MAT 6 UW9

LIBRARY

OF THE

UNIVERSITY OF CALIFORNIA.

i
Class

NATURE TEACHING

NATURE TEACHING

BASED UPON THE GENERAL
PRINCIPLES OF AGRICULTURE

FOR THE USE OF SCHOOLS

BY FRANCIS WATTS, B.Sc., F.I.C., F.C.S.

GOVERNMENT ANALYTICAL AND AGRICULTURAL CHEMIST, LEEWARD ISLANDS,
WEST INDIES

AND WILLIAM G. FKEEMAN, B.Sc., A.E.C.S., F.L.S.

SUPERINTENDENT OF THE COLONIAL COLLECTIONS, IMPERIAL INSTITUTE J LATE SCIENTIFIC

ASSISTANT, IMPERIAL DEPARTMENT OF AGRICULTURE FOR THE WEST INDIES,

AND FORMERLY DEMONSTRATOR IN BOTANY, ROYAL COLLEGE OF

SCIENCE, LONDON

NEW YORK:
E. P. BUTTON £ CO.

1904

L D

GENERAL

Printed in Great Britain

PREFACE

THIS little book was originally written for use in the
West Indies, with the intention of shaping the courses
of study both in secondary and primary schools ; being
employed as a text-book in the former, while in primary
schools it is used by the teachers in preparing and
formulating their teaching.

As it has been found useful in its original form in
the West Indies, it has been suggested that an edition,
rewritten and modified to meet the circumstances of
British conditions, may prove acceptable in the mother
country. I have, therefore, with the assistance of Mr W.
G. Freeman, prepared the present revised edition.

Elementary nature teaching admits a wide range of
subjects, and individuality plays an important part ; but
throughout, if good work is to be done, it must be
impressed upon the teacher that the pupils must do
things for themselves. Mere knowledge of how things
ought to be done, and what they ought to look like if only
they were found and seen, is of little value, and the
absence of the true practical knowledge of things is

a 2

180730

vi PREFACE

soon revealed upon any attempt to ascertain the depth
and reality of the pupil's information.

For this reason but few illustrations are used, lest
both teacher and pupil, seeing how things appear in an
illustration, may consider that "they know all about
that," and may be tempted to shirk the effort of seeing
the natural object for themselves.

In schools where the subject is taken up for the first
time, it will probably be found prudent to do a consider-
able amount of work before attempting anything like a
formal school garden. To this end a great deal of useful
work can be done by growing plants in pots or boxes.
Ideas for the school garden will soon evolve themselves
from this work.

It must be clearly understood that the book is not
arranged in such a manner as to afford a course of
instruction to be taken in the precise order in which
it is written. In work of this kind some skill and
judgment are required to adjust matters, so that
the teaching shall be so distributed as to proceed in
an even manner from week to week, and also that
there shall be no unnecessary delays, as may arise
from waiting for some experiment or demonstration
to mature.

In the appendix, attempts are made to indicate suit-
able courses of work according to the time of year at
which the work is begun, but in this there is ample
scope for the exercise of judgment on the part of
the teacher. Nor are the exercises put forward as
final; they are only indicative of a general course
of study, and the intention is that the teacher shall

PREFACE vii

extend and modify them as surrounding conditions
demand.

In some instances a school garden cannot be
provided, but in rural districts this may usually be
obtained. It is not necessary to have a large piece of
ground.

In connection with school gardening, difficulty is
sometimes experienced in maintaining order, and pre-
venting what should be serious, though interesting,
teaching degenerating into a useless scramble. This
may often be obviated by introducing the elements of
a simple drill into the out-door work, as by marching
the class to the tool-house, then passing out the tools
to the class as it stands in rank, and marching to the
plots where work is to be done, and so on.

In the working-plots themselves the work must be
carried on in a manner similar to that of a laboratory ;
each pupil must have an idea of what he is aiming at,
and proceed independently to the fulfilment of his
object. In many cases it is well for the pupils to work
in pairs.

In the garden itself, two kinds of work have to be
distinguished, and it is well to keep them distinct in the
minds of teacher and pupil. Some plants are to be
grown with the object of studying their mode of growth :
they are to be examined, and possibly destroyed in
process of examination, in various stages. Other plants
are to be grown for the sake of the crop they afford,
whether the crop be ornamental, as in the case of flowers
and decorative plants, or useful, as in the case of fruits
and vegetables. The proper arrangement of both kinds of

viii PREFACE

work requires care and thought on the part of the
teacher.

In all the work, drawing, measuring, and weighing
should be insisted on wherever circumstances permit

F. W.

August^ 1903.

Official duties having called me to Southern Nigeria
for some months, it has been impossible for me to revise
the final proofs.

My deepest thanks are due to my wife for kindly
undertaking this laborious task, and compiling the
index, in addition to the valuable assistance she has
given throughout the progress of the work ; and in
particular, in preparing, especially for this book, the
whole of the illustrations. W. G. F.

February 28, 1904.

CONTENTS

CHAPTER I

THE SEED

The Parts of a Seed — Plant Food in Seeds — Germination —
Practical Work— The Conditions of Germination— Rais-
ing Seedlings — Seed Beds — Observations on Seed-
lings— Testing Vitality of Seeds ....

CHAPTER II

THE ROOT

Uses of Roots. Practical Work — Root-Hairs — Root-Caps —
Growth in Thickness — Growth in Length — Absorption
by Roots — Roots and Gravitation — Roots and Water —
Propagation by Cuttings ..... 24

CHAPTER III

THE STEM

Uses of Stems— Structure of Stems— Grafting and Budding.
Practical Work — Uses of Stems— Structure of Stems
— Grafting and Budding . . . . .41

x CONTENTS

CHAPTER IV

THE LEAF

PACK

Uses of Leaves — Structure of Leaves — Transpiration —
The Atmosphere — Plants and the Atmosphere — The
Food of Plants. Practical Work— Uses of Leaves-
Structure of Leaves — Transpiration — Plants and the
Atmosphere — The Food of Plants . . .66

CHAPTER V

THE SOIL

Water in Soils— Clay— Vegetable Matter in Soils— Chalk
in Soils. Practical Work — Mechanical Analysis of Soil
— Water in Soils — Vegetable Matter in Soils — Chalk in
Soils 101

CHAPTER VI

PLANT FOOD AND MANURES

Nitrogenous Matter — Leguminous Plants and Nitrogen —
Mineral Matter — Manuring — General Manures — Nitro-
genous Manures — Phosphatic Manures — Potassic
Manures. Practical Work — The Food of Plants-
Experiments with Manures — Leguminous Plants . 122

CHAPTER VII

FLOWERS AND FRUITS

Parts of a Flower — Uses of the Parts of a Flower— Insects
and Flowers — Wind-Pollinated Flowers — Fruits and
Seeds — Dispersal of Fruits and Seeds — Variation in

CONTENTS xi

PAOE

Seedlings. Practical Work— Parts of a Flower— Ex-
periments in Cross-Fertilisation — Dispersal of Seeds —
Wind-Borne Seeds — Dispersal by Water — Dispersal by
Animals — Dispersal by Explosive Action . 139

CHAPTER VIII

WEEDS

Practical Work — Preserving Plant Specimens . 164

CHAPTER IX

ANIMAL PESTS OF PLANTS

Life-History of a Caterpillar — Life-History of a Beetle —

Remedies. Practical Work — Remedies . . .169

GLOSSARY ....... 179

APPENDICES—

I. Suggested Courses . . . .185

II. Apparatus and Materials Required . . .186

INDEX ........ 189

NATURE TEACHING

CHAPTER I

THE SEED

(S

IN all agricultural and gardening work, seeds are so
constantly employed for the purpose of raising new
crops that every one is more or less familiar with
them.

We know, as the result of experience, that if we sow
seeds we shall in the course of time obtain young plants
or seedlings, and that these, if properly looked after,
will grow into large plants, and in due course flower and
bear seeds themselves, from which a second crop of
plants can be raised. This order of events is the same
whether our experience has been gained by growing
poppies, mignonette, hollyhocks, etc., in the garden, or
wheat, turnips, and clover in the field, or whether we
have been practically engaged in starting a new oak
wood from acorns.

We have learnt also, as the result of our experience,
that each seed has apparently hidden away in it the
beginnings of a new plant of the same kind as that from

A

2 NATURE TEACHING

which the seed was obtained, and that if we wish to grow
bean plants we must sow bean seeds, and acorns if we
wish to raise oaks.

We know, also, that although a dry seed is to all
appearances a mere dead thing, it soon springs into life,
or germinates, if we place it in a warm place and give it
a supply of moisture.

Moreover, we are aware that even dry seeds cannot
be stored for a very long time without gradually dying,
for the farmer or gardener who is anxious to raise good,
full crops is careful to secure good seed, obtained usually
from the crop of the season before, and does not sow
any old seed which may be to hand.

This general knowledge is most valuable, inasmuch
as it is the outcome of the practical or experimental
work of ourselves, and of those before us who have
handed down their results. It is not, however, enough
in itself, and we should endeavour to understand how,
and as far as possible why, the events follow each other
with such certainty.

A correct knowledge of the seed and of the conditions
for its germination, and for the successful growth of the
seedling and plant, touches the very foundation of that
sound agricultural practice so essential to success at the
present time.

The Parts of a Seed.

In order to distinguish the various parts of a seed,
it is best to examine one which has begun to grow, or,
as is more commonly said, to germinate, for in this
condition the parts can be more easily separated and

THE SEED 3

distinguished. Among the simplest and most easily
understood seeds are any of the ordinary peas or beans.
An examination of a very young plant of the French or
kidney bean — one which has just made its appearance
above the surface of the soil — will reveal the following
parts : two thick leaves (in the case of the scarlet runner
and some others, these leaves do not come above the
surface of the soil); between these there is a very small
leaf-bud with minute leaves, whilst below there is a
stem which terminates in a root, the root itself being
branched.

The parts of the young bean plant should now be
compared with a bean seed which has not germinated,
but which has been soaked for a few hours in water in
order to soften it. The seed-coat will strip off without
difficulty, and it will then be found that enclosed by
the seed-coat is a structure which easily splits into two
halves, and a little thought will show that these two
halves correspond to the two thick leaves which have
been spoken of already. These leaves are called the
cotyledons or seed-leaves. Between the cotyledons there
will be seen a small curved body, one portion of which,
when the seed germinates, becomes the stem with leaves
upon it, while the remaining portion develops into the
root. These portions are known respectively as plumule
and radicle. With the help of a pocket lens, the
plumule is seen to consist of very small leaves folded
together. There thus exists in the seed a minute
plant with rudimentary root, stem, and leaves. When
seeds are placed under suitable conditions these rudi-
mentary organs grow, and the seed is said to germinate.

4 NATURE TEACHING

Plant Food in Seeds.

The first stages of germination take place at the
expense of the store of plant food which exists in every
seed. In the case of the bean, which has just been
examined, the store of plant food is contained in the
thickened seed-leaves. If some germinating kidney
beans, growing in soil, are observed from day to day,
it will be seen that the seed-leaves gradually become
smaller and smaller, and finally shrivel up. In the
scarlet runner a similar thing happens, although here
the cotyledons never came above the surface of the
ground. A great many plants with which we are
familiar have their supply of plant food for germination
stored away in the seed-leaves ; this, for instance, is the
case with all the peas and beans, with the seeds of
oak, apricot, cabbage, radish, lettuce, cucumber, orange,
and many others.

There are many seeds in which the store of plant
food for germination is not contained in the seed-leaves,
nor in any other part of the small plant in the seed, but
exists as a separate store. In these seeds we find
inside the seed-coat an embryo, as in the bean, but only
small cotyledons, and, in addition, a separate store of
plant food. These may be made out in the seed of
buckwheat,, marvel of Peru, etc., where the embryo is to
be seen enveloping, but perfectly distinct from, the store
of plant food which makes up the greater portion of
the seed. .

In wheat, barley, maize, etc., the embryo lies at one
side of the seed, near the pointed end (base), and easily

THE SEED 5

distinguishable as a white patch. In maize or barley
which has been soaked for a few hours in water, the
embryo may be readily separated from the rest of the
seed, when it will be seen how large a part of the seed
is occupied by the store of plant food.

This separate store of plant food is often spoken of
as the albumen* and seeds are described as albuminous
or exalbuminous in accordance with the presence or
absence of this albumeru The seeds of wheat, barley,
maize, all the cereals and grasses, beet, carrot, buck-
wheat, marvel of Peru, onion, and date, afford examples
of albuminous seeds.

If we now refer again to the seed-leaves or cotyledons
which exist in every seed, we have to note that the
embryos of some seeds have two cotyledons, as in the
case of the bean and buckwheat, while the embryos of
other seeds have only one. Barley, wheat, or maize may
be taken as examples of the latter class. In some
cases it is an easy matter to ascertain whether one or
two cotyledons are present in the seed, while in others
it is matter of some difficulty. It is found that the
presence of either one cotyledon, or of two cotyledons,
is usually associated with other constant characters of
plant structure to which fuller reference is made later.
Seeds with embryos having one cotyledon are described
as monocotyledonous, while those in which two cotyledons
are present are known as dicotyledonous.

* The term "albumen" is an unfortunate one, as the same
term is commonly employed to denote a large class of chemical
substances. There should be no difficulty, however, in under-
standing the limited sense in which it is employed here.

6 NATURE TEACHING

Germination.

When a gardener or farmer sows seeds, he takes
care to proceed in such a manner in preparing the soil
and placing the seeds in it as previous experience has
shown him produces the best results. It is well, then,
that we should learn what takes place during germina-
tion, in order that we may know what conditions are
essential to success.

If on alternate days a few seeds of various kinds of
beans are planted in moist soil, and this is continued
until those first planted have developed into small
plants some four or five inches high, an ample supply
of material may be to hand for purposes of study.

Take a bean, which has been soaked in water but
not planted, remove the seed-coat, separate the cotyle-
dons, and bring into view the body lying between them.
Next, dig up carefully one or two of each of the beans of
different ages and compare them with the ungerminated
seed. There will be no difficulty in recognising that
germination produces changes whereby that portion of
the embryo known as the radicle develops into the root,
whilst the plumule becomes the stem with its leaves. The
cotyledons become smaller and smaller as the develop-
ment of the young plant proceeds, the stores of food
which they contain being used by this young plant to
build up its own structures.

This is one of the simplest methods of germination ;
but we should observe that the young and tender plant
has certain definite objects to attain. The plantlet
must get out of the seed-coat, and it must be able to

THE SEED 7

force its way through the soil in which the seed is
sown.

Observation of germinating kidney beans shows that
the root, on its emergence from the seed, does not grow
straight down into the soil, but bends in an arch near the
seed and then grows straight downwards. This arch is
generally the first thing which makes its appearance
above the soil, and, from its form and structure, is well
fitted to thrust aside the particles of earth. After the
arch is formed, the young plant is firmly anchored in the
soil by means of the root.

The arch has now another duty to perform ; the
seed-coat still covers the cotyledons and the plumule ;
these must be liberated. The seed-coat is held fast by
the soil sticking to it ; the arch continues to grow in an
upward direction, and, as a result, the cotyledons are
withdrawn from the seed-coat, much in the same manner
as a hand is drawn out of a glove. When this is done,
the arch straightens out and the plant grows into an
upright position.

In order that the seed-Coat may be held firmly by the
soil and not be drawn out by the plant's movements
during germination, seeds are frequently provided with
projections, spines or hairs, which, becoming attached to
the soil, afford the necessary firmness of hold. In some
cases, for instance, linseed (flax) and cress, the seeds are
provided with a seed-coat which becomes mucilaginous
and sticky when wet, thus effecting the same purpose.

On looking over a plot where a number of beans are
germinating, it may often be noted that some of the
seeds have not been able to rid themselves of their seed-

8 NATURE TEACHING

coats, owing to the fact that the soil did not hold down
the coats sufficiently firmly, so that they were pulled up
when the plant tried to draw out the cotyledons. Such
plants are often greatly hindered in their growth by the
presence of these no-longer-wanted coats. Cases such
as this should be borne in mind in attempting to dis-
cover what are the uses of spiny or warty coats of many
seeds.

In some seeds, for example, scarlet runners, peas, and
acorns, the seed-leaves are not drawn out of the seed-
coats in the manner described, but remain below the
ground. The young stem makes its appearance above
ground in an arched form, but, in this case, the arch is
formed above the point of attachment of the cotyledons
to the plumule. The growth of the arch now merely
draws out the plumule with its tender leaves. The
young plant lives for some time on the store of food
in the cotyledons, which gradually become thin and
shrivelled, exactly as in the case of the French bean,
where, coming above ground, the changes in the cotyle-
dons are more easily watched.

The seeds of the vegetable marrow and cucumber
exhibit interesting peculiarities in their germination.
The root makes its appearance first, and assumes the
curved or arched form in a similar manner to that of the
bean. The seed being flat, usually lies upon one side.
On the other side of the arch, and quite close to the
small hole through which the root makes its appearance,
there is formed a protuberance. This protuberance
catches the lower edge of the seed-coat and holds it
firmly against the soil. The cotyledons, still within the

THE SEED 9

seed-coat, are soon thrust upwards by the curved form
of the growing root ; this leads to the splitting of the
seed-coat into two halves, whereby the young plant is
set free. It is worth observing that the protuberance is
only formed on one side, the under one ; and that if,
when germination has proceeded to a slight extent, the
seed be turned over so as to bring the upper side to the
under side, then a protuberance will form on the side
finally downwards. This will happen even if a slight
protuberance has begun to form before the turning took
place.

In the instances of germination already referred to,
the supply of plant food is stored in the cotyledons,
whence it readily passes to the growing parts of the
young plant. In those cases, however, where there is a
separate store of plant food, that is in albuminous seeds
there must exist some means whereby this food can be
made use of by the young plant. It will be well to
describe one or two examples showing how this is
accomplished.

The common buckwheat affords an interesting and
readily observed case. If some buckwheat is sown in a
pot of sawdust, seedlings can easily be obtained in
various stages of development for us to see that as in
the preceding cases the radicle first bursts through and
grows downwards into the soil. Above ground appears
the little stem, not as a mere arch as in the bean, but
curled round in a complete loop, bearing at the free end
the whole seed, with the cotyledons still inside. The
cotyledons remain enclosed for some time in the seed,
which fits them as a kind of cap. Slowly they throw off

10 NATURE TEACHING

the husk, and open out as a pair of green leaves. The
husk will then be found to be quite empty, all the food
it contained having been absorbed by the cotyledons and
passed on to the young plant. Whilst this is going on
the stem has also straightened out.

The onion has an albuminous seed. In germination
the young root first makes its appearance, and, immedi-
ately afterwards, there appears the lower portion of the
cotyledon. This assumes the arched form as described
in the case of other seeds; the tip of the cotyledon
however is not withdrawn, but remains for some time
within the seed-coat in contact with the supply of food
stored up there. Upon the portion of the cotyledon in
contact with this food there is formed what may be
described as a sucker, an absorbing organ, which takes
up the stored food arid passes it on to the growing
plant. When all the food store has been absorbed, the
cotyledon is withdrawn from the seed-coat and the
young seedling becomes erect, the cotyledon being now
green, and acting as an ordinary leaf.

A somewhat similar condition of things occurs in
the germination of the seeds of many palms, and may
be studied in 'the date. The germination of the seeds
of the date palm is of great interest, inasmuch as it
supplies an excellent illustration of the way in which
many plants overcome the difficulties of their surround-
ings. The date palm is well known as a plant which
can thrive in sandy, desert regions, where the water
supply is scanty. Most ordinary seedlings are delicate,
and easily killed if kept without water. How then
does the young date palm manage to survive? As the

THE SEED 11

seed germinates, it puts out a structure which bores
down into the soil like a root. As we shall see later,
this is much more than a root, and really consists of the
root, cotyledon, leaf-bud, and, in fact, the whole of the
young plant. The upper portion remains inside the
seed and gradually absorbs all the food contained in the
seed, passing it down to the young plant, which gradually
is thrust quite deep down in the soil. Here it forms its
roots, so that when, later on, the first green leaves
appear above the surface, the little seedling date palm
has well-grown roots, and can get water for itself from the
deeper layers of the soil, and is thoroughly able to exist
even through very dry weather, when many seedlings
would die. In this manner the seedling date grows at
the expense of the hard food-supply stored up in the
seed as the hard, horny substance which makes up a
date "stone."

The seeds of the castor-oil plant are albuminous ;
when germination takes place the albumen is withdrawn
from the seed-coat, together with the cotyledons, the
albumen remaining attached to the back of the cotyle-
dons. The plant food is then absorbed during the first
few days after germination.

The seeds of all the ordinary grasses and cereals are
albuminous. The manner in which the store of plant
food is absorbed during germination can be studied in
the case of barley and maize. Some grains of each
should be planted on three or four successive days, in
moist sand or sawdust, so as to furnish a number of
specimens in different stages of germination. Thdse
should then be compared with grains in an ungerminated

12 NATURE TEACHING

condition, and with some which have merely been soaked
for a few hours in water to soften them.

On examining the grains, the embryo or " germ "
may be seen as a white patch lying on one side of the
grain near the pointed end ; in the case of those grains
which have been soaked, the embryo can be readily
detached from the rest of the seed. The seed is mono-
cotyledonous, and careful examination of the detached
embryo shows that the single cotyledon does not grow
or extend through the seed-coat, but forms the means of
communication through which the reserve of plant food
passes into the young growing plant. The cotyledon,
here known as the scutellum^ lies upon the surface of the
albumen, which in these seeds consists almost entirely
of starch. As soon as germination begins, the scutellum
secretes a digestive fluid which converts the insoluble
starch into soluble substances, which are readily absorbed
by the scutellum and" passed on to the growing plantlet,
lying on, and attached to, the other side of the scutellum.
As the starch is dissolved and used up, the scutellum
presses forward into the vacant space, finally taking up
all the starch and leaving the seed-coat empty. While
this is going on, the young plant is growing in size,
thrusting its roots into the soil and its leaves into the
air, so that by the time the supply of starch within the
seed is exhausted it is able to obtain its own food.

PRACTICAL WORK

The following exercises are suggested in illustration
of the principles already discussed ; they may be per-
formed by the pupils themselves or by the teacher, and

THE SEED 13

used by him as demonstrations in his object-lessons.
They admit of considerable modification and variation,
and, in their present form, are merely intended to be
suggestive. The precise manner in which they are con-
ducted must necessarily depend on the circumstances
surrounding each class of students, but too much stress
cannot be laid on the advantage of the pupils actually
performing all the experiments for themselves whenever
there are no reasons rendering this quite impossible.

The Conditions of Germination.

Moisture, air, and warmth are necessary for the ger-
mination and continued growth of seeds. In order to
demonstrate this, take four rather small but wide-mouthed
bottles, two of which are furnished with good corks.
Label these bottles A, B, C, and D respectively. In A,
having first taken care that it is perfectly dry, place
some dry seeds (wheat, barley, peas, or beans), cork the
bottle, and seal with sealing-wax or beeswax. In B,
place two or three layers of wet blotting-paper at the
bottom, then put in the seeds, and cork and seal as
before. Treat C exactly as B, but leave the bottle un-
corked.

Place seeds in bottle D, and then fill the bottle com-
pletely with water, which has been boiled and allowed to
cool, to drive out the air it contains. By this means the
air originally in the bottle is displaced with water, and
now closing the bottle with a cork, we have the seeds
wet but with practically no air.

Put A, B, C, and D away side by side, preferably in
a dark place, and examine daily. It should be found that

14 NATURE TEACHING

in A the seeds do not germinate at all ; they have no
water at all, and very little air. In B the seeds have
water but again very little air; they will probably ger-
minate and grow for a short time, and then, having
exhausted the air, die. The seeds in C have water, and,
the bottle being open, air also. (The blotting-paper in
C should be kept moist by the addition of water from
time to time.) They should germinate and grow well.
Those in D, although provided with water, have no air.
They should grow but slightly, if at all. The experi-
ment has so far shown the necessity of water and air.
Keep careful notes of this experiment, recording the
number of seeds which germinate at all in each bottle
and the heights the seedlings attain.

In order to show the influence of temperature, take
two pots filled with soil, properly prepared for the recep-
tion of seeds (see p. 1 5). In each pot place two or three
seeds of several different kinds, for example, beans, peas,
barley, radish, etc. Label the pots, and place one out of
doors and keep the other indoors in a warm place, such
as in the kitchen, or warm school-room. Keep the soil
in both pots suitably moist. Note in your note-book the
date when the seeds were sown and the dates on which
the various seedlings first appear above the surface of
the soil. Measure the heights of the young plants at
regular intervals. Compare the rate of germination and
early growth of the plants in the pot kept warm and in
that exposed to cold, and draw conclusions as to the
effect of temperature upon plant life.

Note. — This experiment should be made between
the months of October and March.

OF

NIVERSITY]

J THE SEED 15

Raising Seedlings.

Observations are readily made on seeds sown in
boxes. For this purpose it is necessary to provide suit-
able boxes and material. The boxes should be shallow,
from 4 to 6 inches in depth, with sides securely fastened
so that they may bear the weight of the moist soil. A
number of holes, about half an inch in diameter, should
be bored in the bottom of each box in order to secure
free drainage. In addition to wooden boxes, useful seed
boxes may be made from large biscuit-tins.

The soil for filling the boxes should be prepared by
Sifting, first, through a sieve having holes of about an
inch in diameter ; this removes the large stones : the
sifted soil should next be passed through a second sieve
having holes of about a quarter of an inch in diameter ;
this separates the gravel from the fine soil. A small
quantity of soil should be passed through a still finer
sieve. It is advisable to prepare a good supply of soil
and to store it in a dry place, so that, whenever required,
stones, gravel, or fine soil may be available.

A tool is useful for levelling and lightly pressing down
the soil as it is placed in the boxes. This is simply
supplied by a piece of smooth board, half an inch in
thickness and about 8 by 4 inches in area, with a suit-
able knob or handle fixed on the back.

A supply of dry, finely-chopped grass (for instance,
lawn mowings) or preferably coco-nut fibre refuse, is
also required.

To prepare a box for sowing seeds, place at the
bottom a layer about I to 2 inches deep of the

16 NATURE TEACHING

stones separated from the soil by means of the coarsest
sieve. Over the stones place a layer of about the same
depth, of coco-nut fibre or of the dry chopped grass, to
prevent the finer material choking up the spaces between
the stones. Over the fibre or grass put a layer of the
gravel, and fill up the box with sifted earth. Level this
last layer by means of the tool, at the same time com-
pressing the earth slightly. If the soil is very dry it is
advisable to water it now, as less damage is likely to be
done than by heavy watering after the seeds have been
sown.

The seeds may now be sown, the method of proced-
ure depending on the size and kind of seed. If small
seeds, like lettuce, are being sown, all that is necessary
is to scatter them evenly and thinly over the surface, and
then to distribute a layer of the very fine soil over the
seeds, sifting the soil lightly on and adding only so
much as is required to cover the seeds without burying
them at all deeply. If larger seeds, such as peas or
beans, are being sown, place them in shallow furrows,
lightly marked out with a piece of stick or with the
finger, and cover with very fine earth as in the previous
case. Very large seeds, such as horse chestnuts or
acorns, may be placed in position, buried by pressure
about half their own depth in the soil, and then covered
with moderately fine earth.

Everything being completed, press the soil gently
down with the tool. This pressing down has the effect
of producing a firm seed bed which is necessary, in certain
instances, to enable the young plants to free themselves
from their seed-coats. It also serves to keep the top

THE SEED 17

layers of soil moist, for, if left loose and dusty, they
would become dry, and the seeds would suffer from lack
of moisture.

After the seeds have been sown the box must be
watered. This requires care, or delicate seeds will be
washed out of the ground. A watering-can having a
rose with very fine holes, should be used, and the water
only allowed to fall very gently.

The boxes should be placed in a shady place where
they are screened from heavy rain and excessive sun-
shine. It is often of advantage to cover the box with a
sheet of glass. In this way the air is kept moist, and
germination usually hastened. The glass also prevents
damage by rain if the boxes cannot be placed under a
roof.

In order to observe the effect of a firm seed bed sow
onion seeds in two boxes or pots. Compress the soil of
one firmly after sowing the seeds. In the other cover
the seeds lightly with sifted soil, avoiding carefully any
compression. Tend the boxes or pots carefully, and
note the difference in the manner the two sets of
seeds germinate and the seedling grow, recording your
observations in your note-book and making drawings
and diagrams of the seedlings as they grow. Similar
experiments may be made with seeds other than onion.
These experiments should also be tried in garden beds
which are left to receive no watering beyond the natural

rainfall.

Seed Beds.

Seeds are generally sown in garden beds, or, young
seedlings raised in boxes, are transplanted to beds. The

18 NATURE TEACHING

preparation of a seed bed requires some care. Select a
spot, sheltered as much as possible from the sun and
wind, and near the water supply ; remove all the weeds
and fork the ground to a good depth. Mark out, by
means of a line (see below), the paths which shall
separate the beds ; these paths should be about 2 feet
wide, while the beds themselves should be from 3 to 5
feet wide. Having marked out the position of the paths,
and while the line is still stretched in place, remove
with a spade the soil from the paths and distribute it
evenly over the beds. If this is properly done the paths
should now be about 6 or 8 inches below the level of
the beds. Remove all stones with a rake, and so make
up the beds that the centre of each is slightly higher
than the sides. This is of great importance, as it allows
water to drain off freely, for nothing is more detrimental
to good gardening than to have water lying in pools on
the beds.

When working on a garden bed avoid walking upon
it When weeding or planting, it is often necessary to
place the foot upon a bed in order to reach a
particular spot ; in this case use a foot-board, which is
simply a narrow piece of board which can be laid across
the bed, and upon this only should any one be permitted
to place his foot when working. Another appliance in
frequent use is a line for marking. A line consists of a
length of moderately stout cord having a pointed stake
about 1 8 inches long attached to each end. It is well
to have two lines — a long one for laying out beds,
paths, etc., and a short one for working across beds.
After use, lines should always be neatly wrapped

THE SEED 19

around their stakes, and carefully put away in the
tool-house.

When seeds are to be planted in a garden bed
proceed as follows : — Stretch a line across the bed, and,
with the hand, open a furrow in the soil along the line,
making the furrow of a depth suitable to the kind of
seed to be sown, 2 inches deep for large seeds, an inch
or less for small ones. Having made one furrow, move
the line the required distance, fix it in position, mark
out another furrow, and so on. In regulating the
distance between the rows it is convenient to have a
piece of stick of the same length as the distance the
rows are to be apart, and to use this as a measure to
mark the new position of the line every time it requires
to be moved ; this secures regularity and neatness of
work. The furrows being opened, scatter the seeds by
the hand along the bottom of each, care being taken to
scatter them evenly and not too thickly. When the
seeds are in position, gently draw the soil over them,
and after they are covered apply a little pressure to
render the soil around them firm.

Pots are sometimes used for sowing seeds in, par-
ticularly large seeds. They are also of use when the
young plants are to be transferred subsequently to
another spot, as, for instance, cucumbers. Pots are pre-
pared for seed sowing in the same manner as boxes.
In the tropics, pots made of bamboo are frequently
used, and are indeed invaluable. They are made from
large bamboos by cutting them across with a saw just
below each node or joint ; the division or partition found
at each joint thus forms the bottom of the pot, and when

20 NATURE TEACHING

a hole has been made in this to permit of drainage the
pot is ready for use.

Observations on Seedlings.

The pupils should sow all, or at any rate the greater
number, of the seeds in the list below, the teacher
deciding according to circumstances whether they are
to be sown in boxes, pots, or beds. All the various stages
in their germination must be watched, and the observa-
tions recorded in suitable note-books, drawings, even if
only roughly diagrammatic, being insisted on. As
germination proceeds a few of the seeds should be
removed at intervals for purposes of study and observa-
tion. At this stage of the pupils' work the object is not
to raise crops, but to understand how crops grow. The
observations recorded should determine the method of
emergence of the young plant, the curves assumed by
the young root and stem, the manner in which the coty-
ledons are disposed, whether the seed is albuminous or
exalbuminous, and, if the latter, how the reserve of food
material is absorbed by the -growing plant. Careful
attention should be given to any special contrivances to
enable the young plant to escape from the seed-coat, and
the existence of any special means whereby the seed-
coat is held down by the soil while the young plant is
being withdrawn.

Upon examining seed beds containing germinating
seeds, it may often be noticed that a few of the young
plants do not germinate properly. They may fail to rid
themselves of their seed-coats or meet with other
untoward experiences. These cases, in particular,

THE SEED 21

should be observed, as they often throw considerable
light on the methods of germination and impress the
mind with the importance of what may, at first sight,
seem trivial and unimportant details.

After some of the better known kinds of seeds have
been studied, much instructive information may be
gained by collecting seeds of wild plants and studying
their methods of germination. In addition, observations
serving to develop the pupils' powers of perception and
reasoning may be made upon germinating seeds and
seedlings found in a state of nature.

The following list of seeds for study is merely
suggestive ; examples should be selected from different
parts of the list, and the seeds should not be studied
in the order in which they are arranged : —

Peas and Beans Oak (Acorn)

Scarlet Runner Ash

Haricot or Lima Bean Buckwheat

Broad Bean Sycamore or Maple

Garden Pea Marigold

Sweet Pea Tomato

Vetches Barley

Cabbage .Wheat

Radish Maize

Cress Onion

Cucumber or Marrow Castor-oil

Horse Chestnut Date Palm

Seeds of all these plants can be easily obtained. In
the case of dates the seeds from the fruit as sold for
eating purposes are quite good ; it must be remembered,
however, that they take several months to germinate,
preferably in a pot in a greenhouse or warm room,

22 NATURE TEACHING

Testing Vitality of Seeds.

The following method of testing the germinating
power or vitality of seeds is easily carried out, and affords
results of practical value. Pupils should test the vitality
of half a dozen or more of the common kinds of garden
seeds purchased locally. (These experiments should be
reserved for senior pupils and advanced classes.)

"A cheap and convenient form of apparatus for
testing the vitality of seeds at home is the following :—
Choose two earthenware plates of the same size. Cut
out two circular layers of flannel somewhat smaller than
the plates. Between the two layers place 100 seeds of
the variety to be tested. Moisten the flannel with all
the water it will absorb. The two layers of flannel are
placed in one plate and covered with the other and set
in a warm place. If the flannel is thin, several pieces
should be used in order to absorb sufficient water.
Other kinds of absorbent cloth or blotting-paper can be
used, but thick flannel is rather more satisfactory. At
the Kansas Experiment Station we have used damp
sand for a seed bed with good success. . . . The flannel
should be kept moist by the addition of more water
when necessary. Some seeds will commence to germi-
nate on the third day. Each day an examination should
be made, and those seeds which have germinated should
be recorded and removed. For practical purposes, two
weeks is a sufficient time for the test. The results
obtained may be considered as representing the per-
centage of vitality under favourable conditions."

" Grass seeds require as much as three weeks, and

THE SEED 23

seeds of some trees a still longer time. Beet balls
contain from three to seven seeds. With very small
seeds it may be necessary to provide for the circulation
of air by placing small pieces of wood between the
layers of cloth among the seeds. With most varieties
of garden plants the majority of seeds should germinate
within a few days after the first sprout appears. If the
period of germination extends over a longer time it
shows that the vitality of the seed is low. Seeds of the
carrot family and some melon seeds may not show as
high results in the germinating dishes as they do in the
ground."

In good sound seeds the following numbers per
cent, should germinate («): —

(a) From Year-Book, U.S. Department of Agriculture, 1896.

. 90 to 95

. 80 „ 85

• 7o „ 75

• 7o „ 75

• 93 „ 98
. 90 „ 95
. 85 „ 90
. 90 „ 95
. 90 „ 95

* Each beet fruit or " ball " is likely to contain from three to
seven seeds. One hundred balls should give at least 1 50 sprouts.

Barley

. . 90 to 95

Oats .

Beans

• 90 „ 95

Onion

Beet *

150

Parsley

Cabbage .

. 90 to 95

Parsnip

Carrot

. 80 „ 85

Peas .

Clover

. 85 „ 90

Radish

Cucumber .

. 85 „ 90

Tomato

Lettuce

. 85 „ 90

Turnip

Mustard

. 90 „ 95

Wheat

CHAPTER II

THE ROOT

WE have already seen that the first thing to make its
appearance when a seed germinates is the root. This
is at first usually white and tender, but as it grows older
often becomes hard and woody, and covered with a
brown bark. The root may also increase in thickness
to a very considerable size.

If very young roots are examined they will be
found to be clothed with fine down or hairs near their
extremities. Owing however to the very delicate
character of these fine hairs- it is not always easy to see
them, for they are injured if the root is at all roughly
dealt with. These hairs may be seen to great advantage
on the roots of seedlings of barley, Indian corn, etc.,
which have been grown in a moist atmosphere. On
examining such a root it will be noticed that the tip
and the portion immediately behind it is quite bare and
smooth ; this, as we shall see later, is the growing
region. Then follows a downy-looking portion, the
character of which is due to the presence of large
numbers of minute root-hairs ; this is the absorbing
region. The older portions of the root, like the youngest

24

THE ROOT 25

part, are completely free from root-hairs. When a very
young seedling is pulled up from out of sandy soil it
frequently happens that a considerable quantity of sand
remains attached to the root, owing to the root-hairs
adhering firmly to the grains of sand with which they
were in contact.

The end or tip of a root is soft and tender, making
one wonder how so delicate a structure is able to thrust
itself through the hard, rough soil. Careful examination
will show that the tip of every root is covered with a
little cap or shiejd which serves to protect the point
from injury. This root-cap is, in many plants, not very
easy to see without the use of a lens, but may often
be observed in roots growing in water, for instance,
those of the frog's-bit, duck-weed, etc. The screw-pine
(Pandanus), to be seen at many florists and in almost
every botanic garden, throws out a number of roots
from its stem. These roots grow downwards towards
the ground, and, if their tips are examined, they will be
found to be covered with well marked root-caps. These
illustrate remarkably well the nature of the appendage to
be found at the extremity of most roots, including even
their finest and most minute branches.

Roots usually grow down into the soil, throwing out
numerous branches, and permeating the soil with a
network of fine rootlets, each provided with root-hairs
and terminating in a root-cap. The main root exhibits
a strong tendency to grow vertically downwards, in
response to the pull of gravity. This can easily be
.proved by placing a growing seedling so that the main
foot lies horizontally. If this is done it is found that

26 NATURE TEACHING

within a few hours the end of the root bends so that
once again the tip is directed vertically downwards. A
simple experiment such as this is sufficient to show that
plants are not mere passive living things, but can
control the movements of their parts almost as if they
possessed senses similar to those of animals.

Roots increase in length by the addition of new
material at their ends ; the older parts may grow in
thickness, but they do not increase in length. Indeed,
a moment's consideration will show that this must
necessarily be the case, for if roots were to grow in
length anywhere but at their ends they would tear off
their branches, which are firmly embedded in the soil.

Uses of Roots.

Roots have several uses : they fix the plant firmly in
the soil, they absorb water together with the nutriment
which plants derive from the soil dissolved in it. This
absorption of water is only effected by the younger
portions of the roots being .practically confined to the
root-hairs. The region, therefore, which bears the
root-hairs is the absorbing region, and this fact explains
the importance of the young roots and why plants
suffer if these are unduly disturbed or injured. The
older parts of the root have no power of themselves to
take up water and plant food. They are of use as
mechanical supports, and also as the means whereby
the water taken up by the absorbing region is passed
on to the stem and leaves above ground.

Roots frequently act as storehouses of plant food,
particularly in the case of biennial plants. Biennials

THE ROOT 27

are plants which require two years to complete the
cycle of their lives. They usually produce during the
first year an abundance of leaves but no flowers. These
leaves manufacture plant food, in the form of starch or
sugar, in excess of the plant's immediate needs, and this
surplus food is stored away in the roots which usually
become very much enlarged. On the approach of
winter the leaves die down, but the roots remain in the
ground in a dormant condition. In the spring of the
succeeding year the plants put forth new leaves and
finally flower and produce seed, and, in carrying on
these processes, the store of food in the roots is
drawn upon so that by the time the seeds are ripe the
roots are practically exhausted. After the seeds have
been dispersed the plants die. This condition of things
may be well seen in such plants as beet, carrot, and
turnip. In agriculture man takes advantage of these
plants storing up food, and, collecting the roots at the
end of the first year, devotes their hoarded-up food to
his own uses.

The observations made on seedlings have shown
that the roots of a plant usually arise from the radicle
of the little plant in the seed. In many plants, however,
roots arise not only in this manner but also from stems.
A good example is the ground ivy, which puts down
little bunches of roots from its stem as it trails over the
ground. It is obvious that these roots carry on the
ordinary work of absorption of water, because if the
main root dies or is cut away the plant is unaffected.

In some plants the roots formed above ground are
also of use as supports ; thus in the Indian corn a number

28 NATURE TEACHING

of roots arise from the stem, at some distance above the
soil, grow downwards and anchor the plant firmly. In
the screw-pine such roots are still more obvious, and
form curious, stilt-like supporting structures. The ivy
furnishes another excellent example of adventitious roots
borne on the stem. In this case they are of assistance
to the plant, supporting it when climbing up trees, walls,
etc.

In the case of many plants, a portion of the stem,
separated from the parent plant, so that it no longer
receives supplies of water and food, shows a tendency to
attempt to save its life by producing roots of its own.
In this effort it will usually be successful if it happens to
be placed in a moist position. A piece of watercress
placed in a bottle of water quickly develops a number of
adventitious roots. Full advantage is taken of this
tendency by gardeners and agriculturists. Many orna-
mental plants are propagated in this way. Pieces of the
stem are cut ofT and placed in moist earth, when new
roots soon make their appearance, usually from near the
cut end of the stem, and a new plant is obtained. Roses,
geraniums, chrysanthemums, and a number of other
.garden plants are regularly propagated in this manner.
.In tropical countries this method of propagation is used
for many important food crops, for example, sugar-cane,
sweet potato, and cassava (the source of tapioca).

Nor is it only from stems that roots may be developed.
Some leaves, when plucked from their parent plant and
laic! on moist soil, will throw out roots and leaf-buds, so
that, in a little time, a number of young plants may be
raised from a single leaf. The leaves of" fibrous-rooted "

THE ROOT 29

begonias readily form roots when placed under suitable
conditions, and are commonly propagated in this way.

Some plants grow as parasites upon other kinds of
plants ; they thrust their roots into the stems of their
hosts, and live by robbing them of sap, thus weakening
and often killing the plants on which they grow.
Examples of parasitic plants are the strange, thread-like
yellow dodders (Cuscuta), often found injuring clover and
flax, and the mistletoe common in many parts of Britain
on apple and other trees. The method by which this
plant spreads from tree to tree is interesting (see chapter
on Fruits).

The roots of these parasitic plants have no .root-caps
and no root-hairs, these structures being unnecessary
under the peculiar conditions in which these roots grow.
The dodder is at times a troublesome pest on clover, but,
as a rule, parasitic plants are not serious enemies to the
farmer in temperate climates, although they often are so
to the tropical cultivator of cocoa, oranges, etc.

PRACTICAL WORK

Dig up several germinating seeds and young seed-
lings, and examine their roots. Good examples may be
obtained by sowing beans, peas, barley, wheat, etc., at
intervals of a day in a box of moist sawdust or sand.
Water the seeds as required. In warm weather they
will be ready in about a week. In the winter a few days
longer will be required. Observe that plants with two
seed-leaves put out a main, or primary root, which soon
forms numerous branches ; on the other hand, plants
with only one seed-leaf show no main root, but a number

30 NATURE TEACHING

of fine roots more or less equal in size. A comparison
of the root systems of young beans or peas and barley
and wheat will make this difference clear. Make sketches
of all the seedlings examined.

Root-Hairs.

Take a small wooden box, place at the bottom two
or three layers of wet blotting-paper, and then some
barley grains which have been soaked in water for about
twelve hours. Cover the box with a sheet of glass, and
put it on one side ; examine the box from time to time,
and add more water if the blotting-paper should become
at all dry. At the end of two to four days, according to
the season of the year, root-hairs should be present in
abundance, and there should be no difficulty in making
out the characters which have been previously described.
Make sketches of two or three seedlings of different ages,
showing exactly the position of the root-hairs in each
case.

Pull up, very carefully, seedlings which have been
grown in sandy soil ; grains of sand are generally found
adhering in great numbers to the region on which we
now know the root-hairs occur. Wash off this sand very
carefully by gently moving the roots about in a tumbler
full of water. Whilst the roots are suspended in the
water, examine them also for root-hairs. Draw a seed-
ling before and after washing the sand off.

Root-Caps.

Examine, if an opportunity occurs, the aerial roots of
the screw-pine, and observe their root-caps. Then look for

THE HOOT 31

similar, but much smaller and more delicate, structures
on the roots of other plants, such as pea and bean
seedlings. These may often be more easily seen when
the roots are held up against the light, and a magnifying
glass will be found very useful. Examine also roots
growing in water ; some water-plants have no root-caps,
but the frog's-bit (Hydrocharis\ if obtainable, furnishes
good examples, as also do the duck-weeds (Lemna\ so
common on ponds. These roots should be examined
whilst still in water, Grow seedlings and cuttings in
water, and examine their roots for root-caps.

Make simple outline drawings of all the plants

examined.

Growth in Thickness.

The youngest part of a root is usually the thinnest ;
this is readily seen by observing any of the seedlings
already obtained. In most of the plants which have
only one cotyledon the roots soon stop growing in
thickness, and accordingly all the older roots are of
a uniform size : see plants of barley, wheat, maize,
grasses, etc.

In dicotyledonous plants, on the other hand, increase
in thickness may go on for a very long time, and the
roots in consequence become very thick. Take any
opportunity of observing the roots of trees, for instance,
elm, oak, beech, apple, etc. Good examples may often
be seen in lanes with steep banks, where the roots are
frequently left exposed, owing to the soil being washed
away. The main roots are often as thick as the main
branches of the stem. Interesting cases showing an
enormous increase in the thickness of roots can readily

32 NATURE TEACHING

be seen in plants of radish, turnip, carrot, and beet
These plants are biennials (see page 26).

Sow a few seeds of radish, turnip, or beet in a garden
bed, or in a box, between the months of April and June.
Towards winter the leaves die down, and it can be seen
that by that time long roots have been formed under-
ground. The roots may be allowed to remain in the
ground, or, if more convenient, they may be dug up,
labelled and stored for the winter in a moderately warm
dry place, where they run no risk of being frozen. In
April or May weigh the roots and plant them in the
ground or box again, and water as required. In time
new leaves should be formed, to be followed later by
flowers and seed. When the seed is ripe, collect it for
future use, then dig up the roots, dry them as before, and
then weigh and compare their weight with their original
weight when planted in the spring. The roots should, of
course, be marked throughout the experiment with dis-
tinctive numbers. Careful notes should be made of the
facts observed, also of the character of the roots when
planted out, and after the plants have flowered. Draw-
ings are very important to show the changes which go
on in the roots.

Growth in Length.

Germinate some beans in moist sand or sawdust, and
allow them to grow until their roots are about two inches
long ; wash carefully a number of the seedlings, and
select one which has a straight, well-formed root, perfectly
free from injury.

Lay the seedling on a piece of damp blotting-paper,

THE ROOT

33

and, alongside it, a piece of cardboard, so arranged that
the surfaces of root and cardboard are on the same level.
With a fine camel's hair brush and Indian ink make a
number of fine lines on the root, and a corresponding set
on the cardboard, commencing as close to the tip of the
root as possible, and continuing them backward for about
one inch. These lines should not be more than £th inch

FIG. i. — Mode of
measuring growth
in length of the
root of a germinat-
ing bean.

FlG. 2. — Germinating bean
fixed in a glass jar by
means of a pin passing
through the cork. The
root is marked into equal
transverse divisions at the
beginning of the experi-
ment. After a period of
about twenty-four hours
the region of most active
growth may be ascertained.

apart, and in marking them great care must be taken not
to injure the root. Place each bean in a thistle-funnel
standing upright in a tumbler or bottle of water, and
cover the top of the funnel with a watch glass, or small
piece of wood (see Fig. i).

As an alternative method, pin the seedling, with the
root hanging vertically, on the inside of a box or bottle,
the atmosphere in which is kept moist, as in the experi-

C

34 NATURE TEACHING

ment with germinating barley. The best method of
fastening the seedlings is to pass an ordinary pin through
the two cotyledons, taking care not to injure the young
stem or root (see Fig. 2).

Examine after twenty- four hours, comparing the
marks on the root with those on the card.

It should be found that the first one or two divisions,
near the tip, have not altered in length ; that the next
ones have grown a great deal ; while those still further
back have remained stationary like those at the tip.
Make a drawing of a root as first set up, with the marks
at equal distances, and after one, two, and three days,
showing exactly the position of the marks at each of
these times.

From this simple experiment we learn that in a
root the greatest amount of growth is not at the
apex, but some little way behind it, so that the root-
tip protected by its root-cap is, as it were, driven
down through the soil by the rapid growth of the
portion just behind it.

Absorption by Roots.

Take two small bottles having short, narrow necks,
and fill both with water. To one add a few drops of
eosin solution or a little red ink, just enough in either
case to colour the .water distinctly red. To the second
bottle add a little carmine which has been previously
rubbed to a thin paste with water. Take two seedlings,
such as those previously examined for root-hairs (p. 30),
and fix one in each bottle so that its roots are immersed
in the liquid. This may be done by wedging them

THE ROOT 35

in position with some cotton-wool. After a day or so
remove the seedlings, and gently wash them in some
clean water to remove any colouring matter on their
outside. Then cut them lengthwise and across. Note
that the one placed in the weak eosin or red ink has
become red inside, whilst the one from the carmine has
not. The explanation of this difference is to be found
in the fact that eosin and red ink are soluble in water,
whilst carmine is not, but remains in the water as very
fine, solid particles. The red solution can pass into the
roots, but it is not possible for any solid particles, how-
ever small, to make an entry.

This experiment has a very important bearing on
the question of the relative value of manures and other
forms of plant food.

Roots and Gravitation.

Take a wide-mouthed square bottle of clear glass (for
instance, a sweet-bottle) and pour in it a small quantity
of water. Obtain a good cork to fit the bottle, and pass
through it a fine knitting-needle. Take a bean which
has been allowed to germinate in damp sand or sawdust,
and has a root about one inch long, and fix it on the end
of the knitting-needle so that its root points downwards.
Place the cork with the bean in the bottle, and allow it
to remain for twelve hours. The root continues to
grow straight downwards. Now lay the bottle on its
side, when the root will lie horizontally. Examine at
frequent intervals (for instance, of two hours), and note
that the direction of the root changes, the tip soon
curving round until it comes to point vertically down-

36

NATURE TEACHING

wards. The position of the bottle may now be changed
again, and once more the root will be found to bend
round into the vertical position.

A round bottle will serve almost as well, but care
must then be taken to prevent it rolling.

Another simple and equally serviceable method is
to use a box with a movable front. The atmosphere

FIG. 3. — Germinating beans fixed on the sides of a box with
a removable glass front. The beans are fixed with their
roots pointing: in different directions, but at the end of a
few hours the tips of both roots will be seen to have
curved round until they come to point vertically down-
wards.

in the box should be kept damp by means of wet
sponges. Pin the seedling bean to the back of the box,
and turn the box into various positions, as in the case
of the bottle (see Fig. 3).

Careful drawings should be made showing the
position of the root at first, and at intervals after the
bottle or box has been turned round.

THE ROOT 37

Roots and Water.

Sow some peas in an ordinary sieve filled with
damp sawdust, and hang the sieve up. The roots of
the seedlings grow down in the ordinary way, and at
length project through the meshes of the sieve. Then,
however, they usually change their course, and turning
horizontally, they creep along the underneath surface
of the sieve, or even grow vertically upwards into the
damp sawdust. The attraction of the roots for water
here overcomes their tendency to grow downwards.

Make careful drawings of the apparatus, and of the
results noticed.

Propagation by Cuttings.

It is convenient to grow small cuttings in boxes and
to transplant them afterwards into garden beds. Boxes
for this purpose are prepared in the same manner as
boxes for seed planting, but it is desirable to use either
sand or very sandy soil.

Having prepared a box, proceed to plant cuttings of
such plants as roses, geranium, willow, lilac, or coleus.
Ascertain from a gardener what cuttings " strike " easily.
Select a branch which is fairly firm and woody, but not
too young and soft. Cut it into pieces of 4 to 6 inches
in length, making the cut at the lower end close below a
node or joint, as it is from the nodes that roots arise in
the largest numbers. Cut off most of the foliage in
order to reduce the loss of water which takes place from
leaf surfaces (see chapter on leaves), and place the
cuttings in the soil, embedding them to a depth of from

38 NATURE TEACHING

two to three inches. Compress the soil firmly around
the cuttings, for if the soil remains loose the cutting will
suffer from lack of moisture. The work of planting
cuttings is much facilitated by using a piece of wood
about six inches long and about the thickness of one's
little finger for making the hole in the soil to receive the
cutting, and for compressing the soil around its base.
Water and tend the boxes, as in the case of seeds.

Plant a number of cuttings so as to provide material
for examination. At short intervals remove one or
more cuttings from the soil, and note carefully the
changes which have taken place ; these examinations
should continue until the relationship of the resulting
new plant to the cutting is clearly established. Sketches
or diagrams should accompany all the notes.

Place cuttings of watercress and coleus in bottles of
water. After a time, roots will develop, and their growth
and character may be observed. It is convenient to use
a clear bottle wrapped round with paper or cloth to
exclude the light.

Branches of shrubs will frequently take root if they
are fastened down on moist soil. By means of suitable
pegs, secure two or three branches of a rose, or other
tree, firmly upon the ground, covering them with a little
soil where they touch the ground ; water and tend care-
fully. The branch will after a time be found to have
rooted, and may then be severed from the parent tree and
planted in another spot. Rooting may be encouraged
in this operation by removing a narrow ring of bark at
the place where the branch touches the ground.

When valuable trees are to be propagated, and it is

THE ROOT

39

important that no risk be run of the cutting dying, the

last plan may be modified as follows. On the rose,

gooseberry, lilac, or other shrub which it is desired to

propagate, select a branch which is easily accessible, and

from it remove a ring of bark, right round the stem, about

half an inch in width. Have ready a flower-pot, sawn

lengthways into halves, or a small wooden box with one

side removed and a slot in the

bottom to admit the branch, as

shown in Fig. 4. Place the pot in

position round the stem where it

has been prepared, bringing that

part of the stem from which the

bark has been removed, to about

the middle of the pot Tie the

two halves of the pot together, and

secure it firmly in its place by FIG. 4.— Box with top

. . . and one side removed,

fastening it to a stake driven in and slot cut in bottom
the ground. Everything being now Skl^top.25?
in position, put a little dried grass
or coco-nut refuse at the bottom of
the pot and fill up with soil ; keep
the pot watered. After the branch has been for some
time in the pot, begin the process of severing it from the
parent plant by cutting a small notch in it a few inches
below the bottom of the pot ; after three or four days
deepen this notch and repeat the process at intervals
until complete severance is effected. The branch should
now have rooted and become an independent plant which
may be planted in a suitable place.

Peg down on moist sand some leaves of "fibrous

and the box filled with
soil the front should be
slid in along grooves in
the sides.

40 NATURE TEACHING

rooted" begonias, the veins of which have first been
nicked on the lower side with a penknife. The pot or
box should be covered with a sheet of glass, and lightly
watered occasionally as found necessary. In the course
of a week or two roots will begin to be formed at the cut
places, and rough wart-like outgrowths to appear on the
upper side. From these small leaves are later formed,
and develop into little plants. This method is employed
for the propagation of these plants, and is of especial
interest in showing that in some plants, at any rate, roots
and even complete plants are formed by leaves.

CHAPTER III

THE STEM

IN the previous chapter, although attention has mainly
been directed to the root, it can scarcely have escaped
notice that most of the plants examined are made up of
two well-marked and very distinct portions — (i) the
underground root, and (2) the aboveground stem bear-
ing leaves and flowers, and often for convenience spoken
of as the " shoot."

It is true that in some plants — for example, the house-
leek and primrose — the stem is exceedingly short, so that
the leaves appear to spring almost directly from the
ground. In other cases, for instance, in climbing plants
such as the hop, scarlet runner, etc., the stems are very
long and thin, and the same holds good for many creep-
ing plants like the couch grass.

Stems also vary greatly in another respect. Whilst
young they are almost all soft and green ; some remain
permanently in this condition, but others become hard
and woody with age. The comparison of young and old
shoots of elder, and young and old garden balsams illus-
trate this point very well. Putting aside for the moment
all these differences, we may say that plants in general

41

42 NATURE TEACHING

are made up of the underground root, and the above-
ground shoot bearing leaves, flowers, and fruit Root
and shoot are distinct even whilst the young plant is
still contained in the seed, being represented there, as we
have learnt, by radicle and plumule respectively.

The leaves are usually arranged on the stem in a
definite manner ; the places on the stem from which the
leaves spring are known as \hzjoints or nodes, and the
interval between any two nodes is an internode. Nodes
and internodes may be very clearly distinguished on
most growing shoots, e.g., roses, elder, privet, etc.

On examining any leaf-bearing stem it will be
noticed that the oldest leaves are at the base, and that
as we approach the summit of the stem the leaves get
younger and younger. At the apex itself we find the
youngest leaves, often more or less closely packed
together to form a leaf-bud. Similar but smaller leaf-
buds are usually to be found lower down the stem,
situated just above the place where a leaf joins the stem ;
it is very general to find one to each leaf.

In the majority of plants the stem is the above-
ground portion, the root only being below ground.
This, however, is not always the case, and a few of the
more important exceptions will be considered later.

Uses of Stems.

One of the most important functions of the stem of
a plant is to support the leaves and display them to the
air and light in the best possible manner for the work
they have to do. Careful observations should be made
of the arrangement of the leaves on — (i) upright grow-

THE STEM 43

ing plants ; (2) climbers against walls, trees, etc. ; (3)
plants which trail along the ground ; (4) plants in which
some of the branches are upright whilst others lie more
or less horizontally. The privet may be taken as a
good example of the last class. On the upright grow-
ing shoots the leaves are arranged all round the stem,
so that we cannot say which is the upper and which
the lower side of the shoot. If, however, we examine
a shoot growing horizontally, we at once notice that all
the leaves are twisted round to one side, so that on
looking from above we see only the upper sides of
leaves, whilst from beneath only the under sides. Here,
then, we have apparently a distinct upper and lower
side to the branch. Still more careful examination,
however, particularly of the tip of the same branch,
will show that the leaves arise exactly as on the
upright-growing shoots, and twist later into their final
positions. Many creeping plants — e.g., ground ivy,
creeping jenny, etc. — also show very nice arrangements
to prevent the leaves shading one another, and in the
practical work great attention should be paid to them.

Stems, like roots, often serve as storehouses of food.
The majority of the stems which serve as storehouses
grotf partially or entirely beneath the surface of the soil,
probably to protect the valuable stores of food they
contain from injury and cold. In general appearance
these underground stems resemble roots, indeed in some
cases it is difficult to distinguish them from roots. It
may, however, be taken as a general rule that a stem-
whatever use it may serve — always bears leaves. The
examination of the examples given below will show us

44 NATURE TEACHING

that we do not find green leaves in every case, as in
underground stems the leaves are more commonly
reduced to dry, scale-like bodies.

The iris or flag, and Solomon's seal afford good
examples of stems of this kind, running horizontally in
the ground, bearing scale leaves, leaf-buds, and roots.
Stems of this nature are usually spoken of as rJiizomes.
Those leaf-buds which grow above the surface of the
soil form green leaves, but the underground portion of
the stem bears nothing but dry scales.

A potato is an enlarged and swollen stem, and not a
root. Leaves are almost absent, being represented only
by the " eyes? which are in reality leaf-buds, as is easily
seen by keeping some potatoes in a damp place for a
time, when the " eyes " will grow, developing finally into
well-marked stems bearing leaves. Stems of the nature
of the potato are known as tubers. The Jerusalem
artichoke is interesting, as its underground stem, with
its very well-marked scale leaves, serves to connect up
the type of stem met with in the iris and Solomon's seal,
and true tubers, such as the underground potato stems.

Rhizomes and tubers are examples of stems which
are adapted to a special purpose, namely, to hold stores
of food for the future use of the plant.

In the iris the underground stem keeps on growing,
year after year, and by its branching serves also to pro-
pagate the plant, for, as the older portions die away, the
branches become separated and form independent plants.
In the potato this is still more marked, each potato plant
forming each year a large number of tubers, every one
of which can the next year form one or more new potato

THE STEM 45

plants. As is the case of roots, so with stems, man puts
some to his own use, and accordingly cultivates potato
plants and allows them to form their tubers, or stores of
food, which he utilises.

Stems also serve as the means whereby plants climb.
In some cases — for instance, convolvulus and beans — the
ordinary stem twines about any convenient support ; in
others — for example, the white bryony, passion flower,
grape vine, etc. — portions of the stem are modified to
form special climbing organs, known as tendrils.

The crocus affords another example of a stem acting
as a storehouse of food. The stem is here even more
specialised than the potato, and, as we shall see later,
contains not only a store of food, and leaf-buds, but
even the flowers which will come up in the spring after
it is formed, the whole being packed up in, and pro-
tected by, special, tough, scale leaves.

It is of great interest to trace how what appear at
first sight very different and distinct plant structures are
really very much alike, and gradually pass into one
another.

In the creeping jenny and many other plants we find
stems which trail over the surface of the ground but
bear leaves all along their length. In the strawberry
these ordinary creeping stems bearing leaves are
replaced by runners, with only small scale leaves. This
type is the best for the special work they perform of
spreading the plant from place to place. In the iris
and Solomon's seal, underground stems loaded with
food-reserve take the place of the strawberry runners.
The artichoke supplies the connecting link between the

46 NATURE TEACHING

rhizome and the potato tuber ; and finally we get the
crocus corm, a very compact, stem structure containing
food-leaf and flower-buds, with a protective covering.

Structure of Stems.

A piece of the stem of a horse chestnut, elm, oak, ash,
hawthorn, rose, or other tree, when cut across and ex-
amined, is seen to be composed of various parts arranged
in a definite manner. In the middle there is a soft
portion, the pith, small in some cases, large in others ;
this is surrounded by hard wood, which, in the case of
old trees, makes up the greater portion of the stem,
whilst in young branches it only forms a thin ring ; out-
side of all is the bark, sharply marked off and easily
separable from the wood. The bark itself is made up
of three layers (easily recognised in the horse chestnut
or ash) — an inner, fibrous layer; a middle, green portion;
and an outer, thin brown layer, not at all fibrous, but
which readily breaks in pieces if any attempt is made
to detach it.

The region where wood and bark join is of great
importance, for there is present, between these two
conspicuous tissues, a soft, somewhat slimy, thin layer,
best seen in young, vigorously-growing shoots. This
layer is the cambium, or growing layer, and consists of
young growing tissue similar to that which is present at
the apices of stems and roots. The cambium has the
power of producing new tissue in either direction ; that
is to say, situated as it is between wood and bark, it can
add both to the wood and to the inner bark. The
increase in thickness of the wood is generally very much

THE STEM 47

more than that of the bark. This is well seen by ex-
amining the cut end of a felled tree, for instance, an elm
or oak ; the enormous difference in thickness between
such an old tree and a seedling elm or oak being due
almost entirely to the additions made to the wood by
the activity of the cambium layer. The presence of a
cambium is practically restricted to dicotyledonous
plants.

Certain changes take place in the wood of many
trees as it increases in age. From what has already
been said, it will be recognised that the oldest wood is
near the centre, the new wood being formed always on
the outside. It is not uncommon to find the wood near
the centre of the trunk darker in colour. This is par-
ticularly well seen in the laburnum, where the centre
part is deep brown and the outer portion light yellow.
The elm, oak, etc., show the same, although to a less
striking degree. This central dark wood is the heart-
wood, and the outer softer and lighter-coloured wood
the sapwood.

The rate of formation and the character of the new
wood formed from the cambium varies at different
season's of the year. Thus, when a cross-section of a
stem is looked at, rings or layers in the wood are visible.
Trees grown in countries having well-marked seasons
of winter and summer, usually show a definite ring for
each year's growth, and by counting the rings the age
of the tree can be told. In tropical countries the seasons
are often not sharply marked off, and the rings of growth
are accordingly often wanting or indistinct.

Close examination of a cross-section of a stem reveals

48 NATURE TEACHING

the presence of fine lines — well seen in a rose stem —
running through the wood, joining up pith and cambium.
They are also well indicated by radiating cracks, often
formed in posts or felled timber which has been exposed
to the weather for some time. These are the medullary
rays which serve to connect up and maintain com-
munication between the various parts.

If now a stem of maize, cane, or almost any other
monocotyledonous plant is examined, the parts will be
seen to be arranged in a very different manner from
those of the stems already studied. In the stems of
this second set we can distinguish no pith, no ring or
column of wood, no separable bark, and no cambium.
They exhibit in cross-section a groundwork of soft
tissue, in which harder portions are irregularly scattered ;
and whilst the outer portion forms a kind of rind, it is
not essentially different from the rest, but merely con-
tains a much greater proportion of the hard portions,
and very little of the soft ground-tissue. On cutting
such a stem lengthwise, it is readily seen that the hard
portions are in reality fibrous strands which run through
the stem.

For a full description of the various tissues compos-
ing these two types of stems, the reader is referred to
botanical text-books.

Grafting and Budding.

The existence of the cambium in the stems of dicotyle-
donous plants renders possible the carrying out of certain
operations known as grafting and budding. This
depends upon the fact that the cambium, being a region

THE STEM 49

of active growth where new tissue is being regularly
formed, can repair injuries to the bark or to the surface
of the wood, and, moreover, when the cambiums of two
stems are brought together by suitable operations, they
both form new tissues so intermingled that the two stems
unite and grow together.

To carry out grafting in its simplest form, select two
branches, of equal thickness, of different trees of the
same species, and without separating either from its
parent, cut away a portion of the bark and a little of the
wood below it, thus exposing the cambium as a narrow
line surrounding the cut ; take care to make the cuts on
both branches of about the same size and shape. Bring
the cut surfaces together with their respective cambiums
in close contact as far as possible, and securely bind the
branches together in this position. Each cambium now
makes efforts to repair the injuries to the surrounding
tissues, and, all being well, the new growth thus resulting
unites the two branches. One of the branches may now
be severed from its parent tree at a place between the
root and the point of grafting. The upper part of the
branch so severed will have to depend on the root of the
other tree for its support, and thus becomes a part of that
tree, or, as it is usually expressed, is grafted on to it.
This method of grafting is known as "grafting by
approach" because the two plants, each on its own roots,
are brought together.

In other forms of grafting, separate pieces, called scions,
of the tree which it is desired to propagate, are fixed, with
proper precautions, to another tree of the same species,
known as the stock, properly prepared to receive them.

D

50 NATURE TEACHING

In all the methods the essential point is that the cambium
of the scion shall be brought into contact with the cam-
bium of the stock ; any mode of cutting or shaping the
cut surfaces of the stock and scion which enables this
contact of the cambiums to be secured may be adopted
as a method of grafting, and the methods are often
named according to the manner in which the scion and
stock are cut or shaped. The branch or stem which is to
serve as the stock is cut off at the place where it is
desired to insert the scion, and shaped according to the
method to be adopted. In the simplest case the stock
is cut across obliquely, and a scion of the same thickness
is cut in a similarly oblique manner, so that the two cut
surfaces will fit together. Stock and scion being thus
prepared, fit them together, so that their cambiums are
in close contact, and fasten them securely in position by
means of suitable binding material. There is a tendency
for scions thus shaped to slip out of position ; notches
or tongues are therefore often cut in both stock and scion
to diminish this danger of slipping, but care must be
taken to cut the two surfaces in such a manner that they
may fit together accurately.

In some cases it is desired to fix a small scion on a
large stock. The stock is then cut off at the place where
the scion is to be inserted, the end of the scion trimmed
to a thin, pointed, wedge-like form, and thrust in between
the wood and the bark of the stock — into the cambium in
fact. In another method a long narrow V"snaPe<^ incision
is made in the bark and down into the wood of the stock,
the base of the scion is cut to a corresponding shape, fitted
to the stock and secured in position by binding,

THE STEM 51

In all these methods of grafting it is necessary to
cover the junction between scion and stock in order to
prevent the tissues drying, for the cambium would then
die and no union take place. In order to preserve the
tissues in a moist condition it is sometimes the custom
to fix a mass of clay over the place where stock and
scion meet ; this, however, is liable to become dry and to
crack, so that it is preferable to employ soft wax in a
similar manner. More commonly, strips of cloth or
tape are covered with the wax, and these strips are
bound round the joint, thus holding the scion in place,
and, at the same time, forming a waterproof covering
which effectually keeps the tissues from drying.

One particular method of grafting, known as budding,
deserves special mention. It consists in the removal of
a bud together with a little of the wood and bark, and
consequently a portion of the cambium, from one plant,
and its insertion under the bark, that is in the cambium
region, of another plant The inserted bud unites with
the plant in which it is inserted, and, growing quickly,
forms a new branch.

When plants are grown from seed they often differ
very markedly from the parent-plant which produced
the seed. This variation, whilst a useful feature when
the grower is seeking for new forms of plants or striving
to obtain improved varieties, is one which is not
welcome to the cultivator who sows seed and wishes to
raise a crop on the character of which he can rely. It is
still more important in connection with fruit or other
trees which take some years in coming to maturity, for
it is naturally very disappointing to the grower to find

52 NATURE TEACHING

that the tree he has raised does not produce fruit of such
good quality as the tree from which he obtained the
seed, or that the ornamental plant obtained has not the
character which made the parent of value. It is there-
fore important to know of methods by which plants can
be propagated and retain the characters of the plants
from which they are derived. This is secured by
planting cuttings and by budding and grafting : the
plants raised by these methods retaining perfectly the
characters of the original plants. It thus follows that
when a new and desirable variety of plant has been
secured from amongst the varying characters exhibited
by seedlings, the cultivator can produce a large number
of plants possessing the desirable characteristics of the
selected variety by propagating it by means of cuttings
or by grafting or budding.

It will be readily understood that budding and
grafting can only be successfully practised with plants
possessing a cambium, the absence of a cambium zone
making these operations impossible in other plants.
Budding and grafting are successful only when the two
plants operated upon are nearly related, thus the various
varieties of apples may be grafted on one another, and
the different kinds of roses grafted on other roses, but
an apple cannot be grafted on a rose, or a rose on a
cherry.

Plants possess the power of healing up wounds, such
as are made when a branch is sawn or broken off,
gashes made in the stem, etc. The cambium plays an
important part in this process also, and under favourable
circumstances the whole wound may become covered

THE STEM 53

over by the new growths which are formed. Interesting
cases may often be seen in wayside trees.

PRACTICAL WORK

Obtain complete specimens (i.e. with roots, and if
possible flowers) of any ordinary non-woody plants — e.g.,
mangolds, grasses, balsams, primroses, house-leeks, dead-
nettle, etc. ; climbing plants, such as convolvulus, beans ;
creeping plants, such as creeping jenny, couch grass,
strawberry, etc. Notice how in spite of all their differ-
ences they all have an above-ground " shoot," made up of
a stem (sometimes very short) with leaves and flowers,
and a below-ground root, bearing no leaves or flowers.
Make sketches to illustrate diagrammatically the char-
acteristic points of at least one example of each group
— e.g., a balsam, a primrose, a bean, and couch grass.

Examine a leafy shoot of privet, elder, dead-nettle,
or of almost any other plant available, and notice that it
is made up of a stem, bearing leaves. Distinguish the
nodes and internodes, and observe that the internodes
get shorter as you approach the top of the stem, the
leaves accordingly becoming more crowded. At the
very summit the internodes are extremely short, and
the young leaves are packed together to form the
terminal leaf-bud. Observe the smaller leaf-buds which
occur just above the place where a leaf joins the stem.

Examine a privet bush, and notice that whilst some
shoots grow upright, others lie almost horizontally, and
that whilst in the upright shoots the leaves are arranged
equally on all sides of the stem, they are on the hori-
zontal shoots twisted to one side. Examine closely the

54 NATURE TP^ACHING

youngest leaves in both cases, and observe how this
apparent great difference in the arrangement of the
leaves is brought about.

Fasten one of the horizontal shoots, without damaging
it in any way, so that it is upside down, and see how the
young leaves arrange themselves.

Examine also shoots of hazel nut, ivy, horse chestnut,
maple, creeping jenny, and learn that in all these cases
leaves are arranged on the stems so that they may be
well exposed to the light, and do not shade one another.
Make drawings of these leaf arrangements.

Uses of Stems.

Dig up a growing plant of iris or flag, wash it free
from soil, and notice the underground stem with its well-
marked rings. Examine the youngest part, and notice
the sheathing bases of the green leaves. Pull a leaf off
and see the scar it leaves. What have these scars to do
with the rings seen all along the stem ? Look for leaf-
buds along the stem, and ascertain how the stem
branches, and how new plants may be formed. Make
sketches showing all the parts seen, including the grow-
ing portion, the leaf-scars, the buds, and the roots.

Examine " Jerusalem " artichokes, noting the large
number of slightly projecting scale leaves with which
they are covered. If possible, obtain a whole plant as
dug up, carefully wash away the soil, and see that the
artichokes are borne on very short underground stems
which are quite distinct from the roots of the plant.

Make drawings of the whole clump, and of one
separate artichoke,

THE STEM 55

Place a ripe artichoke to germinate. Notice where
the new shoots come from. Notice carefully how, on
the new shoots, there is a gradual transition between
the scale leaves of the tuber and the ordinary green
leaves of the plant. Draw some of the best instances
to show this.

Dig up carefully a potato plant, when the potatoes
are about half-grown, and wash it clean from soil under
a tap. Examine the underground stems on which the
potatoes are borne, looking especially for any small
leaves distinguishing them from the roots. Make draw-
ings. Notice the "eyes" in the potatoes. Get some
seed potatoes and place them in damp sand until they
begin to sprout, and ascertain whether the new shoots arise
anywhere on the potato, or from the eyes only. Make a
drawing of a potato before it has started sprouting,
showing the eyes ; and after it has sprouted, showing the
young shoots.

Obtain some crocus corrris. Gladioli are still better,
being larger, but they are more expensive. Notice the
dry scale leaves forming a protective covering, and the
white pointed buds at the top. Pull off the scale leaves
one by one, and compare the scars they leave with those
already seen in the iris. Cut the corm through length-
wise ; it is solid. It is thus a stem structure, bearing
leaves (the brown scales) at definite places (nodes), and
is in reality a very much swollen stem. With the
help of a lens, it is possible to see the young leaves and
the flower, packed away in the central bud, when it is
cut through. Dig up crocus plants (i) when in flower,
and (2) after the flowers have died. Make out where

56 NATURE TEACHING

the roots spring from ; that the corm is gradually used
up and withers as the plant flowers and that a new
corm, which will flower next year, is formed on top of
the old one. Make careful drawings of — (i) a corm ready
to plant, with its leaves on ; (2) the same cut through
lengthwise; (3) the same with the leaves stripped off;
(4) a plant in flower showing roots, etc. ; (5) a plant after
flowering, showing where the new corm arises.

If the new corm is always formed on top of the old
one, why do not the corms after a few years appear
above the surface of the ground ?

Examine plants of hop, bind-weed, and scarlet runner,
thin flexible stems about any convenient support. Make
out the direction in which the stem twines, and how the
free end of the stem moves in a circle until it meets with
some object to twine around. Make similar observations
on any other twining plants which can be obtained.

Examine the cucumber, white bryony and grape vine,
and notice the special, delicate side branches — tendrils
—by which the plant clings to a support. Those of
the white bryony and cucumber usually twist up in a
beautiful manner, forming a spring, after they have
caught hold of an object, whilst before this they stick
straight out. Two examples only are mentioned here,
but many others will readily be found.

Structure of Stems.

Examine young and old pieces of the stems of any
of the following plants obtainable : elm, horse chestnut,
ash, oak, rose, hawthorn, and note, making careful draw-
ings, all the parts previously described (p. 46). Cut

THE STEM 57

stems both across and lengthways. Examine the cut
ends of any old trees, and compare with young plants of
the same kind, noting particularly the enormous differ-
ence in thickness of the wood.

Examine a thick branch or stem of a tree which has
been cut lengthways, and observe how the branches, can
be traced downwards through the wood of the main
branch or stem, giving rise to knots. Make drawings of
these as seen in both longitudinal and cross sections.
The trees mentioned above, or almost any timber trees,
afford good examples.

Examine, in cross and longitudinal section, stems of
any monocotyledonous plants— for example, maize, any
large grasses, any palm (for instance, in museums).
Note the hard, outer rind, and the inner, soft, ground-
tissue with the hard, fibrous strands running in it. Com-
pare the parts in these stems very carefully with those
of the dicotyledonous stems of the preceding paragraphs.

Grafting and Budding.

To perform these operations, good, sharp and
strong knives are necessary. Much may be done with
an ordinary penknife, but proper grafting and budding
knives greatly facilitate the work. They are inexpen-
sive, and procurable from any dealer in gardening tools ;
a small number should form part of every school's equip-
ment.

Before beginning work it is necessary to prepare
supplies of grafting-wax and budding-tape. The follow-
ing recipe should be followed for preparing grafting-
wax : — Melt together four parts by weight of resin, one

58 NATURE TEACHING

part of beeswax, and one part of tallow. When
thoroughly melted, pour into cold water, and when cool
enough, take out and work by moulding and pulling
until it becomes quite stiff. It is necessary to have
the hands well greased with tallow while handling this
wax.

Budding-tape is prepared by dipping strips of cloth
into melted wax. The wax used is beeswax mixed
with a sufficient quantity of kerosene to render it soft
and pliable, the mixing being aided by the cautious
application of heat ; a mixture of two parts of beeswax
with one of resin is often used, the two substances being
carefully melted together. Various kinds of cloth are
employed ; some workers using linen or calico, whilst
others prefer thin flannel. The cloth is torn into strips
— about | to f inch wide, and of convenient length —
which are dipped into the melted wax, then lifted out,
and all the superfluous wax allowed to drain off; when
cool the strips are ready for use. A sufficient supply of
budding-tape to last for some time should be prepared.

Some of the forms of adhesive plaster, as used by
surgeons, which can be purchased from druggists in
narrow widths (J to f inch) on reels, may be usefully
and conveniently substituted for budding-tape.

Grafting by approach : — Select two trees of the
same kind but presenting some points of difference, as
two apples, two roses, or two currants ; one or both of
the selected trees should be growing in a pot or tub, so
that the two trees may be brought together. Now decide
which tree is to form the stock and which is to provide
the scion. Select a branch of each — conveniently situ-

THE STEM 59

ated, so that the two branches can be brought into close
contact — taking care that the selected branches are of
nearly the same thickness at the points where they are
to be operated upon. Devise some means whereby the
two plants, or at least the two selected branches, may
be firmly secured, so that the scion may be kept in
position on the stock. The method of doing this will
depend on the size and character of the two plants ;
merely binding the two branches together will be
sufficient in many cases, or, if the stock is a large tree
and the plant providing the scion is contained in a pot,
the latter can be secured to the trunk or to a branch of
the stock. Having made these preparations, cut away
a piece of the stock at the selected point, removing
from two to four inches of the bark with a little of the
wood below it, taking care that the cut is smooth and
even. Make a similar cut on the scion, in such a
position that the two cut surfaces may be brought into
close contact and will fit together fairly well. Bring the
two surfaces together, secure them in position by means
of strong, soft twine tied both above and below the
place operated upon, and, finally, wrap a strip of bud-
ding-tape firmly around the united branches covering
the junction completely ; the edges of the tape should
overlap, so as to prevent the evaporation of moisture
from the cut surfaces, or the access of rain-water to the
joint. It is not necessary to tie the budding-tape, for
the end will remain in place if pressed down on the
surface of the tape bandage, the wax holding it securely.
Everything being properly and securely fixed, leave the
plants for a sufficient time for union to take place and

60

NATURE TEACHING

then cut off the scion below the place of grafting, and
trim the cut end neatly with a sharp knife.

Grafting stems of equal size : — In this method we
employ as before a rooted plant as the stock, but
only a detached portion of the plant we desire to graft
on to it as the scion. Cut back the stock to a place
where its stem is of about the same thickness as the
scion. Shape the cut ends of stock and scion, so that

FlG. 5. — Showing modes of shaping the cut ends of stock and
scion when grafting stems of equal size.

they may fit together accurately, with their cambial
regions in contact. As soon as scion and stock are thus
fitted together, secure them in position by firmly bind-
ing with binding-tape, taking great care that they are
so securely fixed that no displacement can take place,
and that the joint is so well covered that the cut
surfaces will not dry.

This method admits of several variations in the
manner of shaping the cut ends of stock and scion (see
Fig. 5). In the simplest case, cut the two ends obliquely

THE STEM

61

and merely place them in position ; the disadvantage of
this method is that they are very liable to slip. Means
must be taken, therefore, to prevent this, and it is usual
to cut a notch in the end of the stock and a correspond-
ing tongue or projection at the end of the scion ; or the
end of the stock may be trimmed to a wedge, and in the
scion a Y-shaped incision made to fit accurately over
the wedge. The form of the joint adopted may be
varied indefinitely, but the great object to be kept
steadily in view is the bringing of the cambial regions
of the two cut surfaces into close contact and retaining
them there.

Grafting a small scion on to a large stock : — In this
case, as the cambium only forms a narrow ring near
the outer margin of the stock,
it is essential that the scion
be placed here also. The
simplest method of working
is as follows : — Trim the end
of the scion to a long wedge
and thrust this wedge into
the cambium of the stock,
that is, between its wood and
bark. Another method is to
cut a V-snaPed piece of bark ,-, , cu .

v FlG. 6. — Showing

til

grafting a small
large stock.

a method of
scion on to a

from the stock, carrying the
incision deep enough to re-
move a portion of the wood also (see Fig. 6). Then cut
the end of the scion to a corresponding shape and fit it
into the stock, and, having taken care to leave the bark
undisturbed on one side of the scion, bring it into posi-

62 NATURE TEACHING

tion so that it fits on to the bark of the stock. Fix the
scion in place by means of grafting-wax, so moulding
and pressing it around the joints and cut surfaces as to
fulfil the double purpose of holding the scion in position
and protecting it from drying up. This mode of graft-
ing is adopted when it is desired to graft on to a thick
branch or the stem of a tree which has had all its
branches removed ; several scions may be put on one
stock.

Apple, pear, apricot, or other fruit trees available, are
suggested for grafting experiments.

Budding: — For practice the pupil should work upon
rose plants. Examine the tree which is to furnish the
bud-wood, cut off two or three vigorous branches with
well-developed side leaf-buds, and carry these to the
tree which is to be the stock. Select a place on a young
but fairly woody branch of the stock, and make a "]~-
shaped incision in the bark, with the downward cut about
an inch and the cross cut about three-quarters of an inch
in length (see Fig. 7). Raise the bark gently from the
wood, taking care not to tear it from the branch — the
flattened end of the budding knife should be used for this
purpose. The stock being now prepared, choose a good
bud on the branches already selected, and cut off the leaf
which accompanies it, leaving only a very short piece of
the leaf-stalk ; then with a firm clean cut remove the bud,
together with a thin slice of the wood beneath. The
whole piece so removed, including bud, bark, and wood,
should be about three-quarters of an inch long and one
quarter wide. Insert the bud thus prepared under the
bark of the stock, proceeding carefully so as not to tear

THE STEM

63

or unnecessarily injure the bark. All these operations

should be performed as quickly as possible, to avoid the

drying up of the cut surfaces. As soon as the bud is in

position fix it by one or two turns of thin, soft twine or

other material, then take a strip of budding -tape and

wrap round the stock with the

inserted bud, beginning slightly

below the place of operation

and allowing the edges of the

tape to overlap at each turn.

The bud may be covered over

completely, or, if very prominent,

it may be left exposed ; the

budding-tape should hot be tied,

the free end being held safely in

position by pressing it down on

the wrapped portion.

Budding is frequently re-
sorted to in tropical countries, FIG. 7.-£u<timg.-The upper

right-hand figure shows the
bud ready for insertion under
the cut bark of the stock
(upper left-hand). The
lower left-hand figure shows

the bud in position, aud the
remaining figure illustrates
it bound up in the budding
tape.

with oranges, lemons and other
citrus fruits, when it is desired
to grow some selected, choice
kind upon a stock of a hardy
variety. For this purpose seed-
lings of the kind to be used for
the stocks — in practice often sour oranges or " rough "
lemons — should be raised in nursery beds. When the
stems are of about the thickness of one's finger, insert
buds of the selected variety in the stem of the stock,
three or four inches above the level of the ground. In
about ten to fourteen days the buds should be found to

64 NATURE TEACHING

be securely united to the stocks, when the wrappings
of budding-tape may be removed. Four or five days
after this, cut part-way through the stem of the stock,
about an inch or two above the inserted bud, and
bend down the top of the stem from the cut point,
so as to lie along the surface of the ground. The
flow of sap to the upper part of the stock is thus
checked, and increased growth of the bud results.
When each bud has developed into a good strong
branch, cut off the now prostrate stem, and trim down
the stump close to the point where the branch aris-
ing from the bud grows out, so that the scar may
heal neatly, and the new branch may grow straight as a
continuation of the stem, and thus form a shapely tree.
Should any bud develop at any point below the place
where budding took place, it must be rubbed or pinched
off.

To ensure success in budding, the work must be done
when the stock is in such a condition that the bark can be
easily raised, this occurring when the cambium is in a
state of active growth. Skill is also necessary in selecting
good bud-wood from which to cut the buds. The work
should be practised regularly, until each pupil can work
rapidly, neatly, and with a small percentage of failures.
This branch of work should not be dismissed in a lesson
or two, but real practical skill should be acquired by
repeated exercise.

Healing of Wounds.

Examine these places on trees where branches have
been cut off or broken off, and notice how, after a time, new

THE STEM 65

growths have formed whereby the wounds are healed.
This healing of wounds is of great importance to the plant,
as, just as in animals, an open wound is often the cause
of the plant developing some disease. All cases seen
should be examined carefully, and accurate drawings
made.

CHAPTER IV

THE LEAF

DURING the previous practical work we have had
occasion to observe the structures, known as leaves,
which are borne on the stems of plants. It is a matter
of common knowledge that the leaves of different plants
vary greatly in size, character and shape,and we commonly
distinguish plants, when not in flower, by the shape of
their leaves. Apart from these minor differences many
leaves agree in having a more or less thin, flattened,
green portion, known as the blade of the leaf, which may
be " simple " in shape, as a privet, elm, or nasturtium leaf,
or much divided, as an ash, rose, or vetch leaf. In many
plants — for example, the sow-thistle or honeysuckle — this
leaf-blade joins directly on to the stem, but in others it
has a thinner, generally rounded, lower portion, the leaf-
stalk, easily seen in a maple, horse chestnut or nasturtium.
In addition to these two parts many, but by no means
all, leaves show, at the point where they join the stem, a
pair of bodies which are known as stipules. These may
be small, as in the garden geranium, or comparatively
large, as in the pea, pansy and hawthorn.

The blade of the leaf has been spoken of hitherto as

THE LEAF 67

a thin expansion. This is true in by far the greater
number of plants, but many plants, especially those which
live in very dry places or near the sea, have leaves which
are either thick and fleshy, as in the house-leek, or very
small, as in the heather and furze. We have also seen
already, when examining iris, artichoke and crocus stems,
that leaves are not always green. Other examples of the
various characters which leaves can assume will be met

with later.

Uses of Leaves.

Leaves are necessary for the health and growth of
most plants, as in them are carried on the processes of
breathing and the manufacture of food-material. The
consideration of these processes is, however, best deferred
until we have made ourselves acquainted with the struc-
ture of leaves. We will therefore first deal with their
other less important uses.

The young leaves of most plants are very delicate
and easily damaged by exposure to the sun, wind, and
frost. It is common to find these young leaves protected
by being enclosed by the older ones, as may be seen in
the leaf-buds of the lilac and privet, and very strikingly
in cabbages and lettuces. In the docks the young leaves
are rolled up within the next older leaf, and specially
protected from drying up by being bathed in a sticky
liquid. The school garden will readily furnish numerous
other interesting cases. In the common red clover the
stipules protect the young leaves. In many plants — for
instance, the pear, apple, and beech — the stipules are
small, and look at first sight mere useless structures.
Examination of the buds of these plants shows that this

68 NATURE TEACHING

is the time when the stipules are of use, as then they are
large in comparison with the young leaves and serve to
cover and protect them.

We have so far confined our attention to the buds
found during the warm season of the year, when the
plants are actively growing, and all that is necessary is
to protect the delicate young leaves from the wind and
sun, and possibly from cold during the night. In some
parts of the world it is "always summer," the plants
there are almost continually growing, and we find buds
of this nature the whole year through. In Great Britain
and other temperate countries, the conditions are very
different, and summer and winter follow each other
regularly. We are all familiar with the sight of trees
and other plants growing through the summer, ceasing
to grow in the autumn, and as soon as the weather begins
to turn cold dropping their leaves and becoming quite
bare. In this condition they remain during the winter,
to all appearance dead, but they are only resting, and as
soon as the weather turns warm again young leaves
reappear and the plants once more enter on their
growing stage. The bursting into leaf of trees and
shrubs is one of the most constant features of the spring
in temperate climates.

If we examine trees — for instance, a horse chestnut
— during the winter we find no leaves, but a number of
large brown bodies — the buds — covered with more or less
sticky scales. One of these buds carefully pulled to
pieces will be found to be covered on the outside by a
series of overlapping brown scales, and to contain inside
a number of small green leaves well wrapped up in what

THE LEAF 69

looks almost like cotton-wool. It is in fact an ideal
arrangement for protecting the young leaves from the
cold and wet. The cotton-wool-like material keeps the
leaves warm, and the overlapping scales, fastened to-
gether by the sticky liquid, make a waterproof covering.

On a warm day in early spring the sticky material
melts, and the buds glisten in the sunshine. If the warm
weather continues, the scales are thrust apart and the
tender green leaves come out and give the well-known
green flush of spring to the whole tree.

How real the protection the buds afford to the
young leaves and flowers is well shown by the great
damage done, if a spell of warm weather sufficient to
make some of the buds open is followed by frosts.
It is the opened buds then which suffer; those which
remained closed being quite uninjured by the frost

We have already seen in the iris and crocus the dry
scale leaves wrapping over the underground buds, and
that when these buds grow into leafy shoots these scale
leaves wither away. In other plants underground leaves
are found, which act as storehouses of food. The common
garden lilies, such as the tiger and white lilies, or an
onion, serve as good examples; and on digging up one
of their bulbs with the above-ground leaves still attached,
it will be readily seen that the thick, fleshy structures
which make up the greater part of the bulb, are really
only the thickened bases of leaves, and are of use to
contain starch and other food-reserves. That is to say,
we find leaves in these plants performing exactly the
same duties which the stem does in the iris, crocus, and
potato, and the root in the radish, turnip and beet

70 NATURE TEACHING

Leaves often act as the climbing organs of the plant,
and all gradations can readily be found between an
ordinary green leaf which has the power to hold on to,
or even twist round supports and the special structures
of other plants, often so much altered to make them
more suitable for this particular use that they have
almost lost their leafy character. Thus in the wild
clematis (traveller's-joy or old man's beard) so common
on chalk and limestone districts, the leaf-stalk twists
round objects and holds the plant up ; similarly in the
garden nasturtium the leaf-stalks of the ordinary green
leaves do the same. In the garden pea only a special part
of the leaf — the long thin end — is of use as a climbing
organ, and similarly in many of the vetches. Examples
like these are of special interest, as they show us how
adaptable the parts of plants are, and how the same part
can serve very different purposes.

Structure of Leaves.

In most leaves the blade has running through it a
number of veins, often conspicuous, especially on the
lower side, as ridges. The leaves of the maple, black-
berry, and indeed almost any ordinary thin leaves, show
them very plainly, and, on holding such leaves to the
light, it is seen that there is a perfect network of these
veins, the small veins being branches of the larger ones.
These veins are really the continuations of the woody
tissue which we have already seen in the stem, and are
of use as a supporting framework to the soft tissue of
the leaf, spreading it out to the light and air, and pre-
venting the leaf from being readily torn. They are also

THE LEAF 71

the means whereby the water taken up by the roots is
brought to the leaf, and the substances manufactured in
the leaf are carried away to the other parts of the plant.

The veins of leaves are arranged in two main ways ;
netted, as in the examples above ; parallel, as in the lily,
wheat, barley, and all grasses where the veins run side
by side and do not form an interlacing network. These"
two types of vein arrangement — netted and parallel —
are, on the whole, characteristic of the leaves of dicoty-
ledons and monocotyledons respectively, and with certain
exceptions; — for instarice, the black bryonyr^-may be
taken as indicating to which of these two groups a plant
belongs.

It is impossible, without' the use of a microscope, to
obtain very much information concerning the internal
structure of leaves. If, however, we select some thicks
leaved plant, such as the iris, we find that both upper and
lower surfaces of a leaf are covered with a colourless skin,
which, with a little care, can be stripped off*. The main
mass of the leaf is seen to be made up of comparatively
soft tissue, through which harder, fibrous strands (the
veins) run. The thin skin makes a kind of waterproof
coating to the leaves, but has an enormous number of
minute openings, called stomata (too small to be seen
without a magnifying glass), through which the gases of
the atmosphere can pass in and out, and so reach the
spongy tissue of the inside of the leaf. This is most
important, for it is in this inner part that the real work
of the leaf, the breathing and building up of new matter,
goes on, and for these processes a free interchange of
gases with the outside air is absolutely necessary.

72 NATURE TEACHING

Transpiration.

Everyday experience shows us that if a leafy shoot
is picked it soon becomes limp and then withers, but
that if we place it in water it remains fresh and stiff for
a longer time. Further, we know that a shoot which
has commenced to wither can often be made fresh
again by placing the cut end of its stalk in water.
Similarly, plants growing in the ground droop and may
die if they are deprived of water for a long time. They
soon revive if water is poured on the soil so as to
penetrate down to their roots. From these various
facts it is clear that the withering and limpness of the
leaves is due to the fact that they give off water, and
that more can be supplied to them either by putting
the cut end of the stalk in water, or, as happens in
nature, by water being taken up by the roots and
passed on through the stem to the leaves.

This loss of water by the leaves is known as tran-
spiration^ and is of great importance to the plant,
because as water is given off from the leaves more is
steadily drawn up through the stem to take its place.
When a plant is growing and has plenty of water at its
roots, water is taken up almost as quickly as it is given
off, and the whole plant remains fresh ; but if there is
none or only very little water to be obtained, as in the
cut shoot or the plant in dry ground, the roots cannot
take up enough to make up for what the leaves give off,
and first the leaves and afterwards other parts of the
plant droop and wither.

In transpiration, the green spongy tissue of the leaf

THE LEAF 73

gives off moisture which escapes into the outside air
through the minute openings in the surfaces of the leaf.
These openings are able to open and close according to
conditions, and so regulate the rate at which water can
be given off. When the air is dry they become smaller,
and so hinder the escape of water. We shall see, too,
from our practical work that light has an important
effect, and that plants give off more water when exposed
to the light than when in the shade. When cuttings of
plants are being taken the shoots are separated from
their roots and cannot obtain much water. It will be
clear now why, under such circumstances, some of the
leaves should be cut off and the cuttings placed in the
shade*

We can easily measure how much water a single
leaf or a whole plant gives out during a certain time,
and experiments for doing so are described in the
practical work on this chapter.

Another point of interest is to find out whether this
water is given off equally from the upper and lower
surfaces of the leaf, or more from one surface than the
other. An experiment to enable this to be ascertained
is also described.

In a long drought there is often insufficient water to
counterbalance that given off by the leaves, and,
although the pores may be closed, there is danger of
injury to the plant from excessive loss of water. To
prevent this, some leaves — for instance, of many grasses,
and particularly those which grow in dry, sandy places —
have the power of curling themselves up so as to cover
the pores (stomata) with the over-arched leaf-blade,

74 NATURE TEACHING

thus further reducing evaporation. Many leaves have
their pores so placed that when the leaf is curled up
during dry weather they are all under cover, none
being present on the exposed outer side. Thus it will
be seen that order prevails even under such disturbing
conditions as those which lead to the withering of
leaves by drought, when all appears confusion. There
are many other contrivances for protecting plants from
excessive loss of water. Amongst the most common
are the thickening of the outer skin, well seen in house-
leek, laurels, box, etc., the provision of a coating of hair,
for instance, in the mullein, and by the reduction in size
of the leaves, as, for example, in the pines, heaths, furze,
and other plants which can live in situations where they
get but little moisture.

It is important that the pores in the leaf should be
enabled to perform their functions under all the
conditions to which the plant may be exposed." We
have already seen how in some plants they are covered
and protected during drought. It is also often essential
that they should not be readily filled by drops of water
during rain or dew, and the surfaces of leaves often
have slightly waxy or hairy coatings, so arranged that
those parts of the leaf which are abundantly provided
with pores are extremely difficult to wet, while surfaces
with few pores are wetted easily. Good instances of
this are seen in leaves which are easily wetted on the
upper surface where there are no pores, but which
throw off water from their under surfaces in a wonderful
manner. The leaves of water-lilies, duck-weed, frog-
bit, etc., cannot be wetted on their upper surfaces,

THE LEAF 75

but the under surfaces live in constant contact with
water.

It is interesting to observe how the leaves of plants,
by their position and arrangement, throw in different
directions the water which falls on them as rain. In
many plants, as, for example, beet, violet, dandelion, the
leaves are so arranged that much of the water which
falls on them is directed towards the centre of the plant,
moistening the ground near its base, where the main
roots are to be found. As the plant grows, the leaves
often bend downwards at the tops while still inclined
inwards at the base. There is thus a division of the
rain, a portion flowing towards the stem, and a portion
towards the outer boundary of the plant, a greater area
of soil being thus moistened. This may be observed in
the sunflower. In many large trees, amongst other
plants, practically all the water is thrown away from
the trunk, so that there is a dry space beneath the
leaves and branches ; water is not wanted there, for
there are no young roots to absorb it near the trunks of
such plants. Close observation has revealed a relation-
ship between the direction and spread of the rootlets
and the drainage system of the leaves of a plant. In
those plants with widely-spreading roots the water is
conducted towards the margin of the plant system (oak
and many other trees). In those with bulbous roots, or
with closely-tufted rootlets, or with deep, penetrating
taproots, the water is commonly conducted towards the
centre (violets, beet, lilies).

A plant breathes, just as animals do, and also
obtains a large proportion of its food from the air

76 NATURE TEACHING

through the agency of its leaves. In order, however, to
understand the various processes which go on in the
leaf, it is necessary to know something concerning the
composition of the atmosphere.

TJte Atmosphere.

The atmosphere consists almost entirely of two gases,
oxygen and nitrogen, which relatively compose one-fifth
and four-fifths of its volume. Oxygen is the substance
by whose agency all burning or combustion takes place,
and which, in the breathing of animals, removes the
waste products from the blood by a process of slow
combustion. Nitrogen, on the other hand, is an inactive
gas which serves to dilute the oxygen and modify
the rapidity and vigour of its action. In addition to
these two gases there are present very small quantities
of water-vapour and carbonic acid gas or carbon dioxide
— so called because it is formed by the union of the two
substances carbon and oxygen.

Carbon exists in various forms, the commonest being
ordinary charcoal, which is very nearly pure carbon. All
organic substances — that is, all substances which are the
product of life, become blackened or charred when
strongly heated. This charring may be taken as proof
of the presence in them of carbon. We thus recognise
the truth of the assertion that all organic matter contains
carbon. If, however, the heating is continued still
further, the oxygen of the air unites with the carbon,
forming the gas carbon dioxide, and the substance has
then, we usually say, " burnt away."

The presence of carbon dioxide can readily be made

THE LEAF 77

visible by taking advantage of the property which it
possesses of combining with lime to form chalk. If a
solution of lime in water — that is, clear lime-water — is
brought into contact with carbon dioxide, chalk is formed,
and, being insoluble in water, becomes at once apparent
by the milky or turbid appearance it gives to the
water.

Plants and the Atmosphere.

On breathing into lime-water it soon becomes
cloudy, owing to the carbon dioxide present in our
breath. Plants can easily be shown to produce a similar
effect. We see, therefore, that both animals and plants
breathe out carbon dioxide, and, as it is also formed in
the burning of wood, coal, and all other substances con-
taining carbon, it follows that carbon dioxide is con-
tinually being added to the air in large quantities. But
carbon dioxide, when present to a certain degree, is
injurious to life, and yet for countless ages the actual
amount of carbon dioxide in the atmosphere has not
increased. It follows, therefore, that there must be some
agency at work whereby its accumulation in the air is
prevented, or all life would become impossible. Plants
are the means whereby this accumulation is hindered.
When carbon dioxide comes in contact with the living
substance of the plant, under certain conditions, it is
split up into its constituent parts, carbon and oxygen.
The carbon is kept by the plant and built up into its
tissues, and the oxygen set free. The conditions referred
to above are the presence of (i) the green colouring
matter (leaf-green or chlorophyll) which gives the

78 NATURE TEACHING

characteristic colour to the leaves,* and in some cases
the stems of plants, and (2) sunlight.

The process which goes on in the leaf whereby the
carbon dioxide is broken up in this way and the carbon
used by the plant is known as assimilation. Assimilation
must be very carefully distinguished from the respiration
or breathing of plants, in which, exactly as in that of all
animals, oxygen is taken in and carbon dioxide given
out. A plant is always breathing, but can only carry on
the process of assimilation under the special conditions
mentioned above. Whilst a plant is in the sunlight the
oxygen given out masks the breathing process, and it is
only when plants are in darkness, either artificial or that
ordinarily occurring at night, that the fact that a plant
does really breathe out carbon dioxide like an animal
can be detected. When later we try experiments on the
breathing of plants, it is essential to remember that the
plants must be kept in the dark.

The Food of Plants.

As the result of the building-up processes which go
on in the leaf, we find that starch is formed. In the
practkal work at the end of this chapter, experiments
are described which enable us to prove (i) that starch is
actually formed in leaves ; (2) that for this formation of
starch, by the living substance of the plant, leaf-green
and sunlight and the presence of carbon dioxide are
necessary conditions.

* In some plants — for instance, copper beech, coleus — the colour
of the leaf-green is hidden by other colours. But the leaf-green is
always there nevertheless.

THE LEAF 79

Starch is a very common substance in plant tissues.
It is one of the chief forms in which plants store up
reserves of food to be used on some future occasion,
when greater demands are made for food than can be
supplied by the assimilation of the moment. In the
production of fresh shoots from potatoes, and in the
germination of seeds, a large amount of growth goes on,
entirely at the expense of the food - reserves stored
away in the tuber or seed. It is only later, when the
new shoot has formed its own green leaves, that it can
do anything at all towards making fresh supplies of food
for itself.

It has already been stated, and will later be experi-
mentally proved, that assimilation, resulting in the
formation of starch, can only go on in the green parts of
plants, and only there when they are exposed to sun-
light. The question naturally arises then : how do we
find starch in tubers, seeds, or other non-green and even
underground parts of plants ? The answer to this, too,
will be supplied by means of simple experiments. If a
growing plant is left exposed to a good light from early
morning to afternoon and its leaves tested then, they
will be found to be loaded with starch. But, place this
same plant in darkness for twelve hours or more, and
its leaves will be found to be almost emptied of starch.
As a matter of fact, the starch formed in them in the
sunlight has been changed into sugar, and in this form
carried away from the leaves in which it was made, and
either used up in growth or often changed back again
into starch and stored up in some other part as a
reserve of food.

80 NATURE TEACHING

It may seem at first sight wasteful on the part of the
plant to make starch, then change it into sugar, and
often change this sugar back again into starch in some
other part of the plant. We shall, however, see that
there is a reason for this, inasmuch as only substances
actually dissolved can be carried about from one part
of a plant to another ; and that, as starch is insoluble,
it has to be changed into a soluble substance (sugar)
to enable it to be moved from the leaves where
it is formed to other parts of the plant where it is
needed.

A plant requires for its complete nourishment other
food - substances besides carbon dioxide and water.
These foods are mainly nitrogen and mineral matters.
They are usually obtained from the soil, being taken up,
dissolved in water by the roots. This watery fluid
which permeates the plant is known as the sap, and is
in constant circulation owing to the evaporation which
we now know goes on from the leaves. As the result of
this circulation the mineral bodies taken up in the sap
by the root are carried all over the plant, and, combin-
ing with the substances formed in the leaves, are
enabled to play their proper part in the nourishment
and growth of the plant.

Thus we see the leaf is one of the most important
organs of the plant. By their leaves plants breathe, and
also obtain a large amount .of their food. The transpira-
tion from the leaves maintains the circulation of the
sap, thereby ensuring fresh absorption of mineral matters
by the root,

THE LEAF 81

PRACTICAL WORK

Examine leafy shoots of, for instance, privet, lilac,
nasturtium, oak, ash, vetch, maple, horse chestnut, sow-
thistle, honeysuckle, and any grasses, paying special
attention to the leaves. Observe that all these leaves
have a thin blade t which is quite simple in shape in the
privet, lilac, nasturtium and grasses, lobed in the sow-
thistle, oak, and horse chestnut, and divided up, so
as to look almost like a number of separate leaves, in
the ash and vetch. Notice which of the leaves have leaf-
stalks. Make sketches of all examined.

Examine the leaves of house-leek, and, if you live
near the sea, such plants as the sea-rocket, sea-kale,
sea-purslane, or any other thick-leaved plants, often to
be found growing by the seashore or in very dry places.
Compare their leaves with those above, noting their
succulent or fleshy character.

Examine also shoots of furze, heather, broom, or
pine. Notice that these plants live in dry situations,
usually on sandy soils, where only little water is to be
obtained.

Uses of Leaves.

Examine the available plants (privet, cabbage,
lettuce, are very good examples to take), and observe
the delicate young leaves forming the leaf-bud. Notice
how they are protected from the sun, wind and rain, by
being more or less covered over by the older leaves.
Then observe the more elaborate methods in the
common docks, where the young leaves are rolled up

F

£2 NATURE TEACHING

inside a special protecting sheath, and covered with a
sticky liquid which prevents them from drying up. Con-
tinue these observations on the other plants to hand.
Carefully sketch all the buds examined.

Examine shoots of the common red clover. At the
end of each will be found a bud completely enclosed at
first by a pair of greenish-white structures, the stipules
of the next older leaf, inside which all the young parts
are packed away. Notice how the bud gradually opens,
and how in the older leaves the stipules gradually dry
up and look mere useless bodies. Compare this
arrangement with the pansy, where the stipules persist
as green, leaf-like bodies. Examine also the buds of
the garden geranium, and note in particular how the
stipules, which look so small compared with an old leaf,
are really able to help protect the leaves whilst these
are young and small. Make sketches to show all these
arrangements, drawing young leaves protected by the
stipules, and older leaves with their comparatively small
and useless looking stipules for comparison.

Collect, in the autumn, twigs of the horse chestnut,
and notice the large buds. Make a sketch of a twig,
showing the buds and the scars left by the fallen leaves.
Examine a bud more closely, and notice how it is
covered by a series of overlapping brown scales.
Commencing at the base of the bud, pull off the scales
one by one, and see how they are stuck together by a
sticky resinous material. When all the outer scales have
been removed, examine carefully the inner portion of
the bud, and see that it consists of young leaves, beauti-
fully folded up and .packed together and covered with

THE LEAF 83

white hairs, so that they appear to be wrapped up in
cotton-wool.

Watch the buds through the winter and in early
spring. Notice how on sunny days they glisten owing
to the warmth melting the resinous coating. When
spring sets in, trace the gradual swelling of the buds and
how finally the scales are burst open, and the young
tender leaves emerge from their long rest.

Make similar observations on the sycamore, apple,
and any other trees near to hand. Sketch carefully
buds in the resting conditions, when half opened, and
again after the young leaves have expanded.

Examine again the underground stems of artichoke
and iris, and observe the thin, dry scale leaves. In
some kinds of potatoes similar scale leaves are well
shown, but in most ordinary potatoes they are almost
entirely absent. Note how they enwrap the delicate,
young, growing points — the buds.

Make similar observations on crocus or gladiolus
corms, cutting them through lengthways and across, and
noting how the dry scale leaves wrap over and protect
the delicate white buds containing the ordinary leaves
and flowers. Make sketches to illustrate your observa-
tions.

Examine a plant of onion whilst it still has green
leaves. Note how it is wrapped round by a number of
dry scales. Look at the fresh leaves, notice what their
lower portions are like, and see that in reality the whole
onion bulb is composed of the thickened bases of leaves,
some of which are already above ground and green,
whilst the younger ones are contained in the centra

84 NATURE TEACHING

bud. These points can be readily made out by cutting
onions both across and lengthwise. Make similar obser-
vations on a hyacinth bulb, and compare the two care-
fully.

Examine, in the hedges, shoots of traveller's-joy
(common only on chalk and limestone districts), and see
how it climbs by twisting its long leaf stalks around
twigs of other plants. In addition or in place of the
traveller's-joy, look at garden nasturtiums, and see how
these support themselves in much the same way.
Make a sketch of a nasturtium holding on to a stick or
other support. Examine the garden pea, sweet pea, or
wild vetches. In all these plants the end of the leaf is
prolonged into a special climbing organ, a tendril, which
can wrap round a stick or string, and so hold the plant
up. Compare young leaves which have not as yet
caught hold of a support and older ones which have.
Sketch one of each.

Structure of Leaves.

Observe the veins of the leaves under examination.
See how much firmer they are than the rest of the leaf;
how they support the softer tissue. Hunt among decay-
ing leaves in wet places under trees, and try to find some
" skeleton " leaves in which the soft parts having rotted,
the hard and more resistent veins remain as a skeleton
of the leaf.

Take some box leaves and boil them for fifteen
minutes in water to which caustic potash has been added,
in about the proportion of -fa oz. of the potash to i oz.
of water. After boiling, pour away the potash and put

THE LEAF 85

the leaves in a large dish of water. Gently brush the
leaves with a stiff camel's hair brush, and if the leaves
have been boiled enough the soft parts can be removed
and the veins left forming a skeleton leaf.

With care it will be found possible, on other leaves
boiled in the same way, to strip off a thin colourless skin
from the upper and lower sides, leaving a middle portion
consisting of the veins and the soft tissue. Examine
the upper and lower skins with a hand lens, and see if
any of the minute pores or stomata can be made out.

Compare all the leaves which can be obtained, and
note the arrangement of their veins, whether netted or
parallel. Examine the stems of the same plants and
see whether, as a general rule, you find stems with
dicotyledonous structure bearing leaves with netted
veins, and monocotyledonous stems parallel-veined
leaves.

Take leaves of the iris, and pull off a portion of the
outside layer of the leaf (this layer is very thin and care
is required, but if the operation is properly done no
green tissue will come away). Note that the outer skin
is colourless, that the underlying tissue is dark green
and soft, and has a number of hard fibrous structures,
the veins running through it. The point of a knife can
easily be got under one of these, and the vein pulled up
like a thread of cotton.

Transpiration.

Pick a number of shoots of any ordinary thin-leaved
plants, such as dead-nettle, lilac, groundsel. Place some
in water and leave others lying on the table. The latter

86

NATURE TEACHING

soon droop and become limp. Now place some of these
in water, first cutting a little off the end of the stem to
make a fresh surface, and notice that, after a time, they
become stiff and fresh again, whilst those left on the
table steadily become more limp and at length wither
and dry up. Treat in the same way, for comparison,

some thick leaves, such as
house-leek, sea -rocket, sea-
purslane, etc., and small-
leaved plants such as heather,
furze, broom, etc., and notice
that these take a very long
time before they show any
signs of drying up, indicating
of what use to these plants,
which can grow in places
where they get very little
water, their thick or small
leaves are.

To prove more directly
that it is the leaves which
FIG. 8.— Experiment to prove that actually give off water, take

leaves give off water. ...

a test -tube provided with a

well-fitting cork. Split the cork lengthwise, and fit the
pieces on either side of a straight leaf, such as wheat or
daffodil (without cutting off the leaf or injuring it in any
way), and put the cork back so that the leaf is inside the
tube as shown in Fig. 8. Let the leaf remain on the
plant, and notice that the glass inside the test-tube first
becomes dimmed, and that later drops of water trickle
down and collect at the bottom of the tube. It is not

THE LEAF

87

essential to use the leaves mentioned above, any leaf with
a fairly long leaf-stalk will do equally well, the cork
being split as before and clipped around the leaf-stalk,
fitted into a slight groove made in one of the half corks
if necessary.

Take a plant growing in a pot, and do not water it
for a day or two. The
leaves droop exactly as
those of the cuttings left
lying on the table. Soak
the pot with water, and the
plant revives. These ex-
periments teach us that
the leaves are continually
losing water, but that if
we supply sufficient water,
either through the stem
directly, or indirectly
through the roots, the
plant will keep fresh.

Take two tumblers

partly filled with water, FIG. 9.— Second experiment to show

that water is given off by leaves.

and cover each with a

piece of cardboard with a small hole in the centre (see
Fig. 9). Put through this hole the end of a leafy shoot
— for instance, of dead-nettle or groundsel — and arrange
matters so that the cut end of the stem dips under
the water. Block the hole with wax or other material.
Cover each of the shoots with a second tumbler, turned
upside down and resting on the cardboard covering the
first Place one set in the light in a window, and the

88 NATURE TEACHING

other at the back of the room where the light is dull.
The inside of the upper glass standing in the window
soon becomes dull with water settling on it, and after a
time actual drops of water will trickle down. The one
in the dull light remains bright much longer. The water
which settles on the inside of the glass must come from
the plant, for the card prevents the water in the lower
tumbler being evaporated. We learn, then, as in our
earlier experiments, that the leaves give off water, and
in addition we have found out that they give off more
water when in the light than when in the dark. Repeat
this experiment with a shoot from which the leaves have
been cut off, and compare results. Make sketches of the
apparatus fitted up, and record all the observations
made.

The last experiment can easily be modified to allow
us to find out how much water a plant actually gives off
in a given time. One method of doing this is as follows.
Take a glazed pot without a hole in the bottom — for
instance, an ordinary jam-pot — and plant in it a young
sunflower or cabbage, in soil. After two or three days,
when the plant has become established, water the plant,
and cover up the earth with some thick tin-foil, wrap-
ping it round the stem of the plant so that no water
can escape except by transpiration through the leaves.
Weigh pot and plant together, and record the weight
and the time in your note-book. Place the pot in bright
sunlight in a window, or out of doors if the weather is
fine, until the next day, and then weigh again. The
difference in the two weights gives the amount of water
transpired in this time. Now lift up one corner

THE LEAF 89

of the tin-foil and water the plant ; weigh again, and
once more record the weight Then by weighing after
another interval you can obtain once more the amount
of water transpired in this time. Vary the experiment
by placing the plant in dull light, or cool places, and see
what difference this makes in the weight of water given
off in a certain time.

There is one point we have not yet determined,
namely, is the water transpired by the leaves given off
equally from both surfaces of the leaf, or does one sur-
face transpire more than the other ? A simple way of
testing this is to place some leaves flat, between two
pieces of glass, and notice whether one piece of glass
becomes bedewed quicker than the other, or whether both
become moist at equal rates. In making these experi-
ments, place the leaves between the glasses, and fasten
the glasses together with a string or elastic bands, and
then stand them upright so that both sides are equally
lighted. Unless this is done you would not be certain
that any differences noted were not due to one side
getting more light than the other, and as our earlier
experiments have taught us, transpiring quicker.

Having found in the previous experiment some leaves
which transpire from one surface and not from the other,
plunge them into boiling water, and watch carefully for
small bubbles of air coming from them. These should
appear on the side from which the water is given off,
the bubbles coming out through the little pores or stomata,
owing to the air inside the leaf getting hot and expand-
ing. In many leaves the bubbles come only from the
lower side.

90 NATURE TEACHING

Examine these same leaves with a lens, looking care-
fully for the very small pores. As the above experiment
has shown, these are often present only on the lower sur-
face of the leaf.

Take a tumbler, fill it half-full of water coloured with
a little red ink or eosin. Place some leafy shoots
(balsams or lime twigs do admirably) with the cut ends
of their stems dipping in the water, and leave them for a
day in a light place in a warm room. The stems become
marked with red lines, and finally the leaves also. This
coloration is due to the water which passes up the
bundles of the stem and their continuation in the leaves
(the veins), and, being red, colours them, thus indicating
the path in the stem along which water travels.

Note the manner in which the leaves of many grasses
roll up during very dry weather. This may also be
observed by bringing the grasses into the room and
noting the change as the leaves become dry. Observe
the positions assumed by the leaves of other plants
during dry weather, or at the middle of the day when
the sun is very hot, noting whether they roll up or droop.
The leaves of house-leeks, laurel, holly, and other thick-
leaved plants do not roll up. They are sufficiently pro-
tected by their thick skin.

Observe during rain, or while watering with a water-
ing-can with a very fine rose, the direction in which the
water is conducted by the leaves of the plants growing
in the garden. Compare this with the distribution of
the roots, and particularly of the young rootlets by which
water is absorbed. Note the course of the water and
the arrangement and character of the roots, in — beet-'

THE LEAF 91

root, dandelion, violets, lettuce, hyacinth, and in trees
such as the apple, pear, oak, etc.

Plants and the Atmosphere.

Put about an ounce of slaked lime (building lime) into
a wine-bottle full of water ; shake well and allow to settle.
The clear liquid is lime-water, and should be carefully
poured off and kept ready for use
in another bottle.

Take a dry wide-mouthed "T^" M

bottle, such as a jam-bottle ; pour -*•* ' — ^
into it a little lime-water and shake
gently. The lime-water remains

J

clear, showing that in ordinary air

very little, if any, carbon dioxide
is present.

Fasten a small piece of char-
coal to a thin wire, ignite the
charcoal, and, using the wire FIG. 10.— Charcoal burning
as a handle, hold it in a dry in glass jar.

wide-mouthed bottle similar to that used in the pre-
vious experiment (see Fig. 10). It is well to pass the
wire through a cork or piece of cardboard, so as to close
the mouth of the bottle while the burning charcoal is in
it. After the charcoal has been burning for a few minutes
the flame will go out, all the oxygen in the bottle having
been used up. Remove it, pour in some lime-water, and
shake gently : the lime-water will become cloudy owing
to the formation of carbonate of lime (chalk) by the union
of the lime with the carbon dioxide produced by the char-
coal burning in the oxygen of the air.

92

NATURE TEACHING

Pour a little lime-water into a tumbler or small
glass, and by means of a tube (of glass, bamboo or
a straw) pass the breath from the lungs through the
lime-water, which will soon become cloudy from the
formation of carbonate of lime as in the last experiment
(see Fig. n). If the breathing is continued for a long
time the lime-water will become clear again, owing to
the chalk being dissolved in the excess of carbon dioxide.

FlG. ii. — Breathing into
lime-water to show that
the breath contains car-
bon dioxide.

FlG. 12. — Experiment to
show that plants breathe
out carbon dioxide.

Into a similar bottle, corked or covered with a piece
of glass, place about a handful of the young tips of
leafy shoots, or opening flower-buds — for instance, man-
golds (see Fig. 12). Add a very little water to keep
them moist, and put away in the dark for about six hours.
Test as before with lime-water, when it should be found
that once again we have had carbon dioxide produced
in considerable amount. Repeat the experiment with
similar leafy shoots, but, instead of placing them in the

(UNIVE:

V
^^t-

THE LEAF 93

dark, keep them in strong sunlight out-of-doors. No
carbon dioxide should now be found, for, as fast as it is
formed by the breathing of the plant, it is used up in
the process of assimilation.

These three experiments teach us that the processes
of burning and the breathing of
animals and plants agree in result-
ing in the formation of carbon
dioxide.

Place some leaves in a wide-
mouthed bottle, fill with water,
and place it in the sunlight (see
Fig. 13). Observe that in a short
time small bubbles of gas appear FIG. 13. — Experiment to

,11 ,. , . ,., show the bubbles of gas

on the leaves which are in reality given off from ]eaves sin
bubbles of oxygen, formed in sunlight.
the process of assimilation and given off by the plant.
On repeating this experiment, but placing the bottle in
the dark, no bubbles will be given off, for, under these
conditions, no assimilation can go on.

The Food of Plants.

Take enough starch just to cover a threepenny-bit,
drop it into about half a pint of boiling water, and, when
cold, add a little iodine solution. The liquid becomes a
deep blue. (If you have too much starch present the
colour will be almost black, and water should be added).
This is a convenient test whereby to recognise the
presence of starch.

Take a few leaves which have been exposed to bright
sunlight for several hours (fuchsias answer admirably),

94 NATURE TEACHING

plunge them into boiling water for about two minutes,
and then place in strong methylated spirits. When the
liquid has become of a deep green colour — owing to the
leaf-green being extracted — pour it off and add fresh
spirit, repeating this until the leaves are free from colour.
Put one or two of these leaves in water containing a
small quantity of iodine solution ; they will turn blue.
The colour will not be a pure bright blue, but, owing to
the brown stain communicated to the tissues by the
iodine, of a somewhat greenish hue.

Take a plant with smooth leaves — for instance, a
fuchsia — growing in a pot, and leave it exposed to the
sunlight from morning to afternoon. Then cut off one-
half only of two or three leaves, leaving the other halves
attached to the plant. Test the cut-off halves for starch
as described above. If they have plenty, place the
whole plant in the dark until the next day, either in a
cupboard or covered up by a box or tin, taking care
that no light at all gets in. Now cut off the remaining
halves of the leaves tested previously, and test these in
exactly the same way. If they have been in the dark
long enough (fuchsias usually require only twelve hours,
but some other plants take twenty-four hours or even
longer to get rid of all their starch) they will be found
to show no blue colour, indicating that all the starch
they contained has been used up during the time they
have been in the dark.

Using the plant which we now know to have no
starch in its leaves, we can prove that starch is only
formed in the parts actually exposed to the light Take
some tinfoil or lead-paper (such as is used for tea pack-

THE LEAF 95

ages), cut out a cross or other pattern, and wrap the foil
round a leaf (attached to the plant) so that the only
portion of the leaf which can be seen is that which shows
through the cut-out pattern (see Fig. 14). Press the tin-
foil tightly down on the leaf, to prevent light getting under
the edge of the cut portion, and expose the plant to sun-
light. If this is done in the morning the plant may be
tested in the afternoon, and it should then be found on

FIG. 14. — Experiment to show that starch is only formed
in the portions of leaves exposed to sunlight. The
left-hand figure shows the leaf wrapped in tinfoil,
from which a cross has been cut. The right-hand
figure shows the leaf after exposure to sunlight and
tested for starch.

boiling the leaf and decolorising it in spirit, and putting
it in iodine solution, that we obtain a pattern, in blue, on
the leaf exactly similar to the portion exposed to the
light. That is to say, the part of the leaf exposed to
the light, and that part only, has been able to form
starch, or, in other words, assimilation only goes on in
the light.

The coloration due to the iodine soon fades away,
but the leaves may be preserved for any length of time

96 NATURE TEACHING

in methylated spirit, and the colour obtained again on
once more putting them into iodine solution. Leaves
can thus be prepared in the summer and kept for use
as required during the winter.

Take a leaf of a variegated geranium or other plant
with green and white leaves, which has been in a good
light for a day. Make a sketch of the leaf, shading in
the green parts. Decolorise the leaf by immersing in
boiling water and methylated spirit, and then place in
iodine solution. A pattern should be obtained similar
to the one drawn, showing that starch is formed only in
the green parts of the leaf, and that the white parts
contain no starch. Draw the leaf after treatment with
iodine, shading the blue parts, and compare it with your
previous sketch.

The following experiment will serve to show that
unless a plant is provided with air no starch can be
formed in its leaves, even though it is placed in the light.
Germinate some peas and beans, and after the first
leaves have expanded, place the young plants in the
dark for a day. Test some for starch : if they contain
none, they are ready for use ; but if they still show the
presence of starch, replace them in the dark until they
are starch-free. Place some of the seedlings in bright
light in a window, giving water to their roots so that
they do not dry up. Put others in a thin glass vessel
full of water which has been boiled and allowed to cool
(this precaution is necessary to get rid of the air dissolved
in the water), and put these alongside the others in the
window. The plants should be weighted with small
stones to keep them well beneath the surface of the

THE LEAF 97

water. Leave them there for several hours, and then
test leaves from both for starch. It should be found
that those exposed to the air have formed starch, whilst
those under the water and consequently deprived of air
have formed none.

Another way of carrying out the above experiment
is to take a plant the leaves of which have been found to
have the pores only on the underneath surface. Place
it in the dark until free from starch. Then smear the
under sides of some leaves with vaseline. This fills up
the pores and prevents air entering the leaf. Expose
the plant to sunlight, and after some hours test for starch
both coated and uncoated leaves. The latter should be
found to contain starch, but the former to contain none.

We can now pursue our inquiry one step further, and
endeavour to ascertain what constituent of the air is
actually necessary for the formation of starch. There
are two chemical substances, soda lime and caustic
potash, which have the power of absorbing carbon
dioxide, and by using these we can obtain an atmosphere
in which oxygen and nitrogen are both present, but
carbon dioxide is not. Let us do so, and see if under
these circumstances a plant can form starch. This
experiment can be arranged as follows : —

Take two bottles of clear glass (not tinted) with wide
mouths ; in each put a tightly-fitting cork with a bent
glass tube, about half an inch in diameter, passing
through it. In one of the tubes put some lumps of soda
lime, but leave the other empty. In the bottom of the
bottle fitted with the tube containing soda lime, place a
little dish with some pieces of caustic potash in it. This

G

98 NATURE TEACHING

caustic potash will absorb what carbon dioxide there is
in the bottle, and the soda lime will prevent any more
entering.

Have ready two fuchsia shoots, which have been in
the dark for a day and have been tested, and are known
to be free from starch. Put the ends of their stalks in
little bottles of water, and place one in each bottle.
Replace the corks. It is best to paint the corks over
with a coating of paraffin wax to make sure that no air
gets through them. Put the bottles thus fitted up, side
by side, in the sunlight, and after say six hours' exposure,
test a leaf from each for starch in the ordinary way. If
there is no appreciable difference leave them for another
day, and test again in the late afternoon. By this time
it should be found that the leaves in the bottle contain-
ing carbon dioxide have formed starch, whilst the others
have not. The success of this experiment depends on
having well-fitted, good corks, and on the glass tubes
fitting tightly in the corks. Any leakage will allow air
containing carbon dioxide to enter, and so spoil the
experiment.

In the course of our experiments we have repeatedly
found that if a plant with its leaves loaded with starch
is put away in the dark and left there for twelve hours
or longer (according to the kind of plant employed), the
starch will have disappeared. What has become of this
starch ? An answer to this question can also be obtained
by experiment, but it is necessary that we should first
make some preliminary experiments so that we may
understand what is taking place.

Place a piece of starch in cold water and let it remain

THE LEAF 99

there some hours. The starch does not disappear. In
other words it is insoluble in the water. Put a lump of
sugar in water. It quickly disappears, being soluble in
water. Starch, then, is insoluble in water, whilst sugar is
soluble. Soluble substances can readily pass from one
part of a plant to another. If now we can show that
starch is changed in the leaf to sugar, we can easily
understand how it may be that a leaf containing starch
in the afternoon may have none in the morning. It may,
in fact, have been altered into sugar and carried away to
other parts of the plant. A convenient method of test-
ing sugar is by adding some to a solution known as
Fehling's solution, and boiling for a minute in a test-
tube. When this is done a red deposit or precipitate
collects in the bottom of the tube, whilst with starch no
red precipitate is formed.

Take two test-tubes, and fill each about one-quarter
full of Fehling's solution. To one add a very little starch,
and to the second add a few drops of honey. Boil both.
In the second a red precipitate collects, whilst no red
precipitate is formed in the first.

Take a little starch on the end of a penknife, mix it
up with some cold water, and drop it into about half a
pint of boiling water, and boil for two minutes. When
cool, add iodine to a small portion. It turns blue, show-
ing the presence of starch. To a second small portion
add Fehling's solution, and boil for not more than a
minute. No red precipitate forms, showing that no
sugar is present

Place in two fresh test-tubes some more of the starch
in water, and add to each some saliva, and put the two

100 NATURE TEACHING

tubes in a glass of warm, not boiling, water. After half
an hour test one for starch and the other for sugar. It
should be found that the starch has disappeared, and that
sugar has been formed.

To two other portions of starch in water add a little
malt (obtained from a brewery). Keep warm in the
same way, and afterwards test for starch and sugar. It
should again be found that the starch has disappeared
and that sugar has been formed.

Repeat the above experiment, but instead of using
malt from a brewery, take a good number (50 to 100) of
just-sprouted barley grains. Break off the young shoots,
and grind them up with a very little water. Add some
of this paste to the two tubes containing starch, and keep
just warm for an hour or two. Test the tubes now for
starch and sugar. As in the previous experiments, it
will probably be found that the starch has gone, and
sugar has been formed in its place. Germinating barley,
therefore, contains something which can change starch
into sugar.

Gather during the night twenty or thirty leaves of
the garden pea, or garden nasturtium. Rub them to a
paste with a little water, and add this liquid to two more
samples of starch in water. Keep warm, and test after
a few hours for starch and sugar. The same process
will be found to have gone on, showing that these green
leaves, like the germinating barley, contain a substance
able to change starch into sugar.

CHAPTER V
THE SOIL

IF we dig a hole in the ground we usually notice certain
changes in the appearance of the earth which we remove
as we go deeper and deeper. That near the surface is
often dark in colour and loose or friable ; below this we
come in succession upon material of a lighter colour,
then probably a rather compact layer with stones, and
finally hard rock. If we look at a place where a deep
trench has been dug, as, for example, in a road-cutting,
quarry, or excavation for the foundation of a house,
or where a heavy rush of water has cut away the soil,
we see that there is a gradual change in appearance
from the upper to the lower layers. The stones of the
lower layers are probably of a similar material to the
rock at the bottom ; similarly the small stones and even
the finest particles which can be picked out are often
recognisable as fragments of the rock which lies beneath.
In other words, we see that soil largely consists of rock
broken up into small particles.

This breaking-up results from the action of various
agencies, but is very largely due to water, containing

carbon dioxide in solution, which dissolves carbonate of
101

102 NATURE TEACHING

lime (chalk), and which also attacks the mineral known
as felspar, dissolving a portion of it and leaving a residue
which is clay. A little search amongst the stones in a
garden is almost sure to reveal that while some of the
stones are quite hard, others are relatively soft ; some
being found which may be crushed in the hand, or
crushed or broken by the spade. In these soft stones
the felspar has been attacked and partly converted
into clay. If the stones are of flint or chert (quartz),
these, being practically indestructible, never become
soft.

Frost is, in temperate climates, an important agent
in breaking up rocks and stones to form soil. Many
rocks and stones are somewhat porous, absorbing
appreciable quantities of water. Now, water expands
in changing from the liquid to the solid state ; in other
words, a certain quantity of water increases in bulk
when it is frozen and changed into ice. This may easily
be shown by filling a bottle with water, tightly corking
it, and exposing it out-of-doors on a cold winter night,
when the bottle breaks, unless the glass is very strong,
in which case we usually find the cork forced out. The
ice must get extra room somehow, and it is merely a
question whether less force is required to break the
bottle or to force out the cork. The bursting of water-
pipes in winter is due to the same cause.

To return to the consideration of a porous rock ; it
absorbs water, and if this water is subsequently frozen it
expands, and in doing so often exerts sufficient force to
crack the rock. The cracking due to any one freezing
may be very small, but when repeated over and over

THE SOIL 103

again, even large blocks of stone are in the course of
time reduced to small fragments.

It requires little observation to see that the particles
of which the soil is composed vary greatly in size. This
variation is of great importance, agriculturally, for the
nature of the soil is greatly influenced by the preponder-
ance of large or small particles. By stirring up a small
quantity of soil with water and pouring it away,
repeating the operation until the water comes away
clear, the fine and coarse particles may be separated
from one another ; and by stirring up the water
containing the finer particles, and pouring away again,
a further separation may be made into fine and very
fine particles. It will be noticed that the water remains
muddy for a long time, indicating the presence of
particles of an extreme degree of fineness ; these very
fine particles are clay. This method, carried out with
certain precautions, is largely employed in ascertaining
the proportions of particles of various sizes existing in
soils, and yields information of considerable value to the
farmer.

The particles are classed as gravel, sand, silt and clay.

Soils are classed as gravelly, sandy, or clayey,
according to which of these constituents predominates.
Gravelly or sandy soils are often spoken of as " light,"
not because they weigh relatively less than other soils,
but because they offer little resistance to implements of
tillage (such as ploughs, spades, and forks) ; that is to say,
they are light or easy to work. Clay soils, on the other
hand, are often called " heavy," because of the difficulty
with which the implements pass through them.

104 NATURE TEACHING

Water in Soils.

Sandy or light soils differ in a marked degree from
clayey or heavy soils as regards their relation to water.
Water drains through sand with ease, while it passes
through clay soils with difficulty. When water falls, or
is poured upon soil, which is then allowed to drain, a
certain quantity of the water is retained by the soil, and
does not drain out. Sandy soils retain only a small
amount of water, and clayey soils a great deal. Thus
sandy soils, while permitting drainage to take place
more freely, retain less water than clayey soils, and
therefore require rain more frequently than clays, or the
crops growing on them would suffer from drought.
Illustrations of these differences, drawn from his own
neighbourhood, will probably occur to the reader.

The explanation of this retention of water by soil is
to be found in its physical structure. There are spaces
between the small particles of soil through which the
water passes. Usually these spaces are filled with air,
but when heavy rain comes the air is largely replaced
by water, returning when the water drains away. The
better the tilth of the soil the larger will be the number
of these fine air-spaces, which are necessary for the
maintenance of vigorous plant growth (roots needing
air as well as moisture). As we shall have occasion to
see later, important changes, requiring free access of air,
are going on in every fertile soil. When water drains
away, the draining is never complete, for soil, after
it has been wetted, always retains some moisture,
however thoroughly it is drained.

THE SOIL 105

This water is retained by "capillary attraction?
which is the power that causes water to flow into any
very small cavities, and is commonly well exhibited in
sugar, blotting-paper, and similar porous substances.
If one of these is gently brought into contact with a
drop of water, the water enters the small pores or
cavities and spreads over a large area, where it is
retained, and from which it will not drain away again.
By means of this power, soils retain a sufficiency of
water for the use of plants, the small spaces being filled
with water while the larger spaces contain air. The
soil is thus provided with both of these requisites for

plant growth.

Clay.

It has already been said that clay is formed from
felspar by the action of water and carbon dioxide.
Pure clay consists of extremely minute particles, but
soils are never pure clay, there being always a
certain amount of sand present. The fine particles of
clay have a tendency to collect together in groups or
masses. If this were not the case all the small openings
and passages in the soil would be choked, and drainage
rendered impossible. Clay also has the power of
absorbing water and becoming plastic ; that is to say, it
can be kneaded and moulded by the hand, a property
which is taken advantage of in making bricks and
pottery. When strongly heated, clay loses this property.

The operations of tillage are partly directed toward
breaking up the masses of clay, admitting air into the
soil, and increasing the size of the capillary spaces.
They also increase the tendency which the fine particles

106 NATURE TEACHING

possess to gather into masses, thus permitting a freer
circulation of water. Lime has a similar effect in
causing the particles to collect or flocculate, and is there-
fore often used as a dressing for stiff, clay lands, in
order to make them lighter, and more easy to till.
Kneading and trampling have the opposite effect ;
breaking up the little collections, groups or floccules of
clay, and thus closing the small openings. Hence it is
that brickmakers and potters, who require firm, compact
masses, thoroughly knead the clay they use before
working it into shape. The cultivator, on the other
hand, desires to bring his clay into a flocculent condition,
so as to permit the circulation of air and water; he
thus, at intervals, digs, forks, or ploughs the soil,
admitting the air and causing the clay to become
flocculent, while he is careful to prevent, as far as
possible, any trampling or walking over the soil which
he has tilled.

Vegetable Matter in Soils.

In digging down through the soil, it was seen that
the upper layers (surface-soil) were darker than the lower
(subsoil}. This is due to the presence of decaying leaves,
roots, and other vegetable matter derived from plants
previously growing on the spot, or brought there as
manure. Some soils are almost entirely made of decayed
vegetable matter — for instance, in woods of beech, oak,
etc., where every year enormous quantities of dead
leaves are added at the approach of winter. In swampy
lands, covered with bog moss, enormous accumulations
of vegetable matter are formed, resulting frequently

THE SOIL 107

in the formation of peat, which is almost pure vegetable
matter. If a little of the surface-soil is burned, by
placing it on a sheet of iron over a fire, it will be seen
that it first becomes dark, owing to the charring of the
vegetable matter ; then, as the vegetable matter burns
slowly away, it becomes lighter in colour, and more like
the subsoil. If the heat be great and long-continued,
the soil undergoes still further changes of colour, often
finally becoming red, like bricks.

This decaying vegetable matter is known as humus,
and is essential to the production of true soil. Mere
crushed, powdered, or disintegrated rock does not con-
stitute true soil, but requires the admixture of humus.
Humus plays several important parts. It increases the
amount of water which sandy soils can retain ; it tends
to preserve the porous nature of stiff clays, facilitating
drainage and admitting more air ; it assists in maintain-
ing the friable condition known as tilth ; and, moreover,
soils rich in humus do not become hard and compact.
It is worth noting that the common expressions " poor
land " and " rich land " usually refer respectively to soils
with little humus and soils with much humus in them.

Earth-worms are very active agents in distributing
humus through the soil. They carry leaves down into
their burrows and bring to the surface, and deposit there,
large quantities of earth in the form of castings. Darwin
estimated that in an English meadow the earth-worms
brought to the surface upwards of 15 tons of earth per
acre per year. Owing to this action of the earth-worms,
objects lying on the surface are slowly buried or appear
to sink into the ground. In 1842 Darwin spread a

108 NATURE TEACHING

quantity of chalk over a field in order to observe at a
future date to what depth it had been buried. At the
end of twenty-nine years a trench was dug across the
field, when a line of white nodules was traced on both
sides of it at a depth of seven inches below the surface.
The mould, therefore (excluding turf), had been thrown
up at an average rate of -22 (or about |) inch per annum
through the agency of earth-worms. It was estimated
that the soil so brought up in this meadow weighed
about 73,000 Ib. From these and similar facts it has of
late years been recognised that earth-worms exercise a
very considerable influence in keeping soils in a fertile
condition.

Natural processes of decay lead to the steady dis-
appearance of humus ; so that if land is cultivated and
the crop steadily removed, there is a tendency for the soil
to become poorer and poorer as the humus, originally pre-
sent, rots away and nothing is added to replace it. When
this happens we hear complaints about the soil being
" worn out." " Wasted " would be a better expression. In
places where no crop is removed, as in woods and forests,
there may be a steady increase of humus owing to the
annual addition of vegetable matter from the fallen leaves
being greater than the amount used up in a year. The
soil of such places, commonly called leaf-mould, is thus
usually very rich in humus, and much sought after for
purposes of cultivation, on account of its fertility. Un-
fortunately this fertility is often rapidly wasted because
the cultivator takes no pains to keep up the supply of
humus.

In the cultivation of all soils it is necessary to add

THE SOIL 109

supplies of vegetable matter from time to time, so that it
may decay and become mingled with the soil as humus.
Good agriculturists take care to save and dig into their
fields and gardens all the available refuse vegetable
matter, such as manure and stable refuse, dead leaves,
twigs and grass. We shall have to refer to these later
when dealing with the question of manures.

The very wasteful habit is often adopted of burning
a great deal of refuse vegetable matter instead of burying
it in the soil to form humus. It is not uncommon to
find a man busily engaged in burning leaves, and other
vegetable refuse, and at the same time lamenting that
this soil is becoming worn out. Instead of being burnt
these things should be dug into the soil, or, if that is in-
convenient or impracticable, they should be thrown into
heaps and allowed to decay partially. Loss of valuable
plant food may be prevented by covering the heap with
layers of soil, which also prevents the production of any
offensive smell or other unpleasantness. Such heaps
are known as compost-lieaps^ and if adopted in every
garden the laments about worn-out soil would cease.
It is often urged that by burning the leaves, twigs, etc.,
plant ashes are obtained which are of value when added
to the soil. This is true. The important fact, however,
is usually overlooked that the leaves before burning are
made up, speaking generally, of ash and organic matter,
and that when burnt the most valuable portion, the
organic matter, burns away and is lost. The ash is thus
added in either case, but by not burning the matter, we
add the most valuable portion, the organic matter, in
addition.

110 NATURE TEACHING

Chalk in Soils.

Carbonate of lime, or chalk, is present in some soils
in such quantities, that they are distinguished as chalky
or calcareous. Other soils contain very small quantities
of carbonate of lime, and are known as non- calcareous.
A large portion of the soils in Great Britain are non-
calcareous, but there are extensive areas where the
principal rocks are chalk and limestone, and as these are
almost pure carbonate of lime, the soils formed from them
are often very rich in this same substance. Examples
of calcareous soils occur in Kent, Surrey, Yorkshire,
Norfolk, Cambridgeshire, Bedfordshire, the Isle of Wight,
in all of which chalky rocks are found. A band of lime-
stone extends right across England from Dorsetshire to
Yorkshire, and on this calcareous soils are found.

Calcareous soils are formed by the breaking down of
the chalk and limestone rocks of these districts.

Carbonate of lime may be recognised by the manner
in which it effervesces when an acid is poured upon it.
This test may be used to distinguish calcareous from
non-calcareous soils, the former effervescing, the latter
not. According to the proportion of fine and coarse
particles entering into their composition, calcareous soils
may be either light or heavy.

Carbonate of lime is an important constituent of soils,
because it takes part in many changes which go on in
them, as will be understood later. Carbonate of lime is
necessary for the production of nitrates from nitrogenous
manures ; it reacts with most of the substances employed
as artificial manures, so that their application uses up a

THE SOIL

111

certain quantity of the carbonate of lime. There is thus
a steady, though small, drain on the carbonate of lime
present. This requires but little thought when an
appreciable amount is present in the soil, but some soils
contain so little that the addition of dressings of carbon-
ate of lime, in the form of chalk or limestone, at long
intervals, may be expected to add to their fertility.

PRACTICAL WORK

Dig a hole or trench in the garden, and note the
character of the soil from the surface downwards (see
Fig. 15). This trench

de-

may perhaps be
signed to fulfil some
useful purpose, or the
observations may be
made when occasion
arises for digging thus
deeply. Sketch what
you see.

Ascertain, if possible,
the character of the rock
lying beneath the garden
either by digging down to it or by observing it at
some place in the immediate neighbourhood where it
comes to the surface, or is exposed, as in a road-
cutting.

Collect the different kinds of stones to be found in
the garden soil, and note whether they are of a similar
character to the underlying rock. If other kinds of
stones are found, endeavour to explain whence they are

IG. 15. — Diagrammatic section illustrat-
ing gradual passage from the soil to
the subsoil, and, finally, the underlying
rock.

112 NATURE TEACHING

probably derived. (A selection of these stones should
be kept in the school.)

In frosty weather select one or two pieces of sand-
stone, and of brick, of very porous character. Wash off
all dust and loose pieces, place them in a vessel of water
so that they are about half covered, and leave them to
soak for two or three hours. Put them out of doors
where they can become thoroughly frozen, and allow
them to remain exposed to two or three nights' frosts.
Then bring them into a warm room, and when they have
thawed completely, examine carefully to see whether any
small fragments have been split off. The stones or bricks
should be placed on clean plates or saucers when put
out in the cold, in order that any small pieces broken off
can be more easily seen.

Mechanical Analysis of Soil.

Separation of soil particles by means of water : — This
operation may be conducted so as to give quantitative
results of interest and value, if a small amount of appar-
atus is procurable. For this work it is necessary to have
three sieves with holes of known sizes ; brass sieves with
circular perforations are preferable to those of wire.
A suitable set consists of three sieves with holes of
2, i, and \ millimetre respectively. (i mm. = JT indi-)
A small scale or balance for weighing the separated
gravel, sand, etc., is also required.

With these proceed as follows : — From a well mixed
sample of soil weigh out 50 grammes (if oz.), stir this
well with water in a glass or cup, and pour the water
through the sieve with 2 mm. holes ; the sieve resting

THE SOIL 113

on a dish or basin. With successive quantities of water,
transfer all the weighed portion of soil to the sieve.
Gently wash the particles of gravel by moving them
about in the sieve with a wooden rod or stirrer (or a
glass rod tipped with rubber), using fresh supplies of
water until the small stones are quite clean. Pour the
water and soil which has passed through the first sieve
through the second, similarly supported on a basin, and
the water and material from the second through the
third. Wash the residues in each of the sieves with
gentle stirring, until the water coming away ceases to be
muddy. Put aside the sieves, with their contents, to dry.
Collect the washing-waters together, and stir well. After
standing two or three minutes pour away the muddy
water from the sandy sediment, wash the sand into a
beaker or tumbler, and again wash with gentle stirring
and rubbing with the wooden or rubber-tipped rod.
After standing a short time once more pour the water
from the sandy sediment. Repeat this process until the
water ceases to become turbid.

Dry the various portions separately and weigh them ;
the different grades may be designated as follows: —
From the first sieve, coarse gravel ; from the second
sieve, gravel ; from the third sieve, coarse sand ; the
residue from washing, sand. The amount carried
away in the water may be found by adding together
the weights of the various grades obtained and de-
ducting this from the total weight taken to be operated
on. The difference may be called silt and clay. The
quantities should be calculated in percentages. Samples
of the separated grades should be put into tubes or

H

114 NATURE TEACHING

small bottles, and kept as a record and for future
reference.

This method gives interesting, and approximately
accurate, results, and is within the capacity of the older
pupils of a school class. For the method of procedure
where great accuracy is required, see such books as
Wiley's Agricultural Analysis, Vol. I. For junior classes
it is sufficient to omit the weighing and to make approxi-
mate separations by washing.

Water in Soils.

Place in separate glass funnels, supported over cups
or tumblers, equal weights of sand, clay and garden
mould ; these should be dry and coarsely powdered.
From 50 to 100 grammes is a convenient quantity.
Place a small piece of blotting-paper (or filter-paper) at
the bottom of the funnel to prevent the soil from getting
into the neck. Shake and tap the funnel gently to cause
the contents to settle down closely. Now pour equal
measures of water on the contents of each funnel, using
enough water to soak the soil thoroughly and to allow
water to drain through into the vessels placed beneath.
Observe that the water flows away with different rapidity
in the three cases, and that when all the water which
will drain away has been collected, the three different
kinds of soil retain different amounts of water.

The funnels with their contents may be weighed
before the water is added, and again after it has drained
away. The difference between the two weighings gives
the weight of water retained in each case, and the results
should be recorded for the different kinds of soil, cal-

THE SOIL 115

culated for convenience of comparison to 100 parts of
soil.

Fit a cork, with a hole in it, into a glass tube, about
f inch in diameter, and arrange a small piece of linen or
blotting-paper over the cork, inside the tube ; now pour
shot into the tube (see Fig. 16). The shot may be taken
to represent particles of soil with their air-spaces. Close
the opening in the cork with the
ringer, and pour water on the shot,
fully covering them. This condition
may be taken to represent soil from
which all the air has been displaced by
water. Remove the finger ; most of
the water will now drain away, but
some will be retained, by capillary
attraction, between the grains of shot.
From this experiment draw inferences
as to the relation of water to small
soil-particles.

Place in a saucer a little water, to Fl°'

which a few drops of red or black ink tention of water be-

, , tween small particles

has been added (merely to colour it), by capillary attrac-

i j. e . f. tion.

and dip one corner of a piece of
blotting-paper into the water : notice how the liquid
rapidly spreads through the whole piece. This is an
example of the action of capillary force.

Take two small pieces of glass (about 3 or 4 inches
square) ; stand them upright in a saucer of water (which
may be coloured if desired) ; bring their edges together
on one side so that the pieces stand like a partly-opened
book standing on its edge (see Fig. 17). Gradually bring

116

NATURE TEACHING

the open edges together, as if closing the book, and notice
that the water rises between the glasses, being highest
where the space between the glasses is narrowest, and
lowest where the space is widest. This is another ex-
ample of capillary attraction, and shows that the effect
is greater in small spaces and cavities than in large ones.
Make diagrams showing the position of the water when

FlG. 17. — Experiment to show that
water rises, by capillary attraction,
higher in narrow than in wide cavities.

FIG. 1 8. — Experiment to
demonstrate the rise of
water in soils by capil-
lary attraction.

the glasses are somewhat widely separated and when
close together.

Take a tube, such as a narrow lamp-chimney, tie a
muslin or linen cap over the bottom end and fill with
soil. Flace the tube, thus filled, upright in a saucer of
water, and note the manner in which the water slowly
rises through the soil (see Fig 18). This experiment may
be made quantitative if the tube is weighed, before and
after filling with soil, to give the weight of soil used ; and
again after standing for some time, say for twenty-four

THE SOIL 117

or forty-eight hours, or until the water has risen to the
top of the soil, to ascertain the weight of water absorbed.
This should be calculated to 100 parts of soil. If
necessary, water must be added to the saucer from time
to time in order to ensure that the soil in the tube is
always in contact with water. Comparisons should be
made of the weight of water absorbed by sand, clay, and
garden-mould ; sand absorbs the least and clay the
most water.

The following experiment will demonstrate the
influence of capillarity in bringing water from the sub-
soil to the surface. Take two large pots, or two tubs or
deep boxes, fill one with soil in the ordinary way for
sowing seeds, as described on page 15. Fill the other
in the same way, but in filling place a layer of fine wire-
gauze horizontally across the box or tub, about 4 or
5 inches below the surface of the soil. This gauze will
serve to interrupt the capillary connections between the
subsoil and the surface. Sow seeds of barley, grass, or
other shallow-rooted plants (more than one kind may
be used) and place the boxes, pots, or tubs side by side
out-of-doors. Give a little water until the plants are
established, and then leave them dependent on the
rainfall. Record the rate of growth and development of
the two sets of seedlings, and determine the effect of
restricting the capillary flow of water. In a very wet
season the pots, etc., should be screened from excessive
rainfall.

Take a small ball of clay — this may be obtained
from the subsoil of the garden — let it dry in the air for
a day or two, and then put it into the kitchen fire for

118 NATURE TEACHING

some hours. When cold, compare it with a portion of
fresh, unburned clay. Note that, although it is still able
to absorb water by capillarity, it has lost its plastic
character and can no longer be moulded into shape by
the hand. Crush it to powder and moisten with water ;
the plasticity is not restored, it is permanently lost.
Note also the change in colour.

Make small bricks of wet earth, sand and clay
respectively. Measure and record their length, breadth
and thickness. Place the bricks on a piece of board and
put them on one side for a day or two until quite dry.
Now measure them again, and note any changes in size.
Note also the looseness or hardness of the dried bricks.

Take a small piece of clay, about the size of a hazel-
nut, and rub it down with water to the consistency of
thin cream. Pour this into a pint of rain water or dis-
tilled water and stir well. After standing a minute or two
pour off the muddy water from any sand which has settled
to the bottom. Now take two similar glass cylinders
or large tumblers, and fill each with the clay water, which
should again be stirred before being poured out. To
one cylinder or tumbler add a tablespoonful or two of
lime-water and stir. Set the two vessels aside for the
clay to settle. Note the difference in the way subsidence
takes place in each, and recognise that lime causes the
fine particles of clay to collect together into larger
masses or floccules which subside quickly.

Vegetable Matter in Soils.

A place should be set apart in the school garden
for a compost heap. All available refuse should be

THE SOIL 119

collected and placed on this heap, and, at intervals, a
layer of soil should be thrown over it to promote decay
and prevent unpleasant smells. The heap should be
kept damp throughout. Care should be taken to select
the place for the compost heap where it will not be
unsightly, and, if a low hedge is planted round the spot,
it need not disfigure the neatest garden. It is convenient
to have two heaps — one in process of formation, the
other ready for use.

To illustrate the influence of vegetable matter on
soil fertility, select in the school garden two beds, of
equal size, with similar soil, and conveniently near
together for purposes of comparison. Give one a good
dressing of stable-manure (which is vegetable matter in
a partially-decomposed condition), or a dressing from
the compost heap, or of such material as grass-cuttings
from a lawn or indeed of any available form of vegetable
matter. (There is a great difference in the rates of
rotting of various substances, some change so slowly as
to be troublesome in a garden ; stable-manure, owing to
its being already partly decomposed, is the most effec-
tive, rotting and mingling with the soil rapidly.) Give
the second plot no manure. Plant similar crops, at the
same time, on the two beds; the nature of the crop
adopted depending on time and local circumstances.
Keep a record of the character and growth of the crops,
noting the development and appearance of the plants,
the effect of dry weather or other climatic conditions.
Note the weight of the various parts yielded by each
crop, and, from time to time, observe the character of
the soil of each plot. These beds should be permanently

120 NATURE TEACHING

established, and at intervals, perhaps once a year, the
manured plot should receive a dressing of manure of a
vegetable nature. In a school garden a succession of
lettuce, beet, beans, and cabbage can readily be grown
on the beds.

Chalk in Soils.

Carbonate of lime — chalk. Place a small piece of
chalk in a saucer and pour upon it a little acid, which
may be strong vinegar, or hydrochloric acid. Note how
it bubbles up, due to its giving off carbon dioxide.
Chalk always does this when acted on by an acid, and
thus this is a useful test to find out whether a soil
contains chalk or not. Repeat the experiment, using
small quantities of soil from different places.* From
the observations made classify the soils as calcareous
and non-calcareous.

If the surrounding district contains examples of both
calcareous and non-calcareous soils, mark their distribu-
tion on a map. For this purpose small samples should
be collected, by the pupils, from a number of localities,
and examined as a class exercise or as a demonstration
by the teacher. A map of the district, on a somewhat
large scale, may be drawn on stout drawing-paper
and hung up in the class-room, or the appropriate map
of the Ordnance Survey may be purchased. Observa-
tions on the character of the soil may be recorded, from

* The teacher should provide himself with a collection of
soils from different places, taking care to have samples of both
calcareous and non-calcareous soils. These samples are preferably
kept in bottles.

THE SOIL 121

time to time, by means of colours upon this map, which
will ultimately become of considerable, interest if the
observations are made carefully. The pupils should
prepare copies of this map, on a smaller scale, for their
own use.

CHAPTER VI
PLANT FOOD AND MANURES

REFERENCE has already been made to water and
carbon dioxide as two of the constituents of plant food.
These two substances are obtained from the atmo-
sphere, the former falling as rain and usually entering
plants through their roots, the latter being absorbed
and assimilated by the green leaves. In addition,
certain constituents of the food of plants are derived
from the soil. We may divide these into two classes :
nitrogenous and mineral matters. This division is
convenient, for the absorption of nitrogen is sufficiently
interesting to make it desirable to devote separate
attention to it. Moreover, when a plant or any other
vegetable substance is burned, the nitrogen disappears
in the gases or vapours, together with the carbon,
hydrogen and oxygen, while the mineral matter remains
behind in the form of ash.

Nitrogenous Matter.

As the air by which we are surrounded consists of
four parts of nitrogen and one part of oxygen, it would

seem reasonable to suppose that its nitrogen would
in

PLANT FOOD AND MANURES 123

amply provide for the needs of plants. Careful in-
vestigations, however, have shown that plants, as a rule,
are unable to use this nitrogen (exceptions will be
referred to later), but obtain their nitrogen from the
soil in the form of complex substances known as nitrates.
We are familiar with nitrates in the form of saltpetre
which is nitrate of potash, and nitrate of soda largely
used as a manure.

All living things, animal and vegetable, contain
nitrogen. When they decay in the soil, their nitrogen
is converted into nitrates, this change being brought
about by the agency of microbes or bacteria which live
in the soil in countless numbers. In consequence of
the results they bring about, these bacteria are spoken
of as nitrifying bacteria. In order that they may live
and thrive and so carry on their useful work, it is
necessary that the soil should present certain conditions.
Moisture and air are needed, for in their absence the
nitrifying bacteria cannot live. A certain amount of
warmth is also necessary, the activity of the bacteria
being suspended, although they themselves are not
actually killed, by the cold of winter. In addition, it
is essential that there should be some lime in the soil.
It will be observed that these conditions are those
which have been repeatedly referred to as the objects
aimed at in good tillage and cultivation ; that is to say,
the presence of moisture, air, and lime, together with
vegetable matter which contains the nitrogen to be
acted upon. Speaking generally, therefore, we find
that those operations and conditions which render the
soil best suited for the life and growth of the nitrifying

124 NATURE TEACHING

organisms are those which most conduce to its fertility.
Practical agriculturists long ago discovered these facts,
and scientific workers have now supplied the explana-
tion.

As plants require their nitrogenous food to be in
the condition of nitrates it will readily be understood
that nitrate of soda is a valuable source of plant food,
for it can be used at once without any change. Other
substances containing nitrogen are slower in action in
proportion to the time they require for the necessary
changes to take place. Such bodies are converted into
nitrates, or, as we say, nitrified, at very different rates.
Sulphate of ammonia is very quickly changed, whilst
horn and leather are very slowly altered and are of less
immediate use as plant food on account of the slowness
with which they are nitrified. Most vegetable sub-
stances change with moderate facility, hence stable-
manure, decaying grass, weeds, and leaves are valuable
sources of nitrogen. Certain animal substances are also
useful, such as blood and refuse from slaughter-houses,
the refuse from fish-curing establishments, as well as
fish themselves, when caught in greater abundance than
required for food.

One fact demands notice. Many substances, when
mixed with soil, are so firmly held by it that they are
not readily washed out by rain and carried away in the
drainage water. This is the case with phosphates,
potash and ammonium salts. With nitrates, however,
it is different ; over these, soil possesses little holding
power, and they are easily washed out and lost. As
all nitrogenous matters eventually pass into the form of

PLANT FOOD AND MANURES 125

nitrates, it follows that the supply of nitrogen in the
soil is peculiarly liable to become diminished. This is
found to occur in practice, for nitrogen is usually the
first item of plant food which becomes deficient in the
soil, and most of the efforts of the cultivator, in the way
of keeping up the stock of plant food, are directed
towards supplying nitrogen.

Leguminous Plants and Nitrogen.

It has just been said that plants are unable to use
the nitrogen of the air ; that they must have a supply of
nitrogen-containing bodies in the soil ; and that nitrifica-
tion makes these useful to plants. There is, however, a
remarkable exception inasmuch as plants belonging to
the pea and bean order (Leguminosa) are able to thrive
in soils containing no nitrogen. It has been found that
this interesting and important property is due to the
presence of great numbers of bacteria (microbes or
germs) which inhabit small nodules or swellings to be
found on the roots of plants of this order. The bacteria
living in these swellings are able to feed on the nitrogen
of the air and pass on this nitrogen to the plants in
connexion with which they live. They thus enable
these plants to use the nitrogen of the air. Now, as
nitrogen is the most expensive constituent of plant food,
this property, possessed by leguminous plants, of using
and building up into their own structures nitrogen from
the air, is of great value to the cultivator. He is able
to grow crops of beans and peas upon soils which are
too poor in nitrogen to produce remunerative crops of
other plants. When the bean crop is reaped the roots

126 NATURE TEACHING

which remain in the ground, together with the leaves,
stems, etc., may be returned to the soil to increase its
nitrogenous store. The result is that the soil is richer
in nitrogen after the crop has been removed than before.
In this case it is assumed that a reasonable proportion
of the growth, that is of roots, leaves and stems, is left
upon the land.

Leguminous plants, accordingly, are frequently made
use of to increase the fertility of soils. Crops of these
plants are grown, and when the crop is well developed,
the whole of it is buried in the soil. This method
increases the store of nitrogen in the soil, that in the
crop being largely derived from the air. At the same
time, it adds greatly to the store of humus. This opera-
tion is usually referred to as "green dressing" from the
fact that in this method of working, the crop is buried
while it is in a green and fresh condition, instead of
dressing the soil with dead or decaying material of
the nature of farmyard manure, or with chemical
substances.

It will be understood why it is more profitable to
use leguminous plants for green dressings than plants
belonging to other orders. The latter will, it is true,
increase the store of humus, yet the nitrogen which they
contain is nitrogen which was already present in the
soil. With leguminous plants there is a gain of
nitrogen — a constituent which it is costly to purchase.

The nitrogen question is of the first importance to
the practical cultivator, a large part of his efforts being
directed towards securing a sufficient supply of this
important plant food. This question also demands

PLANT FOOD AND MANURES 127

especial care and thought owing to the fact that
nitrogenous substances are capable of many changes,
and that, if carelessly dealt with, there are many ways
in which nitrogen may be wasted and lost.

Mineral Matter.

Of the mineral constituents of plant food, lime has
already been mentioned ; others are potash, magnesia,
iron, phosphates, chlorides and sulphates. Of these,
potash and phosphates are often present in the soil in
such small proportions, and are so constantly needed by
plants, that beneficial results follow their addition to
the soil. It is estimated that about the following
amounts of potash and phosphoric acid are removed by
the crops mentioned : —

Potash. Phosphoric Acid.

Potato . . . . 75 Ib. 20 Ib.

Corn (grain only, 30 bushels) . 7 „ 10 „

Manuring.

Every crop taken off the land represents so much
actual weight of nitrogen, phosphates and potash
removed from the soil. This fact is too often lost sight
of in practice, and crops are removed, year after year,
without any attempt being made to keep up the supply
of food-stuffs in the soil. The plants draw upon the
supply of food material present in the soil, and thrive
until it is no longer able to satisfy their wants. The
object of manuring is to maintain this supply, or even
to increase it.

Any method by which the fertility of the soil can be
increased may be included under the general term — •

128 NATURE TEACHING

manuring* Thus thorough tillage of the soil, and the
careful maintenance of the conditions necessary for the
activity of the useful bacteria, are in themselves most
important manurial operations. At the present day,
however, the word manure is only applied to the actual
substance added to the soil.

Manures may be classed according to the substances
they contain. Thus we have nitrogenous manures,
potassic manures, and phosphatic manures, which add,
respectively, nitrogen, potash, and phosphates to the
soil. Such substances as farmyard manure and guano,
which add all the requisite substances for an ordinary
crop, are known as general manures. Farmyard manure,
guano, etc., are also organic manures, being the direct
product of living beings, as opposed to such substances
as nitrate of soda, basic slag, etc., which are spoken of as
artificial or cliemical manures.

General Manures.

Farmyard manure and stable-manure contain all
the constituents of plant food in well-adjusted propor-
tions. The actual amount of plant food contained in
these manures is often comparatively small. Their
great value is due to the fact that they add a large
amount of organic matter to the soil. Light soils are
thus enabled to retain more water, and the crops on
them to withstand droughts better. Heavy soils are
rendered more porous and easier to work. Such
manures, therefore, are of great value to the cultivator,
and are useful for almost all soils and crops. When
* See derivation of the word in the Glossary, page 181.

PLANT FOOD AND MANURES 129

manuring has to be done on a large scale it is not always
easy to procure sufficient quantities of these substances,
and recourse must then be had to artificial manures.

Guano is the excretion of sea-birds, deposited in
rainless, tropical regions. It contains all the essential
constituents of plant food; that is to say, nitrates,
phosphates, and potash in a condition in which they are
most readily assimilated by crops. The nitrogen
exists in various forms, part ready to be used at once
by the plant, part requiring to be changed before use.
Guano is thus both lasting and rapid in its effect.
Rich nitrogenous guano is becoming a scarce com-
modity, and much of that now collected and sold
contains comparatively little nitrogen, but a considerable
quantity of phosphates. These phosphatic guanos are
very inferior in value to the rich nitrogenous ones. In
order to increase their usefulness and value, nitrogenous
substances are frequently mixed with them by the
dealers, but, even then, they are by no means equal to
guanos naturally rich in nitrogen. Guano, when stored,
must be carefully protected from the rain, as it readily
spoils.

Green dressings have already been described. They
are a very valuable means of adding organic matter, and
the various constituents of plant food to the soil. In
particular they supply that most costly and most easily
wasted substance, nitrogen.

Nitrogenous Manures.

Sulphate of ammonia. This is obtained as a by-
product in the manufacture of gas from coal, in the form

130 NATURE TEACHING

of small white or grey crystals. When heated with
lime or other alkali, it gives off ammonia gas, which is
easily recognised by its pungent smell. Sulphate of
ammonia contains about 20 per cent, of nitrogen (equal
to about 24 per cent, of ammonia). It is a quick acting
manure, although not nearly so rapid as nitrate of
soda, and can be applied in comparatively large doses
without risk of loss. It gives excellent results on clayey
lands.

Nitrate of soda or Chili saltpetre. This is obtained
from certain deposits in Chili. It occurs in commerce
in larger crystals than sulphate of ammonia, and has a
tendency to become damp by the absorption of moisture
from the air. For this reason it should be stored in a
perfectly dry place. It may be recognised by placing a
fragment on a piece of burning charcoal, when it flares
up and burns. Nitrate of soda contains upwards of 16
per cent, of nitrogen. It is very rapid in its action ; the
plant being able to use it at once. It is readily washed
out of the soil, and should never be applied in large
doses.

Dried blood occurs in the form of dark brown grains
or powder containing from 10 to 14 per cent, of nitrogen.
It also contains small amounts of potash and phosphate.
Dried blood, being insoluble, cannot be used at once by
the plant, but requires to be altered first. It is therefore
lasting in its action.

Phosphatic Manures.

Phosphate of lime occurs in nature (as an insoluble
substance), in bones and in certain mineral deposits.

PLANT FOOD AND MANURES 131

These are sometimes finely ground and used as manure
without any further treatment, but, as certain changes
are necessary before this insoluble phosphate can be
used by plants, their action is slow. More frequently,
the phosphatic mineral, or the bones, is treated with
strong sulphuric acid, which renders the phosphate of
lime soluble. Thus prepared, the manure is known as
superphosphate. Superphosphate contains from 25 to
45 per cent, of phosphate of lime in a soluble condition.
Basic phosphate, Thomas' phosphate, or basic slag,
is a form of phosphate of lime obtained as a by-product
in the manufacture of steel. It is a heavy, brownish or
purplish-grey powder and should be as fine as flour.
Unlike superphosphate, which is acid, basic phosphate
is alkaline, hence, if mixed with sulphate of ammonia it
will liberate the ammonia. For this reason it must not,
when used as a manure, be put on with sulphate of
ammonia, but if these two substances are to be applied
to the same piece of ground the basic phosphate should
be put on first and worked into the soil, and, some days
later, the sulphate of ammonia should be added.

Potassic Manures.

Kainit. A mineral obtained from the Stassfurt
mines in Germany. It consists of sulphate of potash,
together with common salt and Epsom salts. The
actual amount of potash contained is usually about
12 per cent.

Sulphate of potash. This is really a purer form of
kainit, containing about 50 per cent, of potash.

132 NATURE TEACHING

PRACTICAL WORK

Burn some vegetable matter — for instance, leaves or
twigs — on a sheet of iron over a fire, or some wood in a
grate or stove. Notice that a large amount of the
material disappears, and that a comparatively small
amount of ash remains. This ash is the mineral matter
of the plant, the carbon and nitrogenous substances
having burnt away.

Gently heat a fragment of wood, a little starch, a
lump of sugar, and a leaf, on a sheet of iron over a lamp
or fire. Notice that all of them blacken, thus indicating
the presence of carbon. If sufficient heat is applied the
carbon burns away, forming carbon dioxide and water

(see p. 76).

The Food of Plants.

Take four ordinary flower-pots containing damp
sawdust, and sow in them seeds of barley, buckwheat or
other plants. Place all the pots in the dark until the
seeds have germinated. Now leave two pots in the dark,
and put the other two in a window where they obtain
plenty of direct sunlight. Water all as required.

Make careful notes of the progress of the plants in
each case, noting whether they become green or not,
the growth each makes, and how long they live.

The experiment may be made quantitative as follows.
Weigh out say a dozen seeds for each pot, before sowing,
and record their total weights. Allow the plants to
grow, and then when they have died pull them up
carefully, wash off any sawdust, and drylhem thoroughly
in the sun. Weigh the twelve plants from each pot, and

PLANT FOOD AND MANURES 133

compare their total weight with that of the twelve seeds
sown in the pot.

This experiment should teach us that plants cannot
thrive very long if supplied with nothing else but water,
for they are unable to make any use of sawdust as a
food.

When plants are grown under these conditions, does
it make any difference whether they are in the light or
not? This experiment if carried out carefully should
answer this question.

The above experiment can be usefully extended by
growing some plants in sawdust with the addition of
water only, others in sawdust watered with a solution
containing all the essential things for plant growth, and
others in ordinary good soil.

A useful plant food solution for this purpose is the
following : —

Calcium nitrate . 4 grammes or about 60 grains.

Potassium nitrate . I gramme „ 15 „
Magnesium nitrate . „ „ 1 5 „

Potassium phosphate . „ „ 15 „

Iron chloride . . one or two drops.

Water .... 3 litres or about 5 pints.

Place as before some plants in the dark, and others
in sunlight, and note carefully their growth and appear-
ance in each case. Also dry and weigh a certain
number of seedlings from each set of experiments, and
compare their weights.

These two sets of experiments should teach us the
importance of light and plant food to the life and growth
of plants.

134 NATURE TEACHING

Experiments with Manures.

By cultivating plants in boxes or in isolated garden
plots, experiments may be made as to the action of the
various manures in common use. The soil of an ordinary
garden is usually fairly well supplied with all the necessary
constituents of plant food. In order therefore to obtain
immediate and striking proof of the effects of manures,
it is advisable to use poor soil. Sand is very convenient,
and, if obtainable, should be employed. In most local-
ities accumulations of sand suitable for the purpose can
be found, for instance, on the sea-beach or in beds of
streams. The sand used should be free from salt. Before
using it, therefore, it is advisable to wash it thoroughly to
remove the salt.* The manner of doing this will depend
on the facilities at hand. A convenient method is to
put the sand into a barrel, the bottom of which has a
number of holes bored in it, and to pour water on it.
The water will drain away through the holes, and carry
the salt and other soluble matters with it.

Pure sand is a very unfavourable soil for plants, and
a small amount of moss litter, not more than i per cent,
should be added to it.

Take four boxes, about 2 feet long, 2 feet broad, and
9 to 12 inches deep. Bore a few holes in the bottom of
each to allow of drainage. Place them, side by side in
a hole dug in the garden, with not more than an inch of
the box projecting above the surface of the soil. By so

* Washing is unnecessary if one is reasonably sure of the
absence of salt ; washing is more particularly referred to in case
sea-sand is used.

PLANT FOOD AND MANURES 135

placing the boxes, excessive evaporation from the soil in
them is prevented. A well-drained spot should be
selected for the boxes in order to guard against water
accumulating under and around them. If the soil is
very clayey this object may be secured by putting under
each box a layer of small stones. It is also necessary to
arrange the boxes so that the drainage-water from one
will not run under the next. Mark the boxes A, B, C,
and D.

In all such experiments too much care cannot be
taken to secure uniform conditions for the boxes or
plots to be experimented upon. For instance, if one
box is shaded and another not, and they are treated
differently as regards manuring, it is impossible to be
certain afterwards whether any difference in their crops
is due to the different manures used or to the difference
of lighting.

Fill the boxes with the washed sand, and to this
add the various substances whose effects we wish to
try.

To the soil in A, add nothing. This is the control

or standard.

To B, add about 8 Ib. of well-rotted farmyard or stable

manure. Carefully fork the manure into the sand, or

remove the soil and mix the manure with it in a dry

place, and then return to the box.

To C, add 2 oz. of finely-powdered chalk or marl,

scattering it evenly over the surface, and stir in lightly

with a fork. Then add J oz. of sulphate of ammonia.
To D, add about 2 oz. of finely-powdered chalk or

marl ; mix well, and then apply J oz. basic slag, J oz.

136 NATURE TEACHING

sulphate of potash and \ oz. sulphate of ammonia.*
Scatter these substances evenly over the surface, stirring
each in before the next is added. Dig in the basic slag
somewhat deeply.

Finally, spread an ounce of moist garden soil over
each, in order to ensure the presence of the nitrifying
organisms which would probably be absent from the
washed sand.

If it is convenient to make plots, treat these in
exactly the same way, taking similar precautions with
regard to situation and drainage, as observed in the case
of the boxes. The amounts given above are for boxes
of the size mentioned, 2 feet long by 2 feet broad, that
is with a surface of 4 square feet. Larger or smaller
boxes would require correspondingly larger or smaller
quantities of manure. Similarly, a bed 8 feet long by 3
feet broad, or 24 square feet in surface, would require
six times the amounts given. The four boxes or plots
now stand as follows : —

A. No manure.

B. Farmyard or stable manure, at the rate of about

30 tons per acre.

C. Nitrogen only, as sulphate of ammonia, about

2 cwt. per acre.

D. Nitrogen as sulphate of ammonia, about 2 cwt.

per acre, together with potash and phosphate.
Raise in each box, or on each plot, a similar crop.
Barley, wheat, oats, turnips, beet or cabbage, are recom-

* In accordance with what has been said before, it is advisable
to add the sulphate of ammonia about a week after the lime or
basic slag has been applied, to prevent the loss of the ammonia.

PLANT FOOD AND MANURES 137

mended. The seeds may be sown in the boxes them-
selves, and when they have germinated an equal number
of vigorous and well-placed seedlings kept in each box
Carefully pull up all the seedlings not wanted. If trans-
planted into the boxes, put in each the same number of
seedlings, as far as possible equal in size and vigour.
Care is just as necessary here as in arranging the boxes
at first The ideal to aim at is to have the boxes or
plots exactly alike in everything except the actual
manure added. Make and record observations during
the growth of the crops, noting the general vigour and
character of the plants in each box, their times of flower-
ing, and any other points. When they are mature dig
up and weigh the whole crops, recording the weight of
seed and the weight of the whole plant. Compare the
crops of the different boxes.

Leguminous Plants.

Sow in boxes or in plots, seeds of various plants of
the leguminous order; for instance, various kinds of
beans, peas, etc. (Those sown in the experiment de-
scribed on page 21 will probably be at hand, and if so
may well be examined now.) When the plants have
become well developed, carefully dig them up, wash their
roots, and examine for nodules. These appear as little
swellings along the roots, varying from about the size
of mustard seed. Also, dig up and examine for nodules
any leguminous plants found growing wild. Many may
be recognised by the great resemblance of their flowers
to those of the garden peas and beans, and by their
similarly divided leaves. Study therefore the look of

138 NATURE TEACHING

the leaves and flowers of such garden leguminous plants
as you have, and then dig up similar-looking plants found
growing wild.

Make two or three plots in the garden, taking the
precautions previously described. Weed and dig the
plots carefully. Plant nothing at all on the first plot,
but keep it free from weeds ; that is, in the state known
as bare fallow. On the others sow some leguminous
crop (peas, field beans, lupines). Tend the plants care-
fully until they produce a good growth of foliage, and
cover the ground well. Then pull up the plants by the
roots, dig up the ground and bury the whole growth in
the plot in which it grew. The crop should be buried
whilst still green, and not allowed to remain until it
becomes old or woody.

After the green dressing has been buried several
weeks, plant all the plots, including the one which was
kept bare and received no green dressing, with such a
crop as wheat, barley, turnip, beet or cabbage, and
observe the varying growth on, and the crop produced
from, the various plots. If a poor piece of ground is
chosen for this experiment the results will be the more
striking.

CHAPTER VII

FLOWERS AND FRUITS

MOST plants — for example, those raised from the seeds
sown during the work of Chapter I. — if kept under
observation, are found to pass through well-marked
stages in their life-history. For some time they grow,
producing only new stems, leaves, and roots. Sooner
or later they begin to form flowers, which appear
first as flower-buds, later as open flowers. After the
flowers have been open for some time, certain. parts of
them wither away, but some portions remain and, later,
fruits containing seeds may be expected to be found.
Clearly, fruits and seeds are dependent on and result
from flowers. Everyday experience tells us that it is
useless to look for beans on a bean plant before it has
flowered. In the present chapter we shall try, first of
all, to understand what a flower is, of what parts it is
made, of what use these parts are, and how fruits and
seeds are formed from flowers.

Parts of a Flower.

Flowers at first sight vary very much in appear-
ance ; they are of different colours, sizes and shapes.

140 NATURE TEACHING

When, however, we examine them more closely, we find
that a very large number are built up on a similar plan
just as we found the various kinds of leaves to agree
in essential parts. In selecting the first flowers for
examination it is important to choose those whose parts
are large, simple, and not too numerous. A tulip or
any of the ordinary garden lilies affords an excellent
example.

In a lily or tulip flower the following parts can be
made out: Six large (white, yellow, or red) leaf-like
bodies — the petals which make the outside, showy por-
tion of the flower. They are obviously arranged in two
rings, three being inside and three outside. Inside these
come six bodies, each consisting of a stalk with a swollen
portion at the free end. These are the stamens, the end
portion of each of which is full of a yellow powder, the
pollen, which, when the stamens are ripe and open, is
exposed. In the midst of the stamens is another body,
bearing no pollen-box at its upper end, but swollen
out beneath into a green structure, which, if cut across,
is found to be divided into three compartments, each
containing a large number of small white bodies, the
future seeds. This swollen portion is the ovary and the
little white bodies it contains are the ovules.

Flowers of the common meadow buttercup or crow-
foot may well be examined after we have made out
the structure of such a large and simple flower as the
lily or tulip. Buttercups have the advantage of being
very common and obtainable practically all the year
round. On the outside there is a ring of five greenish-
yellow, hairy bodies, the sepals. Inside these is another

FLOWERS AND FRUITS 141

ring, of five petals ; these are much larger than the
sepals, and of a bright shining yellow colour ; within the
petals are a large number of stamens, which, although
much smaller than those of the lily, consist of the same
parts — a thin stalk with a swollen portion, the pollen-
box at the free end. In the centre of the flower, instead
of the single large ovary of the lily, are a large number
of little green bodies, slightly swollen below, and ending
in a thinner, hooked portion. By examining an older
flower, one from which the petals have dropped off, we
shall find that these little green bodies have grown, and
become hard and brown, and that with care we can open
them and see that each contains one seed. These green
bodies are in reality the ovaries containing each one
ovule, and correspond to the large ovary of the lily
flower. The thin curved portion of each little ovary is
the style, and spreads out at the end into a wider body,
the stigma. Overlooking thus for the time all the
differences, we find that the buttercup agrees with the
lily and tulip in possessing petals, stamens containing
pollen, and ovaries enclosing the ovules which later
develop into seeds.

Other flowers will show other variations in arrange-
ment of parts. In the harebell or Canterbury bell the
large blue portion obviously corresponds to the petals of
the buttercup. It is, however, all in one piece, and only
the lobing at the top reveals the fact that it really
represents a number of separate petals. In some other
plants — for instance, the primrose — the petals are joined
up so as to form a narrow tube below, spreading out
above, however, in five large lobes. Notwithstanding

142 NATURE TEACHING

these differences, all these flowers have the same general
plan : —

(1) Outer leafy bodies which may be all alike as in
the lily and tulip, or divided into two more sets as in the
buttercup. When the latter is the case we often find
only the inner row, the petals, coloured ; and the outer
row, then called sepals, green. Petals and sepals may
be separate, or joined up so as to form cup-like or tube-
like flowers.

(2) Stamens, each consisting of a stalk, and a knob
containing pollen.

(3) The pistil, consisting of a lower swollen portion,
the ovary (containing the ovules), and an upper portion,
the style, which may be long or short, and often ends in
a more or less hairy or sticky stigma.

The lily, tulip, and buttercup have all these parts
contained in one and the same flower. They are examples
of perfect or complete flowers. The cucumber or vegetable-
marrow flower, on the other hand, is different. If a
flowering plant of either of these is carefully looked over,
two kinds of flowers may be distinguished — even whilst
in the bud stage. Both, when open, are large and have
a yellow cup of petals. The centre of one is occupied by
a yellow column which is covered with pollen. The other
kind of flower has its centre taken up with a large, lobed
body, the stigma, sticky and covered with short hair;
and beneath the yellow petals is a swollen portion (obvi-
ously a very young cucumber or marrow), the ovary.
We have, in fact, here stamens and pistil in separate
flowers, which are respectively described as staminate
and pistillate.

FLOWERS AND FRUITS 143

Uses of the Parts of a Flower.

Plants, such as the cucumber, in which the stamens
and pistils are in separate flowers, are very convenient to
employ in endeavouring to understand the uses of the
various parts. Keeping a cucumber plant under obser-
vation, we find that cucumbers are never borne on the
staminate flowers, but always on the pistillate flowers.
Of what use, then, are the staminate flowers ?

Experiments have often been made (and any one
with care can repeat them), which clearly show that both
staminate and pistillate flowers play a part in the pro-
duction of seeds and fruit. A pistillate flower, tied up
just before it opens, in a thin paper bag, and kept tied up,
forms no fruit, but its ovary shrivels up and withers like
the rest of the flower. A second pistillate flower, also tied
up before it has opened, but which when open has had
some pollen from a staminate flower put on its stigma,
forms fruit. The petals of this flower wither up like the
first, but its ovary does not, but commences to grow and
finally forms a ripe fruit with seeds in it.

Thus we learn that for the production of fruit and
seeds, it is necessary for the stigma of the flower to have
some pollen of the same kind of plant placed upon it
When this has been done the flower is said to ^pollinated.
The actual events which take place as the results of pol-
lination cannot be studied without more apparatus than
is at our disposal. They will be found fully described
and illustrated in most botanical text-books. The final
result of pollination is the fertilisation of the flower, and
only when this has happened are seeds formed. Pollina-

144 NATURE TEACHING

tion, the actual placing of the pollen on the stigma, and
fertilisation resulting from this, are two perfectly separ-
ate processes, and should be clearly distinguished.

The other parts of a flower may be naturally absent,
or artificially removed, without hindering the formation of
fruit. They are not essential. Stamens and pistil are
essential, for without them no seeds can be formed. Not
only, too, must they be present, but unless the stigma
receives upon it some pollen, no seeds will be formed.

Sepals and petals are of use in other ways. The
sepals usually protect the more delicate and important
parts when young. They cover the flower-buds and act
in a very similar manner to the scale leaves which pro-
tect the leaf-buds in many plants. The petals usually
make the showy part of the flower, and, as we shall see
later, are of great use in helping to attract insects. They
are aided in this by the sweet smell of so many flowers,
and also by the presence of honey, which is well known
to be very commonly present in flowers, and in most of
those already discussed is to be found in fairly large
amounts.

To sum up, we find that in flowers the stamens
and pistil are essential to the production of seed. The
sepals and petals are not essential ; the former acting as
a protective covering to the young flower, and the latter
having other uses in relation to insects.

Insects and Flowers.

Still bearing in mind such a case as the cucumber, we
have next to discover how the pollen finds its way from
a staminate flower to the stigma of a pistillate flower,

FLOWERS AND FRUITS 145

which, although on the same plant, may be several feet
or yards away. Those who grow cucumbers know that
it is not actually necessary to go to the trouble of putting
pollen on the stigmas ; yet fruits, containing good seeds,
are regularly formed. There must be some way therefore
in which pollen naturally gets from one flower to another.

Careful watching of a bed of cucumbers will often
show that the open flowers have various visitors. Bees
come to the flowers, go down to the bottom where the
honey is, and if it is a staminate flower, have in so doing
to push past the column in the middle which is covered
with pollen. As a result they come .out with a large
amount of pollen on them. Such a bee, if watched, will
probably be found to visit another cucumber flower. If
the second one is also a staminate flower it simply gets
more .pollen on itself. If, however, it goes to a pistillate
flower, that portion of itself which has become covered
with pollen, now rubs against the stigma, to which, being
sticky, some of the pollen adheres. Thus we see that
insects play a very important part in the carrying of
pollen from one flower to another. The importance of
this work of bees and other insects to flowers cannot be
overestimated, and it requires very little observation to
see how general it is. Besides bees, butterflies and
moths carry on the same work. An owner of an orchard
of apples or cherries, for example, who keeps bees, may
not only directly profit by the honey they yield, but also,
perhaps to a much greater extent, by the increased
amount of fruit he obtains from his trees, due to their
visits.

It might at first be thought that whilst the visits of

K

146 NATURE TEACHING

insects were absolutely necessary to plants in which the
stamens and pistils were not in the same flower, that
they were unnecessary to those plants (by far the
greater number) in which both these essential organs
are in the same flower. This, however, is not so. The
stamens and pistils of such " complete " flowers commonly
ripen at different times, so that when the stigmas are
ready to receive pollen, the stamens of that particular
flower have already shed their pollen. In other cases
various arrangements are found whereby the pollen of a
flower is prevented from reaching the stigma of the same
flower. The result is that cross-fertilisation , the fertilisa-
tion of a flower by the pollen of another flower, is the
general rule, and self-fertilisation — that is, by the pollen
of the same flower — is comparatively rare even in plants
which have both stamens and pistils in one flower.

Many flowers can be pollinated by almost any insect.
Others have very complicated arrangements, and are
specially adapted to particular insects. This is well
illustrated by the flower of the vanilla plant (a climbing
orchid, grown in many parts of the tropics), which is so
elaborately made that it must be visited by certain
insects before it can be pollinated naturally; and, as these
particular insects are not found in most of the countries
where vanilla is now grown, the cultivator of vanilla, in
order to be certain of obtaining pods, has to place pollen
upon the stigma of every flower by hand.

Wind- Pollinated Flowers.

As a general rule the flowers visited by insects
are brightly coloured, sweet-scented, and secrete honey.

FLOWERS AND FRUITS 147

Some have all three of these characters ; others only one
or two of them. There are, however, a large number of
flowers which are not brightly coloured, have no sweet
scent, and secrete no honey. The flowers of cereals
and grasses — for instance, wheat, barley, and ordinary
grasses, hazels, many willows, pine trees, etc. — are good
examples. Insects do not visit them much, and their
pollen is carried from one flower to another by the wind.

In these wind-pollinated flowers attractions to make
insects visit them are absent ; but instead they have
other special arrangements. They usually produce com-
paratively large amounts of pollen, which is very dry
and powdery, and easily blown about by the wind. The
stamens often hang out of the flower, so that their pollen
is easily shaken out by the breeze. Their stigmas, too,
project in a similar manner, and are often large and
feathery, so that they present a large surface on which
to catch the pollen. A comparison of such insect-
pollinated flowers as the bean, lime, and wild rose, with
such wind-pollinated flowers as those of grasses, cereals,
some willows, alders, pines, etc., will make these differ-
ences clear.

Wind-pollinated flowers may, just as insect-pol-
linated flowers, have stamens and stigmas in the same
or in separate flowers. Many of the ordinary meadow
grasses, and barley, wheat, and other cereals are examples
of the former group ; maize, willows, hazel-nut and pines
of the latter. In the maize the " tassel " at the top of the
plant consists of a group of staminate flowers from which
the pollen is readily shaken out and blown about by the
least breeze. The beautiful " silk," which protrudes from

148 NATURE TEACHING

the top of every young cob, is a bunch of stigmas, which,
being widely spread out, readily catch the pollen grains
as they float in the air.

Fruits and Seeds.

The production of seeds is the most important
object in the life of most plants, because in their natural
condition this is the chief method by which they
multiply. When the flower has been pollinated and
fertilised, the petals and other non-essential parts often
fade and wither away, their use being over. The pistil
develops into the fruit containing the seeds, each one
of which, as we have already learnt, contains a young
plant, the embryo. It is important to distinguish clearly
between fruits and seeds. Seeds are formed from the
ovules. During their ripening certain changes take place
in the ovary which contains them, resulting in the forma-
tion of the fruit. The fruit, therefore, is the ripened
ovary, and contains the seeds, the ripened ovules.

Fruits are very variable in character, and, accord-
ing to their nature, they are often classified in various
ways. Some of the different kinds of fruits are dis-
tinguished by the names in common use, for instance,
berries, nuts, pods, etc.

When the plant has formed its seeds it is most
important that these should be placed in such positions
that they may germinate, and that the seedlings may
have a good chance of success. Amongst other things
it is of advantage that they should be scattered to some
distance, for if they were merely dropped from the plant
on to the ground beneath, the seedlings would be so

FLOWERS AND FRUITS 149

crowded together that only a very few would live. Many
of the plants which are troublesome weeds are so owing
to their good methods of seed dispersal. In studying
the dispersal of seeds the uses of the different kinds of
seeds and fruits will be seen.

Dispersal of Fruits and Seeds.

There are four principal methods by which seeds
are distributed : — (i) wind; (2) water; (3) animals ; the
seeds being carried either inside or outside the animal ;
(4) by some explosive apparatus.

Wind. Many seeds — for instance, those of the
common grasses — are extremely small and light, so that
they readily float in the air. Some large seeds are
carried about in a similar manner, and these are often
provided with thin appendages of various kinds known
as " wings." Good examples of winged seeds are those
of the pines, whilst in the ash, elm, and maples the whole
fruit has a big wing and is blown about. Other wind-
borne fruits and seeds are provided with downy or silky
hairs which enable them to float; for instance, thistle,
dandelions, lettuce, willow-herbs, etc.

The seeds of many plants lie at the bottom of dry
seed -cases (often open only at the top) and out of which
it looks extremely difficult for the seeds to get until the
seed-case decays. On a still day this is so, and no seeds
escape. When, however, there is a strong wind blowing,
the plants are shaken about and the seeds often thrown
or sprinkled to a considerable distance. It will be easily
understood that this is preferable to having the openings
at the bottom, for in the latter case the seeds would

150 NATURE TEACHING

simply fall through and a dense growth of seedlings
spring up immediately around the parent plant. The
poppy, wild hyacinth or bluebell, and foxglove, afford good
examples. The seeds in such seed-cases which are open
above would be liable to be damaged by rain, and we
often find that this is guarded against. Thus in some
fruits the openings are very small, whilst other fruits
only open in dry weather, closing again when it is wet.

Water-borne fruits. The fruit of the coco-nut,
with its tough fibrous covering, is able to float long
distances without damage. The coco-nut palm is now
found on almost all tropical shores, and is one of the first
plants to reach new coral islands, often many miles from
the nearest land. The seeds or fruits of several South
American and West Indian plants have been found on
the shores of Scotland, Norway, etc., having travelled
some 4000 miles, by the aid of the Gulf Stream. Those
who live near streams and rivers should watch for seeds
and fruits carried down by the water. Interesting
examples may sometimes be seen; for instance, the float-
ing portions of the fruits of the white water-lily enclosing
the seeds, and the seeds of sedges and other similar
plants which grow by the waterside.

Animals. Many fruits are provided with hooks
and spines, whereby they become attached to the coats
of passing animals. The greater number of the fruits
which do this are commonly spoken of as " burrs."
Amongst examples common in Great Britain are the
fruits of butter-burr, cleavers, wood-avens, enchanter's
nightshade, and the wood-sanicle. The sight of these
fruits sticking to a person or an animal who has pushed

FLOWERS AND FRUITS 151

his way through the plants must be familiar to every
one. The fruits with the seeds inside them may be
carried some considerable distance, but sooner or later
they are sure to be brushed off, and some probably fall
in places suitable for their growth, and thus spread the
plant from place to place.

The fruits mentioned in the preceding paragraph
are all small, dry and hard. Animals also play a large
part in the distribution of quite another set of fruits,
namely those which are commonly known as succulent
or fleshy fruits. The fleshy portion is usually the wall
of the fruit, the seeds — the important part to the plant
— being generally small and hard. Animals eat these
fruits for the sake of the fleshy portion, and the
small, hard seeds pass uninjured through their bodies.
Examples of such fruits are numerous ; mention need
only be made here of strawberries, raspberries, the
various kinds of currants, grapes, and elderberries.
Apples and pears are fleshy instead of being pulpy, but
they are equally pleasant to animals, and their seeds
are similarly small, smooth and hard. In plums,
damsons, peaches and other "stone fruit," the seed is
protected by the hard stone, and most animals eating
the fruit leave the seed untouched. The fruits of such
plants are often green, inconspicuous, and unpleasantly
flavoured whilst the seeds are unripe, but after they are
ripe the fruits are often brightly coloured, easily seen,
and sweet to the taste. In all these cases the part of
the fruit of importance to the plant — the seed — is care-
fully protected from injury, and the plant actually
benefits from what seems at first sight a destructive

152 NATURE TEACHING

proceeding, namely, an animal eating its fruit. Many
of the fruits of this class have been greatly altered in
character by cultivation and selection by man, who has
increased the pleasant edible portion, even to the sup-
pression of the seeds ; for instance, bananas, pineapples,
seedless oranges, seedless grapes, etc.

The mistletoe, which has a fleshy berry much
eaten by birds, has an interesting method of seed
dispersal. Its seeds are extremely sticky, and when a
bird eats the fruit the seeds adhere to its bill. The bird,
sooner or later, cleans its bill by rubbing it against the
bark of the tree on which it has been feeding, or of some
other tree to which it has since flown. The seeds stick,
and after germination pierce the bark and so establish
themselves. Mistletoe once introduced into an orchard
may thus spread from tree to tree and become a trouble-
some pest.

Explosive fruits. There are some fruits which possess
power of themselves to throw their seeds to some
distance. Sitting on a hot August day by a furze bush
we may often here a crackling sound, caused by the ripe
pods bursting open, when the two halves twist up
and throw out the seeds. The fruits of the violet when
ripe "flip" out the seeds, owing to the sides of the
seed-box pressing on the smooth seeds, so that they are
shot out just as we can flip a wet apple-pip between
thumb and finger.

The garden balsam and the wild oxalis have special
kinds of fruits which, when ripe, throw out the seeds to
some considerable distance.

FLOWERS AND FRUITS 153

Variation in Seedlings.

As a general rule the seeds produced by plants
which have been fertilised by pollen from another flower
of the same species, that is to say cross-fertilised,
yield more vigorous plants than the seeds from self-
fertilised flowers. When cross-fertilisation takes place
between two plants of the same species, but possessing
some different characters, the. resulting plants usually
possess some of the characters of each parent. Thus a
plant which bears white flowers, crossed with one which
bears red flowers, usually gives seedlings whose flowers
are, in various ways, marked with red and white. These
facts are made use of in the production of new varieties
of plants, both economic and ornamental. A plant,
possessing some one desirable character, is crossed with
another plant of the same species, with some other
desirable character, and the seedlings examined with
care ; those showing the required characters in the
greatest degree are selected, and the others rejected. It
must be remembered that only closely - allied plants
(plants of the same species), are as a rule capable of being
crossed with one another. Thus the various kinds of
peas, evening primroses, orchids, etc., can be crossed with
one another, but you cannot cross a pea with an orchid,
or an orchid with an evening primrose.

These variations in plants are further made use of
when it is desired to produce a plant with some special
character, whether it be the shape or colour of the
flower, the size of the seed, or some particular feature in
the fruit. A large number of seedlings are raised frorn

154 NATURE TEACHING

a plant which possesses the desired character to a
certain degree. Those which show this desired char-
acter to the greatest degree are allowed to grow and
their seed saved. The seedlings from these are again
rigidly selected, and the process repeated, season after
season, until plants are obtained, the seeds of which we
can depend on to give a large number of seedlings with
the particular character in question.

A desirable kind of plant, whether the desired
character be in foliage, flower, seed or fruit, may be
perpetuated by propagation by cuttings, budding or
grafting. The variations presented by seedlings afford
the means of producing new kinds of plants ; propaga-
tion by cuttings or grafts enables us to reproduce these,
otherwise variable, plants with the assurance that their
characters will be permanently retained.

PRACTICAL WORK

Examine any plants which can be obtained, and
clearly make out the relation to each other of flower-
bud, flower, fruit and seeds. Notice how the plant for
some time forms no flowers, and that, later, first flower-
buds appear, then open flowers, and finally fruits con-
taining seeds.

Parts of a Flower.

Examine any of the following flowers obtainable: —
tulip, lilies, buttercups, wild rose, evening primrose, pea,
bean, wallflower, anemone, dead - nettle, primrose,
geranium, cucumber, marrow, hazel, alder, willows, and
pines. Some are \n flower almost the whole year

FLOWERS AND FRUITS 155

round. Others must be examined as occasion offers.
In the text the tulip, lily, evening primrose, etc., were
suggested because they are large and their parts are
easily distinguishable, but many of the others will serve
almost equally well.

In all cases endeavour to distinguish the sepals,
petals, stamens and pistil. Make enlarged drawings of
the stamens and pistils, and show the parts of which
they are composed, and the stages in the progress of the
young ovary into the ripe fruit.

Note carefully those plants which have stamens and
pistil in the same flower, and those which have them in
separate flowers. Examine the flowers for honey, and
make a list of all the flowers found which contain honey.

Under cultivation the stamens of many plants have
lost their original character, and have become converted
into petal-like structures, thus giving rise to what are
known as " double flowers" Many of these flowers form
no seeds, owing to the fact that they have lost the pollen-
bearing stamens, which, as we have already learnt, are
necessary for the production of seed. Many varieties of
roses, geranium, balsams, and hollyhocks furnish good
examples for examination.

The flowers of grasses and cereals have no sepals
and petals in the ordinary sense of the words. They
have a number of scaly structures instead, but their
stamens and pistils are, as a rule, easy to find. Examine
some of the following : — wheat, barley, maize, and the
common meadow grasses.

Examine the " flower " of the sunflower. The yellow
structures around the edge are very different from

156 NATURE TEACHING

the central portion, and at first suggest petals. Where,
then, are the stamens, and the pistil ? Cut the head
through : the middle is seen to be made up of a number of
separate tubular bodies, each of which possesses its own
petals, stamens and pistil. The head is not a single flower,
but a collection of flowers. This is true of all the plants in
the large order to which the sunflower belongs, including
the daisy, groundsel, pyrethrum, Michaelmas daisy, etc.

Experiments in Cross-fertilisation.

Examine the separate pistillate and staminate
flowers of the cucumber or vegetable marrow, and learn
how to distinguish them before the flower-buds are
open. Watch them, and notice that the fruits are only
formed from pistillate flowers. Staminate flowers die
after shedding their pollen.

Tie up two pistillate flower-buds (which are almost
ready to open) in separate bags made of tough paper (for
instance, flat sugar-bags), with a string put through them
as shown in Figs. 19 and 20. When one of these flowers
is open, pluck a staminate flower and remove its petals ;
uncover the pistillate flower, and gently touch its stigma
with the pollen-bearing portion of the staminate flower,
so that some of the pollen sticks. Replace the bag.
Leave the second pistillate flower tied up the whole
time. The first should form a ripe fruit, the second not.

Select two plants of the same kind, but possessing
well-marked differences ; for instance, different-coloured
polyanthus, or begonia. Carefully cut, or pull off, from one
flower some of the stamens which are just shedding
their pollen, and carry them to the flower of the other

FLOWERS AND FRUITS

157

plant in which the stigma is mature (they are then some-
what sticky). Touch the stigma with the stamens, so
that some of the pollen grains adhere. Tie a label or
mark near the flower, that it may be recognised in future,
and make a note in your note-book of the circumstances
of the experiment. Repeat the operation with several
flowers. When the fruit is ripe, gather it, sow the seed,
and, later, plant out the young seedlings in the garden.

FIG. 1 9. — Bag for
pollination experi-
ments. (After
Bailey.)

FlG. 20. — Bag for
pollination experi- .
ments, tied over
flower. (After

Bailey.)

When the plants blossom examine their flowers, and
notice how they differ from each other and from the
parent plants. A similar series of experiments may be
carried out with such plants as coleus, balsam, tomato,
sweet peas, etc.

When it is desired to effect cross-fertilisation with
great accuracy, precautions must be taken to prevent
access to the stigma of pollen from any other flower than
the one selected. Thus in the last experiment pollen

158 NATURE TEACHING

might also have been naturally brought from another
flower in addition to that from the one actually used.
Choose the flower to receive the pollen while still in the
bud-stage, before the anthers have ripened and any
pollen has escaped. Gently open the bud and remove
the stamens, either by cutting them out by means of
fine-pointed scissors, or by pulling off their heads by
means of forceps. Protect the flower, thus prepared,
from insect visits by covering it with a muslin or paper
bag, which may be conveniently fixed over a small branch
having upon it several prepared flowers. After a few
days the stigmas will be mature and ready to receive
the pollen. Then, temporarily remove the bags and
apply pollen from a selected flower to the stigmas. Re-
place the bags immediately, and leave them until the
flower fades. When this has occurred, remove the bags ;
tie a label near to the ripening fruit in order that it may
be identified. As before, raise plants from the seeds,
and compare them with their parents, this time definitely

known.

Dispersal of Seeds.

The practical work on this subject must in the main
consist of observations made out-of-doors. Examine
the weeds which come up in the garden, and endeavour
to find out how they probably got there ; that is to say,
whether their seeds are likely to have been blown by the
wind, carried by birds and other animals, or introduced
in other ways.

In addition to the weeds of the garden, the plants
growing on walls and in the hollows of trees — for instance,
in the crowns of pollarded willows — should be noted, and

FLOWERS AND FRUITS 159

their fruits and seeds examined in the hope of determin-
ing how they also reached these out-of-the-way places.

It is not, as a rule, difficult to suggest the possible
means by which the plants have reached their present
situations, if attention is paid to the previous notes on
seed dispersal, and if a careful study is made of the
examples given below.

Wind-Borne Seeds.

Examine the seeds of ordinary lawn grass and see
how small and light they are, and that they are readily
blown about in the wind. If any wild orchids are to be
found in your neighbourhood examine the seeds of some
of these. They are extremely small and also readily
carried in the air.

Collect dandelion "flowers" in various stages, or
better still keep one particular " flower " under observa-
tion, and notice the changes through which it passes.
At first it appears as a bud ; this opens into the dande-
lion " flower," or, as we know it really is, collection of
flowers. After a time it fades, and then the head closes
up, and might at first sight be mistaken for a bud.
Open another head in a similar stage, and it will not be
difficult to see that the lower parts of the old withered
flowers are swelling and forming little seed-like bodies,
In another few days the head once more opens, but
instead of the flowers we find a large number of small,
dark brown, seed-like bodies, each with a dainty white
parachute attached to it. Blow these ; they float away
through the air carrying the seed-like bodies with
them, and after travelling a longer or shorter distance,

160 NATURE TEACHING

according1 to how windy it is, settle down on the
ground.

Similar observations should be made on the thistle,
lettuce, goafs-beard or salsify, willow-herbs, etc. The
details will vary in each case, but all are alike in possess-
ing some means of enabling their seeds to be readily
blown about by the wind. Additional evidence can be
obtained by going on a dry windy day in summer to a
piece of waste ground which has a lot of thistles growing
on it, and watching the thistle-down blowing about.
Collect some pieces of thistle-down and note the small
seeds attached to them. Then recollect that each little
piece of thistle-down is probably carrying one seed, and
you will understand how thistles are often such trouble-
some pests to farmers, and why it is so important that
they should be cut down before and not after they have
flowered.

Take a ripe pine-cone. Pick out the seeds from
-amongst the scales, and note that each is provided with
<a thin wing or sail.

Examine also the seeds of the white birch. These
•are very small, and each is provided with a delicate thin
wing. In many localities near London and elsewhere,
numerous instances will be seen of young birches coming
up on waste lands, a result due very largely to their
effective method of seed dispersal.

Examine ripe fruits of the maple and ash " keys."
Both of these have wings by which they are blown about
by the wind. Cut some open and see the seeds inside.
In the pine and birch the seed itself had a wing, whilst
in the maple and ash, it is the fruit which is vyinged,

FLOWERS AND FRUITS 161

the seeds inside having no wings. The result is the
same, the seeds in all being blown about. Make sketches
of all the winged seeds or fruits examined.

Look at a ripe poppy fruit, whilst still attached to
the plant. Around the top edge are a number of small
holes, through which it is apparently impossible for the
seeds to get out, until the fruit drops off or decays.

Place a sheet of newspaper under the plant, and then
pull the head to one side and let it spring back with a
jerk. Some of the seeds will probably be thrown out
through the little holes, and will be found on the paper.
On a windy day this process goes on naturally, and the
holes being placed at the top ensures that seeds are only
set free when the conditions are such that they will be
scattered to some distance from the parent plant.

Similar observations can be made on the fruits of
the wild hyacinth, bluebell, etc. Notice how in all of
these plants the seed-cases are placed on the top of long,
springy stalks.

Dispersal by Water.

Examine fruits of water-lilies, sedges, and other
plants found naturally growing by the waterside, and
see if any of them are able to float in water. Collect all
seeds and fruits found floating on streams or ponds and
endeavour to ascertain to what plants they belong.

Dispersal by Animals.

Collect in the hedge-row a spray of goose-grass or
cleavers which has a number of the little round green or
brown fruits on it. Pull the spray along your coat and

L

162 NATURE TEACHING

notice how the fruits stick to the cloth. Make similar
simple experiments with fruiting sprays of the hemp-
agrimony, burdock, enchanter's nightshade, wood-sanicle
or avens, if any of these are obtainable. Examine the
little bodies which stick to your coat in each case, and
satisfy yourself that they are really the fruits of the
plant, and that they do contain the seeds.

Dogs which have been running through copses, or
" grubbing about " in a hedge, will often be found to
have a large number of various fruits sticking to them.
If occasion offers, look these over and try and find out
to what plants they belong.

Make careful drawings of all the fruits examined,
showing the hooks on each.

Examine the following fruits : — strawberry, black-
berry, raspberry, currants and grape. Notice that these
all consist of a pulpy portion, pleasant to eat, and
contain small, hard pips (seeds). Make drawings of all
of these.

Cut an apple across and also lengthways, and make
a drawing to show the position of the seeds.

Similarly make sketches to show the structure of a
plum or other stone fruit. Crack the stone and observe
the seed inside. Show on your drawing the great
thickness of the stone.

Dispersal by Explosive Action.

Watch a furze bush on a hot day in late summer and
try and detect some of the pods opening and scattering
their seeds. Squeeze some ripe black pods at their ends,
and notice how they split and twist up, throwing out

FLOWERS AND FRUITS 163

the seeds. Try the same experiment with pods of
vetches, lupines, and similar plants.

Get some plants of wood sorrel (oxalis), and balsams,
with ripe fruits on them. Slightly squeeze the fruits and
notice how they curl up, and shoot out the seeds. By
placing a sheet of paper under the plant, find out how
far the seeds are thrown.

Make similar observations on the violet. Sketch
the fruits of all these plants before and after they have
opened, and try and understand what really goes on in
each case.

CHAPTER VIII

WEEDS

IN all gardening and agricultural operations the careful
cultivator makes it his constant care to destroy weeds.
These are wild plants which invade the cultivated land
and impede the growth of the crop. Weeds act injuri-
ously in several ways. They crowd out cultivated crops
by their leaves overshadowing and robbing the crop of
the necessary sunlight, which as we have seen, plants
make efforts to secure, being essential to their growth.
The roots of the weeds rob the soil of moisture, thus
retarding the crop's growth. At the same time the
weeds use up some of the available plant food, thus
leaving the crop insufficiently fed. This is particularly
the case with the nitrogen, as when there are many
weeds in the soil their roots compete with those of the
crop in taking up the nitrates as fast as they are formed
in the soil, and thus the crop may be unable to secure a
sufficient supply for the purposes of vigorous growth.

When a piece of land is newly brought under culti-
vation much trouble is often experienced in removing
the weeds, which grow from the seeds lying dormant in
the soil, and from others brought there by the wind, or

164

WEEDS 165

other agents in seed dispersal. Even after years of
cultivation, weeds continue to make their appearance,
owing to the great distances to which the seeds of many
plants can travel. The seeds of weeds, moreover, are
often introduced in stable and farmyard manures, and
compost. For this reason, it is desirable that manures
of this description should be well rotted before being
used.

In getting rid of weeds it is very important to
remove them before they have had an opportunity of
ripening their seeds. If this precaution is not taken the
cultivator will never have his land clean, and will be
subject to unending trouble and expense. Many weeds
propagate themselves by suckers and rooting branches ;
as, for example, couch grass or twitch, coltsfoot, dande-
lions. It is essential that these should be completely
dug up and destroyed ; merely chopping them with a
hoe or spade only helps in spreading them, and thus to
cause future trouble.

The kinds of weeds which make their appearance
in any particular place often indicate very clearly the
character of the soil. Such knowledge may be of con-
siderable use to the cultivator, for he may often thus, at
a glance, learn facts of great value concerning certain
areas.

The traveller's joy or old man's beard (Clematis],
fumitory, rock rose, and salad burnet are almost entirely
confined to chalky or limestone soils, and the beech,
yew, box and wild guelder rose are often characteristic.
Sandy localities are often easily distinguishable by the
presence of heaths, furze, broom, whortleberry, Spanish

166 NATURE TEACHING

chestnut, and birch trees, and by such less conspicuous
plants as the small lady's mantle, corn spurrey, etc.
The presence of the lesser celandine or pilewort is almost
certain proof of the presence of clay. Wheat and mari-
golds are characteristic crops, and oak trees thrive well
on clayey soils. Wet lands are sufficiently indicated
by the growth of rushes, sedges, and other moisture-
loving plants.

PRACTICAL WORK

Examine the plants which occur in the garden, and
endeavour to determine where they come from, and how
it is that some of them appear again and again after all
attempts to get rid of them. In many, this will be found
to be due to a good method of seed dispersal. Others,
which are exceedingly difficult to get rid of, have under-
ground stems, bulbs, and tubers, which remain in the
ground.

Make lists of the plants found on some piece of waste
ground, or which come up as weeds in the garden, and
endeavour to understand how each spreads from place
to place, whether by its seeds or by underground stems
and roots.

Preserving Plant Specimens.

Collect specimens of every weed found in the
school garden, and preserve them for future examination
and reference. This may, with most plants, easily be
done by carrying out the following simple directions.
The first requisite is drying material, which is best of
coarse, stout, and unsized paper. Ordinary blotting-
paper is much too tender except for very delicate plants.

WEEDS 167

If nothing better is available, newspaper answers fairly
well. Cut the paper into single sheets of convenient size
(about 1 6 by 12 inches is recommended). Next obtain
two boards, about half an inch thick, and slightly larger
than the sheets of drying-paper. A few stones or bricks
(best wrapped in stout brown paper) will complete the
plant-drying outfit.

In gathering a plant, take care to get as complete
a specimen as possible. A perfect botanical specimen
should show root, stem, leaves, flowers, and fruit Some
plants are too large to allow of this, and in their case
portions should be selected to make the dried specimen
as fully representative of the plant as possible.

Take one of the boards, and put on it two or more
sheets of the drying-paper. On the top sheet lay the
plant, carefully arranging it so that its parts are as nearly
as possible in their natural positions. On the plant place
some more sheets of drying-paper, and then arrange
another plant. (Two plants must never be placed on
top of one another between the same two pieces of paper.)
Go on in this way until all the plants are spread out, and
finally put on the second board, and the weights.

By the next day the sheets of paper will probably
have become damp, and must be changed for dry ones.
Damp papers should be dried in the sun. When chang-
ing the plants, lift them carefully and take care that their
leaves, etc., are in natural positions. The work of arrang-
ing the parts in position is often best accomplished after
drying has gone on for a few hours. The plant is then
limp, and the leaves, etc., will be found to remain in any
position. When quite dry any attempt to move a part

168 NATURE TEACHING

usually results in breaking it. With good absorbent
paper, used perfectly dry, two changes are often sufficient,
except for thick-leaved plants, which require more.

For future reference it is advisable to mount the
dried plants on sheets of paper. The same size should
be used throughout (16 inches by io£ inches is a common
and convenient size), and only one species of plant should
be placed on any one sheet. Fix the plants to the
sheets by small strips of gummed paper.

Write on each mounted sheet the name of the
plant in the bottom left-hand corner, and add locality
and date of collection, time of flowering, nature of soil in
which it grows, whether it is a troublesome weed or not,
and any other facts of interest. These observations
should be made at the time the plant is collected and
written on a slip of paper, which should be put with the
plant when drying, and then neatly copied on the sheet
on which the specimen is mounted. Plants collected,
dried and mounted without notes made at the time of
collection, giving some or all of the particulars above,
lose much of their value.

A collection of this kind may be made by individual
pupils, but it will usually be found advisable to make a
general collection for the school. The work of drying
arid mounting can then be distributed amongst a number,
and a collection formed which will steadily grow and
become of permanent value and increasing interest.

CHAPTER IX

ANIMAL PESTS OF PLANTS

CONSTANT disappointment and annoyance are caused
to the cultivator by the ravages of insects and other
animals which devour or otherwise injure his crops, so
that in his attempt to raise any crop the pupil is sure to
have the presence of some animal pests and their habits
unpleasantly brought to his notice. Caterpillars are
certain to be amongst the first thus found, and, as an
example of an insect's life-history, we may shortly
summarise what can be observed in their case.

Life- History of a Caterpillar.

A caterpillar is produced direct from the egg laid
by the parent. It will be found to be a soft-bodied
insect, with a head, and a long body divided into
" segments" Behind the head, on each of the first three
segments, is one pair of short-jointed legs. On some of
the remaining segments and on the last will be found
soft " sucker-feet " (or "pro-legs "), but never more than
five pairs in all. The head is hard, and provided with
very small eyes and strong hard jaws. The caterpillar
lives for some time, eating voraciously and casting its

169

170 NATURE TEACHING

skin periodically to allow for growth in size. When it is
full grown and contains a large amount of fat, it again
sheds its skin and appears as the " chrysalis " or "pupa."

This stage is comparatively short and is a period
of rest, when the body of the perfect insect is built
up anew from the body of the caterpillar. At its close,
the hard skin cracks, and the fully developed moth or
butterfly comes out.

The perfect insect has two pairs of large wings
clothed with scales, three pairs of long-jointed legs,
large eyes, and, in place of the jaws of the caterpillar,
a long tubular proboscis which serves to suck up the
honey which may form its food. The female moth or
butterfly then seeks the right food-plant and deposits a
varying number of eggs, from which the caterpillars
hatch. The eggs may be laid singly or in clusters, and
are of very varied appearance. The caterpillars that
hatch therefrom are also very varied in colour, being
white, green, or marked with red, black and yellow ;
some are perfectly smooth, whilst others are covered
with hairs, spines or bristles. Some caterpillars are
very small — for instance, those found in " maggotty "
peas — whilst others are as much as four inches long — for
example, the caterpillars of the goat's-moth, and of the
death's-head moth. The resting or pupal stage is often
spent on the food-plant, sometimes in a cocoon ; but
many chrysalides are found in the earth.

Crops are destroyed only by the caterpillar. Neither
the pupa nor the perfect insect injure plants, and, as has
already been stated, moths and butterflies are important
agents in the pollination of many flowers.

ANIMAL PESTS OF PLANTS 171

Life- History of a Beetle.

Many destructive agricultural pests belong to another
order of insects, the beetles. These go through a similar
series of changes: egg, larva (called " grub" m this
order), chrysalis or pupa up to the perfect insect. The
larvae of beetles are often provided with three pairs of
jointed legs, but have no sucker-feet. Sometimes they
are entirely without legs, and are then usually white and
fleshy. They have very strong biting jaws, and the
segments of the body are not so well marked as in
caterpillars.

The pupae are inactive, often enclosed in a cocoon,
and in them the form of the forthcoming beetle is easily
recognised.

The perfect insect is usually hard, with two pairs
of wings, of which the first pair are hard and long,
forming a sheath for the second pair, which are thin and
membranous. Their jaws are usually strong and well
adapted to biting.

Beetles thus prove destructive both in the larval
and in the mature stage ; they feed upon a great variety
of substances. Some, like the grubs of the flea-beetles,
burrow in the leaves of plants ; others eat the roots
underground — for instance, wire-worms, the grubs of
cockchafers, and of daddy longlegs or " leather jackets."
The death-watch beetle bores into beams in houses, and
several others eat their way into the stems of trees ; and
the ravages of a little beetle, the so-called "furniture
worm," in furniture are well known. Biscuits, grain, and
other stored food-stuffs, are very liable to the attack of

172 NATURE TEACHING

small beetles called weevils, and others have a liking
even for cigars and cigarettes.

Green Fly.

Every gardener is sure at some time or other to
have his attention called to another group of insects,
"green fly," or plant lice. These are often found on
young shoots and buds, and if nothing is done to check
them they increase enormously, and the leaves on which
they are often curl up, wither, and die. Green fly are
provided with a beak or proboscis, which they thrust into
the plant and use to suck up its juices. Each green fly
is very small, but they often occur in such countless
numbers that together they do a great deal of harm
to the plant. Although usually called green fly some
are black ; for instance, the plant lice often found on
beans.

The presence of green fly is often indicated by a
sticky deposit on the leaves of the plants, which some-
time trickles down the stems or drops on the ground.
This sticky liquid is called " honey dew," and is produced
by the green fly. In London the lime trees are often
attacked by green fly, and the honey dew dropped by
them forms damp patches on the pavement, so that
walking along and watching the pavement you can
often tell that you are passing under a lime tree and
that the tree is attacked by green fly.

Rose-growers are often troubled by finding the
leaves of their plants disfigured by having pieces cut out
of them as neatly as if done by a sharp knife. The
offenders are certain biting bees which cut out these

ANIMAL PESTS OF PLANTS 173

pieces and use them to build nests in holes in trees and

similar places.

Flies.

Distinguished from the insects already mentioned,
all of which have four wings (some green fly have no
wings), are the flies which only possess two. The
larvae, usually called maggots, are footless grubs with an
undefined head ; they are thus distinguishable from the
grubs of beetles. The pupae are inactive and often
resemble brown seeds. The adult insects have two
membranous wings, and the mouth is formed for suction
and not for biting.

The grubs of some flies burrow in leaves, and eat
out tunnels in the soft tissue. Thus cineraria leaves are
often disfigured by meandering trails made by the grubs
of the leaf-miner, and the grubs of the celery-fly are
responsible for the blister-like patches often seen on
celery leaves ; in these cases the green tissue of the leaf
is eaten, leaving the colourless upper and lower skin.
The grubs or maggots can often be seen in these
blisters, and here they change into the pupal or resting
condition, whence later the perfect winged fly emerges.

Slugs and Snails.

Slugs and snails also cause a great deal of damage
in gardens. They are obviously very different from the
pests already noticed, and belong to another class of
animals altogether, the Molluscs, or Shellfish. In the
ordinary garden snail the shell is easily seen, but in
most slugs there is no visible shell, it being present only
as a small, hard plate embedded in the flesh of the

174 NATURE TEACHING

animal. Snails and slugs lay eggs in damp places, on
leaves of plants, etc., and from these hatch directly young
snails or slugs, there being in this group no stages cor-
responding to the larvae or pupae of insects.

Most snails and slugs feed on vegetable matter, and
their ravages in gardens are familiar to every one. The
garden snail and the ordinary grey slug are to be found
in almost every garden, and in fields the large black slug

is often met with.

Remedies.

In order to limit the damage done to crops by
injurious insects, various steps may be taken ; first of all
the eggs of butterflies and moths when seen upon leaves
should be destroyed, and the caterpillars should be
picked off and killed. When these remedies are
inapplicable .various insecticides may be dusted or
sprayed upon the plants attacked. Full directions con-
cerning the use of many of these are to be found in the
excellent leaflets of the Board of Agriculture, obtainable,
free of charge, on application to the Secretary, 4 White-
hall Place, S.W.

Many caterpillars are kept in check by being
attacked by other insects which lay their eggs in their
bodies. The insects attacked are not immediately
killed by this operation, which commonly takes place
in the caterpillar stage, but the caterpillars often live
and pass into the chrysalis stage. . By this time the
larvae of the insect which has attacked them have
hatched out and usually kill their host by feeding on it
in this stage, so that instead of the expected moth or
butterfly issuing from the chrysalis, a number of flying

ANIMAL PESTS OF PLANTS 175

insects, the mature form of the attacking insect, make
their appearance. Not only caterpillars, but all kinds of
destructive insects may be thus destroyed by other
insects, and many species that would otherwise become
very injurious are thus kept in check.

Slugs and snails are best kept in check by hand
picking, or by trapping them with cabbage leaves.

PRACTICAL WORK

Collect a few caterpillars, together with portions
of the plant on which they are feeding. Place these in
a box, in the bottom of which is a little garden-mould,
to the depth of about ij inches. Cover the box with
muslin, perforated zinc, or glass, in such a manner that
the caterpillars cannot escape. Supply them with food
morning and evening. When the caterpillar changes
into a chrysalis, note where the chrysalis places itself,
whether it is buried in the soil or whether it attaches
itself to the leaves of its food-plant, and note any other
arrangement which it makes for its protection. Keep
the box with the chrysalides in a safe place until the
moths or butterflies appear. Make notes, with sketches
of the size, colour, and appearance of the insect in the
various stages. Keep an account of the time occupied
by each stage. Record the plant on which the insect
under observation is found feeding. As many insects
as possible should be raised under observation.

Make a list, which may be added to from time to
time, of the insects found upon particular crops, keeping
specimens of the insects, drawings or descriptions, with
notes of the parts of the plants attacked and of the

176 NATURE TEACHING

injuries caused. Thus lists may be made of insects
found upon cabbages, turnips, corn, lettuce, peas, beans,
roses, celery, etc. ; these lists may prove of considerable
interest and value. In preparing these lists, efforts
should be made to observe the habits of the insect and
to obtain all the stages from the egg to the mature
insect

Collect specimens of the snails and slugs found in
the garden. Observe the shell in snails, and note how the
animals withdraw into it when touched or alarmed in any
way. Compare with slugs in which the shell is appar-
ently absent. Put snails and slugs to walk on a piece
of glass, and looking at them from beneath observe
the wave-like contraction of the muscles. Notice their
eyes, their method of feeding. Keep some for a time
in a box, and supply them with leaves ; they may lay
eggs, and if so watch the development of the young
animals.

Insects required as specimens are best killed by
putting them into a "killing-bottle." This is a wide-
mouthed stoppered bottle in which some fragments of
cyanide of potassium have been placed, and some plaster
of Paris, mixed with water to the consistency of thick
cream, poured over the cyanide so as to cover it com-
pletely. When the plaster has set, the bottle is ready for
use, and any insect placed in it is quickly killed. Owing
to the extremely poisonous nature of potassium cyanide,
it is desirable that these killing-bottles should be
purchased ready for use. When the bottles are old and
exhausted, care should be taken in disposing of them, so
as to avoid injury to persons or animals by any remain-

ANIMAL PESTS OF PLANTS 177

ing cyanide. // is impossible to be too careful in this
respect.

Remedies.

Two very generally useful mixtures for spraying
plants with are : —

Kerosene or paraffin emulsion, made by dissolv-
ing half a pound of hard soap in one gallon of boiling
water. When dissolved, add two gallons of kerosene
(paraffin) to the hot liquid, and immediately churn up
well with a syringe until the mixture becomes creamy.
This is the stock solution, and, before using, water
should be added to make it up to thirty-three gallons.
Only rain-water or other soft water (that is without lime)
must be used.

Whale-oil soap. Dissolve one pound of the soap in
one or two gallons of warm water, and use when cold.

M

GLOSSARY

Acid (Latin, acidus, sour). The name given to a large series of
substances, which possess, amongst other properties, (i) a sharp
taste, (2) the power to turn moist blue litmus-paper red, and
(3) to cause carbonates (such as lime or soda) to bubble up and
give -off carbon dioxide. Vinegar is an example of an acid.

Albumen (the Latin word for the white of an egg). Used botanically
for a reserve of plant food contained in the seed. See foot-
note, page 5.

Alkaline (Arabic, al, the ; kali, ashes of a plant, " glass-wort ").
The opposites of acids ; substances which turn moist red litmus-
paper blue, and have as a rule a peculiar burning taste.
Slaked lime and caustic potash are common examples.

Analysis (Greek, analusis, a loosing or breaking-up). The separation
of a substance into the various parts of which it is composed.

Apex (the Latin for summit). The growing point of a stem or root
and the free end of a leaf.

Assimilation (Latin, assimulatio, a making like). Used to denote
the process by which the raw food of a plant is changed into
plant substance. The term is often confined to the formation
of starch and other substances from water and carbon dioxide
in sunlight by plants containing chlorophyll.

Bacteria (Greek, bakterion, a small stick or staff). Minute forms
of plant life, commonly spoken of as germs and microbes.
The decay of animal and vegetable matters is largely brought
about by bacteria.

Berry (Latin, bacca, a berry). A fruit consisting of a thin outer
skin, and a pulpy interior in which the seeds are embedded ;
e.g. a tomato.

Botany (Greek, botanc, grass, or more generally any plant). The
study of plants.

179

180 GLOSSARY

Bulb (Latin, bulbus, a bulb, or round root). Usually an under-
ground leaf-bud, containing reserves of plant food stored up in
thickened leaves, and protected on the outside by scale leaves.
Capillary (Latin, capillus, a hair). Hence any very fine threads,

tubes or cavities.
Carbon (Latin, carbo, a cinder). The substance which forms a

large proportion of all organic matter.

Cereals (Latin, Ceres, the goddess of corn). A general name for
those grasses whose seeds are used as food, e.g., maize, rice,
and Guinea corn.
Chemical (Arabic, Kimia, the hidden art or science). The science

which deals with the composition of matter.
Chlorophyll (Greek, chloros, pale green or grass-green ; phullon,

leaf). Leaf-green.

Chrysalis (Greek, chrysews, golden). The pupal stage (see Pupa)
of butterflies. So called because some chrysalides are golden
yellow in colour.
Cob — The spike of the Indian corn (maize) plant, made up of rows of

pistillate flowers which, when ripe, form the corn grains.
Combustion (Latin, combustum, a burn). The phenomenon of burn-
ing, in which the majority of substances unite with oxygen.
Cotyledon (Greek, kotuledon, a cup-like hollow). Seed-leaves.
Cultivation (Latin, cultus, a tending or taking care of a thing).
In agriculture the term denotes the operations of tillage where-
by the soil is brought into a condition suitable for the economic
production of crops.

Dicotyledons (Greek, dis, two ; kotuledon^ cup-like hollow). A large
subdivision of flowering plants, the members of which have
embryos with two seed-leaves. For other characters see text.
Dormant (Latin, dormio, I sleep). Used to denote the resting
condition of parts of plants — for instance, seeds when kept dry,
tubers before starting into growth, etc.

Effervesce (Latin, effervesco, I foam up). Applied to a bubbling
action like that which takes place when an acid and a carbonate
come in contact.
Embryo (Greek, embnton}. Used botanically for the young plant

present in a seed.
Fertility (Latin, fertilitas, fruitfulness). Used generally of soils.

" Fertile " is usually applied to flowers.

Fertilisation ( Latin, fertilisatio^ the making fruitful). The process
by which the contents of the pollen grain act on the ovules.
After fertilisation the ovules develop into seeds.

GLOSSARY 181

Flower (Latin, flos, a flower or blossom). The reproductive organs,
i.e. the stamens and pistil of a plant, usually together with one
or more protective coverings. The simplest flowers consist of
stamens and pistil only.

Fruit ( Latin, fructus, profit or produce, especially of land or trees).
The ripened ovary together with its seeds. Many things
commonly called vegetables are botanically fruits ; for example,
tomatoes, cucumbers, etc.

Germination (Latin, germinatio, a sprouting forth, a budding).
The first stage of active growth of a seed.

Host — The plant which supplies "board and lodging" to a parasite.

Humus (Latin, humus, earth, soil). Leaf mould. The substance
formed by the decay of vegetable matter.

Internode (Latin, inter, between ; nodus, a knot or joint). The
portion of a stem between two joints.

Larva (Latin, larva, a mask). The first stage of active life of an
insect. Insects in this stage are variously known as maggots,
caterpillars or grubs. The name was originally given because
the caterpillar was thought to hide or mask the future butterfly.

Leguminosae. The Latin word legumen was originally applied to
pulse. Hence, the pod which contained the peas from which
the pulse was made, was called a legume, and the name Legu-
minosce given to all the plants which belong to the pod-bearing
order. In addition to the flower, the plants in this order are
characterised generally by divided leaves and root nodules.
It is the second largest order of flowering plants, and contains
some 7000 species.

Manure (French, manceuvre, to till by hand). The word thus
originally meant cultivation of the soil by hand. It is now
restricted to the special substances added to supply plant
food.

Mechanical (from the Latin, machina, a machine, a work artifically
made). The mechanical analysis of soil denotes the separa-
tion of the constituents of the soil by some method which does
not entail any change in composition of the constituents, e.g.
by washing.

Medullary rays (Latin, medulla, the pith in plants, the marrow in
bones). The bands of tissue which pass from the pith, through
the wood, into the inner bark. The " grain " in oak wood is
due to the medullary rays.

Monocotyledon (Greek, monos, one ; kotuledon, cup-like hollow).
One seed-leaf. The name given to a division of flowering

182 GLOSSARY

plants, the members of which have embryos with only one seed-
leaf.
Nitrification (Latin, nitrum, nitre ; facto, I make). Applied to the

bacteriological process in the soil by which various organic

substances containing nitrogen are changed into nitrates.

The bacteria bringing about the change are called nitrifying

bacteria.
Node (Latin, nodus, a knot or joint). The joints on a stem, at

which the leaves are generally attached.
Nodules (Latin, nodulus, a little knot). Small, rounded swellings ;

for instance, those on the roots of leguminous plants.
Nut (Latin, nux^ a nut, a fruit with a hard shell). Usually applied

to hard fruits, which do not split open, and contain only one

seed.
Organic (Greek, organon, an instrument or implement). Belonging

to life. The name given to all substances which, although not

alive themselves, are the results of living processes. For in-
stance, wood, starch, hair, bones, etc.
Organism — Any living thing, whether animal or plant.
Ovary (Latin, ovum, an egg). That portion of the pistil of a plant

which contains the ovules.

Ovule (Latin, ovulum, a little egg). The young seeds.
Parasite (Latin, parasitus, a fellow-boarder, a guest). An organism

which lives on and obtains its nourishment from another — the

host. Distinguished from epiphytes which live on but do not

obtain nourishment from another organism.
Petal (Greek, petalon, a flower leaf). One of the leafy bodies,

commonly brightly coloured, which usually form the showy

portion of a flower.
Pistil (L2&\T\,pistillum, a pestle). The ovary and stigma (which may

or may not be stalked) of a flower. In some plants the pistil is

pestle-shaped, hence the term pistil.
Plastic (Greek, plastos, moulded). Capable of being moulded or

worked into various shapes. For instance, potters' clay is

plastic.
Plumule (Latin, plumula, a little feather). The name given to the

undeveloped shoot (that is, the stem bud) of the embryo. Its

appearance in such seeds as the bean probably suggested the

name.
Pod — A dry (not fleshy) fruit, containing several seeds. A pod

usually splits open when ripe along both sides.
Pollen (Latin, pollen^ anything as fine as dust j hence, very fine

GLOSSARY 183

flour). The powdery substance contained in the stamens,

essential to the fertilisation of flowers.
Pollination— The act of placing pollen on the stigma of a flower,

usually, but not necessarily, followed by the fertilisation of

the flower. Insects can pollinate flowers, but they cannot

fertilise them.
Propagate (Latin, propago, I propagate, I extend). To increase

the numbers of a plant by means of cuttings, reproduction

by seeds, or other methods.
Pungent (Latin, pungo, I sting). Used to describe the smell of

such a substance as ammonia.
Pupa (Latin, pupa, a baby). The third stage in the life of many

insects, usually inactive. The name was given from the

resemblance of many pupae to a baby bound up in clothes as is

the custom in Southern Europe. Pupa and chrysalis refer to

the same condition.
Radicle (Latin, radix, a root ; hence radicle, a little root). The

young root of the embryo.
Respiration (Latin, respiratio, the act of drawing breath). Used

to denote the breathing process in both plants and animals.
Rudimentary (Latin, rudimentum, a first attempt, a beginning).

Often used to describe parts of plants which have not

reached their full development.
Scutellum (Latin, scutulum, a little shield). A descriptive name for

the body on the embryo of a grass, by means of which it

dissolves and absorbs the food-reserve stored up in the seed.
Sections (Latin, sectio, a cutting). Thin slices cut from a plant.

They may either be cut across the stem — cross-sections ; or cut

lengthwise — longitudinal sections.
Segments (Latin, segmentum, a division or a portion). The

divisions, or rings, which make up the body of an insect.
Sepal (from Greek, skepas, covering or shelter). One of the leafy

bodies, commonly green, which form the outermost portion of

the flower, and usually make a protective wrapping to the

more delicate inner portions.
Species (Latin, species, a kind or sort). All those animals or plants

are said to be of the same species which do not vary more

from one another than might be expected in the produce of

the same parents.
Stamen (Latin, stamen, a thread). One of the essential parts of a

flower, consisting usually of a stalk, bearing a pollen-bo*

containing the pollen grains.

184 GLOSSARY

Stigma (Greek, stigma, a spot). The portion of the pistil which
receives the pollen. It is often hairy or sticky.

Stipules (Latin, stipula, straw, stubble). The bodies borne where
a leaf joins on to a stem ; not present in all plants.

Stoma — (plural, stomata) — (Greek, stoma, a mouth). The small
pores in the surfaces of leaves, and other green parts of plants.

Sucker. This is used botanically in two senses, (i) For a branch
which starts underground, and then comes above. (2) For a
special sucking apparatus by means of which some young
plants empty their seeds of food.

Tendril — A thin structure, branched or not, by means of which a
plant climbs. Stems and leaves are frequently modified to
form tendrils.

Transpiration (Latin, trans, across ; spiro, I breathe). The giving
off of water- vapour through the stomata of plants.

Tuber (Latin, tuber, a swelling). A thickened, usually underground
structure, which may be a root or stem. Important as store-
houses of plant food.

Variation (Latin, variatio, a difference). Used to express the
tendency of living things to differ to some extent from
the ordinary type. The differences which enable us to dis-
tinguish different persons from one another, afford an everyday
illustration of variation in human beings.

Vitality (Latin, mtalis, of or belonging to life). Seeds, for instance,
are said to retain their vitality so long as they are capable of
growing when placed under suitable conditions.

APPENDIX I

SUGGESTED COURSES

IN schools taking up this work in autumn, the following course is

suggested : —

Chap, i . — Parts of a seed.

Plant food in seeds.

Conditions of germination.
Chap. 2. — The general characters of roots.
Chap. 3. — The general characters of stems.

The life-history of a crocus or gladiolus.

The structure of stems.
Chap. 4. — Winter buds.

The structure of leaves.
Chap. 5. — Mechanical analysis of soil.

Water in soils.

Effect of frost on rocks.

Vegetable matter in soils.

Chalk in soils.

The ground in the school garden should be dug up, and if
possible the beds and paths laid out before the frosts set in.

In the spring the remaining portions of Chap. I. can be under-
taken, and the order in the book followed as far as found convenient,
care being taken to start the manurial experiments, collection of
weeds, and observations on insect pests at an early date.

When the work is commenced in the spring, the weather offers
no obstacles. Care must be taken to examine the opening of leaf-
buds, the life-history of the crocus, and to begin the experimental
work on seedlings at an early date.

If not already done, the school garden should be at once put
into order, beds and paths laid out, and seeds sown for transplanting
into the plots for manurial experiments.

As in the previous case, an early beginning should be made in
recording observations on flowers, weeds, insect pests, etc.

185 1*2

APPENDIX II

APPARATUS AND MATERIALS REQUIRED

6 wide-mouthed, corked bottles, e.g., i Ib. jam bottles.

3 small, narrow-necked bottles.

2 square, wide-mouthed bottles, e.g., pickle bottles, and corks to

fit.
12 test-tubes, about | in. diameter, and corks to fit.

1 thistle-funnel.
6 dinner plates.

4 tumblers.

2 glazed jam pots.

2 beakers (4 oz.).

3 glass funnels (3 in. diameter).

i glass tube (i ft. long, f in. diameter).

6 glass plates (4x3 in.), e.g.) clean quarter-plate negative glasses.

1 straight lamp-chimney.

4 saucers.

2 doz. flower-pots (5 in.).
64 flower-pots (8 in.).

£ Ib. starch.

| Ib. paraffin wax.

2 oz. iodine solution.

1 qt. methylated spirit.
4 oz. vaseline.

\ Ib. soda lime.

\ Ib. caustic potash.

\ Ib. paraffin wax.

2 oz. Fehling's solution.

186

APPENDIX II 187

Ib. chalk. ^

Ib. sulphate ammonia. Lar^er quant'"es lf mammal

Ib. basic slag. experiments are to be carried

Ib. sulphate potash. J out in scho°l Sarden'

oz. calcium nitrate.

oz. potassium nitrate.

oz. magnesium nitrate.

oz. potassium phosphate.

oz. iron chloride.
Nitrate of soda.
Dried blood.

Phosphate of lime, f A small quantity of each as a specimen.
Basic slag.
Kainit.
Soap.

Kerosene oil.
Whale-oil soap.
Cardboard.
Tinfoil.
Copper wire.
Camels' hair brushes.

1 Ib. shot.
Muslin.

2 doz. sugar bags.

Fine wire-gauze (i sq. foot).

Sealing-wax.

Beeswax.

Resin.

Coco-nut fibre refuse.

Indian ink.

Budding-knife.

Grafting-knife.

Budding-tape (see instructions in Chap. III.)

i pr. fine forceps.

i pr. sharp-pointed scissors.

£ ream botanical drying-paper (16 x 12).

£ ream botanical mounting-paper (16 x ioi).

i pr. boards (17 x 13).

Gummed labels.

6 pieces of flannel (each size dinner plate).

Balance and weights, to weigh from 100 to ^ gramme.

188 APPENDIX II

Ordinary scales and weights to weigh to 5 Ib.

Box with removable glass or wooden front.

Box with one side removable and slot in bottom.

2 stakes and lines.

Levelling-tool.

Ordinary sieves, i", £", J" mesh.

Brass sieves, 2, I, J mm. mesh.

6 stout wooden seed-boxes, 4 to 6 ins. deep.

4 stout wooden boxes, 2' x 2' x i'.

Box for rearing insects in.

Triplet pocket lens.

INDEX

Acorns, 8, 16

Albumen, 5

Alder, 147, 154

Anemone, 154

Apple, 83, 91, 151, 162; root
system, 31 ; stipules, 67

Apricot, 4

Artichoke, 45

Ash, 21, 46, 56, 81

Assimilation, 77-80

Atmosphere and plants, 77 ; com-
position of, 76

Avens, 162

B

Bacteria in soils, 123

Balsams, 53, 152, 157

Bark, 46

Barley, 4, 5, 21, 23, 147, 155; root

system, 31

Basic phosphate, 131 ; slag, 131
Bean, 4, 13, 23, 53, 147, 154
Beech, 78, 165 ; root system, 31 ;

stipules, 67
Beet, 5, 23, 27, 69, 91 ; arrangement

of leaves, 75
Beetle, life-history, 171
Begonia, propagation of, 29, 40
Pind-weed, 56
189

Birch, 162

Blackberry, 70, 162

Blood, as manure, 130

Bluebell, 150

Box, 74, 165

Breathing of plants, 78

Broad bean, 21

Broom, 81, 86, 165

Bryony (black), leaf-veins, 71 ;

(white), tendrils, 45, $6
Buckwheat, 4, 5, 21 ; germination, 9
Budding, 48, 57, 62
Bulbs, 69
Burdock, 162
Butter-burr, 150
Buttercup, 154
Butterfly, life-history, 170

Cabbage, 4, 23 ; leaf-buds, 67, 81

Cambium, 46, 48

Canterbury bell, 141

Carbon, 76, 91 ; dioxide, 76, 91

Carrot, 5, 23, 27, 56, 143

Cassava, 28

Castor-oil plant, n, 21

Caterpillar, life-history, 169

Celandine, 166

Cereals, II, 147

Chalk, 91 ; in soils, no, 120

Chili saltpetre, 130

190

INDEX

Chlorophyll, 77

Chrysalis, 170

Chrysanthemums, 28

Clay, 103, 105

Cleavers, 150, 161

Climbing organs, 70

Clover, 23, 29, 82 ; stipules, 67

Coleus, 37, 38, 78, 157

Coltsfoot, 165

Compost heaps, 109

Copper beech, 78

Corn, 46

Corn spurrey, 166

Cotyledons, 3, 7

Couch grass, 53, 165

Creeping jenny, 43, 45, 54

Crocus, 45, 46, 55, 67, 69, 83

Cross-fertilisation, 146, 156

Crow-foot, 140

Cucumber, 4, 21, 23, 154, 156;

fertilisation, 144 ; germination,

8 ; tendrils, 56
Currant, 151, 162
Cuscuta, 29
Cuttings, propagation by, 37

Elm, 31, 46, 47, 56
Embryo, 4

Enchanter's nightshade, 162
Evening primrose, 153
Explosive fruits, 152

F

Felspar, 102, 105

Fertilisation of flowers, 143

Flag, 44

Flax, 7, 29

Flies, life-history, 173

Flower, parts of, 139, 154

FooJ of plants, 78, 93, 132

Foxglove, 150

French bean, 3, 8

Frog's-bit, roots, 25 ; root-cap, 31,

74
Fruits, 148 ; dispersal of, 149 ;

explosive, 152
Furze, 152, 162, 165 ; leaves, 67,

74, 81, 86
Fuchsia, 93, 98

Daisy, 156

Damson, 151

Dandelion, 75, 91, 159, 165

Date palm, 21

Dead-nettle, $3. 85» *54

Dicotyledons, root systems, 31 ;

seeds, 5 ; stems, 47
Dock, 67, 8 1
Dodder, 29
Duck-weed, leaves, 74 ; root-caps,

31

E

Earth-worms, work of, 107
Elderberry, i$i

Garden pea, leaf-stalk, 70

Geranium, 37, 82, 96, 154, 155

Germination, 6 ; conditions of, 1 3

Gladiolus, 55, 83

Goat's-beard, 160

Gooseberry, 39

Goose-grass, 161

Grafting, 48

Grapevine, 45, 151, 162; tendrils,

56

Grasses, 73, 147 ; stem structure, 57
Gravel, 103
Gravitation, 35
"Green dressing," 126, 129
Green fly, 172

INDEX

191

Ground ivy, adventitious roots, 27,

43

Groundsel, 85, 156
Grub, 171
Guano, 129
Guelder rose, 165

II

Harebell, 141

Haricot bean, 21

Hawthorn, 46, 56 ; stipules, 66

Hazel-nut, 54, 147, 154

Heart-wood, 47

Heather, 67, 81, 86, 165

Hemp- agrimony, 162

Hollyhock, 155

Honeysuckle, 66, 81

Hop, 56

Horse chestnut, 16, 21, 46, 54, 56,

66 ; buds, 68, 81, 82
Host plants, 29

House-leek, 41, 53, 67, 74, 81, 86
Humus, 107

Hyacinth, 150 ; bulb, 84, 91, 161
Hydrocharis, 25, 31, 74

I

Insects and flowers, 144
Internode, 42

Iris, 44, 45, 54, 67, 69, 71, 83, 85
Ivy, adventitious roots, 28, 54

J

Jerusalem artichoke, 44, 54

K

Kainit, 131
Kidney bean, 3, 7
Killing-bottle, 177

Laburnum, 47

Laurel, 74

Leaf, 66 ; arrangement, 75 ; as a

climbing organ, 70 ; blade, 81 ;

green, 77 ; pores, 73 ; stalk, 66, 81 ;

structure, 70, 84 ; uses of, 67, 8 1 ;

veins, 71, 85
Leguminous plants, nodules on

roots, 137

Lemna, leaves, 74 ; root-cap, 31
Lettuce, 23, 91, 160; leaf-bud, 67,

81

Lilac, 8 1, 85

Lily, parts of flower, 140, 154
Lime tree, 147 ; green fly on, 172
Lime, as manure, 106
Lime-water, 91
Linseed, 7

M

Maggot, 173

Maize, 5, 21, 155 ; root system 31 ;

structure of stem, 48, 57
Manures, 128 ; experiments with,

134

Maple, 54, 70, 81
Marigold, 21, 53
Marrow, 21, 154, 156
Marvel of Peru, 4
Medullary rays, 48
Michaelmas daisy, 156
Mistletoe, 29 ; seed dispersal, 1 52
Molluscs, 183

Monocotyledons, seeds, 5 ; stems, 48
Moth, 170
Mullein, 74
Mustard, 23

N

Nasturtium, 66, 70
Nitrate of soda, 130

192

INDEX

Nitrates, 123
Nitrogen, 76, 80, 81
Nodules, 137

Oak, 47, 76, 81, 91

Old man's beard, 70

Onion, 10, 21, 23, 69

Orange, 4

Orchids, pollination of, 146

Ovary, 140

Ovules, 140, 142, 148

Oxalis, 163

Oxygen, 76

Palms, germination, 10 ; structure

of stem, 57
Pandanus, roots, 25
Pansy, stipules, 82
Parsley, 23
Parsnip, 23

Pea, 4, 8, 13, 21, 23, 153
Peach, 151
Pear, stipules, 67
Pests of plants, 1 74 ; remedies for,

177

Petals, 140, 142 ; uses of, 144
Phosphate of lime, 130
Pilewort, 166
Pine, 74, H7, ^54, 160
Pistil, 142 ; uses of, 144
Pith, 48

Plant food, 78, 93, 132
Plum, fruit, 151, 162
Plumule, 3, 6
Pollen, 140, 142, 144
Poppy, 150; fruit, 161
Potato, 55, 79, 83
Primrose, 53, 141, 154
Privet, 53 ; leaf-buds, 67, 81
Pupa, 170
Pyrethrum, I $6

Radish, 4, 21, 69

Radicle, 3, 6

Raspberry, 151, 162

Respiration of plants, 78

Rhizomes, 44

Rock rose, 165

Root, 24 ; cap, 23, 30 ; hairs, 24,
30 ; systems, 30

Roots, absorption by, 34 ; adventi-
tious, 27, 28, 38, 43, 54; and
gravitation, 35 ; and water, 37 ;
growth in length, 32 ; growth in
thickness, 31 ; of seedlings, 24 ;
uses of, 26

Roses, 37, 56, 147, 154, 155, 172 ;
propagation of, 28, 39

Salad, burnet, 165

Salsify, 1 60

Sand, 103

Sap, 80

Sapwood, 47

Scale leaves, 44

Scarlet runner, 8, 21, 56

Scion, 49

Screw-pine, roots, 25 ; root-caps, 30

Sea-kale, 81

Sea-purslane, 81, 86

Sea-rocket, 81, 86

Sedge, 161

Seed beds, 16, 17

Seed-coat, 3, 7

Seed-leaves, 3, 8

Seed, parts of, 2

Seeds, I, 6, 140; albuminous, 5; dis-
persal of, 158 ; exalbuminous, 5 ;
germination of, 6, 13 ; testing
vitality of, 22

Seedlings, raising, 15 ; variations
in, 153

Sepals, 142 ; uses of, 144

INDEX

193

Shellfish, 173

Shoot, 41

Silt, 103

Skeleton leaves, 85

Slug, 173

Snail, 173

Soil, 101, 106, no; mechanical
analysis of, 112; preparation of,
for sowing seeds, 15 ; vegetable
matter in, 118 ; water in, 114

Solomon's seal, 44, 45

Sow-thistle, 81

Specimens, preserving, 166

Stamens, 140, 142 ; uses of, 144

Starch, 78, 97

Stems, 41 ; increase in thickness of,
46 ; structure of, 46, 56 ; uses of
42, 54 ; as storehouses, 43 ; as
climbing organs, 45 ; of dicoty-
ledons, 46 ; of monocotyledons,
48

Stigma, 142

Stipules, 66, 82

Stock, 49

Stomata, 71, 73

Strawberry, 45, 151, 162

Style, 142

Sugar-cane, propagation of, 28

Sulphate of potash, 131

Sunflower, 75, 155

Superphosphate, 131

Sweet pea, 2 1, 70, 84, 157

Sycamore, 21, 83

Tomato, 21, 23, 157

Transpiration, 73, 85

Traveller's-joy, 70, 84

Tubers, 44

Tulip, parts of flower, 140, 154

Turnip, 27, 69

Twitch, 165

Vanilla, pollination of, 146
Veins of leaves, 70, 85
Vetch, 21, 81, 84, 163
Violet, 75, 91, 152
Vitality of seeds, 22
Vegetable marrow, 1 56

W

Wallflower, 154
Water in soils, 104, 114
Water-lily, 161 ; leaves, 74
Watercress, adventitious roots, 28,

38

Weeds, 164
Wheat, 4, 5, 13, 21, 23; flower,

155 ; root system, 31
Whortleberry, 165
Willow, 37, 147, 154
Willow-herb, 160
Wind-pollinated flowers, 147
Wood, 46

Wood-sanicle, 150, 162
Wounds, healing of, 64

Tapioca, 28
Thistle, 160
Tiger lily, 169

Yew, 165

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Oliver and Boyd

Edinburgh

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