucleus, and in presenting no 
chemical difference between the membrane and the contents. The 
grains of starch are well seen in the cells of the potato (fig. 34). In 





Fig. 34. Fig. 36. Fig. 36. 

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. 
Schleiden affirms that starch is the most widely diffused substance in 
the vegetable kingdom ; its presence may be regarded as in a measure 
indicating the age of the cell. With its formation in many cells, we 
have a limitation of vital activity, by which the organism is brought 
into such a condition that the power of germination may be preserved 
for a very long period. 

Ceystals are found in the interior of cells. They probably owe 
their origin to the union between the acids produced 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 they are sometimes found in a distinct tissue called a cystolith 
(xvarie, bladder, and Xi6og, a stone), suspended from the wall of a 

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



CONTENTS OF CELLS. 



11 



lai^ cell (fig. 39) — filling -what some have supposed to be the base 
of an undeTeloped hair. The crystals are of dififerent 
sixes and forms. OceasionaUy, a single large crystal 
nearly fi lls a cell, as in the outer scales of the onion, 
but in general there are numerous crystals united to- 
gether. Sometimes the crystals radiate from a conmion 
{mint (figs. 40, 41), and form a conglomerate mass ; at 
other times they lie parallel, and have the appearance of 
bundles of fine needles (figs. 37, 38). To the latter, the 
name of Bt^MtUs Qafi;, a needle), or acicular crystals 
(aais, a needle), was originally given. It has been said 
that th^e crystals exist also in the i;itercellular 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 dose to 
a lacuna, the crystals may easily be pushed into it accidentally by the 
knife. Baphides 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 Turkey Rhubarb, the latter of which owes 
its grittiness to their presence. One hundred grains of rhubarb root 




Kg. S 




Fig, SS. 



Kg. 39. 



Kg. M. 



Kg.41- 



contain about 30 or 40 grains of oxalate of lime crystals. Acicular 
crystals may be eaaly seen by making a section of any Liliaceons 
plant, as the hyacinth, and spreading the thick mucilaginous matter 
of the cells on the field of the microscope. Radiating raphides are 
seen in the sepals of Gleranium robertiannm and luddum ; the crystals, 
consisting of oxalate of lime, fill the whole of the cells in the middle 
of the sepal, their size varying from wsif to rim of an inch. Quekett 
found them in all the species of Pelargonium and Monsonia that he 
esunined, and he thinks that they are as general as the beautiful 
markings in the cutide of the petals of these plants. Clustered crystals 
have been detected in Malvaceous plants, under the cutidp of the 

Fig. 37. CeUnlai tissue oT Arom macnlatum. c, OeDs ccmtainiDg chloroph^ r r, 
Bapludiaii cells. Kg. SS. OeDs of Anunnwailatojn. Ctosteisaf lapUdes ijtalaige 

OT»l ceU surrotmded by smaUer cells. Kg. S9. Celhilar tissne from leaf of Hens elastica. 
c, A lai«e celL r, CystoUth, an agglomeration of ciystals (sphffirapliides) sospended in a 
sac 1(y a talie, t «, Ctricles filled mthgiains of clilorophyll. Fig. 40. Cells of Beet with 
conglomerate ladiating ciystals, o. i. Separate cijstals of different fonns. Kg. il. Con- 
^omejtate crystals of oxalate of lime from Khubarb. 



12 CONTENTS OF CELLS. 

Marvel of Peru, 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 
^ ^j, ^ •■ Prunella vulgaris and Dianthus Caryophyllus. 

^^^te^^^N— t^/ In the outer covering of the seed of Ulmus 
yMi^^M^^" campestris, the sinuous boundaries of the ■ 
" "^^^8^^^ compressed cells are traced out completely by 
"^^' ^r.'^^) minute rectangular crystals adhering to each 
^^te^^fer^ '' other. linger detected oxalate of lime crystals 
' '^^^s^^y^ in Ficus indica and Calathea zebrina. Accord- 
' . ing to Dr. Gulliver the presence or absence of 

'^' ■ raphides may be used for distinguishing certain 

natural orders. He says that Balsaminacese, Onagracese, and Galiacese, 
may be specially called Kaphis-bearing orders. In the epidermal cells of 
many Urticacese concretions of carbonate of lime (cystoliths) are found.* 
Chlokophyll (%Xw|i)s, green, and ^vXXov, a leaf), or the green 
colouring matter of plants, floats in the fluid of cells, accompanied by 
starch grains. It difiers from starch in being confijied to the super- 
ficial parenchyma, and in being principally associated with the phe- 
nomena of active vegetable life. It has a granular form (fig. 39, u ; 
42, c), is soluble in alcohol, and is developed under the agency of light. 
It is well seen in leaves. Under the influence of darkness it under- 
goes changes which are seen in the phenomenon of blanching or etiola- 
tion. Its granules are usually separate, but sometimes they unite in 
masses (fig. 37, c). Stokes says that the chlorophyll of land plants 
consists of four substances, two green and two yellow, all possessing 
highly distinctive optical properties. The green substances yield 
solutions exhibiting a. strong red phosphorescence ; the ySUow sub- 
stances do not. These substances are soluble in the same solvents. 
Green sea-weeds agree with land plants. Eed sea-weeds in addition 
to chlorophyll contain a red colouring matter of an albuminoid nature. 
Chlorophyll is important in a physiological point of view. It is 
developed under the influence of light, and the granules exhibit 
marked movements, as have been observed in the leaves of some 
mosses. Chlorophyll gives a black band in the red of the spectrum. 
Green vesicles or granules allied to chlorophyll are found in some of 
the lower animals, as Hydra viridis. 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. 

Oils and Resinous mattee are found in the interior of cells, as well 
as in intercellular spaces. The cavities containing them are denomi- 
nated cysts, reservoirs of oil, and receptacles of secretions. They are easily 

Kg. 42. Cellular tissue of Colooasia odora. c c. Cells with grains of ohlorophyU. 
rrrr, Baphidian cells projecting into a lacuna or intercellular space. 

* See Papers by Dr. Gulliver, in the Annals of Natural History, 3d ser. xv. et seq. 




DEVELOPMENT OF CELLS. 13 

detected in the rind of the orange and lemon, and in the leaves of Myr- 
taceae and Hypericacese. When small portions of the fresh leaf of Sohinus 
Molle 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 Umbelliferse, 
canals occur called vittce (yitta, a head-band, from surrounding the fruit), 
containing oil. 

Air-Oblls, or cavities containing air, consist either of circumscribed 
spaces surrounded by cells (fig. 43), or of lacunae formed 
by the rupture or disappearance of the septa between a 
number of contiguous cells, as in grasses, Equisetum, 
Umbelliferous plants, and pith of Walnut. They are 
often large in aquatic plants, and serve the purpose of 
floating them, as in Pontederia, Trapa, Aldrovanda, and 
sea- weeds. The air-cells of Limnocharis Plumieri are Kg. is.' 
beautiful objects. 

3. — Development and Functions of Gells. 

The subject of Cell-development, or Gytogenesis (xiroj, a cell, and 
yhiaig, origin), has given rise to great diversity of opinion among 
physiologists. We have already noticed that in the interior of grow- 
ing cells there is a mucilaginous matter called protoplasm, which con- 
tains granules. The first lining of the cell-wall arising from the 
protoplasm, is the primordial utricle. It forms a sort of fil'm around 
the protoplasm, and in certain cases it may supply the place of the 
proper cell-membrane. In the protoplasm cavities are sometimes seen 
filled with a watery sap, and called vacuoles. In the interior of the 
young cell may be seen a nucleus or cytoblast (ziiros, a cell, and 
^Ka.gTog, a germ), (fig. 33), composed of protoplasmic matter, and con- 
taining granules, called nucleoli. 

The nucleus often becomes attached to one side of the utricle. It 
is sometimes, however, retained in the centre of the cell by means of 
cords of protoplasm, which ultimately form the boundaries of vacuoles, 
or spaces containing fluid. Most physiologists think that the cyto- 
blast is not specially concerned in cytogenesis, but only takes part in 
the various chemical and other changes which occur in the contents of 
the cell during its growth and nutrition. 

It is supposed by some that cells may be formed by the simple 
aggregation of granular matter, which becomes enveloped in a mem- 
brane, and thus forms a cell with granular contents. Dr. Bennett 
advocates a molecular view of cell formation. He traces cytogenesis 
to the presence of histogenetic (ifTo;, veil, web, or tissue, and yheeis, 
origin) molecules, which unite together to form the cell- wall. New 

Fig. 43. Air-ceUs in Eanunculus aquatilis. ' 



14 



DEVELOPMENT OF CELLS. 




Fig. 44. 



cells are also produced by the division of the primordial utricle, 
which gradually folds iawards about the middle, forming an annular 
constriction, and ultimately a complete separation of the utricle into 
two parts. Each of these afterwards becomes covered by a permanent 
cell-wall. This is seen in Palmella (fig. 44). 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, 
linger traces in Algse the development of new cells 
by a fissiparous (fissus, split, and pario, I produce) 
or merismatic (,u,i§ie//,6g, division) separation of the 
old ones into two or four divisions, in the same 
way as occurs in pollen. In some of the most simple plants, multi- 
plication takes place by a sort of sprouting of new cells from old 
ones, like buds from a stalk : the portion thus shooting out being 
afterwards separated from the parent plant by a partition. This is 
seen in Torula, the yeast plant. 

The various theories of cell-development (cytogenesis) may be re- 
duced to the following : 1. Formation of cells in protoplasm, existing 
in the interior of a cell ; 2. Formation of cells in protoplasm, not 
contained in a cell, but isolated ; 3. Formation of 
cells by merismatic division of the primordial utricle, 
or protoplasmic lining of the cell ; 4. Formation of 
I- C cells by a process of budding. Cells are also formed 
by what has been called Conjugation, or by the union 
of two cells, which by their mutual action give origin 
to a third. This is particularly seen in some of 
the lower Algse, such as Zygnema (fig. 45). 

The formation of cells goes on with great rapidity, 
especially in the case of fungi. From an approxi- 
mative calculation, it is found that in Bovista gigantea 
20,000 new cells are formed every minute. Ward 
1 ^p5& I Va^S ^^^ noticed a similar occurrence in Phallus impudicus.' 
\^^JI\f%^ In warm climates, at the commencement of the wet 
Fig. 46. • season, the production of cells in the higher classes 
of plants proceeds with astonishing rapidity. 

In connection with the propagation of cellular plants much discus- 
sion has taken place as to the existence of their germs in the atmo- 
sphere, which, coming in contact with fluids of various kinds, are said 
to give rise to diiferent species of fungi, such as Torula, Penicillium, , 




Fig. 44. Umcellular Alga (Palmella cruenta). The cell, a, absorbs, secretes, and forms 
new cells, by a process of fissiparous division, first into two, & 6, and then into four parts, c. 
Fig. 45. Two filaments of a cellular plant (Zygtiema), uniting together by means of 
tubes, p. The plant consists of a filament formed by a series of cells united in a single row. 
The cells, c c, appear to have different fanctions. Cell, .i, produced by conjugation. 



DEVELOPMENT OF CELLS. 15 

Bacterium, etc. The doctrine of biogenesis (j8/oc, life), panspermism 
{■^av, all, g-jrii/idj seed), or the development of cells in fluid from germs 
introduced from the atmosphere, has been advocated by Pasteur and 
his followers ; while the doctrine of abiogenesis (a, privative, and j3log, 
life), heterogenesis (sVejos, different, diverse), or what is called spon- 
taneous generation, has been supported by Pouchet and his followers. 
All that is known in regard to the growth of the lower class of plants, 
and their appearance in islands recently elevated by volcanic forces in 
the midst of the ocean, seems, independently of laboratory experi- 
ments, to favour Pasteur's views.* 

The organised cells of plants appear to be the more immediate seats 
of the various changes which constitute the functions of nutrition and 
teproduction. In cellular plants they are the only form of elementary 
tissue produced throughout the whole of life. They absorb nourish- 
ment 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 (ev3ov, inwards, fidu, ^S, I seek), and Exosmose 
(eJw, outwards), were given by Dutrochet to the process of transuda- 
tion, which leads to the motions of fluids of difierent densities placed 
on opposite sides of animal and vegetable membranes. This process 
appears to be of universal 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 process 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-mari- 
golds, the Eose of Jericho (Anastatica), and some Lycopodia. 

Various organic secretions, which are necessary for growth and 
nourishment, are formed by the internal membrane of cells. It is in 
cells that the azotised and unazotised matters are deposited, which 
are afterwards applied to the purposes of vegetable life. In them 
we meet with the protein compounds, albumin, fibrin, and casein, 
consisting of carbon, oxygen, hydrogen, and nitrogen, with proportions 
of sulphur and phosphorus ; as well as starch, gum, sugar, oil, and 
colouring matters, in which no nitrogen occurs. Some of the organic 
matters found in plants have been artificially formed by chemical 
means, while others have as yet only been met with in the living 
organism. Spiral cells sometimes contain air. 

* See Professor Lister on Bacteria, in Medical Jmirnal, October 1873 ; and Dr. Petti- 
grew's Lecture on Physiology, in Lantxt, 15th November 1873. 



16 



FORM AND AEEANGEMENT OF VESSELS. 



Section II. — ^Vasculah Tissue. 

1. Form and Arrangement of Vessels. 

Vasculae Tissue, or Angienchyma (ayyog, 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 of thickening matter. 

Fibrous Tubes, or Ligneous Tissue, Pleurenchyma ('irXivgd, a 
rib, from its firmness), (fig. 46), 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 firm- 
ness. This form of tissue does not exist in cellular plants. Some 
have called this tissue Prosmchyma, a term, however, generally ap- 
plied to shortened fusiform cells only. Pleurenchyma- 
tous vessels lie close together, overlap each other, an3, 
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 
section the tubes present the appearance of concentric 
circles, occasionally with intervals, where the ligneous 
matter is deficient (fig. 47). 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 fibrous 
tissue may be separated from the cellular parts of plants 
by maceration. In this way Flax and Hemp are pro- 
cured, as well as the Bast used for mats. The strength 
of the fibres of different plants varies. Thus, New Zear 
land Max, the produce of Phormium tenax, is superior 
in tenacity to Common Hemp ; while the latter, in its 
turn, excels Common 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 be- 
comes contracted in the process of drying, so as to appear 
twisted when viewed under the microscope. By this cha- 
racter mummy cloth was shown to be composed of 
linen. Fibrous tissue, in fabric, forms muslin, lace, etc. 
(some fine Indian muslins only are formed from this 
tissue ; other muslins are made of cotton) ; when 
reduced to small fragments they constitute the pulp 



I 



Kg. 46. 




Kg. 47. 



whence paper is made. 



Kg. 46. Fibres of Pleurenchyma, from Clematis Vitalba. 
of the same. 



Kg. 47. Transverse section 



FOEM AND AEKANGEMENT OF VESSELS. 



17 




In their ordinary form, Pleurenchymatous tubes have no definite 
markings on their walls ; but in some instances markings present 
themselves in the form of simple discs (fig. 48), 
or of discs with smaller circles in the centre 
(fig. 49). These discs occur in the wood of Firs, 
Pines, and Winter's bark, which has received 
the name of glandular or punctated woody tissue. 
The markings are formed by concave depres- 
sions on the outside of the walls of contiguous 
tubes, which are closely applied to each other, 
forming lenticular cavities between the vessels, 
like two watch-glasses in apposition, and when 
viewed by transmilited light they appear like 
discs (fig. 48). 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. 49). 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. 
50). That these markings are cavities between the 
fibres was prov.ed by Quekett in the case of fossil pine 
wood, where he separated lenticular masses of solid matter 
from the discs. There is sometimes observed a thicken- 
ing layer, in the form of a spiral fibre, surrounding the 
discs more or less completely, as in the yew. The discs 
are usually arranged in single rOws, but they occur also 
in double and triple rows, as in Araucaria, where the 
markings alternate with each other. 

Pibeo-Vasculak Tissue, or Trachenchynia (trachea, 
windpipe ; f^oi.yvs, rough), is formed of membranous 
tubes tapering at each end, less firm than Pleurenchyma, 
and either having a fibre coiled up spirally in their in- 
terior, or having the membrane marked with rings, bars, 
or dots, arranged in a more or less spiral form. 

TuuE Spiral Vessels (spiroidea, trachece), constituting 
the typical form, present themselves as elongated tubes 
clustered together, overlapping each other at their conical 
extremities, and having a spiral fibre or fibres surrounding 
the interior of the cylinder (fig. 51). Their outer mem- 
brane is thin, and consists of cellulose. At the point 

Kg. 48. Woody tubes, with circular spots where the memhrane is thin, Bigrumia. Pig. 49. 
Punctated woody tissue, with double circles or discs, froin common Scotch fir. Pig. 60. Lon- 
gitudinal section of the same, showingthe union between the fibres, and the mode in which the 
circles are formed. Pig. 61. Two spiral vessels united. Pig. 62. Simple trachea, with fibre 
uncoiled. Pig. 53. Spiral vessel with a ribband of united fibres (Pieio(racftea),from the Banana, 





Fig. 52. 



Figs. 



18 



FORM AND ARRANGEMENT OF VESSELS. 



where they overlap, it is sometimes absorbed, so as to allow direct com- 
munication between the vessels. The fibre or spiral filament is 
generally sbgle, forming simple trachem (fig. 52); but sometimes 
numerous fibres, varying from two to more than twenty, are united 
together, as in the banana, assuming the aspect of a broad ribband 
(fig. 53), and constituting Pkiotrachece (ntXi'im, 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. 

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 Plantains, where 
the fibres may be pulled out in handfuls, 
and used as tinder ; in many aquatics, as 
Nelumbium and Nymphsea; and in Lili- 
aceous plants. In hard woody stems they 
are principally found in the sheath sur- 
rounding the pith, and they are traced 
from it into the leaves. They are rarely 
found in the wood, bark, or pith. Spiral 
vessels occasionally exhibit a branched ap- 
pearance. 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. 54, u, a), or it may depend on a 
regular division of the fibres, as is seen in the Mistleto, House-leek, 
and Gourd (fig. 55). 

The fibre is on the inside of the membrane. Quekett has shown 
this in sUicified spiral vessels, where the mark of the 
spil-al 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. 
56), 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 microscope there is often the appear- 
ance of the crossing of fibres (fig. 56), in consequence of 
. 57. 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 

Fig. 54 Spiral vessels, united so as to have a 1)13110116(1 appearance. Pig. 55. Branch- 
ing fibre, from spiral vessels of Gourd (CwitrMto Pepo). Fig. 66. Spiral vessels. Coils 
seen on both sides. Fig. 57. Coils of fibre, much separated in trachea of Gourd. 




Fig. 64. 



Fig. 65. 




FOEM AND ARRANGEMENT OF VESSELS. 



19 



that of the stem. The coils of the spiral fibre may be close together 
(fig. 52), or be separated (fig. 57). Sometimes ■ they become united 
together, and to the membrane of the tube, so that they cannot be 
imroUed. Such vessels are called closed trachese, or closed ducts, and 
are -seen in ferns. 

False or Spueious Teacher, the ducts of some authors, are 
vessels in which the internal fibre does not form a complete spiral 
coil. The chief varieties are annular, reticulated, and scalariform 
or ducts. In annular vessels (annulus, a ring), the fibres 




Fig. 58. 



Fig. 69. 



Fig. 60. 



Fig. 64. 



Fig. 63. 



form complete rings round the tubes (fig. 58). They resemble the 
tracheae of animals more than spiral vessels do. The rings are by no 
means regular ; they may be horizontal or inclined, simple or forked 
(fig. 59), placed near to each other or separated by considerable 
intervals, the intermediate spaces being sometimes occupied by a 
fibre of an elongated spiral form, which is continuous with the rings 
or distinct from them (fig. 60). All these forms are easily recognised 
in the common Balsam. Occasionally, the ring becomes very much 
thickened in a direction perpendicular to the walls of the vessel, so as 
to leave only a 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. 61), the vessels become reticulated 

Figs. 58, 59, 60. Annular vessels from the stem of the Common Balsam. Fig. 61. 

Spiral vessel. Wide coil, and fibre dividing. Fig. 62. Ves.sel showing rings of fibre and 
dots. Pig. 63. Scalariform vessel from the Vine. Fig. 64. Prismatic scalariform 

vessel from Boyal Fern (Osmwida regcdis). 



20 



FOEM AND AKEANGEMENT OF VESSELS. 



(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. 62). 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. 63), they are composed of tubes united to each other 
by thin, broad, oblique extremities ; at other times they taper like 
spiral vessels. They generally assume a prismatic form, the angles 
being unmarked by lines, as is seen in Ferns (fig. 64). 

Pitted Vbssels.^ — Another kind of vessel common in plants is the 
pitted vessel, so called from the appearance of pits or depressions on its 
surface. The tissue formed by pitted vessels has received the name 
of Vasiform tissue, Pitted tissue, Bothrenchyma, or Taphrenchyma (j366§og 
or rd,(pgog, a pit). The vessels are of large size, and are easily observed 
in the Vine (fig. 65), Sugar Cane, Bamboo, Gourd 
(fig. 116 ter), and other plants, in which the sap 
circulates rapidly. They consist of cylinders more 
or, Jess elongated, in which the thickening matter is 
so deposited as to leave part of the membrane un- 
covered, thus giving rise to the porous or pitted 
appearance. The uncovered portions of membrane 
are sometimes absorbed in old 
vessels, and a direct communicar 
tion is established between them. 
The pits or so-called pores have 
sometimes a bordered aspect, 
which, according to Schleiden, 
depends on air contained in -the 
cavities between contiguous ves- 
sels. Pitted or porous vessels 
are usually united to each other 
by a broad and often oblique 
septum. 

This kind of vessel occasion- 
ally presents a beaded appearance, as if formed by pitted cells, with 
distinct constrictions at their point of union (fig. 67). This arti- 
culated Bothrenchyma is by some considered as a form of cellular 
tissue (fig. 22). To vessels exhibiting contractions of this kind, 
whether spiral or pitted, the terms moniliform (monile, a necklace), or 
vermiform (vermis, a worm), have been applied ; and the tissue com- 





Fig. 66. 



Fjg. 66. 



Fig. 67. 



Fig. 65. Pitted vessel (Bothrenchyma) from the Vine, showing its connection with woody 
fibres, and the htoad septa or partitions of the vessel itself. Fig. 66. Pitted vessel from 
Traveller's joy {Clematis Vitalba), Fig. 67. Moniliform pitted vessels from the Common 

Balsam. 



DEVELOPMENT OF VESSELS. 



21 



posed of these moniliform vessels has been denominated phlehoidal 
(pXE^j fi>^E/3o5, a vein). 

Laticipeeous Vessels (latex, fluid, and fero, I bear) form the 
tissue called Cinenchyma (xmu, I move, from movements observed in 
their contents). They are the Milk-vessels, and the Proper vessels 
of old authors, and have been particularly described by Schultz. They 
consist of long, branched, homogeneous tubes, having a diameter of 
about TTTiT of an inch, which unite or anastomose freely (fig. 68), 
thus resembling the vessels of animals. At first the tubes are veiy 
slender and uniformly cylindrical (fig. 69 a),- but afterwards they 
enlarge and present irregular distensions at different parts of their 
course (figs. 69 b, 70), giving rise to an articulated appearance. Their 
walls vary in thickness, and are not marked by any depressions or 




Fig. 68. 



Jll 
Fig. 69. 




Fig. ro. 



fibres. These vessels are met with in the inner bark, and they con- 
tain a granular fluid called latex, which is at first transparent, but 
often becomes of a white, yellow, or reddish colour. Some suppose 
that these vessels are simply intercellular canals lined with a con- 
tinuous membrane, containing a peculiar fluid. The tissue can be 
easily examined in the India-rubber tree, in Dandelion, Lettuce, and 
Celandine, and in various species of Ficus and Euphorbia. 



2. Development and Functions of Vessels. 

The simple cell is the form in which vegetable tissue first makes its 
appearance. It is the primary form of all the textures subsequently 



Kg. 68. Laticiferous vessels (Cinenchyma) from Euphorbia dulcis. 
of Latex from Celandine (Chelidimium majus). i 



Figs. 69, 70. Vessels 




22 FUNCTIONS OF VESSELS. 

produced in vascular plants. To the elongation of cells, and the 
deposition of thickening layers and fibres in their interior, the various 
vessels owe their origin. Thus when cells are elongated, as spindle- 
shaped tubes, and their walls are thickened and hardened by depo- 
sitions of ligneous matter, they give rise to Pleurenchyma ; and when 
elongated membranous tubes are strengthened by spiral fibres, the 
difierent kinds of Fibro-vascular tissue are produced. The spiral 
vessel may be considered as the type of the last-mentioned tissue, 
and aU its varieties may be traced to difierent conditions in de- 
velopment of the fibre. In the case of some vessels, their forma- 
tion can be distinctly traced to cells placed end to 
end, the partitions between which have been ab- 
sorbed. The raoniliform or beaded appearance often 
presented by the different kinds of vessels, more espe- 
cially the Pitted, plainly indicates this mode of for- 
mation. Occasionally cellular prolongations are seen 
in the interior of pitted vessels, giving rise to what 
has been called Tylosis (ruXos, swelling or protru- 
sion). It has been noticed in the vessels of Oak, 
Kg- n. Chestnut, Wahiut (fig. 71 a), Ash, Elm, etc. 

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 osmose. 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 pitted 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. 

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. 
Prom the flrmness 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 
Tracheae, given by Grew and others, was partly from their structure, 
and partly from the idea that they contained air. The accurate 
experiments of BischofiF lead to the conclusion that the perfect spiral 

Fig. 71. Longitudinal section of the stem of a species of Walnut (Juglans einerea), showing 
ylosis in pitted vessels, a. 



FUNCTIONS OF VESSELS. 23 

vessels convey air, which often contains an excess of oxygen in its 
composition. 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. Hofiman 
from his experiments concludes that spiral vessels in the ordinary 
state contain air, but that when a large quantity of fluid is applied 
to the leaves it enters the spirals. Other authors look upon these 
vessels as conveying fluids, while a third set maintain 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 pitted 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 microscope in the 
living plant, exhibit movements in their fluid contents of a peculiar 
kind, which will be considered under Cydosis. 

The cell has been already shown to be the type of all the tissues of 
plants, and to be the basis of aU vegetable structure. It is of equal im- 
portance as regards function. In the lowest plants, as the PalmeUa 
(Protococcus) nivalis, or the Alga found in red snow, and other species of 
FalmeUa (fig. 44), also in Nostoc and Hsematococcus, cells constitute 
the whole substance, and perform all the functions of life ; they absorb 
and assimilate, thus performing the functions of nutrition and secretion, 
and they form new cells, thus reproducing individuals like them- 
selves. When a more complex structure exists, as in the higher tribes 
of plants, certain cells are appropriated for absorption, others are con- 
cerned in assimilation, and others in forming and receiving secretions. 
When a certain degree of solidity is required to support the stem, 
leaves, and flowers, ligneous matter is deposited, and bast fibres 
are 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 ceUs and vessels pervious, and when the elaborated sap is 
conveyed continuously without interruption, anastomosing tubes occur 
in the form of laticiferous vessels. Cells and vessels are thus difiier- 
entiated for the performance of special functions. 

Tabulae Abbangement of Veqetablb Tissues. 

A. — Cellular Tissue (Parenchyma), composed of membrane, or of membrane and 
fibre, having the form of vesicles whose length does not greatly exceed 
their breadth. 
1. Membranous Cellular Tissue; cells formed by membrane alone, of varying 
thickness, but without markings on it ; when thickened and fusiform 
they constitute prosenchyma, composed of bast cells. 



24 AEKANGEMENT OF VEGETABLE TISSUES. 

2. Pitted Cellular Tissue ; cells formed ty membrane, which has heen un- 

equally 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 varying 
thickness, but without markings on it. 

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

ened walls. 

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

often present irregular dilatations, and convey a peculiar fluid, called 
Latex ; this tissue may be formed by intercellular canals lined with a 
continuous membrane. 
n. Pitted Vascular Tissue ; tubes formed by membrane, with markings of a 
more or less circular form on their walls. 

1. Pitted Vessels (Bothrenchyma or Taphrenchyma) ; large pitted tubes 

usually ending in broad extremities, the markings on their walls de- 
pending on internal depressions. This tissue sometimes exhibits con- 
tractions at regular intervals, as if formed of cells placed end to end, 
and then is called Moniliform, or Beaded (Articulated Bothrenchyma). 

2. Punctated Vessels (Glandular Woody Tissue) ; fusiform woody tubes, 

the markings on the walls depending on external depressions, and pre- 
senting the appearance either of single or double, circular discs. 
Iir. Fibro-Vascular Tissue, composed of tubes in which the thickening matter 
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, Ti-achenohyma), in which the spiral fibre is 

elastic, and may be unrolled. 

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

brittle, or its coils so united to each other, and to the membrane, 
that they cannot be unrolled. 
h. 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. Eeticulated Vessels, having fibres which cross each other, or are disposed 

so irregularly as to form a network. 

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 fibre 

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. 



OEGANS OF NUTRITION OR VEGETATION. 



25 



CHAPTER II. 



COMPOUND OEGANS FOEMBD BY THE TISSUES. 

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, pro- 
duce 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 Beproduetive, 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 NuTeition oe Vegetation. 

1. — Structure, Arrangement, and Special Functions. 

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. 

General Integwment. 

Geneeal Integument 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. 72 pp), 
and a deep layer, usually called 
the Epidermis (fig. 72 e e). Dr. 
Carpenter thinks that the term 
epidermis should be dropped 
as regards plants. . He applies 
the term cuticle to the general 
integument. 

The Supeeeicial Cuticle ^..^ ^^_ 

or Pellicle {cutis and pellis. 

Pig 72 General integument of a leaf of Iris germanica. VV, The Cuticular pellicle with 
slits, /, lying upon the proper epidei-mis, e e, formed of hexagonal oeUs, and furnished with 
stomata, s s. 





26 SUPERFICIAL CUTICLE OE PELLICLE. 

skin) is a very thin continuous membrane, 'whicli is spread over all 
parts except the openings called 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, consider 
it as a secretion on the outside of the cells, 
' while Mohl and Henfrey look upon it as com- 
posed of the altered primary walls of the cells. 
J Mitscherlich regards it as a corky substance, 
which preserves the humidity of the plant by 
'' preventing the evaporation of moisture. This 
substance is considered by him to be an im- 
portant constituent of the cell-wall. In many 
plants we meet with a corky epidermis com- 
posed of ceUs containing air. The cork cells 
are flat and thin- walled; and in some cases 
Fig. rs. *^^y ^^^ ^^ peeled off, as ui the cork oak. In 

fig. 73 the peUicle is represented as detached 
from the leaf of the cabbage, forming a sheath over the hairs, hhhh, 
and leaving slits, s s, corresponding to the openings of the stomata. 
The pellicle is perhaps similar to the intercellular substance sur- 
rounding cells, and to the definite mucus (collenchyma) which is seen 
in seaweeds (fig. 29 h). It is possible that this matter, in place of 
being produced on the outside of cells, may be formed within them, 
and ultimately deposited externally by passing through thek parietes. 
On the inner surface of the pellicle the impressions of the epidermal 
cells are sometimes observed. The pellicle is the only layer of in- 
tegument which is present in aquatic plants, and in some of the lower 
tribes. 

The Epidermis (!«', upon, and di^/ia, skin), (fig. 72 e e), is ex- 
tended over all the parts of plants exposed to the air, except the 
stigma. The internal cavities of seed-bearing organs are lined by a 
delicate membrane, termed Epithelium (It/, upon, 6dXXiiv, to flourish). 
On the extremities of newly-formed roots the integument consists of 
loose cells, which are either the ordinary cellular tissue of the plant, 
or an imperfectly-formed epidermis, which has received the name 
of Epiblema (M, upon, and ^Xrj/ia,, 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. 
The cells forming the sheath of young roots are often densely filled 
with granular protoplasm, and contain nuclei. They become coloured 
in Beale's carmine solution. On the aerial roots of Orchidaceous 



Fig. 73. Pellicle of Cal)bage, detached by maceration, covering the hairs, Tihhh, and 
having openings, s s, corresponding to the stomata. 



EPIDEESnS. 



27 



plants, there is an epidermal layer consisting of spiral cells (fig. 23), 
containing air. 

The epidermis is usually formed by a layer or layers of compressed 
cells, ■which assume a more or less flattened tabular shape, and have 
their walls bounded by straight 
or by flexuous lines. Fig. 72 e e, 
represents an epidermis formed of 
r^ular hexagonal cells; fig. 75, 
one composed of irregular hexa- 
gons ; whQe in fig. 74 the bound- 
aries of the cells, «, are flexuous 
and wavy. The cells of the epi- 
dermis are so intimately united 
together, as to leave no inter- 
cellular spaces (fig. 77 e e). 

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 have become thickened by de- 




Fig. 7*. 



posits, and sometimes the layers are so produced as to leave uncovered 
spots, which communicate with the interior of the ceU by canals passing 
through the thickening layers, as in Cycas. In Eochea falcata (fig. 




Fig. 76. <• 

76) the epidermis, e e, consists of two layers of cells— the outer ones 
large, the imier small. The epidermis of Agave and Hoya is thickened 
by numerous secondary deposits ; such is also the case with that of 
the branches of the mistleto. The cells of epidermis are usually 
filled with colourless fluid, but they sometimes contain resmous and 

Fig 74. Epidennis, ftom lower surface of the leaf of Madder (RiMa tinctorum). e, CeU 
of the Epidermis, s. Stoma. Pig. 75. Epidermal layer, from upper surface of a leaf of 
Itanummlus cuprntUis when growing out of water, e e. Epidermal cells, sss s Stomate. 
Fig 76 Vertical section of lower epidermis of the leaf of J!«!*«./oJoo«o. ««, Double epider- 
m£ layer, with very large external cells. smaU internal ones, pierced by a stoma, s, which 
commnniMteswithalacuna,!. p. Parenchyma of the leaf. 



28 STOMATA. 

other substances. Waxy matter is occasionally found in the epi- 
dermis, silica is met with in the integument of grasses and Equiseta, 
and carbonate of lime in that of Chara. The colour of the epi- 
dermis generally depends on that of the subjacent parenchymatous 
cells, from which it can be separated as a colourless layer. The 
epidermal cells are usually larger than those of the tissue below them ; 
but sometimes, for instance in Ficus elastica, they are smaller. 

Stomata (dTofia, 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. 
72 s s, 74 s), supposed to resemble the lips and the orifice of the 
mouth. Stomata open or close according to the state of moisture 
or dryness in the atmosphere, — these changes depending on the 
hygroscopic character of the cells. By examining, under the micro- 
scope, thin stripes of epidermis in a moist and dry state, it wiU 
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 collapse, approach each other, and 
close the orifice. 

The cells surrounding the openings of stomata are sometimes 
numerous, as in Marchantia. In. Ceratopteris thalictroides, Allman 
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 {■m^i, around). 
In Ficus elastica four cells form the stoma. In Equisetum, the 
stomata, which are about tJtt of an inch in their greatest 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). Occasionally 
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. 

Stomata communicate with intercellular spaces (figs. 76 s, 77 s), the 
connection being sometimes kept up by means of a funnel-shaped prolon- 
gation inwards of the cuticle, called, by Gasparrini, a cistoma {xiarrj, a 
cyst or bag, and ero/iix, a mouth). They are scattered over the surface 
of the epidermis in a variable manner. Sometimes they are placed at 
regular iotervals corresponding to the union of the epidermal cells 
(fig. 72 s) ; at other times they are scattered without any apparent 
order (figs. 74, 75) ; 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. 78 s s), Orassula, and some Proteacese. 

Stomata occur on the green parts of plants, especially on the leaves 



STOMATA. 



29 



and their appendages. They are, however, also met with on parts 
not green, as on coloured sepals or petals, as those of the Marsh Mari- 
gold and Ornithogalum. They have also been seen on internal organs, 
as the replum of some cruciferous plants. They are not usually found in 




.p e •;b 




Fig. 77. 



Fig. 78.' 



cellular plants, nor in plants always submerged, nor in pale parasites. 
This is not, however, a universal rule, for stomata have been detected 
in Marchantia and some other Oellulares ; also in the submerged leaves 
of Eriocaulon setaceum,-and in the pale parasite Orobanche Ei;yngii. 
They do not exist on 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. 

Stomata vary in their form. s 

The oval form is very common, 
and may be easily seen in Lilia- 
ceous plants ; the spherical occurs 
in Oncidium altissimum and the 
Primrose, the quadrangular in 
Yucca and Agave. In the Ole- 
ander, in connection with the sto- 
mata, there are cavities in the epi- 
dermis protected by hairs (fig,79s). 

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 granular matter, 
which gradually collects towards the centre of the space, where a sep- 

Fig. 77. Vertical section of epidermis, from the lower surface of the leaf of Madder, 
Bhcvying the intimate union of the epidermal cells, e e, the loose subjacent parenchyma, p, 
with intercellular canals, m, and lacuna, I. s. Stoma. Fig. 78. Epidermis of leaf of Saxi- 
fraga sarmentosa, showing clusters of stomata, s s, surrounded by large epidermal oeUs, e e. 
The cells among which the stomata occur are very small. Fig. 79. Vertical section of 

lower epidermis of the leaf of JVemtm Olea/nder. e, Epidermis composed of several layers 
of cells, p, Parenchyma of the leaf, s. Cavity filled with hairs, at the bottom of which is 
a stoma. 




Fig. 79. 



30 



EPIDERMAL APPENDAGES — HAIES. 



turn or partition is formed. This septum ultimately splits, leaving a slit 
or opening which constitutes the stoma. Mohl has traced this process 
throughout the same leaf in different stages of growth. In Mar- 
chantia, 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. 

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 OP SUREAOE OP THE LEAF. 



Mistleto (Viscum album) 
Spiderwort (Tradescantia) 
Rhubarb (Ebeum palmatum) . 
Crinum amabile 
Aloe ..... 
Carnation (Diantbus Caryophyllus 
Yucca ..... 
Mezereon (Daphne Mezerenra) 



1 amencana . 
Holly (Ilex Aquifolium) 
Olive (Olea europsea) 
Potamogeton natans 
Victoria regia , . , 
Vine (Vitis vinlfera) 
Cherry-laurel (Laurocerasus communis) 
Lilac (Syringa vulgaris) . 



Upper Side. 
200 

2,000 

1,000 
20,000 
25,000 
38,500 
40,000 
None. 
None. 
None. 
None. 
None. 

7,800 
21,600 
None. 
None. 
Few. 



Under Bide. 

200 

2,000 

40,000 

20,000 

20,000 

38,500 

40,000 

4,000 

13,000 

1,560 

63,600 

57,600 

None. 

None. 

' 13,600 

90,000 

160,000 



Appendages op the Epideemis, or Appendicular Organs. — 
The epidermis frequently exhibits projections or papillae on its surface, 
in consequence of some cells being enlarged in an outward direction 
(fig. 76 e e). When these assume an elongated or conical form they 
constitute hairs (pili or villi). 

Haies, then, are composed of one or more transparent delicate cells 
proceeding from the epidermis, and covered with the cuticle (fig. 73). 
They are erect (fig. 80 «), or oblique, or they lie parallel to the sur- 
face, and are appressed. Sometimes they are formed of a single cell, 
which is simple and undivided (fig. 80), or forked (fig. 81) or 



EPIDERMAL APPENDAGES — HAIRS. 



31 



branched (fig. 82) ; at other times they are composed of many cells 
either placed end to end, as in monHifonn or necklace-like hairs (fig. 
83), or united together laterally, and gradually forming a cone, as in 





compound hairs (fig. 84), or branched (fig. 85). When several hairs 
proceed from a common centre, they become stellate (stella, a star), 
or radiated (fig. 86). The latter arrangement occurs in hairs of the 
Mallow tribe, and is well seen in those of Deutzia scabra, and on the 
stem of the Rice-paper plant (Fatsia papyrifera). When stellate hairs 
are placed closely together, so as to form a sort of membranous ex- 
pansion (fig. 87), a scale or scurf is produced. In Bromeliacese the 
scurfiness of the leaves is a marked character. To such expansions of 
the epidermis the name l^is (Xsot's, a scale) is applied, and the 
surface is said to be lepidote. These scales have sometimes a beau- 






Fig. s*. 



Fig. 83. 



Fig. 86. 



tiful silvery appearance, as in Elseagnns and Searbuckthom (fig. 87). 
Surrounding the base of the leaves of Ferns, a brown chaffy substance 

Figs. 80-86. Forms of hairs, e. Epidermis. 80. Simple hair formed of a single, undi- 
Tided, elongated, and tapering cell. 81. Forked or bifurcate haiis of Sisymhrium Sophia, 
formed by one cell of the epidermis, e, dividing into two. 82. Branched hair of Arabis 
alpina, formed by a simple hair of the epidermis, ~e, dividing into nmnerons conical cellular 
blanches. 83. Moniliform hair, from Lychnis chalcedonica. Fig. 84. Partitioned, 

nnbranched hair, from stem of Bryonia alba. Fig. 85. Partitioned, branched hair, from 
flower of Nicandis anomala. Fig. 86. Stellate or star-like hair, from leaf of Althsea 
rosea. 



32 



EPIDERMAL APPENDAGES — HAIRS, 




occurs, consisting of elongated cells, 
to which the name of rwmentaceous 
hairs, or ramenta (ramentum, a shav- 
ing), has been given. In Palms also 
a similar substance (but of firmer tex- 




Fig. 88. 



Fig. 87. 

ture) occurs, called reticulum (reticulum, 
a net), or mattulla, (matta, a mat). 
Prickles or aculei, as in the Rose, are 
hardened hairs connected with the 
epidermis, and differ from spines 
or thorns, which have a deeper ori- 
gin. Set(B are bristles or stiff hairs, 
and the surfaces on which they occur 
are said to be setose or setaceous. Some 
hairs, as those of Drosera, or sundew 
(fig. 88), have one or more spiral fibres 
in their interior. 

Various names have been given 
to the different forms of hairs ; they 
are clavate or cluh-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 ; 
ItooJced or uncinate (uncus, a hook), 
with a hook at ttfeir apex pointing 
downwards and to one side ; ba/rbed 
or glochidiate ('y'^c^X'^t ^ barb), with 
Fig. 87. Scale or scaly hair, from leaf of Hip- 
pophae rhamnoides. Fig. 88. Drosera dichotoma, 
double-leaved sundew, showing leaves covered with 
glandular hairs. The gland is terminal, and there 
is a spiral fibre inside the stalk supporting the 
gland. 




EPIDEEMAL APPENDAGES — HAIES. 33 

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, as in Malpighia urens (fig. 89), and in many cruciferous 
plants ; ciliated (cilium, an eyelash), 
when surrounding the margin of 
leaves. On the pod of the Oowitch 
(Mucuna pruriens), hairs are pro- 
duced with projections on their sur- 
face, which cause irritation of the '®' *^' 
skin. In Venus' Fly-trap (Dioncea muscipula), stiff hairs exist on the 
blades of the leaf (fig. 202 e), which, when touched, cause their closure. 

Hairs occur on various parts of plants ; as the stem, leaves, flowers, 
seed-vessels, and seeds, and even in the interior of vessels. In the 
interior of the spathe of some palms numerous ovate cells, analogous 
with hairs, occur in clusters, and when the spathe is dried they can 
be shaken out in the form of powder. Cotton consists of the hairs sur- 
rounding the seeds of Gossypium herbaceum and other species of Gossy- 
pium. Hairs are developed occasionally to a great extent on plants 
exposed to elevated temperatures, as well as on those growing at high 
altitudes. When occurring on the organs of reproduction they are 
connected with fertilisation, as the hairs on the style of Goldfussia, and 
the retractile hairs on the style of Campanula. Different organs of 
plants are transformed into hairs ; as may be seen in the flowering 
stalks of the Wig-tree (Rhus Ootinus), and in the calyx of Oompositse. 

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 cover 
them. The following are the more important terms ; — Glabrous, 
smooth, having no hairs ; hairy (pilosus), furnished with hairs j 
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 
(tomentvmi) ; woolly, with long curled and matted hairs like wool ;■ 
bearded or stupose (cj-u**), tow), when hairs occur in small tufts. 

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 

Kg. 89. Peltate hair of Malpighia urens, p p, arising from epideimis, e. g, The gland, 
■which comniunicates with the hair, t 

I) 



34 



EPIDERMAL APPENDAGES — GLANDS. 



plants. On young roots cellular projections occur (fig. 97 h), which 
may be called radical hairs. Young leaves and buds are frequently 
thickly covered with protecting hairs. In this instance the hairs grow 
chiefly along the veins ; and as the leaves increase in size, and the 
veins are separated, the hairs become scattered and apparently less 
abundant. On the parts of the flower (as in the Iris), coloured hairs 
occur which have been called corolUne. 

Glands 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 (sessile). 





Fig. 91. 



Kg. 90. 

The former may be called glandular hairs, having the 
secreting cells at the apex. Stalked glands, or glan- 
dular hairs, are either composed of a single cell, with 
a dilatation at the apex (fig. 90 a), or of several cells 
united together, the upper one being the secreting 
cell (fig. 90 b). In place of a single terminating 
secreting cell, there are occasionally two (fig. 90 c) or more (fig. 90 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. 9 1 ), in Loasa or Chili nettle, 
and in Malpighia (fig. 89), and are commonly called stings. In the nettle 
they are formed of a single conical cell, dilated at its base (fig. 91 6), 
and closed at first at the apex, by a small globular button placed 

Fig. 90. Glandular hairs, e, Epidennis. a. Hair formed by a single cell, from Sisym- 
brium chilense. &, Hairs formed of several cells terminated by a secreting cell, from 
flower-stalk of Antirrhinum majua. ci, Hair composed of several cells, terminated by two 
secreting cells united laterally, from flower-stalk of Lysimachia vulgaris, d. Compound 
hair, terminated by several secreting cells united end to end, from Geum nrbanum. Fig. 
91. Conical hair of tirtica dioica, oi 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 this hair 
there are currents of granular protoplasm, ff. 



EPIDERMAL APPENDAGES — GLANDS. 35 

obliquely (fig. 91 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 crushed, 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 (fig. 88). The 
hairs of the latter plant, by this secretion, detain insects which 
happen to alight on them. The hairs gradually close on the insects, 
electrical phenomena taking place during the movement. Some think 
that in this case the insects are used as food by the plant. 

When glands are sessile, they consist of epidermal cells either 
surrounding a cavity or enclosing small secreting cells. In fig. 92 
is represented a gland taken from the flower-stalk of Dictamnus albus, 
cut vertically, to show the cavity surrounded by cells, which is fiUed 
with a greenish oil ; while in fig. 93 there is a 
gland with a short thick stalk, fuU 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 containing m m" km 

a clear fluid, which is said to have an alka- 
line reaction ; in the Chick-pea, similar superficial cells contain an 
acid fluid. Clear glands are also seen on the under surface of the leaf 
of Passiflora lunata. Eesinous glands are seen in the Hop and Hemp 
plants. Glandular depressions or pits occur, surrounded by secreting 
cells. At the base of the petals of the Crown-imperiaJ, for instance, 
cavities are seen containing a honey-like fluid, secreted by what are 
called nectariferous glands. Cavities containing sac- 
charine matter, surroimded by small thin-walled cells, 
are met with in the leaves of Acacia longifolia, also 
in Viburnum Tinus, and Clerodendron fragrans. The 
cavities communicate with the surface of the leaves 
by means of canals. Peculiar glands are found at the 
inner side of the base of the petioles of Cinchona and 
Ipecacuan plants (fig. 94). ^^' **' 

Glands are occasionally sunk in the epidermis, so as merely to have 

Fig. 92. Gland from flower-staUi; of Dictamnus albus, cut vertically, showing central 
cavity, I, flUed with greenish oil, and surrounded by a layer of cells, c, which contain a red 
juice, and are connected with the epidermis, «. Fig. 93. Gland from Eosa centifolia ; e, 
the epidermis. Fig. 94. Cluster of ovate-oblong ceUular glands from the base of the 
stipule of the Ipecacuan plant (Cephaelis Ipecacuanha). 






36 FUNCTIONS OF EPIDERMIS. 

tlie apex projecting ; at other times they lie below the epidermal cells, 
as in the Myrtle, Orange, St. John's-wort, and Eue. In the latter 
case they are sometimes called vesicular, and are formed by cells sur- 
rounding cavities containing oil (fig. 95). When 
they occur in the leaves, they give rise, when 
viewed by transmitted light, to the appearance 
of transparent points or dots. Verrucce, 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 
Fig.'gs. glands, are cellular projections on the surface of 

the bark, arising from its inner part. Trecul says 
that lenticels result from the formation of corky matter under decayed 
or decaying tissues, the corky particles surrounding sub-stomatic cavi- 
ties. The corky matter protects the internal tissue from injurious 
atmospheric influence. Other lenticels are simply cracks of the epi- 
dermis before the production of cork or periderm, while a third set 
are produced on the surface of a peridermic layer. 

The Special Functions of the epidermis and its appendages 
are to protect the parts beneath from various atmospheric and meteoro- 
logical influences. In plants growing in dry climates, the epidermis 
is often very thick, and coated with a waxy secretion, 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 covering. The stomata regulate 
the transpiration ; opening and closing, according to the state of humid- 
ity and dryness of the atmosphere surrounding them. When a plant 
is growing vigorously, the constant passage of fluids keeps the regu- 
lating 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 pur- 
poses. Lymphatic hairs protect the surface, and regulate evaporation. 
Plants thickly covered with hairs, as Verbascum Thapsus (Great 
Mullein), have been known to resist an extended period of drought. 
When organs become abortive they sometimes assume the form of hairs. 
Glandular hairs, and glands in general, form secretions which are em- 
ployed in the economy of vegetation, or are thrown off as excretions 
no longer fitted for the use of the plant itself Many of these secre- 
tions constitute important articles of materia medica. Lenticels keep 

Kg, 95. Vesicular gland from Euta graveolens, or Common Eue. g. Gland formed by 
large transparent cells, surrounding a central lacunaj I. e. Epidermis from upper surface 
of tlie leaf. uc,uc, Cells filled with Chlorophyll. 



STEUCTUKE OF ROOTS. 37 

up a connection between the air and the inner bark, and probably per- 
form the function of stomata in the advanced period of the growth of 
the plant. They are considered by DecandoUe and others as being 
the points where young roots are produced in certain circumstances, 
and on that account they have been called Rhizogms (g/^a, a root, and 
ysndiiv, to produce). They are conspicuous in Willows, the young 
branches of which form roots very readily when placed in moist soil. 
Some hairs occurring on the styles of plants are called collecting hairs, 
from the functions which they perform 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, as in the nettle, a circulation of fluids takes place, 
connected apparently with their nutrition and development (fig. 91). 
In nettle hairs and in the moniliform purple hairs on the stamens of 
Tradescantia, or Spiderwort, this movement may be easily seen under 
the microscope. The subject of the circulation in hairs wiU be con- 
sidered under Rotation. 



KooT OE Descending Axis. 
Structure of Roots. 

Before proceeding to the consideration of the special nutritive organs, 
the root, stem, and leaves, a few remarks are required in reference to 
the general division of plants into three great classes, Acotyledons, 
Monocotyledons, and Dicotyledons. The first of these embraces 
flowerless plants, having a cellular embryo, and no seed-leaf, or, as it 
is called. Cotyledon. Such plants as Ferns, Mosses, Lichens, Sea-weeds, 
and Mushrooms, belong to this class. The second includes flowering 
plants having an embryo with one seed-leaf or Cotyledon, such as Lilies, 
Palms, Grasses ; while the third includes plants which have two seed- 
leaves or Cotyledons, such as ordinary forest trees, and the majority 
of flowering plants. In these classes there are marked difierences in 
the structure of the nutritive organs, to the consideration of which we 
now proceed. 

In the young state there is no distinction between stem and root, 
as regards structure ; both being cellular, and prolongations 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 absence of a 
provision for the development of leaf-buds, and by increasing from above 
downwards. It is not always easy to distinguish between a stem and 
a root. Many so-called roots bear at their upper part a portion called 
their croion, whence leaf-buds arise. Underground stems and roots are 
often confounded. Some plants, as the Moutan Pseony, the Plum-tree; 



38 



STEUCTDEE OF BOOTS. 



Pyrus japonica, and especially Anemone japoniea, have a power of 
forming buds on their roots. The last-mentioned plant develops 
these buds on every part of its extensively ramiiying roots, which 
may be chopped into numerous pieces, each capable of giving rise to a 
new plant. Such is also the case with the annulated root of Ipecacuan. 
The part where the stem and root unite is the collwm, or neclt. In 
woody plants, the fibres of the stem descend into the roots, and there 
is an internal arrangement of woody layers, similar to that seen in 
the stem itself. 

Roots are usually subterranean and colourless. Externally, they 
have a cellular epidermal covering of a delicate texture, sometimes called 
epiblema (p. 26), in which no stomata exist. Their internal structure 
consists partly of cells, and partly of vascular bimdles, 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. 96), the ex- 





Pig. 96. 



Fig, 97. 



tremities of which are composed of delicate cellular tissue, and have 
been erroneously called spongioles or spongelets. They are not separate 
organs, and have nothing of the character of a sponge. Over these 
root extremities a very thin layer of cells is extended, caUed a 
PUeorhiza {■^TXog, a cap, and j/^a, a root). This sometimes becomes 
thickened, and separates in the form of a cup, as in Screw-pines (fig 
98), and m Lycopodia (fig. 1 38). Occasionally the extremities of roots 
are enclosed m a sheath, or ampulla, as in Lemna. Cellular papUte 

Pig. 96. Tapering root of Malva rotundifolia, giving off teanohes and fibrils Fie 97 
Toung root of Madder, showing cellnlar processes, h h h, equivalent to liairs. c. Outer 
cells of the root not elongated into hairs. 



STEUCTaEE OF EOOTS. 



39 



and hairs are often seen in roots, but no true leaves. These hairs 
consist of simple elongated cells, which occur singly, and appear to serve 
the purpose of absorption (fig. 97, h h h). Eoots increase principally 
by additions to their extremities, which are constantly renewed, so 
that the minute fibrils serve only a temporary purpose, and represent 
deciduous leaves. The tissue at the extremities of roots is older and 
more dense than that immediately below it, so as to form a protecting 
covering. 

Eoots, in some instances, in place of being subterranean, become 
aerial. Such roots occur in plants called Epiphytes, or air-plants (i-jrl, 
upon, and (pvrhv, a plant, from growing on other plants), as in Orchi- 
dacese ; also in the Screw-pine (Pandanus), (fig. 98), the Banyan 
(Ficus indica), and many other species of Ficus, where they assist in 
supporting the stem and branches, and have been called adventitious or 





Kg. 98. 



Fig. 99. 



abnormal. In Screw-pines these aerial roots follow a spiral order 
of development. In Mangrove trees (fig. 99) they often form the 
entire support of the stem, which has decayed at its lower part. The 
name of adventitious is applied to roots arising from the sides of 
stems, as for instance those which are formed when portions of stems 
and branches of the Willow and Poplar are planted in moist soU. 
They appear first as cellular projections, into which the fibres of the 
stem are prolonged, and by some are said to proceed from lenticels. 
They frequently arise from points where the epidermis has been in- 
jured. A Screw-pine, in the paJm-house of the Edinburgh Botanic 
Garden, had one of its branches injured close to its union with the 

" Fig, 98. Pandanus odoratissimus, the Screw-pine, giving off numerous aerial roots near 
the tase of its stem. Fig. 99. Ehizophora Mangle, the Mangrove tree, supported, as it 
were, upon piles, by its numerous roots, which raise up the stem. The plant grows at the 
muddy mouths of rivers in warm climates. 



40 FORMS OF EOOTS. 

stem. This branch, was at the distance of several feet above the part 
where the aerial roots were in the coui'se of formation. At the part, 
however, where the injury had been inflicted, a root soon appeared, 
which extended rapidly to the earth, and then divided so as to form 
rootlets; thus the branch was firmly supported. The extremities 
of the aerial roots of Orchids are covered with a layer of delicate 
whitish tissue, composed of spiral cells. This layer is called vdamen 
radicum, or covering of the roots. 

Green-coloured aerial roots are frequently met with in endogenous 
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. Those processes are subservient to the pur- 
poses of support rather than nutrition. In parasites, or plants which 
derive nourishment from other plants, such as Dodder (Guscuta), roots 
are sometimes produced in the form of suckers, which enter into the 
cellular tissue of the plant preyed upon. 

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, 

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 taproot is produced 
(fig. 96). 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 is kvisted, 
as in the contorted root of Bistort. 

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 fibrUs become short and succulent the root is fasciculated, 
as in Ranunculus Ficaria and Asphodelus luteus (fig. 100) ; when the 
succulent fibrils are of uniform size, and arranged like coral, the root 
is coralline, as in OoraUorhiza innata ; when some of the fibrils are 
developed in the form of tubercules, containing starchy matter, the 
root is tubercular ; the tubercules, in such cases, are in reality stem- 
tubers, as seen in the Jerusalem Artichoke (Helianthus tuberosus), and 
in Orchis (fig. 101) ; when the fibrils enlarge in certam parts only, the 
root is nodulose, as in Spiraea Filipendula (fig. 102), or moniliform, as in 
Pelargonium triste (fig. 103), or annulated, as in Ipecacuan (fig. 104). 
Some of these so-called roots are formed of a stem and root combined, 



FOEMS OF EOOTS. 



41 



and when cut in pieces they give rise to buds and new plants. This 
occurs in the Ipecacuan plant. 




Fig. 100. 



Ilg. 101. 



Pig. 102. Kg. 103. 




In some Dicotyledonous roots, as in the Oar- 
rot and Beet, there is a circle of fibro-vascular 
bundles, which are separated by medullary rays. 
In the turnip these bundles are immediately 
under the rind, and in the inner portion of the 
root the bundles are separated from each other by 
a great development of cellular tissue. In these 
peculiar thickened roots it is often difficult to 
determine their structure. They have more of 
the aspect of stems, and have been called Hypo- 
cotyledonary stems. The structure in several 
fleshy Dicotyledonous roots resembles that of 
Monocotyledons. 

In Dicotyledonous plants the root, in its early state, or the radicle, 
as it is then called, is a prolongation of the stem, and elongates 
■directly by its extremity. It then continues to grow in a simple or 
branched state (fig. 98). From this mode of root development, 
these plants have been called Exorhiml (e^ta, outwards, and j/^a, a 

Fig. 100. Fasciculated root of Asphodelus luteus. Fig.' 101. Tubercular roots or stem- 
tubers of Orchis. Several of the radical fibres retain their cylindrical form, whUe two are 
tubercules containing starchy matter. Fig. 102. Nodulose root of Spiraaa Filipendula. 
Fig. 103. Moniliform root of Pelargonium triste. Fig. 104. Ipecacuan (Cepliams Ipeca- 
cuanha), with an anm\lated root. 



Fig. 104. . 



42 FOEMS OF ROOTS. 

root), by Eichard. In their after progress these roots follow the 
arrangement seen in the woody part of the stein. In some cases, as 
in the Walnut and Horse-chestnut, there is a prolongation of the pith 
into the root to a certain extent. 

In Monocotyledonous plants the young root or radicle pierces the 
lower part of the axis (fig. 105 r), is covered with a cellular sheath, c; 
numerous fibrUs, / r' / /, are then developed like adventitious 
roots. These plants are therefore called by Eichard, Endorhizal 
hvdov, within) ; and the sheath is denominated Goleorhiza {xoXehe, a 
sheath). In their after progress they usually retain their compound 
character, consistmg of fibrils, most of which often remain unbranched 
(figs. 100, 101). The first-formed roots which surround the axis, 
if the plant is perennial, gradually die, and others are produced in 





Fig. 106. 

succession farther from the central axis. In Endogenous roots, the 
same structure is observed as in the stem. Thus, fig. 106 represents a 
section of a root of a Palm, composed of cellular tissue, porous vessels, 
V p, modified spiral vessels, v s, fibrous or woody tissue, /, and latici- 
ferous vessels, I. Eoots are pushed out from various parts of the 
stems of many Palms, and are applied closely to the surface of the 
stem. 

Fig. 105. Grain of wheat germinating, g, The nia38 of the grain, t, The young stem begin- 
ning to shoot upwards, r. The principal root from the axis. Lateral roots, / / r* /, covered, 
like the preceding, with small hairs or threads. Coleorhiza or sheath, c c c, with which each 
of the roots is covered at its base, while piercing the superficial layer of the embryo. Fig. 
106. Transverse section of part of the root of a Palm {Dvplothemivm vuiriHtnum), to show 
the mode in which the cells and vessels are arranged, v p, Large porous vessels situated in 
the interior, v s, Scalarifonn or modified spiral vessels more external, and becoming smaller 
the farther they are from the centre. /, Fibrous tissue, or elongated cells, accompany- 
ing the vessels. I, Groups of laticiferous vessels of different sizes, the larger being inside. 



FUNCTIONS OF EOOTS. 43 

In Acotyledonous plants the young root is a development of super- 
ficial cells from no fixed point, and they have been called Reterorhizal 
(ersjos, 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 repre- 
sented in fig. 135, r a. 



Functions of Roots. 

Eoots either fix the plant in the soil or attach it to other 
bodies. They absorb nourishment by a process of imbibition or 
endosmose (flow inward), through their spongioles or cellular ex- 
tremities. 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, which are 
then easily taken up in an uninjured condition, ready to absorb 
nourishment. When an acorn is put into the ground, it first sends 
down a long tap root. This is not well fitted for feeding young 
stems and leaves, and hence numerous fibrous roots appear near the 
surface of the ground. The more numerous these fibres the more 
rapid the growth. The tap root is sometimes cut about seven inches 
under ground at an early period, and this causes numerous fibres to be 
thrown out. 

The elongation of the roots by their extremities enables them to 
accommodate themselves to the soil, and allows the extremities of the 
rootlets to extend deeply without being injured. Roots, 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 re- 
strictive potting, formerly practised in green-houses, often injured the 
natural habit of the plants. The roots filled the pots completely, and 
even raised 1;Jie plants in such a way as to make the upper part of 
the root appear above the soil. 

To roots there are sometimes attached reservoirs of nourishment, 
in the form of tubercules, containing starch and gum (fig. 101), which 
are applied to the nourishment of the young plant. These are seen 



44 FUNCTIONS OF BOOTS. 

in the Dahlia and in terrestrial Orchids. In epiphytic Orchids, 
on the other hand, the roots are aerial, and the stems are much de- 
veloped, forming pseudo-bulbs. Upon the roots of Spondias tube- 
rosa 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 iatended 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. 

Roots also give off excretions of different kinds. These are 
eliminated by a process of exosmose (flow outwards), and con- 
sist 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 deterioration. 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 neces- 
sary. Daubeny and Gyde 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 
son.* In very rich and fertile land the same crop may be grown 
successively for many years. 



Stem or Ascending Axis. 

Forms of Stems, 

The stem is that part of a plant which bears the leaves and flowers. 
It receives the name of OauUs in ordinary herbaceous plants which do 
not form a woody stem, Culm in grasses, Truncus in trees, Gwudex or 
Stock in Palms and in some Cacti, and Sti-pe in Ferns. Herba- 
ceous stems are those of annual and biennial plants, as well as the 
young yearly shoots of perennial plants. The term haulm is probably a 
corruption of culm ; it is used by farmers to designate the stem of grasses 
and the herbaceous stems of plants. The stem is not always conspicuous. 
Plants with a distinct stem are called caulescent ;■ those in which it is 
inconspicuous are acaules. Some plants are truly stemless, and con- 
sist only of expansions of cellular tissue, called a Thallus, and hence 
are denominated Thallogens, or Thallophytes (^aXXis, a frond, ymaeiv, 
to produce, tpurhv, a plant). They have no true vascular system, but 
are composed of cells of various sizes, which sometimes assume an 
elongated tubular form, as in Ohara. The cells are sometimes united 

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



FOEMS OF STEMS. 45 

in one or several rows, forming simple filaments, as in Confervae ; or 
branched and interlaced filaments, as in some Fungi ; or cellular 
expansions, as in Lichens and sea-weeds. 

Stems have usually considerable firmness and solidity, but some- 
times they are weak, and either lie prostrate on the ground, thus 
becoming procumbent ; or climb on plants and rocks by means of 
rootlets like the Ivy, being then called scandent ; or twist round other 
pla,nts in a spiral manner like Woodbine, becoming voluUle. Twining 
plants turn either from right to left, as the French bean, Convolvulus, 
Passionflower, and Dodder, Periploca, and Gourd ; or from left to right 
(left-handed screw), as Honeysuckle, Twining Polygonum, Hop, and 
Tamus. Bryony tendrils twine from right to left, and 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 twining stem of the vine has been 
called sarmentum {sarmentwm, a twig, or cutting of a vine). Some 
stems are developed more in diameter than in height, and present a 
peculiar shortened and thickened aspect, as Testudinaria or Tortoise- 
plant, Cyclamen, Melocactus, Echinocactus, and other Cactacese. 

Stems have a provision for a symmetrical arrangement of leaves 
and branches, — nodei (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). The branching 
of some trees is very peculiar. In the Amazon district many Myris- ' 
ticacese and Monimiaceee have verticillate branches coming off in fives. 
Some Amazon trees taper remarkably downwards, so as to have a form 
like an inverted cone or pyramid. This is seen in the Mulatto tree 
(Eukylista Spruceana), one of the Oinchonacese. 

The buds of trees are developed in different ways. In some, such 
as the Oak and Birch, the terminal bud of each shoot produces 
yearly a new portion of the shootj while the flowers come off from 
axillary buds. Again, in other trees, as LUac and Horse-chestnut, the 



46 FOEMS OF STEMS. 

buds at the extremity produce inflorescence, which thus terminates the 
axis of the shoot, while the shoots of the succeeding year are from 
axillary buds. When the branches of trees bearing terminal buds 
have the axis of the shoot destroyed by wounds or by insects, then 
the lateral leafy buds become developed, giving rise to anomalous 
appearances seen in the Birch and other trees. 

Plants which form permanent woody stems above ground are 
denominated trees and shrubs, while those in which the stems die 
down to the ground are called herbs. The term tree (arbor) is ap- 
plied 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 small tree (arbusculus) is one not above 25 feet high ; a 
shrub (frutex) has a stem about three times taller than a man, and 
branches from near the base : an undershrub (mffrutex or fruticulus) 
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, mffrutieose, and dumose, are derived from these. 

The cylindrical form of the trunk of trees is sometimes interfered 
with by peculiarities in the production of woody tissue. In this way 
protuberances are formed of various kinds. This is very remarkable 
in some kinds of Bombax, and in the Bottle-tree of Australia, where 
the whole stem appears in the form of a large flask or bottle, taper- 
ing to each end, and swollen in the middle. So also, by interruption 
to the growth of the root and other causes, knobby stems are formed, 
as in the Yew (fig. 128). 

Stems have usually a round form. They are sometimes compressed 
or flattened laterally, while at other times they are angular : bping 
triangular, with three angles and three flat faces ; trigonous {rgiT;, 
three, and ycavla, 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, 
etc. Various terms are applied to the forms of stems, as cylindrical 
or terete, jointed or articulated — that is, with contractions at intervals, 
many-angled or polygonal. 

The stem has been called the ascending axis, from being developed 
in an upward direction. It does not, however, always ascend into the 
air ; and hence stems have been divided into aerial, or stems which 
appear whoUy 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. 
Underground stems are common in Monocotyledons, and it is often 
found that the structure of Dicotyledonous underground stems, such 
as Jerusalem artichokes, resemble in structure Monocotyledons. The 
following are some of the more important modifications of stems : — 
The Grown of the root is a shortened stem, often partially under ground, 




FORMS OF STEMS. 47 

which remains in some plants after the leaves, branches, and flower- 
stalks have withered. In this ease 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. 
107) is a stem which runs 
along the surface of the 
ground, being partially cover- 
ed by the soil, sending out 
roots from, its lower side and 
leaf-buds from its upper. It 
occurs in Ferns, Iris, Hedy- rig. lor. 

chium, Aoorus or Sweet Flag, 

Ginger, Water-lily, many species of Oarex, Eushes, Anemone, Lath- 
rsea, etc. By many the term rhizome is applied to stems creeping 
horizontally, whether they are altogether or only partially subterranean. 
The short underground stem of Arum maculatum differs from the 
rhizome of Solomon's Seal, in the presence of the old axes in the latter, 
and their decay in the former. A rhizome may then be considered as 
a series of corms united together, the internodes or individual axes 
being more or less elongated, and usually covered with leaf scales. In 
rhizomes, called definite, the terminal bud gives off flowers, and the 
lateral buds form the stem ; while in indefinite rhizomes the terminal 
leaf-bud is formed annually. A rhizome sometimes assumes an erect form 
as in Scabiosa succisa, in which the so-called prcemorse (proemorms, 
bitten at the end) root is In reality a rhizome, with the lower end 
decaying. The erect rhizome of Cicuta virosa shows hollow internodes, 
separated by partitions. 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 creeping underground stem, 
sending roots from one part and leaf-buds from another, as in couch 
grass, Oarex arenaria, and Scirpus lacustris (fig. 108). It is often 
called a creeping root, but is really a rhizome with narrow elongated 
internodes. A Tuber is a thickened stem or branch produced by 
the approximation of the nodes and the swelling of the internodes, 
as in the potato (fig. 109 t). The eyes of the potato are leaf-buds. 
Tubers are sometimes aerial, occupying the place of branches. 

Fig. 107. Portion of Bhizome, r, of Polygonatum multiflomm, Solomons Seal, forming 
buds and adventitious roots, a, A bud in the progress of development, t, A bud developed 
as a branch at the extremity of the,rhizome. cc. Cicatrices or scars, indicating the situa- 
tion of old branches which have decayed. 



48 



FORMS OF STEMS. 



The ordinary herbaceous stem of the potato, when cut into slips and 
planted, sometimes sends off branches from its base, which assume the 





Fig. 108. 



Fig. 109. 



form of tubers. These tubers occasionally become nodulated, or elon- 
gated, or curved in various ways. Arrow-root is derived from the 
scaly tubers of Maranta anmdinacea. In the Orchis the radicular 
bodies called tubercules, or by some tubers, 
belong to the root system (fig. 101). In the 
didymous (twin) tubers of Orchis mascula, 
we find at the end of the season one of 
them withered, while the other is vigorous, 
and bears a bud at its apex. The lowest 
leaf of this bud gives rise to another bud, 
and when the oldest tuber decays this 
new one enlarges, and next season be- 
comes the bud-tuber, while its parent pro- 
duces the flowering stem. A Corm is a 
solid underground 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. 110). The scales 
are modified leaves specially developed 
on subterraneous stems, and they may 
The corm occurs in Colchicum, Orocus, and 




Fig. 110. 

produce buds in their axils, 



Fig. 108. Soboles, or creeping subterranean stem, r, of Scirpus lacustris. /e, fe. Scales 
or modified leaves on the stem, p a. Aerial portion of the plant. 1 1, Level of the fearth. 
Fig. 109. Lower portion of a potato plant, s s. Level of earth, pa, pa, Aerial portion 
bearing leaves, t, Subterranean portion, showing stem-tubers. T, Tuber showing eyes or leaf- 
buda, covered by scales, 6, which are equivalent to leaves. Fig. 110. Corm or under- 
ground stem of Colchicum autumnale. r. Roots. /, Leaf, a'. Ascending axis of preceding 
year, withered, a", Axis of the year, a'". Point where axis of next year would be formed. 



STRUOTUKE OF STEMS. 49 

Gladiolus. A Corm'is only of one year's duration, while a rhizome or 
root-stock consists of a string of annual growths, persistently con- 
nected. It is distinguished from a root by sending off buds annually 
in the form of small corms or thickened branches, either from the 
apex, as in Gladiolus, or from the side, as Colchicum (fig. 110 a"). 
These buds feed on the original corm a', and absorb it. In the 
Crocus, after flowering, may be seen the withered parent corm ; new 
corms, which are in reality the basis of the flowering axis, branching 
from the old corm ; and in the axil of the leaves of the flowering stem 
small buds ready for another season. In Colchicum autumnale 
(Meadow Safii-on), we find in autumn the flowering stem united to 
the side of the corm at its base. The two lowest sheaths of the 
flowering stem produce buds in their axils. The flowering stem 
withers, and the internodes between the two buds form a new corm, 
while the old one decays. 

Internal Structure of Stems, 

Stems, according to their structure, have been divided into three 
classes : — Exogenous (s^ti), outward, and yivmiiv, to produce), when the 
bundles of vascular tissue are produced regularly in succession exter- 
nally, and go on increasing indefinitely in an outward direction. 
Endogenous (hdov, within), when the bundles of vascular tissue are 
produced in definite bundles and converge towards the interior, addi- 
tions being thus in the first instance made internally. Acrogenous 
{&x^og, summit), when the vascular bundles are developed at the same 
time and not in succession, the- addition to the stem- depending on the 
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 (dig, twice, and xorvXr^uv, a seed-lobe); plants 
with endogenous stems have only one cotyledon, and are called Mono- 
cotyledonous (//^ovog, one) ; while plants with acrogenous stems have no 
cotyledons, and are called Acotyledonous (a, privative). The terms 
connected with the embryo- -will. be afterwards fully explained. 

Exogenous or Dicotyledonous Stem. 

The Exogenous or Dicotyledonous stem characterises the trees of 
this country. It consists of a cellular and vascular system ; the for- 
mer 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 

E 



50 



EXOGENOUS OE DICOTYLEDONOUS STEM. 




Fig. 112. 



appearance of wedges (fig. Ill w w) arranged in a circle round a cen- 
tral cellular mass oi pith (fig 112 p), ■which is connected to the outer 
part or hark by means of cellular processes called medullary rays (fig. 

1 1 1 r r r). At first the cellu- 
lar portion is large, — the 
pith, bark, and rays occu- 
pying a large portion of the 
stem ; but by degrees new 
vascular bundles are formed, 
which are deposited be- 
tween the previous ones 
(fig. 112 nnn). By this 
means the pith is more cir- 
cumscribed, 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. 

The stems of trees and shrubs in their young state exhibit an 
arrangement similar to that represented as occurring in the herbaceous 
stem (fig. 112), 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 suc- 
culent 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. 113 represents a horizon- 
tal or transverse section of the 
upper part of a young branch of 
Acer campestre. In the centre, 
m, is the pith, very large at this 
period of growth, and occupying 

Fig. 111. Young Dicotyledonous or Exogenous stem, w w, Vascular bundles in the 
form of wedges, jj, Kth. r- r r, Medullary rays. Fig. 112. Same stem further advanced; 
the letters as in flg. Ill, nnn. New vascular wedges interposed between those first 
formed. Pig. 113. Horizontal section of young stem of Acer campestre, magnified twenty- 
six diameters, m, Pith, e m, e m, Medullaiy sheath. fb,fb, woody bundles. « p. Pitted 
vessels, r m, Medullaiy rays, c, Cambium or zone of tissue between the xylem or wood 
portion, and phloem or bark portion, fc, Fibres of Endophloeum. v I, Latioiferous vessels, 
e c. Cellular envelope, Mesophtaum. p, Corky envelope, Epiphlceum. e p. Epidermis. 




Fig. 113. 



EXOGENOUS OE DICOTYLEDONOUS STEM. 



51 



at least one-half of the whole diameter,its cells diminishing in size as they 
approach 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 circumference, dividing the vascular circle 
into numerous compact segments, which consist of woody vessels, / b, 
and of pitted vessels, vp. These are surrounded by a moist layer of 
greenish cellular tissue, c, called the cambium layer, which is covered 
by three layers of bark, /c, e c, and p, with laticiferous vessels, v I,' the 
, whole being enclosed by the epidermis, e p. On making a thia vertical 
section of a portion of the same branch, and viewing it under the 
microscope, the parts composing the different portions become more 
obvious (fig. 114). The pith, m, with its hexagonal cells decreasing 







Fig. 114. 



Fig. 115. , 



in size outwards, surrounded by a narrow fibro-vascular zone, the 
meduMry sheath, consisting chiefly of spiral vessels, t ; the medullary 
ray, rm; the vascular zone, consisting of pitted vessels, v p, of large 
diameter, and forming the large round apertures seen in a transverse 
section ; the fibres of the wood, / I, with their thick walls and smaller 
apertures ; the inner bark or liber, / 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 epidermis, e p, having hairs scattered over its surface. 
A transverse section of a bundle of vascular tissue of a dicotyledonous 
plant, magnified 230 times, is represented in fig. 115. The arrow 
indicates the direction from within outwards. We here perceive the 
vascular bundle surrounded by a laxge-celled tissue (a db f). The 

Fig. 114. Vertical section of the same stem more highly magnified, t. Tracheae or spiral 
vessels. /!, /!j /i, Woody fibres. The other letters as in fig. 113. Fig. 115. Tra-nsveise 
section of a bundle of vascular tissue of a Diootyledonons plant, a d, Epidermis, t. Large- 
celled tissue of bark, e, Fibres of bast layer, d, d'. Woody layers and laticiferous vessels 
of Inner bark, d". Cambium cells, g g, and h h, Large pitted vessels, i, Woody tubes. 
/, Large cells. 



52 



EXOGENOUS OB UICOTYLEDONOtTS STEM. 



quadrangular cpUs, a d, form the epidermis, to which succeeds the 
cellular tissue of the bark, b. The latter surrounds a bundle of bast 
(phloem) fibres, c, and ligneous layers of inner bark, with laticiferous 
vessels, d d', which are separated, in the direction towards the interior, 
by a layer of cambium cells, d", from the proper vascular tissue (xylem), 
consisting of pitted vessels with thick walls, g g, and others with thin 
walls, h h, mixed with woody tubes, e. 

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 




Fig. 116 St*. 



Fig. 116 ter. 



of porous and woody tissue, and a zone of fibrous bark, the medullary 
rays being at the same time continued from within outwards. This is 
represented in fig. 116, where 1, 1 indicates the section of the stem 
of the first year's growth (the letters referring to the same parts as in 
figs. 114, 115); and 2 shows the interposed zones of the second 
year, by which the diameter of the stem is increased. 

The Pith, or the central part of a dicotyledonous stem, is com- 

Fig. 116. Vertical Bection of a brancli of common maple (^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. 114 and 115. Fig. 116 &w. 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. 116 ter. A portion of a pitted vessel from the gourd, magnified. 



EXOGENOUS STEM — PITH. 53 

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. 11 1, 11 2 y). 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, Jessamine, and Cecropia peltata ; it is 
then called discoid or disciform (diaxo.^, a disc, from the circular parti- 
tions). At other times, by the rapid growth of the outer part of the 
stem, the 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 vessels occur in pith, as in Elder, Pitcher-plant, and Ferula ; 
and occasionally its cells are marked by pores indicating the formation 
of secondary deposits. The exteat of pith varies in different plants, 
and in difierent parts of the same plant. In Ebony it is small, while 
in the Elder it is large. In the Shola plant, jEschynomene aspera, 
the interior of the stem is almost entirely composed of cellular tissue 
or pith ; from this a kind of rice-paper is made, and light hats. The 
same kind of tissue occurs in the Papyrus of the Nile. Large pith is 
also seen in Fatsia papyrifera, or Chinese rice-paper plant. When the 
woody circle of the first year is completed, the pith remains stationary 
as regards its size, retaining more or less its dimensions, even in old 
trunks, and never becoming obliterated. 

The Medtjllary Sheath is the fibro-vascular layer immediately 
surrounding the pith. It forms the inner layer of the vascular bundle 
of the first year (fig. 114 t), 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. 

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 pitted and ligneous vessels. In subsequent 
years the layer of spiral vessels is not repeated, but concentric zones 
of pitted vessels (fig. 116 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 (x-jxXog, a circle), 
in consequence of exhibiting concentric circles in their stems. On a 



54 



EXOGENOUS STEM — WOOD. 




Fig. 117. 



transverse section, each zone or circle is usually seen to be separated 
from that next to it by a well-marked line of demarcation. This liae, 
as in the Oak (figs. 117, 118), and in the Ash, is indicated by holes 
which are the openings of large pitted 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 
>pitted 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. 49), without any large pit- 
ted vessels, the line of separation is 
marked by the pleurenchyma 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, although often 
inconspicuous, are still visible ; the dry season, during which many 
of them lose their leaves, being their season of repose. 

The woody layers vary 
in their texture at dif- 
ferent periods. At first 
the vessels are pervious 
and full of fluid, but by 
degrees thickening layers 
are deposited which con- 
tract their canal, and 
sometimes obliterate it. 
The first-formed layers 
are those which soonest 
become thus altered. In 

Pig. 117. Horizontal section of the stem of an oak eiglit years old. T>, Wood, showing 
concentric circles or zones, separated by points which correspond to the opening of the 
large pitted 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. 118. 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 m'", r m"", which vary in'extent according to the period when they originated, m. Pith, e c, 
Cellular envelope, p. Corky envelope, which is highly developed, and exhibits several layers. 




Fig. 118. 



EXOGENOUS STEM — ^WOOD. 55 

old trees, there is a marked division between the central Heart-wood 
or Duramen (durus, hard), and the external Sap-wood or Albvjmvm 
(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, while the alburnum is pale ; in the 
Beech, the heart-wood is 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 Poplar, no change in colour takes place ; 
this is also the case in the Chestnut' and Bombax. The relative pro- 
portion of alburnum and duramen varies 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 2|- 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 Lom- 
bardy Poplar, in seven years ; Robinia, Oak, Scotch Eir, Weymouth 
Pine, Silver Fir, were decayed to the depth of half an inch in seven 
years ; while Larch, common Juniper, Virginian Juniper, and Arbor 
Vitse, were uninjured at the end of that time. 

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 6ases, 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. 117 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 
interruption 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 in 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 diameter of the tree. When by the action of severe 
frost, or 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 ipjury may be ascertained by counting the 



56 EXOGENOUS STEM — CAMBlUM. 

number of layers whicli intervene between the imperfectly formed 
circle and the bark. In 1800, a Juniper was cut down in the forest 
of Fontainbleau, 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 in after years 
when a tree is cut down ; so also wires or nails driven into the wood. 
As the same development of woody layers takes place in the branches 
as in the stem of an Exogenous tree, the time when a branch was first 
given off may be computed by countipg the circles on the stem and 
branch respectively. If there are fifty circles, for instance, in the trunk, 
thirty 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. 

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 their fuller 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. 

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 Gamhium 
(cambio, I change, from the alterations that take place in it) has been 
given (figs. 113, 114 c). In this substance cells are formed, called 
cambium 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 thick- 
' ened pleurenchyma. 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, and may be regarded as constituting the active former 
tive tissue of Dicotyledonous stems. It constitutes the thickening zone, 
by means of which the stem is enlarged — the cambium cells situated 
most internally being subservient to the purposes of the wood forma- 
tion, while the external ones give origin to the new bark. According 
to Schacht this is the proper nourishing tissue. 

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 



EXOGENOUS STEM — BAEK. 



57 



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 Epiphloium (Ivl, upon, on the outside, and 
pXo/Js, bark), and the cellular envelope, or Mesophlaum {//I'ssog, middle) ; 
while the vasular system forms the internal portion called Liber, or 
Endophlceum (ivSov, within). 

The inner bark, or endophlceum (fig. 116 / c), is composed of 
elongated pleurenchyma niixed with laticiferous vessels and some 
cellular tissue. It is separated from the wood by the cambium layer. 
The pleurenchymatous 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 Antiaris saccidora (the sack tree of 
Ooorg) are used to form mats, cordage, and bags ; 
and the toughness of the fibres 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, 
from its uses, called the bast-layer. 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 network, in the interstices of which the 
medullary rays are seen. The fibres of the 
lace-bark tree {Lagetta lintearia) are similar. 
In figure 119 is represented the bark of Daphne 
Laureola ; / indicating the woody fibres of 
liber, and r the medullary rays. The en- 
dophlceum increases 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 Viher may be derived from the fact of the inner bark being used 
for writing upon. 

The cellular envelope, or mesophloeam, lies immediately on the 
outside' of the liber. It consists of polyhedral, often prismatical cells 
(fig. 116 e c), usually having chlorophyll, or green colouring matter, 
in their interior, but sometimes being colourless, and containing 
raphides. They are distinguished from those of the epiphloeum by 
their form and direction, by their thicker walls, their green colour, 

Fig. 119. Network formed by liber of Daphne Laureola. //, Fibrous bundles, r r. 
Medullary rays. 




Pig. 119. 



58 EXOGENOUS STEM — BAEK. 

and the intercellular spaces which occur among them. This covering 
is usually less developed than the outer suherous layer, but sometimes, as 
in the Larch and common Fir, it becomes very thick, and separates like 
the epiphloeum. In the cellular envelope latioiferous vessels occur. 

The Epiphloeum is the outer covering of the bark, consisting of 
cells which usually assume a cubical or flattened tabular form (fig. 
116 Us, p). The cells have no chlorophyll in their interior, are 
placed close together, and are elongated in a horizontal direction ; and 
thus they are distinguished from the cells of mesophloeum. In the 
progress of growth they become often of a brown colour. This cover- 
ing 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 well seen in Quercus Saber, the Cork-oak (fig. 118 y) ; hence 
the name suierous, 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 tabular at another, thus giving rise to the appearance 
of separate layers. After a certain period (sometimes eight or nine 
years), the corky portion becomes inactive, and is thrown off in the form 
of thickish plates, leaving a layer of tabular cells or periderm below. 
On the exterior of the epiphloeum is situated the epidermis, which 
has already been described. 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. 

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 
separation 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 times they 
are separated by rings of cellular tissue, and thus remain conspicuous. 
In the case of the cellularjportions of the bark there are also succes- 
sive additions, sometimes to a great exent, but they do not usually 
fehibit any marked divisions. 

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 condensed, 
the fibres are often separated (fig. 119) so as to form meshes (as in the 
lace-bark), its epidermis is thrown off, and the epiphloeum is either de- 
tached 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 disten- 
sible, 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. 



EXOGENOUS STEM — KAYS. 59 

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 epi- 
phloeum 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 
pushes 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 {''rigi, around, and bi^/ia, skin) has been given by 
Mohl. 

From the mode ip which the outer layers of bark separate, it fol- 
lows that inscriptions made on them, and not extending to the wood, 
gradually fall off and disappear. A nail driven into these layers ulti- 
mately 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. Thiis a spiral groove may 
be formed on the surface of the stem by the compression exercised by 
a twining plant, such as honeysuckle.- From what has been stated 
relative to the changes which take place in the bark, it will be under- 
stood that it is often dilEcult to count its annual, layers, so as to esti- 
mate the age of the tree by means of them. This may, however, be 
done in some cases, as shown at fig. 117, where there are eight layers 
of bark, e, corresponding to eight woody layers, h. 

Medullary Kays oe Plates. — While the bark and pith 
become gradually separated by the intervention of vascular bundles, 
the connection between them is kept up by means of processes called 
medullary rays (figs. Ill, 112 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 com- 
pressed and flattened so as to assume a muriform appearance (fig. 
120 TO r). At first they occupy a large space (fig. Ill r); but as 
the vascular bundles increase they become more and more narrow, 
forming thin laminae or plates, which separate the woody layers. On 
making a transverse or horizontal section of a woody stem, the medul- 
lary rays present the aspect of narrow lines running from the centre 
to the circumference (figs. 117, 118 r m); and in making a vertical 
section of a similar stem through one of the rays, the appearance 
represented in fig. 120 will be observed, where a meduUary ray, m r, 
composed of flattened muriform cells, passes from the pith, p, to the 
cellular envelope, e e, crossing the tracheae of the medullary sheath, t, 
the ligneous tissue, I, the pitted vessels of the wood, h, and the fibres 
of the liber, c /. The laminae do not by any means preserve an unin- 
terrupted course from the apex to the base of the tree. They are 



60 



ANOMALOUS EXOGENOUS STEMS. 



broken up by the intervention of woody fibres, as seen in a vertical 
section of a woody stem (fig. 121), tangentially to the medullary 
rays m )•, m r, m r, which are separated by similar interlacing fibres, 
I I. The medullary rays are usually continuous from the pith to the 










1 1 'nt.r 

Pig. 121. 

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. 118, r ro," r m""). Medullary 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. 

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 some- 
times 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 similar kind annually, resembling in this respect the 
formation of woody bundles in the early growth of herbaceous plants 
(fig. 112). In the Pepper tribe, Aristolochiacese, and Menisper- 
maceae, these anomalous stems occur. In Gnetum (fig. 122), the 

Fig. 120. Vertical section of a one-year old iDranch of Acer campestre, highly magnified, 
and extending from the ^ith to the bark, parallel to the medullary rays, m r, A medullaiy 
ray or plate extending from the pith, p, to the bark, c e, crossing tracheaa, (, fibres of 
xylera or wood, I, pitted vessels, 6, and cortical fibres, cf. Fig. 121, Vertical section of the 
same branch at right angles to medullary rays. 1 1, fibres of wood (xylem) which interlace, 
leaving spaces, m r, m r, m r, where the medullary rays pass. 



ANOMALOUS EXOGENOUS STEMS. 



61 



I 



vascular bundles, b b b b h, form zones, which are each the produce of 
several years' growth, and 

are separated by layers, ^ ^ ,a / ? ' !,. 

mill, which may be con- ,7 ^ ' 

sidered as representing dif- 

ferent zones of liber. 

In some of the Meni- 
spermum tribe, the sepa- 
rating layers are of a cellular 
and not of a fibrous nature. 
In Banisteria nigrescens 
(fig. 123), the young stem 
(1) presents a four-lobed 
surface ; the lobes become 
more evident (2) ; and ul- 




Fig. 122. 



timately (3) the stem is divided into a number of separate portions, the 
central one of which alone exhibits pith and medullary rays. The 
portions are separated by interposed cortical layers. 

Many of the Malpighiacese, Sapindaceae, and Bignoniacese of Brazil, 

exhibit stems in which the woody layers are arranged in a very irre- 

1 






Fig. 123. 



gular manner. In the stem of Calycanthus floridus, and of some 

Fig. 122. —Horizontal section of stem of Gnetnm. m. Pith, e m, Medullary sheath. 
& 6 6 6 6, Woody bundles forming seven concentric zones, each of which is the produce of 
several years. II I III, Fibres of liber forming interposed circles, equal in number to the 
woody zones. Fig. 123. Horizontal section of stem of Banisteria nigrescens at different 
ages. 1. Stem presenting four superficial lobes. 2. Six more marked lobes, with inter- 
mediate divisions. 3. The lobes separated by cellular tissue, the middle one alone having 
pith and medullary sheath. The dots indicate the orifices of pitted vessels. 



62 



ANOMALOUS EXOGENOUS STEMS. 



Brazilian Sapindaoese, such as Paullinia pinnata (fig. 124:), Serj^nia 
triternata and Selloviana, there is a centsal woody mass with from 
three to ten small secondary ones round it. Each of the masses con- 
tains true pith, derived either 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. 124). In these anomalous Sapindaoese, the central and 




Fig. 124. 





Fig. 126. Fig. 127. 

lateral woody masses are enclosed in a common bark, with a continuous 
layer of liber. Some have supposed that the lateral masses are un- 
developed branches united together under the bark ; but Treviranus 

Fig. 124. Homontal section of the stem of Paullinia pinnata, one of the Sapindaoese of 
Brazil, showing numerons 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. Hg. 126. 
Horizontal section of the stem of Bignonia capreolata, showing the crucial division of the 
woody layers. Fig. 126. Horizontal section of stem of Heteropterys anomala, one of the 
Braalian Malpighiacese, showing an irregularly lobed surface. The dots indicate porona 
vessels. Fig. 127. Fragment of a stem of climbing species of Banisteria (B. scandens), 

showing the effects of compression. 



ANOMALOUS EXOGENOUS STEMS. 



G3 



considers them as connected witli the formation of leaves, and as 
depending on a peculiar tendency 
of the vascular bundles to be de- 
veloped independently of each 
other round several centres. 

In some Bignoniacese (fig. 
125), the layers of wood are di- 
ivided 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 Aspidosperma 
excelsum (Paddle- wood) of Guiana, 
and in Heteropterys anomala (fig. 
126), the stem assumes a peculiar 
lobed and sinuous aspect ; and in 
some woody climbing plants, pres- 
sure 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. 127). In Firs 
the wood is occasionally produced 
in an oblique in place of a per- 
pendicular 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 pa- 
rents. Occasionally the 
dicotyledonous stem, be- 
comes swollen at certain 
places, especially near the root, and thus exhibits a tuberous appear- 




Hg. 128. 



Fig. 128. Swollen stem of Irisli Tew (Taxus liaooata, va/r. striota). 



64 



ENDOGENOUS OE MONOCOTYLEDONOUS STEM. 



anoe, as shown in fig. 128, which represents an Irish yew with an 
anomalous stem. This peculiar appearance is said to be liable to 
occur in coniferous plants grown from cuttings. A Sequoia (WeUing- 
tonia) gigantea is mentioned in which a tuberous mass was produced 1 
foot 6 inches in circumference, on a plant grown from a cutting, the 
plant being only 3 feet in height, with a stem 2^ inches in circum- 
ference. 




Fig. 129. 



Endogenous or Monocotyledonous Stem. 

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 between pith, wood, or bark. There are no medullary rays, 
nor concentric circles (fig. 129). . 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, increasing in 
number towards the circumference. The central 
cellular mass has no medullary sheath. In 
some cases its cells are ruptured, and disappear 
during the progress of growth, leaving a hollow 
cavity (fig. 130) ; but in general it remains per- 
manent, and is gradually encroached upon by 
the development 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 dT progressive manner. 
These bundles may be considered as representing 
the vascular wedges, produced during the first 
year of an exogenous stem's growth (fig. 111). 
They consist of woody vessels enclosing some 
cellular tissue between them, with spiral and 
pitted vessels. The outer part of the stem is not formed by a sepa- 
rable 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 intervention of medullary rays. 

On making a transverse section of a young endogenous stem 
(fig. 131), there is observed a mass of cells or utricles, u, of various 

Fig. 129. Part of the stem of Asparagus cut transversely, showing the vessels as points 
distributed through the cellular tissue. I, Leaf in the form of a scale. Fig. 130. Trans- 
verse section of stem of Phragmites communis, or common reed. Tlie cellular tissue in the 
centre has disappeared, leaving a iistular or hoUow 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. 




Fig 130. 



ENDOGENOUS OR MONOCOTYLEDONOUS STEM. 



65 



sizes, often small in the vicinity of tlie vascular bundles, spiral 
vessels or tracheae, t, large pitted vessels, v p, laticiferous vessels, I, 
and bast fibres, /, resembling those of liber, thickened by internal 
deposits. A similar section of a farther advanced endogenous stem, 
as of a Palm (fig. 132), 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 
aggregated, forming a darkish zone, b, and are succeeded at the cir- 
cumference by a paler circle of less compact vessels, I, with some com- 
pressed cells, covered by an epidermis, e. The peripherical portion, I e, 
differs from tnie bark, in not being separable from the rest of the tissue. 
It has received the name of false bark, and consists of the epidermal 







v/i _ 



i^^'^iSP^ 




-*^. 



j^ 



Fig. 131. Fig. 182. 

cells, 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 ^bstance resembling cork in many respects. 

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- 
ganium 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. 

It was at one time supposed that the woody portion of these 

Fig. 131. Horizontal section of a vascular bundle from tlie stem of a Palm {Corypha 
frlgida). t, Trachese, or spiral vessels, v p, Large pitted vessels, u. Cells or utricles of 
various kinds surrounding the vessels, and foi-ming the parenchyma, I, Laticiferous 
vessels. /, Fibres analogous to those of liber, tihickened by concentric deposits. Fig. 182. 
Transverse section of paxt of the stem of a Palm (As^ocarywn Murumura). m. Central or 
meduUary portion, in which the woody bundles are distant and' scattered. 6, External 
woody portion, where the fibres are numerous and densely aggregated, so as to form a dark 
zone. I, Paler circle of more slender and less compact fibres, which may be considered 
as analogous to liber, e. Cellular epidermal portion. 

E 



66 



ENDOGENOUS OR MONOCOTYLEDONOUS STEM. 



K 



\ 



(/ 



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. 133, 

1 : hence the term Endogenous 
(eVSok, within, and yiivdnv, to pro- 
duce), meaning internal growth. 
But Mohl has shown that this 
is not strictly correct. For 
although the fibres connected 
with the leaves, in the first in- 
stance, are directed towards the 
centre, and are therefore always 
internal to those previously 
formed, yet, when they are traced 
downwards, they are found not 
to continue in a parallel direc- 
tion, but to arch outwards, so as 
ultimately to reach the circum- 
ference. Hence, the newly-form- 
ed 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, simUar 
to what is represented iu Fig. 
133, 2, where the four vascular 
bundles, abed, are first direct- 
ed towards the centre, and then 
curve outwards towards the cir- 
cumference, so that those last 
formed ultimately become ex- 
ternal. The term Endogenous 
wUl, therefore, only apply strict- 
ly to the fibres at the early part 
of their course. Of late years, 
the terms Endogenous and Exo- 



Kg. 133. 



genous have been discarded by many writers, the terms Mono- 
cotyledonous and Dicotyledonous being substituted. The .true dis- 
tinction between Exogenous and Endogenous stems is, that in the 
former the woody or vascular bundles increase indefinitely at their 

Fig. 133. DiagraniB illustrating the arrangement of four pairs of vascular bundles (a a, 
hb, cc, d d), in endogenous stems. 1. According to the old idea of internal development 
throughout the stem. 2. According to the view of Mohl, -who has shown that the flbres 
interlace, and that those which are at first internal become external, lower down. 



ENDOGENOUS OE MONOCOTYLEDONOUS STEM. 67 

periphery, while in the latter they are arrested in their transverse 
growth at a definite epoch. The investing bark of the former permits 
an unlimited extension of woody growth beneath it ; the fibrous cor- 
tical layer of the latter, by maintaining an intimate union with the 
subjacent tissue, prevents unlimited increase in diameter. Hence we 
find that true endogenous stems do not attain the enormous diameter 
exhibited by some exogenous trees, such as Sequoia (Wellingtonia) 
gigantea and the Baobab, — the former of which has been measured 
116 feet in circumference. 

The composition of the vascular bundles, in different parts of 
their course, varies. Thus, at the upper part, tracing them from 
the leaves towards the centre, they contain spiral vessels, pitted vessels 
with some cellular tissue, a few laticiferous vessels, and woody fibres 
resembling those of liber (fig. 131). As we descend, the spiral vessels 
disappear, then the pitted vessels; and when the bundles have reached 
the periphery, and have become incorporated with it, nothing but 
fibrous tissue, or pleurenchyma, remains, forming a complicated ana- 
stomosis or network. Thus, at the commencement, the bundles are 
large, but as they descend they usually become more and more atten- 
uated. 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 disten- 
sion takes place occasionally at the base of the stem, as in Euterpe 
montana. 

There are many herbaceous plants in this country, as Lilies, 
Grasses, etc., 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 examples. In them the stem forms a cylinder of nearly uniform 
diameter throughout. The leaves are produced from a single terminal 
and central bud, called a PhyUophor or Phyllogen {iphWov, a leaf, and 
(po^iTv to bear, and yivvaen, to produce). Connected with the leaves 
are the vascular bundles, and the bases of the leaves remain attached 
to the outer part of the stem, surrounded by the mattuUa or reticulum. 
While the leaves produced by one bud decay, another bud is de- 
veloped in the centre. As the definite vascular bundles are produced, 
the stem acquires increased thickness, but it is arrested in its trans- 
verse diameter at a certain epoch. The bundles, although developed 
progressively, do not multiply indefinitely; and thus a Palm-stem 
seldom becomes of great diameter. 

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 firmness it resists all further distension, and frequently be- 



68 



ENDOGENOUS OK MONOCOTYLEDONOUS STEM, 



comes so hard as to witlistajid 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 bundles of woody 
fibres and vessels indefinitely, and the formation of a separable bark 
which can be distended ; but in the endogenous stem there is no such 
provision. Hence, when the first formed or lowest part of the stem 
has increased to a certain amount, its progress is stopped by the hard 
indistensible outer fibrous covering ; and the same thing takes place 
successively in the higher parts of the stem, till at length all have ac- 
quired a comparatively uniform size, as is seen in the coco-nut palm 
(fig. 134, 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. 

The growth of endogenous stems may be said to resemble an 
^ upward growth of an Exogen by 

terminal buds only, for there 
is no cambium layer, and no 
peripherical increase. In Palms, 
whUe the terminal shoot is 
developed, there are no an- 
nual rings. The hardening of 
the stem depends, in all pro- 
bability, partly on internal 
changes in the bast fibres, 
similar to what takes place in 
the heart-wood of Exogens. 
Occasionally, at the upper part 
of a palm-stem, there is an ap- 
pearance of zones, but it does 
not continue throughout the 
stem. From the absence of 
concentric circles, the age of a 
Palm cannot be estimated in 
the same way as that of an exo- 
genous tree. The elongation, 
however, of each species of 
—-^ «.;- Palm is pretty regular, and by 

-■- --i:^^ j^ some idea may be formed 

^'s- 134- of its age. The rings on the 

stem do not usually indicate yearly growth. 

Fig. 134. Two endogenous or monoeotyledonous trees, belonging to different fami- 
lies. 1. Cocos nucifera, or coco-nut, belonging to the Palm family. 2. Fandanus odora- 
tissimus, or screw-pine, belonging to Pandanacese. The first has a simple unbranohed 
stem, with a cluster of leaves at the summit ; the second has a branched stem, with nume- 
rous leafy clusters, and peculiar aerial roots, proceeding from different parts of the stem. 
Two Sgoies are given to indicate the height of the trees. 




ENDOGENOUS OR MONOCOTYLEDONOUS STEM. 69 

In Palms, there is in general 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 Doum palm of Egypt {Hy- 
phcene thebaica), the stem divides in a forked or dichotomous (5/;^a, 
two ways, and ri/jiinn, to cut) manner. Gardner, in his travels in 
Brazil, noticed a Palm in which the central bud having been de- 
stroyed, two side ones had been produced, so as to give it a forked 
appearance. Other plants with endogenous stems also produce lateral 
buds. In fig. 134, 2, there is a representation of such a stem, iu the 
case of the Screw-pine (Pandanus odoratissimus), and examples are 
seen in Grasses as the Bamboo, in Asparagus, Oordyline, and 
Dracaena. In these cases the stem is more or less tapering, Kke 
that of Exogens, and the destruction of the terminal bud is not neces- 
sarily followed by the death of the plant. The development of 
lateral buds is often accompanied by an increased diameter of the stem. 
The famous Dracaena Draco, or Dragon tree of Orotava, in the Canary 
Islands, had 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 endogenous 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 same way as the removal of the outer 
part of the wood would destroy an exogenous stem. Professor Piazzi 
Smyth remarked that this famous Dragon tree was covered on the out- 
side with root-like fibres, which descended from the branches to the 
ground. The tree is now destroyed. The branches in such plants are 
formed on the same principle as the stems ; but their fibres do not 
proceed to the centre of the stem, but extend outside the pre-existing 
bundles, between them and the outer false bark (fig. 132, I e), and 
thus give rise to lateral increase. In Grasses, the stem or culm is 
usually hollow or fistular (fig. 130), in consequence of the outer part, 
by its rapid increase, causing the rupture and ultimate disappearance 
of the internal cellular portion. The fibres in some Grasses cross 
from one side to the other, forming partitions, as in Bamboo, which 
add much to the strength of the stem. 

When the intemodes of the caudex of a Palm are not much 
elongated, the scars of the leaves are seen forming spirals on the stem, 
as in the coco-nut and date. In Xanthorrhoea HastUe the same 
arrangement is observed. In Palms, such as species of Chamsedorea, 
the intemodes are much lengthened, and rings are seen on the stem 
at distant intervals, showing thickened node-like joints. Some 
Palm stems, as those of Calamus Kudentum, the common cane, are 
very thin and slender. 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 



70 ACEOGENOUS OE ACOTTLEDONOUS STEM. 

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 in part below ground in the form 
of bulbs, as in Lilies, Tulips, and Hyacinths ; or as corms, in Ool- 
chicum, Crocus, Gladiolus, and Arum. 

In some instances the aerial stem has the usual endogenous struc- 
ture, while in the underground stem the vascular bundles are in the 
form of -wedges, with cellular tissue in the centre, thus resembling 
Exogens. This structure has been remarked in the Smilax or Sarsar 
parilla family. Lindley calls these plants Dictyogms (dlxruov, a net), 
from their netted leaves, by which they differ from most Endogens. 
Henfrey holds that the ring of woody fibres in these plants, as seen 
in Tamus and Smilax, is an alteration of the parenchymatous cells 
of the periphery, and is not produced 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 



Acrogenous or Acoiyledonous Stem. 

This stem, in its general external aspect, resembles that of 
Endogens. It is unbranched, usually of small, nearly uniform 
diameter, and produces leaves (fronds) 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, 
and it often attains the height of 120 feet (fig. 135). A transverse 
section of the stem (fig. 136) exhibits an irregular circle of vascular 
bundles, composed of masses, z I, of various forms and sizes, situated 
near the circumference ; the centre, m, being formed of cellular tissue, 
and often becoming hoUow. 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, and marked with the scars of the 
fronds. 

The vascular bundles are formed simultaneously, and not pro- 
gressively, as in the stems already noticed; and additions are 
made in an upward direction. The stem is formed by additions 
to the summit, and by the elongation of vessels already formed; 
hence the name Acrogenous (oJzgos, summit). The plants are also 
called Acrohrya {axgog, summit, and /3gii£/i/ to germinate). The 
vascular system is of greater density than the rest of the tissue, and 
is usually distinguished by the dark colour of the pleurenchyma or 
prosenchyma (fig. 136 /), which surrounds the paler vessels in the 
centre (fig. 136 v v). There is a continuous woody cylinder in the 
Fern stem. The vascular bundles, however, do not follow a straight 
course, but unite and separate, leaving spaces between them, similar 



AOKOGENOUS OE AOOTYLEDONOUS STEM. 



71 



to the meshes seen in the liber of Exogens (fig. 119). In these spaces 
vessels of communication pass between the outer or cortical, and the 
inner or central portions of the stem. 
Prom the point where the vascular 
bundles unite or anastomose, other 
vessels are given off to supply the 
fronds, ajad some pass into the ad- 
ventitious roots, which are often pro- 
duced abundantly on the outside of the 
stipe (fig. 135 ra). 

The trunk of the Acrogen dififersfrom 
that of the Exogen, by having its 




Fig, 136. 

« 

vascular cylinder penetrated by only 
one kind of horizontal tissue, namely, 
the vascular bundles belonging to the 
fronds ; while the Exogen has in addi- 
tion another horizontal tissue, namely, 
meduUary rays, composed of cellular 
tissue, and performing a totally difierent 
function. 

The acrogenous stem in the young 
state is solid, but it frequently be- 
comes hollow in the progress of. Kg. 135. 
growth, by the rupture and absorp- 

Fig. 135. Tree fem {AlsopJiUa perroteticma), of the East Indies. Stem or^tipe is 
cylindrical, unbranched, and presents at its base, r a, a conical enlargement, formed by a 
mass of adventitious roots. The leaves are terminal, and in the young state are rolled up 
in a circinate manner. Fig. 136. Transverse section of the stem of a Tree Um(Cyatliea). 
m. Cellular tissue, corresponding to pith, occupying the central part, s I, Vascular circle 
composed of numerous irregularly-formed masses. /, Darlc-coloured woody or prosenchy- 
matous 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, communicating with the central portion, e. Hard epidermal envelope, occupying the 
place of the bark. 




72 ACEOGENOUS OR ACOTYLEDONOUS STEM. 

tion 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 
manner as those of the stem, with which they are continuous. The 
vascular system of ferns consists chiefly of scalariform vessels (fig. 64), 
mixed with annular (fig. 62), woody and pitted vessels (fig. 116 ter). 
There are no true tracheae with fibres which can be unrolled. In the 
stems of Lycopodiacese closed tracheae or ducts occur ; and in Equi- 
setaceae the rings of the annular vessels are closely united. 

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. 137), by the formation of two buds at 
its growing point. This, however, is an actual 
division of the stem itself, and differs from the 
usual branching 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, with- 
out giving origin to a conspicuous trunk. In the 
II % f /I common Brake (Pteris aquilina), the arrange- 

i I it:"' //' ment of the vascular system may be seen by 

{* — LS—i/) making a transverse section of the underground 

ii rn. ^'i stem. The plant has received its name aj-MiKsM, 

'^' ' from a supposed resemblance to a spread eagle, 

presented by the vessels when thus cut across. 

The axis of Lycopodiacese or Club-mosses (fig. 138) exhibits a 
vascular bundle of scalariform vessels and closed spirals. The bundle 
is developed in an upward direction as the stem grows, each inter- 
node having its permanent bundle. Vessels pass from the stem to 
the leaves. 

In Equiseta or Horse-tails (fig. 139) there is a circle of vascular 
bundles towards the exterior of the aerial stem ; this vascular ring is 
covered by cortical cells of difierent kinds. The Equiseta have 
underground stems, from which the aerial branches are sent up 
annually. In some species the aerial stem attains a height of 
upwards of 30 feet. The largest species in Britain (Equisetum 
maximum), may be seen 5 to 6 feet high, with a diameter of half- 
an-inch. The aerial stem of the plant consists of hollow internodes, 
each with a transverse diaphragm at the base, and a sheath at the 

Fig. 137. Vertical section of part of the forked stem or stipe of Alsophila perrotetiana. 
m. Cellular central portion. zl,zl, Vascular zone, consisting chiefly of woody ftl)res and 
scalariform vessels. The forking is caused by an actual division of the stipe. 




ACEOGENOUS OR ACOTYLEDONOUS STEM. 



73 



upper end. The sheath of the lower internode embraces the base 
of the internode above it (fig. 139). The vascular bundles unite 
to form a hollow cylinder iu the stem. In fig. 140 is shown the 



Fig. 139. 



structure of a vascular bundle of Equisetum hyemale, with 
a hollow cavity or lacuna, I, round which are large annular and 
spiral vessels, I v, smaller vessels, s v, and peculiar cells, c v ; which, 

Fig. 138. Ly&ypodvum clavaty/m, a species of Club-moss, showing a branch, I, covered with 
mimite pointed leaves, from which proceeds a stalk bearing at its extremity two spikes, f^ 
consisting of modified leaves with fructification. Fig. 139. Fructification of a species of 
Horse-tail (Egmsetitm maaAmvm). The stalk is surrounded by a series of membranous 
sheaths, s s, which are fringed by numerous sharp processes or teeth. The fructification, 
/, is at the extremity of the shoot, in the form of a pyramidal mass of polygonal scales, 
bearing spores on their under surface. The fructification in some species is on the same 
branch with the leaves, while in others it is on a separate branch. 



74 



ACEOGENOUS OE AOOTYLEDONOUS STEM. 



by their union, and the partial absorption of their transverse walls, 
form what are called cribriform or sieve-like vessels (vasa propria), 
thickened bast cells (6 p), and bast fibres {b /). 




Fig. uo. 

In some Thallogens the thallus or frond is supported by a stalk, in 
which there are concentric parenchymatous circles, with divisions in 
the form of rays, but no vascular bundles. These appearances are 
presented by some large antarctic seaweeds (species of D'UrviUsea and 
Lessonia), and by some lichens, as Usnea. 

Fig. 140. Section of vascular bundle of stem of Bquisetum hyemale x 310. Lacuna 
or^a cavity, I ; parenchyma, a form of starch cells, p p ; large vessels, Iv ; smaU vessels, sv; 
bast cells, & p ; and bast fibres, b f; cribriform vessels, c v, formed by united cells, ■with a 
partial absorption of their transverse walls. — Trams. Boi. Soc. Edin. 



DEVELOPMENT AND FUNCTIONS Of STEM. 75 

There are thus three kinds of stems in the vegetable kingdom, 
which may be defined generally as follows : — 

1. Exogenous ov Dicotyledonous, having a separable bark ; distinct 
concentric circles, composed of progressive indefinite vascular bundles, 
increasing at their periphery, the density diminishing from the centre 
towards the circumference ; pith enclosed in a longitudinal canal or 
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 density diminishing from the 
circumference to the centre ; no distinct pith, no medullary sheath 
nor medullary rays, the cellular tissue being interposed between the 
vascular 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 

, medullary sheath nor medullary rays ; conspicuous scars left by the 
bases of the leaves, stem in some cases entirely cellular. 

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

The stem produces the buds from which branches, leaves, and flowers 
are developed ; it exposes these organs 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 450 feet. Some Palms 
attain a height of 200 feet. The trunks of the Baobab and Welling- 
tonia are sometimes 30 or 40 feet in diameter. 

IChe pith, in its early state (fig. 111^), 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 waUs of the cells 
which enter into its composition. The medullary sheath, which is the 
first formed vascular layer (fig. 113 em), 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. 
This is the part of a Dicotyledonous stem in which these vessels 
ordinarily occur. The medullary ra^/s (fig. 114 rm) preserve a com- 
munication 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. 114 c), or the cells be- 
tween the wood and bark, whose function is to aid m the formation of 



76 FORMATION OF WOOD. 

new wood. The lark (fig. 114/c, « c, ^) protects the tender wood, 
conveys the elaborated sap downwards from the leaves, and is the 
part in which many valuable products, such as gum, tannin, and bitter 
principles, are formed and deposited. The vascular bundles (fig. 114 
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 pitted vessels, as well as other kinds of fibro- vascular tissue; but 
in the fibres of the wood it ceases at a certain epoch, 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. 

Considerable difierences 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 formation. Some say that it is produced 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, are also present in the other forms of stems which have 
been described. In Monocotyledonous stems these cambium cells are 
situated in the centre of the bundles, and are concerned in the forma- 
tion of the vascular tissue surrounding them. In woody Acotyle- 
donous stems, as in Tree-ferns, these cells surround the vascular 
bundles. After a certain time the cambium zones in these stems be- 
come ligneous, and then the vascular bundles only grow at their ex- 
tremity by means of unchanged cambium cells. In both these kinds 
of stems the vascular bundles are limited, and the stems can only 
increase laterally by ramifying or dividing dichotomously (fig. 137). 

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 was supported by Petit-Thouars and Gaudichaud. These phy- 
siologists 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 ligneous fibres ; the cellular tissue being more especi- 
ally concerned in horizontal development. Every bud is thus, accord- 
ing to them, an embryo plant ficxed on the stem, sending leaves 
upwards, and roots downwards. The dicotyledonous embryo was 
supposed to be formed by two phytons (puroii, a plant) united, having 
each an ascending and descending system of vessels, while the monoco- 
tyledonous embryo was composed of one such phyton. In Palms, 
Dracaenas, and other Endogenous stems, the peculiar manner in which 
the fibres interlace (fig. 133, 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, 



FORMATION OF WOOD. TV 

■which burst through dififerent parts of the stem in Palms, Screw- 
pines (fig. 134, 2), the Banyan, and in the Fig tribe generally. 
In Vellozias and Tree Ferns, the surface of the stem is often covered 
■with thin roots, protruding at various parts, and becoming so incor- 
porated ■with the stem as to appear to be a part of it. In the Tree- 
Fern, represented in fig. 135, the lower part of the ^tem 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 the stem, and ■when 
portions of bark are removed, a swelling takes place above the parts 
■where the injury has been inflicted, thus apparently proving that the 
new matter is developed from above downwards. 

Gaudichaud endeavours to account for various anomalous forms of 
stems (figs. 123-126), by considering them as depending on the 
arrangement of the leaves, and on the mode in which the woody 
fibres are sent do'wn from them. Thus, the four secondary masses 
surrounding the central one in the stem of Galycanthus 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 orescentic 
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 
Sapindacese (fig. 124), 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, por- 
tions of which are enclosed by the vascular bundles in a centripetal 
manner, or from without, inwards. 

Treviranus states that the fibrous and vascular bundles descending 
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, gi^ving rise to ano- 
malous fasciculated stems. 

Gardner, from an examination of Brazilian Palms, adopts the 
vertical the(wy. It is, however, opposed by most vegetable physio- 
logists, who consider the development of the vascular bundles as 
proceeding from below upwards; in Dicotyledons, by peripherical 
production of woody and vascular 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 de- 
pending on the interstitial changes which take place afterwards in the 
woody fibres. 

All physiologists agree in believing that the formation of woody 



78 FORMATION OF WOOD. 

matter depends mainly on the functions of the leaves being car- 
ried on properly, and this can only be effected by exposure to air 
and light. The more vigorously the plant grows,, the better is the 
wood produced. Experiments made in the British dockyards 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 withstood a greater strain than a similar plank of 
slow-grown oak. The stumps of fir-trees sometimes exhibit a circle of 
woody tissue which has been formed after the trees have been cut 
down, and without the agency of leaves. In some cases the vigour of 
these stumps has been traced to the roots being grafted into those 
of adjoining trees bearing branches and leaves. 

In order that trees may grow well, and that timber may be pro- 
perly formed, great care should be taken in planting at proper dis- 
tances, 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, whOe 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 some of them are subsequently removed the remainder are 
easily blown over by the wind. In thick plantations it is only in 
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 subsequent 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 pro- 
perly planted and thinned, little pruning is required. 



STKUCTURE OF LEAVES. 



79 



Leaves and theie Appendages. 
Structure of Leaves. 

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. The points from which they arise are 
called nodes. In the early stages of their development they are 
undivided. The cellular papiUse, from which they originate, 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. 

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

The Vasctjlae 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 ex- 
ternal, become inferior. Thus, in the 
upper part of the leaf, which may re- 
present the woody layers, there are spiral 
vessels (fig. 141 t), annular, reticulated, 
and pitted vessels, ■;;, and ligneous fibres, 
/; whilst in the lower side, which may re- 
present the bark, there are laticiferous 
vessels and fibres, resembling those of 
liber, I. There are usually two layers 
of fibro-vasoular 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 re- 
moved, and the fibro-vascular tissue is 
left. The vascular system of the leaf 
is distributed through the cellular tissue 
in the form of simple or branching veins. 

The Epidekmis (fig. 142 e s, e i), composed of cells more or less 
compressed, has usually a difi'erent structure and aspect on the two 

Kg. 141. Bundle of fibro-vaseular tissue, passing from a 'branch, t, into a petiole, p. 
The vessels are first vertical, then nearly horizontal, but they continue to retain their 
relative position. Changes take place In the size of the cells at the articulation a. 1 1, 
Tracheae or spiral vessels in which the fibre can be unroUed. v v, Annular vessels. //, 
Fibres of wood. 1 1, Cortical fibres, or fibres of liber, or the inner bark. 




Fig. 141. 



80 



STEUCTTJEE OF LEAVES. 



Burfaces of the leaf. It is chiefly on the epidermis of the lower sur- 
face (fig. 143 e i), 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 detached. The 
upper epidermis (figs. 142 and 143 e s) is frequently smooth and 





Fig. 142. Pig. 143. 

shining, and sometimes becomes very hard and dense. Many tropical 
plants present on the upper surface of their leaves several layers of 
compressed epidermal cells. These appear to be essential for the pre- 
servation of moisture in the leaf. In leaves which float upon the sur- 
face of water, as those of the water-lily, the upper epidermis alone 
possesses stomata (p. 30). 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. 144 pp), and on examina- 
tion under the microscope, the stomata, 
s s, are seen communicating with 
colourless spaces, I 1 1, surrounded by 
green matter. 

The Parenchyma of the leaf is 
the cellular tissue surrounding the 
vessels, and enclosed within the epi- 
dermis (fig. 142 ps, pi.) It has 
sometimes received the names of Diachyma {bia,, in the midst, and 
;^u^a, tissue), or Mesophyllum (/ietrog, middle, and (pvM.ov, a leaf), 
or JDiploe {dmXon], a fold). It is formed of two distinct series 
of ceUs, each containing chlorophyll or green-coloured granules, but 

Fig. 142. Thin vertical section o£ the leaf of a Lily, highly niagnifled. e s. Epidermis of 
upper pagina or surface, e t, Epidermis of lower surface, p s, Parenchyma of upper por- 
tion of the leaf, composed of close vertically-placed cells, p i, Parenchyma of lower portion, 
composed of loose horizontal cells, m, Intercellular passages. 1 1, Laounaj. Fig. 143. 
Similar section of the leaf of Balsam. The letters denote the same parts as in flg. 142. 
s s, stomata. Fig. 144. Strip of the lower epidermis, e e, of the leaf of Balsam, showing a 
network formed by a portion of the parenchyma below, p p, being detached. The spaces of 
the net are lactmEC, III, often corresponding to stomata, s s. 




STRUCTURE OF I,EAVBS. 



81 



differing in form and arrangement. This may be seen on making a ver- 
tical section of a leaf, as in figs. 142 and 143. Below the epidermis of 
the upper side of the leaf there are one or two layers of oblong blmit 
cells, placed perpendicularly to the surface (fig. 142 p s), and applied 
so closely to each other as to leave only small intercellular' spaces (fig. 
142 m), 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. 142 p i), leaving cavities between them, 
I I, which often communicate with stomata (fig. 143 s s). On this 
account 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 
colourless. In some cases the cellular tissue is deficient at certain 
points, giving rise to distinct holes in the leaf, as in Monstera Adan- 
sonii ; such a leaf has been called pertuse (pertusus, bored through). 
In Victoria regia perforations in the leaf seem to be subservient to the 
purposes of nutrition, in permitting the gases collected beneath the 
large expanded leaf to escape, and thus allowing its under surface to be 
brought into immediate contact with the water. > 

SuBMEEGtED Leaves. — Leaves which are developed under water 
differ in structure from aerial leaves. They have usually no fibro- 





Fig. 145. 



Pig. 146. 



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. 145 p), but no 
true epidermis, and no stomata. Their internal structure consists of 
cells, disposed irregularly, and sometimes leaving spaces which are 
filled with air for the purpose of floating the leaf (fig. 145 I). When 
exposed to the air these leaves easily part with their moisture, and 
become shrivelled and dry. In the submerged leaves of Trapa and 

Fig. 145. Perpendicular section through a small portion of the submerged leaf of Pota- 
mogeton perfoliatua. p, Parenchyma. I, Lacuuse. Fig. 146. Fenestrate leaf composed 

of filamentous cells, with intervening spaces. 

G 



82 



STRUCTURE OF LEAVES. 




Callitriche, spiral vessels have been seen. In some instances there is 
only a network of filamentous-like cells formed (fig. 146), the spaces 
between which are not filled with parenchyma, giving a peculiar 
skeleton appearance to the leaf, as in Ouvirandra fenestralis (lat- 
tice plant). Such a leaf has been cal\e& fenestrate (fenestra, a window). 
A leaf, whether aerial or submerged, generally consists of a flat 
expanded portion (fig. 147 I), called the blade, limb, or lamina, of a 
narrower portion called the petiole (petiolus, a little foot or stalk) or 
stalk (fig. 147 p), and sometimes of a portion at the base of the 

petiole, which forms a sheath or vagina 
' ' (fig. 147?), or is developed in the form 
of leaflets, called stipules (fig. 205). 
The sheathing portion is sometimes in- 
corporated with the stem, and has been 
called tigellary (tige, Pr., a stem or 
stalk) by Gaudichaud. These portions 
are not always present. The sheath- 
ing or stipulary portion is frequently 
wanting, 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 
I sit). When sessile leaves embrace the stem, 
they are called amplexicaul {amplexor, I embrace, and caulis, a 
stem). The part of the leaf next the petiole or the axis is the 
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. In some cases leaves, or 
leaf-like petioles, are placed vertically, as in Australian Acacias, 
Eucalypti, etc. In other instances, as in Alstromeria, the leaf be- 
comes twisted in its course, so that what is superior at one part 
becomes inferior at another. 

The upper angle formed between the leaf and the stem is called 
its axil (axilla, armpit), and everything arising at that point is called 
axillary. It is there that leaf-buds (p. 108) 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 iu 
their after growth that articulations are formed. When leaves fall 

Fig. 147. Leaf of Polygonum Hydropiper, with a portion of the stem bearing it. I, Limb, 
lamina, or blade, p, Petiole or leaf-stalk, g, Sheath or vagina, embracing the stem, and 
terminated by a fringe, / 



Fig. 147. 
.s, from sedeo. 



STRUCTURE OF LEAVES. 



83 



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. 201), 
and a joint at times exists between the vS.ginal or stipulary portion 
and the petiole. 



Distribution of the Veins, or Venation of Leaves. 

The distribution of the veins has been called Venation, sometimes 
Nervation. In most leaves this can be easily traced, but in the case of 
succulent plants, as Hoya, Agave, Stonecrop, and Mesembryanthemum, 
the veins are obscure, and the leaves are said to be Hidden-veined (figs. 
186, 187). In the fronds of the lower tribes of plants, 
as seaweeds, and in submerged leaves, there ,are no true 
veins, but only condensations of elongated cellular 
tissue, and the term Veinless (avemia) 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. 148 nm) ; this gives off veins 
laterally {•primary veins) ns ns ns, which either end in a 





Kg. 149. 



Pig. 160. 



curvature within the margin, as in Lilac and Belladonna (fig. 148), or go 
directly to the edge of the leaf, as in Oak (fig. 149) and Chestnut. If 
they are curved, then external veins and marginal veinlets are inter- 
Fig. 148. Leaf of Belladonna, p, Petiole or leaf-stalk. Tjm, Midrib. 715 ns ns, Primary 
veins, ending in curvatures at their extremities. Fig. 149. Leaf of Oalc, pinnatifid or 

divided into lateral lobes ; feather-veined, the veins going directly to the margin. Fig. 
150. Leaf of Banana (Musa), showing the midrib, with the primary veins running parallel to 
each other in a transverse manner, and proceeding to the margin. No reticulation. Plant 
m onocotyledonous. 



84 STRUCTURE OF LEAVES. 

spersed 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 oases, as Sycamore 
and Cinnamon, in place of there being only a single central rib, there 
are several which diverge from the part where 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 com- 
plete network of vessels is produced. To such a distribution of veins 
the name of Reticulated or Netted venation has been applied. 

In the leaves of some plants there exists a central rib or midrib, 
with veins running nearly parallel to it from the base to the apex of 
the leaf, as in grasses (fig. 210) ; or with veins diverging in more or 
less parallel lines, as in Fan Palms ; or with veins coming 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 Plan- 
tain and Banana (fig. 150). In these cases the veins are often united 
by cross veinlets, which do not, however, form, an angular network. 
These are called Parallel-veined. 

Leaves may thus be divided into two great classes, according to 
their venation — Reticulated or netted-veined leaves, in which there is an 
angular network of vessels, as seen generally in dicotyledonous plants ; 
and Parallel-veined leaves, in which the vessels run in a straight or 
curved manner from base to apex, or from the midrib to the margin of 
the leaf, and in which, if there is a union, it is effected by transverse 
veins which do not form an angular network. This kind of leaf 
occurs commonly in monocotyledonous plants. In many acotyledonous 
plants there is no true vascular venation, but when it is present, there 
is frequently a tendency in the veins to divide in a forked (furcate) 
manner. This is seen in many Ferns, which have hence been called 
Fork-veined. Condensed cellular tissue forming false venation is seen 
in mosses and in seaweeds. 

Tabulae Aebanqbment of Venation. 

A. — Reticulated Venation. 

I. Unicostate {unus, one). A single rib or costa in the middle (midrib). 

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

«.. Veins ending in curvatures within the margin (fig. 148), and forming 
■what have been called true netted leaves (Lilac'). 

i. Veins going directly to the margin (fig. 149), tmAiormmgfeather-veinM 
leaves (Oak and Chestnut). 

2. Primary veins coming off along with the midrib (fig. 158) from the base 

of the leaf. 

II. Multicostate {mullus, many). More than one rib. In such cases there are 

frequently three (tricostate), as in fig. 177, or five (quinquecostate), 
as in fig. 173. Authors usually give to these leaves the general 
name of costaie or ribbed. 
1. Convergent. Ribs converging, running from base to apex in a curved 



FORMS OF SIMPLE LEA.VES. 



85 



maimer, as in Cinnamon and Melastoma (fig. 173). There is occa- 
sionally an obscure rib running close to the edge of the leaf, and 
called intramarginal, as in the Myrtle. 
2. Divergent. Ribs diverging or proceeding in a radiating manner (iig. 159). 
This is called radiating venation, and is seen in Sycamore, Vine, 
Geranium, Castor-oil plant (flg. 161). 

B. ^—Parallel Venation. — The term parallel is not strictly applicable, for the veins 

often proceed in a radiating manner, J)iit it is difficult to find a 
comprehensive term. This venation may be characterised as iiot 
reticulated. 

I. Veins proceeding transversely from midrib to margin, usually with convexity 

towards the midrib, as in Musa (fig. 150) and Canna. 

II. Veins proceeding longitudinally from base to apex. 

1. Veins more or less convergent (fig. 188), as in Iris, Lilies, Grasses (fig. 

210). 

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

C. — Furcate Venation {/urea, a fork). Veins dividing in a forked manner, as in 

the case of many Ferns. 



Forms of Leaves. 

Leaves are divided into simple and compound. The former have 
no articulation beyond the point of their insertion on the stem or 





Kg. 151. 



Fig. 162. 




Fig. 163. 



branch, and consist of a single blade, which, however, may be vari- 
ously divided (figs. 151, 152, 153, etc.) The latter have one or more 
articulations beyond the point of their insertion on the stem, and con- 
Fig. 161. Leaf of Ulmus efFusa. Betioulated venation ; primary veins going to the margin, 
which is serrated. Leaf unequal at the Ijase. Fig. 152. Pinnatifld leaf of Valeriana dioioa. 
Fig. 168. Bipinnatifld leaf of Papaver Ai-gemone. Feather-veined. 



86 



FOEMS OF SIMPLE LEAVES. 



sist of one or more leaflets (foliola) separately attached to the petiole 
or leaf-stalk (fig. 156). In a single leaf the blade may be either' 
attached to a petiole or sessile on the stem ; while in a compound leaf 
the blades or leaflets are separately attached to the petiole. In the 
earliest stage of growth aU leaves are simple and undivided, and it is 
only during the subsequent development that divisions appear, which 
may commence at the base or at the apex of the leaf The forms 
which the difierent kinds of simple and compound leaves assume 
are traced to the character of the venation, and to the amount of 
parenchyma produced. 

SiSiPLE Leaves. — When the parenchyma is developed symme- 
trically on each side of the midrib or stalk, the leaf is equal (fig. 164); 
if otherwise, the leaf is unequal or oblique (fig. 151), as in Begonia. 
If the margins are even and present no divisions, the leaf is entire (irir- 
teger), as in figs. 164 and 165 ; if there are slight projections of cellular 
or vascular tissue beyond the margin the leaf is not entire (fig. 151) ; 
when the projections are irregular and more or less pointed, the leaf 
is dentate or toothed (fig. 170); when they lie regularly over each 







Fig. 164. Fig. 165. Fig. 166. 



Fig 16r. Fig. 158. 



Fig. 15B. 



other, like the teeth of a saw, the leaf is seirate (figs. 151, 169); when 
they are rounded, the leaf is crenate (fig. 174). 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 half-way down (figs. 149, 159), it is cleft (fissus), and its lines of 
separation are called fissures (fissura, a cleft) ; when the divisions 
extend nearly to the base or to the midrib (fig. 185), the leaf is 
partite, and its lines of separation are called partitions. 

These divisions take place in simple leaves exhibiting different 
kinds of venation, and give rise to marked jforms. Thus, if they 
occur in a feather-veined leaf (fig. 152), it becomes either pinnatifd 
(pinna, a wing or leaflet, and fissus, cleft), when the segments extend 

Fig 164. Lyrate leaf of Barbarea. Fig. 156. Panduriform, a fldaie-shapcd leaf of 
Rumex pulcher. Fig. 156. Compound leaf, temate, the leaflets being obcordate. 

Fig. 167. Compound leaf ; quaternate, the leaflets being rotundate-ouneiform, or wedge- 
shaped with rounded apices. Fig. 168. Two-lobed leaf, somewhat cordate at the base, 
emarginate, and mucronate. Fig. 159. Palmate leaf, the divisions acute and serrated at 
their margins. Radiating venation. 



rOKMS OF SIMPLE LEAVES. 87 

to about the middle and are broad ; or pectinate (pecten, a comb), wlieii 
they are narrow ; or pinnatipartite, when the divisions extend nearly 
to the midrib. These primary divisions may be again subdivided in a 
similar manner, and thus a feather-veined leaf will become bipinnatifid 
(fig. 153), OT 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 triangular, the 
leaf is runcinate (runcina, a large saw), as in the Dandelion. When 
the apex consists of a large rounded lobe, and the divisions, which are 
also more or less rounded, become gradually smaller towards the base 
(fig. 154), as in Barbarea, the leaf is called lyrate, from its resemblance 
to an ancient lyre. Under the term lyrate some include compound 
pinnate leaves in which the several pinnae are united at the apex of 
the leaf, and the others become gradually smaller towards the base. 
When there is a concavity on each side of a leaf, so as to make it 
resemble a violin, as in Eumex pulcher (fig. 155), it is called panduri- 
form (^ranSoDga, a fiddle). 

The same kinds of divisions taking place in a simple leaf with 
radiating venation, give origin to the terms lobed, cleft, and partite 
(figs. 161, 189). When the divisions extend about half-way through 
the leaves, they may be three-lobed, five-lobed, semn-lobed, many-lobed ; 
or, trifid, quinquefid, septemfd, multifid, according to the number of 
divisions. The name of palmate, or pahnatifid (fig. 159), is the 
general term applied to leaves with radiating venation, in which 
there are several lobes united by a broad expansion of parenchyma, 
like the palm of the hand, as in Passion-flower and Eheum palmatum. 
The divisions of leaves with radiating venation may extend to near 
the base of the leaf, and the names bipartite, tripartite, quinque- 
partite or digitipartite, and septempartite, are given according to the 
number of the partitions, two, three, five, or seven. In Drosera 
dichotoma (fig. 88), bipartite and tripartite leaves are seen. The 
term dissected js applied 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. 185), the leaf is called pedate or pedatifd (pes, a foot), 
from a fancied resemblance to the claw of a bird. 

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. 160), 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 



FORMS OF SIMPLE LEAVES. 



{pelta, a buckler), as in the Castor-oil plant (fig. 161). The edges or 
margins of orbicular and peltate leaves are often variously divided. 

It has been thought by 
some that the order of the 
venation in the leaf bears 
a close analogy to the ar- 
rangement of the branches 
on the stem ; that a cer- 
tain unity so pervades 
vegetable organisation, 
that the root, the stem, 
and the leaves, may, in 
their ultimate arrange- 
ment, be regarded as being 
typical the one of the 
Fig. 161. other. M'Oosh states, that 

the angles at which the veins are given off in the leaves are the same 
as those at which the branches come off from the stem. The angles 
as given by him vary from 30° to 70°.* 

Without attempting to notice all the forms of leaves, 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 paren- 
chyma, the leaf is linear or acicular (acus, a 
needle), (fig. 162), as in Pines and Firs. 
These trees are hence called in Germany madeZ- 
hoker, or needle trees. When' the veins 
diverge, those in the middle being longest, and 
the leaf tapering, at each end (fig. 181), it be- 




ng. 160. 



162. 





169. 



Pig. 160. Orbicular leaf of Hydroootyle vulgaris. Radiating venation, j), Petiole. ;, 
Lamina. Fig. 161. Peltate leaf of the Castor-oil plant {RidMus communis). Radiating 
venation, p, Petiole or leaf-stallt. I, Lamina or blade. Fig. 162. Linear, or acicular leaf 
of Fir. Pig. 163. Spatlmlate leaf of Daisy. Fig. 164. Oval leaf. Fig. 165. Oblong 
leaf. Fig. 166. Petiolated, reticulated, somewhat oblong leaf, truncate at the base. 
Fig. 167. Ovate pointed leaf. Fig. 168. Cordate pointed leaf. Fig. 169. Ovato-lance- 
olate 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. 

* M'Cosh on the plant morphologically considered. Proceed, of the Bdin. Bot. Soc, 
July 1851. Bot. Gazette, September 1861. 



FORMS OF SIMPLE LEAVES. 



89 



comes lanceolate (lancea, a lance). If the middle veins only exceed the 
others slightly, and the ends are convex, the leaf is either rounded 
(rotundatus), as in fig. 179, elliptical (fig. 177), oval (fig. 164), or 
oblong (fig. 165). If the veins at the base are longest, the leaf is 
ovate or egg-shaped, as in Chickweed (fig. 167), and if those at the 
apex are longest, the leaf is obovate, or inversely egg-shaped. Leaves 
are cuneate (cunms, a wedge) or wedge-shaped, in Saxifraga (fig. 170) ; 
spathulate, or spatula-like, having a broad rounded apex, and tapering 
down to the stalk- in the Daisy (fig. 163) ; subulate (fig. 182), 
narrow and tapering like an awl (subula) ; acuminate, or drawn out 
into a long point, as in Ficus religiosa (fig. 174), mucronate, with a 
hard stiff point or mucro at the apex (figs. 175 and 158). When 




the 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 cTna/rginate (fig. 158) as 
having a portion taken out of the margin ; when the apex is merely 
flattened or slightly depressed (fig. 172), the leaf is retuse (retusus, 
blunt) ; and when the apex 
ends abruptly in a straight 
margin, as in the Tulip tree 
(fig. 178), the leaf is trun- 
cate. When the venation is 
prolonged downwards at an 
obtuse angle with the midrib, 
and rounded lobes are formed, 
as in Dog-violety the leaf is 
cordate or heart-shaped (fig. 168), or kidney-shaped (reniform) when the 
apex is rounded (fig. 176), as in Asarum. When the lobes are prolonged 

Fig. 170. Cuneate or wedged-shaped leaf of Saxifraga, ending in an abrupt or truncate 
manner, and toothed or dentate at the apex. Fig. 171. Perfoliate leaf of Bupleurum 
perfoliatum, formed by lobes uniting at the baae on the opposite side of the stem from 
that to which the leaf is attached. Fig. 172. Eetuse leaf, i.e. slightly depressed at the 
apex. Margin slightly waved. Fig. 173. Ovate five-ribbed leaf. Fig. 174. Rounded 
acuminated leaf of Ficus religiosa, with the margin crenate or slightly sinuous. Fig. 176. 
Sub-ovate, retuse, mucronate leaf. Fig. 176. Reniform or kidney-shaped entire leaf of 

Asarum. Radiating venation. Fig. 177. EUiptioal and-somewhat lanceolate leaf ; three- 
ribbed. Fig. 178. Three-lobed, truncate, or abrupt leaf of Liriodendron tulipiferum. 




Fig. 176. 



Fig. 177. Fig. 178. 



90 



FOEMS 01" SIMPLE LEAVES. 



downwards and are acute (fig. 180), the leaf is sagittate (sagitta, an 
arrow) ; when they proceed at right angles, as in Rumex 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. 184), it 
is called auriculate (auricula, little 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, p-ismatical, 
ensiform or sword-like {ensis, a sword), acinaciform {acinaees, a 
scimitar) or scimitar-shaped (fig. 187), and dolabriform (dolabra, an 
axe) or axe-shaped (fig. 186). When the development of cells is such 
that they more than fill up the spaces between the veins, the margins 
become wavy, crisp, or undulated, as in Humex crispus and Rheum 
undulatum (fig. 189). By cultivation the cellular tissue is often 




much increased, giving rise to the curled leaves of Greens, Savoys, 
Cresses, Lettuce, etc. In rushes the shoots which act as leaves are 

Fig. 179. Ronnded entire leaf, ending in a short point. Kg. 180. Sagittate or arrow- 
sliaped leaf of Sagittaria. Fig. 181. Lanceolate, acute leaf, with minute teeth or dentations 
at the margin. Fig. 182. Subulate or awl-shaped leaf. Fig. 183. Whorl or verticil of 
linear-obovate leaves. Fig. 184. Auriculate lanceolate leaf, oblique at the base, with 
minute toothings at the margin. Fig. 185. Pedate or Pcdatifid leaf of Hellebore. Eadi- 
atlng venation. Fig. 186. Dolabriform or axe-shaped fleshy succulent leaf. Hidden- 
veined. Fig. 187. Acinaciform or scimitar-shaped succulent leaf. Hidden-veined. 
Fig. 188. Oval leaf with converging veins ; not reticulated. Fig. 189. Palmately-lobed 
leaf, crisp or undulated at the margin. Radiating venation. 



FORMS OF COMPOUND LEAVES. 



91 



often terete. They are either barren or bear flowers. Their cellular 
tissue is often stellate, 
and the shoots some- 
times exhibit a pe- 
culiar spiral twisting. 
(Fig. 190.) 

Compound Leaves 
are those in which the 
divisions extend to the 
midrib, or petiole (fig. 
191), and receive the 
name oifoliola or leaf- 
lets. The midrib, or 
petiole, has thus the 
appearance of a branch 
with separate leaves 
attached to it, but it is 
considered properly as 
one leaf, because in its 
earliest state it arises 



"■"I'""*'' "i»»""iiiiiiiiiiiiiiiiiiiii)iiiaw.iS5i 

Kg. 190. 






Kg. 191. Kg. 192. 

Fig. 190. Junous effusus, variety, with spiral leaves, called Sorew-rusli. . Fig. 191. Leaf 
of Robinia pseudacacia, often called Acacia. The leaf is impari-pinnate, or alternately pin- 
nate, The pinnse are supported on atallss or petiolules. p, Petiole or leaf -stalk. I, Lamina 
■ or blade divided into separate leaflets or pinna. Fig. 192. Septenate leaf of Horse Chest- 
nut (^sealms Hippoeastwmm). p, Petiole. I, Lamina divided into seven separate 



92 



FORMS OF COMPOUND LEAVES. 



from the axis as a single piece, and its subsequent divisions in the 
form of leaflets are all in one plane. The leaflets are either sessile 
(fig. 192), or have stalks, caRed petiolules (fig. 191), according as the 
vascular bundles of the veins spread out or divaricate at once, or remain 
united for a certain length. 

Compound leaves have been classified according to the nature of 
the venation, and the development of parenchyma. If we suppose that 
in a simple feather-veined unicostate leaf, 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 articulated to the petiole or midrib (fig. 193), 
the leaf becomes compound and pinnate (pinna, a wing or feather). 
If the midrib and primary veins are not covered with parenchyma. 




Fig. 193. 



rig. 196. 



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 hipinnate (fig. 194). 
In this case the secondary veins form as it were partial petioles. A 
farther subdivision, in which the tertiary veins only are covered with 
parenchyma and have separate leaflets, gives tripinnate or decompound, 
in which case the tertiary veins form the partial petioles ; and a leaf 
divided still more is called supradecon^ound (fig. 195). 

When a pinnate leaf has one pair of leaflets, it is unijugate (unum, 
one, and j-ugum, a yoke) ; when it has two pairs, it is hijngate; many 

Fig. 193, Pari-pinnate leaf with six pairs of pinnae (sa^ugate). Fig. 194. Bipinnate leaf, 
witli sessUe foliola or leaflets. Fig. 196. Part of the supradeeompound leaf of Laserpitium 
hirsutmn. 



FORMS OF COMPOUND LEAVES. 



93 



pairs, multijugate (fig. 191). When a pinnate leaf ends in a pair of 
pinnae (fig. 193) it is equally or abruptly pinnate (pari-pinnate) ; when 
there is a single terminal leaflet (fig. 191), the leaf is unequally pinnate 
(impari-pinnate) ; when the leaflets or pinnse are placed alternately on 
either side of the midrib, and not directly opposite to each other, the 
leaf is alternately pinnate (fig. 191) ; and when the pinnae are of dif- 
ferent sizes, the leaf is interruptedly pinnate (fig. 196). 

In the case of a simple multicostate leaf with radiating venation, 
if we suppose the ribs to be covered with parenchyma, so as to form 
separate leaflets, each of which is articulated to the petiole, the digitate 
form of compound leaf is produced ; if there are three leaflets, the form 




Fig. 196, 



Pig. 198. 



is ternate (figs. 156, 197); if four, quaternate (fig. 157); if five, quinate ; 
if seven, septenate (fig. 192), and so on. If the three ribs of a ternate 
leaf subdivide each into three primary veins, which become covered 
with parenchyma so as to be separate articulated leaflets, the leaf is 
hiteirnate ; and if another three-fold division takes place, it is triternate 
(fig. 198). 

General summary of facts connected with the venation and con- 
formation of leaves : — 

1. Leaves of flowering plants are either netted-veined (reticulated) or parallel- 

reined. 

2. Leaves have either a single midrih (nnioostate), or several ribs (multicostate); 

and the latter are either radiating (spreading out from one point), or con- 
'vergent. 

3. Unicostate leaves have veins proceeding at different angles from various points 

of the midrib, and arranged more or less like the parts of a feather. 

Fig. 196. Imparl- alternately and interruptedly pinnate leaf. Leaflets or plniiEe sessile, 
and serrated at the margin. Fig, 197. Ternate leaf of Strawberry. Margin of leaflets, 

toothed or dentate, p, Petiole with projecting hairs. I, Lamina divided into thi'ee 
leaflets. Fig. 198. Triternate leaf. Leaflets cordate. 



94 FOEMS OF PETIOLES OE LEAF-STALKS. 

4. The conformation of leaves depends partly on the venation, and partly on the 

mode in which the parenchyma is developed. 

5. Leaves are either simple, i.e. composed of one piece, or componnd, i.e. com- 

posed of one or more articulated leaflets. 

6. Simple leaves are either entire or divided into segments. When the divisions 

are marginal, they are dentate, serrate, or crenate ; when the divisions are 
deeper, cleft or partite. 
1. Simple unicostate (one-ribbed) leaves having their parenchyma cut laterally 
into various lobes, so that the divisions extend to about the middle of 
each half of the lamina, may be referred to the Pinnatifid type, including 
bipinnatifid, pectinate, pandurifoi-m, runcinate, and lyrate forms ; when the 
divisions extend nearly to the midrib the form is pinnati-partite. 

8. Simple multicostate (many-ribbed) leaves, with the ribs divergent, when cut 

longitudinally into various lobes, the divisions extending to about the 
middle of the lamina, may be referred to the Palmatifid type, including 
trifid, quinquefld, pedate, and dissected forms ; when the divisions extend 
to near the base the forms are palmately-partite or dissected. 

9. Simple leaves, with convergent ribs, are rarely divided deeply, and such is also 

the case with parallel-veined leaves, the margins of which are often entire. 

10. Simple leaves, whether unicostate or multicostate, with lobes or divisions at 

their base, exhibit rcniform, cordate, sagittate, and hastate forms ; with 
lobes or divisions at their apex, emarginate and obcordate forms. 

11. Compound unicostate leaves, having lateral articulated leaflets, may be 

referred to the Pinnate type, including bipinnate, tripinnate, and decom- 
pound forms. 

12. Compound multicostate leaves, with divergent ribs, divided longitudinally into 

articulated leaflets, may be referred to the Digitate type, including temate, 
triternate, quaternate, and quinate forms. 

Petiole oe Leaf-Stalk. — This is the part which unites the limb 
or hlade of the leaf to the stem (figs. 147 and 191 p). It is absent 
in sessile leaves, and in many sheathing leaves is not well defined. It 
consists of one or more bundles of vascular tissue, with a varying 
amount of parenchyma. 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 
epidermal 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. 148, n m), and sometimes several large bundles form 
separate ribs (figs. 161, 177), whilst the ramifications of the smaller 
bundles constitute the veins and veinlets. 

At the place where the petiole joins the stem there is frequently 
an articulation, or a constriction with a tendency to disunion, and at 
the same time there exists a swelling (fig. 220 p), called pulvinus 
(pulvinus, a cushion), formed by a mass of cellular tissue, the cells of 
which occasionally exhibit the phenomenon of contractility. 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 



FOUMS OF PETIOLES OR iEAF-STALKS. 



95 



united to the lamina, or where the midrib joins the leaflets of a com- 
pound 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. 201). 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. 
220. In this soar the remains of the vascular bundles, c, are seen ; 
arid its form furnishes characters by which particular kinds of trees 
may be known when not in leaf. In the case of many Palms and 
Tree-ferns, the scars or cicatrices of the leaves are very conspicuous. 
In fossil plants important characters are founded on them. 

The petiole varies in length, being usually shorter than 
lamina, but some- 
times much longer. 
In some Palms it 
is fifteen or twenty 
feet long, and 
so firm as to 
used for poles 
walking-sticks. 



the 




Fig. 199. 




Fig. 200. 



general, the petiole is more or less rounded in its form, the upper 
surface being flattened or grooved. Sometimes it is compressed 
laterally, 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. 199 p), as in Pontederia and Trapa, 
so as to float the leaf At other times it is. winged, or has a leaf-like 
appearance, as in the pitcher plant (fig. 200 p), orange (fig. 201 p), 

Fig. 199. Leaf with a quadrangular toothed lamina or blade, I, and an inflated petiole, p. 
containing air-cells. Fig. 200. Asoidium or pitcher of Nepenthes, p, Winged petiole 
■which heoomes narrowed, and then expands so as to form the pitcher a, by folding on 
itself, (i, The operculum or lid, supposed to be formed by the blade of the leaf, and articu- 
'lated to the pitcher. Fig. 201. Leaf of Orange, which some call compound. 5, DUated 
or winged petiole, united by an articulation to the blade. In such a leaf, if the vessels of 
the petiole were developed in a circular manner, so as to form a pitcher, the lamina or blade 
would form the jointed lid. 



96 



FORMS OF PETIOLES OE LEAF-STALKS. 



lemon and Dionsea (fig. 202 p). In some Australian Acacias, and in 
some species of Oxalis, Bupleurum, etc., the petiole is flattened in a 
vertical direction, the vascular bundles separating immediately after 
quitting the stem, and running nearly parallel from base to apex. 
This kind of petiole (fig. 204 p) has been called Phyllodiwm {(pdXKov, 
a leaf, and l/Sos, form). In these plants the laminae or blades of the 
leaves are pinnate, bipinnate, or ternate, and are produced at the 
extremities of the phyllodia in a horizontal direction (fig. 204 I) ; but 





"Fig. 202. 



Fig. 203. 



Fig. 204. 



in many instances they are not developed, and the phyUodium serves 
the purpose of a leaf. Hence some Acacias are called leafless. 
These phyUodia, 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 expanded or winged, and the lamina imperfectly 
developed ; and others in which there is no lamina, and the petiole 
becomes large and broad. Some petioles, in place of ending in a 

Fig. 202. Leaf of Dion^a nmscipula, or Venus' Fly-trap, y, Dilated or winged petiole. 
e. Jointed blade, the two fringed halves of which fold on each other, when certain hairs on 
the upper siuface are touched. Fig. 203. Ascidium, or Pitcher of Sarracenia, formed by 
the petiole of the leaf. The lid is not articulated to the pitcher as in Nepenthes (fig. 200). 
Fig. 204. Leaf of Acacia heterophylla. p, PhyUodium or enlarged petiole, with straight 
venation. 1 1, Lamina or blade, which is bipinnate. The blade is frequently wanting, and 
the phyUodium is the only part produced. 



STETTCTUEB AND FOEMS OF STIPULES. 97 

lamina, form a tendril or cirrus (p. 120), so as to enable the plant 
to climb. 

Stipules. 

At the place where the petiole joins the axis, a sheath (vagina) is 
sometimes produced, which embraces the whole or part of the cir- 
cumference of the stem (fig. 147 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 
Rhubarb order, it is large and membranous, and has received the name 
of ochrea or boot (fig. Ii7 g) ; while in Palms it forms a kind of net- 
work, to which the name of reticulum has been given (p. 32) ; and in 
umbelliferous plants it constitutes the perieladium (■rsg;, around, and 
xkdhoi, a branch). In place of a sheath, leaves are occasionally pro- 
duced at the base of the petiole (fig. 205 s s), 

which have been denominated stipules (stipula, ^ 'y^v\ 

straw or husk). These stipules are often two _^<-^^jSv|\ 
in number, and they are important as sup- Ni^:^?^^;;^) 
plying characters in certain natural orders. ^^>^^M^ 
Thus they occur in the Pea and Bean family, ||s 

in Rosaceous plants, and the Cinchona bark * -^ 

family. They are rarely met with in Mono- ^ 

cotyledons, or in Dicotyledons with sheath- 
ing petioles, and they are not common in ^^ " 
Dicotyledons with opposite leaves. Plants having stipules are stipu- 
late; those having none are exstipulate. 

Stipules are formed by some of the vascukr bundles diverging as 
they leave fce 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 distinguishes 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, perform- 
,. ing the office of leaves. 

When stipules are attached separately to the stem at the base of 
the leaf, they are called caulinary. Thus, in fig. 205, r is a branch 
of SaliK aurita, with a leaf, /, having a bud, 6, in its axU, and two 
caulinary stipules, s s. When stipulate leaves are opposite to each 
other, at the same height on the stem, it occasionally happens that the 

a 

Fig. 205. Portion of a branch, r, of Salix aurita bearing a single petlolate leaf, /, whicih 
bas been cut across. . s s, Caulinary stipules. 2), Bud. iu the axil of the leaf, 

H 



'98 



FOEMS OF STIPULES. 



stipules on either side unite wholly or partially, so as to form an inter- 
petiolary or interfoliar (inter, between) stipule (fig. 206 s), as in Cia- 
chona and in Ipecacuan. 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 petiolary stipule, as 
in the Eose (fig, 207 s), or an axillary stipule, as in Houttuynia 




Fig. 208. 



Hg. 209. 



cordata (fig. 208 s). In other instances the stipules unite together 
on the side of the stem opposite the leaf, and become synochreate (nvv, 
together), as in Astragalus (fig. 209 s). The union or adhesion of. 

Fig. 206. Branch, r, and two leaves, //, of CepKalanthus occidentalis. s, Interpetiolary 
or interfoliar stipule, formed by the partial union of two. Fig. 207. Portion of a branch, 
T, of Eosa canina, or dog-rose, bearing a single. leaf, f, with its petiole, p, its petiolary or 
adnate stipules, s, its axillary bud, b, and its aculei or pricliles, a. Fig. 208. Portion of 
a branch, r, of Houttuynia cordata, with a leaf, /, and an axillary stipule, s, formed by the 
union of two. Fig. 209. Branch, r, and portion of the leaf, /, of Astragalus Onobrychis, 
with a synochreate stipule, s, 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. 



99 



stipules is not an accidental occurrence taking place after they have 
been developed, but is intimately connected with the general law, in 
accordance with which the parts of the plants are formed. 

Stipules are sometimes large, enveloping the 
leaves in the young state, and falling off in the 
progress of growth, as in Picus, Magnolia, and 
Potamogeton ; at other times they are so minute 
as to be scarcely distinguishable without the aid 
of a lens, and so fugaceous as to be visible only 
in the very young state of the leaf. They may 
assume a hard and spiny character as in Eobinia 
pseudacacia, or may be cirrose, as in Smilax, 
where each stipule is represented by a tendril; 
while in Cucurbitace^ there is only one cirrose 
stipule. In grasses the sheath or sheathing 
petiole (fig. 210 g v) has a prolongation or fold- 
ing of the epidermis at its upper part, distinct 
from the leaf, to which the name of h'ffule (ligula, 
a small slip) has been given (fig. 210 y 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 leaflets or foliola of a com- 
pound leaf, small stipules are occasionally pro- 
duced, to which some have given the name of itipels. 




Pig. 210. 



Anomalous Forms of Leaves and Petioles. 

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 repetition 
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 Savoys are rendered 
more delicate and nutritious. 

In some plants true leaves are not produced, their place being occu- 
pied by dilated petioles or phyllodia (p. 96), or by stipules (p. 97). 
In other instances scales are formed instead of leaves, as in Orobanche, 
Lathrsea, and young Asparagus (fig. 129 I). Divisions take place in 

;Kg. 210. Portion of a leaf of Phalaris anindinacea, one of the grasses. /, Laminar 
merithal or blade of the leaf, with straight parallel venation, g v, Vaginal, or sheathing 
portion, representing the petiole, ending in a membranous process or ligule, g I, 



100 ASCIDIA OE TITOHEES. 

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 cases. 
When two lobes at the base of a leaf are prolonged beyond the stem 
and unite (fig, 171), the leaf is perfoliate (per, through, a,nd folium, 
leaf), the stem appearing to pass through it, as in Bupleurum perfolia- 
tum, and Chlora perfoliata ; when two leaves unite by their bases 
they become connate (con, together, and natus, born), as in Lonicera 
Caprifolium ; and when leaves adhere to the stem, forming a sort of 
winged or leafy appendage, they are decurrent (decurro, to run down 
or along), as in Thistles. 

The vascular bundles and cellular tissue are sometimes deve- 
loped in such a way as to form a circle, with a hollow in the 
centre, and thiis give rise to what are called fistular (fistula, a pipe) 
or hollow leaves, and to ascidia (aexldiov, a small bag) or pitchers. 
Hollow leaves are well seen in the Onion. Pitchers are formed either 
by petioles or by laminse, and they are composed^ of one or more 
leaves. In some Convallarias, two leaves unite to form a cavity. In 
Sarracenia (fig. 203) and Heliamphora, the pitcher is composed 
apparently of the petiole of the leaf. In Nepenthes (fig. 200) and 
perhaps in Cephalotus, while the folding of a winged petiole, p, forms 
the pitcher, a, the lid, e,, which is united by an articulation, corre- 
sponds to the lamina. This kind of asoidium is called calyptrimor- 
phous (xaXwr^a, a covering, and /ttofpij, form), and may be con- 
sidered as formed by a leaf such as that of the Orange (fig. 201) ; 
the lamina, e, being articulated to the petiole, p, which, when folded, 
forms the pitcher. In Dischidia EaflSesiana, a climbing 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 ampullm. 
Some suppose that pitchers are not due to folding and adhesion, but 
that they are produced by a hollowing out of the extremity of the stalk. 

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

Leaves op DiooTYiiBDioNS. — In Dicotyledons, the venation is 
reticulated, the veins, coming off at various angles, form an angu- 
lar network of vessels (fig. 151), and the tracheae communicate 
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 will be found to occur chiefly in cases where the petiole 
may be considered as occupying the place of the leaf. Examples of 



LEAVES OF EXOaENS, ENDOGENS, AND ACEOGENS. 101 

this kind are seen in Acacias (fig. 204), as well as in Ranunculus 
gramineus and K. Lingua. 

Leaves op Monocotyledons. — In Monocotyledons, the leaves 
do not present an angular network of vessels, nor do they exhibit 
divisions on their margin (figs. 150, 210). Exceptions to this rule 
occur in some plants, as Tamus and Dioscorea, which have been called 
Dictyogens by Lindley, on account of their somewhat netted venation ; 
and in Palms, in which, although the leaves are entire at first, they 
afterwards become split into various lobes. Leaves of Monocotyle- 
dons 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 in Bananas), and .do not fall off by 
an articulation. When there is only a slight divergence of their 
veins, they may be looked upon more as enlarged and flattened petioles 
than as true laminae. This remark is illustrated by the leaves of 
Typha and Iris. In some Monocotyledons, as in Sagittaria sagitti- 
folia, the submerged and floating leaves are narrow, like petioles, 
while those growing erect above the water expand and assume an 
arrow-like shape (fig. 180). 

Leaves of Acotylbdons. — In Acotyledons, such as Ferns and 
their allies, the leaves vary much ; being entire or divided, stalked or 
sessile, often feather-veined, occasionally with radiating venation, the 
extremitieg of the veins being forked. The flbro-vascular bundles of 
the leaves resemble those of the stem both in structure and arrange- 
ment. 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. 

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, raimal; 
on flower-stalks, floral leaves. The first leaves developed are deno- 
minated seminal (semen, a seed), or cotyledons (xoruXridiiv, a name given 
to a plant or a seed-lobe) ; and those which succeed are primordial 
(primus, first, and ordo, rank). 

The arrangement of the leaves on the axis and its appendages is 
caljed phyllotaxis (<pfjXKov, a leaf, and rct^'S, order). In their arrange- 
ment leaves follow a definite order. It has been stated already, p. 45, 
that there are regular nodes or points on the stem (fig. 211 n) at 
which leaves appear, and that the part of the stem between the nodes 
is the internode (fig. 211 m). Each node is capable of giving origin 
to a leaf. Occasionally several nodes are approximated so as to form 



102 



PHYLLOTAXIS OK LEAF-AERANGEMENT. 



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 






Fig. 211. Fig. 212. 

each side of the stem or axis, and at the same level, they are called 
opposite (fig. 212) ; when more than two 
are produced (figs. 183, 213), they are 
verticillate (verto, I turn), and the circle 
of leaves is then called a verticil or whorl. 
When leaves are opposite, the pairs which 
are next each other, but separated by an 
intemode, often cross at right angles (fig. 
212 ab), or decussate (decusso, I cut cross- 
wise), following thus a law of alternation. 
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 ia Lysimachia vulgaris (fig. 213). 

Fig. 211. Portion of a branch of a Lime tree, with four leaves arranged in a distichous man- 
ner, or in two rows, a, The branch with the leaves niunbered in their order, n being the 
node, and m the Intemode or merithal. 6 Is a magnified representation of the branch, 
showing the cicatrices of the leaves and their spiral arrangement, which is expressed by i, or 
one turn of the spiral and two leaves. Fig. 212. Opposite, decussate leaves of Pimelea 
decussata. a, A pair of opposite leaves, b, Another pair placed at right angles. Fig. 
213. Leaves of Lysimachia vulgaris, in verticils or whorls of three. The leaves of each ver- 
ticil alternate with those of the verticils next it. In this plant the number of the leaves in 
a verticil often varies. 




PHYLLOTAXIS OE LEAF-AEEANGEMENT. 



103 



When a single leaf is produced at a node, and the nodes are sepa- 
rated so that each leaf occurs at a different height on the stem, the 
leaves are alternate (fig. 214). The relative position of alternate 
leaves varies in different plants, although it is tolerably uniform in 
each species. In fig. 211, leaf 1 arises from a node, n; leaf 2 is 
separated by an internode, 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 (&h, twice, and erl^og, order), or the leaves are arranged 
in two rows. In fig. 215, on the other hand, the fourth leaf is 
directly above the first, and the arrangement is tristiehous (rgs/j, three, 
and eri^og, order). The same arrangement contiaues throughout the 
stems, so that in fig. 215 the 7th 
leaf is above the 4th, the 10th 
above the 7th ; also the 5 th above 
the 2d, the 6th above the 3d, and 
so on. There is thus throughout 
a tendency to a spiral arrangement, 
the number of leaves in the spire 
or spiral cycle, and the number of 
turns, varying in different plants. 
In plants whose leaves are close to 
each other, the spiral tendency is 
easily seen. In the Screw pine 
(Pandanus odoratissimus), in the 
Pine-apple family, and in some 
Palms, as Copernicia cerifera, the 
screw-like arrangement of the 
leaves is obvious. This mode of 
development prevails in all parts 
of plants, and may be considered 
as depending on their manner of 
growth in an upward and at the same time in a lateral direction. 
Alternation is looked upon as the normal arrangement of all parts of 
plants. This arrangement is liable to be interrupted by many causes, 
so that its distinct existence cannot be always detected. 

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 
froin which the enumeration commenced. This arrangement has been 
expressed by a fraction, the numerator of which indicates the number 




Fig. 214. 



Fig. 214. Part of a branch of a Cherry with six leaves, the 6th being placed vertically 
over the first, after two turns of the spiral. This is expressed by ^ or the quincunx, a 
The branch, with the leaves numbered in order, h, A magnified representation of the brai^ch, 
showing the cicatrices of the leaves or their points of insertion, and their spiral arrangement. 



104 



PHYLLOTAXIS OE LEAF-AEEANGEMENT. 



of turns, and the denominator the number of leaves in the spiral 
cycle. Thus, in fig. 214, ab, the cycle consists of five leaves, the 6th 
leaf being placed vertically over the 1st, 
the 7th over the 2d, and so on ; while 
the number of turns between the 1st 
and 6th leaf is two : hence, this arrange- 
ment is indicated by the fraction |. In 
other words, the distance or divergence 
between the first and second leaf, ex- 
pressed in parts of a circle, is | of a 
circle, or 360° -M = 144°. In fig. 211, 
a b, the spiral is ^, i.e. one turn and two 
leaves ; the third leaf being placed verti- 
cally over the first, and the divergence 
between the first and second leaf being 
one-half the circumference of a circle, 
360° -H J = 180°. Again, in fig. 215, 
a b, the number is i, or one turn and 
three leaves, the angular divergence being 
120°. 

The general forms of Phyllotaxy may be brought out by a con- 
tinued fraction — 

1 




Fig. 215. 



a+l + l + l + 1, etc., 

where a may have the values 1, 2, 3, or 4, etc. 
The actual fractions thus resulting are — when 

« = 1-* -I f * A, etc. 
» = 2,..i i i 1 A> etc. 



a = 


3. 


1 
•s 


1 

T 


■f 


A 


A 


etc 


a = 


4. 


■i 


i 


f 


A- 


A> 


etc 



Each fraction being obtained by adding together the numerator and 
denominator in the two preceding fractions. 

When the leaves or scales are alternate, and run in a single series, 
they are unijugate ; when the leaves are opposite, and there are two 
parallel rows produced, the arrangement is bijugate, while in the case 
of whorled leaves the arrangement may be trijugate or quadrijugate. 

Fig. 215. — ^Young plant of Cyperus esculentus, wil^ii leaves in three rows, or tristichous, 
expressed by the fraction i, or one turn and three leaves, a, The plant, with its leaves 
numbered in their order. ■ i. Magnified representation of the stem, showing the insertion of 
the leaves and their spiral arrangement. 



PHYLLOTAXIS OR LEAF-AEEANGEMENT. 



105 



In cases where tiie 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. 216, there are thirteen 
leaves which are numbered in their order, and five turns of the spiral 
marked by circles in the centre (^ indicating the arrangement) ; but 
this could not be detected at once. So also in Fir cones (fig. 217), 
which are composed of scales or modified leaves, the generating spiral 
cannot be determined easily. In such cases, however, there are 
secondary spirals running parallel to each other, as is seen in fig. 217, 
where spiral lines pass through scales numbered 1, 6, 11, 16, etc., 





Fig. 216. 



Fig. 217. 



and 1, 9, 17, etc., and by counting those which run parallel in differ- 
ent directions, the number of scales intervening between every two in 
the same parallel coil may be ascertained. Thus, in fig. 217, 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, etc. ; the second through 9, 14, 19, 24, etc. ; the third 
through 17, 22, 27, 32, 37, etc. ; the fourth through 30, 35, 40, 45, 
etc.; the fifth through 43, 48, 53, etc' The number of these second- 
ary spirals indicates the number of scales intervening between every 

Fig. 216. Cycle of thirteen leaves placed closely together so as to form a rosette, as in 
Sempervivum. A is the very short axis to which the leaves are attached. The leaves are 
numbered in their order, from below upwarSs. 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 5-thirteenths. Fig. 217. Cone of Abies 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 ftom right to left. 



106 



PHYLLOTAXIS OE LEAF-AEEANGEMENT. 



two scales in each of these spirals — the common difference being five. 
Again, it will be found on examination that there are 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, etc. ; 
the second through 6, 14, 22, 30,.etc. ; the third 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 gene- 
rating spiral may be discovered. 

In the cone of the American larch (fig. 218) there is a quincuncial 
arrangement of scales marked by the fraction ^. There are five 



vertical ranks, 
15 



10 




11 



Fig. 218. 



12 



as marked in the tabular numerical view at the side of 
. the cone— viz., 2, 7, 12 ; 4, 9, 14 ; 1, 6, 11 ; 
14 : 3, 8, 13 ; 5, 10, 15, the common difference 
13 ; ; i in each row being 5. On looking at the cone 
we find also parallel oblique ranks, two of 
which, ascending to the left, are marked by 
the numbers 1, 3, 5, which, if the diagram 
is coiled round a cylinder, continue in the 
numbers 7, 9, 11, 13, 15 ; and 2, 4, 6, 8, 
10, continued into 12, 14. There are thus 
two left-handed spirals, with 2 as the com- 
mon difference in the numbering of the scales. 
Again, three oblique parallel spirals ascend 
to the right, marked by the numbers 1, 4, 7, 
6, 9, 12, going on to 15 ; and 5, 8, 11, 14; 
scales is 3, corresponding 



running into 10, 13 ; 3, 

here the common numbering of the 

with the oblique right-handed spirals. 

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 homodromom (o/io/os, 
similar, and 5f o/ios, a course) ; when the direction differs, they are 
heterodromous (iri^og, another or diverse). In different species of the 
same genus the phyllotaxis frequently varies. 

Considering alternation as the usual leaf-arrangement, some have 
supposed that opposite leaves are due to the development of two 
spirals in opposite directions, whUe others look upon them as pro- 
duced by two nodes coming close together without an intemode. A 
verticil, in the latter view, wiU be the result of the non-development 
of more than one intemode, and may occur in plants, the normal 

Fig. 218. Cone of a species of Larch (Larw; microcarpa), taken from Professor Asa 
Gray's work, with the scales numbered so far as seen. The arrangement is J in the five- 
ranked series. There are five vertical rows of scales, 1, 6, 11 ; 4, 9, 14 ; 2, 7, 12 ; 5, 10, 16 ; 
and 3, 8, 13, as shown in the diagram. 



PHYLLOTAXIS OK LEAF-AEEANGEMENT. 107 

arrangement of whose leaves is alternate. Thus, in fig. 211, if the 
space between 1 and. 2 were obliterated, or the intemode, m, not 
developed, the leaves would be opposite. In fig. 214, 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 verticUlate leaves are naturally 
produced : but in such cases the alternation is still seen in the 
arrangement of the different clmters of leaves. 

In some cases the effect of interruption of growth, in causing 
alternate leaves to become opposite and verticUlate, can be distinctly 
shown, as for instance in Rhododendron ponticum. In other cases, 
parts which are usually opposite or verticiUate 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 verticiUate leaves. When the interruption to develop- 
ment 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 graduaUy shortened, till the nodes were close 
to each other, and the leaves came oflf in bunches. AU modifications 
of leaves follow the same laws of arrangement as true leaves — a fact 
which is of importance in a morphological point of view. 

In Dicotyledonous 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 verticUlate, others by 
their alternate, leaves. Labiate plants have decussate leaves, while 
Boraginacese have alternate leaves, and Tiliacese ,usually have distichous 
leaves ; Cinchonacese have opposite leaves ; Galiacese, verticUlate. 
Such arrangements as f, |, ^\, and -f^, are common in Dicotyledons. 
The first of these, called quincunx (quincunx, an arrangement of five), 
is met with in the Apple, Pear, and Cherry (fig. 214) ; the second, in 
the Bay, Holly, Plantago media ; the third, in the cones of Pinus 
(Abies) alba (fig. 217) ; and the fourth, in those of the Pinus (Abies) 
Picea. In Monocotyledonous 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 
J, J (fig. 215), and |, are common in Monocotyledons, as in Grasses, 
Sedges, and Lilies. In Acotyledons the leaves assume all kinds of 
arrangement, being opposite, alternate, and verticiUate. It has been 



108 LEAF-BUDS AND BKANCHES. 

found in general that, while the number 5 occurs in the phyllotaxis 
of Dicotyledons, 3 is common in that of Monocotyledons. 

Although there is thus, in the great divisions of the vegetable 
kingdom, a tendency to certain definite numerical arrangements, yet 
there are many exceptions. In speaking of Palms, which are Mono- 
cotyledonous plants, Martius states that the leaves of different species 
exhibit the following spirals — |, f , f f , |, A, H, |^. In the species of 
the genus Pinus, f, ^, -i^, ^, fi, occur. Thus, while it has been 
shown that the phyUoplastic (puXXov, a leaf, and nrXaemii, 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. 

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 functions with vigour. The form of the stem is also probably 
connected with the leaf-arrangement. M. Cagnat has remarked that 
an analogy in arrangement of leaves and character of stem may be 
traced. The leaves of juniper are in verticils of three, and the pith 
is triangular ; the leaves of cypress being opposite, the pith presents 
the form of a cross. When leaves are opposite and decussate, the 
stems are often square, as in Labiate plants. The ordinary 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. 

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 morpho- 
logical 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. 

Liof-huds. 

Leaf-buds contain the rudiments of branches, and are found 
in the axil of previously-formed leaves (fig. 219 6a, ha, Id); or, 
in other words, in the angle formed between the stem and leaf. 
They are hence called axillary, and may be either terminal, bt, or 
lateral, ha. They commence as cellular prolongations from the 
medullary rays bursting through the bark. The central cellular 
portion is surrounded by spiral vessels, and is covered with rudi- 
mentary leaves. In the progress of growth, vascular bundles are 



LEAF-BUDS AND BKANCHES. 



109 



ka. 




Fig. 219. 



formed continuous with those of the stem ; and, ultimately, branches 
are produced, which in every respect resemble the axis whence the 
buds first sprang. The cellular portion in the 
centre remains as pith with its medullary sheath, 
which is closed and hot continuous with that 
of the parent stem. Thus, in the stem and 
■ branch, this sheath forms a canal which , is 
closed at both extremities, and which sends 
prolongations 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. 

A leaf-bud may be removed in a young 
state from one plant and grafted upon another, 
by the process of hudding, 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, who' look upon them as embryo plants fixed to the axis, 
capable of sending stems and leaves in an upward direction, and bast 
or ligneous fibres downwards, which, according to them, may be con- 
sidered as roots. A tree may thus be said to consist of a series of 
leaf-buds, or phytons {furh, 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 formation of them, an 
injury iaflicted on the bud in the axis is more likely to have a 
prejudicial effect on the future life of the plant. 

In the trees of temperate and cold climates the buds which 
are developed during one season lie dormant during the wiater, 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 perulm (tegmenta, coverings ; peridx, small bags), which frequently 
exhibit a firmer and coarser texture than the leaves themselves. 
These scales or protective appendages of the bud consist either of the 
altered laminae, or of the enlarged petiolaiy sheath, or of stipules, as 
in the Fig and Magnolia, or of one or two of these parts combined. 



"Fig. 219. Upper portion of a branch of Lonieera nigra in a state of hibernation, that is 
to say, after the fall of the leaves ; covered with leaf-huds. it, A. terminal bud. 6a, 6a, 
6(8, Axillary lateral buds. Below the buds the cicatrix or scar left by the fallen leaves 



no 



VERNATION OR PEiEFOLIATION. 





They serve a temporary purpose, and usually fall off sooner or later 
after the leaves are expanded. The bud is often protected by a coat- 
ing of resinous matter, as in the Horse-chestnut and Balsam poplar, or 
by a thick downy covering, as in the Willow. Linnseus called leaf- 
buds hibernacula, or the winter quarters of the young branch. 

In the bud of a common tree, as the Sycamore (fig. 220), 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 is called an 
imbricated (imbrex, a 
roof tile) manner. On 
making a transverse 
section of the bud (fig. 
221), the overlying 
scales, e e e e, are dis- 
tinctly seen surround- 
ing the leaves,/, which 
are plaited or folded 
round the axis orgrow- 

Fig 220. Fig. 221. . ■ J. T 1 i. 

^ mg point. In plants 

of warm climates the- buds are often formed by the ordinary leaves 
without any protecting appendages ; such leaves are called naked, 

Veenation. — The arrangement of the leaves in the bud has been 
denominated vernation (ver, spring), or proefoliation (jprx, before, and 
folium, leaf), or gemmation {gemma, a bud). In considering vernation 
we must take into account both the manner in which each individual 
leaf is folded and also the arrangement of the leaves in relation to 
each other. These vary in different plants, but in each species they 
follow a regular law. The leaves in the bud are either placed simply 
in apposition, as in the Mistleto, or they are folded or rolled up 
longitudinally or laterally, giving rise to different kinds of vernation, 
as delineated in fig. 222 o-n, where the dot represents the axis and 
the folded or curved lines represent the leaves, the thickened part in- 
dicating the midrib ; figs, a and g being vertical sections ; l-f and 
h-n, horizontal. 

The leaf taken individually is either folded longitudinally from 
apex to base (fig. 222 a), as in the Tulip-tree, and called reclinate 
or replicate ; or rolled up in a circular manner from apex to base, as 

Fig. 210. Leaf-ljud of Sycamore {A(xr 'pseudo-^laiawm} covered with scales. /, The 
branch. ;p, Pulvinus or swelling at the base of the leaf which has fallen, leaving a scar or 
cicatricula, c, in which the remains of three vascular bundles are seen, e e, Imbricated scales 
of the bud. Fig. 221, Transverse section of the same leaf-bud. e e e e. The scales arranged 
in an imbricated manner, like the tiles on a bouse. /, The leaves folded in a plaited manner, 
exhibiting plicate vernation. 



VERNATION OR PR^FOLIATION. 



Ill 



in Ferns (fig. 222 g), and called cirmiate (circino, I turn round) ; or 
folded laterally, conduplicate, as in Oak (fig. 222 b) ; or it has several 
folds like a fan, plicate or plaited, as in Vine and Sycamore (figs. 221 /,, 
222 c), and in leaves witli radiating' vernation, where the ribs mark 
the foldings ; or it is rolled upon itself, convolute or supervolute, as in 
Banana and Apricot (fig. 222 d) ; or its edges are rolled inwards, 
involute, as in Violet (fig. 222 e) ; or outwards, revolute, as in Eose- 
maiy (fig. 222 /). The difi'erent divisions of a cut leaf may be 
folded or rolled up separately, as in Ferns, while the entire leaf may 
have either the same or a different kind of vernation. 

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 




Pig. 222. 



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 
valvule vernation (fig. 222, 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. 220, 221) ; and 
occasionally the margin of one leaf overlaps that of another, while it, 
in its turn, is overlapped by a third, so as to be twisted, spiral, or con- 
tortive (fig. 222 i). When leaves are applied to each other, face to 
face, without being folded or rolled together,.they are appressed. When 
the leaves are more completely folded they either touch at their 

Fig. 222. Diagrams to show the different Icinds of vematiou. o-gr, The folding of indi- 
vidual leaves ; a and g being vertical sections, bode and /being horizontal, a, Beclinate 
or replicate, b, Conduplicate. c, Plicate, d, Convolute, a, Involute. /, Revolute. a 
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, Valvate, i, Twisted, spiral, or contortive. k. Opposite or 
accumbent, with the margins reduplicate. I, Induplicate. m, Bquitant. 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. 



112 . LEAF-BUDS AND BKANCHES. 

extremities and are accumhent or opposite (fig. 222 k), or are folded 
inwards by their margin, and become induplicaie (fig. 222 Z) ; or a 
conduplicate leaf covers another similarly folded, which in turn covers 
a third, and thus the vernation is equitant (riding), as in Privet 
(fig. 222 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 ohvolute, as in Sage (fig. 222 n). The scales of a bud 
sometimes exhibit one kind of vernation, and the leaves another (fig. 
221). The same modes of arrangement occur in the flower-buds, as 
wHl be afterwards shown. 

Leaf-buds, as has been stated, are either terminal or lateral. By 
the production of the former (fig. 219 ht), stems increase in length, 
while the latter (fig. 219 ha, ha, ha) give rise to branches, and 
add to the diameter of the stem. The terminal leaf-bud, after pro- 
ducing 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 leaf-bud continues the growth 
in spring. 

In some trees of warm climates, as Oycas, 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 
they do not attain a great diameter (fig. 134, 1). In other trees, 
especially Exogens, besides the terminal bud there are also lateral 
ones. These, by their development, give rise to branches (rami), from 
which others, called branehlets or twigs (ramuli) arise. Such buds 
being always produced in the axil of leaves are of course arranged in 
a manner similar to the leaves. By the continual production of lateral 
leaf-buds, the stem of exogenous plants acquires a great diameter. 

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. 

When the terminal bud 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 



LEAF-BUDS Al^D BRANCHES. 113 

buds, a woody plant is made to assume a bushy appearance, and thus 
pollard trees are produced. Pruning has the effect of checking the 
growth of terminal buds, and of causing lateral ones 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 fascicula- 
tion 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 (p. 46) is a stem of this nature, forming 
buds and roots. Such is also the case in the stem of Cyclamen, 
Testudinaria Elephantipes, and in the tuber of the potato. The pro- 
duction of lateral in place of terminal buds sometimes gives the stem 
a remarkable zigzag aspect. 

In many plants with a shortened axis, the lateral buds produce 
long branches. Thus the flcu/ellum (Jlagelhim, a whip or twig), or 
runner of the Strawberry and Eanunculus, 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 
fleshy plants from a shortened axis, and developing a bud at its ex- 
tremity, which is capable of 
living when detached, as in 
Houseleek. Fig. 223 repre- 
sents a strawberry plant, in 
which a' is the primary axis, 
ending ia a cluster of green 
leaves, r, and some rudi- 
mentary leaves, /, and not 
elongating ;_ from the axil of 
one of the leaves proceeds a 
branch or runner, a", with a 
rudimentary leaf,/, about the Fig. 223. 

middle, and another cluster 

of leaves, /" and r, forming a young plant with roots ; from this a 
third axis comes ofi", a", and so on. In many instances the runner 
decays, and the young plant assumes an independent existence. 
Gardeners imitate this in the propagation 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 production of adventitious roots, 
cutting off its connection with the parent. 

When the stem creeps along the surface of the ground, as in 
the Ehizome (flg. 107), or completely under ground, as in the Soboles 

Fig. 223. Flagellum or Runner of the Strawbeiry. a'. One axis wlioh has produced a 
cluster of leaves, the upper, r, green, the lower, /, rudimentary. Prom the axil ot one of the 
latter a second axis, a", arises, hearing about the middle a rudimentary leaf, /', and a cluster 
of leaves, r, partly green and partly rudimentary, /", at its extremity. Prom the axil of one 
of the leaves of this cluster a third axis, a, proceeds. 

I 




114 AEEIAL AND SUBTERRANEAN LBAE-BUDS. 

or creeping stem (fig. 108), 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. 108 
(soboles of a Rush), r is the extremity of the axis or terminal bud, / e 
the leaves in the form of scales, f a the aerial shoots or branches, 1 1 
being the level of the ground. Again, in fig. 107 (rhizome of Solomon's 
seal), a is the terminal bud which has been formed subsequently to b, 
'b the bud which has sent up leaves, and which has decayed, c c being 
the scars left by the similar buds of previous seasons. 

Abeial and Subteeranean Leaf-buds. — 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, 
subterranean buds are annually produced, which appear above ground 
as shoots or branches covered with scales at first (fig. 129 I), and 
ultimately with true leaves. The young shoot is called a Turio (turio, 
a, young branch). These branches are herbaceous and perish annually, 
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 
lateral ones may be separated as distinct plants in the form of suckers 
(surculi). The potato is a thicliened stem or branch capable of 
developing leaf-buds, which in their turn form aerial and subterranean 
branches, the former of which decay annually, whUe the latter remain 
as tubers to propagate the plant. Thus, in fig. 109, s s is the surface 
of the soil, ^ a is the aerial portion of the potato covered vrith leaves, 
t is the subterranean stem or tuber covered with small scales or pro- 
jections, 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. 

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 axis is produced which dies 
down. New bulbs, or cloves, as they are called, are produced in the 
axil of the scales arising from the subterranean axis. At the base of 
the scales there is a flattened 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 in fig. 224, where p marks the 



SUBTEERANEAN LEAF-BUDS, BULB, AND OOEM. 



115 



disc or round flat portion formed by the bases of the lateral buds from 
■which the fasciculated roots, r, proceed, e the scales or modified leaves, 
and / the true leaves. In the vertical section (fig. 225), h is the new 
bulb, formed like a bud in the axil of a scale. The new bulb some- 
times remains attached to the parent bulb, and sends up an axis and 
leaves ; at other times it is detached in the course of growth, and 





Fig. 224. 



Fig. 225. 



Fig. 226. 



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 naUed hull of the white lily (fig. 226 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, 
Tulip, and Leek (fig. 224). 

The scales in bulbs vary in number. In Gagea there is only one 
scale ; in the Tulip and Fritillaria imperialis they vary from 2 to 5 ; 
while in Lilies and Hyacinths there are a great number of scales. In 
the Tulip a bud is formed in the axil of an outer scale, and this gives 
rise to a new flowering axis, and a new bulb, at the side of which 
the former bulb is attached in a withered state. In some Liliaceous 
plants the bulbs continue for two or more years. The bulb may 
bear on the same axis growths belonging to two seasons ; or it may 
bear numerous growths or shortened axes of several years. In the 
common hyacinth -there may be seen axes of four distinct generations 
on one bulb. 

The OoEM (xo^//,6s, a stump) has already been noticed under 

Fig. 224. Tunicated bulb of Allium Porrum, or the Leek, r. Boots, p, A circular disc, 
or shortened stem intervening between the roots and the bulbous swelling, e e. Scales or 
subterranean modified leaves. /, Upper leaves which become green. Fig. 225 Vertical 
section of the tunicated bulb of the Leek. The letters indicate the same parts as in the 
last figure, h, Bud situated in the axil of a scale, which, by its development, forms a new 
bulb. Fig. 226. Scaly or naked bulb of Lilium album, r, Boots, eee, Scales or modified 
underground leaves, t, The flowering axis, cut. 



116 ANOMALIES AND TRANSFORMATIONS OF LEAF-BUDS. 

the head of subterranean stems (p. 48, fig. 110). It may be considered 
as a bulb in which the central portion or axis is much enlarged, whUe 
the scales are reduced to thin membranes. Some have called it a 
solid bulb. A Oorm may be generally distinguished from a Bulb by 
a transverse section of the latter presenting a series of circles, equal in 
number to the fleshy scales arranged around its central axis. It is 
seen in the 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 pro- 
duced corms come gradually nearer and nearer to the surface of the 
soil ; or lateral buds, as in Colchicum, represented at fig. 110, where r 
indicates the roots, / the leaf, a' 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. 

Anomalies and Teansformations of Leaf-Buds. — Leaf-buds 
arise from the medullary system of the plant, 
and in some instances they are found among 
the cellular tissue, without being in the axU 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 
J,. 2^. 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 
surrouading 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. 227). The 
nodules sometimes form hnots 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 conveyed 
downward by the bark and cambium cells, and are deposited round 
a nucleus or central mass. 

Pig. 227. Vertical section of a nodule, n, or embryo-lmd embedded in the bark of the 
Cedar. It forms a projection on the surface. The woody layers form zones round a kind of 
pith. 




ANOMALIES AND TEANSFOEMATIONS OF LEAF-BUDS. 117 



Leaf-buds sometimes become extra-axillary (%. 228 6), in con- 
sequence 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. 229 6). 





Pig. 228. Pig. 229. 

Such an occurrence is traced to the presence of latent or adventitious 
buds. Fig. 228 represents a branch, r, of walnut, p the cut petiole, 
and 6 two buds, of which the upper is most developed ; while fig. 229 
exhibits a branch of Lonicera tartarica, with numerous buds, h, in the 
axil of the leaves, the lowest of which 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 /asciaied [fascia, a band) branches, in some cases, 
however, are owing to the abnormal development of a single bud. 

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. 230 b b b). They resemble 
bulbs in their aspect, and consist of a 
small number of thickened scales enclos- 
ing a growing point. These scales are 
frequently united closely together, so as 
to form a solid mass. Bulbils are there- 
fore • transformed leaf-buds, which are 
easily detached, and are capable of pro- 
ducing young plants when placed in 
favourable circumstances. 

Occasionally leaf-buds are produced naturally on the edges of 

Pig. 22S. Portion of a branch, r, of the walnut, bearing the petiole, p, of a leaf which 
has been cut. In the axU of the leaf, several buds, 6, are produced, the highest of which 
are most developed. Fig. 229. 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, h, are seen, the lowest of which are most developed. Fig. 

230. Portion of the stem of Lilium bulbiferum, with three alternate leaves, ///, and three 
bulbils or bulblets, 6 6 6, in their axils. 




Fig. 230. 



118 ANOMALIES AND TRANSFORMATIONS OF LEAF-BUDS. 



leaves, as in Bryophyllum calycinum and Malaxis paludosa (fig. 231^, 
and on the surface of leaves, as in Ornithogalum thyrsoideum (fig. 232). 
These are capable of forming independent plants. Similar buds are 
also made to appear on the leaves of Gesnera, Gloxinia, and Achimenes, 
by wounding various parts of them, and placing them in moist soil ; 
this is the method often pursued by gardeners in their propagation. 
The Ipecacuan plant has been propagated by means of leaves inserted 






Fig. 232. Fig. 233. 

in the soU. In this case the lower end of the leaf becomes thickened 
like a corm, and from it roots are produced, and ultimately a bud and 
young plant, as shown in fig. 233. The cellular tissue near the surface 
of plants seems therefore to have the power of developing abnormal leaf- 
Fig. 231. Extremity of a leaf, I, of Malaxis paladosa, the margin of which is covered with 
adventitious bnds, h i ; thus becoming proliferous. Fig. 282. Portion of the blade of a 
leaf, /, of Ornithogalum thyrsoideum, on the surface of which are developed adventitious 
or abnormal buds, 6 6 6 J, some of which are large. Fig. 233. Ipecacuan leaf, with petiole, 
annulated root, and young plant, a. Lamina or blade of leaf, h, Petiole or leaf-stock, 
c, Swelling at the end of the petiole after being placed in the soil, d. Root proceeding from 
the swelling, showing an annulated form, e. Young plant arising from the swelling of the 
petiole. 



SPINES OE THORNS. 



119 



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 (proks, offspring, and fero, I bear). 

Spines or Thoens. Branches 
are sometimes arrested in their 
development, and, in place of 
forming leaves, become trans- 
formed into spines and tendrils. 
Spines or thorns are undeveloped 
branches, ending in more or less 
pointed extremities, as in the 
Hawthorn. Plants which have 
spines in a wild state, as the 
Apple and Pear, often lose them 
when cultivated, in consequence 
of their being changed into 
branches ; in some cases, as in 
Prunus spinosa, or the Sloe 
(fig. 234), a branch bears leaves 
at its lower portions, and terminates 




Fig. 234. 



rig. 235. 



in a spine. Leaves them- 




Fig. 236. 



Fig. 237. 



Fig. 238. 



Fig. 234. Branch of Pniniis spinosa, or Sloe, with alternate leaves, and ending in a spine 
or thorn. Fig. 235. Pinnate leaf of Astragalus massUiensis, the midrib of which, r, ends 
in a spine, s, Petiolary stipules. /, Nine pairs of leaflets. Fig. 236. Branch ,of Berberis 
vulgaris, or Barberry, the leaves of which, ///, are transformed into branching spines. In 
the axil of each, a cluster, r rr, of regularly formed leaves is developed. Fig, 237. Base 
of the pinnate leaf of Robinia pseudacacia, the stipules of which, s 5, are converted into 
spines or thorns. &, Branch, r. Petiole. Fig. 238. Branch of Ribes Uva-crispa, in which 
the pulvinus or swelling, c c c, at the base of each of the leaves, ///, is changed into a spine, 
which is either simple, or double, or triple, h &, Leaf-buds arising from the axil of the 
leaves. 



120 



SPINES OE THOENS, AND TENDEILS. 



selves often become spiny by the hardening of their midrib or 
primary veins, and the diminution or absence of parenchyma, as in 
Astragalus massiliensis (fig. 235 r), 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. 236), where some of the leaves, ///, 
are produced in the form of spiny branches, with scarcely any paren- 
chyma. In place of producing a lamina or blade at its extremity, the 
petiole sometimes terminates in a spine. Stipules are occasionally trans- 
formed into spines, as in Eobinia pseudacacia (fig. 237 s s), and 
such is also the case with the swelling or pulvinus at the base of the 
leaf, as in Ribes Uva-crispa (fig. 238 c c c). Branches are sometimes 
arrested in their progress at an early stage of their development, 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. 

Tendrils. — A leaf-bud is sometimes developed as a slender spiral 
or twisted branch, called a tendril or cirrus (cirrus, a curl). TendiUs 
have their homologues in various organs, such as stems, branches, leaves, 

stipules, buds, midribs, parts 
of the flower, etc. When 
tendrils occupy the place of 
leaves, and appear as a con- 
tinuation of the leaf-stalk, 
they are called petiolary, as 
in Lathyrus Aphaca, in which 
the stipules perform the func- 
tion of true leaves. In 
Flagellaria indica, Gloriosa 
superba, Anthericum cirrha- 
tum, and Albuca cirrhata, 
the midrib of the leaf ends 
in a tendril ; and in 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 Passion-flower the 
lateral buds are thus altered. 




Fig. 239. 



Kg. 289. Portion of a branch of the Vine (VUls vinifera). a'. First axis, terminated hy 
a tendril or cirrus, i/, which assumes a lateral position, and bears a leaf, /'. From the axil 
of this leaf a second axis, a", comes off, which seems to be a continuation of the first, and 
is terminated also by a tendril, v", bearing a leaf, /". From the axil of this second leaf a 
third axis, a'", arises, terminated by a tendril, v'", and bearing a leaf, /'", from the axil of 
which a fourth axis, a"", arises. 



TENDRIL OE CIEEUS. 121 

with the view of enabling the plant to climb. In the Vine the tendrils 
are looked upon as the terminations of separate axes, or as transformed 
terminal buds, and are sometimes called sarmenta. In the Vine 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. 
239 represents the branch of a Vine, in which a is the primary or first 
formed axis, ending in v', a tendril or altered terminal bud, and having 
a leaf, /', on one side. Between this leaf and the tendril, which repre- 
sents the axis, a leaf-bud was formed at an early date, producing the 
secondary axis, or branch, o", ending in a tendril, v", with a lateral leaf, 
/", from which a tertiary axis or branch, a", was developed, ending in a 
tendril v", and so on. The tendrils of Ampelopsis Veitchii are termi- 
nated by discs which secrete a sticky matter, by means of which they 
adhere to walls, etc. The tendrils, like those of the Vine, are modi- 
fications of the axis. 

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 which produces 
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 the vanUle plant (Vanilla 
aromatica) the tendrils are produced opposite the leaves, until the 
plant gains the top of the trees by which it is supported ; the upper 
tendrils being then developed as leaves. The midrib is sometimes 
prolonged in a cup-like or funnel-shaped form ; this is occasionally 
seen in the common cabbage, and 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. 

Special Functions of Leaves. 

Leaves expose the fluids of plants to the influence of air and 
light. The fluids so exposed are elaborated, and thus fitted for the 
formation of the various vegetable tissues and secretions. For the 
proper performance of this function the structure of the leaves and 
their arrangement on the stem and branches, renders' them well 
adapted. A plant, if constantly stripped of its leaves, is destroyed, 
from non-development of tissue and absence of secretions. On this 
principle, weeds, with creeping stems and vigorous roots, which are 
with difficulty eradicated, may be killed. The elaboration of fluids 
in the leaves necessarily implies interchange of their constituents with 
those of the surrounding atmosphere ; hence two processes are inevi- 
table — a passing inwards into the leaf of the atmospheric elements 



122 FUNCTIONS OF LEAVES. 

by a process of absorption, and. an outward current of the components 
of the plant-juices by a process of exhalation. In the cells of the 
leaves changes take place under the agency of light, by which oxygen 
is given oflf and carbon fixed. These will be considered under the 
head of vegetable respiration. The absorption of carbonic acid and 
of fluids is carried on by the leaves, chiefly through their stomata, 
and most rapidly by the under surface of ordinary leaves in which 
the cuticle is thinnest, the cellular tissue least condensed, and stomata 
most abundant ; the upper surface of the .leaf, which usually pre- 
sents a polished and dense epidermis, with few stomata, taking little 
part in such a process. Hoffman has ascertained that leaves absorb 
fluids in large quantities ; that during a fall of rain the vegetable 
fluids undergo from such a cause a process of dilution, leading to an 
immediate and more rapid descent of sap, which under such circum- 
stances is capable of general diffusion throughout the several vege- 
table tissues. Some physiologists have expressed doubts as to absorp- 
tion being carried on by the leaves in ordinary circumstances. Leaves 
also absorb gaseous matters. Saussure states that oxygen is absorbed 
by the leaves during night, the quantity varying according to the 
nature of the plant. . Boussingault found that the leaves of the Vine 
absorbed carbonic acid from the air. Other experiments prove that 
ammonia and nitrogen are similarly acted on. 

Leaves also give off" gases and liquids by a process of exhalation 
or transpiration. A moderate amount of carbonic acid is exhaled 
during darkness, and a large quantity of liquid is given off by tran- 
spiration. The number and size of the stomata regulate the transpi- 
ration of fluids, and it is modified by the nature of the epidermis. 
The absorbing power of leaves depending on simUar causes, is capable 
of being increased by any process which removes either natural or 
imposed obstructions to the free action of their surface. It is thus 
that rain, while supplying the material for absorption, at the same 
time renders the leaf more capable of such action. In plants with a 
thick and hard epidermal covering, exhalation 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 
phyllodia of Australian plants is probably connected with the dry 
nature of the climate. The process of transpiration is more under the 
influence of light than of heat. It assists the process of endosmose, 
by rendering the fluid in the cells thicker, and thus promotes the 
circulation of sap. 

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 surface of 2736 square 
inches, transpired on an average nineteen ounces per day ; a Vine, 
of 1820 square inches, from five to six ounces. Deheran found that 



EXHALATION OE TEANSPIEATION. 123 

large leaves of Colza evolved in an hour from one to two per cent of 
their weight of water. Experiments have shown that the mean amount 
of water contained in the leaves of the Cherry] Laurel is 6 3 '4: per cent, 
and of this only about 6 per cent could be easily removed by sulphuric 
acid or chloride of calcium. In the sun leaves transpire most in a 
saturated atmosphere. In the shade transpiration ceases when the 
atmosphere is loaded with watery vapour. Experiments on exhalation 
may be 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 ex- 
periment may be varied by puttihg the apparatus in darkness, when 
little or 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 difference 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 exist are chiefly concerned 
in the aeration of the sap, whUst other assimilative processes go on in 
the upper cells. 

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. This change 
of colour is chiefly occasioned by the diminished circulation in the 
leaves, and the higher degree of oxidation to which their chlorophyll 
has been submitted. Leaves which are articulated with the stem, as 
in the Walnut and Horse-chestnut, fall and leave a scar, whUe 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 Gatingas. The period of defoliation varies in 
different countries according to the nature of their climate. 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 
deficiency of light and heat in winter causes a cessation in the 
functions of the cells of the leaf; its fluids disappear 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 ; a process of disjunction 



124 FUNCTIONS OF NUTRITIVE ORGANS. 

takes place by a folding inwards of the tissue at the point where the 
leaf joins the stem or branch, and this gradually extends ; complete 
separation then takes place, and the leaf 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 op the 
Nutritive Organs. 

In order that plants may be nourished, food is required. This food, 
in a crude state, enters the roots by a process of absoi-ption or imbibi- 
tion ; 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 
products and secretions. 

1. — Food of Plants and Sources whence they derive their Nourishment. 
Chemical Composition of Plants, 

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 
conclusions. Much has been done by 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 explained 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 cannot be 
fully explained by 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. 

Plants are composed of certain chemical elements, which are com- 
bined in various ways, to form organic and wiorganic 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 metals, combined with oxygen, other metal- 
loids, and acids. In aU plants there is a greater or less proportion 
of water, the quantity of which is ascertained by drying at a temper- 
ature a little above that of boiling water. By burning the dried plant 
the organic constituents disappear, and the inorganic part is left in 



CHEMICAL COMPOSITION OF PLANTS. 



125 



the form of ash. 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 


67 


French Beans 






. 9317 


619 


64 


Red Beet . 






. 8501 


1390 


109 


Asparagus 






. 9210 


735 


55 


Water Cress 






. 9260 


633 


107 


Sorrel 






. 9207 


702 


91 


Parsley 






. 8430 


1299 


271 


Fennel . 






. 8761 


1048 


191 


Salsafy 






. 7951 


1929 


120 


Mustard 






. 9462 


436 


102 


n analysis of ! 


00 


parts 


of Fruits gives the following results 








Water. 


Organic. - 


Inorganic. 


Strawberry . 


, 


, 


90-22 


9-37 


0-41 


Green Gage, wh 


ole fruit . 


83-77 


16-83 


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 


GooselDerry . 






90-26 


9-35 


0-39 





Wheat. 


Oats 


Carbon . 


. 455 . 


. 607 


Hydrogen 


57 .. 


. 64 


Oxygen . 


. 430 .. 


. 367 


Nitrogen * 


. 35 .. 


. 22 


Ash . 


. 23 .. 


. 40 



The following table, by Johnston, represents the constituents in 
1000 parts of plants and seeds, dried at 230° Fahrenheit, and in the 
state in which they are given to cattle ; the organic matter being 
indicated by the carbon, oxygen, hydrogen, and nitrogen ; the inorganic 
by the ash : — 

Wheat. Oats. Peas. 

465 

61 

401 

42 

31 

By the process of drying, the 1000 parts 
water in the following proportions : — 

Wheat 166 ... Peas 86 

Oats 151 ... Hay 158 

As plants have no power of locomotion, it follows that their food 
must be universally distributed. The atmosphere and the soil ac- 
cordingly contain all the materials requisite for their nutrition. These 
materials must be supplied either in a gaseous or a liquid 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. 



Hay. 


Turnips. 


Potatoes 


458 


... 429 . 


. 441 


50 


... 56 . 


. 58 


387 


... 422 . 


. 439 


15 


... 17 . 


. 12 


90 


... 76 . 


. 50 


of these substances los 


Turnips 925 




; 


Potatoes 722 





126 OEGANIC CONSTITUENTS OF PLANTS. 

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 con- 
cerned in the support of vegetation. 

Organic Constituents and their Sources. 

Caebon (0) is the most abundant element in 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 with oxygen, however, in the 
form of carbonic acid, it is readily taken up either in its gaseous state 
by the leaves, or in combination with water by the roots. The humus 
or vegetable mould in the soil contains carbon, and in soils 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 available for the 
purpose of plant-growth. Carbon has the power of absorbing 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 Tnnr part, arising from the respiration 
of man and animals, combustion, and other processes. A certain 
atmospheric equilibrium is thus maintained, consequent on the dif- 
ference between vegetable and animal respiration, the latter giving 
out carbonic acid, which the former consumes. 

Oxygen (0) enters into the composition of all plants, but never 
in quantity sufficient to convert all the hydrogen and carbon present 
in the plant into water and carbonic acid. In the ash of plants, 
oxygen, next to carbon, is the most abundant constituent. Oxygen in 
the air amounts to about 20' 9 per cent, and it forms f by weight of 
water. Combined with various elements it forms a great part of the 
soil and solid crust of the earth. It is chiefly in its state of combina- 
tion with hydrogen to form water (H^O) that oxygen is taken up by 
plants, but also as carbonic acid (CO^) and oxysalts. 

Hydkogen (H) 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 i by weight of water, and it 
is present in the atmosphere in combination with nitrogen. It is also 
found in the air united with sulphur (S) and carbon, as a product of 
vegetable decay. It is mostly from the decomposition of water by 
the combined action of chlorophyll and sunlight that plants obtain 
their supply of hydrogen. , 



ORGANIC CONSTITUENTS OF PLANTS. 127 

NiTEOGEN (N) is another element found in plants. It forms 79-1 
per cent of the atmosphere, and abounds in animal tissues. It is 
therefore requisite for the purposes of animal life that nitrogen be 
furnished in food. Those vegetables containing the greatest quantity 
of nitrogenous matter are the most nutritive. Animal matters, during 
their decay, give off nitrogen, combined with hydrogen, in the form 
of ammonia (NHs), 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 thunderstorms 
are frequent, the nitrogen and oxygen of the air are sometimes made 
to combine, so as to produce nitric acid (NzOs), 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 disengage- 
ment of ammoniacal salts and carbonic acid by volcanic processes 
going on underneath ; and to the same source he traces the abundance 
of glutra in the crops, as evidenced by the excellence of Italian 
macaroni. 

Mulder maintains that the ammonia is not carried down from 
the atmosphere, but is produced in the soO. by the combination 
between the nitrogen of the air and the hydrogen of decomposing 
matters. The same thing takes place, as ia the natural saltpetre 
caverns of Ceylon, with this exception, that, by the subsequent action 
of oxygen, ulmic, humic, geic, apocrenic, and crenio acids, are formed, in 
place of nitric acid. These acids consist of carbon, oxygen, and 
hydrogen, in different proportions, and they form soluble salts with 
ammonia. By all porous substances, like the soil, ammonia is pro- 
duced, 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 humus become impregnated with ammonia. 

These four elementary bodies then are supplied to plants, chiefly 
in the form of carbonic acid (OO2), water (HjO), and ammonia (NH3). 
In these states of combination they exist in the atmosphere, and 
hence some plants can live suspended in the air without any attach- 
ment to the soil. When a volcano or a coral island appears above 
the waters of the ocean, the lichens which are developed on it are 
nourished in a great measure by the atmosphere, although they sub- 
sequently derive inorganic matter from the rocte, to which they 
are attached. Air plants, as Bromelias, Tillandsias, some Orchidacese, 
and many species of Ficus, can grow for a long time in the air. 
In the Botanic Garden of Edinburgh a specimen of Ficus australis 
lived in this condition for upwards of twenty years, receiving no 
supply of nourishment except that afforded by the atmosphere and 



128 INORGANIC CONSTITUENTS OF PLANTS. 

common rain water, containing, of course, a certain quantity of in- 
organic matter. 

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 glutin, albumin, 
casein, and fibrin. The latter compounds seem to require for their 
composition not merely the elements already noticed, in the form of a 
basis, called Protein, but certain proportions of sulphur and phosphorus 
in addition ; thus, albumin = 10Pr. + 1P + 2S; fibrin = 10 Pr. 
+ 1 P + 1 S ; casein = 10 Pr. + 1 S. The tissues, into the com- 
position of ■which these protein 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 and their Sources, 

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 few of them have 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. 

The organic part of plants, even in a dried state, forms from 88 
to 99 per cent of their whole weight. Consequently, the ash or 
inorganic matter 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 Miilder could 
not detect a particle of ash in Mycoderma vini, nor in moulds pro- 
duced in large quantity by milk sugar. Deficiency of inorganic 
matter, however, in general injures the yigour of plants, and it will 
be found that, in an agricultural point of view, this requires par- 
ticular attention— a distinct relation subsisting between the kind and 
quality of the crop, and the nature and chemical composition of the 
soU 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 



INORGANIC CONSTITUENTS OF PLANTS. 



129 



the same soil, the quantity and quality of the ash varies — the dif- 
ference being greater the more remote the natural affinities of the 
plants are. 

The following are the inorganic elements of plants and their 
combinations : — 



Chlorine (CI.) 
Iodine (I.) 
Bromine (Br.) 

Sulphur (S.) 



combined ■with metals forming 
metals 
metals 
metals 



Phosphorus (P.) 
Potassium (K.) | '" 

Sodium (Na.) 



Calcium (Ca.) 

Magnesium (Mg.) 
Aluminum (Al.) 
Silica (Si.) 
Iron (Fe.) 
Manganese (Mn.) 
Copper (Cu.) 



hydrogen 

oxygen 

oxygen 

oxygen 

chlorine 

oxygen 

chlorine 

oxygen 

chlorine 

oxygen 

oxygen 

oxygen 

oxyg«n 
sulphur 



chlorides, 
iodides, 
bromides, 
sulphides. 

1 sulphuretted hydrogen, or 
hydro-sulphuric acid, 
sulphuric acid, 
phosphoric acid, 
potash. 

chloride of potassium, 
soda, 
chloride of sodium. 

(common salt.) 
lime, 
chloride of calcium. 



alumina, 
silica, 
oxides 
and 
sulphides. 



To these we may add Fluorine (P), the presence of which in plants 
has been recently noticed. The extraordinary attraction of this 
element for Silica renders it a matter of impossibility to procure it 
in a separate state for examination. It is found in those vegetable 
structures in which Silica abounds, as in the stems of the Graminese 
and Equisetacese. 

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 
Dried leaves 
Dried alburnum 
Dried duramen 



60 parts of ash in 1000 
53 

i 

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, 045 ; 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. 
The following tables show the relative proportion of inorganic 
compounds present in the ash of plants : — 



130 



INORGANIC CONSTITUENTS OF PLANTS. 



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


010 


0-30 




11 '77 lbs. 


35-18 lbs 



In 1000 lbs. of the grain of the Oat are contained 25-80 lbs., and of the dry straw 
57-40 lbs. of inorganic matter, consisting of — 



Potash 

Soda . 

Lime . 

Magnesia 

Alumina 

Oxide of Iron 

Oxide of Manganese 

Silica . 

Sulphuric acid 

Phosphoric acid 

Chlorine 



Grain. 


Straw. 


1-50 


8-70 


1-32 


0-02 


0-86 


1-52 


0-67 


0-22 


0-14 


0-06 


0-40 


0-02 


0-00 


0-02 


19-76 


45-88 


0-35 


0-79 


0-70 


0-12 


0-10 


0-05 


25-80 lbs. 


57-40 



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





Field Bean. 


Field Pea. 


Rye-grass 




Seed. 


Straw. 


Seed. 


Straw. 


Hay. 


Potash 


4-15 


16-56 . 


.. 8-10 


2-35 .. 


. 8-81 


Soda 


8-16 


0-50 . 


.. 7-39 


— 


. 3-94 


Lime 


1-65 


6-24 . 


.. 0-58 


27-30 .. 


. 7-34 


Magnesia 


1-58 


2-09 . 


.. 1-36 


3-42 .. 


. 0-90 


Alumina; 


0-34 


0-10 . 


.. 0-20 


0-60 .. 


. 0-31 


Oxide of Iron 





0-07 . 


.. 0-10 


0-20 .. 


— 


Oxide of Manganese 


— 


0-05 . 





0-07 .. 





SUica 


1-26 


2-20 . 


.'.' 4-10 


9-96 .. 


. 27-72 


Sulphuric acid 


0-89 


0-34 . 


.. 0-53 


3-37 .. 


. 3-53 


Phosphoric acid . 


2-92 


2-26 . 


.. 1-90 


2-40 .. 


. 0-25 


Chlorine 


0-41 


0-80 . 


.. 0-38 


0-04 .. 


. 0-06 




21-36 


81-21 


24-64 


49-71 


52-86 



Dr. R. D. Thomson gives the following analysis of the inorganic 
matter in the stem and seeds of Lohum perenne : — 



stem. 


Seed. 


64-57 


42-28 


12-51 


18-89 


— 


3-12 


— 


trace 


— 


3-61 


4-01 


5-31 


6-50 


18-55 


0-36 


2-10 


8-03 


4-80 


2-17 


1-38 



INOEGANIO CONSTITUENTS OF PLANTS. 131 

Silica . 

Phospliorio acid 

Sulphuric acid 

Chlorine 

Carhonic acid 

Magnesia 

Lime . 

Peroxide of Iron . 

Potash . 

Soda . 

These inorganic elements 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 in their composition. Sulphates and 
phosphates are required to supply part of the material necessary for 
the composition of the nutritive protein compounds found in grain. 

Silica (SiO^) abounds in Grasses, in Equisetum, and other plants, 
giving firmness to their stems. The quantity contained in the Bamboo 
is very large, and it is occasionally found in the joints in the form of 
Tabasheer. Reeds, from the quantity of siliceous matter they contain, 
are said to have caused conflagrations, by striking against each other 
during hurricanes in warm climates. In species of Equisetum, the 
silica in the ash is as follows : — 

Ash. Silica. 

Equisetum arvense . . . 13'84 ... 6-38 

limosum . . . 15-50 ... 6-50 

hyemale . . . 11-81 ... 8-75 

maximum . . . 23-61 ... 12-00 

The third of these furnishes Dutch Reed, 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 combine 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 0. vulgaris has one composed of silicic acid and carbonate 
of lime ; and Ohara hispida has a covering of carbonate of lime alone. 
Silica, the only known oxide of Silicon, contains 28 parts silicon, and 
32 parts oxygen. It is in reality an acid, though a very weak one at 
ordinary temperatures. Its insolubility in water prevents the mani- 
festation of its acid properties under ordinary circumstances. In those 
plants in which silica most abounds. Fluorine has also been discovered. 



132 INORGANIC CONSTITUENTS OF PLANTS. 

The test for the presence of the latter rests in acting on the fluoride 
with concentrated sulphuric acid, and so producing hydrofluoric acid, 
which possesses the property of etching glass ; the glass being coated 
with wax, and the design to be etched traced with a pointed instru- 
ment. 

Lime is found in all plants, and in some it exists in large quantity. 
It occurs sometimes in the form of carbonate on the surface of plants. 
Thus, many of the Characese have a calcareous encrustation. The 
crystals or raphides (p. 10), found in the cells of plants, have lime in 
their composition. In the roots of Turkey and East India Ehubarb 
the crystals of oxalate of lime have been estimated at about 25 per 
cent, while in those of the English plant the proportion is about 10 
per cent. In the Cactus tribe crystals of the same kind have been 
observed, the presence of which, in excessive quantity, imparts brittle- 
ness to the stem of the old plant. 

Soda and Potash occur abundantly iu plants. They are taken 
up from the soil in combination with acids. Those growing near the 
sea have a large proportion of soda in their composition, while those 
growing inland contain more potash. Various species of Salsola, 
Salicornia, Halimocnemum, and Kochia, yield soda for commercial 
purposes, and are called Halophytes (ciX?, salt, and ip-jrov, plant). 
The young plants furnish more soda than the old ones. There are 
certain species, as Armeria maritima, Cochlearia officinalis, Plantago 
maritima, and Silene maritima, which are found both on the sear 
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, potash prevails, and iodine disappears. 

Ieon, Manganese, and Ooppee, especially the two latter, exist 
in small quantity in plants. Iron exists in the soil either as an 
oxide, sulphide, or carbonate, usually occurring as peroxide. Iron 
when held in solution as carbonate is capable of being absorbed into 
the vegetable tissues. ' Copper has been detected in coffee. 

All these inorganic matters are derived in a state of solution from 
the soU, and plants are said to have, as it were, a power of selection, 
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 containing 
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 experi- 
ment, and he found that in watery solutions of mixed salts the plant 
' absorbed all in equal proportions. Daubeny states, that if any par- 



ROTATION OF CEOPS. 



133 



ticular salt is not present, the plant frequently takes up an isomor- 
phous one. 

The differences in the absorption of solutions depend, perhaps, 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 solution, varying from half a grain to five 
grains in the ounce of water, are taken up by roots, and that some 
substances which are poisonous to animals do not appear to act 
energetically upon plants : — 



Ziuoio cHoride . c 
Zincio STilphate 
Cuprio sulphate 
Cupric nitrate 
Cuprio acetate 

Mercuric chloride . 

Arsenions acid 
Potassic aiseniate . 
Phimbic acetate 

Potassic "bichromate 

Ferrous nitrate and I 
sulphate J 

Baric chloride 
Baric nitrate . 

Stroutic nitrate 

Calcic chloride, sul- ) 
phate, and nitrate \ 

Magnesic chloride and (_ 
sulphate f 

Sodic phosphate 

Sodic chloride 



Growing Plants. 
1 beans 
cabbages and ■whestt 
beans 



beans 
wheat 



quickly destroyed. 



cabbages and wheat 
barley and cabbages 
beans 

cabbages, beans, barley 4 
beans 



cabbages and wheat 
beans 

beans 

beans and cabbages 

beans and cabbages 
beans and cabbages 



weak solutions did not de- 
stroy. 

destroyed in a few days. 

destroyed unless much di- 
luted. . 

destroyed in a few days. 

quickly destroyed. 

plants uninjured, unless so- 
lution strong. 

improved when very di- 
luted. 

injui'ed, and if strong de- 
stroyed. 

no injury when diluted. 



EoTATioN OF Ceops. — 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 re- 
quired by others. It is on this principle that the rotation of crops is 
founded ; 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 if grown for 
several years in succession in the same field will deteriorate in a 
marked degree. This has been tested by growing plants on the same 
and on different plots in successive years, with the following 
results : — 



134 



COMPOSITION OF SOILS. 



Potatoes 
Max 
Beans 
Barley . 
Turnips . 
Oats 



in the same plot 
in different plots 
same 
different 
same 
different 
same 
different . 



different 

same 

different 



Average of 6 years 


72 '9 lbs. 


tubers. 


92-8 „ 


>> 


15-0 lbs. 




19-9 




32-8 




34-8 




30-0 




46-5 




104-0 




173-0 




28-0 




32-4 





This slio-ws a manifest advantage in shifting crops, varying from 1 to 
75 per cent ; the deficiency of inorganic matter being the chief cause 
of difi'erence. As this matter is of great importance to plants, it 
follo-ws that the composition of soil requires special notice. 

Chemical Composition of Soils. 

Soils have been divided according to the proportion of clay, sand, 
and lime, -which they possess, into — 

1. Aigillaceous 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 dififers much from that on th? 
surface. Into it ■ the rain carries down various soluble inorganic 
matters, which, when brought to the surface by agricultural opera- 
tions, as trenching and subsoil ploughing, may [materially promote 
the growth of crops. The advantages of subsoil ploughing are 
dependent on the nature of the soil. By means of it the subsoil is 
loosened, so as to be easily acted upon by air and water, and the 
efficiency of the drainage is increased. It is not fitted for all soils, 
and in some instances it may do harm. A knowledge of the chemical 
as well as mechanical nature of soils guides the agriculturist to a 
certain extent in his operations ; since, by the judicious application of 
manures, certain deficiencies may be supplied, and, by admixture, 
soils may be rendered more suitable for the purposes of vegetation. 

HuMTTS, or decaying woody fibre, called also ulmine, or coal of 
humus, exists in soik. It is soluble in alkalies, yielding a brown 
solution, which, when treated with an acid, produces a brown pre- 
cipitate, said to contain humic, ulmic, and geic acids ; but the separate 



;ja di 



COMPOSITION OF SOILS. 



135 



existence of these compounds as definite acids is somewhat doubtful. 
Humus absorbs ammonia, and it is slowly acted upon by the atmo- 
sphere, so as to form carbonic 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. 

Silica, in greater or less quantity, is found in all soUs ; but it 
abounds in sandy soUs. In its ordinary state it is insoluble, and it 
is only when acted upon by alkalis in the soil that it forms compounds 
which can be absorbed by plants. Silica, in a soluble state, exists in 
minute quantities in soils, the proportion, according to Johnston, 
varying from 0'16 to 0'84 in 100 parts, while the insoluble siliceous 
matter varies from 6047 to 83"31 in 100 parts. Wiegman and 
Polstorf found that plants took up sUica from a soil composed entirely 
of quartz sand, from which everything organic and soluble had been 
removed. The following table shows the plants which germinated, the 
height to which they grew previously to being analysed, the quantity 
of silica they contained when planted, and the increase : — 







Silica in the ash. 


Silica had 




Height. 


Seed. Plant. 


increased 


Barley . 


15 inches 


.. 0-034 ... 0-355 . 


.. 10 times. 


Oats . 


18 „ 


.. 0-064 ... 0-354 . 


.. 6i „ 


Buckwheat . 


18 „ 


.. 0-004 ... 0-075 . 


.. 18 „ 


Vetch . 


10 „ 


.. 0-013 ... 0-135 . 


.. 10 „ 


Clover . 


3i „ 


.. 0009 ... 0-091 . 


• • 10 „ 


Tohacco 


5 „ 


., 0-001 ... 0-649 . 


.. 500 „ 



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 saline matters, and may prove beneficial in this way. 

Lime is an essential ingredient in all fertile soils. In 1000 lbs. 
of such soil there are, according to Johnston, 56 lbs. of lime ; whUe a 
soil is barren which contains only 4 lbs. The presence of phosphoric 
acid in soils, in the form of phosphates of potash, 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. Calcareous soils contain upwards of 50 per cent of lime. 
The addition of lime to soils is often highly beneficial, by destroying 
noxious weeds, and preventing disease in crops. Lime is a forcing 
agent, and is useful in stiff clayey soils where it decomposes the silicate 
of potash, forming silicate of lime, and liberating the potash which is 
taken up by the plants. In marly soUs lime exists in the proportion of 
5-20 per cent. In loamy soils lime is in smaller quantity. 

A rough way of estimating the general nature of a soil is thus 
given by Professor Johnston : — 



136 APPLICATION OF MANURE. 

1. Weigh a given portion of soU, heat it and dry it. The lose is water. 

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

3. Add hydrochloric acid to the residue, and from this the quantity of 

lime may he determined. 

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

siliceous sand. 

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

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 
thrives best in a heathy soil, incumbent on a pervious subsoU, and 
at a high altitude ; Larch in loam, with a dry subsoil, in a high 
situation, 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 soU, and at 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 Manuee. 

If the soil does not contain the ingredients required for a crop, 
they must be added in the form of manure. The principle of manur- 
ing 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 importance 
of agricultural chemistry to the farmer. 

Various kinds of Manure. 

Natural Manubes, as farmyard 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. Natural manures may be regarded as confer- 



VAEIOUS KINDS OF MANUEE. . 137 

ring on the soil the most lasting advantage, as from the slowness of 
their decomposition their beneficial effects are not so readily exhausted. 
Plants themselves, in a soluble state, would be the best manure. In 
ordinary farmyard 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 unazotispd matters, the former con- 
sisting of protein compounds which supply nitrogen for the muscular 
tissue of man and animals ; the latter of starchy, mucUaginous, and 
saccharine matters, which furnish carbon as a material for respiration 
and the formation of fat. The object of manuring is chiefly to increase 
the former, and hence those manures are most valuable which contain 
soluble nitrogenous compounds. 

The value of manures is often estimated by the quantity of 
glutin 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 
100 parts of each sample of grain produced he obtaiued glutin and 
starch in the following proportions :— 

Without manure 
Cow dung 
Pigeons' do. 
Horse do. 
Goats' do. 
Sheep do. 
Dried night soil 
Dried ox blood 

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 droppings 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 protein compounds which 
furnish the elements for flesh and blood. The guano which is im- 
ported is the excrement of numerous searfowl which frequent the 
rainless shores of South America and Africa. It often contains 
beautiful specimens of Diatoms, as Oampylodiscus, Coscinodiscus, etc. 
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. ■ 

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 



Glutin. 


Starch 


9-2 


66-7 


12-0 


62-3 


12-2 


63-2 


13-7 


61-6 


32-9 


42-'t 


32-9 


42-8 


33-1 


41-4 


34-2 


41'3 



138 



VARIOUS KINDS OF MANUEE. 



Tnatter includes urate of ammonia and other ammoniacal salts, such as 
oxalate, phosphate, and chloride, as well as decayed organic matter of 
animal origin. The term bone earth includes phosphate 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 searshells. The fixed alkaline salts are various salts of sodium, as 
chloride, phosphate, and sulphate ; a little of a potash salt has been 
detected. 



Smith American Guano. 



Fine 
Chmcha. 

Ammoniacal matter 62 

Bone earth . 20 

Fixed alkaline salts 10 
Rock, sand, earth 0'5 
Water . . 7-5 



Middling, 

42 
24 
14 
5 
15 



Inferior. 

28 
30 
21 
3 
18 



100-0 



100 



100 



African Ouano. 



Ammoniacal matter 
Bone earth 
Fixed alkaline salts 
Bock, sand, earth 
Water 



Best Ichaboe. 


Interior. 


45 


28 


20 


21 


12 


16 


1 


3 


22 


32 



Low Qualities. 


12 




15 


50 




37 


10 




5 


15 




34 


13 




9 


100 


100 


Low Quality. 




20 






17 






14 






25 






24 





100 



100 



100 



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. K. D. 
Thomson, of guano gathered on AUsa Craig : — 

Water 50'30 

Organic matter and ammoniacal salts, containing 3'47 per 

cent of ammonia ....... 12'50 

Phosphates of Ume and magnesia ..... 12'10 

Oxalate of lime ........ 1'50 

Sulphate and phosphate of potash, and chloride of potassium I'OO 

Earthy matter and sand 15'00 

Simple Manuees supply only one or two of the materials re- 
quired for the growth and nourishment of plants. The ammoniacal 
liquor of gasworks, in a very diluted state, has been advantageously 
applied to the soil, on account of the nitrogen which it contains. Soot 
has also been used, from furnishing salts of ammonia. Nitrates of 
potash and soda have been recommended not only on account of the 



VAEIOUS KINDS OF MANURE. 139 

alkalies, but also on account of the nitrogen which they contain, in the 
form of nitric acid. The quantity of glutin 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 Searkale. 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. It also neutralises any acids previously in 
the soil, such as occur occasionally in boggy and marshy land, abound- 
ing 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, glutin and the protein compounds 
of plants cannot be formed. Phosphate of lime exists abundantly in 
animal tissues, and hence it must be furnished by plants. The iise 
of bone-dust as a manure depends in a great measure on the phos- 
phate of lime which it contains. Besides phosphate of lime, bone-ash 
contains from 3 to 12 per cent of phosphate of magnesia, carbonate 
of lime, and salts of soda. The gelatine of bones also seems to act 
beneficially, by forming carbonic acid and ammonia. Bones are best 
applied after being acted on by sulphuric acid, so as to form soluble 
phosphates by decomposition. They are broken into pieces, and 
mixed with half their weight of boiling water, and then with half 
their weight of sulphuric acid. The superphosphate thus formed is 
applied to the soil, either in a dry state by the drill, with sawdust 
.and charcoal added, or in a liquid state, diluted with 100 to 200 parts 
of water. Phosphates and other inorganic matters .sometimes exist 
potentially in the soil, but in a dormant state, requiring the addition 
of something to render them soluble. Allowing the ground to lie 
fallow, stirring and pulverising it, are methods by which air and 
moisture are admitted, time being allowed for the decomposition of 
the materials, which are thus rendered available for plants. Sulphur 
exists in considerable quantity in some plants, as Oruciferse, and it 
forms an element in albumin ; hence the use of sulphuric acid and of 
sulphates as manures. Sulphate of lime or gjrpsum is well fitted as 
a manure for clover, by supplying sulphur and lime, and absorbing 
ammonia. Charcoal in a solid state has been applied with advan- 
tage as a manure. It acts partly by taking up ammonia in large 
quantity, and partly by combining slowly with oxygen, so as to form 
carbonic acid. The effects of carbonic acid on vegetation are said to 
be remarkably conspicuous in some volcanic countries, in which this 



140 VAEIOUS KINDS OF MANUEE. 

gas is evolved from the bottom of lakes. When it accumulates in 
large quantities, however, it destroys plants as well as animals. 

Manuring with Green Chops 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 
seaweeds is also resorted to in cases where they are accessible. They 
supply abundance of carbonate, phosphate, and sulphate of lime, be- 
sides 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 seaweeds act beneficially. 

Liquid Manures have of late years been much employed, and 
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 at once available to the crop. Some 
have advocated 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 lb. of each), in ten gallons of water, to steep 
300 lbs. of seeds, which are afterwards to be dried with gypsum or 
quicklime. 

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 lbs. — 



Lot 1. Left untouched ..... 
„ 2. 2 J barrels Irish quicklime . 

,,3. 20 owt. Lime of gasworks 
,,4. 4J- cwt. Wood charcoal powder 
,,5. 2 bushels Bone-dust 

,, 6. 18 lbs. Nitrate of potash 

„ 7. 20 lbs. Nitrate of soda . 

„ 8. 2^ bolls Soot 

,,9. is lbs. Sulphate of ammonia . 

,,10. 100 gallons Ammoniacal liquor of gas 

works, 5° Twaddell's hydrometer t 

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. 



Produce 


Rate 


per Lot. 


per Acre 


420 . 


. 3360 


602 . 


. 4816 


651 . 


. 5208 


665 . 


. 5320 


693 . 


. 5544 


742 . 


. 5936 


784 . 


6272 


819 . 


. 6552 


874 . 


. 6776 


945 . 


. 7560 



EPIPHYTES AND PARASITES. 141 

Plants are thus employed to form from the atmosphere and soil 
those organic products which^ are requisite for the nourishment of 
man and animals. Nutrition derivable from the atmosphere being 
generally diffused, is accessible to all plants, and is perpetually re- 
newed. Nutrition derivable from the soil being fixed to certain 
localities, requires that those elements contributing to it be mechani- 
cally supplied as they become exhausted. While an animal consumes 
carbon so as to form carbonic acid, gives off ammonia in various 
excretions, transforms organised 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 organised 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. 

Epiphytic and Paeasitio Plants. 

Some, plants grow without any attachment to the soU, and are able 
to derive in a great measure, from the atmosphere, all the materials 
required for their growth. Such plants are called Epiphytes {sit}, upon, 
and purov, a plant), or air-plants, and may be illustrated by the Til- 
landsias, Bromelias, and Orchids of warm climates. Such plants, 
when attached to the surface of trees, may perhaps derive some 
nourishment from the inorganic matter in thfe decaying bark ; but they 
do not become incorporated with, nor do they send prolongations into, 
the trees. Orchidaceous plants, which are always perennial, are found 
in the greatest variety and profusion in those regions where heat and 
moisture abound. Extremes of cold or dryness are the least favour- 
able to their growth. Tillandsias and Bromelias flourish in dry hot 
air without any contact with the earth. 

There are other plants, however, which are true Parasites (iragoi, 
beside, and alrog, food, deriving food from another), sending prolonga- 
tion's 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 diseases of corn, called smut and rust, and the dry rot in wood, 
are due to the attacks of these parasitic Eungi. The minute dust or 
powder produced by these plants consists of millions of germs which 
are easily carried alaout in the atmosphere, ready to fix themselves on 
any spot 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 



142 CIECULATION OF THE SAP. 

leaves. The former, including Orobanche or broom-rape, Lathrsea or 
toothwort, Ouscuta or dodder, derive nourishment entirely from the 
plant to which they are united ; while the latter, as Loranthus, Viscum 
or mistleto, Myzodendron, Thesium, Euphrasia, Melampynim, and 
Buchnera, elaborate sap in their leaves under the action of air and 
light. By this power of elaboration, the mistleto is able to grow on 
different species of plants, as on the apple, beech, oak, etc. Some 
parasites are attached by suckers to the roots of plants, as in the case 
of Broom-rape, Toothwort, and Thesium, and are called root-parasites ; 
while others, as Dodder, Mistleto, etc., derive nourishment from stems, 
and are called stem-parasites. The specific names of many parasites 
are taken from the plants on which they grow. The species of 
Cuscuta or dodder inhabit all the temperate and warm parts of the 
globe, and are peculiarly destructive to clover and iiax. 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 
become attached to it by means of suckers, then all connection with 
the soil is severed, and the Dodder lives as a true parasite. A re- 
markable genus of parasites, called RafElesia, has been found in Sumatra 
and Java. The species 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 Rhimnths (g/'^a, a 
root, and a,v6og, a flower). 

2. — Absorption and Circulation of Fluids. 

While the leaves and other aerial organs of plants have the power 
of absorbing fluids, it is chiefly by the roots that this process takes 
place. The cells of the spongioles or fibrils of the roots are covered 
by a very delicate membrane (p. 38), 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 
reception of fresh nutriment for the plant. Animals having the 
power of locomotion are enabled, as they exhaust the nutritive matter 
of one locality, to remove to another. Plants having no provision for 
locomotion would perish, after taking up all the nourishment in the 
soil in their immediate neighbourhood, were it not that the roots spread 
over large areas in search of food. The nutritive materials in the soil, 
partly derived from the decomposition of its 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 colloid and denser than the external liquid crystalloid matters, 
a process of endosmose takes place by which the latter pass in large 
quantities into the cell through its membranous covering, while a 
small portion of the former is excreted by exosmose. These move- 



CIRCULATION OF THE SAP. 



143 



ments in the contents of cells and vessels take place when fluids of 
difierent densities are separated by an animal or vegetable mem- 
brane. 

If, on opposite sides of an animal or vegetable membrane, we place 
two fluids of unequal density, having an affinity for the interposed 
membrane and for each other, the fluid on the one side being thick and 
gelatinous, whilst the other is thin and watery, two unequal and 
opposite currents are at once established — the thin fluid setting with 
a strong and full current through the membrane towards the thicker 
fluid, which it penetrates ; the thicker fluid, with a more feeble current 
and in less quantity, reaching the thin fluid with which it mingles. 
This constitutes Osmose. The inequality in strength and amount of 
the two currents depends, not so much on the density of the liquids, as 
on their character, those of a gluey or albuminous nature passing 
slowly, whilst those of a more liquid' nature transude very rapidly. 
If the membrane form a sac or bladder, in which the thick gelatinous 
fluid is contained, then the thin fluid rapidly passing 
inwards into the sac penetrates the thick fluid, and 
thus the amount of fluid in the bladder is increased 
and its walls are distended. To this inward current 
the term Endosmose is applied, and conversely, Exos- 
mose refers to the slow and feeble outward current of 
the thick contained fluid. In this instance the Endos- 
mose current is the stronger, but a reversal of the 
relation of the fluids to the membrane renders the 
Exosmose current the stronger, consequently the con- 
tents of the sac are diminished in amount and its 
walls collapse. The relative rapidity of the Exosmose 
and Endosmose currents depends on the position of the 
liquids as regards the membrane ; the strongest cur- 
rent always setting in towards the most colloid body. 
In flg. 240 is represented the mode of showing en- 
dosmose 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 iu 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 in the flgure, or by a tube 
with a double curvature, as fig. 242, the lower part of which is filled 
with mercury. In the flatter case the mercury is pushed upwards 
into a graduated tube, and thus an endosmometer {liir^ov, a measure), 
or measure of the force of endosmose, is formed. 




Pig. 240. 



Fig. 240. Instrument to show Endosmose and Exosmose, consisting of a Madder con- 
taining 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). 



144 • CIECULATION OF THE SAP. 

Dutroohet found that with a membrane of 40 millimetres in 
diameter, a tube of 2 mUlinietres, and a solution of sugar, the density 
of which was 1-083, the fluid rose 39 millimetres in the space of an 
hour and a half; with syrup, of density 1'145, the rise was 68 milli- 
metres ; and with syrup, of density 1'228, the rise was 106 millimetres. 
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 J atmo- 
spheres. Thus the velocity and force of the rise depend in this 
instance on the excess of density of the enclosed liquid over that of 
the water outside. Different' substances act with varying intensity 
in producing endosmose. The following ratio expresses the variable 
intensity of endosmose in different cases in which the density of the 
solution was the same : — Solution of gelatin, 3 ; of gum, 5-17 ; of 
sugar, 11 ; of albumin, 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. The 
interposed membrane, whether animal or vegetable, is very actively 
concerned in the intensity and direction of the endosmotic current. 
Graham assigns a chemical character to osmose, accompanied with a 
constant decomposition of membrane. In the living plant the renewal 
of the membrane forming the septum is constantly taking place, and 
thus the osmotic action is kept up. 

The fluid matter,?, absorbed by the roots, are carried upwards 
through the cells and vessels of the stem, as ascending sap ; they pass 
into the leaves, where they are exposed to the influence of air and 
light, and afterwards return through the inner bark as descending or 
elaborated sap, and a portion ultimately reaches the root, where it is 
either excreted or mixed with the new fluid entering from the soil. 
The presence of light is essential for the elaboration of the sap. 
Vegetable growth cannot progress unless the vegetable circulation be 
perfectly accomplished. This act of vegetable vitality may, however, 
be effected while the plant is removed from the action of light, but 
the oxygenation of the juices cannot be perfected without their free 
exposure to its influence. 

Numerous experiments have been performed in order to show the 
course of the fluids in exogenous stems, such as making incisions or 
notches in the bark and wood of trees at different heights, and noting 
the points where the sap first 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 con- 
clusion that the sap ascends chiefly through the alburnum or newer 
wood, proceeds to the leaves, and returns by the bark to the root. 
If incisions are made into the trunk of a tree at different heights 
early in spring, it is found that the flow of ^ap (called bleeding) 



CIRCULATION OF THE SAP. 145 

takes place, first from the lower parts of the incisions, and chiefly 
from the alburnum ; while at a later period of the year it 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 weak solution of acetate of lead (which is capable of being 
absorbed), the metal may be detected by means of a salt of iodine, 
first in the new wood, next in the leaves, and then in the bark. A 
similar experiment may be made by means of weak solutions of potassic 
ferrocyanide, and of a persalt of iron. 

From the minuteness of the tissue, and the difficulty of examining 
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 intercellular spaces, 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, the descent of the sap takes place by the cells 
of the medullary rays. 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. 

Gaseous matters are taken up by the roots of plants, and circulated 
along with the sap as' well as in the spiral vessels. These usually 
consist of air, carbonic acid, and oxygen. Hales showed the existence 
of air in the vessels of the Vine, and Geiger and Proust proved that 
the sap of this plant contained carbonic acid. Some plants, as Ponte- 
deria and Trapa, float in water by means of air contained in the vessels 
or in the intercellular spaces. 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. 

Changes take place in the composition an^ density of the sap in 
its upward course. The chief alterations in it take place in the 
Jeaves, where it is exposed to the influence of light and air. Sy this 
means carbon is fixed, oxygen is given off, and an exhalation of 
watery fluids takes place. The fluids pass from cell to cell through 
the leaves, where they are acted upon by air through the stomata, 
and reach the vascular and cellular tissue of the bark, where further 
changes take place. Walker, from his experiments, concluded that no 
descent takes place until after the development of the leaves. 

The sap, after being elaborated in the leaves, is sometimes clear 
, and transparent, at other times it is milky or variously coloured and 
opaque. The elaborated sap has been called latex, and the vessels 
transmitting it have been denominated laticiferous (p. 21). The 
latex contains granules, which exhibit certain movements under the 
microscope. The movements are analogous to those observed in the 

L 



146 



CYOLOSIS. 



capillary circulation of animals. On account of these movements in the 
latex, the laticiferous vessels have been denominated Ginenchymatous 
(xiviui, 1 move), and the movements themselves are included under 
the name Gyclosis (^auxXog, a circle). 

The plants in which the movements are best observed are those 
having the latex mUky or coloured, such as various species of Ficus, 
Euphorbia, and Ohelidonium. In fig. 241 there is represented 

a small fragment of a leaf of 
Ohelidonium majus (celandine), 
which shows the current of 
orange granules in the lati- 
ciferous vessels, their direction 
being indicated by arrows. 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 modified by 
pricking the vessels or by pres- 
sure. If the microscope be 
applied to the stipule of Ficus 
elastica, while still attached to 
the plant and uninjured, pres- 
sure with any blunt object on the stipule will be observed to cause 
a marked oscillation in the vessels, thus showing their continuity. 
There will also be seen a regular movement from the apex towards the 
base, independent of external influences, when the stipule is allowed 
to lie on the field of the microscope without any pressure or injury 
whatever. This movement has been observed to continue for at 
least twenty minutes. It is of importance to distinguish between 
those molecular movements which are caused by injury and pressure, 
and those which defend on changes going on in the interior of the 
living plant; The elaborated sap descends through the vessels of 
the liber. 

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 stein, passes 

Pig. 241. Bmall portion of the leaf of Chelidonium majus or Celandine (highly magnified), 
Bhowlng a netwoA of laticiferous vessels. The direction of the currents in the vessels is 
indicated toy the arrows. 




Fig. 241. 



CIRCULATION OF THE SAP. 



147 



through the woody tissue, porous vessels, and cells, dissolving starch 
and other matters, and appropriating various new substances. Pro- 
ceeding upwards and outwards, this sap reaches the leaves, 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 commenced ; a small portion is there 
excreted, while the remainder mixes with the newly-absorbed fluids, 
and again circulates in the sap. The rapidity with which the sap 
ascends is dependent on the endosmotic property of the cells in the 
roots, and on the density of the fluids. An absorption of water, con- 
taining various matters in solution, is constantly going on through the 
extremities of the rootlets. The sap thus formed is carried forward 
through the cells, vessels, and intercellular passages, by a force which 
acts by propulsion. The stimulus of light, acting on the cellular 
tissue of the leaves, enables them to elaborate the organic compounds 
which are necessary for vegetable nutrition. The leaf-action may be 
reckoned one of attraction or suction, > transpiration giving rise to a 
constant flow of fluids to supply the place of those exhaled. 

Dr. Pettigrew has given the following views as to the circulation 
in plants, and has illustrated them in the accompanying diagram (fig. 
242). In spring the sap being mainly concerned 
in the growth of the branches, development of buds, 
and evolution of leaves — a vigorous and rapid 
movement takes place in an upward direction, 
as at a. During summer, when the plant is 
elaborating secretions, and storing up nourishment, 
the course of the sap is partly upwards and partly 
downwards, represented by the arrows at cd; the 
ascending and descending currents are indicated as 
continuous in the direction of the leaves and roots, 
and thus as it were constituting a true circulation. 
In autumn, owing to the fall of the leaf, excess 

and a general waning activity in the 

is a marked descent of the sap^ as 
But besides, and consequent on, those main currents, 
Thus the ascending spring and descending autumn 
currents, being in great measure endosmotic, give rise to unequal 

Kg. 242. Diagram representing the ascending, descending, and transverse currents in the 
plant, a. Ascending or spring current. 6, Descending or autumn current, c d, Ascending 
and descending currents of summer ; these being continuous in the direction of the leaves 
and roots, a c. Transverse currents. The aiTows in this diagram represent the endosmotic 
currents, the darts the exosmotic ones. 




of moisture, 
plant, there 
shown at h. 
others exist. 



Kg. 242. 



148 PKOGKKSSION OF THE SAP. 

exosmotic currents in an opposite direction — i.e. downwards and 
upwards respectively. In summer exosmotic currents flow equally 
in both directions. These counter-currents are indicated on the dia- 
gram by darts pointing in a direction opposite to that of the arrows. 
One other current exists — viz., a lateral current, represented by hori- 
zontal darts. By this current, sap which has been abstracted from 
the currents passing along the main channels, is diffused into sur- 
rounding tissue. Although the upward and downward currents are 
respectively most vigorous in spring and autumn, stiU at all periods of 
the year currents of sap pass both upwards, downwards, and transversely. 

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, by which it descends. The cellular tissue is also probably 
concerned in the movements. Cambium is produced in these plants 
in the neighbourhood of the vascular bundles, and is thus generally 
diffused through the textur& 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 ; according to Hoff- 
mann there is no channel for the descent of fluids in Acrogens, the sap 
simply ascending and diffusing itself in the substance of the plant in 
its progress. In cellular plants transmission of the sap takes place 
from one cell to another ; and as their texture is often delicate, the 
movements are rapid. Many of these, as seaweeds, when plunged 
into water, after having been dried by evaporation, imbibe the fluid 
with very great rapidity. 

The Cause of the Pkogeession or the Sap has been investi- 
gated by numerous physiologists. 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 metamorphoses 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 osmotic 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. While the ascending 
movement of the sap is powerfully promoted by the active operation at 
the siurface of the leaves, its lateral movements are no less influenced 
by the individual relations of each distinct cell, since the different func- 
tions of separate cells, when actively exercised, call into action those vital 
agencies by which a transmission of the cellular contents is effected. 



PROGRESSION OF THE SAP. 149 

Draper attributes the movement of the sap to capillary attraction, 
which he considers as an electrical phenomenon. This attraction takes 
place when a fluid moistens a capillary tube, and there can be no flow 
imless a portion of this fluid is removed from the upper extremity ; 
for capillarity wUl 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 diflFerent 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 capUlary tubes), that will pass through most rapidly which wets 
it most completely, or has the greatest affinity for it. Hence, Draper 
explains the phenomena of endosmose and exosmose by referring them 
to capillary attraction, aided by transpiration. 

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 fad« from want of a due supply to 
compensate for transpiration ; and hence the importance of pruning plants 
before transplantiag 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 process of transpiration, therefore, by forming a vacuum, assists 
capillary attraction and the atmospheric pressure, and thus the fluids 
rise. As the process of endosmose and exosmose depends on the 
chemical affinity and physical character of 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 secr'etiona. 

The observations of physiologists and chemists thus lead to the 
conclusion that there are four factors concerned in the circulation 
of the sap m plants — viz. nutrition, acting as a. vis a fronte, as is 
shown by the current setting most strongly in the direction of most 
rapid growth ; osmose, indicated by the difference in density between 
the fluids of the plants and those supplied to it from without ; 
capillary attraction, consequent on the character of the vessels ; and 
lastly, evaporation, by which the capillary attraction is kept up, 
osmose favoured, and nutrition facilitated. To these another may be 
added, — intermittent mechanical strain, produced by swaying in the 



150 PROGRESSION OF THE SAP. 

wind, which, as Mr. Spencer has shown, exercises considerable in- 
fluence not only propulsive on the main ascending and descending 
currents, but also extravasating into the lateral flows. It may be 
said that there is a, vis a tergo, without the presence of leaves, as shown by 
the experiments of Hales (fig. 243), combined with a vis a fronte, 
depending on the suction power of the leaves. 

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 colouring matters 
will enter the tubes. Boucherie found that felled trees, the extremities 
of which were immediately immersed in various solutions, continued 
to. imbibe them with great force and japidity for many days. A 
Poplar, 92 feet high, absorbed in six days nearly sixty-six gallons of a 
solution of pyrolignite of iron. 

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 efiect of leaf-buds in promoting the movement of 
sap, may be exhibited by introducing a single branch of a vine grow- 
ing in the open air into a hothouse during winter, thus exposing it to 
the action of heat as well as light. In this case the leaves are de- 
veloped, 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 increase in the circulation. 

In spring, the first effect of light and warmth is to stimulate the 
leaf-buds. These enlarge, and the osmotic action commences in their 
cells. 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. The starch deposited in 
the previous season becomes converted into sugar and dextrin, it is 
thus readily acted on by the ascending fluids, and in a state of solu- 
tion admits of being generally diffused. 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 equUibriiun 
in the density of the fluids, and ultimately there is a cessation of the 
circulation. 

The height to which the sap rises in 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 a vine, he found in one of his 



MOVEMENTS IN CELLS — ROTATION. 



151 



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. 243, where c is the stem of a i 

vine cut, t is a bent glass tube fitted 
to the cut extremity 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 experi- 
ments, was five times greater than 
that of the blood in the crural artery 
of the horse. 

Special Movements of Fluids. 
— Besides this general circulation of the 
sap, special movements have been 
observed in the individual cells of 
plants, which have been included 
under the name of Rotation (rota, a 
wheel) or Gyration (gyrus, a circuit or 
circle). These motions have been de- 
tected in the cells of many aquatic 
plants, especially species of Ohara and 
Vallisneria, and in the hairs of Trades- 
cantia. The currents proceed in a 
more or less spiral direction, and are 
rendered visible by the granules of 
chlorophyll which they carry along 
with them. There exist also other 
granules in the fluids, whiph are 
coloured yelloy by iodine, and are 
probably of a nitrogenous nature. 

The species of Chara (fig. 244) in 
which rotation has been observed, are 
aquatic plants growing in stagnant 
ponds, and composed of a series of cylin- 
drical cells, placed end to end. Some- 
Fig. 243. Apparatus of Hales, to show the force of ascent of the sap. c, Stem of a vine 
cut. ty A glass tube with a double curvature attached to the upper pai-t of the vine-stem, 
by means of a copper cap, v, which is secured by means of a lute and piece of bladder, m. . 
n n, Level of the column of mercury in the two portions of the tube at the commencement 
of the experiment, n W, Level of the mercury at the conclusion of the experiment. 




Fig. 243. 



152 



MOVEMENTS IN CELLS — EOTATION. 



times the plant consists of a single central cell ; at other times there are 
several smaller ones surrounding it, which must be removed in order 
that the movements which occur in the central cell may be seen. Many 
of the species are incrusted with calcareous matter, and thus become 
opaque, while others, as Ohara or Nitella flexilis, have no incrustation, 
and are transparent. Those plants with unincrusted tubular , cells 
best exhibit movements. In these plants the movements take place 
between the two membranes of which the cell- wall is composed. They 
are not interrupted when a division of the cell has been made by 




c 



\*«<f^ 



r 



Fig. ■2U. 



Fig. 245. 



means of a ligature ; an evident movement may still be observed in 
either section. 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 direc- 
tion. In the cells of the branches the descending current is next to 
the axis. In %ure 244 the course of the currents in different cells 
is indicated by aiTows. 

In Vallisneria spiralis (which includes V. Micheliana and Jac- 

Fig. 244. A small portion of a Clara, magnified to show the intracellular circulation. 
The arrows mark the direction of the fluid and granules in the different cells. The clear 
spaces are parts where there is no movement. The circulation in each cell is independent 
of that in the others. Fig. 245, Large internal cell of Vallisneria, showing the direction of 
the currents in intracellular rotation. There is an occasional nucleus seen in the course 
of the circulation along with the chlorophyll grains. 



MOVEMENTS IN CELLS — ROTATION. 



153 



quiniana), the cells in all parts of the plant, leaf, root, flower-stalk, 
and calyx, contain numerous green granules, and an occasional cyto- 
blast or nucleus, which, under certain circumstances, are carried, with 
the juices of the plant, in continual revolution round the walls of each 
cell (fig. 245). Although in different cells the currents proceed often 
in different directions, still in any given cell the rotation is uniform ; 
for if stopped by cold it resumes the same direction. Eotation 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 micro- 
scope. The part is to be viewed 
in water, between two pieces of 
glass ; and a little heat is some- 
times useful in promoting the 
movements. In Vallisneria the 
motion ceases at about 45° 
Fahr., while in Chara it goes 
on at a lower temperature ; if 
the temperature be raised above 
150° the motion ceases. 

A similar intracellular cir- 
culation is seen in species of 
Potamogeton, Hydrocharis, and 
Anacharis, as well as in the 
moniliform purple hairs on the 
filaments, and in the calycine 
hairs, of Tradescantia yirginica. 
In the examination of these 
hairs a higher microscopic power 
is required than in the case of 
the plants previously mentioned. 
A nucleus is usually seen in the 
cells of these hairs, and it may 
either remain immovable, or 
may be carried along with the 
current. The movements ap- 
pear to be confined between a 
double cell-wall. Fig. 246 shows 
a calycine hair, p, of Tradescantia virginica, with a small portion of 




Kg. 246. 



Fig. 246. Hair, f, taken from the calyx of Tradescantia virginica, with a small portion of 
the epidermis, e c, on which there Is a stoma, s. In each of the epidermal cells there is a 
nucleus, %, and currents (rotation), the direction of which is indicated by the arrows. 



154 MOVEMENTS IN CELLS — ROTATION. 

the epidermis, 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 the 
arrows. In each cell, as seen at a, there are several currents, which 
cross each other at the point where the nucleus is situated, thus 
giving rise to the appearance of an irregular network. The hairs 
of many other flowering plants exhibit rotation (fig. 90), and it is 
probable that in all young cells these currents may be observed. 
The circulating fluid is a mucilaginous protoplasm or formative matter, 
and in Ohara and Vallisneria it forms a uniformly investing layer on 
the inner surface of the cell. The motions would appear to be 
connected in some way with the nutrition of cells and the formation 
of new ones ; and while they continue throughout life in aquatics, 
they often cease in plants living in air, after they have attained a 
certain development. Mohl's experiments have shown that at the 
temperature of 66° Fahrenheit the quickest motion was l-125thofa 
Parisian line,* the slowest, l-600th, and the mean, I-185th. 

Schleiden says that in the Vallisneria cells it is not the ceU-sap 
that is in motion, but a mucilaginous fluid, with which the chloro- 
phyll granules and the nucleus are connected, and which flows in an 
uninterrupted manner along the cell-waUs. In Ohara, also, he states 
it is not the cell-sap which moves, but a denser fluid, present in large 
quantity, and occupying the outer part of the cell cavity. Mohl 
thinks that a homogeneous protoplasm fills these cells at first com- 
pletely, but that during growth it becomes hollowed out into one or 
more cavities, and that around these the mucilaginous matter 
circulates. 

The velocity of the currents in various plants, at 66° to 68° 
Fahrenheit, is thus given by Mohl : — 

Filamental hairs of Tradescantia virginica, — j^ to -^-^ of a Parisian line in a 

second ; mean, -^^. 
Leaves of Vallisneria spiralis — quickest, x^ ; slowest, -^ ; mean, -rir j of * 

line in a second. 
Stinging hairs of Urtioa haccifera — quickest, -^^ ; slowest, -^^ ; mean, yitt- 
Cellular tissue of young shoot of Sagittaria sagittifolia, y^ to tAt j mean, r^. 

„ „ leaf of do., yttit to Tsm ; mesca, j^. 

Hairs of Cuourhita Pepo — quickest, yfj ; slowest, ^p^ ; mean, xAy 

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 seconds 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. 

The cause of those intracellular movements is obscure ; both vital 

* Parisian line = 'OSSSIS of an inch, 



EESPIEATION OF PLANTS. 15o 

and physical causes having been adduced in explanation. By some 
they are considered as connected with the nourishment of the cell, 
the presence of the nucleus, and the process of cytogenesis. Certain 
authors have referred the phenomena to endosmOse, dependent on 
varying density in the cell-contents, while electrical agency has been 
called into requisition by others. In Ohara the chlorophyll granules 
lining the walls of the cells have been supposed to exercise a galvanic 
action upon the sap, and thus. give rise to the motion. 

Dr. Pettigrew, from experiments by which he succeeded in inducing 
similar movements artificially, concludes that the ultimate causes are 
mainly physical, of which absorption, resulting in endosmose and 
exosmose, and evaporation, are the chief; and that the phenomena 
are influenced by the general circulation. He says, " while the cells 
in the root of the plant inaugurate the general circulation, the general 
circulation in its turn influences the intracellular circulation. This 
follows, because when a current of fluid travels up the one side of a 
thin porous cell-wall, and another and opposite current travels down 
the other or opposite side, a certain proportion of the currents pass 
obliquely through the ceU-wall, and cause the fluid contents of the 
cell to gyrate or move in a circle. The cell-contents are made to 
gyrate, even in the absence of opposing currents outside the ceU, 
if endosmotic and exosmotic currents are induced within it ; or if 
evaporation or capillarity be made to act at certain points." 

3. — Respiration of Plan,ts. 

The changes which are produced in the atmosphere by living 
plants have been included under the title of Vegetable Respiration. 
The experiments of Priestley, in 1771, show that plants when ex- 
posed to light in an atmosphere containing a considerable proportion 
of carbonic acid, purify the air by removing carbon and producing 
oxygen. Air in which animals had died was thus rendered again fit 
for breathing. Percival confirmed those observations. 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 com- 
pletely from that in Priestley's experiments, and hence the difierence 
of results. Ingenhouz and Senebier performed numerous experiments, 
which proved that during the day plants gave out oxygen gas, whUe 
during darkness this process was suspended. The former has shown 
that the green portions of all vegetables, irrespective of their specific 
properties, are equally available for such operations ; that it is from 
the under surface of the matured leaves that oxygen is chiefly given 
off; and that in plants placed in shade the action of the leaves 
does, not prevent deterioration of the air. Saussure stated that 



156 RESPIRATION OF PLANTS. 

during the night oxygen gas was ahsorbed in different quantities 
by plants. Fleshy plants absorbed least ; next came evergreens, 
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. De- 
candolle, Ellis, Daubeny, and numerous other observers, have con- 
firmed the conclusions drawn by the early experimenters. The results, 
of aU 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 dark- 
ness no such decomposition takes place, oxygen is absorbed in moderate 
quantity, and some carbonic acid is given ofi. The former process, 
caused by the deoxidising or rather decarbonising power of plants, 
much exceeds the latter in amount. And thus the respiratory process 
in plants and in animals is antagonistic, consisting in the former of 
the elimination of oxygen, while in the latter it is the elimination of 
carbon. 

Burnett endeavoured to show that there are two processes con- 
stantly going on in plants, one being what he calls digestion, consisting 
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 ia 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 day. Carpenter entertains similar opinions, believing that 
under all circumstances vegetable respiration is a process continued 
throughout, and essential for vegetable life ; that it consists of the 
elimination from the system of the superfluous carbon, either by its 
entering into combination with the oxygen of the air, or by giving off 
carbonic acid to replace the oxygen absorbed. Mr. Pepys is of opiaion 
that the evolution of carbonic acid indicates an abnormal condition of 
the leaf, which, in the process of healthy active vegetation, absorbs 
carbonic acid and disengages oxygen. He believes that the action of 
light leads to the greater perfection of this function, which is less 
energetically performed if not wholly suspended during the night. 
The changes produced in the atmosphere are mainly caused by the 
superficial green parts of plants. The oxygen evolved by plants 
appears to be derived from the carbonic acid of the atmosphere, the 
carbon of which is appropriated, and probably partly from the water, 
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. 

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 



EESPIKA.TION OF PLANTS. 157 

will soon be given o£F, which are found to be pure oxygen ; and any- 
carbonic acid in the water will be diminished in quantity. The same 
leaves in darkness will not evolve any oxygen, light being essential for 
the process. 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 be decomposed, and the oxygen will increase. 
During the night the action is reversed, and if the plant is left twelve 
hours in darkness, the oxygen wiU decrease, while carbonic acid wUl 
increase. Daubeny, from his experiments respecting the action of 
plants on a known amount of atmospheric air, states that leaves are 
requisite for the purification of the air, that the action of light on them 
gives rise to the emission of oxygen and the decomposition of carbonic 
acid, that for the elimination of oxygen the presence of carbonic acid 
is requisite, and that the greatest amount of oxygen which can, by 
vegetable respiration, be added to air confined within a jar is 18 per 
cent. The following is a simple experiment showing the production of 
oxygen by green leaves under the action of light. If a green leaf is 
placed in an atmosphere composed of hydrogen and carbonic acid, and 
a stick of phosphorus is introduced, no apparent action takes place 
in the dark, but the moment a beam of light, or the electric light 
rays, are thrown on it, white fumes of phosphorous anhydride are 
instantly produced, indicating the combination of the free oxygen, 
evolved from the leaf under the action of light, with the phosphorus. 

The following are the results of Boussingault's experiments on the 
functions of leaves : — 

1. The volume of COj decomposed, is identical with that of the oxygen produced. 

2. Leaves decompose pwe carbonic acid with extreme slowness. 

3. Leaves in presence of ordinary air and COj effect readily the decomposition of 

the latter. 

4. Leaves decompose COj in sunlight, when it is diluted with hydrogen, nitrogen, 

carbonic oxide, or marsh gas. 

5. Leaves lose the power of decomposing carbonic acid as they lose water (becoming 

dry). 

6. The upper surface of thick leaves, such as those of the Cherry Laurel, decom- 

pose more CO^ than the under, in the proportion of 4 to 1 in the sun ; 
whereas in the shade it is as 2 to 1. Leaves having a thin parenchyma do 
not differ in' the power of decomposing in the upper or under surface. 

The fixation of carbon probably takes place gradually, giving rise, 
at different stages, to the formation of various organic compounds. 
Thus, two molecules of carbonic acid, by losing one atom 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 



158 EESPIEATION OF PLANTS. 

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 chloro- 
phyll, resin, oil, caoutchouc, and wax. 

Carbonic acid in solution, as has already been noticed, is taken up 
in large quantity by the roots of plants from the soil, and it is also 
absorbed from the atmosphere by the leaves. It may even be formed 
in the cells of plants during the various chemical changes connected 
with the elaboration of their juices and secretions. In the interior 
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 consequence of the dissolved acid being no longer assimilated by 
the action of light. The quantity of this acid given off during the 
night is by no means equal to that which is absorbed by the plant 
during the day. 

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 very largely 
given off, even during the day, depending on a chemical change taking 
.place in the starch of the plant, by which it is converted into sugar. 
These periods are germination, flowering, and fruiting. The changes 
alluded to wiU be discussed when these subjects are considered. 
When plants are decaying, or are in an unhealthy state, they undergo 
chemical changes, by which carbonic acid is formed. 

Aquatic plants have the power of decomposing carbonic acid 
highly developed, and thus the preservation of the purity of lakes 
and ponds is provided for. In Batavian ponds Pistia Stratiotes is 
remarkable for its purifying effects, 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. 

In conclusion, three views of the respiratory process in plants have 
been advanced — 

1. That oxygen is exhaled in large quantity during the day, and a 

moderate quantity of carbonic acid given off diuring the 
night. 

2. That carbonic acid is exhaled in greater or less quantity at all 

times, but during the day it is decomposed, so that oxygen is 
evolved. 

3. That no carbonic acid is evolved by leaves in a healthy state of 

the plant, but the elimination of oxygen only occurs. 

The last view is not now accepted by physiologists. Of the 
others each has a number of adherents — many able physiologists 



EFFECTS OF GASES ON PLANTS. 159 

ranging on either side. The view generally adopted is, that plants 
give out carbonic acid at certain times, and that the green parts of 
plants under the influence of light decompose the gas, fix the carbon, 
and eliminate the oxygen. 

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. The light-giving rays, or those nearest the 
yellow, appear to have the greatest effect in the fixation of carbon, 
and in the production of wood ; while the heat-giving, and the tithonic 
or chemical rays, have scarcely any influence. 

The tropics and warm climates, where a sky seldom clouded per- 
mits the 'glowing sun rays to shine on a luxuriant vegetation, are 
the constant and inexhaustible source of oxygen, thus contributing 
to the respiration of the animals, not only of their own latitudes, 
but also of the temperate and colder zones, where artificial light and 
warmth must replace the deficient light and heat of the sun, and 
which thus produce a copious supply of carbonic acid, to be expended 
on the nutrition of the tropical plants. The life of animals is thus 
connected intimately with the vegetable productions of the globe, not 
merely as regards the materials of their food, but also in reference to 
the air which they breathe. 

While the breathing of man and animals, and the various pro- 
cesses of combustion, are constantly abstracting oxygen from the 
atmosphere, and substituting carbonic acid, plants are decomposing 
this noxious gas, and restoring the oxygen. 

Effects of certain Gases on liviTig Plants. 

It has been already stated that plants can live in an atmosphere 
containing a .considerable proportion of carbonic acid, provided they 
are exposed to the light. Thus, an atmosphere which could not be 
breathed by man and animals is capable of supporting vegetable life. 
Experiments 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 
though plants do not thrive in pure nitrogen, nor in hydrogen gas, yet 
their vitality is not destroyed by the presence of these gases. Saus- 
sure observed that a plant of Lythrum Salicaria lived for five weeks 
in an atmosphere of hydrogen gas. Nitrogen has been proved to be 
innocuous. These gases seem of themselves to have no directly 
injurious effects, but to act chiefly by deprivmg the plants of carbon 
and oxygen. 

There are certain gases, however, 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 dis- 



160 EFFECTS OF GASES ON PLANTS. 

organisation; others as narcotic poisons, inducing a drooping and 
decay of the entire plant. To the former class belong sulphurous 
acid gas, hydrochloric acid gas, chlorine and nitrous acid gas ; while 
amongst the latter are included sulphuretted hydrogen, cyanogen, 
carbonic oxide, and ammonia. 

Sulphurous Acid Gas is highly injurious to plants. It pro- 
duces greyish-yellow dry-looking spots on the leaves, which gradually 
extend until the leaves are destroyed. The effect resembles much 
the ordinary decay of the leaves in autumn. The proportion of 
gas, in some experiments, was only 1 in 9000 or 10,000 parts of air, 
and the quantity i of a cubic inch ; and yet the whole unfolded 
leaves of a mignonette plant were destroyed in forty-eight hours. 
This proportion of the gas is hardly or iiot at aU discoverable by the 
smell. 

Hydrochloric Acid Gas produces effects . similar and scarcely 
inferior to those of the last-mentioned gas. When i of a cubic inch 
is diluted with 10,000 parts of air, it acts 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. 

Sulphuretted Hydrogen acts in a different way from the acid 
gases. The latter attack the leaves at the tips first, and gradually 
extend their operation to the leaf-stalks. When in considerable 
proportion, their effects begin in a few minutes ; and, if diluted, the 
parts not attacked generally survive if the plants are removed iato 
the air. But in the case of sulphuretted hydrogen, the leaves, without 
being injured in texture or colour, become flaccid and drooping, and 
the plant does not recover when removed into the air. It requires a 
larger quantity of this gas to produce the effects stated. When six 
cubic inches are added to sixty times their volume of air, the droop- 
ing begins in ten hours. This gas then acts like a narcotic poison, 
by destroying life throughout the whole plant at once. 

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 
grown 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 



GROWTH OF PLANTS IN WAED'S CASES. 161 

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. These Cases are well 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 plants, as Perns, requiring 
a humid atmosphere, thrive well in such Oases. 

But it is not merely as objects of luxury and curiosity that these 
Cases deserve notice. They supply an important means of transport- 
ing 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 searbreeze and to the vicissitudes of climate experienced during 
their transport. Plants of Musa Cavendishii have been thus intro- 
duced into the South Sea Islands, and Tea, Ipecacuan, and Cinchona 
into our Indian possessions. 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, etc., and 
sent them from Britain to Sydney, where they arrived in January 1834. 
The plants were taken out in good condition, and the Cases were re- 
filled 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 rounding 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 watered during the voyage, and received no protection by day 
or by night, nevertheless they reached London in a healthy and 
vigorous condition. 

It is a mistake to suppose that the air in the Cases remains un- 
changed. They are not hermetically sealed ; and by the law of diffu- 
sion of gases there is a constant although gradual mixture of the 
external air with that inside, free however from many impurities. 
Plants wiU continue to grow for a long time, even in Cases hermeti- 
cally 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 of Plants. 

The sap in its progress through the cells and vessels, and especi- 
ally in its passage through the leaves, is converted into organisable 
products, from which the vegetable tissues are nourished and the 

M 



162 YEGETABLE PRODUCTS — STARCH. 

secretions are elaborated. 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 ; a familiar example of which may be 
seen in their culture of Apium graveolens (Celery). In speaking of 
the contents of cells and vessels, allusion has already been made to 
some of the more important organisable 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 medicinal 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 
quinia and morphia, the active .ingredients respectively 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 difiused through- 
out the vegetable kingdom. The latter substances therefore demand 
special 'attention. If a plant is macerated in water and all its soluble 
parts removed, lignin is left, and the water in which it has been 
macerated gradually deposits starch. If the liquid is boiled a scum 
coagulates, formed of albumin and some azotised matters, while gum 
and sugar remain in solution. 

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 
usually found in animal cells. It consists of Og Hj,, Og, and occurs 
in grains of various sizes and shapes, having an external membrane, 
enclosing a soluble substance. By boiling in water, the pellicle bursts, 
and the contents are dissolved, becoming gelatinous on cooling. The 
circular markings and striae seen on the grains, and the part called the 
hilum, have already been noticed (p. 10). The grains of potato starch, 
seen by polarised light, exhibit a well-marked black cross, the centre 
of which corresponds with the hilum. 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 in the potato towards the latter part of the season, it 
decreases when the tubers begin to germinate in spring. It was found 
that 240 lbs. of potatoes, left in the ground, contained of starch — 



In August . 


23 to 25 lbs. 


or 9 '6 to 1 '4 per cent 


„ September 


. 32 „ 38 „ 


„ 13-3 „ 16 


„ October 


32 „ 40 „ 


„ 13-3 „ 16-6 „ 


„ November 


. 38 „ 45 „ 


„ 16 „ 187 „ 


„ Apra . 


38 „ 28 „ 


..16 „ 11-6 „ 


„ May . . 


. 28 „ 20 „ 


„H'6 „ 8 '3 „ 



VEGETABLE PEODUCTS — GUM. 163 

The quantity of starch remained, the same during the dormant state 
in winter, but decreased whenever the plant began to grow. 

Starch is stored up in many seeds. It exists in roots, especially 
in those which are fleshy ; in stems ; in the receptacles of flowers ; 
and in pulpy fruits. The seed-lobes of the Bean and Pea, and 
many other leguminous plants ; the roots and the underground stem 
of Maranta arundinacea (arrow-root), and of Canna coccinea (tous- 
les-mois), Canna Achiras and 0. edulis ; the stem of Sago Palms (Sagus 
Rumphii and farinifera), and of the Cycas order ; 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 of large size, 
with pearly or sparkling lustre, having one or more hila, and frequently 
cracks on the surface. Those of arrow-root are small, and have a dull 
white appearance, while those of tous-les-mois are larger, and glisten 
like potato-starch. In some cases starch is associated with poisonous 
or acrid juices, as in Jatropha Manihot, which yields Cassava and 
Tapioca, and in Arum maculatum, the underground stem of which 
furnishes Portland sago. Inulin (Cs Hj, 0^) is a substance analogous 
to starch, to which Iodine communicates a brown colour. It is found 
in the roots and tubers of Inula Helenium (Elecampane), Dahlia 
variabilis, and Helianthus tuberosus (Jerusalem artichoke) ; while 
Lichenin is a variety of starch occurring in Cetraria islandica (Iceland 
moss). Lichenin or lichen starch consists of C, Hj„ Og, and is de- 
posited on the primary cell-wall of the plant, in the form of an encrust- 
ing layer. By the action of malt, or of sulphuric acid upon starch, by 
long boiling in water, or by heating up to 400° Fahrenheit, a soluble 
gummy substance is produced called dextrin* (Cg Hj,, 0^), which, when 
dried, constitutes British gum. It is one of the steps in the process 
of the conversion of starch into sugar. 

Gum is one of the substances which are produced abundantly in 
the vegetable kingdom. Its composition is Oj^ H^^ Ojj, 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 eold water 
(Arabin, mucilage), and those which only swell up into a gelatinous 
matter (Bassorin or Tragacanth, Cerasin, and Pectin). Arabin is 
familiarly known by the name of gnm-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 

* Dextrin is so called from possessing the property of effecting the right-handed rotation 
of the plane of polarisation of a ray of polarised light. 



164 VEGETABLE PRODUCTS — SUGAE. 

tears. The characters of gum from the same species of plant are 
liable to considerable variation ; the same tree may yield a transparent 
or an opaque, a light or a dark coloured gum. Old stunted trees, in 
hot and dry seasons, jdeld most gum. Arabin exists with cerasin in 
the gum of the Cherry and Plum. Mucilage is present in many of the 
Mallow tribe, as Malva sylvestris, and Althsea oiEcinalis or marsh mal- 
low, also in Linseed. In Sphaerococcus crispus, mucilage is present, of 
which the formula is Oi^ Hj„ Oj„. Bassorin (G^^ B.^ Oj,,) forms the 
chief part of gum-tragacanth (the produce of several species of Astra- 
galus), and of gum-bassora. It exists in Salep, procured from the 
tubercules of Orchis mascula. Cerasin (Cjj Hj, Oj,,) is that part of 
the gum of the Cherry (Gerasus), Plum, and Almond trees, which is 
insoluble in cold water. Pectin 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 
pectio acid, which is found in many fruits and esculent roots. 

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 G-rape sugar, and 
those which are not fermentescible, as Mannite. Gane sugar, C^j Hj, 
On, is procured from Saocharum 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 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 legass), the saccharine juice is extracted, evaporated, and 
crystallised, as Raw or Muscovado sugar, which is afterwards refined 
in vacuo, so as to form foa/ sugar. In 1870 the import of unrefined 
sugar in Great Britain amounted to 12,798,631 cwts., and of refined 
sugar 1,710,176 cwts. 

Maple Sugar is much used in America. It is procured from the 
sugar maple (Acer saccharinum) 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 February to the middle of April. Beet Sugar is the 



VEGETABLE PRODUCTS — LIGNIN. 165 

produce of the root of Beta vulgaris, and is extensively manufactured 
in many parts of the Continent. Manna Sugar, or Mannite, differs' 
from the others in not being fermentescible. Its composition is Ce 
Hj4 Oj. It is the chief ingredient of Manna, which exudes from the 
Ornus europ»a and rotundifolia. Prom Sicily and Calabria it is 
imported under the name of flake-manna. Mannite is found in the 
juices of Mushroom, in Celery, and in Laminaria saccharina, and 
Eucalyptus mannifera. Dr. Stenhouse has determined the quantity 
of Mannite in some sea-weeds as foUows :- 



Laminaria sacoharina 
Halydris siliquosa . 
Laminaria digitata 
Fucus serratus 
AJaria esculenta 
Ehodymenia palmata 
Pucus vesiculosus . 
Pucus nodosus 



12 to 15 per cent of Mannite. 
5 to 6 per cent „ 

4 to 5 per cent „ 

rather less „ 



about the same 
2 to 3 per cent 
1 to 2 per cent 
nearly the same 



Knop and Schnederman have detected Mannite in Agaricus piperatus, 
and other chemists have found it in Cantharellus esculen'tus, and 
Clavellaria coralloides. 

Grape Sugar, called also Starch sugar or Glucose, is composed of 
Og H,5 Og. It occurs in the juices of many plants, and is a product of 
the metamorphosis of starch, cane sugar, and lignin. Vj may be 
extracted from dry grapes, and may be prepared from starch by the 
action of an infusion of malt, or of a substance contained in malt, 
called Diastase. 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. 

Lignin is the substance which gives hardness and solidity to the 
cells and vessels of plants. It exists abundantly in the woody tubes, 
which may be said to be composed of cellulose forming the parietes, 
and lignin or sclerogen, forming the encrusting matter in the in- 
terior. The latter dissolves in strong nitric acid, forming oxalic acid, 
while the former is left undissolved. Lignin cannot be separated in 
the pure state, and hence its exact composition is unknown. 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 everything soluble in 
these agents is removed, a white fibrous mass reniains. This fibrous 
matter exists in linen and paper • and these substances, when sub- 
jected to the action of sulphuric acid, are converted into grape sugar. 
Lignin 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 



166 AZOTISED VEGETABLE PBODUCTS. 

cellular plants it is" absent, and the object of many horticultural 
operations, as blanching, is to prevent its formation. Beet-root and 
■white turnips contain only 3 per cent. Lignin is not coloured by 
iodine. 

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 
the proportion of elements is the same, that is, they are isomeric. 
Thus, cellulose and starch have the same composition (0^ Hj,, 0^), and 
are said to be isomeric. The difference in their qualities seems to depend 
on the mode in which the atoms which make up the molecule are 
grouped. The form is altered by a re-arrangement of the component 
atoms. The unazotised products which have been noticed supply 
materials 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. For example, 
Salicin, Cjg Hjg 0^, a bitter neutral crystalline substance, is procured 
from the bark of Salix alba. Helix, purpurea, viminalis, pentandra, etc. ; 
and Phlorizin, C^j H^^ Oj,,, an analogous substance, occurs in the bark 
of the roots of the apple, pear, cherry, and plum. 

AzoTiSED Peoducts. — 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 glutin. Glutin is composed of certain protein compounds 
(fibrin, casein, albumin, emulsin), containing carbon, oxygen, hy- 
drogen, and nitrogen, with some phosphorus and sulphur. Vegetable 
fibrin is the essential part of the glutin of wheat, and of the cereal 
grains. It may be procured by treating with ether the glutinous mass 
left after kneading wheat flour in linen bags under water. Vegetable 
casein or legwmin 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 albumin occurs in a soluble form associated 
with casein. It forms a small proportion of cereal grains. Wheat is 
said to contain f to 1| per cent ; Eye, 2 to 3f per cent ; Barley, -}^ 
to ^ per cent ; and Oats, i to J per cent. It is distinguished by 
coagulating at a temperature of 140° to 160°, and by not being pre- 
cipitated by acetic acid. Emulsin, or synaptase, has never been 
obtained in a state of purity. It is a nitrogenous 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 



VEGETABLE OILS. 



167 



called amygdalin (G^^ B^ NOu), on which it acts in a peculiar manner, 
producing hydrocyanic acid. IHastase is an azotised substance procured 
from malt, and developed during the germination of plants. It is 
probably fibrin in an altered state, and it has the power of promoting 
the conversion of starch into sugar. 

The azotised products of plants have a composition similar to blood 
and muscular fibre, and hence their value in the food of man and 
animals. The following table gives a general view of the quantity of 
azotised and unazotised matters occurring in certain plants, with the 
amount of water and inorganic matter : — 

Azotised Carbonaceous 





Water. 


matter. 


matter. 


Ash 


Peas . 


16 


29 


52 


3 


Beans 


14 


31 


52 


3 


Lentils 


16 


33 


48 


3 


Oats . 


18 


11 


68 


3 


Barley- 


16 


14 


69 


2 


Potatoes 


72 


2 


25 


1 


Turnips 


89 


1- 


9 


1 



The following arrangement is given by Fromberg of the compara- 
tive value of various plants as articles of food, taking into account the 
protein compounds, and the starch, gum, and saccharine matter which 
they contain, the highest value being 100 : — 



Beans 


100 


Bye . 


55 


Peas 


80 


Barley 


50 


Oata 


75 


Potatoes . 


45 


Wheat . 


70 


Bice . 


35 


Maize 


60 







As regards the produce of different crops per acre, Johnston- gives 
the following estimate of the nutritive products which they yield : — 

Average produce per No. of Iba, of true 

acre of tubers and nutriment in pro- 

grain, duce of an acre. 

Beet, Mangel-wurzel, and Turnip 30 tons . . . 672 lbs. 

Beans .... 30 bushels, or 1980 lbs. 594 ,, 

8 tons ... 358 „ 

20 bushels, or 1160 lbs. 348 „ 

36 bushels, or 1872 lbs. 243 „ 

10 tons ... 224 „ 

25 bushels, or 1500 lbs. 180 ,, 

30 bushels, or 1200 lbs. 132 „ 



Potatoes 

Peas 

Barley 

Jerusalem Artichokes 

Wheat 

Oats . 



Fixed Oils are found in the cells and intercellular spaces of the 
fruit, leaves, and other parts of plants. Some of these are drying oils, 
as Linseed oil, from Linum usitatissimum ; others are fat oils, as that 
from Olives (fruit of Olea europsea); while others are concrete, as 
Palm oil. The solid oils or fats procured from plants, are Butter of 



168 



VEGETABLE OILS. 



Cacao, from Theobroma Cacao; of Cinnamon, from Cmnamomum 
zeylanicum ; of Nutmeg, from Myristica moschata ; of Coco-nut, from 
Cocos nucifera ; of Laurel, from Laurus 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 indioa in India, and from Pentadesma butyracea 
in Sierra Leone. These oils contain a large amount of stearin, and are 
used as substitutes for fat. Castor Oil, from the seeds of Eicinus 
communis, differs from other fixed oils in its composition. 

DecandoUe gives the following table to show the quantity of oil 
got from seeds : — 

White Mustard 36 per cent by weight. 



Hazel-nut . 60 


per cent 


by weight. 


Garden Cress 57 


» 


>» 


Olive ... 50 


)} 


»j 


Walnut . . 50 


n 


J) 


Poppy . . 48 


93 


») 


Almond . . 46 


}J 


)) 


Euphorbia Lath- 






yris . . 41 


)» 


)> 


Colza ... 39 


)) 


)> 



Tobacco 


. 34 


Plum . 


. 33 


Woad. 


. 30 


Hemp 


. 25 


Flax . 


. 22 


Sunflower 


. 15 


Buckwhea 


t . 14 


Grapes 


. 12 



Vegetable 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 Copernicia cerifera, and from the 
fruit of Myrica cerifera (candle-berry myrtle) and Myrica cordifolia. 
By boiling these plants in water and compressing them the wax exudes, 
floats on the water, and may be collected and melted. It is of a 
greenish yellow colour. By saponification it yields stearic, margaric, 
and oleic acids, along with glycerin. It therefore more nearly approxi- 
mated the character of fat than that of wax. Waxy matter also 
occurs on the exterior of fruits, giving rise to the bloom of grapes, 
plums, etc., 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 substance which, when acted upon by nitric acid, yields 
suberic acid. Chlorophyll, or the green colouring matter of leaves, 
is allied to wax in its nature, being soluble in ether and alcohol, but 
insoluble in water. 

Volatile oe 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 specites of 
Pinus and Abies ; oil of juniper, from Juniperus communis ; oil of 
savin, from Juniperus Sabina ; oil of lemon and orange, from the rind 



EBSINOUS PRODUCTS — CAOUTCHOUC. 169 

of the fruit ; and oil of neroli, from orange flowers. A second series 
contain oxygen in addition, as oil of cinnamon, from Oinnamomum 
zeylanicum ; otto or attar of roses, from various species of Eose, 
especially Eosa centifolia ; oil of peppermint, from Mentha viridis ; 
oU of caraway, from Oarum Carui ; oU of cloves, from OaryophyHus 
aromaticus. Oils of this kind are procured from many Labiatse, as 
species of Lavandula, Origanum, Eosmarinus, Thymus ; and from the 
fruit of Umbelliferse, as species of Anethum, Fceniculum, Coriandrum, 
Cuminum, Petroselinum, Pimpinella; and from some Compositse, as 
species of Anthemis, Pyrethrum, and Artemisia. A third series have 
also sulphur in their composition, and have a peculiar pungent, often 
aJQiaceous smeU, with an acrid burning taste, as oU. of garlic, and of 
onion, procured from the bulbs of Allium sativum and Cepa ; oU. of 
assafoetida, from Narthex Assafoetida ; and oU of mustard, which is 
obtained from the seeds of Sinapis nigra when macerated in water by 
a kind of fermentation induced by the action of a nitrogenous body, 
myrosin, on a substance called myronic acid, or myronate of potash. 
A simUar oil exists in many Cruoifer*, as in AUiaria officinalis, 
Armoracia rusticana, and Cochlearia officinalis, and in several Um- 
belliferse, yielding gum-resin, as Opoponax, Ferula, Galbanum, etc. 
Many of the essential oUs deposit a solid crystalline matter, called 
Stearoptene, allied to camphor. This latter substance, which consists 
. of carbon, oxygen, and hydrogen, is procured from Camphora offici- 
narum, a native of Japan and India. There is also another kind of 
camphor, produced in Borneo, from Dryobalanops Camphora. 

Eesinous Peoduots. — The mUky and coloured juices of plants 
contain frequently resins mixed with volatUe oUs, 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 Myroxylon toluiferum; 
Balsam of Peru, from Myroxylon Pereirse ; Balsam of Copaiba from 
various species of Copaifera, especially Copaifera officinalis and mul- 
tijuga ; Carpathian Balsam, from Pinus Pinea ; Strasburg turpentine, 
from Abies pectinata (sUver fir) ; Bordeaux turpentine, from Pinus 
pinaster ; Canada Balsam, from Abies balsamea (Balm of Gilead fir) ; 
Chian turpentine, from Pistacia Terebinthus, etc. 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 officinale ; Dragon's-blood, from Dracaena Draco, and 
Calamus Draco ; Dammar, from Dammara austrahs and orientalis; 
Labdanum, from Cistus creticus, and other species ; Tacamahaca, from 
Calophyllum Cadaba, and from Elaphrium tomentosum ; Eesin of Jalap, 
from Exogonium Purga; Storax, from Styrax officinale; Benzoin, 
from Styrax Benzoin; Copal, from Vateria indica, etc. Lac, from 



170 ACIDS, ALKALOIDS, AND COLOUEING MATTEES. 

various species of Ficus, as Ficus indica, after attacks of Cocci, and 
from Aleuiites laccifera, and Eiythrina monosperma; Euphorbium, 
from Euphorbia offlcinarum, antiquorum, and canariensis. 

Oaoutchottc is in some respects analogous to essential oils. It is 
found associated with them and with resinous matters, in the milky 
juice of plants. It is the inspissated juice of various species of Ficus, 
as Ficus elastica, Kadula, elUptica, and prinoides, also of Urceola 
elastica, Siphonia elastica, and Vahea gummifera. A kind of caout- 
chouc, called gutta percha, imported from Singapore and Borneo, is 
procured from Isonandra Gutta, one of the Sapotaceaa. The milky 
juice of many orders of plants, as of Euphorbiaceee, Asclepiadaceae, 
Apocynacese, Artocarpacese, and Papayacese, contains caoutchouc or 
gum elastic. Some of these coloured juices are bland, as that produced 
by the Cow-tree (Galactodendron utile) ; others are narcotic, as those 
of Poppy and Chelidonium ; others are purgative, as Gamboge j others 
diuretic, as Taraxacum. 

Oeganic Acids are produced by processes going on in living 
plants, and exist in vegetable juices often combined with peculiar 
bases and alkaloids. Thus Citric acid occurs in the fruit of the orange, 
lemon, lime, red currant, etc. ; Tartaric acid, in the juice of the grape, 
and in combination with pofash in tamarinds ; Malic acid, in the fruit 
of the apple, gooseberry, and mountain ash ; Tannic acid or Tannin, 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 specieg 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 in Prunus Laurocerasus, etc., 
and Oxalic acid, which exists in combination with potash in Eumex 
acetosa, and Acetosella, Oxyria reniformis, Oxalis Acetosella, and in 
combination with lime in Ehubarb, and many species of Parmelia and 
Variolaria. 

Alkaloids or Oeganic bases are azotised compounds found in 
living plants, and generally containing their active principles. They 
occur usually in combination with organic acids. Quinia and Cincho- 
nia exist in the bark of Cinchona, the former predominating in yellow 
bark, the latter in pale bark; Morphia, Narcotin, Codeia, Thebaia, 
and Narcein, occur in the juice of Papaver somniferum ; Solania is 
an alkaloid found in many species of Solanum, as Solanum tuberosum, 
nigrum, and Dulcamara ; Veratria exists in Veratrum Sabadilla and 
album ; Aconitia in Aconitum Napellus ; Strychnia in Strychnos 
Nux-vomica, Sancti Ignatii, Colubrina and Tieut^; Brucia also in 
Nux-vomica or false Angustura bark ; Atropia in Airopa Belladonna ; 
Beberia in Nectandra Eodiei j Piperin in Piper longum and nigrum ; 
Emetina in Cephaelis Ipecacuanha; Caflfein (Thein and Guaranin) 
in Coffea arabica, Thea Bohea and viridis, PauUinia sorbUis and 



ORGANS OF EEPRODUCTION. l7l 

Ilex paraguensis ; Theobromin in the seeds of Theobroma Cacao or 
chocolate ; besides numerous others of less importance. These Alka- 
loids are often found in plants having poisonous properties. 

Colouring matters are furnished by many plants, either directly 
or by a process of fermentation. Yellow colouring matters are procured 
from the roots of Curcuma longa (turmeric), from the pulp surround- 
ing the seeds of Bixa orellana (arnotto), from the Ceylon Gamboge 
plant (Hebradendron Cambogioides), and various species of Garcinia, 
as Garcinia Cambogia and' elliptica, from the flowers of Carthamus 
tuictorius (saflower), from the stigmata of Crocus sativus (saflfron), 
from a kind of Mulberry (Morus tinctoria), from Eeseda Luteola 
(weld), and from some Lichens, as Parmelia parietina (parietin or 
chrysophanic acid). Bed colouring matters are produced from the root 
of Anchusa tinctoria (alkanet), from Pterocarpus santalinus, Dracaena 
Draco (dragon's-blood), the root of Eubia tinctorum or madder (aliza- 
rin), the root of Morinda citrifolia (sooranjee), from Hsematoxylon 
campechianum (logwood), Csesalpinia braziliana (BrazU wood), Cam- 
wood, Carthamus tinctorius (darthamine), 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 tinc- 
toria. Anil, cserulea and argentea, as well as from Wrightia tinctoria, 
Marsdenia tinctoria, Nerium tihctorium, Gymnema tingens, and Isatis 
tinctoria, etc. The plants in full flower are cut and put into vats 
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 on the Delta of the Ganges. 
Several Lichens yield nitrogenous colouring matters, which give blue 
and purple colours with alkalies, etc. Lecanora tartarea yields cud- 
bear (Gyrophoric acid). This acid also exists in Gyrophora pustulata. 



Section III. — Organs of Reproduction. 

Structure, Arrangement, and Functions. 

The reproductive organs consist of the flower and its appendages, 
the essential parts being the stamens and pistil. When the flower, or 
at least the essential organs, |are conspicuous, the plants are called 
Phanerogamous (ipuvigbs, conspicuous, and yoc/iog, union or marriage), or 
Flowering plants ; when they are inconspicuous, the plants are Orypto- 
gamous (x^vTTThs, concealed, and ydfiog, union or marriage), or Flower- 
less plants. The former include Exogens and Endogens, the latter 
Acrogens and Cellular plants. On careful examination it will be 



172 



INFLOKESCENCE OR ANTHOTAXIS. 



found that the organs of reproduction and of 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 fibro- 
vascular tissue is ultimately formed ; they are arranged in a more or 
less spiral manner, and are often partially or entirely converted into 
leaves. 



1. — Inflorescence, or the Arrangement of the Flowers on the Axis. 

The arrangement of the flowers on the axis, or the ramification of 
the floral axis, is called Inflorescence or Anthotaxis (ai/^os, a flower, and 
rd^ig, order). Flower-buds, like leaf-buds, are produced in the axU 
of leaves, and these are called floral leaves or Iracts. 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 Rose 
(fig. 247) and Geum, the central part, 
A, is prolonged, and bears leaves or 
flowers. In such cases the flowers are 
usually abortive, the essential organs 
being so altered as to unfit them for 
their functions. Such metamorphoses 
confirm Goethe's doctrine, that all the 
parts of the flower are modified leaves. 
The general axis of inflorescence is 
sometimes called rachis (ga;^'S, the 
spine) ; the stalk supporting a flower, 
or a cluster of flowers, is a peduncle 
(pes, a foot (flg. 252 a') ; and if small 
branches are given off by it, they are 
called pedicels (fig. 252 a"). A flower 
having a stalk is called pedunculate or 
pedicellate (fig. 252) ; one having no 
stalk is sessile (fig. 258). In describ- 
ing a branching inflorescence, it is 
common to speak of the Eachis as 
the primary flotal axis, its branches as the secondary floral axes, 
their divisions as the tertiary floral axes, and so on; thus avoiding 

Fig. 247. Proliferous or monstrous Eoae, 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 numher. /, Coloured leaves representing abortive carpels. 
a, Axis prolonged, bearing an imperfect flower at its apex. 




Pig. 247. 



INFLOEESCBNCE OR ANTHOTAXIS. 



173 



any confusion that might arise from the use of the terms rachis. 
peduncle, aiid pedicel. 

The Peduncle may be 
cylindrical, compressed, or 
grooved ; simple, bearing a 
single flower, as in Prim- 
fose j or branched, as in 
London-pride. It is some 
times succulent, as in the 
Gashew (fig. 248 p), in 
which it forms the large 
coloured expansion sup- 
porting the nut ; spiral, 
as in Cyclamen and Val- 
iisneria (fig. 249); pr spiny, as in Alyssum spinosum, 



/ 




Fig. 248. 



Fig. 249. 

In some 
rushes there is a green terete and sometimes 
spiral floral axis (fig. 190). Sometimes the 
peduncle proceeds from radical leaves; that 
is, from an axis which is so shortened as to 
bring the leaves close together in the form of a 
cluster, as in the Primrose, Auricula, Hyacinth, 
etc. In such cases it is termed a scape. The floral 
axis may be shortened, assuming a flattened, 
convex, or concave form, and bearing numerous 
flowers, as in the Artichoke, Daisy, and Fig. 
In these cases it is called a Beceptacle or 
Phoranthium (pogsw, I bear, and an^os, flower), 
or Clinanthium {xk'nri, a bed, and S,vki;, flower). 
The Floral axis sometimes assumes a leaf- 
like or phylloid (^ipvXXov, a leaf, and iTdog, form) 
appearance, bearing numerous flowers at its 
margin, as in Xylophylla longifolia (flg. 250), 
and in Euscus ; or it appears as if formed by 
several peduncles united together, constituting 
a fasciated axis, as in the Cockscomb (fig. 251), 
in which the flowers form a peculiar crest at 
the apex of the flattened peduncles. Adhe- 
sions occasionally take place between the 
pedimcle 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 peduncles to the stem 

Fig. 248. 'Emit of C&siiew (Anaccurdivm ocGid&ntale). ^, Enlarged peduncle, a. Fruit, or 
nut. Pig. 249. Pistilliferoua plant of Vallisneria spiralis, showing spiral peduncles or 
flower-stalks, by the uncoiling of which the flowers reach the surface of the water, 
previous to fertUiaation. Fig. 250. Leaf-like {pTuylloicl) flattened peduncle, r, of Zylo- 
phylla longifolia. ///, Clusters of flowers developed in a centrifugal or cymose manner. 





174 INELOKESCENCE OE ANTHOTAXIS. 

accounts for the extra -axillary position of flowers, as in many 
Solanacese. When this union extends for a considerable length along 
the stem, several leaves may be interposed between the part where 
the peduncle becomes free, and the leaf whence it originated, and 
it may be diflBcult to trace the connection. 

The peduncle occasionally becomes abortive, and in place of bear- 
ing a flower, is transformed into a tendril (p. 120) ; at other times it 

is hollowed at the apex, so as apparently 
to form the lower part of the outer 
floral envelope, as in Eschscholtzia. 

The termination of the peduncle, or 
the part on which the whorls of the 
flower are arranged, is called the Thala- 
mus or Torus. The term receptacle \s 
also sometimes applied to this, whether 
expanded and bearing several flowers, 
or narrowed so sis 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 ex- 

panded. 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. 260, 2, a) ; in the Strawberry it becomes a conical 
succulent mass, on which the seed-vessels are placed; while in 
Nelumbium it forms a truncated tabular expansion, enveloping the 
seed-vessels. In some cases it bears naked seeds. In some monstrous 
flowers, as in Rose and Geum, it is prolonged as a branch bearing 
leaves (fig. 247). The flowers follow a spiral course round the floral 
axis, which is subject to laws similar to those which regulate 
phyllotaxis ; this is easily traced in such plants as Banksia. 

There are two kinds of inflorescence — one in which flowers are pro- 
duced in the axil of leaves, beyond which the axis continues to 
elongate and bears leaves and flowers ; whilst in the other 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 arrests the axis, 
and the flowers developed subsequently, arise from floral leaves below 
this central flower, and therefore farther removed from the centre. 
The first kind of inflorescence is Indeterminate, Indefinite, or Axillary. 

Fig. 251. Upper part of flattened or fasclated flowering stem of Celosia cristata (Cocks- 
com6), having the form of a crest, covered with pointed bracts, and supporting flowers on 
its summit. 



INFLORESCENCE OE ANTHOTAXIS'. 



175 



Here the axis is either elongated, producing flower-buds as it grows, 
the lower expanding first; or it is shortened and depressed, and 
the outer flowers expand first. The expansion of the flowers is 
thus centripetal, that is, from base to apex, or from circumference to 
centre. This kind of inflorescence is shown in flg. 252, where the leaf 
from which the cluster of flowers is produced, /, represents the bract 
or floral leaf. The rachis, or primary axis of the flower, is a! ; this 
produces small leaflets, 6, which bear smaller flower-leaves or bractlets, 
from which peduncles or secondary axes spring, each bearing single 
flowers. The whole inflorescence is the product of one branch, the 
lower flowers having expanded first, and Isear- 
ing fruit, while the upper are in bud, and the 
middle are in full bloom. In fig.i.253, the 
same kind of inflorescence is shown on a 
shortened axis, the outer flowers expanding 
first, and those in the centre last. 





Kg. 262. 



Fig. 253. 



The second kind of Inflorescence is Determinate, Definite, or Terminal'. 
In this the axis is either elongated and ends in a solitary flower, which 
thus terminates the axis, and if other flowers are produced, they belong 
to secondary axes farther from the centre ; or the axis is shortened 
and flattened, producing a number of separate floral axes, the central 
one expanding first, while the others are developed in succession farther 
from the centre. The expansion of the flowers is in this case centri- 
fugal, that is, from apex to base, or from centre to circumference. It 
is illustrated in fig. 254, where a representation is given of a plant of 
Eanunculus bulbosus ; a is the primary axis swollen at the base in a 
bulb-like manner, b, and with roots proceeding from it. From the 

Fig. 252. Raceme of Barberry (Berberis vulgaris), produced in the axil of a leaf or bract, 
/, whioh has been transformed into a spine, with two stipules, s, at its base, a'. Primary 
floral axis, bearing small alternate bracts, b, in the axil of which the secondary axes, a" a", 
are produced, 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 stiU in bud. Indeterminate simple inflorescence. 
Fig. 253. Head of flowers (cwpitvMvm) of Scabiosa atro-purpurea. The inflorescence is 
simple and indeterminate, and the expansion of the flowers centripetal, those at the circum- 
ference opening flrst. 



176 



INDEFINITE INFLORESCENCE. 



leaves which are radical proceeds the axis ending in a solitary terminal 
flower, /'. About the middle of this axis there is a leaf or bract, from 
which a secondary floral axis, a", is produced, ending in a single 
flower, /", 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, /'". From this tertiary axis a 
fourth is in progress of formation. Here /' is the termination of the 
primary axis, and this flower expands first, while the other flowers are 
developed centrifugally on separate axes. It is a definite inflo- 
rescence, with numerous floral axes. 





Fig. 264. 



Fig. 266. 



Indefinite Infloeescence. — The simplest form of this inflores- 
cence is when single flowers are produced in the axUs of the ordinary 

Fig. 254. Plant of Kanunculus bulbosus, showing determinate inflorescence. a\ Primary 
floral axis dilated at its base, so as to form a sort of bulb, 6, whence the roots and radical 
leaves proceed. /', 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 /'. Oh 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. Fig. 255. Branching 
raceme or so-called panicle of Yucca gloriosa. a', Primary axis or rachis. a", Secondary 
axes or smaller peduncles, a'". Tertiary axes or pedicels bearing flowers, hbhh, Bracts 
and bractlets, in the axil of which the axes are produced. The inflorescence is indeterminate 
and consists of a series of racemes on a common axis, a'. The expansion of the whole in- 
florescence is centripetal, and such is also the case with each of the racemes forming it, the 
flowers at the base of the successive axes opening first. 



INDEFINITE INFLOEESCENCE. ■ 177 

leaves of the plant, the axis of the plant elongating beyond them, as in 
Veronica hederifolia, Vinca minor, and Lysimachia nemoram. The ordi- 
nary leaves in this case become floral leaves or bracts, by producing 
flower-buds in place of leaf-buds. The flowers, being all ofishoots 
of the same axis, are said to be of the same generation or degree, and 
their number, like that of the leaves of this main axis, is indefinite, 
varying with the vigour of the plant. Frequently, however, the floral 
axis, arising from a more or less altered leaf or bract, instead of ending 
in a solitary flower, is prolonged, and bears numerous leaflets, called 
braeteoles or bractlets, from which smaller peduncles are produced, and 
those in their turn may be branched in a similar way. According to 
the nature of the subdivision, and the origin and length of the flower- 
stalks, numerous varieties of floral arrangements arise. When the 
primary peduncle or floral axis, as in fig. 252 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 
secondary floral axes give rise to tertiary ones, the raceme is branch- 
ing, and forms what is by some called a panicle ; but it is better to 
restrict this term to the lax inflorescence of some grasses and rushes. In 





Pig. 266. 



Rgv 267. 



fig. 255 is represented a branching raceme or so-called panicle of Yucca 
gloriosa, a' being the primary axis or rachis with bracts, giving off 
numerous secondary axes, a", which in their turn develop tertiary axes, 

Fig. 266. Corymb of Cerasus Mahaleb, produced in the axil of a leaf wliioli has fallen, 
and terminating an abortive branch, at the base of which are modiiied leaves in the foim of 
scales, e. a', Primary axis, or peduncle, or lachis, producing alternate bracts, 6 6, from the 
axil of which secondary axes or pedicels, a" a", arise, each bearing a single flower. The 
expansion of the flowers is centripetal - Fig. 257. Branching corymb of Pyrus torminalis. 
o'. Primary axis, a" a", Secondary axes, a'" a'". Tertiary axes or pedicels bearing the 
flowers. 6 6 &, Bracts. 

N 



178 



INDEFINITE INI'LOEESCENCE. 



d". The development in each of the secondary axes is centripetal, 
h hhh being the bracts from which the separate axes are produced. 
If in a raceme the lower flower-stalks are elongated, and thus all the 
flowers are nearly on a level, a corymb is formed, which may be simple, 
as in fig. 256, where the primary axis, a, divides into secondary axes, 
a" a', which end ia single flowers ; or branching, as in fig. 257, where 
the secondary axes again subdivide. 





Fig. 268. 



Fig. 259. 



Fig. 260. 



If the peduncles or secondary axes are very short or awanting, so 
that the flowers are sessile, a spike is produced, as in Plantago and 
Verbena officinalis (fig. 258). The spike sometimes bears unisexual 
flowers, usually staminiferous, the whole falling off by an articulation, 
as in Willow or Hazel (fig. 259), and then it is called an amentum or 
catldn ; at other times it becomes succulent, bearing numerous flowers 

Fig. 25S. Spike of Verbena officinalis, showing sessile flowers on a common rachis ; the in- 
florescence indefinite, 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. Fig. 259. Amentum or catkin of Hazel (Corylus Avdlama), 
consisting of an axis or rachis covered with bracts in the form of scales (squatncB), each of 
which covers a male flower, the stamens of which are seen projecting beyond the scale. The 
catkin falls off in a mass, separating from the branch by an articulation. Fig. 260. Spadix 
or succxilent spike of Arum maculatum. 1 Exhibits the sagittate leaf, the spathe or sheath- 
ing bract, h, rolled round the spadix, the apex of which, a, is seen projecting. 2 Shows the 
spathe, 6, cut longitudinally, so as to display the spadix, a. f, Female flowers at the base. 
m, Male flowers. On the spadix above the male flowers there are mimerous abortive flowers 
indicated by hair-like projections. 



INDBEINITE INFLOEESCENCB. 



179 



surrounded by a sheathing bract or spathe, and then it constitutes a 
spadix, which may be simple, as in Arum maculatum (fig. 260), or 
branching, as in Palms. A spike bear- 
ing female flowers only, and covered 
with scales, is either a strobilus, as in 
the Hop ; or a cone, as in the Fir (figs. 
217, 218). In grasses there are usu- 
ally numerous sessile flowers arranged 
in small spikes, called Locustm or 
spihelets, which are either set closely 
along a central axis, or are produced 
on secondary axes formed by the 
branching of the central one; to the 
latter form the term Panicle is applied. 



Fig. 261, 






Fig. 262. 



Fig. 263. 



If the primary axis, in place of being elongated, is contracted. 

Fig. 261. Several umbels, o' o' o' &, 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. & 6 &, Bracts placed alternately on the general axis, d. Shows a double 
budsproceeding from the axU of;[one of these bracts, and thus giving rise to two stalked or 
stipitate umbels, i i i, Vertlcillate bracts, forming involucres at the base of the radii of the 
umbels. Fig. 262. Compound umbel of Carrot {Daucus Garota). a'. Primary axis 

shortened and depressed, so as to present a convex surface, a" a". Secondary axes, or radii 
of the general umbel, each ending in a partial umbel or urabellule, o" o" o" o". a!" a"', 
Tertiary axes of radii of the partial umbels or umbeUules. i', Pinnatipartite bracts, form- 
ing the general involucre, i" i". Simple bracts, forming the partial involucre or involucel. 
Fig. 263. Capitulum, Anthodium, or Head of flowers of Scorzonera hispanica. t. Imbricated 
bracts, forming an involucre. /, Florets or small flowers on the receptacle, having a centri- 
petal evolution. 



180 



INDEFINITE INFLOEESCENCE. 



it gives rise to other forms of indefinite inflorescence. When 
the axis is so shortened that the secondary axes arise from a 
common point, and spread out as 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. 261 and 262. In fig. 
261 the floral axes, a a' a, end in simple 
umbels, o' o' o', and the' umbels are called 
stipitate or stallced ; while in, fig. 262 the 
primary floral axis, a, is very short, and the 
secondary axes, a a, come off from it in 
a radiating or umbrellarlike manner, and 
end in small umbels, o", which are called 
partial umbels or vmibellules, 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. ' 

If there are numerous flowers on a flattened, convex, or slightly 




Fig. 264. 




Fig, 26B. 



Fig. 266. 



Fig. 2&r. 



concave receptacle, having either very short pedicels or none, a capi- 
tulum (head) or anthodium (avhg, a flower, o5o'e, a way or method), 

Fig. 264. Capitulum of Scorzonera hispanica cut verticaUy. r. Receptacle, Phoran- 
thiuin, or the flattened and depressed apex of the peduncle, bearing the florets, /, which 
are surrounded by bracts, b. Fig. 265. Inflorescence of Dipsacus sylvestris. Capi- 

tulum, or head of flowers, each of which is surrounded 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. 266. Inflorescence of Dorstenia Con- 
trayerva, consisting of a broad slightly concave receptacle, r, in which numerous male 
and female flowers, /, are placed. Fig. 267. Inflorescence of Fig (Fi(MS Carica), showing 
the hollow receptacle, r, or peduncle (which is popularly called tlie fruit), covered with 
flowers, /, of various kinds. 



INDEFINITE INTLOEESCENCE. 



181 



or calathium (HaXadiov, a small cup), is formed, as in Dandelion, 
Daisy, and other composite plants (figs. 263 and 264) ; also in 
Scabiosa (fig. 253), and Dipsacus (fig. 265). Such a receptacle or 
shortened peduncle may sometimes be folded so as to enclose partially 




or completely a number of flowers (generally unisexual), giving rise to 
the peculiar inflorescence of Dorstenia (fig. 266), or to that of the 
Fig (fig. 267), where / indicates the flowers placed on the inner sur- 
face of the receptacle, and provided with bracteoles. This inflorescence 
has been called Hypanthodvum (i/*i, under, Sivhg, a flower). 

Lastly, we have what are called compound indefinite inflorescences. 

Fig. 268. Anemone nemorosa. a. Subterranean _stem.- /, Leaf, d, Floral axis producing 
bracts, 6, which form a three-leaved involucre, e, Solitary flower terminating the axis. In- 
florescence deflnite. 



182 



DEFINITE INFLOEESCENCE. 



Thus we may have a group of racemes arranged in a racemose manner, 
on a common axis forming a raceme of racemes or a compound raceme, 
as in Astilbe. In the same way we may have compound umbels, as 
in Hemlock and most Umbelliferse (fig. 262), a compound spike, as 
in Eye-grass, a compound spadix, as in some palms, and a compound 
capitulum, as iu the Hen-and-Chickens Daisy. Again, there may be 
a raceme of capitula, that is, a group of capitula disposed in a race- 
mose manner, as iu Petasites, a raceme of umbels as in Ivy, and so 
on, aU the forms of inflorescence being indefinite in disposition. 

On reviewing these difiierent kinds of inflorescence, it will be 
observed that the elongation or shortening of the axis, and the pre- 
sence 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 is a raceme in which the primary axis is shortened, 
the capitulum or head is a spike in which the same shortening has 
taken place. 

Definite Inflokescence. — The simplest form of this inflores- 
cence is seen in Anemone nemorosa (fig. 268), or in Gentiana acaulis 

(Gentianella), where the axis termi- 
nates in a single flower ; and if other 
flowers are produced, they arise from 
the leaves below the first-formed 
flower. The general name of Cyme 
is applied to the arrangement of a 
group of flowers in a definite inflor- 
escence. It is sometimes difficult to 
understand the mode of development 
or evolution of the flowers in such 
an inflorescence, if the axes are much 
contracted, and the flowers them- 
selves are numerous. It may be 
distinctly traced, however, in plants 
with opposite leaves, in which the 
difierent axes are clearly developed. 
In fig. 269 is represented the flower- 
ing branch of Ery thr«a Centaurium. Here the primary axis, a, 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. 
These are flower-buds, and constitute secondary axes, a a, ending in 
single flowers, /"/", which are thus terminal and solitary; and at 

Fig. 269. Flowering branch of Biythraea Centaurium. a', Primary axis, a" a". Two 
secondary axes, a'" a!" a'", Tertiary axes, four in number, a"" a"" a"". Quaternary axes, 
eight in number. The flowSrs are shown in various stages of development. /', Solitary flower 
which has passed into fruit, terminating the primary axis. /", Flowers less advanced, ter- 
minating 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. 269. 



DEFINITE INFLORESCENCE. 



183 



the base of these axes a pair of opposite leaves is produced, giving 
rise to tertiary axes, a a" a", ending in single flowers,/'"/'"/'", and 
so on. The divisions in this case always take place by two, or in a 
dichotomous {hi-)(a,, in two ways, and riiiveiv, to cut) manner. Had 
there been a whorl of three leaves in place of two, the division would 
have been by three, or trichotomous (rg/^^a, in three ways). 

This inflorescence constitutes the Oyme, by which we mean an 
inflorescence formed by the successive development of unifloral axes 
from pre-existing axes, limited in extent only by the vigour of the 
plant; the floral axes being thus evolved in a centrifugal manner. 
The cyme, elongated according to its development, has been cha- 
racterised as biparous (bis, twice, and pario, I produce), or uniparous 
(unus, one). In figs. 270 and 271, the biparous cyme is represented 





Pig. 270. 



Fig. 271. 



in two species of Cerastium, belonging to the nfitural order Caryo- 
phyUacese, 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. 269 ; the flowers at a a' being the termination 
of the primary axis, and expanding first, the others being subsequently 
developed in a centrifugal order. In some of the Pink tribe, as 
Dianthus barbatus, Carthusianorum, etc., in which the peduncles are 

Fig. 270. Inflorescence (tiparons cyme) of Cerastium grandiflorum. bit. Opposite 
tracts produced at each of the branchings. The axes are indicated as in last figure. The 
primary axis, a', ends in a flower which has passed into fruit. Inflorescence determinate. 
Evolution of flowers centrifugal. Fig. 271. Inflorescence (biparous cyme) of Cerastium 
tetrandrum. Letters have the same meaning as in the last two iigures. , In the quaternary 
axes, a"", the inflorescence becomes unilateral by the non-development of the flower-buds 
on one side. . * - - - - 



184 



DEFINITE INFLOEESCENCE. 



short, and the flowers closely approximated, with a centrifugal expan- 
sion, the inflorescence has a contracted cymose form, and receives the 
name of fascicle. A similar inflorescence is seen in such plants as 
Xylophylla longifolia (fig. 250). When the axes become very much 
shortened, the arrangement is more complicated in appearance, and the 
nature of the inflorescence is only indicated by the order of opening of 

the flowers. In labiate plants, as the 
dead-nettle (Lamium), the flowers 
are produced in 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 from 
its axis two secondary axes rise, and 
the expansion is thus centrifugal. The 
inflorescence is therefore a contracted 
biparous cyme, the flowers being 
sessile, or nearly so, and the clusters 
are called verticillasters {verticillus, a 
kind of screw). Sometimes, especially 
towards the summit of a biparous 
cyme, owing to the exhaustion of the 
growing power of the plant, one of 
the bracts only gives origin to a new 
axis, the other remaining empty, and 
thus the inflorescence becomes uni- 
lateral, and further development is 
arrested (fig. 271 h). 

A branching biparous cyme is 
observed in the privet (fig. 272). In 
this the primary floral axis a' gives rise to secondary axes a" a, along 
its whole length. These, in a similar manner, produce tertiary axes, a", 
which again dividing in a cymose manner, the whole inflorescence 
acquires an appearance not unlike a bunch of grapes, and has re- 
ceived from some the name of thyrsus. 

In the uniparous cyme a number of floral axes are successively de- 
veloped one from the other, but the axis of each successive generation, 
instead of producing a pair of bracts, produces only a single one. Here 
the basal portion of the successive axes collectively forms an apparent 
or false axis, and the inflorescence thus simulates a raceme. In the 
raceme, however, we find only a single true axis, producing in succes- 

Pig. 272. Branching tiparoua cyme or thyrsus of Privet (lAgustrvm vidga/re). The primary 
axis, a', gives oflf secondary axes, a" a", which are opposite to each other, and produce ter- 
tiary axes, a'" of", which are diehotomous, and consequently end in small three-flowered 
cymes, c c. Of the three flowers terminating these tertiary axes, the central one expands 
first, the evolution of the others heing centrifugal. 




Fig. 272. 



DEFINITE INFLOEESCENCE. 



185 





sion a series ofbracts, from whicli the floral peduncles arise, and thus 
each flower is on the same side of the true axis as the bract, in the 
axil of which it is developed ; but in the uniparous cyme the flower 
of each of these axes, the basal part of which unites to form the false 
axis, is situated on the opposite side of the axis to the bract fronj 
which it apparently arises (flg. 275). But this bract is not the one 
from which the axis terminating in the 
flower arises, but is a bract produced upon 
that axis, and gives origin in its axil to 
a new axis, the basal portion of which, 
constituting the next part of the false 
axis (as in' flg. 275), intervenes between 
this bract and its parent axis. The 
uniparous cyme presents two forms, the 
(scorpio, a scorpion), and the 

heUcoid (sX/^, a spire, and 

sidog, form). In the scor- 

pioid the flowers are ar- 
ranged alternately in a 

' double row along one side 

of the false axis (fig. 274),' 

the bracts when developed 
Fig. 273. forming a second double Kg. 274. 

row on the opposite side, as seen in the Henbane ; the whole in- 
florescence usually curves on itself like a scorpion's tail, hence its 
name. In fig. 273 we have a diagrammatic sketch of this 
arrangement. The false axis a b c d is formed by successive genera- 
tions of unifloral axes, the flowers being arranged along one side 
alternately and in a double row ; had the bracts been developed they 
would have formed a similar double row on the opposite side of the 
false axis ; the whole inflorescence is represented as curved on itself. 
In fig. 274 (Forget-me-not) the same scorpioid form of uniparous cyme 
is seen, with the double row of flowers on one side of the false axis, 
but in this case the bracts, which should appear on the opposite side, 
are not developed, and hence the cyme is not complete. 

In the helicpid cyme there is also a false axis formed by the basal 
portion of the separate axes, but the flowers are not placed in 
a double row, but in a single row, and form a spiral or helix round 
the false axis. In Alstromeria, as represented in fig. 275, the axis, 
a', ends in a fiower (cut off in the figure) and bears a leaf. Prom 
the axil of this leaf, that is between it and the primary axis, a', arises 
a secondary axis, a", ending in a flower /", and producing a leaf 
about the middle. From the axil of this leaf, a tertiary floral axis, 

Fig. 273. Diagram to show the formation of a soorpioidal cyme, consisting of separate 
axes, abode. Fig. 274. Scorpioidal or gyrate cyme of Forget-me-not (Myosotis palmtris). 



186 



MIXED INFLOEESCENCE. 



a", ending in a flower/'", takes origin. In this case the axes are 
arranged, not in two rows along one side of the false axis, but are 
placed at regular intervals, so as to form an elongated spiral round it. 
In the Bell-flower (Campanula), (fig. 276), there is a racemose uni- 
parous cyme, developed in a very irregular manner, and giving rise to 
a peculiar mixed inflorescence ; a' a' is the primary axis, ending in a 





Kg. 275. 



Kg. 276. 



flower, /', which has withered, and giving off secondary axes, a" a", 
each terminated by a flower, and developed centripetally, the lowest 
being most expanded. In Streptocarpus polyanthus, and in several 
calceolarias, we probably have examples of compound definite inflores- 
cence. Here there are scorpioid cymes of pairs of flowers, each pair con- 
sisting of an older and a younger flower. 

Mixed Inploebscence. — Forms of inflorescence occur, in which ' 
both the definite and indefinite types are represented. Thus, in Com- 
positae, such as Hawkweeds (Hieracia), the heads of flowers, taken as a 
whole, are developed centrifugally, the terminal head first ; while the 

Kg. 276. False raceme or helicoid cyme of a species of Alstromeria. a' a" a'" a"". 
Separate axes successively developed, which appear to form a simple continuous raceme, of 
which the axes form the intemodes. It is a definite uniparous inflorescence, however, with 
centrifugal evolution. Each of the axes is produced in the axil of a leaf, and is terminated 
by a flower, /' /" /'" /"", opposite to that leaf, and the axes have a spiral aiTangement. Fig. 
276. Uniparous racemose cyme, or cymose raceme of Campanula, a', Primary axis, termi- 
nated by a flower, /', which has already withered, and is beginning to pass into the state of 
fruit, a" a" a". Secondary axes, each tenninated by flowers, /", which are more advanced 
(the lower they are in their position. 



MIXED INFLORESCENCE. 



187 



florets, or small flowers to the receptacle, open centripetally, those at the 
circumference first. So also in Labiatae, such as dead-nettle (Lamium), 
the different whorls of inflorescence are developed centripetally, while 
the florets of the verticUlaster are centrifugal. Sometimes this mixed 
character presents diflBculties in such cases as Labiatse, 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. In Saxifraga umbrosa (London pride), 
and in the horse-chestnut, we meet with a raceme of scorpioid cymes ; 
in sea-pink, a capitulum of contracted scorpioid cymes (often called a 
glomerulus) ; in Laurustinus a compound umbel of dichotomous cymes. 
In concluding this subject of inflorescence, the following diagrams 
m^y serve to lEustrate the different types of inflorescence : — 




Pig. 279. 

Fig. 277 shows an indefinite inflorescence — i.e. one in which all 
the flowers belong to the same axis. Here we have a single elongated 
axis, giving off laterally a floret (1), which expands first ; beyond this 
the axis elongates and gives off another floret (2), which expands 
after the first one — and so on were the axis elongated farther. Thus, 
in this case, the flowers develop from below upwards, and if we were 

Fig. 27T shows Indeflnite inflorescence, in -whioli the lower floret (1) expands first, and 
then the upper floret (2). Fig. 278 shows definite inflorescence, where the terminal floret 
(1) opens first, and then the lower floret (2). Fig. 279 shows definite inflorescence with 
numerous floral axes. The first floral axis hears a flower (I), which opens first ; from this 
axis come off two floral axes (2 2), the flowers of which expand next ; then each of these 
gives off two floral axes (3 3, 8 3), which expand third in order, and so on. 



188 TABULAE VIEW OF INFLOEESCENCE. 

to shorten the axis, and have all the flowers rising from its contracted 
termination, we should find that the outer flowers expanded first and 
were followed by the inner ones, the development heing then centri- 
petal, and as the development of flowers from the main axis is limited 
only by the vigour of the plant, the inflorescence is called indefinite. 
Pig. 278 shows a definite inflorescence. In this case all the flowers 
do not belong to the same axis, but the first axis elongates and 
terminates in a single floret (1), and no more flowers are produced 
on this axis, but if another flower exist in the inflorescence it consti- 
tutes the terminal floret of a new axis (2), similar to the first, and 
arising from it. And the flower of this new axis expands after that 
of the central axis, hence the expansion of florets is from above down- 
wards, or from within outwards, i.e. centrifugal. And as each axis 
has the power of producing only one floret which terminates it, the 
inflorescence is definite. If more florets exist in this inflorescence, 
each one terminates an axis which arises in a manner simijar to that 
already described. Thus the number of florets in such an inflores- 
cence wUl depend on the number of bracts which are produced upon 
the several axes, and which give rise to new unifloral axes. Fig. 278 
represents such a definite inflorescence, where two bracts are produced 
on each axis, giving rise to similar new axes ; the whole inflorescence 
in this case being a biparous cyme. 

Tabulae View of InrLo'iussoENOE. 

A. Indefinite Centripetal Inflorescence. 

I. Flowers solitary, axillary. 

Vnica, Veronica hederifolia. 

II. Flowers in groups, pedicellate. 

1. Elongated form (Kaceine), Hyacinth, Ldburnvm, Cwrrant. 
(Coryml)), Omithogahmi. 

2. Contracted or shortened form (Umbel), Cowslip, Astrantia. 

III. Flowers in groups, sessile. 

1. Elongated form (Spike), Plantago. 
(Spikelet), Grasses. 

(Amentum, Catkin), Willoto, Hazel. 

(Spadix) Arum, some Palms. 

(Cone), Fir, Spruce. 

(Strobilus), Hop. 

2. Contracted or shortened form (Capitulum), Daisy, Dandelion, ScaUous. 

IV. Compound indefinite inflorescence. 
a. Compound Spike, Rye-grass. 

h. Compound Spadix, Palms. 

c. Compound Raceme, Astilbe. 

d. Compound Umbel, Hemlock and most Umbelliferae. 

e. Raceme of Capitnla, Petasites. 

f. Raceme of Umbels, Ivy. 

B. Definite Centrifugal Inflorescence. 
I. Flowers solitary, terminal. 

Oemtianella, Pasony. 



BEACTS OE FLORAL LEAVES. 189 

IL Flowers in Cymes. 

1. Uniparous Cyme. 

a. Heliooid Cyme (axes forming a spiral). 

* Elongated form, Alstromeria. 

* * Contracted form, Witsenia corymbosa. 

5. Scorpioid Cyme (axes unilateral, two rows). 

* Elongated form, i^orjfei-me-Koi, Symphytwmj.Henliane. 

* * Contracted form, Erodium, Alchemilla wrvensis. 

2. Biparous Cyme (Dichotomous), including 3-5-cliotomous Cymes. 

a. Elongated form, Gerastiiim, Stella/ria. 

b. Contracted form (Verticillaster), Dead-nettle, Pelargonium. 

3. Compound Definite Inflorescence. 

Streptocarpus polyanthus, many Calceolarias. 
C. Mixed Inflorescence. 

1. Raceme of Scorpioid Cymes, Morse-chestnut. 

2. Scorpioid Cyme of Capitula, Vernonia centriflora, 

3. Compound Umbel of Dichotomous Cymes, Lawrustinus. 

4. Capitulum of contracted Scorpioid Cymes (Glomerulus), Sea-pirik. 

2. — Bracts or Floral Leaves. 

Flowers 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 hracteoles or bractlets. Bracts some- 
times do not difler from the ordinary leaves, and are then called 
leafy, as in Veronica hederifolia, Vinca, Anagallis, and Ajuga. Like 
leaves, they are entire or divided. In general, as regards their form 
and appearance, they differ from ordinary leaves, the 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. Their phyllotaxis is similar to that of the leaf. When 
the flower is sessile the bracts are often applied closely to the calyx, 
and may thus be confounded with it, as in Malvacese and Eosacese, 
where they have received the name of epicalyx (p. 198). In many 
cases bracts seem to perform the function of protecting organs, within 
or beneath which the young flowers are covered in their earliest stage 
of growth. 

When bracts become coloured, as in Amherstia nobilis. Euphorbia 
splendens. Erica elegans, and, Salvia splendens, they may be mistaken 
for parts of the corolla. They are sometimes mere scales dJ- threads, 
and at other times they are abortive, and remain undeveloped, giving 
rise to the ebracteated inflorescence of Cruciferse and some Boraginacese. 
Sometimes no flower-buds are produced in their axil, and then they 
are empty. A series of empty coloured bracts terminates the inflores- 
cence of 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. 



190 



BEACTS OK FLORAL LEAVES. 




Bracts are occasionally persistent, remaining long attached to 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 
Mrs (figs. 217, 218) 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. 280 a) are of the 
same nature. In Amenta or catkins (fig. 
259) the bracts are called squamce or scales. 
As regards their arrangement, they follow 
the same law as leaves ; being alternate, 
opposite, or verticillate. 

At the base of the general umbel in 
umbelliferous plants, a whorl of bracts often 
exists, called a general involucre (&g. 262 i'), 
and at the base of the smaller umbels or 
umbellules there is a similar leafy whorl 
called involucel or partial involucre (fig. 
262 i"). In Compositse, the name involucre 
is applied to the leaves, scales, or phyllaries, 
surrounding the head of flowers (fig. 263 
6), as in Dandelion, Daisy, Artichoke. This involucre is frequently 
composed of several rows of leaflets, which are either of the same or 
of different forms and lengths, and often lie over each other in an im- 
bricated 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 in- 
volucre are spiny in Thistles and in Dipsacus (fig. 265, e i), and hooked 
in Burdock. Such whorled or verticillate bracts may either remain 
separate (polyphyllous), or may be united by cohesion (gamophyllous), as 
in many species of Bupleurum, and in Lavatera. In the acorn they 
form the cupula or cup (fig. 281, c), and they also form the husky 
covering of the Hazel-nut. In the yew the bracts form a succulent 
covering of the seed. 

When bracts become united together, and overlie each other in 
several rows, it often happens that the outer ones do not produce 
flowers, that is, are empty or sterile. In the artichoke, the outer 
imbricated scales or bracts are in this condition, and it is from the 
membranous white scales or bracts (yaleai) forming the choke attached 

Fig. 280. Fmit of Pine-apple {Ancmassa satvva), composed of numerous flowers united 
into one mass ; the scales, a, being modified bracts qr floral leaves. The crown, b, consists 
of a prolongation of the axis bearing leaves, which may be considered as a series of empty 
bracts, ie. bracts not producing flowers in their axiL 



Fig. 280. 



THE PAETS OF THE ELOWER. 



191 




to the edible receptacle, that the flowers are produced. The sterile 
bracts of the Daisy occasionally produce capitula, and give rise to 
the Hen-and-Chickens Daisy. In place of de- 
veloping flower-buds, bracts may, in certaia 
circumstances, as in proliferous or viviparous 
plants, produce leaf-buds. 

A sheathing bract enclosing one or several 
flowers is called a spatha or spathe. It is com- 
mon among Monocotyledons, as Narcissus, Snow- 
flake, Arum (fig. 260 b), and Palms. In some 
Palms it is 20 feet long, and encloses 200,000 
flowers. It is often associated with the spadix, 
and may be coloured, as in Eichardia sethiopica, ^s- ^^^■ 

sometimes called the ^Ethiopian or Trumpet lily. When the spadix is 
compound or branching, as ui Palms, there are smaller spathes, sur- 
rounding separate parts of the inflorescence, to which the name spaihellm 
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 of the spikelets have been considered as sterile bracts, 
and have received the name of glumes; and in Cyperacese bracts enclose 
the organs of reproduction. 

3. — The Flower and its Appendages, 

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 verticils : — 1. The calyx, the 
outer one. 2. The corolla. 3. The stamens, 
4. The most internal one, the pistil Each 
of these consists normally of several parts, 
which, like leaves, follow a law of alternation. 
Thus, the flower of Crassula rubens (fig. 282) 
presents a calyx, c c, composed of five equal 
parts arranged in a whorl ; a corolla, p p, 
also of five parts, placed in a whorl within 
the former, and occupying the intervals be- 
tween the five parts of the calyx ; five stamens, e e e,m the space 
between the parts of the corolla, and consequently opposite those of 
the calyx ; and five parts of the pistil, o o, which foUow the same law 

Fig. 281. Acorn, or Fruit of the Oak. li, Capula or cap, formed by the imion of 
numerous bracts or floral leaves, the free points of which are seen an'anged in a spiral 
manner. Fig. 282. Flower of Crassula rubens. c c, Foliola of calyx or sepals, f, p. Petals, 
e e. Stamens, o o, Carpels, each of them having a small scale-like appendage, a, at their 




Fig. 282. 



192 



FLORAL ENVELOPES. 




Fig. 283. 



of arrangement. Again, in Scilla itdica, the parts are arranged in 
sets of three in place of five, as shown in fig. 283, where 2)' jj'^ are 
three parts of the external whorl ; p" p" p", three of the next whorl; e', 
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. 

When all the parts of the flower are separate, and normally de- 
veloped, there is no difficulty in tracing this arrangement; but ia 
many cases it is by no means an easy 
matter to do so, on account of chapges 
produced by the union of one part to 
another, by degeneration, by th^ 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 Dichlamydeous (its, twice, 
and yXa/i.iii, a covering) ; occasionally 
one or both become abortive, and then the flower is either Mono- 
chlamydeous (/i6vog, single), having a calyx only, or Achlamydeous (a, 
privative) or naked, having only 

the essential organs, and no DCX «<■ ^-r'/fT" 

floral envelope. pec M\\\ v., //// 

The Floeal Envelopes 
consist of the calyx and corolla. 
In most cases, especially in Di- 
cotyledons, these two whorls 
are easily distinguishable, the 
first being external and green, 
the latter internal, and more or 
less highly coloured. If there 
is only one whorl, then, what- 
ever its colour or degree of de- 
velopment, it is the calyx. Some- 
times, as in many Monocotyledons, the calyx and corolla both display 

Fig. 283. Flower of Scilla italioa. p'p'p'. Three external leaflets, or divisions of the 
Perianth or Perigone. p" p" p". The three internal leaflets, if. Stamens, opposite to the 
flrst or external leaflets, e". Stamens, opposite the second or internal leaflets, o, Ovaries 
united together into one. s. Three styles, consolidated so as to form one. Fig. 28t 
Flower of White Lily {Liliim, dtlyum). p, Perianth or Perigone, having three parts exterior, 
pe, alternating with three interior, pi. e. Stamens, having versatile anthers attached to the 
top of the filaments, s, Stigma at the apex of the style. 




Fig. 284. 



. FLOWER-BUD — ESTIVATION. 193 

rich colouring, and are apt to be confounded. In such cases, the term 
Perianth (-Jrigl, around, S.\ihg, flower), or Perigone {iri^i, and yotij, 
pistil) has been applied to avoid ambiguity. Thus, in the Tulip, 
CrOeus, Lily, Hyacinth, authors speak of the parts of the perianth, in 
place of calyx and corolla, although in these plants, an outer whorl 
(calyx) may be detected, of three parts, and an inner (corolla), of a 
similar number, alternating with them. Thus, the perianth of the 
white Lily (Lilium album, fig. 284 p) consists of three outer parts, 
^e, alternating with three internal parts, 'pi, surrounding the essential 
organs, e, the stamens, and s, the pistil. 

The term perianth is usually confined to the flowers of Mono- 
cotyledons, 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 
only is present. In some plants, as Nymphsea alba (fig. 342), it is 
not easy to say where the calyx ends and the coroUa begins ; as these 
two whorls pass insensibly into each other. 

Flowee-bud. — To the flower-bud, the name alabastrus (meaning 
ros&iud) is sometimes given, and its period of opening has been called 
anthesis (&v6rigig, flower opening), whilst the manner in which the 
parts are arranged with respect to each other before opening is the 
cestivation (cestiims, belonging to summer), or prcefloration (prce, before, 
and flos, flower). The latter terms are applied to the flower-bud in 
the same way as vernation is to the leaf-bud, and distinctive names 
have been given to the difierent arrangements exhibited, both by the 
leaves individually and in their relations to each other. Thus the 
sepals and petals may be conduplioate, or they may be rolled outwards 
or inwards in various ways, or may be folded transversely, becoming 
cruTwpled or corrugated, as in the poppy. 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 sestivation is valvate, as in the calyx of 
Guazuma ulmifolja (flg. 285 c). The edges of each of the parts may 
be turned either inwards or outwards ; in the former case, the sestiva 
tion is induplicate, as in the corolla of Guazuma ulmifolia (fig. 285 
p), in the latter- reduplicate, as in the calyx of Althsea rosea (figs. 
286 c, 287 c). When the parts of a single whorl are placed in a 
circle, each of them exhibiting a torsion of its axis, so that by one oJ 
its sides it overlaps its neighbour, whilst its side is overlapped hi 
like manner by that standing next to it, the sestivation is twisted or 
contortive, as in the corolla of Althaea rosea (figs. 286 p, 288 p). This 
arrangement is characteristic of the flower-buds of Malvaceae and 
Apocynacese, and it is also seen in Convolvulacese and some Caryo- 
phyUacese. When the flower expands, the traces of twisting often 
disappear, but sometimes, as- in Apocynacese, they remain: 





194 



FLOWEE-BUD — ^iESTIVATION. 



In these instances of aestivation, the parts of the verticils are con- 
sidered as being placed regularly in a circle, and about the same height. 




Fig. 285. 



Fig. 286. 



Fig. 287. 



Fig. 288. 




Kg. 289. 



and they are included under circular aestivation.. But there are other 
ca.ses 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. 289 c), 
which cover each other partially like tiles on a 
a house. This aestivation is imhricate. At 
other times, as in the petals of Camellia (fig. 
289^), the parts envelop each other completely, 
so as to become convolute. This is also seen in 
a transverse section of the calyx of Magnolia 
grandiflora (fig. 291), where each of the three 
leaves embraces that within it. When the 
parts of a* whorl are five, as occurs in many 
Dicotyledons, 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 turn partially covered by one of the external 
parts, the aestivation is quincuneial (fig. 290). This quincunx is com- 
mon in the corolla of Rosacese. Fig. 290 is a transverse section of 
the calyx in the flower-bud of Convolvulus sepium, in which the parts 
are iiumbered according to their arrangement in the spiral cycle, and 
the course of the spiral is indicated by dotted lines. In fig. 292, a 
section is given of the bud of Antirrhinum majus, showing the imbri- 
cate spiral arrangement. In this case it will be seen, when contrasted 

Fig. 285. Diagram of calyx, c, and corolla, p, in the tad of Guazuma ulmifolia. .Sstiva- 
tion of calyx valvate, of petals induplicate. Fig. 286. Diagram of calyx, c, and corolla, 
p, in the flower-bnd of Alth^a, rosea. .^Estivation of calyx reduplicate, of petals contortive 
or twisted. Fig. 287. Flower-bud of Althaea rosea in a young state, showing calyx, c, 
still completely enveloping the other parts, and the edges of its divisions touching each 
other. Fig. 288. 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 contortive 
in {estivation. Fig. 289. Flower-bud of Camellia japonica. c. Imbricated sepals of the 
calyx, p, Petals with convolute aestivation. 




FLOEAL ENVELOPES— CALYX. 195 

with fig. 290 that the part marked 2 has, by a slight change in posi- 
tion, become overlapped by 4. In flowers, such as those of the Pea 
(p. 205, fig. 316), one of the 
parts, the vexillum, is often 
large and folded over the 
others, giving rise to vexillary 
aestivation, or the carina may 
perform a similar oflBce, and 
then the aestivation is carinal. ^'s- ^so. Kg. 291. Fig. 292. 

The several verticils often diifer in their mode of sestivation. 
Thus, in Malvaceae, the corolla is contortive and the calyx valvate, or 
reduplicate (fig. 288) ; in St. Johns-wort the calyx is imbricate, and 
the corolla contortive. In Convolvulacese, while the corolla is twisted, 
and has its parts arranged in a circle, the calyx is imbricate and 
exhibits a spiral arrangement (fig. 290). In Guazuma (fig. 285), the 
calyx is valvate, and the corolla induplicate. The circular sestivation is 
generally associated with a regular calyx and corolla ; while the spiral 
sestivations are connected with irregular as well as regular forms. 

The different parts of the flower, besides having a certain position 
as regards each other, bear also definite relations to the floral axis 
whence they arise. An individual part of a flower may be turned to 
one or other side of the axis, to the right or to the left. This law 
often holds good with whole groups of plants, 'and a means is thus 
given of characterising 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 may be inferior, two lateral, and 
one superior, as in the corolla of the Pea tribe ; or one may be in- 
ferior and two superior, as in the corolla of the Kose tribe. 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 alter- 
nation, is inferior. Sometimes the twisting of a part makes a change 
in the f)osition of other parts, as in orchids, where the twisting of 
the ovary changes the position of the labellum. 

Uxternal Floral Whorls, or Floral Envelopes. 

Calyx. — The calyx is the external envelope of the flower, and 
consists of verticillate leaves, called sepals, foliola or phylla (folium, 

Fig. 290. Transverse section of calyx in flower-bud of Convolvulus sepium. Calyx con- 
sists of five sepals corresponding to the numbers in the figure, and the dotted lines indicate 
the direction of the spiral according to which they are arranged. Fig. 291. Transverse 
section of the bud of Magnolia grandiflora, showing the convolute sestivation of the three 
outer leaflets (calyx). Fig. 292. Arrangement of the parts of the calyx in the flower of 
Frogsmouth (Antim-liiMum majus). The arrangement diflfers from that in fig. 290, on ac- 
count of a Blight twisting and overlapping of the parts. 



196 



FLORAL ENVELOPES — CALYX. 



and tpdXKov, a leaf). These calycine leaves are sometimes separate 
from each other, at other times they are united to a greater or less ex- 
tent; in the former case, the calyx is dialysepalous (^diaXveiv, to divide), 
polysepalous or polyphyllous ('iroXug, many) ; in the latter, gamosepalous 
or gamophyllous, monosepalous or monophyllous (ya/ios, union, //,6«o;, 
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. 24-7 c, p. 172), Pseony, etc. 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 unrolled, deli- 
cate woody fibres, and other vessels, — the whole being enclosed in an 
epidermal covering, having stomata and often hairs on its outer sur- 
face, which corresponds to the under side of the leaf. 

In the great divisions of the vegetable kingdom, the venation of 
the calyx is similar to that of the leaves ; parallel in Monocotyledons, 
reticulated in Dicotyledons. The leaves of the calyx are usually 
entire (fig. 293), but occasionally they are cut in various ways, as in 
the Rose (fig. 294 cf), and they are sometimes hooked at the margin, 
as in Rumex uncatus (fig. 295 ci). In the last-named plant there 




Fig. 293. 



Fig. 294. 



Fig. 295. 



are two whorls of calycine leaves, the outer of which, ce, are entire, 
while the sepals of the inner whorl have hooked margins and have 
also swellings, g, in the form of grains or tubercles on the back. The 
outer leaves, ce, may be looked upon in this case as bracts, occupying 
an intermediate place between leaves and sepals. It is rare to find 

Fig. 293. Peiitaphyllous or pentasepalous calyx of Stellaria Holostea ; sepals entire. 
Fig. 294. Flower of Eose, cut vertically, et, Tube of the calyic cf, 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 ends in a stigma, s. r, Receptacle. Fig. 295. Calyx of 
Eumex uncatus, composed of two verticils or whorls ; the outer, ce, having short and 
entii'e divisions ; the inner, ci, having larger divisions, vphich exhibit at the margin narrow 
hooked projections, and have on the back a tubercular swelling, g. 



FLOEAL ENVELOPES — CALYX. 



197 




the leaves of the calyx stalked. They are usually 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 outwards (divergent or 'patulous), or arched in- 
wards (connivent). They are usually of a greenish colour, and are 
called foliaceous or herbaceous ; but sometimes they are coloured, . as 
in the Fuchsia, Tropseolum, Globe-flower, and Pomegranate, and are 
then called petaloid. Whatever be its colour, the external envelope of 
the flower must be considered as the calyx. 

The nature of the hairs on the calyx gives rise to terms similar 
to those already mentioned as applied to the surfaces of other parts 
of plants (p. 33). The vascular 
bundles sometimes have a promi- 
nent rib (figs. 296, 297), which 
indicates the middle of the sepal, 
at other times they have several 
ribs (fig. 298). Thevenation is use- 
ful as pointing out the number of 
leaves which form a gamosepalous 
calyx. At the part where two 
sepals unite, there is occasionally 
a prominent line, formed by the 
union of the vessels of each (fig. 
into two branches, each following the course of their respective sepals. 

In a polysepalous calyx, the number of the parts is marked by 
Greek numerals prefixed. Thus, a trisepalous calyx has three sepals, 
pentasepalous or pentaphylloiis, five, as in Stellaria Holostea (fig. 293), 
and so on. The sepals occasionally are of different forms and sizes. 
In Aconite, one of them is shaped like a helmet, and has been called 
galeate {galea, a helmet). In Oalcophyllum one of the sepals en- 
larges after the corolla falls, and assumes a pink colour. In Clero- 
dendron Thomsonae the white calyx becomes pinkish after the scarlet 
corolla withers. 

In a gamosepalous calyx the sepals adhere in various ways, some- 
times very slightly, as in (Enothera ; 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. 297) ; or they extend down 
the calyx as fissures about half-way, the calyx being trifid (three-cleft), 
quinquefid (five-cleft), as in Primula elatior (fig. 296), according to 
their number ; or they reach to near the base in the form of partitions, 

Fig. 296. Quinquefid or flve-olett calyx of Primula elatior, the oxlip. Pig. 297. Mve- 
toothed inflated calyx of Silene inflata. Fig. 298. Calyx, c, of Hitiscns, with its 
calioulus or epicalyx, 6. 



Fig. 296. Fig. 297. 



Fig. 298. 



298), which divides near the apex 



198 



FLORAL ENVELOPES — CALYX. 



the calyx being tripartite, quadripartite, quinquepartite, etc. 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 a 
two-lipped or labiate calyjc is formed, which, when the upper or 
posterior lip is arched, becomes ringent. The upper lip is often com- 
posed 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 portion where 
the sepals are free is the limb. Sometimes a gamosepalous calyx 
assumes an 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, as in the globe- 
flower, at other times it is bell-shaped, funnel-shaped, turbinate (like a 
top), or inflated as in Silene inflata (fig. 297). 

Occasionally, certain parts of the sepals 
undergo marked enlargement. In the 
Violet, the calycine segments (lacinim) are 
prolonged downwards beyond their inser- 
tions, and in the Indian Oress (Tropseolum) 
this prolongation is in the form of a spur 
(calear), formed by three sepals (fig. 299 e) ; 
in Delphinium it is formed by one. When 
one or more sepals are thus enlarged, the 
calyx is calcarate or spurred. In Pelar- 
gonium the spur from one of the sepals 
is adherent to the flower-stalk. 
In some plants, as in the Mallow tribe, the flower appears to be 
provided with a double calyx, which has been denominated caliculmte, 
the outer calyx being the epicalyx. In fig. 298, c represents the 
calyx of Hibiscus, and b the smaller calyx or epicalyx outside ; and 
in fig. 300, the same thing is shown in PotentUla verna. Many 
authors look upon this epicalyx as a collection of 
whorled bractlets, forming an involucre immedi- 
ately below the flower. In some cases the project- 
ing teeth between the divisions of the calyx, as in 
Kosacese, are to be traced to the transformed 
stipules of the calycine leaves. Degenerations take 
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 Oompositse ; or a mere rim, as in some 
Umbelliferse and Acanthacese, when it is called obsolete or mwrginate. 

p, Pedicel 




Fig. 299. 




Fig. 
Fig. 300. 



199. Calcarate calyx of Tropseolum, Indian cress, e. Spur or calear. 
Calyx, c c, of PotentiUa verna, with its epicalyx or caliculus, 6 6. 



FLOEAL ENVELOPES — CALYX. 



199 



In Compositse, Dipsacacese, and Valerianacese, the calyx is at- 
tached to the pistil, and its limb is developed in the form of hairs, 
called pappus. This pappus is either simple {pilose) (fig. 302), or 
feathery {plumose) (fig. 303). In cases where, to the naked eye, 
the hairs appear to be simple, the examination by a lens sometimes 
exhibits distinct tooth-like projections often irregularly scattered. In 
figs. 301, 302, 303, there are examples of calyces, c, which are 
attached to the pistil, while their limbs, I, show the transition from 
the narrowed thread-like form in Catananche cserulea (fig. 301) to 
the pilose in Scabiosa atro-purpurea (fig. 302), and thence to the 
plumose in Pterocephalus palsestinus (fig. 303). In Valeriana the 
superior calyx is at first an obsolete rim, but as the fruit ripens, 
it is shown to consist of hairs rolled inwards, which expand so as to 
waft the fruit. 






Fig. 301. 



Kg. 302. 



Fig. 303. 



The calyx sometimes falls oflf 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 Labiatse, Scrophu- 
lariacese, and Boraginacese ; or its base only is persistent, as in Datura 
Stramonium. In Bschscholtzia and Eucalyptus the sepals remain 
united at the upper part, and become disarticulated at the ba^e 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.aXh'XT^a, 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- 
Bcholtzia the axis seems to be prolonged so as to form a sort of tube, 
from which the calyx separates. In Eucalyptus the calyx consists of 
leaves, the laminae or petioles of which are articulated like those of 



Figs. 301-303. Examples of calyces, the limbs of which, I, gradually pass into the state 
of hairs or pappus, c t, Calyx, united to the ovary, and forming a narrow column ahove 
it : in figs. 302, 303, the calyx ends in numerous simple .or feathery hairs, I. i. Involucre 
or gamosepalous bracts cut vertically. Fig. 301. Calyx of Catananche cserulea. Fig. 
302. Calyx of Scabiosa atro-purpurea. Fig. 303. Calyx of Pterocephalus palsestinus. 



200^ FLORAL ENVELOPES — COKOLLA. 

the Orange, and the separation between the parts occurs at this 
articulation. 

The receptacle bearing the calyx is sometimes united to the pistil, 
and enlarges, so as to form a part of the fruit, as in the Apple, Pear, 
Pomegranate, Gooseberry, etc. In these fruits the withered calyx is 
seen at the apex. Sometimes a persistent calyx increases much after 
flowering, and encloses the fruit, without being incorporated with it, 
becoming accrescent (accresco, I increase), as in various species of 
Physalis (fig. 304); at other times it remains in a withered or 
marcescent (marcesco, I decay) form, as in 
Erica ; sometimes it becomes inflated or vesi- 
cular, as in sea campion. In Trifolium fra- 
giferum the union of the inflated calyces 
produces the strawberry-like appearance of 
the head of flowers when in fruit. 

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 con- 
spicuous whorl. The gay colours and fra- 
grant odours of flowers are resident in it. It 
is present in the greater number of Dicoty- 
ledons. It is composed of parts which are 
Fig. 304. usually disposed in one or more verticillate 

rows, and which are caRedi petals {-Treray^ov, a leaf). The petals some- 
times form a continuous spiral with the calycine segments, but in 
general they are disposed in a circle, and alternate with the sepals. 

Petals difier more from leaves than sepals do, and are much 
more nearly allied to the staminal whorl. In some cases, how- 
ever, they are transformed into leaves, like the calyx, and occasionally 
leaf-buds are developed in their axil. They are seldom green, although 
occasionally this colour is met with, as in some Cobras, Hoya viridi- 
flora, Gonolobus viridiflorus, and Pentatropis spiralis. As a rule they 
are highly coloured, the colouring matter being contained in cells, and 
differing in its nature from the chlorophyll of the leaves. As regards 
their structure, petals consist of cellular tissue traversed by true 
spiral vessels, and thin-waUed tubes. In delicate flowers, as Convol- 
vulus 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 J inch 
object glass, shows beautiful hexagons, the boundaries of which are 
ornamented with several inflected loops in the sides of the cells. 

Fig. 304. Accrescent calyx, c, connected witli tlie fruit of Physalis Alkekengi. 




FLOKAL ENVELOPES — COROLLA. 



201 




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 their surface. 
Petaline hairs, though sparse and scattered, present occasionally the 
same arrangement as those which occur on the leaves : thus in Bom- 
bacese 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 Eafflesia ; 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 claw ; the upper 
broader, like the blade of a leaf, and called the 
lamina or Uwh. These parts are seen in the petals 
of the Pink (fig. 305), where o is the claw, and I ^s- ^''^■ 

the limb. The claw is often wanting, as in the Rose, and the petals 
are then sessile. Petals having a claw are unguiculate. 

Petals, properly so called, belong to Dicotyledonous plants, for in 
Monocotyledonous the flowers consist of a perianth or perigone, which 
is referred to the calycine envelope. Hence the venation of petals 
resembles that of the leaves of Dicotyledons. 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 ofi', at the same 
or different heights, forming reticulations ; or there may be several 
primary veins diverging from the base of the limb, and forming a sort 
of fan-shaped venation. At other times the median vein divides into 
two. 

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 be- 
comes fimbriated {fimbria, a fringe), as in 
the Pink (fig. 305) ; or laciniated, as in 
Lychnis Flos-ouculi ; or crested, as in Poly- 
gala. Sometimes the petal becomes pinna- 
tifid, as in Schizopetalum. The riiedian 
vein is occasionally prolonged beyond the 




Fig. 306. 



Fig. 307. 



Fig. 805. An ungnioulate pe1al of Dianthus monspeBSUlanua. o, Unguis or claw. 
Z, Limb, which is fimbriated, or has a fringed margin. Fig. 306. A petal of Bryngium 
campestre, with the apex inflexed or turned down towards the base. ,,Fig. 807. A bipartite 
petal of Stellaria media, or common Chickweed. I, The limb split into two. o. The claw. 



202 



FLORAL ENVELOPES — COEOLLA. 



summit of the petals in the form of a long process, as in Strophanthus 
hispidus, where it extends for seven inches ; and at other times it ends 
in a free point or cuspis, and the petal becomes cuspidate ; or the pro- 
longed extremity is folded downwards or inflexed, as in Umbelliferse 
(fig. 306), so that the apex approaches 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 is obcordate. If the separation extends to the 
middle, it is hifid; if to near the base, bipartite, as in Chickweed 
(fig. 307 I). 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 ohliqae petal. 

The limb of the petal may be flat or concave, or hoUowed like 
a boat, cj/mfei/brm or navicular {cymha, a boat, 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 
^Jiv^ form, resembling a horn ; in 
^ * Aconite (fig. 308) some of the 
petals, p, resemble a hoUow 
curved horn, supported on a 
grooved stalk ; while in Colum- 
bine (fig. 309) 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 Borar 
ginacese (fig. 322) there are 
foldings at the upper part of 
the tube of the corolla, r, forming projections concave outwardly, 
which might be considered as small internal spurs. 

When a petal is narrow throughout, as if formed by a prolongation 

Fig. 308. Part of the flower of Aconitum Napellus, showing two irregular hora-like 
petals, j», supported on grooved stalks, o. These used to te caUed nectaries, s, The 
whorl of stamens inserted on the thalamus, and surrounding the pistil. Fig, 309. Single 
spurred petal of Aquilegia vulgaris, common Columbine, formed by a folding of the 
margins. Fig. 310. Cordate or cordiform petal of Genista caudicans. o, The claw. 
I, The limb. 




Fig. 308, 



Fig. 310. 



FLORAL ENVELOPES — COEOLLA. 



203 



of the claw, it is called linear ; when the limb is prolonged at the base, 
so as to form two rounded lobes, it is cordate, as in the petal of Genista 
candicans (fig. 310) ; and when the lobes are acute, it may be sagittate 
or hastate. The meaning of the terms indicating the forms of petals 
will be understood by consideriftg those applied to leaves. As a rule, 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 sestivation. Other petals have a crisp or wavy margin. 

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 from 
monopetalous. In general, the corolla consists of several petals, equal- 
ling the sepals in number, or being some multiple of them. When 
this is the case, the floral envelopes are said to be symmetrical ; when, 
however, by the abortion of some of the petals the numbers do not 
correspond, then the flower becomes unsymmetrical. Under the head 
of floral symmetry the various changes consequent on non-development 
of petals will be noticed. A corolla is dipetalous, tripetalous, tetror 
petalous, or pentapetalous, according as it has two, three, four, or five 
separate petals. 

The general name of polypetalous ('jroXig, many), or dialypetalous 
(bia'kyin, to divide), is given to corollas having separate petals, while 
monopetalous or gamopetalous (/j^ovog, one, and 
yd/jLog, 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, the petals are separate at the base, and 
adhere by their apices. That a monopetal- 
ous corolla consists of several petals united 
is shown in such plants as Phlox amoena, 
where some specimens have petals more or 
less completely disunited, whUe others ex- 
hibit 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 

Fig. 311. Eegular monopetalous or gamopetalona tubular corolla of Spigelia marylandioa. 
c. Calyx, t, Tube of the corolla. I, Limb of the corolla, s, Stigma at the summit of style. 
Fig. 312. Irregular gamopetaloua or monopetalous corolla of Digitalis purpurea. Fox- 
glove, e. Calyx, p. Corolla, t. Tube. I, Limb. 




Fig. 311. 



Fig. 312. 



204 



POLYPETALOUS COROLLAS. 



many Malvaceae 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. 

When a corolla is gamopetalous, it usually happens that the claws 
are united into a tube (figs. 311 t, 312 i), while the upper parts are 
either free or partially united, so as to form a common limb (fig. 311 I), 
the two portions being separated by the faux or throat, which often 
exhibits a distinct constriction or dilatation. The number of parts 
forming such a corolla can be determined by the divisions, whether 
existing as teeth, crenations, fissures, or partitions ; or if, as rarely 





Fig. 313. Fig. 3U. 

happens, the corolla is entire, by the venation. The union may be 
equal among the parts, or some may unite more than others. Some- 
times the tubular portion is bent, as in 
Lycopsis ; at other times the limb is 
curved at its apex, as in Lamium. 

EEGtrLAE PoLYPETALOUS OoEOLLAS. 

— Among them may be noticed the rosa- 
ceous corolla, in which there are five 
spreading petals, having ho claws, and 
arranged as in the single Eose (fig. 313) 
and Potentilla ; the caryophyllaceous co- 
rolla, in which there are five petals with 
long narrow tapering claws, as in many 

Fig. 313. Polypetalous flower of Rosa rabiginosa, the Sweet-brier, t, Bract or floral 
leaf, ct, Hollow torus, which forms the conspicuous part of what is commonly called the 
fruit, cf, cf, cf, cf, cf. Sepals or foliola of the calyx, ppvp. Petals without a claw, e, 
Stamens attached to the calyx Fig. 314. Polypetalous flower of Dianthus monspessu- 
lauus. &, Bracts, c, Calyx. ^ j), Petals with their claws, o, approximated so as to form a 
tube. Pig. 815. Cruciferous flower of Cheiranthus Cheiri, Wallflower, c. Lobes of the 
sepjils ; the two external sepals being prolonged at the base, so as to form a sort of spur or 
swelling (gibbons or saccate), pp. The four petals arranged lilie a cross, e. The four longer 
stamens, the summits of the anthers being visible. 




Fig. 315. 



GAMOPETALOUS COROLLAS. 



205 




of the Pink tribe (figs. 305, 314); the ahinaceous, where the claw is 
less narrow, and there are distinct spaces between the petals, as in 
some species of Chickweed ; cruciform, having four petals, often un- 
guiculate, placed opposite in the form of a cross, as seen in Wall- 
flower (fig. 315), and in other plants called cruciferous (crux, a cross, 
and fero, I bear). 

Ieeegulae Polypetalous Ooeollas.— The most marked of 
these is the papilionaceous (fig. 316), in which 
there are five petals ; one superior (posterior), e, 
placed next to the axis, usually larger than the 
rest, and folded over them in aestivation, called 
the vexillum or standard ; two lateral, a, the ate 
or wings ; two inferior (anterior), partially or 
completely covered by the alse, and often united 
slightly by their lower margins, so as to form a 
single keel-like piece, h, called carina, or keel, 
which embraces the essential organs. This 
corolla occurs in the Leguminous plants of Britain, or those plants 
which have flowers like the pea. Among the irregular polypetalous 
corollas might be included the orchideous (fig. 
317), although it is really the perianth of 
a Monocotyledon. This perianth consists of 
three outer portions equivalent to the calyx, 
and three inner .parts alternating with them, 
constituting the petals. The latter are often 
very irregular, some being spurred, others 
hooded, etc. ; and there is always one, called 
the labellum or lip (Fig. 317 I), which pre- 
sents a remarkable development, and gives rise 
to many of the anomalous forms exhibited by 
these flowers. 

Ebgulae Monopetalous oe Gamopbtal- 
ous Ooeollas. — These are sometimes campanu- 
late or hell-shaped, as in Campanula rotundifolia 
(fig. 318) ; infundihuliform or funnel-shaped, 
when the tube is like an inverted cone, and 
the limb becomes more expanded at the apex, 
319); hypocrateriform or salver-shaped, when 




as in Tobacco (fig. 
there is a straight 



tube surmounted by a flat spreading limb, as in Primula (fig. 

Fig. 316. Irregular polypetalous corolla in the papilionaceous flower of La,tliyrus 
odoratus. Sweet-pea. e, Calyx, e, Vexillum or standard, a. Two alee or wings. &, 
Parina or keel, formed of two petals. Fig. 317. Flower of Twayblade (Listera ovata), seen 
in front, showing a large bifid labellum, I, whieli is different from the other five divisions of 
the perianth. The divisions of the perianth are in two rows of three each. The essential 
organs of reproduction are placed on a column opposite the labellum. The perianth is 
irregular polyphyllous, and is denominated Orchideous. 



206 



GAMOPETALOUS COROLLAS. 



320) ; tubular, having a long cylindrical tube, appearing continu- 
ous with the limb, as in Spigelia (fig. 311), and Comfrey (fig. 321); 
rotate or wlieeir shaped, when the tube is very short, and the limb flat 
and spreading, as in Myosotis (fig. 322) ; when the divisions of the 
rotate corolla -are very acute, as in Galium, it is sometimes called 
stellate or sta/r-lihe ; urceolate or urn-shaped, when there is scarcely any 
limb, and the tube is narrow at both ends, and expanded in the middle. 




IX^^^J. 



Fig. 818. 



Hg. 819. 



Fig. S20. 



Fig. 321. 



as in Bell-heath (Erica cinerea) (fig. 323). 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. 312), which some have called digitaliform. 

Ieregxjlar Monopetalous oe Gamopbtalous Cokollas. — 
Among these may be remarked the labiate or lipped (fig. 324), having 
two divisions of the limb in the form of what are called labia or lips 
(the upper one composed usually of two united petals, and the lower of 
three), separ.ated 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 (ringens, grinning). 
The labiate corolla characterises the natural order Labiates. In Lobelia 



Fig. 818. Regular monopetalous or gamopetalous campanulate or bell -shaped corolla of 
Campanula rotundifolia. c, Calyx. I, Limb of corolla, s, Stigma. Fig. 319. Regular 
monopetalous or gamopetalous infundibuliform corolla of Nicotiana Tabacum, Tobacco. 
c. Calyx. I, Limb of corolla, s. Stigma. Fig. 320. Regular monopetalous or gamo- 
petalous hypocraterifoi-m corolla of Primula elatior, Oxiip. c, Calyx, p^ Corolla, i, Tube. 
I, Limb, a. Anthers. Fig. 321. Regular gamopetalous tubular and somewhat bell- 
shaped corolla of Symphytum ofBoinale, Comfrey. c, Calyx, t, Tube of corolla. 
I, Limb, s, Stigma, r, External depressed surface of folds, which project into the tube of 
the corolla. 



GAMOPETALOUS COROLLAS. 



207 



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 




Kg. 322. 



Kg. 323. 



Kg. 324. 



Pig. 325. 



pressed against the upper, so as to leave only a chink or rictiis between 

them, the corolla is said to be personate or mask-like (persona, a mask), 

as in Frogsmouth (fig. 325), Snapdragon, and some other Scrophu- 

lariacese, and the projecting portion, p, of the 

lower lip is called the palate. In some corollas 

the two lips become hollowed out in a remarkable 

manner, as in Calceolaria, assuming a slipper-like 

appearance, similar to what occurs in the labellum 

of some Orchids, as Cypripedium. The cakeolate 

(calceolus, a slipper) corolla of Calceolaria may be 

considered as consisting of two slipper-like lips. 

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. 
326). This corolla occurs in many composite 
plants, as in the florets of Dandelion, Daisy, and 
Chicory. The number of divisions at the apex 
indicates the number of united petals, some of 
which, however, may be abortive. Occasionally 
some of the petals become more united than others, Kg. 326. 

Fig. 322. Regular gamopetalous rotate corolla of Myosotia palustris, or Forget-me-not. 
c, Calyx, p, Corolla, r. Folds of the corolla, forming projections at the upper part of the 
I tube, which are opposite to the lobes of the corolla. Kg. 323. Regular gamopetalous 
urceolate or urn-shaped corolla of Erica cinerea, or cross-leaved Heath, c, Calyx, t. Tube 
of corolla. I, Limb of corolla, d, Stigma. Fig. 324. Irregular gamopetalous labiate or 
lipped corolla of Salvia pratensis. c. Calyx. *, Tube of corolla. I, Limb, forming two lipa, 
having a gap or hiatus between them, s. Summit of style. Fig. 325. Irregular gamo- 
petalous personate or mask-like corolla of Antirrhinum raajus, or Frogsmouth. c, Calyx. 
t. Tube of corolla, having a gibbosity or swelling, a, at its base. I, Limb of corolla, g, The 
faux or mouth closed by a projection of the lower lip, p. Fig. 326. Irregular gamo- 
petalous ligulate floret of Catananohe cserulea. e. Calyx, with a quinqaefid limb united 
inferiorly with the ovary, o. e. Stamens with united anthers, a (sy7umihBr<ms or syng&nesUms) 
surrounding the style, s, with its bifid stigma.. 




208 



FLOWERS OF GEASSES. 



and then this corolla assumes a bilabiate or two-lipped form, as seen 
in the division of Compositse called Labiatiflorae. In Composite there 
are often two kinds of florets associated in the same head. Thus, in 
the Daisy there are irregular Hgulate white florets on the outside or in 
the ray, while there are regular tubular yellow florets in the centre or 
disc. In Scsevola and in Honeysuckle the corolla is split down to 
its base, so as to resemble somewhat the ligulate form. 

Flowers of Grasses and Sedges. — In these plants, in place 
of verticUlate leaves forming the flower, there are alternate scales 
or glumes. The flowers of grasses usually occur in spikelets (fig. 
327), which consist of one or two glumes, a, covering several flowers, 
b. The spikelets are associated in spikes or panicles. In Wheat 






[Fig. 327. 



Fig. 328. 



Fig. 329. 



Fig. 330. 



these spikelets are arranged alternately along a common rachis. 
Each spikelet (fig. 327) consists of two empty glumes, a a, having 
the form represented in figure 328, and enclosing flowers which are 
composed of scales (pale® or glumellte), delineated in figures 329 and 
330 — the former being the outer, and the latter the inner pale or 
glumella — which are placed at different heights in an alternate manner. 
In the flower of the Oat (fig. 331), after removing the outer pale or 
glumella, the inner one, pi, is seen with two scales (lodiculae.or squamae), 
sq, at the base, enclosing the essential organs of r'eproduction. The 
palesB of grasses are called by some flowering glumes, while hypogynous 
scales (lodiculee) within this are considered as the rudimentary 
perianth. In Wheat (Triticum) there are two empty glumes, and 

Fig. 327. A spikelet of Wheat [Trititnim), consisting of two glumes, a a, enclosing several 
flowers, h h, whicli are composed of two pales (paleas) covering the essential organs of repro- 
duction. The stamens, s, hang out by long slender thread-like filaments. The individual 
glumes aud paleae are placed alternately on the floral axis. Fig. 328. One of the glumes 
of Wheat (Tritwum), seen in profile. These glumes are bracts or floral leaves which consti- 
tute the outer covering of the spikelet. They are placed at different levels, following the 
law of alternation. The glume is marked with three ribs. Fig. 329. External (outer) 
palea or glumella of the flower of Wheat. It is a glumaceous scale marked with two ribs on 
each side of the jnidrib. Fig. 330. Internal (inner) palea or glumella of the flower of 
Wheat. It is thinner and more membranous than the outer glumella (flowering glume), its 
edges are folded inwards and its apex is bifid. 



COEOLLINE APPENDAGES. 



209 



two flowering glumes. In the Oat (Avena) there are two empty 
glumes [gluma, a husk), usually three flowering glumes with awns, and 
two lodicules (hdicula, a coverlet), .representing the perianth. In 
Sedges (Oarices) the male flowers are borne on scales, and so are 
the female, as shown in figure 332, in which the scale, s, is placed 
on one side. Within the scale the female flower is situated, having 
a peculiar bag-like covering, m, termed perigynium. 

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 un- 




Kg. 331. 



Fig. 332. 



Fig. 383. 



Fig. 334. 



usual aspect, as the crown (corona) of Narcissus, the fringes of the 
Passion-flower, etc. If the name is retained, it ought properly to 
include only those parts which secrete a honey-like matter, as the 
glandular depression at the base of the perianth of the Pritillary- (fig. 
333 ?■), or on the petal of Eanunoulus, or on the stamens of Kutacese. 
The honey secreted by flowers attracts insects, which, by conveying the 
pollen to the stigma, effect fertilisation. What have usually, however, 

Fig. 331. Flower of Oat [Avmia saliva), witli tlie two empty glumes, and the outer flower — 
glume removed. The inner glumella or palea, pi, is seen of a lanceolate form, and bidentate 
at the apex. The outer glumella has a long twisted geniculate dorsal awn, with two points 
of bristlei! at the summit. By removing this glumella there are seen two scales (lodicnlse, 
squamse), sg, with the three stamens and two feathery styles. Fig. 332. Female (pistilli- 
ferous or pistillate) flower of a Sedge (Carex), with a single glume or scale, s. The pistil is 
covered by an nroeolate glumaceous bag, u, called perigynium. There is one style, si, with 
three stigmas at its summit. Fig. 333. One of the segments, s, of the perianth of Fritil- 
laria imperialis, or Crown Imperial, with a pit or depression, r, at its base, containing 
honey-like matter. The cavity is colom'ed differently from the rest of the segment, and it 
is often called a nectary, or a nectariferous gland. i'ig. 334. Petal of Lychnis fulgens, 
seen on its inner side, o. Claw. I, Limb, a. An appendage supposed to be form^ by 
chorisis. Tills appendage was called a neotaiy by old authors. 



210 COEOLLINE APPENDAGES. 

been called nectaries, are mere modifications of some part of the 
flower, especially of the corolla and stamens, produced either by 
degeneration or outgrowth, or by a process of dilamination (dis, 
separate, and lamina, a blade), or chm-isis {xu^'Z,i>', I separate). This 
process, called also deduplication, 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 pro- 
duced 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 lamina 
are formed, one posteriorly and the other anteriorly. These scales are 
well seen in Lychnis (fig. 334 a), Silene, Cynoglossum, and Eanun- 
culus, and may be considered as formed in the same way as the ligule 
of grasses (fig. 210, p. 99). Corollas having these scaly appendages 
are sometimes denominated appendiculate. In other cases, as in Cus- 
cuta and Samolus, the scales are alternate with the petals, and may 
represent altered stamens. The formation of these scales is referred 
to under the section of Morphology and Symmetry. 

The parts formerly called nectaries are mere modifications of the 
corolla or stamens. Thus the so-called horn-like nectaries under the 
galeate sepal of Aconite (fig. 308, p. 202), are modified petals, so also are 
the tubular nectaries of Hellebore. The nectaries of Menyanthes and of 
Iris consist of hairs developed on the petals. Those 
of Parnassia (fig. 335 n), and of the Passion-flower, 
Stapelia, Asclepias, and Canna, are fringes, rays, 
and processes, which are probably modifications 
of stamens ; and some consider the crown of Nar- 
cissus as consisting of a membrane similar to that 
which unites the stamens in Pancratium. It is 
sometimes difficult to say whether these nectaries 
are to be referred to the corolline or to the staminal 
row. The paraphyses of the Passion-floWer, the 
crown of Narcissus, and the coronet of Stapelia, 
■p. ggj 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 given names indicating the parts of which they are modi- 
fications, by prefixing the term para {''raga, beside, or close to), using 
such terms as paracoroUa and parastemones. 

Petals are attached to the axis usually by a narrow base, but 

Fig. 335. Petal, p, of Parnassia palustris, or grass of Parnassus, with a so-called nectary, 
rt, which may be an abortive state of some of the stamens, or a process from the petals, 
surmounted by stalked glands. 




DEVELOPMENT OF FLORAL ENVELOPES. 211 

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 fertilisation 
(deciduous'). A corolla which is continuous with the axis and not arti- 
culated to it, as in Campanula, Heaths, etc., may be persistent, and 
remain in a withered or marcescent state while the fruit is ripening. 
A gamopetalous corolla falls off in one piece ; but sometimes the base 
of the corolla remains persistent, as in Khinanthus and Orobanche. 

Development op Floeal Envelopes. — The floral envelopes, 
when gamosepalous and gamopetalous, flrst appear .. 

in the form of a ring, whence various cellular pro- ,mIXIiw\ 
jections arise, representing the sepals and petals ; /> jTvfTu*^ 
when they are polysepalous and polypetalous, the ^^'yJJJUmlly 
ring is wanting. Even when the parts become /-V^ Vj 'fV I 
ultimately unequal, as in Digitalis (fig. 309), they /^-^'^ /"^^\ 
form equal cellular papillae when first developed c \_/ ,. 

(fig. 336). Kg. 336. 

Irregular flowers may be referred to regular types, from which 
they seem to have degenerated. There appear to be three principal 
kinds of irregularity among corollas : — 1. Irregularity by simple in- 
equality in the development of the several segments, often along with ad- 
hesion or atrophy, or arrest of growth : this is the most common kind. 
2. Irregularity of deviation, when the segments, though equal, turn all 
to the same side, as in ligulate florets. 3. Irregularity by simple meta- 
morphosis of stamens, as in Canna. The irregular corollas of Acan- 
thacese, Bignoniacese, Gesneracese, Lobeliacese, and Scrophulariacese, 
are formed at first in a regular manner, by equal projections from a 
sort of cup or ring. In Calceolaria, there is at first a scooped-out cup, 
with four regular and very minute teeth, which are ultimately de- 
veloped as' the corolla ; the nascent calyx has also four divisions. 
In Begoniaceae the floral envelope at first appears as a continuous 
ring, having five equal small segments ; some of these, especially in 
the male flowers, disappear entirely or become atrophied. 

Inner Floral Whorls, or the Essential Orga/ns of Reproduction. 

These organs are the stamens and the pistil, the latter containing 
the seeds or germs of young 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 coroUa, and yet be imperfect if the essential 

Fig. 336. Bud of the irregular gamopetalous flower of Digitalis piUT)urea. c c, Calyx. 
p. Corolla, which in its early development is regular, e, The stamens, at first projecting 
beyond the corolla. 



212 ESSENTIAL OEGANS — STAMENS. 

organs are not present. The name of hermaphrodite or bisexual is 
given to flowers in which both these organs are found ; that of uni- 
sexual (one sex), or diclinous (dig, twice, and xKhri, a bed), to those in 
which only one of these organs appears, — those bearing stamens only 
being- staminiferous (stamen, a stamen, fero, I bear), or male ; those 
having the pistil only, pistilliferous (pistillum, a pistil, fero, I bear), or 
female. 

The absence of one of the organs is due to abortion or non-develop- 
ment. When in the same plant there are unisexual flowers, both male 
and female, the plant is said to be monoecious or monoicous (/jiovog, one, 
and olxlov, habitation), as in the Hazel and Castor-oU plant ; when 
the male and female flowers of a species are found on separate plants, 
the term dicecious or dioicous (dig, twice) is' applied, as in Mercurialis 
and Hemp ; and when a species has male, female, and hermaphrodite 
flowers on the same or difierent plants, as in Parietaria, it is poly- 
gamous (voXxig, many, and yajj^og, marriage). The term agamous (a, 
privative, and ydfiog, marriage) has sometimes been applied to Crypto- 
gamic plants, from the supposed absence of any bodies truly represent- 
ing the stamens and pistil. 

Flowers of the same species of plant sometimes present different 
forms as regards stamens and pistil. Thus, in the same species of 
Primula and Linum there are differences in the size and development 
of the stamens and pistil, one flower having long stamens and a pistil 
with a short style, the other having short stamens and a pistil with 
a long style. The former occur in what are called thumb-eyed prim- 
roses, the latter in those called piu-eyed. Such plants are called 
dimorphic (dig, twice, and A">^pil, form). These plants, and many others, 
have thus two kinds of hermaphrodite flowers on distinct individuals. 
In some plants the stamens are perfected before the pistil ; these are 
called protandrous (rgStrog, first, avri^, male or stamen). Examples of 
these are Ranunculus repens. Lychnis Flos-cuculi, Silene maritima, 
Geranium pratense and sylvaticum, Digitalis purpurea. Campanula 
rotundifolia, and Zea Mais. In other plants the pistil is perfected 
before the stamens, as in Potentilla argentea, Plantago major, lanceo- 
lata, and maritima, Lonicera Periclymenum, and Coix Lachryma. 
These are called protogynous plants (orgSiroj, first, ymr\, female or pistil). 

Stamens. — The stamens (stamina) arise from the thalamus or 
torus within the petals, with which they alternate, forming one or 
more verticils or whorls which collectively constitute the andrcecium 
(Mi§, male, oixloii, habitation), or the male organs of the plant, as 
distinguished from the gyncecium (yuvri, female, olxiov, habitation), 
or female organs of the plant. Their normal position is below 
the inner whorl or the pistil, and when they are so placed (fig. 337 e), 
they are hypogynous (i-ro, under, yuv^, female or pistil). Sometimes 
they become united to the petals, or are epipetalous (kvl, upon, and 



ESSENTIAL OEGANS — STAMENS. 



213 



veraXov, a leaf), and the insertion of both is looked upon as similar, 
so that they, are stUl hypogynous, provided they are independent 
of the calyx and the pistil. In fig. 338, the stamens, e, and the petals, 
p, are below the pistil or ovary, o, and both are separate from it and 
from the calyx, c, and are therefore hypogynous. When the stamens are 
inserted on the calyx, that is, are 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 the latter, and are perigynous {■Tregi, around). This is shown 
in the ilower of the almond (fig. 339), in which the petals, p, and 
the stamens, e, are united to the calyx, c, while the pistil is free. 




Fig. 337. 




Fig. 339. 



When the union of the parts of the flower is such that the stamens 
are inserted on the top of the ovary, they are epigynous (M, upon or 
above). In this case the torus is supposed to be united to the ovary, 
while the calyx is above it, and bears the stamens. In the Orchis 
tribe, where the stamens and pistil are united so as to form a column, 
the flowers are said to be gynandrous. In Aralia spinosa (fig. 340), aU 
the whorls, calyx, c, petals, p, and stamens, e, are united by the torus 
to the pistil, and the two latter whorls appear to rise from the point 
where the calyx joins the upper part of the pistil. These arrange- 
ments of parts have given rise to, certain divisions in classification. 

Fig. 337. Central part of the flower of Liriodendron tulipifera, fixe tulip-tree, composed 
of carpels, c c, ■vrhich 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 hypogynous and extrorse. Fig. 338. Section of a flower of Geranium Rohertianum. 
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 monadel- 
phous. Fig. 389. 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 pistn is free. 



214 



ESSENTIAL OEGANS — ^STAMENS. 




to be afterwards particularly noticed. For instance, the term tha- 
lamifloral is applied to plants having a 
polypetalous coroUa and all the whorls in- 
serted immediately into the torus or thala- 
mus ; calycifloral to those where the petals 
are separate or united, and the stamens are 
inserted directly on the calyx; coroUifloral 
to those in which the united petals are 
placed under the ovary, and the stamens are 
either borne by them, or are inserted inde- 
pendently into the torus. 

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 



Fig. 340. 





Fig. 341. Fig. 342. 

to stamens. Thus, in Nymphsea alba, the White Water-lily (figs. 341, 
342), c represents a sepal, which gradually passes into the petals, p, 
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 into petals, as in the Pseony, Camellia, Rose, 

Fig. 340. Section of the flower of Aialia spinosa. Letters as in last figure. The petals 
and stamens are epigynous, attached to the torus, d, which covers the summit of the 
ovary. The ovary is adherent to the torus, and has been laid open to show its loculaments 
and pendulous ovules. Fig. 341. Flower of Nymphsea alba, White Water-lily, cccc. 

The tour foliola of the calyx or sepals, p p p p, Petals, c. Stamens, s. Pistil. Fig. 342. 
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 foiins, 4, 3, 2, and 1, which gradually re- 
semble the petals. 



ESSENTIAL OEGANS — STAMENS. 215 

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. 
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 (Jsog, 
equal, and eTri//,ui>, a stamen). When the stamens are not equal in num- 
ber to the sepals or petals, the flower is anisostemonous (avieog, unequal). 
When there is more than one whorl of stamens, then the parts of each 
successive whorl alternate with those of the whorl preceding it. 
The staminal row is more liable to multiplication of parts than the 6uter 
whorls. A flower with a single row of stamens is aplostemonous ( aTrXo'os, 
single). If the stamens are double the sepals or petals as regards 
number, the flower is diplostemonous (drnXoog, double) ; if more than 
double, polystemonous (■roXis, many). In diplostemonous and poly- 
stemonous flowers we sometimes find that the inner stamens are the 
younger, and thus alternate with the carpels, as in Oerastium and 
Lilium. In this case the development is centripetal. At other times 
the external are the younger, and the carpels alternate with the 
older stamens, as iu Geranium and Heath. In this case the develop- 
ment is centrifugal. The outer stamens in the latter case may repre- 
sent interst.aminal parts analogous to interpetiolar stipules. In general, 
when the stamens 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, arrest- 
ment of development, and other circrtmstances leading to abnormal 
growth. 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 (/iiiaiti, less). In Cruciferous plants, 
while the petals and sepals are equal in number (four), and alternate 
in arrangement, the staniens are six in number, four long and two 
short ; this imparity of numbers has been supposed to result from the 
splitting of the long stamens by lateral chorisis, a presumption favoured 
by the fact that partial union frequently exists between the two long 
stamens placed next each other (and superposed to the antero-posterior 
petals), that teeth are found only on the outer side of these long 
stamens, and that in many cruciferae only four stamens exist. In the 
case of Gloxinia, where the parts of the flower are arranged in fives, 
there are oilly four perfect stamens, but the fifth one is seen in the 
form of a small conical projection from the base of the corolla, and by 
cultivation the fifth stamen is sometimes fully developed, while the 
flowers assume a regular form, and have an erect in place of an 
inclined position on the peduncle. 



216 ESSENTIAL ORGANS — STAMENS. 

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 upon as caused by the non-appearance of an outer row 
of stamens ; by others it is considered as produced by chorisis or 
separation of laminae from the petals, which become altered so as to 
form stamens, a view which is thought to be confirmed by their der 
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.? 

When the stamens are under twenty they are called definite, and 
the flower is oUgandrous {hXiyog, few, and av)]g, male or stamen) ; when 
above twenty they are indefinite or polyandrous (jiroXijg, many), and are 
represented by the symbol oo. The number of stamens is indicated 
by the Greek numerals prefixed to the term androus ; a flower with 
one stamen being monandrous (/ji,6mg, one) ; with two, diandrous (Sis, 
twice) ; with three, triandrous (Tgiii, three) ; with four, tetrandrous 
(riT^ag, four) ; with five, pentandrous {^itri, five) ; with six, hexan- 
drous (e'5, six) ; with seven, heptandrous (ivrii,, seven) ; with eight, 
octandrous (oKrii, eight) ; with nine, enneandrous (ivvsa, nine) ; with 
ten, decandrous (dixa, ten) ; with twelve, dodecandrous (dude?ca, twelve). 
These terms will be referred to when treating of the Linnsean system 
of classification. 

A stamen consists of two parts — a contracted portion, usually 
thread-like, equivalent to the petiole of the leaf, and termed the fila- 
ment (fllum, a thread) ; and a broader portion, representing the folded 
blade of the leaf, termed the anther (avSri^hg, belonging to a flower), 
which contains a powdery matter, called pollm. 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 
cannot perform its functions. The anther is developed before the 
filament, and when the latter is not produced the anther is sessile 
(sessilis, sitting), or has no stalk, as in the Mistleto. 

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, 
which traverses its whole length, and terminates at the union between 
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 (viraXov, a leaf or petal, eI6og, form), as in 
Canna, Maranta, Nymphsea alba (fig. 342) ; occasionally it is subulate 
(subula, an awl), or slightly broadened at the base, and drawn out 



ESSENTIAL ORGANS— STAMENS. 



217 




Pig. 343. 



into a point like an awl, as in Butomus umbellatus ; and at other 

times it is clwvate (clava, a club), or narrow below and broad above, 

like the club of Hercules, as in Thalictrum. In place of tapering, it 

happens, in some instances, as in Tamarix gallica (fig. 

343), 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. Sometimes the filament is forked, or divided 

at the apex into branches or teeth. In Allium and 

Alyssum calycinum there are three teeth, the central 

one of which bears the anther. In the common garlic 

one of the lateral teeth is somewhat cirrose. 

The filament varies much in length and in firmness. The length 
sometimes bears a relation to that of the pistil, and to the position of 
the flower, whether erect or drooping. The filament is usually of suf- 
ficient solidity to support the anther in an erect position ; but some- 
times, as in Grasses, Littorella, and Plantago, it is very delicate and 
capillary (capillus, a hair), or hair-like, so that the anther is pendulous. 
The filament is usually cnntinuous 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 Tradescantia virginica, blue ; in 
(Enothera and Ranunculus acris, yellow. 

Hairs, scales, teeth, or processes of different kinds are sometimes 
developed on the filament. In Tradescantia 
virginica, or Spiderwort, the hairs are beauti- 
fully coloured, and moniliform (monile, a 
neoldace) or necklace-like. These hairs 
exhibit movements of rotation (p. 153). Such 
a filament is bearded or stupose (stupa, tow). 
At the base of the filament certain glandular 
or scaly appendages are occasionally pro- 
duced, either on its internal or external sur- 
face. These may be either parts of a whorl, 
to be afterwards noticed under the name 
of the Disk, or separate prolongations from 
the filament itself. In fig. 345, a represents 
such a staminiferous appendage found on the 

Kg. 843. Three out of ten stamens of Tamarix gallica, united together by the dilated 
hases of their iilaments. Kg. 344. Stamen of Borago offloinalia. /, Appendioulate fila- 

ment, a, Appendage prolonged in the form of a horn-like process. I, Lobes of the anther. 
Kg. 346. Stamen of Zygophyllum Fabago. /, Filament, connected with a broad scaly 




Fig. 344. 



Fig. 345. 



218 



ESSENTIAL ORGANS — STAMENS. 



inner side of the base of the filament, /, whicli is hence called appen- 
diculate, or sometimes strumose (sti-uma, a swelling). The processes 
noticed in the Boraginacese as modified petals (fig. 344 a) may be 
considered external appendages of the filaments, the stamen being 
regarded as the lamina of a petal. 

Filaments are usually articulated to the thalamus or torus, and 
the stamen falls off after fertilisation ; 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 androecium may unite, forming a tube round the pistil (fig. 338 
«), or a central bundle when the pistil is abortive (fig. 346, 1), the 




Fig. 346, 1. 



Fig. 346, 2. 



Fig. 347. 



stamens becoming monadelphous {/Lovog, one, and &iik(pli, brother), as 
occurs in Geranium (fig. 338), Malva, Hibiscus, and Jatropha Curcas 
(fig. 346, 1) ; or they may unite so as to form two bundles, the 
stamens being diadelphous [dls, twice), as in Polygala, Fumaria, and 

Fig. 346. Male or staminiferous flower (1), and female or pistilliferous flower (2), of 
Jatropha Curcas. c. Calyx, p, Corolla, e, 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 tluee bifid styles at its summit, a, Small glandular appendages 
alternating with the divisions of the corolla. Above each of the flowers is a diagram repre- 
senting the order in which the different pai-ts of the flower are arranged. In diagram 1 are re- 
presented five parts of the calyx, five of the corolla, two rows of stamens, five in each. In 
diagram 2, the staminal rows are abortive, and there are three carpels forming the pistil, in 
the centre. Fig. 347. Triadelphous stamens of Hypericum ffigj'ptiacum surrounding .the 
pistU, 0. //, United filaments forming columns, e e. Anthers free. The outer envelope 
of the flower has been removed, the essential organs alone being left. 



ESSENTIAL OEGANS — STAMENS. 



219 



Pea ; in this case the bundles 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 the filaments are united ia three or more bundles, the stamens 
are triadelphous (rjs/S, three), as in Hypericum segyptiacum (fig. 347), 
or polyadelphous (toXiis, many), as in Luhea paniculata (fig. 348, 1), or 
in Eicinus communis (fig. 349, 1). These staminal bundles may be sup- 
posed to be a compound stamen divided, or they may be looked upon as 
resembling digitately-divided leaves. When there are three stamens in 
a bundle we may conceive the bundle as representing a leaf, with two 
stipules united at its base. In Lauracese there are perfect stamens, 
each having at the base of the filament two abortive stamens or stami- 
nodes (fig. 357), which may be analogous to stipules. The union of the 
filaments takes place sometimes at the base only, as in Tamarix gallica 
(fig. 343); at other times it extends throughout their whole length, so 




Fig. 348, 1. 



Fig. 348, 2. 



Fig. 849, 2. Pig. 349, 1. 



that the bundles assume a columnar form. In certain cases, the co- 
hesion extends to near the apex, forming what Mirbel calls an andro- 
phore (avrig, male or stamen, pogew, I bear), or a column which 
divides into terminal branches, each bearing an anther (347, / e). 
Occasionally some filaments are united higher up than others, and 
thus a kind of compound branching is produced (fig. 349, 2). In 
Pancratium, the filaments are united by a membrane, which may be 
considered as corresponding to the crown of Narcissus. 

Filaments sometimes are united with the pistil, forming a 
columna or column, as i^ Stylidium, Asclepiadacese, Eafilesia, and 

Fig. 348, 1. Flower of Luhea paniculata. cccc, SegmentB of calyx, pp. Petals, e e, 
Stamens 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 bundlesmagnifled, showing 
all the filaments united in a single mass at the base, but separating superiorly, fa. The 
larger internal filaments, each ending in an anther, fs, The shorter outer ones, sterile and 
abortive. Fig. 349, 1. Male fiower of Bicinus communis, or Castor-oil plant, consisting of 
a calyx, c, composed of five refiexed sepals, and of stamens, e, united by their filaments sd 
as to form many bundles, thus being polyadelphous. 2. One of the staminal bundles, /, 
branching above so as to leave the anthers free and separate. 



220 ESSENTIAL ORGANS. — STAMENS. 

Orchidacese. The column is called gynostemium (yuvfi, pistil, and 
(rryifiiav, stamen), and the flowers are denominated gynandrous (yuvri, 
pistil, avri^, male or stamen). 

In the case of certain Achlamydeous (p. 192) 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 iilament, 
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 pro- 
duced at the joint. In this case the apparent anther represents a 
single flower supported on a stalk, all the parts being abortive except 
a solitary stamen. 

The Anther corresponds to the blade of the leaf, and consists of 
lobes or cavities containing minute powdery matter, called pollen, 
which, 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 foimd 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 united upper surfaces of the folded half 

There is a double covering of the anther — the outer, or exothe- 
cium (s^M, outwards, Si^xiov, a covering), resembles the epidermis, and 
often presents stomata and projections of different kinds (fig. 350 ce) ; 
the inner, or endothecium (svBov, within), is 
formed by a layer or layers of flbro-cellular 
tissue (fig. 350 c/), the cells of which have 
a spiral (fig. 23), annular (fig. 24), or reti- 
culated (fig. 25) fibre in their interior. 
This" internal lining varies in thickness. 
Fig. 360. 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. The cells in the endothecium of Armeria 
maritin?^ and Pinguicula vulgaris are reticulated, while annular cells 
occur in the endothecium of Cardamine pratensis. 

Fig. 350. Transverse section of a portion of the covering of the anther of Cobeea scandens 
at the period of dehiscence, ce, Exothecium, or external layer, consisting of epidermal 
cells, c/, Endothecinra, or inner layer, composed of spiral cells or Inenchyma. 




ESSENTIAL OEGANS — STAMENS. 



221 



The anther is developed before the filament, and is always sessile 
in the first instance. In many examples it continues permanently so. 





Fig. 361. Fig. 352. 

It appears in the form of a small cellular projection, containing a mass 
of mucilaginous cells (fig. 351). In the progress of growth, certain 
grooves and markings appear on its surface, and its interior becomes 





Fig. 363. 



Fig. 364. 



hollowed out into two marked cavities, containing a mucilaginous 
matter (figs. 352, 353). In these cavities cells make their appearance 
— the outer small (figs. 352, 353, q>), forming ultimately the en- 
dothecium (fig. 350 cf) ; the interior layer forming cells in which 
the pollen is produced (figs. 352, 353, up). As the cavities become 
larger, the layer of cells (figs. 352, 353, ci) between the endothecium, 
cp, and exothecium, ce, 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 mem- 
branous coverings (fig. 354 I). 

In the young state there are usually four cavities produced, two 
for each anther-lobe, separated by the conmetive, and each divided by 

Fig. 351. Transverse section of an anther of Cuourbita Pepo, or Gourd, taken from a tad 
aljont two millimetres, or l-12tli of an English inch, in length. Pig. 352. Similar hori- 
zontal section from a tad in a more advanced state, ce. Outer layer of cellules (EwtJieGi/mn^ 
forming the epidermis, ci. Intermediate layer of cellules in several layers, most of wliich 
are ultimately absorbed, cp. Internal layer of ceUs (Eniothecmm). up, Anther-cavities 
filled with large cells, which constitute the iirst state of the poUen-utricles, or pollinic cells. 
Fig. 353. Similar section in a still more advanced state. The letters as in the last figure. 
Fig. 864. Anther of the Almond-tree. 1. Seen in front. 'X Seen behind. //, Filament 
attached to the connective, c, by a point. 1 1, Anther-lobes containing poUen. 



222 



ESSENTIAL OEGAifS — STAMENS. 



the septum, which sometimes remains permanently complete, and 
thus forms a quadrilocular (quatuoi; four, loculus, a pouch or box) or 
tetrathecal [Tir^ag, four, SffAri, a sac) anther. The four cavities 
are sometimes placed in apposition, as in Poranthera (fig. 355) and 
Tetratheca juncea (fig. 356), and at other times two are placed above 
and two below, as in Persea gratissima (fig. 357 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 (Slg, twice) as seen in 
figs. 354, 358. Sometimes the anther has a single cavity, and be- 
comes unilocular (unus, one), or monothecal (/ioi/os, one), either by the 
disappearance of the partition between the two lobes, or by the abortion 
of one of its lobes, as in Styphelia Iseta (fig. 359) and Althaea offici- 
nalis (fig. 360). 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. 




Fig. 356. 



Kg. 367. 



Fig. 359. 



The form of the anther-lobes varies. They are generally of a 
more or less oval or elliptical form (figs. 354, 361 I). Sometimes 

Fig. 355, Quadrilocular anther, I, of Porauthera, attached to the filament, /, and opening 
at the summit by four pores, p. Fig. 356. Quadrilocular anther of Tetratheca juncea. 
1. The anther entire, with its four loculaments ending in one opening. 2. Anther cut 
transversely, showing the four loculaments. Fig. 357. Anther of the Avocado pear (Persea 
gratissima), composed of four cavities or loculaments, I I, 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 or staminodes, and which may represent stipules. 
Fig. 358. Pendulous anther lobes, 1 1, of Mercurialis annua, supported on the filament, /, 
and united by the connective, c. Fig. 359. Unilocular or monothecal anther of Styphelia 
laeta, one of the Bpacridaceje, seen in front, 1, and behind, 2. /, Filament. Z, Anther. 
Fig. 360. Unilocular anther of Althaaa officinalis, or Marsh mallow. One of the lobes of the 
anther, I, abortive, f. Filament. 



ESSENTIAL ORGANS — STAMENS. 



223 



they are globular, as in Mercurialis annua (fig. 358) ; at other times 
linear or clavate (fig. 362), curved (fig. 363), flexuose, sinuose, or 
anfractuoae {anfraotus, winding), as in Bryony and Gourd (fig. 364). 
The lohes of the anther are sometimes in contact throughout their 
•whole length (fig. 361), at other times they are separate (figs. 358, 



Kg. 361. Kg. 362. Fig. 363. Kg. 364. 

J 




Kg. 36T. 



Fig. 368. 



Fig. 369. Kg. 370. 



365). In the former ease their extremities may be rounded, forming 
a cordate anther (fig. 354), or the apex may be acute (figs. 344, 345) ; 
in the latter case the lobes may divide at the base only, and end in a 
sagittate or arrow-like manner (fig. 366 I); or at the apex, so as to 
be hifurcate or forked (fig. 367 ^) ; or quadrifurcate, doubly forked 

Fig. 361. Adnate or adherent anther of Begonia manicata, opening by longitudinal de- 
hiscence. I, Anther-lobes. /, Filament' Fig. 362. Forked or bifurcate anther, I, of Aca- 
lypha alopecuToidea, in the expanded flower. Fig. 363. Same anther in the bud, exhibiting 
a curved form. Kg. 364. Sinuous anther, I, of Bryonia dioica. /, Filament. Kg. 365. 
Anther of Salvia officinalis. I f. Fertile lobe full of pollen. I s, Barren lobe without pollen, 
c, Distractile connective. Kg. 366. Anther of Nerium Oleander, with its lobes, 1 1, sagittate 
at the base, and ending at the apex in a long feathery prolongation. Kg. 367. Anther, I, of 
Vaccinium uliginosum. I, Lobes ending in two pointed extremities, which open by pores, 
a. Appendages to the lobes. Kg. 368. Quadrifurcate anther of Gualtheria procumbens. 
I, Lobes ending in four points. Fig. 369. Versatile anther of Poa compressa. /, Filament, 
I, Lobes separating at each end. Fig. 370. Anther, I, of Erica cinerea. /, Filament, r. 
Lobes split partially downwards, a, Scale-lilie prolongations at the base. Kg. 371. Anther 
of Pterandra pyroidea. 1. Entire anther, seen laterally. 2. Lower half after having been 
cut transversely, a a a, Antherine appendages. I ly Anther-lobes, c c, Connective. 



224 ESSENTIAL ORGANS — STAMENS. 

(fig. 368 I) ; or at both base and apex, so as to be forked at each 
extremity, as in Grasses (fig. 369). The cavities of the anther are 
occasionally elongated so as to end in points (fig. 368 I). Sometimes 
the lower part of the antherine cavities is obliterated, and they de- 
generate into flattened appendages (fig. 370 a). It happens at times 
that the surface of the anther presents excrescences in the form of 
warts, awl-shaped pointed bodies (fig. 367 a), or crests (fig. 371 a). 

That part of the anther to which the filament is attached, and 
which is generally towards the petals, is the back, the opposite being 
the face. 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 consequence of 
the valves being unequal. 

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 difierent 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, dividitig it either partially or completely. The septum some- 
times reaches thq 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 he adnate or adlierent (fig. 
361); when the filament ends at the base of the anther, then the 
latter is innate or erect. In these oases 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 movable, and easily 
turned by the wind. This is well seen in what are called versatile 
(ven-to, I turn) anthers, as in Tritonia, Grasses, etc. (figs. 327, 369), 
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. 372). 

The connective may unite the anther-lobes completely, or only 
partially. It is sometimes very short, and is reduced to a mere point, 
(fig. 358), 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. 363 c) ; or of a feathery awn, as in Nerium Oleander 
(fig. 366) ; or of a conical or tongue-like process (figs. 373, 374 c) ; or 
of a membranous expansion (fig. 375 c) ; or it is extended backwards 
and downwards, in the form of a spur, as in fig. 375 a ; or downwards, 
as in the case of the flaky appendage in Ticorea febrifuga. In Salvia 
officiualis (fig. 365), the connective is attached to the filament in a 
horizontal manner, so as to separate the two anther-lobes, and then 
it is called distractile (dis, separate, traho, I draw). In Stachys, 



ESSENTIAL ORGANS — STAMENS. 



225 



the connective is expanded laterally, so as to unite the bases of the 
antherine lobes, and bring them into a horizontal line. 




Fig. 372. 



Pig. 373. Fig. 374. 



Fig. 376. 




The opening of the anthers to discharge their contents is denomi- 
nated 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 de- 
hiscence (figs. 354, 361, 374). 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 
transverse. When the anther-lobes are rendered 
horizontal by the enlargement of the connective 
(figs. 360, 376, aq), then what is really longi- 
tudinal dehiscence may appear to be transverse. 
In other cases (fig. 376 ag), 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. 

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. 375, 2 ; 
370). In other instances the opening is confined to the base or 
apex, each loculament (loculus) opening by a single pore, as in Pyrola 
(fig. 372), Vaccinium (fig. 367), also in Solanum, where there are 

Fig. 372. Pendulous Antlier, I, of Pyrola rotuncUfolia. The Anther is suspended from 
the summit of the filament, /, and opens at its apex by two pores, p. Fig. 373. Anther 

of Humiria balsamifera. 1 1, Anther lobes. /, Filament, ciliated or fringed with glandular 
teeth, c. Conical appendage, which seems to be a prolongation of the connective. 
Pig. 374. Anther of Byrsonima bioorniculata. /, Filament. I, Anther-lobes. The empty 
lobes at the summit are detached, in the form of two small hoi-n-like projections, c, A 
linguiform or tongue-like appendage prolonged from the connective. Fig, 375. Sessile 

anther of Viola odorata, or sweet violet. 1, Seen in front. 2, Seen behind. I, Anther-lobes, 
o, Spur-like appendage from the connective, c. Membranous expansion at the apex of 
anther-lobes. Pig. 376, Corolla of Digitalis purpurea, cut in order 'to show the didyna- 
mous stamens (two long and two short) which are attached to it. t, Tube. /, Filaments 
which are united to the corolla at », and run alohg its inner surface, having formed a marked 
adhesion.' ag, Anthers of the long stamens, ag. Anthers of the short stamens. 



226 ESSENTIAL ORGANS — STAMKNS. 

two, and Poranthera (fig. 355), where there are four. In Tetratheca 
juncea the four cavities (fig. 356, 2) open into a single pore at the apex 
(fig. 356, 1) ; and in the Mistleto 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. 357 v) 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 Guttiferse, as Hebra- 
dendron cambogioides (the Ceylon Gamboge plant), the anther opens 
by a lid separating frorh the apex, or as it is called circumscissile 
(circum, around, scindo, I 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. 

The anthers open at different periods during the process of flowering ; 
sometimes in the bud, but more commonly when the pistil is fully de- 
veloped, and the flower is expanded. They either open simultaneously 
or in succession. In the latter case, individual stamens may move in 
succession towards the pistil and discharge their contents, as in Pamassia 
palustris, or the outer or the inner stamens may open first, following 
thus a centripetal or centrifugal order. The anthers 
are called introrse {introrsum, inwardly), or anticce 
(anticus, the fore part), when they open on the sur- 
face next to the centre of the flower (fig. 377) ; they are 
extrorse (extrorsum, outwardly), ot posticx (posticus, be- 
hind), 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. 369). Sometimes 
■ anthers, originally introrse, from their versatile 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. 

The usual colour of anthers is yellow, but they present a great 
variety in this respect. The are red in the Peach, dark purple in the 
Poppy and Tulip, orange in Eschscholtzia, etc. The colour and appear- 
ance of the anthers often change after they have discharged their 
functions. 

Sometimes a flower consists of a single stamen, as already stated 
in regard to Euphorbia. It is said, also, that in the Coniferse, as in 

Fig. 377. 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, eg, Two 
pairs of long stamens, ep. The short stamens, t, Torus or thalamus to which the stamens 
are attached. 




ESSENTIAL ORGANS — STAMENS. 227 

the Fir, and in the Oycadacese, the stamens are to be regarded as single 
male flowers, supported on scales ; being either a single stamen with 
bilooular anthers, as in Pinus, or unilocular, as in Abies, or several 
stamens united in an androphore, as in Taxus. In the genus Pinus 
there are male cones composed of bract-like processes, bearing on their 
lower side two parallel anther-lobes, beyond which a scale-like con- 
nective extends. In the Yew and Cypress there is a peltate connec- 
tive overhanging the anthers. In Oycads there are numerous anthers 
on the lower surface of the scales of the male cones. 

Stamens occasionally become sterile by the degeneration or non- 
development of the anthers, which, in consequence of containing pollen, 
are essential for fertilisation ; such stamens receive the name of stamirir- 
odia, or rudimentary stamens. In Sorophularia (fig. 378) the fifth 
stamen, s, appears in the form of a scale ; and in many Pentstemons 
it is reduced to a filament with hairs, or a shrivelled membrane at the 
apex. In other cases, as in double flowers, the stamens are converted 
into petals ; this is also probably the case with such 
plants as Mesembryanthemum, where there is a multi- 
plication of petals in several rows. In Persea gratis- 
sima (fig. 357), two glands, g, are produced at the 
base of the filament in the form of stamens, the 
anthers of which are abortive ; the same thing is seen 
in other Lauracese. In these cases the central perfect 
stamen may be considered as representing the true 
leaf, and the two staminodes or glandular bodies, the 
stipules. Sometimes only one of the anther-lobes be- 
comes abortive. In many unilocular anthers, the non- 
development of one lobe is indicated by the lateral ^ g^g 
production of a cellular mass resembling the connective. 
In Salvias, where the connective is distractUe, one of the lobes only 
is perfect or fertile (fig. 365, If), containing pollen, the other (fig. 
365, Is) is imperfectly developed and sterile. In Oanna, in place of 
one of the lobes, a petaloid appendage is produced. 

The stamens, in place of being free and separate, may become united 
by their filaments (pp. 218, 219). They may also unite by their 
anthers, and become syngenesious or synantherous (auv, together, yeveaig, 
origin, avSriga, anther). This union occurs in Composite flowers, and 
in Lobelia, Jasione, Viola, etc. 

Stamens vary in length as regards the corolla. Some are en- 
closed within the tube of the flower, as in Cinchona, and are called 
included (figs. 311, 312, 376) ; 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, 

Fig. 378. Irregular corolla of Scrophularia, "with astaminodium, s, or abortive stamen, ia 
the form of a scale. 





228 ESSENTIAL OEGANS — STAMENS. 

and in the progress of growth become included, as in Geranium stria- 
tum (fig. 379). Stamens also vary in their relative 
lengths as respects each other. When there is more 
than one row or whorl in a flower, those on the out- 
side are sometimes longest, as in Eosaceae (fig. 339) ; 
at other times those in the interior are longest, as in 
Luhea (fig. 348, 2, fa). When the stamens are in 
two rows, those opposite the petals are usually 
shorter than those which alternate with the petals. 

It sometimes happens that a single stamen is 
longer than all the rest. In some cases there exists 
'Fie" 379 ^ definite relation, as, regards number, between the 

long and the short stamens. Thus, some flowers 
are didynamous (dig, twice, b-jvafiig, power or superiority), having 
only four out of flve stamens developed, and the two corresponding to 
the upper part of the flower longer than the two lateral ones. This 
occurs in Labiatse and Scrophulariacese (figs. 376, 378). 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. 377), and give rise to tetradynamous (riT^ae, four, d{jvaf/,is, 
power or superiority) fiowers, as in Cruciferse. 

Stamens, as regards their direction, may be erect, turned inwards, 
outwards, or to one side. In the last-mentioned case they are called 
declinate (declino, 1 bend to one side), as in Amaryllis, Horse-chestnut, 
and FraxineUa. 

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. 353) are surrounded by a 
fibro-cellular envelope, cp, and within this are produced large cells, 
up, containing a granular mass (fig. 380, 1), which divides into four 
minute cell? (fig. 380, 2), around which a membrane is developed, 
so that the original cell, or the parent pollen-utricle, becomes resolved 
by a merismatic division (p. 14) into four parts (fig. 380, 3), each of which 
forms a granule of pollen. The four cells continue to increase (fig. 
380, 4), distending the parent cell, and ultimately causing its absorp- 
tion and disappearance. They then assume the form of perfect pollen- 
grains, and either remain united in fours, or multiples of four, as in 
some Acacias, Periploca grseca (fig. 381), and Inga anomala (fig. 382), 
or separate into individual grains (fig. 380, 5), which by degrees 
become mature pollen (figs. 380, 6 ; 383, 384). 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 

Pig. 379. Bud of polypetalous corolla of Geranium striatum, exhibiting the stamens, e e, 
at first longer than the petals, p p. 



ESSENTIAL ORGANS— POLLEN. 



229 



a viscous matter, surrounding the pollen-grains, as in Onagraeese. 
In Orchideous plants the pollen-grains are united into masses or 
poUinia (fig. 387), by means of viscid matter. In Asclepiadacese 
(fig. 385) the poUinia are usually united ia pairs (fig. 386 b), 
belonging to two contiguous antherine cavities ; - each pollen-mass 
having a caudicular appendage, ending in a common gland, by means 
of which they are attached to a process of the stigma (figs. 385 p, 
and 386 p). The poUinia are also provided with an appendicular stami- 





Fig. 381. 



Fig. 382. 




Fig. 380. 



Fig. 383. 



Fig, 384. 



nal covering (fig. 385 p). 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, according 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 (fig. 387) has a pro- 
longation or stalk, called a caudide (cauda, a tail), which adheres to a 
prolongation at the base of the anther, called rostellum (rostellum, a 
beak), by means of a viscous gland (fig. 387 g), called retinaculum 
(retinaculum, a band or rein). The gland is either naked or covered. 

Fig. 380. Development of the pollen of Viscum album, or tlie Mistleto. 1. Two pollen- 
cells or pollinic 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. Pollinic utricle containing three separate vesicles in its anterior. 5. Two of the latter, 
or the young pollen-grains, removed from the mother-cell or utricle. 6. The grains of poUen 
in their perfect state. Fig. 381. Pollen of Periploca graeoa, showing four grains aggluti- 
nated together. Fig. 382. Pollen of Inga anomala. The grains united in multiples of four. 
Fig. 383. Pollen-grain showing the extine covered with small punctations. Fig. 384. 
Pollen-grain with the extine covered with granulations. 



230 



ESSENTIAL ORGANS — ^POLLEN. 



The term clinandrivm (xXivrj, a bed, and anig, a stamen) is sometimes 
applied to the part of the column in Orchids where the stamens are 
situated. 




Fig. 386. 





Pig. 387. 



When mature, the pollen-grain is a cellular body having an exter- 
nal covering, extine (exto, I stand out, or on the outside), and an 
internal, intine {inius, 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 





Fig. 388. Fig. 389. lit,. "..J. 

by foldings of these membranes. In some aquatics, as Zostera marina, 
Zannichellia pedunculata, Naias minor, etc., only one covering exists, 

Fig. 385. Flower of Asclepias, showing the poUinia or pollen-masses, p, attached to the 
stigma, and covered by appendages. Fig. 386. Pistil of Asclepias, a, with poUen-masses, p, 
adhering to the stigma, s. Pollen-masses, removed from the stigma, &, omited by a gland-like 
body. Fig. 387. Pollinia or pollen-masses of orchis, separated from the point above the 
stigma, with their retinacula or viscid matter attaching them at the base. The pollen- 
masses, p, are supported on stalks or caudicles, c, with glands at base, g. These masses are 
easUy detached by the agency of insects. Fig. 388. PoUen-grain of Passiflora before burst- 
ing. 0, Opercula or lids formed by the extine, which open to allow the protrusion of 
the intine in the form of pollen-tubes. Fig. 389. Pollen-grain of Cucurbita Pepo, or Gourd, 
at the moment of its dehiscence or rupture, o o, Opercula or lids separated from the extine 
by the protrusion of the pollen-tubes, 1 1. Fig. 390. Pollen-grain of Ipomcea, with a reticu- 
lated extine. 



ESSENTIAL ORGANS — POLLEN. 



231 



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. 390). The colour is generally 
yellow, and the surface is often covered with a viscid or oily matter. 
The intine is uniform in difierent 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 enclosed 
in the parent cell. 

Within these coverings a granular 
semifluid matter called fovilla is con- 
tained, along with some oily particles, 
and occasionally starch. The fovilla 
contains small spherical granules, some- 
times the sTshsir of ^1 inch in diameter 
(fig. 391), and larger ellipsoidal or 
elongated corpuscles (fig. 392), which 
exhibit molecular movements under the microscope. 

Pollen-grains vary from ^^ to ^^ of an inch or less in diameter. 
Their forms are various. The most common form of grain is ellip- 
soidal (figs. 392, 393), more or less narrow at the extremities, which 
are called its poles, in contradistinction to a line equidistant from 




Fig. 392. 





Fig. 393. 



Fig. 394. 



either extremity, and which is its equator. In figs. 393, 394, 1 and 
2, the two surfaces of the pollen-grains of Allium fistulosum and 
Convolvulus tricolor are represented with their poles, p, their equator, 
e, and the longitudinal folds in their membrane ; 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, tri- 
angular, trigonal (fig. 396), or polyhedral figure (fig. 398). In the 
latter case, when there are markings on their surface, those at the 

Fig. 391. Pollen-grain of Amygdalus nana, the intine or internal membrane of which is 
protruding at three porefi, under the form of as many ampullae or sacs, ttt. One of these is 
open a£ the extremity, and from it is discharged the fovilla, /, composed of variously-sized 
granules. Pig. 392. Large granules of fovilla of Hibiscus palustris. Fig. 393. Pollen of 
Allium flstulosum, 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. 394. Pollen 
of Convolvulus tricolor. The letters and numbers have the same signification as in fig. 



232 



FOEMS OF POLLEN-GEAINS. 



poles, p, sometimes differ from those at the equator, e. In Tradescantia 
virginica the pollen is cylindrical, and becomes curved; it is polyhedral 
in Dipsacacese and Oompositse ; nearly triangular in Proteacese and 
Onagracese (fig. 396). The surface of the pollen-grain is either uniform 








Fig. 396. 



Fig. 396. 



Pig. 397. 



Fig. 398. 



and homogeneous, or it is marked by folds dipping in towards the centre, 
and formed by thinnings of the membrane. In Monocotyledonous 
plants there is usually a single fold (fig. 393) ; in Dicotyledons, often, 
three (fig. 394). Two, four, six, and even twelve folds are also met 
with. 

There are also pores or rounded portions of the membrane visible 
in the pollen-grain. These vary in number 
from one to fifty. In Monocotyledons, as in 
Grasses, there is often only one (fig. 399) ; 
while in Dicotyledons, they number from 
three upwards. When numerous, the pores 
are either scattered irregularly (fig. 400), or 
in a regular order, frequently forming a circle 
round the equatorial surface (fig. 395). Some- 
times at the place where the pqres 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. 388) and 
Gourd (fig. 389). Grains of pollen have 
sometimes both folds and pores. There may be a single pore in 
each fold, either in the middle (fig. 401) or at the extremities ; or 

Fig. 395. Grain of pollen of Cannabis sativa, or coininon Hemp, e, Equator. j);p, Poles. 
Fig. 396. Pollen-grain of (Enothera biennis, entire, with three angles, where tubes are pro- 
duced. Fig, 397. The same, with one of its angles giving origin to a pollen-tube, which is 
formed by the intine. When the tube protnides, the extine is ruptured. Fig. 398. Poly- 
hedral pollen-grain of Cichorium Intybus, or Chicory. Fig. 399. Pollen-grain of Dactylis 
glomerata, or Cocks-foot grass. Fig. 400. PoUeu-grain of Furaaria capreolata. Fig. 401. 
Grain of pollen of Lythrum Salicaria, showing six folds, three of which are perforated by 
a pore in their middle, and three alternating with them have no pores ; p p, poles ; e c, 
equator. 1. The grain in a Avj state, 2, The grain swollen in water, so as to take a globu- 
lar form and display its folds. The intine or internal membrane begins to protrude through 
the pores. 




Fig. 401. 



CEYPTOGAMIC ANTHEEIDIA. 



233 



folds with pores may alternate with others without pores ; or finally, 
the pores and folds may be separate. 

The form of the pollen-grains is much altered by the application 
of moisture. Thus, in fig. 401, 1, the pollen-grain df Lythrum Sali- 
caria, when, dry, has an ellipsoidal form, but when swollen by the' 
application of water it assumes a globular form (fig. 401, 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 dis- 
tension becomes so great as to rupture the extine irregularly if it is' 
homogeneous, 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. 
396, 401, 2). This efi'ect is produced more fully by adding a Httle 
nitric acid to the water. The internal membrane ultimately gives 
way, and allows the granular fovilla to escape (fig. 391 /). If the 
fluid is applied 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 prolonged outwards like a hernia, and forms an elongated 
tube called a pollen-tube (fig. 397). This tube, at its base, is often 
covered by the 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 fertilisation. The number of poUen- 
tubes which may be produced depends on the num- 
ber of pores. In some poUinia the number of 
tubes which are found is enormous. Thus, Amiei 
calculates that the two pollen-masses of Orchis 
Morio may give out 120,000 tubes. 

In Okyptogamic Plants there are organs 
equivalent to stamens, and denominated antheridia. 
They consist of closed sacs of different forms, 
rounded, ovate, oblong, clavate, flask-like, etc., 
developed in diff'erent parts of the plants, con- 
taining a number of corpuscles immersed in a 
mucilaginous fluid, which at a certain period of 
growth are discharged through an opening at the 
surface. Sometimes the antheridium is a simple 
cell, at other times it is composed of a number of 
cells, as in Hypnum triquetrum (fig. 402, 1). An- ^ ^^^ 

theridia are sometimes confined to particular parts 
of the plant, at other times they are more generally diff'used. Their 

Fig. 402. 1, Antheridium, a, of a moss called Hypnum triquetrum, at the monient when 
its apex is rupturing to discharge the contents, /. 2, Pour utricles of the contents contain- 
ing each a spermatozoid or moving corpuscle rolled up in a circular mamier. 3, Single 
spermatozoid separated. 




234 



ISSENTUL ORGANS — THE DISK. 




contents are small utricles or cellules, varying, like pollen-grains, in the 

different orders of cryptogamic plants, 
and enclosing peculiar bodies called 
phytozoids (pvriv, a plant, and ^£01', 
an animal), or spermatozoids (g-irsg/ia, 
a seed), or antherozoids (fig. 402, 2), 
which are rolled up in a circular or 
spiral manner, as in Hepaticse and 
Mosses (fig. 402, 3). These exhibit 
active movements at certain periods 
of their existence, and resemble in 
this respect animalcules. In Chara 
vulgaris (fig. 403), 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 spermatozoid of a spiral form, which escapes, leaving the 
division empty, 3, and ultimately becomes unrolled, 4, exhibiting two 
vibratile cilia (cilium, an eyelash), to which its movements are 
referred. 

The Disk. — The term dish is applied to whatever intervenes 
between the stamens and the pistil, and 
is one of those organs to which the name 
of nectary was applied by old authors. It 
presents great varieties of form, such as a 
ring, scales, glands, hairs, petaloid append- 
1^/1 ages, etc., and in the progi'ess of growth 
/ it often contains saccharine matter, thus 
■ becoming truly nectariferous. The disk is 
frequently formed by degeneration or trans- 
formation of the staminal row. It may 
consist of processes rising from the torus, 
alternating with the stamens, and thus re- 
presenting an abortive whorl ; or it may 
be opposite to the stamens, as in Crassula 
Fig. 404. rubens (fig. 282 a). In some flowers, 

as Jatropha Ourcas, in which the stamens are not developed, their 

Fig. 403. 1, Portion of antlieridium or globule of Chara vulgaris. Several septate or 
partitioned tubes, (, 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 phytozoid or sperma- 
tozoid. One of the spermatozoids is represented half detached from the cellule. 3, Ex- 
tremity of a tube from which the spermatozoids have escaped, with the exception of the 
terminal cellule. 4, One of the spermatozoids separated. Fig. 404. Disk, d, of Paeonia 
Moutan, or Tree Pseony, covering the ovary, and interposed between the whorl of stamens, 
i, and the pistil, p. 




ESSENTIAL ORGANS — THE PISTIL. 235 

place is occupied by glandular bodies forming the disk (fig. 346, 
2, a). In Gesneracese and Cruciferse the disk consists of tooth-like 
scales at the base of the stamens (fig. 377, t). TJa.e 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. 404, 
d) ; or a 'waxy lining of the calyx tube or hollow receptacle, as in the 
Eose (fig. 29.4, ct) ; or a swelling at the top of the ovary, as in Um- 
belliferse, in which the disk is said to be epigynous. The enlarged 
torus covering the ovary in Nymphsea and Nelumbium may be re- 
garded as a form of disk. 

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 con- 
tains the seeds. It sometimes receives the name of gynxcium (yuH), 
pistil, olxiov, 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 on the ovary, and is then called 
sessile, as in the Tulip and Poppy*(fig. 444), or is elevated on a stalk 
called the style, interposed between the ovary and stigma. The style 
is not necessary for the perfection of the pistil. Sometimes it becomes 
blended with other parts, as with the filaments of the anthers in the 
column of Orchidacese. 

Like the other organs, the pistil consists of one or more modified 
leaves, which in this instance are called carpels (x.ag'jrbg, 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 
their occasional conversion into true leaves, as in Lathyrus latifolius ; 
and from the ovules corresponding in situation to 
the germs or buds found on some leaves, as those 
of Bryophyllum calycinum. When a pistil consists 
of a single carpel it is simple, a state usually de- 
pending on the non-development of other carpels ; 
when it ig composed of several carpels, more or 
less united, it is mmpoimd. 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 from its margins are ■^'^' *"*■ 

developed one or more buds called ovules. That this is the true nature 

Pig. 405. Carpellary leaf of the double-flowering Cheriy. In this plant the pistil is com- 
posed distinctly of one or more leaves folded inwards. I, Lamina or hlade 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. 




236 



ESSENTIAL ORGANS — THE PISTIL. 




-ft'^ 



Fig. 406. i'lg. lUT. 



of the pistil may be seen by examining the flower of the double-flower- 
ing Cherry. In it no fruit is produced, and the pistil consists of sessile 
leaves (fig. 405), 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. 406, 407), the lower part 
of which is enlarged, forming the ovary, o, and 
containing a single ovule, g, attached to its 
walls, with a bundle of vessels, /«, entering 
it, a cylindrical prolongation, t, forming the 
style, and a terminal expansion, s, the stigma. 
It will be seen that in this case two carpellary 
Z'^" leaves have become succulent, and have united 
together so as to form a compound pistil, with 
a single cavity containing one seed. 

The Ovary then represents the limb or 
lamina of the leaf, and is composed of cellular tissue with fibro-vascu- 
lar bundles, and an epidermal covering. The cellular tissue, or paren- 
chyma, often becomes 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 epi- 
thelium, which does not exhibit stomata. The vascular bundles cor- 
respond with the veins of the leaf, and consist of spiral, annular, and 
other vessels. 

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. 407 c), in which there are some loose project- 
ing cells (figs. 408, 409), forming what is called the conducting tissue. 
A transverse section of the style of Crown Imperial (fig. 408) shows 
three vascular bundles, v v v, corresponding to three styles which are 
united into one, and loose cells, p, in the canal of the style. This 
canal is bounded by cellular tissue (fig. 409, e c), traversed by spiral 
vessels, v v, and in its interior, besides the loose cells, p p, there are, 
especially at the period of fecundation, elongated tubes, //, which in 
part fill up the canal. The name, conducting tissue, is given to that 
found in the canSl of the style, on account of the part which it plays 
in conveying the influence of the poUen to the ovules, as will be ex- 

Pig. 406. Pistil or carpel of the single-flowering Cherry in its normal state, o, Ovary, t, 
Style, s, Stigma. JMg. 407. 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 tundle of nourishing 
vessels, fn, terminates, t, Style traversed by a canal, c, which runs from the stigma, s, to 
the cavity of the ovary. 



ESSENTIAL ORGANS — THE PISTIL, 237 

plained under fertilisation. Lindley has shown that in some instances 
the style seems to derive its origin from the placenta. The presence 
of the style is by no means essential to the perfection of the pistil. It 





Pig. 40S. 



Pig. 409. 



varies in its shape and position, being usually apicilar, but from altera- 
tion in the direction of the central axis it occasionally seems to be' 
lateral. Its form and appearance 
also vary ; under ordinary cir- 
cumstances it is rounded in shape, 
but occasionally becomes flattened, 
as in the Iris. In Clematis it is 
furnished with hairs ; in Euphorbia 
it is forked. 

The Stigma is a continuation of 
the cellular tissue in the centre of 
the style, and it may be either ter- 
minal, when the canal opens at the 
top only (figs. 407 «, 410, 1), or 
lateral, when the splitting of the 
canal takes place on one side (fig. 
411 s), or on both sides (fig. 412 s s). 
along the whole length of the style. 




Fig. 410. Fig. 411. Fig. 412. 

The stigma sometimes extends 
In other instances the style is 



absent, and then the stigma is said to be sessile. In Orchideous plants 

Fig. 408. Tfansveree section of tlie style of Fritillaria imperialis, or Crown Imperial. 
The style is composed of three united together, v v v, Three vascular bundles, each 
corresponding to one of the three styles, p, Papillae or cellular bodies projecting into the 
cavity of the canal. Fig. 409. Structure of the canal in the centre of the style of a 
Campanula, c c. Cellular tissue forming its paiietes traversed by trachea, v. p p. Variously 
formed cells, displaced as it were, and along with other elongated and filamentous ones, //, 
obstructing the canal. Fig. 410. 1, Stigma, 5, of Daphne Laureola, terminating the st^le, 
t. 0, Summit of the ovary. 2. A small portion of the surface of the stigma, much magnified 
to show its papillas. Fig. 411. Unilateral stigma, s, of Asimina triloba, i, Style. Fig. 
412. Bilateral stigma, s s, of Plantago saxatilis. o. Ovary. *, Style. 



238 



ESSENTIAL OEGANS — THE PISTIL. 



it is placed on a part of the column called the gynizus (yuvvj, pistil, 
and 1^,01, I sit). It is composed of cellular tissue more or less lax, 
often having projecting cellules in the form of papillse (fig. 410, 2), 
or of hairs (figs. 413, 3 ; 446 s), and at the period of fertilisation 
exuding a viscous iiuid, which retains the grains of pollen, and causes 
the protrusion of tubes. 

A pistil is usually 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. 414, 415), or at diflferent heights in a spiral 
cycle (fig. 337 c). When they remain separate and distinct, thus show- 
ing at once the composition of the pistil, as in Caltha, Eanunculus, 
Hellebore, and Butomus (fig. 415), the term apocarpous (k'tto, separate, 
and xag'jrhg, fruit) is applied. Thus, in Crassula rubens (fig. 414), 
the pistil consists of five verticillate carpels, o, alternating with the 
stamens, e ; and the same arrangement is seen in Xanthoxylon 
fraxineum (fig. 414). In the Tulip-tree (fig. 337) the separate car- 
pels, c c, are numerous, and arranged in a spiral cycle upon an 
elongated axis or receptacle. In the Raspberry the carpels are on a 
conical receptacle ; in the Strawberry, on a swollen succulent one ; and 
'in the Eose (fig. 294 o o), on a hollow one, r r, ct, which is probably 
a prolongation of the torus. 




Fig. 413. Fig. 414. Fig. 416. 

When the fruit consists of several rows of carpels on a flat 
receptacle, the innermost have their margins directed to the centre. 

Fig. 413. 1, Summit of the style, t, of Hibiscus palustris, dividing into five branches, 
which are each terminated by a stigma, s s. 2, One of these branches highly magniHed. 
3, Portion of the surface of the stigma still more magnified, to show its papillse, which are 
elongated like hairs. Fig. 414. Pistil of Xanthoxylon 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. 415. 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 innej: ones, pi^ three 
rows of stamens, eo and ei, and the carpels, ce and d. 



ESSENTIAL ORGANS — THE PISTIL. 



239 




Fig. 416. 



Fig. 417. 



while the margins 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 Eose. 
At other times the carpels are united, 
as in the Pear, Arbutus, and Chick- 
weed, so that the pistil becomes syn- 
carpous (eiiv, together or united). In 
Dictamnus Fraxinella (fig. 416) five 
carpels unite to form a compound pis- 
til. In Scilla italica (fig. 283) the o^ 
three carpels form apparently only one ; 
but on examination it will be found 
that the pistil consists of three carpels 
alternating with the three inner sta- 
mens. The union, however, is not al- 
ways complete ; it may take place by 
the ovaries alone, while the styles and 
stigmata remain free, the pistil being then gamogastrous {yd(Mi, union/ 
and yaSTn^, ovary) ; and in this case, when the ovaries form apparently 
a single body, this organ receives the 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. 
414). 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. 417). 
The union is usually most complete at the 
base ; but in Labiatse the styles are united throughout their length, 
and in Apocynacese and Asclepiadacese the stigmata only. 

When the union is incomplete, the number of the parts of a com- 
pound pistil may be determined by the number of styles and stigmata 
(fig. 417 s) ; when complete, the external venation, the grooves on 
the surface, and the internal divisions of the ovary, indicate the 
number. When the grooves between the carpels are deep, the ovary 

Fig. 416. Portion of the pistil of Dictamnus Fraxinella. Two of the five carpels have 
heen 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 
ia front show their dorsal surface, d, and their lateral surface, I. At the hase of the 
gynophore, g, are seen the cicatrices, c, marking the insertion of the calyx, the petals, and 
the stamens. Fig. 417. Pistil of Malva Alcea. o, Nine ovaries, united so as to form one. 
*, Column formed by nine styles united to near their summit, where'they diverge and separate. 
Bach of the divisions of the style is terminated by a stigma, s. Fig. 418. Horizontal 
section of the four-celled {qiiadrilocndar or tetratliecaT) ovary of Fuchsia coceinea, c c cc^ 
Wall of the ovary, which is formed by four carpellary leaves, a, Quadrangular axis to which 
the carpels are united, o. Ovules attached to the inner margin of the carpels. 




240 



ESSENTIAL ORGANS — THE PISTIL. 



is denominated lobed, being one, two, three, four, or five lobed, 
according to circumstances. In fig. 417 the nine carpels forming the 
ovary, o, are divided by grooves; and in fig. 418 a transverse section 
of the ovary of Fuchsia coocinea shows the four carpels which form 
it. The changes which talie place in the pistil by adhesion, degenera- 
tion, and abortion, are frequently so great as to obscui'e its composi- 
tion, 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. 

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 elongation 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. 419), 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 sHpitate (stipes, a trunk), or sup- 
ported, as in the Passion-flower, on a stalk (figs. 
414, 416 g), called a gynophore (yuK)), pistil, 
and poosM, I bear), or thecaphore (drixri, a case). 
Sometimes the axis is produced beyond the 
ovaries, and the styles become united to it, as 
in Geraniacese and Umbelliferse. In this case 
the prolongation is called a carpophore (xag^Js, 
fruit, and fogiai, I bear). 

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 vascular 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 development of cellular tissue in connection with the 
conducting tissue of the style and with the stigma. By the imion of 
these tissues is formed the placenta, a cellular 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, correspond- 
ing to the margin of the folded carpellary leaf, while the outer or dorsal 
suture corresponds to the midrib of the carpellary leaf The placenta 

Fig. 419. Section of monstrous Hose, as figured at page 172, tlie axis of which is pro- 
longed teyond the flower, and the envelopes removed to show the aboi-tive stamens, r. The 
carpels, /, are attached alternately along the axis in the form of leaves, j), Aliortive floral 
, Stamens in imperfect flower at the apex. 




419. 



FOEMATION OF THE PLACENTA. 241 

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 nnite, but remain 
separate, and consequently two placentas are formed in place of one. 
In fig. 420 the two carpels are folded, so that their margins meet, 
and the placenta is apparently single ; whereas in fig. 421 the margins 
of each carpel do not meet, and the placenta of each is double. 
Again, in fig. 422, the two carpels, after meeting in the centre or axis, 
a, are reflected outwards towards the dorsal suture, sd, and their margins 
separate slightly, each being placentiferous, and bearing ovules, o. 






When the pistil is formed by one carpel, the inner margins unite 
in the axis, and form usually a common marginal 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 
(dissepio, 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 laminse ; 
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. 

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, guinquelocular, or multilocular, 
according as it is formed by two, three, four, five, or many carpels, 
each corresponding to a single cell or loculament (fig. 415, 2, ce, ci). 
In these cases the marginal placentas meet in the axis, and unite so 
as to form a single central one (fig. 420 a). The number of locula- 
ments is equal to that of the dissepiments. In fig. 418 there is 
shown a transverse section of the ovary of Fuchsia coocinea, c c c c 
being its parietes formed by the union of four carpellary leaves, a th« 
axis united to the parietes by dissepiments, and o the ovules attached 

Kgs. 420, 421, 422. Horizontal sections of ovaries, oomposed of two carpellary leaves, 'the 
edges of whicli are folded so as to meet in the axis, a, in fig. 420 ; are turned inwards into 
the loculaments after meeting in the axis in fig. 422 ; and do not reach the axis in fig. 421. 

E 



242 



FORMATION OF THE PLACENTA. 



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. 421), and the placentas are parietal {'paries, a 
wall). A horizontal section of the ovary of Ery thrsea 
Oentaurium (fig. 423) exhibits a unilocular ovary 
with parietal placentas, p, formed at the inner 
margins of each 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. Prom 
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. 

The carpeUary 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 thickenings 
along the walls. In fig. 424 the pistil of Viola tricolor is represented, 
1, cut vertically, and, 2, cut transversely, the ovules being attached 




this it will be 




Fig. 424. Fig. 426. Fig. 426. 

to the walls of the ovary, and the placentas, p, being merely thickened 
portions of the walls. Cases occur, however, in which the placentas 

Fig. 423. Horizontal section of the ovary of Erythrsea Centanrium. c. Wall or paries of 
the ovaryDr carpeUary leaf, jj. The edge on which the placenta is formed, hearing the 
ovules, 0. I, Cell or loculament. Fig. 424. Pistil of Viola tricolor, or Pansy. 1, Vertical 
section to show the ovules, u, attached to the parietes. Two rows of ovules are seen, one 
in front, and the other in profile, jj, A thickened line on the walls forming the placenta, 
c. Calyx, d. Ovary, s. Hooded stigma terminating the short style. 2, Horizontal section 
of the same. j3. Placenta, o. Ovules, s. Suture, Fig, 425. Pistil of Cerastium hirsutum 
cut vertically, o. Unilocular or monothecal ovary, jj. Free central placenta, g, Ovules, 
s. Styles. -Fig. 426. 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. 



FORMATION OF THE PLACENTA. 243 

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 Oaryophyllacese. 
Thus, in Cerastium hirsutum (figs. 425, 426), the ovary, o, is com- 
posed 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, 
g, attached to it. 

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 Primulacese, Myrsinacese, and Santalacese, in 
which no vestiges of septa or marginal ovules can be perceived at any 
period of growth. The free placenta of Primulacese is different from 
that of Oaryophyllacese. 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, throughout its 
organogeny (ogyavov, organ, and y'svigi;, production or development), 
separate and axile. 

Free central 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 supported 
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 Oaryophyl- 
laceae, the second to Primulacese. The latter 
case has been explained, on the marginal 
hypothesis, by considering the placentas as 
formed from the carpels by a process of 
chorisis, and united together in the centre. 

Some consider the axile view of placenta- 
tion as applicable to all cases, the axis in some 
cases remaining free and independent, at 
other times sending prolongations along the 
margins of the carpellary leaves, and thus 
forming the marginal placentas. The oc- ^'^- *^'- 
currence of placentas over the whole inner surface of the carpels or of 

Figs. 427, 428. One of the carpels of Butonius mabellatus, or flowering Eush, cut trans- 
versely in 427, and longitudinally in 428. I, Loculament or cavity of the carpel, o, Ovules. 
s, Stigmata. 




244 DIVISIONS IN OVARIES. 

the dissepiments, as in Nymphsea and in Butomus mnbellatus (figs. 
427, 428) ; also, though very rarely, along the dorsal suture, as in 
Cabomba, or on lines within the margin, as in Orohanche, has been 
supposed to confirm this view. Schleiden argues in favour of it, from 
the case of Armeria, where there are 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. 
This theory of placentation, however, cannot be easily applied to all 
cases ; and Gray says that it is disproved in cases of monstrosity, 
iu 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 Lufia foetida, the 
entangled fibres of the carpellary leaves, even in the young state, 
seem to be connected with perpendicular lines forming the placenta. 
Brongniart mentions a case where the marginal placenta was entire, 
while the axis was prolonged separately, and totally unconnected 
with the placenta ; he also notices peculiar monstrosities, which seem 
to prove that, in some cases at least, marginal placentation must take 
place. 

Upon the whole, then, it appears that marginal, or, as it is often 
called, carpellary placentation, generally prevails ; that axile placenta- 
tion explains easily cases such as Primulaceae; while such instances as 
CaryophyllacesB are explicable on either view. 

Occasionally, divisions take place in ovaries which are not formed 
by the edges of contiguous carpels. These are called spurious dissepi- 
ments. They are often horizontal, and are then called 
pliragmata ((pgdy/j^a, a separation), as in Cathartocarpus 
Fistula (fig. 429), where they consist of transverse 
cellular prolongations from the walls of the ovary, only 
developed after fertilisation, and therefore more pro- 
perly noticed under fruit. At other times they are 
vertical, as in Datura, where the ovary, in place of 
being two-celled, is rendered four-celled ; in Cruciferee, 
where the prolongation of the placentas forms a re- 
plum (replum, leaf of a door) or partition ; in Astragalus 
and Thespesia, where the dorsal suture is folded in- 
^"^^"^ wards ; in Oxytropis where the ventral suture is 
folded inwards ; and in Diplophractum, where the 
inner margin of the carpels is inflexed (fig. 422). In Cucurbitacese, 
divisions are formed in the ovary, apparently by peculiar projections 
inwards from curved parietal placentas. In some cases horizontal 
dissepiments are supposed to be formed by the union of carpels 

Fig. 429. Pistil of Cassia or Catliartocarpus Fistula, in an adranced state, cut longi- 
tudinally, to show the spurious transverse dissepiments, or phragmata. 




ADHESIONS BETWEEN THE TOEUS AND OTAEY. 



245 



situated at different heights, so that the base of one becomes united 
to the apex of another. In such cases the divisions are true dissepi- 
ments formed by carpellary leaves. The anomalous divisions in the 
ovary of the Pomegranate have been thus explained. 

The ovary is usually of a more or less spherical or curved form, 
sometimes smooth and uniform on its surface, at other times hairy 




Fig. 430. 



Fig. 432. 



Kg. 433. 



and grooved. The grooves, especially when deep, indicate the 
divisions between the carpels, and correspond to the dissepiments. 

Fig. 430. Flower of Cucumis Melo, or Melon, o, Inferior ovary covered by the adherent 
torus. Calyx, I, and Corolla, p, being above the ovary. Fig. 431. Flower of Saxifraga 
Geum, eut vertically to show the ovary, o, adherent for half its height to the torus, c. The 
calyx, which is called half-superior, p. Petals, e, Stamens. ;>-. Styles and stigmas. Fig. 
432. Pistil of Hoteia japonica, one of the Saxifragacese, cut vertically, in order to show the 
interior of its 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 torus, c. (, Styles. 
s. Stigmas, p, Placentas covered with ovules, pe, Base of the petals, , Fig. 433. Flower 
of Fuchsia coccinea divided horizontally into two halves, through the middle of the ovary, o. 
The lower half, 2, of the ovary has been left untouched, to show its four cavities or loculi, 
with the ovules attached to their internal angles. (Fig. 418 shows the same section more 
highly magnified.) The upper half, 1, has been cut vertically, to show the ovules, g, ar- 
ranged in a row in each loculament. The torus incorporated with the ovary below bears 
the calyx, t I. p, Petals inserted on the calyx, 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. 



246 ESSENTIAL ORGANS — THE STYLE. 

T^e dorsal suture may be marked by a slight projection, or by a 
superficial groove. 

The ovary, as a rule, is free, in the centre of the flower, and not 
adherent to any of the surrounding organs. It is then termed supenor, 
as in Lychnis, Primula, and Geranium (fig. 338). In many cases, 
however, it is \mited with surrounding parts, — ^most usually with the 
torus (receptacle), which, being prolonged into a cup-shaped expansion, 
becomes adherent to the ovary, and the floral whorls (calyx, corolla, 
stamens), proceeding from it are thus carried upwards, and rise from 
a plane, level with the summit of the ovary,- — which is thus beneath 
their point of origin, and is therefore inferior, whilst they are superior. 
This is well seen in Rose, Almond (fig. 339), Aralia (fig. 340), Melon 
(fig. 430), Pomegranate, Apple, Pear, Gooseberry, and Fuchsia 
(fig. 433). A transverse section of the ovary of Fuchsia (figs. 418, 
433) shows several closed loculaments containing ovules ; while 
the pistil of the Rose when cut vertically exhibits a receptacTilar cup 
or hollow torus, open at the top, and covering numerous' separate 
carpels, arranged on its concave surface, each of the carpels consisting 
of ovary, style, and stigma (fig. 294, p. 196). In these examples the 
torus is adherent to the ovary throughout its entire extent ; but in 
some plants, as Saxifragacese (figs. 431, 432), the union is only par- 
tial, and the term half inferior is applied to the ovary, whilst the 
floral whorls are half superior. 

These appearances were formerly explained by supposing an 
adhesion between the calyx tube of the ovary ; and the term adherent 
was applied to the calyx in cases where the ovary is inferior, and 
the corolla and stamens were considered to be attached to and carried 
upwards by the adherent calyx. But this view has been superseded 
by the one already explained. These adhesions between the torus 
and the ovary will be found to be of importance, as determining the 
epigynous and perigynous condition of the stamens. 

The Style proceeds from the summit of the carpel, and may be 
looked upon as a prolongation of it in an 
upward direction (fig. 406 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 con- 
stituting what is called conducting tissue. 
Fig. 435. which ends in the stigma. In some cases 
the carpellary leaf is folded from above downwards, in a hooded 

Fig. 434. 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 ovyry. Fig. 435. Carpel of Chrysobalanus Tcaco. o. 
Ovary. (, Basilar style, s. Stigma. 




ESSENTIAL ORGANS — THE STYLE. 



247 



manner, so that its apex (as in reclinate' vernation, fig. 222 o) ap- 
proaches more or less the base. When the folding is slight, the 
style becomes lateral (fig. 416); when to a greater extent, the style 
appears to arise from near the base, as in the Strawberry (fig. 434), or 
from the base, as in Chrysobalanus leaco (fig. 435), when it is called 
basilar. In all these cases the style still indicates the organic apex of 
the ovary, although it may not be the apparent apex. 

The carpel sometimes becomes imbedded in the torus, which 
consequently forms an elevated margin round it ; and then, if the 
style is basilar or lateral, it may adhere to a portion of the torus, on 
one side of the carpel, and appear to arise from it. This is seen in 
Labiatse (fig. 436) and Boraginacess (fig. 437), where the four carpels, 
0, 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 prolongation of the 
torus. When carpels are 
arranged round a central pro- 
longation of the torus, with 
which their united style is con- 
tinuous, the arrangement is 
called a gynobase (yuvij, pistil, 
/3aff/ff, base). It is well de- 
veloped in Ochnacese. In Ge- ^"S- *36. Fig. 43r. 
raniacesB there is a carpophore or prolongation of the torus in the 
form of a long beak, to which the styles' are attached. 

The form of the style is usually cylindrical, n;iore 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 Oanna. In Goodeni- 
aceae it ends in a cup-like expansion, enclosing the stigma. 
It may be smooth and covered with glands and hairs. 
These hairs occasionally aid in the application of the 
pollen to the stigma, and are called collecting hairs, as in 
Goldfussia ; in Campanula they appear double and re- 
tractile. In Aster and other Oompositse (fig. 438) hairs 
are produced on parts of the style, pc, prolonged be- 





Fig. 438. 



yond the stigma, s; these hairs, during the upward development of 

Fig, 436. Pistil of Lamium altum, shown hy 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. Fig. 437. Pistil of Eritriohium Jaoquemontianum 
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. 438. Summit of the style, t, of an Aster, separating into two branches, s, 
each terminated by an Inverted cone of collecting hairs, pc. The stigma, s, is seen below as 
a band or line on the inner curvature of the branches. 



248 



ESSENTIAL OEGANS — THE STIGMA. 



the style, come into contact with the already ripened pollen, and carry 
it up along with them, ready to be applied by insects to the mature 
stigma of other flowers. In Vicia and Lobelia the hairs frequently 
form a tuft below the stigma. 

The styles of a syncarpous pistil may be either separate or united ; 
when separate, they alternate with the septa. When united com- 
pletely, it is usual to call the style simple (fig. 433) ; when the union 
is partial, then the style is said to be bifid, trifid, muUifid, according 
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 multipwrtite, 
when the union of two, three, or many styles only extends a short 
way above the apex of the ovary. The style of a single carpel, or of 
each carpel of a compound pistil, may also be divided. In fig. 346, 
2, each division of the tricarpellary ovary of Jatropha Curcas has a 
bifurcate or forked style, s, and in fig. 439 the ovary of Emblica 
ofiicinalis has three styles, each of which is divided twice in a bifurcate 
manner, exhibiting thus a dichotomous division. 

The length of the style is determined 
by the relation which ought to subsist be- 
tween 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 insensibly 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 
faU. off after fertilisation is accomplished, 
and thus be deciduous. 

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 instances, be considered as the placental 
portion of the carpel, prolonged upwards. In Armeria, and some 
other plants, this connection with the placenta cannot be traced. Its 
position may be either terminal or lateral. The latter is seen in some 
cases, as Asimina triloba, where it is unilateral (fig. 411), and in 
Plantago saxatilis (fig. 412), 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. Some stigmata, as those of the Mimulus, 
present sensitive flattened laminse, which close when touched. The 




Fig. 439. 



Fig. 439. Femaleflowerof Bmtlica officinalis, one of the Enphorbiaceffi. c, Calyx, pp. 
Petals, tt Membranous tube surromiding the ovary, o. Ovary, crowned by three styles, s, 
each being twice bifurcate. 



ESSENTIAL OEGANS — THE STIGMA. 



249 



stigma 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 Labiatse. The stigma alternates 
with the dissepiments of a syncarpous pistil, or, in other words, 
corresponds with the back of the loculaments ; but ia 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 dissepi- 
ments, that is, alternates with the loculaments. 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. 

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 Kosaceas), indicating 
apparently that it is a double organ like the placenta. To the division 
of a compound stigma the terms bifid, trifid, etc., are applied, accord- 
ing to the number of the divisions. Thus, in Labiatse (fig. 324), and 
in Oompositse (figs. 326, 438 s), the stigma is bifid ; in Polemonium, 
trifid. When the divisions are large, they are called lobes, and when 
flattened like bands, lamelke; so that stigmas may be bilobaie, trilobate, 
bilamellar, trilamellar, etc. 

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., 440), the quinquefid or five-cleft stigmia indicates 




flllW 

Pig. 440. Kg. 441. Fig. 442. Pig. 443. Fig. 444. 

five carpels, the stigmata of which are separate, although the other 
parts are united. In Bignoniacese (fig. 441), as well as in Scrophu- 

Pig. 440. Stigmas, s, of Campanula rotundifolia. I, Style. Fig. 441, Bilamellar stigmas 
of-Bignonia pandorea. The two lamellae are applied naturally against each other in 1, while 
in 2 they are artificially separated. Fig. 442. Globular stigma of Mirabilis Jalapa. t, Style, 
s. Stigma, Pig. 443. Circular stigma, s, and (, style of Arbutus Andrachne. Fig. 444. 
Pistil, of Papaver somniferam, or opium Poppy, o, Ovary, s, Eadiating stigmas on its 
summit. ^ 



250 



PISTILLIDIA IN CEYPTOGAMIC PLANTS. 



lariacese and Acanthacese, the two-lobed or bilamellar stigma indicates 
a bilocular ovary. Sometimes, however, as in the case of the styles, 
the stigma of a single carpel may divide. It is probable that in 
many instances what is called bifurcation of the style is only the 
division of the stigma. In Graminess and Compositse (figs. 331, 438) 
there is a bifid stigma, and only one cavity in the ovary. This, how- 
ever, may be probably traced to subsequent abortion in the ovary of 
one of the carpels. The stigma presents various forms. It may be ■ 
globular, as in Mirabilis Jalapa (figs. 410, 442) ; orbicular, as in 
Arbutus Andrachne (fig. 443) ; umbrella-like, as in Sarracenia, where, 
however, the proper stigmatic surface is beneath the angles of the 
large expansion of the apex of the style ; ovoid, as in Fuchsia (fig. 
433) ; hemispherical ; polyhedral; radiating, as 
in the Poppy (fig. 444), where the true stig- 
matic rays are attached to a sort of peltate 
or shield-like body, which may represent de- 
pressed or flattened styles ; cucullate — i.e. 
covered by a hood, in Calabar Bean (fig. 445 a), 
where it is situated on the apex of a declinate 
style, bearded (hairy) on its concave surface 
(fig. 445 6). The lobes of a stigma may be flat 
and pointed, as in Mimulus and Bignonia (fig. 
441 J fleshy and blunt, smooth or granular, or 
they may be feathery, as in many Grasses (fig. 
446). In Orchidaceae the stigma is situated 
on the anterior surface of the column formed 
by the union of the styles and filaments ; the 
point where it occurs being called gynizus (p. 
238). In Asolepiadacese the stigmas are united 
to the face of the anthers, and along with them form a solid mass 
(fig. 386). 

In Ceyptogamic Plants there exist organs called ■pistilUdia, 
which have been supposed to perform the function of pistils. They 
are hollow flask-shaped organs, like ovaries, to which the names of 
sporangia {ff'^ro^a, a spore or seed, and ayyog, a vessel), and thecce 
{6ri%ri, a sac), have also been given. They contain bodies called spores, 
equivalent to ovules. These spores being capable of germination, and 
being devoid of cotyledons, have been termed leafless phytons. The 
sporangia, or spore-cases, are sometimes immersed in the substance of the 
plant, as in Eiccia glauoa (fig. 447, 1) ; at other times they are sup- 
ported on stalks, or setm (seta, a bristle), as in Mosses. In Marchantia 
polymorpha they consist of distinct and separate expansions, having a 
flask-shaped appearance (fig. 448), the lower enlarged part, o, contain- 

Pig. 445. Style and stigma of the Calabar Bean (Physostigma vmmosum), showing the 
curved barbate style with hairs, a, on its concave surface, and a hooded (cucullate) stigma, b. 




Fig. 445. 



ESSENTIAL ORGANS — THE OVULE. 



251 



ing the spores, and surrounded by a cellular coat resembling a calyx, c. 
From this ovary-like body there is a prolongation which may be con- 






Fig. 446. 



Fig. 447. 



Fig 448. 




Fig. 449. 



sidered as a style, t, terminated by a cellular enlargement, s, which 
has been compared to a stigma. The styloid pro- j 2 

longation withers and disappears when the spores 
are mature. Sometimes the thecse, as in Lichens, 
consist of a club-shaped elongated cell or ascus 
(fig. 449, 1), coataining nuclei or cells in its in- 
terior, which form the spores. Sometimes these 
are single, at other times united in sets of two 
(fig. 449, 2), or of four (fig. 447, 2), or of some 
multiple of four. There are various modifications 
of sporangia in other Cr3rptogamic tribes. In 
Ferns, they are often surrounded by an annular 
ring, or by elastic bands, which cause their de- 
hiscence ; while in Ohara they are called nucules, 
and present an oval form with a spiral arrangement of tubes. 

The Ovule. — The ovule is the body attached to the placenta, 

Fig. 446. Pistil of Cynodon Daotylon, a Grass, o. Ovary, s, Feathery stigmas. Fig. 447. 
1, Perpendicular section of the frond, /, of Riccia glauca, and of the sporangium or spore- 
case, 0, which is imbedded in it. s. Narrow process or style by which the sporangium com- 
municates with the external surface. I, Its cavity or loculus. .t, Toung 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. Pig. 448. Sporangium or spore-case of Marchantla poly- 
morpha. o, Hollow swelling containing spores, and which has been compared to the ovary. 
t, Narrow process prolonged upwards, and resembling a style, jt, Termination of this cellu- 
lar process, compared to the stigma, c. Cellular covering of the sporangium, or spore-case, 
surrounding it like a calyx. Fig. 449. 1, Theca or ascus of Solarina saccata, a species 
of Lichen, containing eight spores, united in sets of two. 2, Two of theSe double spores, 
highly magniiied. 



252 ESSENTIAL ORGANS — THE OVULE. 

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 Compositae 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 ovules some- 
times appear as mere lobes of the carpellary leaf; in Aquilegia ovules 
■ transformed into true leaves are occasionally produced on either 
margin of the carpel ; and the ovules of Mignonette sometimes assume 
the form of 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. 

The ovule is usually qontained in an ovary, but in Ooniferse and 
Cycadaceee it is generally considered as having no proper ovarian 
covering, and is called Tiaked, these orders being denominated gymno- 
spermous (yvfivbg, naked, and ffTsg/ia, a seed), or naked-seeded. In 
these orders the ovule is produced on the edges, or in the axil of 
altered leaves, which form no evident style or stigma. The scales of 
the cones in Coniferse are by some looked upon as the homologue of 
opened-out carpels bearing exposed ovules. In the common Fir 
there are usually two ovules at the base of the upper surface of each 
scale. In the Juniper each scale bears one ovule. Ih the Cypress 
the scales are peltate, and cover numerous ovules ; while in the Yew 
there is a solitary ovule at the apex of a cone-like organ formed 
by numerous barren scales. In Gnetaeese there is also a solitary 
ovule, the secundine of which is pushed out into a long tube-like 
process. In Oycadacete the ovules are either produced on the edge of 
altered leaves, which some have called leaf-like carpels, as seen in 
Cycas, or, as in Zamia, they are covered by peltate scales, from the 
summit of which they are suspended. The Gymnospermal view is not , 
supported by all botanists ; some maintain that there is a true ovarian 
covering independent of the scales, and others think that the outer coat 
is of the nature of a disk. The subject is still under discussion. The 
carpellary leaves are sometimes united in such a way as to leave an 
opening at the apex of the pistil, so that the ovules are exposed or 
semi-nude, as in Mignonette. In Leontice thalictroides (blue cohosh) 
the ovary ruptures immediately after flowering, and the ovules 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. 

The ovule is attached to the placenta either directly, when it 
is called sessile, or by means of a prolongation called a funiculus 



ESSENTIAL ORGANS — THE OVULE. 



253 




Fig. 460. 



Fig. 451. 



{funis, a cord), umbilical cord, ' or podosperm (orous, a foot, and 
enti^fia, a seed). This cord sometimes becomes much elongated after 
fertilisation. The placenta is sometimes called the trophospertn (r^ifio, 
I nourish). The part by which the ovule is attached to the placenta 
or cord is its base or hilum, the opposite extremity being its apex. 
The latter is frequently turned round in such a way as to approach 
the base. The ovule is sometimes imbedded in the placenta. 

In its simplest form, as in the Mistleto, the ovule appears as a 
small cellular projection. The cells multiply until they assume a 
more or less enlarged ovate form, constituting what has been called 
the nucleus (figs. 450, 451 n), or central cellular m'ass of the ovule. 
The ovular nucleus^alters in the progress of growth so as to be prepared 
for the development of the embryo 
plant in its interior. At the apex of 
the cellular nucleus, an absorption or 
obliteration of cells takes place, by 
which a hollow cavity is formed (fig. 
451 c), which in some plants becomes 
lined by a thin layer of cells or epithe- 
lium (p. 236), whilst in others the cells 
of the nucleus alone form its walls. 
This cavity is the embryo-sac, and contains amnios or mucilaginous 
fluid, in which, after fertilisation has been completed, the embryo 
plant is formed, being attached to the apex of the sac by a thread- 
like cellular process called the suspensor. 

The nucleus (fig. 457 n) may remain naked, and alone form the 
ovule, as in the Mistleto, and a few other plants; but in most 
plants it becomes surrounded by certain coverings during its de- 
velopment. These appear first in the form of cellular rings at the 
base of the nucleus, which gradually 
spread over its surface. In some 
cases only one covering is formed, 
as in Oompositse, Oampanulacese, 
Walnut, etc. Thus, in the latter 
(fig. 452), 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. 453), leaving only 
w. opening at the apex. In other instances (fig. 454), the nucleus, n. 

Fig. 460. Ovule of the Mistleto entire. Fig. 451. Ovule of Mistleto out to show the 
embryo-sac, c, and the whole of the rest of the mass, n, compdsed of uniform tissue, and 
forming a nucleus without integuments. Fig. 452. Ovule of Juglans regia, the Wahiut. 
t. Simple integument, n. Nucleus, the base of which only is covered with integument at 
the early period of development. Fig. 453. The same ovule more advanced, in which the 
nucleus is nearly completely covered. 




Fig. 462. 



Fig. 453.1 




254 ESSENTIAL ORGANS — THE OVULE. 

besides the single covering (fig. 454, 2, ti), has another developed sub- 
sequently (fig. 454, 3, U), which gradually extends over that first 
formed, and ultimately covers it completely, except at the opening at 
the apex. There are thus two integuments to the nucleus, an outer 
and an inner, called respectively .pnOTme, te, and secundine, ti. The 
name tercine has been given to the cells of the nucleus which surround 
the embryo-sac (fig. 451 n). These names aie applied to the coverings 
of the ovule without reference to their order of development. At the 

apex of the ovule the primine 
'®' ■ ^'^ and secundine leave an open- 

ing termed the foramen or 
micropyle (//,ixghg, small, and 
•s-iiXjj, a gate). This foramen 
extends through both coats, 
the opening in the primine 
(fig. 454, 3, ex), being the exo- 
siome(£^iia, outside, and sro/j^a, 
mouth, that in the secundine 
(fig. 454, 3, ed), being the endostome (sv^oi/, within). The micro- 
pyle indicates the organic apex of the ovule, while the part united directly 
or by the funiculus to the placenta is the base or hilum. The name mi- 
cropyle is sometimes restricted to the foramen in the perfect seed. The 
length of the canal of the foramen depends on the development of the 
nucleus, as well as on 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, considering the 
ovule in reference to the embryo, speak of five coverings of the latter — 
viz. 1, primine ; 2, secundine ; 3, tercine, or the covering of the nucleus 
lining the secundine ; 4, guartine, a temporary cellular layer, which is 
occasionally formed at an after period in the form of perisperm around 
5, quintine, or the embryo-sac. By most botanists the nucleus and 
sac, with its two integuments (primine and secundine), are mentioned 
as the ordinary structure of the ovule. Occasionally, as in Mistleto, 
there are two or three embryo-sacs formed. In Veronica and Euphrasia 
the neck of the embryo-sac becomes elongated and swollen, and from 
it are developed certain cellular or filamentous appendages, which are 
probably connected with the nutrition of the embryo. 

All these parts are originally cellular. The nucleus and integu- 

Fig. 454. Ovule of Polygonum cymosum at various ages, n, Nucleus, te. The outer in- 
tegument or primine. ti, The inner integument or secundine, ex, Exostome or opening in 
the primine, ed, Endostome or opening in the secundine. 1, Ovule in the early state, when 
the nucleus is still naked. 2, Ovule in second stage, when the nucleus is covered at its 
tase hy the internal integument or secundine only. 3, Ovule in the third stage, when the 
two integuments, primine and secundine, form a double covering, at the apex of which the 
nucleus still appears. 



ESSENTIAL OEGANS — THE OVULE. 



255 



ments are united at the base of the ovule by a cellulo-vascular process 
called the chalaza (fig. 458 ch). This is often coloured, of a denser 
texture than the surrounding tissue, and is traversed by fibro- 
vasoular bundles, which come from the placenta, to nourish the ovule. 
When the ovule is so developed that the union between the primine, 
seoundine, and nucleus, with the chalaza, is at the hilum or base (next 
the placenta), and the foramen is at the opposite extremity (figs. 453, 
454), the ovule is orthotropal, m-tlwtropous, or atropous (ogdl>g, straight, 
and Tgomg, mode ; or u,, privative, and rfiTru, I turn). This is the 
position of an ovule when it first makes its appearance, and occasion- 
ally, as in Polygonacese, it remains as the permanent condition. In 
such an ovule a straight line drawn from the hilum to the foramen 
passes along the axis of the ovule. 

In general, however, changes take place in the ovule, so that it 
assumes a different form. Thus it may be curved upon itself, so that 
the foramen approaches the hilum or placenta, and ultimately is placed 
close to it, while the chalaza is only slightly removed from the hUum. 
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 
the side of the hUum opposite to that to which the foramen is' inclined. 



IC^ 






Fig. 465. 



Fig. 466. 



Such ovules are called campylotropal or campyhtropous (xa/friiXof, 
curved), when the portions on either side of the line of curvation are 
unequal (fig. 455) ; or camptotropal (xa/^vrrbg, curved), when they are 
equal (fig. 456). Curved ovules are found in Leguminosse, Cruciferse, 
and Caryophyllacese. The union between the parts of the curved 
portion usually becomes complete, but in some cases there is no union, 
and the ovules are licotropal, or horse-shoe shaped (Xsxos, a hollow disk, 
and rjoVos, mode or form). 

Pig. 465. Campylotropal or Campylotropua ovule of the Stock. 1, Ovule eutire. 2, Ovule 
cut lengthwise. /, Faniculus or umbilical cord, c, Chalaza. *, Nucleus, te, Primine or 
outer covering. (^, Secundine or inner covering, ex, Exostorae. ed, Endostome. Fig. 456. 
Carpel of Menispennum canadense, with a curved or camptotropal ovule, o. /, Funiculus. 
s. The base of the style. 



256 



ESSENTIAL ORGANS — THE OVULE. 



When, in consequence of the deyelopment on one side, the ovule is 
so changed that its apex or foramen (fig. 457, 4, n) is brought into 
close apposition with the hUum (fig. 457, 5, h), and the chalaza is also 





Fig. 458. 



carried round so as to be at the opposite extremity (fig. 457, 5, c), 
then the ovule becomes inverted, anatropal or anatropous [avar^iiroi, I 
subvert). In this case (fig. 458) the union of the chalaza, ch, with 
the nucleus, n, is removed from the hilum, and the connection between 
the chalaza and placenta is kept up by a vascular 
cord, r, passing through the funiculus, and called the 
raphe Qatpfi, a line). The raphe often forms a 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. 457, 5, /) folded along the side of the ovule, and 
becoming adherent to it completely ; 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. 

The anatropous form of ovule is of very common occurrence, and 
may probably aid in the process of fertilisation. Ovules which are at 
first orthotropous, as in Chelidonium majus (fig. 457, 2), sometimes 
become anatropous in the progress of development (fig. 457, 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, am/phitropal or heterotropal {dfi<pl, around, 'iripog, diverse). 

The position of the ovule relative' to the ovary varies. When 
there is a single ovule, and with its axis vertical, it may be attached 

Fig. 457. Ovule of Chelidonium majus at different stages of development, h, Hilura or 
umbilicus, ch, Chalaza. /, Funiculus or umhUical cord, r, Eaphe. n, Nucleus, ti, Se- 
cundine. te, Primine. ed, Endostome. ex, Exostome. 1, First stage : nucleus still naked. 
2, Second stage : nucleus covered at its base by the secundine. 3, Thii'd stage : the primine 
developed and covering the secundine at its base. 4, Fourth stage : the ovule completely 
reflected, and its point turned downwards. 6, The same cut longitudinally, to show the 
relation of its different parts. Fig. 458. Anatropous ovule of Dandelion, out vertically. 
ch, Chalaza. r. Raphe, n. Nucleus. 



ESSENTIAL ORGANS — THE OVULE. 



257 



to the placenta at the base of the ovary (basal placenta), and it is then 
erect, as in Polygonaoeae and CompositaB (fig. 459) ; or it may be 
inserted a little above the base, on a parietal placenta, with its apex 
upwards (fig. 460), and then is ascending, as in Parietaria. It may 
hang from an apicilar placenta at the summit of the ovary, its apex 
being directed downwards, and is inverted or pendulous, as in Hippuris 
vulgaris (461), or from a parietal placenta near the summit, and then 
is suspended, as in Daphne Mezereum (fig. 462), Polygalacese, and 





Fig. 459. 



Fig. 460. 





Fig. 162. 



Euphorbiaceae. Sometimes a long funiculus arises from a basal pla- 
centa, reaches the summit of the ovary, and there bending over 
suspends the ovule, as in Armeria ; at other times the hilum or 
organic base appears to be in the middle, and the ovule becomes 
horizontal, peltate (pelia, a shield), or peritropous ('rtigl, around, and 
r^intdi, I turn). AH these modifications are determined by the rela- 
tive position of the hilum and foramen, the length of the funiculus, 
and its adhesion, as well as the position of the placenta. 

When there are two ovules in the same cell, they may be either 
collateral, that is, placed side by side (fig. 463), or the one may be erect 
and the other inverted, as in some species of Spiraea and jEscuIus 
(fig. 464), or they may be placed one above another, each directed 
similarly. Such is also the case with ovaries containing a moderate 
or definite number of ovules. Thus, in the ovary of Leguminous 
plants (fig. 465), 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 attach- 

Figs. 459-462. Carpels belonging to different flowers, cut vertically to show the various 
directions of the solitary ovule, o, contained in them. /, Funiculus, r. Raphe, c, Chalaza. 
s. Base of the style. Fig. 459. Carpel of Senecio vulgaris, with a straight or erect ana- 
tropous ovule. Fig. 460. Carpel of Parietaria oticinalis (pellltory), vrith an ascending 
orthotropous ovule. Fig. 461. Carpel of Hippuris vulgaris (mare's-tail), with a reversed 
or pendulous anatropous ovule. Fig. 462. Carpel of Daphne Mezerexun, with a suspended 
anatropous ovule. 

S 



258 



FUNCTIONS OF FLORAL ENVELOPES. 



ment so constant as to afford good characters for classification. When 
the ovules are very numerous or indefinite, while at the same time the 
placenta is not much developed, their position exhibits great variation, 
some being directed upwards, others downwards, others transversely 




(fig. 466), 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 Crypto- 
gamous plants, in place of ovules there are cellular bodies called spores, 
to which allusion will be made when the seed is considered. 



4. — Functions of the Floral Envelopes. 

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 substance called chlorophyll or phytochlor. They are 
consequently concerned in the assimilation of matters fitted for the 
nutrition of the fiower, and they aid in protecting the central organs. 
The corolla does not in general produce chlorophyll, nor does it give 
off oxygen. On the contrary, it absorbs oxygen from the air. At 
the same time there is a conversion of starch into grape sugar, an 
evolution of carbonic acid gas, and in many instances a very marked 
elevation of temperature, caused by the combination between the 
carbon of the flower and the oxygen of the air. The starch, which is 
stored up in the receptacle and at the base of the petals, by passing 
into the state of dextrin and grape sugar, becomes fitted for vegetable 
nutrition. Important purposes are thus served in the economy of the 
plant. The saccharine or honey-like matter which often collects in 

Fig. 463. Carpel of Nuttallia eerasoides, with two suspended collateral ovules, o, One of 
the ovules. /, Funiculus, s. The base of the style. Fig. 464. One of the loculaments of 
the ovary of .fflsculus hybrida, laid open to show two ovules, o o, inserted at the same height, 
but turned in different directions, m m, Micropyle indicating their apex, s. Base of the 
style. Pig. 465. Carpel or legume of Ononis rotundifolia, with several campylotropous 
ovules, 0, placed one above the other. /, Funiculi, s, Base of the style. Fig. 466. Locu- 
lament of the ovary of Peganum Harmala, with numerous ovules, d, attached to a projecting 
placenta, p, and pointing in different directions, s. Base of style. 



FUNCTIONS OF FLORAL ENVELOPES. 



259 



the cup of the flower, and sometimes in special pits or depressions, as 
in Crown Imperial, and Asarabacca," attracts bees and various insects, 
which are instrumental in disseminating the pollen. 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 absorbed more oxygen than the floral enve- 
lopes ; and that the greatest absorption took place when the stamens 
and pistil were mature. 

The following are the results of some of Saussure's experiments : — 



Name. 


Duration of 
Experiment. 


Oxygen consumed— 
By Flowers entire. ^^ '""'only. °'®''"' 


Stock, single . . 2i hours. 


11 '5 times their vol. 


18" times their vol 


Do. doutle . . „ 


7-7 




)» ' J 




Polyanthes tuberosa, single ,, 
Do. do. double,, 


9- 

7.4 








Indian Cress, single . ,, 


8-5 




16-3 




Do. do. double 




7-25 




J) i 




Brugmansia arborea 
Passiflora serratifolia 




9' 

18-5 








Gourd, male flower 


10 „ 


7-6 




16- 




Do. female 


24 „ 


3-5 




)) J 




Hibiscus speciosus 
Hypericum calycinum 
Cobffia scandens . 


12 „ 
24 „ 


5-i 
7-5 
6-5 




6-3 
8-5 

7-5 




Arum italicum . 




>> J 




30- 




Typha latifolia . 
"White lily . 
Castanea vulgaris 




9-8 
9-1 




J) J 





While this oxidation is going on, carbon is given off in the form 
of carbonic acid, and heat is evolved by the combination between the 
oxygen and carbon. The quantity of carbonic acid evolved is in a 
ratio corresponding to the amount of oxygen absorbed, and the degree 
of heat present is proportionate to the activity of the chemical and 
vital changes taking place. Experiments have been made 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 torus and growing point, and the 
essential organs, attain a high degree of development, forming a spadix 
enclosed in a large spathe. No heat eould be detected when the con- 
tact 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 tha part whence the heat is chiefly evolved. Arum 
cordifolium occasionally had a temperature 20° or 30° above that of 
the surrounding air; Arum maculatum 17° to 20°; and Arum Dra- 
cunculus and other species still higher. The following observations 
were made by Brongniait on the spadix of Colocasia odora. The spathe 



260 



FUNCTIONS OP FLOEAL ENVELOPES. 



opened on the 14th of March ; the discharge of pollen commenced on 
the 16th, and continued till the 18th. The maximum temperature 
occurred at a different hour on each day. 



14tli March. 
15th „ 
16th „ 



Maximum. 

3 P.M. 

4 „ 

5 „ 



Temperature 
above the Air. 

4-6° Cent. 
10-0° „ 
10-2° „ 



17th March. 
18th „ 
19th „ 



Maximum, 
5 P.M. 

11 A.M. 

10 „ 



Temperature 
above the Air. 



11-0° 
8-2° 
2-5° 



Cent. 



Vrolik and De Vriese made a series of observations on the same 
plant, and have given the results for every half-hour of the day. The 
following are some of these results : — 



Ho 
ur. 


Temperature 


Temperature 


Hour. 


Temperature 


Temperature 




of Plant. 


of Air. 


of Plant. 


of Air. 


11-30 


20 -e- 


Cent. 


18-3° Cent. 


3 


25-0° Cent. 


15-6° Cent. 


12 


21-1 




187 „ 


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 „ 


2 


25-6 




17-2 „ 


7 


20-0 „ 


18-7 „ 


2-30 


26-5 




15-6 „ 









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 
maximum occurred at 3 p.m., and on the following day at 1, but then 
it was only 8'2° above that of the air. Decan4olle states that at Mont- 
pellier, Arum italioum attained the maximum of temperature about 5 
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 ladicans, from 0'9° to 3°. From all these experiments it 
would appear that in the Aracese and some other plants, especially at 
the period when the essential organs reach maturity, there is a pro- 
duction of heat, which increases during the performance of their 
functions, attaining a daily maximum, and ultimately declining. 

While these changes are taking place the starch is converted into 
dextrin, and ultimately into grape-sugar, which, being soluble, can be 
immediately applied to the purposes of the plant. 

Flowering takes place usually at a definite period of the plant's 
existence. The process requires a considerable amount of nutrient 
matter, and its occurrence is accompanied by a greater or less ex- 
haustion of the assimilated products. 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, 
time is allowed for accumulating sap, the stems, from being herbaceous, 
become shrubby, and sometimes, as in the Tree-Mignonette, they may 
live and flower for several years. Perennial plants, by the retardation 



PEEIODS OF FLOWERING. 261 

of flowering, are enabled to accumulate a greater amount of nutritive 
matter, and thus to withstand the exhaustion. Many cultivated 
plants which lay up a large store of nutriment in the form of 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 succu- 
lent before the expansion of the flowers, becomes dry as the process of 
flowering proceeds. The juices of plants, when required for the pur- 
pose either of food Or medicine, ought in general to be collected 
immediately before the flowering of the plant. 

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. Eichard 
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. In such cases this vigor- 
ous flowering is often followed by the death of the plant. 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 nourishment, the 
next year's produce is abundant. 

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 yotmg 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 remarks on Fruiting), and at the 
sarne time checking luxuriant branching, contributes to the hastening 
of the period of flowering. 

The period of flowering of the same plant varies at difierent 
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 vege- 
table functions. This stimulation occurs at diiferent 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 



262 



PERIODS OF FLOWERING. 



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. 

Plants are accommodated to the climate in which they grow, 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 neigh- 
bourhood. From such individuals, by propagation, gardeners are able 
to produce early-flowering varieties. 

There is a periodicity as to 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. Linnaeus 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 : — 



Ipomoea Nil . . 




3 to 4 A.M 


Tragopogon pratense 




4 to 5 „ 


Papaver nudicatile 




5 


HypochsEris maralata 




6 


Various species of Sonchus and Hieracium 




6 to 7 „ 


Lactuca sativa ...... 




7 


SpecTilaria Speculum . . . . 


7 to 8 ,, 


Calendula pluvialis ..... 


Anagallis arvensis ..... 


. 8 


Nolana prostrata 




8 to 9 „ 


Calendula arvensis 




9 


Arenaria rubra 




9 to 10 ,, 


Mesembryanthemum ncdiflorum . 




10 to 11 „ 


Omitliogalum umbellatum (Dame d'onze heures) 




11 


Various Ficoideous plants .... 




12 


SciUa pomeridiana . . . . 




2 P.M. 


Silene uoctiflora 




6 to 6 „ 


CEnothera biennis 




6 


Miiabilis Jalapa 




6 to 7 „ 


Cereus grandiflorus . . . . 

A- ^.l.^. .1 il- _;_ J3 ;_ j.T_ - 




7 to 8 „ 



Plants which expand their flowers in the evening, as some species 
of Hesperis, Pelargonium, etc., 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 



.^ 



PERIODS OF FLOWEEING. 263 

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 denominated the " poor man's weather-glass." The 
closing of many flowers in such circumstances protects the pollen from 
the injurious effects of moisture. 

The opening and closing of flowers is regulated by light and 
moisture, and also by a certain law of periodicity. A plant accustomed 
to flower in daylight at a certain time, will continue to expand its 
flowers at the wonted period, even when kept in a dark room. Decan- 
doUe 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. 

Light has been said also to have an effect on the position which 
flowers assume. Some Compositse as Hypochseris radicata and 
Apargia 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 state- 
ment has been made regarding the Sunflower, 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. The effects of light on the direction of the flowers 
has been noticed in many plants, as Narcissus and certain species of 
Melampyrum. 

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 the flowers of certain species 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 flower- 
ing. Eules as to the mode of observing periodical phenomena in 
plants have been drawn up by a committee of the British Association, 
and they have published (1.) a list of plants to be observed for the 
periods of foliation and defoliation ; (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 autumnal equinoxes, and summer solstice, 
for the hours of opening and closing their flowers. 



264 FERTILISATION OR FECUNDATION. 

5. — Functions of the Organs of Reproduction — Fertilisation or 
Fecundation. 

The stamens and pistil are called the Essential Organs of flowering 
plants, inasmuch as without them reproduction cannot be eifected. In 
plants which do not flower, this function is performed either by special 
organs, which have been termed antheridia and archegonia, or it is 
accomplished by a process of conjugation or union of cells. The stamens, 
considered as the male organs, prepare the pollen, which is discharged 
by the dehiscence of the anther. The pistil, or the female organ, is pro- 
vided with a secreting surface or stigma, to which the pollen is applied 
in order that the ovules contained in the ovary may be fertilised. 

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 which 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 cultivated ones, on the erroneous supposition that a similar 
result was produced 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 MUlington, Savilian Professor at Oxford, and by Grew. 
The opinions of these naturalists were subsequently confirmed by 
Malpighi, Kay, Morland, Geoffrey, and others. Linnaeus made these 
organs the basis of his artificial system of classification. 

Numerous proofs have been given of the functions of the stamens 
and pistUs, especially in the case of plants where these organs are in 
separate fiowers, either on the same or on different plants. Thus, a 
pistilliferous specimen of Palm (Chamserops 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 



FERTILISATION OK FECUNDATION. 265 

stamens in the very early state of the flower, before the pollen is 
perfectly formed, prevents fertilisation. Care must be taken, in all 
such experiments, that pollen is not. wafted by the wind or carried 
by insects to the pistil from other plants in the neighbourhood, and 
the result must be put to the test by the germination 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 fertilised 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. 

Some authors maintain that in the case of Hemp, Spinach, 
Lychnis dioica, Coelebogyne ilieifolia, Aberia Caffra, and some other 
plants, perfect seeds have been produced without the influence of 
pollen, but these statements have not been confirmed. Such cases 
are recorded as examples of Parthenogenesis ("ira^Sivog, maiden, ymaig, 
origin), or the production of perfect seeds without fertilisation. In 
Phanerogamous or flowering plants all experiments lead to the con- 
clusion that there are distinct sexual organs, the presence of which is 
required for the production of the embryo. 

In Cryptogamous or flowerless plants there are also organs of re- 
production, although they are not always very conspicuous. In the 
simplest form of Cryptogamic plants, reproduction and nutrition 
progress within the same cell. As we ascend in the scale of vegeta- 
tion, and the plant becomes more complex, there are cells of diiferent 
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 diiferent individuals, one Fig. 467. Fig. 468. 

representing the male and the other the female. 
One of these is the Antheridivmi (avSrighg, 
flowery, eldog, form), a cellular body, containing 
free cells, in which are enclosed Phytozoa ((purbv, 
a plant, and ^tmk, living), (Antherozoids), minute 
bodies which exhibit movements ; the other is 
the Pistillidium or Archegonium (ag;^)], begin- 
ning, and yovog, offspring), containing cells 
which, after contact with phytozoa, are able to 
germinate, and which are sometimes provided ■^'^' *'*• *'s- 47o. 
with cUia (flgs. 467-470), and then are called Zoospores (^wis; living 
and ffwoja, a seed or spore), or moving spores. The phytozoa are re- 
garded as exercising a function similar to that of the spermatozoa in 
animals, and hence they are sometimes called Spermatogoids (c'Trsma 

Figs. 407-470. Spores of different fresh-water Algffl. Fig. 467. Sporesof Conferva, with 
two vibratile cilia. Fig. 468. Spore of Chatophora, with four cilia. Fig. 469. Spore of 
Prolifera, with a circle of cilia. Fig. 470. Spore of Vaucheria, covered with cilia. 




266 



CRYPTOGAMIO EMBEYOGENY. 



seed). A cessation of their active movements has been observed co- 
incident ■with the earliest formation of the embryo. When the 
contents of the antheridia and archegonia are brought into contact, 
a cellular body is produced in the latter. This cell or germ, when 
mature, may either be discharged, or may remain in connection with 
the plant until further developed. 

Fertilisation or Fecundation in Gryptogamous or Flowerless Plants. 

In the simplest Oryptogamic plants, composed of a single rounded 
cell, as the Yeast plant, the Red-snow plant, and Palmella cruenta 
(fig. 44, p. 14), the processes of reproduction and 
nutrition cannot be separated. The same cell ap- 
pears to perform both functions. At a certain 
period of growth divisions take place in the ceU- 
contents, and by the bursting of the parent cell 
germs are discharged which are capable of produc- 
ing new individuals. As we ascend in the scale the 
plants become more complex. In place of one cell 
^ they consist of several, united together either in a 
single or branched linear series, and combined both 
end to end and laterally, so as to form cellular ex- 
pansions. In this state the nutritive and reproduc- 
tive cells are often separate and distinct, as may be 
seen in common Mould, and in Fungi generally. In 
Confervse (fig. 45, p. 14), and in Diatomaceae (fig. 
472), reproductive cells are observed with distinct 
functions. In many of them we perceive at certain 
stages of growth cells uniting by a process of conju- 
gation, the result of this imion being the pro- 
duction of a cellular embryo or spore. This conjugation is a very 
interesting process, and tends to throw light on the subject of 
reproduction throughout the whole vegetable kingdom. It is well 
seen in species of Zygnema, Spirogyra, Tyndaridea, Mougeotia, and 
Staurospermum, which are called Conjugate on this account. The 
cells in these plants have in their interior a granular endochrome, 
which appears to have difierent functions in the different cells. When 
certain cells are brought into contact, tubes are emitted which unite 
the two (fig. 471 6), the endochromes come into contact and the 
result is the formation of a spore, the mixed endochromes being 
surrounded with a proper membrane. Sometimes the contents of 

Fig. 471. Filaments of Zyguema, with conjugating cells. The tubes uniting two cells 
are seen at &, and similar tubes connect two upper cells, a and d. The contents of the cells 
intermingle, and spores or sporoid embryos, c and d, are produced. The upper cells, in 
which there is no conjugation, retain their usual contents ; while some of the lower cellS' 
have lost their contents, and spores are produced in others. 





EMBRYOGENY IN CELLULAR PLANTS. 267 

one cell, considered as the male, pass into the other in which the spore 
is produced, as in Zygnema (fig. 471), and sometimes the contents 
of both cells unite, and the spore is produced in the tube between 
them. Besides this process of conju- 
gation, by means of which a cellular 
embryo is formed, some of these plants 
have a power of merismatic or fissi- 
parous division (fig. 472), by which 
cells are separated, capable of inde- 
pendent existence. This may be 
compared to the process of budding, Kg. 472. 

and is thus distinct from fecundation. 

In many of the Confervse, however, spores appear to be produced 
without the conjugation of separate filaments. In such instances it 
is conjectured that different cells in the same filament perform different 
functions, and are so placed that at a certain period their contents by 
coming into contact develop a fertile germ. The same filament may 
thus contain both- male and female cells ; although botanists as yet 
have not been able to show the difference between them. In some 
species of Meloseira the endochrome at each end of the cell appears 
to have a different property, and mixture takes place in the cavity 
of a single frustule. In this case there is a movement towards the 
centre of the cell where the spore is formed. 

Proceeding to other divisions of Acotyledons, we find different 
kinds of reproductive organs, which can, however, only be observed 
at certain periods of development, and frequently cannot be seen after 
the embryo has been fully formed. In the same way as in flowering 
plants, when the seed has been ripened the stamens have generally 
withered and fallen off, and sometimes also the style and stigma. It 
is of importance, therefore, in all investigations into Cryptogamic 
reproduction, to examine the plants at an early period of their growth. 
The reproductive organs have received different names in the several 
orders of Cryptogams. The usual name applied to the male organs 
is antheridia, containing sperm-cells with phytozoa ; and to the female 
organs, archegonia, containing germ-cells. 

We shall now proceed to examine the reproductive organs and 
their functions in various divisions of flowerless or Cryptogamous plants. 

In the case of Fungi (the mushroom order), reproductive bodies 
called spores are produced, either naked (often stalked) or contained in 
sacs called thecce (6rixri, a box) or asci (asms, a bag). Many of the 
spores, such as those called conidia (xovig, dust), are rather of the nature 
of buds. In some fungi, as Peronospora, a conjugation of cells has been 

Fig. 472. Diatomaceous Alga (Diatcnna TnariTvwm), the cells of wMcli are increased by a 
constant process of fissiparous or merismatic division. The plant increases by abscission 
of segments. 



268 



EMBEYOGENY IN FUNGI. 



observed, and in Zyzygites megalocarpus as well as in species of 
Ehizopus (R. nigricans), the formation of a compound spore by the 
complete amalgamation of two cells has occasionally been noticed. 
This compound spore is termed a zygospore (^uyiv, a yoke). The 
bodies called ajstidia (xiidTig, a bladder), seen in Fungi, are supposed 
to represent antheridia ; while others called oogonia (dibv, an egg, and 





Fig. 473. Kg. 474. 

yovos, offspring), are reckoned as equivalent to archegonia or sporangia, 
in which, after the action of the antheridia, a fertilised spore is 
formed, which is denominated an oospore. 

In Lichens, which are Thallogens, reproductive bodies called spores 





Fig. 475. Fig. 476. Pig. 477. 

occur in thecse or asci, which are united in the form of open discs or 
apothecia {a-jrh, from, Shun, box), and in hollow conceptacles called 
perithecia ('Jti^i, around). On the thallus of lichens smaller hollow sacs, 
called spermagones (ff^rsj/ia, seed, yovog, offspring), also occur (fig. 473). 
These when cut through show bodies inside called spermaiia (fig. 
474), which some consider as representing antherozoa or sperma- 
tozoids ; they are supported on stalks called sterigmata (aTri^iy//,cx,, a 

Fig. 473. Two Spermagones on thalli of Lichens. Fig. 474. Spermagones of a Lichen 
cut through, showing outer filaments, /(hyplm), with rounded green cells, g (garddia) ; in the 
interior sterigmata and spermatia ; opening at top, o. Fig. 475. Sterigmata, a, and sper- 
matia, 6, of Cladonia flmbriata. Fig. 476. Pycnides of a parasitic Lecidia on thallus of a 
Cladonia. Fig. 477. Basidia, a ; stylospores, h ; free stylospores, c, from pycnides of same 
Lecidia, 



EMBEYOGENY IN LICHENS. 



269 



support), (fig. 475). Besides the spermagones, other externally 
similar reproductive bodies, oaWed pycnides (vumhg, crowded) (fig. 476), 
are, though less regularly, produced on the thallus, containing minute 
bodies denominated stylospores (fig. 477 i), which are either attached 
to style-like stalks (basidia), a, or are found free, c. 

The fertilisation of Lichens is still very obscure, and the functions 
of their several reproductive organs require further examination. In 
the thallus of lichens there are interlaced filaments or threads, forming 
what is called the hypha (fig. 474 /), (i/p^, weaving), in the midst of 
which are peculiar green-coloured rounded bodies, called gorddia- (fig. 
474 g) (yoKos, offspring, ilbgi, form), which appear to be concerned 
in vegetative propagation, like the zoospores of Algse. These gonidia 
have been shown in some cases, as in Parmelia parietina, to contain 
corpuscles capable of development into zoospores. 

In the division of Thallogens called Algse, embracing Cryptogams, 
■which inhabit salt and fresh water, there are more evident organs 
of fecundation. We have already noticed these in the case of the 
conjugation of confervse (fig. 471), when two cells being difierent, the^ 
contents unite to form a spore or germinating body. This process 
is seen also in Diatoms and Desmidiese. In the minute Closterium 
Lunula there is a fissiparous division of the plant, and the contents of 
the two ruptured cells unite to form a rounded body, containing a 
spore. Besides the process of conjugation, there are also other modes 
of reproduction in Algse ; the same plant is seen forming cells which 
separate as independent plants, and also antheridia and archegonia 
which give rise to spores. In Vaucheria there 
is a multiplication by zoospores or moving cells, 
which are discharged from the extremity of a fila- 
ment (fig. 478 a and h). This zoospore (fig. 478 
6) is a vegetative reproductive body, independent of 
fertilisation. The plant also produces a recurved 
horn-like organ, which performs the part of an an- 
theridium, and a slightly recurved organ close beside 
it, which represents the sporangium, from which 
a beak-like process is turned in the direction of the 
antheridium. These two organs are then in direct 
communication by their bases with the tube of the 
Vaucheria, but they are afterwards separated from 
it, each forming a septum. Spermatozoids, contained in the an- 
theridium, afterwards penetrate the beak-like process of the spo- 

Fig. 478 a. Clavatecellularfilamentof^Alga(rawcAerm(M;oidea). The terminal portion 
becomes .separated from the rest by a partition. In this portion the single spore, s, is de- 
veloped, which is discharged through an opening, as seen in the figure. The spore has cilia, 
by means of which it moves about for some time in water after being separated from the 
parent cell. The lower part of the filament contains green endoohrome. The spore is of a 
very dark gre'en colour. 2), Zoospore of an Alga {Vaucheria), surrounded by moving cilia. 




Fig. 478. h. 



270 EMBRYOGENY IN ALG^. 

rangium, and thus fertilisation is effected, and the true spore is formed 
in the interior. 

In Vaucheria there are thus three reproductive organs : — 

1. Zoospores, which are vegetative or bud-like reproductive organs (moving spores). 

2. Antheridia, with sperm-cells containing fusiform corpuscles, which move hy 

means of two cilia. 

3. Sporangia, with germ-oells, which are fertilised by the ciliated corpuscles- and 

form resting spores, whence the new plants arise. 

Pringsheim has examined the reproduction in two minute Algae, 
(Edogonium and Bulbochaete. The greater part of the cells of (Edo- 
gonium contain each a zoospore (fig. 479, 1, a), provided anteriorly 
with a complete crown of cilia. This body (zoospore) is produced 
without sexual intercourse ; it germinates and gives rise to a new 
plant in the same way as a bud does. Between the common cells 
of the cellular plants occur other utricles, usually more swollen, 
(fig. 479, 1, 2, b 6), either isolated or in groups. In these are formed 
motionless spores (or resting spores), which are the female sexual 
organs. In the individuals which produce these female cells, as well 
as in others which have no such cells, there occurs a third kind of 
cell, shorter than the common cell of the plant, and forming often 
irregular groups. The third kind gives birth to spermatozoids, either 
at once or after the appearance of an intermediate production of a 
special nature, which becomes detached from the primordial filament, 
and contains the male sexual apparatus. In CEdogonium ciliatum, a 
small species, found attached to the leaves of aquatic mosses, the cells 
containing the male organs are formed towards the anterior extremity 
of the filament, between the setiform terminal cells (fig. 479, 1, 2, d) 
and the upper female organ. In each of these cellules there is formed, 
at the expense of the contained plastic materials, a single small 
zoospore called microgonidium (/i,ix^bg, small). This, according to 
Pringsheim, is the antecedent or generator of the male organs. These 
male organs have been called androspores (avjjj, male). These andro- 
spores, furnished with a circle of cilia at their anterior and transparent 
part, after quitting their mother-cells, move about at first, and then 
become fixed (in a determinate manner in each species) either to the 
female organ itself or in its neighbourhood. Pringsheim has seen in 
(Edogonium ciliatum several androspores fix themselves on the surface 
of the female organ (fig. 479, 1, 2, c c c). The latter organ continues 
to be developed, while each androspore becomes a sort of compound 
cellular plant. In one part of this the spermatozoids are formed, and 
hence it is called the antheridium. The fixed androspore acts like a 
mother-ceU. The antheridium, properly so called, represents the 
secondary utricle produced at the upper part of the androspore, and 
the stalk of the antheridium is formed by the secondary inferior 
utricle. The antheridium bears at its summit a small lid, formed 



EMBEYOGENT IN ALG^. 



271 



from the upper part of the membrane of the androspore. This 
antheridium, at first unicellular, divides into two cells, which become 
the mother-cells of the spermatozoids. The whole plastic contents of 
each mother-cell are employed in the formation of a single spermato- 
zoid of considerable size. When the spermatozoids are mature then 
the upper spermatozoid raises slightly the lid of the antheridium 
(fig. 479, 1, 2, c). In the meantime the female organ is going 
through a pf ocess of development. When its contents are mature, the 
membrane of the female organ is ruptured all at once a little below 
its summit, the upper part forming a sort of lid, and the filaments 
which surmount it are turned to the side by the swelling of the plastic 
contents (fig. 479, 1, 2, d). 
There is thus a space on one | ^ 
side between the lid and the 
lower part of the female organ. 
Then the mucous colourless por- 
tion of the endochrome protrudes 
from the aperture, and its colour- 
less cellular membrane presents 
a distinct lateral opening turned 
towards the antheridium. When 
the female organ has undergone 
these further changes in its con- 
tents, the lid of the antheridium 
is completely detached, and 
allows the upper cuneiform 
ciliated spermatozoid to escape. 
This spermatozoid, after mov- 
ing around the female organ 
for some time, enters the open- 
ing. The spermatozoid reaches 
the female globule, which is 
then fertilised, and seems to 
be absorbed in its substance. 




Fig. 479. 



After this the female globular body becomes more and more definite, 
and finally is surrounded by a double membrane. 

In the cells of another Alga, called Sphseroplea annulina (fig. 480 
a 6), there are produced stellate spores, very like the reproductive 
bodies of Volvox stellatus. In spring' the contents of these spores 
divide into two, then into four or eight parts, which become zoospores. 

Fig. 479, 1. Entire plant of (Edogonivm dliatwrn. a, Ordinaiy cells containing zoospores, 
which ultimately escape and form new plants. 6, Sporangium, containing spores, c, 
Androspore fixed on the sporangium, bearing at its summit an antheridium with a lid. d, 
Setiform prolongation of the plant. Fig. 479,S2. Sporangium, with spores. S, Magnified, 
c, Androspores bearing antheridium, with the lid at the top. d, Filament bending to the 
side, so as to expose an opening into the spore-case, by which the spermatozoids enter. 



272 



EMBEYOGENY IN ALG^. 



These zoospores swim about, and then fix themselves, giving rise to 
yonng Confervse. This is a first asexual generation. The young 
Conferva is a sort of prothallium, for it bears certain sexual organs. 
One kind of organ presents itself in the form of cells covered by a 
membrane, pierced with a certain number of apertures, and having 
contents which become converted into spores. These are the arche- 
gonia (fig. 480 6). A second kind has a membrane also pierced with 
several apertures, and contains small mobile baculiform (rod-shaped) 
bodies. These are the antheridia, with their spermatozoids (fig. 480 a). 
The spermatozoids come out from the cells, and enter the openings in 
the spore-bearing cells, and thus fertilise the spores. 

Saprolegnieae, including the genera Achlya, Saprolegnia, and Py- 
thium, are cellular plants which grow on dead and living animals. 
The name is derived from ffatrgss, putrid, and Xeyvov, a coloured border. 
The bodies of flies thrown into water often 
become covered with these minute thread- 
like organisms. Gold fish in tanks have 
their gills sometimes covered with Achlya 
prolifera. They resemble in appearance 
the mucors or moulds, and some have 
placed them amongst the Fungi. They 
seem, however, to be more nearly allied 
to filamentous Algse, such as Vaucheria. 
At the end of the filaments a cell is 
formed, which becomes separated from the 
rest of the filament by a septum. Zoo- 
spores (fig. 481 a a) are developed, which 
escape by the bursting of the cell. The 
filaments of Saprolegniese also produce 
lateral branches, at the ends of which are 
swellings, which are divided from the rest 
of the tissue. In them sacs called oosporangia are formed (fig. 481 5). 
These are fertilised by the union of cells containing spermatozoids, in the 
same way as Vaucheria, and oogones {dih, an egg) are formed. Thus 
there are two modes of reproduction — one by asexual zoospores (fig. 481 
a b), and the other by sexual antheridia and oosporangia (fig. 481 c d). 
In the red sea-weeds, called Rhodospermeae or Ploridese, fecunda- 
tion is effected by antheridia, containing motionless corpuscles, and a 
peculiar hair-like body called trichogynium (^g/^, hair, yuv>i, female). 
At the base of this latter organ there is a cell which, after 
fertilisation, is transformed into the cystocarp (xvsrig, a bladder 

Fig. 480 a &, Sphasroplea (mnvXi/na. Male filament, a, consisting of cells with vacuoles, 
and with spermatozoids which are passing out ot the cells by openings in the walls. Female 
filament, &, formed by cells containing spores, which are being fertilised by the spermato- 
zoids, which enter the cells by openings in the walls, and come in contact with the cellular 
spores. 




Fig. 480. 



EMBETOGENT IN ALG^E. 273 

and xcx.g'jrog, fruit), which is sometimes supported on a cellular body- 
called trichophore {6§i^, t-j'%05, hair, 
pojEw, I bear). In some cases, as in 
Nemalion, the fertilisation is direct, 
the influence of the antheridian cor- 
puscle being at once conveyed by 
the trichogynium to the rudiment- 
ary cell of the cystocarp. In other 
cases, as in Dudresnaya, the action 
is less direct — the influence of the 
antheridian corpuscles being con- 
veyed by connecting tubes which 
pass laterally from the base of the 
trichogynium to numerous fructi- 
ferous filaments, on which the 
cystocarps are iinally developed. 

In Floridese there are also bodies 
called tetraspores (^rer^dg, four), on 
account of their being divided into 
four spore-like organs. These are contained in a distinct sac (fig. 
482). They are probably concerned in vegetative and not in sexual 
reproduction. In the brown seaweeds (Fucacese) there are concep- 




6 
Fig. 481. 







Fig. 482. 



Pig. 483. 



Fig. 484 a. Fig. 484 6. Fig. 485. 



tacles (fig. 483) containing antheridia (%. 484, a and 6) and archegonia 
(^g. 485), either separate or combined, the plants thus \}emg monoecious 
or dioecious. 



Fig. 481. Saprolegnia sliowing organs of reproduction, act, Filaments containing aaeXual 
zoospores, some of which are being emitted from the end of the cell. 1), Stalked sporangium 
(oosporangium) ending in a rounded cell c, containing in its interior cells called oogones 
ready to be fertilised, d, Antheridium coming into contact with the female cell, and sending 
tubes to the oogonia so as to fecundate them. Fig. 4S2. Tetraspore, i, of one of the rose- 
coloured Seaweeds (Callithamnion cruciatim). It is a sac formed by the metamorphosis of 
the lowermost pinnule of the frond, and contains four germinating spores. Fig. 483. Cell 
of a conceptacle of Fucus containing spores and abortive filamenfe. Tlie spores Escape at 
the opening, o; other conceptacles contain antheridia. Fig, 484. Antheridia of a Sea- 
weed (Fucms serratits), a, Antheridium, containing sperm atozoids, 6, Antheridium with two 
spermatozoids havtag vibratile cilia attached. Fig. 485. Archegonium (sporangium) of a 
seaweed containiag pear-shaped spores which germinate. 

T 



274 



EMBEYOGENY IN HEPATIC^. 



In Oharacese, which, are aquatic cryptogamic plants found in 
ponds, there are two fertilising organs, one called, from its rounded 
form, the globule (fig. 486 g), corresponding to the antheridium ; and 
another (fig. 486 m), the nucule (nucula, a small 
nut), representing the archegonium. The globule 
contains a definite number of cells, which meet in 
the centre and form a round mass, whence jointed 
filaments containing spermatozoids arise (fig. 487). 
The colour of the globule is red. The nucule is 
a large oval cell (archegonium), round which five 





Fig. 486. Kg. 487. 

filaments are spirally twisted, ending at the summit in five or ten 
tooth-like processes. The central oval cell in the nucule is fer- 
tilised by sperma.tozoids from the jointed filaments of the globule 
coming into contact with it. After fertilisation the nucule drops 
off and ultimately forms a new plant. While the nucule may be 
considered as equivalent to the archegonium, it is in reality a com- 
bination of that organ and a spore. 

In Hepaticse (Liverworts), including Marchantise and Jungerman- 
nise, the reproductive organs consist of antheridia and archegonia. 
The antheridia are small cellular sacs of a globular, ovoid, or flask- 
like form. They have a single or double cellular covering, enclosing 
viscid matter, in which are developed four-sided cells, in each of 
which is a small filiform spermatozoid (phytozoon), rolled up in a 
circular manner, and displaying rapid movements. The spermatozoids 
are finally liberated, and unrol themselves, appearing as filaments 
swollen at one extremity, and gradually tapering to the other. In 
Marchantia (fig. 488) the antheridia occur in the upper side of an 
elevated disk or receptacle, r. When this disk is cut vertically, as in 
fig. 489, they are seen at a a, as flask-like cellular sacs separated by 
air-cavities, cc, which communicate with stomata, ss.i In fig. 490 
an antheridium is shown discharging its minute cells containing sperma- 
tozoids. In some Hepaticae the antheridia occur in the substance of 
the thallus, while in others (as in some Jungermannise) they 
appear in the axil of the leaves. 

Mg, 486. CeUular tubes of Chara, with vertioiilate branches, from the axil of -which 
proceeds the 'nucule, n, containing a germinating spore, while below the branch is placed 
the red globule, g, containing antheridian cells and spermatozoids. Fig. 487. Filament 
from the globule of Chara, consisting of numerous sperm-cells (phytozoary cells). A sper- 
matozoid, s, is seen escaping from one of them. 



EMBEYOGENT IN HEPATIC^. 



275 



The archegonia of Hepaticse are either situated in the substance 
of the thallus, as in Eiccia and Anthoceros, or they are raised upon 




Pig. 488. 



stalks, as in Marchantia (fig. 491) and Jungermannise. In Mar- 
chantia these stalks bear radiated receptacles, r, on the under surface 
of which the sporangia are placed, which are peculiar bottle-shaped 
bodies (fig^ 492) containing germ-cells. 

The spermatozoids enter the archegonia, and thus a cell is fertilised, 
from which the sporangium or spore-capsule, a distinct body, is pro- 
duced (fig. 491 s), constituting the second generation. In Junger- 
mannia bicuspidata (fig. 493) there is represented at a an arche- 
gonium containing an unimpregnated germ-cell, and at 5 an arche- 
gonium containing an impregnated germ-cell, which is the rudiment- 
ary spore-capsule. The germ-cell, after fertilisation, shows two 
nucleated cells, c, and from it, as a second generation, the fruit- 
Fig. 488. A species of Liverwort (JlfarcAaw(m poZywiorpfea), with its green thaUus, t, bearing 
a cup-like body, g, in which minute cells or free buds (sporules of some) are seeli, and a 
stalked receptacle, s r. In the substance of the disk -like receptacle, r, cells are produced con- 
taining spermatozoids. These are considered antheridia. Fig. 489. Vertical section of the 
disk-like receptacle of Liverwort (Ma/roha/ntia), showing the antheridia, a a, in its substance. 
These antheridia are flask-shaped sacs containing phytozoary cells. They communicate 
with the upper surface, and their contents are discharged through It. Between the anther- 
idia there are air cavities, e c, connected with stomata, s s. 



276 



EMBRYOGENY IN MOSSES AND LIVERWOETS. 



bearing stalk is produced. Around the orifice of the canal leading to 
the germ-cell and rudimentary spore-capsule are seen numerous sper- 
matozoids, s s, which have been discharged from the antheridia. 





Fig. 490. 



Fig. 491. 



Fig. 492. 



In Mosses there is a free germ-cell (embryonal cell) at the base of 
the archegonium. Spermatozoids, from the sperm-cells of the anthe- 
ridium (fig. 494), reach it, and then it is developed into the sporangium 
or spore-case (fig. 495), which is the second generation of the plant. 
The spores produce the leafy plant, bearing antheridia and archegonia. 
In fig. 496 is shown the conferyoid prothallium, p, of a Moss pro- 
duced from the spore, and bearing buds, a b, which produce leafy 
individuals with organs of reproduction. After the contact of these 
organs, a single ceU of the archegonium is developed into the com- 
plete fruit (theca or sporangium), which is often borne upon a stalk 
(fig. 495). The complete fruit contains spores, which, when 
discharged, again develop the foliaceous plant. 

In leafy Mosses and in Jungermanniae there is also an increase 
by buds. The confervoid filament produced by the spore gives origin 
to a number of buds (fig. 496), whence leafy stems proceed, and 

Fig. 490. Antheridiiun of Liverwort {Mcvrcliantia) discharging its sperm-cells, that is, 
cells containing spermatozoids. Fig. 491. Thallus of Liverwort (Ma/rchantia polyvwrpha), 
bearing a stallced fruit, a, which is the product of the impregnated cell of the archegonium. 
The receptacle at the apex of the stalk bears on its under surface sporangia containing 
spores and elaters. The spores, when germinating, produce a thallus, on which antheridia 
and archegonia are formed. Fig. 492. Pistillidium or archegonium of Liverwort (Ma/r~ 
clioMtia), containing in its interior a cell, which is impregnated by the spermatozoids of the 
antheridium. 



EMBRYOGENY IN MOSSES AND LIVERWORTS. 



277 



these leafy stems also produce buds or gemmse, called innovations. 
There is thus a multiplication by sexual reproduction and by gem- 
mation, as in higher plants. 




Kg. 497. 



Fig. 496. 



Fig. 495. 



Fig. 493. Archegonia of Jiingermaimia bicuspidata. a, Unimpregnated archegonium, 
witli a tube leading to a cavity, near tlie base of wMeb is a cell. 6, Ajchegonium after 
impregnation, with the cell divided into two nucleated portions. This double nucleated 
body is the rudiment of the fruit-bearing stalk. At the apex of the canal leading to the cell 
are seen spermatozoids, s s. Fig. 494. The male organs of a Moss (PolytricTivm). a, 
Antheridium containing sperm-cells, two of which are seen at c. These spfirm-cells contain 
spermatozoids, which are discharged so as to impregnate the archegonium. Surrounding 
the antheridium there are filaments or paraphyses, p. Fig. 495. Sporangium of a Moss 
{Polytriclmm), supported on a stalk. This stalked sporangium ik produced by the impreg- 
nated cell of the archegonium. It constitutes the second generation. Fig. 496. Con- 
fervoid filament forming the prothallium, p (exothallium), of a Moss {Fwrnria hygrometHm), 
consisting of a congeries of cells arranged in a filiform manner. This prothallium originates 
from the spore, and bears a bud, a, and a young stem, h, from the base of which roots 
proceed. Fig. 497. End of fructiferous branch of Lyoopodium clavatnm, common Club- 
moss. The leafy branch, I, ends in a stalk bearing two spikes of fructification, /. 



278 



EMBETOGENY IN LTCOPODIACaE. 



Lycopodiacese, Club Mosses (fig. 497), have sporangia which are 
either all alike as in Lycopodium, or of two forms as in SelagineUa. 
The dimorphic sporangia consist of micro-sporangia (fig. 498), 
(/i/x^o's, small), containing numerous granules (microspores or antke- 
ridia), (fig. 499), and macrosporangia (fig. 500), (/iaxgog, long), 
called by some megasporangia (//^eyag, great), or oophoridia (aihv, 
an egg, pog'eia, I bear), of a large size containing often four macro- 
spores or megaspores, in the interior of which a cellular prothallus 
is formed (fig. 501, p), on which archegonia are developed (fig. 




Fig. 502. 



Fig. 503. 



502 a). In the microspores of Isoetes and Lycopodium there is a 
sort of male prothallium bearing antheridia with spermatozoids. No 
germination has been observed in the microspores of the genus Lyco- 
podium. The process of impregnation in Lycopodiacese is supposed 

Fig. 498. Antheridium of a Club-Moss (Lycopodivm), containing microspores, whicii are 
cells containing spermatozoidal cellules, as seen in fig. 499. Fig, 499. Small spore (pollinic 
spore) of a Lycopod {Selagmdla helvetica), bursting and discharging cellules, c, containing 
spermatozoids. Fig. 500. Oophoridium or macro-sporangium of a Club-Moss (Lycopodivm), 
opening and showing four large spores in its interior. These macrospores or megaspores 
contain a cellular prothallium or endothallium in their interior, bearing archegonia. 
Fig. 501. Macrospore discharged from the oophoridium of a Lycopod (SelagiTiella MerteTisii), 
with the outer coat removed to show the young cellular prothallium, p, at the upper end. 
Fig. 502. Vertical section of the prothallium and upper half of a large spore of a Lycopod 
(SrlajjineUa dentvadatd). There are several archegonia, and in one of them, at a, there is a 
central free cell, whence the leafy frond ultimately proceeds. Fig. 603. Vertical section 
of a small portion of the prothalliiun and upper part of the large spore of a Lycopod (Sda- 
ginella dentieidata), showing the embryo, e, developed from a central cell of one of the 
archegonia, a, carried down by the growth of the suspensor, so as to be imbedded in the 
cellular tissue at the upper part of the spore. 



EMBEYOGENT IN MAESILEACB^ AND FEKNS. 279 

to take place by the spermatozoids of the small spores coming into 
contact with the large spore after the coat of the large spore has 
burst at its apex, so as to expose the Cellular prothallium and its 
archegonia (fig. 502 a). The free central cell of the archegonium 
then enlarges, divides, and elongates into a filament, which grows 
down into the prothallium (fig. ' 503). A suspensor is thus 
formed, at the end of which is the embryo, e, imbedded in the 
cellular tissue at the upper part of the large spore. The embryo 
finally produces its radicle and its bud, which is developed as the 
leafy frond. ' 

In Ehizocarps (MarsUeacese) there are also antheridia and arche- 
gonia. The former are sacs containing small spores, which produce 
inside a small prothallium, on which are borne antheridia contaiaing 
spermatozoids. The latter are sporangia containing large spores 






Fig. 504. Fig. 506. Pig. 506. 

which produce a prothallium like that of Lycopods, on which 
archegonia appear. The prothallium usually produces only one 
central archegonium, the spermatozoids get access to the arche- 
gonia, and thus the young plant is produced. 

In Ferns there is a prothallus bearing antheridia and archegonia 
at the same epoch. It is produced by the spore during its gfermination, 
and consists of cells, as shown in fig. 507. The antheridia occur 
on the under surface of the prothallus, and they consist of a cellular 
papilla having a central cavity (fig. 508). This cavity contains free 
cellules, which are discharged by a rupture at the apex, b, and each 
of these little cellules, in bursting, gives exit to a ciliated spiral 
filament (spermatozoid), (fig. 509), which swims actively in water, 
advancing with a rotatory motion through the water when seen under 
the microscope. The archegonia (fig. 510) exist on the under side of 
the prothallus, near the notch of the border. They are less numerous 
than the antheridia (varyiiig from three to eight), and consist of 
cellular papiUee formed by ten or twelve cells. They are larger than 

Fig. 504. The small spore of a Ehizocarp (Pil/idaria gloiulifera, PiUwort). The inner 
coat is protruded, and the outer coat has hurst, so as to discharge cellules containing sper- 
matozoids. Some of the spermatozoids are separate, and are seen coiled up in a spiral form. 
Pig. 505. Large spore of a Rhizocarp {Ma/rsilea, Fepperwiyrt), which contains a cellular pro- 
thallium hearing archegonia. The mammillary projection is the point whence the gem- 
mation of the emhryo proceeds after impregnation. Fig. 606. Vertical section of prothal- 
lium of a Bhizocarp {Pilularia gldbvMfe/ra), containing a central archegonium, a, hefore 
impregnation. 



280 



EMBEYOGENY IN FEENS. 



the antheridia, and have a central canal, a, leading down to a large 
globular cell, c, imbedded in the substance of the prothallus, and 
containing the embryo-germ, e. The canal is closed at first, and then 
opens. The spermatozoids enter the archegonial canal and fertilise 
the germ-cell. After a time this cell divides and gives rise to the 






Fig. 507. 



Pig. 508. 



Kg. 609. 





Fig. 510. Pig. 511. 

embryonic body, whence the stem of the Pern arises (fig. 511 /). 
The life of the sporangiferous plant is indefinite, as seen in Tree 
Ferns, while the prothallus is of very short duration. Thus in 
Ferns the spores contained in the sporangium form the prothallus 
without impregnation, while this latter process is necessary for the 
development of the germ, which gives rise to the leafy sporangiferous 

Fig. 507. Cellular prothallium (exothallluin) of a Pern {Pteris hyngifolia), produced by a 
spore, s, and giving off a root, t, at one end. It consists of numerous cells, and it giyes 
origin to antheridia, and pistillidia or archegonia. Pig. 508. Antheridia from the prothal- 
lixun of the Common Bralce [Pteris aguUvna). a, An unopened antheridium ; 6, antheridium 
bursting at the apex, and discharging free cellules, each containing a spermatozoid : c, 
antheridium after the discharge of the cellules. Fig. 509. A spermatozoid with cilia, 
discharged from a cellule in the antheridium of the Forked Spleenwort [Asplenium s&pteti- 
trioncde). Fig. 510. Archegonium of the Forked Spleenwort (Aspkmwm sept&ntrumaU) 
immediately after impregnation. a, Canal leading to the ovule or large cell, u, at the 
base of the archegonium ; e, nucleated embryonic cell, whence the sporangiferous frond 
proceeds. Spermatozoids from the antheridium reach the canal of the archegonium, and 
impregnate the ovule. Fig. 511. Touhg plant of a Fern {Pteri£ paiUacea), showing the 
commencement of the sporangiferous frond, /, arising from the impregnated ovule in the 
archegonium ; the prothallium, j>, being still attached. 



EMBEYOGENY IN EQUISETACE^ AND EEENS. 281 

frond ; while in Mosses the spore forms the prothallus and the leafy 
stem without impregnation, and this operation gives rise to the 
formation of the stalked theca. 

The reproduction of Equisetacese (fig. 512), Horsetails, resembles 
much that of ferns. Their spores, which are surrounded 
by hygrometric filaments, caUed elaters, germinate 
and form a lobed prothallus bearing antheridia at the 
top of its lobes and archegonia at its base. The an-- 
theridia appear as ovoid swellings containing at first 
globules, which ultimately are developed as spermatozoi4s 
(antherozoids).' The archegonia consist of globular 
bodies, terminated by a long neCk with a four-lobed 
opening at the top. The spermatozoids enter by the 
opening and fertilise a cell in the archegonium, which 
ultimately constitutes the germ of the new plant. 

Ferns, Ophioglossacese and Equisetacese, are called 
isosporecB (/tfos, equal), because they produce a single 
kind of spore, which in its turn gives origin to a pro- 
thallus furnished with chlorophyll and roots, and capable 
of independent existence. On the same prothallus, or 
on two neighbouring ones, antheridia first of all origin- 
ate, and when mature emit spermatozoids, then follow 
archegonia generally formed of a central cell, to which 
access is gained by a canal opening outwards. Fecun- 
dation being effected by the entrance of spermatozoids 
into the archegonium, the first period is closed, and then 
commences the asexual generation. The embryo is 
developed at first in the substance of the prothallus, but 
afterwards becomes disengaged from it, and passes 
through the different phases of its development. 
Finally, the second generation terminates its evolution ^' ^^^' 
by the development of the organs of multiplication as spores, which 
always originate from a normal or modified leaf. 

Fertilisation or Fecundation in Phanerogamous or Flowering Plants. 

In flowering plants the organs of reproduction are stamens and- 
pistils, the former representing the male element, and the latter the 
female. The cellular pollen (sperm-cells) produced by the former 
must be applied to the cells contained in the latter (germ-ceUs), in 
order that the embryo plant may be formed in the seed. 

Fig. 512. Fructiflcation of Equisetum maxmnim. Great Water Horsetail, showing the 
stalk surrounded Ijy membraoiouB sheaths, ss, which are fringed by numerous processes or 
teeth. The fructification, /, at the extremity, is in the form of a cone bearing polygonal 
scales, under which are spore-cases containing spores "with clavate filaments. 



282 FERTILISATION IN FLOWERING PLANTS. 

In flowering plants various provisions are made for insuring the 
application of the pollen to the stigma. The saccharine secretions of 
the flower, 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 
poUen. The number of pollen-grains produced is also very great. In 
a floret of wheat Wilson reckoned about 7000 pollen-grains. Hassall 
says that a single head of Dandelion produces upwards of 240,000, 
each stamen of a Pseony 21,000, a Bulrush 144 grains by weight. 
It has been stated that a single plant of Wistaria sinensis produced 
5,750,000 stamens, and these, if perfect, would have contained 
27,000,000,000 pollen-grains.* In a single flower of Maxillaria F. 
Miiller estimated the poUen-grains at 34,000,000. This same flower 
produces 1,756,000 seeds. In Orchis mascula the poUen-grains in a 
single flower have been estimated at 120,000. In the case of Ever- 
greens, such as Firs, the quantity of pollen is enormous, apparently 
to insure its application notwithstanding the presence of leaves. The 
poUen from pine forests has been wafted by the winds to a great 
distance, and sometimes falls on the ground like a shower of sulphur. 
It is thus that some kinds of coloured rain, occasionally witnessed, 
may be accounted for. The pollen powder transmitted to considerable 
distances remains floating in the air till carried down by a passing 
shower. 

The quantity of pollen required for impregnation varies. Koel- 
reuter says, that from fifty to si:^y grains of the pollen of Hibiscus 
Trionum are required to fecundate the fruit completely, containing 
about thirty ovules. The ovary of Mcotiana, Datura, Lychnis, and 
Dianthus, according to Gsertner, may be completely fertilised 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 fertilise from eighty to one hundred and thirty ovules contained in 
the ovaries. 

In many trees in which the organs of reproduction are in separate 
flowers (as in Hazel and Willow), the leaves are not produced until 
fertilisation has been effected. The protection of the pollen from the 
direct influence of moisture is efiected by the closing of the flowers, 
by the elasticity of the anther-coat only coming into play in dry 

* The following estimate was made of the amount of flowers, stamens, etc., in a single 
specimen of Wistaria sinensis ; — 

Number of clusters of Flowers 9,000 

individual Flowers 676,000 

Petals 3,375,000 

Stamens 6,750,000 

Ovules 4,050,000 

For the purpose of fertUising these ovules, the anthers, it perfect, would have contained 

about 27,000,000,000 poUen-grains, or about 7000 grains to each ovule. 




FERTILISATION IN FLOWERING PLANTS. 283 

weather ; and in aquatics, either by a peculiar covering and structure 

as in Zostera, or by the flowers being developed above water, as in 

Kymphsea, Lobelia, Stratiotes, and Hottonia. In Vallisneria spiralis 

(fig. 613), a plant growing in ditches in the south of Europe, the stami- 

niferous flowers are detached from the 

male plant, float on the surface of the 

water, and scatter their pollen ; while 

the pistilliferous plant, b, sends up a 

long peduncle, 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 fertilisation is efiected. 

Lagaxosiphon muscoides, an aquatic 

plant from Africa, shows similar phe- "^ Pig s^, 

nomena in regard to impregnation 

as are seen in Vallisneria. 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 

Ukely to extend to all. Stamens are protected in various ways from 
wind and moisture. In Iris by the petaloid divisions of the style, 
in Phyteuma by the upper united part of the corolla, in TroUius by 
the sepals turned inwards, so as to form a ball (hence the name globe- 
flower), and in Arum by the spathe (flg. 260, p. 178). In many 
flowers the perianth gives shelter to the stamens. In Orchids the 
pollen is well protected. 

In some plants the Stamens, at a certain period of their develop- 
ment, move towards the pistil, before the contents of the anther are 
discharged. In Parnassia palustris (fig. 514) and Rue they do so in 
succession. In Kalmia the anthers are contained in little sacs or 
pouches of the corolla, until the poUen 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 Parie- 
taria oflScinalis, and in the Nettle, the spiral filament is kept in a 
folded state until the perianth expands, and then it rises with elastic 
force and scatters the pollen. Similar phenomena are observed in the 
Comus 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 pistU. The anther opens by recurved 

Fig. 513. Male and female plants of Vallisneria spiralis, a, The male plant, the 
flowers of which are detached, and rise to the surface of the water so as to mature 
its pollen and scatter it ; 6, the female plant, which remains fixed in the mud, and sends up 
a spiral peduncle, which uncoils according to the depth of the water, and hears the pistil- 
liferous flowers above the water, so as to allow the pollen to be wafted upon them. 



284 FEETILISATION IN FLOWERING PLANTS. 

valves, which are covered with pollen-grains. 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 fertilisation. 
In some plants the pollen is scattered by the wind, and they are 
called anemophilous (avif/jo;, wind, and p/Xos, love) ; whUe in other cases 
animals are the agents employed in its distribution, and the plants 
are called zoophilous (^<io\i, animal). It has been ascertained that 
self-fertUisation is by no means common in flowers, that Is to say, the 
pollen is not always applied to the pistil of the flower in which it is 
produced. We constantly find that pollen produced by the anther of 
one flower is applied by the medium of wind or insects to the pistil 
of another flower on the same plant, or on difierent plants. This is 
seen very evidently in monoecious and dioecious plants. It also occurs 
in dimorphic plants where there is a difierence in the development of 
the stamens and pistil in the case of individual flowers ; as is well 
seen in some species of Primula, and of Linum. Flowers visited 
by insects are often highly coloured and odoriferous, and secrete 
honey-like matter. Night-flowering and night-smelling plants attract 
crepuscular insects. These may be illustrated by Pelargonium triste, 
Hesperis tristis, and Nyctanthus Arbor-tristis. Stapelias (carrion 
flowers) by the fetid odour of their flowers attract blow-flies, which 
deposit their eggs amongst the hairs of the flower. The eggs in due 
time are hatched, and then the maggots in search of food press the poUen 
masses downwards to the stigma and so cause fertilisation. In Oxalis 
Acetosella the flower is erect during the day, and is open to the visits 
of insects; it describes an arc of more than 100 degrees when the 
sun sets, and flnaUy has its opening directed to the ground. 

The poUen in the case of plants fertilised by insects is sometimes 
elliptical with three or more longitudinal furrows, as in Ranunculus 
Ficaria, Aucuba japonica, and Bryonia dioica ; at other times it is 
spherical or elliptical, and covered with projecting processes (echinate), 
as in many Oompositse, Malvacese, and Cucurbitacese; or, thirdly, the 
pollen grains are attached together by threads or a viscid secretion, 
as in Eichardia Rhododendron and (Enothera. In plants fertilised by 
the wind, as in most grasses, Hazel and Populus balsamifera, the 
pollen is almost perfectly spherical, and has no processes, and is 
generally light and dry. Dr. Dyer remarks that while in Cmciferae 
fertilisation is generally effected by insects, in Pringlea antiscorbutica 
(Kerguelen Island Cabbage), which differs from the plants of the order 
in having no petals, no honey glands, an exserted style and papillose 
stigma, fertilisation is effected by the wind. It has been stated by some 
authors that in the case of the cereal grains impregnation is effected 
before the flowers are open, and that thus self-fertUisation takes place. 



HETEROMOEPHIO FERTILISATION. 285 

This has been specially noticed by Hildebrand in the case of barley, 
and Mr. Stephen Wilson states that the same thing occurs in wheat 
and oats. Delpino remarks that in an ear of barley there are certain 
flowers differently constructed from the rest, in which cross-fertilisation 
is possible, and that in the oat the process varies according to the 
weather. ' In fine warm weather the flowers open freely, and cross- 
fertilisation is favoured ; while in cold wet weather they remain 
closed, and self-fertilisation is inevitable. In rye, fertilisation from the 
pollen of other flowers is provided for.* 

Certain flowers of Primrose are called pin-eyed, having a long style 
with the rounded stigma projecting beyond the tube of the corolla, 
and standing high above the anthers, which are situated half-way 
down the tube ; others are called thumb-eyed, having a short style, 
with the anthers attached at the mouth of the tube, and therefore 
high above the stigma. These flowers occur on distinct plants. 
Such species are dimorphic, and may be conveniently called dioeciously- 
hermaphrodite — that is, having two kinds of hermaphrodite flowers 
on distinct plants. EflBcient fertilisation is only attained by the 
application of the pollen from stamens of a given length to styles of ^ 
a corresponding length. The short styles are of the same length as 
the short stamens, and the long styles as the long stamens, and it 
appears that the best fertilisation and the greatest number of seeds 
are produced by the application of the pollen of the short-styled 
flowers to the long-styled. This is called heteromorphic fertilisation, 
in contradistiuction to homomorphic where the pistil is fertilised by 
the pollen of its own flower. In the Ipecacuan plant (Oephaelis 
Ipecacuanha) dimorphic flowers occur of a similar kind. Lythrum 
Salicaria is trimorphic ; that is, it presents three forms of flowers. 
Each of these has stamens and pistils, each is distinct in its pistil 
from the other two forms, and each is furnished with two sets of 
stamens difiering from each other in appearance and function. There 
are three lengths of stamens — long, medium, and short — but, two 
lengths only occur in the same plant ; and there are also three lengths 
of styles, but they are not associated with stamens of corresponding 
length. There are then three forms of flowers — 1. With short and 
medium stamens, and long style ; 2. With short and long stamens, 
and medium style-; 3. With medium and long stamens, and short 
style. The stigma is best fertilised by pollen from stamens of lengths 
corresponding to the styles. Two of the three hermaphrodite forms 
must co-exist, and the pollen must be conveyed reciprocally from one 
to the other, in order that either of the two may be fuUy fertile ; , but 
unless all three forms co-exist there will be waste of two sets of 
stamens, and the organisation of the species as a whole ■^^ill be im- 
perfect. On the other hand, when all three hermaphrodites co-exist, 

* See Stephen Wilson's paper in Trcms. Sot. Soc., Edin., 1874. 



286 DICHOGAMOUS PLANTS. 

and the pollen is carried from the one to the other, the scheme is 
perfect. The three forms are divided according to their styles into 
long-styled, mid-styled, and short-styled. Such plants may be called 
trioeoiously hermaphrodite. The fertilisation is effected by the agency 
of insects. The insect in passing from flower to flower will brush 
against a stigma at a given level with the same part of its head or 
body which has brushed off the pollen from an anther at a corre- 
sponding level. The object of all these arrangements is the pre- 
vention of close inter-breeding. Homomorphic unions, where a pistil is , 
supplied with pollen from its own flower, or from a flower of the same 
form, result either in very diminished fertility, or, as in the dimorphic 
species of Linum (Flax), in absolute sterility. 

The same object — namely, the prevention of close inter-breeding — 
may be effected by other means ; sometimes, as in Orohidacese (fig. 
317, p. 205), and Asclepiadacese (figs. 385, 386, p. 230), by the 
mechanical arrangement of the parts of the flowers, and, more 
especially, the consistence of the pollen, being such that fertilisation 
cannot occur without the agency of insects, which carry the pollen 
masses (poUinia) from one flower to another. In the species of 
Orchids, such as Orchis mascula, the pollen masses (fig. 387, p. 230) 
have each a caudicle, which is firmly attached to a viscid disk, con- 
sisting of a minute oval or rounded piece of membrane, with a ball of 
viscid matter on its under side. These balls are contained within a 
cup-like rosteUum, the lip of which is easily depressed by contact with 
a foreign body, such as the proboscis of an insect. The pollinia be- 
come thus attached to the proboscis. At first they stand erect, but 
ultimately, by the contraction of the minute disk, they bend down- 
wards and forwards towards the point of the proboscis. In this way 
the pollen is in a position to be at once applied to the stigma when 
the insect visits another flower, and thus fertilisation is effected. 

The prevention of close inter-breeding is also accomplished in many 
cases by the physiological condition of the parts concerned in fertilisa- 
tion, as occurs in what are called Dicho- 
gamous plants — that is, plants in which 
the stamens and stigmas of the same flower 
do not reach maturity at the same time — 
the stamens being matured first in what 
are called protandrous plants, and the 
stigmas first in protogynous plants. (See 
notice of Protandrous and Protogynous 
plants, at page 212.) In Pamassia palus- 
^^' ^^^ tris (fig. 514) the stamens move in suc- 

Fig. 514. Flower of the Grass of Parnassus {Pa/r7iassia paZustris), the stamens of which 
move in succession towards the pistil, and discharge their pollen. In the figure some 
stamens are seen applied to the pistil, and others removed from it. 




FERTILISATION EFFECTED BY MEANS OF INSECTS. 287 

cession towards the pistil, and after the pollen has been discharged 
they curve back to the petals. But the stigma is not perfect at that 
time. It becomes developed after the pollen has been discharged and 
the anthers have retired. It requires the agency of insects to effect 
complete fertilisation. The pollen is discharged on the part visited 
by insects, and they take it up on that part of their bodies which 
touches the perfect stigma in other flowers, and thus fertilisation is 
effected. In Lobelia we have an instance of the stamens being com- 
plete and the pollen discharged before the stigma is perfect. After 
the poUen has been discharged, the style elongates and carries the 
stigma upwards beyond the syngenesious anthers, and then the stigma 
becomes perfect, so as to be ready for the pollen applied by insects. 
Both these flowers are Protandrous. 

In Euphorbia jacquiniflora, several days before the stamens burst 
through the involucre which closely invests them, the pistil with its 
ovary on the long pedicel has protruded itself beyond, expanded its 
stigma, and received pollen from neighbouring flowers. It is there- 
fore Protogynous. 

In the case of Aristolochia Clematitis (fig. 515), the flowers, as 
long as the essential 
organs are in a state 
fit for fertilisation, 
stand erect, with their 
oblique mouth turned 
outwards, by which an 
insect can enter easily, 
and pass down the tube 
till it comes to the 
column bearing the 
stamens and stigma. 
It is prevented from 
returning by inverted 
hairs in the tube. It 
is detained in the tube 
tiU the pollen is fully 
matured, and then the 
hairs collapse so as to 
permit its escape. It 
carries with it pollen 
grains. It then visits 
a flower where the 
stigma is matured, and 
which presents the open 
mouth of the tube in an erect condition, and on reaching the cavity 

Mg. 615. Jflowering stalk of Common Birthwort (AristolocMa Clematitis}. Fertilisation 
is effected by insects. 




Fig. 615. 



288 FEETILISATION EFFECTED BT MEANS OF INSECTS. 

at the bottom of the tube, fertilises the pistil with the pollen which 
it has carried with it from another flower. This plant is proto- 
gynous, the stigma being matured before the stamens. When the 
flower is duly fertilised it sinks down, no longer presenting a tempting 
orifice for the entrance of insects. If no insect visits the chamber, 
then the stigma passes its maturity before the pollen of its own flower 
is ripened, and no fertilisation takes place. 

Orchids with very long nectaries, such as Anacamptis, Gymna- 
denia, and Platanthera, are habitually fertilised by Lepidoptera, while 
those with only moderately long nectaries are fertilised by bees and 
Diptera. The length of the nectary is correlated with that of the pro- 
boscis of the insect which visits the plant. Orchis Morio has been 
seen fertilised by the hive-bee (Apis meUifica), to some of which 10 
or 16 poUen-masses were attached; by Bombus muscorum, with 
several poUinia attached to t'he bare surface close above the mandibles ; 
by Eucera longicomis, with 1 1 poUinia attached to the head, and by 
Osmia rufa. Empis livida has been seen fertilising Orchis maculata. , 

In Listera (fig. 317, p. 205) the viscid mass of the rostellum bursts 
with force, and then allows the poUinia to escape. The nectar in 
some species of Orchids is secreted between the outer and inner mem- 
brane of the nectary, and bees puncture the inner lining of the 
nectary and suck the fluid contained between the coats. In some 
Orchids, as in Neotinea intaota, there is evident self-fertilisation, 
although there is also provision for fertilisation by insects. So also in 
Ophrys apifera, Gymnadenia, Platanthera, Epipactus, Cephalanthera, 
Neottia, Epidendrum, Dendrobium. In Disa grandiflora the weight 
of the pollen masses bends the caudicle. In this plant the posterior 
sepal secretes nectar. In Ooryanthes, Gongora, Catasetum, Stan- 
hopea, etc., the extraordinary crests and projections on the labeUum 
are gnawed by insects, and while doing so they are sure to touch the 
viscid disk of the poUinia and remove them. The flowers of these 
plants exhibit remarkable animal forms, probably with the view of 
attracting insects. It has been remarked that in Orchids the forms 
of the perianth resemble those of the insects belonging to the native 
country of the plant. The flowers also secrete a large amount of 
saccharine matter, and are odoriferous ; their pollen masses are very 
easUy detached, and are very adhesive. AU these circumstances seem 
to be connected with their mode of impregnation. In Asclepiadacese, 
which have also peculiar pollinia (fig. 386, p. 230), insects are 
attracted by the odour of the flowers (sometimes very fetid, as in 
Stapelia), as well as by saccharine matter. 

Darwin states that bees always alight on the left wing petal (ala) 
of the scarlet kidney-bean, and in doing so depress it ; and this acts 
on the tubular and spiral keel petal (carina), which causes the pistil 
to protrude. On the pistil there is a brush of hairs, and by the 



FERTILISATION EFFECTED BY MEANS OF INSECTS. 289 

repeated movement of the keel petal the hairs brush the poUen beyond 
the anthers on to the stigmatic surface. He found, in many instances, 
that if the plants were protected from bees, the number of fertile 
seeds produced was much smaller than when the bees were freely 
admitted. In the common bean the bees alight on the wing petals 
(alse), and cause the rectangularly-bent pistil and the pollen to protrude 
through the slit of the carina. 

In Erica Tetralix each anther-ceU adheres, just in the part where 
its opening is situated, to the corresponding part of the adjoining cell 
of the next placed anther in the circlet. Thus the pore of a cell, say 
the right ceU of an anther, is, so to speak, closed by the pore of the 
left cell of the next adjoining anther, and so on all the way round. 
A very little power, however, dislocates the chain of anthers ; a slight 
pressure on the antherine processes or spurs effects this. An insect 
accomplishes this easily, and thus its head becomes covered with poUen 
and applies it to the stigma of another flower. 

Polygala is one of the flowers in which a provision is made for 
insect fertilising. " The corolla consists of five petals united into one 
piece and folded in the form of a two-lipped tube. The lower lip has 
a sort of cup-shaped appendage, with a beard of gland-like bodies ; 
this lip opens in front by a narrow vertical slit. The filaments are 
united, and the stamens expand within the cup of the lower lip into 
a two-lobed membrane crowned by the anthers. The pistil has two 
stigmas, — one is placed at right angles to the upper side of the style and 
is perfect, the other is transformed into a spoon-shaped petaloid pro- 
longation of the pistil reaching to the opening of the lower lip of 
the corolla, and dividing the interior of the flower into two cham- 
bers, in the lower of which are the stamens, which are thus separated 
from the true stigma. The entrance to the flower is closed by hairs 
pointing outwards and meeting in front, on the mouse-trap principle. 
A narrow passage is left open above the petaloid stigma. On each 
side of the interior of the tube of the corolla, above the style and just 
behind the true stigma, is a group of white hairs pointing down, the 
tube and meeting above the style. An insect lights on the beard, 
finds a narrow passage leading over the stigma into the upper chamber. 
It is prevented by hairs on the coroUa from returning, and is obliged 
to crawl out through the lower chamber and over the stamens, and 
thus carries the pollen to other flowers. The calyx, at first tempting 
to insects, gradually assumes a green colour, and closes over the ripen- 
ing seed-vessel." (Hart.) 

In Scrophulariacese and Labiatse (figs. 324, 325, p. 207) the axis 
of the flower is horizontal, and the stamens are approximated beneath 
the upper lip of the corolla. An insect in passing separates the 
anthers, and causes the pollen to fall from them, and thus 
transports it to a more advanced flower. In some Leguminosse the 

U 



290 CHANGES IN STYLE AND STIGMA. 

insect touches the back of the keel, -which throws itself hastily back- 
ward, and the insect receives a few grains of poUen, with which it 
impregnates a neighbouring flower. In Fumariaceee the stamens and 
pistil are enclosed between two petals. At the base of the petals, 
which is prolonged into a spur, there is a quantity of nectar which 
attracts insects. To reach this an insect must pass between the two 
petals, the uppfer parts of which, being borne upon a sort of hinge, 
separate easily ; then the insect is covered with pollen, which is 
applied to the stigma. 

Hermann Miiller states that there are two forms of Euphrasia offici- 
nalis in which the mode of fertilisation is different. In the large 
form there is provision for insect fertilisation or cross-fertilisation; 
while in the smaller-flowered form there is regularly self-fertilisation. 
In Rhinanthus Cristar-galli there are also two forms, one small and the 
other large. In the former there is self-fertilisation, whUe in the 
latter this is not the case, as the stigma so far overlaps the anther 
as to render self-fertilisation impossible. 

Other animals, besides insects, are instrumental in distributing 
pollen. Humming-birds, when inserting their bills into the nectaries 
of plants in some countries, carry the pollen on their head feathers from 
one flower to another. They are said to act as pollen-distributors in 
the case of a species of Erythrina in Nicaragua. In Marcgraavia 
nepenthoides there are peduncular pitchers below the flowers con- 
taining a sweet liquid, attracting insectivorous birds which come and 
feed on their contents, and in so doing burst the anther and carry 
the pollen to other plants. 

WhOe the pollen is being elaborated, the stigma is also under- 
going changes. It becomes enlarged, and secretes a viscid, usually 
saccharine, matter, ready to detain the poUen-grains when they 
are discharged. In Goldfussia anisophylla, and in species of 
Campanula, as C. media, C. Eapunculoides, 0. Trachelium, 0. 
rotundifolia, the style is covered with collecting hairs (fig. 
516), 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 mak« the stigma come into contact 
with the hairs. In Campanula the style is at first slightly 
longer than the stamens, but it soon becomes twice their 
length, and during its elongation the hairs upon it brush the 
pollen-grains out of the anther-eases. The stigma consists of 
two branches, which are at first erect and closely applied to 
Fig^ie ^^^^ other, but afterwards, by changes in the cells, become 
revolute. This completely developed state of the stigma does 
not occur until some time after the poUen of its own flower has been 

Fig. 616. Style of a species of Bellflower {Camiianula), covered with liaixs, which brash 
out the pollen from the anthers. 




FERTILISATION IN GYMNOSPEEMS. 291 

discharged. The plant is dichogamous and requires the pollen of 
another flower to fertilise the pistil. In rare instances, 
as in the Searpink (Armeria ma/ritima), the conduct- 
ing tissue of the style at its lower part becomes 
elongated so as to pass into the ovary, and ultimately 
comes in contact with the ovide, when impregnation 
takes place (fig. 517). 

The length of time during which the pollen re- 
tains its vitality, or power of effecting fertilisation, 
varies in different plants. According to Gsertner and 
others, the pollen of some species of Mcotiana retains 
its vitality only for forty-eight hours ; pollen of various 
species of Datura, two days ; pollen of Dianthus ^'s- 6i7. 

CaryophyUus,' three days; pollen of Lobelia splendens, eight or nine 
days; poUen of Oheiranthus Cheiri, fourteen days; pollen of Orchis 
abortiva, two months ; pollen of OandoUea, one year ; pollen of Date 
Palm, one year or more. Michaux says that in some Palms, as Date 
and Ohamserops humilis, the pollen may be applied successfully after 
having been carefully kept for eighteen years. The pollen retains 
its vitality longer when not removed from the anthers ; and the finer 
it is, the more quickly it loses its fecundating property. 

In most flowering plants the pollen is applied directly to the 
stigma, but in some cases when the plants are Gymnospermous, that 
is, have no proper ovarian covering, and no stigma, the pollen is 
applied directly to the ovule. The pollen then undergoes changes 
by the formation of tubes, through which the fovUla passes in order 
to come in contact with the minute cells in the ovule. The matter 
called fovilla covered by the intine consists of minute molecules, 
which often exhibit movements, to which the term molecular has 
been applied. 

Embryogenic process in Gymnospermous Flowering Plants. 

In Gymnospermous plants, such as Coniferse (Firs and Pines, fig. 
518) and Oycadaceae (fig. 519), impregnation is eflfected by direct 
contact between the pollen and the ovule. There is no true 
ovary bearing a stigma. Such is the view taken by many 
botanists. There are however others of equally high authority 
who do not adopt this opinion, and who look upon the so-called outer 
covering as not solely composed' of the spermoderm, but as formed 
partly of it and partly of the ovarian coat. Some speak of the 
ovuliferous leaves in Oycads as being open carpels, and they also look 

, Fig. 517. Ovary, ov, of Sea^pmk (Armeria maritima}, in which the orule is suspended 
hy a curved cord, cor, and the' conducting tissue, s, of the style elongates in a downward 
direction. 



292 FEKTILISATION EFFECTED BY MEANS OF INSECTS. 



upon the bracts of Conifers in the same light. In these cases there is 
no evidence of the presence of a stigma. Gnet^cese seem to form a 
link between Cycads and Conifers. They have an open ovary without 




l:> 



Fig. 518. 




style or stigma. The name of ArcMsperms (aj%>i, beginning, ffTTB^fia, 
seed) has been given by some to Gymnospermous plants ; while the 
term Metasperms {/iira, after) has been applied to Angiospermous 
plants. These views will be noticed when 
the natural orders are described. In treat- 
ing of the embryogenic process it is probably 
not of much importance which view we adopt. 
The ovules of the so-caUed Gymnosperms (fig. 

520 ov, and fig. 521) consist of a nucleus (fig. 

521 a) covered by one or more integuments, 
and having a large micropyle (fig. 520 mdc, and 
fig. 521 m). In the delicate cellular nucleus 
(fig. 521 a) there is developed an embryo- 
sac, h, sometimes more than one, as in the 

Yew tribe. The poUen-grains enter the large micropyle and come 
into contact with the nucleus, and then send their tubes into its apex 
(fig. 522 c). This process sometimes requires several weeks or 
months. After this the embryo-sac (fig. 522 b) becomes gradually 

Fig. 518. A Coniferotis tree, tlie Stone-pine, whicli belongs to the Gymnospermous divi- 
sion of Phanerogams, the seeds being [naked, that is, not contained in an ovary with a 
stigma. The seeds are in cones covered by scales. Fig. 519. A Cycadaceons plant (Cycas 
revobuia), belonging also to the Gymnospermous division. The seeds in Cycads are produced 
on the edge of abnormal leaves or on the lower side of scales of cones. Fig. 520. Female 
flower of a Pine, consisting of a scale, eca, and two ovules, ov, attached to its base ; mw, the 
foramen of the ovule. The ovules are nailed, not being contained in a true ovary. 




Pig. 620. 



EMBKTOGENT IN GYMNOSPEEMS. 



293 



filled with cellular tissue or endosperm cells, and at the same time 
enlarges. This development of endosperm cells occupies frequently 
a long time, especially in the Abietinese, which require two years to 
ripen their seeds. After the embryo-sac has become filled with 
cellular tissue, certain cells at the micropylar end of the sac enlarge 
and form the corpuscles of Brown, the secondary embryo-sacs of 
Mirbel and Spach (fig. 523 d). Each corpuscle is at first separated 






Kg. 521. 



Fig. 622. 



Fig. 623. 



from the inner surface of the embryo-sac by a simple cell, which after- 
wards divides into four by the formation of two septa crossing each 
other ; then a passage is formed between the inner angles of these 
cells leading to the corpuscle. In the cavity of each corpuscle free 
cells appear. After the corpuscles become evident, the pollen tubes 
resume their growth, pass through the tissue of the nucleus, and reach 
the outside of the embryo-sac, one over each corpuscle. The tubes 
then perforate the membrane of the embryo-sac, reach the canal be- 
tween the four cells, and come into contact with the corpuscle (fig. 
523 d). A cell at the lower end of the corpuscle then enlarges, and 
forms the embryonal vesicle. A free cell in the vesicle divides into 
eight cells by vertical and transverse septa, and these together consti- 
tute a short cyclindrical cellular body (fig. 524), the pro-embryo, as 
it is called by Hofmeister. The four lower cells of this pro-embryo, 
by the elongation of the upper ones (fig. 525), are finally pushed 

Fig. 621. Vertical section of the ovule of the Austrian Pine {Films amstriaca), showing 
the nucleus, a, consisting of delicate cellular tissue containing deep in its substance an 
embryo-sac, &, formed before impregnation by the coalescence of a vertical series of a few 
cells. The micropyle, m, is very wide, and through it the pollen-grains come into contact 
with the summit of the nucleus, into the substance of which they send their tubes. Fig. 
622. Vertical section' of the ovule of the Scotch Fir,(Pi?iii5 sylvestris) in May of the second 
year, showing the enlarged embryo-sac, h (full of endospermal cells), and poUen-tubes, c, 
penetrating the summit of the nucleus after the pollen has entered the large micropyle of 
the ovule. Fig. 623. Vertical section of the embryo-sac, &, and of part of the nucleus, a, 
of the ovule of the Weymouth Pine (Pvnus Strohus). At the micropylar end of the embryo- 
sac, two cells called corpuscles, d, have made their appearance. Each of these is at first 
separated from the inner surface of the micropylar end of the sac by a single cell, which 
afterwards divides intd four, leaving a passage from the surface of the sac down to the 
corpuscle. The pollen-grain, c, on the summit of the nucleus, then sends down a tube 
which perforates the embryo-sac, and reaches the corpuscle through the intercellular canal. 



294 



EMBEYOGENY IN GYMNOSPEEMS. 



into the substance of the nucleus. The four elongated pro-embryonic 
cells (fig, 526, 1) now appear as isolated suspensors (fig. 526, 2), 
and the cell at the end of each suspensor becomes an embryo, g. 
There are thus four times as many rudimentary embryos as there are 
corpuscles. Usually one of these only becomes developed as the 
embryo of the ripe seed. 




Fig. 524. 



Fig. 626, 



Fig. 625. 



In many points this process resembles what takes place in Lyco- 
pods. The anthers of Gymnosperms may be considered as corresponding 
to the microsporangia, and the grains of pollen to the microspores. 
Certain cells in the anther may represent the prothaUus, while a cell 
forming the poUen-tube may be the antheridium. The embryo-sac 
in Gymnosperms may be reckoned equivalent to the macrospores, and 
the endospermal cellular development may be analogous to the pro- 
thaUus produced in the large spore of Selaginella (see page 278). 
The prothaUus in some Ferns, as Ophioglossacese, is produced inside 
the spore, whUe in others it grows out from it in the form of a green 
expansion, bearing both antheridiaand archegonia (fig. 507, p. 280). 



Emhryogenic process m Angiospermous Flowering Plants. 

In the case of Angiospermous Phanerogams, the pollen-grains 
(fig. 527 gp) are discharged from the anther, and are applied to the 
stigmatic surface of the pistil (fig. 527 ps), either directly or by the 

Fig. 524. Nucleated ceUs of what Hofmeister calls the pro-embryo, in tlie ovule of the 
Weymouth Piae {Pinus Sirdbim). The cells are pushed downwards into the ceUular tissue 
of the nucleus hy the elongation of the upper ceils, which finally form the suspensor. 
Fig. 525. The same pro-emhryonic body in the ovule of the Weymouth Pine, with the lower 
ceUs pushed farther down by the elongation of the upper suspensory cells. Fig. 526. 
Suspensors taken from the ovule of the Weymouth Pine [Pymis Strolms): In No. 1 the four 
suspensors are united. They form a cylinder composed of four elongated cells, »nd at the 
end, J), are seen some of the lower nucleated cells of the pro-embryo. In No. 2 the suspen- 
sors have separated, three of them, a, are cut off, and the remaining one, 6, is connected 
with the embryo, g, at its extremity. 



EMBRYOGENY IN ANGIOSPEEMS. 



295 



agency of wind or insects. The viscid fluid secreted by the stigmatic 
cells {pi) causes a rupture of the extine, and the intine passes out in 
the form of a tubular prolongation, -which gradually elongates (tp, tp) 
as it proceeds down the loose conduct- 
ing tissue (tc, te) of the style tiU it 
reaches the ovule. The length attained 
by the pollen-tube is sometimes very 
great. In Cereus grandiflorus, Morren 
estimated that the tubes, when they 
reached the ovary, extended as far as 
1150 times the diameter of the pollen- 
grain ; in Orinum amabile, Hassall says 
that they reach 1875 times the diameter 
of the grain; in Oleome speciosa, 2719 
times ; in Oxyanthus speciosus, 4489 , 
times ; and in Oolchicum autumnale, 
9000 times. The length of time which 
the poUen-tabe takes to traverse the 
conducting tissues of the style in Anglo- 
sperms varies. 

On reaching the ovule the pollen- 
tube enters the foramen, and finally 
comes into contact with the embryo-sac pj 527 

(fig. 528 e). In the interior of this 

sac one or more nucleated germ-vesicles are produced before impregna- 
tion in the midst of the endospermal cells and protoplasmic matter 
(fig. 530 e). In fig. 529 an anatropal ovule is represented with the 
raphe r, the opening in the primine and secundine ra, en, the nucleus 
n, the embryo-sac es, and the pollen-tube pt, in contact with the 
germ-vesicle e. , 

After the contact of the poUen-tube, one of the embryonal vesicles 
becomes enlarged, and is then divided by septa into two, the upper 
division growing out in a filamentous form, constituting the suspensor 
(fig. 530 s, 531 h), while the lower portion enlarges and divides re- 
peatedly so as to form a cellular globule — the embryo (fig. 530 s, 
531 c). The parts of the embryo being finally differentiated into 
cotyledonary and radicular portions, as shown in fig. 532, 1-4. 

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 
fertilisation. In Oiyptbgamic plants this has been traced, particularly 




Fig. 527. Portion of the stigma of Antiixhinum majus at the time of fecundation, ^s, 
j)s, Superficial cells forming the papillae, tc, te. Deep elongated cylindrical cells forming 
the conducting tissue, g'p, Graiils 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. 



296 



EMBRYOGENY IN ANGIOSPEEMS. 



in certain cases of conjugation ; where the two cells come into contact, 
a tube is formed between them, and the contents of the one unite 





Fig. 528. 



Fig. 529. 






Fig. 531. 

Fig. 528. Section of ovule of an Orchis (Orchis Morio), showing the poUen-tube passing 
through the endostome, and reaching the embryo-sac in the nucleus. The closed and 
enlarged end of the tube, t, is applied to the sac, in which a germ-vesicle had been pre- 
viously formed. Transudation of fluids takes place, and the embryo, e, is developed at the 
lower end of the germinal or embryonal vesicle while the upper part of the vesicle elon- 
gates, and forms a confervoid suspensor. Fig. 529. Section of anatropal ovule, r. 
Raphe. cA, -Chalaza. j?, Primine. s, Secundine. ac, Exostome. en, Endostome. %, 
Nucleus, es. Embryo-sac. 'pU Pollen-tube. 5, The germ-cell which forms the emhryo. 
Fig 530. Section of the ovule of (Enothera, showing the poUen-tube, «, with its enlarged 
extremity applied to the end of the embryo-sac, and introverttag it slightly ; one of the 
germinal vesicles ia the sac has been impregnated, and has divided into two parts, the 
upper part forming a confervoid septate suspensor, s, and the lower dividtug into four parte, 
which form a globular mass— the rudimentary embryo, surrounded hy endospermal cells, e, 
Kg. 531. Ovule of Orchis mascula. a, Primine. &, Secundine. c, Embryo, e, Confervoid 
filament which proceeds from the embryo towards the placenta. Fig. 532, The embryo in 
diflferent stages of development. 1, Embryo in young state as a globular mass at the end 
of a suspensor. 2 and 3, Embryo more advanced. 4, Embryo showing the division 
into two cotyledons. 



PRODUCTION OF HYBEIDS. 297 

with those of the other, giving rise to a germinating body. In 
Phanerogamic plants, also, there are two cells with different contents 
— the pollen-grain with its granular fovUla, and the ovule with its 
protoplasm. These are brought into connection by means of the 
poUen-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 
formation of the embryo is determined, which commences as a cellular 
body or germinal vesicle, in the interior of which other cells are sub- 
sequently formed in a definite order ,of succession. 

The Production of Hybrids. — If the pollen of one species is 
employed to fertilise the ovules of another, the seed wUl often pro- 
duce plants 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 the different species of the same genus. 
Thus, different species of Heath, Fuchsia, Oerens, Rhododendron, 
and Azalea, readily inoculate each other, and produce interme- 
diate forms. It is found, however, that many plants which seem to 
be nearly related do not hybridise. Thus, hybrids are not met 
with between the Apple and the Pear, between the Gooseberry and 
Currant, nor between the Easpberry and Strawberry. The ovules of 
Fuchsia coccinea, fertilised with the pollen of Fuchsia fulgens, pro- 
duce 'plants having intermediate forms between these two species. 
Some of the seedling plants closely resemble the one parent, and 
some the other, but they aU partake more or less of the characters of 
each. By the examination of the foliage, conclusions may be drawn 
as to what wiU be the character of the flower. Mr. Thwaites men- 
tions 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. While hybrids 
are produced between two species, crosses are produced between two 
varieties. 

In the case of hybridisation, 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 poUen-grains require to be of the same form 
and dimensions in order to admit of artificial union taking place ; but 
this is a mere conjecture. It is, however, requisite for successful 
hybridising, that the pollen should be in a state of fuU maturity, and 
the stigma perfect. Hybrids perform the same functions as their 
parents, but they do not perpetuate themselves by seed. They must 
be propagated by offsets or cuttings. If not absolutely sterile at first, 



298 PRUIT OE MATURE PISTIL. 

they usually become so in the course of the second or third generation. 
Herbert mentions instances of hybrid Narcissi, from which he at- 
tempted 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 fertilised, however, by the pollen taken 
from one of the parents, and then the ofispring assumes more or less 
the characters of that parent. 

Hybrids are rarely produced naturally, as the stigma is more likely 
to be affected by the pollen of plants of its own species than by that 
of other species. In dicecious plants, however, this is not the case, 
and hence the reason, probably, of the numerous co-called species of 
Willows. Hybrids are constantly produced artificially, with the view 
of obtaining choice flowers and fruits, the plants being propagated 
afterwards by cuttings. In this way many beautiful Eoses, Azaleas, 
Rhododendrons, Pansies, Cactuses, Pelargoniums, Fuchsias, Calceo- 
larias, Narcissuses, etc., have been obtained. By this process of 
inoculation, and carefully selecting the parents, gardeners are enabled 
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 Amary Hides, 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, re- 
semble the male. 

G.— Fruit, or the Pistil arrived at Maturity. 

After fertilisation, 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, whUe 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 
(•s-Ef /', around, and %af ots, 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 
Gooseberry, 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 unfavourable weather, than 
those which have the calyx attached, as the Gooseberry, the Melon, 
and the Apple. 

In general, the fruit is not ripened unless fertilisation has been 



TEUIT OK MATUEE PISTIL. 299 

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 
abortive, 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-development of seeds seems to lead to a larger growth and a 
greater succulence of fruit. 

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 tha,t 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 (unus, one, and loculus, box or cavity) ; or many, muUilocular 
.(multus, many), etc. 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, 
however, always remain permanent in the fruit. Great changes are 
observed 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 unsymmetri- 
■cal, that is, not equal to, or not a multiple of, the parts of 
the flower ; and at times they are developed more in one 
"direction than another, so as to assume an irregular appear- 
ance. In the Ash (fig. 533) an ovary with two cells, each 
containing an ovule attached to a central placenta, is changed 
into a imUocular fruit with one seed ; one ovule, I, having 
become abortive, and the other, g, gradually ex- 
tending 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. Similar changes take place in the 
Horse-chestnut, in which the remains of the abor- 
tive ovules are often seen in th e ripe fruit. In the ^s- 633. 
Coco-nut, a trilocular and triovular ovary is changed into a one-ceUed, 
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 

Kg. 533. Samara or Samaroid fruit of Fraxinus oxyphylla. 1, Entire, with its wing, a. 
2, Lower portion cut transversely, to show that it consists of two loculaments ; one of 
which, I, is abortive, and is reduced to a very small cavity, while the other is much enlarged, 
and filled with a seed, g. 





300 FEUIT OR MATURE PISTIL. 

of the ovary, divisions may take place in the fruit which did not 
exist in the ovary. In Pretrea zanzibarica a one-celled ovary is 
changed into a four-celled fruit by the extension of the placenta. In 
Cathartocarpus Fistula (fig. 429, p. 244) a one-celled ovary is 
changed into a fruit having each of its seeds in a separate cell, in con- 
sequence of spurious dissepiments being pro- 
duced in a horizontal manner, from the inner 
wall of the ovary after fertilisation. In Tri- 
bulus terrestris, each cell of the ovary (fig. 
534) has slight projections, c, on its walls, in- 
terposed between the ovules, o, which, when 
the fruit is ripe, are seen to have formed dis- 
_. ,„. tinct transverse divisions (fig. 535 c), or 
spurious dissepiments, separating the seeds, g. 
In Astragalus, the folding of the dorsal suture inwards converts a one- 
ceUed ovary into a two-celled fruit ; and in Oxytropis the folding of 
the ventral suture gives rise to a similar change in the fruit. 

The development of cellular or pulpy matter frequently alters the 
appearance of the fruit, and renders it difficult to discover its formation^ 
In the Strawberry, the axis becomes succulent, and bears the carpels 
on its convex surface ; in the Rose there is a fleshy hollow torus or 
disk, which bears the carpels on its concave surface. In the Goose- 
berry, 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 ceUs, which are 
produced from the inner partitioned lining of the pericarp. 

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. 536), represents the 
carpellary leaf, and the seeds correspond to the ovules. The pericarp 
consists usually of three layers ; the external (fig. 536 e), or epica/rp 
It/, upon, or on the outside, xajTos, fruit), corresponding to the lower 
epidermis of the leaf; the middle (fig. 536 m), or mesocarp (//.'eeo;, 
middle), representing the parenchyma of the leaf; and the internal 
(fig. 536 n), or endocarp (evdov, within), equivalent to the upper 
epidermis of the leaf, or the epithelium of the ovary. In some plants, 
as Bladder Senna (Colutea arborescens), the pericarp retains its leaf- 
like appearance, but in most cases it becomes altered both in con- 
sistence 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 thickened by the addition 

Fig. 534, CeU or loculament of the ovary of Tribulus terrestris, cut verticaUy, to show 
the commencement of the projections, c, from the paries, which are interposed between the 
ovules, 0. Fig. 535. 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. 



lEUIT OE MATUEE PISTIL. 301 

of cells, and can be taken off in the form of what is called the skin ; 
the mesocarp becomes much developed, forming the flesh or pulp, and 
hence has sometimes been called sa/rcoca/rp (tfajf, 
flesh), while the endocarp becomes hardened by ,,*"'-^-^'* 

the production of woody cells, and forms the ^--r^^^^w^ 
stone oiputamen (putamen, a shell), immediately "-"rMj^^ k 
covering the kernel or the seed. The same ' Ls^^^^M 
arrangement is seen in the fruit of the Cherry, i&Mfi'*''*'^^ ill 
Apricot, and Plum. In these cases, the meso- '■''||iff || 
carp is the part of the fruit which is eaten. In |w| I If 

the Almond, on the other hand, the seed is used ilfll m 

as food, while the shell or endocarp, with its ^ili § 

leathery covering or mesocarp, and its greenish ^wll't'/ 

epicarp, are rejected. The pulpy matter foimd "Mh'// 

in the interior of fruits, such as the Gooseberry, i^g- 536. 

Grape, and Oathartocarpus Fistula (fig. 429, p. 244), is formed from 
the placentas, and must not be confounded with the sarcocarp. 

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 the epidermal covering ; the fleshy portion is 
the mesocarp, formed by the cellular torus; while the scaly layer, 
forming the walls of the seed-bearing cavities in the centre, is the 
endocarp. In the Medlar (fig. 568, p. 314) 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 external and internal part. The rind of the Orange 
consists of epicarp and mesocarp, while the endocarp forms partitions 
in the interior, filled with pulpy ceUs. 

While normally the divi-sions of the fruit ought to indicate 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 (fig. 543, p. 304), 
Euphorbia, and Mallow (fig. 548, p. 305). Occasionally, the endo- 
carp remains attached to the centre, forming cells, in which the 
seeds are placed, while the outer layer separates from it at certain 

Fig. 636. Lower portion of the carpel or legume of the Bean, Faha sativa, cut trans- 
versely, to show the structure of the pericarp, e, Epicarp, or external epidermis, m, 
Mesocarp. n, Endocarp. s d,, Dorsal suture, s v. Ventral suture, g, A seed situated at 
the upper part of the section, and cut also transversely. 



302 



FEUIT OE MATUEE PISTIL. 



points, and leaves a row of cavities in the substance of the pericarp 
itself. 

In some fruits the calyx is superior, or in other words above the 
pericarp, while in others it iS closely applied to the ovary, but 
separable from it. Thus in the fruit of Mirabilis Jalapa (fig. 537, 1), 
when a section is made longitudinally (fig. 537, 2), the hardened 
calyx (perianth), c c, is distinct from the fruit, /, which is in this 
instance incorporated with the seed, but at once distinguished by its 
style, s. The same thing occurs in Spinach (Spinacia). Again, in 
the Yew (fig. 538), there is an external succulent covering, ic, 
formed by modified bracts, which here occupy the place of a pericarp, 
and surround the seed, g, which is naked, inasmuch as it is not con- 
tained in a true ovary with a stigma. 



1 

i 



Fig, 637, 1. 




Fig. 537, 2. 




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 AlchemUla, Fragaria, 
Labiates, and Boraginacese, it is at the base or side (figs. 434, 435, 
436, pp. 246, 247). The style sometimes remains in a hardened form, 
rendering the fruit apiculate ; at other times it falls ofij leaving only 
traces of its existence. The presence of the style or stigma serves to 
distinguish certain single-seeded pericarps fi-om seeds. 

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. 539 sv), while the back, corresponding with the midrib, is the 
dorsal suture (fig. 539 sd). 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 inwards of the 
carpellary edges ; and occasionally the outer or dorsal suture is also 

Fig. 637. Fruit ot Mirabilis Jalapa. 1, Entire. 2, Cut longitudinally, to show its com- 
position, c c. Lower part of perianth hardened, and forming an outer envelope. /, The true 
fruit, covered by the perianth. The integuments of the fruit are incorporated "with those of 
the seed, which has been also cut. The fruit is distinguished by the rema i ns of the style, s, 
at the apiculus or summit. Fig. 638. Fruit of Taxus baccata, the Yew. h, Imbricated 
bracts at its base, ic, Fleshy envelope taking the place of the pericarp. This envelope 
covers the seed, g, partially, leaving its apex naked. 



INDEHISCENT AND DEHISCENT FEUITS. 



303 



a'v\ 




Fig. 539. 



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 ex- 
ternally ; but in cases where the placentation is 
' either parietal or free central, the edges of the sepa- 
rate carpels, being near the surface, may present also 
externally the marks of the ventral sutures. 

Where the sutures are formed, there are usually 
two bundles of fibro-vascular tissue (fig. 539), one 
on each edge. The edges of the sutures are often 
so intimately 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, or at both, so as 
to allow the seeds to escape, and then it is dehiscent 
(dehisco, I open). By this dehiscence the pericarp becomes 
divided into different pieces, which are denominated 
valves, the fruit being univalvular, bivalimlar, or multi- 
valvular, etc., according as there are one, two,- or many 
valves. These valves separate either completely or par- 
tially. In the latter case, the divisions may open in the 
form of teeth at the apex of the fruit, the dehiscence 
being apicilar, as in Caryophyllacese (fig. 540 ■;;), or as 
partial slits of the ventral suture, when the carpels are 
only free at the apex, as in Saxifrages. 
Indehiscent Fettits are either dry, as the Nut, or fleshy, as the 
Cherry and Apple. They may be formed of 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 pseudospermous (-^evS^g, false, and 
(f-rsj^a, seed), or false-seeded, and are well seen in the grain of Wheat. 
In such cases the presence of the style or stigma determines their true 
nature. 

Dehiscent Fruits, when composed of single carpels, may open 
by the ventral suture only, as in the follicles of Pseony, Hellebore (fig. 
539), and Calthea; by the dorsal suture only, as in Magnolias and 
some Proteacese ; 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 




g. 640. 



Fig. 639. A single carpel of HeUetorus foetidus after dehiscence, sd, Dorsal suture. 
St), Ventral suture. The carpel, when mature, opens on the ventral suture, and fonns iJie 
truit denominated a foUiole. Fig. 640. Capsule or dry seed-vessel of Cerastium triviale 
after dehiscence, c, Persistent calyx, p. Pericarp dividing at the apex, v, into ten teeth, 
wliich indicate the summits of as many valves united helow. 



304 



DEHISCENT FRUITS. 



the dissepiments, so that the fruit will be resolved into its original 
carpels, as in Khododendron, Oolchicum, etc. This dehiscence, in 
consequence of taking place through the lamellse of the septum, is 
called septicidal (septum and ccedOj I cut) (figs. 641, 542). The valves 




Fig. 544. Fig. 545. Fig. 546, 

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. 

Fig. 541. Capsule of Digitalis purpurea at the moment of dehiscence, Tvhen 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, g. Fig. 542. Inferior portion of the same cap- 
sule cut transversely, to show the formation of the septum, formed hy the two inner 
faces of the carpels, c c. pp, Placentaries reflected and projecting into the interior of the 
cavities, g. Seeds. Fig. 543. Capsule {tricoccous regma) of Eicinus communis. Castor-oil 
plant, at the moment of dehiscence. The three carpels or cocci, c,e c, are separated from 
the axis, a, by which they were at first united [see fig. 549), and which remains in a colum- 
nar ;form. These cocci begin to open by their dorsal suture, sd. Fig. 544. Capsule of 
Iris opening by loculicidal dehiscence. Fig. 545. Capsule of Hibiscus esculentus, show- 
ing loculicidal dehiscence, vvv, Waives of 'the seed-vessel, c. Septum or partition, g, 
Seeds. Fig. 546. Capsule of Cedrela angustifolia, the valves of which, vvv, separate from 
the septa, c c, by septifragal dehiscence. The separation takes place from above down- 
wards, in such a manner that the axis, a, remains in the centre, with five projecting angles, 
corresponding to the septa, g^ The seeds contained in the loculaments. 



DEHISCENT FEUITS. 



305 



543 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 loculaments, as in the Lily and Iris (fig. 544). 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. 545), or leaving them in the centre. This 
dehiscence is locuUcidal (loculus, 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. 546), leaving them 
attached to the centre, as in Thorn Apple (Datura Stramonium). This 
is called septifragal dehiscence (septum and frango, 1 break), and may be 
looked upon as a modification of the loculicidal. The separation of 
the valves takes place either from above downwards (fig. 546), or from 
below' upwards (fig. 547). 

Sometimes the axis is prolonged as far as the base of the styles, as 
in the Mallow (figs. 548; 417, p. 239), and Castor-oil plant (fig. 549), 




Kg. 547. 



Fig. 648. 



Kg. 549. 



the carpels being united to it by their faces, and separating from it 
without opening. In the Umbelliferse (fig. 550) the two carpels 
separate from the lower part of the axis, and remain attached to a 
prolongation of it, called a carpophore (xa^-jrog, fruit, and pof e'w, I bear), 
or 'podocarp {'^roig, foot, and xagTo's, fruit), which splits into two 
(fig. 550 a), and suspends them. Hence the name cremocarp (xgs/taiw. 

Kg. 647. Capsule of Swietenia Mahagoni, opening by valves from Ibelow upwards. The 
letters have the same signification as in fig. 546. Fig. 548. Fruit of Malva rotundifolia, 
with half the carpels composing it removed, to show the axis, a, to which they are attached. 
This axis ends at the point where the style, s, is produced, o e, The carpels, which are left 
attached to the axis, around which they are arranged in a vertieillate 'manner. The lateral 
surface of the two carpels in front, (f, is exposed. Kg. 549. Tricoceous capsule of Rici- 
nus communis. Castor-oil plant, cut vertically, to show the axis, a, prolonged between the 
carpels, and terminating by small cords or funiculi, /, wjiich project into the loculaments, 
and are attabhed to seeds, g g, Seeds exposed, each surmounted 'by a fleshy caruncula, c. 
pp, Pericarp. 

X 



306 



DEHISCENT FETJITS. 



I suspend or hang), applied to this fruit. By some authors the term 

schizocarp {syjZfi), I split) is applied to such dry fruits consisting of one or 
more; one-seeded or few-seeded, indehiscent carpels. 
In Geraniacese 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 ventral suture 
(fig. 551). Carpels of this kind are called cocci 
(xoxxog, kernel), and the fruit is said to be tricoc- 
cous, etc., according to the number of separate 
carpels. In the case of many Euphorbiacese, as 
Hura crepitans, the cocci separate with great 

force and elasticity, the cells being called dissilient (dissilio, I burst 

asunder). 

In the Siliqua, or fruit of CruciferBe, as Wallflower (fig, 552), the 

valves separate from the base of the fruit, leaving a central replwm, or 




Fig. 550. 






...p 



Fig. 551. Fig, 562. Pig. 653. 

frame, r. The replum 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- 
dacese (fig. 553) the pericarp, when ripe, separates into three valves, 

Fig. 650. Fruit or cremocarp of PraDgos uloptera, an umbelliferous plant. Fruit some- 
times caUed schizocarp. The carpels, mericarps, or acheenia, c c, separate from the axis, a, 
and are each suspended by a carpophore, s s. Persistent styles with swollen bases, formed 
by an epigynous disk. Fig. 551 . Fruit or mature carpel of Geranium sanguineum. c. Persis- 
tent calyx, a. Axis prolonged as a beak, t t, the styles at first united to the beak, and 
afterwards separating from below upwards, along with the carpels, o o, which dehisce by 
their ventral suture, s. Stigmas. The fruit is sometimes called gynobasic. Fig. 552. 
Siliqua of Cheiranthus Cheiri, Wallflower, dehiscing by two valves, v v, which separate from 
a frame or replum, r. g, Seeds arranged on either margin, s, Two-lobed stigma. Fig. 
553. Capsule of Orchis maculata at the period of dehiscence, c. Remains of the perianth 
crowning the fruit, v v, Segments of the pericarp which are detached in the form of valves. 
p p. Arched repla or placentas which remain persistent, and bear the seeds. 




Fig. 666. 



Fig. 556. 



DEHISCENT FRUITS. 307 

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 diflBcult 
to teU whether the dehiscence is 
septicidal or loculicidal, inas- 
much as there are no dissepi- 
ments, 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 carpellary 
leaves, as in septicidal dehis- 
cence, or only halves united, as 
in loculicidal dehiscence. In 
some instances, as in Linum 
catharticum, the fruit opens 
first by loculicidal dehiscence, and afterwards the carpels separate 
in a septicidal manner. 

Another mode in which fruits open is transversely, the dehiscence 
in this case being called circumscissile (circum, around, and scindo, 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. 554), and in Henbane (Hyo- 
scyamus), (fig. 555), and hence the fruit is often denominated operculate 
(operculum, a lid). In some instances the axis seems to be prolonged 
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 (the Monkey-pot) and in Couratari the calyx is superior, 
and the lid is formed at the place where the calyx is attached. 

Transverse divisions take place occasionally in fruits formed by a 
single carpel, as in the pods of some leguminous plants. Examples 

Fig. 664. Pyxidium or oapsiile of Anagallis arvensis, opening by eiroumsoissile dehis- 
cence, 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. 555. Operculate capsule or pyxidium of Hyoscyamus niger, Henbane. 
0, Operculum or lid separating and allowing the seeds to appear. Fig. 566. Lomentaceous 
legume or lomentum (transverse sehizooarp) of Hedysarum coronarium. 1, Bntii'e, 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 poitions by solubility. 



308 



CARPOLOGY. 




are seen in Omithopus, Hedysarum (fig. 556), Entada, Coronilla, and 
the Gum-arabic plant (Acacia arahica), in -which each seed is con- 
tained 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. 
The name schizocarp has been also applied to such fruits. In 
Cathartocarpus Fistula transverse partitions occur without exhibit- 
ing evident separations of the parts externally. Some look upon 
these pods as formed by pinnate leaves folded, and the divisions 
as indicating the points where the different pairs of pinnae are 
united. Dehiscence may also be effected by partial openiags 
in the pericarp, called pores, which are situated either at the 

apex,' base, or side. In the Poppy 
(fig. 444, p. 249) the opening takes 
place by numerous pores under the 
peltate processes bearing the stigmas. 
In Campanulas there are irregular 
openings towards the middle or base 
(fig. 557 t), which pierce the pericarp. 
In Progsmouth or Snapdragon (fig. 
558) 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. 

Oahpology. — Much has been done of late in the study of car- 
pology (xa^mi, fruit, and Xoy og, discourse), or the formation of the 
fruit ; but much still remaius 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. 

Fruits may be formed by one flower, or they may be the pro- 
Fig. 557. Capsule of Campanula persicifolia, opening by holes or pores, ( t, alDove tlie 
middle, c. Persistent calyx, separating above the pericai-p, p, into five acute segments, in 
the midst of which is seen the withered and plaited corolla, in the form of indnviae, a. The 
holes perforate the walls of the pericarp. Fig. 568. Capsule of Antirrhinum majus. Frogs- 
mouth, after dehiscence, c c. Persistent calyx, p. Pericarp perforated near the summit by 
three holes, ( (, 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, s. 



Fig. 667. 



Fig. 568. 



INDEHISCENT APOCAEPOUS' FRUITS. 



309 



duct of several flowers combined. In the former case they are 
either apocarpous {pLnro, separate, and xagwSg, fruit), or dialycarpous 
(biaXba, I part asunder), that is, composed of one mature carpel, or 
of several separate free carpels ; or syncarpous (guv, 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 (avhi, flower, and xagTos, fruit). The 
term simple is perhaps properly applied to fruits which are formed by 
the ovary of a single flower, whether they are composed of one or 
several carpels, and whether these carpels are separate or combined. 
Simple fruits are hence sometimes denominated MonogyruBcial (fiSvog, 
one, yunj, pistil, and olxiov, habitation), as being formed by one gynoe- 
cium ; while multiple fruits are called polygyncecial (toXvi, many) as 
being formed by many gynoecia. 

Simple or Monogyruxcial Fruits which are the produce 
of a Single Flower. 

Apocarpous Fruits. — 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 
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. 

Indehiscent Apocarpous Fruits, when formed of a single mature 
carpel, frequently contain only one seed, being thus monospermous (fiomg, 
one, and d'jrig/jita, seed). In some 
instances there may have been 
only one ovule originally, in /^^^BB, I 

others two, one of which has ^^ mlMk v^J-^iL-, 
become abortive. 

The Aclicenium (a, privative, 
and ^oilvat, 1 open) is a dry 
monospermous fruit, the pericarp 
of which is closely applied to the ^'g-. 559. Pig. seo. 

Fig. 559. Achjeniuiii or indehiscent monospermous carpel from the pistil of a Ranunculus. 
Pig. 660. 1, Similar aohsenium, with rough points on the pericarp, from the pistil of Ranun- 
culus muricatus. 2, Aehsenium cut transversely to fehow the seed, g, not adherent to the 
parietes. 




310 



INDEHISCENT APOCAEPOUS FEUITS. 



seed, but separable from it (fig. 559). It may be solitary, forming a 
single fruit, as in the Cashew (fig. 248 a, p. 173), where it is supported 
on a fleshy peduncle, p ; or aggregate, as in Eununculus (fig. 560), where 
several achaenia are placed on a common elevated receptacle. In the 
Strawberry the achsenia (fig. 434, p. 246) are placed on a convex 
succulent receptacle. In the Eose they are supported on a concave 
receptacle (fig. 294, p. 196), and in the Pig they are placed inside 
the hollow peduncle or receptacle (fig. 267, p. 180), which ultimately 
forms what is commonly called the fruit. In Dorstenia (fig. 266, p. 
180) the achenes are situated on a flat or slightly concave receptacle. 
In the Eose the aggregate achsenia, with their covering, are sometimes 
collectively called Gynarrhodum (xiwv, a dog, and ^odov, 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 
achsenia, in the form of feathery appendages, as in Clematis, where 
they are called caudate (cauda, a tail). 

In Compositse the fruit, which is sometimes called Gypsela (xu-^sXri, 
a box), when ripe, is an achaenium (fig. 301 t, p. 199). The calyx in the 




Fig. 661. 



Fig. 662. 



Fig, 663. 



Compositse sometimes becomes pappose, and remains attached to the 
fruit (fig. 303, p. 199), as in Dandelion and Thistles. A pappose 
calyx occurs also in some Dipsacacese (fig. 302, p. 199). When the 
pericarp is thin, and appears like a bladder surrounding the seed, the 
achsenium becomes a Utricle, as in Amarantacese. This name is often 

Fig. 661. Seed-vessel of Acer Pseudo-platanus (Sycamore, called in Scotland Plane), com- 
posed of two samaras or winged monospernious carpels united, d. Upper part forming a 
dorsal wing. I, Lower portion corresponding to tlie loculaments. Fig. 662. Samara 
taken from the fruit of Hirsea. s, Persistent style. I, Part corresponding to the locula- 
ment. a a. Marginal wing or ala. Fig. 663. Caryopsis of Secale cereale, Bye. 1, Entire. 
2, Cut transversely to show the seed adherent to the parietes of the pericarp. 



INDEHISCENT APOCAEPOUS FRUITS. 311 

given to fruits which differ from the achsenium in being composed of 
more than one carpel. When the pericarp is extended in the form of 
a winged appendage, a samara (samera, seed of Elm) or swmaroid 
actuenium is produced, as in the Ash (fig.- 533, p. 299), common Sycamore 
(fig. 561), and Hiraea (fig. 562). In these cases there are usually 
two achsenia united, one of which, however, as in Fraxinus oxyphylla 
(fig. 533), may be abortive. The Wing (fig. 561 a) is formed by the 
carpel, and is either dorsal, i.e. a prolongation from the median vein 
(fig. 561 a), or marginal, that is, formed by the lateral veins (fig. 
562 a). It surrounds the fruit longitudinally in the Elm. When 
the pericarp becomes so incorporated with the seed as to be inseparable 
from it, as in grains of Wheat, Maize, Eye (fig. 563), and other 
grasses, then the name caryopsis (xA^vov, a nut, and o'^ig, appearance) 
is given. 

There are some fruits which consist of two or more achsenia, at 
first ' united together, but which separate when ripe. Of this nature 
is the fruit of the Tropseolum or Indian Cress, also that of Labiatee 
and Boraginacese, which is formed of four achsenia attached to the 
axis (fig. 436, p. 247), 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 achsenia to single-seeded dehiscent peri- 
carps. The cremocarp (x^ifidu, I harig), or the fruit of Umbel- 
liferse (fig. 550, p. 306), is composed of two achsenia united by a com- 
missure to a common axis or carpophore (x.ag'jrog, fruit, and <pogiia, I 
bear), from which they are suspended at maturity. It is sometimes 
denominated diachmnium (dig, twice), from the union of two achsenia, 
which in this instance receive the name of mericarps (/^egos, part), or 
hemicarps {rfuevg, half, and x.ag'Trog, fruit). 

The Nut or Olans.- — 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 hush, and by the Acorn, in -tvhich the leaves or bracts 
are united so as to form a cupula or cup (fig. 281, p. 191). The parts 
of the pericarp of the Nut are united so as to appear one. In Sagus, 
or the Sago Palm, the nut is covered by peculiar tesselated epicarp, 
giving the appearance of a cone. 

The Drupe (drupm, 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 



312 DEHISCENT APOCARPOUS FEUITS. 

generally pulpy and succulent, so as to be truly a sarcocarp (ffaf|, 
flesh), as in the 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 per- 
fection. In the Walnut, the endocarp, which is easily separable into 
two, forms prolongations which enter into the interior, and cause the 
brain-Uke divisions in the seed. It has been sometimes called Tryma. 
In the Kaspberry and Bramble several drupes or drupels are aggre- 
gated so as to constitute an Etcerio (sra/gos, a companion). This name is 
also given by some to the aggregate achenes of the Strawberry and Eose. 
Dehiscent Apocahpotjs Feuits. — These open in various ways, 
and usually contain more than one seed, being either few-seeded, 
oligospermous {okiyog, few, and eiri^iia, a seed), or many-seeded, poly- 
spermous (woXue, many). 

Follicle {folliculus, a fittle bag). — This is a mature car- 
pel, containing several seeds, and opening by the ventral 
suture (figs. 539, p. 303 ; 564). It is rare to meet with a 
solitary follicle forming the fruit. There are usually several 
aggregated together, either in a circular manner on a short- 
ened receptacle, as in Hellebore, Aconite, Delphinium, 
Orassulaoese (fig. 282, p. 191), Butomus (fig. 415, p. 238), 
and Asclepiadaceee ; or in a spiral manner on an elongated 
receptacle, as in Magnolias, Banksias, and Liriodendron (fig. 
Kg. 664. 337^ p_ 213). Occasionally, some of the follicles open by the 
dorsal suture, as in Magnolia grandifiora and Banksia. 

The Legume or Pod {legwmen, pulse) is a solitary, simple, mature 
carpel, dehiscing by the ventral and dorsal suture, and bearing seeds 
on the former. It characterises leguminous plants, and is seen in the 
Bean and Pea (fig. 565). In the Bladder-senna (fig. 566) it retains 
its leaf-like appearance, and forms an inflated legume. In some 
Leguminosse, as Arachis and Cathartocarpus Fistula (fig. 429, p. 244), 
and the Tamarind, the fruit must be considered a legume, although it 
does not dehisce. The first of these plants produces its fruit under- 
ground, and is called earth-nut ; the second has a partitioned legume ; 
and both the second and third have pulpy matter surrounding the 
seeds. 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 difierent divisions of the pod separate from each other. This 
constitutes the Lomentum (lomentum, bean-meal) or lomentaceou^ legume 
of Hedysarum coronarium (fig. 556, p. 307), CoroniUas, Ornithopus, 
Entada, and some Acacias. In Medicago the legume is twisted like 
a snail (fig. 567), and in Csesalpinia coriaria, or Divi-divi, it is ver- 

Fig. 664. Foniole or dehiscent many-seeded carpel of AquUegla vtilgaris. Columbine. 
The follicle dehisces by the ventral suture only. 



INDEHISCENT SYNCAEPOUS FEUITS. 



313 



miform or curved like a ■worm ; in Oarmichaelia the valves give way 
close to the suture, and separate from it, leaving a division. 





Fig. 665. 



Fig. 686. 



Fig. 667. 



SYNCAEPotrs Fruits are formed by several carpels, which are 
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. 

Indbhiscent Syncaepous Fbuits. — The Berry (bacca) 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 
Grooseberry and Currant, in which the ovary is inferior, 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 superior, as in the Grape, Potato, and 
Ardisia, and the placentas are central or free central. The latter 
might be separated under the name Uva (grape). Jn general, the 
name of baccate or berried is applied to aU pulpy fruits. In the Pome- 
granate there is a peculiar baccate many-celled inferior fruit, 
having a tough rind, enclosing two rows of carpels placed above 

Fig. 565. 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 the pericarp, jj. The epicarp or external layer of the pericarp, 'p', Endocarp or internal 
layer. Between these the mesocBrp 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, sv. sd, The dorsal suture corresponding to the midrib of the 
carpellary leaf. Fig. 566. Legume of Bladder-senna {Colutm arboresc&ns), showing an in- 
flated, foliaceous pericarp. Fig. 567, Twisted or spiral legume of Medloago. 



314 



INDEHISCENT SYNCAEPOUS FBTJITS. 



each other. The seeds are immersed in pulp, and are attached 
irregularly to the parietes, base, and centre. The fruit has been 
called Balausta {halaustiwm, flower of pomegranate), and the tough 
rind is called malicorium (a name applied to it by Pliny). 

The Pepo or Peponida (nrivuv, a pumpkin) is illustrated by the 
fruit of the Gourd, Melon (fig. 430, p. 245), and other Oucurbitacese, 
where the calyx is superior, 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 calyx is not superior. 

The Eesperidium (golden fruit in the garden of Hesperides) is the 
name given to such fruits as the Orange, Lemon, and Shaddock, in 
which the epicarp and mesocarp form a separable rind, and the 
endocarp sends prolongations inwards, forming triangular divisions, in 
which pulpy cells are developed so as to surround the seeds which are 
attached to the inner angle. Both Pepo and Hesperidium may be 
considered as modifications of the Berry. 





Pig. 668. 



Fig. 669. 



The Pome (pomum, an apple), seen in the Apple, Pear, Quince, 
Medlar, and Hawthorn, is a fleshy fruit with the calyx attached, and 
has an outer skin or epicarp, a fleshy mesocarp, and a scaly or horny 
endocarp, the core enclosing the seeds. Some look upon the so-called 
epicarp and mesocarp as formed by the prolonged receptacle or torus 
with a fleshy lining ; whUe the endocarp represents the true carpels. 
In this view the endocarp might be regarded as consisting of a number 
of iniehiscent follicles (usually five) surrounded by a pulpy torus. In the 
Medlar the endocarp (or what may be called the true pericarp) is of a 

Fig. 568. Fruit of common Medlar (Mespilus germanica). Transverse section showing, e, 
epicarp; s, Sarcocarp; 71, Endocarp, forming stony coverings of tlie seeds. Tlie fruit has 
heen called nuculanium, and the hard central cells pyrense. In the Medlar, as well as in 
the Apple, Pear, and Quince, the fruit may he considered as composed of stony or parch- 
ment-lilie follicles, covered hy a pulpy disk. Fig. 569. Fruit of Comus mascula, com- 
mon Cornel, 1, Transverse section detaching the upper half of the fleshy portion, s, so as 
to show the central kernel, n. 2, Transverse section of the fruit through the central por- 
tion, TO, showing that it consisted of two loculaments. I, One of the loculaments empty, 
the other containing a seed, g. 



DEHISCENT SYNOARPOUS FEUITS. 315 

stony hardness, while the outer pulpy covering is open at the summit. 
The stones of the Medlar are called pyrence {m^rjv, the stone of fruit) ; 
some apply the term nuculanium (nucula, a nut) to the Medlar. Taking 
this view of the Pome it may be said to resemble the fruit^of the Eose, 
with this difference, that the Rose produces achenes, and the Pome 
closed foUioles. In Comus mascula (fig. 569, 1, 2) there are two stony 
ceUs, n, surrounded by the fleshy epicarp and mesocarp, and as they 
are close together, and one is often abortive (fig. 569, 2, I), there is a 
direct transition to the Drupe. 

Dehiscent Syncaepous Fruits. — The Capsule (capmla, a little 
chest). This name is applied generally to all dry syncarpous fruits, 
which open by valves or pores. The valvular capsule is observed in 
Digitalis (fig. 541, p. 304), Hibiscus esculentus (fig. 545, p. 304), 
Cedrela angustifolia (fig. 546, p. 304), Mahogany (fig. 547, p. 305), 
and Cerastium triviale (fig. 540, p. 303). The porose capsule is seen 
in the Poppy (fig. 444, p. 249), Antirrhinum majus (fig. 558, p. 308), 
and Campanula persicifdlia (fig. 557, p. 308). Sometimes the capsule 
opens by a lid, or by circumscissile dehiscence, and it is then called a 
Pyxidiwm (pyxis, a box), as in Anagallis arvensis (fig. 554, p. 307), 
Henbane (fig. 555, p. 307), and Monkey-pot (Lecythis). The capsule 
assumes a screw-like form in 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 the Sandbox tree 
(Hura crepitans), and other Euphorbiacese, where the cocci, containing 
• each a single seed, burst asunder with force (fig. 549, p. 305) ; and in 
GeraniacesB, where the cocci, each containing, when mature, usually 
one seed, separate from the carpophore, and become curved upwards 
by their adherent styles (fig. 551, p. 306). In the former case, the 
fruit collectively has been called Regma [griy/ia, a rupture). 

The Siliqua (siliqua, a husk or pod) (fig.' 552, p. 306) 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 parietal 
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 SiUcula. It occurs in cruciferous plants, as 
WaUflower, Cabbage, and Cress. The sUiqua 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 abortive. 
There are four bundles of vessels in it, one corresponding to each 
valve, which may be called valviila/r or pericarpial, and others running 
along the edge called placental. The replum consists of two lamellae. 



316 



CONFLUENT OK POLYGYNCEOIAL FETJITS. 



It sometimes exhibits perforations, becoming fenestrate {fenestra, a 
window). At other times its central portion is absorbed, so that the 
fruit becomes one-celled. 



Multiple or Polygynoecial Fruits which are the produce of 
several Flowers united. 



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 Honey- 
suckle. 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, Confluent, ot .Polygynoecial. The 
term Anthocarpous (at^os, a flower, %a,^ir6s, fruit) has also been applied 
as indicating that the floral envelopes as well as the carpels are con- 
cerned in the formation of the fruit. 

The Sorosis (ffwjo'e, a congeries or cluster) is a, confluent fruit 
formed by a united spike of flowers, which be- 
comes succulent. The fruit of the Pine-apple (fig. 
570) is composed of numerous ovaries, floral enve- 
lopes, and bracts, combined so as to form a succulent 
mass. The scales outside, cc, are the modified 
bracts and floral leaves, which, when the develop- 
ment of the fruit-bearing spike terminates, appear 
in the form of ordinary leaves, and constitute the 
crown, /. Other instances of a sorosis are the Bread- 
fruit and Jack-ftniit. 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, 
Easpberry, and Mulberry appear to be very like each other, but they 
differ totally in their structure. The Strawberry and 
Easpberry are each the produce of a siugle flower, the 
former being a succulent edible receptacle bearing achsenia 
on its convex surface ; the latter being a collection of 
drupes placed on a conical unpalatable receptacle ; while 
the Mulberry (fig. 571) is a sorosis formed by numerous 
flowers united together, the calyces becoming succulent 
and investing the pericarps. 

Syconus (aijxov, a fig) is a confluent anthocarpous fruit, 
in which the axis, or the extremity of the peduncle, is 

Fig. 570. Polygynoecial or confluent fruit of Ananaasa sativa. Pine-apple. Axis bearing 
numeiouB flowers, tlie ovaries of whicli are comMned with tlie bracts, c c, to form the fruit. 
/, Crown of the Pine-apple, consisting of empty bracts or floral leaves. Fig. 571. Antho- 
carpous fruit of the Mulberry, formed by the union of several flowers. The flOTal envelopes 
become succulent, and cover the pistil. 




Fig. 670. 




Fig. 671. 



CONFLUENT OK POLYGYNCECIAL FRUITS. 



317 



hollowed, so as to bear numerous flowers, all of which are united in one 
mass to form the fruit. The Fig (fig. 267, p. 180) is of this nature, 
and what are called its seeds are the achaenia or monospermal seed- 
vessels of the numerous flowers scattered through the pulpy hol- 
lowed axis. In Dorstenia (fig. 266, p. 180) the axis is less deeply 
hollowed, and of a harder texture, the fruit exhibiting often very 
anomalous forms. 

Strobilus (ffrgo^/'Xos, fir-cone) is a fruit-bearing spike more or less 
elongated, covered with scales (fig. 572), each of which represents a sepa- 
rate flower, and has often two seeds 
at its base. The scales may be 
considered as bracts, or as flattened 
carpeUary leaves or branches, 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, and W^^^^Kv Fig 573 

Cedars, which have received the 
name of Coniferee, or cone-bearers, 
on this account. The scales of the 
strobilus are sometimes thick and 
closely united, so as to form a more 
or less angular and rounded mass, 
as in the Cypress (fig. 573) ; while 
in the Juniper they become fleshy, 
and are so incorporated as to form 
a globular fruit like a berry (fig. 
574). Thejdry fruit of the Cypress, and the succulent fruit of the 
Juniper, have received the name of Galbulus (galbulus, nut of the 
cypress). The fruit of the Yew {Taxus baccata) is regarded as a cone 
reduced to a single naked seed, covered by succulent scales, which 
unite to form a scarlet fleshy envelope. In the Hop the fruit is called 
also a strobUus, but in it the scales are thin and membranous, and the 
seeds are not naked but are contained in pericarps. 

Fig. 572. Cone of Pinus sylvestris, Sootch Fir, consisting of numerous 1)13013 or floral 
leaves, eacli of wMoli covers two winged seeds. These seeds are called naked, in conse- 
quence of not being contained in an ovary, with a style or stigma. Pig. 678. Cone of 
Cupressus sempervixens. Cypress ; one of the Gymnospermous or naked-seeded plants, like 
the Pine. Fig. 674. Succulent cone or Galbulus of Juniperus macrocarpa. eeee. The 
different scales or bracts united so as to enclose the seeds. 




Fig. 672. 



Pig. 674. 



318 



TABULAK VIEW OF CAKPOLOGY. 



Tabular Abeangement of Pbttits. 

A. Simple or Monogynoecial Fruits formed by the gyncecium of a single flower, 
and consisting of one or more Carpels either separate or comhined ; thus 
including Apocarpous, Aggregate, and Syncarpous Fruits. 

I. Indehiscent Pericarps. 



1. Monospermal^usnaUy containing a single seed : 



Separable from the seed 



Achemia enclosed in a hollow fleshy torus, 
Inseparable from the seed 
Inflated 

Having a cupulate involucrum . 
. Having winged appendages ... 
Covered by a Pericarp, consisting of Epicarp, Saroocarp, ) j)j.^_g (cimny) 
and Endocaip. ) 

Drupe, with a two-valved Endocarp, having divisions extending from its 

inner surface, Tryma (Walnut). 
Aggregate Drupes, Stcerio (Easpberry). 



C Achaenium (Lithosper- 

mum). 
•{ Mericarp and Cremocarp 
I in Umbelliferse, and 
L Cypsela in Compositse. 

CyTmrrhodum (Rose). 

Caryopsis (Grasses). 

Utricle (Chenopodium). 

Glans (Acorn). 

Samara (Sycamore). 



2. Polyspermal — containing two or more seeds : 

' Ovary inferior. Placenta parietal, attachment | 
of seeds lost when ripe . . . ) 

attachment permanent, rind ) 

thick and hard j 

Peculiar berried many-celled fruit, with two i 
or more rows of Carpels . . . j 
Ovary superior. Placenta central 

Placenta parietal 

Having a spongy separable rind, and separable 
pulpy cells ...... 

( Endocarp horny, covered by a fleshy Mesocarp 
) and Epioarp formed by the disk . 
S Endocarp stony, covered by a fleshy Mesocarp 
( and Epicarp formed by the disk . 



t>» 


^ 


bO 


<o • 


E § 


=8 a 


.3 »- 


-S^ 


« p 


a ° 


g 


l-H 


■ -4-3 


niJ o 


s.g « 


o -3 pn 




H.g 



Bacca (Gooseberry). 
Pepo (Gourd). 

Balansta (Pomegranate). 

Uva (Grape). 
Papaw fruit. 

Hesperidium (Orange). 
Pome (Apple). 
Nuculanium (Medlar). 



Pi 
I- 



II. Dehiscent Pericarps. 

■ Opening by Ventral Suture only . . Follicle (Paeony). 

Opening by Ventral and Dorsal Suture . Legume (Pea). 

Lomentwm, a Legume separating into distinct pieces, each containing 
a seed (Ornithopus), a kind of Schizooarp. 
Opening by two valves which separate from a ) Siliqua (Cabbage). 

Central Eeplum or Frame 
Opening by Transverse or Circumscissile De- 
hiscence ...... 

Opening by several valves or pores, without ) 
Ventral or Dorsal Sutiire or Eeplum 
Capsule inferior 
A long pod-like Capsule . 
.Opening by separation of elastic Cocci 



SUioula (CapseUa). 
■ Pyxidium (Henbane). 

• Capsule (Poppy). 

Diplotegia (Campanula). 
Ceratium (Glaucium). 
Eegma (Hura). 



MATUEATION OF THE PBEICAEP. 319 

B. Polygnoecial or Multiple Fruits formed by the imion of several Flowers, and 
consisting of Floral Enyelopes, as well as Ovaries ;4 these are Anthocarpous. 

Hollow Anthocarpous Fruit. — Syconus (Fig). 

(formed by Indurated or ScalyCatkin. — Stro- 
bilus (Fir Cone and Hop), 
formed by Succulent Spike. — Sorosis (Bread- 
fruit, Mulberry, Pine-apple), OaUntlus 
(Juniper). 

Professor Dickson gives the following classification of Fruits (ma- 
ture pistils). 

1. Oapsule. Dry, dehiscent, allowing the seeds to escape — Capsule, Siliqua, 
Follicle, Legume, Regma, Diplotegia, Pyxidium, etc. , of authors. 

2. Schimcarp. Dry, breaking up into two or more, one- or few-seeded 
indehiscent pieces — Carcerulus {Malva, Tropceolvm, Lammm, etc.). Samara {Acer), 
Lomentum, Cremooarp, of authors. 

3. Achene. Dry, indehiscent, one- or few-seeded, not breaking up as the last 
— Achene, Caryopsis, Samara {Fraxdnus, etc.), Cypsela, Glans, of authors. 

4. Berry. Indehiscent. Seeds imbedded in pulp. Outer portion of variable 
consistence — Uva, Hesperidium, Amphisarca, Pepo, Balausta, Bacca, of authors. 

5. Drupe. Indehiscent. Seed or seeds inclosed by the distinctly defined and 
indurated endocarp. Outer portion of variable consistence (ileshy, fibrous, etc.) — 
Drupe, Tryma, Pome, of authors.* 

Where several distinct (apocarpous) fruits are produced from one flower ; the 
term Etoerio designates a collection of Achenes, Drupes or Follicles (?), upon a 
more or less convex receptacle ; and Gyna/nhodum a collection of Achenes upon 
the inner surface of a hollow succulent receptacle. 

Where the fruits from an inflorescence are massed together the whole forms a 
" confluent fruit." (a) Syconus — Achenes, upon a flat or hollow, dry or succulent 
axis of inflorescence, (i) Sorosis — Achenes, Drupes, or Berries, with succulent 
perianths, or succulent bracts, or both, upon a, more or less elongated axis of 
inflorescence ;' — Sorosis and Galbulus of authors, (c) Strobilus — Achenes, with 
dry bracts, and sometimes scale-like secondary peduncles, upon a more or less 
elongated axis of inflorescence. 

7. Matwration of the Pericarp. 

After fertilisation, 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 ofi', or remains attached as a 
hardened process or apiculum ; whUe the embryo plant is developed 
in the ovule. Certain fruits, such as Oranges and Grapes, are some- 
times produced without seeds. It does not appear, therefore, necessary 
fojr the production of fruit in all cases, that the process of fertilisation 

* The above classifloation is founded upon the idea that the definition or description of 
a fruit as such, should Involve the structwal modification undergone by the pistil iu ripen- 
ing, rather than the origin of the fruit from superior to inferior ovary, etc., which is to be 
imderstood or taken for granted, from the description of the immature pistil. From such 
a principle not being recognised, the terms indicating different fraits have been needlessly 
multiplied. 



320 MATURATION OF THE PEEICAEP. 

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 fuU 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 dis- 
appear altogether. 

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. 
Perennials, 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 is of importance to allow an aocumidation 
of sap to take place before the plant flowers. The wood should be 
well ripened. When a very young plant is permitted to bear fruit, it 
seldom brings it to perfection. When a plant produces fruit in very 
large quantity, gardeners are in the habit of thinning it early, in 
order that there ipay be an increased supply of sap to that which 
remains. In this way. Peaches, Nectarines, and Apricots, are ren- 
dered 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. 

The pericarp is at first of a green colour, and performs the same 
functions as the other green parts of plants, decomposing carbonic 
acid under the agency of light, and liberating oxygen. Saussure 
found by experiments that all fruits in a green state perform this pro- 
cess of deoxidation. As the pericarp advances to maturity, it either 
becomes dry or succulent. In the former 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 sometimes great hardness, when it is 
incapable of performing any active process of vegetable life ; in the 
latter it becomes fleshy in its texture,, and assumes various bright 
tints, as red, yellow, etc. In fleshy fruits, however, there is fre- 
quently a deposition of ligneous cells in the endocarp, 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 con- 
tents of the cells near the circumference of succulent fruits are thick- 
ened by exhalation, and a process of endosmose goes on, by which the 
thinner contents of the inner cells pass outwards, and thus cause 
sweUing of the fruit. As the fruit advances to maturity, however, 
this exhalation diminishes. In all pulpy fruits which are not green 
there are changes going on by which carbon is separated in combina- 
tion with oxygen. 



MATURATION OF THE PEKICAEP. 321 

Dry fruits may remain attached to the tree for some time before 
they are fully ripe, and ultimately separate by disarticulation. 
Occasionally, ■when the pericarp is thick, it separates in layers like the 
bark. Succulent fruits contain a large quantity of water, along with 
cellulose, 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, 
containing pectose, the characteristic constituent of unripe fruits. 
This substance is quite insoluble in water, but during the ripening of 
the fruit it is converted by the vegetable acids into pectine, which is 
soluble in water, and exists in the pulp of fruits, as Apples, Pears, 
Gooseberries, Currants, Raspberries, Strawberries, etc. This substance 
undergoes a further change, being converted into pectic acid 
(Q16 JJ22 Qis) and pectosic acid (0=^ H« O'^). These are easily soluble 
in boiling water and gelatinise on cooling (•s-jjzro's, congealed) ; hence 
their 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. 
Oily matters are also found in the cellular tissue of many fruits. Thus, 
a fixed oil occurs in the Olive, and essential oils in the Orange, Lemon, 
Lime, Eue, Dictamnus, etc. 

During ripening much of the water disappears, while the cellulose, 
lignine, and the dextrine, are converted into sugar. Berard is of 
opinion that the changes in fruits are caused by the action of the 
oxygen of the air. Fremy found that fruits covered with varnish did 
not ripen. As the process of ripening becomes jierfected the acids com- 
bine with alkalies, and thus the acidity of the fruit diminishes, whUe 
its sweetness iacreases. The formation of sugar is by some attributed 
to the action of organic acids on the vegetable constituents, gum, dex- 
trine, and starch ; others think that the cellulose and lignine are 
similarly changed by the action of acids. The sugar of fruits is grape 
or starch sugar, called also Glucose. Its formula is C H" 0'. In the 
Grape, when young, there is abundance of tartaric acid ; but as the 
fruit advances to maturity 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. 

The following analysis of the Cherry in its unripe and ripe state, 
as given by Berard, exhibits generally the chemical composition of suc- 
culent fruits : — 



322 



MATURATION OF THE PEKICAEP. 





Unripe. 


Eipe. 


Chlorophyll 


. 0-05 


• 


Sugar 


. 1-12 


18-12 


Gum or dextrine 


6-01 


3-23 


Cellulose . 


. 2-44 


1-12 


Alhumen , 


. 0-21 


0-67 


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 : — 





Water. 


Sugar. 


Cellulose. 




Unripe. 


Ripe. 


Unripe. Bipe. 


Unripe. 


Eipe. 


Apricot . 


. . 89-39 


74-87 . 


. 6-64 16-48 . 


. 3-61 


1-86 


Peacli 


. . 90-31 


80-24 . 


. 0-63 11-61 . 


. 3-01 


1-21 


Chen-ies . 


. . 88-28 


74-85 . 


. 1-12 18-12 . 


. 2-44 


1-12 


Plums 


. . 74-87 


71-10 . 


. 17-71 24-81 . 


. 1-26 


1-11 


Pears 


. 86-28 


83-88 . 


. 6-45 11-52 . 


. 3-80 


2-19 



It is not easy in all cases to determine the exact time when the 
fruit is ripe. In dry fruits, the period immediately before dehiscence 
is considered as that of maturation ; but, in pulpy fruits, there is much 
uncertainty. It is usual to say that edible fruits are ripe when their 
ingredients are in such a state of combination as to give the most 
agreeable flavour. This occurs at difierent periods in 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 hUtting (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 oxi- 
dation the whole fruit is ultimately reduced to a putrefactive mass, 
which probabl^acts beneficially in promoting the germination of the 
seeds when the fruit drops on the ground. 

The period of time required for ripening the fruit varies in dif- 
ferent 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 Coniferae, 
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 time required for the maturation of different 
kinds of fruit : — 



EFFECT OF GRAFTING ON FEUITS. 323 

Grasses 13 to 45 days. 

Easpterry, Strawberry, Cherry 2 months. 

Bird-cherry, Lime-tree . . . . . , 3 ,, 
Roses, White-thorn, Horse-chestnut . . . . 4 ,, 
Vine, Pear, Apple, Walnut, Beech, Plum, Nut, Almond, 5 to 6 , , 

Olive, Savin 7 ,, 

Colohicum, Mistleto 8 to 9 ,, 

Many Conifers 10 to 12 ,, 

Some Coniferae, certain species of Oak, Metrosideros, ahove 12 ,, 

The ripening of fruit 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. It has been observed 
that plants subjected to a high temperature not unfrequently prove 
abortive, ■which seems to result from the over-stimulation causing the 
production of unisexual flowers alone. Trees are sometimes made to 
produce fruit by checking their roots when too luxuriant, and by 
preventing the excessive development of branches. 

Geafting. — A very important benefit is produced, both as regards 
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 aflBnity between the 
graft and the stock as regards their sap, etc. 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. Fortune gives an instance in the Punjaub 
of a Peach growing out of an old Mango tree about six or eight feet 
from the ground. In this case the Peach had its roots in the ground, 
and had grown through the hollow stem of the Mango. In India the 
Peepul tree (Ficus religiosa) occasionally grows on the stumps of other 
trees, and sends its roots down so as to cover the stump completely, 
and thus presents the appearance of two kinds of trees growing from 
one root. By grafting the branches of hedge plants together good 
fences are occasionally formed (see drawing of such hedges and trees, 
Trans. Bot. Soc. Edin., vol. x. p. 452). 

The object which gardeners wish to secure by grafting, is the 
improvement of the kinds of fruit, the perpetuation of good varieties, 



324 DIFFERENT MODES OF GRAFTING. 

which could not be procured from seed, and the hastening of the period 
of 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 time to its tendency to produce leaves. 
Although the general law is, that grafting can only take place between 
plants, especially trees, of the same family, there are certain exceptions. 
Loranthaceous parasites can form a union with genera in different orders. 

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 had been taken. In this way he 
endeavoured to account for the supposed extinction of some valuable 
varieties of fruit, 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, and tubers, 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 propa- 
gated 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 Achimenes by scaly bodies like tubers. 
The fruits, moreover, which Mr. Knight thought had disappeared, 
such as Eed streak. Golden pippin, and Golden Harvey, still exist, and 
any feebleness exhibited by them 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 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 many 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 con- 
stitutional energy than that taken from a vigorous stock. 

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. 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 con- 
tinued vigour of the stump of Spruce-trees cut down on the Swiss 
mountains. This natural grafting of roots has been observed in the 



DIFJfEEENT MODES OF GKAJFTING. 325 

White Pine (Abies pectinata), and sometimes in the Red Pine (Ahies 
&xelsa), as well as in the Scotch Fir {Pinus syhestris) and the Larch 
(Larix europcea). 

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. Whip- 
grafting or tongue-grafting is performed by inserting a tongue or cleft- 
process of the stock between the lips of a cut in the scion. Side-grafting 
resembles whip-grafting, but it is performed on the side of the stock 
without heading it down. Sometimes several slips are placed in a 
circular manner round the inside of the bark of the stock by crovnv- 
grafting ; or the bark of a portion of tfie stock is removed, and that of 
the scion is hoUowed 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 the plants, but herbaceous parts may also be united in this way. 
The graft and stock are secured by clay, or by bees'-wax and taUow, 
or by Indian rubber, gutta percha, or collodion. 

By grafting, all our good varieties of apples have been produced 
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 eSect on the 
stock. Slips taken from plants with variegated leaves, and grafted on 
others with non-variegated leaves, have sometimes caused the leaves of 
the latter to assume variegation, and the eifect, when once established, 
has continued even after the slip was removed. The effects of grafting 
are well seen in the case of the Red Laburnum, when united to the 
YeUow species. The Red Laburnum is a hybrid between the common 
Yellow Laburnum and Cytisus purpureus (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 Fertilised Ovule arrived at Maturity. 

I 

While the pistil undergoes changes consequent on the discharge 
of the pollen on thfe stigma, and ultimately becomes the fruit, the 



326 SEED OR MATURE OVULE. 

ovule also is transformed, and, when fully developed, constitutes the 
seed. After fertilisation, the foramen of the ovule contracts, the 
young plant gradually increases in its interior, by the absorption of 
the fluid matter contained in the sac of the amnios (embryo-sac), 
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 append- 
ages. When ripe, the seed contains usually a quantity of starchy 
and ligneous matter, azotised compounds, as caseine and vegetable 
albumen, oily and saline matters. It sometimes acquires a stony 
hardness, as in the case of the seed of Phytelephas macrocarpa, which 
yields vegetable ivory. Oare'must be taken not to confound seeds 
with single-seeded pericarps, such as the Achsenium and Caryopsis, in 
which a style and stigma are present ; nor with bulbils or bulblets, 
as in Lilium bulbiferum and Dentaria bulbifera, which are germs or 
separable buds developed without fecundation. 

Seeds are usually enclosed in a seed-vessel or pericarp, and hence 
the great mass of flowering plants are called angiospermous (ayyoz, or 
ayyitov, a vessel, and dncigiho,, a seed). In Ooniferae and Oycadacese, 
however, the seeds are generally looked upon as having 
no true pericarpial covering, and fertilisation therefore 
takes place by the direct application of the poUen 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 gymnospermous 
Hg. 676. (yu/ii/oj, naked, and g<?rig/ia, a seed). Occasionally, by 
the early rupture of the pericarp, seeds originally covered become 
exposed. This is seen in Leontiee and Cuphea. In Mignonette, the 
seed-vessel (fig. 575) opens early, so as to expose the seeds, which 
are called seminude. 

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 or covering of the nucleus, the secundine, 
and the primine. In fig. 576 there is a representation of the seed of 
Nymphsea alba, in which se indicates the embryo-sac, containing the 
embryo, e; n, the cellular farinaceous covering (quartine), formed 
round the embryo-sac ; mt, membrane formed round the nucleus 
(tercine) ; mi, 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 

s ; Kg. 675. Fruit or capaule of Mignonette (SeseiZa odarata), opening early, so that the 
ovules become seminude. 




SEED OK MATUEE OVULE. 



327 




in the secundine, so tliat in the ripe seed, all that can be detected is 
the embryo with two coverings. The general 
coveruig of the seed is called spermoderm 
(<S'7tsg/ji,a, seed, and S's^fj,a, covering). In 
order to correspond with the name applied 
to the covering of the fruit, it ought more 
properly to be denominated perisperm {•jrigi, 
around, and dvig/na, seed). This latter 
term, however, has been appropriated to 
a certain portion of the seed, to be after- 
wards noticed under the name of albumen. 

The Speemodbem usually consists of 
two parts an external memlrane, called the 
episperm or testa [siri, upon, or on the out- 
side, and (svigfia, a seed ; testa, a shell), and 
an internal membrane, called endopleura (hSoii, 
within, and -rXsuga, side or rib). The former 
may consist of a union of the primine and 
secundine, or of the primine only, when, as 
occasionally happens, the secundine is ab- 
sorbed; the latter, of a combination be- 
tween the membrane of the nucleus and the 
embryo-sac, or of one of these parts alone, 
remains distinct in the seed, forming what has been called a mesosperm 
(fieeog, middle) ; and when it assumes a fleshy character, it has re- 
ceived the name of sarcosperm or sarcoderm (cajf, flesh). 

The Epispeem consists of cellular tissue, which often assumes 
various colours, and becomes more or less hardened by depositions in 
its interior. In Abnis precatorius and Adenanthera pavonina it is 
of a bright red colour ; in French beans it is beautifully mottled ; iu 
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 CoUomia, Acan- 
thodium, and other seeds, it contains spiral cells, from which, when 
moistened with water, the fibres uncoil in a beautiful manner. Spiral 
cells are also seen in the episperm of the seeds of Oobsea and' Calem- 
pelis soaber. In the episperm of the seed of Ulmus campestris the 
cells are compressed, and their sinuous boundaries are traced out by 
minute rectangular crystals adhering to their walls. 

Fig. 676. Young seed of Nymphsea alta cut vertically. /, Fuuioulua or umbilical cord, 
a, Arillus derived from the placenta, r, Eaphe. c, Chalaza or cotyledonary end of the 
seed. Ji, Hilum or base of the seed, m, Micropyle or foramen. (, Testa or primine. mi, 
Secundine. mt, Terbine or membrane of the nucleus, n, Farinaceous external perisperm 
or albumen formed by the nucleus, and probably constituting the quartine of Mirbel. se, 
se. Internal perisperm or endosperm formed by the embryo-sac. e. The embryo. 



Fig. sra. 
Sometimes the secundine 



328 



SEED OR MATURE OVULE. 



The Endopleuea 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 Nymphsea, Zingiber, Piper, etc., it forms a covering to 
which the name of vitellus (vitellus, yolk of an egg) was given by 
Gsertner. 

Aeillxjs. Sometimes there is an additional covering to th'e seed, 
derived from an expansion of the funiculus or placenta after fertilisa- 
tion, to which the name arillus has been given. This is seen in the 







Pig. 677. 

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, constituting, 
in the former case, the substance called mace ; and, in the latter, the 




Fig. 678. 

bright scarlet covering of the seeds (figs. 577, 578). In such instances 

Fig. 577. 1, 2, 3, 4, Various states of the arillus of the spindle-tree (Euonymus). The 
figures show the mode in which it is developed from the edges of the foramen, a a a a, Aiil- 
lode. ////, Foramen or Exostome. 

Fig. 578. Development of the same aiillus, a, around the ovule, o, exhibited in a different 
position. 1, 2, 3, 4, are foxir successive stages of development. In fig. 4 the arillus has been 
cut vertically to show its relation to the ovule, which it surrounds completely. 




SEED OR MA.TUEB OVULE. 329 

it has been called by some an arillode. This arillode, after growing 
downwards, may be reflected upwards, so as to cover the foramen. 

On the testa, at various points, there are pro- „ 

duced at times cellular bodies, which are not 
dependent on fertilisation, to which the name of 
strophioles (strophiolum, a little garland), or car- 
mioales {caruncula, a little piece of flesh), has been 
given, the seeds being strophiolate 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. 579 c), or they may occur in the 
course of the raphe. ^'s- ^'^^■ 

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 sus- 
pendrog it from the follicle. The point of the seed by which it is 
united to the cord, or the soar left on its separation, is called the hilwm 
or umbilicus, and represents its base. The hilum frequently exhibits 
marked colours, being black in the Bean, white in many species of 
Phaseolus, etc. It may occupy a small or large surface, according to 
the nature of the attachment. In the Calabar bean and in some 
species of Mucuna and Dolichos it extends along a large portion of the 
edge of the seed. The part called the foramen in the ovule becomes 
the micropyle (/iix^og, small, and ■ruX>i, gate) of the seed, with its 
exostome and endostome. This may be recognisable by the naked eye, 
as in the Pea and Bean tribe. Iris, etc., 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 
called emiryotega (tego, I cover). The flbro-vascular bundles, from the 
placenta pass through the funiculus and reach the seed, either entering 
it directly at a point called the omphalode (ofi,(paX6g, navel), which forms 
part of the hilum, or being prolonged between the outer an,d inner 
integument in the form of a raphe Qdip^, a seam), and reaching the 
chalam (■^dXal^a, a pimple or tubercle), or organic base of the nucleus, 
where a swelling or peculiar expansion may often be detected, as in 
Crocus. In fig. 576 the spiral vessels, r, are seen entering the cord, /, 
passing through the hilum, h, forming the raphe, r, between the testa, i, 
and endopleura, mi, and ending in the chalazal expansion, c. So also 

Kg. 679. Vertical section of a carpel of Bioinus communis, and of the seed which it 
contains, a. Pericarp. I, Looulament. /, Funiculus or umbilical cord, t. Integuments of 
the seed, having at their apex a caruncula, c, which is traversed hy the small canal of the 
exostome. The exostome does not correspond exactly with the endostome, which is imme- 
diately above the radicle, r, Eaphe. cS., Chalaza, p. Perisperm or albumen, the upper 
portion of which only is seen, e, Embryo, vnth its radicle, er, and its cotyledons, ec. 




330 SEED OR MATURE OVULE. 

in fig. 577, where / is the funiculus, r the raphe united to the hilum, 
and chalaza, c, whence vessels, n, penetrate the seed. In some seeds, 
as Narthecium ossifragum, the vessels are said not to appear tUl after 
fertilisation, and in Habenaria viridis none have been detected. The 
chalaza is often of a dififerent colour from the rest 
of the integuments. In the Orange it is of a reddish- 
brown colour, and is easily recognised at one end of 
the seed when the integuments are carefully removed. 
Sometimes, however, its structure can only be recog- 
nised by careful dissection. It indicates the cotyle- 
donary extremity of the embryo. The hilum and 
Pig. 680. chalaza may correspond, or they may be separated 
from each other and united by the raphe (fig. 580). The raphe is 
generally on the side of the seed next the ventral suture.' 

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 (ogSoi, 
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 
(xafi^'ri'Kog, 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 (avargs'Tna, I reverse).* 

The position of the seed as regards the pericarp resembles that of 
the ovule in the ovary, and the same terms are applied — erect, ascend- 
ing, pendulous, suspended, curved, etc. (figs. 459, 460, 461, 462, 456, 
pp. 257, 255). 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 hack. Seeds exhibit great varieties of forms. 
They may be flattened laterally, compressed; or from above downwards, 
depressed. They may be round, oval, triangular, polygonal, rolled up 
like a snaU, as in Physostemon; or coUed up like a snake, as in 
Ophiocaryon paradoxum. 

The object of fertilisation is the formation of the embryo in the 
interior of the seed. In general, one embryo is produced, constituting 
what is denominated monembryony (fiSvog, one) ; but in ConiferiB, 
Cycadaceae, Mistleto, etc., there are frequently several embryos, giving 

Hg, 580. Seed of the Hazel. /, Funiculus, r, Baphe. c, Chalaza. n. Veins spreading 
in a radiating manner over the integuments of the seed. 

* See pp. 266, 266, where these terms are more fully explained when treating of the ovule. 



SEED OB MATURE OVULE. 



331 



rise to what is called ■polyemhryony {vo'khg, many). Sometimes two 
embryo^ become united together in the same seed. In the coniferous 
seeds numerous corpuscles are seen, whence the embryos proceed. The 
process of fertilisation 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. 576, e is the embryo, and se the embryo-sac. 
In this sac there is at first a protoplasm, in which cells are developed. 
The embryonic cell (fig. 581 v), still attached to the sac by its suspensor, 
s, contains distinct nucleated cells (fig. 581, 2 e). These gradually 
multiply, and form at length a cellular mass, at first undivided 
(fig. 581, 3 e), but afterwards showing a separation of parts, so that the 
axis and lateral projections or rudiments of leaves can be distinguished. 



582. 



684. 




Fig. 681. 



Fig. 683. Fig. 686. 



Fig. 587. 



In figs. 582 to 587 all the stages of the formation of embryo can be 
traced; appearing first as a simple cell (figs. 582, 584), forming others 
in its interior (figs. 585, 586) ; and finally, the parts of the embryo 
becoming visible, figs. 583, 587, where g r \s the axis representing the 
stem and roots, and e'e are the lateral projections, which are developed 
as leaf-like bodies, called cotyledons (KorSXtiSiiv, the name of a plant 
having leaves like seed-lobes). 

Peeispeem oe 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 

Fig. 581. First development of the embryo of Draba verna. o, Suspensor, wbicli in this 
plant is very long, v. Embryonic or germinal vesicle, e, Embryo. 1, First siage, in which 
the embryonic vesicle only is seen. 2, Second stage, showing several cells formed in the 
embryonic vesicle. 8, Third stage, in which the embryo becomes more conspicuous in 
consequence of the formation of numerous small cells. Fig. 582. Monoootyledonous 

embryo of Potamogeton perfoliatus in its early stage, appearing as a vesicle or simple ceU. 
Pig. 583. The same, further advanced, showing radicle, r, gemmule or plumule, g, and the 
cotyledon, c. Fig. 584. Dicotyledonous embryo of (Enothera crassipes in its early stage, 
appearing as a vesicle or cell. Fig. 585. The same, further advanced, showing three 
united utricles or cells. Fig. 686. The same, more developed, showing numerous cells. 
Fig. 687. The same in a more developed state, showing radicle, r, gemmule, g, and cotyle- 
dons, cc. 



332 



PEEISPEEM OE ALBUMEN OF THE SEED. 



integuments and embryo alone. In Santalum, Osyris, and Loranthus, 
Griffith says the ovule is sometimes reduced entirely to a sort of 
embryonary 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 encroaching slightly on the cells of the nucleus. The cells sur- 
rounding the embryo then become filled with a solid deposit called 
albumen, consisting of starchy, oily matter, and nitrogenous compounds. 
To this some have applied the term perisperm (tiiI, around, and eiri^f/.a, 
seed); others, that of endosperm {tvbov, within). The name, perispermic 
■albumen, or perisperm, is often restricted to that found in the cells of 
the nucleus alone, outside the embryo-sac (fig. 576 n) ; endospermic 
albumen, or endosperm, to that found within the embryo-sac alone 
(fig. 576 se), as in Chelidonium majus, Eanunculacese, Umbelliferse, 
and in many Endogens, etc. Sometimes both kinds of albumen occur 






Fig. 689. 



Fig. 590. 



in the same seed, as in Nympheeaceae and Piperacese. In some instances 
the albumen is produced in the region of the chalaza. In some Scrophu- 
larias the 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 exaUmminous (ex, without), 
as Oompositse, Cruciferse, 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. 588 to 590 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 hUum, and c the chalaza. In fig. 588 the embryo is 

Fig. 588. Anatropal mature seed of Helleborus niger, cut TerticaUy. The embryo, c, is 
small, as compared with the perisperm or albumen, p. t, Spermoderm or coverings of the 
seed. /, Funiculus, h, Hilum. c, Chalaza. Fig. 689. Matm'e seed of Diphylleia peltats, 
showing an embryo, e, which occupies a larger portion of the seed than in fig. 588. Letters 
indicate the same parts as in the previous figure. Fig. 590. Ripe seed of Berberis vulgaris, 
exhibiting a larger embryo, e, as compared with the perisperm, p. Letters as in figs. 588 
and 589. 



PEEISPEEM OE ALBUMEN OF THE SEED. 



333 



minute, and occupies only a small part of the apex of the albumen; ia 
fig. 589 it is larger, and has encroached on the perisperm ; while in 
fig. 590 it is still more developed, much of the albumen having been 
absorbed. 

The albumen varies much in its nature and consistence, and fur- 
nishes important characters. It may be farinaceous or mealy, consisting 
chiefly of cells filled with starch (fig. 591), as in Cereal grains, where 
it is abundant ; flesh%j or cartilaginous, consisting of thicker cells which 
are still soft, as in the Coco-nut, and which sometimes contain oil, as 
ia the oily albumen of Croton (fig. 592), Ricinus, 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 in 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 Anonacese, and some Palms (fig. 593), where it is called 
ruminated. This mottled appearance depends often on the endopleura 






Kg. 591. 



Fig. 592. 



Fig. 693. 



or iuner 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. 

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 
hulk of the seed, weighing many ounces, while the embryo is minute, 
weighing a few grains, and lies in a cavity at one extremity. In OoSee 
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 homy albumen of 
this Palm, as weU as in that of the Attalea funifera, the Date, and the 
Doom Palm, the concentric deposition of secondary layers, leaving a 

Kg. 591. Section of a smaU portion of the farinaceous perisperm or albumen of Zea 
Mais, Indian com. otc. Cells. ///, Grains of starch in the cells. Kg. 592. Section 
of a small portion of the oily perisperm or albumen of Croton Tiglium. c c c c, Cells. AAA, 
Drops of oil contained in the cells. Fig. 593. Vertical section of the fruit of Areca 
Catechu, c, Perianth. /, Pericarp, p, Ruminated perisperm or albumen, e. Embryo. 



334 



PAETS OF THE EMBKYO PLANT. 



small cavity in the centre of the cells, and radiating spaces uncovered 
with thickening matter, is well seen under the microscope. 

The embryo consists of cotyledons or rudimentary leaves, the 
'plumule (plumula, a little feather), or gemmule (gemma, a bud), repre- 
senting the ascending axis, radicle (radix, root), or the descending 
axis, and their point of union the collum, collar or neck ; that part of 

Othe 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 dif- 
Fig. 594. ferent divisions of the vegetable kingdom. In acrogenous and 
thallogenous plants it continues as a cell or spore, with granular matter 
in its interior (fig. 594), without any separation of parts or the produc- 




Fig. 696. 



Fig. 696. 



Fig. 597. 



tion of cotyledons. Hence these plants are called acotyledonous (ol privar 
tive, %orDX>)5w»). Endogenous and Exogenous plants, on the other hand, 
exhibit a marked separation of parts in their embryo, the former 
having one cotyledon, and hence being monocotyledonous (//lovog, one) ; 
the latter two, and hence dicotyledonous (Sis, twice). Thus, the 
whole vegetable kingdom is divided into three Classes Ijy the nature 
of the embryo, the first of which classes corresponds with the 
cryptogamic division of plants, the second with the endogenous 
division of phanerogamous or flowering plants, the third with the 
exogenous division of the same. Fig. 595 represents a monocotyle- 
donous embryo, with its cotyledon, c; while figs. 596 and 597 exhibit 
a dicotyledonous embryo, with its cotyledons, c c. 

The Spore of acotyledonous plants (fig. 594) is a cellular body. 

Fig. -694. Acotyledonous embryo of Marchantia polymorplia. Such embryos bear the 
Dame of spores. Fig. 595. Monocotyledonous embryo of Potamogeton perfoliatus nearly 
mature, r, Radicle, t, Caulicule or tigellus. c, Cotyledon, g, Gemmule or plumule. 
Fig. 696. Mature dicotyledonous embryo of the common Almond, r, Radicle or young 
root. Fig. 597. The same, with one of the cotyledons removed, r. Radicle, t, Tigelle or 
caulicule. c, One of the cotyledons left, ic. Cicatrix left at the place where the other 
cotyledon was attached, g, Gemmule composed of several smaU leaves. 



PARTS OF THE EMBRYO PLANT. 335 

from which a new plant is produced. Germination takes place in 
any part of its surface, and not from fixed points. It sometimes 
presents filaments or vibratUe cUia on its surface (figs. 467-470, p. 
265), by means of which it moves about in fluids, like some of the 
Infusoria. When it germinates, these cUia disappear. Sometimes 
spores are united in definite numbers, as in fours, surrounded by a 
cellular covering, or perispore {•rri^i, around, and a'Tto^a, offspring), or 
sporidium, and thus forming the reproductive body called a tetraspore 
(rsT^Ag, four), which is common in Algse (fig. 482, p. 273). 

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 
former indicating the point whence the young root or radicle is to 
proceed, and the latter that whence the leafy stem is to arise. The 
part which produces the first leaves or cotyledons is called the cotyle- 
donary extremity of the embryo, while the other is the radicular 
extremity. The radicular extremity is thus continuous with the 
suspensor, and consequently points towards the micropyle (fig. 590 h), 
or the summit of the nucleus, an important fact in practical botany ; 
while the cotyledonary, being opposite, is pointed towards the base of 
the nucleus or the chalaza (fig. 590 c). Hence, by ascertaining the 
position of the micropyle and chalaza, the two extremities of the. 
embryo can in general be discovered. In some rare instances, in 
■consequence of a thickening in the coats of the seed, as in Eioinus 
(fig. 579, p. 329), and some other Euphorbiacese, there is an alteration 
in the micropyle, so that the radicle does not point directly to it. 

The part of the axis which unites the radicle and the cotyledon 
or cotyledons is denominated caulicule or tigelle (figs. 595 i, 597 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 ordo, 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. 597 
the embryo of the Almond exhibits the 
gemmule, g, lying on one of the cotyledons, 
the other having been removed and leaving 
a cicatrix, ic ; while in fig. 595 the gem- 
mule, g, of Potamogeton perfoliatus is 
covered by the single cotyledon, c. 

The gemmule as well as the cotyledon 
are sometimes obscurely seen. Thus in ^z- 698. Kg. 599. 

Fig. 698. Spiral embryo of Cusouta or Dodder. Fig. 699. Embryo of Caryocar buty- 
rosum. *, Thick tigelle or caulieule, 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. 




336 MONOCOTYLEDONOUS EMBRYO. 

Cuscuta (fig. 598) the embryo appears as an elongated axis without 
divisions ; and in Caryocar butyrosum (fig. 599) the mass of the embryo 
is made up by the radicular extremity and tigelle, t, in a groove of 
which, s, the cotyledonary extremity lies embedded, which when 
separated, as in the figure, shows only very small cotyledons. In 
some monocotyledonous embryos, as in Orchidaceee, it requires a micro- 
scopic examination to detect the cotyledonary leaf. 

Monocotyledonous Embryo. — In this embryo the single coty- 
ledon in general encloses the gemmule at its lower portion, and 
exhibits on one side a small slit (fig. 600 /), 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. 600). At first sight there seems to be no dis- 
tinction of parts ; but on careful examination, by moisten- 
ing the embryo, and making a vertical section, there wUl 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. 595 t r, 
"■ 600 r), which may be said to represent both the tigelle 

^' ■ and radicle. The upper portion or chalazal end of the 
embryo is the cotyledon (figs. 695, 600 c), which is sheathing at its 
base, so as to enclose the gemmule. In some cases, as in the com- 
mon oat [Avena sativa), there is a peculiar process which covers the 
plumille, and which is considered by some as an axillary stipule of 
the cotyledon. 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 macropodous embryo (/laxgog, 
long, and 'nroug, a foot). Thus, in fig. 601, t represents the long radi- 
cular 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 an enlarged mammHlary 
projection, whence the rootlets (adventitious roots) proceed , by 
bursting through it, and carrying with them a covering or sheath, 
coleorhiza (fig. 105, p. 42). 

When considering endogenous or monocotyledonous stems, it was 
shown that the leaves are produced singly and alternately, in a 
sheathing manner, each embracing the subsequently developed bud. 
So it is in the monocotyledonous embryo. There is a single leaf or 
cotyledon produced, and if in any instance there is more than one, it 

Kg. 600. Embryo of TriglooUn Barrelieri. r, Badicle. /, Slit corresponding to the 
gemmnle. c, Cotyledon. 



DICOTYLEDONOUS EMBEYO. 337 

is alternate - with the first formed. In the Oat an abortive organ 
called the epihlast (^XadTog, a shoot) is produced, which may be con- 
sidered a rudimentary second cotyledon. 
The cotyledon (fig. 600 c) is fi)lded either 5^ 

partially, as in Dioscorea, or completely. 
Its sheathing portion (vagina) embraces the 
bud or gemmule, which appears as a mam- 
miUary projection ; its position being indi- 
cated by a cleft or slit (fig. 600/, p. 336), 
where the edges of the sheath unite. All the 
portion of the embryo above the gemmule 
is the cotyledon ; all bfelow, the radicle. 

Dicotyledonous Embeyo. — 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. 596) 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. 597), leaving 
scars, ic, the gemmule or plumule, g, is 
seen included between them, with its cauli- 
cule or tigelle, t. 

The cotyledons are not always, however, 
of the same size. Thus, in a species of 
Hirsea (fig. 602), one of them, c', is smaller 
than the other; and in Carapa guianensis 
(fig. 603) there appears to be only one, 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 em- 
bryos have been called psmio-monocotyle- 
donous (-^/ivdrjg, false). When there are 
two cotyledons, they are opposite to each 
other. In some cases there are more than two present, and then 



_— / 



Kg. 601. S i 



Fig. 601. MonoGotyledonouB 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. Cotyledon, g, Gemmule or plumule. ; 

Z 



338 



DICOTYLEDONOUS EMBEYO. 



they become verticillate. This occurs in Coniferse, especially in the 
Pir (fig. 604), Spruce, and Larch, in which six, nine, twelve, and even 
fifteen have been observed. In such cases it is probable that the 
cotyledons are split by collateral chorisis, and thus divided into 
several. 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 denominated polycoty- 
ledonous. Duchartre thinks that the multiple cotyledons of the Pirs 





Fig. 604. 

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 Pkius Pinaster and excelsa. Thus, the arrangement 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. In Welwitschia there are two coty- 
ledons which last throughout its life (more than a century), and in the 
course of time they grow to an enormous size, being sometimes six 
feet long and two or three in breadth. They constitute the only 
leaves of the plant. In species of Streptocarpus the cotyledons are 
also permanent and act the part of leaves. One of them is frequently 
largely developed, while the other is small or abortive. 

The texture of the cotyledons varies. They may be thick, as in 
the Bean, exhibitiag only slight traces of venation, with their fiat 
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 

Fig. 602. Embryo of Hirsea Salzmanniana, cut vertically, to show^the inequality of the two 
cotyledons, one of which, c, forms almost the whole mass of the embryo, c*, The small coty- 
ledon, g, Gemmule or plumule, r, Eadicle. Fig. 603. Bmbiiyo of Carapa guianensis, cut 
vertically to show the union of the cotyledons, the distinction between which is only 
indicated by a faint line, o. r, Eadicle. g, Gemmule. Fig. 604. Embryo of Fii. 1, 
Taken from the seed. 2, Beginning to germinate, r, Eadicle. c. Cotyledons, which are 
numerous ; the plant being polycotyledonous. 



DICOTYLEDONOUS EMBEYO. 



339 



sides, and having distinct venation, as in Eicinus (fig. 605), Jatropha, 
Euonymus, etc. In the former case they are called fleshy, or seminal 
lobes ; in the latter, foliaceous, or seminal leaves. 

Cotyledons are usually entire and sessile. But they occasionally 
become lobed, as in the Walnut and the Lime (fig. 606), where the 
cotyledon, c, has five lobes ; or petiolate, as in Geranium molle (fig. 
607 p) ; or auriculate, as in the Ash (fig. 608 o). Like leaves in the 
bud (see Vernation, p. 110), cotyledons may be either applied directly 
to each other (fig. 605), or may be folded in various ways. In the 




JFig. 608. 



Fig. 609. 



Pig. 610. 



Fig. 611. 



Almond (fig." 596) they lie in the direction of the axis. In other cases 
they are folded laterally, condupKcate (fig. 609) ; or from apex to base, 
rec}inate (fig. 222 a, p. Ill); or rolled up laterally, so as partially to 
embrace each other, convolute (fig. 610) ; or rolled up like the young 
fronds of ferns, cininate (fig. 611). In these cases, both cotyledons 
follow the same direction in their foldings or convolutions, but, in 
other instances, they are folded in opposite directions, resembling the 

Fig. 605, Embryo of Ricinus comimmis talcen out of tlie seed (see fig. 579, p.'329), and cut 
transversely. The two halves are separated so as to show the two cotyledons, c, applied to 
each other, r, Badiole. Fig. 606. Bmhryo of the Lime, r. Radicle, c. One of the divided 
or palmate cotyledons. Fig. 607. Emhryo of Geranium moUe. r, Radicle, c, Cotylec^ons 
attached to the coUar by a stalk or petiole, p. Fig. 608. Embryo of the Ash. r. Radicle, 
c, one of the cotyledons, o o, Auricular appendages to the cotyledon. Fig. 609. Embryo 
of Brassica oleracea, Cabbage, r. Radicle, o. Cotyledon. 1, Entire embryo. 2, Embryo 
out transversely, showing the cotyledons folded on the radicle or conduplicate. The radicle 
is dorsal, or on the back of the cotyledons. Fig. 610. Embryo of Punioa Granatum, 

Pomegranate, cut into two halves. The upper half removed to show the convolute coty- 
ledons, c, Radicle. Fig. 611. Circinate embryo (spirolobese) of Bunias orientalis. 



340 



DICOTYLEDONOUS EMBKTO. 



equitant (fig. 222 m, p. Ill) and semi-equitant (fig. 222 n, p. Ill) 
vernation. 

The radicle may be either straight or curved, and, in particular 
instances, it gives a marked character to the seed. Thus, divisions 
of the order Cruciferse are founded on the relative position and folding 
of the radicle and cotyledons. In the division Pleurorhizm (TXeuga, 
side, and g/^a, root), the cotyledons are applied by their faces, and 
the radicle (figs. 612, 613 r) is folded on their edges, so as to be 
lateral, whUe the cotyledons, c, are accumbent (accumbo, I lie at the 





Pig. 612. 



Fig. 613. 




side). In Notorhimm (viZrog, the back) the cotyledons (fig. 614'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 (incumbo, 
I lie upon, or on the back). In Orthoplocece (og^og, straight, and 
'jtXoKTi, a plait) the cotyledons are conduplicate (fig. 609, 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. 611), 
and the cotyledons follow the same course. In the Dodder (fig. 598) 
the embryo appears as an axis without divisions, having several turns 
of the spiral on different planes. 

The seed sometimes is composed of the embryo and integuments 
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. 588, 589, 590). When 
the embryo is surrounded by the perisperm on all sides except its 
radicular extremity (fig. 590, p. 332), it becomes internal or intrarius 
(intra, within) ; when lying outside the perisperm, and only coming 
into contact with it at certain points, it is external or extrarius (extra, 

Fig. 612. Embryo of a Pea, cut transversely. Upper half separated to show the fleshy 
aecumhent cotyledons, c. r, Radicle applied laterally. Fig. 613. Embryo of Isatis tinctoria. 
c, Accumbent cotyledons, r, Radicle. 1, Embryo entire. 2, Transverse section of the 
embryo. Fig. 614. Embryo of Cheiranthus Cheiri, Wallflower, d, Incumbent cotylcdons_ 
r. Radicle. 1, Embryo entire. 2, Transverse section of the embryo. 



POSITION AND FOKM OF THE EMBRYO. 



341 



without). When the embryo follows the direction of the axis of the 
seed, it is axils or axial, and it may be either external, so as to come 
into contact with the perisperm only by its cotyledonary apex (fig. 
615), or internal (figs. 588, 589, 590, see p. 332). In the latter case, 
the radicular extremity may, as in some Coniferse, become incorporated 
with the perisperm apparently by means of a thickened suspensor. 




Fig. 616. 



Kg. 616. 



Fig. 617. 



Fig. 618. 



"When the embryo is not in the direction of the axis, it becomes 
abawile or abaxial (fig. 616 e) ; and in this case it may be either 
straight or curved, internal or -external. In the straight seed of 
Grasses the perisperm is abundant, and the embryo lies at a point 
on its surface immediately below the integuments, being straight and 
external. In Campylotropbus ovules the embryo is curved, and in 
place of being embedded in perisperm, is frequently external to it, 
following the concavity of the seed (fig. 618), and becoming peripheri- 
cal (■ffsg/psgw, I carry round), with the chalaza situated in the curva- 
ture of the embryo. 

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, che 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 Primulacese, Plantaginacese, and many Palms, especially 
the Date (fig. 616). The position of the embryo in difierent kinds 
of seeds varies. In an orthotropal seed the embryo is inverted or 
antitropal (avri, opposite, rgswiu, I turn), the radicle pointing to the 
apex of the seed, or to the part opposite the hUum (fig. 617). Thus, 
fig. 619 represents an orthotropal seed of Sterculia Balaoighas, at- 

Fig. 616. Grain of Carex depauperata, cut vertically, t. Integuments, p, Perisperm. 
<!, Embryo. Fig. 616. Seed or kernel of the Date, p, Perisperm or horny albumen, e. 
Embryo. 1, Entire seed. 2, Seed cut transversely at the point where the embryo, e, is 
situated. Fig. 617. Winged fruit of Rumex, cut vertically to show the abaxile or abaxial 
slightly curved embryo. Fig. 618. Carpel of Mirabilis Jalapa, out vertically, with the 
, seed which it oontaius. a. Pericarp crowned with the remains of the style, s. t, Integu- 
ments of the seed or spermoderm. e, Peripherical embryo, with its radicle, r, and its coty- 
ledons, c. J), Perisperm or albumen surrounded by the embryo. 



342 



POSITION AND FOEM OF THE EMBRYO. 




tached to the pericarp, pe, by the funiculus, /. The chalaza and 
hUum are confounded together at ch, the micropyle being at the 
opposite end. The integuments of the seed, t, cover the embryo with 

its perisperm, ps ; the coty- 
ledons, c, point to the Mlum 
and chalaza ; while the 
radicle, r, points to the 
micropyle, and the embryo 
is thus reversed or inverted. 
Again, in an anatropal seed 
(figs. 589, 590, p. 332), 
where the micropyle is close 
to the hHum, and the 
Kg- 619. Kg. 620. chalaza at the opposite 

extremity, the embryo is erect or homotropal (S/ioiog, like, and 
Tgs'jnii, I turn), the radicle or base of the embryo being directed to 
the base of the seed. In some anatropal ovules, as in Castor oU 
(fig. 579, p. 329), 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. 455, p. 255) the embryo is folded so 
that its radicular and cotyledonary extremities are ap- 
proximated, and it becomes amphitropal (a//-f>i, around, 
r^B'?rcii, I turn). In this instance the seed may be 
exalbuminous, and the embryo may be folded on itself 
(fig. 620), or albuminous, the embryo surrounding more 
or less completely the perisperm, and being peripherical 
(fig. 618). In fig. 620 the seed of Erysimum cheiran- 
thoides is shown, with the chalaza, ch, and the hUum, h, 
nearly confounded together, the micropyle, m, the embryo 
occupying the entire seed, with the radicle, r, folded on the cotyledons, 
c, which enclose the plumide, fl'. Thus, by determining the position 
of the hilum, chalaza, and micropyle, the direction of the embryo may 
be known. 

According to the mode in which the seed is attached to the 

Fig. 619. Orthotropal seed of Sterculia Balanglias^ cut longitudinally, -with the portion 
of the pericarp, pc, to which it is attached. /, Funiculus, ch, Chalaza and hilum con- 
founded together, i. Integuments of the seed, or spermoderm. ps, Perisperm, the sum- 
mit of which only is seen, c. One of the cotyledons. The other cotyledon has been re- 
moved to show the gemmule, g. r. Radicle which is directed to the foramen at the apex 
of the seed. The embryo is antitropal or inverted. Fig. 620. Campylotropal seed of 
Erysimum cheiranthoides, cut longitudinally, m, Micropyle. ch, Chalaza not far removed 
from the hilum, h. t, Testa or episperm, mi. Inner covering of the seed or endopleura. 
r, Radicle, c, Cotyledons, g, Gemmule. The embryo is curved or amphitropal Fig. 
621. Vertical section of the carpel of Triglochin Barrelieri. p, Pericarp crowned by the 
sessile stigma, s. g, Seed. /, Funiculus, r. Raphe, c, Chalaza. 




Fig. 621. 



FUNCTIONS OF THE SEED. 343 

pericarp, the radicle may be directed upwards or downwards, or 
laterally, as regards the ovary. In an orthotropal ovule, attached to 
the base of the pericarp, it is superior (fig. 617). So also in a 
suspended anatropal ovule, as in fig. 579, p. 329. In other anatropal 
ovules, as in figs. 588, 600, 621, the radicle is inferior. When the ovule 
is horizontal as regards the pericarp (fig. 619), the radicle, r, is either 
centrifugal, when it points to the outer wall of the ovary; or 
centripetal, when it points to the axis or inner wall of the ovary. 

9. — Functions of the Seed. 

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 occurs in the perispermie or albuminous seed of Euonymus, 
and the aperispermic or exalbuminous seeds of most Cruciferse. 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, etc., and of laying up a store of nourish- 
ment 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 preserv- 
iag the vitality of the embryo. In some instances where air is con- 
tained in their envelopes seeds float iu water. 

When seeds are matm*ed, they are detached from the plant in 
various ways. Th^ separate from the funiculus at the hilum, and 
remain free in the cavity of the pericarp, 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 Oardam'ine. In the Geranium (fig. 551, p. 306) the seed-rvessels 
are coiled upwards on the elongated beak, and in this way the seeds 
are dropped. In the Cyclamen the peduncle curves towards the 
earth so as to place the seed-vessels in a position suitable for germina- 
tion. In the succulent frijit of Ecballium Elaterium, or squirting 
Cucumber, the cells vary in their size and contents in difierent parts ; 
and by the force of endosmose a rupture of the valves takes place at 
their weakest points-=-viz., where they are united to the peduncle. 
By the elasticity of the valves the seeds and fluid contents are sent 
out with great force through the opening left by the separation of the 



344 GERMINATION — EEQUISITES FOE IT. 

peduncle. In the Balsam (Impatiens noli-me-tangere) 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 
ceUs. The seeds are discharged before they are dry. In the Mig- 
nonette (fig. 575, p. 326) the seed-vessel opens early, so as to expose 
the seeds ; and in Ouphea the placenta bearing the seeds pierces the 
ovary and floral coverings, and is raised above them. Fleshy fruits, 
which fall to the ground when ripe, supply by their succulent portion 
the most suitable nutriment for the young embryo in its earliest 
stages of growth. 

Wind, water, animals, and man, are instrumental in the dissemina- 
tion of seeds. Some seeds, as those of Mahogany, Bignonia, Tecoma, 
Pine, Asclepias, Epilobium, and the Cotton plant, have winged or 
hairy 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 achsenia'of Dandelion, 
Thistles, etc. Moisture, as well as dryness, operates in the bursting 
of seed-vessels. The pod of the Eose of Jericho (Anastatica hiero- 
chuntina), and the capsule of some Fig-marigolds (Mesembryanthe- 
mum Tripolium) 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, disseminate 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 hyjpocarpogean {b-ao, under, x.ag'^rog, fruit, yia, y^, earth). 
This is seen in the Ground nut (Arachis hypogsea). Other plants, 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 compensated for by the vast number pro- 
duced, 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. 

Geemination.- — The act by which the embryo of a seed leaves 
its state of torpidity, and becomes developed as a new plant, is called 
germination (germinatio, springing). In order that this process may 
go on, a certain combination of circumstances is necessary. The chief 
requisites are moisture, air, and a certain temperature. Exclusion 
from light is also beneficial. In Cotyledonous plants germination 
may be defined as the act by which the fecundated embryo of a seed 
leaves the state of torpor in which it has remained for a longer or 
shorter period, starts into life, as it were, comes out from its envelope, 
and sustains its existence until such time as the nutritive organs are 
developed. 

Moisture is necessary in order that the nutritive matters may be 
taken up in a state of solution, and that certain changes may take 



GERMINATION — EEQUISITES FOE IT. 345 

place in the seed. Dry seeds -will not germinate. Until water be 
absorbed no circulation of fluids in the seed can take place. The 
quantity of water absorbed by seeds is often very large. Decandolle 
found that a French bean, weighing 544 mUlegrammes, absorbed 756 
of water. The swelling of Peas by absorption of water is familiar to 
all. The- kernels or seeds of stone-fruits by this means are enabled to 
burst their hard coverings. 

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 ex- 
posure for a short time to the heat of boiling syrup ; others after 
exposure to a cold of -39° F. Cereals and beans can only bear 
immersion in water at 110° F. for a few minutes. In steam they 
will bear 140° F. ; and in dry air 170° 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; and 113° P. as the highest they can bear in sand or 
earth. Vegetable life has been observed progressing under much 
higher temperatures. In the Manilla Islands, a hot spring, which 
raised the thermometer to 187°, had plants flourishing in it and on 
its borders. A species of Chara grows in the hot springs of Iceland, 
and various Confervas in the boiling springs of Arabia and of the 
Cape of Good Hope. Dr. Hooker states that on the edge of hot 
springs in the valley of the Soane in India, the temperature of which 
was sufficient to boil eggs, there occurred sixteen species of flower- 
ing plants, — Desmodium, Oldenlandia, Boerhaavia, some Compositse, 
Grasses, and Cyperacese. Moseley noticed specimens of Botryococcus, 
Braunia, Diatoms, and other Algse, in the hot springs of Furnas in 
the Azores. Hooker found Confervas in the hot springs of Bel- 
cuppee on the Behar Hills, at 168° F. Cyperacese grew in water of 
100° P. Dr. Wood of California found Nostoc calidarium and Chry- 
sococcus ,thermophilus in the hot springs of Benton, at 160° P. Abel 
mentions an Arenaria growing in soil at a temperature of 110° P. 
Cyperus polystachius and Pteris longifolia were found by Schouw 
in very hot soil which burnt the hand. Wheat, Oats, and Barley, are 
said to thrive in any country where the mean temperature exceeds 
65° P. 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. , 

Air, or rather oaoygen, 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 



346 GERMINATION — REQUISITES FOR IT. 

from half-an-incli to two inches, according to the nature of the soil. 
The following experiments were made by Petri : — 



Seed sown to the 
depth of 

i inch 

1 „ 

2 „ 


Came above ground 

in 

11 days 

12 „ 

18 , 


No. of plants that 
came up. 

7-8ths. 

all. 

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. 

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 subsoU 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 pre- 
viously seen in the locality. After the great fire in London, plants 
sprang up, the seeds of which must have long lain dormant ; and the 
same thiog is observed after the burning of forests and the draining 
of marshes. Gardner says that the name capoeira is given in Brazil 
to th'e trees which spring up after the burning of the virgin forests 
(matos virffens), 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 mic- 
rantha sprang up ; and seeds gathered from under six feet of peat- 
moss in Stirlingshire have been known to germinate. A weak solution 
of chlorine is said to accelerate germination, probably by the decom- 
position of water, and the liberation of oxygen. Weak solutions of 
chlorate of potash, of nitric acid, and of oxalic acid, are also said to 
accelerate the sprouting of seeds. 

Darkness is favourable to germination. Seeds germinate best 
when excluded from light. M. Boitard showed this by experiments 
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. Senebier con- 
cluded that the height and size of a plant were proportionate to the 
intensity of the illumination, its verdure dependent on the quality of 
the rays. Mr. Hunt says that the luminous or light-giving rays, and 
those nearest the yellow, have a marked effect in impeding germina^- 
tion; the red or heat-giving rays are favourable to the process, if 
abundance of water is present ; while the blue rays, or those concerned 



GERMINATION — REQUISITES FOR IT. 347 

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 conservatories. By this means he expects that 
the scorching rays of light will be excluded, while no hindrance is 
given to the passage of the others; the green colour being a compound 
of yeUow or luminous, and of blue or chemical rays. A delicate 
emerald-green glass has been employed, at his suggestion, in glazing 
the large Palm-house at Kew. 

In order that plants may germinate vigorously, moisture, heat, and 
air must be supplied in due proportion. If any of them are deficient, 
or in excess, injury may be done. It is of great importance, therefore, 
in agricultural operations, that the ground should be well pulverised, 
the seeds regularly sown at a proper and equal depth, and the soil 
drained. Pulverised soU, 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 ; 
in a properly 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. Great ■ 
attention should be paid to the temperature of the soil in which seeds 
are sown. Frost has an important eflfect in pulverising the soil, by 
the expansion of the water contained in the particles, when it is con- 
verted 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 accom- 
modate itself to the mild atmosphere. Snow contains often much 
oxygen. 

If a field is not equally planted, the seeds will sink to different 
depths, and will spring up very irregularly. In ordinary productive 
soils seeds should be 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. There has been a dis- 
cussion as to whether shallow or deep draining is the best. Much 
depends on the nature of the soD, and it is impossible ,to lay down 
any fixed rule applicable to all cases. Mr. Smith says that drains in 



348 VITALITY OF SEEDS — ITS DURATION. 

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. 

Vitality op 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 ab- 
sorbing oxygen, and the chemical changes thus induced. Considerable 
discussions have taken place as to the length of time during which 
seeds wiU retain their germinating powers. Lindley mentions a case 
in which yoimg plants were raised from seeds found "in an ancient 
barrow in Devonshire, 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 Eoman 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 preserved in circumstances which cannot be easily imitated. The 
statements relative to the germination of Mummy Wheat, that is to 
say, grain actually deposited in the case along with the mummy, have 
not been confirmed, and there are many sources of fallacy. 

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, etc., seem to be of importance 
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. Com, 
pulse, and farinaceous seeds generally, will live for a long time if 
gathered ripe, and preserved quite dry. In sending seeds from foreign 
countries; they should be put up into dry papers and exposed to free 
ventilation in a cool place ; as, for instance, in a coarse bag suspended 
in a cabin. Oily seeds, and] those containing much tannin, as beech- 
m£ist, 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 eaith and sand, and pressed hard, 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. Earthenware 
bottles, containing ordinary soil, moderately dry, are useful for the con- 
veyance of seeds. A common wooden box, about 10 inches square, with 



TRANSPORTATION OF SEEDS. 



349 



the sides f of an inch thick, is also suitable for the purpose. In the box 
may be put alternate layers of earth and seeds, the whole being pressed 
firmly together. Seeds enveloped in wax sent from India germinated 
well. They had been kept for three months, and were quite firm and 
fresh. Spanish Chestnuts and Filberts have been sent enveloped in 
wax to the Himalaya, 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. Living plants are best transported in Wardian Cases (fig. 622), 
and seeds and fruits may also be put in the earth of the Cases. When 
plants are sent in pots the Case may be divided into separate com- 
partments, as shown in fig. 623, each compartment containing only 




Fig. 622. 




Fig. 623. 



Fig. 624. 



one pot (fig. 624). The pots should be enveloped in moss, and they 
should be kept in their place by means of fine galvanised iron-wire. 
The bottom of the Case should be perforated with six or eight holes, in 
order to allow the escape of superfluous moisture. Strong white cotton 
may be used in sokie instances for covering the Case in- place of glass ; 
the cotton to be moistened from time to time during transit. 

M. Alphonse DecandoUe made experiments on the vitality of seeds. 

Fig. 622. Wardian Case, used for transporting living plants and germinating seeds. The 
top may be glazed with thick glass, or strong white cotton may be fli'mly stretched over it. 
Fig. 623. Wooden partitions, which may be inserted in the Case to hold pots, which must be 
carefully fastened to prevent injury during transit. Kg. 624. Section of the Case, showing 
the separate pots, with plants, in the interior. 



350 



CHANGES IN THE SEED DUEING GEKMINATION. 



He took 368 species of seed, fifteen years old, colleoted in the same 
garden, and sowed them at the same time, and in the same circum- 
stances as nearly as possible. Of the 368 only 17 germinated, and com- 
paratively few of the species came up. The following are the results : — 

Per cent. 
0-60 
0-20 
0-03 
0-00 
0-00 
0-00 
0-00 
0-00 
0-00 

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 ,, . . 67 



Malvacese 


5 


;ame up 


out of 10 species 


Leguminosse 


9 




„ 45 „ 


Labiatse . 


1 




., 30 „ 


Scrophulariaceas 







„ 10 „ 


UmbellifersB . 







„ 10 „ 


Caryophyllacese 







„ 16 „ 


Gramineae 







„ 32 „ 


Cruciferse 







„ 34 „ 


CompositaB 







„ 45 „ 



16 



357 



4-4 



Ligneous species thus seem to preserve the power of germinating 
longer than others, while biennials are at the opposite end of the scale j 
perennials would appear to lose their vitality sooner than annuals. 
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. Oompositae and Umbelliferse 
lost their germinating power very early. From these experiments 
DecandoUe concludes that the duration of vitality is frequently in an 
inverse proportion to the rapidity of the germination. 

Chemical Changes during 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 
exalbmninous 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. While this 
conversion of starch into sugar proceeds, oxygen is absorbed, carbonic 
acid is given off, and heat is produced. It is probable that at this 
period there is a certain amount of electric disturbance. Carpenter 
states that the conversion of the starch of the seed into sugar involves 



STAGES OF GERMINATION. 351 

the liberation of carbonic acid, with a small quantity of acetic acid ; 
-and as all acids are negative, and like electricities repel each other, it 
is probable that the seed is at the time in an electro-negative condition. 
The phenomena of germination are well seen in the malting of barley, 
which consists in the sprouting of the embryo and the formation of 
-sugar. 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. During 
growth and evolution it would appear that all living beings, whether 
plants or animals, give out carbonic acid (carbon dioxide), whilst oxy- 
gen or some oxidising substance is absorbed. Growth and evolution must 
be considered in a dififerent way from the decomposition of 00^ by 
leaves, under the influence of light, to provide the starch, gum, sugar, 
and other materials that are to be organised. 

When aU 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 
conversion of starch into sugar, and are accompanied with the evolu- 
tion 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 untU it fills the cavity of the seed, and ultimately bursts 
through the softened integuments. In cases where there is no peri- 
sperm, the exalbuminous embryo occupies the entire seed, and the 
process of germination goes on with greater rapidity. The embrjfo 
speedily swells, 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 Eape see^l. 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 independent plant. 

The embryo, nourished at the expense of its perisperm and coty- 
ledons, continues to grow, and usually protrudes its radicular extremity 
(fig. 625, 1) in the first instance, which is nearest the surface, 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. 625, 2J, 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. 625, 3 51), 
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 




352 DIRECTION OF PLUMULE AND EADICLE. 

gradually absorbed like the perisperm. In the former they assume 

a more or less leafy aspect, exercis- 
ing the functions of leaves for a 
certain period, and ultimately decay- 
ing. While the radicle descends 
towards the centre of the earth, pro- 
ducing roots of a pale colour, the 
plumule has a tendency to ascend, 
forming the leafy axis, and assuming 
a green colour under the influence of 
light and air. 

Direction of Plumule and Hadicle. — 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 certain agencies are obviously concerned in 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 thinks that the direction of stem and 
roots may be traced to gravitation, and 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 pro- 
duced, 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 explanation 
is given by Dodart. Dutrochet refers the phenomena to endosmose, 
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, according to him, the diminution 
takes place in the reverse manner. Large cells distend more rapidly 
than smaU ones ; and, according to their position in the axis, wiU 

Fig. 625. Germination of the dicotyledonous aperispermic seed of Acacia Julibrissin. 
e, Spermoderrn or testa, r. Radicle of the embryo.* t, Tigellus or cauliculus. c. Cotyledons. 
g, Gemmule or plumule. 1, First stage : in which the radicle ruptures the envelope or 
spermoderrn, and appears externally at the micropyle. 2, Second stage : where the parts 
of the embi-yo are further disengaged from the covering, the summit of the cotyledons only 
being retained by the spermoderrn. 3, Third stage: where the embryo is entirely dis- 
engaged from the envelope or spermoderrn, and the cotyledons, c c, are separated so as to 
exhibit the plumule, g. 



DIRECTION OF PLUMULE AND EADIOLE. ' 353 

thus cause curvature outwards or inwards, the largest occupying the 
convexity 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 neutralise the tendency to 
incurvation on the upper side, which will therefore be directed either 
upwards 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. 

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 up- 
ward direction. If their positions are reversed they will become 
twisted, so as to recover their natural positions. Henfrey remarks 
that " so far as we are in a position to tell, there is some definite, 
and as yet unknown, cause which makes the radicle first grow towards 
the earth or other source of nourishment, which it penetrates by elonga^ 
tion, a resisting point being offered by the weight of the seed or the 
earth covering it ; and then, in its further growth downward, it 
requires a point of resistance to be afforded by the adhesion of the 
earth around the collar, ring, or neck of the root, since the elongation 
takes place in the structures just above the point of the root, thus 
exerting a pressure upwards and downwards, which if the upper part 
of the root be kept free, and the weight of the plant balanced, wiU 
cause the whole to rise bodily upwards. Thus, when seeds germinate 
in damp moss lying upon a hard surface, the elongation of the root 
will push the stem up through the moss, unless the root branches so 
as to get fixed down by entanglement among the loose matter. We 
may admit, therefore, that we are at present totally ignorant of the 
cause of the direction taken by roots. All the notions hitherto 
advanced having been purely speculative." 

The effect of light on the steni may be illustrated by the growth 
of plants in circumstances where a pencil of light only is admitted on 
one. side. Dr.'Poggioli of Bologna was the first who observed the 
infiuence exercised by the rays of the spectrum in causing flection of 
plants.. Experiments on this subject have been made by Payen, 
Dutrochet, and Gardner. They consider the blue rays as those which 
have the greatest eff'eot on the plumule. .Hunter observed, that if a 
barrel filled -with earth, in the centre of which are some beans, was 
rotated for several days horizontally, the roots pointed in a direction 

2 A 



354 MONOCOTYLEDONOUS GERMINATION. 

parallel to the axis of rotation. Kniglit* put Mustard seeds and 
Prench 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 
intermediate between that impressed by gravitation and by the centri- 
fugal force — viz., downwards and outwards, while the stems were 
inclined upwards and inwards. In the latter, where the force of 
gravitation was neutralised by the constant change of position, the 
centrifugal force acted alone, by which the roots were directed out- 
wards, at the same time that the stem grew inwards. To explain 
these results, there must be allowed — 1. A more or less liquid con- 
dition 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 wheel 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 way that their lower surface is exposed. Some plants grow 
indifferently in all directions at the period of germination. The 
Mistleto and other parasites direct their radicles towards the centre 
of the plants to which they are attached, while the plumule grows 
perpendicularly to the surface. 

MONOCOTYLEDONOUS Geemination. — 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 intrarseminal portion of the cotyledons, as in 
Canna (fig. 626), and especially in the Coco-nut, becomes developed 
as a pale cellular mass, which increases much, and absorbs the nutri- 
ment required for the embryo. In some Monocotyledons the perisperm 
disappears entirely ; in others, as in the Phytelephas or Ivory Palm, 
while certain soluble matters are removed, the perisperm stOl 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, corresponding to the petiole, becomes often much elongated, 
■as in the double Coco-nut, and ends in 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 
indioa (fig. 626), where e is the envelope of the seed; p, the peri- 

* See Knight's Horticultural Papers, London, 1841, p. 124. 



MONOCOTYLEDONOUS GEEMINATION. 



355 



sperm 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, /, the plu- 
mule, g, protrudes, supported on the axis or cauliculus, t ; while the 






Fig. 626. 

radicles, r and /, pierce the iategument at the base, and are each 
covered with a separate sheath, m, called coleorhiza (fig. 105, p. 42). 
In aperispermic Monocotyledons, as Alismacese and Potamese (fig. 595, 
p. 334), the cotyledon does not remain within the seed, but is raised 
above the ground, c, giving origin to the plumule, g, which is at first 
enclosed in its sheath. 

Thus the cotyledon follows the development of i^eaves. Its 
limb is first produced, and is either pushed above ground, or 
is confined within the seed. In the latter case it is arrested iu 
its progress ; subsequently, a sheath is formed which may either 
be a direct continuation 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 rootlets in Monocotyledons during 
germination (fig. 105 r r, p. 42) pierce the radicular extremity of the 
embryo, and become covered with sheaths or coleorhizas, c c, formed 
by a superficial layer of cellular tissue. As the radicular extremity 

Pig. 626. Germination of tlie monocotyledonous perispermic seed of Canna indica. The 
seed is cnt to show the relation hetween the perisperm and the embryo at different stages, 
the former 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. 
J), Perisperm or albumen, c. Cotyledon, r, Eadicle or young root. / /, Secondary 
radicles, w, Coleorhiza or sheath of the roots. /, Slit indicating the position of the gem- 
mule ; at this slit an elongated sheath, v, is protruded, o o. Narrow portion of the cotyle- 
don (corresponding to the petiolary portion), intermediate between its enlarged portion, t 
(corresponding to the lamina or limb of the leaf), and its sheathing or vaginal portion, v. 
t, TigeUus or cauliculus. g, Gemmule or plumule. 1, First stage, in which the radicle, r, 
begins to appear through 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, /, is also seen with a coleorhiza. 3, Third stage, 
when all the parts are more developed, and the gemmule, g, appears on the outside of the 
slit, /, the edges of which are prolonged in the form of a sheath or vagina, u. 



356 



DICOTYLEDONOUS GERMINATION. 



thus remains within the embryo, and sends out radicles (adventitious 
or secondary rootlets) from its surface, the plants are said to be endo- 
rhizal (eydov, within, g/^a, a root). See page 42. 

Dicotyledonous Geemination. — In Dicotyledons, the cotyledons 
generally separate from the integuments, and either appear above 
ground in the form of temporary leaves (figs. 627, 628 c c), which 
differ in form from the permanent leaves of the plant (fig. 628 g), or 
remain below as fleshy lobes. In the former case they are epigeal (it!, 





Pig. 627. 



Pig. 629. 



upon or above, yea, y\ the earth), in the latter case (as in Beans, 
Araohis, etc.), they are hyjwgeal (v'tto, under). The cotyledons usually 
separate, but sometimes they are united, and appear as one. In all 
cases, the plumule (figs. 627, 628 g) proceeds from between the two 
cotyledons, a.nd does not pierce through a sheath as in monocotyle- 

Fig. 627. Germination of the dicotyledonous embryo of Acer Neguildo. m, CoUum, 
collar or neck, r, Root, t, Caulicule or stem, c c, Cotyledons. ^, Gemmule or plumule. 
Pig. 628. Upper part of tlie same embryo more developed, cc, Cotyledons, g, Gemmule, 
the first leaves of which are already expanded, i, Caulicule or stem. -Pig. 629. Acotyle- 
donous embryos or spores of Marchantia polymoi-pha, 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. 



ACOTYLEDONOUS GEEMINATION. 357 

dons. The root (fig. 627 r) is a direct prolongation of the axis, t, in 
a downward direction, separating from it at the collar, m, and the 
embryo is here exorhizal (sgw, outwards). See page 41. 

AcoTYLEDONOus Geemination. — In Acotyledons the spore (fig. 
629) has no separate embryo in its interior." It may be considered 
rather as a cellular embryo than a seed. It germinates by sending 
off cellular root-like prolongations from all parts of its surface, hence 
it is called hderorlmal {ersgos, diverse) (see p. 43). These ceUular 
processes may be formed either from the entire wall of the spore or 
from its inner covering. In fungi the spore gives origin to a cellular 
axis called spawn (mycelium), on which ultimately the fructification is 
developed. The spores of Fungi often germinate in anomalous posi- 
tions, such as the organs of other plants, and the bodies of animals and 
man. Much injury is often occasioned in crops by the attacks of these 
spores. In the higher acotyledons the spores form in the first instance 
a cellular prothallus, in which the organs of reproduction ultimately 
are developed (see p. 279). In speaking of the germination of Hypho- 
mycetous Fungi, Lister states that these spores (conidia) germinate 
in three ways. 1. They may form their sprouts, which become 
plants Kke the parent. 2. They may multiply by puUulation, like 
the yeast plant, and, under some circumstances, this toruloid growth 
may continue for an indefinite period, though the resulting progeny 
will, under favouring conditions, reproduce a fungus like the original. 
3. The conidia may shoot out sprouts of exquisite delicacy, which 
break up into Bacteria. These Bacteria, like the fungi whence theyare 
derived, are of various totally distinct kinds, both morphologically 
and physiologically. They give rise to difierent fermentative changes, 
and some refuse to grow in media in which others thrive. Bacteria 
cannot be classified merely by forms, we must take into account their 
physiological peculiarities. 

Some seeds commence the process of germination before being de- 
tached from the plant. This occurs in a remarkable degree in the 
Mangrove tree, Khizophora Mangle, which grows 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 been 
found in the interior of Gourds, as well as in the fruit of Carica Papaya, 
the Papaw. The seeds of the Banyan, or Bo-tree (Ficus iridica), seldom 
germinate on the ground. The fig-like fruit of the tree is eaten by 
birds, and the seeds are deposited in the crown of Palms, where they 
grow, sending down roots which embrace and generally kill the Palm. 

Pkolifeeous 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 'prolifer- 
ous (proles, offspring, and fero, I bear), or viviparous (vivus, alive, and 
pa/rio, I produce). They are met with in many alpine grasses, as 



358 PROLIFEEOUS OE VIVIPAROUS PLANTS. 

Festuca ovina, var. vivipara, Aira caespitosa, var. alpina, Poa alpina, 
etc., as well as in Alliums, Trifoliums, and Ferns. Buds of a similar 
kind may be produced on the edges, or in the axil of leaves, as in 
Bryophyllum calycinum, Malaxis paludosa (fig. 231, p. 118), many 
species of GeSnera, Gloxinia, and Achimenes ; and the bulbils of Lilium 
(fig. 230, p. 117), Ixia, Dentaria, Ornithogalum (fig. 232, p. 118), 
some Saxifrages (S. cernua and S. foliolosa), seem to be peculiar 
forms of buds, capable of being detached, and of assuming indepen- 
dent growth. Buds, however, difier from true embryos in the 
direction of the roots being towards the axis of the plant. In uni- 
cellular plants, and others of the lowest class, it is common to find 
each cell possessing the power of producing a new individual, either 
by simple division or by the formation of a cellular bud. In higher 
plants this mode of propagation is carried out by means of an assem- 
blage of cells, which are developed into an organ or bud of a more 
complicated nature, before it is detached. Multiplication by division 
of cells is very common among the lowest Algae, such as Desmidiacese 
and Diatomaceae (fig. 472, p. 267). In the case of Lichens, the 
thallus produces gonidia (p. 269), which appear to be a collection of 
cellular buds capable of producing independent individuals. On the 
thallus of Liverworts (Marchantia) cup-like bodies are produced con- 
taining gemmae (fig. 488 g, p. 275). In Mosses the power of repro- 
duction by gemmae is very marked. Almost every cell of the surface 
of Mosses, according to Sohimper, is capable of giving origin to a leafy 
plant . or innovation. Ferns are propagated by buds, and gemmae 
occasionally occur on their prothallium. The higher classes of plants 
may be considered as consisting of numerous buds united on a common 
axis (fig. 219, p. 109). These possess a certain amount of independent 
vitality, and they may be. separated from the parent stem in such a 
way as to give origin to new individuals. In some instances buds 
are produced which are detached spontaneously at a certain period of 
a plant's life. The cloves formed in the axils of the scales of bulbs 
are gemmae or buds, which can be detached so as to form new plants. 
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 exposed 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 : — 

Amarantacese 9 days. 

CruciferiB ........ 10 „ 

BoraginaceEe, Caryophyllaceas, Chenopodiaoeae, Malvaceas . 11 „ 



DUEATION OF THE LIF^ OF PLANTS. 359 



Compositse, Convolviilaceaa, Plantaginaoese 
Polygonaoese ...... 

Campanulaoeffi, Leguminosse, Valerianacese 
Gramineae, Labiatse, Solanaceffi 
Eosaceae ..... 

Eanimciilacese .... 

Antirrhinums, Onagi'acese . 
TJmbelliferEe . . . , , . 



12 days. 

13 „ 
H „ 
15 „ 
17 „ 
20 „ 

22 „ 

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 respectively. 

Dtjeation of the Life of Plants. — Plants, according to the 
duration of their existence, have been divided into annual, biennial, 
and perennial. 'The firsts of these terms imports that the seed ger- 
minates, and that the plant produces leaves aad flowers, ripens its 
seed, and perishes within the year ; the second, that a plant ger- 
minates 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, 
whUe the last may do so several times 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 years' duration ; the annual Mignonettej 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. 

Plants, as regards their flowering and fruiting, have also been 
•divided into monocarpic {/iovoe, one, and •/.a.^'itoi, fruit), or those which 
flower once only and then die ; and polycarpic ('TroXiig, 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 polycarpic. Some perennial woody plants live to a great age. 
The Baobab of Senegal, the WeUingtonia, the Dragon-tree, the Yew, 
the Oak, the Lime, the Cypress, the Eucalyptus, the Olive, the Orange, 
Banyan, and Chestnut, often attain great longevity. 



360 DURATION OF THE LIFE OF PLANTS. 

The folio-wing 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 to 250 „ 
Height of specimens of Wellingtonia (Sequoia) gigantea . 450 „ 
Trvmks of some Baobahs (Adansonia) have a girth of . .90 „ 
Trunli of Dragon-tree (Dracaena) of the Canaries has a girth of 45 „ 
That of a Maple (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 Fountains Abbey, Eipon 1200 ,, 

Yews in churchyard of Crowhurst, Surrey .... 1450 ,, 
Yew at Fortingal, Perthshire . . . upwards of 2000 , , 
Yew at Hedsor, Bucks 3200 ,, 

A specimen of the Banyan (Picus indica), -which grew tUl recently on 
an island in the river Nerbudda, was 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. The 
chief trunks of this tree greatly exceeded our English Oaks and Elms 
in thickness, and were above 350 in number. The smaller stems 
were more than 3000 in number. The Maronites believe that some 
Cedars near the village of Eden in Lebanon are the remains of the 
forest which furnished Solomon with timber for the temple, full 
3000 years ago. 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 circum- 
ference, and 117 feet in the spread of its boughs. 

Decandolle has given a list of the ascertained ages of certain 
trees : — 

Elm 336 years. 

Cypress, about 350 

Cheirostemon (Hand-tree), about .... 400 
Ivy- ...... . . 450 

Larch 576 

Sweet Chestnut, about 600 

Orange 630 

Olive 700 

Platanus orientalis (oriental Plane) .... 720 

Cedar 800 

Many tropical trees, according to Humboldt, about . 1000 
-Wellingtonia, according to Torrey .... 1120 

Lime 1076, 1147 

- Oak 810, 1080, 1500 

Yew 1214, 1458, 2588, 2820 

Taxodium ) , ■ , 

Adansonia \ Probably as old as the Yew. 

Decandolle states that the Yew increases little more than one line 
in diameter annually, during the first hundred and fifty years, and a 
little more than one line afterwards, and in very old specimens he cou- 



DURATION, OF THE LIFE OF PLANTS. 361 

siders their age to be at least equal to the number of lines in their 
diameter. This average, however, is probably too high for young 
trees, and too low for old ones. In 1836, Mr. Bowman measured the 
trunks of eighteen Yews in the churchyard of Gresford, near Wrex- 
ham, in North Walep, which were planted out in 1726, and found 
their average diameter to be 20 inches, or 240 lines. Comparing 
them with the dimensions of other trees whose ages are known, he 
came to the conclusion, that for Yews of moderate age, and where the 
circumference is less than 6 feet, at least two lines, or ^ of an inch of 
their diameter, should be allowed for annual increase, and even three 
lines or more if growing in favourable circumstances. He states that 
a Yew in the same churchyard, whose mean diameter is 8 feet 6 inches, 
or 1224 lines, and whose age, by DecandoUe's method, would be as 
many years, was in reality 1419 years old. Sections taken from 
different sides of the trunk contained as follows : — 

, T j> 1 . ■ V ( On the north side 43. 

Average numher of annual nngs per inch, q^ ^^^ ^^^^^ ^.^^ ^ 

counted on the horizontal plane . i r, i-u 4.1, 1 -j ic 
■^ [On the south-west side 15. 

giving a general average of 34§ rings in an inch of the diameter. 
Supposing that this tree, when 150 years old, had a diameter equal to 
that of the eighteen already mentioned, and among which it grows, 
and had continued to increase in the same ratio up to 150 years, and 
also making additional allowance for an intermediate rate of increase 
between 150 and 250 years, Mr. Bowman arrives at the following 
result : — At 150 years old, its diameter would be 25 inches; at 246 
years old, 33 inches, leaving 5 feet 9 inches of the diameter for subse- 
quent increase, the radius of which, at 34 rings to the inch, would 
contain 1173 rings, or years of growth; to this add 246, and its 
present age would be 1419 years. 

Another Yew in Darley churchyard, Derbyshire, is mentioned by 
Mr. Bowman, in which sections taken from its north and south sides 
gave 44 annual rings in the inch, so that its radius would contain 286 
such rings, supposing them to be of equal thickness throughout, but 
making the same deductions as before, its present age may be esti- 
mated at about 2006 years. This examination shows the Gresford 
Yew to be about 200, and that at Darley about 650 years older than 
DecandoUe's standard of one line per annum of the diameter would 
indicate, and consequently, that for old trees his average is too low. It 
also shows that the Darley tree, with a greater diameter than the 
other of only 1 1 inches, is 587 years older, the excess arising from the 
extreme thinness of its annual deposits. No precise rule can there- 
fore be laid down, and actual sections must be resorted to if anything 
like accuracy be required. 



362 VEGETABLE METAMOKPHOSES. 

10. — General Observations on the Organs of Plants, and on the 
Mode in which they are arranged. 

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 of being made to grow on another tree 
by grafting ; and although each has thus a vitality of its own, it is 
nevertheless 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 Gaudi- 
chaud a phyton (<pvTov, a plant), and in it he recognises three parts or 
merithalli {/J-'sgog, a part, and SaXXog, a young shoot), the radicular 
merithal corresponding to the root, the cauline to the stem, and the 
foliar to the leaf In Acotyledonous plants the embryo or spore consists 
of united cells, and it is only after 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. 

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 
fuU 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 wUl 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, as into true 
leaves ; or, in other words, the cellular papiUse 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 inwards, by an ascending or direct metamorphosis, as in the 
case of petals becoming stamens ; or from within outwards, by descending 
or retrograde metamorphosis, as when stamens become petals. 

Bracts are very evidently allied to leaves, both in their colour and 



SYMMETRY OF OEGANS. 363 

form. Like leaves, too, they produce buds in their axil. - The mon- 
strosity called Hen and Chickens Daisy depends on the development 
of buds in the axil of the leaves of the involucre. The sepals 
frequently present the appearance of true leaves, as in the Rose. 
The petals sometimes become green like leaves, as in a variety of 
Eanunculus Philonotis mentioned . by DecandoUe, and in a variety of 
Campanula rapunouloides noticed by Dumas. At other times they 
are changed into stamens. DecandoUe 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 Kymphsea 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, etc. Petit-Thouars noticed a plant of 
House-leek, 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. In a 
monstrosity of Wallflower the placenta gave origin to flowers. It is 
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, etc. 
Increased vigour seems to be required for the development of stamens. 
Some fir trees in their young state bear cones, and produce male 
flowers only when they reach the prime of life. 

' Symmetey of Organs. — In the progress of growth the plants 
belonging to the difierent divisions of the vegetable kingdom follow 
certain organogenic laws (ogySiioi', an organ, and ymdca, I 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 alternat- 
ing portions. This orderly and similar distribution of a certain 
number of parts is called symmetry, and flowers are thus said to be 
symmetrical with various numbers of members. When the number 
of parts is two the flower is dirkerous-ihii, twice, /(tegos, a part) (fig. 
630), and the symmetry two-membered. When the number of parts 
is three the flower is trimerous (rgsTg, three), and when the parts 
are arranged in an alternating manner (fig. 631) the symmetry is 
trigonal or friangular {T^iTg, three, yavla, an .angle), as in the Lily. 
When there are four parts the flower is Utramerous (rer§di, four), 
and the symmetry is tetragonal or square (flgs. 632, 633), as in Galium 
and Paris. When there are five parts the flower is pentamerous 



364 SYMMETRY OF ORGANS. 

(mvn, five), and the symmetry pentagonal (fig. 634), as in Ranun- 
culus. The number of parts in the flower is indicated by the 
following symbols : — Dimerous ^, Trimerous ^, Tetramerous ^, Pen- 
tamerous ^. 




Pig. 630. Kg. 631. Fig. 632. Fig. 633. 



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 in 
the arrangement of the stamens of Cruciferae. 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 mammiUse, in a symmetrical 
manner. In the case of irregular corollas the parts at first appear 
regular. 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 Solanacese are 
pentamerous, and have a dimerous ovary, yet they are called sym- 
metrical. In Oruciferae the flowers are, properly speaking, unsym- 
metrical, for while there are four sepals and four petals, there are six 
stamens in place of four. This condition of the stamens depends pro- 
bably on deduplication (p. 210). In Papilionaceous flowers the parts 
are usually symmetrical, there being five divisions of the calyx, five 
petals, and ten stamens in two rows. In these flowers there should 
normally be five carpels, but there are very rarely more than one. 

In Dicotyledonous plants it is common to meet with pentagonal 
(figs. 634, 635, 636) and tetragonal (figs. 632, 633) symmetry, the 
parts being arranged in fives and fours, or in multiples of these num- 

Fig. 630. Diagram of the dimerous flower of Circtea Lutetiana, Enchanter's Nightsliade. 
Tliere are two carpels, two stamens, two divisions of the corolla, and two of the calyx. The 
flower is Isostemonoua. Fig. 631. Diagram of the trimerous Isostemonous flower of 
Cneorum tricoccum. The floral envelopes are arranged in sets of three, and so are the 
essential organs. Fig. 632. Diagram of the tetramerous Isostemonous flower of Zieila. 
The organs are arranged in verticils of four parts each. Fig. 633. Diagram of the tetra- 
merous Diplostemonous flower of Euta graveolens. There are four carpels, eight stamens, 
or four in each verticil, four folioles of the calyx, and four petals. 



TERATOLOGY — SUPPRESSION OF ORGANS. 365 

bers. The stamens are often 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 verticUs. No doubt 
the verticils are often traced with difSculty, more especially when 










Vr 




Fig. 636. "Pig. 636. Fig. 637. 

cohesions or adhesions take place. In Monocotyledons (fig. 637) the 
parts are usually in sets of three, or in some multiple of that number, 
exhibiting trigonal symmetry. 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 Acotyledons are also arranged in fours (fig. 482, 
p. 273). 

Teratology. — There has thus been traced a tendency to symmetri- 
cal arrangement. 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 organisation, 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 interfere with the symmetry of 
the flower. Alteration in the symmetrical arrangement, as well as in 
the forms of the difierent parts of plants, have been traced to suppression 
or the non-development of organs, degeneration or imperfect formation, 
mhesion or union of parts of the same whorl, adhesion or union of the 
parts of dififerent whorls, multiplication of parts, and deduplication 
(sometimes called chorisis). The study of Teratology (rs^ag, a mon- 
.strosity, and Xoyog, treatise), or of the monstrosities occurring in plants, 

Fig. 634. Diagram of tlie pentamerous Isostemonous flower of Crassula rubens. ccccc. 
Parts of the calyx, pp P!PP, Petals alternating with the leaves of the calyx, ee eee, 
Stamens alternating with the petals, a, Accessory hodies in the foim 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. 636. Diagi-am of 
the pentamerous flower of Sedum Telephium. The stamens are ten, arranged in two alter- 
nating verticils. The flower is Diplostemonous. Fig. 636. Diagram of the pentamerous 
Diplostemonous flower of Coriaria myrtifolia ; the parts of the four whorls alternating, the 
verticil of stamens being double. Fig. 637. Diagram of the trimerous Diplostemonous 
flower of Omithogalum pyrenaicum. Stamens six, in two alternating verticUs. 



366 



TERATOLOGY — SUPPRESSION OF ORGANS. 



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.* 

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 abnormali- 
ties. 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. 638) there are five parts of the calyx, five 
petals, five stamens, and only two carpels ; in many Caryophyllacese, 
as Polycarpon and Holosteimi (fig. 639), while the calyx and coroUa 
are pentamerous, there are only three or four stamens and three car- 
pels ; in Impatiens noli-me-tangere (fig. 640) the calyx is composed 
of three parts, while the other verticils have five ; in Labiate flowers 
there are five parts of the calyx and corolla, and only four stamens ; 
and in Tropseolum pentaphyllum (fig. 641) there are five sepals, two 








<^3 



Fig. 638. 



Fig. 639. Fig. 640. Fig. 641. 

petals, eight stamens, and three carpels. In all these cases the "want 
of symmetry is traced to the suppression of certain parts. In the last- 
mentioned 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. 64:1) ; there are two rows of stamens, in each of 
which one is wanting, and there are two carpels suppressed. In many 

Fig. 638. Diagram of the flower of Staphylea pinnata. The parts of the calyx, corolla^ 
and stamens are pentamerous, while the pistil, in consequence of the suppression of three 
carpels, is dimerous. Fig. 639. Diagram of the flower of Holosteum umbellatum. There 
are five ealycine 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 unsymmetrioal. Fig. 640. Diagram of the flower of Impatiens parviflora, with 
one of the ealycine 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 suppres- 
sion. Fig. 641. Diagram of the flower of Tropseolum pentaphyllum, with a spurred or 
calcarate ealycine 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. 



* For a complete treatise on this subject, see Vegetable Teratology, by Dr. M, T. Masters. 




TERATOLOGY — SUPPEESSION OF OEGANS. 367 

instances the parts wMch are afterwards suppressed can be seen in the 

early stages of growth, and occasionally some vestiges of them remain 

in the fuUy developed flower. Sometimes 

the whorl of the petals is wanting, the 

flowers being apetalous (a, privative, and 

■riraXov, a leaf) (fig. 642), and in such cases 

it is common to see the stamens opposite to 

the segments of the calyx which is the whorl 

^verticil) next to them, as in Chenopodiacere ^^- **^- ^'s. 64S. 

(fig. 643). That this suppression of the petals takes place is shown 

in the case of certain allied plants, as in the natural orders Caryophyl- 

lacese and Paronychiacese, where some species have petals and others 

want them. 

By the suppression of the verticil of the stamens, or of the carpels, 
flowers become unisexual (unus, one, and sexus, sex), or diclinous (big, 
twice, and xXhn), a bed, and are marked thus, S 9 ; the first of these 
symbols indicating the male, and the second the female flower. Thus, 
in Jatropha Curcas (fig. 346, p. 218), the flowers have five segments 
of the calyx, and five petals, while in some (fig. 346, 1) the pistil is 
wanting ; in others (fig. 346, 2), the stamens. In the genus Lychnis 
there are usually stamens and pistU present, or the flower is hermaphro- 
dite, or monoclinous (/j^ovo;, one, and xXhrj, a bed) ; but in Lychnis 
dioica some flowers have stamens only ; others pistils only. Thus it 
is that monoecious or monoicous and dioscious or dioicous [imovos, one, big, 
twice, and ohiov, a habitation) plants are produced by the suppression 
of the essential organs of the flowers, either in the same or in different 
individuals of the same species ; while polygamous [irdk-jg, many, and 
yai/iog, marriage) plants are those in which, besides unisexual, there 
are also hermaphrodite or perfect flowers. 

Some parts of the pistil are generally suppressed in the progress of 
growth, and hence it is rare to find it symmetrical with the other 
whorls. When the fruit was treated of (p. 299) 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 numbers 
from the ovary and ovules. If the whorls of the calyx and coroUa are 
wanting the flower becomes naked or achlcmiydeous (p. 177). 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 sup- 
pressed, then the flower, however showy as regards its envelopes, is 

Fig. 642. Diagram of the flower of Glaux maritima, showing the suppression of the verticil 
of the corolla. There are five divisions of the calyx, Ave stamens alternating with them, 
and five divisions of the ovary, with a central plaoentation. Fig. 643. Diagram of the 
flower of Chenopodium album, showing the suppression of the verticil 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 ovaiy are not easily seen, the placentation being central. 



368 



TERATOLOGY — SUPPRESSION OF ORGANS. 



unfit for its functions, and is called neuter. Flowers having stamens 
only are staminiferous, staminal, sterile; those having pistils only are 
pistilliferous, pistillate, OT fertile. The suppression of various verticils, 



644. 645. 646. 647. 648. 649. 

and parts of them, is well seen in the family of the Euphorbiacese (figs. 
644-649). Thus, in fig. 644 is delineated an apetalous trimerous 
staminal flower ; in fig. 645 one of the stamens is suppressed, and in 
fig. 646 two of them are wanting. Again, in figs. 647, 648, 649, 
the calyx is suppressed, and its place occupied by one, two, or three 
bracts (so that the flower is, properly speaking, achlamydeous), and 
only one or two stamens are produced. In fig. 649, 1, there is a sterile 
flower, consisting of a single stamen with a bract ; and in fig. 649, '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. 

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 de- 
veloped, if any accident 
Deficiency of light and of air, and 

Figs. 644-649. Diagrams of flowers of Euphorbiaceous plants, TDecoming more and more 
simple. (1.) The calyx is the only envelope, and consists of three parts, in iigs. 644, 645, 
and 646. It is completely suppressed in flgs. 647, 648, and 649, and its place is occupied by 
a bract, in the axil of which the flower is produced ; this bract being accompanied in 
flgs. 647 and 648 with two small bractlets. (2.) The male flowers in flg. 644 have three 
stamens, in figs. 645 and 646 they have two, in figs. 646 and 648 one stamen only is developed, 
and in fig. 649, 1, the solitary stamen has only one anther-lobe. (3.) The female flower in 
fig. 649, 2, is reduced to a single carpel, with a bract in the axil of which it is produced. 
Fig. 644. Diagram of a staminiferous flower of Tragia cannabina. Fig. 645. Diagram of a 
staminiferous flower of Tragia volubilis. Fig. 646. Diagram of a staminiferous flower of 
Anthostema senegalense. Fig. 647. Diagram of a staminiferous flower of Adenopeltis 
colliguaya. Fig. 648. Diagram of a staminiferous flower of a Euphorbia. Fig. 649. 

1, Diagram of a staminiferous flower of Naias minor. 2, Of a pistiliferous flower of Naias 
major. Fig. 650. Capitula of Daisy, in which small tufts of greenish leafy scales occupy 
the place of the flowers. A represents the Capitulum of the Daisy with tufts of leaves in 
place of flowers, and a leaf on the scape. B, Section of the Capitulum. C, Section through 
one of the leafy tufts. 




occurs, or if the plant is pruned. 



TERATOLOGY — DEGENERATION. 369 

want of proper nourishment, are capable of producing abortions of 
various kinds. The non-development of a branch gives rise to clustered 
or fascicled (fascis, 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 (p. 120) ; or the petiole may be 
developed in a peculiar way, as in the phyllodia (p. 96) of some 
Acacias. 

Degeneration, or the transformation of parts, often gives 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 (p. 119), as in the Hawthorn and Wild-plum ; and 
by culture these spines may be converted into leaf-bearing branches. 
Leaves often become mere scales, as in Lathrsea, Orobanche, and in 
Bulbs. The limb of the calyx may appear as a rim, as in some Um- 
belliferse ; or as pappus, in Compositae and Valeriana. In Scrophu- 
laria the fifth stamen appears as a scale-like body, called staminodium 
(fig. 378, p. 227) ; in other Scrophulariacese, as in Pentstemon, 
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 undeveloped stamens in the form of filiform bodies or 
scales. To many of these staminal degenerations Linnaeus gave the 
name of nectaries. In double flowers transformations of the stamens 
and pistils take place, so that they appear as petals. In Oanna, 
what are called petals are in reality metamorphosed stamens. In 
the capitula of Oompositae we sometimes find the florets converted 
iqto green leaves (fig. 650). Allusion has already been made to the 
various changes which the dififerent 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. 

Cohesion, or the union of parts of the same whorl, and Adhesion, or 
the growing together of parts of different whorls, are very common 
causes of changes both as regards form and symmetry. The union of 
stems gives rise occasionally to anomalies, as in the fasciated stalk 
of Cockscomb (fig. 251, p. 174), and the flattened stems of some 
Coniferae (p. 117), and probably also the peculiar stems of certain 
Sapindaceae and MenispermaccEe of Brazil (p. 62). Some of these,, 
however, may perhaps be- traced not to union, but to an abnormal 
development of buds, producing wood only in one direction, in place 
of aU 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 

2b 



370 



TERATOLOGY — COHESION AND ADHESION. 



cohesion of two leayes by their bases forms a connate leaf, and the 
union of the lobes of a single leaf on the opposite side of the stalk 
gives rise to perfoliate leaves (fig. 171, p. '89). The union of the 
edges of a folded leaf forms Ascidia, or pitchers (figs. 200, 203, pp. 
95, 96). The diflferent parts of the same verticil of the flower unite 
often more or less completely, giving rise to a monophyllous or gamo- 
phyllous involucre (p. 190) ; a monosepalous or gamosepalous calyx 
(fig. 297, p. 197; a monopetalous or gamopetalous corolla (figs. 318, 
319, p. 206) ; monadelphous (figs. 338, p. 213 ; 346, 1, p. 218), 
diadelphous (p. 218), and polyadelphous (figs. 347, p. 218; 651) 
stamens ; syngenesious anthers (p. 227) ; a gynandrous column (p. 
220), and a syncarpous ovary (fig. 417, p. 239). The different verti- 
cils of the flower are frequently adherent. The calyx is often united 



<SiN 





Fig. 651. 



Fig. 652. 



to the coroUa or to the stamens, or both (fig. 339, p. 213); the sta- 
mens may adhere to the corolla (fig. 652) ; or there may be a union 
of the torus with the ovary, so that the calyx becomes superior (fig. 
340, p. 214). In some instances, when the axis is elongated, adhesions 
take place between it and certain whorls of the flower. Thus, in some 
Caryophyllacese (fig. 653), the calyx, c, bearing the stamens, e, and 
petals, J), becomes united to the axis, g, which supports the ovary, o. 
In Oapparidacese (fig. 654), the calyx, c, and petals, f, occupy their 
usual position, but the axis is prolonged in the form of a gynophore, 
ag, to which the stamens, e, are united. Occasionally, contiguous 
flowers may unite, giving rise to double fruits, as is sometimes seen in 
Apples, Grapes, and Cucumbers. 

Multiplication, or an increase of the number of parts, gives rise 
to changes in plants. It is often found that in plants belonging to 

Fig. 651. One of the five bundles of stamens taken from the polyadelphous flower of 
Malva miniata. Stamens are united by their filaments. Fig. 652. Portion of the gamo- 
petalous or monopetalous corolla, p, of a CoUomia, showing part of the tube, (, 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. 



TERATOLPGY — MULTIPLICATION AND CHOKIZATION. 371 



the same natural order the number of stamens in one is greater than 
that in another, either in consequence of additional stamens beiog 
developed in the vertjcil, or on account of the production of additional 





Fig. 653. 



Fig. 664. 



verticUs. The same thing is met with in the case of the other whorls, 
and is well illustrated in the formation of the disk (p. 234). Multi- 
plication causes a repetition of successive whorls, which still follow 
the law of alternation. 

Parts of the flower are often increased by a process of deduplication, 
unlining, dilammation, or clwrization, i.e. the separation of a lamina 
from organs already formed (p. 210). This is believed to take place 
in a remarkable degree in the case of appendages to petals. Thus, in 
Eanimculus, the petal (fig. 655) has a scale at its base, a, which is 
looked upon as .a mere fold of it. This fold may in some cases be 
more highly developed, as in Oaryophyllacese, and in Crassula rubehs 
(fig. 282 a), and it may even assume the characters of a stamen, 
which will therefore be opposite the petal, as iu Primulacese. Some 
do not consider the production of scales or stamens opposite to the 
petals as the result of chorization. Lindley argues against it from 
what is observed in CameUia 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 

Fig. 653. Flower of Lychnis Viscaria, one of the Caryophyllaceae, cut lengthwise, to show 
the relation of its different parts, c, Gamosepalous calyx, p, Petals with their elongated 
unguis or cla'w, u 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 ovaiy, o, and five styles, s. Pro- 
longation of the axis g, in the form of a gynophore or anthophore, bearing the petals, the 
stamens, and the pistil. Fig. 654. Flower of Gynandropsis palmipes, one of the Cappari- 
daccEB. c, Calyx, p, Petals, e. Stamens, ag, Gynophore or elongated intemode or axis 
bearing the stamens, ag", Gynophore or elongated intemode bearing the pistil, of. Pis- 
til composed of an ovary, o, a style and a stigma, / 




372 TERATOLOGY — MULTIPLICATION AKD CHORIZATION. 

run in several regular lines from the centre to the circumference. 
Again, by this process of deduplication it is supposed one stamen may- 
give rise to several. Thus, in Luhea paniculata (fig. 348, 
p. 219), in place of five stamens there are five bundles, 
composed partly of sterile filaments f s, 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. This process, therefore, repeats the single 
organs, and causes opposition of parts. Such cases may 
be explained by supposing each stamen to represent a com- 
pound leaf, or a single leaf divided in a digitately-partite 
manner (p. 219). In the case of the four long stamens of 
Fig. 66a. Cruciferse (p. 364), 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 supported by cases in which the filaments 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 appearance as the shorter ones, and 
occupy their usual position of alternation with the petals. In some 
instances, by pelorination (■rsAwg/os, monstrous), it is found that tetra- 
dynamous plants become tetrandrous, with stamens of equal length 
alternating with the petals. 

The mdde of explaining anomalies is well illustrated by Darwin's 
view of the formation of the flower of an Orchid (fig. 656). According 
to him " An Orchid flower consists of five simple parts — namely, 
three sepals and two petals ; and of two compounded parts — namely, 
the column and labellum. The column is formed of three pistils, and 
generally of four stamens, all completely confluent. The labellum is 
formed of one petal and two petaloid stamens of the outer whorl, 
likewise completely confluent. " This view of the nature of the 
labellum explains its large size, its frequently tripartite form, and 
especially its manner of coherence to the column, unlike that of the 
other petals. As rudimentary organs vary much, we can thus also 
probably understand the variability of the excrescences on the labellum. 
With respect to the six stamens or anthers which ought to be repre- 
sented in every Orchid, the three belonging to the outer whorl are 
always present, with the upper one generally fertile, and the two 
lower ones invariably petaloid and forming part of the labellum ; the 
three stamens of the inner whorl are less plainly developed, especially 
the lower one, which, when it can be detected, serves only to strengthen 

Fig. 655. Petal of Ranunculus Ficaria, viewed on the inside. I, The limb, a. Small 
scaly appendage at its base, formed by chorization or dilaminatiou. 



ANOMALIES IN FLOWER OE OECHID. 



373 



the column, and, in some rare cases, according to Brown, forms a sepa- 
rate projection or filament. The upper two anthers of this inner 
whorl are fertile in Cypripedium, and in other eases are generally 
represented either by membranous expansions or by minute auricles 
without spiral vessels. These auricles, however, are sometimes quite 
absent, as in some cases of Ophrys." On this view of the homologies 
of Orchid flowers, Darwin further remarks — " We can understand the 
existence of the conspicuous central column, — the large size, generally 
tripartite form, and peculiar manner of attachment of the labeUum, — 
the origin of the clinandrium, — the relative position of the single fer- 
tile anther in most Orchids, and of the two fertile stamens in Cypri- 
pedium, — the position of the rosteUum, as well as of aU the other 
organs, — and, lastly, the frequent occurrence of a bilobed stigma, and 
the occasional occurrence of two distinct stigmas." 

Upper or posterior sepal. i 



Upper 
petal. 




Upper 
petal. 



LabeUum. 

Kg. 656. 

Section of the Plowbe of an Oechid {Darvdn). 

Fig. 656. The little circles show the position of the spiral vessels, which 

alternate in five -whorls, the three central groups running to the three petals are 

■connected ty a triangle. 

S S. Stigmas ; S„ stigma modified into the rostellum. 

A^. Fertile anther of the outer whorl ; Aj, Ag, anthers of the same whorl com- 
hined with the lower petal, forming the lahellum. 

«i a^. Rudimentary anthers of the inner whorl (fertile in Cypripedium), gene- 
rally forming the clinandrium ; a^ third anthgr of the same whorl, when 
present, forming the front of the column. 



374 EFFECTS OF CULTIVATION ON OEGANS. 

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, etc. The changes in the coloilr 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 Eanunculus, the Au- 
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, and to present what are- 
caUed pelorian varieties. 



Section IV. — Some General Phenomena connected with 
Vegetation. 

1. — Vegetable Irritability. 

Under this head are included certain sensible movements of living 
plants not referable to mere elasticity, or to the hygroscopic nature of 
the tissues. These motions are influenced chiefly by light and heat, 
and, like many phenomena occurring in organised beings, they cannot 
at present be fully 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, stUl, in some in- 
stances, their use is obvious. 

Among the lowest classes of plants there are some peculiar move- 
ments of this kind. The simplest members of the searweed tribe- 
occasionally move throughout their whole substance. OscUlatorias, 
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. The spores of many Crypto- 
gamic plants, especially species of Vaucheria, and Conferva, and 



VEGETABLE lEEITABILITY. 375 

Prolifera, exhibit motions which depend on the presence of cellular 
hair-like processes called cilia. These mobile 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. 467, p. 265) there are two of 
these cilia or filiform tentacida, which project from a colourless 
rostrum. In Chsetophora elegans, var. fusiformis, four have been 
seen (fig. 468, p. 265) ; in Prolifera (fig. 469, p. 265) there is a circle 
of cilia, and in Vaucheria (fig. 478, p., 269) the spore is entirely 
covered with very short cUia, the vibration of which determines their 
forward movement. These spores, from their movements, have re- 
ceived the name of Zoospores (p. 265). Mr. Thwaites accounts for 
the rhythmical movements of cilia by electrical currents. In certain 
cells of Cryptogamic plants," especially in what are called Antheridia, 
bodies are met with called Phytozoa or Spermatozoids (p. 265), which 
also exhibit movements during a part of their existence. They are 
well seen in (Edogonium (p. 271), Sphseroplea (p. 272), Saprolegnia 
(p. 273), Fucus (p. 273), Hepaticse (p. 276), Mosses (p. 277), and 
Ferns and their allies (pp. 279, 280). 

Eemarkable movements have also been observed in the higher 
classes of plants. The foviUa contained in the poUen-grain in a young 
state, when m,oistened 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 
considered as merely molecular, and similar to what takes place be- 
tween the minute particles of inorganic matter — as, for instance, finely 
powdered Gamboge suspended ia water. These fovilla movements 
are easily seen in the very young pollen of Antirrhinum majus. Cer- 
tain movements also take place in the floral envelopes. Thus many 
flowers open and close at particular . periods (p. 262); these pheno- 
mena 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 Linnaeus the 
sleep of plants is the change produced on leaves by the absence of 
light. It is by no means analogous 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 are hardened, the irritability is often much diminished, as is seen 
in Oxalises. The folding of the leafiets of compound leaves usually 
takes place from below upwards, but sometimes in the reverse manner, 
as in Tephrosia Oaribsea ; so also with the common petiole, which is 
directed upwards during sleep in the Cassias and downwards in 
Amorpha. When,' besides the common petiole, there are partial 



376 



VEGETABLE lEKITABILITY. 




petioles, as in tlie Sensitive plant, they may be bent inwards towards 
each other, while the common petiole is bent downwards. 

Mimosa sensitiva and pudica (fig. 657), 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 mechanical and 
other stimuli. They have bipinnate 
leaves with four partial petioles pro- 
ceeding from a common rachis, and each 
of the petioles is furnished with nume- 
rous pairs of leaflets (about twenty), 
which are expanded horizontally during 
the day. During darkness, or when 
touched or irritated in any way, each 
leaflet moves upwards towards its feUow 
of the opposite side, which in its turn 
I * rises up, so that their upper surfaces 
Fi& 657. 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 have a tendency to become parallel to the common 
petiole, at the extremity 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, it is found that its 
leaves expand, and that they close when put into a dark room 
during the day, showing the influence which light has on these 

Fig. 657. Branch and leaves of Sensitive plant (Mvmosa pudica), showing the petiole in 
its erect state, a, and in its depressed state, h ; also the leaflets closed, c, and the leaflets 
expanded, d. At the base of the petiole a swelling or intumescence (pulvinus) is observed, 
and smaUer swellings exist at the base of each partial petiole, and at the base of each 
leaflet. During darkness the leafstalks hang down, and the leaflets are closed, while the 
reverse is the case during light. The cellular swellings at the base of the petioles and leaves 
are concerned in the movements. Protoplasmic contractions probably take place in the 
cells. 



SENSITIVE PLANTS. 377 

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 phenomena of folding and opening will go on, although 
at very in-egular intervals. 

The leaf of the Mimosa is sensitive of various kinds of stimuli, 
such as shaking, wounding, burning, contact of irritating fluids, elec- 
tric and galvanic shocks. Many chemical stimuli cause the leaves to 
fold. Thus the vapour of prussic acid, of chloroform, and of ether, is 
found to produce this effect ; and in such cases the irritability of the 
leaves is either destroyed, or, at all events, a considerable period of time 
elapses before it is restored. One or two drops of chloroform placed 
on the base of the petiole make it droop, and cause the leaflets to close 
in succession from apex to base. The influence extends to the other 
partial petioles and their leaflets. Although the leaflets expand after- 
wards, yet they are nearly insensible to the excitement produced by 
touch. When chloroformised several times they at length lose their 
contractility. Professor Simpson found that the vapour of chloro- 
form affected the sensitive plant. If the vapour was either too strong 
or too long continued, the plant was destroyed. When it was weak, 
and applied only for a few minutes, the leaflets in some plants closed, 
as when irritated, and did not expand again for an unusual length of 
time. In other plants under exposure to chloroform, no closure of the 
leaflets took place, and in a few minutes the plant became so anees- 
thetised that the mechanical and other irritations of the leaflets and 
petiole did not produce the common movements, nor did the irrita- 
bility become restored for a considerable time afterwards. The 
Yellow Water Sensitive plant (Neptunia plena), found in the East 
and West Indies and in South America, exhibits irritability in its 
petioles and leaflets. 

The temate leaves of many species of Oxalis (fig. 658) fold not 
merely during darkness, but also when agitated or struck lightly and 
repeatedly. Each of the leaflets folds upon itself, and then bends 
downwards upon the common petiole. The plant called Desmodium 
gyrans of the East Indies (fig. 659), the Gorachand of Bengal, or 
Telegraph plant, 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 



378 



VEGETAELE lEEITABILITY. 



oscillatory movement the leaf becomes inclined in various ways, often 
assuming a remarkably oblique direction. The upward and downward 
movements seem to depend on the influence of light and darkness. 





Kg. 668. 



Pig. 669. 



During the day the leaf becomes more or less horizontal, while during 
darkness it hangs down. Similar movements are seen in other species 
of Desmodium, as D. gyroides and vespertilionis. 

The movements in these' cases have been referred to certain 
changes in the organs, causing distension or contraction of the 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 freque^tly 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 move- 
ments 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. The contraction of the protoplasm in the cells may 
also be concerned in the leaf movements. Mechanical and chemical 

Fig, 663. Wood-Sorrel (Oxcdis Acetosella), with its temate leaves, wMch are said to dis- 
play a certain amount of iiritaMlity when exposed to bright sunshine. During the night 
eaeh of the thi-ee leaflets, forming the compound leaf, fold on their midrih, and then fall 
down towards the common petiole. Some say that this plant is the true Irish Shamrock. 
Fig. 659. A portion of the branch and leaf of the moving plant of India (Hedysarwii or 
Desmodium gyrcms). The leaf is impari-pinnate, and often pinnately-trifoliolate. The large 
odd leaflet, a, becomes more or less horizontal, under the influence of light and heat, and 
is depressed during darkness or cold. Besides the movement of rising and falling, it has 
also a lateral oscillatory motion, so that it often becomes oblique in its position relative to 
the leaf-stalk. At its base there is a cellular intumescence. The smaller leaflets, 6, of 
which there are either one or two pairs, have also swellings at their base. They exhibit 
constant jerking movements, by which they approach and retire from each other, and these 
motions go on to a certain extent during darkness. 



SENSITIVE PLANTS. 379 

stimuli are supposed t6 act by inducing alterations in the contents of 
the vessels and cells. 

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 irrita- 
tion 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 wfeather, 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 con- 
tractile, 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 disten- 
sible. The turgescence of the latter, which is kept up by light, 
counteracts the contractility of the former, and maintains an equili- 
brium, so as to keep the petiole erect ; but when acted on by cold, 
mechanical irritation, etc., the equilibrium is disturbed, and the 
contractility operates in depressing the petiole. A careful microscopic 
dissection of the sweUings, shows peculiar cells in some parts, which 
seem to differ in their contents from others in their vicinity. 

In the sensitive species of the Desmodium and Oxalis, the move- 
ments 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 that 
the movements seem 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 movement of gyration. 
In such a case, however, the motion ultimately ceases, while it con- 
tinues in the uncut leaflet. So also, if a leaflet is divided longitudi- 
nally into two parts, each of them continues to move for a time, but 
the motions cease as the process of desiccation goes on. 

The leaves of plants belonging to the natural order Droseracese 




380 VEGETABLE IRRITABILITY. 

(Sundews) show marked irritability. The leaf of Dionsea muscipula 
(Veaus's Ply-trap), a plant of that order, exhibits movements when 
touched. The leaf represented in figure 660 is composed of a pyUoid 

petiole, 'p, and a lamina, I, consist- 
ing of two movable halves united 
by a strong midrib. The lobes 
when open are placed at right angles 
to each other. Along the edge of 
each of them there are about 
twenty spiny hairs ; on the reddish 
upper surface there are numerous 
glands and three stiff hairs, a, with 
glandular bases on each division 
of the lamina. These, when touch- 
ed, cause the leaf to close with 
Jig. 660. considerable force. An insect alight- 

ing on these hairs is instantly 
entrapped. If it is very small it may escape through the grating 
formed by the crossing of the teeth, and the leaf will soon open 
again ; but if it is large it cannot get out, as the two halves of the 
lamina close firmly on it, and the spines at this edge interlace more 
and morp completely, like the teeth of a rat-trap, the irritation being 
kept up by the struggles of the insect. If the hairs are touched with 
a camel-hair pencil the leaf closes, and may remain so for twenty- 
four hours. Such is also the case if a small piece of any mineral and 
indigestible matter is placed in the leaf But if a fiy is caught] then 
the closure continues for a week or more. During the progress of 
the pressure the spiny hairs at the margin lose their interlacing posi- 
tion and become more or less erect, and finally the lamina opens. 
There is often a bulging on the outside of the lobes caused by the 
body of the insect contained within them. 

During the , time of closure the glands pour forth a peculiar 
secretion of an acid nature, as shown by the effect on litmus paper. 
This secretion acts upon the insect, which is gradually digested, 
nothing being left ultimately but the dry outer covering of the animal. 
The same thing occurs when a very small piece of flesh is grasped by 
the leaf. The leaf closes on it, and it is so completely digested that 
when the leaf opens there is nothing left. If too large a quantity of 
flesh is inserted digestion is not carried on properly, and th.e lamina 

Fig 660. Leaves of Veniis's Fly-trap {Iiwrwsxi muscipula), which exhibit evident irrita^ 
bility. The leaf consists of two parts, a lamina or blade, I, and a petiole or leafstalk, p. 
The two halves of the blade are united by a sort of hinge, a, and there are on each of them 
three hairs, which, when touched, cause the folding of the lamina in the way represented 
at I and b. At the base of each of the hairs there is a swelling. The irritation seems to be 
communicated by means of the vessels to the midrib, and the folding is owing to the tur- 
gescence of the lower cells of the midrib. The motion is of the nature of a hinge-joint. 



DIONiEA MUSCIPULA. 381 

shows symptoms of decay. The phenomena seem to resemble very 
much those which take place in animals in whom food is subjected to 
the action of ptyaline in the mouth and of pepsine in the stomach, 
along with the formation of hydrochloric acid. Both in the leaf and 
in the animal stomach an acid is formed with the view of promoting 
digestion. The plant has therefore been called insectivorous and 
carnivorous, as requiring the presence of albuminous animal food for 
its growth and nutrition. There is marked irrito-contractility ; first 
irritation and then contraction. Every living substance is capable of 
being excited into action — that is, of having its stored-up force dis- 
charged. There is a change of form, seen usually in some mechanical 
work. There seems, as Dr. Burdon Sanderson remarks, to be a 
resemblance between the contraction of muscle and the contraction of 
a leaf. The muscle exhibits chemical changes, consisting in disinte- 
gration of chemical compounds and dissipation of force stored up in 
these compounds. These phenomena are more especially seen when 
muscle contracts and when heat is developed. 

The muscle in its living state is electro-motive, and the force 
depends on the vigour of the muscle. When the muscle and the leaf 
contract, electro-motive force disappears and work is done. There is, 
however, no conversion of the one into the other, and there is no 
evidence that the force is electrical. 

Dr. Burdon Sanderson gives the following account of the elec- 
trical phenomena which accompany irritation of the leaf of Dionsea : — 

" 1. When the opposite ends of a living leaf of Dionsea are placed on 
non-polarisable electrodes in metallic connection with each other, and 
a Thomson's reflecting galvanometer of high resistance is introduced 
into the circuit thus formed, a deflection is observed, which indicates 
the existence of a current from the proximal to the distal end of the 
leaf. This current I call the normal leaf-current. If, instead of the 
leaf, the leaf-stalk is placed on the electrodes (the leaf remaining 
united to it) in such a way that the extreme end of the stalk rests on 
one electrode; and a part of the stalk at a certain distance from the 
leaf on the other, a current is indicated, which is opposed to that 
in the leaf. This I call the stalk-current. To demonstrate these two 
currents, it is not necessary to expose any cut surface to the electrodes. 

"2. In a leaf with the petiole attached, the strength of the cur- 
rent is determined by the length of the petiole cut off with the leaf, 
in such a way that the shorter the petiole the greater is the deflec- 
tion. Thus, in a leaf with a petiole an inch long, I observed a deflec- 
tion of 40. I then cut off half, then half the remainder, and so On. 
After these successive amputations, the deflections were respectively 
50, 65, 90, 120. If in this experiment, instead of completely sever- 
ing the leaf ait each time, it is merely all but divided with a sharp 
knife, the cut surfaces remaining in accurate apposition, the result is 



382 VEGETABLE IRRITABILITY. 

exactly the same as if the severance were complete ; no further effect 
is obtained on separating the parts. 

" 3. Effect of constant current directed through the petiole on the 
leaf-current. — If the leaf is placed on the galvanometer electrodes as 
before, and the petiole introduced into the circuit of a small Daniell, 
a commutator being interposed, it is found that on directing the 
battery-current down the petiole {i.e. from the leaf), the normal deflec- 
tion is increased ; on directing the current towards the leaf, the deflec- 
tion is diminished. 

" 4. Negative variation. — a. If, tiie leaf being so placed on the 
electrodes that the normal leaf-current is indicated by a deflection 
leftwards, a fly is allowed to creep into it, it is observed that the 
moment the fly reaches the interior (so as to touch the sensitive hairs 
on the upper surface of the lamina), the needle swings to the right, 
the leaf at the same time closing on the fly. 

" 6. The fly having been caught does not remain quiet in the leaf; 
each time it moves the needle again swings to the right, always 
coming to rest in a position somewhat farther to the left than before, 
and then slowly resuming its previous position. 

" c. The same series of phenomena present themselves if the sensitive 
hairs of a still expanded leaf are touched with a camel-hair pencil. 

" d. If the closed leaf is gently pinched with a pair of forceps with 
cork points, the effect is the same. 

" e. If the leaf-stalk is placed on the electrodes as before, with the 
leaf attached to it, the deflection of the needle due to the stalk-cur- 
rent is increased whenever the leaf is irritated in any of the ways 
above described. 

"/. If half the lamina is cut off, and the remainder placed on the 
electrodes, and that part of the concave surface at which the sensitive 
hairs are situated is touched with a camel-hair pencil, the needle 
swings to the right as before." * 

Species of the genus Drosera (Sundew) exhibit excitability in the 
leaves, with a certain amount of contractility. The leaves are of 
various forms, some narrow and elongated, others spathulate or 
rounded, aR bearing on their surface and at their edges beautiful 
glandular hairs, with a spiral cofl. in their interior, and a globular apex 
containing peculiar secretions (fig. 661). They are also insectivorous. 
"When insects alight on the leaves they are entangled by the viscid 
matter of the glandular hairs, which gradually close upon them, and 
prevent their escape. The apex of the leaf turns inwards, so as more 
effectually to secure the prey. This is well seen in some Australian and 
African species. Droseras are by no means so excitable as the Dioneea, 
but they seem to act in a similar manner upon insects. Small por- 
tions of flesh placed upon the leaves induce movements of the hairs ; 

» Proceedings of the Royal Society of Loudon, Nov. 20, 1873. 



DEOSEKA AND SAEEACENIA. 



383 




Kg. 661. 



and it would appear that albuminous food is thus taken up by the 
plant for its nourishment. 

The species of Drosera are widely distributed; 
three species and some varieties being found in 
Britain, and numerous species occurring in Australia 
{fig. 88, p. 32), Equatorial America, and South 
Africa. Experiments have been made upon the 
British species, as well as upon Drosera Whittakeri 
•of Australia, D. filiformis of Forth America, and 
on some African species. In all these, leaf move- 
ments, of the nature described, have been observed 
in a greater or less degree. 

The species of the genus Pinguioula appear also 
to secrete a viscid fluid, which detains insects. The 
leaves curl in at the margin, but the presence of 
irritability is doubtful. 

We may here make some remarks on plants which seem also to be 
insectivorous, although not displaying excitability and contractility. 
We may specially notice the species of Sarracenia (Trumpet-leaf). The 
leaves of these plants are all radical, with a more or less tubular petiole, 
the blade being small, and often lying over the orifice of the tube (fig. 
203, p. 96). In some of the tubular petioles honey-like matter is secreted, 
and this attracts insects, and a secretion collects at the bottom of the 
tube, which seems to have the power of destroying them. In the 
case of Sarracenia variolaris (Spotted trumpet-leaf) the inner surface 
of the tube or pitcher, from the mouth to midway down, is smooth 
iind velvety to the touch, as the finger is passed downwards ; from 
midway there are retrorse bristles, increasing in size downwards, and 
ceasing near the base. Insects are attracted by a viscid, honey-like 
substance, secreted from the internal surface of the pitcher, and ex- 
tending a short way from the margin, and in passing downwards they 
slip down into the secretion at the bottom, and are prevented from 
getting out by the hairs. The fluid in this species seems to destroy 
insects, but it has not yet been proved that it feeds upon them. 

Hooker says that th