The flowering plant: as illustrating the first principles of botany

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104 Charing Cross Road, ~
“LONDON. W.C. _ al

J. POOLE & COW
Educational ‘Booksellers,

THE FLOWERING PLANT.

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Bu the same Author.

———~>———

In large crown 8vo, handsome cloth, 12s. 6d.

AN INTRODUCTION TO BIOERGEY,

For THE USE OF STUDENTS.
Comprising Vegetable and Animal Morphology and Physiology.

By J. R. A. DAVIS, B.A.,

Lecturer on Biology at the University College of Wales,
Aberystwyth.

GENERAL CONTENTS.

Part I. VEGETABLE MORPHOLOGY AND PHYSIOLOGY: Fungi;
Alge; The Moss; The Fern; Gymnosperms; Angio-
sperms.

Comparative Vegetable Morphology and Physiology ; Classi-
fication of Plants,

Parr II, ANIMAL MORPHOLOGY AND PHYSIOLOGY : Protozoa ;
Coelenterata; Vermes; Arthropoda; Mollusca; Amphibia;
Aves ; Mammalia.

Comparative Animal Morphology and Physiology ; Classifi-
tion of Animals.

With Bibliography, Examination Questions, Complete Glossary,
and 158 Illustrations.

‘‘Furnishes a clear and comprehensive exposition of the
subject in a systematic form. For the highest three groups
of animals the types described are the frog, the pigeon, and
the rabbit. So full are the details of the Morphology,
Physiology, and Development of these three types, that
150 pages are occupied in their description, illustration, and
comparison, Yet nowhere does there seem to be a single
phrase in excess. A valuable Bibliography is appended,
besides Index-Glossary.”—Saturday Review.

“The volume is literally packed with information.”—
Glasgow Medical Journal.

‘* As a general work of reference, Mr. Davis’ Manual will

be highly serviceable to amateur or professional scientists.”
--British Medical Journal.

LONDON : CHARLES GRIFFIN & COMPANY, LIMITED
EXETER STREET, STRAND,

THE FLOWERING PLANT:

AS ILLUSTRATING THE

FIRST PRINCIPLES OF BOTANY.

BY

J. R. AINSWORTH DAVIS, B.A.,

TRINITY COLLEGE, CAMBRIDGE;
PROFESSOR OF BIOLOGY AND GEOLOGY IN THE UNIVERSITY COLLEGE OF ABERYSTWYTH;
AUTHOR OF ‘‘A TEXT-BOOK OF BIOLOGY.”

Hith Pumerous Ellustrations, Appendix on Jractical WAork,
AND EXAMINATION QUESTIONS.

SECOND EDITION.

LIBRARY
NEW YORK
SOTANICAL

GARDEN,

LONDON:
CHARLES GRIFFIN AND COMPANY, Lmitep,

EXETER STREET, STRAND.
1892.

[ All rights reserved. ]

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PREFACE.

—>++—

THE present work has been written with the intention of
illustrating the First Principles of Botany by means of
common Flowering Plants. No previous knowledge is
assumed, and the style is made as simple as possible, the
technical terms necessary being carefully explained as they
occur. ‘The paramount importance of Practical Work is
insisted on throughout, and, wherever possible, easily
obtained objects are described instead of rare ones, so that
the student can readily verify most of the facts mentioned.
A short Practical Appendix is also added.

No attempt has been made to “ write up” (or “ down”)
to any syllabus, but it is believed that the book will meet the
requirements of most Elementary Examinations in Botany.
A selection of South Kensington and London Questions
has been appended.

My best thanks are due to Professor J. von Sachs for
permission to use several figures; and also to my friend
and former colleague, Mr. John Brill, M.A., who has given
me much kind help during the progress of the work.

Any corrections or suggestions for improvement will be
gladly received.

J. It. A. D.

ABERYSTWYTH,
December, 1889.

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CONTENTS.

CHAPTER I.
INTRODUCTORY,
PAGE
ScoPE AND SUBDIVISIONS OF THE SUBJECT . ‘ : : : é I
DIFFERENCES BETWEEN PLANTS AND ANIMALS. : : ‘ 2
DIFFERENCES BETWEEN LIVING AND Non-LiIvING Marrer , ; 4
CHAPTER II.

ELEMENTARY MORPHOLOGY AND PHYSIOLOGY.
MEMBERS AND ORGANS ,
STRUCTURE OF PLANTS . : : : : 8
LIFE UNDER SIMPLE CONDITIONS . : : : : : ; : 8

CHAPTER ITI.
THE ROOT.

MOoRPHOLOGY . - . ‘ ; ; : sin eles
PHYSIOLOGY . , : : : ; : ‘ . + paie
CHAPTER IV.

THE STEM.

MORPHOLOGY . : : ; : : : : : : : eee
PHYSIOLOGY . : 3 : : ; : ; : : koe
CHAPTER V.

BUDS AND LEAF ARRANGEMENT : .; “Ab
CHAPTER VI.
FOLIAGE AND SCALE LEAVES.
MORPHOLOGY . ; : : : 3 ; , ; ‘ ; 3) Coaeee

PHYSIOLOGY . : J : : : : ; : : é 66

Vill ~ CONTENTS.

CHAPTER VII.
BRACTS AND FLORAL LEAVES.

PAGE
GENERAL DESCRIPTION . : : : : : , : 5° 94
INFLORESCENCE ‘ : : : ; : : . ; : ee 3
SYMMETRY OF FLOWER . ; ‘ ' , 4 ‘ : 5 . - 80
FLORAL RECEPTACLE. : ‘ ‘ ; ; : ; 2° OSH
RELATION OF PARTS. : : ; : : : : : “2
CaLyx . ‘ ; : : : : : F : ; ‘ dae
CoRoLLA : ‘ : y : : : : , ‘ : . 86

CHAPTER VIII.
ESSENTIAL FLORAL LEAVES.
STAMENS : - . : ; ‘ , : ia se
CARPELS : : ; Mig TPE ; » ahh
OVULES . 3 : : : : : ; 4 : : : . 107
PROOF THAT FLOWER IS A SHOOT . ‘ . ; - tea
CHAPTER IX.
PHYSIOLOGY OF FLOWERS.
PROTECTION III
RESPIRATION . 114
REPRODUCTION 114
POLLINATION . 114
Cross- POLLINATION 15
SELF-POLLINATION . 130
FERTILIZATION : , 5 : : : ‘ : , + 9h
MorIiLity, IRRITABILITY, AND SPONTANEITY . d : ‘ : |
CHAPTER X.
SEEDS AND FRUITS.

MorPHOLOGY . : : : P ‘ : ; : lye
PHYSIOLOGY . é : : : : F ; a.
APPENDIX A.

PRACTICAL WORK ; : ; - 245
APPENDIX B.
EXAMINATION QUESTIONS : ; 445%

INDEX (5. 0... . ) . . oe

LIST OF ILLUSTRATIONS.

—++-—

FIG. PAGE
1. Sectional View of a Unicellular Plant (original) : : ; 9
2. Diagram of a Dicotyledon (Sachs) . : 2 : : ‘ Bel abe
3. Seedling of White Mustard (Sachs) . : : : : , ae
4. Diagram of a Young Maize Plant (Sachs) : ; , F Ue gee
5. Diagrams of Anatomy of Vegetative Organs (Prantl) : : mr BO
6. Structure of Sunflower Stem (Prantl) : 22
7. Minute Structure of Vegetative Organs (Prant/ and original) . “oY 35
8. Secondary Thickening of Stem (Sachs) , F be aay
g. Phyllotaxis of Cherry . ; : . ; : : R uy 50
10. Part of Grass Leaf . : 2 : : : : ‘ 4 oy 53
11. Base of Willow Leaf : : ‘ : ‘ : ; : tun 52
12. Bipinnate Leaf of Acacia . : : . : : , : AT he
13. Oblique Leaf of Elm ; ; : : : ? : ‘ rues
14. Oblong Leaf. p : E : ? : : : a i
15. Spathulate and Oval enka : : : : ‘ . : eee
16. Rounded and Arrow-Shaped Leaves F : ‘ : : Yaad
17. Peltate Leaf. : P : : ‘ sv, 58
18. Lanceolate, Awl-Shaped, ih Whorled nan es ’ ; , 3 58
19. Ovate Leaf 7 , : i : . : ‘ F ‘ ae ake
20. Cordate Leaf . : : : : mo) Me
21. Kidney-Shaped, Elliptical, ae Mee i ; ; Broth 58
22. Oak Leaf . : ; : ‘ : : : : : : 4 go
23. Poppy Leaf . s ; : ; F : ; E : ia Se
24. Pinnate Leaf . : : , 3 : : so See 2, ta
25. Strawberry Leaf. : , : ‘ ‘ ‘ : fe
26. Horse-Chestnut Leaf : : é : ‘ é é : . 6c
27. Pitcher of Nepenthes - P : : : : ; ; ‘y 02
28. Leaf of Knot-Grass . ; z Z : : , : : a ae
29. Leaf of Scarlet Runner . : : . : - , ; i age
30. Flower of Buttercup F é ; . A : : : Bee Sy

LIST OF ILLUSTRATIONS.

. Raceme of Barberry

. Spike of Verbena

. Spadix of Arum

. Section of Fig . :

. Forked Cyme . : :

. Helicoid Cyme of Forget-me-Not

. Relation of Parts of Flower (Prantl)
. Floral Diagram of White Lily (original) .
. Floral Leaves of White Water-Lily .
. Flower of Rose

. Petal of Pink

. Sweet Pea 5

. Labiate Corolla of Sage

. Ligulate Floret :

. Flowers of Scotch Fir (original)

. Stamen of Sage

. Pollinia of Orchid :

. Placentation and Ovules (Prantl)

. Diagram of a Flower

. Flower of Grass :

. Structure of Pansy (Sachs)

. Early Purple Orchis (original) .

. Section of Albuminous Seed

. Section of a Maize Fruit (Sachs)

. Fruit of Mulberry

. Achene of Buttercup

. Splitting Fruit of Geranium

. Samaras of Sycamore

. Diagrams of Capsules (original)

. Pyxidium of Henbane

. Browning’s Field Microscope

PAGE

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IMRARY
EY YORK
SUT ANICAL

LADDERS,

THE FLOWERING PLANT.

CHAPTER I.
INTRODUCTORY.

Scope and Subdivisions of the Subject.—The science of Borany
endeavours to answer all questions relating to plants. It is
subdivided into numerous branches, which share these questions
between them.

The query, ‘‘ What is its shape, and why is it so?” is answered
by Vegetable Morphology. This deals not only with outward
form (Descriptive Botany), but also with inward form or structure,
the larger details of which can be made out by the unaided eye or
by means of a lens (Vegetable Anatomy), while the finer points
cannot be cleared up without the help of a compound microscope
(Vegetable Histology). Another primary question is, ‘‘ How does
it act?” and this time the answer is given by Vegetable Physio-
logy. But plants may also be considered in relation to one
another. Resemblances and differences are apparent even to the
most casual observer. Such a word as “lily” is the expression
of a popular conviction that certain flowers (white lily, tiger lily,
&e.) have a general resemblance to one another, and are at the
same time different from other plants, such as ‘“ grasses,” for
example. Arrangement into groups according to resemblances and
differences is Classification, and the question, ‘‘ How are plants
arranged, or how related?” is answered by Systematic Botany,
which is the application of classification to the vegetable world.
Any merely popular classification, as into “lilies,” “ grasses,” &c.,
is of necessity unsatisfactory, for resemblances and differences
must be noted with a critical eye. An “arum lily,” for example,
is quite different from other lilies, and the name is incorrect.
Systematic Botany has two chief uses. It enables us, in the first
place, to remember a far greater number of facts than would
be possible without a methodical arrangement. And, again, the

A

2 . THE FLOWERING PLANT.

resemblances which connect plants into groups are not the result
of mere chance, but express actual relationship, what, in animals,
would be called ‘ blood’’-relationship. The different groups of
plants do not form a “ linear series,” 2.¢., they cannot, as regards
affinity, be placed in a line, the most complex members of one
group coming just below the least complex of the next group, and
so on; but they naturally fall into a tree-like arrangement. This
is now believed to represent, in a general sort of way, a genea-
logical tree. The second great use of Systematic Botany is, there-
fore, to help in the construction of plant-genealogies. Apart from
the great theoretical interest attaching to this kind of work, there
is a very practical application affecting medicine and many manu-
factures. Broadly speaking, closely related plants have similar
properties, and a classification which represents affinities with fair
accuracy will be of the greatest service in the search for new
drugs, dyes, fibres, &c., &c. The uses, if any, of a newly-discovered
plant can also be judged of with some accuracy even without
experiment. The branch Economic Botany, which deals with the
question, “Of what use to man?” is therefore an appendix to
Systematic Botany. The present volume, however, has little or
nothing to do with this branch, nor is it concerned with Geo-
graphical and Fossil Botany, which endeavour to answer the
questions, ‘‘ Where found?” and “When found?” that is to
say, try to elucidate problems regarding distribution im space
and time. |

Differences between Plants and Animals.—It might at first
be thought that plants, with which Botany deals, could easily be
distinguished from animals, which form the subject-matter of the
sister science, Zoology. No one is in danger of confounding a
cow with a cabbage, and, as a matter of fact, ordinary plants are
marked off with sufficient distinctness. But when we come to
lower forms, often of minute size, it is frequently difficult to say
for certain whether a given form be plant or animal. The recog-
nition of this fact has emphasized the close connection between
the two divisions of the organic world, and called into existence
the science of Biology, which deals with life generally, and in-
cludes both Botany and Zoology.

The largest subdivisions of the vegetable kingdom are those of
Flowerless Plants (Cryptogams) and Flowering Plants (Phanero-
gams), without and with conspicuous flowers respectively. Wha
flowers exactly are will be seen in the sequel. We shall here
deal, from an elementary point of view, with Flowering Plants
only. These differ from animals in several important par-
ticulars :—

(1.) A typical member of the group is dependent upon gaseous

INTRODUCTORY. 3

food, contained in the air, and liquid food, present in the earth.
These are sucked in or absorbed by the general surface of the
body, the area of which is much increased by the freely-branched
or diffuse form so characteristic of plants. Animals, on the other
hand, utilize a great deal of solid food, which is usually taken in
by a mouth, and received into a digestive cavity, where it is, to a
greater or less extent, brought into a state of solution, or else of
fine division. ‘The shape of animals is compact, in accordance
with the solid nature of their food.

(2.) Again, plants, at any rate green plants, live on very simple
food, namely, the carbon dioxide or carbonic acid (CO,) of the air,
and watery solutions of mineral substances (salts) contained in the
soi. These they can build up into the complex substances com-
posing their own bodies. Animals require complex food, derived
from plants or other animals.

(3.) The nature of the food also exerts an influence upon the
plant or animal in another direction. The air and earth are full
of plant-food, and, by extending branches of the stem and root
into them, a tree or herb can obtain an abundant supply. Hence
powers of spontaneous locomotion are not possessed by plants.
The complex food of animals is less uniformly distributed, and
conspicuous powers of locomotion are generally possessed by them,
one main aim being to find and secure suitable food.

(4.) Higher animals are also characterized by the possession of
a nervous system, 2.e., organs for regulating the body generally
‘and rendering it sensitive to external influences. There are central
organs (brain and the like) exerting control, and these are placed
in communication with all parts of the body by definite strands
or nerves, along which impulses pass, and the sole use of which is
to convey such impulses. No such arrangement is found in any
known plant, although a local sensitiveness is sometimes exhibited
(e.g., sensitive plant).

(5.) It may be mentioned as a further point, that plant-hairs
and membranes are largely composed of a complex substance,
cellulose, allied to starch and composed of carbon, oxygen, apd
hydrogen. Cotton is a very pure form of this body. In the
animal kingdom cellulose is mainly conspicuous by its absence.

Exceptions.—The preceding tests are not absolute, even among
the higher plants. Some few are not green (e.g., clover-dodder),
and these, like animals, require complex food, though this is not
taken into the body as solid: particles. Such forms are termed
parasites when they prey upon living organisms, saprophytes
when they subsist on complex compounds derived from the dead
bodies of plants or animals. The “ insectivorous” or “ carni-
vorous ” plants, again, partly live on flies and the like, parts of

4 THE FLOWERING PLANT.

which they reduce to solution, often in a kind of external stomach
(e.g., pitchers of the pitcher plant). On the other hand, some
animals, all rather low in the scale, contain chlorophyll, and by
its means utilize the carbon dioxide of the air and simple salts
dissolved in the water around them; and it is not unlikely that
animals exist which contain so much chlorophyll as to obviate
altogether the necessity for solid food. Some comparatively high
animals, such as the tapeworm, which are not green, can dispense
with such food in another way. They live as endo-parasites, 2.e.,
within other animals, and feed at their expense on the soluble
products of digestion, which, however, are by no means simple in
composition. This mode of life may, and often does, do away
with the necessity for an internal digestive ai: as in the
example quoted.

The branching form and absence of locomotor powers cease to
be plant-tests among many microscopic forms, which may be oval
or spherical, and capable of the most active locomotion. And
many comparatively high animals (oyster, &ec.) are sedentary,
though their embryos swim actively about. There is no trace of
a nervous system in the lowest animals; and, lastly, cellulose is
not exclusively a vegetable product. It is found in some few
animals, as, e.g., the sea-squirts (Ascidians).

But in spite of these partial exceptions, there is no difhiculty
whatever in distinguishing plants from animals, except in the
very lowest forms. These are believed to be nearer a common
stock from which all organisms have sprung, and are, therefore,
more alike than are the higher plants and animals, which have
diverged more or less in different directions from that stock.

Differences between Living and Non-Living Matter.—At this
point the question naturally arises, ‘‘ How does organic living
matter differ from inorganic non-living matter?’’ Here, so far
as we yet know, sharp boundary-lines can be drawn.

(1.)! The elementary chemical substances, some seventy In num-
ber, are supposed to be ultimately made up of infinitely minute
particles, atoms. Even in an element, these are built up into
small aggregates or molecules, while the molecules forming che-
mical compounds are built up from more than one kind of atom,
and are the smallest quantities in which a compound can exist
as such. When a very large number of atoms enter into a mole-
cule, it is said to be complex, and this is characteristic of the com-
pounds of which organisms are composed. All plants and animals
are essentially made up of a jelly-like substance, known as proto-
plasm, the molecule of which is undoubtedly of extreme complexity.

1 Students who have read no chemistry are strongly advised to work through
such a book as Roscoe’s Primer.

INTRODUCTORY. 5

Protoplasm has been called the ‘“ physical basis of life,’’ because
life, whatever that may be, is always associated with it. In fact,
some very simple organisms are entirely (or mainly) composed of
protoplasm. The Ameba, for example, one of the lowest of ani-
mals, is a minute speck of semifluid protoplasm, which, notwith-
standing its simplicity, can and does perform all the functions of
life. Generally, however, the existence of protoplasm is more or
less hidden by the presence of other substances, formed by or from
it, or taken in from the outside. Take, for example, a peeled
potato. This is mostly made up of an immense number of micro-
scopic compartments (cells or units of structure), each of which
contains its modicum of protoplasm. The walls of the compart-
ments are made of cellulose, which forms a firm framework, and
each of them contains a large number of minute granules of starch.
Both cellulose and starch, which form the obvious parts of the
potato, are formed from protoplasm. This itself is far less evi-
dent, but makes up part of the slime that may be observed on the
peeled surface. The vital substance of which we are speaking is,
like most very complex compounds, very unstable. After death it
breaks down at once, not into elements, but into other simpler
compounds, which enter into the composition of its molecule.
These simpler compounds are, however, very complex themselves.
The most important of them are prote/ds, composed of a great
many atoms of carbon, hydrogen, oxygen, nitrogen, sulphur, and
perhaps, in some cases, phosphorus. If, then, the composition of
the proteid molecules is so complex, it is obvious that the mole-
cule of protoplasm must be far more so.

It must not be imagined, from what has just been said, that we
know enough of protoplasm to regard it as a chemical compound
of definite composition. Nor is to be supposed that all the sub-
stances found in protoplasm by chemical analysis necessarily help
to build up its living molecules. For ‘“ protoplasm” appears to
consist of an excessively fine network of living organized matter,
the meshes of which enclose other substances that are unorganized
and not living.

(2.) Organisms are also characterized by the nature of their
external form, which is definite, and bounded by more or less
curved surfaces. Non-living matter either has no very particular
form (7.e., is amorphous’, or else assumes a regular crystalline
shape. Crystals are geometrical forms, which are almost always
bounded by flat surfaces meeting in sharp edges.

(3.) Furthermore, organisms exert a great deal of kinetic
energy, and this is gained by the breaking-down of the protoplasm
into simpler substances. A complex chemical molecule is a store
of potential energy, and this is changed into the kinetic form by

6 THE FLOWERING PLANT.

the breaking-down of the molecule. The instability of organic
matter is due, not only to its complexity, but also to the presence
of nitrogen as a component. This element does not readily com-
bine with other elements, and the union, when effected, is a very
weak one. The continual wasting of organisms must be made up»
for by the taking in of food from the exterior, which is built up
into new protoplasm. All the protoplasmic parts of an organism
are continually breaking down, and new molecules are, therefore,
formed in all parts of the body. In brief, an organism undergoes
constant waste and as constant renewal.

(4.) If more food is taken in than is necessary to make up for
waste, growth may result to a certain extent, and this is effected
by formation of new molecules in all parts of the body (dntussus-
ception). A plant or animal is, then, only constant as regards
form, and not as regards the substance of which it is composed.
This has been illustrated by comparison with a whirlpool, which
may remain for a long time constant in shape, though new par-
ticles of water are constantly entering it to replace those passing
out.

Inorganic matter does not undergo the constant breaking-down
and renewal just described, and though it may exhibit a sort of
growth, as seen in a crystal or a stalactite, this is not by mtussus-
ception, but by the addition of new layers to the outside (accretion).
Thus the inner part of such a growing body is always older than
the outer. Further, there is no fixed limit to this kind of growth,
provided the external conditions are favourable.

(5.) Lastly, organisms have what may be called a definite life-
history.! ‘They come into existence, carry on certain functions,
attain a maximum size, and lastly die, when their bodies break
down into the simpler compounds from which they were originally
derived.

Having defined Botany and indicated the boundary-lines which
mark off organisms from inorganic matter and plants from ani-
mals, the importance of practical work must next be insisted on.
The great use of all branches of Natural Science is to teach the
habit of accurate and careful observation, and afterwards to build
up theories on the facts thus obtained. Botany is extremely well
suited to beginners in science, since abundant material is easily
obtainable, and the instruments necessary in the early stages are
comparatively few. Details will be found in the Appendix on
Practical Work.

1 This term has recently been employed in a wider sense,

CHAPTER II.
ELEMENTARY. MORPHOLOGY AND PHYSIOLOGY.

Members of a Plant.—An ordinary plant, eg., sunflower,
regarded from a morphological point of view, is composed of
parts which, though they present a great variety of shapes, can
all be classified under four main categories—Hair-structure, Root,
Stem, and Leaf. By repetition of these members a plant is built
. up, and they have even been regarded by some as individuals
collectively forming a colony. All structures which come under
one of these four headings, as say that of hair-structure or
““ Trichome,”’ are homologues, and are said to be homologous, or
to display homology. ‘This signifies an agreement in relative
position and manner of origin. It does not mean that they are
necessarily similar in shape or perform the same office in the
economy, although this may be and often is the case. All hair-
structures agree in being superficial members, developed from a
skin-like coating, the epidermis, with which plants are clothed.
Anything which agrees with this definition is a hair-structure,
whether it be a thread, simple or branched, a scale, or what not.
And again, some hair-structures keep off. unwelcome visitors,
others (as in horse-chestnut leaf-buds) form a kind of glue to
protect the young leaves from cold, while still others assist in
processes which lead to the formation and scattering of the seed,
and so on,

Organs of a Plant.—If, on the other hand, a plant is regarded
from a physiological standpoint, it is found to be made up of
organs, 2.é., structures fitted to perform special kinds of work.
Thus we have organs of nutrition, organs of respiration, con-
cerned with breathing, &c., &c. Organs belonging to any one of
these categories are analogues, and are said to be analogous, or
to display analogy. Relative position and mode of development
are here of no moment, the essential agreement being solely in
the nature of the work performed. Now, although all hair-
structures, roots, stems, and leaves are respectively analogous to
a large extent, they are by no means entirely so. Hair-structures,
for example, may (as mentioned above) perform very different

) THE FLOWERING PLANT.

functions. And again, different members may be similar organs,
and hence display analogy. Thus, among climbing plants, the
ivy climbs by its roots, the convolvulus by its stem, the pea by
modified leaves, and the hop by both stem and hair-structures.

Structure of Plants.—Careful examination of plant-members
shows that they are not homogeneous in structure. A thin skin
can be peeled from the upper and lower surfaces of most leaves,
and then comes a green pulp, traversed by firmer strands, popu-
larly called nerves or veins. They are the parts which make
up ‘‘skeleton” leaves, the softer structures having rotted away.
These different components of leaves, &c., are called tissues, and
it can be shown by the microscope that they, in their turn, are
made up of smaller parts known as ce//s and cell-derivates. These
cells, which are the units of plant-structure, just as bricks and
stones are in architecture, are for the most part microscopic,
though sometimes of large size. The pulp of an orange, for
example, is made up of such large cells, resembling in this case
spindle-shaped bags, and containing a good deal of fluid. Botani-
cal knowledge is based on the structure and physiological powers
of cells, and the very simplest plants known (and simplest animals
too) are single cells, in other words, they are unicellular.

Life under Simple Conditions.—Without reference to any
special example, we will consider the structure and conditions
of life in one of these simplest forms, and then see what modifi-
cations exist in multicellular plants, 7.e., those made up of many
cells.

The general form of the body in our ideal example is spherical,
and this appears to be a common result of uniformly distributed
external influences. The shape is distinct and permanent, owing
to the presence of a firm elastic membrane, the cell-wall, which
forms a kind of superficial skin, Within the wall, and forming
a lining to it, comes a slimy layer, the protoplasm, and part of
this is of different texture to the rest, and forms a firmer round
or oval nucleus, which again contains a nucleolus. There are
also present a number of granules of dense protoplasm, permeated
with chlorophyll, a green colouring matter. These are chlorophyll
granules, The larger internal space or vacuole is full of fluid, the
cell-sap, which consists of water holding various substances in
solution. It is also supposed to permeate the protoplasm and cell-
wall. A cell from the pulp of an orange corresponds fairly well
with this description, but a slight modification of shape has taken
place. So much for the morphology. The most essential phy-
siological fact with which to start is that the protoplasm is the
only living part of the cell. Very young cells contain no vacuole,
which is produced later on, owing to the fact that growth in

ELEMENTARY MORPHOLOGY AND PHYSIOLOGY. 9

volume outstrips growth in mass.

Cells are also known which

possess no cell-wall, and this in all cases appears to be formed

by the protoplasm, probably from
transformation of a surface layer.
Another important point is that
the active vegetable cell is in a
turgid state, t.e., the cell-wall is
kept on the stretch by pressure
from within. This turgidity, which
causes the firmness of freshly-cut
flowers, and the want of which
makes them flaccid when faded, is
a phenomenon largely independent
of life in the plant. It is a well-
known physical fact that if two
different liquids are separated by
a membrane which both can
moisten, diffusion currents will
pass through the membrane in
both directions, but not to an

Dies

FIG. 1.—Sectional View of a Unicellular

Plant, much magnified. [Original.]
1. C.w. cell-wall; Pr. protoplasm;
N. nucleus; n. nucleolus; ch. chlo-
rophyll bodies (granules), the black
dots in which represent starch; V.
central vacuole, full of cell-sap; the
arrows on right indicate direction of
streaming movements in two proto-
plasmic threads. 2, 3. Stages in divi-
sion; in 2, the nucleus and protoplasm
have divided, and a cellulose partition
has been formed ; in 3, the two halves

equal extent. The gain in volume #¥e beginning to separate.

will be on the part of the liquid, usually the denser one, which
can wet the membrane more readily. The phenomenon is
called osmosis, the passage inwards being endosmosis, that outwards
exosmosis. These processes can be conveniently studied in an
artificial cell, constructed in the following way :—A short piece of
fairly wide glass-tubing, filled with a solution of sugar, is closed at
both ends by vegetable parchment, and placed in water. Osmotic
currents are set up, but more water passes into the denser sugar
solution than vice versd, and the result is that the elastic parch-
ment ends bulge out and are placed on the stretch. Some sugar,
however, does diffuse out, and slightly sweetens the water outside.
The natural cell turgesces in a similar way, but, of course, is
bounded by an extensible membrane on all sides. If, at the end
of this experiment, the external fluid is made denser than the in-
ternal, a flattening of the membranes takes place. Such flattening
might also be caused by evaporation through the membranes. We
now see in what way the ideal plant can jeed, 7.e., by taking in
osmotically water that contains various salts and carbon dioxide
in solution. The chemical nature of the liquids largely affects the
rapidity of the osmotic currents, and the cell contains in its sap
osmotically-active substances (e.g., organic acids), which increase
endosmosis to a large extent.

Having considered the reception of food, the next point to be
dealt with is the exact nature of that food. Information on this

10 THE FLOWERING PLANT.

head is obtained in two ways—(1) by chemical analysis of plants ;
(2) by cultivating them in various solutions, and determining
which are most suitable.

The essential elements (always found on analysis, and compounds
of which form a suitable food-solution) are the following :—Carbon,
hydrogen, oxygen, nitrogen, sulphur, phosphorus, potassium,
calcium, magnesium, and iron. ‘The first six actually make up
the plant-body, while the remaining four have a beneficial in-
fluence upon the vital processes. For example, chlorophyll can-
not be formed when ron is absent. Carbon is obtained from
carbon dioxide; hydrogen from water and ammonia or its com-
pounds ; oxygen from water and numerous salts; nitrogen from
either ammonia and its salts, or else nitrates; sawlphur from sul-
phates; phosphorus from phosphates; potassium from various
compounds, especially chloride; calcium and magnesium as sul-
phate, phosphate, nitrate, and carbonate; iron from numerous
compounds.

Reception of food is followed by assimilation. That is to say,
the simple food-substances are built up step by step into the
complex compounds which constitute the plant-body. The first
step consists in the formation of non-nitrogenous organic matter
from carbon dioxide and water, with liberation of oxygen. The
equation

CO, + H,O = CH,O + 0 Qy
carbon dioxide and water give non-nitrogenous matter and oxygen
roughly represents this. It must not, however, be supposed that
the liberated oxygen is all derived from the carbon dioxide, though
half must be, while the other half comes from the water. The
oxygen in question passes off, at any rate to a large extent, into
the surrounding medium. It is most essential to remember that
this process has nothing whatever to do with the breathing of plants.

This first step in assimilation, which bridges the gap between
inorganic and organic compounds, can only be effected by the
agency of chlorophyll in the presence of light. It has been
already mentioned that kinetic energy is liberated when chemical
compounds break down. Conversely, kinetic energy is converted
into potential when chemical compounds are built up. The neces-
sary kinetic energy appears to be obtained by the chlorophyll
from light-rays.

When organisms contain no chlorophyll, they cannot live on
simple inorganic compounds only ; hence the complex nature of
animal food. There is also no evolution of oxygen.

The first visible product of assimilation is starch, which has
a chemical composition closely allied to that of cellulose. The
ultimate product of assimilation is protoplasm.

ELEMENTARY MORPHOLOGY AND PHYSIOLOGY. II

The expenditure of energy on the part of plants involves, as
previously mentioned, a constant decomposition of protoplasm.
This has been termed Katabolism. Such products of breaking-
down may be passed out of the organism or excreted. Carbon
dioxide is such a waste product, and the passage out of this (and
water), with concomitant passage in of oxygen, is known as
Respiration. ‘The oxygen effects the decomposition, which is a
process of oxidation. It is most important to remember that all
organisms, plant and animal, with very few exceptions, respire or
breathe, and in the same way, 7.e., by taking in oxygen and
giving out carbon dioxide. It is popularly, but very erroneously,
stated that “plants breathe in carbon dioxide and breathe out
oxygen.” Green plants do, in the presence of light, give off
oxygen, as seen above, but this is simply a part of their food
which they do not utilize. The amount of oxygen is so large
as to disguise the fact that carbon dioxide is also being evolved,
though in much smaller quantities. The true state of things
becomes apparent at night, when, since the chlorophyll is not at
work, the evolution of carbon dioxide is not masked. This is
why plants help to vitiate the air at night, and are therefore best
excluded from a sleeping-room.

If a plant receives and assimilates abundant food, it will grow
to a certain extent, and also reproduce or give rise to new indi-
viduals. Reproduction, in a simple unicellular form, such as we
are considering, takes place most simply by division or fission
into two equal parts (fig. 1). The nucleus divides into two—a
cellulose partition is formed across the cell, and the two halves
gradually round off and separate.

Our example may also exhibit movements, and such Motility is
most commonly seen in the form of currents in the protoplasm,
which are rendered evident by the presence of granules (fig. 1).
These are swept along from place to place.

The last physiological heading is that of Irritability and Spon-
taneity. In other words, the organism is sensitive to agents
or stimuli (mechanical, chemical, thermal, &c.), which act upon
it from without or within. Jrritability means sensitiveness to
external stimuli. The protoplasmic currents, for example, men-
tioned in the last paragraph, can, to a certain extent, be altered
in rapidity by raising or lowering the temperature of the external
medium. On the other hand, spontaneity is sensitiveness to
internal stimuli. Movements of protoplasm, to take the same
instance, are often so constant that it is scarcely possible to sup-
pose them entirely the direct result of external influences. They
must be regarded as spontaneous, or the result of internal stimuli,
as chemical change, &c, &e. It must be borne in mind that

{2 THE FLOWERING PLANT.

movements and their modifications are only one result of spon-
taneity and irritability.

Multicellular plants carry on precisely the same functions as
unicellular ones, namely :—

. Nutrition (z.e., Reception and Assimilation of food).
. Katabolism (including Respiration).

Reproduction.

. Motility.

. Irritability and Spontaneity.

Here, however, different cells undertake different functions,
and are specially modified for the performance of those functions.
In other words, physiological division of labour is accompanied
by morphological differentiation. ‘This principle is most strik-
ingly exemplified in the highest, 7.e., the flowering, plants ; but all
gradations of complexity are found in the vegetable kingdom,
from the simple cell upwards.

In the following chapters, Root, Stem, and Leaf will be treated
of ; and as Hair-structures may occur on any or all of these, they
will not be dealt with in a separate chapter, but be mentioned
where necessary.

Lon

wm bwin

CHAPTER III.
THE ROOT.

MORPHOLOGY.

A SUNFLOWER or bean-plant may be regarded as consisting of
two slender cones placed base to base (fig. 2). One of these, the
primary stem, grows upwards ; the other, the primary root, down-
wards. When such a main axis forms the most prominent part
of the root, it is said to be a tap-root, and this is very strikingly
seen in the carrot, turnip, and radish. The primary root
generally possesses numerous branches, and these may be re-
garded as so many slender cones attached by their bases to the
main one. These secondary roots are commonly in the form of
fibres. But the primary root is very often extremely short, and
in that case (eg., grasses) the plant is fixed in the ground by
means of adventitious roots (fig. 4), which usually grow from the
stem, but may also arise from the leaf-stalks or leaves. Such
roots may also be present in addition to the primary and secondary
ones, as, for example, in the ivy, where they are used for climbing.
The “striking” of cuttings means the development of adventi-
tious roots from the end of a piece of stem pushed into the soil.
The majority of roots are underground, but aquatic plants possess
water-roots, and air-roots are also known. These last may be the
only ones present, as In many tropical orchids ; or, as in the ivy,
they may exist in addition to roots of the ordinary kind. The
orchids in question are epiphytes, that is to say, they simply live
on other plants, but not at their expense. Plants exist, however,
such as the clover-dodder, and mistletoe, in which the roots are
parasitic, penetrating and deriving nourishment from the tissues
of other plants.

Young roots are white or pale in colour, old ones generally
brown. Under no circumstances is the green colouring matter,
chlorophyll, present. Leaves are never found upon the root.

The external form of a root system depends mainly on three
things: (1) the presence or absence of a tap-root; (2) the nature

14 THE FLOWERING PLANT.

and amount of branching; (3) the thickness. The branching is
always monopodial, that is to say, the branches are not formed
by forking, but arise as outgrowths from the side of a pre-existing
axis. The thickness partly depends upon the duration of life. In
annuals, which live for one year only, the parts of the root system
are usually of no great thickness. Biennials, which live for two
years, develop in many cases a greatly dilated tap-root, which
contains a store of reserve material that is used up the second
year, when flowering takes place, as in the carrot, turnip, and
radish. Perennials, which live for more than two years, fre-
quently have thickened roots, eg., dahlia, where there is a bunch
of secondary roots swollen into spindle-shaped bodies.

The structure of roots is somewhat complex, and can only be
very briefly dealt with here. Just as (see p. 8) a leaf is divisible
into three systems of tissue, so also is a root. This may be con-
veniently illustrated by the main root of a young bean-seedling
grown in damp sawdust. The younger part of this, z.e. the part
near the tip, will be covered by a thin ill-defined skin, the
epidermis, composed of a single layer of flattened’ cells, from
which numerous delicate unicellular root-hairs grow out (c/. fig.
7, H). Such hairs are seen much better in the case of mustard-
seedlings (fig. 3). If the root is cleanly cut across and examined
with a lens, an outer spongy-looking portion can be distinguished
from an inner denser portion. These correspond, respectively,
to a sort of external jacket, the cortex, and an internal firm
vascular cylinder (cf. fig. 2). In roots which, like those of the
bean, increase in thickness, the epidermis and cortex are early
thrown off, being replaced by a brown layer of cork formed in
the outer part of the vascular cylinder. This may easily be
made out in the roots of an old bean-plant. Suitable cross-
sections through the young root show that the secondary roots
run in to the vascular cylinder. If the cortex is peeled off, which
can be readily done, the secondary roots remain behind, attached
to the cylinder. These roots then arise endogenously, 7.¢., from
the internal tissue, and break their way through the cortex to
the exterior (figs. 5, B, and 7, H). This way of origin is charac-
teristic of all roots, primary, secondary, and adventitious.

The cortex is composed of the second kind of tissue, which has
received the name of fundamental or ground tissue. This term
is a very broad and general one, and it must by no means be sup-
posed that all the component cells are of the same shape or nature.
On the contrary, several varieties of tissue may be included under
this system. The commonest and most important is parenchyma
(fig. 7, H), which is made up of cells that are fairly equal in
length, breadth, and thickness. The cells in question are not

THE ROOT. 15

SUI Mp
GEa
ij} Wy

Se

wg

(from Sachs]. I. and II. embryonic stages ; III. after
w', w’, secondary roots (developing endogenously and
leaves (developing exogenously
d vascular bundles, black;

Fic. 2.—Diagram of a Dicotyledon
germination ; w, primary root ;
acropetally) ; h, hypocotyl; ¢, ¢, cotyledons ; b, b’, 6”, 6",
and acropetally); kk, k’, axillary buds. Growing points, an
the parts becoming elongated, grey. Root-caps white.

16 THE FLOWERING PLANT.

spherical, but many-sided (7.e., polyhedral), a natural result of
growing together in numbers. This point may be illustrated by
pressing together soft clay pellets, when the spaces between them
get filled up, and a many-sided form is consequently acquired.
Mutual pressure is similarly exerted by growing cells owing to
their turgidity (p. 9), and a spherical shape cannot therefore
be assumed. In sections of parenchyma the constituent cells of
course appear polygonal in outline. The cell-walls are of cellu-
lose, and protoplasm with nucleus is present, with cell-sap in
addition.

The vascular cylinder is chiefly made up of the vascular system
of tissue, which is the most complex. It is composed not only of
cells, but also of cell-derivates, ¢.e., structures derived from cells.
In this case, the most important of them are tubular in nature,
and may be broadly spoken of as vessels ; hence the term ‘‘vascular”
tissue. Their structures will be dealt with later on (pp. 31 and 34).
It is only necessary here to emphasize the fact that even in very
young roots they are aggregated into a central ‘ cylinder.”

All roots are capable of zncreasing in length. Wpidermis, cortex,
and vascular cylinder gradually become more indistinct as the
apex of the root is reached, and ultimately merge into a minute
mass of small cells, which constitute the growing point. Their
walls are extremely thin and their protoplasm abundant. New
cells are continually being formed by divisions somewhat as
described on p. 11. Here, however, there is no rounding off,
but those cells which are nearest the older parts of the root
increase in size and alter in shape, ultimately becoming mature
cells of the epidermis, &c., &c. The growing-point is not at the
actual apex of the root. If it were so, its delicate cells would be
exposed to constant injury from the hard particles of earth,
against which they would be forced by the growth in length.
The extreme end is occupied by a thimble-like sheath, the root-
cap, Which is made up of numerous layers of flattened cells, and
covers over the growing-point, protecting it from injury (figs. 2
and 4). As the outer layers of the root-cap are worn away, new
inner layers are added by the growing-point. All roots are char-
acterized by the presence of a root-cap, and it is present even in
water-roots, as may be well seen by examining those of the duck-
weed under a low power of the compound microscope. As a root
increases in length, branches may arise from it. These are deve-
loped in regular order, the youngest being nearest the growing-
point (fig. 2). Technically described, they arise in acropetal suc-
cession. Adventitious roots are an exception to this.

Some roots increase not only in length but in thickness as well.
This increase is effected by a cambium layer, situated within the

THE ROOT. 17

vascular cylinder, and composed of cells which differ from those
of the growing-point chiefly in their elongated shape. Cambium
and increase in thickness will be more fully spoken of on pp. 31
and 36.
We are now in a position to make a somewhat wider classifica-
tion of tissues. They may be grouped as follows :—
I. Formative Tissue or Meristem.
Composed of actively-dividing cells, with thin cellulose walls
and abundant protoplasm.
1. Primary Meristem. Making up growing-points and. the
whole of very young structures.
2. Secondary Meristem or Cambium. Forming layers bounded
internally and externally by permanent tissue.
II. Permanent Tissue.
Composed of cells not in a state of active division (though they
may retain the power of dividing) and cell-derivates.
1. Hpidermis. An external layer of flattened cells, to which
hair-structures may be attached.
2. Ground-tissue. Largely composed of parenchyma.
3. Vascular system. Composed of cells and vessels.

PHYSIOLOGY.

The root of a land plant is protected to a great extent by its
position in the soil, the root-caps protecting its delicate growing-
points from injury. The epidermis at first protects from evapo-
ration, and, in older examples, from which parts external to the
vascular cylinder have peeled off, its place is taken by layers of
cork (cf. p. 40).

The root serves as an organ of support to the stem and leaves.
It is often firmly fixed in the soil by numerous branches, and the
nature of the vascular cylinder is such as to give firmness. The
- root is essentially a vegetative organ, 7.e., is concerned with main-
taining the life of the individual, and consequently plays a very
important part in Nutrition, since, in land plants, all the food,
with the exception of carbon dioxide, is absorbed by it. The soil
is made up of variously-sized particles, with spaces between them,
that contain, according to circumstances, more or less water with
various substances dissolved in it, the part not thus occupied
being filled with air. Part of this water is readily drained off,
and has been termed /ree water, while the remainder is in the
form of films that surround the particles. These films, consti-
tuting the hygroscopic water, are the part which furnishes the
plant with nutriment, and may be looked upon as a natural food
solution. The absorption is effected by the young epidermic cells

B

18 THE FLOWERING PLANT.

and root-hairs, by means of osmosis, much as described on p. 9.
The particles of soil are also more or less corroded by the acid sap
of the root-hairs, &e., to which they closely adhere (fig. 3). This
permeates the cell-walls with which the particles
come into close connection. If the roots of a
plant are allowed to grow over a polished slab
of marble, this will be corroded at the points of
contact, and a kind of rough etching of the
root system produced. Roots thus help in the
preparation of the solutions which they absorb.
This solvent action is aided by the carbon
dioxide excreted in respiration. The roots of
water plants can easily avail themselves of the
surrounding medium with the substances dis-
solved in it. Parasitic roots come into such
close relation with the tissues of the plant preyed
upon, that they form a physiological part of it,
and can by its means receive not only simple
food, but also material that can at once be built
up into protoplasm.

Circulation of Liquids.—The substances ab-
sorbed by the root ultimately reach the leaves
by various routes and in various ways. Just as
they can enter the root-hairs and young epider-
mal cells by means of osmosis, so can they in
the same way reach cells that are more deeply
situated, and so on. We also know that liquids
Ae ee travel very largely by means of certain vessels

eae as a (cf. p. 41), chiefly,as one would expect, in their

Sapna) a as taken interior. ‘This has been noticed for a very long:

particles of earth time in the.case of vines. When these are

faite ie B thee. pruned in spring, a great deal of sap exudes

Hele aelp ges diy from the cut surfaces. In popular language,

‘bove are ; the plant ‘‘ bleeds,” and careful examination

Above are seen the a he

i Peon ae shows that the liquid oozes out from the

these and the root- cavities of the vessels. This phenomenon was

hairs, the hypocotyL formerly ascribed to a mysterious force called
root pressure, operating before the leaves unfold. It was
erroneously supposed that at other times liquids travel only in
the walls of the vessels, and not within them.

Roots may perform another important office in nutrition, 2¢.,
the storage of reserve materials, which are supplies of nutriment
destined for use at some future time. The matter is chiefly stored
as starch, but it may assume other forms, e.g., cane-sugar, as in
the beet-root.

rw
hs
f

Wy i il \
"DDI Dy i YY fl

AACA

THE ROOT. 19

Like all other parts of the plants, roots carry on Respiration.
A supply of free oxygen is therefore necessary. In the case of
aquatic plants this is dissolved in the surrounding water, while in
land plants air is present in the interstices between the particles
of soil, and enters the plant dissolved in the cell-sap. It is
evident, therefore, that if these interstices get completely filled
with water, the roots cannot respire properly (since, unlike water
roots, they are not adapted for utilizing oxygen dissolved in water) ;
hence the sickliness of overwatered pot-plants. Carbon dioxide,
of course, diffuses out of roots in respiration, and, as mentioned
previously, helps to bring the food into solution.

Circulation of Gases.— Within the root gases can circulate as
well as liquids. In fact, the cell-sap contains gases dissolved in
it, which, of course, participate in its movements. There are,
however, special channels for the circulation of gases, viz., (1.)
the cavities of certain vessels, which, except In spring, contain no
liquid, and (2.) intercellular spaces, which are chinks or crevices
that exist between the cells of parenchyma and some other tissues,
and which form a set of irregular but communicating channels.

It is comparatively seldom that Reproduction is effected by
the root, and when this is the case, it is always vegetative (cf. p. 43),
t.e., by development of ordinary leafy shoots; and not of special
reproductive organs. One of the best examples is the common
acacia (Robinia pseudacacia) of gardens, the roots of which spread
horizontally and send up shoots that become new trees. Another
case is that of the dahlia, which can be propagated from its root-
tubers.

Improbable though it may seem, the root exhibits a consider-
able amount of Motility. Protoplasmic movements occur in some
root-hairs, and young growing root-tips are in constant slow
movement from side to side, forcing their way between the particles
of soil. The older parts of the root move in a different manner,
z.e., they shorten, and this causes the plant to be anchored very
firmly in the ground. Rosettes of leaves like those of dandelion
are thus prevented from being raised by growth of the stem. It
has been remarked that a root burrows in the soil as an earth-
worm does. The narrow anterior end of this animal makes its
way between the particles of earth; the rest of the body then
shortens and is pulled up to it.

Irritability of the root is shown by its sensitiveness to various
stimuli, such as gravity, light, moisture, and contact. Spontaneity
is seen in the persistence of its movements. eotropism refers to
the influence of gravity in determining the direction of growth.
Roots are positively geotropic, z.e., grow towards the earth’s centre.
The primary root takes a vertical direction, and the lateral ones

20 THE FLOWERING PLANT.

a more or less oblique one. If a seedling is placed with its
primary root in a horizontal direction, this will very soon curve
round and grow downwards, while the stem curves upwards. By
keeping seedlings in a state of slow revolution in a vertical plane,
the effect of gravity is neutralized. The result is that root and
stem do not in this case grow downwards and upwards, but have
a tendency towards the horizontal direction. Heliotropism is the
term employed to designate the influence of light on direction
of growth. Roots are generally negatively heliotropic, z.e., turn
away from the light. Hydrotropism refers to the influence of
moisture. Roots are positively hydrotropic in that they grow
towards moisture. This is commonly the case with trees. If
seedlings are placed in a perforated vessel full of damp moss, and
the apparatus is then hung up, the primary roots will grow down
as a result of positive geotropism, and make their way through
the perforations. If the surrounding air is moist, the roots will
continue to grow downwards, but if dry, they will bend up towards
the damp moss. The tips of roots are also sensitive to contact,
which causes them to curve.

It is evident that reaction to all the above stimuli is of such a
nature as to fit the root for its share in nutrition.

CHAPTER IV.
THE STEM.

MORPHOLOGY.

Just as the well-developed primary root may be regarded as a
descending cone with apex below, so may the primary stem be
looked upon as an ascending cone with apex above. This doubly-
conical shape is characteristic of gymnosperms and dicotyledons
(fig. 2). In monocotyledons, where there is no tap-root, the stem
is typically in the shape of a cone with apex downwards, which is
fastened in the soil by adventitious roots which proceed from it
(fig. 4).*

The stem must be looked upon as the most important part of
the plant, since it is the only one always present. Hair-structures
are by no means constant, leaves may be absent, as in duckweed,
where the little flat green expansions are stem structures, and
lastly, roots, in rare cases, are non-existent, as, for example, in a
kind of duckweed (Wolfia arrhiza), the body of which consists
solely of a minute cellular green disc.

A stem not only bears, as a rule, secondary stems or branches,
which are similar to it in shape and structure, but also other

1 This is a convenient place to remark that plants are classified into several
large groups, which are again subdivided, and so on, till at last we reach
species. These include individuals which differ only in slight features, such as
size, and are evidently descended from a common ancestor. The subdivisions
of plants in order of size are: group, division, class, subclass, series, cohort,
order (or family), genus, species. Flowering Plants form a group with two
divisions : (1.) Gymnosperms, including pine, fir, yew, juniper, larch, cypress,
&c. ; (2.) Angiosperms, embracing most flowering plants, as, e.g., all those with
coloured flowers. This division has two classes: (a.) Monocotyledons (the
smaller division), taking in palm, arum, lily, tulip, onion, snowdrop, iris,
sedges, grasses, &c. ; (b.) Dicotyledons, to which most British forms may be
relegated, e.g., the majority of trees and shrubs, buttercup, wallflower, pink,
poppy: violet, waterlily, geranium, gorse, rose, daisy, dead nettle, primrose,

c., &c.

Every plant has, for the sake of identification, a double scientific name,
compounded of the names of its genus and species. For example, daisy is
Bellis perennis. Bellis = genus, perennis = species.

22 THE FLOWERING PLANT.

members, /eaves, which usually differ considerably from it. This,

among other points, dis-
tinguishes the stem from
the root. We have also
seen that stems often
bear adventitious roots
(fig. 4), but this is not of
primary importance, at
least from a morphologi-
cal point of view.

Stem and leaf are so
constantly associated that
it is impossible to treat
of one without reference
tothe other. <A collective
name, that of shoot, has
therefore been given to
the stem with its leaves.
The broadest grouping
that can be made of plant
members divides them
into only two sets, viz.,
roots and shoots.

The regions of the stem
to which leaves are at-
tached receive the name
of nodes, while the in-
tervening portions are
known as_ inter-nodes.
Nodes are often thick-
ened, and adventitious
roots generally arise from
them. Where a leaf joins
the stem there is an upper
angle formed (usually
acute), and a lower angle
(usually obtuse). The

| \' former is known as the
W °F axil of the leaf. This

FIG. 4.—Diagrammatic Longitudinal Begiion sootelts point is mentioned here
Young Maize Plant (Zea mais) [from Sachs]. W. pri- F =
mary root; ¢, ¢’, 6”, 6”. adventitious roots spring- because ib is the rule
ing endogenously from the ies (s)3 / e ou eit in flowering plants for
leaves, cut off short; b’’”. young leaves of the termina : :
bud; k, k. axillary buds. The erowing points are branch stems to arise

' represented black, the elongating parts grey ; the in leaf-axils (figs. 2, 4,
parts left white are fully grown. The white tips of h ie
the root are root-caps. and 35). Such branches,

THE STEM. 23

as in the case of the root, may be regarded as slender cones
attached to the side of the primary one. Here, too, then suc-
cession is regular and acropetal. Adventitious stems may also
be formed, and this is the nature of most of the slender twigs
which often sprout from old tree stumps.

The majority of stems are arial, but water stems, partly or
entirely submerged, are naturally present in marsh and water
plants. Aérial stems are sometimes parasitic, as in clover-dodder,
which possesses suckers on its stem that become intimately united
with the stem of the clover. It is commonly imagined that all
underground structures are roots. This, however, is a mistake,
since a great many stems are more or less subterranean.

The external form of a stem is influenced by a number of
factors. The most obvious is that of s¢ze and duration. Upon
this depends the old and somewhat vague classification into herbs,
shrubs, and trees, as well as the division already mentioned into
annuals, biennials, and perennials.

Herbs ave plants, usually of no great size, in which either the
whole plant dies after a year’s growth (annual herbs), or else the
subaérial portions die away every year (biennial and perennial
herbs). The stem is not at all or scarcely woody. Shrubs are
perennials, mostly less than twenty feet high, with woody stems
that branch from or near the ground. Tees are perennials,
generally more than twenty feet high, with a distmet woody
primary stem or trunk. There are, however, no sharp boundaries
between these divisions. Herbs pass into shrubs, the intermediate
small woody perennials being called wndershrubs ; and shrubs,
again, are connected by all possible gradations with trees. The
names herb, &c., refer to the shape of the overground parts of the
plants taken as a whole. The jorin of the individual stem is, in
the majority of cases, cylindrical and solid. Some herbs, how-
ever, possess Square or triangular stems, while ribbed and flattened
forms are not uncommon. It may happen that the last kind are
winged, or produced at the sides into thin green expansions.
Hollow or jistular stems are often found among herbs, growth in’
thickness having exceeded increase in substance, the result being
that the internal tissues have been ruptured. ‘This is very typi-
cally seen in grasses, where the tubular internodes are separated
by swollen nodes. Bamboo and any kind of straw will serve as
examples. These stems are called culms. Not only may the size
of the whole stem system be considered, but also the size of the
individual parts as regards length and thickness. The maximum
length is attained in the trunks of trees, where, as in all long
stems, the internodes are well developed. Great development of
the internodes may cause the stem to be thin and weak, as in

24 THE FLOWERING PLANT.

many climbing and creeping plants. On the other hand, the
internodes may be so extremely short as to make the stem a
scarcely recognisable stump, the leaves being at the same time
crowded into a tuft or rosette. Good examples are daisy, dande-
lion, and house-leek. Such an abbreviated stem is sometimes
termed a root-stock, while the leaves growing from it are radical,
the old (but erroneous) idea being that they grew from the root.
It may also happen, as in the buttercup, that the internodes are
very short in the lower part of the stem only. The leaves borne
by that part are then also called radical.

The thickness of a stem is dependent on other conditions besides
the state of the internodes. Perennial gymnosperms and dicoty-
ledons (rarely monocotyledons) undergo an annual increase in
thickness, and many stems and branches, particularly underground
ones, are thickened in connection with the storage of reserve
materials.

The chief factor determining the general shape of a stem
system is the nature of the branching. This is monopodial, as in
the case of the root, and two kinds may be distinguished: (1.)
Racemose, where, as in most cases, the main axis continues to
grow, and is larger and longer than its branches, which, in their
turn, bear a similar relation to its subordinates. The pyramidal
outline of many trees, e¢.g., firs, is due to this cause. (2.) Cymose,
where the main and other axes cease growing after a time, and
are outstripped by their branches. This may result in false
dichotomy, 2.e., apparent forking, as in the mistletoe; or a psewd-
axis or sympodium may be formed, where the direction of an axis
is continued by one of its branches, which after a certain time is
supplanted by one of zts branches, and so on (ef. p. 48). The
name pseud-axis is given because, at first sight, we have to deal
with a case of racemose branching. Examples are found in the
twigs of elm and beech. ‘The main branching of these trees is,
however, racemose. Special branch systems or inflorescences are
often developed, upon which the flowers are borne. These will be
dealt with later on in connection with the flower.

The last important point which determines the shape of the
stem is its direction, whether vertical, horizontal, or otherwise.

In giving a brief account of various stems, it will be convenient
first to speak of aérial forms and then to proceed to subterranean
ones.

Aérial Stems.—As already mentioned, the typical overground
main stem is erect and self-supporting. This requires a consider-
able amount of strength, which may be gained by size and solidity,
as in tree-trunks, or where there is comparatively little substance
this may be disposed in the most advantageous manner, 7.¢., on

THE STEM. 25

the principle of the hollow column, as in the culms of grasses.
Overground stems may serve as receptacles for reserve materials,
and in this case the internodes may either be of considerable
length, as in the trunks of trees, which during winter contain
large quantities of starch, &c., or they may be much shortened.
A familiar example of such a condensed stem is the cabbage, in
which plant, however, nutriment is stored not only in the short-
ened stem, but also in the bases of the leaf-stalks.

Overground stems which are not erect may have a greater or
less tendency towards the horizontal position, or, on the other
hand, they may compensate their want of strength by climbing.
In the former case, the first approach to a horizontal position is
found in ascending stems which grow obliquely upwards. When
a stem commences by being erect or ascending, and then turns
down and runs along the ground, it is said to be recumbent. The
opposite of this is seen in decumbent stems, which first run along
the ground and then become ascending. Lastly, the horizontal
direction may be taken from the first, when the term procumbent
or prostrate is employed. Such a stem is creeping if it gives rise
to adventitious roots at its nodes. A few terms that are applied
to branches which serve for the multiplication of plants may here
receive mention. Suckers are ascending branches of subterranean
stems. The green shoots commonly growing up from near the
base of standard roses are of this nature, and so are the new
‘‘canes”’ developed each year from raspberry bushes. Stolons
are prostrate or reclined branches which take root at the end,
where a new shoot then grows upwards, and a fresh plant is thus
formed. Slender elongated stolons are runners, as in strawberry,
while short thick ones are offsets, as in house-leek. Short suckers
are also called offsets.

Climbing Stems.—In many climbing forms the main stem
itself winds round and round a support. Such twining stems
form either right-handed or left-handed spirals. In the former
case, which is the commoner, and of which scarlet runner and
convolvulus are examples, the coils ascend from left to right, as
in a corkscrew. The exact opposite is the case in the hop and
certain other stems, which form left-handed spirals. Another
large class may be called tendril-climbers, since they possess irri-
table clasping organs in the form of tendrils, which are thin,
elongated, stem-like structures, capable of turning round and
round a support. ‘Tendrils may be either modified parts of the
stem, or flower-stalks, or parts of leaves. In the cucumber
and vegetable marrow the tendrils are branches, while in the
vine they take origin opposite the leaves (p. 27). The same thing
is true of the Virginian creeper, where, in addition, there may be

26 THE FLOWERING PLANT.

adhesive dises at the ends of the tendril branches. Leaf-tendrils
will be spoken of in another place, as also will leaf-climbers
generally, in which the leaves are used for ascending, with or
without the development of tendrils. oot-climbers make another
class, and ivy is the best-known example. Lastly, we have hook-
climbers, as in the cleaver or goose-grass (Galiwm), where iInnumer-
able minute hooks grow out from the superficial part of the stem.

We now come to subterranean or underground stems. ‘These
come under four categories—corm, bulb, rhizome, and tuber. A
corm, like that of the crocus, is a solid, rounded, main axis, full
of reserve materials. Adventitious roots grow from its lower
surface, and there are a few scaly leaf-bases. upon its exterior, in
the axils of which young corms may be formed as fleshy buds.
From the upper surface a flowering shoot proceeds, and several
internodes at the base of this thicken into the main corm of the
following year, to which a shrivelled remnant of the main corm
of the previous year may adhere. In the sowbread (Cyclamen) a
vertically-flattened corm is present. A du/b resembles a corm
in being a condensed stem, but differs from it by being mainly
composed of thickened leaves or bases of leaves, surrounding a
flattened disc-like stem. <A rhizome differs from the two pre-
ceding in direction and form, Instead of being vertical, it is
oblique or horizontal, while its internodes are often of consider-
able length, and its shape more or less cylindrical. It may
either be thin, as in mint and sedges, or else thick, as in the iris
and Solomon’s seal. Zwbers resemble corms in structure, but
differ from them in being thickened branches. The Jerusalem
artichoke and potato are good examples, and in both these cases
several internodes are dilated, while the leaves borne upon the
nodes are scale-like, and axillary buds, popularly known as
“eyes,” are developed in their axils. Some tubers, however, con-
sist of only one internode thickened. In a potato plant grown
from an eye only adventitious roots are present, but in examples
raised from seed there is a well-developed branching main root.
By heaping earth around a tuberous plant, branches with tubers
upon them can be formed higher up than would otherwise be the
case. Bulbs, thickened rhizomes, and tubers all (like corms)
serve as stores of nutriment, chiefly starch. Other reserve
materials may also be present. For example, in potatoes many
of the cells immediately within the rind contain minute cubes or
crystalloids composed of proteid matter. The term crystalloid is
used because, although the form is crystalline, yet the bodies in
question are not hard, but possess the power of absorbing water
with consequent swelling up. It is obvious from the above that
the ordinary method of peeling potatoes, instead of cooking them

THE STEM. 27

in their skins, reserves the most nutritive parts for the pigs.
All the swollen underground stems just spoken of are especially
characteristic of dry climates, for which they are well suited, as
the condensed form offers comparatively little surface from which
evaporation can take place.

Modified Stems.—Hitherto we have had to do with typical
undeniable stems, easily recognizable as such to the ordinary
observer, except perhaps stem-tendrils. here are, however,
numerous cases where stems are so modified, for the purpose of
performing special functions, that they can only be recognized by
homology. In other words, relative position and mode of develop-
ment must be taken as criteria, and not the functions performed.
This has already been spoken of on p. 7. Let us apply this to
stem-tendrils. A direct continuation of an organ is evidently of
the same nature as that organ. In the vine the youngest tendril
is a continuation of the stem, and may therefore be regarded as
part of it. This was previously the case with the youngest
tendril but one, which, however, has been pushed on one side, its
place being taken by a new stem borne in the axil of the youngest
leaf. And so on for the next tendril. Thus, in any branch, the
tendrils taken in succession, commencing with the oldest, have in
turn occupied the end of that branch. We have therefore to deal
with a sympodium (see p. 24). Another reason for not regarding
the axis of a vine branch as a simple stem bearing branches in the
usual way, is the fact that the tendrils do not grow from the axils
of leaves. Examination of passion-flower tendrils shows that
these do grow from leaf-axils, and we are therefore justified in
considering them to be branches. Vine tendrils are further
regarded as modified flower-stalks, because all possible gradations
are found between the two. Stems may also bear branches modi-
fied into spines and thorns for protective purposes. These are
known to be of stem nature from their axillary development and
the presence of leaves upon many of them. It sometimes happens
that stems undergo modification owing to the fact that the leaves
are very small or absent. This means that some of the functions
of the ordinary leaves have to be carried on by the stem, which
in this case may be called a phylloclade. In cacti, for example,
apart from the flowers, the leaves are reduced to minute spines,
and the green stem assumes the most remarkable forms, globular,
jointed, prismatic, &c., all of them very compact, and suited for
dry climates (see above). In other cases, as asparagus and
butcher’s broom (fuscus), branches assume a flattened, leaf-like
form, and are lable to be mistaken for leaves. Such phylloclades
are termed cladophylls or cladodes. The stem of duckweed may
perhaps best be placed in this category.

28 THE FLOWERING PLANT.

The last heading to be mentioned regarding the external form
of stems is that of surface. Not only may a stem be more or less
ridged, grooved, &c., but also it may possess a more or less com-
plete clothing of hair-structures, and different names are employed,
such as silky, hirsute, &c., to indicate the kind of surface produced
by them.! Absence of hairs is denoted by the term glabrous.
Hairs on the stem (and leaf) are rarely so simple as root-hairs.
They are sometimes, however, unicellular, but in this case often
assume more or less complicated forms. The stems (and leaves)
of the wallflower, for example, are covered by spindle-shaped
hairs, attached by their centres, and upon the stems (and leaves)
of the stock and shepherd’s purse much-branched unicellular
hairs are present. It is more common, however, to find the hairs
upon the stem (and leaf) multicellular, and they may then either
be simple or branched threads, or else more or less complex scales,
with or without stalks. Glandular hairs are also common, and
these usually consist of a rounded head, supported upon a short
stalk. The protoplasm of the head is capable of producing or
excreting a sticky or oily substance, often of fragrant nature. <A
thin cross-section of a young pelargonium flower-stalk or vege-
table marrow stem will, when placed under a low power of the
microscope, be seen to possess numerous multicellular hairs,
glandular and non-glandular.

The surface of the stem may be more or less covered by prickly
structures, and these are not all of the same nature. Some are
true hair-structures, 7.¢e., they are developed from the epidermis
only, as in hop, cleaver, and borage. Others again are modified
stem or leaf structures, e.g., in the sloe and hawthorn. In this
case the terms thorn and spine are best employed. But there
‘still remains a third kind, of which the prickles of the rose and
bramble are examples. These are not hair structures, since not
only epidermis but ground-tissue as well helps in their formation,
Nor are they modified stems or leaves, for they arise in no definite
order, nor do they contain vascular bundles. The name emer-
gences has been given to them, but it must be remembered that
all possible gradations are found between them and _ hair struc-
tures, on which account some have proposed to group them with
these last.

! The following terms describe the character given to the surface of stem, leaf,
&c., byhairs :— Hoary (canescent), whitish, owing to presence of numerous ininute
hairs ; pubescent, with short or soft downy hairs; pilose, with soft distinct
hairs ; hirsute, with numerous coarse hairs ; setose (hispid), with bristly hairs ;
villous, with long soft hairs ; tomentose, with matted hairs; silky, with soft
straight hairs pressed closely to the surface; woolly, with long crimped and
matted hairs ; hairy, a general term, applied when the separate hairs are dis-
tinctly visible ; ciliate, applied to a leaf-margin fringed with hairs.

THE STEM. 29

We have now to deal with the structure of the stem, and this
may be considered under the two headings of anatomy, which
treats of so much as can be made out with the eye alone or by
help of a lens, and histology, which goes into the finer details by
employing a compound microscope. We may commence by an
examination of sunflower and asparagus stems.

Anatomy.—A good-sized example of a sunflower stem will be
more or less cylindrical in shape, somewhat ridged, and studded

with stiff hairs. If
an internode is cut
across with a sharp
knife, and the surface
smoothed by a scalpel
or razor, the three
systems of tissue can
be made out. There
is first the hair-bear-
ing epidermis, and
some little distance
within this a circle
of small oval areas,
separated by inter-
spaces. These are the
cut ends of the vas-
cular bundles, and
are best seen with a
lens. The rest of the
stem is made up of
ground-tissue, which
is divisible into a
large white central
part, pith or medulla ;
another part, cortex,
between the epider-
mis and_ vascular
bundles ; and thirdly,
medullary rays, stcips
of tissue running be-
tween the vascular
bundles, and _ con-
necting pith with cor-
tex. If now a piece
of the stem is halved

;
SS
S
S
S
S
=

SS
S
SS
SS
~S
S
SS

S
S
S

Fic. 5.—Diagrams of Anatomy of Vegetative Organs [after

A. relation of stem and leaves; 7. leaves; 0.
buds; g.p. growing-point; v.b. vascular bundles. The
double line on outside represents epidermis. B. origin of
lateral roots as seen in longitudinal section of bean; ?.c.
vascular cylinder ; /.7. lateral roots; 7.c. root-caps. C, D.
course of vascular bundles in stems of monocotyledon and
dicotyledon. JU. leaves; p. pith; co. cortex. E. piece of
wood to show course of medullary rays ; m.7r. rays ; as seen
in a cross-section ; m.?”. rays as seen in a radial section;
mr”, rays as seen in a tangential section.

Prantl).

longitudinally (taking care to include a node, and to cut through
the attachment of a leaf), and the pith carefully scraped away

30 THE FLOWERING PLANT.

with blunt needles, it will be seen that the vascular bundles are
firm strands which traverse the ground-tissue in the long direc-
tion. With a little care it can be shown that at the node the
bundles are more or less united with one another, while fresh
bundles run in from the leaf. All the bundles are common to
stem and leaf, since any one of them commences in a leaf and
then runs downwards in the outer part of the stem (cf. fig. 5, D).
The above description is applicable to most herbaceous gymno-
sperms and dicotyledons. Similar observations may with advan-
tage be made on the broad bean (Vicia faba), where, however, the
stem is square and glabrous, the bundles follow the external shape,
and the pith is traversed from end to end by a large air cavity
(cf. p. 23). That this has been caused by rupture of the internal
tissue may be seen by the presence of ragged fragments on the
walls of the cavity. A very young green stem of the Scotch fir
may also be examined, but the parts are much smaller and more
difficult to see.

The asparagus stem is a typical monocotyledonous one, and a
cross-section shows that the vascular bundles are not arranged
in a ring, but scattered through the ground-tissue, so as to forbid
the existence of sharply defined cortex, pith, and medullary rays
(fig. 7, D). Asin the previous case, they are common, but instead
of running directly downwards, run inwards and downwards,
thickening as they go, and then take an outward and downward
course (cf. fig. 5, C). The bundles are connected together at the
nodes by numerous cross branches. Owing to the way in which
the bundles thicken, it is clear that those nearest’ the centre at
any point should appear largest in a cross-section taken at that
point, and this is actually seen to be the case. The course of the
bundles cannot be followed with the same ease as in the sunflower.
The hollow stems of grasses bear a similar relation to the aspar-
agus stem that the bean stem does to the sunflower stem. The
nodes, however, are solid, as can easily be shown by splitting the
stem longitudinally.

We now come to the histology of the two herbaceous stems
taken as examples, and it is necessary to explain that longi-
tudinal sections are of two kinds, radial, corresponding with a
radius of the cross-section, and tangential, at right angles to this.
The cells of the epidermis in the sunflower stem are flattened,
and their cellulose walls thick externally. A very thin mem-
brane, the cuticle, covers the outside of the epidermis, but though
part of this, it is not divided into areas corresponding with
the cells, and may perhaps be regarded as a hardened surface
excretion. The substance cutin, of which it is composed, contains
the same elements (C, O, H) as cellulose, but in different propor-

THE STEM. «3a

tions, and is practically impervious to moisture, though not to
gases. Protoplasm and cell-sap occupy the interior of the epi-
dermic cells, and chlorophyll granules are also found there. Most
cells of the kind do not contain such granules. The hairs appear
as large multicellular structures growing from the epidermis, and
small openings, known as stomata are present. These are more
abundant in leaves, and will be spoken of in connection with those
members (p. 65). They are never found in roots. The ground-
tissue is mainly composed, as in the root, of parenchyma (cf.
p- 14), with cellulose walls and protoplasmic contents; but the
parenchyma of the cortex differs from that of the root in the pos-
session of numerous chlorophyll granules. There is, besides, in
the cortex another kind of tissue, collenchyma, forming a band
beneath the epidermis. This differs from parenchyma mainly in
the fact that the cells are thickened at their angles. Numerous
chlorophyll granules are imbedded in their protoplasm. It is
best to examine the vascular bundles in sections of a very young
stem, as they are then quite distinct from one another.! In a
properly stained cross-section (¢f Appendix) we shall be able,
with a low power of the microscope, to distinguish the bundles as
oval areas, each of which is composed of an outer part, the bast
or phloém, and an inner part, the wood or xylem, separated by a
band of very thin-walled cells known as the cambium. As seen
with a high power (fig. 6), the bast is made up of an outer some-
what crescentic portion, the hard bast, the elements of which,
bast fibres, have very thick walls and no protoplasm, and an inner
part, the soft bast, the components of which have thin cellulose
walls. Some of these, the szeve tubes, are large, others, making
up the bast parenchyma, are much smaller. A number of the
sieve tubes present an appearance reminding one of the perforated
top of a pepper-castor. This appearance is due to the presence
of sieve plates pierced with small holes. The most conspicuous
components of its wood are the wood vessels, large rounded ele-
ments with very thick walls and no protoplasm. The remaining
parts are wood parenchyma and wood fibres, the latter closely
resembling the bast fibres. The cells of the cambium have very.
thin cellulose walls and abundant deeply-stained protoplasm.
Their shape is rectangular, with the long diameter tangential,
and they are arranged in radial rows, two or three cells in a row.
These features show that division has taken place in a tangential
direction. Imagine a cell, square in cross-section, with two sides
at right angles to a radius of the stem. Then suppose this cell
to be bisected by formation of a new wall parallel to the two in

+ In buttercup and some other plants the bundles remain distinct through-

32 THE FLOWERING PLANT.

question. ‘Two rectangularly-shaped cells making a radial row
would then be formed. Further divisions would give a radial
row with more numerous cells, This is the kind of process which
goes on in cambium. It is, in fact, a meristem, or actively-dividing
formative tissue (cf. p. 17), with abundant protoplasm and thin
cellulose cells, as might be expected. It is secondary meristem,
because it abuts externally and internally upon permanent tissues,
and the cells formed by its division undergo various changes,
finally becoming bast and wood elements. Bundles which con-
tain cambium are termed open, because they are able to increase
in size by its means. Such bundles characterize gymnosperms
and dicotyledons. The entire ring of bundles is enclosed by a
sheath or layer of small starch-containing cells, which crosses over
the medullary rays. This is the bundle sheath or starch-layer.
By studying a radial longitudinal section we shall get clearer
ideas regarding the elements of the bundles. Beginning as before
at the outside, we shall find the hard bast composed of thick-
walled fibres, bast fibres, with tapering ends, by means of which
they dovetail together. A tissue with elements united in this
way is said to be prosenchymatous. The bast fibres, moreover,
are not cells, but cell-derivates, t.e., they have been derived from
cells. The presence or absence of protoplasm is the miain test of
cell nature or the contrary. What then has been the history of
a bast fibre? It was originally a small cell, not specially elon-
gated, with thin cellulose walls, and completely filled with proto-
plasm. Growth in length then rapidly took place, and at the
same time alterations both of the wall and contents went on.
The cellulose wall, kept on the stretch by the turgidity of the
cell, had layer after layer of woody matter deposited on its inner
side by the agency of the protoplasm. Thin places or pits, in
this case resembling canals, were, however, left. The layers in
the thickened and lignified cell-wall can be recognized in the
cross-section, as well as the original party-walls between the adja-
cent cells, now known as the middle lamella. The pits appear as
streaks running across the thickened wall. They run from the
interior of the fibre to the middle lamella, which closes them, so
to speak, and forms a pit membrane. It will be seen from the
above that woody matter is not limited to the wood or xylem,
though mainly characteristic of it. As regards the protoplasmic
contents of the original cell, these became vacuolized (cf. p. 8),
2.€., Small vacuoles were formed which then coalesced so that the
protoplasm became limited to a parietal layer. This layer gradu-
ally used itself up in the thickening of the wall, and the bast
fibre became complete. Such a fibre is not therefore living, and
it plays a purely physical part in the organism. The fibres belong

THE STEM. 33

to a type of tissue known as sclerenchyma, characterized by thick-
ened woody cell-walls and absence of protoplasm. In the soft bast
thereis nothing very
remarkable about
the parenchyma, but
the sieve tubes are
very important.
They are the essen-
tial part of the bast,
and are always pre-
sent in it, at any
rate in phanero-
gams. ‘The radial
section will show, if
carefully prepared,
that each sieve tube
is made up of a
series of elongated
members or joints,
somewhatswollenat
their ends, and sepa-
rated by transverse
partitions, the szeve
plates perforated (as
we have seen in the
cross - section) by

numerous pores. :

= Fic. 6.—Transverse and Radial Sections of Sunflower Stem, to
We have aes to show structure of a Vascular Bundle. [After Prantl.] Much
deal, in all proba- magnified. B.sh. bundle sheath; P. pith; co. cortex; X.

oS : Ec xylem; ss. spiral vessels; ¢t. pitted vessels; 2.7. xylem
bility ? with cell-deri- fibres : Ph. phloém ; s.t. sieve tubes ; ph.f. phloém fibres;

vates. Each mem- C.J, C.i. cambium.

ber was originally one of a row of cells. The walls of the
mature tubes, although thickened, remain of cellulose, but the
protoplasm seems to have disappeared. Hach member is lined
by a slimy substance, which is denser, and therefore stains
more deeply than the rest. The transverse party-walls between
the original row of cells appear to have been thickened, pits,
however, having been left, which corresponded on opposite
sides.. Hence at any spot where these occurred there would be
a pit or depression on either side, the two being separated by
the pit-membrane, absorption of which would lead to formation
of a little canal, piercing the sieve plate. In the sieve tube the
slime in one member is connected with that in the adjoming ones
by threads of the same material running through the sieve plates.
We have here an example of a cell-fusion or vessel, which terms

Cc

LE
Z|

RY

TAN
ahs
ise

ti,

ithe
he
\]

Shue OHS
Reeago!
i Sau,

NTT
fy Ba
Aaeaea

af i

34 THE FLOWERING PLANT.

are applied to tubular cell-derivates that have been formed by the
more or less complete coalescence of adjoining cells. In the wood
no special notice need be taken of the wood parenchyma, nor of
the wood fibres, which closely correspond to the bast fibres. The
essential parts are the wood vessels, which, like the vessels of the
bast, are cell fusions made up of numerous joints. Here, how-
ever, the cell nature is still more completely lost, for the walls
are thickened and lignified, and the protoplasm has completely’
disappeared, being replaced by air. The transverse partitions
have been almost entirely absorbed, so that a continuous tube
is formed. The more external vessels are pitted, and obviously
made up of joints, while next. the pith smaller vessels occur in
which the thickening of the wall has taken place in a spiral or
ring-like manner. ‘These spzral and annular vessels are the oldest
parts of the wood, and therefore termed protorylem. Having
had more time to develop than the other vessels, their members
are longer, and the pointed nature is not so obvious. The cam-
bium is not easy to make out in longitudinal section, but its cells
appear elongated, and are in fact rectangular prisms with rather
oblique ends. It has been stated that cells derived from the
cambium go to increase the bast and wood, and before this can
be effected must evidently undergo various changes, according to
the nature of the structures formed. A prismatic cell may become
a fibre pretty much as described on p. 32, but of course less
elongation is here necessary. Short parenchymatous cells may
be derived from such a cell by the formation of transverse walls,
while the origin of sieve tubes and wood vessels will be under-
stood from what has been said above. It must further be added
that the prismatic cells enlarge and become cylindrical before
they can be converted into members of sieve tubes or wood
vessels, The stem, like the root, terminates in a growing-point
(cf. p. 16), but there is nothing to correspond to the root-cap.
The above histological description of the sunflower stem will
serve pretty well for most herbaceous dicotyledons, but the bast
‘and wood fibres are often absent. When they are present the
bundle is jibro-vascular. The most important points may be put
in a tabular form :—

Hard Bast.—Bast fibres or sclerenchyma.
{. Bast or Phloém. ; Soft Bast.—Bast vessels or sieve tubes,
bast parenchyma.

Il. Cambium.

j Wood fibres.
IlI. Wood or Xylem. ; Wood vessels.
Wood parenchyma,

juniper, correspond
in their main histo-

THE STEM.

7 35
Very young stems of most gymnosperms, ¢.g., Scotch fir and
: \ fj.
r a
a % x

logical features with
those of dicotyledons
(fig. 7, A, B). The
most important dif-
ference is found in
the wood. This is
almost entirely made
up, not of vessels,
but of elongated
tapering elements,
with pitted lignified
walls and no proto-
plasm. These dead
skeletons of elon-
gated cells which
have lost their liv-
ing portion are
tracheides. | Wood
vessels and trache-
ides may collectively
be called trachez.
The pits in the wall
are somewhat pecu-
har. In __ surface
view they present
the appearance of
two concentric
circles, and = are
therefore called bor-
dered pits (fig. 7, C).
The mouth of the
pit, z.e., its opening
into the cavity of
the tracheide, is
narrower than the
bottom of the pit,
and (the whole sec-
tion being transpa-
rent) it therefore
appears as the inner
circle, and the latter
as the outer. In gym-
nosperms, again, the

oy
RO
Nass

ke

Bs
‘oe
i)

I)

=
~

We SS
Kr NH)
Poa Oe
4 Ke A — e= = —
SRR SAA); Y) Stet TAINO Tha
morse (RRS
STE CSRS
WAPI DH (eas y
ES 5 Ratatat
AAAS AX LS

Fic. 7.— Minute Structureof Vegetative Organs [G, I, K, after

Prantij. All more or less magnified. A. cross-section of
young shoot of Scotch fir. B. part of same enlarged ; ep.
epidermis; p. pith; co. cortex; x. xylem; ph. phloém;
c. cambium ; m7. medullary ray. C. small piece of radial
section of fir wood, showing tracheides with bordered pits ;
mr. medullary ray. OD. cross-section of asparagus stem,
showing bundles. E. one bundle of same, magnified ; 2.
xz’. xylem; ph. phloém. F. piece of lower epidermis from
geranium leaf; g.c. guard-cells of stomata. G. cross-
section of beech leaf; ep. upper epidermis; ep’. lower
epidermis ; pp. palisade parenchyma; sp. spongy paren-
chyma; st. stomata. H. part of cross-section of buttercup
root; ep. epidermis; Jr. lateral root; gt, cortex; rh.
root-hairs. I. section of elder lenticel; ep. epidermis;
co. cork; 1. loose cork of lenticel; ¢.e. cork cambium.
K. part of cross-section of four-year-old lime twig; p.
pith; co. cortex; c. cork; ph. phloém; 2, 1, 2, 3, 4.
annual rings of xylem.

5

36 THE FLOWERING PLANT.

steve tubes are different in structure from those of sunflower, and
much more difficult to study. On the other hand, there are dico-
tyledonous stems which are superior to sunflower for the study of
sieve tubes. In the cucumber and vegetable marrow, for example,
they are extremely large, and easy to see. ‘These stems are,
however, abnormal in some respects, since there is not only bast
external to the wood, but also some internal to it. A band of
sclerenchyma will also be found in the cortex not far from the
epidermis.

We now come to the histology of herbaceous monocotyledons.
In the stem of asparagus (fig. 7, D, E) we shall find epidermis of
the usual kind, while the ground-tissue is largely composed of
parenchyma. Each vascular bundle is made up of: (1.) Wood,
which in cross-section forms a V-shaped or U-shaped mass, with
apex pointing inwards. It is chiefly composed of vessels. As in
the sunflower, there is protoxylem, composed of spiral and annu-
lar vessels, which occupy the apex of the V. (2.) Bast, which is
almost all soft, and is situated on the outer side of the bundle,
chiefly within the limbs of the V. There is no cambiwm, and the
bundle is therefore closed, since no addition of new elements can
take place. Such closed bundles, with wood arranged in a V or
U, characterize monocotyledons generally. Examination of any
good-sized grass stem will show these features more clearly than
in asparagus. In addition, the whole bundle is surrounded by a
sheath of sclerenchyma, and there are also masses of this tissue
beneath the epidermis.

Thickening of Stems.—It is the presence of cambium in the
stems of gymnosperms and dicotyledons that enables perennials
belonging to these groups to increase in thickness, sometimes to
a very large extent. This process may commence in herbaceous
stems, but has no time to go any great length. The increase is
mainly in the wood or xylem, and what are popularly called woody
stems owe their nature to this. But it must not be forgotten
that all stems contain a certain amount of wood or xylem, so that
the term herbaceous is not exactly opposite in meaning to the
term woody. If we take such a tree as a Scotch fir or elm, suc-
cessive examination of older and older stems will enable us to
understand how secondary increase of thickness takes place. We
will at first mainly consider the vascular bundles. A cross-
section through the axis of a bud will present a ring of primary
bundles, completely isolated from one another. ‘This condition
is retained through life in some herbaceous stems, such as those
of the buttercup. The bundles are separated by strips of ground-
tissue, the primary medullary rays, and each of them consists of
primary bast on the outside and primary wood on the inside, the

THE STEM. 37
two being separated by what may be called fascicular cambium,
since it occurs within the bundle. In a rather older stem some
of the cells making up the medullary rays have begun to divide
actively, giving rise to cambium between the primary bundles
or interfascicular cambium. This, together with the fascicular
cambium, forms a 2
cambium ring, ex-
tending right round
the stem. This and
even a later stage is
reached in the stouter
stems of sunflower.
Still older examples
present a compact
mass of vascular tis-
sue, most of which
has been formed by
the active division of
the cambium, produc-
ing secondary bast on
the outside and secon-
dary wood on the in-
side, not only in the
region of the primary
bundles, but also be-
tween them. ‘The
elements making up
the new bast and
wood are similar to
those already de-
scribed, but spiral
and annular air tubes
are limited to the
protoxylem. Secon-
dary increase is far
ereater vee the ca a Fig. 8.—Secondary Thickening of Stem. [After Sachs.] A,
of the xylem, giving _B, C. cross sections of same stem at different ages. A.
Bichito' the ‘wood: « Tames bunplen aati eerie am ee copes Tes
of shrubs and trees, and phloém present, formed by activity of cambium ring ;

: ‘c ” s H. pith; R. cortex ; medullary rays in A and B are the
while the bark” is broad spaces between bundles, in C are represented by

largely composed of _ streaks; p, fp. phlotm; @, fh, ifh. xylem.

secondary bast. The primary medullary rays are reduced
to exceedingly narrow strips, running through from pith to
cortex. Secondary or short medullary rays are also formed,
taking origin in the cambium, and only extending part of

7
Pa |

38 , THE FLOWERING PLANT.

the way from pith to cortex. It must not be supposed that
in the thickened stem a medullary ray has a great vertical
extent, for it is often only a few cells high. If we imagine a
lath-shaped mass of cells running through the vascular tissue in
a radial direction, possessing convex sides which face sideways,
and edges facing upwards and downwards, we shall have some
idea of such a ray. In cross-section (fig. 5, E) it will look like a
narrow streak or “ray” running in a radial direction. A radial
section will display it as a broader band running at right angles
to the direction of the elongated vascular elements ; and, lastly,
a tangential section will cut across it, giving an outline resem-
bling in shape the cross-section of a biconvex lens.1_ The “silver
grain’ of wood is due to the presence of medullary rays, which
are always excessively numerous. In the oak they are of un-
usually large size, and give the characteristic grained appear-
ance. It is a familiar fact that in a piece of stick, a log, or a
tree-trunk the wood presents, as seen in cross-section, a series
of concentric layers in “annual rings,” surrounding a more or
less evident pith, which is generally dead and dry. Generally
speaking, one ring is formed per annum, hence the name (fig.
7, K). It is not usual for the pith to occupy the geometrical
centre, so that the rings are not exactly circular, nor is any
one ring necessarily of uniform thickness all the way round.
Since the new layers are formed by the cambium, it is evi-
dent that the inner rings are older than the outer. In many
timber trees the internal “‘ heart-wood” or dwiamen is extremely
hard and dry, while the outer “ sap-wood ” or alburnum is much
softer, and, as the name indicates, full of sap. The appearance
of annual rings is caused by the difference in texture between wood
formed at different seasons of the year. Spring wood is com-
posed of comparatively large, thin-walled elements, but, as growth
proceeds, smaller and smaller elements are produced, with thicker
and thicker walls, till, in the autumn, growth ceases altogether.
Hence the dense autumn wood of one year is abutted upon by
the much looser spring wood of the next year, and, as the colour
also is generally rather different, the boundary between the two
is distinctly seen. Annual rings of different years may vary
very considerably in thickness. Owing to this method of increase
in the wood, viz., by the addition of layer after layer to the out-
side, dicotyledons (and gymnosperms too, which were formerly
grouped with them) were called exogens, or outside growers.
Monocotyledons received the converse name of endogens. This,
however, was founded on mistake. The plants in question rarely

| The very large medullary rays of oak are much flattened from side to
side,

THE STEM. 39

increase in thickness at all. When they do so, as in some tropi-
cal trees akin to lilies, the bundles remain closed, no cambium
being formed in them. A ring of cambium is formed in the
ground-tissue outside the original bundles, and in the ring new
bundles are developed, so that growth here also is really by exter-
nal additions. It is therefore best to drop altogether the terms
exogen and endogen, but the adjectives exogenous and endogenous
may be conveniently retained, as denoting the origin of certain
organs or tissues. A root, for example, is endogenous, being
developed from internal tissue layers, while a leaf, as we shall see
farther on, is exogenous (fig. 5). Before leaving the secondary
wood, it will be useful to examine, in the light of what has been
said, the appearances visible in a wooden plank, composed say of
fir wood, 7.e., deal. The ends will be more or less accurate cross-
sections of the trunk, and will therefore present small segments
of the annual rings. The pith may possibly be seen as a circle,
but will be insignificant in size. The medullary rays appear as
narrow radial streaks. A plank running right through the centre
of the annual rings will have a number of more or less parallel
lines running along its faces in the long direction. The pith, if
seen, will be a narrow longitudinal streak, and, of course, the
stripes immediately bounding this belong to the first annual ring,
the next stripes to the second ring, and so on. The medullary
rays appear as streaks rather broader than before, parallel to the
ends, and for the most part very discontinuous, since the section
is not likely to run very far along any one of them. ‘The edges
of the plank display the ends of the rays, and, if rather oblique,
may cut through several annual rings, the boundaries between
which will be irregularly wavy. Most planks are, however, more
or less tangential, and either side of such a plank will, near its
centre, cut along a single ring for some distance, till in fact the
ring curves quite out of the plane of section. There will thus be
a central strip, running longways, and bounded by straight lines.
Outside this will be pairs of strips, one of each pair on either
side, getting narrower and narrower, till near the edge a prac-
tically radial section is seen. As we pass from the centre, the
medullary rays will be first cut right across, and then obliquely,
and lastly in the direction of their length. No mention has yet
been made of “‘ knots.” These are simply dead branches of diffe-
rent age, which in tangential section are cut transversely, when
their age can be determined by counting the rings they possess.
Their nature is well seen in radial sections, where they will be
observed to run out as transverse brown stripes from annual
rings of different age. We can therefore tell when they began
to grow. ‘The foregoing description will be perfectly useless with-

40 THE FLOWERING PLANT.

out a little thought on the part of the student, and examination
of actual specimens.

We may now pass to the consideration of bark. A twig can
generally be “ peeled” with ease, and this is owing to the delicate
nature of the cambium ring, which is broken through in the
process of peeling. As the wood receive annual additions on its
outside from the cambium, so does the bast receive similar addi-
tions, the difference being that they are very much thinner and
formed on the inside. There is never such a regular appearance
of annual rings as in the wood (fig. 7, K). It is evident that the
method of increase described must. subject the external tissues to
a great deal of tension. The epidermis may for some time keep
up with the growth in thickness, but sooner or later, in most
cases, it bursts and is thrown off. Its place is taken by brown
layers of cork cells formed in the following way. A layer of cells
in the cortex, @.¢., outer part of the ground-tissue, begins to
divide actively and forms a layer of meristem, known as cork
cambium (fig. 7, I). Its cells, however, are not elongated like
those of ordinary cambium. ‘The cells formed on the outside by
division of this layer become cork elements. These, as seen in
cross-section, are rectangular in shape and arranged in radial
rows (cf. p. 31). Their walls are thickened, brown, and com-
posed of a substance, suberin, probably allied to cutin (p. 30).
‘They contain no protoplasm. An examination of elder-shoots
of different age will illustrate these points. The youngest are
bright green, since the chlorophyll-bearing cells of the cortex
can be seen through the transparent epidermis, but older ones
are brown, owing to the formation of cork. ‘This is not very
transparent, and so does not permit the green cortical tissue to
be clearly seen from the outside. A cross-section will show the
relation of the different parts. If this is made through a branch
about half an inch thick, the following points can be easily made
out by the eye alone. A large part of the interior will be occu-
pied by the bright, white, spongy pith, the colour of which is due
to the fact that the cells are dead and contain air instead of pro-
toplasm. Then follows a whitish-brown band of wood, in which
medullary rays are plainly seen. The cambium forms an ex-
tremely narrow band, the position of which is shown by the fact
that the outer part of the stem can be peeled off at this point.
Next comes a narrow greenish-white zone, the bast, and this is
succeeded by a narrower dark-green portion, the chlorophyll-
bearing cortex. This is invested by a thin papery layer of
whitish-brown cork, which can easily be detached, owing to the
delicate nature of the cork cambium. That it is subjected to
tension may be seen by the presence of numerous little fissures,

THE STEM. 4i

taking a longitudinal direction. A number of raised, brown,
spongy-looking spots may also be observed on the surface. These
are lenticels or porous parts of the cork, where the cells are
rounded, with numerous intercellular spaces between them (fig.
7,1). The bark of trees is mostly made up of bast and cork, which,
owing to the increase in size of the wood, are thrown off from time
to time in shreds or flakes, and are frequently traversed by numer-
ous cracks and fissures. The rugged nature of many tree-trunks
is, therefore, a result of secondary increase in thickness.

PHYSIOLOGY.

The chief uses of the stem are to display the leaves, so that they
may best carry on their functions of assimilation and reproduction,
and also to serve as a means of communication between them and
the roots. Like the root, the stem is a vegetative organ. An organ
of support requires to be more or less firm in texture, and this is
effected by means of the hard lignified tissue making up most
of the xylem, as well as by the sclerenchyma that may occur in
the bast and cortex. Collenchyma, again, helps to some extent.
These supporting or mechanical tissues have collectively been
called the stereome, and this is naturally best developed in erect
perennials. Weaker stems make use of the ground, other plants,
&¢e., as supports, and attach themselves to these by the means
described on pp. 25-26. Stems also present various protective
appliances. Spines, thorns, and prickles help to keep off brows-
ing animals, and, when closely set, repel the attacks of soft-
bodied creeping forms, such as snails and slugs. There may
also be viscid substances, excreted by glandular hairs or by the
general surface, which prevent wingless insects from reaching
the leaves and flowers. In one species of willow the stems
of the flowering shoots are coated by a slippery layer of wax,
over which no insects can pass. Again, protection is needed
from the weather, and this is afforded by epidermis and cork,
which are practically water-tight. Hairs on the stem (and leaf)
help to keep off wingless. insects.

Stems assist in nutrition by conveying to the leaves the water
with substances in solution absorbed by the root, and, on the other
hand, carrying the materials formed in the leaves to the plant
body generally. The ascending or crude sap travels chiefly (see
p. 18) in the cavities of the lignified wood vessels and tracheides,
and an active movement towards the leaves is brought about by
the vital activity of the cells of the medullary rays and wood-
parenchyma, which act alternately as suction-pumps and force-
pumps. By means of the pits liquid can filter from one element

42 THE FLOWERING PLANT.

to another. Some crude sap also passes through the parenchy-
matous parts of the stem by means of osmosis. The whole of the
wood in annual stems can conduct water, but in perennials possess-
ing sap-wood and heart-wood only the former can do so, This is
shown by an old experiment, in which a ring of tissue was removed
from the stem of an oak, exposing the duramen. ‘The result was
that the leaves quickly withered. Since removal of a ring of bark
alone did not cause such an effect, it was concluded that the
outer or sap-wood conducted water upwards. This is confirmed
by the fact that trees can flourish without pith and duramen,
as shown by hollow specimens. The leaf-protoplasm, aided by
chlorophyll (see p. 10), forms organic matter from the crude sap
and the carbon dioxide of the surrounding medium ‘This organic
matter, the elaborated sap, travels from the leaves to all parts
of the body which contain protoplasm, compensating waste and
rendering growth possible. In many plants it is stored up as
reserve materials, e.g., starch, erystalloids, &c., in thickened roots,
stems, and other receptacles. Part of this organic material is in a
soluble diffusible form. This can travel through the parenchyma.
Another part, consisting of proteids, travels by means of the
sieve tubes, which form a continuous series of canals. Klaborated
sap, then, traverses the outer part of the stem. The experiment
of removing a ring of bark conclusively proves this, for no growth
takes place below the wound, since the supply of nutriment is
cut off, while, on the other hand, increase goes on as usual above
the wound. Trees are not infrequently seen in country places
with the lower part of the trunk comparatively small, and abruptly
succeeded by a considerable bulge. This is generally due to a metal
hoop having been placed round the stem years previously, which,
as increase in size took place, first became very tight, and then
cut through the bark. One or two facts in practical gardening
illustrate the same point. It is sometimes required to hasten the
ripening of fruit on some special branch of a tree. This is effected
by ‘‘ringing” the branch, when the elaborated sap formed in its
leaves cannot pass beyond the wound, and is employed in building
up the fruit. Again, on a plum tree for example, the fruits will
not ripen unless they have at least one leafy shoot beyond them.
If this were not the case, they would not be in the course of the
descending current of elaborated sap.

Where the stem contains chlorophyll, it assists the leaves in
the formation of organic matter, and this function is mostly or
solely carried on by the stem in plants which possess phylloclades.

As we have seen, thickened stems, such as corms, rhizomes,
&e , serve as stores of reserve materials, and this is also the case
with the trunks of trees which shed their leaves in autumn. ‘The

THE STEM. 43

‘fall of the leat” is not, as might be imagined, a great waste of
protoplasm. All the contents of the leaf cells are, in fact, with-
drawn into the stem before this takes place. The fall itself is
effected by formation of a layer of cork running right across the
insertion of the leaf-stalk, ¢.e., the pomt where it joins the stem.
Separation now readily occurs, leaving, not a raw surface, but a
neat ‘scar’ covered by cork.

The protoplasmic parts of the stem carry on respiration, as we
have seen to be the case in the root (p. 18). The circulation of
gases mainly takes place in the cavities of the trachez, and inter-
cellular spaces of the ground-tissue. In aquatic stems these last
form air chambers of considerable size. In terrestrial stems com-
munication between the intercellular spaces and the exterior is-
kept up by the stomata and lenticels (see further p. 65).

The stem, or more correctly speaking the vegetative shoot, may
subserve the function of reproduction, which in this case is termed
vegetative. Reproductive organs proper are specially modified for
the performance of their function, and are not concerned with
nutrition. Vegetative organs, on the other hand, have mainly to
do with nutrition, and, if they reproduce, are either not modified
at all for that purpose, or at any rate not so profoundly as to
interfere with their chief use. Vegetative reproduction depends
upon the power of the stem to produce adventitious roots. One
of the simplest cases is where branches are liberated by the rotting
of the main stem, and become fresh plants. A notable example
is the common aquatic weed, water-thyme (Anacharis or Elodea),
found abundantly in all our rivers, canals, &e. This plant is a
native of North America, and was introduced into Ireland about
1836, and into England about 1841. Reproducing solely in the
way described, it soon became a serious nuisance, even hindering
canal navigation. Attempts were made to destroy 1t by means
of cutting implements, but as every little bit cut off became a
new plant, its increase was only augmented. Somewhat similar
to this is the case of creeping stems, each node of which can
develop roots and send up a shoot. Rotting or severance of the
internodes makes the new individuals quite independent of the
parent plant. The same sort of thing occurs with horizontal
underground stems. Stolons and suckers are branches specially
adapted for vegetative reproduction, and any strawberry bed will
show how well the former are able to produce new plants. Cut-
tings (see p. 13) form an artificial means of propagation akin to
the preceding. ‘ Layering,” in which branches are fastened to
the ground and induced to form adventitious roots, is of the same
nature. Grafting is practically the planting of a shoot in an
incision made in another stem instead of in the ground. Vegeta-

44 THE FLOWERING PLANT.

tive reproduction is often effected by means of buds, 7.e., unex:
tended shoots. Corms and bulbs are modified underground buds
developed by annuals for this purpose. At least one of these
structures is produced every year, and very frequently the main
corm or bulb develops several smaller ones in its leaf-axils. In
the tiger-lily small rounded black bodies may be seen during
summer in the axils of the leaves. These are small aérial bulbs,
which, sooner or later, fall to the ground and grow into fresh
individuals. They are known as bulbils or bulblets. The buds or
“eyes” occurring upon tubers, as the potato, serve the same end,
and this fact is largely taken advantage of in cultivation. The
operation of ‘“ budding” may be mentioned here. It bears a
close relation to grafting, and consists in the removal of a bud
with a small piece of the tissues external to the cambium from
one tree, and insertion of the same under flaps cut in the back of
another tree. Close contact with the cambium of this tree is
thus brought about.

Motility is exhibited very conspicuously by the stem under
various forms. Protoplasmic streamings (cf p. 11) may some-
times be seen under the microscope in the cells of some of the
hairs which clothe it. This point will be spoken of more fully in
a later chapter (p. 72). Larger movements are very frequently
met with, especially in growing parts, as is strikingly seen in the
case of many twining and other climbing stems. The young
shoots of a hop plant, for example, exhibit what is termed czreawm-
nutation, that is to say, they sweep round and round in search of
a support, and if they find one, twine round it. Darwin’s experi-
ments show that in the hop a complete revolution is effected in
from two hours to two hours twenty minutes. In a special case
noted by him the moving part was about fifteen inches long, and
curved in such a way as to describe a circle of nineteen inches in
diameter. These data give a maximum rate for the end of the
shoot of nearly half an inch per minute. The tip of the minute
hand in an ordinary watch, the movement of which can easily be
seen, only travels about a quarter as fast as this.

Irritability and Spontaneity are also possessed by the stem,
often in a high degree. As in the case of roots (cf. p. 19),
gravity exerts an important influence in determining the direc-
tion of growth, but the geotropism here is not positive, but
negative. The main stem, when strong enough, grows vertically
upwards, and its branches have mostly an upward tendency.
The experiments with seedlings, described on p. 20, are as
instructive here as in the case of the root. Negative geotropism
is as necessary to stems for the suitable display of their leaves as
positive geotropism is to roots for bringing them into relation

THE STEM. 45

with the soil. The heliotropism of the stem is, again, opposed
to that of the root, for similar reasons. It is, except in special
cases, positive. Light is essential to leaf functions; and many
plants which in open localities have comparatively short stems
become extremely elongated when surrounded by a dense under-
growth. The excessive development in length of shoots grown
in a dark or badly-lighted place may also be interpreted as an
effort to reach the light. The sprouting of potatoes in damp
cellars is a familiar example. There is, however, another fact to
be,taken into consideration, namely, that light retards growth.
A further instance is that of plants grown in a window. These
curve over towards the light to such an extent as in many cases
‘“‘to break their backs.” The side turned towards the room here
grows more rapidly than the other side in its attempt to reach
the light, with the result mentioned. Climbing stems do not
exhibit strong positive heliotropism, as this would often take
them away from their supports. They may even be negatively
heliotropic. This is seen in the tendrils of the Virginia creeper,
which turn away from the light and attach themselves to the
wall up which the plant climbs. Again, stems are often very
sensitive to mechanical contact, and this is particularly the case
with stem (and other) tendrils. The best example is a kind of
passion-flower (Passijlora gracilis), where, according to Darwin,
a perceptible curving takes place half a minute after the tip
is lightly touched. When, therefore, such a tendril comes into
contact with a support, it is enabled to attach itself very quickly.
A very interesting case is that of the white bryony (Bryonia dioica).
The long tendrils of this plant coil their ends round supports, and
this affects the unattached parts of them near the stem, causing
these to coil up like corkscrews. Two ends are served. ‘The
plant is pulled upwards and firmly stretched, and the coiled parts
in question act like so many springs, which yield in a strong
wind, and prevent it from tearing the stems from their support.

CHAPTER V.
BUDS AND LEAF ARRANGEMENT.

Ir has already been pointed out that the two parts of the
shoot, z.e., stem and leaf, are very closely connected, so that one
cannot be defined without reference to the other. Leaves are, in
fact, outgrowths from the side of the stem, which generally differ
from it in shape, and are developed acropetally (figs. 2, 4, and
5 A). Most leaves are flat, and, in a general sort of way, they
may be looked upon as modified pieces of stem. Not uncom-
monly the sides of a stem are produced into green wing-like
expansions. If these, instead of being continuous, were very
much developed at some points and reduced at others, something
very like leaves would result. Curiously enough, some leaves
actually do become continuous at their insertions, with wings on
the stem, as in the thistle.

There is much more to be said about the leaf than was the
case either with the root or stem. Their arrangement will first
be considered, and then the various kinds of leaf will be dealt
with consecutively.

Leaving the flower out of consideration for the present, imma-
ture leaves have a certain arrangement in the bud, which leads
up to the arrangement of the mature leaves on the fully-developed
stem.

Buds, as previously mentioned, are young shoots, in which all
the parts are very small, and the internodes non-elongated. The
best examples are to be found in trees, which may be instructively
studied in early spring. Every branch typically ends in an apical
or terminal bud, within which the year’s growth is, so to speak,
mapped out, nothing but increase in size being needed to produce
a leafy shoot (figs. 2, 4, and 5 A). In racemose branching (p. 24)
a branch or twig may grow indefinitely in this way, an apical
bud being formed every year ready for the next year’s growth.
A very good instance is the horse-chestnut. An examination of
an apical bud of this tree in spring will show a number of firm
over-lapping scales on the outside, which are extremely sticky
owing to the secretion of a resinous substance. <A longitudinal

BUDS AND LEAF ARRANGEMENT. 47

section of the bud brings to view the young leaves, crowded on
the stem, and overlapping its growing point. As the bud
expands, the protective scales, which must be regarded as the
lowest leaves of the shoot, fall off, and, as the internodes between
them do not elongate, leave behind narrow scars, which form a
band of ridges round the stem, marking the commencement of
the year’s growth.! Development of these internodes would serve
uo useful purpose, but simply give a long piece of bare stem.
The remaining internodes elongate, and in the summer the shoot
will be found bearing about three pairs of large leaves, and termi-
nated by a large bud for next year. It may be noted here that
large leaves are always borne in small numbers. Overcrowding
would result from the presence of many, and the access of air and
light would be hindered. In a well-developed branch of horse-
chestnut» the growths of several years can be distinguished by
noticing the successive bands of scars left by the bud scales of
different seasons. After a certain time, however, the scars are
obliterated by formation of bark, &c. We may also notice
in such a branch the large heart-shaped scars of the ordinary
leaves (p. 43). Within each scar are seven small rounded eleva
tions, following the lower curve. These are the ends of the
vascular bundles that entered the leaf.

Besides terminal buds we have avillary buds, quite similar in
structure, and developing into lateral shoots (figs, 2, 4, and 5 A).
If every leaf-axil gave rise to a shoot which elongated, it is clear
that branching would follow the leaf arrangement. This, however,
is not the case. Sometimes buds are only developed in some of
the axils, and again many buds either die or remain undeveloped
or dormant. Examine once more the horse-chestnut. Two large
axillary buds will be seen near the end of every present or
current year’s shoot.- Other dormant buds will be seen as little
brown bodies in the axils of the older leaves. This non-develop-
ment of many buds is of considerable importance. In the first
place, overcrowding is prevented, and then, should the first
shoots be blighted from any cause, as by a return of severe
weather in the spring, they can be replaced by growth of the
dormant buds. It may happen, as a regular thing, that the
terminal bud dies. If, as in mistletoe, the leaves are borne in
opposite pairs, the axillary buds of the last two grow vigorously,
and as the dead end of the parent stem is very small, it appears
to have forked. This is false dichotomy (p. 24). It also occurs
in many branches of the lilac. A shoot from this plant generally
exhibits at its end a pair of vigorous lateral buds, between which
is a small terminal bud. This last sometimes grows on, and pro-

1 Such bands are very beautifully seen in the beech.

48 THE FLOWERING PLANT.

duces a weakly terminal shoot, or it may, so to speak, be jostled
out of existence, when a false dichotomy results. On the other
hand, where the leaves are scattered, ¢.e,, placed singly on the
nodes, the terminal bud may be replaced by the axillary bud
of the last leaf. ‘Take, for example, a well-grown shoot of
elm. The current year’s growth may be recognised by its
greenish colour and the presence of the ring of scars at its base.
The end of the shoot is occupied by a bud, apparently terminal.
It is really, however, situated in the axil of the last leaf, and at
its base, opposite the leaf, is a small scar, formed by the death
of the terminal bud. Similarly, the current year’s shoot is itself
developed from an axillary bud. Just below the ring of scars is
a, crescentic mark, showing where the corresponding leaf fell off.
Opposite this is a little rounded projection, where last year’s
terminal bud was attached. The same reasoning applies to still
older parts. We have, in fact, to deal with a sympodium (p. 24),
though the main branches are developed racemosely. The same
remark applies to birch, beech, hazel, and other forms. It
must be carefully noted that facts like these are not obvious.
Very careful examination of shoots in different phases of growth is
necessary to verify them. The definite yearly increase described
above takes place chiefly in trees and shrubs with well-protected
scaly buds. Cases like the elm, where the ends of the shoots
perish, lead on to the numerous plants in which ¢ndefinite growth
takes place in the summer, without formation of strong buds near
the ends of the shoots, as a provision for the following year.
Here (as, for example, in the rose), the later part of the annual
growth perishes in autumn, and the axillary buds of the older
part expand into leafy shoots the next spring. Owing to this,
many shrubs branch very irregularly. A further stage is seen
in perennial herbs, where all overground -parts die down an-
nually, and are succeeded by outgrowths from buds belonging
to the underground portion of the stem.

The statement made on p. 44, that corms and bulbs are thick-
ened underground buds, will now be more clearly understood.
The main corm or tuber produced yearly (as well as the smaller
ones) is an axillary bud. Jt may be taken as a general rule that
where one of two correlated organs is much and rapidly enlarged,
the other will be correspondingly reduced. Thus, in a corm, the
stem is very much thickened, while the leaves are very small,
and conversely for a bulb. Bulbils (p. 44) are axillary buds with
small thickened leaves.

Lateral buds, as we have seen, are typically axillary, and it
sometimes happens that more than one bud is produced in an
axil, These accessory buds may be placed side by side or one

BUDS AND LEAF ARRANGEMENT. 49

above another. If, in the latter case, the upper one develops, an
extra-axillary branch is the result. Adventitious buds may also
. occur, which observe no regularity in their place or time of
development. Most of the shoots on old tree-trunks belong to
this category, and they may also be produced on some roots, or
even on leaves. An example of the last is seen in begonias. A
leaf of one of these plants if fixed in the earth will develop roots
from the end of its stalk, and buds in various places.

The terms prefoliation and vernation are applied to the ways in
which leaves are packed in the buds. The individual leaves are
disposed in various manners, and their mutual relation is different
in different cases.!| We now come to the arrangement of mature
leaves on the stem. This partly depends on the length of the
internodes (p. 24) and partly on the size of the leaves. But
apart from this, it is found that, in a given plant, the leaves are
always attached or inserted at points which bear a definite rela-
tion to one another, which relation may be expressed numerically.
Arrangement of the leaves, in this sense, is known as phyllotaxis.
A node may bear two or more leaves, when the term whorled is
used, or else only one, which fact is denoted by the words scattered
or alternate. In the simplest case a whorl consists of two mem-
bers, as in dead nettle, pink, horse-chestnut, and lilac Such
opposite leaves are generally decussate, 7.e., successive pairs alter-
nate with one another. ‘This is very well seen in the dead nettle,
and even a cursory examination will show that the leaves here
form four lines, ranks or orthostichies, along the stem, one ortho-
stichy corresponding to each of its four flat sides. Angled and
ridged stems frequently exhibit a relation of this kind. A whorl
in other cases may consist of three or more members, and here
also the leaves are respectively above and below the spaces between
the members of the whorl below and the whorl above. Transi-
tions between the whorled and alternate arrangement are com-
monly met with. For example, the rapidly-growing stems of the
Jerusalem artichoke (Helianthus tuberosus) bear opposite leaves
below and alternate ones above, the two ways of arrangement
gradually passing into each other. And in all, or nearly all

1 The following are the chief terms applied to the ways in which individual
leaves are folded or rolled in leaf (and flower) buds :-—

(1.) When folded : platted (in some palmately-veined leaves), when folded
like a fan; conduplicate, doubled up longitudinally, the upper surface internal ;
infleced, the upper part bent down on lower,

(2.) When rolled: convolute, in a continuous roll, upper side being internal,
and one margin forming centre of roll ; involute, both margins rolled inwards ;
revolute, both margins rolled outwards ; circinate, rolled from the tip down-
wards, like a crozier; crumpled, explains itself. Compare also footnote,
p. 84.

D

50 THE FLOWERING PLANT.

dicotyledons, the two first leaves (the cotyledons or seed-leaves)
are opposite, however the following leaves may be disposed (fig. 2).
Seedlings of mustard and cress show this very well (fig. 3).
When the leaves are alternate, they are arranged so that their
angular distance from one another is constant. That is to say,
if the stem were telescoped so as to bring any two successive
leaves to the same level, and if two radii were drawn from the
centre of the stem at that level through the insertions of the two
leaves, the angle enclosed by the radii would be constant, generally
speaking, for the same plant. Diagrams of phyllotaxis represent
the stem as being extremely conical, and looked at from above,
the leaf insertions being marked by thick curves. The simplest
case is that of grasses, &c., where any particular leaf is succeeded
by one placed on the opposite side of the stem. The divergence is
evidently 180°, and this may be expressed by the fraction 4, 7.e.,
half of the entire circumference of the stem, or 360. If a line
is drawn round and round the stem in the same direction, cutting
the insertions of the leaves, it will form what is called the genetic
spiral. Of course a spiral line might be drawn according to
pleasure in either direction, right to left, or the opposite. It is
agreed, however, always to take the shorter course. Starting
from any leaf and proceeding upwards, the spiral will wind once
or more round the stem, till a leaf is reached immediately above
the first, 7.e., in the same rank or orthostichy. Such a portion
of the spiral is called a cycle.
The numerator of the fraction
+ shows us that the cycle takes
one turn round the stem, while
the denominator signifies that
the cycle contains two leaves,
and that there are two ortho-
stichies. The series 4, i, 2,
3, ;, &c., includes the com-
monest divergences. From 2
onwards the numerator and
denominator of any fraction
are respectively the sums of
the numerators and denomi-
nators of the two preceding
fractions. ‘The two-ranked (3)
arrangement not only occurs
in grasses, but also in many
other monocotyledons, and in
twigs of the lime, elm, beech, &c. The three-ranked (3) distribu-
tion is characteristic of sedges, and the alder and aspen. Most

Fig. 9.—2 Phyllotaxis of Cherry.

BUDS AND LEAF ARRANGEMENT. 51

-dicotyledons, ¢.7., willow, oak, rose, apple, and cherry, display
five-ranked or quincuncial (2) phyllotaxis (fig. 9). Here there
are five orthostichies and five leaves in the cycle, which makes
two turns round the stem. An eight-ranked (2) case may be
seen in the holly, while the other divergences chiefly occur in
cases where the leaves are much crowded. The house-leek, for
example, presents the thirteen-ranked (,;%,) arrangement. It
frequently happens that irregularities are brought about from
twisting of the stem and other causes, In the elm and beech,
for instance, the two ranks of leaves are not exactly opposite each
other, but are nearer together on the under than on the upper
side of the branch. Here also we get a bilateral arrangement,
i.e., the leaves are all approximately in the same plane ; hence
it becomes possible to distinguish between upper and lower sur-
faces in the branch. This also is caused by displacement of
parts.

We now come to a consideration of the kinds of leaf. These
are generally taken to be four in number :—

1. Foliage (euphyllary) leaves.

2. Scale (cataphyllary) leaves.

3. Bracts (hypsophyllary) leaves.

4. Floral leaves.

These will be described in the following chapter.

CHAPTER VI.
FOLIAGE AND SCALE LEAVES.
MORPHOLOGY.

THE ordinary green leaves of a plant are known as Foliage Leaves.
They vary very greatly in shape, but in all of them certain parts
can be recognized, which are known by distinctive names. Exa-
mine, for instance, a shoot of a garden geranium. Lach leaf
will be seen to present two distinct parts, the leaf stalk or petiole,
and the expanded blade or lamina supported by this. The leaf is
horizontally directed, with upper surface (back) facing the stem,
and lower surface (front) turned away from it. <A vertical plane
passing through the stem will bisect the leaf into two corre-
sponding halves. This plane is called the median or antero-
posterior plane, and the leaf is said to be bilaterally symmetrical.
In other words, it can only be divided by one plane so as to give
corresponding halves, which in this case may be termed right and
left. Each of them is, so to speak, the reflection of the other,
z.e., if one half of the leaf is placed with its cut edge against a
mirror, the reflection will resemble the missing half. Optically
speaking, each half resembles the other half laterally inverted.
The typical stem, on the other hand, is radially symmetrical, in
that a nwmber of planes can divide it into corresponding halves.
There is consequently no distinction between surfaces and sides,
right and left.1 In a three-sided stem there are three such
planes, in a four-sided one four, and in a smooth cylindrical stem
an infinite number. The lamina, being the important part of
the leaf, is rarely absent (see p. 53), but the petiole is frequently
so, and the leaf is then said to be sessile, as in the majority of
monocotyledons, and in many dicotyledons. This is probably a
more primitive condition, and all gradations are found between
- it and cases where a stalk is present. That is to say, the boundary
between lamina and petiole is not always sharp. ‘The latter may
be winged, there being a thin green strip on either side of it,
directly continuous with the lamina. And if this strip is fairly
broad, we no longer speak of a winged petiole, but of a narrow
region of the lamina. There are, however, still other regions in
certain leaves. A blade of grass will be found at its base to be

1 Horizontally-directed stems are bilaterally symmetrical.

FOLIAGE AND SCALE LEAVES. ‘ 53

continuous with a sheath that closely surrounds the stem (fig. zo).
It can, however, easily be removed, since it is not a complete
tube, there being a longitudinal split traversing it on the side
opposite to the lamina. In a sedge the sheath is a complete
tube. This structure is especially common among monocotyledons,
though by no means confined to them. The sheath is often pre-
sent in a very rudimentary way, as, e.., in
the leaves of the common groundsel, which,
by the way, illustrate the difficulty of distin-
guishing between a winged petiole and a nar-
rowed region of the lamina. Here we, per-
haps, have to do with the latter condition.
Again, many leaves possess stipules, which are
membranous or leaf-like outgrowths situated
on either side of the insertion of the leaf.
Hxamine once more a young shoot of the
garden geranium, and note a green expansion
or stipule on either side of the point men-
tioned. In an older shoot they will be
withered and brown (cf. fig. 11). The dif-
ferent regions enumerated, petiole, lamina,
sheath, and stipules, may now be considered
in greater detail.

Little need be added to what has already
been said about the Periote. Like the leaf
as a whole, it is generally bilaterally sym- ,, ... part of a Grass
metrical, and its upper surface is very fre- Leaf. gv. sheath; f.
quently grooved, its lower surface being atthe "4e; 9" lsule.
same time ridged (fig. 29). In some leaves, especially those
which possess the power of movement, the petiole presents a
swelling at its base, the pulvinus or motile
organ (fig. 29). This may be seen in
the scarlet runner, sensitive plant, and
the common garden acacia (Robinia pseud-
acacia). The peculiar tremulous move-
ment of the leaves of the aspen is due to
the fact that the leaf-stalks are vertically
flattened, thus presenting a considerable
surface to the wind [Examples are A Se nn ee
known, but not among British plants, pee einies. ore see
where climbing is effected by means of ®xillary bud, 6.
the leaf-stalks, which are capable of twisting round a support.
Just as the stem may become flattened and assume the functions
of the leaf, so also may the petiole make up for the small size
or absence of the lamina. Such flattened phyllodes are espe-
cially characteristic of the Australian eucalypti and acacias. These

54 THE FLOWERING PLANT.

trees cast no shadow, for the phyllodes are vertically expanded.
Several considerations show that the structures in question are
actually petioles. An ordinary acacia leaf is complex in shape,
and there is one species, Acacia melanoxylon, which possesses
both phyllodes and ordinary leaves. Not only so, but upon the
same tree numerous gradations
are found between the two, from
examples with well-developed
lamine and slightly flattened
stalks, down to others with much
reduced laminz and _ phyllode-
like stalks. Again, although a
mature acacia may possess no-
thing but phyllodes, yetthe early
leaves of the seedling are nor-
mal. These are succeeded by
others which are more and more
phyllode-like, till, finally, only
phyllodes are produced (ef.
figere)).

A number of plants are now
known which are carnivorous or
insectivorous, that is, they attract
insects by various devices, and
make use of them as food. The
pitcher-plants are well-known
examples. The “pitchers” are

FIG. 12.—Bipinnate Leaf of Acacia, with hollow leaf structures, and, in
Bee RE the North American Sarrace-

nias, belong mainly to the petiole, though a small hood-like

lamina is present which overhangs the mouth of the pitcher.

The surface of the petiole may be glabrous, or else provided
with hairs or emergences.

We now come to the Lamina. This is generally expanded
horizontally, so that in shoots which grow upwards the upper side
is turned towards the stem. The twigs of many trees, as, e.g., the
beech, elm, and yew, are more or less horizontally directed, and
their leaves are twisted upwards so as to retain their normal
position with regard to the light. Bilateral shoots are the result.
The same thing occurs in many creeping, trailing, and climbing
forms, of which periwinkle (Vinca) and ivy may be taken as
examples. The bilateral arrangement is generally limited to
alternate leaves. Opposite leaves under the same circumstances
would overlap. The horizontal position is not, however, assumed
by all leaves. Some of them are vertical, like the phyllodes of
acacias, and in this case the same end, 7.e., protection from a

FOLIAGE AND SCALE LEAVES. 55

strong sun, may be served, as in most of the Australian myrtles,
&e. A very interesting example is the compass-plant (Silphium
laciniatunm) of North America, in which the vertical leaves are
directed with their edges north and south. All these cases are
only apparent exceptions, for careful examination shows that the
vertical position is the result of a twist at the base of the leaf.
A very curious case is presented by the leaves of the iris and its
allies. The internodes of the stem are here extremely short, so
that the two-ranked leaves are closely crowded together. They
would overlap one another by expanding horizontally, and the
densely packed sheathing bases put a twisting into the vertical
position out of the question. No attempt is therefore made
to expose the upper surface to the light, but the leaf doubles
inwards, so that the under side is so exposed. This folding
together causes the bases of the older leaves to overlap or stride
over those of the younger ones, on which account the term
equitant has been applied. But this is not all. In the free part
of the leaf more or less union has taken place between the two
halves, the edges of which can be easily recognized by their
whitish membranous appearance. It will also be easily seen
that in this free part there is present, in addition to the
obviously doubled portion, an outer thinner region. This is a
vertical outgrowth from the under side of the leaf, by which
a large amount of leaf-surface is gained.

The lamina is usually bilaterally symmetrical, but radial
symmetry is exhibited in some cases, as in the tubular leaves of
onion and the cylindrical leaves of rushes. In these cases, as in
iris and many other monocotyledons, it
may perhaps be best to regard the
leaves not as lamine, but as examples
of undifferentiated leaf-structures, 7.e.,
showing no distinction of parts (¢/.
p- 52). Not only are there some in-
stances where the symmetry is greater
than usual, but also others where it is
less. The common begonias of green-
houses are the best example of such un-
symmetrical leaves. Here the base of
the lamina bulges out on either side
into a lobe, one of which is much larger
than the other. No plane will divide
such a leaf into two exactly correspond-
ing halves. The same peculiarity is

exhibited, to a less extent, by the elm Fic. 13.—Oblique Leaf of Elm,
( fio with serrate margin.
g. 13).

Considerable importance is attached to the venation of leaves,

56 THE FLOWERING PLANT.

7.e., the manner in which the vascular bundles, popularly known
as veins, nerves, or ribs, are distributed. These are generally
visible externally, especially on the under side, where they may
project considerably. It may happen, particularly in fleshy
leaves, like those of the stonecrop, that this is not the case.
Dissection shows, however, that they are present, though not
obvious externally, so that the term /izdden-veined may con-
veniently be applied. ‘T'wo principal kinds of venation are dis-
tinguished, parallel and reticulated. In the former, which is
characteristic of monocotyledons, the chief veins, without under-
going division, run more or less parallel with one another, either
from base to apex, or from a central midrib to the margin,
Their course is either straight or curved. Most of our common
monocotyledons are basal-veined, 2.e., possess no midrib, as may
be seen, for instance, in grass leaves (fig. 10), iris, lily of the
valley, &c. Many exotics, such as the banana, illustrate the
costal-veined arrangement, in which a midrib is present. ‘There
is, however, no sharp line of demarcation between these two
methods of distribution. If in a costal-veined leaf we suppose
the midrib to be telescoped, then the lateral veins would radiate
from the base of the leaf in a fan-like manner, their parallelism
being lost. The leaves of fan-palms are veined in this way.
Parallel-veined leaves, as a rule, do not exhibit anything like a
network in the arrangement of their vascular bundles, but very
small veins or veinlets can often be seen running straight across
the interspaces between adjacent veins, and connecting these
together. In four British monocotyledons, of which the two
commonest are the black bryony and the wild arum, the vena-
tion resembles that of the second type, @e¢., the reticulated
or netted, which is characteristic of dicotyledons. The lamina
is here traversed by a complicated and irregular network of
small veins (fig. 13). The leaves of dock and apple furnish
good examples, respectively coarse and fine. This sort of vena-
tion presents two chief varieties. Compare the leaves of beech,
Spanish chestnut, or lilac with those of ivy, sycamore, or garden
geranium. On the one hand, the lamina will be seen to be
traversed by a central midrib, giving off branches in a feather-
like manner (fig. 13); on the other, several strong veins will
be noticed, radiating from the attachment of the ‘petiole. In
both cases a great deal of branching may be observed, the
ultimate branchlets uniting or anastomosing into a network.
The leaves described, and others like them, are pinnately or feather-
veined and palmately or radiately-veined. The relation between
these two kinds of veining is similar to that existing between the
costal and radiate types in monocotyledons, and numerous grada-

FOLIAGE AND SCALE LEAVES. 57

tions exist. In the sunflower, for example, there is a well-
marked midrib, but the pair of lateral veins next the base are
much stronger than the remainder. Exceptional dicotyledons
are known in which the venation is more or less parallel. The
wild plantains (Plantago) illustrate this. In them a number of
strong veins take a curved course from base to apex, having
between them, however, a typical network formed by small
veins.

The general shape or form of the lamina is correlated with the
venation. Monocotyledons have generally leaves with simple
outlines, which are longest when basal-veined. In dicotyledons
long and short forms are associated respectively with pinnate
and palmate venation. Details will be given below.

It may be noted, as a general rule, that the most complicated
outlines occur in small herbs, especially when these occur in
crowded situations. The largest leaves are also, in many cases,
found nearest the ground. The leaves of the same plant are
by no means uniform either in shape or size. ‘This is especially
noticeable in herbs. ‘Take, for example, a tall buttercup plant.
The lowest, so-called radical leaves, are here the largest and most
complicated. They-gradually pass into smaller and less compli-
cated upper leaves. Much greater uniformity is found among
the leaves of trees.

It is not possible to make any exact classification of the in-
numerable kinds of general outline found among leaf-blades. We
may, however, distinguish between forms of fairly equal breadth,
or broadest in the middle, and those with broader base or apex.

Fig. 14.—-Oblong FIG. 15.—Spathulate and Fig. 16.—Rounded and
Leaf. Oval Leaves. Arrow-shaped Leaves.

In the first case, we can gradually pass from the needles of the
fir to broader grass leaves, and so through oblong (fig. 14), oval
(fig. 15), and rounded (fig. 16) forms to circular ones (fig. 17).
Where the blade is broader at the base, the form may distantly
resemble that of a lance-head, an egg, &c., hence receiving the
name of lJanceolate (fig. 18), ovate (fig. 19), &e. Very commonly
the base is notched, and projects on either side of the leaf-stalk
as a more or less prominent lobe of various form. Heart-shaped

58 THE FLOWERING PLANT.

(cordate), arrow-shaped (sagittate), kidney-shaped (renzform) leaves,
&e., exemplify this (figs. 20, 16,21). The lobes of a sessile lamina
of this kind may clasp the stem more or less closely. The leaf is
then amplexicaul. Or they may from the first be united together
on the opposite side of the stem, which then appears to pierce the
perfoliate leaf. A similar origin (7.e., union of lobes) accounts
for peltate leaves (fig. 17), and two opposite leaves may be con-
tinuous or connate. When the lamina passes into a wing on the
stem (cf. p. 52), the leaf is decurrent. When the blade is broader
at the apex, the outline is often similar to that of lanceolate,
ovate, cordate, &e., leaves, but reversed. This is expressed by

(

FIG. 17.—Peltate Leaf, seen Fig. 18.—Lanceolate, Awl-shaped, FIG. 19.-—Ovate
from below. and Whorled Leaves. Leaf.

FIG. 20.—Cordate Fig. 21.—Kidney-shaped, Elliptical, and Abrupt
Leaf. Leaves.

prefixing ob, as oblanceolate, obovate. Special regions of the
lamina, as extremity and margin, are also very varied in character,
and numerous terms are employed in describing. Hither ezx-
tremity, t.e., base or apex, may be more or less pointed, rounded,
or notched, and the latter may also be provided with a sharp
projection. The margin may be entire, that is, devoid of marked
projections and indentations, or it may possess them. In the
latter case, the edge may be either undulating or provided with
small tecth of various shape.! From leaves of this sort we can
pass, by intermediate gradations, to lobed or segmented leaves,

1 Leaves are serrate (fig. 13), with sharp teeth pointing to apex; crenate
(fig. 17), with rounded teeth ; dentate, with sharp irregular ones.

FOLIAGE AND SCALE LEAVES. 59

in which the margin is more deeply excavated. Projections,
whether small, as teeth, or large, as lobes, generally correspond to
smaller or larger veins. Lobes
and the like which follow the
latter are therefore arranged
either pinnately or palmately.
A distinction is drawn between aN
lobed, cleft, and parted leaves, ne
where the excavations extend,
respectively, not more than
half way, half way or more,
and almost the whole way to
the midrib or base. In the
first case, either the lobes or in-
terspaces are rounded, and in
the second, sharply cut. Thus
we get pinnately and palmately
lobed, cleft, and parted leaves
(figs. 22 and 23). ‘The lobes
may be of very unequal size i
and shape (as in potato), their }y¢.22—Pimnately- Fic. 23.—Pinnately-
margins varying like those of lobed Leaf of Oak. cleft Leaf of Poppy.
complete leaves. Secondary lobes are thus produced in many
cases, and still smaller subdivisions may also occur. Examine in
this connection the thrice pinnately-parted leaves of the yarrow
or millefoil.

In a large number of leaves division actually extends to the
midrib or base, giving pinnately or palmately-divided forms. The
lobes are then termed leaflets, and the leaves are compound, as
opposed to simple leaves, such as those described up to this point.
Leaflets may be either sessile or stalked, and their general out-
line, &c., are described in the same terms as simple leaves. Pin-
nately and palmately-divided compound leaves are termed pinnate
or palmate. Examples of the former condition are seen in elder,
ash, and rose (¢/7. fig. 24). The axis upon which the leaflets are
borne clearly answers to the midrib of a simple leaf, and cases
are not infrequent in which the end of a pinnate leaf is not
completely divided. This may be seen very well in the jessamine.
The strawberry (fig. 25) and horse-chestnut (fig. 26) furnish
typical instances of palmate leaves, where the leaflets are attached
together at the tip of the petiole. Leaflets, like leaves, are often
attached by means of a joint or articulation, where separation
readily takes place. ‘This enables us to distinguish between pin-
nate and palmate leaves with only three leaflets. Compare these
structures, for example, in scarlet runner (fig. 29) and clover.

ENNNRS

——

60

THE FLOWERING PLANT.

In the former case, the petiole is continued into what is evidently
the common leaf-stalk, at the base of which are jointed a pair of

\

)
Z

———
=
——=sS

Fig. 24.—Pinnate
Leaf.

leaflets, while it is terminated by an odd leaflet
jointed in the same manner. ‘This, then, is a
pinnate leaf. The three leaflets in the clover
are all attached to the end of the petiole, which
is the only common leaf-stalk. We have here,
therefore, a palmate leaf. The general appear-
ance, however, is usually a sufficient guide.
The leaflets of the palmate leaf are either all
sessile or with stalks of equal length, while in
the abbreviated pinnate leaf the terminal leaflet
appears to be stalked even when the other two
are sessile, for the common leaf-stalk seems
to belong to it. Similarly, when the lateral
leaflets are stalked, the terminal one apparently
has a longer stalk. The lower part of this
apparent stalk is, however, common leaf-stalk.
A compound leaf may even be reduced to one
leaflet, and is then liable to be mistaken for
a simple leaf. In the barberry, for example,
the small leaves are jointed on short stalks. <A
simple leaf is not jointed in this way upon its
petiole. The inference that it is a reduced com-

pound leaf is borne out by comparison with the closely allied
yellow-flowered mahonias frequently found in gardens. Here

FIG. Z 5.—Ternate Leaf of Fig. 26.—Palmate Leaf of Horse-
Strawberry. Chestnut.

the leaves are normally pinnate, with a terminal and two to four
pairs of lateral leaflets. The ash presents a similar case. The

FOLIAGE AND SCALE LEAVES. 61

ordinary form (Fraxinus excelsior) has well-marked pinnate leaves,
but in an allied species (Fraxinus heterophylla) others, reduced to
one leaflet, are found in addition. The remarks previously made
about the variations in size and shape of the lobes in simple
leaves apply with equal force to leaflets. Many leaves are much
divided or decompound, the primary leaflets being split up into
secondary, and these in some cases into tertiary, &c. Thus we
have bipinnate (fig. 12), tripinnate, &c., leaves. Palmate examples
when thus compounded are usually of ternate type (fig. 25), 7.e.,
with successive trifurcations, and may be biternate, triternate, &e.
The lamina, like the petiole, may be absent, as in phyllodes, or
it may undergo special modifications. Many tendrils are leaf-
structures, and the best examples are found in the pinnate leaves
of peas, vetches, and the like. Compare in this respect the
common field vetch or tare, the edible pea, and the sweet pea.
The leaves of the first possess seven pairs of normal leaflets, but
one or more pairs at the end are transformed into tendrils, and
the axis also ends in a tendril. The leaf of the edible pea is
similar, but there are five tendrils, one being terminal, and only
two pairs of green leaflets. Im the sweet pea there are an odd
and two to four pairs of tendrils, and only one pair of leaflets, as
a rule. Sometimes, however, a third leaflet occurs with a tendril
opposite to it, the nature of which is thus clearly proved.

Protecting spines are often formed by the modification of the
lamina. Sometimes only part is thus modified, as in the holly,
but the transformation may be complete, as in gorse. Here we
get branch spines bearing leaf spines. The nature of the latter
may be well observed in seedlings, the early leaves of which
are ternate. In succeeding leaves the leaflets gradually become
narrower and more spiny. ‘The barberry is another instructive
example, presenting, as it does, in the same shoot all gradations
between leaves with spiny edges and three to seven-branched
leaf spines.

The leaf blades of insectivorous plants (cf. p. 54) are often
modified for the purpose of securing prey. In the round-leaved
sundew (Drosera rotundifolia), which is not uncommon in marshy
places, the flower-bearing stems rise from the centre of a rosette
of leaves, each of which possesses a short stalk and a rounded
blade, the upper side and margin of which bear a large number
of so-called ‘“tentacles.’”” These are emergences, resembling
minute pins in shape, the heads being glandular. In fresh leaves
each gland is tipped by a drop of the viscid clear excretion,
the appearance of which has given rise to the popular name.
Venus’ fly-trap is a plant closely related to the preceding, and is
found in North Carolina. The petiole is here broadly winged,

62 THE FLOWERING PLANT.

and separated by a constriction from the lamina, which is com-
posed of two oval halves, the margins of which are provided with
bristles, while the upper surface of each bears about three slender
highly sensitive hairs. In one of the
pitcher - plants, Nepenthes (fig. 27),
species of which occur in Madagascar,
Ceylon, and the Kast Indies, the mid-
rib of the simple leaf extends beyond
the apex of the lamina as a tendril,
which terminates in a lidded pitcher
resembling a hot-water jug in shape.
The bladder-wort (Utricularia) is an
aquatic herb, sparsely distributed in
British ponds and ditches. Its leaves
are pinnately parted into numerous
narrow lobes, some of which bear
small-stalked bladder-like structures,
each of which possesses an inwardly-
opening valve-like aperture.

The texture of the lamina may be either herbaceous, leathery,
or succulent. The first characterizes most of our common leaves,
which are deciduous, 2.e., shed annually (p. 43). Leathery leaves,
capable of greater endurance, are found in evergreens, which
owe their name to the fact that the foliage is shed gradually,
so that the branches are never bare. Swcculent leaves, such
as those of the aloe, are especially characteristic of arid climates
(cj. Dp, 27):

The colour of the lamina is not uniform. Not to mention
spotted, mottled, and variegated leaves, it usually happens that
the upper side is of a darker green than the lower. This is
principally due, as we shall see, to the way in which the internal
green tissue is arranged. But the colour is also dependent on
the nature of the surface. This may be glabrous, especially in
evergreens, or more or less hairy, and in the latter case it is usual
for the hairs to be more numerous on the under side, giving this
a whitish hue. Silverweed (Potentilla anserina) is a beautiful
example, and the same thing is seen to a less extent in wallflower,
buttercup, &c. Some leaves are of a bluish-green colour, and
this may be due to the presence of wax, as in the garden poppy.
Glandular hairs are frequently found on the lamina, and these
very often secrete a fragrant oil, as in lavender, where short
glandular hairs are mixed with larger branched non-glandular
ones. The perfume patchouli is obtained from a similar source,
and the odour of sweet-briar is also due to such hairs. Stinging
hairs may be present on the lamina (petiole and stem) as in the

He WG:
1 U

FIG. 27.—Pitcher of Nepenthes.

FOLIAGE AND SCALE LEAVES, 63

nettle. Emergences are also found in many cases, especially where
the veins project on the lower side. (For SHeatu, cf p. 154.) |

We next come to the consideration of SripuLEs (cf. p. 53).
These are not always of the same nature. In the pansy, for
example, they are extremely large and foliaceous or leaf-like,
and very likely correspond to the lateral lobes of a ternately-
parted sessile leaf. The same, or something similar, appears to
be true of many /oliaceous stipules, as perhaps in the case of
the bean, pea, &c., where they look like a basal pair of leaflets.
In fact, they may be the sole organs for performance of the leaf
functions, as far as nutrition is concerned. The wild-peas, be-
longing to the genus Lathyrus, illustrate in a very interesting
way the mutations to which the regions of the leaf are liable.
There are several British species. In one of these, the black
pea (Lathyrus niger), the midrib of the pinnate leaf ends in a
point ; there are fair-sized stipules, and several pairs of leaflets.
Another species, the blue marsh-pea (LZ. palustris), has leaves
tendrilled at the ends, larger stipules, and fewer leaflets. The
leaves of the meadow-pea (L. pratensis) possess only one pair of
leaflets and more tendrils. Lastly, in the yellow pea (L. Aphaca),
the whole leaf is converted into a tendril, with the exception of
the stipules, which are extremely large. Curiously enough, there
is one species of Lathyrus, the grass-pea (L. Nissolia), in which
neither leaflets nor tendrils are present, and the stipules are very
small. The leaf-axes are here converted into phyllodes shaped
like grass leaves. This condition is led up to by one or two other
species where the petiole is winged.

Many stipules are membranous, and very unlike the foliaceous
examples already mentioned ; and also they are not necessarily
in the form of two free expansions, but may be united in various
ways. Examine, for instance, a rose leaf, in illustration of the
latter point. The petiole is sheathing at the base and bordered
by a green wing on either side, which ends in a pointed lobe some
distance from the first pair of leaflets. These two wing-like pieces
are called adnate stipules, from the idea that they represent two
of these structures adherent to the petiole. Such stipules are
probably simply surviving bits of a once more extended wing.
In many roses the adnate stipules are much smaller and not
green. ‘This. is also the case in clover. <A pair of stipules may
unite in the leaf-axil to form an azillary stipule. Something
akin to this is found in a membranous Jigule, which in grasses
projects from the upper side at the junction of sheath and lamina
(fig. 10). Indeed, this and many undoubted stipular structures
appear to belong to the leaf-sheath. Two stipules may also be ~
united into an opposite stipule, placed on the opposite side of the

64 THE FLOWERING PLANT.

stem from the leaf insertion. Adhesions in this direction form
transitions to sheathing or ochreate stipules, which, as in dock,
sorrel, and knot-grass (fig. 28), or
bistort, form a membranous sheath
surrounding the stem for some dis-
tance above the leaf insertion. The
stipules of opposite leaves may unite
on either side into an <interfoliar
stipule. 'Tendrils rarely and spines
more frequently (garden acacia) re-
sult from modifications of this part
of the leaf. The leaflets of com-
pound leaves may possess single
stipels, as in scarlet runner (fig. 29).

Fig. 28.—Leaf of Knot-Grass. - - Bye 5
l. lamina; p. petiole; g. sheathing As in the lamina, we can distinguish

stipules. different textures and varieties of

surface. Membranous stipules often fall off early, and are then
said to be deciduous, as in beech and lilac.

Scale Leaves are much simpler in character than foliage leaves,
and in fact may be regarded as reduced representatives of these.
They alone occur on subterranean stems, and in this case appear
to represent leaf-sheaths. In this situation they may be insigni-
ficant scales, like those in the axils of which potato-eyes are
developed, or else, as in bulbs, they may be considerably thickened
in connection with the storage of reserve materials. Scale-leaves
are also found on underground stems, and in some forms which
are parasitic or saprophytic they entirely supplant the ordi-
nary leaves. The broom rape (Orobanche) and yellow bird’s-nest
(Monotropa) are examples of this. Most frequently, however,
overground scale leaves are found as bud scales, either for storage,
as in bulbils, or for protection, as in the buds of trees (p. 46).
In the latter case they often grade insensibly into the ordinary
leaves of the bud, when their leaf nature becomes evident. They
may correspond to leaf-sheaths (fir and horse-chestnut), laminze
(lilac), or stipules (beech). The sticky substance bud-glue or blas-
tocolla, found in horse-chestnut and many other cases, is ex-
creted by special glandular hairs known as colleters.

Structure of the Leaf.—It is not necessary to give any details
regarding the structure of the leaf-stalk, since this is constructed
almost precisely like a young stem, the chief difference being
that the bilateral symmetry usually perceptible externally extends
also to the interior.

The lamina of an ordinary foliage leaf (fig. 7, G) consists of
upper and lower layers of epidermis, between which is the green
pulpy ground-tissue, here called mesophyll, traversed by the

FOLIAGE AND SCALE LEAVES. 65

vascular bundles or veins, which, as we have seen, may be dis-
tributed in various ways.

The epidermis, which can be conveniently examined both in
sections and by peeling off pieces, is composed, as seen under the
microscope, of flattened cells, the boundaries between which may
be straight or curved (fig. 7, F). The outer walls of the cells are
covered by a cuticle, and besides this, especially in leathery leaves
like those of the holly, are often much thickened and euticularized,
z.e., their cellulose is more or less completely converted into
cutin (cf p. 30). ‘The prickles upon many leaves owe their
firmness to the thickness of the epidermic cell-walls. Protoplasm
and cell-sap are contained in the cells, but, as a general rule,
chlorophyll granules are absent. In the under epidermis of a
leaf, and often to a less extent in the upper epidermis as well, a
large number of minute openings are found. These stomata
(fig. 7, G) are intercellular spaces formed as small splits between
adjacent cells.1 Hach of them is bounded by two kidney-shaped
guard-cells, the concavities of which face one another. These two
cells not only differ in shape from the ordinary epidermic cells,
but also in the possession of chlorophyll granules. In many
cases some of the neighbouring cells are of different character
from those making up most of the epidermis. Stomata are not
confined to the foliage leaves, but occur with more or less fre-
quency in the epidermis of all organs except roots. They are
also absent in entirely submerged leaves and stems, while the
stomata of floating leaves only occur in the upper epidermis.

The hair structures, developed from the epidermis of many
leaves, present the same variety as in the case of the stem
(p. 28). The structure of the stinging hairs of the nettle will
be described further on (p. 72).

The ground-tissue (fig. 7, G) or mesophyll, like the epidermis,
is not constructed in exactly the same manner above and below.
An ordinary horizontal foliage leaf is, in fact, b¢facéal in struc-
ture. ‘The upper part of the mesophyll is composed of one or
more layers of cells elongated at right angles to the surface,
and termed from their appearance palisade parenchyma. Their
cellulose walls are thin, and they contain a great many chlorophyll
granules. The lower part of the mesophyll is made up of cells
differing from the preceding in their very irregular shape.
This spongy parenchyma is traversed in all directions by inter-
cellular spaces which communicate with one another, and, by
means of the stomata, with the exterior. Under each stoma
there is a specially large intercellular space known as a respir'a-

‘ The stomata of the white lily are favourable objects for study. They are
large enough to be seen with a lens.

E

66 THE FLOWERING PLANT.

tory cavity. The centinuity of this system of cavities and
its connection with the exterior can be proved by a simple
experiment. Take a large stalked leaf and immerse the
lamina in water. Now apply the mouth to the cut end of
the stalk and blow vigorously, when numerous small air-bubbles
will escape from the surface of the part under water. The
vascular bundles mostly run between the two regions of the
mesophyll, and they are generally surrounded by parenchyma
made up of small colourless cells. The ground-tissue may also
contain sclerenchyma, especially in the leaves of grasses, and
intercellular spaces containing secretions. These spaces are
formed by the breaking down of cells, and they contain
ethereal oils, which are often odorous. The fragrance of
crushed myrtle leaves arises from this cause, and other examples
of such secretory reservoirs are found in rue and in the
common St. John’s wort (Hypericum perforatum). The leaves of
the latter present from this cause numerous transparent spots,
which appear like perforations, whence the specific name.

The vascular bundles of the leaf, in dicotyledons as well as
monocotyledons, are devoid of cambium. ‘The wood is. above,
and its tubular elements are always tracheides, never vessels.
The bast presents the same structure as in the stem, but its
elements are small and difficult to make out. It underlies the
wood. The respective upper and lower positions of wood and
bast, which also obtain in the petiole, may be understood by
turning up the leaf into a vertical position, when what were
upper and lower now become inner and outer. The mature
leaf differs from root and stem in possessing no growing-point,
and since cambium is absent, its growth is /imzted. This accords
with its comparatively transitory character. It is interesting to
note that when the petiole is used for climbing, it often thickens
and persists. |

It must not be imagined that a// leaves possess the bifacial
structure described in the preceding paragraph. When the
general form is radially symmetrical, so also is the structure.
Such leaves are said to be centric, like those of the stonecrop.
Here there is no palisade parenchyma, but this may also be
absent in flat leaves, e.g., those of grasses. On the other hand,
vertical leaves have palisade parenchyma on both sides, which
also are equally rich in stomata.

PHYSIOLOGY.

As in the stem (p. 41), so also in the foliage leaf support is
afforded by the firmer part of the vascular bundles, by scleren-

FOLIAGE AND SCALE LEAVES, 67

chyma and by collenchyma. The larger vascular bundles keep
the lamina stretched and extended, acting like the ribs of an
umbrella. They and the rest of the stereome (p. 41) are also
arranged so as to prevent the delicate mesophyll from being
crushed between the two layers of epidermis. ‘Tearing is largely
prevented by thickening of the epidermic walls, as especially
in leathery leaves. This takes place to a greater extent at the
edge, which is, of course, the place most likely to tear, than
elsewhere. Additional firmness is given where a wavy course is
taken by the lateral cell-walls of the epidermis, as an increase in
amount of supporting substance is thereby gained. The epider-
mis of some plants (grasses, Wc.) is strengthened by silica. The
remarks made on p. 41 about protection of stems by thorns, Wc.,
and hair structures apply to the leaf also. The presence of
distasteful substances also prevents animals from eating many
leaves. Protection from the weather is effected as in stems
(p. 41), with the exception that cork is never present. The
glossy leaves of evergreens are peculiarly adapted for preventing
the accumulation of snow upon them. Protection from the sun
has been mentioned already (p. 54). Buds are often protected
by means of scale-leaves, and when these secrete blastocolla the
protection is still more complete. It also often happens that
young foliage leaves in the bud have a warm covering of woolly
hairs, which afterwards fall off.

The main function of foliage leaves is that of nutrition. By
means of their chlorophyll they are able (cf. p. 10) to build up
organic compounds from the carbon dioxide of the surrounding
medium, and the crude sap brought to them by the wood of the
vascular bundles. This building up or assimilation is effected in
the chlorophyll granules. The first easily recognizable product
is starch, and this can readily be detected in leaves which have
been in strong sunlight for some time. They are bleached with
spirit, then made transparent with chloral hydrate, and, lastly,
soaked in a solution. of iodine, when they turn a bluish-black.
This is a well-known colour-test for the substance in question.

The starch and other organic substances formed in the leaf are
largely converted into a soluble form (generally sugar in the case
of starch), and travel osmotically in the parenchyma all over
the plant, compensating waste and rendering growth possible.
Non-diffusible proteid matters can travel by means of the sieve
tubes. It may also happen that the various substances com-
‘posing the elaborated sap are reconverted into the solid form
within thickened roots, stems, leaves, or, as we shall see farther
on, seeds. They then become reserve materials.

Chlorophyll is absolutely dependent on light for the performance

68 THE FLOWERING PLANT.

of its constructive function. A plant placed in darkness soon
gets pale and unhealthy, and though it may grow considerably in
length, gradually becomes less in weight, ultimately dying. Such
a plant is said to be etiolated. Celery, and some other garden
plants, are purposely reduced to this condition by heaping earth
around them. They thus become very sickly, and the tissues
not being vigorously developed, are very tender. Also, in the
case of celery, the characteristic essential oil is too strong and
too abundant under normal conditions to let the shoots be eaten.
Chlorophyll cannot be formed, in most cases, unless light is pre-
sent. If a bean-seed is germinated in the dark, a yellowish
etiolated seedling is produced, which grows to a certain extent
at the expense of the reserve materials stored up in the seed.
The yellow colour is due to the development of etiolin, which is
closely related to chlorophyll, and exists, like it, diffused through-
out the substance of protoplasmic granules (cf. p. 8). It is
also to be noticed that the seedling weighs Jess than the seed
from which it grew. A very feeble light suffices to convert
the etiolin into chlorophyll, so that the granules in which it
occurs become chlorophyll granules. If the now green seedling
is placed in a fairly strong light, it will rapidly increase in size
and weight, since its chlorophyll is able to build up organic com-
pounds. ‘The roots of the seedling must of course be placed in a
suitable soil or food solution, but this alone is useless if light is
excluded.

Since carbon dioxide is one principal item of food, it is obvious
that chlorophyll cannot work unless supplied with it. This is
readily proved by growing plants under a bell-jar to which air is
freely admitted which has been deprived of its carbon dioxide by
means of caustic potash. Under these circumstances the plant
does not increase in weight, and starch cannot be detected in its
leaves. ‘The palisade parenchyma is the most important part of
the leaf for the purposes of assimilation, and therefore, as we
have seen, is developed on the side turned towards the light.
Where, as in vertical leaves, the conditions of illumination are
equalized, there may be such tissue on both sides. It is also
interesting to notice that, in plants with dense foliage, such as
trees, the leaves most exposed to light are thicker than the
others, owing to the formation of extra palisade layers.

As already explained (p. 10), the assimilatory process carried
on by chlorophyll involves the liberation of a large quantity of
oxygen, which passes off into the surrounding medium. ‘This is
easily proved by experiments, one of which consists in cutting off
a vigorous shoot from a water plant, and, by means of a small
weight, keeping this submerged, cut end up, in a vessel of fresh

FOLIAGE AND SCALE LEAVES. 69

spring water. If now the apparatus is placed in bright sunlight,
bubbles of gas will escape from the cut end. These are easily
collected in a test-tube, and can then be proved to consist of
oxygen by the usual methods, e.g., re-ignition of a glowing match-
end plunged into the tube. The leaves (and other parts to a less
extent) of a land plant are constantly giving off a large amount
of aqueous vapour into the air; in other words, they transpire.
This transpiration is made up for by the active powers of absorp-
tion that the root possesses. Numerous familiar facts receive
their explanation in this, such as the fading of cut leaves and
flowers (p. 9). The loss of water experienced by these makes
their cells lose turgidity, and this causes limpness. That water
is actually given off on the one hand and taken up on the other
is easily demonstrated. A plant growing in a food solution, the
surface of which is guarded from evaporation, is covered with a
bell-jar, and placed under ordinary conditions of light and heat.
Two things soon become evident—aqueous vapour is given off
from the plant and condenses on the inner side of the glass, and
the food solution gradually diminishes in quantity. The amount
of transpiration depends upon a number of conditions. It is
naturally greater in dry than in damp air, and in the sun than
in the shade. The latter point is shown by a simple experiment.
A number of vigorous stalked leaves are collected. Half of these
are placed with their stalks in one glass of water and the other
half similarly disposed in another glass. It is convenient to
employ perforated cards, through the holes in which the stalks
are passed. If dry glasses are now inverted over the two lots of
leaves, and these are placed in the sun and shade respectively,
transpiration will proceed vigorously in the former case, but
much less so in the latter. ‘ This is shown by the fact that, after
the lapse of some ten minutes, abundance of moisture will have
condensed on the inner side of the glass which covers the sunned
leaves, while that covering the shaded ones remains almost or
quite clear. The amount of transpired water may be very con-
siderable. It has been shown that a sunflower plant presenting
5616 square inches of leaf-surface loses in this way, on an average,
twenty ounces by weight of water during a day of twelve hours.
The corresponding loss at night is only about three ounces.
Transpiration in the mature leaf takes place partly from the
general surface and partly by means of the stomata. The former
(“cuticular”) transpiration is greatest in herbaceous leaves with
a thin cuticle, and least in leathery leaves where the outer cell-
walls of the epidermis are thickened and cuticularized and covered
by a well-developed cuticle. Stomatal transpiration is much more
important, and, in fact, the chief use of stomata is to effect this.

70 THE FLOWERING PLANT.

The quantity of water thus lost depends not only upon the num-
ber of stomata present, but also upon their condition. That is to
say, a stoma is not always open, and when it is, the aperture is
not always of the same size. Stomata generally close at night or
on wet days, and open in sunny weather. This is due to the
guard-cells. Their action is complicated, but the main principle
is easily understood. The fact that these cells always contain
chlorophyll granules now receives its explanation. In the sun
these granules begin active assimilation, and this causes crude
sap to diffuse into the guard-cells, which thus become extremely
turgid and increase in size. Curved cells, like the ones we are
dealing with, naturally become more curved when they increase in
size. In the case of the guard-cells this means that the stoma
opens. But this is not all. The parts of the walls of the guard-
cells which face outwards and inwards (7.e., towards the outside
and inside of the leaf) are very much thickened, and at night or
in the wet, when the cells are not very turgid, act like springs,
which tend to flatten the cells in the plane of the leaf-surface.
Since the walls of the guard-cells are very thin and flexible where
they face one another, this flattening causes them to bulge into
the slit of the stoma, making it smaller, or even closing it.
When the guard-cells are very turgid the outer and inner spring-
like parts of their walls are forced away from one another, while
their thin parts are easily pulled into a position more or less
vertical to the surface of the leaf, thus opening the stoma. The
walls of the intercellular spaces with which the stomata com-
municate present a very large surface, from which the evaporation
of water can take place.

The importance of transpiration to land plants is seen from
the fact that where it is checked by an over-damp atmosphere
sickliness invariably ensues. On the other hand, excessive trans-
piration is harmful. This is often observed in the case of plants
grown in the hot air of a room. Even when abundantly watered,
many of them droop and die, because the roots are unable to
absorb rapidly enough to keep pace with the evaporation from
the leaves. This is particularly the case when the plants are
herbaceous in texture. Protection from too vigorous trans-
piration may be afforded by a condensed form presenting rela-
tively little surface, or by much thickened and cuticularized cell-
walls (aloe, &¢.), or again by the assumption of a vertical position,
the best example of which is found in the phyllodes mentioned
on p. 53. ‘Transpiration is of importance for two chief reasons.
In the first place, young shoots contain 90 per cent. or more of
water, without an abundant supply of which they cannot be
formed. Such a supply would be out of the question if it were

FOLIAGE AND SCALE LEAVES. — yas

not for the vigorous ascending currents facilitated by transpira-
tion. Transpiration causes the pressure within the trachez to be
least nearest the leaves, towards which, therefore, the sap natur-
ally flows. Again, the formation of organic substance, to any
extent, means not only a plentiful supply of carbon dioxide and
water, but also of the simple salts dissolved in water. Yet the
amount of these is so small in the liquid absorbed by the roots
from the soil that it has been compared to ordinary drinking-
water. It is necessary, therefore, in order that enough of these
compounds may be obtained, for a very large quantity of water to
be absorbed by the root, much more, in fact, than is retained in
the plant. Where, as in cacti and similar forms, this process is
very sluggish, little organic matter can be formed and growth is
extremely slow.

Saprophytes and parasites, getting, as they do, organic com-
pounds ready prepared, may dispense partly or entirely with
chlorophyll. In the latter case the leaves are much reduced in
size (broom-rape, &c.), or even entirely absent (dodder).

Insectivorous plants (cf pp. 54, 61) lay themselves out for the
capture of animal food, although they are abundantly provided
with chlorophyll and can thrive fairly well without it. Jn the
pitcher-plants a sugary substance is secreted at or near the
orifice, and in some cases, as in Sarracenia variolaris, there is
even a sugary track leading up from near the ground. Insects,
especially ants, are thus attracted, and if they venture to set foot
on the slippery inner side of the pitcher, no efforts can save them
from sliding down into the liquid within, where they are drowned.
In the case of these and the other insectivorous plants the proteid
substances of the prey are brought into solution by a digestive
excretion poured out from innumerable glandular hairs or emer-
gences. ‘The solution then diffuses into the interior of the leaf.
The excretion closely resembles in composition and function the
gastric juice of an animal’s stomach.

Leaves, like roots and stems, carry on the function of respira-
tion, but it is only easy to detect this in the dark, since in the
light the taking up of oxygen and giving out of carbon dioxide
are hidden by the exactly opposite process involved in assimi-
lation (cf. p. 68).

Vegetative reproduction by shoots has already been spoken
of (p. 43).

The leaf exhibits various forms of motility. Protoplasmic
movements may sometimes be observed in the cells of the
mesophyll. This is the case, for example, in Vallisneria spiralis,
an aquatic form commonly grown in fresh-water aquaria, where
the protoplasm, carrying with it the chlorophyll granules, may

72 THE FLOWERING PLANT.

be observed, under the microscope, to move bodily round the
cells in the direction of their length. Streaming protoplasmic
currents can also be observed in the cells of many hairs. An
instructive and common instance is found in the stinging hairs
of nettle. If one of these is carefully removed from a young
leaf, and examined under a microscope, it will be found to con-
sist of a unicellular hair produced into a hollow brittle spike
terminated by a minute knob. ‘The base of the hair is embedded
in a dome-shaped emergence. ‘The inner part of the protoplasm

FIG. 29.—Pinnate Leaf of Scarlet Runner in the position of ‘‘Sleep” [after Sachs]. a.
The large motile organ at base of grooved leaf-stalk and its continuation d, d; }, ec.
small motile organs of the leaflets, e, e,e. Stipules are seen at base of leaf-stalk,
also an axillary bud; stipels at the origins of the leaflets.

within the hair is broken up into a network of strands by means

of vacuoles. Currents taking various directions can be observed

in the strands. It may be noted in passing that the stinging
property is due to the presence of formic acid in the cell-sap.

The tapering end of the hair readily perforates the skin, when

it breaks off and the poison flows into the wound. Movements

on a larger scale are also exhibited by leaves, of which the best
known example is the sensitive plant. The leaves of wood-
sorrel, scarlet runner, and many other plants perform what are
known as ‘sleep’? movements, by which the leaflets sink down

FOLIAGE AND SCALE LEAVES. 73

at night (fig. 29). Among insectivorous plants Venus’ fly-trap is
a good example of motility. If an insect alights on the upper side
of the leaf and happens to touch one of the sensitive hairs on
the lamina, the two halves move rapidly upwards, and by the
interlocking of the marginal bristles a very efficient trap is
formed.

Leaves show a high degree of irritability. They are trans-
versely geotropic and heliotropic, that is to say, under the
influence of gravity and light bifacial leaves at any rate tend
to place themselves horizontally. Sensitiveness to contact is
shown by leaf-tendrils as well as stem-tendrils, and other more
obvious cases are the sensitive plant and Venus’ fly-trap. The
tentacles of sundew when a fly alights upon one of them all bend
towards the centre of the leaf and entangle it. All the insecti-
vorous plants pour out their digestive excretions as the result of
contact, and this often depends on the chemical nature of the
touching substance, so that we have sensitiveness to chemical
stimuli.

Spontaneity is shown in the protoplasmic movements in
hairs, &c., and on a larger scale in an Indian form, the tele-
graph plant (Desmodium gyrans), which possesses ternate leaves.
The lateral leaflets of these are in a constant state of up and down
movement, quite rapid enough to be visible with the unaided
eye.

CHAPTER VIL
BRACTS AND FLORAL LEAVES.

MORPHOLOGY.

WE now come to the consideration of the remaining two kinds of

leaf, z.e., bracts and floralleaves. ‘The latter make up the greater
part of the flower, which may be defined as a shoot specially
modified for carrying on the function of reproduction. Bracts
are leaves, usually much reduced, which occur near the flower.
It will be necessary, in order to understand the various parts
which make up a flower, to carefully examine a simple example.
It is usual to select a buttercup for this purpose. First, with a
sharp penknife or scalpel divide the flower into halves, in which
operation it is desirable to commence by splitting the flower-
stalk or peduncle. The cut thus made is then continued. If
this is done successfully, it will readily be seen (fig. 30) that the
continuation of the peduncle within the flower forms a conical
structure upon which are crowded numerous parts of different
shapes and sizes. This conical body, the floral receptacle or
torus, is in reality the stem part of the floral shoot, while the
structures situated upon it are the leaf part of the same. ‘The
crowding is caused by non-development of internodes, a common
occurrence, as we have already seen, in the ordinary vegetative
shoot. Now, in another specimen, proceed to examine the various
kinds of floral leaf, beginning at the outside. First comes a
whorl of five small yellowish-green leaves, the sepals, collectively
forming the calyx. Then follows another whorl of five much
larger bright-yellow leaves, the petals, which make up the corolla
and alternate with the sepals. Now pull off the calyx and corolla,
and, before examining the more internal parts, carefully inspect
the glossy inner side of a petal. Close to its attached end will
found a minute scale covering a spot which excretes honey or
nectar, and is known as a honey gland or nectary. Within the
pertanth (=calyx+ corolla) are a very large number of yellow
threads arranged spirally, though this is not easily made out.
The threads are stamens, and their collective name is andrecium.
The thin stalk of a stamen is its filament, and the thickened end
its anther, within which an immense number of minute pollen

BRACTS AND FLORAL LEAVES. 75

grains are developed. These escape, when ripe, as a yellow dust.
When the andreecium is removed there still remain behind a lot
of little spirally arranged green bodies, the carpels, called alto-
gether the pistil or gynecium. Within each carpel is a cavity
containing a minute oval body known as an ovule. In overblown
specimens all the structures above described fall off except the
carpels, which enlarge considerably, and form the buttercup /rwit,
while the ovules become seeds. Sepals, petals, stamens, and
carpels are alike floral leaves, though they depart more and more
widely from the type presented by the foliage leaf. They will be
dealt with in the above order, but it is first desirable to consider
some points concerning the flower as a whole, and the receptacle.

The inflorescence or arrangement of flowers upon the plant
varies considerably in different cases. Since flower-buds are just
as much young shoots as leaf-buds, we may expect to find them
developed in corresponding situations, and this is actually the

FIG. 30.—Flower of Buttercup. A. a vertical section; c. sepals; pe. petals; e. stamens;
pi. carpels. B. extrorse anther seen from outside, showing lobes. C. anther seen
from inside. D. section of carpel; o. ovary; s. stigma; g. inverted ovule. E.
section of an achene ; jf. pericarp; ¢. seed-coat; p. endosperm ; e. minute embryo.

case. In very rare cases, ¢.g., tulip, there is a single flower on

the end of the main stem. The plantis then wnzaxzial. The vast
majority of flowers, however, belong to axes of higher order.
The different kinds of inflorescence are classified under two
headings, racemose and cymose, corresponding exactly to the
methods of monopodial branching described on p. 24, (1.) The
racemose or indefinite type possesses lateral flowers, which, in
the simplest cases, e.7., pansy, spring from the axils of ordinary
leaves. The growth in length of a stem ceases when a flower-
bud is developed at its end, and this type is called “indefinite ”
because the axis ends in an ordinary leaf-bud, and therefore
continues to elongate. The simplest case of (2.) the cymose or
definite type is seen in the tulip and some other cases, where,
as mentioned above, the main axis develops a flower-bud at its
end and ceases to elongate. No other flower is developed. If

70 THE FLOWERING PLANT.

a flower-stalk bearing one or a cluster of flowers grows right
up from the ground, it is termed a scape, and may either belong
to definite inflorescence, as in tulip, or indefinite, arising in
the latter case from a leaf-axil belonging to an underground
or abbreviated shoot, as in primrose and cowslip.

Tt is usual for flowers to occur grouped together into clusters.
In other words, they are formed upon special branch-systems,
to which the term! inflorescences is usually given. ‘The
branches of such a cluster arise from the axils, not of ordinary
leaves, but of bracts, which are mostly small, simple, and useless
for the purposes of foliage. Many plants, as orchids, show a com-
plete gradation between foliage leaves and bracts. On the other
hand, the transition may be very abrupt. In some exceptional
cases, ¢.g., Shepherd’s purse, the flower clusters possess no bracts,
so that the flower-bearing branches are not axillary. The con-
verse of this is not uncommon, 2.¢., the occurrence of bracts
without branches in their axils. They then, owing to their
small size, receive the name of bractlets or bracteoles, and are
situated not far from a flower, as, for instance, in pansy and
violet (fig. 51). Bracts may become large or otherwise con-
spicuous for special purposes. When brightly coloured, as in
hyacinth, they are termed petaloid, because tints other than
green are most usually found in the petals. A large sheath-
like bract, then known as a spathe, may surround an inflor-
escence. The large green structure enclosing the central column
of arum is of this nature (fig. 33). Another case is seen in the
onion. Smaller examples are found in the membranous structures
ensheathing the scapes of narcissus, daffodil, and snowdrop.
A spathe may be petaloid, as in the arum lily, where it is large
and of a brilliant white colour, which makes it look something
like a corolla.

When the flowers are in the axils of ordinary leaves, their
stalks may be called peduncles, but in the case of a flower cluster
they are pedicels, the word peduncle being reserved for the main
axis. If the cluster branches more than once, the intermediate
stem structures are called partial peduncles.

Racemose inflorescences are either simple or compound, 1.e., the
lateral axes either terminate in flowers without branching, or
else branch to a greater or less extent. Otherwise expressed,
the lateral axes are pedicels in the former case, partial peduncles
in the latter. Scmple racemose inflorescences are again sub-
divided according to the state of the internodes in the main
axis, which is long or short as these are well or ill developed.

Inflorescence, therefore, may mean :—(1.) Arrangement of flowers ; (2.)
a special flower-bearing branch system.

BRACTS AND FLORAL LEAVES, 77

(1.) When the main axis is long or fairly long, it may bear
stalked flowers, and is then a raceme (fig. 31). A good

example is the hyacinth, and here, as in
all indefinite flower clusters, the blossoms
open in acropetal order, so that the lowest
flowers have withered before the upper-
most ones are even open. Further in-
stances are found in foxglove, snapdragon,
wallflower, barberry (fig. 31), and currant.
The last two racemes are pendulous, owing
to the weaknesss of the main axis, while
bracts are absent in the wallflower. Where,
as in hawthorn and edible cherry, the axis
is comparatively short, and the pedicels
farther from the apex are larger than those
nearer it, so as to bring the flower to about
the same level, we have acorymb. This
is only a variety of raceme. The flowers
here open centripetally, 2.e., the outer ones

FIG. 31.—Raceme of Bar-
berry.

open before the inner ones, since they are first developed. When

FIG. 32.— FIG. 33.—Spadix of Arum. 1. Closed;
Spike of Verbena. 2.cut open. a. axis; b. spathe;/.
female flowers ; mm. male flowers;

those above are aborted.

an elongated main axis bears sessile flowers, a spike (fig. 32) is

78 THE FLOWERING PLANT.

the result, common examples of which are wild plantain and
wheat. Varieties of spike are the spadix (fig. 33), with fleshy
axis (e.g., arum), and the amentum or catkin, with scaly bracts,
as seen in willow and hazel.

(2.) We now come to cases of simple racemose inflorescences,
where, by suppression of internodes, the main axis remains
extremely short. Imagine a telescoped raceme. The pedicels
would all start very close together from the abbreviated axis,
looking, so to speak, like the ribs of an umbrella turned inside
out. Such an inflorescence is an wmbel, as seen in ivy. Its
nature may be known by the centripetal way in which the flowers
open. In a case like this, the bracts, from the axils of which the
pedicels arise, if they do not disappear altogether, are crowded
into an ¢nvolucre or circlet. The capitulum or head is what we
should get if a spike were telescoped, or if the flowers of an
umbel became sessile or nearly so. The axis is here more or
less dilated, and may be rounded, conical, or globular in shape.
Common red and white clover are good examples, and the bracts
are here readily seen. A further interesting point about clovers
is the fact that among the numerous species we find all gradations,
from short spikes (crimson clover, a cultivated form) down to
well-marked heads. The stumpy axis is often called receptacle,
but must not be confounded with the jloral receptacle. The
extremely large and important family of Composites, including
daisy, dandelion, sunflower, thistle, &c., &c., is characterized by
the possession of heads. Take, for instance, a daisy. A beginner
would very likely mistake the white part for a corolla, and a lot
of little green leaves outside this for a calyx,
but would then be puzzled by the yellow
centre. We have, in fact, not a single
flower, but a very large number, crowded
into a head, and often termed, from their
small size, florets. They can easily be picked
off the receptacle, and it is not difficult to
make out the nature of the central ones which
compose the yellow “‘disk.”” The white “ray ”
is made up of somewhat modified florets. The
: apparent calyx is an ¢nvolucre made up of the
Mis, a4-—Section of Hig. “outer bracts. It can easily be seen that the

mon receptacle ; 7, florets open centripetally. In thistle, dande-
toity mins the lion, and groundsel the florets are all alike.
The fig is a modified head bearing florets on

the inner side of a thickened hollow common receptacle (fig. 34).
Compound racemose inflorescences have their branches, of secon-
dary or higher order, constructed on one or more of the types

BRACTS AND FLORAL LEAVES. 79

above described. Thus there are compound racemes and corymbs,
where the branches of highest order are themselves racemes and
corymbs. If the branching is irregular, a panicle is the result.
The iarge group of Umbelliferze is characterized by the occur-
rence of umbels, usually compound. Hence the name. Carrot,
parsnip, hemlock, and the like are examples. Bracts may be
absent or form a general involucre round the origins of the
primary branches, and partial ones where the branch or par-
tial umbels arise. Compound spikes occur in many grasses.
Jt does not always happen that the branching is of the same
kind throughout. Thus, in grasses, the spikelets (¢.c., small
spikes) are not always arranged in compound spikes, but may be
in racemes or panicles.

Cymose or definite inflorescences branch in the way already
described on p. 24. They are called “definite” because the main
axis after producing a flower at its end ceases to elongate, and
is overtopped by its branches, which grow in the same manner.
Simple and compound cymes may be distinguished. Taking the
former first, a subdivision may be made into forms where a
pseudaxis or sympodium is (1) absent, (2) present. The false
dichotomy of mistletoe (p. 4) exemplifies the first kind, and so
do the dichotomous or two-rayed cymes of campion and stitchwort
(cf. fig. 35), where, however, the end of the main axis is of fair

>

3) at
wy +o

us e Y fs Lp >
Rs 0 Ny NH > (BS
s \A ‘ BED Z
S rs SS)
\
~Q | . xf

FIG. 35.—Forked Cyme. Fig. 36.—Helicoid Cyme of
Forget-me-not.
length, and bears a flower, so that the forking is obviously due
to lateral branches. The central flower opens first, then those
terminating the first pair of branches, and so on. For this
reason cymose inflorescences have been called centrifugal. <A

80 THE FLOWERING PLANT.

cyme may also be three-rayed, four-rayed, &c., when three, four,
&e., lateral branches overtop the main axis. (2.) The nature
of a pseudaxis or sympodium has already been fully explained
(pp. 24, 48). The pseudaxis may either be formed by branches
developed on either side alternately, when it is scorpioid, or by
branches belonging to one side only, when it is helicoid. The
vegetative shoots of elm, &c., and flowering shoots of deadly
nightshade are instances of the former, while forget-me-not
illustrates the latter case, where the pseudaxis naturally curls
round in a spiral way (fig. 36).

Compound cymes are distinguished by the fact that branches
of secondary or higher order themselves bear cymes instead of
terminating in flowers. Elder is a common example. A com-
pact cyme is termed a /ascicle, and if so condensed as to look like
a capitulum, it is a glomerulus.

Mixed inflorescences, which combine more or less the racemose
and cymose types, are not uncommon. As might be expected,
flower clusters of this nature are usually compound. Compara-
tively few special names have been given to these cases, since it
is easier to describe the general and partial ways of branching
separately. The heads of Composites, for example, are often
arranged in a cymose manner. Panicles are frequently mixed,
and the general name thyrsus has been given to elongated com-
pact forms in which the primary branching is racemose and the
secondary cymose, as in the flowering shoots of lilac and horse-
chestnut. The verticillaster is a variety of thyrsus found in some
plants, such as dead nettles, where the leaves are opposite and
decussate. At first sight there appears to be a circlet of flowers
at each node, the uppermost circles being youngest, so that the
general arrangement is racemose or indefinite. Careful exami-
nation shows, however, that each apparent circlet is in reality
composed of two very short cymose flower clusters in the axils of
the opposite leaves.

The flower, as a whole, generally displays a certain symmetry,
as seen on ground-plan. It is usually either radially symmetrical
or bilaterally symmetrical (cf. p. 52).! In the latter case the median
or antero-posterior plane is in most cases the one which divides it
into similar halves.

Lastly, a flower may be asymmetrical, when it is not divisible
by any plane into similar halves. Flowers coming under the
second and third cases may conveniently be called zrregular. In
determining the irregularity or otherwise of a flower, calyx and

1 Radially symmetrical flowers are also termed regular, polysymmetrical, or

actinomorphic, and bilaterally symmetrical ones zygomorphic or monosym-
metrical,

BRACTS AND FLORAL LEAVES. SI

corolla only are as a rule considered, ey., the andreecium and
gynecium of a radially symmetrical flower may or may not agree
with the general symmetry.

The floral receptacle, like the receptacle of a shortened flower
cluster, may exhibit considerable diversity of form (fig. 37). If
it is elongated, conical, or flattened, the flower is said to be hypo-
gynous, 2.¢., the andreecium, corolla, and calyx evidently grow
from a region below
the gynecium, or at
any rate do not start ~.
from a higher level
(fig. 37, A). But the
receptacle may cease
growing at the centre «as
but not at the edges,
when it forms a cup-
like structure, on the
rim of which andre-
cium, corolla, and calyx
are situated. Two con-
ditions are here dis-
tinguishable. Hither
the gyneecium remains
free, and can readily *
be dissected away from
the receptacle, or else
it becomes inseparably
fused with this. In
the former case (fig.

A

FIG. 37.—Relation of Parts of Flower [after Prantl]. A,
Bh, C. diagrams of longitudinal sections of hypogynous,

ais B) the flower is perigynous, and epigynous paisa pr ee

oe ep Fe dotted in A and B; in C the inner half of dotted part
termed perigynous, be- is wall of ovary, the outer half is receptacle; ca.
cause the floral leaves calyx; co. corolla; an. stamens; gz. pistil; ov. in-

verted ovule.
external to the gyne- verted ovule

cium grow on a ridge round about it; in the latter (fig. 37, C),
epigynous, Since they appear to grow upon it. Buttercup, rose,
and fuchsia are good examples of hypogynous, perigynous, and
epigynous respectively.

In the buttercup, as we have seen, the perianth leaves are
arranged in whorls, and the stamens and carpels in a spiral.
Such a flower is called hemicyclic, because a part only of its leaves
are arranged in whorls (cycles). Departure from this type may
take place in two directions. On the one hand, an acyclic flower,
like the white waterlily, has all its parts in a spiral; on the
other hand, a cyclic ower has all its parts arranged in whorls,
as may be seen in stonecrop and white lily (fig. 38).

F

82 THE FLOWERING PLANT.

The relation of parts in a flower to one another and, in a
lateral flower, to the main axis is conveniently represented by
a floral diagram which may be regarded as a generalized ground-
plan (fig. 38).. The position of the axis is shown by a dot; the
‘sepals, petals, and stamens are represented by conventional
marks ; and the carpels by a rough drawing of their appearance
in cross-section. A line drawn
through the axis dot and the centre
of the diagram serves to represent
the median or antero-posterior plane,
which divides the flower into right
and left halves. A line running
through the centre of the diagram
perpendicular. to the first line there-
fore represents the lateral plane, a
vertical plane at right angles to the
FIG. 38.—Floral Diagram of White Lily. median . plane, which divides the

st. stem on posterior side of flower ; flower into a posterior half next

reno Ob cblaue planes: ss, the axis and an anterior half turned

x. sepals; 2, 2, 2. petals; 3, 3,3. away from it. Two oblique vertical
_ outer stamens; « 4-4. her St planes intersecting the preceding at

nating whorls. 45 degrees may also be represented
in the diagram. It may seem unnecessary to distinguish so many
imaginary planes, but it is very convenient in practice to designate
particular parts of the flower as anterior, posterior, or oblique.
In the Pea-flower family, for example, there are five sepals, of
which one is always anterior. This is, therefore, one of the
distinctive features of the family.

A. study of the innumerable sorts of flower actually existing
shows that for cyclic forms the most typical condition consists in
the possession of six whorls, all the whorls having the same
number of parts, and the parts of successive whorls alternating,
just as in decussate foliage leaves. Such a flower, say, with five
members per whorl, can be represented either by a floral diagram,
or as follows, the dashes representing the floral leaves, which are
supposed to be picked off and laid in straight lines :—

ee eee

ee ie pee oy ee Ae ee Petals.

Stamens
(outer).
Stamens

(inner).
Carpels
(outer).
Carpels
(inner).

Se ib > 2 la
|

BRACTS AND FLORAL LEAVES. 83

Thus the members of contiguous whorls (e¢.7., sepals and petals)
alternate with one another, while the members of alternate whorls
are superposed, 7.e., are in the same rank or orthostichy. There
are ten ranks in the example supposed. Comparatively few
flowers are constructed so regularly as this, but a great many
can be explained by supposing alterations to have taken place
either in the number of whorls or the number of parts in certain
whorls. Very commonly both kinds of change appear to have
happened. Abundant examples will be found in the sequel.

We have now to consider in detail calyx, corolla, andrecium,
and gynecium. Five headings may be conveniently taken in
each case, viz., Number and Arrangement, Cohesion (union of
like parts), Adhesion (union of unlike parts), External Charac-
ters, and Structure. :

The Catyx, or outer whorl of the perianth, departs less from
the foliage leaves in nature than any other part of the flower,
and a gradation may sometimes be traced between sepals and
such leaves. In the dog-rose, for example, there are five sepals
arranged in a very short spiral. The two or three lowest bear
small leaflets in a pinnate manner, thus resembling the pinnate
foliage leaves of the same plant.

Number and Arrangement.— In acyclic flowers, such as those of
Cacti, the spirally arranged sepals may be indefinite in number,
and pass, on the one hand, into bractlets, on the other, into
petals. The cyclic and hemicyclic flowers of dicotyledons are
generally characterized by the numbers five and four (or multiples
of the same). The former number very frequently indeed goes
with a phyllotaxis of two-fifths. Examine once more the wild
rose. The foliage leaves are here arranged with the above
divergence (cf. p. 50), which means that each cycle includes
five leaves and turns twice round the stem. The five-leaved
calyx is here just such a cycle telescoped, but the spiral arrange-
ment can still be made out. A little further change would alto-
gether obliterate the spiral, and give us a whorl of five members,
as in buttercup. The number four is found in wallflower, stock,
shepherd’s purse, and many other plants. An examination of
the calyx in a wallflower will show that the sepals are in two
alternating whorls, each containing two sepals. This may per-
haps correspond to the opposite decussate arrangement found in
foliage leaves (p. 49). In wallflower, however, the foliage leaves
are not arranged in this manner, which fact tells against the ex-
planation. Three (or a multiple of it) is by far the commonest
- number among monocotyledons (fig. 37). The three large white
sepals of snowdrop furnish a striking example. This number is
associated, as might be expected, with a phyllotaxis of one-third.

84 THE FLOWERING PLANT,

Two sepals are occasionally found, as in the poppy, and this may
be here explained as a reduction from a higher number, probably
once possessed. In a good many flowers the perianth consists of
one whorl only, which is then considered to be, in most cases, a
calyx. In cases of doubt it is best simply to use the general
word perianth. Here again we see reduction. It is also to be
noted that in many small epigynous flowers (composites, umbelli-
fers, &c.) occurring in dense clusters, the calyx is very much
reduced in size, or even absent. Reduction may, lastly, be
carried to such an extent that both corolla and calyx are absent,
as in certain small inconspicuous flowers, like those of willow. In
the great majority of gymnosperms (fir, yew, juniper, &c.) no
perianth is present, but this does not appear to be a case of reduc-
tion from a former condition.

Mention has still to be made of arrangement in the bud,
which, in the case of flowers, is called cestivation or prejlora-
tion,| and corresponds to the prefoliation of foliage leaves

a0):

: OL ee sepals are often quite /ree from one another,
as in rose, buttercup, and wallflower, when the calyx is poly-
sepalous or aposepalous. This is strikingly seen in poppies,
where the sepals are caducous, 7.e., fall off very early. In many
flowers, on the contrary, the sepals are more or less united into
a tube. <A gamosepalous or synsepalous calyx of this kind occurs,
for instance, in the bean, primrose, and Canterbury bell. We
are here reminded of the cup-like or tubular structures formed
by connate leaves and sheathing stipules.

Adhesion.—-According to the most modern views, the members
of other floral whorls adhere but seldom to the calyx. It may
not be amiss, however, to explain here some older ideas which
caused the invention of certain terms that are still current in
many books. The perigynous and epigynous conditions of the
flower have been explained (p. 81) as the result of the growth
of the floral receptacle into a cup-like structure, upon the rim of
which sepals, petals, and stamens are inserted (fig. 37). This
cup was formerly held to be part of a gamosepalous calyx, and
was therefore termed the calyx tube, the real sepals being looked

1 The ways in which individual leaves are arranged have been defined in
the footnote to p. 49. Sepals and petals (as also foliage leaves) are disposed
in the bud with reference to one another as follows :—I. open, the par'ts
separated ; II. closed, the parts approximated: (1) valvate, touching at the
margins; (2) overlapping at the margin; (a) wmbricate, both margins of one
or more leaves covered ; (b) obvolute, every leaf with one covered and one
uncovered margin.

These points may be determined by cutting through the bud trans-
versely

BRACTS AND FLORAL LEAVES. 8

oat

upon simply as the free lobes of the calyx. In a perigynous
flower, therefore, the petals and stamens were regarded as
adherent to the calyx. The union between the hollow receptacle
and the gynecium (p. 81) in an epigynous flower was similarly
taken to be an adhesion between “calyx tube” and gynecium.
In this case the calyx was termed ‘superior,’ because its
‘“‘lobes”’ had a position obviously above the adhering part of
the gynecium. In other cases it was called “ inferior.”
External Characters.—The calyx may be radially or bilaterally
symmetrical. When polysepalous, the individual sepals can be
described in the terms used for foliage leaves. They are never
stalked, but may possess stipules at their points of attachment.
These, if large, look like an outer whorl of sepals, which receives
the name epicalyx, as in strawberry and marsh-mallow. An epi-
calyx may also be formed by bracteoles. The sepals are some-
times divergent or spreading, as in the tallest form of buttercup
(Ranunculus acris), or again they may be reflexed, t.e., bent back,
of which another common kind of buttercup (Ranunculus bulbosus)
is an example. Sepals are frequently more or less swollen or
saccate at their base. This is the case with the two lateral sepals
of wallflower and shepherd’s purse. Such a swelling may be
exaggerated into a tubular structure termed a spur, which is then
usually a nectary, secreting honey on its inner surface. In the
buttercup, as we have seen (p. 74), the nectaries form part of the
petal, and indeed these organs vary very much in position accord-
ing to the kind of plant examined. In some cases they are found
away from the flower altogether. Examine the bilaterally sym-
metrical calyx of a pelargonium, first removing the petals. Five
sepals will be seen, a large pair on the anterior side, then a
smaller pair, and lastly, a much larger unpaired posterior one.
By looking down upon the calyx a small -hole will be seen be-
tween the odd sepal and the pink structures in the centre of the
flower. A néedle pushed into this will enter a short tube which
can be seen as a ridge on the outside of the flower-stalk. A
transverse section at this point will show both tube and stalk.
We have here a spur, belonging to the posterior sepal, and firmly
adherent to the flower-stalk. A spur, however, is not always a
nectary. In the larkspur there are five large blue sepals, the
posterior one of which is produced into a large spur. This
simply serves as a cover to two small spurred petals, parts of
which, together with two small unspurred petals, are seen in the
centre of the flower. Monkshood is somewhat similar. The
“hood” formed -by the posterior sepal encloses two small petals
(here the only ones), which are entirely changed into nectaries.
When the calyx is gumosepalous the united part forms a tube

86 THE FLOWERING PLANT.

of varying extent, and the free parts of the sepals, collectively
forming the /imb, usually appear in the margin of this as small
pointed teeth or larger lobes. The general shape, when radially

symmetrical, may be tubular, funnel-shaped, bell-shaped, inflated, ©
&e. (ef. p. 89). The most common form of bilaterally symme-
trical calyx is the labiate or lipped, where the free anterior and
posterior portions form projecting lips. Dead nettle, sage, and
gorse furnish examples. In all three cases there are five sepals,

and in the first two the odd sepal is posterior, so that the upper
or posterior lip is composed of three sepals, and the lower or
anterior of two. Exactly the reverse is true of gorse. The out-
side of the gamosepalous calyx is often strongly ribbed, the ridges
corresponding to the midribs of the united sepals. The gamo-
sepalous calyx of Indian cress (garden nasturtium) possesses a
large posterior spur.

The surface of the calyx is very frequently provided with hair
structures, especially on the outside, where prickles may also
occur. More will be said about this in the sequel.

Sepals are typically green in colour, but the brightly tinted or
petaloid condition is very common, especially among monoco-
tyledons, as snowdrop, tulip, lily, hyacinth, orchis, &e. Many
dicotyledons also present examples of the same thing, e.g., many
buttercups, larkspur, gorse, barberry.

The texture of sepals varies considerably. They may be
delicate, firm, membranous, or scaly. This has an influence on
their duration, whether caducous (shed when the flower opens),
deciduous (falling off when the seeds begin to ripen), or persistent
(remaining during the ripening of the seeds). The last condition
is especially characteristic of gamosepalous examples. |

Structure.—It need only be stated under this head that an
ordinary green sepal resembles a foliage leaf, while a petaloid
one is more or less like a petal.

The Corotia, in most dicotyledons at any rate, is the most
brightly coloured part of the flower, and diver ‘ges more from the
type of the foliage leaf than the calyx.

Number and “Arrangement. —The petals of an acyclic flower
are generally indefinite in number, and not sharply marked off
in character from the other floral leaves. Thus, in white water-
lily, there is a gradual transition from sepals to petals, and from
these again to stamens (fig. 39). Hemicyclic and cyclic flowers
in dicotyledons generally possess five or four petals, while three
is the usual number among monocotyledons. The same reasons
may be given for this as in the case of the calyx (p. 83). Two
petals sometimes occur (enchanter’s nightshade), and more rarely
one. Many flowers possess no corolla at all, and in this case

BRACTS AND FLORAL LEAVES. 87

there may be a petaloid calyx, as in anemone and marsh-marigold,
or no perianth at all, e.g., willow.

FIG. 40.—Flower of Rose. 0b.
bract ; ct. cup-like receptacle;
FIG. 39.—Floral Leaves of White Waterlily. cf. sepals; p. petals; e. sta-

c. sepal; p. petals; e. stamens. mens.

The corolla and calyx, when arranged in whorls, are usually
isomerous, t.e., they contain an equal number of members, which,
in this case, regularly alternate with one another. When petals
and sepals are unequal in number, the former are sometimes
more numerous (¢.g., poppy, petals four, sepals two), sometimes
less so (e.g., monkshood, petals two, sepals five).

The terms hypogynous, perigynous, and epigynous (cf. p. 81)
are applied to the corolla specially, as well as to the flower as a
whole.

Prejloration or arrangement of leaves in the flower-bud equally
concerns both divisions of the perianth.

Cohesion.— When the petals are jvee and distinct, as in rose,
buttercup, and wallflower, the corolla is polypetalous or apopetalous
(fig. 40). Frequently, however, there is more or less union, with
formation of a tube, cup, or the like, as in the gamopetalous or
synpetalous corollas of primrose, Canterbury bell, snapdragon, and
convolvulus. :

Adhesion.—The commonest union is one between corolla and
stamens, which will be mentioned later (p. 95). Compare also
p. 84.

External Characters.—The very greatest variety is developed
in the corolla, which, as a whole, may be radially symmetrical,
bilaterally symmetrical, or asymmetrical. The individual petals,
when free, can, like sepals, be described in the same terms as
foliage leaves. They are usually narrowed at their attached end,
and, not infrequently, as in the pink (fig. 41), there is a distine-
tion between stalk and blade, termed in this case claw and limb.
There may be, e.g., in ragged-robin and red campion, a small out-

88 THE FLOWERING PLANT.

growth at the junction of the two, which is termed a ligule from
its resemblance as regards position to the structure of that name
in grasses. The ligules are collectively called the corona. One
or more petals of the polypetalous corolla may be saccate or
spurred. In the pansy and violet the lower petal is produced
into a large spur (fig. 51).
Larkspur and monkshood
(p. 85) have two spurred
petals, while all five petals
have conspicuous spurs in
the closely allied colum-
bine, where the corolla is
regular. A very common
and striking form of 7rre-
gular corolla with free
petals is seen in gorse, pea,
FIG. 41.— Petal of Fic. 42.—Sweet Pea. c. bean, wistaTia, clover, Xe.

Pinks) } lo elimi 10: calyx; e. standard ; a. It has been termed papl-

Se EE Peper lionaceous or butterfly-
shaped (fig. 42). The odd posterior petal is here larger than the
rest, and being somewhat upright, is known as the standard
(vexillum). In front of this come a fairly large pair of petals,
the wings (alw), which overlap a third smaller pair that are
united into a boat-shaped structure, the keel (carina), enclosing
the stamens and pistil. The union of the last two petals is not
complete, for they have separate stalks, nor is it very close,
as they can readily be separated. Petals, like sepals, may be
spreading or reflexed, and when they are clawed the limb may
be bent sharply on the claw. ‘Thus, in the wallflower there are
four equal petals, diagonal in position, and with long claws.
The limbs spread abruptly out transversely to the claws, and the
corolla is strikingly c7oss-shaped in consequence, for which reason
it is termed cruciferous.

Some of the most remarkable forms of, irregular corolla are
found in orchids, especially tropical ones. Perhaps the com-
_ monest British species is the early purple orchis (Orchis mascula),
which flowers from April to June. There are here three petaloid
sepals, an upper one, arching over the central structures, and
two spreading or reflexed lateral ones. Alternating with these
are three other purple flower leaves, two smaller upper petals,
arching like the upper sepal, and a much larger three-lobed one,
the Jabellum. The central lobe of this last is regarded as the
lower petal, and the two side lobes as petaloid stamens fused with
it. These conclusions are based upon comparison with allied but
less modified plants and the structure of the parts. Details would

BRACTS AND FLORAL LEAVES. 89

be out of place in an elementary book like this. Two further
points may be noted about the purple orchis. The labellum pos-
sesses a large spur, and the flower is so twisted round that upper
parts are really lower, and vice versd (fig. 52).

The gamopetalous corolla usually presents certain well-marked
regions. The united part is termed the tube, while the more
or less distinct teeth or lobes which represent. the free ends of
the petals form the /imb. The commencement of the tube is
the throat. Sometimes the limb is absent, and the number
of petals is then found by counting the most prominent veins
(z.e., midribs of the petals), or is inferred by comparison with the
calyx and also with the corollas of closely related plants. The
principal shapes found among regular forms are the following,
in which the tube becomes of greater relative importance as we
proceed in the series. In potato and forget-me-not the tube is
extremely short, and the limb flat and spreading, giving a certain
resemblance to a wheel, whence the term rotate or wheel-shaped.
A corolla of this kind may be slightly irregular, as in speedwell.
The word stellate is applied to cases where the tube is very short
and the spreading lobes very pointed, as in cleaver, while a sawcer-
shaped corolla differs from a rotate one in being concave instead
of flat. If in a wheel-shaped or saucer-shaped corolla the tube
were considerably elongated, we should get a salver-shaped (hypo-
crateriform) example, as in primrose and plumbago. A _ bell-
shaped or campanulate corolla, like that of harebell, Canterbury
bell, &c., gradually enlarges almost from its beginning, the limb
being small. An irregular example of the same is foxglove. A
bell-shaped corolla by contracting at its mouth would become
inflated or urn-shaped (uzrceolate). The different kinds of heath
(but not heather) are good instances. Yubular and funnel-shaped
corollas are respectively cylindrical and conical, the limb being very
small or absent. Thistle-florets and convolvulus are examples.

The zrregular gamopetalous corolla may be ae are: or markedly
so. The speedwell, mentioned above, is an —
example of the former condition, while in
the latter case a labiate or lized form is
the commonest. The white (or red) dead
nettle is a typical illustration (cf. fig. 43). fe
Since in this plant (and allied forms) there yg, ,,.--Labiate Corolla
are five sepals, the odd one posterior, it is of Sage.
evident that of the five alternating petals the odd one must
be anterior, so that the lower lip consists of three petals, and
the upper lip of two. In this particular example the two
petals forming the upper lip are so closely united that its
double nature cannot easily be recognized, but the union is not

Qo: THE FLOWERING PLANT.

so close in ground-ivy and some other related forms. The triple
nature of the lower lip is more readily seen. It is chiefly
made up of a large central lobe, corresponding to the free part
of the anterior petal, while a small pointed tooth on either side
of this indicates the existence of another petal. In ground-ivy
the lower lip is three-lobed, and though the middle one is largest,
yet there is not the same disproportion as in the other case.
A labiate corolla is said to be helmet-shaped (galeate) when the
upper lip forms a curved hood covering the stamens, &ec., as
in the white dead nettle, and it is termed gaping (ringent) when,
as in the same instance, the throat is freely open. The upper lip
may be very much reduced in size, as in blue lobelia, bugle, and
wood-sage. Examination of the irregularly bell-shaped corolla
of foxglove will show that here too is an instance of the lipped
condition. The upper lip is broad, and its double nature is
indicated by a slight notch. The lower lip is composed of three
lobes well marked off from one another. ‘Two of these are
lateral, while the third and largest one projects somewhat, is
spotted, and covered inside with soft, rather long hairs. A
remarkable modification of the labiate corolla is found in snap-
dragon. The larger upper lip is deeply cleft, and obviously
represents two petals, while the lower lip pos-
sesses three lobes, of which the middle one is
smallest, just the opposite to the preceding
cases. But this is not all. Projecting from the
upper side of the lower lip is a large, differently
coloured outgrowth, the palate, which blocks up
the throat. Such acorollais masked (personate).
It may be noted in addition that the tube is
saccate near its attachment, at a part which
belongs to the posterior petal. ‘The wild yellow
toad-flax agrees generally with the above descrip-
tion, but the posterior petal, instead of being
saccate, is produced into a long pointed spur.
In all the preceding cases one lip has been com-
posed of three, the other of two lobes. Other
groupings are known of the same number of
petals. Thus, in honeysuckle there is a narrow
BiG. tte iulate tube, a large four-lobed upper lip and a narrow
. 0. inferior :

ovary: ¢. rudimen. One-lobed lower lip. All the lobes are reflexed.

wa Neca ge, The strap-shaped (ligulate) corolla is not very

thers’; s. style with removed from the labiate one, e.g., wood-sage,

ah ae ae with a reduced upper lip. Take, for example,
the cultivated scarlet lobelia. The narrow tube here terminates
in a deeply five-lobed limb. The corolla, in fact, looks as if

BRACTS AND FLORAL LEAVES. gl

it had been partly split open and spread out. The same pecu-
liarity is carried to a greater extent in the florets of dande-
lion and the ray florets of daisy. ‘The strap-shaped limb in the
former case has five teeth at its termination, the latter only three
(cf. fig. 44). The surface of the corolla may be glabrous or
present hair structures or hair-like outgrowths. Its texture is
usually delicate, corresponding with its deciduous nature. The
colour may be simple, or streakings and mottlings-may occur ;
bright tints are the rule.

Structure.— Petals (and petaloid sepals) are covered on either
side by a delicate epidermis. Internally they are made up of
one or more layers of spongy parenchyma (cf. p. 65), traversed
by delicate vascular bundles, which, as in the foliage leaf, give a
veined appearance. ‘The colours of flowers are due to pigments
contained in the epidermal cells. Blue and red are dissolved
in the cell-sap, as in larkspur and rose. Yellow and orange are
usually contained in variously shaped colour bodies, e.g., in Indian-
cress (garden nasturtium), where a large number are found in
each cell.

CHAPTER VIII.
ESSENTIAL FLORAL LEAVES.
MORPHOLOGY.

THE andrecium and gynecium may collectively be called the
essential organs, since they have to do with the formation of
seed.

It is a familiar fact that, at certain times of the year, brown
patches appear on the backs of fern leaves. These are made up
of minute cases filled with excessively small brown grains. The
cases are termed sporangia, and the contained grains spores.
Club-mosses, common in mountainous districts, also produce
spores, and the yellow powder sold by chemists under the name
of lycopodium consists entirely of these. The bodies in question
can give rise to new plants under favourable conditions. _

Flowering plants also produce spores. Pollen is made up of
innumerable small grains which are of this nature, and every
ovule, as we shall see further on, contains a cell, the embryo sac,
which is also a spore. Since stamens and carpels produce these
bodies, they may be termed spore-leaves or sporophylls, and
from this point of view the flower may be defined as “a shoot
modified for spore-bearing.”

The stamens are termed male spore-leaves and the carpels
female spore-leaves.

The SraMENs, as we have seen in the buttercup, differ very
much from the typical leaf form. In the white waterlily, how-
ever, there are all possible stages between them and petals (fig.
39). On the other hand, no links connecting stamens and carpels
are found in normal flowers.

Number and Arrangement.—In acyclic and hemicyclic flowers
a large number of spirally arranged stamens are found. An
instructive example of the former kind is seen in the Scotch fir.
The flowers of this plant (fig. 45) possess no perianth, and are
of two kinds—male, with stamens only, and female, with carpels
only. The ordinary “cones” are the latter, while the former are
much smaller, and crowded together into clusters. They are best
examined in June, when the pollen is ripe. Hach one consists of

ESSENTIAL FLORAL LEAVES. 93

an axis upon which numerous stamens are crowded in a spiral
manner. They are here more flattened and leaf-like than, for
example, in the buttercup, which is a good example of the hemi-
cyclic condition. The most typical cyclic flowers possess two
whorls of stamens (fig. 38)—an outer, alternating with the petals
(and superposed to the sepals), and an inner, alternating with the
sepals (and superposed to the petals). As in the case of the
perianth, five and four are the typical numbers in a whorl for
dicotyledons, and three for monocotyledons. ‘Ten stamens occur
in papilionaceous flowers, but the two five-membered whorls are
here indistinguishably united together. Fuchsia, willow-herb,

Fic. 45.—Flowers of Scotch Fir [original]. Various scales. A. Group of
male cones. B. A stamen; ps. pollen sac; f. filament. C. Pollen grain;
ex. extine; w. wing; 7.c., v.c. cells. D. A female cone. E. An ovyule-
bearing scale; ov. ovule; mp. micropyle. F. A seed.

and evening primrose possess two whorls of four each, while
snowdrops, lilies, and rushes have six stamens in two whorls.
Very frequently one whorl is suppressed, usually the inner one.
Thus a very large number of dicotyledons are provided with five
stamens alternating with the petals, as, for example, in parsnip,
disk florets of daisy, potato, violet, convolvulus, and forget-me-
not. Others have four similarly placed stamens, as in plantain
and verbena. Again, in monocotyledons the outer whorl only
may be present, as in iris, where there are three stamens. Far
more rarely the outer whorl is suppressed. This is seen in prim-
rose and its allies, which possess five stamens superposed to the
lobes of the gamopetalous corolla. That a whorl has been here
suppressed is proved by the fact that in brookweed or water-pim-
pernel, a closely allied plant, rudiments of the outer whorl are
actually present. But reduction may go still farther, and leave
only part of a whorl. White dead nettle is a case in point. Here
there are five sepals and five petals, but only four stamens, two

94 THE FLOWERING PLANT.

long and two short (didynamous). It will be remembered that
in this flower the odd petal is anterior, and there should, there-
fore, be an odd posterior stamen, since the outer whorl of stamens,
which alternate with the petals, is retained. This, however, is
almost always absent. Very rarely, however, a minute stamen
is found in this position. Snapdragon is a similar case. Take
one of its flowers, and carefully split open the gamopetalous
corolla along one side. Upon spreading it out, you will find in
its posterior side (7.e., next the stem and opposite the rounded
swelling at the base of the corolla tube), near its attachment to
the receptacle, a minute white projection. ‘This is the remains
of the lost fifth stamen. The foxglove, a near ally, possesses
four stamens and no rudiment, while pentastemon, a common
garden flower related to this, possesses a very large fifth stamen,
devoid, however, of an anther, which curves down to the lower
side of the flower. Finally, mullein, also a relative, has five
perfect stamens. The speedwell, which belongs to the same
group of flowers, presents still further reduction. The sepals
and petals are four, but the stamens only two. In most orchids
there is only one perfect stamen, the anterior one of the outer
whorl. One orchis, however, ladies’-slipper (Cypripedium), has
two stamens, belonging in this case to the inner whorl. These
facts, and the presence of more or less complete rudiments of
other stamens (cf. p. 88), lead to the conclusion that the one-
stamened orchis is descended from forms which possessed six
perfect stamens, arranged in two alternating three-membered
whorls, as, for example, in snowdrop and lily (fig. 38). Stamens
are absent altogether in female or pistillate flowers, and this often
appears to be the result of reduction. Some of the flowers on
certain plants are neuter, 7.e., devoid altogether of sporophylls,
and reduction has undoubtedly taken place in such cases.
Stamens are sometimes increased in number in cyclic flowers,
instead of being reduced. In the wallflower, for instance, there
are four sepals and four petals, but six stamens—four long and
two short (tetradynamous). The petals are diagonally placed,
while the short stamens are Jateral in position, and the long ones
are grouped in two pairs, one anterior and the other posterior.
'Each pair appears to have arisen by the splitting of a single
stamen. This is supported by the fact that in some tetradynamous
flowers a partly-split stamen is occasionally found instead of a
pair. Branching may also occur. In St. John’s wort there are
three or five groups of stamens, each group of which has been
formed by the branching of a single stamen at an early stage of
development. Mallows and hollyhocks, again, possess numerous
stamens formed by the branching of five originalones. The terms

ESSENTIAL FLORAL LEAVES. 95

hypogynous, perigynous, and epigynous are applied to stamens
(efp. Sr). -

Cohesion.—Stamens may either be united together by their
stalks (filaments) or by their thickened heads (anthers). In the
former case they are termed mon-, di-, tri-, or polyadelphous,
forming respectively one, two, three, or more than three groups.
Monadelphous stamens are found in some papilionaceous flowers,
as gorse and broom. The lower parts of the ten filaments are here
united into a tube which surrounds the gynecium. A somewhat
similar state of things exists in mallow and hollyhock. Many
papilionaceous flowers exemplify the diadelphous condition, Exa-
mination, for example, of clover, bird’s-foot trefoil, pea, or bean
will show that the staminal tube is formed by the bases of
nine filaments only, while the remaining upper or posterior
stamen is free. The only British examples of more numerous
groups of stamens are the St. John’s worts. The andrecium is
here commonly said to be triadelphous or polyadelphous, although,
as stated above, it is really an example of branching.

The stamens are synantherous or syngenesious When their anthers
cohere together into a cylinder. This is the case in the large group
of Composites, of which dandelion, daisy, thistle, sunflower, dahlia,
and groundsel are common examples. Pull off, for instance, one
of the disk florets from a single dahlia (double or quilled ones
have become abnormal by cultivation), and hold it up to the light.
Projecting from the mouth of the five-toothed tubular corolla is
a thickened fork. This is the upper part of the gyncecium.
Within the upper part of the translucent corolla is a dark rod-
like body, the united anthers, surrounding the middle of the
gyneecium, and below this are some wavy threads, the filaments
(cf. p. 126). By tearing open the corolla with needles these
points can be made out more clearly. The same thing can be
seen with greater difficulty in the much smaller florets of dande-
lion, &e. (fig. 44). In lobelia the stamens are both synantherous
and monadelphous. . Something similar takes place in the male
flowers of cucumber and vegetable marrow.

Adhesion.—Stamens are sometimes united to the petals of a
polypetalous corolla, as is the case with the inner five stamens
of bladder-campion, and very frequently to the tube of a gamo-
petalous corolla, as in foxglove, dead nettle, primrose, speedwell,
and snapdragon. In either case they are termed epipetalous.
Split open a foxglove bell, and you will find the filaments of the
four stamens partly free and partly represented by prominent
ridges running down to the attachment of the corolla.

Far more rarely there is adhesion between stamens and carpels.
The commonest examples of this are orchids, where the single

96 THE FLOWERING PLANT.

gynandrous stamen is fused with the gynecium, upon the top of
which it is perched.

External Characters.—Hxamine carefully a buttercup stamen
(fig. 30). It presents two regions, a stalk or jilament, and a
thickened head or anther. The latter possesses a grooved anther
lobe on either side, the two being separated by a continuation of
the filament, called the connective. Within the anther lobes a
yellow dust is formed, the pollen, which escapes by a longitudinal
slit formed on either side in the ripe anther. All the parts
described present different forms according to the plant exa- —
mined.

The filament may be very short or absent, when the anther is
sessile, as in the epipetalous stamens of primrose. If they are
long, the stamens may be exserted, 2.e., project from the corolla.
Filaments are generally more or less slender, but they may be flat-
tened, asin some of the stamens of white waterlily. Appendages
or outgrowths are sometimes present. In the violet and pansy,
for example, there are five stamens, the anthers of which appear
at first sight to be united, though in reality only closely approxi-
mated. Carefully slit open the spur of the lower petal, when two
little white rods will be seen projecting into it. These, when
traced, prove to be outgrowths from the filaments of the two
lower stamens, close to their junction with the anthers.

If the connective is a direct prolongation of the filament, the
anther is basifived, and in that case its lobes are either lateral,
internal, or external; and the descriptive terms cnnate, introrse,
and eaxtrorse are used. The last two are included in the wider
meaning word adnate. It frequently happens that the filament
is attached to the back of the anther, which is then basifixed,
and if in this case the attachment is very loose, the anther can
swing freely about or is versatile, as in grasses (fig. 50) and
white lily.. When the connective is narrow the anther lobes are
parallel, as in buttercup, but it may be broadened so as to make
the lobes divergent, ¢.g., in marjoram, dead nettle, and foxglove.
The connective may even form a sort of cross-bar, hinged upon
the filament. This state of things is seen in the meadow and
garden sages and an ornamental crimson form belonging to the
same genus (fig. 46). The andrecium here consists of four
stamens, two of which are aborted or reduced to minute rudi-
ments, like the odd stamen of snapdragon. The connectives of
the other two are elongated, and bear a perfect anther lobe at
one end and an aborted one at the other. The connective does
not usually extend beyond the anther lobes, except in some few
cases, as in violet and pansy (fig. 51), where it forms an orange-
coloured triangular expansion in this position.

ESSENTIAL FLORAL LEAVES. Q7

The anther lobes present various shapes, linear, oval, kidney-
shaped, &c., and they may possess tail-like appendages, as in
heath. One lobe may be aborted, as in sage
(fig. 46), while in mallow the anthers produced
by branching have also but one lobe, and are,
so to speak, half-anthers. ‘The surface of the
anther may be more or less hairy, as in dead
nettle. When the pollen is ripe, the anthers
open or dehisce to liberate it. Most commonly
each lobe splits longitudinally, and the slit faces
to the side, interior, or exterior, according as
the anther is innate, introrse, or extrorse. In
other cases, as potato and heath, a pore or minute
fissure is formed at the tip of each lobe. In
barberry the dehiscence is valvular, 7.e., part of
the wall in each lobe becomes detached and turns [i
up as a kind of flap, which remains united to yg 46 bait as
the tip of the anther. Sage. f. filament;

Pollen is usually in the form of a fine sticky iin ne
or dry powder, composed of an immense num- 8. aborted anther
ber of minute pollen grains. Inheathandrho- °”
dodendron several grains are united together, and in orchids the
whole of the pollen in each lobe of the solitary anther is agglu-
tinated into a club-shaped mass termed a pollinium (fig. 47).

Stamens sometimes occur in which the anthers are absent.
They are then termed staminodes, and are often leaf-like. Com-
pare the allied forms, mullein, pentastemon, snap- , ©
dragon, and foxglove (cf. p. 94). These possess,
respectively, five stamens, four stamens and a large
staminode, four perfect and one aborted stamens,
and four stamens. We are justified, therefore, in
concluding that an odd fifth stamen has been sup- |
pressed or absolutely done away with in foxglove,
especially as, so to speak, there is a ‘‘ vacant chair ”’ mS
left byit. Similarly (cf p. 93), if we take the closely Fic. 47.—Pollinia
related water-pimpernel and primrose, we shall find ian
that one has five perfect stamens superposed to the petals and five
staminodes alternating with them, the other five stamens super-
pose to the petals. Hence the conclusion is reached that a whorl
of stamens has been suppressed in primrose. Observations like
these, extended over a large number of cases, have led to the
conclusion that tivo whorls are typical for the andrcecium.

Yellow is the most common colour for stamens, especially the
anthers, but this is by no means an invariable rule.

Structure.—The three systems of tissue can be recognized in

G

98 THE FLOWERING PLANT.

‘stamens. Their exterior is covered with epidermis, which fre-
quently produces hairs, and may possess stomata. The filament
and connective are traversed by a central vascular bundle, and
the ground-tissue is made up of parenchyma. A cross-section of
a young buttercup bud will give numerous thin slices of anthers.
In these it will be seen that each lobe contains two compartments
filled with pollen grains, and hence called pollen sacs (cf. fig. 51).
The pollen grains have been formed by active division of paren-
chymatous cells belonging to the ground-tissue. Later on the
party-wall between the two sacs in each lobe breaks down, and
their contents escape to the exterior by formation of a. slit.

Pollen grains are mostly spherical. They are invested by two
membranes, a firm outer one, the extine, often produced into
spines, knobs, or ridges, and in the fir into a pair of little air
bladders (fig. 45, C) ; and a delicate inner one, the intine. Within
the coatings are two or a few small cells in gymnosperms and
pr otoplasm with two nuclei in angiosperms.

The Carpets depart even more widely from the ordinary leaf-
type than the stamens. They collectively form the pistz or
gynecium, which occupies the centre of the flower.

Number and Arrangement.—In acyclic and hemicyclic flowers
an indefinite number of carpels are frequently present. The
ordinary cones of the Scotch fir consist of a large number of
spirally arranged woody scales (fig. 45). These are carpels, or, at
any rate, outgrowths from them. We have previously seen (p. 75)
that a large number of carpels are present in the hemicyclic
flowers of the buttercup. It is probable that two alternating
whorls of carpels are typical for the cyclic flower. One entire
whorl, however, is generally suppressed, and the remaining one
is very frequently reduced. Dicotyledons often possess five or
four carpels, as in geranium and holly respectively, but a smaller
number is extremely common. Thus, pansy (fig. 51) has three,

wallflower, dead nettle and foxglove two, and papilionaceous
flowers only one. A few British” monocotyledons, as flowering
rush and frogbit, retain six carpels in alternating whorls of three

each. Far more commonly the inner whorl is suppressed, so
that three carpels only are present, as in lily (fig. 38), tulip,
snowdrop, and orchis. Still further reduction takes place in
most grasses, which have only two carpels, while duckweed, wild
arum, and maize retain but one. In male flowers carpels are, of
course, absent, and in this case they may have been suppressed
or else never have existed. As mentioned previously, neuter
flowers contain no essential organs.

Most flowers are bisexual, 2.e., possess both stamens and car-
pels, some are wnisexual ; and are then male, with stamens only,

ESSENTIAL FLORAL LEAVES. 99

and female, with carpels only. Several terms used in this con-
nection, are given in the following table :—

monecious, with both kinds
on same plant, e.g., fir,
hazel, arum; diacious,
with the two kinds on
different plants, e.g., wil-
low, nettle, hop.

unisexual flowers are
Plants possessing

unisexual flowers + bi-
sexual flowers are

polygamous, e.g., ash.
The instances mentioned may now be briefly described.

Fir (fig. 45).—Male cones small, crowded into a cluster on the
sides of a shoot which produces leaves beyond it. Dusty when
ripe from yellow pollen. Female cones occur singly for the most
part. They take two years to mature their seeds, and in early
summer cones in three stages may be found on the same plant.
(1.) Small green cones with pink-tipped scales, occurring close to
the ends of the youngest shoots, and belonging therefore to the
current year. (2.) Larger green cones, belonging to the previous
year, and situated on older shoots. (3.) Brown woody cones with
ripe seeds, placed on still older parts of the stem, and two years
old.

Hazel.—The pendent catkins seen in March are male inflores-
cences, and consist of a large number of scaly bracts. Each of
these bears four stamens on its under side, but, as each of these
is forked, there appear to be eight. Their true nature is shown
by the fact that they bear but one anther lobe. The female eat-
kins are very small, and being closely surrounded by bracts, look
like buds. Lach of them consists of five or six flowers, the only
parts of which are visible externally resemble a number of small
threads, bright pink in colour. :

Arum (fig. 33).—The upper part of the spadix is club-shaped
and brightly coloured. Lower down comes a circlet of aborted
male flowers, a little distance beneath which is a lot of small male
flowers, each of which consists of one stamen. These are crowded
into a ring round the stem. A ring of female flowers forms the
base of the inflorescence. It is separated by an interspace from
the preceding. ach female flower has a single carpel, but, like
the male flowers, is devoid of perianth. Those at the upper part
of the ring are aborted.

Willow.—Both male and female catkins are here short and
upright. The former are readily distinguished by their bright
yellow colour, and consist of a large number of male flowers with-
out perianth. Lach consists of two long stamens placed in the
axil of an oval bract provided with long hairs. At the base of

*.

100 THE FLOWERING PLANT.

the filaments is a glandular projection or nectary. The female
catkins are green, and a female flower corresponds to the above
description, except that, instead of two stamens, there is a pistil
formed by two cohering carpels.

Nettle.—There are two common British forms, the small and
the large, which are monecious and dicecious respectively. The
latter kind is easily recognized by its greater size and by its
elongated paniculate inflorescences. The small male flowers have
a four-lobed calyx, superposed to which is a whorl of four stamens.
A minute knob, representing an aborted pistil, is seen in the
centre. ‘The female flowers possess a pistil, composed of a single
carpel, but no traces of stamens.

Hop.—The minute male flowers are arranged in cymes. Each
consists of a whorl of five sepals, with five superposed stamens.
The female inflorescences are short broad catkins, the large over-
lapping bracts of which give a cone-like appearance. They form
the “hops” of commerce. <A pair of female flowers are situated
in the axil of each bract. Their perianth is rudimentary, and
encloses a pistil formed of two united carpels.

Ash.—The small flowers are borne in short racemes, and are
without perianth. The bisexual ones are provided with two pur-
plish-black stamens and a pistil of two united carpels. The male
and female flowers are similar; but in one case stamens, in the
other carpels, only are present. ‘This is a very interesting case
of reduction, for in the flowering ash, a South European species,
all the flowers are bisexual, and possess four sepals and four
petals, as well as stamens and carpels. This is also the case in
the flowers of privet and lilac, both allied forms.

Cohesion.—The pistil is said to be apocarpous when its con-
stituent carpels are free. In buttercup, for example, the small
green bodies in the centre of the flower are separate carpels (fig.
30); here they are very numerous. Instances of smaller numbers
are found in columbine (five), larkspur (generally three), and gorse
or pea (one). Much more frequently the pistil is syncarpous, its
carpels being united, as already alluded to in willow, ash, and
hop. ‘The union may be more or less complete. Hxamine the
flower of a saxifrage, such as London pride. A deeply bilobed
pistil will be found, evidently consisting of two carpels. In pink
or carnation the seed-containing part (ovary) is undivided, but
projecting from the top of this are two curved threads (styles),
which point to the presence of a pair of carpels. The same thing
is indicated by the forked end of the style in dead nettle, sage,
and most grasses (fig. 50). In the white lily the existence of
three carpels can be recognized by the trilobed stigma, and the
three compartments seen in a cross-section of ovary (fig. 38).

ESSENTIAL FLORAL LEAVES. IOI

The pistil of primrose, consisting of five united carpels, presents
a case of very close union, where the true state of things can
only be inferred from analogy.

Adhesion.— Mention has already been made of gynandrous
stamens (p. 95). The most important example of union between
pistil and other structures is presented by the epiqynous flower
(p. 81). Take, for example, a snowdrop, female flower of vege-
table marrow, or bloom of fuchsia. Immediately beneath the
calyx a green swelling will be found, which careful examination
shows to be the ovary, containing seed rudiments or ovules. By
examining flowers of different ages, it will be seen to become the
fruit. The most reasonable explanation supposes an 7nfertor ovary
like this to be formed by an intimate union between it and a
cup-shaped floral receptacle (cf. fig. 37). If a Californian poppy
(Eschscholtzia), which is an orange-coloured flower commonly
cultivated, is cut accurately in half, its ovary will be seen partly
embedded in a shallow cup formed by the receptacle. It is, so
to speak, becoming inferior.

Where, as in hypogynous and perigynous flowers, the ovary is
Free, t.e., attached to, but not fused with, the receptacle, it is said
to be supervor.

External Characters.—The simplest kind of pistil is found in
gymnosperms. Examine one of the large green cones found upon
the Scotch fir in early summer. With some difficulty the scales
crowded upon it can be detached. Look at the upper surface of
one of them, and observe, close to the end that was attached, a
pair of small oval whitish elevations (fig. 45, E). These are
seed rudiments or ovules. That part of a carpel to which ovules
are attached is termed a placenta, and this very frequently forms
a more or less considerable outgrowth. In this particular case
the carpels proper are extremely small, and the scales making up
the cone are extremely large placentas. Note that but for the
overlapping of adjoining scales the ovules would be quite unpro-
tected. This condition is characteristic of gymnosperms, which
owe their name to it.

The ovules of angiosperms (fig. 48), on the contrary, are situated
in a closed chamber, the ovary. It will be the simplest plan first
to consider apocarpous pistils, and afterwards syncarpous ones,
which are more complex. An apocarpous pistil is either mono-
carpellary or polycarpellary, t.e., made up respectively of one and
more than one carpel. Papilionaceous flowers are examples of
the former class. Take, for example, a pea flower, and strip off
the corolla and diadelphous stamens, leaving the pistil behind.
It consists of a laterally flattened ovary, from which a curved rod
projects. This is the style, and at its tip there is a small sticky

{02 THE FLOWERING PLANT.

area, the stigma, to which pollen may often be found adhering.
By splitting open the ovary, several little green ovules may be
found attached along its upper margin. Now examine a young
pea-pod, which is a further developed pistil, At one end the
stalk and calyx will be seen, at the other the remains of the
style, while the pod is the developed ovary. By holding it up
to the light, a row of matured ovules, 7.¢., seeds, will be observed
running along one side. Split open the pod on that side and
spread it out. It will then look like an ordinary leaf, with well-
marked midrib and thickened edges bearing ovules. Every
carpel of an apocarpous pistil is, in fact, regarded as a folded
leaf, the thickened edges of which bear ovules, and are united
together in a seam or suture, called the ventral suture. The
other edge of the carpel may be called the dorsal margin, which
corresponds to the midrib. The thickened edges here form the
placenta, and the arrangement or placentation of the ovules is
here said to be marginal (fig. 48 D). In order to grasp the idea
that a pistil like that of the pea corresponds to a folded leaf,
take some simple leaf that tapers gradually to a point, e.g., one
from a fuchsia, and fold it upon the midrib; you will then see
that the broader part answers to the ovary, and the narrower
part to the style. It sometimes happens in abnormal flowers
that carpels remain partly or entirely open, thus showing their
true nature, and the syncarpous pistil of mignonette never com-
pletely closes at the top (cf also p. 107). In gymnosperms
folding has not taken place at all. We may consider that the
pea has descended from ancestors somewhat resembling the
gymnosperms of the present day, and that the formation of a
closed ovary has taken place gradually in the course of innu-
merable generations. The next question is, ‘‘ Which surface of
the folded leaf is inside, upper or lower?” ‘This query cannot
easily be answered by reference to the pea alone, but examination
of apocarpous pistils with more than one carpel will readily
give a solution. Kxamine, for instance, a head of ripe fruit
in larkspur, columbine, or marsh-marigold, where three, five,
and several carpels are respectively present. It will be seen
that the ventral sutures face inwards, for in the fruit they will
have split open, allowing the seeds to be seen attached to their
edges. But facing inwards means facing the shortened axis or
receptacle, and since folding has taken place in this direction,
the upper surface of the leaf must bound the internal cavity.
Take a piece of stem with a foliage leaf attached, and fold this
up so that the approximated edges face the stem, and the nature
of the above process will be seen. In the single carpel of pea
the ventral suture faces upwards; and since there are five sepals,

ESSENTIAL FLORAL LEAVES. 103

five petals, and ten stamens, we may consider this odd carpel
as the remains of an outer whorl of five (cf p. 82). The four
suppressed members of this whorl must all have been on the
upper side of the one still remaining, for we see from the
columbine that the ventral sutures of a whorl are all turned
towards one another. Hence the odd carpel of pea is the sur-
viving lower or anterior member of a whorl of five. We can
show in another way that the supposed whorl would have had
its odd member placed anteriorly. The parts of the flower in
the pea are placed in fives. It can easily be seen that sepals
and petals alternate, and the same is true of the two whorls
of stamens, though this is difficult to make out in the mature
flower, owing to their diadelphous state. We can observe easily
at starting that the odd sepal is anterior. Therefore—

5 sepals —— oddone — anterior.
5 petals we posterior.
5 outer stamens _——— anterior.
5 inner stamens — posterior.

[5] outer carpels anterior.

Where, as in larkspur, &c., an apocarpous pistil possesses more
than one carpel, each has its own ovary, style, and stigma.
Examine once more the buttercup, and note that the style isa
short “beak,” upon which the stigma exists as a rough sticky
line. The ovary contains but one ovule (fig. 30, D).

Rose, blackberry, raspberry, and strawberry are further ex-
amples of apocarpous pistils composed of several or many carpels.
Kach carpel contains a single ovule. The flower of rose (fig. 40)
is perigynous, and the carpels are attached to the inner side of
the fleshy cup-like receptacle. In strawberry the style is not at
the end of the carpel, but attached to the ventral margin of the
ovary. It is, therefore, termed ventral. ‘This can readily be
seen in any one of the brown “‘seeds”’ (really fruits) scattered
over a ripe strawberry.

The syncarpous pistil (ef. p. 100) consists of a complete or
reduced whorl of carpels more or less completely united into one.
The least constant part of such a pistil is the style. When it is
absent, the stigma is sessile on the ovary. ‘This is the case, for
instance, in poppy, where the stigma is represented by a number
of roughened lines radiating from the centre. When more than
one style is present, each has its own stigma (fig. 50). Styles
generally grow from the apex of the ovary, but they may be
lateral or basal, 7.e., arising respectively from the side or base
of the ovary. ‘Their length varies considerably in different forms.
In shape the style is typically cylindrical. It is frequently bent

104 THE FLOWERING PLANT.

or curved, and in many cases its exterior is provided with hairs.
The stigma is a roughened and viscid region of the pistil. It
may be a mere spot or streak, but often forms a distinct projec-
tion. The general shape of the ovary may be described by such
terms as globular, ovoid, elongated, flattened, &c. It often pre-
sents a particular number of sides and angles, corresponding to
the number of united carpels. The ovaries of tulip and lily, for
instance, are three-sided. Prominent ribs or conspicuous veins
may correspond to the midribs of the united carpels. The surface
of the ovary is often more or less beset with hairs. One or more
ovule-containing compartments (/ocwl’) may be found within the
ovary, and we will now try to ascertain what this has to do with
the folding of the carpels. Imagine the five separate carpels of
a columbine to fuse together. An ovary possessing five com-
partments or loculi would be formed, each of which would have
an outer wall formed by the dorsal side of a carpel, and two side-
walls or dissepiments
separating it from ad-
jacent compartments
(fig. 48, G). The side-
walls would evidently
be double in nature.
Finally, the ventral
sutures would become
internal, and the ovules
would spring from the
inner angle of the
loculus. This kind of
placentation is termed
axile. Good examples
are found in orange
(several carpels), dit-
tany (five), snowberry
(four), lily (three), and
foxglove (two). It is
evident that if two or
more carpels become

Fig. 48.—Placentation and Ovules [after Prantl]. D-G. united by their edges
diagrammatic cross-sections of ovaries. D. simple ith foldi
ae E. ne showing parietal placentation. F. W ithout any toiding,

itto, but tending towards G, which represents axile
placentation ; p. placenta; v.s. ventral suture ; H-K. they would form =
straight, inverted, and bent ovules; f. funicle; mp. untlocular ovary, 2.€.,
micropyle ; int, int’. integuments ; nw. nucellus; e.s. 5 .
Aap G ka an ovary with one
compartment. This
condition is well exemplified in the three-sided ovary of violet or

pansy (fig. 51). A cross-section shows that the angles corre-

A B c

ESSENTIAL FLORAL LEAVES. -105

spond to the united edges, for at each of them is a ridge-like pla-
centa bearing ovules, This kind of placentation is parietal (fig.
48, E). The same term is applied where the united carpels are
partly folded, so that the single loculus is divided into chambers
at its margin. Thus in poppy there are a great many chambers,
and the parietal placentas, which bear an immense number of
minute ovules, project into the ovary. This can easily be verified
in the dried poppy-heads sold by druggists (cf. fig. 48, F).

Some ovaries are divided up by false or spurious dissepiments,
so called because they are not partitions formed by union of
adjacent carpels, but outgrowths from the wall of the ovary. In
yellow corydal and Dielytra, both common garden plants, the
synearpous pistil is formed by the union of two lateral carpels.
The ovary is unilocular, and the ovules are borne on two parietal
placentas, one anterior, the other posterior. Wallflower, stock,
and shepherd’s purse, which are not very distantly related, pre-
sent precisely the same arrangement, with this exception—the
ovary is divided by a partition into right and left halves. This
evidently does not correspond to the infolded edges of carpels, or
the placentation would be axile. It is, however, parietal, and
this fact, supported by comparison with the allied dielytra, &c.,
prove the partition to be an ingrowth. A study of the develop-
ment confirms this view. Again, in dead nettle and sage the
end of the style forks into anterior and posterior branches, which
leads one to suspect the existence of two carpels, one anterior,
the other posterior. The ovary, however, is fvwr-lobed, and con-
tains four loculi. This points to four carpels. The evidence
given by the style is here really correct. Development shows
that two is the actual number, but an ingrowth occurs from the
dorsal margin of each carpel, dividing its cavity into two. Borage,
forget-me-not, and their allies present the same feature, but are
even more misleading, since in them the style is undivided, or at
most slightly notched.

The inferior syncarpous ovary (fig. 48, C), though its outer wall
is partly formed by the cup-like receptacle, corresponds very
closely in form and placentation with the superior syncarpous
one. Snowdrop and orchis will here serve, respectively, as
examples of axile and parietal placentation.

There are still other ways in which ovules may be arranged.
Kach one of the ten carpels of the flowering rush contains a large
number of ovules which are scattered over the walls of the loculus,
and not limited to the united margins. This is superficial pla-
centation. It isa rare form, but also occurs in the syncarpous
pistils of white and yellow waterlilies.

Transverse and longitudinal sections of the ovary of a pink or

100 THE FLOWERING PLANT.

primrose will show that there is a single cavity into which a
knob-like placenta projects, upon which numerous ovules are
situated. This kind of placentation is /ree central. The presence
of two styles points to two carpels, but in primrose the pistil is
from the first absolutely devoid of branching or lobation. Is it
then a single carpel? If so, it would naturally have a ventral
suture, and be bilaterally symmetrical, as is the case in the pea.
But the pistil of primrose is absolutely terminal and radially
symmetrical ; and in thrift, a plant belonging to a closely related
family, the flowers agree very nearly with those of primrose,
excepting only that five styles are present. A great deal of
discussion has arisen as to the nature of the knob-like placenta
in the primrose and other forms. Some regard it as the dilated
end of the axis. If so, the placentation is axial, 7.e., the ovules
are borne by the axis, and not by the carpels. (V.6b.—Do not
confound this term with azile.) But the knob may very possibly
be more or less formed from the carpels. It is best, for the
present, to keep the word free-central, as that simply refers to
the way of arrangement. ‘There are other cases in which the
ovules are, or appear to be, developed on the axis, In docks, for
instance, a single ovule grows straight up from the bottom of the
unilocular ovary, apparently forming the end of the axis. The
florets of daisy, dandelion, sunflower, &c., present a seed-like
structure beneath the coloured corolla. This is the inferior ovary.
Although there are two cohering carpels, as shown (fig. 44) by
the forked style (cf p. 100), the ovary contains but one cavity,
from the base of which a single ovule rises. Just by the side of
it is a minute knob. This represents the end of the axis, upon
the side of which the ovule appears to be borne.

An ovule may take various directions. When growing up
from the bottom of a loculus, it is erect, as in dock. An ovule
developed on the side of a loculus is very frequently horizontal, as
in lily. Advantage is taken of this fact in procuring longitudinal
sections of the ovules, 7.e., transverse sections of the ovary are
made. Or such an ovule may be directed upwards, ascending, e.9.,
buttercup, or hanging downwards, pendulous, as in rose. If it
hangs down from the top of the loculus, it 1s suspended. Anemone
is an instance. When one or a few ovules only are present, more
attention is paid to their direction than when a large number exist.

Nectaries may be situated on the pistil. The best example of
this is found in inferior ovaries, upon the top of which a fleshy
honey-secreting cushion, commonly called the disc, is often pre-
sent. Parsnip, hemlock, and daisy are good examples. The
nectary of dead nettle is a fleshy outgrowth from the front of the
ovary.

ESSENTIAL FLORAL LEAVES. 107

Structure.—The pistil is made up of the usual three systems
of tissue, but only a few of the more important details can be
given here. Cross-sections through one of the ovaries of larkspur
or columbine will show a well-marked notch on the ventral side,
corresponding to the ventral suture. A layer of epidermis is
present on the outside, which can be traced right through the
wall where the notch occurs, after which it becomes continuous
with a layer of epidermis lining the loculus. The carpel being a
folded leaf, we might have expected this. The outer and inner
epidermis correspond, in fact, to the lower and upper layers of
epidermis in a foliage leaf (c7. p. 64), and in a very young ovary
of larkspur the margins of the carpel will be found in contact,
but not united. It is also interesting to note that the inner epi-
dermis possesses stomata as well as the outer, though they appear
to be useless in such a position. Between the epidermic layers
comes the parenchymatous ground-tissue traversed by numerous
vascular bundles. Each margin of the carpel is swollen slightly
at the ventral structure, so as to form a placenta, upon which
a row of ovules is borne, as can be seen in a longitudinal
section.

Cross-sections through a syncarpous ovary, such as that of lily,
hyacinth, or violet, do not show sharp boundaries between the
constituent carpels (cf. fig. 51). The outside is covered by a
continuous layer of epidermis, which does not dip inwards where
the carpels unite. ach loculus is lined by its own separate
layer of epidermis.

The style is sometimes traversed by a pollen canal, as in lily
and hyacinth. This canal may open to the exterior in the centre
of the stigma, as in pansy (fig. 51). More frequently the centre
of the style is occupied by a very delicate, loose, conducting tissue,
as, é.g., in fuchsia and evening primrose.

The stigma is frequently provided with delicate hairs, and its
cells generally form minute projections or papille at the surface.
They also secrete a sticky fluid when the stigma is mature.

An OVULE (figs. 48 and 49) is a minute ovoid body, in which
there is an attached base or chaluza and a free apex. The base
is in most cases fixed to the placenta by a slender stalk, the
funicle, which is traversed by a vascular bundle. The ovule is
covered by either one or two skins or integuments, within which
is a central mass of cells, the nucellus. The integuments do not
cover the extreme apex of the ovule, where a short canal, the
micropyle, is left, which leads down to the nucellus. One integu-
ment only is present in gymnosperms and most gamopetalous
dicotyledons, while there are two in nearly all monocotyledons
and many dicotyledons. In the latter case the inner coat, being

108 THE FLOWERING PLANT.

first developed, is termed the primine, the other being the
secundine.

FIG. 49.—Diagram of a very simple flower in longitudinal section [from Sachs]. d, d. leaves
of perianth cut off short; a. anther before dehiscence, cut across to show four pollen
sacs; b. anther dehiscing longitudinally; h, h. lobed stigmas upon which are pollen
grains, 7,7, i, developing pollen tubes; g. style traversed by a pollen tube, /; f, f.
ovary containing a single inverted ovule; n. funicle; p, p. outer integument; q, q.
inner integument; o. base of ovule; s, s. nucellus containing embryo sac, full of
protoplasm with vacuoles, t, central nucleus, co-operating cells, v, egg-cell, z, and
antipodal cells, wu; a pollen tube is seen entering the micropyle at m, e, e. nec-
taries projecting from the receptacle. Vascular bundles indicated by dark lines.

The ovule is termed. (fig. 48) straight or orthotropous when
nucellus and funicle (short in this case) are in the same straight

1 These two terms are often employed in exactly the reverse way.

ESSENTIAL FLORAL LEAVES. 109

line. ‘This condition is common among gymnosperms. A female
flower of yew, for instance, consists of a single straight ovule
terminating a short axis crowded with scale leaves. It is much
rarer among angiosperms. The solitary ovules of docks and
nettles are examples. Sometimes the nucellus, with its covering,
is bent or campylotropous, as in campion and shepherd’s purse.
The commonest condition, however, is the znverted or anatropous
one. Here the ovule turns sharply down on its stalk, part of
which unites with the integuments, and forms a ridge or raphe.
Cross-section of larkspur, lily, or hyacinth ovaries will show
this well. The ovules of pinus, though without stalks, must be
considered anatropous, since their micropyles are downwardly
directed.

It will be remembered that the flower was defined (p. 92) as a
spore-producing organ, and we have seen that a pollen sac is a
spore case or sporangium, producing numerous pollen grains or
spores. An ovule is another kind of sporangium, which produces
only one spore, called in this case an embryo sac, for reasons that
will presently appear. One of the cells of the nucellus in a
young ovule very early becomes larger than its neighbours.
This is the embryo sac. It does not, like a pollen grain, become
free, but is destined, if the conditions are favourable, to originate
a rudimentary plant or embryo within it, which, surrounded by
other structures developed from the ovule, will ultimately consti-
tute the ripe seed. The embryo sac in the mature ovule of the
angiosperm ! (fig. 49) is no longer a simple cell; it occupies a
considerable part of the nucellus, and its apex directly adjoins
the micropyle. In its interior is an abundance of protoplasm,
with large vacuoles, and a central nucleus, the embryo sac nucleus.
Six small cells are also contained within the embryo sac, three
at its apex and three at its base. The former are known as the
egg apparatus, the latter (being exactly opposite) as the antipodal
cells. Two of the cells composing the egg apparatus are smaller
than the third, and situated rather nearer the micropyle. They
are known as co-operating cells. The third and larger cell, the
ovum or egg-cell, is of greatest importance, since it gives rise to
the embryo.

Proofs that the Flower is a Shoot.—I. The floral receptacle is a stem
because it bears lateral members, differing from it in shape, and developed
acropetally, just as in an ordinary shoot. The internodes are usually
suppressed, but this is a common occurrence in ordinary shoots. Some-
times, too, there is a distinct internode between the pistil and other mem-
bers, or between essential organs and perianth. It happens in some

1 The scope of this work will not allow of reference to gymnosperms in this
connection.

IIo THE FLOWERING PLANT.

monstrosities (e.g., among roses) that the receptacle keeps on growing for
some time, even ending in a second flower.

II. The sepals, petals, stamens, and carpels are considered to be leaves
for the following reasons:—(1.) Like foliage leaves, they are lateral mem-
bers, developed acropetally on an axis from which they differ in shape.
(2.) They are arranged like foliage leaves, 7.e., spirally or in whorls.
(3.) As already stated, certain normal flowers present gradations from
ordinary leaves, through bracts to sepals, petals, and stamens. (4.) In
abnormal or monstrous flowers, which are especially common in cultiva-
tion, the gap between stamens and carpels is bridged over by transitions,
It also appears that any one kind of floral leaf is capable of either partial
or complete metamorphosis into any other kind. ‘‘ Double” flowers
are the best examples. In them stamens, or stamens and _ carpels,
become transformed into petals. (5.) All the various kinds of floral leaf
may, in abnormal specimens, be green in colour, and shaped more or less
like foliage leaves. The most interesting cases are those where, as in
double-flowering cherry, the carpels are in the form of small green leaves,
some quite flat and others partly folded. (6.) Very rarely a bud may
make its appearance in the axil of a petal or stamen, giving proof of its
leaf nature. ;

III. Nectaries are not found in flowers alone, but may be “extra-
floral” and variously situated.

CHAPTER IX.
PHYSIOLOGY OF THE FLOWER.

THE flower, as a whole, is, of course, supported by the stem, and,
as in other cases (but here to a less extent), the various parts
are rendered firm by vascular bundles. Flowers need protection
(1.) from certain animals, (2.) from the weather.

As regards animals, many insects, especially winged ones, and
more rarely birds, are ‘‘bidden guests.” For them nectar is
excreted, and, in many cases, an otherwise unnecessary amount
of pollen developed. For these favours, as we shall see, uncon-
scious returns are made (p. 118). Other animals have been
called ‘‘unbidden guests.” Some, ¢e.g., browsing animals, would
devour the flowers altogether, if not deterred in some way:
others, of which small wingless insects are the most important,
would carry off pollen or nectar without conferring equivalent
benefit. Protection against these attacks is secured in various
ways, more or less complete, but rarely entirely so. It is here
important to point out that one of the chief uses of the perianth
is to protect the essential organs, the pollen and the nectar.

Protection from Animals.—(a.) Browsing animals, as also soft-
bodied insects, caterpillars, and snails, are kept off to a large
extent by the presence of thorns, spines, prickles, &c., upon the
leaves and stems. Bracts are very often prickly, as, for instance,
those making up the involucre of a thistle.

(o.) Flowers always, or nearly always, contain (like some
foliage leaves) substances (as more particularly volatile oils)
which are distasteful to browsing animals and caterpillars. They
thus escape being eaten, and may even help to protect the foliage
leaves ; for when very small flowers are present in large numbers
among ordinary leaves, cattle will reject both. Dried flowers
mixed up with hay are, however, often eaten at once, as the
obnoxious substances are frequently volatile, and therefore dis-
appear in the process of drying.

(c.) In countries where white ants are common, objects such
as tables can be protected by placing their legs in vessels of
water. Many plants keep off creeping insects in a similar way.

TE2 THE FLOWERING PLANT.

Such water-holding receptacles are generally formed by rosettes
of leaves, but sometimes by connate leaves, as in the teasel,
where the cups thus constituted also digest insects that tumble
into them. It is superfluous to remark that aquatic plants are
protected from creeping land insects by the water surrounding
them.

(d.) Sticky excretions may also keep off insects. Slippery wax
(cf. p. 41) sometimes serves this purpose, but most commonly
sticky substances, excreted by the general surface of the epi-
dermis or by glandular hairs, play this part. ‘The seat of the
secretion may be foliage leaf, stem, bract, or part of the flower.
The butterwort, for instance, a small plant not uncommon in the
marshy parts of mountainous districts, possesses a basal rosette
of simple leaves, slippery from the presence of a secretion. From
the centre of the rosette rise several scapes terminated by flowers
something like small violets. The excretion, to the feel of which
the plant owes its name, is poured out from innumerable mush-
room-shaped glandular hairs. As in teasel, two purposes are
served ; for not only are the flowers protected, but the excretion
can digest small insects, and the edges of the leaf are sensitive,
curling over such insects and holding them fast. Butterwort,
therefore, is an “‘insectivorous”’ plant, and, in fact, is closely
related to the bladderwort, previously described (p. 62). Again,
gooseberry has glandular hairs on the outside of the cup- |
shaped receptacle, and Plumbago upon the calyx. <A very in-
teresting example is found in Polygonum amphibium, a plant
which grows with its lower part in ditches. When there is
plenty of water, the stem is glabrous, but it develops glandular
hairs if the water dries up. These disappear again when enough
moisture collects to surround the base of the plant.

(e.) Hair structures proper and thin hair-like outgrowths of the
corolla, &c., are often arranged so as to prevent unsuitable insects
from reaching the nectar. Instances of this kind are so numerous
that only a few can be mentioned. <A ‘‘weel” of hairs (ze, a
circlet of straight flexible hairs with ends slanting inwards) is
often found within the tube of a gamopetalous corolla, as in dead
nettle, verbena, and speedwell. In passion-flower the whole
corona is split up into narrow threads. The way to the nectar
may also be blocked by tangled masses of hairs growing on
various parts of the flower.

(7.) It frequently happens that foliage leaves, peduncles, bracts,
or else parts of the flower are so shaped or arranged as to hinder
the access of small insects. Opposite leaves (more rarely stipules
or scattered leaves) often form a kind of collar, over which in-
sects cannot climb from below. ‘This is the case in many gentians.

PHYSIOLOGY OF THE FLOWER. its

Pendulous flowers, such as snowdrop, often present an insur-
mountable barrier in the form of a slippery curved stalk. Re-
flexed bracts and perianth leaves act in a similar way. We shall
see (p. 121) that if an insect is to benefit.a flower by its visit, it
must, so to speak, go in by the front door. Bees, even such as
could get the nectar in a legitimate way, sometimes prefer to bite
a hole at the side. Certain gamopetalous corollas are frequently
found neatly drilled in this way. The calyx, epicalyx, and bracts
often check such a proceeding, either by the toughness of their
tissue, or, in the last case, by crowding. It also seems likely that
an inflated calyx, like that of the bladder-campion, is a special
arrangement for protecting the nectar. Parts of the flower are
often so arranged or shaped as to entirely or partly block up the
way to the nectar (which lies deep down in the blossom), in such
a manner that small insects are unable to get at it. Very strik-
ing examples are afforded by the personate corollas, e.g., that of
snapdragon. Only humble-bees are sufficiently heavy and strong
to force down the lower lip of this flower. Stamens may also
form obstacles. In heath the large anthers serve this end; in
harebell and Canterbury bell, the dilated bases of the filaments.
Cinquefoil secretes nectar on the inner side of the concave recep-
tacle, and the numerous perigynous stamens slant upwards and
inwards, thus forming a roof forit. Narrow or constricted corolla
tubes—knobs, ridges, or swellings in the. perianth—nectar-con-
taining spurs—crowded petals, stamens, and carpels, all these
frequently have to do with the protection of nectar from unbidden
guests. Still other devices are found.

(g.) Wingless insects are most active when the dew has evapo-
rated, and this is a signal for the closing of many flowers.

(h.) Some forms again secrete substances in parts away from
the flower, which serve to divert the attention of unwelcome
insects. Beans and vetches, for instance, possess “ extra-floral ”’
nectaries on the stipules, while common laurel, almond, and peach
develop them at the base of the leaf-stalk.

Equally varied are the means of protection against wet and wind.
(a.) Many flowers close in unfavourable weather. (b.) Parts of
the perianth often form a kind of roof or penthouse which covers
over the internal organs, and the efficiency of which is often
enhanced by a covering of hairs. Good examples are seen in the
hairy calyx and forwardly directed standard (p. 88) of gorse,
and the arched upper lip of the dead nettle. The spathe of arum
protects an entire inflorescence (fig. 33). Rain will obviously
run off the outside of pendulous flowers, such as harebell and
snowdrop, without doing them much injury. (c.) Nectar, again,
is so slippery in nature, that rain can only with difficulty wash

p32!

mac THE FLOWERING PLANT.

it away. (d.) Polypetalous flowers are the most likely to be —
blown open and damaged by wind. The sweet-pea illustrates
very well how such flowers are protected. In the first place, the
peduncles are extremely strong and at the same time flexible,
so that they yield without injury to gusts of wind. Again, the
petals are firmly locked together at their bases by means of
knobs and corresponding hollows. In this special case of the
papilionaceous flower, the most important part is specially
strengthened, 7.e., the two lowest petals are united into the keel
(p. 88). Lastly, the standard serves as a sail, causing the flower
always to point away from the wind. Further examples are
unnecessary, aS many devices are sufficiently obvious on a little
consideration.

Flowers are not organs of nutrition, but any chlorophyll they
may contain assists in the building up of organic matter (cf.

y £0).

ee is carried on very vigorously by flowers, and some
crowded inflorescences, such as those of arum, can conveniently
be used for demonstrating this process. Flowers also commonly
excrete, or pass out to the exterior, other substances besides
carbon dioxide formed by the breaking down of protoplasm (cf.
p. 11). Such, for example, are nectar and the volatile substances
to which the odour of many flowers is due. ‘These excretions are,
in a sense, ‘‘ waste products,” but they are not useless. The same
remark applies to blastocolla, the digestive juices of ‘ insecti-
vorous plants,” and the viscid substances on stems, leaves, Xc.,
by which insects are kept off.

We now come to the main function of the flower, that of true
reproduction. This differs from ‘vegetative reproduction (p. 43)
in that special reproductive cells or spores are formed. The
pollen grains, when ripe, are liberated by dehiscence of the anther,
and then, by various means, are transferred, in gymnosperms to
the micropyle of the ovule, in angiosperms to the stigma. This
transference of pollen is called pollination. ‘The viscid substance
excreted by the stigma stimulates the pollen grains to a sort of
growth ; that is to say, each of them sends out a delicate pollen
tube! (fig. 49), which grows down through the style by forcing
its way between the delicate cells of the conducting tissue, or by
traversing the slime in the canal, if this is present. Arrived at
the ovary, the tube makes its way to the micropyle of an ovule
and applies its tip to the apex of the nucellus. The two co-
operating cells now absorb some of the protoplasm from the

1 Pollen grains laid in a drop of weak (not more than Io per cent.) sugar
solution on a microscopic slide, and placed in the dark for a few hours, will
be found to have emitted pollen tubes.

PHYSIOLOGY OF THE FLOWER. II5

pollen tube and pass it on to the egg-cell. This is now fertilized,
and is able to produce an embryo plant. The union of protoplasm
from the pollen tube with the egg-cell is known as fertilization.
This leads to the formation of seed and fruit, which will be con-
sidered in Chapter X.

It might be imagined that the pollen of a bisexual flower would
generally effect the pollination of that flower. Such self-pollina-
tion can and does occur in many cases, but many arrangements
exist, often very elaborate, by which cross-pollination is brought
about, 7.¢., the transference of pollen from one flower to another,
either on the same or a different plant. Cross-fertilization,}
which follows cross-pollination, results In more numerous and
healthier seeds.

Cross-Pollination.—(1.) It is obvious that self-pollination is
out of the question in wnisexual flowers, where stamens and pistil
do not occur together. Even, however, in bisexual flowers self-
pollination is avoided in various ways. (2.) It frequently hap-
pens that flowers are dichogamous, 7.e., the stamens and stigma
are mature at different times. Dichogamy is exhibited under
two different forms—(a.) Proterandry, much the commoner, when
the stamens mature first; (b.) Proterogyny, when the opposite is
the case. (3.) Often again herkogamy is presented. In other
words, there are mechanical arrangements by which the pollen of
a flower is prevented from falling upon the stigma of the same
flower. (4.) The flowers of some plants are even sel-sterile, 7.e.,
their pollen, if it reaches the stigma, has either no effect at all, or
else a baneful one. What then are the agents effecting cross-
pollination? ‘The answer is simple—water, wind, insects, and
birds.

Some aquatic plants are water-pollinated. Perhaps the best
example that can be given is Vallisneria spiralis, a plant com-
monly found in aquaria. This possesses female flowers placed on
long spiral stalks, by means of which they can be brought to the
surface of the water when mature. The small male flowers, on
the contrary, do not possess such stalks, but when their pollen is
ripe they become detached, rise to the surface, and pollinate the
female flowers.

Wind-pollinated (anemophilous) flowers are characterized by
their small size. The perianth is often absent or imperfect ;
when present, it is regular and devoid of bright coloration.
Large size would here simply interfere with the action of the
wind and prevent pollen from being blown freely to and from
the flowers. Brilliant hues would be thrown away on an inani-

1 This term is often erroneously employed to designate cross-pollination.

116 THE FLOWERING PLANT.

mate agent, and, for the same reason, both scent and nectar are
wanting. Stamens and stigmas project well out of the flower
when they are mature, so as to catch the wind. Pollen is pro-
duced in very large quantities, as it is evident much must be
wasted, while at the same time it is dry and powdery, its grains
also being generally smooth. In firs and pines each pollen grain
is provided with a pair of little air-bladders (fig. 45), which offer
an increased surface. The stigmas, again, are remarkable for
their size and the presence of numerous hairs or roughnesses.
Frequently, too, they are branched, and, in short, are admirably
adapted for catching pollen. It is also to be remarked that the
flowers are mostly unisexual. Our native trees are for the most
part wind-pollinated, and so inconspicuous are their flowers that
many are popularly believed to have none at all. They usually
flower in early spring, before the foliage leaves are unfolded, and
this evidently has to do with the unimpeded dispersal of pollen.
All catkin-bearing trees (except willow) may be cited as examples,
the principal kinds being alder, birch, hornbeam, hazel, beech,
oak, and poplar. These possess all the above-mentioned charac-
teristics of wind-pollinated flowers. Poplar is dicecious, the others
moncecious.

Take, for instance, hazel, the flowers of which have already
been described (p. 99). The male catkins are pendulous upon
slender stalks, and the slightest breath of air can move them.
Their character is well expressed by the popular name of ‘ lambs’-
tails.” The group of pink threads projecting from the bud-like
female catkins are the forked stigmas.

The Scotch fir is another excellent example of wind-pollination,
It is monecious, and the smallest female cones (cf. p. 99) are the
ones ready for pollination. Vast quantities of pollen are pro-
duced in June, and even a gentle breeze blows it away in yellow
clouds. The so-called “sulphur showers ” of North America are
of this nature, and they often form a scum on the surface of
water miles distant from fir forests. Such a shower occurred in
Inverness-shire in 1858, covering the ground to a depth of half
an inch. More pollen is necessary in this case, since blooming
takes place when abundance of foliage is about, although the
evergreen needle-like leaves of the fir do not block up the flowers,
as broader ones would do. Between the scales of the female
cones ready for pollination a viscid substance is excreted. This
catches pollen grains, and then gradually dries up, drawing them
down to the micropyles as it does so.

Willow and lime, although their flowers possess no scent,
and an inconspicuous perianth respectively, are both insect-polli-
nated. The former is diccious (cf p. 99), and every male and

PHYSIOLOGY OF THE FLOWER. oO

female flower possesses a nectary at its base. The lime blossoms
in summer, is markedly proterandrous, and characterized by fra-
grance and abundant nectar. Bees are excessively fond of it.

Some smaller plants than those described are wind-pollinated,
as docks, sorrels (not wood-sorrel), nettles, rushes, wild plantains,
sedges, and grasses.

Docks have numerous small bisexual flowers, arranged in
terminal and axillary racemes. Each flower can easily swing
about on its slender pedicel. Both calyx and corolla are incon-
spicuous, each consisting of three members, stamens six. The
syncarpous pistil possesses three short styles, each terminating in
a fringed stigma.

Sorrels are similar, but the flowers are unisexual.

Rushes possess small brown bisexual flowers, arranged in
panicles, and often proterogynous. All the floral leaves are in
alternating whorls of three, viz., three free sepals, three free
sepaloid petals, three outer and three inner stamens, on slender
filaments ; three carpels, united into a superior ovary, with short
style, and three rough spreading stigmas.

Nettles (cf. p. 100) are remarkable for the elastic nature of
their filaments, which, when the flower-buds open suddenly, scatter
the light pollen in the air.

Wheat may serve as an example of a grass. The inflorescence
is here a compound spike, the bracts and bractlets of which are
overlapping scales, known as glumes. Numerous
spikelets are situated on the main axis, in two
alternating rows. Hach spikelet possesses a short
axis, bearing from three to five sessile flowers,
also in two alternating rows. These flowers are
in axils of glumes, termed lower pales (flowering
glumes). Each of these is produced into a short
spine or awn (very long in barley). The two
lowest flowers are rudimentary, and the large
lower pales belonging to them ensheathe the base
of the spikelet, and receive the special name of
outer glumes. Hach flower has an upper pale on

E . : : : Fig. 50.—klower of
its inner side, and consists (fig. 50) of arudimen- — Grass, magnified ;

tary perianth, three stamens, and a syncarpous cee
pistil. The perianth is constituted by two small _ thery stigmas; e.
scales, the lodicules, which expand when the ‘S*tls anthers.
flower is mature, force the glumes apart, and allow the essential
organs to project externally. The stamens, when mature, elon-
gate very rapidly. Their delicate filaments and versatile anthers
are well adapted for catching the wind. ‘Two feathery stigmas

grow from the top of the superior ovary.

118 THE FLOWERING PLANT.

Sedges, again, possess minute flowers, often unisexual. The
perianth, when present, is reduced to bristles or scales, the
stamens have slender filaments, and there are two or three
spreading roughened stigmas.

Wild plantains are all characterized by the following features,
which, after what has been said, will speak for themselves.
Flowers small, green, bisexual, arranged in spikes (or heads),
proterogynous. Sepals four. Corolla salver-shaped, with.four
small lobes alternating with the sepals. Stamens four, epipeta-
lous, alternating with corolla lobes, possessing long slender fila-
ments and large versatile anthers. Style long, covered with hairs
and with two stigmatic lines. As might be expected from such -
a description all wild plantains are pollinated mainly or entirely
by the wind.

Insect-pollinated (entomophilous) flowers are as conspicuous as
wind-pollinated ones are insignificant. They are characterized by
some or all of the following features. Perianth brightly coloured,
often irregular; pollen grains mostly rough or sticky; odorous
and nectar-producing. A modern botanist graphically describes
the state of things thus :—‘‘ The animate [pollinating] agent .. .
as a general rule is an insect. This must be allured to the
flower ; and this accordingly appeals to either sight or smell by
brilliant colours and by attractive scents. These colours and
these scents draw the insect to a flower from a distance ; but by
themselves they would be but empty gratifications, unprofitable
to insect and to flower alike. Something more substantial must
be afforded, something that will prevent the insect from merely
loitering about the flower in idle satisfaction, and that will induce
it to probe the recesses of the blossom, and in so doing to transfer
the pollen of one flower to the stigma of another. This further
allurement is addressed to the palate; and though in some cases
it is nothing more than the pollen itself, in most it is supplied by
the secretion of a sweet fluid, the so-called nectar.

“Now Nature, who at first sight often appears a prodigal, is
always found, on closer examination, to be the most rigid of
economists. If no insects are to be allured, she gives... no
nectar ; she cuts off the bright petals, and suppresses the attrac-
tive odours. Nor even when a bait is wanted will she give it
one minute sooner than necessary. The brilliancy, the scent,
and the nectar are only furnished when the flower is ready for
its guests, and requires their presence; just as a thrifty house-
wife lights her candles when the first guest is at the door. The
mature bud is furnished with no such attractions. Still more,
even when the flower is mature, when its pollen is ready for
transference or its stigma for pollination, when all the allure-

PHYSIOLOGY OF THE FLOWER. I19Q

ments are consequently displayed and insects invited to the feast,
she still shows her economy. Guests might come who were not
of sufficient importance, and the banquet be wasted on them ; for
it is only when insects have a certain shape, size, or weight that
she requires their visits, and can use them profitably for her
purposes. She requires, moreover, that they should make their
entrance by the main portal, which she has specially adapted to
suit their and her requirements. All insignificant and unre-
munerative visitors, all such, moreover, as would creep in by the
back entrance, must be kept out... .”!

We will now first of all consider, in a general way, the most
important features, and then briefly review the arrangements
found in certain well-known flowers.

Conspicuousness.—The corolla, calyx, bracts, and even the
flower-stalk, may all display more or less colour. In the simpler
flowers yellows are displayed, which seem attractive to small
insects and beetles. White in a great many cases either attracts
small insects or night-flying ones. A walk round a flower-garden
in the dusk will show how conspicuous white flowers are at this
time. ed is found in many of the most complex flowers, and
reddish-brown blooms are often visited by wasps and carrion
insects. Purple and blue are the rarest colours. They are pre-
ferred by bees. Aggregation of flowers of course makes flowers
much more conspicuous than they would otherwise be, as a
blossoming gorse-bush or bed of foxgloves will show. This is
one reason for the existence of inflorescences, and the small size
or absence of bracts in many of them. Even very small flowers
may be made striking by aggregation, as especially is parsnip,
hemlock, &c., and Composites like sunflower and daisy. Flowers
may even possess a much enlarged perianth (accompanied by
corresponding reduction of the essential organs), by which their
efficiency as “flags” is increased. This is the meaning of the
ligulate ray-florets of Composites, which are either female or
neuter, as in daisy and millefoil on the one hand, dahlia and sun-
flower on the other. Compare in this connection the compound
cymes of the closely allied elder and guelder rose. The former
possesses numerous small white flowers, and, though scented,
secretes no nectar. It is visited by insects to some extent. In
guelder rose the outer flowers are enlarged and neuter, while the
inner ones secrete nectar, by which many insects are attracted.?
The same tendency is seen in some Umbellifers, as cow-parsnip
and carrot. Here all the flowers are small, and the corollas of

1 Ogle, in the preface to his translation of Kerner’s “‘ Unbidden Guests.”
2 A cultivated variety produces neuter flowers only. Hydrangea is a
similarly abnormal case.

120 THE FLOWERING PLANT.

the outer ones irregular and much larger than in the inner
ones.

The most closely related flowers often differ remarkably in
character, and this is correlated with differences in pollination.
Compare, for instance, the common mallow (Malva sylvestris)
and the dwarf mallow (MZ. rotundifolia). 'The flower of the former
is much the larger, and the numerous stigmas form a tuft above
the ends of the monadelphous stamens (cf. p. 95). It is insect-
pollinated. The latter has much smaller flowers, and the stigmas
and stamens intertwine, favouring self-pollination. A similar
pair is found in the large-flowered, proterandrous rose-bay willow
herb (Hpilobium angustifolium), and the small-flowered willow
herb (£. parviflorum), the stamens and stigmas of which mature
simultaneously. The following table! compares, in this connec-
tion, four of our native wild geraniums.

| Blue Meadow Mountain | Dove’s-Foot Small-Flowered
Geranium | Geranium Geranium Geranium

| (G. pratense). | (G.pyrenaicum). (G@. molle). (G. pusillun).

| | - : es

|
Flower . 4 Large. Small. Smaller. Smallest.
Proterandry Complete. Partial. Partial. Slight.
Pollination Never self- ee Often self- | Generally self-

Monocotyledons are remarkable from the fact that, although
they include some of the minutest wind-pollinated forms (sedges,
grasses, and rushes), yet, on the other hand, many of the most
conspicuous flowers are found among them. Not only is the
calyx frequently as bright as the corolla, e.g., in lly, tulip, and
hyacinth, but also stamens may become petaloid, as in orchids
(cf. p. 88), and the three styles of 277s are in the same condition.
Their bracts also are frequently petaloid, as in many orchids and
hyacinth, while in some exotic arums the enlarged spathe plays
the part of a corolla. In many arums, too, the fleshy axis of the
spadix compensates for the lack of perianth.

Odour.—This varies according to the visitors required. ra-
grant flowers attract bees, butterflies, moths, and higher insects
generally, while more rarely JSoetid odours are given out with the
view of enticing flies. Many flowers which to us appear scentless
are probably not so to insects, which seem to be gifted with
unusually keen powers of smell. There can be no doubt, for

1 Modified from Lubbock.

PHYSIOLOGY OF THE FLOWER. 121

instance, that nectar, whenever present, is powerfully odorous
from the insect point of view, even when in minute quantities.
A jar of honey possesses a well-marked odour, easily perceived
by us, but a minute drop of the same appears scentless; yet to
an insect such a drop is relatively large. Nectar that is com-
pletely hidden from sight will thus be smelt out, just as wasps
rapidly find their way through the open window of a room con-
taining sweet stuffs.

A powerful scent is often more attractive to insects than bright
colour or large size, as may be well seen by comparing certain
closely allied forms. Thus, the sweet violet is visited much more
frequently than the larger and brighter, but scentless, pansy.
Similarly, the small field bindweed (Convolvulus arvensis) is a
much greater favourite with insects, owing no doubt to its
fragrance, than the large white odourless form, Calystegia sepium.

The willow and lime (cf: p. 116) are good examples of inconspicu-
ous but insect-pollinated flowers, which attract by fragrance.

Mignonette also makes up for its insignificant appearance by
a fragrant smell and the excretion of abundant nectar on the
back of a sort of plate which projects from the floral receptacle.
It is a favourite with certain bees.

Flowers pollinated by night-flying insects reserve their fra-
grance for this time.

The preceding features concern the attraction of insects ; the
following have to do with their reception.

Trregularity.—This always has reference to insect visitors.
By it a landing-stage is generally provided, as in labiate flowers,
and it may also have to do with the excretion of nectar, as in the
spur of toad-flax, or the storing of nectar, as in pansy (fig. 51).
The landing-stage is always in such a position that the insect is
brought into contact with stamens and stigma. If a part of its
body gets dusted in one flower, things are so arranged that this
part will touch the stigma of some other flower, and soon. It
is also to be remembered that irregular flowers lay themselves
out to secure the services of special insects, and, in such cases,
correlated modifications of structure are found in insect and
flower. This may be advantageous, as insects are often kept in
this way to the same kind of flower, and therefore effect cross-
pollination more certainly than they otherwise would ; but there
is a corresponding disadvantage. Thus, red clover sets no seed
in some of our colonies, owing to the absence of humble-bees, by
which, in this country, it is usually pollinated. This flower also
shows in what a complex way organisms are linked together, for,
to use a well-known illustration by Darwin, red clover is depen-
dent on cats for the formation of its seeds. These animals destroy

122 THE FLOWERING PLANT.

field-mice, which, if left to themselves, would cause the extinction
of humble-bees (here the pollinating insects) by demolishing
their nests.

Some regular flowers, however, also court the visits of special
insects, and in these the nectar is excreted at the bottom of a
long corolla tube, and is only accessible to the long proboscis of a
butterfly or moth.

An instructive comparison has been drawn between regular
and irregular flowers in reference to the number of insect visitors.
The following conspicuous regular flowers, with nectar easily
reached, have the number of useful guests shown by the figures :—
Meadow buttercup (over 60), blackberry (67), wild strawberry
(25), hawthorn (57). In striking contrast to this are larkspur
and monkshood (larger bees only), foxglove (3), toad-flax (about
9 bees), early purple orchis (8). All these are conspicuous,
irregular, and with nectar difficult to reach.

Honey-Guides.—Many flowers are spotted or streaked with -
bright colours in such a way as to indicate the position of the
nectar. The petals of geraniums and the lower lips of many
labiate corollas show this. Prickles may also serve as “ path-
pointers.”” When intended to keep off creeping insects, they are
generally directed downwards, while, if turned up, they may have
the other function. Both these points are illustrated by the
involucres of thistles.

Honey or Nectar.—As already shown, this may be excreted by the
most various parts. It is always situated deep down in the flower.

Pollen.—This, as stated above, is either rough or sticky, being
thus adapted for clinging to the bodies of insects, and at the
same time prevented from being blown away. Where the
arrangements for effecting crossing are simple, many stamens
and much pollen may be present, while if these are complex the
converse is often true.

We will now take a few special cases in illustration of the
points involved in cross-pollination, commencing with simple
regular flowers, and ending with complex irregular ones. Space
will only admit of very brief descriptions.

I. Regular Flowers.—Buttercups are as simple here as in
structure. Numerous small insects are attracted by the yellow
colour, and in obtaining the nectar, are pretty sure to get dusted
with pollen, especially as the outer stamens are matured first.
Moderately proterandrous.

The poppy is visited for pollen, of which a superabundance is
formed by the numerous stamens. The broad flattened top of
the pistil is well adapted as an alighting platform, and it also
bears the radiating sessile stigmas.

PHYSIOLOGY OF THE FLOWER. 123

Raspberry, blackberry, strawberry, apple, and hawthorn all agree
in the possession of numerous stamens and excretion of honey
by the receptacle. In blackberry the stigmas are mature before
the inner stamens, which turn outwards as they ripen. The last
three display well-marked proterogyny, and, except the straw-
berry, are sweet-scented.

Roses do not excrete nectar, but are visited for pollen. The
styles and stigmas project in the centre, and form a landing-
place, so that crossing must often be effected, although many
stamens are mature at the same time.

Gooseberry, red currant, and black currant possess small greenish
flowers, with minute petals, and five stamens. Nectar is excreted,
however, from the top of the inferior ovary, and the first is pro-
terandrous and self-sterile.

Snowdrop excretes honey in groves on the inner surfaces of the
small petals, upon which green streaks serve as honey-guides.
The pendulous flower is approached by flying insects from below,
when they are sure first to touch the stigma, which is placed on
the end of the simple style that projects beyond the six stamens.
The anthers dehisce by pores at their pointed ends, so that pollen
can readily fall out upon an approaching insect.

Wallflower and stock do not present many remarkable features.
The stamens are tetradynamous, and the shortness of two of
them is partly due to the fact that they have to curve round two
of the nectaries, which are here small rounded green projections
of the receptacle between them and the ovary. Two other similar
nectaries are also present, one outside either pair of long stamens.
The long claws of the petals are held firmly by the calyx against
the structures within, and an insect alighting upon the platform
constituted by the spreading limbs is, if already dusted with
pollen, pretty likely to deposit some on the stigma, and to carry
off a fresh supply while probing down to the nectar.

Fuchsia is attractively coloured, and abundant honey is excreted
by the top of the inferior ovary. Pollination takes place as in
snowdrop, but the stigma is protruded more, and the anthers
dehisce by slits. In fuchsia and snowdrop there is no specialized
arrangement for causing pollen to fall upon insects. .

Heath (not heather) provides for this in a rather elaborate
way. The flower is pendant, and the contracted mouth of the
urceolate corolla (for the shape of which we shall now see a
reason) is almost blocked up by the style and stamens. The
former projects somewhat, ready (as in most pendulous flowers)
to receive pollen from approaching insects. The stamens, eight
in number, arise from a honey-excreting receptacle, and their
anthers form a ring round the style. The pollen escapes from

124 THE FLOWERING PLANT.

terminal pores, but, in the undisturbed state, is prevented from
falling out by the apposition of adjacent pores. Further, a
slender process or “tail” stretches from the base of each anther
towards the corolla. A bee, in trying to thrust its tongue up to
the nectar, is sure to touch some of these tails, the anther-ring is
disarranged, and a shower of pollen falls down.

Barberry possesses irritable stamens. An insect landing on
the top of the syncarpous pistil (which possesses a stigmatic
margin) is sure to touch them in trying to get nectar, here ex-
creted by paired nectaries on the bases of the six petals. ‘The
stamens then spring suddenly inward, not only dusting it with
pollen, but often frightening it off to another flower.

We now come to some flowers in which examination of several
specimens will show that the same relative position is sometimes
occupied by the stamens, sometimes by the stigma.

In the pink, for instance, there is well-marked proterandry,
and a young flower presents five stamens projecting in the centre.
Later on these wither, and the two stigmas are protruded in the
same place. In this case we have successive elongation of organs
which are rendered parallel by the enclosing claws of the petals.

A similar end is served by movement of the stamens in the
blue meadow-geranium. Here the style rises in the centre of the
flower, and (as this is another case of proterandry) the five lobes
(stigmatic internally) which terminate it are at first closely
pressed together. There are five spreading petals and ten spread-
ing stamens. The outer five of these rise parallel to the style,
shed their pollen, and retire, their action being followed by the
five inner stamens. Now the stigmas separate, and can be polli-
nated. Note here that maturity is reached from without inwards,
as in a centripetal inflorescence.

The rosebay willow-herb, which, by the way, presents a case of
proterandry known since 1790, attains the same end by move-
ment of the style. The whole flower is epigynous, with four
spreading sepals, four spreading petals, and eight stamens
directed downwards. The style, which resembles that of the
geranium just described, but possesses four lobes only, at first
curves back between the petals. After the pollen is shed it
bends forwards, and the four stigmas expand. It is hardly
necessary to remark that, in the four cases described, different
flowers are in different stages at the same time, so that the
expanded stigmas are sure of receiving pollen.

Similar results to the preceding are attained, without pro-
terandry, in primrose and purple loosestrife, by the occur-
rence of bisexual flowers of different kinds (heteromorphism or
heterostyly).

PHYSIOLOGY OF THE FLOWER. 125

A bunch of. primroses,! examined with a little care, will show
that the flowers are of two kinds (dimorphic)—(1.) long-styled,
with the stigma in the throat of the corolla tube, and anthers
deep down in it; (2.) short-styled, with these positions reversed.
Imagine now, in a long-styled flower, an insect alighting on the
convenient platform afforded by the salver-shaped corolla, and
inserting its trunk into the tube to get nectar. A particular
part of the trunk will be dusted with pollen, and, if a short-styled
flower is next visited, that part will touch the correspondingly
placed stigma. A new part will also be dusted, with similar
result. Moreover, the pollen from a short-styled flower is made
up of /arger grains, since the pollen tubes are destined to reach a
greater length.

Purple loosestrife is trimorphic, t.e., possesses three kinds of
flowers, each of which has a style of certain length, and two sets
of stamens different from the style and from another in that
respect. Thus there are the following three sorts of flower :—
(1.) Long-styled, with medium and short stamens; (2.) mediwm-
styled, with long and short stamens ; (3.) short-styled, with long
and short stamens. A little consideration will show that pollen
from a stamen of particular length will be carried to the stigma
of a style of the same length. ‘The best effect will be thus pro-
duced, but other combinations are not excluded.

Although the wild arum (fig. 33) has no perianth, yet it is
degraded from a condition when a regular one was present, and
so may be considered here. The inflorescence has already been
described (p. 76). The aborted upper male flowers form a circlet
of threads radiating downwards and touching the spathe. Small
insects, attracted by the bright axis, can enter, but are not able
to get out again. The female flowers are first matured, and
some of the insects are likely to carry in pollen for their benefit.”
After pollination they excrete nectar, no doubt to the great joy
of the hungry captives, which remain in durance, however, till
the pollen is shed, when they, all dusty, are freed by withering
of the chevaux-de rise. Gladly they sally forth, and perchance
falling into a like prison, brush their coats against a new lot of
stigmas.

A pretty arrangement for preventing self-pollination is found
in zris. This presents three admirable landing-stages for bees
in its reflexed petaloid sepals. Facing the alighting insect is a
stamen with outwardly dehiscing anther, arching over which is
a little shelf borne by a petaloid style. The stigmatic upper side
of this shelf is likely to be pollinated as the insect settles. The

1 Chinese primrose, cowslip, oxlip, or polyanthus will serve equally well.
* As many as a hundred small insects have been found imprisoned.

126 THE FLOWERING PLANT.

nectar is excreted deep down between sepal and style, and the
bee, in backing out, rubs its head against the anther. The little
shelf is not stigmatic below, and is simply lifted up out of harm’s
way for a moment.

The most daring way by which self-pollination is avoided by
regular flowers is where the style actually assists in the distribu-
tion of pollen. ‘This is seen in harelell (and Canterbury bell) and
many Composites. In the former case the anthers shed their
pollen before the flower opens, and a great deal of it adheres to
the hairy outer surface of the style. Later on, the three (or
more) lobes in which the style terminates expand and display
their stigmatic inner surfaces.

The regular disk florets of a daisy or sunflower will illustrate
the method in many Composites, and show the meaning of
syantherous stamens. ‘Take, for example, a half-blown example
of the larger form. The youngest inner florets are still shut.
Outside these come a large number in which the brown anther-
rings are very conspicuous. Dehiscence is internal, and by
looking at older and older florets (7.e., passing gradually to the
outside), you will find that first a small heap of pollen is seen on
the top of the anther, and then the elongating style gradually
emerges. It is provided with a little brush of hairs at its end,
and, in fact, sweeps the pollen clean out of the tube, afterwards
spreading into two lobes, stigmatic, as will be anticipated, mter-
nally. The most external disk-florets will be found already
pollinated, with stigma and stamens withered. Aggregation
not only renders Composites conspicuous, but also makes them
favourites with insects, since a great deal of nectar is attainable
in a small area. Their visitors alight in what must relatively
be a perfect thicket of anthers and stigmas in various stages.
Cross-pollination cannot but be extremely frequent.

IL. Irregular Flowers.—Larkspur contrasts strongly with the
closely related buttercup. Bees alight on the large petaloid
sepals (cf. p. 85), and to reach the nectar contained in the two
spurred petals, must pass their tongues through a small opening
between the upper leaves of the perianth. Now the principle
alluded to on p. 121 comes into play. The stamens mature first,
and successively raise themselves into this opening, retiring
afterwards. Lastly, the stigmas ‘are lifted up into the same
position.

Indian-cress (so-called garden nasturtium) works on the same
lines, but the nectar is here contained in the spur of the gamo-
sepalous calyx.

Papilionaceous flowers present many interesting modifications.
In all of them the wings (cf. p. 88) serve as a landing-stage,

PHYSIOLOGY OF THE FLOWER. 127

and the weight of the insect effects more or less disarrangement
of parts. There are four chief ways of action :—

(1.) In bird’s-foot trefoil and lupin the pollen collects in the
end of the keel, and when an insect alights, some of it is forced
out and the stigma is also protruded.

(2.) Clover presents similar features, but the stamens are pro-
truded as well.

(3.) Sweet and everlasting peas, broad bean, and scarlet runner
possess a style which presents a hairy region near its end, the
use of which is to sweep out pollen. The stigma is also protected
by hairs from self-pollination.

Scarlet runner is the most complicated, and here the keel is
drawn out into a narrow spiral “snout,” occupied by the similarly
curved style and stamens. The pressure of a bee on the wings
causes the oblique stigma, protected by a circlet of hairs, to be
protruded, and then the hairy part of the style with its attached
pollen grains.

The seven flowers just described all recover their normal shape
when the insect leaves, but in (4.) broom and gorse the newly-
opened flowers are in a state of tension. ‘The pressure of a bee
causes it to ‘‘explode,” as the projections at the bases of the
petals are unlocked from the corresponding depressions.

Where the stamens are monadelphous, as in lupin, broom, and
gorse, pollen only is afforded. The remaining flowers named
above excrete nectar on the inner side of the staminal tube, and,
as the upper stamen is free, this can readily be reached from
above.

Pansy (fig. 51) recalls the heath, in that it presents a special
arrangement for dusting its visitors. Here the base of the style
is slender and bent, while the stigma is dilated, hollow, and pro-
vided with a receptive lip facing downwards. The anthers with
their triangular appendages closely surround the style, leaving,
however, a space between them and it, which receives the shed
pollen. If an insect now alights on the lower petal, its proboscis,
when thrust into the spur, must touch the stigma-lip, upon which
it leaves pollen if other flowers have been previously visited. At
the same time the insect’s head will push against the head of the
stigma, causing the slender style to bend and pollen to fall out.
The proboscis when drawn out folds up the stigma-lip (cf. iris),
and any grains that happen to be on it at once adhere to the
sticky fluid with which the-stigma is filled. V¢olet is similar, but
the stigma is shaped differently.

We are now in a position to understand why the posterior
stamen is aborted in so many irregular flowers (c/. p. 94). The
style is thus enabled to occupy the upper side of the corolla, out

128

THE FLOWERING PLANT.

of the way, so to speak. An upper stamen would be so blocked
up by it as to be of little use. |

FIG. 51.—Structure of Pansy [from Sachs].
All but A. magnified. A. longitudinal
section of flower. B. ovary and anthers,
the former fertilized and swollen; the
filaments have been broken off and the
anthers carried forwards by growth of
ovary. C. stigma, style, and top of ovary.
D. transverse section of ovary. E. trans-
verse section of young anther, showing
two pollen-sacs in each lobe and con-
nective uniting lobes; v. bracteole ; 7, U’.
sepals; ds. appendage of sepal; ¢, ¢, ¢.
petals; cs. spur of lower petal; a. anthers ;
J. filaments; fs. nectar-excreting appen-
dages of lower stamens; n. stigma; o.
opening of stigma ; Jp. lip of stigma; gr.
style; fK. top of ovary; sp. placentas ;
sk. ovules.

Take, for example, foxglove.
The lower lip forms a landing-
stage from which an insect can
creep into the bell. Only a large
form like the humble-bee is use-
ful, as the size of the corolla pre-
vents others from touching the
stigma and anthers. The flower

is to some extent proterandrous,

and, as in so many cases, the
stigma projects beyond the sta-
mens. The didynamous con-
dition is well adapted for dis-
playing the anther lobes, which
are at first transverse, but after-
wards move into a vertical posi-
tion.

The personate corollas of toad-
flax and snapdragon can only be
forced open by bees. In the
latter case humble-bees are
almost the sole visitors, as others
are not strong enough to press
down the lower lip.

Musk is particularly interest-
ing among lipped forms, from
the fact that the stigma is in
the form of two flattened sens7-
tive (especially in the large
scentless musk) lobes, which
close on contact. Pollen can
thus be deposited in it by an
arriving, but not by a departing

uest.

White dead nettle presents an
arrangement common in labiate
flowers. The lower lip forms a
convenient landing-stage; the
upper one not only protects the
stamens and pistil, but keeps
them pressed firmly down. A

visitor settling on the lower lip touches first the forked stigma,
which hangs down a little, and then the anthers of the didy-

PHYSIOLOGY OF THE FLOWER. I29
namous stamens. This flower also presents other points of
interest. The corolla tube is strengthened by a backward bend
just where the weight of an insect produces most strain, and the
tube of the calyx is also thickened. Unbidden guests are deterred,
not only by the general hairiness of the plant, but also by a weel
of hairs in the corolla tube.

The allied forms thyme and wood-sage are both proterandrous.
The former reminds one of the pink (p. 124), since first the four
stamens project from the corolla, two at a time, diverging widely,
and then the style grows rapidly, its forked end sticking right out
of the flower. Wood-sage takes advantage of the rudimentary upper
lip to curve its stamens sharply back after their pollen is shed.

The two next examples, meadow-sage and orchis, show in a
very striking way the reduction in number of stamens that is
often associated with elaborate arrangements.

Meadow-sage (also garden-sage and a large red garden form) pos-
sesses only two fertile stamens, and these are modified (« f. P- 97)
in a very curious way. ‘The filaments are
short, and the elongated curved connec-
tives are loosely swung upon them. The
longer upper part of each connective bears
a fertile anther lobe, while the shorter
lower part is united with its fellow into
a curved plate! When undisturbed, the
anther lobes are situated under the hood-
like upper lip, and the forked stigma
projects beyond them, well out of the
way of self-pollination. If, now, a bee
lands on the lower lip of the corolla and

Fic. 52.—Semi-diagrammatic

probes the tube for nectar, its head is sure
to strike against the curved plate men-
tioned. ‘The result is that the anther lobes
are swung downwards and forwards so as to
deposit pollen on its back. Further, the
sage is markedly proterandrous. The
stigma of the young flower is placed too
high to be touched, but when mature it
bends downward and hangs in front of the
flower, so that it must be touched before a
bee can settle on the lower lip.

Early purple orchis (fig. 52). The flower

has already been partly described (Pp. 88).

flower is occupied by the “ column,”

Viewof Early Purple Orchis
[original]. 1. St. stem;
Br. bract; S, S, S. sepals;
P, P. upper petals; L. la-
bellum, the streaks are
honey-guides, directed to
the opening of the spur
(shaded black); Sp. spur
of labellum; An. bilobed
anther dehiscing by slits ;
R. rostellum, below which
isthe broad stigma(dotted);
Ov. inferior ovary, twisted
so that posterior side of
floweris below. 2. pollinia,
immediately after removal
by pushing end of pencil
against rostellum; 3. the
same a little later.

The centre of the

or top of the pistil with a

1 Though two fertile stamens are present, they only produce as much pollen

as one, for each has but one anther lobe.

I

130 THE FLOWERING PLANT.

sessile anther upon it. Hach lobe of the anther contains an
agglutinated club-shaped pollen mass or pollinium. The stalks of
the two pollinia slope down to a little viscid knob, the rostel/um,
below which is a broad sticky stigma. A bee alighting on the
labellum, for the purpose of piercing the tissue of the spur and
licking up the sweet sap (nectar is absent), is sure to strike the
rostellum, which becomes detached, and draws with it the pol-
linia. The bee leaves the flower with these structures attached
to its head like a pair of horns. They soon droop forwards, and
are likely to strike the stigma of the next blossom visited, these
remaining in whole or part.

Some American flowers are bird-pollinated, their visitors being
humming-birds, and in some cases small insects are not excluded,
as they attract these larger useful visitors. It is also believed
that many Cape flowers, excreting as they do large quantities of
nectar, are specially suited for the visits of small birds.

Self-Pollination.—The fact that the majority of flowers are
bisexual leads one to suspect that this process occurs not unfre-
quently. Many forms which lay themselves out for cross-pollina-
tion provide for the other form as a last resort. ‘Thus, in the
forget-me-not, the stigma at first protrudes from the flower, but
later on the corolla tube elongates, and brings its circlet of sessile
anthers to the same level. Again, in Composites, the branches
of the stigma, if not cross- pollinated, sometimes curl round and
touch the top of the anthers with their receptive inner surfaces.
This curving regularly takes place in certain small self-pollinated
Composites, as groundsel.

Little specialized forms, like buttercup and rose, must often be
self-pollinated, and the only perfect bars are complete dichogamy
and self-sterility.

Comparison of several closely allied flowers often bring out the
fact that the smaller ones are self-pollinated (cf p. 120). Com-
pare, for instance, the large white flowers of stitchwort with the
small ones of chickweed. Regularly self-pollinated flowers are
characterized by inconspicuousness, partly due to their small size
generally as a whole, and still more to the minuteness of the
petals, which are white or pale and devoid of honey-guides.
Scent and nectar are practically absent, and the stigmas are so
placed that pollen can easily reach them from the anthers of the
same flower. The stamens are often few in number, and pro-
duce comparatively little pollen.

All this is carried to the extreme in cleistogamous flowers, 7.e.,
minute self-pollinating ones, which never open, and exist in —
addition to ordinary ones, The best example is dog-violet. In
summer the ripe fruit of the cross-pollinated flowers will be found,

PHYSIOLOGY OF THE FLOWER. Rae

and, close to these, minute bud-like structures. These are the
cleistogamous flowers ; their anthers are so placed that the pollen
grains can send their tubes straight to the stigma. Such a flower
produces, perhaps, only two hundred pollen grains, as opposed to
some thousands in an ordinary blossom.

Fertilization results in changes in the egg-cell, nucellus, in-
teguments, carpels, and frequently other parts as well. The
fertilized egg-cell gives rise to an embryo, the primary root of
which is directed towards the micropyle. Nutritive substances
are formed in the nucellus, known as albumen. This is endosperm
if produced in the embryo sac, perisperm if originated outside it.
Seed-coats are developed from the integuments, while enlargement
and other changes in the carpels, &c., give us fruits.

Motility, irritability, and spontaneity have been sufficiently
illustrated by the movements often performed in connection with
pollination.

CHAPTER X.
SEEDS AND FRUITS.
MORPHOLOGY.

A seed or matured ovule belongs to one of two categories : (1.)
exalbuminous, (2.) albuminous, 2.e., without and with albumen
respectively.

A broad bean is a good example of the former sort. If pre-
viously soaked in water the examination will be facilitated. A
black mark will be seen at one end. ‘This is the scar or hilum,
from which the stalk has been detached. As the ovule was
inverted (p. 104) the seed must be so. The micropyle should
therefore be close to the scar (fig. 49), and in squeezing the seed
a drop of water will ooze out, and prove its presence. A trian-
gular swelling on this side! the scar marks the position of the
radicle, which is in part (cf p. 143) the primary root of the
~embryo. A slight ridge, the raphe (p. 109), runs from the other
side of the scar half way along the seed to what correspond with
the base of the ovule, exactly opposite the micropyle. The long
axis of the seed is therefore the direction of breadth. A skin or
seed-coat can readily be peeled off, consisting of a thick outer and
a thin inner layer, developed respectively from outer and inner
integuments of the ovule. The greater part of the seed is made
up of two thickened fleshy cotyledons or seed-leaves, which are the
first leaves of the embryo (cf. figs. 2 and 5). Note also the white
pointed radicle. Now separate the seed-leaves, and observe that
the radicle is continuous with a minute curved plumule, or primary
shoot. The space within the seed-coats is entirely occupied by
the embryo, and all trace of the nucellus has disappeared. The
presence of two seed-leaves characterizes dicotyledons generally.
A dried pea, the kernels of almond and hazel-nut,.apple and
orange pips, can all be understood by comparison with bean.

A large and typical albuminous seed is that of castor-oil, obtain-
able from any druggist. It is oval, flattened, and mottled. At
one end is a small knob, the caruncle, which marks the position
of both hilum and micropyle, for the seed is a reversed one.

1 J.e., left when the bean is placed so that the scar is below and to right.
132

SEEDS AND FRUITS. i328

Comparison of cross and longitudinal sections shows that we have
here a straight embryo lying in the centre of the seed, with its
radicle pointing towards the caruncle, and a pair of flat, beauti-
fully veined seed-leaves closely pressed together. There is no
evident plumule. Surrounding the embryo is a cheesy substance,
the albumen, which fills up the space between it and the seed-
coat. With care, it can be scraped away, leaving the embryo
entire. The seeds of violet can be understood after examina-
tion of the preceding, but the embryo is much smaller in propor-
tion (cf. fig. 53), while in buttercup (fig. 30) and larkspur most
of the seed is occupied by albumen. In all these ae hs
cases the nutritive matters are formed in the
embryo sac, which increases in size and fills up
the whole of the space within the seed-coat. Such
albumen is called endosperm. In a few cases,
however, the embryo sac, with its contained endo-
sperm, is comparatively small. Most of the albu-
men is in this case perisperm, and belongs to the
nucellus. ;

Examine now a grain of maize (Indian-corn). yy, .. section
This is really a fruit, as it includes the wall of of Albuminous
the ovary, here dry and closely adherent to the Pee wane
seed. A little pointed projection on the broad end — rounded by en-
of the grain is the remains of the style. The yellow Si weet
part of the grain is endosperm, but on one side, near the pointed
base, is a whitish patch. This is the embryo, situated, as in all
grasses, outside the endosperm. It can be detached from a soaked
grain; and careful scrutiny will show that radicle and plumule
are wrapped up in a single seed-leaf or cotyledon, part of which is
closely applied to the endosperm, and receives the special name
of sewtellum. By cutting through a grain longitudinally, taking
care to halve the embryo, the relation of parts will readily be
understood, and a loose, white region of the endosperm will be
seen (fig. 54). Grains of wheat, barley, and oat may usefully be
compared with maize. All of them possess a single seed-leaf,
which is a leading character of monvcotyledons. A date-stone
is a monocotyledonous seed of different type. Here the endo-
sperm is horny, and composed of thickened cellulose cell-walls.
On one side of the stoneis a groove; in the centre of the opposite
side the micropyle will be found as a small depression. By cut-
ting the seed transversely across through this, a small embryo will
be found, its radicle directed towards the micropyle. The cotyle-
don is sheath-like, and encloses a microscopic plumule.

A huge seed belonging to the same class of plants is the cocoa-
nut. The hard shell does not belong to the seed, the coat of

134 THE FLOWERING PLANT.

which is a brown layer covering the edible endosperm, here form-
ing a relatively thin layer. surrounding a milk-containing cavity.
At one end of the cocoa-nut
are three round marks. One
of these corresponds to a soft
part adjoining the micropyle
of the seed. The minute em-
bryo is to be found imbedded
in the endosperm at this point.

The various parts of the seed
are subject to considerable
variation, as the above ex-
amples show. Straight, bent,
and inverted ovules develop
into similarly termed seeds
(cf. p. 104). The seed-coat is
of one or two layers, according
to the number of integuments
possessed by the ovule. It
frequently happens that out-
. growths from the seed-coat or
His, 24 ganginginal Section of a Fut fanicle are poesenie, Milliens

c. pericarp; 7. remains of style; fs. attached constitute an aril 9 which may

base of fruit; eg. dense yellow endosperm, consist of hairs only, as in

between which and the pericarp is seen the ; A

seed-coat ; ew. loose white endosperm; sc. cotton, willow-herb, and wil-

scutellum of embryo, its continuation can ‘ °

be traced round the embryo below; ss. its low; or it may be a knob

apex ; e. its epidermis (shaded like seed-coat) ~O1 ;

on endosperm side; k. plumule ; w. (below) (castor- oil seed) , ridge, crest,

radicle, tipped by root-cap; ws. its root- or complete extra covering.

sheath ; 2. (above) adventitious roots arising

from embryonic stem. Vascular bundles, Examples of the last kind are

white (note pith in vascular cylinder of radi- geen in the red fleshy cup en-

cle, as well as in stem). :

closing the solitary seed of

yew, the loose orange-coloured investment of spindle-tree seeds,
and ‘‘ mace” which surrounds the nutmeg.

Both in albuminous and exalbuminous seeds, but especially in
the latter, the embryo may be packed away in the most various
manners. The cotyledons particularly are often folded, rolled, or
crumpled in an elaborate way.

Little need be said here about the minute structure of the
seed. It is enough to state that reserve materials are laid up in
the albumen (or cotyledons if this is absent) under three chief
forms: (1) starch grains; (2) aleurone grains, which are minute
masses of proteid matter, often containing crystalloids (¢/. p. 26) ;
(3) oily matters ; (4) cellulose. The date is an example of (4);
and oily seeds, such as brazil-nut and castor-oil, of (3). Aleurone
grains are commonest and largest in oily seeds. A thin section,

SEEDS AND FRUITS. 135

for example, from the endosperm of castor-oil, shows them in the
form of oval bodies crowding the small parenchymatous cells.
Each grain contains a crystalloid and also a rounded mass of
mineral matter known as a globoid. A microscopic section
through the cotyledon of a ripe pea shows that here numerous
minute aleurone grains are associated with far larger oval starch
grains. In wheat the external layer of endosperm cells contains
aleurone only, the internal part starch only. The preparation of
flour for white bread involves the removal of this external highly
nutritious layer. Hence the value of whole flour bread where it
still remains (cf. p. 26). .

Starch is by far the commonest reserve material in seeds, and
grains differ in shape according to the kind of seed. Hence
the adulteration of flour, &c., can be detected by means of the
microscope.

Fruits are seed-containing structures resulting from a growth
of the ovary, and sometimes other parts, which follows fertiliza-
tion. The terms superior, inferior, apocarpous, and syncarpous,
are used here in the same sense as when dealing with the pistil
(pp. 100, ror). A distinction is made between (1.) true fruits,
developed from ovary alone, and (2.) spurtous or false fruits
( pseuclocarps), which involve other structures as well.

I. Spurious Fruits.—These necessarily consist of one or more
true fruits or developed ovaries surrounded by or imbedded in
other structures. An entire flower cluster sometimes gives rise
to a single fruit, termed in this case multiple or collective. Fig,
pine apple, and mulberry are the commonest examples.

The flesh of a jig (fig. 34), for instance, is the succulent
common receptacle, and the “seeds” within it are the true
fruits. The term “fruit” does not necessarily imply edibility,
from a botanical point of view at least. Again, each
of the little red swellings making up a mulderri y (fig.
55) is simply the calyx of a flower become juicy
and surrounding a small hard fruit. The pine-apple
is developed from a spike of small crowded flowers,
the ovaries and floral receptacles of which have
fused with bracts and axis into a fleshy mass. Each
lozenge-shaped area in the outside corresponds to
a single flower. Seeds are absent as a result of "gs in"
cultivation.

Aggregate fruits are formed in another way in leech and sweet
chestnut. Here the “ nuts” are true fruits, and the prickly husk
in which they are enclosed is formed by bracts which have en-
larged and grown over them.

The best types of spurious fruits formed from a single flower

136 THE FLOWERING PLANT.

are strawberry, rose-hip, apple (and pear), and acorn. The edible
part of a strawberry is the dilated floral receptacle, and the
“seeds” scattered over it are the true fruits. Similarly, the
searlet part of a hip, to which the sepals are still attached, is
obviously the hollow receptacle of the perigynous flower. Within
it will be found the true fruits. An apple presents an advance
on this condition. At the end opposite the stalk will be found
the withered remains of the sepals, and sometimes of the stamens.
The syncarpous ovary of an apple-flower is half inferior, 7.e.,
with its lower half fused to the receptacle. It forms the apple-
core (its seeds being the “ pips’’), while the flesh belongs to the
receptacle. ‘This kind of fruit is a pome.

Strictly speaking, all inferior ovaries develop into spurious
fruits, since a part of them is receptacle (cf p. 101). The union,
however, between ovary and receptacle is so intimate that they
are mostly classed under true fruits, eg., gooseberry. It is
just here that the distinction between the two kinds breaks
down. In acorn we have a single true fruit, partly surrounded
by a cup-like structure formed by the growth and union of
bracts.

Il. True Fruits.—These are mainly (inferior fruits) or entirely
(superior fruits) formed from the developed ovary. Their walls
are termed the pericarp, and are often divisible into outer,
middle, and inner layers, known as epicarp (often the epidermis),
mesocurp and endocarp respectively. The subdivisions of true
fruits are best shown in a tabular form.

A. Dry Fruirs.—Pericarp woody or tough.

1. Indehiscent.—Pericarp encloses seeds till germination.
Seed-coat thin, and often fused with pericarp.
a. One-seeded.

(a.) Achene, of one carpel, superior, pericarp
membranous, and free from seed-coat. Hz.
Buttercup (fig. 56), strawberry.

(6.) Caryopsis.—Like (a), but usually of two
carpels, and pericarp closely adherent to
seed-coat. Hv. All grasses, as wheat,
maize, oat, We. (fig. 54).

g (c.) Cypsela.—Like (6), but inferior. Hz. All

FIG. 56.—Achene Composites, as sunflower, dandelion, We.

of Buthencuny (d.) Nut, synearpous, superior, pericarp woody,

and free from seed-coat. Hx. Hazel-nut
(two ovules always present in ovary.
This accounts for occasional existence of
two kernels.)

SEEDS AND FRUITS. 137

b. Many-seeded.—Splitting fruits (schizocarps). Sepa-
rate into one-seeded parts (mericarps), resembling
nuts or achenes. x. Maple, parsnip, carrot,
carraway (2), Indian-cress (3), forget-me-not,
borage, dead nettle (4), geranium (5) (fig. 57),
mallows (many). A winged mericarp, as in
maple, is a samara (fig. 58).

2. Dehiscent.—Pericarp opens when ripe to liberate the
seeds, which are usually numerous, and enclosed by
hard or thick coats. 3

a. Follicle, of one carpel, superior. Dehisces along
the ventral suture. Hz, Larkspur, columbine,
marsh marigold, peony.

b. Pod or Legume.—Like (a), but dehiscing dorsally
as well (cf. fig. 48, D). zx. Papilionaceous
flowers, as pea, bean, gorse, and broom.

Fig. 57.—Splitting Fruit FId. 58.—Samaras of Sycamore.
of Geranium.
ce. Siliqua, of two carpels, superior, cavity divided
into two bya spurious dissepiment or replum (cf.
p. 105). Placentation parietal. Er. Wallflower,
stock, cabbage.
d. Silicula.—A short, broad siliqua. Hz. Shepherd’s
purse.
e. Capsule, of two or more carpels. Dehisces—
(a.) Longitudinally (fig. 59), with formation of
teeth or valves for a greater or less distance
from the top. If the constituent carpels
separate where united, the capsule is
septicidal, and when there are more than
one loculus, this means splitting of the
dissepiments. Hx. Gentian (one loculus),

THE FLOWERING PLANT.

FIa. 59.—Diagrams of Capsules [original.] A-E. cross-sections of dehiscing capsules.
A. unilocular septicidal; B. plurilocular septicidal; ©. unilocular loculicidal; D.
plurilocular loculicidal; E. septifragal; p. placentas (thickened edges of carpellary
leaves), split in A, B, D (ef. B with follicle); m-r. midribs of carpellary leaves, split
in C, D, E (cf. D with legume); d. dissepiments (formed by sides of adjacent carpel-
lary leaves), split in B; s. seeds, represented small for the sake of clearness, compare
with fig. 48. F. capsule of primrose, dehiscing above ten teeth. G. capsule of poppy,
dehiscing above by pores, beneath each of which is a valve.

FIG. 60.—Pyxidium of
Henbane,

foxglove (two loculi), saffron (three). Or,
again, each carpel may split along its
dorsal margin. ‘The dissepiments then
either separate from one another, when
the capsule is loculicidal, e.g., tulip, lily,
and iris, or remain united, forming a
column in the centre of the fruit, when
the capsule is septefragal, e.g., rnododen-
dron. Where, as in violet, a capsule con-
tains but one loculus, and its carpels split
along their midribs, this may be termed
loculicidal. When the placentation is
free-central, dehiscence is usually by teeth,
as in primrose and pink.

(b.) Transversely (pyxidium).—Here a lid falls

off. Hx. Scarlet pimpernel, plantain,
henbane (fig. 60).

(c.) By pores (porous capsule).— Ex. Snapdragon,

(two pores), poppy (many). (Fig. 59, G.)

B. Succutent Frurrs.—Pericarp more or less fleshy.
1. Indehiscent.-—Pericarp does not burst.
a. Stone-fruit or drupe, superior, single-seeded, epi-
carp membranous, mesocarp succulent, endocarp

SEEDS AND FRUITS. 139

hard and thick, forming the wall of the stone,
seed-coat thin (the seed is the “kernel”). zx.
Cherry, plum, peach, &e.

b. Berry, usually many-seeded, unilocular, epicarp
tough, mesocarp and endocarp succulent, sur-
rounding the seeds, which have firm coats.

(a.) Superior. x. Grape, date (with one
seed and a papery endocarp).:

(v.) Inferior. x. Gooseberry, currant, cu-
cum ber.

c. Hesperidium.—Allied to (b.) Many carpels, loculi,
and seeds, superior ; epicarp and mesocarp form-
ing a rind or peel; endocarp a thin membrane,
from which numerous succulent hair structures
have grown out, forming a pulp by which
the loculi are filled and the seeds surrounded,
Ex. The term is restricted to the fruit of
orange, lemon, and closely allied forms.

2. Dehiscent.—Pericarp bursts and liberates the seeds.

a. Succulent Capsule.—The pericarp splits into valves
and sets free the seeds. Hx. Horse-chestnut,
where the prickly green husk is pericarp (it
must not be confused with the similar structure
found in beech and sweet chestnut, p. 135).

6. Dehiscent Drupe.—Epicarp and mesocarp fleshy,
bursting to liberate the seed, still enclosed in
the hard endocarp. x. Walnut, the shell of
which is endocarp. (V.£.—The shell of hazel-
nut is pericarp. Walnuts are pickled when the
entire pericarp is present, and before the endo-
carp has hardened.)

ce. Dehiscent Berry.—Resembles berry, but firm outer
layer of pericarp bursts to liberate seeds.

When an apocarpous pistil consists of more than one carpel,
each of these ripens into a simple fruit, and the ripe carpels taken
together form an aggregate fruit. Thus, in buttercup there is such
a fruit made up of achenes, and so on. In some an aggregate
fruit appears to be a simple one, as in raspberry and blackberry.
These are collections of minute drupes, drupels as they may be
termed.

140 THE FLOWERING PLANT.

PHYSIOLOGY.

Protection of seeds, during the early period of their growth, is
largely effected by the perianth ; and the calyx, especially when
gamosepalous, often persists and surrounds the fruit. A protec-
tive function may also be assumed by bracts, as in sweet chestnut
and beech. Seeds are also frequently provided with hard coats,
and, when this is not the case, all or part of the pericarp serves
the same end, e.7., in dry indehiscent and stone fruits. Succulent
fruits, again, are almost inedible till ripe, when, as we shall see,
they lay themselves out to be eaten, so to speak. In water plants
the seeds generally remain protected in the mud at the bottom
till ready to germinate. Vallisneria is a very interesting plant in
this respect. The spiral stalk (cf p. 115) of the female flower
coils up after pollination, drawing it down to a place of compara-
tive safety for the ripening seeds. Such protective movements
are also known in some land plants. The stalk of Cyclamen or
sowbread coils up spirally, and the peduncle of dandelion moves so
as to bring the ripening fruit close to the ground.

Distribution of fruits and seeds is brought about in a variety
of ways. Incomparatively few cases is there any special provision
for setting the seeds close to the parent plant. Some forms,
however, are heterocarpic, 2.e., producing two kinds of fruit, one
of which is suitable for this purpose. There is, for example, a
kind of vetch which produces, in addition to the ordinary pods,
small pointed ones, which grow near the ground, and are forced
into it by the growth of their stalks. The capsules produced by
the cleistogamous flowers of sweet violet are also situated near the
ground. Asa general rule, however, there are special arrange-
ments for dispersing the seeds and fruits to a distance. The
chief agents for effecting this are—(1) the plant itself, (2) water,
(3) wind, and (4) animals.

(1.) The plant itself distributes its seeds in many forms, usually
as a result of the elasticity of the fruit, which in this case is
either a splitting fruit or else dry and dehiscent. In geraniums
we have an example of the former kind (fig. 57). The axis of
the fruit is here produced into a kind of beak, at the base of
which are five distinct lobes, each attached by a thin elastic rod
to the beak. When the fruit is ripe these rods suddenly curl up,
and the lobes (or seeds they contain) are detached and thrown to
a considerable distance. The same kind of thing takes place in
balsam (hence called scientifically Impatiens noli me tangere).

The legumes of some plants, such as vetch and broom, split
violently open when ripe, and violently eject their seeds. A

SEEDS AND FRUITS. I4!I

similar state of matters exists in some si/iqguas, where the valves
suddenly fly up from below on the slightest touch. A good
example of this is a small cruciferous! plant with white flowers.
the hairy bittercress (Cardamine hirsuta), which grows abundantly
in waste places. A hand passed lightly over a patch of these
plants, when the fruits are ripe, elicits a brisk discharge of
seeds.

Capsules are adapted in some cases for throwing their seeds to
a distance, of which the dog-violet is a very good example. Here
the capsule bears three rows of seeds on parietal placentas. When
ripe, it splits between these into three valves, which separate widely.
The edges of each valve now curl up and press against the seeds,
here extremely smooth, with the result that they are shot to some
distance, just as an orange pip can be projected from between the
finger and thumb.

Succulent fruits are but rarely adapted for ejecting their seeds,
but this is the case with the squirting cuewmber, common in South
Europe. The ripe fruit is in such a state of tension that the
lightest touch separates it from the stalk and causes the contents
to squirt out with much force.

(2.) Water effects the distribution of many seeds, especially
such as are enclosed in a covering which is watertight and at
the same time light enough to make them float. Experiments
have been made on this head, leading to the conclusion that the
seeds of about one plant in ten could be floated across a sea goo
miles broad and still remain capable of germination. Earth,
containing seeds, may also be carried for long distances in the
crevices of drift-timber. The cocoa-nut is one of the best examples
of a fruit which is safely transported by water for an immense
distance without injury. Owing to this it is common on the
coral islands of the Pacific.

(3.) Wind plays a very important part in the dispersal of
seeds. ‘These are sometimes suited for this by their small size,
as in orchids, Such small seeds are often found in porous
capsules, like those of snapdragon and poppy, and in these the
pores are situated near the top. The seeds cannot, therefore,
fall out, but are shaken out by the wind. . Hach pore in the
poppy capsule is provided with a little flap on the lower side,
which is said to move up and close the pore in damp weather.

Coverings or tufts of haz are often present upon seeds and
fruits, materially assisting in their dispersal by wind. The
commonest example is found in the “ pappus ” of many Composites,
a sort of crown, representing the calyx, which surmounts the

1 With cross-shaped corolla (¢f. Appendix A), a characteristic of the group
Cruciferze, of which wallflower and stock are typical examples.

142 THE FLOWERING PLANT.

fruit, as in dandelion, ‘‘thistledown,” &c. The dandelion is of
further interest because the peduncle, which during ripening is
directed along the ground, raises itself so that the fruits can
readily blow away. ‘The perianth of cotton-grass (really a sedge)
consists of bristles which grow out into long hairs; a crown of
hairs is found on the seeds of willow-herb, while a more general
covering of hairs is present on willow and cotton seeds. The seed
of stork’s-bill, a near relative of the geranium, possesses a long
feathery awn adapted for catching the wind. The base of the
awn is also twisted, and this part when moist tends to screw the
pointed seed into the ground.

Many fruits or seeds, especially those of trees, are provided
with an expanded “ wing,” of various nature. In lime the stem
of a flower cluster is provided with a large adherent bract, and
in hornbeam the single fruit is in the axil of a trilobed bract.
The fruits of maple, sycamore (fig. 58), bérch, ash, and elm are
themselves winged, and there is a membranous margin in those
of dock and parsnip. Scotch fir presents an example of winged
seeds,

(4.) Animals help to distribute seeds and fruits in a variety of
ways. Many fruits are provided with hooks, and some with
sticky hairs, by which they become attached to the coats of
animals. Such cases are found among plants low in stature,
where alone they would be useful. The calyx of forget-me-not
and fruits of burdock and cleaver are common British examples. .
In Plumbago the calyx with its viscid glandular hairs (p. 112)
persists and answers the same purpose.

Succulent fruits appear to be especially adapted by their colour,
scent, and edibility to attract animals, particularly birds. The
well-protected seeds they contain are able to resist digestion, and
are, doubtless, frequently transported to considerable distances.

Small portions of earth containing seeds must also frequently
became attached to various animals.

Germination.—This simply means the development of a seed
into a young plant up toa period when it is able to obtain food
from the exterior. The embryo contained in a seed is in a
dormant state, and if the conditions are unfavourable, may so
remain for a considerable length of time. A seed when kept
damp and exposed to the air will germinate if the temperature is
suitable (say about 35° centigrade). ‘Take, for example, an ex-
albuminous seed, like that of bean. ‘The contained embryo first
swells and bursts the seed-coat. The radicle elongates, and then
the plumule, at first strongly curved, raises itself from between
the cotyledons and rapidly grows. The cotyledons remain within:
the seed-coat, and here simply serve as stores of reserve materials,

SEEDS AND FRUITS. 143

which are gradually converted into the soluble form, and diffuse
into the young plant, forming its first nutriment. Active respira-
tion here takes place, carbon dioxide being given off in consider-
able quantities. Hence the necessity for air, or rather for the
free oxygen which it contains. Acorn, pea, and most forms with
large cotyledons, germinate like the bean, and in nature the coty-
ledons remain below ground, enclosed in the seed-coat. Such
germination is therefore called hypogean. It is to be noted that
only a small part of the so-called radicle is really root. The
region between this and the cotyledons is the base of the stem
or hypocotyl (figs. 2 and 3). Where the cotyledons are small and
comparatively poor in reserve materials, as in mustard and
cress, they escape from the seed-coat by elongation of the hypo-
cotyl, and becoming green, function as the first leaves. Such
germination is epigean (fig. 3).

The chief point in which a germinating albuminous seed differs
from the preceding is that the cotyledons (or cotyledon) act as
organs of absorption. They remain within the seed-coat, and so
influence the reserve materials in the endosperm that they become
transformed into the soluble state, when they can readily be
absorbed. Castor-oil seeds furnish a good dicotyledonous example.
Among monocotyledons grasses (maize, wheat, oat, barley, &c.) and
date may be mentioned. The scwtellum (cf. p. 133) of the former
effects absorption, and the radicle and plumule elongate in oppo-
site directions, the former having to break through a layer of
tissue known as the root-sheath (fig. 54). In date the tip of the
sheath-like cotyledon remains within the seed, while its base elon-
gates considerably, thus pushing radicle and plumule (which latter
it surrounds) completely out of the seed.

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ier

A.—APPENDIX ON PRACTICAL WORK.

THE importance of practical work in Natural Science is now universally
admitted, and it is therefore unnecessary to enlarge upon it here. This
book is mainly written for students who are anxious to verify the lead-
ing facts of Botany, and, in accordance with this end, common plants
have been used wherever possible for purposes of illustration.

Practical work in Botany may be considered under the following
headings :—I. Description or Prants; IJ. Anatomy; III. His-
tToLocgy ; IV. PHystIoLoey.

I. DESCRIPTION OF PLANTS.

We are here mainly concerned with the external features, and the
apparatus required is of the simplest description: (1.) A sharp pen-
knife is necessary for cutting through stems, buds, flowers, ovaries, &c.,
in various directions (pp. 29, 30, 74, 84, and fig. 48). (2.) Dissecting
needles, preferably three-sided glovers’ needles, mounted in handles,
serve for separating out the individual parts of small flowers, &c.
Pieces of fresh twig form useful handles. The blunt ends of the
needles are pushed into the pith, and, after a few weeks, contraction of
the wood will have fixed them firmly. (3.) A botanical lens is essential
for examination of the flower. Without it the placentation (p. 104),
among other things, could not be made out in small flowers. A three-
fold lens, such as opticians sell for about 3s., is the best form. For a
small sum a stand for this can be obtained, consisting of a vertical rod
fixed below to a heavy foot-stand. A hole is bored in the fittings of
the lens just large enough to admit the rod, and allow of sliding up and
down. Both hands are thus left free to dissect with needles, or other-
wise, small objects placed on a sheet of white paper. The sliding action
permits accurate focussing. It may not be superfluous to point out the
right way of using a lens. It should be brought close to the eye, and
then near the object, taking care to have a good light. Beginners fre-
quently place the lens near the object, and then try to look through it
from some distance, as if they were inspecting a photograph through a
large magnifying-glass. (4.) Small pins (sold in shops as “ minikins ”)
are useful for fixing down the parts of a flower in the form of a diagram.
A piece of thin deal board affords a convenient basis. (5.) A pair of
small brass botanical forceps will be found extremely useful, perhaps

145 K

146 APPENDIX ON PRACTICAL WORK.

indispensable, in the examination of small objects, or in arranging them
on paper. The cost is about 1s. (6.) A blank drawing-book (say octavo
size) and an F or HB drawing-pencil are as important as any of the
preceding. More real knowledge is gained by making a careful sketch
than by repeated inspection only. It is not necessary to sketch whole
plants, but individual parts that present any noteworthy features should |
be neatly outlined. From an examination point of view, answers illus-
trated by diagrams are far the best, for mere “cram” rarely enables a
student to use these correctly and consistently.

The correct description of an ordinary flowering plant should take
from half to three-quarters of an hour. Work of this kind is most
valuable in training the eye and cultivating the faculty of accurate
observation. Slovenliness must be avoided above all things, and, to
ensure methodical work, some settled order of procedure should be
adopted. The subjoined scheme may perhaps answer the purpose :—

I. Haprr.—Herb (annual, biennial, or perennial), shrub, or tree (p.
23). Size. General appearance.

Me heonr=—

1. Kind (p. 13).—Whether (a.) a tap-root, and if so, relative size of
primary and secondary roots; or (b.) mainly adventitious. Note in
this case the places of origin. Observe also if special kinds of root are
present, as aérial, &c.

2. Branching.—Amount, in 1 (a). :

3. Form.—(a.) Fibrous, made up of numerous unthickened fibres.
Chiefly seen in 1 (a.), eg., in grasses. (b.) Tuberous, more or less
swollen. The primary root itself may be the dilated part, as especially
in biennials. The two chief shapes in this case are spindle-shaped (e.g.,
radish) and napiform (turnip-shaped). Or, again, there may be two or
more swellings, formed from secondary or adventitious roots. Note
number and shape.

4. Direction Which way it chiefly extends, vertically or horizon-
tally. Angle at which secondary branches come off from primary.

5. Texture.—Herbaceous, succulent, or woody.

6. Surface and Colouwr.—Smooth, wrinkled, or irregular.

it. Srems—

1. Kind.—(a.) Aérial (pp. 24-26), or (b.) underground (p. 26). Note
the particular sort in either case. Also remark the length of the inter-
nodes. If very short, the stem is condensed. Observe whether any
branches are developed into runners, &c., &c. (p. 25). If any of the
modifications described on p. 27 are present, mention them.

2. Branching.—See pp. 24 and 47-48.

3. Form.—Cylindrical, square, &c. (p. 23). Note if the nodes are
swollen.

4. Direction.—Erect, &e. (pp. 25-26).

5. Texture.—As for root. Also cut through longitudinally, and de-
termine whether solid or fistular (p. 23).

6. Surface and Colowr.—Smooth, ridged {in this case number and
relative size of ridges), or rough. State as regards emergences and
hair structures (p. 28). Form a judgment as to use of these (pp. 26,
Ar). Green, brown, &c.

APPENDIX ON PRACTICAL WORK. 147

IV. Fourace LEAF :—

1. Composition.—(a.) Stalked or sessile (p. §2). (0.) Stipulate or
exstipulate (i.e., without stipules). (¢.) With sheath or without. (d.)
Simple or compound (in this case the kind) (pp. 59-61).

2. Arrangement.—(a.) In the bud (chap. v.). First note distribution
of the buds and then the way in which the leaves are packed in them.
(b.) If radical, cauline, or both (p. 24). (¢.) Horizontal, vertical, or
equitant (pp. 54-55). (d.) Phyllotaxis (pp. 49-51). Look out for bila-
teral arrangement (p. 51).

3. Petiole (and leaflet stalks in compound leaf).—(a.) Relative length.
(b.) Form, whether grooved above, winged, &c. Note whether a pul-
vinus is present (p. 53). (c¢.) Surface and colour. SeeStem. (d.) Modzifi-
cations (pp. 53-54).

4. Lamina.—Average specimens should be selected. Radical and
cauline leaves often need separate descriptions. Treat the leaflets of
compound leaves like the blades of simple leaves, noting also whether
there are striking differences between the leaflets in the same compound
leaf.

(a.) Size. (b.) Tf tubular, cylindrical, or oblique (p. 55), mention it.
(c.) Venation (pp. 55-57). Note if veins project on under side. (d.)
General shape (pp. 57-58). (e.) Base; practicaliy included under (d.),
as many of the terms on p. 58 are due to its modification. (f.) Apex ;
the same remark is true as for base. Special terms are also used, as
acute, tapering evenly to a point (fig. 18) ; acwminate, suddenly tapering
to a point (fig. 26); mucronate, ending in a short hard point (Galium) ;
obtuse, suddenly rounded off ; emarginate, with a shallow notch ; retuse,
with a deep notch. The last form graduates into obcordate. (g.) Mar-
gin (pp. 58-59, footnote p. 28). Note also that the margin may be wary
and spiny (both in holly). (h.) Texture (p. 62). (v.) Surface and colour
(p.62). SeeStem. Note differences between upper and lower surfaces.
A bluish-green colour, caused by wax-particles, is termed glaucous (e.g.,
white poppy). (k.) Modifications (p. 61).

5. Sheath.—(a.) Relative size, (b.) Whether forming a complete tube
or not. (c.) Texture.

6. Stipules.—(a.) Arrangement (pp. €3-64). (b.) Texture, foliaceous
or membranous.

V. Scae LeaF (p. 64) :—

1. Arrangement.—(a.) On overground buds. (b.) On underground
parts of stem.

2. Form.

3. Texture.

4. Surface and colour.

VI. INFLORESCENCE AND Bracts (pp. 75-80) :—

. Position.—Terminal or axillary.

. Kind and Size (including number of flowers).
. Branching.—Its amount.

. Direction.—Erect, spreading, pendent, &c.

. Peduncles and Pedicels.—Describe as stem.

. Bracts.— Describe like foliage leaves.

Own &&N &

148 APPENDIX ON PRACTICAL WORK.

VIL. Tre FLOWER :—

1. Symmetry (p. eo
2. Floral receptacle (p. 81).
3. Relation of parts—Shown by a floral diagram (p. 82).
4. Calysx.
5. Corolla.
6. Andrecium ; and
7, Gynecium.—Described under five headings, preferably in a table or
schedule.
No.1 Arrange, Cohesion. Adhesion. Pree |
Fas p. 83 p. 84 p84 | pp. 85-85
aR ee pp. 86-87 p. 87 p. 87 pp. 87-91
Andreecium—
Filaments | pp. 92-94 P- 95 Pp. 95 pp: 96-97
Anthers .
| Gynwcium—
| Stigma ;
| bye EU. aes pp. 98-100 | pp. 100-101 pp. IO1 | pp. 101-106
Ovary.
Ovules

In the case of unisexual flowers two schedules will be required.

8. Nectarves.

9. Protection and Cross-Pollination.—Endeavour to make out some of
the arrangements described in Chapter LX.

Ue FRUIT AND SEEDS :—
. Kind of Fruit (pp. 135-13
2. Number and Arrang gement. 2 Seeds (cf. pp. 104-106).
3. Protection and Distribution of Seeds—Try to identify some of the
methods described on pp. 140-142.

LX. CLASSIFICATION.

Remarks on Preceding Headings.—The beginner will undoubtedly
find considerable difficulty in attempting plant description. It is
better to make a preliminary study of roots, stems, &c., &c., before try-
ing entire plants. Above all things, never describe an absent part,
about which you happen to know something. Technical terms will be
gradually acquired, but in default of them use ordinary language, as
tersely and clearly as possible.

I, Hasit.—A judgment as to the kind of plant has often to be formed
rom a small part of it. A woody stem points to a perennial, and if a
cross-section shows annual rings (p. 38), this is certain. Leathery leaves
generally belong to perennial evergreens. On the other hand, an isolated

1 A large number is indicated by co

APPENDIX ON PRACTICAL WORK, 149

herbaceous stem proves nothing. A rhizome (p. 26) belongs to a peren-
nial. A dilated succulent tap-root generally indicates a biennial.

II. Roor.—If an underground structure possesses scale leaves, buds,
or chlorophyll, it does not belong to the root at all, but to the stem.

IIT. Stem.—See last paragraph. In the examination of corms and
bulbs, note the appearances made by cutting through them in the
middle ; (a.) from above downwards, (b.) across. The difference (p. 26)
between the two kinds of structure will readily be seen, and buds can
also be detected in the typical situations. As examples of bulb, take
onion, lily, and hyacinth ; for corms, examine crocus, colchicum, and
eyclamen (sold as “bulbs” by florists).

IV. Foutace LEAF :—

1. Composition.—Remember that stipules may fall off early (p. 64),
and therefore do not put exstipulate unless young leaves are present.
Say rather, “apparently exstipulate.”

Note that there may be great variation in the foliage leaves of the
same plant.

2. Arrangement.—Satisfy yourself that so-called “radical” leaves
really arise from a condensed lower part of the stem. Take, for
example, an entire daisy plant, and halve it with a knife. The crowded
nodes can then be made out. No root possesses nodes and internodes.
Remember that adventitious root-fibres are, as a rule, given off from all
underground structures.

Arrangement in Bud.—Relative arrangement of leaves is seen by
cutting across (footnote, p. 84). The arrangement of individual leaves
(footnote, p. 49) is partly shown by the same method, partly by cutting
through the bud longitudinally, and also by separating the individual
leaves. The following are examples of the terms used for foliage
leaves :—Imbricate, grasses and sedges; plaited, maple and currant ;
conduplicate, bean and oak ; inflexed, tulip-tree ; convolute, cherry and
apricot ; involute, violet and waterlily ; revolute, sorrel and rosemary ;
curcinate, sundew and ferns. The remaining terms in the footnotes are
used in the case of flower buds. Note if the young leaves are protected
by down (p. 67).

Phyllotaxis.—To determine the divergence (p. 50) take any leaf, call
it 1,and mark it. Then find the next leaf which comes immediately
above it, say the 9th. g—1=8, the number of leaves in the cycle, and
denominator of the divergence fraction. Verify this by determining
the number of ranks or longitudinal leaf-rows. This should be 8.
Suppose also that it is necessary to go three times round the stem in
passing from 1 tog. This gives the numerator of the fraction, which
is therefore 2 (compare fig. 9).

V. ScaLe Lear.—tIn the case of the bud, try to find the relation
between the scales and young foliage leaves, and prove what region
they represent (p. 64). Observe whether blastocolla is present.

In the case of underground scale-leaves, observe whether thickened
as storage organs. Look for axillary buds, ¢.g., in a potato.

VI. INFLORESCENCE AND Bracts.—Note the position of the yowngest
flowers. If these are at end (figs. 31 and 32) or in centre (¢.g., daisy
and carrot), the inflorescence is centripetal, indefinite, or racemose. If

150 APPENDIX ON PRACTICAL WORK.

the oldest flowers are in the above position (fig. 35), the inflorescence is
centrifugal, definite, or cymose.

VII. THe FLOWER :—

2. Receptacle.—Cut through the flower longitudinally, and determine
whether the flower is hypogynous, perigynous, or epigynous (fig. 37).
The receptacle is often very much shallower than in B ; as, for example,
in gorse and sweet-pea.

3. Relation of Parts, as shown in a floral diagram. Take fig. 38 as
a model. Note position of axis, denoting back of flower. In a bila-
terally symmetrical flower, rising, like a pansy, from a condensed stem,
the back is above and the front below. A flower may be more or less
twisted round, especially in orchids (p. 89).

Note carefully whether there is an anterior or posterior sepal (p. 82).
Make a good-sized drawing (say three times as big as fig. 38), and do not
crowd the stamens and carpels. When these last are numerous, as in
buttercup, do not trouble to count them, but put a fair number of the
conventional marks.

It is very useful practice to pin out the parts in the form of a dia-
gram, marking with pencil the front, back, and planes (fig. 38). If
the calyx or corolla has its elements cohering, cut it into longitudinal
pieces between the lobes or teeth, and lay them out as if originally
separate.

A floral formula can be made to express a great deal. Thus the
diagram in fig. 38 can by represented by

Ca.2;,Co: 3, An.3:-- 3, Gm

Ca, = calyx ; Co. = corolla; An. = andrecium; Gn. = gyneecium,
A parenthesis () signifies cohering parts. In the case of the gyncecium,
a line below means superior, a line above inferior. Superposition be-
tween the whorls is indicated by |. Thus, in primrose :—

Ca (5), Co (5) | An 5, Gn %,
or | can be omitted if An o + 5 is inserted.

Other typical formule are :—

Buttercup :—
Ca 5, Co 5, Anw~, Gn CO w,
(Here ~ = spirally arranged.)
Carrot :—
Ca 5, Co 5, An 5 + o, Gn@,.
Orchis :—

Ca 3, Co 3, An 1 + o, Gn@.
Most Grasses :—

Cao, Co 2, An 3 + 0, Gn.
The o signifies suppression of a whorl.

For arrangement in bud, see footnotes pp. 49 and 84.

4. Calyx.— See alsoiv. 2. Remaining terms in footnotes: open,

5. Corolla.— petals of mignonette ; valvate, sepals of fuchsia ; obvo-
lute, petals of fuchsia; crwmpled, petals of poppy.

APPENDIX ON PRACTICAL WORK. I5I

6. Andrecium.—When the stamens are double the number of the
petals, both the typical whorls are present (p. 82). If equal in number,
the inner stamens have generally been suppressed (see above, formule
for carrot and grasses). More rarely (see formula for primrose) the
outer stamens are suppressed. It is easy to tell which whorl is left, for
the outer stamens alternate with the petals, while the inner ones are
superposed to them. If the stamens are fewer than the petals, they
usually represent part of the outer whorl (see formula for orchis).

7. Gynecium.—This is typically composed of two whorls of carpels,
but do not put o to represent the usually suppressed whorl, as it is
not possible in many cases to tell easily which whorl is suppressed.
Thus the formula for gorse is properly (p. 103)—

Ca (5), Co 5, An (5+5), Gn 1 +o,

but it is enough to write Gn I.

Superior and Inferior.—If, as in hypogynous and perigynous flowers,
the ovary is free, term it superior ; if, as in epigynous flowers, adherent
to the cup-shaped receptacle, inferior.

Placentation.—In most cases a transverse cut will show this. If not,
divide another specimen longitudinally. This will show erect and
ascending ovules. Determine the number of ovules if a few only are
present. When they are very numerous, write indefinite (0 ).

8. Nectaries—These vary immensely in size, nature, and position.
They may be mere points, streaks, or surfaces where nectar is excreted,
but, on the other hand, may be conspicuous projections. They are so
placed that the stigma, or anthers, or both, must be touched before an
insect can reach them. The chief situations are :—(a.) on receptacle
(wallflower, willow, mignonette) ; (b.) as a spur to calyx (garden nas-
turtium) ; (¢.) on corolla, as glandular spots (buttercup), or spurs (lark-
spur); (d.) on andrecium (pansy, fig. 51) ; (e.) on ovary (dead nettle).

9. Protection and Pollination.—N ote characteristics of wind-pollinated
and insect-pollinated flowers (pp. 115, 118). Do not immediately con-
clude that an inconspicuous flower is wind-pollinated, for it may make up
for want of brilliancy by the possession of nectar (e.g., willow and lime)
or scent (eg., lime). If flowers are present in all stages, it is easy to
determine whether proterandry or proterogyny obtains. The stamens
will be dehiscing, in the former case, in very young flowers ; vice versé in
the latter case.

VIII. Fruits anp Sereps.—First master the main divisions of the
table on pp. 136-139, and then attack the sub-divisions, examining for
yourself as many of the examples as you can get. For dehiscence very
ripe fruits are necessary.

Spurious fruits will give little trouble. All the common kinds are
described on pp. 136-139.

Arrangement of seeds in the fruit is determined like that of ovules in
the ovary (see above).

For the structure of seeds examine the types described on pp.
132-134.

TX. CLassIFICATION.—First determine the sub-division, class, sub-
class, and series, by means of the following table. Remember that
here are no sharp boundary-lines in Nature, so that a plant need not

152 APPENDIX ON PRACTICAL WORK.

necessarily possess all the characters of the group to which it belongs.
The balance of evidence must be taken. Classify by means of what is
present in your specimen.

FLOWERING PLANTS
possess seeds, and, usually, conspicuous flowers.

Sub-division I.—GYMNOSPERMS.

Ovules not enclosed in an ovary, but situated either on the axis or on
open carpels, Stamens scale-like, with pollen-sacs on their wnder side.
Perianth almost always absent. Endosperm of seed formed before
fertilization.

Exs.—Yew, pine, fir, larch, cedar, araucaria, cypress, juniper.

Sub-division IT.—ANGIOSPERMS.

Ovules enclosed in an ovary. Stamens not scale-like. Perianth
generally present. Endosperm formed after fertilization.

Cuass I1.—MONOCOTYLEDONS.

Roots adventitious, the radicle of embryo being arrested in develop-
ment. Stem with scattered closed vascular bundles. No well-
marked distinction between pith, cortex, and medullary rays.
No bark. Leaves frequently possess a sheath ; parallel-veined.
Flower with parts in 3’s or a multiple of 3. Calyx and corolla
generally much alike. Seed, embryo with one cotyledon ; endo-
sperm generally abundant.

Sub-class 1.—Nudiflore.

Pertianth o or scaly. Ovary superior.
Series (1).—Spadiciflore.
Flowers generally in a spike or spadix.
Series (2).—Glumiflore.
Flowers in heads or spikelets. bracts scaly, and known as
glumes. Pervanth, when present, of scales or bristles.

Sub-class 2.—Petaloidez.

Flowers usually bisexual. Perianth always present, and generally
brightly coloured.
Series (1).—Hypogyne.
Ovary superior.
Series (2).—Hpigyne.
Ovary inferior.

Cuass II.—DICOTYLEDONS.

Root frequently a tap-root, 7.e., with main axis formed by developed
radicle of embryo. Stem, when young, with a circle of open
vascular bundles, pith, medullary rays, and cortex ; when older,
with annual rings of wood, formed by cambium ring, and separ-

APPENDIX ON PRACTICAL WORK. 153

able bark. Leaves generally without a sheath, net-veined.
Flowers with parts in 4’s or 5’s, or a multiple of those numbers.
Calyx and corolla usually unlike. Seed, embryo with two coty-
ledons ; endosperm often absent.

Sub-class 1.—Incomplete.

Flowers often unisexual. Calyx inconspicuous or o. Corolla, o.
Series (1).—Hypogyne.
Ovary superior.
Series (2).— Epigyne.
Ovary inferior.

Sub-class 2.—Polypetale.

Flowers generally bisexual, Calyx and corolla both present, as a rule,
the latter polypetalous, and generally bright coloured.
Series (1).—Thalamzflore.
Flower hypogynous. Stamens often numerous.
Series (2).—Calyciflore.
Flower perigynous or epigynous. Calyx generally gamose-
palous.

Sub-class 3.—Gamopetale or Corollifiore.

Flowers generally bisexual. Calyx generally present, gamosepalous.
Corolla generally present, gamopetalous, and, as a rule,
brightly coloured. Gynaciwm usually synearpous.

Series (1).—Hypogyne.

Ovary superior. Stamens mostly epipetalous.
Series (2).—EHpigyne.

Ovary inferior.

Having determined the sub-division, class, sub-class, and series to
which a plant belongs, the next step is to find its natural order or
family. The following table will enable this to be effected. Details
are not given of Gymnosperms, and as there are some ninety natural
orders represented among British Angiosperms, only the most important
of these can receive notice.

Crass Il.—MONOCOTYLEDONS.

Sub-class 1.—Nudiflore.
Series (1.)—Spadiciflore.

Order 1.—Aroidacer.—Herbs. Leaves, net-veined (N.B. exception
to rule). Inflorescence, a spadix, often surrounded by a large
spathe. Fruit, a berry.

Eas.— Arum, arum lily (Richardia).
Order 2.—Lemnacee.—Minute aquatic herbs. Stem,adisc. Leaves,

o. Flowers, monecious. Stamens, 1. Carpels, 1.
Exs.—Duckweeds (Lemna and Wolffia).

Order 3.—Typhaceze.—Erect marsh plants. Inflorescence, spadix
without a spathe. Flowers, moncecious, male inflorescences upper-

154 APPENDIX ON PRACTICAL WORK.

most. Perianth, o, or of hairs or scales. Stamens, generally two
or three.
Exs.—Bur-reed (Sparganium), bulrush.
Series (2).—Glumiflore.

Order 1.—Graminacex.——Stem, fistular, swollen at nodes. Leaves,
with a split sheath, and usually a ligule ; divergence 3. Flowers,
usually bisexual. mbryo, on one side of endosperm.

xs. — Grasses,

Order 2.—Cyperacez.—Grass-like herbs. Stem, solid. Leaves, with
a tubular sheath and no ligule ; divergence 4. Hmbryo, enclosed
in endosperm.

H«s.—Sedges.

Sub-class 2.—Petaloidee.
Series (1).—Hypogyne.

Order 1.—Liliacez.—Mostly herbs. Flowers, regular. Floral
formula, generally Ca 3, Co 3, An 3 + 3, Gn®, Placentatzon,
axile. Jrutt, a capsule or berry.

Kas.—Lily, hyacinth, tulip, onion, garlic, leek, asparagus,
butcher’s broom (a shrub).

Order 2.—Juncaceze.—Grass-like herbs. Leaves, cylindrical. Flowers,
inconspicuous and regular. Sepals and petals, brown and scale-
like. Floral formula, as Liliacee. Srwit, a capsule.

Has.—Rushes.
Series (2).—Lpigyne.

Order 1.—Iridacexz.—Herbs. Stem, forming bulb, corm, or rhizome,
Leaves, equitant. Floral formula, Ca 3, Co 3, An 3 + 0, Gn @,
Placentation, axile. Fruit, a 3-chambered loculicidal capsule.

Kxs.—Iris, crocus, gladiolus.

Order 2.—Amaryllidacez.—Herbs. Stem, bulbous. Flowers, usually
regular. Floral formula, usually as Liliacee. but Gn @. Placen-
tation, axile. Fruit, generally as in Iridacee.

Exs.—Snowdrop, daffodil, narcissus.

Order 3.—Orchidacez.— Herbs. Roots, tuberous. Inflorescence, a.
spike or raceme. Flowers, irregular, twisted completely round.
Floral formula, usually Ca 3, Co 3, Ani+o, Gn @. Perranth
generally spurred. Stamen, gynandrous. Placentation, parietal.
Fruit, a 1-chambered loculicidal capsule.

Hxs.—Orchids.

Crass I11.—DICOTYLEDONS.

Sub-class 1.—Incompletz.
Series (1).—Hypogyne.

Order 1.—Urticacee.—Herbs or shrubs, frequently covered with
stinging hairs. Flowers, unisexual. Calyx, regular, with four or
tive divisions. Stamens, superposed to the sepals. Ovule, single,
straight, erect.

ixs.—Nettles.

APPENDIX ON PRACTICAL WORK. 155

Order 2.—Amentacez.—Trees or shrubs. Leaves, scattered. Jnflor-
escence, catkins. Flowers, unisexual. Male and female flowers
arranged in different catkins. Gyneciwm, syncarpous. Car-
pels, 2.

Exs.—Willow, birch, aider.

Order 3.—Chenopodiacee.—Herbs. Leaves, exstipulate. Flowers,
small, green, regular, bisexual. Calyx, 5-lobed. Stamens, super-
posed to sepals. Gynecium, synearpous. Carpels, 2.

Exs.—Goosefoot (Chenopodium), spinach, beetroot.

Order 4.—Polygonacez.—Herbs. Stem, dilated at the nodes. Leaves,
scattered, with ochreate stipules. Flowers, small, regular, gene-
rally bisexual. Sepals, 4 to 5. Stamens, superposed to sepals
Gynecium, synearpous. Carpels, 3. Ovule, single, straight, erect.

Exs.—Knotgrass, dock, sorrel, rhubarb.
Series (2).-—Epigyne.

Order 1.—Cupulifere.— Shrubs or trees. Leaves, scattered, stipulate.

Flowers, small, green, unisexual, Male flowers in catkins. Female

flowers surrounded by bracts. Fruit, a nut.
Exs.—Oak, beech, hazel, hornbeam.

Sub-class 2.—Polypetale.
Series (1.)— Thalamiflore.

Order 1.—Ranunculacee.—Generally herbs. Leaves, usually scat-
tered. Stamens, indefinite, spirally arranged. Gyneciwm, apo-
carpous. Carpels, generally indefinite and spirally arranged.
Fruit, generally an achene or follicle.

Exs.—Clematis, anemone, buttercup, lesser celandine, Christ-
mas rose, marsh marigold, larkspur, monk’s-hood, peony.

Order 2.—Papaveraceze.— Herbs with milky juice. Leuves, scattered,
exstipulate. Flowers, regular. Sepals, 2, usually caducous.
Petals 4. Stamens, indefinite, arranged in alternating whorls.
Gynecium, synearpous. Placentation, parietal.

Exs.—Poppy, greater celandine, Californian poppy (Esch-
scholtza).

Order 3.—Crucifere.—Herhs. Leaves, scattered, exstipulate. In-
Jlorescence, a raceme without bracts. Flowers, generally regular.
Sepals, 4, in two whorls. Corolla, cruciform, Petals, 4, alternating
with sepals, and placed obliquely (see fig. 38). Stamens, tetrady-
namous, in two whorls. Gynwecium, syncarpous. Carpels, 2,
lateral. Fruzt, a siliqua.

Kzs.—Wallflower, stock, watercress, cabbage, turnip, horse-
radish, radish, shepherd’s purse, candytuft.

Order 4.—Violacee.—Herbs. Leaves, scattered, stipulate. Flowers,
irregular. Iloral formula, Ca5, Co 5, An 5, Gn ®. Petals, the
odd anterior (lower) one with a spur. Stamens, two lower ones
with nectaries. Placentation, parietal. Fruit, a loculicidal
capsule.

Exs.—Violet, pansy.

Order 5.—Caryophyllacez.—Herbs. Stem, usually swollen at the

nodes. Leaves, decussate. Inflorescence, cymose. Flowers, regular,

156 APPENDIX ON PRACTICAL WORK.

parts usually in 5’s. Placentation, generally free-central. Frwit,
usually a capsule.

Exs. —Chickweed, stitchwort, campion, ragged-robin, pink,
carnation.

Order 6.—Malvacez.—Undershrubs or herbs. Leaves, scattered,
stipulate. Flowers, regular. Calyx, frequently with epicalyx.
Stamens, monadelphous, branched. Gyneciwm, syncarpous. Fruit,
a spht-fruit with numerous parts.

Exs.—Mallow, hollyhock.

Order 7.—Geraniacee.—Herbs. Floral formula, Cas5,Co5,An5+5,

Gn ©, Ovary, with a beak-like projection. Fruit, a split fruit.
Hxs.—Geranium, pelargonium.

Series (2).—Calyciflore.

Order 1.—Leguminose.— Leaves, usually scattered, compound, and
stipulate. Flowers, perigynous, and generally irregular. Sepals,
5, the odd one anterior, Corolla, usually papilionaceous. Stamens,
generally 10, mon- or diadelphous. Gyneciwm, superior. Carpels,
I, anterior. fruit, a legume.

Hxs.—Gorse, broom, lupin, laburnum, clover, bird’s-foot tre-
foil, vetch, bean, pea.

Order 2.—Rosaces.—Leaves, scattered, usually stipulate. Flowers,
perigynous, regular, Sepals, generally 5, the odd one posterior.
Stamens indefinite. Gynecium, apocarpous, superior.

Hus.—Rose, meadow-sweet, japonica, peach, apricot, plum,
cherry, laurel (cherry 1.), sloe, lady’s mantle, cinquefoil,
strawberry, raspberry, blackberry, hawthorn, pear, apple,
mountain ash (rowan).

Order 3.—Onagracesz.— Herbs or shrubs. Leaves, exstipulate. Flowers,
epigynous, usually regular ; parts in 4's. Calyx, often petaloid,
with along tube. Gynaciwm, syncarpous, superior. Placentation,
axile. Fruzt, a capsule or berry.

Kxs.—Willow herb, evening primrose, enchanter’s nightshade,
fuchsia.

Order 4.—Umbellifere.—Herbs. Stem, generally fistular. Leaves,
scattered, exstipulate, sheathing at base, generally deeply divided.
Inflorescence, an umbel. Flowers, epigynous, usually regular.
Floral formula, Ca5,Co5,Ans5,Gn. Calyx, very small. Fruit,
a splitting-fruit, dividing into two.

Hxzs.—Hemlock, celery, carraway, fennel, coriander, parsley,
parsnip, carrot.

Sub-class 3.—Gamopetale or Corolliflore.

Series (1).—Hypogyne.

Order 1.—Boraginacez.—Hispid herbs. Leaves, scattered, entire, ex-
stipulate. Inflorescence, cymose, helicoid. lowers, generally
regular. Floral formula, Ca 5, Co 5, An 5, Gn &. Stamens,
epipetalous. Carpels, lateral. Ovary, 4-lobed. Fruit, a splitting
fruit, separating into 4.

Exs.—Bugloss, borage, comfrey, forget-me-not.

APPENDIX ON PRACTICAL WORK. 157

Order 2.—Solanacee.—Usually herbs. Leaves, exstipulate. Jn-
florescence, cymose. Flowers, usually regular, with parts (except
gyncecium) in 5’s. Stamens, epipetalous. Carpels, 2. Placentu-
tion, axile. Fruit, a berry or capsule.

Exs.—Bittersweet, potato, winter cherry, tomato, Chili pepper,
deadly nightshade, tobacco-plant, petunia, thorn-apple,
henbane.

Order 3.—Scrophulariacee.—Herbs. lowers, more or less irregu-
lar. Stamens, 4 (didynamous), 2, or (in mullein) 5; posterior
stamen absent, except in last case. Carpels, 2. Placentation,
axile. Ovules, numerous. Fruit, usually a capsule.

Ezs.—Mullein, snapdragon, toad-flax, musk, calceolaria, penta-
stemon, foxglove, figwort (Scrophularia), speedwell, yellow
rattle.

Order 4.—Labiate.—Herbs. Stem, square, fistular. Leaves, decus-
sate, aromatic, Inflorescence, apparently in whorls, really cymose
(in verticillasters). Flowers, irregular. Calyx and Corolla, 2-
lipped. Stamens, 4 (didynamous), or, more rarely, 2; posterior
stamen always absent ; epipetalous. Carpels, 2. Ovary, 4-lobed
and 4-chambered. Placentation and Ovules, one erect ovule in
each chamber of the ovary. Fruit, as in Boraginacee.

Exs.—Basil, lavender, mint, marjoram, thyme, sage, rosemary,
ground ivy, dead nettle, horehound.

Order 5.—Primulacee.—Herbs. Leaves, simple, exstipulate. Plowers,
regular. Floral formula, Ca 5, Co 5 | An 5, Gn ®. Stamens,
epipetalous. Placentation, free central. Fruit, a capsule.

Has.—Primrose, cowslip, polyanthus, auricula, cyclamen, scarlet
pimpernel.

Series (2.)—Epigyne. .

Order 1.—Dipsacez.—Herbs. Leaves, opposite, exstipulate. In-
florescence, a dense head, surrounded by an involucre. Flowers,
small (florets) ; outer ones generally ligulate. Calyx, usually
reduced to scales or bristles ; surrounded by a cup-like epicalyx.
Stamens, epipetalous ; quite free from one another. Carpels, 2.
Style, unbranched. Ovary, with one chamber. Placentation.and
Ovules, one suspended ovule. Fruit, a cypsela.

Exs.—Teasel, scabious.

Order 2.—Composite.—Herbs, often with milky juice. Leaves,
usually scattered ; exstipulate. Inflorescence, a dense head, sur-
rounded by an involucre. /'lowers, small (florets) ; outer ones
often female or neuter. Calyx, when present, reduced to scales
or hairs (pappus). Stamens, epipetalous, syngenesious. Carpels,

2. Style, forked. Ovary, with one chamber. Piacentation and
Ovules, one erect ovule. Fruit, a eypsela.
Kus,—Colt’s-foot, aster, daisy, groundsel, oxeye daisy (mar-
guerite), chamomile, sunflower, Jerusalem artichoke,
dahha, dandelion, lettuce.

Order 3.—Campanulacee.—- Usually herbs, with milky juice.
Leaves, scattered, exstipulate. Flowers, usually regular, parts
(except gyncecium) in 5’s. Corolla, bell-shaped. Stamens, often

158 APPENDIX ON PRACTICAL WORK.

united at base, Carpels, generally 3, Placentation, axile. Fruit,

a capsule,
Exs.—Harebell, Canterbury bell.

I].—Anatomy,—Root (p. 14). Stem (p. 29).—-Try to follow, mainly
by longitudinal slicing, the course of the bundles in a piece of aspara-
gus stem (cf. fig. 5, C). Leaf—The distribution of vascular bundles is
plainly seen in most herbaceous forms, and may be rendered still more
plain by bleaching in spirit, and then soaking in chloral hydrate.
Compare the distribution in monocotyledons and dicotyledons.

III. Hrstonoay.—_-A compound microscope is necessary for this.
Browning’s field-microscope, shown in fig. 61, will answer the purpose
for a beginner, and even if
a larger microscope is after-
wards purchased, will always
be useful for carrying about.
It consists of a stand, eyeprece,
and objectives. The stand is
supported by three legs, and
carries a sliding tube above,
and a perforated plate or
stage below, upon which the
object to be examined is
placed. Below the stage
swings a small concave mir-
ror, from which light can be
reflected upwards through

= E the aperture. The eyepiece
Tae slips into the upper end of
the tube, while the objective
screws into the lower end, Objectives are named, according to the
distance at which they must be placed from the object, two-inch,
inch, half-inch, quarter-inch, &c., &. Inch and half-inch objectives
will be sufficient for elementary purposes, and will be called low power
and high power in the rest of this Appendix. The price of Browning’s
field-microscope, with one eyepiece and the two objectives named, also
with case and forceps (as in figure), is £2, 1s. 6d. Suitable glass slips
(say two dozen) and cover-glasses (4 0z. of small squares) can be obtained
for a small sum of the same maker.!

We may examine objects in two ways: (1) by reflected light ; (2) by

transmitted light. It is perhaps easier to commence with the former.
_ (1.) Opaque objects are best suited for viewing with reflected light.
Pollen grains (preferably of mallow or hollyhock), small seeds, or flat
bits of leaf with hair structures are good examples. Place one of these
objects on a piece of black paper on the centre of a glass slip. Screw
on the low power, and pull out the inner half of the microscope tube
till a groove upon it is seen. Put the slip under the two spring-clips of
the stage, and turn the mirror so that it reflects no light through the -
hole. To focus, slide down the tube near to the object, apply the eye to
the eyepiece, and slide up the tube till the object is seen. ‘This sliding
action is the coarse adjustment. The fine adjustment is brought into

1 63 Strand, London, 8. W.

APPENDIX ON PRACTICAL WORK. 159

action by turning a screw at the back of the tube frame, A good light
is, of course, necessary. Now remove the low power and follow the
same course with the high one. A higher magnification can be effected
by pulling out the inner part of the microscope tube further than the
oove.

alle) Objects when viewed by transmitted light require more elaborate
treatment, and the following additional apparatus will be required :—
(a.) A razor for section cutting. A shilling army-razor will answer
perfectly well. (b.) Some pieces of elder pith. (c.) Half a dozen watch-
glasses. (d.) A small camel’s-hair brush. (e.) Half a pint of methylated
spirit, an 8-oz. bottle of glycerine, and the following reagents put up in
1-02. phials, through the corks of which pieces of glass rod are passed
(any chemist will do this) :—Dvalute glycerine (half glycerine, half water),
vodine solution (dilute the liquor zodi of chemists to a dark-sherry colour),
magenta solution (Judson’s magenta dye diluted to port-wine colour),
caustic pctash solution (five per cent.), and strong sulphuric acid.

Take, for example, a small piece of a delicate leaf treated with chloral
hydrate, a daisy floret torn open, some pollen, or a bit of epidermis
pulled from the lower surface of a geranium leaf. Now, with a glass
rod place a small drop of dilute glycerine in the centre of a slide, put
the object in the drop, and cover with a cover-glass. One edge of this
should first be made to touch the slide, and the glass then gently lowered
with a mounted needle. Now proceed as before, but, in addition, turn
the mirror so as to reflect light upwards through the object. N.B.—
Perfect cleanliness is necessary in all microscopic work. The microscope
lenses should be kept clean with a piece of new wash-leather, while
cover-glasses are cleansed by rubbing them gently with a piece of old
silk between the thumb and forefinger. Of course they should first be
washed in water if smeared with glycerine, &c.

Transmitted light is most useful for thin sections of root, stem, leaf,
anther, ovary, &c. These should be preserved in methylated spirit, and
placed in a half and half mixture of this and glycerine for twenty-four
hours before required. Small objects may be held in a slit in a piece
of elder pith, while leaves can be rolled up. There is no royal road to
section cutting, and nothing but practice will give the requisite skill.
A few hints may, however, prove useful. Hold the object firmly in the
left hand, and, grasping the middle of the razor firmly with the right,
its edge away from you, make a steady diagonal sweep from the base of
the blade. Do not push or saw. The razor should be kept wet with
water for fresh objects, with spirit for spirit specimens. With a sharp
razor the weight of the blade should be sufficient to carry it through if
a slight swing is given. Many prefer to cut towards them, using the
first finger of the left hand as a support for the razor-blade. A number
of sections should be made, and placed in a watch-glass containing dilute
glycerine. From this the thinnest can be picked out with the brush and
mounted as before. A piece of black paper placed beneath the watch-
glass will enable the sections to be seen more clearly. Do not be con-
tented till your sections are so thin that the cover-glass will lie quite
fat, and so transparent that all the details can be made out with the
high power.

In many cases sections are made clearer by staining, since different
elements are affected differently. This process is conveniently effected

160 APPENDIX ON PRACTICAL WORK.

by placing the sections, as cut, in a watch-glass holding the reagent,
transferring after a time to dilute glycerine. Reagents can also be
added to a mounted section by placing a small drop on one side of the
cover-glass, and drawing it under by means of a pointed fragment of
blotting-paper placed on the other side. Jodine colours protoplasm and
sieve-tube slime brownish yellow, cuticularized and lignified cell-walls
yellow, cellulose pale yellow, and starch blue. Magenta stains generally,
but colours the protoplasm most deeply. If an object is mounted in
iodine, and a drop of strong sulphuric acid run under the cover-glass, the
cellulose walls will be coloured blue.

Sections can be cleared, 1.e., rendered more transparent, by mounting
in caustic potash solution. This method is especially useful in the case
of roots.

In all the preceding cases it, is essential to mount the object in a
very small drop of liquid, just enough to spread out under the cover-
glass. If too much is taken, the inclined stage (if the field-microscope
is used) will cause the cover-glass to slide off.

Students who wish to learn a little vegetable histology, but have no
time to make their own sections, can obtain for ros. 6d. a set of fifteen
permanent slides, illustrating the chief points, from Mr. Arthur Shrubbs,
Cambridge.

IV. PHYSIOLOGY.

1. Plant Food.—Germinated beans, grains of Indian-corn, &ce., will
flourish in a food solution containing the essential elements (p. 10}, pro-
vided air and light have access. Such a food solution may conveniently
consist of—1 pint distilled water, 86 grains potassium nitrate, 43 grains
sodium chloride, 43 grains calcium sulphate, 43 grains magnesium sul-
phate, 43 grains of finely divided calcium phosphate, and a trace of ferric
chloride. The omission of any constituent will cause the plants to be
sickly and stunted. The carbon dioxide in the air forms part of plant
food. See p. 68.

2. Action of Chlorophyll,—Green plants grown in the dark become
etiolated (p. 68). See also p.67 Oxygen is evolved. See pp. 68-69.

3. Transpiration.—See p. 69.

4. Resptration.—The necessity for oxygen is proved by growing plants
in nitrogen. They sicken and die. A large wide-mouthed bottle is
one-third filled with germinating peas, and closed with a tightly-fitting
stopper. After a few hours enough carbon dioxide will have collected
to put out a burning candle-end lowered into the bottle.

5. Growth of Pollen-tubes.—See note on p. 114.

6. Germination.—Beans, &c., can be germinated in sand or sawdust,
mustard and cress on flannel, They require (a.) water, (b.) access of air
containing oxygen, (c.) a moderately warm temperature. They do not
require light, or other food than water, since the cotyledons or endo-
sperm contain a store of nutriment in the form of reserve materials.
But when these are used up germination is completed, and food and
light become essential.

The growth of shoots from bulbs, corms, and tubers may take place
under the same conditions as the germination of seed. ;

APPENDIX B.

EXAMINATION QUESTIONS.

8.K.E.=South Kensington Elementary. S.K.A.=South Kensington Advanced.
These questions are chiefly in Subject xv., Elementary Botany; but someare
in Subject xvi., Vegetable Morphology and Physiology. L.M.=London
Matriculation. L.I.=London Intermediate Science,

1. Root.

1. Describe the organs by which a 5. What is the channel by which
bean-plant absorbs water, and give an | the leaves of a plant make up for
account of the process of absorption. | the loss of water by transpiration?

(L.I.) Where does the water come from?
2. Describe the structure, and state | (S.K.E.)
what are the functions, of root-hairs. 6. Explain why the root of a turnip
By what means is a root able to absorb | first grows faster than the stem, and
from the soil substances which are in- | then stops while the stem grows
soluble in water? (S.K.A.) rapidly? (S.K.E.)
3. Whatisthe use of aroot? Under 7. Describe the way in which roots
what circumstances may plants exist | grow. (S.K.E.)
without one? (S.K.E.) 8. What part of a plant’s food is

4. What is root pressure? At what | taken up by the roots? (S.K.E.)
period is it most conspicuous? (S.K. A.)

2. Stem.

g. State the broad facts as to the de- 13. State generally what is the com-
velopment of branches. What is the | position of a vascular bundle. De-
difference between a sympodial and | scribe the longitudinal course of the
a monopodial branch system? Give | vascular bundles in the stem of any
illustrations of both cases from the | dicotyledon. (S.K.E.)

British flora. (S.K.A.) 14. What is the nature of the vas-
to, Explain why a potato is cou- | cular bundles of endogens? (S.K.E.)
sidered to bea stem. (S.K.E.) 15. Explain precisely what are meant

11, What is the structural differ- | by the terms ‘‘ pith” and “ medullary
ence between a prickle (as in the rose) | rays.” How do these structures origi-
and a spine (as in the blackthorn)? | nate? (S.K.E.) é
(S.K.E.) 16. What is the precise nature of

12. What are the principal modifica- | bast? In what part of the plant is it
tions of stem structure? (S.K.A.) | to be met with? (S.K.E.)

L

162

17. What is the cause of the ring-
like inarkings seen in the cross-section
of a tree-trunk? (S.K.E.)

18. Describe and explain as much
of the texture of a deal plank as can
be made out with the naked eye.
(S.K.E. )

19. Describe, with diagrams, the
primitive structure and the mode of
growth in thickness of the stem of a
dicotyledonous plant. Why does the
stem of dicotyledonous plants usually
increase in thickness? (S.K.E.)

20. Explain the modes by which
stems may increase in diameter. Point
out the causes of the difference be-
tween the spring and the autumn wood

EXAMINATION QUESTIONS.

of dicotyledonous trees with annual
erowth. (S.K.A.)

21. Explain the difference in the
crowth of the bark of a tree and that
of the wood. (S.K.E.)

22. What is the structure of thie
cambium; how does it originate in
the stem, and to what tissues does it
give rise? (S.K.A.)

23. From what source is the starch
derived which is stored up in a potato
tuber? By what means has it been
transported thither? (8.K.E.)

24. State what is the tissue in which
water travels from the root to the
leaves, mentioning illustrative experi-
ments. (S8.K.E.)

3. Foliage Leaf.

25. Describe a bud. ‘To what struc-
tures do the outer coverings corre-
spond? What is the origin and use of
the resinous secretion with which they
are often covered? (S.K.E.)

26. How do the outer leaves of a
bud generally differ from the inner?
(S.K.E.)

27. What isaleaf? What is its use
to the plant? (S.K.E.)

28. Of what parts is a leaf made up?
What is the use of the leaf as a whole,
and what are the uses of the several
parts? (S.K.E.)

29. Give instances of foliar organs
in which only the part corresponding
to the petiole of the leaf is developed.
(S.K.A.)

30. Describe the nature of stipules,
and illustrate from British plants the
forms which these organs may assume.
“(S..K.A.)

31. Whatarestipules? Describe the
stipules of the rose and of the sweet-
pea. (S.K.E.)

32. What is the general plan of ar-
rangement of leaves ona stem? Why
is it the most advantageous to the
plant? (S.K.E.)

33. Give instances in which leaves
are only imperfectly developed. What
useful purposes may they serve in such
cases? (S.K.E.)

34. Mention, with examples, special |

purposes to which leaves are adapted
in different plants. (S.K.A.)

35. Describe the structure of
onion. (S8.K.E.)

an

{
i
1

36. What is the use of the leaf to an
ordinary green plant? (L.M.)

37. What components of the atmos-
phere are taken from it by plants, and
for what purpose? (S.K.E.)

38. From what source does a green
plant obtain its carbonaceous food, and
in what form and by what organs does
it absorb it? What are the conditions
upon which the assimilation of the car-
bonaceous food depends? (8.K.E.)

39. Plants are said to ‘starve in the
absence of light.” Explain this state-
ment, (S.K.E.)

40. State why absence of light is in-
jurious to plants. (S.K.E.)

41. Explain what is meant by trans-
piration, and state how this process
may be experimentally demonstrated.
(S.K.E.)

42. What is meant by transpiration ?
Under what circumstances do plants
transpire most? (S.K.E.)

43. Explain why it is that plants
droop on a hot day, and recover their
freshness in the evening. (S.K.E.)

44. Describe the structure, develop-
ment, and mechanism of the stomata.
What is the effect of exposure to light
upon the stomata? (8.K.A.)

45. A withered branch on a tree with
deciduous leaves retains its leaves in
winter when the living branches have
lost theirs. Explain the reason of this.
(S.K.A.)

46. When a branch is cut off a plant,
theleaves uponit shortly begin to droop.
Explain why this happens. (S8.K.E.)

EXAMINATION QUESTIONS.

163

4. Inflorescence and Flower.

47. Give a sketch of the different
kinds of inflorescence, with examples
ofeach. (S.K.A.)

48. Explain precisely the kinds of
inflorescence to which the names spike,
raceme, and panicle are given. Show
in what respects they differ, and give
examples from familiar plants. (S.K. E.)

49. Briefly describe, giving examples,
the following forms of inflorescence,
and point out the relation which exists
between them: spike, spadix, raceme,
head. (S.K.E.)

50. Detine raceme, spike, catkin,
umbel, capitulum, corymb, and panicle,
and give one or more examples of each.
(S.K.E. )

51. Describe the structure of the
inflorescence in arum. (S.K.A.)

52. Describe the structure of the
flower of any flowering plant. In what
part of the flower is the seed formed ?
What events must take place before a
flower ‘‘ goes to seed’’? (S.K.E.)

53. Describe, with examples, the
structure of (a.) a hypogynous, (0.) a
perigynous, and (¢c.)anepigynous flower.
(S.K.E. )

54. What isa flower? What struc-
tures compose it, and what are their
use? (S8.K.E.)

55. Describe the typical arrangement
of the parts of a flower; how is this
modified in a leguminous and labiate
plant, and in an orchid and a grass?
(S.K.A.)

56. Describe and compare the struc-
ture of the staminal and carpellary
flowers of Pinus. (S.K.A.)

57. Give an account of the structure
of the head of a daisy. (S.K.E.)

58. Describe the structure of the
floret of a grass, and explain the homo-
logy of its different parts. (S.K.A.)

59. What grounds are there for re-
garding the parts of a flower as modi-
fied leaf organs? (S.K.A.)

60. Explain fully the various respects
in which a petal differs from a leaf.
(S.K.E.)

61. Describe the typical form of a
stamen, and illustrate from British

plants any remarkable deviations from |

it. (S.K.A.)

62, Explain, and illustrate by means
of examples, the following terms relat-
ing to the stamens of flowers :—Tetra-
dynamous, didynamous, diadelphous.
syngenesious.

What is the meaning of |

the statement that the flower of the
Orchidacez is gynandrous? (S.K.E.)

63. Describe the structure of the
stamen of a flowering plant. What
bodies are produced by it, and what
happens to them after they are shed
on the stigma? (S.K.E.)

64. Describe the structure and state
the uses of anthers. What is the evi-
dence that a stamen may be regarded
as a modification of the leaf? (S.K.E.)

65. Describe in detail the structure
of an anther and of a pollen grain.
(S.K.E.)

66. What is pollen? What is its use?
(S.K.E.)

67. Describe the ordinary structure
of a grain of pollen, and the change
which takes place when it is applied
to the stigma. (S.K.E.)

68. Describe the pistil of any flower-
ing plant. What is the nature and
what is the use of the various parts of
which it is composed? State briefly
the changes by which, as in the bean,
a young pistil is converted into a ‘‘ripe
pod.” (S.K.E.)

69. What is the explanation of the
origin of the syncarpous pistil? Enume-
rate the families in the British flora in
which it occurs with a parietal placen-
tation. (S.K.A.)

70. What is a placenta? Describe
the placentation in the Cruciferz, the
Leguminose, and the Liliacez. (S.K.E.)

71. Explain the use of the stigma,
and point out the mode in which its
minute structure is adapted to its use.
Give illustrations of modifications in
its form from British plants. (S.K.A.)

72. Describe the structure and state
the use of ovules. What is necessary
for the final development of these
organs? (S.K.E.)

73. In what points of structure does
an ovule differ from a seed? (S.K.E.)

74. What is a “‘nectary”? Give
examples of such a structure amongst
British plants. (S.K.A.)

75. What are meant by polygamous
plants? Give instances. (S.K.A.)

76. Give illustrations from British
plants of contrivances to protect the
floral organs from the attacks of in
sects. (S.K.A.)

77. Enumerate the British plants
which are wind-fertilised, and explain

in what respects their flowers are

adapted accordingly. (S.K.A.)

104

78. Explain the way in which insects
are of use to flowers, and the means by
which flowers attract them. (S.K.E.)

79. Show how- pollination is effected
in any two of the following flowers :—
Foxglove, white dead nettle, broom,
violet, hazel, willow. (L.M.)

80. What is meant by dichogamy ?
Illustrate your answer by examples
taken from the British flora. (S.K.A.)

81. Describe the different kinds of
flowers which exist in the genus Viola,
and show for what purposes and in what
manner they are adapted. (S.K.A.)

82. Some English plants have one,
others have two, and even three kinds
of flowers. Explain how this is pos-
sible. (S.K.E.)

83. How do you explain the fact that
while the leaves of most plants are
green, their flowers are of some other
colour? (S.K.E.)

84. Explain briefly the biological

EXAMINATION QUESTIONS.

significance of (a.) brightly coloured
and (b.) irregular flowers, as compared
with (c.) inconspicuous and (d.) regu-
lar flowers. Give examples. (L.I.)

85. What is meant by an irregular
flower? Give examples and explain
in each case the advantage of the
modification. (S.K.E.)

86. How do you account for the for-
mation of ‘‘spurs” from floral organs?
What is their use? Illustrate your
answer by examples from native plants.
(S.K.A.)

87. In some plants the style is made
the instrument of distributing the pol-
len which it is not itself to use. Ex-
plain and illustrate this statement by
examples. (S.K.A.)

88. Describe the process of fertilisa-
tion in any angiospermous phanero-
gam, giving a full account of the
structure of the ovule at the time of
fertilisation. (S.K.A.)

5. Seed and Fruit.

89. Explain precisely in what points
of structure a seed differs from an
ovule. (S.K.E.)

go. What is the botanical meaning
of the term ‘‘fruit’’? Describe the

structure of a plum, a strawberry, a |

blackberry, and an apple. (S8.K.E.)

ot. From what parts of the flower |

may the fruit be developed. Describe
an achene, a follicle, and a nut, giving
examples. (8. K.E.)

92. Describe a broad bean or pea,
or any other large seed, and the parts
of which it is composed. Describe also
the changes which take place when a
bean issown and germinates. (S.K.E.)

93. Describe aripe strawberry ; com-
pare and contrast its structure with
that of a fig. What is the use of the
fleshy part? (L.M.)

94. Explain the essential differences
of structure in the fruits of the straw-
berry and blackberry. (S8.K.E.)

95. Describe the structure of a plum
and of an apple. What important
organ enters into the one and not into
the other? (S.K.E.)

‘96. n what important respects does
the fruit of a cruciferous plant (such
as shepherd’s purse) differ from that
of al eguminous plant (such as a pea)?
How can the differences be accounted

or? (S.K.E.)

97. Describe the fruits of a butter-

cup and of a pink. In what respects

| do they agree, and in what respects do

they differ? (S.K.E.)

98. What isa berry? What is the
advantage to a plant to have this kind
of fruit? (S.K.E.)

99. Describe fully the structure of a
erain of wheat, and explain the nature
and fuuction of its several parts(S.K. A.)

100. Describe and compare the seeds
of the bean and of the wheat. (S.K.E.)

1o1. What is the structural differ-
ence between a horse-chestnut and a
sweet chestnut? (S.K.A.)

102. Describe the various modes by
which seeds are disseminated, and give
illustrative examples. (S.K.A.)

103. Give a detailed account of the
germination of any one of the follow-
ing:—A bean, a grain of wheat, an
acorn, ora date. (L.M.)

104. Why are some of our fruit
trees thorny in the wild state, but not
when cultivated? (S8.K.E.)

105. Describe the germination of a
pea and of a grain of wheat. (S.K.E.)

106. Give an account of the external
conditions requisite for germination of
a seed and growth of the embryo, and
explain how these conditions operate.
(iz)

107. The seeds of mustard and cress
will germinate on flannel soaked with
rain-water. Will they go on growing
under these circumstances, and if not,
why not? (S.K.E.)

EXAMINATION QUESTIONS.

6. Classification.

108. Describe the male flower of any |

Conifer you please, and state the struc-
tural differences which distinguish the
flower of gymnosperms from that of
other phanerogams. (S.K.A.)

Icg. Give the essential characters of
Orchidez. (S.K.A.)

t10. Contrast the character of grasses
and Cyperacee. (S.K.A.)

Ii1. Give a precise account of the
structure of the flower of any Crucifer,
and draw a diagram showing the
arrangement of the different parts,
(S.K. E. )

|
|
|

112. Describe the typical structure
of a stamen. State the peculiarities
characteristic of those of a Crucifer, a

Composite, a Labiate, and a Gruas~.
(S.K.E. )

113. Give the principal cliaracters of
Rosacee. (S.K.E.)

114. Draw a diagram showing the
arrangement of the parts of the flower
of a leguminous plant as seen in trans-
verse section. Point out in- what re-
spects it differs from the arrangement
typical of flowers generally. (S.K.E.)

7. General, Comparative, and Miscellaneous.

115. State what is meant by annual,
biennial, and perennial plants, giving
examples. (S.K.E.)

116. Giveexamplesof different kinds
of climbing plants, briefly describing
the mode of climbing in each case.
(S.K.E.)

117. What are the chief differences
between a root andastem? (S.K.E.)

118. Suppose a piece of the axis of
some flowering plant were shown to
you, what appearances would enable
you to decide whether it was part of
a root or of astem? (S.K.E.)

t1g. Compare the structure of the
root of any flowering plant with that
of its stem. Mention and briefly de-
scribe cases in which (a.) the stem and
(6.) the root has become modified to
serve as a depository of reserve mate-
rials. (S.K.E.)

120, Give a botanical description of
the part, in each of the following plants,
which is commonly used as food: the
potato, the onion, the turnip, and the
carrot. (S.K.E.)

121. What are tendrils? Of what
organs may they be modifications?
Give examples. (S8.K.E.)

122, Give examples of plants which
climb by means of tendrils, and ex-
plain how a tendril acts. (S.K.E.)

123. Describe the structure of a liv-
ing parenchymatous plant-cell. What
chemical elements enter into the com-
position (a.) of the cell-wall, (b.) of the
protoplasm? (S.K.E.)

124. What is a “ growing-point ”?
What is the difference between the
growing-points of stems and those of
roots? (S.K.E.)

125. State what are the general
characteristics of the epidermal tis-
sue of the sub-aérial parts of plants.
(S.K. A.)

126, What are fibro-vascular bundles?
Of what are they formed? What pur-
poses do they serve? (S.K.E.)

127. What isa sieve-tube? What is
its structure? What is its position in
a dicotyledon? What is its probable
function? (L.I.)

128. What is meant by a vessel?
How is it formed, and what is its use?
(S.K.E.)

129. What are the differences be-
tween the vessels of the wood and
those of the bast? (S.K.E.)

130. Why can a tree be transplanted
more safely in the winter than in the
summer? (S.K.E.)

131. Why will a plant grown in a
dwelling-room be less vigorous than
one grown in the open air? (S.K.E.)

132. Write an account of the func-
tions performed by the epidermal tis-
sue. (L.I.)

133. Why does heaping earth round
celery cause the stalks to be white?
(S.K.E.)

134. What remarkable change do
plants show when they are grown in
the dark? (S.K.E.)

135. When any vegetable material is
burned, what constituents go off as
gas? Whatareleft behind? (S.K.E.)

136. Describe the method by which
the importance of the various mineral
constituents of a plant’s food has
been most satisfactorily ascertained.
(S.K.E.)

137, What parts of a green plantare

1660

ereen and what are not? What gives
the greenness to the green parts? What
is the great difference in function be-
tween the parts which are not green
and those which are? (S8.K.E.)

138. What is the nature of and
composition of chlorophyll? Where
is it found, and how is it formed?
(S.K.E. )

139. What constituents of sunlight
are most effective in producing the
chemical changes on which the nutri-
tion of plants depends? (S.K.E.)

140. What is the nature of starch?
How is it formed, and what is its use?
(S.K.E. )

141. Why do plants require nitrogen,
and in what form do they take it in?
(S.K.E.)

142. From what source and in what
forms do plants usually absorb their
nitrogenous food? Mention cases in
which the nitrogenous food is absorbed
from other sources and in other forms.
(S.K.E.)

143. Give a brief account of the genus
Drosera, and describe its insectivorous
mechanism. (S.K.A.)

144. Give an account of the move-
ment of water in the plant, and state
the tissues. that take part in it.
(S.K.A.)

EXAMINATION QUESTIONS.

145. Trace the course of the sap from
the root to the leaves. (S.K.E.)

146. What is meant by respiration?
Describe an experiment for showing
that plants respire. (S.K.E.)

147. What are stomata? Whereare
they found in the plant, and what is
their use? (S.K.E.)

148. What is the difference in the
physiological action of green and
coloured leaves? (S.K.A.)

149. Explain precisely how a tendril
acts. (S.K.E.)

150. What is the cause which enables
a plant to climb round a support?
(S.K.E.)

151. Describe an experiment by
which it can be shown that the upward
growth of a stem and the downward
crowth of a root is in each case to be
attributed to the action of gravity.
(S.K.A. )

152. Explain why it is that, when
a seed germinates, the stem grows
upwards and the root downwards?
(S.K.E. )

153. Describe the processes which
lead to the conversion of an ovule
into a seed, and state which is the
difference between albuminous and
exalbuminous seeds, giving examples.
(S.K.E.)

- INDEX.

A.

ABORTED, 97, 99, 127.

Absorption, of food, 9, 17-18, 69, 143, 160.

Acacia, 53, 543; false a. (see Robinia).

Accretion, 6.

Achene, 136, 137, 155-

Acid ; carbonic a. (see Carbon dioxide) ; for-
mic a., 72; sulphuric a., 159, 160.

Acorn, 136, 143.

Acropetal succession, 16, 23, 46, 71.

Actinomorphie, 8o.

Acuminate, 147.

Acute, 147.

Acyclic, 81, 83, 86, 92, 98.

Addition of reagents, 160.

Adhesion, 83; of sepals, 84-85, 148; of
petals, 87, 148; of stamens, 95, 148; of
carpels, 95, 148.

Adjustment, 158.

Adnate, 56, 96.

stivation (see aes

Aggregate, 1355 13

Air, 3, 4, 17) 34; = 40, 47, 70, 142, 143, 160;
air-bladder, 98, 1163; air-cavity, 30, 43,
66

Ale, 88.

Albumen (of seeds), 131,

Albuminous, 132, 134, 143.

Alburnum, 38, 42.

Alder, 50, 116, 155.

Aleurone grains, 134, 135.

Almond, 113, 132.

Aloe, 62, 70.

Alternate; a. whorls, 83, 151; a. leaves
(see Scattered).

Amaryllidacez, 154.

Amentacez, 155

Amentum (see Catkin).

America, North, 43, 55, 116.

Ammonia, 10.

Ameeba, 5.

Amorphous, 5.

Amplexicaul, 58.

Anacharis, 43.

Analogous, 7.

Analogue, 7.

Analogy, 7

Analysis, ro.

Anatomy, 1; of root, 14, 158; of stem,
29-30, 158; Of foliage leaf, 64-66, 158.

Anatropous (see Inverted).

Ancestors, 102.

132,

reer

Andreecium, 74, 81, 83, 92-98, 150, 151, 152
153, 154; 155, 150, 157 (see Siamen).

Anemone, 87, 106, 155.

Anemophilous (see Wind-pollinated).

Angiosperms, 21, 101, 109, 114, 152-158.

Angular distance. 50.

Auimals, how differing from plants, 2-4;
breathing ofa.,11; digestion of a.,71;
browsing a., 41, 111 5 creeping a., 413
soft-bodied a., 41; relation to flowers,
111-130 ; relation to seeds and fruits,
142.

Annuals, 14, 23, 44, 146.

Annual rings, 38, 39, 40, 152.

Anterior, 82, 94, 103, 150, 155.

Antero-posterior, 52, 82.

Anther, 74, 95, 96, 114, 118, 123, 124, 126,
128, 130, 131, 151, 159; a. lobe, 97, 128,
129; a. ring, 124, 126, 127.

Ants, 71, 111.

Apex ; of foliage leaf, 58, 147 ; of ovule, 107,
109, IT4.

Apocarpous, I00, Io!,
155.

Aposepalous, 84.

Apparatus, 145-146, 158-159.

Appendages ; of stamens, 96, 127 ; of seeds
and fruits, 141, 142.

Appendix ; on practical work, 145 ; exami-
nation questions, 161.

Apple, 51, 56, 123, 132, 136, 156.

Apricot, 149, 156.

April, 88.

Aril, 134.

Aroidaceze, 153.

Aromatic, 157.

Arrangement; of foliage leaves, 46-51, 110,
147, 149}; Of stipules, 63-64, 147; of
scale-leaves, 147 ; of flowers, 75-80, 147,
149-150 5 of sepals, 83-84, 148; of
petals, 86-87, 148; of stamens, 92-94,
148 ; of carpels, 98-100, 148 ; of seeds,
104-106, 148.

Arrow-shaped, 58.

Artichoke (see Jerusalem a.)

Articulation, 59.

Arum, 21, 56, 76, 78, 98, 99, 113, 114, 120;
125, 153-

Ascending, 25.

Ascidians, 4.

Ash, 59, 60, 61, 99; 100, 142.

Asparagus, 27, 29, 30, 36, 158.

Aspen, 50, 53-

702, 103; 135; 139)

168

Assimilation, ro, 67 (see Nutrition).

Aster, 157.

Atoms, 4.

Auricula, 157.

Australia, 53, 55.

Autumn, 38, 42, 48.

Awn, 117, 142.

Axial, 106.

Axil, 22, 26, 27) 44, 47) 64, 75> 76, 100, 109,
IIo.

Axile, 104, 106, 154, 157, 158.

Axillary, 22, 63, 149.

Axis; of root, 13, 152; of stem, 13, 21; of
inflorescence, 77, 78, 79, 80, 82, 135, 150;
of flower, 74, 81, 92, 152.

B.

Back ; of leaf, 52; of flower, 150.

Balsam, 140.

Bamboo, 23.

Banana, 56.

Barberry, 60, 61, 77, 86, 97, 124.

Bark,. 37, 40; 41, 42, 44, 47) 152, 153-

Barley, 117,133, 143-

Basal, 103

Basal-veined, 56, 57.

Base ; of foliage leat, 58, 147; of ovule, 107,
109, 132.

Basifixed, 96.

Basil, 157.

Bast, 31, 34, 40, 41, 66; hard b., 31, 32, 343
primary b., 36; secondary b., 37; soft
b., 31, 33) 34) 363 b. fibres, 31, 32, 34;
b. parencuyma, 31, 33, 34; b. vessels
(see Sieve-tube).

Beak, 103, 140, 156.

Bean, 13, 14, 30, 63, 68, 88, 95, 113, 127, 132,
142, 143, 149, 156, 160.

Beech, 24, 47, 48, 50, 51, 54, 56, 64, 116, 135,
139, 140, 155.

Bees, 113, 117, 120, 121, 122, 124, 126, 127,
129.

Beetles, 119.

Beet-root, 18, 155.

Begonia, 49, 55.

Bellis (see Daisy).

Bell-jar, 68, 609.

Bell-shaped, 86, 89, 128, 157.

Bent, 109.

Berry, 139, 153,154, 156, 157-

Bidden guests, 111.

Biennials, 14, 23, 146, 149.

Bifacial, 65, 73.

Bilateral, 51, 54, 64, 80, 85, 86, 87, 147.

Biology, 2.

Birch, 48, 116, r42, 155.

Bird-pollinated, 130.

Birds, 111, 115, 130, 142.

Bird’s-foot tretoil, 95, 127, 156.

Bird’s-nest, 64.

Bisexual, 98, 99, 100, 115, 117, 152, 153, 155-

Bistort (see Knot-grass).

Bittercress, 141.

Bittersweet, 157.

Blackberry, 28, 103, 122, 123, 139, 156.

Black-currant, 123.

Bladder-campion, 95, 113.

Bladderwort, 62, 112.

Blade (see Lamina).

Blastocolla (see Bud-glue).

Bleeding of vines, 18.

INDEX.

Blossom (see Flower).

Blue, 85, 90, 91, 119, 120, 124, 160.

Boat-shaped, 88.

Borage, 28, 105, 137, 156.

Boraginacee, 156, 157.

Botany, 1; scope and subdivisions, 1-2;
descriptive, 1; economic, 2; fossil, 2;
geographical, 2; systematic, 1-2.

Bract, 51, 74, 76, 78, 99, 100, III, I12, 113,
117, I19, 135, 136, 142, 147, 149, 152, 155-

Bracteole (see Bractlet).

Bractlet, 76, 83, 85, 117.

Bramble (see Blackberry).

Branches ; of root, 13,146; of stem, 21, 25,
26, 27, 39, 43, 75-80, 147; b. spines, 27,
61.

Branching; of root, 12, 16, 146; of stem,
24, 46, 75-80, 146; of stamens, 94, 156.

Brazil-nut, 134.

Bread, 135.

Breathing, 10 (see Respiration).

Bristles, 62, 73, 118, r52.

Brookweed, 93, 97.

Broom, 127, 137, 140, 156.

Broom-rape, 64, 71.

Browning, 158.

Browsing animals, 41.

Bryonia (see Bryony, white).

Bryony, black b., 56; white b., 45.

Brush, of hairs, 126.

Bud, 26, 145; accessory b., 48; adventi-
tious b., 49; apical or terminal b., 46,
48; axillary b., 47, 48; dormant b.,
473; flower b., 49, 75, 84, I10, 117) 149;
leaf b., 7, 36, 44, 46-50, 64, 67, 75, 147,
149; b. glue, 7, 64, 67, 114, 149.

Budding, 44.

Bugle, go.

Bugloss, 156.

Bulb, 26, 44, 48, 64, 149, 160.

Bulbil (see Bulblet).

Bulblet, 44, 48, 64.

Bulrush, 154.

Bundles, vascular; of root, 14-16 ; of stem,
29) 30, 31, 36, 152, 158; of foliage leaf,
47, 50, 65, 66, 67, 158; Of petal, ox; of
stamen, 98; of carpel, 107; of ovule,
107 ; closed b., 36; common b., 30, open
b., 323 primary b., 36; b. sheath, 32.

Burdock, 142.

Bur-reed, 154.

Butcher’s broom, 27, 154.

Buttercup, 21, 24, 31, 36. 57, 62, 74, 81, 83,
84, 85, 86, 92) 93, 96, 98, 100, 103, 122,
126, 130, 136, 139, 151, 155-

Butterflies, 120, 122.

Butterfly-shaped, 88, 98, 114, 126, 156.

Butterwort, 112.

C.

CABBAGE, 25, 137, I55-

Cactus, 27, 71, 83.

Caducous, 84, 86, 155.

Calceolaria, 157.

Calcium, 10, 160.

Californian poppy (see Eschscholtzia).

Calyciflorz, 153, 156.

Calystegia, 121.

Calyx, 74, 78, 80, 81, 83-86, 89, 100, 102,
T13,° 117, ‘120, 123,29, 2g5,140,n bails
142, 148, 150, I51, 152, 153, 154, 1555
156, 157; (see Sepal) ; c. tube, 84-85.

INDEX.

Cambium, 17, 31, 34, 36, 37, 38, 39, 40 44
66; fascicular c., 37; interfascicular
c.. 37; cork c., 40; c. ring, 37, 39, 40.

Camel’s-hair brush, 159.

Campanulacee, 157.

Campanulate (see Bell-shaped).

Campion, 79, 87, 109, 156 (see Bladder c.).

Campylotropous (see Bent).

Canal, 43 (see Pollen-canal).

Candy-tuft, 155

Canes, 25.

Canescent, 28.

Canterbury bell, 84, 89, 113, 126, 158.

Cape, 130.

Capitulum (see Head).

Capsule, 137-138, 130, 141,
157, 158. <A

Carbon, 3, 5, 10; ¢. dioxide, 3, 9, 10, 11,
17, 18, 19, 42, 67, 68, 71, 114, 143, 160.

Carbonic acid (see Carbon dioxide).

Cardamine, 141.

Carina (see Keel).

Carnation, 100, 156.

Carolina, North, 61.

Carpel, 75, 82, 92, 95, 98-109, 110, 113, 136,
137, 138, 150, 151, 153, 154, 155, 156,
E77 cho

Carraway, 137, 156.

Carrot, 13, 79, 119, 137, 150, 151, 150.

Caruncle, 132, 133-

Caryophyllacez, 155.

Caryopsis, 136.

Castor-oil seed, 132, 134, 135, 143-

Caterpillar, 111.

Catkin, 78,99 100, 116, 155.

Cats, 121.

Cattle, rrr.

Cauline, 147.

Caustic potash, 68, 159, 160.

Cedar, 152.

Celandine, 155

Celery, 68, 156.

Cell, 5, 8; antipodal c., 109; artificial c.,
9; co-operating C., 109, 1143 egg-c. (sve
Egg-cell); endosperm ec. (see Endo-
sperm); guard c., 66, 70; c. derivate,
8, 16, 17, 32, 33, 343 Cc. fusion, 33, 34;
c. nucleus (see Nucleus); ce. protoplasm
(see Protoplasm); c. san, 8, 16, 18, 19,
3r, 65, 72; Cc. Wall, 8, 16, 17, 18, 30, 31,
32, 33, 34, 35, 38, 65, 67, 70, (see Tissue).

Cellular, 45.

Cellulose, 3s 4, 10, EI, 10,
134, 1

Central ee Free central).

Centric. 66.

Centrifugal, 79, 150.

Centripetal, 77, 124, 149.

Ceylon, 62.

Chalaza (see Base of ovule).

Chamomile, 157.

Chenopodiacez, 155.

Chenopodium, 155.

Cherry, 51, 77; 110, 139, 149, 156; c. laurel,
156.

Chestnut, 135, 139,140; (see Horse-chestnut).

Chevaux-de-irise, 125.

Chickweed, 156.

Chili pepper, 157.

Chinese primrose, 125.

Chloral hydrate, 67, 158.

Chlorides, 10, 160.

154, 155, 156,

3% 31, 32, 33, 65,

169

Chlorophyll, 4, 8, 10, 11, 40, 42, 67, 68, 71,
149, 160; c. granules or corpuscles, 8,
315 6s, 67570, 71.

Christmas rose, 155.

Ciliate, 28.

Cinquefoil, 113, 156.

Circinate, 49, 149.

Circular, 57.

Circulation ; of gases, 19, 43; of liquids, 18.

Circumnutation, 44.

Cladode, 27.

Cladophyll, 27.

Class, 21, 151, 152, 153, 154.

Classification, 1, 21, 148, 151-158, 165.

Claw, 87, 88, 124.

Cleanliness, 159.

Clearing, of sections, 160.

Cleaver (see Goosegrass).

Cleft, 59

Cleistogamous, 130-131, I4o.

Clematis, 155.

Climate, dry, 27, 62.

Climbers, 25-26, 53.

Clover, 59, 60, 78, 88, 121, 127, 156.

Club-moss, g2.

Club- shaped, 99.

Coats, of animals, 142; of ovule (see In-
tegument); of seed (see Seed-coat).

Cocoa-nut, 133, 134, 141.

Cohesion, 83: of “sepals, 84, 148; of petals,
87, 148; of stamens, g5, 148; of carpels,
Ioo-to1, 148.

Cohort, 21.

Colchicum, 149.

Collar, rr2.

Collective, 135.

Collenchyma, 31, 41, 67.

Colleter, 64.

Colour ; of root, 18, 1463 of stem, 146; of
petiole, 147; of lamina, 62, 147; of
scale-leaf, 147; of flower, 115, 118, 152;
of calyx, 86; of corolla, 91, 153; of
stamen, 97; c. body, or.

Coltsfoot, 157.

Columbine, 88, 100, 102, 104, 107, 137-

Column, 129.

Comfrey, 156.

Common bundles, 30.

Compartment (see Loculus).

Compass plant, 55.

Composite, 78, 80, 84, 95. 119, 126, 130, 136,
E41, E57-

Composition, of foliage leaf, 147, 149.

Compound, 59, 79, 147, 156; c. microscope
(see Microscope).

Condensed, 146, 149, 150.

Conducting tissue (see Tissue, conducting).

Conduplicate, 49, 149.

Cone, 92; 98, 99, 101, 116.

Conical, 8r

Connate, 58, 112.

Connective, 96, 129.

Conspicuousness, 119-120.

Contact, 19, 20, 45, 73, 128.

Convolute, 49, 149.

Convolvulus, 8, 25, 8a, 93, 121.

Coral islands, 141.

Core, of apple, 136.

Coriander, 156.

Cork, 17, 40, 41, 43, 67; ¢. cambium, 4o.

Corm, 26, 42, 44, 48, 149, 154, 160.

Corolla, 74, 78, 81, 83, 86-91, 101, 112, 113,

170

117, 118, 120, 122, 125,127, 129, 148, 150,
151, 152, 153, 154, 155, 156, 157, (see
Petal).

Corolliflorze, 153, 155-158.

Corona, 88, 112.

Cortex ; of root, 14; of stem, 28,30, 31, 36,
38, 40, 41, 152.

Corydal, tos.

Corymb, 77, 79.

Costal-veined, 56.

Cotton, 3, 134, 142.

Cotton-grass, 142.

Cotyledon, so, 132, 133, 134, 135, 142, 143,
I52, 153, 160.

Cover-glasses, 158, 159, 160.

Cow-parsnip, 119.

Cowslip, 125, 157.

Cram, 146.

Crane’s-bill (see Geranium).

Creeping, 25, 43, 54.

Cress, 50, 143, 160.

Crocus, 26, 149, 154.

Cross-fertilization, 115

Cross-pollination, 115-130, 148.

Cross-shaped, 88, 141, 155.

Crozier, 49.

Cruciferse, 141, 155. :

Cruciferous (see Cross-shaped).

Crumpled, 49, 134, 150.

Cryptogams, 2.

Crystal, 5, 6.

Crystalloid, 26, 42, 134, 135.

Cucumber, 25, 36, 95, 139; squirting c.,
I4I.

Culm, 23, 25.

Cultivation, 135.

Cupuliferee, 155.

Currant, 77, 123, 139, 149.

Cuticle, 30, 65, 69.

Cuticularized, 65, 70, 160.

Cutin, 30, 40.

Cutting, of sections, 159

Cuttings, 13, 43-

Cyclamen, 26, 140, 149, 157.

Cycle, 50, 51, 81, 83, 149.

Cyclic, 81, 82, 83, 86, 93, 98.

Cylinder, vascular (see Vascular c.).

Cylindrical, 23, 29, 52, 103, 146, 147.

Cyme, 79, 80, 100.

Cymose, 24, 75, 79, 150, 155; 156, 157.

Cypress, 21, 152.

Cypripedium, 94.

Cypsela, 136, 157.

D.

DAFFODIL, 154.

Dahlia, 14, 19, 95, 157."

Daisy, 21, 24, 78, 93, 95, 106, 119, 126, 149,
157, 159.

Dandelion, 19, 24, 78, 95, 106, 136, 140, 142,
I5I.

Dark, 160.

Darwin, 44, 45, 121.

Date, 133, 134, 139, 143-

Deadly nightshade, 80, 157.

Dead-nettle, 21, 49. 80, 86, 89, 90, 93, 95, 96,
97, 100, 105, 106, 113, 128, 137: 151, 157-

Deal, 30.

Deciduous, 62, 64, 86.

Decompound, 6r.

Decumbent, 25.

INDEX.

Decurrent, 58.

Decussate, 49, 80, 82, 155, 157-

Definite (see Cymose).

Dehiscence ; of anther, 114, 126; of fruit,
137-138, 139, 140-141, 151.

Description of plants, 145-158.

Desmodium, 73.

Development, 7, 27 (see Germination)

Dew, 41, £23;

Diadelphous, 95, 103, 156.

Diagonal (see Oblique).

Diagrams, 146; of anatomy of vegetative
organs, 29; of capsules, 138 ; of dicoty-
ledon, 15; of epigynous flower, 81; of
hypogynous flower, 81; of monocoty-
ledon, 22; of ovules, 104; of perigynous
flower, 81; of secondary thickening, 37;
of simple flower, 108; of unicellular
plant, 9; f. diagrams, 82, 148, 150.

Dichogamous, 115.

Dichogamy, 115, 130.

Dichotomous, 79.

Dichotomy, false d., 24, 47, 79.

Dicotyledons, 21, 24, 30, 32, 34, 35, 36, 38,
50; 51, 52, 55, 57, 66, 83, 86, 98, 107, 152-
153) 154-158; diagram of, 15.

Didynamous, 94, 128, 157.

Dielytra (Dicentra), ros.

Differences between plants and animals,
2-4; between living and non-living
matter, 4-6.

Differentiation, 12.

Diffusion, 9 (see Osmosis).

Digestive excretion, 71, 73, 114.

Dimorphism, 125.

Dicecious, go.

Dipsaces, 157.

Direction ; of growth, 24, 23; of root, 146;
of stem, 146; of inflorescence, 147; of
ovules, 106.

Disc, 106.

Disk, 78, 95, 126.

Dissecting needles, 145.

Dissection of plants, 145, 149, 150, 158.

Dissepiment, 104, 105, false or spurious
d., 105, 137.

Distasteful substances, 67, rrr.

Distilled water, 160.

Distribution ; of plants, 2; of fruits and
seeds, 140-142, 148.

Ditches, 62.

Dittany, 104.

Divergence, 50, 51, 83, 149, 154.

Divergent, 85.

Division, 21; of cells, r1, 16; of labour, 12.

Dock, 56, 64, 106, 109, 117, 142, 155.

Dodder, 2, 11, 23, 71.

Dog-rose (see Rose).

Dog-violet, 130, 141.

Dorsal margin, 102, 138.

Double flowers, 110.

Dove’s-foot geranium, 120.

Drawing, 146; d. book, 146.

Dried flowers, rrr.

Drift-timber, 141.

Drugs, 2.

Drupe, 139

Drupel, 139.

Dry fruits, 136-138, 140.

Duckweed, 21, 27, 98, 153.

Duramen, 38, 42.

Duration of life, 14, 23.

INDEX.

Dusk, 119.
Dwarf mallow, 1z0.
Dyes, 2.

E.

EARTH, 3, 19 (see Soil).

Earthworm, 19.

Edge (see Margin).

Egg-apparatus, 109.

Egg-cell, 109, 115) 131-

Hight-ranked, 5r.

Elder, 40, 59, 80, 119, 159.

Elements ; chemical, 4; essential, 9, 160.

Elm, 24, 36, 48, 50, 51, 54, 55, 80, 142.

Hlodea, 43.

Emarginate, 147.

Kmbryo, 131, 133, 134, 142, 152, 153, 154:

Embryo-sac, 109, 133-

Emergences, 28, 54, 61, 63, 71, 72.

Enchanter’s nae ages 86, 156.

Indocarp, 136, 13

Endodermis (see oodles sheath).

Endogenous, 14, 39.

Endogens, 38, 309.

Endoparasites, 4.

Endosmosis, 9.

Endosperm, EIT TSS, T3450 E52; 2530 0545
160.

Energy, 11; kinetic, 5,10; potential, 5, ro.

Entire, 58, 156.

Entomophilous (see Insect-pollinated).

Epipetalous, g5, 118, 153, 156, 157.

Kpicalyx, $5, 156, 157.

Epicarp, 136, 139.

Epidermis, 7, 17; of root, 14; of stem, 28,
29, 30, 31, 36, 40, 41; of leaf, 64, 65, 67 ;
of petal, gt ; of stamen, 98; of carpel,
107 ; of fruit, 136.

Epigean, 143.

Kpigyne, 152, 153, 154, 155, 157.

Epigynous, ae Re 85, 87, 95, IOI, 124, 150,
TSE) L535

Epilobium os: Willow herb).

Epiphytes, 13.

Kquitant, 55, 154.

Erect, 24, 41, 146, 153, 157.

Eschscholtzia, IOI, 155.

Essential floral leaves (see Essential organs).

Essential organs, 92-131.

Etiolated, 68, 160.

Itiolin, 68; e. granules, 68.

Hucalyptus, 53.

Europe, South, 141.

}vaporation, 41.

Evening primrose, 93, 107, 156.

livergreens, 62, 67.

Iiverlasting pea, 127.

Exalbuminous, 132, 142.

lxaminations, 146; exam. questions, 161-
166.

Excreted, 11

Excretion, 15, 71; 73; 74; 1l2, 114, 12%, 122,
123.

Exogenous, 309.

Ixogens, 33, 39.

Exosmosis, 9.

Explosion of flowers, 127.

Exserted, 06.

Exstipulate, 149, 155, 156, 157.

External characters ; of calyx, 85-86, 148;
of corolla, 87-91, 148; of stamens, 96-
97, 148; of carpels, 101-106, 148.

jeg

Extine, 08.

K}xtra-axillary, 4

Extra-floral nectaries, 110, 113.
Extrorse, 96, 97.

Eyepiece, 158.

yes, 26, 48, 64.

FADING, 9, 69.

Fall, of the leaf, 42.

False; dichotomy. (see Dichotomy, false) ;
dissepiment (see Dissepiment, false);
fruit (see Pseudocarp).

Family, 21, 106.

Fan, 49.

Fan-palms, 56.

Fascicle, 80.

Feeding, 9 (see Nutrition).

Female; spore-leaf, 92; catkin, gg, 100, 1533
cone, 92, 99, 116; flower, 92, 94, 99, 100,
IOI, 109, II5, 117, IIQ, I2I, 125, 140, 155,

157:

Fennel, 156.

Ferns, 92, 149.

Ferric chlor ide, 160.

Fertilization, 115, 131, 1523 cross-fertiliza-
tion, 115.

Fertilized, 115.

Fibre, 2, 146, 140.

Fibrous, 146.

Fibro-vascular, 34.

Field-microscope, 158.

Field-mouse, 122.

Fig, 135.

Figwort, 157.

Filament, 74, 95, 96, 98, 100, 113, 117, 118,
129.

Fir, 21, 24, 30, 35, 36, 39, 64, 84, 92, 93, 98,
09, IOI, 116, 142, 152.

Fission, rr.

Fistular, 23, 154.

Five, 83, 86, 87, 89, 91, 93, 94) 96, 97, 102,
103, 104, 117) 153, 155, 156, 157-

Five-ranked, 51

Flaccidity, 9

Flag, rig.

Flannel, 160.

Flattened, 23, 104, 132.

Fleshy, 56, 76, 78, 103, 106, 123, 135, 139.

Flexible, 112, 114.

Flies, 3, 120.

Floral diagram (see Diagram, floral).

Floral formula, 150, 151, 154, 155+ 156, 157.

Floral leaves, 74, 75, 81, 131 (see Flower).

Floral receptacle, 74, 8x, 84, IOI) 109, I21;
description of, 148, 150, 151.

Floret, 78, 89, 91} 93, 95) 106, 119, 126, 157,

18

Flour, 4 35-

Flower, 2, 21, 24, 41, 69, 743 flower-cluster
(see Inflorescence), description of, 148,
I50-151; examination questions on,
163-164; morphology of, 74-110, 152,
153) 154) 155, 156, 157, 158; physiology
of, 111-131; flower-stalk, 25, 28, 76,

I1Q.

lower bad (see Bud, flower).

Flowering ash, 100.

Flowering glume, LI7s

Flowering plants, 12, 92, 146; Classification
of, 151-158.

v2

Flowering rush, 98.

Fly-trap, 61, 73.

Focussing, 145.

Foetid, 120.

Folded, 49.

Foliaceous, 63.

Foliage leaf, 51, 52-73, 76, 83, 85, 102, 116,
152, 153, 154, 155, 156, 157; arrange-
ment of, 110, 1123 assimilation by, 66-
69; blade of (see Lamina) ; description
of, 147; examination questions on,
1623 irritability of, 73; kinds of, 59;
morphology of, 52-66 ; motility of, 71-
723 parts of, 52; physiology of, 66-
733 protection Of, 16736 Yepr oduction
by, 7X5 respiration of, 71; spontaneity
ot, 73; stalk of (see Petiole); structure
of, 64-66, 86, 107, 158, 1593 support
of, 66-67; transpiration of, 69-71;
venation of, 55-57 (see also Sheath and
Stipule).

Follicle, 137, 155.

Food, 6; of plants and animals, 3; recep-
tion of, 9 (see Nutrition) ; nature of, 9 ;
food solution, 9, 10, 17, 68, 69, 160.

Forceps, 145.

Forget-me-uot, 80, 89, 93, 105, 130, 137, 142,
186.

Forking (see Dichotomy).

Form ; of plants v. animals, 3, 4,5; of non-
living matter, 5; of simplest plants,
8; of root, 13-14, 146; of stem, 23-27,
146; of lamina, 57-62, 147; of petiole,

3, 1473 of scale-leaf, 64, 147; of hairs,
28 (see External characters).

Formic acid, 72.

Four, 83, 87, 93, 94, 97, 100, 104, 105, 124,
153) 155, 156, 157.

Four-lobed, 1o5.

Four-rayed, 80.

Four-sided (see Square).

Foxglove, 77, 89, 90, 94, 95, 97, 98, 104, 119,
T22 Te Oen OS Oslh 7

Fragrance, 114, 118, 120, 12t.

Fragrant substances, 28, 66.

Fraxinus, 61.

Free, 84, 87, 88, ror, 151.

Free central, 106, 138, 156.

Frightening of insects, 124.

Frogbit, 98.

Front, 106, 150

Fruit, 42, 75, 102, 103, 132-143 ; description
of, 148, 1513 distribution of, 140-142;
examination questions on, 164.

Fuchsia, 81, 93, ae ae I07, 123, 150, 160.

Funnel-sh: uped, 86,

Funicle, 107, 108.

G.
GALEATE, 90
Galium (see Goose-grass).
Gamopetalee, 153, 156-158.
Gamopetalous, 87, 89-90, 94, 107, 112, 113,

153-
Gamosepalous, 84, 85-86, 126, 153.
Gaping, go.
Gardening, 42, 43, 44, 68, 95, 110.
Garden-sage, 129.
Garlic, 154.
Gases, 19, 31.
Gastric juice, 71.

INDEX.

Genealogy, 2, 21.

General exam. questions, 165-166.

Genetic spiral, so.

Gentian, 112, 137.

Genus, 21.

Geotropism, 19, 20, 44, 73.

Geranium, 21, 52, 53, 56, 98, 120, 124, 137,
140, 142, 156, 159.

Germination, 68, 136, 140, 142-143, 160.

Glabrous, 28, 30, 54, 62, gi, 112.

Gladiolus, 154.

Gland, 61.

Glandular, 61, 71, too, 112, 151.

Glaucous, 147.

Globoid, 135.

Globular, 27, 104.

Glomerulus, 80.

Glossy, 67.

Glovers’ needles, 145.

Glume, 117, 152.

Glumifloree, 152, 154.

Glycerine, 159, 160.

Gooseberry, 112, 123, 136.

Goosefoot, 155.

Goosegrass, 26, 28, 142, 147.

Gorse, 21, 61, 86, 88, 95, 100, 113) 119, 127,
137, D5O;05is0L 50s

Grafting, 43.

Grains, pollen (see Pollen).

Graminacez, 154-

Granules ; ohlaccaniyll (see Chlorophyll g.) ;
etiolin (see Etiolin g.).

Grape, 139.

Grasses, 13, 21, 30, 36, 50, 52, 56, 63, 66, 67,
79, 96, 100, 117, 120, 136, 143, 146, 149,
I50, I51, 154.

Grass-pea, 63.

Gravity, 19, 20, 44, 73-

Greater celandine, 155.

Grooved, 28, 53.

Ground-ivy, 157.

Groundsel, 53, 78, 95, 130, 157-

Ground-tissue (see ‘Tissue, g.ound).

Group, 21.

Growing-point, 16, 34, 47, 66.

Growth; of cell, 8; of inorganic matter,
6; in length, 16, 32, 45, 47, 663; of
organic matter, 6; of plants, 42, 71 ; of
pollen-tube, 114, 1603; in thickness,
16, 23, 24, 36, 1523 delimiters, vor
direction of g., 19, 20, 24, 443 inde-
finite g., 48.

Guard-cell, 66, 70.

Guelder rose, 119.

Guests; bidden g., 111, 118-1303 unbidden
&.5 III-113, 11g.

Gymnosperms, 21, 24, 30, 32, 35, 36, 38, 98,
IOI, IO2, 107, 109, II4, 152, 153.

Gynandrous, 96, ror. 154.

Gyneecium, 75 (see Pistil).

H.

HaBIT, 146, 148-149.

Hair, 3,:7, 8, 16, 07, 2%, 28,820)) Sina eee
54, 62, 65, 67, 72, 73, 86, 90, 98, 99, 107,
Ir2 I13, 116, 120,227) a2q. TA
branched h., 62; elaudular h., 28, 41,
62, 71, 125 sensitive h., 62, 73 ; sting-
ing h., 62, 72, 154.

Hair-structure (see Hair).

Hairy, 28, 62, 113, 126, 127, £20.

INDEX.

Hairy bitter cress, 141.

Half-anther, 97.

Handles, for dissecting needles, 145.

Harebell, 89, 113, 126, 158.

Hawthorn, 28, 77, 122, 123, 156.

Hay, x11.

Hazel, 9, 48, 78, 116, 155; h. nut, 132, 136,
139.

Humble-bee, 113, 121, 122, 128.

Humming-bird, 130.

Husk, 135, 139-

Head, 78, 80, 157 ; of bee, 129, 130.

Heartwood, 38, 42.

Heat, 69, 160.

Heath, 89, 97, 113, 123, 127.

Heather, &9, 123.

Helianthus tuberosus (see Jerusalem arti-
ehoke).

Helicoid cyme, 80, 156.

Heliotropism, 20, 45, 73-

Helmet-shaped, go.

Hemicyclic, 81, 83, 86, 93, 98.

Hemlock, 79, 106, 119, 156.

Henbane, 138, 157.

Herb, 23, 48, 57, 1532 154, 155, 156, 157.

Herbaceous, 62, 69, 70, 146, 1490, 158.

Herkogamy, 115.

Hesperidium, 139.

Heteromorphism, 124.

Heterostyly, 124.

Hidden-veined, 56.

High power, 158, 159.

Hilum, 132.

Hip, 136.

Hirsute, 28.

Hispid, 28. ;

Histology, 1, 145; of root, 14-16; of stem,
30-41 ; of foliage leaf, 64-66; of flower,
86, 91, 97-98, 107-109}; practical h.,
158-160.

Hoary, 28.

Hollow (see Fistular).

Holly; 51, 6%, 65; 147-

Hollyhock, 156, 158.

Homologue, 7.

Homology, 7, 27.

Honey, 121 (see Nectar).

Honey-gland (see Nectary).

Honey-guide, 122, 123, 130.

Honeysuckle, go.

Hood, 85.

Hoodlike, 120.

Hook, 26, 142; h. climber, 26.

Hop, 8, 25, 28, 44, 99, 100.

Horehound, 157.

Horizontal, 54, 65, 106, 147.

Hornbeam, 116, 142, 155.

Horse-chestnut, 7, 46, 47, 49, 59, 64, 139.

Horse-radish, 155.

Hot-water jug, 62.

House-leek, 24. 25, 57-

Hyacinth, 77, 86, 107, 109, 123, 149, 154.

Hydrangea, 119.

Hydrogen, 3, 5, 10.

ILydrotropism, 20.

Hypocotyl, 143.

Hypocrateriform, 89.

Hypogean, 143.

Hypogyne, 152, 153, 154, 156.

Hypogynous, 81, 87, 95, I01, 150, 151,
153-

173

ILLUMINATION, 68.

Imbricate, 84, 149.

Impatiens, 143.

Incomplete, 153, 154.

Inconspicuousness, 116, 121, 130, 151, 154.
Increase (see Growth).

Indefinite, 148, 151, 155 (see Racemose).
Indehiscent fruits, 136, 137, 139.

Indian, 73.

Indian-corn, 133, 136, 143, 160.
Indian-cress, 86, 91, 126, 137, 35r.

Indian, East, 62.

Inferior, 85, 101, 105, 106, 123, 136, 139, 153,

157-

Inflated, 86, 89, 113.

Inflexed, 49, 149.

Inflorescence, 24, 25, 27, 75-80, 100, 113,
114, I17, I19, 125, 153, 154, 155, 156,
157; female, 99; male, gg, 153;.de-
scription, 147-149, 150; examination
questions on, 163.

Innate, 96.

Insectivorous plants (see Plants, insecti-
vorous).

Insect-pollinated, 118-130, 151.

Insects, 41, 71; digestion of (see Plants,
insectivorous); as pollinating agents,
II5, 118, 130; as unbidden guests, 111-

TES.

Insertion, of leaf, 43.

Integument, 107, 108, 13r.

Intercellular spaces, 19, 41, 43, 65, 66, 70.

Interfoliar, 64.

Internode, 22, 23, 24, 26, 29. 46, 47, 49, 55,
74; 76, 78, 109, 146, 149.

Intine, 98.

Introrse, 96.

Intussusception, 6.

Inverness-shire, 116.

Inverted, 109, 132, 134.

Involucre, 78, 79, 111, 122.

Involute, 40, 149.

lodine, 67, 159, 160.

Treland, 43.

Iridacex, 154.

Iris, 21, 26, 55, 56, 123, 127, 138, 154.

Iron, ro.

Irregular, 79, 80, 88, 89, 118, 120, 126, 146,
154, 156, 157-

Jrregularity, 121-122.

Inritability, 11-12; of flower, 131; of reco‘,
19; of stamens, 124; of stem, 44-45.

Tsomerons, 87.

Ivy, 8, 13, 26, 54, 56, 78.

J.
JAPONICA, 156.
Jerusalem artichoke, 26, 49, 157-
Jessamine, 59.
Joint, 59, 60.
Jointed, 27.
Judson’s dye, 159.
Juice, 155; 157-
June, 88, g2, 116.
Juniper, 21, 35, 84, 152.

Ke.
JXATABOLISM, 121, 12.
Keel, 88:

174

Kernel, 136, 139.

Kerner, 119.

Kidney-shaped, 58, 65, 97.

Kinds; of foliage leaf, 147; of fruit, 148;
of inflorescence, 147; of root, 146; of
stem, 146.

Knife, 209.

Knob, 113, 114, 134.

Knot-grass, 64, 155.

Knots, 39.

L.

LABELLUM, 88, 89, 130.

Labiatee, 157.

Labiate, 86, 89, 90, 121, 122.

Laburnum, 156.

Ladies’ slipper, 94.

Lady’s mantle, 156.

Lambs’ tails, 116.

Lamella, middle, 32.

Lamina, 52, 54, 62; apex of, 58; base of,
58 ; colour of, 62; description of, 147;
form of, 57-58; margin of, 58-59;
modifications of, 61-62 ; position, 54-55;
structure of, 64-66; support of, 67;
surface of, 62-63; symmetry of, 55;
texture of, 62; venation of, 55-57.

Lanceolate, 57.

Landing stage, 121, 123, 126, 128.

Larch, 21, 152.

Larkspur, 85, 86, 88, g1, 100, 102, 103, 107,
I0Q, 122, 126, 133, 137, 151, 155-

Lateral, 56, 75, 76,*82, 85, 88, 90, 94, 103,

105.

Lathyrus, 63.

Laurel, 113, 156.

Lavender, 62, 157.

Layering, 42.

Leaf, 10, 11. 19, 20, 45, 47) 54, 55, 67, 68,
159, 160; arrangement of, 46-50; cata-
phyllary 1. (see Scale leaf) ; euphyllary
1. (see Foliage leaf); floral 1. (sce
Floral leaf); foliage 1. (see Foliage
leaf); hypsophyllary 1. (see Bract);
kinds of, 51; scale 1. (see Scale leaf) ;
seed 1. (see Cotyledon) ; 1. climber, 26,
Bone Wem iMserulon. 50, 1595 0455) i
margin (see Margin); 1. scar, 43, 47,
48; 1. spine, 61; 1. stalk (see Petiole) ;
1. tendril, 61, 73.

Leaflet, 50, 60, 61, 63, 72, 73, 83,.147-

Leathery, 62, 65, 67, 69, 148.

Leek, 154.

Legume, 137, 140, 156.

Leguminosee, 156.

Lemna, 153.

Lemnacee, 153.

Lemon, 139.

Length of stem, 23.

Lens, 29, 65, 145.

Lenticel, 41, 43.

Lesser celandine, 155.

Lettuce, 157.

Life, 2, 5; physical basis of, 4; under
simple conditions, 8-10.

Life history, 6.

Ligulate, go, 157.

Ligule, 63, 88, 154.

Lilac, 47, 56, 64, 80, 100.

Liiiaceze, 154.

Lily, 21, 39, 86, 93, 94, 98, 104, 107, 109,

INDEX.

120, 138, 149, 1545 tiger dy) x, 4g = lok
the valley, 56; white 1., 65, 96, 100.
Limb, 85, 87, 89, 123.

lime; 50; 116, 107, ekem music.

Limited growth, 66.

Linear, 97.

Lip, 86, 89, 90, 127, 128, 129.

Lipped (see Labiate).

Liquor iodi, 159.

Lobe, 55, 58, 59) 61, 62, 86, 89, 90, 93; 96, 97.
118, 124, 128, 129.

Tobed, 58, 59, 118.

Lobelia, go, 95.

Locomotion of plants and animals, 3, 4.

Loculicidal, 138, 154, 155.

Loculus, 100, 104, 105, 106, 107, 137, 138.
139.

graale: Tey

Log. 38

Londen pride, roo.

Long-styled, 125.

Loosestrife, 124, 125.

Low power, 158, 159.

Lubbock, 120.

Lupin, 127, 156.

Lycopodium, ge.

MACE, 134.

Madagascar, 62.

Magenta, 159, 160.

Magnesium, 10, 160.

Mahonia, 60.

Maize, 98, 133, 136, 143, 160.

Male; catkin, gg, 116, 155; cone, 92, 995
flower, 92, 95, 98, 99; 100, 115, 125, 155
inflorescence, 99, 153.

Mallow, 94, 95, 97, 120, 137, 156, 158.

Malva (see Mallow).

Malvaceze, 156.

Many-seeded, 137.

Maple, 137, 142, 149.

Marble, 18.

March, go.

Margin ; of lamina, 56, 58-59; of carpel,
102, 104, 105; dorsal m., 102, ro5.

Marginal, ro2.

Marguerite, 157.

Marjoram, 96, 157-

Marsh, 61; m. mallow, 85; m. marigold,
87, 102, 137, 1553 M. pea, 63.

Masked, go.

Matter, 4-6.

Meadow ; m. geranium, 124; m. pea, 63;
m. sage, 96, 129.

Meadow-sweet, 156.

Medium-styled, 12s.

Medulla (see Pith).

Medullary ray, 29, 30, 32, 38, 39: 152;
primary or large m. r., 36; secondary
or short m. r., 37-

Member, 7, 8.

Membrane, 3.

Membranous, 55, 63, 64, 76, 86, 139.

Mericarp, 137.

Meristem (see Tissue, formative).

Mesocarp, 136, 139.

Mesophyll, 64, 65, 66, 67, 71.

Metamorphosis, rro.

Methylated spirit, 159.

Micropyle, 107, 109, 114, 116, 131, 132. 133-

INDEX.

Microscope, 29, 44, 72, 158, 159, 160; use of,
158-160.

Middle lamella, 32.

Midrib, 56, 57, 59, 62, 63, 86, 89, 102, 104.

Mignonette, 102, 121, 150, 151.

Milky, 155, 157-

Millefoil, 59, 110.

Minikins, 145.

Mint, 26, 157.

Mirror, 158, 159.

Miscellaneous examination questions, 16s,
166.

Mistletoe, 18, 24, 47, 79.

Mixed inflorescences, 80.

Modification ; of stem. 27; of petiole, 53,
543; of lamina, 61-62, 147.

Moisture, 19, 20, 31, 69, 112 (see Water).

Molecule, 4.

Monadelphous, 95, 120, 156.

Monkshood, 85, 87, 88.

Monocarpellary, ror.

Monocotyledon, 21, 24, 30, 36, 38, 50, 52, 53)
55) 56, 57, 66, 83, 86, 93, 98, 107, 120,
133, 152, 153-154, 158; diagram of, 22.

Moneecious, 99, 100, 116, 153.

Monopodial, 14, 24, 75-

Monosymmetrical, 80 (see Irregular).

Monotropa, 64.

Monstrosities, r10.

Morphology, 1; elementary, 7-8; of root,
13-17 ; of stem, 21-413; of buds, 46-50;
ot foliage leaf, 52-66; of scale leaf, 64 ;
of bracts and inflorescence, 74-80; of
flower, 80-110.

Moth, 120.

Motility, 12; of root, 19; of stem, 44; of
foliage leaf, 71-73; of peduncle, 140;
of flower, 131; of stamen, 124; of style,
124; of stigma, 128.

Mottled, 62.

Mountain; m.

. 120.

Mounting of microscopic objects, 159.

Movement (sce Motility).

Mucronate, 147.

Mulberry, 135.

Mullein, 94, 97, 157.

Multicellular, 8, 28.

Multiple, 135.

Mushroom-shaped, 112.

Musk, 128, 157.

Mustard, 18, 50.

Myrtle, 55, 66.

ash, 156; m. geranium,

N.

NAMES, scientific, 21.

Napiform, 146.

Narcissus, 70, 154.

Nectar, 85, 112, 112, 113, 114, 116, 117, 118,
TIQ, 121, 122, 123; 124, 125, 126, 120,
130.

Nectary, 74, 85, too, 106, 110, 117, 123, 124,
148, I51, 155-

Needles, 30.

Nepenthes, 62.

Nerves, 3.

Nervous system, 3, 4.

Nest, 135, 136.

Nettle, 63, 65, 72, 99, 100, 109, 117.

Net-veined, 56, 153.

Network of veins, 56.

175

Neuter, 94, 98, 119.

Night, 11, 70.

Night-flying insects, rrg, rer.

Nightshade (see Deadly nightshade, En-
chanter’s nightshade).

Nine, 95

Nitrates, 10, 160.

Nitrogen, 5, 6, 10, 160.

Nitrogenous organic matter, ro.

Node, 22, 23, 20, 30, 43, 48, 149, 154, 155.

Non-nitrogenous organic matter, ro.

North, 55.

North America, 55, 116.

North Carolina, 6r.

Nucellus, 107, 108, 109, 114, 131, 133.

Nucleolus, 8.

Nucleus, 8, 11, 16; of embryo sac, 109.

Nudiflorze, 152, 153-154.

Number, 83; of carpels, 78-100, 148; of
seeds, 148; of sepals, 83, 148; of
stamens, 92-94, 148; of petals, 86-87,

8

148.
Nutrition, 11, 17-18, 41-42, 63, 67-71, 114.

OF

Oak, 38, 42, 51, 116, 149, 155.

Oat, 133, 136, 145.

Objective, 158.

Oblanceolate, 58.

Oblique, 82, 88, 94, 147, 155.

Oblong, 57.

Obovate, 58.

Obvolute, 84, 150.

Ochreate, 64, 155.

Odour, 116, 117, 118, 120-121.

Offset, 25.

Ogle, 110.

Oil, 28, 62, 66, 68, 111, 134.

Onagraceze, 156.

One, 84, 86, 94, 97, 98, 99, 100, ror, 106.

Onion, 21, 55, 76, 154.

Opaque objects, 188.

Open, 32, 84, 150.

Opposite, 49, 54, 63.

Orange, 8, 104, 132, 149, 141.

Orange-coloured, gt, 96, ror.

Orchids, 13, 86, 94, 95, 97, 98, 120, 141, 154.

Orchidacee, 154.

Orchis, 88, 89, 105, 122, 129-130, 150, 1&7.

Order (see Family).

Organic matter, 10, 42, 67, 71, 114.

Organs, 7-8; essential, 92; reproductive
43, 923 vegetative, 17, 29, 41, 43.

Origin of roots, 14; of stems, 22.

Orobanche, 64.

Orthostichy (see Rank).

Orthotropous (see Straight).

Osmosis, 9, 17, 18, 41, 67.

Outline (see Form).

Oval, 57, 97.

Ovary, 100, 101, 102, 103, 104, 106, 107, I17,
123, 145, 152, 153, 156, 157, 159; de-
scription of, 148, 151.

Ovate, 57.

Ovoid, 144.

Ovule, 75, 92, 101, 102, 104, 105, 106, 107-
I0Q, II4, 132, 136, 152, 154, 155; 1573
description of, 148, 157.

Ovum (see Egg-cell).

Ox-eye daisy, 157.

Oxidation, 11.

176

Ox-lip, 125.
Oxygen, 3, 5, 10, II, 19; 71; 143, 160.
Oyster, 4.

Ps

PACIEIG) TAK. a

Pony, 137, 155-

Palate, go.

Pale, 117.

Palm, 21, 56.

Palmate, 59. 60.

Palin itely ; p. cleft, 59; p. divided, 59; p.
lobed, 59; p. parted, 59.

Panicle, 79, 80, 100, 117.

Pansy, 63, 75, 76, 88, 96, 98, 104, 121, 127,
150, I51-

Papaveracez, 155.

Papilla, 107.

Pappus, 141, 157.

Parallel-veined, 56, 152.

Parasite, 3, 64, 71-

Parenchyma, 14, 19, 31, 36, 41, 42, 67, 98,
135; palisade p., 65, 66, 68; spongy p.,
66, 67, OI.

Parietal, 105, 137, 154, 1555 p- layer, 32.

Parsley, 156.

Parsnip, 79, 106, 119, 142, 156.

Parted, 509.

Partial ; p. involucre, 79; p. peduncle, 76.

Passiflora (see Passion-flower).

Passion-flower, 27, 45-

Patchouli, 62.

Path-pointer, 122.

Pea, 61, 82, 88, 95, 100, 101, 102, 106, 114,
127, 135, 137, 143) 150, 156.

Peach, 113, 139, 156.

Pea-flower family (see Leguminoseze).

Pear, 136, 156.

Pedicel, 76, 78, 117, 147-

Peduncle, 74, 76, 85, 102, 112, 115, 140, 142,
147-

Peely 139: ,

Peeling ; of potatoes, 26; of twigs, 4o.

Pelargonium, 28, 85, 156.

Peltate, 58.

Pendent, 99, 123, 147-

Pendulous, 77, 106, 113, 116, 123.

Penknife, 74, 145.

Pentastemon, 94, 97, 157:

Pepper-castor, 31.

Perennials, 14, 23, 41, 42, 48, 146, 148, 149.

Perfoliate, 58.

Perianth, 74, 81, 83-91, 92, 99, 113, II5,
116, 117, 118, 119, 126, 140, 142.

Pericarp, 136, 137, 139, 140.

Perigynous, 81, 84, 85, 87, 95, 101, 113, 136,
159, I51, 1535 156.

Perisperm, 131, 133-

Periwinkle, 54.

Permanent slides, 160.

Persistent, 86.

Personate, go, 113.

Petal, 74, 75, 76, 82, 83, 85, 86-91, 93, 94, 95;
TOS, TL; 13; 622; 1235 1275 150) 151,
154, 155, 156, 157.

Petaloid, 76, 86, 87, 88, 120, 125, 126, 156.

Petaloidez, 152, 154.

Petiole, 52, 53-54, 56, 59, 60, 61, 63, 64, €6;
description of, 147.

Petunia, 157.

Phanerogams (see Flowering plants).

INDEX.

Phloém (see Bast).

Phosphates, 10, 160.

Phosphorus, 5, 10.

Phylloclade, 27, 42.

Phyllode, 53, 54, 63, 70.

Phyllotaxis, 49-51, 83, 147, 149.

Physiology ; elementary, 8-10; of root,
17-20; of stem, 41-45; of foliage leaf,
66-73 ; of flower, 111-131 3 of seeds and
fruits, 140-143; practical, 160.

Pigment, or.

Pilose, 28.

Pimpernel (see Scarlet p., Water p.).

Pine, 21, 116, 152.

Pineapple, 135.

Pink, 21, 49, 87, 100, 105, 124, 129, 138, 156.

Pinnate, 59, 60, 61, 63.

Pinnately; p. cleft, 59; p. divided, 59; p.
lobed, 593; p. parted, 50, 625; p. veined,

_ 58; 57, 59:

Pins, 145.

Pinus (see Fir).

Rip, 132), G30,.04n

Pistil, 81, 83, 85, 92, I15, 122, 124, 128, 120,
152, 153, 154, 155, 156, 157, 158; de-
scription of, 148, 151.

Pistillate, 94.

Pit, 32, 33, 553; bordered pit, 35; p. mem-
brane, 32, 33.

Pitcher-plants, 4, 54, 62, 71-

Pith, 29, 30, 34, 38, 39, 40, 42, 152, 159.

Placenta, 101, 102, 104, 106, 107.

Placentation, 102, 104, 105, 106, 137, 154.
155, 156, 157, 158; description of, 151.

Plaited, 40.

Plane, antero-posterior p. (see Median) ;
lateral p., 82; median p., 52, 82;
oblique p., 82.

Plank, 309.

Plantago (see Plantain).

Plantain, 57, 78, 93, 117, 118, 138.

Plants, how differmg from animals, 2-4;
aquatic p., 11, 18, 19, 23, 43, 68, 112,
115, 140; climbing p., 8, 243; creeping
p., 24; flowering p:, 2, 12, 21,6335
flowerless p., 2; green p., rz ; insecti-
vorous or carnivorous p., 2, 54, 61-62,
71, 73, 112, 1143 land p., 17, 19, 43, 69,
70; marsh p., 23; multicellular p., 8,
12; unicellular p., 8.

Plum, 42, 139, 156.

Plumbago, 84, 112, 142.

Plumule, 132, 133, 142, 143.

Pod, 102, 137, 140.

Point, growing (sce Growing-point).

Pollen, 74, 75, 92, 96, 97, 99, ILI, 114-131;
p. canal, ro7, 114; p. grain, 98, 109,
114, 116, 118, 123, 131, 1585 p. Sac, 98,
109, 152; p- tube, 114, 115, 125.

Pollination, 114, 140, 151; by birds, 130;
cross, 115-130; by insects, 118-130;
self, 115, 130-131; by water, 115; by
wind, 115-118, 120.

Pollinium, 97, 130.

Polyadelphous, 95.

Polyanthus, 125, 157.

Polycarpellary, tor.

Polygamous, gg.

Polygonacee, 155.

Polygonum amphibium, 112.

Polypetale, 153, 155, 156.

Polypetalous, 87, 88, 114, 153.

INDEX.

Polysepalous, 84, 85.
Polysymmetrical, 80 (see Regular).
Pome, 136.
Ponds, 62.
Poplar, 116.
Poppy, 21, 62, 84, 87, 101, 103, 105, 122,
138, 141, 150, 155-
Pore, 97, 123, 124, 138.
Porous capsule, 138, 141.
Position, relative, 7, 27.
Posterior, 85, 86, 89, 94, 95, 103, I05, 127,
156.
Potassium, 10, 160.
een 5) 17, 26, 44, 45, 59, 64, 89, 93, 97;
149, 157-
Potentilla, 62.
Power (of microscope), high p., 31; low
p., 31-
Practical work, 6.
Preefloration, 84, 87.
Preefoliation, 84, 140.
Prickle, 28, 41, 65, 86, 111.
Primary, 132, 146; leaflet, 61.
Primine, 108.
Primrose, 76, 84, 87, 89, 93, 95; 96, 97, 101,
106, 124, 125, 138, 151, 157-
Primulacez, 157.
Prismatic, 27.
Privet, roo.
Procumbent, 25.
Prosenchymatous, 32.
Prostrate, 25.
Protection ; of buds, 47 ; of flower, 111-114,
148, 151; Of foliage leaf, 61 ; of lamina,

543; of root, 17; of seeds, 140, 148; of

shoot, 27, 40, 61.

Proteids, 5, 26, 42, 67, 71.

Proterandry, 115, 117, 120, 122, 123, 124,
128, 129, I5I.

Proterogyny, ELS, LEZ; LL, Lek, F2s, Thr.

Protoplasm, 4, 5, 8, 10, 11, 17, 28, 31, 32,33;
34, 35s 4, 42, 43, 65, 71, 72, 73, T14, T15,
160; composition of, 5; structure, ZX

Protoxylem, 34; 30, 37-

Pruning, 18.

Eanes a (see Sympodium).

Pseudocarp, 135-136, 151.

Pubescent, 28.

Pulp, 8, 139.

Pulvinus, 53, 147.

Purple, 88, 89, 119, 124.

Purple loosestrife, 124, 125.

Purple orchis (see Or chis).

Pyxidium, 138.

Q.
QUILLED dahlia, 95.
Quincuncial, 51

R.

RACEME, 77, 78, 79, 117, 154, 155.
Racemose, 24, 46, 75, 76, 80, 149.
Radial, 30.

Radical, 24, 57, 147, 149.
Radicle, 132, 133) 142, 143, 152.
Radish, 13, 14, 155.

Ragged- -robin; 87, 156.

Rain, 113.

Rank, 83. 149.

Ranunculacex, 155.

177

Ranunculus (see Buttercup).

Raphe, 109, 132.

Raspberry, 25, 103, 123, 139, 156.

Razor, 29, 159

Ray, 78; ray Roe et (see Floret).

Reagents, 159, 160.

Receptacle, 78, 121 ; for water, rre.

Le een 25.

Red, 9

Redan brown, 119.

Reduction, 84, 94, 96, 129.

Reflected light, 158.

Refiexed, 85, 88, 90, 113, 125

Regular, 80, 88, 80, 123-126, 154, 155, 156,
57

Bastion of floral leaves, 82, 148, 150 (see
Floral diagram).

Relationships (of plants), 2.

Renewal of organisms, 6.

Reniform, 58.

Replum, 137.

Reproduction, 12; true, 114-131; vegeta-
tive, 19, 43, 44: 71, 114.

Reproductive, 19.

Re-erve materials, 14, 18, 24, 25, 26, 42, 64,
67, 68, 134, 142, 143, 160. :

Respiration, 11, 12; of flower, 114; of foli-
age leaf, 71 ; of germinating seed, 143;
of root, 18-19; of simpie plant, 11; of
stem, 43

Respiratory cavity, 66.

Reticulated, 56.

Revolute, 149.

Rhizome, 26, 42, 154.

Rhododendron, 97, 138.

Ribbed, 23.

Richardia, 153.

Ridged, 28, 29, 40, 53, 146.

Ringent, go.

Ringing, 42.

Rings, annual, 38, 39.

Ripening, of seed, 86, gg.

Robinia, 19, 53; 64.

Room, plants in, 70.

Root, 7, 8; adventitious, 13, 14, 19, 21, 22,
26, 43, 49; air, 135 Yr. cap, 16, 17, 345 1
climbers, 26; description of, 146, 149;
development of, 14, 39} examination
questions in, 161; fibre, rag se Ts
hairs, 14;,18, 29): jiachneuee E35 175
21, 143, 152; ; ‘parasitic, 13, 18; physio-
logy, 17-20; 42, 44, 45, 67, 693 T. pres-
sure, 18; primary, 13, 14, 19, 20, 213
secondary, 13, 14, 19; Yr. Sheath, 143;
structure of, 14-15, 31, 66,159; tap, 13,
145 2%), £46, I525\ Ty CLS; 9, cose.
tubers, 14, 19; underground, 13;
water, 13, 18.

Rootstock, 24.

Rosacez, 156.

Rose, 21, 25, 28, 48, 51, 59, 63, 81, 83, 84, 87,
103, 106, 110, 123, 130, 156.

Rose-bay willow-herb, 120, 124.

Rosemary, 149, 157-

Rosettes of leaves, 19, 24, 61, 112.

Rostellum, 130.

Rotate, 89.

Rounded, 57.

Round-leaved sundew, 11.

Rowan, 156.

Rows of cells, 3132. 33, 40.

Rudiment, 94, 9

178

Rue, 66.

Runner, 25, 146.

Rupture, 30.

Rupture, of tissues, 23.
Ruscus (see Butcher’s broom).
Rush, 55, 93, 117, 120, 154.

8.

SACCATE, 85, 88.

Saffron, 138.

Sage, 86, 96, 97, 100, 105, 157-

Sagittate, 58.

St. John’s wort, 66, 94.

Salts, 3, 4, 9, 10, 71, 160.

Salver-shaped, 89, 118, 125.

Samura, 137.

Sand, 160.

Saprophyte, 3, 64, 71-

Sap, 8, 38, 130; ascending or crude, 41, 42,
67, 71; course of, 41-42; elaborated,
42, 67 (see Cell-sap).

Sap-wood, 38, 42.

Sarracenia, 54, 71.

Saucer-shaped, 89.

Sawdust, 160.

Saxifrage, 100.

Scabious, 157.

Seule, 28, 64, 98, 99, ror, 152, 154 (see Scale-
leaf).

Scale-leaf, 46, 61, 64, 67; description of,
147, 149.

Scalpel, 29, 74.

Scaly, 78, 86, 152.

Scape, 76, 112.

Scar, 132 (see Leaf-scar).

Scarlet pimpernel, 138, 157.

Scarlet runner, 25, 53, 59, 64, 72, 127-

Scattered, 48, 49, 112, 155, 156, 157-

Schizocarp, 137.

Sclerenchyma, 33, 34, 36, 41, 66.

Scorpioid cyme, 8o.

Scotch fir (see Fir).

Scrophularia, 157.

Scrophulariacez, 157.

Scutellum, 133, 143.

Sea-squirt, 4.

Secondary ; bast, 37; leaflet, 61; lobe, 59;
root, 13; stem, 21; wood, 37.

Secretion, 66.

Secretory reservoir, 66.

Section ; cross-s. (see Transverse s.); longi-.
tudinal s., 30, 107, 149; preparation of,
159-160; radial s., 30, 32, 33, 38; tan-
gential s., 30, 38; tramsverse S., 30, 31,
38, 40, 98, 106, 149.

Section-cutting, 159.

Secundine, 108.

Sedges, 21, 26, 50, 53, 117, 118, 120, 142, 149,

T54.

Seed, 7, 67, 68, 75, 86, 102, 109, 115, 136, 137,
139, 152, 153, 154, 158, 160; description
of, 148, 151; distribution of, 140-142 ;
examination questions on, 164; ger-
mination of, 142-143 ; morphology of,
132-135 ; physiology of, 140-143; pro-
tection of, 140.

Seed-coat, 132, 134, 136, 137, 139, 140, 142,
I43-

Seedling, 19-20, 44, 50, 54, 61, 68.

Segmented, 58.

Self-pollination,115, 120, 125, 126, 127, 129,
131.

INDEX.

Self-sterile, 115, 123, 130.

Sensitiveness, 3 (see Irritability).

Sensitive plant, 3, 53, 72.

Sepal, 74, 75, 82, 83-86, 87, 88, 103, rr0, 118,
125, 120.

Septicidal, 137, 138.

Septifragal, 138.

Series, 21, 151, 152, 153, 154, 155, 156, 1575
linear s., 2.

Serrate, 58.

Sessile, 52, 58, 59, 63, 96, 103, 117, 122, 147.

Setose, 28.

Seven, 61.

Shadow, 54.

Shape (see Form).

Sheath, 53, 63, 64, 76, 152, 153; description
of, 147.

Sheathiny, 55, 63, 84, 156.

Shepherd’s purse, 28, 76, 83, 85, 105, 109,
137, 155-

Shoot, 19, 22, 25, 26, 40, 41, 42, 43, 44, 46,
54, 61, 68, 70, 71, 74, 75, 76, 80, 92, 99,
109, 132, 160.

Shortening, of root, 19.

Short-styled, 12s.

Shrub, 23, 48, 146, 154, 155;

Sieve-plate, 31, 33.

Sieve-tube, 31, 33, 34) 35, 36, 67.

Silica, 67.

Silicula, 137.

Siliqua, 137, 141, 155.

Silky, 28.

Silphium, 55.

Silver grain, 38.

Silverweed, 62.

Simple, 59, 76, 78, 79.

Six, 82, 93; 94, 98, 99, 117, 123.

Size, of plants, 23, 146.

Skeleton leaves, 8.

Sleep, of plants, 72.

Sleeping-room, 11.

Slides, 158-160.

Slit, 124.

Sloe, 28, 156.

Slugs, 41.

Small-flowered geranium, 120.

Smooth, 146 (see Glabrous).

Snails, 41, 111.

Snapdragon, 77, 87, 90, 94. 95, 96, 97, 113,
128, 138, 157-

Snowberry, 104.

Snowdrop, 21, 76, 83, 86, 93, 94, 98, ror,
105, 113, 123, 154.

Sodium, 160.

Soft-bodied insects, 111.

Soil, 17, 19, 45, 141, 142.

Solid, 23, 146.

Solomon’s seal, 26.

Solution, of food, 10, 17, 18, 69; how to
prepare, 160.

Sorrel, 64, 117, 155:

South, 5s.

Sowbread (see Cyclamen).

Spadiciflorze, 152, 153-154.

Spudix, 78, 99, 120, 125, 152, 153.

Spanish chestnut (see Chestnut).

Sparganium, 154.

Spathe, 76, 120, 125, 153.

Species, 21.

Speedwell, 89, 94, 95, 157-

Spike, 77, 78, 117, 118, 152, 154.

Spikelet, 117, 152.

INDEX.

Spinach, 155.

Spindle-shaped, 14, 28

Spindle-tree, 134.

Spine, 27, 28, 41, 61, 64, 111.

Spiny, 147.

Spiral, 25, 74, 75, 80, 81, 83, g2, 110, I15,
140, 155; genetic 8., so.

Spirit, 159.

Splitting fruit, 137, 156, 157.

Spontaneity, 11, 12; of root, 19; of stem,
44-45; of foliage leaf, 73; of flower,
131.

Sporangium, 92, 109.

Spore, 92, 109, 114; S. Case, 109.

Spore-leaf, female (see Carpel); male (see
Stamen).

Sporophyll, female (see Carpel); male (see
Stamen).

Spotted, 62, go, 122.

Spreading, 85, 88, 118, 123, 124, 147.

Spring, 18, 19, 38, 46, 47, 116.

Spring-clip, 158.

Spring-water, 69.

Spur, 85, 90, 121, 130, 151, 155-

Spurious fruit (see Pseudocarp).

Spurred, 85, 88, go.

Square, 23, 30, 52, 146, 157-

Squirting cucumber, 141.

Stage, 158, 160.

Staining, of sections, 159-160.

Stalactite, 6.

Stalk (see Funicle,
Petiole).

Stalked, 52, 59, 60, 69, 77, 147-

Stamen, 74, 75, 82, 85, 86, 87, 88, 92-98, 100,
IOL, 103, I10, 113, I15, 116, 118, 120, I2t,
122, 123, 124, 125, 127, 128, 129, 130, 152,
153) 154) 155, 150, 157; description of,
148, I5I.

Staminode, 97.

Stand, 158.

Standard, 113.

Standard rose, 25.

Starch, 3, 10, 18, 25, 42, 67, 134, 135-

Stellate, 89.

Stem, 21-45; adventitious s., 22; aerial,
23, 24-25; climbing s., 25-26, 44, 45;
creeping S., 25, 43; description of, 146,
149; examination questions on, 161-
162; external form of, 23-27; kinds
of, 24-273; length of, 23; modified s.,
27; morphology of, 7, 21-41, 46, 52, 99;
overground s. (see Aerial s.) ; parasitic
S., 23; physiology of, 8, 20; 41-45, 67,
7I, 1113; primary s., 13, 21; structure
of, 29-41, 64, 66, 159; surface of, 28 ;
secondary s., 21 (see Branch); subter-
ranean 8., 23, 24, 26-27, 43, 64, 1463
thickness of, 24; underground s. (see
Subterranean s.); water s., 23; s. ten-

» 275 73:

Stereome, 41, 67.

Sticky substances, 28, 41, 46, 61, 64, 107,
EI2) 104, 116,117, 118, §42-

Stigma, 100, 102, 103, 104, I07, 114, II5,
416, 117, 118, 120, I2I, 122,123, 127,
128, 129, 130, 1313; description of, 148.

Stimuli, 11, 19, 73-

Stinging hairs, 62, 65, 72, 154.

Stipel, 64.

Stipule, 53, 63-64, 85, 112, 113; description
of, 147; kinds of, 63-64, 84, 155; sur-

Pedicel, Peduncle,

179

face of, 64; texture, 64; s. spine, 64;
s. tendril, 64.

Stitchwort, 79, 156.

Stock, 28, 83, 123, 137, 141, 155.

Stolon, 25, 43.

Stoma, -ta, 31, 41, 43, 65, 66, 69, 70, 98, 107.

Stomach, 4, 71.

Stone-crop, 66.

Stone-fruit, 139, 140.

Storage ; of reserve materials, 18, 24, 25, 26,
42, 64, 67, 134, 142, 160; Of nectar, rar.

Stork’s-bill, r42.

Straight, 108.

Strain, 120.

Strap-shaped, go.

eels {136, 156.

TAWVELLY, 25, 43, 50,,05; TOs, F222, 125)

Streaked, eae 43; 59; 95; 2 b) ]

Streaming, of protoplasm, 11, 44, 71, 72.

Striking, of cuttings, 13.

Structure, 1, 8, 83; of root, 14-17; of stem,
29-41; of foliage leaf, 64-66; of sepal,
86; of petal, 91; of stamen, 97-98; of
pistil, 107-109 ; of seed, 134-135.

Stumps, 23.

Style, 100, 101, 102, 103, 106, 107, 114, 117,
123, 124, 126, 127,157; description of, 148.

Subclass, 151, 152, 153, 154, 155, 156.

Subdivision, 151, 152.

Suberin, 40.

Submerged, 6s, 68.

Succulent, 62, 146.

Succulent capsule, 1309.

Succulent fruits, 139, 140, 142.

Sucker, 23, 25, 43.

Sugar, g, 18, 67, 71.

Sulphates, 10, 160.

Sulphur, s, ro.

Sulphuric acid, 159, 160.

Sulphur showers, 116.

Summer, 47, 48, ror.

Sun, 55, 67.

Sundew, 61, 73.

Sunflower, 13, 29, 30, 34, 36, 37, 56, 69, 78,
95, 166, 119, 126, 136, 157.

Sunlight (see Light).

Superficial, 105.

Superior, 85, ror, 117, 135, 136, 151, 152, 153.

Superposed, 83, 93, 97, 154, 155.

Support, 17, 24, 25, 41, 44, 45, 66-67, 111.

Suppression, 78, 103, 109, 151.

Surface ; of root, 146; of stem, 28, 146; of
petiole, 54, 147; of lamina, 62, 147;
of stipule, 64; of scale-leaf, 147; of
calyx, 86; of corolla, 91 ; of ovary, 104.

Suspended, 106.

Suture (see Ventral suture),

Sweet-briar, 62.

Sweet-chestnut (see Chestnut).

Sweet-pea (see Pea).

Swollen, 8s.

Sycamore, 56, 142.

Symmetry, 148; bilateral s., 52, 55, 80, 85,
86, 87, 106; radial s., 52, 55, 66, 80, 81
86, 87, 106. .

Sympodium, 24, 27, 48, 79, 8o.

Synantherous (see Syngenesious).

Syncarpous, 100, 101, 102, 103, 105, 107, I17,
124, 135, 136, 153, 154) 155, 156, 157-

Syngenesious, gs, 126.

Synpetalous, 87.

Synsepalous, 84.

180

T.

TAIL, 124.

Tangential, 30.

Tapeworm, 4.

feo (see Root).

Tare, 6

Teasel, 112, 157+

Teeth, 58, 59, 86. 89, 90, 137, 138.

Telegraph plant, 73.

Ten, 93; 95, 103.

Tendril, 25-26, 275 45, 61, 62, 64; t. climbers,
255 26, 43>

Tension, 40, ee

Tentacle, 61, 73.

Terminal, 147.

Ternate, 61.

‘ernately-parted, 63.

Tertiary, leatiet, 61.

Test-tube, 69.

Tetradynamous, G4, 123, 155.

Texture ; of corolla, g1 ; of lamina, 62, 1473
of root, 146; of scale-leaf, 1473 of se-
pal, 863 of sheath, 1473; Of stem, 41,
1463; of stipule, 64, 147; of wood, 38.

Thalamifloree, 153, 155-156.

Thickening (see Growth in thickness).

Thickness ; of root, 13, 143 of stem, 24.

Thirteen-ranked, 51.

Thistle, 46, 78, 89, 95, 111, 122, 147.

Thorn, 27, 28, 41, 67, 111-

Thorn-apple, 157.

Three, 83, 86, 88, 93, 94, 98, 100, 104, 117,
126, 138, 152.

Three-sided (see Triangular).

Three-ranked, 50.

Three-rayed, 80.

Thrift, 106.

Throat, 89.

Thyme, 129, 157. .

Thyrsus, 80.

Timber, 38.

Tissues, 8; classification of, 17 ; conduct-
ing t., 107, 114; formative t., 17, 32
(see also Cambium and Growing point);
fundamental (see Ground tissue);
ground t., 14, 17, 28, 29, 30, 31, 36, 40,
43, 64, 65, 66, 98, 107; mechanical or
supporting t., 41; permanent t., 17;
vascular t., 16, 17, 18, 19, 28, 20, 30, 36,
41, 66, 91, 98, 107, III, 152.

Toad flax, go, 122, 128, 157.

Tobacco plant, aS

Tomato, 157.

Tomentose, 28.

Torus (see Floral receptacle).

Trachee, 35, 43.

Tracheide, 35, 42, 66:

Trailing, 54.

Transmitted light, 159.

Transpiration, “69-71; 160. [tropism, 73.

Transverse, 128 ; geotropism, 73; helio-

Tree, 23, 25, es "38, 41, 46, 49, 54 64) 68,
136, 140,

Trefoil ‘(see Bird’ s-foot trefoil).

Triadelphous, gs.

. Triangular, 23, 52.

Trichomes ( sce Hairs).

Trifurcation, 6r.

Trimorphie, 125.

'l'ripinnate, 6r.

Triternate, 61.

Tropical, 88.

INDEX.

True fruits, 135, 136-139.

Trunk, 23, 25, 38, 42, 49.

Tube, 84, 85, 87, 89, 95, 127 ; of microscope,
158, 159.

Tuber, 26, 44, 1603

Tuberous, 146, 154.

Tubular, 55, 84, 85, 89, 147-

Tulip, 21, 75, 76, 86, 98, 104, 120, 138.

Tulip-tree, 149.

Turgid, 9.

Turgidity, 9, 32, 69, 70.

Muri, 135 Tass ss

Turnip-shaped, 146.

Twig, 40, 46, 54.

Twining, 25, 44.

Twisted, 55, 89, 154.

Two, 61, 84, 86, 87, 88, 93, 94, 96, 97, 98,
100, 104, 106, 124, 136, 137, 138.

Two-ranked, 50, 55.

Two-rayed, 79.

root tubers, 14, 19.

U.

UMBEL, 78, 79, 156.

Umbelliferze, 79, 119, 156.

Umbrella, 67, 7

Unbidden guests, 111-113, 119, 129.

Undershrubs, 23, 156.

Undifferentiated, 55.

Uniaxial, 75.

Unicellular, 8, 28, 72.

Unilocular, 104, 105, 106, 139.

Union ; of foliage- leaf margin, 553; of lobes,
58 (see Adhesion and Cohesion).

Unisexual, 98, 99, 115, 116, 118, 121, 154,

155:
Units of structure, 5.
Unsymmetrical, 55.
Urceolate, 89, 123.
Urn-shaped, 89.
Urticaceze, 154.
Utricularia, 62.

VACUOLE, 8, 32, 72.

Vacuolized, 32.

Vallisneria, 71, 115.

Valvate, 84, 150.

Valve, 62, 137.

Valvular, 97.

Vapour, 60.

Variegated, 62.

Vascular, 16.

Vascular cylinder (of root), 14, 16.

Vegetable marrow, 25, 28, 36, 95, 101.

Vegetative, 175715 74s

Veinlet, 56.

Veins, 55-57, 63, 65, 91, 104.

Venation, 55-57, 147-

Ventral, 103, 107-

Ventral suture, 102, 104, 106, 107, 137.

Venus’ fly-trap, 61, 73.

Verbena, 93.

Vernation (see Prefoliation).

Versatile, 96, 117, 118.

Vertical, 54, 55, 68, 70, 128, 146, 147.

Verticillaster, 157, 180.

Vessel, 16, 33-34, 41 (see Tissue, sesauiuate =
annular V.5. S4b0036)5 pitted Vigna
spiral v., 34, 36.

Vetch, 61, 113, 140, 156.

INDEX.

Vicia faba (see Bean).

Villous, 28.

Vinca, 54.

Vine, 18, 25, 27.

Violacex, I55-

Violet, 21, 49, 76, 88, 93, 96, 104, 107, 121,
_ 127; 138, I40, I4I, 149.

Virginian creeper, 25, 45.

Viscid (see Sticky).

We

WALL, 45.

Wallflower, 21, 28, 62, 77, 83, 84, 85, 87, 88,
94, 98, 123, 137, I4I, I5I, 155.

Walnut, 139.

Wash- leather, 159-

Wasp, 119, 121.

Waste of organisms, 6.

Waste products, rr.

Watch, 44.

Watch-glasses, 159, 160.

Water, 3, 4, 10, 11, 19, 41, 42, 67, 68, 69, 70,
71, 112, 115, 140, 141, 160 (see Moisture) ;
conduction of water, 42; free W., 17;
hygroscopic w., 17; of soil, 17.

Water-cress, r55.

Water-lily, 21, 86, 92, 96, 105, 149.

Water-pimpernel, 93, 97.

Water-pollinated, 115.

Water-thyme, 43.

Wavy, 147.

Wax, 41, 62, 112.

Weather, protection from, 41, 47, 67, 113-
11g; Sunny W., 70; WEL W., 70.

Weel, 112, 129.

Wet (see Weather).

Wheat, 78, 117, 133, 135;

Wheel-sh aped, 89.

White, 76, 83, 119, 141;
lily (see Lily).

Whole flour, 135.

Whorl, 81, 82, 83, 85, 87, 93, 94; 97, 110, 155,
EST.

136, 143.

w. bread, 1353; w.

181

Whorled, 49.

Wind, 45, 53, 113, 114, 115-118, 140, 141-
142.

Window, 45.

Wind-pollinated, 115-118, 120.

Wing, 58, 63, 126, 127, 142.

Winged, 23, 46, 52, 61, 63, 142.

Wingless imsects, 41, III, I13-

Wild pea, 63.

eg 41, 51, 78, 84, 87, 99, 100, 116, 121,

315 55+

Ww Sige hah, Q3, 120, 124, 142, 156.

Winter cherry, 157-

Winter, 2s.

Wisteria, 88.

Wolffia, 21, 153.

Wood, 31, 34, 37, 40, 41, 42, 66, 67, 1525 W.
Hbre; 3%, 32, 2443 heart wi; 38:3) w-
parenchyma, 31, 32, 343 primary w.,
36; sap w., 38; secondary wW., 37; W
vessels, 31, 32, 34, 36, 66.

Wood-sage, go, 129.

Wood-sorrel, 72, 117.

Woody, 36.

Woolly, 28, 67.

Wrinkled, 146.

XYLEM (see Wood).

Ve
YARROW, 509.

Yellow, 60, 74, 75, 78; 901 9% 97+ 99s 205;
119, E22, ‘x60'% yo bird's nest; 6¢>" y-
pea, 63; y. rattle, I57-

Yew, 21, 54, 84, 134, 152.

Z.

ZOoLoey, 2.
Zygomorphic, 80 (see Irregular).

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« SHILINBILNY MHAAD,, SNOAGL PUY YANGUVD “WW wWoay

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LaTE oF Guy’s HospiTAt,

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GEO. REID, M.D., D.P.H,

Mep. Orricer, Starrs. County Council,

With Appendix on the Management of the Sick-room, and many Hints for the
Diet and Comfort of Invalids.

In its New Form, Dr. SPENcER THOMSON’s ‘‘DICTIONARY OF DOMESTIC MEDICINE”
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The most recent IMPROVEMENTS in the TREATMENT OF THE SICK—in APPLIANCES
for the RELIEF OF PAIN—and in all matters connected with SANITATION, HYGIENE, and
the MAINTENANCE of the GENERAL HEALTH—will be found in the New Issue in clear and
full detail ; the experience of the Editors in the Spheres of Private Practice, of Hospital
Treatment, and of Sanitary Supervision respectively, combining to render the Dictionary
perhaps the most thoroughly practical work of the kind in the English Language. Many
new Engravings have been introduced—improved Diagrams of different parts of the Human
Body, and Illustrations of the newest Medical, Surgical, and Sanitary Apparatus.

*,” All Directions grven in such a form as to be readily and safely followed,

FROM THE AUTHOR’S PREFATORY ADDRESS.

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a calely trodden, there is a wide and extensive field for exertion, and for use ees
an

emigrant it is INVALUABLE.”

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“* The amount of useful knowledge conveyed in this Work is surprising.” —Medical Tisnes and Gasette.

‘“‘ WoRTH ITS WEIGHT IN GOLD TO FAMILIES AMD THE CLERGY.”—Oxz/ford Herald.

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MANY THOUGHTS OF MANY MINDS:

A Treasury of Reference, consisting of Selections from the Writings of the
FIRST AND SECOND SERIES.

most Celebrated Authors.

COMPILED AND ANALYTICALLY ARRANGED

By HENRY SOUTHGATE.
—_—_——_o—___

Each Series is complete in itself, and sold separately.

Presentation Edition, Cloth and Gold, . : :
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12s. 6d. each volume.
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great authors quoted. Here all are seeds or gems.”
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““We have no hesitation in pronouncing it one
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oe it has special uses for them.”—Hdinburgh Daily

view.

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LONDON: CHARLES GRIFFIN & CO., LIMITED, EXETER STREET, STRAND.

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