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A ; 5 i

F A N Y

• • , .

DIOLOGY
U

A Manual of

Botany

FOR

INDIAN FOREST
STUDENTS

By R. S. JJOLE, F.C.H., F.L.S.. F.E.s.

Deputy Conservator of Forests
and Forest Botanist at
the Imperial Forest Research
? Institute of Dehra Dun 3

CALCUTTA

SUPERINTENDENT GOVERNMENT PRINTING. INDIA
1909

BIOLOGY

LIBRARY

Li*.

ERRATA.

Page 11, lines 14-15 for are called stolons read is called a stolon.

„ 27, line 19, for plant ssuch read plants such.

„ 34, „ 24,/0rlormed read formed.

„ 34, „ 25, for farge read large.

„ 41, „ 8, after Dolichandrone delete comma.

„ 41, „ 9, from below, for typica read typical.

„ 50, „ l,for ligutiform read liguliform.

„ 50, footnote, for jurnished read furnished.

„ 55, line 14 from below, insert comma after one.

„ 57, marginal note, for Diagrams Floral read Floral Diagrams.

„ 58, „ „ „ S ed read Seed.

„ 63, line 3, after falling off insert or fading.

„ 70, „ 11 from below, for Alcurene read Aleurone.

„ 81, footnote, line 4 from below, for — a wrinkle) read( = a, wrinkle).

„ 89, line 2 from below, /or orophyll read chlorophyll.

„ 96, marginal note, for Wtaer read Water.

„ 107, line 4 from below, after side delete comma.

„ 109, „ 4 from below, for i.e. read e.g.

„ 111, „ 1 5, for A read As.

„ 111, „ 25, after These insert are.

„ 111, marginal note, Jor ertilisation read fertilisation.

„ 135, line 14 from below, for forest read forests.

„ 154, footnote, for Physiiogy read Physiology.

„ 156, line 17 from below, for asexua read asexual.

„ 180, „ 16, for ha s read has.

„ 227, marginal note, for Plant read Plants.

„ 239, line 3 from below, for mong read Among.

„ 244, marginal note, for Wesern read Western.

„ 245, „ „ „ Forest read Forests.

„ 249, line 23, for of read or.
Index, Page ii, after Bark internal, for 80 read 79.

„ „ after Bast internal, for 80 read 79,

„ „ X, after Internal bark, for 80 read 79.

„ „ xviii, after Stomata, for 48 read 84.

„ „ „ „ Stool-shoots, for 71 read 171.
In Explanation of Figures, Plate IV, last line, for pedately-parted read

pedately-di vided.
In Explanation of Figures, Plate VI, line 5 from below, for branche read

branch.
In Explanation of Figures, Plate XVII, line 9, for wood parenchyma-bearing

read wood-parenchyma bearing.

In Explanation of Figures, Plate XVII, line 11, for vessel read tracheid.
In Explanation of Figures, Plate XVII, lines 12 and 14, for trachea read

tracheid.

lu Explanation of Figures, Plate XIX, line 2, for Ureao-spoies read Uredo-
spores.

S. G. P. J.— 224 I. G. F.— 10-1-10— 1,100- S. C. L

PREFACE.

1. THIS Manual has been pre-
pared primarily for the use of the students of the Imperial
Forest College, Dehra Dun. In the absence of a suitable botani-
cal text-book a great deal of the time of the instructors and
students at the Forest College has hitherto been spent in dic-
tating and copying lecture notes, respectively. The publi-
cation of the present Manual, which contains the back-bone, as
it were, of the College course of botanical lectures, will enable
the instructor to profitably employ much of the time formerly
wasted on dictation in repeating parts of the course, in further
explaining and illustrating points which are found to give diffi-
culty, and in frequently examining and explaining the character-
istics of living plants in the field and in class. Although some
plants have been mentioned as examples in the Manual, the
number of these is necessarily very limited. It must, however,
be remembered that much may be learnt from any individual
plant and that the constant illustration of the facts mentioned
in the lectures by a reference to living plants is essential if the
teaching is to be made interesting and of any practical value,
and if it is to have any result other than the committal to
memory of a mass of imperfectly understood facts to be repro-
duced at an examination and then forgotten.

2. The object of the present

Manual is to give a general introduction to the science of Botany
in accordance with modern knowledge, in so far as this is pos-
sible in the limited time available for botanical instruction at
the Forest College, particular attention being paid to those
points which at present seem to be of special importance for the
Forest Officer in India.

3. I have throughout endea-
voured to keep in view the needs of the practical Forest Officer.

PREFACE.

He should for example possess a good knowledge of the charac-
ters most commonly employed in plant descriptions and thus be
able to identify plants from their written descriptions and to
use a Flora with advantage. He should also have an eye for
those characters of bark, habit, etc., which enable one to recog-
nise on sight different species in the forest at different times
of year.

Such characters are dealt with in Part I of the Manual.
Those for whom this book is primarily intended have very little
time for microscopic work both during their course of training
and thereafter. Anatomy therefore is very briefly dealt with
in Part II and only so far as has been considered necessary for
a fairly clear idea of the main facts of Physiology and Pathology
as given in Parts III and V.

4. In accordance with the in-
structions which were received regarding the preparation of
this Manual systematic botany is treated very shortly in Part IV.
An attempt has there been made to explain the principles of
classification, and while avoiding unnecessary detail to give a
fair idea of the chief characters and general appearance of the
plants contained in the main divisions of the Vegetable
Kingdom, as until a student is able to place any plant, accord-
ing to the aggregate of its characters, into at all events its main
group with fair accuracy he cannot be considered competent to
use a special Flora which only deals in detail with one- or more
minor groups. The detailed classification of Dicotyledons and
Monocotyledons has not been dealt with but the students at
the Forest College are required to fully utilise every opportunity
they may have of collecting, examining and endeavouring to
classify the plants met with on their tours — a task in which they
are assisted by Kanjilal's most useful Forest Flora of the School
Circle which contains full descriptions of most of the important
forest species likely to be found, and also by a short course of
lectures delivered during the students' tours, giving the charac-
ters of the most important cohorts and natural orders of
together with the names of the chief plants of

PREFACE. Ill

economic importance which they contain. If a future edition of
this Manual is called for it will probably be then advisable to
add a section dealing with this part of the subject.

5. It is to be hoped that in a few

years' time our knowledge of injurious fungi will be suffi-
cient for the compilation of a fully illustrated hand-book des-
cribing the most important forest fungi and paying particular
attention to characters which can be recognised in the forests.
For the present, however, the correct identification of any
particular fungus depends on skilled microscopic work and
must be left to the expert. The paragraphs of this book which
deal with fungi may therefore be considered unnecessarily
detailed for students who have little opportunity for working
with the microscope. The facts regarding fungi given in Parts
/Fand V and the plates illustrating the same, however, merely
aim at giving an idea of the general appearance of some typical
fungi (the majority of which also the student will have oppor-
tunities of seeing and becoming familiar with on his tours),
of their life history and injurious action on the plants attacked
and also of the microscopic characters on which their classi-
fication depends, with the object of helping the student to
recognise in the forest the presence of an unknown injurious
fungus, to select specimens of the same necessary for its identi-
fication by the expert and to form some idea as to the best
remedial and protective measures to be taken pending the
identification of the pest.

6. The question of Plant Dis-
eases has perhaps been treated on rather broader lines than
is usual in an elementary text-book. The principle that a
plant's welfare depends on the balance struck between the effects
of a numbei of injurious and favourable factors and that a
disease is rarely due to a single factor frequently appears to be
insufficiently appreciated, while, until we know more about the
normal physiology and life history of our important forest species
and about the relations which exist between them and other
organisms, plants as well as animals, very little real progress

IV PREFACE.

in the investigation and prevention of the diseases of ouf
valuable forest plants and in our efforts to favour the reproduc-
tion of the same appears possible. An attempt has been made
to emphasize this point of view in Parts V and VI of the Manual.

7. While endeavouring in all

cases to avoid didactic assertions on points which have not yet
been sufficiently proved. I have not hesitated to indicate the
possible bearing of well-established botanical facts on Indian
forest phenomena with the object of stimulating further obser-
vation and research, and in this respect it is hoped that the book
may possibly be of some use to others besides those for whom
it is primarily intended.

With reference to the plants which have been quoted as ex-
amples of the various points considered, I have as a rule selected
those which the College students will frequently meet with on
their tours, but, with the object of making the book more inter-
esting to Forest Officers generally, I have also included a few
well-known species which are not found wild in the neighbour-
hood of Dehra Dun. In such cases, however, the species in
question are usually available for reference in the College

Herbarium or Museum.

8. As regards the illustrations,

in the time available for the preparation of this Manual only a
limited number of plates could be prepared and those have been
selected which at present seem most likely to be useful. Thus
no drawings of the minute structure of plants for example were
prepared, there being a good series of anatomical wall-plates
available for instruction purposes in the Forest College.

9. My special thanks are due to

Mr. S. Eardley Wilmot, Inspector General of Forests to the
Government of India, who very kindly entrusted me with the
present work ; to Dr. E. J. Butler, Imperial Mycologist of the
Pusa Agricultural Research Institute, who has most generously
allowed me to use his original work and drawings for the purpose
of this book and to whose help the value of the portions dealing
with fungi is entirely due ; to Mr. H. H. Haines of the Imperial

PREFACE. V

Forest Service who has most kindly read the proofs of Parts IV,
Fand VI and given me many valuable suggestions and criticisms
most of which I have been able to give effect to, and to Captain
Gage, Director of the Botanical Survey of India, for his kind
help and advice.

10. During the preparation of

this book, covering as it does the main sub- divisions of the whole
science of botany, the number of books referred to has neces-
sarily been large and only those to which I am most indebted can
be mentioned here. These are : —

(1) The various works of the late Professor H. Marshall

Ward, for whose inspiring teaching and encourage-
ment also the writer takes this opportunity of ex-
pressing his deep sense of gratitude.

(2) Asa Gray's Botanical Text- Book., Volume I.

(3) Dr. E. Strasburger's Text-Book of Botany.

(4) A Students' Text-Book of Botany, by S. H. Vines.
(5) . Sachs' Lectures on the Physiology of Plants.

(6) Physiology of Plants, by Dr. W. Pfeffer.

(7) Species and Varieties, their origin by Mutation, by H.

de Vries.

(8) Diseases of Trees, by R. Hartig, Eng. Trans., edited

by H. Marshall Ward.

(9) Plant Geography, by Dr. A. F. W. Schimper.

(10) Brandis' Flora of North- West and Central India.

(11) Brandis' Indian Trees.

(12) Gamble's Manual of Indian Timbers.

(13) Indian Forester.

(14) Mr. P. H. Clutterbuck's Working Plan for the Forests

of Jaunsar-Bawar.

VI PREFACE.

11. Finally it must be noted

that all the figures for PUtes I to IX, XI to XIII and XX in-
elusive, with the only exception of the diagrams included in
Plates II and IX have been drawn from nature by my wife, to
whose work therefore this book owes much of any interest or
value it may possess.

R. 8. HOLE.
April 1908.

CONTENTS.

INTRODUCTION.

Two Biological Sciences — Plants and Animals — Sub-divisions of Botany —
Principal Plant Organs and their Functions — Selection of Types for
Description ...........

PAGE.

1—4

PART I- MORPHOLOGY.

CHAPTER I.— THE ROOT.

Primary, secondary and adventitious roots — Types of Root Systems — Deve-
lopment of Root precedes that of Shoot — Root Suckers — Fibrous,
Tuberous, Woody, Subterranean, Aquatic and JSrial Roota] . .

CHAPTER II.— THE STEM.

Nodes, Internodes, Position of Leaves and Buds — Kinds of Stems — Branch-
ing— Shape of Stem — Stem Structure, Bark — Leaf-scars, Lenticels —
Pith, Heart- Wood, Sap- Wood, Annual Rings, Medullary Rays, Pores,
Resin-Canals, Vascular Bundles . . . . . • •

CHAPTER III.— THE LEAF.

Lamina, Petiole, Nerves — Venation— Leaf-margin — Simple and Compound
Leaves— General Shape of Leaves— Polymorphic JLeaves — Leaves of
Young Plants— Other Characters of Leaves— Colour — Smell — Taste-
Glands— Characters of Petiole — Leaf-Base — Stipules — Metamor-
phosed Leaves— Phyllotaxy— Buds — Vernation — Homologous, Ana-
logous Members .,....••••

6—8

)— 19

20—36

CHAPTER IV.— THE INFLORESCENCE AND FLOWER.

Flowering-Shoot — Bracts — Peduncle, Pedicel,— Types of Inflorescence —
Parts of the Flower, Perianth, Stamens, Pistils, Torus — Pollination and
Fertilisation — Characters of Perianth — Position and Numbers of Floral
Parts— Distribution of Sexual Organs— Symmetry of Flower — Floral
Parts are Leaves — Cohesion and Adhesion — Hypogynous, Perigynous
and Epigynous Flowers— Disc — Descriptive Terms for Petals and
Sepals— Estivation— Characters of Stamens— of Pistils— of Ovules-
Types of Flowers which may cause Difficulty— Wheat— Pea— Pine—
Gyinnosperms and Angiosperuis— Floral Diagrams and Short-hand

37—57

viii CONTENTS.

PART I.— MORPHOLOGY— concld.

CHAPTER V.— THE SEED AND FRUIT.

PAGE.

The Seed — Testa, Tegmen, Aril — Albuminous and Exalbuminous Seeds —

Cotyledons, Radicle and Plumule of Embryo — Epicotyl — Hypocotyl —
i Monocotyledons and Dicotyledons — The Fruit — Different Types of
Fruit — Descriptive Terms for Shape of Fruit and Seed . . . 68 — 62

CHAPTER VI.— GENERAL.

Duration of Plant Members — Texture of Plant Members — Prickles, Hairs,
Scales, Glands — Habit — Herbs, Trees, Shrubs, — Annuals, Biennials,
Perennials — Gregarious and Sporadic Plants — Evergreen and Deci-
duous Plants . . . . . 63—67

PAET IL-ANATOMY.

CHAPTER I.— CELLS.

Protoplasm — The Cell— Cell-contents — Cell-division — Pits and Thickening

of Cell-wall— Middle Lamella— Shape of Cells 68—72

CHAPTER II.— TISSUES.

Different kinds of. Tissues and their Elements — Tegumentary, Vascular
Bundle and Fundamental Tissue Systems — Structure and Develop-
ment of Vascular Bundles . . . . . . . . 73 — 76

CHAPTER III,— STRUCTURE AND DEVELOPMENT OF PLANT

MEMBERS.

Stem of Gymnosperms and Dicotyledons — of Monocotyledons — Root? —
Abnormal Development — Periderm and Bark — Lenticels — Shedding
of Leaves — Development of Secondary Members — Root-cap — Root
hairs — Shortening of Roots — Structure of Leaves .... 77 — 84

PART III-PHYSIOLOGY.

CHAPTER I.— FUNCTIONS OF PLANTS IN GENERAL.

General Conditions of Plant Life — Osmosis — Turgescence — Transpiration
— Manufacture of Organic Food Materials — Respiration and Meta-
bolism— Conditions of Existence in a Highly Organised Plant . . ^5 — 92

CHAPTER II.— FUNCTIONS OF THE HIGHER PLANTS IN DETAIL.

Plant Food Materials — Essential and Non-essential Substances — Avail-
ability— Absorption and Ascent of Water in Plants — Transpiration —
Assimilation — En/ymes — Respiration — Growth — Plant Movements —

CONTENTS. IX

PART III.— PHYSIOLOGY— concld.

CHAPTER II.— FUNCTIONS OF THE HIGHER PLANTS IN

DETAIL— concld.

PAGE

Reproduction — Sexual and Asexual Methods — Cross and Self-Fertili-
sation— Anemophilous, Entomophilous, Ornithophilous Plants — Con-
trivances for Facilitating Cross- Fertilisation — Fertilisation of t Flowers
of Salvia lanata and Berberis Lycium — Cleistogamic Flowers — Dis-
semination of Seeds ......... 93 — lift

PART IV.-CLASSIFICATION.

CHAPTER I.— DEFINITIONS AND EXPLANATIONS.

Necessity for Classification — Natural and Artificial Systems — Unit of Classi-
ijcation-^Species, Sub-species, Variety, Race, Genus and larger Natural
Groups — Nomenclature — Practical Determination cf the Natural
Groups . 117—125-

CHAPTER II.— PRINCIPAL SUB-DIVISIONS OF THE
VEGETABLE KINGDOM.

Cryptogams and Phanerogams — Sub-divisions of the Cryptogams — Algae
— Bacteria — Practical Importance of Bacteria — Fungi — Classification
of Fungi — Phycomycetes — Ascomycetes — Basidiomycetes — Ustila-
ginaceae — Uredinaceaa — Lichens — Liverworts and Mosses — Ferns,
Horsetails and Club-Mosses — Phanerogams divided into Gymnos-
perms and Angiosperms — Classification of Gymnosperms — Angios-
perms divided into Monocotyledons and Dicotyledons — Synopsis of
Principal Sub-divisions of the Vegetable Kingdom .... 126—147

CHAPTER III.— THE ORIGIN OF SPECIES.

Struggle for Existence — Importance of Sub-species and Races — Hybrids —
Fluctuating Variability — Mutations — Other Kinds of Variation —
Heredity — Selection — Origin of Species in Nature .... 143 — 161

CHAPTER IV.— COLLECTION AND PRESERVATION OF
SPECIMENS.

Collection — Preservation — Herbarium . . . . . . 162 — 164

PART V- WOUNDS AND DISEASES.

CHAPTER I.— WOUNDS.

Healing of Wounds by means of a Cork Layer — Callus Formation and heal-
ing by Occlusion — Bruises — Pruning — Girdling — Cuttings — Pollard-
Shoots, Stool-Shoots, Root-Suckers — Propagation by Layers and Guti
—Grafting— Budding ..... ... 165—175

X CONTENTS.

PABT V.- WOUNDS AND DISEASES-cow^.

CHAPTER II.— DISEASES.

SECTION I.— INTRODUCTORY REMARKS.

a: PAGE.
Duration of Plant Life — Definition of Disease — Struggle for Existence —

Factors influencing the Relations existing between Organisms — Sapro-
phytes— Competitors, Parasites, Symbionts — Symptoms of Disease —
Disease rarely due to one Factor alone — Knowledge required for
Investigation of Diseases — Sub-division of the Subject . , . 176—183

SECTION II.— INFLUENCES OF OTHER PLANTS ON PLANT-
DEVELOPMENT.

(a) PLANT COMPETITORS.

Deodar and Blue Pine — Teak and Bamboos — Trees and Grasses — Trees and

Strobilanthes — Climbers — Epiphytes ...,,, 183 — 186

(&) PLANT PARASITES.

PhytophtJiora infestans — PhytophtJiora omnivora — Fames annosus — Armil-
laria mdlea — Tramcies Pini — Puccinia graminis — Mcidium montanum
— Orobanche indica — Cuscuta reflexa — Loranthus longiftorus — Parasi-
tism of Santalum album 186 — 202

Lichens — Bacteria and Leguminosce — Mycorhizas — Distant Symbiosis

between Green and Non-green Plants — Decay of Wood . . . 202 — 205

SECTION III.— INFLUENCES OF THE SOIL ON PLANT-DEVELOPMENT.

Necessary Salts in suitable Condition and Quantities — Poisonous Sub-
stances— Necessary Water and Oxygen — Accumulation of Starch in
Leaves indicates Root Trouble 205 — 208

SECTION IV.— INFLUENCES OF THE ATMOSPHERE ON PLANT-
DEVELOPMENT.

Extremes of Temperature — Effects of Excessive Heat — Of Excessive Cold —
Effects of Light — Of Excessive Moisture—Of Winds — Of Poisonous
Substances — Lightning 208 — 216

SECTION V.— EFFECT OF FIRE.

Effect of Fire — Necessity of studying Indirect Effect of each Factor . . 216—217

CONTENTS. Xi

PART VI -GEOGRAPHY.

CHAPTER I.— FACTORS INFLUENCING THE DISTRIBUTION

OF PLANTS.

PAGB.

-Available Water — Soil — Temperature — Light — Air — Existence of other

Plants — Existence of Animals — Fire — Action of Man — Necessity of
avoiding Hasty Conclusions as to Factors responsible for Distribution
— Power of Adaptation — Xerophytes, Hygrophytes, Tropophytes . 218 — 230

CHAPTER II.— PRINCIPAL TYPES OF VEGETATION.

Woodland, Grassland and Desert — Their Distribution depends chiefly on
Moisture, Soil, and Action of Man — Pioneer Plants — Succession of differ-
ent Plant Generations or Crops — Action of Man in altering Course of
Natural Events is limited — Conversion of Grassland into Forest — Trees
producing Root-suckers favoured in the Struggle with Grasses . . 231 — 236

CHAPTER III.— PRINCIPAL TYPES OF, INDIAN FORESTS.

Types of Forests— Factors responsible for their Distribution— Arid-country
Forests — Deciduous Forests — Evergreen Forests — Hill Forests — Tidal
or Littoral Forests — Riparian Forests — Distribution of important
Species ...... .... 237—250

INTRODUCTION.

1. All living beings are said to Two

belong either to the Animal or Vegetable Kingdom, in other Biplo8ical
words they are classed, respectively, as Animals or Plants.
Biology is a term applied to the study of all living beings,

i.e. of both animals and plants, The two biological sciences
are Zoology and Botany, the former embracing the study of
animals, the latter that of plants.

2. So long as we confine our plants and

attention to those highly organised forms of life which Animals,
have an elaborate and complicated structure we find no
difficulty in distinguishing the members of the two natural
kingdoms. Hence, in early times, when the total number of
plants and animals known to scientists was comparatively

small while those which were known belonged to the
higher forms, a definite line of distinction could be easily
drawn between them. With the progress of time knowledge
has gradually extended, and with the help of the microscope
we have gradually passed from a consideration of the large
and obvious to a study of the minute and formerly invisible
things of life, and we are now aware of the existence of a
number of simple forms of life to which the ordinarily ac-
cepted notions of what constitutes an animal, or a plant, fail to
apply and which, in consequence, we cannot classify as either.
The study of such forms which stand at the bottom of the
scale drives us to the conclusion that no definite boundary line
can be drawn between the Animal and Vegetable Kingdoms,
and it should be borne in mind that the substance which con-
stitutes the basis of life, viz. protoplasm, is essentially the
same in both animals and plants. With the exception of such
simple forms, however, there is generally a great difference
between the members of the two kingdoms, and it is obviously
convenient for the purpose of study to keep them separate.
Animals, then, as compared with plants, usually have more
independence of action, while perhaps the mo&b characteristic
distinction of the majority of plants consists in the fact that
they possess a green colouring matter called chlorophyll (a
word which means leaf -green), by means of which they are

able to manufacture the food materials necessary for the main-
tenance of life from the carbon dioxide of the air and water.
Animals, being unable to do this, are obliged to maintain them-
selves by consuming the food manufactured by plants, and if
plants were exterminated all life on the earth would cease. Thus
plants are often called the great food-producers and animals
the great food-consumers. At the same time it must be noted
that a large group of plants known as the Fungi are excep-
tional in this respect, for they possess no chlorophyll and like
\ animals depend on green plants for their food.

Sub-divisions 3. Botany may be sub-divided

of Botany. jn^o fae following divisions :—

I. Vegetable Morphology.

II. ,, Anatomy.
IIT. „ Physiology.
IV. Classification or Systematic Botany.

V. Vegetable Pathology.
VI. Geographical Botany.

The study of the economic uses of plants and of their pro-
ducts is also sometimes treated as a separate branch which is
then termed Economic Botany.

Vegetable Morphology comprises the study of the form of
plant bodies and of the several parts of such bodies as visible
to the naked eye.

Vegetable Anatomy comprises the study of the minute struc-
ture of plant bodies as seen by the aid of the microscope.

Vegetable Physiology comprises the study of the plant as a
living being. Just as morphology regards each plant body,
or part of such body, as a fact, as something which exists and
possesses a certain shape and structure, so Physiology regards
it as a factor, as something which is capable of action and of
performing definite work. While morphology is content with
the knowledge of the existence of certain plant structures,
Physiology asks what function these structures fulfil and how
they do it. Eegarded from a purely morphological stand-point,
the various parts of a plant body are called members. When
such parts are regarded as performing some particular kind of
work, i.e. from the physiological point of view, they are
termed organs. The greater the number of organs, each being
adapted to the performance of one or more functions, possessed
by a plant, the more highly organised is the plant said to be.

Although Part III of this book is devoted to Physiology, a

few physiological details have also been mentioned, here and
there, in the other parts where this has been thought advisable.

Classification aims at arranging all plants in groups accord-
ing to their resemblances, with the object of facilitating the
identification of plants and of enabling anyone to rapidly ac-
quire a knowledge of the plants of any particular region and of
their correct names, as universally recognised by botanists.

Vegetable Pathology includes the study of plant diseases,
wounds and injuries.

Geographical Botany considers the distribution of plants
over the earth and its causes.

4. If we take a seedling of any of Principal
our common forest trees we can at once distinguish : — anTt

(a) The Root which goes downwards and firmly anchors
the plant in the substratum on which it is grow-
ing.

(6) The Shoot which goes upwards in a direction dia-
metrically opposite to that of the root and which
consists of an axis, or stem, bearing green leaves.

It will help us to understand the various forms assumed by
these two sets of organs and their behaviour under different
circumstances if we realise, at the outset, that the root ab-
sorbs from the substratum in which it is growing water with
mineral substances in solution, which, however, are as yet use-
less to the plant as food and which may be therefore called
raw food materials. This water ascends the stem and passes
into the green leaves. The protoplasm in these leaves, by the
aid of the green chlorophyll and when it is supplied with
water by the roots and has air and light in contact with it, is
able to build up a carbohydrate, which usually first becomes
visible in the form of starch, from the carbon dioxide of the
air. This starch contains the energy by means of which the
plant is able to live, grow and perform its vital functions — is
able not only to feed and keep alive its protoplasm, but also to
actually manufacture additional living protoplasm from the
inorganic substances brought up by the roots and to carry out
other work. The root must thus grow and spread in the dark
and moist substratum, while the shoot must come forth into
the sunlight and air in order to obtain its supplies of carbon
dioxide and to expose its chlorophyll to the rays of sunlight.

The shoot also eventually gives rise, first, to flowers and
then, to fruits, the latter containing the seeds which will once

more develop into seedlings and new plants. All plant organs
may thus be primarily subdivided into :—

(1) Vegetative Organs which enable the plant to exist

and maintain itself alive, such as the root, stem
and leaves.

(2) Reproductive Organs the function of which is to pro-

duce new plants, such as flowers.

The root may be distinguished from the shoot by the fact
that the former never directly gives rise to leaves, or true re-
productive organs.

Selection 5. Finally, it is necessary to

of Types for p0int out that the forms of plants and of their members
Description. ^re a^mos^ infinitely various and that, probably, no two
members of even one and the same plant are ever exactly
alike, although the differences between them are frequently
extremely minute. Hence it is obviously impossible to
separately define every form which exists. Generally speaking,
therefore, morphology aims at the selection of broad types
for description, which can be easily distinguished from one
another and each of which may be taken as fairly represent-
ing the most important characters of a large number of
subordinate forms between which the differences are very
slight and difficult to distinguish. At the same time, it must
be noted that these typical forms are generally connected by
intermediate forms, through which one type passes over by
almost insensible gradations into another, and that, therefore,
although the descriptions of the types apply to a large propor-
tion of all existing forms, there are always some forms for
which it is not easy to decide which typical description is most
suitable At the same time this is no practical disadvantage,
for forms which are precisely intermediate, may, with equal
justice, be referred to either of the two types between which
they stand, while all others are referred to the types which
thev resemble most closelv.

PART I.-MORPHOLOGY.

CHAPTER I.— THE EOOT.

6. The first root developed by Primary,

a seedling is called the primary root. All other roots Secondary
whether developed from the primary root, or from other Adventitious
parts of the plant, are called secondary. The root, like the Roots. . ^
shoot, is capable of branching and rebranching, the new
roots being normally developed in longitudinal rows, laterally,
on the parent root, in such a way that the youngest are always
nearest the growing-apex of the mother-root, i.e. they are
developed in acropetal succession and a line, following the
course of development of the lateral roots, passes from the
oldest ones at the base of the parent-root to the youngest ones
at its apex.

The young roots are developed from the inner tissues of
the parent-root and as they grow they break through the outer
tissues. This can be well seen in the long roots which hang
from the branches of the Banyan (Ficus bengalensis), the
young roots pushing through cracks in the outer tissues of the
parent roots. The aggregate of roots developed by a plant
constitutes its root-system. All roots which are not branches of
the primary root, or which, being such branches, are not
developed in acropetal succession, are said to be adv entitious,
this term being applied to all parts of plants which develop
either in abnormal positions, or out of their proper order.
Roots, therefore, may first of all be classified according to their
mode of origin into : —

(1) Primary.

(2) Secondary ] }?> t V

J {(0) Adventitious.

Roots which spring from the stem are therefore adventi-
tious, such as are those often seen on the sugarcane as shown
in Plate I, Fig. 4.

7. If we examine the seedling Types Of

of one of our common forest trees, say an Oak. we shall Root-
find that the primary root elongates and continues to yst< IM§
grow vigorously for a considerable period. Such a root is
termed a tap-root and all the roots developed from it are its
lateral roots, see Fig. 7, Plate I. If the tap-root is injured a

lateral root usually takes its place and continues its growth, in
the direction of the original tap-root. A root-system with a
tap-root has thus a distinct main axis and usually penetrates to
a considerable depth in the soil. A strong tap-root is deve-
loped by many of our forest trees, e.g. Teak (Tectona grandis) ,
Sissoo, (Dalbergia Sissoo) and Anjan (Hardwickia binata).
Such a root of Sissoo, or Anjan, may attain a length of six
feet in the first year.

In many plants, however, such as grasses and their allies, the
first root sent out by the seedling dies off after a short time, or
does not develop vigorously, and stronger roots then spring
from the base of the stem above the primary root. These,
although they often arise above the ground in the air, may
ultimately penetrate the soil and branch there, and in many
plants the entire root-system consists of such adventitious
roots. They may be well seen in the sugarcane. For illustra-
tions, see Plate I, Figs. 3 and 4.

The question whether a plant develops a strong tap-root,
or a superficial root-system, is of great practical importance.
Plants with the same type of root-system compete with each
other in the same layers of soil for water and raw food
materials. A tree with a long tap-root, like the Sissoo, is thus
a good nurse to protect tea-bushes from the effects of frost,
the roots of these two plants not interfering with each other,
while the superficial roots of Toon (Cedrela Toona) and other
species, which are often planted in avenues near field crops, are
injurious to the latter.

The extent of the root-system developed by a plant depends
on the amount of green foliage produced by the shoot. The
greater the latter, the larger and more vigorous is the former.
Plants with leaves floating in water usually have a small total
area of leaf surface, while water also is plentiful close at hand,
and such plants usually possess a small root-system. If, on the
other hand, we collect all the roots of a large forest tree, such
as the Sal, and place them end to end they would probably
cover a distance of several miles.

Development 8. In the case of many of our

of Root forest trees the development of the root to a great extent

itf*A/%nri<vQ •» 1*1

precedes that of the shoot. The plant, as it were, has to
make sure of its foundations below ground before pro-
ceeding with the superstructure and the development of the
shoot above ground may often be quite insignificant for several
years, during the early life of the seedling. Fig. 1, Plate I,
shows the strong well-developed tap-root of a young seedling of

ih.eJ$euciOsk(Quercusmcana) and the insignificant young shoot.
In some cases no true leaves at all are developed during the
first year but only rudimentary leaves, small scaly structures, such
as are seen in Figs. I and 2, Plate I. In many cases the young
shoot of the seedling dies back year after year more or less
completely, while the development of the root-system steadily
progresses, such as frequently happens with Teak and SaL Even-
tually, when a vigorous root-system has been developed, a strong
shoot is sent up which is capable of ultimately forming a full-
sized mature shoot. The advantage of this procedure is often
obvious, such as is the case for example with those trees like
Sal, Harra (Terminalia Chebula), Jamun (Eugenia Jambolana),
and Mahua (Bassia latifolia), which, in the plains of India,
come into leaf during the hot dry season from March to May,
when the roots are obliged to send up large quantities of water
to supply the leaves, and it is therefore necessary that the roots
should be in the deep moist subsoil and not in the parched
surface soil. In such trees, therefore, a strong deep-going root-
system must be formed before a vigorous shoot can be
developed.

9.^Although roots never direct- Root

ly give rise to leaves, they are capable, under certain Suckera-
circumstances, of bearing buds which may develop into
leafy shoots called root-suckers, which are characteristic of
many of our forest trees and shrubs, such as Sissoo, Tendu
(Diospyros tomentosa) and many others. They are often found
springing from roots which have been exposed to the light at
the sides of a road- cutting, or on the banks of streams, for
example.

10. A typical root is usually Fibrous and '
cylindrical in shape and when fine and thread-like it is
termed fibrous. Many plants manufacture more food material
than is required for immediate consumption, this excess
material being stored until it is wanted. The subterranean
roots and the lower part of the stem are favourite reservoirs
for such food and as they are stuffed with the material they
become much swollen and lose their ordinary shape. In some
plants, such as the Radish, Turnip, Carrot and Beet, the tap-
root is swollen, in others, such as the Dahlia, the secondary
roots are stuffed. Such swollen roots are said to be tuberous.
If the swollen root is broader in the middle and tapers towards
both ends, like a spindle, it is said to be fusiform, if it is like a
turnip, broader than high, it is napiform. and if tapering re-
gularly from a broad base to the tip like a carrot, it is conical.

Woody 11. In the case of most trees

Boots. the old roots become hard and woody as they thicken and
then they no longer absorb water and food materials from
the soil but merely serve as conducting pipes to pass on
to the stem the supplies which have been collected by the
younger roots. They also anchor the tree more strongly in
the ground, the massive roots resisting the lever-like strains
exerted by the heavy trunk with its great crown of foliage,
as it sways in the wind. In the case of many Indian trees the
roots form woody supports, like buttresses, at the base of the
trunk, which are for instance very characteristic of Bombax
malabaricum, see Fig. 4} Plate XL

Subterra- 12. According as roots are

nean developed in the earth, water, or air, they may be called

JSdai Roots, subterranean, aquatic or cerial. The aerial roots of the
Banyan on reaching the soil, branch and develop a vigorous
root-system therein, while the aerial portions become woody
and support the horizontal branches like columns. In Rubus
lasiocarpus, the serial roots produced at the tips of the long
curved branches give rise to young plants, which become inde-
pendent and are separated from the parent by the decay of the
connecting branches.

Other aerial roots serve as attachment organs and enable
climbing stems to cling firmly to their substratum ; these are
iound in the Ivy, Ficus scandens, and many others. These
roots are also in some cases able to absorb moisture and food
materials, provided that such are available. Thus some climbing
stems are able to exist after they have been cut and their
connection with the subterranean root system severed.

Sometimes the aerial roots originating on the stem grow
obliquely downwards into the ground and form remarkable
stilt-like supports which may be seen in Screw-Pines (Panda-
mis), Mangroves (Rhizophora), and, in miniature, sometimes
in the Maize (Zea Mays). Some aerial roots possess the excep-
tional power of being able to absorb moisture from the air by
means of a spongy outer sheath of tissue called the velamen,
found in many orchids. In a few cases also the aerial rootF
are green m colour and possess chlorophyll.

CHAPTER II.— THE STEM.

13. As has been noted above, Nodes,
the stem of a plant bears the structures which we call

• T £ i J.T_ A j-x.

leaves. If we examine an ordinary stem we rind tnat tne Leaves and
leaves are situated at certain definite positions on it, which Buds,
are separated by a more or less considerable length of stem
which bears no leaves. The places where the leaves are
borne are called the nodes, the piece of stem lying between two
successive nodes is called an internode. The nodes are often
swollen and are sometimes marked by a distinct line or joint,
as in Gnetum. The youngest leaves are found to be nearest the
growing apex of the stem, i.e. they are developed in acropetal
succession. If only two leaves occur on one node they are on
opposite sides of the stem and are said to be opposite, if there
is only one leaf at each node, the leaves are said to be alternate, or
scattered. If more than two leaves occur at a node, they are
situated at equal distances apart and are then said to be in
whorls (or in verticils) or whorled (or verticillate). If at each
node there are two leaves which are nearly, but not quite,
opposite, they are said to be sub-opposite. When more than two
leaves occur at a node which are nearly, but not quite, at the
same level, they are said to be in false whorls (or verticils). In
practical . descriptive botany, however, the difference between
true and false whorls (or verticils) is often not insisted on,
both being merely called whorls (or verticils). When pairs of
opposite leaves are arranged on the stem in such a way that
the longitudinal axis of each pair is at right angles to the axis
of the pair above and below it, the leaves are said to be
decussate, and are then in four vertical ranks. When leaves
are arranged in two vertical ranks they are distichous, or bifa-
rious. When two or more leaves are inserted very close together
so that they appear to be in tufts, the leaves are said to be
fascicled, or in fascicles, as in the Deodar. The upper angle
between a leaf and the stem is called the axil. On the stem,
in addition to leaves, we find the structures which we call buds
and which are capable of growing out into new stems, or
branches. These buds are normally found in the axils of the
leaves when they are called axillary, or at the apex of the stem
when they are said to be terminal. The leaf, in the axil of
which a bud appears, is called the subtending leaf, while the bud,
having a leaf close below it, is said to be subtended by the leaf.

This fact that buds, and the branches which develop from
them, as a rule occupy a definite position as regards the leaves
is of great importance, and we are thus helped in doubtful
cases to arrive at a decision as to whether a certain member is
to be regarded as of the nature of a branch or of a leaf. What-
ever first arises in the axil of a leaf may usually be regarded as
a branch, and what' subtends a branch as a leaf.1

Various 14. A stem which is soft and

*?S?f more or less succulent is said to be herbaceous, if firm, and

more or less tough and hard, it is said to be woody.

In some plants there is very little, if any, stem and they
are said to be stemless, or acaulescent, e.g. Plicenix acaulis.
In others there are several stems of equal vigour ; such stems,
occurring in tufts, are said to be caespitose, as in many
Bamboos.^
Sterjcwfare : —

erect, when ascending perpendicularly,

ascending, when rising obliquely,

decumbent, when erect, but with the basal portion

horizontal, or nearly so,

reclining, when the basal portion is more or less erect
and the upper portion curved downwards with the
apex trailing on the ground,

procumbent, or prostrate, when lying on the ground,
repent, or creeping, when prostrate and also rooting as

they grow,

soandeni, when climbing,

twining, when they climb by spirally coiling around a

support. Twiners may ascend in two directions, i.e.

they may ascend from left to right, as viewed from

outside the coil, in which case they are said to be

dextrorse and to move in an anti — or counter-

clockwise direction, or they may ascend from right

to left, when they are said to be sinistrorse and to

move in a clockwise direction, see Fig. 1, Plate II.

Stems may also climb by means of special organs called

tendrils. These are slender, thread-like bodies, simple or

branched, which firmly attach themselves to a support by coiling

around it, or by adhering to it, and thus hold the stem secure-

ly. Others climb by means of hooks and spines, e.g.

Calamus tennis.

The stems of some plants, although not distinctly climbing,
are wide-spreading and may often be found resting on, and
more or less entangled with, the stems and branches of other

plants. They are, as it were, weak, or imperfect, climbers,
and are usually described as rambling, or straggling, e.g.
Quisqualis indica and Deeringia celosioides.

A large climber with a woody stem is called a liane, e.g.
Bauliinia Vahlu.

A stem rising directly from the ground, bearing flowers,
but no green leaves, is called a scape, e.g. Orobanche indica.

The peculiar jointed stems of grasses and bamboos which
are hollow between the joints are called culms.

The unbranched columnar stem of palms and Tree Ferns is
termed a caudex.

An a3rial or subterranean branch, rooting and giving off
shoots which become independent plants, by the decay of the
branch connecting them with the parent stem, are called
stolons. The Potato has subterranean stolons, while the
rooting branches of Rubus lasiocarpus are a3rial stolons.

A runner is a slender stolon with long internodes, well seen
in the Strawberry. A plant which produces a number of
stolons, or runners, is said to be sarmentose.

A rhizome is a stem of root-like appearance prostrate on, or
buried under, the ground, giving off slender roots usually at the
nodes and producing erect serial shoots, or leaves, progressively
from the growing apex, as found in many Grasses, Bamboos and
the common Bracken Fern, Pteris aquilina.

Stolons, runners, and rhizomes, are sometimes very like roots,
but they may always be distinguished from roots by the fact
that they directly give rise to leaves in the axils of which buds
appear, although such leaves are usually minute and scale-like.

A bulb is a short shoot with a flattened or conical stem,
provided with thick, fleshy, scale-like leaves and from the
base of which roots are developed, e.g. the Onion.

A corm is like a solid bulb, the main portion of the corm con-
sisting of the thickened stem which is naked, or with a few
inconspicuous, scaly, investing leaves.

A tuber is a short thickened shoot, or part of a shoot, bearing
. inconspicuous scaly leaves, with buds in their axils. In the
Potato, tubers are formed at the ends of stolons, the so-called
"eyes" being the axillary buds. A tuber can be distinguish-
ed from a tuberous root by the fact that it bears scaly leaves,
in the axils of which the buds arise. Small bulbs, corms and
tubers sometimes appear on a3rial stems in the leaiL-axils and
they are then called bulbils, which are found in many species
of Dioscorea. They are capable of developing roots and
producing independent plants.

A cladode is a stem coloured green, with, or without,
inconspicuous scale leaves, which more or less resembles a leaf
and performs the functions of a leaf, e.g. the stem of the
prickly pear, Opuntia Dillenii.

Branching. 15. Branching, i.e. the pro-

duction of new stems from the parent stem, takes place in two
principal ways termed, respectively, dichotomous and lateral
branching. In the first the growing point of the parent
stem divides into two ; two branches of equal vigour are thus
formed, as in a two-pronged fork, and there is no continuous
main axis. This method of branching is very rare.

In lateral branching the growing point of the parent stem
does not divide and new stems are developed laterally from the
parent. There are two principal kinds of lateral branching,
the monopodial and cymose. In the former there is a distinct
and simple main axis, formed by the elongation of the parent
stem. Such a main axis is termed a monopodium. Such a
system of branching is well seen in a Pine tree in which the
leader has uninterruptedly developed from the terminal bud.

In cymose branching there is no simple main axis formed
by the elongation of the parent stem and the lateral branches
grow faster, or for a longer period, than the parent. Of this
form of branching there are two types, the sympodial and
falsely di- or tri-chotomous. In sympodial branching there is a
main axis but this, instead of being a simple axis consisting of
the parent stem, is built up of the basal portions of a number
of lateral branches. On each segment of such an axis, one
lateral branch develops more vigorously than any other, i.e.
there is one leader. The axis so formed is termed a sympo-
dium, or false axis, and is at first crooked but frequently
straightens subsequently, see Fig. 3, Plate II. This may often
be seen on the twigs of trees the terminal buds of which have
died, or not developed vigorously, and the leaders have been
formed by the axillary and therefore lateral buds. In false-
ly dichotomous branching, such as occurs for instance in
Rhamnus virgatus, the branches are forked and at first
sight there appears to have been a division of the grow ing point
of the parent stem. On closer inspection it appears that in
this plant the growing point really terminates in a spine and
that there is no dichotomy. In some plants the terminal
bud becomes a flower, and in others it dies, or does not develop.
A system of branches each one of which forks in this way
and produces a pair of lateral branches of equal vigour

is called a false-dichotomy, or a dichasium. If three lateral
branches develop with equal vigour the branching is falsely tri-
chotomous. In botanical descriptions, however, no distinction
is as a rule made between falsely and truly di- or tri-chotom-
ous, the branching being merely described as dichotomous, or
trichotomous, respectively. We are accustomed to associate the
word branching principally with the stem of plants, but it
must be remembered that precisely similar branching may be
exhibited by the root, or leaf, or other members.

Branches as a rule arise normally in acropetal succession and
in the leaf axils, i.e. they are axillary. Those which originate
otherwise are adventitious, i.e. they are developed out of
their proper order, or in altogether exceptional positions.

As branches are usually axillary their arrangement follows
that of the leaves, and like leaves they may therefore
be opposite, sub-opposite, alternate, whorled and so on.
In many plants while some branches remain stunted and
short, others grow rapidly, and there are in consequence
elongated and dwarf shoots. These occur, for instance, in
Randia dumetorum and Pyrus Pashia, see Fig. 3, Plate II.
Such dwarf shoots in many cases develop into spines and at
first sight it is not always easy to decide whether such spines
are to be regarded as altered (metamorphosed) leaves, or stems,
but as a rule they are found in the axils of leaves, or they
themselves directly give rise to leaves, thus indicating that
they are stems, or rather branches. The spines of the Bel,
Aegle Marmelos, of Flacourtia Cataphracta and others may
frequently be seen bearing leaves, see Figs. 1 and 2, Plate III.
In the Pine we find that there are two kinds of leaves.
The first are small and scale-like, in the axils of which small
dwarf shoots with brown scales at the base and terminating in
two or more long green leaves, or needles, are borne. On the
dwarf-shoots of the Deodar the internodes remain so short
that the leaves (needles) appear to be in tufts, or fascicles.

The tendrils of Gouania leptostachya do not at first sight
appear to be branches but, as in the case of the spines of the
Bel, the true nature of these organs is indicated by the fact
that they originate in the leaf -axils and bear leaves, just as do
normal branches, see Fig. 3, Plate III.

In some plants the stem remains simple and does not
branch, e.g., in the majority of Palms. In a plant in which
the stem repeatedly branches, the branches thus produced
again branching and so on, such as is the case with most of our

Shape of
Stem.

Stem

Structure,

Bark.

forest trees, the smallest branches which have been produced
most recently are called twigs, the smaller branches branchlets,
and the larger ones branches.

16. The shape of the stem and

branches varies considerably in different plants and often helps
the Forester to distinguish his trees in the forest. Many trees
have large buttresses at the base of the trunk, e.g. Bombax
malabaricum, see Fig. 4, Plate XI. In Ougeinia dalbergioides
the stem -is usually short and almost always crooked. In
Acacia leucophloea it is almost always crooked and knotty
(gnarled). In the Hornbeam. Carpinus viminea, it is distinctly
fluted, i.e. with broad, shallow, curved grooves.

In many plants the stem is cylindrical, i.e. terete, in
others the stem has 3, 5, or more distinct ridges or angles.
Sometimes, in addition to being angled, the stem is more or
less deeply grooved, or hollowed out between the angles, and
it is said to be channelled. If the stem is marked with more
or less parallel furrows it is sulcate, if the furrows are very
minute and look like mere lines the stem is said to be striate.
The stems of lianes are frequently irregular in shape and are
flattened or deeply grooved.

Such peculiarities, although as a rule not noticeable on
the old stems and branches of trees and shrubs, are often very
characteristic of branchlets and twigs. The branchlets of
Flemingia stricta, for instance, are 3-angled (triquetrous), those
of Coriaria nepalensis are quadrangular, those of Teak are
channelled, and those of Flemingia congesta are sulcate.

17. If .now we cut through

a stem of one of our common forest trees, say the Teak,
and examine the cut surface, we find the greater portion
of the interior of the stem to be solid and hard, consisting
of the so-called wood', which is enveloped in a comparatively
thin external coat of softer substance of a different colour,
which can be detached from, and stripped off, the solid woody
cylinder which it covers. This outer coat is the so-called
cortex, or bark, of the Forester ; its characteristics vary greatly
in different species and the Forester finds them very valuable
for the identification of trees in the forest. In some plants,
e.g. Palms and Bamboos, there is no true bark. The first
characteristic of the bark to be noted is its thickness ; on the
stems of young plants and the twigs of old plants it is very
thin. On the old stems of trees and shrubs its thickness varies
greatly in different species. Thus in Ougeinia dalbergioides it

is only about one-sixth of an inch thick, whereas in Sal its thick-
ness is from 1 to 2 inches.

There is usually a considerable difference both in colour and
texture between the outer and inner layers of bark, thus in
Phyllanthus Emblica the outer bark is pale grey and the inner
substance is red ; in most trees and shrubs also the inner sub-
stance is distinctly moist while the outer tissue is dead and dry.

On the stems of young plants and twigs of old trees the
exterior of the bark is usually smooth, but on the old stems of
trees and shrubs the degree of roughness varies greatly in
different species. InSterculia wrens, for example, it is very
smooth and affords a marked contrast to the rough bark of say
an old Sal tree. Smooth stems may, or may not, be shining :
in Anogeissus latifolia the smooth stem is not shining, while
in the Birch it is.

The colour of the external bark is not only different in
different species but varies on different parts of one and the
same plant. Thus the twigs and branches of Carissa spinarum
are bright green, but the old stems are grey, or yellowish.

The twigs and branches of Berberis aristata are dark red, of
Rubus lasiocarpus purple and of Salix daphnoides dark green,
or almost black. The colour of the bark on the stems of trees
and shrubs is very important for identification and the follow-
ing may be noted as examples : —

In Betula utilis it is almost white.

In Albizzia procera it is greenish.

In Boswellia serrata it is yellowish.

In Stephegyne parvifolia it is bluish-grey.

In Anogeissus latifolia it is pale grey.

In Terminalia Arjuna it is pale pinkish-grey.

In Diospyros tomentosa it is almost black.

In Sterculia urens it is sometimes dark red.

The texture of the bark also varies greatly in different
species : in Betula utilis it is papery, in Erythrina suberosa
corky, while in Teak and Cupressus torulosa it is fibrous, i.e.
it breaks up into thin long threads.

The bark of old branches and stems may, or may not, have
fissures, or cracks, of various kinds. The stem of Anogeissus
latifolia is smooth without characteristic fissures. When there
are fissures they may be shallow as in Teak, or deep as in
Pinus longifolia. The way in which such fissures run, whether
vertically or horizontally, and the way in which they join, or
cross, one another are also characteristic. In Buchanania

Leaf -Scars

and

Lenticels.

Internal
structure.

Pith.

latifolia these fissures cross at right angles cutting the surface
of the bark into small squares and producing a tessellated
appearance ; in other cases strips and plates, or scales, of various
shapes and sizes are produced.

As the stem of a tree or shrub increases in size the outer
layers of bark are cast off and the way in which this is done is
often characteristic. In the Birch, the bark peels off, i.e. ex-
foliates, in rolls, in the Khair (Acacia Catechu) in long narrow
strips which remain for some time on the trees giving a ragged
appearance, and in Gmelina arborea in large, irregularly shaped,
scales, thus exposing patches of pale yellowish surface below
which contrast strongly with the grey external bark.

18. The bark on young stems,

on branchlets and on twigs often exhibits peculiar and
characteristic marks, the principal of which are the
so-called leaf-scars which mark the spots from which the
leaves have fallen, and the lenticels. The leaf -scars of course
follow the arrangement of the leaves and in deciduous species
we can at once see from the position of these scars whether
the leaves are opposite, alternate, whorled and so on. Their
size and shape vary greatly in different species. A reference
to Figs. 1 and 2, Plate XI, will indicate how we may readily
distinguish two trees (Odina Wodier and Hymenodictyon ex-
celsum), which, when bare of leaves, are somewhat alike in the
forest, by an inspection of their twigs and principally by the
shape and arrangement of their leaf-scars. In some cases the
entire leaf is not shed and the bases of the leaves persist and
give the stem a ragged appearance, as in species of Phoenix.

Lenticels are interruptions in the outer coat of bark which
allow air to penetrate to the internal tissues and they usually
appear as raised corky spots, or lines, of varying shape and size.
In the Birch, for instance, they are horizontal lines, being very
large and conspicuous, while in Pyrus Pashia they are small
spots. They are often of a paler colour than the surrounding
bark and are thus made conspicuous.

19. If now we look at the cut

surface of that portion of our teak stem which lies inside the
bark we find certain peculiarities which require notice.

In the centre there is a small area of soft tissue called the
pith which, in young stems, branches and twigs, is often large
and conspicuous. The size and shape of the pith varies in
different species. As a rule it is small, but in Teak it is rela-
tively large and conspicuous. In the Walnut and Prinsepia
uiilis it is divided into characteristic large chambers, In cross

section it is quadrangular in Teak, nearly circular in Corylus
Colurna, the shape of a cross in Bauhinia Vahlii, usually
oblong in Birches and pentagonal in Oaks.

The remainder of the stem lying between the pith and the Heart- and
bark is occupied by the wood proper and, unless our stem is Sap~Wood>
too young, we shall find that the central portion of this woody
cylinder is dark-coloured and is surrounded by a belt of paler
wood. The former is the heart-wood or duramen and the latter
the sap-wood or alburnum. In some trees, eg. the Silver Fir,
there is no heart- wood, but when this is present its colour and
size in comparison with those of the sap-wood are important
characters. In Teak the heart-wood, when fresh, is dark golden
yellow and the sap-wood is white.

In the wood, arranged around the pith, we find numerous Alinual
lines which divide the wood into concentric layers ; the latter Rmgs'
are the annual rings, so-called because each of them usually
represents the amount of wood formed in one year and
hence by counting these rings the age of the stem may be
calculated. These rings are due to a difference in the density
of adjacent concentric layers of wood, the wood formed on the
outer side of each ring being denser than that on the inner
side of the next ring which adjoins it. In several species no
annual rings are found, e.g. the Mango ; in others there are
so-called false rings, i.e. bands of tissue which do not pass
uninterruptedly around the stem and which often run into
one another. These may be seen in Pongamia glabra and
Quercus semecarpifolia.

Through the wood, passing from the centre outwards, Medullary
towards the circumference of the stem, are radiating lines called Rays>
the medullary rays. The presence or absence, width and other
characters, of these rays are important points in the identi-
fication of different woods. If we split a piece of the Teak
stem radially we find the medullary rays appearing on the
surface of the radial section as shining plates, giving an orna-
mental appearance to the wood and constituting the so-called
silver-grain. Looking again at the cross section of our stem we
find a number of minute pores which are larger and more Pores-
numerous in the inner part of each annual ring than in the
outer part. The size of these pores and the way in which they
are distributed throughout the wood are important characters
for the identification of trees from their wood.

The hardness and weight of wood are also well-known
characters for distinguishing trees. With Teak, for example,
we may compare the much softer, lighter wood of Erythrina

tuberosa and the considerably harder and heavier wood of
Xylia dolabriformis.

Finally the characteristic scent of the Teak wood should be
noted and compared, for example, with that of the wood of
Sandal, Toon and Deodar.

The stem of our example, the Teak, of which we have now
shortly considered the most important and obvious characteris-
tics, may be taken as typical of the stems of the great majority
of the trees and shrubs of our forests, and some of the modi-
fications of this typical structure found in different species
have also been noted. It must be mentioned, however, that in
some species there is a remarkable departure from the type in
that there are narrow, more or less concentric, bands of soft,
bark-like tissue, alternating with bands of woody tissue
throughout the stem. These are found for example in
Dalbergia paniculata and Cocculus laurifolius. A similar
structure is often seen in the woody stems of climbers, e.g. in
Bauhinia Vahlii, in which the layers of porous wood alternate
with soft, red, bark-like tissue.

If now we look at a section of a Deodar stem we find,
as before, a pith, distinct bark, and wood showing both
heart- and sap-wood, while in the wood are annual rings and
medullary rays. There is, however, a great difference from the
Teak wood in that here we have no pores, the annual rings
being marked by the darker colour of the denser wood on
the outside of each ring contrasting with the lighter colour
of that on the inside of the rings. This absence of pores is
characteristic of the wood of all the trees and shrubs commonly
known as Conifers. In some conifers, although there are no
Resin-o.uals. pores, there are wThat are called resin-canals or -ducts, which on
a transverse section may at first be mistaken for true pores.
They may be distinguished by their irregular outline and they
are usually sparsely distributed through the wood. They are
well seen on a transverse section of Pinus longifolia.

If now we look at the section of a Palm, e.g. Borassus
flabellifer, we find that there is no distinct bark which can be
stripped off and there are no medullary rays or annual rings.
Scattered throughout the soft tissue of the stem, we find
numerous rounded, hard, black areas, in the interior of some
Vascular of which is a large pore. These are the so-called vascular
bundles. Those situated towards the exterior of the stem are
usually without pores and are closer together than those
towards the centre, and the outer portion of the stem is conse-
quently much harder and denser than the interior. The section

of the stem of a Bamboo is somewhat similar, but the vascular
bundles are not so conspicuous and the interior of the stem
is usually hollow, except at the joints. In the stem of a Tree
Fern also there is no distinct bark, and we find an exterior coat
consisting of the bases of fallen leaves and adventitious roots
and a central portion of soft tissue, which often disappears
and leaves a hollow in old stems, while between these lies
a ring of harder woody tissue which contains characteristic
vascular bundles, usually crescent-shaped and with a dark-
coloured border.

CHAPTEII III.— THE LEAF.

20. If we look at the foliage leaf

of say the Teak tree we at once recognise that it consists
of two principal parts (1) the expanded apical portion called
the blade or lamina and (2) the stalk, or petiole. In some
Nerves. plants the leaves have no petiole and they are then said
to be sessile, whereas leaves with a distinct stalk are petiolate.
On looking at the lamina we find a framework of firm ribs
traversing its surface in all directions, between which the
soft green tissue is stretched, much like the cloth over the
ribs of an umbrella. The largest and most prominent of these
are usually distinguished as ribs, nerves, or veins, and the
smallest as veinlets. For the present we may include them
all under the general term strands. These strands of firm
tissue, if followed up, will be found to extend from the
leaf blade through the petiole and stem down to the root, the
strands in the leaf being, in fact, branches of similar stouter
strands in the stem, which are the so-called vascular bundles.
These give the necessary rigidity and strength to the plant
enabling the stem to stand erect and the flat leaf-blades to
remain extended in the sunlight. These cords of tissue also
contain minute pipe-like structures which will be considered in
detail later, but through some of which, it may now be noted,
water with mineral salts in solution passes from the roots to
the green leaf, while others bring back into the stem the food
materials manufactured in the leaf by the help of the green
chlorophyll under the influence of sunlight, and carry them
to those points where they are required. When leaves are
cast oft', the places where the vascular strands pass into the
stem from the leaf are usually distinguishable on the resulting
leaf -scars as more or less, evident dots, or rounded marks.
The number, shape, and arrangement of these marks on the
scar are often very characteristic.

Veration. 21. The way in which the strands

are arranged in the leaf is important and is called the venation
of the leaf. Two main classes of leaves are usually distin-
guished, viz :—

(1) Parallel -veined.

(2) Reticulate- or net-veined.

In parallel venation all the strands which can be easily seen

with the naked eye run approximately parallel to one another «
They usually run from the base of the leaf to the apex, as in a
Grass, or Bamboo. The term, however, is also applied to cases
where there is one main strand traversing the leaf-blade from
base to apex, called the midrib, and from which all other
noticeable strands run approximately parallel to each other
towards the leaf-margin, as in a Banana leaf. In both cases a
few minute, inconspicuous, and generally straight, strands
usually connect the main strands and run at right angles to
them. These are conspicuous in the leaves of Arundinaria
spathiflora. In reticulate venation the strands are seen to
branch in all directions and thus give rise to an elaborate net-
work, as in a Teak leaf. When there is a distinct midrib from
which all the other nerves, directly or indirectly, spring, the
nerves which spring from the midrib are called lateral nerves
and the leaf is said to be penninerved, or pinnately-veined. In
such cases also the midrib is said to be the primary nerve, the
larger nerves springing from the midrib are called secondary
nerves, and the smaller nerves springing from the latter the
tertiary nerves.

In some cases in this type of leaf, the lower pair or two of
lateral nerves are much more prominent than the remainder,
as in Cinnamomum Camphora, see Fig. 5, Plate IV. Such
cases bring us by insensible gradations to the next type of
venation in which there is more than one main rib, or primary
nerve, entering the base of the blade and the leaf is then said
to be palminerved, or palmately- or digitately -veined. Accord-
ing to the number of the strong basal nerves the leaf is said to
be palmately — or digitately — 5 nerved, 7 nerved and so on.

Nerves may be straight or more or less curved. Those
which are slightly bent in the form of a bow and run in a
regular sweeping curve are called arcuate, those which are
more sharply bent are arched. A leaf of Quercus incana may
be taken as an example of a penninerved leaf with straight-
secondary nerves, see Fig. 1, Plate IV. Such a leai differs
from a typical parallel-veined leaf, such as that of the Banana,
in having the secondary veins further apart and the spaces
between them rilled with distinctly reticulated strands. A
leaf of Acer caesium, Fig. 2, Plate IV, furnishes an example
of a palminerved leaf with straight primary nerves. The
penninerved leaf of Cornus macropliylla, Fig. 3, Plate IV,
has arcuate secondary nerves. The palminerved leaf of
Smilax parvifrtia, Fig. 4, Plate IV. has arcuate primary nerves.
By some botanists the term palminerved is restricted to cases

in which the primary nerves are practically straight; when
they are curved, the leaf is merely described as having 5,
7, or more, basal nerves. When the secondary nerves are
curved each one frequently runs into and joins the next secon-
dary above it, the junction taking place near the leaf margin.
A continuous strong nerve, composed of the ends of the
secondary nerves, is thus formed close to the leaf margin.
This is called a marginal, or intramarginal, nerve and may
be seen in Ficus bengalensis, or Eugenia Jambolana. Such a
nerve prevents the leaf blade from being easily torn. A
Banana leaf has no such nerve and is quickly torn into strips
by the wind. If this were not so the enormous leaf blade
would offer great resistance to the wind and the plant's
tissues would be subjected to a dangerous strain. As a rule
a midrib divides the leaf blade into two practically equal divi-
sions. When these divisions are unequal the leaf is said to
be oblique, as is the case in Ficus Cunia. When nerves
continually fork and divide into two branches of approxi-
mately equal size, the venation is called furcate and is charac-
teristic of many Ferns, see Fig. 6, Plate IV.

Leaf margin. 22. The margin of a leaf is said

to be entire when it is an even line not indented in any
way, serrate when with sharp teeth directed towards the
leaf apex, bi-serrate when each main tooth is again serrated,
serrulate when serrate with very small teeth, ruminate
when serrate with the teeth directed backwards, dentate or
toothed when the teeth are triangular and directed out-
wards, crenate when with rounded teeth, repand when it is
a gently undulating line, sinuate, or undulate, when the
undulations are more pronounced. When the margin is
fringed with fine and close-set hairs it is ciliate, and when it
is cut into a number of long narrow segments it is fimbriate.
W'hen the incisions are deeper, but do not extend more
than half-way to the midrib in the case of a penninerved
leaf, or to the base of the blade in the case of a palminerved
leaf, the leaf is said to be lobed or cleft, according as the leaf
divisions, or the spaces between them, are broad and rounded
or narrow and acute. WThen the incisions extend still deeper,
the leaf is said to be partite, or parted, and when they reach
the midrib or base of the blade, thus dividing the leaf into
distinct parts, the leaf is said to be divided. In this case the
parts so divided off are called segments and they cannot be
separated from the midrib or petiole without the lamina being
torn. When each of these divisions has a separate insertion

'23

of its own, there being no trace of lamina at the place of
insertion, and when each of them can he separated from the
common leaf -stalk without tearing, just as the whole leaf may
be separated from the stem, the leaf is known as a compound
leaf, in contra-distinction to a simple leaf which is not thus
divided. The parts of a simple leaf blade are known as Simple and
segments, or lobes, while each separate division of a com- Compound
pound leaf is called a leaflet. The terms given above for the
description of a simple leaf, as to its venation, margin and so on,
are equally applicable to each leaflet of a compound leaf.
Each leaflet may be sessile or provided with a stalk, the latter
being called a petiolule. The various shapes of the leaf blade
are. caused by portions of the leaf growing faster than others,
and we get first an uneven margin, then a lobed, cleft, parted,
and finally a divided, or compound leaf. As in such cases the
growth in the direction of the main nerves is usually more
vigorous than that of the portions of the blade between them,
a pinnately-nerved leaf gives rise to a pinnately-lobed, —
cleft, — parted, — divided, or compound leaf, and a palmately-
nerved leaf to a palmately, — lobed, — cleft, — parted, — divided,,
or compound leaf. Pinnately- and palmately -cleft are synony-
mous with, and often replaced by, the terms pinnatifid and
palmatifid respectively

Similarly the terms pinnately — and palmately — divided
are synonymous with the terms pinnatisect and palmatisect.

23. The following terms are most General

frequently employed for describing the general shape of the shape of
blade of a leaf or leaflet. They are of course applicable to Leaves-
any plane surface and so may be used for other organs
besides leaves. As they refer to plane surfaces with an
entire margin, in order to describe the general shape of a
leaf the margin of which is not entire, it is usual to con-
sider the general shape as defined by an imaginary line
passing through the base and apex of the leaf-blade and
touching the summits of all the principal teeth, lobes, or
segments, of the lamina.

1. Acicular ; needle-shaped, very much longer than

wide and tapering to a point, such as a Pine leaf.

2. Linear ; several times longer than wide with almost

parallel sides.

3. Subulate ; awl-shaped, acicular with a broad base.

4. Lanceolate ; like a spear-head. Several times longer

than wide but tapering to both ends, with the
•'. - greatest width below the centre.

5. Oblong ; two or three times as long as broad with

almost parallel sides.

6. Elliptical; oblong with a regularly curved outline.

7. Oval ; broadly elliptic. The width more than half

the length.

8. Ovate ; like the outline of an egg with the broader

end at the base.

9. Orbicular ; circular or nearly so.

10. Cuneate ; wedge-shaped. Broad at apex and narrow

at base.

11. Deltoid or triangular ; cuneate with the width at

the base.

12. Spatulate ; spoon-shaped. Rounded above, long a.nd

narrow below.

13. Reniform ; kidney- shaped.

14. Falcate ; sickle-shaped. Curved like the blade of a

sickle, or scythe.

For describing the extremity of the leaf, whether the
base or apex, the following terms are most commonly used,
1 to 9 being generally applied to the apex and 10 to 13 to
the base.

1. Acuminate ; with a long tapering point.

2. Acute : ending in an acute angle, the point not

being prolonged.

3. Obtuse : with a blunt or rounded apex.

4. Truncate : ending abruptly as if with the end cut

off by a straight line.

5. Retuse : with a shallow notch in a rounded apex.

6. Emarginate : with a decided terminal notch.

7. Mucronate : ending abruptly in a short, stiff, sharp

point.

8. Cuspidate : ending in a long, tapering, stiff, sharp

point.

9. Caudate : ending in a long slender tail.

10. Cordate : when of two broad rounded lobes one

on either side of a deep notch.

11. Aurided : when of tw o narrow rounded lobes one

on either side of a deep notch,

12. Sagittate : when the lobes on each side of tho

notch are pointed and directed downwards.

13. Hastate : when the lobes on each side of the notch

are pointed and directed outwards.

An ovate leaf which is cordate at the base and pointed at
the apex is called a cordate leaf ; similarly a leaf which is
sagittate, or hastate, at the base and pointed at the apex is
called a sagittate, or hastate, leaf. If in a lanceolate, ovate,
or cordate leaf we imagine the petiole to be attached to the
apex instead of to the base, we get an ob-lanceolate, ob-ovate,
or ob-cordate leaf, respectively.

A peltate leaf is one in which the petiole instead of being
attached to the margin of the leaf-blade is joined to some part
of its under-surface, so that the leaf-blade is more or less at
right-angles to the petiole, as in Nelumbium speciosum.

If in a deeply cordate leaf we imagine the basal lobes to
grow together and join in front of the petiole we get a peltate
leaf ; if now such a cordate leaf was sessile on the stem and the
same thing happened, the stem would appear to pass through
the leaf. Such a leaf is said to be per/oliate and the base
of the leaf which thus embraces, or clasps, the stem is said
to be amplexicaul. If the base only partly surrounds the stem
it is semi-amplexicaul. Occasionally the bases of two opposite
sessile leaves grow together and are then said to be connate. In
some cases the leaf-blade is continued along the stem below
the leaf insertion and the leaf which thus seems to run down
the stem is called decurrent, as seen in Verbascum Thapsus.
Pinnately — and palmately — compound leaves are usually known
as pinnate and palmate leaves, respectively.

The prolongation of the petiole of a pinnate leaf, which
corresponds to the midrib of a pinnately-veined simple leaf, is
called the rhachis.

When the rhachis terminates in an odd leaflet the leaf is
said to be impari — , or odd — pinnate and when there is no termi-
nal leaflet it is pari — , or abruptly — pinnate.

The leaflets of a pinnate leaf are usually opposite to each
other in pairs, but sometimes they are alternate on the rhachis.
The impari-pinnate leaves of Sissoo have alternate leaflets.
When the leaflets of a pinnate leaf vary greatly in size the
leaf is interruptedly-pinnate. When the terminal leaflet or
pair of leaflets is largest, those below it gradually decreasing
in size with the smallest at the base, the leaf is lyrately pinnate,
as are the leaves of Picrasma quassioides.

WThen the rhachis of a pinnate leaf, instead of giving rise
directly to leaflets, develops branches on which the leaflets
are borne, these branches are termed pinnae and the whole
leaf is said to be bi-pinnate, such as are the leaves of Khair
(Acacia Catechu). When pinna3, instead of bearing the leaflets

directly, also develop branches on which the leaflets arise, these
secondary branches are termed pinnules and the leaf is said
to be tn-pinnate, as are often the leaves of Moringa pterygosperma.
A compound leaf is usually described by the number of leaflets,
thus J}i~, tri-, quadri-foliolate and so on.

It is not always easy at first sight to distinguish between
a pinnately-and palmately-trifoliolate leaf, but on close in-
spection it will be seen that in the former the leaflets do not
all spring from the same point — see the pinnately 3-foliolate
leaf of Desmodium tilicefolium, Fig. 1, Plate F, in which an
obvious rhachis extends from the point of insertion of the
pair of lateral leaflets to that of the terminal leaflet. The
junction between the rhachis and the base of the terminal
leaflet, or of its petiolule, is often marked by a distinct joint
or articulation ; sometimes also the petiolule of the terminal
leaflet is swollen and is thus easily distinguished from the
rhachis. The leaf of Desmodium tiliaefolium may be compared
with the palmately 5-foliolate leaf of Holboellia latifolia in
which all the leaflets spring from a distinct joint at the apex of
the petiole, Fig. 2, Plate V.

It is not always easy to at once decide whether foliar
structures are leaves or leaflets. If we look at a branch of
Phyllanthus Emblica we find the small leaves arranged in two
ranks along the twigs giving the latter the appearance of
pinnate leaves. Minute buds may, however, be often found
in the axils of these small leaves, thus indicating that they
are true leaves, no buds being normally produced in the angle
between a leaflet and the axis from which it springs. Moreover
flowers are found on these leaf-bearing twigs thus showing that
the latter aje branches of the stem and not petioles, rhachises,
or branches of them, on which no flowers normally arise.

A leaf which is at first palmately 3-nerved but in which
each of the lateral nerves is forked, the outer branch of each
fork sometimes again forking, is said to be pedately -nerved.
Such a leaf may be lobed, cleft, parted, divided or compound,
just as is the case with an ordinary palminerved leaf, and in
the last case we get a pedately -compound leaf, which is usually
simply called a pedate leaf. See Fig. 7, Plate IV.

The principal terms which are usually employed for
describing the general shape of leaves have now been
enumerated above, but it must be remembered that the forms
of leaves are infinitely various and that it is neither possible
nor desirable to have separate names and definitions for every
form that may be met with. Here, as elsewhere, morphology

selects and describes types, and we must expect to find a
number of forms intermediate between the types. For each
intermediate form we employ the term which seems to describe
it most correctly, and in many cases a combination of terms,
such as ovate-lanceolate, oblong -lanceolate, and so on, are found
to be most suitable. The student should collect leaves of
various plants and endeavour to frame terse descriptions of
the same, so that another person from the descriptions may
be able to picture to himself the exact form of the leaves in
question. On one and the same plant all the leaves are not
exacthr the same size or shape, and hence, when describing the
leaves of the plant, the extremes must be given, such as
:' varying from ovate to elliptic, length of blade 4-6 inches,
breadth 2-3 inches."

24. When the size and shape of Polymorphic

the leaves on one and the same plant vary very consider- Leayes-
ably the plant is said to be heterophyllous and the leaves are
said to be polymorphic. This is the case in many climbing
plant ssuch as Ficus pumila, the Ivy and others, see Figs. 1
and 2, Plate VI.

To understand this phenomenon we must remember that
the function of the green leaves, viz. that of manufacturing
food for the plant, can only be properly performed when the
green leaf-blades are exposed to the sunlight and cannot be
carried out in the dark, and that the amount of food which can
be manufactured depends on the amount of green surface
exposed to the light. Creeping stems which are often found in
shady places on the ground, or on the trunks of other trees,
must make the most of the faint light at their disposal and
must keep as large a surface of green leaf-tissue exposed to
the light as possible. We thus find beautiful arrangements of
leaves of very various size and shape, small leaves occupying
the spaces between the large ones and the lobes and segments
of some leaves fitting into the spaces between similar lobes
and segments of adjoining leaves. Each leaf is thus arranged
so as to shade its neighbours as little as possible and no light
is allowed to pass through on to the substratum below with-
out being utilised.

Such arrangements of leaves are called leaf-mosaics. When
such creeping stems send up erect serial stems standing away
from the substratum covered by the leaf-mosaic and which
ultimately give rise to flowers and fruit, the leaves borne by such
stems usually differ considerably from those on the creeping stems
and are more uniform in size and shape, see Fig. 2, Plate VI.

Leaves of

Young

Plants.

Other
Characters
of Leaves.

Such aerial stems are usually surrounded by brighter light
than are the creeping stems and their leaves are exposed not
only to overhead light, but also to considerable lateral
illumination, so that in their case the partial shading of the
lower leaves by the upper ones is not so important, the loss of
overhead light being compensated by the addition of lateral
light. Moreover as in such stems plenty of room is available
to enable the leaves to develop at different levels it is not so
necessary that the leaves arising at any one level should fit
together closely and accurately, for the light which passes
through the interstices of the upper leaf-layers may be received
and utilised by the lower leaves and is not therefore lost to
the plant. Hence in these shoots leaves of such size and shapa
as are necessary to form a close-fitting, more or less flat,
mosaic are not required.

Although hete^ophylly is one of the expedients resorted to
by plants in order to have as large a leaf surface as possible
exposed to the light, it is by no means the only one, and in other
plants the same end may be attained in a variety of ways.

25. The leaves of seedlings and

young plants usually differ considerably from those of mature
plants. Fig. 5, Plate XII, shows a seedling of Oroxylum
indicum and indicates the difference which may exist between
the first leaves and those subsequently developed, for the
leaves there shown bear not the least resemblance to the
enormous bi- and tri-pinnate leaves of the mature tree.
The leaves of young pfants of Quercus semecarpifolia have
spines and are toothed, while on old trees they are usually
entire, and in Gardenia turgida the leaves of young plants
are quite unlike those of older plants. In species of Phcenix
the leaves of young plants are usually entire while those
of mature plants are pinnate. Similarly the leaves on coppice
shoots often differ considerably in size and shape from
those on uninjured plants. On coppice shoots of Pyrus
Pashia the leaves are often lobed or cleft, whereas they are
normally crenate. This point is one of practical importance
for Foresters, who, unless they are able to recognise their
trees and shrubs at different stages of their life-history, can
know very little about the reproduction of their forests.

26. Leaves may be glossy or

shining, like those of Cocculus laurifolius, or dull and not
shining like those of Euonymus Hamiltonianus and in this,
as in other respects, the upper and lower surface of the leaf-
blade may differ considerably. As regards colour, mature

leaves are usually of some shade of green and the lower sur- Colour,
face is frequently paler than the upper. The colour of young
leaves is sometimes characteristic and is often of some shade
of red or purple. As examples we may note the pinkish, or
purplish, young leaves of Quercus incana, the bright red ones
of Acer caesium, the beautiful purple and brown of those of
Mango and the dark red brown of Cassia Fistula. Mature
leaves frequently undergo a striking change of colour before
they fall off the plant. Such colours are usually called
autumn tints and often enable the Forester to recognise his
trees from a long distance. As examples we may note :

The yellow of Odina Wodier, the pale leather-brown of
Lagerstrcemia parviflora, the brick -red of Antidesma diandrum,
the beautiful red, purple, and orange of Sapium sebiferum, and
the dark red, or bronze, of Anogeissus latifolia. Some leaves,
on drying, undergo a characteristic change of colour ; those of
Dalbergia paniculata turn black and those of many species of
Symplocos turn bright yellow.

Many leaves have a strong and characteristic smell especially Smell,
when they are crushed. As examples may be noted the un-
pleasant smell of leaves of Viburnum foetens, Premna latifolia
and Solanum verbasci folium, the aromatic odour of those of
Skimmia Laureola and Cinnamomum Tamala, the black-cur-
rant-like smell of Pogostemon plectranthoides and the well-known
smell of TJiymus Serpyllum.

The taste of leaves is also often peculiar. The leaves of Taste-
Eauhinia malabarica, Acacia pennata and Antidesma dian-
drum, for example, have a characteristic acid taste.

Leaves which are strongly aromatic frequently have the Glands,
ethereal oil, to which the smell is due, stored in small recep-
tacles called glands in the leaf tissue. Such glands, being
translucent, are easily seen when the leaf is held up to the
light as pale spots. Such leaves are said to be gland-dotted.
As examples may be taken a leaf of the Orange, or of Zan-
thoxylum alatum.

The texture of leaves, as well as excrescences, such as
hairs, scales and so on, which commonly appear on other parts
of the plant besides the leaves, will be considered later, when
the detailed account of each member has been completed.

27. The principal points to be p™™jfrs of
paid attention to as regards the petiole of the leaf are its
lengthy which varies greatly in different plants, and its gen-
eral shape. In some plants it is very slender and thread-like
and is said to be filiform, in others it is stout. Like the

stem, the petiole may, or may not, be terete, flattened,
angled, grooved, striate, and so on. Very frequently it is
channelled, or grooved, on the upper surface as in Viburnum
cotinifolium, see Figs. 8 and 9, Plate IX.

In some cases the lamina is continued along the sides of
the petiole which thus appears to be winged, as seen in the
Orange.

Leaf-Base. 28. In some cases [the base of

the leaf is more or less clearly differentiated from the rest
of the leaf and in many plants it becomes a swollen cushion of
tissue called the pulvinus, well seen for example at the base
of the petiole of Millettia auriculata, and the small pulvinus
often found at the base of leaflets is called a pulvinule.

. This differentiation, however, is particularly remarkable in
many Bamboos in which the leaf-base is large and forms a
long sheath to the stem, the petiole of the lamina being
separated from the sheath by a distinct joint or articulation.
The sheaths which arise directly from the Bamboo culms,
called the culm -sheaths, in the axils of which the branches
arise, usually develop no leaf -blade, or only an imperfect one,
but all gradations between sheaths with no blade and those
with a normal lamina may frequently be seen.

This sheath is very characteristic of Bamboos and Grasses
generally, as is also the peculiar structure known as the ligule,
a membranous outgrowth developed from the inner face of
the leaf -sheath at the junction of the lamina, or petiole, with
the leaf-sheath, and which may be well seen in Arundinaria
falcata.

In Berberis Lycium a distinct joint is found between the
leaf-base and the lamina of the apparently simple leaf, see Fig.
4, Plate V. In Berberis nepalensis, however, a plant which
in important characters resembles B. Lycium and which there-
fore, being considered to be fairly closely related to it, bears
the name of Berberis, the leaves are pinnate and there is a
distinct joint between the terminal leaflet and the rest of
the leaf and at the insertion of the lateral leaflets, see
Fig. 3, Plate V ; hence it is concluded that the leaf of B.
Lycium is really a compound, i.e. pinnate, leaf, reduced to
the terminal leaflet. The apparently simple leaf of the
Orange is also articulated to the petiole and is considered to be
a unifoliolate compound leaf.

Stipules. 29. The leaf -base frequently de-

velops two more or less noticeable lateral branches called

stipules, there being normally two stipules to each leaf,
one on each side of the petiole. These are very large
and leaf-like in Albizzia stipulate and the common Pea ;
sometimes they are like small bristles and are said to be
setaceous and in Capparis spinosa they are developed as
thorns. Stipules frequently fall off shortly after their first
appearance and often before the leaf to which they belong
is fully developed, as in Holoptelea integrifolia. In falling,
however, more or less noticeable scars are left behind and by
observing these it can be known that stipules were developed
and an idea formed of their shape and size. The large stipules
of many species of Ficus for instance leave ring-like scars.

In Rosa the stipules are adnate to the petiole. In some
cases where the leaves are opposite a stipule of one leaf be-
comes united to the stipule which is opposite to it and which
belongs to the other leaf on the node, there thus being
apparently two large stipules at each node, situated between
the petioles of the leaves. Such a stipule is called an inter-
petiolar stipule and is well seen in Stephegyne parvifolia, where
each large stipule can be easily separated into its component
stipules along their line of junction, see Fig. 9, Plate VIII.

In some plants in which there is only one leaf at each
node, the stipules cohering by their outer edges, entirely
embrace the stem and there is apparently one stipule opposite
the leaf. In some cases the stipules cohere both by their
outer and inner margins and thus form a complete tubular
sheath around the stem, called an ocrea, as seen in many
species of Polygonum.

The leaflets of a compound leaf often have stipules which
are then called stipels. These may be seen in Desmodium
tiliaefolium, Fig. 1, Plate V.

Leaves which produce stipules are said to be stipulate and
those which do not are exstipulate. Similarly leaflets which
produce stipels are described as stipellate.

• 30. True leaves, like other organs, Metamor-
are often found to be metamorphosed, or altered in form, in
order that they may be able to carry out other work than
that usually performed by leaves. In Gloriosa superba the
apex of the leaf-blade is prolonged and becomes a tendril, in
the common Pea some of the terminal leaflets are trans-
formed into tendrils, in Clematis montana the petiole coils
round supports and serves as a climbing organ, in Berberis
Lycium the entire leaf is often transformed into a three-

pronged spine and on one and the same shoot intermediate
forms between the typical spine and normal foliage leaf can
often be found, see Fig. 3, Plate VI.

That these spines are really leaves is indicated by the fact
that buds and branches arise in their axils just as they do in
the axils of true leaves ; moreover the base of the spines is
furnished with minute stipules j list as are those of the normal
leaves.

31. The way in which the leaves

are arranged upon the stem is called phyllotaxy, or phyttotaxis.
Some of the arrangements commonly found, such as opposite
leaves, alternate leaves, and so on, have already been noted
above, but it is usual to distinguish some additional types of
the alternate arrangement by fractions, such as ^, f, f and
so on. To determine the phyllotaxy of a plant one leaf is
selected on the stem as a starting point which we may
call (a) and then, passing up the stem, we note the first
leaf which is situated exactly vertically above it which may
be called (b). A spiral line is then traced from the start-
ing point (a), passing the shortest way around the stem
through the insertions of all the leaves situated between (a)
and (b) in consecutive order and ending at (b). If this line is
found to have passed twice around the stem and to have
passed through 5 leaves, omitting (a) but including (6), the
phyllotaxy is said to be -f ; if the line has passed three times
around the stem through 8 leaves it is f and so on. When
alternate leaves are distichous, therefore, the phyllotaxy is ^
and when they are tristichous, i.e. in three vertical ranks, it is |-.

The phyllotaxy occasionally varies on one and the same
plant ; thus on erect branches of Coriaria nepalensis the leaves
are decussate in 4 vertical ranks, whereas on horizontal branches,
by a twisting of the stem, they become distichous and the
leaves are also twisted so that their blades are practically
horizontal, i.e. with the leaf-surface perpendicular to the
direction of the rays of light coming from above, see Plate
XIII.

We have noted already how important it is for plants to
secure a suitable degree of illumination for their green leaf-
surface, and this necessity is to a great extent responsible for
the different forms of leaves and for the way in which they
are arranged upon the stem. It must, however, always be
remembered that all plants have not identical requirements,
that, for instance, the most suitable degree of illumination for
one plant may be injurious to another, and secondly that the

same object may be attained by different plants in entirely
different ways. Thus one plant may obtain the best illumi-
nation for its foliage b}T heterophylly, another by adopting
a different arrangement of the leaves upon the stem, or by
varying the lengths of the petioles, another by adopting a
climbing habit, and so on.

32. Buds normally arise in the Eud8-

leaf axils, or at the apex of the stem or branches. Those
arising elsewhere are adventitious. Some buds contain only
rudimentary foliage leaves, others rudimentary flowers and
some both rudimentary leaves and flowers.

If we examine an ordinary foliage bud, especially when
it is bursting into vigorous growth, we can easily satisfy our-
selves that it is merely a young stem, or branch, bearing the
as yet imperfectly developed leaves and with very short inter-
nodes.

Some buds are covered with dry scales which protect the
delicate young parts within them from being dried up and
killed; these are well seen in the large buds of the Horse Chestnut,
Aesculus indica. The bud is often still further protected by a
coating of wax, gum, or resin, while the young parts inside the
scales are also often protected by a covering of wool, or hair.
Other buds have no protecting scales and are said to be naked,
e.g. those of Teak. If we watch the development of a scaly
bud we find that, shortly after the bud opens and begins to
grow vigorously, the scales which previously covered and pro-
tected it fall off, leaving behind several small scars close
together on the stem, indicating the spots where they were
inserted. These can be well seen in Fig. 1, Plate VII, which
shows a twig of Acer caesium from the terminal bud of which
4 leaves have developed, the bud-scales having just been shed.
In all trees and shrubs therefore in which the growth of stems
and twigs is stopped once annually, scaly buds being produced
at their apices during the period of rest, it is clear that we .
can calculate their age, so long as these scars of the bud-scales
are visible. In Fig. 1, Plate VII, for instance, the twig
shows the completed growth of 3 years, while that of the 4th
year has just commenced. In the spruce, Picea Morinda, the
bud scales do not fall off singly, but cohere, ac.d are carried
up like a cap on the tip of the young expanding shoot.

In connection with this question of the age of shoots should
be noted also the fact that in Pines one whorl of lateral
branches is usually developed each year, so that the age of

branches and young trees can be calculated by counting such
whorls, allowance being of course made in the case of stems
for the number of years required before the first whorl is formed
on the seedling. There are, however, exceptions and unusual
conditions may cause the development of more than one whorl
in the year, but it is important to note this as an example
of what may be done by carefully watching the development of
different species. Bud scales are sometimes metamorphosed
leaves. If we examine an opening bud of Aesculus indica we
find that, while the outermost scales remain dry and fall off,
some of the inner scales begin to grow and those which grow
the most very closely resemble normal leaves. Figs. 1 — 8,
Plate VIII, give a series of such scales removed from an open-
ing bud which clearly shows the bud -scales to be normal leaves
which have been arrested in their development and made to
function as a protective covering to the other young leaves.
Fig. 2, Plate VII, shows a young shoot developing from the
bud of Carpinus viminea, and in this case the bud-scales are
seen to be stipules, the inner scales being situated one on
each side of a leaf petiole just as are normal stipules. The
bud-scales of species of Ficus are also found to be stipules and
in Stephegyne parvifolia the large interpetiolar stipules act as
bud-scales, see Fig. 9, Plate VIII. All the buds which are
lormed on a plant do not necessarily develop ; in many cases a
farge number remain dormant for long periods and develop only
under exceptional circumstances, such as when neighbouring
buds, or young shoots, are destroyed, such resting buds are
termed dormant buds.

Usually there is only one bud in each leaf axil, but not
infrequently there are additional buds situated on each side of,
or above, the true axillary bud ; these are termed accessory
buds. In some cases these are obviously only the lowest
buds of a normal axillary shoot, which, at first sight, appear
to spring directly from the parent stem, owing to the lower
nodes of the axillary shoot remaining very short.

In Prinsepia utilis there is frequently an accessory bud
which develops into a spine and serves as a protection to the
axillary bud below it, see Fig. 10, Plate VIII. Buds which arise
outside of the leaf -axil are termed extra-axillary.

Buds vary greatly in size, shape, colour, in the number of
their external scales and other characters which are useful for
identifying deciduous trees and shrubs in the forest.

In the Plane, Platanus, the buds are found to be complete-
ly covered by the hollow base of the petiole and only become

visible when the leaves fall off, a characteristic circular scar
around the bud then showing where the leaf was inserted.

33. The way in which the young Vernation

leaves, or leaflets, are folded in the bud, which is called
vernation, varies in different species. In some cases the edges of
the leaf are rolled in towards the midrib on the upper surface of
the leaf when the vernation is involute. In other cases the edges
are similarly rolled in towards the midrib on the under surface,
the vernation being revolute. In others the leaf is not rolled
and the longitudinal halves of the blade, turning on the midrib
like a hinge, are placed flat face to face with their upper surfaces
in contact, the vernation being conduplicate. In others the leaf
is so folded on its longitudinal axis that the under-surface is
outside and one edge covers the other, the vernation being
convolute. In others the leaf is coiled inward from the apex,
the vernation being circinnate. In others the leaf-blades are
folded between the nerves, the vernation being plicate.

For illustrations see Plate IX.

Finally, in some cases, there is no obvious folding, or
rolling, and the young leaves are placed practically flat, or
slightly curved, one against another.

A young leaf in the early stages of its development has its
tissues imperfectly developed, and the soft green tissue lying
between the nerves is particularly susceptible to injury and
is liable to be dried up and destroyed if fully exposed to the,
sun and air.

Some protection is therefore commonly provided for it,
sometimes by the folding of the lamina, sometimes by the
position assumed by the young leaves, and sometimes by
protective coverings of hair, wax, gum, or resin.

Thus in Viburnum cotinifolium we find the young leaves
erect on the stem, each pair of opposite leaves having their
upper surfaces placed close together, while only the under
surfaces are exposed to the light and air.

The upper surface of each leaf is concave, the under
surface convex, and the lamina is plicately folded, the delicate
green tissue being thrown into deep folds between the nerves,
these folds projecting into the concavity of the upper surface.
Thus the green tissue is effectively protected during its early
development by the close-set framework of nerves which alone
are exposed on the exterior of the young leaves. As the young
leaves are thus erect and closely adpressed, we find that tfce
upper surface of the petioles is grooved, room biding thus
provided for the terminal bud between the opposite leaves.

As eacli leaf gets older the folds of green tissue are flattened
out. the leaf is thrown outward and downward and the lamina
is expanded more or less horizontally, with the upper surface
directly exposed to the sun's rays. See Figs. 7 — 9, Plate IX.
Homologous 34. Several cases of the so-

and Analo- ca}iefi metamorphosis of plant members have been incidentally
Members. mentioned in this and the previous chapters from which it will
be seen that members which are alike in their mode and place
of origin and general plan of structure are regarded as
morphologically the same, however different they may super-
ficially appear to be in their form, or function. Members
which are thus of the same morphological value are said to
be homologous, whereas those members which, although alike
in some respects, are not morphologically the same, such
as the spines of Berberis and Bel, are called analogous.

CHAPTER IV.-THE INFLORESCENCE AND FLOWER.

35. A shoot which bears a flower Flowering-

is called a flowering-shoot, and like an ordinary leafy shoot it shoot>
may be axillary, or terminal. In some species the flowering
shoots spring from the older branches, or stems, from which

the leaves have disappeared, as in Ougeinia dalbergioides and
Ficus Cunia.

The flowering shoot frequently branches and produces, not inflorescence.
one, but several flowers. The collection of flowering shoots thus
formed is the inflorescence. According as the flowering shoots
are stiff and erect, or drooping and pendulous, so is the
inflorescence described as erect, or pendulous. The inflorescence
varies greatly in size : in the Teak it is very extensive and is
then described as ample, or merely large, whereas in other
cases it is reduced to a few small flowers, or even to a single
flower, in which case the flowers are solitary, and the inflores-
cence may be further said to be many- or few-flowered, and much-
branched or little-branched. Again if its branches are close
together the inflorescence is compact, or dense, otherwise it is
lax, or loose.

The first important point to notice regarding the flowering Bracts,
shoots is that the leaves which they bear, and from the axils
of which they spring, are usually smaller than the ordinary
foliage leaves, of* a different shape and sometimes also of a
different colour. Such altered leaves are called bracts. Those
which are borne on the ultimate branches of the flowering
shoots, i.e. on the stalks of the individual flowers, are distin-
guished by the name of bracteoles. A flowering shoot on which
bracts are produced is said to be bracteate, if no bracts are
produced it is ebracteate.

The stalk of a flower is the peduncle ; when the peduncle
branches, that portion of it from which the lateral flowering
branches arise is the rhachis and the stalks of the single
flowers are then called pedicels, terms which will recall the
analogous ones of petiole, rhachis and petiolule employed for
the leaf. Stalked flowers are said to be pedunculate, or
pedicellate, as the case may be, while flowers without a stalk
are sessile.

36. We have seen above that

there are two principal kinds of branching, viz., monopodial
and cymose, and according to the way in which the flowering

ceuce

shoot branches two main types of inflorescence are distin-
guished as under, although here, as in other cases, intermedi-
ate forms are found :

(1) Monopodial or racemose. — Here there is a distinct main

axis formed by the continued elongation of the
parent flowering shoot.

(2) Cymose. — Here there is no main axis formed by the

elongation of the parent flowering shoot and lateral
flowering shoots grow more vigorously than the

o <-> c? */

parent axis.
The principal kinds of racemose inflorescences are :—

(a) Raceme. — The main axis is elongated and bears
pedicellate flowers.

(6) Corymb. — This ia a raceme in which the main axis
is short and the lower pedicels are longer than
the upper ones, the inflorescence being more or
less flattened and with a convex outline.

If in a raceme, or corymb, the main axis, instead of directly
producing pedicels, develops lateral branches which, directly
or indirectly, bear the pedicels, we get a compound-raceme or
-corymb, respectively.

flowers. A small spike is called a spikelet. A
spike having inconspicuous unisexual flowers
and which falls off entire from the plant after
flowering, or fruiting, is a catkin. It is usually
pendulous.

(d) Spadix is a spike with a thick or fleshy axis. A

spadix is usually more or less enclosed in a large
bract which is called the spathe. In palms the
spadix is branched and has several spathes.

(e) Umbel. — The main axis bears a number of pedicel-

late flowers at its apex. The pedicels which all
radiate from the same point are called the rays
of the umbel. At the apex of the peduncle
bracts are often found forming a whorl below the
pedicels, or rays, which is called the involucre.
When the rays instead of bearing flowers bear
secondary umbels, the latter are termed umbellules
and their involucres are involucels, while the
inflorescence becomes a compound umbel.
(/) Head or Capitulum. — The main axis bears a number
of sessile flowers at its apex. Here also there

is usually an involucre of bracts below the flowers.
The apex of the peduncle on which the flowers are
borne and which is really the shortened rhachis
is here called the receptacle of the inflorescence.
Small scale -like bracts are often found on the
receptacle subtending the individual flowers.
In a typical raceme there is no obvious reason why the
main axis should not continue to grow and produce lateral
branches in acropetal succession indefinitely, whereas if it soon
produced a terminal flower, as is the case in a cyme, its growth
is at once checked and the further development of the
inflorescence then devolves on the lateral branches. Racemose
inflorescences are therefore often called indeterminate, or
indefinite, and cymose inflorescences determinate, or definite.
Again if a plan is drawn of a raceme the youngest flowers are
in the centre and the oldest are outside, while a line following
the course of development from the oldest to the youngest
flowers of such an inflorescence passes from the outside to the
centre, whereas in a cyme the reverse is the case, the oldest
flower being in the centre. Hence racemose inflorescences are
called centripetal and cymose inflorescences centrifugal. In the
case of inflorescences in which the shoots are much reduced in
length and the flowers are therefore brought together more or
less at the same level, it is often not easy to decide to which
type they must be referred and the relative position of the
flowers then often helps us to decide the question. In a head,
for instance, the facts that the oldest flowers which open first
are on the outside and that the youngest which open last are in
the centre, indicate that the inflorescence is racemose. A
compound racemose inflorescence also is usually easily
recognised by the fact that there is a distinct main axis with
the oldest and longest branches at its base and the youngest
and shortest at the apex.

The principal kinds of cymose inflorescences are : —

(a) Dichotomous cyme.. — The main axis terminates in
a flower and two vigorous and equal lateral
branches develop. If there are three equally
vigorous lateral branches instead of two the
cyme becomes tricJiotomous. If this kind of
branching is continued and each lateral branch
in its turn terminates in a flower and in its turn
develops 2 or 3 vigorous lateral branches and
so on,the inflorescence becomes a compound di-
or tri-chotomous cyme respectively.

(6) Helicoid cyme. — The main axis here terminates in
a flower as before, but the further growth of the
inflorescence is carried on, not by 2 or 3 equally
vigorous lateral branches, but by one only, the
latter also soon terminates in a flower and
produces another lateral branch and so on, the
lateral branches always developing on the same
side of the parent axis.

(c) Scorpioid cyme. — This is similar to (b) but the lateral
branch, instead of always developing on the same
side of the parent axis, develops alternately on
opposite sides.

In both (b) and (c) there is thus a sympodium, or false axis.
When this false axis straightens, as it usually does, the inflores-
cence has a strong superficial resemblance to one of the racemose
type. In such cases the position of the bracts often indicates
at once the true character of the inflorescence, for the flower
stalks, instead of springing from the axils of the bracts, as they
would do in a raceme, are opposite to the bracts.

A Fascicle is a general term for a tuft or cluster of
flowers, or of flowering shoots, without reference to
its being of the racemose or cymose type, and is used
when the true character of the inflorescence is not
easily made out.

Panicle is a much used term which is applied to all
compound and much branched inflorescences of which
the first ramifications are racemose. A panicle
which is ovate or lanceolate in outline is called a
thyrsus.

A cyme which, in outline and general appearance, resem-
bles a raceme, corymb, or umbel, is called a racemiform, co-
rymbiform, or umbelliform cyme, and similarly a panicle may
be racemiform, corymbiform, or umbelliform.

For illustrations of some of the above types of inflorescen-
ces see Figs. 1 tu 10, Plate X.

Finally there are the more complicated so-called mixed
inflorescences in which more than one type is combined.
Thus the ultimate ramifications of a panicle, the first branches
of which are developed according to the racemose type, may
be cymes, and such a panicle may be described as a cymose
panicle, or, perhaps better, we may describe the inflorescence
as one consisting of cymes arranged in a panicle.

If the student will examine for himself the following
examples of typical inflorescences, they will help him to

realise how the above terms may be employed in practical
descriptive botany : —

(1) Lax, long, pendulous racemes of Cassia Fistula.

(2) Dense, pedunculate racemes of Abrus precatorius.

(3) Flowers of Desmodium pulchellum in small fascicles

in the axils of 2-foliolate bracts arranged in ter-
minal and axillary racemes.

(4) Few --flowered corymb of Dolichandrone, falcata.

(5) Spike of Terminalia belerica.

(6) Spadix of Arisaema Wallichianum, the Cobra Plant.

(7) Fascicled heads of Acacia Farnesiana.

(8) Compound trichotomous cymes of Eugenia operculata.

(9) Flowers of Trewia nudifiora fascicled in pendulous

racemes.

(10) Many -flowered umbelliform cymes of Leptadenia

reticulata.

(11) Sessile flowers of Wendlandia exserla, in large

conical, or pyramidal, panicles.

(12) Panicle of heads of Acacia caesia.

(13) Panicle of umbels of Heptapleurum venulosum.

(14) Dichotomous cymes of Cornus macropliylla in large

terminal panicles.

(15) Heads of Albizzia odoratissima in compact corymbs,

arranged in large panicles.

(16) Compact thyrsus of Phlogacanthus thyrsiflorus.

37. In a typical flower we can Parts of the

at first sight distinguish 3 obviously distinct kinds of organs ; p^J^
the outer ones are more or less clearly leaf -like in shape, often stamens'
with a distinct venation and sometimes green in colour. These Pistils,
may be called the floral envelopes and together constitute the
perianth. One of the important duties which the perianth has
to perform is to envelop and protect, especially when they
are young, the essential floral organs situated within them and
which are the stamens and pistils. The former together con-
stitute the male portion of the flower, called the androzoium,
and the latter the female part, called the gyncecium. A typica
stamen consists of a swollen head called the anther, situated
on a slender stalk called the filament. In the anther is stored
a yellow powdery substance called pollen, contained in two
little bags which are placed side by side in the anther and which,
when the anther is mature, open and scatter the pollen.
This opening is termed the dehiscence of the anther. A typical
single pistil consists of a swollen hollow, base, called the ovary,
which contains the small rounded bodies called ovules (these

Torus or
sceptacle.

Pollination
Fertilisation.

eventually developing into what are known as seeds), an
elongated neck called the style, which is frequently more or
less expanded at its apex and there forms the so-called
stigma. The stigma is a specially differentiated part of the
style, usually with a moist and sticky surface, which varies
greatly in shape and size ; sometimes it is a rounded knob ;
sometimes it is merely a single, or double, line running along
the side of the style, while sometimes the apex of the style is
forked and the sticky surface of the stigma (called the stig-
matic surface) is found on the branched tip of the style. The
essential parts of the pistil are the ovary and the stigma.
The style may be, and often is, absent, the stigma then
being sessile. The ovary being the principal part of a pistil, the
word ovary is often used to signify the whole pistil. A flower
may contain one or several pistils.

The perianth leaves, stamens and pistils are all inserted
cjose together on the more or less expanded apex of the
flower -stalk and this portion of the stalk from which the
floral organs spring is called the torus, or floral receptacle.

38> The object of the flower is

^° Pr°duce seeds which are capable of developing new and
independent plants. No seeds, however, can arise in a pistil
unless some of the powdery pollen which is contained in the
anthers is able to reach the stigma. The small grains of pollen
which happen to be caught by, and to adhere to, the sticky
stigma develop minute tubes which penetrate the style and
grow down into the ovary to the ovules, the contents of each
pollen grain passing into its tube. When one of these tubes
reaches an ovule, a part of its contents pass into and fuse
with a part of the contents of the ovule, which is then said
to have been fertilised and which thereafter grows and
develops into a seed, containing the embryo of a new plant.
The transference of pollen to the stigmas (pollination) is
thus of vital importance, it being essential for fertilisation
and the production of seeds. In some plants such as
Grasses, this is done by the wind and these plants have no
conspicuously-coloured flowers ; in other plants this work is
done by insects and birds who visit the flowers for the sweet
juice, or nectar, which they contain, get dusted by pollen in the
process, and carry this away to the stigmas of other flowers.
Those flowers which can be most easily seen and found by birds
and insects obviously therefore have the best chance of being
visited and of having their ovules fertilised, and this is the
reason why so many flowers possess conspicuous and brightly

•coloured perianth leaves and attractive scents. From this we
see that, however conspicuous the perianth leaves of a flower
may be, these are after all of only subsidiary importance and
that the really essential organs of a flower are the stamens and
pistils, without which no seed can be formed. There are
indeed some flowers which only contain each a single pistil,
•or a single stamen, but which nevertheless must be regarded
as true flowers.

39. The perianth of a flower Perianth'

may consist of leaves which are all alike, or it may consist of
two distinct sets of leaves, the outer of which are usually
green and the inner of more delicate texture, and, being white,
or of some colour other than green, the latter serve to make
the flower conspicuous. The former are called sepals and
together constitute the calyx, the latter are the petals and
together constitute the corolla. In Rosa, moschata for instance,
we find no difficulty in distinguishing the inner 5 large white
petals from the outer green sepals.

A flower which has both sepals and petals is said to be
dichlamydeous, one which is without both sepals and petals,
i.e. with no perianth, is achlamydeous, while one which has
only sepals, or only petals, is monochlamydeous. A flower
which has no petals is also said to be apetalous. When the
perianth leaves are all similar and there is therefore no
obvious calyx and corolla, the leaves are merely called perianth
leaves. If they are all coloured like petals the perianth is
said to be petaloid, whereas if they all resemble sepals the
perianth is sepaloid. If the perianth, calyx, or corolla, of a
flower consists of distinct leaves, which are separate from one
another and each of which has a distinct insertion of its own
upon the receptacle, the perianth, calyx, or corolla, respectively,
is said to be polyphyllous, polysepalous, or polypetalous. On
the other hand a 'perianth, calyx, or corolla, of united, or
connate, leaves, is said to be gamopliyllous, gamosepalous, or
gamopetalous. According to the degree of cohesion between
the respective perianth leaves, sepals, or petals, they are
said to be connate at the base, to or beyond the middle, nearly
to the apex, and so on.

In cases of cohesion, where there is a distinct narrow base
formed by the lower connate portions of the leaves, this is
called the perianth-, calyx-, or coiolla-tube and the upper
expanded portion is called the limb. The intermediate portion,
usually slightly more expanded than the tube and not so much
expanded as the limb, is called the throat. The calyx or

Position and
Number of
Parts of the
Flower.

corolla is also said to be toothed when the sepals or petals
are united nearly to the apex, deft, or lobed, if divided to
about the middle, and parted if divided nearly to the base.
The same terms may also be used for the perianth.

40. When both calyx and

corolla are present the number of sepals is very frequently
equal to the number of petals. The organs of the flower are
usually inserted in whorls on the receptacle ; the internodes
between the whorls being as a rule very short, the whorls are
all brought close together and the members of successive whorls
are seen to alternate with each other. Thus we find an outer
whorl of say 5 sepals and then, inside and above them on the
receptacle, a whorl of 5 petals so arranged that each petal
stands in the gap between two sepals, then inside the petals
a whorl of 5 stamens alternating with the petals and each
stamen therefore opposite a sepal, then another and inner
whorl of stamens alternating with the outer and each of its-
stamens therefore opposite a petal, and finally the pistil, or
pistils. Some flowers have a whorl of bracteoles outside the
calyx, which at first sight may be mistaken for an extra whorl
of sepals. By carefully counting the obvious petals and sepals,
however, their true nature may usually be detected. Thus in a
flower of Hibiscus Rosa-sinensis we find, outside the stamens,
5 large red obvious petals and then a gamosepalous calyx of 5
connate sepals alternating with them. In addition to these,
however, we find 6 or 7 linear bracteoles. If the latter formed
a normal whorl of sepals they would be 5 in number alternating
with the whorl above, which they do not, but even if they
were 5 in number and did correctly alternate with the sepals
above them, by including them among the sepals the latter
would become twice as numerous as the petals, which is unusual.
Again in the cotton plant (Gossypium) we find an obvious,
corolla outside the stamens composed of 5 large yellow petals
with a purple centre and a gamosepalous calyx of 5 connate
sepals and then 3 large leafy bracteoles j ust below the calyx.
One or more whorls of bracteoles which in this way resemble
an outer calyx of a single flower form what is called an
epicalyx and remind us of the so-called involucre of bracts at
the base of a head or umbel of several flowers.

What has been just said must of course not be taken to
mean that in a flower, in which both calyx and corolla are
present, the number of sepals must equal the number of petals
and the members of each whorl must alternate with those of the
next, as there are obviously several flowers in which this is not

so, such as those of the Poppy, in which there are 4 petals and
2 sepals. The fact is only here emphasized that this is the case
in a very large number of plants and the fact will often be
found useful in helping us to readily diagnose flowers in the field.

If now we look at a flower of Berberis Lycium we find,
outside the 6 stamens, 12 perianth leaves, the inner 6 of which
are all the same size and colour and at first sight appear to be in
one whorl with a stamen in front of each of them. The outer 6
perianth leaves, however, are distinctly arranged in two whorls,
each of 3 leaves, the outer 3 being greenish and sepal-like
alternating with the 3 inner leaves which are larger, brighter
yellow, and obviously more like petals. If we examine the
flower more carefully and remember that as a rule the number
of sepals and petals is equal, we find that it is really quite
normal with 2 whorls each of 3 sepals, 2 whorls each of 3
petals and 2 whorls each of 3 stamens, the members of each
whorl alternating with those of the next. In this case the
outermost 3 leaves are more or less obviously sepal-like,
but the 3 leaves in the next whorl are undoubtedly more like
typical petals, and this indicates that the only real difference
between sepals and petals is one of position, the former being
the outer and the latter the inner set. Outside the outer whorl
of sepals there are usually also 2 or 3 small bracteoles which
closely resemble the outer sepals, and we see that, so far as mere
appearance goes, it is not always possible to readily distinguish
bracteoles from sepals. A flower which has its parts in whorls
of 2, 3, 4, 5, or 6 respectively is said to be di-, tri-, tetra-,
penta- or hexa- merous.

According as the number of stamens in a flower is one, two,
three, or many, it is said to be mon-, di-, tri-, or poly-
androus.

41. A flower which contains Distribution

both stamens and pistil, or pistils, is said to be hermaphrodite,
or bisexual ; a flower which either has no stamens, or no pistil,
is unisexual ; a unisexual flower with stamens is a male, or
staminate, flower, and is usually shortly written thus — $ flower,
while one with pistils only is a female, or pistillate, flower and
is written ? flower. When the flowers of a plant are unisexual
but both $ and s flowers occur on the same individual plant, the
flowers are monoecious and the plant itself may be described as
moncecious. When the flowers of a plant are unisexual and the <?
and ? are found on different individuals the flowers and plant
are said to be dioecious. When the flowers of a plant are both
unisexual and hermaphrodite, which may, or may not, occur

on the same individual, the plant and flowers are said to be
polygamous. A flower which produces no seed is said to be
sterile ; this may be because it possesses no pistil, or because its
pistils fail to produce seed.

Symmetry of 42. A flower is normally borne

in the axil of a bract which is said to subtend the flower,
just as an ordinary foliage leaf subtends its axillary branch.
That part of the flower which faces the flowering shoot from
which it springs laterally is called the upper, superior, or
posterior, while the opposite part facing the subtending bract is
the lower, inferior, or anterior. The plane which passes through
the posterior and anterior part of the flower, and therefore
through the parent flowering axis and the middle of the
subtending bract, is the median plane, or section, of the flower,,
while a vertical plane passing through the flower at right
angles to the median plane is called the lateral plane or section,
and any other plane which passes through the intersection of
these may be called the oblique plane or section.

A radial longitudinal section of a flower is one which is
parallel to its longitudinal axis and passes through the centre
of the flower, while a transverse section is one at right angles to
its longitudinal axis.

If in a flower the members of each whorl of floral organs are
all alike in size and shape, the flower is regular. If not it is
irregular. The regularity or otherwise of a flower is naturally
most noticeable in the perianth leaves and especially in the
corolla, these being as a rule the most conspicuous part of the
flower, and hence when in descriptive botany a flower is
spoken of as regular, or irregular, these terms may as a rule be
taken to refer to the corolla, or perianth leaves.

A flower which is divisible in two or more radial longitudinal
planes into similar halves, so that in each section one half is to
the other as an object is to its image seen in a mirror and the
halves in one section are similar to those in the other sections,
the flower is actinomorphic. When there is only one radial longi-
tudinal section in which a flower can be divided into similar
halves it is said to be zygomorphic, and if there is no plane in
which it can be divided in this way it is asymmetric.

The p»rts of 43. The flower is really a short-

ate LeavJ enec^ shoot and its parts, which compose the calyx,
corolla, androecium and gynoecium are really nothing
but leaves. The flower bud like the bud of an ordinary leafy
shoot is either terminal, or it arises in the axil of a leaf, the
latter being a normal green leaf, or one which has only been

slightly altered in character in which case it is called a bract.
The green sepals are often large and obviously leaf-like ; the
petals also in shape more or less resemble leaves and they often
have a distinct venation. Colour alone is a characteristic of
very little importance in enabling us to decide on the true
nature of a member, as is shown by the fact that the bracts of
several plants, although they are obviously leaves, are
brilliantly coloured like petals, e.g. the bracts of Bougainvillea.
The remarkably conspicuous pure white, or coloured, calyx
lobe of Mussaenda should also be noted. Stamens it is true do
not at first sight at all remind us of leaves, but in some
flowers, especially in those which have numerous petals, as in
the Water Lily (Nymphaea), we find that the petals gradually
pass into the stamens through a series of intermediate forms,
which clearly indicate how one and the same organ may, by
a number of slight modifications, become a normal, more or
less leaf-like, petal, or a perfect stamen.

The pistil also does not at first sight resemble a leaf, but if
we take a simple pistil such as a young pea-pod, and compare
it with an involutely-folded leaf, the margins of which are
brought together and made to cohere, we see that very slight
modifications would, after all, suffice to convert what would
ordinarily develop into a normal leaf into a pistil.

Occasionally also, e.g. in Roses, examples may be found of
so-called "green-flowers," in which the different members,
instead of assuming their ordinary shape and colour, appear as
more or less perfectly developed green leaves. The facts noted
above which indicate the true nature of the floral members are
found to be confirmed by a microscopic examination of their
mode of origin, minute structure and development during the
early stages of their growth, when they are found to be
indistinguishable from true leaves. The floral parts arise on
the flower stalk just as leaves do, on an ordinary shoot. Occa-
sionally they are in spirals, but as a rule they are arranged in
whorls. The internodes in the flower usually remain very short,
and all the floral parts are therefore crowded close together on
the portion of the shoot from which they spring, i.e. on the
so-called receptacle, or torus. This, however, is not always the
case, and in Capparis there is a distinct internode between the
stamens and the pistil, the latter appearing to have a stalk
which is called the gynophore ; internodes are also occasionally
developed between other floral parts, e.g. between the petals and
stamens in species of Grewia, and a stalk which thus appears
to bear both the stamens and the pistil is called a gonophore.

Cohesion.

Flowers.

Although the apex of the floral axis as a rule ceases to grow
at a very early stage in the development of the flower, excep-
tional cases are known in which this axis has continued to
grow, and we find a green leafy shoot growing apparently out
of the centre of the flower. Very rare cases are also known
in which buds have been developed in the axils of the floral
members, just as they are usually developed in the axils of
normal leaves.

44. Owing to the very limited

growth of the floral axis and to the non-development of its
internodes the floral parts are, as has already been noted,
crowded close together and in many cases this crowding
results in the young members, which originate separately on
the receptacle, coalescing at their bases, and they then grow
up together instead of separately. This is how a gamosepalous
calyx, or a gamopetalous corolla, for instance, arises. When
members belonging to the same whorl become thus fused
together the phenomenon is termed cohesion and the members
are said to be connate.

Members belonging to adjacent whorls also often become
fused together and we find, for example, stamens fused with
petals, the stamens looking as if they had grown out of the
corolla. In such a case we say there is adhesion. Members
which are thus adnate appear to originate not directly from
the receptacle in the usual way but at some distance from it,
their apparent point of insertion having been carried, as it
were, away from the receptacle. Cohesion then is the union
of members belonging to the same whorl, adhesion the union
of those developed at different levels, while members which
are neither connate nor adnate are said to be free.
, 45. When there is no adhesion

an(l the sePals> petals and stamens all arise directly from the
receptacle, these members obviously originate directly below
the gyno3cium. The sepals, petals and stamens are then
said to be hypogynous, or inferior, and the gyncecium is free and
superior. The entire flower may also be described as hypogynous.
When, however, there is some degree of adhesion and the
petals and stamens, instead of springing from the receptacle,
appear to spring from the calyx-tube, the apparent insertions
of the sepals, petals and stamens are no longer directly
below the gynoecium, but are carried out away from the
receptacle and form a circle around the gynoecium. In
this case the sepals, petals and stamens are per igy nous
and the flower itself is said to be perigynous. Here, however,

there is no adhesion between the gynoeciuin and the other
floral members, the gynoscium is still quite free from the
latter and is superior. Finally, there are cases in which
the other floral members are united with the gynoecium and
in which the adhesion is carried right up to the top of the
gynoecium, so that the latter appears to be completely enclosed
and covered in, while the sepals, petals, and stamens appear
to arise on the top of, or above, the gynoecium. The sepals,,
petals and stamens are here said to be epigynous, or superior,,
the flower itself is epigynous and the gynoecium is inferior. For
illustrations see Figs. 11 — 14, Plate X. The typical cases noted
above are linked together by a number of intermediate forms ;
thus in some flowers there is adhesion between the gynoecium
and the other members, but this adhesion only extends about
half-way up the gynoecium. Such flowers are best considered
as imperfectly epigynous, and the gynoecium may be described
as half -inferior. In the case of other flowers, where the
insert ons of the petals and stamens are only very slightly re-
moved from the receptacle, it is often difficult to decide if
they should be classed as hypogynous or perigynous. The
fact that, sometimes, the so-called calyx-tube is found to bear
rudimentary leaves, indicates that this is', in many cases, really
an outgrowth of the floral axis, or receptacle, and that it does
not consist merely of the coalescent bases of the sepals and
other floral leaves.

46. The torus, or floral recep- The Diso.
tacle, frequently grows out and forms what is called a

disc, this being merely an expansion of the receptacle.
It is usually a fleshy, swollen ring of tissue which may,
or may not, be lobed, or divided. When the disc is
divided into distinct portions the separate parts of it are termed
glands. The disc and glands frequently excrete a sweet,
sugary fluid commonly known as nectar and each is then called
a nectary. The disc is usually developed between the stamens
and the gynoecium, but sometimes also between the petals and
stamens, and sometimes it bears the insertions of the petals
and stamens. According to its apparent place of origin, the
disc may be hypogynous, perigynous, or epigynous.

47. In addition to the terms Descriptive

which have been already given for ordinary leaves, the Terms for
following are often used for describing the shape cf sepals and

and petals. If they have a narrow base supporting a broad
expanded blade, the former is termed the claw and the latter

the blade, or lamina. If strap-shapsd they are termed

liguliform.* Sometimes there is an outgrowth from the
inner face of the petals, usually at the junction of the blade
and claw, or at the throat of a gamopetalous corolla, which
is often scale-like and reminds one of the ligule of Grasses.
Such outgrowths in a flower, collectively, constitute the so-
•called corona.

The calyx or corolla is said to be :—

Bi-labiate, if divided into two more or less distinct lips.

Rotate, or wheel-shaped, when with a spreading limb
and very short tube.

Crateriform, or cup-shaped, when like rotate but with
the limb curving upwards.

Hypocrateriform, or salver -shaped, when with a long
narrow tube, abruptly expanding into a broad
limb.

Trumpet-shaped, if salver-shaped with the tube
expanding near the top.

Infundibuliform, or funnel-shaped, when the tube
expands gradually from the base.

Campanulate, or bell-shaped, when the tube is expand-
ed from the base, with its length not more
than i/wice its breadth and with the sides
spreading outwards at the top.

Urceolate, or urn-shaped, when the tube is swollen
in the middle and contracted at the top and base.

Tubular, when there is a conspicuous nearly cylin-
drical tube and a relatively inconspicuous limb.

Gibbous, when with a small pouch-like swelling near
the base.

Ventricose, when swollen on one side, like the corolla
of several species of Strobilanthes.

Saccate, when swollen at the base like a bag.
Spurred, when with a slender, hollow prolongation.

The limb or lobes of the calyx are sometimes reduced to
hairs or bristles which are often branched and feathery and
which constitute the so-called pappus. The calyx in such a
case is said to be pappose. The pappus is often more or less
invisible in the flower and only becomes fully developed when
the fruit ripens, as is the case in Valeriana Wallichu.
. 48. The way in which the

parts of the flower are arranged in the bud is called

* The term ligulate is sometimes used in th;s sense but. it also means
furnished with a ligule.

-aestivation. The aestivation of the sepals and petals is : —

crumpled, when they are irregularly folded ;

valvate, when ..their margins are in contact and there
is no overlapping. When the margins, besides
being in contact, are turned straight inwards it
is valvate-induplicate, and when the margins are
involute it is valvate -involute ;

imbricate, when their margins overlap and at least
one of each whorl has both margins covered ;

contorted, when every one of the same whorl has one
margin covered and one margin uncovered. Assum •
ing that the observer stands outside the whorl and
therefore behind the sepals, or petals, as the case
may be, when the right-hand margin of each is un-
covered they are said to overlap to the right and
when the left-hand margin of each is uncovered to
overlap to the left.

In addition to overlapping the leaves may be twisted,
and this twisting may, or may not, be in the same
direction as the overlap.

plaited, or plicate, when they are in longitudinal
folds.

For illustrations see Figs. 15 — 19, Plate X.

49. As already noted a normal characters

.-stamen consists of a swollen head (the anther) on a stalk of Stamens,
(the filament).

A typical anther consists of two longitudinal halves, or
lobes, called thecae, each of which, at least when young, contains
2 cells, or chambers. These cells contain the pollen and are
called the pollen-sacs. When mature the anther opens (i.e.,
dehisces) and allows the pollen to escape. Each theca com-
monly opens by a longitudinal slit in such a way that one slit
opens at once into both sacs, each theca thus appearing to be
one-celled. The two sacs in each theca also are sometimes
confluent before dehiscence. In a few cases the anther has only
one cell. According to the number of cells it is uni-, bi-, or
quadri-locular. The anthers sometimes dehisce by means of
small holes (pores) and sometimes by valves. That portion of
the filament which runs up between the anther-lobes is called
the connective. The filament is sometimes wanting and then
the anther is said to be sessile. Sometimes the anther is not
developed and sir.ch an imperfect stamen is called a siaminodium

f)T staminode.

E 2

The stamens are said to be :—

monaddphous, when their filaments are all united into -

a tube ;

diadelphous, when in two sets, or bundles ;
polyadelphous, when in several sets ;
syngenesious, when the anthers are united in a ring ;
didynamous, when there are 4 stamen s; two of them

long and two of them short ;
tetradynamous, when there are 6 stamens, 4 of them

long and two of them short.

If the stamens are inserted on the petals they are cpi-
peialous, and if opposite the petals they are antipetalous.

If the stamens are the same number as the sepals and
petals, the flower is isostemonous, if the stamens are double the
number, the flower is diplostemonous, and if they are double
the number and they do not alternate correctly with the
petals, the flower is obdiplostemonous.

Stamens which protrude beyond the corolla are said to be*
exserted ; if hidden by the corolla they are included.

The anther is said to be :—

introrse, when the thecse are turned inwards towards the
centre of the flower, i.e. when the thecaB are on
that side of the anther which faces the floral axis
(ventral side) ;

', «. extrorse, when the theca3 are turned outwards, facing
away from the floral axis, i.e. when the thecse
are on that side of the anther which is turned
away from the axis (dorsal side) ;

innate, when the filament appears to be fixed in the
centre of the base of the anther, the thecaa not
facing inwards or outwards. The anther is also
sometimes said to be basi fixed in this case ;

adnate, when the filament appears to run up at the back,
or front, of the anther, the thecae facing inward s,.
or outwards ;

versatile, when it swings freely at the end of the filament ;

dorsifzed, when the filament appears to be inserted in
the back of the anther ;

The stamens sometimes branch, e.g. in the Castor Oil Plant.
This is often indicated by the anthers being only one-celled,
i e. each is really half a stamen, although in some cases this may
be due to the non-development of half the stamen Anther:?

may be provided with bristles, points, spur-or horn -like pro-
cesses. The connective is also sometimes prolonged ' into a
point beyond the anthers. The filament is usually slender, but
varies in shape and is sometimes provided with wings.

Pollen is usually a powdery substance, which, when magni-
fied, is seen to consist of distinct grains. The shape and size of
the grains varies in different plants and the surface of the
grains may, or may not, be provided with points, knobs,
ridges, or other markings. In those plants, the pollen of which
is distributed by the wind, the grains are smooth and in others,
the pollen of which is distributed by insects, or birds, the
grains are usually sticky. In some plants the grains adhere
together in masses, the latter being called pollinia.

50. As has been already pointed characters

out, a simple pistil really consists of a single infolded of
leaf which bears the ovules on its inner margins. Such
an ovuliferous pistil-leaf is called a carpel. A pistil con-
sisting of one carpel is said to be simple, if of more than
one carpel it is compound. A gynoecium consisting of simple
pistils is called apocarpous, the carpels being distinct, a gyn-
cecium consisting of a compound pistil is syncarpous, the
carpels being combined. In a simple pistil the lower
surface, or back, of the carpel is represented by the exterior
of the pistil, the upper surface, or front, of the carpel forms
the interior of the pistil. The united margins of the carpel
which bear the ovules look towards the centre of the flower
(the axis) and form what is called the ventral suture or seam.
The opposite ridge, along the back of the pistil, representing
the midrib of the carpel, forms the dorsal suture. In a com-
pound pistil the carpels may be joined by their margins only,
or these may grow inwards and be united in the centre of
the pistil. In the former case the pistil is one -celled and in
the latter it is divided by partitions called dissepiments into
several cells, there being as a rule as many cells as there are
carpels. (Sometimes this is not the case, there being so-caQed
false-partitions which grow in from the back of the carpels.)

The surface on which the ovules are borne, which is often
more or less enlarged, is called the placenta and the way in
which the placentae are arranged is called the placentation. In
the case of a compound pistil in which the carpels cohere by
their margins only, the placentae are on the walls of the pistil
and the placentation is called parietal ; when the margins are
brought together and cohere in the axis of the pistil, the
placentae are in the inner angles of the cells, and the placenta-

tion is called axile. In some cases the ovules are borne on a
central axis which is not connected by dissepiments with the
walls of the ovary and the pistil is consequently one -celled.
The placentation in such cases is called free-central.

As a rule the ovules are borne on the margins of the
carpels, but in some cases they are developed all over the
internal face of the carpels and the placentation is then
called superficial.

In a compound pistil the styles may, or may not, be more
or less completely combined and the number of styles, or of
the divisions of the style, or stigma, often indicates the
number of carpels in the pistil.

Owing to one side of the ovary growing more rapidly
than another, the style sometimes becomes displaced to one
side and appears to arise from the base instead of from the
apex of the ovary. Such a style is said to be qynobasic.

In some cases the floral receptacle, or torus, is prolonged
upwards between the carpels forming a kind of beak to which
the ovaries and styles adhere and from which they separate
when the fruit ripens. Such a beak is called a carpophore.
Characters 51. The rounded out-growths

of Ovules. Of -f/kg carpeis wnich are destined to become the seeds
are called ovules. These may be sessile, or they may be
provided with a distinct stalk called the funicle. A
typical ovule consists of a central portion of soft tissue
called the nucellus which is invested with one or two coats
called the integuments. The latter do not completely cover in
the nucellus, a narrow hole being left at the apex which is
called the micropyle. The spot from which the integuments
originate at the base of the ovule is called the chalaza.

Ovules are : —

erect, when they rise from the base of the ovary ;
ascending, when they rise obliquely and are attached near

the bottom of the ovary ;
horizontal, when they are borne on the side of the

ovary with their long axis horizontal ;
suspended, when hanging from the apex of the ovary;
pendulous, when hanging obliquely from near the apex

of the ovary;
orthotropous, when they are straight, with the chalaza

and micropyle in one straight line and the chalaza

at the apex of the funicle ,
campylotropous, when the line joining the chalaza

and micropyle is curved, the micropyle being brought

round and down near the chalaza. This is caused
by one side of the ovule growing faster than the
other ;

anatropous, when they are completely inverted. The
chalaza and the micropyle are in the same straight
line, but the upper part of the funicle is apparently
adherent to the side of the ovule and forms a ridge

called the raphe.

Intermediate forms between the above types of course
occur.

The spot where the end of the funicle is joined to the ovule
is called the hilum. When the ripe seed separates from its stalk
a scar marks the position of the hilum. In orthotropous and
campylotropous ovules the hilum and chalaza coincide ; in
anatropous ovules they are at opposite ends of the ovule.
When the raphe is turned towards the ventral suture of the
carpel it is said to be ventral and when turned towards the
dorsal suture it is dorsal. In the nucellus of the ovule there is
a large cell called the embryo-sac, containing protoplasm which
is more or less divided up into separate da lighter- cells which
may, or may not, be provided with delicate cell-walls. When
a ripe pollen-grain reaches the sticky, surface of the stigma it
germinates. Its outer coat is burst and a long delicate tube is
sent out, called the pollen-tube into which pass the proto-
plasmic contents of the pollen-grain. This tube penetrates
the tissue of the stigma, and of the style if there is one, usually
enters the micropyle and grows until its tip comes in contact
with the apex of the embryo-sac. A portion of the protoplasm
then passes out from the pollen-tube and unites with a part
of the protoplasm in the embryo-sac, and with the fusion of
these separate masses of protoplasm into one fertilisation is
completed. The lump of protoplasm surrounds itself with a
cell-wall, begins to divide, and develops into the so-called
embryo, or young plant, the ovule now having become the
seed.

52. Having completed our Types Or

examination of the parts of the flower a few points which Flowers
may cause difficulty remain to be noted.

In cases where some of the floral parts are suppressed Difficulty,
and not developed, it is not always easy to decide on the true
nature of the parts which are present. Thus in the flower of
Clematis, there are usually 4 conspicuous leaves which look
like petals, but which are really sepals, no petals being develop-
ed. This is indicated by the fact that rudimentary petals are

sometimes found in their proper place inside the petal-like
sepals. The presence of rudiments is thus seen to be of im-
portance, and in doubtful cases a careful comparison of allied
plants often helps us to arrive at a decision.

The student should carefully examine the flowers of the
following plants as they may cause some difficulty. They are
fairly typical of the flowers of a large number of important
plants and a few special terms are necessary for their des-
cription.

wheat, (a) Wheat. — The flowers are in spikelets, and each spikelet

contains from 3 — 5 flowers. Each flower consists of 3 stamens
and one pistil with two feathery stigmas, while the perianth is
represented by two small hypogynous scales called lodicules.
Each flower is enclosed between 2 scaly bracts, the outer of
which is the flowering -glume, while the inner and smaller is the
palea. Finally outside of all, at the base of the spikelet there
are two more dry, scaly bracts, which are called the outer-
glumes.

The flowers of grasses RW! I am boos closely resemble this
type.

Pea- (b) Common Pea, Bean, Butea frondosa, or a Dalbergia. —

The striking peculiarity here is in the corolla, which is
called papilionaceous from some supposed resemblance to
a butterfly. The two lower anterior petals, which are inside
the others, are narrow and fit close together, forming the so-
called keel (carina). Outside the keel are two more narrow
petals called the wings (alae), one on each side of the keel,
while finally, outside the wings, there is a large posterior
upper petal called the standard (vexillum). It should also
be noted that the filaments of the stamens are more or less
united into a tube.

Pine. (c) Pine (Pinus). — The flowers are unisexual. The male

flower consists of an axis around which are spirally arranged
the numerous scale -like stamens, each stamen bearing two
pollen-sacs on its under surface.

The female flower also consists of an axis with numerous
spirally-arranged scales which represent the carpels. In the
axil of each carpel there are two ovules, lying on another scale
called the placental scale. As the fruit ripens, the placental
scales become woody and form the familiar Pine cone. In
this nase the flowers are of very simple construction and there
is no perianth. Both the stamens and carpels are scale-like,
and finally the carpels do not form an enclosed ovary, the
ovules merely lying exposed on their upper surfaces. Plants

like this which have their ovules uncovered are called Gymno-
sperms (naked seeded plants), while other plants having their and Anglos
ovules enclosed in an ovary are distinguished as Angiosperms. P6™8-

53. When studying flowers it

is convenient to be able to shortly and clearly express Di,grarrs
on paper the number, relative positions and other Floral
characteristics of the floral parts, instead of giving and Short-
long written descriptions. This can be done by floral hand-
diagrams and formulae. A floral diagram is a plan of the
flower in which the position of the various floral parts is in-
dicated by a diagramatic cross-section. To indicate the
posterior and anterior sides of the flower, the position of the
bract, in the axil of which the flower is borne, must be shown
.and of the main axis from which the flower springs.

In floral formulae the following equivalents are used: —

K=calyx (sepals).
C= corolla (petals).
P = perianth.

A=andro3cium (stamens).
G = gynoacium (carpels).

The following examples will indicate how formulae are
;<written : —

G (3). — The flower has a polyphyllous perianth
of 6 leaves, in two whorls, each of 3 leaves.
There are 6 free stamens, also in two
whorls, each of 3, and a syncarpous,
infeiior gynoecium of 3 carpels. Nothing
being said to the contrary the flower is
regular.

€5 A <» Goo. — There are here 5 free sepals and 5 free
petals, while the stamens and carpels are
too numerous for easy counting. The
stamens are free and the gyncecium apocar-
pous and superior.

A €5 A(s + 5) GI. — Here there is a gamosepalous calyx
of 5 sepals, a zygomorphic corolla of 5
free petals, 10 stamens with their fila-
ments united into a tube and a gyncecium
of one superior simple pistil.

S ed.

Testa,
Tegmen Aril.

Albuminous
Ex albumin-
ous seeds.

Cotyledons
Radicle and
Plumule of
Embryo.

CHAPTER V.— THE 'SEED AND FRUIT.

54. The normal seed is en-
veloped in one or two outer coats which correspond to
the integuments of the ovule. The outer is usually firm
and often hard and is called the testa ; the inner, when it is
present, is thin and delicate and is called the tegmen. In some
cases there is an additional covering to the seed developed
after fertilisation has taken place and which is accordingly not
visible on the ovule. This covering usually originates from
the funicle or placenta but occasionally also from the micro -
pyle. It is known as an aril, e.g. the pulp of the Lichi.

An outgrowth morphologically similar to an aril but
which is smaller and may develop from various parts of the
seed is called a caruncle, or sfrophiole.

The testa of the seed sometimes grows out into a
membranous wing, as in Oroxylum indicum, see Fig. 1, Plate
XII, and sometimes is provided with long soft hairs, as in the
Cotton plant, these structures aiding the distribution of the
seed by wind.

Inside the seed- coats we find what is popularly called the
kernel ; this may consist only of the embryo, or the latter may
occupy only a portion of it, the remainder of the kernel
consisting of the so-called albumen. (This is cellular tissue
densely packed with food-materials, such as starch, or other
substances, which are to serve as food for the young embryo.)
In the former case the seed is said to be exalbuminous and
in the latter albuminous. As examples of the former we may
take those of the Oak and Oroxylum indicum, see Figs. 1 and 2,
Plates I and XII, and of the latter the seed of the Pine (Pinus).

If the albumen has originated inside the embrvo-sac it is

o v

called endosperm, if it is a part of the tissue of the nucellus it
is called perisperm.

Albumen may be mealy (when it is easily broken into
powder), oily, fleshy, or hard, and even bony. If the outer
surface of the albumen is crumpled, or puckered, into narrow
folds it is said to be ruminate.

In a well-developed embryo wre can distinguish an axis
bearing one or more minute leaves ; these leaves are called
cotyledons. That part of the axis situated below the insertion
of the cotyledons and from which the primary root of the
seedling will be developed is called the radicle, while the part
of the axis above the cotyledons, which is the end of the

minute shoot, is the plumule. The radicle of the embryo
always points towards the micropyle. The position of the
embryo in the albumen is often characteristic ; it may be
straight or curved, it may be in the centre of the albumen
(axial), eccentric, or external to it as in Grasses. The cotyledons
may be placed straight in the seed or variously folded. The
cotyledons are :—

incumbent, when the radicle is laid along the back of

one cotyledon ;

accumbent, when the radicle is laid along the edge of
the cotyledons.

In exalbuminous seeds all the food material is stored in
the tissue of the embryo itself, and usually in the cotyledons,
which are then thick and fleshy. In other cases the cotyledons
are thin and more or less foliaceous. On germination taking
place the cotyledons may remain below the ground, as in the
Oak, see Figs. 1 and 2, Plate I, or be raised up on the growing
stem into the light and air, when they usually become green
and more or less like ordinary leaves, as in Oroxylum indicum,
see Plate XII. The portion of the stem of a seedling situated
below the insertion of the cotyledons is called the hypocotyl Hypocotyi.
while that part of the stem lying between the insertion of the EPlcotyi-
cotyledons and that of the first foliage leaf or leaves is the
epicotyl.

The plants termed Angiosperms, which have been men- Monocotyie-
tioned above, are sub-divided into two great groups known
as the Dicotyledons and Monocotyledons respectively. In the dons,
former, which includes most of our important forest species
the embryo has typically two opposite cotyledons'; in th3
latter, which includes such plants as the Grasses, Bamboos
and Palms, the embryo has typically only one cotyledon.

55. The mature gyncecium of a Fruit.

flower containing the seeds, with everything which may be
joined to it, constitutes the fruit. The fruit may consist
of a single ripe pistil, in which case it is a simple fruit,
or of the collection of separate pistils belonging to one
flower when it is an aggregate fruit, or of the pistils belonging
to several flowers united together, when it is a multiple fruit,
or infructescence. If it is provided with a stalk the fruit is
said to be stipitate, if not, it is sessile.

The ovary wall becomes the wall of the fruit which is"
called the pericarp and this immediately surrounds the seeds.
The position occupied by the embryo with reference to the
rest of the fruit is important, and the radicle is said to be

superior when it points upwards towards the apex of the fruit
and inferior when it is directed downwards towards the base.
The pericarp may, or may not, be differentiated into definite
layers and sometimes as many as 3 can be distinguished, in
which case the outer layer is called the epicarp, the inner
layer the endocarp, and the middle layer the mesocarp.

In many cases a conspicuous part of the fruit is not deve-
loped from the pistils, but from some other part of the flower.
Thus in the Strawberry the succulent portion, which forms the
greater part of the fruit, is developed from the receptacle, in
the Sal the calyx persists and develops into large veined
wings, in Semecarpus Anacardium the base of the calyx
and the receptacle form a conspicuous fleshy base to the
fruit, while in the Oak the "cup"' of the acorn is formed of bracts.
Fruits which, when ripe, open to let the seeds escape are
said to be dehiscent, those which do not do so are indehiscent.
Types of 56. The principal types of fruits

Fmit.

A. — DRY AND DEHISCENT.

(1) Follicle, consisting of one carpel and dehiscing by one
suture.

(2) Legume, consisting of one carpel and dehiscing both by
the dorsal and ventral sutures. A legume which is much con-
stricted between the seeds is called a lomentum. This often
breaks up into one-seeded joints when ripe.

(3) Capsule, arising from a compound pistil. May be one
or many celled. If a capsule splits open along the dis-
sepiments its dehiscence is septicidal, if it splits open through
the back of each carpel the dehiscence is loculicidal. In both
cases the dissepiments separate from the axis. When the
dissepiments remain attached to the axis and the valves merely
separate from the ends of the dissepiments, as in Cedrela
Toona, the dehiscence is septijragal. In some cases the dehis>
cence may be partly according to one and partly according to
another of these types. In septicidal dehiscence, for instance,
if the dissepiments remain attached to the axis, the valves of
the capsule may separate from the ends of the dissepiments as
in septifragal dehiscence.

(4) Schizocarp, arising from a compound pistil and break-
ing up at maturity into distinct portions, each of which is
usually indehiscent and looks like a separate fruit, being
called a coccus. When a coccus is small and one -seeded it is
called a nutlet.

B. — DRY AND INDEHISCENT.

(5) Nut, a one-seeded fruit with a hard, dry, pericarp
such as the acorn of the Oak.

(6) Achene, a one-seeded fruit with a thin, leathery,
pericarp.

(7) Caryopsis, similar to an achene but the pericarp is
closely adherent to the seed, the latter completely filling the
cell, whereas in the achene this is not so.

(8) Samara, any dry indehiscent fruit which is provided
with a wing developed from the pericarp.

C. — SUCCULENT.

(9) Berry, the whole pericarp with the exception of the
outer skin (epicarp) is succulent and the seeds are immersed
in the pulp.

(If)) Drupe, the pericarp is differentiated into three layers;
the inner, or endocarp, is hard and forms the so-called stone
of the fruit, containing the seed, or seeds, and which may be
one or more celled. The stone is immersed in the mesocarp
which is generally succulent, while the epicarp forms a skin
over the mesocarp. The succulent mesocarp is sometimes
called the sarcocarp and the hard endocarp the putamen.
In the Mango the portion eaten is the sarcocarp and the
endocarp is fibrous.

When a drupe is formed from a gyncecium composed of
more than one carpel and the carpels separate and give rise
each to a distinct endocarp, so that in the ripe drupe there is
more than one stone, each of these stones is called a pyrene,
as in Grewia.

51, For describing the shape General

of fruits, or seeds, the terms which have been noted above in Terms for
connection with other solid parts of plants may be used, thrshape of
such as fusiform, conical and so on. The terms given for flat Seeds and
surfaces are also employed for describing the outline (as seen
in elevation) of solid parts and in addition the following
terms are frequently used :

cylindrical, elongated with circular cross section.

spherical, round ;

globose, or spheroidal, nearly spherical ;

ovoid, an egg-shaped solid ;

ellipsoid, an elliptical solid ;

discoid, circular, and flat, or depressed, in centre ;

compressed, flattened sideways ;

depressed, flattened from above ;

clavate, club-shaped, thickened above and slender below ;

turbinate, top-shaped, ob-conical ;

pyriform, pear-shaped ;

didymous, slightly 2-lobed ;

plano-convex, flat on one side, convex on the other;

concavo-convex, concave on one side, convex on the other ;

moniliform, cylindrical, but constricted at intervals like

a string of beads ;
torulose, slightly moniliform.

CHAPTER VI.— GENERAL.

58. According to their duration Duration of
pirts of plants are said to be :— Sant,

iii )

fugacious, falling off very early, almost as soon as
they are developed, as the petals of Linseed, or
Reinwardtia trigyna ;
caducous, falling off early, e.g. petals falling before the

flower is fertilized ;

deciduous, falling at the usual season, e.g. petals which
fall soon after the fertilization of the flower has taken
place ;

persistent, remaining attached to their support beyond
the usual season, e.g. petals, or sepals, which remain
attached to the fruit.

Parts which wither, but still remain attached to their
support, are said to be marcescent ; parts which persist and
increase in size are said to be accrescent, such as the sepals of
Sal which become enlarged in the fruit.

59. According to their texture Texture of
parts of plants are said to be : — Members.

osseous, bony, e.g. the stone of many fruits ;
corneous, like horn, e.g. albumen of Date Palm ;
cartilaginous, hard and tough like parchment, e.g.
endocarp of an apple which surrounds the " pips," or
seeds.
chartaceous, thin, like paper, e.g. outer bark of young

Birch stems ;

coriaceous, firm and tough like leather, e.g. leaf of Mango ;
•sub- coriaceous, thin and pliable like leaves of Berchemia

floribunda ;

membranous, very thin and pliable and somewhat trans-
parent like skin. e.g. leaves of Staphylea Emodi.
If membranous but dry and more or less colourless,
the texture is scarious ;

-paleaceous, like chaff ; scarious but rather stiff ;
-fleshy, thick and soft, like leaves of Saxifraga ligulata ;
succulent, fleshy and juicy, like leaves of Fedum rosulatum;
crustaceous, hard and brittle, like the r'nd, or epicarp;

of fruit of Grewia pilosa.

The texture often varies according to the age of the
member, thus leaves which are membranous when young
may become coriaceous when mature.

60. The outer skin or surface
of plant mem bers is often provided with pricldes. These Gland's.

may be distinguished from spines, which are really branches,
i.e. continuations of the internal tissues, by the fact that they
are superficial structures which are easily broken off, and if
the bark is stripped off they often come away with it such as
do those of Roses and Rubus.

A few of the terms used for describing the surface of
plant members have been given above and in addition to them
the following are in common use :-—

echinate, with sharp prickles, like a hedgehog;
verrucose, or tuberculate, warty, with knobby excrescen-
ces;

scabrous, rough to the touch ;
rugose, wrinkled.

The surface is also often provided with hairs, or wax, and
said to be : —

glabrous, if without hairs ;

glabrescent, almost glabrous, with very few hairs ;
pubescent, with short, soft, straight hairs; if the hairs
are very close together and the surface feels like
velvet it is said to be pilose, if the hairs are very-
short and only just perceptible to the touch the
surface is puberulous ;

hirsute, pubescent but the hairs are longer and stiffer ;
villous, shaggy. The hairs are long and weak and not

matted ;
tomentose, densely pubescent, but the hairs are matted

and the surface feels softer and more woolly ;
woolly, tomentose with long hairs, looking like wool ;
floccose, woolly but the hairs are easily detached, e.g.
those on the undersurf ace of leaves of Pyrus lanata ;
mealy, hairs are very short and are easily rubbed off like
powder, e.g. those on young leaves of Loranthus
pulverulentus ;

hoary, or canescent, with a greyish-white appearance, due
to very minute hairs, too small to be easily distin-
guished ;
strigose, with pointed, straight, stiff hairs, lying along

the surface ;

silky, with closely adpressed, soft, fine hairs ;
hispid, rough with rigid hairs ;
glaucous, pale bluish green in colour, often due to a thin

coating of wax, or so-called bloom,
pruinose, with a covering of wax, or bloom, e.g.
branches of Rubus lasiocarpus.

The surface is sometimes covered with scales, as in
Elaeagnus, when it is said to be lepidote and in other
plants with a sticky secretion when it is said to be viscid.
Hairs which have branches radiating from one point are
called stellate, and those with a swollen head excreting a
sticky ^ substance are called glandular, e.g. the hairs on
Roses and on the petiole of Corylus Colurna. Structures
known as glands are often found on the surface of plants.
These are more or less prominent, somewhat fleshy, swellings
which may, or may not, secrete sticky substances. They
are common on the leaf-stalks of Acacias. Other kinds of
glands have been described in previous paragraphs.

61. The general appearance of Habit.

a plant is called its habit. This depends largely on the
stem, whether it is erect, prostrate, climbing and so
on, also on whether the stem is branched or not. The
simple columnar stem of most Palms is thus readily dis-
tinguished from those of the majority of our forest trees
which are much branched. Habit also depends on the
position, arrangement, and number of the branches-, branchlets,
and twigs, and on their size and mode of growth. Most trees
for instance are bare of branches for some distance from
the ground, whereas the stems of shrubs branch close to the
ground. Bombax malabaricum also is easily recognised in the
forest by the fact that its branches are arranged in whorls, or
false whorls, see Fig. 3, Plate XI. In some trees .the branchlets
and twigs are thick and few in number, in many of the fleshy
Euphorbias and some Sterculias, for instance : in others there
is a large number of small branchlets and twigs, as in Hard-
wickia binata. In old Deodar the branches are almost horizon-
tal and form terraces of foliage, while in the spruce, from the
more or less horizontal branches, the branchlets and twigs hang
downwards. In Ailanthus excelsa the branches are more or less
decumbent. In many trees, the branches or twigs are pendulous
or 'drooping, such as are the terminal shoots of young Deodar,
the branchlets of Anogeissus acuminata and Anjan, and the
branches of Salix babylonica. Branches which leave the
parent-stem or branch at a wide angle are said to be divaricate,
such as those of Combretum ovalifolium, or Hamiltonia suaveo-
lens. On the branches also to a great extent depends the general
shape of the crown which is often very characteristic ; in
Albizzia stipulata the crown is broad and flat-topped, in che Silver
Fir it is more or less cylindrical, in the spruce conical, and in
the mahua, Bassia latifolia, usually rounded.

Herbs, Trees, ^ plant the serial stem of which is herbaceous and dies
down to the ground annually is called a herb. There are
some plants the stem of which, although it, dies down
annually, is firm and more or less woody, e.g. Psoralea
corylifolia. They are also usually classed as herbs. Plants
of which the serial stems, or the greater part of them, per-
sist for more than one year and which are more or less woody*
are classed as shrubs and trees respectively.

A shrub is distinguished from a tree by its smaller size
and by the fact that it usually has branches near the base.

According to their size, shrubs andtrees are again usually
sub-divided into shrubs, large shrubs, small trees, medium-
sized trees, large and very large trees.

An undershrub is a plant, of the aerial stem of which a
very small portion persists for more than one year. Such a
plant is also sometimes said to be suffruticose, or suffru-
tescent.

Large herbs which in size and general appearance re-
semble true shrubs are usually described as shrubby, e.g.
Sesbania aculeata.

Climbing plants are termed herbaceous if their aerial stems
are herbaceous and die down annually, and woody if the
stems persist for more than one year and are more or less
woody.

Biennials, A plant, or part of a plant, which only lives for one year

Perennials, is called an annual, one which lives for 2 years a biennial and

one which lives for more than 2 years a perennial. Annual

plants are always herbs, biennial plants are usually herbs,

while a perennial plant may be a herb, shrub, or tree.

The persistent basal portion of the stem of an undershrub
and the persistent base of an herbaceous perennial, lying at,
or just below, the ground surface, and usually including a
small portion of the bases of the aerial stems and the upper
thickened portion of the roots and from which new herbaceous
stems are annually produced, is called a stock, or sometimes,
also, a root-stock.\

Such root -stocks gradually increase in size and often

* In a few cases stems which persist for more than one year are distinctly
herbaceous, e.g. those of the Banana.

| A rhizome is also called a root-stock by some botanists.

form large woody masses at, or close below, the ground sur-
face. Examples are :—

Clerodendron serratum, Careya lierbacea and Combretum
nanum.

A plant which is usually found growing in company with Gregarious
many other plants of the same species is said to be gregarious, p"ant8p°
such as the Sal, many Bamboos and species of Strobilanthes.

A plant the individuals of which are widely scattered from
each other is sporadic.

Although the above distinctions are useful for describing
plants it must be understood that here, as elsewhere in mor-
phology, the distinctions are not absolute. Intermediate forms
between the types selected are frequently found while in one
and the same plant the distinctions cannot always be in-
sisted on. In our Indian forests we have many examples
of plants which in some localities are climbers while in
others they are erect shrubs, or trees, e.g. Acacia pennata
and Carissa spinarum. Again in some localities Leea aspera
and Clerodendron serratum are perennial herbs, in others
undershrubs, and in others large shrubs. Trees which are
continually browsed by cattle when young may be prevented
from developing normally and be temporarily reduced to
shrubs ; in other cases their serial stems may be more or
less completely killed down to the ground annually by fires,
or frost, and they may thus be reduced temporarily to
undershrubs, or perennial herbs, new shoots being sent up
yearly from the stock.

The common arhar, Cajanus indicus, is usually an annual,
but is sometimes biennial. By artificially preventing the
flowering of some plants, also, it has been found possible to
convert an annual into a perennial. In annuals the whole
plant dies annually, and although in perennials this does not
happen, still some portion of the plant usually dies and
is shed annually. In many trees and shrubs the leaves do
not live for 12 months and the plants are consequently
bare of green foliage during some part of the year. They are
called deciduous, while those plants which have green foliage ^

, , , . , T TIL Evergreen

throughout the year are evergreen. In some trees and shrub? Deciduous
small twigs die and are thrown off, as in Pines, Phyllanthus Plants.
Emblica and Strobilanthes Wallichii, while in the American
Swamp Cypress, Taxodium distichum, large branches are
periodically shed.

PAET II.-ANATOMY,

Hf; CHAPTER I.— CELLS.

Protopksm. 62. The bodies of plants and of

animals consist primarily of protoplasm ; this is a colourless
substance, the consistency of which varies with the quantity
of water it contains from that of a viscid fluid to that of a
firm substance almost like wax. Protoplasm always contains
carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus
and iron. When heated strongly protoplasm gives off water
and then it blackens and gives off ammonia. If heated to
red heat an ash is left consisting of small quantities of mineral
substances. Protoplasm, however, is a living substance which
can be easily killed by too high a temperature, by small
quantities of poisons and by other factors. It must not be
regarded as a simple chemical compound, and we cannot
produce protoplasm artificially by collecting and mixing to-
gether all the elements which appear to enter into its compo-
sition.

Some plants exist which consist of only a naked mass of
protoplasm. Such a mass of living protoplasm is found to be
capable of creeping movements, portions of the protoplasm
being pushed out which draw the remainder of the protoplasmic
body after them. It is also capable of taking up and absorb-
ing bodies containing nourishing materials with which it
comes in contact, of building up new protoplasm and thus of
growing and increasing in size, of respiration, i.e. of absorbing
oxygen from the air and giving off carbon dioxide, and finally
of throwing off pieces of itself which are capable of an inde-
pendent existence. In addition to these powers of movement,
nutrition, growth, respiration and reproduction, living pro-
toplasm, in common with all living matter, possesses the
remarkable characteristic of irritability, i.e. it is sensitive to,
and capable of re-acting in response to, a stimulus. The
quality is most easily recognised in cases where the response
is greatly out of proportion to the stimulus. If the leaves of
the sensitive plant, Mimosa pudica, are lightly touched, the
leaflets and pinnae all close together and the whole leaf
sinks downwards. In this case contact with another body
has supplied the stimulus to which the living protoplasm has

re-acted or responded in a particular way, the final result of
such response being manifested in the obvious movements of
the leaf and leaflets.

63. The protoplasm in the The Cell.

majority of plants does not occur in naked masses but sur-
rounds itself with an elastic, membranous wall, of a substance
called cellulose, inside of which it lives. Such an enclosed
piece of protoplasm is called a cell and its outer envelope the
cell-waU. Many plants are known, each of which consists of

only a single cell, but the body of the more highly organised
plants with which we are chiefly concerned is made up of a
multitude of such cells which live together in intimate contact,
although every such plant originally began life as a single
minute cell.

64. If a thin section from the Ceil

growing apex of such a plant is examined with a microscope, it Contents.
will be found to consist of a number of nearly cubical cells,

each of them being provided with a delicate cell-wall and all of
them fitting closely together. Each cell is full of protoplasm
and contains in the centre a rounded body called the nucleus
which is separated by a definite boundary from the rest of
the protoplasm. If the protoplasm is treated with a suitable
stain, the nucleus is seen to consist of a number of fine
twisted threads, or filaments, which become more deeply
coloured than the rest of the protoplasm. The latter, which
fills all the rest of the cell outside the nucleus and which
usually contains distinct granules, is distinguished as cytoplasm.
As such a cell increases in size the protoplasm is no longer
able to completely fill its cavity and spaces, the so-called
vacuoles, arise in the protoplasm which usually occupy the
greater part of the mature cell, the protoplasm being confined
to a layer around the cell-wall, with perhaps a few connecting
threads across the cell cavity. However large the vacuoles
may be, there is always a continuous layer of cytoplasm
surrounding the nucleus and lining the inside of the cell- wall.
The vacuoles contain a watery fluid termed cell-sap which con-
tains a variety of substances in solution, some intended as food
for the protoplasm and others having been excreted by the
protoplasm as waste products. The cell-sap also frequently
contains a red, or blue, colouring matter called antliocyanin,
to which the colour of many flowers, fruits and young leaves
is due. The cytoplasm in such a cell is often seen to be in active
movement, the latter being indicated by the granules contained
in it, which are seen to be carried along by the living pro-

toplasm like grains of sand in a stream. If the living cell
examined is in a part of the plant exposed to the light, such
as a leaf, it will be found to contain, in addition to the. nucleus
and cytoplasm, the so-called chlorophyll corpuscles. These
are green bodies, generally ellipsoidal in shape, consisting
of dense protoplasm and which owe their colour to the green
pigment called chlorophyll which they contain. This pigment
is soluble in alcohol and if leaves are boiled and placed
in alcohol the green colour can be extracted in the
form of a solution. These chlorophyll corpuscles possess the
power of making starch from water and the carbon dioxide
of the air under the influence of light. The small starch grains,
when formed, are dissolved and go to feed the protoplasm,
or to be accumulated and stored in certain cells as reserve
food material until wanted. In parts of plants not exposed
to light, protoplasmic corpuscles essentially similar to the
chlorophyll corpuscles are^formed but without the characteris-
tic green pigment and sometimes, as in flowers and fruits, the
green pigment is replaced by a red, or yellow, one.

The living contents of the cell thus comprise : —

The Nucleus
„ Cytoplasm
„ Chlorophyll Corpuscles

for all of which, collectively, the general term, protoplasm is
commonly employed. Among the non-living substances fre-
quently found in living cells the most important are : —

Starch grains. — Large grains are only found in cells where
a store of reserve starch is being accumulated. Such grains
usually exhibit a distinct stratification, their substance being-
arranged in layers. They turn blue when treated with a
solution of iodine.

Alcurene or Proteid grains, — These consist chiefly of albu-
minous substances and turn yellow-brown when treated with
a solution of iodine. They frequently contain albumen crystals
which can be distinguished from crystals of inorganic sub-
stances by the fact that they absorb stains and swell when
treated with water. They also usually contain rounded, or crys-
talline, masses of mineral matter. They are common in seeds.

Albuminous substances are the most complex bodies
found in the plant, with the exception of the living proto-
plasm itself, and they contain carbon, oxygen, hydrogen,,
nitrogen, sulphur, and phosphorus.

Other substances are tannins, fats, ethereal oils, resin,
caoutchouc, and mineral crystals the latter usually consisting
of Calcium Oxalate

65. So far as is known at pre- ceil
sent, every cell originates from a pre-existing cell and this
is usually brought about by normal cell-division. The whole
cell about to divide increases in size, the filaments contained
in the nucleus contract and become converted into a few
thick threads of equal length. The nuclear membrane en-
closing the nucleus then disappears, while each of the threads
divides into two longitudinal halves, the latter separating and
passing to opposite ends of the cell. The halves collected at
each end again coil up and each mass forms a new nucleus
provided with a membrane, while between them the forma-
tion of a cell-wall completes the division into 2 cells. In this
way an accurate division of the nuclear substance contained
in the cell is insured.

66. The cell-wall is at first very Thickening of

thin, but when the cell has attained its full size the wall is *J® j^."^*11
more or less thickened, the thickening substance being applied tion of pits,
in layers to the original membrane. Such thickened walls
are therefore, as a rule, distinctly stratified. Parts of the
original cell- wall, however, usually remain unthickenecl. Some-
times very small areas are thus left and narrow channels
through the thickening layers consequently arise, forming the
so-called pits. The pit in the wall of one cell is usually
continued through the thickening layers of the wall of the
adjacent cell, so that the cells are connected as it were by
a narrow channel which is, however, blocked in the middle
by the membranous primary wall. A bordered-pit is a modi-
fication of the simple pit, the channel of which is wide in
the centre and narrow at the ends, the centre of the original
w^all which blocks the middle of the channel being thickened
and forming the so-called torus, exactly facing the narrow en-
trances to the channel. In this case the thickening layers are
built out into a dome, instead of being closely adpressed to
the primary wall as is the case with a simple pit. The
entrance to the bordered-pit is at the apex of the dome.

In other cases when the greater part of the original wall
remains unthickened, the thickening portions take the form
of narrow bands which sometimes anastomose and form a net-
work. The cell- wall consists chiefly of cellulose, a carbohydrate
which after treatment with sulphuric acid turns an iodine
solution blue, but as it thickens it is usually more or less

changed by the addition of various chemical substances and
is often converted into wood, i.e. is lignified, or into cork,
i.e. is suberised. The communication between the living
protoplasm of adjacent cells is, however, not cut off by the
thickening of the wall, for exceedingly fine connecting threads
of protoplasm are found to pass chiefly through the thin
membranes of the pits but sometimes also through the thick-
ened wall.

When a cell-wall separating two adjacent cells has become
thickened, its central portion which occupies the position of
Middle the original primary wall is called the middle lamella, and this
Lamella. differs more or less markedly from the rest of the wall. In
lignified cell- walls it is, as a rule, more highly lignified than
the rest of the wall, and if a piece of wood is treated with a
solution, such as nitric acid with chlorate of potash, which is
capable of dissolving woody substance (lignin), the individual
cells which compose the woody mass will be isolated by the
dissolution of the middle lamella and the structure of the
wood is consequently destroyed. In this case only the outer
thickening layers of the walls will persist which consist mainly
of cellulose and contain less lignin than the middle lamella.
In some cases the latter dissolves easily in boiling water and
some cells can thus be dissociated by being placed in hot
water.

Shape of 67. Young cells such as those at

Cells- the growing points of plants, are at first more or less cubical,

or rectangular, in shape, but as they grow older and increase
in size, as they do just behind the growing points, they may
undergo a great change of form, and may also lose their
living protoplasm, in which case they are often termed dead
cells, although really they are then only cell cavities bounded
by the cell walls.

CHAPTER II.— TISSUES.

68. A single cell which continues Different

to grow and divide will result in producing an aggregate of K.inds of
cells all of which are coherent from the time of their origin; and^heii
such an aggregate of cells which are more or less similar, which Elements,
erow in the same way and which have similar duties to per-
form is called a tissue. As the cells of a tissue grow older their
walls frequently separate somewhat from one another and
spaces arise between them which are called intercellular spaces.
The tissues of plants may be first classified as : —

(A) Meristematic, or embryonic. — Those consisting of cells

still capable of growing and dividing and thus of
producing new cells.

(B) Permanent. — Those consisting of cells which have com-

pleted their growth and have ceased to divide.

The cells of permanent tissues vary greatly in size, shape,
thickness of their walls, and in other particulars. They may
remain more or less rectangular, or cubical, in shape, and a
tissue consisting of such cells is named parenchyma. The cell
walls are usually thin and the cells usually contain protoplasm.
Sometimes the cells have their walls thickened, but the thick-
ening substance is situated mainly at the corners of the cells,
in which case the tissue is called collenchyma. In other cases
the cells become much elongated in proportion to their width
and their ends are pointed. They then usually contain no
protoplasm but only air and water, while their walls are
generally thickened and provided with simple pits. Such cells
are called fibres. Cells, whether parenchymatous, or fibrous,
which have their walls very much thickened and in which the
cell-cavity is consequently very small and in some cases almost
obliterated, are said to be sclerenchymatous, and together form
the tissue known as sclerencltyma. Cells similar to fibres but
which are somewhat shorter and wider, with blunter ends, are
called tracheids.

By the absorption of their transverse partitions, also, rows of
cells may become converted into long tubes which are termed
vessels, or tracheae. Both vessels and tracheids frequently
have typical bordered pits on their walls and they are also
distinguished as annular, spiral, or reticulate, when the
thickening bands on their walls form distinct rings, spirals, or
a net work, respectively. When the bordered pits of a vessel

are transversely elongated and are situated close together, one-
above the other, the thickened portion of the wall alternating
regularly with the pit apertures, they look like the rounds o± a
ladder and the vessel is then described as scalariform.

The essential difference between a vessel and a tracheid
consists in the fact that the latter is a single cell and the former
. is produced by the fusion of several cells. The tr cheid corre-
sponds, as it were, to a single joint of a vessel. Vessels, however,
frequently attain a much larger diameter than do tracheids
and they are often clearly visible to the naked eye as pores
on the transverse section of a stem. Neither tracheids
nor vessels contain protoplasm, they are tubes whose special
duty is the conveyance of water from the roots to the leaves.
Intermediate forms between these typical elements often occur.

The so-called sieve-tubes are formed, like vessels, by the
fusion of a number of cells, but in this case the transverse
partitions, instead of being completely absorbed, are penetrated
by a number of small holes, such perforated partitions
being called sieve-plates. The walls of sieve-tubes are never
lignified and are usually thin, with an interior lining of living
protoplasm. They are the principal conductors of organic
food substances from the leaves to the places where they are
required.

Many plants contain so-called laticiferous -tubes or -vessels.
Sometimes these arise by the continued growth and elongation
of a single cell and sometimes by the fusion of several cells, as
in ordinary vessels.

Laticiferous tubes are usually branched, their walls have a
thin lining of protoplasm and are usually thin, while their sap
consists of a milky, usually white, fluid. Such tubes are
common in Figs, Euphorbia, and many other plants, and their
latex often contains valuable caoutchouc and gutta-percha.
The so-called resin-canals of Conifers are really intercellular
spaces into which resin is excreted from the neighbouring
cells. The oil glands in the leaves of the Orange, Lime and
other plants are formed by the disorganisation of a group of
cells, the cell walls being absorbed and the cavity so formed
-being more or less filled with ethereal oil.

Jyssstems. 69. The tissues of the higher

plants are usually classified in three groups, or systems, as
follows : —

(1) Tegumentary Tissue System.

(2) Vascular Bundle Tissue System.

(3) Fundamental Tissue System.

The Tegumentary System comprises the epidermis, or entire Tegu

i • -c J.-L i j. v i, n -_t £ -i System.

outer skin 01 the plant, which usually consists ot a single "

continuous layer of cells. These fit close together and, in the

serial parts of plants at all events, have their external walls

more or less thickened and cuticularised, i.e. converted into

cutin, a substance resembling cork but which is more resistant

to the action of caustic potash and strong sulphuric acid.

When such cuticularised external walls are very thick their

outermost layers are more cuticularised than the rest and

form the so-called cuticle, which can often be detached as a

separate membrane from the other thickening layers. The

epidermis is also frequently provided with an additional external

covering in the shape of deposits of wax, or various forms of

hairs, the latter being outgrowths of the epidermal cells. The

cells of the epidermis do not usually contain chlorophyll. It vascular

was pointed out, in Part I above, that the firm nerves, to Bundle

which the venation of the leaves is due, pass into the stem, ys

where they join on to stouter similar strands which are again

continued into the root, and also that these strands were

called vascular bundles. In some Balsams, the stems of which

are more or less transparent, these strands passing down the

stem can be seen with the naked eye and in other cases they

may often be isolated from young stems which have been

allowed to rot in water by carefully washing away the softer

tissue. Vascular bundle skeletons of leaves, also, are often

naturally produced as the leaves slowly decay. These vascular

bundles together constitute the Vascular Bundle Tissue System.

A.11 tissue which does not belong either to the Tegumentary Fundamental

or Vascular Bundle System is classed as Fundamental, and system.

consists usually of parenchyma, but also often contains collen-

chyma and sclerenchyma.

70. A vascular bundle consists structure o£

of two portions, the Xylem, or Wood portion and the Phloem, Bundles*
or Bast portion. The former consists chiefly of vessels and
tracheids, or sometimes of tracheids alone, with some paren-
chyma, while the phloem portion contains sieve-tubes and
parenchyma. Fibres may also be present in bothxylem and
phloem. Most commonly the xylem and phloem are in contact
on one side only and the bundle is said to be collateral. In
the stem the xylem and phloem portions of a collateral bundle
are found on the same radius of the stem, the xylem being
nearest the centre of the stem and the .phloem nearest the
circumference. In some cases the xylem has phloem not only
on the outside, but also on the inside, the xylem being placed

between two groups of phloem and in this case the bundle
is bi-collateral. In cases where either the xylem or the
phloem is entirely surrounded by the other, the bundles
are called concentric. In some cases all the cells of a vascular
bundle develop into either xylem or phloem elements, but
in others certain cells remain meristematic, i.e. retain their
power of growth and division. In the former case the bundle
is said to be closed and in the latter open, the meristematic tissue
being called the cambium. On the outside of the vascular bundle
sclerenchymatous fibres are usually found, which often form a
more or less complete sheath to the bundle,

Devei m ^' ^ vascular bundle does not of

of Vascuia?n course suddenly arise in the plant tissues with all its parts corn-
Bundles, plete, but is developed gradually, like all other parts of the
plant, from cells which at first are homogeneous. In the very
young plant embryo in the seed the vascular bundles are not
yet recognisable. As the embryo develops, however, certain rows
of cells grow longer than their neighbours and, dividing tangen-
tially, give rise to strands of narrow elongated cells, which are
destined to become the vascular bundles. The form of these
cells gradually changes as they complete their growth, some
elongate to form fibres and tracheids, the width of others
increases to form vessels, their walls become variously thickened
and pitted and their chemical composition is altered, many
cells lose their protoplasmic contents, while in other cases the
cross walls are more or less absorbed to form vessels and sieve-
tubes. This differentiation of a collateral vascular bundle
proceeds from the exterior of the bundle on both sides inwards
and the first formed elements of the xylem and phloem, which
are thus in this case the outermost, are called protoxylem and
protophloem, respectively. In the protoxylem annular or spiral
vessels or tracheids are found which do not occur in fche rest
of the xylem.

The cells at the growing apices of the shoots and roots of
older plants are also practically homogeneous and meriste-
matic, just as they are in the plant embryo, and it is only
at some distance behind the so-called growing points that we
find the vascular bundles fully developed.

CHAPTER III. -STRUCTURE AND DEVELOPMENT OF
PLANT MEMBERS.

72. If the young stem of a s,tem of

Gymnosperm, or Dicotyledon, is* cut across after the colla- pfrmg03"
teral vascular bundles have become differentiated, the latter and Dicoty--
will be found to be in a circle around the stem, the xylem of Ied°ns.
each bundle being nearest the centre of the stem and the
phloem nearest the circumference. The fundamental tissue
occupying the centre of the stem, inside the circle of vascular
bundles, forms the pith, while that between the bundles con-^ " ary
stitutes the primary medullary rays. In perennial stems,
and sometimes also in annual stems, after the differentiation
of the primary vascular bundles, a further process sets in
termed secondary growth in thickness. This is accomplished
by the activity of the cambium of the vascular bundles which
is a layer of elongated, delicate-walled cells, full of protoplasm,
situated between the xylem and phloem, and by the forma-
tion and growth of a similar thin layer of cambium in the
primary medullary rays between the bundles, which, uniting
with the cambium of the bundles, forms a complete ring
around the stem. From this cambium new cells are
continually being formed, through the division of the

cambium cells by tangential walls, both on the inside and
outside of the ring, towards the centre and circumference
of the stem respectively ; the former develop into xylem and
the latter into phloem elements. The primary medullary rays
are thus broken up by the formation of new xylem and phloem
elements from the cambium between the bundles. These
elements, however, follow a more or less sinuous course longi-
tudinally leaving a net-work of narrow elongated openings
which are filled by rows of cells of fundamental tissue, chiefly
parenchyma, running horizontally from the centre of the stem
towards the circumference. These cells constitute the second-
ary medullary rays and as the cambium cells opposite these
rays continually form new medullary ray cells opposite thorn,
both on the inside and outside of the cambium ring, a medul-
lary ray, once started, is kept open as the stem increases in
thickness and extends both through xylem and phloem elements.
As the circumference of the stem gradually enlarges, now
medullary rays originate from the cambium between those al-
readv formed. By mean0 of the medullary ravs communication

tf w • , •

Annual
Rings.

Heart-
Wood

Wood
Elements

Bast
Elements.

Stem of
Monocoty-
ledons.

is insured between all the lining cells of the stem. The rays
first formed extend from the pith to the circumference, while
those arising later originate at some distance from the pith.

In plants the growth of which exhibits periods of activity
alternating with periods of rest, there is usually a more or less
marked difference between the wood formed at the beginning
and end of the period of activity respectively. In the former
the vessels are often larger, or more numerous, or, in the
absence of vessels, the other elements are usually wider and
with thinner walls, and the wood of which they constitute a part
contrasts strongly with that which it adjoins formed at the end
of the previous season's period of activity, the elements of which
are denser. More or less obvious concentric rings thus arise in
the wood, which are the so-called annual rings. What is known
as heart-wood consists of dead cells, the cavities of which are, as a
rule, blocked up by gums, or other substances, and which, being
more or less saturated with tannins, is usually of a dark colour.

The wood of Conifers consists almost entirely of tracheids
which have bordered pits chiefly on their radial walls, with some
parenchyma, and also sometimes with scattered resin ducts.

The wood of Dicotyledons consists of vessels, tracheids,
parenchyma, and fibres.

The phloem, or bast, of both Gymnosperms and Dicoty-
ledons consists of sieve-tubes, parenchyma, and long, thick-
walled, fibres ; the latter, unlike the fibres of the wood, usually
have their walls very slightly, or not at all, lignified, and they
are therefore tough and flexible. It is owing to this fact that
the bast of many species is of commercial value for the manu-
facture of ropes and cordage.

The above elements occur in varying proportions, the wood
or bast of a particular species having more of a certain element
than that of another species while in some species certain
elements may not be represented.

73. In the young stem of a Mono-
cotyledon the primary collateral vascular bundles, instead of
being arranged in a circle, are often irregularly scattered
throughout the fundamental tissue of the stem. The xylem
of each bundle is turned towards the centre of the stem as
before, but the bundles are all closed, i.e. no meristematic
tissue remains in them to produce secondary growth in
thickness. In this case no distinction can be made between
the pith and primary medullary rays. In a few Mono-
cotyledons, e.g. some Palms, secondary growth in thickness
does occur, a cambium ring arising in the fundamental tissue
outside the vascular bundles, but this, instead of forming

'continuous wood on the inside of the ring, produces only new
areas of fundamental tissue with isolated vascular bundles.

74. In the young roots of Mono- Roats.

cotyledons, Dicotyledons, and Gymnosperms the arrangement
of the primary vascular bundles is different from that found in
the stem. The xylem and phloem strands of each bundle
separate from each other as they pass into the root and are
there arranged side by side on different radii of the root and
the bundles are then said to be radial. The xylem strands
also become twisted on themselves so that the protoxylem,
instead of being internal, as in the stem, is external.
Sometimes the xylem strands meet in the centre of the root
and sometimes they do not, there then being a central
pith. These separate strands of xylem and phloem follow a
straight longitudinal course in the root instead of curving as
do the bundles of the stem. In the roots of Dicotyledons and
Gymnosperms secondary growth in thickness occurs simul-
taneously with the similar growth in the stem. In the roots
cambium layers first appear on the inside of the phloem strands
and, extending thence laterally on both sides, they eventually
coalesce opposite the xylem strands, and thus form a complete
-cambium ring. This jing gives rise to xylem elements on the
inside and phloem elements on the outside, as in the stem,
broad medullary rays being usually formed opposite the primary
-xylem strands. The wood of an old root is usually more
porous than that of the stem but otherwise they very closely
Tesemble each.~oth.er in the possession of annual rings and other
characters. The cambium of the root is a continuation of
that of the stem, there thus being an uninterrupted cambial
layer throughout the stem and root and their branches.

In those Monocotj'ledons which exhibit secondary growth
a, cambial layer may arise in the root outside the primary
hurdles but it only produces closed vascular bundle strands
scattered in fundamental tissue, as in the stem.

75. In addition to the typical Abnormal

mode of secondary growth above described, cases of abnormal Deveiop-
•development are not uncommon among Dicotyledons andmentt
Gymncsperms. In Cocculus laurifolius, Bauhinia Vahlii, Cycas,
and several other plants, the cambium ring first formed ceases
to grow alter a time and then a second cambium ring arises
-outside the bast formed by the first. This also ceases to grow
after a limited time and a third ring arises, and so on, the
stem in consequence exhibiting very characteristic, more or
less concentric, bands of wood and soft bark-like tissue, which
have been already mentioned on page 18.

In other cases the cambium forms much more wood or bast
at certain points than at others, and, on a cross section., radial
masses of wood and bast are formed alternating with each other,
the cambium forming an undulating layer instead of a circle.
Periderm 76. In those Dicotyledons and

Gymnosperms in which the interior of the stem is con-
tinually increasing in thickness through the activity of the
cambium ring, the fundamental tissue and epidermis, which
at first surrounded the primary vascular bundles, is sub-
jected to pressure and tension. In some cases the cells com-
posing these tissues continue to grow and divide and thus
keeping pace with the internal development are able to*
persist. This occurs in most annual stems and in perennial
stems during the first year of their development and occa-
sionally for a longer period. In the majority of perennial
stems, to wards the close of the first year's growth, the epidermis
being no longer able to withstand the strain becomes ruptured
and falls off. Before this happens, however, a layer of cells
has been produced close below the epidermis which acts like a
secondary cambium and is called the Phellogen 9 or Cork Cambium.
By the active growth and division of this layer new cells are
added both towards the exterior and interior of the stem. The
former lose their protoplasm and become converted into cork,
forming the so-called Phellem., while the latter retain their
protoplasm and usually contain chlorophyll, constituting the
Phelloderm. The term Fender m includes the Phellem, Phellogen
and Phelloderm. The cork cells of the phellem form an elastic
protective covering to the stem which is almost impermeable
to air and water and which effectually takes the place of the
ruptured epidermis. It is owing to the formation of this layer
of cork that the colour of young twigs usually changes from
green to some shade of brown, the chlorophyll in the cells of
the fundamental tissue beneath it being no longer visible as
was the case when these cells were covered by the thin epider-
mis. In some cases the periderm, instead of originating close
below the epidermis, is formed deeper down in the funda-
mental tissue, and sometimes close to the vascular bundles. In
such cases, a? all the living cells outside it are prevented from
obtaining the supply of water and food necessary for their
existence, on account of the impermeable cork layer, they diy
np and die, forming the rough outer bark which is sooner
or later exfoliated. In some trees, e.g. the Birch, the first
formed, or primary, phellogen remains active for several years
and in some species it persists through the entire life of the
tree, new cork cells being added below as the outer ones are-

exfoliated. In this way a thick corky bark may be formed.
As a rule, however, its activity ceases after a short time and
another, or secondary, phellogen arises deeper in the stem
beneath the first and nearer the actively growing cambium
layer. In this case again all the living cells outside the second-
ary phellogen die and are added to the dead outer bark just
as happens when the primary phellogen develops deep in the
fundamental tissue. In this way a number of successive peri-
derms may be formed, succeeding each other at short intervals.
It will thus be seen that the outer dead bark may consist of
cork cells only or. in addition, of dead elements which originally
formed a part of the primary fundamental tissue, or of successive
periderms, or even of the phloem developed from the cambium.
Taking also the word cortex, or bark, in the usual sense as-
including all the tissues outside the cambium ring, it will be
seen that this consists of an outer portion of dead elements and
an inner part which is largely composed of living cells containing
protoplasm. According as the periderm forms a regular circle
around the stem, or only arcs of a circle, so do the outer layers
of dead bark exfoliate as rings or scales.*

Dead bark which does not exfoliate rapidly becomes deeply
cracked and fissured.

In the roots of Dicotyledons and Gymnosperms which
exhibit secondary growth the primary phellogen usually origi-
nates close to the primary phloem, all the tissue external to it
then peeling off, while subsequent phellogens arise as in the stem.
In the stems and roots of those Monocotyledons which possess
a cambium ring and which therefore increase in thickness^
periderm is also formed outside the cambium ring in the way
just described only in this case the cambium, instead oi
producing bast continuously on the outside, gives rise to new
fundamental tissue.

77. At certain points in both
roots and stems the phellogen, instead of producing cork cells

* In this book the word '•' bark " is used in its ordinary sense and denotes all
tissues situated outside the cambium. In some botanical books it is applied in a res-
tricted sense to the dead tissues situated outside the phellogen. For the latter, however,
the word rhytidomc seems preferable.

The word rJiytidome appears to have been first employed in Indian Botanical
literature by W. R. Fisher in his Morphological Botany (Roorkee 1888), but it has
not as yet been generally adopted by botanists. In that book Mr, Fisher has
spelt the word in two ways rfiytiderm (page 76) and rJiytidome (page 12C). In his

Tree*, 8f,rub?, and Wcody Climbers of the Bombay Presidency, 2nd edition, page x,
Mr. W. A. Talbot has adopted the word rJiytidome. The word is believed to be
derived from Greek pvn$ = a wrinkle) and Zepua. ( = skin, hide) and thus signi-
fies wrinkled, or shrivelled, skin. pvn$ has already given rise to words which are
generally accepted in botanical literature, such as rytidocarpus (= wrinkled fruit),

so that a better spelling of this useful term would appear to be rytiderm.

Shedding of
Leaves.

Develop-
ment of
Secondary
Members.

Develop-
ment of
the Root.
Root- cap.

which fit close together without intercellular spaces, gives rise
externally to a number of loosely united cells which often
protrude considerably beyond the surface. These areas of
loose cork cells are the lenticels, and they allow the necessary
interchange of gases to take place between the intercellular
spaces in the interior of the plant and the outer air.

78. When leaves are about to

be shed a layer of cork, continuous with the periderm of
the stem, is formed across the base of the petiole, which is,
however, penetrated by the vascular strands which descend
from the, leaf. Shortly after its formation a layer of cells,
a little distance above it in the petiole, becomes absorbed,
resulting in the entire separation of the tissues of the leaf
from those of the stem and the leaf accordingly falls off. The

<_> •/

cork layer below the surface of the scar now protects the
inner tissues of the stem from injury and this protection is
completed by the blocking up of the cavities of the vessels
and sieve-tubes with gums or cork.

79. Young leaves and branches

first appear on the stem as minute humps caused by the
growth and division of a group of cells situated close below the
epidermis. As these cells grow the epidermis increases in area
accordingly but not in thickness, and it thus remains as a con-
tinuous layer over the leaves and young branches and stems.
Young roots, on the other hand, originate deep in the funda-
mental tissue of the parent root, just outside the vascular
bundles, and as they develop they force their way through
and rupture the tissue lying between them and the exterior
of the root, so that they emerge through slits in the tissue of
the parent. Each young root also, as a rule, originates just
outside a xylem strand of the parent, and they are therefore
found in straight longitudinal rows, there being usually as
many rows as there are xylem strands in the parent root.
These lateral roots also always first appear at some distance
behind the growing apex of the parent root, where the
tissues have already become differentiated

80. The growing point of a root,

unlike that of a stem, is protected by a mass of tissue
called the root-cap formed by the growth and division of
the external layer of cells at the apex. The outer cells of
this cap are continually exfoliated while new cells are con-
tinually added at the base. The actually elongating portion
of a growing root comprises a relatively small area, situated
immediately behind the apex, and as this elongates it pushes
the root apex, protected by its slippery conical cap, in front of
it into the earth like a shield. If the roots of a young

plant, e.g. a wheat plant such as is shown in Plate 7, Fig.
3, are carefully removed from the soil and examined, their
lower portions will be found projecting from a mass of
soil particles like naked white threads. Closer inspection shows
that these soil particles are clinging to a number of minute
hairs which look like very fine shining lines. These are the
so-called root-hairs which attach themselves so firmly to the Root-hairs.:
soil particles that the latter can only with difficulty, if at all,
be separated from them. When looked at with a microscope,
each of these hairs is seen to be a tubular outgrowth of a single
epidermal cell, into which it opens at the base, with a thin cell
wall of cellulose and containing living protoplasm. It is prin-
cipally by means of these hairs that roots absorb their
necessary supplies of water and substances in solution from
the soil, the older parts of the roots taking no part in this work
of absorption. If these delicate hairs were formed on the
portion of the root which is rapidly elongating they would be
rubbed off as the root pushes downwards into the soil, and
hence the elongating region is destitute of these hairs. The
root -hairs as a rule only live for a few days and then die off, so
that they are absent from the older parts of the root, but as
new hairs are continually being formed behind the elongating
region a zone of active living hairs is constantly maintained
there. Owing to the strong adhesion of the root-hairs to the
soil particles, the root is firmly held in the soil and the elonga-
tion of the area immediately behind the apex must drive the
tip of the root down into the soil, as it cannot force up the
firmly anchored part of the root behind it. To enable the root
to obtain as much water and mineral salts as possible from
the soil, it is obviously an advantage for it to have a large ab-
sorbing surface which shall come in contact with as many soil
particles as possible. Accordingly, the tip of the root as it glows
downwards, usually follows an irregular spiral course, and the
multitudes of root-hairs give it a very large absorbing surface.
The root-hairs having obtained all the supplies they can from
the soil within their reach die off, while the lateral roots then
tap those layers of soil which were beyond the reach of the
hairs of their parent root.

The upper older portion of the young roots of seedlings Shortening
frequently exhibits the peculiar property of contracting, or of Roots-
shortening. A pull is thus exercised on both the root and
stem, and as the former is strongly anchored the lower portion
of the stem is pulled down into the soil and the young plant
is thus firmly established. The rooting tips of the branches
of Rubus lasiocarpus may thus be seen to be drawn into the
ground and similar contraction i« often seen in the older roots

Q tf

of mature plants, especially of those plants which have rosettes-
of leaves close to the ground. In such plants the short stem
increases slightly in length each year and the new leaves arise
higher and higher on the stem but, notwithstanding this, the
new leaves are always situated close to the ground. Trans-
verse wrinkles, or folds, at the base of the root, where the
tissues have shrunk, are often clearly visible where such
contraction has taken place.

Structure of gl. The leaf is composed of funda-

mental tissue traversed by vascular bundles and covered by
an epidermis, all of which are continuous with the corresponding
tissues of the stem. The xylem of each bundle is nearest the
upper surface of the leaf and the phloem nearest to the lower
surface. The fundamental tissue of the leaf may be uniform,
but is usually differentiated into, the so-called palisade tissue,
situated under the upper epidermis, and the spongy parenchyma,
which extends from the palisade tissue to the lower epidermis.
The palisade tissue consists of cylindrical cells, rich in chloro-
phyll, situated close together, with their long axes perpendicular
to the leaf surface. The spongy parenchyma consists of irre-
gularly shaped, often stellate, cells, containing less chlorophyll,
and between which there are large intercellular spaces. In the
leaf, as in other parts of the aerial shoot of the plant, the cells
of the epidermis fit close together except at the spots where the
openings, termed stomata, occur. These stomata are particularly
numerous on the leaves and in the leaves of land plants they
are found almost exclusively on the undersurface. A stoma
is formed by the division of an epidermal cell into two
daughter cells, which then separate from one another by the
splitting of the wall between them, an opening into the tissues
of the leaf thus being formed. These two cells contain
chlorophyll, are sausage-shaped, and are called the guard-cells.
Immediately below the guard-cells is a large intercellular
space which is in communication with the other intercellular
spaces of the leaf, so that the internal tissues of the leaf are
placed in communication with the air which can thus obtain
access to the cells, while the escape of gases and water vapour
from the leaf is also provided for. According to the quantity
of water in the guard-cells their free walls which adjoin the
stomatal opening, approach, or recede from, each other, thus
closing, or opening, the stoma. When the guard-cells are
turgid and full of water their free walls are drawn apart and the
stoma is opened, while if the guard-cells lose water and their
walls are no longer tightly stretched, as they are in turgescence.
their free walls are pushed together and close the stoma.

PART IIL-PHYSIOLOGY.

fp4
CHAPTER I.— FUNCTIONS OF PLANTS IN GENERAL.

82. It has been noted in Part II General

•that the essential living substance of plants consists of pro- Conditions '
toplasm and that this protoplasm is capable of doing various01 >lantLlfe-
kinds of work, of performing various functions, such as those of
nutrition, respiration, growth, movement and reproduction. See
page 68.

Protoplasm can, however, only perform these functions
provided that the external conditions are favourable. If
no water is available protoplasm at once becomes inactive
and may die, while it is easily destroyed by too high or too
low a temperature.

The protoplasm contained in the cell from the growth
and development of which a Teak tree is ultimately produced
must clearly have a very different structure from that contained
in the cell which eventually develops into a Sal tree : with the
bost microscopes at present available, however, no such
difference can be detected. Still we must not on that account
expect the protoplasm of different plants to always behave
in exactly the same way when the external conditions are
the same, and, as a matter of fact, we know that different
plants have different needs and that the effect of one and
the same factor on different plants may be very various. The
amount of light, for instance, which is absolutely essential
for the healthy development of some plants (ligkt-demanders)
is often injurious to those plants which live in shady places
(shade bearers).

In all ordinary green plants, however, a suitable supply
of water and mineral salts, a suitable amount of light and heat,
as well as of free oxygen and carbon dioxide, are essential
for their existence and for the vital activity of their protoplasm.

In Physiology, then, we must consider, on the one hand,
the living, irritable, protoplasm, and on the other hand, the
non-living factors of the plant's environment which are capable
of acting as stimuli to the protoplasm, of inducing it to behave
in a certain way and to perform definite work, while, under
certain circumstances, they may be able to altogether prevent
its activity and even to kill it.

For every such external factor there is in fact for each in-
dividual plant a minimum., maximum, and optimum, degree of
intensity with reierence to its effect on any particular function,
the first two being the extremes beyond which the function
ceases to be performed and the last being that degree of inten-
sity under the effect of which the protoplasm is best able to
exercise the function in question. Green plants, for instance,
cannot manufacture their organic carbonaceous food from inor-
ganic materials without light, while if the light is too intense
the green chlorophyll, by means of which the manufacture is
made possible, is destroyed, so that the manufacture of food
is only possible provided that the intensity of the light is
suitable. Again if the temperature of the soil falls below
a certain minimum, or rises above a certain maximum, the
protoplasm in the root-hairs becomes inactive and the roots
can no longer provide the plant with the necessary water
and salts from the soil.

83. The entire body of some

minute green plants which live in water and are called alga3
consists of a single cell, such as has been described in Part II,
in which more or less of the cavity of the cell is occupied by
the so-called vacuolea, filled with cell-sap and surrounded by
a layer of protoplasm which lines the thin outer wall of
cellulose and in which are imbedded the nucleus and chlorophyll
corpuscles. Such a minute plant is just as capable of exercis-
ing the functions of nutrition, growth, respiration, and repro-
duction, as are plants the bodies of which consist of enormous
numbers of such cells and exhibit an elaborate differentiation
into ^rgans. Such a cell, for instance, is able to absorb
fro n the water in which it lives water with traces of mineral
salts in solution. This is effected by osmosis or diosmosis,
a phenomenon by means of which two different liquids, or gases,
which are capable of mixing and which are separated by a
thin membrane permeable to both of them, are able to diffuse
through the membrane until a condition of equilibrium is
attained, the liquid or gas on each side of the membrane then
being of the same density and composition. If the membrane
is more easily permeated by one solution than by the other a
larger quantity of the former will pass through it and the
latter will consequently increase while the former decreases in
volume. The current which flows towards the solution which
increases in volume is distinguished as endosmose and the cur-
rent in the opposite direction is exosmose. Endosmose usually
takes place towards the denser liquid and if a pig's bladder is-

filled with a strong solution of common salt, or some other
solution denser than water, and is then immersed in pure
water the quantity of water passing into the bladder is con-
siderably greater than that of the solution which passes out of
it. The more concentrated the solution also, the more rapid
is the endosmotic current. The wall of a plant cell, like other
organised substances, is capable of imbibing water and swelling.
Protoplasm is in this way able to imbibe water to the extent of
90 % of its entire weight, although it then becomes almost fluid.
That great pressures may be created by this property of im-
bibition is shown by the fact that the swelling of wooden
wedges, which have been moistened with water, will suffice
to split granite rocks, thus indicating how strong this
attraction for water is. The walls of living active cells are
always saturated with the water they have imbibed and in
this condition they are permeable to solids and gases, pro-
vided these are in a state of solution, and in this state these
substances are able to diosmose freely through the cell walls.

In the living cell, however, another factor besides the cell-
wall enters into the case which is able to a certain extent to
control and regulate this purely physical phenomenon of dios-
mosis and that is the living protoplasm which lines the interior
of the cell-wall. It by no means follows, for example, that
substances which are able to readily pass through the cell-wall
will be able to pass through the protoplasmic lining and thus
penetrate to the cell-sap. The protoplasm in fact decides what
shall, and what shall not, pass respectively from the cell-sap to
the exterior of the cell and from the exterior into the cell-sap.
Seeing that the protoplasm of one plant differs more or less
fundamentally in character from that of another plant and
that the protoplasm of each individual thus has its own parti-
cular requirements to satisfy, we should natural!}' expect
that the materials absorbed should differ in different cases,
and that while one plant takes up large quantities of a particular
substance another may take up less, and this is actually the case.
Moreover, plants on account of this selective power are able
to collect and accumulate large amounts of substances which
exist only in very small quantities in their surrounding medium,
diffusion from outside continually replacing the small quantities
of any particular substance which the plant may absorb from its
environment.

84. The controlling power of the Turgescence.
living protoplasm is also responsible for the phenomenon
called turgescence. In the cell-sap of the living alga, for

iastance, strong solutions of sugars and other substances
exercising a powerful attraction for water are formed by the
protoplasm and are held by it in the cell, so that a
current of water is drawn rapidly into the cell by endos-
mosis just as happens in the case of the pig's bladder. Any
Rubstances also which are in solution in the water surround-
ing the cell which are either absent from the cell-sap, or of which
a smaller proportion exists in the cell-sap than is present
in the surrounding water, will also pass into the cell-sap with
the water current, provided that the protoplasm permits them
to pass.

Now, although the protoplasm in this way allows a solution
of particular materials to pass through its substance into the
cell-sap, it does not permit it to filter back again out of the cell,
but holds it fast. As water continues to pass into the cell
the protoplasmic lining is pressed outwards against the cell-
wall which in its turn becomes distended, but which, by its
resistance to the pressure, develops a state of tension in the
cell. A cell in this state becomes stiff just like a bladder
distended by air and is said to be turgid, or in a state of tur-
gescence.

The young growing leaves and shoots of the higher plants,
whioh consist almost entirely of living cells, each one of which
closely resembles our algal cell, are enabled to stand erect
and to exhibit considerable rigidity, owing to a number of the
cells being turgid and stiff. If a young shoot is cut and kept
without water we know that it soon droops and becomes
flaccid, the cells composing it having lost water and being
no longer able to remain turbid.

Again, if a living cell is brought into contact with a con-
centrated solution of a substance which has a stronger attraction
for water than have the substances contained in the cell-sap
water may be drawn out of the cell to such an extent that it
is no longer able to remain turgid and the protoplasm becomes
inactive and unable to perform its functions. It is on this
account that plants are, as a rule, unable to obtain their supplies
of water and hence also of dissolved mineral salts from concen-
trated solutions.

Transpira- 35 . As the mineral salts required

as raw food materials must thus enter the living turgid cell
as very dilute solutions, in order that the cell may obtain a
sufficiency of salts a large quantity of water must continually
be got rid of, and the protoplasm, while not allowing the salts
which it requires to pass out of the cell and be lost, does

^continually permit the water which is in excess of that re-
- quired to maintain the cell in a state of turgidity to escape.
In terrestrial plants this excess water passes off in the form
of water- vapour and the phenomenon is termed transpiration.
Room is thus made in the cell for more water and a con-
tinual fresh supply of water and salts is provided for.

86. Not Only solids, but also Manufacture

gases, in solution are able to enter the cell by osmosis andpoj[gan
oxygen and carbon dioxide, which are dissolved in the water Material,
surrounding it, are thus able to penetrate into the algal
cell. Now, provided that the temperature is suitable and
there is sufficient light, the protoplasm is able, by the help
-of the green chlorophyll, to decompose the water and car-
bon dioxide contained in the cell and to build up from
them an organic carbohydrate which is usually starch, oxygen
being given off. This is merely a preliminary process consist-
ing in the building up of a food material which in this case
precedes, and is quite independent of, nutrition proper, just
as the collection, or cooking, of food may precede actual
feeding. Some plants indeed exist which, as we shall see
later, can dispense altogether with this preliminary process,
although they are composed of living protoplasm which
requires feeding just as does that of green plants. Such plants
possess no chlorophyll, but by various means they are able to
obtain their organic food materials ready-made for them by
-green plants.

87. Living protoplasm, as has Respiration

been already noticed, respires, and plants, like animals, absorb Metabolism.
oxygen and give off carbon dioxide. During this process

some of the substance of the protoplasm itself appears to be
destroyed and broken down into simple compounds, energy
being evolved which is in great part dissipated in the
form of heat. If therefore the protoplasm is to be main-
tained alive and enabled to grow, there must be a continual
supply of energy available by means of which the very com-
•plex protoplasm may be again built up from simpler sub-
stances, and further in order that the protoplasm should
actually increase in bulk and grow, it is obvious that not
only must those molecules be replaced which have been des-
troyed but additional molecules must be constructed. This
constant source of fresh energy is, in green plants, supplied by
the starch which is being continually manufactured in the
orophyll corpuscles, and a considerable proportion of
which is a#ain being continually broken down into carbon

dioxide and water in respiration. By the breaking up of a
molecule of starch energy is liberated and this energy can be
employed by the protoplasm in so working on the various
mineral salts and other substances in the cell that they, or
some of them, are bound together into protoplasm which is
thus continually nourished and enabled to grow, while surplus
energy is also available for various kinds of work, such as the
building up of substances having a strong attraction for water
and which are thus able to cause osmotic currents. One
and the same substance, however, may be dealt with by the
living protoplasm in various ways according to its needs
at the time. The starch which has been manufactured in the
chlorophyll corpuscles, for instance, may be stored as reserve
material and put aside in the form of starch grains, as not
being at present needed, it may be converted into cellulose
and built into the cell- wall, it may be used as food and built up
into protoplasm, or it may be at once broken up in respiration,
made to give up its contained energy and converted again
into carbon dioxide and water.

When it is considered also that there is a variety of
substances in the living cell, both mineral salts, organic
substances and gases, and that they all may be dealt with
in a variety of ways, it is obvious that the actual processes
going on in the cell are exceedingly complex and as a
matter of fact they are very little understood. The main
fact known about them is, however, that they may all be
placed in two great groups — (1) those which consist in
the breaking down of complex to simple substances result-
ing in the liberation of energy, some of which passes off as
heat but some of which is always available for work in the
cell, and (2) those which consist in the building up of complex
from more simple compounds, the ultimate, or end, product
being the exceedingly complex protoplasm itself. The latter
processes collectively are termed assimilation, or anabolism,
and the former disassimilation, or Jcatabolism, while all these
processes together are termed metabolism, which thus means the
sum total of all the chemical changes which go on in a living
cell. The building up of starch by green plants is thus a process
of assimilation. A large number of the substances which are
formed in the cell during these various changes are of further
use to the plant and can again be used in anabolism, or kata-
bolism, but some are of no further use and these so-called
waste -products are got rid of by the protoplasm and if possible
are excreted, i.e. passed out of the cell.

88. If now, instead of consider- Conditions of

ing a single cell, we turn our attention to a large plant like a f Highly! 1E
tree which has, as we have already seen., a very complicated Organised
structure, we begin to realise the necessitv for its variously plant'

o ** «/

differentiated parts. If the body of such a plant were com-
posed of an aggregate of thin-walled cells, it is obvious that
turgidity alone would not suffice to enable it to stand erect and
to resist the enormous strains to which it is subjected. Many
cells therefore are deprived of their protoplasm and are converted
into thick-walled elements such as fibres, which serve to strength-
en and support the plant body. Further, although food
materials in solution could diffuse through such a large plant
body if it were composed entirely of thin- walled living cells, by
osmosis from cell to cell, the currents thus produced would be too
slow to satisfy the plant's requirements and hence we find
that some cells are converted into conduction pipes, such
as the vessels and tracheids, which are able to conduct water
and salts rapidly from the roots to the leaves, and the sieve-
tubes which conduct the organic food from the leaves to the
places where it is required. By means of a system of inter-
cellular spaces, also, which communicate with the outer air,
fresh currents of carbon dioxide and oxygen are continually
brought into contact with the walls of the living cells, while
the water vapour exhaled by the latter is able to quickly pass off
into the outer air. That water is actually absorbed by the
roots and is given off by the leaves of a highly-organised
plant can be easily seen, if the uninjured roots of a young
plant are put in an air-tight vessel of water, the whole
being placed in a balance. .The amount of water then taken
up by the roots can be directly measured, while the amount
given off by the leaves is given by the loss of weight indicated
by the balance.

If the external conditions remain constant, the amount of
water absorbed by the roots is equal to the amount given off
by the leaves.

The fact that green plants can grow and develop
normally in pure sand, or distilled water, to which certain
mineral salts have been added, but which contains no carbon,
shows that the carbon required for their organic food is not
obtained from the soil. The further fact that starch is actually
formed by .the green leaves is also easily shown by the follow-
ing experiment.

Part of a healthy, living leaf on a plant which has been kept
in the dark for some hours is covered with a piece of tinfoil,

or other substance, which does not allow light to pass through it,
and the plant with its partly covered leaf is then placed in
bright sunshine for some hours. The leaf is then cut off
and killed by being placed a short time in boiling water.
It is then placed in warm alcohol and thus decolourised, the
chlorophyll passing into the alcohol in solution. The leaf is
then placed in a solution of iodine and finally washed with water,
when all parts which had been exposed to the light will be found
to have turned blue-black, the colour indicating the presence of
starch, the manufacture of which was only possible in those
parts where the chlorophyll corpuscles were exposed to the
light.

CHAPTER II.— FUNCTIONS OF THE HIGHER PLANTS IN

DETAIL.

89. It has been already pointed SaffcF,ood

-, • i t ^ i ^i • i- <• • , Materials.

out that the higher plants absorb their supplies of mineral
salts and water mainly by means of the root-hairs, each of
which is merely the prolongation of a single, living, epidermal
cell, provided with a thin wall of cellulose and containing
protoplasm, a nucleus, and cell-sap. In all essential details, in
fact, it resembles our algal cell except that the green chlorophyll
corpuscles are absent. In such a root-hair, therefore, the
assimilation of a carbohydrate from inorganic materials cannot
take place, but respiration and the absorption of mineral
substances in solution can take place, as in the alga.

The chemical constituents of the plant body can be found
by analysis. Water in considerable quantities always occurs
In a living plant, and in turgid herbaceous plants water
may amount to as much as 90% of the entire weight of
the plant. About half the dry weight of a plant is made up of
carbon.

In Part II we have seen that a large number of additional
substances enter into the composition of the protoplasm, but
other substances also occur and practically all known elements
have, at one time or another, been detected in plants.

In order to discover which of all these substances are Essential
absolutely essential and in what quantities they are required Substancss.
for the growth and development of various plants, the latter
must be grown in pure water to which only known quantities
of known substances are added. By such water-culture ex-
periments it has been discovered that the following are indis-
pensable for the higher plants : —

Carbon. Phosphorus.

Hydrogen-. Potassium.

Oxygen. Magnesium .

Nitrogen. Calcium.

Sulphur. Iron.

All of these substances, excepting potassium, magnesium

and calcium, are believed to enter into the composition of

the protoplasm itself. The calcium appears to be often

useful in combining with poisonous substances, e.g. oxalic

acid, which are then deposited in the plant in a harmless

form. Of some of these essential substances only very small Quantities

quantities are required, but if that small quantity is absent teiu!l'ei1-

plant growth and development are impossible. Thus very
little iron is required, but unless the necessary minimum
is present no chlorophyll is developed. Of these various
elements the carbon is obtained from the carbon dioxide
of the air, oxygen is obtained partly from the air and
partly from water, hydrogen from water and the others are all
Availably, absorbed in solution by the roots from the sc-il. Large quanti-
ties of these necessary substances, however, may be present in
the soil and yet not be available for the plant, because they
occur in a form in which the plant can make no use of them.
As only substances in solution can penetrate the cell-wall and
thus enter the absorbing root-hairs, only such substances as
are soluble can be utilised by the plant. Although it appears
that some of the higher plants can directly utilise ammonium
salts, most of them can only obtain their nitrogen readily
.Soil— when it occurs in the form of nitrates. It a solution of organic

Absorption. an(j morganjc substances is poured on ordinary soil, it will
be found that the water which filters through is usually
different in composition to that originally added. This is due
to the power possessed by the soil of absorbing and retaining
various substances, partly on account of chemical combi-
nations taking place, and partly on account of the attraction
exercised by the particles of soil. Soils vary considerably with
regard to their absorptive power ; those containing humus
absorb the most and are thus able to store up large
quantities of valuable plant food-materials, while sandy soils
have very little absorptive power. All substances, however,
are not retained with equal vigour ; ordinary soils allow the
valuable nitrates to filter through and pass away in drainage
water, while phosphates, potassium salts and ammonium are
usually strongly held. Such absorbed substances can, however,
be gradually washed out again if sufficient water is continually
added to the soil, so that from the stored substances the
dilute solutions required by plants are thus made available
in a moist soil.

Living active root-hairs are continually excreting carbon
dioxide as a product of their respiration, and this, passing into
the water which surrounds them, aids materially in dissolving
and making available for the plant useful substances in the
soil. Calcium carbonate, for example, is readily soluble in
water containing carbon dioxide and, if a plant is allowed to
grow with its roots touching a polished marble plate, the
latter will be corroded and etched where the roots have come
in contact with it.

Power of
Plants to
obtain

Necessary
-Substances.

Plants, however, differ considerably in their power of extract-
ing their supplies of necessary substances from the soil and those
which can tap supplies which are not available for other plants
may therefore develop normally on soils where the latter cannot
exist. As a general rule, the substances which the higher plants
seem to find most difficult to obtain in sufficient quantities are
nitrogen, phosphorus, and potassium, and these substances in
suitable combinations are, generally speaking, the most valu-
able manures for field crops, the soil being able to supply
a sufficiency of the other substances. Those plants which
have special difficulty in obtaining any one of these substances
from ordinary soil may therefore, if grown continually on the
same ground, be unable after a few years to obtain a sufficient
supply for their vigorous development and the yield of agricul-
tural crops may thus sink to Jrd the average produce.

To show how plants vary in this respect, however, it should be
mentioned that, according to experience in Europe, although
turnips remove large quantities of nitrogen and potassium from
the soil, they as a rule only require a manure containing phos-
phorus, whereas barley and many other field crops usually
require an additional supply of nitrogen in the form of manure,
if a good crop is to be produced. Again, experiments extending
over 50 consecutive years have shown that, when barley :s
grown on one and the same soil continuously, only nitrogen
and phosphorus being given as manure and no potassium,
the crop will still be nearly normal and equal to that produc-
ed when a full manure of potassium, nitrogen and phospho-
rus is given. If grown continuously for the same period in
the same soil with no manure at all, the crop will sink to nearly
^rd the normal, while if nitrogen is omitted from the manure
the yield sinks to less than \ the normal.

Very little is known regarding the peculiarities of our forest
trees in this respect, but it is clear that we have to consider
not only the quantity of essential substances contained in the
soil and actually removed by the plants, but also the difficulties
which each species in nature experiences in availing itself of
the substances which are present in the soil, as on this
may depend the question of whether, or not, a certain species
can be grown continuously for long periods in the same soil.

The root systems of different plants also develop in different
layers of soil, and on such facts in great measure depends the
theory of rotation of crops and the growing of mixed crops.

Many plants are in nature found to take up large quantities of
substances which, so far as we can judge from water- culture Substances.

Absorption
and Ascent
of Wtaer in
Plarts.

Root-
Pressure.

experiments, are not essential for their growth and de\ elopment.
These substances, however, may often be indirectly useful ;.
thus silica is often taken up in large quantities and in many
plants is deposited in the epidermal cell-walls. This increases
the hardness and rigidity of the plant and may aid it
considerably in the struggle for existence by rendering it nn~
palatable to grazing animals. In this way the existence of
a plant, in its natural surroundings, may depend on the
presence of substances which appear, at first sight, to be un-
necessary for its healthy development.

90. Substances in solution pass

into the root-hairs by osmosis as in the case of the algal
cell, but, unlike the latter, an individual root-hair does not
remain in a continual state of turgidity. The protoplasm
of the turgid root-hair after a time appears to relax its
resistance to the outward pressure of the water and sub-
stances in solution which have accumulated in the cell-sap
and this absorbed water with substances in solution conse-
quently filters back out of the cell under a pressure corre-
sponding to that previously exercised by the protoplasm sup-
ported by the cell- wall by means of which the state of tur-
gescence was attained. That this pressure can be very consi-
derable is indicated by the fact that, when a young root pene-
trates a crack in a rock, or masonry wall, as the root increases
in size, the pressure exercised by its cells, in their efforts to
become turgid and grow, may suffice to split the rock, or wall,
as the case may be.

The water, however, which is thus pressed out of the root-
hairs, instead of passing out into the soil and thus being lost to
the plant, finds its way from cell to cell of the fundamental
tissue of the root and eventually passes into the vessels and
tracheids of the vascular bundles.

That water with salts in solution is thus pressed by the
roots into the vessels and tracheids, and often with consider-
able force, can be seen by felling a tree when the so-called
"sap" is rising, i.e. just before the leaves appear and when the
roots have commenced to actively absorb water from the soil.
The water can be plainly seen to exude from the vessels and
tracheids on the cut section and if analysed it is found to contain
various substances in solution. By attaching a bent tube con-
taining mercury to the rooted stumps of cut plants the pres-
sure with which this water is pumped up can be measured, and
it is found to frequently exceed that of one atmosphere.

Such " bleeding " may continue for several days, or even
weeks, and if the roots are kept warm and well supplied with
water the quantity of fluid exuded may be large, and often
considerably exceeds in volume the total volume of the root
system.

That this so-called root-pressure, however, in itself does not
suffice to explain the ascent of the water current in high trees is
shown by the following facts. If the total quantity of water
given off by such bleeding stems is measured it is found to be
very much less than the amount actually required and given
off by the transpiring leaves. Again if an actively transpiring
plant in full leaf is cut, the stump, instead of exuding water,
will at first actively absorb it, and water placed on the cut section
will be taken up by the vessels and tracheids, thus showing
that, instead of a positive root-pressure existing in the latter,
the existing pressure is less than that of one atmosphere. It
has been ascertained also that when transpiration is actively
proceeding the water does not occur in continuous columns
in the conducting elements, but as short columns, alternating
with bubbles of air, and that the pressure in them generally
decreases towards the top of the tree.

Now, if for any reason there exists a demand for a particular
substance in a certain cell, that substance will continue to
be attracted to the cell until the demand is satisfied. If.
for instance, owing to the presence of a concentrated solution
of a substance having a strong attraction for water, an osmotic
current into the cell is created, and further, if this water is driven
off in the form of vapour as fast as it enters the cell, the inward
current will continue to flow, since the needs of the cell in res-
pect of water remain unchanged. If, on the other hand,
the water is allowed to dilute the solution and to continually
carry off some of the same to neighbouring cells by exosmosis,
a condition of equilibrium will sooner or later be reached,
the concentration of the solution in all the cells being the
same. Glucose, or grape-sugar, is a soluble substance derived
from starch by the addition of a molecule of water, and if we
suppose that a dilute solution of glucose is flowing into a cell
by osmosis and that on reaching the cell the glucose becomes
converted into insoluble starch, which is deposited as starch
grains, the inward flow of glucose will continue, the cell's needs
in respect of glucose remaining unsatisfied. It is in this way
that large quantities of the so-called reserve food-materials
are accumulated and stored in certain cells until they are
required. Similarly, although currents of water with salts

Sucking-
Force in
Leaves.

Transpira-
tion.

in solution are continually flowing by osmosis into the living
cells of the leaf, each of which, like the algal cell, is busily
engaged in the sunlight in manufacturing starch and in building
up protoplasm to replace that lost by respiration, yet, as the
water which enters is again continually exhaled in transpiration
and as the salts which entered with the water are continually
being seized on by the protoplasm, made to combine with other
substances and built up into protoplasm, or otherwise changed,
the attraction exercised by the cells for water and these par-
ticular salts in solution remains unchanged, so long as the vital
processes mentioned continue actively, and water and
salts are in consequence continually withdrawn by the living
cells of the leaves from the vessels and tracheids with which they
are in contact. In this way a backwardly-acting sucking force is
developed which, in some way not yet clearly understood, extends to
the roots and causes fresh supplies of water and salts to continually
pass into the xylem elements of the vascular bundles from
the root-hairs. So much, however, is certain that there is no
enormous pressure acting from below which forces the water up
to the summit of high trees, and that, although the suction
force acting from above is considerable, it also by itself is not
sufficient to account for the transpiration current. The
most recent researches show that, if the living cells in the wood
are killed, the latter soon loses its power of conducting water,
and it is thought that the living cells of the medullary rays
and wood parenchyma which are in contact with the vessels
and tracheids assist in helping on the flow from point to point.
It has, however, been ascertained that the water current ascends
mainly in the cavities of the vessels and tracheids and not in
their walls, and by compressing transpiring shoots and thus
diminishing the sectional area of the cavities of their elements
the water current can be greatly reduced. It has also been
ascertained that the water current ascends in the younger
layers of wood and that when heart- wood is present it takes
no part in the conduction of water.

91. In large thin leaves the

living cells are not shut off from the outer air so
effectually as are those in the stem and branches which
are soon protected by an outer coat, several layers of
cells in thickness, of cork, or other more or less impervious
material, and hence, although the outer walls of the epidermal
cells of such leaves are usually more or less thickened, a certain
quantity of water is continually abstracted from the leaf by
evaporation. This process also is largely promoted owing to

the fact that, by means of the numerous stomata and large
intercellular spaces in the leaf tissue, the atmospheric air is
•able to actually come in contact with the thin walls of the
living turgid cells in the interior of the leaf which are saturat-
ed with water. Room is thus made in these cells for more
water which accordingly flows into them from the vessels
and tracheids of the leaf vascular strands and continually
brings with it a fresh supply of the necessary salts. This
evaporation of water from the leaves is called transpiration.
Within certain limits plants are able to regulate and control Regulation of
the amount of water which shall thus escape from them byTranspiratioiu
closing the stomata, by developing a thick coating of hairs, or
other protective covering, from the epidermis, or by other
devices, and consequently the quantity of water transpired
from a given surface of living leaves is always less than that
which would have evaporated from an equal surface of water
while a dead leaf, also, loses water by evaporation quicker than
a living leaf. With this proviso, however, the factors on which
transpiration depends are essentially the same as those which re-
gulate ordinary evaporation, and the amount of water transpired
therefore depends on the temperature of, and amount of
water contained in, the surrounding air, the presence or absence
of air currents, and the area of the surface exposed to eva-
poration. As a general rule, the rapid removal of water
from the actively assimilating cells of the leaf is very necessary
to enable them to obtain the necessary quantity of salts they
require from the very dilute solution absorbed by the roots.
There are, however, obvious cases in which rapid transpiration
may be highly injurious, such as when the roots can obtain
very little water from a dry soil, and it is essential that plants
should be able to regulate this loss of water. That this can
only be done within definite limits is indicated by the fact
that, during a hot dry day, plants may frequently be seen to
droop and become flaccid, the amount of water which has been
lost by transpiration, in such cases, being so great that the
living cells have been unable to obtain sufficient water from the
roots to enable them to remain turgid. They have accordingly
become inactive and unable to perform their vital functions.
Unless the loss of water has been too great such plants usually
recover in the night, owing to the diminished transpiration.
In some cases when little or no evaporation can take place,,
owing to the saturation of the atmosphere, or other cause,
plants may become filled with an excess of water and salts
in solution which is pumped into them by the active roots.

H 2

100

Water-Pores ^his excess water is often got rid of by exudation from the
ordinary stomata, or from special openings in the leaves called
water- pores, such as are found for instance at the tips of the
leaves of Colocasia antiquorum. Such pores are usually
larger than ordinary stomata, and, as their guard-cells contain
no living protoplasm and cannot therefore alter their shape,
the pores are always open. In the early morning drops of water
may often be seen exuding from the leaves of grasses and other
plants which have become surcharged with water by the
actively absorbing roots during the night. In such cases
the escaping water carries with it salts in solution, whereas
in transpiration only the water escapes in the form of vapour,
the salts remaining behind. As has already been noted, plants
can to a certain extent control transpiration by opening or
closing their stomata and this is effected mainly by the guard-
cells ; when the latter are turgid the stomata open and vice
versa. The guard-cells become turgid when active transpira-
tion is advantageous, in strong sunlight when plenty of water
is available, or when the surrounding air is moist, while they
become flaccid and thus close the stomata when active trans-
piration is likely to be injurious owing to the failure of the
water supply, or other cause. In dry localities where roots
can obtain very little water from the soil, only those plants
can exist which possess very efficient means of preventing
rapid transpiration, or which get over the difficulty in some
other way. Thus in desert plants the total area of the leaf
surface is usually greatly reduced and leaves in many species
may be entirely absent, the living, chlorophyll- containing
cells being situated in the thick stems and protected by a
more or less impervious epidermis, instead of being arranged
in large thin leaves provided with numerous stomata.

In many localities the water difficulty only becomes acute
• during certain seasons of the year and plants are able to exist
provided they can complete their development during the
period when the soil around their roots is sufficiently moist
to supply their needs. Thus in the plains of India, most
grasses and herbs complete their development during the rainy
season and die down in the hot weather. Deciduous trees
also lose their leaves and remain inactive during the seasons
when #n account of either the low temperature of the soil,
or the scarcity of water, the roots would find difficulty in
obtaining their supplies. Evergreen trees on the other hand
may be able to exist through such seasons owing to the
effective checks on transpiration possessed by them in the

101

way of a reduced leaf area, protective coverings to the leaf,
and so on. That such arrangements may be very effective is
indicated by experiments carried out in Europe which have
shown that the amount of water transpired by evergreen
conifers is frequently only iVth of the amount transpired by
deciduous dicotyledons, a result which is not surprising
when we consider the small area of leaf-surface exposed to the
air in the narrow coniferous needles, the strongly thickened
cuticle, the stomata sunk below the surface of the needles and
thus protected from air-currents, and the presence of scler-
enchymatous tissue beneath the epidermis which, as a rule,
surrounds and protects the thin- walled chlorophyll- contain-
ing parenchyma of such needles. Again, owing to their deep-
going root-systems some trees are able to tap a perennial
water supply and can thus produce fresh foliage and transpire
actively in the hottest, dryest season of the year.

92. That a carbohydrate, which Assimilation.
is usually starch, is formed in the green leaves of a healthy
plant exposed to sunlight, from water and the carbon dioxide
of the air has already been pointed out. During this process
oxygen is evolved, the volume of oxygen given- off being
approximately equal to that of the carbon dioxide absorbed.
If a green plant is placed in an air-tight jar in an atmos-
phere from which the carbon dioxide has been removed,
no starch is formed in the leaves, thus indicating that
the carbon dioxide of the atmosphere is essential for the
process. If the cut stem of a green aquatic plant is placed
in a cylinder of water in the sunlight, bubbles of gas will be
found to escape from the intercellular spaces at the cut surface
which can be easily collected and proved to be nearly pure
oxygen. By counting the number of bubbles given off per
minute, an idea can be formed of the rate at which carbon
dioxide is being absorbed and starch manufactured. That
light is essential for this assimilation is shown by the fact
that no starch is formed in that part of a green leaf which is
covered with tinfoil, or otherwise protected from the light.
On the other hand it can be shown by experiment that all the Rays of Light
rays of light are not of the same value for this process. If, for re^uired«
instance, a bright solar spectrum is projected on a green leaf
for several hours, the leaf then being decolourised with alcohol
and treated with a solution of iodine as before described, the
blue-black colour, indicating the presence of starch, will be
found to be most intense in that part of the leaf which was ex-
posed to the red and orange rays. The same thing can also

102

be shown by means of the green water p^ant mentioned in the
previous experiment, for if it is placed in a cylinder of red
glass the bubbles will be evolved almost as quickly as in ordinary
sunlight, whereas in a cylinder of blue glass, which intercepts
and cuts off the red and orange rays, the evolution of bubbles
Light absorb- almost ceases. If the light which has passed through a
e<* by chlor° solution of chlorophyll is decomposed by a prism, a dark band
will be found in the red and orange indicating that these
rays have been absorbed by the chlorophyll. The, latter,
the presence of which is essential for the assimilation of carbon
in the higher plants, is thus seen to absorb energy from the
sun in the shape of certain rays of light. Assimilation is,
however, a vital function performed by the living protoplasm
which, in some way which is not yet understood, utilises
the energy absorbed by the chlorophyll in decomposing the
Formation of wa-ter and carbon dioxide and in building up from them a carbo-
Starch. hydrate, such as starch. The chlorophyll is thus merely
a part of the apparatus which the protoplasm employs in this
work of assimilation. As might be expected, it 'will be found
that a leaf exposed to the light which has passed through
fi solution of chlorophyll, or through another green leaf, is
unable to assimilate carbon in the way described, the effective
light rays being no longer available for the process.

Among the factors which directly influence assimilation
are a suitable supply of iron and carbon dioxide, the tem-
perature, and light, for each of which there is an optimum
degree of intensity. It has been already noted that no chloro-
phyll is formed unless the necessary quantity of iron is available
and that without carbon dioxide the assimilation of carbon
becomes impossible. The amount of carbon dioxide in the
air is as a rule very small, about "04 % and provided
that the light is sufficiently intense assimilation may be
increased by increasing the amount of carbon dioxide in the
air up to a certain extent. More than 10 % car-
bon dioxide, however, has a decidedly injurious effect
and many plants die if continually exposed to air containing
as little as 4 %. Temperature has a marked effect on assi-
milation, as well as on all other vital functions, and if the
temperature is below a certain minimum the protoplasm
forms no chlorophyll. In the absence of light assimilation
ceases at once, while it increases in proportion to the intensity
of the light until the optimum degree of intensity is reached,
after which it again decreases. If the intensity of the light
continues to increase the chlorophyll is ultimately destroyed.

103

93. The starch formed in the leaves
is not allowed to accumulate there, but is continually being
transported to other parts of the plant where it is required for use,
or storage. This transport goes on both day and night, but as,
during the day, the amount of starch manufactured is consider-
ably in excess of that removed, starch does accumulate in the
leaves to a certain extent, which , however, is usually removed
during the night. Thus leaves as a rule contain more starch at
nightfall than in the early morning. Only those substances which
are soluble are able to traverse the cell-walls and they can thus
be transported easily and quickly from cell to cell in a plant.
Starch, however, is not soluble in water at the ordinary tem-
perature, and hence, for the purposes of transport in the plant, it
is converted into a soluble sugar, such as glucose, or maltose, and
this is effected by means of the substances called enzymes. The
latter are chemical substances formed by the protoplasm
during metabolism which possess the power of more or less
altering various compounds without being themselves effected
and many are able to convert insoluble into soluble substances.
Diastase is a general term for a group of enzymes which are
frequently found in plants, some of which can turn starch
into glucose, or fruit-sugar, while others turn it into maltose,
or cane-sugar. In addition to this power of enabling valuable
food materials to be easily transferred from place to place,
enzymes are also frequently employed by plants for converting
compounds into substances which can be readily assimilated
and food materials stored in seeds are often thus made available
for assimilation by the young plant,

94. All plants, like animals, K*sPiration-
require to breathe, and. like animals, plants absorb oxygen
and give off carbon dioxide, heat being evolved in the
process which is known as respiration. In the day time
respiration is, as a rule, not obvious in green plants growing
in the sunlight and which are found to continually enrich
the air with oxygen. This is due to the fact that the quantity
of oxygen evolved in carbon-assimilation is as a rule much
in excess of that required for respiration and that nearly all
the carbon dioxide produced during respiration is reassimilated
in the cells containing the green chlorophyll. If a green
plant, however, is placed in an air-tight jar and covered with
black cloth, or otherwise protected from the sunlight, it will
be found to absorb oxygen from the air in the jar and to give
off an equal volume of carbon dioxide. Again, if a quantity
of germinating seeds are placed in an air-tight jar and after

104

some hours a lighted taper is introduced into the jar, the
taper may be extinguished owing to the exhaustion of the
oxygen and the accumulation of carbon dioxide. In such seeds
which contain no chlorophyll there is no carbon-assimilation,
but respiration, nutrition, and growth are still actively going
on at the expense of the food materials stored in the seeds.
The fact that seeds can germinate and that seedlings can develop
and attain considerable dimensions in the dark, when no carbon-
assimilation is possible, clearly shows that nutrition is by no
means the same thing as carbon-assimilation. In the case
of such seedlings which have developed in the dark, nutri-
tion and growth have taken place at the expense of the organic
food materials contained in the seed and the dry weight of such
a seedling is found to be actually less than that of the seed
from which it sprang. These substances have in fact been lost
in respiration, the process which has supplied the energy
necessary for nutrition and growth. If on the other hand
a seedling is allowed to develop normally in the sunlight, green
leaves are produced, carbon is assimilated, and the dry weight
of the plant is soon considerably in excess of that of the seed
from which it sprang, owing to the fact that more organic
substance has been manufactured in the leaves than has been
required for respiration.

Growth. 95. During the growth of cellular

plants the actual enlargement of the cells is effected more by
increasing the actual surface-area of the cell- walls than by in-
creasing the substance of the protoplasm, although the latter
does of course take place. This enlargement of the cell-walls
can only take place provided that the cells are in a state of
turgidity and hence a liberal supply of water is essential for the
growth of such plants. Like other vital phenomena, growth is
only possible within a definite range of temperature. When the
latter falls below 0° C, or rises above 40° or 50° C, growth
as a rule becomes impossible, while the optimum tem-
perature for growth usually lies between 22° and 37° C.

Light retards growth and plants which have developed
in the dark as a rule have unusually long internodes, while
their tissues contain more water and their cell-walls are thinner
than would have been the case if the plants had been exposed
to the sunlight. As carbon-assimilation is impossible in the

Ligkt. 6C y dark, even if leaves were developed they would be unable
to perform their essential functions and plants which have
developed in the dark as a rule form no green chlorophyll.
Moreover in such cases material and energy are not

C?*'

105

wasted on the construction of leaves of normal shape and size
and the leaves which are formed are as a rule unusually
small or thin, the plant's efforts being mainly devoted to
increasing the length of the stem, with the object of enabling
it to reach the sunlight where green leaves can once more
assimilate carbon from the air.

Provided that other important factors, such as the amount
of available water and the temperature, remain constant,
plants, as might be expected, usually grow more at night
than in the day.

The rays of light which have most effect on growth are the
so-called ' ' chemical rays ' : which are situated at the blue-
violet end of the spectrum. In plants which have developed
in a red light, therefore, the retarding effects of light which
prevent excessive growth are not seen, and although in such
plants chlorophyll is formed, and carbon-assimilation enables
them to increase in weight, their growth in other respects
resembles that of plants grown in deep shade.

96. Owing to its remarkable Plant Move-

power of irritability the living protoplasm of plants is, as it m
were, able to perceive the existence of external factors and
to regulate its actions accordingly, a fact which is often made
manifest by the obvious movements of plant organs.

Thus the protoplasm in the roots and stems of the higher
plants is sensitive to the force of gravity and, guided by the
direction in which this force acts, it is able to direct the growth
of the elongating portions of these organs in such a way that
they assume the positions best suited for the performance of
their functions. Thus if a healthy seedling is placed with its
primary shoot and root in a horizontal position, the growing
portions of these organs will be found to curve in such a way
that the tip of the root and stem respectively point directly
downwards towards the centre of the earth and vertically up-
wards in a directly contrary direction, growth then being
continued in these directions without further curvature. The
curvatures to which these movements are due can only take place
in those parts of the root and stem which are still growing and
they are caused by the unequal growth of the opposite sides of
the organ concerned. In the root the upper side grows more
rapidly and in the stem the opposite occurs. This phenomenon
of movement executed in response to the force of gravity is called
geotropism. The root which grows towards the centre of the
earth, i.e. in the direction along which the force of gravity is
acting, is said to be positively geotropic, while the stem which

106

grows in the opposite direction, away from the centre of the
earth, is negatively geotropic. Those parts of plants which grow
horizontally, i.e. in a direction at right angles to that along
which gravity acts, are said to be dia-geotropic, such as are
often the primary branches of the stem and root. It is also
found that if the seedling, after being placed in a horizontal
position, is continuously and evenly rotated so that no side
of the root or stem is allowed to remain stationary, no geotropic
curvature takes place, inasmuch as no sooner does any part of
the root or stem receive a stimulus to grow faster than the side
opposite to it than it almost immediately receives a contrary
stimulus which neutralises it. In these movements, as in the
case of those of the leaves of Mimosa pudica, we see that the
response of the plant is out of proportion to the stimulus applied
and the result is quite different to that obtained when the
same stimulus is applied to lifeless matter. Thus in this case
the shoot moves in a direction exactly opposite to that followed
by a lifeless body acted on by gravity, and which falls down-
wards towards the centre of the earth merely by its own
weight. Moreover a primary root growing geotropically down-
wards is able to penetrate and force its way into mercury which
is specifically much heavier than itself, which would not be the
case if the root was composed of lifeless substance and was acted
on by gravity. The irritability of a plant organ may vary at
different periods of its existence, as is shown by the fact of a
dia-geotropic lateral root becoming positively geotropic and
taking the place of a tap-root which has been cut off, or injured,
and the same thing occurs when a lateral branch replaces a
damaged leading shoot. This question of the movements of
plant organs is complicated by the fact that in nature one
and the same organ is frequently exposed to the influence of
several factors, or stimuli, to each one of which individually it
may be able to respond in a particular way. Thus the move-
ments of such an organ would be the result of the combined
influence of all the stimuli affecting it at one and the same time.
Hydrotro- Thus roots are also found to be sensitive to the presence of water
and are able to regulate their growth with reference to the
source of moisture, i.e. they are hydrotropic. If a primary
root is growing in soil with plenty of moisture available on all
sides, it will proceed downwards, following the direction
suggested by gravity, but if it is situated in a very dry soil, in
which moist patches occasionally occur, the root will be found
to grow towards the moist areas, it thus being positively hy-
drotropic, irrespective of whether these areas lie directly below it,

J07

or in any other position, the hydrotropism of the root in this case Heiiotropism.
overpowering its geotropism. The aerial roots of some climbing
stems are also found to be sensitive to the direction of the rays
of light which fall upon them and they respond by growing
away from the source of light, i.e. they are negatively
heliotropic. Such roots being also positively hydro tropic and
very slightly, if at all, positively geotropic, turn towards the
moist dark crevices of their support and not downwards
towards the centre of the earth.

The primary stem, in addition to being negatively geotropic,
is also sensitive to the direction of the rays of light falling on it
and responds by turning its apex towards the source of light, i.e.
it is positively heliotropic. In this case heliotropism is usually
more powerful than geotropism and if the stem is exposed to il-
lumination on one side it will grow obliquely towards the light
rather than vertically upwards. Most leaves are also sensitive
both to gravity and also to light, they being both dia-geotropic
and dia-heliotropic, but their position in nature depends mainly
on the direction of the light rays. As a rule they place them-
selves at right angles to the incident rays of light with their upper
surface turned directly towards the source of light. Plate XIII
for instance shows how the leaves of Coriaria nepalensis secure
this position on erect and horizontal branches, respectively. In sleep-
addition to this sensitiveness to the direction of the light rays, themc
floral envelopes and also the foliage leaves of many plants are
found to be sensitive to variations in the intensity of light and
also to variations of temperature. Thus, with a rising tempera-
ture and light becoming more intense, many flowers open, while
they close with a fall of temperature and a diminished intensity
of light. The so-called sleep-movements of some foliage leaves
are due to the same cause, the leaves in this case assuming a
different position at niotfit to that taken up in the day, and as the
temperature falls, arid the intensity of the light decreases, in the
evening, these leaves, or leaflets, are found to close together and
to usuallyexpose only their edges to the zenith. In some cases it
appears that these movements are of service to the plant in pre-
venting excessive loss of heat by radiation. The so-called night-
position may also be taken up in some cases in the daytime,
owing to the light being too intense, or the temperature too great.
Many tendrils are found to be sensitive to contact with
rough solid bodies, as a result of which the side, in contact with
the substance grows slower than the opposite side, and the
tendril accordingly coils around the obstructing object, (unless
the latter is too large) and supports the plant stem.

108

The movements hitherto considered are those which are
brought about chiefly by the unequal growth of opposite sides
of the organ concerned and hence they are only possible in parts
which are still growing. Those organs which have completed
their growth therefore have become fixed in position, and this
position isthe one which is onthe whole the best suited for the
performance of the functions of each individual organ, having
regard to the conditions of its environment. Thus a leaf which
is no longer able to move according as the direction of the light
rays falling on it changes, takes up a fixed position in which
it receives the full benefit of the greatest quantity of the
most suitable light rays.

Movements In addition, however, to the movements which are brought
a^>out by a difference in the rate of growth of different parts of
organs, plants are also in some cases able to effect the movement
of organs after the latter have completed their growth, in res-
ponse to contact, light, temperature, and other stimuli. In these
cases the movement is brought about by an alteration in the
turgidity of the cells on opposite, sides of the organ concerned.
In foliage leaves the pulvinus and pulvinule are organs especially
adapted for effecting movements of this description, which can
be well seen in the leaves of Mimosa pudica. If the cells on
the upper side of the pulvinus are turgid, while those on the
lower side are flaccid, the leaf will move downwards, and vice
versa, the leaf in each case turning on the pulvinus like a hinge.
As cells are only capable of becoming turgid when the cell walls
are elastic and not rigid, we find that the greater part of the
pulvinus consists of parenchymatous cells with non-lignified
elastic cell-walls, the vascular strands and strengthening
tissue being united in a central strand where it offers least-
resistance to bending, instead of being distributed nearer the
circumference.

Eeproduc- 97. There are two modes of repro-

SS' AseS1 Auction m tne Vegetable Kingdom known as the Asexual, or
Methods. Vegetative) and the Sexual, respectively. In the former a portion
of the protoplasm of the parent plant, which may be a single
cell, or a multicellular structure such as a bud, separates from
the parent and, either at once, or after further growth, consti-
tutes a new individual plant. In sexual reproduction a new
individual plant can only be produced after the union of two
pieces of protoplasm has taken place which have been developed
on different plants, or on different parts of the same plant.
Several plants exist which propagate themselves only by the
asexual method, others are found to do so only by the sexual

109

method, while others again employ both methods. In the
higher plants asexual reproduction is often brought about by
means of stolons and runners, as in the Potato, Strawberry,
and Rubus lasiocarpus. The young plants developed become
separated from, and independent of, their parent by the decay
of those portions of the stolons and runners which lie between
the young plants and their parent. The same thing apparently
often occurs in the case of root-suckers which become indepen-
dent by the decay of the connecting roots. Asexual reproduction
is also effected by means of tubers, bulbs, corms, bulbils, and
tuberous roots.

Sexual reproduction in the higher plants is effected by means
of seeds. From the fact that two methods of reproduction occur
and that some plants which depend only on the asexual method,
and some which depend only on the sexual method, are able to
exist and successfully maintain themselves in different parts of
the earth, we should naturally infer that each method possesses
certain advantages. There seems to be no doubt that this is
the case and that, under the conditions of existence to which
plants are exposed in nature, at one time one method, and at
another time the other method, may prove most advantageous.
Compared with the structures by means of which asexual re-
production is effected, such as bulbs, corms and tubers, seeds are
usually smaller in size, are usually produced in larger numbers
and generally possess more efficient means for their wide dis-
tribution. In the higher plants, therefore, sexual reproduction
tends to result in the establishment of a large number of young
plants scattered at a considerable distance both from their
parent and from each other. To a great extent, therefore, the
roots of each young plant are able to develop in layers of soil
which have not been exhausted by the roots of its parent, and
each young plant is to a great extent freed from a severe com-
petition for its necessaries of life with other young plants of its
own species, which have the same needs and requirements.

With asexual reproduction, on the other hand, it is found that
the young plants, although they are not so effectually separated
from their parent and each other, grow, at all events at first, more
vigorously and attain large dimensions quicker than do those
developed from seed. This power of vigorous growth during early
youth may often be of vital importance for the existence of the
plant, i.e. in forest areas which are covered with a heavy growth
of grass in which the slow-growing young seedlings of forest
trees are often smothered and killed, whereas strong- growing
root-suckers may be able to successfully establish themselves.

110

As regards sexual reproduction, it is clear that in an herma-
phrodite flower it is possible (1) for the pistil to be fertilised with
pollen developed in the same flower, in which case the flower
is said to be self -fertilised and (2) for the pistil to be fertilised by
pollen developed in another flower occurring on the same plant
or in a flower belonging to a separate plant, in which case the
flower is said to be cross-fertilised. Now, a young plant
arising from a seed resulting from the second kind of
cross-fertilisation must inherit something from each of its
parents, and it therefore tends to vary and to exhibit
characters which were not found in the mother-plant. It
appears that this tendency to differ from the mother-plant also
exists to a certain extent in plants arising from seed produced by
self -fertilisation, and all plants raised from seed tend to differ
more or less considerably from the mother-plant. In asexual
reproduction this is not the case and the young plants are
invariably found to resemble their mother-plant very closely.
In the case of the young plants arising from seed, a large pro-
portion of which frequently find themselves at a long distance
from their mother and exposed to conditions of existence more
or less fundamentally different from those under which their
mother-plant developed, the possession of slightly different
characteristics may obviously be of the utmost use in enabling
them to develop successfully. On the other hand considerable
variation in the case of asexually produced offspring, established
in the immediate neighbourhood of their parent, would as a rule
be a disadvantage.

98. As regards the respective

Seif-Fertiiisa- advantages of cross and self-fertilisation, it has been
tion. proved by actual experiment in the case of several plants in

Europe that cross-fertilisation results in the production of
more seeds, which in their turn are able to produce more
vigorous plants, than is the case with self-fertilisation. Even
if this were universally the case, which has not been proved,
it must always be remembered that cross-fertilisation is effected
with considerable difficulty and is therefore far more uncertain
than self-fertilisation, inasmuch as fewer flowers are likely to be
fertilised. It would therefore be quite possible for a plant
which uniformly produces a large number of young plants as
the result of self -fertilisation to be equally, even if not more,
successful in the struggle for existence, in comparison with a
plant which habitually produces very few offspring as the result
of cross-fertilisation, even if the offspring of the latter were
slightly more vigorous than those of the former. It is in fact

Ill

probable that, as is the case with sexual and asexual methods,
according to the conditions under which plants exist, sometimes
self- fertilisation, and sometimes cross-fertilisation, may be most
advantageous. That cross-fertilisation, however, is, on the
whole, most advantageous in the majority of cases, is indicated
by the fact that a very large number of contrivances exist which
appear to aim at on the one hand the prevention, or at least the
postponement, of self -fertilisation, and on the other hand at
facilitating cross -fertilisation.

99. For the transference of

pollen from the stamens to the stigmas the principal agencies pilous, Omi
employed by plants are wind, insects, and birds. Plants which thophii
are pollinated by the wind are called anemophilous and usually
have small inconspicuous flowers, with no brightly-coloured
perianth, and with no sweet nectar or attractive odour. A
the pollen is distributed in all directions by the wind, it is
usually produced in very large quantities to insure some of it
reaching the female organs, as is the case for instance in Pines
and Firs. In Grasses wind -pollination is aided by the fact that
the large anthers are versatile and swing freely in the wind,
while the feathered stigmas offer a large catchment surface for
the pollen. Anemophilous plants are also frequently gregarious,
such as are Pines and many Grasses.

Plants which are pollinated by insects are termed entomo-
philous and* those pollinated by birds are ornithophilous. These
as a rule characterised by the possession of conspicuously-
coloured floral envelopes with often also nectar and attractive
scents. The insects, or birds, attracted to the flowers obtain
nectar, or pollen, or both, as food and in their visits carry out
for the plant the desired transference of some of the pollen
to the stigmas.

100. The chief contrivances by

means of which plants endeavour to bring about cross-fertili- ing Cross
sation are:—

(1) The separation of the sexes. — This is effectually secured
in dioecious and monoecious plants and to a certain
extent also in polygamous plants. This is also
effected by dichogamy, i.e. although the stamens
and pistil occur in the same flower they mature at
different times. Flowers in which anthers mature
fost are protandrous, those in which stigmas mature
first and become ready for the pollen before the
stamens dehisce are protogynous.

112

(2) Heterostyly. — In some plants it is found that all the
flowers on some individuals have stamens and styles
of different lengths from those in the flowers of other
individuals of the same species. These plants and
flowers are .said to be heterostyled. In species of
Primula the flowers are dimorphic, or of two forms.
The flowers on some individuals have short styles
with the anthers situated above them at the throat
of the corolla, and those on other plants have long
styles with the stigma at the throat of the corolla
and the anthers below them, deep in the corolla
tube. Other plants exist which have trimorphic
flowers, some with long, some with short, and
others with medium-sized styles, with the anthers
also arranged at corresponding heights in different
flowers, the stigma and anthers of the same height
never occurring on one and the same plant.
In such plants it is found that full fertility is only obtained
when the stigma is fertilised by the pollen taken
from anthers standing at a corresponding level
(i.e. by pollen taken from the flowers of another
plant). All other crosses are termed illegitimate
and are found to be more or less sterile, i.e. very few
seeds are produced as a result of them and if seeds
are produced there is less chance of healthy plants
developing from them than in the case of a legiti-
mate cross. As the anthers and stigmas standing
at the same level in different flowers must come in
contact with the same part of the bodies of the insects
which visit them, cross-fertilisation is more or less
frequently insured, while self -fertilisation is not
prevented. Several heterostyled plants occur in
India, e.g. Reinwardtia trigyna and Woodfordia ftori-
bunda.

(3) Mechanical arrangements. — As illustrations of the truly
remarkable mechanisms found in various flowers two
plants have been selected, viz. Salvia lanata and
Berberis Lycium, both of which are common in
Jaunsar. For illustrations to compare with the
following accounts see Plate XIV.
Fertilisation 101. In Salvia lanata the

corolla is divided into two obvious lips, the lower lip
forming a convenient landing-place for insects, while the
upper, helmet-shaped lip rises above it like a hood. Nectar

113

is excreted by the yellow disc at the base of the ovary
and collects in the corolla tube. The flowers are much
\isited by bees and a bee alighting on the landing-stage
and wishing to get at the nectar has to pass forward under the
hooded upper lip of the corolla and it then finds the entrance
into the nectar-containing tube effectually blocked by an in-
genious piece of mechanism consisting of the two stamens which
is shown in Fig. 1, dissected from the flower. Each stamen is
attached to the corolla by a short filament on which the long
connective swings like a lever on its fulcrum. The upper longer
arm of the connective is slender and, together with the pollen-
bearing anther-lobe which it carries at its apex, is concealed in
the hooded upper corolla lip. The lower thickened connective
arm is joined to that of the other stamen which is placed side by
side with it in the flower, the metamorphosed lower anther-
lobes borne at their extremities coalescing to form a little pouch-
like structure which effectually blocks the entrance to the corolla-
tube, like a trap-door. See Fig. 2. The anthers dehisce by a
longitudinal slit which directly faces the landing 'stage. A bee
wishing to get at the nectar and pushing against the obstructing
door will move the latter upwards and backwards, the path to
the nectar thus being opened, while the upper connective arms
descend towards the landing stage and bring their pollen-covered
anthers down on the bee's back. See Fig. 3. So soon as the
bee withdraws, the stamens swing back into their former posi-
tion. The flowers of this plant are protandrous, i.e. the anthers
mature and begin to shed their pollen before the stigma is
ready for pollination." In a young flower the stigma occupies
the position shown in Fig. 4 (a), the stigmatic surfaces being close
together and well out of the way of an insect entering the flower.
As the flower gets older the style becomes depressed towards
the landing stage while the stigmatic lobes separate and become
recurved, Fig. 4 (6). A bee, before it can enter the flower at all,
must first bring its back, which has probably been dusted with
the pollen of a separate younger flower, in contact with the
stigmatic surface and cross-fertilisation is thus effected.

102. In the case of Berberis Fertilisation

Lycium, if we look at a flower-bud we find the stamens stand- of Flowers of
ing erect in the centre of the flower with their anthers close to
the stigma, but the anther-valves are then unopened as shown in
Fig. 5 (a), Plate XIV. As the flower expands and the petals
open out the stamens are bent back with them, the back of the
filaments being closely adpressed to the upper surface of the
petals. As the flower opens, also, the anthers dehisce. During

114

dehiscence the valves remain attached only at one point at the
top of the connective, and, hinged on this point, each valve
gradually rises up, pulling out, as it does so, most of the pollen,
which remains attached to its inner surface. Fig. 5 (b). Each
valve after rising to an almost horizontal position turns its inner
surface which is covered with pollen inwards towards the centre
of the flower. Fig. 5 (b) and (c).

In the open flower these pollen-covered valves are protected
from the rain and weather by means of the shelter afforded by
the curled-in tips of the petals, so that in looking into the ex-
panded flower the valves are hidden from sight. Fig. 6. Look-
ing again at the open flower we see that each staminal filament
widens out at its base so as to come in contact with the neigh-
bouring filament on each side of it. Also a little above the base
of the filament, on each side of it, there is an oval, orange-
coloured, gland which excretes nectar, two of these so-called
nectaries being situated near the base of each petal on its upper
surface. Figs. 6 and 7. Each staminal filament fits in closely
between two nectaries and, as already noted, lies with its back
closely pressed against the surface of the petal. The nectar
excreted by the nectaries flows over the base of the filaments
and forms a glistening ring around the base of the ovary. The
bell-shaped flowers of this plant are either horizontal, or they
hang downwards, and the sepals and petals effectually prevent
rain from entering the flower and damaging the nectar, or
pollen. It will also be noted that as the petals have their tips
curled in to protect the pollen they are not so conspicuous as
they would be if they were fully expanded, but to compensate
for this and to make the flower more noticeable, the three inner
sepals are much enlarged and coloured bright yellow. Fig. 6,
If now the base of one of the filaments in the expanded flower is
touched with a pointed instrument such as a thin pencil, the
stamen, with a sudden spring, flies up from its sheltering petal
and resumes the erect position it occupied in the unexpanded
bud. The pollen- covered valves are thus brought into violent
contact with the pencil, but when the latter is removed it will
be seen that the valves are not near enough to the centre of the
flower to actually touch the stigma. Fig. 8.

A bee, searching for nectar with its proboscis and touching
the irritable base of one of the filaments, will thus cause the
stamen to spring inwards and dust with pollen that side of its
head which is turned away from the stigma. The insect being
struck by the stamen will often fly away at once and after
visiting a few flowers its head will be dusted all over with

115

pollen, so that, on visiting any other flower, it must inevitable
rub off some of this pollen on to the edge of the stigmatic disc
and may thus effect cross-fertilisation. The flowers of this
species are often visited by small ants and beetles which
consume both the pollen and the nectar. Such insects only
occasionally spring a stamen and then, as they do not leave the
flower at once, but continue to crawl about in search of food,
they must at all events occasionally bring about the pollination
of the stigma with the flower's own pollen. Moreover, as the
pollen- covered valves of a sprung stamen are practically on the
same level as the stigmatic surface, it seems certain that some
of the flower's own pollen must, sometimes at least, reach its
stigma. Thus while self -fertilisation is not prevented, more
or less frequent cross-fertilisation is insured.

103. It must always be re-
membered that, although cross-fertilisation may be, and
apparently is as a rule, preferable to self -fertilisation, it is
easy for a plant to, as it were, over-reach itself, if in endeavour-
ing to secure the former it makes the latter absolutely
impossible ; for in the event of cross-fertilisation not being
effected, which is in many cases a possible contingency,
no seeds at all would be formed and sexual reproduction
would absolutely fail. Thus many plants appear to find it
safest to at all events insure self -fertilisation in the event of the
failure of their efforts to secure cross-fertilisation. This is
perhaps most clearly seen in plants which, like many violets,
possess two kinds of flowers, (1) large conspicuous flowers
adapted for cross-fertilisation, and (2) small, inconspicuous
closed flowers adapted solely for self-fertilisation ( — cieisto-
gamie flowers], the latter insuring a supply of seed in the
event of the ordinary flowers not being fertilised.

On the other hand there are certain species which trust en-
tirely to cross-fertilisation. The pollen of some of these plants
not only fails to effect the fertilisation of its own flower but
acts as a poison, and if applied to the stigmas results in the
death of the flower. Finally it must be noted that if a stigma
has been pollinated with pollen from its own flower, self -fertilisa-
tion may be prevented and cross-fertilisation effected, even if
the stigma is pollinated after a considerable interval with
pollen formed in another flower of the same species, owing to
the latter pollen being prepotent, i.e. able to effect fertilisation
quicker than the flower's own pollen.

104. To insure the wide distribu- insemina-
tion of seeds various devices are employed by plants. In tiou of Seeds-

i %

116

some cases the seed or fruit is provided with outgrowths
which tend to make it buoyant and adapted for dispersal
by wind, such as the hairs on the seed of Holarrhena
antidysenterica and the wing of the seed of Oroxylum indicum
(Plate XII). In other cases the seed or fruit is adapted
for conveyance by water, such as are the seeds of Sissoo which
remain enclosed in the light pod, the latter serving as a float.
The wing-like outgrowths also of many seeds and fruits appear
to serve equally well for transport by water or wind. The
winged Sal fruit for instance is often carried considerable dis-
tances by water. In other cases the seeds are distributed by
animals which eat the fruit and excrete the undigested seeds.
The seeds of species of Zizyphus appear to be widely distri-
buted in this way by jackals. The seeds of species of Loran-
ihus are largely distributed by birds which eat the pulp of the
fruit and rub off the seeds on the branches when wiping their
bills.

Sometimes the seeds are forcibly expelled to a considerable
distance by the bursting of the ripe fruit, as in the case of the
capsule of species of Impatiens.

Finally, fruits, and rarely also the seeds, may be provided
with spines, hooks, or bristles, by means of which they adhere
to clothing, the hair or fur of animals, etc., and are thus carried
long distances.

117

PART IV.-CLASSIFICATION.

CHAPTER I.— DEFINITIONS AND EXPLANATIONS.

105. The fact that there are Necessity for

numerous distinct kinds of plants has been recognised from Classifica-
very early days, and the uneducated native of our forests tlon'
has required no botanical training to teach him, for instance,
that the Sal tree (Shorea robusta] is distinct from the Sam
(Terminalia tomentosa) or to enable him to recognise these
two kinds, or species, of tree in the forest. In early days,
when the total number of plants known to any single
individual was insignificant the want of an elaborate system
of classification was not felt, for one could readily acquire
and retain in the memory an intimate knowledge of the
characteristics of the known plants, which explains how it is
that the aboriginal is often found to be well acquainted with,
and able to recognise at sight, the majority of the plants
growing in the jungle near his village. It, however, soon
became evident that, if any individual desired to con-
siderably extend his knowledge of plants and to be able
to become quickly acquainted with those of foreign countries,
some system of classification was essential, under which all
plants could be shortly and concisely described (only essential
points of difference being noted) and grouped in such a way as
would enable one to quickly refer to its group any plant, where
its brief description and correct name would then be obtained.
Once the botanical name of a plant has been ascertained, all
the information that has ever been placed on record regarding
it can then be obtained by referring to the necessary books.
Botanical classification thus aims at placing all plants in groups
under groups, according to their resemblances, the smallest groups
being combined to form larger groups and the latter again
formed into still larger groups and so on, the plants included
in the smallest of these groups being all very much alike,
while those included in the largest groups have fewer points of
resemblance. The peculiarities which enable us to distinguish
one plant from another are called characters,

In a Flora, therefore, which is a book containing the descrip-
tions of all the plants of any given country or district, the
essential characters which enable us to distinguish the plants

iis

in any one of the largest groups from those in all the others are
first given ; then under each of the largest groups follow the
essential characters distinguishing the next lower plant groups
from one another and so on, so that, if we compare the characters
of any given plant with those given in the Flora, we are led
quickly on from group to group until ultimately we arrive at the
smallest group and the correct name of our plant, without wast-
ing time or getting confused in reading and comparing long
descriptions of unimportant characters.

Natural 106. It has been recognised from

a very earlyPeriod tnat " h^e begets like," that, with plants
as with animals, the offspring resemble their parents, and hence,

tion. also, it has been accepted as a fact from early times that all

organisms which closely resemble each other must be nearly
related.

When botanical classification was commenced, it became
necessary, first, to analyse and clearly define the essential points
of difference between individual plants, i.e. their characters,
and, secondly, to group together those plants with similar
characters. It was then found that, if only one character was
relied on, plants were often placed in entirely different groups,
although, as regards all their other characters, they were very
much alike and were in consequence held to be very closely
related. A system of classification, therefore, which only relied
on single characters, regardless as to whether, or not, the plants
which were most nearly related were thus kept together, was
known as an Artificial System, whereas a system, according to
which all characters were taken into account and which resulted
in placing the most closely allied plants in the same group,
was known as the Natural System.

The best known example of an artificial system is the
so-called "sexual system" of Linnaeus. Under this system
only the characters of the stamens and the distribution of the
sexual organs in different flowers were taken into consideration,
and all known plants were accordingly classified under 24 groups.
As an instance of the artificial nature of this scheme of classifica-
tion it may be noted that Class XXI Moncecia includes two such
distantly related plants as the Maize (Zea Mays), a Monocoty-
ledon, and the Oak (Quercus), a Dicotyledon.

A good artificial system which does not concern itself with
the fact as to whether nearly related plants are, or are not, kept
together in the groups which it defines, but which merely refers
to isolated and easily recognised characters, often enatyes us to

119

quickly assign any given plant to the group where its description
is to be found, and thus in many cases facilitates the work of
identification, for which reason it is still utilised to some extent
in modern Floras in the compilation of keys to the larger
natural groups.

Striking characters, however, are often inconstant and by
themselves are not always trustworthy guides in classification,
while, apart from the fact that reliance on a single character
is apt to lead us wrong, it must be remembered that, if we
depend on one or two characters only, we are quite unable to
classify any plant unless the individual in question exhibits
those characters at the particular moment of its life- history
when we happen to see it. If, for instance, we rely only on
the number of cotyledons for the definition of primary groups
and the cotyledons are not to be found on our plant, we are
at once brought to a standstill and are unable to proceed with
the identification. We are then driven to the conclusion that,
as a rule, in botanical classification, an aggregate of characters
is of more value than one or two striking points of difference,
both in indicating general resemblance, and therefore relation-
ship, and in the work of identification. At the present day,
botanists endeavour to make all permanent classification as
natural as possible throughout, and hence, before deciding to
which group any plant belongs, all characters are as far as
possible taken into consideration and we then decide which
group it, on the whole, appears to resemble most, the plants
in any one natural group resembling, in the sum of theiv
characters, each other more than any other plant.

107. Although, as has been The Unit of

pointed out above, it has been recognised from a remote 9assifica'
period that the offspring of any given plant closely resem-
bles its parents, yet close observation showed that, in
reality, no two individual plants were ever exactly alike. If
then we accept similarity of form and structure alone as
the basis of classification, we must adopt the individual plant
as the unit. Since, however, every individual plant has
only a limited period of existence and sooner or later dies,
such a procedure would lead to no practical results. With
the individual as the unit we should, for instance, require an
unlimited number of names for all the individuals which
now exist or which will arise in the future from existing forms
by reproduction ; we should only be able to catalogue and de-
scribe a very small number of all the individuals ever existing
on the earth at one and the same time ; while the descriptions,

120

after the death of the individuals to which they refer, would be
useless for the purpose of identifying living plants and would,
therefore, be of little value to us or our successors. It has,
however, long been recognised that although the immediate
offspring of any individual usually differ slightly from their
parents and each other, they, on the whole, invariably resemble
their parents and each other very closely, and this undoubted
fact that, within certain limits, all organisms breed true,
affords the only basis for a natural history classification which
shall be of practical value. By discovering within what
limits each different kind of plant breeds true, i.e. *by determin-
ing which characters are always transmitted truly to its
immediate offspring, we are able to obtain a unit which, so far
as we can see, is permanent, the marks which distinguish the
individuals belonging to this unit from all other plants being
always transmitted unchanged from parents to offspring
through successive generations. Such a unit can conse-
quently be recognised and studied by our' successors, while, by
only giving a separate name to each such unit instead of to
each individual, the number of names which will be re-
quired is enormously reduced. Such considerations have led to
the selection of the so-called species as the unit of classification.
It will be seen also that the morphological characters which
are most important in classification are those which are
always transmitted unchanged from parents to their offspring
and which therefore indicate genetic relationship.

Species, ( 108 With these preliminary remarks

Variety,0* ' tne following definitions are now given :—

Genus. DEFINITION 1. — A SPECIES is the smallest group of plants

existing wild in nature which can be readily distin-
guished from all other groups owing to the fact that the
individuals composing it all possess in common certain
well marked characters (=• specific characters) by
which they can be distinguished from all other plants.
The individuals also which compose the species are,
when developed normally in a state of nature, always
able to transmit their specific characters unchanged to
the majority of their immediate offspring.

DEFINITION 2. — A SUB-SPECIES is a group essentially
similar to a species but subordinate to it. The
differences separating any two individuals belonging to
different sub-species not being so great as those which
separate individuals belonging to different species.

121

DEFINITION 3. — A VAKIETY is a group of plants subordinate

to a species. The differences between any two varieties

{ of the same species are not constant, i.e. they are not

always transmitted unchanged from the parent to the

majority of its immediate offspring.

DEFINITION 4. — A RACE is a variety of considerable fixity.
The characters distinguishing the individuals which
compose it from those constituting the rest of the
species are frequently (e.g. in certain localities or
under certain conditions of existence), but not always,
transmitted from the parent to the majority of its
immediate offspring.

DEFINITION 5. — A number of species which closely resem-
ble one another with respect to their important
morphological characters are combined into a higher
group termed a GENUS.

Every species in the same genus bears the same name, Nomencla-
known as the generic name, while, to distinguish the various ture-
species included in a genus, each one is given an additional
name known as the specific name. The name of every species,
therefore, consists of two words. Thus all plants belonging to
the oak genus bear the common generic name of Quercus,
while the various species are distinguished by their specific
names, thus we have Quercus incana, Quercus glauca, and so
on. The same specific name cannot be used for more than one
species in the same genus, but may, of course, be used in another
genus.

In the majority of modern Floras no distinction is drawn
between sub-species, races and varieties, all sub-divisions of
the species being indiscriminately termed varieties. Of such
varieties those which are held to be most important are
given separate names, the varietal name following the specific
name, thus Cedrus Libani var. Deodara. Unimportant varieties
are merely noted below the description of the species in which
they are included and are designated by numbers or letters.
As different botanists have sometimes given different names
to one and the same plant and as different plants have some-
times received the same name, it is necessary, in order to avoid
confusion, to write after the name of the plant the name, in
full or abbreviated, of the author who first gave it that name :
thus Rhus Wallichii Hook f. means that J. D. Hooker was the
botanist who first gave the plant this name. A name of a
plant which has been superseded by another, owing to
its having been considered incorrect for some reason, is

Natural
Order, and
Class.

Principal
Natural
Groups
of Plants.

122

known as a synonym. Thus Rhus Wallichii Hook f. syn R.
vernicifera Brandis means that the plant, the correct name of
which is considered to be R. Wallichii given by J. D.
Hooker, is the same as that which had been also named
R. vernicifera by Sir Dietrich Brandis. The author, whose
name, or abbreviated name, is attached to each species, is the
person who first put the plant into the correct genus and who
therefore is not necessarily the person who was the first to
describe the plant or to give it a name.

Just as species are combined into genera, so are a number
of genera which closely resemble one another in their impor-
tant morphological characters combined into larger groups
known as NATURAL ORDERS, and the latter are similarly
combined into still higher groups termed CLASSES.

109. The principal groups of

plants therefore which are the most frequently met with, and
which form the groundwork of all systems of classification
are as follows, commencing with the largest : —

Class
Order
Genus
Species
Variety

These groups, however, are not sufficient to indicate all
the degrees of resemblance which are found to exist, and hence
they are often sub -divided, while additional groups are also,
if necessary, created. The following is a list of the names
most frequently employed for such sub-divisions of the
Vegetable Kingdom, given in sequence commencing with the
largest. It must, however, be noted that several of these
terms have been applied to groups of somewhat different value
by different botanists :•—

Sub -Kingdom
Division

Class .

Sub-class
Series
Cohort
Order*
Sub -order

* According to the Rules adopted by the International Botanical Congress,
held at Vienna in 1905, the groups usually known hitherto in English literature
as cohort and order respectively should be designated order and family.

Tribe
Genus
Section
Species
Sub-species
Race
Variety.

The main object of classification is to enable us to rapidly
become acquainted with the principal groups of plants
indigenous in various countries, and it must be remembered
that the above definitions refer to groups of plants as they
exist growing wild in a state of nature, and that there are many
plants which, in the garden, breed true and give the impression
of being constant forms and of constituting good species which
are not found as wild species in a natural state, owing to
their being unable to survive in the struggle for existence
or to other causes. Hence, if terms similar to those given
above are used for analogous groups of cultivated plants, it
should invariably be stated that plants under cultivation
are referred to.

110. Proof that a particular group Practical

of individuals has descended from another group is not in Determina-
itself sufficient reason for combining them together as one ^ of the
species, for, in the course of time, the intermediate forms which Groups,
once united the two groups may have disappeared, causing
the two groups to occur in nature as distinct species separ-
ated by well-marked and constant differences.

A species is a group of plants which actually exists in
nature, the recognition and correct definition of which are
independent of the way in which the group originated.

With a few exceptions, the individuals of one and the
same species cross readily and produce fertile offspring while
individuals belonging to distinct species very frequently do
not do so. At the same time fertility cannot be accepted as
an infallible criterion of species, for illegitimate unions between
the different forms of flowers which occur in one and the same
species, in plants with dimorphic and trimorphic flowers,
produce very little fertile seed and the plants raised from such
seed are sterile inter se, just as is frequently the case with
the illegitimate unions between distinct species. The male and
female forms of some organisms differ widely from each other
in many important characters, while an organism may also
exhibit an entirely different appearance at different periods

124

of its life-history. However great such differences might "be
they would obviously not justify our classing different forms
of one and the same organism as distinct species. When
defining species, therefore, care must be taken not only to
observe what characters are likely to vary in the immediate
offspring of one and the same individual plant, but also to
note how the characters of the same plant vary at different
periods of its life-history. An imperfect knowledge of life-
histories has led to mistakes being made in the classification
of some fungi, different stages in the life-history of one and
the same individual having been sometimes described as entirely
distinct species. The words " always able to transmit" in
definition 1, while indicating constancy under varying condi-
tions of existence, also imply that, while plants capable
of both sexual and asexual reproduction cannot constitute a
species if they only transmit their essential characters truly by
asexual reproduction, organisms only capable of asexual repro-
duction are not thereby precluded from forming a true species.

The characters which are used to define species must
not only be constant, but, also, in order to facilitate identi-
fication, they should, as far as possible, be such as can be
easily recognised, and further, to be of use in written descrip-
tions, they must be such as can be easily described in words.

Among the higher flowering plants, with which we are
chiefly concerned, characters of the floral structure are as a
rule most constant and important and, hence, special atten-
tion is paid to them in most Floras, but these, owing to their
minuteness, are often difficult to recognise, while flowers are
also only available at certain seasons ; just as, however, the
savage, who pays no attention to such minute characters,
is still able to recognise the different trees in the forest, so can
also the expert forester, by utilising characters referring to
the buds, leaf-scars, kind of bark on young and old stems,
the method of branching, the colour of the foliage at different
seasons, and others, which, as a rule, are not included in
botanical books, owing to their not being easily described in
words, to their not being easily recognisable in herbarium
specimens, or to their not being sufficiently constant over
large areas and in different localities. For this reason, also,
a botanical classification based on a single character is not
necessarily artificial, for such a character may be correlated
with several others, the latter having been omitted from the
scheme of classification owing to their being difficult to de-
scribe or to distinguish. ^

125

In order to determine whether particular groups of plants
found wild are to be considered as species, sub-species, races,
or varieties, a knowledge of the life-history, as well as of the
appearance of the seasonal forms of individual plants, and of
the kind and amount of variation which may occur among the
immediate offspring of one and the same individual, growing
under different conditions, is essential. It is, however, as a
rule, impossible to ascertain with certainty the parent of a
plant found wild, and very few species have been experiment-
ally cultivated with the object of recording the variation
exhibited by them. The systematic botanist, therefore, must
rely for his determinations mainly on morphological char-
acters, coupled with his knowledge of the development and
variation of the few forms which have be*en studied.

His conclusions are, consequently, liable to error and to
correction in the light of subsequent research, while, in the
present state of our knowledge, there is obviously room for
considerable difference of opinion as to the kind of characters
and the amount of variation which should be held sufficiently
important to constitute an inter-specific gap, in consequence
of which plants which are regarded by some botanists as
distinct species are considered to be varieties by others.
The discovery of intermediate forms, also, sometimes leads
to two groups of plants, hitherto considered distinct, being
combined as one species, it being possible, in such a case, to
arrange a complete series of individuals between which there are
no marked differences, the slight differences noticed being such
as might be expected to occur in the offspring of one individual.
In defining the limits of the larger natural groups and
in deciding which species are to be included in the same
genus, which genera in the same order, and so on. there
is even more room for difference of opinion, and it must be
remembered that the difference is not so much as regards
facts, such as, for instance, the existence of certain characters,
but rather as regards decisions on such questions as to whether
the possession of certain characters in common by several
plants, may, or may not, be considered to prove a relationship
between them, and as to the degree of such relationship. It
will thus be seen that the Natural System of Classification is,
as yet, by no means perfect, and is liable to modification and
alteration as our knowledge extends.

126

CHAPTER II.— PRINCIPAL SUB-DIVISIONS OF THE
VEGETABLE KINGDOM.

. . 111. All plants are first divided

-Division • , .-I i i • i i-i-i

of the into the two great groups, or sub -kingdoms, called respec-

Vegetabie tively Cryptogams and Phanerogams. The term Cryptogam
is derived from two Greek words signifying " hidden mar-
Cryptogams riage " and was originally applied to all plants whose reproduc-
and tive organs were minute and inconspicuous.

Phanero-
gams. From the absence of what are usually called flowers, or

structures containing stamens, or pistil, or both, this great
group of Cryptogams is sometimes referred to as the one
containing " flowerless," or " non-flowering," plants, while the
group of Phanerogams is similarly termed that which includes
the " flowering " plants.

The essential difference between Cryptogams and Phanero-
gams, however, consists in the fact that the latter produce
true seeds, i.e. many-celled bodies containing the multi-
cellular embryo or young plant, whereas Cryptogams, in place
of seeds, produce spores which are unicellular structures.
These spores may be developed asexually, or they may arise
as the result of a sexual process, the latter being manifest in
the mingling together of the protoplasmic contents of distinct
cells. When the sexual cells are externally similar, each is
termed a gamete, when one is smaller and more active than the
other, the small active cell is termed the spermatozoid, and
the large passive cell the egg-cell, or oosphere. Spores which
are capable of remaining dormant for considerable periods are
distinguished from those capable of germinating immediately
after their formation by the name of resting spores.

the 112' These tw° great gr°UPS are

Cryptogams, further sub-divided as follows : —

CRYPTOGAMS.

I. — THALLOPHYTA. ") Cellular plants with no true vas-
II. — BRYOPHYTA. j cular bundles.

III. — PTERIDOPHYTA. Vascular plants with true vas-
cular bundles.

Thaiio- THALLOPHYTA. — The plants in this group show no distinct

phytes. differentiation into stem and leaves and the cellular body

127

which serves such plants for stem and leaves is called a thallus.
For our purposes the plants in this group may be sub-divided
as follows : —

1. Algae . Plants containing chlorophyll.

3* ^Ta]°olourleSS plants without chlorophyll.

1 13. Algae. This group is of very

little importance to the Forest Officer and contains plants of
simple structure which live, chiefly, in fresh or salt water, but
also on a damp substratum, such as moist soil, the bark of
trees in shady forests, etc. Many are coloured green ; others
are blue-green, brown, red or purple, in such cases some
other pigment more or less masking the green chlorophyll.
Many are unicellular, or consist of minute filaments, while
some of the so-called " seaweeds v are more elaborate in
structure, some possessing a root-like attachment organ and
with a floating thallus which may attain a length of 800
feet, or even more.

114. Bacteria. This group in- Bacteria.

eludes the smallest of all known plants. They are exceed- Account
ingly minute and of very simple structure, being unicellular
or filamentous, with no indications of any specialised tissue.
Many are always present in the air and soil, others live in
water, and others in dead or living organic matter. Many
are well known in connection with animal diseases and are
popularly spoken of as " germs," or " microbes."

Regarding the size of bacteria, we may take, as a fairly
typical example, Bacterium aceti, the little individual rods of
which have a length and breadth of about — ^ of an inch
and —OQ of an inch, respectively. Many are capable of active
movement by means of exceedingly fine, hair-like processes
termed cilia or flagella.

The presence or absence of these flagella and the shape of
the individual cells are important characters for the classi-
fication of bacteria. The following forms, for instance, are dis-
tinguished by the characters given : —

(a) Cocci, minute spherical cells.

(b) Bacteria, rod-like cells with no flagella.

whole surface of the cell.

(d) Spirally curved forms (Vibrio closely wound, usually

with one polar flagella, Spirillum closely wound

128

with polar tufts of flagella, Spirochaete loosely
wound, long and filamentous).

The form of one and the same individual, however, may
vary considerably at different stages of its life-history or ac-
cording to the medium in which it is living. The individual
bacterial cells are thus sometimes united into chains, or
masses of varying form, and owing to the partial dissolution
and swelling of the outer layers of the cell walls of the indivi-
dual cells such masses are often distinctly mucilaginous or
gelatinous.

Plants which are thus capable of assuming several different
forms are termed polymorphic.

So long as conditions are favourable, bacteria grow and
multiply very rapidly. Each tiny bacterial cell, whether
spherical, rod-shaped or curved, having grown to a certain
size, becomes divided by a cell- wall into two equal portions,
and, these segments separating from one another, two distinct
individuals are formed, each of which then continues to grow
until it has attained the normal size, when it also divides into
two, and so on. This mode of multiplication by cell-division
and the separation of the segments is very characteristic of
the bacteria which are in consequence often called the Fission —
or Splitting-Fungi (Schizomycetes). When, from the exhaus-
tion of the substratum or some other reason, conditions become
unfavourable for growth, the preservation of the plant is
insured by the formation of resting spores which can exist for
long periods without further development. In the formation
of spores the protoplasm of the individual cells rounds itself oil
and becomes surrounded by a specially thickened membrane,
each cell thus becoming a spore. On germination, the protec-
tive coat disintegrates and the cell proceeds to grow and form
new individuals by division as before. All species are not known
to form spores. There is no sexual reproduction and, when
spores are formed, no special spore-bearing organ is developed.
Many bacteria which can be destroyed by boiling after ger-
mination are able to resist high temperatures in the spore
condition. Hence boiling a substance or liquid once is by
no means always sufficient to sterilise it, i.e. to absolutely
destroy all life in it. The boiling should be repeated several
times, an interval of a day being allowed to elapse between
each operation, so that some of the spores which might have
survived the previous operations may have time to germinate.
Direct sunlight is, as a rule, prejudicial to the growth and
development of bacteria.

129

115. Bacteria are of great practical Practical
importance for the following reasons :-

(1) Many species possess the power of more or less de-

composing, and altering the composition of, the
material from which they obtain their food.

Bacterium acidi lactici breaks up milk causing it to
become sour.

Bacterium aceti, the Vinegar Bacterium, converts alco-
hol into acetic acid.

Bacillus vulgaris is the most common cause of the
decomposition of meat.

Such decomposing actions are sometimes spoken of as
decay or rotting, sometimes as fermentation, and
sometimes, owing to the evolution of evil-smelling
gases, as putrefaction.

(2) Many species cause very virulent and dangerous animal

diseases.

Bacillus tetani is found in the soil and causes tetanus.
Bacillus typlii causes typhoid fever.
Vibrio cholerae causes cholera.

(3) Many species help other plants to obtain the supply

of valuable nitrogenous materials which are neces-
sary for their existence.

Bacillus radicicola lives in tubercles on the roots of vari-
ous plants and is able to fix the free nitrogen
of the air and to pass it on in a form in which it
can be utilised by these plants, this source of
nitrogen being otherwise not available for them.

The so-called Nitrifying Bacteria live in the soil and con-
vert ammonia to nitrous and nitric acid. Nitrates are thus
eventually formed which are the most valuable source of
nitrogen for the majority of the higher plants.

It will be seen that, although bacteria are responsible
for many of the most virulent animal diseases, they seldom
affect other plants injuriously, this being partly due to the
difficulty which such minute organisms find in passing
through the cell walls of plant tissues.

116. Fungi. In this group are in- Fun?!-

eluded a great variety of plants which are popularly known by
various names, such as moulds, rusts, toadstools, mushrooms,

etc. They are of special importance to the Forester on
account of their being responsible for the majority of the
most destructive of known plant diseases. Some fungi are

130

very minute and with a structure scarcely more elaborate
than that of the bacteria. The common Brewers'-
Yeast Plant, for instance, consists of single, oval
cells, each cell having a diameter of about ~^ of an inch.
It can, however, be at once distinguished from the bacteria
by, among other things, its considerably larger size, its
peculiar mode of multiplication by what is known as budding,
or sprouting., and ' by the way in which the spores are formed
as will be clear from the life-history given below. The
majority of fungi, however, have a much more elaborate
structure than that of the simple Yeast Plant, and, although
they never show traces of leaves, there is commonly a more
or less clear differentiation into root-like and shoot-like portions.
Special spore-bearing organs are commonly developed and
sexual reproduction is often met with. Many of the simpler
forms resemble colourless alga3. Some fungi then are unicellular,
but the majority consist of slender, thin- walled, more or less
branched filaments, or tubes, called hyphae, which are only
capable of growing in length at their apices. These hyphae
may possess cross- walls which thus divide them into segments,
in which case they are said to be septate, or they may be
aseptate, i.e. undivided. The whole vegetative body of the
fungus consists of these hyphae and is called the mycelium.
This ramifies in the substance from which the fungus derives
its nourishment and absorbs the necessary food materials
from it and, like the roots of higher plants, usually remains
out of sight. Fungi are, therefore, best known by their
reproductive organs, which are developed at the surface of the
substance on which the fungus is growing, or on aerial bran-
ches of the hyphae. Sometimes the mycelium is superfi-
cial and only specially developed short branches of the hyphae,
termed haustoria, or suckers, penetrate the substance on which
the fungus is growing and absorb the necessary food
materials.

The mycelium may consist of a few delicate hyphae and
thus be invisible to the naked eye, or the hyphae may be
collected into dense masses and become visible in the form
of papery or skin-like membranes, or thick, felt-like sheets
and masses. In some species the slender thin-walled hyphae
are united into bundles, which are provided with a hard,
dark-coloured, protective coat. Such strands may some-
times be mistaken for the fine roots of higher plants, which
they resemble in general appearance, and they are, in conse-
quence, termed rhizomorphs. or root-like structures. Pro-

131

tected in these strands, the tender hyphae are able to spread
through areas which are unsuitable for their growth and
development, the hyphae being again extruded to absorb
nourishment when favourable conditions are met with.

The fungi may be divided into the following groups : — Classifica-

tion of

I. — Phy corny cetes. Fungi.

II. — Ascomycetes.

III. — Basidiomy cetes.

IV. — UstUaginaceae.
V. — Uredinaceae.

117. Phi/corny cetes. The hyphae are
generally aseptate. Mycelium does not form a compact m-7ce
mass. Sexual reproduction is common. The asexual spores
may be developed in spore-cases (— sporangia), the protoplasmic
contents of which divide up to form the spores, or the end cf
a hypha may swell up, the swollen tip eventually separating
from the hypha to form a spore, which, in such a case, is
called a conidium, • and the portion of the hypha on which it
is borne is called a conidiophore.

Phytophthora infestans causes the potato disease. This
has been selected as a typical example of this
group and its life-history is given in detail in Part
V below.

Other species of Phytophthora and species of Pythium are
very destructive to seedlings and to palm trees.

118. Ascomycetes. Hyphse are septate.

Spores are produced in a special kind of elongated sporangium
termed an ascus. The number of spores produced in an ascus
is almost always definite, usually eight, whereas in a sporan-
gium the number of spores is usually indefinite. In an ascus,
also, the protoplasmic contents are not all used up in the for-
mation of the spores, as is the case in a sporangium. These
asci may be without any covering, or may be grouped in
special structures, called the ascocarps, thus forming the ascus-
fruits. A completely closed ascocarp is called a cleistothe-
cium, one with a small aperture at the apex a perithecium, and
one which is open, saucer-shaped, or hat-shaped, an apothecium.
Sexual reproduction sometimes occurs.

Among the interesting fungi included in this group };

are the minute, unicellular plants known collectively as the

Yeast Fungi, or the Saccharomy cetes, which are capable of

causing the alcoholic fermentation of sugar solutions. \Ve

Jmow that, if the sweet juice extracted from the sugarcane

132

is not at once boiled and is left exposed to the air, the process
known as fermentation rapidly sets in and that if this is
allowed to continue we ultimately obtain in place of the sugar
solution one which contains alcohol, carbon dioxide gas being
evolved during the process. Yeast Fungi are therefore of
great commercial importance in the manufacture of wine
from the sugar in grapes, in the preparation of spirit from the
sweet-tasting mahua (Bassia latifolia) flowers and in the manu-
facture of wine, beer and spirits, generally. If the minute oval,
or spherical, cells of a Yeast Fungus are placed in a suitable
nutrient sugar solution they are found to grow and multiply
with great rapidity, the peculiar method of multiplication
being termed budding. The cell wall of the Yeast Plant
bulges out and a protuberance is formed which gradually
increases in size, the neck connecting it with the mother-celt
remaining narrow. A cell- wall is then formed across the
narrow neck at the point of union and the swollen protu-
berance, separating from the mother-cell, becomes a separate
cell which then behaves in the same way. When all the sugar
has become converted into alcohol and the food material is
consequently exhausted, the yeast cells can no longer continue
growing and budding and they proceed to form spores. The
protoplasm in each cell divides into four little blocks, each
block becoming a spore, which is eventually set free by the
disintegration of the wall of the mother-cell. Under favour-
able conditions each of these spores germinates and at once
proceeds to grow and bud off new cells as described.
Ferment It has been noted above that bacteria are capable

Qf causmg various kinds of fermentation but they do not
produce the alcoholic fermentation so characteristic of the
Yeasts. Plants, such as bacteria and fungi, which are able
to produce fermentation are known as Ferment Organisms
(sometimes also as Organised Ferments). Such plants appear
to owe their power of producing fermentation mainly to the
chemical substances known as Enzymes which they containr
and which, of course, are not living organisms. The action
of the Yeast on the sugar solution will be understood from
the following equation : —

(grape sugar) (alcohol) (carbon dioxide)

and it should be noted that, although the Yeast derives its
food f-rom the sugar, yet only a very small proportion of the
solution is actually utilised as food, the remainder being

133

decomposed and broken up into simpler compounds. Thus
only 5 per cent, of the sugar may be actually used as food
while 95 per cent, is reduced to alcohol and carbon dioxide.

Other interesting plants belonging to this group are
the species of Meliola which form sooty black patches of mould
on the leaves of various trees, e.g. the Sal, Mango^and Orange.
The mycelium is entirely superficial and does not penetrate
the leaves, the fungi living on the sweet juices excreted by
aphides, scale and other insects. These fungi, unless excep-
tionally numerous, do very little harm to the trees. Preven-
tive measures should aim at destroying the insects.

Rosellinia bunodes is a species which has been found to
be very destructive to forest trees, such as Litsaea angusti folia,
Schleichera trijuga and others, in Mysore and Assam.

The roots are first attacked and the fungus is best recog-
nised by the clusters of small, round, black perithecia, con-
taining the asci, which appear at the base of the attacked stems
just above the ground surface. These perithecia have a car-
bonaceous structure and appearance and can be crushed in
the fingers like fragments of coal.

119. Basidiomyceles. — This' group
includes the most highly developed forms of fungi among mycetes.
which are those commonly known as Mushrooms and Toad-
stools. The hyphse are septate. There is no sexual repro-
duction. The asexual spores are developed on elongated,
club-shaped, terminal cells of the hyphse, which are called
basidia. These basidia are usually placed close together, side
by side, and form the hymenium or hymenial layer. At the
top of each basidium are situated four spores, each on a little
stalk. This hymenial layer may be smooth and flat, it may
cover the sides of thin lamellae or gills, it may line the
interior of pores or tubes, or it may cover the surface of
raised spikes, knobs, or irregular folds. A large number of
species are known to be injurious to Indian trees, of which
only a few can be mentioned.

Armillaria mellea (perhaps better known as Agaricus mel-
leus) is a very destructive species in Europe and is believed
to occur in India.

In Europe it is particularly destructive to coniferous trees.
It is one of the few species characterised by the development
of rhizomorphs from which in this case the mushroom-like
spore-bearing organs, or sporophores, arise. The sporophore
consists of two principal parts, the stalk, or stipe, and the
umbrella-shaped cap, or pileus. On the under-surface of the

pileus are a number of radiating lamellae, or gills, the sides of
which are covered with the hymenial layer, on which the spores
are produced. The sporophores are usually found in clumps
near the base of the attacked tree — the pileus is yellowish, or
brownish, in colour, with dark scales, and the stipe bears a mem-
branous, collarlike ring. The sporophores are edible. The
mycelium forms firm white sheets between the bark and the
wood on the roots, or at the base of the trunk. The fungus
spreads by means of its spores, which are disseminated in
myriads as a fine white powder and which are capable of
producing a new mycelium, and also by means of the
rhizomorphs, which spread through the soil, bore into sound
roots and produce a vigorously growing mycelium in them.

Fomes annosus causes the well-known Deodar root-disease.

Trametes Pini has been found destroying Pinus excelsa.

The life histories of these two species is given in detail in
Part V below.

Much of the so-called " dry rot " of timber which has been
used in construction is, in Europe, caused by a fungus named
Merulius lacrymans, which is believed to occur also in India.

Fomes Pappianus is destructive to babul (Acacia arabica).

120. Ustilaginaceae.—Kyphdd are

septate. No sexual reproduction. The mycelium produces
dark-brown, or black, resting spores. Each of these on
germination produces a short tube from which numerous
small conidia called sporidia are abstricted. If supplied
with sufficient nourishment, as would be the case in a
field which has been manured, these conidia are capable of very
rapid multiplication, by budding, or sprouting, after the manner
of yeast cells. As the nourishment becomes exhausted, each
conidium develops a hypha, and proceeds to form the mycelium
which produces the resting-spores. These fungi are particularly
destructive to cereal crops, such as wheat, oats, maize, and
others, and are also found on many wild grasses, the mycelium
living in the tissues of these plants and ultimately developing
masses of dark-coloured resting spores. These characteristic
spores, resembling as they do a sooty powder, have caused the
fungi in this group to be characterised by the popular name of
smuts. Several fungi in this group, e.g. one of the commonest
species occurring on oats, are characterised by the fact that the
mycelium is only able to enter, and infect, the plants attacked
when the tissues of the latter are very young and tender, i.e.
shortly after the germination of the seed. Having once gained
an entrance, the mycelium of the fungus spreads through the

135

tissues of the plant attacked, and as the latter grows, the
mycelium grows along with it, without, however, so far as cne
can see, injuring the plant in any way. The presence oi the
fungus is indeed only made manifest to the ordinary observer
shortly before the time of harvest. The hyphae of the fungus
entering the flowers feed on and destroy the substances which
should have been devoted to the development of the grain, and
eventually, instead of the ripe corn, we find the soot-like masses
of resting spores.

Ustilago Maydis is common on maize in India and is easily
recognised by the boil-like swellings, or blisters, which may occur
on leaves, stem, flowers, or fruit heads. These blisters, .which
may attain the size of one's fist, contain the spores and, when the
latter are ripe, the blisters burst and the dark-coloured spores
escape. The maize heads are usually attacked and the grain,
is consequently destroyed.

121. Uredinaceae. Hyphse are,. ,.

septate. Sexual reproduction doubtful. The fungi included in
this group are characterised by their polymorphism. Several
kinds of spores are usually produced by them and their com-
plicated life-history will be best understood from the detailed
account of Puccinia graminis given below in Part V.

Owing to the frequent development of masses of orange-
yellow, or rust-coloured, spores, which give the appearance of
rusty streaks, or patches, on the leaves of the plants
attacked by them, these fungi, in contradistinction to those of
the previous group, are popularly known as rusts. A very
large number of these fungi occur on the leaves of our Indian
forest trees and shrubs, but, as a rule, they are not very
injurious and are, consequently, not of great importance. Only
a few of those which are most noticeable in the forest of the
North- West Himalaya will be mentioned here.

One of the most remarkable is that known as Bardaydla
deformans (formerly named Aecidium Thomsoni) which causes
the orange-red tassels so frequently seen in the forests of
Jaunsar-Bawar on the spruce, Picea Morinda (see Plate XV,
Fig. 1 (a) and (b) ). Only the current year's shoots are attacked,
these being "stunted, thickened and densely covered with
curved needles." Every needle on the attacked shoot is affected
and they afford a striking contrast to the straight-, healthy
needles. The masses of orange-red spores (teleuto-spores)
form " two continuous flattened beds on the upper surface "
and two smaller beds on the under-surface of the needles.
When young, the tassels emit a disagreeable odour. The

136

attacked shoots eventually shrivel up and turn black. As a
rule, the damage done is not great, the leading shoot not being
often attacked. The teleuto-spores may, also, be sometimes
found on the cone scales (see Fig. 1 (b) ).

The needles of Pinus longifolia, the chir, are often seen to
produce prominent, flattened, reddish-yellow blisters, usually
about one-fifth of an inch long and one-tenth of an inch high.

Those contain the spores (secidiospores) of the fungus
Peridermium complanatum. The mycelium lives in the
needles, but not much harm results. Sometimes the orange
blisters may be seen on the stem, or young branches, and as, in
such cases, the mycelium destroys the cambium and young
cortex the damage is more severe. This form on the
stem is considered to be a variety of the above fungus and
is distinguished by the name of corticola.

Peridermium brevius (see Plate XV, Fig. 2) is a fungus closely
resembling the last which attacks the needles of Pinus excelsa.
The blisters are smaller than those caused by P. complanatum.
Chrysomyxa Himalense causes the very noticeable, orange -red
blisters often seen on the petioles of Rhododendron arboreum and
R. campanulatum.

Gymnosporangium Cunninghamianum (see Plate XV, Figs.
3 and 4) is an interesting example, inasmuch as it is one
of the many species known in this group, which, for its
full development and completion of its life-history, requires to
live on two distinct species of plants. Part of its life is spent on
the cypress, Cupressus torulosa, and the remainder on the pear,
Pyrus Pashia. On the small branches and twigs of the cypress
homisperical, or elongated, dark brown spore masses (teleuto-
spores) arise, which, during moist weather, swell up enormously
into gelatinous masses. These soon become yellowish in colour
owing to the germination of the teleuto-spores and the forma-
tion of small, orange-red conidia, called sporidia, which are
abstricted from the teleuto-spore germ-tube as described in the
case of the resting spores of the Vstilaginaceae. These
conidia are capable of developing a mycelium in the leaves of
the pear. These leaves ultimately produce conspicuous,
thickened patches which may be |" in diameter, orange-red
above and yellowish below. On the lower surface of these
patches, little tubular structures are found, 1 — 2-mm. long,
which are called the aecidia and in which the aecidiospores are
produced. These spores on germination infect the cypress.
This fungus does a lot of harm to young cypress seedlings and
plants in Jaunsar. It is thought that the eradication of the

137

pear near the cypress plantations would lead to the disappear-
ance of the pest, the fungus being then unable to complete its
normal life-cycle.

Perhaps the most remarkable rust of all is that called Gam-
bleola cornuta which is often seen on Berberis nepalensis in
Jaunsar and near Mussoorie. It produces clusters of long,
black, wavy hairs on the under -surface of the leaves and some-
times on the twigs. Each hair consists of chains of teleuto-
spores which adhere closely to one another (see Plate XV, Fig. 5).

122. Before leaving the great Lichens,
group of the Thallophytes, we must shortly consider

the curious plants called Lichens. The general
appearance of a lichen is well known, viz. that of a crust on
stones, earth, trees, etc., of an irregularly shaped, foliaceous
structure adhering loosely to the substratum ; or again, that
of a tufted, shrubby mass of elongated branching processes,
such as is often seen festooning the stems and branches of trees •
in cold damp forests of the Himalayas ; while others form
gelatinous, jelly-like masses. A lichen consists of two distinct
plants which live together, in partnership so to speak, one of
these partners being a fungus, usually belonging to the
Ascomycetes, and the other a minute alga. The green,
chlorophyll-containing cells of the latter are enmeshed in
the closely woven hyphae of the fungus, the latter being res-
ponsible for the general form and outline of the lichen. The
lichen is attached to the sub-stratum by root-like hairs, or
attachment organs, developed by the hyphae of the fungus.
The fructification of the lichen is developed by the fungus, but
the germinating fungus spores usually perish if unable to find a
suitable alga with which to enter into partnership. Lichens are
commonly reproduced by minute buds, each of which contains a
few algal cells entwined with hyphse. These are distributed by
the wind and grow into new lichens. The gelatinous lichens
are usually dark-brown, or olive-green, in colour, while others
;are usually greyish-green, or yellowish.

123. We now pass on to the Bryophytes.
second great sub-division of cryptogams, viz. the BRYOPHYTA.

The plants in this sub-division are divided into two groups :—

(1) The Liverworts (Hepaticae).

(2) The Mosses (Musci).

Liverworts are minute plants of no forest importance which Liverworts,
may be found growing in damp soil, on rocks, tree-trunks and
even in the water. Many of them show no differentiation
into stem and leaves and possess a lobed thallus, thus resem-

138

bling the Algae. They are included in the Bryophyta mainly
on account of their life-history and the structure of their
reproductive organs. Those which possess leaves usually have
the leaves inserted in two rows.

Mosses. The mosses are small herbaceous plants, showing a distinct

differentiation into a slender, often wiry, stem and small
green leaves, which are commonly found growing in damp
shady places, on the ground, on trees, rocks, etc.

The leaves are usually arranged spirally and not in two rows
as in the Liverworts. They possess no true vascular bundles,
and consequently the leaves, which have a very simple
structure and are usually only one cell thick, exhibit no distinct
venation, although a rudimentary midrib may be present.
The roots of these plants do not possess the elaborate structure
of true roots, but are very simple organs, consisting of single
rows of cells and are known as rhizoids. The characteristic
fruit of a moss is a stalked capsule, called the sporogonium,
which contains microscopic spores. These, on germination,
develop a growth of minute green filaments called the protonema,
on which buds arise. From these buds are produced what we
know as the moss plant. The microscopic reproductive organs
arise in groups at the apex of the shoot, or in the leaf axils.
The male organs, termed antheridia, are stalked and club-
shaped and contain a number of small cells. When mature the
antheridium ruptures at the apex and expels these cells.
Each of the latter then liberates a minute twisted filament
called the spermatozoid which is provided with two long
cilia. The female organs, termed the archegonia, are flask-shaped
with a slender neck. The dilated basal portion contains a
, naked mass of protoplasm called the egg-cell, or oosphere, which
lies in the bottom of the archegonium like jelly in a flask. The
spermatozoids, swimming by means of their cilia, in the dew or
rain water with which the sponge-like moss tufts are so often
saturated, reach the archegonium, pass down its neck and one of
them penetrates the oosphere. With the fusion of the proto-
plasm of these two bodies fertilisation is accomplished and the
fertilised oosphere, which is now called the oospore, surrounds
itself with a cell-wall and at once begins to grow and to divide.
After the first cell-division has taken place, the body is no longer
called the oospore but the embryo. By further growth and
division this embryo eventually develops into the sporogonium,
bearing the well-known moss-capsule at its apex and with its
foot sunk in the tissues of the moss plant. The capsule itself
is called the them and it is often provided with a long stalk called

139

the seta. In this capsule are produced the asexual spores. As
the embryo develops in the archegonium, the wall of the latter
is stretched and eventually ruptures, a portion of the torn
investment being carried up on the capsule, as the seta
elongates, and thus forms the cap, or calyptra. The capsule is
usually closed, until ripe, by a lid called the operculum and a row
of minute teeth, called the peristome, is often found fringing the
upper edge of the capsule inside, just below the operculum.
We thus see that there are two distinct stages in the life -history
of a moss, the general form and appearance of the plant varying
considerably in the two stages. There is thus the sexual stage,,
the ordinary moss -pi ant, which arises from the asexual spore
and produces the sexual reproductive organs. As a result
of the sexual process of fertilisation, the oospore is formed, and
with this commences the asexual stage which ends with the
production of asexual spores. Each of these stages is called a
generation, and when they alternate regularly, as in the moss^
the phenomenon is termed an alternation of generations. The
sexual generation is called the Oophyte, or Egg-plant, and the
asexual the Sporophyte, or spore-plant. The former arises from
a spore produced asexually, the latter from a spore produced
sexually. The life-history of the moss may be shortly expressed
as follows : —

Sporophyte Oophyte

Spore — — ^-Protonema

I
Moss Plant

c? antheridia $ archegonia

! I

spermatozoid = oosphere

Sporogonium^— — -oospore

124. We now come to the third Pterido-

and last great group of cryptogams, viz. the PTERIDOPHYTA. P^*63-
The plants in this group exhibit a distinct differentiation
into root, stem and leaves and possess true vascular bundles,
while in the case of these plants, as in the Bryophyta, Ferns,
there is a distinct alternation of generations. The plants
of most forest importance included in this group are those
known as the Ferns (Filices). The leaves of ferns are called
fronds, their venation is usually furcate and their vernation
circinnate. The young stem and leaf-stalks are usually

140

provided with remarkable, brown, scaly hairs called ramenta.
The primary root does not persist and form a tap root, but
soon dies back, its place being taken by adventitious roots
springing from the stem or leaf-stalks. Most ferns are her-
baceous with a creeping rhizome of which the common bracken
(Pteris aquilina) is a good example and which sends up each
year one or more large fronds. Others, however, are known as
Tree Ferns and attain a height of some 50 feet and a diameter
of 1 foot with fronds 12 feet in length. In their general
appearance these Tree Ferns resemble some species of Palms
with their unbranched stems and terminal rosettes of large
pinnate leaves. The venation and vernation of the leaves,
however, is usually very characteristic, while the stem
exhibits a different structure from those of other woody plants.
The stems of the Pteridophytes contain no permanent cam-
bium and hence there is no secondary growth in thickness.
The closed vascular bundles are usually concentric and
arranged more or less in a circle. A section across the stem
of a Tree Fern therefore shows :— -

(1) A central portion of cellular tissue which often decays

and leaves a hollow in old stems.

(2) An outer mass composed of the bases of the fallen

leaves and adventitious roots.

(3) An intermediate zone between (1) and (2) containing

the closed vascular bundles, each of which is
usually crescent-shaped with a dark-coloured
border.

On the fern fronds and usually on their under-surface
are produced the little capsule-like spore-cases, or sporangia
which to the unaided eye look like little granules. Those
leaves which bear the sporangia are distinguished from the
barren fronds by the term sporophylls ( — spore-bearing leaves).
The sporangia are usually collected in groups, each group being
termed a sorus, and in many cases they are protected when
young by an outgrowth of the leaf-tissue called the
indusium. The rupturing of the sporangium results in the
dispersal of the microscopic spores, each of which, on germina-
tion, is capable of producing a small, flat, usually heart-shaped
structure called the prothallium, which resembles a minute
cordate leaf and is usually considerably less than an inch in
diameter. This usually contains chlorophyll, and, developing
numerous root-hairs from its under-surface, becomes free
from the spore. On the under-surface of the prothallium
arise the microscopic reproductive organs, termed antheridia

141

and archegonia, which are, in the main, similar to those
described above for the mosses, only of somewhat simpler
structure. The oosphere contained in the archegonium, on
being fertilised by one of the spermatozoids liberated by the
antheridia, becomes an oospore, surrounds itself with a cell
wall and proceeds at once by growth and cell-division to develop
into the young fern plant. The latter remains attached to-
the pro thallium by a special organ termed the foot, by means
of which it obtains its nourishment from the prothallium
until, with the development of its own leaves and roots, it
becomes independent and then the prothallium withers and
dies. The oophyte in the fern, therefore, is represented by
the prothallium, while the fern plant itself is the sporophyte.
The prothallium of the Pteridophyta is consequently homo-
logous with the protonema and what we call the ' ' plant ' ' of
the Bryophyta, while the ' ' plant ' : of the Pteridophyta is
homologous with the sporogonium of the Bryophyta. The
life history of the fern may be shortly expressed as follows : —

Sporophyte Oophyte

Spore _ Froth allium

d" antheridia ? archegonia

spermatozoid = oosphere

Fern Plant<— —oospore

It should be noted that in both the Bryophyta and
Pteridophyta water is necessary for fertilisation, to enable the
spermatozoids, which swim in the wrater, to reach the arche-
gonia.

The Pteridophyta are usually sub-divided into the follow-
ing three groups : —

1. Ferns proper. Plants with well-developed large classification

leaves. Sporophylls are usually similar to the of Pterido-
foliage leaves and are not aggregated into cone- Phytes-
like structures. Each sporophyll usually bears
numerous sporangia.

2. Horsetails. Plants with well-developed stems with Ferns,

distinct nodes and internodes, more or less ribbed •horsetails,
and with small leaves in whorls, forming a sheath
at each node. The small peltate sporophylls are
aggregated into a cone-like flower at the apex of
each fertile shoot.

142

3. Club-mosses. Plants with numerous small scattered
leaves. Sporophylls resemble foliage leaves but are
sometimes aggregated into conelike flowers.
Sporangia are borne singly either on the upper
surface of the sporophyll, or on the stem.

Now, in the true ferns, the asexual spores are all alike and
one and the same prothallium bears both antheridia and
archegonia. In some Pteridophytes, however, the spores
are of two kinds, the larger ones being termed macrospores
and the smaller ones microspores. These are contained in
separate sporangia which are called, respectively, macrospor-
angia and microsporangia ; the leaves bearing the former
being the female sporophylls and the leaves bearing the latter
the male sporophylls. From the macrospore is developed a
female prothallium which produces only archegonia and
from the microspore a male prothallium producing only antheri-
dia. Moreover, in such plants, the prothallium is in every
case pulled further back into the spore, from which it now
never becomes independent, as we have seen to be the case
in the ferns. The male prothallium in particular becomes
very much reduced and consists of only a few cells. Moreover,
in the Horsetails and some Club mosses the sporophylls are
aggregated into small, cone-like flowers. These plants thus
lead us up to the great group of the most highly developed
plants, known as the :—

125. Phanerogams. — This contains

all the plants which are not included in the groups already
enumerated and briefly described above, and hence it
includes practically all our forest trees and shrubs. These
plants exhibit a distinct differentiation into true root, stem
and leaves, and possess true vascular bundles. They are
characterised by the production of true seeds., and the
majority possess flowers containing structures which we at
once recognise as stamens and carpels. In Phanerogams,
as in the higher Cryptogams, there is an alternation of
generations, although at first sight this is not obvious,
owing to the great reduction in the oophyte, that which
we see and recognise as the ' ' plant ' : being the sporo-
phyte. The various organs and members of phanerogamic
plants were described and received definite names when the
life histories of most of the cryptogams were very imperfectly
known. This led to different names being given to organs
which are really homologous and this has resulted in further
obscuring the resemblances between the plants of these two

143

great groups. Thus we find that the male and female
sporophylls of phanerogams are called stamens and carpels
respectively. The sporophylls with the portion of the shoot
on which they are borne constitute the flower, while in many
cases other leaves surround the sporophylls and form a perianth.
The microsporangia are the pollen-sacs., the macrosporangia,
the ovules. The microspores are the pollen grains, the
macrospore is the embryo-sac ; both kinds of spores containing
as usual a single nucleus, the division of this nucleus in each
case is the first step towards the formation of a prothal-
lium (i.e. the oophyte). The male prothallium is always
minute and consists of only a few cells, the most noticeable
portion of it being the so-called pollen-tube. Spermatozoids
are rarely formed and are usually represented by two small,
naked, nucleated, male cells which travel down the pollen
tube and eventually pass out at the apex. The cells arising
from the repeated nuclear division in the macrospore consti-
tute the female prothallium, which is sometimes large and
forms the tissue known as endosperm. In the prothallium
an oosphere arises, either as a naked cell, or in an arche-
gonium. Fertilisation is accomplished with the fusion of the
nucleus of a small male cell with that of the oosphere ; while,
from the resulting oospore, the embryo, or young sporophyte,
is produced. Here then the prothallium never has an in-
dependent existence apart from the spore which has pro-
duced it. The female prothallium remains altogether inside
the macrospore, the latter remains inside the macrospo-
rangium, and the latter remains for a long time attached to
the parent plant or sporophyte. Eventually the whole
macrosporangium with the macrospore and contained embryo
separates from the parent plant as the seed. Thus the
oophyte does not form a distinct and separate stage in the
life history. The embryo during its growth and development
frequently absorbs the rest of the tissue formed in the
macrosporangium and consequently the kernel of the ripe seed
consists of the embryo alone. In such cases the seed is said
to be eocalbuminous. In other cases some of the tissue of the
macrosporangium persists in the ripe seed and the latter is
said to be albuminous. Such persistent tissue is distinguished as
endosperm, or perisperm, according as it has developed within,
or without, the macrospore. See also p. 58. Phanerogams
are divided into the two following main divisions : —
I. Gymnosperms.
II. Angiosperms.

144

Gymno-
sperms.

Cycadace*.

126. Gymnosperms. The ovules are

naked and not enclosed in an ovary. The pollen grains
are thus able to come directly in contact with the micropyle
of the ovule. The oophyte developed by the macrospore is
represented by a mass of tissue which completely fills the
macrospore (embryo sac) and is called endosperm. The
oosphere is contained in an archegonium. There is no
distinct perianth to the flower. The flowers are unisexual.
Cotyledons, two or more, usually appearing above ground
on germination, are perennial trees and shrubs, usually resin-
ous. Leaves are often acicular. The primary root persists
and forms a tap-root. The vascular bundles are open, col-
lateral and arranged in a circle round the pith. Secondary
growth in thickness takes place by means of a normal cambium
ring and the stem consequentlv exhibits a central pith, with
distinct bark and wood, while it increases in size by rings of
new growth added at the outside of the wood-cylinder and
immediately beneath the bark. True vessels are not present
in the wood except in that of Gnetaceae. Gymnosperms are
sub-divided into the following three orders :—

Cycadacese.

Conifers.

Gnetacea3.

127. Cycadaceae. In this order are

included the plants which are often seen in Indian
gardens and are sometimes wrongly called the Sago Palms.
The columnar, usually unbranched, stem with the
terminal rosette of large pinnate leaves of these plants
gives them a superficial resemblance to the Palms.
In India they rarely attain a greater height than 30 feet.
The wood is characteristic owing to its possessing alternate
layers of woody and bast tissue with no true vessels, and the
pith is usually large. The flowers have no perianth and are
dioecious. They are situated at, or near, the apex of the
stem, the male flower being a cone with a number of thick
scales, on the under-surface of each of which are situated
numerous pollen-sacs. In the female Cycas tree the charac-
teristic macrosporophylls, or carpels, arise on the apex of
the main stem, taking the place as it were of the foliage leaves.
Although smaller and not green, these carpels somewhat
resemble the foliage leaves. The upper portion of the carpel
is pinnate, the ovules, wrhich may attain the size of small
plums, being borne laterally on the basal portion in the posi-
tion of leaflets. Cycas Rumphii, and C. pectinata are well-

145

known Indian trees, from the stems of which sago or starch
is obtained.

128. Coniferae. These include Conifer®.

much branched woody plants with undivided, usually acicuiar,
leaves. The wood does not contain true vessels but often
possesses resin ducts. The flowers have no perianth and are
usually cones, i.e. shoots carrying scale-like sporophylls, the
latter bearing the ovules and pollen-sacs. In this group
are included very many important forest-trees such as the
Pines, Firs, Spruces, Cedars, Larches, Cypresses, Junipers
and others.

129. Gnetaceae. The leaves are un- Gnetaceae.
divided, often broad and usually opposite. The stem and
branches are jointed at the nodes. The flowers are not cones,

they have a rudimentary perianth and are usually arranged in
slender spikes. The wood contains true vessels.

Ephedra Gerardiana is a small, apparently leafless, shrub,
fairly common in Jaunsar.

Several species of Gnetum occur in India. They are
generally climbers with broad, well developed, opposite leaves.

130. Angiosperms. The macrospo- Angiosper
rophylls, or carpels, form closed cavities called ovaries, within
which are contained the ovules. The pollen is received not

on the micropyle of the ovule, but on a specialised portion of
the carpel called the stigma. The oophyte developed by the
macrospore is small and consists of only a few cells which are
usually without cell-walls, one of these naked cells being
the oosphere. After fertilisation has taken place,
however, the cavity of the spore becomes filled with
tissue which has also been called endosperm, but which is
clearly not the same, morphologically, as the endosperm of
Gymnosperms which is developed before fertilisation. The
flowers are, typically, hermaphrodite with a perianth. The
Angiosperms are sub-divided into two groups : —

Monocotyledons.

Dicotyledons.

131. Monocotyledons. The embryo Monocoty-

has typically one cotyledon which usually remains below the ledons-
ground. These plants are usually herbaceous and are
rarely shrubs (species of Smilax for example), or trees
(Palms and Bamboos). The flowers have their parts typically
in whorls of three. The leaves usually have parallel
venation. Species of Smilax and Dioscorea are the most
important exceptions with reticulate venation. The leaves

146

are usually without stipules, with a well-developed leaf base
and not disarticulating readily from the parent axis. The
primary root soon dies and its place is taken by adven-
titious roots which arise successively higher and higher on
the stem. The collateral, closed vascular bundles are scat-
tered irregularly through the stem. Secondary growth
in thickness rarely occurs, but when it does and a cambium
ring is present, the latter does not form a continuous ring
of wood on the inside, but produces closed vascular bundles
scattered in fundamental tissue. Perennial stems usually
have no distinct bark, no annual rings, and no medullary
rays, but possess true vessels.

Dicotyle- 132. Dicotyledons. Embryo has

dons. typically two opposite cotyledons which may remain within

the seed, or become green and appear above the ground in
germination. These plants are herbs, shrubs or trees. The
ilowers have their parts usually in whorls of 5 or 4. The
leaves generally have reticulate venation. The leaves often
have stipules, rarely have a conspicuous sheathing leaf-base,
and usually disarticulate freely from the parent axis. The
primary root usually persists to form a tap root. The collateral,
open vascular bundles are arranged in a circle. Secondary
growth in thickness takes place in perennial stems by means
of a complete cambium ring which continually forms woody
tissue on the inside and cortical tissue outside. Perennial
stems usually possess distinct bark, annual rings, medullary
rays and numerous vessels.

Synopsis of 133. The following Key will now

theSub-divi- help us to bring into focus the principal groups of the Vegetable
which we have considered above : —

Kingdom.

CRYPTOGAMS. Plants not forming true seeds.

(" Algae . . Plants contain-

THALLOPHYTA. ing chloro-

phyll, chiefly
aquatic.
Cellular plants with no differentia- -^ Bacteria. -• Very^

tion into stem and leaves. An

altogether wanting or irregular.

minute plants i Colourless plants

alternation of generations is multiplying by L without

splitting. i chlorophyll.

L Fungi. J

BRYOPHYTA.

f Mosses . .~] Plants contain-
| Liverworts. — i ing chloro-

•Cellular plants usually showing a | ^mute plants | phyll.

differentiation into stem and j
leaves, and with a distinct alter- |
nation of generations, the t
oophyte constituting "the I
plant."

PTERIDOPHYTA.

"Plants showing a differentiation
into stem and leaves. Possess
true vascular bundles, and
with a distinct alternation of-
generations, the sporophyte con-
stituting the " plant." Chiefly
herbaceous. Only a few of the
Ferns attain the dimensions of
trees.

often with no f- Chiefly terres-
| d i S e rentiation I trial.
i into stem and I
L leaves J

f Ferns. — Plants with relatively large

leaves. Sporophylls are not

aggregated into cones.
Horsetails. — Plants with distinct

nodes and internodes and small

leaves in whorls. Peltate sporo-

phylls aggregated into cone -like

flowers.
Club-mosses. — Plants with small

scattered leaves. Sporophylls

resemble foliage leaves, but are
sometimes aggregated into
cone -like flowers.

PHANEROGAMS. Plants forming true seeds.

GYMNOSPERMS.

Ovules not enclosed in an
Trees and shrubs.

ANGIOSPERMS.

or
no

fCycadaceae. — " Sago Palms
Cycads. Flowers have
perianth and are usually cones.
Ccniferae. — Freely branching trees
ovary. •{ and shrubs. Flowers cones with

no perianth.

Gnetaceae. — Flowers are not cones
and have a rudimentary
^ perianth.

r Monocotyledons. — Embryo with one
J cotyledon.

Ovules enclosed in an ovary. ] Dicotyledons. — Embryo with two
Trees, shrubs and herbs. L opposite cotyledons.

148

CHAPTER III.— THE ORIGIN OF SPECIES.

struggle for 134. On all sides around us, in

existence, nature, the great battle of life is always going on, or,
as it is often termed, the struggle for existence. On all
sides we find organisms directly destroying others, carni-
vorous animals preying on other animals, some plants, such
as fungi, killing and feeding on other plants, while every-
where animals are found injuring and destroying plants.
Not so obvious, but no less severe, is the competition
between similar organisms for the same kind of food. This
is usually most severe between organisms which require the
same food materials and similar external conditions for
their existence. To realise this we have only to watch the
development of crowded seedlings in a nursery seed-bed,
or in the forest. The roots of all are ramifying in the same
layers of soil and are competing with each other for the same
moisture and the same solutions of mineral salts — the stems
of all are competing in their endeavours to expand their green
leaves in the same light and air. Some individuals are soon
seen to be growing more slowly than their vigorous neigh-
bours— their leaves turn pale, their steins grow weak and
finally they die, while the seedlings around soon cover over
the gaps caused by their disappearance, leaving no trace
of those which have been starved and killed. The Forester,
therefore, in order to secure the best development of the
individuals belonging to his valuable species, is obliged to
interfere in this struggle between plant and plant and to
transplant his seedlings and to clean and thin his young
woods. Realising, also, that the competition between plants
belonging to different species is often scarcely less severe, he
takes measures to prevent undesirable species interfering
with the healthy development of his valuable trees, while
the agriculturist carries out essentially similar operations
in his fields, by eradicating the "weeds" which, year after
year, appear, in addition to those plants which alone he wishes
to cultivate. In order to maintain itself, also, every organism
is obliged not only to fight against other living organisms,
but, in addition, to struggle against the unfavourable
factors of its non-living environment, e.g. climatic influences,
great heat and cold, drought, excessive moisture, and so on.
The importance and universality of this natural phenomenon
of the struggle for existence is perhaps best realised by a

consideration of the great powers of increase possessed by all
living organisms. It has been calculated, in the case of a small
herbaceous plant, about two feet in height, which produces
on an average 10,000 seeds annually, that, if all the seeds
developed and produced fertile plants, each of which in their
turn ripened a similar number of seeds and so on, all the
dry land on the earth would be completely occupied
by such plants at the end of five years. Many plants, also,
produce a greater number of seeds than the example given,
and an ordinary Tobacco plant is calculated to produce, on
an average, 360,000 seeds annually. That no single species
is able to actually monopolise the earth in this way is due
to the struggle for existence.

" While the offspring always exceed the parents in num-
ber, generally to an enormous extent, yet the total number
of living organisms in the world does not, and cannot, increase
year by year. Consequently every year, on the average, as
many die as are born, plants as well as animals ; and the
majority die premature deaths. * * There is thus a
perpetual struggle among them which shall live and which
shall die ; and this struggle is tremendously severe, because so
few can possibly remain alive."*

135. It has been noted above that importance

in many Floras all sub -divisions of the species are indiscri- of s?b~
minately termed varieties. Obviously such varieties are by no
means all of the same value. We may find that the distinguish-
ing characters of a particular variety are always, under
varying conditions of existence, transmitted unchanged from
the parent to its immediate offspring, that the variety is,
in fact, a true sub-species. Since the characters which
distinguish a particular sub-species from the rest of its species
may include the power of producing a valuable commercial
product, immunity from particular forms of injury and
disease caused by fungi, insects or other injurious factors such
as frost, and so on, a knowledge of such sub-species is
obviously of great importance for the Forester, as well as for
the Gardener and Farmer. Many races, again, the distinguish-
ing characters of which only remain constant under cer-
tain conditions of existence and which are therefore of sub-
ordinate importance in nature, are of considerable importance
in cultivation where the conditions of their existence can be
regulated so as to keep their characters constant. The
selection of the most suitable sub-species and races for culti-

* Darwinism — by A. R. Wallace, page 11.

150

vation, therefore, plays a very important part in modern
agriculture and horticulture. In a single field of wheat, or
other cereal, several different sub-species may, and usually do,
co-exist. The most desirable of these may be observed to
constitute a very small proportion of the crop when culti-
vated without special care. The reason for this is usually
to be sought in the struggle for existence, the conditions being
more favourable to the less valuable sub-species and thus
enabling them to overcome and kill out their less vigorous
neighbours, just as we have seen to be the case in a crowded
seed-bed, and this is especially the case in unfavourable
seasons. The Farmer, therefore, carefully isolates and saves
the seeds of the desirable sub-species, say those with the
largest ears and the biggest, most numerous grains, and cul-
tivates it separately, treating all other kinds of the cereal
as weeds, and endeavouring, as far as possible, to eliminate
them from his fields.

Again the distinguishing characters of some races of plants
do not remain constant when they are grown in the vicinity
of other plants by which they are easily fertilised. This
does not prevent such plants being of great value to the horti-
culturist who endeavours to isolate such races and to pre-
vent, as far as possible, intercrossing with allied plants. The
beds in which such plants are grown, however, can rarely
be separated sufficiently to prevent occasional crossing by
bees, which carry the pollen from one to the other.

Frequently, therefore, the seed of some of our best garden
flowers, as sold in the market, cannot be guaranteed as pure,
some of the resulting seedlings invariably showing aberrant
characters, owing to their parents having been crossed by
allied forms.

136. Plants raised from the seed

Hybrids, produced by the crossing of two plants belonging to distinct
species, or varieties, are called hybrids, or bastards, and
are usually distinguished as species-hybrids and variety-
hybrids. Very commonly the crossing of individuals belong-
ing to distinct species is accompanied by entire or
partial sterility, i.e. there is less chance of fertile seed
resulting from the cross and of fertile individuals being deve-
loped from such good seed as may have been produced,
than is the case in normal fertilisation. Such sterility varies
greatly in degree, for while crosses between very nearly related
species, or between varieties of the same species, may be,
and usually are, perfectly fertile, crosses between specieSv.

151

which are not closely allied are characterised by a consider-
able degree of sterility and are often entirely sterile. As
fertilisation consists essentially in the union of two sexual
cells, a portion of the protoplasm of each cell entering into
the constitution of the embryo which results from such a
union, we should naturally expect the distinguishing charac-
teristics of each parent to become more or less apparent
in the hybrid. This is the case and the hybrid is found either
to be intermediate between the parents, the characters of
both parents being combined in it, or else to resemble one
parent more than the other. Occasionally also it may pre-
sent entirely new characters. In some cases the result of
hybridisation is different according to which parent is chosen
as the father or mother respectively. Thus a cross may
only be possible when an individual of a certain species is
always chosen as the father, the reciprocal cross with the
same individual as the mother being sterile.

Again, the hybrid in some cases is always found to re-
semble one parent, e.g. the father, more than the other. Fertile
hybrids are those which, when fertilised by their own
pollen or by that of another individual of the same hybrid
cross, produce fertile seed from which fertile plants are
developed. Fertile hybrids may be constant, as regards their
distinguishing characters, from the first, but in the majority
of cases they are found to split, i.e. to revert to the parent
forms in subsequent generations. In such cases of reversion,
however, a few individuals are often found which remain
constant hybrids, with characters distinguishing them from
both parents. A hybrid may be successfully crossed not
only with another hybrid but with one of its parents ; if this
is repeated, the derivative hybrid obtained from such a cross
being again crossed with the same parent and so on, the off-
spring are found to resemble that parent more and more,
and finally to completely revert to it. The hybrid, instead
of being crossed with one of its parents, may be crossed with
an individual belonging to an entirely distinct species and
this operation may also be repeated. In this way it has
been found possible to obtain a derivative hybrid in which
the characters of six, or even more, different species are com-
bined. Hybrids occur in nature but not very frequently ;
probably this is partly due to the fact that, in the majority
of cases, where the flowers of a plant are simultaneously pol-
linated by different plants, the pollen o£ an individual belong-
ing to the same species is prepotent, i.e. it is able to accom-

152

plish fertilisation quicker than the pollen of plants belonging
to different species. The action of such foreign pollen being
thus excluded, hybridisation is prevented. In other cases
the plants resulting from hybridisation may be unable to
establish themselves in nature, owing to the severity of the
struggle for existence with other plants. Among the char-
acters which are frequently, possessed by hybrids and which
serve to distinguish them from their parents are an increased
tendency to variation, a more luxuriant and vigorous vege-
tative growth, and larger, more brilliantly coloured flowers,
which also often tend to become double. For this reason
alone hybrids are important in horticulture. The great
importance of hybridisation, however, depends chiefly on the
fact that it affords a means of combining in one plant the
valuable attributes of several, and a species yielding a valuable
commercial product which is liable to damage by frost, or to a
particular form of disease, may thus be rendered hardy by
crossing it with an allied, but hardy, species, the hybrid off-
spring, while yielding the valuable product of one parent,
possessing also the hardy attributes of the other. If such
a desirable hybrid is obtained it would of course be carefully
isolated and cultivated in such a way as to prevent, as far
as possible, intercrossing with other plants. At the same
time it must be remembered that the practical attainment
of such a result is attended with great difficulties, the greatest
obstacles to successful work in this direction being the
inconstancy of many hybrids and the comparative sterility
of others. For successful hybridisation the flowers of the
plant chosen as the mother (if hermaphrodite) should be
deprived of their stamens before the latter are mature, the
flowers then being covered with paper caps to prevent the
access of insects and possible fertilisation by the pollen of
other plants. With a clean camel-hair brush the pollen is
then taken from the plant selected as the father and gently
and lightly applied to the stigmas of the protected mother
flowers. The caps are then replaced on the latter. If the
cross has been successful the flower will quickly wither, and
if this does not occur the cross should be repeated.

137- If we examine a large number
Variability, of adult plants all raised from the seed of a single
individual, we shall find a few exceptionally tall, and
a few exceptionally short, specimens, while the great
majority will be seen to be intermediate between these two
extremes, of moderate, or medium height, and differing very

153

slightly from each other in this respect. A large number
of adult men placed in a row would give a similar picture
•of variability. Again if we examine and carefully measure
the leaves on a tree, we find a few unusually large, and a few
unusually small, specimens, while the great majority are
intermediate and of moderate dimensions. The-same thing
•occurs in the shape and size of seeds and fruits. Numbers
also vary in the same way, as is seen in the number of lateral
veins in leaves and leaflets. Small numbers, however, are
usually more constant than large numbers and a considerable
degree of constancy usually characterises the numbers of the
different floral organs. Such characters as the percentage
of sugar in the sugarcane, or of starch in potatoes, as well as
the power of resistance to frost, and so on, obey the same rule,
and we may say that this phenomenon of Fluctuating Vari-
ability is almost universal. This type of variation is obviously
•directly dependent to a great extent on nutrition, and therefore,
indirectly, depends on the factors which together constitute the
plant's environment. On vigorous, well-nourished coppice
shoots the leaves are as a rule considerably larger than on
normal branches, while gardeners know that, by diminishing
the total number of flowers or fruits on a plant, and by thus
increasing the amount of food available for the remainder, the
size of the latter can be materially increased. The various
factors of the environment also Have a marked effect. A plant
accustomed to a damp locality, on being transferred to a dry
one, may be so changed in appearance as to resemble another
species. In such cases the size of the leaves and the
growth in length of all shoots are often greatly reduced
and thorns and spines are frequently developed. The common
Brinjal (Solanum Mdongena), for instance, when cultivated in a
well-watered garden, has large leaves which are often almost
unarmed. It may, however, be often seen as an escape from
cultivation, in dry rocky places, with small and intensely
prickly leaves. In India also we have several examples of
plants which, in dry localities, are erect shrubs, or small trees,
and in damp situations climbers — such as Toddalia aculeata and
Alangium Lamarckii. The nature of the soil also frequently
appears to affect plant characters, and individuals growing in
soil containing large quantities of lime, or other substances,
may differ very considerably from individuals of the same
species growing in ordinary soil. Light is also a factor affect-
ing the form of plants, although it is sometimes difficult to
•decide how far an observed result is to be ascribed to any one

factor, such as light, and to what extent other factors, such as-
available moisture, may have contributed to it. In shady situ-
ations, in the case of one and the same species, not only may
leaves be found to be thinner, and often of a different colour,,
consistency, size, and shape, than they are in places exposed to
bright sunlight, but their anatomical structure may also be
fundamental i y changed, and we find sun-leaves with an epidermis
devoid of chlorophyll, provided with a thick cuticle, and with
well-developed palisade tissue, while shade-leaves often have
no palisade tissue and an epidermis with very thin walls and
provided with chlorophyll. Anatomical variations also may
be found in the petioles, stems and roots. Cases are known
of so-called dimorphic species which are able to maintain
themselves on high mountains and also in the lowlands, or
on dry land, as well as under the water, and variability is
thus seen to be a very useful character, inasmuch _ as vari-
able plants are thus enabled to adapt themselves to varying
conditions of existence and to widely extend their area of
distribution. Variations of the kind now under discussion
appear to us to be temporary and inconstant, and individuals
belonging to the alpine — or aquatic — form of a dimorphic
species, after existing for many generations on the moun-
tains or under water, are found to assume the characters
of the lowland — or terrestrial — form, respectively, when cul-
tivated in the plains or on dry land. At the same time cases
are known in which plants .under the influence of certain con-
ditions have undergone a slow but progressive change and
have thus acquired definite characteristics which have
become constant and hereditary. With regard to this point
the study of bacteria is of special value seeing that, in their
case, " experiments can be readily extended

over a far greater number of generations than in the case of
flowering plants, for a bacterium which divides once an hour
passes through as many generations in ten days as an annual
plant does in 240 years."* By continued cultivation under
special conditions, it has been found possible to permanently
eliminate in certain species of bacteria the power of producing
poisons, pigments, and even the important character of the
power of spore production. Such changes do not occur sud-
denly, but only gradually become fixed and hereditary and
if, after short exposure to the special conditions, the bacteria
are returned to their original environment, the power of pro-

* Physiiogy of Plants, by Dr W. Pfeffer, Volume 11. pages 192—193.

155

ducing poison, pigment, or spores, returns. Attention has
hitherto been confined to the so-called fluctuating variability,
and it must be remembered that, although in a series of such
variations, the two extreme forms may be widely dissimilar,
these are always linked together by a number of intermediate
forms which differ very slightly from each other; there is
no gap in the chain and no sudden and considerable variation,
only a number of very slight differences. We have also seen,
that such variations are inconstant, although in some cases
at least, under suitable conditions, they can be gradually fixed
and rendered hereditary.

In contrast with such variations are those known as spon- Spontaneous
taneous variations, sports, or mutations. Our knowledge of Variations,
these and of their mode of occurrence in nature depends
chiefly on the experiments carried out by Professor Hugo De
Vries. He has demonstrated that plants of the species Oenothera
Lamarckiana in addition to producing normal offspring bearing
the characteristic marks of their parents, produced also con-
siderable numbers of individuals which possessed definite and
appreciable characters not seen in their parents. Such indivi-
duals are termed mutants ; they suddenly come into existence,
there is no progressive change, and no intermediate forms are
found linking them with the species from which they spring,
they are due in fact to a sudden variation, i.e. a mutation. A
mutant, when isolated and fertilised with its own pollen, is
found to be constant from the time of its origin and to transmit
its essential characters truly to its offspring. This constancy
sharply distinguishes mutations from the inconstant fluctuating
variations. The species mentioned was found to produce several
different types of mutants, differing in various ways from the
original form, several individuals of each type usually appeared
simultaneously, while each type was liable to be reproduced at
intervals by the parent species. The causes of mutations are at
present unknown. The great majority of species in nature
are fixed and constant, but from the case of this Oenothera
it appears possible that all species at some period of their
existence throw off mutants in considerable numbers. Such
a mutating period probably forms only a small part of the
total life of a species. Such a period moreover does not neces-
sarily involve the death of the parent species which, as seen
in this Oenothera, in addition to producing mutants, ma}'
continue to transmit its specific characters truly to the majority
of its offspring. Mutations are not entirely confined to such
mutating periods; occasional mutants may arise at any time,

156

Variations

but so far as is at present known, they are rare. The occur-
rence of double flowers in species with usually single flowers,
of regular flowers in species with usually irregular flowers,
of divided leaves in species with entire leaves, of a weeping,
or fastigiate, habit in trees and shrubs with an erect, or spread-
ing, crown, respectively, are among the most common examples
of mutations at present known.

Monstrosities. Very striking variations which give the impression of an
altogether abnormal structure are called monstrosities. They are
often termed malformations and frequently give rise to diseased
conditions. They are of rare occurrence in nature ; the
cauliflowers and turnips of cultivation are believed to have
arisen from monstrosities. Finally it must be noted that
remarkable variations in the form of plants may be caused by

Mutilation. insects and fungi, which may, for instance, be responsible
for the peculiar structures known as " galls " and " witches'
brooms." Mutilation also may exercise a far-reaching effect
such as is seen in plants which are continually browsed cr
grazed by animals, while some annual species may be made
perennial by removing the flower buds and thus preventing
their reproduction.

Heredity. 138. By heredity is understood the

transmission of characters from a parent to its offspring.
This transmission is rendered possible in plants by means
of their powers of sexual and asexual reproduction. Many
variations can only be transmitted truly to the offspring
by asexua propagation, and for this reason individuals
which exhibit a desirable variation are usually propagated
in horticulture by asexual methods. This is particularly the
case with hybrids which are frequently very inconstant if
propagated by seed. The younger a plant or organ is, the greater
will be the effect of any factor which is capable of influencing its
development, and the early stages of the growth of the embryo
constitute the most susceptible period. If this period could
be cut out, as it were, from a plant's life history we should
expect it to be less subject to variation and to resemble
its parent more closely than would be the case if the individual
were raised from seed, and this is precisely what is effected by
asexual propagation. It must, however, never be forgotten
that in sexual reproduction effected by the crossing of two
distinct individuals a portion of the protoplasm of each parent
enters into the composition of the young plant, which must
therefore inherit something from its father and something from

157

its mother. When both parents possess similar characters the
offspring will naturally tend to strongly resemble the mother
plant, although this depends to some extent on the conditions
under which the young plant develops, but if this is not the
case the results of the cross may be very various, as has been
noted in the remarks on hybrids. We have also seen that,
when a hybrid form is repeatedly crossed with one of its
parents, it tends to quickly revert to that parent form, and in
this way sexual reproduction may help to eliminate new vari-
ations and to keep species constant in nature. A character
which may appear to have been lost is frequently found to be
really only dormant, or latent, and although it may be
inherited in this state during many generations it is always
likely to reappear and again become active. This phenomenon
of the reappearance in a plant of an ancestral quality which
has been latent in its parents is termed atavism.

139. We have seen above that a Selection.

large proportion of all living organisms which come into
existence must perish prematurely and that in nature those
which are best adapted to the conditions under which
they exist are selected, or chosen, as it were, by nature,
and survive, while the remainder are rejected and perish. This
Survival of the Fittest, therefore, is seen to be the result of the
so-called Natural Selection. Selection has been well likened to a
sieve, only those individuals which possess the necessary
qualifications are able to remain and are selected, while the
remainder pass through the sieve and are rejected. It is advis-
able to distinguish two kinds of selection, viz. that which
selects a particular sub-species, or race, from among other sub-
species and races, and that which selects particular individuals
within one and the same sub-species, or race. An example of
the first occurs when, in a field of wheat, a single sub-species is
selected from among the others growing with it and is then
isolated and separately propagated. The same thing occurs in
nature when, from a number of mutations, only those which are
best adapted to the conditions of life are selected and survive,
while the others perish. In addition to this, however, we know
that, within one and the same sub-species, or race, there is
always fluctuating variability — that no two individuals are ever
exactly alike — and that the same quality or character is
exhibited in different degrees by different individuals. Hence
it might be inferred that breeding entirely from those indivi-
duals which exhibit a desirable character in a marked degree
would result in the production of similarly characterised

158

offspring ; and that a race could, in this way, be improved and
•confined, as it were, to a few of the best individuals, the large
number of moderate, or inferior, individuals usually occurring
in the race being thus excluded. To a great extent this is
found to be the case, and modern horticulture and agriculture
depend largely on these two principles of (1) the selection of the
most suitable race or sub-species and (2) the improvement of the
selected strain by breeding only from the best individuals. In
cases of fluctuating variability the greater the number of indivi-
duals examined the more chance there is of finding an indivi-
dual which exhibits a particular character in an extreme degree
and for this reason large cultures are often resorted to in horti-
culture. Professor Hugo De Vries records a case in which
40,000 plants were cultivated, only a single individual being
finally selected from this multitude for further propagation, all
others being destroyed. Such an individual, when found, can
only be propagated with certainty by asexual reproduction.
Many plants, however, cannot easily be propagated in this way
and such large cultures are very inconvenient. In addition to
this the asexual method of reproduction affords no means of
effecting further considerable improvement of the race. It is,
however, found 'that such desirable variations can also be
obtained and to a certain extent be propagated by sexual
methods. Experience shows that if individuals exhibiting a
certain character in a marked degree are chosen as parents,
although the average of the offspring raised from their seed do
not exhibit this character in so high a degree as their parents,
they do show a distinct improvement in this respect and are
superior to the average of the race from which they have arisen.
By continuing this method for some generations the same
degree of improvement can be .obtained with comparatively few
individuals, which could only be obtained in one generation
by cultivating a very much larger number of plants. Moreover
the sexual method possesses the great advantage of enabling us
to continue the work of improvement. This principle is a very
important one in modern agriculture. The fact that not one,
but several, characters have almost invariably to be taken
into consideration is one of the great difficulties in the way
•of successful practical work in this line. If, when selecting
certain individuals in a race of wheat, we were only to pay
attention to the quantity or quality of grain yielded, we might
select those plants which are also very susceptible to disease or
climatic influences, and the selection would thus effect no
practical improvement. It .is generally recognised that the

159

best results are, as a rule, obtained by selecting not those
individuals which exhibit the best visible characters, but those
plants which are found to produce the most desirable offspring ;
in other words, the value of a plant is gauged not by its visible
attributes but by its power to transmit desirable qualities to its
descendants. For this purpose the seeds of each individual are
sown separately and, to obtain an average value for the offspring
of each individual, 100 seedlings are carefully examined and their
qualifications considered. Only those groups which contain the
greatest number of desirable individuals are then selected for
further cultivation. This method is based on the idea that a
single plant, or even a few individuals, may owe their qualifica-
tions not to any inherited attribute but to extraordinarily
favourable conditions to which they have been subjected during
their own life-time. Although great improvements have been
wrought on the lines indicated above, no permanent improve-
ment has, up to date, been effected and no new and constant
race has been produced. Experience hitherto gained has shown
that whatever standard of selection is adopted, a limit to the
improvement effected is soon reached beyond which it is impos-
sible to go, and, further, that when a desirable degree of
improvement has been reached, this can only be maintained by
continued selection, for if selection ceases, the race soon reverts
to its original type.

140. Linnaeus, the most famous of Origin of
the early botanists who worked at classification, thought t
each species had been separately created at the beginning of the
world and that the individuals of a species were only capable of
producing other individuals like themselves, i.e. that existing
species had remained unchanged from the creation. Charles
Darwin, however, subsequently proved thatthis was not the case
and that, from one species, other and totally distinct species
could arise in the progress of time. The theory of evolution in
the animal and vegetable kingdoms is now universally accepted
as correct, as is also the fact that this evolution is mainly
dependent on two factors, which are : —

(1) the variability of living organisms, and

(2) the struggle for existence, owing to which only those

organisms are able to survive which are most per-
fectly adapted to the conditions under which they
exist, which are best able to withstand unfavourable
conditions of soil, or climate and which can best
hold their own against other injurious organisms.

160

Such a view also satisfactorily accounts for the fact
that everywhere in nature we find animals and
plants exhibiting the most beautiful adaptations to
the conditions of their environment, by means of
which they are favoured in the struggle for
existence.

Opinions, however, differ as to which type of variation has
played the most important part in the history of species. The
variations which are believed to be most important from this
point of view may be divided into three main classes as
under : —

(1) Variations due to the crossing of different

forms, i.e. to hybridisation.

(2) Fluctuating variations.

(3) Mutations.

It may also be premised that, in order to form the beginning
of a new species, a plant must be able to maintain itself under
the conditions of existence to which it is exposed in nature, it
must be able to transmit its essential characters truly to its off-
spring, it must occur in considerable numbers and be sufficiently
fertile to produce numerous offspring. Such a plant may possibly
result from hybridisation alone. As regards fluctuating vari-
ability, experience with bacteria indicates that, if the conditions,
to the stimulating action of which the variation must be
ascribed, are kept constant, in some cases, at least, a new and
constant form may be gradually evolved which may also be
able to establish itself as a new species. In the case of plants
reproducing sexually, such a progressive change would be
aided by natural selection, for all individuals not exhibiting the
variation, which, under the circumstances, is favourable to
their existence, would perish, while only those possessing the
variation in a high degree would remain to cross and produce
offspring. We have seen also that new, fertile, and constant,
forms in considerable numbers may arise by mutation, and
those which are able to survive in the struggle for existence
may form the beginning of new species. Just as the small
fluctuating variations may be gradually accumulated and
increased in the same direction by natural selection, so
may be also mutations, for, providing the conditions remain
constant, of all the mutants produced during successive
mutating periods only those mutants which vary in the
same direction will be able to survive, and thus evolution
will continue along the same lines, just as with fluctuating

161

variations, until those marked differences are produced which
distinguish the actually existing species in nature. Valuable
results, however, in the way of producing new forms have been
obtained in horticulture and agriculture by a combination of
the operations of selecting the best strains, of crossing distinct
strains, and of selecting for propagation those individuals which
exhibit the most desirable fluctuating variations, and we must,
therefore, be careful not to hastily ascribe to any one type of
variation, or to any single factor, pre-eminent importance in the
evolution of species in nature.

162

CHAPTER IV.— COLLECTION AND PRESERVATION OF

SPECIMENS.

•

Collection 141. It is of the first importance

of Speci- that specimens should be gathered which exhibit those parts
mens. an(j organs, the characters of which are included in the

descriptions and keys of our Floras. So far as possible the
specimens selected should indicate the average condition and
the range of variability of the important organs found on one
and the same individual and on the different individuals of the
same species found growing together, and in any case should
not be confined to those parts, or individuals, which show
extreme variations, or abnormal development. The specimens
must not be allowed to wither before they are laid in the drying
papers and are usually placed, immediately after they are
gathered, in a tin case which should be kept as cool as possible.
The specimens having been laid in the drying papers are
usually placed between two boards with a weight on the top.
For camp perhaps the most portable and useful press is one
consisting of two pieces of strong wire lattice of convenient
size which can be firmly bound together with straps and
buckles, or with a piece of thin rope.

The specimens are kept in this until dry, the drying papers
being of course changed and dried when necessary, and they can
then be packed in boxes in layers between sheets of paper, care
being taken to keep them from damp. A small notebook
should always be carried in which sunh details as the vernacular
name, dimensions, habitat, habit, and general appearance of
the living plant should be invariably noted, on the spot, and
not left to memory. To each specimen, before being placed in
the drying papers, should be fastened a small label with a
number, and great care should be taken to see that these labels
do not become subsequently detached. A journal should also
be kept up in which the specimens collected should be entered
daily, serially, under their respective numbers, with the date.
Here also should be recorded the details noted in the field, the
name of the plant and natural order (if determined), the results
of the inspection of the specimens with diagrams or sketches of
the parts examined, the locality where collected, and careful
details of all characters observed which are not exhibited by
che specimens themselves, such as the colour of the fresh
flowers. It is important that all specimens should, so far as
possibly preserve their natural appearance and colour, and for

. 163

this purpose they must be dried as quickly as possible.
The drying papers should be changed at least once a day for the
first few days and the following note may well be borne in mind :
" Two or tlyee changes of the driers during the first 24 hours
will accomplish more than a dozen changes after the lapse of
several days. The most perfect preservation of the beautiful
colours of some orchids has been effected by heating the driers
and changing them every two hours during the first day."*
In order to hasten the drying of succulent plants they should
be dipped (with the exception of the flowers) in boiling water,
and this is also a good plan to adopt in the case of those
specimens which are apt to lose their leaves in drying. To
reduce the thickness of some specimens, such as hard fruits and
so on, they may be thinned by cutting away the underside,
care being taken to see that the original shape can be made
out.

142. The specimens when com- Preservation

pletely dried should be mounted, and this is perhaps best done of Speci-
by sewing them on to the sheets with a needle and thread, never m
more than one species being fastened to the same sheet.
Fragile specimens must, be glued to the sheets, care being
taken not to use more glue than necessary, especially on the
flowers. Before being placed in the herbarium all speci-
mens should be poisoned to protect them from mould,
insects and vermin. Corrosive sublimate (bichloride of mercury)
is the poison usually employed which should be dissolved in
spirits of wine in the proportion of about \ oz. of the poison to
one pint of spirit. This should be applied to the specimens with
a large soft brush. The solution should not be allowed to come
in contact with metal or discoloration may result. Leaves and
other parts of the specimens which become detached should be
placed in small envelopes, the latter then being fastened to the
mounted sheets. At the foot of each mounted sheet should be
carefully noted the natural order, scientific and vernacular
name of the plant, locality where found, date of finding, name
of collector and details of useful characters not exhibited by
the specimen itself, such as colour of the fresh flowers, habit oi
the plant, and so on. All the sheets of the species belonging to
one and the same genus should be placed in one folded sheet of
strong paper, on the outside of which should be written the
natural order, the generic name and the names of the contained
species. A collection of dried specimens is termed a herbarium Herbarium,
and should be stored in cabinets, or small almirahs, provided

*Asa Gray's Botanical Text Book, Volume I, page 377.

M2-

164

with close-fitting doors and fitted inside with pigeon-hole com-
partments in which the genus covers are placed and are thus
readily accessible for reference. The name of the natural order
is placed above the pigeon-holes containing the sheets belonging
to that order, while it is sometimes convenient to affix an
index of the genera in each pigeon-hole on the inside of the
cabinet doors, or a list of the genera may be placed on the
top of the sheets in each compartment.

Before examining or preparing sections of dried flowers and
fruits they should be placed in cold water and then gradually
heated until sufficiently soft

165

PART V.-WOUND3 AND DISEASES.

CHAPTER I.— WOUNDS.

143. If a mass of living cells is cut Healing of

through with a sharp knife, the exposed surface at first turns ^JJJjfjf1^
brown and then becomes covered with a protecting coat of Cork Layer,
corky tissue. The cells actually cut through die at once, and in
consequence of the access of air some of their contents become
oxidised, this process causing the brown discolouration. The

layer of cork is formed by the uninjured cells immediately
below the cut surface which, by their growth and division,
give rise to layers of flat tabular cells. These soon die and,
their cell walls having become converted into cork, form a pro-
tective coat several layers of cells in thickness which, although
elastic, is very impervious to air and water, and consequently
the rapid drying up and destruction of the .living cells beneath
it is effectually prevented. This process may be well observed
on the cut surface of a potato, although the wounded surface
of any mass of living cells, in the root, stem, leaf, or elsewhere,
will present essentially the same phenomenon.

144. If the cells below the cut Callus-
surf ace are growing and dividing when the cut is made, the first ^^^lin
thing which happens is the dying of the actually cut cells and of Wounds
then the external corky coat is formed as before. Now, this by Ooclu-
thin layer of cork being very elastic, the pressure exerted by it Slon>

on the living growing tissues beneath it is very much less than
was caused by the original external tissues which have been re-
moved by the cut. These living tissues are consequently
able to grow far more vigorously than before and they give
rise to a juicy cushion of thin-walled cells which is called a
callus. This at first consists of a mass of embryonic cells ;
some of these remain capable of growing and forming new
cells, thus retaining their character as embryonic tissue, while
the remainder become gradually differentiated, very much as
is the case in normally growing tissues. This process may be
well seen on the vigorously growing stem of a young sapling.
Suppose, for instance, that we cut away a longitudinal strip
of the external tissues from such a stem, the cut extending
down to the wood which is thus left exposed. The wound at
first gapes owing to the contraction of the tissues of the cor-

166

tical jacket, which, before the wound was made, was tightly
stretched and exerted considerable pressure on the tissues
below it. The living cells of the cortex and the cambium at
the edges of the wound at once protect themselves with a
layer of cork and then rapidly develop a callus as above
described, which pushes out towards the surface of the
wound, i.e. in the direction where there is the least
resistance, and thus forms a thick pad-like rim around the
wound. A layer of cells in this callus, continuous with the
cambium of the stem, retains its embryonic character and acts
as a cambium, .the tissue formed on the inside of the layer,
abutting on the old wood, becoming differentiated into wood
and that outside the cambial layer developing into cortical
tissue. This wood formed in the callus is called wound-wood
and, owing to the diminished pressure and abnormal conditions
under which it is developed, it usually differs considerably
from normal wood in its structure. The cortex of the
callus usually remains thin and exerts far less pressure on
the tissues beneath it than old cortex would do. These
callus cushions may consequently continue to grow very
rapidly for several years, and the whole surface of the wound
may thus become quickly and completely covered over,
owing to the various cushions coming in contact with
one another and coalescing. In many cases no thick, outer
bark consisting of layers of dead elements has been
formed on the callus pads when thev thus come in contact,
and, as they continue to grow and press against one another,
the thin cork layers lying between them are ruptured and
squeezed out, while the cambium and living cortical tissues
of the adjacent lips come into direct contact and grow together.
The cambium of the various cushions thus uniting, a con-
tinuous cambial layer is formed over the whole surface of the
wound, and then further growth in thickness continues in the
normal way as if nothing had occurred, and very soon no
external sign of the injury can be seen. If thick layers of dead
bark have been formed on the callus when the various cushions
come into contact, the complete coalescence of the latter is
rendered much more difficult and may be much delayed. In
some species the living cells of the medullary rays on the sur-
face of the exposed wood also take part in this healing process
and form callus pads, in addition to those developed at the
margins* of the wound. A wound which is healed in the man-
ner described is said to have been occluded, and this healing
process is termed occlusion.

167

It must be noted that no growing together, or intimate
union, is possible between the living cells of the callus and
the dead elements of the wood which were exposed on the
wound surface, and, although the callus grows over and is
closely adpressed to the wood, the junction between them
always remains as a distinct line of separation." This is often
well seen in the case of hammer-marks stamped on the
exposed wood of a blaze, the latter having been subsequently
completely healed over as described above. Years afterwards
such a mark may be clearly . distinguished deeply embedded
in the trunk, the letters and figures having been merely covered
over by the new wood and hence not obliterated.

145. If, in the above example, Bruises,
the outer tissues of the sapling had been crushed and bruised

by a blow from a hammer, or other means, instead of being
removed by a clean cut, rapid healing in the manner describ-
ed would have been impossible. The bruised cambium and
cortical tissues die, contract, and remain adhering to the wood
below, thus obstructing the formation of a callus by the living
tissues bordering the wounded patch. Such wounds in conse-
quence do not heal easily.

146. Now, instead of wounding Wounds

the stem itself, we will suppose a branch to have been °aused b
cut off. If the cut has been made just above one or more

leafy shoots, the latter will keep the living tissues of the
stump alive and the severed end will eventually be healed
over by callus tissue. If the stump carries buds* the
wound may stimulate the development of these into leafy
shoots and the healing process will be as before. If, on the
contrary, such a branch stump bears no buds, or leaves, the
tissues will dry up and die. The living cambium and cortical
tissues of the stem, at the base of the dead stump, now develop
a ring of callus tissue around the stump, but the formation
of this callus and its further extension up the stump are much
impeded by the dead cortical tissues of the latter, which remain
adhering to the dead wood and under which the callus has to
force its way. The healing is consequently much delayed and
the dead tissues of the stump frequently rot before the' process
is complete, the decay then spreading into the sound wood of
the trunk and causing a hollow stem. Hence, in all cases of
pruning branches, the latter should be cut off close to the
stem, the cut surface being parallel to the surface of the stem,
the healing process then being similar to that described for a
simple stem wound, In order to prevent decay spreading in

168

the wood exposed on the surface of the wound, it is important
to see that rain water is not allowed to lodge on the wound
and that air is excluded as far as possible. In Conifers the
wound is often well protected by a copious exudation of resin
and in many Dicotyledons gums, to a certain extent, serve
the same purpose, but it is always best to cover the cut
surface with wood tar, or some other substance, which will
not interfere with the process of occlusion and will prevent air,
water, and fungus spores obtaining access to the wound until
the healing is complete. In connection with artificial pruning
may be mentioned the case of the lower branches of trees
growing in a dense wood, which are killed by the heavy shade.
If such branches are .small their wood is usually soft, which
soon becomes quite rotten. Such branches in consequence
quickly fall or are broken off close to the stem and, the
wound soon healing, little harm is done. In the case of larger
branches, however, which often contain well marked heart-wood,
the dead stumps persist for several years and, as the stem in-
creases in thickness, these gradually become enclosed in the
wood of the stem. No intimate union being possible between
the dead stumps and the living tissues of the stem which
gradually envelop them, such stumps form knots in the wood
which may fall out after conversion and cause holes. In
addition to being a source of weakness such stumps are usually
more or less decayed and may cause wide-spreading decay in
the sound wood of the stem.

Girdling or 147. Killing trees by girdling or

Ringing. ringing is a common forest operation, e.g. in the case
of Teak in Burma. If a deep circular cut is made in a
Teak tree, down to, and into, the heart-wood, thus com-
pletely severing the connection between the layers of
cortical tissue and sap-wood situated respectively above
and below the wound, the tree will quickly die. This is due
to the fact that the heart-wood is incapable of water conduc-
tion, and hence the transpiring crown of the tree situated
above the girdle no longer receives, from the soil, the ne-
cessary supplies of water to replace that lost by transpiration
and the ultimate death and drying up of all parts above the
ring is consequently assured. This, generally speaking, holds
good for all trees which possess a well-marked heart-wood.
Trees, however, which possess no distinct heart-wood can also be
killed by girdling, e.g. the Himalayan Spruce and Silver Fir, but
in the case of such trees the effect of girdling is frequently very
slow, the trees often remaining alive for several years. In such

169

cases, it is not possible to ascribe the death of the tree to
any one single factor. It is known that, as a general rule, the
water-current from the roots passes chiefly through the younger
external layers of wood, but it must be remembered that all
living tissues are more or less capable of water conduction, and
that the ascending water-current under ordinary circumstances
only makes use of the young wood layers because it can pass
through them more rapidly than it could through any other
tissue. If a ring- wound through the young wood now interrupts
these rapidly conducting channels the water- current is compelled
to make use of some other and less satisfactory channels.
Girdling may thus result in the water-current being carried
through the inner and older wood-rings which, under ordinary
circumstances, would not have been utilized, and although
this interferes with the rapidity of the current and is thus
more or less injurious, the death of the tree may not result from
this cause for a considerable period. It should also be noted
that the longer the distance which the water-current has to tra-
verse in slowly conducting channels, the greater will be the
interference with the rapidity of the current and, consequently,
the wider the ring, the more likely it is to be effective in causing
the death of the tree. We must, however, consider not only
the effect of the wound on the upward water-current, but also its
effect on the supply of food materials descending the stem from
the leaves. These food substances are mainly carried through
the sieve-tubes of the cortex. That the downward passage of
these materials is interrupted by the ring- wound is indicated
by the fact that a callus often begins to form only along the
upper edge of the ring, the severed tissues along the lower
edge, which now receive no food supplies from the crown,
being unable to produce a callus. Now if the passage of the food
materials from the crown to the base of the stem and the roots
is thus prevented, it is obvious that although the reserve mate-
rials in the tissues of the roots and the base of the stem may
for a time suffice for the nourishment of the cambium, for the
extended growth of the roots, and for the production of new root
hairs and water conducting layers of wood ; this cannot continue
indefinitely, and if no other source of food materials is made
available, the supply of water obtained from the soil by the
roots will gradually decrease, and the death of the tree eventu-
ally result from this cause alone. That the reserve materials
in the roots are thus sometimes exhausted is indicated by
the fact that, in some cases, no coppice shoots arise from the
stumps of trees which have been killed by girdling, there

170

being no reserves in the tissues of the stump and roots avail-
able for the production of such shoots. If the severed living
tissues on the lower edge of the ring receive sufficient
nourishment from leafy shoots situated below the ring, they
will also proceed to form a callus, which may meet and coalesce
with that developed from the upper lip, the wound being thus
healed over and the normal continuity of the tissues re-estab-
lished, although, here again, the wider the ring, the longer
will the healing be delayed and the more injurious will be the
wound. Cases will be occasionally met with which do not
appear to admit of an explanation according to the above
facts, and such exceptions will be found due to the existence of
special conducting tissue in the interior of the stem, wood which
has retained its power of conductivity, internal phloem, etc.
As a general rule, however, the non-success of girdling is due
to the operation not having been thoroughly performed,
complete interruption of the ordinary conducting channels not
having been secured. In some cases it is possible that the failure
of the operation is due to the roots of the girdled tree being in
intimate connection with the roots of neighbouring trees, and to
their thus being able to obtain their necessary food materials
from such trees.

-. . 148. Now the callus which, as

we have seen above, so frequently results from a wound,
consists, at all events in the early stages of its development,
largely of embryonic cells, i.e., cells which must have the
capacity of producing any part of the plant body in which they
occur, for the whole plant has been built up by the activity
of such cells. Hence it is not surprising that the callus is often
found to give rise to roots, and buds capable of developing into
shoots. Such roots and buds are termed adventitious, as are all
structures which occur in places where under normal conditions
they would not have been developed. This may be well seen
in the case of cuttings, these being shoots which have been
separated from the parent plant by a clean knife cut. The base
of such a cutting, if kept moist by being placed in soil or damp
air, soon becomes covered with a callus developed from the
living growing tissues adjoining the cut surface, in the manner
described above. Roots then spring from this callus and through
the cortex at the base of the cutting, the latter thus becoming
an independent plant. It is important to restrict evaporation
from the cutting as much as possible until the new roots have
been developed, and the cuttings are often first laid sloping-
wise in the ground and entirelv covered with earth with the

171

exception of the upper buds, until they strike, i.e. develop roots.
The removal of the transpiring leaves from the cutting also, to
some extent, serves the same purpose. In India large posts
of Boswellia serrata, Erythrina suberosa and other species which
have been placed in village fences may often be seen which have,
after the manner of cuttings, developed roots from the base and
shoots from the upper end and thus become independent trees.

149. In the case of many species,

the felling of the tree results in a more or less vigorous develop- Poiiard-
ment of callus from the living tissues on the wounded shoots,
surface in which adventitious buds may arise, while the wound an
also often stimulates the cambium to form adventitious budssuckers.
elsewhere on the stump or on the roots. If now there is a suffi-
cient stock of food materials in the stump, or roots, or both,
a vigorous development of shoots from the adventitious buds
in the callus, or from the adventitious or dormant buds
elsewhere on the stump, or from the adventitious buds
on the roots, may result. When the young shoots arise
on, or close to, the cut surface, the latter is usually quickly
covered over by the healthy tissue at the base of the vigorous
young shoots and, the access of air and water being thus
obstructed, the spread of decay into the stump and root
system is prevented. When the stump of the tree is high
and the shoots arise at some distance from the ground
they are usually known as pollard- shoots, whereas if the tree is
cut low and the shoots arise close to the ground they are called
stool -shoots, or coppice- shoots, while the shoots springing from the
roots are termed root-suckers. Root- suckers usually develop
young roots of their own, and this often occurs also with stool-
shoots which arise at, or near, the surface of the ground. By
directly wounding the roots themselves and by thus stimulating
the development of callus, and of adventitious root-and-shoot-
buds on, and near, it, the production of root-suckers may often
be increased. When considering the phenomena here alluded
to, care must be taken to distinguish those cases in which
the individual plant is merely trying to recover from the
severe injury which it has received from those in which a more
or less complete process of reproduction may be recognised,
consisting in a division of the mother-plant and the establishment
of new and independent individuals. The latter, for instance,
occurs when root-suckers become independent of the mother-
tree and are furnished with vigorous root -systems of their own.
The same thing also appears to occur in cases where stool-shoots
produce roots of their own which, owing to the rapid disinte-

172

gration of the old stool, are able to develop vigorously and with-
out obstruction in all directions. In the case, however, of pollard-
shoots and frequently also in the case of stool-shoots, there
is, correctly speaking, no true reproduction. Here the normal
development of the individual tree has received a very severe
check, the individual has been badly wounded and injured by the
removal of its crown of foliage, and the plant sets about repairing
the injury as well as it may, just as we have seen is done in the
case of other wounds. Thus the tree at once endeavours to
replace the crown of foliage which has been removed by a
vigorous growth of pollard or stool- shoots. As a general rule,
it appears that the closer the resemblance between the new
crown of foliage formed by the young shoots and the old crown
of which the tree has been deprived, the better will the new
crown be able to fulfil its duty in providing for the healthy
maintenance and extended growth of the old root-system, i.e.
the more perfect will be the tree's recovery. In other cases the
process of recovery is slower and appears to resemble in a
general way that exhibited by a tree, the crown of which has
been severely damaged by drought or frost. In such a case,
if the injury has not been too severe, young shoots appear on
those portions of the stem and branches which are still alive.
These grow and gradually take the place of the dead branches
which ultimately fall off, and in a few years the recovery may
be so complete that we can see no signs of the damage remain-
ing. A very similar process often takes place in the case of a tree
which has been pollarded or coppiced ; the young crown of
foliage being unable to supply sufficient food material to the
old roots, many of the latter begin to die back from their tips,
while a crop of young roots is adventitiously developed from
those parts of the old roots which still remain alive. The
tree, as it were, appears to be trying to start life again with
a new crop of shoots and young roots. Just as a tree may
completely recover from severe damage by frost, drought, or
other injuries, so may it also satisfactorily recover from the
injury inflicted by coppicing or pollarding, but it should be
remembered that any demand made on the powers possessed
by a plant of recovering from an injury is usually very harm-
ful if repeated, and in Europe experience has shown that if ash
or maple are repeatedly cut over they often die after the
second or third operation.

Propagation 150. Propagation by means of

by means of layers and by guti are operations often resorted to by gardeners
GutiT *n India m preference to propagation by cuttings, they being as

173

a rule more certain of success. Layering is described as fol-
lows by Firminger : " Select a branch of ripened wood of the
plant to be layered, that will bear being bent down to the earth
without breaking. Cut the branch half through with a sharp
knife just under one of the leaf buds towards its extremity
and then pass the knife upwards, so as to slit the branch about
an inch or two up. The slit-piece, with the leaf-bud at its ex-
tremity, called the ' tongue, ' should be kept open by inserting a
small piece of tile. Remove the earth to the depth of two or
three inches from, or place a flower-pot over, the spot just
where the tongue falls on the branch being bent down ;
then carefully bend the tongued part of the branch into the
earth, or into the flower-pot ; secure it in that position by a peg,
and cover it over with earth, which should be pressed down and
watered.* " A callus is developed from the cut surface of the
tongue from which roots arise just as in the case of cuttings, but
the layer differs from a cutting in that it receives supplies of
water and salts in solution through the wood of the unsevered
portion of the branch. So soon as the layer has developed
its own roots and thus become independent of this source of
supply, it may be completely severed from the parent plant.
The operation may be hastened by making a half-ring wound
on the unsevered half of the branch down to the wood. The
food materials descending from the leaves of the layer which
would have passed down .to the parent plant along this half
of the branch are thus intercepted and are also devoted to the
production of callus and new roots.

The operation known as guti consists in completely ring-
ing a branch down to the wood, the latter being carefully
scraped to insure the removal of all the cambium and cortical
tissues. The wound is then covered with a lump of adhesive
earth or moss which is maintained in position by a bandage
and kept moist. Here the passage of the water current along
the young wood of the branch is not interrupted and the
leaves are enabled to manufacture food materials vigorously ;
these materials passing down the sieve tubes in the cortex are
intercepted in their course at the upper edge of the ring
where they are devoted to the production of a callus and new
roots. So soon as the latter are well developed, the branch
may be completely severed from the parent and an indepen-
dent plant is produced. Ficus elastica is frequently propagat-
ed in this way.

* A Ms.mial of Gardening for Bengal and Upper India by Thomas A.
Fumkvger, 3rd edition, 1874, page 81.

174

Grafting. 151. When describing above the

occlusion of wounds it was noted that the cambium and
living tissues of one callus cushion, coming into contact
with those of another cushion, coalesced with, and
became intimately united to them. This power possessed
by living tissues of thus growing firmly together is taken
practical advantage of in several ways in the operations
known collectively as grafting. Ordinary grafting consists
in bringing the cambium and living tissues of one plant
into close contact with similar tissues of another plant.
These ultimately coalesce, and from the union of parts of
two distinct plants we thus get a single plant ; one of the
partners, called the stock, which was provided with roots,
supplying water and mineral salts from the soil, the other
partner called the scion, which possessed shoot buds, supply-
ing food materials which it manufactures in its leaves. Such
a union is, however, as a rule, only possible between closely
related plants. In the majority of cases of successful graft-
ing each partner is found to preserve its own individual
characteristics ; if one of them naturally grows faster than the
other it continues to do so after grafting has taken place and
a distinct line of demarcation between the fast-and slow-grow-
ing tissues of the partners is visible in the stem of the plant
resulting from the grafting ; similarly an Alphonse mango
grafted on an ordinary country-mango stock, continues to pro-
duce Alphonse mangoes as before and not the unpalatable coun-
try fruit. At the same time rare cases are known where graft-
ing has resulted in more or less altering the characteristics of
the partners. The method of grafting usually adopted in India
is that known as inarching. Firminger describes the oper-
ation as follows : " Procure a seedling of about one or two
years old, of the plant to be inarched, or where a seedling is
not to be obtained, a rooted cutting of the same age, of the
plant that is to supply the stock. Put it in a pot, and when
it is well established it will be ready to be operated upon.
Slice away from one side of the young stem a piece of bark,
with a thin layer of the wood beneath it, about two inches long ;
do the same to a young stem of the plant to be inarched from,
and then bring together the two stems that have thus been
operated upon so that the cut parts lie close in contact face to
face, and bandage them with cotton-twist. In course of
time, when the parts have united, head down the stook and
dissever the scion from the parent plant by cutting it through
below the bandage. The grafted plant must then be put

175

somewhere in a shaded place and not removed from its pot
till it has made a vigorous growth, and stock and scion have
become thoroughly incorporated." *

This operation of inarching is often performed naturally,
and it is not uncommon to find branches of trees which, after
pressing and rubbing against the stems and branches of neigh-
bouring trees, have become joined to them at the- points of
contact. This is even more frequently the case with roots,
and such natural root grafting probably explains some cases of
failure in ringing trees and instances of stumps producing
coppice shoots which, as a rule, are unable to do so.

152. Budding is another variety Budding.

of grafting which is commonly practised. This must be
carried out when the sap is up and is best done just
before the period of vigorous growth. A T-shaped cut is
made in the cortex of the stock down to the wood. A piece
of cortex, called the " shield," bearing a healthy stout bud
is detached from the wood of the scion and inserted in the
T cut, the latter being then bound round tightly with
cotton-twist or other bandage. The inside of the shield thus
lies closely against the wood of the stock and the bud projects
through the slit in its cortex. One or several buds may be
thus grafted on the stock, and when these have developed
vigorous shoots, the branches of the stock are cut back
close above the budded shoots, so that the water-current from
the roots may not be diverted from the latter.

* Op. cit., pages 84-85.

176

CHAPTER II.— DISEASES.
SECTION I. — INTRODUCTORY REMARKS.

Duration 153. So far as we know at pre-

of Plant sent, all the embryonic tissue of plants, such as the cambium,
which has hot become converted into specialised tissue or
organs, is capable of unlimited life, providing the external
conditions are such as to allow of its growth. The continued
existence of plant life upon the earth in fact depends on
this property of embryonic cells. Thus bacteria, the cells
of which all retain their embryonic character and power
of continued growth and of producing new individuals, possess
within themselves the power of unlimited life. In annual
plants the death of the plant ensues on the production of
the seed. The seeds, however, contain embryonic cells, and
the continued existence of the latter renders the mainten-
ance of the species possible. Trees, on the other hand,
owing to the presence of the embryonic cambium, are
often capable of living for very long periods and may reach
an age of more than 1,000 years. In a tree considerable
portions continually die in the ordinary course of natural
development. Thus the root-hairs only live for a short time,
large quantities of wood are killed to form heart-wood, masses
of external tissue die and become dead bark, the leaves live for
a few years only at the longest, sepals, petals and stamens have
a very brief life, so that in an old tree the actually living tissue
which has arisen from the embryonic cambium and become
converted into special tissue, or organs with a particular func-
tion to perform, is at most but a few years old. Not only in
annuals, but in some plants which do not flower for several
years, such as some species of Strobilanthes, Bamboos and some
Palms, the production of flowers and seed causes such
exhaustion of the plant's vitality that death ensues. In some
cases it has been found possible to prolong a plant's existence
by artificially preventing the production of flowers, and cases
are known .in which annuals have thus been made perennial.
Whether on account of internal or external causes, however,
so far as we know at present, every individual plant does
sooner or later die.

Definition of 1^^:- ^n nature the development

Disease. of every organism depends on the number and intensity of the

injurious and beneficial influences, not only of other organisms,

but also of the non-living environment, which affect its develop-

177

ment. Only when all the factors which influence the develop-
ment of an organism combine to act in the most favourable
way can an ideally healthy development become possible.
In nature, however, this is probably never realized, except
perhaps for very limited periods in the life of any particular
organism, and, with the gradually increasing predominance
of injurious over beneficial factors, we get at first a condi-
tion which we recognise as disease and eventually death.
Seeing, however, that an ideally healthy development, for even
limited periods in the life-history of any particular organism,
is rarely, if ever, possible, it is obviously very difficult
to define exactly what we mean by disease. We have seen
that the ordinary course of the normal development of a
plant in itself necessitates the death of considerable portions
of the plant-body, or even of the entire plant in cases where
death naturally follows the production of flowers and seed,
yet here we can hardly speak of disease. For practical pur-
poses, however, we may regard as diseased any condition of
the plant, or of any part of it, which, unless ameliorated, will
lead to the obviously premature death of the plant, or of some
part of it.

155. In Part IV above, it has Strugg'e for

been noted that what we call the struggle for existence Existence-
is responsible for the premature death of organisms, and
that ,every organism, in order to maintain itself, has to
struggle with other living organisms and to fight against,
such factors as unfavourable climate, excessive heat and
cold, drought and so on, see p. 148. When it is considered
that these factors affect various organisms in very different
ways, we begin to realize how complex the relations
are which bind together the organic world. Hence when
studying the diseases of a particular plant, w3 must
not only consider the effect exercised upon it directly by such
factors as soil, moisture, temperature, light and such like,
but we must also discover how other organisms, plants as
well as animals, affect it, what factors influence the develop-
ment of all such correlated organisms, and in what way. To
illustrate how two organisms, between which at first sight we
should say there was absolutely no connection, may be de-
pendent on each other for their existence, we cannot do
better than take the following well-known example given by
Darwin : —

" Humble-bees alone visit red clover, as other bees cannot
reach the nectar. * * Hence we may infer as highly

178

Factors
which in-
fluence the
Relations
existing
between
Organisms
in Nature.

probable that, if the whole genus of humble-bees became
extinct or very rare in England, the * red clover would
become very rare, or wholly disappear. The number of
humble-bees in any district depends in a great measure upon
the number of field-mice, which destroy their combs and
nests. * * Now the number of mice is largely de-

pendent, as everyone knows, on the number of cats. *
Hence it is quite credible that the presence of a feline
animal in large numbers in a district might determine, through
the intervention first of mice and then of bees, the frequency
of certain flowers in that district ! " * We frequently do not
realize the severity of this great struggle for in nature a bal-
ance is generally maintained between the conflicting forces,
a position of more or less stable equilibrium being eventually
arrived at, which, however, a very trifling circumstance may
entirely upset. The plant known as Lantana aculeata is a
native of America and was introduced into Ceylon about 1824.
Since then it has spread with extraordinary rapidity over the
Peninsula of India, where it " now covers, with a dense network
of intertwined branches, large areas of country, almost to
the complete exclusion of other vegetation." f This well
illustrates how a plant, the development of which is favoured
more than is that of other species by the factors of the locality,
soon succeeds in eliminating all other vegetation. Again
man, by forming pure forests of a single species of tree, has
favoured the development of the insects and fungi which prey
upon it, by collecting together and making easily accessible
for them masses of their favourite food, a procedure which
more than once has led to the total destruction of extensive
forests in Europe, while in the teak forests of India we clearly
see how much more damage is done in pure forests than in
mixed by defoliators, such as Hyblae:i puera and Pyrausta
machoeralis.

156. Let us now try to realize

the factors which induce one organism to injure or help
another and which enable it to do so, as well as the conditions
which enable life to still continue on the earth amidst so much
destruction.

Complex carbon compounds generally known as organic
materials form an essential part of the food of all living
organisms. Green plants alone among all living organisms

* Origin of Species. By Charles Darwin, 6th Ed., pages 53 — 54.
t A Manual of Indian Timbers. By J. S. Gamble, 1902, page 524.

179

•

(with a few rare and unimportant exceptions) are able to manu-
facture their organic food from the carbon dioxide of the air ;
all other plants and animals must obtain their carbonaceous
food from materials which directly, or indirectly, have been
manufactured for them by green plants. Without green plants
then all life on the earth would eventually cense. These
organic compounds contain energy, or in other words capacity
for doing work, and they can be made to yield up this energy
which is stored within them for the use of living organisms,
in various ways. Some of them, for instance, such as wood and
coal, when burnt in a fire are made to give up their energy in
the form of light and heat. Others can be used as food and
made to give up their energy in the process known as respira-
tion. Whether these substances are slowly burnt off in living or-
ganisms as food, whether they are quickly consumed in a fire,
or whether they are slowly oxidised and disintegrated under the
chemical and physical actions of air and water, the end product
of the decomposition is carbonic dioxide. Now when green plants
first construct these organic materials large quantities of car-
bon dioxide are removed from the air ; a certain amount of
this is again returned by mankind and animals by utilising
organic matter as food or fuel. Large quantities of carbon,
however, still remain locked up in the dead bodies of plants
and animals which have not been utilised in this way, and if
these dead bodies were to remain unchanged, the available
supply of carbon dioxide in the air would eventually become
exhausted and all living beings would be driven out of exist-
ence. We know, however, that this is not the case, but that
all such dead remains rot, decay, or putrify, and are eventually
broken up into the elements of which they were formed, car-
bon dioxide being again set free. Ordinary oxidation, as
already mentioned, is responsible for a certain amount of this
decomposition, but we now know that living organisms (espe-
cially bacteria and fungi) which derive their carbonaceous
food from these dead bodies take an exceedingly active part
in this work and are hence indispensable for the maintenance
of life. Plants which thus derive their carbonaceous food
from the dead bodies of other organisms, or from substances
manufactured by other organisms, are termed saprophytes. They Saprophytes,
do not obtain their supplies directly from the living tissues of an
organism. Green plants then, we see, are continually building
up organic matter and thus not only provide a continual sup-
ply of food for animals and other plants but also prevent the
accumulation of poisonous quantities of carbon dioxide in the

180

air ; non-green plants and animals, on the other hand, are con-
tinually consuming organic matter and by returning carbon
dioxide to the air keep up the supply of raw material necessary
for the manufacture of fresh organic material by green plants.
From the fact that the average percentage of carbon dioxide
in the air remains practically constant, we see that a balance
is maintained in nature between this work of construction on
the one hand and of destruction on the other, a continuance
of life being thus assured.

We may then divide all living organisms into the following
two great classes :—

(1) Green Plants obtaining their carbonaceous food from

the air.

(2) Non-green Plants and Animals obtaining their carbon-

aceous food directly or indirectly from green plants.
Now although, as ha s been shown above, each of these
great classes as a whole depends upon the other for its exis-
tence, yet we know that in nature individual organisms, owing
to their great powers of increase and to the limited quantity of
food materials available, are continually being injured and
destroyed in the struggle for . existence by other organisms.
Regarding their relations then to any particular organism or
group of organisms, all others may be classed as follows :—
Competitors. (i) Competitors. Those which are indirectly injurious owing
to their competition for the same necessaries of life.

Parasite?. (2) Parasites. Those which are directly injurious owing

to their obtaining some or all of their necessaries
of life directly from the living bodies of organisms.
The organism from which a parasite obtains its
supplies is called a host.

Symbionta. ^3) Symbionts. Those which not only are not injurious but

are actually beneficial and are hence more or less
necessary for the existence of the organisms bene-
fited.

The phenomenon of two organisms living together with
benefit to one or both of them is termed symbiosis. If both or-
ganisms are benefited it is called reciprocal symbiosis ; if only
one organism is benefited it is called antagonistic symbiosis, as
in the case of a parasite and its host. Symbiosis also may be
close when the organisms live in intimate connection with
each other, or distant when there is no direct or fixed union
between them. It is of course often impossible to insist on
these distinctions ; organisms, which at one period of their
life may be beneficial (symbionts), at other times may be

181

directly injurious (parasites), and in cases of close symbiosis it
is often difficult to decide whether or not one organism is slight-
ly injured by the other, that is, whether they are to be regarded
as reciprocal symbionts, or as parasite and host.

157. The symptoms which indi- Symptoms

catea diseased condition are of course very various01
according to the different factors at work and may
consist of unusual pallor of the leaves, discoloured spots

or blotches on the leaves, premature death of leaves, or
branches, and so on. At the same time such symptoms in
themselves by no means necessarily indicate the factors which
are responsible for the disease. Premature death of twigs
and branches may, for instance, be due to the effects of fire,
frost, drought, an unfavourable condition of the soil or the
attacks of scale insects.

158. In some cases the direct One Factor

connection between the injurious factor at work and the diseased alc"ie ls
condition of the plant produced by it is obvious. We may, for p^n/biiTfor
example, see a larva directly feeding on and destroying the a Disease.
leaves, or we may notice that the death of our tree follows
immediately after an unusually severe frost, and in such cases it

is natural to conclude that in the absence of the larva or frost the
disease would have been avoided. At the same time from what
has been said above regarding the struggle for existence it will
be realized that one factor alone is rarely responsible for a
disease and this may frequently be the case even in such appar-
ently obvious examples as the above. The destructive larva,
for instance, might not have harmed our trees if the weather
or some other factor had not favoured its development to an
unusual extent, the frost might not have injured our trees if
they had not been growing in a damp valley, their twigs in
consequence having remained soft and full of watery sap in-
stead of becoming lignified and matured like those of the trees
on the hills around. The discovery of one obviously injurious
agent at work is thus by no means necessarily a satisfactory
conclusion to the investigation of any particular disease. In
cases where we have not ourselves been able to note the first
appearance of a disease, it is of course most important to
ascertain, as far as possible, the character of the first visible
symptoms, the time when they were seen, and whether the
existen.ce of any unusual external influence, such as severe
drought, the occurrence of a fire, etc., was noticed when the
disease first appeared.

182

Knowledge
necessary
for a suc-
cessful In-
vestigation
of Plant
Diseases.

Sub-divi-
sion of the
Subject.

159. In order that our study of

tne diseases of our forest plants shall be of practical value,
we must by careful observation and study :—

(1) Be able to recognise the first symptoms of a diseased

condition. This among other things necessitates
a knowledge of the life-history of our plants. We
should, for instance, be inclined to ascribe such
phenomena as the annual dying back of the seed-
lings of bamboos and other species, or the shed-
ding of shoots of some species of Strobilanthes,
to a disease, if we did not know that these are
necessary in the ordinary course of the plant's
development.

(2) Be. able from these symptoms to at once form an

approximate idea as to the nature of, at all events,
some of the principal factors causing the disease.

(3) Be acquainted with, and know the mode of action of,

all important factors which either beneficially or
injuriously affect the normal development of our
plants. This will then enable us to discover in
any given case of disease any unusual absence of
beneficial factors or presence of injurious influ-
ences and, while thus indicating the principal factors
responsible for the disease, will help us in deciding
on the most advisable remedial and preventive
measures.

(4) Be acquainted, as far as possible, with the life-histories

of plants and animals which are capable of bene-
fiting, or of injuring, our forest plants and with
the factors which influence the development of
the same, so that we may be able to take measures
for their destruction, if injurious, or for their
advantage, if beneficial.

160. A detailed account of the

life 'histories of the various animals which influence the develop-
ment of forest plants, their mode of action, the symptoms
by which the diseased conditions caused by them may
be recognised, together with an account of the measures
to be taken for their destruction, or advantage, form
the subject of Forest Zoology. It is, however, interesting
to note that several cases of symbiosis between plants and
animals are known. Insects, for instance, effect the pollina-
tion of flowers in return for nectar or pollen received

the flowers, birds and other animals disseminate seeds in

183

return for food in the shape of fruit, etc., while some ants in
return for food provided by the plant protect the latter against
other injurious insects.

The following sub-divisions of the subject will now be con-
sidered in detail :—

Influences of other Plants on plant development.

Influences of the Soil on plant development.

Influences of the Atmosphere on plant development.

Effect of fire on plant development.

SECTION II. — INFLUENCES OF OTHER PLANTS ON PLANT DE-

VELOFMENT.

161. Following the classification

proposed above, we will consider, in order, the effect exercised
by plants in their capacity as (a) Competitors, (b) Parasites,
and (c) Symbionts.

(a) Competitors,

162. We have to consider here

not only the competition among roots for the water and Plant Com-
mineral salts in the soil, but also that among shoots forPetlt°rs-
the sun-light and air. In so far as competition with the
higher plants above ground goes, their insignificant de-
velopment in the air renders the Cryptogams of little or
no importance, but in the soil their competition may be
injurious. The mycelia of many saprophytic fungi, for
example, are known to compete actively with the root hairs of
higher plants in the soil by taking up large quantities of valuable
mineral salts, especially of phosphorus and potassium. The
most injurious competitors with the higher plants, however, are
undoubtedly to be found in the ranks of the higher plants
themselves, i.e. among the Phanerogams. This subject has
already been alluded to in Part IV above, see p. 148, and only a
few striking examples of competition can be mentioned here.

In the mixed forest of Deodar and Blue Pine in the Deodar and
Western Himalayas, the latter has continually to be girdled Blue Pme
to prevent its suppressing and ousting the more valuable
Deodar. A similar state of things exists in all our Indian
mixed forests and the forester has to girdle, or fell, trees which,
as yet, are of no value to prevent their vanquishing the better
kinds in this competition for the necessaries of life.
Another well-known case of competition is afforded by the Teak and
relations existing between Teak and various gregarious species
of bamboos. In Burma, for instance, the dense shade afforded
by the gregarious Bambusa poiymorpha often effectually

184

Trees and

Grasses.

Trees and

Strobil-

anthes,

Climbers

prevents the establishment of any Teak reproduction beneath
them. Even when such seedlings have become established
during the gregarious seeding and dying back of the bamboos
the young trees may still be caught up and suppressed by
the young bamboos resulting from the general seeding.

In areas which have been cleared for cultivation in our
forests and then abandoned, the dense growth of grasses
which quickly takes possession of the ground often prevents
for many years the re- establishment of tree-species. The
mass of grass to some extent prevents the tree seeds from
reaching the ground, the dense network of grass roots in-
tersecting the superficial layers of soil in all directions have got
the start in the competition for water and mineral salts
and compete with the delicate roots of the few seedling trees
which may have germinated, while the heavy growth of grass
above the ground effectually prevents the struggling plants from
obtaining the light and air indispensable for their development.

Similar in many respects, with regard to their effect on the
development of other plants, are some species of Strobilanthes.
The stems of the gregarious S. Wallichii in the Western Himala-
yas, for instance, " form a dense matted covering to the soil, and
prevent the seeds of the forest trees, chiefly oaks like Quercus
dilatata and semecarpifolia, and firs like Picea Morinda and Abies
Pindrow, from reaching the ground, or if they do reach the
ground, obtaining sufficient light fojr germination and growth."*

163. Climbing plants again are

often very injurious competitors of which our forests
contain many examples, the most striking perhaps being
the well-known Bauhinia Vahlii. The damage done by such
plants consists chiefly in the injurious competition for
light between their foliage and the crowns of the trees on which
they climb. The species mentioned, for instance, climbing to the
tops of the highest trees, eventually envelops them with its
mantle of enormous leaves which sometimes measure as much as
18 inches across. The dense curtains of its foliage effectually
prevent the access of light to the tree branches covered by them,
and the leaves on the latter being unable to manufacture food,
the tree is ultimately starved. The roots of such climbers also
*ire more or less injurious by competing in the soil with the
roots of the plants on which they climb for water and mineral
salts. Moreover, the pressure exerted by the coils of woody
climbers on the thickening stems and branches of the plants

Manual of Indian Timbers by J. S. Gamble, 1902, p. 519.

185

supporting them more or less interferes with the descent of food
materials from the leaves in the tissues of the cortex and conse-
quently with the nourishment and growth of the cambium. The
latter may be thus killed in places and the stems or branches
become deformed and irregular, often assuming a corkscrew
shape owing to the growth in thickness taking place in a spiral
direction. It is, indeed, not uncommon to find dead stems which
have been effectually girdled by such climbers.

164. This brings us to a considera- Epiphytes,
tion of the effect of so-called epiphytes on other plants. The
student must be careful not to confuse the term epiphyte with
that of parasite. An epiphyte is a plant which grows on
another plant, the term having reference merely to position
and thus serving to distinguish plants which grow on other
plants, from those which grow inside other plants (endo-
phytes), or on the earth (terrestrial), or in the water (aquatic). The
word parasite, on the other hand, refers essentially to the manner
in which the plant obtains its food, and an epiphyte in conse-
quence may or may not be also a parasite. We often see a
young Banyan (Ficus bengalensis), or Pipal (Ficus religiosa),
growing on the top of a large Mango or other tree. Year by
year the fig grows bigger and, as its dense crown of foliage
develops, it shades the Mango leaves more and more from the
sunlight. The Mango then begins to languish, and ultimately
dies. After several years an enormous fig tree alone is to be
found on the spot and no sign remains of the Mango on whose
branches it first started life. If we carefully watch the develop-
ment of such a fig we find that the young plant sends out its
so-called serial roots which rapidly spread downwards in all
directions along the branches and stem of the tree attacked
towards the soil. These become woody and frequently become
grafted together at points where they come in contact with
one another, thus forming a tightly-fitting, latticed, woody
mantle over the attacked stems. These roots also produce from
their under-surface small absorption-roots which, being nega-
tively heliotropic and positively hydrotropic, cling tightly to
the bark and penetrate into its dark cracks and fissures where
moisture and small quantities of dust and humus accumulate.
The latticed roots themselves also provide lodgment places for
dust and organic debris, and from this alone do such epiphytic
roots derive their nourishment, for they do not penetrate the
living tissues of the stem on which they grow. If such roots are
torn away from the stem enveloped by them, it is surprising what
a large quantity of dust and earthy matter may often be found

186

adhering to them. When these serial roots eventually reach
the ground they branch therein and rapidly develop a
wide-spreading root-system in the soil. If by this time
the death of the tree attacked has not been caused by the com-
petition of the fig's crown of foliage, the competition of the
fig roots in the soil now help in effecting this result, and the
fig with its own root-system established in the soil no longer
requires the help of its first support. Many epiphytic species of
Ficus are thus capable of destroying our forest trees, and it is
interesting to note as an historical fact that the famous Banyan
" in the Calcutta Botanic Gardens began life as an epiphyte on a
wild date-tree of which all trace has long disappeared."* This
tree is said to have been about 100 years old in 1886, with 232
supporting trunks developed from serial roots. The circumference
of its crown was then 857 feet, and it was growing vigorously.

Although they are not competitors in the sense here ascribed
to the term, the fungi belonging to the genus Meliola deserve
mention here as injurious epiphytes. As has already been men-
tioned in Part IV above, these minute plants growing on the
surface of the leaves of trees and shrubs, and feeding on the sweet
juices excreted by insects cover the leaves with black incrusta-
tions which, by preventing the access of light to the green chloro-
phyll, are more or less injurious, see p. 133.

Here also may be mentioned the Lichens which are so often
found growing on the stems and branches of trees. A luxuriant
growth of lichens is primarily an indication of a moist atmos-
phere and also frequently of very slow growth in the trees on
which they are found, for quick growth combined with the rapid
ex-foliation of the outer layers of bark prevent the establish-
ment of a vigorous growth of lichens. In so far as direct injury
"is concerned the latter are usually of very little importance,
their injurious action, being apparently confined to inter-
ference with the access of oxygen to the living tissues through
the lenticels.

(b) Parasites.

165. The most injurious plant

parasites are undoubtedly to be found among the Fungi, of
which only a few typical examples can here be considered in
detail, viz. : —

(1) Phytophthora infestans.

(2) Fomes annosus.

(3) Trametes Pini.

(4) Puccinia graminis.

* Flora Simlensis by Colonel Sir Henry CoJlett, page 459.

187

166. This fungus belonging to (l) phytoPh-

the great group of the PJiycomycetes causes the most virulent \nfestans
disease from which the potato plant (Solanum tuberosum) is De Bary.
known to suffer, and in countries where potatoes are exten- Species
sively grown the damage done by it not infrequently amounts attacked<
to a national calamity. In Ireland, for instance, one of
the worst famines of modern times has been caused by
this disease, and again in 1879 the loss occasioned by it
in that country was estimated at nearly £6,000,000. Up to
the present the disease in India has been chiefly confined to the
moister localities such as Assam, the Eastern Himalayas and the
Nilgiris, and experience in Europe has shown that an exposure
of 4 or 5 hours to a dry heat of 104° F. is fatal to the furigus.
From the fact, however, that the disease has of recent years
established itself also in the plains of Bengal it appears probable
that it will gradually spread throughout the country wherever
potatoes are cultivated. This fungus is also known to attack the
tomato (Lycopersicum esculentum) and a few other plants belong-
ing to the Solanaceae and Scrophidariaceae.

The presence of the disease is usually first indicated by the Signs of
occurrence of brown patches on the leaves of the potato plants. the Dlsease-
These increase in size and depth of colour, coalesce with neigh-
bouring patches, and gradually extend over the whole leaf
surface. Similar patches often occur also on the petioles and
stem. The attacked leaves eventually shrivel up and drop off
leaving the bare stalks standing, or the leaves and stalks are com-
pletely converted into a rotten mass which emits a characteristic
and disagreeable odour. This latter is chiefly due to the decom-
posing action of bacteria on the tissues which have been killed
by the fungus. The extension of the disease is particularly
rapid in damp warm weather.

If one of the attacked leaflets is now turned over and one of Life History
the characteristic brown patches on the under surface examin- and Damase
ed with a lens, a number of pale silky threads will be seen
standing up from the leaf surface at the edges of the dark spot,
thus producing a characteristic pale mouldy margin to the patch
which is particularly noticeable in damp weather. See
Plate XVI (1). These more or less erect threads are the
serial hyphae, or conidiophores, of the fungus which have been
sent out singly or in tufts through the stomata on the under
surface of the leaf for the purpose of bearing the conidia, or
asexual reproductive organs. These fine tubular conidiophores
are branched, and at the tip of the main filament and of each o{
its branches the minute egg-shaped conidia are produced

188

which, if sufficiently numerous, appear as a fine white powder
through the lens. The conidia usually fall off or are blown off by
the wind almost as soon as they are formed, small swellings in
the hyphse indicating the places where they originated. See
Plate XVI (2). The mycelium or main body of the fungus
consists of a branched net- work of fine tubular hyphse
which spread and branch in all directions in the intercellular
spaces of the leaf-tissue. If a single hypha is examined with
the microscope it will be seen to consist of a long tube, with a
transparent thin wall of cellulose, containing water, protoplasm
and other substances. The hyphse are, as a rule, not septate,
but transverse partition walls are occasionally developed at
irregular intervals to separate the parts of the hyphse which
are still growing and full of protoplasm from those which have
completed their growth and are empty. These hyphae push
their way between the cells of the leaf, and as a rule do not
directly enter the cells. Occasionally, however, they develop
small branches which dissolve their way through the neighbouring
cell-walls by means of an enzyme which they secrete, and which,
acting as absorbing organs, are called haustoria, or suckers.

Whether the hyphse enter the cells or not, however, the
result is the same ; they consume a quantity of the oxygen and
water which is required by the living leaf -cells, they directly ab-
sorb the products of assimilation which would ordinarily have
been devoted to the development of the tubers, and finally they
destroy the living protoplasm and kill all the living cells with
which they come in contact. The cell-walls turn brown wherever
the hyphae touch them, the colour extending for some distance
along the walls beyond the actual point of contact. Here and
there the ends of the hyphse emerge from the leaf tissues and
develop the branched conidiophores as above described. The
conidia being very minute and falling rapidly are blown about
and distributed by the wind like fine powder, thus enabling the
fungus to spread rapidly and infect fresh leaves and plants.

The conidia may germinate in one of the three following
ways : —

(1) If the conidium falls into a drop of rain or dew the proto-
plasm divides into from 6-16 parts, the tip of the
conidium dissolves, and these little masses of proto-
plasm escape. These are called zoospores, and each
is provided with two very fine hair-like appendages
called cilia which lash the water and enable the zoos-
pore to swim and move about in the water. In a
quarter of an hour or so these zoospores lose their

189

cilia and come to rest. Each then develops a very
fine tube which grows out into a hypha. The latter
dissolves its way into the cells of the leaf, or stalk,
among which it then grows and spreads and soon
reproduces the mycelium above described. See
Plate XVI (3)-(6).

(2) The conidium instead of forming zoospores itself puts

out a germ-tube which directly enters the plant tjs-
sues and forms the mycelium. See Plate XVI (7).

(3) The conidium forms a germ-tube as before, but this

instead of entering the plant tissues forms a secondary
conidium at its apex which in its turn falls off and
gives rise to zoospores or to another germ-tube which
directly enters the plant-tissues.

The first of these processes is the most frequent especially
with conidia which come in contact with water shortly after
falling. Conidia lose their power of germinating in about three
weeks, and dry weather is unfavourable to their production and
germination. Conidia which are washed by rain upon tubers can
infect the latter directly, the germ-tube penetrating the tissue
and forming a mycelium there. The mycelium may also pass
down the potato stalks and infect the tubers in this way. The
mycelium having reached the tubers may proceed to destroy
them in the same way as the leaves, the numerous bacteria in the
soil assisting in the decomposition of the diseased tissues, or the
mycelium may remain in the tubers in a dormant condition.
Such infected tubers on being cut open usually exhibit dark
patches and when stored frequently rot. If infected tubers are
planted out the next season the mycelium again becomes active
and growing along with the young shoots sent out by the tuber
reproduces the disease.

The plants may be sprayed with Bordeaux mixture which Preventive
has been described as " the most effective and cheapest fungi- Measures-
cide known ". This does not poison the tubers or make them
unfit for consumption, but it kills the conidia and zoospores and
prevents their germination. In addition to its action on the fun-
gus this mixture has actually proved beneficial to the potato
plant and results in an increased yield of tubers. The copper
in the mixture in some way which is not clearly understood
increases the amount of chlorophyll in the leaves and conse-
quently the assimilating powers of the foliage.*

Care must be taken not to use infected tubers for seed.

* For instructions regarding the preparation and application of Bordeaux
mixture see Potato Diseases of India by Dr. E. J. Butler, published in the Agr -
cultural Ledger, 1903, No. 4, pp. 108-109.

omnivora.

190

Some varieties of potatoes have been found to resist
the disease better than others. Tubers, for instance, with
exceptionally thick skins offer more resistance to the entrance
of the hyphse than do others with thin skins. In order to
keep up the power of resistance of the potato plant to the
disease, care must be taken to always select the most resistant
tubers for continued cultivation, and to raise new and stronger
varieties from the seed obtained by crossing good, selected,

«/ c? o

varieties. Diseased stalks, leaves and tubers should be burnt
and, to prevent risk of infecting sound tubers from living
conidia lying on the ground, the tubers should not be raised
for three weeks after the complete dying down of the plants.

As moisture favours the development and spread of the
fungus, wet localities should be avoided as far as possible.
Irrigation of the crop should be carried out with caution, and
the tubers should be stored in a dry well-ventilated place.
Phytoph- 167. Very closely allied to the

above fungus is another named Phytophthora omnivora De
Bary, which in Europe has proved very destructive to the
seedlings of forest trees. It is probable that the " damping
off " of seedlings in many of our forest nurseries in India
will be found to be caused by it or by some other nearly
related fungus with an almost identical life-history and
mode of attack- The first signs of attack are usually dark
spots on the stern, cotyledons, or first leaves of the seedling,
and if the weather is warm and damp the young plant is
soon destroyed. Frequently only the " collar ' is attacked
and the seedlings then fall over. If only the upper leaves are
attacked the seedlings may recover. The damage gradually
spreads from one seedling to those around it, and the
circle of diseased plants gradually spreads outwards from
the centre. The growth and injurious action of the my-
celium of this fungus in the tissues of the attacked plant
are almost precisely similar to those of P. „ infestans, except
that the hyphse more commonly absorb their nourish-
ment by means of haustoria. The most important point of
difference between them consists in the fact that this species
produces sexual resting spores (oospores) in the tissues of the
attacked plant. These spores have the power of remaining
dormant for several weeks or months before germinating and
hence their name of resting spores. In the formation of these
spores the end of a hypha swells up into a rounded knob, and
the protoplasm inside it forms into a ball thus producing what
is called the oosphere or egg-cell. The end of another hypha
then coming in contact with the swelling, sends out a small

191

tube which pierces the cell wall and penetrates to the oosphere.
the protoplasm of the hypha then passing into and mixing
with that of the oosphere, through the short connecting tube.
The oosphere is then said to be fertilized and is called the
oospore. These spherical oospores soon develop a hard pro-
tective cell-wall and are capable of retaining thejr vitality
and power of germinating for a considerable period. These
spores find their way from the decaying tissues of the seedlings
into the soil and, if seed is sown in the same soil, the new
crop of seedlings is almost invariably severely attacked by
the disease, the oospores in the soil germinating and producing
hyphse which then proceed to branch and form conidia as
before. This fungus is as a rule only destructive to seedlings,
young plants one year old and upwards being rarely injured.
It is also capable of living in the soil for a long time as a
saprophyte and thus can exist independently of seedlings,
although it is always ready to resume its parasitic mode of life
on any suitable seedlings it may meet with.

As in P. infestans moisture favours the spread and deve-
lopment of the pest; consequently shading the seed beds is
inadvisable as this would prevent the rapid evaporation of
moisture. Spraying with Bordeaux mixture will aid in pre-
venting the spread of the disease. Isolated specimens of
diseased seedlings should be carefully removed and burnt,
care being taken not to infect fresh seedlings by shaking of?
the conidia. If a considerable number are affected the best
way of preventing the dispersal of the conidia is to cover
the patch carefully with soil. People passing through the
seed-beds may convey the conidia on their clothes, or boots,
to healthy individuals which should be avoided as far as pos-
sible. Seed-beds must be frequently inspected so that timely
measures may be taken to check the disease. A seed-bed
which has been attacked should not be used again for seed-
lings of the same species. In some cases good may be done
by burning rubbish on the infected seed-bed, sufficient heat
being produced to kill the spores in the soil.

168. This fungus is also known (2) Fames

by Hartig' s name of Tmmetes radiciperda. In Europe it has «f »°*«*
been found to attack Pinus, Picea, Abies, Juniperus, Thuja, the species
Beech, and other dicotyledonous trees. It is most destructive to attacked,
conifers, and in India it is at present best known on account
of the damage done by it to the Deodar, Cedrus Libani var.
Deodara, which it attacks and kills. The fungus is frequently
seen in the forests of Jaunsar.

192

Signs of the Young Deodar trees 6-15 feet in height are chiefly attacked.
One tree generally dies first and then the disease spreads to
others near it, gaps being formed which quickly extend cen-
trifugally. Resin at first begins to e%ude from different

o «/ o

points along the stem and then the needles turn yellow and
fall off. Stems usually take two years to die completely.

The sporophores or fruiting organs are developed at the base
Life-History of the Deodar stems and will also probably be found
and Damage On the roots below the ground surface. They arise from
done. cushions of mycelium which force their way to the

surface of the stem or root at these points, where the sporo-
phores first appear as small, rounded, chocolate -brown
nodules. These increase in number and run together forming
a brown incrustation broken by numerous ledges and tuber-
cles. On the younger portion of the sporophore a series of
imbricate bracket-like protrusions are developed. The lower
surface of these brackets is white and contains numerous
minute pores, on the walls of which the spores are developed,
while the upper surface is rough, brown, and covered with
tubercles and concentric ridges. It is probable that these
spores are often carried in the ground on the fur of mice and
other burrowing animals and are rubbed off on healthy roots.
On germination they give rise to very delicate hyphse which
penetrate between the bark scales, force their way into the
wood and give rise to characteristic white sheets and bands
of mycelium, between and under the bark scales. The roots
are not the only parts affected. Broad bands of the
mycelium invade the collar, ascending the stem and forcing
their way along the cambial layer, in feathery strands of
snow-white tissue. These completely destroy the cambial
layer. In addition to this the wood is directly attacked
and destroyed by the minute hypha3 which bore their way
from cell to cell by means of a cellulose-dissolving enzyme
which they exude. The lignin in the cell-walls of the
attacked wood is dissolved out first by the hyphae and
the middle lamella is destroyed, so that the wood
elements fall apart. As a result of this action white areas
of diseased wood arise which are very characteristic and which
are usually elongated in the direction of the long axis
of the stem. They consist of dissociated cells of prac-
tically pure cellulose, which, being themselves ultimately
decomposed, leave small hollows in the wood. Before de-
composition is completed the cell-walls show a fine striation
and, later, large spiral cracks. Living cells in the wood paren-

193

chyma and medullary rays attacked by the hyphse become
filled with a brown substance, probably caused by the
decomposition of the protoplasm. This discoloration is more
noticeable in the roots than in the stems of the Deodar. A
remarkable characteristic of this fungus is the possession of
rhizomorphs. These are branched, cylindrical, or~ flattened,
bodies composed of an outer, black and somewhat brittle,
cortex, formed of interwoven tough brown hyphse and of a
central, tough, flexible, whitish portion composed of fine
hyphal filaments. In general appearance these resemble the
black petioles of some ferns and are not unlike the ordinary
fine Deodar roots. They are, however, blacker, of a different
consistency, and do not taper regularly towards the apex.
They can be distinguished by splitting them longitudinally
when the silky white medulla can be teased out with the
fingers. These are organs of propagation possessing the
power of apical growth. Springing from the mycelium in
the roots of diseased trees, they travel below the surface
of the ground and, penetrating below the cortex of any healthy
Deodar roots which they may encounter, develop in them
the ordinary mycelium, and thus spread the disease from tree
to tree. Trees growing close together in the forest often have
their roots in close contact and are frequently found grafted
together. It is probable that infection often takes place by
the mycelium thus growing directly from one root into
another which is in contact with it. For illustrations, see
Plate XVII.

The only measures likely to be effective are the removal of
attacked trees to prevent the formation of sporophores and the
isolation of infected areas by trenches dug a few feet deep
and sufficiently far from the centre of infection to include
all diseased roots and rhizomorphs. It is doubtful if this
could be done profitably on a large scale.

169. In its life-history and

action on the plant attacked, Armillaria mellea, which has been
briefly noted in Part IV above, has several points of resem-
blance with the fungus just described, see page 133. Armillaria,
however, is particularly interesting as being one of those f ungi
which, although living at times in a purely parasitic manner,
are also able to exist as saprophytes. This fungus may
accordingly sometimes be found thriving on wood used in
construction, e.g. in bridges, and also on dead roots and
stumps, and at others as a virulent parasite attacking
and killing living trees. From cases such as these we

194

conclude that no hard and fast line can be drawn between
these classes of saprophytes and parasites, and there is every
reason to believe that the one mode of life has led to the other.
At the same time it must be remembered that a hypha, which
is able to pierce the cell- walls of a plant's tissues, is not by
any means necessarily able to kill the living protoplasm in
the cells.

ni 17°' In India thiS destmctive

Species" fungus has been found on Pinus excelsa near Simla, and
attacked. it is well known on various conifers in Europe.

Signs of the The characteristic sporophores usually first indicate the
Disease. presence of the fungus. These appear on the stem usually near
the stump of a dead branch, and are hard, bracket-like, masses
often triangular in section. The upper surface of the sporo-
phore is rough, blackish-brown in colour and with concentric
grooves, the fawn-coloured lower surface is covered with the
minute pores in which the spores are developed. See Plate
XVIII (a).

L'!TT iRtory ID nianv respects the damage done by this pest resembles

and Damage • v J £ v

done. that described above m the case ot tomes annosus,

but it is important to note that, whereas the latter
fungus can attack sound roots, Trametes Pini can only
attack a tree through an existing wound, and it is consequently
termed a " wound parasite". The spores, alighting on a
wound which is not covered with resin or other protective
substance, on germination produce hyphse which penetrate
into the stem. The hyphar bore through the cell-walls and
extract the lignin in them so that practically pure cellulose
is left behind. Characteristic white spots, which eventually
become holes, then appear in the attacked wood, see Plate
XVIII (6). The growth of the mycelium may also cause cup-
shake, or ring-shake. The timber is thus rendered useless, and
if the tree attacked cannot oppose the invading mycelium by
a copious flow of resin the hyphse may spread to the cortex
and kill the tree. Wounds caused by breaking or cutting off
old branches which contain heart-wood are favourite points
of attack, for little or no turpentine exudes from the central
portion of such wounds, into which in consequence the hypha3
readily penetrate. For the same reason such wounds also
afford a convenient passage free of resin by means of which
the mycelium can pass from the interior of the stem to the
outside for the purpose of producing sporophores, the latter
frequently appearing at such places. Sporophores are not
as a rule produced until a luxuriant growth of mycelium has

195

established itself in the interior of the stem, and if one sporo-
phore is removed another as a rule soon takes its place.

Diseased trees must be removed as quickly as pos- Preventive
sible. Wounding and injuring living trees must be avoided, and Measures.
cut surfaces should be covered with tar or other protective sub-
stance. So far as we can, we must help the cambium to
cover over as quickly as possible all wounds which may arise.

171. It has been estimated (4) Pyccmia

that the annual financial loss in India, on account of fhegraminis
damage done to cereal crops by the fungoid diseases popularly ^ers>.
known as Rusts, is probably not less than Us. 4,00,00,000. attacked.
The best known rust in India is Puccinia graminis which is
very destructive to wheat, and which we may also take as a
type of the great group of parasitic fungi to which the rusts
belong, viz. the Uredinaceae.

The first sign of the disease consists in the appearance of Signs of the
orange-red streaks and patches on the green wheat leaves, Dlsease-
culms and even on the ears, which in Northern India usually
happens in January — February. These rust pustules swell
and, bursting through the epidermal tissue of the wheat
plant, scatter spores which look like reddish dust and are
called uredospores.

If the tissues of the wheat plant are examined with Life History
the microscope the mycelial threads of the fungus will beand Damage
found ramifying in all directions between its cells. This done>
mycelium derives its nourishment from the green cells
of the wheat plant and consumes the food materials
which should go to form the grain ; consequently the yield
of the latter is enormously reduced. After growing and
spreading in the tissues of the wheat plant for two or three weeks
the hyphse turn towards the epidermis, and the orange, oval,
one-celled uredospores are budded off from their tips ; the
gradual accumulation of these hyphal branches and the spores
which they shed result in the swelling of the pustule and
ultimate rupture of the epidermis with the scattering of the
spores. If these spores fall into water they germinate and
send out two or more germ filaments [see Plate XIX (2)], one of
which outstrips the rest and either dies in the absence of a
suitable host or, in the event of its having alighted on a wheat
plant in a drop of rain or dew (which would often happen in
a wheat field), finds its way into a stoma and rapidly gives
rise to a new mycelium, which in due course produces a fresh
crop of uredospores. The function of these spores is thus
to spread the disease rapidly from plant to plant, wind aiding

196

their distribution. Now as the season progresses, the myce-
lium which, for some weeks, has only produced uredospores,
now begins to form a totally different kind of spore, which
are known as teleutospores. These, instead of being orange or
reddish in colour, are dark purple -brown or black, and their
formation can be recognized by the appearance of grey streaks
and patches among the orange ones which spread and get darker
in colour, until ultimately the black pustules entirely replace the
rust- coloured ones which preceded them [see Plate XIX (1)].
These teleuto -spores are formed in the same manner as the uredo-
spores and by the same mycelium, the latter in the beginning
of the season producing only uredospores, then later a few
teleutospores among the uredospores, and ultimately nothing but
teleutospores. These spores which are formed by the fungus
in the later stage of its life-history, besides being quite distinct
in appearance from the uredospores, have a different function,
they being virtually resting spores. Besides the difference in
colour, each teleutospore instead of being one-celled is divided
across the middle into two cells or chambers. They are more
elongated and club-like in shape and have a thicker wall. They
are also as a rule not shed so quickly as the uredospores but
remain firmly attached to the wheat straw. They are generally
incapable of germinating for some months after their formation.
When they do germinate each cell sends out a short hypha
which then becomes divided by cross partition walls into
segments. From each segment a short lateral stalk (sterigma)
is produced, the tip of which swells and then falls off — the
minute, ovoid, spore-like bodies so formed being called sporidia.
The short hyphal filament developed from the teleutospore is
known as the promycelium. See Plate XIX (3).

Now in Europe it was found that these sporidia could only
develop if placed on a new host-plant, a species of Berberis, i.e.
an altogether distinct species from that on which the teleuto-
spores were formed. Germinating then on the leaf of a suitable
host-plant, these sporidia send out their germ tubes which
directly pierce the leaf -tissue of the Berberis and develop a
parasitic mycelium within it, the mycelium deriving its nourish-
ment from the cells of the Berberis tissue. Although the
Berberis plant is thus more or less injured, the damage done is
usually nob severe, and the great practical importance of this
fungus depends on the injury done to the wheat plant, which
resubs in an enormous decrease in the yield of grain. The
presence of the mycelium in the Berberis induces swellings in the
leaf tissue on which two different kinds of spores are produced.

197

The first to appear called spermatia arise in small cup-like recep*
tacles on the upper surface of the leaf. They are very minute,
and their function is at present unknown. On the under-surface
of the leaf, larger, golden-yellow, cup -like receptacles arise, which
are clearly visible to the naked eye and are often, known by
the popular term of "cluster-cups". These cups have fringed,
white margins and are rilled with golden-yellow spores. They
arise first beneath the epidermis as hollow balls, the membranous
walls of which are formed by the fungal hyphse and constitute
what is known as the peridium. The base of these balls is
formed by a number of short hyphae with their ends directed
towards the apex of the ball. From the ends of these hyphae
spores are ab jointed in succession from the apex downwards,
long chains of spores being thus produced. As the formation
of spores proceeds, the ball swells and ultimately the epidermis
of the leaf and the peridium covering are ruptured and the ball
becomes a cup-shaped receptacle projecting from the leaf sur-
face. As the spores escape from these receptacles and are dis-
tributed by the wind, fresh ones are developed from the hyphae
at the base to replace them. See Plate XIX (4), (5) and (6). This
form of the fungus developed upon the Berberis was at first
thought to belong to a distinct genus from that which included
the form occurring on the wheat ; it consequently received the
name of Aecidium Berberidis, and it was long before the connec-
tion between the two was established. The cluster cups are
called aecidia and the spores developed in them aecidiospores.
These spores are very like the uredospores except that they are
more golden-yellow in colour and are often somewhat polygonal
in form, owing to the pressure which they have undergone.
These spores, alighting on a damp wheat plant, send out germ
tubes which, finding their way through the stomata, give rise to
the mycelium in the plant tissue from which uredo- and teleuto-
spores are ultimately produced as before. Aecidium Berberidis
is found on Berberis Lycium near Simla and also probably occurs
on other Indian species of Berberis.

We thus see that the complete life-history of this fungus
comprises two distinct stages which may be called the Pucci-
nial and Aecidial respectively, and these stages may be sub-
divided into four as follows :—

C (1) The parasitic mycelium in the wheat
Puccinial I plant developed from aecidiospores and

, "! giving rise to uredospores.

i (2) The formation of teleutospores from

Lthe same mycelium.

198

f (3) The germination of the teleutospores
| giving rise to a promycelium and sporidia.
Aecidial J This is a non-parasitic stage,
stage. (4) The germination of the sporidia to

J form a parasitic mycelium which ultimately
(^produces secidiospores.

In our typical example the puccinial and aecidial stages
are passed on different host-plants ; such a fungus is said to be
heteroecious, and the host which nourishes the aecidial stage is
in this case called an intermediate host. Other allied fungi
pass both the puccinial and the aecidial stage on the same
host-plant andare consequently called autoecious.

Now in the central areas of India Puccinia graminis is one
of the commonest wheat rusts, and it has been found widely spread
in places over 600 miles from any species of Berberis which
in India are confined to the high hill ranges. In Europe also
it has been found that wind-blown secidiospores can ordinarily
only infect plants within a radius of 25 yards from the bush
on which they arise, and hence it is improbable that wind-
blown a3cidiospores could in such cases be responsible for the
disease. This rust also is common in parts of Australia,
e.g. in Victoria, where no Berberis grows wild and very few are
cultivated. Again, if the secidial stage on the Berberis is
always necsssary for the continued existence of the fungus,
the complete destruction of all species of Berberis should suffice
to eradicate the disease in the areas treated. This, however, has
not been found to be the case. Finally Aecidium Berberidis is,
in India, restricted to a portion of the Himalayan Eange, and
it is precisely in this area that Puccinia graminis is extremely
rare on cereals. We are therefore driven to the conclusion
that the fungus can, and often does, dispense with the a^cidial
stage and continues to exist on the wheat, year after year, in
the puccinial stage. How this is managed is not yet clearly
understood. It has been suggested that the uredospores may
pass from the wheat to some wild perennial grass and that the
fungus may thus continue to maintain itself on the latter in the
puccinial stage until the season for the next wheat crop comes
round again. In Europe this fungus has been found on 150
different species of grasses, including oats, wheat, barley and
rye, these being known as collateral hosts. It has, however, been
found that the form on wheat is exclusively limited to the wheat
and cannot impart the disease to any other collateral host,
with the sole exception of rye and barley, which in rare cases

199

may be infected. On the other hand, uredospores from other
collateral hosts fail to infect the wheat, except in rare cases
under very favourable conditions. It has in fact been clearly
established that this wheat rust is a highly specialized form of
the fungus which possesses very little capability of directly
passing on to and infecting other nearly allied" species of
plants.* Another suggestion is that the uredospores may live in
the soil during the period when wheat is out of the ground
(between April and November) and be able to infect the young
crop in December — January. Experiments, however, with
allied fungi have shown that the uredospores soon lose their
power of germination, especially when they are exposed to a
high temperature, as they would be in the hot season in the
plains of India.

These explanations therefore can hardly account for the per-
sistence of the disease. Again it has been suggested that the
sporidia may be able to give rise to a mycelium in the wheat
plant capable of producing uredo- and teleuto-spores. This is
improbable and there is no evidence to support it. The most
recent researches on the subject indicate that the rust on wheat
may be a truly hereditary disease. The protoplasm of the
fungus is said to be able to exist in intimate union with the
protoplasm of the wheat plant, and its presence then can only
be detected with great difficulty. This state of things may
continue for months, or even years, the disease germs passing
on from generation to generation in the seed, and it is only
under certain favourable conditions of moisture, heat, and of the
state of the host-plant itself, that the fungus becomes distinctly
visible in the form of a mycelium, which takes place just before
the rust pustules begin to appear.

The only practical measures at present available for com- Preventive
bating this fungus consist in selecting the most rust-resistant Measur^s>
varieties of wheat for continued cultivation and in endeavour-
ing to produce new and improved varieties by inter-crossing.

* Seeing that the various forms of this fungus, occurring on different collateral
hosts, are each more or less confined to some special species of plant we cannot
doubt that in some way they differ essentially from one another. At the same
time, so far as visible microscopic characters are concerned, these forms cannot be
distinguished and hence they are all grouped under the species Puccinia graminis.
Here we appear to have an example of the power possessed by some plants of
adapting themselves to changed conditions, and we see that, having become
accustomed to one set of conditions, they do not readily adapt themselves to
another, although hi time a specialized form may arise which can do so.

200

Aecidium
mnntanum.

Parasitic
Phanero
gams.

172. The life-history of several

other rust-fungi exhibit the two stages described above, viz. the
Puccinial and Aecidial, but, as our selected example clearly
shows, these two stages are not always necessary. Thus there
are species of Puccinia of which no Aecidial form is known
and vice versa. As an example of an Aecidium of which no
puccinial stage is known, we may take the " cluster-cups ' ' so
often seen on Berberis Lycium, B. coriaria, and B. aristata, in
Jaunsar and near Mussoorie. This species has been named
Aecidium montanum. The mycelium of this species is peren-
nial, the hyphae running in the cell walls and intercellular spaces
of the stem and leaves and obtaining food by means of little
finger-like haustoria pushed through the walls. Its presence
in the tissues of the Berberis causes the formation of very
characteristic witches' brooms. The affected shoots become
dwarfed, bear malformed leaves and grow vertically upwards,
the long, yellow, aecidial cups occurring in masses on the under-
side of the leaves and also scattered on the shoots and
sometimes on the peduncles, from which the clouds of powdery
orange aecidiospores are shed and disseminated by the wind.
Sometimes more than half the bush may be affected in this way.
A healthy bush on first infection shows large, reddish, or scarlet,
patches on the upper surface and numbers of the long aecidial
cups below. In this case there is no deformity beyond a pucker-
ing of the leaves, and it is uncertain whether first infection takes
place by aecidiospores or by sporidia. If by the latter, the
puccinial form bearing the teleutospores is still unknown.
This species is distinguished from A. Berberidis by the witches'
brooms, by the greater length of the aecidial cups, which may
amount to 4 mm., and by the greater size of the patches seen
on newly affected normal leaves, which ranges from J to f of
an inch in diameter.

173. The following may be
taken as typical examples of parasitic phanerogams : —

(1) Orobanche indica.

(2) Cuscuta reflexa.

(3) Loranihus longiflorus.

(1) Orobanche
indica.

174. The handsome spikes of

pale purple, or blue, flowers of this plant are often seen
in the mustard fields of Northern India, and the total
absence of green leaves at once strikes us as peculiar.

201

This species being thus unable to manufacture for itself the
carbonaceous organic food materials which it requires is obliged
to obtain them ready-made from other plants. If the soil is
carefully removed from the roots of an Orobanche plant these are
found to be joined to, and in intimate connection with,
the roots of the neighbouring Jmustard plants from~which they
take their necessary food materials.

175. This is the well-known (2) Cuscvta

leafless Dodder, masses of whose wire-like stems may often be seen reftexa'
enveloping trees and shrubs with a yellow, or greenish,
mantle. Although the plant contains a little chlorophyll,

this is quite insufficient for the manufacture of the food
it requires. If we examine the twining stem we find that,
where it comes in contact with the stem or twigs of the
host, small wart-like protuberances are developed which
pass into and are in intimate connection with the tissues of
the host from which it derives its water and nourishment.
These suckers, or haustoria, are able to force their way into the
tissues of the host without difficulty, partly owing to the action
of dissolving enzymes which their filaments excrete after the
manner of fungal hyphae. The seed of this species germinates
on the ground, but the rootlet which is developed soon dies off,
and if the filamentous stem fails to encounter a suitable host
the seedling perishes. If allowed to develop undisturbed
the Dodder may kill the plant attacked, and gaps in garden
hedges caused by it may often be seen.

176. This very common plant (3)L<"anthu3

. , f . , • i P ji • longiftorus.

may be taken as iairly typical ot the numerous species
of Loranthus and Viscwn which occur in Indian forests.
Their chief peculiarity consists in the fact that they pos-
sess a considerable supply of chlorophyll, many of them, like
our example, being provided with well-developed green leaves.
This plant appears to be chiefly distributed by birds who
deposit the seeds on the branches and stems of trees where
they germinate and grow. The young radicle, piercing through
the cortex of the branch or stem attacked, penetrates to the
young wood, in the tissues of which it spreads and develops.
This plant obtains its supplies of water and mineral salts
directly from the wood elements of its host and the portion of
the branch or stem above the point of attachment of the para*
site, being deprived of its water-supply, dies and we get stag-
headed trees. The attacked branches become swollen and dis-
figured while the parasitic roots, being embedded in the wood,

202

render the latter more or less worthless for construction. It
is probable that this plant transfers some of its carbonaceous
food materials to its host, but it is not known whether it absorbs
any organic food substances from the host in addition to the
supplies of v,Tater and mineral salts. The chief practical
method oi combating this pest consists in cutting off and de-
stroying the attacked branches.

177. Among parasitic phane-
rogams which are furnished with an abundance of chlo-
rophyll the well-known sandal tree (Santalum album,) re-
quires brief notice. It is now known that this tree is
dependent to a very large extent on the roots of the plants
near which it grows for its supplies of water and mineral salts,
the Sandal roots developing numerous haustoria which
penetrate the root tissues of the host-plants and draw from
them the necessary supplies of food materials. No definite
information is at present available as to the extent to
which the host-plants are damaged by this parasitism, and it
appears probable that they may benefit to some extent by a
supply of carbonaceous food which has been manufactured in
the green sandal leaves, in which case the partnership would
be more or less a reciprocally-symbiotic one. Numerous costly
attempts have been made to artificially propagate sandal in pure
plantations which, owing to the absence of other trees and shrubs,
were of course failures, and although this tree is of such great
economic importance it is a remarkable fact that its para-
sitism was until quite recently regarded as uncertain. It
is, therefore, not a matter for surprise that the artificial pro-
pagation of this tree was frequently a failure, or that the
notorious " spike " disease from which it suffered had baffled
all attempts at explanation and prevention. Until we know
the principal conditions essential for the healthy development
of our important species, it is obvious that we -cannot expect
to propagate them successfully or to discover the cause of,
or remedy for, any disease which may attack them. Hence
we must recognize the paramount importance of studying
the life-histories of our forest plants and the relations which
exist not only between them and their non-living environ-
ment but also between them and other living organisms.

Leaving parasites we now pass on to :—

Lichens.

example of

178. Perhaps the most typical
symbiosis among plants is afforded by

203

the lichens. As has been seen above, a lichen con-
sists of two distinct plants, viz. an alga and a fungus, see page
137. The fungus receives carbohydrates from the alga in
return for which it protects the alga from drought and pro-
vides it with water and mineral salts.

179. Another well-known exam- Bacteriaand

pie is furnished by the bacteria which, as noted in Part IV Leguminosae.
above, see page 129, live in the tubercles often found on the roots
of the Pea, Bean and allied plants belonging to the Natural
Order Leguminosae. The best known of these bacteria is named
Bacillus radicicola which, passing through the root hairs,
gives rise to the peculiar tubercles in the root cortex of the
infected plants. The bacteria are localized in these tubercles
and do not spread to neighbouring tissues. While the bac-
teria live on the carbohydrates supplied by the host they,
in their turn, are able to provide the host with valuable
nitrogenous food materials, owing to the power possessed by
them of fixing the free nitrogen of the air and of manufac-
turing from it a compound which can be utilized as food by
higher plants. Owing to this remarkable symbiosis by means
of which most leguminous plants can accumulate nitrogenous
organic material in their tissues, a crop of such plants can
actually enrich a soil poor in nitrates. Hence in agriculture
it is a common practice to grow such plants and to plough
in the crop as manure.* In a soil rich in nitrates, leguminous
plants can obtain their nitrogenous food without the aid
of these bacteria, and in such cases very few, if any, tubercles
are formed.

180. The majority of the Mycorhizae.

higher plants cannot directly utilize as food the organic
substances, such as the dead remains of plants, wood, leaves,
etc., which compose the humus of the Forester. Hence
such plants are found to grow normally when supplied
solely with water and the necessary mineral salts. Many
plants, however, such as pines, oaks, the hazel and others,
can thrive on humus soils, and in the majority of such
plants their roots are found to be living in symbiosis with
the mycelia of fungi. The fungal hyphse are sometimes
found chiefly inside the cells of the root cortex, a few fila-

*lf leguminous plants could be grown continually on the same soil the supply
of nitrogen, in the latter might clearly be increased indefinitely, but unfortu-
nately this is not at present possible. Experiments in Europe have shown that
clover can only be successfully grown on the same soil about once in four 37ears
and sometimes even not so frequently. The reason for this is at present unknown.

204

Distant

Symbiosis

between

Green and

Non-green

Plants.

Decay of
Wood.

ments here and there extending into the soil, and at other
times they cover the roots externally with a felt-like mantle.
Such mycelial growths are called mycorliizas. In Europe
it has been found that if trees like the oak and pine are grown
in sterile soil and are thus deprived of these mycorhizas their
growth is retarded and sometimes entirely prevented. The
precise nature of the symbiotic relation in this case is not yet
known, but it is probable that the host supplies the fungus
with carbohydrates, while the fungus helps the host to obtain
water, mineral salts (probably phosphates and potassium
chiefly) and simple nitrogenous compounds.

181. The above are all instances

of close symbiosis, i.e. in which two organisms live in
intimate connection with each other. As an example of distant
symbiosis we may take that existing between green and non-
green plants.

We have had frequent occasion to mention above the
decomposing action of many bacteria and fungi which give
rise to various processes popularly called rotting, putrefaction,
fermentation, nitrification, etc., such organisms being able
to feed on complex organic materials and to break them down
into simpler substances on which the higher green plants
feed. By the activity of such organisms, for instance, the
carbon dioxide required by green plants is being continually
returned to the air, while nitrogenous organic substances
such as albuminoids, amides, and others are also broken down
and nitrates produced which are the chief source of nitro-
genous food for higher plants. Many of these decomposing
processes are accompanied by a liberation of energy in the
form of heat, and we know that the heat may be so great,
in a stack of rotting hay, for instance, that spontaneous com-
bustion is produced.

182. Before leaving this sub-
ject of decay a few words will be added on the decay
of timber. In the first place care must be taken to
distinguish between the terms dead and decayed. Plant
tissues become dead when their elements lose their living
protoplasmic contents, they do not become decayed until
they have undergone a further process in which they become
disintegrated and their structure is destroyed. A piece of
sound, Teak heart- wood, which is really dead tissue, and which
is known to be the best and most durable wood for construc-
tion, compared with a fragment from a hollow tree which

205

can be crumbled in the fingers will illustrate the difference.
For the decay and destruction of structural timber fungi
are mainly responsible, their hyphae excreting enzymes which
destroy the wood tissue, as has been made clear in the examples
of Fomes and Trametes, and it is therefore important to
remember that, as a general rule, the conditions nrrost favour-
able for the development of such fungi are:—

(1) A supply of organic food materials such as carbohy-

drates and proteid substances which are com-
monly found in sapwood.

(2) Warmth.

(3) A liberal supply of moisture and absence of free

ventilation.

(4) A supply of oxygen.

Thus sapwood, especially if kept damp, quickly decays,
and in the case of posts driven into the ground we frequently
see that decay spreads most rapidly in that portion of
the post situated in the upper, well-a3rated, layers of soil.

Seeing also how fungal hyphse may spread from a decayed
piece of wood to a sound piece in contact with it, and how
easily the minute spores are distributed, it is clear that the
greatest care must be taken if we wish to preserve sound
wood from infection.

SECTION III.— INFLUENCES OF THE SOIL ON PLANT DEVE-
LOPMENT.

183. For the healthy develop- Presence of

ment of plants the soil must contain a sufficient supply of all ^eoewaiy
the essential mineral salts. These may, for instance, be suitable Con-
so diminished by the competing roots of neighbouring dition and in
plants as to cause disease and death, the absence of •^lltab|e.
any one of them making growth impossible. Further these

salts must exist in such a state of combination as to enable
the plant to make use of them as food materials, and they
must not be present in excess. The best nutrient solution
for most phanerogams, for example, should not contain more
than 0*5 per cent, of salts.

184. Any substance which may Presence of

cause disease or death in plants may be broadly classed as a Substances.
Poison. If the solution of salts in the soil becomes concentrated
beyond a certain limit, rarely exceeding five per cent, owing to

the osmotic processes being interfered with, the roots of plants

206

are no longer able to obtain their necessary supplies of water
from the soil and are thus in danger of desiccation. At the
same time plants vary in this respect and there are many
(usually known as halophytes) which can thrive on saline
soil and are able to recover the necessary water from con-
centrated solutions of salts. There are also many substances
which have a more directly poisonous effect on plants and
such are as a rule the salts of the heavy metals, e.g. sulphate
of zinc and others. Free acids and alkalies are also very
poisonous even when dilute. Carbon dioxide is continually
excreted by the roots of plants and, in water-logged localities,
the accumulation of this gas may have a poisonous effect.
The escape of coal-gas from underground pipes, or chemical
solutions from factories, such as dye-works, may also kill and
injure plants. Again many essential mineral salts, and others
which, though not essential, are often found to be taken up
by plants, may have a poisonous effect if present in large
quantities. A trace of iron is thus essential for plants, but
a very dilute solution of an iron salt may be poisonous, the
quantity of the salt present being above the optimum. Cal-
cium appears to be injurious in some cases, while as regards
common salt it is not clear if its injurious effect is merely
due to its osmotic properties or to a more direct poisonous
action. In the majority of cases the exact way in which
the poison acts is not known, but sometimes at all events
the poisonous substance appears to enter into chemical
combination with some constituents of the protoplasm, much
as in the case of animals carbon monoxide combines with
haemoglobin. Humus by its absorbing action has a most
beneficial effect in protecting plants from poisons. Poisonous
metallic salts may thus be strongly held by the humus and only
allowed to pass into the soil in very dilute, harmless solutions.
The principal product which is excreted in large quantities
by the roots of higher plants is carbon dioxide, and this being
a gas rarely accumulates sufficiently to be injurious.

Many plants are also able to accumulate considerable
quantities of poisonous substances without injury, by
depositing them in dead tissues, or in living ones in such a way
that they cannot penetrate the living protoplasm.

185' Umess the root-hairs are
Water and able to obtain a sufficient supply of water and oxygen in the
Oxygen. soil they cannot perform their functions properly, and a good
soil, besides being sufficiently moist, must, therefore, be open and
well aerated. The amount of available water in a forest

207

soil may be decreased by a diminished rainfall and by the
more or less complete failure of the monsoon, by draining,
by the removal of litter, or by interrupting the leaf canopy,
and this may cause trees to become stag-headed. The same
result may be caused by underplanting trees with a species
which absorbs large quantities of moisture fronT the soil.
In an ordinary well-drained soil oxygen is always present
as gas in the interspaces and also dissolved in the water. If
this oxygen is removed the root-hairs are killed and the roots
rot, the trees becoming stag-headed. This may be caused
by water being allowed to stagnate around the roots as hap-
pens in swampy ground, and it commonly occurs also in dense
soils and in soils with an impermeable substratum. The
available oxygen in such cases is gradually exhausted, that
utilized by the roots being not replaced sufficiently quickly
by the admission of fresh air. The same result may be caused
by other factors which interfere with the free aeration of the
soil, such as heavy grazing which hardens and increases the
density of the soil. The roots of plants grown in glazed
pots are unable to obtain a sufficient supply of oxygen and
often rot in consequence. Similarly trees growing in
towns are often unhealthy, owing to the buildings and
close pavements preventing sufficient water and air entering
the soil.

The free aeration of the soil is also important for another
reason. We have seen above that organic substances, such as
humus, cannot be directly used by the higher plants as food,
although such substances always contain a certain quantity
of the elements, such as phosphorus, potassium, nitrogen,
etc., which are essential for the existence of such plants. With-
out the aid therefore of fungi and bacteria which break down
this organic material and liberate these elements in a suitable
condition, they could not be utilized by the higher plants
and consequently humus would accumulate in our forests
and the soil would gradually become poorer in the essential
food materials, until eventually no trees could grow in it.
Now a sufficient supply of oxygen is absolutely necessary
for the existence of a large proportion of these useful fungi
and bacteria, and they are in consequence found in the upper
layers of the soil,* where, moreover, their presence is most

* Experiments have shown that when impure sewage water containing large
numbers of bacteria is passed through sandy soil most of the bacteria are retained
in the superficial well-aerated layers of soil, on which fact the system of filtering
water throug'i sandy soil is chiefly based.

208

Accumula-
tion of
Starch in
the Leaves
indicates
Root
trouble.

needed, seeing that this is where organic debris chiefly
accumulates. Thus from this point of view alone we
see how enormously important is the proper aeration of
the soil, as also is, of course, the quantity of moisture in the
soil, and its temperature, and indeed all factors which may
favour or retard the development of these useful living
organisms.*

186. Now if for any of the above

reasons a plant is unable to obtain its necessary supplies of water
and mineral salts from the soil, the carbohydrates manufactured
in the leaves cannot be converted into plastic materials
and thus be conducted away to the growing tissues which
require them, but, owing to the deficiency of water, have to be
put aside as starch, and hence an accumulation of starch grains
in the leaves is often an indication that we must look to the
roots for the cause of a disease.

ture.

SECTION IV. — INFLUENCES OF THE ATMOSPHERE ON PLANT

DEVELOPMENT.

187. For every external factor

which affects the growth and development of a plant, such
as temperature, light, etc., there is, as has already been noted
in Part 1 1 1,, a, certain degree of intensity called the optimum
which is most favourable to the plant, see page 86. Any
Tempera8 * considerable departure from this limit may cause disease and
if carried far enough death. Thus, as regards temperature,
the death of plants may be caused either by excessive
heat or cold. The power of a plant to withstand extremes
of temperature depends chiefly on the species of plant and its
stage of development. Most flowering plants are killed by
a long exposure to a temperature of 45° C., while some bacteria
grow well at a temperature of 70° C. Potato plants may be
killed in one night by a temperature of — 4° C, while some bacteria
can withstand a temperature of — 200° C. Khair (Acacia Catechu)
and Ber (Zizyphus Jujuba) are frost-resistant, while Aonla
(Phyllanthus Emblica) is frost-tender in the climates where

* In connection with this breaking down of organic material by fungi and
bacteria it is interesting to note that this process may not only result in the pro-
duction of very valuable plant food materials, but may also convert evil smelling
organic substances, such as are contained in sewage, into simpler substances which
are absolutely free from odour and inoffensive, a fact which is utilized in the
disposal of sewage in towns, the sewage being collected in tanks where it is
exposed to the action of various fungi and bacteria.

209

they usually grow. Again, as regards the stage of de-
velopment, we know that many trees which are easily
killed by extremes^ of temperature as seedlings are
resistant when older, and that, for example, flowers and young
leaves may be readily injured while resting buds are very
resistant. The quantity of moisture also present" in a plant
materially affects its power of withstanding extremes of tem-
perature. Many mosses and lichens are easily killed when
moist, but are extremely resistant when dry. The more water
contained in plant tissues the more likely are they to be
injured by frost.

188. Excessive heat most com- Effects of
monly injures plants in one of the following ways : — Excessive

.ti.C£ii»

(1) By causing the drying up and death of leaves, twigs,

branches, or even entire plants and trees, owing to
the abstraction of water from the plants themselves
and from the soil in which they grow. The roots
are thus unable to obtain sufficient moisture from
the soil to make good the losses occasioned by
increased transpiration. This form of injury is
most destructive in India in years when the more
or less complete failure of the monsoon has lowered
the level of all springs and considerably reduced
the amount of moisture ordinarily available in the
soil.

(2) By splitting the stems of trees. Intense heat, drying

up the outer tissues of a stem and thus causing them
to shrink, gives rise to splits in the wood very
similar to frost cracks. Thin-barked species, such
as Phyllanthus Emblica, may thus bo found split
to the centre, especially in years of drought.

(3) By directly scorching and killing the cambium and

other living tissues, thus causing cancerous patches
on the stems, or the death of entire trees. This
is often caused by the sun's rays impinging on
thin-barked stems, especially those which have
grown up in shade and then become exposed by
the felling of the surrounding growth, as happens in
the case of standards in a coppice.

189. Excessive cold usually results Effects of
in one of the following modes of injury :—

(1) The direct freezing and killing of parts of plants, such
as the leaves, twigs, etc., and even of entire plants

210

and trees. The injury or death is in this case
caused by some change in the protoplasm brought
about by the low temperature in a way which is not
yet understood, and which varies for different species.
On freezing, ice usually forms in the intercellular
spaces, water being withdrawn from the cells. This
withdrawal of water and drying of the cell contents
appears to be the cause of death in some cases. As a
rule the rapidity or otherwise of the freezing or thaw-
ing has no specially injurious effect, the injury being
due to the low temperature, although we can
generally only see if a plant is dead or alive after
thawing. (This action must be distinguished from
that of indirect desiccation, (2) below, in which a
sudden rise of the air temperature may be very
injurious, by increasing transpiration from the leaves
while the roots are still inactive in frozen soil. ) The
temperature of plants may be very considerably
reduced by radiation which may result in the tem-
perature of the plant being as much as 8° C. below
that of the air. Radiation is reduced by fogs,
clouds, dust, or smoke, and the kindling of smoky
fires is often efficacious in preventing frost damage,
as also are artificial coverings of various sorts.
The temperature of the leaves, twigs, and more
delicate serial portions of plants chiefly depends
on the temperature of the surrounding air, and
hence the damage done by frost depends to a
great extent on the locality. The absence of air
currents is one of the most important factors which
affect the air temperature and hence low-lying
enclosed situations where there is little or no cir-
culation of air are particularly liable to frost damage.
Such are the grassy blanks so frequently seen in
Sal (Shorea robusta) forests, in which the circulation
of air is prevented by the dense wall of high Sal
forest surrounding them on all sides and where the
cold air collects and stagnates. In such places
all Sal shoots are killed down year after year by
frost, whereas small patches of Sal forest may often
be seen in the same locality untouched by frost,
owing to the open cultivated ground on all sides
oi it promoting the free circulation of air currents.
In these frosty localities the cold air collects like

211

water in a lake, and the height to which it rises is
usually clearly marked by a definite line above
which growth is uninjured. This was well seen in
the Sal forests of the Dehra Dun during the
severe winter of 1904-05, a definite line being clearly
visible, running along the flanks of the Siwaliks,
below which the leaves on every tree were brown
and dead, those above the line being green and
uninjured. The presence of large quanti-
ties of water in the soil may considerably reduce
the air temperature, as may also a heavy growth
of grass which reduces the temperature by
radiating heat, transpiring moisture, interfering
with the free circulation of air, and with the access
of heat to the soil. Observations have shown
that the temperature on an area covered with
grass may be 16° F. lower than that of a similar
area with no vegetation. The effect of frost
depends of course largely on the condition of the
plant itself. Consequently two trees of the same
species may be very differently affected in different
localities. One growing in a damp warm valley
may be killed, while another, in a more exposed
situation at a higher elevation, may escape injury ;
the former owing its susceptibility chiefly to the
longer period of its vegetative activity, the larger
quantity of water in its tissues and to the latter
being less completely lignified or otherwise matured.
(2) The indirect drying up and killing of plants or parts of
them, the injury being caused in precisely the same
manner as in the case of drought. When the soil
temperature falls below a certain point the root
hairs are no longer able to absorb the necessary
supplies of water. While the roots are thus inactive,
the leaves may be actively transpiring moisture
under the influence of bright sun-light and dry air-
currents. The leaves and branches may thus become
completely dried up and killed. Trees which retain
their leaves in winter are particularly liable to this
form of damage and mahua (Bassia latifolia) and
achar (Buchanania latifolia) may frequently be seen
injured in this way. This mode of injury may often
be recognised by the leaves commencing to die
back from the tip, the tissues at the base of the

212

leaf-blade and especially near the midrib being
often uninjured and green, while the rest of the
leaf is shrivelled and brown, i.e. just those portions
escape injury which can first intercept the water-
supply on its entrance into the leaf and which only
allow that quantity of water to pass on to the
more distant cells which is in excess of their own
needs. See Plate XX. The damage can often be well
seen in a nursery after a frosty night, no injury to
the leaves being usually noticeable until the plants
have been exposed to the bright sunlight for some
hours. It is obviously important that trees grow-
ing at high altitudes, where the leaves are often
exposed to the bright sunlight when the roots are
in soil still frozen, should be able to prevent trans-
piration as far as possible. We thus find that the
high-level Rhododendron campamdatum and Quercus
semecarpifolia have the undersurface of their leaves
covered with dense tomentum. With regard to
this form of injury it must be pointed out that
roots situated in the superficial layers of soil are
more subject to the effects of sudden changes in
temperature, while those in the deeper layers of soil
are chiefly affected by prolonged cold temperature.
Thus in some cases we find seedlings suffer more
than older plants, while in other cases the reverse
happens. In the latter case the superficial roots,
under the influence of a few hours hot sunshine,
having been sufficiently warmed to become active,
whereas the deeper roots are still in frozen soil.
An artificial covering- of straw, dead leaves, etc.,
on the soil over the roots of a plant may often
prevent injury by frost, by moderating the tem-
perature of the surface soil, and it is probable
that the beneficial action of watering plants is
often due to the temperature of the roots being
raised sufficiently to become active thereby.

(3) The splitting of stems of trees. When the temper-
ature is sufficiently low ice is always formed
in plants, usually in the intercellular spaces, but
in wood, where intercellular spaces are usually
absent, in the lumina of the wood elements.
As these spaces contain considerable quantities of
air besides water, the water finds ample space for

213

expansion on being converted into ice. During the
formation of ice, water is abstracted from the cell
walls, and this results in the drying and shrinkage of
the wood, just as happens when cut timber is dried
in the air. During severe cold, especially if the
temperature falls very rapidly, the outer wood layers
shrink more rapidly than the inner warmer layers,
and longitudinal cracks and fissures are caused
in the stem. Such cracks may become occluded in
the usual way, but subsequent frost frequently
re-opens the wounds, and if this is repeated several
times prominent ridges, or frost-ribs, result.

(4) The formation of cankers. Frost cankers are usually

found at the base of a young branch which has
been killed by frost down to the main stem. The
callus forming at the base of the dead shoot is
again killed by subsequent frosts, and with recur-
ring frosts the cancerous area spreads. The growth
of the callus is also interfered with by the pressure
of the dead tissues under which it forms, and
such diseased areas usually heal slowly, if at all,
and aiford a favourable point of attack for wound
fungi. Cankers due to frost may be distinguished
from those due to fungi as they only increase in size
in frosty years.

(5) The uprooting of seedlings. When the soil freezes,

the expansion which the water in its interstices
undergoes, on being converted into ice, raises the
surface of the soil and pushes up the roots above
their original position. When the ice melts with
the thaw the particles of soil fall away from the roots
which become exposed and the plant falls over and
dies.

(6) The mechanical bending and breaking of stems or

branches, owing to the accumulation of snow or ice
upon them. On hill sides the pressure of snow
against the upper side of young stems often causes
the latter to curve outwards at the base, and this
curve, being retained as the plant grows older, is
often visible in mature stems. This bending over
of young stems often also ruptures the tissues on the
uphill side and causes wounds which may give
access to injurious fungi.

214

(7) The more or less complete destruction of flowers, leaves,
twigs, and young stems, by hail. The damage done
depends largely on the state of development of the
plant. While mature leaves may only be penetrated
by the hail-stones, giving rise to so-called " shot-
holes," the injury being more or less local, tender
young leaves may be torn into shreds and the tree
completely defoliated. Such complete defoliation
results in the loss of valuable food materials con-
tained in the young leaves, while the tissues have
to be depleted of their food reserves for the for-
mation of fresh foliage, this reduction in the avail-
able food supply resulting in loss of increment and
diminished production of flowers and seed.

of 190. All plants may be killed by

sufficiently strong light, and the fact that disease-produc-
ing bacteria may be killed by a sufficiently long exposure
to sunlight is obviously of great practical importance. In
green plants the chlorophyll corpuscles are usually more
subject to injury than the rest of the protoplasm. If the light
is too intense these corpuscles lose their power of assimila-
tion and may become permanently bleached. The necessity
of protecting the chlorophyll corpuscles from intense light is
indicated by the presence of colouring matters such as antho-
cyanin, to which the red or purple colour of many young
leaves is due, and which acts as a protective screen to the
chlorophyll, by the general absence of chlorophyll in the
epidermis,[and by the fact that the chlorophyll corpuscles when
exposed to strong light arrange themselves in such a way in the
cells as to be least exposed to its action.

On the other hand, deficiency of light may be no less injurious.
In the absence of light, green chlorophyll is as a rule not
formed and, the manufacture of food materials in the leaves
being impossible, the death of the plant by starvation ensues.
We know, for instance, how easily so-called ' ' light-demanding ' :
species may be killed by shade. Insufficient light causes the
diseased condition known as etiolation, which is characterised
by the development of abnormally long and thin internodes and
small, or very thin, yellowish leaves, with unusually watery
tissues. The thickness and rigidity of the cell walls is also
diminished, and the laying of cereals is due to the shading of
the lower portion of the haulms which thus become too weak
to support the weight of the plants. Unless the etiolated

215

condition has gone too far the plants may recover with the access
of sufficient light, but, owing to their abnormally thin and watery
tissues, they are particularly liable to be killed or damaged by
frost, fungi, and other injurious influences.

191. Somewhat similar to etiola- E£Eect ?f
tion is the condition produced by an excess of moisture

in a plant. This is chiefly due to transpiration not being
sufficiently active to deal with the quantity of water
pumped into the plant by the roots. The tissues become
over-saturated with water, food materials are excessively
diluted and can only be transported in sufficient quantity
very slowly from one part of the plant to another, in conse-
quence of which, as in the case of etiolation, growth in
length is considerable, but the watery tissues are not properly
matured and are very liable to be damaged by fungi, insects,
frost, etc. This condition is, of course, distinguished from
etiolation by the fact that green chlorophyll is present in the
leaves and that the disease occurs in plants which have access
to light. Plants with an abundance of water available for
their roots, which are growing in a saturated atmosphere, are
liable to suffer from the condition here described.

192. Winds, besides uprooting Effect of

trees, breaking their stems and branches and causing the '
development of stunted and misshapen crowns usually
bending away from the prevailing wind direction,
impoverish the soil by dispersing dead leaves and debris,

thus preventing the accumulation of humus and also diminish
the available supply of moisture in the soil. Winds may be
also exceedingly destructive to plants by increasing transpira-
tion. Dry winds in cold frosty weather are particularly
injurious, the roots in the cold soil being then unable to replace
the water removed by transpiration, the plants being more or
less injured, if not killed, by desiccation.

Observations have shown that the velocity of a wind which,
at a height of Ij feet above the ground, was only 22 '2 miles
per hour, may be as great as 42*7 miles per hour, at a height of 51
feet above the ground. Consequently tall plants and especially
tree -growth suffer much more from winds than shrubby or
herbaceous growth. It should be noted that in the case of the
Banana the tearing of the large leaves by the wind is a normal
condition leading to advantageous aeration of. the leaves.
Winds are also advantageous in the way of distributing pollen
and seeds and aiding the distribution of plants.

216

Presence 193. The presence of poisonous

Substance ** substances in the air may cause disaster to plants just
as may their presence in the soil. More than 4 per
cent, of carbon dioxide in the air is injurious to many
plants. Sulphur dioxide and fumes of hydrochloric acid are
especially harmful, to which fact is to be attributed the injurious
effect of an excessive amount of coal smoke, such as occurs in
many towns, and of the fumes from iron-smelting furnaces,
alkali and other chemical works. The foliage of plants thus
injured usually turns yellow, and the plants become sickly and
may eventually die. Trees usually suffer more than herbaceous
growth and forests have been injured at a distance of 4| miles
from the place of origin of the poisonous fumes. The Plane
(Platanus) is able to withstand the injurious effect of coal smoke
and grows well in smoky cities, as do also as a rule maples,
horse-chestnut and elms.

Effect of 194. The action of lightning

Lightning. in causing the death or disease of plants is not clearly under-
stood. In some cases a tree struck by lightning remains
practically uninjured ; a narrow strip of the cortical
tissues is separated from the wood and the wound is soon
occluded. In other cases, where the external signs of injury
are similar, the entire tree may die. Stems of trees in some
cases may be completely barked by lightning, in other cases they
may be shattered into fragments and occasionally set on fire.
The injurious effects may be confined to a single tree, or the
lightning, passing from the stem originally struck to others near
it, may damage a large group of trees. In the latter case the
extensive damage appears to be often due to the lightning
passing from root to root in the ground owing to the bad con-
ducting nature of the soil. In such a case the injury spreads
from a certain point in a centrifugal direction. Trees injured
by lightning may sometimes remain alive for 4 or 5 years and
then die.

SECTION V. — EFFECT OF FIRE ON PLANT-DEVELOPMENT.

195. The injurious action of fires

consists in destroying leaves, flowers, seeds, twigs, branches,
seedlings and young plants, and in scorching, and more or
less extensively injuring, the roots, cortex and cambium of
older trees.

Moreover, the soil may be injuriously affected owing to the
destruction of humus and to a decrease in the amount of avail-
able moisture. Fires may thus be responsible for wounds and

Effect of

'217

a diminished vitality, which render trees more liable to injury
by fungi and insects, for loss of increment and for interference
with reproduction. It has been noted above that different
species vary in their power of resisting excessive heat, and
while some plants are very sensitive to damage from fires others
are less so. The effect of the fire on any particular species of
plant depends mainly on the intensity of heat produced by the
fire and on the state of development of the plant itself. A %
fire which may be beneficial shortly after the fall of the seed,
by hastening germination, would be very destructive after ger-
mination has actually commenced. Seedlings of deciduous
species which have their serial parts destroyed by fire
in the resting season may be very little damaged, while
others burnt in the vegetative season may be seriously
injured. The seeds of some species also are readily destroyed
by fire, while those of others are protected from injury by hard
or corky coverings, etc., and in the case of some species the ger-
mination of the seed appears to be aided rather than hindered
by fire.

196. Finally, it must never be Necessity of

forgotten that a factor, in addition to any direct beneficial j^jjjjf the
or injurious action which it has on the development of Beneficial or
any particular plant, may also exercise a by-no-means less injurious
important indirect beneficial or injurious action, by Eff?ct of
affecting the development of correlated organisms. Thus68
winds may be directly beneficial in aiding fertilisation
and the distribution of seeds of a certain species, while they are
indirectly injurious by performing the same services for an
injurious plant competitor, or by distributing the spores of an
injurious parasitic fungus. Again fires may be indirectly
injurious by damaging symbionts, such as useful soil bacteria
or fungi, and indirectly beneficial by destroying, or retarding
the development of, injurious plant competitors or parasites.

218

PART VL-GEOGRAPHY.

CHAPTER L— FACTOKS INFLUENCING THE DISTRIBU-
TION OF PLANTS.

Factors 197. The principal factors affecting

affecting the distribution of plants will first be shortly considered under

Distribution. ^ f0Howing neads ._

(1) Water. (5) Air.

(2) Soil. (6) Existence of other Plants.

(3) Temperature. (7) Existence of Animals.

(4) Light. (8) Fire.

(9) Action of Man.

(l) WATER. 198. The water available for plants

Available depends chiefly on the rainfall. In deserts, where the amount of
depends moisture available for plants is exceedingly small, owing to the
chiefly on scanty rainfall, very few plants are able to survive and no forests
the Rainfall. exist. In India " really thriving forests are only found where the
rainfall exceeds 40", and rich luxuriant vegetation is limited
to those belts which have a much higher rainfall. " * Owin<*
to the low temperature prevailing at high elevations, mount
ains tend to condense aqueous vapour and thus receive more
rain than the adjoining lowlands. The greatest rainfall,
however, usually occurs at a comparatively low elevation and
at higher altitudes, instead of periodic heavy falls of rain
frequent mists and light rain occur, the rarefied air having
a very small capacity for aqueous vapour. This accounts for
the luxuriant growth of mosses and lichens often found cover-
ing the stems and branches of trees at high elevations. The
outer ridges of a range of hills, also, which first intercept the
currents of moisture -laden air, receive more rain than the inner
hills, and thus Deoban, for instance, on the outer ridge in the
North- West Himalayas, receives a greater rainfall than either
Mundali or Kathian, while, at the same time, Kalsi, at the foot
of the outer hills (elevation 1820'), receives a greater rainfall

* Cn the JJislribulion of Forests in India by Dietrich Brandis, p. 6.

219

than Deobaii at the top of the outer ridge (elevation 9300').

The amount of moisture in the soil may be largely due to Also on

percolation from rivers, canals, or lakes, to which fact is largely Percolation.

due the characteristic vegetation of river-banks and of areas

near large sheets of water.

An important Indian tree which requires a very heavy
rainfall is Ficus elastica, the Caoutchouc tree, and another
tree which is usually confined to areas near rivers or to swampy
ground is Lagerstroemia Flos-Reginae, one of the most im-
portant timber trees of Assam and Burma. On the other
hand, Prosopis spicigera is a tree of some importance which
can thrive in districts with a very small rainfall.

Under this head, also, must be considered the importance Action of
of water as an agent for distributing seeds. The sea is a ^.a*e.r, m, .

i T -i • ciii rrn Distributing

great obstacle to the distribution 01 land plants. Ine geed?.
fruit of the Cocoa Nut tree is provided with buoyant
tissue which enables it to float, and its seeds are able to
germinate after prolonged immersion in sea water. Many other
plants have similar contrivances; their seeds are often
distributed great distances by marine currents, and they are thus
able to establish themselves on distant shores.

Water is largely responsible for the distribution of the
spores of fungi, while rivers and streams play an important
part in distributing the seeds of many plants. The seed of
Sissoo (Dalbergia Sissoo), for instance, is chiefly distributed by
water, and that of Khair (Acacia Catechu) frequently so.

Finally must be noted the denuding action -of water which, injurious
by washing away the soil, exposes the roots of plants, thus Denuding
injuring the roots more or less, even if the plants are not
actually up-rooted. The shrub Rhabdia lycioides, common
in river-beds, with its creeping, rooting branches, is well
adapted to withstand the action of torrential streams.

199. On bare rocks an insignifi- (2) SOIL.

cant vegetation, consisting chiefly of lichens, alone can exist, Depth of
and on very shallow soil, capable of supporting a good growth Soil,
of grasses, the majority of forest trees cannot thrive, hence the
depth of the soil is of primary importance.

It has been rioted in Part V above that, for healthy plant Supply of
development, the essential mineral salts must be present in the Mineral
soil, and these must exist in a suitably dilute solution, see page Salts>
205. As the solution of salts in the soil becomes concentrated
beyond a certain limit, plants experience increasing difficulty in
obtaining their necessary supply of water from the soil. Many
substances, also, exercise a directly poisonous effect on plants

220

Supply of
Moisture.

and calcium and salts of iron often appear to be injurious in this
way. Plants, however, vary greatly in their power of with-
standing such injurious influences, and while some plants can
thrive on a saline, or calcareous soil, others cannot exist there,
a fact which is largely responsible for the characteristic vege-
tation of such soils. Among important Indian trees, Butea
frondosa is remarkable for being able to grow on soil contain-
ing large quantities of salt.

Supply of A supply of °xygen being essential for the healthy action of

Oxygen. the roots of plants, the water in the soil must be well aerated and
hence not stagnant. Many of our Indian trees are exceedingly
sensitive in this respect and cannot exist unless the subsoil is
well drained. The Deodar, Pinus longifolia, Sal, and many
others, all require well- drained soil. On the other hand, many
species can thrive in water-logged localities, e.g. Butea frondosa,
Terminalia Arjuna and others.

The physical and chemical properties of the soil itself, and
of the subsoil, influence the amount of available moisture to a
considerable extent. Finely divided soils, such as clays, have
the greatest power of absorbing water, and also, being very
impermeable, of retaining it. Sand on the other hand, being
very permeable, can retain very little water. Calcareous soils
again have very little power of absorbing water, while those
with an admixture of humus are capable of absorbing and
holding large quantities of water. Among Indian trees which
thrive best on clayey soils the well-known Sain, or Saj
(Terminalia tomeniosa), may be mentioned. Among trees often
found on calcareous soils are Khair (Acacia Catechu) and Satin
Wood (Chloroxylon Swietenia)., but the fact that both these trees
are commonly also found on non-calcareous sand, and on other
soils in dry forests, indicates that the important factor in this
case is the small amount of moisture in the soil and not the
Characteris- Presence of a particular chemical constituent. Two very
tics of characteristic and widely distributed types of Indian soils require
Laterite and brief mention here, viz. (1) Laterite and (2) Regur, generally
known as Black, or Cotton, Soil. The first is remarkable for its
very low capacity for holding water and for containing a large
percentage of iron. The Eng, or In (Dipterocarpus tuberculatus),
a valuable timber tree of Burma, is almost exclusively found
on laterite. Many other species, often found on laterite,
occur just as frequently also on other dry soils. Regur is
generally found in the neighbourhood of trap rocks and con-
sists largely of clay with a considerable admixture of organic

221

substances. It is characterized by its great adhesiveness
when wet and by an extraordinary power of expansion and
contraction under the influence of moisture and heat respect-
ively. In the dry season it is traversed by great fissures,
often many feet in depth. As a rule it is very fertile, especially
for herbaceous plants and field crops, one of its names being
due to its suitability for the cultivation of cotton. The Babul
(Acacia arabicd) is frequently found on this class of soil, as
also is Eutea frondosa.

Aspect, slope and the character of the underlying strata Aspect,
also obviously affect the loss of water from the soil through Slope and
evaporation and drainage. S^t?"18

Finally, there is the important factor of the presence, or Effect of
absence, of vegetation on the soil. A covering of forest vegeta- Vegetation,
tion protects the soil from insolation and the effect of winds and
thus diminishes evaporation ; it leads to the formation of humus
which absorbs and retains water well ; the force of rain is broken
by the leaves, twigs, and branches, from which it falls gently,
and percolates into the soil, whereas on an area bare of vegeta-
tion much of the rain water runs off and is lost, especially on
steep slopes. It must also not be forgotten that the rain water
contains appreciable quantities of useful nitrogenous compounds
and of mineral salts which are essential plant food-materials, so
that, by intercepting the rain water alone, humus may con-
siderably increase the fertility of a soil.

The character of the soil appears to be the principal factor Soil the
determining the distribution of the Sal tree, this species Principal
requiring a loose well-drained soil, containing a con- j-j^?*.
siderable proportion of humus. It cannot thrive on the mining the
heavy soil which usually overlies trap rocks and, in Central Distribution
India, the extension of Sal westwards is abruptly checked of Salt
by these rocks, Teak forest commencing where the Sal forest ends.

200. The effect of temperature on (3) TEMPER-

the distribution of plants has been recognised from very early ATURE-
days, and it was found that, if the surface of the globe was Vegetation
divided into zones of the same mean annual temperature, each due to Tem-
of these zones was characterized by possessing particular Perature-
species of plants, which did not thrive far beyond the limits
of their particular zone. These zones are given in consecutive
order below, that with the highest mean temperature first,
and that with the lowest last.

I. Tropical Zone. — This is sometimes sub- divided into
the Equatorial, Tropical and Sub-Tropical Zones.

222

II. Temperate Zone, — This is also usually sub -divided
into the Warm Temperate and Cold Temperate
Zones.
III. Arctic Zone. — This is sometimes divided into the

Sub -Arctic, Arctic and Polar Zones.

The Zones in the northern hemisphere are usually termed
Boreal and those in the southern hemisphere Austral.

The Tropical Zone is characterized by possessing Palms,
Bamboos, Bananas, Tree Ferns, Cycads and Screw
. j. Pines (Pandanus), while the most important forest

t trees in this Zone, in India, belong to such natural

orders as Leguminosae, Dipterocarpaceae, Combre-
taceae, Urticaceae, Meliaceae, Verbenaceae, Guttiferae
and others.

In the Temperate Zone the most important forest trees
•„ belong to the Coniferae and Cupuliferae, the latter in-

cluding the Oak, Beech, Chestnut, Hazel, Hornbeam,
Birch, and Alder. Other characteristic trees are the
Poplar, Willow, Elm, Walnut, Maples, and Holly,
while among shrubs, Berberis, Rhamnus, and Euony-
mus, are common. One of the most typical
natural orders is perhaps that of the Rosaceae.
The Arctic Zone. The species found in the cold tem-
perate zone also extend into the arctic zone, but, in
the latter, there are fewer species, and the vege-
i tation is especially characterized by being stunted.

The limit of tree growth is usually regarded as the
natural boundary of the arctic zone, in the latter
the trees becoming shrubs, while shrubs and herbs
are much reduced in height. Plants in this zone
usually have small leaves and well-developed roots,
while large and brightly coloured flowers are
common.

Although the above suffices to illustrate in a general way the
of Tempera- importance of temperature as a factor influencing the distribu-
ture. t ion of plants, it must be borne in mind that the mean annual

temperature is very much less important than the extremes of
temperature in any locality, and also that the effect of a certain
temperature on a particular plant depends largely on the season
of the year and the stage of development of the plant. Some
plants require high temperatures throughout the year, others
uniformly cold temperatures, while yet again others require high
temperatures at certain seasons and low temperatures at others.
Thus although the temperature in a given locality may be

223

sufficient for the germination of the seed and subsequent growth

of a particular species, it may not be sufficiently high to enable

the plant to produce fertile seeds, and hence, its distribution by

seed being prevented, its chances of naturally, establishing itself

are small. The facts that luxuriant vegetation is characteristic

of the hottest areas in the tropics, provided there4s sufficient

moisture, and that good forests exist in the coldest known

spots of the earth, i.e. in parts of Siberia, suffice to show

that other factors besides temperature are responsible

for the distribution of plants, and for the absence of trees in

parts of the tropics and in the arctic zone. Since a similar Low Tem~

reduction in temperature may be caused, not only by increas- U^T0U! to G

ing latitude, but also by increasing elevation above sea-level, increasing

we should expect, on ascending mountains, to find charac- Latitude but

teristic zones, or regions, of vegetation resembling those met Elevation

with when proceeding from the equator towards the poles, and, above Sea

to a great extent, this is the case. It must, however, be re- l*vel.

membered that, although temperature is often the dominant

factor influencing the distribution of plants in both cases, on

mountains the increasing rarefaction of the air has an important

effect on the climate and therefore on the vegetation, which

is not the case in the lowlands.

Under temperature, also, we must not only consider the importance
temperature of the atmosphere but also that of the soil, seeing peratureTof
that, when the soil temperature falls below a certain point, the the Soil,
roots are no longer able to absorb the necessary supplies of
water and salts from the soil. If, while the roots are thus
inactive, the leaves are actively transpiring moisture under the
action of bright sunlight and dry air, the plant must suffer
from desiccation, as has already been pointed out in Part V
above, see page 211. Shallow-rooted, low plants, such as
grasses, on the whole probably suffer less in this respect than
do trees.

In the case of the former, as the temperature rises and
transpiration increases, the roots situated in the superficial layers
of soil are soon warmed sufficiently to enable them to make good
the loss, while the tree roots situated in the deeper layers of cold
soil are unable to do so. Moreover low plants, with their
serial portions situated in the calm, damp, lower layers of the
atmosphere, do not transpire so actively as do the crowns of
trees fully exposed to the action of drying winds. This factor
is of great importance in high mountains where, owing to
the short vegetative season, many trees find it necessary to
remain in leaf throughout the year, their roots being in winter

224

buried in frozen soil and their crowns exposed to drying
winds, and it is in fact mainly responsible for the absence of
trees in the arctic zone and at high elevations. The temper-
ature of the soil depends partly on its physical properties,
sand possessing a far greater capacity for becoming heated,
for instance, than clay ; partly on its depth, the deeper layers
only being affected by prolonged winter cold or summer heat ;
partly on the aspect, and partly also on the presence or absence
of vegetation and the character of such vegetation.

Temperature is the principal factor determining the dis-
tribution of the valuable Hill Forests in India containing
the Deodar and other important Conifers and Oaks. It
also appears to be largely responsible for the distribution
of Teak, no good natural forests of this species occurring north
of cold- weather (i.e., November-February) isotherm 65°. An
important Indian tree which appears to require high temper-
atures throughout the year is the Red Sanders (Pterocarpus
santalinus).

(4) LIGHT. 201. It has been noted in Part V

above, see page 214, that light may injure plants by being (a)
too intense or (6) too feeble. On high mountains the light is
more intense than in the lowlands and is of importance in
regulating the distribution of plants at high elevations- On
the other hand the too feeble light makes it impossible for
many plants, e. g. grasses, to live in the undergrowth of a
dense forest, while a heavy growth of grasses may in turn, by
preventing the access of light, be responsible for the death of
tree seedlings. Many of our most important Indian trees
require a great deal of light and cannot grow well in the shade
of other plants, such as Teak, Sissoo (Dalbergia Sissoo), Khair
(Acacia Catechu), Babul (A. arabica), Blue Pine (Pinus excelsa),
and the Chir (P. longifolia), while others can stand a consider-
able amount of shade, e. g. Xylia dolabriformis, Sal and Sain.

(5) AIR. 202. The humidity of the air is of
Humidity of great importance for plants, inasmuch as (1) the supply of
the Atmos- wa^er m the so{\ obtained from rain, dew, snow, hail and from

DilGrC'

the condensation of aqueous vapour depends upon it, and (2)

it regulates the degree of transpiration from the aerial parts of

plants (transpiration ceasing in saturated air and increasing in

dry air) and of evaporation from the soil. Radiation of heat is

also slower in moist than in dry air. As noted in' Part V above,

Action of see page 215, winds may injure plants directly by uprooting,

Winds. breaking and rending them, and also indirectly by increasing

transpiration, The second mode of action is particularly

225

injurious at high elevations and may there be sufficient to
prevent the existence of trees. Winds, by distributing pollen,
aid in the fertilisation of flowers and production of seeds, and
also help in the distribution of seeds. Grasses are thus parti-
cularly favoured in windy localities and so are conifers among
trees. The fact that the light, large-winged seed of the
Blue Pine is distributed further by the wind than is the seed of
the Deodar is one of the causes which handicap the latter
in its struggle for existence with the former. Finally the
presence of poisonous substances in the air may make it pr=>sence Of
impossible for some plants to survive in certain* localities, Poisonous
e.g. in smoky towns, near Iron Works, or Chemical Factories. Substances.

203. The Forester in India knows (6) Existence

from experience that, if he wishes to create forests oi some of of other
his valuable species, he must in the first place establish on Plant9-
the area a growth ^of . other plants under the shelter of^any1"5
of which his valuable species can be successfully introduced, Species on
whereas in the open their existence, at all events when young, °ther P^t3
would be impossible. This question of dependence on other Existence
plants may often decide which species shall survive in a given
locality. On hot dry aspects, for instance, shelter during
youth is essential for Deodar, which in such situations usually
establishes itself naturally under the shade of species of Indi-
gofera, Desmodium, and others. The seedlings of the Blue
Pine on the other hand grow readily in the open and, in this
respect, this species is favoured in its struggle for existence
with the Deodar. The Sal also usually establishes itself best
in open grassy areas if it is preceded by a growth of shrubs
of inferior species, such as Mallotus philippinensis, and others,
under the shade of which the young Sal are able to exist, a
phenomenon which may be often seen on the edges of grassy
blanks where the Sal forest is gradually extending and en-
croaching on the grassland. A very interesting case on record
in this connection is that of the Bhinga Forest of the
Bahraich Division of Oudh. In 1875 this was practically
a ruined Sal forest, very open with no Sal regeneration ; closure
to grazing and the encouragement of a growth of Mallotus
philippinensis and other shrubs has gradually resulted in the
establishment of a growth of young Sal. An even more
remarkable case is afforded by the Spruce and Silver Fir
forests of the North-Western Himalayas. Here the natural
reproduction of these species is usually conspicuous by its
absence, and if a clearing is made, instead of good fir re-
generation taking place, the ground is at once occupied by

brambles, willows, poplars, and other plants. After such plants
have occupied the ground for some time, reproduction fre-
quently reappears beneath their shade and again establishes
itself on the area, the inferior species thus appearing to have
prepared the way for the Spruce and Silver Fir and to have
made their existence once more possible.

Although in all these cases it is obvious that certain plants
are in some way helped by, and are in a measure dependent
for their existence on, others, the exact way in which this help is
given is by no means always clear.

In some cases mere shade from intense light may be the
beneficial factor. In other cases the shade may be beneficial on
account of its effect on the temperature of the plant and soil,
and on the quantity of available moisture in the soil and air.
In other cases again the benefit may consist solely in the fact
that the shade has been sufficient to prevent the growth and
development of injurious plant competitors, as would appear
to be often the case when shrubs prepare the way for trees by
killing out grasses.

It has been often thought that plants during life con-
tinually excrete poisonous waste products, the accumulation
of which in the soil might render impossible the continued
existence either of the same species or of other plants and
that therefore some plants were able to poison the plants they
displaced and that others even made their own existence im-
possible after a certain period. Although in the case of the
higher plants this has not yet been proved, still it does un-
doubtedly hold good in the case of many fungi and bacteria. In
the case of a particular tree therefore occupying a given area for
a long period, it is possible that the accumulation of substances
excreted by fungi and bacteria in the soil may render impos-
sible the existence of those symbiotic fungi and bacteria which
are employed in breaking down the humus, in which case
the soil may become so impoverished that it can no longer
support a crop of the tree in question, see also the remarks on
page 95 in connection with the rotation of crops and also those
on page 207. Similarly the existence of the symbiotic fungi
which form the so-called mycorhizas may be prevented for
a time, and the natural regeneration of certain tree species
consequently rendered impossible. Any factor injuriously
affecting these symbiotic organisms, such as insufficiency of
oxygen or water, excess of water, too low a temperature, absence
of sufficient organic food materials, and so on, would obviously
produce the same result,

227

Enough, however, has now been said to show that the (6) ExIS'
presence of an injurious plant parasite, or competitor, or the 0/OTHER
absence of a useful symbiont, may suffice to prevent the exist- PLANT.
ence of a given plant in a particular locality, and hence it will be
seen how necessary it is to avoid generalisations and to study in
detail the case of each individual species in different localities.
The valuable Sandal tree, we have seen above, depends to a,
large extent on other plants for its supply of water and mineral
salts, and the existence of such plants is undoubtedly an im-
portant factor influencing the distribution of this tree.

204. In India examples of forests (7)Exis-

which have been practically ruined by excessive grazing are not ^ANIMAI
uncommon. In such areas species which are readily eaten by injurious
cattle are rapidly exterminated, all young growth being destroy- and Useful

j IT. iu • • 4-i, Action of

ed and there being, in consequence, no young stems to replace the ^^^
mature trees which must sooner or later die. Goats are parti-
cularly destructive, and in areas continually browsed by them,
the forest is frequently reduced to a scrub of scattered thorny
shrubs and small trees, which alone are able to survive. Some
of our important trees are not readily eaten by goats, and this
fact has considerably affected the distribution of such trees as
Pinus excelsa, Terminalia tomentosa, and Butea frondosa. Xylia
dolabriformis is also an important tree which is, as a rule, little
eaten by cattle. On the other hand, insects and birds are
largely instrumental in helping plants to exist in certain localities
by pollinating their flowers, while birds and other animals are
often the most important agents for scattering seeds. Many
species of plants may thus have their areas of distribution con-
fined to that of definite insects, birds, or other animals. Red
Clover is a well-known instance ; this plant, being exclusively
pollinated by humble bees, is only able to form fertile seed
where humble bees exist. In India the flowers of Butea
frondosa are largely pollinated by the rose-coloured starling
(Pastor roseus) ; the seeds of species of Loranthus, Ficus, Morus,
and of the Sandal tree are chiefly distributed by birds, while
jackals are believed to be largely responsible for distributing the
seed of species of Zizyphus. The seeds of Babul also are said to
germinate best after they have passed through goats. From
such instances it is obvious that the presence of an injurious
parasitic, or the absence of a useful symbiotic, animal may suffice
to explain the absence of a particular plant in a certain locality*

205. If grasslands are burnt many (8) Sire.
of the most valuable fodder grasses, which are delicate annuals,

are killed out and only the coarser species remain. Fires also,

228

(9) ACTION
OF MAN.

Action of
MaD*

Necessity
of avoiding

Inclusions
as to the
Factors

Distribution
of any Plant

by destroying seed, seedlings and young growth,, may in time
reduce a good forest to open grassland. Here, however, as
in the case of all other factors influencing the distribution
of plants, when studying their effect on a particular species of
plant, we must consider not only their direct effect on that plant
alone but also their effect on all those organisms which influ-
ence the development of the plant concerned. Thus pro-
tecting a forest from fire with the object of favouring the
development of a particular species may have very unexpected
results ; for the growth of injurious competitors may be so
much favoured by the fire protection as to enable them to
oust the species it was desired to protect. This is reported
to have occurred in certain fire -protected forests in Burma,
where the teak is in danger of being ousted by some species
of bamboos.

206. On the one hand, man is

responsible for the absence of forest trees over enormous areas
which have been cleared for cultivation, or more gradually
devastated by reckless fellings, fires and excessive grazing ;

•/ o o ~

on the other hand, he helps many plants to extend their range
of distribution and to establish themselves in areas they could
not have reached without his intervention. Lantana aculeata,
for instance, a native of America, has been established in
Ceylon and India. Anona squamosa, also, introduced from
the West Indies, is now wild in many parts of India, and
several other instances might be given.

207. There are thus a large number

o| f actOrs which influence the distribution of plants, and hence
we must guard against hastily ascribing to any one factor a
result which may be due to the combined action of several,
an(j agamst concluding that the factor, which appears most
obvious, is primarily responsible for the distribution of any
particular plant. Thus the fact that Salai (Boswellia serrata)

. jg usuai]y found in barren places where the soil is very poor
and shallow must not lead us to conclude that this tree requires
such soil for its development and cannot thrive on any other.
As a matter of fact Salai will grow well in good deep soil, but
in nature it is ousted from such localities by stronger competing
trees which there find suitable conditions for their development,
the result being that Salai is driven into the barren spots where
it can exist, but where the majority of other trees cannot. Thus
the fact that in nature Salai is, as a rule, only found on very poor
rocky soil is due not, as might be supposed, to Salai 's preference
for such places? but to the presence of injurious competitors in

229

others. Similarly the fact that the Cocoanut tree (Cocos nucifera)
in nature usually occurs on the saline soil of the seashore
formerly led to the belief that the tree required a large quantity
of salt in the soil. The fact that this tree grows well in gardens
on ordinary soil, however, disproves this, and we are driven to the
conclusion that the tree can only thrive m nature on saline soils
owing to the fact that, in such localities, the majority of other
plants cannot exist, and that it is driven out of more favour-
able localities by stronger competitors.

208. Another important point power Of

concerning plant distribution is the fact that most plants possess Adaptation
a considerable power of adapting themselves to a new environ- *° ^itff1"611*
ment, to changed conditions of existence. We very often hear,
for instance, of plants which have become acclimatised. Some
species possess this power in a high degree, others are less adapt-
able. It must be remembered that a plant which thus adapts
itself to new conditions undergoes a more or less fundamental
change, acquires as it were a somewhat different constitution,
and this may, or may not, be manifested by an obvious change
in its outward form, or habit. We have already seen, in Part V
above, that certain individuals of one and the same fungus
nourished by different hosts may differ essentially from one
another although they cannot be distinguished by any visible
character, see page 199. This undoubtedly also occurs in higher
plants, but in many cases also remarkable changes are notice-
able, some of which have been already mentioned under varia-
tions in Part IV above, see pages 152 — 155. In some cases
plants show the change they have undergone by flowering
and leafing at different periods of the year, or by becoming
more or less deciduous, or evergreen.

209. A plant which is adapted to Xerophytes.

thrive in a locality where very little water is available is termed ^^ and
a xerophyte. Such plants are usually provided with a large and T£-( pophytes.
well developed root-system and with devices for preventing
excessive loss of moisture by transpiration. Thus they fre-
quently have small leaves (the transpiring surface being thus
reduced), which are coriaceous, or fleshy, with a thick-walled
epidermis, and often provided with a protecting covering of
hairs, etc. They also often possess water-storing tissue. They
are often provided with thorns, or spines, and sometimes with
mobile leaflets which close up in strong sunlight. Hygrophytes,
on the other hand, are plants adapted to thrive in a locality
where an abundance of water is always available. They are
usually provided with contrivances for accelerating trans-

230

piration, oversaturation of the tissues with water being the chief

danger to be guarded against in this case. Tropophytes are

plants which at one season of the year are xerophytes and at

another hygrophytes ; such are many trees in the deciduous

forests of India which are hygrophilous in the rains and xero-

philous at other seasons. A plant growing in a soil containing

abundance of water need not necessarily be a hygrophyte ; the

water may for instance consist of a concentrated solution of

salts, in which case the roots can only obtain the necessary

supply of water and salts slowly and with difficulty. A xero-

phiious structure is thus necessitated. Such a structure may

be due to any factor which either favours transpiration or

interferes with the ready absoiption of water from the soil by

the roots.

231

CHAPTER II.— PRINCIPAL TYPES OF VEGETATION,

210. The vegetation of the earth Types of
may be broadly divided into three great types : — Vegetation.

(1) Woodland in which woody plants predominate.

(2) Grassland 'in which grasses predominate, usually in

company with other herbaceous plants.

(3) Desert where the climatic conditions render luxuriant

vegetation of any kind impossible and only a few
plants are able to survive.

Grassland containing isolated trees is usually called savannah.
Of each of these great types a multitude of varieties exist
which however do not concern us at present. The distribution Factors

of the above types is influenced chiefly by three factors, viz.,'11 .

(1) Moisture which depends principally on the amount and Distribution.

distribution of the rainfall, (2) Soil and (3) the Action of Man.

These will be shortly considered below :

211. Typical deserts are charac- (i) Moisture-

teristic of areas with a very small rainfall. Grasses, being Different
usually shallow-rooted plants, depend mainly on the moisture Mature
in the surface soil. Typical grassland, therefore, can thrive if the produce
rainfall is sufficient to keep the surface soil moist in the Desert,
vegetative season. The majority of trees on the other hand a 'or

depend mainly on the water in the subsoil and therefore
require a rainfall sufficiently great to keep the subsoil per-
manently moist. No more remarkable instance of the
dependence of vegetation on moisture can perhaps be given
than that quoted below : —

' The station of Jacobabad is a striking example of the effect
of water supply in that climate. It was founded in 1844 by
General Jacob, in the midst of a barren, treeless desert. A
canal was led to it from the Indus, and now the plain is a dense
forest of babool and other trees, upwards of sixty feet high,
sheltering the houses and gardens of the inhabitants. A ride
of a few miles takes you into the desert which skirts the hills
-of Beloochistan, a level plain of splendid, fertile, alluvial soil,
but hard, naked, and barren, like a threshing floor, without
shrub, herb, or grass, except in the vicinity of the canals,
where vegetation is rich and luxuriant. " *

It has been noted above that in mountains the greatest
rainfall usually occurs at a comparatively low elevation and

* Sir Dietrich Brandis op. cit., p. 11.

232

(2) SoiL

Existence
of Desert,
Grassland

depend
the Soil.

Pioneer

becomes less as the elevation increases. Hence in high moun-
tains. also, the effect of moisture on the vegetation may often
be clearly seen. On the lower slopes with a heavy rainfall
we find forests, at higher altitudes grassland and finally, if the
line of perpetual snow does not extend to the grassland, desert.
As already noted also the quantity of water available for deep-
rooted plants at high elevations depends not only on the
amount of the rainfall but to a great extent also on the tempera-
ture of the soil.

212. A study of the gradual

changes in the soil and vegetation which may pften be seen
occurring in an area covered with naked rock, before
or luxuriant vegetation finally establishes itself there, demonstrates
ver^ clearty the dependence of the type of vegetation on
the soil. The rocks are first weathered and broken up,
slowly it may be but none the less surely, by the mechanical
action of heat and cold and the chemical action of the
atmosphere and water. On the decomposing rocks and
rocky particles small algae and lichens usually soon establish
themselves. Lichens aid in the work of decomposition by
keeping the rock surface moist and by the action of their
absorbing hyphae. The decaying remains of such plants,
mixing with the particles of rock, produce a little soil on
which mosses, grasses, and other higher plants can establish
themselves. In cracks and clefts in the rock also where
more soil accumulates than elsewhere, woody plants soon
appear which by the action of their roots play an important
part in the disintegration of the rock and in the formation
of new soil. Many trees and shrubs which in themselves may
not be valuable on account of their timber or other products
are for this reason of the greatest value to the Forester, they
being the pioneers which prepare the way for more valuable
species and make the existence of the latter possible. Among
such pioneer plants should be noted the very common and wide-
ly distributed Salai (Boswellia serrata) and Kulu (Sterculw
urens). As this preparatory work proceeds and the accu-
mulation of soil increases, more and more trees succeed in estab-
lishing themselves, and eventually woodland arises where at
first there was only barren rock. Thus here, as the naked rock
becomes converted at first into shallow and later into deep
soil, we can trace corresponding changes in the vegetation, the
desert at first passing into grassland, while the latter eventual-
ly gives way to woodland. It is important for the Forester to
realize the part played in nature by the pioneer plants noted

233

above for, on the one hand, much money has been uselessly
spent in parts of India on sowings and other operations with
the object of forestalling the slow operations of nature by
quickly afforesting areas occupied by pioneer plants with more
valuable forest trees and, on the other hand, cases have occur-
red where the premature wholesale removal of sueh pioneers
has retarded the natural evolution of valuable forest by many
decades.

From what has been said above we see that a virgin forest,
in a sense, represents the final product of centuries of work on pjant
the part of nature, the final result of countless struggles in Generatkms-
which only those plants survived and for a time occupied the or Cr°Ps-
ground which were able to exist under the conditions of the
environment prevailing at the time. At first, the absence
of a suitable nutritive substratum rendered impossible the
existence of the majority of plants, and minute alga3 and
lichens were left in undisturbed possession. Later, the
accumulation of humus soil which could retain a sufficient
quantity of moisture allowed grasses and herbaceous plants
to obtain a footing, and they ousted the algae and lichens.
Finally, a still deeper soil with moist subsoil enabled
woodland to vanquish the grassland. The first plant settlers
have to struggle against the very unfavourable conditions
of the non-living environment, while later arrivals have to
face a keen fight for existence against other competing
plants. The scientific Forester, it is true, has to interfere with
the operations of nature to a certain extent, since it is his busi-
ness to see that the most valuable plants, from his point of
view, are favoured as much as possible in the struggle for exist-
ence. At the same time this power can only be usefully ex-
ercised within very definite limits and the interference to be
useful must be intelligent and exercised so far as possible in the
light of a good knowledge of the principal factors at work in
each case. Man cannot, for instance, establish flourishing
woodland in a locality which can only support grassland and
by an unintelligent interference with the vegetation on an area
he may reduce woodland to a desert.

213. A phenomenon analogous in Succession

many respects to the succession of different types of vegeta- communities
tion noted above may often be seen in the Sub-Himalayan on alluvial
tract of India. Here on the banks of boulders, shingle and deposits
sand brought down by the rivers the first arrival is frequent- Simaia aa
ly Dalbergia Sissoo which in such places forms gregarious forests. Tract.
This species with its deep and far-reaching ro Dt .system helps to

234

fix and protect these " flood-plains," as they are sometimes
called, against the action of subsequent floods, while the soil
is gradually enriched by the accumulation of organic debris.
Sissoo, being a light demander, the forests of this species thin
out and become open with increasing age, thus leaving room
for various miscellaneous species which soon establish them-
selves and eventually, ousting the light- demanding Sissoo,
give rise to a mixed forest of inferior species. As time goes on
however and the soil is still further improved by the accumula-
tion of humus and by the continued shelter from climatic in-
fluences, the struggle for existence between the competing trees
becomes more severe, more trees finding on it congenial condi-
tions for their development, and cases may often be seen on the
older alluvial deposits where the Sal, partly owing to its capa-
city of withstanding the injurious effects of a considerable
degree of shade, has been able not only to obtain a footing in
the mixed forest but to entirely oust other miscellaneous species
and to form pure forests of its own.

Action of 214. From these two instances the

Man in important part played by plants themselves in forming soil

Ordinary ° an<^ *n a^ering its physical and chemical properties is clearly

Course of recognized, and we see that some plants are able to create

Natural ^ne conditions necessary for the existence of others ; this

necessarily Par^ °^ *ne subject, however, has been more fully discussed

Restricted, in Chapter I above under Existence of other Plants, see pages 225,

226. Cases such as these also show us that in nature a particular

type of vegetation is not always able to maintain possession of

an area for an indefinite period, and that an area carrying a

good forest of a particular species may not necessarily be able,

in the natural course of events, after the removal of that crop,

to at once produce a second crop of the same species. Further

we must remember, as already stated above, that although

man can to a certain extent interfere with and alter the

process of natural development yet his power in this respect

is limited.

(3) Action of 215. Several cases are on record

Man. in India in which man, by destroying the forest growth on

orSesert! hill-sides, has reduced woodland to desert, and the Forester is
Grassland, often now employed in the difficult task of inducing vege-
and Forest tation to re-establish itself on the barren, rocky slopes and
depends on °^ transforming the desert once more into woodland. In many
the Action of cases, however, the destructive influence of man has not pro-
Ma11- ceeded so far, and his action has resulted in establishing
grassland where flourishing forests once existed. Throughout

235

India such instances are extremely common, the forest having
been first cleared for cultivation and grassland now occupying
the abandoned fields. It has been well said that : " woodland
and grassland stand opposed to one another like two equally
powerful but hostile nations, which in the course of time have re-
peatedly fought against one another for the dominion over the
soil,"* and nowhere does the Forester perhaps realise the truth
of this more strongly than in India. The seedlings of many of
our most valuable tree species, in the first year or two of their
existence, may only attain a height of a few inches above the
ground and have no chance of surviving in the struggle for
existence in a dense mass of grasses which effectually shut out
the necessary light.

216. In many parts of India the Conversion

afforesting of these grass lands is one of the most difficult pro- of Grassland
blems which the Forester has to solve. The difficulty of the 1U
task, moreover, is often increased by the fact that these
clearings were frequently made in the middle of dense forests.
Tall tree-growth therefore, in such cases, surrounds the clearings
like a wall which, by interfering with the free circulation of
air, is largely responsible for the grassy area becoming what
is known as a frost-hole, where only the most frost-hardy
species can exist. In many cases it has been noticed that
if such grasslands are protected from fire and grazing they
become in time naturally reconverted into woodland. At
first small grasses form a dense mantle completely covering
the ground and hiding it from view ; the grass-crop then
becomes gradually thinner, and the small species are replaced
by taller, coarser grasses, under the shade of which patches of
unoccupied soil are visible. Between these grasses a growth of
.shrubs then creeps in, the shade of which while sufficing to kill
off the grasses still allows the seedlings of many tree species to
establish themselves. Finally the thinning out of the shrub
growth allows these seedlings to develop, and the area becomes
once more covered with forest. That this process has occurred
and is still in operation in many of our fire-protected forests
there can be no doubt, but at the same time the process is often
exceedingly slow. Various plans have been resorted to in differ-
ent parts of India with the object of hastening the naturally
slow progress of events. In some cases the seeds of tree species
are sown with low-growing field crops, the injurious competi-
tive action of which is less injurious than that of the wild

* Plant Geography by Dr. A. F. W. Schimper, Eng. Edn., 1903, p. 162.

236

grasses, while the cultivation prevents the development of such
grasses. In other cases grazing has been allowed with the
object of keeping down the grass-growth until the tree-seedlings
have become established, and elsewhere, quick-growing, accom-
modating tree-species have been introduced artificially into the
grassland in the hope that they will oust the grasses. Providing
the soil is suitable, the greater the rainfall, the more quickly
as a rule does woodland reassert itself in India on grasslands
from which the forest has been cleared, and vice versa.
. 217. Root-suckers which are capa-

Roo "suckers ^e of attaining a height of several ' feet in one year are
Favoured obviously more able to hold their own in such grasslands than
in the are minute seedlings, and species which reproduce them-

with^ 6 selves readily by root-suckers are thus often able to successfully
Grasses. conquer the grasses in such areas. Evidence of this is often
seen in India in the practically pure forests of Ougeinia
dalbergioides and Diospyros tomentosa which now occupy the
sites of old abandoned fields.

237

CHAPTER III.— PRINCIPAL TYPES OF INDIAN
FORESTS.

218. For the purposes of a brief

and general description the forests of India may be divided
broadly into the following types :—

(1) Arid-country Forests.

(2) Deciduous Forests.

(3) Evergreen Forests.

(4) Hill Forests.

(5) Tidal or Littoral Forests.

It must be remembered that as each type of forest often passes
very gradually into a different type, the boundary line between
the various types cannot always be clearly denned; moreover
differences in the soil, local conditions affecting the amount of
moisture available, and other factors may entirely alter the
type of forest over small areas, which cannot be taken into con-
sideration in a broad and general account. The approximate
distribution, however, of these types is shown in Plate XXII
areas bearing no forest not being separately shown. In each of
these main types also numerous sub -types of course exist which
it is impossible to note in detail here. The principal factor Factors
responsible for the distribution of types 1 to 3 is the amount of responsible
available moisture as measured approximately by the annual Distribution,
rainfall, which is clearly shown by a comparison of Plates XXI
and XXII ; type 4 owes its existence mainly to low temperature
caused by the elevation above sea-level, while type 5 is due
mainly to the large quantities of salts dissolved in the sea-water
and to the action of the tides.

219. The principal tract of country (i) Arid-

which, with reference to its rainfall, may be called arid, the country
annual rainfall being less than 20 inches, occurs in the North- Forests-
Western corner of India, including Sindh, the southern portion

of the Panjab, and a large part of Rajputana. A large
portion of this area is occupied by desert, the principal
woodlands being the so-called rakhs of the Panjab in the north
and the belts of the riverside forest along the Indus and its main
tributaries. The rakhs occupy the high ground between the
rivers and are poor, scanty woods of small trees and shrubs, the
most characteristic species being Prosopis spicigera and species
of Salvadora and Capparis. Owing to the great depth of the
subterranean water the species occurriDg in these rakhs are
often characterised by possessing roots of immense length and a
taproot of Prosopis measuring 86 feet in length has been exhibit-

238

ed. The riverside forests occupy the alluvial soil watered by
the rivers, either by percolation, or by the annual floods, and:
they owe their existence to the supply of moisture thus obtained.
The principal species are Babul (Acacia arabica), Populus
euphratica and species of Tamarix. Both the babul and the
poplar occur more or less pure over considerable areas
and at other times as standards over an underwood of Tamarix.
These forests are often washed away as the river changes its
course, and the fresh alluvial deposits thrown up by the river
are quickly covered with a dense growth of seedlings. This
arid region occupies the extreme eastern end of the great belt
of desert which stretches from Northern Africa, through Arabia,
South Persia and Baluchistan, to beyond the Indus. The
comparatively small number of species occurring in it is a
noticeable feature, and it is also remarkable that some of them
occur both in the African and Indian area, e.g. Salvadcra
persica and Capparis spinosa. The forests of this arid Indian
region become richer in species towards the north and east,
passing then gradually into deciduous forests. Towards the east
Ancgeissus pendula is a common and characteristic species, it
being the chief forest tree in Meywar and Merwara.

220. A reference to the map Plate
XXII will show the enormous area which is included in

Ous j? orcst-s. . r» i i • i t* i"i • i

the region 01 the deciduous forests which, with reference
to its rainfall, may be called the moist Indian Eegion, the
annual rainfall ranging from 20 to 70 inches. These are
commercially the most valuable forests of India, including as
they do the greater part of the Teak and Sal forests, besides
other valuable species such as the Sandal, Ked Sanders, Sissoo
and many others. In the drier regions this type of forest merges
into arid forest and in moist localities into evergreen forest, but
on the whole the growth, while better than that in the arid
forests, is not so luxuriant, and the trees do not attain such large
dimensions as in the evergreen forests. In the deciduous
forests the great majority of the trees are deciduous in the dry
season. While a large number of species are found almost
universally distributed in this type of forest, others are confined
more or less to local areas. Among the most widely distributed
species are the following : —

Terminalia iomentosa (The Sain or Saj, usually on clayey
soil).

Terminalia belerica.

Terminalia Chebula.

Lagerstrcemia parviflora.

239 . . /

Butea frondusa (Palas).

Bombax malabaricum.

Buchanania latifolia.

Adina cordifolia.

Stephegyne parvifolia.

Mqle Marmelos.

Cassia Fistula.

Acacia Catechu (The Khair, often gregarious on ' flood-
plains' and scattered in dry forest).

Albizzia odoratissima.

Bauhinia racemosa.

Bauhinia variegata.

Erythrina suberosa (in dry forests).

Eugenia Jambolana (in moist places and along river
banks).

Ficus glomerata (in moist places and along river
banks).

Ficus hispida (common in shady moist places).

Ficus infectoria.

Flacourtia Ramontchi (on dry hills).

Gardenia turgida (in dry, rocky places).

Grewia asiatica.

Holarrhena antidysenterica.

Hymenodictyon excelsum (in dry forests).

Kydia calycina.

Phyllanthus Emblica.

Schleichera trijuga.

Schrebera swietenioides.

Stereospermum suaveolens.

Garuga pinnata.

Zizyphus Jujuba.

Zizyphus CEnoplia.

Zizyphus rugosa.

Boswellia serrata (not in Burma) ) i T.-II

StenuKa urens. ' ) on dry rocky bulls.

Odina Wodier ( in dry forests).
Careya arborea.
Bassia latifolia (the mahua).
Dendrocalamus strictus.
Phoenix humilis.

Anogeissus latifolia (not in Burma),
imong climbers the commonest are —
Butea superba.
Bauhinia Vahlii.

240

Acacia pennata.
Acacia caesia.
Cryptolepis Buchanani.
Vitis sp.

Parasitic Loranthaceae are also very common in these
forests. The limits of the distribution of some of the most im-
portant species of these forests, i.e. of Sal, Teak, Sandal and
Red Sanders, are shown in Plate XXIII.

The Sal is strongly gregarious, and is by far the most
numerous tree in the forests in which it occurs. In the Sub-
Himalayan tract the Sal forests usually occupy the higher
tracts of old alluvium lying between the rivers, while the more
recent alluvium, consisting of beds of shingle and sand, in and
near the river beds, is often covered with gregarious forests of
Sissoo and Khair.

In damp places in the Sal forests, the Indian Red Cedar
(Cedrela Toona), Trewia nudiflora, and Pterospermum aceri-
folium are common.

The Teak, unlike the Sal, usually occurs in mixed forests,)
where it frequently forms only a small proportion of the stock.
Although the Sal and Teak areas meet in Central India and to a
certain extent overlap, these trees are not found together. An
isolated patch of Sal for instance occurs inside the Teak area, at
Pachmarhi, in the Central Provinces. Teak is occasionally
found practically pure on alluvial ground, but its best growth
is obtained on well drained slopes. A large number of species
found in the Indian Teak area are also found in the Teak forests
of Burma and, besides those already mentioned, the Ironwood
of Pegu and Arracan (Xylia dolabriformis) should be noted. On
the other hand several species found in the Indian area do not
extend to Burma and vice versa. In the Indian area the follow-
ing are important trees : —

Pterocarpus Marsupium (Bijasal).
Pterocarpus santalinus (Red Sanders).
Hardwickia binata (Anjan).

Dalbergia latifolia (Shisham, or Bombay Black Wood).
Chloroxylon Swietenia (Satin Wood).
Ougeinia dalbergioides (Sandan, or Tinas).
Santalum album (Sandal).

The Burman Teak forests on the other hand contain such
species as —

Dillenia parviflora.
Homaiium tomentosum.

241

Cassia siamect.
Pterocarpus macfocarpus.

Peculiar species of Sterculia.

And above all are characterised by possessing many
different bamboos such as —

Bambusa Tulda.

Bambusa polymorpha.

Cephalostachyum pergracile.

Dendrocalamus longispathus.

Oxytenanthera albociliata.

In the Burman deciduous forest area also are found the so-
called Eng, or In forests, usually on formations of latente. Dip-
terocarpus tuberculatus is here the most characteristic tree with
which occur the following : —

Pentacme suavis,
Shorea obtusa,
Dillenia pulcherrima,
Dalbergia cultrata,

and others. The well-known Andaman Padauk tree, Ptero-
carpus dalbergioides, is found in the Andaman Islands, usually
in deciduous forests.

221. These are found, as will be (3) Evei"
seen from the maps, in the wet region which has an annual
rainfall exceeding 70 inches. They are in their characteristics
the most essentially ' ' tropical ' ' of our Indian forests. They
are especially remarkable on account of the large number of
evergreen species which they contain, their luxuriant vegeta-
tion, and the enormous dimensions attained by some of
their trees. A rich growth of giant climbers (lianes) and of
epiphytes usually covers the stems of the trees, and the under-
growth is frequently so dense as to be practically impenetrable.
The number of species is very much greater than in the
deciduous forests. The general characteristics of this class of
forest are excellently described in the following passage : —

" In a tropical evergreen forest, growing under favourable
conditions, we find four storeys of vegetation. Immediately
covering the soil are seedlings mixed with shrubs and herbaceous
species and in the next zone, or storey, small, or medium-sized
evergreen trees 50 — 75 feet high. The top canopy of great ever-
greens, often 150 feet above the ground, is crowned by giant,
sometimes deciduous, trees, of which Tetrameles nudiftora is one
of the most common and remarkable. The tree stems are in
many instances covered with epiphytic Utricularias, Orchids,

242

Aroids, and Ferns. In North Kanara where the evergreen
tropical Kans ( a local name for evergreen forests) are contiguous
to, or surrounded by, mixed deciduous forest the divergence
between the classes of vegetation is very striking. There is
considerable physical relief in passing abruptly from the strong
glaring sunlight of the open deciduous jungle in the hot season
to the cooler atmosphere and deep, somewhat gloomy, shade
of the lofty evergreens. The bewildering diversity, height and
size of the trees, the universal green and general absence of
colour, the great climbers with fantastic shaped stems, the
epiphytic orchids, aroids, and ferns, the general stillness and
apparent absence of animal life, appeal to the naturalist, who
is satisfied that here at least the action of man has not affected
and changed the original flora of these truly primeval forests.
The principal forces of nature are in constant action, and there
is no annual period of rest, corresponding to the winter in tem-
perate and arctic regions or the hot seasons in the dry tropics.
On the shady, moist, well-covered soil, the growth is continuous,
and the struggle for existence amongst the many species in the
zones of vegetation is very great. The principal causes prevent-
ing the predominance of any one genus or species over more than
a limited area are to be found in the very favourable conditions
in which this strongly differentiated and extremely rich flora
is placed. *

It is very difficult to correctly identify on the spot many
of the high trees growing in the Kans. The rapid and conti-
nuous growth produces generally a thin, smooth, greyish
bark with scarcely any rhytidome. The great height of many
of the stems prevents examination of their foliage, the
flowers are also often inconspicuous and appear at different
seasons of the year. These, together with the diversity
of the species, make a satisfactory interpretation of the flora
almost impossible. In the smaller, less varied and more open
deciduous forests such examination is not attended with similar
difficulties. It is of common occurrence to see a tall tree in full
bloom in the evergreens and to be unable to procure specimens
of the flowers, except by felling or sending up a native climber,
both usually very tedious operations. Much of the evergreen
region of North Kanara is somewhat difficult of access, as the
dense undergrowth often bars the way of the observer. The
forest pathways are also usually bounded by monotonous walls
of verdure, without the relieving colour of conspicuous flowers. ' ' *

* The Distribution of the Forest Flora of the Bombay Presidency and Sind by
W. A. Talbot. Indian Forester, Vol. XXXII, pp. 56—58.

243

Bamboos, being as a rule light-demanders, are usually
absent in the evergreen forest although they are found along
open water-courses, in clearings and on the borders of the forest.
It is only possible here to mention a very few of the most
characteristic and useful trees and genera found in this type of
forest as follows : — >.

Tetrameles nudi flora.

Alstonia scholar is.

Antiaris toxicaria.

Chukrasia tabularis.

Dipterocarpus.

Diospyros.

Dysoxylum.

Canarium. •.. „ .

Swintonia.

Sterculia.

Lagerstrcemia Flos Reginae.

Mesua ferrea.

Vitex.

Cedrela Toona.

Pterospermum.

Mangifera indica.

Calophyllum.

Myristica.

Artocarpus.

Ficus.

Cinnamomum,

Aporosa.

Memecylon.

Garcima.

It will be noticed that a few species found in the deciduous
forests also extend into the evergreens, such as Cedrela Toona.

In many places an intermediate type of forest can be more
or less clearly distinguished in which many species of the deci-
duous forests are found, but where the luxuriance of the vege-
tation rather resembles that of the evergreen forests. In such
areas trees like Teak, Xylia dolabriformis, Dalbergia latifolia and
Terminalia tomentosa are found and there attain large
dimensions.

Among climbers of the evergreen forest many species of
Calamus are common, while screw pines and palms are often
met with, among the latter Arenga, Caryota, Livistona and
Licuala being noticeable.

O .•.

244

222. The most important area

(4) Hill of hill forest in British territory is situated in the North -West

inn?* ts Himalaya, as will be seen from the map, Plate XXII. A brief

in North- description of the zones of forest traversed on ascending the

We? em Himalayas, starting, say, from Kalsi in the Dehra Dun and

Himalaya, proceeding via Chakrata, will give a fair idea of the chief

characteristics of this type of forest. The different zones of

vegetation may be conveniently numbered serially as below,

beginning with the lowest, it being of course remembered that

the transition from any one zone to the next is often gradual

and not sharply denned.

ZONE I.— Elevation 1500'— 3000 .

SAL predominates, mixed with several species of the deci-
duous forests, such as Terminalia tomentosa, Anogeis-
sus latifolia, Ougeinia dalbergioides, Adina
cordifolia, Odina Wodier and others.
The Ghir Pine (Pinus longifolid) also occurs as
scattered trees, or in small patches, and the
Sal here usually attains only small dimensions.
Common and characteristic species also in these outer
hills are —

Boehmeria rugulosa, Bauhinia retusa and Engelkardtia
spicata.

ZONE II.— Elevation 3000'— 6000'.

CHIK PINE predominates, mixed with small trees of Zone
I at lower elevations and higher up with —
The Ban Oak (QuercAis incana) Rhododendron

arboreum, Pieris ovalifolia.

In valleys Quercus glauca, Meliosma pungens,
Albizzia Julibrissin, Rhus Cotinus, Ccltis
australis and Olea glandulifera are common.

ZONE III.— Elevation 6000'— 8000'.

DEODAR predominates, mixed with Rhododendron
arboreum, Ban Oak, Moru Oak (Quercus dilatata),
Blue Pine (Pinus excelsa), Spruce (Picea Morinda]
and many broad-leaved trees such as Betula alnoides,
Populus ciliata, Horse-chestnut, Walnut, Elm, Hazel,
Hornbeam, Maples, and Holly. Among shrubs
occurring in this zone are — Berberis, Euonymus,
Rhamnus, Abelia, Viburnum., Lonicera, Deutzia,
Indigofera, Desmodium, Spiraea, Rubus, Rosa,
Cotoneasier, and Salix. A.mong climbers are

245

Clematis, Holbcellia latifolia, Hydrangea altissima,
Vitis semicordata (Himalayan " Virginia Creeper ")
and the Ivy.

Above 7000 feet Quercus dilatata usually replaces

the Ban Oak.
In this zone also occur—

The Cypress (Cupressus torulosa) often on lime-
stone precipices.

The Box (Buxus sempervirens) usually on calcareous
soil, but also on other kinds of soil in moist
sheltered valleys.

The Yew ( Taxus baccata) in shady places, but perhaps
more often met with in the next higher zone.

ZONE IV.— Elevation 8000'— 1 1000'.

KARSHU OAK (Q. semecarpifolia), which is often gregarious,
predominates. In its zone are found the Spruce,
Silver Fir (Abies Pindrow) and some broad-leaved
species. Rhododendron campanulatum is also found
which extends into the next zone.

ZONE V. — Elevation above 11000'.

WHITE BIRCH (Betuta utilis) predominates, often with a
tangled undergrowth of the shrubby, gregarious
Rhododendron Anthopogon. In this zone also
occurs another shrubby Rhododendron, R.
lepidotum, and species of Juniper, e.g. Juniperus
recurva on the northern slopes of Chansil.

Beyond the region of shrubs, if the snow-line does not inter-
vene, we find grasses with Gentians, Edel Weiss (Leontopodium
alpinum] and other herbs and then perpetual snow.

223. A detailed description of the Hill Forest

hill forests of the Eastern Himalaya, Assam, and Burma can- of Eastern
not be given here although botanically they are more inter- As^mt'an'd
estmg than the hill forests of the Western Himalaya. While Burma,
some species, as might be expected, are widely distributed
throughout the hill forests, others are more or less confined to
local areas.

Rhododendron arboreum and Taxus baccata for instance are
found throughout the Himalaya, in Assam, and in Burma.
On the other hand each region possesses certain species of its

246

own, and those mentioned below are more or less confined to
the regions shown : —

Kegion. Conifers. Oaks.

Western Himalaya. (1) Deodar. (1) Quercus dilatata.

(2) Cupressus torulosa. (2) Q. incana.

(3) Pinus Gerardiana (3) Q. Ilex.

(inner dry hills of the
Himalayas and in Af-
ghanistan).

(4) Abies Pindrow.

(5) Juniperus com-
munis.

(6) J. macropoda.

Eastern Himalaya. (1) Tsuga Brunoniana (1) Q. lanuginosa.

(Indian Hemlock
Spruce).

(2) Larix Griffithii.
Assam. Cephalotaxus Mannii. (1) Q. Olla.

(2) Q. xylocarpa.
Burma. Pinus MerJcusii (I) Q. calathiformis.

(2) Q. Brandisiana.

(3) Q. Lindleyana.

(4) Q. eumorpha.

The following conifers are found both in the West and
East Himalaya : —

Pinus excelsa., Picea Morinda, Juniperus Wallichiana,
Pinus longifolia, Juniperus renurva.

Pinus Khasya is found in Assam and Burma, often form-
ing pure forests with an undergrowth of grass.

Quercus semecarpifolia and Q. glauca are found throughout
the Himalaya and also in Assam. Several oaks occur both in
the Eastern Himalaya and in Assam, e. g. Q. lamellosa, Q. pachy-
phylla, Q. spicata and Q. dealbata.

Several also occur both in Assam and Burma, e.g. Q. semiser-
rata, Q. mespilifolia, Q. polystacliya, Q. truncata and Q. Hel-
feriana.

Common to the Eastern Himalava, Assam, and Burma are —

Q. serrata, Q. Griffithii, Q. fenestrata, Q. lineata, species of
Castanopsis, Bucklandia, Machilus, PTicebe and Nyssa. Notice-
able features of some of the hill forests of the Eastern Himalaya
are the occurrence of a large number of Rhododendrons, many
of which are gregarious shrubs forming dense thickets, and

247

the presence of several magnoliaceous trees with beautiful
flowers, e.g. Magnolia Campbellii.

224. These forests are found on (5) Tidal or

the mud-banks bordering the sea and tidal rivers. The trees Littoral
are here never large, and the commonest species are those I
usually known collectively as mangroves, whence fhisTtype of
forest is often called mangrove-forest. Owing to their peculiar
environment, the plants in this class of forest have to contend
chiefly with —

(1) The action of the wind, waves, and tides tending to

uproot the trees growing in the soft mud.

(2) The excess of salts in the water around the roots.

(3) The difficulty of obtaining sufficient oxygen for their

roots.

(4) The danger of having their seedlings submerged and

killed by the rising tide.

We should therefore naturally expect that comparatively
few species would *"be able to exist under these unfavourable
conditions and that those which are able to survive would
possess certain definite and well-marked characteristics.

In the littoral forests of India and Burma " the species of tree
which forms the advanced line along the sea and which, by its
slow forward march, causes a gradual elevation of the coast,
is Rhizophora mucronata. No mangrove-tree is better equip-
ped for resisting the movements of the tide on the soft mud,
for propagating itself under these difficult conditions, and
for recovering from the frequently quite undilute salt sea-
water, the water lost in transpiration. The scaffolding of bow-
shaped stilt-roots supporting the stem represents a complete
system of anchors, which is strengthened by new roots growing
down from the branches to balance the growth of the crown."
(In other species of mangrove growing further from the sea
these anchoring roots are less strongly developed or are alto-
gether absent.) : The leaves possess a marked xerophilous
structure with a thick cuticle. protected

stomata, and especially a large-celled thin- walled aqueous tissue,
the dimensions of which increase with the age of the leaf and
with the corresponding rise in the amount of salt contained. Old
leaves serve essentially as water- reservoirs for the younger
leaves."*

* Schimper op. cit., p. 396.

248

In order to insure a sufficient supply of oxygen for the rootd,
many trees in these forests are supplied with so-called pneumato-
phores, or aerating roots. In some species these grow up from
the ground and look like thick shoots of asparagus, in others
the roots bend up out of the ground and form knee-like struc-
tures, while in some -cases the upper surface of the roots
alone projects above the ground. These serial roots, or portions
of roots, are usually covered with thin cork and possess abundant
lenticels. " The mode of propagation is most remarkable in
Rhizophora mucronata, which in this respect agrees in the main
with the other Rhizophoraceae living in the mangroves. The fruit
leathery and indehiscent and about the size of a hazel-nut,
soon after the completion of its growth is pierced at its summit
by the green hypocotyl, as the embryo does not undergo any
period of rest, but continues to develop without interruption.
The hypocotyl in R. mucronata is club-shaped and attains a
length of 60 centimetres, sometimes even more, before it falls
down, leaving behind it the fused cotyledons which served as
absorbing organs. As its lower end is thicker, the seedling falls
vertically, with its root-tip downwards into the mud, and within
a few hours develops roots that fix it firmly."*

The principal genera in these forests are —

Rhizophora. Carapa.

Ceriops. Avicennia.

Kandelia. Sonneratia.

Bruguiera. Lumnitzera.

Among shrubs Acanthus ilicifolius (with leaves like holly
and blue flowers) and Mqiceras are common.

The two small palms Nipa trulicans and Phoenix paludosa
form gregarious thickets in the Sundarbans and littoral forests
of Burma. Common climbers are species of Denis ; epiphytes
are scarce and there are usually no mosses. Ferns and grasses
often form the undergrowth in the drier spots.

Further inland above high-tide mark, on ground which is
only occasionally, if ever, flooded, the following are
characteristic : —

Hentif.ra Fomes. The Sundri, which is the most important
tree in the Sundarbans.

Thespesia populnea.
Hibiscus iiliaceus.

* Schimpor op. cit., pp. 396—398.

249

Excce:aria Agnllocha,

Cerbera Odottam.

Scaevola.

Clerodendrcn inerme.

Erythrina indica,

Pongamia glabra.

Casuarina equisetifolia.

Pandanus tectorius.

225. The principal types of Riparian

Indian forests have now been considered in detail above, and it F01^3*8-
only remains to briefly mention the sub-type, often called
riparian forest, which is found along the banks and in the beds
of rivers and streams and in swampy places. Forests in such
localities usually have an abundant supply of fresh water
available in the soil, and consequently the belt of land imme-
diately bordering perennial streams in the arid region may be
able to support forest of the ordinary deciduous type, while
similar streams in the zone of deciduous forests may be fringed
with more or less evergreen forest. At the same time the
conditions under v hich the plants of these forests exist are
often peculiar in many respects.

The ground on which they grow is, for instance, often liable
to more of less prolonged submersion in water at certain seasons
which, by causing stagnation of water around the roots, may
eiiectually prevent the latter from performing their functions
on account of the want of sufficient oxygen. A very common
species in riparian tracts is Ficus cjomerata which sheds its
leaves during the rainy season, possibly owing to the roots
being then unable to perform their normal functions.

In addition to this also many of our Indian rivers and streams
are entirely dry for several months in the year, when the sandy
shingly soil in and near their beds becomes dried and excessively
heated to a considerable depth. Other factors to be consi-
dered also are the action of floods in washing away the soil
and exposing the roots and the utility of water as a seed distri-
butor, those species possessing devices favouring this mpde of
seed-dispersion having an advantage in the struggle for exist-
ence in riparian tracts, as has been noted above in the case
of Sissoo and Khair. It is therefore not surprising that many
species which are characteristic of riparian tracts, are not often
iound elsewhere. Among such may be mentioned—
Anogeissus acuminata.
Barrincjtonia acutangula.
Eugenia sp.

250

Ixora sp.
Tamarix sp,
Pongamia glabra. '
Trewia nudiflora.
Terminalia Arjuna.
Ficus hispida.
F. glomerata.
Homonoia sp.
Salix tetrasperma.

As indicating that the plants in these forests often find it
difficult to obtain their necessary supply of moisture, it is
noticeable that Anogeissus acuminata and Eugenia Heyneana,
which are common riparian species, are characterized by being
small-leaved species of their respective genera, small leaves
being as a rule very characteristic of xerophytes, while several
plants which occur in riparian tracts are also often found in
very dry localities, e.g.—

Anogeissus acuminata (occasionally),

Vitex Ne^undo,

Streblus asper,

Acacia Catechu,

Balanites Roxburghii,

Capparis aphylla,
and others.

An interesting and perhaps one of the most widely distri-
buted plant characteristic of dry river-beds is Rhabdia lycioides,
with its minute leaves and creeping, rooting branches which
enable it to withstand successfully the action of violent
floods.

Distribution 226. The distribution of all im-

of important portant Indian trees, so far as it is at present known, is given

Species ^n detail in Brandis' Indian Trees and in Gamble's Manual

of Indian Timbers and will not be repeated here. The

approximate 'limits of the distribution of Teak, Sal, Deodar,

Sandal, Red Sanders and Caoutchouc have, however, been

indicated in the map, Plate XXIII.

The principal factors responsible for the distribution of the
chief types of forest have been given above, and in a few cases
the factors which appear to have a considerable influence
on the distribution of individual species have been incidentally
mentioned. In the present state of our knowledge it is impos-
sible to indicate, with any degree of certainty, the factors which
determine the distribution of many of our important species.

INDEX.

PAGE.

Abdia 244
Abies 191

PiOB

^Estivation . . . . 50
Afforesting grasslands . . 236
Agaricus melleus . . . 133
(see also Armillaria mellea).

„ Pindrow . . . 184, 245, 246
Abnormal growth . . .18, 79
Abruptly-pinnate ... 25
Abrus precatorius . . . 41
Absorption by plants 83, 86-88, 91, 93, 94,
96, 206, 207, 211
„ soil ... 94
Acacia 65
. arabica . . 134,221,224,238
caesia . . . .41, 240
Catechu . 16, 25, 208, 219, 220, 224,
239, 250
Farnesiana . . .41
leucophlcea ... 14
pennata ... 29, 67, 240
Acanthus ilicifolius . . . 248
Acaulescent plants ... 10
Accessory buds ... 34

Age of stems . . . 17,33
Aggregate fruit .... 59
Agricultural crops, yield of . . 95
Ailanthus excelsa ... 65
Air, its effect on plant-distribution 224
Alae (wings) .... 56
Alangium Lamarckii . . . 153
Albizzia JuUbrissin . . . 244
„ odoratissima . . .41, 239
„ procera ... 15
„ stipulata . . .31, 65
Albumen 58
„ crystals [. . . 70
Albuminoids .... 204
Albuminous seed . . .58, 143
„ substances . . 70
Alburnum . . . . 17
Alcohol 129, 132

Acclimatised .... 229
Accrescent .... 63
Accumbent .... 59
Acer caesium ... 21, 29, 33
Achar 211
Achene ..... 61
Achlamydeous .... 43
Acicular . . . . 23
Acorn ..... 61
„ cup .... 60

Alcoholic fermentation . . 131-133
Alder 222
Aleurone-grains ... 70
Algae . 86, 127, 137, 146, 232, 233
Alstonia scholaris . . . 243
Alternate leaves. . . . • 9
Alternation of gener-
ations . . . 139, 142, 146, 1*7
Amides 204
Ammonia . . . . . 68, 129

Acropetal development . . 5, 9
Actinomorphic .... 46
Acuminate .... 24
Acute 24
Adaptation, power of . 154 199 229

Ammonium .... 94
Ample inflorescence ... 37
Amplexicaul .... 25
Anabolism .... 90

Adhesion ..... 48
Adina cordifolia . . . 239, 244
Adnate 48,52

Anatomy, Vegetable" . . . 2,68-84
Anatropous .... 55
Andaman Padauk . . . 241

„ stipules ... 31
Adventitious, branches . . 13
„ buds ... 33
„ roots . . . 5, 6
„ structures . . 170
jEcidia 136,197
^Ecidiospores .... 136, 197
JEcidium Berberidis . . 197, 198, 200
„ montanum . . . 200
„ Thomsoni . . . 135
JBgiceras ..... 248
Mgle Marmelos. . . .13, 239

Andrcecium . . . . 41
Anemophilous . . . . Ill
Angiosperrns . .57,59,143,145-147
„ classification of . 145
Animal Kingdom ... 1
Animals . . .1,2, 116, 180, 182
„ their effect on plant-dis-
tribution .... 227
Anjan . . . . 6, 65, 240
Annual . . . .66, 67, 80, 176
„ rings . . . . 17, 78
Annular vessels .... 73, 7 6

Crating root .... 248
Oration of soil . . . 206-208, 220
Mrinl, roots ... 8, 107, 185
Msculus indica . . . c 33, 34

Anogeissus acuminata . 65, 249, 250
„ latifolia . 15, 29, 239, 244
„ pendula . . , 238
Anona squamosa . . , 228

INDEX.

PAGE.

Antagonistic symbiosis . . 180

Anterior side of flower . . 46
Anther .... 41, 51, 52

Antheridia .... 138, 140

Anthocyanin . . . 69, 214

Anliaris toxicaria . . . 243

Anti-clockwise twiner . . 10

Antidesma diandrum ... 29

Antipetalous .... 52

Ants 183

Aonla 208

Apetalous .... 43

Aphides , ... 133

Apocarpous , ' . . . 53

Aporosa ..... 243

Apothecium . . . . 131

Apple 63

Aquatic plants . . . . 185

„ roots .... 8

Arched nerves . . . . 21

Archegonia .... 138, 141

Arctic Zone .... 222

Arcuate nerves . . . . 21

Arenga . . . . . 243

Arhar 67

Arid-country Forests . . . 237-238

Aril 58

Arisaema Wallichianum . . 41
Armillaria mellea . . . 133, 193

Aroids . . . . 242

Arrangement of leaves . . 9, 32, 33

„ ,, parts of flower . 44, 47
Artificial classification . 118-119,124

Artocarpus .... 243

Arundinaria falcata ... 30

,, spnthiflora . . 21

Ascending ovule ... 54

„ stems ... 10
Ascent of water in plants . 96-98, 168-169

Ascocarps .... 131
Ascomycetes .... 131, 137

Ascus ..... 131

Aseptate hyphse . . . 130

Asexual generation . . . 139
Asexual reproduction . 108, 156, 158
Assimilation . . .90, 101-104

Asymmetric .... 46

Atavism . . . . . 157
Atmosphere, its influence on

plant-development . 208-216
„ its influence on

plant-distribution 224

Auricled . . . . 24

Austral Zones .... 222

AutoBcious .... 198

Autumn tints .... 29

Availability .... 94

Available water . . . 206, 218

Avicennia .... 248

Axial embryo .... 59

Axil .'.... 9

Axile placentation ... 54

Axillary huds .... 9
flower . . .37

PAGE.
Babul . 134, 221, 224, 227, 231, 238

Bacilli 127

Bacillus radicicola . . . 129, 203
„ tetani .... 129

„ typhi . ' . . . 129

Bacillus vulgar is . . . 129

Bacteria . 127-129, 146, 154, 176, 179,
187,203,204,207,208,214,
226.

,, nitrifying . . . 129

Bacterium aceli .... 127, 129
„ acidilactici . . 129

Balanites Roxburghii . . . 250

Balsams ..... 75

Bamboos . 10, 11, 14, 19, 21, 30, 56, 59,
67, 145, 176, 182, 183, 222,

228, 243

Bambusa polymorpha . , . 183, 241

Tulda ... 241

Banana . . .21, 22, 66, 215, 222

Ban Oak .... 7,244,245

Banyan . . . . 5, 8, 185, 186

Bardayella deformans . . 135

Bark . . . 14,15,16,18,80

„ internal . . . .18,80

Barley 95

Barrinatonia acutangula . 249

Basal nerves . . . .21,22
Base, leaf— . . . . 24, 30
Basidia ..... 133

Basidiomycetes . . . . 131, 133
Basifixed ..... 52

Bassia latifolia . . 7, 65, 132, 211, 239

Bast 75,78

„ fibres .... 78

„ internal .... 18, 80

Bastards 150

Bauhinia malabarica ... 29

„ racemosa . , . 239

„ retusa . . . 244

Vahlii 11, 17, 18, 79, 184, 239

,, variegata . . . 239

Bean 56,203

Beech 191,222

Bees . . 113, 114, 177, 178, 227

Beet 7

Bel 13,36

Bell-shaped .... 50

Ber 208

Berberis . . .36, 196, 222, 244

aristata . . . 15,200

„ coriaria. . . . 200

Lycium 30, 31, 45, 112-115, 197,

200
,, „ fertilisation of

flowers of

Berberis nepalensis . . . 30, 137
Berchemia ftoribunda .
Berry ..... 61

Be tula alnoides .... 244

Betula utilis . . . .15, 245
Bi-collateral vascular bundle
Biennial , . . 66,67

INDEX.

Ill

Bifarious leaves
Bifoliolate
Bijasal
Bilabiate .
Bilocular .
Biological sciences
Biology
Bipinnate
Birch

white

PAGE.

240

15-17, 63, 80, 222
245

Birds . 42, 111, 116, 182, 201, 227

Biserrate 22

Bisexual ..... 45

Black Soil .... 220

Blackwood 240

Bleeding, of stumps .
Bloom
Blue Pine .
Bcehmeria rugulosa
Bombax malabaricum .
Bombay Blackwood .
Borassus flabellifer
Bordeaux mixture
Bordered-pit
Boreal Zones

183, 224, 225, 244
244

. 8, 14, 65, 239
240

18
189

71
222

Boswellia serrata 15, 171,228, 232, 239
Botany ..... 1

„ subdivisions of 2

Bougainvillea .... 47

Box 245

Bracken Fern . . . . 11, 140
Bracteate . . * . . . 37

Bracteoles. ... 37, 44, 45
Bracts ... 37, 40, 44-47, 60

Brambles 226

Branches . . . .10, 12-14, 65

„ development of . . 82

Branching. . 5, 12, 13, 37, 52, 64, 65

Branchlets . . . . 14, 65

Brinjal 153

Browsing, by cattle ... 67

Bruguiera .... 248

Bruises 167

Bryophyta . . . 126, 137, 147

Buchanania latifolia . 15,16,211,239

Bucklandia .... 246

Budding 175

„ of Yeast . . . 130, 132
Buds . . .9, 10, 33, 34, 46, 48

„ accessory .... 34

„ position of ... 9

Bud-scales . . . . 33, 34

Bulb 11, 109

Bulbils 11, 109

Bundles, vascular . 18-20,74-79,84

Butea frondosa . 56,220,221,227,239

„ superba .... 239

Buttresses. . . . . 8, 14
Buxus sempervirens . . . 245

Caducous .
Csespitose stems

Cajanus indicus
Calamus .

tenuis .
Calcareous soil .
Calcium .
Callus

'alophyllum
Calyptra
ialyx

„ limb

„ throat

„ tube
Cambium .

cork .
Campanulate
Campylotropous
Canala, resin
Canarium
Canescent
Cane-sugar
Cankers
Caoutchouc

Tree
Cap, root —
Capitulum

PAGE.

243

. 220,245

71,93, 206, 220

165, 169, 170

- . 243

139

43, 50, 60
43
43

. 43, 49

76, 77, 79

. 18,74

243

103

213

. 71, 74

. 219,250

Capparis 47, 237

aphylla ... 250

spinosa . . .31, 238

Capsule 60

Carapa 248

Carbohydrate, manufacture of a . 3, 89

101, 102

Carbon . . .68, 70, 91, 93, 94

Carbonaceous food . . . 178-180

Carbon dioxide . 2, 85, 89, 94, 101, 102,

103, 132, 179, 180,

204, 206, 21 C

Carbon dioxide, excreted by root-
hairs ..... 94
Careya arborea .... 239
,, herbacea .... 67
Carina . . . . _ 56
Carissa spinarum . . . 15, 67

Carpel 53, 143

Carpinus viminea . . .14, 34
Carpophore .... 54

Carrot ..... 7

Cartilaginous .... 63

Caruncle ..... 58

Caryopsis . . . . 61

Caryota 243

Cassia Fistula . . . 29,41,239
• . 241

Castanopsis .... 246

Castor-Oil Plant ... 52

Casuarina cquisetifolia . . 249

Catkin 38

Caudate 24

Caudex . . . . . 11

Cauliflower .... 156

Cedar, Red .... 240

Cedars 145

Cedrela Tooni . . .6. 60, 240, 243
Cedrus Libani par Deoiara .121, 191

INDEX.

PAGE.

Cell . . . . . . 69

contents .... 69

dead ... 72

division . . . . 71

guard 84,100

—sap .... 69

shape of . 72

wall 69

thickening of 71

Cellular plants . . . .126,146
Cellulose .... 69,71,90
Celtis australis .... 244

Centrifugal inflorescence . . 39

Centripetal „ 39

Cepkalostachyum perrjracile . . 241

Ce-phalotaxus Mannii - . . 246

Cerbera Odollam ... 249

Cenops 248

Chalaza 54

Channelled .... 14

Characters . . 117, 119, 124, 125

important . . 120

latent . . . 157

of ovules . . . 54, 55
„ perianth . . 43

„ petiole ... 29

„ pistils . . .53, 54
„ stamens . . 51, 52

Characters, specific . . . 120

Chartaceous .... 63

Chestnut 222

Chir .... 136, 224, 244

Chlorophyll 1, 2, 70, 75, 94, 102, 214, 215

,, corpuscles . 70, 214

„ light absorbed by . 102

Chloroxylon Swietenia . 220, 240

Chrysomyxa Himalense . .

Chukrasia tabvlaris 243

Cilia .... 127, 138, 188

Ciliate ... 22

Cinnamomum .... 243

„ Camphora . . 21

Tamala . • . 29

Circinnate . . . .35, 139

Cladode 12

Class 122

Classification . . . 2, 3, 117-164

artifici.il . 118-119, 124

natural . 118-119, 123-125

„ necessity for . . 117

„ of Angiosperms . 145

„ fungi . . 131

„ „ Gymnosperms . 144

„ unit of . . . 119

Clavate 62

Claw 49

Clay 220

Cleft .... 22, 23, 44

Cleistogamic flowers . . . 116

Cleistothecium . . . . 131

Clematis 55, 245

,, montana ... 31

Cterodendron inerme . . . 249

,. terratum . . 67

PAGE.

Climbing plants . 10, 33, 65, 66,184

Climbing plants, are sometimes

erect 67, 153

Clockwise-twiner ... 10

Closed vascular bundle . . 76

Close symbiosis .... 180

Clover . . . 177, 178, 203, 227
Club-mosses . . . 141,142, 147
Cluster-cups . . . . 197

Cobra Plant .... 41

Cocci 127

Cocculus laurijolius . . 18, 28, 79
Coccus ..... 60

Cocoanut Tree . . . 219, 229

Cocos nucifera .... 229

Cohesion ..... 48

Cohort 122

Cold, excessive .... 209-214
Collateral host .... 198

„ vascular bundle . . 75

Collection of specimens . . 162

Collenchyma . . . . 73, 75
Colocasta antique/rum . . . 100

Colour of bark .... 15

„ „ leaves . . .28, 29
„ „ perianth . . 42, 43, 111
„ „ twigs ... 80

Combretaceae .... 222

Combretum nanum ... 67

„ ovalifolium . . 65

Communities, succession of plant . 233

Compact, inflorescence . . 37

Competition . . 6, 109, 148, 184
Competitors . . 180,183,226,228
Compound corymb ... 38

cyme ... 39

leaf .... 23

pistil ... 53

raceme ... 38

umbel ... 38

Compressed . . . . 61

Concavo-convex ... 62

Concentric vascular bundle . . 76

Conditions of plant life . . 85

„ „ existence in a highly

organised plant . 91

Conduplicate .... 35

Cone . . . .56, 144, 145

Conical 7,61

Conidiophore . . . . 131, 187
Conidium .... 131, 187, 189
Coniferae . . . 144, 145, 147, 222
Conifers . 18, 74, 78, 101, 168, 191, 194,
224, 225, 246

Connate . ... 25, 43, 48
Connective . . . , 01, 53
Contorted .... 51

Contraction, of root ... 83

Contrivances, for facilitating cross-
fertilisation . . . . Ill
Conversion, of grassland into

forest . . . . i 235

Convolute .... 35

Coppice, leaves of . . 28, 153

INDEX.

Coppice-shoots .

PAGE.
. 169, 171

PAGE.

Cyme, helicoid . 40
„ racemiform . . 40
„ scorpioid . . 40
„ trichotomous . . 39
„ umbelliform . . 40
Cymose branching -— , __ 12, 37, 38
„ inflorescence . . 38-40
Cypress .... 136,145,245
„ Swamp ; 67

Cordate
Coriaceous
Coriaria nepalensis
Cork . . 72,
„ cambium .
Corm

24
63
. 14, 32, 107
75, 80, 81, 82, 165
80
. 11, 109

Corneous .
Cornus macrophylla
Corolla

63
. 21, 41
. 43, 50

„ limb
„ papilionaceous
„ throat .
„ tube
Corona
Corpuscles
„ chlorophyll
Cortex
Corylus Colurna
Corymb
Corymbiform
Cotoneaster
Cotton Plant

56
43

43
50
70
. 70, 214
14, 81
. 17, 65
38
40
244
44. 58

Dahlia . ... 7

Dalbergia ...... 56
„ cultrata . . . 241
„ latifolia . . . 240, 243
„ paniculate, . . .18, 29
Sissoo . 6,219,224.233
Date Palm .... 63
Dead cells .... 72
„ tissue .... 204
Death, of plants. . . . 176
Decay . . . . • . 129, 179
,, of wood .... 204
Deciduous 63 67

Cotton Soil .... 220
Cotyledons . . . . 58, 59
Counter-clockwise twiner . . .10
Crateriform .... 50
Creeping stems .... 10
Crenate ..... 22
Crops, mixed .... 95
„ rotation of . . .95, 226
., succession of . . 233
Cross-fertilisation . . . 110-115
„ „ contrivances
for facilitat-
ing . . Ill
„ illegitimate . . .112, 123
Crown, shape of ... 65
Crumpled ... KI

„ Forests . . 230,237-241
plants . . 100, 101, 229
Decumbent . . 10 65

Decurrent .... 25
Decussate leaves ... 9
Deeringia celosioides . . . li
Definite inflorescence ... 39
Dehiscence, of anther . . 41,51
Dehiscent fruit .... 60
Deltoid .... 24

Dendrocifamus longispathus . 241
„ sntwuo . . 239
Dense inflorescence . . 37
Dentate . . 22

Crustaceous
Cryptogams
Cryptole.pis Buchanani
Crystals .

63
. 126, 146, 183
240
71

Denuding action ot water . .219, 249
Deodar . 13, 18, 65, 183, 220, 224. 225,
244, '246, 250
„ Forests . . 183, 224, 225, 244
„ root-disease . 134, 191-193
Depressed ... 62
Derris .... 248

Culms
Culm-sheath
Cuneate .
Cup, of acorn
Cupressus torulosa
Cup-shaped
Cupuliferae
Ciiscuta reflexa .
Cuspidate
Cuticle
Cuticularised
Cutin
Cuttings .
Cycadaceae
Cycads

11
30
24
60
15, 136, 245, 246
50
222
201
24
75, 101, 154, 247
75
75
. 170,171
. 144, 147
. 147, 222

Descriptive terms, for petals and
sepals . . 49
,, ,, for shape of
fruit and seed 61
Desert ..... 231-234
„ plants . . . . loo
Desmodium .... 225, 244
„ piilchellum . . 41
„ tiliaefolium . . 26, 31
Determinate inflorescence . . 39
Determination, of natural groups 123
Deiitzia ..... 244
Development, abnormal . . 79
„ of plant-members . 77
„ of root . . « 6, 7, 82
„ of secondary mem-
bers . 82

Cycas
„ pectinata .
„ Rumphii
Cylindrical
Cyme, corymbiform .
„ dichotomous .

. 79, 144
144
144
61
40
39

INDEX.

PAGE.

Development, of vascular bundles. 76

Dextrorse twiners ... 10

Diadelphous .... 52

Diageotropic .... 106

Diagrams, floral ... 57

Diaheliotropic .... 107

Diandrous. .... 45

Diastase ..... 103

Dichasium .... 13

Dichlamydeous .... 43

Dichogamy . . . . Ill

Dichotomous branching . . 12, 13

„ cyme ... 39

Dicotyledons 59,77,78,101,145-147, 168

„ root of . . 79, 81

„ stem of . . . 77

„ wood of 78

Didymous .... 62

Didynamous .... 52

Digitately-veined ... 21

Dillenia parviflora . . . 240

,, pulcherrima . . . 241

Dimerous . . . . 45

Dimorphic flowers . . . 112, 123

„ species . . . 154

Dioecious ..... 45, 111

Dioscorea . . . . 11, 145

Diosmosis .... 86

Diospyros ..... 243

„ lomentosa . . 7, 15, 236

Diplostomonous ... 52

Dipterocarpaceae . . . 222

Dipterocarpus .... 243

,, tuberculatus . . 220, 241

Disassimilation .... 90

Disc . . . . .49, 113

Discoid 61

Disease, definition of . . . 176

„ rarely due to one factor . 181

„ spike—. '-. . . 202

Diseases .... 129, 176-217

„ investigation of . . 182, 202

„ symptoms of . . 181

Dissemination of seeds . . 115

Dissepiments .... 53

Distant symbiosis . . . 180, 204

Distichous . . . 9, 32

Distribution, of important species 250

Distribution, of plants depends on

action of man . . . 228

Distribution, of plants depends on

action of air .... 224
Distribution, of plants depends on

action of animals . . . 227
Distribution, of plants depends on

action of fire .... 227
Distribution, of plants depends on

action of light . . . 224
Distribution, of plants depends on

action of other plants . . 225
Distribution, of plants depends on

action of soil . . . .219
Distribution, of plants depends on

action ot temperature . . 221

PAGE.

Distribution, of plants depends on

action of water
Distribution, of

„ seed 58, 109, 115,

„ ,, sexual organs

„ „ types of forests .

Divaricate ....

Divided leaf ....

Division .

„ cell— .

Dodder .

Dolichandrone falcata .

Dormant buds ....

Dorsal raphe ....
,, side .

Dorsal suture ....

Dorsifixed ....

Drupe ...

Dry-rot ....

Duramen .....

Duration, of plant life

,, „ ,, members

Dwarf shoots ....

Dysoxylum ....

218

182

219,

227
45

237

22,23

122
71

201
41
34
55
52
53
52
61

134
17

176
03
13

243

Ebracteate .
Eccentric embryo
Echinate ..
Economic Botany
Edelweiss ..
Egg-plant .

216,

42, 55, 58. 59,
. 73,

58
3, 89, 90,

Elements, of tissues

Ellipsoid .

Elliptical .

Elm

Elongated shoots

Emarginate

Embryo .

Embryonic tissue

Embryo-sac

Endocarp

Endophytes

Endosmose

Endosperm

Energy, in plants

Eng

Enrjelhardtia spicafa .

Entire margin ....

Entomophilous ....

Envelopes, floral —

Enzymes 103, 132, 188, 192,

Ephzdra Gerardiana

Epicalyx .....

Epicarp .....

Epicotyl .....

Epidermis 75, 80, 82, 84: 96, 99

Epigynous ....

Epipetalous ....

Epiphytes . . 185,241,

Equatorial Zone

Erect inflorescence

245
139
65
73
61
24

222, 244
13
24

138, 143
170, 176
55,143
60,61
185
86

, 143-145

102, 104

220, 241

244

111

201, 205
145
44

60,61
59

•101, 214
49
52

242, 248

221

INDEX.

vii

Erect ovule
„ stem
Erythrina indica

„ suberosa
Essential food-materials

PAGE.
54

. 10, 65
249

15, 17, 171, 239,
• 93

„ „ power of

plants to obtain . . .94, 95
Essential mineral salts . . 205,219
Ethereal oils . . . 29,71,74
Etiolation .... 214

Eugenia ..... 249

,, Heyneana . . . 250

Jambolana . . 7,22,239
„ operculata ... 41

Euonymus .... 222, 244
„ Hamiltonianus . . 28

Euphorbia .... 65, 74

Evergreen .... 67

„ Forests . . . 241-243
plants . 07, 100, 101, 229
Evolution, theory of . . . 159

Exalbuminous seed . . . 58, 143
Excess of salts . . . .205,247
Excessive cold .... 209-214
heat .... 209

,, moisture . . . 215

Exccecaria Agallocha . . . 249

Excretion . . . 90,206,226

Exfoliation, of bark . . .16, 81
Existence, conditions of, in a high-
ly organised plant . 91
Struggle for 96, 148-149, 159, 177-
178

Exosmose .... 86

Exserted stamens ... 52

Exstipulate .... 31

External embryo ... 59

Extra-axillary .... 34

Extremes, of temperature . . 208, 222

Extrorse 52

Eyes, of Potato . ... 11

Factors causing disease . 177, 181, 217
„ influencing plant distribu-
tion .... 218-230
„ influencing relations be-
tween organisms . . 178

Falcate 24

False axis . . . 12 ,40

dichotomous branching . 12
dichotomy . . .

dissepiments ... 53

rings .... 17

trichotomous branching . 12, 13

whorls . . . 9, 65

Family 122

Fascicle ..... 40

Fascicled leaves . . . £,13

Fats ..... 71

Female llower 45

PAGE.

Ferment Organisms . . . 132

Fermentation . . 129, 131, 132, 204

Ferns . 22, 139-141, 147, 242, 248

„ life-history of . . . ]4i

„ Tree . . . 11, 19, 140, 222

Fertilisation . T 4i', 55, 143, 145

,, cross . . . 110-115

„ ,, contrivances

for facilitating .
,, of Bryophyta .

„ of flowers of Berberis

Lycium
„ of flowers of Salvia

lanata .

„ of Pteridophyta

self— . ' .
Fertility, of species
Fibres ....

,, bast —
Fibrous root
Ficus

bengalensis
Cunia
elaslica
glomerata .
hispida
infectoria .
pumila
religiosa .
scandens .
Figs

Filament .
Filices

Filiform

Filtering water ....
Fimbriate ....

Fir Forests of N.-W. Himalaya
Fire, effect on plant-distribution

of 227-228

,, its effect on plant-develop-
ment ....
Fires ....

Firs Ill, 145

Fission Fungi . . . . 128

Fissures, in bark
Flacourtia Cataphracta
„ Ramontchi
Flagella .
Flemingia congesta

„ stricta
Fleshy
Floccose .
Flood-plains . .•
Flora
Floral-axis

diagrams .
envelopes .
formulae .
parts
receptacle
shorthand

111

141

112-115

112, 113
141

110-115
123

. 73, 91

31,34,186,227,243

5,22, 185

-2 37

. 173,219

. 239, 249, 250

. 239,250

239

185

41, 51, 52
139
29
207
22
225

216
67

Flower

bud
parts ot

15
13
239
127
14
14
63
64

. 234,239
117,119,121,124
. 48, 49
57
41
57

41,44,46
.42, 49, 60
57

3,4,37,41-57,143

41, 44, 46

INDEX.

PAGE.

Flower, parts of, are leaves . . 46

j, „ „ position and num-

ber of 44

„ symmetry of ... 46

Flowering plants . . . 126, 142
„ shoot .... 37

Flowerless plants . . . 126

Flowers . . . . . 126

„ green—. ... 47

„ types of which may cause

difficulty ... 55

Fluctuating variability 152-155, 157, 160
Fluted stems ... 14

Follicle 60

Fomes annosus . . . . 134

(See also Trameles radiciperda.)
„ life history of . . . 191-193
„ Pappiamis . . . 134

Food-materials, plant 3, 20, 89, 91, 93, 103,

104, 178-180

„ „ storage of . . 7

Foot of fern .... 141

Forests, Arid-country . . . 237, 238
„ Deciduous . . . 238-241
„ Evergreen . . . 241-243
„ HiH . . . 224, 244-247
„ Littoral . . . 247-249
„ Riparian . . . 249-250
„ Tidal .... 247-249
„ types of and factors res-
ponsible for their distri-
bution ... 237
Formulae, floral — ... 57

Free 48

Free-central .... 54

.Fronds . . . . . 139

Frost 67

„ cankers .... 213

„ holes .... 235

„ injury by . . 209-213,215
,, resistant species . . 208

» ribs .... 213

„ tender species . . . 208

Fruit 3,59

„ aggregate .... 59

„ descriptive terms for shape

of .... 61

„ multiple .... 59

„ simple .... 59

„ — sugar .... 103

^ „ types of . . . . 60, 61

Fugacious .... 63

Functions of plants . . 2,3,85,86

„ of higher plants . 93

Fundamental tissue . . 74, 75, 84

Fungi 2, 127, 129-137, 146, 156, 179, 183,

186, 204-205, 207, 208, 213, 219, 226

Funicle 54

Funnel-shaped .... 50

Furcate venation . . . .22, 139

Fusiform 7, 61

Fusion, root— .... 170,175

Galls

Gambleola cornuta

Gamete

Gamo-petalous .
„ phyllous
,, sepalous .

Garcinia .

Gardenia turgida

Garuga pinnata .

Gases, in the plant

PAGE.
156
137
126

43,48
43

43,48
243

28, 239
239
82, 84, 87, 89

Generations, alternation of . 139, 142, 146
„ plant, succession of . 233

Generic name .... 121

Gentians ..... 245

Genus ... . 121-123

Geographical Botany . . 2, 3, 218-250
Geotropism . . . . 105

Germinating seeds ... 103

Germination" .... 59

Germs . . . . . 127

Gibbous 50

Gills 133

Girdling .... 168-170, 185
Glabrescent .... 64

Glabrous 64

Gland-dotted . . ... 29

Glands . . 29,49,63,66,74,114

Glandular hairs . . . 65

Glaucous ..... 64

Globose .... 61

Gloriosa siipefba . . . 31

Glucose 97, 103

Glume, flowering .. 56

„ outer .... 56

Gmelina arborea ... 16

Gnarled stems • . : . 14

Gnetaceae .... 144, 145, 147

Gnetum 9, 145

Goats 227

Gonophore .... 47

Gossypium .... 44

Gouania leptosiachya . . . 13

Grafting ..... 174

Grain, silver . . . . 17

Grains, aleurone ... 70

„ starch . . . 70, 97

Grape-sugar . . . . 97, 132

Grasses .6,11,21,30,42,50,56, 59,100,

111, 134, 184, 219, 223, 224,

225-227, 231-235, 245, 248

Grassland . ... 231-236

„ afforestation of . . 235-236
Gravity, its effect on plants. . 105-107
Grazing . . 96,156,207,227,236
Green-flowers .... 47

„ plants . . . 178-180,204
Gregarious .... 67, 111

Grewia 47, 61

„ asiatica .... 239

,, pilosa .... 63

Groups, natural . . . 122, 123

Growing-apex . . . 69, 76

INDEX.

.
IX

PAGE.

Growing points . .

. 72, 76

Hilum ....

. - 55

Growth . . . 68,85,89,104,105

Hirsute ....

i i

1 8 7Q

,, abnormal
„ retarded by light
Guard-cells

. . lo, rj
. 104, 105
. 84, 100

Hoary ....

Holarrhena antidysenterica ,

64
. 116,239

Gum

78, 82, 168

Holbodlia latifolia

. 26, 245

Guti

. 172, 173

Holly . . .

. 222,244

Gutta-percha
Guitiferae .

74
222

Holoptelea integrifolia
Homalium tomentosum

31
240

Gymnosperms . 57, 77,
„ _ bast of

78, 143-145, 147

Homologous
Homonoia

36
250

i „ classification of . 144

Hooks ....

. 10, 116

„ .root of

Horizontal ovule

,, stem of

Hornbeam

14, 222, 244

Gymnosporangium Cunningham-
ianum ..... 136

Horse Chestnut
Horsetails

33, 216, 244
141, 142, 147

Gynobasic

Host ....

180

Gynoacium

. 41, 53

„ collateral .

198

Gynophore

„ intermediate

198

Humble-bees

. 177,227

Humus . 94,203,206,207,

220, 221, 226

Hyblaea puera .

178

Hybrids ....

150-152, 160

Hydrangea altissima . .

245

Habit

Hydrogen . .

68, 70, 93, 94

Hail, damage by

214

Hydrotropic

106

Hairs . 33, 35, 58, 63-65, 75, 99

Hydrotropism

106

„ on seed

. 58, 116

Hygrophyte

229

,, root —

Hymenial layer .

133

Half -inferior

Hymenium

133

Halophytes

206

Hymenodittyon excdsum

. 16, 239

Hamiltonia suavcolcHs

Hvphse

. 130, 188

Hardness, of wood

• • UO

Hypocotyl

Hardwickia binata

6, 65, 240

Hypocrateriform

Harra

Hypogynous

Hastate

,, leaf

Haustoria

130, 188, 200-202

Hazel

. 203, 222, 244

Head

Illegitimate-cross
Imbibition
Imbricate

. 112, 123
87
fil

Healing of Wounds .
Healthy development

165
177

Heart-wood . . 17, 78, 98, 168, 204
Heat, excessive .... 209
Helicoid cyme .... 40

Impari-pinnate .
Impatiens
In

• t-J-L

116
. 220, 241

Heliotropism
Hemlock Spruce, Indian

107

246

Inarching ....
Included stamens

174

Hepaticae .
Heptapleurum venulosum
Herbaceous
Herbarium

137
41

10, 66
. 163, 164

Incumbent
Indefinite inflorescence
Indehiscent fruit
Indeterminate inflorescence

59
39

60
39

Herbs

66 67

Indian Forests, distribution of . 237
„ „ types of . . 237
Indigofera .... 225, 244
Induplicate, valvate — . . 51
Indusium ..... 140
Inferior 43,49
,, radicle ... if

Heredity .
Heritiera Fomes
Hermaphrodite .
Hetercecious
Heterophyllous .
Heterophylly

156
248
45
198
27
. 28, 33

Heterostyled

112

,, side of flower . .

'. 46

Heterostyly .

112

Inflorescence

37-41

Hexamerous

mixed

4.0

Hibiscus Bosa-sinensis
„ tiliaceus

44
248

„ types of .
Infructescence .

•

. 37-40
69

Hill-Forests

. 224,244-247 Infundibuliform. . '.

INDEX.

PAGE, i

PAGE.

Innate ....

52 { Lamella, middle —

. 72, 192

Insect-pollination

. 42, 111 Lamina ....

20 49

Insects . 42, 111, 112, 115,

156, 182,227 Lanceolate ...

Integuments

54 , Lantana aciileala

. 178,228

Intercellular-spaces . 73,

74,84,91,99 | Larches .

145

Intermediate forms . 4,

123,125,155 ! Larix Grifflthii .

246

,, host

198 j Latent character

157

Internal bark

18, 80 j Lateral branching

In tern odes

9 j „ nerves .

„ in the flower

44/47,48 „ plane .

Inter petiolar stipule .

. "31, 34 „ roots

. 5,6,82

Interruptedly- pinnate

,, section .

Intramarginal vein

Laterite (soil)

. 220, 241

Introrse ....

Latex ...

Investigation, of diseases

. 182, 202

La ticiferous- tubes

Involucel ....

Lax inflorescence

Involucre ....

38, 39, 44

Lavers

172

Involute ....

35 Leaf-apex

,, , valvate —

,, base ....

24 30

Iron . . 18,93,94,

102, 206, 220

„ blade

Ironwood of Pegu

240

^compound

Irregular flower

, margin

. 22, 23

Irritability

68, 85, 105

, mosaic

Isostemonous

, scars

16, 20, 35

Ivy . . . . .

.8,27,245

, season for coming into .

Ixora ....

250

, segments .

, sheath

, shedding .

, simple

, stalk

Leaflet ....

Jackals ....

. 116,227

„ distinguished from leaf

Jamun ....

Leaves . . 3, 4, 9, 13, 20-36, 46, 153

Junipers ....

145

„ arrangement of

9,32

Juniperus]

191

,,J [colour of

. 28, 29

„ communis .

246

„ development of

„ macropoda .

246

„ metamorphosed

13, 31, 34

„ recur va . .

. 245, 246 j , movements of

107

, WallicJiiana

246

, of young plants

, parts of flower are .

, polymorphic .

, position of

, protection of young

. 35, 36

Kanddia ....

248

, shape of

. 23, 32

Kans ....

242

, smell of .

Karshu Oak

245

, structure of

Katabolism

, taste of .

Keel

Leea aspera

Kernel, of seed .

Legitimate cross

112

Khair . 16, 25, 208, 219, 220, 224,

Legume ....

239, 240, 219

Legummosae

222

Kinds of stems .

„ and bacteria

203

„ „ tissues

Leguminous plants, absorption

Kingdom, Animal

nitrogen by .

203

„ Vegetable .

Lenticels . . . 16,81,186,248

„ „ subdivisions of 126-147

Leontopodium alpinum

245

Knot?, in wood .

168

Lepidote ....

Kulu ....

232

Leptadenia reliculala .

Kydia calycina .

239

Liane ....

. 11, 241

Lichens . 137, 186, 203, 209

, 218, 219,

232, 233

Lichi ....

Licuala ....

243

Lagtrstrcemia Flos-Eegines .

. 219,243

Life, duration of plant —

17<i

„ jtarviftora .

. 29, 238

„ plant — , conditions of .

INDEX.

Light absorbed by chlorophyll
„ demanders . . 85
„ growth retarded by .
,, injury by .

„ its effect on plant-distribu-
tion

„ its effect on plant-move-
ments .

„ required for assimilation
„ variations caused by .

Lightning, injury by .

Lignified ....

Lignin ....

Ligulate . .

Ligule ....

Liguliform

Lily, Water

Limb, calyx
„ corolla
„ perianth .

Lime ....

Linear . . . . .

Linnaeus, sexual system of .

Linseed ....

Litsaea angustifolia

Littoral Forests .

Liverworts

Livistona ....

Lobed ....

Lobes, leaf —

Loculicidal

Lodicule ....

Lomentum

Longitudinal section .

Lonicera ....

Loose inflorescence

Loranthaceae

Loranthus

,, longiflorus .

„ pulvsmlenius

Lower side of flower

Lumnitzera

Lycopersicum esculentum

Lyrately-pinnate

Machilus ....

Macrosporangia

Macrospores

Magnesium

Magnolia Campbellii .

Mahua . . 7, 06, 132

Maize ....

„ smut of .
Male flower
Malformations .
Mallotus philippinensis
Maltose ....
Man, action of, effect on plant-dis-
tribution

„ action of, effect on type of
Vegetation .

PAGE.

102

Man, action of, is limited . . 234

>, 214, 224

Mangifera indica . . . 243

. 104, 105

Mango . 17, 29, 61, 63, 133, 174, 185

. 214, 215

Mangrove .... 8, 247

Mangrove-forests . . . 247

224, 226

Manufacture, of organic -food-

materials . . . 3, 89

107

Manures, plant .... 95

101, 102

Maples .... 21 \5, 222, 244

153

Marcescent .... 63

216

Margin, leaf — .... 22

Marginal vein .... 22

Maximum intensity ... 86

Mealy ..... 64

. 30,50

Median plane .... 46

,, section .... 46

Medullary rays . . .17, 77, 98, 166

Meliaceae 222

Meliola 133, 186

Meliosma pungens , . . 244

Members, plant .... 2

„ ,, development and

118

structure of . 77

,, „ duration of . 63

133

„ ,, texture of . . 63

. 247-249

„ secondary, development

. 137, 147

of ... 82

243

Membranous .... 63

22-23, 44

Memecylon . . . 243

. 23, 24

Meristematic tissue . . .73, 76

Merulius lacrymans . . . 134

Mesocarp ..... 60, 61

Mesua jerrea . . . . 243

Metabolism . . . . 89, 90

244

Metamorphosed leaves . 13, 31, 34

„ stems . . 13

240

Metamorphosis .... 36

. 116,227

Microbes . . . . . 127

201

Micropyle .... 54

Microsporangia .... 142, 143

Microspores .... 142, 143

248

Middle-lamella . . . . 72, 192

187

Midrib 21,22

Millettia auriculata ... 30

Mimosa pudica . . .68, 106, 108

Mineral crystals ... 71

Mineral salts, essential . 205, 219, 221

Minimum intensity ... 86

24$

Mixed crops .... 95

142, 143

,, inflorescence ... 40

142, 143

Mobile leaflets . . , . . 229

Moisture, effect of, on type of vege-

247

tation . . . 231, 233

2 211, 239

,, excessive . . . 215

8,118

Monadelphous .... 52

134

Monandrous .... 45

Moniliform .... 62

156

Monochlamydeous ... 43

225

Monocotyledons . . 59, 78, 79, 145, 147

103

„ root of . . 79, 81

„ stem of 78

228

Monoecious . . . . 45, 111

->f

Monopodial branching . 12, 37, 38

234

„ inflorescence . . 38

Xll IN]
PAGE.

Monopodium . . . . 12
Monstrosities .... 156
Moringa pterygosperma . . 26
Morphology, Vegetable . . 2, 5
Moru oak ..... 244
Morus 227
Mosaic, leaf — .... 27
Mosses, . 137-139, 147, 209, 218, 232, 248
„ ,club— .... 141
„ life history of . . . 139
Moulds 129
Movement, of protoplasm . 68, 69, 85
Movements, plant . . . 105-108
sleep ... 107
Mucronate .... 24
Multiple fruit .... 59
Musci 137-139
Mushrooms .... 129, 133
Mussaenda .... 47
Mutants ..... 155
Mutations . . . . 155, 160

DEX.

PAGE.
Obcordate. ... <>5

Obdiplostemonous ... 52
Oblanceolate .... 25
Oblique-leaf . .22
„ plane ..... 46
„ section .... 46
Oblong 24

Obovate 25

Obtuse .... 24

Occlusion, of wounds . . . 165-167
Ocroa 31

Odd-pinnate .... 25
OdinaWodier . . 16,29,239,244
Oenothcra Lamarckiana . . 155
Oil-glands . . . . 29 74

Oil? 29 71, 74

Olca slan<? ulifera . . . 244
Oniou ..... 11
Oophvte . , . 139, 141-145, 147
Ousphere . . . 126, 138, 141, 143
Oospore .... 138, 141, 143
Open vascular bundle . . 76
Operculum . . 139
Opposite leave? .... 9
Optimum intensity . . .86, 208
Opuniia Dillenii. . . . 12
Orange .... 29, 30, 74, 133
Orbicular .... 24

Mutilation . . . . 156
Mycelium . . . . . 130
Mycorhizas . . . 203-204,226
Myrisiica .... 243

Naked budi, .... 33
Napiforru root .... 7
Natural classification . 118,119,122-125
„ grafting . . . .175
„ groups .... 122, 123
„ order .... 122
„ selection . . 157
Nectar . . . 42,49,111,114
Nectary 49, 114
Negatively geotropic . . . 106
„ heliotropic . . 107
Nelumbium speciosum . . 25
Nerves ..... 20
Nipa iruticans .... 248
Nitrates ... 94, 129, 203, 204
Nitrifying bacteria . . . 129
Nitrogen . 68, 70, 93, 94, 95, 129, 203, 207
Nodes 9
Nomenclature . . . . 121
Non-essential substances . . 95, 96
Normal roots .... 5
Nucellus ..... 54
Nucleus . . . . 69, 70, 71
Number, of parts of flower . . 44
Nut . 61
Nutlet 60
Nutrition. . . 68,85,89,104,153
Nymphaea .... 47
Nyssa 246

Oak . 6, 17, 58-60, 118, 203, 222, 224
Oats, smut of . 134

Orchids .... 241

„ roots of ... 8
Order, Natural . . . . 122
Organic material . . . 178-179
,, „ manufacture of . 3, 89
Organised ferments . . . 132
„ plant, highly . . 2, 91
„ substance ... 87
Organisms,f actors influencing rela-
tions between . . 178
Organs, plant . . . . 2, 3
,, „ functions of . . 3
», „ reproductive . 4
», ,, sexual ... 45
„ „ vegetative . . 4
Origin, of species . . . 148-161
Ornithophilous . . . . HI
Orobanche indic.a . . . 11,200
Oroxylum indicum . .28,58,59,116
Orthotropous .... 54
Osmosis .... 86-87

Osseous ..... 63
Ougeinia dalbergioides 14, 37, 236, 240, 244
Oval .... 24

Ovary .... 41,54,145
Ovate 24

Overlap

Ovoid .... 61

Ovule 41, 143
„ characters of . . . 54,55
Oxalate, calcium . . . 71
Oxalic acid .... 93
Oxygen . 68, 70, 85, 93, 94, 101, 103, 205-
207, 220, 247, 249
Oxytenanthera albociliata . . 241

INDEX. xiii

PAGE.

241

Perfoliate 25

Palas ...

239

Perianth . . . .41, 43, 44, 143

Palea

„ limb .... 43

Paleaceous

„ throat .... 43

Palisade tissue .

» tube ... 43

Palmate lf»af

Perioarp , _ < 59

Palmately-cleft . .
fejp- divided

. . *-'J

23
23

Periderm . . . . , 80 81

Peridermium brevius . . . 136

lobed

„ complanatum . 136

, parted

Peridium . . . . 197

trifoliolate

Perigynous . . . .48,49

veined

Perisperm . . . .58, 143

Palmatifid

Peristome . . . . 139

Palmatisect . .

Perithecium .... 131 133

Pal minerved

Permanent tissue ... 73

Palms . 11, 13. 14,

18, 38, 59, 65, 78,

Persistent «. 63

145, 176, 222, 243

Petaloid perianth . . 43

„ Sago

. 144, 147

Petals . . . 43,44,47

Pandanus

. S, 222

„ descriptive terms for . 49

„ lecforius

249

Petiole . . 20,29-31,33,34,35,37

Panicle

Petiolule . . . . 23 37

,, corymbiform

Phanerogams . 126, 142-147, 183, 200

„ cymose .

Phellem 80

„ racemiform

Phelloderm .... 80

„ umbelliform .

Phellogen 80 81

Papilionaceous . .

Phloem .... 76-79

Pappose .

Phlogacanthus thyrsi fiorus » . 41

Pappus

Phoebe . . . . . 246

Parallel -venation

Phcenix 16, 28

Parasites .

180,185, 186,227

Phcfnix acaulis .... 10

„ wound —

194

,, humilis . . . 239

Parasitic Phanerogams

. 200-202

„ paiudosa . . . 248

Parasitism of Santalum album . 202

Phosphates . . . . ' 94, 204

Parenchyma

, 73, 75

Phosphorus . 68, 70, 93, 95, 183, 207

„ spongy .

Phycomycetes .... 131, 187

Parietal .

Phyllanthus Emblica . 15, 26, 67, 208, 209,

Pari-pinnate . .

239

Parted leaf

. 22, 23

Phyllotaxis .... 32

Partite „ .

Phyllotaxy .... 32
Physiology, Vegetable . .2,86-116
Phytophthora infestans . . 131
„ „ life history

Parts, of flower .... 41
„ „ „ are leaves . . 46
»» ' » »» position and nuni-

"L. £ * *

ber of

of . 187-190

Pastor roseus

227

,, omnivora . . 190-191

Pathology, Vegetable .

2,3

Picea 191

Pea .

. 31, 203

„ Morinda 33, 135, 184, 244, 246

„ flowers of .
Pear.
Pedate leaf

56
136
26

Picrasma quassioides ... 25
Pieris ovalifolia .... 244
Pileus ..... 133

Pedately-com pound .

Pilose ..... 64

„ nerved .
Pedicel . . .

26
37

Pine (Pinus) . 12, 13, 33, 56, 58, 67, 111,
145 191 203

Pedicellate
Peduncle .
Pedunculate

37
37
37

„ Blue . . . 183, 224, 225, 244
„ flowers of .... 58

Pinnae 25

Pendulous branches .
„ inflorescence

'. \ 65
37

K.A

Pinnate leaf . . ... 25
Pinnately-cleft .... 23
— divided ... 23

,, ovule .
Penninerved . .
Pcniacme suavis
Pentamerous
Percolation .

• * u4
21
241
45
219

—lobed ... 23
— parted ... 23
—trifoliolate . . 26
— yeined ... 21

Perennial . . .

66,67,80, 176

Pinnatifid .... 23

XIV

INDEX.

Pinnatiaect
Pinnules .
Pinus excelsa

„ Gerardiana
„ Khasya .
„ longi folia

PAGE.

23
26

134, 136, 194, 224, 2^7,

244, 246

246

15, 18, 136, 220, 224, 244,
246
246

. 232, 233
185
63

41-43, 47 53, 54
. 53, 54

„ Merkusii
Pioneer plants .
Pipal
Pips
Pistil

Pistil, characters of

Pistillate flower ... 45

Pith .... 16, 17, 77

Pits ...... 71

Placenta ..... 53

Placentation .... 53

Plaited ..... 51

Plane (Platanus) . . . 34, 216
,, lateral .... 46

„ median .... 46

„ oblique .... 46

Plano-convex .... 62

Plant-communities . . . 233

,, crops, succession of . . 233

„ — distribution, factors affect-

218

3,20,89,91,93, 103,
104, 178-180

mg
food-materials

generations, succession of .
highly organised
life, conditions of

,, duration of
members, development and

structure of .
members, duration of
members, texture of .
movements

233

2,91

176

77
63
63
105-108

Plants 1,2

deciduous . 67, 100, 101, 229
„ dependent on other plants 225, 226
„ effect on plant-distribu-
tion ... 225
„ evergreen . 67, 100, 101, 229
„ functions of . .2, 3, 85, 86
„ green . . 178-180,204
„ gregarious ... 67
„ higher, functions of . 93
„ pioneer . . 232, 233
„ sporadic ... 67
„ their influence on plant-
development . . 183
Platanus . . . . ..34,216

Plicate 35,51

Plumule 59

Pneumatophores . . . 248

Pogostemon plectranthoides . . 29

Poisonous substances 93,205,206, 216,225
„ „ excretion of

by plants 226

Polar Zone ... 222

Pollard- shoots .
Pollen

,, grains
„ sacs
„ tube

Pollination . 42, 111

Pollinia
Poly-adelphous .

,, androus
Polygamous
Polygonum >
Polymorphic leaves .
„ plants .

Poly-petalous
,, phyllous .
,, sepalous
Pongamia glabra
Poplar ....
Poppy . .

Populus ciliata .

,, euphratica .
Pores ....

,, water
Position, of leaves and buds.

,, of parts of flower
Positively geotropic .
,, heliotropic .
,, hydrotropic
Posterior side of flower
Potassium. . . 93-95,
Potato ....

„ disease .
Premna latifolia
Prepotent pollen
Preservation, of specimens .
Pressure, root

Prickles ....
Prickly Pear
Primary nerve .

„ root
Primula

Prinsepia utilis .
Procumbent stems
Products, waste
Promycelium
Prosopis spicigera
Prostrate stems
Protandrous

Protection, of young leaves
Proteid grains
Prothallium
Protogynous
Protonema
Protophloem
Protoplasm . . 1,

„ continuity of
Protoxylem
Pruinose .
Pruning .
Psoralea corylifolia
Pteridophyta . . 126,
Pleris aquilitta , , t

PAGE.

171

41,51,53,111

. 53, 143

. 51, 143

. 55, 143

,115,182,22?

. 46, 111
31
27

. 128, 135
43
43
43

17, 249, 250

. 222,226

244

238

17, 18, 74

100

44
105
107
108
46

183, 204, 207

11, 109, 208

131, 187-190

. 115, 151

103

96, 97

112

16, 34

. 69, 90
196

. 219,237

10, 65

. Ill, 113

. 35, 36

. 70, 205

140, 142, 143

111

138

68-70, 85-90
72

. 76, 79
64

.' 167, 168
66

139-142, 147
11,140

INDEX. XV

PAGE.

Pterocarpus dalbergioides

241

Racemose inflorescence . . 38, 39

„ macrocarpus

241

Radial vascular bundles . . 79

„ Marsupium

240

Radicle ..... 58

,, santalinus

. 224,240

,, inferior . < . . . 60

Pterospermum

243

,, superior ... 60

„ acerifolium

240

Radish ..... 7

Puberulous

Rainfall . . . 218^237, 238, 241

Pubescent
Puccinia graminis

64
135

,, its effect^on type of vege-
tation " . . 231

„ life history of
Pulvinule .

. 195-199
. 30, 108

„ its effect on type of forest 237
Rain-water . . . . 221

Pulvinus .

. 30, 108

Rakhs ... . 237

Pure forests
Putamen .

178
61

Rambling plants . . . 11
Ramenta ..... 140

Putrefaction

. 129, 179, 204

Randia dumetorum . . ' . 13

Pyrausta machceralis .

> 178

Raphe ..... 55

Pyrene

Raw food-materials ... 3

Pyriform .
Pyrus lanala

62
64

Rays, medullary — . .17,77,98, 166
,, of umbel .... 38

„ Pashia
Pythium .

. 13, 16, 28, 136
131

Receptacle, of flower . . 42, 49, 60
„ of inflorescence . 39

Reciprocal symbiosis, . . . 180

Reclining stems ... 10

Red Sanders . . 224, 238, 240, 250

Quadrangular stems .
Quadri-foliolate

26
51

Regular flower ... . . 46
Regulation of transpiration . 99-101
Regursoil .... 220

,, locular . .
Quercus
,, Brandisiana .
„ calathiformis .
,, dealbata.
,, dilatata
„ eumorpha

. 118, 121

246
246
246
184, 244 245, 246
246

Reinwardtia trigyna . . . 63, 1 12
Relations, between organisms . 178
Reniform ..... 24
Repand 22
Repent stems .... 10
Reproduction . 68, 85, 108-110, 156, 158,

,, jenestrata
,, glauca .
„ Griffithii
,, Helferiana

246
. 244, 246
246
246

Reserve materials . . 97, 169, 171
Resin .... 71, 168, 194
Resin-canals ")
ducts I • . • 18,74,145

llfr

246

, . U.UL/LS j

, , L (OX • •

,, incana .

7, 21, 29, 244, 246
246

Respiration . 68, 85, 89, 103, 104, 179
Response to a stimulus . . 68

„ lanuginosa
, Lindleyana
, lineata .

246
246
246

Resting spores . . 126, 128, 190, 196
Reticulate venation . . . 20
„ vessels ... 73

, mespilifolia .
Olla

246
246

Retuse ..... 24
Revolute ..... 35

, pachyphylla .
, polystachya .
, semecarpifoha

246
246
17, 28, 184, 212,

Rhabdia lycioides . . .219, 250
Rhachis 25, 37
Rhamnus . 222, 244

• . I c>

245, 246

,, virgatus

„ semiserrata

246

Rhizoids 138

,, serrata . .

246

Rhizome 11,66

„ spicata .

246

Rhizomorphs . . 130, 133, 134, 193

,, truncata

246

Rhizophora . . 8,248

,, xylocarpa

246

,, mucronata . . 247, 248

Quisqualis indica

Rhododendron Anthopogon . . 245
arboreum . 136,244-245

,, campanulatum 136, 212, 245

„ lepidotum . . 245

Rhus Cotinus .... 244

. 121, 123

,, vernicifera . . . 122

,, importance of .

149
38

„ Wattichii .... 122
Rhytidome . . . .81, 242

Raceme ...
Racemiform

Ribs 20

XVI

INDEX.

PAGE.

Ringing 168-170

Rings, annual . . . . 17, 78

Riparian Forests . . . 249-250

Root . 3-8,11,79,81,107,109,185

„ aerating .... 248

„ cap 82

„ contraction of. . . 83

„ development of . . . 6, 82
„ fusions .... 170, 175
„ hairs .... 83

„ „ absorption by . 86, 93, 94, 96
206, 207, 211

„ pressure . . . . 96, 97
„ shortening of . . 83

„ stock .... 66

„ structure of ... 79

„ suckers . . 7,109,171,236
Root system .... 5

„ „ development of . 6, 7, 82
„ „ types of . . . 5, 6
„ tubercles .... 129,203
„ wood of .... 79

Ro&a 31,244

„ moschala .... 43

Bosaceae ..... 222
Rosdlinia bunodes . . . 133

Roses .... 47,64,65

Rotate 50

Rotation of crops . . .95, 226
Rotting . . . . 129, 179, 204
Roughness of bark . . . 15

Rubus 64,244

„ lasiocarjMs 8, 11, 15, 64, 83, 109
Rudiments .... 56

Rugose 64

Ruminate albumen

Runcinate. . . . . 22

Runner . . . ... 11, 109

Rust- fungi . . . . 135

Ruats .... 129, 135, 195

Saccate . .
Sacchar^mycetes
Sagittate . .
„ leaf .

50
131

24
25
144, 147

Sam . .
Sai .

. 117, 220,

224, 238
220, 238

Sal . 6,7,15,60,63,67,116.117,133,210,
220-221, 224, 225, 234, 238, 240,
244, 250
„ Forests 210, 211, 221, 22o, 234, 240

Salai 228,232

Saline soil . . . 206,220,229

Salix . . 244

„ bahylonif,a ... 65

„ daphnoidea . . . 15

„ ietrasperma . . . 250

Salt 206

Salts, excess of . . ' . .205, 247

Salvadora . ... 237

pertica ... 238

PAGE.

Salver-shaped .... 50

Salvia lanata .... 112-113

„ fertilisation of flowers of . 112

Samara 61

Sand 220

Sandal . 18,202,227,238,240,250

Sandan 240

Sandy soils .... 94

Santalum album . . . 240

„ „ parasitism of . 202

Sap, cell — 69

„ rising of . . 96

Sapium sebiferum ... 29

Saprophytes . . . 179, 191, 193

Sap-wood 17, 205

Sarcocarp .... 61

Sarmentose . . . . 11

Satin Wood .... 220,240
Savannah .... 231

Saxifraga ligulata . . • 63

Scabrous 64

Scaevola 249

Scalariform vessels ... 74

Scale-insects .... 133. 181

„ like leaves. . . . 11, 12

Scales 63,65

„ bud— . . . . 33,34

„ of bark ... 16

Scaly buds .... 33

Scandent stems . . . . 10

Scape ..... 11

Scaiious ..... 63

Scars, leaf . . . 16,20,35

„ of bud scales ... 33

., of stipules . . . :?1

Scattered leaves. ... 9

Scent, of flowers . . .43,111

,, of wood .... 18

Schizocarp .... 60

Schizomycelf.8 . . . . 128

SrMeichera trijuga . . . 133, 239

Schrebera su-ietenioides . . 239

Scion 174

Sclereuchyma ... . 73, 75, 101
Scorpioid cyme .... 40

Screw Pines . . . 8,222,243
Scrophulariace.ae, . . . 187

Seaweeds 127

Secondary growth . . .77, 79
„ members, development

of .... 82

21
5

123
46
46
46
46
46
63

59, 109
28
190-191

„ nervros
„ roots .

Section, .

„ lateral .
„ longitudinal .
„ median
„ oblique .

„ transverse
Sedum rosulalum .
Seedlings

leaves of
damping off of

Seeds . 3, 42, 54, 55, 58, 59, 70, 109,

126, 143

INDEX.

XVH

PAGE.

Seeds, descriptive terms tor shape of 61
„ distribution of . 58, 109, 115,
182, 219, 227
„ germinating . . . 103
Segments leaf - • • 22, 23

PAGE,

Sinuate 22
Sissoo 6, 7, 25, 116, 219, 224, 234, 238,
240, 249

„ Forests . , . 233, 240
Skimmia Laureola 29
Sleep-movements - — -»— 107
Smell, of leaves . 29
Smilax . . 145
„ parvifolia . . 21
Smut-fungi . . 134
Snow, damage by •. . 213
Soil, absorption by 94
„ calcareous . . . 220, 24 5
„ cotton . . . 220
„ depth of . 219
„ effect of vegetation on .221, 234
„ formation of ... 232
„ its effect on plant develop-
ment .... 205-208
„ its effect on plant distribu-
tion 219-221

Selection' .... 157-160
„ natural . . . 157
Selective power of protoplasm . 87
Self-fertilised . . - . HO
Kemecarfiui Anacardium .
Semi-amplexicaul . »
Sepaloid perianth ... 43
Sepals .... 43,45,47,49
„ descriptive terms for
Septate hyphse . . . . 130
Septiddal .... 60
Sept.fragat .

Serrate .....

Sesbania aculeata ... 66
Sessile 20, 37, 42, 51, 51, 59
Seta 139

„ its effect on the type of vege-
tation .... 232
„ laterite .... 220,241
„ moisture in 206-208,220-221,233
„ oxygen in . , 206-208,220,249
„ regur .... 220
„ saline . . . 206, 220, 229
„ temperature of . 86, 100, 208, 211,
212, 223, 232

„ variations caused by . . 153
,, water-logged . . . 220
„ well-drained . . . 207,220
Solanaeeae .... 187
Solanum Melongena . . . 153
„ tuberosum . . . 187
„ verbascifolium . . 29
Solitary flowers . .37
Sonneratia ....
Sorus 140
Spaces, intercellular . 73, 74, 84, 91, 9S
Spadix •
Spathe

Sewage, disposal of . ,. 208
Sexes, separation of .
Sexual generation . . . 139
Sexual organs, distribution of . 45
„ reproduction . . 108, 156, 158
„ system of classification . 118
Shade-bearers . . . 85,224
Shape, of cells ....
fruit ....
„ leaves . . . 23, 32
„ root ....
„ seeds . 61
„ stems ....
Sheath, leaf .... 30
Shedding of leave? .
Shield (in budding) . . . 175
Shining leaves ....
„ stems .... 15
Shiaham 240
Shoot . . . . 3, 4, 6, 7

„ development of
„ flowering
„ pollard ....
„ stool .... 171
STiorea obtusa .... 241
„ robu^.a . . . .117,210
Shortening, of roots .
Shorthand, floral ... 57
Shot-holes.
Shrubby plants
Shrubs' . ... 66,67
oieve-nlates ...
„ tubes . . 74,91,169
Silica
Silky . . 64
Silver Fir . .17, 65, 168, 225, 245
„ grain . •
Simple, fruit
„ leaf ... 23
„ pistil ... 53
ginistrorse twiners ... 10

Species .... 117,119-125
„ constancy of .
„ distribution of important. 250
hybrids ... 150
origin of . . . 148-161
.I sub .... 120,123
„ „ importance of .
Specific characters . • • 120
,, name .
Specimens, collection of
preservation of .
Spectrum, of chlorophyll . 102
Spermatia • • '100
Spermatozoid . • »*y, 100,1 A
Spherical . •
Spheroidal

Spike . ' ' 909
„ 'disease . • •'"'*

Spikelet . •

XV111

INDEX.

PAGE.

PAOE,

Spines 10, 12, 13, 32, 34, 36, 64, 116,

Straggling plants . . 11

153, 229

Strands, leaf . . . 20

Spiraea . .

244

Strawberry . . 11, 60, 109

Spiral vessels

73,76

Streblus asper . . . 250

Spirillum

127

Striate . ... 14

Spirits, manufacture of 132

Strigose . ... 64

Spirocheete
Splitting-Fungi

128
128

Striking, of cuttings . . . 171
Strobilanthes . . 50,67,176,182,184

Spongy parenchyma .

„ Wattichii . .67, 184

Spontaneous variations 155

Strophiole .... 58

Sporadic .

Structure, of leaves ... 84

Sporangia

131, 140

„ „ plant-members . 77

Spores

126

,,root . . . 79

Sporidia .

134,136,196

„ „ stem . . 14, 16, 77

Sporogonium

138

„ „ vascular bundles . 75

Sporophore

. 133, 192, 194

Struggle for existence 96, 148, 149, 159,

Sporophyll .

140-143, 147

177, 178

„ female.

. 142, 143

Style 42,54

>, male

. 142, 143

Sub- Arctic Zone ... 222

Sporophyte

139

class 122

Sports

Iffl

coriaceous 63

Spruce . 33, 65, 135, 145, 168, 225, 244, 245

divisions of Botany . . 2

Spurred ...

Vf*orpi"fl Vil A TCiti or.

Stamen . . 41,43,47,51-53,143

jj jj V vgC U£v UIU -IVIIJ.^-

dom . . 126-147

„ characters of .

. 51, 52

Kingdom .... 122

Staminate flower

opposite leaves ... 9

Staminode

order .... 122

Staminodium

species . . . . 120, 123

Standard

„ importance of . . 149

Staphylea Emodi

terranean roots ... 8

Starch . 3,70,89-92,97,101.103,208,

Tropical Zone ... 221

„ grains

. 70, 97

Suberised ..... 72

Stellate hairs

Subtending bract ... 46

Stem

. 3,4,9-19,65

leaf .... 9

kinds of .

Subulate 23

of Dicotyledons

. 77, 78

Succession of crops, or plant

„ Gymnosperms

. 77, 78

generations .... 233

„ Monocotyledons . . 78, 79

Succulent ..... 63

„ Tree Ferns

140

^ „ fruit .... 61

shape of .

Suckers, see Haustoria!

structure of .

. 14, 16, 77

Suckers, root . . 7,109,171,236

Stephegyne parvifolia

15,31,34,239

Sucking force, in leaves . . 98

Sterculia .

. 65, 241, 243

Suffrutescent .... 66

„ urens .

. 15, 232, 239

Suffruticose .... 66

Stere.ospe.rmum suaveolens . . 239

Sugar, cane . . . . 103

Sterigma .

196

„ fruit .... 103

Sterile flower

Sugarcane . . . . 5, 6, 131

Sterility .

. 112, 123, 150

,, adventitious roots of. 5, 6

Sterilize, to

128

Sulcate 14

Stigma

42, 54, 145

Sulphur .... 68, 70, 93

Stigmatic surface

Sundri 248

Stilt roots

8, 247

Superficial placentation . 64

Stimulus .

68, 85, 106

,, root-system . . 6

Stipe

133

Superior 48,49

Stipel

„ radicle ... 60

Stipellate .

,, side of flower . . 46

Stipitate .

Suppression of floral parts . . 55

Stipulate .

Suspended ovule ' . . . 54

Stipules .

, 30, 34

Survival of the Fittest . . 157

Stock

. 66, 174

Sutures, of carpel . . .

Stolons

11, 109

Swamp Cypress ... 67

Stomata, . .

. 48,99-101,247

Swelling, of wood

Stone, of fruit .

Swintonia .... 243

Stool-shoots

Symhionts - . 180,202-204,226

PAGE.

Symbiosis . . 180, 182, 202-204
„ between Green and
Non-green Plants 204
„ distant . . 180,204
Symmetry of flower . . 46
Symplocos ... 29
Sympodial branching . . 12
Sympodium . . . 12, 40
Symptoms of disease . . 181, 182
Syncarpous ... 53
Syngenesious ... 52
Synonym .... 122
Synopsis of sub-divisions of Vege
table Kingdom . . 146
Systematic botany . . 2
Systems, of classification . 118
„ tissue ... 74

T
Tamarix 238, 250

DEX. XIX

PAGE.

Tetramdes midiflora . , .241, 243
Tetramerous .... 4,1
Texture, of bark ... 15
„ of plant members . . 63
Thallophytes . . . 126, 146
Thallus .... 127

Theca, of moss . . — ; — . 138
Thecse .... 61
Thespesia populnea . . . 248
Thickening, of cell-wall .• . 71
Thickness, of bark . . .14, 15
Thorns . . . .31, 153, 229
Throat, calyx ....
„ corolla .... 43
„ perianth ... 43
Thuja .... 191

Thymus Serpyttum ... 29
Thyrsus 40
Tidal Forests .... 247-249
Tides . . . 237,247

Tinas 240
Tissues 73

Tissue-system .... 74
Toadstools .... 129, 133
Tobacco plant .
Toddalia aculeata . • 153
Tomato 187
Tomentose
Tongue, of layers . • • 173
Toon ... 6, 18

Tannins 71, 78

Tap-root . . . . . 5, 6
Taste of leaves .... 29
Taxodium dislichum ... 67
Taxus bacf.ata .... 245
Teak . 6, 7, 14-18, 20, 21, 33, 37,
168, 178, 183, 204, 221,
224, 228, 238, 240, 243, 250
„ Forests 178, 183, 221, 224, 240, 243
Tectona grandis .... 6
Tegmen 58
Tegumentary tissue . . .74, 75
Teleuto-spores . . . 135, 136, 196
Temperate Zone, cold . . 222
„ „ warm . . 222
Temperature . . . .85, 102
„ effect on plant-move-
ments . 107
„ extremes of . . 208, 222
„ influence on growth 104
„ its effect on plant
distribution 221-224, 237
of soil . 86,100,208,211,
212, 223, 232
Tendrils ... 10, 13, 31, 107
Tendu ...
Terete ... .14
Terminal buds .
„ flower . . 37
Terminalia Arjuna . 15, 220, 250
„ belerica . . 41,238
Chebvla . . 7,238
tomentosa . 117, 220, 227, 238,
243, 244
Terme, descriptive, for petals and
sepals . 49
„ „ for shape of
fruit and eeed 61
Terrestrial plants . . - 185
Tertiary nerves .
Testa
Tetradycamous «

Toothed . . .22, 44

Torulose 62
Torus .... 42,49,71
Torus, of pits ....
Tracheae . 73
Tracheids . . . 73,74,78,91,98
Trametes Pini ....
„ life-history of . 194,195
„ radiciperda . . • 191
(see also Fames annosus.)
Transpiration . 88, 98, 212, 215, 223, 229
current . . 98,169
„ regulation of . . 99-101
Transport, of substances in plant 91, 97, 98
103
Transverse section
Tree Ferns . . 11,19,140,222
Trees . . .66,67,225,231
„ and Grasses . . 184,224,226
„ „ Strobilanthea
Trewia nudiflora . . 41,240,250
Triandrous .
Triangular .... 24
Tribe 123
Trichotomous branching . • 12, !•*
cyme .
Tri-foliolate .... Jj
Trimerous . • • F-ftriS
Trimorphio flowers . • • lw» "*j!
Tri-pinnate .
Triquetrous . **
Tristichous
Tropical Zone .

INDEX.

PAGE.

Tropophyte .... 229,230

Trumpet-shaped ... 50

Truncate . .... 24

Tsuga Brunoniana „ . - 246

Tube, calyx . . . . 43, 49

„ corolla .... 43

„ perianth .... 43

Tuber 11,109

Tuberculate .... 64

Tuberous root ... 7, 11, 109

Tubular 50

Tufts, of leaves .... 13

Turbinate .... 62

Turgescence . . .87, 88, 96, 108

Turgid 88

Turnip . . . . 7,95,156

Twigs .... 14,65,80

Twining stems . . . 10

Twisted aestivation . 51

Types, of flowers which may cause

difficulty . . . 55

of forests ... 237
„ „ factors respon-
sible for their distribution . 237
of fruit . . . .60,61
„ inflorescence . . 37-41
,, vegetation . . . ' 231
„ „ factors in-
fluencing their distribu-
tion ... 231
selection of, for description 4, 27

Umbel ..... 38

Umbelliform .... 40

Umbellule .... 38

Undershrub . . . . 66, «7
Undulate . . .

Unifoliolate compound leaf . . 30

Unil ocular . . . . 51

Unisexual .... 45

Unit of classification . . . 119

Upper side of flower ... 46

Urceolate ..... 50
Uredinaceae . . . 131,135,195

Uredospores . . . . 195

Urn-shaped . 50

Urticacece 222

Ustilaginaceae .... 131, 134

Ustilago Maydis. . . . 135

Utricularia . . . . 241

Vaeuoles .
Valeriana Wallichii .
Valvate

,, induplicate .

,. involute
Variability, fluctuating
Variation ,

69
50
51
51
51

152-1S5, 157, 160
110, 152-156, 229

PAGE.

Variation due to fungi . „ 156

„ „ insects . . 156

„ „ mutilation . 156

„ spontaneous . . „ 155

Varietal name .... 121
Variety .... 121-123, 149

hybrids . . . 150
Vascular-bundle . . 18-20,74-79,84

„ development of 76

„ structure of . . . 75, 76

„ tissue . . .. „ 74, 75

„ plants ... 126

Vegetable Kingdom ... 1
„ „ subdivisions

of . . 126-147
„ „ subdivisions
of, synopsis

of ' . 146

Vegetation, types of . . . 231
„ ,, „ succession of

different . 232-234
„ „ „ their distri-
bution de-
pends on ac-
tion of man.. 234
,, y, „ their distri-
bution depends
on moisture . 231
„ „ „ their distri-
bution depends on
soil ... 232
„ zones of . . . 221
Vegetative reproduction . . . 108
Veinlets „ . . , 20
Veins . . , 20
Velameti „ 8
Venation . ... 20-22
„ in Ferns . . .139
„ ,, Mosses , . . 138
Ventral raphe . . . „ 55
„ side ...» 52
„ suture , 53
Ventricose .... 50
Verbascum Thapsus ... 25
Verbenaceac .... 222
Vernation . . „ .35, 139
Verrucose .... 64

Versatile 52, 111

Verticils ..... 9
Vessels ... 73, 74, 76, 91, 98

Vexillum 56

Vibrio 127

„ cholerae . . . . 129

Viburnum .... 244

„ cotinifolium . 30, 35, 36

„ fattens . . . " 29

Villous 64

Violets 115

Virginian Creeper, Indian . . 245

Viscid ..... 65

Viscnm 201

Vitcx 243

„ Negundo .... 250

Vitis 24o

„ semicordata . . 245

INDEX.

XXI

PAGE.

Wood, knots in .

168

„ of root .

Walnut .... 16,222,244

„ sap —

17, 205

Waste-products . . .69, 90

,, wound — .

166

Water, absorption of, by plants 83, 86, 88,

Wocdfordia floribunda

112

91,93,96,211

Woodland

231-236

„ ascent of in plants . 96-98, 168-169

Woody roots . —

„ available . . . 206,218

„ stems .

10, 66

„ culture . . . .93,95

Woclly .

„ denuding action of . .219, 249

Wound-parasite

194

„ distribution of seeds by 116, 219, 249

Wounds .

165-175

„ imbibition of . . . • 87

„ healing of

165

„ in plants ... 93

Wound-wood

166

„ its effect on plant-distribu-

tion .... 218,219

,, its effect on the type of

vegetation . . . 231,232

Xerophyte ....

229, 250

„ Lily .... 47

75 77

„ pores . . . 100

Xylia dolabriformis 18. 224, 227,

240, 243

„ required for growth . . 104

Wax . . . .33, 35, 64, 75

(

Weeds 148

Weight, of wood . . . 17

Wendlaiidia exserla ... 41

131 132

Wheat, flower of . . . 56

„ Plant ....

130

„ rust of .... 195

Yew

245

„ smut of. . . . 134

Yield, of agricultural crops .

Wheel-shaped .... 50

Young plants, leaves of

Whorls . . . . 9, 33. 34, 65

Willow 222, 226

Wind, distribution of seeds by 58 116, 225

„ injury by . . 215, 224

„ pollination . . 42, 111

Zanthoxylum alctium .

„ utility of. . . 215, 225

8 118

Wine, manufacture of . 132

llfi 227

Winged fruit . . . 61,116

„ Jujuha

208, 239

„ petiole ... 30

„ Oenoplia

239

„ seed ... 58, 116

„ rugosa

239

Wings (alas) ... 56

Zones of vegetation

221

Witches' brooms . . 156, 200

1 182

Wood . . 14, 17, 18, 72, 75, 78,79

Zoospore .

188

„ decay of . . . . 204
„ heart . 17, 78, 98, 168, 204

Zygomorphic

CALCUTTA

STJMMNTENDENT GOVERNMENT FEINTING, INDIA
8, HASTINGS STBEET

EXPLANATION OF THE FIGURES.

PLATE I.

Fig. i. Germinating acorn of Quercus incana. («), the short shoot of the young
seedling bearing small scale-like leaves (i) (V). (c), the primary root
which here becomes a vigorous tap-root, (e) (#), the secondary lateral
roots. (d\ the petioles of the cotyledons. The latter in this case are
thick and fleshy and remain inside the acorn, below the ground, in
germination.

„ 2. Seedling of Quercus incana with the cotyledons (e) removed from the
acorn, otherwise lettering as before

„ 3. Young wheat plant, (#). wheat-grain from which the plant has sprung
and which contains the single cotyledon ; (d), stem bearing green leaves
(') > (^) and (c) roots. In this case there is no vigorous primary root
forming a tap-root, and a number of roots of approximately equal vigour
(&) (3). are found springing from the base of the stem (rf>. Vigorous
young adventitious roots (c) (c) have also subsequently developed
higher on the stem (d), just below the green leaves. The active roots
and their branches are seen to have particles of soil clinging to them
which are adhering firmly to the living roots-hairs, but the elongating
tips of the roots (/) (/) have no root-hairs, and are free of foil
particles, as are also most of the older roots (<5) (<5) and their branches,
their root-hairs having died off, and they themselves having ceased to
grow.

„ 4. Base of a stem of Sugarcane showing adventitious roots (a) (a) springing
from the stem ; (J), a bud.

All the figures X |.

Fig. 3

Fig. 2.

PLATE I.

EXPLANATION OF THE FIGURES.

PLATE II.

Fig. I. Diagramatic plans showing the course followed by twining stems, (a),
dextrorse stem moving in a counter • or anti-clockwise direction ; (&),
sinistrorse stem moving in a clockwise direction, z'.<?., in the direction
followed by the hands of a clock or watch.

„ 2. Diagrams showing (a) monopodial branching ; (Z>), sympodial branching.

In (c), the sympodium, or false axis, has become straightened and has a

superficial resemblance to a monopodium. (d) (<f), lateral branches

springing from the leaf-axils.

,, 3. Twigs of Pyrus Pashia showing the relative development of shoots

produced in one year. X f -

Some of the buds (a) (a) have remained dormant, others have produced
dwarf spineless shoots (b) (&), others have produced dwarf spiny shoots
00 (c)> and others have produced long branches (d~) (d~).

Fig. 3

Fig. 1. «

Fig SJ.

PLATE II

EXPLANATION OF THE FIGURES.

PLATE III.

Fig.l. (a). Spine of Aegle Marmelos. The spine arises in the axil of the trifolio-
late leaf (V) and at its apex bears a rudimentary leaf (c), thus
indicating that it is a branch. X \.

„ 2. (a). Compound spine of Flacourtia Cataphracta bearing three normal

green leaves (5) (i) and thus indicating that it is a branch. X-J-

„ 3. Stem of Gouania leptostachya. The tendrils (a) (a) arise in the axils of

the leaves (J>) (J), and they themselves frequently give rise to normal

leaves as at (c), thus indicating that they are branches. X £.

PLATE III.

EXPLANATION OF THE FIGURES:

PLATE IV.

Fig. I. Pennincrvcd leaf of Qutrcus incana. (a), midrib ; (J), straight secondary

nerves ; (<:), reticulate tertiary nerves. X f •
„ a. Palminerved leaf of Acer caesium with straight primary nerves. X §.

3. Penninerved leaf of Cornus macrophylla, with arcuate secondary nerves.

X f.
„ 4. Leaf of Smilax parvifolia with curved basal nerves. X \>

(a), broad leaf base; (&), tendrils.
5. Penninerved leaf of Cinnamomum Camphora. (a), strongly developed pair

of lateral nerves. X \-
„ 6. Portion of leaf-blade of a Fern, (a), midrib from which spring furcate

lateral nerves. X \.
„ 7. Pedately-parted leaf of Delphinium. X |.

.4?

Fig. 5.

PLATE ir.

EXPLANATION OF THE FIGURES.

PLATE V.

Fig. I. Pinnately trifoliolate leaf of Desmodium tiluefolium. (a) (a), petiolulee of
leaflets ; (£) (£), stipels ; (c), rhachis ; (d), petiole. X r

„ 2. Palmately 5-foliolate leaf of Holboellia latifolia ; (a) (a\ petiolules ; (3),
petiole. X f •

» 3- Upper portion of pinnate leaf of Berberis nepalensis ; (a), rhachis. Note
the distinct joint (ft) at the base of the terminal leaflet and at the
insertion of the lateral leaflets. X J.

„ 4. Leaf of Berberis Lycium. Note the distinct joint (a) between the leaf-
blade and leaf-base. X -J-

PLATE V.

EXPLANATION OF THE FIGURES.

PLATE VI.

Fig. i. Creeping stem of Ivy (Hedera Helix) with aerial roots (a). Note great

variety in the shape of the leaves. X f .
„ 2. Erect fruiting branch of Ivy. Note how the leaves differ from those in

Fig. i. X \.
„ 3. Stem of Berber is Lycium. X \.

(a), normal leaf in the axil of which a shoot bearing two small leaves is

developing. Note the minute stipules at (d~) ; ( J), a three-pronged spine

which is really a leaf as indicated by the fact that a leafy branche

is developing in its axil. Note the minute stipules still visible at (<?).

(0, a three-pronged green leafy structure intermediate between the normal

leaf (a) and the spine (J). The leaf-nature is revealed by the presence

of the leafy branch in its axil. Note also its minute stipule at (/) .

Fig.

PLATE VI.

EXPLANATION OF THE FIGURES.

PLATE VII.

Fig. I. Twig of Acer casium from the terminal bud of which four leaves have
developed. At (a) (a) the bases of the petioles of 3 leaves which have
been cut off are shown. (6), scars marking the position of the bud-
scales which have just been shed, (c) (c), scars marking the position
of the bud-scales which have similarly been shed at the beginning of the
annual growth in previous years. The twig thus shows the completed
growth of 3 years and is just commencing its 4th year's growth.
„ 2. Twig of Carpinus viminea which has just commenced its annual growth.
(a) to (£), part of the winter twig ; (^) to (c), part of the spring shoot
which has just developed from the terminal bud of the winter twig. At
(3), the lowest brown bud-scales have fallen off, but the pair of scaly
stipules at (</), which flank the petiole of the lowest leaf, were actually
present as bud-scales in the winter-bud, and at their tips the dark brown
portions which were exposed on the outside of the winter-bud are still
visible At (e) (*), the stipules are larger, but in them also the dark
portions which were exposed in the winter-bud are still visible. At (c),
the stipules are normal and no dark portions are visible. In this case
the bud-scales are obviously modified stipules.

.3rd y*

fig i

PLATE VII.

EXPLANATION OF THE FIGURES.

PLATE VIII.

Figs. I — 8. Showing the transition from an obvious bud-scale (i), taken from the
exterior of the bud, to a normal leaf (8), taken from the interior of
the bud, observed in an opening bud of the Horse Chestnut (Aesculus
indic(i), indicating that the winter bud-scales are really leaves which
have been checked in their development at an early stage and
converted into protective coverings for the bud. Minute points
representing the rudimentary leaflets are recognisable at the tips of
the scales (i) to (4). X -j-

„ 9. Young shoot of Stephegyne parvifolia. («), base of petiole of leaf which

has been cut off to show the large interpetiolar stipules (?>) (/>).
The terminal bud is concealed and protected by the stipules, one of
which (0) is facing the observer. X -f .

„ 10. Stem of Prinsepia ut'ilis ; (a), leaf in the axil of which is situated a
bud (3) and also a stout spine (tf), the latter protecting the bud
(<5). (d) (rf), other axillary buds, the subtending leaves of which
have fallen off. At (<?), the axillary bud has produced a leafy
shoot. One of the spines bears a leaf (/) showing the spines to be
branches. X 4-

Fig. 10

PLATE VIII.

EXPLANATION OF THE FIGURES.

PLATE IX.

Fig. i. Diagram of involute vernation.
„ 2. „ revolute „

„ 3. „ conduplicate vernation.

,,4. „ convolute „

,. 5. „ circinnate „

„ 6. „ plicate „

(a) (a) throughout is the midrib ; (<$), the upper surface, and (<:), the

lower surface, or back of the leaf.

Figs. 7 — 9. Stages in the development of the leaves of Viburnum colinifolium.
The opposite leaves (a) (a), when very young, are erect, and with
their upper surfaces in close contact, only the lower surface being
exposed to the light and air. The lamina is plicately folded, and the
delicate green tissue is protected by the close-set framework of nerves
which alone are exposed on the lower surface. As development
proceeds the folds of green tissue are flattened out and the leaf is
thrown outward and downward, the upper surface being finally
exposed to the full rays of the sun as in Fig. 9.
The petioles of the young leaves are grooved on their upper surface,
so that space is provided for the terminal bud between them. In
Fig. 8, (b) represents the terminal bud in cross section, and (c) (c)
the closely adpressed petioles also in section.
Figs. 7 and 8 slightly enlarged, Fig. 9. X J.

Fig. 4

Fig. 5.

PLATE IX.

EXPLANATION OF THE FIGURES.

PLATE X.

Fig. I. Diagram of a raceme.
,,2. „ „ corymb.

„ 3- „ „ spike.

„ 4. „ „ umbel ; (c~), the involucre.
„ 5. „ „ head or capitulum ; (<:)) the involucre.

„ 6. „ „ compound umbel ; (c), involucre ; (a1) (d), umbellules ;

(') (*)i involucels ; (/), rays.
„ 7- „ „ panicle.
„ 8. „ „ dichotomous cyme.
„ 9. „ „ helicoid „

„ 10. „ „ scorpioid „

Throughout (a) (a) are flowers; (<5) (<5), the bracts.
„ II. Diagram of a hypogynous flower; (a), sepal; (6), petal; (c~), stamen;

(d), ovary.

„ 12. and 13. Diagrams of a perigynous flower — letters as before.
„ 14. Diagram of an epigynous flower — letters as before.
„ 15. „ valvate — aestivation.

„ 16. „ valvate — induplicate „

„ 17. „ „ involute „

„ 18. „ of an imbricate „

„ 19. „ contorted „

Overlap to the right.

Fig 13

Fig 12

Fig. 13.

Fig. 14.

Fig. 15.

Fig. 16.

Fig. 17.

Fig. 18.

Fig. 19.

PLUTE X.

EXPLANATION OF THE FIGURES.

PLATE XI.

Fig. i. Winter twig of Odina Wodier. (a), leaf-scara — note their shape and alter-
nate arrangement.

„ 2. Winter twig of Hymenodictvon excelsum. (0), leaf-scars — note their shape
and opposite arrangement.

„ 3. Photograph of Bombax malabariciim. Note the branches in whorls.

„ 4. Photograph of Bombax malaharicum showing the woody buttresses at the
base of the stem.

EXPLANATION OF THE FIGURES.

PLATE XII.

Fig. I. Seed of Oroxylum indicum. X $.

(a), membranous wing developed from the testa ; (fi), the embryo

enveloped in the testa.
„ 2. Embryo of Oroxylum indicum extracted from the seed. X \.

(a), radicle ; ($), lower surface of one cotyledon, its upper surface

being placed flat against that of the opposite cotyledon, which is not

visible in the drawing. The plumule also is not visible.
„ 3. Young seedling of Oroxylum indicum. (a), (5), the two cotyledons with

their upper surfaces separating from each other ; (c), the hypocotyl ;

(<Z), primary root ; (c), secondary lateral roots. X \-
„ 4. The same at a later stage ; (/), the minute terminal bud of the stem,

otherwise letters as before. X T*
„ 5. The same at a still later stage; (^), the first pair of foliage leaves; A,

the epicotyl, otherwise letters as before. X T.
The root not shown.

PLATE XII.

EXPLANATION OF THE FIGURES.

PLATE XIII.

Fig. I. Erect branch of Coriaria nepalensis seen from the side. X -j--

Note the decussate leaves arranged in four ranks on the 4-angled stem
with their upper surfaces at right angles to the rays of light coming
from above. The stem is not twisted.
„ 2. Horizontal branch of Coriaria nepalensis, seen from above. X \.

Note the distichous leaves with their upper surfaces practically horizontal
and at right angles to the rays of light coming from above. Also the
twisting of the 4-angled stem caused by the efforts of the leaves to
place themselves at right angles to the incident rays of light.
In both figures one side of the 4-angled stem is shown shaded throughout.

PLATE XIII.

EXPLANATION OF THE FIGURES.

PLATE XIV.

Fig. I. Lever-apparatus dissected from flower of Salvia lanata. X 4 (a), (a),

filaments ; (<5), pouch formed by the metamorphosed lower anther-lobes ;

(c~), pollen-bearing anthers ; (d), upper arm of connective. If the pouch

(&) is pushed back the anthers (c) descend as indicated by the arrows.
„ 2. Flower of Salvia lanata. X 3 with half the calyx and corolla removed

showing the lever-apparatus in position, (a), hypogynous disc which

excretes nectar ; (i), ovary; (<?), style ; (<?), stigma. The arrow shows

the direction in which pressure is applied by a bee.
„ 3. The same with the pouch-like trap door pushed back and the anthers

consequently brought down close to the landing stage. Letters as

before.
„ 4. Complete flower ot Salvia lanata. x 3. (a), position of the stigma in a

young flower ; (i), its position in an older flower.
„ 5. A stamen of Berberis Lycium.

(a), from the back, the anther valves are closed.

(b~), also from the back, the right-hand valve is opening and beginning to

move upwards carrying the pollen with it.
The left-hand valve after completing the upward motion has turned

inwards so that the mass of pollen faces the centre of the flower.
(c), from the front showing both the pollen-covered valves facing the centre

of the flower.
„ 6. Expanded flower ol Berberis Lycium. X 5. (a), inner large yellow

sepals ; (i), outer petals ; (c), inner petals ; (d~), filaments ; (#), nectary.
„ 7. Single petal of Berberis Lycium showing the position of the two large

orange nectaries at the base.
„ 8 Showing position of a stamen which has sprung up on being irritated,

(a), stimatic surface ; (J), ovary.

Fig. 3.

Fig. 4

Fig. 6

Fig. 5.

Fig. 7.

Fig. 8.

PLATE XIV.

EXPLANATION OF THE FIGURES.

PLATE XV.

Fig, I. (a). Barclayella deformans on Picea Morinda. x {• Note the orange-
red curved needles on the attacked shoot and compare them with
the straight healthy needle shown below.
(3). Cone scale of Picea Morinda attacked by the Barclayella, showing

the beds of teleuto-spores. x £.
„ 2. Peridermium brevius on Pinus excelsa. Note the reddish-yellow blisters.

The needles have been cut short for convenience. X \.
,, 3. Teleuto-form of Gymnosporangium Cunninghamianutn on Cupressus torulosa.

Note the gelatinous spore-masses. x \.
„ 4. Aecidium form of Gymnosporangium Cunninghamianutn on Pyrus Pashia.

Note the tubular aecidia. x -f.

„ 5. Gambleola cornuta on Berberis nepalensis. Note the black hairs of teleuto-
spores. X \,

(All after Butler).

PLATE XV.

EXPLANATION OF THE FIGURES.

PLATE XVI.

Phytophthora infestans.

Fig. i. Back of potato leaflet attacked by the fungus showing the characteristic

dark spots with pale mouldy margins.
., 2. Conidiophores bearing conidia emerging from a stoma on the underside

of a leaflet. Highly magnified.
„ 3. Conidium with protoplasm dividend into blocks, the latter being liberated

as zoospores in Fig. (4).

„ 5. Zoospore coming to rest and losing its cilia.
„ 6. A zoospore which has germinated.

„ 7. A conidium which has germinated directly and sent out a germ-tube.
Figs- (3), (4), (5), (6) and (7) very highly magnified.

PLATE XVI.

PHYTOPHTHORA INFESTANS.

EXPLANATION OF THE FIGURES.

PLATE XVII.

Fig. I. Sporophore of Fames annosus on deodar showing the brown tuberculate
incrustation, and bracket-like active portion with white hymenium
below ; a, a, brown, mostly sterile portion ; b, b, recent spore-forming
portion.

„ ^. White mycelial sheets under the bark of the collar.

,, 3. Drawing of a portion of the surface of a block of wood cut from a diseased
tree, showing the white areas in the wood.

„ 4. Tissue elements modified by the action of the parasite, a, a, cells of
the wood parenchyma-bearing starch ; t>, bore-holes of the hyphae with
a filament extending across between two ; 0, spiral cracking of the wall ;
d, pitted vessel with a hypha penetrating it ; *, network from the
crossing of two spirals, the trachea is seen with the upper wall removed
so that the network is made up of the spiral of the lower wall of this
trachea and that of the upper wall of the subjacent one ; f, dissolution
of the middle lamella which results in the isolation of the elements.

„ 5. A rhizomorph.

(All after Butler),

PLATE X*ll.
Fig. 1.

FOMES ANNOSUS. Fs.

PLATE XVII.
Figs, fi-5

POMES ANNOSUS. F».

(a)

(b)

PLATE XVIII.

TRAMETES PINI, FRIES.

(«). Sporophore.

(b). Wood of Plnus excelta rotted by the fungus.
(After Butler).

EXPLANATION OF THE FIGURES.

PLATE XIX.

Puccinia graminis. Pers.

Fig. I. Wheat stem and leaf with teleuto-spores . x f
„ 2. Ureao-spores. The one on the right has developed two germ-tubes.

Highly magnified.
,. 3- Ideuto-spores. The one on the right has germinated, the upper cell

producing a pro-mycelium (a) from which spring sterigmata, bearing

sporidia (J). Highly magnified.
„ 4- Under-surface of leaf of Serberis Lycium showing the ceci&ia on a dark

brown patch, x \.

„ 5. An open aecidium from above. Magnified.
„ 6. Transverse section (of Berleris leaf, (a), is lower surface of leaf. Two

secidia are shown, one of which has not yet burst through the leaf

epidermis. Highly magnified.

PLATE XII,
PUGCiNIA GRAMINIS PERS.

PLATE XX.

LEAF OF A YOUNG MAHUA PLANT (BASS1A LATIFOLIA) INJURED
INDIRECTLY BY FROST, x*.

Pboto.-Mechl. and Litho. Dept.. TbontMon Oollege, Hoorkee.

THE AVERAGE ANNUAL DISTRIBUTION

REFERENCES.

8ELOW 20 INCHES C_ I

20 TO 70 INCHES d
ABOVE 70 INCHES f~! ZU

PLATE XXI.

Pboto.-Ziuoo.. January, 1908.— No. 29 .so -uoo.

IE RAINFALL.

DISTRIBUTION OF THE PRINCIPAL TYI

REFERENCES

ARID-COUNTRY FORESTS

DECIDUOUS FORESTS

EVER-QREEN FORESTS

HILL FORESTS C

TIDAL OR LITTORAL FORESTS L.

L_
L

PLATE XXII

! V.OO

OF FORESTS

LIMITS OF THE DISTRIBUTION OF THE PRir

REFERENCES.

LIMKT OF TEAK (TECTONA GRANDI8)

„ SAL (8HOREA ROBU8TA)

DEODAR (CEDRU3 LIRANI)

CAOUTCHOUC (FICU8 ELASTICAX___
RED 8ANDER8 (PTEROCARPU8 SANT
SANDAL (SANTALUM ALBUM). _

PLATE XXIII.

AL KINDS OF TREES.

Ao. 2350-2. 1100

UNIVERSITY OP CALIFORNIA LIBRA RY
BERKELEY

THIS BOOK IS DUE ON THE LAST DATE
STAMPED BELOW

MAS 10

JAN 30

MAY
OCT 1- 1941

20m-ll,'20

UNIVERSITY OF CALIFORNIA LIBRARY

1 mem

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