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AGRICULTURAL BOTANY 



AGRICULTURAL BOTANY 



THEORETICAL AND PRACTICAL 



BY 

JOHN PERCIVAL, M.A., Sc.D., F.L.S. 

EMERITUS PROFESSOR OP AGRICULTURAL BOTANY 
THE UNIVERSITY, READING 



EIGHTH EDITION 



DUCKWORTH 

3 HENRgETTA STREET, LONDON, W.C.2 



First Edition . . . . 
Second Edition .... 
Third Edition .... 
Fourth Edition (ist Impression) 
Fourth Edition (2nd Impression) 
Fifth Edition (Revised) . 
Sixth Edition (Revised) . 
Seventh Edition (Revised) 
Eighth Edition (Revised) . 
Eighth Edition (2nd Impression) 
Eighth Edition (jrd Impression) 
Eighth Edition (4th Impression) 
Eighth Edition (5th Impression) 
Eighth Edition (Oth Impression) 
Eighth Edition (?th Impression) 



May 1900 
March 1902 
October 1907 
March 1910 
April igi3 
September 1918 
January ig2i 
January 1926 
January 1936 
July 1942 
November 1943 
April 1945 
March 1946 
June 1947 
March 1949 



All Rights Reserved 



Made and Printed in Great Britain by 
Thomas Nelson 6- Sons, Ltd., Parksiae, Edinburgh 



PREFACE 

PRACTICAL men and the agricultural press have from time . to s 
time complained of the absence of text-books of botany suitea 
to the wants of the student of agriculture, those in existence 
being works which treat^the subject from a purely scientific 
standpoint and contain a large amount of matter which, though 
important to the botanist, is nevertheless of little interest or 
value to the agriculturist whose time for training in such matters 
is necessarily limited. 

The recent growth of interest in technical instruction, which 
has resulted in a large increase in the number of colleges and 
schools for agricultural education,' has rendered it imperative 
that so serious a defect should be remedied, and this I have 
endeavoured to do by writing the present volume. 

The contents are based upon many years' experience in teaching 
and lecturing to students, practical farmers and gardeners, and 
embrace all those botanical matters which such experience has 
led me to consider essential to a sound working knowledge of 
the general principles of the science and its more immediate 
application to the crops of the farm. 

Although the book has been primarily written for the benefit 
of students of agriculture, the greater portion of it is iqually 
well adapted to meet the requirements of gardeners and all who 
desire to obtain an insight into the general structure and life- 
processes of plants, a knowledge of which must undoubtedly 
conduce to a more satisfactory and economical management of 
all cultivated plants. 

Un|il quite recently botanical knowledge has apparently 
been 'deemed of little importance in examinations in the 
science and practice of agriculture, the science of botany 
being usually treated as an * optional subject/ It is, how- 
ever, gratifying to note that in the new regulations for the 
examination for the National Diploma in the science and practice 
of Agriculture, issued by the National Agricultural Examination 
Board, Botany takes its proper place as an obligatory subject 
beside its sister science Chemistry. 



VI PREFACE 

All the drawings in the work are original, and witri the excep- 
tion of the diagrammatic figures have been made by the author 
from living or natural examples. The panicles or ' ears ' of the 
grasses are all drawn the natural size of average specimens, 
in order that the figures may be of use in the identification 
of these important plants. 

The farm seeds are also drawn to a uniform scale ; their rela- 
tive sizes may therefore be seen at a glance. 

In this as in all scientific study, practical work is absolutely 
essential to 4 proper understanding of the subject ; in recognition 
of the importance of such work I have introduced into the text 
of the volume a series of exercises and experiments, illustrative 
of the principles and facts to be studied. These and others, 
which will suggest themselves to intelligent students, should be 
attacked and carried out in the spirit of research, so that students 
may learn to observe, record and discover things themselves. 

In conclusion, I tender my sincere thanks to my colleague 
Mr Cousins, and also to Mr W. H. Hammond, Milton Chapel, 
Canterbury, and Dr A. B. Rendle, of the British Museum 
(Natural History Department), for valuable criticism and assist- 
ance in reading through the proofs. 

JOHN PERCIVAL. 

SOUTH-EASTERN AGRICULTURAL COLLEGE, 

WYE, KENT. 
March, 1900. 



PREFACE TO THE SECOND EDITION 

THE very appreciative reception and rapid sale of the first edition 
have pfoved that a real want has been met by the book. 

The present edition has been emended and revised throughout 
in accordance with recent work and the criticisms of botanical 
friends. 

I shall be grateful for any further suggestions which may be 
deemed necessary to render the work more complete for educa- 
tional purposes or more useful to the student of this and allied 
branches of applied botany. 

JOHN PERCIVAL. 

Nov. 1901, 



PREFACE Vll 



PREFACE TO THE FOURTH EDITION 

To this edition a new chapter has been added and very consider- 
able additions made throughout the work, with a view of improving 
its usefulness and keeping the matter up to date. 

It is gratifying to find that the volume is highly appreciated 
by teachers and students in all countries wherever English is 
spoken. 

JOHN PERCIVAL. 

Jan. 1910. 



PREFACE TO THE FIFTH EDITION 

A CHAPTER on the Polygonacese has been added and other 
parts revised and emended. 

JOHN PERCIVAL. 
Sept. 1918. 



PREFACE TO THE SIXTH EDITION 

THE work has been revised throughout. 

JOHN PERCIVAL. 
Die. 1920. 



PREFACE TO THE EIGHTH EDITION 

THE text has been revised throughout, and additions made to 
chapters ix and xxii. 

JOHN PERCIVAL. 

THE UNIVERSITY, READING. 
Nov. 1935. 



CONTENTS. 

PART I. 
GENERAL EXTERNAL MORPHOLOOY. 

CHAFTKX *AGB 

I. INTRODUCTORY . . i 

II. SEEDS: THEIR STRUCTURE AND GERMINATION . 7 

The common bean, j \ White mustard, 16 ; Onion, 19 ; Wheat, 22. 

III. THE ROOT ..... r 25 

Primary and secondary roots, 25 ; Adventitious roots, 28 ; Root- 
hairs, 32. 

IV. THE VEGETATIVE SHOOT : STEMS, LEAVES AND BUDS 34 

Buds, 37 ; Branching of stems, 40 ; Twigs of trees in winter, 42 ; 
Spurs, 44 ; Dormant buds, 50 ; Adventitious buds, 51 ; Stems 
and their varieties, 52 ; Recognition of trees by means of twigs in 
winter, 6z. 

V. THE LEAF. . 63 

Foliage-leaf, 68 ; Modified leaves, 72 ; Leaf-arrangement, 74 ; 
Bud-arrangement, 76 ; Leaf-fall ; Evergreens, 76. 

VI. THE FLOWER ... 78 

Arrangement, symmetry and number of floral leaves, 80; The 
receptacle, 81 ; Non-essential parts of the flower; perianth, 83; 
The Calyx, 83 ; The Corolla, 83 ; The essential parts of the flower, 
. 83 ; The Androecium, 84 ; The Gynaecium, 85 ; Placentation, 87 ; 
Monoclinous and diclinous flowers; monoecious and dioecious 
plants, 87. 

VII. THE INFLORESCENCE .... 89 

Racemose inflorescences, 89; Cymose inflorescences, 92; Mixed 
inflorescences, 93. 

VIII. THE FRUIT: DISPERSAL or SEEDS . . 95 

Indehiscent dry fruits, 96 ; Schizocarps, 97 ; Dehiscent dry fruits, 
97 ; Succulent or fleshy fruits, 99 ; Dispersal of seeds, ico. 

ix 



Xll CONTENTS 

CHAFTKX FACB 

XXV. CANNABACEJE . . . . 332 

The Japanese Hop, 333 ; The common Hop, 339 ; Hemp, 348. 

XXVI. POLYGON ACK^E . . . . 350 

General character of the Order, 350 ; Common Buckwheat, 351 ; 
Tartarian Buckwheat, 355. 

XXVII. CHENOPODIACB-* . . . . 356 

Sea Beet, 357; Common Beet, 357 ; Mangel Wurzel, 358 ; Sugar- 
Beet, 367. 

XXVIII. CRUCIFEIUE .- . . . .371 

Wild Cabbage, 373 ; Cultivated cabbage and its varieties, 373 ; 
Turnip, 377 ; Swede, 381 ; Rape, cole or coleseed, 385 ; Black 
mustard, 387 ; White mustard, 389 ; Charlock, 391 ; Wild Radish, 
392. 

XXIX. LINAGES " 395 

General character! of the Order, 395 ; Flax or Linseed, 395. 

XXX. ROSACES . . . ^ . . .403 

Plums and Cherries, 403 ; Sloe, Bullace, Wild Plum and Apricot, 
405; Dwarf Cherry, Gean, Bird Cherry, Almond, Peach, 406; 
Strawberries, 407 ; Raspberry and Blackberry, 409 ; Dog Rose, 410 ; 
Pear, 411; Apple, 412; Medlar, Whitethorn and Quince, 413; 
Lesser Burnet, 414. 

XXXI. LEGUMINOS^:^ . . . .416 

Peas, 418 ; Bean, 422 ; Vetch, 424 ; Vetchling, 426 ; Red clover, 
437 ; Zig-zag clover, 431 ; Alsike, 431 ; White clover, 431 ; Crimson 
clover, 432 ; Yellow suckling, 434 ; Hop clover, 434 ; Black medick, 
435 ; Lucerne, 435 ; Melilot, 438 ; Sainfoin, 438 ; Serradella, 440 ; 
Kidney Vetch, 440 ; Bird's- foot trefoil, 441 ; Gorse, 443 ; Rest- 
Harrow, 443 ; Lupins, 443. 

XXXI L UMBELLIFER/E . . . . .447 

Wild carrot, 450 ; Cultivated Carrot, 450 ; Parsnip, 458 ; Hemlock, 
460 ; Water Hemlock or Cowbane, 460 ; Water Dropwort, 461 ; 
Fool's Parsley, 461. 

XXXIII. SOLAN ACEA ^ 462 

Potato, 463 ; Bitter-Sweet, 474 ; Black nightshade, 474 ; Deadly 
nightshade, 474 ; Henbane, 475. 

XXXIV. COMPOSITE < 476 

General characters of the Order, 476; Yarrow: Millefoil or 
Thousand-leaf, 479- 

XXXV. GRAMINE^L. TRUE GRASSES . . .481 



CONTENTS Xiii 

CHAPTER PACK 

XXXVI. GRAMINEA (continued). CEREALS . .489 

XXXVII. CULTIVATED AND WILD OATS (Genus Avcna) . 499 

Wild Oat, 499 ; Bristle-pointed Oat, 500 ; Animated or Fly Oat, 
500 ; Short Oat, 500 ; Common Cultivated Oats, 500. 

XXXVIII. CULTIVATED BARLEYS (Genus Hordeum) . 506 

Cultivated Barleys, 507 ; Distinguishing features of Barley-grains, 
512 ; Characters of a good malting barley, 514. 

XXXIX. CULTIVATED RYE (Genus Secale) . . .518 

XL. CULTIVATED WHEATS (Genus Triticum) . 521 

XLI. COMMON GRASSES OF THE FARM . . 536 

XLII. GRASSES AND CLOVERS FOR TEMPORARY AND 

PERMANENT PASTURES . . . 564 

Grasses and clovers for leys of one, two or three years' duration, 
566 ; Grasses and cloves for temporary pastures lasting from three 
to six years : Grasses and clovers for permanent pasture, 569 ; 
Weight of seed to be used, 577. 

PART V. 
WEEDS OF THE FARM. 

XLI 1 1. WEEDS: GENERAL . . . 579 

Their injurious effects, 579 ; Mistletoe, 583 ; Duration of weeds, 
585 ; Habit of growth of weeds, 587 ; How weeds are spread, 588 ; 
Extermination of weeds, 590. 

XLIV. WEEDS: SPECIAL ... -597 

Weeds of arable ground, 597 ; Weeds of pastures, 6xa. 

PART VI. 
FARM SEEDS. 
XLV. FARM SEEDS: GENERAL . . . .622 

Purity, 624 ; Germination capacity, 628 ; Speed of germination 
or germination energy, 634; Weight, 637; Form, colour, bright- 
ness and smell, 643. 

XLV I. FARM SEEDS: SPECIAL . , . 647 



XIV CONTENTS 

PART VII. 

FUNGI, CONSIDERED CHIEFLY IN RELATION TO SOME 
OOMMON DISEASES OF PLANTS. 

CHAPTER PAGE 

XLVII. FUNGI: GENERAL . . . . .687 

Hypba and mycelium, 687 ; Reproduction, 689 ; Germination of 
spores, 692 ; Mode of Life : Saprophytes and Parasites, 693 ; General 
advice to be followed when dealing with plant diseases, 696. 

XLVII I. FUNGI (continued) PHYCOMYCETES . . . 698 

Eumycetes, 698 ; Phycomycetes (sub-class i. Zygomycetes), 699. 

XLIX. FUNGI (continued) PHYCOMYCBTES . . .702 

Phycomycetes (sub-class ii. Oomycetes), 702 ; Damping-off, 703 ; 
Potato diseases, 707. 

L. FUNGI (continued) BASIDIOMYCBTES . . 725 

' Smut ' of Oats, 726 ; ' Smuts ' of wheat, barley and rye, 728 ; 
Bunt of wheat, 733 ; Rust and mildew of wheat, 736 ; Other species 
of rusts, 745 ; The common mushroom, 750. 

LI. FUNGI (continued) ASCOMYCETES . 755 

Yeasts, 756 ; Mildews, 758 ; Ergot, 768. 
LI I. * CLUB-FOOT* DISEASE . . . .773 

PART VIII. 
BACTERIA, 

LI 1 1. BACTERIA: THEIR MORPHOLOGY AND REPRODUC- 
TION . . . . . .779 

Forms of Bacteria, 779 ; Vegetative reproduction, 780 ; Reproduc- 
tion by means of spores, 781 ; Conditions affecting development, 
784 ; Sterilisation and pasteurisation, 786. 

LIV. BACTERIA: THEIR WORK . . . .789 

Lactic fermentations, 790; Butyric fermentations, 792; Acetic 
fermentations, 794 ; Fermentation of cellulose, 795 ; Fermentation 
of urea, 796 ; Putrefaction, 797 ; Nitrification, 799 ; Denitrification, 
8oa; Fixation of free nitrogen, 803; Bacteria and diseases of 
animals, 813 ; Diseases of plant! caused by bacteria, 8x5 ; Black 
rot of cabbages, 816. 



PART I. 

GENERAL EXTERNAL MORPHOLOGY. 

CHAPTER I. 
INTEODUOTORY. 

i. THE things met with every day can be separated into two dis- 
tinct classes or groups, namely, those which are alive, such as 
birds, insects, cattle, trees, flowers, and grasses, and those which 
are never possessed of life, such as air, water, glass, and iron. 

Although it is impossible to give a complete and satisfactory 
account of what life is, for all practical purposes the difference 
between the two classes of objects is easily recognised, and a 
more extended study of them leads to the conclusion that between 
the living and the inanimate world there is a hard and fast line 
of separation. 

The chief and most obvious peculiarity of living things is theii 
power of giving rise to new individuals that is, their power of 
reproduction. They are ordinarily separated into two classes, 
namely animals and plants. The term Biology in its widest 
sense is used to denote the study of all forms of living things, 
that branch of it dealing with animals being known as Zoology, 
while the science of Botany is concerned with the study of plants. 
The most familiar animals have the power of moving about in 
a way which is not possessed by plants. Moreover, the former 
require as food, substances which have been derived from other 
living things, such as flesh of all kinds, milk, bread, potatoes, 
and similar materials ; while most common plants are capable of 
utilising substances whxh belong entirely to the inanimate world, 



2 INTRODUCTORY 

such as carbon dioxide, water, and various minerals. Although 
these points of difference between plants and animals . are 
sufficient to separate the two classes from each other, so far as 
the purposes of everyday life are concerned, it must be mentioned 
that a further examination of living things shows that there are 
some which in structure and power of utilising inorganic sub- 
stances as food-materials resemble plants, but which are never- 
theless able to move about as freely as animals, and that other 
structures usually considered as animals move very little. Then, 
again, there are living things always classed as plants, which pro- 
duce flowers and seeds, although they cannot live when supplied 
with carbon dioxide, water and minerals, but must be fed upon 
the same or similar substances to those needed by animals. 
Indeed, all attempts to draw a hard line of separation between 
plants and animals are found to end in failure. The living sub- 
stance within them appears to be the same, and between the so- 
called animal and vegetable kingdoms there is no distinct point 
of difference. The living world is essentially one, and not two, 
and it is very necessary to constantly bear in mind that plants 
are just as much living structures as animals are, since by far the 
larger number of mistakes in the management and cultivation of 
plants are due to want of proper appreciation of this fact 

2. For the present our attention will be confined to the common 
plants of the farm and garden. In form and structure these 
are altogether different from animals, and as the difficulty of 
defining the two classes of living things is only met with in 
studying minute and practically unseen organisms it may be 
dismissed for the present. 

It will be readily understood that plants may be studied from 
a great many different points of view, and consequently special 
branches or divisions of the science arise. Attention may be 
confined to an investigation of the uses of the various parts of a 
plant's body to the work which the leaves, roots, and flowers 
perform in the life of the plant ; this part ef the subject is known 



INTRODUCTORY 3 

as physiology. Another branch is concerned with the form, 
origin, development, and relationship of the various parts to 
each other, without any reference to the work they do : the term 
morphology is used to denote this division of the science. 

Then, again, the structure and arrangement of the various parts 
of plants may be studied in order to determine their points of 
similarity and of difference with a view of placing together in 
groups all those possessing certain degrees of resemblance : this 
is usually termed Systematic Botany. For purposes 'of con- 
venience and methodical extension of knowledge of the subject 
many other divisions of the Science are made, and in each of 
them the study of plants is made from a somewhat different 
standpoint. Although other classes of the vegetable kingdom 
need attention it is advisable to confine our study at first to the 
seed- bearing plants, as this division includes all those which are 
everywhere most familiar. It is essential that farmers and all 
who are interested in the management of plants for pleasure or 
profit should examine and investigate them from as many differ- 
ent aspects as possible, as only by so doing can real progress be 
made in their cultivation. 

3. Most plants of the farm belong to the class known as Sper- 
matophytcsw seed-bearing plants; the latter are sometimes called 
Flowering plants or Phanerogams, but their chief characteristic is 
the production of seeds. The life-history of a spermatophyte is 
a continuous process of development or unfolding of parts in 
which we may recognise four fairly distinct periods, namely : 

(1) Germination of the seed and the escape of a young plant 

from it ; 

(2) The development and growth of roots, stems, and green 

leaves ; 

(3) The flowering period or formation and opening of flowers \ 

and 

(4) The production and ripening of fruits with their contained 

seeds. 



4 INTRODUCTORY 

The succession of events is generally in this order, and usually 
the formation and unfolding of roots, stems, and leaves occupies 
by far the greatest portion of the plant's life. 

There is, however, great variation in the time taken to 
reach the several stages of development, and the periods 
are not always of the same duration in the same species of 
plant. 

4. So far as their total duration of life is concerned, plants 
may be usefully divided into annuals^ biennials^ and peren- 
nials. 

By an annual is meant a plant which completes its life-history 
in one growing season. Starting as a seedling in spring or early 
summer, it develops root, stem, and leaves, and then produces 
flowers and seeds, after which it dies, leaving behind it offspring 
in the form of seeds. The time taken by annuals to reach the 
stage of seed-production is not always the same ; usually the 
whole of the season, from spring to autumn, is necessary, and 
only one generation is produced in that time. Some of them, 
however, termed ephemerals, such as chick weed and groundsel, 
produce seeds in a few weeks, and these may germinate and pro- 
duce a second and third crop of plants before frost cuts them 
down in autumn and winter. 

Biennials^ beginning life as seedlings in spring or summer, 
occupy the first growing season in the production of root, stem, 
and leaves only. They then rest during winter, and in the 
following year start growth again, and produce a stem bearing 
flowers and seeds, after the ripening of which the plant dies. 
Wild carrot, parsnip, and some varieties of thistles behave in this 
manner. 

Perennials are plants which live more than two years, and 
often several seasons elapse before flowers and seeds are produced. 
They are frequently divided into two classes, namely, (i) herbaceous 
perennials and (2) woody perennials. In the former the leaves 
and stems above ground are of a soft nature and die down at the 



INTRODUCTORY > 

cna 01 me growing season, the parts of the plant which still 
remain to carry on growth in subsequent years being under- 
ground : the stinging nettle, hop, and potato are representa- 
tives of this class. In woody perennials, of which all trees 
and shrubs are examples, the stems above ground are hard 
and woody. 

This method of dividing plants according to their length of 
life, although useful, is by no means a strict one, as the duration 
is dependent to some extent upon season, time of sowing, and 
the treatment which they receive. Wheat, for example, if sown in 
early spring behaves as an annual, but if sown in late summer or 
autumn does not perfect its seed and die until the following 
year. If kept continually cut or cropped down by animals it 
may even remain two years or more without dying, especially when 
thinly sown on good soils and allowed plenty of room for branch- 
ing. Annual mignonette of gardens is often made to last several 
years in pots by pinching off the flowering stems as soon as they 
begin to form. 

Turnips and other plants, usually biennials in ordinary farm 
practice, are invariably annuals if sown early in the year, say in 
February. 

Climate and soil also influence the duration of plants, annuals 
in some districts becoming biennial or even perennial in others. 

Ex. 1. Sow short rows ot the cereals and 'roots' mangels, turnips, 
swedes and carrots on the first day of each month during a whole year, and 
make careful observations and notes on their subsequent growth up to the time 
of seed production. Interesting and useful results are obtained. 

5. As the duration of flowering plants is subject to such varia- 
tion and their classification into annuals, biennials, and peren- 
nials, consequently somewhat arbitrary, they are sometimes 
placed in groups according to the number of times they are able 
to produce seeds. 

Those which yield only one crop and then die are termed 



6 INTRODUCTORY 

monocarpic plants : annuals and biennials are of this nature, and 
some perennials also. 

Such plants as most trees and shrubs, thistles, bind-weed, 
coltsfoot, and many grasses which are able to produce flowers 
and seeds during an indefinite number of seasons are described 
as polycarpic. 



CHAPTER II. 
SEEDS: THEIR STRUCTURE AND GERMINATION. 

i. IT is well known that one of the most ordinary methods of 
raising plants is to sow what are called seeds, yet how few there 
are among the many who use them who fully appreciate their 
real nature and capabilities. This want of knowledge is not due 
perhaps so much to want of interest in them, as to the fact that 
for their proper management they are usually buried away in the 
ground, and are therefore unseen ; moreover, many of them are so 
small that their structure is difficult to observe with the naked eye. 

In order to understand the true nature of a seed it is neces- 
sary to examine its origin and construction, and watch its 
development as far as possible from the earliest stages to the 
time when it gives rise to a completely formed young plant. 

The Common Bean. A broad bean is one of the largest seeds 
met with in ordinary farm or garden practice, and as its parts 
are all sufficiently large to be observed without the special aid 

of anything more than . ___ 

an ordinary pocket lens, 
it is especially fitted for 
study. 

When a nearly ripe pod 
of a broad bean plant is 
opened, each seed within 
it is found attached to 

the inside by means Of FIG. i.- Piece of bean pod showing the funicle (/) 

a short stalk or funicle and its attached seed ' 

(Fig. i), and it is through this stalk that all the nourishment 




8 SEEDS ! STRUCTURE AND GERMINA~N 



passes from the parent to enable the young seed to aeveiop. Ai 
first the pod exists in a rudimentary form in the centre of a flower 
and its parts and contents are very small ; they are nevertheless 
readily seen with a pocket lens. After the fading of the flower, 
the pod and seeds within it grow larger and larger at the expense 
of food supplied by the rest of the plant, and ultimately when 
ripe the funicles wither and dry up, and the seeds become de- 
tached from the parent which has produced them. 

When dry and ripe each bean seed is hard, with an uneven 
surface, but its internal construction cannot be clearly examined 
in this condition. On soaking in water for twelve hours, 
however, it becomes softer, and the parts can then be easily 
investigated. 

The outside, which is a pale buff colour, is smooth, and has at 
one end a narrow elongated black scar called the hilum of the 
seed. It is known popularly as the ' eye ' of the bean, and marks 
the place where the broad end of the funicle separated from the 
seed when it ripened in the pod. 

Quite close to one end of the hilum is a very minute hole 
known as the micropylt, easily seen with a lens, and through 
which water oozes out usually accompanied by bubbles of air 

when soaked beans 
are squeezed be- 
~C tween the finger and 
thumb. This open- 
ing communicates 
with the interior of 
the seed, and is the 
only one it possesses. 

FIG. a. Bean embryo, show- FIG. 3. The same as Fig. 2, Qn slitting TOUnd 

ing (r) radicle and (c) after removal of one coty- > & 

cotyledon. ledon ; r radicle ; b the the edge with a knife. 

plumule ; c cotyledon of ' 

embryo. the outer part of the 

bean can be stripped off as a pale, semi-transparent, leathery 
membrane ; this is known as the testa or sed-coat, and is thickest 




THE COMMON BfiAN 9 

and of softest texture where the hilum is situated The rest of 
the seed after the testa is removed, is of oval flattened shape 
similar to the complete bean, and is divisible into two large 
fleshy halves called cotyledons (Fig. 3, *), which, however, are not 
completely separate from each other, but connected at the side 
with a conical projecting body (Fig. 3, r) y one end of which is 
found to fit into a hollow cavity in the seed-coat exactly opposite 
the micropyle ; the other end is bent and turned inwards between 
the fleshy cotyledons. The extent and shape of this small curved 
structure is most easily observed when one of the cotyledons is 
removed completely ; it remains attached to the other as in Fig. 3. 

Ex. 2. Soak some broad beans in water and keep them in a warm place 
all night. Examine them next day and make drawings of the various parts 
seen both before and after stripping off the testa. Observe the relative 
position of the parts of the embryo in reference to each other and to the 
seed-coat. 

Examine and compare the structure of the following seeds after soaking in 
the same way : Pea, scarlet runner beans, vetches, and red clover. 

The bean seed contains nothing more than what has already 
been described ; the nature and relationship of its component parts 
only become intelligible when the seed is placed in the ground 
or maintained under certain conditions, and allowed to grow. 
When growth commences the lower end of the small curved 
structure (Fig. 3, r) elongates and breaks its way through the 
coat of the seed at a point very close to the micropyle, but 
not, as often erroneously stated, through the micropyle itself. 
It soon assumes the form seen in Fig. 4, and is recognised as a 
root of a young bean plant The upper bent half, which lies 
between the cotyledons, also pushes its way out of the same 
opening in the seed-coat and develops into a stem, from the 
tip of which leaves are gradually unfolded. It is thus seen 
that the seed of a broad bean is a packet containing a bean 
plant in a rudimentary condition. 

This plantlet is callai an embryo, and the portion of it which 



10 SEEDS I STRl/CTURE AND GERMINATIQN 




becomes root and stem is its primary axis. The part of the 
primary axis which is below the point where the cotyledons 
are attached consists of a very small piece of stem, the hypocotyl^ 
at the end of which is the radicle or primary root. Where 

the stem ends and the root 
begins cannot be determined 
in the bean seedling without 
the aid of the microscope and 
i examination of the internal 
structure of the axis of the 
plant. 

The curved end of the 
primary axis above the cotyle- 
dons is the plumule of the 
embryo, and consists of a 
very short piece of stem, 
the epicotyl on the top of 
which is a bud. From the 
latter is derived the ordinary 
stem which comes above 
ground with its green leaves 
and flowers. 

In the early stages of the 
growth of the embryo from 
the seed the hypocotyl grows 
very little, the part of the 

FIG. 4. Bean embryo after four days' growth. . . 

One cotyledon has been removed. <:Coty- Stem which grOWS HlOSt being 
ledon ; r primary root ; b epicotyl with . . . _ . 

bud at its tip. the epicotyl. It is on account 

Compare with Fig. 3. ,. . . . .. , . 

of the elongation of this 

portion of the plantlet that ttye plumule with its young leaves 
are driven above ground, the cotyledons remaining below en- 
closed within the seed-coat. 

The upper part of the stem bearing the plumule comes out of 
the seed bent, as in Fig. 4, and it maintain^ this curved shape for 




THE COMMON rfEAN II 

some time after emerging. By this behaviour the delicate 
leaves of the plumule are protected from injury during their 
progress upwards when a seed is sown in earth or sand. 

Ex. 3. Fold up some soaked beans in two thicknesses of white flannel 
made damp, and place them on a plate. Cover them with another plate 
placed upside down, and leave them in a warm room. Examine them twice 
a day, leaving them, exposed to the fresh air for a few minutes each time, 
and keeping the flannel damp, not wet. When they sprout notice the place 
where the radicle has come out of the seed-coat. Let some grow till the 
radicle and plumule are well out of the seed, and compare the various parts 
of the sprouted seeds with unsprouted ones. 

2. GERMINATION. When the pod of the bean is developing, the 
embryo in the seed is being fed by the parent and visibly grows 
until ripeness is attained. The young plant then assumes a dor- 
mant or resting state within the seed without showing any signs 
of life. Under certain conditions, however, the plantlet begins 
to wake up, and soon escapes from its protective coat to lead 
a separate and independent life. This awakening from a resting 
condition to a state of active growth is called germination^ and 
is dependent upon an adequate supply of (i) water, (2) heat, 
and (3) air or oxygen. It is also essential, of course, that the 
plantlet in the seed must be alive. 

The exact nature of the dormant state of seeds is not 
understood, but in old seeds and those which are gathered 
in an immature condition or badly stored the embryo is often 
weakened or actually dead ; in the latter case no germina- 
tion is possible. The exact length of time which seeds may 
be kept before death of the embryo takes place has never 
been satisfactorily determined; it varies with the species 
of the seed, its ripeness and composition, and also with the 
method of storage. In the case of most farm and garden seeds 
kept in the ordinary way, few of them are found capable of growth 
after ten years, and a large number die in two or three years, but 
on this point more will be said in a later chapter. For present 
purposes it will suffice merely to mention that age is a deter- 



12 SEEDS I STRUCTURE AND GERMINATION 

mining factor in the germination of seeds, apart from the three 
conditions previously mentioned. 

3. That water is necessary is well known, as beans may be kept 
indefinitely in a sack or drawer at various temperatures and with 
access to air without germination taking place. When placed in 
moist ground, or between damp blotting-paper, they absorb 
water very readily. This is most easily observed when beans are 
soaked for twelve hours in a dish containing water. The water 
is transmitted through all parts of the coat, but much more 
quickly and easily through the micropyle and the line of softer 
material which runs the whole length of the centre of the hilum. 
It is rapidly brought into contact with the part of the embryo 
which grows first, namely, the radicle. The soft spongy 
thicker part of the inside of the testa lying beneath the hilum 
stores up a considerable amount of water for the benefit of the 
developing plant, and the whole of the embryo and the seed- 
coat absorb water and become softer and larger in consequence ; 
it is only after this swelling has happened that a bean begins to 
show any signs of germination. 

Ex. 4. To show the influence of the micropyle and hilum in the absorp- 
tion of water, take twenty beans all as near the same size as possible. Paint 
over the micropyle and hilum of ten of them with quick -drying varnish 01 
1 cycle black ' ; on the other ten paint streaks of the same size on the sides 
of the seeds, leaving the micropyle and hilum untouched. Weigh both lota 
separately, and place them together in a basin of water all night. Take 
them out next morning, dry them carefully with a towel, and weigh again, 
and see which lot has increased most. 

4. The need of an adequate temperature for germination is a 
matter of common knowledge among those accustomed to sow 
seeds. If soaked beans are placed in the ground in midwinter 
they show little or no signs of waking from their dormant con- 
dition, yet when placed under a glass on damp blotting-paper 
indoors, the radicle makes its exit from the seed in a few days. 
Seeds differ in the temperature which is necessary to induce 
them to germinate, the embryos in som# commence to extend 



THE COMMON BEAN 13 

their radicles and push their way through the seed-coat even if 
just kept above freezing point ; others require a temperature of 
9 or 10 C. to start growth. If attempts are made to grow beans 
at 45 C. it will be found to be too hot, and they make little or 
no progress. Between this high temperature at which growth 
appears impossible, and the freezing point where the develop- 
ment of the embryo of the bean is also suspended, there is a 
temperature at which the embryo makes the most rapid progress, 
and emerges from the seed-coat in the shortest possible time ; 
this most favourable temperature is about 28* C., both above it 
and below it the germination of the bean is retarded. 

Ex. 5. Arrange two separate lots of similar-sized beans soaked for the 
same length of time in damp flannel as described in Ex. 3, and place one 
in a warm kitchen and the other in a cold cellar. Observe which show 
their radicles first. 

5. The supply of fresh air is also an essential condition for growth 
of the young plant from the bean seed, but the evidence for its 
need is not so manifest or so generally recognised as the necessity 
for moisture and warmth. It will be found, however, when 
beans are placed in a flask or bottle containing carbon dioxide or 
hydrogen gas they refuse to germinate, even when they are sup- 
plied with a proper amount of water, and kept at summer heat 

Ex. 6. Place ten soaked beans in a wide-necked bottle. Fill the bottle 
with carbon dioxide gas or coal gas, and cork it up with a tightly-fitting 
indiarubber stopper. 

Arrange another bottle in the same way, but with ordinary air in it instead. 
Take out the stopper of this one twice daily and blow in fresh air, so as to 
ensure a good supply to the seeds. Place both in a warm situation and 
observe which germinate best. 

6. The peculiar extension or growth of the parts of the interior 
of the bean seed, and the fact that a suitable supply of water, air 
and heat is necessary for the manifestation of these changes, 
suggests to us that we are dealing with a living structure. This 
becomes all the moreapparent when we observe that the oxygen 



14 SEEDS: STRUCTURE AND GERMINATION 

of the air is absorbed, and in its place carbon dioxide is given off 
into the surrounding air, for this is what happens in the breathing 
of a living animal. 

Bac. 7. Carbon dioxide is produced when beans germinate. Place twenty 
soaked beans in a wide-mouthed bottle, and cork them up after showing that 
a match burns freely in the bottle. Leave them in a warm place for twenty- 
four hours, and try if a match will now burn in the bottle. 

The carbon dioxide gas can be poured out into a beaker containing lime 
water; on shaking, its presence is proved by the lime water becoming 
c milky ' owing to the precipitation of carbonate of lime. 

The particular use of the water, heat and air to the plant we 
cannot at present discuss. It may, however, be mentioned that 
without water the embryo would have little chance of becoming 
free from the tough and hard seed-coat surrounding it; water 
softens the latter, and makes it more easily torn by the extending 
radicle and plumule. 

In the early stages of the life of the bean plant, from the com- 
mencement of germination up to the time when the first green 
leaves are unfolded, the development and building up of the 
elongating rootlet and shoot depend upon the thick cotyledons. 
At first the latter are thick and fleshy, but as the radicle and 
plumule grow the cotyledons become softer and thinner, ulti- 
mately shrivelling considerably. The cotyledons are leaves, the 
interior of which is packed with food for the rest of the growing 
embryo, and a large amount of the water absorbed by the seed 
is used for the purpose of dissolving the nutrient material in 
them, and carrying it from them to the various parts of the root 
and shoot of the young plant where growth is going on. 

Ex. 8. Germinate beans in damp flannel a in Ex. 3, and show that the 
cotyledons are essential to the development of the root and shoot of the em- 
bryo by cutting them off as soon as the two latter parts have emerged from 
the seed-coat. Try separating one cotyledon and then two at various stages 
of development, and see if the axis (root and shoot) can be made to develop 
without them. The growth should be allowed to continue some time in 
order to obtain well-marked effects. 

7. Not only do the changes observed innhe embryo of a ger- 



THE COMMON flEAN 15 

minating bean point to the conclusion that it is a living structure 
and like an animal dependent on a proper supply of water, heat 
and air for the manifestation of its life, but the parts of a young 
bean plant after emerging from the seed soon give evidence of 
the possession of peculiarities which are associated with life. 
When put in the ground, the radicle, in coming out of the seed, 
turns straight downwards and continues to grow in this direction. 
This is the case no matter in what position the seed is placed. 
If, after germination has commenced, it is taken and replanted 
with the primary root pointing to the surface of the soil, the tip 
of the root soon begins to curve downwards again, and will 
maintain this course until again disturbed. 

The plumule behaves in exactly the opposite manner ; after 
emerging from the seed-coat its bent tip grows upwards and 
away from the root; if the seed is reversed and replanted the 
plumule begins to curve in such a manner that its tip is driven 
upwards towards the surface of the ground. That these peculi- 
arities are somehow connected with life is clear, as dead embryos 
show no such behaviour. 

Ex. 9. Sow soaked beans in a flower pot or box filled with ordinary garden 
soil placing them in various positions in it, some laid on the flat side, some 
with the hilum directed upwards, and others with the hilum downwards. 
Allow them to grow in a warm place : take them up as soon as signs of germin- 
ation are noticed, and observe the direction the root and shoot have taken. 

The peculiar tendency for the root always to go downwards and stem 
upwards can be investigated by sowing beans in ordinary garden soil and 
afterwards reversing them. To avoid error all should be taken up, and 
then placed again in the soil in various positions some as they were, a 
few with their roots and stems reversed, and others laid in a horizontal 
position. They may be re-examined at the end of a week. 

Another method of showing the same peculiarity may be carried out 
thus : Germinate soaked beans in damp flannel as in Ex. 3. When the 
roots have extended about half an inch take two seeds and suspend them by 
means of thread side by side in a bottle with their roots downwards and stem 
upwards. The bottle should contain a little water to keep the air damp. 
When the roots have grown about two inches reverse one of the seeds so that 
its root points upwards tad stem downwards. Notice that the tip of the 



16 SEEDS: STRUCTURE AND GERMINATION 

root of the reversed seed in about twelve hours begins to turn downwards, 
while the plumule more slowly bends in such a way as to assume the position 
it had before it was reversed. The bottle should be placed in a dark box or 
cupboard to avoid the influence of light on the plant, and fresh air should be 
blown into the bottle twice a day. 

8. Although seeds vary almost indefinitely in regard to size and 
shape they are similar to the bean in so far as they all contain a 
young plant packed away within the seed-coats. In this essential 
feature all seeds agree with few exceptions, and it is on account of 
the existence of a young plant within them that they are of use 
in the raising of crops or plants. 

The manner, however, in which the embryo is arranged, and 
the relative size and appearance of its various parts, differ con- 
siderably in seeds; moreover, the growth during and after 
germination is not the same in all cases. A few of the more 
important and common variations in these respects must be 
noticed. 

White Mustard. The seed of white mustard (Brassica alba 
Boiss.) contains an embryo which like that of the bean consists of 
a radicle, plumule and two cotyledons; the latter, which are 
folded together, are relatively thinner than those of the bean and 
deeply notched as in Fig. 5. The radicle is bent round and lies 
in the fold of the cotyledons, between which is the very small, 
almost invisible plumule. 

On germination the cotyledons, instead of remaining within 
the seed-coat and below the ground as in the case of the broad 
bean, escape from the enclosing coats altogether and grow up 
out of the ground, enlarging at the same time, and becoming 
green like ordinary leaves. They are the first ' smooth ' leaves 
of the seedling mustard plant 

After a short time the plumule grows up from between the 
cotyledons and forms a stem upon which are gradually unfolded 
the ordinary divided ' rough ' leaves. 

Bx. 10. Soak white mustard seeds, and examine their structure, noting 
especially the way in which the embryos are packet in them. Allow some to 



WHITE MUSTARD 17 

germinate and grow for a week or more on damp flannel, and examine them 
in various stages of development, noting the notched cotyledons with small 

C 




Fio. 5. x. Seed of White Mustard. 2. Folded embryo as seen after 
removal of seed-coat. 3. The same unfolded. 4. Seed ger- 
minating. 5. Young seedling. 6. Same as 5, but a week older. 

c Cotyledons or 'smooth leaves'; h hypocotyl: r radicle and 
primary root ; / first foliage leaf (' rough leaf') ; p petiole 
of another leaf similar to / with blade removed ; b terminal 



bud ; x surface of the soil. 



plumule, well-marked hypocotyl, and distinct separation between the latter 



and the root. 



1 8 SEEDS: STRUCTURE AND GERMINATION 

9. The term hypogean is applied to cotyledons which remain 
below ground, those coming above being epigean, the relative 
amount of growth in the hypocotyl and epicotyl determining 
their position. If the hypocotyl grows vigorously during or 
after germination the cotyledons are forced above ground ; when 
only the epicotyl grows the plumule is lifted up above the soil, 
but the cotyledons remain below where the seed is placed. 

In the broad bean the hypocotyl is very short, and the point 
where it ends and the root begins is not clearly denned. In a 
mustard seedling, however, the point of separation between the 
root and stem is somewhat swollen and readily distinguished 

(Fig. 5). 

10. All plants whose embryos, like those of the bean and 
mustard, possess two cotyledons, are known as Dicotyledons j 
they form a very large, well-marked class of the flowering or 
seed-bearing plants. 

n. The seeds hitherto mentioned contain within their coats 
nothing but an embryo plant, which depends for the develop- 
ment of its root and shoot upon the substances stored up in 
some part of its body, its cotyledons chiefly. This is true even 
in the case of seeds like those of white mustard, in which the 
cotyledons of the embryo are comparatively thin. There are, 
however, a number of plants, such as the ash, mangel and 
potato, which, although belonging to the Dicotyledons, have 
seeds in which there are stores of food inside the seed-coat, 
but free from the embryo and its cotyledons (Fig. 109). Such 
separate reserve-food is stored in that part of the seed known 
as the endosperm or 'albumen, 1 and seeds in which it is pre- 
sent are called endospermous or albuminous seeds. Those like 
the bean, pea, and vetch, mustard, and turnip, which have 
no separate reserve-food, are known as exendospermous or 
exalbuminous seeds. 

Ex. 11. Take out a seed from the fruit of the ash tree in autumn ; carefully 
cut thin shavings from the flat side of the seed, starting about the middle of 



ONION 19 

the seed and cutting towards the narrow end. Note the white embryo with 
its well-marked radicle, hypocotyl and two flat cotyledons lying within the 
semi-transparent endosperm. 

12. Some of the most commonly occurring endospermous 
seeds will be found to have embryos within them which are not 
dicotyledonous, and whose structure is in many respects very 
different from those we have hitherto mentioned. A good 
example is met with in the onion. 

Onion. The seed is black, somewhat oval in outline, with 
one side convex, the other almost flat. Each contains within it 
endosperm and an embryo which lies curled up inside in the 
form seen in i, Fig. 6. When germination commences, the 
curved part (c) imbedded in the middle of the endosperm grows 
and forces the end (a) of the embryo out of the seed. From 
this exposed end, which is the radicle, a straight, slender, primary 
root develops, the extent of which is seen at 3 and 5, Fig. 6. 

The part of the young seedling which extends from the root 
into the interior of the seed, grows very rapidly at first, at 
the same time assuming a sharply bent outline (2, Fig. 6). It 
comes above ground in the form of a close loop (c), but on further 
growth the end within the seed is pulled out of the soil, and 
grows up in the air. The tip within the seed changes and 
absorbs the endosperm, and usually remains there until all the 
nutrient material has been transferred from it to the various 
centres of growth in the young plant. After the food-reserve 
is exhausted the tip withers and becomes free from the seed-coat. 
In loose soils the latter is pulled above ground before the endo- 
sperm is exhausted, and remains on the end of the tip for some 
time. In other cases where the soil is damper and of a stiffer 
nature the seed-coat remains below ground altogether. 

The curved part of the embryo which comes above ground 
is a leaf. It is the cotyledon of the embryo, and is in reality a 
thin hollow leaf like those of the full grown onion plant : within 
it is the plumule, which consists of a series of hollow conical 



20 SEEDS I STRUCTURE AND GERMINATION 



leaves arranged one inside the other. Just at the point where 
the root joins the cotyledon there is a thickening which marks 

,C 




FIG 6 x. Section of an Onion seed, a, Germination of same. 

3 . Young seedling. 4 and 5. Same as 3, but some days 

older. In 3 and 5 a secondary root is seen. > ^ 
a Radicle and primary root ; c cotyledon ; * slit in cotyledon 

from which the first foliage-leaf of the seedling emerges ; J 

endosperm of seed ; ground line. 

the place where the plumule is situated within, and at a short 



ONION 



21 



distance above this is a very narrow slit (s), through which the 
first green leaf of the plumule makes its exit (j, 5, Fig. 6). 
After one leaf emerges others soon follow, the younger ones 
coming out in regular order through slits in the sides of those 
immediately older than themselves. 

Ex. 12. Soak fresh onion seeds in water for a few hours. With a razor 
cut through some parallel to their flat sides in order to show the embryo 
within, as at I, Fig. 6. 

Sow others in damp blotting-paper; allow them to germinate and the 
seedlings to develop ; make observations of them at different stages of growth. 

Watch the germination of seeds sown in boxes or pots containing ordinary 
garden soil. 




FIG. 7. i. Outline of wheat grain showing the position and form of the 
embryo. *. Longitudinal section through a wheat grain. 3. Wheat 
grain germinating. 

Sc Scutellum ; / plumule ; r 1 primary root ; r* one of the first pair of 
secondary roots ; ce coloorhiza ; e endosperm. 

13. Plants whose embryos possess only one cotyledon are 
known as Monocotyledons, and form the second large class of 
seed-bearing plants. 

Few of the representatives of this class with which we are 
ordinarily familiar have true seeds large enough for examination. 
The onion is probably one of the best commonly occurring 



22 SEEDS I STRUCTURE AND GERMINATION 



examples which may be considered typical of the monocotyledons 
and easily obtainable. 

To this class, however, belong all the grasses, but their seeds 
and embryos are so different in many respects from those of the 
onion that it is necessary to examine one of them in detail. 

Wheat. A wheat grain, which may be taken as an example, 
is not a seed, but a kind of nut with a single seed within it. 
The seed grows in such a way as to completely fill up the in- 
terior of the nut, and become practically united with its inside 
wall. The embryo occupies only a 
small part of the grain, the rest being 
taken up by the floury endosperm of 
the seed (e 2, Fig. 7). 

The embryo is easily seen at the 
base of a soaked grain on the side 
opposite the furrow. When removed 
it has the appearance seen at i, Fig. 7. 
The part of it which lies close up 
to the endosperm is a flattened 
somewhat fleshy shield-shaped struc- 
ture called the scutcllum (sc)\ attached 
to the front of the scutellum is the 
plumule (/), consisting of a bud 
formed of an extremely short stem, 
upon which are sheath -like leaves 
enclosing each other. The embryo 
generally possesses five roots, one 
primary and two pairs of secondary 
FIG. s. i. Seedling wheat plant, rootlets ; the former and one pair of the 
latter are seen in Fig. 7. They are all 
& completely enclosed by a sheath which 
j s con ti nuous w j t h the scutellum, and 
are consequently not visible from outside ; their position, how- 
ever, is marked by projecting bosses. The sheath round the 




WHEAT 23 

roots is termed the coleorhiza (GO 2 and 3, Fig. 7), and when germi- 
nation takes place it expands and bursts the coats of the grain, the 
roots about the same time breaking through the enclosing coleo- 
rhiza. When a wheat grain is sown in the ground it remains there, 
but the plumule grows upwards, its first leaf, the coleoptile, ap- 
pearing above the soil as a single pale tube-like structure ; from 
a slit in the tip of the latter the first flat green blade soon appears 
(/, Fig. 8), and is followed by a succession of single green leaves, the 
younger ones growing from within the older ones in regular order. 

Ex. 13. Soak some white wheat grains in water until well swollen out, 
and note the following points : The furrow along the back of the grain, the 
bearded tip, and the side opposite the furrow. Keep them damp a day. 
The embryo, which is easily seen through the semi-transparent coat, can be 
removed by slitting round the circular cotyledon with a needle. Examine its 
structure, and compare with Fig. 6. 

With a sharp knife or razor cut through from back to front, so as to 
divide the grain into two longitudinal halves, and note the floury endosperm 
and the shape and parts of the divided embryo. 

Place a folded sheet of damp blotting paper on a plate, sow some soaked 
wheat grains on it, and cover with a tumbler. The grains will germinate. 
Watch their development up to the time the first green leaf appears, taking 
out the embryo and examining it at different stages of its growth. 

There is difference of opinion as to which part of the embryo 
is to be considered the cotyledon. Soine authorities regard the 
scutellum as the cotyledon, while others give this name to the 
coleoptile or first sheathing leaf which comes above ground, and 
which has no green blade (/>, Fig. 8). Others, again, consider 
that the first sheathing leaf is an extension of the scutellum, and 
the two combined is therefore the cotyledon. In any case, there 
is only one cotyledon present, and wheat therefore belongs to the 
class of monocotyledonous plants. 

14. During the growth of the embryo of a wheat grain, it will 
be noticed that the endosperm becomes soft and decreases in 
quantity as the roots and plumule expand and develop ; the 
endosperm is the food upon which the young plant depends 
during the early staggs of its life, the scutellum acting as a 



34 SEEDS: STRUCTURE AND GERMINATION 

structure for changing, absorbing, and transferring this reserve- 
food to the growing parts which need it 

Br. 14. Note the softening of the endosperm in germinated wheat grains 
and its decreased amount after seedlings have grown considerably. 

Remove the embryos from well-soaked grains, and grow them without 
the endosperm on damp blotting-paper. Allow ordinary uninjured grains to 
grow with them. Both the embryos in the grains and those removed from 
the grains develop, but there is a great difference in the results after a few 
days. 

15. The store of reserve-food on which the young plant 
depends for its early development is sufficient to enable it 
to form a root, stem, and several leaves, as is evident when 
seeds are allowed to germinate upon damp flannel or blotting- 
paper, from which nothing but water is absorbed. 

No food-materials or manures are needed for this primary 
development, and seeds germinate and the seedlings grow for 
a considerable time as well in poor soil or sand as in good 
rich ground. As soon as the reserve store is exhausted hunger 
becomes apparent, and unless the plants are then supplied with 
suitable nutriment from the soil and air, and are also placed 
under conditions favourable for growth, weakness and death 
are likely to occur. 

Among the larger seeds, such as beans and peas, where there 
is an abundant store of reserve-food, the young seedlings begin to 
manufacture food for themselves from materials absorbed from 
the soil and air, long before their reserve is exhausted. In 
small seeds the reserve is sometimes almost consumed before 
the roots and leaves are sufficiently developed to carry on 
their work properly, in which cases a more or less temporary 
starvation and check to growth ensues. Especially does this 
happen when seeds are sown too deeply, for a large amount 
of food is then used in the production of a stem long enough 
to lift the leaves up into the air. 



CHAPTER III. 
THE ROOT. 

i. From observations made upon the seedlings mentioned in 
the preceding chapter, it is seen that each of them is made up of 
distinct parts, namely, root, stem, and leaves. These parts are 
usually present in all the common flowering plants, and it is 
needful to examine them separately and in detail. 

Primary and Secondary Boots. It was noticed, when deal- 
ing with the bean seedling, that its two ends always grow in 
opposite directions ; the plantlet can be considered as an elon- 
gated axis, one end of which bears the leaves and invariably 
comes above ground, while the opposite end never bears leaves, 
and persistently follows the plumb-line downwards. The de- 
scending part is known as the root. As will be pointed out 
later, all roots do not behave in this manner, and it is to be 
specially noted that many of the underground parts of plants 
are not roots ; the exceptions, however, may be left for future 
consideration. 

The first or primary root which the bean plant possesses is 
merely an extension of the radicle of the embryo which exists 
nrithin the seed. Soon after making its exit from the seed, it 
takes a downward course, and elongates by growth taking place 
near its tip. 

Ex. 15. Germinate a broad bean on damp flannel. When the primary root 
is about j of an inch long, make small dots upon it about A of an inch apart, 
with a pen or fine brush dipped in Indian ink. Wrap the bean in damp cotton 
wool, allowing the marked root to be free, and place it in the bottom of a 
glass funnel with a narrow stem, so that the marked root projects down the 
latter Cover over the ninvel with a piece of glass or cardboard to prevent 

26 



THE ROOT 



evaporation, and, after allowing it to grow in a dark place two or tnree days, 
take it out and notice the position of the dots on the elongated root. Measure 
the distances apart, and find out which part of the root has grown most. 

After it has grown two or three inches long, branches arise 
upon it similar in appearance to the primary root itself, only 

thinner (Fig. 9). Instead of grow- 
ing vertically downwards, they grow 
away from the primary root almost 
at right angles to it. These lateral 
branches lengthen in the same man- 
ner by growth near their tips, and 
are called secondary roots. They 
ultimately produce tertiary roots, 
which grow out obliquely from the 
secondary ones, and further branch- 
ing may go on in this manner until 
a very extensive collection of roots 
is obtained, the whole of which is 
called the root-system of the plant. 
2. On careful examination of a 
well-developed root of a seedling 
bean, the secondary roots are seen 
arranged in five rows along the 
primary root, and not in irregular order, as appears at first sight. 
They are not, however, equi-distant from each other in the rows. 
The first to appear arise near the cotyledons, followed subse- 
quently by others, which grow out at points nearer the tip, the 
youngest being always nearest the apex of the primary root, 
the older ones farther away from it. The relative age of the 
various lateral roots can therefore be determined by examina- 
tion of their position on the primary root. This kind of 
sequence where the youngest parts are nearest the tip of the 
axis on which they grow, and the older ones farther away from 
rt in regular order, is known as acropetal^uccession. 




FlG. 9.^, Primary root of bean, 
showing lateral secondary roots ; h 
root hairs. B, Longitudinal section 
of a similar root, illustrating the en- 
dogenous origin of the 'lateral roots. 



PRIMARY AND SECONDARY ROOTS 27 

3. Another point to be noted is that the lateral roots do not 
arise as up-growths on the surface of the primary root, but come 
from within it, and are described as endogenous. The slits which 
they make in the substance of the primary root, and through 
which they emerge, can be readily seen in a bean seedling 
(A, Fig. 9, a). A section of a root lengthwise, as at 2?, shows 
that the secondary lateral roots are connected with its central 
more solid core ; the three lowest ones, although they have just 
begun to grow, have not yet penetrated the outer layer of the 
root, and would not be visible on the outside of the latter. 

This mode of origin is characteristic of lateral roots generally 
wherever they are met with. 

Ex. 16. Germinate and allow broad beans to grow upon damp flannel as 
in Ex. 3. Watch the development of secondary roots, noting their position 
and longitudinal rows on the primary root. Slice some and note the endo- 
genous origin of the secondary roots. 

Very carefully dig up a half-grown mangel, turnip, and carrot ; wash away 
the soil and note the arrangement of the secondary roots on the primary root. 

Make a deep longitudinal slit with a knife through the ' rind ' down to the 
1 core ' of a carrot. Split off the ' rind ' and examine the ' core ' from whence 
the secondary roots arise. How many rows of the latter are there ? 

4. Many dicotyledonous plants have roots similar to those of 
the bean plant. When, as in this case, the primary one continues 
to grow, keeping distinctly larger than the lateral ones, it is called 
a tap root. Very good examples are met with among cultivated 
plants in the carrot, mangel, red clover, and mustard j in shep- 
herd's-purse, poppy, and many other weeds, as well as in most 
broad-leaved trees. 

A number of plants have swollen fleshy roots in which food 
materials are stored for future use ; they are described as tuberous 
roots, and must be distinguished from tubers, which are fleshy 
underground stems. 

To designate the different forms of thickened roots various 
special terms are in use. The typical carrot root is conical] that 



28 



THE ROOT 



of the turnip napiform. The root of the radish is spoken of as 
fusiform. 

In some instances the primary root is soon rivalled in size by 
its branches ; it may even cease growth altogether. Such plants, 
on being pulled out of the ground, exhibit a bunch of slender 
roots, the chief of which are all much the same diameter and 
length ; roots of this character are described as fibrous^ and are 
well exemplified in common groundsel and grasses. 

5. Adventitious Roots. The roots of monocotyledonous 
plants differ in their development from those of dicoty- 
ledons. The single primary root of 
the onion, for example, lasts but a 
short time, and is succeeded by others 
which do not arise as branches upon 
the primary one, but spring from the 
very short stem of the plant. Roots 
which arise on stems and leaves, or on 
various parts of the roots of plants, 
but not in acropetal succession are 
described as adventitious. They are 
very common upon all monocoty- 
ledonous plants of the farm and garden, 
and may be considered the chief 
ones which such plants possess. In 
wheat, for example, the embryo within 
the grain possesses three roots; in 
barley, five or six. These are, how- 
ever, merely temporary structures of 
FIG. 10.- Young barley plant show- use during the earlier stages of growth. 

ing adventitious roots (a) grow- ^ ^ ,, , i_ i i 

ing out from the first jomt or By the time the wheat or barley plant 

nodeof the stem. 




ground the primary roots of the embryo are succeeded by 
adventitious roots which grow out from the lower nodes or joints 
of the stem near the surface of the soil (Fig. 10). 



ADVENTITIOUS ROOTS 29 

Although common upon monocotyledons adventitious roots 
are not confined to this class. Examples are abundant upon 
many kinds of dicotyledonous plants. Good instances are met 
with on the underground stems of mint, potato (Fig. 144) and 
hop, and on the runners of the strawberry, stems of creeping 
crowfoot (Fig. 21) and white clover, as well as many others. 

They are generally produced at the joints where leaves grow 
upon the stem, and may arise in some plants (e.g., on strawberry 
runners) from internal causes apart from any external influences ; 
in other instances their development depends upon contact of the 
stem with water or moist soil. Almost all parts of certain plants 
may be made to produce them, and the propagation of plants 
Buch as gooseberries, currants, roses and hops by means of slips 
and cuttings depends upon their development. Pieces of stem 
cut off just below a leaf, and placed in moist earth soon develop 
adventitious roots near the cut end. Advantage is taken of their 
formation in the propagation of plants by means of layers. 

Ex. 17. Examine the roots on young strawberry runners in July. Also 
those on creeping crowfoot, young shoots of ivy, underground stems of 
potato, couch-grass and mint, and on the lower parts of the stems close 
to the ground, of oats, wheat, and barley. Note the position, number, and 
extent of these roots. 

Examine the roots upon any cuttings or slips which can be obtained, and 
observe whether they arise on the cut surface or at a point some distance 
away from it. 

Usually adventitious roots are thin and fibrous, but those of 
the dahlia are tuberous. 

6. The complete root-systems of plants vary enormously in 
extent, but in all cases the total length is much greater than is 
usually anticipated. That of an ordinary oat plant, although not 
spreading through more than a cubic yard or two of soil, 
measured in one instance over one hundred and fifty yards in 
length. 

A tree uprooted by the wind exposes to view a small number of 



30 THE ROOT 

stout roots similar to the thicker branches of the crown, and from 
these are given off a larger number of a finer texture. By far 
the greater bulk, however, which the tree possessed remain in the 
ground in the form of extremely fine rootlets or fibrils extending 
outwards generally as far, or a little farther, than the branches 
and leaves of the tree, but in some instances to much greater 
distances. Not only do the roots grow out horizontally and near 
the surface of the soil, but they extend downwards as well. In 
isolated instances, where an adequate supply of air has been 
maintained along open cracks and fissures, roots have been 
found to descend many yards into the ground, but in general 
the roots of the tallest trees rarely go down more than seven 
or eight feet The want of air and presence of noxious sub- 
stances in the lower regions of the soil checks further growth in 
this direction. 

With many plants almost every cubic inch of soil immedi- 
ately beneath their shade contains fine delicate rootlets, and the 
extent of their root-branching is very rarely realised on account 
of the ease with which these hair-like fibrils are broken off when 
the plant is pulled up or disturbed. 

Many forest trees have a natural habit of sending their roots 
several feet into the soil Examples of fruit-trees belonging to 
this class, and requiring a deep soil for proper growth, are the 
cherry and wild pear. 

Some trees, such as larch, keep their root-system nearer 
the surface, spreading out more horizontally in the ground. 
The quince, used as a stock on which to graft pears, has roots 
which remain in the upper regions of the soil. Similar surface- 
rooting habit is very marked in the * Paradise J apple on which 
apples are grafted, and in Prunus Mahaleb upon which cherries 
are often grafted. 

The root-system of wheat penetrates more deeply than that 
of barley ; the mangel sends its fine rootlets more extensively 
into the deeper layers of the soil than cabbage or turnip; 



EXTENT OF ROOtS 31 

red clover roots more deeply than white clover, and almost all 
plants have distinct and peculiar habits in this respect 

7. The character and extent of root-development is not, how- 
ever, altogether dependent upon the species of the plant con- 
cerned, but is materially influenced by external circumstances, 
such as the texture of the soil, and the amount of water in it. 
In deep open soils and loose sands the root-system of a plant 
is much larger than that of a similar plant grown in compact 
heavy ground. 

In soils which are not water-logged, increase of moisture up 
to a certain extent increases the branching of the root, and 
excellent examples of the influence of water, coupled with good 
air supply, are seen in well managed plants in pots, and also 
among plants growing near wells and in drain pipes ; the latter 
in some instances become completely blocked by the large 
number of fine rootlets of trees growing in their neighbourhood. 

The root-system is also considerably modified by the totyl 
amount and kind of the manures or food-materials present 
in the soil. Up to a certain point an increase of nutrient 
substances increases root-development; an excess hinders it. 

Mutilation influences the development of the root-system. If 
the growing-point of the tap root of a cabbage or tree is cut off 
its further elongation is prevented, but the secondary roots make 
up for the loss by more vigorous growth and often many adven- 
titious roots arise near the cut end. 

In order to properly cultivate plants of all kinds it is very 
important to study the habit or manner of branching of their 
roots and the relative proportions of the thick tap and second- 
ary roots to the fine ramifications to which they give rise and 
which spread through the soil in all directions. The proportion 
of root-system below ground to the branches and leaves above is 
also worthy of attention. 

The adaptability of plants to the various kinds of soils, their 
need of water, the cultivation which the ground should have and 



32 THE ROOT 

the rational application of manures to the plant are best under- 
stood and appreciated after a careful study of these points. Tap- 
rooted crops, such as sugar-beet, mangel, carrot, and parsnip, 
require the soil to be well-worked to some considerable depth. 

Surface-rooting plants, such as barley, can be grown upon 
comparatively thin soils. The same is true of pears grafted on 
the quince and apples on the Paradise stock, and such plants 
respond more quickly to, and are more benefited by, top-dressings 
of soluble manures than plants with a deeply-penetrating root- 
system. 

Ex. 18. The student should dig up and examine specimens of the roots 
of all the chief plants of the farm ; especially is it necessary to investigate 
the general form and extent of the roots of the common weeds of arable 
and pasture land. Begin with the examination of young seedlings, which are 
readily obtained in a complete condition. Note the presence or absence of 
tap root, extent of branching, the depth to which they descend, and their 
horizontal extension. 

8. Boot- Hairs. On the root of a seedling bean grown on damp 
flannel or blotting-paper is seen a fine white silky band of hairs. 
These are called root-hairs, and they are never present at the 
extreme tip of the root but arise at some distance behind its 
growing point. As the root elongates the root-hairs on the 
older parts die and turn brown, but others are produced on 
the younger parts, so that no matter what the length or size of 
the root may be for a short distance behind its tip it is clad 
with these delicate transparent hairs. When secondary roots make 
their appearance hairs are produced upon them in the same 
manner and follow the same order of development as those upon 
the primary root. 

Their size and abundance are dependent on the species of the 
plant, and the amount of moisture surrounding the root. Plants 
growing in very wet situations or completely in water have 
few or no root-hairs. In very dry soils their development is 
checked, the greatest abundance being met with in moderately 
damp soils. 



ROOT-HAIRS 33 

A good supply of lime is found to increase the number and 
length of the root-hairs of many plants. 

The hairs are hollow tube-like structures and should not be 
confused with fine small rootlets. They are outgrowths from 
the surface of the root (Figs. 72 and 78), and as long as they 
last are concerned with the absorption of water and various in- 
gredients in solution from the soil. 

Upon plants growing in the ground the root-hairs are very 
intimately in contact with the particles of soil and are of so 
delicate a nature that it is practically impossible to remove a 
plant without destroying them. 

Ex. 19. Germinate beans, mustard, oats, barley, and wheat in damp 
flannel, and examine the root -hairs on the primary roots. Note their delicate 
nature, and their position, length, and abundance. 

Although almost invisible they are among the most important 
organs which plants possess. All the food constituents obtained 
from the soil and from the various manures applied to the latter 
are taken in by the root-hairs. By their means plants are kept 
constantly supplied with water ; their destruction in the process 
of transplanting or any disturbance of their development and 
action, such as may be caused by excessive dryness or imperfect 
aeration of the soil, leads to a deficient water supply and con- 
sequent withering of the plant 



CHAPTER IV. 

THE VEGETATIVE SHOOT : STEMS, LEAVES, 
AND BUDS. 

i. IT has been already noticed that the seedling bean plant consists 
of a descending portion, the root, and an ascending part which 
comes above ground. The latter is known as the primary shoot, 
and consists of an axis the stem upon which are arranged a 
series of lateral appendages which are called leaves. The points 
on the stem to which the leaves are attached are usually slightly 
thickened, and are called nodes or 'joints/ the lengths of stem 
between them being termed internodes. Flowers ultimately 
arise upon the shoot, and it is one of the characteristics of seed- 
bearing plants that seeds are always produced on their shoots and 
never on roots. For the present, however, flowers may be left for 
future consideration, and attention paid to the origin and nature 
of the vegetative shoot or stem with its ordinary green leaves. 

a. In the earliest stages of the development of a bean plant the 
primary shoot is very short and bears the cotyledons or primary 
leaves, its tip ending in the plumule. 

The latter is a bud, and at the time when the seed commences 
to germinate, its parts cannot be fully made out by observations 
with the naked eye. As soon as it comes above ground, however, 
the bud is found, on examination, to consist of a short stem 
hidden by a number of enfolding leaves. An external view of it 
in this stage is given at i, and a longitudinal section at 2, Fig. n. 

As growth proceeds, the short stem inside the bud elongates, 
and the leaves, which at first are crowded upon it, become 



STEMS, LEAVES, AND BUDS 



35 



separated from each other. Marks 
made upon the stem as previously 
explained for the root in Ex. 15, 
reveal the fact that the increase in 
length takes place at the tip of 
the shoot. After reaching a certain 
length the lowest intervals between 
the leaves cease to elongate; the 
upper, younger and shorter ones 
also lengthen and cease 
in a similar manner, to 
be followed in turn by 
still younger parts of the 
stem nearer the tip. The 
stem, before the growing 
season is over, may thus 
reach a height of two or 
three feet, or even more, 
the extreme tip, or grow- 
ing-point as it is called, 
remaining young all the 
time, and acting as a 
manufactory for the ad- 
dition of more stem and 
leaves. The growing- 
point, which is of a 
tender and delicate 
nature, is protected by 
the enfolding young 
leaves, the latter aris- 
ing as outgrowths from 
its external surface. The 
youngest leaves are al- 
ways nearest the tip of 




FIG. ii. 

x. Epicotyl of bean, with plumule. 

2. Longitudinal section of the same ; ep epicotyl ; 

/ terminal growing point of the plumule ; a a 
leaf in whose axil is a bud b' ; b buds in axils of 
inner leaves of the plumule. 

3. Epicotyl, with plumule unfolding. 

4. Later stage of growth of 3, showing connection 

with bean seed ; ep epicotyl ; a first leaf 
(rudimentary), in whose axil is bud V ; /"second 
leaf (rudimentary) ; c and e ordinary foliage 
leaves ; g buds in axils of the cotyledons ready 
to develop into stems which may come above 
ground. 



36 THE VEGETATIVE SHOOT 

the stem which bears them, the older ones being further removed 
from it in regular order that is, they arise in acropetal suc- 
cession, and adventitious leaves are never met with. 

Ex. 20. I. Sow beans in pots or boxes containing a mixture of damp sand 
and garden soil. 

Cut longitudinal sections, and examine the structure of the stem and terminal 
bud of a seedling as soon a* it has come above the surface of the soil. 

2. Watch the development of the stem up to the time of unfolding of 
the green leaves. 

Observe the rudimentary character of the first leaves. 

3. Make small marks on the stem about a quarter of an inch apart with 
Indian ink, and observe which part elongates most. 

4. Make similar observations upon the seedlings of mustard and peas. 

3. While numerous annuals, such as mustard and charlock, and 
some perennials, resemble the bean, many plants differ somewhat 
from it in the development of the plumule. Instead of the latter 
growing at once into a long shoot, bearing leaves at some dis- 
tance from each other, the primary axis within the plumule 
elongates very little, its internodes remain very short, and the 
leaves arising upon it appear crowded together, usually in the 
form of a rosette, a short distance above where the cotyledons 
were placed ; this form of stem with short contracted inter- 
nodes is well illustrated in the first season's growth of mangels, 
turnips, carrots, certain thistles, and red clover. In such plants 
as these, the primary root and hypocotyl become much thickened 
by the deposition within them of reserve-food prepared by the 
leaves, and it is only during the following year that the 
growing-point of the stem, which is hidden in the centre of the 
rosette, elongates and produces a shoot with long internodes, 
and bearing a series of new leaves at considerable intervals. 

In the onion and many bulbous plants the primary stem also 
remains very short, and the reserve-foods prepared by them 
are deposited in the bases of the leaves, instead of being 
stored in the root and stem, as in the former instances (see 
Fig. 24). 



BUDS 



37 



4. Buds. The stems and leaves of all flowering plants originate 
from buds in the manner indicated above ; buds may therefore be 
termed embryonic or incipient shoots. It is by their growth that 
trees, which appear so bare in winter, become clothed with fresh 
green leaves in the succeeding spring. The relationship which 
they bear to the leaves and stems produced by them is easily 
discerned by examining the structure and watching the develop- 
ment of the terminal bud of a young sycamore tree (Fig. 16). 

On the outside is observed a series of scaly leaves, which 
overlap each other, 
and protect and cover 
up the delicate grow- 
ing point of the twig. 
A section through the 
bud (Fig. 12) shows 
the disposition of 
these scaly leaves 
and within are also 
seen the ordinary 
leaves (/) arranged 
upon a very short 
stem (s). In spring 
the inner scaly leaves 
grow for a time (a, 
Fig. 13), and 




FIG. 12. Longitudinal sec- 
i ilQn of a terminal bud of a syca- 
Ultl- more tree as seen in autumn. 



f 11 er i bud-scales; j rudimentary stem, 

fall On, leaV- with foliage-leaves /; b lateral 



FIG. 13. Terminal bud 
of sycamore, similar to 
that of Fig. 12, develop- 
ing in spring, a. bud- 
scales ; / foliage-leaves ; 
b lateral bud. 



ing small scars where u 
they were attached to the twig. The stem (s\ which bears 
the rudimentary green foliage-leaves (/), elongates, and the latter 
are pushed out from between the protective scaly leaves of 
the bud (Fig. 13). After a week or ten days, the stem has 
reached a considerable length, and the leaves, which were rudi- 
mentary and packed away in the bud, unfold themselves and 
grow out flat as in Fig. 14. 



38 THE VEGETATIVE SHOOT 

The number of foliage-leaves present upon a developed shoot 
is often indicated in the bud, but in some plants, especially those 
of a herbaceous character, the growing point of the bud con- 
tinues to produce new leaves until frost checks it in autumn. 

Ex. 21. Cut longitudinal sections through a Brussels sprout and the ' heart ' 
of a cabbage. Note the stem, leaves, and axillary buds within. 

Ex. 22. Examine with a lens longitudinal sections of the buds of sycamore, 
horse-chestnut, oak, beech, and other trees. 




FIG. 14. Later stage of development of bud in Fig. 13. a Bud-scales falling off; 
j stem ; / foliage-leaves in axils of which are lateral buds h. 

5. The vegetative shoots of plants usually end in 
terminal buds> and an examination of almost any kind of 
plant shows that not only are buds present at the tips of the 
stems, but on their sides as well. These lateral buds arise 
ordinarily in the upper angles formed where the leaf-bases and 
stem join each other. The angles are termed the axils of the 
leases, and the buds are designated axillary buds. Most fre- 



BUDS 39 

quently only one bud is produced in each leaf-axil, but in some 
instances, two or more may be present. 

6. Generally the first leaves of the bud which are outermost 
or lowest down on the stem, are rudimentary structures, smaller 
and different in appearance from those which unfold later. In 
the primary bud or plumule of the bean (Fig. n), and many 
similar herbaceous plants, this is observable, but it is most 
evident in buds which are met with upon perennials, such as 
shrubs and trees. In the latter the outermost leaves of the buds 
are generally more or less firm, tough structures, termed scales or 
scale-leaves, which protect the interior of the bud from being in- 
jured by frost, rain, and other agents during the winter. Buds, 
such as those of the sycamore (Fig. 16) and pear (Fig. 17), 
having scales are termed scaly buds, those without, such as mealy 
guelder-rose, being known as naked buds. 

7. Buds similar to those of the bean and sycamore, previously 
described, which develop into shoots bearing green foliage- 
leaves, are termed leaf -buds : when met with upon trees they are 
sometimes named wood-buds, as it is from them that new woody 
twigs are produced. Many buds, however, on opening, give rise 
to flowers only, and are termed flower-buds : a third kind is met 
with producing short shoots bearing both green leaves and 
flowers; these are mixed-buds. Among gardeners the two 
latter forms are known as fruit-buds, as it is from them that 
fruit is obtained. The general appearance and development 
of a mixed bud from a pear tree is illustrated in Figs. 17 
and 1 8. 

It is not possible in all cases to distinguish fruit-buds and 
wood-buds by their outward appearance, although for budding and 
pruning operations and the general management of fruit-trees it 
is desirable to do so. In apples and pears the wood-buds are 
small and pointed, the fruit-buds being blunter, more plump, 
and of larger size. In cherries and plums both kinds are very 
similar in appearance ifc winter, and it is only in spring when 



40 THE VEGETATIVE SHOOT 

they begin to develop that the stouter and blunter characters of 
the fruit-buds show themselves. 

Their position upon the shoots is a great aid in distinguishing 
the two classes of buds (see pp. 44-50). 

8. Branching of Stems. The axis or stem of the primary 
shoot of plant is at first single, and may continue to grow 
as a simple straight structure. Usually, however, after a time, 
branches or secondary axes arise upon it, and these in all cases 
proceed from buds. In Fig. n, of the primary bud of a bean, 
secondary lateral buds are seen in the axils of the leaves of & 
and If : these are flower-buds, and consequently do not produce 
long leafy shoots ; but secondary axes bearing green leaves fre- 
quently occur in the bean, and are generally produced from 
buds in the axils of the cotyledons as at g (Fig. n). 

In many plants the buds in the axils of each leaf of the 
primary stem develop into leafy shoots, and upon the latter 
branches may again arise in a similar manner. The total 
number of stems bearing leaves may thus become very large 
on a single plant. In the best fodder crops, where large yield 
is always a desirable feature, branching is exhibited in high 
degree, and the same may be observed in trees of all kinds, 
and many weeds, such as groundsel and chickweed. 

9. The main stem of a plant is spoken of as a primary axis, or 
axis of the first order, the branches upon it being secondary axes, 
or axes of the second order, those borne by the latter tertiary 
axes, and so on. For purposes of convenience in description, 
any axis may be considered a main one, its branches then 
being secondary axes. 

10. When a stem continues to grow at its apex, for a long 
time it is spoken of as indefinite in growth : the branches upon 
it are usually many in number, and smaller than the main stem. 
This form of branching is spoken of as racemose (a, Fig. 15). 

In many plants the terminal bud produces a flower or a 
collection of flowers, and the main axis ''.hen ceases to elongate ; 



BRANCHING OF STEMS 41 

such a stem is definite in growth. When lateral branches arise 
upon it, they are generally few in number, and soon equal or 
exceed the main stem in vigour. Branching of stems of definite 
growth is said to be cymose \ it often resembles the diagrammatic 
sketch , Fig. 15. Cymose branching, however, sometimes 
leads to the formation of what at first sight appears to be a 
simple main axis of indefinite growth, but which is in reality 
composed of a series of short axes of different orders. At 
r, Fig. 15 is a main or primary axis i, which ends at x, its 
growing point having developed a flower or been destroyed 
by frost, wind, insect attacks or other means, and elongation 




FIG. 15. Diagrams illustrating (a) indefinite growth of stem, 
and racemose branching ; (&) and (c) definite growth of stem and * 
cymose branching, x, 2, 3, axes of first, second, and third order 
respectively. 

thereby prevented. Below its tips a lateral bud has pro- 
duced the branch or secondary axis 2 : the latter axis soon 
ceased growth, and a branch of the third order, 3, was pro- 
duced, a further one, 4, being developed in a similar manner. 
The whole shoot from A to J?, although crooked at first, may 
ultimately straighten and appear similar to a simple single axis 
of the first order of indefinite growth : when this happens such 
a stem is termed a false main-axis or symfodium. 
The branches of elm, hazel, and many other trees which 



THE VEGETATIVE SHOOT 



appear straight and of indefinite growth, are often in reality 
sympodia, the terminal bud upon each annual shoot having 
been destroyed or terminated by a flower, and a false axis 

formed by the subsequent 
vigorous growth of the 
highest lateral bud. The 
' spurs ' or short shoots on 
pear (Fig. 17), apple (4, 
Fig. 19), and currant trees 
and also many of the under- 
ground shoots of grasses 
are examples of sympodia. 

Ex. 23. Examine the kind of 
branching of the shoots of vari- 
ous common plants, such as 
groundsel, chickweed, nettle, 
charlock, mustard, vetches, 
beans, peas. Note the origin 
of the branches above the leaves. 

ii. Twigs of Trees in 
Winter. A study of the 
appearance of the shoots 
of trees in winter and their 
subsequent development 
during the following spring 
and summer is instructive. 

On the sycamore branch 
shown in Fig. 16, large 
terminal buds are visible 
and several lateral ones, 

FXG. 16. Piece of sycamore stem as seen in autumn. U pnfkqt U w hirh are well- 
For explanation see text. DCneain WHICH are ^ Gil 

marked leaf-scars, as at 2, 

indicating the place where the leaves were attached in the previ- 
ous summer. In 1896 the part marked c i897 did not exist, but 




TWIGS OF TREES IN WINTER 43 

the twig was terminated by a bud similar to that of Fig. 12, and 
had also two small lateral buds resembling , Fig. 13. In 
the spring of 1897 the buds opened, and the bud-scales fell 
off and left scars at 4. The terminal bud then grew as in Figs. 
13 and 14 and produced a considerable length of stem marked 
1897, with several lateral buds upon it, each of which developed 
in the axil of a leaf, as at h, Fig. 14. From the small lateral 
buds just beneath the terminal one short shoots originated in 
a similar manner. 

12. The amount of growth of twigs during one year or one 
growing-season is represented by the length between two sets of 
bud-scale scars (4, Fig. 19, n l to 2 ). 

As the scars are often visible upon the bark for several years 
they are useful aids in the determination of the age of any length 
of tree, stem, or twig. Frequently small buds are present in the 
axils of bud-scales, and as the internodes between the latter 
remain short such buds appear crowded together upon the twigs 
and are often visible after the scars have been obliterated (Fig. 
57, between A and -#). 

The length of stem which a bud produces during a year's 
growth is very varied, some leaf-buds giving rise to shoots not 
more than a small fraction of an inch long, while others reach a 
length of several feet. Much depends upon the kind of plant, 
its age, treatment, and the position of the bud upon the tree, as 
well as upon external circumstances, such as climate and soil 
In trees which are unmolested the length of the shoots produced 
each year by the terminal buds goes on increasing from extreme 
youth onwards until a certain age is reached, after which the 
yearly length of the shoots begins to diminish. The age at which 
the growth is at a maximum is different for different trees, some 
forming their longest shoots when they are 1 5 to 20 years old, 
others not until 30 to 40 years have elapsed. In old age the large 
number of buds to be supplied with water and food-constituents, 
their increasing distance from the water-supply in the 



44 THE VEGETATIVE SHOOT 

ground, prevents the extensive growth which is noticed in youth : 
the shoots upon aged trees are therefore very short. 

The difference in the general appearance between young and 
old trees is striking ; so long as long shoots are produced the 
crown or head remains open and largely composed of long 
straight branches, but when the formation of short shoots begins 
the crown assumes a denser aspect. 

In most trees the terminal bud of a shoot usually develops 
the strongest shoot, the lateral buds giving rise to shorter 
branches in regular decreasing order from the tip to the base, 
where the buds usually produce very short shoots or none at 
all. In the ash and willow, however, the branches on a shoot are 
much the same size from top to bottom, and in a few instances 
the branches are short near the tip and base and long near the 
middle of the shoot In good soil and a favourable climate the 
branches of trees are longer than where the ground is poor and 
lacking in moisture or where the climate is severe. 

Nitrogenous manures and absence of light due to overcrowding 
tend to the production of long shoots, while the bearing of fruit 
checks the vigour of trees and leads to the formation of short 
shoots. 

13. * Spurs/ The short branches upon trees often grow very 
little each year and may take many years to reach a length of 
even four or five inches. They are readily recognised by the 
large number of ring-like scars which mark the place where the 
bud- scales have fallen off each year. Upon fruit-trees they are 
known as spurs or fruit-spurs^ and they need special attention, 
as it is upon them that fruit buds are most frequently borne in 
some kinds of trees. 

The formation of a fruit-spur and its development is illustrated 
in Figs. 17 and 18. 

4, Fig. 19 is a typical piece of a long shoot of an apple tree 
three years old bearing fruit-spurs. 

The part 1898 is one season old, anti grew from a terminal 



SPURS 



45 



bud arising at 2 , the bud-scale scars being visible at this point 
The three buds upon it similar to a are wood-buds : they may 
in 1899 develop into (i) long shoots, or (2) short ones, or (3) 
remain undeveloped. The part of the shoot between the bud 
scale-scars n l and 2 is the previous year's growth, namely, that 
of the summer of 1897. The buds upon it in the winter of 1897 
were similar to those marked a: during the summer of 1898, 
when the terminal bud at n 2 was growing into a long leafy shoot, 
they developed short leafy shoots, similar to B and C, Fig. 1 7, each 
of which went to winter rest with a terminal fruit-bud upon it. 





FIG. 17. A) Piece of last season's shoot of pear tree with wood or leaf-bud as seen in 
autumn. J3, The same in the following midsummer ; the bud has now given rise to a short 
shoot or ' spur' bearing leaves and terminated by a fruit-bud. C, The same as B after 
leaves have fallen in autumn, showing 'spur* terminated by the plump fruit-bud. 

Parts similar to , therefore, are not merely stalked buds, but 
short branches bearing terminal fruit buds ; they are one-year-old 
fruit-spurs, the terminal buds of which in 1899 will open into a 
short stem bearing flowers similar to B y Fig. 18. At d is a bud 
still in the undeveloped condition in which it was first produced, 
and is therefore similar to a, except that it is two years old : it is 
a dormant bud. 



4 6 



THE VEGETATIVE SHOOT 



Upon the three-year-old piece of the shoot marked 1896 are 
two spurs, c and *, two years 1 old. In 1897 they resembled b, 




FIG. 18. Fruit-bud of pear (same as C of previous Fig.), showing various stages of its 
growth. A, opening in spring ; B< later with flowers and leaves expanded ; (', later still, 
only one flower has 'set or developed into a fruit, the re t having fallen off at b\ a t a 
lateral bud which will continue the growth of the spur in the following year. 

and in the spring of 1898 opened into a stem bearing flowers, 
such as j, Fig. 18. Fruit was produced during the summer, and 



SPURS 



47 



1838 



1898 




FIG. 19 Shoots of various fruit-trees. 
x. Morello cherry. A to B, Ion* shoot of last sea on, 1898, with fr*it-buds t f\ 

nmiiar shoots of 1897 and earlier years are practically bare, w a spur. 
a. Black currant. A to B, long shoot of last season, with frvit-b*ds t b ; long shoots 



of previous year havefruibbiidt on spurs, *. 

3. Plum. A to B) long shoot of last season, with wood-bud* t b\ long shoots of pre- 

vious year have jrvit-buds on spurs, which terminate in a wood-oud, *, and bear 
lateral fruit-buds, x. 

4. Apple. * a to /", long shoot of last season, with vtood-buds, a \ long shoots of pre- 

vious year have spurs which terminate in fruit-buds, b and o. For further ex- 
planation Me text. 



48 THE VEGETATIVE SHOOT 

the large scar at x indicates that one apple ripened, the small 
fruit-scar at x on spur e being evidence that the fruit fell from 
the latter prematurely. 

It must be noticed that after the production of fruit such a 
spur as this cannot continue growth in the same line ; it may 
die altogether, but usually one or more lateral wood-buds arise 
upon it in the axils of its leaves, and these continue its future 
growth. On spur c the lateral bud o has arisen in this manner 
during 1898 when the fruit was being ripened. The spurs of 



f 





A B 

FIG. 20. A , 4 Spur ' of pear tree which has borne one mature fruit at x ; a a fruit-bud. 
B, An old 'spur' from the same tree; i, 2, and 3, growth of three suc- 
cessive years, forming a sympodium : x large scars left where fruit has 
matured and fallen off ;/ fruit-buds. 

the apple and pear, therefore, present a zig-zag appearance (see 
Fig. 20); those of black currant are* similar. 

The spurs of the plum terminate in wood-buds, and con- 
sequently grow in a straight line ; the lateral buds are fruit-buds 

(3 Fi g- J 9)- 

No hard and fast rule can be laid down in regard to the 

position of the fruit-buds upon trees, as it is not absolutely 
constant for any one kind ; exceptions occur due to manuring, 
cultivation, season, kind of tree, and the pruning it has received. 



SPURS 49 

Three fairly distinct classes of trees may, however, be recog- 
nised. Some trees, such as the peach, bear almost entirely on 
long shoots one year old and have few or no spurs, while others 
produce their fruit-buds chiefly at the apex or on the sides of 
spurs, the long shoots of the tree bearing only wood-buds in 
their first year ; a third group bears almost equally both upon 
long shoots and spurs. 

The apple and pear produce fruit-buds chiefly upon spurs, 
and rarely upon long shoots which are only one season old. A 
few varieties of apples, however, such as Cox's Orange pippin, 
Ribston pippin, and Irish peach, sometimes produce fruit-buds 
freely on the long shoots of last season. 

The plum bears largely upon spurs (j, 3, Fig. 19), but sometimes 
the fruit-buds may appear upon its young long shoots : when the 
latter happens they are usually accompanied by wood-buds placed 
on each side. 

The red currant carries its fruit chiefly upon spurs ; the black 
currant, both on young long shoots and spurs, but chiefly on the 
former. 

In the black and white Hearts, Bigarreau and Duke cherries, 
the fruit-buds are mostly met with upon spurs, but the Morello and 
Kentish types bear largely upon the one-year-old long shoots 
(i, Fig. 19). 

The gooseberry and apricot resemble the black currant in the 
arrangement of their fruit-buds. 

The raspberry bears upon leafy shoots, which arise in summer 
from buds on the previous year's cane. The canes or stems 
which come above ground are biennial. The fruiting cane dies 
down in autumn, but before this takes place the buds at its base 
on the underground rootstock grow up into canes : in the fol- 
lowing year the buds upon the latter open out into leafy shoots 
which bear the fruit, after which these canes die away, and are 
followed by a new set of young canes which originate in a similar 
manner. 

5 



SO THE VEGETATIVE SHOOT 

There is considerable difference in the age to which fruit-spurs 
attain ; some, like those of apple and pear, live many years ; upon 
red currant they remain productive longer than upon the black 
currant ; the spurs on the Morello cherry are shorter lived than 
those upon the other varieties. In pruning those trees with 
spurs of short life, endeavour should be made to secure relays of 
young long shoots at frequent intervals. 

14. Dormant Buds. On examining trees in spring when the 
buds are beginning to develop, it will be observed that some of 
them remain inactive and continue in this condition all the 
summer. Not only may they refuse to grow in what may be 
termed their proper season, but they frequently remain unde- 
veloped for long periods. Such buds are termed dormant or 
resting buds, and are met with upon almost all kinds of plants, 
chiefly near the base of the stems, as at </, 4, Fig. 19. 

Although many dormant buds soon die, some remain capable 
of development for several years after their formation, and may 
give rise to what are termed deferred shoots. In fruit-trees they 
are termed c water-sprouts ' j if they spring from beneath the 
surface of the ground they are known as ' suckers.' They not 
uncommonly arise upon 'stocks' which have been grafted or 
budded 

Destruction of the terminal and lateral buds near the top 
of a stem tends to promote the growth of deferred shoots from 
dormant buds at its base. This is well illustrated in shoots of 
fruit-trees and roses when they are pruned severely. Moreover, 
pinching out the terminal buds of herbaceous and other plants 
is often practised with a view to insure the development of all the 
lateral buds upon it, and the formation of a bushy plant instead 
of one with a single main stem and few branches. 

The grazing and mowing of grasses promotes the full develop* 
ment of all their buds, and a consequent increase of leafy 
stems. 
Not only does cutting away or pinching dff the terminal buds 



ADVENTITIOUS BUDS 51 

promote the development of basal buds likely to become dor- 
mant, but anything which impedes the movement of water or 
'flow of sap' to the terminal and highly-placed buds tends 
towards the same result. 

In the early formation of cordon fruit-trees, where it is important 
that all the buds upon the main stem should develop shoots or 
short spurs, bending the shoot for a time is practised in order to 
promote the ' breaking ' of those buds at the base of the stem 
which might otherwise remain dormant and leave a length of 
unfruitful wood. 

15. Adventitious Buds. Dormant buds, mentioned above, are 
buds which have arisen in regular order in the axils of leaves, but 
which have remained inactive some time ; the only irregularity 
about them is their period of development. Buds may, however, 
arise at any point of a plant, not necessarily in the axil of a leaf, 
but on any part of the stem, or even upon roots and leaves : such 
are termed adventitious buds. Examples are met with on the 
roots of docks, poplars, roses, and many other plants, especially 
when the upper bud-bearing parts have been removed. They 
frequently arise and produce shoots upon stems which have been 
injured. In some instances they proceed from the callus cover- 
ing the wounds where branches have been cut off ; some of the 
shoots of ' pollard ' trees spring from adventitious buds originat- 
ing in this manner. 

Adventitious buds are often produced upon leaves which have 
been removed from the parent and pegged down on moist sand 
or loam. Gardeners take advantage of this peculiarity in pro- 
pagating begonias. 

Similar buds occur upon some kinds of leaves when they are 
severed from the plant and their petioles stuck in moist ground : 
the scales of the hyacinth and other bulbs give rise to new 
plants in this manner. 

Ex. 34. Examine twigs of ash, sycamore, elder, horse-chestnut, oak, 
beech, and other trees and shrubs in winter. Make notes of the arrange- 



52 THE VEGETATIVE SHOOT 

ment of the buds, the scars left where the foliage-leaves and old bud -seal ei 
have fallen off, and the hairyness, smoothness, and any other peculiarities of 
the bark and buds. (See Tables, page 6 1.) 

Ex. 25. Measure the lengths of intcrnode between successive buds on last 
year's shoots of the common trees and shrubs. At which parts, those which 
are youngest or those which are oldest, are the buds most closely placed on 
the stems? 

Ex. 26. Examine young ash, sycamore, oak, and other trees in winter. 

(1) Try and find out the yearly growth in length of the various parts of 
each. 

(2) Make observations in regard to the length of the branch produced by 
buds near the apex, middle and base of each year's growth. Note the pre- 
sence or absence of "dormant " buds. 

(3) Find out if the branching is generally racemose or cymose. Look for 
sympodia upon hazel, beech, elm, and horse-chestnut, and other trees. 

(4) Note the difference in length of yearly growth of branches in very old 
trees and young ones of the same species. 

Ex. 27. Examine the long shoots and short shoots (' spurs ') of apple, pear, 
plum, cherry, gooseberry and currant. Observe the size and form of the 
buds upon the various parts of the shoots. Cut longitudinal sections and 
examine with a lens : endeavour to determine which are wood-buds and which 
are fruit-buds. 

Ex. 28. Examine the unfolding buds upon the chief fruit trees in spring 
when the different kinds of buds can be easily distinguished : observe the 
position of the leaf-buds, mixed-buds, and flower buds respectively. 

1 6. Stems and their Varieties. Stems which are soft and 
which usually last but a short time, are termed herbaceous \ 
practically all our annuals have stems of this nature, and many 
perennial plants also, e.g. nettles and hops. Most stems 
which last several seasons develop within themselves consider- 
able quantities of wood, and are harder and firmer in con- 
sequence : such stems are said to be woody. It must be 
pointed out, however, that herbaceous stems in reality also 
possess wood, but only in the form of thin strands, which are 
relatively small in amount when compared with the remaining 
soft parts. All stems, moreover, are soft and herbaceous when 
very young, so that no real distinction exists between herbaceous 



STEMS AND THEIR VARIETIES 53 

and woody stems, as it is a matter of degree of development 
of the wood within them : a wall-flower or a rose, for example, 
may be soft and herbaceous in its upper parts and hard and 
woody below. 

Trees and Shrubs have well-developed woody stems, the 
former possessing a single main stem or trunk, which is devoid 
of branches for some distance above the ground; the latter 
have no very distinct main stem, and the chief branches are 
all much the same in thickness and spring from a point either 
on or close to the ground. 

Many plants have stems which are too weak to maintain an 
erect position ; they consequently grow along the surface of 
the soil. Some plants have weak stems which always remain 
prostrate^ while others, designated climbing plants^ have stems 
which, although too weak to stand upright of themselves, are 
nevertheless able to use suitable objects near them as supports. 
Climbing plants support themselves in various ways. In ivy, 
adventitious roots are developed on one side of the stem, and 
these serve to fix the plant to bark of trees, walls, and rocks. 

Tropaeolums of gardens and wild clematis are supported by 
their leaves, the petioles of which curve round the stronger 
branches of plants growing near them. 

Peas and vetches are also enabled to climb by means of their 
leaves, some of the leaflets of which are modified into thin thread- 
like structures termed tendrils. The latter are sensitive to contact, 
and wind round any slender object which they touch. Plants 
such as the blackberry, rose, &c., are supported by means of 
their stiff prickles. 

In twining plants the whole stem upholds itself by twisting 
round neighbouring objects. The stems of some of them 
always twine to the right when growing round a support; the 
hop is an example : others, such as bindweed, twine to the 
left 

17. A number of peculiar modifications of shoots are met with, 



54 THE VEGETATIVE SHOOT 

many of which receive special names; the most familiar are 
mentioned below: 

i. Above ground. 

(a) In the wild pear, wild plum, hawthorn, sloe, and buckthorn, 
some of the branches end in hard, sharp points, termed thorns 
or spines. That they are modified shoots is seen from the fact 
that they arise in the axils of leaves, and also themselves bear 
leaves and lateral buds in some instances. 




FIG. si. Runner of Creeping Crowfoot (Ranunculus refens L.). 
r Adventitious roots; s intcrnodes. 

(b) A runner or stolon is a shoot which extends horizontally over 
the surface of the ground. Its internodes are long, and from its 
nodes adventitious roots are produced, and grow into the soil 
(Fig. 21). The buds present on the runner then become 
fixed to the ground, and, developing into upright shoots, form 
separate plants as soon as the internodes at s die away or are 
severed. 

Strawberry runners and those of creeping crowfoot are good 
examples. 



STEMS AND THEIR VARIETIES 



55 



Ex. 29. Examine the thorns upon the hawthorn, sloe, wild plum, wild pear, 
and buckthorn. Note their origin in the axils of leaves, and that some of 
them bear buds and leaves. 

Ex. 30. Examine the origin of the runners upon strawberry plants, mouse- 
ear hawkweed, and creeping crowfoot. Observe the position of the leaves 
and buds upon the runners. 

ii. Underground. 

Stems within the soil sometimes resemble roots, but they can 
be distinguished from the latter by the possession of leaves and 
buds, and by their originating in the axils of leaves. 

(a) A rhizome or ' rootstock ' is an underground shoot, which 
grows more or less horizontally. Adventitious roots arise at the 
nodes, and the internodes may be long or short, thick or thin, so 





ViG.-22.-i. Diagram illustrating growth of an indefinite rhuome. A to B, 
indefinite primary axis which remains below ground permanently, i, and 3, 
lateral branches of A B which come above ground. 

2. Diagram illustrating growth of a definite rhizome. A to /?, definite 
primary axis which has flowered and decayed away ; a, a branch from the 
primary axis coming above ground ; 3, a branch from 2 ; 4, a branch from 3. 
The whole stem from A to C below ground is a sympodium or false main-axis. 

that the general appearance of a rhizome is variable, those of 
couch and other grasses being long, thin straggling shoots, while 
in iris, hop and other plants they are thick and fleshy. When 
leaves are present, they are generally reduced to the form of 
membranous scales. 

Rhizomes may be indefinite or definite in growth ; in the 
former case, the true and main axis continues to grow at its 
tip, and always remains below ground ; the parts which come 
above ground are secondary or lateral branches, which arise in 
the axils of its scaly l*aves (i, Fig. 22). Most rhizomes are, how- 



56 THE VEGETATIVE SHOOT 

ever, definite in growth, the main axis, after growing a longer or 
shorter distance below, comes above ground, the continuation of 
the rhizome within the soil being carried on by lateral branches 
(2, Fig. 22). In perennial rhizomes of definite growth, such as 
those of sedges, grasses, and many other plants, the permanent 
part which remains below ground is a false main-axis or sym- 
podium (p. 41). 

(&) The term sucker is applied to any adventitious shoot which 
originates below ground on the stems or roots of shrubs and 
trees. It possesses adventitious roots and by separation from 
the parent may become a new individual plant. Suckers often 
develop very rapidly and rob the parent of water and nutriment, 
so that except for purposes of propagation they should be 
destroyed. 

Ex. 81. Examine the underground parts of couch-grass, bindweed, mint, 
potato, horse-radish, asparagus, raspberry, and hop, and observe the scale- 
leaves and the buds in the axils of some of them. 

Note the connection of the shoots which come above ground with the 
underground parts. 

(c) A tuber is a shoot with a short, thick, fleshy stem, and 
minute scaly leaves, in whose axils are buds or 'eyes.' The 
most common tubers are developed below ground e.g. those of 
potato and Jerusalem artichoke but they may occur on parts 
of plants above the soil. The scaly leaves are not visible on 
the fully-developed potato tuber, as they drop off or shrivel 
up before ripening is accomplished. For the development and 
structure of the potato tuber see pp. 462-469. 

(<t) A corm is a short, thick, fleshy stem, with a few thin, scaly 
leaves covering it, and bearing one or more buds at its apex. 
Examples are seen in the ordinary crocus and gladiolus of 
gardens. 

Fig. 23 is a section of a crocus in flower. At b is the solid, 
fleshy stem of the corm, with the remains of an old corm (a) ad- 
hering to it, and several adventitious roots (r). From its summit 



STEMS AND THEIR VARIETIES 



57 



at h y the terminal bud has grown in spring into a short stem (<:), 
bearing on its sides thin, membranous leaves (d) and ordinary 
green foliage leaves (e\ which come above ground. One or 
more flowers are produced 
from the axils of the leaves, as 
at / The substances stored 
in the stem of the corm (b) are 
used up in production of these 
leaves and flowers, and conse- 
quently, at the end of summer, 
this part becomes shrivelled 
and dead, like a. The green 
leaves (e), however, after they 
have developed, manufacture a 
considerable amount of food, and 
this descends from the leaves, and 
is stored in the short stem (<:), 
which thickens in consequence 
and becomes a new corm at the 
end of the season. The buds (x) 
in the axils of the leaves of the 
new corm remain near its apex, 
carry on the production of a new 
series of flowers, leaves and corms 
in the following year. 

A corm, instead of possessing 
only one bud at its summit, as 
at h, often has several buds there, 
each of which develops into a 
new corm in the manner de- 
scribed; thus one corm may give rise to many in a single 
season. 

(e) A bulb often resembles a corm in external appearance, but 
consists of a comparatively small stem, upon which is arranged a 




FIG. 23. Section of Crocus in flower. 
For explanation, see text. 



THE VEGETATIVE SHOOT 



number of thick, fleshy, scale-leaves, which overlap each other 

more or less com- 
pletely. The whole 
structure is practi- 
cally a huge bud, 
and in the axils of 
some of its scales 
are small, rudimen- 
tary buds. Familiar ex- 
amples are met with 
in the onion, tulip, 
lily, hyacinth, snow- 
drop, and narcissus. 

The onion seedling, 
figured on page 20, 
develops several leaves 
during summer, as 
at A, Fig. 24, and 
the plant swells at its 
base and forms a bulb. 
A section, as at ./?, 
reveals its structure. 
Tracing the leaves 
from the green parts 
downward, it is ob- 
served that the bases, 
especially of the inner 
ones, are thickened, 
and it is these leaf- 
bases which form the 
main mass of the bulb, 
the stem (s) upon which 
they grow being com- 
pa*ratively small. At 




B A 

FIG. 24.^, Young onion plant ; a remains of an 
old leaf; c c younger leaves. 

B, LonRitudinafsection of the same ; j short stem ; 
b leaves and leaf-bases forming the chief part of the 
bulb ; / growing point of stem. 



STEMS AND THEIR VARIETIES 59 

the end of summer, the green parts of the leaves die and shrivel ; 
their lower parts, which have become thin, act as a cover for the 
rest of the bulb, and prevent the rapid loss of water from the 
interior. 

The onion bulb, if planted next year, forms adventitious roots 
from the base of the stem, and the terminal growing-point (/) 
inside grows up into the air, and produces leaves and an inflor- 
escence of white flowers at the end of a long hollow stem. The 
buds in the axils of the scale leaves develop usually in the same 
manner, so that from one bulb several flowering shoots are often 
produced. The materials stored in the bulb-scales are used up 
in this development of the flowering stems, and after the pro- 
duction of ripe seeds, the whole plant is generally exhausted, 
and dies away, in which case the onion is a biennial plant. 
Occasionally, however, some of the lateral buds from the axils of 
the scales do not produce inflorescences, but leafy shoots only, 
which form small bulbs in the same manner as an onion seedling. 
After the death of the parent, these smaller bulbs remain, and 
carry on the growth in the succeeding year. The onion plant 
in this instance is a perennial. 

A tulip bulb in autumn consists of a short, thick stem, upon 
which are placed a series of large, overlapping, fleshy scales. 
The latter are complete leaves, and not merely leaf bases, as 
in the onion. At the apex of the stem is an embryonic shoot, 
having leaves upon it, and bearing a terminal flower; in the 
axils of some of the scales are rudimentary buds. 

In spring the flower-bearing stem grows from within the bulb 
and comes above ground, carrying with it the flower and two 
or three leaves, as indicated in Fig. 25. This development 
takes place at the expense of the food stored in the scales (o) : 
the latter therefore soon become soft, and at the end of the 
season shrivel up and decay. The leaves (e) on emerging 
from the soil turn green, and during the spring and summer 
manufacture a consfderable amount of food; that part of it 



6o 



THE VEGETATIVE SHOOT 



not needed for the plant's immediate requirements is trans- 
ferred to lateral axillary buds below ground, and is there stored. 
These buds consequently grow rapidly and become young 

daughter bulbs; one of them is 
shown at n in course of development. 
Bulbs like the onion, tulip, and 
hyacinth, which have broad, concave 
scales arranged in such a manner 
that the outer ones completely en- 
close those within, are known as 
tunicated bulbs. In lilies the bulb 
scales are not so broad, and are 
arranged to overlap each other like 
the tiles on a roof : such bulbs are 
said to be imbricated. 

Ex. 32. Cut a longitudinal section 
through a young onion plant when the 
bulb is well formed. Watch the develop- 
ment of a young plant into an old bulb. 
Cut sections of a mature onion bulb and 
compare its internal structure with that of 
a Brussels sprout. 

Ex. 33. Examine old onion bulbs which 
have been kept all winter and allowed to 
sprout. Note the number of separate sets 
of green leaves produced by it. Cut it 
open and examine the origin of the latter. 

Ex. 34. Cut longitudinal sections of 
tulip, hyacinth, snowdrop, and narcissus 
bulbs. Note the stem, the number of 
scales, and their relative thickness in each ; 
also the presence or absence of rudimentary 




FIG. 25. Section of a tulip in 
flower. / Stem on which are fleshy 
bulb scales, o ; p flowering stem 
bearing green leaves, e ; a ovary ; b flowers and axillary buds, 
stamens ; c perianth of the flower ; 
n bud developing into a new bulb ; 
t small dormant buds. 



Ex. 35. (i) Examine the structure of 
a crocus corm in autumn. Pull off the outer 
scaly leaves and observe the position and number of the buds on the thickened 
stem. (2) Cut longitudinal sections of a corm. (3) Examine a corm in 
bloom, and observe the roots, remains of old cormS, foliage and membranous 
scale-leaves, and number and position of the flowers. Compare with Fig. 23. 



BUDS OPPOSITE EACH OTHER 61 

RECOGNITION OF TREES BY MEANS OF TWIGS 
IN WINTER. 

The chief deciduous British forest and fruit trees and shrubs 
may be recognised in winter by the character and arrangement 
of the buds, as given below : 

GROUP I. 

BUDS OPPOSITE EACH OTHER ON THE TWIGS (Fig. 26). 
The following belong to this group : 



Dogwood. 

Mealy Guelder-Rose. 

Common do. 

Ash. 

Spindle-Tree. 

Privet. 



Honeysuckle. 
Elder. 
Sycamore. 
English Maple. 
Norway do. 
Horse-Chestnut. 



Buckthorn. 

1. Buds naked, i.e. without protecting bud-scales. 

(a) Young twigs, smooth, slender, and blood-red in colour. 

Dog- wood : Wild Cornel ( Cornus sanguined L. ). 

(b) Twigs with a powdery grey covering consisting of stellate 

hairs. 
Mealy guelder-rose : Wayfaring-tree ( Viburnum 

Lantana L, ). in s opposite ar- 

2. Visible bud-SCaleS few (One Or tWO). rangementof buds. 

(a) Bud-scales sooty black. 

Ash (Fraxinus excelsior L.). Twigs smooth, greenish-grey ; 
terminal bud much larger than the round lateral ones. 

(b) Bud scales pinkish. 

Common guelder-rose (Viburnum Opulus L.). Young twigs 
with longitudinal ridges or angles, especially near their tips ; 
lateral buds closely pressed to stem. 

3. Several bud-scales visible ; closely and compactly arranged. 

(a) Twigs slender, bright sage green. 

Spindle-tree (Euonymus europaus L.). The bud-scales are 
green, with pinkish margins and tips. 

(b] Twigs slender; grey, brownish -grey, or brown; all buds small 

and similar in size, including the terminal ones. 
* Bud-scales smooth. 
Buckthorn (Rhamnus catharticus L.). Many of the branches 



62 THE VEGETATIVE SHOOT 

terminate in a thorn : the buds of the shrub are not always 
opposite; bud scales dark reddish-brown. 

Privet (Ligustrum vulgare L.). Without thorns; buds much 
smaller than the preceding, and their scales dark olive-brown ; 
leaves often remain on all winter. 
** Bud scales hairy, especially at the tips. 

Common maple (Acer campcstre L.). The twigs are stiffer than 
the two preceding shrubs; hairy when young Bolder parts of 
bark with longitudinal cracks or fissures. 
(t) Twigs stiffer and thicker ; terminal buds usually much larger than 

the lateral ones. 

Horse-chestnut (Atsculus Hippocastanum L.). Buds brown 
in spring, covered with a sticky resinous substance ; large 
triangular leaf-scar. 
Sycamore (Acer Pseudo- plat anus L.). Bud-scales yellowish-green 

with dark-brown margins and tips ; leaf-scar well marked. 
Norway maple (Acer platanoidcs L.). Bud -scales pinkish or 
reddish-brown, sometimes greenish at t.heir bases ; leaf-scar 
narrower than in sycamore. 
4. Several bud-scales visible, very loosely arranged. 

Elder (Sambucus nigra L. ). Twigs pale brownish-grey, with longi- 
tudinal ridges and distinct lenticels ; bud-scales brownish-red and 
puckered ; very wide spongy pith. 

Honeysuckle (Lonicera Periclymenum L.). The young twigs which 
climb up and wind round supports are shining and cylindrical, with 
a hollow pith. Bud-scales brownish -green. 

GROUP II. 
BUDS ALTERNATE; ARRANGED IN TWO LONGITUDINAL ROWS 

ON OPPOSITE SIDES OP THE TWIGS /Fig. 27). 
The following belong to this group : 



Spanish chestnut. 

Limes. 

Hazel. 



Elms. 
Beech. 
Hornbeam and (Birch). 



I. Buds roundish -oval : each about twice as long as broad. 
(A) Visible bud- scales few (one or two). 

* Young twigs with longitudinal ridges or angles. 
Spanish chestnut (Castanea vulgaris Lam.). Twigs deep red 
or reddish-green, straight : the buds are placed not immedi- 
ately above the distinct leaf-scar, but slightly on one 
side. 



BUDS ALTERNATE 63 

** Young twigs cylindrical ; one large and one small bud- scale 

to each bud. 

Common lime ( Tilia vulgaris Hayne). Twigs smooth, blood-red 
or orange-red, with a shining surface, somewhat long and 
bowed. 

Small-leaved lime (T. parvifolia Ehrh). Similar to the pre- 
ceding species, but bark lighter colour and a smaller 
tree. 
Broad-leaved lime ( T. platyphyllos Scop. ). Twigs slightly hairy : 

a larger tree than T. parvifolia Ehrh. 
(B) Several bud-scales visible. 

* Buds flattened on one side ; bud-scales pale, brown- 
ish, or reddish-green. 
Hazel (Coryhis Avellana L.). Young twigs hairy and 

with a few stalked glands. 
** Buds rounder and more pointed ; bud-scales dark 

brown or dark maroon. 

Common elm (Ulmus campestris Sm.). Young twigs 
more or less hairy ; older twigs with fine rich 
brown-coloured fissures on the bark. A variety 
(7. suberosa Sm.) with longitudinal thick ridges of 
cork is met with. 

Wych elm (U. montana Sm.). Twigs and buds 
similar to the preceding, but twice or three times 
the sire. The leaf-scars are large. 

2. Buds pointed, often three or more times as long as broad. 
Beech {Fagus sylvatica L.). Twigs slender, smooth ; the 
buds are usually over half an inch long, round in section, 
and jut out from the stem. 

Hornbeam (Carpinus Betulus L.). The buds lie closer to 
the stem, and are not nearly so long as those of beech ; 
they are also slightly angular in section. 
Birch possesses twigs and buds somewhat similar FIG. 27. Twigof 

T , , i i t i i i A-. Spanish chestnut 

to Hornbeam, and although it belongs to Group showing alternate 

III., it sometimes has buds nearly arranged as in arrangement of 

_'__ , , .,, buds. 
Group II., and may be noticed here. 

Birch (Bctula alba L.). The twigs are slender and elastic : in some 
varieties they are hairy, in others covered with small resinous 
tubercles. 



6 4 



THE VEGETATIVE SHOOT 



FIG. 28. 
Twig of Plum 
tree, showing 
spiral arrange- 
ment of buds. 



GROUP III. 

BUDS ARRANGED SPIRALLY ON THE TWIGS (Fig. 28). 
To this group belong : 

Birch. .Plums. 

Walnut. Cherries. 

, Oaks. Pear. 

Willows. Apple. 

Poplars. Black Currant. 

Alder. Red Currant. 

Black Alder. Gooseberry. 

Wild Service. Raspberry. 

White Beam. Blackberry. 

Mountain Ash. Barberry. 

Hawthorn. Wild Dog Rose 

Blackthorn. 

1. Pith divided into chambers. 

Walnut (Juglans regia L.). Young twigs thick, 
leaf-scars very large. Lateral buds small, round, 
black and smooth, the terminal one much larger 
and hairy. 

2. Buds naked, i.e. without protecting bud-scales. 

Black alder (Rhamnus Frangula L.). Young twigs 
reddish. 

3. Buds distinctly stalked. 

(a) Apparently only one bud-scale visible. 

Alder (Alnus glutitiosa Gaert.). Young twigs irregu- 
larly triangular in section, brown or reddish-brown 
in colour. The buds are angular, dark brownish- 
red, and their stalks j-inch or more long. 

(b) Several bud-scales visible. 

Black Currant (Ribes nigrum L.). Twigs smooth, 
pale brown or pale greyish buff; buds plump, 
round, blunt at tips, bud-scales dark pink or 
brownish-pink, sometimes greenish. With aid of 
a lens yellow glands are visible on the bud stalks 
and scales. 

Red Currant (Ribes rubrum L.). Twigs with loose, 
fluffy, ashy grey bark ; buds thinner, longer, and 
more pointed than black currant; their scales 
dark chestnut brown, with fine woolly hairs. 



BUDS ARRANGED SPIRALLY 65 

4. Buds sessile, with apparently only one large bud-scale (really two 

united). 

Willows (Salix Sp.). The willow hybridises so freely that it is im- 
possible to distinguish all of them by characters of the buds and 

twigs alone. 

The following, however, may be mentioned : 
Those with hairy buds : 
Osier (Salix viminalis L.). Buds of unequal size; older twigs 

smooth and shining. 

Grey Sallow (S. cinerea L,). Very soft hairy twigs and large buds. 
White Willow (S. alba L.). Very small buds; older twigs reddish- 

grey and dull. 

Those with smooth buds : 
Crack or Redwood Willow (S. fragilis L.). Twigs brown and 

polished ; buds almost black. 
Bay-leaved Willow (S. ptntandra L.). Similar to above, but buds 

brown. 

Rose Willow (S. purpurta L.). Very long pointed buds. 
Great Sallow (S. caprea L.). Short, plump, yellowish or reddish buds. 

5. Buds sessile, each with several visible bud- scales. Twigs with 

spines (hairs and emergences) upon them, but no spiny branches 
present. 
(a) Spines straight, situated just below the buds only. 

Gooseberry (Rtbes Grossularia L.). Twigs round, light yellowish- 
grey ; buds pointed and slightly stalked. 

Barberry (Bcrberis vulgaris L. ). Young twigs, with slight longi- 
tudinal ridges, thin ; buds bluntish at tips, and sessile. 
(3) Spines with stout bases, tips bent backwards usually, and irregu- 
larly arranged on the twigs. 
Wild Dog-Rose (Rosa canina L.). Twigs round ; buds smooth, 

roundish, blunt-tipped. 
Blackberry (Rubus fruticosus L.). Twigs angular; buds hairy, 

longer, and more pointed ; spines very irregularly placed. 
(c) Many small soft spines, and hairs on twigs. 

Raspberry (Rubus IJaus L.). Twigs pale reddish or yellowish- 
brown, shining ; bud-scales loosely arranged. 

6. Buds sessile ; several bad-scales visible. 

(a) Bud-scales green, with narrow brown edges. 

Wild Service Tree (Pytus torminalis Ehrh.). Buds oval, bluntish 

tips, smooth, and somewhat flattened on one side. 
White Beam (Pyrus Aria Sm.). Buds hairy at tip, longer than 
the preceding, and pointed ; bud-scales keeled. 

6 



66 THE VEGETATIVE SHOOT 

(J) Bud-scales black or dark purple. 

Rowan-tree or Mountain Ash (Pyrus Autuparia Gaert.). Buds 

large, often J inch long or more. 
(f) Bud-scales hairy all over. 

White Poplar (Populus alba L.). Young twigs covered with a 
white, loose cottony film : older ones smooth, yellowish-grey ; 
buds plump and pointed. 

Apple or Crab (Pyrus Malus L.). Twigs partially hairy ; small 
wood -buds on long shoots closely pressed to stem and triangular 
in outline. In the wild or crab-apple short branches ending in 
a " thorn " are present. 
(</) Bud-scales smooth or hairy only at the tips or margins. 

(1) Several buds crowded at the tips of the long shoots. 
Common English Oak (Quercus pedunculata Ehrh.). Young 

branches greyish -brown, without hairs and furrowed. The 
buds stand out from the stem, are yellow or chestnut-brown 
colour, quite smooth, plump, and rounded at the tips. 
Durmast or Sessile Oak (Quercus sessiliflora Sails.). Young 
branches slightly hairy ; buds longer than the preceding, 
and their scales tipped and edged with hairs. 

(2) Long narrow-pointed buds, chestnut-brown in colour, and 

covered with resin at tips ; twigs furrowed. 
Black Poplar (Populus nigra L.). Bud-tips straight or 

pointing outwards. 
Aspen (Populus tremula L.). Tips of the buds pressed close 

to stem. 

(3) Buds dark brown ; leaf-scar a narrow crescent. 

Pear (Pyrus communis L.). Twigs smooth, yellowish- 
brown ; not hairy. In wild pear short branches terminat- 
ing in " thorns " are present. 

Hawthorn or White Thorn ( Crataegus Oryacantha L. ). Twigs 
greyish -purple or greenish-grey ; buds paler than the pear 
and rounder; usually two together one large, the other 
smaller. Generally spiny branches are present at the side 
of the buds. 

(4) Buds dark brown ; leaf-scar rounder, almost a semicircle. 

* Buds small and round. 
Sloe or Blackthorn (Prunus spinosa L.). Young twigs 

smooth, greyish-brown ; older ones black. Buds very 

small, usually two or three together. 

** Buds larger and conical. 
Apricot (Prunus Armeniaca L.). Young twigs greenish- 



BUDS ARRANGED SPIRALLY 67 

brown or reddish-green, smooth and shining ; usually three 

buds together above leaf-scar. 
Bullace (Prunus insititia L.). Young twigs hairy; older 

ones smooth and dark brown. Bud-scales hairy. 
Wild Plum (Prunus domestica L.). Young twigs smooth, 

reddish or purplish brown. 
*** Buds oval. 
Bird Cherry (Prunus Padus L.). Young twigs thinnish, 

reddish-brown. Buds large (i inch long and more) and 

pointed. Bud-scales chestnut-brown, keeled, mucronate 

tip. 
Gean: Bigarreau and Hearts (Prunus Avium L.). Twigs 

stout and short, reddish -brown and grey. Buds large and 

crowded on short shoots. Bud-scales chestnut-brown ; not 

keeled. 
Dwarf Cherry : Morello and Kentish (Prunus Cerasus L.). 

Twigs thin and slender, yellowish or greenish -brown and 

grey. Buds smaller (J inch long). 
Btahaleb (Prunus Mahahb L.). Buds smaller and not so 

plump as the dwarf cherry : stand closer to the stem. 

Twigs similar in colour. 



CHAPTER V 
THE LEAF. 

i. As previously noted leaves arise in all cases from buds, and 
are side or lateral appendages of the stems of plants. They may 
be of many forms but are generally flattened structures, and, with 
the exception of those known as floral leaves, usually have buds 
in their axils. Their growth differs from that of the stem and 
root in being of short duration, for after reaching a certain 
size their increase ceases. 

2. Foliage-leaf. Those which are most conspicuous upon 
plants are green and are designated 
foliage-leaves. They are important organs 
generally concerned with the manufacture 
of food needed by the growing part 
of the plant, and are also organs from 
which much of the water taken from the 
soil by the roots is given off into the 
air. A typical green foliage-leaf (Fig. 29) 
consists of the following parts (i) a broad 
expanded portion termed the blade or 
lamina ; (ii) a slender stalk or petiole ; and 
(iii) a somewhat flattened basal sheath 
which connects the leaf to the stem. 

The leaf-sheath often bears two appen- 
dages the stipules which may be broad 
and wing-like as in the clovers and pea, or small and narrow 
as in pear and apple; leaves possessing them are said to be 
stipulate, while those without are exstipufate. 




Fro. 29. Foliage-leaf of 
plum / Lamina or blade ; 
p petiole ; s stipule. 



FOLIAGE-LEAF 69 

The parts of the leaf are of very varied form. In the grasses 
the sheath completely embraces the stem, and in the Umbelliferae 
(eg. carrot, parsnip, and celery) it is very prominent ; in many 
plants it is scarcely visible. 

The petiole where present is usually narrow and cylindrical ; 
frequently it is very short or missing altogether, in which case 
the leaf is described as sessile. 

The blade is generally the most obvious part of a foliage-leaf 
and the points of importance to notice at present are its venation, 
outline, margin, apex, and character of its surface. 

(a) Venation of leaf -blade. The substance of the leaf is 
traversed by a number of woody strands which are termed 
veins or nerves, although it must not be inferred that they 
are similar in structure or function to the veins or nerves of 
animals. The arrangement of these strands is termed the 
venation of the leaf, of which there are two common types, 
namely (i) parallel and (2) reticulate or net- venation. In the 
first type the chief strands all run parallel to each other from the 
base of the leaf to the tip, as in the leaves of grasses, onion, 
hyacinth, lily-of-the-valley, and Monocotyledons generally. 

In net- veined leaves the smaller very delicate strands form a 
fine net-work within the leaf and this arrangement is charac- 
teristic of Dicotyledons. 

Of reticulate veined leaves two divisions are made according to 
the arrangement of the main strands. In one, the leaves have a 
central strand or mid-rib running down the middle of the leaf and 
from it are given off slightly smaller branch strands as in Fig. 
29; such leaves are pinnately veined or feather-veined, those 
of the apple, plum, and peach are good examples. 

In the other division each leaf has several strong strands which 
start from the base of the blade and spread across to its margins 
somewhat like the fingers of an outstretched hand ; such a leaf is 
described z&palmatdy veined. Ivy, sycamore, and currant leaves 
show this type of venation. 



THE LEAF 



(b] Forms of blade. The outline of the blade of the leaf may 
assume almost any geometrical figure (Fig. 30). When it is 




67" ^ 

FIG. 30. Common Forms of Leaves: i, Linear; 2, lanceolate; 
3, ovate; 4, elliptical, 5, cordate; 6, sagittate; 7, hastate; 8, 
reniform ; 9, spathulate. 

much elongated and narrow as in grasses it is termed a linear leaf. 

It may also be lanceolate as in the narrow-leaved plantain ; ovate 
egg-shaped); elliptical; reniform or kidney- 
shaped; cordate (heart-shaped); sagittate 
(arrow-shaped) ; spathulate (spoon-shaped) as 
in the daisy ; and hastate (halberd-shaped) as 
in sheep's sorrel. 

(c) Leaf-margin. The edge of the leaf-blade 
is sometimes entire as in privet ; or variously 
indented with larger or smaller incisions. (Fig. 
31.) Leaves having margins like the edge of 




4. 3. 2. 1. 



a saw are serrate : when the small tooth-like 

FIG. i. -Leaf- margin: ... 

i, Entire ; 2 , serrate ; 3 , incisions stand out at right angles to the edge 

dentate ; 4, crenate. . . c, - 

of the leaf it is described as dentate ; the term 



FOLIAGE-LEAF 



crenate is used when the edge has small semi-circular prominences. 
If the indentations are deeper the leaf is then described as lobed 
(fid), parted (-partite), or dissected (-sect) respectively, according 
as the divisions reach about one half, three quarters, or nearly 
the whole way down towards the midrib. 

As the indentations follow the direction of the main strands 
or veins of the leaf we have two types of lobed, parted or dis- 
sected leaves namely: (\) pinnatifid (i, Fig. 32) pinnatipartite, 
pinnatisect and (2) palmatifid (3, Fig. 32), palmatipartite, and 
palmatisect. 

So long as the divisions of the blade do not quite reach to 
the main ribs the leaf is said to be simple; in many cases, 
however, the partitions are such that the leaf appears to have 
several distinct blades; it is then compound, and the separate 
parts are its leaflets (t, Fig. 32). 
Compound leaves are either pinnate 
as in pea, vetch, potato, rose and 
ash ; or palmate as in clover, horse- 
chestnut, and lupin. 

(d) Surface. The surface of the 
blade is smooth or glabrous, or some- 
times covered on one or both sides 
with hairs. 

(e) Aj>ex.-~The tip of the leaf. 
when it is pointed is acute; when 
drawn out to a longer point it is 
acuminate : it may also be obtuse 
(blunt), emarginate (notched), or 

. . . FIG. 32. T. Simple pinnatifid leaf , 

mucronate ; m the latter case the s bbe. 2 . Compound pinnate leaf; 

. i , . . i t leaflet. 3. Simple palmatifid leaf; 

midrib appears to project as a sharp , i he. 4 . Compound palmate leaf; 
point see leaves of lucerne (Fig. /leaflet - 
133) and trefoil. 

Ex. 36. Examine and describe the leaves of the chief farm plants and as 
many of the common weeds *v> possible. Observe first if they are simple or 




72 THE LEAF 

compound, then note the presence or Absence of stipules and petiole, aftei 
which describe their form, margin, apex, and surface. 

3. Modified Leaves. Structures are often met with upon 
plants which although they do not possess all the parts of a 
foliage leaf as just described, are, nevertheless to be regarded 
as leaves on account of their origin and position upon the plant, 
and also by the fact that they frequently bear buds in their 
axils, and under some circumstances may become changed into 
ordinary green leaves. Several of these modified leaves 
receive special names as indicated below, according to their 
position upon the stem, or according to their texture, colour, 
and other peculiarities. 

(a) Cotyledons or seed-leaves. These are the first leaves which 
a flowering plant possesses, and are nearly always simple and 
entire, and without stipules. 

Some coniferous trees (pines and firs) have seedlings with 
several cotyledons, but dicotyledons usually possess only two 
(Figs. 5, 103, no), while in monocotyledonous plants only 
one is present. 

In the bean, pea, and vetch they serve merely as storehouses 
for the food upon which the seedling depends for its early 
growth. In the cereals and grasses generally, the chief work 
of the cotyledon is to absorb the endosperm of the seed, and 
transfer it to the growing-points of the young root and shoot ; 
while in the turnip, mangel (Fig. no) and many other plants they 
come above ground and carry on the work of 'assimilation,' 
thus behaving as ordinary foliage-leaves. 

(b) Scales. These are usually thin membranous leaf-struc- 
tures, generally brown, white, or yellowish in colour, and may 
be either complete leaves, or merely the sheaths and stipules of 
leaves the blades of which have not developed. 

On the stems above ground they are often present as coverings 
to the buds of trees and shrubs, acting as a protection for the 
interior of the bud against frost, heat, rUin, and the attacks of 



MODIFIED LEAVES 



73 



t 



insects. Scales are always present upon the underground stems 
of perennial plants, and vary much in size. Upon the rhizomes 
of couch-grass and potato, they are small and membranous, 
while the leaves of a resting bulb are large scales, some of which 
are thick and fleshy, and stored with food. 

(c) Bracts and Bracteoles. The leaves which occur upon the 
stem at points where 

the flowers and inflores- 
cences arise are termed 
bracts and bracteoles (see 
p. 89). They are very 
variable in size, texture 
and colour. In some 
plants they cannot be 
distinguished from the 
ordinary green foliage- 
leaves except by their 
position ; more often 
they are rudimentary 
leaves somewhat re- 
sembling scales. The 
chaffy bracts surround- 
ing the flowers of grasses 
are termed glumes. In 
Arum, Iris, Narcissus, 
and snowdrop, a large 
bract, termed a spathe, 
encloses the whole in- 
florescence. 

The cup of the acorn and the husk of the filbert and hazel- 
nut are persistent united bracts. 

Bracts are sometimes brightly coloured. 

(d) Floral leaves. The special leaves constituting the chief 
parts of a flower are termed floral leaves (see next chapter). 




st 



Fie, 33. A single compound leaf of pea : 
Stipule ; / leaflet ; t tendril. 



74 THE LEAF 

(e) Leaf-spines. In the sloe and other shrubs and trees certain 
branches are found which have been modified into short, stiff 
spines. That the latter are branches or shoots is seen from the 
fact that they frequently bear small leaves and buds. 

In some plants however, such as barberry, the spines are 
evidently not branches, but modified leaves, for buds and stems 
frequently appear in their axils, and in the barberry all stages 
of transition between an ordinary green leaf and a branched 
spine are frequently observable on the same plant. 

(/) Leaf-tendrils. In the vetch and pea (Fig. 33) the terminal 
leaflets, instead of being green, are modified into thin, thread- 
like structures termed tendrils. They are sensitive to contact 
and wind round any small object which they touch. 

In some plants, such as the vine and passion-flower, the 
tendrils are not leaves but modified branches. 

Kr. 37. Examine the cotyledons of the seedlings of weeds springing up 
on garden soils and arable ground. Note the difference between these and 
the first foliage-leaves. 

Examine the cotyledons of seedlings of the common farm crops. 

Ex. 38. Examine the scales of an onion, tulip, and lily bulb, and those 
upon the underground stems of couch-grass and other plants. 

Ex. 39. Examine the spines on a gooseberry bush. Do they belong to 
the leaves or are they modified shoots ? 

Note both the leaf-spines and stem-spines upon ordinary gorse. 

Compare with Ex. 29. 

Er. 40. Note the form and position of the tendrils of a retch and pea, 
both when free and when wound round a support. 

4. Leaf-arrangement. Although to a casual observer the 
leaves appear to be without any regular arrangement upon a 
plant, careful inspection shows that they are distributed on the 
stems in a very definite order, which is usually constant for each 
species. 

In some, such as the sycamore (Fig. 14), dead-nettle, and 
cleavers, two or more leaves arise at the same node of the stem. 
Each collection of leaves is then called a whorl> and the 



LEAF-ARRANGEMENT 75 

individuals comprising it are always separated from each other 
by regular angular intervals. Thus, if two leaves are present 
they are half the circumference of the stem apart or exactly 
opposite each other, and not both on the same side; if three 
arise at the same node, they are separated from each other 
by regular intervals of 120 degrees, or one-third of the circum- 
ference, and so on for any number of leaves. 

On many stems the leaves are not in whorls but scattered 
singly along it, only one leaf arising at each node : such an 
arrangement is spoken of as alternate or spiral. A line drawn 
from the bottom to the top of a shoot in such a manner that 
it touches the base of each successive leaf is a spiral. The 
distances between the leaves measured along the stem are 
variable, some being an inch apart, others two or more; their 
angular intervals apart are, however, as definite and regular as 
in plants with the whorled arrangement. 

The divergence or angular distance is usually expressed in 
fractions of the circumference. In elm, Spanish chestnut and 
grasses, it is ^, that is, the spiral in passing from one leaf to the 
next winds half round the stem. In birch it is J, while in pear 
and plum the angular distance is f of the circumference. 

The divergences most frequently met with are, , , |, f , and 
r Y On inspection these spirally arranged leaves are seen to be 
in straight longitudinal rows along the stems; plants with a 
divergence of \ having two rows, those with \ three rows, and 
those with f five rows, and so on, the denominator or lower 
figure of the above fractions indicating the number of rows 
present. 

If any particular leaf in a row is selected and the spiral traced 
round the stem touching each successive leaf until another leaf 
is reached on the same row, the number of leaves touched, not 
counting the one at which we start, is equal to the number 
of the denominator of the fractions expressing the angular 
divergence, and the numerator indicates the number of com- 



76 THE LEAF 

plete turns round the stem which the spiral line traces. For 
example, the angular divergence of the leaves on a pear shoot 
is : selecting any one leaf as a starting point, the spiral line 
passes twice round the stem by the time that it reaches the 
next leaf on the same row, and in doing so touches the bases 
of five leaves. To determine the leaf-arrangement upon any 
particular shoot, it is necessary to observe the bases of the 
leaves and not the blades, as the position of the latter is affected 
by external conditions, especially by light and the force of 
gravitation. Occasionally the stems become twisted during 
growth, and the leaves are consequently displaced from their 
normal position. 

The orderly arrangement of the leaves upon stems is de* 
pendent on the internal forces of the living plant. By growing in 
this manner all the leaves become equally exposed to light and 
air, and interfere very much less with each others requirements 
in this respect, than would be the case if the leaves were disposed 
irregularly. 

Ex. 41. Examine and describe the leaf-arrangement upon the shoots of all 
common farm plants, trees, and weeds. 

5. Bud-arrangement. As buds arise normally in the axils of 
leaves, it follows that the arrangement of buds upon trees in 
winter will be similar to that of the leaves during the previous 
summer. A careful recognition of the position and arrangement 
of buds upon the shoots of plants is of some importance in the 
practice of pruning, where buds are required to produce branches 
growing in some particular direction. 

For the arrangement of the buds upon the chief shrubs and 
trees, see pp. 61-67. 

6. Leaf fall : * Evergreens.' In most of the broad-leaved trees 
and shrubs of temperate regions the leaves produced from buds 
in spring usually last only one growing-season, and then all fall 
off before the plants enter a state of rest iii the following winter. 



LEAF-FALL 77 

A number of shrubs and trees, however, appear clothed with 
green leaves at all times of the year. These are described as ever- 
green. In such plants the leaves produced from buds in spring are 
not shed in the following autumn or winter, but live sometimes 
several seasons before they die and fall off. The length of time 
during which the leaf remains on a so-called evergreen tree after 
it is produced depends upon the kind of tree, the climate, 
situation, soil and other conditions. 

In privet the leaves often remain on the twigs during winter, 
and fall off when the new buds open in spring ; while in some 
conifers the leaves are not shed until they are ten years old or 
more. 

The leaf usually separates from the shoot bearing it, at a point 
close up to the latter, and a more or less conspicuous mark, 
termed the leaf-scar, is left upon the shoot. The dangerous 
effects of an open wound is prevented by the formation of a 
protective layer of cork over the surface of the scar, which 
layer originates some time before the actual fall of the leaf. 

Leaf-fall is not merely the dropping off of dead, withered 
leaves, but a distinct physiological process, which does not 
take place in leaves which are prematurely killed by the action 
of frost or excessive heat Moreover, the leaves do not fall off 
from branches of trees and shrubs broken or cut off, in early 
summer. 

Ex. 42. Observe the manner of leaf-fall upon the common shrubs and trees, 
paying special attention to those with compound leaves, such as ash and 
horse chestnut. 

Note the form and size of the leaf-scars. 

Try and determine how long the leaves persist upon box, laurel, privet, 
hotly, silver-fir, Scotch pine, and other common evergreen shrubs and trees, 



CHAPTER VI. 
THE FLOWER. 

i, THE root stem and green leaves which have been under con- 
sideration in the last three chapters are termed the vegetative 
organs of the plant. Although our attention has been chiefly 
directed to their morphology or origin, form and relationship to 
each other, it may be remarked that the work which these 
organs perform, for the benefit of the plant, is principally 
concerned with the maintenance of the life of the individual 
which bears them. 

2. Sooner or later, however, flowers arise upon the plant, the 
special function of which is reproduction : in them seeds are 
produced containing embryos capable of developing into a new 
generation of plants when opportunity offers. 

Before discussing the work of the flower it is necessary to 
become acquainted with the form and arrangement of its parts, 
and for this purpose it is advisable to begin with the study of 
a simple example such as a buttercup, A section through the 
latter is given in Fig. 34. In the centre of the flower is seen a 
stem-like axis (r) which is a continuation of \hzpcduncle or flower- 
stalk. This is the receptacle of the flower and upon it is arranged 
a considerable number of lateral appendages of which there are 
four distinct forms present The lowermost of these appendages, 
that is, those farthest away from the apex of the receptacle, are 
yellowish-green in colour and resemble boat-shaped scales (m)** 
There are five of them free from each other and arranged in a 
whorl : each is termed a sepal, and the whole collection or whort 
is known as the calyx of the flower. 

78 



THE FLOWER 



79 



Immediately above the sepals, and alternating with them, are 
five bright yellow heart-shaped leaves (n) ; these are the petals, 
the whole collection of which is termed the corolla of the flower. 

Next to the whorl of petals are the stamens (s), of which there 
are a large number. Each consists of a thin thread-like stalk 
surmounted by a swollen and elongated tip. In the buttercup 
the stamens are not arranged in a whorl but in the form of a 
closely wound spiral round the receptacle ; the whole collection 
of them is the andr&cium of the flower. 

Occupying the highest position upon the receptacle is a series 
of small, green, flask-shaped bodies (c) ; they are hollow and it 





m 



A B 

B'lG. 34. A, Flower of Buttercup (Ranunculus acris L.). B, 
Vertical section through the same, r Receptacle of the flower ; m sepal 
of the calyx; n petal of the corolla; s btumen of the androecium ; c 
carpel of the gyruucium. 

is within them that the seeds of the plant are produced. Each 
is termed a carpel, and the whole collection is known as the 
gynacium or pistil of the flower. 

3. Although the flower of a plant appears different in many 
respects from anything we have yet examined it is in reality a 
form of simple shoot or a stem with leaves upon it. The whole 
of its parts, however, have been modified to serve the purpose 
of seed production, and at first sight its likeness to a simple 
vegetative shoot is not appreciated. 

That a flower is essentially equivalent to a simple shoot with 



80 THE FLOWER 

very short internodes is, however, apparent from a study of its 
origin and position upon the plant and also from an examina- 
tion of abnormal or monstrous flowers which occasionally occur. 

A flower always occupies the position of a shoot; it arises 
either at the apex of a stem or in the axil of a leaf. Its receptacle, 
which normally ceases growth in length at an early period, occa- 
sionally grows on through the centre of the flower and develops 
into an ordinary leafy vegetative shoot. 

The sepals, petals, stamens and carpels occupy the position of 
leaves upon the receptacle or axis of the flower ; they are lateral 
appendages of the receptacle and are termed floral leaves. More- 
over, the leaf-like character of the sepals and petals is generally 
obvious, and in so-called ' double flowers ' some or all of the 
stamens and carpels assume the appearance of petals. 

4. Arrangement, Symmetry and Number of Floral Leaves. 
When the whole of the floral leaves are arranged in whorls, the 
flower is said to be cyclic : if they are inserted in a spiral line on 
the receptacle, the flower is described as acyclic. The term hemi- 
cyclic is applied to those flowers which like the buttercup have 
some of their floral leaves in whorls and others in spirals. 

Generally the successive whorls alternate with each other : the 
petals for example are not opposite to the sepals, but occupy 
the spaces between the latter; the stamens alternate with the 
petals and the carpels with the stamens. 

Very often the individual members of each separate whorl in 
a cyclic flower are all alike in shape and size ; such a flower is 
regular^ while those in which this is not the case, as in the pea 
and violet, where some of the petals are larger than the rest, the 
flower is irregular. 

All those flowers which can be divided into two equal and similar 
halves by a plane passing through the axis of the receptacle are 
symmetrical. Usually regular flowers can be divided into two 
halves by planes passing through the axis in several different 
directions : they are designated actinomorphic flowers, examples 



THE RECEPTACLE 8 1 

of which are chickweed, poppy and wallflower. Those which 
can be cut into two equal halves in one direction only are 
zygomorphic ; for example vetch, pea and dead-nettle. 

The number of members constituting each whorl in a flower 
is subject to much variation, but it will frequently be observed 
that in Monocotyledons each whorl consists of three floral leaves 
or some simple multiple of three (such as six or nine). In 
Dicotyledons the floral leaves are usually in fours or fives. 

The pattern flower just described consists of four distinct 
kinds of floral leaves and is termed a complete flower. Sometimes 
flowers are met with in which one or more entire sets of floral 
leaves are missing either calyx, corolla, androscium or gynaecium ; 
such are spoken of as incomplete flowers : examples are seen in 
the mangel and ash. 

5. The Receptacle. In the Buttercup the receptacle is an 
elongated cylindrical or conical axis and the whorls of floral 
leaves are arranged upon it at successively higher levels, the 
gynaecium occupying the highest and the calyx the lowest 
points respectively, with the corolla and androecium between. 
In many cases the receptacle is thicker and not so long as that 
of the buttercup, but the relative positions of the parts upon it is 
the same. Flowers which like the buttercup have the corolla 
and andrcecium inserted on the receptacle at a lower level than 
the gynaecium and free from the latter are termed hypogynous 
flowers, and the gynaecium is described as superior (i, Fig. 35); 
examples are charlock, poppy and chickweed. 

In the plum the apex of the receptacle ceases to grow at an 
early stage, but the parts below the apex grow up all round it 
and form a hollow basin or urn-shaped structure, on the edge 
of which the calyx, corolla and stamens are arranged (Fig. 124). 

The gynaecium, consisting of a single free carpel, is placed at 
the bottom of the hollow receptacle (2, Fig. 35), this point being 
the real apex of the floral axis. 

Flowers in which the corolla and androecium are arranged on 



82 



THE FLOWER 



the edge of a more or less hollow receptacle, surrounding the 
free gynsecium, are perigynous and the gynaecium is said to 
be superior as in hypogynous flowers. The flowers of plum, 
cherry, strawberry, are examples : in the strawberry, the part of 
the receptacle which bears the gynaecium is a solid lump, but 
round the latter the rest of the receptacle forms a flattish rim 
on which the petals and stamens are borne (Fig. 125). 

In some flowers the receptacle appears to be hollowed out as in 
the plum, but the carpels instead of being free from it are closely 
invested by its walls and completely adherent to the latter, so 
that the receptacle and gynaecium appear to be one structure : 
the ovaries of the carpels are imbedded in the receptacle, and 




FIG. 35. Diagrammatic vertical section through I. a hypogynous flower ; II. a 
perigynous flcwer ; and III. through an epigynous flower, r Receptacle ; s sepal 
of calyx ; / petal of corolla ; a stamen of androecium ; o the gynaecium. 

only their stigmas and upper parts are free and exposed. In 
such flowers the sepals, petals and stamens, seem as if they were 
produced on the upper part of the gynaecium, or its ovary, 
although in reality they spring from the receptacle which encloses 
and is completely united with the latter. Flowers of this type are 
described as epigynous^ and the gynaecium is inferior (3, Fig. 35). 
Examples are seen in the apple, pear, gooseberry and carrot. 
The exact limits of the receptacle and the gynxcium cannot be 
seen or understood in fully developed flowers, and in many cases 
uncertainty exists in regard to them. The above description and 



THE ESSENTIAL PARTS OF THE FLOWER 83 

diagram (Fig. 35), however, are sufficient to enable students to 
distinguish epigynous flowers from hypogynous or perigynous 
ones. 

6. Non-essential parts of the flower: the Perianth. The 
calyx and corolla whorls of floral leaves together constitute the 
perianth of the flower, and as they are not directly concerned in 
the production of seeds are termed the non-essential parts of the 
flower. 

When one of the whorls of the perianth is absent as in the 
mangel, male hop, and anemone, the flower is spoken of as 
monochlamydeous ; if both calyx and corolla are absent, as in the 
ash and willow, the flower is naked or achlamydeous. 

(i) The Calyx. The calyx forms a protective covering for the 
rest of the flower when the latter is still young, and may either 
lall off when the flower opens, in which case it is caducous^ or 
remain attached to the receptacle for an indefinite period, when 
it is described as a persistent calyx. It is usually green but 
may assume some other colour, in which case it is spoken of as 
petaloid. 

A calyx which consists of free separate sepals, as in the butter- 
cup, is termed polysepalous ; those in which the sepals are united, 
as in the primrose and pea, are said to be gamosepalous. 

In groundsel, thistle, and other plants belonging to the 
Compositae, the calyx takes the form of a ring of hair known as a 
pappus (Fig. 148), which generally develops rapidly after the 
corolla has faded and acts as a float for the distribution of the 
seed-case by means of the wind. 

(ii) The Corolla. This part of the flower is usually of bright 
colour and serves mainly as an attraction for insects. When 
the petals forming it are free from each other, as in the buttercup 
and rose, the corolla is polypetalous ; the term gamopetalous is 
applied to corollas which are composed of united petals, as in 
the primrose and Canterbury bell. 

7. The essential parts of the flower. The andrcecium and 



8 4 



THE FLOWER 



gynaecium are directly concerned in the production of seed, as 
explained hereafter (Chap, xxii.), and are termed the essential 
parts of a flower. 

(i) The Andrcecium consists of stamens, each of which, as 
previously stated, is a modified form of leaf, although its 
appearance and structure is very different from the petals and 
sepals of the perianth. 

A stamen usually consists of a more or less elongated thread- 
like portion the filament surmounted by a swollen thicker 
part termed the anther (Fig. 36). 

The anther consists of two somewhat elongated halves or 
anther-lobes (0), which are situated usually on opposite sides of the 

upper part of the filament : the 
part of the filament uniting the 
anther-lobes is termed the con- 
nective (c). 

Running lengthwise in the 
interior of each anther-lobe are 
two chambers or hollow spaces 
named pollen-sacs, within which 
\hefollen is produced usually in 
the form of loose round or oval 
pollen-grains. In a young state 
the latter are completely en- 
closed in the anther-lobes, but 
in a longer or shorter time after 
the opening of the flower the 
partition between the pollen- 
sacs is ruptured and the anther- 




FIG. 36. A, A common form of stamen. 
./The filament ; a anther-lobe ; c the connec- 
tive. B t View of stamen showing internal 
structure. /"Filament ; c connective, on each 
side of which are the anther- lobes ; /r pollen 
sacs, between which is a partition d, when the 
anther is young ; O n the right the anther-lobe 
has dehisced, setting free the pollen-grains 
p ; e empty pollen-sac. 



lobes open by longitudinal slits 
along the line of union of the two pollen-sacs (B y Fig. 36), the 
pollen-grains being then set free in the form of dust-like powder. 
In some cases the pollen-grains escape by pores or valve-like 
openings situated near the apex of the anther. 



THE GYN^ECIUM 85 

Most frequently the stamens of the androecium are distinct 
and completely free from each other as in the buttercup, but in 
some flowers the filaments of the stamens are united together and 
only the anthers are free. When all the filaments are united 
the stamens are described as monadelphous ; if two or several 
separate bundles of united filaments are present the stamens 
are said to be diadelphous and polyadelphous respectively. 

In the daisy, dandelion, and most plants belonging to the 
Composite, the anthers are united and the filaments are free ; 
such stamens are termed syngenesious. 

Stamens attached to the petals, as in the potato flower, are 
described as epipetalous. 

(ii) The gynaecium is composed of carpels, each of which 
generally consists of three parts : (i) a swollen hollow basal por- 
tion termed the ovary, 
(2) a thin more or less 
elongated part called 
the style, at the apex of 
which is (3) the stigma. 

The style is in many 
instances missing and 

the Stigma is then SeS- FIG. 37. Pod of a pea (a single carpel), v The ventral 
suture ; d the d >rsal suture ; s style ; t stigmatic surface ; 
Slle Upon the Upper part /funicle of the seed ; a seed. 

of the ovary. 

Within the cavity of the ovary are small round or oval bodies 
termed ovules, which under certain circumstances to be mentioned 
later develop into seeds. The part inside the ovary on which 
the ovules are borne is termed the placenta, 

The carpel may be considered as a leaf which has been folded 
along the midrib and united at its edges. The line correspond- 
ing to the united edges of the leaf is termed the ventral suture 
of the carpel, and it is along this line that the ovules are generally 
attached in two rows one row belonging to each edge ; the line 
corresponding to the mWrib of the folded leaf is the dorsal suture. 




86 



THE FLOWER 



These parts are readily seen in the pod of a pea (Fig. 37), 
which bears considerable resemblance to a folded green leaf. 

The gyngecium may consist of separate carpels as in the 
buttercup, in which case it is said to be apocarpous. Frequently 
the carpels are united and then form what is termed a syncarpous 
gynaecium (2, Fig. 38). The amount of union among the carpels 
varies, but very frequently their ovaries are completely united to 
form one common ovary : in such cases the styles are generally 
united to form one common style, the corresponding stigmas 
usually remaining free. When the carpels of the syncarpous 




FIG. ^3. i. Gynaecium, consisting of a single carpel. 
v Ventral suture ; o ovules , / style ; s stigma. 2. Syncarpous 
gynaicium, consisting of three completely united carpels. 
o Ovary ; i style ; s stigma. 3. Transverse section of a syn- 
carpous gynaecium which is unilocular. c The extent of one of 
the component carpels ; the ovules are on parietal placentas. 
4. Transverse section of a syncarpous gynaecmm which is 
trilocular / A loculus ; d a partition or dissepiment ; c the 
extent of a single component carpel ; the ovules are on axile 
placentas. 

gynaecium are united by their edges as at 3, Fig. 38 the ovary 
possesses only one cavity or loculus^ and is said to be unilocular. 
In other examples the carpels are folded so that their edges meet 
in the middle of the ovary, the united parts forming partitions or 
dissepiments dividing up the common ovary into several cavities 
(4, Fig. 38) j such ovaries are described as m^ltilocular^ and each 
loculus corresponds to a single carpel. 

Occasionally the number of loculi insftie an ovary does not 



MONOCLINOUS AND DICLINOUS FLOWERS 87 

correspond with the number of carpels present in the latter, as 
dissepiments occur which are not formed from the united walls 
of two neighbouring carpels but which are produced by the 
growth inwards of a portion of the ovary wall. The latter are 
termed false dissepiments, an example of which is the septum 
which divides the ovary in the Cruciferae. 

8. Placentation. The arrangement of the placentas or points 
from which the ovules arise inside an ovary is termed placentation. 
When the ovules are arranged in lines on the wall of the ovary, 
as at 3, Fig. 38, the placentation is parietal. 

In multilocular ovaries, such as at 4, Fig. 38, the ovules are 
generally arranged in the angles formed at the centre where 
the edges of the carpels are united, and the placentation is 
described as axile. 

In the primrose and chickweed families of plants the ovules 
are attached to a placenta which arises in the form of a short 
column from the base of the ovary and has no connection with 
the sides : this arrangement is known as free central placentation, 

9. Monoclinous and diclinous flowers : monoecious and 
dioecious plants. When both the essential parts are present in 
the same flower, as in the buttercup, charlock, and the majority 
of common plants, the flower is described as monodinous ; some- 
times the terms perfect, hermaphrodite or bisexual are applied to 
such flowers. 

In certain flowers, as those of the cucumber, melon, hop, 
hazel, and willow, one or other of the essential parts are 
missing : such are said to be diclinous^ imperfect or unisexual. 
Diclinous flowers may be of two kinds, namely, (i) those in 
which the andrcecium is alone present and described as staminatt 
or male flowers, and (2) those in which only the gynaecium is 
met with and spoken of as carpellary, pistillate or female flowers. 

When both kinds of diclinous flowers are met with on the 
same individual plant, as in the case of the cucumber and hazel, 
the plant is said to be moncecious ; in examples, such as the hop 



88 THE FLOWER 

and willow where the two kinds of diclinous flowers are pro- 
duced on separate individuals, the plants are spoken of as 
dioecious. 

Ex. 43. The student should examine a large number of flowers and 
specially note the peculiarities of the receptacle, calyx, corolla, androecium 
and gynaecium in each : note the arrangement of the ovules within the 
ovary. 

He should also make himself thoroughly familiar with the terms employed 
in this chapter. 

Ex. 44. Examine the flowers of the bean, pea, cherry, buttercup, prim- 
rose, apple, anemone, vegetable marrow, cucumber, tomato, hyacinth, tulip, 
snowdrop, willow, hazel, ash, oak, sycamore, lime, oat, wheat, and any 
others at hand. 

Determine which are monoclinous and which are diclinous. If diclinous, 
are the plants monoecious or dioecious ? 



CHAPTER VII. 
THE INFLORESCENCE. 

IN many plants the flowers are borne singly and terminally at the 
end of the main axis, as in the poppy, or singly and laterally in 
the axils of the foliage-leaves of the stem or its branches, as in 
pimpernel and ivy-leaved speedwell. Such flowers are described 
as solitary. In most instances, however, flowers are grouped 
more or less compactly together on a special shoot or axis of the 
plant, as in the hollyhock, foxglove and hyacinth ; such a flower- 
bearing shoot with its flowers is termed an inflorescence, and the 
leaves upon it, in the axils of which the flowers arise, are known 
as bracts (see p. 73). The axis of the inflorescence is termed 
the rachis or peduncle, and the individual flower-stalks are called 
pedicels (p, Fig. 39), the leaf-like structures upon the pedicels 
being spoken of as bracteoles or prophylla. 

A great variety of forms of inflorescence are met with differing 
in their manner of branching, the length and thickness of their 
axes, the presence or absence of pedicels, and in many other 
particulars. They are conveniently divided into two groups, 
namely (i) racemose or indefinite, and (2) cymose or definite 
inflorescences, in accordance with the principles of branching 
described on pp. 40 and 41. 

I. Racemose Inflorescences. 

In this type of inflorescence the main axis, or rachis, bears 
either lateral sessile flowers, or flowers with pedicels, developed 
in acropetal succession? that is, the youngest flowers are nearest 

89 



THE INFLORESCENCE 



the apex and the oldest nearest the base of the rachis. If the 
flowers are sessile, or borne immediately on pedicels, that is, on 
lateral branches of the first order, the inflorescence is described 
as simple (P'ig. 39) ; when the main axis branches more than 
once before bearing the flowers the inflorescence is compound 
(Fig. 41). 

A. SIMPLE RACEMOSE INFLORESCENCES. In these the main 
axis bears either sessile flowers or flowers with pedicels. 

(i) With elongated axis and sessile flowers. 

The spike (A, Fig. 39). Examples are seen in Greater Plantain 

(Plantago major L. ) 
and Verbena. 

Parts of the in- 
florescences of most 
grasses are small spikes 
or spikelets (see p. 484). 
The spadix is a form 
of spike with a thick, 
fleshy axis. Sometimes 
a large bract, termed 
a spathe, encloses this 

f rm f ^florescence, 





A B C 

FIG. 39. Racemose, or indefinite inflorescences, with 
elongated axis. A a spike ; K a raceme ; C a corymb ; ^ j^ 
b bract ; r rachis ; / pedicel. 

(Arum maculatum L.), 
white * Trumpet-Lily ' (Richardia), and many palms. 

The catkin is a spike-like inflorescence, which bears only 
unisexual flowers. Examples of catkins of staminate flowers are 
seen in the hazel and willow ; catkins of carpellary flowers are 
found on the willow. 

In some plants the catkins are compound inflorescences. 

(ii) With elongated axis and stalked flowers 
The raceme (B, Fig. 39). In this form of inflorescence the 
flower-stalks or pedicels are of nearly equul length. Examples 



COMPOUND RACEMOSE INFLORESCENCES 91 

are seen in the hyacinth, lily-of-the-valley, wallflower, snapdragon, 
mignonette, and currants. 

The corymb (C, Fig. 39) has its pedicels of different lengths, 
those at the base of the rachis being longest, followed by pedicels 
of decreasing length upwards ; all the flowers are nearly on the 
same level. Examples occur in candytuft. 

(iii) With shortened axis and sessile floivers 

The capitulum or head (A y Fig. 40) possesses a short thick 
rachis termed the receptacle (r) upon which are a number of 
closely-packed, small, sessile flowers. Examples are seen in the 




A B 

FIG. 40. Racemose indefinite inflorescences with short axes. 
A A capitulum ; r "receptacle" ; i involucre of bracts ; scale-like 
bracteole or palea. B Simple umbel ; z involucre of bracts. 

daisy, marigold, dandelion, groundsel, and all the Composite 
(Chap, xxxiv.). 

Usually one or more dense whorls of bracts surround the 
whole head and are collectively termed the involucre of the 
capitulum : in many instances a small, scale-like bract termed 
a palea is also associated with each flower of the head. 

(iv) With shortened axis and stalked flowers 

The umbel (B> Fig. 40). In this form the main axis is short 
and bears a number of flowers with stalks of similar length. 
Examples occur in ivy, cowslip, and onion. 

B. COMPOUND RACEMOSE INFLORESCENCES. In these the 
main axis does not ^ear sessile or pedicellate flowers directly, 
but bears lateral branches which are themselves inflorescences. 



THE INFLORESCENCE 



(i) With elongated main axis 

The panicle (A, Fig. 41). In this form of compound inflor 
escence the lateral branches of the main axis are racemes 
or more complicated branched racemose inflorescences witl 
stalked flowers. Examples occur in the vine and lilac. 

The compound spike (^, Fig. 41) bears lateral inflorescence 
which are spikes. Examples are seen in wheat and rye-grass. 

In meadow-grasses, oats and other grasses the inflorescence 
are panicles of spikelets, but are commonly termed panicle 
only (see pp. 484-486). 






ABC 

FIG. 41. Compound inflorescence : A panicle or compound raceme : /> compoun 
spike : C compound umbel. / involucre, z 1 involucel. 

(ii) With shortened main axis 

The compound umbel (C, Fig. 41). In this compound infloi 
escence the lateral inflorescences are arranged in the form c 
an umbel and are themselves simple umbels. The carro 
parsnip, hemlock, parsley and nearly all the Umbelliferae (Cha{ 
xxxii.) furnish examples. 

II. Cymose Inflorescences. 

In this type of inflorescence the main axis terminates in 
flower and its growth is therefore stopped. If other flowers aris 



MIXED INFLORESCENCES 



93 



upon the axis they must spring from lateral axillary buds below 
the apex. Usually each axis bears one, two, or a few branches 
only, which grow more vigorously and overtop the main one : 
these lateral axes terminate in flowers and repeat the same form 
of branching. The terminal flower of the main axis opens first, 
and is followed by those terminating the secondary, tertiary, and 
other axes in regular succession. 

There are a number of complicated forms of cymose inflores- 



monest simpler types being : 
ehasium (A and .Z?, Fig. 42) in which 
its successive branches have each 




cences the com 

(i) The mono 
the main axis and 
only one lateral 
branch ; exam- 
ples occur in 
forget - me - not 
(Myosotis\ rock 
rose (Helianthe- 
mum)j and some 
species of Ger- 
anium. 

(ii) The dicha- A B C 

x ' FIG. 42. Cymose or definite inflorescences. A and />. Mono- 

Slum Or forked chasia ; C, dichastum : i, main axis ; 2, 3, 4, and 5, axis of second, 
third, fourth, and fifth orders respectively. 

cyme (C, Fig. 42) 

in which the main axis has two lateral branches, and each of the 
latter again bear two branches ; examples are met with in stitch- 
worts (Stellaria) and centaury (Erythraa). 

(iii) The polychasium in which more than two secondary 
branches are given off from the main axis and below each flower 
of the inflorescence ; examples of polychasia are seen in many 
spurges (Euphorbia). 

III. Mixed Inflorescences 

are frequent in which the first branches of the main axis exhibit 
a racemose arrangement, while the subsequent branches are 
cymose in character, and vice versd. 



94 THE INFLORESCENCE 

Ex. 45. The student should examine the inflorescences 01 as many plants 
as possible, and determine which are racemose and which cymose in type. 
Pay special attention to the position of the bracts whenever present. 

He must understand that a large number of complicated inflorescences are 
met with, to which no names have been given. 

The structure and nomenclature of those of the simple racemose and 
cymose types should be specially studied. 



CHAPTER VIII. 
THE FRUIT. DISPERSAL OF SEEDS. 

i IT is from the flower of a plant that the fruit arises after the 
completion of a physiological process known as fertilisation. A 
satisfactory account of the latter and its effects can, however, only 
be given after the student has become acquainted with the finer 
details of plant structure ; it is therefore deferred to Chapter xxii. 

It is sufficient here to remark that the process consists in the 
union of a certain portion of the contents of the pollen-grain with 
a minute structure termed an egg-cell situated within the ovule, 
after which the latter grows and finally becomes a seed. 

Soon after fertilisation has taken place, the andrcecium and 
corolla of the flower usually drop off or wither up, and sometimes 
the calyx falls also. The stigma and style of the gynsecium 
generally wither, but the ovary in all cases remains, and grows 
extensively to allow the rapid development of the seeds within it 

When the gynsecium has reached its full state of development 
and the seeds within its ovary have become ripe, it is termed the 
fruit of the plant, and the carpel-walls of the ripe gymecium 
enclosing and protecting the seeds constitute the pericarp of 
the fruit 

It must be observed that the term ' fruit, 1 in popular language, 
is applied to a number of different parts of plants which are 
often in no way connected with the ripe gynaecium of the flower, 
and are therefore not fruits in this restricted botanical sense. In 
the strawberry and apple, for example, the succulent edible por- 
tion is the enlarged receptacle of the flower, the true fruit in the 
former being the smail seed-like bodies (achenes) studded over 

05 



96 THE FRUIT I DISPERSAL OF SEEDS 

the receptacle, while the ripened gynaecium of the apple is its 
'core* (see p. 412). 

The tomato, vegetable marrow, and cucumber are true fruits, 
that is, they are the products of the gynaecium only, but are 
nevertheless popularly designated ' vegetables/ 

The term pscudocarp^ or 'spurious fruit? is frequently used 
for structures, such as the apple, strawberry, fig, and mulberry, 
produced from a flower or inflorescence, but which include 
something more than the gynsecia and their contents. 

2. A complete satisfactory classification and nomenclature of 
fruits is still wanting : they may, however, be divided into four 
groups as indicated below, according to the texture of the 
pericarp and the manner in which the seeds are set free from 
the fruit. 

I Indehiscent Dry Fruits. 

In these the pericarp is dry and woody or leathery in texture, 
and does not split or open along any definite lines. The seeds 
are set free by the decay of the pericarp. As the necessary 
protection for the embryo and its store of food against adverse 
climatic influences and the attacks of animals, is afforded by 
the strong pericarp, the testa of the seed itself is usually thin 
in these fruits. 

The following are the commonest forms of fruits of this 
class : 

(i) The nut is a one-seeded fruit, with a woody pericarp ; 
it is developed from an inferior syncarpous ovary. Examples are 
hazel-nut, beech-nut, acorn and Spanish chestnut. 

The fruit of the horse-chestnut is not a nut, but a berry-like 
capsule. 

The fruit of the Composite (Figs. 147, 148) is termed a cypscla, 
and is a form of nut developed from a syncarpous inferior ovary 
of two carpels. Its pericarp is thin, and contains within it only 
one seed ; the calyx is frequently present as a pappus. 



DEHISCENT DRY FRUITS 97 

(ii) The achene is a one-seeded fruit, with a thin leathery peri- 
carp ; it is the product of an apocarpous superior ovary. Examples 
are seen in the buttercup (Fig. 226), rose, and strawberry. 

In the rose, the achenes or true fruits, are enclosed within 
the hollow receptacle which, when ripe, is scarlet and soft. 

In the strawberry the receptacle is succulent, the true fruits 
being the small achenes studded over it (see Fig. 125). 

(iii) The caryopsis is a superior one-seeded fruit resembling 
an achene, but the seed within it, instead of being free as in the 
latter, is united with the wall of the pericarp. The fruits of 
grasses are caryopses. 

(iv) The samara resembles an achene, but the pericarp is 
furnished with wing-like appendages, e.g. ash, elm and sycamore 
(a double samara). 

n. Schizocarps. 

These are dry syncarpous fruits, the united carpels of which, 
when ripe, separate from each other, but do not set free the 
contained seeds as in the dehiscent fruits mentioned below. 
Each separate carpel of the fruit is termed a mcricarp^ and 
usually contains a single seed enclosed within it. 

Sycamore fruits, and those of the carrot, parsnip, and other 
Umbelliferae, are examples of schizocarps (see Fig. 134). 

HI. Dehiscent Dry Fruits. 

In these the pericarp splits in various ways or opens by pores. 
The interior of the fruit is exposed, and the seeds, which usually 
have thick protective testas, are set free. 

Most dry fruits of this class have many seeds. 

The commonest forms of dry dehiscent fruits are mentioned 
and described below. 

(i) The follicle is a superior fruit consisting of a single carpel 
which opens along one suture only, most frequently the ventral 
one. Columbine fruits are examples (Fig. 43). 

(ii) The legume is also a superior fruit of one carpel, but 



9 8 



THE FRUIT ! DISPERSAL OF SEEDS 



it dehisces along both the dorsal and ventral lines (Fig. 37). 
The pods of peas and beans are examples. 

(iii) The siliqua (Fig. 44) is an elongated 
superior fruit composed of two united carpels. In 
the interior of the fruit is a thin false dissepiment or 
partition, termed the replum, which separates the 
fruit into two chambers. When ripe the two carpels 
dehisce from below upwards and leave the seeds 
attached to the placentas and replum. Examples 
FIG. 43! Foi- are met with in the turnip, cabbage, and wallflower. 
b?ne (%fK/4g?a) The term silicula is applied to fruits of this descrip- 
cen*e ln a1ong e on<i ^ on which are short and broad as in shepherd's 
5uture - purse. 

(iv) The term capsule is generally applied to practically all 
forms of syncarpous, dry dehiscent fruits except those just men- 
tioned. They may be either superior or inferior, 
and usually contain many seeds, The manner 
and amount of dehiscence is very varied : most 
frequently it is longitudinal, but in some cases 
it is transverse. The dehiscence may extend a 
part of the way along the fruit and the carpels 
remain partially united with each other; or it 
may extend the whole length of the capsule and 
the carpels become free and fall away from each 
other. If the latter happens and the splitting 
takes place along the dorsal suture, the dehiscence 
is described as locidicidal \ the term septicidal is 
used when the dehiscence occurs along the line of 
union of the carpels. 

In some cases the outer parts of the capsules 
fall off as separate pieces or valves leaving the partition or septa 
of the gynaecium attached to the flowerstalk : such dehiscence 
is described as septifragal. 
Dehiscence by pores is seen in the capsules of the poppy. 




FIG. 44. Siliqua 
of wallflower, 
showing manner 
of its dehiscence ; 
v valves of fruit ; 
^replum withseeds 
attached (cf. Fig. 




SUCCULENT OR FLESHY FRUITS 99 

The pyxis or pyxidium is a form of capsule in which the 
dehiscence is transverse, the upper part of the carpels falling 
off in the form of a cap or lid (Fig. 45). Examples are seen 
in plantain, pimpernel, and red clover. 

IV. Succulent or Fleshy Fruits. 

In these the pericarp is more or less soft and sappy and, when 
ripe, is usually of considerable thickness. The commonest forms 
are mentioned below. 

(i) The drupe is an indehiscent superior fruit of this class, 
consisting of a single carpel, and usually 
with one or two seeds. In the ripe peri- 
carp three layers are visible, namely, (i) an 
outer thin delicate skin, the exocarp or 
epicarp, (2) a soft, thick, fleshy middle layer, 
the mesocarp, and (3) a hard, bony layer, 
the endocarp, which forms the so-called F ' G - 4S.-Pyxidjum of 

* ' greater plantain (7 / ant ago 

* stone' of the fruit. The seed of course is ""v r L ->' a clos ^ ; b 

upper part removed arid 

quite separate from the ' stone/ but enclosed showing the seeds within, 
within it (Fig. 124). The fruits of the plum, cherry, apricot, peach 
and almond are drupes. The individual separate carpels in 
a single raspberry flower become small drupes or drupels, so 
that the whole fruit is a compound one consisting of a collection 
of drupels. The fruit of the walnut is a form of drupe differing 
only from those above mentioned in being the product of a 
syncarpous gynsecium : the endocarp develops partitions which 
extend irregularly into the fleshy lobes of the single seed. 

(ii) The berry is an indehiscent succulent fruit in which both 
the mesocarp and endocarp are soft and fleshy. Sometimes 
the berry is the product of superior ovary as in the grape, 
tomato, and potato 'apple/ while in other instances it is inferior 
as in the gooseberry (Fig. 46), currant, and cucumber. 

' Dates' are berries the 'stone 7 of which is a true seed not to 
be confused with the * Stone ' of a drupe. 



100 THE FRUIT I DISPERSAL OF SEEDS 




(iii) Thefonie, of which an apple or pear are good examples, 

is an indehiscent 
fleshy pseudocarp 
whose gynaecium or 
true fruit is em- 
bedded in the re- 
ceptacle. When the 
pseudocarp is ripe 
the pericarp belong- 
ing to each carpel 
of the gynaecium 

Fit.. 46. Flower and fiuit of Rooseheiry. A the flower, develops & tOUgh, 

calyx-tube, o inferior ovai y ; C longitudinal section of the IporVjprv /-vr- 

flower; B transverse section of the youn^ ovary, p placenta 1CttLllci y U1 

with ovules attached ; D half-ripe fruit. inner Wall it 

carp the rest of the pericarp being in some cases fleshy, in 
others hard and bony. Surrounding and united with these fleshy 
or bony carpels is the thick, fleshy receptacle of the flower which 
forms the chief edible portion of the pome (see Fig. 126 and 
chapter on Rosaceae, p. 41 2). 

Ex. 46. The student should watch the development of the common fruits 
of the garden from the opening of the flowers to the ripe fruit. 

Observe what becomes of the receptacle, calyx, corolla, and andrcecium 
in each case. 

He should also examine the fiuits of all useful plants of the farm, and 
those of common weeds. 

Careful descriptions of each should be made, noting whether they are : 

(1) Dry or succulent. 

(2) Dehiscent or indehiscent and manner of dehiscence. 

(3) Developed from an apocarpous or a syncarpous gynaecium. 

(4) Developed from a superior or an inferior ovary. 

(5) One or many-celled, and the number of seeds in each. 

3. Dispersal of Seeds. In some cases the ripe seeds or the 
fruits containing them fall to the ground in the immediate 
neighbourhood of the parent plant ; it will however, be 
observed, that by far the larger proportion of plants exhibit 



DISPERSAL OF SEEDS IOI 

special adaptation to secure the dispersal of their seeds to 
longer, or shorter, distances. 

The chief agents at work in the transport of the seeds are 
wind, water, and animals. 

In some instances the pericarps of the fruits when ripe are 
subject to spring-like tensions, and at the time of dehiscence 
open, more or less violently, and scatter the seeds in all directions, 
often to a distance of several feet. The ripe pods of many legu- 
minous plants, such as peas, beans, and bird's-foot trefoil, 
disperse their seeds in this manner, and the valves of the pods 
after the opening of the fruit twist or curl up suddenly. 

Fruits, which scatter their seeds by the sudden released 
mechanical strains when dehiscence takes place, are also met 
with on the bitter-cresses (Cardamine hirsuta L. and C. 
impatiens L.) several species of cranesbill (Geranium) and 
many balsams (Impatiens). 

The wind is, however, the most powerful and most obvious 
agency at work in the distribution of seeds, and an enormous 
number of modifications are noticeable among plants to secure 
dispersal by this means. 

In the orchises, poppies, and other plants, the seeds are small 
enough to be readily blown considerable distances in the air as 
soon as they escape from their capsules. Some seeds are smooth 
and round, and easily roll along the ground. More commonly, 
however, the adjoining bracts or some portion of the flower, fruit 
or seed, is modified in such a manner that it presents a large and 
light surface to the air, and the whole structure is thus rendered 
buoyant. 

In many plants of the Compositae (Chap, xxxiv.), such as 
thistles, groundsel, and dandelion (Fig. 148), the catyx is repre- 
sented by a tuft of long delicate hairs which act as a parachute 
capable of preventing the rapid fall of the fruit when once the latter 
is taken up by the wind. Even in a moderate breeze the fruits 
of such plants are canied long distances before they finally drop. 



102 THE FRUIT I DISPERSAL OF SEEDS 

In the kidney-vetch (p. 440) the calyx is large, thin, and 
inflated, and in some species of clover the faded corolla is large 
and of small weight in comparison with the single-seeded pod 
which it encloses. 

The perianth in many docks developes into thin wing-like 
projections surrounding the fruit, and winged extensions of the 
pericarp are seen in the ash, sycamore, elm, and certain um- 
belliferous plants. Some of these fruits are of such weight that 
they fall almost vertically when allowed to do so, although 
with a slow spinning motion. They are, however, only de- 
tached by strong winds or gales, and under these circum- 
stances, may be carried considerable distances. Not only are 
the external parts of the pericarp and other portions of the 
flower modified for wind distribution, but the seeds themselves 
of many dehiscent fruits show similar adaptations to the same 
end. In the willow, poplar, willow-herb (Epilobium), and 
cotton, the testa is more or less covered with long, silky, 
buoyant hairs, and many seeds, such as tulip and yellow rattle 
(p. 6 1 8), have thin, wing-like membraneous margins. 

In the hop, and most grasses, the buoyant agents are the 
bracts surrounding the fruit. 

Water-plants have fruits and seeds, the bracts of which enclose 
more or less air which enables them to float some distance. 

A large number of seeds are spread over the earth by animal 
agency. Upon the pericarp of the carrot, hedge-parsley ( Torilis)> 
and other umbelliferous plants, and also that of cleavers (Galium 
aparine\ and many medicks, spinous and hook-like structures 
are present, which cling to the fur, wool and feathers of animals. 
Similar hook-like projections are seen also on the receptacle of 
agrimony and on the involucral bracts of the common burdock 
(Arctium Lappa L.). Eventually the fruits are rubbed off or fall 
off the animal's coat in another locality from that in which they 
were collected ; in this manner seeds may be transported long 
distances. 



DISPERSAL OF SEEDS 103 

Moreover a number of succulent fruits are eaten as food by 
animals of various kinds, especially birds, and the seeds of such 
fruits pass through the stomach and intestines without injury. 

The protection of the embryo against the action of the 
digestive liquids of the body is generally afforded by the hard 
parts of the pericarp, or the seed coats. The alluring or 
attractive succulent parts of the fruit in drupes cherry, sloe, and 
plum, and in all berries, is the pericarp, or some part of it, while 
in the strawberry, rose, apple, and hawthorn, the receptacle 
is the attractive portion. 

In the stone-fruits and hawthorn the hard, bony endocarp 
protects the embryo while passing through the body of an 
animal, and in berries the testa of the seed serves the same 
purpose. In the strawberry and rose-hip the seeds are pro- 
tected by the hard pericarp of the achenes. 

It will be noticed that when the seeds are unripe and unfit 
for dispersal the parts of the fruit used as food in all these cases 
are at first green, sour, and firm in texture. But at the time of 
ripening of the seeds, or soon afterwards, when they are ready 
for distribution the parts of the fruit change to some conspicuous 
colour, become softer and sweeter, and often develope a distinct 
and characteristic odour. 

Ex. 47. Examine the fruits of common weeds and endeavour to find out 
how the seeds are dispersed in each. 

Ex. 48. Notice the number and kinds ot seeds and fruits attached to the 
wool of sheep ; also to the fur of dogs after passing through a dense copse in 
summer or autumn. 

What means of attachment do the fruits exhibit ? 

Ex. 49. Look out for evidence of the dispersal of seeds by birds : 
(a) Examine the excreta of fieldfares and thrushes in winter, 
() Observe the kinds of shrubs and trees which grow sometimes on 

the face of cliffs and walls of old ruins. Have they mostly 

succulent fruits? 
(c) What kinds of fruit have the plants found growing away from the 

ground on ojd trees? 



PART II. 

INTERNAL MORPHOLOGY (ANATOMY). 



CHAPTER IX. 
THE PLANT CELL: CELL-DIVISION: TISSUES. 

i. IN the preceding chapters we have been concerned with 
the larger external features of the bodies of flowering plants. 
It is now necessary to study the internal and minute structure 
of root, stem, leaf and flower in order that the physiology, or 
the work which each of these organs carries on may be satis- 
factorily understood. 

2. A knowledge of the internal structure is obtained by cutting 
thin slices of the various organs with a 
sharp razor, and examining these slices or 
sections as they are called with the naked 
eye and with the microscope. For a 
complete understanding of the nature and 
relationship of the several internal parts 
of any plant organ, it is not sufficient 
C to examine a section through it in one 
direction only : sections must be made in 
several directions. In stems, roots, and 
other parts, which are longer than broad, 
it is usual to make sections in the manner 
indicated in Fig. 47. Those cut at right 
angles to the main axis as at C, are 

termed transverse sections : those which are . cut parallel to 
the main axis are longitudinal section '5 u the terms radial and 

104 




THE CELL 



105 



tangential being added respectively to the latter according as 
the sections pass through the centre of the stem as at A> or 
not, as at B. 

3. The Cell. If a very thin section of a turnip ' root ' is 
examined with a microscope a kind of net-like structure is seen 
as in Fig. 48. By further examination of slices taken in several 
different directions, a 
similar appearance is 
observed in each case, 
from which we con- 
clude that the sub- 
stance of the turnip 
is composed of an 
enormous number of 
very small more or 
less cubical or spheri- 
cal compartments sur- 
rounded by thin 
walls. These closed 
chambers are called 
cells. Although they 
vary in size they 
are usually quite in- 

. ., . , -i j FIG. 48. Cells from the fleshy 'root' of a turnip, a Cell- 

VlSlDle tO the Unaided wall; s cell-cavity; n nucleus; i intercellular space. (Eu- 
i , larged 180 diameters.) 

eye, being rarely more 

than YJ-tf of an inch and not unfrequently as small as J^TT of an 
inch in diameter. A full-grown living cell (C, Fig. 49) taken 
from near the apex of a root or stem is seen to consist of the 
following parts : 

(i) A thin completely closed membrane (a) termed the cell- 
wall ; 

(ii) A continuous lining (r) of a substance known as proto- 
plasm ; and 

(iii) A central space (v\ the vacuole^ which appears to 




io6 



THE PLANT CELL 



be empty, but which is filled with a, watery liquid termed 
cell-sap. 

(i) The cell-wall is formed of a solid, elastic and transparent 
dead material, called cellulose by chemists ; it acts as a protective 
covering for the protoplasm and is manufactured by the latter. 

(ii) The protoplasm, which is the most important part of the 
cell, is a more or less slimy or jelly-like substance containing 



Jl 




Fig. 49. A) Very young cell from near the tip of a root. .#, Two older 
cells. C, Single full-grown cell ; a cell-wall ; r cytoplasm : n nucleus ; / 
plastids; v vacuole. (Enlarged about 350 diameters.) 

a considerable proportion of water. Its chemical nature is not 
understood, but within it there always appears to be a complex 
mixture of protein compounds. It is the substance directly 
associated with the peculiar phenomena which we call life. 
The process of respiration, and all the remarkable chemical 
changes involved in ' assimilation ' and nutrition generally, are 
due to the protoplasm, as well as the powers of growth and 
reproduction possessed by living organisms of all kinds, plants 
and animals alike. Wherever life is, protoplasm is present, and 
death implies its decomposition or destruction. 



PROTOPLASM 107 

In many cells the living protoplasm exhibits a characteristic 
spontaneous movement ; in some instances it flows in one 
direction in a continuous stream round and round the cell, in 
others, currents in several different directions are observed in the 
protoplasm. 

From Fig. 49 it is seen that the protoplasm of the cell is 
not homogeneous, but consists of the following parts : 

(a) A dense more or less spherical or oval portion (), the 
cell-nucleus ; 

(b) A number of smaller bodies (/), termed plastids or 
chromatophores \ and 

(c) A more liquid and finely granular substance the cell-plasm 
or cytoplasm (r), in which the nucleus and plastids are always 
imbedded. 

In very young cells (A, Fig. 49), the protoplasm entirely fills the 
cell-cavity and it is only after the growth of the cell that vacuoles 
appear. In the majority of living cells of the higher plants a 
single nucleus is present in each; in some long cells, how- 
ever, several nuclei are frequently found. 

All nuclei arise by the division of previously existing nuclei. 
Their functions are not completely known, but cells artificially 
deprived of them soon die. As the essential part of the sexual 
fertilisation process consists in the union of two nuclei it is 
thought that the latter are the carriers of the hereditary characters 
of the parent organisms from which they are derived. Moreover, 
in cell-division which results in multiplication of cells the nucleus 
seems to initiate and control the process of division. 

The thin lining of cytoplasm, or the primordial utricle as it is 
sometimes called, controls the passage of soluble substances into 
and out of the cell-sap filling the vacuole. 

The plastids are small bodies of protoplasm resembling nuclei 
in density : three kinds are recognised, namely 

(a) chloroplastSy (b) chromoplasts^ and (c) leucoplasts. 

They always arise frftm previously existing plastids by division 



108 THE PLANT CELL 

and like the nucleus are never produced de novo. The chloro- 
plasts, sometimes known as chlorophyll-granules , are green, their 
substance being saturated with a green-colouring matter named 
chlorophyll. All green parts of plants owe their colour to the 
chloroplasts in their cells, and the very important * assimilation ' 
process (chapter xvi.) is due to their activity. 

The chromoplasts, which are frequent in the cells of flowers 
and fruits, are yellow or red, instead of green, the parts of the 
plants in which they occur being rendered conspicuous by them 
and attractive to birds and insects. 

The term leucoplast is applied to all colourless plastids: 
examples are met with in roots, tubers and other underground 
parts of plants. They possess the power of forming starch-grains 
from sugar. The three kinds of plastids are convertible into one 
another ; the chloroplasts of green unripe fruits usually become 
chromoplasts when the fruit is ripe, and the leucoplasts of a 
potato tuber become green when the latter is exposed to light. 

(iii) The cell-sap filling the vacuole of the cell consists of 
water in which a number of substances are dissolved. In the 
cells of beetroot, as well as in many fruits, flowers, and leaves, 
the cell-sap contains a purple or reddish colouring-matter ; most 
frequently, however, it is colourless. It is generally acid, but the 
nature and amount of the compounds present in it often varies 
from cell to cell in different parts of the same plant. Various 
products of the activity of the protoplasm, such as sugars, soluble 
proteid, acids, and organic salts, are commonly present, as 
well as nitrates, sulphates, phosphates, and other inorganic com- 
pounds, absorbed from the soil. 

Most of the peculiar taste of the fruits and vegetables we eat 
is due to the substance dissolved in their cell-sap, the protoplasm 
and cell-wall being tasteless. 

4. The cells of the body of a plant at the time of their forma- 
tion at the growing-points of the root and stem, are all about the 
same size and cubical or polyhedral' in form. They soon 



THE CELL-SAP 



109 



increase in size and become variously modified in shape and 
structure in accordance with the special functions which they 
have to perform in the fully-developed organs of the plant. 

If during growth the cell-wall increases in all directions alike, 
the original cubical or polyhedral form is maintained ; most 
frequently, however, growth is irregular and the cells assume a 
great variety of shapes, the chief of which will be mentioned 
when dealing with the organs of the plants in which they occur. 

A great many cells after a time lose their protoplasmic contents 
and nothing then remains except the cell-wall and the cell-cavity 




FIG. 50. Diagrammatic illustration of thickened cell-wall; A t uniformly thickened 
wall ; K, wall with simple pits; C, wall with bordered pits. 

generally filled with air To these empty shells the term cell is 
commonly applied although some other term would be more 
suitable. Sometimes the cell-walls remain thin, but very often 
they become greatly thickened before the cell completely loses 
its protoplasm; such thickened cell-walls give firmness and 
strength to the structures which contain them and act as 
mechanical supports for the delicate parts of the plant 

The thickening consists in the deposition of successive layers 
of some form of cellulose on the inner surface of the cell-wall. 



1 10 



THE PLANT CELL 





Sometimes the layers are disposed uniformly all over the inside 
as in A) Fig. 50, but more frequently the increase in thickness 
goes on at some points more rapidly than at others. In some 
cases small areas of the cell-wall are left unaltered ; these thin 
places appear as bright spots termed pits when a surface view of 

the cell is examined. In simple 

<^ ~^> fC^^Sl pits (B) the cavity left unthickened 

I ^ : r~\ kxj: . ' -d is roughly cylindrical and viewed 

end on appears as a circle or ellipse. 
The cavity left unthickened in a 
bordered pit is funnel-shaped, and 
in surface view appears as two 
concentric circles or ellipses (C). 
The pits of one cell-wall are gener- 
ally exactly opposite the pits of an 
adjoining cell-wall, and serve as a 
means of communication between 
the two cells. 

Thickening in the form of spiral 
and annular or ring-like bands is also very common (Fig. 51). 

5. Cell-division : Mitosis: continuity of protoplasm. With 
the extension in length of the stem and root, and the production 
of new organs at the growing-points of ordinary green plants, 
a great increase in the number of cells takes place. This cell 
increase is the result of division of previously existing cells, all of 
which in any individual plant have originated from the division 
of a single cell, namely, the fertilised egg-cell of the ovule. 

During the process of division of a cell at the growing-point of 
a shoot or root, the nucleus first divides into two exactly similar 
halves. The two halves or daughter-nuclei then recede from each 
other a short distance in the dividing cell, and a new cell-wall arises 
midway between them. The new cell-wall divides the cytoplasm 
into two distinct parts, and is always placed at right angles to a 
straight line drawn from one nucleus to the other (Fig. 52). 



FIG. 51. Portions of vessels show- 
ing (i) annular, (2) spiral thickening 
of their walls. 



TISSUES iioa 

This process of division of a cell into two daughter-cells, termed 
mitosis, is complicated, and for a detailed account of it textbooks 
of cytology must be consulted ; it is sufficient here to refer briefly 
to the most important changes which take place in the nucleus 
when a living cell undergoes such division. 

In the so-celled resting stage, the nucleus is a spherical, or ovoid 
body, containing within a thin membrane, a variety of substances 
and structures, whose composition and arrangement need not be 
discussed here. 

By ' fixing ' the cell in certain chemical solutions, and staining 
it with various dyes at the time when the dividing process has 
begun, a long, thin, coiled thread is seen within the nuclear 
membrane (Fig. 520). Later this thread contracts and thickens, 
and then breaks into short pieces the chromosomes each of 
which is split lengthwise into two halves exactly similar in form 
and structure. 

The split chromosomes soon take up a regular position in the 
middle of the cell, as in Fig. 5 Fig. 52^, the nuclear membrane, in 
the meantime, having disappeared. 

The halves of each chromosome then separate from each other, 
one set of halves moving to one pole of the cell, the other corre- 
sponding set to the other pole, where they ultimately become 
incorporated into two new nuclei. Between the latter a cell-wall 
is formed, the original cell becoming completely divided into two 
daughter-cells each containing exactly the same number of 
chromosomes as the parent. 

The lengthwise division and separation of the chromosomes in 
mitosis ensures that the daughter-cells shall not only receive the 
same number of chromosomes as that possessed by the parent cell, 
but that each cell shall receive an equal share of every part of each 
chromosome. 

Chromosomes differ much in size and shape, and the number 
present in the vegetative or somatic cells of different species of 
plants varies between wide limits. 

The following are the chromosome numbers in a few common 
plants : 

Crepis virens . 6 Mangold . .18 
Broad Bean . 12 Cabbage . . 18 

Pea . . .14 Turnip . . 20 
Barley . . .14 Macaroni Wheat . 28 
Onion . * . 16 Bread Wheat . 42 



nob 



THE PLANT CELL 



The number is always even, for there are always present in each 
cell two sets of chromosomes each composed of an equal number, 
one set coming from the male, the other from the female side 











7 8 

FIG. 5a. Diagram illustrating mitosis of a vegetative cell, i, cell with resting nucleus; 
a, nucleus with coiled thread (spireme) ; 3, four chromosomes arising from transverse 
divisions of spireme, two (a 1 ) being derived from one parent, two (a*) from the other: 
4, the chromosomes split longitudinally ; 5, chromosomes at centre of cell (equatorial 
plate) ; 6, their separation ; 7, nuclei of daughter-cells, each with four chromosomes as in 
the parent cell ; 8, daughter-cells with resting nuclei. 

(4, Fig. 5 2 a) ; thus the chromosomes in the body cells of a plant 
or animal exist in pairs, the individuals of each pair being homolo- 
gous or exactly alike in form, structure and chemical composition. 
A study of the process of the formation of the gametes or 



TISSUES 



ill 




uniting cells taking part in fertilisation will make these facts 
clear (see p. 279). 

From ordinary examination of cells and their contents, it 
might be concluded that 
the living material of a 
typical plant-cell is com- 
pletely shut off by the 
cell-wall from communi- 
cation with its immediate 
neighbours. 

It has, however, been l 2 3 

shown thit in a number of FlG> 52 --i- Youn K cell previous to cell-division ; 
snown inai manumoer or ^ the , amea ft<-rdiv.s.on of the nucleus; 3 , cell- 
instances, the protoplasm division completed (enlarged 500 diameters). 

of one cell is connected with that of adjoining cells, by means 
of extremely delicate protoplasmic strands which pass through 
minute openings in the cell-walls, and it appears very probable 
that the whole protoplasm of an organism is continuous. 

In some instances, as in the embryo-sac of the ovule, the suc- 
cessive division of a nucleus and its associated cytoplasm goes on 
fora time without being immediately followed by the formation of 
corresponding cell-walls ; sooner or later, however, the protoplasm 
of almost all vegetable cells becomes enclosed in a cell-wall. 

6. Tissues. The body of a plant consists of a vast number of 
cells of very varied forms. These different kinds of cells, instead 
of being distributed uniformly through the plant, are associated 
together in the form of bands, plates and cylindrical masses : 
such associated groups of cells are spoken of as tissues. The 
latter may be classified in many ways according as we take into 
consideration their origin, structure or function. A tissue con- 
sisting of thin-walled living cells which are embryonic and capable 
of division is termed a meristem or formative tissue^ the fully- 
developed adult tissues being spoken of as permanent. 

Taking into consideration the form of the cells composing 
them, two chief types *)f tissues may be distinguished, namely, 

9 



112 THE PLANT CELL 

parenchyma and prosenchyma. Between them no sharp distinction 
can be made, but the former usually consists of cells which are in- 
dividually much the same in length, breadth and thickness, and 
each cell is united to its neighbours by broad flat ends and sides. 
Although in young tissues all the cells are in complete contact 
at all points of their surfaces, in permanent parenchymatous tissues 
the common cell-walls of adjoining cells frequently separate from 
each other at the angles and give rise to intercellular spaces (/, Fig. 
48), which are generally rilled with air. It is important to note, 
however, that in some cases intercellular spaces arise through the 
complete dissolution or drying-up of masses of cells in which 
instances the cavity left is most commonly filled with gums, oils, 
resins and other excreted products. 

The cells of prosenchymatous tissue are long and pointed at 
both ends ; moreover, the ends dovetail between each other and 
fit closely without intercellular spaces. Prosenchymatous and 
parenchymatous tissues, whose cell-walls are thickened and hard, 
are distinguished as sclerenchyma. 

Ex. 50. Take one of the inner fleshy leaves of an onion bulb, and, after 
making a shallow cut into the surface with a sharp knife, tear or strip off a 
small portion of the ' skin.' Place it in eosin solution or red ink for a few 
minutes : then wash it and mount in a drop of water on a glass slide. 
Examine with a microscope, first using a low, and subsequently a higher 
power. Notice and make drawings of the cells, their cell- walls, stained 
nuclei, protoplasm, and vacuoles. 

Ex. 51. Cut very thin slices of a turnip with a sharp razor and examine 
in a similar manner ; observe the intercellular spaces between the cells. Cut 
slices of A coloured beet-root : examine without staining, and notice the 
coloured cell -sap. 

Ex. 52. Make and examine a section of Elder pith : observe the form and 
size of the dead cells and also the thickness and markings of the cell-walls. 

Ex. 53. Make transverse and longitudinal sections of the wood of an 
ordinary safety match, notice the thickness and markings of the cell-walls. 
Examine in a similar manner pieces of other common woods. 

Ex. 64. Cut thin slices of the leaves or any green part of a plant : 
examine the cells and notice the greenness is not due to coloured cell -sap, 
but to the existence of numerous small green chloroplasts. 



CHAPTER X. 
THE ANATOMY OF THE STEM, ROOT, AND LEAF. 

WE propose in the present chapter to discuss the general 
arrangement and structural character of the various ordinary 
tissues in the different plant organs and incidentally to mention 
their uses in the economy of the plant leaving the more detailed 
account of physiological processes for subsequent chapters. 

THE STEM. 

A. The Herbaceous stems of dicotyledons. 

A great portion of the herbaceous stems of dicotyledons consists 
of soft succulent tissue, in which are imbedded a number of 
thin, tough, stringy strands termed vascular bundles. The latter 
give firmness to the stem, but their chief function is the conduc- 
tion of sap to all parts of the plant. 

Covering the surface of the stem 
is a thin skin or tissue of cells called 
the epidermis. To the remainder of 
the tissues, that is, to all except the 
epidermis and vascular bundles, the 
term fundamental or ground tissue is 
applied. 

In a transverse section of the stem 
the vascular bundles are seen to be 
arranged side by side in a circle 
(Fig. 53). That part of the fundamental tissue enclosed by the 
ring of vascular bundles is spoken of as the medulla QI pith (/), 
the part outside the ring is the cortex (c), while the small narrow 

113 




114 ANATOMY OF STEM, ROOT AND LEAF 

bands running radially between the bundles and connecting the 
cortex with the medulla are the medullary rays (m\ 

The vascular bundles, together with the medullary rays and 
pith, form a cylindrical mass of tissues known as the vascular 
cylinder or stele, which extends continuously throughout the 
plant from the tip of the stem to the growing-point of the 
root. 

(i) The epidermis is usually one cell thick and acts as a pro- 
tective coat for the plant, preventing the latter from too rapid 
loss of water and also defending the delicate internal cells of the 
plant against mechanical injuries due to rain, hail, frost and 
insect attacks. 

The cells are tubular flattened cells fitting quite closely to- 
gether, except where the openings named stomata occur : as 
the latter are more abundant in the epidermis of a leaf, their 
structure is deferred to page 145. Usually the outer cell- wall 
of each epidermal cell is much thicker than the lateral and 
inner walls, and is differentiated into two or three layers, the 
outermost layer in contact with the atmosphere being spoken of 
as the cuticle. The cuticle is composed of a substance known as 
cutose, which is very impervious to water, and a remarkably stable 
body capable of resisting the action of various solvents which 
dissolve ordinary cellulose. 

On the cuticle of the stems and leaves of cabbages, swedes, and 
many varieties of cereal and other grasses, as well as on grapes 
and plums, an ash-coloured bloom is seen. It is an excreted 
product of the epidermal cells, and consists of minute round, 
rod-like or scaly particles of wax. Surfaces of the different parts 
of plants covered with this bloom lose less water than those 
from which the substance has been removed by rubbing. 

This waxy layer appears also to act as a partial protection 
against the attacks of fungi and insects. 

The cells of the epidermis contain the usual cell-contents 
with the exception of chloroplasts which are generally missing j 



CORTEX IIS 

they are especially rich in cell-sap, which is often tinted pink, 
red or purple by a colouring matter which appears to protect the 
cells of the cortex from excessive light. In some plants, if not 
in all, the cell-sap of the epidermal cells functions as a store 
of reserve water upon which the more internal cells of the stem 
can draw in time of need. 

It is well known that the surface of stems and other parts of 
plants are frequently covered with hairs. These belong to the 
epidermis, and in their simplest form are merely single cells 
which have grown much longer than their neighbours. Some 
hairs are, however, multicellular extensions of the epidermis 
(h, Fig. 54), and like the unicellular hairs may assume a great 
variety of shapes. 

Hairs are often harsh to the touch, and furnish a means of 
defence against insects and animals generally. They also act as 
a mantle which prevents too rapid escape of water from the 
plant, and acts as a screen against excessively bright sunshine. 

In young stems and buds, hairs protect the tender parts 
against injury by frost. Certain hairs function as secreting 
organs, and are then designated glands (Fig. 106) : they often 
produce resinous and oily compounds, which in the case of 
mint, hop, and other plants have a characteristic odour. Many 
excreted products of such hairs are sticky, and effectually prevent 
insects such as ants from climbing up the stem and getting 
at the nectar of the flower. 

(ii) The cortex of the stem extends from the epidermis to 
the vascular cylinder. A great part of it generally consists of 
living parenchymatous cells which contain abundant chloroplasts. 
The cells of the portion immediately beneath the epidermis 
frequently have their cell-walls thickened at the corners, and 
form what is spoken of as collenchymatous tissue : the latter serves 
to strengthen the epidermis, and gives rigidity to the whole 
stem. The innermost layer of cells belonging to the cortex 
forms a continuous sneath surrounding the vascular cylinder 



Il6 ANATOMY OF STEM, ROOT AND LEAF 

termed the endodermis (<?#, Fig. 54) ; its cells are not very much 
differentiated from the rest of the neighbouring cortical cells, but 
they usually contain numbers of starch-grains which render them 
somewhat conspicuous in sections of certain stems. 

(iii) The vascular cylinder or stele includes all the tissues 
inside the endodermis, namely, the vascular bundles described 
below, and also the medulla or pith and the medullary rays. 




FIG. 54. Transverse section of the stem of a sunflower (enlarged 
about 8 diameters.) Jf, portion including a vascular bundle ; e epi- 
dermis ; h a hair ; c cortex ; en endodermis ; w wood ; b bast ; fc 
fascicular cambium ; ie interfascieular cambium ; b pericycle fibres; 
m medulla or pith. 

The outermost portion of the stele which lies immediately 
in contact with the endodermis is known as the pericycle. The 
latter may consist of a single layer of cells or of more than 
one layer; in some stems, its cells are thin-walled, and from 
it arise most adventitious roots and shoots. 

The medullary rays and pith are composed of thin-walled 
parenchymatous cells ; the cells of the medullary rays generally 
retain their living contents for a long-time, but those of the 
pith live for a short time only. 



VASCULAR CYLINDER OR STELE n; 

If we select an individual bundle in the internode of almost 
any dicotyledon and trace it upwards it will be found to pass 
out of the stele across the cortex and into the leaves, where it 
branches and forms the veins. Bundles of this kind common 
to both leaf and stem are termed common bundles^ that part of 
each present in the stem being spoken of as the leaf-trace of the 
bundle. From each leaf one or several bundles may enter the 
stem, and on being followed downwards they are found to 
descend perpendicularly through one or more internodes, finally 
uniting with bundles which have entered the stem from older 
leaves lower down. The bundles in their descent all keep about 
the same distance from the centre, so that in a transverse section 
they appear arranged in a circle. 

Great variation exists in the manner and amount of branching 
and union of the bundles in different plants, but the arrange- 
ment is always such that the vascular bundles of the leaves, 
stems and roots form a continuous conducting system of tissues 
specially adapted to facilitate rapid and easy transmission of sap 
to all parts of the plant. 

In this type of stem each vascular bundle consists of three 
kinds of tissue, namely : 

(1) xylem or wood (n, i, Fig. 55); 

(2) phloem or bast (d) ; and 

(3) a thin-walled meristem tissue termed the cambium of 

the bundle (c). 

These tissues are arranged side by side in such manner that 
in a transverse section of the stem a radius drawn from the 
centre to the outside passes through all three; the cambium 
lies between the wood and the bast, the wood being nearest 
to, and the bast farthest away from the pith. 

Bundles in which the wood and bast lie on the same radius 
are termed collateral bundles ; when as in dicotyledons they 
also possess cambium they are said to be open. 

(a) Wood or xylem. The structural elements met with in the 




wood 



fast 



FIG. 55. i. Transverse section of a vascula^ bundle of a sunflower 
stem (enlarged about 12 " 

2. Longitudinal radial 

n the wood; d the bast , . 

f fibre ; o pitted vessel ; s sieve tube ; t companion-cell ; b pcricycle fibres; 



120 diameters). Enlargement of X J" previous fig. 
lal section through the same. / Medulla of stem ; 
bast ; c the cambium of the bundle ; a spiral vessel ; 



VASCULAR CYLINDER OR STELE 119 

wood are usually (i) vessels or trachea ', (2) tracheids^ (3) fibres 
and fibrous cells, and (4) wood-parenchyma, all of which 
commonly have much thickened firm cell-walls consisting of 
lignocellulose. The proportion is not the same in all bundles 
and in some cases certain structures are missing altogether ; 
tracheae or tracheids, however, are constantly present in all wood. 

The vessels or trachea (a and o) are not cells, but long con- 
tinuous open tubes, each formed from a row of superimposed 
cells, many of the transverse cell-walls of which have been ab- 
sorbed or dissolved away. In some climbing plants the cavities 
of the vessels are 9 or 10 feet long : according to Adler's 
measurements, the vessels of oak wood average about 40 
inches long, those of hazel and birch about 5 inches. Their 
walls always exhibit either annular, spiral, or reticulate thicken- 
ing or pits. Those first formed in the bundle possess only 
annular or spiral thickenings, and constitute the protoxy- 
lent. 

At first all vessels contain protoplasm, but during their growth 
the living substance is used up in the thickening of the cell walls: 
when fully formed they are dead empty structures which serve 
for the conduction of water. 

Tracheids resemble vessels in the character of their cell-walls 
and in their function : they are, however, long, single, empty 
cells and not compound structures. 

The fibrous cells are long and pointed at both ends ; they 
possess living contents and their cell-walls are most frequently 
thickened and sometimes marked with small pits. Fibres (/) 
are similar thick- walled cells which have lost their protoplasmic 
contents and contain air or water only. 

The wood-parenchyma consists of somewhat elongated cells 
with square, blunt ends and living contents : the cell-walls are 
thickish and slightly pitted. In these cells starch is often stored. 

() Bast or phloem. The elements composing the bast or 
phloem are (i) sieve-tube* or bast-vessels (s) with their companion 



120 ANATOMY OF STEM, ROOT AND LEAF 

cells (/), and (2) a certain amount of thin-walled bast-parenchyma ; 
their cell-walls consist of ordinary cellulose. 

The bast-vessels are long thin-walled cells arranged end to end, 
The transverse or end-walls which separate one vessel from 
another, are not completely absorbed as in the vessels of the 
wood, but merely perforated by open pores through which the 
contents of adjoining vessels are in 'continuous open communica- 
tion : these transverse perforated walls are called sieve-plates. 

When mature the bast-vessels contain a thin lining of cytoplasm 
but no nucleus : the rest of the cell-cavity is filled with an alkaline 
slimy substance, rich in proteids, and frequently containing 
starch-grains as well. 

The bast-vessels serve for the conduction of various complex 
organic substances, but more especially for those of a proteid 
character. 

The companion-cells are long narrow cells which lie alongside 
the sieve-tubes : they are filled with granular cytoplasm in which 
a nucleus is always present. Both the sieve-tube and its com- 
panion-cell arise from the same mother-cell. 

(c) Cambium. The cambium lies between the wood (t, Fig. 
55) and the bast, and consists of a layer of thin-walled meris- 
tematic cells, each of which has the form of a long, narrow, 
rectangular prism with obliquely pointed ends. 

In young stems the cambium is confined within the vascular 
bundles, but in older ones a new and exactly similar meris- 
tematic tissue termed the interfascicular cambium arises in the 
medullary rays, and extends across the latter, joining the 
cambium of one bundle with that of the next (/V, Fig. 54). We 
thus have in the older stems a thin complete cylinder of dividing- 
cells which in transverse section appears as a narrow zone, spoken 
of as the cambium-ring. 

The cambium-ring adds new elements to the wood and bast 
of the stem in a manner explained below ; but in short-lived 
herbaceous dicotyledons this additional growth soon ceases, so 



VASCULAR CYLINDER OR STELE 121 

that its effect is not so noticeable in these as in perennial woody 
stems. 

Ex. 55. Cut across the young soft stems of the sunflower, Jerusalem arti- 
choke, groundsel, bean, potato, and any other common herbaceous plants. 
Examine the cut surfaces with a pocket lens, and observe the presence and 
arrangement of the vascular bundles and pith. 

Ex. 56. Place some young sunflower stems in a mixture of two-parts methy- 
lated spirit and one-part of water. Keep them in this mixture for further 
use. From a stem which has been in the mixture three or four days cut 
very thin transverse sections with a razor wetted with the mixture. Transfer 
the sections to a watch glass containing water ; after remaining in the water 
for a few minutes, take one out and mount it in a drop of water on a glass 
slide. Cover with cover-slip and examine with the lowest power of the 
microscope. 

Make drawings indicating the position and general character of the 
(a) epidermis, 
(6) cortex, 

(c) endodermis, 

(d) vascular bundles, 

and ((} pith and medulla; y ray tissue between the bundles. 

Examine with a high power, and make sketches of small portions of the 
various parts above-mentioned, paying especial attention to the wood, 
cambium and bast (compare Fig. 55). 

Try and see if the interfascicular cambium has been formed across the 
medullary rays. 

Ex. 57. Take a piece of sunflower stem about a quarter of an inch long, 
preserved as in preceding exercise, and cut longitudinal sections so as to 
pass through a vascular bundle. (In cutting longitudinal sections of stems, 
the razor should cut from one side of the stem to the other, not from end 
to end.) 

Examine first with a low and then with a high power : make sketches of 
the form of the cells met with in the epidermis, cortex, bast, cambium, wood 
and pith respectively. 

Try and determine which cells of the longitudinal section correspond with 
those seen in the transverse sections. 

Ex. 58. Make a careful study of the anatomy of a stem of groundsel, 
bean, and other common herbaceous dicotyledons. 

Always begin the examination of sections with the lowest power at dis- 
posal, namely, with the naked eye or a good pocket lens. After the general 
arrangement of the chief tissues is understood, then apply higher powers in 
succession. 



122 ANATOMY OF STEM, ROOT AND LEAF 



B. The perennial woody stems of dicotyledons. 

(a) Division of the cambium-cells. In the earliest stages of 
the stems of shrubs and trees the arrangement and constitution 
of the tissues are essentially the same as in simple short-lived 
herbaceous stems. With an increase in age there is, however, a 
steady increase in thickness from year to year, and in transverse 
sections of such thickened stems the isolated small vascular 
bundles, so obvious when the stems are very young and soft, 
are no longer visible. 

The greatest part of the increased bulk of tissues in such stems 

as these, is brought about by divi- 
sion of the initial cells of the 
cambium-ring. 

Each initial cambium-cell (a, 
Fig. 56) divides in two by a wall 
parallel to the surface of the stem ; 
one of these two daughter-cells 
remains capable of division while 
the other is either directly con- 
verted into a permanent cell, or 
divides once or twice, after which 
the cells produced become gradu- 
ally changed into permanent 
structures. The change into a 
permanent cell or cells may hap- 
pen to either of the two produced by division of the initial 
cell ; if the inner one is modified it is added to the wood (w), if 
the outer one is altered it goes to increase the bast (b). 

Division of the cambium-cells, and the growth and development 
of the products continue from spring to autumn ; in winter, cell- 
division ceases. Since the cambium extends in the form of a con- 
tinuous cylinder within the mature stem, a new cylinder of wood 
is added every growing season to the outside of that already 




FIG. 56. Transverse section through 
a small portion of the cambium-ring 
in a young black currant shoot, c Cam- 
biurn ; a initial cell ; iv wood ; b bast; 
/;/ medullary ray. ( Enlarged about 450 
diameters ) 



ANNUAL-RINGS : KNOTS 



123 



present, and a similar addition is made to the bast on its inside. 
The amount of wood produced by the cambium is always very 
much greater than the bast. Moreover, the bast tissue consists 
chiefly of thin-walled elements which become crushed into very 
thin sheets by the pressure of the expanding wood and the re- 
sistent bark, whereas the wood with its thick-walled cells and 
vessels suffers little in this manner ; in transverse sections of the 





a 



FIG. 57.- i Piece of a stem of an ash tree A, Portion three 
years old ; B, portion two years old. 2. Longitudinal and 
transverse sections of same. 

trunks and branches of trees and shrubs the cambium appears to 
the naked eye to produce wood only. 

(b) Annual rings : knots. If a tree is sawn across and the 
cut surface then smoothed with a chisel a number of ring-like 
zones are noticeable in the wood (Figs. 57 and 58); these are 



124 ANATOMY OF STEM, ROOT AND LEAF 

termed annual-rings and each represents the wood-tissue pro- 
duced by the cambium during one active vegetative period. 
From the beginning of one vegetative period to the commence- 
ment of another is generally one year, so that in a two-year-old 
stem two rings are visible, in one three-year-old three rings are 
seen, and so on (Fig. 57). 

It is on account of certain differences between the wood made 
at the commencement of the growing season and that produced 
at the end that we are able to recognise these successive yearly 
additions to the wood as distinct bands, for if the structures pro- 
duced by the cambium were of exactly similar character through- 
out its life, it would not be possible to determine the points at 
which the cambium had ceased or recommenced its growth. 

When the cambium commences growth in spring it gives rise 
to vessels and cells with thinner walls and wider cell-cavities 
than those which it manufactures in late summer and autumn ; 
in each annual ring (r, Fig. 64), therefore, two more or less 
distinct portions are visible, namely, (i) a layer of spring-wood (s) 
produced early in the growing season, and (ii) a layer of what is 
termed autumn-wood (a) produced in late summer and autumn. 

The spring-wood is generally of soft nature and pale colour ; in 
oak, elm, ash, and Spanish chestnut its vessels are so wide that 
they appear to the naked eye as a zone of pores. 

The autumn-wood is harder and generally of darker colour ; 
fewer vessels are present in it, and they are usually too small to 
be seen with the naked eye. 

The cambium of a stem is continuous with that of its 
branches, and in a longitudinal section (Fig. 58) the annual 
increment to the wood of the stem is seen to be continued in 
the branches, although in the latter the amount added per 
annum is smaller than in the stem, and consequently the annual 
rings of a branch are narrower than those of same age in the 
stem. 

It will be seen from the above Fig. 5^ that the basal portions 



ELEMENTS PRODUCED BY THE CAMBIUM 125 

of a branch become buried by the wood added to the stem 
year by year : on cutting a longitudinal board as indicated at 
C, the buried part of the branch is cut almost transversely, and 
appears as an oval knot (fc). 

(c) Structures produced by the cambium : medullary rays. 
As the cambium lies between the wood and bast, it is obvious that 
the primary first-formed wood and bast of the vascular bundles 




FIG. 58. A, Stem of a tree six years old with branch b ; B, longitudinal section of the 
same, snowing all annual rings of stems except the first continued in branch; D } longi- 
tudinal board cut from A; Xrknot (transverse section of branch b) ; / pith. 

must be gradually pushed further apart by the secondary wood 
and bast produced by the cambium, so that in old stems the 
primary wood is found surrounding the pith in the centre, 
while the primary bast is met with near the outside (<7, Fig. 60), 
The structural elements forming the secondary wood are similar 



126 ANATOMY OF STEM, ROOT AND LEAF 

to those of the primary wood, namely, tracheae or vessels, 
tracheids, fibres, fibrous cells and wood-parenchyma; the vessels 
and tracheids, however, are never spirally or annularly thickened, 
but usually marked with bordered pits and reticulate thickenings. 

All these structures may be present or only a few; for 
example, the wood of the yew consists of tracheids only, that of 
the bulk of coniferous trees of tracheids and wood-parenchyma, 
while the wocd of most dicotyledons contains all the above- 
mentioned structures. 

The elements of the secondary bast are similar to those of 
the primary bast, namely, sieve-tubes with their companion-cells 
and parenchyma; bast-fibres and living fibrous cells are also 
present in some cases. After functioning for a short time as 
conductors of food, the sieve-tubes, companion-cells and most of 
the bast-parenchyma become empty, and in the older parts are 
compressed into an irregular mass in which no cell cavities are 
visible. When firm thick-walled bast-fibres are abundant, as 
in lime and other trees, the bast in transverse sections appears 
in the form of thin, ring-like bands. 

Besides the production of wood and bast, certain cells of the 
cambium-ring become changed into medullary ray cells (0, 
Fig. 56); the primary medullary rays existing between the 
first-formed vascular bundles of the unthickened stem are con- 
tinued by the interfascicular cambium when thickening begins 
and therefore always extend right through from the pith to 
beyond the bast. Totally new secondary medullary rays are 
subsequently started by certain cells of the cambium ring at 
successive irregular intervals during the growth in thickness. 
These new medullary rays extend from the annual rings of 
wood in which they first appear to the corresponding bast 
rings on the opposite side of the cambium ; they are therefore 
of variable length. 

The medullary rays are of variable width even in the same 
stem. Sometimes they are only one cell thick and in trans- 



HEART-WOOD AND SPLINT-WOOD 127 

verse sections are scarcely visible to the naked eye, while in 
oak, beech and other kinds of timber, many of them are several 
cells thick, and in transverse sections appear as distinct light- 
coloured radial bands (m t Fig. 64). In true radial longitudinal 
sections, when seen at all, they appear as transverse bands of 
variable vertical diameter running from the pith outwards 
(Fig. 62), the primary rays have the greatest vertical breadth. 
In longitudinal sections cut obliquely to the radius of the 
stem small portions only are visible as bran-like spots. 

The cells of the medullary rays are brick-shaped, generally with 
thick pitted walls and living contents, which they often retain for 
a long time. They conduct various food-products manufactured 
in the leaves, and in winter starch and various food-substances 
are stored in them for use in the following season. Air circulates 
to all parts of the wood and bast in the intercellular spaces be- 
tween the medullary ray cells. 

(d) Heart-wood and splint-wood. In the old stems of oak, 
walnut, larch, yew and other trees, the wood of the annual rings 
in the centre of the tree is heavier, harder, darker in colour, and 
drier than that of the younger rings near the cambium: this 
dark wood is known as heart-wood or duramen^ while the light- 
coloured softer wood surrounding it is termed splint-wood } sap- 
wood or alburnum. The width of the splint-wood or the number 
of annual rings over which it extends is not the same in all trees, 
nor is it always the same in the same species of the same age. 

The splint-wood is the part which conducts the * sap ' and many 
of its parenchymatous cells are still living: starch, sugar and 
other compounds readily attacked by fungi are generally stored in 
it, and from its liability to rot it is valueless as timber. 

The heart-wood acts as a strong support for the rest of the 
tree : its vessels no longer conduct water and the parenchyma 
of the wood and medullary rays have lost their living contents. 
Various gummy and resinous compounds block up the cell- 
cavities and in some cases calcium carbonate is present in 

10 



128 ANATOMY OF STEM, ROOT AND I EAF 



them. Tyloses or peculiar bladder-like protrusions from the 
adjoining thin-walled cells also block up the cavities of the 
vessels. Tannin and colouring matters are also present in 
the cell-membranes and cavities of the heart-wood of many trees. 
Some of these substances act as preservatives against the attacks 
of insects and fungi, and to them the durability of the heart- 
wood is due. Whilst in oak, ash, elm, walnut, apple, laburnum, 
larch, various pines, and many other trees a considerable 
difference in colour is observable between the heart-wood and 
splint-wood ; in beech, hornbeam, sycamore, lime, silver-fir, and 
spruce no such distinction of colour is visible to the naked eye ; 
but the heart-wood of these trees can frequently be distinguished 
from the splint-wood by its dryness, although small numbers of 
living cells are sometimes present in wood of this character right 
through to the pith even in trees of considerable age. Trees of 
the latter type are more liable to become hollow than those in 
which a coloured heart-wood is present. 

(e) Periderm. In annual 
and perennial herbaceous 
stems, the epidermis and 
primary cortex grow at the 
same time as the cambium 
is increasing the bulk of wood 
and bast in the vascular 
cylinder, so that a continuous 
covering is maintained in 
such stems in spite of the 
internal growth in thickness. 
Even in some woody stems, 
such as mistletoe and holly, 
the epidermis persists and 
keeps pace for years with the 
growth of the wood and bast within. In the majority of woody 
stems, however, the epidermis and primary cortex are ruptured 




'hel- 



FIG. 59. Transverse section throu 
derm of a young black currant shoot, 
logen ; c cork ; b phelloderm just forming J f 
bast of the stem ; ^withered primary cortex ; t 
epidermis. (Enlarged 270 diameters.) 



PERIDERM 129 

by the pressure exerted by the growth of the wood, and their place 
is taken by totally new tissues which arise by division of a meristem 
tissue known as the phellogen or cork-cambium (a, Fig. 59). 

This phellogen may arise in the epidermis itself, in the cortex 
or even in the pericycle within the vascular cylinder. The 
divisions of its cells take place in a manner similar to those of 
the ordinary cambium, but instead of producing wood and bast 
tissue it gives rise on its inside to phelloderm or secondary cortical 
tissue (b) and on its outside to cork (c). To the phellogen and 
the products of its growth the term periderm is applied. 

In most aerial stems little or no phelloderm is formed : when 
present its cells have thin walls, and protoplasmic contents ; 
chloroplasts are generally present in the tissue when it is 
developed near the surface of the stem. 

The cork-tissue formed by the phellogen shields and protects 
the interior of the stem from mechanical injuries and prevents 
the stem from losing water by transpiration. 

Cork is also a bad conductor of heat and efficiently protects 
the delicate phellogen and cambium from excessive heat in 
summer and frost in winter. 

It consists of a number of layers of cells which fit closely 
together in regular radial rows (c). The cells soon die and 
generally become rilled with air only ; their walls are mostly thin, 
often brownish in colour and impermeable to water and gases. 

' Corks ' for bottles are cut from the extensive cork-tissue of 
the Cork Oak (Quercus Suber L.). 

When the phellogen originates in a deep layer of cortical 
cells or in the pericycle, all the tissues outside it become cut 
off from water and food supply by the cork which is formed : 
these tissues dry up in consequence, and, together with the 
cork constitute what is sometimes spoken of as bark by botanists, 
although in popular language the term bark is applied to all 
tissues which are external to the cambium of a stem. 

Scattered over the outer surface of the periderm of most woody 



130 ANATOMY OF STEM, ROOT AND LEAF 

branches and stems are small brownish or whitish spots termed 
lenticcls\ they are well seen on stems of the elder, potato tubers, and 
A B 




C' 



FIG. 60. Diagrams illustrating secondary growth in thickness of the stem of a dico 
tyledon. A, A young stem before the formation of interfascicular cambium. J3, After inter- 
fascicular cambium has formed. C, The same stem two years old. ( e Epidermis ; c cortex ; 
it endoderrnis ; t pericycle ; w primary wood ; r cambium ; b primary bast of a vascular 
bundle ; r 1 interfascicular cambium; / pith or medulla ; tn medullary rays; n phellogen ; 
o cork ; c 1 secondary cortex ; x^ and x* annual rings of secondary wood ; f 1 and ** 
rings of secondary bast. , 



HEALING OF. WOUNDS ON WOODY STEMS 131 

young apple and pear shoots. On ordinary shoots they are 
developed at the places where stomata occur in the epidermis 
and serve for the admission of air through the periderm into the 
intercellular spaces of the medullary rays and other parts of the 
stem. 

(/) Healing of wounds on woody stems. Wounds made into 
the soft parenchymatous parts of herbaceous stems, leaves, tubers, 




FIG. 61. A, Stem with amputated branch (J) ; c callus. 

B, Longitudinal section of A ; c callus formed by exposed cambium ; b exposed wood 
of the branch. 

C, Longitudinal section after the exposed wood of the branch has been completely 
covered over by five annual growths (). 

and fruits soon become healed over by the formation of a layer 
of cork-cells which develop from the uninjured cells exposed 
by the wound. When the mature wood of a stem or branch 
is exposed (l>, Fig. 61) it becomes covered by the gradual 
extension of a tissue manufactured chiefly by the cambium. 
The cambium exposed ,by the cut and the very young cells of 
the wood and bast at first give rise to a mass of soft parenchyma- 



132 ANATOMY OF STEM, ROOT AND LEAF 

tous tissue termed callus (c\ In the outer parts of the latter 
there soon forms a cork-cambium while within it is developed 
a new cambium from which wood and bast are ultimately pro- 
duced. Year by year the new tissues produced by the cambium 
extend further and further inwards over the exposed wood (b) 
until the edges meet all round, after which time the cambium 
exists as a continuous layer over the wounded surface (C 1 , Fig. 61). 

The new wood formed as a cap-like covering over the exposed 
old wood (<) does not actually coalesce with the latter and the 
position of old wounds into the wood can always be easily 
recognised in sections, although they may be so completely 
overgrown and buried in the succeeding growth that no external 
sign of their existence is visible. 

The length of time necessary to cover a wound depends upon 
its size, and the vigour and nutrition of the cambium. Clean 
cut wounds heal more rapidly than jagged ones, and when large 
branches are amputated with a saw it is advisable to trim the 
exposed edges of the cambium with a sharp chisel or knife. 
In the case of wounds where a considerable portion of old 
wood is laid bare and which cannot therefore be overgrown 
in a short time it is also important to cover this portion of 
the wounded surface with Stockholm tar or some similar 
antiseptic dressing to prevent its decay. 

Ex. 69. Cut across one, two and three year old branches of ash, and 
make the surface of the section smooth with a sharp knife : notice the annual 
rings in each. 

Make longitudinal sections of similar pieces of ash twigs, and notice the 
arrangement of the yearly growths where one piece joins another a year 
younger (compare with Fig. 57). 

Make similar observations on as many common trees as possible. 

Ex. 60. Prepare sections of a piece of a larch pole 4 or 5 inches in 
diameter : cut with a saw and then carefully smooth with a sharp chisel or 
plane. 

Transverse, longitudinal, and oblique sections should be made. 

Study the arrangement of the yearly rings in sections cut as in Fig. 58 to 
illustrate the nature of a knot. 



HEALING OF WOUNDS ON WOODY STEMS 133 

Ex. 61. Examine boards of different kinds of wood : observe the arrange- 
ment of the annual rings on the sides and ends. Try and determine whether 
the boards were cut from near the middle or the outside of the trees. 
Observe also the distribution and size of the knots. 

Ex. 62. Cut blocks as in Fig. 62 of various kinds of common timber. 
Examine with the naked eye and with a pocket lens : notice the presence 




FIG. 62. Diagram showing transverse, radial, and tangential 
views of a block of wood from a tree five years old. p Pith or 
medulla; r' pnmaiy, r" secondly medullary rays; j zone of 
porous spring- wood. 

or absence of wide vessels in the spring zone of the annual ring, and the 
number, width and other characters of the medullary rays as seen in transverse 
and longitudinal sections. 

Ex. 63. Notice the well-marked heart-wood in transverse sections of 
larch, laburnum and other trees ; test whether the splint-wood is harder or 
softer than the heart-wood. 

Ex. 64. Notice the development of callus at the edge of the wound where 
a thickish branch has been cut off an apple, pear or other tree. 

Ex. 65. Make transverse sections through a young stem of a black 
currant about mid-summer, mount them in a drop of water or glycerine. 

Sketch the parts as seen with a low power ; afterwards use a high power, 
and make drawings of small portions of the epidermis, cortex, cork, phellogen, 
bast, cambium, wood pith and medullary rays. 



134 ANATOMY OF STEM, ROOT AND LEAF 

Cut longitudinal sections of the same j examine and make sketches of the 
various parts. 

Ex. 66. Cut and examine in a similar manner young one-year-old shoots 
of beech, oak, elm and ash trees. 

Also make and compare under a low power, transverse, radial and tan- 
gential, longitudinal sections of pieces of the common timbers. 

In the following tables are given the characters of the common 
timbers, which can be easily distinguished with the naked eye 
and a pocket lens : 

I. TIMBER OF CONIFEROUS TREES. 

In some of these timbers the annual rings are very distinct (Fig. 63), the 
autumn- wood is hard and dark-brown or reddish in colour, and sharply 
^^^^gjgmjimj^^^^ marked off from the spring-wood, which is soft and 
^HHRHIRIHIH much paler in tint. Neither medullary rays nor 
RRl^UliVflffflllffl porous rings arc visible. 
WlffliltliHllHIM ' Heart-wood same colour as the Splint-wood. 

(a) Silver Fir (Abies pectinata D. C.). 

(b] Common Spruce (Picea excelsa Lk.). 

Both these are soft 'white woods/ pale 
yellowish or reddish-white in colour. The 
spruce possesses a few fine resin ducts in 
its autumn-wood which may be seen in 
cross-sections as very small light spots : 

they are missing from the wood of the 
FIG. 63. Transverse sec- ., fi 

tion through annual rings of silver nr. 

larch timber. (Four times 2. Heart- wood in old dry timber, reddish-brown ; 
natural si.) splint-wood, pale yellow. 

(a) Larch (Larix europaa D. C.) Rings of autumn-wood dark red and 
very distinct. The branches arise irregularly on the stem, so that 
the knots on larch boards are scattered irregularly. 
() Scots Pine (Finns sylvestris L.). Rings of autumn-wood not so 
dark as larch, and contains larger, more distinct resin-ducts. The 
branches arise in whorls at regular intervals, and the knots are 
similarly distributed on boards cut irom this tree. 

IL TIMBER OF DICOTYLEDONOUS TREES. 

GROUP A. 

Vessels of the spring- wood of each annual ring visible to the naked eye 
as a distinct circle of pores (Fig. 64) ; autumn- wood denser. 




TIMBER OF DICOTYLEDONOUS TREES 135 



To this group belong : 

Oak. Elm. 

Ash. Spanish Chestnut. 

I. Many medullary rays wide, and visible as light coloured radial bands. 
Oak ( Quercus Robur L. ). (Fig. 64. ) 




Trt 



FIG. 64. Transverse section through 
annual rings of oak timber, r One annual 
ring ; s spring-wood ; a autumn-wood ; 
m broad medullary ray. (Four times 
natural size.) 





FIG. 65. Transverse section 
through annual rings of ash. (Four 
times natural size.) 




FIG. 66. Transverse section FIG. 67. Transverse section 

through annual rings of elm. through annual rings of Spani-h 

(Four times natural size.) chestnut. (Four times natural 

size.) 

8. All medullary rays narrow, and fcarcely, or not at all, visible to the 
naked eye. 

(a) Asfc (Fraxinus excelsior L.). With a lens the fine vessels in the 
autumn-wood appear few and scattered fairly regularly throughout. 
(Fig. 65.) 



136 ANATOMY OF STEM, ROOT AND LEAF 



(#) Elm (Ulmus campestris Sm.). The fine vessels in the autumn-wood 
appear arranged in many light coloured bands or lines more or less 
parallel to the boundary of the annual ring (Fig. 66). The wood 
of elm is darker than that of ash. 

(c) Spanish Chestnut (Castanea vulgar is Lam.). The fine vessels of 
the autumn-wood are arranged in radial lines (Fig. 67), dis- 
tinguished from oak, which it somewhat resembles in colour, by 
absence of wide medullary rays. 

GROUP B. 

Annual rings with little or no difference between the spring and autumn 
portion ; vessels scarcely, or not at all, visible to the naked eye. 

To this group belong : 

Beech. Lime. 

Hornbeam. Willow. 

Sycamore. Poplar. 

I. Some of the medullary rays broad and readily visible to the naked eye, 
the rest fine and only seen with a lens. 

(a) Beech (Fagits sylvatica L.). (Fig. 68.) 
Wood reddish ; medullary rays with a 
silky-shining lustre. 

(/>) Hornbeam (Carpi >i us Betidus L.). 
Wood yellowish- white ; medullary 
rays dull and indistinct. 

2. All the medullary rays very narrow, but 
appearing to the naked eye as very fine distinct 
lines. 

(a) Sycamore (Acer Pseudo-plat anus L.). 

Wood hard, heavy, and white or pale 
yellow in colour. 

(b) Lime (Ttlia Sp.). Wood light, soft, 

and reddish-white. 

3. Medullary rays quite invisible to the naked 
eye. 

(a) Willow (Salix caprea L.). Splint- 
wood very pale red ; heart -wood deeper. 
(b} Poplars (Populits Sp. ). Splint-wood white ; heart-wood brownish. 




FIG. 68. Transvtrse section 
through annual rings of beech. 
(Four times natural size.) 



C. Stems of Monocotyledons. 

In transverse sections through the stem of a monocotyledon, 
a conspicuous difference is seen in the arrangement of the 




STEMS OF MONOCOTYLEDONS 137 

vascular bundles from that met with in dicotyledons. Instead 

of being arranged in a single ring, they appear scattered in 

several irregular circles throughout the ground 

tissue (Figs. 69 and 70). Usually the cortex is 

very narrow and inconspicuous and a distinct pith 

is rarely present. The bundles are common to 

leaf and stem as in dicotyledons, but on entering 

from a leaf they bend gradually inwards to near 

the middle of the stem, and then generally curve 

outwards again, finally joining other bundles 

near the outside of the stem. vJsfs^uhTSgh 

In addition to these differences, measurement JtemT^h^tSS 
shows that the older parts of such stems which natural Mze -> 
have ceased to grow in length are no thicker than the young parts 
near the tip ; that is to say, the stems of most monocotyledons 
do not increase in thickness when once they have ceased to grow 
in length. This incapacity for growth in thickness is due to the 
fact that the vascular bundles do not possess a cambium tissue, nor 
is such meristem developed in the ground tissue except in a few 
special cases which we cannot deal with here. Vascular bundles 
in which no cambium is present are known as closed bundles. 

In most grasses the vessels of the wood of each bundle are 
few in number, and in transverse section appear arranged in 
the form of a V (Figs. 70 and 71) ; the vessel nearest the centre 
of the stem is annular, the others being spirally thickened. 
Tracheids are not uncommon and thin-walled wood-parenchyma 
is always present. 

The bast which lies between the free limbs of the V-shaped 
wood consists entirely of sieve-tubes and companion-cells. 
The ground-tissue immediately surrounding each bundle is 
generally thick-walled and gives mechanical support and pro- 
tection to the soft parts of the bundle. Similar thickened ground- 
tissue in larger or smaller amount is met with beneath the 
epidermis, the rest being thin-walled tissue. 



138 ANATOMY OF STEM, ROOT AND LEAF 



Ex. 67. Cut sections through the stems of maize, asparagus, or any 
species of lily : observe with a lens the scattered arrangement of the vascular 
bundles. 








Fio. 70. i. Transverse section through a barley stem, b Vascular bundles ; o ground" 
tissue ; d hollow cavity. (Enlarged 14 diameters ) 

2. Enlarged view of portion A, a Thick-walled ground- tissue cells and epidermis; 
o thin-walled ground-tissue cells ; b vascular bundle. (Enlarged about 90 diameters.) 



o 




Kxo. 7T. x. Transverse section of a. vascular bundle in 
fca.rley stem. (Enlarged 4.20 diameters.) 

a. Longitudinal section through portion ground- tissue 
and a. vascular trundle along line _* in previous figure. 
a. Epidermis and trtick.~\valled ground tissue cells ; o thin- 
walle^l ground tissue cells ; s sieve- tube ; c companion- 
cell of the bast; rt annular vessel; ft* and v" spiral 



140 ANATOMY OF STEM, ROOT AND LEAF 



Ex. 68. Make thin transverse sections of a wheat or barley stem. Ex- 
amine with a low power : observe the thick walls of the epidermal and 
subjacent ground-tissue cells ; note also the scattered vascular bundles and 
hollow centre. 

Sketch a single vascular bundle as seen under a high power ; note especially 
the absence of cambium. 

Take two or three pieces of barley or wheat straw each about a quarter of 
an inch long, and press them flat. After placing them together, hold them 
in your fingers and cut longitudinal sections, some of which will pass wholly 




FIG. 72. i. Young 

ot of a pea. // Root- 

irs of the ptliferous 

per ; c root-cap. 

wice natural size. ) 

2. Transverse section through a young root of a pea near h in i. 
h Root-hairs ; c cortex- , p piliferous layer : e endodermis : n pericycle ; 
w wood strand ; .rits protoxylem ; b bast strand. (Enlarged 48 dia- 
meters.) 

or in part through a vascular bundle. Examine the sections first with a low 
and then with a high power ; make sketches of the epidermis, thick and thin 
walled ground-tissue, and annular or spiral vessels of the wood. 

THE ROOT. 

The outermost part of a young root, corresponding in position 
with the epidermis of the stem, consists of a single layer of cells 



THE ROOT 141 

termed "the piliferous layer : it is directly concerned with the 
important work of absorbing watery solutions from the soil. In 
a transverse section (2, Fig. 72) taken at a point not far away 
from the extreme end of the root, many of the cells of this layer 
are seen to be much elongated ; these are the root-hairs^ pre- 
viously mentioned in chapter iii. The cell-walls are all thin and 
uncuticularised and are readily permeable to water, thus differing 
essentially from the epidermal cells covering the parts above 
ground. 

Immediately beneath the piliferous layer is the cortex (c), which 
is continuous with the same ground-tissue in the stem. The cells 
of the cortex are usually parenchymatous and thin-walled with 
many intercellular spaces between them; chloroplasts are fre- 
quently absent, hence the pale colour of most young roots. 

The innermost layer of the cortex, or the endodermis (*), is 
generally very distinct in roots. Its cells are closely united with 
each other in the form of an uninterrupted circle, an arrange- 
ment which effectually prevents the leakage of gases from the 
intercellular spaces of the cortex into the water-conducting tissues 
of the central cylinder. The transference of water from the root- 
hairs and cortex through the endodermis into the conducting 
tissues of the central cylinder is, however, not interfered with. 

In most roots the central cylinder is of smaller diameter, and 
contains less parenchyma than that of the stem, although one is a 
continuation of the other. It is, however, in the disposition of 
the tissues within the central cylinder that the most important 
differences between stems and roots are seen. 

The pericycle (#), like that of a stem, may consist of a single 
layer or several layers of cells. From this internal tissue arise all 
lateral secondary roots, which must therefore necessarily bore 
their way outwards through the surrounding cortex before they 
become visible on the outside of the root (see Fig. 9). The 
wood (w) and bast (ft) portions of the vascular bundles, instead 
of being conjoined as in a stem, are arranged alternately side by 



142 ANATOMY OF STEM, ROOT AND LEAF 

side on separate radii drawn from the centre of the root with 
small intervening bands of ground-tissue between them. 

Moreover, in roots the first-formed, narrow-bored elements (x) 
of the primary wood are nearest the outside, while in stems they 
are nearest the centre. 

According as the number of separate strands of wood is two, 
three, or many, the roots are described as diarch, triarch (as in 
Fig. 72), <x poly arch respectively. 

The number of rows of secondary roots generally corresponds 
to the number of strands of primary wood in the parent root, 
each row being formed in the pericycle almost opposite a wood 
strand. 

In all roots the development of the primary wood proceeds in- 
wards and frequently it goes on until the several strands unite to 
form a mass which occupies the centre to the complete exclusion 
of pith. Nevertheless, in some roots, and especially those of 
monocotyledonous plants, pith is present. 

The roots of perennial dicotyledons increase in thickness 
just as the stems do, but owing to the different disposition of 
the primary tissues the first formation of the cambium is not 
the same as in a stem. In roots the cambium first forms in 
the ground-tissue on the inside of the bast-strands, and sub- 
sequently within the pericycle opposite the primary wood ; in 
transverse sections, therefore, the cambium in the early stages of 
its existence appears as a wavy band of meristem (2, <:, Fig. 73). 

When active growth of the cambium takes place, the wavy 
outline is soon lost and it is then seen as a simple ring of 
meristem, producing secondary wood and bast in a manner 
precisely similar to the cambium of an ordinary stem. 

In roots which grow in thickness, a phellogen arises in the 
pericycle and like that of thickening stems produces cork ex- 
ternally and phelloderm internally. In consequence of the 
formation of a ring of cork by the phellogen, all the tissues 
external to it, namely, the endodermis, primary cortex and 



THE ROOT 



143 



piliferous layer, wither and shrivel. The older portions of a 
root after becoming covered by a protective periderm lose 
their absorptive function and henceforward act chiefly as con- 
ductors of the watery solutions absorbed by the younger parts 
still possessing root-hairs. For an account of the characteristic 
root-cap which covers the growing point of practically all roots 
see pp. 149 and 150. 

1 2 




s 



FIG. 73. Diagram illustrating secondary growth in thickness of 
the root of a dicotyledon, i. Transverse section of a very young 
root. 2. The same after the cambium (c) has formed a continuous 
band. ^. The same after secondary thickening has been in progress 
some time. / Piliferous layer ; * primary cortex ; e endodermis ; 
*pericycle; b' primary bast; w' primary wood; c cambium; 
b " secondary bast ; w " secondary wood ; r secondary cortex 
in primary medullary ray. 

Ex. 69. Soak some peas and barley grains in water for six or seven 
hours, and afterwards allow them to germinate on damp blotting paper or 
flannel as in Ex. 3. When the root-hairs are visible on the young roots 
examine them with a lens and make sketches noting especially their origin 
away from the extreme tip. 

Strip off with forceps a piece of the outer portion of a root, so as to 

II 



144 ANATOMY OF STEM, ROOT AND LEAF 

include the root-hairs : mount it in water and examine first with a low and 
then with a high power. 

Ex. 70. Cut transverse sections of a young root of a bean or pea through 
the region bearing root-hairs, and place them for twenty minutes in ' Eau 
de Javelle ' (Ex. 75) : wash them and mount in glycerine. 

Examine with a low power ; observe and sketch the piliferous layer bear- 
ing root-hairs, the parenchymatous cortex and the central vascular cylinder. 

Examine with a high power and make drawings of the wood and bast 
strands, pericycle and endodermis. 

Ex. 71. Cut transverse sections of the older parts of the root of a pea or 
bean, near where the lateral roots are just beginning to appear. Clear with 
*Eau de Javelle' and mount in glycerine. Make a sketch of a section 
which shows the lateral roots boring their way through the cortex. 



THE GEEEN FOLIAGE-LEAP. 

The leaves are built up of the same tissues as the stems and 
roots, namely, of epidermis, vascular bundles, and ground-tissue, 
but the arrangement and constitution of these tissues are different. 
The vascular bundles coming from the stem run into the leaf 
and in dicotyledons branch repeatedly in one plane to form a fine 
net-work of strands, which conducts sap to and from all parts of 
the leaf and at the same time acts as a firm framework for 
the support of the soft ground-tissue. In monocotyledons the 
main branches of the bundles which enter a leaf generally take 
a parallel course and are connected by smaller oblique strands. 

The bundles of the leaves are always closed, there being no 
need for an active cambium in parts of the plant which are of 
such limited growth. 

As the bundles curve out of the stem into the leaf without 
twisting, the wood comes to lie nearest the upper surface of the 
leaf, and the bast nearest the lower surface. 

With the exception of the absence of cambium the larger 
vascular bundles of the leaf resemble those of the stem. The 
wood of the finer strands, however, consists of spirally thickened 
elements only, and the extreme tips of the bundles which in 



THE GREEN FOLIAGE-LEAF 145 

dicotyledons end blindly among the ground-tissue cells, are 
formed entirely of tracheids. 

The bast-tissue also undergoes a reduction of elements : as 
the end of the bundle is approached, the sieve-tubes and com- 
panion-cells are replaced by single long cells which do not extend 
so far as the woody elements of the bundle. Surrounding 
each bundle of the leaf is a sheathing tissue of parenchyma 
which is continuous with the parenchyma of the vascular 
cylinder of the stem. Such bundle-sheaths conduct carbohydrates 
from the leaf to the stem and frequently contain small starch- 
grains. 

The epidermis covers the whole leaf and, like that of the 
stem with which it is continuous, consists of a single layer of 
cells, the outer walls of which have a protective cuticle. 

A surface view (Fig. 74) shows that the cells fit closely 
together except where the stomata occur. Each stoma consists 
of two curved sausage-shaped cells (a) termed guard-cells, which 
are joined together at the ends in such a manner that a narrow 
slit-like pore or opening is left between them. The pore leads 
through the epidermis into a 
somewhat large air-chamber 
just inside the ground-tissue 
of the leaf, and this chamber 
communicates with the air- 
filled intercellular spaces all 
through the leaf. 

Changes in the curvature 
of the guard-cells reduce 

or increase the size of the -/ P ^ f == ^^^/\J U 
pores of the stomata ; when 

., n i j FIG. 74. Surface view of the epidermis of 

the Cells are mUCh Curved ? bean leaf, a Guard-cells of a stoma;<nheopen- 

the pore is widely opened ing between them ' (Enlarged 32 diameters -> 
and when they become straight the slit is closed. 

The stomata are organs specially adapted for the escape of 




146 ANATOMY OF STEM, ROOT AND LEAF 

water-vapour in the transpiration process, and are concerned 
also with the interchange of gases which goes on between the 
atmosphere and the air within the plant in the process of 
respiration and 'assimilation.' 




FIG. 75.--I. Transverse section through a plum leaf (somewhat diagrammatic). 
2. Enlarged view of portion A from i. * Epidermis ; x stomata ; p palisade parenchyma J 
s spongy parenchyma ; b vascular bundles. (Enlarged 160 diameters.) 

The ground-tissue of the leaf is a continuation of the cortex 
of the stem and is termed the mesophylL In ordinary flat leaves 



THE GREEN FOLIAGE-LEAF 147 

it is generally differentiated into two distinct parts, namely, 
(i) the palisade parenchyma which lies beneath the upper 
epidermis of the leaf, and (ii) the spongy parenchyma which 
extends between (i) and the lower epidermis. A transverse 
section across a leaf is given in Fig. 75. The cells forming 
the palisade tissue are somewhat cylindrical with their long cells 
at right angles to the surface of the leaf; they have very few 
intercellular spaces between them. The cells of the spongy 
parenchyma are very irregular in form and enclose large inter- 
cellular spaces. 

All the cells of the mesophyll contain numerous chloroplasts 
but it is in the palisade cells that they are most abundant, a 
fact which, together with the comparative absence of intercellular 
spaces, accounts for the upper side of a leaf being usually a 
deeper green colour than the lower side. 

Ex. 72. Strip off a piece of the lower epidermis of a bean leaf and mount 
it in water. Note the irregular outline of the cell-walls and the way in which 
they fit one with another. Make sketches of these and of the stomata with 
their guard-cells. Examine, in a similar way, the upper and lower epidermis 
of the leaves of turnip, plum, apple, onion, grasses and other common plants. 
Note the form of any hairs which are present. 

Ex. 73. Cut five or six pieces, each about one-eighth of an inch broad 
and half an inch long, from the blades of a plum leaf. Place them one on 
another, hold them in the fingers and cut transverse sections. Mount some 
of the thinnest sections in water and examine first with a low and then with 
a high power. 

Sketch the parts seen, namely, 

(1) The upper and lower epidermis with nuclei, protoplasm, and clear 

cell-sap ; 

(2) The palisade tissue of several layers ; and 

(3) The spongy parenchyma in which are many large intercellular spaces. 
Possibly the sections of one or more stomata may be seen. 

Ex. 74. Cut transverse sections through the mid-rib and petiole of several 
different kinds of leaves. Note and sketch the position and character of the 
wood and bast of the vascular bundles cut across ; and also the thickness 
of the walls and nature of the contents of the cells surrounding the bundles. 

Ex. 75. Prepare some * Eau de Javelle ' by first dissolving two ounces of 
carbonate of soda in a pint of water and then adding one ounce of * bleaching 



148 ANATOMY OF STEM, ROOT AND LEAF 



powder.' Allow the mixture to stand after stirring, and pour off the clear 
liquid into a well-stoppered glass bottle: keep in the dark. 

Collect a few thin leaves of plants and kill them by immersing them for a 
minute in boiling water. Then place them in some ' Eau de Javelle ' ; 
leave them in it a few hours and when quite bleached, wash in water for 
an hour or two and then mount in weak glycerine. Examine with a low 
power, observe the ramifications and endings of the bundles, also the parcn- 
chymatous bundle-sheath. Focus on the surface and note the form, number, 
and size of the stomata and hairs. 




FIG. 76. Diagrammatic longi- 
tudinal section through the apex of a 
stem, d Dermatogen which gives rise 
to the epidermis e \ c cortex produced 
from pcnhlem a ; s vascular cylinder 
produced from plerome b ; / leaves. 




FIG. 77. Enlarged view of the apex of 
the stem in the previous figure, d Derma- 
togen ; a periblem ; b plerome ; v vessels 
of the protoxylem ; /rudimentary leaves. 



THE GROWING-POINTS OF STEMS AND BOOTS. 

The growing-points or regions where the formation of new 
organs and tissues takes place are situated at the end of the 
stems and roots. 

(i) Growing-point of the stem. The apex of the stem is 



GROWING-POINTS OF STEMS AND ROOTS 149 

always completely enclosed and protected by young leaves 
(Fig. 76) and consists of a dome-shaped mass of meristem, 
from which are derived all the various tissues already studied in 
the mature stem and leaf. The cells forming the meristem, are 
approximately uniform in size and form : they possess thin walls 
and are rich in protoplasm. 

In a favourable longitudinal section through the growing-point 
three distinct strata are often visible (Figs. 76 and 77). Covering 
the apex is a single layer (d) termed the dermatogen which divides 
only by walls at right angles to the surface and gives rise to the 
epidermis of the plant. 

Beneath the dermatogen comes the periblem (a) from which 
the cortex is derived. At the extreme apex it may be only one 
cell thick, but in the older parts division takes place in several 
directions and a many-layered stratum is produced. 

Occupying the centre is a solid mass of meristem termed the 
pkrome (b): from it the vascular cylinder is developed within 
which at a short distance from the apex the differentiation of the 
vascular bundles begins to appear. 

The leaves of the plant are first seen as slight projections (/) 
on the surface of the growing-point ; the tissues taking part in 
their formation are the dermatogen and a portion of the periblem. 

The branches which arise in the axils of the leaves are also 
developed from the dermatogen and periblem ; the plerome 
is not concerned in the production of either leaves or 
branches. 

(ii) Growing-point of the root. The apex of a root differs very 
considerably from that of a stem. The delicate meristem in the 
latter always exists within a bud and is protected from external 
injurious influences by the rudimentary leaves which curve 
round it. 

Roots, however, produce no leaves, but the tender cells of the 
meristem at the apex of each are protected by a covering of 
cells termed the root-cap. Moreover, as fast as the exterior of 



150 ANATOMY OF STEM, ROOT AND LEAF 



the root-cap dies off or is worn away by the soil in which the 

root is growing, additions are being made to the interior of the 

cap where it is in union with the meristem. 

A common arrangement of the tissues at the end of a root 

is seen in Fig. 78. 

The innermost part of the 
meristem which gives rise to the 
vascular cylinder is the plerome 
(), while round it is the peri- 
blem (#), from which the primary 
cortex of the root is derived. 
In almost all respects these 
portions of the apical meristem 
are identical with those present 
in the apex of the stem. The 
outermost part of the meristem 
is termed the calyptrogen or cap- 
forming layer; instead of re- 
maining a single layer as in the 
stem it divides by walls parallel 
to the surface as well as per- 
pendicular to the latter, and thus 
a many-layered root-cap (c) is 
formed. 

In many instances the inner- 
most single layer of cells pro- 




J 



FIG. 78. Longitudinal section through 
the apex of a root, b Plerome ; a penblem ; 
c root-cap ; d external dead and dying cells 
of root-cap ; e pericycle ; v vessels of the 



(EnJ " gcdab ut duced by the" calyptrogen "be- 

comes the piliferous layer : the rest of the cells which are 

continually cut off towards the outside form the root-cap 
proper. 

Ex. 76. Soak some beans or peas, and allow them to germinate. As 
soon as the tip of the radicle is visible through the micropyle, strip off the 
coat of the seed and cut longitudinal sections of the young root. Place them 
for half an hour in Eau de Javelle (see Ex. 75), then wash in water and 



GROWING-POINTS OF STEMS AND ROOTS 151 

mount in dilute glycerine. Examine first with low and then with a high 
power. Make a sketch showing the general arrangements of the parts 
seen, viz., root-cap, plerome and periblem. 

Endeavour to prepare sections of the apex of the roots of maize, peas, and 
other large seeds. 

Ex. 77. Cut longitudinal sections through the apex of stems within the 
terminal buds of common trees. Treat and examine as indicated above. 
Observe and sketch the parts seen : note the first beginnings of leaves. 



PART III. 

PHYSIOLOGY OF PLANTS. 

CHAPTER XL 
THE CHEMICAL COMPOSITION OP PLANTS. 

t. AFTER becoming acquainted with the external and internal 
structure of plants, it is necessary to proceed to study the work 
which the various parts perform in the maintenance of the life of 
the plant : this branch of the science of Botany is termed physi- 
ology. Among the higher forms of plants various members and 
tissues are adapted to carry out certain functions or certain kinds 
of physiological work ; the individual members and tissues by 
which the functions are performed being termed organs of the 
plant. 

It is at the outset important to emphasise the fact that all the 
various functions are dependent upon the living protoplasm, and 
that the activity and power of the latter to carry them on satis- 
factorily is bound up with certain external conditions, namely, a 
suitable temperature, adequate supply of food-materials, and in 
the case of green plants a certain intensity of light, and access to 
free oxygen of the atmosphere; without the fulfilment of these 
conditions death takes place and the various vital phenomena 
cease. 

The functions of plants may be divided into two groups : 
(i) The nutritive functions which are concerned with the 
absorption, elaboration, and appropriation of the food-supply 
and therefore specially adapted to the maintenance of the life of 
the individual, 

152 



CHEMICAL COMPOSITION OF PLANTS 153 



and (ii) the reproductive functions concerned with the produc- 
tion of new individuals and the maintenance of the species. 

2. Before examining the nutritive processes in detail, it is 
necessary to learn something about the substances entering into 
the composition of plants. 

If a fresh plant is dug up from the ground and placed in an 
oven heated to a temperature a little above that of boiling water 
(105- 1 10* C.) it soon loses weight, the loss being due to the 
escape of water from the tissues of the plant. By continuing the 
drying process for some hours, all the water from the cell-sap, 
protoplasm, and the cell-walls is expelled, and there remains 
only the solid matter of the plant. 

This residue or dry matter consists of a great variety of 
chemical compounds, organic and inorganic ; when ignited and 
burnt it always leaves a small amount of white or yellowish 
incombustible ash, composed of inorganic compounds, the chief 
constituents of which have been originally absorbed from the 
soil by the roots of the plant. 

The following table shows the amounts of water, dry matter, 
and ash in 100 parts by weight of the seeds, fruits, leaves, and 
other portions of a few common plants : 

Water. 



Wheat (grain), 


14*3 


Barley . 


14*3 


Oat . 


14-3 


Beans, . 


15-0 


Turnip-seeds, 


n-8 


Apples, 


84-8 


Roots of Carrot, 


85-0 


Swede, . 


87-0 


Mangel, . 


88-0 


Potato tubers, . 


75' 


Good dry hay, 


'4*3 



loiai 
dry 
matter. 


Combustible 
portion. 


Ash. 


857 


76-5 


9*2 


857 


727 


13*0 


857 


757 


ro'o 


85-0 


79*5 


5*5 


88-2 


84-3 


3*9 


*S'* 


14-8 


0*4 


J 5' 


14-1 


0-9 


13-0 


1 2*0 


I'O 


12'0 


n'2 


0-8 


25'0 


24-1 


0*9 


857 


79*5 


6'2 



154 CHEMICAL COMPOSITION OF PLANTS 



Meadow grass (green), 80*0 20*0 18*0 2*0 

Red Clover, . . 80-4 19*6 18-3 1*3 

Green potato haulm, 85*0 15-0 13-4 i'6 

Swede leaves, . 88*4 11*6 9*3 2*3 

Mangel leaves, 90*5 9*5 77 1*8 

The amount of water in ripe seeds is comparatively small, 
generally averaging from 10 to 15 per cent. In succulent fruits, 
fleshy roots, tubers, green leaves and fresh vegetative organs, it 
is rarely less than 75 per cent, and not unfrequently as high as 
85 to 90 per cent, of their total weight. 

The proportion of ash in the dry matter of seeds and succulent 
roots and tubers is generally very much smaller than in the 
leaves and bark of plants. 

Ex. 78. Weigh pieces of carrot, turnip, mangel, potato, apple and 
strawberry in separate porcelain dishes, then cut each piece into several small 
pieces and place the porcelain dishes and contents in a warm oven or ' water- 
oven. ' Weigh at intervals of three hours and note the loss in weight. 

Ex. 79. Repeat the previous experiment with leaves of potato, turnip, 
ash and other trees, freshly-cut grass, and freshly-ground ' whole-meal ' 
flour, oat-meal and bean-meal. 

3. The dry matter of a plant consists of (i) a small amount of 
unutilised inorganic substances absorbed from the soil ; and (2) 
a large amount of various organic compounds manufactured by 
the plant out of the food-materials which it has absorbed from 
the soil and air. 

To merely give a list of the compounds met with in plants 
would fill a large volume : it is, however, not needful here to 
describe more than the chief organic substances of which the 
plant-body is composed : for present purposes they may be 
classified into two groups, namely : ( i ) non-nitrogtnous and 
(2) nitrogenous substances according as they are free from 01 
contain nitrogen. 



CARBOHYDRATES 155 

I. NON-NITROGENOUS ORGANIC SUBSTANCES. 

The most important members of this group are the carbo- 
hydrates, fats, oils and acids enumerated below. 

i. Carbohydrates. These compounds form the largest part 
of the body of all plants and contain carbon, hydrogen and 
oxygen, the elements hydrogen and oxygen being present in the 
same proportion as they exist in water. The chief carbohydrates 
are the sugars, starch, inulin, celluloses and pentosans. 

a. Sugars. Almost all the sugars possess a more or less 
sweet taste, and are generally met with dissolved in the cell-sap. 
The commoner representatives are glucose, fructose, cane-sugar 
and maltose. 

(i) Glucose, dextrose or grape-sugar (C 6 H 12 O 6 ), occurs in most 
fruits, and especially in grapes whose cell-sap may contain from 
20 to 30 per cent. ; ripe apples contain on an average 7 to 10 
per cent. ; cherries 9 to 10 per cent., and plums 3 to 5 per cent 
of this sugar. 

(ii) Fructose Jruit-sugar, or levulose (C 6 H 12 6 ) is found also in 
ripe fruits associated with grape-sugar. 

Both dextrose and levulose reduce Fehling's solution, and are 
directly fermentable by yeast. 

Ex. 80. Dissolve 35 grams of copper sulphate in 500 c.c. of water, label 
this solution A : then dissolve 160 grams of caustic potash and 173 grams of 
sodium potassium tartrate in 500 c.c. of water and label the solution B. By 
mixing equal quantities of A and B, Fehling's solution is produced. (The 
solution A and B should be kept separate and only mixed when needed as 
the mixture does not keep long. ) 

Squeeze a few drops of grape juice into a test tube containing 10 c.c. of the 
Fehling's solution : heat over a Bunsen flame and note the reddish precipitate 
of cuprous oxide (Cu*O). 

Test the juice of ripe plums and other fruits in the same way. 

(iii) Cane-sugar or saccharose (C^H^On) occurs dissolved in 
the cell-sap of the stems and roots of many plants and especially in 
the sugar-cane, mangel and sugar-beet, from which it is extracted 
on a commercial scale. 



156 CHEMICAL COMPOSITION OF PLANTS 

Sugar-cane stems contain from 1 5 to 20 per cent., the sugar- 
beet from 12 to 1 6 per cent, of this carbohydrate. 

It differs from the two previous sugars in that it does not 
reduce Fehling's solution and cannot be fermented directly by 
yeast. When boiled with dilute acids or acted upon by the 
enzyme invert ase^ which is present in yeast and in various 
tissues of plants, it decomposes into a mixture of dextrose and 
levulose which mixture is termed invert-sugar, 

Ex. 81. Boil some pieces of mangel or sugar-beet in water and 
(i) Test some of the solution for a * reducing ' sugar as in Ex. 80. 
(ii) Take 10 c.c. of the solution and add to it three or four drops of strong 
hydrochloric acid : boil for twenty minutes, and after neutralising the acid 
with a solution of sodium carbonate, boil and test again with Fehling's 
solutions. 

(iv) Maltose (C 12 H 22 O n ) is a variety of sugar formed by the 
action of the enzyme diastase upon starch and is present in 
malted barley and other germinated grain. It is capable of 
direct fermentation by yeast, and reduces Fehling's solution but 
not to the same extent as grape-sugar. 

b. Starch (C 6 H 10 O 6 ) n . This carbohydrate is found in the 
form of minute solid, organised grains, built up of several 
successive layers of the substance arranged round a more or 
less central nucleus or hilum\ sometimes two or more nuclei 
are visible in the same grain in which case the latter is described 
as compound. 

Starch-grains are usually manufactured by the plastids of the 
cells, and occur in greatest abundance in roots, tubers and seeds 
where they form a store of reserve-food : from 50 to 70 per 
cent of the dry weight of cereal grains, and 10 to 30 per cent, 
of potatoes is starch. 

The grains are variable in size and form even in the same 
plant : nevertheless, in many cases the starch-grains from certain 
plants are so characteristic in shape and dimensions that they 
may be readily identified under the microscope. 



CARBOHYDRATES 



157 



Those from potato tubers are flattened irregularly oval grains 
of comparatively large size, with an excentric nucleus (i, Fig. 79). 

Large and small grains are present in the endosperm-cells of 
wheat, barley and rye ; they are all flattened and lentil-shaped 
with a central nucleus (2, Fig. 79). 

In the cotyledons of the seeds of pea, bean and other legu- 
minous plants, the grains are oval and kidney-shaped as in 4, 
Fig. 79, with radiating cracks or fissures in the centre. 

In oats the grains are oval and compound (3, Fig. 79), the 
component fragments (;/) being small and angular. 




FIG. 79. (i) Starch-grains of potato : n nucleus of a grain, (a) 
Starch-grains of wheat. (3) Siarch-grains of oat ; a a compound 
gram ; n fragments of a compound grain. (4) Starch-grains of bean. 
(All enlarged 360 diameters.) 



158 CHEMICAL COMPOSITION OF PLANTS 

The substance forming the grain is termed starch or amylose, 
of which there appears to be two slightly different modifications. 
When treated with a solution of iodine it turns a characteristic 
deep violet-blue colour. 

The enzyme diastase converts it into maltose and various 
soluble gum-like carbohydrates termed dextrins. 

Formerly Nageli and others considered that a starch-grain 
consisted of two substances, namely, granulose^ and a substance 
starch-cellulose or farinose which remains as an insoluble residue 
when starch-grains are treated with saliva or weak acids : this 
residue, however, does not pre-exist in the starch-grains but is 
a product of the action of the solvents employed, and according 
to A. Meyer is amylodextrin. 

On boiling with dilute acids starch is changed into glucose 
and dextrin. 

Heated with water starch swells and forms an insoluble jelly- 
like paste : subjected to dry heat or roasted to a temperature of 
150 to 200 C. it turns brown and becomes altered into a form 
of dextrin. 

In certain cases starch-grains contain amylose with a larger or 
smaller proportion of amylodextrin : the latter is coloured wine- 
red by a solution of iodine. 

Commercial starch is obtained chiefly by mechanical separation 
with water from crushed potato tubers, or from maize and wheat 
grains. 

Ex. 82. Divide a grain of wheat, barley, oat, rye, maize and rice trans- 
versely with a knife. Gently scrape off a very small portion of the endosperm 
and mount in water. Examine the starch-grains with a low and a high 
power, noting whether simple compound, their form and relative size, and 
also the shape and position of the hilum in each. 

Ex. 83. Cut through the cotyledons of a bean and pea seed and also 
through a potato tuber : gently scrape the cut surface with the point of a knife 
and transfer the starch -grains obtained to a drop of water on a slide. Examine 
and note the form, size and shape of the starch-grains. 

Ex. 84. Cut thin sections from a piece of potato tuber and from a wheat 



CARBOHYDRATES 159 

grain : examine with a low power and make drawings of the starch-grains 
within the cells observed. 

Ex. 85. Make a strong solution of potassium iodide in water and add to 
it a few crystals of iodine. Allow the mixture to stand for twelve hours, and 
shake occasionally in order to facilitate the solution of the iodine. When the 
latter is all dissolved, add more water until the whole is the colour of dark 
sherry. 

When examining the starch-grains in Exs. 82 to 84, place a drop of this 
solution near the edge of the cover -slip so that it may run under the latter 
and come in contact with the starch-grains. Note the change in colour of the 
starch-grains. 

Ex. 86. Make an extract of malt diastase as follows : Shake up five grains 
of ground malt with 50 c.c. of cold water and after allowing it to stand for 
four hours, filter so as to get a clear solution. 

Next grind some starch with water in a mortar and pour a little of the 
mixture into a 200 c.c. flask of boiling water. When cool pour about 20 c.c. 
of this thin starch paste into three test tubes : show the presence of starch by 
adding a few drops of the solution of iodine mentioned in Ex. 85 to one 
tube, and to the other two tubes add 3 or 4 c.c. of the diastase extract, and 
warm them to 60 C. Test for the presence of starch in one of these two tubes 
by taking out at intervals of five minutes a few drops with a pipette and adding 
them to weak solutions of iodine kept in a series of test tubes. 

After a time the starch is changed into sugar and dextrin : When this has 
happened show the presence of the sugar by means of Fehling's solution. 

See if Fehling's solution is acted upon by the thin starch- paste when no 
diastase is added. 

c. Celluloses. The solid fabric of a plant consists mainly of 
cell-walls which are produced by the protoplasm of the cells. 
At first the walls are thin, but in many cases thickening takes 
place by the deposition of layer after layer of sybstance on the 
inside of the walls where they are in contact with the cytoplasm. 
Where cells are in a state of division and new walls are being 
produced, the latter are first visible in the form of thin plates of 
cytoplasmic substance stretched across the dividing cells, and in 
the process of thickening the new layers appear to be produced 
by a conversion of the outermost layers of the cytoplasm, for 
where thickening of a cell-wall takes place there is always noticed 
a gradual diminution of the protoplasmic cell-contents until at 
last none remain within the cell-cavity. 

12 



i6o CHEMICAL COMPOSITION OF PLANTS 

It has been customary to term the material forming the cell- 
wall cellulose, as if it were a single chemical substance. A 
variety of celluloses are, however, now known and the cell-walls 
of plants invariably consist of mixtures or compounds of these 
with several other substances. 

What may be named the typical cellulose can be readily 
obtained from cotton-wool and flax-fibre by treating the latter 
with various chemical reagents to eliminate the substances com- 
bined or mixed with it : it is a carbohydrate possessing the 
empirical composition represented by the formula (C 6 H 10 O 5 ) B . 
This typical cellulose is insoluble in dilute acids and alkalies, 
but is soluble in ammoniacal cupric oxide, hot concentrated 
solutions of zinc chloride and other solvents. 

It stains blue when treated with sulphuric acid and iodine or 
with * chlor-zinc-iodine,' and when acted upon with concentrated 
sulphuric acid yields dextrose sugar. 

Another type of cellulose is present in the cell-walls of 
lignified tissues. When obtained free from the substances with 
which they are combined or mixed, these celluloses differ from 
the cellulose obtained from cotton fibre not so much in empirical 
composition as in chemical structure. They contain a slightly 
higher percentage of oxygen, are less resistant to hydrolysis, and 
yield only small quantities of dextrose and mannose sugars when 
treated with sulphuric acid ; moreover the aldehyde furfural is 
produced when celluloses of this type are hydrolysed with dilute 
hydrochloric acid. 

The cell-walls of the cells of the endosperm-tissue and coty- 
ledons of seeds are formed of substances termed hemicelluloses, 
which are so different in chemical properties from the two types 
just mentioned that they have little right to be considered cellu- 
loses at all, except that . they resemble the latter in appearance 
and are the materials of which certain cell-walls are composed. 
Hetnicelluloses are very easily hydrolysed by dilute acids and 
alkalies into galactose, mannose and pentose sugars. 



CARBOHYDRATES 161 

None of the above-mentioned celluloses are ever met with in 
a pure state in plants ; they are always combined or mixed with 
other substances forming three main types of what may be termed 
compound celluloses as indicated below. 

(i) Pectocelluloses. These are compounds or intimate mixtures 
of typical celluloses with pectose \ the latter when hydrolysed with 
dilute acids or alkalies yields pectin, a substance whose solutions 
gelatinise easily. The cell-walls of raw cotton, flax-fibres and 
other unlignified fibres, as well as most parenchymatous tissues 
and especially those of fleshy roots and fruits, such as carrots, 
mangel, turnips, apples, pears and currants, consist chiefly of 
this form of compound cellulose. 

Mangin asserts that the first walls produced during cell-division, 
consist mainly of pectose, the secondary thickening-layers of 
most unlignified cell-walls being formed of cellulose and pectose 
combined. 

Closely allied to pectocelluloses are the mucocelluloses composed 
of cellulose and substances which yield mucilaginous solutions with 
water : they are chiefly met with in certain seeds and fruits. 

(ii) Adipocelluloses. The cell- walls of cork-tissue appear to be 
composed chiefly of a fatty or waxy substance termed suberin 
combined with a very small amount of cellulose. Allied to these 
are the cutocelluloses forming the cell-walls of the epidermis of 
plants : the substance eutin closely resembles suberin in its 
composition and properties. Both suberised and cutinised cell- 
walls turn brownish-yellow when treated with ' chlor-zinc-iodine ' ; 
they are impermeable to water and successfully prevent the loss 
of water from tissues covered by them. Whether cutin and 
suberin are products of the direct conversion of cellulose is a 
question at present unsolved. 

(iii) Li%nocelluloses. The cell-walls of the woody tissues of 
plants consist vi lignocelluloses which are homogeneous compounds 
of (a) cellulose or oxycellulose, 

(&) a pentosan known as wood-gum, 



162 CHEMICAL COMPOSITION OF PLANTS 

and (f) certain aromatic compounds not yet isolated in a pure 
state : the substances b and c are together generally spoken of as 
lignin or lignonc. Lignocellu loses are primary constituents of 
plant tissues, and are not celluloses on which c lignin ' is encrusted 
or deposited as the result of secondary chemical changes. 

Lignified walls become pink when treated with phloroglucin 
and hydrochloric acid, and stain a yellow colour in solutions of 
aniline chloride ; with chlor-zinc-iodine the walls become yellow. 

The cell-walls of lignified tissues in the heart-wood of trees, 
and other parts of plants, frequently become stained by tannin 
and various colouring matters. 

Paper of all kinds consists chiefly of cellulose obtained from 
linen rags, cotton, wood and straw. 

Ex. 87. To prepare ' chlor-zinc-iodine,' dissolve 25 parts of zinc chloride 
and 8 parts of potassium iodide in 8J parts of water, and add as much iodine 
as will make the solution a dark sherry colour. 

Cut sections of the stems and other parts of plants, and mount them in the 
solution ; note the blue colour of the unlignified and uncuticularised walls- 
Notice the effect of the solution upon ' cotton-wool/ and upon sections of wood 

Ex. 88. Cut sections of the seeds with a dry razor ; mount and examine 
some of the sections in water, and some in pure glycerine. Soak some white 
mustard and flax-seeds (linseed) in water ; note the slimy mucilaginous nature 
of the surface of the seeds when wetted. 

Ex. 89. Cut sections of the stems of various plants, and mount them in a 
saturated solution of aniline chloride, to which a few drops of hydrochloric 
acid have been added ; the lignified walls stain a golden yellow colour. 

d. Pentosans. Associated with the cellulose of plant tissues 
are carbohydrates termed pcntosans (C B H 8 O 4 ). When heated 
with dilute acids they are hydrolysed and converted into the 
pentose sugars (C 5 H 10 O 5 ) arabinose or xylose. 

Pentosans are produced during the early stage of growth, and 
the amount generally increases with the age of the plant. 
These carbohydrates appear to be of little use in the nutritive 
processes of plants, but are partially digested and assimilated by 
herbivorous animals, They are common in all plant tissues and 
are especially abundant in grasses and cereal straw. 



FATS AND FIXED OILS 163 

e. Inulin is a carbohydrate possessing the same percentage 
composition as starch ; it is soluble in water, and is met with dis- 
solved in the cell-sap of many plants belonging to the Composite, 
Campanulaceae and other orders. It is also found in the bulbs 
of many plants belonging to the Liliaceae and Amaryllidaceae, as 
well as in the leaves and other vegetative parts of these plants. 

Inulin is especially abundant in dahlia and chicory roots, and 
in tubers of Jerusalem artichoke, where it takes the place of starch 
as a reserve-food. When portions of these roots and tubers are 
placed in dilute alcohol for several days, the inulin separates in 
the form of solid spherical masses of needle-like crystals, arranged 
in a characteristic radiated manner (sphaerites). 

Inulin does not reduce Fehling's solution, but when boiled for 
a long time with water, or for a short time with dilute acids, it is 
converted completely into levulose. 

Ex. 90. Soak a piece of a dahlia root in strong methylated spirit for several 
weeks : cut sections and mount in pure glycerine. Examine and draw the 
sphaerocrystals of inulin. 

2. Fats and fixed oils. These substances, which are mixtures 
of different compounds of glycerine and fatty acids, contain the 
same three elements as the carbohydrates, but possess less oxygen 
proportionately to hydrogen than the latter substances. They 
are at first most frequently observed in the form of small round 
drops of irregular softish semi-solid particles within the cytoplasm 
of cells : afterwards the drops run together and are then excreted 
into the cell-sap where they accumulate. 

Oils and fats are reserve plant-foods, and are consequently 
most abundant in the endosperm and cotyledons of seeds, and 
in certain fruits. The seeds of the rape plant contain on an 
average 42 per cent. ; flax-seeds (linseed), 36 per cent., and cotton 
seeds, 25 per cent, of oil. 

. The various kinds of ' Oil-cakes ' used for feeding cattle are 
formed from the residue of different seeds and fruits, the greater 



164 CHEMICAL COMPOSITION OF PLANTS 





c 



portion of whose oil has been extracted from them by crushing 
and other means. 

Ex. 91. Cut thin sections of the seeds of the almond, rape, Brazil-nut 
and linseed. Mount in water and examine with a high power : note the 
round bright oil-drops in the cells, and in the water round the section. 

3. Volatile or essential oils. To these compounds are due 
the aroma or odour of various plants, such as roses, mint, hops, 
and lavender. 

Many essential oils are composed of carbon and hydrogen 

only, while others contain oxygen 
in addition to these elements. 
They frequently occur in the 
form of drops in the cytoplasm 
of the cells, and are sometimes 
accumulated and deposited in 
special parts of glandular hairs 
and other receptacles. 

4. Organic acids. The com- 
monest examples of these com- 
pounds found in the cells of 
green plants are oxalic, malic, 
,. , , , citric, and tartaric acids. They 

FIG. Bo. a Single large crystals of 

calcium oxalate in ceils of the parenchyma are met with either in the free 

of a red clover leaf; b crystal-aggregates 

from a rhubarb leaf; c raphides from a State, OF Combined With VariOUS 

leaf of a fuchsia. 

organic or mineral bases to 
form acid and neutral salts. 

The commonest acid in plants is oxalic acid, which occurs, 
free, or more commonly combined with calcium or potassium, 
in the parenchymatous tissue of leaves, stems and roots ; to the 
acid potassium salt, is due the sour taste of the leaves of SorreJ 
(Rumex acetosd) and Wood-sorrel (Oxalis acetoselld). 

Crystals of calcium oxalate are very common in the tissues 
of a great variety of plants; they are formed in vacuoles within- 
the cytoplasm, and occur in the form of (i) single crystals (a, 



PROTEINS OR ALBUMINOIDS 



I6 S 



Fig. 80)^(2) radiating crystal aggregates (), or (3) bundles of 
needle-shaped crystals or raphides (c). The latter form is 
frequent in the cells of many monocotyledons. 

Malic, citric and tartaric acids are also found free or combined 
with calcium or potassium, especially in unripe fruits of various 
kinds. A lemon contains from 5 to 7 per cent, of free citric acid. 

Ex. 92. Mount a very small portion of rhubarb jam in water, and look 
for crystal-aggregates of calcium oxalate resembling b> Fig. 80. Many will 
be observed within the thin parenchymatous cells present in the jam. 

Ex. 93. Treat some clover, vetch, fuchsia and other leaves with Eau de 
Javelle as in Ex. 75, wash in water and mount a small piece in glycerine : 
note the form of the crystals of calcium oxalate, and their position in the 
leaves. In which special tissues of the leaves are they most abundant ? 

II. NITROGENOUS ORGANIC SUBSTANCES. 
These compounds contain nitrogen and frequently other 





b 



FIG. 81. i Transverse section of a wheat-grain, p Pericarp ; a l aleuron-layer ' ; 6 starchy 
part of the endosperm ; /"furrow at back of the grain. 

a Part A of i (enlarged 160 diameters), t Pericarp ; a ' aleuron-layer ' showing small 
aleuron-grains and a central nucleus within each cell ; b cells of endosperm containing starch- 
grains. 

elements such as sulphur and phosphorus, in addition to carbon, 
hydrogen and oxygen. 

The most important examples are the proteins or albuminoids 
amides and alkaloids. 

i. Proteins or albuminoids. The proteins are exceedingly 



166 CHEMICAL COMPOSITION OF PLANTS 

complex compounds to which no chemical formula can yet be 
given. They are generally slimy like the white of an egg, and 
like the latter substance many of them coagulate on heating; 
some of them are soluble while others are insoluble in water. 
The simplest proteins are composed of carbon, hydrogen, oxygen, 
nitrogen and sulphur; they contain from 15 to 17 per cent of 
nitrogen and from to 3 per cent, of sulphur. 

As protoplasm consists largely of proteins, they are met with 
in all living parts of plants : moreover some of these compounds 
are found dissolved in the cell-sap. 

Certain proteins are stored in the vacuoles and cell -sap of seeds 
and other resting-organs as nitrogenous reserve -food in the form 
of round or irregularly-shaped solid grains; such grains are 
termed akuron- si protein-grains. In cereals the aleuron-grains 
are very small and round, and are chiefly stored in the outermost 
cell layers of the endosperm (Fig. 81). In other starchy seeds 
such as beans and peas they are small, but in many oily seeds 
such as those of the castor-oil plant and Brazil-nut, the aleuron- 
grains are large, and generally contain a small round particle or 
globoid of calcium and magnesium phosphates, together with a 
larger or smaller protein-crystal or crystalloid. 

The seeds of the lupin contain on an average about 34 per 
cent., beans 24, wheat-grains 13, barley-grains 10, straw 3, 
potatoes 2, and turnips about i per cent, of proteins. 

Solid proteins stain a yellow colour with iodine. 

Ex. 94. (a) Divide a wheat-grain in two transversely : then cut a thin 
section to include a small portion of the pericarp and aleuron-layer as in Fig. 81. 

Mount in dilute glycerine and run a drop of iodine solution under the cover- 
slip : note the colour of the starch-grains and the aleuron-grains. 

(b) Cut a similar section of a barley and an oat grain. Are the aleuron- 
layers in these grains the same as in wheat ? 

Ex. 95. Cut sections of the cotyledons of beans and peas: mount and 
examine in dilute glycerine : note the small aleuron-grains in the cells along 
with large starch-grains : stain with iodine and re-examine. 

2. Amides. These are soluble crystalline nitrogenous com- 



ALKALOIDS 167 

pounds found dissolved in the cell-sap. Most of them are amido- 
acids or simple derivatives of the latter. They are reserve-foods 
chiefly present in the rhizomes, bulbs, tubers and roots of plants 
and rarely in resting seeds. 

The most widely distributed representative is asparaginc, which 
is present in the parenchyma of almost all parts of plants : it is 
more particularly abundant in the young shoots of asparagus, 
sprouts and tubers of the potato and in seedlings of lupins, vetches 
and other leguminous plants grown in the dark. 

Other common amido-acids are glutamine, betaine, leucine, and 
tyrosine met with in the mangel, sugar-beet, turnip and other 
roots. 

3. Alkaloids. The alkaloids are organic compounds of a 
basic nature ; most of them are poisonous and form the active 
principle of many plants used as drugs. The most familiar 
examples are morphine^ obtained from the opium poppy, nicotine 
from the tobacco plant, coninc from hemlock, and strychnine 
from Strychnos Nux vomica. 



CHAPTER XII. 
THE COMPOSITION OF PLANTS (continued). 

i. The elementary constituents of plants. Chemical analysis 
has shown that the following elements are always present in the 
compounds which form the body of a healthy green plant, 
namely, carbon, hydrogen, oxygen, nitrogen, silicon, sulphur, 
phosphorus, chlorine, potassium, sodium, calcium, magnesium 
and iron. 

In sea-weeds bromine and iodine are usually present, and 
many other elements, such as aluminium, zinc and copper, have 
been occasionally discovered in small quantities in certain 
species of plants. 

On burning the dry matter of a plant, the carbon, hydrogen, 
oxygen and nitrogen within it escape into the air in the form 
of water, carbon dioxide, free nitrogen and other volatile 
compounds : the other elements are left in the ash. 

While chemical analysis enables us to determine the particular 
elements of which the body of a plant is composed, it does 
not furnish a means of deciding which and how many of these 
elements are necessary for the plant's existence. 

Since the majority of plants contain no zinc, tin or lead, it is 
clear that these elements and others which are only occasionally 
present are not necessary for plant-growth. On the other hand, 
that carbon, hydrogen, oxygen and nitrogen are absolutely 
essential may be inferred from the fact that these elements are 
essential components of the organic compounds of which the 
cell walls and protoplasm are constructed. It does not, however, 

183 



ELEMENTARY CONSTITUENTS OF PLANTS 169 

follow that elements which are invariably present are therefore 
absolutely necessary for the life of a plant. 

To determine with certainty which elements are indispensable 
for proper nutrition and growth, cultivation experiments must be 
carried out in soil or other media, the composition of which is 
accurately known, and which can be regulated and kept under 
control. This is best achieved by the methods of water-culture 
and sand-culture^ which consist in growing the plants in pure 
water or in pure sand, to which are added compounds of the 
various elements whose influence is to be studied. By means of 
such experiments it has been proved that only ten elements are 
really essential for the growth of green plants, namely, carbon, 
hydrogen, oxygen, nitrogen, sulphur, phosphorus, potassium, 
magnesium, calcium and iron ; possibly to this list chlorine 
should be added. 

All attempts to grow plants in soil, water or air from which any 
one or more of these elements are excluded end in failure. The 
other elements sometimes found in plant ash are superfluous; 
even sodium and silicon, which are present in all plants growing 
in ordinary soils, are not indispensable, for healthy specimens 
capable of producing seed can be reared without them. 

Ex. 96. Water-culture. For the growth of plants in nutrient solutions 
glass cylinders or wide-necked bottles holding about 600 or 700 c.c. of water 
should be used. 

Before use the cylinder must be rinsed out first with nitric acid and then 
thoroughly washed with distilled water. It should be fitted with a cork bung 
through which two holes should be bored, one for the exit of the stem of the 
plant to be grown, the other into which a short glass tube is fitted being con- 
venient for adding water to replace that which is lost by transpiration. 

The solutions to be used must not contain more than from 2 to 5 grams of 
dissolved salts in 1000 grams of water : a higher concentration is detrimental 
to growth. 

Moreover a slightly acid reaction should be maintained, alkaline solutions 
being injurious. 

For complete nutrition the composition of the solution may vary consider- 
Ably so long as the essential elements are present in a suitable state for 
Absorption by the roots of the plants. The following solution contains all 



170 CHEMICAL COMPOSITION OF PLANTS 



that is needed by green plants, the necessary carbon being obtained from the 
carbon dioxide of the air : 



Water, . 

Calcium nitrate, . 
Potassium chloride, 
Magnesium sulphate, 



Grams 
1500 
2 
i 

4 



Grams. 



Acid potassium phosphate 

(KH 2 P0 4 ), 
A few drops of ferric chloride 

solution. 



For demonstration purposes buckwheat, barley, maize, small dwarf-beans, 
and wallflowers are easily grown. Seeds should be germinated in damp 
sawdust or on damp blotting-paper, and when 
the seedlings are large enough to handle they 
should be arranged as in Fig. 82, so that their 
roots dip into the culture solution, their stems 
being allowed to develop through the hole in 
the cork (c). Seedlings of maize, barley and 
beans may be fastened in position by means of a 
pin pushed through the side of the pericarp or 
the seed-coat into the lower side of the cork ; or 
they may be supported by inserting cotton wool 
in the hole through which the stem emerges. 

It is important to see that only the roots dip 
into the solution : wetting the endosperm, 
cotyledons, or hypocotyl frequently leads to ill- 
health and death of the plant. 

The sides of the glass cylinder should be 
covered with cardboard or several thicknesses of 
paper to prevent access of light and heat to the 
solution : or the cylinder may be sunk in a box 
containing cocoa-nut fibre. 

Avoid placing the culture in the direct sun- 
light so that the solution in which the roots are glas> vessel ; s culture solution : 

r ._J 1. 1 _ 




immersed may remain cool. 



c perforated cork bung. 



In experiments extending over a period of several weeks the culture 
solution should be changed every week, and the plant should be placed 
occasionally for a day or two with its roots in distilled water, or water con- 
taining a small amount of calcium sulphate. 

Ex. 97. Fit up a water-culture as above but do not add ferric chloride or 
any other compound of iron to the solution : compare the growth of the plant 
with one growing in a complete solution. 

Ex. 98. Note the differences between plants growing in a complete solu- 
tion as above and some growing in the following solutions in which nitrogen 
and potassium are respectively missing. 



ELEMENTARY CONSTITUENTS OF PLANTS 171 



SOLUTION WITHOUT NITROGEN. 

Grams. 

Water, .... rooo 

Calcium sulphate, . . I 
Acid potassium phosphate, . 
Magnesium sulphate, . . 
Potassium chloride. . . A 



SOLUTION WITHOUT POTASSIUM. 

Grams. 



Water, . . 

Calcium nitrate, * 
Magnesium sulphate, 
Acid sodium phosphate 
Sodium chloride, . 



1000 
I 



To both the solutions add a few drops of ferric chloride solution. 

2. Essential elementary constituents of plants. The follow- 
ing is a brief account of the elements which are absolutely 
necessary for the nutrition of plants. 

(i) Carbon. Carbon is one of the essential constituents of 
protoplasm, and enters very largely into the composition of the 
cell-wall, and many reserve foods of plants. The amount present 
in plants usually amounts to between 40 and 50 per cent, of the 
dry matter within them. The greater portion of it is derived 
from the carbon dioxide of the atmosphere, but in some cases, 
and perhaps in all, a certain amount of carbon is taken from the 
soil in the form of organic compounds. 

Fungi among the lower, and Dodder (Cuscutci), (p. 605), 
Broom-rape (Orobanche\ (p. 607), and Bird's-nest orchis (Neottia) 
among the higher plants, obtain their carbon in the form of 
organic carbon compounds from living animals and plants, or 
from the decaying remains of these organisms. 

(ii) Hydrogen and oxygen are found combined with carbon 
and other elements in the protoplasm, cell-wall, sugars, fats, and 
other compounds present within the plant. 

Hydrogen is a constituent of water, and in this form is chiefly 
absorbed from the soil. Between 5 and 6 per cent, of the dry 
matter of a plant is hydrogen. 

The amount of oxygen present in the dry matter of plants 
averages between 35 and 45 per cent. It is absorbed in a free 
state from the air in the respiration-process, and is also taken up 
from the soil in nitrates, sulphates, carbonates and phosphates. 

(iii) Nitrogen. This element enters into the composition of 



172 CHEMICAL COMPOSITION OF PLANTS 

protein or albuminoid substances, amides and a few other less 
important organic substances ; it is also found in the inorganic 
nitrates which are frequently present in small quantity in the 
cell-sap of plants. 

The amount of nitrogen present is especially high in the seeds 
of leguminous plants, being in peas 4*8 per cent., in beans 5 
per cent., and in yellow lupins as much as 7 per cent, of the 
dry matter : in starchy cereal grains such as wheat, barley, and 
maize the amount is usually less than 2 per cent. 

The vegetative parts of leguminous plants are generally richer 
in nitrogen than those of most other plants : for example, in red 
clover and lucerne cut in bloom the amount present is from 2 
to 2\ per cent., while in grasses the average amount is about if 
per cent, of the dry matter. 

With the exception of leguminous plants which derive most of 
their nitrogen from the free nitrogen of the atmosphere (see 
p. 806), green plants take up this element from the soil chiefly in 
the form of nitrates. It has been proved by means of water 
cultures that they are also able to absorb and utilise the nitrogen 
of ammonium compounds, but as the latter when applied to the 
soil become changed into nitrates in the process of nitrification 
(see p. 799) it may be said that nitrates are the chief natural 
source of nitrogen for green plants. 

Although it has been shown that most plants can grow equally 
well with nitrogen in the form of ammonium salts as with nitrates, 
Maz^ found that solutions of the former when more concentrated 
than about '5 gram in 1000 damage the plants, whereas bad effects 
are not visible with nitrates until the solution applied to the roots 
contained 2 parts in 1000 of water. 

Nitrogen when supplied to plants in considerable quantity 
specially increases the luxuriance of their leaves, stems and 
vegetative organs ; such plants are dark green in colour, and 
show little tendency to produce reproductive organs and seeds. 

(iv) Phosphorus. Phosphorus is a constituent of several kinds 



POTASSIUM 173 

of protein compounds, and is more especially abundant in the 
protein of the nucleus of plant-cells. 

Besides being met with as a constituent element of organic 
compounds, it is often present in the form of inorganic phosphates. 

Phosphorus constitutes a large proportion of the ash of seeds, 
and without an adequate supply of this element, the formation 
and development of seeds do not take place satisfactorily. 
The amount of phosphorus calculated as phosphoric acid in the 
ash of wheat-grains averages from 45 to 50 per cent, and in 
beans about 40 per cent. : in the ash of the vegetative parts the 
amount is considerably smaller, e.g., in wheat-straw about 5, in 
turnips 7, in hay 6, and in potato tubers about 17 per cent. 

Phosphorus is absorbed by plants from the soil in the form 
of phosphates of potassium and calcium. 

(v) Sulphur enters into the composition of proteins, although 
the amount is small, rarely exceeding 2 per cent. It is also 
a constituent of ' mustard-oil ' obtained from many cruciferous 
plants, and is found in the form of inorganic sulphates in which 
condition it is absorbed from the soil. 

(vi) Potassium. This element is specially abundant in the ash 
of the young actively-growing part of plants where cell-division 
is going on, and probably is an essential constituent of the 
protoplasm of all cells. It also exists combined with tartaric, 
oxalic, malic, and other organic and inorganic acids in the cell-sap. 

Tissues containing large reserves of carbohydrates are frequently 
rich in this element ; for example, in potato tubers 2*3 per cent, 
in grapes about 3 per cent., and in 'mangels 4 per cent, of the dry 
matter is potash (K 2 O). 

It is taken up from the soil chiefly as nitrate, chloride, car- 
bonate, sulphate and phosphate. 

The part which potassium plays in the economy of the plant 
is not known with certainty. According to De Vries its salts 
are especially concerned with the maintenance of the turgidity 
of the cells, and as the latter condition is essential for growth 



174 CHEMICAL COMPOSITION OF PLANTS 

the particular abundance of the element in growing tissues is 
thus partially explained. 

It has been observed that the ' fixation of carbon ' in green 
tissues ceases when potassium isabsent, and cereals and peas grown 
with an insufficient supply produce small thin grains and seeds. 

The place of potassium in the economy of the plant cannot be 
taken by any of the other nearly allied elements such as sodium 
and lithium. 

(vii) Calcium. Fungi appear to be able to dispense with calcium, 
but for green plants it is an essential element. It is absorbed 
from the soil in the form of a nitrate, phosphate or sulphate. 

In the young parts of plants calcium is generally present in small 
quantity only and in some instances it may be missing altogether 
from such parts for a time, its absence leading to no apparent in- 
jurious effect. It is most abundant in the older parts of plants, such 
as fully-developed and dying leaves, bark and pith, and occurs in 
the form of salts of organic and inorganic acids more especially as 
oxalate and carbonate. The amount of lime (CaO) in the ash of 
barley, oat, and wheat straw is generally about ^ per cent. 

Although seedling plants may continue to grow for one 01 
two months without calcium, they always appear stunted under 
such conditions and present other features of ill-health ; if calcium 
compounds are still withheld death takes place. 

Like some other essential elements calcium plays a many- 
sided role in plant-nutrition. 

Oxalic acid and soluble oxalates are formed in certain plants 
and when present in very slight excess act injuriously upon the 
nucleus and other cell-constituents ; in the presence of calcium 
salts their accumulation and poisonous action is prevented by the 
formation of insoluble calcium oxalate. 

Calcium is, however, not exclusively utilised for the neutralisa- 
tion of oxalic acid, for there are many plants which never contain 
oxalic acid, and yet it is found that such plants still require this 
element for perfect growth. The assumption that calcium oxalate 



NON-ESSENTIAL CONSTITUENTS 175 

is a waste product is not apparently true in every instance, for 
there is evidence to believe that it is dissolved again sometimes 
and utilised as a reserve of calcium. 

(viii) Magnesium is found in the ash of all parts of the plant, 
but more especially in that of seeds. About 1 2 per cent, of the 
ash of wheat grains consists of magnesia (MgO), while the ash of 
the straw and vegetative parts contains less than 2 per cent. 
Magnesium is taken from the soil, chiefly as carbonate and 
sulphate, but its use to the plant is still very obscure. 

(ix) Iron. The amount of iron in green plants is generally 
very small, rarely exceeding 0*2 per cent, of the ash. It is, 
nevertheless, absolutely necessary for their nutrition since with- 
out it no chlorophyll is formed. Sufficient iron is present in 
seeds for the production of a certain amount of chlorophyll, 
and the first few leaves of seedlings grown in culture solutions 
free from iron are green \ the subsequent ones are, however, 
pale and incapable of utilising the carbon. 

3. Non-essential elementary constituents of plants. Some 
of the elements are of such rare and abnormal occurrence in 
plants that they need not be mentioned. Others, such as silicon, 
sodium and chlorine, although found to be non essential to the 
growth of green plants, are universally met with in the ash and 
demand brief notice. 

Although healthy plants can be grown in the absence of several 
elements, which are commonly met with in ordinary plant ash, 
these so-called non-essential constituents may be, and probably 
are, of use in stimulating or depressing the activity of various 
functions carried on by plants. 

Silicon is specially abundant in the cell- walls of the external 
portions of the stems and leaves of barley, wheat, oats and grasses 
generally : more than one-half of the total ash of the cereals 
consists of silica (SiO 2 ). 

The accumulation of silicon in the cell-walls was formerly 
supposed to be the cause of the rigidity and firmness of well- 
grown straw and the * lodging ' of cereal crops was attributed to a 



176 CHEMICAL COMPOSITION OF PLANTS 

lack of this compound. * Lodging ' is, however, due to a weakness 
caused chiefly by want of proper amount of light for normal 
growth, and firm-strawed, well-developed plants of maize, oats, 
and other cereals have been grown in water-cultures without 
silicon. Moreover, analysis has shown that the straw of ' lodged ' 
crops generally contains more silicon and is much more brittle 
than straws of crops which have stood upright. 

Jodin grew four generations of maize plants without any silicon. 

Cultures of oats from which this element is missing do not 
yield so much grain as those to which it is applied. 

Silicon is absorbed from the soil in the form of soluble silicates, 
the bases with which the latter are associated being apparently 
utilised in the nutritive processes. 

Sodium in the form of sodium chloride is frequent in all 
plants, but is absorbed in greatest amount by halophytic plants 
which flourish on salt-marshes near the seashore, or inland near 
salt-mines and salt-lakes, where the amount of salt present in 
the soil is more than can be tolerated by ordinary inland plants. 

Many halophytes, such as Glasswort (Salicornia herbacea L.), 
Saltwort (Salsola Xa/iL.), beet and mangel, and species of A triplex, 
belong to the Chenopodiacese (p. 356). Several cultivated cruci- 
ferous plants, such as the cabbages and seakale, are descendants 
of halophytes ; asparagus is another example of the same class. 

Culture experiments have shown that even the most typical of 
these halophytes can be grown without salt ; nevertheless when sup- 
plied with it, they present a different appearance and have different 
physiological characters from plants deprived of the compound. 

Under the influence of an abundance of salt the vegetative 
organs become plumper, more fleshy and succulent and transpire 
less than they do when grown without much salt. 

Plants, such as the cereals and others not habitually growing 
near the sea, are killed by solutions containing more than i or i \ 
per cent, whereas sea-beet and certain species of Atriplex are 
not destroyed by solutions containing 3 or 4 per cent, of salt. 



CHAPTER Xin 
OSMOSIS : ABSORPTION OP WATER. 

i. Osmosis. When a bladder filled with a solution of sugar has 
the opening into it tightly tied with string and then placed in a 
vessel full of pure water it is found that a considerable amount 
of the latter soon passes through the walls of the bladder into 
the interior and mixes with the sugar-solution, in spite of the 
fact that no visible openings are present through which the 
water travels. 

The result of this inward transference of water is that an out- 
ward pressure is set up within the bladder and it becomes more 
and more distended, just as it would be if water or air were 
forced into it mechanically. The amount of internal pressure 
set up under these circumstances depends upon the amount 
of sugar dissolved in the sugar-solution and also upon the 
temperature at which the experiment is made : with a con- 
centrated solution a greater pressure is produced than when a 
weak solution is used, and at a high temperature the pressure is 
greater than at a lower one. 

Similar internal pressure tending to expand the bladder is 
observable when solutions of potassium nitrate, copper sulphate, 
and many other substances are used instead of sugar solution. 
Each of these soluble compounds possesses a different power of 
attracting water through the walls of the bladder ; the pressure 
set up by a solution of say one per cent, of sugar is not the 
same as that induced by a solution of one per cent, of potassium 
nitrate. 

In these experiments it will be found that while pure water 

177 



OSMOSIS: ABSORPTION OF WATER 

passes inwards through the walls of the bladder a certain amount 
of the sugar or the other soluble compounds employed passes 
outwards into the pure water within the vessel : and it is noticed 
that the process of diffusion or passage of the dissolved substances 
goes on through the membrane until the percentage, composition, 
or strength of the solution is the same inside and out. 

Certain membranes are, however, known which allow water to 
pass through them but which are not permeable to sugar and 
other dissolved compounds. 

The diffusion or passage of liquids and solutions of sub- 
stances through membranes in which no visible openings are 
present is termed osmosis: the pressure set up in the interior 
of closed permeable membranes is spoken of as osmotic pressure, 
and the dissolved substances upon which the pressure is primarily 
dependent may be designated osmotic substances. 

A bladder or other structure distended by osmotic pressure 
becomes firm or rigid instead of limp and flabby and in this 
condition is spoken of as turgid, 

Dissolved in the cell-sap of all living plant cells are osmotic 
substances, such as sugars and salts of various kinds, which have 
the power of attracting water into the interior, and when plant 
cells are immersed in pure water they become turgid. 

In all living parts of plants which are adequately supplied 
with water, and especially in those regions in which active growth 
is going on, the cells are distended by osmotic pressure, and this 
state of turgidity is the cause of the elasticity and firmness ex- 
hibited by the thin-walled living parenchymatous tissues of leaves, 
growing-points, and other delicately-constructed portions of plants. 

The pressure within young turgid cells usually amounts to five 
or ten atmospheres and under its influence the cytoplasm is forced 
outwards into close contact with the cell-wall at all points ; the 
cell-wall becomes stretched until its elastic recoil equals that of 
the outward pressure. In the cells of fruits containing consider- 
able amounts of osmotic substances in the cell-sap the pressure set 



OSMOSIS 179 

up in wet weather when abundance of water is conducted to them 
is sometimes sufficient to burst the cell-walls and the fruits split. 

The osmotic properties of a plant cell are, however, not the 
same as those of a bladder filled with sugar-solution, for in many 
instances cells containing sugar or other substances do not allow 
these to pass out into water in which the cells may be immersed. 

It is obvious that even a very slight permeability of the sub- 
stances to which turgidity is due would make it practically 
impossible for any submerged water-plant to remain turgid, and 
the accumulation and retention of sugars and other soluble 
substances in the roots of beet and similar plants growing in 
damp soil would be equally difficult if the protoplasm and walls 
of the external cells were permeable to such compounds. 

Whatever substances pass into or out of a living plant cell 
must permeate both the cell-wall and the thin lining of cytoplasm. 
While pure water finds a ready passage through both membranes 
the cytoplasm is very frequently either quite impermeable or per- 
meable in a very different degree to many substances which easily 
travel through the cell-wall. Moreover, the permeability of the 
cytoplasm to any particular substance is not the same at all times. 

When a turgid cell is immersed in a solution of a substance 
whose attraction for water is greater than that possessed by the 
substances dissolved in the cell-sap, a larger or smaller amount 
of water is abstracted from the cell and the osmotic pressure is 
reduced, the cell becoming smaller and more or less limp. If 
the vitality of the cytoplasm is not destroyed and the osmotic 
action of the solution continues, more water is abstracted from 
the vacuole, but the cytoplasm instead of remaining in contact 
with the cell-wall and allowing the solution to penetrate into the 
vacuole, shrinks away from the cell-wall and takes the form of a 
nearly spherical hollow ball in the centre of the cell-cavity : a 
living cell in this condition is said to be plasmotystd. The space 
between the cell-wall and the shrunken cytoplasm becomes occu- 
pied by the solution which has penetrated inwards through the 



180 OSMOSIS I ABSORPTION OF WATER 

cell-wall, but none is allowed to pass through the living cytoplasm. 
Moreover, the osmotic substances dissolved in the cell-sap do 
not travel outwards through the cytoplasm. Cells plasmolysed 
in this manner regain their turgid condition when placed in pure 
water ; the plasmolysing substance which has passed through the 
cell-wall diffuses out and water again enters the vacuole so that 
the cytoplasm becomes forced into contact with the cell-wall. 

When a leaf or a branch with leaves upon it is cut from a 
plant and left exposed to the air, water soon escapes from the 
cells in the form of vapour ; the turgidity of the cells is rapidly 
reduced and, in consequence, the leaves instead of maintaining 
their elasticity and firmness, become limp and unable to support 
themselves in a normal position. 

This flaccid state of * wilted ' or * faded ' parts of plants is always 
brought about by the loss of water from the cells whereby their 
turgid stretched condition is reduced, although the conditions 
which lead to the loss of water is not the same in all cases. 

If the loss of water from a cut shoot has not gone too far, and 
the cytoplasm is still living, it is generally possible to renew the 
former turgid state of its cells by placing the end of the stem in 
water, or by forcing water into the * wilted' shoot as in Ex. 105. 

From various extensive observations and experiments it is 
evident that the passage of substances in solution into or out 
of a cell, is under the control of the living cytoplasm ; the 
phenomena of turgidity and other osmotic properties are de- 
stroyed when death of the cytoplasm takes place. 

Ex. 99. Stretch a piece of wetted bladder across one end of a glass lamp- 
chimney and firmly tie it with string ; then fill about of the chimney with 
a saturated solution of sugar, and suspend it in a vessel of water, so that 
the sugar-solution inside the glass chimney is level with the surface of the 
water outside. Allow it to remain for a few hours ; note that the water 
passes inwards through the bladder into the sugar solution and causes the 
level of the latter to rise. 

Ex. 100. Repeat the preceding experiment, using a strong solution of 
copper sulphate or potassium bichromate. Observe if the copper sulphate 
or potassium bichromate passes outwards and colours the clear water. 



OSMOSIS 



iSl 



Ex. 101. Cut a few slices, about J of an inch thick, through a beetroot 
or sugar beet ; wash them in distilled water and place 

(1) Some in a vessel in distilled water. 

(2) Others first in boiling water for a minute or two to kill the cytoplasm 
of the cells, and then into a vessel containing distilled water. Allow them 
to remain for four hours ; afterwards take out a small quantity of water 
from each vessel and test for sugar by boiling with a drop or two of 
hydrochloric acid and subsequently adding Fehling's solution (see Ex. 80). 

Ex. 102. Cut a transverse section through a portion of a garden beetroot. 
First wash it in water in a watch-glass, and then mount in water and 
examine with a low power of the microscope. 

( i) Observe the presence of pink cell-sap in the uninjured cells ; note that 
it does not escape into the surrounding water. 

(ii) Run under the cover-glass a few drops of a 4 per cent, solution of 
common salt, and observe that as the colourless solution of salt penetrates 
into the cell plasmolysis begins and the cytoplasm recedes from the cell- 
wall. Notice that although water is withdrawn through the cytoplasm, the 
latter does not allow the colouring matter of the cell-sap to 
diffuse outwards, for the salt-solution which passes inwards 
through the cell-wall remains uncoloured. 

(iii) Remove the cover-glass when the cells have become 
plasmolysed, wash away the salt-solution by soaking the 
section for a second or two in pure water, and then re- 
mount in water. 

Examine with microscope and note that the cytoplasm 
gradually recovers its original position close to the cell- 
wall. 

Ex. 103. Cut a similar section of a piece of beetroot, 
and dip it for a moment into methylated spirit to kill 
the cytoplasm of the cells ; wash quickly and then mount 
in water ; note that the pink cell-sap now diffuses out into 
the surrounding water. 

Ex. 104. Make careful measurements of portions 2 or 
3 inches long of the young primary roots of beans and 
peas, young hop shoots, young flower-stalks of a dandelion, and other turgid 
portions of plants. Place them in a 10 per cent, solution of salt for six or 
seven hours and measure again ; note the shrinkage and flabbiness of the 
parts due to loss of turgidity of the cells. 

Ex. 105. Cut off a shoot of a Jerusalem artichoke and leave it to wither 
in an ordinary room for about an hour ; note the limp state of its leaves 
after that time. After cutting off half an inch of the stem fasten it to a 
bent glass tube by means of a short piece of rubber tube (r) as in Fig. 83. 




FIG. 83 



182 OSMOSIS: ABSORPTION OF WATER 

Firmly tie the rubber tube to the glass tube and to the stem of the plant, 
and then partially fill the glass tube with water taking care that no air is left 
between the end of the stem and the water. Pour in mercury until the level 
in the free limb of the tube is considerably higher than in the other (6) ; the 
pressure of the mercury will force the water (a) into the shoot and the leaves 
will soon begin to assume their natural position and firmness. 

2. Absorption of water. In all actively-growing plants water 
forms considerably more than half their total weight ; it satur- 
ates the living protoplasm and the cell-walls, and is the chief 
component of the cell-sap. 

Water is utilised by plants for maintaining the turgidity 
of their cells, and a small amount is employed as a food-material. 
It is also of the greatest importance for the purpose of dissolving 
the various foods present in the plant and conveying them to the 
different organs requiring nourishment. Moreover, the absorp- 
tion of water is the only means which a plant possesses of 
obtaining the various essential food-materials which are derived 
from the soil, for it is only when these necessary constituents 
are dissolved that they can find an entrance into plants : no 
solid particles of manures or other components of the soil, how- 
ever small, are taken up by them. 

Water and the dissolved compounds which plants absorb pass 
into them by osmosis and therefore only gain an entrance 
through organs whose external cell-walls are uncutinized or 
unsuberized. During the life of an ordinary farm or garden 
plant, the absorption of water and the absorption of dissolved 
food-materials are necessarily carried on at the same time : they 
may, however, be treated as separate phenomena. 

The nature of the dissolved substances which are absorbed 
by plants, and the conditions which govern their absorption, are 
dealt with in chapters xii. and xv. ; at present it is advisable to 
consider the absorption of water alone. 

Plants which live completely immersed in the sea and in 
ponds and rivers rarely have a well-developed cuticle and take 



ABSORPTION OF WATER 183 

in water through the surfaces of their stems and leaves as well 
as through their roots, but the crops of the farm and garden 
and all ordinary land-plants absorb all the water which they 
require from the soil by means of their roots only. 

When the soil in a pot in which a plant is growing is allowed 
to become dry the plant begins to droop and wilt, and no amount 
of syringing or even immersion of the leaves and stems in water 
will completely revive and sustain the life of the plant so long 
as the soil is kept dry. 

In good well-drained soil, the chief amount of rain which falls 
upon it sinks through into the subsoil, but a certain amount 
remains behind in the form of more or less thin films of water 
surrounding each solid particle of which the soil is composed. 

In such soil some water is retained in the minute spaces 
present in it, and a certain amount of water travels upward from 
the subsoil by capillarity into these spaces in the upper layers 
of the soil. Good well-drained soils, while thus retaining an 
adequate supply of water, allow a free penetration and circula- 
tion of air within them. Only in water-logged soils totally 
unsuited to the growth of ordinary farm and garden crops are 
all the spaces between the component particles of the soil 
completely filled with water, and air excluded. 

Soon after the appearance of the primary root from a seed 
secondary roots spring from it, and from these new roots arise, 
so that the soil becomes penetrated in all directions by fine 
rootlets, near the ends of which numbers of root-hairs are 
developed. The growing rootlets push their way through the 
small crevices in the soil and the root-hairs are brought into 
close contact with the small particles of soil and with the films 
of water surrounding the latter. 

Formerly the absorption of water was supposed to take place 
through the root-caps which were termed * spongioles ' ; experi- 
ments, however, have shown that plants are able to absorb all 
the water they need when the root-caps are exposed to the air 



184 OSMOSIS: ABSORPTION OF WATER 

or destroyed, so long as the other young parts of the roots are 
kept in contact with water. 

It has been experimentally proved that it is only through the 
root-hairs and the youngest parts in the immediate neighbour- 
hood of the root-hairs that the absorption of water occurs : 
through the older parts on which the root-hairs have shrivelled 
and which have become covered with a tissue of cork-cells water 
is unable to penetrate. 

The walls of the root-hairs consist of ordinary uncutinized 
cellulose through which water readily passes, and it is on 
account of the existence of osmotic substances in the cell-sap 
within the hairs that water with which they come in contact is 
attracted into them. 

After carrying on their work for a short time they wither and 
die, but before this occurs a new set of hairs arises on the 
extending rootlet. 

The greatest development of root-hairs occurs upon roots 
which are allowed to grow in damp air or in a moderately dry 
soil. When roots are immersed altogether in water, root-hairs 
are generally absent; the necessary absorption in such roots 
is carried on by the unextended superficial cells of the piliferous 
layer, there being no need for the extension of these cells into 
long hairs. 

In very dry soils the development of root-hairs is feeble or 
entirely checked. 

On account of the delicate nature of the root-hairs it is not 
possible to remove a plant from the soil without breaking the 
connection of the hairs with the fine particles of earth and 
permanently destroying many of them ; transplanted plants, 
therefore, always suffer for want of water until new hairs are 
formed on the rootlets. Among certain plants new roots and 
root-hairs do not form readily and such plants cannot be trans- 
planted. When trees or other plants are removed, it is advisable 
to specially preserve the youngest rootlets from which fresh 



ABSORPTION OF WATER 185 

growths are most easily produced, and after re-planting her- 
baceous plants exposure to a dry atmosphere, or to strong light 
and other influences which promote loss of water from the leaves 
by transpiration (see chap, xiv.), should be avoided for a time 
wherever possible. 

The osmotic absorption of water by the root-hairs of plants only 
goes on when the following conditions are fulfilled, namely : 

(i) A certain degree of warmth of the surrounding soil, 
(ii) Access to fresh air ; and (iii) A suitable supply of water. 

Cabbages and many other plants are able to absorb consider- 
able amounts of water at freezing-point, but at the low tempera- 
tures of winter absorption generally ceases or is vastly decreased 
and it is not until the return of warm days in spring that the 
activity of the roots is manifest. 

The application of water from wells to the roots of tropical 
and sub-tropical plants growing in pots in warm houses frequently 
checks their absorptive power by lowering their temperature 
considerably. 

Sachs showed that the absorption by a tobacco plant at a 
temperature of 4 or 5 C. was so small that withering com- 
menced in spite of the fact that the roots of the plant had 
access to an abundance of water. 

In consequence of the presence of a considerable amount of 
water which requires much heat to warm it, the temperature of 
imperfectly-drained soils is usually lower than that at which the 
roots of ordinary farm and garden plants do their work best. 
Moreover, such soils do not allow of the free circulation of fresh 
air within them, and the respiration process carried on by the 
living protoplasm of the root-hairs is interfered with. 

Without the access of an adequate supply of oxygen, or where 
there is much carbon dioxide in the soil, poisonous compounds 
are formed within the roots as the result of imperfect respiration 
and the plants become unhealthy. Over-watered plants growing 
in pots commonly exhibit injuries of this character. 



1 86 OSMOSIS I ABSORPTION OF WATER 

Roots die or develop badly when plants are transplanted and 
put into the soil too deeply. Although the root-hairs come 
into very intimate contact with the small particles of earth, and 
are specially adapted to use the thin films of water surrounding 
the latter, they are not able to withdraw the whole of the water 
which a soil is capable of holding. When soils are allowed to 
dry, plants growing in them begin to wither as soon as the water 
present sinks below a certain amount, which varies with the 
composition of the soil in question. Beans, tobacco and 
cucumber plants have been found to wither and die in good 
garden soils containing 12 to 15 per cent, of water and in loams 
containing 8 per cent. 

Ex. 106. Grow a dwarf-bean in a pot of sandy soil and one in a pot of good 
garden soil. When the plants have three or four well -developed leaves allow 
the soil to become dry and when the plants are dead shake out the soil from 
each pot and determine what percentage of water remains in it. To do this, 
weigh a porcelain dish ; then place a small amount of the soil in the dish and 
weigh again ; the difference gives the weight of the soil taken. Place the 
dish with the soil in a * water-oven ' to drive off all the water ; leave for five 
or six hours and when cool weigh again ; the loss gives the amount of water 
which has evaporated from the amount of the soil taken ; from these weights 
calculate the percentage loss of water. 

Ex. 107. Select three seedling cabbages as near the same size as possible ; 
take one of them up carefully with a small amount of earth with it so as to 
damage the roots as little as possible ; the second take up and shake off all 
the soil ; take up the third and after shaking off all the earth from its roots 
pull off all the finest rootlets. Then transplant all three and notice the 
further growth of the three plants for ten days. 

3. Exudation-pressure. Boot-pressure: 'bleeding' of plants. 
After water has been absorbed from the soil by the root-hairs, it 
passes by osmosis from the latter into the adjoining parenchyma- 
tous cells of the cortex (c, 2, Fig. 72). The cortical cells then absorb 
from each other until they all become highly turgid, and the same 
turgid condition is soon reached by the parenchymatous cells 
within the vascular cylinder of the root. When a certain degree 
of pressure is attained within the innermost parenchymatous cells 



EXUDATION-PRESSURE I ROOT-PRESSURE 187 

bordering on the wood-strands (w, 2, Fig. 72), the protoplasm 
ot the former becomes permeable, and a portion of the cell-sap 
within them is forced into the cavities of the vessels and tracheids 
with which the cells are in contact. 

The pressure thus set up by the turgid parenchymatous cells 
of the cortex and the cells of the ground tissue within the 
vascular cylinder of a root is termed root-pressure. 

Under this pressure the vessels and tracheids of the vascular 
bundles become filled with water, and on cutting off the stem of 
a tree in spring after the roots have begun their absorptive work 
and before the buds have opened, the water is forced out of the 
cut end of the stump still connected with the root in larger or 
smaller quantities ; such outflowing of water from plants which 
have been cut is spoken of as c bleeding. 1 The liquid forced out 
of a * bleeding ' plant is not pure water, but a solution containing 
small quantities of various substances,- such as soluble carbo- 
hydrates, acids, organic and inorganic salts, and proteids. In 
the sugar maple the liquid contains over 3 per cent, of sugar 
which in some parts of the world is profitably extracted from it 

In the case of the vine, sycamore, birch and other trees, 
'bleeding 1 may continue for several days, during which time 
several pints of ' sap ' may be exuded, 

By attaching a suitable manometer or pressure-gauge to the 
stump of a ' bleeding ' stem, the pressure with which the sap is 
forced out can be measured : in the vine it frequently amounts 
to more than one atmosphere, or sufficient to support a column 
of mercury 760 mm. in height. 

The root-pressure of a stinging nettle was found to be sufficient 
to balance a column of mercury 460 mm. in height, while that 
of an ash tree was only able to support a column of 20 mm. of 
mercury. 

The phenomena of root pressure and 'bleeding* are best 
observed in woody perennials, such as the vine, birch and 
sycamore, in spring and early summer about the time when the 



i88 OSMOSIS: ABSORPTION OF WATER 

buds are opening. At this season, the warmth of the soil 
encourages very active absorption by the roots and trie water 
taken into the plant finds no outlet : the vessels and tracheids 
of the young wood throughout the plant become, therefore, 
gorged with water and cutting into the stems allows the water 
to escape. Later in summer, however, when the leaves are 
expanded, the water absorbed by the root and forced into the 
vascular cylinder, travels through the stem and into the leaves, from 
whence it escapes into the air in the form of vapour as described 
in the next chapter. The rapid loss of water from the leaves 
results in the removal of large quantities of water from the 
cavities of the vessels and tracheids and these latter elements 
of the wood are then found to contain considerable amounts 
of air as well as water : plants cut at this season do not ' bleed.' 

Moreover, the evaporation of water from the leaves goes on so 
rapidly that a partial vacuum is created and a negative pressure 
is set up in the vascular system of the plant; under such 
conditions, instead of water being pressed out with considerable 
force from the cut stump of a plant connected with its root, 
the stump is found to absorb any water given to it, and not 
until it has become saturated can a positive root-pressure be 
detected. 

Root-pressure and * bleeding* are not confined to trees and 
shrubs, but are observable in greater or lesser degree in many 
plants when evaporation of water from the leaves is retarded 
or prevented. They may be as readily observed in many 
herbaceous plants, such as the sunflower, potato, tobacco, dahlia 
and maize, as in woody plants. 

The force of root-pressure is usually highest in the afternoon 
and lowest in the early morning. Like other vital processes, it 
is influenced by external conditions : an increasing temperature 
of the soil increases it. 

Although the pressure set up by the osmotic activity of the 
parenchymatous cells of the cortex and other parts of the root 



EXUDATION-PRESSURE : ROOT-PRESSURE 189 



and stem is not sufficient to force water to the top of tali trees, 
it brings about the introduction of water into the conducting 
channels and helps in the rapid translocation of water throughout 
the vascular tissues of the plant. 

When the absorptive activity of the root of a plant is encouraged 
by warmth of the soil and at the same time the loss of water in 
the form of vapour from the leaves is diminished or prevented 
by a damp atmosphere, the plant becomes overcharged and 
water is forced out of the tips and edges of the leaves in drops 
which are frequently mistaken for dew-drops. 

This emission of drops of water may be often observed on the 
tips and edges of the leaves of such plants as balsams, ' Arum 
lilies' and fuchsias when growing in warm houses in which a 
damp atmosphere is maintained. Similar drops are sometimes 

nseen in the early morning on the tips and edges of 
the leaves of species of Troptzolum, Alchemilla, 
and many wild plants after a warm night when the 
sky has been overcast. 

The * bleeding ' of cut stems and the exudation 
of drops of water from uncut plants is not caused 
exclusively by the osmotic pressure of the cells 
in the root, but is due in some degree to the 
parenchymatous cells of the leaves and the 
medullary rays and wood parenchyma of the stem, 
for ' bleeding * from the cut end of a leafy stem 
which has no connection with a root can often 
be induced by immersing its young and easily- 
wetted leaves and stem completely in water. 

The osmotic pressure which results in the 
'bleeding* of plants when cut, or the forcible 
emission of drops of water from leaves and other 
parts is a general phenomenon observable in 
FIG. 84. greater or lesser degree throughout the body of 
the plant; it is best termed Exudation-pressure' or *bkeding- 



b 



a. 




i9o OSMOSIS: ABSORPTION OF WATER 

pressure? root-pressure being merely a special example of its 
activity. 

Ex. 108. Water a well-developed sunflower, tomato, or tobacco plant 
growing in a pot as in Fig. 84, and place it in a warm shaded situation for 
two or three hours. Then cut off the stem and fasten a glass tube to the 
stump by means of a piece of rubber-tube (r). Pour in a little water and 
tap the tube to displace air-bubbles ; mark the height at which the water 
stands as at a. After a time a considerable amount of sap will be forced from 
the cut end of the stem and will rise in the glass tube. 

Ex. 109. Cut off the stem of a young vigorously -growing stinging nettle 
in spring, and after wiping the cut surface of the stump notice with a lens 
that the sap which is exuded afterwards comes from the vascular bundles 
and not from the pith. 

Ex. 110. Sow a few barley grains in a pot of good garden soil, and when 
the plants are about 2j or 3 inches high place the pot in a warm shaded or 
dark place and cover the pot with a bell glass. Notice after three or four 
hours that from the tips of the young leaves drops of water are exuded. 
Remove the bell-glass and leave the plants uncovered until quite dry, then 
cover again and notice a further execretion of water, 



CHAPTER XIV. 



'CL 



TRANSPIRATION : THE TRANSPIRATION- 
CURRENT. 

Transpiration. If the leaf of a growing sunflower or Jerusalem 
artichoke is enclosed on a warm bright day in a wide test-tube 

as in Fig. 85, and the end of 
the tube closed with a split 
cork (<r) or a plug of cotton- 
wool, it will be noticed that 
the inside of the tube soon 
becomes covered with a dew- 
like film of pure water which 
gradually trickles down and 
collects in considerable amount 
as indicated at a. 

From all parts of ordinary 
land plants there is going on 
a continuous invisible loss of water in the form of vapour, and 
unless precautions are taken to collect the water in some manner 
similar to that described above the existence of its escape from 
plants into the air is not easily realized. 

The exhalation of water in the form of vapour from living 
plants is termed transpiration : it is not a mere physical process 
of evaporation or drying such as occurs when a damp towel is 
exposed to the air, but is a physiological process, which, although 
influenced by external conditions, is nevertheless controlled to 
some extent by the living protoplasm of the plant. Dead 

191 14 




FIG. 85. 



TRANSPIRATION 

portions of plants lose water more quickly than similar living 
portions. 

The amount of water transpired by a sunflower 3 \ feet high on 
a warm day was found by Hales to be 20 ounces in twelve hours, 
and an ordinary cabbage gave off 15 ounces in the same time. 
At this rate an average crop of cabbages would give off between 
3 and 4 tons of water per acre per day. As the loss by the upper 
parts of the plant must be compensated by absorption of water 
from t]ijs0il, it will be readily understood that land bearing a 
crop is always drier than bare fallow. 

If transpiration goes on at a greater rate than the absorption 
by the root the turgid state of the cells is more or less decreased 
and * wilting' appears. This 'wilted' condition of plants not 
unfrequently happens in bright hot weather, in dry soils contain- 
ing too little water, but it may occur in ordinary soils even when 
the roots are actively taking in what would be a sufficient 
quantity of water for the needs of the plants, if the brightness, 
high temperature and other conditions encouraging excessive 
transpiration were reduced. 

' Wilting ' does not necessarily imply that no water is entering 
the plant : it is merely an indication that the plant is losing more 
than it is taking in. 

Unavoidable mechanical injury to the absorbing region of the 
root when plants are transplanted, injuries from the attack of 
insects, and reduction of the temperature of the soil below that 
at which the root is able to carry on its work satisfactorily, are 
responsible for inadequate absorption of water and consequent 
'wilting': moreover, an insufficient supply of air to the root 
which happens when the latter is growing in water-logged soil 
prevents proper absorption and may result in flagging of the 
leaves of the plant 

Among all kinds of plants, and especially among those species 
living in dry situations, various Adaptations are observable which 
tend to prevent a too rapid loss of water. 



TRANSPIRATION 193 

The rate at which transpiration is carried on is influenced by 
the character of the external cell-walls of the various parts of the 
plants. 

From cells with suberised and cutinised walls the loss of water 
is small, hence, from the stems and leaves of cactuses and house- 
leek, from many fruits such as apples and pears, with a well- 
developed cuticle, and also from stems and tubers covered with 
cork-tissue and bark, the amount of transpiration is comparatively 
slight : vegetable marrows, potatoes, and many kinds of apples 
containing a large proportion of water, retain a large amount of 
it for many weeks and even months. 

The presence of a covering of woolly hairs upon the leaves 
and other parts of plants aids in the prevention of excessive 
transpiration, and the excretion of a waxy ' bloom ' on the exterior 
of the epidermis of many leaves such as those of the cabbage, 
swede and onion, and upon fruits such as plums and grapes, acts 
in a similar protective manner. Experiments show that when 
the ' bloom ' is rubbed from leaves and fruits a greater loss of 
water takes place than from similar parts untouched. 

The amount of what may be termed cuticular transpiration, or 
loss through the external cell-walls of leaves, stems and parts 
normally exposed to the air, is slight in all cases, except in the 
youngest members whose epidermal cells have not yet become 
fully cutinised. 

The chief escape of water is by diastomatic transpiration, that 
is by loss through the openings of the stomata, and as these are 
always met with in greatest abundance upon the leaves of plants, 
the latter may be considered as the chief organs of transpiration. 

The cells of the spongy parenchyma of the leaf (j, Fig. 75) 
possess uncutinised walls which freely allow the passage of 
water-vapour into the intercellular spaces, and it is mainly from 
these spaces that the vapour escapes by way of the stomata 

(*) 
Generally there are more stomata on the lower surfaces of 



194 TRANSPIRATION 

ordinary leaves and it may be shown (Expt. 114) that in such 
cases transpiration is most active from the lower sides. 

Unless their surfaces are specially protected by a dense 
cuticle, plants with leaves of large area usually transpire and 
need considerable amounts of water for proper growth : they are 
frequently met with in damp situations unfavourable to trans- 
piration and therefore where a large transpiring surface is a 
necessity in order to get rid of surplus water. 

On the other hand the leaves of plants adapted to live in dry 
situations are frequently small and narrow, the transpiring surfaces 
being reduced often to a minimum. 

In diastomatic transpiration from a leaf or stem the opening 
and closing of the aperture between the guard-cells of the stomata 
(a, Fig. 74) regulates and controls the amount of water-vapour 
given off, and it is the turgidity of these guard-cells which 
determines whether the pore is open or shut. When the cells 
are highly turgid they curve away from each other and the 
opening is* as wide as possible; when they become flaccid 
they straighten and the aperture between them decreases until 
the free edges of the cells touch and completely close the pore. 

The turgidity of the guard-cells, and therefore the possibility 
of the escape of water-vapour from the leaf, is influenced both by 
internal and external circumstances. About the nature of the 
internal vital conditions little is known, but it may be remarked 
that, when the loss of water is excessive and is not completely 
compensated by absorption from the soil, the stomata begin to 
close before actual ' wilting ' is observable. 

The chief external conditions which influence transpiration 
are: 

(i) the intensity of the light to which the plant is exposed, 
(ii) the water-content of the surrounding atmosphere, 
(iii) the temperature of the air and soil, 
(iv) the movement of the air, 
(v) the water-content of the soil and the concentration and 



TRANSPIRATION 195 

chemical nature of the substances present in the solu- 
tions absorbed by the plant. 

(i) At night and in darkened rooms plants transpire very little ; 
in diffuse daylight an increase is noticed, but when exposed to 
bright sunlight the amount of water given off is vastly augmented. 
In one of Wiesner's experiments 100 sq. cm. of leaf-surface of 
a well-grown maize plant gave off in the dark 97 milligrams of 
water per hour, while in diffuse daylight 114 milligrams were 
lost and in bright sunlight 785 milligrams. 

Usually under the influence of light the turgidity of the 
guard-cells is increased, the stomatal pore therefore opens and 
water-vapour is thus allowed to escape freely from the leaf. 
The action of light upon transpiration is independent of the 
effect of heat which usually accompanies it ; it is not, however, 
simply connected with the increased opening of the stomata 
under its influence, for a similar increase of transpiration is 
noticed when fungi which possess no stomata are exposed to 
light of increasing intensity. Light appears to act as a direct 
stimulus upon the protoplasm, and under this stimulation the 
latter becomes more permeable to the water of the cell-sap. 

It must also be remarked that light indirectly influences 
transpiration by modifying the structure of the tissues and the 
composition of the cell-walls of the leaves. Plants grown in 
well-exposed situations with full access to light have a greater 
development of cuticle and smaller intercellular spaces within 
the leaves than those grown in shaded situations; from the 
former less water is transpired than from the latter. 

(ii) When the air is saturated, as on a dull day or in a close 
damp greenhouse, transpiration is almost entirely checked ; on the 
other hand a dry atmosphere, even if cold, leads to considerable 
loss of water, and the injury which occurs to delicate leaves and 
other recently expanded parts of plants at low temperatures in 
spring is perhaps caused as much by the dryness of the air at 
such times as by its coldness. 



196 TRANSPIRATION 

(iii) Some plants have been found to transpire slightly at tem- 
peratures below freezing-point. Increasing the temperature within 
certain limits accelerates the opening of the stomata, and even 
in parts of plants free from these openings transpiration is 
augmented thereby. 

(iv) Plants exposed to draughts and stronger currents of air lose 
considerable amounts of water even when the stomata are closed. 

(v) A great decrease of water within the soil in which a plant 
is growing results in decreased transpiration. 

The absorption of a somewhat concentrated solution also 
decreases transpiration ; and plants which have taken up con- 
siderable amounts of common salt transpire less than those 
which have no access to this substance. 

Sachs and others found that the alkalies, potash, soda and 
ammonia in small quantities tended to increase transpiration, 
while acids decreased it. 

Ex. 111. Collect water from a leaf of a sunflower or other plant in a test- 
tube arranged as in Fig. 85. 

Ex. 112. (a) Take three flasks, each holding about 100 or 150 c.c., and 
pour water into each until about three-quarters full. 

Cut two similar branches 2 feet long from an apple tree and remove the 
leaves from one of them ; place the branches in two of the separate flasks, 
and after marking the level of the water in each flask with a piece of gummed 
stamp paper, expose all three flasks in a well-lighted window or out of doors. 
Observe the loss of water in each flask after six hours : which branch tran- 
spires most ? 

(&) To obtain a more accurate knowledge of the loss of water, weigh each 
of the flasks and the branches separately at the commencement and the end 
of the experiment. It will be observed that the water taken up by the 
leafy branch is not merely absorbed into its substance but is transpired 
by its leaves, for its weight at the beginning anfl end of the experiment are 
nearly the same, although the weight of water lost from the flask has been 
considerable. 

(f) Repeat the experiment, but keep the apparatus in a dark room. 

Ex. 113. Transpiration from a shoot may be demonstrated by arranging 
as in Fig. 86. Push the freshly cut shoot (a) through a bored cork : it 
should fit the hole in the cork tightly and should project a little way through 
it. Fill the U-tube () completely with water and put the cork and shoot 



TRANSPIRATION 



197 




into one end of the tube. See that the other end is completely full of water 
and then insert into it a cork with a bent tube (). Some of the water will be 
forced along the tube to a point (0), which should be marked with gummed 
paper. Arrange the apparatus so that the tube b is horizontal and expose 

to a bright light : the 
transpiration from the 
leaves of the shoot soon 
causes a withdrawal of 
water along the tube. 

It is necessary that the 
joints of the apparatus 
should be air-tight and 
no bubbles of air should 
remain in the tube (). 

Ex. 114. The differ- 
ence in the transpiration 
from the two surfaces of 
a leaf possessing a great 



many more stomata on 
FlG - 86 - one side than on the other 

may be shown by placing the leaf between paper which has been steeped in 
cobalt chloride solution and dried. 

Make a 3 per cent, solution of cobalt chloride and soak some pieces of 
blotting-paper or circular filter papers in it. Allow the latter to cliyin the 
air. When damp, the cobalt chloride on the paper is pink, but after drying 
before a hot fire so as to drive off the small remaining amount of water, it 
becomes bright blue : on absorbing a slight amount of water from the air or 
from other sources it becomes pink again. 

Place a leaf of a scarlet-runner between two blue dry pieces of cobalt 
chloride paper, and put the whole between two sheets of glass to prevent 
absorption of water from the air. After a quarter of an hour, examine the 
papers and note whether that in contact with the lower or the upper side of 
the leaf is pinkest. 

Repeat the experiment with leaves of lilac, elder, pear, poplar, plum and 
other plants. 

Ex. 115. To show the influence of a covering of cork in preventing loss of 
water by transpiration, take two potatoes as near the same size as possible. 
Peel one of them and weigh both separately : leave them exposed to the air 
for two hours and weigh again to determine which has lost most water. 

Show in the same manner that when the cuticle of an apple is removed, 
a much more rapid loss of water takes place than when the cuticle is 
present. 



198 TRANSPIRATION 

Transpiration-current. The very extensive loss of water from 
plants by transpiration would soon end in flagging and death if 
more water were not absorbed to take the place of that which 
is given off. The necessary absorption takes place at the root 
in the manner previously explained and between the root- 
hairs, where the water enters, and the leaves, where the bulk of 
it escapes into the air, there is a continuous upward movement 
of a stream of water through the root and stem of a growing 
plant. This current of water is termed the transpiration-current. 

By its means the necessary turgidity of the living cells in all 
parts of the plant is maintained, and it is concerned with the 
conveyance of a constant supply of dissolved food-materials 
from the soil. 

The water absorbed by the root contains dissolved in it 
various substances which are essential for the nutrition of the 
plant, and these substances are carried to the cells of the leaves 
and other organs where they are left and utilized, only pure 
water escaping in the transpiration-process. Moreover, it may 
be noted that the conditions which bring about jtctive transpira- 
tion and rapid movement of water, namely, a high temperature 
and exposure to bright daylight, are just the conditions which 
are essential for the rapid formation of organic substance from 
the food-materials and for the utilisation of the food in the 
nutritive processes carried on by the plant. 

The movement of water in all parts of plants from cell to cell 
by simple osmosis, is much too slow to be of use in maintaining 
an adequate supply to the upper parts of plants where rapid 
loss is occurring. The transpiration-current travels more rapidly : 
in certain herbaceous plants it has been found to move at the 
rate of 5 or 6 feet per hour, when the conditions for trans- 
piration have been favourable; probably it is slower than this 
in most trees. 

The path along which the water is conducted is the wood of 
the plant That it is not conveyed by the pith of a tree is clear 



TRANSPIRATION-CURRENT 199 

from the fact that many trees carry on their functions after the 
pith is destroyed and the centre has become hollow and de- 
cayed. 

It can also be readily shown that the bark and bast do not 
conduct the rapid upward current, for after a narrow ring-like 
portion of tissues, as far as the cambium have been removed all 
round a branch, the leaves above the place where the bark and 
bast have been cut away do not wither. 

By various experiments it has been proved that the current 
travels in the youngest or outermost annual rings of woody stems 
and apparently in the greatest amount, if not entirely, in the 
cavities of the vessels and tracheids ; the heart-wood does not 
conduct water but acts as a mechanical support 

By placing the cut stems of herbaceous plants and the petioles 
of leaves in coloured solutions of certain dyes, and subsequently 
making sections of the stems at intervals, and by holding the 
leaves up to the light, it will be observed that the solutions 
have travelled along the vascular bundles which have become 
stained, the rest of the tissues remaining colourless for a long 
time after the bundles have been coloured. 

The cause of the movement of the water through plants, or the 
force which propels the transpiration-current, has been the subject 
of very extensive research for more than a century. 

No adequate explanation can, however, be given which will 
meet all the facts of the case. The osmotic action of the living 
cells of the root and stem which results in * bleeding-pressure,' and 
the osmotic attraction of substances within the parenchymatous 
cells of the leaves, which results in a sucking-force withdrawing 
water from the vascular bundles, help to set up rapid movement 
of water in a plant. 

In plants of low stature, these forces depending on the activity 
of living cells, may be sufficient to account for the movement of 
the transpiration-current, but the conduction of water to the top 
of very high trees, cannot be satisfactorily explained at present. 



2OO 



TRANSPIRATION 



Ex. 116. (a] Dip the petiole of a leaf of elder in a weak solution of eosin 
or red ink and place the whole in a blight situation. After an hour hold the 
leaf up to the light and examine with the naked eye or a pocket lens ; the 
solution is absorbed and travels along the vascular bundles which will be 
seen to be coloured red. 

Cut thin slices of the petiole and observe with a lens that the solution has 
not diffused much into the tissues round the vascular bundles. 

(b] Repeat the experiment with other leaves and herbaceous leafy stems. 
(<:} Dip the peduncles of snowdrops, pansies, crocuses, narcissi and other 

flowers in the solution and note that 
the thin vascular bundles in the petals 
become stained red. 

Ex. 117. Remove a ring of bark, 
J an inch wide^ from the branch of a 
tree in summer and note that the leaves 
above the cut do not wither, 

Ex. 118. To show that a rapidly 
transpiiing shoot possesses a consider- 
able sucking-power arrange a shoot of 
a sycamore, raspberry or sunflower as 
in Fig. 87. 

Take a piece of rubber-tube (r) about 
2 inches long and slip one end on the 
end of the shoot, the other on a glass 
tube (a). Firmly tie the rubber-tube 
to the shoot and the tube with string. 
Allow the shoot to hang down, and 
then pour water into the tube ; gently 
tap the latter and squeeze the rubber- 
tube so as to get rid of all air bubbles. 
When the tube is full of water close 
the end with the thumb, turn up the 
apparatus into the position indicated in 
the Fig, 87, and place the end of the 
fir tube below the water (n) and mercury 
J/fc- (6) in the glass dish. Support the shoot 
21P?fr by means of the clip and expose the 
whole in a bright window. The water 
in the tube is transpired by the leaves of 




FIG. 87. 



the shoot, and a considerable amount of the mercury is lifted into the tube, 
as shown at (A 1 ). 



CHAPTER XV. 
THE ABSORPTION OF FOOD-MATERIALS. 

i. Food and food-materials. The protoplasm or the living 
material within actively growing plants and animals is continu- 
ally undergoing chemical changes which result in its destruction 
and the formation from it of simpler compounds. To repair its 
waste and to enable it to carry on the work of constructing new 
parts, food is necessary. 

The nature of the/<ra/ of a plant, or the substances which are 
utilised by the protoplasm for the formation of new organs and foi 
its own nutrition, is mot readily understood after a consideration 
of the materials which are consumed during the growth of an 
embryo plant from a seed. 

The substances stored by the parent in the endosperm or within 
the tissues of the embryo for the nutrition of the latter are chiefly 
complex organic compounds such as starch, fats, and proteids, 
and it is these substances, or very slightly altered forms of them, 
which are consumed in the processes of nutrition and growth 
which occur when germination commences. 

Similarly, the substances upon which the young shoots of a 
sprouting potato tuber or the young leaves and flowering shoots 
of a growing bulb are fed, are carbohydrates, fats, and proteids 
or organic compounds of analogous complex constitution. 

The developing buds of a tree in spring are also nourished by 
similar compounds, and there is every reason to conclude that 
the protoplasm in plants and animals alike, depends at all 
times for its immediate nutrition upon organic materials of this 
character. 

801 



202 ABSORPTION OF FOOD-MATERIALS 

Animals and parasitic and saprophytic plants obtain these 
compounds directly or indirectly from the bodies of other living 
or dead organisms, and without a supply of such substances they 
soon die. Green plants likewise need food of a similar complex 
nature for development and growth ; they are, however, not 
generally adapted to obtain compounds of this character from 
their surroundings, but are able to manufacture them from 
inorganic compounds such as carbon dioxide, water, and various 
salts which they derive from the atmosphere and the soil. 

Although these simple inorganic materials absorbed from the 
air and the soil are frequently spoken of as the food of plants, 
it is better perhaps to speak of them as food-materials , for the 
living substance of a plant cannot directly nourish itself upon 
them. It is only after they have been elaborated or built up 
into more complex compounds that they become food which 
can be used for the nutrition of the protoplasm and the formation 
of the tissues of growing organs. 

A seedling after it has consumed the food stored for its use 
by its parent, is unable to make use of carbon dioxide and simple 
salts supplied to it until it is exposed to light under certain 
conditions which allow it to elaborate and synthetically build up 
from these inorganic materials compounds similar to those 
which it has already consumed, and which were supplied ai>d 
manufactured previously by its parent. 

2. Food-materials and their absorption. The food-materials 
absorbed by ordinary green plants are derived from the sur- 
rounding atmosphere and soil upon which the plants grow. 

By the methods of sand-culture and water-culture it has been 
proved that for complete and perfect nutrition, green plants 
must be supplied with food-materials which contain collectively 
some ten or eleven elements as explained in chapter xii. 

It has also been determined by the same experimental 
methods that plants are by no means indifferent as to the form 
in which any particular element is presented to them. For 



FOOD-MATERIALS AND THEIR ABSORPTION 203 

example, they are not able to utilise all nitrogenous compounds 
as sources of nitrogen, nor are they able to obtain their necessary 
carbon from all kinds of carbon-compounds. 

A compound to be of service as a food-material capable of 
supplying a particular element for the nutrition of a plant, must 
(i) be soluble and able to diffuse through the cell-wall and proto- 
plasm of the cells, and (ii) must also possess a certain chemical 
structure. 

The carbon dioxide gas present in the air is the chief source 
from which the carbon is obtained ; the absorption and subse- 
quent use of the gas is discussed in the succeeding chapter. 

The food-materials furnishing the rest of the elements needed 
by plants are obtained from the soil by osmosis through the 
root-hairs. Before they can enter the latter they must be in 
solution, since no solid particle however small is able to 
pass through the closed cell-rnembranes of the absorbent 
hairs. 

Moreover it is only from weak solutions of food-materials that 
plants can absorb what they need ; plants grown by the 
method of water-culture make the most satisfactory progress 
when the total amount of solids dissolved in the water does not 
exceed from *2 to *5 per cent, or 2 to 5 parts in 1000 of water. 
Solutions containing 2 or 2\ per cent, of dissolved substances 
act injuriously upon the protoplasm of the plant, and prevent 
growth : hence the importance of avoiding readily soluble 
manures in excess. 

The water of the soil from which plants obtain all they need 
usually contains not more than *oi to '03 per cent, of solid 
matter dissolved in it 

Carbon dioxide gas is produced within the soil in the processes 
of putrefaction and decay of the manures present, and is excreted 
to a slight extent in the respiration process carried on by the 
protoplasm of the root-hairs. This gas indirectly assists plants 
to absorb useful food-materials, for some of the latter which are 



204 ABSORPTION OF FOOD-MATERIALS 

insoluble in pure water, dissolve appreciably in water containing 
carbon dioxide. 

It must also be noted that carbon dioxide, potassium hydrogen 
phosphate and other substances possessing an acid reaction 
permeate the cell-walls of the root-hairs, and enable the latter 
to corrode and dissolve certain mineral compounds such as 
calcium phosphate and the carbonates of calcium and magnesium 
with which they come into contact. 

3. When the roots of a plant are immersed in a vessel of water 
containing a substance in solution, the dissolved substance may 
not be able to pass through the cell-wall or the cytoplasm of the 
root-hairs in which case none enters the plant. If, however, the 
substance can diffuse through both cell-membranes, it will pass 
into the root-hairs and from there into the rest of the cells ot 
the plant until the cell-sap contains the same proportion of it 
as the water outside the plant ; when this condition is reached, 
equilibrium is established and no more of the dissolved material 
is absorbed. Should the substance after entering the plant be 
used up in the processes of nutrition, or changed into an insoluble 
or non-diosmosing compound, the osmotic equilibrium in regard to 
this particular material is destroyed, and more of it can then enter. 
In this manner a plant is able to completely extract the whole 
of a substance dissolved in water to which its roots have access, 
and can accumulate within itself large amounts of certain elements 
from solutions containing the merest traces of them. For example, 
sea-water contains not more than one part of iodine in 100 millions 
of water, and yet certain sea-weeds accumulate such quantities 
that from i to 3 per cent, of their ash consists of this element. 

The total amount of any particular element occurring in the 
ash of a plant is dependent (i) upon the amount of the soluble 
material containing it present in the soil upon which the plant 
is growing; (2) upon the peculiar specific permeability of the 
protoplasm of the root-hairs ; and (3) also upon the question 
of whether the plant utilises, transforms or removes the par- 



FOOD-MATERIALS AND THEIR ABSORPTION 205 

ticular material from its cell-sap so that more can enter by 
osmosis. 

Two different species of plants growing in the same nutrient- 
solution or with their roots in the same soil are generally found 
to contain very different amounts of each of the various a*sh- 
constituents. For example, the amount of silica in the ash of 
the white water-lily is generally less than a per cent., while that 
of the common reed (Phragmitcs communis Trin.) growing on the 
same marshy soil contains more than 70 per cent, of silica ; and 
while the ash of pea plants is found to contain not more than 
about 7 per cent, of this substance, that of grasses growing on 
the same soil contains over 20 per cent, of it. 

This different quantitive selective power is chiefly due to the 
difference in the power of making use of silica by the two species 
of plants compared; the substance from which the silica is 
derived probably diffuses with equal freedom through the cell- 
walls of both, but whereas the reed continually removes the 
compound from the cell-sap and deposits large quantities of 
silica in its cell- walls thus allowing more to flow in, the water- 
lily uses very little and a state of osmotic equilibrium is soon 
reached, after which no more enters the plant. 

The amount of any particular substance absorbed from the 
soil by a plant is in direct proportion to the amount used in the 
chemical processes carried on by the plant, so that a substance 
present in abundance may be absorbed in very minute quantities 
only, whereas a compound present in small amount may be 
completely extracted from the soil. 

4. The nature of the various inorganic compounds from which 
green plants obtain their supply of the elements essential for 
complete nutrition, has already been mentioned in discussing 
the composition of plants in chapter xii. 

Practically all these food-materials except carbon are absorbed 
from the soil. 

Experience proves that the continuous growth and removal 



206 ABSORPTION OF FOOD-MATERIALS 

of crops from the land end sooner or later in reducing such 
land to a state in which it refuses to grow a remunerative crop 
of any kind unless manures are applied to it. 

This more or less barren condition of land from which many 
crops have been removed is explained by the fact that plants 
lift into their bodies from the soil on which they grow a certain 
amount of its constituents, and the removal of a crop therefore 
means the removal of a considerable weight of the most im- 
portant components of the soil : since the latter does not in 
any case contain an unlimited supply of these plant food- 
materials in a soluble and available form, it will be readily 
understood that the continuous removal of crops from a field 
must eventually lead to exhaustion, and that plants grown upon 
it would starve, unless a new supply of food-material is added 
to take the place of that previously removed. 

It is true that the soil under such treatment does not become 
so completely exhausted of its useful constituents that plants 
altogether refuse to grow upon it, for soluble food-materials 
are constantly being released or renewed from the store of 
insoluble material composing the soil by the disintegrating 
influence of frost and heat, and the chemical action of the 
air and water upon it. Nevertheless, in this country, for the 
production of a remunerative crop, the direct application of 
manure containing food-materials or from which the latter can 
be readily set free, is necessary in the case of most soils from 
which two or three successive crops have been taken. 

Plants cannot grow unless they are supplied with all the 
elements mentioned as essential on pp. 171 to 175 ; should one of 
these be totally missing from the soil, growth becomes impossible. 
From this peculiarity the power of the soil to yield a crop is 
controlled by the essential element which is present in the least 
amount. 

If a soil contains too small an amount of phosphates 
for the growth of a crop, the fact that elements such as 



FOOD-MATERIALS AND THEIR ABSORPTION 207 

nitrogen or potassium are present in great abundance avails 
nothing, for these cannot be utilised until the necessary phos- 
phates are available. 

The food-materials from which plants obtain the sulphur, iron, 
magnesium, calcium, carbon, hydrogen and oxygen are almost 
always present in the soil and air in sufficient abundance for the 
needs of all crops, but the compounds which yield nitrogen, 
phosphorus and potassium are generally removed in such 
quantities that the supply is soon reduced to such a point that 
for full crops manure containing one or all of these elements 
must be added to the soil. 



CHAPTER XVI. 

CARBON-FIXATION; 'ASSIMILATION; OR 
'PHOTOSYNTHESIS/ 

i. THE source from which plants obtain the large quantity of 
carbon of which more than half their dry weight consists, has 
been the subject of extensive investigation for a long time. 

Parasitic plants, such as dodder, broom-rape and many fungi, 
attach themselves to other living organisms and absorb the 
carbon they need in the form of sugar, proteids and other 
elaborated carbon compounds from their victims. Saprophytes, 
such as the bird's-nest orchis (Neottia\ mushrooms, and the 
majority of common fungi, which like the above-mentioned 
parasites are devoid of chloroplasts, obtain their carbon in a 
similar elaborated form from the carbon compounds present in 
the remains of dead plants and animals upon which they grow. 

It is probable also that all green plants absorb and utilise 
organic carbon compounds from the humus or decaying vegetable 
and animal remains within the soil, although it has been proved 
that this source is insufficient to supply all the carbon needed 
for the perfect healthy nutrition of plants of this kind. 

By the method of water-culture or sand-culture it may be 
readily shown that ordinary green plants flourish and increase 
in carbon-content when their roots are supplied with a solution 
of food-materials containing no carbon, so long as the solution 
contains all other essential elements. 

Under these circumstances the only source of carbon is the 
carbon dioxide of the atmosphere surrounding the leaves, and 
although the proportional amount of this gas present in the 

203 



1 ASSIMILATION/ OR ' PHOTOSYNTHESIS ' 209 

air is very small, averaging about 2*8 parts in 10,000, it is from 
this source that the whole of the carbon of plants grown by the 
method of water-culture is derived. 

In the processes of fermentation and decay going on in 
ordinary soil carbon dioxide is produced and the air permeating 
the interstices of the soil may contain as much as 5 per cent, of 
this gas, some of which enters the roots of plants dissolved in 
the water of the transpiration-current : it has, however, been 
shown by Cailletet and Moll's experiments that the supply 
of carbon dioxide obtained in this manner is insufficient for the 
requirements of ordinary green plants. 

Extended and carefully-conducted investigations have proved 
beyond doubt that the chief food-material utilized by green 
plants for their carbon-supply, is the carbon dioxide of the air, 
and that this gas is absorbed by means of the leaves. Moreover, 
it is through the stomata that the gas enters into the tissues 
and only in slight degree, if at all, through the cuticle of 
the epidermal cells. 

The rate at which the absorption of the gas is carried on 
by the leaves has been investigated by Brown and Escombe : 
the amount absorbed by a sunflower exposed to diffuse daylight 
was found, in one instance, to be 412 cubic centimetres per 
square metre of leaf-surface per hour ; the hourly absorption for 
a Catalpa leaf was 345 c.c. for each square metre. Under 
favourable conditions the rate of absorption of the gas by a leaf 
was found to be equal to one-half that of a strong solution of 
caustic potash of equal area, and, since the actual openings 
between the guard-cells of the stomata in the leaf investigated 
amounted to not more than yj^ part of ttoe whole area of the 
leaf, it follows that the rate at which carbon dioxide entered 
was fifty times as rapid as that at which the gas is absorbed by a 
solution of catfstic potash, a truly astonishing result. 

This absorptive activity on the part of green vegetation would 
soon result in the total removal of carbon dioxide from the air, 



210 'CARBON-FIXATION,' 4 ASSIMILATION 

were it not for the fact that the atmosphere is being continually 
replenished with carbon dioxide which is produced in the 
process of respiration carried on by all living things, and by the 
combustion of coal, wood and other kinds of fuel containing 
carbon. 

After entering into the cells of the leaf the carbon dioxide, 
together with a certain proportion of water, undergo chemical 
changes which result in the formation of soluble carbohydrates, 
oxygen being also set free during the process. 

The carbon of the carbon dioxide thus beconres * fixed, 1 and 
a rapid accumulation of carbohydrates takes place in the tissues 
of the plant, the oxygen escaping into the air. 

The process may be represented thus : 

carbon dioxide + water = a carbohydrate -f oxygen. 
It has been customary among botanists to use the term 
assimilation for the synthesis of carbohydrates by green plants in 
this manner from carbon dioxide and water, but it would be 
better to reserve the term for the conversion of foods into the 
substance of the tissues, as is done by animal physiologists, and 
employ another for this synthetical production of carbohydrates 
which is peculiar to green plants. As the operation is dependent 
upon light the term photosynthesis has been suggested and some 
such term or the expression ' carbon-fixation* is much to be 
recommended instead of ' assimilation. 1 

The exact nature of the carbohydrate first formed during the 
process is not known. Von Baeyer suggested that formaldehyde 
(CH 8 O) is first produced according to the equation 

CO 2 + H 2 O = CH 2 O + O 2 , 

and that this compound subsequently undergoes condensation 
into a carbohydrate of the formula C 6 H 12 O 6 . However, formal- 
dehyde cannot be detected in the tissues in which the process 
of ' carbon-fixation ' is going on, and although Bflkorny's experi- 
ments show that under certain conditions formaldehyde can be 
utilised by plants for the production of carbohydrates, the view 



OR 'PHOTOSYNTHESIS' 211 

that this compound is the first step in the formation of carbon 
compounds from carbon dioxide and water is nothing more than 
a hypothesis. 

What is certain is that sugars are soon formed in the 
cells of the leaf-parenchyma after the green leaves of plants 
absorb carbon dioxide from the air, and the investigations 
of Brown and Morris point to the conclusion that cane-sugar 
is the first sugar to be manufactured, and that subsequently 
dextrose, levulose and maltose sugars make their appearance in 
leaves in consequence of the action of enzymes upon the 
previously-formed cane-sugar and starch. 

In a great many plants when the accumulation of sugar within 
the cells of the leaves reaches a certain point the chloroplasts 
form starch-grains from it; the starch-grains appear within the 
substance of the chloroplasts and are the first visible products of 
* carbon-fixation.' 

The total amount of carbohydrates produced by leaves of 
the same area depends upon internal vital peculiarities of the 
different species of plants ; for example, in a given time a 
sunflower leaf produces more than a leaf of a dwarf-bean of the 
same area. The amount manufactured by a sunflower during 
twelve hours on a moderately bright day was found by Brown and 
Morris in one instance to be a little more than 12 grams of 
carbohydrates per square metre of leaf-surface. 

2. The manufacture or synthesis of carbohydrates in the 
manner indicated above is dependent upon various conditions, 
of which the following are the most important : 

(i) The plants must be living. 

(ii) Carbon dioxide must be present in the air surrounding 
their leaves. 

(Hi) The leaves must contain chloroplasts. 

(iv) A certain intensity of light is essential, and 

(v) an adequate degree of temperature is necessary for the 
process. 



212 ' CARBON-FIXATION/ ' ASSIMILATION ' 

(vi) ' Carbon-fixation ' is also influenced by the presence or 
absence of certain mineral substances, especially compounds of 
potassium obtained from the soil, but the particular part which 
these substances play in the process is not known. 

' Carbon-fixation ' is a vital process and ceases with the death 
of the plant. 

Plants grown in air from which the carbon dioxide has been 
extracted do not increase in dry weight, and after a time death 
takes place from starvation. They are not able to live in an 
atmosphere of pure carbon dioxide, but are able to carry on 
* carbon-fixation ' in air containing as much as 20 or 30 per cent, 
of the gas. According to the experiments of Montemartini the 
formation of carbohydrates is carried on best and most rapidly 
in air containing 4 per cent, of carbon dioxide, an amount six 
or seven times as great as that normally present in the atmosphere. 

* Carbon-fixation ' is apparently carried on only by specialised 
portions of the protoplasm of the cells, namely, by the chloro- 
plasts, for it only occurs in the leaves and parts which are green. 
The roots, the petals of flowers, and the white portions of 
variegated leaves from which chloroplasts are absent take no 
part in the process, and parasitic and saprophytic plants which 
are devoid of these structures are also incapable of utilising 
carbon dioxide for the formation or synthesis of carbohydrates. 

The leaves of the copper-beech, purple cabbage, red beet 
and many other plants have reddish cell-sap which disguises the 
green colour of the chloroplasts : the latter are nevertheless 
abundant in the palisade and spongy parenchyma of such leaves, 
and the plants as readily carry on the process of 'carbon- 
fixation ' as those having ordinary green leaves. 

The chloroplasts are small structures imbedded in the cyto- 
plasm of the cell; their substance is permeated with a green 
pigment named chlorophyll, associated with which is a reddish 
orange substance known as carotin^ and a yellow material 
termed xanthophyll allied to the latter. 



OR ' PHOTOSYNTHESIS 213 

The chemical nature of chlorophyll is unknown : its production 
is, however, in some way dependent upon the presence of iron 
in plants although it does not appear to contain this element. 

The chloroplasts of plants grown in the dark or covered up for 
a time, lose their green colour and become colourless or pale 
yellow. With the exception of the chlorophyll of the chloroplasts 
present in the embryos of certain plants, the production of this 
green pigment is dependent upon light : the cotyledons and first 
leaves of most seedlings and the leaves from underground buds of 
perennial plants only become green when they reach the surface 
of the soil. Moreover, the formation of chlorophyll is influenced 
by heat ; the plastids (see p. 107) of many plants grown in the 
dark do not develop a green tint even when exposed to light 
when the temperature is below freezing-point, but do so at 
higher temperatures. 

Chlorophyll, perhaps in a more or less altered form, can be 
extracted by means of alcohol : its solutions are fluorescent, 
appearing blood-red when seen by reflected light, and green 
when viewed by transmitted light. When acted upon by acids 
it changes to a dirty brownish-green colour. After death of 
the cytoplasm of the cells, the acid cell-sap, which is confined 
within the vacuole of the cells when the plant is living, diffuses 
through the cytoplasm to the chloroplasts, causing them to 
change to the brownish-green tint so characteristic of dead leaves. 

Light is not only essential for the formation of chlorophyll, 
but it is also directly necessary for the process of 'carbon- 
fixation,' as it is from the energy of the sun's rays that the 
energy required to effect the decomposition of the carbon 
dioxide and water used in the process is derived. 

In darkness, green plants are unable to effect the synthesis of 
carbohydrates from carbon dioxide and water, and under such 
conditions they decrease in dry weight owing to the loss caused 
by respiration, which goes on at all times (see chap. xix.). 

In shady places, in badly-lighted rooms, and in greenhouses 



214 'CARBON-FIXATION/ 'ASSIMILATION* 

during the dull days of winter, the manufacture of carbon com- 
pounds is usually slow, and is often insufficient to supply the 
proper needs of plants. Similar partial starvation due to want 
of light occurs among thickly-planted crops and in the inner 
boughs of trees bearing an excess of leaves, and in all cases of 
over-crowded plants. With an increased intensity of light, 
'carbon-fixation' increases proportionally up to a maximum, 
which for many plants is not attained until they are exposed 
to direct sunlight. 

Certain shade-loving plants, however, need only a moderate 
intensity of light for proper nutrition ; exposure to intense 
light retards or altogether suspends their activity in this respect, 
and at the same time acts injuriously upon their chloroplasts 
and other protoplasmic cell-contents. 

In the majority of plants, the epidermal cells are free from 
chloroplasts, and the cell-contents of this tissue no doubt screen 
the chloroplasts of the deeper-lying tissues from the deleterious 
action of too brilliant light. Moreover, the chloroplasts are 
moved into more advantageous positions within the cells, when 
the intensity of the light falling upon the leaves becomes too 
great. 

The red, orange and yellow rays present in sunlight are most 
effective in promoting ' carbon-fixation/ the purple and violet 
rays having very little effect upon the process. 

In many plants * carbon-fixation ' goes on to a slight extent 
at one or two degrees above freezing-point : with increasing 
temperature the process increases in activity up to about 20* or 
25* C., beyond which temperatures it decreases until at about 
56 C. it ceases altogether with the death of the plant. 

Ex. 119. Place some shoots of Potamogeton^ Ehdea canadensts, mare's tail 
(Hippuris) or mint in a beaker full of well water. Slide a glass funnel into 
the beaker as indicated in Fig. 88, and over the end of the funnel place a test* 
tube full of water. Expose the whole to bright daylight, and notice that 
bubbles of gas rise from the leaves of the plants and collect at o in the test-tube. 

After a few c.c. of gas have been collected, remove the test-tube, and 



OR 'PHOTOSYNTHESIS 



215 



O 



place the thumb over the open end of the tube while it is below water, so 
as to prevent air from getting in. Take out the tube completely, turn it 
up, and keep the thumb over the end of the tube all the time ; then 
remove the thumb, and plunge a smouldering match-stalk into the gas. 

Although the gas collected is not pure oxygen, 
it contains a considerable proportion of the latter, 
and causes a smouldering match to burst into 
flame when placed in it. 

Ex. 120. (i) Tie a terminal shoot of Elodea 
4 to 6 inches long to a glass rod, and place so 
that the broken end of the shoot is uppermost 
in a tall glass cylinder full of well water. 

Expose the whole to bright daylight ; notice 
and count the number of bubbles of oxygen which 
rise from the broken end of the shoot in two or 
three minutes. 

(ii) Move the apparatus to a badly-lighted 
room, and count the bubbles rising in the same 
time as before. Do more bubbles rise when the 
plant is exposed to bright light than when exposed 
to a dim light ? 

Ex. 121. Repeat the above experiment, using 
boiled water from which all the carbon dioxide 
has been driven off. Notice that little or no gas 
is evolved. Now supply carbon dioxide to the 
water by blowing through a glass tube into it. 




FIG. 



Ex. 122. Repeat Ex. 119, using roots, flowers, or other portions of plants 
which are not green, to show that oxygen is not evolved from such parts. 

Ex. 123. (i) In the afternoon of a warm, bright day pluck off a leaf from 
several common broad-leaved plants, and test for starch in them, thus : 

First place them in boiling water for a minute, after which transfer them 
to a vessel containing warm methylated spirits to dissolve out the chlorophyll 
and other pigments. Leave them in the latter for a few hours until they are 
pale in colour, and then transfer them to a saucer containing a solution of 
iodine (see Ex. 85). 

If they contain starch they will turn black or deep purple. 

(ii) Test for starch in leaves variegated with white patches and show that 
none is formed in the white parts from which chloroplasts are absent. 

Ex. 124. (i) Smear one half of a pear or poplar leaf with cacao butter or 
best lard on both sides to block up the stomata. Leave for two days, and 
in the afternoon of the following day, test the whole leaf for starch, after 
removing the butter with hot water. 



216 4 CARBON-FIXATION ' 

Note that no starch is formed in the half to which access of carbon dioxide 
is prevented. 

(ii) Smear the upper surface only of a pear or poplar leaf, and the lower 
surface only of another similar leaf. Leave for three days as before, and then 
test for starch. 

Find out which leaf possesses most starch ; then determine with micro- 
scope on which surface stomata are most abundant. 

Ex. 125. To show the effect of darkness on starch formation, tie up a leaf 
of Tropaolum in a thick brown -paper bag so that no light can get at it. 
Leave it covered up for two days, and then test for starch. 

Ex. 126. Boil a quantity of young grass leaves for a minute or two and 
then extract the chlorophyll by placing the leaves in strong alcohol in a 
dark cupboard. 

Pour some of the solution into a beaker or large test-tube ; note the green 
colour when held up to the light, and dark red colour when viewed by 
light reflected from it. 

Note the effect on the colour when a few drops of hydrochloric acid are 
added to the solution. 

Ex. 127. Grow some seedlings of wheat, mustard, or peas in total dark- 
ness, and note that the leaves are not green. Expose the plants to light 
and observe when the first signs of a green colour are visible. 

Ex. 128. Place a large can, bowl or basin upside down on a lawn or 
grassy field so as to exclude light from the plants beneath it. Leave it for 
one or two weeks and then examine the grass beneath ; note the loss of 
green colour. 



CHAPTER XVII. 

FORMATION OP PROTEINS. TRANSLOCATION 
AND STORAGE OF FOODS. 

i. WITHIN the body of a living plant a great variety of chemical 
changes, which are collectively referred to as metabolic processes 
or metabolism, are always being carried on. Some of these 
changes, like those discussed in the preceding chapter, result in 
the formation of complex compounds from simpler ones; such 
constructive chemical processes are spoken of as anabolism^ 
the destructive chemical changes, such as those involved in 
the respiration-process, which result in the breaking down or 
decomposition of complex compounds into simpler ones, being 
included in the term catabolism. 

The conditions under which the chemical reactions take place 
within a living plant, are very much more complicated and 
probably of a very different class from those met with in a 
chemical laboratory, and our knowledge respecting the chemical 
changes involved in the production of the many different organic 
compounds present in plants is still very scanty and imperfect, 

2. Formation of proteins. During the growth of green plants 
there is not only the synthesis or construction of sugars and 
other carbohydrates from simple inorganic food-materials, but 
other organic compounds are built up, the chief of which are 
those containing nitrogen, namely, amides and proteins. 

The natural sources from which green plants obtain the 
nitrogen necessary for the production of these compound* 
are: 

(i) The free uncombined nitrogen of the atmosphere. 

217 



218 FORMATION OF PROTEINS 

(ii) The complex nitrogenous organic compounds of the humus 
in the soil. 

(iii) The ammonium salts, and 

(iv) Nitrates also present in the soil. 

Among the higher plants only the Leguminosae appear to be 
able to utilise the free nitrogen of the air (see p. 806), and it has 
been proved by means of sand- and water-cultures that although 
green plants are able to make immediate use of ammonium salts 
and a great variety of organic nitrogenous compounds, such as 
urea and leucine, they nevertheless thrive best when supplied 
with nitrogen in the form of nitrates ; this is true even of 
leguminous plants, which can, under certain conditions, obtain 
nitrogen from the atmosphere. 

As ammonium salts and the nitrogenous organic compounds 
of dung, urine and humus when placed in the soil are ultimately 
changed into nitrates (see p. 799), it is inferred that crops 
ordinarily obtain the chief portion of the nitrogen which they 
need from the nitrates of calcium, magnesium, potassium and 
sodium present in the soil. 

The chemical changes which nitrates undergo after their absorp- 
tion by plants and in what tissues or organs these changes take 
place are still practically unknown. 

Plants differ very much in regard to the method of taking up 
and utilising nitrates ; in some species nitrates can be detected 
in all parts of the plants, while in others they can only be found 
in the stem or roots, and in some none are found, in which latter 
case the decomposition of these compounds appears to take place 
at the very threshold of entry into the plant, namely, in the root- 
hairs and delicate fibrils of the root. 

It may safely be concluded that between the simple nitrates 
absorbed from the soil, and the proteins produced in the plant, 
there are many intermediate products manufactured. What 
these products arc is not known with certainty, but there is 
no doubt that asparagine (amido-succinamic acid) and probably 



TRANSLOCATION AND STORAGE OF FOODS 219 

other amides and amido-acids are among the intermediate nitro- 
genous compounds from which proteins are ultimately con- 
structed with the aid of previously-formed carbohydrates. 

The construction of proteins from asparagine and sugars appears 
in certain cases, to take place in the leaves and may go on in 
the dark, but in some instances the process is favourably in- 
creased when the plants are exposed to the light. Similar 
manufacture of proteins occurs in roots and probably in other 
parts of plants. 

Schultze and others have shown that plants can utilize nitrates 
and ammonium salts for the manufacture of asparagine and allied 
amido-compounds. According to Suzuki, the conditions for 
the formation of asparagine from nitrates are a somewhat high 
temperature and the presence of sugar. 

Besides being produced synthetically from absorbed nitrates or 
ammonium salts and sugars, asparagine is apparently produced in 
plants by the decomposition of proteins, and this asparagine can 
be utilised again for the regeneration of proteins when a suitable 
supply of carbohydrates is present to complete the synthesis. 

In addition to nitrates, other inorganic compounds such as 
sulphates and phosphates take a part in the formation of proteins, 
for the latter contain sulphur and sometimes phosphorus as well ; 
probably some of the metallic elements, such as potassium and 
calcium, which are known to be essential for proper nutrition 
of plants, are also more or less directly indispensable to the 
formation of complex proteins. 

3. Utilisation, translocation and storage of plant-foods. 
The various organic compounds manufactured by anabolic 
processes are utilised in different ways. A certain amount of 
sugars and fats are consumed in the respiration-process, and in 
the case of plants grown in the dark and in the earliest stages of 
the growth of seeds, tubers and bulbs, the destructive respiratory 
process results in a considerable loss of carbon which is given 
off as carbon dioxide into the air ; under such conditions there 



220 FORMATION OF PROTEINS 

is therefore a decrease in the dry weight of the plants. However, 
when the leaves and organs which effect * carbon-fixation ' have 
been developed, there is usually a continuous increase in dry 
weight from the beginning to the end of the life of a plant, 
anabolism being largely in excess of catabolism. 

The larger proportion of the sugars, fats, proteins and other 
organic compounds manufactured by the plant, are employed in 
the construction of the cell-walls and protoplasm of the new cells 
arising at the growing points, and in nourishing the protoplasm 
of more mature cells and also in thickening the walls of the latter. 
Under ordinary conditions of growth more organic material is 
constructed than is needed for the immediate nutritive require- 
ments of the individual plant : the excess is stored for the 
nutrition of its offspring, and, in the case of a perennial, for 
its own nutrition at subsequent periods of its growth. 

According to Brown and Morris' researches cane-sugar appears 
to be the first sugar formed in the 4 carbon-fixation ' process 
carried on by green leaves. 

The cane-sugar appears to be subsequently transformed by the 
enzyme invertase in the leaves into dextrose and levulose ; the 
latter sugars then travel from the leaf-blade through the petiole 
and into the stem along which they are translocated to the buds, 
growing-points and other parts of the root and shoot where 
growth and the formation of new organs or new tissues are 
taking place, and also to the centres, where storage of reserve- 
foods is occurring. 

The starch formed in the chloroplasts of the leaf-blade, is 
acted on by the enzyme diastase present in the cells and 
becomes transformed into maltose which travels from the leaf 
with the rest of the sugars to the centres of nutrition and 
storage. 

Diastase increases in leaves kept in the dark, and in con- 
sequence the disappearance of starch goes on most rapidly at 
night 



TRANSLOCATION AND STORAGE OF FOODS 221 

The sugars and other soluble carbohydrates travel in the 
plant osmotically from cell to cell, by far the largest amount 
being transferred from the leaves to the stem through the bast 
and elongated parenchymatous cells surrounding the vascular 
bundles \ in the stem and roots these compounds travel through 
the tissues of the bast and probably to a slight extent through 
the inner parts of the cortex also. 

The medullary rays receive from the bast the materials 
manufactured in the leaves, and convey them to the cambium 
and living portions of the wood needing nourishment. 

Proteins, which diffuse very slowly or not at all through cell- 
walls, are transferred long distances in stems and roots through 
the open sieve-tubes of the bast. These compounds are also 
frequently acted upon by enzymes which decompose them into 
peptones and the amides, asparagine, leucine and tyrosine, which 
diffuse with greater ease. 

The stream of sap conveying crude food-materials from the 
soil to the leaves travels through the wood, but the elaborated 
foods are translocated chiefly through the bast. 

The removal of a complete ring of * bark ' from the stem of a 
tree as far as the wood-tissue does not interfere with the 
upward flow of water and food-materials, but it prevents the 
stream of elaborated food from passing down to the roots, and 
unless the wound is healed by the formation of new conducting- 
tissue across the exposed part, the roots ultimately die of 
starvation and the whole tree succumbs. The time during 
which a tree will live after being * ringed ' depends upon the 
kind of tree and also upon the amount of organic material 
stored in the root-stock and roots before the wound was made. 

' Ringed ' trees may, however, live an indefinite period if 
adventitious shoots arise below the ' ringed ' part, for these 
leafy shoots manufacture organic material and as there is an 
uninterrupted connection between such new shoots and the 
root-system, the latter can receive a certain amount of nutrient 



222 FORMATION OF PROTEINS 

material which may be sufficient to enable it to grow for a long 
time. 

The substances manufactured in a shoot or branch of a tree 
are prevented from leaving it when the branch is ' ringed,' and 
the shoot and fruits upon it grow more luxuriantly in consequence 
of their increased food-supply. 

There is often a special growth of the wood and bast tissues 
just above the ' ringed ' part in consequence of the accumulation 
and utilisation of organic material at that point. 

Similar thickening or enlargement of the stem arising from 
impeded flow of elaborated sap is seen immediately above the 
point where scions have been inserted on stocks in the grafting 
process, especially where the union of the two grafted parts is 
imperfect. 

Wire or string tightly bound round the stems and branches of 
trees leads to similar results. 

Ex. 129. Remove leaves from tropseolum, clover, and other plants in the 
afternoon and test for starch in them with iodine as in Ex. 123. Remove 
from the same plants similar leaves in the early morning of next day and 
test for starch. 

Compare the two sets of leaves and note the greater amount of starch in 
those plucked in the evening 

Ex. 130. Remove in spring or early summer a ring of bark about half an 
inch wide from the branches of several kinds of trees. Also from some of 
the branches remove two or three similar rings of bark near each other, so as 
to leave a bud on some of the unringed portions and no buds on others. 

Note the subsequent growth and development of the various parts of the 
shoots above and below the ' ring/ Do the buds lying between two ' rings' 
develop satisfactorily ? 

Ex. 131. In spring before the leaf-buds are open make cuttings of the 
willow about a foot long from well-ripened portions of last season's shoots : 
'ring' the cuttings about one and a half inches from their base and place 
some in water and others in damp soil. Leave them until adventitious roots 
develop ; note the relative size and rate of development of the roots and 
buds above and below the ' ringed ' part. 

Bx. 133. Tightly bind string or wire twice or three times round the branch 
of a tree, and observe the subsequent development of the various organs above 
and below the bound part. 



TRANSLOCATION AND STORAGE OF FOODS 223 

4. The surplus organic material manufactured by a plant is 
transferred to various parts of its body to be stored for future 
use. Among annuals the reserve-food is accumulated only in 
the seeds ; in wheat and other cereals the endosperm of the 
seed becomes gradually filled with it, while in peas, beans and 
many annuals the reserve is stored in the cotyledons of the 
embryo. 

Among biennials and perennials, the seeds are similarly stored 
with reserve-food; but such plants, before the end of one 
growing-season, accumulate and store a considerable quantity of 
organic material in their vegetative organs, which material serves 
for the nutrition and growth of the cambium, buds and roots 
during the earlier part of the succeeding season. 

In turnips, carrots and mangel the reserve-material is stored 
in the roots : in onions and tulips it is accumulated in the leaves 
of the bulbs, in potatoes in the tubers, while in hops and many 
herbaceous perennials it is hoarded in the rhizomes or rootstocks. 

Trees and shrubs store their reserve-material chiefly in the 
parenchyma of the cortex and medullary rays in the stems. 

In the onion and many bulbs the carbohydrate reserve is 
stored chiefly in the form of dextrose, while many fruits store 
levulose also in their cell-sap. 

In the sugar-cane, sugar-beet, turnip and other roots the 
reserve is cane-sugar dissolved in the cell-sap ; in the tubers of 
the Jerusalem artichoke inulin takes the place of sugar. In 
the majority of plants the reserve-materials are chiefly stored in 
a solid insoluble form, in which state they take up less space than 
they would do in solution. 

The commonest solid carbohydrate reserve-material is starch 
which occurs in the form of small grains previously described 
(p. 156). In some instances very minute particles of starch are 
temporarily formed within the cytoplasm but the largei starch- 
grains present in the special storage centres are produced by the 
leucoplasts (see p. 108) of the cells from sugars which are trans- 



224 FORMATION OF PROTEINS 

ferred to them from the leaves where 'carbon-fixation' is going 
on. Thus, the starch in the cereal grains, in the tubers of 
potatoes, and in the medullary rays and cortex of trees in winter, 
is formed from sugars primarily manufactured in the leaves. 

Starch-grains formed by the leucoplasts are usually much 
larger than those temporarily formed and stored in the allied 
chloroplasts of the leaves. 

In certain seeds some of the carbohydrate reserve is stored in 
the form of thickened cell- walls consisting of hemicellulose. 

The fats and fixed oils occurring in the seeds of flax, cotton, 
and rape are non-nitrogenous reserve-materials, which are first 
visible in the form of minute drops in the protoplasm ; the 
small drops run together ultimately and form larger drops. In 
some cases the fats and oils appear to be manufactured from 
dextrose and other sugars, while in others they arise by the 
conversion of starch. 

Asparagine, leucine, glutamine, and other amido-compounds 
frequently form the chief store of nitrogenous materials present 
in the cell-sap of tubers, roots and rhizomes of plants. With 
increasing maturity of the root or tuber some of these 
compounds are converted into proteids. In most ripe seeds 
the nitrogenous reserve-material consists almost entirely of 
proteins stored in the form of solid aleuron-grains and other 
more or less amorphous masses : only a small proportion of 
amido-compounds are present. 

It will be observed that the substances actually stored are 
usually different in chemical constitution and solubility from the 
organic materials transported into the cells where the storage is 
proceeding. One form of sugar is changed into another after 
entering into the cell or is utilised by the leucoplasts for the 
formation of starch-grains ; the cell-sap, therefore, becomes less 
concentrated in the particular sugar entering it, and a further 
osmotic diffusion into the cell takes place. 

By these changes a continuous accumulation of reserve-materials 



NUTRITION OF SEMI-PARASITES 225 

becomes possible ; without them the cell-sap of the storage-tissues 
would soon become so concentrated that a further movement of 
material into the cell by osmosis could not occur. Moreover, the 
change of a soluble osmotic substance into an insoluble form 
prevents the turgidity of the cells from becoming excessive. 

Ex. 133. Cut transverse sections of last season's branches of ash and other 
trees in winter : place them for a moment in iodine solution (see Ex. 85) and 
then mount in water. Examine with a low power and note in what tissues 
the starch is most abundant. 

5. Nutrition of semi-parasites and semi-saprophytes. Cer- 
tain green plants, in addition to their power of forming organic 
compounds from carbon dioxide, water, nitrates and other 
simple inorganic substances, appear to derive some organic 
materials ready formed either from other living plants or from 
humus. 

To the former class belong Yellow-rattle (Rhinanthus Crista- 
galli L.), Eyebright (Euphrasia offidnalis L.), Red-rattle (Pedicu- 
laris sylvatica L.), species of Melampyrum, and other semi-para- 
sites not uncommon in meadows and pastures. Certain portions 
of the roots of these plants attach themselves by small haustoria 
(suckers) to the roots of other plants growing near them and no 
doubt absorb a certain amount of organic substance from the 
latter, for unless they become attached in this manner to other 
plants they do not grow satisfactorily. 

Many flowering plants, such as bird's-nest orchis (Neottia) 
and species of Monotropa, possess few or no chloroplasts, 
and live upon humus : numbers of plants, such as Heaths, 
Rhododendrons, Azaleas and Winter-green (Pyrola) belonging 
to the Ericaceae, Beech, Hornbeam and other representatives of 
the Cupuliferae, as well as pines and Coni ferae generally, while 
possessing chloroplasts appear to supplement their own manu- 
factured supply of organic material by absorbing organic com- 
pounds from the decaying humus or leaf-mould in which many 
of their roots are found growing. 



226 FORMATION OF PROTEINS 

The roots of all these humus-loving saprophytes and green 
semi-saprophytes possess few or no absorptive root-hairs, but 
are associated with the mycelium of certain fungi present in the 
humus : the associated fungus and root is termed mycorhiza. In 
heaths, orchids and some other plants the mycorhiza is endophytic^ 
the fungus living partially within the cortex of the root, while in 
beech and most Cupuliferae the fungus clings to and covers the 
surface of the fine rootlets with a web-like mantle of mycelium 
from which separate hair-like hyphse grow out into the humus 
and absorb portions of it : the latter type is spoken of as an 
epiphytic mycorhiza. 

It is probable that some of the organic constituents of the 
humus are dissolved by the fungus, and, with the other absorbed 
constituents of the soil, are finally transmitted to the plant with 
which it lives in union. The fungus thus appears to act as a 
beneficial absorptive agent, and without its aid the plant does 
not thrive ; beech and pine seedlings are found to grow feebly, 
and die off altogether after a time, in forest soil which has 
been subjected to boiling water or steam so as to kill the fungus. 

As the plants of this class possessing green leaves have no 
absolute need of carbohydrates from other than the usual 
sources, it is possible that the fungus is concerned mainly with 
the absorption and transmission of ammoniacal and organic 
nitrogen compounds, as well as substances containing the ash- 
constituents of the plant. 



CHAPTER XVIII. 

ENZYMES AND THE DIGESTION OF 
RESERVE-MATERIALS. 

i. THE substances stored in seeds, tubers, roots and other organs 
of plants are chiefly solid, insoluble materials, such as starch and 
aleuron-grains, which cannot be moved out of the closed cells in 
which they occur, or are compounds such as oils and fats which, 
although liquid, are unsuitable for rapid osmotic diffusion. 

Before these reserve-materials can be removed from the tissues 
in which they are stored to the centres of growth where they are 
needed, they must be digested or transformed into soluble, 
easily diffusible substances, which can travel in the ordinary 
channels available for the translocation of foods. In certain 
cases the necessary transformation appears to be due to the 
direct action of the living protoplasm, but in many instances it 
is accomplished by the chemical activity of substances termed 
enzymes or unorganised ferments, which are secreted by the 
protoplasm. 

A considerable number of distinct enzymes are known. They 
all appear to belong to the protein class of organic compounds, 
and a very small amount of each is able to transform an almost 
unlimited bulk of the material upon which it acts without 
changing or suffering much diminution in the process. Enzymes 
are inactive at low temperature, and most of them are totally 
destroyed when their solutions are heated to about 70" C. : the 
optimum temperature at which they carry on their work best lies 
between 30 and 50* C. Their chemical activity is usually greatest 

227 



228 ENZYMES AND 

in the dark ; exposure to bright light suspends and gradually 
destroys it. 

2. The following are the most important kinds of enzymes 
occurring in plants : 

(i) Those which transform the different insoluble carbohydrates 
into sugars. 

(a) To this class belong diastase which attacks starch and by 
a gradual and continuous process of decomposition converts 
it ultimately into maltose and a small proportion of a gum- 
like substance termed dextrin. Other forms of dextrin arise 
during the intermediate stages of the process but are soon 
split up into maltose : some of them give a reddish -brown 
colour with iodine. 

Two slightly different forms of diastase are met with in plants. 
The one known as diastase of secretion is concerned with the 
dissolution of starch in germinating seeds, and is especially 
prevalent in the germinating' grains of barley and other cereals 
and grasses. This form of diastase which is the characteristic 
enzyme in malt, corrodes and eats pit-like depressions in the 
substance of starch-grains before finally dissolving them. 

In the seeds of the Gramineae this enzyme is secreted by the 
long cylindrical cells forming the surface-layer or epithelium of 
that side of the scutellum of the embryo which adjoins the endo- 
sperm. After its formation by the epithelium, the diastase 
diffuses into the endosperm and transforms the starch into 
maltose, which is ultimately absorbed by the scutellum and 
transferred to the growing-points of the developing embryo. 

The other form of diastase is spoken of as diastase oj 
translocation. It is more widely distributed than the diastase 
of secretion, being found in the leaves, shoots and other 
vegetative parts of plants. The amount present in leaves is 
greatest during the night or when the plant is kept in darkness. 
By its agency, the starch produced in the chloroplasts of green 
leaves during the daytime is transformed into sugar at night. 



DIGESTION OF RESERVE-MATERIALS 229 

The same form of diastase is found in all parts of sprouting 
potato tubers, but is especially abundant near the ' eyes' where 
growth commences. It converts the starch of the tuber into 
sugar, which latter compound is subsequently transported to 
the growing shoots. Small amounts are also secreted by the 
' aleuron-layer ' in the endosperm of cereal grains when germina- 
tion takes place. Translocation-diastase acts more readily at 
lower temperatures than the diastase of secretion and dissolves 
starch-grains without previously corroding them. 

(b) During the germination of the cereal grains it is found that 
the cell-walls of the endosperm-tissue lying near the embryo 
and near the * aleuron-layer ; are disintegrated and dissolved by 
the activity of an enzyme, which commences its work before the 
diastatic enzyme begins to dissolve the starch in the grain. 

This enzyme, named cytase, is secreted partially by the 
epithelium of the scutellum, but more especially by the cells 
of the * aleuron-layer/ It is also present in the cotyledons of 
germinating peas and in the endosperm of buckwheat. Its 
function in these cases appears to be that of getting rid of the 
cell-walls, so as to allow of an easier diffusion and therefore a 
more rapid action of diastase upon the starch-reserve. 

Cytase is also found in the seeds of the date-palm, and is most 
probably present in germinating seeds of all those plants whose 
store of reserve-food for the embryo consists of thickened 
cell-walls composed of hemicellulose. 

(ii) The reserve-material, inulin, which is present in the tubers 
of the Jerusalem artichoke, is transformed when germination 
begins into levulose by the action of an enzyme named inulase. 
The existence of the same enzyme has been demonstrated in 
the growing bulbs of snowdrop and other liliaceous plants 
which contain inulin. 

(iii) A very common reserve-material of wide distribution 
in the vegetable kingdom is cane-sugar. Experiments suggest 
that as such it is of little or no value for the immediate 



230 ENZYMES AND 

nutrition of protoplasm. It is however changed by the 
enzyme invertase or invertin into a mixture of dextrose and 
levulose, both of which sugars possess immediate nutritive value. 
In roots, such as sugar-beet and carrot, a great part of the 
organic material manufactured in the leaves during the first 
year of growth is sent down to the root and stored in the form 
of cane-sugar. This reserve-material is utilised during the 
second year for the production of new stems, flowers and 
seeds, but before transmission from the root to the seats of re- 
newed growth, the enzyme invertase decomposes the cane-sugar 
into dextrose and levulose according to the following equation : 

C,,H M U + H 2 = QH U 0, + C 6 H 12 

cane-sugar \rater dextrose levulose 

This form of decomposition of a compound which involves 
the fixation of the elements of water is termed hydrolysis or 
hydrolytic decomposition, and is characteristic of the action of 
the majority of enzymes of all kinds. 

Invertase has been found in leaves, in the roots of young 
plants, in germinating pollen-grains, and in other portions of 
plants where cane-sugar "is present 

(iv) Certain substances known as glucosides occur commonly 
in plant-tissues : their exact function and nutritive value to the 
plant are not yet understood. However, under the influence of 
acids and special enzymes, they are hydrolysed into useful 
sugars and other bodies, usually aldehydes or phenols. 

The sugar produced is generally dextrose (glucose), hence 
the term glucoside applied to such compounds. 

The best known examples are amygdalm, present in many 
rosaceous plants (see p. 404), sinigrin^ abundant in mustard and 
other Cruciferae (see p. 388), and salicin in the willows. Some 
of the astringent compounds so widely distributed in all parts of 
plants and known as tannins are also glucosides. 

The decomposition of amygdalin is effected by the enzyme 



DIGESTION OF RESERVE-MATERIALS 231 

emulsin in the presence of water, and gives rise to benzoic alde- 
hyde, prussic acid and glucose according to the following 
equation : 

C 20 H 2r NO n + 2H 2 O - C 7 H 6 O + HCN + 2C 6 H 12 O 6 
Amygdalin Benzoic prussic glucose 

aldehyde acid 

The glucoside sinigrin is decomposed by the enzyme myrosin 
as explained on page 389. 

(v) A large amount of reserve-material in the seeds of flax, 
rape or colza, castor-oil and other plants exists in the form of oil 
or fat. During the germination of such seeds the oil suffers 
hydrolysis through the activity of an enzyme which has been 
named lipast. The products of the decomposition in those cases 
which have been carefully examined appear to be free fatty acids 
and glycerin ; the fate of the former substances is not clear, but 
it is probable that the glycerin is transformed into some kind of 
sugar which travels into the tissues of the growing embryo where 
some of it is not unfrequently converted into a temporary 
reserve of small starch-grains. 

(vi) Another group of enzymes exists in plants by means of 
which the various insoluble and indiffusible proteins are hydro- 
lysed into simpler diffusible proteins, termed peptones, together 
with a larger or smaller amount of amides. So far as they have 
been examined they all resemble the enzyme secreted by the 
pancreas of the higher animals, and are termed vegetable trypsins. 

The chemical changes which proteins undergo in their migra- 
tion from place to place within the tissues of plants are not the 
same in all cases, but the reserve proteins of many seeds are made 
available for the embryo through the action of tryptic enzymes. 
When germination begins the insoluble and slowly diffusible pro- 
teins in the cotyledons and endosperm are decomposed into sol- 
uble peptones, and one or more amides, such as asparagine, leucine 
or tryosine, all of which substances circulate readily to the various 
parts of the growing embryo needing nitrogenous nutriment. 



232 ENZYMES 

Trypsins are also met with in the leaves, stems and developing 
fruits of many plants where they facilitate the rapid translocation 
of proteids in such organs. 

3. The power which parasitic and saprophytic plants possess 
of absorbing and utilising as food the starch, proteins and various 
organic materials belonging to other plants, is dependent to a 
large extent upon their power of secreting diastatic and other 
enzymes. 

Certain parasitic fungi penetrate into the tissues of their 
victims by secreting an enzyme which is capable of dissolving 
the obstructing cell-walls. 

The production of alcohol from sugar by yeast is apparently 
effected by an enzyme named zymase, which is present in the 
yeast-cells, and some of the chemical changes brought about by 
bacteria are the result of the action of enzymes secreted by 
these organisms. 

Ex. 134. Germinate some barley grains on damp blotting-paper ; when 
the plumule just appears taste the endosperm and compare its sweetness with 
that of a soaked ungerminated grain. 

Compare the taste of malt with that of ordinary barley grains, 

Ex. 135. Prepare some thin starch-paste and a solution of malt-diastase 
as described in Ex. 86. 

Take two tubes of starch -paste and into one pour some of the diastase- 
solution, and into the other some of the same solution after it has been 
boiled three minutes and then cooled. Test with iodine for starch in both 
tubes every five minutes as indicated in Ex. 86. What has been the effect 
of boiling the diastase solution ? 



CHAPTER XIX. 
RESPIRATION. 

Ordinary Respiration in the presence of free oxygen of the 
atmosphere: aerobic respiration. One of the most familiar 
physiological processes carried on by living animals is that of 
respiration, during which there is a constant interchange of gases 
between the body of the animal and the surrounding air : the 
oxygen of the air is inspired into the lungs, and from the latter 
carbon dioxide gas is breathed out into the atmosphere. So 
long as life exists respiration goes on continuously, and one of 
the certain signs of death is the cessation of the process. 

Respiration, however, is not confined to animals, but is 
carried on by all ordinary plants, and is as necessary for 
their existence as for the existence of animals. 

The amount and rapidity of respiration is usually much greater 
in animals than in plants, but the process is essentially the same 
in both classes of organisms. It is well known that animals die 
when the supply of fresh air is cut off, and plants soon show 
signs of ill-health under similar conditions. In ordinary farm 
and garden practice the parts above ground always obtain 
sufficient oxygen for all their requirements, but the roots of 
plants are often seriously injured through want of a suitable 
supply of fresh air in the soil. The unhealthy appearance of 
over-watered pot plants and of crops growing in badly-drained 
ground is primarily due to an insufficient supply of oxygen to 
their roots. Seeds buried too deeply do not obtain sufficient 
fresh air for normal respiration and either do not germinate at 
all or do sp in an unsatisfactory manner. 

233 



234 RESPIRATION 

Each living cell of the body of a plant respires, the oxygen 
necessary for the process being supplied from the air which 
penetrates through the stomata and lenticels and permeates 
throughout the plant in the intercellular spaces. 

In all the higher plants the products of respiration under 
normal conditions are carbon dioxide gas and water. As the 
carbon of the carbon dioxide is derived from the compounds 
within the body of the plant, it is clear that the process is a 
destructive one and must result in a decrease in the dry weight 
of the plant The seedlings of cereals and many other plants 
when allowed to grow in the dark often lose about half their dry 
substance in two or three weeks. 

In this respect respiration is essentially the opposite of the 
* assimilation ' process in which there is a fixation of carbon and 
a consequent increase in dry weight of the plant. Moreover, 
respiration goes on in all living cells, both in darkness and in 
light, whereas * carbon-fixation ' is only carried on by those cells 
which contain chloroplasts, and in these only when they are 
exposed to light. 

During respiration oxygen is consumed and carbon dioxide is 
set free into the air, but in green plants exposed to daylight the 
' carbon-fixation ' process consumes twenty or thirty times as 
much carbon dioxide as is produced by respiration during the 
same time, so that when both processes are going on there is always 
a decrease in the carbon dioxide and an increase in the oxygen 
of the atmosphere, and only at night or in the dark does the 
process of respiration become apparent. However, in parts 
of plants which are not green, such as the roots, flowers 
and germinating seeds, respiration is readily detectable at all 
times. 

The carbon compounds which disappear while respiration is 
going on, are carbohydrates, such as starch and the various 
sugars and fats. The oxidation of these substances does not 
take place at ordinary temperature outside the plant, and the 



RESPIRATION 235 

manner in which they are utilised within the tissues of plants 
during the respiration process is not understood. The oxidation 
is controlled and 'is dependent upon the protoplasm, for respira- 
tion ceases when life becomes extinct, and the amount and nature 
of the chemical changes carried on are not altered either by con- 
siderably reducing or increasing the amount of oxygen in the 
surrounding atmosphere. 

The absorption of oxygen and the subsequent emission of 
carbon dioxide are the beginning and end respectively of a 
long series of chemical changes, the intermediate stages of which 
are at present unknown. 

The disappearance of starch, sugars, fats and other carbon 
compounds during respiration is not due to simple direct oxida- 
tion ; probably the protoplasm itself is directly attacked by the 
absorbed oxygen after which it uses up the carbon compounds 
to repair its waste. 

The proportion of oxygen absorbed to the carbon dioxide gas 
given off is dependent on the energy of growth and on the 
materials consumed during respiration. In certain plants the 

volume of carbon dioxide produced , , P , . . 

ratl ^volume of oxygen Juried- haS been f Und tO be aS loW 

as *3, while in others it has been observed as high as 1*2. 

In germinating seeds, tubers and bulbs containing starch and 
sugars, and in most flowering plants, the volume of oxygen 
taken from the air during active normal respiration, is equal to 
that of the carbon dioxide exhaled ; but in the respiration carried 
on during the germination of seeds containing fats and oils, the 
volume of oxygen consumed is greater than that of the carbon 
dioxide exhaled, some of the oxygen absorbed by such seeds 
being apparently used up in oxidising the fats into some form 
of carbohydrate. 

It is by means of the energy set free by the oxidation of 
various compounds in the respiration-process that the plant is 
enabled to maintain its vital activity, and the vital energy of 



236 RESPIRATION 

animals originates in a similar manner : when the physiological 
oxidation is prevented growth ceases, the streaming movement 
of the protoplasm within the cells is stopped, and the move- 
ments of the leaves, roots, stems and other organs of plants are 
suspended. 

In all cases heat is produced during respiration, and in warm- 
blooded animals it is easily perceived. In plants, oxidation is 
generally much less energetic than in animals, and the heat 
produced is so slight that no difference in temperature can be 
detected between green plants and that of the air surrounding 
them. Moreover, in ordinary green plants exposed to the air, 
the cooling effect of transpiration masks any slight rise in tem- 
perature due to respiration. However, when actively germinat- 
ing seeds or rapidly expanding flowers and buds are heaped 
together, a rise of two or three degrees above that of the 
atmosphere may be readily observed, by placing the bulb of 
a thermometer among them. 

The amount of respiration is dependent on external and 
internal conditions, and in different parts of the same plant 
the activity of the process is not the same. In all young actively 
growing parts rich in protoplasm, such as germinating seeds, 
expanding buds and flowers, respiration is vigorously carried on, 
and the same is noticeable in injured cut portions of plants. 
In dormant bulbs, tubers and buds little or no respiration is 
observable. In dry seeds respiration seems to be entirely 
suspended, and many have been kept for twelve months in a 
vacuum, and in nitrogen and other gases under conditions which 
render respiration impossible, yet after such treatment the seeds 
germinated freely. 

At freezing-point and a degree or two below it, where growth 
is stopped, respiration may frequently be detected. With in- 
creasing temperature there is a steady increase in the amount of 
respiration up to the point where death takes place, and the 
process stops suddenly. 



RESPIRATION 



237 



Light appears to have no direct influence upon it, respiration 
continuing very similarly both in darkness and light. 

It has also been found by experiment that the process goes 
on quite normally even when the proportion of oxygen in the 
surrounding atmosphere is reduced to less than half that 
ordinarily present in the air. 



Ex. 136. Soak a handful or two of peas or barley grains in water for 
twelve hours. Take them out of the water and allow them to germinate on 
damp blotting-paper for twelve hours. Then put them in a wide-necked 
bottle, cork the latter and place it in a warm, dark room. Cork and place beside 
it another similar but empty bottle. Allow both to remain for twelve hours, 
after which time test for the presence of carbon dioxide by introducing a 
lighted match or taper into the bottles : the light is extinguished by carbon 
dioxide. Arrange another similar experiment, and test for carbon dioxide 
with lime-water : pour in the lime-water, and shake the bottles ; the lime- 
water becomes milky if carbon dioxide is present. 

Ex t 137. Partially fill a wide-necked bottle with half expanded young 
dandelion or daisy * heads' ; cork and leave for twelve hours, after which 
time test for carbon dioxide as above. 

Ex. 138. Repeat the experiment above, using green leafy shoots, expand- 
ing buds, bulbs, tubers and other portions of plants. 

Ex. 139. Soak some peas for twelve hours, 
and after taking them out of the water allow 
them to germinate on damp blotting-paper for 
a few hours. Then place them in a flask ar- 
ranged on a retort stand, with a tightly fitting 
rubber stopper and bent glass tube as in Fig. 
89. Slightly warm the flask with the hands 
and dip the open end of the tube (a) into 
mercury in a beaker (/?). Leave the apparatus 
for ten or twenty minutes and fasten a piece 
of gummed paper on the tube (a) at a point 
(x) up to which the mercury rises in it. Keep 
the whole in a room of even temperature for 
D ten or twelve hours, and observe the position 
-of the mercury at the end of that time. If 
the volume of oxygen absorbed is equal to that 
of the carbon dioxide emitted, the mercury will remain at the same place in 
the tube. 

Repeat the experiment with oily seeds, such as hemp, linseed and turnip. 




FIG. 



2 3 8 



RESPIRATION 



With these the mercury rises in the tube, for the volume of oxygen absorbed 
by them is greater than that of the carbon dioxide emitted. 

Ex. 140. Show that heat is developed during respiration of germinating 
seeds. 

Soak some barley grains or peas 
in water for a few hours and then 
allow them to begin germinating on 
damp blotting-paper. Place them in a 
large glass funnel (/>'), suppoitcd in a 
beaker or glass cylinder (6") containing 
a small quantity of a strong solution of 
potash (D] ab in Fig. 90 ; dip into 
the seeds the bulb of a thermometer (A] 
reading to half a degree. Cover the 
whole loosely with a cardboard or 
wooden box [E], leaving a hole in the 
top for the thermometer tube. 

For comparison, fit up a similar 
apparatus by the side of the first with 
balls of blotting-paper soaked in water 7 * 
in the funnel instead of seeds ; compare 




<lG ' 



the readings of the t\\o thermometers on three succeeding days. 

Anaerobic or Intramolecular respiration. When living plants 
or parts of plants are placed in an atmosphere devoid of free 
oxygen, they continue to give off carbon dioxide gas for a longer or 
shorter time before death occurs. This production and evolution 
of carbon dioxide by living organisms in the absence of free 
oxygen is termed anaerobic or intramolecular respiration, 

The length of time which plants will live under these circum- 
stances depends upon the kind of plant and the vigour of its 
growth : actively-growing maize seedlings live and continue to 
give off carbon dioxide in the absence of oxygen, for twelve 
or fourteen hours at ordinary temperatures, while ripe fruits, 
such as pears and apples, live for several months under similar 
conditions. 

In the majority of cases the amount of carbon dioxide thus 
produced is considerably smaller than that which is given off 
by the same plants when exposed to the air ; for a short time, 



RESPIRATION 239 

however, bean seedlings and other plants emit the same or 
a greater volume of carbon dioxide when placed in an atmo- 
sphere free from oxygen, as they do when growing normally in 
the air. 

During intramolecular respiration carbohydrates and fats 
disappear from the tissues of the plants just as in ordinary 
respiration in the presence of abundance of oxygen, but the 
production of carbon dioxide is accompanied by the formation 
of alcohol and other compounds. The alcohol produced during 
the intramolecular respiration of ripe cherries amounted in 
one of BrefekTs experiments, to more than two per cent., and 
in pea seedlings to over five per cent, of their fresh weight. 

While the higher plants are unable to maintain their vitality 
in the absence of free oxygen for more than a short time, 
many of the lower forms of plant life, such as yeasts and 
bacteria, are independent of the presence of free oxygen and 
continue to live and multiply without it (p. 785). 



CHAPTER XX. 
GROWTH. 

i. Growth. We have seen in a previous chapter that at the 
apex of a stem or root of an ordinary green plant, there is usually 
a formative region where the component small cells are in a state 
of division, and new cells are being manufactured. Immedi- 
ately behind this is a longer or shorter portion which may be 
designated the growing region of the stem or root. Here the 
cells are found to be turgid, and in consequence of the pressure 
within them have increased in size, and at the same time many 
of them have become changed in form. 

These changes of size and form, owing to increased turgidity 
do not, however, necessarily constitute growth, although they 
are always associated with growth. Cells which are growing not 
only become distended by the osmotic pressure within the 
vacuoles, but also undergo a permanent change in size, form 
and structure, in consequence of the deposition of substances 
in their cell-walls and other parts; on withdrawing water from 
such cells the original state in which they existed when first 
produced in the formative region is not again reproduced by 
such a proceeding. Moreover, since the growth of a cell cannot 
go on without increased turgidity, and as this involves an 
addition of water to the vacuole of the cell, there is always an 
increase in the total weight of the cell when growth is proceed- 
ing : however, on account of the loss of substance by respiration, 
there may be a decrease in its dry weight if such loss is not 
compensated by anabolic nutritive processes. 

What is true of a single growing cell is also true in the case 

240 



GROWTH 241 

of the whole growing region of a shoot or root, for the latter 
is merely composed of a number of active cells. 

Although it is not possible to define in a single sentence the 
exact meaning or connotation of the term growth, it may 
generally be taken to imply a permanent change in the form 
of a living organism or some of its members, and that the region 
which is growing is also increasing in weight. 

The actual growing regions of the shoots developed in the 
dark from a potato tuber not only change their form but also, 
while they are growing, increase in weight at the expense of 
the water and reserve-food drawn from the tuber. It will be 
found, however, that the total weight of the tuber (which does 
not grow) and its growing shoots decreases in consequence of 
the loss of water by transpiration and by loss of carbon dioxide 
in the respiration process. 

During the early stages of its life when a plant emerges from 
the seed, growth takes place in all parts of its body. After a 
time, however, growth is confined to certain special localised 
portions, or growing points , and to the cylindrical cambium- 
tissue which brings about secondary growth in thickness of 
dicotyledonous stems. 

The growing-points in the case of stems and roots are generally 
terminal, or situated near the ends of these members : in such 
cases the youngest part is nearest, and the oldest part farthest 
away from the apex of the shoot or root. 

In the stems of grasses their increase in length is due to the 
activity of growing-points which are situated at the base of the 
internodes ; moreover the growth in length of the long leaves of 
onions and rushes, and that of many peduncles of flowers goes on 
at the base of the structures, their tips being the oldest parts : 
growing-points of this character are described as intercalary. 

When a cell or a plant member begins to grow its rate of 
growth is at first slow ; afterwards it grows more and more 
rapidly until a maximum rate is attained, after which the growth 



24* GROWTH 

diminishes gradually until it ceases altogether when the part is 
mature. The time occupied by this gradual rise and fall is 
termed the grand period of growth. 

It is also noticed that the vigour or energy of growth of a stem 
or other member varies during the grand period : at one stage 
of the development of the complete stem the growing part either 
grows more rapidly or continues its growth longer than at 
another stage. For example, during the youngest stages of the 
development of most stems the energy of growth is low and 
short internodes are produced, later the energy increases, and 
larger internodes arise, afterwards the length of the internodes 
diminishes in consequence of a gradually decreasing energy 
of growth. 

Ex. 141. In autumn before the leaves have fallen, cut off branches from 
the common trees and shrubs, and measure the length between the several 
internodes on that part of each branch which has grown during the same 
season. 

Note the general rise and fall in the length of the internodes. 

Note also the relative size of the leaves at each node. 

Make similar measurements on the stems of annual herbaceous plants. 

Ex. 142. Repeat experiments 15 and 20: similarly mark with Indian 
ink at intervals of & inch the second and third leaves of a young onion plant 
soon after they appear ; measure the intervals after the leaves have con- 
siderably lengthened, and compare the growth with that of a bean root. 
Is the region of greatest growth near the end of the leaf? 

Ex. 143. Select a stem of wheat or barley in which the ear is just ap- 
pearing ; cut about half-an-inch below the first and also below the second 
visible node from the top, so as to obtain about one internode of the stem. 

Remove the leaf-blade and a small portion of the leaf-sheath and care- 
fully measure the total length of the stem and the small part of it below 
the node. Make five or six marks with Indian ink J of an inch apart at 
the upper part of the stem. Then place the lower end of the stem in 
water, cover the whole if possible with a glass globe and leave it in a warm 
room for twenty-four hours; or place the stem in a glass cylinder with a 
little water at the bottom for a similar period. 

Measure again the total length ; how much has the stem grown, and has 
the growth taken place near its upper marked end or near the base ? Has 
the small portion below the node grown at all ? 

Ex. 144. Measure the length of the internodes on a few shoots of any 



CONDITIONS WHICH INFLUENCE GROWTH 243 

rigorous common trees, shrubs or herbaceous plants in early summer when 
they are beginning to grow, and at intervals of two or three days for some 
time afterwards. 

Determine the time during which an internode continues to grow in length. 

2. Conditions which influence growth. Only living plants 
grow and the cells of the growing parts must be in a youthful 
state. Various external conditions are also necessary for healthy 
growth, the chief of which are : (i) a suitable temperature ; 
(ii) an adequate supply of water ; (iii) appropriate food or food- 
materials ; (iv) the presence of oxygen, (v) Light although not 
absolutely essential to growth has a beneficial influence upon it. 

(i) Heat. It is well known that growth in winter, when the 
temperature of the surrounding aii and soil is low, goes on 
very slowly or not at all. As the temperature rises in spring 
seeds readily germinate and the buds of plants commence to 
grow ; with the increasing warmth of summer growth becomes 
more and more energetic. 

By subjecting a plant to a gradually decreasing temperature, a 
point is at last reached at which growth entirely ceases ; this 
is described as the minimum temperature for growth. It is 
not the same for all plants ; the seeds of many common weeds, 
and mustard and cress germinate, and the fully developed 
plants continue to grow near freezing-point, while those of the 
cereals are stopped when the temperature falls to about 5 C. 
On the other hand the seeds and plants of maize and the 
scarlet-runner bean cease to grow at about 10* C., while the 
minimum temperature for the germination and growth of the 
cucumber, melon, and many tropical plants is as high as 19 
or 20* C. 

By raising the temperature from the minimum, a point is 
reached at which growth goes on most rapidly ; this is termed 
the optimum temperature. By further increasing the temperature 
beyond the latter point, growth becomes slower and slower 
until a maximum is attained, at which growth is entirely checked 



244 GROWTH 

Thus it is seen that plants may be too hot or too cold for 
growth, and between these extremes there is an optimum or 
best temperature where they make the most satisfactory 
progress. 

The optimum temperature for most common farm and garden 
plants is about 28* C., while the maximum usually lies between 
38 and 43* C. ; the optimum for maize, scarlet-runner, bean and 
cucumber is about 33 or 34 C., the maximum about 46 C. 

It may be conveniently noticed here that although ordinary 
plants in an active state of growth have their development 
stopped at the temperatures indicated above, the death of the 
protoplasm does not usually take place until the higher tempera- 
ture of about 56 C. is attained or until it has been cooled to 
freezing-point or several degrees below the latter. 

The power of withstanding heat and cold depends very largely 
upon the amount of water which the plant contains. 

Well-ripened shoots and buds containing little water do not 
suffer so much from the effects of frost during winter as sappy 
immature shoots which contain a larger proportion of water. 
Turgid seedlings, buds just opening and recently unfolded 
leaves, plants watered in the evening, succulent roots and all 
parts containing considerable amounts of water are often injured 
by exposure to sharp frost for a few nights. 

Usually when a plant is subjected to a temperature of 2* to 5* C. 
the cytoplasm allows a certain amount of pure wat^r in the vacuole 
to ooze out of the cell into the surrounding intercellular spaces 
where it freezes into small crystals of ice : death in such cases 
is somewhat analogous to death by drying. Although plants are 
sometimes killed in the process of freezing, this formation of ice 
is not always fatal, for in many cases, if the frozen part is thawed 
very slowly, the cells re-absorb the water and the tissues assume 
their normal state. If, however, the frozen part is thawed rapidly 
the water does not re-enter the cells and death takes place. 

Frozen potted plants should not be exposed to the direct rays 



CONDITIONS WHICH INFLUENCE GROWTH 245 

of the sun ; syringing with ice-cold water is often a useful method 
of thawing them. 

In long-continued frost the water frozen on the outside of the 
cells may gradually evaporate into the dry cold air ; under such 
circumstances the frozen parts shrivel and die of thirst. 

Dormant seeds contain little water and are able to withstand 
the lowest temperature attainable without injury ; recently Dewar 
and Dyer found that the seeds of mustard, wheat, barley, pea 
and other plants germinated freely after being soaked for six 
hours in liquid hydrogen, the temperature of which was 453* F. 
below freezing-point. 

In actively growing plants the protoplasm becomes disorganised 
and its vital powers destroyed at temperatures about 45 or 50 C 

Many dry seeds withstand a dry heat of 80 C. or higher for 
an hour or longer; after soaking, however, they are killed by 
10 to 30 minutes' exposure to a temperature of 51 or 52 C. 

(ii) Water. Water is necessary for the maintenance of the 
turgidity of the growing cells. It is itself a food-material and is 
also essential as a vehicle for the transport of foods and food- 
materials needed for the nutrition of the growing organs. 

When plants from the beginning of their lives suffer from want 
of water their size is much diminished, although in other respects 
their development appears normal; individually they become 
dwarfs. 

On persistently dry soils and in dry seasons the bulk of the 
hay crop, the size of the 'roots' of turnips, the height of the 
straw of cereals, and the size of the various members of plants 
are proportionately decreased, while in damp seasons or upon 
soils which hold considerable amounts of water, the growth of 
plants is much increased. The growth and consequent size of 
plants in pots is similarly increased or decreased by judiciously 
varying the water-supply during the time that growth is pro- 
ceeding. 

Somewhat sudden diminution in the supply of water results in 



246 GROWTH 

the rapid cessation of growth followed by withering of the whole 
plant. 

(iii) Food is essential for the construction of the protoplasm 
and cell-walls of the growing parts. 

(iv) Oxygen is necessary for the process of respiration without 
which all vital functions cease. 

(v) Light. The various members of a plant's body grow more 
rapidly in feeble light than when they are strongly illuminated : 
that is, light retards growth. 

When grown in darkness for a considerable time plants 
become peculiarly modified, in which condition they are said to 
be etiolated. 

Among dicotyledons the internodes of the stems of etiolated 
specimens are abnormally elongated and much more slender 
than similar parts grown under ordinary conditions of day 
and night. Their cells are larger than usual and the cell- walls 
remain thin; the stems in consequence become weak and 
are unable to maintain a normal erect position. The whole 
plant contains more water proportionately to its size and the cell- 
sap is usually more acid than that of normally grown plants. 

The leaves of etiolated dicotyledons do not develop but 
remain small and scale-like and as the chlorophyll does not 
develop in the plastids the whole plant appears pale in colour. 

A few stems such as those of iris and onion, and the 
hypocotyls of many plants, such as the bean, which ordinarily 
grow in the dark, do not exhibit the peculiar phenomena 
of etiolation, nor are the leaves of iris and other similar 
rhizomatous and bulbous monocotyledons dwarfed when grown 
in darkness. 

The development of the flowers of plants goes on in darkness 
much the same as in the light. 

Ex. 145. Sow two sets of peas, beans, mustard, and barley in pots, 
and allow them to germinate. When the young plants just appear on the 
surface of the soil, place one set of each in a light situation but not in the 



SPONTANEOUS MOVEMENTS OF GROWTH 247 

direct rays of the sun, and the other set near them but covered with boxes 
which exclude all light. 

(i) From time to time measure and compare the diameters of the stems and 
the lengths of the internodes of the plants growing in the light with those of 
the plants growing in the dark. 

(ii) Measure and compare the length and breadth of the leaves of the two 
sets of plants. 

(iii) Note the differences in the colour and firmness of the two sets of plants. 

Ex. 146. Make observations similar to the above on the shoots developed 
in light and in darkness respectively, from the tubers of the potato and 
artichoke, those springing from the roots of the dahlia, and the leaves 
of onions. 

3. Spontaneous movements of growth : nutation and tissue- 
tension. Growth rarely proceeds evenly in all parts of a shoot, 
root, or other organ of a plant ; certain portions grow more 
rapidly or continue to grow for a longer period than adjoining 
parts. In consequence of this uneven growth the organs of 
plants (i) exhibit peculiar, slow, spontaneous movements, and 
(2) their tissues become subjected to pressures and tensions in 
various directions. 

In stems and roots the growth of one side is more rapid than 
the other : the more rapidly growing side becomes slightly longer 
than the other, and the whole growing part forming the end of 
the stem or root becomes bent or curved in consequence. 

The side on which most rapid growth occurs is not always 
the same but varies from hour to hour, so that the growing 
organ bends over in different directions and the tip travels 
slowly round and round, following a spiral line in its upward 
or downward growth. Movements of this kind are spontaneous 
and automatic : like the rise and fall in the rate of growth 
during the grand period they originate within the growing 
organ itself and occur whether the plant is kept in darkness or 
exposed to the light. 

To such slow nodding movements the term nutation is 
applied. 

In most stems and roots their tips travel round from right 



248 GROWTH 

to left or in a direction the opposite to that of the hands 
of a clock ; but the apex of the stem of a hop, honeysuckle 
and some other plants moves round from left to right when 
nutating. 

By means of such movements roots are enabled to make 
easier progress through the soil, and climbing stems and ten- 
drils which nutate very conspicuously are enabled by the same 
means to reach neighbouring supports around which they wind. 

The ends of the subterranean shoots of many dicotyledonous 
plants are bent round by the excessive growth of one side 
in the manner indicated in Fig. 4. By such arrangement 
the delicate tissues of the terminal buds are considerably 
protected against injury when the shoot is growing forward 
or upward through the soil. After such a bent shoot emerges 
from the soil, rapid growth takes place on its concave side and 
the curved portion soon becomes straight. 

In a young state the leaves forming the buds of plants are 
curved round the delicate growing-point or curled up in a 
characteristic manner in consequence of the growth of one side 
of each leaf proceeding faster than that of the other side : when 
the buds open the side which previously grew more slowly grows 
at a greater pace and the curled leaf consequently unfolds and 
eventually becomes flat. 

In most stems the pith and cortex continue to grow for a 
longer period than the woody tissue : the pith and cortex strive 
to elongate but the woody tissue hinders them to a certain 
extent. The result of such unequal growth is the production 
of longitudinal tensions in the growing parts. On splitting in 
two the stems of elder, sunflower and other rapidly growing 
plants longitudinally the pith elongates a little and the two 
separated halves curve outwards. 

The bark of many trees does not grow so rapidly as the wood 
within, and consequently becomes more or less stretched. 

It must be mentioned that movements of plant organs and 



SPONTANEOUS MOVEMENTS OF GROWTH 249 

tensions in their tissues may be set up by inequalities in the 
turgidity of the various component cells as well as by irregular 
growth : both causes play a part in many instances of plant 
movements. 



Er. 147. (i) On a warm day when there is no wind examine some young 
plants of scarlet-runner beans, hops and other twining plants which are 
growing round upright poles or string. Draw a line on the ground from the 
base of the pole, in the direction in which the tip of the stem is found at the 
time. Examine the plants at intervals of half an hour and similarly mark 
the direction in which the tip is curved over at these times ; try and deter- 
mine how long it takes the tip to make a complete revolution round the pole 
as a centre. 

(ii) Make similar observations on the nutation of the tip of the stems of 
runner bean plants grown in large pots and allowed to wind round sticks 
stuck in the soil. The plants should be placed out of doors, not in direct 
sunlight. 

Ex. 148. Place some soaked broad beans with the micropyle downwards 
in damp sawdust, and allow them to germinate. When their roots are about 
an inch long take them up and select one with the straightest root. Pin it 
through the narrowest diameter of the cotyledons to a slender stick or thin 
piece of wood and place the latter through a hole in a sheet of cork or card- 
board. Then place the cardboard with the bean attached over the neck of a 
wide-mouthed bottle containing a very little water, and arrange that the root 
is vertical within the bottle. 

Stand the whole in a dark cupboard or cover it with a box to exclude the 
light. 

Examine the root after 12, 24, 36 and 48 hours and see if it remains 
vertical or if it nutates in any way. 

Does it nutate more in the plane of the cotyledons than at right angles to 
this plane ? 

Ex. 149. Cut pieces two inches long from ihe full-grown stems of a sun. 
flower and other plants. Carefully measure and then split them into longi- 
tudinal strips, so as to include in some the pith only and in others the cortical 
tissues only. Measure the separate strips and compare their lengths with 
each other and with the original length of the whole piece. 

Note also the form of the separate pieces. 

Ex. 150. In July or August and at other times remove a complete ring of 
bark an inch long from three or four-year-old branches of sycamore, birch, 
beech and willow. Then try and place the bark in its original position on 
the shoot : does it fit exactly ? 



250 GROWTH 

4. Induced movements of growth. In addition to the vital 
movements previously discussed which arise in consequence 
of internal inherited causes operating within the plant organs 
themselves, other movements are observable in various organs 
of plants, which are induced by some external provocation or 
stimulus. 

The protoplasm of living plants is irritable and sensitive like 
that of animals only in a somewhat different manner, and is 
capable of responding to the action of various external influences. 

The chief exciting causes which induce movements in the 
different plant members are (i) contact with a foreign body ; (ii) 
alterations in temperature and the periodic alternation of day 
and night ; (iii) lateral or one-sided illumination ; (iv) the force 
of gravitation ; and (v) variations in moistness of the surrounding 
soil and atmosphere. 

(i) Movements induced by contact with a foreign body, 
The best examples of movements of this class are met with in 
tendrils and roots of plants. 

The tendrils of peas, vetches, vines, passion-flowers and other 
plants are susceptible to slight contact. 

If a tendril while nutating round and round touches a foreign 
body, such as the stem or twig of a neighbouring plant, it begins 
to curve towards the irritating structure. If the latter is not too 
thick and contact with it is prolonged the tendril becomes more 
turgid on the side not irritated and also grows more rapidly on 
the same side, so that the tendrils soon coil completely round 
the structure. 

The particular part of the tendril which is sensitive varies in 
different plants : sometimes a considerable portion all round the 
tip is irritable, while in other cases the sensitive region is limited 
to a short part on one side only. The curvature of the tendril 
is not confined to the portion actually irritated, but the stimulus 
is usually transmitted backwards along the tendril, and coiling 
takes place in the parts which have not been touched. 



VARIATIONS IN TEMPERATURE 251 

Similar response to contact with a neighbouring foreign body 
is met with in the sensitive petioles of certain climbing species 
of Tropaolum and Solanum, and in a lesser degree is observable 
in many twining and climbing stems. 

Small portions near the tips of roots are sensitive to prolonged 
lateral contact : when such parts touch stones and other hard 
objects in boring their way through the soil, they curve away 
from the irritating bodies and the root tips continue their 
growth in a new direction. 

On the other hand the older portions of growing roots when 
stimulated by contact curve towards and endeavour to grow 
round the irritating objects. 

Both these and the nutating movements previously mentioned 
are such as enable roots to pass obstructing objects in their path. 

Ex. 151. (i) Observe the form of the free tendrils of the vetch, pea, vine 
and white bryony (Bryonia dioica L.). Compare with tendrils attached to 
their supports. 

(ii) Arrange so that some of the free tendrils which are about three parts 
grown shall come in contact near their tips with small twigs or other similar 
support. Examine at intervals of a few hours and note the amount of 
twining of the tendril round its support. 

(iii) Stimulate the concave side of the curved end of a tendril of white 
bryony, cucumber or melon for about a minute by rubbing with a moderately 
smooth piece of wood, and then watch its subsequent behaviour for two or 
three minutes. Does its curvature increase ? 

Ex. 152. Examine the mode of climbing of Solatium jasminioides. 

(ii) Movements in response to variations in temperature, and 
the changes of day and night. Tulips, crocuses and other 
flowers open on a warm day or when brought into a warm room 
and close when placed in a cool situation. The opening and 
closing movements go on independently of light and are brought 
about by alterations in the growth and turgidity of the cells 
forming the upper and lower sides of the petals ; the change of 
temperature stimulates the protoplasm in such a manner that 
varying amounts of water are allowed to pass through it into 



252 GROWTH 

and out of the vacuoles of the cells, and the turgid condition of 
the cells becomes altered in consequence. 

The flowers of scarlet pimpernel and other plants close in the 
daytime if the weather is dull and the air damp. By closing 
during unfavourable weather the stamens and other reproductive 
parts are protected against possible injury from rain and other 
causes, and by opening on warm days the plant secures a better 
chance of cross-pollination, for only at such times are insect 
visitors abundant. 

The leaflets of the compound leaves of the clovers, medicks 
and other Leguminosae, as well as those of wood-sorrel and other 
plants, fold together or change their position in a characteristic 
manner at night and open out again next morning. Movements 
of this kind are termed nyctitropie or sleep-movements^ and are 
effected by the plants in response to the stimulus of varying 
temperature and altered illumination occurring during the 
changes from day to night. Frequently the edges of the leaves 
and leaflets are turned upwards at night, or the whole leaf 
droops or is folded in such a way that the leaf-area presented 
to the sky is much diminished, and loss of heat by radiation is 
consequently reduced. By taking up such positions at night 
the leaves are considerably protected from being injured by cold 

Ex. 153. Examine the ' day' and 'night positions ' of the leaves of clover, 
medicks and runner beans. 

In the daytime cover up a white clover plant with a bowl or basin, and 
after two hours compare the induced ' night position ' of the leaflets of the 
darkened plant with the day position of the leaflets on a neighbouring ex- 
posed plant. 

Ex. 154. Compare the day and night positions of the flowers of wild 
carrot, Herb Robert (Geranium Robertianum}> and wild pansy. 

Pluck two or three full-grown crocus and tulip flowers when closed in the 
morning of a dull day ; place their stalks in water and convey them to a 
warm room. Notice how soon they open : after opening, stand them in a 
cool place and observe how soon they close. 

Ex. 155. On a bright day pluck some well-opened heads of daisies and 
dandelions : place the stalks in water and then transfer them to a dark 



LATERAL ILLUMINATION I HELIOTROPISM 253 

cupboard. Note that the heads close after being kept an hour or two in 
darkness. Remove them to a bright situation and observe if they open 
again. 

(iii) Movements induced by lateral illumination: heliotropism. 
When a plant is allowed to grow undisturbed in the window 
of an ordinary room, one side of its stem is illuminated much 
more than the other ; in consequence of such lateral illumination 
the growing part slowly bends over towards the light so that the 
tip and a certain amount of the stem behind it ultimately points 
in the direction from which the light comes. Similar curvature 
is seen in stems of plants growing near walls, and in other situa- 
tions where they receive light on one side more than the other. 

This bending like other cases of the curvature of growing 
members is due to a difference in the rate and amount of 
growth on the two sides of the stems, and like the movements of 
leaves and roots mentioned below, is effected in response to the 
stimulus of light falling upon the stem from one side. A small 
portion near the tip of the stem is specially sensitive to lateral 
illumination, and the stimulus it receives appears to be conducted 
back to the part which bends in the peculiar manner described. 

If the tip of the stem of a seedling which exhibits such move- 
ments is cut off or carefully covered by a cap of some material 
through which light cannot pass, the characteristic curvature 
does not occur. 

The same stimulus of lateral light when applied to roots 
induces an opposite movement from that observable in the 
growing part of a stem. The growing part of a root curves 
away from the stimulating light, and the tip and a small portion 
near it, although they lie in the line of the incident light, point 
away from it. 

The movements in response to the stimulus of lateral light 
in which the plant members turn towards the light, like stems, 
are spoken of as heliotropism or positive heliotropism^ while the 
term apheliotropism or negative heliotropism is applied to move- 



254 GROWTH 

ments in which the organ stimulated curves away from the light, 
like roots. 

The utility of these movements is clear : by such movements 
stems are enabled to reach the light and so place the leaves 
which they bear in the most favourable position for carrying on 
their function of * carbon-fixation/ and roots are aided in finding 
their way and penetrating into the dark crevices of the soil. 

The leaves of an onion and the flat sword-like leaves of 
certain monocotyledons appear to be heliotropic like stems, but 
the majority of the ordinary green leaves of plants behave 
differently from either roots or stems. They usually turn or 
twist on their petioles so as to place the upper surfaces of 
their blades at right angles to the direction in which the light 
falls upon them; plant members taking up such a position in 
reference to the incident light are described as diaheliotropic. 

A few stems, such as those of the ivy, appear to be dia- 
heliotropic. Instead of bending away from a wall they grow 
close up to it, and need no special training to keep them there. 
The ordinary heliotropic stems of fruit-trees, however, growing 
in a similar situation curve away from the wall, and if this is 
to be prevented the growing tips must be secured until they 
have become mature and firm. 

Experiments have proved that only the blue and violet rays 
of light are effective in inducing heliotropic movements : no 
response is made to red and yellow rays. 

Ex. 156. Sow some mustard seeds in two small three-inch flower-pots, 
and when the plants are about an inch high place one pot of the seedlings 
in a box in total darkness, the other pot cover with a box blackened in the 
inside with lamp black, and having a hole bored in one side about on a 
level with the top of the seedlings. 

Allow the seedlings to grow, and in a day or two compare the direction 
of growth of their stems in the two pots. 

Ex. 157. Germinate a few mustard seeds in damp sawdust, and when 
their primary roots are about an inch or an inch and a half long take one 
or two of the seedlings and push their roots through holes in a strip o/ 



FORCE OF GRAVITATION I GEOTROPISM 255 

cardboard. Afterwards plug the holes gently with cotton wool so as to 
prevent the seedlings from slipping, and then place the cardboard over a 
beaker of well water so that the roots of the plant may dip vertically into 
the water. 

Place the whole in the darkened box with a hole in the side as described 
above, and allow the seedlings to grow : examine in a day or two and note 
if the root and stem are vertical as arranged when first put into the box. 

Ex. 158. Examine fuchsias, geraniums and other plants growing in 
windows, and note the bending of the stems towards the light. 

Note that the leaves have their upper surfaces towards the light. 

Observe the leaves of ivy shoots and other plants growing close to a wall ; 
their upper surfaces are towards the light. Do the leaves grow out all on one 
side of such stems ? Have the petioles curved in any way ? 

(iv) Movements in response to the force of gravitation: 
geotropism. All bodies on the earth behave as if they were 
attracted towards the centre of the earth by a force which is 
spoken of as the force of gravitation. This force exerts a 
peculiar stimulating influence upon the various members of 
living plants. Most primary stems grow vertically upwards 
against the force and away from the earth ; when displaced 
into a horizontal position, the growing regions near the ends 
of the stems slowly bend upwards until they are again vertical. 
Primary roots, on the other hand, grow downwards with the 
force and towards the centre of the earth : when the primary 
roots of seedlings which have been allowed to grow straight 
down are placed horizontally, their growing parts soon curve 
through a right angle and take up a vertical position with 
the tips pointing downwards. 

Roots are described as geotropic or positively geotropic^ while 
stems which grow away from the earth are spoken of as apogeo- 
tropic or negatively geotropic. 

The rhizomes of couch-grass, potatoes, and other plants are 
generally diageotropic ; they grow in a horizontal position and 
when placed vertically begin to slowly curve to one side until 
the growing regions and tips are parallel with the surface of 

the ground. 

18 



256 GROWTH 

These movements go on in the dark, and are the result of 
stimulus of gravity acting upon the sensitive tips of the stems 
and roots and not directly upon the growing parts which become 
curved. 

The lateral secondary branches of roots and stems appear 
to be less sensitive to the action of gravity than primary 
members ; for example, secondary roots grow obliquely and 
not vertically downwards in the soil. 

The peduncles of most flowers are generally apogeotropic but 
in some cases their geotropic irritability changes when the flower 
opens : many varieties of daffodil become diageotropic when the 
flower opens, the * trumpet ' of the corolla then taking up a more 
or less horizontal position. 

The stems of wheat, barley and grasses generally curve up- 
wards at the nodes when they are bent on one side by the wind 
and rain, and the upper internodes and ears may eventually 
attain an erect position after the crop has become * laid/ if the 
latter does not happen too late in the season. 

This apogeotropic movement of a cereal stem is due to the 
stimulus of gravity which induces a renewal of growth in the 
tissue forming the swollen leaf-bases close to the nodes. 

Ex. 159. Repeat Ex. 9, and note the geotropic behaviour of the roots 
and stems of the beans employed. 

Ex. 160. Sow a runner bean in a pot of garden soil and keep in a dark 
place. When the stem of the seedling is two or three inches long turn the 
pot on its side so that the young stem is horizontal and leave it to grow in 
the dark as before. After a few hours examine and note the curvature of 
the stem : which part has curved most ? 

Ex. 161. Cut a straight piece of a young barley or wheat stem with a 
node about the middle of it, and place the lower cut end through a hole in a 
cork which fits into a small flat medicine bottle. Fill the bottle with water, 
insert the cork with the straw through it, and place the bottle on its side so 
that the straw is horizontal. Leave it in a dark cupboard all night and 
examine next morning. Is the straw still horizontal ? 

(v) Movements induced by variations in moistness of the 



MOISTNESS OF THE SOIL : HYDROTROPISM 257 

soil: hydrotropism. The tips of roots are sensitive to changes 
in the moisture of the soil : while growing through the ground 
they bend towards the parts which are dampest. In consequence 
of this peculiarity, the roots of plants frequently find their way 
into drain pipes, wells and water courses some considerable 
distance away from the place where the stems are growing. 



CHAPTER XXI. 
REPRODUCTION. 

i. THE physiological processes previously discussed have been 
concerned with the maintenance of the life of the individual 
plant. It is now necessary to consider the process of reproduc- 
tion^ or the power of giving rise to new and separate individuals, 
which is one of the most characteristic peculiarities possessed by 
all living organisms. 

Among flowering plants two distinct modes of reproduction 
are met with, namely, (i) vegetative reproduction and (ii) sexual 
reproduction. 

VEGETATIVE REPRODUCTION. 

2. The essential feature of vegetative reproduction consists 
in the separation either naturally or artificially of portions of the 
vegetative organs of the parent, each detached part subsequently 
developing into a new and complete individual plant. A good 
instance of natural vegetative multiplication is seen in the potato. 
Thin underground rhizomes grow out from the parent plant and 
become thickened and form tubers at their tips ; at the end of 
the summer the parent plant dies and leaves only the tubers, 
which in the following year develop into new separate plants. 
Almost all plants with underground branching rhizomes behave 
in a similar manner ; the older main portions die off and leave 
the young lateral rooted branches to carry on their existence 
as separate individuals. 

The buds on the stolons or runners of the strawberry and 
creeping crowfoot (Fig. 21) become rooted to the ground 

258 



CUTTINGS 259 

and after the death of the bare internodes form separate 
plants. 

Other examples of vegetative multiplication are seen in the 
growth of bulbous and corm-bearing plants (pp. 56-60). 

3. In addition to the natural modes of reproduction just 
mentioned, various artificial modes of vegetative propagation 
are known. Detached pieces of the roots, stems or leaves of 
many plants when placed under certain conditions indicated 
below, give rise to those organs which are necessary to make 
the part a complete plant : thus the shoots of plants when cut 
off and placed in suitable soil soon develop a system of ad- 
ventitious roots, and pieces of roots treated in a similar manner 
produce buds from which leafy shoots arise. It is a remarkable 
fact that although roots may be formed when either end of a 
cutting is inserted in the earth, the best development of roots 
always takes place when that end of the cutting which was nearest 
the root of the parent plant is buried in the soil. Also when a 
root-cutting is buried in the ground, the greatest growth of roots 
originates from that end of the cutting which was nearest the apex 
of the root, the other end giving rise to adventitious buds. The 
severed shoots of certain conifers and other plants do not appear 
to be able to form roots, nor are their roots capable of forming 
buds : plants such as these cannot be reproduced vegetatively. 

The commonest examples of artificial vegetative reproduction 
are seen in the propagation of plants by means of cuttings and 
layers and in the processes of budding and grafting so extensively 
practised by nurserymen and gardeners. 

4. Cuttings. The term cutting is applied to any portion of a 
root, stem or leaf cut from a plant and used for propagation. 
A few plants, such as pelargoniums, have the power of forming 
adventitious buds upon cut portions of their roots, and may be 
propagated by root-cuttings. The leaves x)f gloxinias, begonias 
and other plants, when cut through the midribs and fastened 
down or merely laid on damp sand, and kept at a suitable 



260 



REPRODUCTION 



temperature, produce buds and roots which develop into new 
plants at points where the midribs are cut. 

In the majority of cases, however, shoots are selected for 
cuttings : tHey generally give best results 
when cut through just below a node, for in 
most instances it is only at the latter points 
that adventitious roots are formed. Those 
of leafy herbaceous plants are placed in 
loose, warm soil to induce a rapid formation 
of roots and are kept in a somewhat close 
damp atmosphere to prevent too rapid loss 
of water by transpiration during the time that 
the shoots are without roots. 

Woody cuttings contain a sufficient store 
of food for the formation of callus-tissue 
and roots : herbaceous cuttings, however, 
usually possess but very small amounts of 
ready - formed plastic materials and must 
therefore be exposed to light so as to carry 
on the work of * carbon-fixation.' 

Currants, gooseberries and vines are very 
readily increased by cuttings : pears and 
apples may also be reproduced in a similar 
manner, but the production of roots by the 
shoots of these trees is very uncertain. 

The cuttings of fruit trees are usually 
8 or 10 inches long and taken from well- 
matured wood of the previous season's 
growth, after the shoots have lost their 
leaves in autumn. The buds on the portion 
of the shoot inserted in the soil should be 
cut out where 'suckers' are to be avoided, 
and only the buds needed for the formation of the bush or tree 
left on the part above ground (Fig. 91). 




FIG. 91. Cutting 
of gooseberry showing 
formation of adventi- 
tious roots below 
ground. 



LAYERS 



261 



In the apple and pear, roots form more readily when the 
cuttings include a ' heel ' or small basal piece of wood from the 
older branch on which the cutting originally grew. 

Hops are propagated by cuttings (p. 344), and the tubers of a 
potato when very large or the variety a scarce one are sometimes 
cut longitudinally so that each piece possesses an 'eye' or 
collection of buds which develops into a new plant when the 
piece is placed in the ground. 

5. Layers. The process of layering consists in bending and 
pegging down a shoot of a plant into the soil as indicated in 

Fig. 92. From the bent por- 
tion in the earth roots are 
sooner or later emitted, after 
which the shoots spoken of as 
layers may be severed com- 
pletely from the parent plant. 
The mere bending and cover- 
ing the shoot with moist warm 
soil is sometimes sufficient to 
induce the emission of roots, 
but more generally one or other 
of the various plans of ' tongue- 
ing,' 'ringing,' and ' notching,' must be adopted to secure a good 
formation of root. 

'Tongueing' is a term applied to the process of cutting an 
oblique slit upwards as at a almost through the stem at a node. 
'Ringing 7 (b) consists in removing a complete half-inch wide 
ring of bark or tissues as far as the cambium of the stem : by 
'notching' is meant the cutting of a V-shaped incision half 
through the stem. All these devices and others which are 
practised retard the flow of elaborated sap backward from the free 
portion of the shoot above ground, and the consequent accumula- 
tion of plastic material in the part of the shoot beyond the cut 
tends to induce the formation of adventitious roots upon it. 




FIG. 92. Diagram illustrating method 
of layering, b Ringed branch ; a. tongued 
branch. 



262 REPRODUCTION 

Layering is usually more successful than propagation by 
cuttings, for the latter are liable to die before a root-system is 
developed adequate to their requirements : in the process of 
layering the shoot remains attached to the parent until it is 
rooted, during which time it derives its water-supply and a 
certain amount of food from the latter. 

Currants and grapes are readily increased by layers, and the 
process is adopted for the rapid production of apple, pear, plum, 
quince and other stocks which are subsequently employed for 
budding and grafting purposes. The layering of these usually 
takes place in autumn, the layers being left attached to the 
parent about twelve months or until a satisfactory root-system 
is developed, after which time they may be completely severed 
from the parent and planted out. 

6. Budding and Grafting. In the process of budding^ a bud is 
taken from one plant and inserted into the stem, or stock as it is 
termed, of another; ingrafting a portion of a shoot with several buds 
upon it is treated in a similar manner. The shoot, which in the 
grafting process is inserted into the stock, is termed a graft or scion. 

The inserted bud and stock or the scion and stock when 
properly treated become organically united with each other and 
behave as one plant. The roots of the stock supply the bud or 
scion attached to it, with water and other ingredients from the 
soil, and the leaves of the shoots developed from the bud or 
scion elaborate plastic material for the nutrition and growth of 
the root. Nevertheless, in nearly all cases the scion and stock 
preserve their own individual morphological peculiarities, and 
in this respect behave as distinct, separate plants. 

It is stated that in some instances budded or grafted plants 
give rise to shoots which in form of leaf, colour of their flowers, 
and other morphological characters, resemble those of the scion 
and those of the stock as well. Shoots produced in this manner 
with such blended characters are described as graft-hybrids-, 
they are of very rare occurrence. 



BUDDING AND GRAFTING 263 

Budding and grafting are processes mostly applied in practice 
to woody dicotyledons; herbaceous plants may, however, be 
made to unite satisfactorily. Attempts to graft monocotyledons 
with each other rarely succeed. 

One species of plant can often be successfully grafted on a 
totally distinct species, as, for example, the peach on the plum, 
the apple on the pear, the pear on the quince, and the tomato 
on the potato. Moreover, certain species belonging to different 
genera unite and grow satisfactorily, as the medlar on the 
hawthorn, and the Spanish chestnut on the oak. Apparently, 
however, only plants can be grafted on each other successfully 
when they belong to the same Family or Order. 

Although a variety of pear, whether grafted on the quince, 
apple, wild pear or other stock, remains a pear and possesses 
all the special characters for which it is grown, the scion is 
nevertheless influenced in the size and flavour of its fruit, in 
the earliness or lateness of its fruit-bearing power, its habit of 
growth, and in other ways, by the stock on which it is grafted. 
Similar influence of the stock on the scion and its produce, is 
observable in most other fruit trees, and appears to be connected 
with the mechanical difficulty of transport of the food material 
through the wood at the point of union of stock and scion. 

Fruit trees on their own roots are less fruitful and the fruit is 
of poorer quality than that obtained from the same variety of 
tree grafted on another appropriate stock. 

For the production of dwarf trees which fruit at an early age 
the pear is usually grafted on the quince and similarly the apple 
is grafted on the so-called ' Paradise ' stock, a name given to 
certain surface-rooting dwarf varieties of apple. 

Where larger trees are required which do not fruit so soon but 
which are of greater longevity than dwarfs, the pear is grafted on 
stocks raised either from seeds of the wild pear or from common 
varieties of pear used in the manufacture of perry, and the apple 
is grafted on stocks raised from seeds of the crab or wild apple, 



264 



REPRODUCTION 



or upon the so-called Free stocks raised from seeds of cider 
apples. 

Heart and Bigarreau varieties of cherry are budded and grafted 
on seedlings of the Wild Gean (Prunus Avium L.), the Morello 
and Duke types being inserted on stocks of Dwarf cherry (Prunus 
Cerasus L.). 

Mussel and St Julicn plums are frequently used as stocks for 
plums. A great many different ways of preparing and inserting 
the buds and scions are practised. 

In the propagation of fruit trees and roses by budding, the 
commonest method is that known as shield-budding, which is 
usually performed in July or August when the bark of the stock 
can be readily separated from the wood along the active 
cambium-ring. The buds selected for insertion must, of 
course, be wood buds, and are taken from shoots produced 

in the same year. They 
must not be too young 
nor too old, and are 
therefore cut from the 
middle portion of the 
shoot where the wood 
is about half-ripe. 

The bud to be used 
is cut from the young 
shoot in the manner in- 
dicated at a /;, Fig. 93 : 
a shield-shaped piece 
of the bark is removed 
with the bud, and also 
a small portion of the 
wood of the shoot, which 
F|G - 93 ' must be carefully pulled 

from the bark and thrown away. If in withdrawing this small 
piece of wood the rudimentary vascular cylinder or axis of the 




BUDDING AND GRAFTING 



265 



bud comes with it, the bud appears hollow when viewed from 
inside and is useless, for it cannot develop. The leaf in whose 
axil the bud is growing is severed as at x so as to leave about a 
quarter of an inch of petiole attached to the bark. This done 
a T-shaped incision (A, Fig. 94) is cut in the stock and the 
bark gently raised as at B : the prepared bud is then inserted 
in the slit as at D and the whole firmly tied round with raffia- 
grass or cotton-wick so as to press the wounded parts together, 
leaving the bud itself exposed (E, Fig. 94). 




FIG. 94. Diagram illustrating a common method of ' Budding.' 

The bandage should be removed or released in about three 
weeks or a month after budding, and after the upper part of the 
stock has been cut off in autumn no growth except that from 
the inserted bud should be allowed. 

In budding operations carried out as above, the healing-tissue 
or callus formed by the cambium of the transplanted bud becomes 
united with that formed by the cambium of the stock upon 
which the bud is placed, and as the cambial surfaces brought 



266 



REPRODUCTION 



together are comparatively large, a good union is very readily 
made. 

In the process of grafting a short piece of a shoot with from 
two to four buds upon it is united with the stock. 

In the grafting of fruit trees the grafts or scions are cut in 
January or February before vegetative growth commences, from 
well-ripened shoots of the preceding year's growth. They are 
then placed in moist sand or garden soil on the north side of a 
wall, or kept in a cool cellar in order 
to prevent them from drying up and 
to keep them dormant until they are 
needed in March or April when the 
actual operation of grafting is generally 
carried out. 

The upper part or ' head ' of the tree 
or stock is cut off completely at a 
point a little way above where the 
scion is to be grafted. This prepara- 
tion of the stock must be done before 
growth begins in spring, the best time 
being usually in the early part of 
February. 

Very numerous methods of uniting 
the scion to the stock are practised by 
gardeners and nurserymen. 

In all cases it is important to re- 
member that the callus or healing- 
tissue which brings about the union, 
arises chiefly from the cambium of the scion and stock and the 
cells immediately bordering on the cambium : the old matured 
portion of the wood takes no part in the process. 

The commonest modes in use are tongue- or whip-grafting 
and rind- or crown-grafting, the former being largely adopted 
where the scion and stock are approximately the same in thick- 




FIG. 95. Diagram illus- 
trating mode of tongue-graft- 
ing. I. Stock a and scion b 
separate. II. The same fitted 
together before being bound 
and waxed. 



BUDDING AND GRAFTING 



26 7 



ness, the latter where the scions are grafted upon much thicker 
branches and stems. 

In tongue-grafting the scion is first cut with a long sloping cut 
2 or 3 inches long, and then notched as at , Fig. 95. The stock 
is treated in a similar manner so that when placed together the 
scion and stock fit as at II, Fig. 95. The two parts are subse- 
quently bandaged firmly, and the wound 
covered either with grafting-wax or clay 
to exclude air and rain. 

As soon as the buds on the scion have 
grown into shoots 6 or 8 inches long the 
bandages and covering should be care- 
fully removed, and the scion and stock 
tied to a supporting stake. 

In crown-grafting one or more scions 
are cut with long sloping cuts and then 
inserted into longitudinal slits 2 inches 
long, cut through the bark of the stock 
as shown in Fig. 96. The wounded 
parts are then bound and covered with 
clay or wax as in tongue-grafting. 

The growths from bulbs, tubers, cuttings, 
grafted buds and scions are, strictly speak- 

wuh three scions inserted. ing> nQt new p } ants> but Simple CXten- 

sions of the body of the parent which produced them : with 
rare exceptions, they possess the same morphological and 
physiological characters as the plant from which they were 
derived. Whatever qualities the parent possesses which make 
it valuable, the same are met with in the plants derived from 
it by the various methods just described, and it is largely on 
account of this fact that the farmer, gardened, and nurseryman 
makes use of the power of vegetative reproduction. , 

Plants raised from the seeds of choice varieties of apple, pear, 
cherry and other fruit trees usually differ very widely from their 




a 



FIG. 96,-Diagram iiius- 



268 REPRODUCTION 

parents, and the same want of resemblance between parent and 
offspring is seen when seedlings of carnations, chrysanthemums, 
dahlias, potatoes, hops, and a vast number of other cultivated 
plants are compared with their progenitors. 

The reproduction of plants by seeds cannot, therefore, in such 
cases, be relied on as a means of obtaining a number of 
examples all resembling their parent : the only method of 
obtaining the desired result is to take advantage of the power 
of vegetative reproduction. 

Another reason for the employment of the power of vegetative 
reproduction is the great saving of time which is effected when 
the rapid multiplication of certain kinds of plants is the object in 
view. To raise a remunerative crop of potatoes from true seeds 
would take five or six years, and an even greater time would be 
needed to produce an orchard of fruitful trees from the ' pips ' 
of pears or apples : by the use of tubers in the former, and by 
grafting on well-established stocks in the latter cases, the end is 
attained in a comparatively short time. 

The same saving of time is seen in the raising of strawberries 
from separated runners instead of seeds, and in the propagation 
of tulips, hyacinths, and narcissi by means of bulbs rather than 
by seeds. 

Ex. 162. Examine cuttings and layers ol carnations, pelargoniums, goose- 
berry, black-currant and any others obtainable after they have rooted. Make 
drawings of the rooted ends. 

Ex. 163. All students should be required to bud a rose and graft a fruit 
tree of some kind. 

Examine the external feature of budded and grafted trees in orchards 
and gardens. Notice it' the stock and scion grow ifl thickness at the same rate. 



CHAPTER XXII, 

REPRODUCTION (continued}. 

SEXUAL REPRODUCTION. 

i. THE essential feature of the sexual reproduction of plants 
and animals also, is the fusion of two special kinds of cells, 
namely, a male reproductive cell, and a female reproductive 
cell, which after complete coalescence or commingling of parts, 
give rise to a single cell capable of growing into a new organism. 

In the very exceptional cases of parthenogenesis > a female ceil 
develops into a new plant without previously uniting with a 
male cell ; as a rule, however, neither a male cell nor a female 
cell is capable of further development by itself, and it is only 
after the process of fertilisation or union of the male cell with 
the female cell that the latter grows into a new individual plant. 

The two uniting cells, or gametes as they are termed, are 
produced in special reproductive organs which vary very much 
in different divisions of the Vegetable Kingdom. We can, at 
present, only deal with the sexual cells and reproductive organs 
of ordinary flowering plants. 

The reproductive organs of these plants form the essential 
parts of flowers as mentioned in chap. vi. ; the stamens are 
the male organs and the carpels the female organs of the 
plant. 

The male reproductive cell is enclosed within the pollen-grains 
produced in the stamens : the female reproductive cell lies with- 
in the ovule as explained below. 

2. Structure and Germination of the Pollen-Grain. Pollen- 
grains vary much in form, size and colour: they are, however, 



270 



REPRODUCTION 



generally oval or spherical bodies of a yellowish colour. The 
exterior of the grain usually consists of a stout cuticularised 
cellulose coat the exine 
often elaborately ornamented 
"with spiny, wart-like, or net- 
like thickened markings ; here 
and there more or less de- 
finitely arranged, thinner areas 
are visible on the coat. Lining 
this outer protective covering 
is a delicate transparent cellu- 
lose membrane the intine 
(Fig. 97). The interior of the n- 
grain is filled with cytoplasm, 
in which are present two nuclei, 
representing two cells, between 

... . . . . . , . FIG. 97. i and a. Pollen-grains of a species 

Which there IS nO dividing of hly, with netted exine, on which small drops 

i, ,i s\ r 1.1. / \ ^ Ol1 are visible. 3. Section of a pollen-grain : 

Cell- Wall. Une Ol them () a exine; b inline ; v nucleus of the vegetative 

cell ; g nucleus of the generative cell. 4. Ger- 
minating 




is the generative Cell y the minating pollen-grain; ^/ pollen-tube; r nucleus 
/ v i , j ,1 of the vegetative cell; eg two male nuclei 

Other (V) being termed the produced by division of the nucleus of the 

vegetative cell of the pollen- generative cclh 

grain. Within the cytoplasm, starch, sugar, oil and other food 

materials can often be recognised. 

When a pollen-grain is placed in a weak solution of sugar, and 
kept at a suitable temperature, it absorbs water, and emits a 
closed slender tube-like structure, termed the pollen-tube (//), which 
grows from the vegetative cell of the grain, and may under certain 
conditions attain a length of several millimetres. The pollen-tube 
is a protrusion of the intine, and makes its way through the 
specially thin or otherwise modified places in the exine of the 
grain. 

During the germination of the pollen-grain the two nuclei 
present in it travel into the pollen-tube; the nucleus of the 
vegetative cell ultimately becomes disorganised and disappears, 



THE OVULE AND ITS STRUCTURE 271 

but the nucleus of the generative cell divides into two portions 
(g g, 4, Fig. 97), the male gametes or male cells^ which take part 
in the fertilisation-process described hereafter. 

Ex. 154. Shake out, or otherwise transfer to a dry slide, pollen -grains 
from the anthers of shepherd's-purse, sunflower, cucumber, dandelion, apple, 
mallow, sweet-william, tulip, and any other flowers at hand. 

(1) Examine with a low power, allowing the light to fall on them from above. 
Note the colour, and sketch the form and arrangement of the markings on 
the outer wall. 

(2) Mount a few of each of the pollen-grains in water or alcohol, and 
examine with both a low and a high power. 

Ex. 165. Make a 3 per cent., 5 per cent., and a 10 per cent, solution of 
cane-sugar; place some of each in separate watch glasses, and shake into 
them various kinds of pollen-grains. Cover each watch glass with another, 
and keep the whole in the dark in a warm room. Examine with a high 
power some of the pollen-grains from each glass after twelve or eighteen 
hours, and note the production of pollen-tubes from many of them. 

3. The ovule and its structure. As previously explained in 
chapter vi. (p. 85), the ovules are minute roundish or egg- 
shaped bodies found in the ovary of the carpels of a flower. In 
most cases each ovule is attached to the placenta of the carpel 
by means of a short stalk orfunicle. 

The chief part of an ovule consists of a central kernel of thin- 
walled parenchymatous tissue termed the nucellus (n, Fig. 98). 
Surrounding the latter are one or two coats or integuments (c) 
which have grown up from the base of the nucellus so as to 
cover it completely except at its apex where a very narrow 
canal (m) the micropyle is left. 

The ovules of umbelliferous plants and most dicotyledons with 
gamopetalous flowers have only a single integument; those of 
the monocotyledons and most apetalous and polypetalous dico- 
tyledons possess two integuments. 

The point (h) where the coats and the tissue of the nucellus 
are united is termed the chalaza of the ovule. 

Various forms of ovule are met with in different kinds of 
flowering plants. In the dock, walnut and buckwheat, the funicle, 

19 



272 



REPRODUCTION 



chalaza and micropyle are all in the same straight line, as at 
i, Fig. 98 : such ovules are described as orthotropous . 

When the ovule during its development becomes inverted as 
at 2, Fig. 98, the micropyle lies close to the funicle : this form 
is met with in the majority of common flowering plants, and is 
spoken of as an anatropous 
ovule. Among cruciferous 
plants, and also among the 
Caryophyllaceae and Cheno- 
podiaceae, the ovules are 
more or less kidney-shaped, 
the nucellus and integu- 
ments being curved or bent : ,. 
ovules of this type are-/ 
described as campy lotropous. 

At an early period in the 
development of the ovule a 
specially large cell termed 
the embryo-sac makes its ap- 
pearance in the tissue of the 
nucellus at a point near the 
micropyle of the ovule. 
Within it a series of seven 
new cells are developed 
somewhat as follows. The 
primary nucleus of the 
embryo-sac first divides, and 
the two halves then travel 
to the poles or opposite ends 
of the cell, one to the micro- 
pylar end, the other to the antipodal or chalazal end. Here each 
of these two new nuclei divides into four, so that at this stage eight 
nuclei are present, each of which has a certain portion of cytoplasm 
associated with it. After this, one of the nuclei from the chalazal 




-ft 



FIG 98 i. External view of an orthotro- 
pous ovule. 2. The same of nn anatropous 
ovule. 3. Longitudinal section of i. 4. 
Longitudinal section . of 2. / Funicle ; 
m micropyle ; h chala/a ; C coats of ovule ; 
n nucellus ; t embryo-sac. 



FERTILISATION AND ITS EFFECTS 273 

end and one from the micropylar end travel back to the centre 
and fuse with each other to form what is termed the secondary^ 
definitive^ or fusion nucleus of the embryo-sac (h, Fig. 99) : it is 
fat primary endosperm nucleus. 

The three nuclei at the end of the embryo-sac farthest away from 
the micropyle become surrounded with a certain amount of cyto- 
plasm and then develop cell-walls ; the cells produced are termed 
antipodal cells (a). At the end nearest the micropyle the nuclei 
and associated cytoplasm remain without cell-walls and constitute 
what is known as the egg-apparatus ; two of these three cells are 
termed synergidce, the third is the female gamete^ ovum, egg or 
oosphere(e). The ovum is the special female reproductive cell of the 
plant which after fusion with the male reproductive cell ofthepollen- 
grain, begins a new life as it were, and develops into a new plant. 

Ex. 166. Tease out with needles the ovules from the ovaries of the recently 
opened flowers of pea, bean, tulip, and others of similar size ; Amount in a drop 
of water and examine with a low power, noting if possible the funicle and 
position of the micropyle. 

Ex. 167. Cut transverse sections of these ovaries and mount the sections 
in a i per cent, solution of caustic potash. Observe and sketch under a low 
power the form, structure and attachment of the ovules to the carpels. 

Ex. 168. Place some flowers of marsh marigold (Caltha palustris L.) 
which have just opened in methylated spirit, After hardening a few days 
strip off the petals and stamens and cut a number of transverse sections 
through the carpels with a razor wetted with the spirit ; many of the sections 
will also pass through the ovules within the carpels. Transfer the sections 
into a watch glass containing a mixture of equal parts of methylated spirit 
and glycerine. Now pick out one or two sections which appear to have 
passed through the ovules and mount them in a drop of pure glycerine. 

I. Examine and sketch under a low power, noting 

(1) The section of the wall of the carpel ; 

(2) The anatropous ovule and its funicle ; 

(3) The large embryo-sac. 

a. Examine and sketch the embryo-sac under a high power, noting 

within it 

(i) The central fusion nucleus ; 
(2) The antipodal cells at one end ; and 
(3) The ovum and synergida at the other. 

4. Fertilisation and its effects. When a pollen-grain is placed 
on the stigma of the carpel of a suitable flower it germinates 



274 



REPRODUCTION 



St 



and produces a pollen-tube which penetrates into the tissues of 
the stigma and grows down through the style into the cavity 
of the ovary : the time taken to reach this point may vary from 
a few hours to several weeks, according to the kind of plant 

The advancing pollen-tube is 
guided in some way not completely 
understood into the micropyle of the 
ovule and at length comes into con- 
tact with the apex of the embryo-sac 
close to the egg-apparatus (Fig. 99). 
On reaching this point its tip be- 
comes disorganised and one of the 
male cells of the pollen-grain travels 
on through the open end of the tube 
S until it meets the ovum. The male 
-K gamete and the ovum then fuse into 
one, their parts becoming com- 
pletely intermingled. This fusion 
^ of a male cell with the ovum is the 
I essential feature of the sexual act 
and is spoken of as fertilisation. 

In several instances the second 
male nucleus from the pollen-grain 
has been found to fuse similarly with 
the fusion nucleus in the embryo-sac. 
The fusion of both male cells, one 
with the egg, the other with the 
primary endosperm nucleus, has 
been referred to as double, fertilisa- 




f 



FIG 99 Diagram of a longitudinal 
section of a carpel containing an ortho- 
tropous ovule: designed to illustrate 
the arrangement of the various parts 
about the time of fertilisation, o Ov- 
ary ; s style ; st stigma of the carpel ; 
^ pollen-grain germinated on the 
stigma; // pollen-tube; r one of the 



male gametes ;/funicle; M chalaza; //^ . ft J s general among angio- 



c integuments of ovule ; n nucellus ; 
r /embryo-sac, /ovum or egg; A fusion- 
nucleus (primary endosperm nucleus) ; 
a antipodal cells. 



sperms. 

Unless the ovum is fertilised both 
it and the whole ovule wither and die, but as soon as fertilisation 
is effected the ovum commences to divide and grow, developing 
into an embryo plant, the whole ovule finally becoming a seed. 



FERTILISATION AND ITS EFFECTS 275 

The development of the embryo of a dicotyledonous plant 
from the fertilised ovum may be easily studied in the common 
weed ShepherdVpurse (Capsella Bursa-pastoris L.). 

The ovum first surrounds itself with a cell-wall and subse- 
quently divides into two cells : of these, the upper one or that 
nearest the micropyle, by further transverse divisions gives rise to 
a single row of cells termed the suspensor (j, Fig. 100). The other 




FIG. 100. i. Diagram of ovum. a. The same after first division. 3 and 
4. Suspensor (f ) and embryo-cell (e) of Shepherd's-purse ; in 4 the embryo- 
cell (e) has undergone division ; A, hypophysis. 5. Later stage of the de- 
velopment of the embryo, showing portion of the suspensor still attached 
to it ; d dermatogen ; periblem ; p plcrome of embryo. 6. Fully-formed 
embryo ; r its radicle ; c two cotyledons. 

or lower spherical cell (e) is carried at the end of the suspensor 
some distance into the cavity of the embryo-sac ; it is spoken 
of as the embryo-cell since from it the whole of the embryo is 
developed except the tip of the radicle and the root-cap. 

The single embryo-cell divides in three directions so that eight 
cells are formed : four of these nearest the suspensor by continued 
division produce the hypocotyl and radicle, while the other four 
give rise to the cotyledon and plumule of the embryo. The 



276 REPRODUCTION 

tip of the radicle and the root-cap originate by division of the 
hypophysis, or end cell (h) of the suspensor, 

BT T 169. Pull off from an inflorescence of Shepherd's-purse (Capsella) an 
ovary of a flower from which the petals have just fallen. Open the ovary 
with needles and remove a few of the ovules : place one or two of the latter 
in a drop of water on a glass slide and cover with a cover-slip. 

(1) Examine with a low power and sketch the parts of a single ovule and 
its funicle. 

(2) Press gently on the cover-slip with the end of a lead pencil, so as to 
burst the ovule : try and find with a low power the embryo and suspensor, as 
at 3 or 4, Fig. 100, among the contents squeezed out. When found examine 
and sketch under a high power. 

(3) Repeat the above with ovules obtained from successively older ovaries, 
and trace the development of the embryo up to the time when well-marked 
cotyledons and radicle are clearly visible with a low power. 

At the same time as the development of the embryo is going 
on, changes occur in other constituents of the embryo-sac and 
also in the nucellus of the ovule. The synergidae and the anti- 
podal cells usually become disorganised and disappear. The 
primary endosperm nucleus of the embryo-sac, however, unites 
with one of the male gametes from the pollen-grain and the com- 
pound nucleus arising from such union divides repeatedly until 
a large number of naked cells are produced, between which cell- 
walls ultimately arise, the whole then forming a parenchymatous 
tissue within the embryo-sac : this tissue is termed the endosperm 
(e, Fig. 10 1 ) and is stored with food on which the embryo lives 
during its development. 

In wheat, barley, onion and other species of plants the embryo 
does not disorganise and consume all the endosperm before the 
seed ripens, so that in these cases a certain amount of endosperm 
is present in the mature seed (3, Fig. 101). 

In others, however, such as the bean, pea, and turnip, the 
developing embryo absorbs practically the whole of the endo- 
sperm and the nucellus before the seed ripens, so that mature 
seeds of these plants contain little or no endosperm-tissue and 
are described as exendospermous (4, Fig. 101). 

Most commonly the tissue of the nucellus is disorganised 
and absorbed during the development of the embryo, but in 



FERTILISATION AND ITS EFFECTS 277 

certain plants it becomes stored with food and is present in the 
ripe seed: such stored nucellar tissue is termed pcrisperm (n, 2, 
Fig, 10 1). 

The fertilisation act brings about the production of an embryo, 
and stimulates the growth of other parts of the ovule, so that 



r 




FIG. ioi. Diagrammatic longitudinal sections of an ovule (i) and the seeds (2, 3, and 4) 
which may be derived from it. 

x The ovum which after fertilisation becomes the embiyo of the seed j tn micropyle ; 
ch thalaza ; f funicle ; / coats of ovule | embryo-sac; n nucellus .' r radicle of embryo ; 
c cotyledons of embryo. 

2 and 3 are 'albuminous' seeds, tissues derived from the nucellus and embryo-sac being 
present in them. In 2 the tissue n is termed perisperm ; it is absent from 3. In 3 the 
endosperm tissue e produced within the embryo-sac is alone present with the embryo. 

4 U an ' exalbuminous ' seed, both penspeim and endosperm being absent. 

the latter is finally converted into a seed: the corresponding 
parts of the ovule and the seed are indicated below : 
The Ovule. The Seed. 

The egg or ovum becomes the embryo, 
integuments seed-coats or testa. 
micropyle micropyle. 

funicle funicle. 

In so-called ' albuminous ' seeds, the * albumen ' may re- 
present storage-tissue developed in the embryo-sac and termed 
endosperm, or it may be derived from the nucellus, in which 



278 REPRODUCTION 

case it is designated perisperm ; some seeds may contain both 
endosperm and perisperm. 

After fertilisation has been accomplished, the style and stigma 
of the carpels and also the corolla of most conspicuous flowers, 
wither and fall off. The stimulus of the sexual act incites the 
ovule to grow, and a similar influence is transmitted to the 
tissues of the ovary- wall, which also grow and expand to allow 
the development of the seeds within : the gynaecium of the flower 
becomes converted into a fruit. 

Moreover, the act of fertilisation frequently induces growth 
and change in the receptacle and flower-stalk, as in the apple, 
pear, and strawberry. 

Some cultivated plants, such as varieties of cucumber, grape, 
pine-apple, orange, and banana, produce 'seedless fruits,* the 
walls of the ovaries developing extensively apart from any seed 
production. However, in the tomato, melon, plum, and the 
majority of plants, fruits either do not develop at all or drop 
off long before they reach normal size, when fertilisation does 
not take place. 

That the development of the seed influences the growth of 
the fruit may be seen by watching the development of an 
apple flower in which some of the five stigmas present have 
been pollinated and others left : the * fruit * from such an 
incompletely pollinated flower becomes somewhat one-sided 
and unsymmetrical in form, for only the carpels corresponding 
to the pollinated stigmas produce seeds, and it will be found 
that the part of the ' fruit ' in which the seeds a*re present grows 
more rapidly than the seedless part. 

Tomatoes and strawberries also develop into one-sided, 
irregular fruits when pollination is incomplete. 

Only one pollen-grain is necessary to fertilise a single ovule, 
and more pollen is always produced by flowers than is absolutely 
necessary for the impregnation of all the ovules within their 
carpels. There is however some evidence to believe that when 



THE FORMATION OF GAMETES 279 

an excess of pollen is applied to the stigmas of flowers, the tissues 
of the pericarp are stimulated to develop more extensively, and the 
fruit is consequently larger than when a small amount of pollen 
is applied. 

5. The formation of gametes : meiosis, or the reduction 
division. As already explained, in the fertilisation process two 
reproductive cells, namely, a male gamete from the pollen-grain 
and the female gamete or ovum in the ovule, unite to form a 
single cell, which divides by the ordinary process of mitosis, first 
into two cells, and then similarly again exactly as in the division 
of the vegetative cells of root-tips and growing-points of stems 
described previously (p. 269). 

It is clear that if the uniting gametes contain the same number 
of chromosomes as the rest of the cells of the body of the plant 
producing them, the fertilised ovum will have within it twice as 
many chromosomes as the cells of the parent plant, and all the 
cells which develop from the fertilised ovum will likewise have 
double the number of chromosomes ; similarly, the chromosomes 
in the cells of plants would be again doubled in each succeeding 
generation. 

It is found, however, that the number of chromosomes remains 
constant from generation to generation, a result due to the fact 
that the nuclei of the uniting gametes contain only half the 
number present in the rest of the cells of the plant. This reduced 
number in the gametes is brought about in the manner described 
below. 

Mitosis, with longitudinal splitting of the chromosomes goes on 
in all cells of the plant up to the period when the pollen grains, 
or microstores, begin to form in the stamens and the embryo sac 
arises in the ovule. 

The pollen-mother cells from which the male gametes are pro- 
duced, like all other cells of the plant, possess the unreduced 
number, 2w, of chromosomes (termed the diploid or double number), 
but at the first division of such cells the individual chromosomes, 
instead of splitting longitudinally into two halves as in mitosis, 
come together undivided in pairs in the equatorial region of the 
cell (3, Fig. ioia). The individuals of the different pairs then 
separate from each other, half of them (the haploid or single 
number n) going to one pole of the cell, the other half to the 
opposite pole. 

The two opposing groups, each containing half the number of 



REPRODUCTION 












Fio ioia. Diagram of Meiosis, or reduction division of pollen mother-cell, i. Mother- 
cell, with resting nucleus. 2. Cell showing four chromosomes (the unreduced double, or 
dvploid number) in the nucleus. 3. The four chromosomes forming two pairs on equatorial 
plate of the cell. 4. Separation of whole chromosomes. 5. Daughter-cells of the first (the 
reducing) division, the nucleus of each with two chromosomes (the reduced, single or haploid 
number). 6. Mitosis of the two daughter-cells. 7. Resulting four cells, each with nucleus 
containing the reduced number of chromosomes. 8. Four fully formed pollen grains 
(microspores) arising from pollen mother-cell x. 



SEXUAL REPRODUCTION 



2796 




PIG. loift. Diagram of gamete formation in the pollen grain, i. Pollen grain with two 
chromosomes in nucleus. 2, 3, 4. First mitotic division of nucleus giving rise to two nuclei, 
each with two chromosomes, one the nucleus of the vegetative cell, the other the nucleus 
of the generative cell of the pollen grain. 5, 6, 7. Mitosis of nucleus of the generative cell. 
8. Pollen grain with resting nucleus of the vegetative cell () and two male gametes (f). 



279' 



REPRODUCTION 






SEXUAL REPRODUCTION 279^ 



FIG. xoic. Diagram of meiosis and gamete formation in the embryo sac mother-cell. 

x. Mother-cell of embryo sac or macrospore, with resting nucleus. 2. Nucleus of i with 
four chromosomes (the unreduced diploid number). 3. Pairing of whole chromosomes on 
the equatorial plate. 4. Reduction division complete, with formation of two cells (potential 
embryo sacs) each with two chromosomes (the reduced haploid number). 5. Embryo sac 
with resting nucleus. 6. Nucleus showing the reduced (haploid} number (2) of chromo- 
somes. 7, 8. First mitotic division of embryo sac, with production of two reduced nuclei. 
9. Cell with four nuclei, the result of mitosis of 8 (the second mitotic division of the nucleus 
of the embryo sac nucleus). 10. Third mitotic division with production of eight nuclei. 
IT. Embryo sac ready for fertilisation ; o, ovum or female gamete ; s, synergidaa ; a, anti- 
podal cells ; d, primary endosperm nucleus, or ' fusion ' nucleus of embryo sac with four 
chromosomes (the diploid number) derived from the fusion at the centre of one cell from 
each of the two groups of four at the poles of 10 ; p, pollen tube with two male gametic 
nuclei, one of which on fusion with the ovum, gives fo t the fertilised ovum, from which a 
new plant develops with the full double complement of chromosomes in each cell, the 
other male nucleus combining with the primary endosperm nucleus, which later gives rise 
by mitosis to endosperm tissue, each cell of which contains an extra set of chromosomes. 



chromosomes of the parent cell, ultimately become incorporated 
in the two new nuclei of the daughter-cells ; each daughter-cell, 
therefore, contains the reduced (haploid) number of chromosomes, 
and the division which leads to this result is termed meiosis, or 
the reduction division. 

Later, these two cells, each with the reduced number, divide 
mitotically as in ordinary vegetative cells, giving rise to four cells 
which without further nuclear changes develop into pollen-grains 
(Fig. ioia). 

It is within the pollen-grains that the male galetes are formed 
after two mitotic divisions as illustrated in Fig. ioi&. 

A reduction division, similar to that described in the production 
of a microspore or pollen-grain, precedes the formation of the 
macrospore or embryo sac, within which the female gamete or 
ovum is produced. 

The nucleus of the macrospore mother-cell, like that of the 
microspore mother-cell, contains the unreduced (diploid) number 
of chromosomes (Fig. loi^r). At division, pairing of whole chromo- 
somes occurs, with subsequent separation of the individuals of 
each pair into two reduced (haploid) groups, exactly as in the 
reduction division of the pollen mother-cells. (Compare 1-7, 
Fig. ioia, and 1-4, Fig. ioic). 

The reduction division of the embryo sac mother-cell results 
in the formation of two daughter-cells, both potential embryo 
sacs, each containing the reduced (haploid) number of chromo- 
somes. This is usually followed by a mitotic division of the two 
cells, and a longitudinal row of four cells appears ; usually only 
one of these functions as an embryo sac or macrospore, the other 
three degenerating. 

It is after three more mitotic divisions of the nucleus within the 
embryo sac that the female gamete or ovum arises as illustrated 
in 5-11, Fig. ioic. 

It must be observed that while the reduction divisions bring 
about the production of cells each with half the number of 
chromosomes present in the parental cell, it is only after two or 
three mitotic divisions of these cells that the actual gametes 
which take part in fertilisation are produced. 

In the fertilisation process one of the male gametes, with its 
reduced number of chromosomes (n\ unites with the ovum of the 
embryo sac, giving rise to the fertilised ovum with a full comple- 
ment of chromosomes (2). From the latter a new plant develops 



POLLINATION 2797 

by repeated mitosis, producing a seedling in each cell of which 
there is the same number of chromosomes (2n) as in those of the 
parent plant. 

The second male gamete from the pollen-grain combines with 
the fusion nucleus of the embryo sac (' double fertilisation '), 
adding to it a third set of chromosomes ; leading to the formation 
of the primary endosperm nucleus. The latter is in reality the 
product of a triple fusion of one paternal with two maternal 
nuclei, which on repeated mitosis gives rise to the endosperm 
tissue, each cell of which contains $n chromosomes (n, Fig. ioic}. 

6. Pollination : self- fertilisation and cross- fertilisation. It 
will be understood from the foregoing account that among plants 
with completely closed carpels the fertilisation-process is preceded 
by and dependent upon the deposition of the pollen-grain on the 
stigma of the carpel of a flower. Although the pollen-grains 
may be induced to germinate on other parts of the carpel, the 
pollen-tubes have no power of penetrating the tissues of the 
latter except when placed on the specially receptive stigma. 
This necessary transference of pollen-grains from the anthers of 
the stamens to the stigmas of the carpels is termed pollination. 

Where the stigma receives pollen from the anthers of the same 
flower the latter is said to be self -pollinated : frequently, however, 
the stigma in one flower receives pollen from a flower growing 
on another distinct plant, in which case the flower receiving the 
pollen is spoken of as cross-pollinated. 

A simple term is needed for the intermediate case where the 
pollen of a flower is transferred to the stigma of another flower 
growing on the same plant. 

Where self-pollination is followed by fertilisation the plants 
are said to be self-fertilised or close-fertilised ; the term cross- 
fertilisation is applied to cases where the fertilising pollen is 
derived from another distinct flower of the same species of 
plant. 

Since most plants have their sexual organs close together in the 
same flower it might be imagined that self-fertilisation would be 
the rule among flowering-plants. A number of plants with open 
flowers are undoubtedly self-fertilised and certain plants such 
as pansy, violet, wood-sorrel and barley, possess cleistogamous 
flowers which never open and which therefore insure certain 
self-fertilisation. 

Extensive and careful observation, however, shows that a large 



280 REPRODUCTION 

number of flowering plants are cross-fertilised, and experiments 
have proved that the plants derived from seeds which have 
arisen from cross-pollinated flowers are in many cases taller, 
more robust in constitution and productive of earlier flowers and 
more seeds than those arising as the result of self-fertilisation. 

A great many devices are met with among flowering plants 
which are calculated to secure a preponderance of cross-fertilisa- 
tion over self-fertilisation. The chief arrangements tending more 
or less completely to this end are the following : 

(i) The flowers are often diclinous (p. 87); that is, the 
sexual organs are produced in separate flowers, which may occur 
either on the same plant, as in the hazel and pine, or upon 
different individual plants, as in mercury (Mercurialis\ hop and 
willow. 

(ii) Although the male and female sexual organs in 
monoclinous flowers are in close proximity to each other, they 
frequently do not ripen together : plants bearing flowers of this 
kind are described as dichogamous. 

Two types of flowers are met with upon dichogamous plants, 
namely, (a) protandrous flowers, or those in which the anthers 
ripen and shed their pollen before the stigma is in a suitable 
condition to receive it, and (b) protogynous flowers in which the 
stigma is receptive some time before the anthers open and set 
free their pollen. 

Protandrous flowers are abundant ; the sunflower, daisy, dead- 
nettle, carrot, bean, vetch, parsley and most Umbelliferae, 
Leguminosae, Compositse, and Labiatae are familiar examples : in 
these, the pollen necessary for the fertilisation of any particular 
flower usually comes from a younger one, because its own pollen 
has been shed before the stigma is receptive. 

Protogynous flowers are less common : examples are seen in the 
apple, pear, plantain (Plantago\ meadow foxtail and sweet vernal- 
grasses, rushes, hellebore, and species of Speedwell ( Veronica), 
and Calceolaria. In these the stigmas are pollinated from the 



TRANSFERENCE OF POLLEN 281 

anthers of flowers which have opened previously, their own 
anthers being not yet ripe when the stigma is fully developed. 

(iii) Among monoclinous flowers which are homogamous y that 
is, which develop and ripen their sexual organs simultaneously, 
the distance apart or the relative position of the anthers and the 
stigma is often Such that the transference of pollen from the 
former to the latter is rendered uncertain : examples exhibiting 
adaptations of this class are met with in the primrose and cowslip. 

(iv) Among certain plants, especially some orchids, the pollen 
has no fertilising effect upon ovules produced in the same flower. 

Transference of pollen. Since the pollen-grains of plants have 
no power of spontaneous movement, they must be carried from 
one flower to another by some external agency. 

In certain cases snails, birds, and currents of water effect the 
transference of pollen from place to place, but the chief agents 
which carry the pollen-grains from one flower to another are 
(i) the wind and (2) insects. 

Flowers which are cross-pollinated by aid of the wind are said 
to be anemophilous or wind-pollinated : those in which the pollina- 
tion is brought about by the agency of insects are described as 
entomophilous or insect-pollinated flowers. 

Wind-pollinated flowers are sometimes loosely described as 
wind-fertilised and insect-pollinated flowers as insect-fertilised: 
it must, however, be clearly understood that the function of 
the wind and insects is merely the transference of the pollen- 
grains from the anthers of one flower to the stigma of another, 
and that these agents have no direct influence upon the act of 
fertilisation which subsequently takes place in the ovule. 

As examples of plants .whose flowers are wind-pollinated may be 
mentioned the hop, docks, almost all grasses and sedges, and many 
trees and shrubs, such as hazel and birch. Their flowers are gener- 
ally small and inconspicuous, without scent : ' honey ' is generally 
absent, and the pollen-grains, which are usually produced in large 

quantities, have a smooth and dry external surface. The anthers 

20 



282 REPRODUCTION 

in many cases have long slender filaments which allow of theii 
easy movement even by gentle breezes : the stigmas are often 
very large and feathery and specially adapted to catch the floating 
pollen-grains. 

Insect-pollinated flowers, of which roses, honeysuckle, clovei 
and primrose may be mentioned as examples, usually have 
brightly-coloured petals or sepals, and are often highly-scented, 
Nectaries or honey-glands which secrete nectar, a sweet liquic 
commonly called 'honey,' occur on various parts of the 
flower. 

Their pollen-grains are less abundant than in wind-pollinated 
flowers and generally have an ornamented sticky surface which 
enables them to cling together and to the bodies of insects. The 
stigmas of such flowers are comparatively small, and when read] 
for pollination often exude a viscous liquid to which the 
pollen-grains readily adhere, and in which they germinate 
freely. 

The insects which visit flowers are mainly beetles, flies 
moths, butterflies, and bees. The various tints of flowers 
their odour and the nectar which is secreted by them, serve 
to attract these visitors, and in certain measure enable the 
latter to distinguish the particular species of plant which the] 
wish to visit. 

Insects feed upon nectar and also to some extent upon pollen 
which they obtain in part from wind-pollinated flowers whicl 
contain no nectar. 

In their search for a livelihood bees and other insects uncon 
sciously render useful service to the plants which they visit b] 
bringing about cross-pollination. 

Where the nectar is exposed or easily accessible, as 5i 
most unbelliferous plants and buttercups, a great variety o 
insects belonging to different families are attracted, and man] 
of them creep about and often merely self-pollinate th< 
flowers. In many cases, however, the nectar is secretee 



TRANSFERENCE OF POLLEN 



283 



and stored at the base of long, tubular corollas and calyces, 
or in places otherwise difficult of access, where it can only 
be reached by insects, such as moths, butterflies, and bees, 
possessing long proboscides and tongues, or some particular form 
and weight of body. In flowers of this character, the insects 
during their search for nectar, touch the anthers, and the 
pollen becomes dusted on to their bodies, often at some 
particular point, which point is brought into contact with the 




71 



FIG. 102. i. Flower of white dead-nettle (Lamium 
album L). 2 Section of the same ; s stigma ; 
a stamens ; r ring of hairs ; n nectary. 

stigma of a flower subsequently visited, and cross-pollination is 
effected. 

An example of the adaptation of a flower to the visits of 
large bees may be studied in the common White Dead- Nettle 
(Lamium album L.) (Fig. 102). The flower has a conspicuous, 
white, two-lipped corolla. The upper lip (u) is arched and 
protects the pollen from being washed away by rain ; it also 
prevents rain from passing down to the nectary which is present 
at the base of the ovary (n). When visiting such a flower, the 



284 REPRODUCTION 

bee alights on the lower lip (/) of the corolla which acts as a 
convenient landing-stage, and pushes its head down the tube 
of the corolla in search of the nectar concealed below. The 
body of a large bumble bee or a hive bee fits almost exactly 
into the mouth of the corolla, and the back becomes dusted with 
pollen from the anthers (a) under the upper lip (u). On enter- 
ing another flower, the back of the bee with the pollen upon 
it comes first into contact with the lower half of the bifid 
stigma (s) which projects a short distance below the anthers, 
and cross-pollination is readily effected. Pollen from this 
second flower is removed on leaving and transferred to a 
third, and so on. The tongues of flies and other insects 
whose bodies are not stout enough to fill up the mouth of the 
corolla, and come in contact with the anthers, are too short to 
reach the honey ; moreover, a ring of hairs (r) arranged across 
the lower part of the corolla tube prevents small insects from 
robbing the flower of its nectar. Almost all zygomorphic flowers, 
such as the bean, clover, sainfoin, mint, snapdragon, and many 
others, exhibit striking adaptations to secure cross- pollination 
by the agency of insects, and many of these, when insects 
are prevented from visiting them, are practically unable to 
effect self-fertilisation, and hence produce little or no seed 
under such circumstances. 

It must, however, be mentioned that although many flowers, 
such as those of the broad-bean, broom, carnation, red clover 
and foxglove, are either unable to produce seed, or produce but 
few, when insects are excluded, others which show special adapta- 
tion for cross-pollination by insects, and which are usually and 
most advantageously pollinated by these agents, have also the 
power of self-fertilisation, and often exercise it in dull weather, 
or at other times when insect-visitors are scarce. For example, 
the flowers of vetch, pea, dwarf-bean (Phaseolus vulgaris) and 
tobacco produce seeds when specially protected from being 
cross-pollinated by insects. Many protogynous flowers in a 



SEXUAL AFFINITY 285 

young state are adapted for cross-pollination, but if the latter 
does not take place, the stigma frequently receives pollen from 
its adjoining anthers at a later stage of development of the 
flower. 

Ex. 170. Examine the following wind-pollinated flowers: grasses, sedges, 
rushes, oak, walnut, birch, alder, hazel, hop, plantain and dock. 
Note (i) the absence of conspicuous calyx or corolla. 

(2) Powdery, dry, character of the pollen. 

(3) The extensive receptive surface of the stigmas. 

(4) General absence of scent and nectar. 

Ex. 171. Examine the following insect-pollinated flowers: buttercup, 
columbine, monk's-hood, poppy, cabbage, pansy, violet, pink, carnation, 
primrose, stitchworts, mallows, horse-chestnut, bean, clovers, birds' foot 
trefoil and other leguminous plants, strawberry, apple, pear, cherry, plum, 
dandelion, sunflower, thistle, knapweed, parsnip, carrot and other un- 
belliferous plants. 

Make an examination of the flowers in different states of development, and 
note : 

(1) Whether they are protogynous or protandrous. 

(2) Where the nectar is secreted and stored if any is present : it may be at 
the base of the stamens, on the receptacle, ovary, or in specially constructed 
parts of the petals and sepals. Frequently ridges and variegated stripes of 
colour on the petals point in the direction of the nectary, and apparently 
serve as guides to insect-visitors. 

(3) Determine whether there is any specially convenient landing-place for 
insect-visitors, and try and find out whether the stigma or anthers are touched 
first when insects visit the flowers. 

(4) Whenever opportunity offers, carefully watch insects at work extract- 
ing honey or collecting pollen from flowers. 

7. Sexual affinity : hybridisation and hybrids. A fertile 
sexual union between the male cell of a pollen-grain and 
the egg-cell within an ovule does not take place indiscrimin- 
ately among plants. A certain relationship or sexual affinity 
must exist between the parent plants before their reproductive 
cells will unite. 

Although self-fertilisation is possible, and among certain plants 
is a normal process, experience teaches that in many cases 



286 REPRODUCTION 

the pollen of a flower has no fertilising effect on the egg-cells 
of ovules present in the same flower or in flowers on the same 
individual plant. 

Moreover, it is generally found that fertilisation between the 
reproductive cells of plants widely different from each other, say, 
between those of a cabbage and a potato, or those of a peach 
and a turnip, does not take place. 

In some instances the cause of the failure of the pollen 
of one plant to fertilise the ovules of another may possibly 
be due to the want of power of the pollen-grain to develop 
pollen-tubes long enough to reach from the stigma to the 
ovules within the ovary ; or the tissues of the style may offer 
some mechanical obstruction to the advancing pollen-tubes. 
In most cases, however, it would appear that there is 
some other quite unknown cause at work which prevents 
the living substance, composing the reproductive cells of 
certain plants, from exercising a fertilising influence on each 
other. 

When the relationship between the male and female repro- 
ductive cells is too close, and also when it is too remote, fertility 
is reduced. For the production of the most vigorous and the 
most prolific progeny there must be a certain degree of difference 
between the productive cells which unite. 

As pointed out previously (p. 279) the most fertile sexual 
union takes place between the reproductive cells of flowers 
which arise on different individual plants of the same species. 
The progeny resulting from such cross-fertilisation grow 
luxuriantly and produce numbers of seeds capable of giving 
rise to equally robust offspring. 

It is also found that well-marked, wild and cultivated varieties 
and races of the same species of plant generally cross readily : 
thus, the cross-pollination of different varieties of wheat, barley, 
turnips, apples, carnations, roses and other plants, results in the 
production of ^flfcoring. The progeny arising from cross-fertilisa- 



SEXUAL AFFINITY 287 

tion between two varieties or races of the same species are termed 
cross-breeds, or variety-hybrids. 

Variety-hybrids usually possess the following characters : 

(i) They are often more luxuriant and robust in constitution 
than their parents ; their roots are frequently extensive and the 
shoots and leaves large. 

(ii) They usually grow more rapidly, flower earlier, and 
produce a larger number of flowers than the parents. 

(iii) The power of seed-production is strong and their seedling 
offspring is generally very vigorous. 

It has been found in a large number of instances that the 
pollen of one plant cannot impregnate the ovules of another 
widely differing from it, but we have no means of determining 
beforehand whether any two particular species will cross suc- 
cessfully ; nothing save actual trial will decide. 

Many examples are known where cross-fertilisation does take 
place between different species of plants, as for example, between 
the raspberry and blackberry, wheat and rye, different species 
of strawberry (Fragaria) and various species of Pelargonium, 
Dianthus, Narcissus, Digitalis, Viola, Gladiolus, Begonia and 
many other ornamental flowering - plants. Cross - fertilisation 
between distinct species of plants is termed hybridisation, and 
the progeny of such crossing are termed hybrids-, when the 
species crossed belong to the same genus, the progeny are some- 
times designated species-hybrids, to distinguish them from genus- 
hybrids, or bigeneric hybrids the progeny of species belonging to 
different genera. 

Few or no crosses are known with certainty between plants 
belonging to different Families or Orders ; even genus-hybrids 
are comparatively rare. 

Generally the more nearly allied the species are the more 
readily do they hybridise. . 

The species belonging to certain Orders seern naturally in- 
clined to hybridisation ; especially is this true of the Composite, 



288 REPRODUCTION 

Orchidaceae, Iridaceae and Scrophulariaceae : on the other hand, 
among the Cruciferae, Leguminosae and Umbelliferae hybrids are 
uncommon. 

True hybrids or crosses between distinct species of plants 
usually exhibit the following characters : 

(i) If the parents are very widely different from each other, 
the offspring is usually delicate and difficult to rear, but where 
the parents are more nearly related the offspring is frequently 
taller and more vigorous and luxuriant in its vegetative organs 
than either of the parents. 

(ii) In nearly all cases hybrids are less fertile than their 
parents: their sexual organs are weak, and frequently they are 
absolutely sterile, the anthers producing no pollen or the 
carpels no ovules, so that seed-formation is impossible. In 
certain rare instances there appears no inclination or power 
to form flowers. In those which do produce flowers and 
seeds the pollen-grains are generally smaller in size and 
number, and the ovules more or less imperfectly formed : the 
male reproductive organs are more deleteriously affected than 
the female organs. 

(iii) The petals and coloured parts of the flower are generally 
larger and more lasting than those of either parent. ' Doubling ' 
of the flowers and other pathological malformations are more 
common among hybrids. 

(iv) In the first generation raised from seeds obtained by 
cross-pollinating distinct species, all the individual plants are, in 
most instances, similar to each other, but the degree of 
resemblance to the two parents varies considerably. 

The individuals of the second or later generations, that is, 
the offspring which arise from self-pollination or cross-pollination 
of the flowers of hybrids, vary much in form and in other ways : 
they do not resemble each other nearly so much as those of 
the first generation. Some of them almost exactly resemble 
the female, others the male parent, while many show the 



MENDELIAN LAWS OF INHERITANCE 289 

characters of both parents combined in various degrees. More- 
over, in many instances, entirely new characters, not seen in 
either parent, arise among the offspring of succeeding generations 
of hybrids. 

(v) Hybridisation is usually, though not always, reciprocal : 
if the pollen of a species A is effective upon the ovules of 
another species B, the pollen of B is usually similarly effective 
upon the ovules of A. 

In most instances there is no difference between the offspring 
of reciprocal crosses. 

It has been noticed also that in the crossing of certain species 
the hybrids produced always resemble one of the species more 
than the other, no matter whether it is used as the male or the 
female parent of the cross. 

Almost all hybrids are more easily crossed with pollen derived 
from one of the parent species than with pollen from its own 
flowers or from flowers of another hybrid of the same origin as 
itself : the progeny of such crossing are termed derivative hybrids. 

Most derivative hybrids are intermediate between the parent 
and the original hybrid : they are more fruitful than the 
latter, and some of them frequently come true from seed. 
If such hybrids are again pollinated by the same parent, 
the progeny or members of the third generation resemble the 
pollinating parent more closely ; by a repetition of the crossing 
with the same parent up to the fourth or fifth generation, all 
trace of the original second parent of the hybrid is lost or un- 
recognisable in the progeny. 

True hybrids may be crossed with another species different 
from either of the parents, and the offspring, which may be 
termed trispecific hybrids^ can be crossed again with still another 
distinct species. In this manner plants have been obtained 
combining the characters of three, four, or more species : the 
offspring of such crossed plants are very variable. 

8. Mendelian laws of inheritance. (i) Since 1900 much 



2pO REPRODUCTION 

attention has been devoted to experimental work upon the 
character of hybrids, or crosses between varieties of plants, and 
those exhibited by their offspring. 

Some remarkable facts were observed by Gregor Johann 
Mendel in Germany about 1866, but the published accounts of 
his work and the ' laws of inheritance ' deduced from it were lost 
sight of until about 1900, when De Vries in Holland, Correns in 
Germany, and Tschermak in Austria rediscovered similar facts. 

Mendel worked chiefly with garden peas, and crossed certain 
varieties which differed from each other in regard to some 
simple character or pair of characters. 

Among other experiments he crossed a variety of pea having 
smooth round seeds with one bearing wrinkled indented seeds, 
and found that the offspring consisted invariably of plants which 
bore only smooth round seeds : the wrinkled character of the 
parent crossed was not seen in the hybrid obtained. 

That character of the parent which appeared in the offspring 
of the first cross he termed dominant^ the character not seen 
being spoken of as recessive. 

Seeds arising from the self-fertilisation of the flowers of the 
round-seeded hybrid gave rise not only to round-seeded peas 
but to plants with wrinkled seeds as well 

The number of seeds showing the dominant round character 
was found to be three times as many as those exhibiting the 
recessive wrinkled character. 

Mendel continued the raising of plants from these seeds 
through several generations, and found that the wrinkled seeds 
bred true : they were as pure in respect of the recessive 
character as the original parent, and never gave rise to round 
peas. 

The round seeds, however, behaved differently. One in every 
three bred true ; it was pure in regard to the dominant character, 
but two of the round seeds in every three gave offspring which 



MENDELIAN LAWS OF INHERITANCE 291 

bore both round and wrinkled seeds. They were hybrid like 
the first cross, and the proportion of round seeds to wrinkled 
ones which they produced was 3 to i . 

If we assume that each plant produces say 4 seeds, the 
following scheme indicates the proportion of each kind obtained 
in three successive generations ; 

Parent Parent 

R x W 

round crossed with wrinkled 
gives rise to 



RW 1st hybrid 
4 round (impure) generation 
dominants 

From these 
are obtained 


(termed the 
F! generation) 

(F, generation) 




-^~ 
12 round 
(dominant) 


+ 


7" 

4 wrinkled 
(recessive) 

4 pure 
(W) 


4 pure 

(R) 


+ 


8 impure 
(RW) 



I 

16 round 24 round + 8 wrinkled 16 wrinkled (F, generation) 

(all pure \ / 8 pure + 16 impure \ /all pure\ /all pure \ 
R H * RW )( W )( W ) 

(ii) That certain characters of plants are dominant over 
others when crossing takes place was well known before 
Mendel's time, and that among the later generation or off- 
spring of crosses, individuals bearing the parental character 
not seen in the first generation are obtained, was also known, 
but the average numerical proportion of each was not noticed 
previously. 

The most important feature of Mendel's work, however, lies 
in the explanation which he offered of the facts. 

He propounded the hypothesis that, so far as a pair of char- 



292 REPRODUCTION 

acters which exclude each other or are opposed to each other are 
concerned, each male or female reproductive cell or gamete of the 
hybrid carries only one of the characters, not both. It is assumed 
that in each gamete there exists something which induces or 
controls the appearance of a character in the offspring of a plant : 
this is termed & factor or gene. Thus, there are factors or genes for 
height of plant and for shape of seed in- the gametes of peas. 
There is considerable evidence that the genes are carried in the 
chromosomes of the nuclei of the gametes. 

Although the hybrid plant arising from the union of reproduc- 
tive cells of, say, a pea, with round seeds, and one bearing wrinkled 
seeds, contains both of these characters, even if both are not 
visible, its reproductive cells carry only the round or the wrinkled 
character in a pure state; its pollen-grains and ovules or the 
generative nuclei in them, are either pure ' round ' or pure 
* wrinkled/ 

Moreover, Mendel assumed that the number of male cells (ancf 
female cells) bearing the ' round ' character was on an average 
equal to those carrying the ' wrinkled ' character. 

Such assumptions being made, the result of the union when only 
self-fertilisation is allowed will be understood from the following : 

A hybrid plant produced by the crossing of a parent bearing 
round seeds (R) with one bearing wrinkled seeds (W) possesses : 

Male Gametes. Female Gametes. 






Some bearing the character R ^^ ^ R 




Any male gamete bearing the R (round) character has an 
equal chance of meeting with a female gamete carrying R or W. 
If it meets with R the plant produced will bear round seeds, and 
will be quite pure (RR) in respect of this character of round- 



MENDELIAN LAWS OF INHERITANCE 293 

ness. If it meet with a gamete bearing W, the resulting plant 
will be hybrid, and will not breed true, 

We thus see that on an average there will be formed from 
the male gametes carrying the round character, uniting at 
random with the female gametes available 



T>T i 

pure RR plants 

-, -DT X r r proportion to 

nd RW P 



^ i 
jhyb 



Similarly, from the male gametes possessing the wrinkled 
character (W) we should have 

(pure WW plants) in the ' WW 

1u u :A T>\\T I proportion ^ 

^hybrid RW J f 



Taking the combination of all the gametes at random, where 
the number of male and female sex cells each bearing only one 
(R or W) of two characters is the same, we should have the 
following proportional result : 

i plant 2 plants i plant 

RR RW W\V 



Dominant. Recessive. 

As the round is dominant over the wrinkled character, the 
impure hybrid plants (RW) will look like the pure (RR) plants. 
Therefore the proportion of plants showing the round dominant 
to those exhibiting the recessive wrinkled character would be 
3 to i, which is what Mendel found to be actually the case in 
his experiments. 



294 



REPRODUCTION 



When the hybrid was crossed with the parent bearing the 
wrinkled character, instead of being self-fertilised, the off- 
spring consisted of round and wrinkled peas in equal pro- 
portion, which is also what would be expected from Mendel's 
hypothesis. 



Gametes of 
Hybrid. 

R 



Gametes of 
Parent. 




RW 
WW 

RW 
WW 



i RW 
to 
i WW 



(iii) Characters which exclude or contrast with each other, as 
the ' roundness ' and * wrinkledness ' of peas, are spoken of as a 
pair of allelomorphs. 

A plant or animal which arises from the union of two distinct 
germ-cells is sometimes termed a zygote. 

The individual plant formed from the fertilisation of sexual 
cells bearing similar allelomorphs is termed a homozygote (RR for 
example). Where the allelomorphs are antagonistic the resulting 
plant is spoken of as a heterozygote (as RW). 

(iv) The following have been found by experiment to behave 
as allelomorphic pairs of characters : 



In 
Peas 



Wheat 



Lychnis 

Chelidonium 

Maize 

(Enothera 

Sweetpea 

Many plants 



majus 



Dominant. 

Tall habit 
Yellow cptyledon 
Brown skin 
Round seeds 
Absence of awns 
Rough chaff 
Red chaff 
Hairiness 
Entire petals 
Starchy endosperm 
Long style 
Oval pollen-grains 
Coloured flowers 



Recessive. 

Dwarf habit 
Green cotyledon 
White skin 
Wrinkled seeds 
Presence of awns 
Smooth chaff 
White chaff 
Smoothness 
Laciniate petals 
Sugary endosperm 
Short style 
Round pollen-grains 
White flowers 



MENDELIAN LAWS OF INHERITANCE 295 

(v) Mendel crossed peas varying in several characters and 
obtained results similar to those found in crossing plants with 
round and wrinkled seeds described above. For example, crosses 
between tall and dwarf varieties give seeds from which are grown 
the first (Fj) generation of hybrid plants, all of which have tall 
stems, * tallness ' being a dominant factor. Segregation or split- 
ting into tall and dwarf plants, in the proportion of 3 tall : i 
dwarf, takes place in the second (F 2 ) generation, but it is not until 
the plants of this generation attain their full development that 
their characters in respect of height can be determined. 

Similarly, in the cross between a plant with coloured flowers 
in which the colour factor for colour is dominant and one with 
white flowers, the flowers of the first (F x ) generation are usually 
all coloured. Segregation also occurs in this, as in the other cases, 
among the plants of the second (F 2 ) generation, but, of course, it 
is again not until they are fully developed that both coloured and 
white flowers are seen. 

One of the classic examples of the crossing of peas by Mendel 
was made between plants with yellow seeds and those with green 
seeds. The peculiar tint of the seeds of these peas is due to the 
colour of the cotyledons of the embryo plants within the seeds, 
which colour is visible through the translucent seed coats. 

In the cross mentioned, yellow is the dominant factor, and the 
seeds in the pods of the cross are all yellow. These seeds, when 
sown, give rise to the first (Fj) generation which bear yellow and 
green seeds, often both kinds in the same pod, in the proportion 
of 3 yellow : i green. 

To one who repeats this experiment for the first time the result 
is somewhat puzzling, for he does not expect to meet with both 
yellow and green seeds until ripe pods are developed on the full- 
grown plants of the second (F 2 ) generation : that they are found 
in pods of plants of the first (F x ) generation is surprising. 

The difficulty, however, is removed if it is realised that the 
two kinds of plants segregated in the second (F 2 ) generation are 



296 REPRODUCTION 

present as embryos, with cotyledons of their respective colours in 
the seeds borne on plants of the first (F x ) generation ; it is there- 
fore not necessary to raise full-grown plants of the second (F 2 ) 
generation in order to observe the characters whose transmission 
from generation to generation is being studied, as it would be if 
the hereditary transmission of flower colour or height of plants 
were being investigated. 

In the examples previously given of the crossing of two varieties 
of pea, each differing from the other in respect of ' roundness ' 
and ' wrinkledness ' of their seeds, or yellow and green colour of 
their cotyledons, the homozygous and heterozygous dominants 
are indistinguishable ; the recessive is completely hidden by the 
dominant character in the first, or F x generation : its presence in 
the hybrid is unsuspected although its existence is immediately 
revealed in the progeny of the F 2 generation. 

Such complete dominance is, however, not an invariable rule, 
for all the individuals of a cross between a tall and a dwarf variety 
of a plant are frequently intermediate in height, being shorter than 
the tall and taller than the dwarf parent. 

Similarly, in a cross between two varieties of the same species 
of plant, one with deep rose, the other with white flowers, all the 
individuals of the F x generation bear pale pink flowers : self- 
fertilisation of the latter gives in the F 2 generation, progeny of 
three types, namely, plants with rose, pink and white flowers 
respectively, in the ratio : 

12 I 

rose pink white 

like one like the like the 

grandparent hybrid parent other grandparent ; 

typical Mendelian segregation, the only unusual feature being the 
flower colour of the heterozygous individuals, which differs from 
that of the homozygous dominants. 
The character of the segregation is clear, if it is assumed that 



MENDELIAN LAWS OF INHERITANCE 297 

the rose parent is a homozygous rose plant, RR, having a double 
dose of the R factor for rose, the hybrid being heterozygous, RW, 
with only one dose of R. 

Thus : 

Rose Parent. White Parent. 

RR WW 

Gametes. 




RW pink hybrid. 



Male Gametes of the hybrid. 

R, W 



Female Gametes of the hybrid. 

R, W 



A male gamete, R, has an equal chance of mating with either 
an R or W female gamete ; and likewise the other male gamete, 
W, has an equal chance of fusing with an R or W female gamete. 

The possible combinations are given in the diagram below ; 



Male Gametes of the hybrid. 
Female R W 
Gametes. __ 



R 

W 

or, i RR 
rose 


RR 


RW 


i WW 

white 


RW 


WW 


. : 2 RW : 
pink 



As already noted, self-fertilisation, or inbreeding, oi netero- 
zygotes leads to segregation of the parental types in the offspring. 
A true-breeding race exhibiting only the special characters of the 
heterozygote cannot, therefore, be obtained, and attempts to 
'fix' such plants is doomed to failure; these special characters 
are not represented in the gametes of the hybrid, their appearance 
there being due to the meeting of dissimilar gametes. 

Among other examples of heterozygous * unfixable ' characters, 

21 



REPRODUCTION 

are (i) the commercial carnation with * double ' flowers and non- 
bursting calyces, the product of the crossing of plants with ' single ' 
flowers and plants with excessively ' double ' flowers whose crowded 
petals split the calyces along one side ; (2) Blue Andalusian fowls, 
the particular tint of which appears when black and white varieties 
of the breed are crossed ; (3) the roan colour of Shorthorn cattle 
obtained when white and red animals are crossed. 

Many other examples might be mentioned of imperfect dominance, 
in which the heterozygote differs from the homozygous dominant. 

(vi) After dealing with peas varying in one pair of characters, 
Mendel crossed varieties exhibiting two pairs of allelomorphs 
and determined the distribution of the parental features among 
the offspring. 

When a pea plant having tall stems and round seeds is crossed 
with a plant with dwarf stems and wrinkled seeds, two allemorphic 
pairs are involved, viz., (i) ' tall ' and ' dwarf ' ; (2) ' round ' and 
1 wrinkled/ 

(1) * Tall ' stems are dominant to ' dwarf ' stems. 

(2) ' Round ' seeds are dominant to ' wrinkled ' seeds. 

All the plants from the first cross, or the F x generation, are 
found to be tall plants with round seeds. 

On self-fertilisation the F 2 generation is obtained. This yields 
four types of plants, namely : 

1. Tall plants with round seeds 3. Dwarf plants with round seeds 

2. wrinkled 4. wrinkled 

in the following proportion : 

9 : 3 : 3 ' i 

tall, round tall, wrinkled dwarf, round dwarf, wrinkled 

Two of these types are like the original parents in appearance, 
but in addition to these, two new varieties have been obtained, 
namely, tall plants with wrinkled seeds and dwarf plants with 
round seeds. 



MENDELIAN LAWS OF INHERITANCE 2976 

On Mendel's hypothesis, this result, both as regards the height 
of the plants and shape of the seeds, as well as the proportion 
of each, is to be expected, as appears from the diagram below 

Parent. Parent. 

TR X DW 



TRDW F! generation, 
a tall plant bearing round seeds, since ' tall ' and * round ' are 
dominant to ' dwarf ' and ' wrinkled ' characters respectively. 

The gametes of the hybrid would be 

Male. Female. 

TR TR 

TW TW 

DR DR 

DW DW 

The TR male gametes have an equal chance of mating with 
either TR, TW, DR or DW female gametes. 
Similarly TW do. do. do. do. 

DR do. do. do. do. 

DW do. do. do. do. 

The possible combinations are seen in the following diagram. 

Male Gametes. 
Female TR TW DR DW ' 



Uametes. 

TR 
TW 
DR 
DW 


TR X 
TR 


TW X 
TR 


DR X 
TR 


DWj 
TR 


TR t 
TW 


TW 2 
TW 


DR t 
TW 


DW a 
TW 


TRj 
DR 


TWi 
DR 


DR 3 
DR 3 


DW 3 
DR 


TR, 
DW 


TW 2 
DW 


DR 3 
DW 


DW 4 
DW 



REPRODUCTION 

a. Those marked (i) in which TR occurs will all be alike in 
appearance, viz., tall plants with round seeds, * tall ' and * round ' 
being dominant characters. Of these there are nine. 

b. Three marked (2), TW TW, DW TW, TW DW, are tall 
plants with wrinkled seeds ; R is absent. 

c. Three marked (3), DR DR, DW DR, DR DW, are dwarf 
plants with round seeds. T is absent and R is dominant. 

d. One marked (4), DW DW, is a dwarf plant with wrinkled seeds. 
One of the nine tall plants with round seeds, namely, TR TR, 

is exactly like one of the original parents of the cross and will 
breed true, the single dwarf plant with wrinkled seeds, DW DW, 
being the true-breeding segregate like the other parent. 

One of the three plants with tall stems and wrinkled seeds, 
TW TW, a new combination, will breed true. 

One of the three dwarf plants with round seeds, DR DR, also 
a new combination, will breed true. 

The remainder of the plants obtained are impure or hybrid' in 
respect of one or other allemorphic pair of characters and con- 
sequently will not breed true, but will segregate in various ways 
when self-fertilised. 

From the above example it is seen that certain characters 
existing in two separate varieties of plants may be combined in 
one variety, and this is not an isolated case. Many others have 
been worked out experimentally. 

(vii) In some cases the independent factors of an allelomorphic 
pair interact with each other, leading to complicated examples of 
inheritance, which at first sight seem to contravene Mendelian 
laws. 

A remarkable example of such has been observed in the cross- 
ing of certain varieties of Sweet Peas. Two different pure white- 
flowered varieties are known, each of which breeds true to the 
white colour ; these when crossed give rise in the first (F x ) genera- 
tion to plants with purple flowers closely resembling those of the 
Wild Sweet Pea, from which all the garden varieties have been 



MENDELIAN LAWS OF INHERITANCE 297** 

derived. In the second (F 2 ) generation both white and purple 
flowered plants are obtained in the proportion of 9 purple : 7 
white, numbers which suggest the Mendelian ratio of 9:3:3:1 
observed in the progeny of the hybrid between a tall, round 
seeded and a dwarf, wrinkled seeded plant just described, and 
in many other crosses between varieties of plants differing in two 
pairs of allelomorphic characters. 

It would appear that the purple colour is the result of the 
coming together of two independent dominant factors, the absence 
of one or both of which in the zygote gives a white-flowered 
plant. 

Representing one of these factors by X, the other by Y, and 
their absence by x and y respectively, one white parent may be 
denoted by XXyy, the other by YYxx. 

Gametes of the two white parents. 

Xy Yx 



Xy Yx F x hybrid 

The gametes formed by the F x hybrid are XY, Xy, xY, xy ; 
their possible combinations are indicated in the following diagram. 



Female 
Gametes. 

XY 
Xy 
xY 


Male Gametes. 
XY Xy xY xy 


XY 1 


Xy, 
XY 


xy 


& 


Xy 1 


Xy a 
Xy 


Xy 


$ 


xY 1 


xY 1 


xY. 
xY 3 


xY 3 


xy 


Xy, 
xy 


xY 8 

xy 


xy 



298 REPRODUCTION 

Nine marked (i) contain both X and Y, and are therefore 
purple flowered. In the three marked (2) Y is absent ; in the 
three marked (3) X is missing \ while in (4) both X and Y are 
wanting ; all these are therefore white-flowered. 

The ratio is 9 : 3:3:1 
purple white 

(viii) The Mendelian conception of distinct unit characters 
which are capable of being inherited independently of each other 
has given precision to our views of the nature of heredity and the 
constitution of pure breeds and hybrids or crosses. 

A pure-bred individual is one which has developed from the 
union of male and female cells containing similar elements or 
characters, while a hybrid or cross-bred organism has arisen from 
sex cells conveying different allelomorphic elements. A plant 
may be pure bred in respect of one character and yet be cross- 
bred in regard to another character. 

This hypothesis of the distinctness of hereditary characters 
greatly assists the efforts of the plant breeder, inasmuch as it 
indicates the line along which crossing must take place to effect 
a desired combination in one plant of characters only met with 
in separate varieties, and makes his selection among the offspring 
of crosses to obtain the wished-for result simpler and more direct 
than heretofore. 

(ix) It has been long known among hybridists that certain 
cross-bred varieties of plants which exhibit characters different 
from either of the two parents cannot be fixed. On self-fertilisa- 
tion the new character is not met with in all the offspring, there 
being many individuals (rogues) which have to be discarded. 
No amount of selection or self-fertilisation is found to fix the 
new type. 

These hybrid forms are generally merely heterozygotes, and 
on Mendel's hypothesis ought to break up into 25 per cent. 



ARTIFICIAL POLLINATION 

like each parent, with 50 per cent, hybrid again, which they 
generally do. 

Mendelism, moreover, throws considerable light on various 
forms of * reversion ' (p. 318). 

Some " ' reverted ' individuals which appear among what is 
thought to be a selected so-called pure stock, are merely 
recessives which have never had the chance of showing them- 
selves. The majority of the selected stock might be pure in 
MendeFs sense yet if some were impure and contained the 
recessive character the latter would only be seen when crossing 
took place between individuals possessing the same recessive 
character, and the chances in favour of this occurrence might 
be very remote on account of the numbers of pure population 
among which the impure individuals were mixed. 

Such * reverted' individuals ought to breed true when 
crossed among themselves or self-fertilised, and this is sometimes 
the case. 

There are other * reversions ' which do not breed true among 
themselves in the first (Fj) generation, yet show a small 
percentage which breed true to the reversionary character in the 
second (F 2 ) generation, and cannot therefore be of heterozygote 
nature. 

Such cases are seen in what is termed Reversion on 
crossing/ 

These can also be explained on Mendelian lines, but further 
information regarding them must be sought in works specially 
concerned with the subject. 

9. Artificial pollination : methods of crossing plants. Several 
plants, such as the melon, peach, tomato and egg-plant, which do 
not set fruit unless the ovules are fertilised, must be cross- 
pollinated artificially when grown under glass and forced to 
bloom in early spring or at other seasons of the year, when 
pollinating insects are not abundant, 



300 REPRODUCTION 

The process consists merely in a transference of pollen to the 
stigmas of the flowers by means of a camel's-hair brush, a plume 
of pampas-grass, or a rabbit's tail fastened to a small stick. 

In the case of the tomato, peach, and other plants with mono- 
clinous flowers, merely shaking the plants is sometimes sufficient 
to distribute the pollen satisfactorily, but the most efficient 
method in the case of the peach and melon is first to collect 
the pollen from the anthers by means of a camel's-hair brush, 
and then apply the pollen-laden brush to the stigmas of the 
flowers : with tomatoes it is best to shake a quantity of pollen 
from several flowers into a watch glass or spoon, and then dip 
the stigmas of the flowers into the pollen so collected. 

In the case of the melon where the flowers are diclinous, 
the staminate flowers are sometimes pulled off the plant, and 
after rolling back the corolla, the exposed anthers may be gently 
brushed over the stigmas of the pistillate flowers intended to be 
pollinated, or a whole male flower may be pushed into the corolla 
of one of the latter and left there. Of course, in these and all 
other instances the anthers must be in a dehiscent condition, so 
that the pollen-grains are fully formed and easily set free, and 
the stigmas must be in a receptive condition. 

Where it is desired to cross or hybridise two particular varieties 
or species of plants, it is necessary to proceed in a more careful 
manner. One or more flowers upon the plant which is to act as 
the female parent or seed-bearer, must be selected for the opera- 
tion, and must be prevented from receiving any other kind of 
pollen upon their stigmas except that from a flower from the 
plant which has been chosen as the male parent. 

Before attempting to cross two plants it is important to study 
and become familiar with the structure of their flowers in regard 
to the number and position of their sexual organs and whether 
the flowers are protandrous or protogynous ; moreover, a know- 
ledge of the appearance presented by the stigmas when they are 



ARTIFICIAL POLLINATION 301 

ready to receive pollen, and the mode and time of dehiscence of 
the anthers when the pollen is mature, is useful. 

The receptive surfaces of the stigmas of flowers when mature 
are often moist or sticky : in other cases they enlarge and appear 
rough and covered with very small round prominences when 
viewed with a lens. Where the stigmas are bifid the two halves, 
which in an immature state lie close together, separate and curl 
away from each other when mature. 

The details of the actual method of cross-pollination varies 
with the structure and arrangement of the flowers to be operated 
upon, and also to some extent upon the taste and fancy of 
the operator. The following plan gives excellent and accurate 
results : 

(i) First select the flower to be used as the seed-bearer. This 
must be done before the flower has opened and before its own 
anthers are mature enough to shed their pollen. Unless this 
precaution is adopted self-pollination or cross- pollination by 
agency of the wind or insects may have already taken place. 

Where several flowers are borne somewhat close together as 
in the apple and wheat, one or two only should be crossed and 
the others removed, so that the crossed specimens may have a 
better chance of developing. 

(ii) Open the flower and carefully remove the stamens with 
fine-pointed forceps taking hold of each stamen by its filament 
so as not to crush the anther and thereby run the risk of setting 
free the pollen. 

Where the stamens are epipetalous and in other instances it 
is sometimes more convenient to cut off the calyx, corolla, and 
stamens with fine scissors. Be careful not to touch or injure 
the style and stigma of the gynaecium. 

After this process of emasculation or removal of the male 
sexual organs, the flower or the shoot bearing it must be 
enclosed in a paper bag tied up at the mouth so as to exclude 



302 REPRODUCTION 

insects and prevent wind-pollination : allow the stigma to mature, 
which usually takes two or three days according to the age of 
the flower when emasculated. 

(iii) When the stigma is ready, remove some ripe stamens 
from the flowers of the plant to be used as the male parent of 
the cross, and after lightly crushing the anther on the finger- 
nail so as to set free the pollen, transfer the latter by means of 
forceps to the stigma. To ensure absolute accuracy the flowers 
from which the pollen is taken should have been previously 
enclosed in a paper bag and allowed to open there: if this 
precaution is neglected and stamens are merely taken casually 
from open flowers on the male parent there is no certainty about 
the cross for foreign pollen may have been brought into contact 
with them by the wind or by insects. 

(iv) After pollination has been effected the flower must be 
again enclosed in a paper bag and kept there until the seeds 
have been fertilised and the fruit has begun to grow. 

The bag may then be removed and the fruit and seeds allowed 
to ripen in the ordinary way ; in the case of fruits, such as apple, 
pear and raspberry, it is necessary to protect the ripening fruit by 
means of a muslin bag or coarse net. 



CHAPTER XXIII. 

CULTIVATED PLANTS AND THEIR ORIGIN: 
PLANT BREEDING. 

i. FROM the most remote ages the human race has derived 
much of its sustenance from the Vegetable Kingdom. At first, 
no doubt, men were content to roam about and feed upon the 
roots, stems, leaves, fruits and seeds of various species of plants 
found growing wild, just as the lowest savage races do at the 
present day. With a settled mode of life and increasing 
population would come the necessity to select and cultivate 
close at hand particular species possessing useful and agreeable 
qualities, so that a constant and more certain supply of food 
might always be obtained. 

By whom or at what period in the history of mankind was 
begun the selection and first cultivation of the different wild 
plants which have given rise to our chief cultivated food-plants, 
is not known. Extensive researches by De Candolle and others 
have shown that the majority of our common vegetables, fruits and 
cereals have been in cultivation for many hundreds and in some 
instances thousands of years : during this time they have under- 
gone extensive modification. 

In the case of common bread wheat, maize, broad bean, and a 
few others, the wild species from which they have been developed 
are unknown ; in most cases, however, the wild prototype of the 
various cultivated farm and garden plants can be recognised with 
more or less certainty. On comparing cultivated varieties with 
the wild species it is noticed that the former differ from the latter 
in possessing a greater development and generally an improved 

80S 



304 CULTIVATED PLANTS AND THEIR ORIGIN 

flavour of those parts of the plants, for which they are grown, 
the other parts or members of the plant being much the same 
in both the wild and the cultivated state. 

For example, among apples, pears, plums, strawberries and 
other plants which are grown for their fruits, the flowers, stems 
and leaves are similar to those of the crab, wild pear, sloe and 
strawberry from which they have been derived, but how different 
are their fruits. 

In the cases of plants grown for their roots only, it is the root 
which manifests the greatest amount of deviation from the wild 
prototype, as may be seen by comparing the roots, stems, leaves 
and flowers of the wild carrot and wild parsnip with those of the 
cultivated varieties. 

The peculiar characteristics which distinguish cultivated from 
wild plants are seen to be connected with increased usefulness 
to mankind, and it is through man's agency that these useful 
modifications have reached their present state of development : 
without the care and constant attention of the farmer and 
gardener the cultivated types would disappear. 

In addition to the maintenance of cultivated varieties at their 
present level of excellence endeavours are continually being 
made to modify and improve them ; old varieties are being 
altered so that either the yield of their useful parts is increased, 
or the colour, size, form, flavour, time of ripening, keeping 
qualities or hardiness are improved. The mode in which this 
improvement takes place is indicated in the subsequent paragraphs 
of this chapter. 

2. Bud-varieties or ' sports/ The buds upon a plant resemble 
each other so much that they all develop into shoots very closely 
alike, so far as the colour and form of their stems, leaves, 
flowers and fruits are concerned. It is, however, occasionally 
noticed among perennial farm and garden plants that single buds 
upon certain individuals grow out and produce shoots which 
differ very greatly from the shoots arising from the rest of the 



'SEMINAL SPORTS' 305 

buds upon the plant. Thus, single buds upon peach trees have 
been observed to develop into shoots which, instead of bearing 
peaches, bear nectarines, and plum trees ordinarily producing 
purple fruit have been known to give rise to a single shoot 
bearing yellow plums of a totally different character from any 
previously known. 

Such sudden and extensive variation is termed bud-variation 
or 'sporting,' and is most frequently met with in those species of 
perennial plants which have been under cultivation for very long 
periods of time. It is extremely rare among annual plants and 
is also uncommon among perennials which have only recently 
been introduced into the garden. 

Very few c sports ' can be propagated by seeds ; they must 
consequently be removed from the parent and multiplied vege- 
tatively, that is, by cuttings and layers or by budding and grafting. 

Many examples of new varieties of plants which have originated 
from bud-variation are met with among garden flowers such as 
roses, carnations, chrysanthemums, tulips and pelargoniums. 

Also in this manner have arisen practically all the variegated- 
leaved and * weeping* forms of ash, willow, box, holly, and 
other trees and shrubs. 

Among farm crops potatoes are subject to bud-variation, but 
its occurrence is extremely rare : varieties bearing tubers with 
purple skins have, however, been known to produce single white 
tubers among those of ordinary colour, and purple-skinned tubers 
have been observed with one or more white * eyes ' which, on 
being cut out and propagated, have grown into plants bearing 
white-skinned tubers only. 

3. Variation among seedling plants. 

(a) ' Seminal sports ' : selection and fixation of varieties. 
One of the most important peculiarities of living things of all 
kinds is the variability of their sexually-produced offspring. 
Although bean seeds always produce bean plants and wheat 
grains invariably give rise to wheat plants, nevertheless no two 



306 CULTIVATED PLANTS AND THEIR ORIGIN 

seedlings of these or any other species are exactly alike in all 
respects. The variation may be merely morphological, that is, 
it may consist in an alteration in the form and size of the leaf, 
stem, or other part of the plant : the individuals may also differ 
physiologically from their parents and from each other; for 
example, among potatoes the seedlings differ in their power of 
starch formation and storage, and in their capability of resisting 
frost and the attacks of irwects and parasitic fungi. 

The differences between the parents and their offspring in the 
case of wild plants are usually slight, but among a number of 
cultivated plants the amount of variation seen in the seedlings 
is often very considerable. 

A seedling which differs appreciably from its parent in some 
of its morphological or physiological characteristics may be termed 
a ' seminal sport? 

In some instances the peculiar variations are of the nature of 
permanent modifications and transmitted to the offspring of 
succeeding generations ; such variations are termed mutations, in 
contradistinction to fluctuations or transient modifications, which 
are not hereditary. 

Although many * seminal sports' differ considerably from 
the parent stock from which they have been obtained, it does 
not follow that these varieties are necessarily improvements upon 
the parents; the majority are often mere curiosities, or distinctly 
inferior varieties, with no intrinsic value from the farmer's or 
gardener's point of view; others, however, frequently possess 
characters of sufficient novelty and distinctness to render them 
especially worthy of cultivation. 

The latter is perhaps most commonly the case among orna- 
mental flowering plants, where each new variation in the 
colour of the leaves or flowers is often sufficient to make the 
plant attractive. 

Careful investigation into the origin of the many varieties of 
apples, pears, and other fruits leads to the conclusion that by far 
the larger number of them are 'seminal sports' produced from 
seeds casually sown in woods, hedgerows, and fields by birds or 



'SEMINAL SPORTS' 307 

self-sown in gardens : long ago they attracted the attention of 
some one who considered the varieties worthy of cultivation. 

Several of the more modern varieties of fruits have arisen as 
'seminal sports' from pips or seeds selected in a haphazard 
manner. Scarcely any of them l come true ' from seed ; the 
peculiar characters which they exhibit are not hereditary; for 
example, the seeds of a Cox's Orange pippin or a Worcester 
Pearmain apple when sown do not produce trees bearing apples 
of these kinds, neither do the seeds of the different varieties of 
roses or carnations (except in rare instances) give rise to plants 
bearing flowers similar to their parents. But in these cases, just 
as in most perennial * bud-sports,' the fact that their characters are 
not transmitted to seedling offspring is no drawback to their use- 
fulness, for they can be and are readily propagated vegetatively. 
'Seminal sports' are not unfrequent among annual plants; 
in such instances, their peculiar character to be of use must 
be hereditary, for there is no practical satisfactory method of 
propagating these plants except by seeds. Numerous examples 
of annuals are known in which the new characters presented 
by them are transmitted, without material modification or altera- 
tion, to all plants of succeeding generations derived from them. 

Many of the best cereals are ' seminal sports ' of this class 
vhich were originally discovered on some roadside or growing 
imong the plants of an ordinary crop. The late Mr Patrick 
>hirreff of Mungoswells, Haddington, Scotland, who introduced 
everal new and excellent varieties of cereals into the market, 
?as in the habit of systematically searching his fields of wheat 
ind oats for plants presenting new and marked peculiarities of 
;rain or straw, and although he attempted to raise new varieties 
>y crossing and repeated selection as described below, his best 
ntroductions appear to have been ' seminal sports ' discovered 
n his fields with all their meritorious qualities ready-made and 
ransmissible without change to their seedling offspring. 

The sowing of large numbers of seeds, selected at random, of 
he apple, pear, and other cultivated plants, in the hope that a 
raluable variety may turn up suddenly, is a game of chance in 



308 CULTIVATED PLANTS AND THEIR ORIGIN 

which enormous odds are against the raiser; nevertheless, the 
method has often led to successful results. 

One of the best varieties of potato ever raised, namely, the 
Magnum Bonum, was obtained by Mr James Clarke of Christ- 
church, who found it among a batch of seedlings derived from a 
promiscuously selected lot of potato * apples ' ; and many other 
useful and ornamental varieties of cultivated plants have had a 
similar haphazard origin. 

In the case of a new form occurring among seedlings of 
perennials, such as shrubs, fruit-trees, strawberries, potatoes, 
roses and other plants which can be propagated vegetatively, 
and also in the cases of those new forms of annual plants whose 
peculiarities are completely and faithfully transmitted by seeds 
to all their offspring, the work of the plant-breeder is reduced 
to the mere propagation of the new variety. 

Most frequently, however, it will be found that on sowing the 
seeds of a new form or ' sport/ the majority of the seedlings do 
not inherit the peculiar features of the parent but resemble the 
original plants from which the parent * sported. 1 For example, 
if in a batch of tomato plants bearing wrinkled inferior fruit, a 
single individual were observed with superior smooth round fruit, it 
would generally be found that a large number of the plants raised 
from the seeds of such * seminal sport ' would have wrinkled fruit, 
and none at all or only a few would bear smooth fruit. When a 
new variety makes its appearance among crops propagated by 
seeds, it is generally necessary not only to simply grow it, but to 
take steps to ' fix ' the variety, so that all the seedlings raised from 
it or from its descendants shall exhibit the peculiar characters 
which make it worth the special attention of the grower. To 
' fix ' and establish a new variety with constant characters from 
such * seminal sports/ the following process of continued selection 
is most frequently practised by seedsmen and other plant-breeders. 

The seeds of the plant showing the new features are sown, 
and those individuals of the offspring possessing the same 



'SEMINAL SPORTS' 309 

peculiar characters as the parent are allowed to produce 
seed, all others being pulled out and discarded. The seeds of 
this first selected generation are then sown, and a further 
selection and sowing of those possessing the new attributes 
is made. This process is repeated for several generations until 
no weeding out is found necessary, that is until the new char- 
acters become constant in all the offspring, after which the 
variety is said to be 'fixed* and 'comes true' from seed. The 
time taken to 'fix* a variety in this manner depends upon the 
power which the plant possesses of transmitting its characters 
to its offspring. This power is exceedingly variable and no 
rules can be laid down in regard to it; in some instances 50 
per cent, or more of the first generation may resemble the parent, 
and, on sowing the seeds of these, 90 per cent, of the seedlings 
may ' come true ' ; in such cases fixation of a new variety is 
tolerably easy and may be effected in three or four generations. 
In other cases the number of plants true to type in each succeed- 
ing generation may be very small, and even after selection has 
been carried on for many generations a large proportion of the 
plants obtained at each sowing may possess none of the char- 
acters of the variety which the plant-breeder wished to establish. 

H. Vilmorin stated that some of his hybrid varieties of wheat 
took six or seven years of cultivation and selection before they 
were of sufficiently fixed character to be put on the market for trial. 

The process applied to five or six generations of plants is 
generally found to be sufficient to 'fix' many new varieties of 
cereals, beans, peas, cabbages, turnips, tomatoes and other 
annual and biennial plants; probably the raising and selection 
of a similar number of succeeding generations of plants would 
be needed to make a variety of a perennial plant c come true ' 
from seed. However, on account of the fact that several years 
often elapse before seed is produced by many seedling perennials, 
the process of fixing new varieties of such plants by selecting and 

propagating in the above manner has rarely been carried out ; 

22 



310 CULTIVATED PLANTS AND THEIR ORIGIN 

hence all our varieties of apples, pears, strawberries, tulips, 
narcissus and many other cultivated plants do not ' come true ' 
from seed ; so far as their usefulness is concerned there is no 
necessity for them to do so, for the single original sport, when 
once obtained, may be propagated vegetatively by cuttings, 
runners, grafts and bulbs. Of course, varieties whose peculiar 
characters are not hereditary cannot be ' fixed ' at all. Varieties 
which are the result of hybridisation often vary for many genera- 
tions. On this account when fixation is being attempted , the 
several generations raised for the selective process should be 
protected or prevented as far as possible from crossing with other 
varieties and with the untrue seedlings. 

A knowledge of the Mendelian ' laws ' of inheritance is of great 
assistance to the plant-breeder in his work of selection among the 
offspring of hybrids. 

Self-fertilisation or in-breeding, when not carried to an extreme, 
tends to fix the characters of new varieties. 

(b) Seminal or seedling varieties. As previously mentioned 
no two seedling plants are exactly the same; even when they 
are derived from seeds taken from the same pod they differ from 
each other in one or more particulars. It may be that the 
colour of the flowers is not exactly the same, or the form of the 
leaf, the thickness of the root, or the size and habit of growth of 
the stem may differ in different individuals. Where the variation 
from the common type is obvious and distinct we have termed 
the plant a c seminal sport ' ; seedlings showing lesser deviations 
which are scarcely noticeable may be named ' seminal varieties! 
Between a ' seminal sport ' and a ' seminal variety ' there is no 
essential difference ; it is a matter of degree of variation only. 

These very slight indefinable deviations from the common 
type are of much importance, for experience teaches that many 
of them may be vastly increased by selecting and cultivating the 
plant in which the peculiarity is most marked in each successive 
generation ; the development of the peculiarity and its fixation 
go on simultaneously in such cases. 



SEMINAL OR SEEDLING VARIETIES 311 

For instance, if among a bed of plants whose flowers are 
ordinarily purple a single individual is observed whose flowers 
have a tinge of red, it is often possible to raise and fix a distinctly 
red variety by selecting from each succeeding generation the plant 
in which the redness of petals is most marked. Not only can 
the tints of flowers be modified and increased, but almost all 
other characters, however they may appear at first in the selected 
plant, may be increased in a similar manner. 

In, 1890 E. v. Proskowetz sowed in good garden soil seeds of 
the wild sea-beet obtained from specimens growing on the south 
coast of France. All the seedlings had much branched roots 
like their wild parents, and sent up flowering shoots the same 
year in which the seeds were sown : the average sugar-content 
was low although it exhibited wide variation, namely, between 
0*3 and 11*2 per cent. 

The plants of this generation, with good sugar-content and 
with thn least-branched and thickest roots were selected and 
their seeds sown. The majority of the plants of this selected 
second generation resembled their parents, but some of them 
behaved as biennials and sent up no flowering stems in the first 
year of their growth. 

From these biennial forms a further choice was made and 
their seed sown ; in consequence of the selection and good 
culture, the roots in 1893 had an average sugar-content of 15*93 
per cent, and each had an average weight of 426 grams. In 
another series of selected plants the average sugar-content in 
1894 was i6'99 P er cent, and the average weight of a root 368 
grams. Although the seeds of these plants still gave rise to a 
few annual plants resembling the original wild parents most of 
the seedlings proved to be biennials, and in form of root and 
amount of sugar greatly resembled some of the ordinary culti- 
vated races of sugar-beet. 

In order to determine to some extent how much of the 
increased sugar-content and size of the root was due to the better 
garden soil in which the plants were raised, and how much due 



312 CULTIVATED PLANTS AND THEIR ORIGIN 

to the selection of the best forms and the rejection of the worst, 
another part of the garden was sown in 1890 with the wild seed 
and the plants were allowed to remain and sow themselves down 
year by year. The average sugar-content of the roots of the 
latter rose year by year : in 1893 it was 4*5 per cent, in 1894 
9-38, their average weight in 1893 was 147 grams and in 1894 
232 grams. By a comparison with the previous figures it will be 
seen that the process of selection had nearly doubled the sugar- 
content and very considerably raised the average weight of each 
root. 

A. L. de Vilmorin by the selective process continued through 
four generations, obtained from the slender-rooted annual wild 
carrot (Daucus Carota L.) biennial plants having thick fleshy 
roots resembling some of the ordinary types of cultivated carrots 
in colour, form and size. 

Professor J. Buckman is said to have raised the large hollow- 
crowned * Student ' parsnip from the small-rooted wild parsnip* 
by a similar process of selection. 

These may be taken as instances of the rapid modification of 
wild species by choosing and propagating by seed what are 
considered the best specimens of several succeeding generations, 
all other plants being rejected or destroyed. 

Cultivated varieties now existing can be * improved 1 or 
rendered more useful than they are at present in a similar 
manner, and generally more easily than wild species. 

4. Variations: how induced. From the foregoing account 
it will be understood that the improvement of plants depends 
primarily upon their variability ; for if plants were all alike, and 
did not vary at all, there could be no selection. Moreover, in 
plants raised from seeds, the variation must be hereditary, for 
unless the peculiar quality or character possessed by a specially 
selected individual plant is passed on to the next generation, the 
selection becomes useless. For example, no progress can be 
made in the development of a stiff-strawed race from a kind of 



VARIATIONS: HOW INDUCED 313 

barley or wheat with weak stems, by selecting and propagating 
an individual plant with rigid straw, unless such stiffness is trans- 
mitted to the descendants of the selected plant. 

Which variations exhibited by plants are transmitted to their 
seedling offspring, and which are not, can only be determined by 
trial. The variations of plants and animals must arise from 
specific changes in the constitution of their protoplasm, often 
especially in the chromosomes of their nuclei, but in many in- 
stances little certain knowledge is available regarding the nature 
of these changes, and to cause a plant to vary with certainty in 
some particular and desirable manner is at present impossible. 
Even to make a plant vary at all appreciably is often a matter of 
great difficulty, some species being very stable. However, when 
variation once begins, the desired character very frequently 
appears sooner or later among the plants, so that the first step in 
plant improvement is to ' break the type,' or to make the type it 
is intended to improve vary in any manner whatever. 

Since the variations of plants are the starting points from which 
improvement or modification begins, it becomes important to en- 
quire if there are any^ methods by which variation can be induced. 

Experience has taught that variation can be induced 

(1) by varying the external conditions of life of the plant ; 

(2) by crossing and hybridisation. 

It is well known that an abundance of manurial constituents 
leads to luxuriance of the various organs of a plant, while a re- 
duction of these substances results in lowness of stature, and 
general diminution of all parts ; poverty or richness of soil, there- 
fore, leads to variation among plants. Similarly, the intensity of 
the light, the warmth or coldness of the summer induces variations 
in sweetness of almost all kinds of fruit. The size of the grains of 
wheat, bar ley,, and other cereals, and that of many seeds and other 
parts of plants, is also dependent on the cultivation of the ground 
in which they are grown, and upon the season and the length of 
time during which growth goes on: other external conditions 



314 CULTIVATED PLANTS AND THEIR ORIGIN 

bring about changes in the structure and function of various 
organs of plants. Generally it may be said that variations of 
this kind, induced by changes in the amount of food-constituents 
in the soil, or by alterations of season and climate, are rarely, if 
ever, hereditary ; they appear under certain conditions, but when 
the conditions are altered the variations disappear. 

For instance, by growing tall varieties of peas, beans, or any 
other plants upon poor soil, successive generations of short 
individuals may be obtained so long as the poverty of the soil 
is maintained ; the seeds of such plants, however, when grown 
upon good soil at once give rise to tall plants, showing that the 
dwarfness of habit induced by such soil conditions is not a 
permanent hereditary modification. 

Wheat, oats, and other cereals, when grown upon good garden 
soils, at wide intervals apart, as has been done by some propagators, 
develop tall straw, long ears, and large grain, but no new permanent 
variety can be produced in this manner. 

By growing beets possessing ' fanged ' roots close together, they 
have no room to develop their disfiguring branches, and may thus 
be made to assume a good form ; nevertheless, seeds raised from 
such plants, when grown under ordinary conditions of cultivation, 
immediately give rise to plants with ' fanged ' roots like their 
ancestors. When attempting to develop a new race of any kind 
of plant, it is therefore important that the modification taken as 
a basis upon which the selective process is carried out, should 
not have arisen merely as the result of external conditions. 

Where increased size of certain organs is the feature desired 
in a new race, it is perhaps best to raise the successive genera- 
tions of plants from which the selection is to be made upon a 
moderately poor soil, rather than a specially rich one ; any in- 
creased size of one plant over that of another under such circum- 
stances would be less likely to be due to an accidental excess of 
manure, and more likely to be due to an innate hereditary quality 
of the plant. 



VARIATIONS: HOW INDUCED 315 

The most certain method of inducing variation in a plant is 
to cross or hybridise it with another individual. In this process, 
there is a mixing of the protoplasm of two distinct plants, and 
the offspring therefore consists of living matter derived from two 
distinct and unlike sources. Sometimes the plants of the first 
and second generation obtained from such a cross all resemble 
each other very closely. Succeeding generations, however, exhibit 
very great variability, the plants showing the characters of the two 
original parents blended in very variable degree, and peculiarities 
not seen in the parents are very frequently observed among them. 
The latter characters although apparently new are often those pos- 
sessed by the grandparents or earlier ancestors of the plant which 
have been transmitted in a latent state through several generations. 

Variations which appear as the result of crossing are much more 
frequently hereditary than characters produced by the action of 
external conditions ; moreover, they can generally be increased 
by selection. Not only is crossing of use for the purpose of in- 
ducing variability among plants so that selection may be begun ; 
it may be resorted to in order to combine in one variety of plant 
characters previously possessed only by two different and separate 
varieties. A tender variety which is of good quality in other 
respects when crossed with a hardy kind of poorer quality, some- 
times gives rise to one or more descendants, combining the good 
quality of the former with the hardiness of the latter : similarly 
other qualities of two distinct varieties may be blended, as in the 
example of the crossing of pea plants with round green with 
wrinkled yellow seeds, leading to the production of two new types, 
namely, plants yielding round yellow and wrinkled green seeds 
which breed true (see pp. 289-298). It must, however, be 
observed that the combination of certain peculiarities in one and 
the same plant cannot be attained by any means ; it is often 
better to grow one variety for one purpose and another for another 
purpose, rather than attempt the combination of antagonistic 
features (see next paragraph). 



316 CULTIVATED PLANTS AND THEIR ORIGIN 

5. Correlated variability. The various parts of the body of 
a plant or animal are so co-ordinated with each other that any 
change in the structure or function of one organ very frequently 
brings about some necessary change in another. The nature 
of the connection between the correlated variations is in many 
instances obscure ; nevertheless the existence of this kind of 
variability must be always borne in mind by those who seek to 
improve plants. Moreover, it is important that every endeavour 
should be made to elucidate its nature, for a correct and 
complete understanding of the structural and functional re- 
lationships between the different parts of plants would enable 
the plant-breeder to save much valuable time. There is little 
doubt that through want of knowledge on such matters, plant- 
breeders have not unfrequently attempted to do that which is 
impossible. 

In most cases quantity of produce and good quality are so 
connected that beyond a certain point the increase of one brings 
with it a decrease of the other, and to combine both characters 
in maximum degree in one variety appears to be impossible. 
For example, all attempts to obtain a race of sugar-beet with 
the highest yield of roots per acre and highest known sugar- 
content are found to fail when a certain percentage of sugar in 
the root is reached \ with every increase of sugar-content beyond 
this point there is invariably a decrease in size and weight of the 
' root.' 

It appears to be impossible to breed a wheat of richest 
gluten-content, with as high a yielding power of grain per 
acre as * rivet ' starchy wheat ; this difficulty is partially de- 
pendent on the fact that the glutinous proteins are largely 
stored in the outer layers of the endosperm which be- 
come filled first, the central parts being filled up later 
chiefly with starch ; the longer the assimilation goes on 
the more starchy the grain becomes, and the larger the 
crop* 



DEGENERATION OF VARIETIES 317 

Investigation has shown that thin-stemmed races of barley 
always give the best quality of grain for malting purposes, and to 
breed a variety combining the highest quality of grain with great 
stiffness of straw is probably impossible. 

It is generally known that seed-production and luxuriance of 
vegetative organs are mutually antagonistic; for example, with 
high yield of tubers of good quality, seed-production in the 
potato has been vastly reduced, and in the case of oats and 
wheat short-strawed varieties usually give a greater proportion of 
grain than long-strawed kinds. A turnip of slow, long-continued 
growth yields a greater dry weight per acre than a rapid-growing 
variety, for there is a greater time for the manufacture, accumula- 
tion and assimilation of food in the former than in the latter; 
the attempt to produce a variety of turnip of rapid growth and 
high feeding-value would fail after a certain point of excellence 
was reached; fortunately in this case there appears plenty of 
room for systematic work and improvement before the limit is 
attained, and the same is probably true of practically all farm 
plants. 

6. Reversion, ' throwing-back,' atavism: degeneration of 
varieties. A new variety of a plant becomes established 
and ' fixed ' by destroying all those individuals of each 
generation which do not resemble the general type. ' Fixation ' 
is, however, a relative term, for even in cultivated varieties in 
which the process of destruction has been systematically carried 
out and which have 'come true, 1 from seed during many 
generations, t false plants' or Brogues' departing considerably 
from the type appear among the offspring at irregular in- 
tervals. 

For example, individuals resembling the wild pansy ( Viola 
tricolor L.) in form, colour and size of the flowers and leaves, 
occasionally make their appearance among plants raised from 
seeds of the best large-flowered cultivated types of pansy ; and 



3l8 CULTIVATED PLANTS AND THEIR ORIGIN 

among crops of green-topped turnips, purple-topped individuals 
sometimes occur. * Rogues ' most frequently exhibit characters 
possessed by the ancestors of the variety in which they are 
found. 

The tendency of plants to revert to long-lost characters is 
termed atavism, ' thr owing-lack, or reversion. Some of the plants 
which exhibit ( reversion ' to characters seen in remote ancestors 
are doubtless Mendelian recessives, to which reference is made 
previously (p. 299)* 

Very few if any varieties of plants propagated by seeds remain 
like the type first sent out by the raiser for more than a limited 
number of years. In a great many instances where almost 
everybody raises seed, destruction of * rogues' is not efficiently 
or thoroughly carried out, and through the consequent mixing 
with the progeny of the reverted plants, the type rapidly degener- 
ates in purity. 

Apart from the incompetence to distinguish slightly reverted 
forms and laziness in carrying out their destruction, other changes 
take place in the type through the different ideal which each 
raiser of seed sets up before his mind when he selects the indi- 
viduals to be employed as seed parents. For example, three 
different raisers of seed of ' Gubbins' " Incomparable " pea ' are 
almost certain to hold different views from Mr Gubbins and 
from each other in regard to the relative importance of the 
various characters of a good pea ; selection is therefore carried 
out from three different standpoints, and in a few generations 
the * Incomparable * variety no longer exists except in name, 
unless Mr Gubbins himself also carries on the propagation : three 
different types bearing the same name would arise. It is there- 
fore very necessary for the farmer and gardener not to be led 
away by the fascination of an old name, for it does not follow 
that anything useful is obtained with it ; at the same time it must 
be remarked that a new name does not necessarily represent 
any new quality or character in the seeds to which it is applied ; 



DEGENERATION OF VARIETIES 3*9 

new names may easily be applied to old articles when the latter 
cannot be sold by their original names. 

Much valuable experience can be gained by growing small 
trial plots of several differently named varieties of farm and 
garden plants of the same species. 

Moreover, a useful lesson can be learnt by sowing small plots 
of seeds of a variety of turnip, pea or other plant bearing the 
same name and obtained from half a dozen different firms 
of seedsmen. Farmers rarely do enough testing of this 
kind, 



PART IV. 

CLASSIFICATION AND SPECIAL BOTANY 
OF FARM CROPS. 

CHAPTER XXIV. 
THE CLASSIFICATION OF PLANTS. 

i. SYSTEMATIC or Classificatory Botany is concerned with the 
naming, describing and arranging of plants into groups. 

Various systems of classification have been proposed from 
time to time, the one which has superseded all others being the 
so-called Natural System. Underlying it is the assumption that 
all the different kinds of plants on the face of the earth have 
been derived by natural descent from a few ancient ancestors, 
and the object of this system is the arrangement of plants into 
groups according to their affinity or blood-relationship. 

The evolutionary history and genetic affinity of plants can 
never be known accurately, and there are no universal rules by 
means of which the relationship of organisms can be determined 
with certainty. However, in forming the groups into which the 
Vegetable Kingdom is divided, botanists endeavour to take into 
consideration as many peculiarities or characters of the plants as 
possible, and place together only those which agree in a number 
of characters^ it is reasonably contended that by this method 
plants which are related to each other by descent are likely to be 
brought together. 

a. The terms employed to denote the different groups are 
indicated below. 



GENUS: PLANT-NAMES 321 

Individual and species: variety and race. When a red 
clover seed is sown and allowed to grow it produces a single 
plant, which after a time gives rise to a number of seeds, each ot 
which can grow and produce ofTspring similarly, so that in a 
few years a very large number of individual red clover plants 
may be obtained. It will be found that these individuals, 
although not exactly like each other, are nevertheless very 
similar in the form, colour, size and other features of their roots, 
stems, leaves and flowers. Such plants, and all those upon the 
face of the earth which resemble them to such an extent that 
they may be considered to have descended from a common 
ancestor, are grouped together by botanists, the whole group 
being termed a species. 

While the majority of the characters possessed by the various 
organs of a species are constant, certain features, such as the 
hairiness of the leaves and stems, or the colour of their flowers, 
may vary: thus we may find in a field of red clover, plants 
bearing white flowers instead of purple ones : such are described 
as varieties of the red clover species. The peculiar characters 
of a variety are usually transmitted to few or none of its 
descendants. 

Varieties presenting some considerable variation from the 
most prevalent characters of the species are termed sub-species or 
races when the variation is known to be hereditary for many 
generations. 

Many of our cultivated crops are permanent varieties, or races 
developed by the process of selection (see chap, xxiii.) from wild 
species. 

Genus: plant - names. Even cursory examination of the 
various species of plants commonly met with, reveals the fact 
that a certain number of them resemble each other, especially 
in the form, arrangement and number of the parts of the flower. 
Thus, red clover, Alsike clover and white clover, although differ- 
ing from each other in the colour of their flowers and in the 



322 THE CLASSIFICATION OF PLANTS 

shape, size and habit of their vegetative organs, are nevertheless 
very similar in the construction and form of their flowers. 
Species possessing such close resemblances in the structure 
and arrangement of their reproductive organs are grouped to- 
gether and are spoken of as a genus. 

The scientific or botanical name of a plant consists of two 
Latin words, the first of which indicates the genus and the second 
the species to which the plant belongs. For example, the true 
clovers constitute the genus Trifolium, the species red clover 
being named Trifolium pratense, while Alsike clover is known 
as Trifolium hybridum. Similarly the various species of butter- 
cups collectively form the genus Ranunculus, two common species 
of the genus being Ranunculus repens (creeping crowfoot) and 
Ranunculus bulbosus (bulbous buttercup). 

As the same species has sometimes been named differently by 
different botanists and the same name has not uncommonly 
been used for two or more distinct species, to prevent confusion 
it is customary in systematic works to add to the name of the 
plant the full or abbreviated name of the botanist who gave the 
plant its name and described it. 

For example, the name Bellis pertnnis Linn, or Bellis pertnnis 
L., indicates that Linnaeus gave the name and it also implies 
that the plant denoted is the particular species which Linnaeus 
described under this name. 

Just as species are grouped into genera, so are genera re- 
sembling each other grouped into Orders or Families. 

Orders possessing similar characters form Classes, and classes 
having common distinctive characters are finally grouped together 
into Divisions. 

Where some of the representatives of a Genus, Order, Class* 
or Division possess characters which mark them off more or 
less distinctly from the rest of the group to which they belong, 
it is sometimes useful to subdivide these groups into Sub-genera, 
Sub-orders, Sub-classes and Sub-divisions. 



THALLOPHYTES 323 

3, The following are the chief Divisions of the Vegetable 
Kingdom : 

Division I. Myxomycetes, 
II. Thallophyta. 
III. Bryophyta. 
IV. Pteridophyta. 
V, Spennatophyta. 

The plants included in the first four divisions are often spoken 
of as Flowerless plants or Cryptogams. Among them repro- 
duction is carried on chiefly by means of minute one-celled 
bodies termed spores > which are set free from the parent plant 
and afterwards germinate and give rise to new plants. 

The Spermatophytes (Division V.) were formerly designated 
Flowering plants or Phanerogams. In these, reproduction is 
carried on chiefly by means of seeds, each of which contains an 
embryo-plant. 

Division I. The Myxomycetes are commonly known as 
slime-fungi. In a vegetative state the bodies of these organisms 
consist of naked masses of protoplasm termed plasmodia^ and 
are capable of creeping about in a manner similar to the 
movement of an ordinary amoeba. The Myxomycetes are devoid 
of chlorophyll, and almost entirely saprophytic, that is, they 
feed mainly upon decaying organic remains, many species being 
common upon rotten wood and dead leaves. In several respects 
they greatly resemble the lowest forms of the animal kingdom, 
and are by some authorities included in the latter and spoken 
of as Mycetozoa, or fungus-animals : their method of reproduc- 
tion by means of spores is, however, similar to that prevalent 
among certain Fungi. 

One organism generally included in this division and described 
in chapter Hi., is parasitic, and the cause of the disease known 
as ' Finger-and-toe ' or * club-root ' among turnips and cabbages, 

Division II. The Thallophytes are plants, such as sea-weeds, 



324 THE CLASSIFICATION OF PLANTS 

lichens and toad-stools, the bodies of which are of simple 
construction and exhibit no differentiation into stem, root and 
leaf. When branching does take place, the members produced 
are usually all essentially alike, and resemble the previously 
existing parts from which they arise : the body of a plant of 
such simple structure is termed a thallus. In some instances 
each plant is very minute, being merely a single cell, while in 
others, the thallus consists of thousands of cells : in all cases, 
however, the cells possess a distinct cell-wall. 

The Thallophytes are divided into several sub-divisions of 
which two, namely, the Sehizophyta and the Fungi are of 
great practical importance : the former includes the Bacteria 
or Schizomycetes. 

Division III. The Bryophytes comprise two classes of plants, 
namely, liverworts and mosses. 

Division IV. The Pteridophytes include ferns, horsetails 
and club-mosses. 

Some of the above divisions of the Vegetable Kingdom, such 
as those including the sea-weeds, mosses and ferns, are without 
practical interest or importance for the farmer, and want of 
space prohibits more than a mere mention of their existence. 
Students wishing for information in regard to those divisions are 
referred to the ordinary text-books of systematic botany. 

The Bacteria and Fungi, however, which are included in the 
Thallophyta, need special attention on account of their practical 
bearing, and are dealt with in subsequent chapters. 

Division V. The Spennatophytes or Phanerogams include 
all those plants which produce seeds. This division is split up 
into two sub-divisions namely : 

Sub-division i. Gymnosperms. 
and Sub-division 2. Angiosperms. 

In the Gymnosperms, of which the cone-bearing firs and pines 
are examples, the carpels are flattened structures and the ovules 



CHORIPETALJE 325 

and seeds lie naked or exposed on the surface of the latter: 
fertilisation is effected by pollen-grains which come into direct 
contact with the micropyle of the ovule. 

The Angiosperms possess carpels which are hollow closed 
structures, the ovules and seeds being developed within the 
completely closed cavity or ovary of the carpels. In these plants 
the pollen-tube must first pass through the tissues of the carpels 
before reaching the ovule. 

4. As practically all farm plants belong to the Angiosperms it is 
important to enter into greater detail in regard to the classification 
of this sub-division of the Vegetable Kingdom. The following is 
an outline of the arrangement and chief features of the Classes, 
Sub-classes, and a few common Orders included in it. 

Sub-division 2. ANGIOSPERMS. 

Glass I. Dicotyledons. In these plants the embryo has two 
cotyledons and the floral-leaves are usually in fours or fives. In 
a cross-section of the stem the vascular bundles appear arranged 
in a single ring round a central pith and in perennial species 
concentric zones or * annual rings ' of wood are present, the 
* annual rings ' being formed by a cambium-tissue. The leaves 
are generally net-veined. 

Sub-class I. Choripetal. The corolla when present is poly- 
petalous. 

In some plants of this sub-class the flowers are imperfect; 
either the corolla or calyx is absent or both parts of the 
perianth are missing. 

(i) Flowers regular, hypogynous y usually with a single green or 
white perianth : fruit one-seeded. 

Order. Cannabacca (see p. 332). 

Order. Polygonacea (see p. 350). Flowers small with a perianth 
of three to six tree segments : stamens five to eight opposite the 
perianth segments ; gynsecium of two or three united carpels, the 

ovary generally triangular or oval in section, and containing a single 

23 



326 THE CLASSIFICATION OF PLANTS 

erect ovule ; fruit an angular nut ; seed endospermous. The 
stems are mostly herbaceous and bear alternate leaves, which 
possess membranous tube-like stipules (the ochrece) clasping the 
stem. Common plants of this Order are Dock and Sorrel 
(Rumex), Knot-grass (Polygonum aviculare L.), Black Bindweed 
(Polygonum Convolvulus L.), and Buckwheat (Fagopyrum Sagit- 
tatum Gilib.). 

Order. Chenopodiacea. This Order which is described in 
chapter xxvii., possesses close affinities with the CaryophyllacecB 
mentioned below. 

(2) Flowers, usually with both calyx and corolla present. 

(a) Flowers hypogynous : gynascium apocarpous. 

Order. Ranunculacece. Flowers mostly regular, with free 
sepals, numerous stamens and one or many free carpels. The 
fruit is an achene or a follicle. Most plants of the Order are 
herbaceous and contain acrid poisonous j uices. Common examples 
are Buttercups (Ranunculus), Columbine (Aquilegia), Monkshood 
(Aconitum), and Anemone. 

(b) Flowers hypogynous : gynaecium syncarpous. 
(i) Ovules on a free-central placenta. 

Order. CaryophyllacecB, Flowers regular with four or five 
persistent sepals and the same number of petals : stamens usually 
eight or ten ; fruit a capsule with few or many endospermous 
seeds. The stems have opposite leaves and thickened nodes 
and the flowers are generally pink or white. Common examples 
are Pinks and Carnations (Dianthus), Campions (Lychnis), Chick- 
weed (Stellaria), and Spurrey (Spergula). 

(ii) Ovules on parietal placentas. 

Order. Papaveracecs. Flowers regular with two sepals, four 
petals and many stamens. Fruit a capsule dehiscing by pores 
and containing many small endospermous seeds. Plants belong- 
ing to this Order contain milky or coloured latex and are often 
poisonous : poppies are common examples. 

Order. Cruci feres (see p. 371). 

(iii) Ovules on axile placentas. 

Order. Linacea (see p. 395). 



SYMPETAL^: 327 

(f) Flowers perigynous : gynaecium superior and apocarpous. 

Order. Rosacece (see p. 403). 

Order. Leguminosa (see p. 416). 

(d) Flowers epigynous : gynaecium inferior and syncarpous. 

Order. Umbellifera (see p. 447). 

Sttb-Class II. Sympetalse. Corolla gamopetalous. 

(1) Flowers hypogynous. 

(a) Corolla regular. 

Order. Boraginacea. Flowers with a five-lobed calyx and a 
five-lobed corolla; stamens five; gynsecium of two united carpels ; 
the ovary is four-lobed and four-chambered with a single ovule 
in each chamber ; fruit a schizocafj) which splits into four 
nut-like mericarps. Examples of plants belonging to this order 
are Comfrey (Symphytum\ Borage (Borago\ and Forget-me-not 
(Myosotis). 

Order. Solanacea (see p. 462). 

(b) Corolla irregular zygomorphic. 

Order. Scrophulariacea. Flowers with a five-lobed calyx and 
a four- or five-lobed corolla ; stamens epipetalotrs, generally four, 
with a rudimentary fifth ; gynaecium of two united carpels ; ovary 
two-celled ; fruit a capsule, containing many endospermous seeds. 
Common representatives of the order are : Snapdragon (Antir- 
rhinum)^ Foxglove (Digitalis)^ Speedwell (Veronica), Yellow- 
Rattle (Rhinanthus\ and Eyebright (Euphrasid). 

Order. Labiate. Flowers with a five-partite ribbed calyx, 
and a two-lipped zygomorphic corolla; stamens two or four, 
didynamous, epipetalous ; gynaecium of two united carpels ; ovary 
four-celled, with one ovule in each cell ; fruit a schizocarp 
splitting into four nut-like mericarps. The stems of the plants 
are four-angled, and bear opposite or whotled leaves. Common 
examples are Mints (Mentha\ Self-heal (Brunclla or Prunella), 
Dead-nettle (Lamium). 

(2) Flowers epigynous. 
Order. Composite (see p. 476). 



328 THE CLASSIFICATION OF PLANTS 

Glass II Monocotyledons.-^-The embryo of these plants has 
only a single cotyledon, and the floral-leaves are in threes or 
fours, never in fives. A cross-section of the stem shows a 
number of isolated vascular bundles, not in a single ring but 
usually scattered and without any distinct central pith: no 
cambium is present in the stems. The leaves are usually 
parallel-veined. 

(1) Perianth absent or represented by small scales or bristles. 
Order. Graminea (see p. 481). 

Order. Cyperacea. Flowers unisexual or bisexual, arranged 
in spikelets, eath flower in the axil of a small bract (glume). 
Perianth none or consisting of three to six bristles; stamens 
generally three ; gynaecium syncarpous, with a one-celled ovary 
and a single style, with two or three simple filamentous stigmas ; 
ovule one, erect The fruit is a three-sided or flattened nut 
containing a single endospermous seed which is generally free 
from the pericarp. The plants of this Order are often confused 
with grasses, but have mostly solid triangular stems and entire 
leaf-sheaths. 

Common examples are the Bulrush (Sdrpus\ Cotton-grass 
(Eriophorum), and Sedge (Carex). 

(2) Perianth present and regular, 
(a) Gynaecium superior. 

Order. Liliacece. Flowers with a six-partite coloured perianth : 
androecium of six stamens. 

Common plants belonging to the Order are Lily-of-the-valley 
(Convallaria majalis L.), Ramsons (Allium ursinum L.), and 
other species of 'Garlic* (Allium\ Hyacinth, Tulip and Meadow 
Saffron (Colchicum autumnale L.). 

Order. Juncacea. flowers small with a six-partite green or 
brown perianth, andrcecium usually of six stamens. Fruit, a one- 
or three-celled capsule. 

Common examples of the Order are various species of Rush 
(Juncus) and Wood-rush (Luzula) (see p. 620). 



MONOCOTYLEDONS 329 

(b) Gynaecium inferior. 

Order. Iridca. Flowers with a six-partite brightly coloured 
perianth: androecium of three stamens, the anthers of which 
open outwards ; gynaecium syncarpous, three-celled, the simple 
style often surmounted by three leaf-like coloured branches on 
which are the stigmas. Fruit a capsule containing endospermous 
seeds. Common plants of the Order are Yellow flag (Iris 
Pseud-acorus L.), Crocus and Gladiolus. 

Order. Amaryllidea. Flowers with a six-partite coloured 
perianth : androecium of six stamens, the anthers of which open 
inwards. The gynaecium and fruit resemble those of the Iridea. 
Common examples are Daffodil (Narcissus) and Snowdrop 
(Galanthus\ 

(3) Perianth present ) cpigynous, and zygomorphic. 

Order. Orchidca. Flowers irregular, generally with one stamen, 
which is united to the style. Gynaecium inferior, ovary mostly 
one-celled with parietal placentas. The fruit is a capsule con- 
taining a large number of very minute seeds. Common ex- 
amples are Purple Orchis (Orchis mascula L.), Spotted Orchis 
(Orchis maculata L.) and Tway-blade (Listera ovata Br.). 

Ex. 172. Students should describe as many common plants as possible, 
taking their parts in the order indicated below. 

(i) Habit and general appearance. Whether annual, biennial or perennial ; 
herbaceous or woody. 

(ii) Root. Fibrous or with a distinct tap-root ; presence or absence of 
adventitious roots. 

(iii) Stem. Herbaceous or woody ; erect, decumbent, prostrate, or wind- 
ing, &c. ; shape in transverse section, square, round, ribbed, &c. ; hairy, 
spiny, with harsh or hispid hairs, or glabrous : colour. 

(iv) Leaf. Radical or cauline ; opposite, whorled or alternate; simple or 
compound ; if compound, pinnate or palmate ; stipulate or exstipulate ; sessile 
or petiolate ; shape of blade or leaflets ; character of the margins and tips ; 
smooth or hairy surfaces. 

(v) Inflorescence. Definite or indefinite; kind; presence or absence of 
bracts and bracteoles. 

(vi) Flower. Complete or incomplete ; regular or irregular ; tygomorphic 
or actinomorphic. 



330 THE CLASSIFICATION OF PLANTS 

(vii) Calyx. Inferior or superior ; polysepalous or gamosepalous ; number 
and form of the sepals or lobes of the calyx. 

(viii) Corolla. Hypogynous, perigynous or epigynous ; polypetalous or 
gamopetalous ; number, form and colour of petals or lobes of corolla. 

(ITU) Andraecium.'^ Hypogynous, perigyuous, epigynous or epipetalous ; free, 
monadelphous, diadelphous, polyadelphous or syngenesious ; di- or tetra- 
dynamous. 

(x) Gynacium. Superior or inferior ; apocarpous or syncarpous ; number 
of carpels, styles and stigmas ; if syncarpous, whether ovary is one, two or 
more celled ; ovules on axile, parietal or free central placentas. 

(xi) Fruit. Dry or succulent ; indehiscent, splitting or dehiscent ; 
kind. 

The following may be taken as an example of plant description : 

Bulbous buttercup (Ranunculus bulbosus L.). 

Habit. A hairy perennial with bulbous rootstocks, erect stems about a 
foot high, divided leaves and yellow flowers ; common in meadows and 
pastures. 

Root* Fibrous. 

Stem. Herbaceous, lower part bulb-like, branches erect ; peduncles 
furrowed. 

Leaves. Radicle and cauline; cauline leaves alternate; simple, exstipulate ; 
lower leaves with long petioles ; upper leaves cut into narrow segments ; the 
blade cut irregularly into three lobes which are tri-partite. 

Inflorescence. Definite ; the main axis and its branches, each end in a single 
flower. 

Flower. Complete, actinomorphic. 

Calyx. Inferior, polysepalous, five sepals, reflexed. 

Corolla. Hypogynous, polypetalous, five petals, yellow, each petal with a 
nectary at its base. 

Andrcecium. Hypogynous j stamens free and indefinite. 

Gynacium. Superior, apocarpous, carpels many spirally arranged on a 
conical receptacle. 

Fruit. Many tree achenes. 

Ex. 173. After describing the plants as in previous Ex., their position in 
the Vegetable Kingdom should be assigned in accordance with the following 
scheme : 

(i) Division. 
(ii) Sub-division. 
(iii) Class. 
(iv) Sub-class* 
(v) Order. 
(ri) Genus. 
(vii) Sptcitt. 



MONOCOTYLEDONS 33 1 

The position of the bulbous buttercup is represented thus* 
Division : Spermaphyte. 
Sub-division : Angiosperm. 
Class: Dicotyledon. 
Sub-class: Choripetalac. 
Order: Ranunculacex. 
Genus: Ranunculus. 
Species : bulbosus. 



CHAPTER XXV. 
OANNABACEJE. 

i. General characters of the Order. Flowers unisexual ; dioe- 
cious. ' 

Male flowers with a five-leaved perianth and andrcecium of 
five stamens, the filaments of which are erect in the flower-bud. 

Female flowers hypogynous, with a small entire cup-shaped 
perianth surrounding the ovary. The gynaecium possesses a 
one-celled ovary with a single ovule within; styles two, decidu- 
ous, long and papillose. Fruit, a form of nut, dry, indehiscent, 
containing a single, pendulous seed. Seed with a curved or 
spirally-rolled embryo and very small reserve of endosperm. 

This is a very small Order containing but two genera and 
three species. It is often treated as a sub-order of the Urticaceae 
or nettle family. The flowers are wind fertilised. 

The plants representing the whole Order are The Common 
Hop (Humulus Lupulus L.) ; Japanese Hop (Humulus japonicus 
Sieb. et Zucc.) ; and Hemp (Cannabis sativa L.). 

2. The Japanese Hop (Humulus japonicus Sieb. et Zucc.) is an 
annual sometimes grown in gardens as an ornamental climbing 
plant on account of its rapid growth. It resembles the Common 
Hop in its stems and leaves, but the female inflorescences or 
strobiles contain no ' lupulin ' and are consequently useless for 
brewing purposes. 

3. The Common Hop (Humulus Lupulus L.) is a perennial 
herbaceous plant, cultivated almost entirely for the female in- 
florescences, which are employed in the manufacture of beer. 
It is probably indigenous in the British Isles, but most of the 

882 



THE COMMON HOP 



333 



so-called wild hops so frequent in the hedges in the south of 
England, are no doubt generally escapes from cultivation or 
seedlings from cultivated plants in the neighbourhood. 

The short young shoots are occasionally utilised as a substitute 
for asparagus, and from the ' fibre ' of the stem a coarse kind of 
cloth can be made, but these uses of the plant are of no practical 
importance. 

SEED AND GERMINATION. In autumn the female inflor- 
escences or 'hops,' if left on the 
plants, readily break up, and the 
bracts (mentioned below) to which 
the fruits are attached are carried 
some distance by the wind. The 
single seed within each fruit con- 
tains a spirally curved embryo, 
which germinates only after a rest 
during the winter. In spring the 
young plants appear above ground, 
and possess two narrow strap- 
shaped cotyledons (Fig. 103). 

ROOT. The primary root of a 
seedling hop produces several 

r Root; Ahypocotyi;, cotyledon. branches which goon equal ft fc 

thickness. From all the thicker roots a great abundance of 
hair-like fibrils are given off. 

A striking feature in both old and young plants is the exceed- 
ingly large root-system which they possess in comparison with the 
parts which come above ground. The thicker roots are covered 
with a mass of loose reddish-brown bark. Some of them penetrate 
to very great depths in the ground, entering cracks and openings 
wherever the subsoil is rocky ; others remain nearer the surface, 
and spread horizontally in the upper layers of the soil, giving 
rise at the same time to an enormous number of fine fibrils. 
Adventitious roots are abundant on the underground stems. 




FIG. 103. i. Seedling hop, one week 
old. 2. The same, two weeks old. 



334 CANNABACE^ 

THE STEM. The stems, which are generally termed 'bines, 1 are 
herbaceous, angular and hollow, and of variable colour, being, in 
some varieties, purplish-red, in others pale green, or green streaked 
with red. They make their appearance in spring from buds of 
the underground perennial * rootstock ' or rhizome, and die 
down in autumn. The lower part, however, of each ' bine ' 
below ground does not die, but thickens and forms a further ex- 
tension of the * rootstock/ The * sets ' used in propagating the 
plant are these thickened underground parts of the stems ; they 
are cut off the parent plant in spring, and readily form adventi- 
tious roots when planted. The herbaceous stems above ground 
bear thin opposite lateral branches, which are of considerable 
length about the middle of the main stem. It is upon the 
lateral branches that the female inflorescences are produced, 
hence their formation and preservation is of the utmost import- 
ance to the hop grower. 

The stems, although too weak to stand erect by themselves, 
are able to wind round any support such as a pole, a piece 
of stretched string or wire, or another plant placed near them, 
and frequently reach in this manner a height of 25 or 30 
feet. In ascending a support the free tip of the stem slowly 
moves round in a circle, from left to right, in the same direction 
as the hands of a watch. The most rapid growth in length takes 
place when the support is upright, and in stems growing erect 
the internodes are longer than upon stems which are allowed to 
grow along a string inclined away from the vertical. The 
growth continues for a longer period, and is more even in its 
rate on sloped supports than on erect ones. When the support 
is inclined at an angle of between 45 and 60 degrees away from 
the vertical, the stems are unable to climb satisfactorily without 
external aid, their tips needing to be trained or assisted to 
wind, otherwise they hang away from the support. In all kinds 
of hop, but especially in the wild and coarse cultivated varieties, 
the "stems and also the leaf petioles and main 'veins' have 



THE COMMON HOP 335 

several lines of strong hooked hairs which make the plant rough 
to the touch, and help it to cling to its support 

THE LEAF. The hop has opposite leaves which vary con- 
siderably in shape even on the same stem. To some extent the 
variation depends upon the position on the stem and the age 
and variety of the plant. Upon young seedlings and on the 
youngest upper branches of older hops they are mostly cordate, 
with a deeply serrated margin. On older parts the leaves are 
large and broad, generally palmately three or five lobed, with 
deep acute serrations. Each possesses a petiole about half as 
long as the blade, and is stipulate ; the stipules of opposite 
leaves are united and broadly triangular. 

THE INFLORESCENCE AND FLOWERS. The hop plant is 
dioecious, the male flowers, growing upon one individual plant, 
while the female ones occur upon another. Occasionally ex- 
amples are found which are monoecious, that is, both kinds of 
flowers are present upon the same plant. 

a. The inflorescences bearing the male flowers are much 
branched cymose panicles, which grow either from the axils of 
the main stem or from the axils of the lateral shoots. 

Each MALE FLOWER is about a quarter of an inch in diameter, 
and possesses a five-leaved sepaloid perianth, opposite which are 
five stamens. The latter have very fine short filaments and long 
anthers, which dehisce by slits opening most widely at the apex 
(*/, Fig. 105). 

b. The inflorescences of female flowers somewhat resemble 
fir cones in external appearance, and are borne on branches which 
arise either directly from the leaf axils of the main stem itself 
or from the axils of the leaves upon lateral shoots produced by 
the main stem, They are spoken of as strobiles (A, Fig. 104), 
and are the * hops ' of commerce. 

A fully developed strobile when ripe possesses a long central 
axis covered with fine downy hairs, and is popularly termed the 
' strig ' of the ' hop ' in Kent (B, Fig. 104). 



336 



CANNABACE^B 



Upon opposite sides of the latter are alternate pairs of 'stipular 
bracts' (sl>) which appear to form four rows along its entire 
length. Each pair of these ' stipular bracts ' is in reality a pair 
of stipules belonging to a leaf which has not developed a blade. 
In some hops, however, notably the coarser varieties, an excess of 
nitrogenous manure leads to the monstrous development of the 
missing leaf-blades and the scaly bracts of the hop strobile appear 
interspersed with small green leaves, a pathological condition 
which is to be avoided. 




D 



FIG. 104. A, Hop strobile or female inflorescence. s& ' Stipular bract ' ; b bracteole. 

5, Axis of the strobile (the ' strig '). a The main axis j d the cymose branches of 

! axis on which the female flowers are borne ; sb point of insertion of * stipular bract ' ; 



FIG. 104.- 

, A * 
the axh 
b point where bracteoles are attached (see D). 

C, Piece of axis of the strobile showing the disposition of the ' stipular bracts ' s&, and 
the bracteoles b. 

DI Same as C, with the stipular bracts and one bracteole removed. 



In the axil of the true bract, and therefore appearing to arise 
at a point on the main axis opposite the gap between a pair of 
its stipules, is a very short cymose axis (d) upon which four 
female flowers arise. Each flower is subtended by a bracteole (b) 
whose base partially envelops the former. 

The bract-like stipules and bracteoles are popularly termed 
' petals ' by hop growers. 



THE COMMON HOP 



337 




The FEMALE FLOWER is very minute (4, Fig. 105), and pos- 
sesses a cup-shaped perianth (c) with an entire edge. The ovary 

is superior, and contains a single pen- 
dulous seed. Two long styles (s) 
are present, each covered from end 
to end with small elongated papillae. 

The FRUIT (6, Fig. 105) is oval, 
about the size of a white mustard seed, 
indehiscent, and generally described 
as a nut, although it is superior. 

The SEED possesses a curved em- 
bryo and a very small amount of 
endosperm. When the strobile or 
female inflorescence is very young 
the * bracts ' are small and scarcely 
visible except those near its base. 
The stigmas of the flowers, however, 
the hop. 's Perianth (sepal) ; st sta- are very conspicuous, and form the 

T'perianth of male flower with SO-Called ' brush ' of the hop. 

anthers of the stamens removed; the rrii i , j , i , i > 

short filaments are visible. The plants are said to be * in burr 

^^^r^^^ when the strobiles have reached this 

jMjyta., the brush ' of the flowers stage O f development. 

entire"cup?!?ke peT^ Soon afterwards the stigmas con- 

sty 5 ! e Abra C teoi e w surrounding the stituting the ' brush ' drop off, and 

ripe fruit. /The corolla ; o apex of about the same time a rap j d growth Q f 
6. The ripe fruit (a nut). the bracts takes place The stro bil e 

then begins to assume its characteristic shape of a fir-cone, and 
at this period the plant is said to be ' in hop/ 

Although the bracteoles develop to a considerable extent and 
the hop * grows out/ even when the flowers in their axils are 
unfertilised and abortive, nevertheless the largest bracteoles in 
a ' hop ' are those in whose axils fertile fruits are present : the 
fertilisation of the ovule, to a certain extent, stimulates the growth 
of the bracteole subtending the flower. 



5 6 

FIG. 105. T. Single male flower of 



338 CANNABACE^E 

The ' Lupulin '-Glands of the Hop. In the interior of a 
full-grown hop strobile are seen a large number of golden-yellow 
pollen-like grains attached to the outer surface of the bracteoles, 
especially near their bases. The perianth surrounding the fruit 
is also studded with them, and a smaller number are present 
upon the bases of the bract-like stipules. They are not met 
with upon the ordinary leaves or stems of the plant. When 
hops are shaken or knocked about these small grains are easily 
detached, and may be obtained in the form of a bright yellow 
powder sometimes spoken of as * hop-meal 7 or * lupulin' 
Among hop-growers this powder is often designated the c con- 
dition ' of the hop, and so far as a brewer is concerned the chief 
value of a sample depends upon the amount and nature of the 
' hop-meal ' present in it, all the rest of the hop, such as its 
axis, bracts, and fruits, having little more than an indirect and 
comparatively small value in the production of beer. 

In an unripe ' hop ' the ' lupulin ' particles are brilliant and 
transparent, of a golden yellow hue. As the ' hop ' ripens they 
lose their transparency, becoming opaque, and assume a pale 
sulphur or citron yellow colour. This change in transparency 
of the 'lupulin,' which is easily observed with a pocket lens, is 
the best criterion of the ripeness of a hop. In practice hops are 
generally picked unripe ; they should, however, be left until a 
Few opaque citron yellow particles are seen interspersed among 
the transparent ones on the lower bracteoles. 

When rubbed between the finger and thumb, the ' lupulin' 
feels oily, and emits a characteristic odour which, in the best 
varieties, is somewhat pleasant, while in the less valuable coarser 
kinds the odour resembles that of garlic. 

Each particle of * hop-meal ' or ' lupulin ' has the form and 
structure given in Fig. 106. It originates from a single epidermal 
cell, and at the time the 'hop* is just showing the * brush, 
appears in the form of a hollow cup supported on a very short 
stalk, consisting of two or three cells (2, Fig. 106). The cup is 



THE ' LUPULIN '-GLANDS OF THE HOP 



339 




one cell thick, and each cell possesses a thick cuticle, dense 
protoplasmic contents, and a well marked nucleus. Before the 
hop has quite assumed its cone-like shape, the cells of the cup 
begin to produce a secretion which collects within the substance 

of the upper cell-wall of each 
cell, and gradually lifts up the 
cuticle much as the skin is lifted 
up by matter in a blister. 

As more and more of the 
secretion is poured out by the 
secretory cells the hollow space 
of the cup becomes filled up with 
it, and the cuticle which covers 
the secretion as a fine thin skin 
is bulged out above the margin 
of the cup, as at Fig. c, 106. The 
outline of the cells is seen upon 
the cuticle. 

3. Fully developed gland, s Secretory . 

cells; c cuticle. The whole structure arises from 

4. Vertical section of 3. s Secretory . , . , 

cells; c cuticle; o cavity filled with resin the epidermis of the bracts, and 

and oily contents. . - P . . .. t . . 

is a form of multicellular hair. 

On account of its power to secrete it is termed a gland or 
glandular hair. The connection of each gland with the surface 
of the bract is very small and delicate only the width of one 
or two cells consequently they are readily broken off when 
touched. 

By rough treatment on the hair-floor where the hops are dried, 
and also by careless shovelling when on the ' cooling ' floor, the 
hops often become broken, and a considerable loss of these 
valuable glands takes place. For the nature of the secretion 
contained in the glands, see p. 346. 

VARIETIES. So far as names are concerned a very large number 
of varieties of hops are grown in England. Many of them, how- 
ever, exist only in name, the same variety passing under dif- 



3 4-. 

FIG. 106. Lupulin-gland of the hop 
(magnified). 

1. On very young hops in 'burr ' stage. 

2. Vertical section of i. 



340 CANNABACE^E 

ferent names in different localities or on distinct farms. Only 
a small number of distinct kinds are in existence ; they vary 
in length and colour of 'bine/ hardiness, period of ripening, 
and quality of the 'hop/ 

A Good Hop. The undermentioned points are of import- 
ance in estimating the quality of any variety of hop in a natural 
fresh state : 

(1) The yield should be good, and the plant should be 
hardy and capable of resisting the attacks of mould and aphis. 

(2) The ' lupulin '-content of the strobiles should be high ; 
the ratio of the weight of the ' lupulin ' to the weight of the rest 
of the strobile (its ' petals/ axis and fruits) should be as great as 
possible. 

(3) The aroma should be fine. It is not possible to define 
this point, but it must be observed that the best prices are only 
paid for those hops whose odour is agreeable and free from any 
smell resembling that of onions or black currant shoots. 

(4) In the best varieties the stipular bracts of the strobile 
are generally smooth and broad, while those of the. coarser 
less valuable kinds, with poor aroma, are narrow and almost 
always ribbed, appearing as if puckered or crumpled. 

(5) The stipular bracts and bracteoles in the fine varieties 
are thin and firm, and packed closely upon the axis of the 
strobile. The more ' petals ' per inch of ' strig ' or axis the 
better the 'hop/ The axis should be thin, and the fewer the 
matured fruits with seeds within them the better, as the seeds 
are said to impart an unpleasant flavour to beer. 

(6) When quite ripe the natural colour of those varieties 
which sell for the highest prices is a pale golden yellow with 
a faint tinge of orange : the less valuable early sorts are deeper 
yellow with darker greenish stipular bracts. 

In order to preserve the ' hops ' after picking they are dried 
in specially-constructed kilns, and during the drying process are 
subjected to the action of the fumes of burning sulphur (sulphur 



MID-SEASON OR MAIN CROP VARIETIES 341 



dioxide gas), which bleaches and very considerably modifies their 
natural tint : the greatest alteration, due to this treatment, takes 
place in unripe hops. The colour of English commercial 
samples is therefore unlike that of the natural hop. 

The following are the chief kinds of hops grown in this 
country : 

A. Early Varieties 
Prolific and Mtopham. 

These hops have red bines, and long coarse strobiles of poor 
quality which, when ripe, have a somewhat orange or brownish 
tinge. They yield good crops, and usually ripen in the order given. 

Early Hobbs\ An early hop resembling the Prolific, but 
smaller with a green bine. 

Henhanfs Jones. An oval medium-sized hop, thin in * petal* 
and poor in lupulin, but of good colour and aroma. This name 
is often applied incorrectly to the Meopham and 
similar coarse hops. 

Bramling. This is an early variety of good 
quality, and is the kind most extensively grown 
for early picking in the best hop districts. The 
strobile is firm and compact, of medium length, 
roundish in cross-section, and the stipular bracts 
and bracteoles are broad and rounded at the 
tip. The yield is moderate. 

White's Marly. This and the Bramling are 
the only early varieties of good quality. White's 
Early is a superior kind, exceptionally early, but ^ 
usually a poor cropper : the ' petals ' are thinner hng Hop> 
and paler than those of the Bramling, and the strobile not so 
long. The tip of the strobile is generally open and loose. 

B. Mid-Season or Main Crop Varieties 
Rodmersham or Mercer's Hop ; CobVs Hop. 

These are comparatively modern varieties of medium quality, 

hardy and good croppers. They resemble the Canterbury White- 

24 




342 CANNABACE^E 

bine hop in form and were derived from this variety. Both are 
pale in colour with thin petals. 

They are usually ready to pick after Bramlings and before the 
Canterbury Whitebines. 

Canterbury Whitebine ; Farnham Whitebine. 

These two strains of hop, grown originally in the neighbour- 
hood of Canterbury in Kent and around Farnham in Surrey 
respectively, are apparently the same variety, no differences, so 
far as botanical features are concerned, being noticeable. 

They take the first place among hops for quality and also 
yield good crops on deep rich soils. They are, however, some- 
what delicate in constitution. 

The * bine ' is pale green, often slightly mottled with red streaks. 
The strobiles are medium-sized, roundish-oval in shape, with 
smooth thinnish 'petals' which, when ripe, are a pale golden- 
yellow colour. 

The former variety has several names : it is grown on the best 
hop ground in East Kent. 

Tfo Golding. At the end of the i8th and beginning of the iQth 
century a hop known as the Golding was largely grown. It was 
stated by Marshall in 1798 to have been selected from the Canter- 
bury Whitebine hop by a Mr Golding, living near Maidstone. The 
true Golding hop is larger than the Canterbury Whitebine variety, 
and grows more singly on the * laterals ' : its flavour and lupulin- 
content are excellent. The bine is shorter than that of the 
Canterbury Whitebine, and much more spotted with red. 

At present the term Golding is often applied fraudulently to 
many inferior varieties of hops. 

Mathon or Mathon White. A variety originating or largely 
grown first in the parish of Mathon, in Worcestershire. It ranks 
practically equal in quality to the Canterbury Whitebine, which it 
much resembles in form and colour of hop. 

Cooper's White. An old Worcestershire variety very similar in 
shape, colour, and texture of * petal ' to the White's Early of Kent. 

It is less hardy than the Mathon. Both the above kinds 



LATE VARIETIES 343 

appear to be degenerating in constitution as the plants do not 
last so long as formerly. 

Fuggle's Hop. A modern variety raised about sixty years 
ago, and now largely grown throughout the country on the stiffer 
soils, where the best quality hops yield but a poor crop. 

It produces an elongated pointed * hop ' of rather large size and 
squarish in cross-section : the stipular bracts and bracteoies are 
narrow, stiff, and somewhat pointed. 

The crop is large but of medium quality. 

C. Late Varieties 

Bates' Brewer. A variety usually ripening after the Fuggle. 
The strobiles are very compact, the bracts being arranged very 
evenly and closely on the axis. Both the stipular bracts and 
the bracteoies are broad and firm with well-rounded tips, and 
resemble those of the Bramling variety in shape and texture. 

It is one of the most distinct varieties of hops, and is con- 
sidered of good or medium quality, although the flavour is 
generally somewhat inferior. In most localities the crop is 
generally small. 

Grape Hops. There are several strains of grape hops many of 
them having their strobiles closely placed on the branches in 
dense clusters like grapes, hence the name. 

The individual strobiles vary much in size in the different 
strains, but all are pointed and somewhat triangular in outline. 

In some of the examples we have examined the bracteoies are 
broadish and roundish at the tip, but usually both the stipular 
bracts and bracteoies are drawn out to a point at the tips and 
partially resemble a Fuggle hop in these particulars. 

The grape hops are a pale golden colour when ripe, but vary 
much in quality, some of the smaller strains being classed as good, 
while those producing larger strobiles are of medium quality only 

Among the grape-varieties the best quality late hops are found. 

Colgate. A very late variety, not much grown because of its 
rank objectionable aroma. The strobiles are small and a pale 



344 CANNABACE^C 

yellow or greenish colour : they hang in dense clusters like those 
of the grape varieties. The stipular bracts and bracteoles are 
narrow and pointed. 
Wild Hops. 

Bus? Hops. 

These two varieties are practically identical in shape and quality. 
The strobiles are somewhat small, roundish-oval in shape, with 
thin pointed stipular bracts and bracteoles ; when ripe the latter 
are a pale whitish straw colour. The pale colour is very charac- 
teristic of these varieties, and both are very poor in ' lupulin.' 

It is worthy of mention that the wild hop here mentioned 
is really a well-selected cultivated variety, and the seedlings often 
met with wild in hedges are usually quite different from it in 
form and size. 

CLIMATE AND SOIL. Some of the roots of the hop plant descend 
to great depths in search of water, and for the successful 
cultivation of the choicest varieties a deep porous loam rich in 
humus and containing a considerable proportion of lime is 
needful. 

When grown at all on the stiffer clay loams only the coarser 
and less delicate varieties are planted : very stiff clays and dry 
sands are, however, unsuited to the hop plant. 

Hops of the best quality are generally grown in open situations 
with a south sunny aspect, and where a free circulation of air 
is met with : they must, however, be sheltered from cold or 
violent winds. 

PLANTING. Hops are propagated by ' sets ' or ' cuttings ' 
which are obtained as a by-product when the plants are ' cut ' 
or ' dressed ' in spring. 

If the plants are allowed to grow freely, in a very few years 
the rhizomes spread over too large an area for convenient 
cultivation and training of the 'bines 1 : to prevent this and 
keep them within bounds the soil round each plant is scraped 
away in spring so as to expose the upper pans of the rhizome, 



LATE VARIETIES 



345 



after which the thickened basal portions of each of the previous 
year's ' bines ' are cut off within a quarter of an inch or less 
of the old rhizome. The latter, therefore, extends but a short 
distance each year, and the thickened pieces cut off are called 
'cuts' and are either used for the formation of * sets' for the 
propagation of the crop, or are thrown away. 

Each ' cut ' is from 4 to 6 inches long and bears upon it two 
or three opposite groups of buds (Fig. 108). 

The 'cuts' are either planted out in the 
garden at once, in which case they are known 
as ' cut sets,' or are placed in beds in a nursery 
until autumn, at which time they are removed 
to their permanent quarters in the hop-garden : 
the latter is the best and most usual practice, 
and ' cuts ' treated in this way are known as 
' bedded sets.' 

The 'sets' are planted in rows, the rows 
being from 6 to 10 feet apart, and the plants 
from 5 to 8 feet apart from each other in the 
rows. Usually they are planted at the corners 
of squares of 6 or 7 feet side. 

Hops may also be raised from ' seed ' (fruits) 
sown in autumn. About half the plants ob- 
tained in this manner are males and of no use 
to the grower; the rest female plants are 
generally of poor quality, and very rarely re- 
semble the female parent. For example, most 
of the female seedlings from the choice Canter- 




or 'cutting/ a ]?iece of bury Whitebme variety yields strobiles which 

d bine or 



old dead 1 



buds as at b. 



| are coarse and of objectionable aroma. The 
\ large preponderance of plants of very poor 
quality among seedlings is no doubt connected 
with the fact that one of the parents, namely, the male, is always 
practically a wild form, for, on account of their being of no use 



346 CANNABACE^E 

to the grower, males have never been subject to special selection 
and improvement. 

It is somewhat curious that, although female seedlings show 
considerable variation, we have never seen any morphological 
differences among males, no matter what their origin, except in 
one or two solitary instances where the fines' were a paler 
colour than usual. 

Raising from 'seed* is, however, the only way of obtaining 
new and vigorous distinct varieties, but as the practice involves a 
great deal of time, labour, and patience in the selection and 
subsequent propagation of the plant, it is rarely attempted. 
With one or two unimportant exceptions all the modern intro- 
ductions have been casual selections of individual plants which 
have shown some peculiarity different from their neighbours 
in an ordinary hop garden. 

YIELD, The hop crop is subject to very great fluctuation, 
due to adverse climatic influences and the attack of parasitic 
fungi and insects. 

Cultivation and the application of manures also very largely 
modify the yield. On some farms not more than five or six cwt. 
of dry hops is obtained even in the best seasons, while on, others 
a ton per acre is not uncommon. 

The average crop in this country for the last ten years is about 
8 cwt. of dry hops per acre. 

COMPOSITION. The secretion contained in the 'lupuhV or 
hop-glands is a complex mixture of several substances, the chief 
of which are (a) hop-oil and () resins. 

The hop-oil is an essential volatile oil, which gives the hop 
strobile its characteristic aroma ; it appears to be secreted most 
vigorously when the gland is young. 

The different aroma of the* different varieties is no doubt due 
to uninvestigated compounds present in the hop-oil. 

Of the resins three varieties have been isolated. Two of 
these, designated soft-resins, are intensely bitter, and communi- 



LATE VARIETIES 347 

cate their taste to beer; they also have antiseptic properties, 
and are said to prevent the deleterious fermentative action of the 
lactic acid and other bacteria inimical to the brewer's work, 
without affecting the action of yeast and the acetic acid bacteria. 
The third resin, possibly an oxidation product of hop-oil, is 
pleasantly bitter, with little or no antiseptic power. 

On keeping, the two soft resins lose their useful properties, 
becoming changed into hard forms. Old hops/ therefore, are 
of inferior value to the brewer. 

The volatile oil present in hops varies from '2 to *8 per cent. : 
the total resin-content is usually from 13 to 18 per cent. 

Besides the secretion of the glands the bracts and bracteoles of 
the hop strobilecontain within their cells various com pounds usually 
met with in vegetable leaf-tissue. One of the substances present 
is hop-tannin, which, with its nearly-allied phlobaphene, is no doubt 
of service in the precipitation of albuminous material from beer 
wort, although there is much difference of opinion on this point. 

Ex. 174. Make observations on hop ' sets ' and cuts ' obtained when the 
plants in a hop-garden are ' dressed ' in spring. 

Note the thick basal portion of the ' bine ' which has borne * hops' last 
season, and also the number and position of the buds upon it. 

Split one of these ' cuttings ' longitudinally, and note how far the * bine * 
has died back. 

Ex. 175. Examine which way a hop ' bine ' twines round its support. 

Observe the colour and roughness of the stem, and the shape and position 
of the leaves upon it. 

Ex. 176, Examine the structure of a full grown strobile or female inflor- 
escence of a hop. 

Note (i) the thickness and length of the ' strig ' or axis ; (2) the shape and 
relative sire of the stipular bracts and bracteoles ; and (3) the presence 
or absence of ripe fruit. 

Which bracteoles are largest, those subtending fertile fruits or those sub- 
tending abortive fruits. 

Ex. 177. Carefully slit open a. ripe fruit and set free the embryo of the 
teed ; examine the embryo for radicle and cotyledons. 

Ex. 178. Examine young strobiles 'in burr.' Make sections of it, or 
dissect so as to show the female flower and its parts, and the small stipulat 
bracts and bracteoles. 



348 CANNABACE^E 

Carefully watch the strobile from day to day in order to understand the 
change from ' burr f to ' hop.' 

Ex. 179. Examine the flower and inflorescence of a male hop plant. 

Ex. 180. On which part of the bracteoles of a strobile are the Mupulin* 
glands situated? Are any present (i) on the axis of the strobile, (2) on its 
stipular bacts, or (3) on the perianth of the female flowers? 

Ex. 181. Examine the ' lupulin '-glands with a low-power microscope. 

4. Hemp (Cannabis sativa L.). An annual dioecious plant in- 
troduced to Europe from the East. It is cultivated for its tough 
bast fibres, from which sail-cloths, sacking, and other coarse 
textile materials are prepared. 

Its fruits, popularly termed ' seeds, 1 are also used for feeding 
small cage-birds and poultry. The seeds contain from 20 to 
25 per cent, of a fatty oil, sometimes used as a substitute or 
adulterant of linseed oil. The ' oilcake ' is utilised as a manure. 
The stems of the plant, which produce many branches, are erect 
and stiff, and usually grow to a height of 5 or 6 feet. The 
bast fibres within are not so fine as those of flax, even when the 
plants are grown thickly together. 

The leaves are large and palmate, with from five to seven long 
lanceolate serrated leaflets. 

The male flowers have five-lobed perianths and five stamens ; 
they resemble those of the hop, and are borne in loose panicled 
inflorescences as in the latter plant. The female flowers are also 
very similar in structure to those of the hop, and are produced 
on separate plants usually of larger growth than those on which 
male flowers are borne. 

Sparsely scattered glandular hairs are met with on the leaves 
and stems of the plant. In the hot climates of India, Syria, -and 
elsewhere these glands secrete a volatile oil, and a resin which 
has powerful narcotic properties ; in colder climates the secretion 
is almost devoid of poisonous qualities, although the plant pos- 
sesses a peculiar stupefying odour. Hemp * succumbs to a 
moderate degree of frost, consequently when grown in this 



HEMP 349 

country for its fibre or its fruits, the 'seed* is not sown until 
the beginning of May, after the disappearance of late spring 
frosts. 

When the seedlings are established they grow very rapidly, 
but a satisfactory crop can only be obtained on deep rich loams 
and alluvial soils containing a considerable amount of humus. 

Ex. 182. Examine ordinary hemp ' seed ' ; note its form and colour ; 
dissect out and examine the embryo of the seed within. 

Ex. 183. Sow some hemp seeds in good garden soil, and make observa- 
tions on the seedlings and full grown plants. 



CHAPTER XXVI. 
POLYGONACEJE. 

i. Essential characters of the Order. Flowers small, usually 
bisexual, with a regular perianth of three to six free segments. 

Andrcecium perigynous or hypogynous, of five to eight stamens 
opposite the perianth segments. Gyngecium superior, of two or 
three united carpels, the ovary unilocular, usually triangular or 
oval in section and containing a single erect basal orthotropous 
ovule. Fruit an angular nut, usually more or less covered by 
the persistent perianth. 

Seed endospermous, the endosperm white and floury. 

The Order includes about 750 species, most of which are 
herbaceous perennials found in temperate regions. 

The stems are frequently hollow with swollen nodes. 

The leaves are alternate, simple with membranous connate 
stipules which form a tubular sheath the ochrea embracing the 
lower part of the inter nodes. 

The roots are often astringent, due to the presence of tannic 
and gallic acids, and in many plants the leaves contain con- 
siderable amounts of oxalic acid or acid oxalates. 

Important genera are Rheum (Rhubarbs), Rumex (Docks and 
Sorrels), Fagopyrum (Buckwheats), and Pofygonum> a large genus 
from which the Order takes its name. 

2. The genus Polygonum has small, bisexual flowers in 
racemes or spiked clusters. 

The perianth is five-partite, stamens five to eight, styles two 
or three, fruit a triangular or oval nut. 

Two common annual weeds belonging to the genus are 

850 



COMMON BUCKWHEAT 351 

Black-bindweed (P. Convolvulus L.) (p. 609) and Knot-grass 
(P. aviculare L.) (p. 609). 

3. The genus Ritmex has small unisexual or bisexual flowers, 
generally arranged in long panided or racemed whorls. 

The perianth is six-partite in two whorls, the three inner 
segments enlarged when the fruit is formed; stamens six, in 
pairs ; styles three, filliform ; the fruit a triangular shining nut, 
enclosed by the enlarged inner segments of the perianth. Im- 
portant weeds are the Docks (p. 608) and Sorrel (p. 618). 

4. To the genus Fagopyrum belong two cultivated species, 
viz. : 

(1) Common Buckwheat (Fagopyrum sagittatum Gilib.). 

(2) Tartarian Buckwheat (Fagopyrum tataricum Gaert). 
The name Buckwheat means ' Beech '-wfieat, the ' seeds ' of 

the plant resembling in miniature the seeds of the Beech tree, 
the German name for which is * Buche/ 

(i) Common Buckwheat or Brank (Fagopyrum sagittatum 
Gilib. = F. esculentum Moench. or Polygonum Fago- 
pyrum L.). 

Common Buckwheat appears to be derived from Fagopyrum 
cymosum Meiss., a wild species found in India, Manchuria, and 
the adjacent regions north of the latter country ; it was intro- 
duced into Europe in the Middle Ages. 

The plant is popularly included among grain crops, but it is 
not a true cereal and in no way related to wheat. 

Its 'seeds' yield a white flour used extensively in many 
parts of Central and Eastern Europe, various countries of Asia, 
and in North America, for human food. Though deficient in 
gluten and unsuited for bread-making, the flour makes excellent 
easily digested cakes and porridge. Buckwheat meal is also 
useful, in moderate quantities, as food for horses, cattle and pigs, 
and the whole grain is largely employed in the feeding of 
poultry and game birds. 

The green crop can be fed in small amounts to cattle and 



352 POLYGONACE^E 

sheep, although in larger quantity it is liable to produce vertigo 
and other illness. Mixed with peas and vetches it may be used 
as green food for dairy stock, equal parts of seed of the three 
plants being sown broadcast. 

Its chief use in a green state is for ploughing in as manure 
before a wheat crop. 

Bees are able to obtain considerable amount of honey from 
the flowering crop. 

ROOT. The root system consists of a tap root and numerous 
short laterals, which do not spread far or deeply into the 
ground. 

STEM. The stem has few branches and is upright, from i to 3 
feet high, hollow, angular, and more or less downy, with swollen 
nodes. 

LEAVES. The leaves are alternate, the upper ones almost 
sessile, the lower ones with petioles up to 4 inches long ; the 
blades are hastate or cordate triangular, acute, 2 to 4 inches 
long, with hairs on the veins beneath. The stipules are short. 

INFLORESCENCE AND FLOWERS. The inflorescences consist of 
axillary and terminal cymes with more or less densely clustered 
flowers. 

The perianth is five-partite, usually pink or pinkish white, not 
enlarged in fruit. The stamens are eight ; alternating with them 
at their bases are a similar number of rounded yellow glands, 
which secrete honey. The ovary is triangular, one-celled, and 
contains a single erect ovule ; the style is tri-partite, each part 
with a knob-like stigma. 

The flowers are dimorphic. Some of the plants bear flowers, 
the stamens of which are short and the styles about one-third 
longer ; in others the stamens have long filaments which project 
some distance above the stigmas of the short styles. 

Pollination is chiefly carried on by bees and other insect 
visitors, and crossing between the long and short-styled plants 
is probably most frequent : pollination, however, between 



COMMON BUCKWHEAT 353 

flowers of the same structure as well as self-pollination are also 
possible. 

FRUIT. The fruit of the Common Buckwheat is a three- 
angled ovate nut about 6 mm. long and 3 mm. broad, at the base 
of which some of the dry perianth remains (Fig. io8a). The faces 




FIG. io8a. t. Fruit or 'grain' of Common Buckwheat, a. Cross 
section of i showing section of cotyledons (S-shape) surrounded by 
endosperm. 3 Fruit of Tartarian Buckwheat. 4. Cross section of 3. 

are glabrous, somewhat polished, generally slightly convex, and 
the angles of the fruit more or less acutely keeled. The colour 
is brown or grey marbled with darker spots and lines. 

SEED. The seed has a pale brown testa and is triangular like 
the fruit and free within it. The endosperm, which is white and 
opaque, contains much starch in the form of round or polygonal 
grains. 

The embryo is embedded in the centre of the endosperm, 
and possesses two thin, broad cotyledons which in transverse 
sections of the fruit are seen folded in the form of an S. 
(Fig/ ioa). 

VARIETIES. There are several varieties of Common Buck- 
wheat, differing chiefly in height, branching habit, and colour of 
the stems, as well as in size and colour of the grain ; the chief of 
these are : 

(a) Common Buckwheat with brown or greyish brown fruits. 



354 POLYGON ACE^ 

(b) Silver Grey Scotch or Silver Hull Buckwheat, a shorter, 
somewhat more hardy, and more branched form with small ashy 
grey fruits. 

(c) Japanese Buckwheat, a tall, green-stemmed, late variety, 
with large dark brown fruits, the angles of which are acute and 
extended almost into the form qf wings. (For size and weight 
of fruits, see p. 667). 

CLIMATE AND SOIL. Buckwheat succeeds best in a mode- 
rately cool, moist climate ; continued drought, especially when 
the plant is in bloom, reduces the yield of seed. It is a delicate 
plant, very easily damaged by two or three degrees of frost, 
but on account of its rapid growth may be ^rown in countries 
where the winter is severe if sowing is delayed until the early 
summer. 

It gives a useful yield on poor land, and is specially 
adapted for growth on sandy loams and acid soils where few 
other crops succeed ; on stiff clays it does not thrive. Heavy 
doses of manure are detrimental, as they lead to the lodging of 
the crop. 

SOWING. When a crop of grain is the object, the seed is sown 
at the end of May or early in June, after all likelihood of frost 
is past, the most suitable temperature for germination being 
about 60 F. 

It may be sown broadcast, or in drills 12 to 15 inches apart, at 
the rate of i bushel when drilled up to 3 bushels per acre when 
broadcasting is adopted, the seed being covered by i to 2 inches 
of soil. . For ploughing in as green manure the seed should 
be broadcasted at the rate of 2 to 2^ bushels per acre in June or 
July, the plants being turned in when they are beginning to 
bloom. 

HARVESTING AND YIELD. The seeds ripen very unevenly, 
the upper parts of the inflorescence continuing to bloom after the 
seed is ripe on the lower portions. The crop is ready for har- 
vesting when the seeds on the lower part of the plant are ripe 



COMMON BUCKWHEAT 355 

at the end of August or early in September, 12 to 14 weeks after 
sowing. 

The average yield of grain is about 24 bushels, but under 
favourable climatic conditions on good soils, a return of 40 to 
50 bushels per acre is sometimes obtained. 

Since many of the stems and leaves are still green, when the 
crop is cut it is difficult to harvest except in seasons when there 
is a succession of not less than 10 to 15 dry hot days, and as 
the seeds shed easily careful handling is necessary. 

COMPOSITION. The pericarp forms about 40 to 43 per cent, 
and the true seed 57 to 60 per cent, of the fruit or 'grain.* 

According to Wolff, Buckwheat ' grains ' have the following 
composition : Water 13 to 14 per cent., carbohydrates 58 to 59 
per cent,, proteins 10 per cent, and fibre 15 per cent. The 
haulm is used for litter, and sometimes for fodder, but it is 
coarse and of poor quality; it contains about 10 per cent, of 
water, 4 per cent, proteins, 46 per cent, fibre, and 33 per cent, 
carbohydrates. 

(2) Tartarian Buckwheat (Fagopyrum tataricum Gaert). 

Cultivated largely in India and other parts of Eastern Asia, as 
well as in Europe and North America in lesser degree ; it is a 
more hardy and coarser plant than Common Buckwheat, with 
taller stems (2 to 3 feet high), which are usually green and less 
branched. The leaves are similar in shape to those of Common 
Buckwheat, but smaller. 

The flowers are white, in small clusters. The fruit is ovoid, 
conical with more or less wavy outline, brownish grey in colour, 
with dull irregular faces, on each of which is a deep furrow ; the 
angles of the fruit are rounded except near the tip, where they 
are slightly keeled (Fig. io8a). 

One variety of this species (var. himalaica Batalin) has small 
grey dehiscent fruits, the seeds of which are exposed when 
ripe. 



CHAPTER XXVII. 
CHENOPODIAOEJE, 

i. General characters of the Order. Flowers small, regular ; 
hypogynous, except in the genus Beta, which has epigynous 
flowers. Perianth green, five partite, persistent Andrcecium 
of five stamens opposite to the perianth segments. Gynaecium 
with a one-celled ovary containing a single ovule. Fruit usually 
a nut, more or less enclosed by the perianth, which is mem- 
branous, fleshy or woody. Seed endospermous with a curved 
embryo. 

The plants of this Order are generally herbaceous, with simple, 
entire exstipulate leaves. The latter are often fleshy, and in 
some genera appear covered with a whitish powder or meal. 

This appearance is due to short hairs which grow from the 
epidermis, each hair consisting of a stalk of one or two cells, 
terminated by a large round or star-shaped cell containing clear 
watery cell-sap. 

Most representatives of the Chenopodiaceae are met with near 
the sea and on the shores and marshes surrounding inland salt 
lakes. 

Many weeds belonging to the Order are specially luxuriant 
upon well-manured ground and on waste places where urine and 
faecal matter have been deposited. The whole Order seems 
specially adapted to exist in soils much impregnated with* 
common salt, nitrates of sodium and potassium, and similar 
compounds, and the application of common salt to the mangel 
and beet crop usually improves the yield. 

The genera belonging to it which need special mention are 

356 



SEA-BEET 357 

Chenopodium (Goose-foot or Fat Hen), Atriplex (the Oraches), 
and Beta (Beet and Mangel). 

The genus Chenopodium includes a number of annual species 
widely distributed on waste ground, and often prevalent as weeds 
upon well-manured arable land. They are all very variable 
plants and difficult to distinguish from each other. Perhaps 
the commonest species is White Goose-foot or Fat Hen (C. 
album L.) (see p. 608). 

Good King Henry or All-good (C. Bonus-Henricus L.) is a 
perennial species sometimes used instead of spinach as a pot- 
herb, and frequently found on waste ground near villages. 

The genus A triplex embraces a number of variable species, 
most of which somewhat resemble the Goose-foot in outward 
appearance. They are however monoecious (see p. 608). 

To the genus Beta belong wild sea-beet, and the cultivated 
garden and field beets. 

2. Sea-Beet (Beta maritima L.) is a perennial plant common 
on muddy sea shores. The root is tough, moderately thick, and 
fleshy. The angular stems, which are many and branched, are 
prostrate below, but their tips curve upwards to a height of 
i or 2 feet. The lower leaves are smooth, about 3 or 4 
inches long, fleshy, ovate-triangular, and the blade narrowed into 
the broad petiole ; the upper ones smaller and lanceolate. The 
inflorescence, flowers, and fruit resemble those of the mangel 
described below. 

3. A large number of cultivated forms of beet are known, some 
of which are grown chiefly in gardens, and used as a vegetable 
for human consumption, while others, such as mangels and 
sugar-beet, are cultivated on the farm. They vary much in the 
colour and sugar content of their so-called fleshy * roots, 1 and also 
in their resistance to frost. The shape and amount of the ' root ' 
which appears above the soil is also subject to variation. All 
the forms appear to be merely varieties of one species, which has 
been named Common Beet (Beta vulgaris L.) They differ from 

25 



358 



CHENOPODIACE^B 



the wild sea-beet of our coasts (B. maritima L.) in being 
biennial in habit and in having straighter upright flowering 
stems, and a more well-defined uniform tap root. These 
cultivated forms most probably originated from a variety grow- 
ing wild on the western coasts of the Mediterranean and on 
the Canary Isles, and known as B. vulgaris L., var. maritima 
Koch. Whether this plant is really distinct, or is itself a variety 
of Beta maritima L., is not certain. 

Of the garden forms little can here be said. Their roots are 
mostly of conical or napiform shape, with deep crimson tender 





0) 

FIG. 109. i. Mangel 'seed' (fruit) germinating, a Primary roots 
from two separate^embryos. 

2. True seed separated from x. 

3. Longitudinal section of 2. a Root ; b cotyledons ; c hypocotyl ; 
x endosperm. 

flesh, which is rich in sugar. A variety known as Chard Beet 
(B. vulgaris L., var. Cicla L.) is sometimes cultivated for the 
broad pale fleshy midribs of its leaves, which are cooked and 
eaten like sea-kale. 

4. Mangel Wurzel or Field Beet. Mangel Wurzel is the Ger- 
man for 'Root of Scarcity] by which phrase this plant was 
known about the time of its introduction into England as a 
field crop about 100 years ago. 

This appellation appears to have arisen from the fact that 
it often produces a great crop when other plants fail. It 



MANGEL WURZEL OR FIELD BEET 359 

equally deserves the name from the fact that it keeps well until 
late spring and early summer, when turnips and swedes have 
been consumed and grass and other forage crops are scarce. 
SEED AND GERMINATION. The parts known in commerce as 
mangel * seeds' are in reality fruits, two or three of which are 
often joined together. Each fruit contains a single endosper- 
mous seed. 




FIG. no. 4, Seedling mangel; 5 and 6. Older examples of the same, a Root; coty- 
ledons ; c hypocotyl ; d first foliage-leaves of plumule. 

The seed is kidney- shaped, about the size of a turnip seed, 
with a dark smooth testa. Just within the latter lies the 
embryo, which is curved round the central endosperm. Dur- 
ing germination the cotyledons absorb the endosperm and 
remain within the seed-coat some time after the root has made 



36o 



CHENOPODIACE^E 



its exit (3, Fig. 109). Eventually the cotyledons become free from 
the seed and appear above ground. The young plant possesses 
two narrow cotyledons, a well-marked hypocotyl, and a primary 
root, which is quite distinct from the latter (4, Fig. no). 

ROOTS AND HYPOCOTYL. The primary root is well-developed, 
and secondary roots arise upon it in two longitudinal rows 
(6, Fig. no). The total root-system is very extensive and often 
penetrates to great depths in suitable 
soil. It is not infrequent to find drains 
4 and 5 feet below the surface of the soil 
blocked by them. In the subsequent 
growth of the plant the hypocotyl be- 
comes pulled more or less into the ground 
by the contraction of the roots, but the 
hypocotyl and root always remain more 
or less distinct ; the former rarely bears 
any adventitious roots. 

The ' mangel ' of the farm, which is 
generally termed a 'root,' consists of 
thickened hypocotyl and true root; the 
relative proportion of each part is not 
however, the same in all varieties. In 
the long-red and ox-horn varieties the 
hypocotyl grows out of the ground; in 
others, such as the sugar-beet, the hypo- 
cotyl is shorter and pulled beneath the 
surface of the soil. 

A collection of leaves is seen at the 
apex of the mangel, and just below them R * c : Ti^ 
are the remains of the old leaf-bases, whcre cot y ledon was present 
which give to this part a rough rugged appearance (Fig. 114). 

A transverse section (Fig. 112) shows a series of concentric 
rings of firm vascular tissue alternating with rings of soft thin- 
walled parenchymateus bast; the cell-sap of the parenchyma, 




MANGEL WURZEL OR FIELD BEET 361 



midway between the vascular rings, often has a crimson or yellow 
tint. In white-fleshed varieties the cell-sap is clear, and these 
parenchymatous zones are translucent when thin slices are held 
up to the light. The vascular rings consist of isolated strands 
or groups of vessels with thin-walled parenchymatous medullary 
rays between. 

It is outside the scope of the present work to deal with the 
complex growth in thickness of the root and hypocotyl of the 
mangel ; but it may be mentioned that each ring of vascular 
strands, with the medullary rays between and the corresponding 
zone of thin- walled bast, is the 
product of a separate cambium 
tissue. 

The individual cambium-rings 
arise in the pericyle of the root in 
rapid regular succession from the 
centre outwards. 

Sooner or later the cell-division 
of the inner ones ceases, but the 
exact length of time during which 
r 





FIG. us. i Transverse section of mangel 4 root. 1 

2. Longitudinal sect ion. ^ r Lateral roots ; a ring of vascular bundles ; b thin-walled 
parenchyma (chiefly bait-tissue). 

each cambium-ring remains active is not certain. In ordinary 
varieties usually six or seven cambium-rings complete their 



362 CHENOPODIACE/E 

growth in the six months during which the mangel is growing 
in this country. 

Sometimes it is assumed that mangels with yellowish zones of 
parenchyma, such as is present in the Golden Tankard variety, are 
richer than those with quite white flesh. This, however, is an 
error, as very frequently white-fleshed varieties, e.g. most sugar- 
beets, are much richer than those with yellow or crimson flesh. 
There appears to be no direct connection between the colour of 
the ' flesh ' and sugar-content. 

The .sugar is not evenly distributed in the tissues of the 
mangel, the rough * neck ' contains much less than the rest of the 
' root.' Moreover, the greatest amount of sugar is present in the 
cell-sap of the parenchyma lying close to the vascular ring, the cells 
in the middle of the zone of parenchyma between two successive 
rings of vascular tissue being comparatively poor in this sub- 
stance. The richest mangels are therefore those in which the 
vascular rings are most closely placed together, and in which the 
parenchyma, poor in sugar, is consequently reduced to a minimum. 
For 'roots ' of the same diameter the best kind are those which 
have the greatest number of vascular rings. 

INFLORESCENCE. During the first year the mangel usually 
stores up reserve-food in its hypocotyl and root, and the stem 
above the cotyledons remains short and bears a number of leaves 
in a close rosette. 

In the following year the terminal bud and axillary buds of 
this very short stem send up strong leafy angular stems which 
rise to a height of 3 feet or more, and these and their branches 
terminate in inflorescences. 

The inflorescence consists of an elongated axis upon which at 
short intervals the flowers are arranged in dense sessile clusters, 
each containing from two to seven flowers (A, Fig 113) ; below 
each cluster is a small bract. 

THE FLOWER (B> Fig. 113) is epigynous and about \ of an 
inch in diameter. It is bisexual and possesses a small green 



MANGEL WURZEL OR FIELD BEET 363 



five-leaved perianth, the lower part of which is united with the 
fleshy receptacle. The androecium consists of five stamens 
opposite to the perianth. 

The ovary of the gynaectlim is 
sunk partially in the fleshy 
receptacle and contains a single 
ovule (C, Fig. 113). 

The flowers of the mangel and 
beet are protandrous, and flowers 
' set ' no fruit if specially isolated 
or prevented from receiving pollen 
from neighbouring flowers. Cross- 
pollination appears to be effected 
by the agency of small insects and 
the wind. 

THE FRUIT. After fertilisation 
the fleshy receptacle and base of 
mon of the inflores- the perianth of each flower enlarge 
c Toneo P Tn an a g n e done closed flower of considerably and the separate 
mang , e , l< . , e a ^ I flowers in each cluster become 

C, Vertical section of a flower, o Ovule. 

z>, Cluster of two fruits developed from m ore or less firmly united with 

flowers of B. Such clusters constitute / 

commercial mangel 'seeds.' each Other (Z>, Fig. 113). The 

fleshy parts with the imbedded ovaries eventually turn hard and 
woody, and the clusters of spurious fruits finally fall off or are 
thrashed off the long axis of the inflorescence and come into 
the market as ' seeds.' 

The latter are in reality collections of two or more spurious 
fruits. Each spurious fruit consists of the hardened receptacle 
and perianth with the ripened gynaecium containing a single 
seed, and as several of these fruits may be present in each 
commercial c seed ' it will be readily understood that when one 
of the latter is sown several seedlings may spring from it. 
This peculiarity necessitates the separate hand thinning of a 
young crop of mangels, otherwise by growing so closely together 




364 CHENOPODIACE^ 

the seedlings injure each other and produce deformed and 
small * roots/ 

The true seed is very small, a fact which must be taken into 
consideration when sowing is contemplated as it is readily buried 
too deeply for proper germination. 

VARIETIES. Mangels may be conveniently divided according 
to their shape and the colour of the skin of the parts below 
ground. Usually the petiole and main veins of the leaves 
resemble the skin of the ' root ' in tint, and there is frequently a 
tendency for the parenchymatous zones or soft rings of the flesh 
to be similarly coloured. 

Much variation, however, exists in the colour of the skin and 
flesh, few crops proving quite ' true ' in these respects. The best 
varieties, especially the Golden Tankard, are most subject to 
reversion, and need constant attention on the part of the seeds- 
man to keep the strain ' true.' 

A good mangel should yield a heavy crop, and the feeding 
quality should be as great as possible. Besides these points it 
is of importance to note the depth to which it grows in the soil, 
as the expense of lifting a deeply-seated crop may materially 
reduce its usefulness from the farmer's point of view. 

It must, however, be borne in mind that, so far as composi- 
tion is concerned, mangels with ' roots ' below the ground are 
richer in sugar and of better feeding-value than those with 
* roots ' above ground. 

The continuation of the tap root should be single and small ; 
those with * fanged/ thick secondary roots are more difficult to 
pull and clean, and generally of a coarse and fibrous nature. The 
' neck ' or rough upper part of the mangel should be as small as 
possible, and its flesh firm and solid, with no tendency to spongi- 
ness in the centre. 

The variety should be as ' true ' as possible, so far as its shape 
and colour of skin is concerned, and its keeping qualities should 
be good. 



OX-HORN VARIETIES 



A common fault with some strains is their inclination to ' bolt ' 
or behave as annuals, and produce an inflorescence the first 
season without forming a thickened ' root.' 

Long Varieties. In these the c roots ' are three or four times 
as long as they are broad (A, Fig. 114), and are generally about 





FIG. 114. Chief forms of mangel 'roots.' A, Long. , Inter- 
mediate. C, Tankard. D t Globe. 



a half or two-thirds above the soil. These varieties give the 
greatest yield per acre of any kind of mangel, and are suited to 
deep soils, especially clays and loams. They are divided into 
(i) long red and (2) long yellow varieties, according as the skin 
is red or yellow. 

The long yellow kinds are somewhat superior in quality to the 
long red ones, but both are coarse and fibrous, and of lower 
feeding value than most of the varieties mentioned below. 

Ox-horn Varieties. These are very closely allied to the 
long red and long yellow varieties, but their * roots ' assume 
a twisted horn-like shape. The part below ground does not 
descend below the depth of the plough furrow : they are therefore 
suited to shallower soils; but their irregular growth makes it 



366 CHENOPODIACE^E 

difficult or impossible to cultivate between the rows. The quality 
is not good, but the yield is large. 

Intermediate or ' Gatepost ' Varieties. These have large 
oval roots (2?, Fig. 1 1 4), somewhat intermediate between the long 
and globe varieties. They may be either red, yellow, or orange 
in colour of skin, and are suited to comparatively shallow soils. 

Tankard Varieties. The typical shape of these resembles 
C, Fig. 114. Two kinds are grown, namely, Golden Tankard, with 
orange coloured skin, and flesh with yellow zones ; and Crimson 
Tankard, in which the skin is crimson or rose colour, and the 
flesh with crimson rings. 

All tankard varieties have small ' roots/ and give small crops, 
unless grown somewhat closely in the rows. 

The nutritious quality of the Golden Tankard, however, sur- 
passes that of all other varieties of mangel 

Globe Varieties. In these the * roots * are spherical or nearly 
so, and by far the larger part of each grows above ground 
(Z>, Fig. 1 14). They are especially suited to the light and shallower 
classes of soils, where they may be made to produce an excel- 
lent crop, which is readily lifted or pulled from the soil. Per- 
haps the commonest form is the Yellow Globe, the nutritive 
value of which ranks second to the Golden Tankard. Red and 
orange varieties are also grown. 

CLIMATE AND SOIL. The mangel requires a warm, dry 
climate, that of the south of England being much more suited 
to its growth than the north. The most satisfactory soils are 
deep clays and loams, especially for the long varieties, but 
lighter soils, except those of loose sandy character, produce good 
crops of Globes and Tankards. 

SOWING. The ' seed ' is generally sown between the middle 
of April and the beginning of May in drills 27 inches apart 
for the Globe and Tankard, and 2 1 to 24 inches apart for the 
longer varieties. It requires a somewhat high temperature to 
germinate satisfactorily, and it should not be drilled at a greater 



GLOBE VARIETIES 367 

depth than f of an inch below the surface, for, although the so- 
called ' seed ' is of some considerable size, the true seed is small, 
and has little power to make its way upward if buried too deeply. 
The amount of ' seed ' used is from 6 to 8 Ibs. per acre. The 
young plants are subsequently * singled' so as to leave from 10 
to 14 inches between each plant in the row, the smaller distances 
being adapted for the long varieties, especially if smaller and 
relatively more nutritious ' roots ' are desired. 

YIELD. The average yield of ' roots' per acre is about 18 to 
25 tons. 

COMPOSITION. Cane-sugar is one of the chief ingredients in 
the mangel. The amount varies from 3 or 4 per cent, in the 
large long red varieties to about 7 or 8 per cent, in the Golden 
Tankard and well-grown Globes. 

The water-content varies from 86 per cent, in the best kinds to 
92 in the poorer varieties. Usually they are much superior in 
composition to turnips, but in damp, cold seasons large roots 
may be as watery as white turnips. 

Mangels cannot be fed to stock immediately after being re- 
moved from the land in autumn, as they contain some ingredient 
which produces ' scouring ' in animals ; what the substance is 
which is responsible for this effect is not clear ; possibly it is 
a nitrate or oxalate. Nitrates are present in considerable 
abundance in autumn, but these compounds gradually diminish 
in amount if the mangels are kept till spring. The injurious 
substance, whatever it is, disappears to a large extent on keeping, 
the yellow-skinned varieties are generally ready to feed to stock 
before the red ones. 

The nitrogenous substances in mangels average about 1*2 per 
cent, of which a little less than half are albuminoids. Several 
distinct amides are generally present, especially when the 
4 roots * are not ripe. The fibre averages about "9 per cent. 

5. Sugar-Beet. The name sugar-beet is given to selected varie- 
ties of mangel which are specially grown for their sugar<ontent 



368 



CHENOPODIACE^E 



The mangel first selected for improvement was a White 
Silesian variety (Fig. 115, A\ which may be considered as the 
parent of all the chief varieties now grown. 

Sugar-beets are comparatively small, the best weighing about 
i J to 2 \ Ibs., and of conical or elongated pear shape. Unlike the 
ordinary mangels the sugar-beets have their thickened 'roots 1 
entirely buried in the soil, those with large ' necks ' above 
ground being less valuable in many ways and poorer in sugar. 






FIG. 115. Chief forms of sugar-beet. 

A, White Silesian Beet or Mangel. 

P, Knauer's Imperial and Klein-Wanzlebener. 

C t Vilmorin's Improved. 

The * roots ' should not be ' fanged,' and in good varieties 
the skin is white, and the flesh firm and white, with a large 
number of close concentric rings of vascular bundles. Beets 
with upright leaves and long petioles are always less rich in sugar 
than those with leaves which lie close to the ground and have 
shorter petioles. 

The chief forms are exhibited in the varieties mentioned 
below : 

Vilmorin's Improved. The ' root ' is conical in shape (Fig. 



SUGAR-BEET 369 

115, Q, and the leaves spread out as a flattish rosette on the 
ground when ripe. 

Knauerti Imperial (Fig. 115, .#).- A pear-shaped variety, 
usually with white flesh sometimes inclined to a roseate hue. 
The leaves, which have reddish veins, grow more upright than in 
the former variety and have somewhat crenated and puckered 
margins. 

Klein-Wanzlebener. A variety resembling the preceding one 
but with more spindle-shaped root and green leaves. 

CLIMATE AND SOIL. Sugar-beet thrives best in a climate 
possessing a warm and moderately damp summer, and having 
somewhat dry, hot months of August and September, during 
which time the sugar is stored in the root in greatest abundance. 

Climates such as are met with in Southern Europe are too dry 
and the North is too wet for satisfactory sugar production by 
sugar-beet. In wet climates the roots are poor in sugar. 

Average seasons in the British Isles are probably too damp 
for successful cultivation of this crop, although fair yields of 
roots with good sugar-content have been grown for experi- 
mental purposes during the last two or three somewhat dry 
seasons. 

The soil most suited to the crop is a medium loam of good 
depth containing a considerable proportion of lime. 

Heavy wet clays or very dry sandy soils are not suitable. If 
farmyard dung is used as manure it is essential that it should 
be ploughed in during autumn or applied to a previous crop. 
The quality of. the roots is much influenced by a good supply 
of potash salts especially the carbonate; phosphates are also 
beneficial and the yield is increased by an application of nitrate 
of soda or ammonium sulphate applied in the early stages of 
growth of the plant. 

SOWING. The seed is drilled or dibbled in rows about 14 or 
15 inches apart and the plants are subsequently singled by hand 
when about a quarter of an inch thick, so as to stand 6 to 8 



370 CHENOPODIACE./B 

inches asunder in the row. As the young plants are very 
susceptible to frost the seed should not be sown before about 
the middle of April or the beginning of May. The amount 
of seed necessary to drill an acre is about 30 Ibs. : it is usually 
soaked in water for 24 hours before sowing, and should not be 
buried more than an inch deep. 

HARVESTING. The vegetative period necessary for the satis- 
factory production of a 'ripe* root is from 140 to 150 days in 
England, so that if sown at the proper time the crop is usually 
ready to be harvested from about the middle to the end of 
September, at which time the roots are dug up with a narrow 
spade or a two-pronged fork. 

YIELD. The yield is usually from 12 to 16 tons per acre. 

COMPOSITION. The water-content of a sugar beet is about 
82 per cent. The amount of cane sugar present averages 15 
or 16 per cent, in good varieties; the woody fibre about 1.3 
per cent. 

Ex. 184. Germinate some mangel 'seeds* in damp sand. Find out how 
the root escapes from the fruit. 

Carefully extract some of the true seeds with a strong needle or a knife, 
and cut sections to show the curved cotyledons and endosperm. 

Ex. 185. Examine seedling mangel plants in various stages of development, 
paying special attention to the primary root, hypocotyl, and secondary roots. 

Ex. 186. Cut transverse and longitudinal sections of a full grown mangel 
'root. 1 Note the distribution of the vascular tissue and soft parenchyma. 
Observe which parts are coloured pink, crimson, or yellow, and which are 
white. 

Ex. 187. Cut transverse sections and count the 'rings* in large and 
small mangel * roots ' from the same crop. Note if the difference in total 
diameter of the ' roots ' is due to greater width of each ring or to a greater 
number of rings in the larger specimens. 

Ex. 188. Examine and describe the stem, leaves, and flower of a * bolted * 
mangel or a normal second year plant. 

Ex. 189. Examine a number of commercial mangel ' seeds.' Observe the 
shrivelled tips of the perianths, and find out the number of true fruits in each 
so-called 'seed.' 

Ex. 190. The student should become acquainted with the chief character! 
of the common species of Chtnopodium and A triplex. 



CHAPTER XXVIII. 
CRUCIFERJE. 

i. General characters of the Order. Flowers (Fig. 116, A), 
regular, hypogynous. Calyx polysepalous, four sepals in two 
t t whorls, deciduous; corolla 

^ polypetalous, four petals in 
one whorl : andrcecium of six 
stamens in two whorls, tetra- 
dynamouS) that is, four sta- 
mens with long filaments, and 
two with short ones. (Fig. 
1 1 6, B\ Gynsecium (Fig. 




FIG. 116. A, Flower of turnip. ^5,The.same, 
after stripping off the calyx and corolla, 



^ f\ cvnrnrnnn*; twn rnr 
, O > C / SyncarpOUS, tWO Car 

showing the androecium and gynaecium. s Two pe l s . the OVUleS are arranged 

short stamens; / four long stamens; st stigma * 

of gynatcium; n nectary. C, Gynaecium. o Its O n tWO parietal placentas J the 
ovary ; b style; st stigma. f f 

ovary is sometimes unilocular, 

but more frequently divided into two compartments by a * false ' 
partition, which is an outgrowth from the placentas. 

Fruit, usually a dehiscent silique or silicula (see Raphanus, p. 
392), seeds without endosperm or with only traces of it. When 
placed in water the cuticle of the testa of the seeds from the 
dehiscent fruits generally swells up into a slimy sticky substance, 
which fixes the seed to the ground, tends to store up water dur- 
ing germination, and also aids in the distribution of the seeds. 
Situated on the receptacle, generally at the base of each of the 
two short stamens, are greenish nectaries. 

Pollination is chiefly brought about by insects. The anthers 
are so placed in regard to the stigmas and nectaries, that insects 

871 



372 CRUCIFER^C 

frequently effect cross-fertilisation when searching for honey. Self- 
fertilisation is however common, and productive of good seed. 

The Order comprises about 1200 species, mostly of herbaceous 
or slightly shrubby character ; practically all are non-poisonous 
and extensively represented in temperate and cold regions. 

The inflorescences are usually simple racemes without bracts 
or bracteoles. 

Many plants belonging to the Cruciferae, such as cabbage, kohl- 
rabi, turnip, swede, rape, and white mustard, are very valuable 
to the farmer. 

Acrid, pungent compounds are present in various parts of 
mustard, charlock, radish, and many other cruciferous plants. 

Instead of starch being stored as reserve food-material for 
the young plants, the tissues of the embryos of nearly all the 
Cruciferae contain considerable quantities of oil. 

The seeds of several species belonging to the genus Brassica 
furnish oil which is sold under the name of Colza oil or Rape oil. 

A number of plants, such as charlock, wild radish, shepherd's- 
purse, Jack-by-the-hedge, and hedge mustard, belonging to the 
order are common weeds of the farm, while others, such as 
the wallflower, stock, and candy-tuft, are ornamental plants 
of the garden. 

So far as the fanner is concerned, the most important genus 
of the Cruciferae is the genus Brassica, which includes the turnip, 
swede, rape, and the cabbage and its varieties : some botanists 
include black mustard, white mustard, and charlock in it, while 
others place these plants in a separate genus, Sinapis: the 
former plan is adopted here. 

2. Wild Cabbage (Brassica oleracea L.). This plant, which is 
the parent of all the cultivated forms, grows on the sea cliffs in 
the south of England and various pans of northern Europe. 
It is a biennial, or perennial with a stout erect stem from i to a 
feet high. The lower large, broad leaves, are obovate with 
lobed margins, smooth, and of ashy green hue. The upper 



CULTIVATED CABBAGE 373 

leaves are smaller and sessile. The flowers are pale yellow, 
often an inch in diameter, arranged in long racemes. 

The siliques are smooth, about 2 or 3 inches long, and stand 
out from the main axis of the inflorescence. 

3. Cultivated Cabbage, and its varieties (Brassica oleracta L.). 
Few plants have given rise to so many fixed varieties or races 
as the cabbage. Almost every part of its structure, except the 
root and seeds, has been modified by man for his own use. 

The seeds of all the varieties are so similar that they cannot 
be distinguished from each other with certainty (p. 647). The 
young seedlings also present great similarity, and have two 
notched cotyledons, similar to those of the turnip in Fig. 117 j 
the first foliage-leaves are quite smooth and of glaucous tint 

In all the forms of cultivated cabbage the inflorescence, 
flowers, fruit, and seeds are similar to those of the wild cabbage 
mentioned above : it is in the growth of the vegetative parts 
and the young inflorescences that the most striking variations 
are seen. 

All the cultivated forms are biennial and fall into several groups, 
namely : 

i. Brassica olcracea L., form accphala. 

The terminal and axillary buds of the varieties in this group 
grow out into leafy shoots in the first season, and therefore give 
rise to an elongated stem and branches bearing a considerable 
number of green foliage-leaves for which these plants are grown. 
These varieties most nearly resemble the wild cabbage : repre- 
sentatives are the Borecoles, especially Scotch kail, and Thousand- 
headed-kail. 

ii. Brassica oleracea L., form gemmifcra. 

This form resembles the preceding one in possessing an erect 
elongated stem, but the axillary buds upon it, instead of 
branching out immediately, become more or less compact and 
round. The plant is grown for these buds, which are usually 
about i or 2 inches in diameter. The chief representative 
is the Brussels Sprout. g 



374 CRUCIFER^E 

iii. Brassica okracea L., form capitata. 

In this group the stem remains short and the terminal bud 
develops into a very large 'head* of closely overlapping smooth 
leaves. The so-called ' white' and 'red 1 (really green and 
purple) Drumhead cabbages are examples. 

iv. Brassica okracea L., form subauda or bullata. 

This name is applied to what are known as Savoy cabbages. 
They are similar in structure to the capitata forms, but have 
puckered or wrinkled leaves. 

v. Brassica okracea L., form gongy lodes or caulo-rapa. 

In this form the stems above the cotyledons remain short and 
become very thick and fleshy. It is known as Kohl-rabi of 
turnip-rooted cabbage. 

vi. Brassica okracea L., form botrytis. 

In this group the axis of the inflorescence and all its many 
branches are formed during the first year's growth, and become 
thickened and fleshy when young. The hardy forms are known 
as Broccoli, those more tender and liable to injury by frost are 
spoken of as cauliflowers. 

Many of the varieties of cabbage are only grown in gardens. 
A few, however, are useful crops of the farm ; the chief ones 
grown as food for stock are Thousand-headed kail, Drumhead 
and Savoy cabbages, and Kohl-rabi. 

4. Thousand-headed kail This form of Brassica okracea 
grows to a height'of 3 or 4 feet, sending out leafy branches all 
along the strong woody stem, and these again branch until an 
extraordinarily large amount of succulent forage is produced. 
The leaves are dark green, with wavy, slightly crinkled margins. 

Thousand-headed kail is very hardy and rarely suffers from 
even prolonged frosts. It is chiefly used as food for ewes and 
lambs in autumn and spring and generally consumed on the 
field where it is grown. 

5. Cabbage. The word cabbage is generally applied to all those 
varieties the leaves of whose terminal buds form a compact 



375 

round or oval head. They differ considerably in rapidity of 
growth, and may be classified into early and late varieties 
Some of the early varieties reach maturity of 'head' in the 
early autumn of the same year in which they are sown, while 
the late varieties during the same period of growth are but half 
grown and comparatively immature. 

They may also be classified according to the shape into (i) 
Drumheads with flattened spherical 'heads,' which take up 
lateral space and require to be planted some considerable 
distance apart ; and (ii) Ox-hearts which have oval or bluntish 
cone-shaped 'heads.' The latter varieties take up less space 
and may be planted nearer together than the Drumheads. 

The cabbages are fairly hardy, but the 'heads' contain a 
considerable amount of water (generally 89 per cent.), and do 
not stand wet weather or frost so well as the open Thousand- 
headed variety. Cabbages are largely grown for feeding dairy 
cattle and sheep, and are more nutritious than white turnips. 
They increase the flow of milk and in moderation are less liable 
to give a taint to it than turnips, especially if the outermost 
leaves are discarded. 

Savoy cabbages are more hardy than those with smooth leaves, 
and are therefore more adapted for winter use than the latter 
varieties. 

6. Kohl-rabi is a form of cabbage with a thickened turnip-like 
stem which stands quite above the ground although in good 
strains, often close to it. 

The fleshy part is developed from the stem above the 
cotyledons, none of the hypocotyl or root being present in it : 
it thus differs from the turnip, mangel and carrot. 

As Kohl-rabi suffers very little in the driest weather it is 
sometimes designated 'the bulb of dry summers.' It re- 
sembles the swede turnip in feeding-quality and yield, but 
stands frost better. The leaves as well as the stem are useful 
food for stock. 



376 CRUCIFEIUE 

The varieties differ in the shape of the thickened stem, some 
being almost spherical while others are oval. 

They vary also in colour, some being glaucous green and others 
a purplish tint. 

Both early and late varieties are known. 

CLIMATE AND SOIL. All the varieties of cabbage produced on 
a farm are capable of growing in climates which are much too 
dry for the proper development of the turnip. They are also 
better adapted for growth on strong loams and clays than the 
latter plant. 

SOWING. In many cases the cabbage and its varieties are 
drilled or sown broadcast in small prepared seed-beds, upon 
sheltered ground. The young plants are subsequently trans- 
planted out in the field when 6 or 8 inches high. 

Most of the crops may, however, be drilled in rows in the 
field where they are to grow, the superabundant plants being 
thinned out and the remainder left to develop. 

The seed may be sown at varying intervals of time in 
such a manner as to provide a succession of green food almost 
throughout the whole year. Usually in those cases where the 
crop is to be used during the autumn and early winter, the seeds 
are sown in beds in February, March and April, the young plants 
transplanted in June and July, and the crop ready for consumption 
from September to December. When drilled on the field where 
they are to grow June and July are the months for sowing, the 
crops being utilised from September to December. 

Seeds of the hardier varieties may be sown in beds in August, 
the young plants transplanted in October and November, and the 
crop will be ready for consumption in the following spring and 
summer. 

The seeds may also be drilled in August and September to 
produce a crop during the following spring and summer. 

The rows of plants vary from 20 to 30 inches apart, according 
to the variety grown, and other circumstances. 



TURNIP 



377 



Usually the plants are equidistant from each other, both in the 
row and from row to row. 

The amount of seed when the plants are raised in a seed-bed 
is i Ib. for each acre to be subsequently planted ; if drilled on 
the field direct 4 or 5 Ibs. per acre are necessary. 

YIELD. An average crop of cabbages is about 30 tons, that 
of Kohl-rabi about 20 tons per acre. 






FIG. 117. A, Seedling of turnip (Brasst'ca Rata L.). T Root ; h hypocotyl; 
c cotyledon; p first foliage-leaf ('rough leaf 1 ). , Seedling of charlock 
(Brassica Sinapis Vis.). 

COMPOSITION. Kohl-rabi is richer in albuminoids and * fibre* 
and poorer in carbohydrates than swedes, ^he average water- 
content is about 88, the digestible carbohydrates about 7, fibre 
1*5, and albuminoids 2*3 per cent, respectively. 

7. Turnip (Brassica Rapa L.). This name is applied to a 



378 



CRUCIFERyE 



biennial plant grown extensively for its thick fleshy so-called 
'roots/ which are produced during the first season of growth 
and used as late summer, autumn and winter food for various 
kinds of stock. 

SEED AND GERMINATION. The seed is almost round, with a 
reddish purple testa, and contains an embryo which resembles 
that of white mustard in general form (Fig. 5). The seedling 
possesses two smooth notched cotyledons and a hypocotyl and 
root very distinct from each other. The first foliage-leaves are 





FIG. 118. i. Longitudinal section of a turnip 'root.' 2. Transverse Tection of the 
same, d Bast and secondary cortex; c cambium-ring ; a, degenerate wood, forming 
main mass of the root ; r normal secondary root, originally produced when the primary 
root was thin (almost all above this point is thickened hypocotyl) ; b old leaf-scars. 

grass-green in colour, roundish with irregularly serrate margins and 
their surfaces have scattered hispid hairs upon them. 

ROOT AND HYPOCOTYL. A single tap root generally exists 
from which a number of thin secondary roots arise. The total 
root-system, although fairly extensive, does not descend to any 
great depth, but spreads horizontally in the upper layers of the soil. 

During the first year, both the hypocotyl and primary root 
increase in length and thickness, the combined thickened 



TURNIP 



part, in popular parlance, being variously termed the 'turnip/ 
turnip 'bulb' or turnip 'root.' In all cases the amount of 
bypocotyl is considerable, but the relative proportion of this 
part of the plant to the true root is not the same in all varieties, 
smd probably varies with the soil and cultivation which the plants 
receive. 

The swollen fleshy ' root ' of a turnip possesses essentially the 
same arrangement of tissues as is common in ordinary roots 
and stems. The relative proportion and composition of each 
tissue is, however, very different. 

A transverse section (2, Fig. 118) of a turnip 'root* shows an 
outer layer about J of an inch thick, chiefly bast (d) ; within is 
the wood (a) which forms the main mass of the ' turnip ' ; it is 
produced by the cambium (c). Almost the whole of the wood 
consists of thin-walled, unlignified wood-parenchyma, imbedded 
in which appear radial lines of vessels in small isolated groups. 
Medullary rays are present, but these are not readily dis- 
tinguished from the degenerate wood-parenchyma: they form 
but a comparatively small part of the fleshy ' root.' 

LEAVES The stem upon which the leaves grow remains very 
short during the first year : the leaves consequently appear in a 
rosette-like bunch at the top of the so-called bulb. The first 
foliage leaves are roundish with irregularly serrate margins, those 
growing later being pinnatifid or pinnate with a large oval 
terminal lobe (lyrate). All produced during the first year's 
growth are grass-green and beset with rough harsh hairs. 

In the second season the terminal bud in the centre of the 
rosette of radical leaves, develops into a strong erect stem with 
many branches. The leaves upon the latter are somewhat 
glaucous and smooth, the upper ones being ovate-lanceolate, 
sessile, with bases which partially clasp round the stem. 

The ends of the branches and main stem terminate in 
inflorescences. 
* INFLORESCENCE AND FLOWERS. The turnip inflorescence is a 



CRUCIFER^E 



raceme which when young resembles a corymb, the open flowers 
equalling or overtopping the buds which appears crowded 
together. As the flowers open, the axis of the inflorescence 
elongates, and the flowers then become separated from each 
other by longer intervals. The flowers are small, about an 



T 






FIG. 119. Chief forms of turnip 'roots.' i. Long. 2. Tankard or spindle-shape. 3. 
Round or globe. 4. Flat variety. 5. A typical bad 'root,' many-necked 'top 1 and fang- 
like roots. 

inch in diameter, of the ordinary cruciate type (Fig. 121), with 
almost erect calyces and yellow corollas. 

FRUIT. The fruit is a smooth elongated silique with a short 
seedless beak. 

VARIETIES. Turnips may be classified according to their shape 
into the following groups. 



TURNIP 381 

i. Long varieties in which the fleshy 'root 'is three or more 
times as long as it is broad (i, Fig. 119). 

ii. Tankard or Spindle-shaped varieties (2, Fig. 119), in which 
the greatest diameter of the * root ' is between * top ' and * tail.' 

iii. Round or Globe varieties in which the ' roots ' are almost 
spherical (3, Fig. 119). 

iv. Flat varieties in which the shortest diameter is between 
'top* and 'tail' (4, Fig. 119). 

Many intermediate forms are prevalent, but the above repre- 
sent the chief most distinct groups, so far as shape is concerned. 

Turnips may be also placed in groups according to the colour 
of the upper part of the ' root/ which is exposed to the light 
and air above ground and the colour of the ' flesh. 1 

A. White-fleshed varieties. 

These have white flesh and bright canary-yellow flowers. 

They are generally of low feeding value, many of them with 
soft flesh, liable to be injured by frost. 

Their growth is rapid, and a considerable amount of produce 
is yielded in a short time. They are chiefly adapted for feeding 
in autumn and early winter, and are conveniently divided into 
(i) 'white tops/ (2) * green tops/ (3) 'purple or red tops/ 
and (4) ' greystones/ according to the colour of the upper part 
of the * root' The greystone variety has its upper part mottled 
with transverse green and purple streaks. 

2?. Yellow-fleshed varieties. 

These have firm reddish-yellow flesh and flowers of a reddish- 
yellow tint. The leaves are rough and grass-green in colour. 
These varieties are more robust, of slower growth, and superior 
feeding value to the white-fleshed turnips ; they are, moreover, 
less injured by frost and keep sound for a longer period during 
winter. 

Yellow-fleshed varieties are conveniently divided into (i) 
' yellow tops/ (2) ' green tops/ and (3) ' purple tops/ according 
to the colour of the upper part of the ' root.' 

These plants are sometimes erroneously described as 
1 hybrid turnips/ the pale reddish-yellow flesh suggesting a cross 
between the white-fleshed turnip and swede. Hybrids of the 
two latter plants have indeed been produced . but they are, 
however, unlike the yellow-fleshed turnip and sterile. 

8. Swede Turnips (Brassica Napo-brassica D.C. and Brassua 
Rutabaga D.C.). 




382 CRUCIFER^E 

These plants are grown for the same purpose as the turnip. 
They differ from the latter, however, in the following points : 

(1) The first foliage-leaves of the seedling swede are rough 
like those of the turnip, but glaucous in colour, never grass-green. 
The leaves developed later are smooth and glaucous. 

(2) The swede has a distinct short stem or 'neck* on the 

upper part of the thickened ' root ' with well- 
marked leaf-scars upon it (Fig. 120). 

(3) The 'roots' are rarely so perfect in 
form and outline as those of the turnip ; but 
they keep much better during winter, and are 
easily stored for use in spring. 

(4) The seeds are usually larger and of 
darker colour than those of the turnip, 

Swede turnips may be divided like the 
common turnips into two groups, namely : 
(a) White - fleshed and () Yellow - fleshed 
varieties. The white-fleshed forms (B. Napo- 
brassica D.C.) have firm white-fleshed 4 roots' 
FIG. no. Swede turnip pf irregular form and rough green skin ; they 
gS'ed* ck rind' CM- * very hardy but rarely grown in this country, 
pare with Fig. n 9 . xhe flowers of these varieties are a bright 
canary colour like those of white-fleshed turnips but larger. 

The yellow-fleshed swedes (B. Rutabaga D.C.) are the forms 
most commonly cultivated ; they have solid yellow-fleshed roots 
turbinate or oval in shape, with comparatively smooth skin, 
which may be (i) green, (2) purple, or (3) bronze a mixture of 
purple and green. The flowers are of buff yellow or pale 
orange tint. 

CLIMATE AND SOIL. For perfect development, both common 
turnips and swede turnips require a somewhat damp, dull 
climate, the north of England producing much finer crops than 
the south. Where the air is dry the yield of * roots ' is small. 

The best soils for their growth are open loams, the common 
turnips being grown on the lighter kinds, swedes upon the stiffer 
loams. Neither of them can be grown very satisfactorily upon 
stiff wet clays, nor on dry sands or gravels. 

SOWING. Turnips are drilled in rows on ridges where the 
rainfall is considerable, and on the flat in warm, dry climates. 

The distance between rows varies from 1 8 to 25 in. for white and yellow 
turnips, and 20 to 27 in. for swedes. 



SWEDE TURNIP 383 

Common turnips being of more rapid growth are usually sown 
later than swede turnips. 

The sowing of the main crop of swede turnips usually takes 
place from the middle to the end of May in the north ; the yellow- 
fleshed turnips are sown somewhat later, and the white turnips 
last of all, namely, from June ist to 2oth. In the south of Eng- 
land these crops are sown about a month later than in the north. 

The amount of seed used is from 2 to 3^ Ibs. per acre ; the plants 
are singled so as to stand from n to 13 inches apart in the rows. 

For feeding early in autumn small areas are often sown earlier 
than the dates mentioned above. 

Turnips may also be sown in August in order to provide green 
leafy succulent food for sheep in spring. 

YIELD. The average crop of white turnips weighs from 20 to 
25 tons, yellow-fleshed turnips about 20 tons, and swedes from 
15 to 20 tons per acre. 

COMPOSITION. White turnips usually contain from 91 to 93 per 
cent, of water ; swedes about 89 per cent. ; although in well-grown 
crops of the latter the water -content is often as low as 87 per cent. 
A great deal of variation exists ; even * roots ' growing near to- 
gether in the same field sometimes vary widely in water-content, 
and the particular variety, or ' strain ' of seed, manuring, width of 
row, soil, climate, and ripeness, all influence the composition. 

The amount of soluble carbohydrates, most of which is sugar, 
averages about 5^ per cent, in well-matured white turnips and a 
little over 7 per cent, in swedes. The fat-content is usually the 
same in both, namely, *2 per cent., the albuminoids in white 
turnips average '5 per cent., in swedes about 7 per cent ; the 
fibre '7 and *8 per cent, respectively. 

'Roots' of large size almost invariably contain more water, 
and are therefore poorer in dry matter than smaller ones. 
The difference is most marked in white-fleshed turnips, but 
swedes, and we may say all ' roots/ exhibit similar variation in 
composition. 



384 CRUCIFER^ 

It is instructive to note that in two ' root ' crops whose water- 
content is 87 and 92 per cent, respectively, every hundred Ibs. 
of the former contains 13 Ibs. of dry substance, while too Ibs. 
of the latter yield 8 Ibs. of solid substance when completely 
dried : in other words, 20 tons of the former are equal in dry 
weight to more than 32 tons of the latter. Differences in 
water-content similar to these ordinarily exist between average 
crops of swedes and white turnips, and even the same varia- 
tions in composition have been met with in two swede crops, 
one composed of somewhat small well-matured 'roots/ the 
other consisting of very large immature 'show roots.' 

As the turnip 'root' matures the percentage of water in it 
decreases, and the percentage of carbohydrates, principally 
sugars, increases. 

The dry substance of the ' root ' also alters in composition as 
the ripening proceeds; in unripe roots much of the nitrogen 
exists in the form of amides, compounds which are of little 
nutrient value, whereas in mature roots the amides have largely 
disappeared, being transformed into useful albuminoids, 

9. A good turnip. The following points are important in 
determining the value of a turnip or swede. 

(1) The yield should be high. 

(2) The feeding-quality, so far as composition is concerned, 
should be good ; roots of high specific gravity are generally more 
valuable in this respect than those of low specific gravity. 

(3) Their resistance to frost is to be considered. It is to 
some extent dependent on inherent vital differences, and also to 
the manner of growth of the ' root ' ; varieties which grow mainly 
buried in the soil are usually more resistant to frost than those 
whose ' roots ' are mainly above the surface of the soil. 

(4) Varieties which stand well out of the ground are however 
more easily pulled up and more readily and completely consumed 
by sheep than those deeply buried. 

(5) Turnips should have no 'neck' and that of the swede 



RAPE, COLE, COLESEED 385 

should be thin. The 'skins' of the fleshy 'root* should be 
as thin, smooth, and tender as possible. Both the tap root 
and leafy top should be single and small. Turnips or swedes 
with several tops and fang-like roots, as in 5, Fig. 119, are 
generally of poor feeding-quality, and involve much waste in 
their consumption. 

The upper part of the ' root ' should be convex ; when con- 
cave, as partially seen in 4, Fig. 119, rain-water is liable to be 
held in the depression and decay thereby encouraged. 

10. Rape, Cole, Coleseed (Brassica Napus L.). This plant is 
a biennial, grown in many places instead of a turnip crop, and as 
a ' catch crop ' for its succulent leaves and stems which are 
utilised as food for sheep. 

The seeds are dark purple or black, and the young plants 
have glaucous foliage-leaves which are sparsely covered with 
rough hairs. Both seeds and seedlings are identical in appear- 
ance with those of swede turnips, and not unfrequently rape seed 
has been sown in mistake for that of the swede, and the young 
plants hoed out as for a root crop ; in such instances it is 
impossible to detect the error until the plants have grown 
some time, when the want of * bulbing* propensity betrays 
them. 

The root is slender ; the stem which grows to a height of 2 
feet or more is smooth, with many branches. The lower leaves 
are lyrate, the upper ones ovate-lanceolate, clasping the stem. 
The flowers are bright yellow, like those of the white-fleshed 
swede. 

Seed is sown at intervals, usually from May onward, in order 
to provide a succession of crops during the autumn and winter. 

It is generally sufficiently advanced in three months from the 
time of sowing to provide a large bulk of green food. 

The seed is sown broadcast, at the rate of 10 Ibs. per acre, or 
more frequently drilled at the rate of 4 or 5 pounds per acre. 
In the latter case, the superabundant young plants are hoed out 



386 CRUCIFER^ 

and the remainder left a little nearer together than the ' roots ' 
of a white turnip crop. 

The green rape crop usually contains about 86 per cent, of 
water, 4 per cent, digestible carbohydrates, and 2 per cent, of 
albuminoids. 

The seeds are very rich in oil, usually averaging about 42 per 
cent, of this constituent. 

n. Oil- Yielding Rapes. On the Continent several forms of 
plants belonging to the genus Brassica are grown for their seeds, 
from which oil is expressed or extracted, and the refuse sold 
as ' rape cake.' In this country the oil is sold indiscriminately 
as colza oil or rape oil. 

One of these oil-yielding plants greatly resembles the swede 
except in its roots, which are not fleshy. Its flowers are bright 
yellow. This is the same plant as that grown in this country 
chiefly as a green fodder crop, and known as rape, cole, or 
coleseed. The winter variety, of which there are several named 
strains, is sown usually in August, and the seed harvested in the 
following June and July. This variety gives the largest yield 
of the best oil. There is also a summer variety of the same 
plant which is sown in April and harvested in September of the 
same year : it is not quite so rich in oil, and gives a poorer yield 
than the winter one. 

Besides the above, an oil-yielding plant is grown which 
resembles the turnip, except in its want of a thick fleshy * root.' 
The oil from its seeds is sold as rape or colza oil. There are 
also winter and summer varieties of this * rape/ the first sown 
in August and September, and the second in May. They differ 
from the previously mentioned rape in ripening earlier. More- 
over, they are smaller plants, give a smaller yield of oil, and are 
more suited to sandy soils ; they are also hardier than the 
swede-like rape. None of these forms of turnip-like 'rape 1 
are grown in this country. 

12. The nomenclature and relationship of these forms of 



BLACK, BROWN, OR RED MUSTARD 387 

Brassica to each other is not clear, as hybrids and crosses are 
frequent. Possibly all are derived from one species : some 
authorities are, however, disposed to notice two species with 
varieties, thus : 

Species i. Brassica campestris L. 

Oil-yielding summer variety : form anntia. (a) Summer turnip -like Rape. 

Do. winter do. : form oleifera. (/>) Winter do. do 

Variety with thick fleshy ' root ' form rapifera 



Species 2. Brassica Napus L. 

Oil-yielding summer variety : form annua. (a) Summer Swede-like Rape. 

Do. winter do. : form olctfera (b) Winter do. do. 

Variety with thick fleshy ' root ' : form rapifera : Swede Turnip : 

B. Napo-brassica D.C. i. white-fleshed. 
B. Rutabaga I) C ii- yellow- do. 

13. Black, Brown, or Red Mustard (Brassica nigra Koch. = 
Sinapis nigra L.). An annual plant grown for its seeds. The 
latter are ground and the * flour/ after removal of the dark- 
coloured testas, is used as a condiment, namely, ordinary table 
mustard. 

The seeds contain oil which is sometimes extracted and used 
for burning in lamps, in the same manner as rape or colza 
oil. 

The plant is a wild indigenous plant in this country, but most 
frequently met with under hedges and in waste places as an 
escape from cultivation. The seeds have the property of re- 
maining in the ground for several years without germinating, 
and when a crop is once allowed to seed, some of the shed seed 
is certain to give rise to plants in many of the subsequent crops 
grown on the same land. It may thus become a troublesome 
pest of arable land. 

SEED AND GERMINATION, The seeds are oval with a 
reddish-brown coloured testa when well harvested, and the 



3 88 CRUCIFEIUE 

seedling resembles that of a turnip plant with somewhat small 
cotyledons. 

STEM AND LEAVES. The stem grows to a height of 2 or 3 
feet, and is branched and covered with rough hairs. The lower 
leaves are large and rough, lyrate, and of a light green colour : 
the upper leaves lanceolate and smooth. 

INFLORESCENCE, FLOWER, AND FRUIT. The inflorescence is a 
long raceme ; the flowers are small, about J to an inch across, 
have spreading narrow sepals and pale yellow petals, the broad 
parts of which are slightly notched. 

The fruit, which grows upright, and closely adpressed to the 
stem, is a somewhat short smooth silique about to f of an inch 
long with a short slender beak (5, Fig. 123); each valve of the 
silique has a single strong well-marked longitudinal nerve. When 
ripe the pods and seeds are of dark colour, hence the name 
Black Mustard. 

The whole plant resembles charlock, but can readily be dis- 
tinguished from the latter by the length, shape, position and 
nerves of its siliques. 

Black mustard requires for its growth a deep, rich, fertile soil, 
on which it is generally sown broadcast, at the end of March 
or beginning of April. It is hoed and thinned in May and then 
left until September, when it is cut rather green and allowed to 
ripen in small carefully made stacks. 

COMPOSITION. The seeds of black mustard contain about 25 
per cent, of a fixed oil, which is sometimes extracted from the 
* dressings ' obtained in the manufacture of table mustard, and 
used for adulterating or mixing with rape and other oils. The 
seeds when ground and mixed with water give rise to a some- 
what volatile product known as ' mustard oil ' ; the latter does 
not, however, exist ready formed in the seed, but is produced 
by the action of an enzyme, myrosin^ upon a glucoside known 
as sinigrm or potassium myronate, both of which are present 
in the seeds. In the presence of water the my rosin decomposes 



WHITE MUSTARD 389 

the potassium myronate, splitting it 'into potassium hydrogen 
sulphate, sugar and allylthiocarbimid or ' mustard oil. 9 
The decomposition may be represented thus : 

C 10 H 18 KNS,0 IO - KHS0 4 + C^O, + C 3 H 5 NCS. 

Potassium myronate. Potassium hydrogen Sugar. ' Mustard oil* 

sulphate. 

1 Mustard oil ' has an extremely pungent taste and smell ; it 
gives off vapour, small quantities of which bring tears to the 
eyes ; when the oil is applied to the skin, it immediately pro- 
duces blisters. 

14. White Mustard (Brassica alba Bobs. * Stnapts alba L.). 
An annual plant grown chiefly as food for sheep in this 
country, and for ploughing in as a green manure to enrich the 
ground in humus. Its seeds are also used for the manufacture 
of oil, and for the preparation of table mustard as in the last 
species. Young seedlings are used as a salad with cress. 

Some botanists consider white mustard not a true native of 
the British Isles. 

When grown for seed it does not occasion any trouble as a 
weed in subsequent crops after the manner of black mustard, as 
its seeds all germinate at once when conditions are favourable, 
and the young plants are then readily destroyed. 

SEED AND GERMINATION. The seeds are much larger than 
those of black mustard and pale yellow. 

The seedling has notched cotyledons, and its first foliage-leaves 
are pinnatifid or pfnnately lobed, as in Fig. 5, thus differing 
from turnip and black mustard. 

STEM AND LEAVES. The stem grows from i to 3 feet high, 
and is generally branched and covered with rough hairs. 

All the leaves are bright green and rough; they are lyrate- 
pinnatifid or pinnate, with irregular lobes. The terminal lobe of 
the leaf is usually small compared with those of the leaves of 

turnip and black mustard. 

27 



390 CRUCIFER^E 

INFLORESCENCE, FLOWER AND FRUIT. The inflorescence is 
a long raceme, the flowers small, about \ an inch across, 
with narrow spreading sepals and pale yellow petals. The fruit 
is a hispid silique, about ij or 2 inches long, with a long, 
slightly curved sword-shaped beak; the valves of the silique 
have three nerves. 

When ripe the siliques and seeds are of pale colour, hence 
the name white mustard in contrast to the black species with 
dark-coloured siliques and seeds. 

Its leaves and siliques at once distinguish it from the other 
species of Brassica mentioned. 

For sheep-feed it is usually sown broadcast any time from 
April to August, at the rate of 20 Ibs. of seed per acre. Its 
chief merit is its very rapid growth, which makes it of service for 
catch-cropping after vetches, potatoes, and other similar crops, 
or where turnips have failed and the time for sowing a more 
useful crop has past. It is ready for folding with sheep from six 
to eight weeks after the seed is sown. For use as 'green 
manure ' it is generally sown in July or August and ploughed in 
during October and November. 

COMPOSITION. The green plant in full bloom contains on an 
average about 83 per cent, of water, 7^ per cent, of carbohydrates, 
2 per cent, albuminoids, and 6 per cent fibre. 

The seeds contain 26^ per cent, of a fixed oil similar to that 
in other cruciferous seeds ; when extracted it is used for mixing 
with rape oil. 

The seeds of white mustard when ground and stirred with 
cold water, have not the odour so characteristic of the black 
species ; nevertheless the pungent taste is very similar in both 
species. 

A glucoside, which is named sinalbin, is present in the seeds 
of white mustard, and the enzyme my rosin. When water is 
added to both, the myrosin decomposes, the sinalbm into jiucose, 
an acid salt of sinapin, and sinalbin mubtard oil (CyH 7 O'NCS). 



CHARLOCK 391 

The latter is somewhat less pungent than allyl mustard oil 
obtained from black mustard seeds and is not volatile at 
ordinary temperatures. 

15. Charlock (Brassica Sinapis Vis. = Sinapis arvensis L). 
A native annual unfortunately often too common in corn 
fields. 

SEED AND GERMINATION. The seeds are dark brown similar 
in size to those of turnip, from which they cannot be readily dis- 
tinguished when the two are mixed. When sown they germinate 
irregularly and often remain capable of growth for several years 
when deeply buried in the soil. 

The seeds contain a considerable amount of oil and are sold 
by many farmers to oil-cake manufacturers, finally appearing 
as impurities in rape and other * cakes.' 

The seedling is somewhat like that of a turnip, but can be 
distinguished from the latter by the first foliage-leaves, which 
are a darker green colour and of longer and somewhat different 
shape (B, Fig. 117). It is more pungent in taste than a seedling 
turnip. 

STEM AND LEAVES. The stem is rough from i to 2 feet high 
and branched. The lower leaves are stalked, ovate, partially 
lyrate or lobed, the upper ones lanceolate, irregularly serrate, 
and sessile. 

INFLORESCENCE, FLOWER AND FRUIT. The inflorescence is 
a raceme. The flowers are larger than those of black mustard, 
being generally J to j of an inch across ; they possess spreading 
narrow sepals, and pale yellow petals. 

The fruit is a silique from i to 2 inches long, usually with 
rough deflexed hairs upon it, but occasionally smooth ; the valves 
of the silique have three faint veins (2, Fig. 123). 

The whole plant resembles that of black mustard, but has 
larger flowers and differently shaped siliques, which latter are 
spreading and not pressed to the stem. 



392 



CRUCIFER^E 



1 6. TABLE OF THE CHIEF DISTINCTIONS BETWEEN THE 
COMMON SPECIES OF BRASSICA. 

A. Sepals erect or nearly so (Fig. 121). 

i. Leaves of 1st year's plant glaucous (ashy grey). 

a. All leaves smooth, flowers pale lemon 

yellow. Cabbage. 

b. First leaves of seedling with a few 

stiff hairs, flowers buff, or pale 
yellow. Swede and swede-like 
'Rape.' 

FIG. Ji.-Flower " Le aves of 1st year's plant grass-green 

of cabbage, showing with Stiff hairs, flowers bright yellow, of charlock, showing 

erect sepals, s. Turnlp and tumip.jiHe Rape. spreading sepals, * 





FIG. 122. Flower 



B. Sepals spreading (Fig. 122). 

i. Siliques erect, closely pressed to main axis on which they grow : 

valve of silique with one nerve. Black Mustard. 
ii. Siliques spreading, valve of silique with three nerves. 

a. Silique with sword -like 'beak/ seeds pale yellow or straw- 
colour. White Mustard. 
b. Silique with cylindrical straight 
beak, seeds dark -brown. Char- 
lock. 

17. Wild Radish: Jointed Charlock 

(jRaphanus Raphanistrum L.). An 
annual weed common and troublesome 
in cornfields in many districts although 
unknown in others. 

The stems are from i to 2 feet 
high and covered with scattered rough 
FIG. 123. Siiiquesof: i. Turnip hairs. The leaves are rough, coarsely 

(Brassica Rata L.). 2. Char- , . , . , . , ,. 

lock (Brassica Smafis vis.), serrate, and simply lyrate (with few 

3. White Mustard (Brassica . ., . . . 

alba Boiss.). 4 . wild Radish pmnatifid segments and a large ter- 
minal lobe). It has racemose in- 
florescences. The flowers are about 
f of an inch across with erect sepals, and usually pale straw- 
coloured petals often veined with purple lines ; occasionally the 
petals are white or pale lilac tint. 




(RagJtanus Raphanistrum L.). 
5. Black Mustard (Brassica 
ttifra Koch.). 



WILD RADISH: JOINTED CHARLOCK 393 

The siliques, which are from i to 3 inches long, have 
long slender beaks and are constricted above and below each 
seed (4, Fig. 123) ; they are indehiscent, but separate at the 
* joints 1 into barrel-shaped pieces, each containing a single 
seed. 

The seeds are oval and reddish-brown in colour. 

The whole plant somewhat resembles ordinary Charlock, but 
may be distinguished from the latter by its erect sepals, usually 
veined petals, and smooth 'jointed' siliques. 

Ex. 191. Examine seeds of cabbage, swede and turnip in bulk, and indi- 
vidually with a lens. Compare them with seeds of black mustard and 
charlock. Taste all of them separately in the above order and note any 
differences in flavour. 

Ex. 192. Grow seedlings of cabbage, swede turnip, black mustard, white 
mustard, and charlock. Note the shape of the cotyledons and first leaves of 
each. 

Ex. 193. Compare the external appearance of a full grown swede with that 
of a white turnip. 

Ex. 194. Carefully examine and describe the leaves, flowers and fruits of 
the crucifers mentioned in detail in the text, and draw up a table of differ- 
ences, paying special attention to the calyx, the colour and form of the 
corolla, and the form of the siliques. 

Ex. 195. Watch the growth of the fleshy 'root* of a turnip or swede. 
Find out which part is hypocotyl and which true root. Make marks with 
Indian ink, & of an inch apart, on the hypocotyl of young seedlings, and 
note their position from day to day. 

Ex. 196. Make careful observation on the development of a kohl-rabi 
plant from the young seedling stage up to the time when the stem is 2 
inches thick. Find out whether the part of the stem above or below the 
cotyledons thickens most. 

Ex. 197. Growbrussels sprouts, savoys, broccoli, and thousand-headed kail 
side by side and watch their development : make notes of the differences in 
length of stem and the development of the buds in the axils of the leaves 
upon it, in each kind of plant. 

Ex. 198. Examine the various forms of cabbage when the inflorescences 
are well developed and their flowers open. 

Are the flowers of the different forms alike in all respects ? 

Ex. 199. Compare and contrast longitudinal and transverse sections of a 
turnip, a carrot and a mangel respectively. 



394 CRUCIFER/E 

Ex. 200. Procure a small amount of seed of each of the chief kinds of 
turnips and swedes from various seedsmen. Sow short rows of each on the 
farm in order to become acquainted with the form and colours of the root, 
and the hardness and colour of the flesh. Note the differences in the 
size of the neck and tap root, and the amount of * root ' above and below 
ground. 

Ex. 201. Sow a few seeds of rape or cole and swede side by side in differ- 
ent rows or in different pots of earth and compare the seedlings before and 
after the foliage- leaves appear. How soon does the swede show that it 
differs from the rape plant ? 

Ex. 202. Grind up the seeds of black mustard and mix with water : do 
the same with those of white mustard. Smell and taste both. 

Ex. 203. The student should become acquainted with such common 
cmcifers as shepherd's-purse, Jack-by-the-hedge. and hedge mustard, 



CHAPTER XXIX. 
LINAGES. 

i. General Characters of the Order. Herbs, shrubs, or trees. 
Leaves simple, entire, generally alternate and exstipulate, or 
with small stipules only. 

Flowers regular, hypogynous. Calyx, inferior, four or five 
sepals, persistent. Corolla polypetalous, four or five petals 
twisted or imbricate in the bud, soon falling. 

Andrcecium of four or five perfect stamens, often alternating 
with a similar number of teeth or abortive stamens, all united 
to a hypogynous ring. 

Gynaecium, syncarpous, three to five carpels, the ovary having 
three to five loculi, each of which is sometimes partially divided 
by a false dissepiment, 

One or two pendulous ovules in each loculus. 

Fruit, a roundish capsule, splitting along the dissepi- 
ments. 

Seeds eight or ten in each fruit, with a small amount of endo- 
sperm and a straight embryo. 

The Linaceae comprises a small Order of about 150 
species. 

The genus Linum includes about ninety species, some of which 
are cultivated in gardens on account of their brilliantly coloured 
flowers. The most important species belonging to the Order is 
Flax or Linseed (Linum usitatissimum L.). 

2. Flax or Linseed (Linum usitatissimum L.). Flax has been 
grown from time immemorial for the manufacture of linen, a 

895 



396 LINAGES 

fabric which is woven from the bast fibres of the stem of the 
plant. 

The plant is also grown for its seeds, which contain a large 
quantity of oil. The latter is extracted and sold under the name 
of linseed oil, the crushed seed after extraction of most of its oil 
being made up into oilcake and utilised by the farmer for feeding 
stock. 

The original unextracted seed is sometimes employed as food 
for calves and other animals, and the fibre of the stem, in addition 
to its being used in the manufacture of linen, is also made into 
a tough and very durable paper. 

SEED AND SEEDLING. The seeds are oval and flattened, about 
4 to 6 mm. long, of a yellowish brown colour and possessing a 
smooth shining surface. The epidermis of the coat of the seed 
is formed of cubical cells with very thick walls, consisting of a 
peculiar mucilaginous substance, which swells up into a slimy 
mass when put in water. 

Within the seed coat is a small amount of endosperm and a 
large straight embryo. Germination takes place readily when 
fresh seed is sown, and the young plant sends its two elliptical 
cotyledons above ground. 

ROOT. The root-system of the plant is comparatively small, 
consisting of a weak tap-root and a few short lateral roots, none 
of which penetrate deeply into the soil. 

STEM. The stem is slender, and when the plants are 
grown closely together for the production of good fibre, rises 
to a height of i to 2 feet without branching, except in its 
upper part. 

The internal arrangement of the structural elements is 
seen in Fig. I23A, where a portion of a transverse section 
of the stem is given. On the outside is a well-marked 
epidermis, beneath which comes the cortex, consisting of 
parenchymatous cells, some of which contain chloroplastids. 
Next is observed an interrupted ring of bast fibres, arranged 



FLAX OR LINSEED 



397 



C 



in larger or smaller bundles. Some of the larger bundles have 
from twenty to thirty fibres in each, and are very strong. 

In a full-grown stem each fibre has a very thick cell-wall and 
small cell-cavity: it is 
pointed at each end, and 
varies in length from 4 to 
66 mm. 

The fibrous bast strands 
or 'flax' when isolated 
are a pale yellowish tint 
in the best kinds of plants, 
and possess a silky lustre. 

When flax fibre is the 
object for which the plant 
is grown the stems are 
carefully pulled by hand 
before the seed is ripe, 
and laid on the ground 
for about a day, during 
which time they dry a 
little. 

The following day the FIG. i2 3 A.-Tran S vcrsc section of portion of a Flax 
ef/ame ar<* firrl intr\ email stem, a, epidermis; 6, cortex; <r, bast fibres 

stems are tied into small ( , flax . } . ^ wood or xylem of the stenu 
straight sheaves, 4 to 8 

inches in diameter, and the latter are then set up in stooks 
to dry more completely. In eight or ten days the plants 
are 'rippled,' that is, the seed capsules are removed by 
pulling the stems between the teeth of iron combs. The 
capsules are afterwards threshed and the seed is either kept 
for sowing, or, if unripe, utilised by the oil-crusher. After 
cutting off the roots, the stems are subjected to the process of 
* retting ' or rotting, the object of which is to loosen the tissues 
of the stem so that the bast fibres can be easily freed from 
the cortex, wood, and other parts of the stem. 




398 LINAGES 

Various methods of 'retting* are practised in 'different dis- 
tricts, one of the oldest and best being that adopted in the 
Courtrai district of Belgium. 

The dry flax stems are there kept from the time of harvest- 
ing in one season until the middle of April or later in the 
following year. They are then tied into bundles and sunk 
in crates in the River Lys. After remaining under water 
seven or eight days the bundles are taken out and arranged 
in small stacks to dry. 

When dry they are sunk a second time for ten or twelve days, 
and after being removed from the river and dried again, the 
* retting ' is complete. 

During this process the middle lamella between the 
adjoining cells of the tissues forming the stem becomes more 
or less completely dissolved, and the component cells are 
loosened from each other. The middle lamella, according 
to Mangin, consists of calcium pectate, and its solution is 
brought about by the fermentative activity of two or three 
kinds of bacteria, most of which are anaerobic (see p. 785) or 
nearly so, carrying on their work best in the presence of a small 
amount of oxygen only, under conditions which obtain below 
water. These organisms are most active at a temperature of 
1 8 to 20 C. 

After the retting is completed the dried flax stems are sub- 
jected to the processes of ' breaking ' and ' scutching ' in order 
to separate the brittle epidermal and woody parts from the more 
elastic tough fibres. 

LEAVES. The leaves are small, linear-lanceolate in shape, 
with smooth surfaces, and arranged alternately on the 
stems. 

INFLORESCENCE AND FLOWERS. The upper part of the 
single stems are branched in a corymbose manner, and 
the flowers are borne on these branches in many-flowered 
cymes. 



FLAX OR LINSEED 



399 



The sepals are five in number, ovate, pointed and ciliate. 
The polypetalous corolla is twisted when in bud and consists of 
five blue or white delicate thin petals, which readily fall after a 
few days ; these are connected to a hypogynous ring or disk on 
which are five glands probably representing abortive stamens 
opposite to the petals. 

The flower possesses five stamens, and on the ovary are 
five long styles. The ovary is five-celled, the cells being 







1 2 3 4 

FIG. 1238. -i Flower and pottion of stem of Flax (Linutn usitatissimunt L.)- 
2. Gynaecium and androecium. 3. Transverse section of ovary. 4. Ripe 
capsule. 

divided into two by spurious dissepiments, in each of which 
is a single ovule (Fig. 1238). 

THE FRUIT is a capsule (Fig. 1233), which splits longitudinally 
when ripe and sets free the ten seeds within. 

VARIETIES. The typical form of Linum ttsitatissimum L., 
grown for flax production, is an annual with an upright solitary 
stem and capsules which remain closed when ripe : the 
partitions in the capsules are smooth. A variety (L. humiU 



400 LINAGES 

Miller = Z. crtpitans Boning.), grown in some countries for 
oil seeds, has dwarfer, more branched stems and larger cap- 
sules, which open and set free their seeds when ripe ; the 
dissepiments are hairy. 

CLIMATE AND SOIL. Flax succeeds best in a moderately 
damp and warm climate. The soil most adapted for its growth 
is a deep, well-drained, sandy loam, although it can be cultivated 
upon a variety of soils, so long as they are not too dry and are 
free from stagnant water. 

On stiff clays, peaty soils, or soil containing much lime, flax 
produces fibre poor in quality. 

SOWING. As young flax plants are very easily destroyed by a 
sharp frost, the seed should not be sown until all likelihood of 
damage in this manner is past. 

The middle of April is soon enough for most districts in 
which the crop is grown ; but it is sometimes sown as early 
as March or as late as May. The earlier the better, for 
early seeding not only increases the yield and quality of the 
fibre, but there is also more time left for the drying and 
other processes connected with the preparation of the stem 
before * retting'; the ground is shaded early in the season, 
and the moisture in the soil thereby preserved from loss by 
evaporation. 

The amount of seed to be used for sowing varies according as 
the crop is to be grown for fibre alone, for fibre and unripe seed, 
or for seed only. 

When the crop is cultivated for its fibre, or chiefly for the 
fibre with a certain amount of partially ripened seed, the plants 
should stand closely together, so as to induce the production of 
long thin unbranched stems ; a thick seeding is therefore needed, 
and the amount in such cases should be not less than 3 bushels 
of seed, or about 160 to 170 Ibs. per acre. 

If a crop of ripe seed is desired, the plants should have plenty 
of room for healthy development, and from 70 to 100 Ibs. of 



FLAX OR LINSEED 401 

seed per acre is enough, the smaller amount being used when 
the seed is drilled in rows 5 or 6 inches apart, the latter when it 
is broadcasted by hand. 

The seed saved from a partially-ripened crop of flax 
grown mainly for the fibre, should be used for oil extraction 
and oilcake manufacture, and not for sowing for another fibre 
crop. 

The best yield of flax, so far as fibre is concerned, is said by 
some to be obtained from seed which has been carefully dried 
and kept in tightly closed barrels which exclude moisture for two 
or three years, experiments having shown that seed stored in this 
way gives longer stems and finer bast than fresh seed ; others 
consider that the highest yield of fibre is secured from the fully 
ripened seed, harvested from a crop raised from * barrel' flax 
seed. 

Flax seed is readily damaged by heating, especially when 
damp, and is liable to lose its germinating power very quickly 
unless care is exercised in its storage. It should have a ger- 
mination capacity of 90 per cent, at least, and should be sown at 
a uniform depth on a clean, well-prepared seed bed. 

HARVESTING AND YIELD. The crop is harvested in different 
ways, according to the kind of produce required. Where the 
finest white silky flax is the object, the plants are pulled up soon 
after the fall of the petals of the flowers, at which time the stems 
are still green in the upper parts, although the lower half is 
yellow and has lost its leaves. The seeds in the young capsules 
are then whitish in colour. Where both seed for oil-crushing 
and flax are wanted, the crop is taken when the stem and cap- 
sules have turned yellow, the seeds being then brown and well 
formed. The flax produced is greater in bulk but is coarser 
in texture, and does not become so white when bleached as in 
the case of plants harvested earlier. 

Where only seed for sowing is needed, it is essential that the 
plants be allowed to stand until dead ripe. 



402 LINAGES 

The yield of raw flax, that is, the dry stems after the retting 
process, varies from | to i tons per acre. About 80 per cent, 
of this is removed in the breaking and scutching processes, 
about 20 per cent. (;'.<?. 3 to 6 cwt.) remaining as fine scutched 
flax. 

The seed obtained from a crop grown for fibre should not be 
more than about 4 cwt. per acre ; when the crop is grown for 
seed only, the amount produced varies from 8 to 1 1 cwt. per acre. 

COMPOSITION. The seeds from the ripe capsule contain from 
31 to 39 per cent, of linseed oil and from 19 to 25 per cent, of 
nitrogenous substances, chiefly proteins in the form of large 
aleuron-grains ; these reserve foods are stored both in the 
endosperm and in the cotyledons of the embryo. 

The oil is used in the preparation of varnishes, oil-paint, and 
printers' ink, for the manufacture of soft-soap and oilcloth, and 
partially as food in some countries. 

The nitrogen-free extract, consisting of the mucilage of the 
epidermis of the seed and hemicelluloses of the cell-walls of the 
embryo and endosperm, averages 22 per cent., the amount of 
water generally 1 2 per cent., the woody fibre 5 or 6, and the ash 
about 4*3 per cent, of the seed. 

The residue of the seed, after extracting the oil, is made into 
linseed 'oilcake,' the composition of which varies very much 
according to the method adopted for extraction. 

Linseed cake of fair average composition usually contains from 
ii to 12 per cent, of water, 10 to 12 per cent, of oil, 28 or 29 
per cent, of nitrogenous substances, 29 to 30 of carbohydrates, 
9*5 to ii of fibre, and 77 to 8 '8 per cent, of asft. 



CHAPTER XXX. 
ROSACES. 

i. General characters of the Order. Flowers regular, and 
usually perigynous. Calyx gamosepalous, five sepals ; in some 
genera an epicalyx is present. (See strawberry below.) Corolla 
polypetalous, five petals. Andrcecium, usually of many stamens. 
Gynaecium, apocarpous, sometimes more or less syncarpous, one 
or many carpels. Fruit various. Seeds exendospermous or with 
scanty endosperm. 

The Order Rosaceae comprises about 1000 species of herbs, 
shrubs, and trees. The leaves are generally compound, and 
possess stipules. 

There is no plant of the Order of much importance to the 
farmer as a fodder crop, but all our most valuable edible fruits 
of the orchard and garden belong to it. The genera, the struc- 
ture of whose fruits it is important to notice, are mentioned 
below. 

2. Genus Prunus. Plums and Cherries. The plants of this 
genus are shrubs or trees with simple leaves. The flowers are 
perigynous ; the receptacle has the form of a hollow cup, around 
the edge of which are arranged five sepals, five petals, and fifteen 
to twenty stamens (Fig. 124.). The single carpel, which pos- 
sesses a long terminal style and two ovules, is placed at the 
bottom of the hollow receptacle. After fertilisation the latter 
divides by a circular cut near its base at /, Fig. 124, and soon 
withers and falls off, carrying the calyx, corolla, and androecium 
with it Sometimes the withered receptacle and its appendages 
remain for a time surrounding the growing carpel. 

403 



404 



ROSACES 



Eventually the single carpel which is left develops into a 
drupe (the fruit) (J3, Fig. 1 24). The ovary wall (/) increases in 
thickness, and when ripe exhibits three layers of tissue of different 
texture, viz. : (i) an inner, hard, bony layer (e) next the seed 
termed the * stone ' of the fruit or endocarp^ consisting of scleren- 
chymatous cells ; (2) a soft parenchymatous layer (m) the 
* flesh ' or mesocarp with sweet cell-sap ; and (3) an outer 
thin skin or epicarp. 

During the early growth, increase in size of the fruit proceeds 




FIG. 124. A t Vertical section of the flower of a plum, x Receptacle; o petal ; a 
stamens ; 6 ovary, inside which is seen an ovule. The part of the receptacle above the 
lineyCr falls off after fertilisation. . 

B % Fruit (drupe) developed from the gynaecium of the flower A. p The pericarp, of which 
e is the endocarp or * stone ' ; m the mesocarp or ' flesh ' ; s seed ; J/ point where style 
has fallen off; x small remaining part of the receptacle. 

rapidly up to what is known as the ' stoning period ' when the 
endocarp is beginning to harden, at which time growth in 
diameter almost ceases. As soon as the ' stone' has become 
firm the fruit begins again to increase in diameter, the chief 
growth in thickness taking place in the mesocarp. 

3. A glucoside, known as amygdalin, is present in the bark, 
leaves, and seeds of many species of this genus : it is a non- 
poisonous compound, but under the influence of the enzyme, 
cmulsin, which is often associated with it, and in the presence 



APRICOT 405 

of water, amygdalin decomposes into benzaldehyde (oil of bitter 
almonds), sugar, and the veiy poisonous prussic acid. 

4. The chief species of Prunus are the sloe, bullace, plum, 
cherry, apricot, almond, and peach. 

They may be divided into two groups according to the way in 
which the leaves are packed in the bud. 

SECTION I. Leaves rolled in the bud. 

Sloe or Black-thorn (Prunus spinosa L.). A small shrub, 
with almost black bark, many spiny branches, and white 
protogynous flowers which appear in spring before the narrow 
lanceolate foliage leaves. The fruit is a small round drupe, 
about \ an inch in diameter, with a glaucous * bloom ' and 
smooth peduncle. 

Bullace (Prunus insititia L.). A shrubby tree with a few 
spiny branches and dark-brown bark. The young twigs are 
usually covered with a soft down, and the broader almost ovate 
leaves are also downy on the under surfaces. The flowers are 
white and usually appear with the leaves. The round fruits are 
black or yellow, about J to i inch in diameter, with downy 
peduncles and glaucous bloom. 

The damson is a form of bullace with oval fruits. 

Wild Plum (Prunus domestica L.). This is a small tree 
similar to the Bullace in the shape of its leaves and the colour of 
the bark. The branches do not possess spines and are devoid 
of downy hair. The fruits are oval or oblong, about i to ij 
inches long, black, with smooth peduncles. 

The wild plum is not a native of this country, although well- 
established in woods and hedges as an escape from cultivation. 

The cultivated plums have arisen from the above and several 
other species most probably by cross fertilisation : the origin of 
many varieties is however unknown. 

Apricot (Prunus Armeniaca L.). An introduced tree origin- 
ally derived from Mongolia and Turkestan (not Armenia as its 
name implies). The branches are smooth and the flowers appear 

28 



406 ROSACES 

before the leaves. The fruit is yellow, round or oval, and has a 
hairy velvety surface. 

SECTION II. Leaves folded (conduplicate) in the bud. 

Wild Cherry : Dwarf Cherry (Prunus Cerasus L.). A small 
shrubby tree, from 4 to 8 feet high, with slender branches. The 
leaves are dark green, smooth on both sides, and possess short 
petioles. 

The inner scales of the flower-buds are leafy and the sepals of 
the flowers are serrated. The fruit is round and red, with soft, 
juicy, acid ' flesh.' 

This species appears to be the parent of the Morello, Duke, 
and Kentish cherries. 

Oean: 'Wild Cherry* (Prunus Avium L.). A taller tree 
than the last, often 20 to 30 feet high, with erect, short, rigid 
branches. The leaves are pale green, somewhat hairy beneath, 
and with a long petiole ; they hang down more than those of the 
dwarf cherry. None of the scales of the flower-buds are leafy, 
and the sepals of the flowers are entire. The fruit is heart- 
shaped, black or red, and has firm bitter flesh. 

This species appears to be the parent from which the Heart 
and Bigarreau cherries have been derived. 

Bird Cherry (Prunus Padus L.). A tree from 10 to 20 feet 
high. It differs from the previously-mentioned cherries in having 
its flowers in loose pendulous racemes from 3 to 6 inches long. 
The fruits are round or ovoid and small, about \ of an inch in 
diameter, with a bitter taste. 

The Almond (Prunus Amygdalus Hook. **Amygdalus corn- 
munis L.) has a hairy fruit with a leathery tough mesocarp: 
when ripe the latter separates irregularly from the woody 
wrinkled 'stone* which contains the seed. Two races are 
known, namely, one with bitter the other with ' sweet ' seeds. 

The Peach (Prunus Persica Benth. et Hook. - Amygdalus 
Persica L.) very closely resembles the almond in all characters 
except those of the fruit. The latter is usually covered with 



STRAWBERRIES 407 

velvety hair, and has a soft juicy mesocarp ; the nectarine, how- 
ever, which is only a sport from the peach, has smooth-skinned 
fruits. 

Ex. 204. Examine the flowers of the plum, cherry, and sloe, cut longi- 
tudinal sections of the flowers, and note the form of the receptacle and the 
form and position of the various parts of the flowers, paying special attention 
to the gynaecium. 

Ex. 205. Watch the development of the ovary of a plum flower, when tb 
latter begins to fade. What becomes of the receptacle ? 

Ex. 206. Examine a half-grown plum or cherry. Observe the place where 
the style was placed on the ovary, and also the position of the ventral 
suture. 

Cut sections both longitudinal and transverse of the ovary every week from 
the time the flower fades up to the time the fruit is ripe. Note especially the 
growth in thickness of the parts of pericarp, viz., the endocarp or 'stone,' 
and the mesocarp or * flesh. 1 

Ex. 207. Measure the diameter of three or four fruits every week and 
determine when the increase in the diameter is greatest. 

Ex. 208. Make a collection of stones of the different varieties of plums and 
cherries. In what ways do they differ from each other ? Compare the stones 
of the peach, apricot, and nectarine. 

5. Genus Fragaria. Strawberries. This genus comprises 
three or four species of plants all with edible ' spurious fruits/ 
of which the wild strawberry or any of the garden varieties may 
be taken as an example. 

The calyx of the flower is gamosepalous of five sepals. Out- 
side the calyx, and alternating with it, is a whorl of five sepal- 
like members, constituting what is known as an cpicalyx. Each 
sepal-like member of the epicalyx represents two united stipules 
belonging to the adjacent true sepals. 

A vertical section of the strawberry flower is given in Fig. 1 25. 

The receptacle is of peculiar form : it is a solid roundish or 
cone-shaped structure, round the base of which extends a flat 
rim. To the flattened rim is attached the corolla (&) of five 
petals, and the andrcecium of many stamens (s) ; the numerous 
small carpels constituting the gynaecium are inserted upon the 



408 



ROSACES 



central raised part of the receptacle. Each carpel has a lateral 
style, and contains a single ovule. As the calyx, corolla, and 
androecium are inserted on the receptacle surrounding and free 
from the centrally placed gynsecium the flower is perigynous. 

The flowers are protogynous, and cross-pollination is usually 
effected by insects. In some cultivated varieties the flowers 
possess no stamens ; neither the fruits proper, nor the receptacles 
of such pistillate flowers develop unless pollen is brought from 
another flower, hence the necessity of planting kinds bearing 
staminate or bisexual flowers near them in order to secure a 
crop of ' fruit ' of such varieties. 

After fertilisation the gynaecium develops into the fruit, which 
is composed of small one-seeded achenes, and the receptacle 




B 



FIG. 123. A , Vertical section of a strawberry flower, a Sepal ; b petal; s stamens ; 
c carpel. 

B) Section of the 
parts of 



Section of the 'spurious fruit' developed from the flower A : the corresponding 
of the flower and ' fruit ' are connected by lines. 



grows to a large size, becoming at the same time succulent. The 
succulent growth of the receptacle appears to depend on the 
fertilisation of the ovules within the carpels ; should any of the 
carpels be injured and fertilisation be prevented, the part of the 
receptacle on which such carpels are situated does not develop, 
and the result is a deformed strawberry. The achenes, which 



RASPBERRY BLACKBERRY 409 

at first are crowded together, become much separated from each 
other by the growth of the receptacle, 

It is the receptacle or terminal part of the flower-stalk which 
is the edible part of a strawberry, the true fruit (ripened 
gynaecium) being the achenes. 

6. The common Cinquefoils (Potentilla reptans L., and P. 
Tormtntilla Scop.) and Silver Weed (Potentilla anserina L,) 
are weeds belonging to the Rosaceae, with yellow flowers resem- 
bling the strawberry in structure ; their receptacles, however, 
do not become fleshy, and the fruit is a collection of closely 
arranged achenes. 

To an unobservant eye the flowers of some of the Potentillas 
resemble those of the buttercup species of Ranunculus : they are, 
however, readily distinguished from the latter by the possession 
of an epicalyx and a comparatively large receptacle. 

7. Belonging to the Rosaceae is the genus Rubus , of which 
the Raspberry (Rubus Idaus L.) and Blackberry (Rubus fruti- 
cosus L.) may be taken as types for study of the flowers and 
fruit. The flowers of these plants generally resemble those of the 
strawberry in structure : no epicalyx is present however, and each 
carpel possesses two ovules instead of one. The flattened border 
of the receptacle on which the petals and stamens are inserted is 
broader in the raspberry and blackberry than in the strawberry, 
but the central lump on which the carpels are placed is very 
similar in all these flowers. 

After fertilisation the central portion of the receptacle, unlike 
the strawberry, remains comparatively small, and does not become 
succulent ; the carpels, however, develop into small succulent 
drupes, which are red or yellow in the raspberry and black or 
deep purple in the blackberry. 

Thus the part which is eaten in the raspberry is a true fruit, 
consisting of several one-seeded little drupes or drupels. 



410 ROSACES 

Ex. 209. Examine the flower of a strawberry. Make sections to illustrate 
the shape and extent of the receptacle. 

Ex. 210. Watch the growth of a strawberry from day to day until the fruit 
is nearly ripe. Observe what becomes of the calyx, petals, and stamens. 

Examine the form and content of the carpels and the achenes which de- 
velop from them. 

Make a vertical section of the nearly ripe 'fruit.' Note the distribution 
of the vascular bundles in it. 

Ex. 211. Compare a raspberry or blackberry flower with that of a straw- 
berry. Watch the growth of the fruit after the flower fades, noting the 
development of the little drupes from the carpels. 

Examine the structure of a young carpel and compare it with that of a 
drupel. 

8. The genus Rosa includes the wild Dog-Rose (Rosa canina 
L.) and several other indigenous species, as well as the many 
introduced species and their hybrids and crosses much cultivated 
as ornamental plants in the garden. 

The flowers are markedly perigynous. 

In the wild roses the calyx consists of five sepals ; the corolla 
is polypetalous of five large petals, and the andrcecium possesses 
numerous stamens. The receptacle is deeply-hollowed out like 
that of the plum, but the upper part is constricted. The 
gynaecium is apocarpous, and consists of many free carpels 
inserted on the bottom and sides of the hollow urn-shaped 
receptacle: the styles and stigmas of the carpels protrude 
through the narrow opening of the receptacle. After fertilisa- 
tion the carpels develop into achenes with hard, bony pericarps, 
and the receptacle which surrounds them becomes somewhat 
fleshy and red. 

The 'hip* of the rose is therefore a spurious fruit, which 
consists of a scarlet or red receptacle inclosing the true fruit 
(the achenes). 

Ex. 212. Cut a vertical section of the wild rose. Note the form of the 
receptacle, and compare it with that of a plum, cherry, or sloe. 

Observe the number, shape, and structure of the carpels ; also the position 
of the sepals, petals, and stamens of the flower. 



WHITE BEAM 



411 



What parts of the flower are still present in a ripe 'hip/ 
Ex. 213. Examine the structure of a double garden rose and compare it 
with that of a wild one. 

9. Genus Pyrus. To this genus belong the Pear (Pyrus 
communis L.), Apple (Pyrus Mains L.), Medlar (Pyrus ger- 
manica Hook.), and several other species, such as Mountain Ash 
(Pyrus Aucuparia Gaert.), Wild Service (Pyrus torminalis 
Ehrh.), and White Beam (Pyrus Aria Sm.). 




FIG. 126. A, Vertical and transverse section of a 
pear flower, n Sepal; a 'calyx-tube* of the recep- 
tacle ; r lower part of the receptacle ; c carpels im- 
bedded in r ; o ovules ; b petal ; s stamen ; st style. 

B) Pome developed from the flower A . 

The flower and fruit of the pear, illustrated in Fig. 126, may 
be taken as an example of the genus. 

The receptacle of the flower is hollowed out, and the gynaecium, 
consisting of five carpels, is sunk in the hollow space. 

In the plum (cf. Fig. 124) and rose, which also have similarly 
hollowed receptacles, the carpels are free from the sides of the 



41* ROSACES 

latter ; but in the pear the ovaries of the carpels are fused with 
the receptacle, and also united with each other except near their 
ventral sutures (see the middle of the transverse section, Fig. 
126, A) and along the styles, which are free. The ovary is 
inferior and five-chambered : in each carpel are two ovules. 

The upper part (a) of the receptacle is sometimes termed the 
calyx-tube of the flower ; to it is attached the calyx of five sepals, 
the corolla of five white petals, and the andrcecium of many 
stamens. 

After fertilisation the petals fall off, the stamens and styles 
wither, and the rest of the flower develops into a peculiar 
* false fruit ' termed a pome. 

At the upper part of the pome is seen the * eye ' of the ' fruit,' 
consisting of the so-called calyx-tube with the remains of the 
sepals (n) and stamens (s) attached to it : the withered styles 
(st) are also frequently visible. The carpels of the gynaecium 
which constitute the true fruit are fleshy, but their inner walls 
develop into a thin, tough, horny endocarp surrounding 
the seeds. The main bulk of the pear for which the * fruit ' 
is grown is the very large receptacle which envelops the 
gynaecium. 

The flowers of the pear are protogynous and have white petals : 
the pome is top-shaped. Self-fertilisation is possible even with- 
out the visits of insects : cross-fertilisation is however most 
common in the chief rosaceous genera. Cross-fertilisation is 
necessary for the ' setting ' and development of the ' fruit ' of 
several varieties of pears : after pollination from the same flower 
or from plants of the same variety no fruits 'set/ hence the 
importance of planting several distinct varieties in an orchard of 
pears. 

Most of the cultivated Pears appear to be hybrids and selected 
crosses between several species of Pyrus. 

10. The Apple differs from the pear in possessing flowers with 
pink and white petals and styles which are united at their bases 



QUINCE 413 

within the calyx-tube : the pome moreover is somewhat spherical 
or conical with an indented base where it joins the peduncle. 

n. The Medlar (Pyrus germanica Hook.) is sometimes placed 
in a separate genus and named Mespilus germanica L. Its 
1 fruit ' is a roundish top-shaped pome to which are attached the 
five large leaf-like sepals. The receptacle is hollowed out as in 
the apple and pear, but it does not completely enclose the 
carpels; the latter are consequently exposed within the broad 
open calyx-tube. Each carpel, of which there are five, de- 
velops a hard bony wall which protects the single seed within it 

21. Allied to the medlar in structure of the fruit is the White- 
thorn or Hawthorn (Cratagus Oxyacantha L.), so valuable for 
hedges. 

The ' fruit ' when ripe is a scarlet round or ovoid pome, but 
the upper part of the receptacle or calyx-tube is more con- 
tracted than in the medlar and the sepals are small. The carpels 
are usually only one or two in number : they develop hard bony 
walls. 

13. The Quince (Cydonia vulgaris Pers.) belongs to another 
genus of the Rosaceae. 

The * fruit ' or pome is hard and possesses a woolly surface 
when young but is smooth when ripe. It resembles the pear or 
apple in shape and structure, but within each of its five carpels 
are many seeds arranged in two rows. The sepals at the apex 
of the fruit are leaf-like. 

The testa of the quince seeds abounds in gum which with 
water swells up into a mucilage. 

Ex. 214. Compare the flowers of the apple and pear. In what do they 
differ from each other ? 

Ex. 215. Make longitudinal and transverse sections of the flowers of an 
apple and a pear. Observe the position and extent of the receptacle and the 
part of it termed the calyx-tube ; in each note also the number of carpels 
and the ovules in the latter. 

Bx. 216. Examine a half-grown apple and pear : observe the calyx- 
tube. What part of the apple and pear flower is still visible in the fruit 



414 ROSACE^E 

Cut longitudinal and transverse sections of an apple and a pear Note 
the number and position of the seeds in each loculus within the * fruits.' 

Ex. 217. Examine the structure of a hawthorn flower. 

Watch the growth of the * haws ' after the flower fades : cut sections and 
examine the structure of young and old ' haws.' Compare a * haw ' with 
an apple. 

Ex. 218. Repeat Ex. 217, using a quince and medlar instead of the haw- 
thorn. 

14. Common weeds belonging to the Rosaceae and possessing 
flowers and fruits somewhat different from any previously dis- 
cussed are : 

Meadow Sweet (Sptraa Ulmaria L.) ; Wood Avens (Geum 
urbanum L.) ; Agrimony (Agrimonia Eupatoria L.), and species 
of Burnet (Poterium). 

The fruit of meadow sweet consists of five or six follicles each 
containing usually two seeds ; that of wood avens is composed 
of achenes which when ripe have long hooked styles. In agrimony 
the fruit consists of one or two achenes imbedded in a small 
spinous woody receptacle. 

Lesser Burnet (Poterium Sanguisorba L.). A perennial 
herbaceous plant common on dry calcareous soils in various 
parts of the country. It grows to a height of 18 inches or 2 feet, 
and has a slightly angular stem bearing pinnate leaves, with 
from five to ten pairs of coarsely serrate leaflets. The flowers 
are small of reddish-green colour and arranged in dense heads at 
the end of long furrowed stalks. The upper flowers of the 
head are female with one or two carpels : the lower ones male or 
bisexual with twenty or thirty stamens. None of the flowers 
possess a corolla. 

The fruit consists of one or two achenes enclosed in a four- 
winged receptacle. The margins of the wings are entire, the part 
between the wings being netted or irregularly veined. 

Forage Burnet (Poterium polygamum W. and K. = P. muri- 
catum Spach.) is a continental species similar to P. Sanguisorba 
but larger in all its parts, including the inflorescence and fruit. 



FORAGE BURNET 415 

The four wings of the fruit are usually toothed along the 
margins and the parts between the wings deeply corrugated and 
pitted (C, Fig. 206). 

The truits constitute a common impurity of unmilled sainfoin 
' seed/ especially that of foreign origin, and samples of the latter 
should always be examined for them. 

The Burnet recommended by seedsmen for forage is usually 
this species, but the native species is also used occasionally. 
Both these plants have been praised for growth on dry calcareous 
soils, alone or in mixture with grasses and clovers, especially for 
sheep food. 

By themselves they are of little value as they are liable to 
become hard and woody, and are rejected by all kinds of stock 
unless the latter are pressed by hunger. In mixtures even, we 
think, they have little or nothing to recommend them except for 
use upon very dry chalky ground where nothing better can be 
grown. 

Ex. 219. The student should examine and become practically acquainted 
with Meadow Sweet, Wood Avens, Agrimony, Lesser Burnet, Forage 
Burnet and the common species of Potentilla. 



CHAPTER XXXI 
LEGUMINOS^. 

i. THE Order Leguminosae ranks next to the Composite in 
number of species, about seven thousand being recorded. The 
Order is divided into three Sub-orders, namely, Casalpinea^ 
Mimosect) and Papilionacect The two former are almost entirely 
tropical and possess little of interest or importance for the 
farmer : the Papilionacese, however, includes some of the most 
important fodder crops known, and the seeds of several species 
are utilised as human food. 

SUB-ORDER PAPILIONACEJB. 

2. General characters of the Sub-Order. Flowers irregular, 
protandrous, medianly zygomorphic, slightly perigynous ; calyx 
gamosepalous, five-partite ; corolla, usually polypetalous, though 
in red clover and some other plants of this order the bases of 
the petals are united with each other and with the filaments of 
the stamens ; the lower part of the corolla in such cases is 
tubular. The petals are irregular and five in number, the 
posterior one is large and conspicuous and is termed the 
* standard ' or vexillum of the corolla ; besides this are two 
lateral petals known as the ' wings ' or ala, and two anterior 
petals more or less coherent by their margins and forming a 
boat-shaped structure called the 'keel' or carina in which the 
gynaecium and stamens are enclosed and protected. This form 
of corolla, from its fanciful resemblance to a butterfly, is termed 
papilionaceous, and is characteristic of the sub-order. The andro* 

416 



GENERAL CHARACTERS OF SUB-ORDER 417 

cium consists of ten slightly perigynous stamens, either all the 
filaments are united (monadelphous\ or nine are united and the 
posterior or upper one free (diadelphous). The gynaecium is 
superior, of one carpel, and contains one or many ovules. Fruit 
generally a legume; seeds with a firm leathery testa, exendo- 
spermous ; the embryo possesses thick fleshy cotyledons. 

The cotyledons of the bean, vetch, and pea remain permanently 
below ground, while others, such as those of the clover, sainfoin, 
and lucerne, come above the ground soon after germination 
commences. 

The flowers of the Papilionaceae are all specially adapted 
for insect pollination. The * standard ' acts as a conspicuous 
attractive banner. The 'wings' and 'keel' petals are often 
interlocked near their bases in such a manner that when an 
insect of sufficient weight alights on the 'wings' these are 
pressed downwards and in turn depress the 'keel' petals; 
the stamens, style, and stigma are by this movement forced out 
at the apex of the ' keel,' and the pollen is brought into contact 
with the underneath part of the insect's body. The insect 
visiting another flower brings the pollen on its body into contact 
with the stigma which, on account of its length and position, is 
generally forced out first from the apex of the 'keel'; cross- 
pollination is thus effected. 

Some plants, such as field and garden peas, sweet pea, common 
and hairy vetch, dwarf kidney-bean, hop-clover, and hop-trefoil, 
while undoubtedly posessing flowers specially adapted for insect- 
pollination are capable of self-pollination, and are also fertile and 
able to produce seeds when insects are excluded. Others, such as 
red, white and crimson clovers, scarlet-runner bean, and broad 
bean are more or less sterile when insects are prevented from 
visiting the flowers. 

All parts of the plants, and especially the seeds, contain 
considerable quantities of nitrogenous substances, upon which 
much of their feeding-value depends. 



41 8 LEGUMINOS^E 

Through symbiosis with a bacterium which penetrates the 
roots, the Leguminosae are able to thrive upon ground which 
is devoid of combined nitrogen : the nitrogen which they require 
for growth is obtained indirectly from the free nitrogen of the air 
(see p. 806). 

Usually a cereal and especially wheat is taken after the growth 
of a leguminous crop. 

Some species, such as vetches and lupins, are occasionally 
grown on poor, dry ground to be subsequently ploughed in as a 
' green manure ' ; this practice largely increases the nitrogen- 
content of the soil and at the same time augments the stock 
of humus in the latter. 

3. The genera most important from a farmer's point of view 
are the following : 

Pisum (peas), Vicia (vetches and common bean), Trijolium 
(the true clovers), Medicago (the medicks lucerne and yellow 
trefoil), Onobrychis (sainfoin), Anthyllis (kidney-vetch), and Lotus 
(birds'-foot trefoil). 

Some common plants of less importance belonging to other 
genera are Gorse or Whin (genus Ulex), Bokhara clover (genus 
Mdilotus\ Everlasting pea (genus Lathyrus\ Lupins (genus 
Lupinus) ; and in gardens Scarlet Runner and Dwarf Kidney 
Beans of the genus Phascolus* 

4. Peas (genus Pisum). The cultivated varieties of peas are 
usually supposed to belong to two species, namely : (i) the 
Field Pea (Pisum arvense L.), which is said to be found in a 
wild state in the south of Europe, and (2) the Garden Pea 
(Pisum sativum L.), which is not known wild, and may possibly 
be a modified form of the former species. 

The Garden Peas, of which there are endless varieties, have 
white flowers, and seeds of uniform yellowish white or bluish 
green colour: they are also more delicate and suffer more 
readily from frost and drought than the field pea. 

Some of the garden forms for human consumption are grown 



FIELD PEA 419 

on farms near large towns, and are a profitable crop on suitable 
lands under such circumstances. 

The Field Pea, of which there are comparatively few varieties, 
is more hardy than the garden pea, and the flowers have purple 
or lavender coloured * standards ' and ' wings * of deeper purplish 
red ; the colour of the seeds is greyish brown, dun-colou/ed, or 
grey speckled with fine spots. 

SEED AND GERMINATION. The seeds do not germinate freely 
below a temperature of '5 C. 

The young seedling resembles that of the bean in general 
structure. It possesses a strong tap root, two cotyledons which 
remain permanently below ground, enclosed by the testa of the 
seed, and an epicotyl, which comes above ground in a curved 
form. 

ROOT, STEM AND LEAVES. The pea possesses a marked 
tap root and a number of branching secondary roots. The 
stems are round and too weak to stand erect without a 
support. 

The leaves are pinnately compound with large leaf-like stipules, 
the leaflets, of which there are generally two or three pairs, are 
ovate, with mucronate tips. The end of the leaf possesses one 
or more opposite pairs of tendrils and a terminal one, all of 
which are modified leaflets (Fig. 33). The tendrils are sensitive 
to contact, and wind round any small support which they touch ; 
by their aid the plant is enabled to support itself in a more or 
less erect position by clinging to neighbouring objects 

INFLORESCENCE, FLOWERS AND FRUIT. The inflorescences 
are axillary racemes with few flowers, often only one or two. 
Each flower is perigynous; the calyx gamosepalous and five- 
lobed ; the corolla papilionaceous (Fig. 127); the andrcecium is 
diadelphous consisting of ten stamens, one of which is free, the 
rest united by their filaments. 

The gynaecium of the flower is superior and consists of a single 
carpel with many ovules ; the stigma is placed at the end of the 



42O 



LEGUMINOS^E 



curved style which bears a number of hairs on its concave or 
upper side. The fruit is a typical legume (Fig. 37). 

VARIETIES. The following are the commoner varieties of 
field peas : 

Common Grey Field Pea. A prolific late variety suited to 
light chalky soils. The c straw ' is liable to be long and on good 
soils becomes * laid ' before the pods and seeds are ripe. 



5 




o 



FIG. 127. i. Flower of a field pea. 2. Section of same ; s ' standard ' ; w ' wing,* 

united filaments of nine 
style of gynaecium. 4. The 



and k 'keel' petals respectively. 3. Andrcecium; / united filaments of nine 
stamens ; f filament of single free stamen ; 



gynaecium ; o ovary, s style with hairy stigma. 

The legumes are almost cylindrical, and contain from six to 
eight dun-grey or bluish-green self-coloured seeds. 

This kind is sometimes grown in mixture with Scotch horse 
beans, which act as supports for the peas. 

Early Grey Warwick. This is a rapid grower, and adapted 
to late districts where the soil is in rich condition. It has dun- 
coloured seeds spotted with purple. 



GREY ROUNCIVAL OR DUTCH PEA 421 

Partridge. An early prolific variety of good quality, and suit- 
able for growing in late districts. 

The stems are soft, and usually about 4 feet long with broad 
leaflets. The pods often grow in pairs, each containing from 
five to seven roundish seeds of a pale brown colour beautifully 
speckled with small darker spots and lines. 

Grey Maple. This variety has speckled seeds like those of 
the Partridge variety, but larger ; it is adapted to the better kinds 
of soil in districts with mild climate. 

Grey Rouncival or Dutch Pea. A very late field pea with 
very long ' straw ' and large dun-coloured wrinkled seeds. The 
stems are often 7 or 8 feet long, and the pods generally grow in 
pairs and contain five or six seeds. This variety is only suited 
to light soils in early districts. 

SOIL. Peas give the most satisfactory yield of seeds upon 
soils of a medium or somewhat inferior character. In all cases 
it is necessary that the ground should contain a considerable pro- 
portion of lime. Upon good rich soils or those of a peaty and 
damp character the stems and leaves grow too long and become 
laid : the crop then yields few peas. 

In cases where the ground is comparatively rich, but not stiff 
enough to yield a good crop of beans, a mixture of beans and 
peas at the rate of i J bushels of the latter to 2^ of the former 
often gives good results. The stiff erect bean stems act as sup- 
ports for the luxuriant weak stems of the peas, and the latter are 
enabled to secure an adequate amount of light and air for seed 
production. 

SOWING. The seed is best sown in February or March in drills 
at a distance of 14 or 18 inches apart and 2 to 3 inches deep : the 
amount needed is 2 to 4 bushels per acre according to the size of 
the individual seeds. On very clean ground the seed is occasion- 
ally sown broadcast at the rate of 4 or 5 bushels per acre. 

YIELD. Peas are one of the most uncertain of farm crops, only 
one crop out of every three or four being satisfactory. The yield 
on the best soils adapted to the crop averages about 30 or 35 
bushels of seed and about a ton of straw per acre, but on unsuitable 
soils in bad seasons the yield of seed may be practically nothing. 

COMPOSITION. Peas are slightly less nitrogenous than beans, 
but they contain more soluble carbohydrates and less ' fibre ' 
than the latter. 

29 



422 LEGUMINOS^E 

Peas contain on an average 14 per cent, of water, 20 per cent, 
of albuminoids, about 54 per cent, of soluble carbohydrates, and 
5i per cent, of ' fibre.' 

Vetches (Genus Vicia.) 

5. Bean (Vicia Faba L., or Fab a vulgaris Moench). A well- 
known annual plant whose seeds are excellent food for all kinds 
of stock on the farm. The stems and leaves (' haulm or straw ') 
when well-harvested make fodder little inferior to good hay. 

SEED AND GERMINATION. The nature of the seed and seed- 
ling of a bean has been discussed in Chapter II. 

ROOT, STEM AND LEAF. The primary root is strongly de- 
veloped. The stems, which stand erect, are unbranched, and 
from 2 J to 5 feet high, according to the variety. They are ' fleshy ' 
and stiff, four-sided and slightly winged. 

Usually three stems spring from one seed, viz., the main stem, 
and two lateral ones. 

The leaves are pinnately compound, with one, two or three 
pairs of elliptical entire leaflets. 

INFLORESCENCE, FLOWER AND FRUITS. The inflorescences 
are axillary racemes of two to six flowers. The flowers are of 
the common papilionaceous type; the petals are usually all 
white, with the exception of the wings, which have a large black 
spot upon them. 

The fruit is a legume which, when young, is fleshy and has a 
thick velvety lining. After ripening the valves of the legume 
become tough and hard. 

VARIETIES. Several varieties of the bean, such as the Long 
pods and Broad Windsor, are cultivated mainly in gardens and 
cannot be noticed here. The following kinds are those most 
generally grown as farm crops : 

Scotch Horse Bean. A very hardy, fairly prolific variety, with 
stems about 4 feet high. The pods contain on an average three 
seeds. Each seed is buff or pale brown in colour, and about 



MAZAGAN 423 

half an inch long, slightly flattened on the sides with a black 
hilum. 

The Scotch horse bean grows best on strong, well-drained 
clays. 

Tick Bean or English Horse Bean. This variety, of which 
there are a large number of named strains, is closely related 
to the above. 

Its seeds are not flattened on the sides but are almost 
cylindrical, rounded at the ends and slightly smaller than the 
Scotch horse bean. 

The tick bean is very prolific and more suited to the climate 
of the south of England, where it grows upon lighter soils than 
those essential for a good crop of the Scotch horse bean. 

Winter Bean. A variety resembling the tick bean, which, on 
account of its hardy nature, can be sown in October to stand 
the winter. It is usually harvested in the following July or 
August. 

Mazagan. This is an early variety of fine quality, sometimes 
grown in gardens. When grown as a farm crop it requires moder- 
ately stiff land in good condition to obtain the best results. 

The stems of the plant are slender, and 4 or 5 feet high. The 
pods are long and narrow, and generally contain four seeds, each 
of which is about three-quarters of an inch long, with flattened 
and slightly wrinkled sides. 

SOIL. The soils best suited to the growth of beans are well 
drained, clayey loams. On light soils the total produce is small, 
while on those rich in humus the plants grow tall and leafy, but 
yield few seeds. 

SOWING. With the exception of the winter variety beans are 
sown in February or March. The crop is cut in late autumn, 
when the stems are brown with a few small green patches upon 
them ; the hilum should be black, and the seeds free from the 
funicles in the pod before cutting the crop. 

The seed is sown in drills usually about 18 inches or a feet 



424 LEGUMINOS^E 

apart ; the amount used is from 2 to 4 bushels, according to the 
size of the bean. 

YIELD. The average yield is about 30 bushels of seed and 
from 20 to 30 cwt. of ' straw.' 

COMPOSITION. Bean seeds contain 14 per cent, of water and 
about 23 per cent, of albuminoids, mainly in the form of fine 
aleuron-grains in the cells of the cotyledons of the embryo. The 
carbohydrates, the chief of which is starch, average 48 per cent; 
the fat, i per cent. ; and the fibre, 7 per cent. 

6. Common Vetch or Tare (Vicia satjva L.). An annual 
vetch with trailing or climbing stems and compound pinnate 
leaves. The primary stems branch extensively from the axils 
of the lower leaves, and the secondary and tertiary branches also 
branch freely. 

The first few leaves of the seedling plant have one or two 
pairs of narrow leaflets and no tendrils ; those appearing later 
are, however, furnished with two or three terminal tendrils and 
six or seven pairs of leaflets, which are broader and oblong or 
obovate in form, with a stiff mucronate point. 

The stipules are small and pointed, with a dark purple blotch 
in the centre. 

The flowers, which are reddish purple, are borne singly or in 
pairs on very short stalks in the axils of the leaves. 

The fruit is a more or less hairy legume, containing from four 
to ten smooth round seeds. 

The cultivated vetch (V. sativa L.) is probably merely a 
form of Vicia angustifolia Roth., which lis a common wild plant 
in dry soils throughout the country. 

There are two races of the cultivated vetch or tare, namely, 
Winter Vetches and Spring Vetches. ' 

The Winter Vetch is a hardy form, capable of enduring 
frost ; it has smoother, more cylindrical pods, with smaller 
seeds than the summer variety, and gives less bulk of stem and 
leaves. 



SPRING VARIETY 425 

This form is usually sown in September, October, or Novem- 
ber, either alone or mixed with rye, winter barley, or oats for 
early spring fodder. 

The cereal is not only nutritious but acts as a support for the 
vetches, and keeps the latter from trailing on the ground and 
rotting at the base of the stem. 

The Spring Variety grows more rapidly and luxuriantly 
than the winter one, and is a more delicate plant. When used 
for green fodder it is sown either alone at the rate of 4 bushels 
per acre, or in mixture with oats or barley at the rate of 2\ 
bushels of vetches to i\ bushels of the cereal. 

Small areas are sown from February onwards at short intervals 
so as to provide a succession of crops during the summer. 

It must be borne in mind that the spring variety is uncertain 
for autumn sowing, and that the true winter variety if sown re- 
peatedly in spring produces seeds which give rise to somewhat 
delicate plants. 

As the botanical morphological features of its seeds present no 
points of constant difference by which the winter form may be 
distinguished from the spring one, the farmer is compelled to de 
pend on the honesty of the vendor when purchasing either kind. 

Vetches grown for hay should be cut when in bloom ; at this 
stage of growth it is superior in nutritive value to good meadow 
hay ; when grown for seed, the yield of which is always very 
uncertain, vetches may be sown alone or in mixture with beans 
whose stiff stems act as supports and enable the crop to obtain 
a better supply of the light and air necessary for healthy 
growth. 

The seeds of the vetch have practically the same composition 
as those of the field bean. 

Ex. 220. Sow the seeds of bean, pea and vetch in garden soil or pots ; dig 
up the seedling as soon as two full-grown leaves appear on the stems above 
ground, and examine the root system and the form and size of the leaves on 
the stem above the cotyledons. 



426 LEGUMINOS^E 

Ex. 221. Dig up completely a half-grown plant of bean, pea and vetch, 
and study the manner of branching in each. 

Ex. 222. Compare the flowers of the bean, pea and vetch, and note any 
points of difference between them Compare their leaves also. 

Ex. 223. Make a collection of seeds of the different varieties of field bean, 
field pea, and vetch. 

7. Vetchlings or Everlasting Peas (genus Lathyrus). This is 
an extensive genus of climbing plants much resembling vetches, 
but with fewer leaflets and a flattened style. Eight or nine 
species are wild in this country, and are known as vetchlings or 
everlasting peas, although some of them are annuals. They 
are all eaten by cattle. 

The commonest species is the meadow vetchling (Lathyrus 
fratensis L.), which is frequent in meadows and hedges. It 
grows 2 or 3 feet high, and has narrow lanceolate leaflets and 
racemes of bright yellow flowers. 

The Wood Vetchling (Lathyrus sylvestris L.) grows in 
woods and thickets ; it has winged stems, and often climbs to 
a height of 5 or 6 feet The leaves possess tendrils and have 
one pair of large lanceolate leaflets from 3 to 6 inches long and 
half an inch broad. 

Usually four or five flowers are present on each long peduncle : 
the 'standard' petal is rosy-pink, the 'wings' purple. This 
plant has been selected and cultivated on the continent as a 
perennial fodder crop,* and is termed Wagner's Everlasting Pea 
(Z. sylvestris L., form Wagncrf). Like lucerne it withstands 
drought, and when once established gives very large yields of 
highly nutritious food. 

The seed is at present expensive, and germinates very slowly 
in the open field. 

Wagner's everlasting pea possesses few, if any, advantages 
over lucerne and other leguminous crops at present in use on the 
farm, and we see little need of its introduction. 



RED OR PURPLE CLOVER 427 

Clovers (Genus Trifolium). 

8. Red or Purple Clover ( Trifolium pratensc L.). Red clover 
is the most extensively cultivated species of Trifolium^ and 
ranks first among fodder plants for excellence of yield, nutritive 
value, and adaptability to various soils and climates. It is 
grown alone or in mixture with grasses for leys of short duration 
Soils upon which a crop has been raised refuse to grow a 
second crop of remunerative size until a certain period has 
elapsed, usually not less than four years, often much more. 
Such soils are said to be 'clover-sick/ and although there is 
no doubt that the dying away of clover sown on ground ex- 
hibiting this peculiarity is due to several different causes, none 
of the latter are yet very clearly understood. 

SEED AND GERMINATION. The seeds absorb about their own 
weight of water, and germinate in two or three days. The 
seedling possesses a well-developed primary root and hypocotylj 
the two elliptical cotyledons come above ground. The first 
foliage-leaf of all the clovers is different from the succeeding 
ones in being simple and rounded instead of compound and 
ternate as in those which arise later upon the plant 

ROOT AND STEM. The primary root of red clover develops 
into a strong tap root with three lines of secondary roots which 
spread extensively through the soil. ' Nodules ' are abundant 
upon the roots. When sown in spring with a cereal, the epicotyl 
of the young plant develops very little, but a great many 
buds and short branches arise in the axils of the closely-packed 
leaves, and by the contraction of the root the short stem and 
its buds and leaves are pulled down so that they lie close to 
the ground in the form of a rosette during autumn and winter. 
Usually in the following spring but sometimes in the autumn 
of the year in which the seed is sown, the buds grow out into 
ascending branches, each from i to 2 feet high, bearing leaves 
and terminating in dense flower-heads. 



428 LEGUMINOS^E 

LEAF. The leaves are stipulate and compound, with three 
ovate leaflets, each of which is bordered with hairs. 

The stipules are membranous with greenish-purple veins and 
united to the petiole except at their tips which end in a fine 
point (i, Fig. 128). 

INFLORESCENCE AND FLOWER. The inflorescences are 
terminal, ovoid or spherical capitula about i or i| inches in 






1. 2. 3. 

FIG. 128. Stipules of the leaves ot (i) red clover; (2) alsike clover; (3) crimson clover 
or ' Trifolium ' ( T. incamatum) (all natural size ) 

length and composed of many small flowers crowded together. 
Beneath each inflorescence are two leaves. 

The flower is protandrous and has a gamosepalous calyx with 
five free teeth at its apex, the inferior one being longer than the 
rest. 

The corolla is medianly zygomorphic and consists of a 
standard, wings, and keel; the petals, however, instead of being 
free as in the pea, are united at their bases to form a tube 
nearly half an inch long (i, Fig. 129). 

The andrcecium is diadelphous; nine united stamens are 
fused with the corolla tube and the posterior one is free. 



RED CLOVER 



429 




The single carpel of the gynaecium has a long style and a one- 
celled ovary containing two ovules. 

The fruit of red clover, is a one-seeded capsule (Fig. 130) 
the upper part of which separates from the lower along an 
irregular transverse line (pyxidium). 

VARIETIES. Eed Clover ( Trifolium pralense. L.) is a wild plant 
common in meadows and pastures 
throughout Europe. In a wild state 
it is variable in its habit of growth 
and durability, but usually lasts from 
three to four years. The seeds of 
this truly wild indigenous plant 
would no doubt be very useful in 
mixtures for leys and permanent 
pastures, but none are met with in 
commerce except in name. 

The cultivation of the plant as a 
fodder crop was introduced into 
this country from the Continent in ?/. rcd r cl 9 ve /- '.?. l >' ie ; ^ s vgma. 3 . 

' Ripe fruit (pyxidium) containing the 

the early part of the seventeenth single seed 4. s . Gynaecium.of white 

J r clover (two and a half times the 

century, and from that 'time to the natural sue.; 
present its cultivation has spread 
extensively. 

So far as our experience goes no 
seeds appear to be in commerce 
which have been derived from the 
wild plant within recent times, all 
those sold being the progeny of 
plants which have been under the 
influence of cultivation for long 
periods of time. 

Among these samples obtainable from the seedsman are a con- 
siderable number of varieties varying in hardiness, yielding 
capacity, and slight botanical features. 



FIG. 1291. Firmer of red clover. 
Calyx; j 'standard;' w ' wings ; 
k ' keel ' of the corolla. 2. Gynaecium 




FIG. 130. Fruit (pyxidium) of red 
clover ; on the upperpart a portion of 
the withered style is seen (enlarged.) 



430 LEGUMINOS^ 

Although they are extremely variable in form and pubescence 
of leaves, solidity of stem and shape of the capitula, the different 
commercial forms may be divided into two classes or groups, 
namely: (i) 'Ordinary Red* or 'Broad Red Clover/ and 
(2) 'Perennial Red/ 'Single cut Cow-grass' or 'Mammoth' 
Red Clover (' Trifolium pratcnsc pcrenne*}. 

The former class embraces the rapid-growing forms of short 
duration, being little more than biennial plants. They give two 
cuts or more per annum, and are specially suited for short leys. 
After being mown once they produce a second crop, from which 
a good yield of seed may often be obtained. 

The leaflets of the plants are oblong, bluntish and pubescent 
on both surfaces, the flower-heads round and sessile, and the 
stems frequently hollow. 

Representative of the second class is Single-cut Cowgrass, 
a more permanent and hardier plant, which produces her- 
bage for several seasons, and therefore useful for long leys and 
permanent pasture. The leaflets are longer, narrower and less 
hairy than those of Broad Red Clover, the stems more or less 
solid, and the flower-heads ovoid and often on short stalks. It 
blooms ten to fourteen days later than Broad Red Clover, gives 
only one cut of hay or fodder per annum, and produces com- 
paratively few seeds. 

The existence of numerous intermediate forms renders it 
impossible to state with certainty to which class or group certain 
individual plants should be assigned. 

The forms to use for particular purposes is a matter of no small 
importance to the farmer, but as it is impossible to distinguish 
them accurately either in the seed or when growing, he must 
depend upon the reputation of the vendor (see pp. 627 and 
656) when he purchases the seed. 

CLIMATE AND SOIL. Red clover grows readily upon almost 
all soils except those which are very dry or which contain an 
execs'? of stagnant water. It thrives best, however, on some- 
what heavy loams containing a fair proportion of lime. 

It is sensitive to spring frosts, and varieties obtained from the 
warmer parts of Europe and America often die off completely 
during autumn and winter in England. 

SOWING. The seed is sown generally with a cereal crop in 
spring ; the amount needed for a crop when used alone is 16 Ibs. 
per acre, if the seed is pure and of good germinating capacity. 



WHITE OR DUTCH CLOVER 431 

9. Zig-Zag Clover: Marl-Grass: Meadow Olover (Trifolium 
medium L.). A perennial clover which grows most commonly 
upon dry banks and in dry elevated pastures. At first sight it 
may be mistaken for red clover, the flower-heads being of similar 
colour. The stem is, however, straggling and bent in a zig-zag 
manner at every node. The leaflets are narrower and longer 
than those of red clover, and the free part of the stipules is 
longer, more pointed, and narrow. 

The flowers are a deeper purple colour and not so densely 
crowded together in the capituium; the latter, moreover, is 
stalked, the first pair of opposite leaves being a short distance 
below the base of the flower-head instead of close to it as in 
red clover. 

Seed of this species is not met with in commerce, and the 
plant is of little agricultural value. 

10. Alsike or Swedish Clover: Hybrid Olover (Trifolium 
hybridum L.). A perennial clover introduced into England 
from Sweden in 1834. 

It is a distinct species and not a hybrid as its name seems to 
imply. 

The stems are smooth, of upright habit, from i to 3 feet 
high. 

The free part of the stipules of the leaves are drawn out to a 
long tapering point (2, Fig. 128), and have pale green veins. 

The flower-heads, which are round, arise on peduncles 
springing from the axils of leaves on the main stems. 

The flowers are pale pink or white, resembling those of white 
clover; the fruit is an indehiscent pod, containing from one to 
three small seeds. 

Alsike, of which there are no specially cultivated varieties, is 
a more permanent plant than red clover, often lasting five or six 
years on suitable soils. It is also much more hardy and better 
suited to stiff damp soils, where other species of clover would 
scarcely thrive at all. 

Pure sowings are rarely made, but it is of great value in 
mixtures of grasses and clovers on all stiff moist soils, although 
the yield is not so good as that of the red species. 

11. White or Dutch Clover (Trifolium rtpcns L.), (Fig. 131). 
A well-known perennial clover, common in all good pastures 
throughout the country. It differs in habit of growth from red 
clover and alsike. Like these species it has a well-formed tap 



432 



LEGUMINOS^E 



root, but the stems, which are smooth, creep over the surface or 
just beneath the soil, and from their nodes adventitious roots 
are given off. The leaves have very long petioles and small 
ovate membranous-pointed stipules. 

The round flower-heads are produced at the ends of long 

stalks, which arise in the 
axils of the leaves and grow 
upwards (Fig. 131). 

The flowers are white or 
pinkish ; when the corolla 
fades it turns brown, and 
the whole flower becomes 
deflexed. 

The fruit is an elongated 
pod containing from four to 
six small seeds. 

Fig. 132 illustrates the 
early stages of growth of 
a seedling, which may be 
taken as typical of all the 
cultivated clovers. 

Three varieties of white 
clover are met with in com- 
merce, namely (i) 'Wild 
FIG. 131. Portion of white clover plant, showing White,' a small permanent 

the^' creeping 'habit of the stem, r Adventitious form ^hoSG Seeds are 

harvested from old natural 

pastures stimulated by applications of basic slag; (2) 'Culti- 
vated White Clover,' the larger commonly cultivated form ; 
and (3) Giant, Mammoth or Ladino White, a still taller Italian 
form adapted for heavy soils or irrigated land in a warm climate. 
(See Erith's Monograph on White Clover.) 

White clover is more permanent than either red clover 
or alsike, and grows upon almost all soils. It is sometimes 
grown alone for sheep food, but its chief use is in mixtures 
for laying down pastures for grazing purposes. 

12, Crimson or Italian Clover: Trifolium (Trifolium incar* 
natum L.). An annual species, with erect hairy stems from i to 2 
feet high. The stipules of the leaves are broad and the free 
part is rounded, often with a dark purple margin (3, Fig. 128). 
The flower-heads are terminal, and placed some distance above 




CRIMSON OR ITALIAN CLOVER 



433 



the last leaf of the stem : they are oblong or cylindrical, with 
rich crimson, rose or white flowers. 

Early and late varieties are met with in commerce, one of the 
latest being a white-flowered form with pale cream-coloured seeds. 




FIG. 132. Seedling of White or Dutch Clover at different stages of growth. In 2 the 
first foliage leaf is seen to be simple ; in 3 the ordinary trifoliate leaves have appeared. 

A variety, Trifolium Molinerii Balb., with shorter stems 
and pale, almost white, flowers, is native in Cornwall, and is 



434 LEGUMINOS^E 

probably the original form from which the cultivated crimson 
clover has been derived. 

Crimson clover is tender and cannot be grown except in the 
warmer parts of this country. In the south of England it is 
grown generally as a catch-crop, the seed being sown on the 
stubbles in autumn, and the produce fed off or cut for hay in 
the following May and June. 

13. Yellow Suckling (Trifolium dubium Sibth. = T. minus 
Sm.). An annual clover with ascending, or prostrate, wiry 
stems, sometimes a foot or 18 inches long, and small yellow 
flowers. The flower-heads are small, and formed of about a 
dozen flowers closely crowded together. 

Yellow suckling is a useful plant in pastures. The produce is 
scanty but nutritious to farm animals, and the plant indirectly 
adds nitrogen to the soil which benefits the grasses associated 
w ith it. 

Trifolium filijorme L. is another species very nearly resemb- 
ling T. dubium Sibth., but with only five or six flowers in each 
capitulum, and slender short stems not more than 5 or 6 inches 
long. Both are met with on dry, gravelly pastures. 

14. Another annual species, namely, Hop-Clover, sometimes 
termed Hop- Trefoil (Trifolium procumbens L.), is met with 
on dry, gravelly pastures. It resembles the above two species 
in general appearance, but the flower-heads look like miniature 
hops and possess about forty flowers of a tawny, yellow colour. 

The three last species are often confused with black medick 
(Medicago lupulina L.), which they resemble in habit as well 
as in colour and size of flower-heads. Black medick can, how- 
ever, be easily distinguished by its leaflets : these are obcordate 
as in the clovers, but the midrib is prolonged into a sharp 
(mucronate) point, while the yellow clover leaflets are without 
this projection. 

Bz. 234. Examine and compare the habit of growth in red, white, Alsike, 



LUCERNE OR PURPLE MEDICK 435 

and crimson clovers. Note which are upright growers and which are 
creeping. 

Make drawings of the stipules, and also note any differences of form and 
colour of the leaflets in each species. 

Ex. 225. Sow seeds of the above-mentioned clovers in garden soil or in 
pots in spring, and observe the form of the cotyledons, the relative size of 
the hypocotyl and root in the young seedlings. Watch the development of 
young plants up to the time of flowering, noting particularly the production 
of branches in each species. 

Sz. 226. Compare the flowers, fruits, and seeds of the chief clovers. Note 
the manner of dehiscence in the several pods, and the number of seeds in 
each. 

Medicks (Genus Medic ago ^ 

15. Black Medick : Nonsuch Glover: Hop-Trefoil, Yellow 
Trefoil (Medicago lupulina L.). An annual or biennial plant 
wild on waste ground all over the country, especially in cal- 
careous districts. 

The stems are much branched, from 6 inches to a feet long ; 
the lower parts spread over the surface of the ground but do not 
develop adventitious roots ; the upper parts are ascending. 
The leaves are trifoliate and the leaflets have a projecting mid- 
rib which distinguishes the plant from the somewhat similar 
yellow suckling and hop-clover. The flowers are yellow in small 
compact oval flower-heads. 

The fruit is a kidney-shaped, indehiscent black pod about an 
eighth of an inch across with a spirally curved tip ; it contains 
a single seed. 

Black Medick is sometimes sown alone on poor calcareous soils 
and used for sheep and lamb food. In suitable districts where 
the soil is dry and inferior, a small amount is a useful addition 
to grass mixtures for short leys. Occasionally a small quantity 
is sown with sainfoin to increase the bulk of produce during the 
first year when the sainfoin is not fully established. 

1 6. Lucerne, Alfalfa or Purple Medick (Medicago sativa L.). 
-A perennial introduced plant with erect branched stems i to 3 



436 LEGUMINOSiC 

feet high. The primary root is strongly developed and forms 
a tap root which in old plants is often three-quarters of an inch 
in diameter : this and the secondary roots penetrate several feet 
into the earth on ground with an open subsoil. The leaves are 
trifoliate ; each leaflet is obovate, dentate, with a notched tip 
and a projecting midrib (f y Fig. 133). 

The flowers are usually purple, but sometimes yellow, in 
dense axillary racemes, the peduncles of which are longer than 
the leaves. 

The fruit is a dehiscent legume coiled two or three times into 
a loose spiral : it contains several seeds. 

Lucerne is one of the most valuable fodder plants for warm 
climates and succeeds well in the south of England on ground 
with an open subsoil. It suffers very little from drought when 
once established and gives two or three heavy cuts of fodder 
every season, the first of which is ready more than a fortnight 
earlier than red clover. 

It is most frequently used green, but can be made into hay ; 
in the latter case it must be cut before flowering or it becomes 
hard and woody, and special care must be taken to prevent loss 
of leaves in handling. 

In the first season the young plants develop large root- 
systems and few stems and leaves above ground, consequently a 
small crop only is produced. 

Instead of the part of the stem above the cotyledons remain- 
ing short for some time and its leaves forming a rosette on the 
surface of the ground as in red clover, the internodes of the 
epicotyl in lucerne elongate at once (3, Fig. 133), and the main 
stem grows erect with comparatively few branches in the first 
season. The crop therefore in the earlier stages of growth often 
looks thin and disappointing. 

Vigorous branches, however, spring up later from the lower 
nodes of the stem and from the axils of the cotyledons (4, Fig, 
133), especially after being cut once. 



LUCERNE OR PURPLE MEDICK 



437 



In the second and third years a stout rootstock is formed from 
which a large number of stems are sent up and the plants yield 
a heavy crop of nutritious fodder. 

Under some circumstances a lucerne ley will last a very long 




FIG. 133. Four successive stages of development of Lucerne Seedling (Mtdicago sativa 
L.). The first foliage-leaf (</) is simple, the second and all others trifoliate, as at f* 
a Hyppcotyl ; b root \ c cotyledons ; a first foliage-leaf; e plumule ; /second foliage-leaf; 
g first internode of epicotyl. In 4 note the buds in the axils of the cotyledons. 

time but it usually becomes overrun with weeds in six or seven 
years, after which time it is ploughed up. 

Seed is sown from April to the end of June at the rate of 30 
Ibs. per acre in drills 6 or 8 inches apart to allow of the use of 
horse and hand hoes. ~ 



438 LEGUMINOS-^E 

For this and all perennial crops whose growth is slow at first, 
the ground should be especially clean before sowing or weeds 
may ruin the crop before it is established. 

Melilots (Genus Melilotus). 

17. The melilots have upright stems with trifoliate leaves, re- 
sembling those of lucerne. The flowers are small, yellow or 
white, arranged in one-sided axillary racemes. 

The fruit is a round or oval legume, which is only partially 
dehiscent ; it usually contains from one to four seeds. 

White Melilot \ Sweet Clover (Melilotus alba Desr.), which is a 
rather uncommon plant doubtfully native in Britain, is some- 
times introduced under the name of Bokhara Clover, and recom- 
mended as a forage crop. It is biennial, and produces a large 
bulk of leaves and stems, which have a fragrant odour like that 
of sweet vernal grass ; owing to its bitter taste it is, however, 
disliked by cattle, and also has the objectionable feature of rapidly 
becoming hard and woody. 

The seed is cheap, and possibly the plant may be found of 
service for ploughing-in as a green manure. 

Hubam Clover is the name given to a selected annual form of 
white melilot. 

Another commoner species, namely, Yellow Melilot (Melilotus 
ojficinalis Willd.), grows 2 or 3 feet high, and possesses deep 
yellow flowers. It is an annual, and met with in corn fields. 

Sainfoin (Genus Onobrychis). 

18. Sainfoin (Onobrychis sativa Lam.). A perennial plant, 
probably indigenous in the midlands and south of England on 
dry chalky soils. 

The primary root is thick and fleshy, and penetrates to a depth 
even greater than lucerne roots in open dry subsoils. 

The young plant forms a rosette of leaves close to the ground, 
and resembles red clover in its early habit of growth. 

From the rhizome several almost erect stems are sent up, each 
of which is from i to 2 feet high, ribbed, and slightly downy. 



GIANT SAINFOIN 439 

The first foliage-leaves of the seedling are small and simple 
with long petioles; the second and third are trifoliate, all the 
subsequent ones being pinnately compound with six to twelve 
pairs of opposite leaflets and a terminal one. The leaflets are 
narrow, obovate, and entire. 

The inflorescences are axillary, compact racemes, the peduncles 
of which are long, slender, and erect. Each flower is about half 
an inch long, rosy-red, with darker pink veins, papilionaceous, 
the * wing ' petals very short 

The fruit is almost semi-circular in outline and about a quarter 
of an inch long, its pericarp covered with a coarse raised net- 
work of lines on which are spiny projections (Fig. 206) ; it is 
indehiscent, and contains a single olive brown seed, in shape 
like a small bean. 

Sainfoin' is a valuable fodder plant for growth on dry, barren 
calcareous soils. 

It resists frost better than lucerne, but damp sub-soils are 
destructive of both plants. 

It is extensively used as sheep food, and cut green for soiling 
cattle and horses. The produce makes excellent hay of very 
high nutritive value when cut just in flower. 

Two cultivated varieties are met with, namely, (i) The Old 
Common Sainfoin, and (2) Giant Sainfoin. 

The former variety is more lasting than the latter, a ley of it 
being generally useful during four to seven years. It gives only 
one cut per annum, after which the subsequent growth is 
grazed. 

Its stems are shorter, and the flowering period a week or ten 
days later than the giant variety. 

The giant sainfoin is a more rapid and luxuriant grower, and 
is usually kept down only one or two seasons, during which it 
yields two or more heavy crops per annum. If seed is required 
the plant is cut once and the second growth of the season 
reserved. 



440 LEGUMINOSJE 

When seed of the Old Common variety is wanted the first 
growth of the year must be reserved for the purpose. 

The seed is drilled in March or April, usually on a cereal 
crop at the rate of 4 bushels (100-110 Ibs.) of 'seed in the husk/ 
or 50 Ibs. of ' milled ' (true) seed per acre. 

The seed should be drilled about i inch deep in rows 9 to 1 2 
inches apart. 

Ex. 227. Dig up and examine young seedling plants of Sainfoin, Lucerne, and 
Black Medick. Note the form and extent of the roots and branches of the plants. 

Examine full-grown plants of each species, paying special attention to the 
structure and form of their flowers, fruits, and seeds. 

Serradella (Genus Ornithopus\ 

19. To the genus Ornithopus belongs Serradella (Ornithopus 
sativus Brot.), a wild Portuguese and Spanish species, intro- 
duced to many parts of the Continent as a useful plant for 
growth upon dry sandy ground, and sometimes mentioned in 
this country. It is grown largely for ploughing-in as a 'green 
manure,' and is also utilised green as fodder or made into hay. 

Serradella is a slender annual, about 12 or 18 inches high, 
with compound pinnate leaves and small pale rose-coloured 
flowers, of which from two to five grow together in a cluster at 
the end of long axillary peduncles. 

The fruit is curved, and breaks up transversely into many one- 
seeded ' joints ' j three or four fruits growing together resemble 
a bird's foot. An allied species O. pcrpusiltus L. grows wild in 
sandy and gravelly places in this country. 

Kidney Vetch (Genus Anthyllis). 

20. Kidney Vetch (Anthyllis Vulneraria L.). An herbaceous 
perennial common in dry pastures and on banks in calcareous 
districts. 

It possesses a strong underground branched rhizome, from 
which ascending stems arise from 8 to 18 inches in length. 
The latter are more or less softly hairy and bear few leaves. 

During the first year the young plants possess a rosette of 
leaves close to the ground : these leaves are mostly simple and 



COMMON BIRD'S-FOOT TREFOIL 441 

ovate with long petioles. Subsequently branches are produced in 
the axils of the radical leaves, and upon them are borne pinnatifid 
or compound pinnate leaves, each with a large terminal lobe. 

The inflorescences are dense heads of yellow flowers, the 
calyces of which are inflated and covered with long downy 
hairs. The andrcecium of the flower is monadelphous, the 
gynaecium stalked, containing two ovules. 

The ripe fruit is a flattened legume and contains a small seed, 
one half of which is yellow, the other half bright pale green. 

The kidney vetch is a useful plant sown alone for sheep food 
upon calcareous or marshy soils too poor to grow anything else. 
It is capable of resisting prolonged drought, and makes nutritious 
hay although it is scarcely suited to this purpose on account of 
the procumbent character of the stems, much of which escapes 
the scythe. 

Seed is sown in spring in drills 12 or 14 inches apart, at the 
rate of 17 Ibs. per acre. 

In mixtures, either for long or short leys on dry ground, the 
kidney vetch is worthy of a place both on account of its nutritive 
quality and its permanence. 

Bird's-foot Trefoils (Genus Lotus). 

ai. Common Bird's-foot Trefoil (Lotus corniculatus L.). An 
herbaceous perennial common in dry pastures. From the 
short thick rhizome spreading decumbent stems arise, each of 
which is from 4 to 16 inches long. The leaves are pinnately 
compound with five leaflets; the lowest pair of the latter are 
separated considerably from the three upper ones, and resemble 
the stipules of a trifoliate leaf, so much so that at first sight the 
leaf appears to be trifoliate and not pinnate : hence the name 
of trefoil. 

The flowers, five to ten in number, are arranged in umbel- 
like cymes at the end of long slender axillary peduncles. 

The corolla of the flower is bright yellow, the 'standard* 
being frequently tinged with deep orange or red. The fruit is 



442 LEGUMINOS^E 

a long slender legume purplish red in colour; within it are a 
number of small brown roundish-oval seeds, partially separated 
from each other by transverse false partitions. 

Bird's-foot trefoil is a nutritious plant much liked in a young 
state by all kinds of stock. It is not very productive, but on 
account of its good quality and permanence is a leguminous 
plant worthy of inclusion in permanent grass mixtures for the 
lighter classes of soil. Unfortunately genuine seed is expensive 
and liable to be adulterated with its allied species, Greater or 
Marsh Bird's-foot Trefoil (Lotus uliginosus Schk. = Z. major 
Sm.) (see p. 663), which is a native of damp meadows, and only 
of agricultural value for use on marshy ground. 

Bird's-foot trefoil is a very variable plant in habit of growth, 
and size of stem, leaves, and flowers : some varieties are smooth 
while others are hairy. 

Gorse (Genus Ulex). 

22. Gorse, Furze, or Whin (Ulex europaus L.). A perennial 
bushy shrub growing from 2 to 5 feet high, and frequent on 
heaths and dry commons throughout the country. 

The first foliage-leaves appearing after the cotyledons are 
trifoliate like those of clover, but with smaller rounded leaflets, 
On the older parts of the plant the leaves are very narrow, about 
a quarter of an inch long, and end in short, soft spines ; in 
their axils arise rigid furrowed branches which end in stiff spines. 

The flower is solitary and axillary, with yellow corolla, a 
deeply two-cleft calyx : the andrcecium is monadelphous. 

The fruit is a two-valved legume, slightly longer than the calyx, 
and containing two or three seeds. 

A small variety of this plant, named Ulex strictus Mackay, 
is met with in parts of Ireland; it has soft, spiny branches, 
but does not come true from seed. 

Two other British species of Ulex are known, but they are 
of no practical importance. 



WHITE LUPIN 443 

Common gorse is cultivated in some districts upon thin, 
apparently sterile sandy soils, and utilised as food for horses 
and cows in winter. It forms very nutritious fodder, and cows 
are said to give a better yield of milk when fed with gorse than 
when they are given good meadow hay ; moreover, the milk is 
of rich quality. 

Before being fed to stock, the stiff spiny branches of the 
plant are generally crushed between rollers or otherwise bruised 
and softened by special simple machinery. 

The. seed is drilled in rows 10 to 18 inches apart in April or 
May on clean ground at the rate of 10 to 15 Ibs. per acre. 

The young plants are slow in growth, and the first cut is 
taken in the second year. After being established the crop is 
cut chiefly in winter and spring when green food is scarce. 

In some districts an annual cut is taken, while in others the crop 
is cut once every two years ; in the latter case alternate rows are cut. 
Dyer's Greenweed or Woad-wax (Genus Genista). 

To this genus belongs Dyer's Greenweed (Genista tinctoria L.), 
a shrubby leguminous weed of stiff clay soils (p. 614). 
Best-harrow (Genus Ononis). 

23. To this genus belongs Rest-harrow (Ononis spinosa L.), a 
shrubby weed common in many districts, and difficult to exter- 
minate on account of its deeply-penetrating roots (see p. 6 1^5). 

Lupins (Genus Lupinus). 

24. The genus Lupinus includes a large number of species of herb- 
aceous and half shrubby plants many of which are grown in gardens 
for their handsome spikes or heads of brightly-coloured flowers. 

Several annual species are cultivated on the Continent as farm 
crops for * green manuring/ the chief of these being Yellow 
Lupin {Lupinus luteus L.), and in lesser degree Blue Lupin (Z. 
angustifolius L.) and White Lupin (L. albus L.). 

All the species are exceptionally rich in nitrogenous constitu- 
ents and grow on poor sandy soils, which they enrich enormously 
when ploughed in. 



444 LEGUMINOS^E 

Many sandy districts on the Continent which were practically 
valueless have been very materially improved in fertility by the 
utilisation of these plants as ' green manure.' 

Lupins contain a greater amount of digestible albuminoids 
than any other known crop, and besides their use as a manure 
are also used in a green state folded off by sheep; they are 
occasionally made into hay. The plants contain a variable 
proportion of a bitter alkaloid which makes them unpalatable to 
horses and cattle, and sheep at first appear to dislike the crop. 

In addition to the bitter alkaloid, lupins under certain 
indefinite conditions of soil, manuring, and storage sometimes 
contain a poisonous compound named lupinotoxine, which 
rapidly produces fatal results in sheep when the latter are fed 
with even moderate amounts of the cut green fodder or hay. 
Of the various methods to render the lupin crop perfectly 
innocuous, heating with steam under pressure of one or two 
atmospheres has proved the most certain. 

Lupins succeed best on dry sands or light sandy loams. On 
light calcareous ground they do not grow satisfactorily ; even on 
sand resting on a chalky subsoil they often fail. Stagnant water 
in the subsoil or an excess of humus in the soil is also detri- 
mental to their development. 

In the early stages of growth the tap root develops extensively 
while the parts above ground grow very slowly. 

25. Yellow Lupin (Lupinus luteus L.). This species is the 
one most generally grown as a farm crop. It is an annual, with 
erect hairy stem from 2 to 3 feet high. The leaves are palmately 
compound with from seven to nine lanceolate leaflets. 

The inflorescences are loose pyramidal heads consisting of 
several (five to twelve) whorls of bright yellow papilionaceous 
flowers* 

The ripe legumes contain three or four seeds and are from 
i \ to 2 inches long ; they appear swollen at the seeds, and the 
valves are woolly on the outside. 



WHITE LUPIN 445 

Each seed is roundish kidney-shaped about the size of a pea, 
of whitish colour flecked with black spots and small streaks. 

The seeds are drilled in rows from 9 to 15 inches apart on a 
clean seed-bed in May or June; i to 2 bushels per acre are 
needed. 

26. Blue Lupin (Lupinus angustifolius L.) is an annual with 
taller stems, more woody than those of the yellow species, and 
hence not so suitable for fodder ; the leaflets are narrow and the 
flower spikes have fewer flowers and these are blue in colour. 
The seeds are rough, about the size of a small bean seed and 
generally buff coloured flecked with rusty spots. 

The White Lupin (Lupinus albus L.) is a South European 
species grown extensively in warmer parts of France, Spain 
and Italy for green manuring and for its seeds, which are used as 
food after the bitterness has been removed from them by steeping 
in water ; it requires a hot climate to ripen its seeds properly. 

Ex. 228. The student should examine all the leguminous plants mentioned 
which have not previously been dealt with in order to become practically 
acquainted with the peculiarities of each species. Make a point of watching 
their development as far as possible, and compare their flowers .fruits and seeds. 

SUMMARY OF THE GENERIC CHARACTERS OF LEGUMINOUS 
FARM-PLANTS. 

1. Leaves pinnate, ending in tendrils (Fig. 33), except in the bean the 
petiole of the leaf of which ends in a short bent point. Andrcecium di- 
adelphous : legume two-valved, dehiscent. 

a. Free end of staminal tube cut off at right angles to its length ; style, 
threadlike. Genus Vicia (Vetches and Bean). 

h Free end of staminal tube cut off obliquely ; style flattened. 

(i) Style not grooved, Genus Lathyrus (Everlasting Fea). 

(ii) Style grooved, Genus Pisum (Garden and Field Pea). 

2. Leaves pinnate, with two or more pairs of opposite and one single 
terminal leaflet. 

a. Andrcecium diadelphous. 

Fruit indehiscent, but split transversely into one-seeded nut-like 
joints (a lomentum). Genus Ornithopus (Serradella). 

Fruit a one-seeded nut Genus Onobrychis (Sainfoin). 

Fruit a long two-valved dehiscent legume. 

Genus Lotus (Bird's-foot Trefoil). 



446 LEGUMINOS^E 

b. Androecium monadelphous (in the single British species). 
Calyx inflated ; fruit a one-seeded nut. 

Genus Anthyllis (Kidney- Vetch). 

3. Leaves with three leaflets. 
a. Androecium diadelphous. 

(i) Flowers in a dense head. 

Faded corolla encloses the fruit. Genus 7*rifolium (Clovers). 

Faded corolla drops away from the fruit ; legumes curved or spirally 
twisted. Genus Medicago (Lucerne and Yellow Trefoil), 

ii) Flowers in open elongated racemes. 

Fruit short, indehiscent, with one to three seeds. 

Genus Melilotus (Melilot). 
J. Androecium monadelphous. Genus Ononis (Rest Harrow). 

4. Leaves simple. 

(i) Leaves spinous. 

Calyx deeply two-lipped. Genus Ulex (Gone), 

(ii) Leaves flat. 

Calyx shortly two- lipped. Genus Genista (Dyer's Weed). 

5. Leaves digitate with more than three leaflets. 

Genus Lupinus (Lupin). 



CHAPTER XXXII. 
UMBELLIFERJE. 

i. General characters of the Order. Inflorescence generally 
a compound umbel ; flowers small, bisexual, usually regular and 
epigynous. The outer flowers of the compound umbel are often 
irregular and zygomorphic, the petals directed outwards being 
larger than those pointing inwards. 

Calyx superior, often absent ; when present it generally con- 
sists of five minute tooth-like projections. Corolla polypetalous, 
five petals, obcordate or obovate, usually curved inwards at the 
free tip, mostly white, yellow, or pink. Androecium of five 
stamens curved inwards in the young flower. Gynaecium in- 
ferior, syncarpous, two carpels ; each carpel contains one pendul- 
ous ovule. The ovary bears on its summit a fleshy swollen 
nectary termed the stylopodium (d t Fig. 134). From the stylo- 
podium arise two styles, which are often slightly curved outwards. 

The line of union of the two carpels is known as the commissure 
(c, D, Fig. 134). Each carpel frequently bears on its outer or 
dorsal surface nine more or less well-marked raised lines or 
ridges. Five of them are described as primary ridges ; two of 
these, the marginal ones, are close to the commissure, the other 
three, dorsal ridges, being regularly placed on the back or dorsal 
part of the carpel (Z>, Fig. 134). Sometimes occupying the 
spaces intermediate between these five ridges are four secondary 
ridges, which are occasionally as prominent or more so than the 
primary ones; they are, however, often missing or but feebly 
developed. 

r 447 



448 



UMBEL-LIFERS 



The ridges may be continuous simple raised lines or may 
consist of lines of prickly, hairy, or knob-like projections. 

In the wall of the ovary are longitudinal canals termed vitta, 
which most frequently are present in the substance of the furrows 
between the primary ridges (#, Fig. 134), and when the fruit is 
ripe can often be seen as dark brown or black lines on the peri- 
carp wall. They contain secretions of volatile oils, balsams, and 
gum-resins, which generally give to the fruit its peculiar odour 
and taste; the characteristic taste of caraway, coriander, and 
other similar fruits of the Umbelliferse is due to essential oils in 
their vittae 






FiG. H4. A, Fruit of Wild Chervil (Chtfrophyllum sylvestre L.). 

B, The same later, showing the manner of splitting, c carpophore ; m mericarps; d 
stylopodium. 

C, Transverse section of A. x Commissure ; v vittae ; e endosperm of the seed. 

D % Transverse section of the ovary of Fennel (F&niculum officinale All.), p Primary 
ridges ; v vitta; ; c commissure. 

The number and arrangement of the ridges and vittse are best 
seen when the ovary is cut transversely. 

The fruit is a schizocarp which divides into two mericarps ; 
each of the latter is a closed carpel containing a single endo- 
spermous seed. When the fruit is ripe the mericarps separate 
from each other and remain suspended on a thin, usually divided, 
extension of the flower axis, termed the carpophore (c, B> 

Fig. 134). 

The seed is endospermous and generally united with the inner 
wall of the pericarp. The endosperm contains a considerable 
proportion of oil and no starch. The embryo is small, embedded 



PARSNIP 449 

in the endosperm in the part of the seed nearest to the apex of 
the fruit. 

The flowers are generally pollinated by small insects, which 
easily obtain the exposed nectar secreted by the stylopodium. 
Protandrous dichogamy is common ; the stamens often set free 
their pollen and wither up before the stigmas are developed. 

2. The Umbellifera is an Order comprising about 1300 
species of plants, generally herbaceous, and most largely repre- 
sented in temperate regions. 

The stems are frequently hollow. The leaves are alternate, 
their blades usually very much divided in a pinnate manner, 
and the petioles often very broad and inflated, forming a sheath 
which partially clasps the stem. 

There is a great similarity among many of the species and 
genera of the Order, and only careful attention to details of the 
form of the fruit, its ridges and vittae, and the presence or 
absence of involucres below the umbels and umbellules will 
enable a student accurately to distinguish the various species he 
may meet with. 

A common characteristic of umbelliferous plants is the pos- 
session of secretory canals, which become filled with essential 
oils, balsams, or gum-resins. These canals are not only met 
with in the pericarp of the fruit but are frequently present in the 
stems, roots, and leaves, and it is from the substances secreted 
in these canals that many of the plants derive their strong 
aromatic odour and taste. 

Many of the representatives of the Order, such as hemlock and 
cow-bane, contain poisonous alkaloids ; the dangerous compounds 
are not present in any special canals or ducts, but are common 
in the cell-sap of all parts of the plants, but sometimes more 
especially present in their stems, leaves, or roots. 

The only plants cultivated on the farm belonging to the Urn- 
belliferae are the Carrot (Daucus Carota L.) and Parsnip (Peuce- 
danum sativum Benth.). Besides the above those common in 



450 UMBELLIFEIUE 

gardens also included in this order are Celery (Apium graveolens 
L.), Parsley (Carum Petroselinum Benth.), and Caraway (Carum 
Carui L.). 

A number of species of Umbelliferae are important on account 
of their poisonous qualities ; the chief ones are mentioned later. 
A few are weeds of the farm, but practically none of these need 
serious attention. 

3. Wild Carrot (Daucus CarotaL,.). A well-known plant com- 
mon in dry pastures and on roadsides throughout the country. It 
most frequently behaves as an annual, though it is occasionally 
biennial. With the exception of its root, which is comparatively 
thin and woody, it resembles the cultivated forms in stem, leaf, 
flower, and fruit. 

The wild carrot affords one of the best examples of the 
possibility of rapid modification of plants by special selection 
and improved cultivation. M. Vilmorin raised passable garden 
varieties with thick fleshy ' roots ' and of biennial habit in four 
generations from the wild species, and there is no doubt that all 
the cultivated forms of carrot have been derived from the same 
source. 

4. Cultivated Carrot. 

SEED AND GERMINATION. The so-called carrot 'seed 1 used 
for raising a crop consists of the mericarps of the fruit (see 
below). 

The young seedling possesses two long narrow cotyledons, a 
well-marked hypocotyl which at first grows above ground, and a 
slender primary tap root (i, Fig. 135). The hypocotyl and root are 
quite distinct from each other in colour and general appearance 
in the early stages of growth. 

ROOT AND HYPOCOTYL. Without going into the internal ana- 
tomy it is always possible in very young seedlings to distinguish 
these two parts of the plant. 

The hypocotyl is free from roots, but the primary root bears a 
number of secondary ones chiefly in four longitudinal rows. 



CULTIVATED CARROT 



451 



After a time it is noticed that in many cultivated forms, and 
especially those grown in gardens, the hypocotyl, which is at 




FIG. 135. Carrot seedlings at four successive stages of growth, a Hypocotyl ; b cotyledon ; 
c root ; d first foliage-leaf. 

first above ground, becomes gradually drawn below the surface 
by the contraction of the root ; the hypocotyl itself sometimes 



452 UMBELLIFEIUB 

contracts also and the cotyledons, which were originally some 
distance above the soil, now lie close upon it 

Soon thickening commences, both in the primary root and hypo- 
cotyl, and as adventitious roots make their appearance from the 
internal tissues of the latter, the distinction between the stem and 
the true primary root becomes rapidly obliterated so far as external 
appearances are concerned. In some field carrots a good deal of 
the hypocotyl continues to grow above ground, thus resembling 
mangels and turnips. 

On good soils the primary root extends to a considerable depth, 
but only the upper portion of it becomes thickened ; the lower 
part, which is left in the ground when the 'carrot 1 is pulled or 
dug up, is long, thin, and cord-like, and bears many fine branch- 
ing rootlets. 

As in the case of all fleshy farm ' roots,' except kohl-rabi, the 
'root 1 of the carrot, for which the plant is cultivated, consists of 
hypocotyl and root combined, the relative amount of each vary- 
ing in different * races ' or ' strains * of the plant. 

On the outside of the 'carrot* are seen delicate secondary 
roots which are arranged in four longitudinal rows ; but on account 
of irregular growth the rows do not always remain straight 

The thickened fleshy 'root* of the carrot, like that of the 
turnip, presents the same general arrangement of tissues as is 
met with in ordinary typical dicotyledonous roots and stems: 
the differences consist in the abnormal development of the 
elements composing its tissues. 

A transverse section of a carrot (2, Fig. 136) shows a layer 
consisting of parenchymatous bast and secondary cortex (</), 
which is wide in comparison with that of the turnip 'root/ and 
of red or scarlet hue in red varieties. In the centre is the 
1 core ' of wood (a), generally yellowish or dull white in colour. 

The relative proportion of wood to bast varies in different 
'races' of carrots; the endeavour of the plant breeder is to 
obtain a relatively wide cylinder of bast (d) and a small core, 



CULTIVATED CARROT 



453 



as it is in the former that the greatest amount of sugar and 
other nutrient materials is stored. 

The wood in the first season of growth contains no fibres or 
fibrous cells, but consists mainly of thin walled unlignified 
vessels and delicate wide-ceiled wood-parenchyma. Narrow 
medullary rays are visible. In the second season and in 
Bolted' carrots which have run to 
seed in the first season, the wood last 
produced by the cambium-ring (c) be- 
comes strongly lignified and fibrous by 
the time that flowering commences. 

STEM AND LEAVES. During the first 
season of growth the carrot stores up 
reserve food in its thickened root and 
hypocotyl; the epicotyledonary por- 
tion of the stem remains short until 
the second season, when the terminal 





1. 

FlG. 136. d) Longitudinal ; (2) transverse section of carrot 'root, 1 showing disposition 
of tissues, d Thin -walled parenchymatous bast and secondary cortex ; a. wood ('core')* 
t cambium-ring ', r secondary root. 

bud sends forth a furrowed, somewhat bristly, solid stem 2 or 
3 feet high with spreading branches. 

The radical leaves have long petioles ; all are bipinnate with 
deeply pinnatisect leaflets, the ultimate segments being small 
and narrow. 

INFLORESCENCE AND FLOWERS, The inflorescence is a com- 

3i 



454 



UMBELLIFER^E 



pound umbel: the bracts 'of the involucre extend as far as or 
beyond the flowers, and are pinnatifid, the segments very narrow 
ind acuminate. The umbellules have involucels of narrow, 
3r pinnatifid bracteoles. 

After flowering the outermost main branches of the compound 
jmbel curve inwards, and the whole inflorescence then forms a 
lollow cup or nest-like structure. 

The flowers (i, Fig. 137) are epigynous : the calyx superior, con- 
sisting of five short tooth-like sepals : the corolla is composed of 
ive white incurved petals alternating with the sepals (the petals 
rf the central flower of the umbel are often pink or reddish) ; the 



5 




1. 



3. 



FIG. 137 i. Flower of Carrot (Daucus Carota. L.). c Minute sepal of calyx ;/ petal ; 
ovary ; st withered stamen ; ^stylopodium ; s style and stigma. 

2. Fruit of Carrot. The ovary is covered with long spines and hairs, d Stylopodium ; 
style and stigma. 

3. Transverse section (magnified) of ovary through line A, B,d (2). / Primary ridges ; 
secondary ridges ; v vittae ; rb vascular bundles ; cm embyro of seed ; e endosperm. 

mdroecium possesses five stamens, which set free their pollen 
tnd fa 1 ! away soon after the flower opens \ the gynsecium is 
nferior and syncarpous, consisting of two united carpels; the 
ipper part of the ovary has a white fleshy stylopodium which 
:>ears two curved styles. 

The four secondary ridges on each carpel are more prominent 
,han the primary ones, and bear ten or twelve long spinous pro- 
ections, on the end of which are three or four slightly hooked 



RED ALTRINGHAM 455 

hairs: the five primary ridges (/>, 3, Fig. 137) bear long uni- 
cellular hairs. 

THE FRUIT AND SEED. The fruit is a schizocarp. Upon the 
two dry mericarps the spiny secondary ridges are conspicuous, of 
light brown tint. It is on account of these spiny projections that 
the mericarps cling together and prevent the * seed ' from being 
sown evenly without previous rubbing and mixing with sand or 
dry ashes. 

Each mericarp contains a single endospermous seed, with a 
minute dicotyledonous embryo. 

Within the wall of the pericarp in each secondary ridge is one, 
rarely two, vittse (3, Fig. 137, v), containing an oil which gives the 
ripened mericarps a characteristic odour most easily recognised 
when the latter'are rubbed vigorously in the hands. 

VARIETIES. Carrots vary much in the length, rapidity of 
growth, and colour of their * roots/ 

They also differ in their feeding-value, and the proportion of 
' rind ' to ' core. 1 Moreover, some varieties grow with a consider- 
able proportion of their thickened * root ' (hypocotyl) above 
ground, while others have their * roots' entirely buried in the 
ground. 

Of all varieties the White Belgian gives the largest crop. The 
upper part of the * root ' is pale dull green, the lower part and 
flesh white. The * roots' are of moderate length, very thick, 
and grow with the upper parts about 6 inches above the ground : 
from to | of the white root is below ground. It is a hardy variety 
adapted to almost all soils. The feeding-quality is low compared 
with the red varieties. 

Of slightly superior quality, but smaller yielding capacity, is the 
Yellow Belgian, with yellow flesh, but otherwise resembling the 
white variety. 

Of red varieties the best cropper is Red Altringham. It 
possesses thick long roots ending somewhat abruptly : the upper 
part grows slightly above ground and is of greenish-purple 



456 UMBELLIFER>E 

colour; the rind is pale orange-red, the rather small core 
is yellow. It needs good deep soil for proper growth and is 
superior in feeding value to the White Belgian variety. 

For growth upon shallower soils the * Scarlet Intermediate ' 
Varieties are best. They are very thick, usually only about 
two-thirds the length of the Red Altringham, and of excellent 
feeding-quality. Some of them are adapted for market-garden 
purposes. 

Long Bed Surrey is a variety with tapering roots of great 
length in proportion to their thickness ; the rind is deep red, core 
yellowish. For field cultivation it is not so good as Altringham. 

SOIL. Stiff soils and those which are very shallow are unsuited 
to this crop. 

The long varieties of carrots require a deep well-pulverised 
sandy loam : on shallow soils, especially where the subsoil is 
stony or imperfectly broken up, the deep-growing varieties 
lose their symmetrical shape and become irregular, 4 fanged ' or 
'forked/ some of the secondary roots becoming thickened as 
well as the main primary root. To some extent the variety can 
be adapted to the character of the soil ; a few of the short thick 
kinds sometimes produce a fair crop on comparatively shallow 
soil 

SOWING. The 'seed' of the carrot germinates somewhat 
slowly, and the young plants on account of their small narrow 
leaves are liable to be smothered by annual weeds. To avoid 
this it is advisable to damp the ' seed ' and allow it to remain in 
a small heap for seven or eight days until signs of germination are 
apparent before drilling. The ' seed ' is best mixed and rubbed 
with dry sand or ashes previous to sowing. The crop is gener- 
ally drilled in rows from 1 8 to 24 inches apart, on well-cleaned 
and finely pulverised soil. The superabundant young plants are 
subsequently hoed out, and the remainder singled and left about 6 
or 7 inches apart. From the beginning to the end of April is the 
best time for sowing ; earlier than this the temperature is too low 



LONG RED SURREY 457 

to promote vigorous growth of the carrot and the plants are liable 
to be smothered by annual weeds if germination and active 
growth is delayed. 

The amount of good, new, well-cleaned seed necessary for one 
acre is 4 or 5 Ibs. 

YIELD. The average yield varies from 10 to 20 tons per acre 
according to the variety grown. 

The White Belgian variety occasionally gives a crop of 30 
tons per acre. 

COMPOSITION. In a wild state the carrot stores up starch in its 
' roots,* the cultivated forms however rarely or never store this 
carbohydrate in them, its place being taken by sugar. 

The amount of water in White Belgian carrots is on an average 
about 88 per cent.; the red varieties contain from 86 to 87 per 
cent. The soluble carbohydrates, of which the greatest propor- 
tion is sugar, averages 9*2 per cent., the nitrogenous substances 
generally reach 1*2 per cent, of which a little more than half are 
albuminoids. The ' fibre ' is rather high, namely 1*3 per cent. 

With the exception of parsnips and potatoes, red carrots con- 
tain more nutritious dry matter per ton than any other root crop 
ordinarily grown as food for stock : the leaves or ' tops ' are 
excellent, as well as the ' roots.' 

Ex. 229. Examine the commercial 'seeds' of the carrot. Note the 
secondary ridges of spines. How many ridges are there on each ? Cut thin 
transverse sections of the mericarp and examine them for the vittse. 

Note the odour when the * seeds ' are rubbed in the hands. 

Ex. 230. Raise carrot seedlings in damp sand 01 sandy soil, and note the 
length and shape of the cotyledons, hypocotyl, and primary root. Observe 
the amount of hypocotyl above ground in a bed of seedling carrots in the 
garden and watch the withdrawal of the hypocotyl into the ground as tht 
plants increase in age. 

Ex. 231. Carefully dig up a half-grown carrot, taking care to go deep 
enough to obtain the fine extension of the tap root, and also the secondary 
roots. Wash away the earth carefully and examine the extent, thickness, 
and position of the lateral roots 



458 UMBELLIFER^E 

Ex. 232. Cut longitudinal and transverse sections of an old carrot. Note 
the colour, thickness and texture of the various parts. Observe that the 
lateral roots run through the orange parenchymatous bast and secondary 
cortex. 

Ex. 233. Examine the stem, branches, leaves, and inflorescences of a 
'bolted carrot,' or the same parts in a wild carrot. 

Ex. 234. Examine and describe individual flowers of the compound umbel 
of a carrot. Observe the colour of the flower in the centre of each compound 
umbel. 

Note the ovary and its two united carpels. Cut sections of young fruits 
and examine them with the microscope. 

Ex. 235. Obtain as many kinds of 'carrots' as possible. Note their 
colour, shape, length, and proportion of ' rind ' to ' core ' when cut across. 



5. Parsnip (Peucedanum sativum "Renth. Pastinaca 
A wild annual or biennial plant occurring on roadsides and 
waste places, especially on calcareous soils. Like the wild carrot 
this plant is very easily modified by cultivation, and all the field 
and garden parsnips have undoubtedly arisen from the common 
wild species. 

The cultivated forms differ from the wild plant chiefly in the 
thickness of the root ; the leaves and stems are generally less 
hairy than the wild parsnip, but in other respects there is no 
difference between the two. 

SEED AND GERMINATION. The 'seeds' sown fora crop are 
thin flat mericarps of the fruit, each of which contains a single 
true endospermous seed. 

The seedling has two narrow cotyledons and its first foliage- 
leaves are cordate or palmately three-lobed with coarsely serrate 
margins. 

ROOT AND HYPOCOTVL. These parts of the plant resemble 
those of the carrot. 

STEM AND LEAVES. The flowering stem sent up in the 
second season of growth is stout, with deep longitudinal furrows. 
It is hollow and grows to a height of 2 or 3 feet. 

The leaves are oblong, pinnate, with two to five pairs of 
leaflets each from i to 3 inches long, ovate, with deeply 



* HOLLOW CROWN ' 459 

serrate margins ; the terminal leaflet is three-lobed. The upper 
surfaces of the leaflets are smooth, the lower surfaces soft and 
hairy. 

INFLORESCENCE AND FLOWERS. The inflorescence is a com- 
pound umbel without bracts or bracteoles. The flowers are 
epigynous : calyx superior, of five very small teeth ; corolla of 
five small, bright yellow incurved petals : androecium of five 
stamens : gynaecium syncarpous, of two carpels, dorsally com- 
pressed with a broad commissure : each carpel has five primary 
ridges, the two marginal ones forming wing-like projections. 

FRUIT. The fruit is a dorsally compressed schizocarp ; the 
mericarps are thin and flat, of oval or circular outline, six dark 
brown vittse reaching not quite to the base, are visible on 
each, four on the dorsal, and two on the inner (commissure) 
side. The fruit has a divided carpophore. Within each mericarp 
is a single flat, endospermous olive-green seed. 

VARIETIES. There are comparatively few varieties of this 
1 root.' Those cultivated as food for cattle are generally long- 
rooted varieties resembling the long carrots in shape. 

The only two common varieties are (i) the Large Cattle 
Parsnip, which has the upper part of the * root ' rounded or con- 
vex, and (2) the * Hollow Crown,' which has a slightly shorter 
and thicker depressed or concave ' top*. 

A form met with in gardens having a relatively very short 
thick 'root' is known as the 'Turnip-rooted' parsnip. 

SOIL, CULTIVATION AND SOWING. Parsnips can be grown on 
soil usually too stiff for a good crop of carrots, but the cultivation 
and general management needed for the latter is appropriate for 
the parsnip. 

The ' seed ' is best sown in March, an earlier date than that 
adapted to the carrot, at the rate of about 6 or 7 Ibs. per acre. 
Less seed would suffice if new, but commercial samples are 
usually very poor in germinating capacity and nearly always 
mixed with old dead seed. 



460 UMBELLIFER> 

The drills are drawn about 15 inches apart, and the plants 
eventually singled out to a distance of 6 or 7 inches asunder. 

The average yield of ' roots ' per acre is about 1 1 tons. 

COMPOSITION. The parsnip properly grown contains less water 
than the carrot, and is the most nutritious of ordinary ' root f 
crops. The amount of water appears to average about 83 per 
cent : starch is present in small quantity, but the chief useful 
carbohydrate is sugar. 

Ex. 236. Carry out experiments and observations upon the parsnip similar 
to those mentioned for the carrot on pp. 457, 458. 

The poisonous Umbelliferae, with which it is desirable that the 
student of agriculture should be acquainted, are the following : 

6. Hemlock (Conium maculatum L.). A common biennial 
plant, generally 2 to 3 feet high, occurring in hedges, fields, and 
waste places in many parts of the country. The stem is smooth, 
hollow, of dull green colour with a thin grey bloom upon it, and 
spotted with small brownish-purple blotches. The leaves are 
large tripinnate, with lanceolate pinnatifid leaflets: they are 
of peculiar dark glossy-green tint. The compound umbels of 
white flowers possess both bracts and bracteoles. 

The fruit is oval or round; each mericarp possesses five 
characteristic knotted primary ridges. 

The whole plant has a foetid smell, and is excessively poison- 
ous. Its dangerous qualities are due to the presence of several 
narcotic alkaloids which are met with in greatest abundance in 
the leaves, young shoots, and fully-developed green fruits ; the 
chief of these poisonous compounds is conine. 

7. Water Hemlock or Cow-bane (Cicuta virosa L.). A some- 
what uncommon tall perennial met with in ditches and by the 
side of rivers. The flowers are white and the stem from 3 to 4 
feet high, thick and furrowed ; its leaves are large, twice or thrice 
pinnate, the leaflets about 2 or 3 inches long and lanceolate, 
with serrate margins. Cows are sometimes poisoned by eating 
it, hence its name. 



FOOL'S PARSLEY 461 

8. Water Dropwort (Oenanthe crocata L.). A tall perennial 
resembling celery and sometimes mistaken for it with fatal 
results. It grows in situations similar to those suited to wild 
celery, namely, near rivers and ditches. The flowers are pale 
yellow, and the juice squeezed from the plant is yellow, and 
stains the skin. 

9. Poors Parsley (Atthusa Cynapium L.). A common annual 
weed of cultivated ground, both gardens and fields. Its stem is 
slightly furrowed and generally about a foot high. The leaves 
are bipinnate, smooth and shining, of dark green colour, and 
when bruised have a strong stinking odour. The flowers are 
white, and the small umbels have involucels of three or four long, 
narrow, slender bracteoles which point outwards and downwards. 
By the smell and the conspicuous bracteoles the plant is readily 
distinguished from others of similar general appearance. It has 
occasionally been mistaken for parsley with bad effect, but 
rarely, if ever, led to fatal results. 

Ex. 237. The student should examine the roots, stems, leaves, inflor- 
escences, and fruits of as many common wild umbel lifers as possible. He 
should also become especially acquainted with the botanical characters of 
the poisonous species just mentioned 



CHAPTER XXXIII. 
SOLANACE^E. 

1. General Characters of the Order. Herbs or shrubs, 
Leaves usually alternate, exstipulate. Flowers generally regular, 
hypogynous. Calyx, inferior gamosepalous, 5-fid, persistent. 
Corolla hypogynous, gamopetalous, 5-lobed, usually campanu- 
late or salver-shaped. 

Andrcecium of 5 epipetalous stamens. Gynaecium syncarpous, 
2 carpels ; ovary usually 2-celled with many ovules on a thick 
axile placenta. Fruit a capsule or berry ; seed endospermous. 

An extensive Order of plants, chiefly found in the tropics and 
especially in South America, Poisonous alkaloids occur in 
many plants belonging to the Order. 

The genus Solanum, from which the Order is named, embraces 
about 800 or 900 species, many of them ornamental plants. 
Only five or six species bear tubers, the chief being the common 
potato. 

2. Potato (Solatium tuberosum L.). Introduced into Europe 
in the sixteenth century, first into Italy and Spain, and indepen- 
dently into the British Isles a little later in the same century. 

SEED AND SEEDLING. The endospermous seed germinates 
readily and produces a young seedling with well-marked primary 
root and two ovate cotyledons (4, Fig. 138). The plumule 
develops intp an upright stem with leaves, and from the axils 
of the cotyledons, whose petioles lengthen considerably, shoots 
arise which are positively geotropic (Fig. 140). These shoots 
soon find their way into the ground, and after the growth of two 
or three intcrnodes their tips become tuberous (</, Fig. 141) 

462 



POTATO 



463 



through the deposition within them of reserve foods, the chief 
of which is starch. Similar tube-bearing shoots may also arise 
from buds in the axils of the foliage leaves above the cotyledons. 
The thin part of the underground rhizomes bear scale-like 
leaves, and these are also present on the young tubers, but 
eventually shrivel up before the latter are ripe. Usually only 





FIG. 138. 

1. Potato seed germinating. 

2. Section through the same, showing position 

of cotyledons and endosperm (shaded). 

3. Seedling nearly free fiom seed-coat. 

4. Seedling quite free (10 days 1 old); a hypo- 

cotyl ; b root ; c cotyledons. 



FIG. 139. 

Potato seedling (16 
days old), later stage of 4, 
in previous Fig., showing 
plumule f. The coty- 
ledons c have become 
broader ; a hypocotyl ; 
b root. (Natural size.) 



one tuber is developed at the end of a rhizome in seedling 
plants. Sometimes, however, lateral branches which bear 
tubers are produced from the axils of the scaly leaves of the 
rhizomes. 

At the end of the growing season the stems and leaves above 



464 



SOLANACE^E 



ground and the thin parts of the underground stems die ; the 
tubers remain dormant below during winter, and in the following 
spring germinate and send forth new shoots from their ' eyes.' 

The tubers from a one-year-old plant are small, often not 
larger than a broad bean, and it is only after three or four years 
growth that they reach the size of ordinary potatoes. 





FIG. 140. 

Potato seedling (26 days' old), later stage 
of Fig. 139 The Plumule * has developed 
considerably, and in the axils of the coty- 
ledons two shoots d have been produced. 
a hyp^cotyl; b root; c cotyledons; e 
epicotyl ; x ground-line (Natural size). 



FIG. 141. 

Potato seedling (jo weeks' old), later 
stage of Fig. 140. The shoots d have 
now pushed their way below ground and 
at their tips small tubers have formed. 
(Natural size) 



ROOT. The roots of the potato plant extend themselves 
chiefly in the upper layers of the soil, and are fibrous and 
copiously branched. The primary root and its branches are 
distinct from the tuber-bearing rhizomes (Fig. 141), but from the 
nodes of all the stems below ground adventitious roots arise in 



POTATO 465 

abundance. The extensive development of the latter depends 
upon the presence of moist air; in dry air they do not 
appear. 

The tubers themselves never bear roots, and are, therefore, 
unlike the Jerusalem artichoke tubers in this respect. 

STEM AND TUBER. The stems are herbaceous; two forms 
are present upon the potato plant, namely, the upright stem 
above ground and the horizontal rhizome below. 

Although their geotropic behaviour is not the same, they are 
essentially the same in structure ; the rhizome can be changed 
into an ordinary shoot with green foliage-leaves by bringing it 
above ground. 

The rhizome is usually not more than from i to 3 inches long 
in early varieties, and the tubers consequently appear heaped up 
round the stem when dug. Those giving heavier crops have 
longer and more branched rhizomes, while varieties with very 
long rhizomes usually give an unsatisfactory yield, although 
individual tubers may reach a large size. 

Leafy stems resembling that from which Fig. 142 was drawn, 
and showing tuber development in the axils, are readily produced 
by allowing old tubers to germinate in spring in a darkened cellar 
kept somewhat damp. Moreover, if the potatoes are picked 
off below ground as fast as they form, the plant develops tubers 
in the axils of the leaves above ground. 

The first internodes of the rhizome below ground are of con- 
siderable length ; those produced later at its tip remain shorter, 
but increase in thickness rapidly, and form a tuber. 

TUBER. That the potatoes are thickened pieces of stems is 
seen from a study of their origin ; the rhizomes, of which they 
are merely the ends, arise in a normal manner in the axils of 
leaves below the soil and although they occur under ground, 
they have no connection with the root-system of the plant. 

A well-grown tuber usually shows at its base or c heel ' a piece 
of the withered rhizome, and on its surface many * eyes ' which 



466 



SOLANACE^E 




are arranged spirally. At the * rose ' end, or the morphological 
apex of the tuber, the * eyes ' are more crowded together than at 

its c heel ' or base, the older 
internodes being longer than 
the younger ones. Each 'eye ' 
appears as a collection of buds 
lying more or less in a de- 
pression ; the latter is the 
axil of a scaly leaf which was 
visible when the tuber was 
young, but now withered up 
and lost. The number of 
buds in each ' eye ' may be as 
many as twenty, but three is 
the usual number. 

In reality the ' eye ' is a 
lateral branch with unde- 

FIG. 142. Leafy stem of potato, showing tuber , , . . , , . 

growing in the axiU of an ordinary leaf a Tuber VelOped intemodeS, the Whole 

Mrtoftr: tuber being generally a richly 
branched shoot-system and 
not a simple shoot. 

Tubers are not always of the same form ; three moderately 
distinct and fairly constant types are prevalent, namely, (i) 
'round,' (2) l oval] and (3) 'kidney' shapes. The round 
type is somewhat spherical, and has fewer internodes and ' eyes' 
than (2) and (3), both of which are elongated. The kidney 
potatoes are thickest at the ' rose ' end and taper towards the 
' heel/ while the oval varieties are thickest in the middle and 
taper towards both ends. Those differences are sufficiently 
marked and constant to form a basis of classification of the 
varieties in cultivation. 

In some instances the tubers are of very irregular shape. 
When long-continued dry weather checks vegetation, and is 
followed by rains, the partially-ripened tubers, instead of 



,ub e rina x ,iofieaf,. 



POTATO 467 

increasing regularly in thickness when active growth begins 
again, grow out from the ends or about the lateral 'eyes.' The 
new growths may form irregular lumps or even smaller tubers on 
the older ones; this is known as super-tuberation or second 
growth, and is most common in kidney and oval varieties. 

The anatomy of the tuber in its young state resembles that of 
the rhizome, to which it belongs, and like all similar stems 
possesses epidermis, cortex, and vascular cylinder with its cam- 
bium-ring and central medulla. The disposition of the tissues 
is readily seen in a young tuber (Fig. 143). 

In a fully developed tuber the epidermis is replaced by peri- 
derm, the outer layer of which consists of cork-cells ; the latter 
afford protection against excessive loss of water from the interior 
of the tuber. Beneath the 
* skin ' or periderm is the 
cortex, and in its outer cells 
the cell sap is frequently 
coloured, giving a charac- 
teristic tint to the different 
varieties of potatoes. The 

Cambium in its growth pro- FlG> US- -Longitudinal section of a young 
idiiiuiuiii in ua giuwiu piu potato tuber. c cortex ; v vascular bundle ; \m 

duces much wood, and it is r" ll " a ; J . sca . 1 ? l f f in the axil of which is a 

7 bud ; t terminal bud. 

this tissue which forms the 

main bulk of the tuber; instead of the wood, however, con- 
sisting of lignined tissue it is almost entirely made up of 
parenchymatous thin-walled cells, with only a few isolated 
groups of lignified elements, and cannot therefore be readily 
distinguished from the medulla and cortex. 

The chief reserve-food stored in the tuber is starch, the 
largest amount being found in the innermost parts of the cortex, 
the degenerate wood-tissue, and part of the medulla. In thin 
slices of the potato the bast, cambium and centre of the medulla 
appear semi-translucent, and contain little or no starch. 

GERMINATION OF THE TUBER. Ripe potatoes cannot be 




468 SOLANACE^B 

made to germinate before a certain time has elapsed. Some 
varieties need a rest of two months only, while others ripened 
in autumn do not show signs of growth before January or 
February, or even later. 

The minimum temperature for germination is about 8* or 
10* C, so that tubers planted very early make little or no 
growth. 

The cause of the resting-period and the chemical changes 
which go on during that time are not clear. Respiration which 
is carried on at the expense of the starch can be recognised; 
at first it is slow, but increases rapidly towards the end of the 
resting-period. 

When germination commences, the enzyme diastase is formed, 
whereby the starch is changed into sugar: the latter is trans- 
ferred to the growing buds, where it is utilised in the formation 
of new cells. The first development of the shoots is carried on 
at the expense of the stores of reserve-food within the tuber. 

Rarely do two buds on the same tuber develop equally 
strongly, the most vigorous being the terminal one, or the 
central bud in the * eyes ' near the apex of the tuber. The 
buds at the base of the tuber are weakest, and often remain 
dormant altogether. When tubers are cut for 'sets' so that 
each piece contains one ' eye,' those pieces from the ' rose ' end 
always produce the most vigorous plants and the best yield. 
If the main shoot produced from the central bud ot an ' eye ' 
is broken off or otherwise destroyed, the lateral buds in the 
1 eye ' grow out, but their shoots are never so strong or vigorous 
as the lost one. 

The shoots produced from the growing buds of potatoes 
exposed to the light during germination have short internodes 
and scaly leaves, in the axils of which three lateral buds are 
usually visible. After planting the tuber, the tip of the main 
axis of each shoot grows upwards into the open air, where the 
unfolding leaves carry on 'assimilation.' The food manufac- 



POTATO 



469 



tured by the leaves passes down the stem, and from the middle 
bud in each leaf-axil below ground a thin rhizome develops, 
which, after reaching a variable length, generally forms a new 
tuber at its end (Fig. 144). When the old dead tuber has been 
exhausted of its store of food, it still contains water obtained 



formed a tuber ; r roots (adventitious). 




from the surrounding soil, and acts as a reservoir for the growing 
plant in the dry part of the season. 

It must be observed that rhizomes only produce tubers when 
they are kept in the dark, hence the value of ' earthing up,' 
and the necessity of doing it at intervals so that newly-formed 
rhizomes resembling p in the above Fig. may be properly ex- 

32 



470 



SOLANACE^E 



eluded from the light. Rhizomes exposed to light become 
ordinary green-leaved shoots. 

Before planting tubers it is important to germinate them, if 
possible, in the light, in order to obtain from each awakening 
' eye ' a short, thick piece of stem with many nodes upon it, as 
it is from the axils of the leaves at the nodes that the rhizomes 
are produced which bear tubers. This practice influences the 
yield to a considerable extent, for if the tubers are allowed to 
start growth in the dark, either indoors or below ground, the 
shoots from the ' eyes ' have longer internodes and fewer 
points for the production of tuber-bearing rhizomes under- 
ground ; moreover, the leafy shoots sent above ground are 
weak when the latter method is adopted. 

LEAF. The leaves are compound, interruptedly pinnate, 
opposite pairs of small leaflets alternating with pairs of larger 
size. 

FLOWER (Fig. 145). The flowers are in cymes: calyx in- 
ferior, gamosepalous, five-partite ; 
corolla hypogynous, gamopetal- 
ous, five-lobed, rotate, violet, 
lavender or white. Andrcecium 
epipetalous, five stamens, with 
yellow anthers dehiscing by pores 
at the tip. Gynsecium superior, 
syncarpous, 2 carpels, ovary 
bilocular. 

FIG. i 4 5.--Section of potato flower, c FRUIT. The potato " apple " 
calyx ; / corolla ; s stamen ; o ovary ; a . . 

style ; t stigma of the gynaecium. or fruit is a berry with many 

seeds attached to a thick axile placenta (/, Fig. 146.) Many 
varieties of the potato rarely produce flowers when cultivated 
in the ordinary way ; even those which do so are often unable 
to ripen fruit and seeds. This is especially the case with varieties 
which yield large crops of tubers; the latter attract the food 
manufactured by the leaves, and little or none remains for the 





THE LATE OR MAIN-CROP VARIETIES 471 

development of the flowers and fruit. If flowers are needed 
for hybridising purposes, plucking off the early-formed tubers 
often produces the desired result. 

VARIETIES. Considerable attention has been 
paid to the improvement of the potato, and many 
varieties are in existence differing in yield, ripening 
period, shape, quality of tuber, and in many other 
points. They may be classified in several ways, FIG. 146. Trans- 

. it i j j . ^i verse section of 

but are usually placed in groups according to their ovary of potato 

. r . i-i i flower, a Wall of 

time of ripening, their shape, or colour. ovary ; /placenta; 

The early varieties are consumed in an unripe " ovules> 
condition, and are adapted for forcing for early markets. To 
this class belong Ashleaf, Epicure, Duke of York, Snowdrop, Early 
Regent, and others. 

The mid-season or second earlies are dug green for the summer 
market, and may be left to mature with the later varieties. Sir 
John Llewellyn, British Queen, Arran Comrade, Majestic, and 
Stirling Castle belong to this class. 

The late or main-crop varieties ripen in autumn, and often 
grow until cut down by frost. Up-to-Date, Golden Wonder, 
Kerr's Pink, King Edward VII, Ben Cruachan, may be mentioned 
as typical of this section. 

It is of little use to attempt to raise new varieties by selec- 
tion of tubers only, as these are merely divisions of the parent 
and cannot be expected to give rise to new offspring unless the 
tubers chosen happen to be true bud-variations or 'sports.' 
The latter are, however, of rare occurrence in the potato plant. 
Marked variations are obtained in seedling plants, and it is from 
these that selection is made in order to obtain new and im- 
proved varieties. 

The chief points of a good variety are the following : 

(a) Strong disease-resisting power. 

(b) Good cooking quality ; when steamed or boiled, the 

tuber should break easily into a glistening floury condi- 



472 SOLANACE^E 

tion without any appearance of clamminess or wetness, 
and should preserve a white colour even when cold. 
(e) The yield per acre should be high. 

(d) High starch-content is needed where the tubers are used 

for the manufacture of starch or in the distillery. 

(e) Shallow 'eyes/ and few of them, are looked for in the 

best quality, as those with deep depressions hold dirt, 
and necessitate considerable waste of substance when 
peeling is practised before cooking. 
(/) Good keeping quality. 

(g) Trueness to type of tuber should be aimed at. Whatever 
form the tuber takes whether round, kidney, or oval 
the crop should be as uniform as possible in this 
respect, and tendency to super-tuberation should be 
avoided. 

CLIMATE AND SOIL. The potato succeeds best in a warm 
and comparatively dry climate, and is unable to stand frost, 
exposure to a temperature of freezing point for a single night 
being sufficient to destroy the stems and leaves of a young crop. 
The soils best suited to its growth are deep, sandy loams, 
lying upon porous subsoils; stiff clays and undrained peaty 
soils, with excessive amount of moisture present, are almost 
valueless for potato culture, unless well drained and cultivated, 
and even then the quality of the tubers produced upon such soils 
is unsatisfactory, although the yield is sometimes high. 

SOWING. New varieties are raised from true seeds, the 
resulting tubers being propagated for three or four years before 
a decision can be arrived at in regard to their usefulness. 

The main crops of the farm and garden are raised by planting 
tubers ('sets'). Although large c sets' almost invariably give 
the greatest yield of crop, for economical reasons tubers about 
the size of a hen's egg, and weighing about 3 or 3^ oz., are 
usually employed with good results. Small tubers produce weak 
plants. The best results are generally obtained by planting whole 



THE LATE OR MAIN-CROP VARIETIES 473 

tubers ; but tubers may be cut into small pieces, each of which 
may be planted provided that it bears one or more ' eyes/ from 
which stems may arise. 

From 12 to 18 cwt. of ' sets ' are needed to plant an acre. 
Early varieties are planted in February and March, later ones 
in April, in drills from 24 to 27 inches apart, the tubers being 
placed about 15 inches asunder in the rows. 

As far as possible the drills should run north and south, on 
somewhat stiff soils inclined to dampness ; on drier soils east 
to west. 

YIELD. The average yield per acre is 7 or 8 tons. 

COMPOSITION. The most important ingredient in the tuber 
is starch, the amount of which varies from 10 to 26 per cent. ; 
the best varieties usually contain about 18 to 22 per cent. 

Sugar is absent from well-ripened tubers, and there is only a 
trace of fat in them. 

The nitrogenous substances average a little over 2 per cent., 
of which about 1-2 are albuminoids, present in the protoplasm, 
in solution in the cell-sap, and also in the form of solid ' proteid- 
crystals.' The latter occur chiefly in the cells of the cortex. 

The water-content averages about 75 per cent. 

A poisonous substance solanin is present in nearly all parts of 
the plant, the young etiolated shoots of the tuber and the berries 
containing most. 

Ex. 238. Sow true seeds of potato plant in boxes or pots of earth, and ex- 
amine at different stages of growth. Note the form of the cotyledons, the 
extent and position of the root, and the origin of branches which bear tubers. 

Ex. 239. Examine the arrangement of the ' eyes ' on a large, long, 
coarse tuber, and note the relative number at the * heel ' and ' rose ' 
end respectively. 

Cut longitudinal and transverse sections of the tuber, so as to pass through 
one of its ' eyes, 1 and note the cortex, vascular part, and irregular outline of 
the medulla. 

Ex. 240. Examine several sprouted tubers which have been allowed to ger- 
minate in the dark on a stable or cellar floor without touching each other. 



474 SOLANACE^: 

Note which * eyes ' have produced the strongest shoots, and the number of 
shoots from each ' eye. ' 

Ex. 241. Carefully dig up a complete potato plant in June including the 
old tuber. Examine the roots and rhizomes bearing the young tubers, and 
note their position upon the plant. If very small tubers are present, look 
with a lens for the scale leaves near their ' eyes. ' 

Ex. 242. Scrape away the earth from a young potato plant, and cut off all 
the tubers which are beginning to form, taking care not to injure the roots. 
Cover up the latter, and repeat the process at a later date. Watch the future 
development, and note the formation and structure of the tubers in the axils 
of the foliage-leaves. 

Ex. 243. Uncover an elongated underground rhizome ot a potato plant 
which has just begun to form a small tuber at its tip, and allow it to grow 
above ground or on the surface of the soil where light can get at it. Observe 
the changes in its appearance from day to day for a fortnight. 

Ex. 244. Examine and make sections of the flower and fruit of a potato 
plant, and compare them with those of the tomato and woody nightshade. 

3. Belonging to the genus Solatium are two wild indigenous 
plants, viz., Bitter-Sweet and Black Nightshade, both of which 
are poisonous and sometimes erroneously called Deadly Night- 
shade. 

4. Bitter-Sweet (Solatium Dulcamara L.) is a shrubby peren- 
nial common in woods and hedges. The upper leaves are 
hastate, the lower ones cordate-ovate. The purple flowers re- 
semble those of the potato but are smaller; the fruit is a red, 
ovoid berry. 

5. Black Nightshade (S. nigrum L.), is a smaller plant, herba- 
ceous and annual, with ovate leaves; most frequent in waste 
places. Its flowers are white, and the fruit a round, black berry. 

Other plants occasionally met with belonging to different 
genera of the Solanaceae are Deadly Nightshade and Henbane. 

6. Deadly Nightshade (Atropa Belladonna L.) is an herbaceous 
perennial, about three feet high, met with about ruins and chalky 
waste places, but of comparatively rare occurrence. It possesses 
large broad, ovate leaves, and purple, drooping, bell-shaped 
flowers. The berries are a deep violet colour, and of sweetish 
taste. The whole plant contains hyoscyamine and atropine, 



HENBANE 475 

both of which are extremely poisonous alkaloids. The con- 
sumption of a few berries has led to fatal results. 

7. Henbane (Hyoscyamus niger L.). A hairy biennial, about 
two feet high, possessing a strong fetid odour, and growing on 
waste ground. The broad leaves are sessile and clasping, with 
pinnatifid margins ; the flowers of greenish-yellow colour, veined 
with purple. The fruit is a two-celled capsule. The leaves and 
flowering shoots contain the poisonous alkaloid hyoscyamine, 
nearly related to atropine. 

The tomato and tobacco plants also belong to this Order : 
also the poisonous Thorn- Apple (Datura Stramonium L.) which 
sometimes occurs in this country as a casual weed of cultivated 
land. 



CHAPTER XXXIV. 
COMPOSITE. 

i. THE Composite is the most extensive Order, and comprises 
from 10,000 to 12,000 species, or roughly about one-tenth of all 
known seed -bearing plants. 

A number of species, such as Arnica montana L., chamomile 
and wormwood, are of medicinal value ; others, of which the 
artichoke and lettuce may be taken as examples, are useful food 
plants of the garden. 

Plants belonging to the genera Zinnia, Chrysanthemum, 
Dahlia, Aster, Gaillardia, Helianthus, and others are largely 
grown as ornamental plants. 

Not a single species, however, is grown as an ordinary farm 
crop in this country, though not a few, such as dandelion, thistle, 
groundsel, coltsfoot, mayweed, and ox-eye daisy are objectionable 
weeds (see pp. 602, 615). 

2. General characters of the Order. The most characteristic 
feature of the Order is the structure of the inflorescence : the 
latter is a capitulum, and consists of a number of small flowers 
collected into a compact head resembling a single large flower. 

A common form of capitulum is seen in the ox-eye daisy 
(Fig. 147), the parts of which, with the dandelion described below, 
may be taken as typical of the commonest forms in the Com- 
positae. On its underside is a series of narrow scaly bracts 
termed phyllaries, arranged in whorls ; the whole series of 
phyllaries is spoken of as the involucre of the capitulum. 

In the centre of the capitulum are a number of small yellow 
flowers the so-called disk florets each of which has the 

470 



GENERAL CHARACTERS OF THE ORDER 477 

form shown at 2, Fig. 147. Each floret or small flower is 
regular and epigynous ; the corolla gamopetalous and five-lobed ; 
no calyx exists, or is only present in the form of a minute ring 
round the upper part of the ovary. The androecium consists of 
five stamens with filaments attached to the inside of the corolla 
(epipetalous) ; the anthers of the stamens are united together, 
and form a tube through which the style passes. (Stamens with 
united anthers and free filaments are described as syngenesious.} 
The ovary is inferior and syncarpous, consisting of two 
united carpels; within it is a single erect anatropous ovule. 
The straight style has a divided tip. 




FIG. 147 i. Capitulum of Ox-eye Daisy (Chrysanthe- 
mum Leucanthetnunt L ). r The ' ray' ; d the ' dibk." 
2. ' Disk' floret (magnified), o The cvaivl c tubular 
corolla ; a, anthers ; j stigma. 3. * Ray ' floret (magni- 
fied), o Ovary ; s stigma ; c ligulate corolla ,/ fruit. 

The fruit (/, Fig. 147) is one-seeded and indehiscent with a 
series of longitudinal ribs on its outer surface : it is a kind of 
nut or achene to which the special name cypsela is given. 
The seed is without endosperm. 

Besides the disk florets and surrounding them, there is a 
single ring of white flowers (f) resembling narrow strap-like 
petals. They form the ' ray ' of the capitulum, and are termed 
ray florets. Each of the latter is a small unisexual (female) 
flower, and possesses a white corolla, the lower part of which is 
tubular, while the upper part is drawn out into a long narrow 



478 



COMPOSITE 



structure, the tip of which is notched (3, Fig. 147). A corolla 
of this form is described as ligulate. The rest of the parts are 
similar to those of the disk florets. 

Both the ray florets and the disk florets are sessile upon a 
short, thick button-shaped axis which is designated the receptacle 
of the capitulum, an unfortunate term likely to be confused with 
the receptacle of a flower, with which however it has nothing 
to do. 

A large number of genera, the species of which have capitula 
composed of tubular florets only, or of tubular florets and an 
outer whorl of ligulate florets, are united to form a division of 
the Composite known as the TUBULIFLOILE. Plants belonging 
to this series have watery juice in their stems and leaves. 

Another group of genera, termed the LIGULIFLOR^S, is formed 
of those species whose capitula bear only ligulate flowers. Plants 

belonging to the Liguliflorae, 
of which the dandelion and 
sow-thistle are examples, 
have milky juice (latex] in 
their stem and leaves. 

A single flower from the 
capitulum of the dandelion 
is seen in Fig. 148. It is 
bisexual with a ligulate 
corolla formed of five petals 
shown by the five notches 

1 3. 

FIG. 148. i. Single Floret of Dandelion (Tar- 




at its tip. The calyx is 
composed of silky hairs 
which encircle the upper 
part of the ovary. This ring 
of hairs grows most rapidly 
after fertilisation of the 
flowers when the fruit is ripening: it is termed \hepappus, and 
acts as a parachute for the distribution of the fruit by the wind. 



axacum officin.aU Web ). o Inferior ovary ; 
> pappus (calyx) ; a. anthers of stamens ; /their 
filaments ; style and divided stigma ; c ligu- 
late corolla. 

a. Fruit (cypsela) developed from i. s Stalk 
of the pappus/. 

3. Fruit (cypsela) of Groundsel (Senecie 
vulgaris L.) with, sessile pappus. 



YARROW I MILLEFOIL OR THOUSAND-LEAF 479 

In the dandelion the pappus is stalked, that is, situated at 
the end of the prolonged upper part or beak of the fruit 
(2, Fig. 148). In groundsel (3, Fig. 148) the pappus is 
sessile. 

Ex. 245. (i) Examine the inflorescences of ox-eye daisy, common daisy, 
sow-thistle, dandelion, groundsel, and any other common Composite. Note 
the form and extent of the involucre, the presence or absence of disk and ray 
florets. 

(2) Cut vertical sections of the capitula and observe the form of the 
receptacles, whether flat, convex, concave, or conical. Note the presence or 
absence of small bristly or chaffy scales (bracteoles) on the receptacles near 
each flower. 

(3) Examine the fruits of the above-mentioned plants. Note the presence 
or absence of a pappus ; also the smoothness or roughness of the pericarp. 
Are the hairs of the pappus simple or branched ? 

3. Yarrow : MillefoU or Thousand-leaf (Achillea Millefolium 
L.) is a perennial plant belonging to the Compositse, common in 
poor dry pastures, and possessing an extensive creeping root- 
stock. The stems are from 6 to 18 inches high, and furrowed. 
The leaves are 2 or 3 inches long, narrow, oblong, and much 
divided, the segments being very fine. The capitula, which 
are crowded together in a corymbose manner, are small, usually 
not more than \ or \ inch in diameter, with white or pinkish 
ray florets. 

The fruits, commercially known as ' seeds, 1 are compressed, and 
have no pappus. Yarrow grows very early in spring, and pos- 
sesses a strong aromatic odour when bruised. Sheep are fond 
of the young leaves, and generally keep the plants eaten down 
in pastures. But when it has developed its strong woody stem 
stock refuse it. 

Yarrow is sometimes recommended for mixture with grass 
seeds when sowing down land for sheep pasture, but its use 
must be restricted to the narrowest limits, or it will soon dis- 
figure and usurp the ground which should be allotted to better 



480 COMPOSITE 

plants. It should be left out of all grass mixtures where the 
produce is to be mown. 

Ex. 246. Dig up and examine a complete plant of yarrow in flower. Note 
the character of the rootstock, its tough stem and much divided leaves, and 
its corymbose collection of small capitula. 

Carefully examine a single capitulum, noting the number and form of the 
ray and disk florets respectively. 

Examine the fruits of yarrow. 



CHAPTER XXXV. 
GRAMINEJE. TRUE GRASSES. 

i. General characters of the Order. Herbs. Roots fibrous, 
chiefly adventitious. Stems cylindrical, hollow, with solid nodes. 
Leaves alternate with split leaf-sheath and ligule. 

Inflorescence a spikelet, bearing chaffy bracts or glumes, which 
hide the flowers. Flower small, bisexual, hypogynous. Perianth 
missing, or consisting of two scales (lodicules). Androecium of 
three stamens with versatile anthers. Gynaecium a single carpel, 
with two styles, having feathery or brush-like stigmas ; ovary 
with one seed. Fruit a caryopsis. 

a. This is one of the most valuable and extensive Orders 
of plants, and comprises between 3000 and 4000 species. To 
it belong the cereals which supply the chief part of the food of 
the human race, and also the meadow and pasture grasses so 
important as food for the stock of the farm. 

The general character of the roots, stems, leaves, and flowers 
of grasses are here dealt with, while in the subsequent chapters 
the cereals and those grasses of which it is essential that the 
agriculturist should possess a good knowledge are treated in 
greater detail. 

ROOT. The roots which emerge from the seeds of grasses on 
germination are few in number and short-lived, but an extensive 
system of adventitious, thin, fibrous roots develops later from all 
the underground nodes of the stems. 

STEM. The stems, which are termed culm^ are cylindrical 
and usually hollow when full-grown, except at the nodes, where 

481 



482 GRAMINE>. TRUE GRASSES 

they are solid : maize is exceptional in having stems solid 
throughout. 

Branches arise only in the axils of the lowermost leaves. 
1 Tillering ' is the term employed to designate this form of branch- 
ing in grasses, and its nature is discussed on pages 490-494. 

Generally the buds break through the base of the enclosing 
leaf-sheaths ; the branches produced are designated extravaginal 
branches and grow more or less horizontally for a time, often 
underground, forming longer or shorter rhizomes, from which 
leaves and flowering stems are sent up. Grasses behaving in 
this manner soon cover considerable areas of the ground with a 
close turf. Couch-grass, smoothed-stalked meadow-grass, and 
fiorin are good examples. 

Less frequently the branches are intravaginal, that is, they 
grow up between the leaf-sheath and the stem, emerging near 
the ligule, but ultimately, tearing the subtending leaf, as in x, 
Fig. 153. Branching of this character leads to the formation of 
compact tufts, and grasses exhibiting this manner of growth are 
unable to cover the ground except in isolated patches. The 
cereals (see pp. 490-494), annual broine-grasses, meadow and 
sheep fescues, rye-grasses, and cocksfoot are examples. 

The perennial rhizomes of grasses are usually sympodia 
(2, Fig. 22). 

LEAF. The leaf of a grass consists of two parts, the blade 
and the sheath. The Uaf-shtath surrounds the stem like a tube 
split down one side, its free edges overlapping in some instances 
(&Fig. 149). In cocksfoot, dodder-grass, and some of the meadow- 
grasses it is not split but forms a completely closed tube. It acts 
as a support for the stems while they are young and soft, and 
protects the tender growing points within from the injurious 
effects of frost and heat. Most grasses appear swollen at the 
nodes (d, Fig. 149) ; this is not usually due to thickening of the 
stem, but to the presence of a mass of soft tissue at the base 
of the leaf-sheath. 



484 



GRAMINE^E. TRUE GRASSES 



The leaf-blade is generally long, narrow, and flat, but in 
grasses growing in dry places it is often folded and appears 
almost cylindrical (Fig. 183). 

The first leaf of the embryo and those upon the underground 
rhizomes are almost always modified structures representing leaf- 
sheaths the blades of which remain undeveloped or rudimentary. 
It is important to notice the arrangement of the leaves in the 
bud as it often affords a ready means of 
distinguishing nearly -allied species of 
grasses. Most frequently the leaves are 
rolled up from one side in a spiral form, 
and the young shoot appears round (Fig. 
191), but in several grasses they are 
simply folded down the middle, the shoot 
then appearing flattened (Fig. 188). 

At the point where the 
blade 'joins the sheath the 
inside of the latter often 
protrudes as a tongue-like 
membranous structure (/ 
Fig. 149), termed the ligule. 

Fig. 150. i. Spikelet from grass of Fig. 149. rr> , . . , . 

t. The same slightly opened to show separate 1 lie latter VariCS HlUCh 111 

length in different species. 
Near the ligule the sides of 
the leaf sometimes terminate 
in claw-like projections which partially or entirely encircle the 
stem as in Figs. 154 and 189. 

INFLORESCENCE. In the figure of annual meadow-grass (Fig. 
149), the branched upper part popularly termed the * flower ' 
is a complex inflorescence bearing flowers which are very small 
and completely hidden from view. The parts c are termed 
spikelcts, and it is within these that the flowers are enclosed. 

A single spikelet is illustrated in Fig. 150. On examination 
it is seen to consist of an axis r y the rachilla^ upon which is 




glumes and florets, a Empty glume ; /flowering 
glume of second floret; rrachilla or axis of spikelet. 

3. Single floret of 2. f Flowering glume ;/ palea; 
o ovary of gynaecium ; r piece of rachilla. 

4. The flower. / Lodicules; o ovary ; s stigma ; 
a stamen. 



GENERAL CHARACTERS OF THE ORDER 485 

arranged a series of sessile bracts in two alternate rows. These 
bracts are termed glumes, and in the axils of all except the two 
lowermost ones (a a) flowers are produced which on account of 
their small size are not seen. The glumes a a are termed the 
empty glumes of the spikelet, the others similar to / are the 
flowering glumes. Attached to the very minute stalk which 
each flower possesses is another bract, named the/a/<? or palea 
seen at p. It lies opposite to the flowering glume, and be- 
tween it and the latter the flower is enclosed more or less 
completely. 

The empty glumes are usually two in number, but there is 
only one in rye-grass, and the spikelet of sweet vernal-grass 
possesses four. Sometimes they are small and narrow as in rye, 
or they may be large and completely enfold the rest of the 
spikelet as in oats. 

The flowering glumes often differ from the empty ones in 
having 'beards' or bristle-shaped structures termed awns. In 
barley and ' bearded ' wheats the awns are of great length, while 
in some instances they are merely short points at the tip of the 
glume. 

Awns are said to be terminal, dorsal, or basal according to 
whether they arise from the tip, middle of the back, or the base 
of the glume. 

The number of flowers in each spikelet varies considerably: in 
some species, as timothy grass and florin, only one is present, in 
Yorkshire fog two, while in meadow-grasses, fescues, and rye- 
grasses there are several. 

All our grasses resemble each other in having their flowers in 
spikelets, the latter, however, do not constitute the whole in- 
florescence but are only parts of it In wheat, rye-grass, and 
barley the spikelets are sessile upon opposite sides of a straight 
unbranched main axis, the rachis, the total inflorescence being 
termed a spike ; in reality it is a spike of spikelets. 

In the majority of grasses the rachis is much-branched and 

33 



486 GRAMINE^E. TRUE GRASSES 

the spikelets are borne at the ends of the branches as in Fig. 149. 
Such an inflorescence is termed a panicle. 

When the branches of the panicle are long and the spikelets 
consequently separated from each other, the panicle is described 
as spreading open, or diffuse (Figs. 174, 181, &c.). 

When the branches of the panicle are very short, so that the 
spikelets lie close to the main axis as in foxtail and timothy grass 
(Figs. 172 and 173), a false spike or spike-like panicle is formed. 

THE FLOWER. As pointed out previously the glumes are bracts 
of the inflorescence and do not, of course, constitute a part of 
the flower. The latter (4, Fig. 1 50) consists of an androeciurn of 
three hypogynous stamens and a gynaecium of one carpel. At 
the base of the ovary on the side opposite to the pale, that is, 
on the side next to the flowering glume, there are two small 
transparent scales, the lodicules^ /; they are usually considered 
rudiments of the perianth, but may possibly represent a second 
palea. 

The filaments of the stamens are long and slender and 
attached to near the middle of the anthers ; the latter are readily 
moved by the slightest breeze. 

In sweet vernal-grass two stamens only are present. 

The gynaecium consists of a single carpel with an ovary most 
frequently surmounted by two styles with brush-like stigmas (j). 

The grasses are cross-fertilised, though self-fertilisation is also 
frequent At the time of flowering the base of the lodicules 
generally swell up and force the pale and flowering glume 
apart; the filaments of the stamens grow rapidly about the 
same time and push the anther out at the sides of the 
glumes ; the pollen is then distributed by the wind and caught 
by the feathery stigmas. 

In a short time (often not more than an hour or two) the 
lodicules lose their turgidity and shrivel, and the pale and 
flowering glume close up again shutting the ovary and stigmas 
from view. 



GENERAL CHARACTERS OF THE ORDER 487 

THE FRUIT AND SEED. The fruit of grasses is in most cases 
a caryopsis or a one-seeded form of nut, the seed of which has 
grown completely into union with its surrounding thin pericarp. 
The wheat grain discussed on p. 22 may be taken as typical of 
a caryopsis and its enclosed seed. 

In young flowers the ovaries of the grasses are quite free from 
the glumes and may remain so even when the fruit is ripe as in 
the case of wheat, rye and oats; sometimes, however, during 
growth after fertilisation the caryopsis grows up to between the 
glumes and becomes united with the latter as in the case of 
ordinary barley. 

In oats and many grasses the glumes so closely invest the 
caryopsis that the latter does not fall out from the glumes when 
the ripe panicles are shaken or thrashed ; nevertheless, in these 
cases the caryopsis is free and easily separable from the glumes, 
which is not the case in barley and many other grasses. 

The seed contains a large proportion of starchy endosperm, 
at the side of which the embryo is placed. In some grass seeds, 
and particularly those of certain varieties of cereal grains, such as 
Hard wheats, the endosperm is flinty^ or hard and semi-trans- 
parent, while in others the endosperm, which is described as 
mealy> is opaque and chalky when cut across. 

The different appearance of flinty and mealy endosperm is 
due to the fact that in the first the starch grains within the cells 
are embedded in a dense matrix of proteid material, while in 
the mealy endosperm the cells are not completely filled with 
reserve materials, but very minute air spaces exist between the 
starch-grains within the cells. 

The embryo (Figs. 7 and 151) possesses one cotyledon (the 
scutellum), a short plumule, and in most cases a single primary 
root covered by the coleorhiza. In the cereals and some other 
grasses secondary roots appear upon the very short hypocotyl of 
the embryo while the latter is still within 'the caryopsis and they 
make their exit at the same time as the primary root, when 



488 GRAMINE^E. TRUE GRASSES 

germination commences; in most grasses, however, secondary 
roots first appear some time after the single primary root has 
grown out from the caryopsis. 

Ex. 247. Examine the roots of any grass. Observe as far as possible 
their origin, and note if they branch extensively. 

Ex. 248. Cut transverse and longitudinal sections of any well-developed 
grass stem at and between the nodes. Note if hollow or solid all through. 

Examine the leaves of barley and oats and many common grasses. Note 
the split leaf-sheath, the flat or rolled blade, and the character of the ligule 
if present. 

Ex. 249. Make an examination of the inflorescences of a number of common 
grasses in order to understand the various parts, viz., the rachis, and the 
spikelet with its rachilla and bracts. Which are the empty glumes, flowering 
glumes, and palea in each spikelet ? 

Ex. 250. Dissect out the flowers from any common grasses, noting the form 
and position of the stigma, the number of stamens, and the position, number 
and form of the lodicules in each. 

Ex. 251. Watch the unfolding of the total inflorescences of Yorkshire Fog, 
Tall Oat-Grass, and other grasses with panicles. What positions do the 
branches take before and after flowering ? 

Ex. 252. Cut transverse sections of several grains of barley, oats, wheat, 
rye and maize. Note the ' mealiness ' or ' flintiness ' of the endosperm in 
each. 



CHAPTER XXXVI, 
GRAMINE43 (continued). CEREALS. 

IN Europe perhaps the most familiar crops of the farm are wheat, 
barley, rye, and oats. 

These crops, designated Cereals, are grown mainly for their 
fruits or grains which form the most important food of mankind 
and are also of great value as food for the stock of the farm. 

Besides being utilised as bread-corn large quantities of the 
cereal grains are employed in the manufacture of starch, beer, 
whisky, gin, and other spirits. 

Moreover, the cereals are frequently grown for green fodder and 
the straw in a ripe state is fed to stock, made use of as litter, or 
employed for thatching, and many similarly useful purposes. 

The common cereals of the tropics are rice, maize, millet, and 
sorghum or dourra, but these, with the exception of maize, which 
is occasionally employed in a green state as horse and cattie 
fodder or made into silage, have no practical interest for the 
farmer of this country. 

The cereals are grasses and therefore possess general char- 
acters described in the last chapter \ they are, however, of such 
importance that further treatment of their peculiarities is needed. 

FRUIT AND GERMINATION OF SEED. (a) An account of the 
fruit and the germination of the embryo of wheat has previously 
been given (chap, ii.); the grain of rye is similar to this in 
almost all respects, but the roots of its embryo are generally four 
in number instead of three as in wheat. 

(b) In barley the caryopsis or fruit is firmly united with the 
enclosing flowering glume and pale, and the plumule of the 

489 



490 



GRAMINE^E. CEREALS 



embryo does not make its exit where the coleorhiza and roots 
emerge but grows on beneath the glume, and ultimately appears 
at the opposite end of the grain sometime after the roots have 
come forth (Fig. 151). 

The number of roots vis- 
ible on the embryo within 
the barley grain is generally 
five or six. 

(c) In the oat the caryopsis 
is free from the glumes, but 
the latter more or less tightly 
surround it and on germina- 
tion the plumule of the em- 
bryo behaves as in barley, and 
emerges from the grain at the 
end opposite to that at which 
the roots appear ; the number 
of roots of the embryo is 
three. 

ROOTS. In the cereals, as 
in all grasses, the roots of 
the embryo within the seed 





Fio^s^Barleygrainshowingembryo^dits 



Ut 



Commences I 



germination 

these may be 

J 



termed 'seminal* roots. They 

' 



development during germination. . 

1. Longitudinal section of gram showing 

embryo at rest. 

2. J he same after germination has begun ; the 

roots have made their exit from the gram, but the are of importance in the early 

Slumule c is still within it enclosed by the . ' 

owering glume. life of the young plant, but 

3. Later stage of the germinated grain showing ' . 

the plumule c outside the grain. subsequently die off and their 

e Endosperm; a. coleorhiza; b root; c plumule; . 

^scuteiium. work is undertaken by the 

so-called ' coronal* roots which arise from the lower nodes of the 
stems as explained below (see Figs. 152 to 154); 

* TILLERING/ A^ Fig. 152 gives the appearance of a young 
barley plant after a single green leaf has appeared above ground. 
At this stage it possesses a small bunch of roots which have come 



GRAMINE^E. CEREALS 



491 



from those which were easily seen in the embryo within the 
seed. 

Soon afterwards more leaves show themselves, as at B, Fig. 
152, and often about the same time the terminal bud, which was 




A B C 

FIG. 152. A, Young barley plant, showing 'seminal roots, c First sheathing leaf; 
/ blade of first green leaf. 

B, Young barley plant, a later stage of A. a 'Seminal* roots; n first node of 
stem. 

C, Longitudinal section of B at *. c Sheathing leaf ; Astern; a terminal bud; b lateral 
bud (first k tiller 4 ) ; e adventitious root forming. 

originally within the grain, is carried up to near the surface 
of the ground by the growth of the first internode, the second 
and succeeding internodes remaining undeveloped for some 
time. When the primary bud has reached this position rapid 
formation of lateral buds takes place in the axils of its leaves. 



492 



GRAMINE^E. CEREALS 



A longitudinal section of a portion of a plant in this early stage 
is seen at C, Fig. 152, where a is the terminal bud, and b a 
lateral bud just forming. In Fig. 153 a similar plant is shown in 
a further stage of development ; the leaves of bud b have now 
come above ground. 

A shoot may arise in this manner in the axil of each of the 
lower leaves on the primary stem, the internodes of the latter 




FIG. 153. I. Young barley plant, a later stage of B y Fig. 152. The leaves from bud If 
in latter figure haxe now grown out and burst the enclosing leaf-sheath. 

II. Longitudinal section of I. at first node , showing the short stem within terminated 
by a minute ear. Besides the bud b a rudimentary one is seen in the axil of the lower leaf 
of the main stem, e Adventitious root ; n first node. 

remaining very short all the time (//., Fig. 153). The secondary 
stems may also develop in a similar fashion. It is thus seen 
that from a single grain the production of a large number of 
shoots is possible, and these breaking their way out from the 
enclosing leaf-sheaths appear finally as a tuft of stems, each of 
which may subsequently develop an ear of corn. 

This formation of many shoots which spring from near the 



GRAMINE^E. CEREALS 493 

surface of the soil is termed * tillering] and is a common mode of 
branching met with in all the cereals, and in grasses generally. 

No matter at what depth the seed is placed branching only 
takes place at the nodes near the surface of the ground. If 
placed deeply the first internode or two (d, C, Fig. 152, and a, 
Fig, 154) elongate considerably, and are noticed as a tough, 
wiry piece of stem when the plants are pulled up ; in shallow 
sowing the internodes are short and scarcely visible. 

The number of ear-bearing shoots produced from a single 
grain may, under some circumstances, be 100 or more; usually 
it is not more than five or six. Varieties of cereals grown largely 
for straw should tiller considerably ; for production of grain of 
good quality two or three stems from each is sufficient. The 
ears of much-tillered plants ripen unevenly as the stems are neces- 
sarily not all of the same age, and those produced last are 
smaller and weaker than the primary stem and its first two or 
three branches. 

The amount of * tillering ' depends upon both internal and ex- 
ternal causes. Some species of grass * tiller' more than others 
wheat and barley, for example, more than oats ; varieties of the 
same cereal also differ considerably in this respect. 

Plants exposed to plenty of light * tiller ' more extensively than 
those grown in shade. Thin-sowing promotes it by allowing 
more light to reach each plant. Moreover, in thin-sown crops 
more food-constituents are at disposal in the ground for each 
plant than when crowded together, and the plants ' tiller ' more 
in consequence. 

On poor soils fewer stems arise from a single plant than on 
good soils, and early sowing gives more time for the formation 
and development of shoots, winter-sown wheat * tillering ' more 
than that drilled in spring. 

1 SHOOTING ' OF THE CORN. The branches for some time after 
they are produced in the * tillering ' process remain with unde- 
veloped internodes ; and it is only the blades of the leaves upon 



494 



GRAMINE^E. CEREALS 



each shoot that are seen above ground in spring, the actual stems 
being extremely short and quite close to the 
ground. A longitudinal section of the lower 
portion of the young plant at //., Fig. 153 
shows the disposition of its parts. 

It is seen that even in this stage the main 
stem is surmounted by a visible ear, and it 
will be readily understood that grazing the 
crop by running sheep over it, or mowing off 
the leaves in spring, does not injure either 
the stem or the ear, as the latter are placed 
so low down and are protected by the en- 
veloping leaf-sheaths. 

In the middle of June or thereabout the 
rapid extension of the internodes takes place 
and the corn is then said to 
shoot. The ear and lowest 
internode in the bud begin 
to grow first ; the rest of the 
stem then develops in or- 
derly succession from below 
upwards and forces the ear 
out of the uppermost leaf- 
sheath. 

Germination, * tillering/ and 
c shooting ' of spring-sown 
crops proceed more or less 
continuously without any dis- 
tinct cessation of growth, but 
autumn -sown cereals grow 
little in winter. 

1 LODGING ' OR * LAYING ' 
OF CROP. It is noticed that 
after ' shooting' into ear 




FIG. 154. I. Barley plant 6 inches high, just 
commencing to ' shoot, a Rhizomatous stem ; 
j, primary stem; a and 3, 'tillers' lateral 
branches ; f seminal roots ; e adventitious roots. 

II. Same barley plant with leaves removed to 
show primary stem and five oranches 'tillers' 
springing from its lower nodes ; the primary stem 
has begun to 'shoot,' i e. its nodes are lengthen- 
ing rapidly ; a small ear is visible at Its tip. 



GRAMINE^E. CEREALS 495 

corn crops very frequently become 'laid' or 'lodged.' The 
straw is weak and it is found that the second and third inter- 
nodes near the ground are longer than usual and the cells 
beneath the epidermis and round the vascular bundles, upon 
which the stems depend for mechanical support, are longer and 
have thinner walls than those of straw which is not laid. 

The weakness is not caused by a deficiency in the amount of 
silica in the cell walls as was formerly imagined, but is due to 
an inadequate supply of light to the young plants, the lower 
parts being etiolated by overcrowding. 

Nitrogenous manures tend to the production of much leaf 
surface in all plants, and when used in excess on corn crops the 
plants shade each other and are liable to become laid in 
consequence. 

Heavy rain and wind increase the evil, but the weakness may 
be such that the weight of the upper part of the straw is sufficient 
to make it fall without the aid of wind or rain. 

It might be imagined that well-tillered crops, where many 
stems arise from each plant, would be specially subject to 
( lodging. 1 This is, however, not usually the case ; the ' tillering ' 
process is dependent upon light, and the fact of its having gone 
on extensively is evidence that each plant has had an adequate 
exposure to light; shaded plants * tiller ' very little. 

Thick-sowing or drilling in too close rows promote c lodging,* 
for from the first soon after germination the plants shade 
each other. 

FLOWERING AND FERTILISATION. Most cereals open their 
flowers in the morning from four to seven o'clock and only when 
the temperature rises to about 75 F. At the time of flowering 
the flowering glume and pale are forced apart by the increased 
turgidity of the lodicules, and the anthers are pushed out by the 
rapid growth of the filaments of the stamens. At the same time 
much of the pollen is shed into the air, but in almost all cereals 
some of it falls on the feathery stigmas of the same flower, and 



496 GRAMINE/E. CEREALS 

self-pollination results. In wheat, barley and oats self-pollina- 
tion is followed by fertilisation and the production of fertile 
seeds, whereas in rye self-pollinated flowers are almost always 
sterile and considerable decrease of yield results to the crop 
when damp, dull weather prevails for a long time and prevents 
the proper opening of the flowers and distribution of the pollen. 

In wheat the first flowers to open are those situated about one- 
third of the way from the apex of the ear, the rest follow in 
succession upwards and downwards from this point. Each 
flower remains open from 8 to 30 minutes, and the whole ear 
completes its flowering usually in eight or nine days, 

In barley the complete period of flowering of the ear is shorter, 
and when the flowers open they remain expanded a longer time 
than those of wheat. Frequently, however, the flowers of barley 
never open at all and self-fertilisation is the rule. In fact all the 
cereals, except rye, are generally self-fertilised, although natural 
crosses among wheats and among oats have been observed 
occasionally. Hybrids between rye and wheat have been pro- 
duced. 

RIPENING. A few hours after pollination the pollen-tube 
reaches the ovule, and fertilisation of the ovum is effected. The 
latter then gradually becomes an embryo and in the embryo-sac 
around it the formation of endosperm-tissue takes place. 

Within the endosperm-tissue there is also a gradual accumula- 
tion and storage of proteins and carbohydrates. 

Some of the proteins are laid down in the outermost layer of 
cells of the endosperm in the form of aleuron-grains, and it is 
important to note that the filling of the aleuron-layer and the 
parts immediately beneath it takes place before the central portions 
of the endosperm are completed. In small and rapidly-ripened 
grains of cereals the percentage of proteins in comparison with 
the carbohydrate starch is higher than in slowly-matured plump 
grains in which longer time has been allowed for the accumula- 
tion of starch* 



GRAMINE^E. CEREALS 497 

In barley for malting purposes, where the proportion of nitro- 
genous compounds should be as low as possible, it is essential 
that the crop should have time to accumulate carbohydrates in 
the grain in large amount or its value for malting is much reduced. 

While the ear and grains are ripening, changes are going on 
in the roots, stem and leaves. There is a general movement 
of water from below upwards and at the same time a transla- 
tion of useful plastic materials (sugars, amides and proteins) 
from the lower leaves and stem to the upper parts of the plant, 
these materials being finally utilised in the formation of the 
embryo and its store of starch and other reserve-foods in the 
neighbouring endosperm-tissue within the grain. 

Death also takes place, gradually from below upwards, the 
roots dying off some time before the grains are ripe. 

Although the ripening changes go on continuously it is useful 
to notice four stages, known respectively as (i) the milk-ripe, 
(2) the yellow-ripe^ (3) ripe> and (4) the dead-ripe stages. 

In the milk-ripe stage the endosperm tissue contains much 
water and when the grain is squeezed a white milky juice oozes 
out consisting of the watery cell-sap and numbers of starch 
grains. Although the lowermost leaves are dead the leaf- 
sheaths and the blade of the uppermost leaf are still green ; 
the glumes are also green, so that the whole crop wears a 
green unripe tint. 

In the yellow-ripe stage, on cutting across or breaking the 
grain, the endosperm is found to be somewhat tough and kneads 
like wax. The pericarp of the grain has lost its green colour and 
the straw has assumed a yellow tint, except at the upper nodes 
of the stem where the cells are still soft and sappy and contain 
green chloroplastids. 

In the ripe stage, which in hot weather occurs three or four days 
after yellow ripeness, the straw is usually of lighter tint, and the 
nodes which die last are now dead, shrunken, and brown. The 
grain is harder and firmer. 



498 GRAMINE^E. CEREALS 

If left longer the crop becomes dead-ripe^ in which state the grain 
is brittle when cut across or broken, and the straw loses much of 
its brightness ; if left on the field the straw also is liable to 
become greyish and dirty in appearance, and often so brittle that 
in certain varieties of cereals the ears may drop off whole, and 
much of the grain be lost in handling the crop. 

For most cereals it appears to be best to cut the crop in the 
yellow-ripe stage when no trace of chlorophyll can be detected 
in any part of the pericarp of grains selected at random in 
several parts of the field. 

Ex. 253. Germinate grains of all the cereals on damp blotting-paper and 
carefully note the number of roots which make their appearance from the 
different kinds. Observe the way in which the plumule makes its exit from 
the grain. Extract the embryos complete and note the shape of the scutellum 
in each. 

Does a naked caryopsis of oat or barley germinate similarly to that of 
wheat ? 

Ex. 254. Carefully dig up young plants of any of the cereals and note the 
position and number of the ' coronal ' and ' seminal ' roots. 

Ex.255. Make longitudinal sections of young ' untillered ' plants and 
1 tillered ' ones in early spring or winter. Examine with a lens or microscope 
and observe the number of axillary buds. 

Ex. 256 Make similar sections when the stems are 6 or 8 inches high, and 
note the presence and position of the young inflorescences or * ears ' within. 

Ex. 257. Examine an ear of wheat, barley, and oats just after it appears 
from the uppermost leaf-sheath. Note the character of the flowers. Make 
examination at intervals later in order to watch the growth of the caryopsis 
between the glumes. Which grains of the ear develop most rapidly ? 

Ex. 258. Cut across grains at various intervals and observe the different 
changes which come over the grain and its contents during ripening. 

Note the order of disappearance of greenness from the stems, nodes, leaf- 
sheaths, and leaf-blades. Endeavour to observe the (i) milk-ripe, (2) 
yellow-ripe, (3) ripe, and (4) dead -ripe stages, and how they pass one into 
the other. 



CHAPTER XXXVII. 



CULTIVATED AND WILD OATS (Genus A vena). 

i. Characters of the Genus. The inflorescences or ' ears ' of oats 
are panicles, the branches of which in some races spread out 
widely, while in others the branches are more or less closely 
pressed to one side of the main axis. 

The spikelets contain from two to six flowers ; the empty 
glumes are membranous, unequal, many-nerved, and generally 
longer than the spikelet (Fig. 156). The flowering glume 
terminates in two more or less distinct projecting points, and 
is thick and' firm with a bent, 
twisted dorsal awn ; the awn of 
the flowering glume is missing 
from some of the finest cultivated 
oats. The empty glumes are 
always pale yellow or straw colour, 
but the flowering glumes may 
be white, yellow, dun, brown or 
black. 

The caryopses are spindle- 
shape, furrowed on one side, free, 
hairy on the tip and sides, and firmly clasped by the flowering 
glume and pale, except in the naked oat, the fruit of which 
readily falls out from between the glumes when shaken or 
thrashed. 

The following are the chief species and varieties met with 
on the farm : 

2. Wild Oat (Avena fatua L.). A common weed with long 

499 




of Wild Oat (AvfM 



500 CULTIVATED AND WILD OATS 

slender stems and large open spreading panicle. The spikelets 
generally contain three flowers, the flowering glumes of which 
bear a strong bent awn. The rachilla and base of the flowering 
glumes are covered with long reddish-brown hairs (Fig. 155). 

3. Bristle-pointed Oat (Avena strigosa Schreb.). An annual 
weed often confused with the previous species, from which it 
differs in having one-sided panicles and fewer branches. The 
flowering glumes are, moreover, more deeply divided at the apex 
and the two segments prolonged into short bristles or awn-like 
projections ; the rachilla and base of the flowering glume are 
smooth. 

This species was formerly cultivated on poor exposed land 
in the northern parts of Scotland as a bread-corn, but is now 
most frequently seen as a weed among the superior cereals. 

It is also sometimes cultivated as green fodder for cattle. 

4. Animated or Fly Oat (Avena sterilis L.). A species grown 
in gardens as a curiosity. The panicle is spreading and the 
' grain ' very much resembles that of the wild oat, except that 
it is much larger and has longer reddish-brown hairs on the 
flowering glume ; the rachilla is glabrous. When the dry, strong 
twisted awn absorbs moisture it untwists and gives a creeping 
motion to the grain. 

5. Short Oat (Avena brevis Roth.). A species of oat with 
thin grass-like stems and bulky crop of leaves, sometimes grown 
for green fodder for cattle or to be made into hay. 

The panicle is one-sided and the spikelets contain one or twc 
flowers with awned flowering glumes. The ' oats ' are plump, 
brownish and about a quarter of an inch long. 

6. Common Cultivated Oat. This cereal in the northerr 
countries of Europe is an important bread-corn, but in th< 
warmer and drier parts the grain is chiefly used as food foi 
stock, especially horses. It is also grown as an early spring 
green crop. 



TARTARIAN OATS 501 

The various cultivated forms appear to have been derived from 
the wild species, A.fatua L., A. stcrilis L., and A. barbata Brot. 

Two races are recognised which are sometimes treated as 
distinct species, viz. : 

RACE I. Common Oat (A vena sativa L.) with open spread- 
ing panicles (Fig. 157), and 

RACE II. Tartarian Oats (Avena orientalis Schreb.) with 
contracted one-sided panicles (Fig. 158). 

The spikelets usually contain two or three flowers, the upper 
one of which is liable to produce either a small grain or none at 
all. The flowering glume of the lowest flower frequently bears a 
straight awn ( Fig. 1 56) which when strong is 
a sign of degeneration of the stock or an 
evidence of the coarseness of the variety. 

There is considerable diversity among 
the different varieties of cultivated oats in 
(i) the colour and thickness of the husk 
or flowering glume ; (2) the form of the 
grain ; (3) the period of ripening ; (4) the 
length of the straw, and (5) the tendency 
to shed the grain when ripe. ij 

For meal the grain should be somewhat Flf x , 6 _ Spikclct O f common 
short and plump, with a thin, clean white <^^^^^ft 
husk : the varieties with long grains are /%J - /f8 three flowcrs - 
best adapted for feeding stock, and the colour of the husk is of 
little importance. In some districts black oats are preferred 
apparently with no-sufficient reason, except that in such localities 
the black varieties are the most productive and the most familiar. 

The early varieties give a larger yield of grain, but less straw 
than the late varieties. These oats, which are easily shed when 
ripe, have thin husks as a rule and are of better quality for the 
manufacture of oatmeal. 

Late varieties possess longer grains, more adapted for feeding 
stock, with thickish husk and a comparatively small proportion 

3 Tr 




502 



CULTIVATED AND WILD OATS 



of ' kernel.' They produce, however, a larger bulk of superior 
straw, are hardier and more suited to inferior soils than the 
finer early varieties. On good soils too much straw is produced 
and the crop is liable to become 'laid.' 
RACE I. Common Oat (Avena sativa L.). 




FIG. 157. Panicle of Common Oat (Avena sativa L.). 



The following are a few of the commoner varieties of this race 
usually met with in this country. 

(i.) Potato Oat. An early and prolific variety with a somewhat 
compact ear and pale yellow straw of medium length. The grain 
is white, short and plump, and of excellent quality for millers ; 
its flowering glumes rarely bear awns unless the stock is 
degenerating. 



TARTARIAN OAT 503 

It is liable to shed its seeds when too ripe, and is best suited 
to good soils in a favourable climate. 

Early Hamilton appears to be an improved earlier form of the 
potato oat with superior straw and said to be more productive. 

(ii.) Sandy Oat. A tall, stiff-strawed early oat with small grain, 
the colour of which is white with a reddish tinge. It is inferior 
in quality of grain, but is much less liable to shed the latter 
in a gale than the potato oat. It is suited to all classes of 
soils. 

(iii) Abundance. A white, late variety, much grown at the 
present time : the straw is tall and leaves broad with a bluish 
green hue. Grain white, plump and large, with a thick husk. 
It is very similar, if not the same, as Newmarket, Giant Eliza, 
and Ligowo oats. Victory Oat also resembles Abundance in 
some of its characters. 

(iv) Golden Bain. An early oat with yellow grains in small 
spreading panicles. It is a prolific sort, with stout straw. 

(v.) Winter Dun or Grey Oat. This variety is sown in the 
southern parts of this country in autumn, and fed off green with 
sheep in spring, after which it is sometimes left for seed. 

Though not unfrequently killed by severe frost it may be 
considered hardy, and gives a fair yield of grain. The husk of 
the grain is dark at the base, brown in the middle, and pale 
brown at the tip, somewhat resembling that of a degenerate 
black oat. 

Several varieties of common oat having longish thin grains, 
with reddish, bluish, and black husks respectively are met with ; 
some of them are prolific but of poor quality, and scarcely 
deserving of cultivation even as food for stock. 

RACE II. Tartarian Oat (Avena oritntalis Schreb.) (Fig. 158). 
The varieties belonging to this race have one-sided panicles, 
as explained previously, and spikelets, whose empty glumes are 
slightly longer than those of the common oat. 

The grains are long, often of low bushel-weight, and wanting 



504 CULTIVATED AND WILD OATS 

in plumpness ; the straw is stiff and reedy, and inferior in feeding 
value to that of the previous race. 

Their productiveness, however, is superior to that of the 
common oats, and especially is this the case upon soils in 
warm climates unsuited to the growth of the latter race. 

In the south of England, where as much straw and grain as 
possible is the object without much regard to quality, these 
varieties are very extensively cultivated. 
Tartarian oats are adapted for cul- 
tivation on marshy and peaty soils, 
heavily dunged hop-gardens, and, in 
fact, on all soils in which a considerable 
amount of humus is present. 

The following are two common 
varieties : 

(i.) White Tartarian Oat. A late 
variety, with very tall stiff straw, and 
grain the husk of which is dull white 
with a long awn. It requires a good 
soil for satisfactory growth. 

(ii.) Black Tartarian Oat. One of 
the most extensively cultivated black 
oats, earlier and more liable to shed 
its grain than the white Tartarian oat. 
The straw is of medium length, the 
grain black with paler tips, and plumper 
than the white variety; the awns on 
the flowering glumes are not so stout 

FIG. i 5 8.-"panicle of Tartarian as On the latter kind. 
O* (Anna orientate Schr*.). g^ kjnds Qf Tartar j an Qats are 

grown for horses, sheep, and stock generally, but the black 
variety sometimes yields good meal. 

CLIMATE AND SOIL. Oats require a cool, moist climate ; the 
north and west of the British Isles therefore grow better samples 




BLACK TARTARIAN OAT 505 

than the south and east. In a dry climate, unless the soil is 
retentive of water, the oat develops a long thin grain, and a thick 
husk, which often bears a strong awn ; the branches of the 
panicles become dry and apparently hinder the translocation of 
materials necessary for the formation of a plump grain. 

This cereal may, however, be grown upon almost all classes of 
soil 

SOWING. With the exception of the winter dun oat and one 
or two similar varieties, oats are sown in spring. In the south 
of England they are generally drilled or broad-casted in January 
or February, while in the north the crop is sown in March and 
April. 

When drilled 3 to 4 bushels of seed per acre are used, accord- 
ing to the size of the grain, the tillering power, and the locality. 
Up to 6 bushels per acre are broadcasted. 

YIELD. The yield of grain per acre varies from 40 to 80 
bushels or more ; the straw weighs from 25 to 40 cwts. per acre. 

COMPOSITION. Oats have more * fibre ' than any of the other 
cereals, reaching on an average 10 per cent, of the grain. The 
soluble carbohydrates average 57 per cent. \ the fat-content is 
over 5 per cent, an amount much higher than any other cereal 
except maize. The albuminoids average about n per cent 

Ex. 259. Examine the spikelets of any common oat. Note the number of 
flowers in each, the form and extent of the empty and flowering glumes, and 
the form of the naked caryopsis. 

Which flowering glumes have awns? 

Ex. 260. Compare the inflorescences of Tartarian and Common Oats, and 
also the grains and flowering glumes of each. 

Ex. 261. Examine and compare the spikelet and grain of a wild oat with 
that of any of the cultivated forms. 



CHAPTER XXXVIII. 



CULTIVATED BARLEYS (Genus Hordeuni). 

i. Characters of the Genus. The inflorescences or * ears' are 
spike-like and consist of many groups of three single-flowered 
spikelets (Fig. 159) arranged from top to bottom of an elongated 
rachis. 

Each spikelet appears practically sessile on the rachis ; but 
a triplet of single-flowered spikelets really represents a primary 
branch with two opposite lateral 
branches each bearing one 
flower. The rachilla on which 
the spikelet grows laterally is 
prolonged and appears as a 
small bristle - like structure, 
readily seen with a lens, lying 
within the * furrow ' of a barley ( 
grain as in Fig. 163. 

The groups of spikelets are 
arranged alternately at notches 

j r ,1 i- FIG. 150. A Piece of rachis of six-rowed 

On Opposite Sides Ot the rachlS, barl( . y showing a triplet of single-flowered 

so that the whole ear appears to /flowering glume! fthe ear ' * empty fi ume ' 
have six longitudinal rows of shfiinga^Hpie^ 

the central flower fertile, the two lateral 
flowers (a) imperfect, r Rachis of the ear ; e 
e \f flowering glume ; a imper- 




The empty glumes (e, Fig. 
159) are very narrow and stand 
side by side in front of the flowering glume. The latter is 
broad and possesses a long awn which acts as a transpiring 
organ. The longest awns are usually attached to the largest 

606 



FOUR-ROWED BARLEY 507 

and best developed grains ; when the awn is cut off or destroyed 
the grain is long and thin when ripe. Usually the flowering 
glume is pale yellow, but in some varieties it is black or deep 
purple. 

The fruit or caryopsis in the commoner varieties of culti- 
vated barleys is adherent to the flowering glume and pale, and 
on being thrashed does not separate from the latter. 

Varieties termed naked barleys, however, exist, in which the 
caryopsis is free from the glumes and falls out of the ear as 
readily or more so than a grain of wheat. 

2. Cultivated Barley (Hordeum sativum Pers.). The cultivated 
forms of barley are all considered to belong to one species, 
which has been named Hordeum sativum ; this has probably 
been derived originally from a two-rowed species Hordeum 
spontaneum Koch., which is met with wild in Western 
Asia. 

The cultivated varieties fall into the three undermentioned 
races, which have sometimes been treated as distinct species : 

RACE I. Six-rowed Barley (Hordeum sativum hexastichon =- 
H. hexastickon L.) (A> Fig. 160). In the six-rowed barleys all the 
flowers of each triplet of spikelets on both sides of therachis are 
fertile and produce ripe fruits, hence the ear possesses six longi- 
tudinal rows of grain : moreover, the rows are arranged at equal 
distances from each other all round the rachis. 

This race has short erect ears, short straw, and coarse thin 
grain. It is hardy and gives a good yield, but is rarely met 
with, as the very poor quality of its grain debars it from being 
of any use to the farmer in this country. 

RACE II. Bere: Bigg: Four-rowed Barley (Hordeum sativum 
vulgar* = Hordeum vulgare L.) (J3, Fig. 160). In this race all the 
flowers of each triplet are fertile and the ear is possessed of six 
rows of grain as in the previous race ; the rows, however, are not 
arranged regularly at equal distances round the rachis. The 
central fruits of each triplet form two regular rows on opposite 



^:^^|Ty';f;^v|jf^ 




A B W 

FIG. 160. A, Six -rowed Barley (Hordtum htxatttchon. L,.). 

B, Here (Hordcutn vutg*rt L ). 

C. Himalayan Barley {H*rd*um tvifitrc+tutn Jacq.) 



FOUR-ROWED BARLEY 509 

sides of the rachis, but the lateral spikelets of each triplet which 
in the six-rowed race form four straight single regular rows, in 
this race form two irregular double rows, hence the whole ear 
appears irregularly four-rowed, especially in its upper part. 

Bere, of which there are one or two improved varieties, 
has erect ears about 2^ inches long, and usually contains from 
forty to fifty grains in each. The grains are thinner and longer 
than those of the two-rowed race, and the awns are stiff and 
adhere so firmly to the flowering glume that they are difficult 
to remove when thrashed. 

Bere is mostly grown in the northern parts of this country as 
a spring-sown crop, and used as food for stock and the pro- 
duction of whisky. Varieties of this and the six-rowed barleys 
are also sown in autumn to be fed off in spring as a green fodder 
crop. 

On account of its rapid growth and power of giving a moderately 
good crop on poor soils, bere is the most suitable cereal for 
the northern parts of Europe where the summers are of short 
duration ; in such localities it forms the chief bread-stuff. 

Formerly this race of barley was used in the preparation of 
malt and beer, and to a slight extent this is still the case ; the 
proteid-content of the grain is, however, frequently too high 
and the starch-content too low for the preparation of a good 
malt, and the two-rowed races on account of their superiority 
in these respects have now almost entirely superseded bere for 
malting purposes. Moreover, on good soil the yield of the two- 
rowed varieties is equal to, if not superior to, that of bere. 

To this race belong Naked Barley (Hordeum ccclestc L.) and 
Himalayan Barley (Hordeum trifurcatum Jacq. **H. ALgiceras 
Royle.) (C, Fig. 160). In both of these the caryopses are quite 
free from the glumes, and fall out as readily, or more so, than 
those of wheat. Himalayan barley is peculiar in having three- 
pronged awns which are shorter than the grain, and bend back 
in the form of small horns ; it is sometimes termed Nepal wheat, 



510 CULTIVATED BARLEYS 

the brown 'free caryopses somewhat resembling rather large 
pointed wheat grains. 

RACE III. Two-rowed Barley (Hordeum sativum distichon 
^Hordeum distichon L.) (Fig. 161). In the two-rowed race 
only the middle spikelet of each triplet is fertile, the lateral 
spikelets being barren (male-flowered); the ear, therefore, possesses 
only two longitudinal rows of grain. 

This race is the one most commonly grown in the British Isles 
and on the Continent, and comprises a considerable number 
of sub-races and varieties among which are the finest malting 
barleys. When not sufficiently good either in composition or 
colour to be used for malting, the grain is a valuable food for 
stock. 

Several fairly distinct sub-races of Two-rowed Barley are met 
with of which the following are the chief: 

SUB-RACE I. Peacock, Battledore, Sprat, or Fan Barley, 
formerly described as a species, viz., Hordeum Zeocriton L. The 
straw is stiff and the ears erect and short, about 2\ inches long, 
broad at the base and narrow at the tip (A, Fig. 161). Except 
the lower ones of the spike, the grains are thin and of poor 
quality, with long spreading awns. The whole ear has a fanci- 
ful resemblance to an outspread peacock's tail or fan, hence the 
name peacock, fan, and battledore barley applied to it. It is of 
little agricultural importance. 

SUB-RACE II. Broad Erect-eared Barleys (Hordeum distichon 
erectum). In this sub-race the ears are erect and broad, with 
plump grains closely packed on the rachis (2?, Fig. 161). The 
straw is stiff, and on this account barleys belonging to this sub- 
race are useful for growing on somewhat heavily-manured soils 
where the danger of ' lodging ' is great for the finer Chevallier 
variety. 

The grain, although of excellent form and size, usually pos- 
sesses a higher proteid-content than is suitable for the production 
of the best malt ; nevertheless in exhibitions of making-barley 



^\VStv. "'.'.!'-: : r|tf ; ev^ -::; -i 






LWw 

B-V^-S%^ , 'jt 

r^i.^vv 
f,^!*^: 

f\ i 1 1 - * '* 

;#&.,;.- 

i: - :1 

'rC '.' ' 't., tr ,', " v ,f1 

%- J '^V' T -V'i,l 
bjt j t ' 4,'i^-t tf t- ;.^ 

It 4 r ' ' 




ABC 

FlG. 161. Two-rowed Barleys. 

A , Sprat or Fan Barley {Hordeum ZeocritoH L.). 
2?, Broad erect-eared form (CioldthorpeX 
C, Narrow bent-eared form (Chevalhcry 



512 CULTIVATED BARLEYS 

varieties belonging to this division of the two-rowed race have 
not unfrequently taken very high places. 

Examples of varieties belonging to this sub-race are, Q-old- 
thorpe and Plumage. 

SUB-RACE III. Narrow Bent-eared Barleys (Hordeum dis- 
tichon nutans). In these barleys the ripe ears bend over on one 
side and hang down so as to become almost parallel with the stem. 

The ears are narrower and longer than those of the previous 
sub-race, the smaller width across the ear being due to the fact 
that the grains are placed farther apart on the rachis and jut out 
from the latter at a smaller angle than the grains on an erect- 
eared variety (C, Fig. 161). 

To this sub-race belongs the Ghevallier variety raised by the 
Rev. Dr Chevallier from a single ear selected by a labourer in the 
parish of Debenham, Suffolk, in 1819. 

Chevallier barley and the various selections from it are superior 
to all others for malting purposes ; they are, however, somewhat 
delicate and liable to lodge on highly-manured soils. 

Many other varieties included among nodding-eared barleys 
are met with, all of which produce useful malting samples when 
carefully managed : common representatives are Old Common, 
Nottingham long-ear and others with seedsmen's special names 
attached. The grains of these varieties are generally darker in colour 
than Chevallier barley, and possess thicker glumes and pericarp. 

Plumage-Archer and Sprat- Archer barleys, now widely grown 
in Great Britain, are hybrids between varieties belonging to sub- 
races II and III. They have stronger straw than Chevallier and 
therefore better adapted for growth on soils in high condition. 

3. Distinguishing features of barley grains belonging to dif- 
ferent races and sub-races. One of the essential conditions for 
the production of a good malting sample of barley is that the seed 
sown should be as far as possible of the same variety, so that the 
ripening of the crop and the composition of the grain should be 
uniform. As it is not difficult to distinguish the grains of the chief 
races and sub-races from each other, farmers should make a 



DISTINGUISHING FEATURES OF GRAINS 513 



point of becoming acquainted with their peculiarities, especially 
of those belonging to the erect-eared and bent-eared two-rowed 
barleys in order to be able to examine samples before purchasing 
for seed purposes. 

The following are the chief points of difference of the common 
races of barley : 

(i) The grains of the six-rowed race are elongated, not plump, 
with thick glumes ; generally a considerable portion of the base 
of the awn is visible on the flowering glume. 







Fio. 162. i. Base of grain of bent-eared two-rowed barleys (Chevallier, Old Common, &c.). 
3. Diagrammatic longitudinal section of i showing the sloping base. 3. Base of grain of erect- 
eared two-rowed barleys (Goldthorpe). 4. Diagrammatic longitudinal section of 3. 

The grains of bere are larger and plumper than those of the 
typical six-rowed sub-race, but in other respects the two are 
similar. 

In six-rowed barley and bere the two lateral grains of each 
triplet growing at a notch of the rachis are twisted, so that the 
two halves of each grain when viewed on the furrow-side are 
seen to be dissimilar in size and form ; the presence of these lop- 
sided grains in a sample is evidence of their origin. 

The middle grains of each triplet are symmetrical on both 



514 



CULTIVATED BARLEYS 



sides of the furrow line and very closely resemble the grains of 
the two-rowed races. 

(ii) The broad erect-eared barleys, such as Goldthorpe and 
Plumage, are easily recognised by the presence of a small deep 
transverse furrow across the base of the grain, below which is also 
a distinct rounded lump (4, Fig. 162). 

The rachilla lying in the longitudinal furrow at the back of the 
grain is short and usually bears a number of long thin straight 
hairs (3, Fig, 163) : in some varieties of this class, however, the 
rachilla is woolly, like i, Fig. 163. 




FIG. 163. A, Base of barley grain showing the portion of the rachilla a. landa. RacKilla 
of narrow btnt-eared barleys ; i ofChevallicr variety \* of Old Common, Nottingham long- 
eared, and many so-called ' Prolific variet es. 3. Rachilla of most broad erect-eared 
barleys, c.g Goldthorpe and Imperial varieties; some have rachilla like i. 

(iii) The narrow bent-eared barleys have neither transverse 
furrow nor lump at the base of the grain, but slope off as at 2, 
Fig. 162. Those belonging to the Chevallier stock have a rachilla 
which is covered with short wavy wool-like hairs (i, Fig. 163). 

The rachilla of the Old Common, Nottingham long-ear, and 
so-called ' Prolific ' but inferior malting barleys is longer and the 
straight hairs shorter than on the rachilla of the erect-eared 
barleys (2, Fig. 163). 

4. Characters of a good malting "barley. The following points 
are of importance in estimating the suitability of barleys for malt- 
ing purposes ; the features of greatest significance are only obtain- 



CHARACTERS OF GOOD MALTING BARLEY 5*5 

able by chemical analysis, but some of the external and readily 
observable characters mentioned below frequently indicate the 
value of samples. 

a. Composition. In the malting process the starch of the 
grain is changed into soluble compounds dextrin and maltose 
which are extracted by means of water and ultimately fermented. 
The amount of starch should therefore be high in order to obtain 
a rich extract ; the best samples contain from 62 to 64 per cent, 
of starch. 

The proteid-content of barley varies from 6 to over 17 per 
per cent. ; it should be as low as possible, as it is found that 
barleys with a high percentage of proteids give turbid worts, and 
the keeping quality of the beer prepared from them is reduced. 

In the best samples the proteids usually average not more than 
9 per cent. : medium samples contain 10^ or n per cent., while 
poor ones frequently contain 12 per cent. 

The amount of water in the grain is important, as it is found 
that the drier barleys germinate more quickly and evenly than 
the damper samples. Moreover those with a high water-content 
sooner lose their germinating capacity and are more liable to be 
injured and overrun by saprophytic fungi (moulds) than drier 
ones. The amount of water present in the grain depends upon 
the ripeness when cut, the method of harvesting, subsequent 
sweating in the stack, and upon other conditions. Good samples 
contain an average of 14 per cent. 

b. Germination Capacity and Germination Energy. The 
quicker the germination the more even the malt and the better 
the yield of extract. In good samples 96 per cent, of the grains 
germinate in seventy-two hours when kept at a temperature of 
1 8 to 2oC. ; if the percentage is as low as 85 in this time the 
sample should be rejected. 

c. Plumpness and Weight. The grains should be short and 
thick and of uniform shape, and the sample should be free from 
broken grains or those with injured skins. The bushel- weight of 



5l6 CULTIVATED BARLEYS 

good barleys is 56 Ibs. ; samples exhibited in the Brewers' 
Exhibition usually vary from 53 to 60 Ibs. One hundred grains 
should weigh between 4 and 5 grams ; in the erect-eared barleys 
the latter weight is sometimes exceeded. 

d. Mealiness. When cut across the grains should show a 
snow-white surface, but rarely do we find samples perfect in this 
respect, most of them containing a larger or smaller number 
of flinty grains. 

e. 'Skin.' The proportion of 'skin' or husk (glumes and 
pericarp) to the rest of the grain is subject to much variation ; 
in some cases the percentage of husk is as low as 8 per cent, while 
in others it is as high as 16. In thin-skinned samples the grains 
show a series of delicate transverse lines or puckers due to loss 
of water and slight shrinkage of the internal contents during 
ripening. Thick-skinned grains show no such lines. 

/. Colour. The sample should be pale yellow or a pale 
clean straw colour and uniform all over the grain. A stained 
or discoloured appearance is often associated with inferior and 
damaged samples ; grains, therefore, with brown bases, or which 
are grey or of dark tint are to be avoided. The brown tips of 
the grains are frequently caused by dark coloured fungi, but 
occasionally it is the natural tint of the barley, and may in such 
cases be no indication of inferiority of sample. 

Barleys exposed to heavy dews and rain are generally darker 
in colour than well-harvested crops. 

g. Smell. Samples which have been soaked with rain during 
stacking often give evidence of the injury by its musty smell. 

h. Freedom from broken or cut grains. Great care should be 
taken when thrashing malting-barley to have the machine 
properly set, so that the awns are not cut off too short nor 
the grains cut in two. Closely cut grains often have the 
embryo so damaged that the latter will not germinate, and cut 
grains are liable to become mouldy when damped and placed on 
the making-floor. 



CHARACTERS OF GOOD MALTING BARLEY 517 

SOIL AND CLIMATE. The northern parts of the country are 
usually too wet for the production of mealy grains, but in the 
eastern and south-eastern counties of England the best malting 
barleys of the world are grown. In hot, dry continental climates 
the grain is usually ' thin ' and flinty. 

Barley grows most satisfactorily upon light soils; sandy and 
calcareous loams free from excess of nitrogenous manures are 
best. 

SOWING. 'Seed* should be drilled as early as possible in 
February or March in order to gife the plant plenty of time 
for 4 assimilation ' previous to the building up of a well-nourished 
grain. 

In some favourable districts barley may be sown in January 
but the greater amount is sown in early March. 

The amount drilled is from 2 to 3 bushels per acre, the larger 
quantity being used on thin soils. 

YIELD. The average yield is 32 bushels per acre ; as much as 
60 bushels are occasionally obtained. 

COMPOSITION. Barley grains contain on an average 14 per 
cent of water, 66 per cent, of soluble carbohydrates, loj per 
cent, of proteids, and 5 per cent, of 'fibre/ 

Ex. 262. Examine an ear of six-rowed, four-rowed, and two-rowed barley 
respectively. 

Observe the arrangement of the spikelets on the rachis and the number 
and character of the flowers whether unisexual or bisexual in each. 

Ex. 263. Observe at intervals the growth of the caryopsis between the 
glumes of a barley floret from the time just after the ear emerges from the 
leaf-sheath up to the time when the grain is ripe. Is the caryopsis always 
united with the glumes ? 

Ex. 264. Cut off the awns from some ears of barley when very young and 
compare their growth with those of uninjvrred ears growing near them. 

Ex. 265. The student should examine and thoroughly master the details 01 
the grains of different races and sub-races of barley. 

Note the base of the grain, the rachilla, and also the lodicules of the 
flower which are easily dissected from soaked grains. 

35 



CHAPTER XXXIX. 



CULTIVATED RYE (Genus Secale). 

i. Characters of the Genus. The inflorescences or 'ears' are 
spike-like (Fig. 164), resembling those of wheat in 
general structure. The rachis bears two opposite 
rows of sessile spikelets. 

A single spikelet is placed at each notch of the 
rachis, and consists of three flowers, two of which 
generally produce grain, the third being in most 
cases rudimentary. 

The empty glumes are very narrow 
and the flowering glumes broad, keeled 
from the base, and terminated by a long 
awn ; the keel of the glume is fringed 
with stiff hairs. 

The caryopsis is free from the glumes, 
narrower and longer than a wheat grain, 
and usually of brownish-olive or greyish- , 
brown tint. 

2. Cultivated Rye. Only one species, 
namely, Common Eye (Secale cereale 

T\- i A j T L c Common Rye. 

L.), is cultivated. It appears to be of Empty glume; 
more recent origin than the other com- KiumeTrrachni 
mon cereals, and is considered to have oflhe ' ear/ 
arisen from Secale montanum Guss., a species met 
with wild in various elevated districts of southern 
FIG i6 4 . Ear' and eastern Europe and western Asia. 

of Rye (Secale _, . ,. rr 

cereakL). The latter species differs from common rye in 

618 




MIDSUMMER RYE 519 

being perennial instead of annual, and in the possession ol 
shorter ears and smaller grains. 

On the continent, especially in Germany, Russia, Norway, 
Sweden, and Denmark, rye forms the principal bread-corn, the 
flour of which is made into black-bread. In this country its use 
as a bread corn is very limited ; it is, however, extensively grown 
as green fodder for sheep and cows, for use in early spring and 
summer, and is also cut green for foiling' horses in the stable. 

When grown for corn the straw, which is longer than that of 
wheat, is practically useless for fodder, but on account of its stiff, 
tough character it is well adapted for thatching and litter. 

No well-marked races of rye are met with, and the number of 
constant varieties is small The latter are characterised only by 
differences in yield, tillering power, and hardiness, their morpho- 
logical peculiarities being so slight that they furnish no certain 
means of distinguishing one variety from another. 

The commonest and most useful varieties are those of hardy 
constitution, termed Winter Eyes ; in contrast with these are a 
few Summer Ryes, which are earlier, less productive, and sown 
in spring. 

One small-grained variety known as St John's Day or Mid- 
summer Rye, possesses extraordinary tillering power, and appears 
to be somewhat more nearly allied to the wild species Secale 
tnontanum Guss., than the ordinary forms. It is usually sown at 
the end of June or beginning of July, and may be fed off with 
sheep or cut green in the autumn and following spring, after 
which, if left, it will frequently give a good yield of grain. 

CLIMATE AND SOIL. Rye is one of the hardiest of cereals, 
and is capable of withstanding the severe frost of a continental 
winter. 

It grows well upon almost all light soils, but especially so upon 
such as are sandy ; stiff clays and damp soils rich in humus are 
unsuited to its requirements. 

SOWING. For corn production the winter rye is drilled at the 



520 CULTIVATED RYE 

rate of 2 to 3 bushels per acre, usually in September or October, 
as early as possible, as tillering goes on chiefly in autumn and 
not much in spring. 

Summer rye is sown generally in March and April. 

When sown for green spring food more seed is sown, usually 
from 3 to 4 bushels per acre. 

YIELD. The average yield is from 25 to 30 bushels of corn, 
and from 30 to 40 cwts. of straw per acre* 

COMPOSITION. Rye has practically the same composition as 
wheat. 

Ex. 266. Examine the various parts of an ear of rye, and compare them 
with those of an ear of wheat 



CHAPTER XL. 
CULTIVATED WHEATS (Genus Triticum). 

i. Characters of the Genus. The inflorescences or 'ears* are 
spike-like, with two rows of sessile spikelets placed singly at each 
notch of the rachis. 

The spikelets (Fig. 166) generally possess from two to five 
flowers, one or more of the upper ones are always abortive; 
usually not more than two or three are fertile and produce ripe 
fruits. 

The lower spikelets of the * ear ' are often sterile even in the 
best selected varieties. 

The empty glumes (Fig. 166, e) are broad, thus 
differing from rye, and usually have but a short 
awn or blunt apex ; the flowering glumes possess 
a long or short blunt awn. 

The fruit (caryopsis), which is free from the 
glumes, has a deep furrow on the back and a hairy 
tip ; the colour of the * grain ' may be white, yellow, 




let of common 2 ^ g 00( i w h e at grain should be plump, with a 

Wheat, t rnipty * * 

plume, /flower- smooth, thin, well-filled skin. For the purposes of 

mjj glume ; r ra- r r 

chi of the ' ear.' the baker it should be somewhat translucent or 
semi-glassy when cut across: samples containing many trans- 
lucent grains are known on the market as ' strong wheats/ those 
with soft floury endosperm being ' weak/ 

The grains in a sample should also be of uniform colour, size, 
and shape. 

For sowing the germination rapacity should not be less than 



522 CULTIVATED WHEATS 

98 per cent, and the weight of 100 grains not less than 4 grams. 
The grains should have a hairy tip and the embryo at its base 
should be prominently visible through the pericarp; if, on 
examination with a lens, the hairs at the tip appear few and 
much broken, the sample has most likely been subjected to 
rough treatment in order to give it an artificially bright ap- 
pearance. 

The pericarp of fresh good grain is bright ; in old seed it is 
dull; the sample should have neither musty smell nor bad 
taste. 

3. Cultivated Wheats. With the exception, perhaps, of 
Small Spelt and Emmer, none of the cultivated wheats 
have been met with in a wild state and their origin is 
unknown. 

Whether the hundreds of forms in cultivation are the product 
of a single species or of several is also not certain. 

The following are the chief races or species of cultivated 
wheats. (See Percival's Monograph on the Wheat Plant.) 

While typical examples of each species are readily distinguished, 
transition forms resulting from hybridisation or mutation make 
it impossible to define with precision the lines of demarcation 
between them. 

RACE I. One-grained Wheat or Small Spelt (Triticum 
monococcum L.). This race is of pale grass-green colour when 
unripe, and possesses a flat, short, compact ear at first sight 
resembling two-rowed barley (A, Fig. 167). The spikelets have 
two flowers, one of which is abortive; the other produces a single 
ripe grain. The flowering glume of the fertile flower bears a 
long awn and the straw is stiff and almost solid. 

The grain is free from the glumes but does not fall out 
when the ear is thrashed; the rachis of the ear is brittle, 
and behaves on thrashing as Emmer and Spelt mentioned 
below. 

One-grained wheat is sometimes cultivated on poor soils in the 







r: " :1 ,, 1T t 
^r:^ 



A B C D 

FIG. 167. X, Small Spelt (Triticu** ntonococcum L.). 

^5, Emmer (Triticttm amyifttm Ser. = 7\ dicoccup* Schub.) 
C, Common Spelt or Dinkel (Triticum Sftlta L.)., Bearded. 
A Common Spelt or Diokel (Triticum b+tlt* L.), Beardless. 



524 CULTIVATED WHEATS 

mountainous districts of Spain, Switzerland, and Eastern Europe, 
but is of little practical importance. 

The yield is from 35 to 35 bushels of spelt grain per 
acre. 

Small Spelt has doubtless been derived from Triticum agilo- 
poidcs Bal., a wild species of grass common in the Balkans and 
Asia Minor. 

RACE II. Emmer (T. dicoccum Schub.). This race possesses 
ears narrow across the face, with the spikelets somewhat 
closely packed on the rachis (B, Fig. 167) ; each spikelet 
ripens only two grains, and the flowering glumes always have 
long awns. 

Two-grained spelt is grown in Abyssinia, India, and certain 
parts of southern Europe, where it is sown in spring ; its grain 
is utilised chiefly for bread and as food for horses. 

In this race the grain is free, but so closely invested by 
the firm glumes that it does not fall out when the ear is 
thrashed. The rachis of the ear is very brittle, and when 
thrashed breaks up at each notch where the spikelets are 
inserted; the produce after thrashing, therefore, consists of 
more or less complete spikelets, to which are attached short 
pieces of the rachis. 

Emmer has probably been derived from Triticum dicoccoides 
Koern, a wild species met with in Syria, Palestine, and western 
Persia, 

RACE III. Macaroni, Hard or Flint Wheat (Triticum durum 
Desf.) (Fig. 1 68, A.). This name is applied to a large number 
of spring-sown wheats chiefly cultivated in the Mediterranean 
regions and Asia Minor. All the varieties have hard, flinty, 
somewhat pointed grains and flattish, empty glumes sharply 
keeled to the base ; the flowering glume always has a long awn, 
and the straw is stiff, generally solid or filled with pith. The 
grain is very rich in gluten, and utilised extensively for making 
macaroni. 



RIVET, CONE OR TURGID WHEAT 525 

RACE IV. Polish Wheat (Triticum Polonicum L.) (C, Fig. 
1 68). This race has long ears of glaucous tint when unripe, 
and is readily distinguished from all others by its empty glumes, 
which are often an inch long and enclose all the flowers in the 
spikelet. 

In straw, leaf and grain it exhibits close relationship to 
Macaroni wheats, and is probably a monstrous form of Race 
III. 

The flowering glumes are awned and each spikelet contains 
four flowers, only two of which are usually fertile. 

The c grain ' is f of an inch long and narrow, of reddish 
colour, flinty, hard and transparent. 

The straw is almost solid. 

It is chiefly grown in Spain and Italy. 

The yield is too small and the plant too tender for cultivation 
in this country. 

RACE V. Rivet, Cone or Turgid Wheat (Triticum turgidum 
L.) (Fig. 1 68, ). The Rivet or Cone wheats on the Continent 
are frequently termed ' English Wheats/ although in England 
they are not very much grown. 

The ears are large and four-sided with the spikelets 
closely packed on the rachis, and the straw yery tall, stiff, 
often solid in the upper internodes, and not irt all liable to 
lodge. 

The empty glumes are somewhat short, inflated and keeled, 
and the flowering glume possesses a long awn which often falls 
off when the grain is ripe. 

The Rivet wheats, of which the author's 'Blue Cone' is a 
well-known form, are very late in ripening and only suited to 
warm soils in the south of England, where they give very large 
yields of grain and long rigid straw of little use except for litter 
and thatching purposes. 

The grain is short and plump, with a blunt, flattish apex 
and a characteristic 'hump' on the dorsal side. It is 




A B C 

FIG. 168. A, Macaroni Wheat (Triticutn durum Dcsf.). 

B, Rivet Wheat, Blue Cone form (Triticunt turgmum L.). 

C, Polish Wheat ( Triticum Jolonicum L.). 



COMMON WHEAT 527 

exceptionally rich in starch and poor in gluten ; the flour is 
somewhat dark-coloured and unsuitable for bread-baking ex- 
cept when mixed with that from more glutinous varieties of 
wheats. 

RACE VI. Common Bread Wheat (Triticum vulgare Host.). 
To the race of common wheat belong all the most important 
varieties in cultivation in the great wheat-growing districts of 
Europe, Australia, and America. 

The common wheats have empty glumes, keeled only in the 
upper half. 

Several hundreds of varieties are recorded. Some of the chief 
forms grown in this country are mentioned below. 

By farmers they are ordinarily grouped, according to the colour 
of the grain, into red and white wheats. 

Those wheats with white grains require good soils and a dry 
warm climate. Such grain often yields flour of good quality, but 
the plants are more tender and not so productive as the red- 
grained varieties. The latter stand wet winters better than the 
white kinds, and are often grown on somewhat inferior wheat 
soils. 

The presence or absence of awns on the flowering glumes 
is the most permanent feature of varieties of wheats. The latter 
are, therefore, usually placed in two groups, namely, (i) awnless 
or beardless, and (2) awned or bearded varieties. The groups 
are then subdivided according to the colour of the glumes 
white or red and again according to the smoothness or hairiness 
of the glumes. 

These may be separated again into types with (i) lax (A and 
B, Fig. 169), (2) denser (C, Fig. 169), and (3) compact ears 
(Z>, Fig. 169) respectively, and a final division made according 
to the colour of the grain. 

It is impossible here to mention more than a very few of the 
varieties in cultivation, and new ones, or so-called new ones, are 
being raised annually. A detailed description, with illustrations 



528 CULTIVATED WHEATS 

of all those met with in this country at the present time is given 
in the author's " Wheat in Great Britain " ; a few of the varieties 
widely grown are mentioned below. 



SECTION I. Beardless varieties. 

a. Glumes white, smooth ; grain white. 

(1) Wilhelmina. A somewhat variable sort of winter wheat 
with short, dense ears, and plump, white grain of fair quality. 
A prolific Dutch wheat selected from a cross. 

(2) Victor. A hybrid variety raised by Messrs Carton. It 
is a prolific winter wheat, resembling Wilhelmina in some of its 
characters. 

(3) Starling II. A selection raised by the author from a mixed 
stock of Wilhelmina. A high-yielding variety giving fine plump 
grain of good milling quality. 

Million III and Imperial are varieties also belonging to this 
group. 

b. Glumes white, smooth ; grain red. 

Varieties included in this group are among the most widely 
cultivated Bread Wheats. 

(;) Bed Marvel, or Japhet. An early sort of wheat originally 
produced in France. The straw is somewhat tall and slender, 
with long, lax ears. It gives good yields even when sown in 
February or early March. 

(2) Yeoman. A hybrid winter wheat raised by Sir Rowland 
Biffen. It has strong straw, ears of medium density, and grain 



1 ' r v v ''r!V" Li "y%i, 1 ^' tj ' i' 1 '.! 1 ^ V ''^Ji- " '^'V'^^Vstf'iiift'.'A^* 11 Lili v-'r ir ''V' 

i' h ' ''''ik V",l/ ," ' , r ' '- '' , f- ' n ,, ' r rj 4 ' ,^'lnrTOffa;,,, ,;[!' '-iv' i-'< 




A tS *-> ^ 

FIG. 169. A, B t C k Beardless Bread Wheats (Trilicum vulture Host.). 
<4, Lax-eared form. 

B, Dense -eared form. 

C, ' Squarehead ' form. 

O. Beardless Club or Dwaif Wheat (Triticum compactwn Host.). 



$30 CULTIVATED WHEATS 

of high milling quality. Highly productive on soils in good 
condition. 

(3) Squarehead. An old variety which first came into pro- 
minence about 1870, The name is now given to a number of 
winter wheats with short, dense ears and stout straw. All are 
prolific varieties, with red grain of fair quality. On account of 
weak tillering power they should be sown rather thickly. 

Many wheats with new names are selections of the old Square- 
head variety. 

c. Glumes red, smooth ; grain red. 

^i) Little Joss. A hybrid wheat, somewhat variable in colour 
of chaff and form of ear, raised by Sir Rowland Biffen. It is an 
early sort, which can be sown in autumn or spring up to the end 
of February or first week of March. Straw long, with moderately 
long, lax ears containing plump grain of fair quality. 

(2) Squareheads Master. This is the variety most widely 
cultivated in Great Britain at the present time. It is an old 
winter wheat which first appeared about 1888-90. The straw 
is stout of medium length, with dense well-filled ears containing 
brownish red grain of fair milling quality. It is a high yielding 
sort which grows well on a variety of soils. 

Bed Standard or Standard Red are names given to a variety 
of wheat which closely resembles Squareheads Master, and is 
possibly a selection of the latter. 

SECTION II. Bearded varieties. In these the flowering 
glumes have long awns as in Fig. 170. Some of them are hardy, 
but most are tender wheats only suitable for spring sowing, and 
not much grown in England. 




Flo. 170. Bearded Common Bread Wheat (Triticwn vulgare Host.). 

A, Lax-eared form. 

B. Dense-eared form. 



532 CULTIVATED WHEATS 

They are usually grouped similarly to the beardless varieties 
mentioned above. 



April Bearded. A rapid-growing variety, capable of ripening 
grain even when sown as late as April or first week of May in 
certain favourable localities. It has long, lax ears of reddish 
colour. The spikelets often contain four grains, which are light 
red and of fair quality. 

This variety is apparently a slightly improved form of the Old 
Fern Wheat. 

In all spring sown varieties the yield is inferior to those sown 
in autumn. 

CLIMATE AND SOIL. For its full development wheat requires 
a warm, somewhat dry, climate. 

In hilly districts the plants are small and the yield scanty, 
while in wet localities the straw is abundant, but the grain poor 
in amount and quality also. 

Varieties are met with capable of giving good yields upon 
almost all soils except those of the lightest class, and stiff, wet 
clays; the soils, however, best suited to growth of the most 
valuable wheats are stiff clay loams. 

SOWING. Winter wheats are sown in autumn, from September 
to December, in this country most frequently in October; 
the spring varieties from January to March, most usually in 
February. 

The seed is drilled in rows from 7 to 10 inches apart, the 
amount used varying from i to 3 bushels per acre. 

YIELD. The average yield in this country is about 2#| 
bushels, but 60 bushels or more per acre are sometimes 
obtained; a yield of 40 bushels is usually considered a good 
crop. 



DINKEL OR LARGE SPELT WHEATS 533 

CoMPOsmoN.~-.The composition of the wheat grain varies 
much with the climate, soil, manuring, and variety of the plant. 
The ' soluble carbohydrates/ mainly starch, average about 66J 
per cent. ; the albuminoids, nj ; the ' fibre/ 3 ; the fat, ij ; the 
water-content usually about 14 per cent. 

The albuminoids in some grains are as low as 8 per cent., 
while in others they may be as high as 24 per cent. ; the flinty 
grains are usually richer in this class of substances than the 
mealy ones of the same variety of wheat. 



RACE VII. Club, Cluster or Dwarf Wheat (Triticum com- 
pactum Host.) (Fig. 169, D). The Club wheats usually have 
short, stiff straw and exceedingly dense short ears which are rarely 
over two inches long ; the empty glumes are keeled in the upper 
half and rounded in the lower half. 

They are chiefly grown in parts of Germany, Switzerland, 
Chili, Turkestan, and the Pacific coastal regions of the 
United States. The awned forms are known as ' Hedgehog 
Wheats/ 

The grains of all the varieties are small and plump and yield 
flour of moderate quality only. 

The Club wheats are closely related to the Common Bread 
wheats (T. vulgare). 



RACE VIII. Dinkel or Large Spelt Wheats (Triticum Spelta 
L.). The varieties of this race have ears with spikelets placed 
rather widely apart (C and D, Fig. 167) ; the glumes may be 
white, red, or other colours, smooth or velvety, and in some 
varieties the flowering glumes are awned, while in others they 
are without awns. 

The ears possess a brittle rachis which breaks like those of 
Emmer and Small Spelt when thrashed. Each spikelet ripens 

36 



534 CULTIVATED WHEATS 

two or three narrow, elongated grains, wliich are triangular in 
section. 

This race of wheat is cultivated on poor soils in Switzerland, 
S. Germany, and Spain. The yield is from 35 to 50 bushels 
spelt grain per acre. 

Ex. 267. Examine the spikelcts of a ripe ear of common wheat, and note 
the number of flowers which have produced well-formed grains, and the 
number of abortive flowers. 

Ex. 268. If possible obtain specimens of the various species, races, and 
varieties of wheat. Note the shape and colour of the caryopsis, the presence 
or absence of an awn and keel on the empty and flowering glumes, and 
the stiffness, solidity, or hollowness of the internodes of the straw of 
each. 

Ex. 269. The student should also make a point of examining the general 
form of the ears of different common-named varieties of wheat. Measure 
how many spikelets are arranged on 2 inches of rachis in each ear. Note 
also the colour of the chaff and grain in each. 



RECOGNITION OF YOUNG CEREALS BY THEIR LEAVES. 

(Examine with a good lens.) 

A. Young leaf-sheaths without hairs. 

(1) Barley. Base of leaf-blade with two large clasping claw-like 

projections as in Fig. 189. 

The leaf- blades are very broad with eighteen to twenty-four veins, 
and rolled to the right. 

(2) Oat. Base of leaf-blade without projections as in Fig. 190. 

The leaf-blades are not so broad as those of barley and are a darker 
green colour ; they are generally rolled to the left and have eleven 
to thirteen veins. 

B. Young leaf-sheaths hairy. 

(3) Wheat, Young leaf- sheath densely covered with short hairs. The 

leaf-blades have claw-like projections intermediate in size be- 
tween those of barley and rye ; they are rolled to the right and 
have eleven to thirteen veins. 

Close to the claw-like projections at the base of the blade are a few 
long bristly hairs. 



YOUNG CEREALS . 535 

(4) Bye. Young leaf-sheaths covered with short hairs among which 
are a number of sparsely-scattered long ones easily perceived 
with the naked eye. 

The first leaf-sheath which comes above ground is a purplish-red 
colour ; the blade is rolled to the right and has eleven to thirteen 
veins. The claw-like projections are smaller than those of wheat 
and the accompanying bristly hairs are shorter and fewer in 
number. 



CHAPTER XLI. 



COMMON GRASSES OF THE FARM. 

i . THE Order of Grasses includes a total of over 3000 species, 
of which about 130 or 140 are represented in the British 
Flora. Many of the species indigenous to this 
country are comparatively rare and without any 
practical importance to the farmer. The chief 
grasses, however, which are met with in most of 
the best pastures and meadows are described 
below, and a brief mention is also made of those 
which require attention on account of their dele- 
terious nature as weeds or because of their general 
distribution. 

Genus Anthoxanthum. 
Panicle spike-like ; spikelets one-flowered, flowers 
protogynous ; four empty glumes, two lowest un- 
equal, smooth, the upper covered with chestnut or 
dark brown hairs ; one of them also bears a long, 
bent, twisted dorsal awn, the other a shorter, 
straight awn; flowering glume, awnless, very 
small, smooth; stamens only two. 

FIG. 171. Sweet Vernal-Grass (Anthoxanthum odoratum 

P aricif P of c sweet L.). A fibrous-rooted perennial, growing about a 
uiTTb? 1 *?! B? foot high, and usually present in pastures and 
Hguie af c^kSl meadows upon all kinds of soils. It is one of the 
(twice natural size). ear ij est g rasse s, often commencing to grow rapidly 
in February and March, reaching the flowering stage before the 

638 




MEADOW FOXTAIL 



537 



end of April. The leaves are hairy, broad and flat, somewhat 
rapidly tapering to a fine long point. The whole plant, especially 
when dry, emits a fragrant characteristic perfume, due to a small 
amount of coumarin in it ; this pleasant odour it imparts to hay, 
in which it is present, and on this account is frequently but 
erroneously considered a useful pasture grass. We consider the 
inclusion of this grass in mixtures as a serious mistake from 
the farmer's point of view, and would strongly recommend the 
agriculturist to completely discontinue its use. The yield is in- 
significant, and it is refused by almost all kinds of stock when 
anything better is to be obtained: moreover, 
the price of the seed is always high, and specially 
liable to be inferior in quality and purity. Its 
place, so far as earliness is concerned, can pro- 
fitably be taken on most soils by the far superior 
grass, foxtail. 

Fuels Vernal-Grass (A. aristatum Boiss. = 
A. Puelii Lee. et Lam.) resembles the former 
species but its panicle is not so dense and the 
stems and leaves more slender and narrower. It 
is moreover an annual, and has but a faint odour. 
It is a useless weed introduced by * seeds ' used 
for the adulteration of those of sweet vernal-grass 
(see p. 673). 

Genus Alopecurus. 

Panicles cylindrical and spike-like, spikelets 
one-flowered, compressed, flower protogynous; 
empty glumes without awns, fringed with hairs 
on the keel and generally more or less united at 
their bases ; flowering glume with a bent dorsal 
awn, no pale present. 

Meadow Foxtail (Alopccurus pratensis L.). 
A slightly creeping perennial grass growing best upon damp 
and stiffish soils. When sown on dry soils soon dies out. It is 




an '% U pjUt 



(twice 



538 COMMON GRASSES OF THE FARM 

one of the best permanent meadow and pasture grasses and 
characterised by early and abundant growth. Although it grows 
well after being cut, it is best suited for grazing land as its 
flowers are shed and its leaves often withered before the time 
for cutting grass for hay. 

For leys of less than ihree years' duration it cannot be recom- 
mended as it is of slow maturation and does not produce its full 
yield before the third or fourth year after sowing the seed. 

The empty glumes are united about J or J of their length. 

Slender Foxtail: Black-Grass (A. myosuroides Huds. =A. 
agrcstis L.). An annual resembling the last but distinguished 
from it by its longer, more slender, tapering panicles, rougher 
stems and its empty glumes, which are united about half their 
length. The empty glumes are not so hairy and feel harsher 
than those of meadow foxtail, and the flowers are not produced 
and ripened till late in summer and autumn. It is a troublesome 
pest on arable ground and is also present in small quantity in 
pastures and meadows and by waysides in the south of England. 
Stock refuse it. 

Floating Foxtail (A. genieulatus L.) is another useless species 
of this genus common in wet places and near the edges of pools 
in damp meadows. Its panicle is i to 2 inches long, slender and 
cylindrical, and the stem decumbent and bent at the nodes. 
Genus Phleum. 

Panicles cylindrical and spike-like : spikelets one-flowered, com- 
pressed : empty glumes with short stiff point or awn : flowering 
glume membranous, smooth, and awnless. 

Timothy : Catstail (1'hleum pratcnse L.). A perennial 
growing generally in tufts and often mistaken for meadow foxtail. 
Apart from differences in structure it is, however, a much later 
grass, and rarely flowers until the spikelets of foxtail begin to fall 
from the rachis. Timothy is among the most useful grasses and 
can be sown alone or in mixture for leys and permanent pasture. 
It is one of the best grasses for heavy clays and produces a large 



MARRAM-GRASS I MAT-GRASS 



539 



bulk of especially heavy hay of high nutritive value. On thin 
dry soils, the lower nodes of its stems became thickened and the 
whole plant is then of little value. 

As it grows hard and fibrous when allowed 
to ripen its seed it should be cut before the 
spikes are out of the leaf-sheaths. Unlike 
foxtail it yields little aftermath. As the seed 
is especially cheap and the yield and nutritive 
value good, it should form a constituent of all 
leys on land which is at all stiff. 

Genus Ammophila (Psamma\ 

Panicles spike-like, spikelets large, one-flow- 
ered, compressed : empty glumes two, narrow, 
awnless, equal to or just exceeding the flower- 
ing glume in length ; flowering glume with 
silky hairs at the base and a very short awn. 

Marram-Grass : Mat-Grass (Ammophila 
arundinacea Host. = Psamma artnaria R. 
& S.). A perennial grass which grows on dry 
sandy sea-shores. Its stems and leaves are 
strong, rigid, and somewhat glaucous, the 
former from 2 to 3 feet high ; panicles gener- 
ally 3 to 4 inches long, cylindrical. 

7 T b . 

It possesses an extensive system of rhizomes 
which spread through loose sands in all directions, and bind them 
into more or less solid banks capable of resisting the action of the 
waves. By its action the sea is prevented from encroaching upon 
the land, and for this service it is specially protected by Act of 
Parliament. 

Genus Agrostis. 

Panicle spreading ; spikelets one-flowered, very small ; empty 
glumes two, unequal, larger than the flowering glume, awnless ; 
flowering glume either awnless, or with a slender dorsal awn. 

An extensive genus ; most of the species belonging to it are 
of little value to the British farmer. 




. 11 , . 

Spikelct (twice nat- 

sue). 



540 COMMON GRASSES OF THE FARM 



Florin : Marsh Bent-Grass : Red Top (Agrostis alba L.). A 
perennial, from 6 inches to 2 feet high, with short, flat, rough 

leaves; it is very variable in appear- 
ance and habit and met with upon 
almost all soils. On drier arable 
lands it is as troublesome a pest 
as true 'couch,' with which it is 
often contused, and in poor, damp 
pastures it often abounds 

Red Top is one of the most im- 
portant perennial pasture grasses 
of the United States, but it is not 
found on the best pastures and 
meadows in this country. 

A variety with trailing stems and 
B stolons, which take root at the 
nodes, is the plant generally re- 
ferred to as Fiorin, and named 
Agrostis stoloniftra Koch. On re- 
claimed bogland, wet meadows, 
near river banks, and on moist soils 
generally, this variety grows luxuri- 
antly and crowds out almost all 
other competitors. A special 
feature of this grass is its late 
autumn growth and power of 
remaining green until the following spring. 

Fine Bent-Grass : Purple Bent : Black Couch (A. vulgaris 
With.=^. ienuis Sibth.). A perennial very similar to the preced- 
ing species. It is equally useless except for lawns, for which it is 
adapted, as it stands mowing and treading well. Purple bent fre- 
quently has purple and reddish stems and leaf-sheaths. It usually 
has a short blunt ligule, and the panicle is open when the fruit is 
ripe, while Fiorin possesses a long acute ligule, and the branches 
of the panicle close up to the main axis when the fruit is ripe, 




FIG. 174. A, Panicle of Fiorin or 
Marsh Bent-Grass (natural size). 
B, Spikelet (twice natural size). 



CREEPING SOFT-GRASS 



541 



This species is known as Rhode Island Bent in the United 
States, although this name is sometimes given erroneously to 
A. canina (see below). 

Brown Bent-Grass (A. canina L.) is another common species 
which grows upon wet peaty ground. It has fine, smooth, 
narrow leaves, and the flowering glume differs from that of the 
other species mentioned in having a long slender dorsal awn. 

Genus Holcus. 

Panicle spreading; spikelets two-flowered, upper one male, 
with awned flowering glume, 
lower one bisexual, with awnless 
flowering glume; empty glumes 
keeled. 

Yorkshire Fog: Woolly Soft- 
Grass (Holcus lanatus L.). An 
extremely common grass about 
a foot or 1 8 inches high, with soft 
woolly hairs on its leaf-sheaths, 
blades, and spikelets. It has a 
tufted habit; the awn of the 
flowering glume of the male 
flower is bentlikeafishhook, and 
scarcely visible above the empty 
glumes when the seed is ripe. 

Creeping Soft - Grass (//. 
mollis L.) is similar in general 
appearance, but more locally 
distributed in the country than 
the preceding species. In some 
districts it is common, especially on sandy soils and by the side 
of shady woods and hedges. It differs from the above by having 
somewhat extensive rhizomes, and the awn of the flowering glume 
of the male flower is nearly straight 




B 



FIG. 175.^, Panicle of Yorkshire Fog (na- 
, Spfkelet (twice natural sire). 



542 COMMON GRASSES OF THE FARM 



Almost all hairy grasses are refused by stock, and both these 
species are no exceptions to the rule. They produce a 
large amount of ' seed ' and often rapidly overrun leys. 
In Holland and the eastern counties of England on 
damp, somewhat marshy land Yorkshire fog is less 
hairy than on drier soils, and is eaten freely by stock : 
under these conditions the grass is more palatable, and 
animals thrive upon it. 

Genus Arrhenatkerum. 
Panicle spreading : spikelets two-flower- 
ed, the lower flower male, with a flowering 
glume possessing a strong bent, twisted 
basal awn ; the upper flower is bisexual, with 
a short dorsal awn on its flowering glume. 

Tall Oat -Grass: French Rye -Grass 
(Arrhenatherum avenaceum Beauv. : some- 
times named Avena elatior L.). A fibrous- 
rooted perennial grass, growing usually 
about 3 feet high, and especially common 
B in hedges upon light soils. Its spiketets par- 
tially resemble those of a small common oat. 

Though not always placed in the first class of 
fodder grasses, it yields a large bulk of fairly nutritive 
produce on marly soils, and begins to grow early in 
spring. It stands cutting well, and in some districts 
will give two good crops of hay in one season. 

The plant has a bitter taste, and when grown alone 
stock seem to dislike it at first. 

It rapidly attains maturity, often producing a fair 
crop the same season as it is sown, but does not last 
more than three or four years. 

It is sometimes utilised instead of Italian rye-grass 
in leys of longer duration than one year. 

> A 'bulbous-rooted' variety, in which the 
r"n* lower nodes are greatly thickened, is common 
natural size), in some localities, and is sometimes known as 
< Onion couch.' 




(twice 



'HASSOCK' GRASS 



543 



This variety when established on arable land is a troublesome 
pest, only satisfactorily eradicated by hand picking. 

Genus Deschampsia (Aira). 

Panicle spreading; spikelets with two flowers and a rudimen 
tary third; empty glumes keeled, unequal, blunt; flowering 
glume with a dorsal or nearly basal awn. 

Wavy Hair-Grass (Deschampsia flexuosa Trin. ^Airaflexuosa 
L.). A perennial grass, growing about 12 to 1 8 inches high, with 
very narrow, almost solid, 
leaves : common on dry 
sandy heaths and pastures. 

The branches of the 
rachis are often wavy or 
flexuous, hence the name. 

The spikelets are pur- 
plish or brownish green in 
colour, and have a shining 
silky appearance. 

This grass is of no agri- 
cultural value, but its * seeds ' 
are sometimes substituted 
for those of golden oat- 
grass or used in adulterat- 
ing the latter (see p. 677). 

Tufted Hair-Grass : * Tus- 
sock ' Grass ; * Hassock ' 
Grass (D. caspitosa Beauv. 

= Aira Caspitosa L.). A FIG. 177 A t Panicle of Wavy Hair-Grass 

* ' (natural size). 

perennial resembling the ** Spikeiet (twice natural size), 
previous species in colour of spikelets and several other par- 
ticulars. Its leaves are, however, flat, and of leathery texture ; 
the awn of the flowering glume is shorter than that of the preced- 
ing species, and scarcely exceeds the length of the empty glumes. 




B 



544 COMMON GRASSES OF THE FARM 

It grows in dense tufts, popularly termed ' hassocks ' or ' tus- 
socks/ which appear to be raised slightly above the level of the 
ground. The most luxuriant development is seen when tufted hair- 
grass grows in wet meadows and woods, but its unsightly tufts of 
coarse, useless herbage are common on drier meadows and pastures. 




B 



FIG. 178.^, Panicle of Golden Oat-Grass (natural size). B, Spikelet (twice natural size). 

Genus Trisetum. 

Panicle spreading ; spikelets two- or three-flowered ; empty 
glumes unequal and keeled ; flowering glumes with a somewhat 



BRISTLE-POINTED OAT 545 

hairy base, two awn-like tips, and a long, bent, twisted dorsal 
awn. 

Yellow or Golden Oat-Grass ( Trisctum flavescens Beauv. * 
Avena flavescens L.). A somewhat creeping perennial 
grass, which grows from i to 2 feet high; met with upon 
almost all soils, but especially prevalent on those of 
calcareous nature. The spikelets are shining and of yellowish 
colour. 

It is a useful grass, and is liked by all kinds of stock, but the 
yield is somewhat small. 

The 'seed' is high in price, usually of poor germinating 
capacity, and occasionally adulterated with worthless wavy hair- 
grass (see p. 677). 

Genus Avena. 

Panicle spreading ; spikelets with two or more flowers ; empty 
glumes, thin, membranous, equalling or exceeding the flower- 
ing glumes in length ; flowering glumes stouter, rounded on the 
back, with a long, bent, twisted dorsal awn. 

Cultivated Oat (Avena sativa L.). (See p. 500.) 

Wild Oat (Avena fatua L.). An annual with a large spreading 
panicle, probably the origin of the cultivated oat, but differing 
from it in the possession of a tuft of reddish yellow hairs at the 
base of the flowering glumes (Fig. 155). 

It is a troublesome weed among corn crops when once 
established. 

Bristle-Pointed Oat (Avena strigosa Schreb.) is an annual 
much resembling the common cultivated oat, but with smaller 
spikelets. It is distinguished from the latter by its flowering 
glume being divided, and the tips of the two parts prolonged 
into awn-like points or bristles; between these lies the 
dorsal awn, the whole glume appearing to possess three 
awns. 



546 COMMON GRASSES OF THE FARM 

It is met with among corn crops, but is rarer than the wild oat. 
Two species of Avena, namely, Narrow-leaved Oat-Grass 
(Avena pratensis L.) and Downy Oat-Grass (Avena pubescens 
Huds.), are perennial grasses growing from i to 2 feet high, and 
common in dry pastures, the former especially on calcareous 
soils. Neither of them, however, is of any agricultural value, 
their produce being small and generally passed over by stock. 

Genus Cynosurus. 

Panicles spike-like, dense, one-sided : spikelets of two forms, 
one completely sterile consisting of several 
bristle-like empty glumes arranged alter- 
nately on opposite sides of a short rachilla, 
the other fertile with three to five flowers ; 
flowering glumes of the latter leathery, 
three-nerved, with a stiff rigid point. 

Crested Dogstail (Cynosurus cristatus 
L.). A perennial grass abundant in mea- 
dows and pastures throughout the country, 
perhaps especially so on the drier upland 
sheep walks. We have, however, seen it in a 
few damp meadows in exceptional quantity. 
After flowering the stems become tough 
and wiry : it is therefore not very well 
adapted for mowing, but is one of the best 
pasture grasses. The short and abundant 
leaves, when fresh and young, are very 
nutritious and greedily eaten by all kinds 
of stock. 

The formation of the objectionable and 
FIG. i 7 a.A, Spike -like unsightly wiry flowering stems can be 

panicle of Crested Dogstail j t j- 11 r 

(natural size). avoided by judicious early depasturing of 

Bwe of leaf-blade and 




feie%!keiet c (SS^lrS It is not very early, and only begins to 
natural sue). gj ye j^ g f u u yield two or three years after 



COCKSFOOT I ORCHARD-GRASS 



547 



sowing, so cannot profitably be used in short leys. It should, 
however, be included in all mixtures for permanent pastures and in- 
cluded in leys of five or six years' duration. It is a good lawn grass. 

Genus Dactylis. 

Panicle of dense clusters of spikelets all arranged on one side: 
spikelets with three to five flowers : empty glumes with a short 
rigid point, keeled ; flowering glume keeled, with a short almost 
terminal >tiff rough awn. 

Cocksfoot : Orchard-Grass (Dactylis glomerata L.). One 
of the commonest of all grasses 
perennial, with a strongly - tufted 
habit of growth. Its leaf-sheaths 
are flattened and blades large and 
flat. It is met with upon all soils, 
and ranks in the first class of forage 
grasses on account of its heavy 
yielding power, high nutritive quality, 
and power of rapid growth after 
being cut. Cocksfoot is one of the 
first grasses to spring up after a field 
is mown. It is, however, not well 
adapted for meadows for hay as its 
unsightly tufts become coarse and 
woody if allowed to grow until the 
remainder of the grasses are ready 
to cut. 

Pastures in which Cocksfoot is 
abundant should be kept well grazed. 
It is slow to mature, and should not 
be used for leys of shorter dura- 
tion than three or four years ; but 
in mixtures for longer leys and per- * 
manent pasture it should always be 
included in moderate amount. 




- B A 

FIG. 1 80.^, Panicle of Cocksfoot 



. and ii ?u ie. 
c > Splkclet (twicc natural S12C) - 



548 COMMON GRASSES OF THE FARM 

Genus Poo. 

Panicles spreading; spikelets compressed, with two to six 
flowers ; rachilla often * webbed ' or clothed with woolly tangled 
hairs ; empty glumes shorter than the flowering glumes ; flower- 
ing glume keeled the whole length, awnless. 

Annual Meadow-Grass (Poa annua L.). A very common grass 
on all soils, and especially noticeable when on waste ground. It is 
annual, and met with in flower during almost every month in the 
year. The rachilla is not webbed. Stems about 6 to 1 2 inches 
long often lying close to the ground. It possesses little 
agricultural value, although stock eat the early growth with 
avidity. 

Smooth-stalked Meadow-Grass : Kentucky Blue-Grass (Poa 
pratcnsis L.). A common perennial grass with well-developed 
rhizomes and smooth stems above ground from 12 to 15 inches 
high. Rachilla webbed; flowering glume with five nerves, 
three of them hairy. Upper leaf-sheath longer than the 
blade, the ligules of the leaves short and blunt. It is an 
excellent bottom grass and especially suited to the lighter and 
medium soils. This meadow grass commences to grow early 
in spring, but produces only a moderate aftermath when cut 
for hay. 

Flat-stemmed Meadow-Grass: Canada Blue-Grass (Poa 
comprtssa L.) resembles P. pratcnsis, with flattened stems and 
compressed shoots decumbent at the base and rhizomatous. 
The upper leaf-sheath is about equal in length to the blade, the 
rachilla webbed, the flowering glume with three hairy nerves. 

It is found on dry banks and walls, and adapted for sandy 
and arid soils ; in Canada it grows on poor clay where better 
grasses do not succeed. 

Rough-stalked Meadow-Grass (Poa trivialis L.).- A common 
perennial much resembling the preceding species. It has, how- 
ever, no long rhizomes. The stems are somewhat rough, the 



LATE MEADOW-GRASS 



549 



upper leaf-sheath longer than the blade, the ligule long and 
pointed. Rachilla webbed; flowering glume five-nerved, only 
the central nerve hairy. It is one of the best ' bottom ' grasses, 
and is to be preferred before all others for sowing on the stiffer 
and damper class of soils in sheltered situations. It is less hardy 
than smooth - stalked meadow- 
grass, suffering more readily from 
frost and drought, and does not 
start growth so soon in spring. 

Wood Meadow - Grass (Poa 
ntmoralis L.). A perennial grass 
resembling the three previous 
species, but with more slender 
stems, and generally confined to 
shady places and woods. It has 
narrow leaves, the sheaths not 
longer than the blades, and a 
very short ligule. Rachilla 
webbed, flowering glume with 
five nerves, three of them hairy. 
Although it will endure a certain 
amount of drought when grown 
in the open meadow, its practical 
agricultural value is small. 

Late Meadow - Grass (Poa 
palustris Z. P. serotina Ehrh.) is 
not a native British species, but its seeds are sometimes sold in 
place of those of the two previous species. It is a coarse, tufted 
kind of Poa adapted for growth in marshy places, where it yields 
a good late crop of grass. 

Genus Festuca. 

Panicles usually spreading; spikelets with three or more 
flowers; empty glumes unequal, shorter than the flowering 

37 




FIG. 181. A> Panicle of Rough -stalked 
Meadow-Grass (natural size). 
B % Spikekt (twice natural size). 



550 COMMON GRASSES OF THE FARM 



glume; lower half of the flowering glume rounded on the back, 

upper part often keeled, awned from the tip or with a short, stiff 

point ; styles terminal on the ovary. 

Meadow Fescue (Ftstuca pratensis Huds.). A perennial broad, 

flat-leaved grass grow n^ iiom 2 to 3 feet high, and common in 
damp meadows. Although somewhat 
tufted in habit it tends to cover the 
ground very evenly. It is among the 
earliest of grasses to start growth in 
spring, often rivalling meadow foxtail 
in this respect. It yields a large 
amount of nutritious fodder and grows 
rapidly after mowing or depasturing with 
stock. 

Meadow fescue produces its full yield 
only after three years growth from the 
seed, and is therefore most suited for the 
longer leys and permanent pasture. 

Tall Fescue (Fcstuca elatior L.) re- 
sembles the last species but is more 
tufted in habit, and its leaves, stems, 
and other parts are larger and of coarser 
texture. It is met with on river banks 
and in wet places generally, where it 
frequently grows to a height of 4 or 
5 feet. Although it is eaten by all 
kinds of stock its coarseness unfits it 
for use in leys and permanent pasture. 
Possibly meadow fescue is merely a 
ciiKsneriVs of this nlant 

SUDS PedeS OI IHIS piam. 

Fest'tca arundinacea Schreb., which 
grows near the sea coast in many parts 
of the country, is a large form of tall fescue with rough leaf- 
sheaths. 




Meadow Fescue (natural ->ize). 
By Spikclet (twice natural 
size). 



RED FESCUE 



5SI 



Sheep's Fescue (Festuca ovina L.). A small perennial grass, 
usually not more than a few inches high and growing in tufts, 
with narrow, almost solid, bristle-like leaves and smooth leaf- 
sheaths. It grows well on dry soils, and is 
one of the chief constituents of upland sheep 
pastures. 

A variety of fine-leaved sheep's fescue (F. 
ov. var. tenuifolia Sibth.) has almost awnless 
spikelets. 

Hard Fescue (Festuca duriuscula L.) resembles 
the last species, but has narrow, flat leaves, 
downy leaf-sheaths, a more open panicle, and 
does not grow in such dense tufts. It is also 
of larger growth than sheep's fescue. 

Both these grasses are constituents of the 
best sheep pastures on the higher ground of 
this country, and are almost unaffected by the 
driest weather. Their produce is small but 
nutritious and more succulent than the general 
appearance of the leaves indicates. Hard 
fescue may be used with advantage, in 
moderate amount, as a 'bottom' grass in 
all mixtures for permanent pasture in dry 
situations. 

Red Fescue (Festuca rubra L.) is a perennial 
grass very nearly related to the last two species. sh y in g 

o / / f Action and manner 

It possesses narrow, flat leaves, pale red of folding, 
spikelets, and creeping rhizomes. 

The limits of the last three species of Festuca are ill-defined, 
as a large number of varieties exist which are intermediate in 
character between them. 

Little or no attempt is ma'e by seedsmen to supply 'seeds' 
of these species true to name, and for practical purposes there is 
no necessity to do so. 




Sheep's Fescue (nat- 
ural size). 

B. Base of leaf- 
blade and piece of 
stem 

A, Piece of leaf 



552 COMMON GRASSES OF THE FARM 

Genus Bromus. 

Panicles spreading : spikelets large with five or more flowers : 
empty glumes, unequal, acute : flowering glume generally with a 
divided tip and an awn which arises just below the tip. Styles 
lateral on the ovary. 

An extensive genus of coarse, harsh or hairy-leaved grasses, 
the species of which are nearly all useless or of small importance 
as forage plants. 

Awnless Brome-Grass : Hungarian Forage-Grass (Bromus 
tnermis Leyss.). A tall perennial grass with long rhizomes and 
smooth leaves sometimes over half an inch broad. It is grown 
extensively in Hungary, and the north-western United States, 
alone or in mixture with lucerne, on dry soils where it gives very 
large yield of grass, which if cut early makes fairly nutritious 
hay. 

It grows slowly in spring, but two cuts are often secured 
on the Continent in one season when the plant is thoroughly 
established. 

Our experience with it in this country has not been successful 
even on the looser soils, for which it has been specially recom- 
mended. 

Rescue Grass: Schroder's Brome-Grass (Bromus unioloidcs 
H. B. K. = B. Schraderi Kunth.). An annual or biennial grass 
with harsh broad leaves, recommended sometimes on account 
of its productiveness on thin soils. 

It is a native of South America, and grown for forage in warm 
climates. 

After several years' trial we cannot advise its being grown by 
the British farmer, as it rapidly becomes coarse, grows in massive 
tufts, and is liable to die off in winter and become patchy in the 
second or third year after sowing. 

Soft Brome-Grass (Bromus mollis L.). An annual or biennial 
grass very common on dry roadsides and waste places and 
growing about a foot high. It has thin broad leaves, the 



RYE-LIKE BROME-GRASS 



S53 



sheaths and blades of which are soft and downy ; the spikelets are 
also covered with soft hairs. It is a pest of temporary pastures. 

Somewhat similar is Bromus raccmosus L. with glossy, almost 
smooth, spikelets and 
slightly hairy leaves. 

Field Brome-Grass (B. 
arvensis L.) is an intro- 
duced grass from i to 
2 feet high with wide 
spreading panicle and long, 
narrow, drooping spikelets 
usually of violet-brown 
tint. It is sometimes grown 
in Sweden and other 
countries for green fodder 
or hay, though in this 
country considered a weed 
of corn crops. Rye-like 
Brome-Grass (B. secalinus 
L.) is a troublesome weed 
of corn-crops. 



Genus Brachypodium* 

Panicles spike-like, the 
cylindrical spikelets have 
very short stalks, and are 
arranged on opposite sides 
oftherachis. Eachspikelet 
possesses five or more 
flowers : empty glumes 
two : flowering glume with 
a terminal awn. A small 
genus of harsh perennial useless grasses. 
British species, namely : 




B 



FIG. 184. /4, Panicle of Soft Brome-Grau 
(natural sue). 
B % Spikelet (twice natural sue). 

There are two 



554 COMMON GRASSES OF THE FARM 

False Brome-Grass (Brachypodium pinnatum Beauv.), Fig. 256, 
and Slender False Brome-Grass (Brachypodium sylvaticum R. 
and S.). The farmer species has an erect panicle and is 
common on open downs and poor pastures in chalky 
districts : it is known as ' Tor grass ' in Kent. The 
latter species has a drooping inflorescence, and is met 
with in woods and on hedge-banks. 

Genus Nardus. 

Inflorescence a spike : spikelets one-flowered arranged 
one at each notch of the rachis, and on one side of the 
latter: no empty glumes : flowering glume narrow with 
a short awn. 

Mat-Grass (Nardus stricta L.). A small stiff peren- 
nial grass 6 or 8 inches high. Common on dry heaths 
and moors. Its stems and leaves are wiry and rejected 
by sheep. 

Genus Hordeum. 

Inflorescence a spike : spikelets one-flowtred arranged 
three together at each notch of the rachis and alter- 
nately on opposite sides of the latter. All three 
spikelets at each notch may be bisexual or only the 
central one, the lateral spikelets being in the latter case 
male or neuter : empty glumes two, very narrow, awned, 
placed partially in front of the spikelet. Flowering B ^ 
glume with a long terminal awn. FIG. 185. 

Cultivated Barley (Hordeum sativum Pers.). (See M'at ?Gras S 

' ^ (Nardus 

P. 506.) strida L.) 

Meadow Barley (Hordeum pratense Huds.). A per- s?ze)! ura 

... . . /Mtaseof 

ennial species common m wet or damp meadows near leaf- blade 
riversides where it grows about 18 inches high. a " lgu e * 

It possesses a slender stem and narrow flat leaves. Meadow 
barley grows early in spring and may be considered a useful 
pasture grass when not allowed to flower. In hay, however, 



PERENNIAL RYE-GRASS : RAY GRASS 555 



the awns of the spikelets are irritating and injurious to 
stock. 

Wall Barley (Hordeum murinum L.). An annual much re- 
sembling meadow barley, but met with on dry waste ground and 
about footpaths and roadsides near walls. 

It is not so tall as meadow barley, and is of no agricultural 
value. 

Genus Lolium. 

Inflorescence a spike ; one spikelet at each notch of the 
rachis ; the spikelets are many-flowered, 
and are inserted so that they stand in 
the median line of the rachis, that is, the 
plane passing through the middle of the 
glumes passes through the rachis also. 
The terminal spikelet has two empty 
glumes, the lateral spikelets only one 
(the outer empty glume) ; flowering 
glume awned or awnless. 

Perennial Rye-Grass : Ray Grass 
(Lolium perenne L.). A perennial 
common in all the best pastures and 
meadows throughout the country, and 
used probably more extensively than 
any other grass in mixtures for leys and 
permanent pastures. 

The leaves are folded in the bud, 
and the flowering glumes awnless. 

It grows most luxuriantly on soils 
which are loamy or stiffish in char- 
acter. On dry soils the produce is 

FIG iSfi.-^, Spike of Perennial Sma11 and f Httle VaUlC - 

^S^onSSudTidiign^ , Perennial rye-grass is a variable 
B, Spikelet of Italian Rye-Grass, plant, and manv varieties are met with 
(twte C c C naturai c K ial Rye " differing chiefly in yield, fineness of 
leaf, density of spike, and durability 




5 56 COMMON GRASSES OF THE FARM 

No systematic attempt appears to be made, now to obtain pure 
seed of any of these varieties, although formerly such attempts 
were made with success. 

The names Pacey's rye-grass, Devonshire Eaver, fine-leaved 
rye-grass, and others at present used in commerce, do not 
represent different varieties of plants, but are merely names at- 
tached to * seeds ' of a certain size or weight. ' Seeds ' passing 
through a small sieve usually give rise to young plants with fine 
thin leaves. 

Often all ' seeds ' above a certain weight per bushel have the 
term 'Pacey' added; such samples are generally superior to 
those of lower weight, and a somewhat higher price is charged 
for them. 

Perennial rye-grass grows somewhat in tufts, and gives a good 
yield of fairly early produce. Its nutritive value is only moderate, 
and the aftermath or second cut is not often large. 

Upon dry soils its duration is short, usually two or three years \ 
but on land suited to its requirements it is for all practical 
purposes a lasting grass, even when not allowed to produce seed 
and become self-sown. 

For leys of short duration it is excellent, but should be used 
sparingly in permanent mixtures. 

Its lavish use by the seedsman in expensive ' mixtures,' which 
should have been cheaper, and the partial abuse of it by the 
farmer himself in employing it in excessive amount for purposes 
to which it is unsuited, have tended to the depreciation of the 
grass in some quarters. Nevertheless, its rapid growth, good 
yield, fair nutritive value, hardiness, power of forming an excellent 
* bottom ' on almost all classes of soil, and other features, place 
it in the front rank of all grasses when judiciously used. 

Italian Bye-Grass (Lolium italicum A. Br.) is not met with 
in a wild state, and is no doubt a cultivated form of perennial 
rye-grass. Its leaves, which are paler than those of perennial 
rye-grass, are involute or rolled in the bud, and the plant has 



WHEATS 557 

barren leafy shoots; the flowering glumes are awned. This 
grass is of short duration usually, not more than over two years, 
but like perennial rye-grass becomes readily self-sown. 

It is one of the most rapidly growing grasses, producing 
heavy crops in the same season in which it is sown, is superior 
in feeding quality to the previous species, and very extensively 
used for one or two years' ley. For permanent pasture mixtures 
it should be left out altogether, or employed in very small amount. 

Lolium multiflorum Lam. is the strictly annual form of this 
grass with no barren shoots. 

Darnel (Lolium temulentum L.). An annual grass with stout, 
erect stems i to 2 feet high met with as a weed among corn crops. 
It resembles perennial rye-grass, but its spikelets only have five 
or six flowers, and the empty glume generally exceeds the 
spikelet in length. The flowering glume is mostly awned as in 
Italian rye-grass. In certain plants the fruits are infected with 
che mycelium of a fungus, and are said to be poisonous. 

Z. arvenst With, is a variety of Darnel with four- or five-flowered 
awnless spikelets. 

Genus Secale. 

Inflorescence a spike without a terminal spikelet : spikelets 
somewhat compressed, two- or three-flowered, transverse to 
rachis, that is, the edges of the glumes next to the rachis : one 
spikelet at each notch of the latter. Empty glumes vqry narrow, 
flowering glumes keeled to the base, and with a long terminal 
awn ; keel with a fringe of strong hairs. 

Eye (Secale ctreale L.). (See p. 518.) 

Genus Triticum. 

Annual grasses. Inflorescence a spike with a terminal spike- 
let : spikelets inflated, two to five flowers, transverse to the 
rachis, that is, the edges of the glumes next to the latter: 
empty glumes with an awn or strong tip : flowering glume with 
one or more long or short awns. 

Wheats (see p. 521). 



558 COMMON GRASSES OF THE FARM 



Genus Agropyrum. 

Perennial grasses (sometimes included in the genus Triticuni). 
Inflorescence a spike : spikelets somewhat compressed, three- or 
more-flowered, transverse to the rachis, that 
is, the edges of the glumes towards the 
latter (opposite in arrangement to Lol- 
ium) : empty glumes shorter and narrower 
than the flowering glumes : flowering glumes 
stiff, with or without a terminal awn. 

Couch : Quitch : Twitch : Whickens : 
Creeping Wheat-Grass (Agropyrum repens 
Beauv.). A perennial grass with long creep- 
ing rhizomes, and well-known as one of the 
most troublesome weeds of arable ground. 
The leaves are flat, smooth, and somewhat 
ashy green in colour. The inflorescences 
(spikes) are 2 or 3 inches long, and most 
frequently observed on specimens growing 
in hedges and on waste ground, the plants t 
occurring on arable ground being rarely 
allowed to flower. 

The flowering glumes end in a stiff acute 
point which is sometimes prolonged into a 
short awn. Stock readily eat the young 

leaves Of COUCh-graSS, 

Bearded Wheat-Grass (Agropyrum cani- 
num Beauv.). A perennial grass of tufted habit, without long 
rhizomes, and usually found in moist woods and on banks and 
damp waste ground. It also differs from the preceding species 
in possessing rough awns on its flowering glumes. 

Bearded Wheat-Grass is useful in producing a fairly large 
supply of early leaves, which are greedily eaten by all kinds of 
stock. 



B A 

FIG. 187.^ 



Spike of 



Spikelet (twice natural 



COMMON FARM GRASSES 559 

SUMMARY OF GENERIC CHARACTERS OF THE COMMON FARM GRASSES. 

A. Inflorescence a panicle : in some cases the stalks (pedicels) of the spike- 
lets are very short, and the panicle is spike-like. 

1. Spikelets with only one flower. 

a. Empty glumes four ; panicle spike-like. Anthoxanthum. 
b Empty glumes two. 

(i) Panicle spike-like (Fig. 172). (See p. 537.) Ahptcurus. 

(See p. 538.) Phleum. 

(See p. 539.) Ammophila. 

(ii) Panicle spreading (Fig. 174). Agrostis. 

2, Spikelets with two or more flowers. 

a. Empty glumes equal to or longer than the flowering glumes often 

hiding from view the rest of the spikelet. 
The flowering glume generally awned ; awn dorsal, twisted and bent 

(B t Fig. 176), except in Dcschampsia. 
(i) Spikelets with two flowers ; upper one male, 

lower one bisexual. Holcus. 

(ii) Spikelets with two flowers ; lower one male, 

upper one bisexual. Arrhenatkerum. 

(Hi) Spikelets with two or more bisexual flowers. 

(See p. 543.) Deschampsia. 
(See p. 544.) Trisetum. 
(See p. 545.) Avcna. 

b. Empty glumes shorter than the flowering glumes, the rest of the 

spikelet generally visible (#, Fig. 182). 
When the flowering glume is awned, the awn is terminal and 

generally straight (Fig. 184). 

(i) Panicle spike- like (Fig. 179). Cynosurus. 

(ii) Panicle of dense clusters of Spikelets (Fig. 180). Dactylis. 
(iii) Panicle spreading (Fig. 181). 

* Flowering glume compressed with a keel 

along its whole length ; no awns. , Poa. 

** Flowering glumes rounded on the backhand 
upper part only keeled ; sometimes awned. 

(See p. 549.) Fes f Ufa. 
(See p. 552.) Bromus. 

B. Inflorescence a spike (Fig. 186) : the spikelets sessile, arranged directly 
in notches on the single main axis. 

I. Spikelets one- flowered, 

a. One spikelet at each notch (Fig. 185). Nardus. 

b. Three spikelets at each notch (Fig. 159), Hordtum. 



560 COMMON GRASSES OF THE FARM 

2, Spikelets with two or more flowers. 

a. One spikelet at each notch. 

(i) Glumes with their backs towards the notch of 

rachis (Fig. 186). Lolinm. 

(ii) Glumes with their edges towards the notch of 

rachis (Fig. 187). 

Empty glumes narrow, subulate. Secale. 

Empty glumes broad. (See p. 557.) Triticum. 

(Seep. 558.) Agropywrn 

b. Two or three spikelets at each notch. Elymus. 



RECOGNITION OF THE CHIEF MEADOW AND 
PASTURE GRASSES BY THEIR LEAVES. 



GROUP I. 

LEAVES FOLDED IN THE BUD (Fig. iSS) : THE SHOOT APPEARS 
FLATTENED. 

This feature is readily determined by cutting across the shoot with a sharp 
knife and examining with a pocket lens. 
The following grasses belong to this group : 



Perennial Rye-Grass. 
The Meadow -Grasses. 
Cocksfoot. 



Crested Dogstail. 
Sheep's Fescue. 
Hard and Red Fescue. 



1. Base of leaf with claw-like appendages which clasp the stem more 

or less (Figs. 186 and 189). 

Perennial Rye-Grass (Lolium perenne L.). This grass is not hairy, 
and its lower leaf-sheafs just below ground are pink. The ligule is 
extremely short, and the upper surface of the leaf-blade possesses 
well-marked longitudinal ribs. 

The latter are seen best when a leaf is cut across with a sharp 
knife and the section examined with a lens. 

2. Base of leaf without claws (Fig. 190). 

a. Leaf-sheaths below ground bright yellow. 



CHIEF MEADOW AND PASTURE GRASSES 561 



Crested Dogstail (Cynosurus cristatus L.). The grass is not 
hairy ; its leaves are thick and firm, generally concave or not 
quite flat, with prominent longitudinal ribs on the upper surfaces 
of the blades. 

The leaves are firmer than those of Perennial rye-grass, and 
sometimes slightly rolled so that the shoot is rounder. 

Leaf-sheaths not yellow. 

(i) Leaves almost cylindrical or bristle-like (Fig. 183). 

Sheep's Fescue (Fcstuca ovina L.) and the allied Hard and 
Red fescues. The latter forms have leaves which are flatter 
or not so closely folded as those of the typical sheep's 
fescue. 

All have strong longitudinal ribs on the upper surface. 
(ii) Leaves flat, without prominent longitudinal ribs. 
* Leaves narrow ; two white longitudinal lines are seen 
one on each side of the mid-rib when the leaf is 
held up to the light and examined with a lens. 

Meadow- Grasses or Poas. 

Rough Stalked Meadow- Grasses (foa tnvialis L.). 





FIG. 189. 




FIG. 190. 



FIG. 



Ligule acute ; tufted habit ; generally with an acute 
keel to the leaf-sheath. 

Smooth-Stalked Meadow-Grass (Poa ptattnsis L.). 
Ligule short ; rhizomes below ground. The leaves 
are thicker and a darker green colour in this species than in the 
previous one. 
** Leaves broad, without the white longitudinal lines. 

Cocksfoot (Dactylis glomcrata L.). Prominent keel to the leaf- 
sheath ; the under surface of the blade is duller than that of 
rough-stalked meadow-grass, which is sometimes confused with this 
species. 



562 COMMON GRASSES OF THE FARM 



GROUP II 

LEAVES ROLLED IN THE BUD (Fig. 191) : THE SHOOT IS CYLINDRICAL. 

The following grasses are included in this group : 



Italian Rye- Grass, 
Meadow Fescue. 
Tall Oat- Grass. 
Yellow Oat-Grass. 
Timothy or Catstail. 
Foxtail. 



Sweet Vernal -Grass. 

Yorkshire Fog. 

Couch. 

Fiorin. 

Soft Brome-Grass. 



I. Base of leaf with claw-like appendages (Fig. 189). 

a. Leaf-sheaths pink below ground, smooth and shining. 
Italian Rye-Grass (Lolium italicum A. 
Br.). Margin of the leaf -blades 
smooth ; the blade with indistinct 
veins when held up to the light. 
Meadow Fescue (Festuca pratcnsis 
Huds.)- Margin of the leaf- blade 
rough (test with the tongue) ; the 
veins of the leaf-blade appear as 
white lines when held up to the light. 
4. Leaf-sheaths not pink, often with a few 

scattered hairs. 

Couch {Agropyrum rtpens Beauv. ). Dis- 
tinguished also from the two preceding 
species by its well-marked rhizomes. 

2. Base of leaf -sheath without claw-like appendages 
(Fig. 190). 

a. Leaf-sheaths hairy. 

(i) Leaf- sheath white with pink veins. 

Yorkshire Fog (Holcus lanatus L.). 
(ii) Leaf-sheaths without pink veins. 

Soft Brome-Orass (Bromus motlis L.). 
Leaf-sheath keeled and entire ; the 
blades are thin, dry, and very soft. FlG - I 9 I - 

Sweet Vernal - Grass (Anthoxanthum 

odoratum L.). Leaf-sheath not keeled. The grass has a 
1 characteristic odour and bitter taste ; base of leaf-blade 

rounded with a fringe of long hairs. 

Yellow Oat-Grass (Trisetum flavtscens Beauv,). Leaf-sheath 
not keeled. 




CHIEF MEADOW AND PASTURE GRASSES 563 

*. Leaf-sheaths smooth (sometimes sparsely hairy in Tall Oat-Grass), 
(i) Old leaf- sheaths below ground, dark maroon. 

Foxtail ( Aloptcttrus pratensis L. ). Rhizomes present. Ligule 

not so long as it is broad, and hairy on the back, 
(ii) Old leaf-sheaths pale. 

Timothy ( Phkum praUnse L. ). Tufted habit of growth with- 
out long rhizomes. Ligule longer than broad and without 
hairs on the back. Ribs on blade low and flat. 
Florin (Agrostis alba L.). Has well-developed rhizomes. 
Ligule long and hairy on the back. Blade rough on both 
sides, with prominent ribs. 

Tall Oat-GraflB (Arrhenathcrum avenactum Beauv.). Short 
rhizomes. Ribs on blade low and flat. 



CHAPTER XLTI. 

GRASSES AND CLOVERS FOR TEMPORARY AND 
PERMANENT PASTURES. 

i. THE seeds of the grasses and clovers are very extensively 
mixed and sown for the purpose of forming temporary and 
permanent pastures. The constitution of these mixtures, both 
in regard to the choice of the species of plants to be used 
and the amount of seed of each species to be sown, is at 
present a matter upon which there exists great difference ot 
opinion. Nevertheless there are certain general principles for 
guidance in the choice of grasses and clovers for particular 
purposes, which it is useful to point out. 

No rational, satisfactory, or economic use can be made of 
any species of grass or clover unless its character in regard to 
the following points is understood : 

(i) Durability. Some grasses, such as Italian rye-grass, are 
annual, and die off after seeding once ; while others, such as 
meadow foxtail and cocksfoot, are perennial No hard and fast 
line exists among plants in regard to their duration (see p. 5), 
as the time during which they live is dependent on climate, soil, 
and the treatment which they receive : for present purposes, 
however, they may be divided into (a) those which are short- 
lived and suitable only for one, two, or three years 1 duration, 
and (K) those which are permanent and adapted for use in 
pastures to be kept down for longer periods. 

(ii) Rapidity of growth after sowing. Many grasses reach 
their highest state of development in the first or second year.. 
This is generally true of the less permanent plants, such as the 
rye-grasses, tall oat-grass and red clover. Others, such as cocks- 

66* 



GRASSES AND CLOVERS 



565 



foot, meadow foxtail, meadow fescue and all the more lasting 
grasses, do not attain their maximum of growth until the third or 
fourth year after sowing. 

(iii) Tufted and creeping ' habit? Some grasses grow in more 
or less isolated tufts, and are incapable of forming a compact 
turf when sown alone ; while others, such as meadow foxtail and 
smooth-stalked meadow-grass, have underground stems or rhizomes 
similar to those of couch grass, which spread in various directions 
and send up green leafy shoots over considerable areas. In order 
to obtain an even and uniform ' sole f of turf, it is essential that 
mixtures should contain an adequate proportion of both classes. 

(iv) Height. The grasses and other plants used for mixtures 
vary considerably in stature : the tall-growing kinds of special 
use in leys for mowing are designated 'top-grasses* while the 
shorter kinds are termed 'bottom-grasses' and are employed 
to form c bottom ' in meadows and pastures. 

Although no hard line of demarcation exists between 'top- 
grasses' and 'bottom-grasses/ the following classification represents 
the general character of the common grasses and clovers in this 
respect. Some of the plants mentioned, such as perennial rye- 
grass and rough-stalked meadow-grass, may reasonably be 
included in both divisions : 



(a) Top-grasses. 
Italian Rye-grass. 
Cocksfoot. 
Tall Oat-grass. 
Timothy. 
Meadow Foxtail. 
Rough-Stalked Meadow-grass. 
Red Clover. 
Alsike Clover. 



(b) Bottom-grasses. 
Golden Oat-grass. 
Crested Dogstail. 
Perennial Rye-grass. 
Smooth-Stalked Meadow-grass 
Sheep's Fescue. 
Hard Fescue. 
Fiorin. 

Sweet Vernal-grass. 
White Clover. 
Kidney-Vetch. 
Bird's-Foot Trefoil. 
Black Medick. 



CHAPTER XLII. 

GRASSES AND GLOVERS FOR TEMPORARY AND 
PERMANENT PASTURES. 

i. THE seeds of the grasses and clovers are very extensively 
mixed and sown for the purpose of forming temporary and 
permanent pastures. The constitution of these mixtures, both 
in regard to the choice of the species of plants to be used 
and the amount of seed of each species to be sown, is at 
present a matter upon which there exists great difference ot 
opinion. Nevertheless there are certain general principles for 
guidance in the choice of grasses and clovers for particular 
purposes, which it is useful to point out. 

No rational, satisfactory, or economic use can be made of 
any species of grass or clover unless its character in regard to 
the following points is understood : 

(i) Durability. Some grasses, such as Italian rye-grass, are 
annual, and die off after seeding once ; while others, such as 
meadow foxtail and cocksfoot, are perennial. No hard and fast 
line exists among plants in regard to their duration (see p. 5), 
as the time during which they live is dependent on climate, soil, 
and the treatment which they receive: for present purposes, 
however, they may be divided into (a) those which are short- 
lived and suitable only for one, two, or three years' duration, 
and (d) those which are permanent and adapted for use in 
pastures to be kept down for longer periods. 

(ii) Rapidity of growth after sowing. Many grasses reach 
their highest state of development in the first or second year*. 
This is generally true of the less permanent plants, such as the 
rye-grasses, tall oat-grass and red clover. Others, such as cocks- 

664 



GRASSES AND CLOVERS 



565 



foot, meadow foxtail, meadow fescue and all the more lasting 
grasses, do not attain their maximum of growth until the third or 
fourth year after sowing. 

(iii) Tuftfd and creeping ' habit? Some grasses grow in more 
or less isolated tufts, and are incapable of forming a compact 
turf when sown alone ; while others, such as meadow foxtail and 
smooth-stalked meadow-grass,have underground stems or rhizomes 
similar to those of couch grass, which spread in various directions 
and send up green leafy shoots over considerable areas. In order 
to obtain an even and uniform ' sole ' of turf, it is essential that 
mixtures should contain an adequate proportion of both classes. 

(iv) Height. The grasses and other plants used for mixtures 
vary considerably in stature : the tall-growing kinds of special 
use in leys for mowing are designated ' top-grasses? while the 
shorter kinds are termed 'bottom-grasses' and are employed 
to form ' bottom f in meadows and pastures. 

Although no hard line of demarcation exists between * top- 
grasses 1 and 'bottom-grasses, 1 the following classification represents 
the general character of the common grasses and clovers in this 
respect. Some of the plants mentioned, such as perennial rye- 
grass and rough-stalked meadow-grass, may reasonably be 
included in both divisions : 



(a) Top-grasses. 
Italian Rye-grass. 
Cocksfoot. 
Tall Oat-grass. 
Timothy. 
Meadow Foxtail. 
Rough-Stalked Meadow-grass. 
Red Clover. 
Alsike Clover. 



(b) Bottom-grasses. 
Golden Oat-grass. 
Crested Dogstail. 
Perennial Rye-grass. 
Smooth-Stalked Meadow-grass 
Sheep's Fescue. 
Hard Fescue. 
Fiorin. 

Sweet Vernal-grass. 
White Clover. 
Kidney-Vetch. 
Bird's-Foot Trefoil. 
Bkck Medick. g 



566 GRASSES AND CLOVERS FOR LEYS OF 

(v) Earliness and lateness of growth. Sweet vernal -grass, 
meadow-foxtail, cocksfoot, meadow fescue, and tall oat-grass 
commence to grow in early spring, while timothy and florin are 
much later in the production of their leafy shoots. 

(vi) Power of growth after being cut, or the yield of aftermath 
to be obtained from a grass is a matter for careful consideration. 

(vii) Quality and yield of produce. The feeding quality of 
the grasses and other plants depends upon their specific nature 
to a considerable extent, but it also varies with their age, the 
particular stage of their development, and soil upon which 
the plants are grown, as well as upon several other conditions. 
For all practical purposes in the choice of the different common 
grasses mentioned below as suitable for leys, we must at present 
rest content to treat them as of equal value in this respect 

(viii) Adaptability to certain soils and climates. All the best 
grasses, such as are adapted for use in the formation of leys and 
permanent pastures, and capable of yielding valuable fodder, 
grow readily upon all classes of soils. Some however, such as 
timothy, rough-stalked meadow-grass and alsike clover, grow 
most satisfactorily upon the stiffer, damper soils, while tali oat- 
grass, hard fescue, kidney-vetch, and others are adapted to drier 
soils. 

For the best results with grasses their soil-requirements must 
be considered. 

2. Grasses and Clovers for Leys of One, Two, or Three 
Years' Duration. 

In these leys which are to be kept down for a short time only, 
the grasses and clovers must fulfil the following requirements : 

(i) They should have the power of growing rapidly and should 
reach their maximum state of development within the time 
during which the ' ley ' is to be utilised. 

(ii) They should yield a large bulk of produce ; and 

(iii) Should be of good feeding-quality. 



ONE, TWO, OR THREE YEARS DURATION 567 

Moreover, the necessary seeds should be cheap as the outlay 
for them occurs often. 

As the ' leys ' are to be ploughed up at the expiration of two 
or three years, the question of their durability or permanence 
beyond this period is of no importance. 

The grasses and clovers most nearly satisfying the above 
conditions are : 



Red Clover. 
Alsike. 

White Clover. 
Black Medick. 



Italian Rye-grass. 
Perennial Rye-grass. 
Timothy. 
Tall Oat-grass. 



Usually only one, two, or three of the above species are 
employed in each mixture. Which individuals should be 
selected depends upon the character of the soil, the manner in 
which the produce is to be used, and the duration of the ' ley. 1 

Red clover, black medick, and Italian rye-grass are prac- 
tically annual and therefore only useful for one or two year leys. 
The other plants are more durable and used when the leys are 
left down three years. 

Black medick is chiefly employed on the somewhat inferior, 
dry, calcareous soils; Timothy and Alsike are adapted to the 
stiffer soils, the latter clover taking the place of red clover where 
clover-sickness is feared. 

For grazing with sheep, white clover is usually a prominent 
constituent of the ley. 

The following examples may be taken as illustrations of the 
spegies to be employed, and the proportions of each to be used, 
in the formation of mixtures for short leys. 

As the clovers grow freely, produce large bulk, and are more 
nutritious than the grasses, the proportion of ground covered 
by them should range between 50 and 100 per cent., the greater 
amounts being taken on good soils free from 'clover-sickness. 1 



568 GRASSES AND CLOVERS 

On poor soils, or those on which the clovers do not grow 
satisfactorily, the proportion of grasses should be increased so 
as to cover the ground more or less up to 50 per cent, of the 
whole. 

(a) Mixture for one year on good medium soil. 

Percentage of ground 
covered. 

(i) () 
Red Clover . . . 80 or 90 

Italian Rye-grass . . 20 or 10 

(b) Mixture for two or three years on good medium soil. 

Percentage of ground 
covered. 

Red Clover ... 80 

Timothy . . . 10 

Italian Rye-grass . . 10 

(c) Mixture for two or three years on heavy damp soils. 

Percentage of ground 
covered. 

(i) or (ii) 

Red Clover . 35 

Alsike . . . 45 70 

Timothy . . . 15 25 

Perennial Rye-grass . 5 5 

(d) Mixture for one year's sheep pasture. 

* Percentage of ground 
covered. 

White Clover ... 66 

Black Medick . . 34 

(e) Mixture for tivo or three year? sheep pasture. 

Percentage of ground 
covered. 

White Clover ... 80 

Perennial Rye-grass . . 20 



FOR TEMPORARY PASTURES 569 

3. Grasses and clovers for temporary pastures lasting from 
three to six years : Grasses and clovers for permanent pasture. 

Mixtures for the longer leys and for permanent pasture have 
a great deal in common, so that their composition may be 
discussed together. Failure to establish a satisfactory long ley 
or a permanent pasture may be due to the employment of bad 
seed, wrong manuring, imperfect mowing or grazing, and other 
causes, some of them beyond human control. Want of success 
is, however, sometimes the outcome of the wrong choice of 
plants for the ley, and to avoid failure on this account requires 
very careful consideration, both in regard to the choice of the 
species of plants to be used, and in the determination of the 
amount of ground to be covered by each. 

It is obvious that the plants previously mentioned as suitable 
for leys of * one, two, or three years' duration are by themselves 
quite unsuited for the longer leys and permanent pasture, in- 
asmuch as in the third or fourth year they die out almost 
completely, and the ground, under such circumstances, either 
becomes bare or is rapidly overspread by weeds which take the 
place of the disappearing grasses and clovers. 

In order to impart durability some of the permanent grasses 
must be introduced into the * leys.' 

Permanence is, however, not the only point to consider. It is 
desirable that from the beginning to the end of the ley there 
should be an uniform yield of produce, and not a high yield 
during the first year or two, followed by a dearth in the later 
years, or vice versd. This can only be attained by carefully 
balancing the rapid-growing, short-lived plants with the more 
permanent species, which are slow in growth, and do not give 
their full yield until they are well established. 

When too great a number of rapid-growing, short-lived grasses 
are introduced the yield at nrst is very heavy, but the small, 
slow-growing, permanent plants are weakened almost beyond 



570 GRASSES AND CLOVERS 

recovery, or totally destroyed by being overshadowed by their 
strong-growing neighbours. On the other hand, if too large a 
proportion of permanent grasses are employed, the yield of pro- 
duce during the first few years is very materially reduced. 

For leys of from three to six years' duration the best authorities 
consider that the ground should not be covered to a greater 
extent than 30 or 40 per cent, by the clovers, the smaller pro- 
portion being used in those leys which are intended to last 
longest. If a larger proportion is used, the pastures in a few 
years become thin and patchy owing to the dying-off of the 
clovers, none of which are permanent, except the white species. 

The rest of the ground, namely, 60 to 70 per cent., is covered 
by grasses, one-half of which should belong to the short-lived, 
the other to the more permanent species ; if a larger amount of 
short-lived grasses is sown the pasture becomes patchy in the 
later years. 

For permanent pastures the amount of clovers sown should be 
such as will cover not more than 20 per cent, of the ground, the 
remaining 80 per cent, being taken up by grasses, of which be- 
tween 50 and 60 per cent, should be permanent. 

The following tables indicate the general composition of these 
two classes of mixtures : 

(a) For leys of three to six years' duration. 

Percentage of ground 
covered. 

Clovers , . . 30 or 40 

Grasses | Short - lived ' ' 35 or 3 

I Permanent . . 35 or 30 

(b) For permanent pasture. 

Percentage of ground 
covered. 

Clovers . , .20 

Grasses I Short " lived * ' 3 or 20 

I Permanent . 50 or 60 



FOR PERMANENT PASTURE 571 

The plants available for long leys and permanent pastures 
are: 

CLOVERS. 

(i) (ii) 

Short-lived. Permanent* 

Red Clover. White Clover. 

Alsike Clover. Bird's-Foot Trefoil 

Black Medick. 

GRASSES. 
(i) (ii) 

Short-lived* Permanent. 

Italian Rye-grass. Rough-stalked Meadow-grass, 

Perennial Rye-grass. Smooth-stalked Meadow-grass, 

Timothy. Cocksfoot. 

Tall Oat-grass. Meadow Fescue. 

Meadow Foxtail 
Crested Dogstail 
Golden Oat-grass. 
Sheep's Fescue. 
Hard Fescue. 

Which of these species, and how many of them should be 
selected for any particular ley, will depend upon the soil, the 
duration of the ley, and the purpose which the latter is intended 
to serve. If for mowing chiefly, about two-thirds of the ground 
allotted to the grasses in the above tables, (a) and (), should be 
given to ' top-grasses ' ; whereas if the pasture is intended mainly 
for grazing, the 'top-grasses 1 may be conveniently reduced to 
one-half. 

On light soils the amount of 'bottom-grasses 1 should be 
slightly increased in order to keep the moisture on the land, 
but in damp soils they should be decreased. 

As a rule, the larger the number of species in a mixture the 
better, because when one grass fails on account of the dampness 



572 GRASSES AND CLOVERS 

or dryness of the season or soil, another species often succeeds. 
Moreover, no single plant will continue to grow and provide 
food for stock from spring to autumn ; but by judicious selection 
of a number of different species according to the earliness or 
lateness of their growth, a continuous production of forage can 
be obtained during many months of the year. 

In addition to the principles previously indicated for guidance 
in the choice of species, the agriculturist should determine the 
species of grasses which grow in the best meadows and pastures 
on similar soils in the neighbourhood, and give prominence to 
these in any mixture he intends to use, especially where the 
pastures are to be permanent. 

It is very necessary, however, to point out that the practices 
of sowing sweepings of the hay-loft, or seeds obtained from a 
specially-saved crop of hay from the best meadows of the farm, 
are both very unreliable, although in some cases they have led 
to good results. Neither of these methods provides seeds of all 
the good plants of the meadow. Investigations we have carried 
out in regard to the composition of such home-produced mixtures 
have invariably shown that the latter contain the seeds of only a 
small number of species of grasses just those which were ripe 
at the time the hay was cut and frequently a number of common 
weed seeds ; all the early grasses are missed, as their seeds have 
been shed, and the seeds of the best late grasses are rarely 
obtained, as the meadow is usually mown before they are 
ripe. 

The following prescriptions are not intended to be slavishly 
copied, but may be taken as illustrative of the principles laid 
down. The farmer should use his own judgment in regard to 
the amount and nature of each plant used, bearing in mind their 
particular individual qualities in regard to durability, habit of 
growth, adaptability to special soils, and other points mentioned 
at the beginning of the chapter (see also Chapter xli.). 



MIXTURES FOR TEMPORARY PASTURE 573 



A. Mixtures for Temporary Pasture of four to six years 1 

duration on good average loams. 

In such mixtures as these the amount of ground covered by 
Italian rye-grass should not be more than 5 per cent., perennial 
rye-grass not more than 10 per cent., and the red clover not 
more than 25 per cent, respectively, as none of these plants 
last six years as a rule. 



r Red Clover . 

Clovers , . -| Alsike Clover 
[ White Clover 

(Italian Rye-grass . 
Perennial Rye-grass 
Timothy . . 
Cocksfoot . 
Meadow Fescue 
Meadow Foxtail . 



Permanent Grasses 



Smooth-stalked Meadow-grass 
Crested Dogstail . 



Percentage of 
ground 
covered by 
each species. 

( IS 

33%] 


. I 10 


33%- 


5 
10 


. 


. 18 




10 


, 


IO 


34 % < 


3 


-grass 


7 





4 



IOO 



On heavier soils the Alsike clover, perennial rye-grass, Timothy 
and meadow foxtail should be increased and the other plants de- 
creased correspondingly. Rough-stalked meadow-grass should 
be added. 

On dry soils the Timothy and meadow foxtail should be de- 
creased, and tall oat-grass and golden oat-grass should be added 
to the mixture. 

For six year leys the amount of space alloted to red clover 
should be reduced, and a corresponding area given to the Alsike 
and white clovers. 

B. Mixtures for Permanent Pasture. 

In mixtures for permanent pastures, Italian rye-grass should be 



574 



GRASSES AND CLOVERS 



left out altogether; perennial rye-grass should be allotted not 
more than 5 per cent., red clover not more than 10 per cent., 
and timothy not more than 15 per cent, of the total area. 
Moreover, on account of the tufted coarse habit, cocksfoot should 
not be allowed to usurp more than 15 per cent, of the ground, 
and especially so if the pasture