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PLANT LIFE
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BLACK1E AND 5ON LIMIIXI
LIBRARY
UNIVERSITY OF CALIFORNIA.
_. BIOLOGY
Class x , LIBRARY
THE STUDY OF PLANT LIFE
First Impression October 1906.
Second Impression February 1907.
Second Edition 1910.
sr fns
ANCIENT PLANTS
BEING A SIMPLE ACCOUNT OF THE
PAST VEGETATION OF THE EARTH
AND OF THE RECENT IMPORTANT
DISCOVERIES MADE IN THIS REALM
OF NATURE STUDY
Illustrated. Demy 8vo, 4s. 6d. net
" Miss Stopes's book is an enterprising and able attempt to popu-
larize a difficult subject. The really keen student will undoubtedly
be stimulated to pursue the study of fossil plants further, and even
those who are not students will get some new ideas and derive a
certain amount of interest from a book which is sometimes brilliant
but never dull." Nature.
" Dr. Marie Stopes has made a name for herself in this special line.
Anyone who takes an intelligent interest in the subject cannot fail to be
charmed with the pleasant manner in which Dr. Stopes conveys her
information." Athenaeum.
PLATE I.
THE STUDY OF
PLANT LIFE
BY
M. C. STOPES
\\
D.Sc.(LoND.), PH.D.(MUNICH), F.L.S.
Lecturer in Palseobotany at the University of Manchester
Second Bdition
* *
LONDON: BLACKIE & SON, LIMITED
NEW YORK: D. VAN NOSTRAND COMPANY
1910
BIOLOGY
LIBRARY
G
PRINTED AT
THE VILLAFIELD PRESS
GLASGOW
PREFACE
As a result of the present efforts to raise the standard of education in
this country, many different " Methods of Teaching " are receiving
our grave consideration. So insistent are their advocates, that we
stand in some danger of forgetting that learning, rather than
teaching, is the essential factor in education. It is not the know-
ledge given us ready-made by the teacher, but that which we
learn, acquiring it by our own efforts, which enters into our being
and becomes a lasting possession.
Therefore this little book does not pretend so much to teach as
to act as a guide along the road for those who desire to learn
something about the plants around them ; hence it points out how
much they can easily see for themselves of the wonderful life and
work of the silent plants.
It is planned for children, whose quick sympathies are more
readily drawn towards the life of things than to the dry facts of
morphology or classification. Its " Leitmotif" is therefore the story
of life, and those of its activities which find expression in the plant
world. Perhaps it may serve to awaken interest in some older
people who have not yet been initiated into these mysteries.
As is inevitable, most of the actual facts in this book are already
the common property of botanists, though some of the suggested
work, such as the mapping, is only now being adopted by the
Universities.
The most interesting subjects are often left out of the more
elementary books, or even if given are frequently set forth in
such a lifeless and pedantic fashion, that little real interest or
understanding has been awakened in the young student. The
present work attempts to avoid the time-worn methods of arranging
the subject. Children generally know more about the behaviour
vil
223979
viii. PREFACE
of animals than that of plants (being themselves animals and fre-
quently having kittens or other pets) j hence, the parallels between
the life-functions of plants and those of animals are pointed out
whenever possible. Once the idea of their " livingness " has been
fully realised, it is time to go on to the study of the details of the
plant's body, and then to the communities of plants which grow
together. In this way the child can work out from its own obser-
vations a complete and logical idea of the living plant, instead of
having merely acquired a detailed but fruitless knowledge of barren
facts.
To burden a child's memory with long names is not only useless
but harmful, therefore an effort has been made to use only short
and simple words. A few scientific terms are introduced where
they are really of value as describing things which are not generally
noticed, and so do not come into the usual English vocabulary.
In such cases it is far better for the child to learn the correct
scientific name than to be provided with a clumsy translation
consisting of several English words which can never give the
precise meaning.
The use of a microscope is not to be recommended for those
beginning the study of plant life, and the chapters have been planned
so that no greater magnification than that of a good hand lens will
be needed. This, however, makes it difficult to explain the life
histories of the fern and other primitive plants; hence in the chapters
bearing on them stress has not been laid on many of the funda-
mental points which are only to be seen with the microscope, but
on those facts which can be observed without it.
The chapters on the families of plants attempt to bring out the
reasons for the separations of the few great groups only ; detailed
classification of the flowering plants has so long been considered the
chief part of botany, that it is to be found in nearly every school-
book on the subject.
If this book should be used as the text-book for young children,
the teacher will probably find it necessary to enlarge on the instruc-
tions for the work suggested in the last three chapters, which
were added chiefly for the guidance of those who may assist the
PREFACE
youthful students in carrying out the practical work therein out-
lined.
I sincerely hope that those who wish to learn, and are prepared
to study the plants themselves, may get some help from this little
guide-book.
M. C. STOPES.
The University, Manchester,
July i go 6.
PREFACE TO SECOND EDITION
THE public and the critics have been so kind to the first edition of this
book that I am encouraged to offer them a second. There are no
considerable changes in it, but I have profited by some suggestions
regarding points of detail which several friends have been good enough
to offer, and hope that the book has now fewer blemishes, and will be
more useful. In Chapter XXXIV. two interesting photographs of
drowning trees have been added, which illustrate a problem in Ecology
less generally studied than its converse.
It has been very pleasant to hear from many teachers, some in distant
parts of the earth, that the book has been useful to them, and I hope
they will continue to allow me the privilege of their criticism or
appreciation.
M. C. STOPES
The University, Manchester,
October igio.
ACKNOWLEDGMENT
FOR the right to reproduce the photographs I am much indebted
to the following gentlemen, to whom I express my warm thanks :
viz. to the Rev. J. S. Lea, of Kirkby Lonsdale, for Plate VII. and
fig. 149 ; to Prof. F. W. Oliver, of London, for Plate VI. ; to
Dr. O. V. Darbishire, of Manchester, for Plate IV. and fig. i 30;
to Prof. K. Fujii, of Tokio, for Plate III.; to Dr. F. F. Blackman,
of Cambridge, for fig. 144; to Mr. Crump, of Halifax, for fig. 140 ;
to Mr. R. Welch, of Belfast, for Plates I. and V., and fig. 138 ;
to Dr. H. Bassett for figs. I 54 and 155.
To Dr. W. E. Hoyle of Manchester, and to Miss Mary
McNicol, B.Sc., I am also much indebted for their kindness in
reading the proof-sheets.
I have drawn all the text illustrations specially for this book.
M. C S.
CONTENTS
PART I.
THE LIFE OF THE PLANT
CHAP. PAGE
I. Introductory - I
II. Signs of Life - 4
III. Seeds and Seedlings - 8
IV. Food Materials of the Older Plant i. In the Soil - 14
V. Food Materials of the Older Plant 2. In the Air - 18
VI. The Food Manufactured by the Plant 23
VII. The Circulation of Water 28
VIII. Light and its Influences 35
IX. Growth in Seedlings - 40
X. Movement - 45
Summary of Part I. - 49
PART II.
THE PARTS OF A PLANT'S BODY, AND THEIR USES
XI. Roots - 53
XII. Stems - 58
XIII. Leaves 64
XIV. Buds - 72
XV. Flowers 78
XVI. Fruits and Seeds 86
XVII. The Tissues Building up the Plant Body - 92
xi
xii. CONTENTS
PART III.
SPECIALISATION IN PLANTS
CHAP.
XVIII. For Protection against Loss of Water
XIX. Specialisation for Climbing-
XX. Parasites
XXI. Plants which eat Insects -
XXII. Flower Structures in Relation to Insects -
PART IV.
THE FIVE GREAT CLASSES OF PLANTS
XXIII. Flowering Plants ....
XXIV. The Pine-Tree Family
XXV. Ferns and their Relatives ...
XXVI. Mosses and their Relatives -
XXVII. Algae and Fungi ....
PART V.
PLANTS IN THEIR HOMES
XXVIII. Hedges and Ditches
XXIX. Moorland ....
XXX. Ponds - .
XXXI. Along the Shore ....
XXXII. In the Sea - -
XXXIII. Plants of Long Ago -
XXXIV. Physical Geography and Plants
XXXV. Plant Maps -
XXXVI. Excursions and Collecting -
Index ...
(C260)
PART I.
THE LIFE OF THE PLANT
CHAPTER I.
INTRODUCTORY
MANY people do not realise that plants are alive. This
mistake is due to the fact that plants are not so noisy
and quick in their ways as animals, and therefore do
not attract so much attention to themselves, their lives,
and their occupations.
When we look at a sunflower, surrounded by its
leaves and standing still and upright in the sunlight, we
do not realise at first that it is doing work ; we do not
connect the idea of work with such a thing of beauty,
but look on it as we should on a picture or a statue.
Yet all the time that plant is not only living its own life,
but is doing work of a kind which animals cannot do.
Its green leaves in the light are manufacturing food for
the whole plant out of such simple materials that an
animal could not use them at all as food. Even its
beautiful flower is creating and building up the seeds
which will form the sunflowers of the future. All
animals directly or indirectly make use of the work
done by plants in manufacturing food, for they either
live on plants themselves, or eat other animals which
do so.
Plants are living, and therefore require food of some
kind as well as air and water in the same way, and for
the same purposes as do animals. As a rule, we cannot
see them breathing and eating, but that is because we do
not look in the right way. In our study of plants we
must first learn how to see and question them properly,
and when we have done this they will show themselves
t C 260 ) 1 B
CHAP. I.
to us and tell us stories of their lives which are quite as
interesting as any animal stories.
Now the sunflower we have just thought of is
probably growing in a garden well looked after by
a gardener, who sees that it gets all the light and water
and just the kind of soil it needs. It is therefore pro-
tected and cared for to a certain extent, but who looks
after the wild plants which manage to grow everywhere ?
These have not only their own lives to live, but by
their own efforts must overcome difficulties which are
not even felt by the cultivated ones.
They succeed in a wonderful way, and r some plants
manage to grow under very difficult conditions, even
in places where they get no water for months under a
burning sun, or in forests where the overshadowing
trees cut off the light and rain, or under the water
where they get no direct air. They have to do all the
usual work of plants, and at the same time struggle
against the hardships of their surroundings. They are
like men fighting for their lives with one hand and
doing a piece of work with the other.
The result of this is that they sometimes make them-
selves strange-looking objects, and in some plants which
have had a very hard struggle it is difficult to know
which part of the plant is which. Look, for example,
at a Cactus (see fig. 48), which grows in the desert ; it
appears to have neither stem nor leaves like an ordinary
plant, and to consist merely of a roundish green mass
covered with needle-like prickles. Yet when you come
to study the Cactus you will find out that the thick,
fleshy mass is really its stem, and the prickles its leaves
which have taken on these strange shapes. By means
of its unusual form the Cactus can live where our
common plants would die of the dry heat in a day or
two. The power plants have of changing their bodies
so as to fit themselves to live under all kinds of
conditions is one of the strongest proofs that they are
alive.
CHAP. I. INTRODUCTORY
All the parts of plants have some special life-work,
just as we have legs and arms for different purposes,
and every part is formed in some way to suit the needs
of the plant and help it to get on well in its home.
The main thing to realise at the beginning of the study
of plants is that they are living things, and therefore to
try to discover the importance of the shape and arrange-
ment of all their parts and their relation to the life of
each plant as a whole.
We will begin by looking carefully for all the signs of
life in them, and noting how often these are the same as
those of the animals, even though the whole plant-body
is so different from that of an animal.
CHAPTER II.
SIGNS OF LIFE
IF you were asked to give the signs of life in an
animal, it is likely that you would think at once of its
power of breathing, eating, growing, and moving.
Now when we ask the same question about plants the
answer does not appear to be quite so easy to find, because
at first sight plants do not seem to do any of these things
except the growing. However, the same answer would
be quite correct for plants, as well as animals, for they
are really able to breathe, eat, grow, and move ; all you
have to do is to watch them in the right way to see that
this is the case.
We are not in the habit of treating dry seeds as
though they were alive ; beans are stored away in sacks
all the winter and may be left for months in dry cellars,
and the precious seeds which will give us our beautiful
flowers in the summer are put away in boxes through
the winter. Yet you know that if you place seeds
in the earth and keep them warm and moist, little
plants will come up and will grow. What gives them the
power of growth which is not possessed by the stones
and earth around them ? Warmth and moisture alone
could not put this power into the seeds when we planted
them. This power, which only belongs to living things,
was there all the time, but was lying asleep, shut in
and protected so that it was not easily disturbed till
suitable conditions made it time for it to wake.
You know when you are asleep that you do not eat or
run about, but simply lie still and breathe. This is
CHAP. II.
SIGNS OF LIFE
what the seed was doing before the baby plant began to
break through its protecting coat and show itself to the
world as a living thing.
Let us watch some of these young plants just waking
up to activity, and see if we can find in them the four
signs we take as being the tests of animal life.
First let us see if we can show that they breathe.
You know that when you breathe
you take air into your lungs, use
some of it, and give the rest out.
You can show that plants also use
up some part of the air. If you
would actually prove this to your-
self or anyone else, take some peas
or beans, soak them in water, and
leave them in damp sawdust for a
day or two till the tiny plant has
just begun to show. Then put
them on wet blotting-paper in a
jar which has a very well-fitting
cork with no leakage, and through
which a fine bent glass tube is
fitted. Place a small tube of
caustic potash in the jar. Then
place the end of the bent tube in
a dish of water, which acts better
if you have dissolved some caustic
potash in it (see fig. i) . Once it has
begun to rise in the tube, mark the
level of the water with a small
label. If then you mark it daily
the labels will show how much
water has risen each day, and the amount of water
rising in the tube shows us the amount of air which
has been absorbed by the growing beans.
This tells us, therefore, that air is absorbed by plants in
the course of their growth. But there is another thing we
must notice about breathing which is equally important.
--2
Fig. i. Jar (A) with well-
fitting cork, in which young
bean plants are growing.
The tube leading from the
jar dips into dish of water
(s) which has risen to levels
marked in the course of
three days, (b) Small tube
of caustic potash.
SIGNS OF LIFE CHAP. II.
You will find that you yourself, as well as all animals,
not only use up a part of the air, but also give out
a waste product which we call carbonic acid gas.
You can see one of the characters of this gas from your
lungs if you take a jar of lime water and breathe into it
for some time. Compare this with a similar jar of lime-
water through which ordinary air has been pumped at
about the same rate for
the same time, and you
will see that the one
you have breathed into
has gone very much
more cloudy-white than
the other (see fig. 2).
The cloudiness in jar A
is caused by the waste
gas (carbonic acid gas) Fig, 2. Jar A contains lime-water through
which VOU breathe Out which human breath has passed. Jar B,
j yuu Ui ccuiic yui, lime _ water through which ordinary air has
and Which Combines been pumped for the same time. Note how
with the lime in the JgftJJf 1 * * *" milky deposit * A
lime - water to make
solid grains of chalk. Fine white chalk grains always
form in lime-water when this gas is present, so that a
jar of clear lime-water is a very good test for the
presence of the gas.
The giving out of carbonic acid gas is one of the
most characteristic things about animal breathing, and
we can show that plants in breathing give out this gas
too.
To prove this, take another jar with a well-fitting cork,
and put some beans and peas, which are just beginning
to grow, into it, with a little damp blotting-paper to keep
them sufficiently moist. Leave the jar closed for a day
or two and then open it and quickly and gently pour in
some lime-water. Put the lid on again at once and
shake it up. You will find that the lime-water turns
quite milky, showing that the same waste gas is given out
by the plants as was given out in your own breath.
CHAP. II. SIGNS OF LIFE
These experiments show us that plants breathe in a
part of the air, and also breathe out some of the same
waste gas which is given off by animals in breathing. So
that we have found that plants do breathe.
Now to go to the other signs of life. I think you will
hardly need to do any special experiment to show that
seedlings grow into big plants, you must have seen it so
often for yourself in the woods and fields and gardens.
We have still to show that plants eat and move, but
before we can do this properly, we must learn a little
more about the parts of the bodies of the plants them-
selves, for they have quite a different set of organs to
those we are accustomed to in animals, and their way of
eating is so different from that of animals that we cannot
understand it immediately.
CHAPTER III.
SEEDS AND SEEDLINGS
IF we wish to follow the whole life of a plant, we cannot
do better than begin by watching the baby plant
" hatching " out from its seed at the beginning of its
active life.
There are many seeds which would be good to begin
work on, any kind would be interesting, but it is best to
use some nice big ones which allow us to see the parts
easily. Good ones to choose would be broad beans or
peas. Notice first the size and shape of the dry seed of
the bean, make a drawing of it, and then place it in
water. After a few hours you will see that the outside
skin wrinkles up ; this is because the skin absorbs water
and increases in size, and so becomes too big for the
rest of the seed (see fig. 3, A, B). After the water has
soaked right
into the sub-
stance of the
seed you will
find that the
outer skin fits
again and is
once more
smooth, and
that the whole
seed is larger
than it was before it was soaked (see fig. 3, C).
Take one of these soaked beans and examine its
structure. Notice the black mark where it was attached
to the parent pod, and the little triangular ridge pointing
Fig. 3. A single Bean seed, A dry ; B half soaked,
when the skin wrinkles ; C fully soaked and swollen.
CHAP. III.
SEEDS AND SEEDLINGS
towards it (see fig. 4, A). Now carefully peel off the
skin, noticing that there are two skins, an outer thick
one and an inner thin one, which protect the parts
within. When you have removed the skin, you will
find that the inner portions of the seed split very readily
into two thick fleshy parts, and that lying between
them is a tiny young plant. Notice how this young
plant is connected on either side with the fleshy parts,
so that to separate them you must tear one side or the
other as in fig. 4 B, where at (a) we see the scar left
where the tiny plant (p] was torn from the side. The
two big fleshy parts
are really portions of
the young plant, and
are in fact its two first
leaves, but they are
very different from or-
dinary leaves, and are
packed with food sub-
stances, and are called
the cotyledons, or
" nurse-leaves." Notice
also the tiny root of
the baby plant or em-
bryo, as it is called ; it
bends a little to the
outer side, and fits into a kind of pocket in the skin of
the coat. You can see the shape of the root even from
the outside of the dry bean (see fig. 4, A (r) ). You will
find in the pea, cucumber, and many other seeds, that
there is also the tiny embryo with its two nurse leaves,
the whole being protected by strong coats. The differ-
ences between the bean, pea, and cucumber seeds are
only in the details of shape and colour, not in the actual
parts of the seed.
In the case of maize and corn, however, you will find
that the seed does not split into two equal parts like the
bean, but that the young plant lies at one side of the
B.
Fig. 4. A, outside of Bean; (h] black
scar showing where the bean was attached
to the pod ; (r) ridge made by young root ;
B, bean split open ; () nurse leaves ; (p)
baby plant ; (a) scar where the baby plant
was separated from the nurse leaf on that
side.
10
SEEDS AND SEEDLINGS
CHAP. III.
.-.-*/&.
Fig. 5. A, outside of
Maize fruit, showing the
embryo (e) on one side;
B, sprouting plant, show-
ing the root (r) and shoot
(s) ; C, the same further
grown.
seed, and a solid white mass fills the rest of the space
(see fig. 5). There are also differences in the seedlings
which you will notice when they begin to grow.
Now that you have ex-
amined some seeds, you
should start a number
growing, so as to have
plenty to watch. They
will grow more quickly
if you soak them in water
for a night before you
plant them in damp saw-
dust, and keep them
moist and fairly warm all
the time. You should
have a number of seeds
of each kind planted to-
gether to provide enough
for you to dig up one of them every day and examine
it fully, inside as well as out. Make a drawing of each
one so that you will have a complete series of drawings
showing how the young plants grow. This will kill
them, so that you must leave at least one seedling
which is never touched,
and which you can
watch all through its
life.
As the young plant
grows, notice how it
breaks away from the
protection of its nurse
leaves ; first the root
comes out and bends
downwards into the saw-
dust (see fig. 6 A), then
the little shoot which
bends up into the air.
Whichever way you plant the seeds you will find this
Fig. 6. Growth of Bean seed-
ling : A, the root only showing ;
B, the root lengthening and shoot
appearing.
CHAP. III.
SEEDS AND SEEDLINGS
ii
is always the case, for even if you start with the root
pointing up, it will bend round and grow downwards
while the shoot bends up (see p. 41).
As the plant gets bigger, side roots grow out from
the main one, and the little leaves of the shoot begin
to open out the whole plant is
growing (see fig. 7).
Now we may perhaps begin
to find out something about the
question of feeding in plants.
What are the nurse-leaves doing all
the time the plant is growing ? You
will find in the bean that the seed
coats may split open a little, but
that on the whole the cotyledons
remain all the time enclosed in
them, and attached to the young
shoot (see fig. 7). Examine the nurse
leaves of seedlings of different ages,
and you will see that they are much
less thick and fleshy in the older
seedlings. As the plant gets bigger
the nurse-leaves get thinner and
less until they become merely dry
shrivelled remnants.
Now, what use could the cotyle-
dons be if they only shrivel away?
Take a freshly soaked seed and
cut a thin slice of the nurse-leaves
and drop it into a little solution of
iodine ; * the tissue will go a violet
blue colour. Then drop iodine on
a piece of bread, a piece of potato,
and some boiled rice, and you will find that they also
go blue, or almost black. The food in the nurse-leaves
Fig. 7. Later stage in
the growth of Bean seed-
ling ; side roots developed,
and the shoot enlarged.
* Get a chemist to make a solution of iodine and potassium iodide,
which should be a bright, clear, orange colour.
12 SEEDS AND SEEDLINGS CHAP. III.
is in some ways the same as that in bread, potato, and
rice, and in many other things we eat.
The part of the food which goes blue with iodine is
starchy and this blue colouring of starch with iodine is
an easy and safe test for it. You will see the same
colour if you take some ordinary laundry starch and stir
it up with hot water and a little iodine. Look now at
the corn seed ; the white solid mass in the seed con-
tains starch, as you can prove with iodine, and although
it is not in the cotyledon, yet it is quite near the young
plant, which can get at it easily.
We have found, therefore, that young plants have a
store of food in their nurse-leaves, 01 near them in the seed,
and that this food is the same as very much of our own
food, that is, it is starch. There are other food sub-
stances present, too, but they are more difficult to find.
The seed, therefore, contains not only the young living
plant itself, but also a storehouse of food for its use, and
as the plant grows we see this store getting less and less
in the shrivelling cotyledons. This shows that the
young plant uses up this food in the course of its
growth.
But you must not forget that, although we find the
young plants provided with food in this way, we have
not yet settled the question of the food supply for all
plants. As we see, the cotyledons shrivel up and are
emptied of their store long before the plant is full
grown. Remember that baby calves have milk for food,
while old cows have grass. And when the store of food
supplied in the seed is finished the older plants must
find new supplies for themselves.
In growing seedlings you must always keep them
well supplied with water, the soil or sawdust in which
they grow must be kept moist. If you take one out of
the sawdust and try to grow it only in the air, you will
find that it soon dies. Even for the seedling the store-
house of food is not enough ; it requires to have water
too.
CHAP. III.
SEEDS AND SEEDLINGS
You can keep seedlings growing
if you place them in glass jars so
that their roots are in water, or
even in closed glass jars stand-
ing over water, so that the air is
thoroughly moist. You will then
be able to see very well numbers
of fine white hairs on the roots
(see fig. 8). These hairs are very
important and absorb the water
which keeps the whole plant
moist.
You have now seen that seed-
lings require water for their life
just as animals do; and also that
young plants are provided by their
parents with a store of food which
is largely starch, and which they
use up during their early growth.
quite well, however,
Fig. 8. Maize seedlings
growing enclosed in damp
air, supported on a wire
stand over dish of water
so that their roots do not
touch it, but grow in the
air. Notice the " root hairs "
growing out from the roots.
CHAPTER IV.
FOOD MATERIALS OF THE OLDER PLANT
(l) IN THE SOIL
As we have just seen, young seedlings are supplied
with stores of food, starch, and other things, which are
packed in their cotyledons and are used up by them as
they grow. But we also saw that as the plant gets
older these stores get emptier, and finally the nurse
leaves shrivel up entirely when their contents are ex-
hausted. All the same, however, the plant continues
to grow. Surely it cannot do this on nothing, any more
than an animal could ? When the young calves cease to
be fed with milk, their food changes, and they begin to
eat grass ; this gives them individually more work, for
grass is not a " prepared food " like milk. Very much
the same thing happens with seedlings. Their prepared
food supply gets used up, and they must find food for
themselves. Where do they find it?
When you remember the fine hairs on the young
parts of roots which absorb water from the soil or saw-
dust, it is quite natural to think at once of the soil as
a possible place for them to find their food ; and, in-
deed, this is partly the case. The water in the soil is
not perfectly pure, for there are many different " salts "
dissolved in it. By " salts " one does not mean only
table salt, but also any kind of mineral in solution, such
as salts of iron or portions of chalk or limestone, or even
some of the minerals which make up granite. These
may all be dissolved in rain-water just as sugar is dis-
solved in your tea, and so spread equally through it.
CHAP IV. FOOD MATERIALS IN THE SOIL
Fig. 9. Root hairs growing among soil particles.
As the water enters the roots of plants through the
hairs, these dissolved salts come in with it, and so get
distributed
over the
whole plant.
The root
hairs can-
not " eat "
particles of
soil, but
they twine
in among
the fine grains and absorb the little films of water which
cling to them.
You can find out some of the importance of these
mineral salts in the life of the plant, if you do the
following experiment.
Take several seedlings which have already grown
enough to have nearly exhausted the supply of food in
their cotyledons. These you must grow in jars of pure
distilled water, to which you have added certain salts
which have been found to be the important ones in the
soil water and plant food. By giving the plant nothing
but these salts and distilled water you know just what
it gets. Distilled water is made by catching and con-
densing steam, and it has no salts dissolved in it ; while
ordinary tap water has run off some mountain side or
risen in some spring from the rocks, and it has many
salts in it already, so that it is useless for this experiment.
Take three big glass jars, each with one litre of distilled
water, and label them A, B, and C. Into A put nothing
further, into B put the following salts, which have been
weighed out carefully either by you or by a chemist :
Potassium nitrate - - i gramme
Calcium sulphate - - J
Sodium chloride -
Magnesium sulphate -
Calcium phosphate
i6
FOOD MATERIALS IN THE SOIL CHAP. IV.
then add to C all these salts, and also one or two drops
of a dilute solution of iron chloride.
Into the jars fit corks which are split, with a hole in
the centre, and pack a plant into each with the part of the
stem between the corks wrapped
round with cotton wool (see fig. 10),
and so fix the plant that its roots
are in the solution and its stem
and leaves in the air* (see fig. n).
Wrap black cotton or paper round
the jars so as to keep the roots
dark as they would be in the soil.
Do not use too small vessels;
in fact, if you had bigger jars and
took double quantities of every-
thing it would be better.
You may make the experiment
more complete by preparing a
whole series of solutions with one
of the salts left out each time. In
this way you would be able to see the effect of the
different elements on the growth of the plants, and you
would find nitrates are very important. Put a plant,
similar to the one you are experimenting with, into a
pot of soil or the garden, and keep it well watered.
This is called the " control plant."
Very soon you will find that the plant in jar A (the
one with only distilled water) is not growing so fast
as the others, and after a time will die off completely.
The one in jar C with all the salts, on the other hand,
should grow quite as well as the control plant in the
garden, which you should take as the standard.
The plant in jar B, when it has everything but iron,
should act in a curious manner. At first it should
grow all right and outlive the one in distilled water,
Fig. 10. Plant packed in
split cork, (/t) Hole in cork ;
(c) cotton-wool packing the
stem.
* Weigh the plant, which you are putting in jar C, carefully, and keep
a record of its weight for future use (see p. 18).
CHAP. IV. FOOD MATERIALS IN THE SOIL
but after a time its leaves should get paler, till the new
ones formed are
quite yellow in-
stead of green,
and soon after
this the plant
will die. If, how-
ever, you add
two drops of the
iron solution
before it dies, it
may recover,
become green
again, and go on
living. It turned
a whitish yellow
colour because
there was no iron
Fig. ii. Three jars in which seedlings of the m ^8 su Ppty of
same age are growing ; A, in distilled water ; B, salts and Water.
in the food solution without iron; and C, in the T , ,
complete food solution. JUSt as When
people get pale
and white the doctor orders them iron, so it is necessary
for plants to have iron when they begin to lose their
green colour. Later on you will find how very important
the green colour is, for without it they cannot grow
(see Chap. VI.),*
From these experiments you see that it is not the soil
which is necessary to the plants, but that certain salts in
solution in the water held by the soil particles are very
important. When all the salts are present in the water,
as was the case in jar C, the plant can grow just as well
as one in the soil; but when it has not these salts it
must die. The salts in solution, therefore, must be a
very important part of the food. Are they the only food
the plant gets ?
* This experiment is sometimes difficult to manage successfully, though
it appears so simple. Great care should be taken not to overdose the
plant with iron.
( C 260 ) C
CHAPTER V.
FOOD MATERIALS OF THE OLDER PLANT
(2) IN THE AIR
THE experiments you have just done show that plants
absolutely require the mineral salts dissolved in the
water of the soil or of their food solutions. Yet although
these salts are so necessary, they do not use a large
quantity of them, as you may prove by taking the
solution C, which is left after the plant has grown
in it, and slowly drying off all the water (taking care
not to destroy a part of the salt crystals) by gentle
heat, and then weighing this dry salt, and comparing its
weight with that of the salts you put into C. You will
find that the growing plant has only removed a small
quantity of the salts. Yet the plant should have grown
to some considerable size. Of course, the water itself
goes into the plant tissues, but you can drive this off by
gentle heat. Before drying it, however, cut off a part of
the plant which is equal in weight to the weight of the
young plant you put into the food solution at first (see
p. 16), so that you have only to deal with the amount of
its growth while using the food solution. Then if you
weigh the fully dried plant, you get the weight of the
solid structure added to its body while it was growing
in the food solution, and you will find that this is much
heavier than the amount of the salts it used during its
growth.
What is this extra substance?
Now let us examine the dried plant more carefully.
Heat it on an open dish, and you will find that it goes
CHAP. V. FOOD MATERIALS IN THE AIR 19
black and chars, very like the charred wood on a fire or
specially prepared charcoal. The black charcoal is well
known to consist chiefly of carbon, and so does this
black plant-ash. You know that charcoal can burn, and
so will this charred plant if you heat it more strongly.
Although you can burn the carbon (that is, you can
make it combine with oxygen gas and go off in an in-
visible form), yet you cannot absolutely destroy it. Like
all elements it is not to be made or destroyed by us, nor
can the plant make carbon for itself.
If you examine the list of substances you put into the
food solution once more, you will find that carbon is not
among them, nor is it contained in any of them.
Carbon, then, is the extra substance which makes the
weight of the plant greater than that of the salts used from
its food solution.
Where does the plant find this carbon?
You may know that there are three chief gases in the
air: oxygen and nitrogen, which are the important
parts for our breathing, and a little carbonic acid gas,
which you may remember is breathed out by animals
and plants (see p. 6), and is made of carbon joined with
oxygen. As there was no carbon in the food solution,
and the plant was surrounded by air containing carbon
and oxygen in the invisible form of gas, the idea is sug-
gested that perhaps it is from the air that the plant gets
its carbon. Now let us see if this is true by trying the
effect of removing the carbonic acid gas from the air in
which the plant is growing.
To do this we must set up an apparatus which will
allow only air freed from carbonic acid gas to surround
the plant. Such an apparatus is shown in the figure 12.
The plant is grown in the closed bell jar D, which
stands over the dish C filled with lime-water, which
prevents carbonic acid gas entering through the cracks
between the foot of the jar and the table. All the air
which enters the jar D must come first through jar A,
which is filled with a solution of caustic potash that has
20
FOOD MATERIALS IN THE AIR CHAP. V.
the power of absorbing the carbonic acid gas, and then
through jar B with lime-water. You can draw plenty
of air through jar D for the use of the plant by sucking
at the indiarubber tube G, which must be carefully shut
with a clamp when you stop the current. The bell- jar
D will now be rilled with air which is quite free from
carbonic acid gas, and the small quantity which is
Fig. 12. Apparatus used to keep a plant without any carbonic acid
gas. A, jar of caustic potash, B, jar of lime water, which absorb the
carbonic acid gas, through which all the air entering jar D must pass ;
C, basin of lime water to absorb any of the gas given out by the plant
growing in D ; G, indiarubber tube which can be closed or attached to
a siphon to draw air through D.
breathed out by the plant itself will be absorbed by the
lime-water in dish C. Place the whole in a light or
sunny position, and change the air every day or two in
the way you filled it, that is by drawing at G so that the
fresh air comes in through A and B, and is free from
carbonic acid gas.
If you keep the plant growing under these conditions
for some time you will find, in comparison with another
quite similar plant growing in the open near it, that its
growth is very slow. The leaves it forms are smaller,
CHAP. V.
FOOD MATERIALS IN THE AIR
21
and finally its growth almost ceases. Further, if you
test the leaves of the plant growing out in the air for
starch (see pp. 24 and 25), you will find that they contain
plenty, but that the leaves on the plant in the bell-jar
are empty of starch. Now all healthily growing green
leaves contain starch, so that this is a good proof that
something is seriously wrong with the plant, which has
been deprived of the supply of carbon in the air. This
shows us that plants use the carbonic acid gas in the air
for their growth.
Carbonic acid gas is composed of a union of carbon
and oxygen gas. If, then, the carbon is used by the
plant, what happens to the oxygen ?
You must have noticed bubbles rising from the " pond
scum " and water-plants when they are in the sunlight,
the little bubbles sometimes coming up in a quick,
regular succession from the leaves and
stems. Let us collect this gas and
test it to find out what it is. This is
more easily done if the plants are
living in glass jars, where you can
see them and get at them readily. A
very good plant to use is the common
Canadian water-plant (Elodea), which
you can buy in aquarium shops if you
cannot get it from the ponds for your-
self. Place a handful of this plant in
a tall, glass jar filled with fresh water,
and cover it with a glass funnel,
so as to collect the bubbles as they
rise. See that the funnel is well
under the water and support over it
a test tube full of water, as in fig. 13.
Place the jar in as bright sunlight as
possible, when you should see the
bubbles beginning to come off quite
quickly. As the bubbles rise in the tube A, the water
is forced out till the whole vessel is filled with the gas.
Fig. 13. Jar of Elodea
in water, giving off bub-
bles of oxygen gas in
the sunlight.
22 FOOD MATERIALS IN THE AIR CHAP. V.
Then place your thumb over the mouth of the tube of
gas, and remove it quickly from the water. Test it by
plunging into it a splinter of wood which has been
burning, but just blown out, so that it is still glowing.
If you plunge it quickly enough into the tube, it should
catch fire and burn brilliantly. Now this is the test
for oxygen gas, so that we have proved that the tube
was full of oxygen. This oxygen is the part of the
carbonic acid gas which is given off by the plant as it
uses the carbon and frees the oxygen it does not need.
You will find that the gas bubbles are given off much
more rapidly when the plant is placed in bright sun-
shine than when it is shaded, and that when the plant
is in darkness the bubbles stop altogether. This seems
to show us that the sunshine must assist the plant to
split up the carbonic acid gas, and we will find out more
about this later on (see p. 25).
We have now found that carbon forms a large part of
the plant body, that plants cannot grow in air in which
there is no carbonic acid gas, and that in getting the
carbon from the carbonic acid gas, they split it up and
give off the oxygen. So that we see that plants use
the carbon in the air as well as the salts dissolved
in the water of the soil as raw materials, with
which they finally build up their food. We must
now try to find what food substance it is that they build
up from these raw materials.
CHAPTER VI.
THE FOOD MANUFACTURED BY THE PLANT
You will remember that much of the food provided in
the nurse leaves consisted of starch, and that the baby
plants use this food as they grow.
In the full grown plant we also find much starch ; in
fact, nearly all the parts of plants which we eat as food
contain large quantities of starch, as you can test with
iodine in potatoes, turnips, radishes, oatmeal, flour, and
a host of our other vegetable foods. This is also the
case in many parts of plants which we do not generally
use as food, for example, in the lily and tulip bulbs,
underground stems of Solomon's Seal, and the stems and
leaves of most plants. So that we find that the food
grains of starch are developed in grown plants, and are
not only provided for the young ones.
What is starch made of? Try heating a piece of
laundry starch on an iron plate or the bars of the grate,
and you will see that it blackens, and finally, if you put
a light to it, may burn. If you simply heat it without
quite burning it, you will find that it chars and goes
black like a piece of charcoal. The solid element oj
starch is carbon. Now you may remember that in the
plant growing under the bell- jar from which we shut out
all the carbonic acid gas, we found that the leaves did
not show any starch (see p. 20). The plant had not been
able to build up starch without the carbon obtained
from the air.
The leaves of a plant are spread out in the sunshine
and air, and it is in the leaves that we get the starch
first formed. The leaves, in fact, are the food factories
2 4
FOOD MANUFACTURED
CHAP. VI.
of the plant. You should study the appearance of starch
in the leaves. As their green colour hides the iodine
colouration, it is better first to remove it from any leaves
you are studying in the following manner. So soon
after picking them as possible, throw them on to some
very hot or boiling water for a moment. This kills them
quickly and makes them soft ; then put them in a jar or
tube of alcohol,* and leave them in it overnight. By
next day the green colour should be gone, having been
absorbed out of the tissues by the alcohol, and the leaves
left yellowish or white. Then put them to soak in water
till the stiffness caused by the alcohol has gone, when
you should add the iodine. If you examine ordinary
leaves in this way you will find that they go violet or
brownish blue, showing that they contain starch.
Now do leaves always contain starch? You will
remember that the oxygen bubbles were given off much
more quickly from the plants in the sunlight than from
those in the dark (see p. 21). This shows that the leaves
in the sunlight split up the carbonic acid gas more
quickly than the others, which would give them more
carbon to work on, and therefore it seems that they
should be able to build up more starch in the light than
in dull weather or dark-
ness. You can see if
this is true by doing a
simple experiment.
If you take a leaf
growing in the sunlight,
and cover a portion of
it, leaving the rest ex-
posed, you will be able
to see the effect of light
and darkness on the starch-building powers of this par-
ticular leaf. To do this use two flat pieces of cork or
Fig. 14. Leaf partly covered with cork
sneets, A, and placed ii
(compare Fig. 15).
in sunny position
* Ordinary methylated spirit is rather impure alcohol, which will
do if you cannot get any better.
CHAP. VI. FOOD MANUFACTURED 25
thick cardboard, covered with silver paper or tin foil
about i in. to i J in. big, and of the same size and shape.
Place a part of a healthy leaf between them and bind
them tightly together, as in fig. 14. If the weight of the
cork makes the leaf bend down out of the full sunlight,
then support it so that it lies in a position where it is
well lighted. Leave it untouched for three days, and
then in the middle of a bright day cut the leaf from the
tree, remove the cork when you get into the house, and
immediately treat it as described above for the iodine
test. You will find that the part of the leaf which was
exposed shows a good
violet colour, proving
that starch is present
there, while the part
which was covered is
only yellowish, showing
Fig. 15. Same leaf as in Fig. 14 treated that Starch has not been
with iodine. It shows that the covered part , t , . . , .
had formed no starch. developed in thlS por-
tion (see fig. 15). This
proves that the covered part of the leaf could not build
starch, so that exposure to the light and air seems to be
necessary, as we expected. This further suggests that
it is only in the daytime that the plant can build starch.
You can see that this is actually the case by testing
leaves from the same tree at different times of the day
and comparing the starch in them. For example, test a
leaf from a certain plant in the early afternoon, when it
has been exposed all day to good sunlight, and compare
it with one which is gathered just before sunrise, if you
can get up so soon (this is, of course, easier in the spring
or autumn, when the sun does not rise so early as in
midsummer). You will find that the leaves picked in
the early afternoon are packed with starch, while those
picked before the day begins show very little or none.
What then becomes of the starch during the night ?
You will remember that we found much starch in
potatoes, which you know grow right underground, and
26 FOOD MANUFACTURED CHAP. VI.
therefore, according to the experiments we have just
done, should not contain starch. But it is found that
the starch is made in the leaves through the day, and is
slowly carried down the stems in solution, and then
stored (not made} in the underground parts, such as
bulbs, potatoes, thick roots, and many others. It is like
the shopkeeper, who collects some money each day and
sends it every evening to the bank to be stored for him.
The leaves of the plant are then fresh next day to
begin the work of building up more starch.
One of the great contrasts between the leaves in the
air, and the parts of the plant underground, is that the
leaves are bright green in colour, and the underground
parts are yellowish or brown. It has been found that
the green colour in leaves is very important in the build-
ing up of the starch. You can see this in the case of
leaves which have parts quite colourless, as in those
which are variegated or striped.
Take the leaves of such a plant,
which have been exposed to a good
light, and test them in the usual way
for starch. You will find that the
pale stripes of the leaf show no
colour with iodine, because they
are empty of starch, owing to the
fact that the green colour was not
Fig. 16. striped leaves; there to build it up. The value of
the white stripes show no the green colour is that it absorbs
starch when stained with ., f ., 1-11. j
iodine. the energy of the sunlight, and
uses it to get the carbon from the
carbonic acid gas, and then to build the carbon into
starch.
Now you will remember in doing the experiments on
the food solutions (see p. 17), that one of the plants lost
its green colour, turned yellowish, and finally died.
That was the plant which had no iron in its food solu-
tion. We have found, therefore, that without iron a
plant cannot build up its green colour, and without its
CHAP. VI. FOOD MANUFACTURED 27
green colour it cannot use the store of carbon in the air
to build up its food. This is only one example of the
importance of mineral salts to the plant. Salts con-
taining nitrogen are equally vital, while a number of
mineral compounds are necessary for healthy growth.
So that we see that the minerals absorbed in solution
by the roots, as well as the carbonic acid gas absorbed
from the air by the leaves, and the energy of light absorbed
by the green colour are all equally necessary to the life of
the plant, as all help in the building up of its food.
We have now seen that plants require food just as
much as animals do ; but that they use different and
simpler elements from which they build it up for them-
selves, unlike the animals, which require their starchy
foods to be ready built up for them. The foods which
plants make they use in growing, and the other activities
of their lives, just as animals do.
CHAPTER VII.
THE CIRCULATION OF WATER
As we have already found out, water is one of the things
which are necessary for the well-being of plants. Seed-
lings can begin to sprout only when they are well sup-
plied with it, and in the growing plant it is the water in
the cells which keeps it firm and fresh. Directly the
plant is deprived of some of its water it becomes limp
and flabby, and " withers." We noticed in Chapter IV.
that the rootlets absorb the water (with its salts contained
in solution) from the soil, and from them it travels all
over the plant. The salts dissolved in water, however,
are in very weak solution, and to provide the plant with
sufficient of them for its
growth it is necessary that
a continuous stream of
water should enter the
plant. Howis this stream
kept up ?
The leaves play a very
important part in the
water circulation, their
thin expanded surfaces
giving a large area from
which the evaporation of
water can take place. The
water which comes off
from them is not gener-
ally visible to us, because
it comes off as vapour. However, you can easily make
experiments which will show you that it actually does
come off from the leaves.
Fig. 17. Experiment to show that
leaves give off water. Notice the drops
collecting in the tube, which is closed with
cotton-wool.
CHAP. VII. THE CIRCULATION OF WATER 29
Take a large test tube or a small glass flask, and place
it over a good-sized fresh green leaf, which you leave
attached to a healthy plant or a branch in water. Round
the leaf -stalk wrap cotton wool till it fits like a cork in
the neck of the flask, so that it shuts the leaf into the
vessel, leaving no communication with the outer air, and
at the same time does not injure it in any way (see fig.
17). Very soon, even after an hour or two, you will
find a misty appearance inside the glass, and this will
settle gradually in the form of drops of water which
collect together and run down the sides of the flask.
You do not see all this water coming off from the leaf
under ordinary conditions because it goes into the air
as invisible vapour, but when it is given off continually
into a closed space the air soon gets saturated with all
it can hold, and the rest must form liquid drops which
we can see. If you keep a record of the time of your
experiment, and also measure the amount of water
collected in the flask, and then measure the size of the
leaf, it only needs a little simple arithmetic to give you
a rough idea of the quantities of water which must be
given off every day by a single leaf. From that you
can imagine the amount passing away from a whole
plant or a great tree ; and I think you will be surprised
to find how much it is.
Another simple experiment shows us that the leaves
play an important part in giving off water. Take
three flasks with long, thin necks, and of as nearly equal
sizes as possible. In one place a branch to which a
number of fresh, green leaves are attached, in another
a branch of the same size with only small buds (cut off
the leaves if necessary), and leave the third as a check
to show how much water has simply evaporated away.
Fill all the flasks up to the same level with water, and
mark this in all three when you start. Leave them for
a day or two and then mark the level of the water, some
of which will now have evaporated (see fig. 18). This
will show clearly that more water has gone from the
THE CIRCULATION OF WATER CHAP. VII.
one with the branch than from the empty flask, and
that a great deal more water has gone from the one in
which was the
branch with big
leaves attached.
You can see
roughly the rate
at which the
water goes off
from the leaves
by completely
filling with water
an apparatus like
that in fig. 19. As
the leafy branch
(which is firmly
fastened in the
cork with no air
leakage) uses up
the water, it must
be drawn along
the narrow tube,
which is gradu-
ated so as to show
the quantity lost.
From these experiments we find that even although
we do not actually see it coming off, yet the leaves of the
Fig. 18. Experiment to show that leaves give off
water. The flasks were all filled to the same level I.,
and left for the same time. The one with the leaves
in it loses far more than the others.
Fig. 19. Experiment to measure the amount of water given off by leaves
m a given time. At first the tube is full of water, which is drawn back to
points i, 2, etc.. as the leaves use it.
CHAP. VII. THE CIRCULATION OF WATER
plant give off a great deal of water in the form of vapour.
By this process large quantities of water are drawn
through the plant, and the salts in weak solution in it
are kept and used by the plant as they are needed for
building up its structure.
Now you may think that the loss is simply the result
of evaporation from the leaves, because the surface of
the leaves is great, and they would therefore naturally
lose a considerable amount of water by evaporation.
But this view is only partly correct, because the giving
off of water by leaves or "transpiration," as itds called,
is regulated by a number of little pores in the skin of
the leaf, which can open and close. You can see the
importance of these pores as water regulators in plants
which have them only on one side of the leaf, because
practically all the water escapes from the side on which
they are situated.
To see this, take three leaves of the indiarubber tree,
which is grown so often in rooms. Choose three which
are as nearly as possible just alike in size and shape. Of
one of them care-
fully cover the whole
of the lower side, and
the cut-end of the
stalk, with vaseline
or coco butter; do
the same to the upper
side and the cut-stalk
of the second leaf,
and leave the third
untouched. Fasten
all three separately
on to a string so that
they all hang with
both sides exposed to the air, and leave them for some
days. The leaf which was not greased will shrivel up ;
as it gives up its water and can get no more, it " withers "
and dies completely. The leaf which was greased on
Fig. 20. Leaf A greased on the lower side, leaf
B on the upper side, and C not at all. B withers
as fast as C.
32 THE CIRCULATION OF WATER CHAP. VII.
upper side also withers at about the same rate as the
ungreased one, but the one which was greased on the
lower side remains fresh and green (see fig. 20). This is
because all the pores are on the lower sides of these
leaves, and in the one greased on the lower side the
vaseline had completely closed them, and so prevented
the water from passing away through them. The upper
surface is well protected against ordinary evaporation by
a thick skin which does not allow the water to pass
through it. The leaf greased on the upper side had all
its pores left open, and so in this way was withered as
quickly as one not greased at all. Not all leaves have
their pores only on one side, but in nearly all plants the
pores can open and shut. These facts show that tran-
spiration is more than mere evaporation ; it is a " life
process," that is, a physical process which is regulated
by the structure of the living plant.
Transpiration is very important for plants, for it helps
to keep the continual stream of water going through
them, which brings with it the necessary food salts.
Some plants cannot afford to let much water pass away,
for they find it very hard indeed to get enough to keep
them fresh ; such plants as live in deserts or on bare,
sandy places, for example, protect themselves from
much transpiration by various devices and special
arrangements, which we will study in Chapter XVIII.
We have already observed the fact that water enters
the plant at its roots, and have just seen that it passes
off as water-vapour from its leaves. Let us now con-
sider for a moment the manner of its entrance. How
can water enter the roots of plants ?
Let us first look at a somewhat similar case in non-
living things which will, perhaps, help us to understand
the process in living plants.
Take a small " thistle-funnel" and tie tightly over the
wide opening a piece of bladder ; then pour some very
strong solution of sugar into the funnel and place it in
a glass of pure water. Mark the level of the sugar with
CHAP. VII. THE CIRCULATION OF WATER
33
L.S
a label (see fig. 21, S). Leave this for a short time, and
you will find that the water has entered the funnel
tube and run up it for quite a
long way.
You should take another similar
tube and do everything in the
same way, except that you leave
out the sugar solution. Then
you will find that the water re-
mains inside the funnel at just
the same level as in the outer
jar. This is the usual behaviour
of water, and in the first case,
where the water rose inside the
funnel, the
rise was due
to the influ-
ence of the
sugar, which
hasthepower
of drawing in
water. Now
we can com-
pare the skin
of the root
hairs (set fig.
9) to the bladder membrane cover-
ing the funnel, and it has been found
that inside the cells are substances
which have the same power of at-
tracting water as we found was
possessed by the sugar. So that
the entrance of water into the roots
depends chiefly on the attraction of
the substances within its cells.
That a large amount of water
enters the root in this way you can see if you cut off
a quickly growing plant (a vine is very good if you can
Fig. 21. "Thistle funnel"
covered with bladder B, filled
with sugar solution up to level
S, and placed in a jar of water.
After a time the water is seen
to have risen to W.
Fig. 22, Plant P, which
has been cut off near the
root, is attached by the
indiarubber tube I to a
tall glass pipe, which is
supported by stand S.
On the glass are marked
the levels reached by the
water rising from the
root.
(C260)
34 THE CIRCULATION OF WATER CHAP. VII.
get it) just near its base, and attach to the cut-end a
long glass tube in place of the shoot you have cut away.
You must fasten this tube by a very well-fitting india-
rubber tube, which you bind tightly so that it will allow
no leakage, and support the glass. Pour a few drops of
water down the tube to keep the cut-end of the plant
from drying up at the beginning of the experiment.
Then mark the level reached by the water, and do this
every day as it rises in the tube. You should find that
for some time it steadily rises day by day (see fig. 22).
We see in this way that the roots take in a large and
continual supply of water, and this must get pressed up
the stem even without the influence of the transpiring
leaves. This is called the " root pressure," and is a very
important factor in supplying the plant with water. In
a plant which is growing under usual conditions, both
the transpiration of the leaves and the root pressure are
at work, and are both necessary to keep a good stream
of water passing through the plant. This stream of
water provides it with its mineral food materials, and
also keeps it stiff and fresh, and is, as we have seen,
absolutely necessary for the growth of the plant.
CHAPTER VIII.
LIGHT AND ITS INFLUENCES
WHEN we were experimenting on the building of starchy
food in leaves (Chapter VI.) we saw how very important
and even essential light is for the activity of the plant,
and it is therefore natural to expect that light should
influence its growth very considerably.
You may see the effect of light which comes only from
one side on plants grown in the windows of rooms. If
they are left in one position they grow in a one-sided
manner with only the bare stalks toward the darker side
of the room and all their leaves turned towards the
window through which the light comes. If you want
them to look pretty towards the room side also, they
must be turned round frequently, so that the leaves
are drawn in many directions instead of one only.
The usual effect of light is to make the leaves grow
towards it. You may
see this still more
clearly by placing a
pot of seedlings in a
blackened box with
a small hole on one
side. Very soon they
will bend over to-
wards the light enter-
ing by it (see fig. 23).
Leaves can absorb
most light when their,
upper surfaces are at right angles to it, and you will
find some leaf-stems will bend right round in order to
Fig. 23. Grass seedlings growing in an
earthenware dish enclosed in a strong box
blackened inside so that the light only enters
at a. (Note how the seedlings bend towards it.)
35
LIGHT AND ITS INFLUENCES CHAP. VIII.
allow their leaves to get into this position. For example,
if you take a pot of nasturtiums growing in the usual
way, and support the pot on a stand,
and cover it over with a bell jar which
has been blackened, or with a black
box, so that all the light reaches the
plant from below, you will find that
in a day or two the leaves will have
turned completely round on their
stalks and are now facing the light, so
that they are upside down in their
relation to the position of the whole
plant (see fig. 24).
In a small plant, or one with only
a few big leaves, this desire for the
light is easily arranged for, as there
is room
for each
of them.
But if
all the
leaves of
a great
tree were turned in the
same direction, you will
see that many of the under
ones must be shaded by
the others. This is not so
bad as one might expect,
however, owing to the
wonderful way in which
the leaves arrange them-
selves so as to use every
bit of space they can, and
yet to overlap and screen
each other as little as
possible. Particularly in plants which grow flat on the
ground or against walls, and which therefore get all
Fig. 24. Nasturtium
covered over, so that
the light only enters
from below. The leaf
surfaces bend over to
face it.
Fig. 25. Spray of Maple showing
stalks of leaves of the same pair of
very different lengths, so as to place
the leaves well as regards light.
CHAP. VIII. LIGHT AND ITS INFLUENCES
37
their light from one side, this is very well shown. In
plants with the leaves in opposite pairs you will often
find one leaf of the pair big, and the other one small, or
that the leaf-stalks are of different lengths, and if you
examine this pair in relation to the rest of the branch,
you will see how it is developed in this way so as to use
every bit of space it can and get as much light as pos-
sible without overlapping its neighbours (see fig. 25).
Although it is true in one way that each leaf works as a
separate individual, yet each separate
leaf is only a small part of the plant,
and they all work together for the
good of the whole. Branches which
have their leaves arranged in this way
so that they seem to fit into a pattern,
form what is called " Leaf Mosaic."
You may see this kind of arrange-
ment among the leaves of very many
plants (see figs. 25 and 26).
//, as we have already seen, light is
so very important for the plant, what
is the result of growing it in the dark?
As you know, it will not be able to
build itself food, and so would finally
starve and die. If, however, we
choose a plant which has already
much food stored up and can there-
fore grow for a time without making
a new supply, then we can study the effect of darkness
on its growth.
Take some beans which are just beginning to sprout,
plant them in a pot, and place the pot in some quite
dark place such as a cellar or a dark room, or cover
them with a well-made blackened box which shuts out
all the light. Also take a potato which is just beginning
to sprout at its " eyes," and keep it in the dark. Both
these plants have food in reserve ; the beans have much
in their nurse-leaves, and the potato is packed with
Fig. 26. Leaves of
Ivy growing out from
the stem so as not to
overlap each other.
LIGHT AND ITS INFLUENCES CHAP. VIII.
starch, as you saw before. At the same time grow a
potful of beans and a potato plant in the light, so that
you can compare the growth of the plants under the
two different conditions of light and darkness.
You will find that those grown in the dark are very
straggling and of a
sickly yellowish co-
lour, and are a great
contrast to the shorter
sturdier young green
plants grown in the
open air. The stems
of those grown in the
dark are long and
limp, and not able to
support themselves
upright, while the
distance between
the leaves is very
great, and the leaves
themselves are small
and useless (see fig.
27).
Why should
these plants have
such a great length
of stem? It shows
us, that when the
plant is already sup-
plied with food, dark-
ness does not prevent
mere growth in length. A grown in the light ' B in the dark -
In fact it grows faster in length in the dark, which is an
effort on the part of the plant to grow away from the
darkness into the light. It economises in material and
does not form stiff, thick stems and big leaves which
would be useless until it reaches the light.
If you now make a small chink in the black box with
Fig. 27. Seedlings of Bean of the same age,
CHAP. VIII. LIGHT AND ITS INFLUENCES 39
which you cover the plants, you will find that they grow
towards it and through it into the light. Once the tip of
the stem is outside in the light, it will form the usual
leaves at the proper intervals from one another.
The power of rapid growth in length of a plant grow-
ing in darkness, which economises the material gener-
ally used for strengthening the plant, and its power of
growing towards the light, combine to be of practical
use to a bulb or seed which is planted too deep in the
earth. You will find that the part underground has
much the same character as a plant grown in artificial
darkness, until it reaches the surface. These weak
underground stems bring the growing part into the
light, and the plant does not waste material in forming
large leaves and strong stems underground where they
would be useless.
Although light is so important, it does not follow that
the stronger the light, the better it is for the plant ; just
as it does not follow that because we like to be warm,
we like to be as hot as possible. It has been found that
plants bend away from the light when it is too strong
for them, as you may see in some plants near one of
those very brilliant electric lamps. The sun even is
sometimes too brilliant (English plants, however, do not
suffer from that very much), and many plants living in
the tropics and regions of strong sunlight, protect them-
selves from its direct rays by a number of different
devices.
CHAPTER IX.
GROWTH IN SEEDLINGS
WHEN once the young plants start growing under
suitable conditions they steadily get bigger. At first
sight they appear to grow equally all over, stretching out
in each direction as
indiarubber does
when it is pulled.
Let us try to find
out whether this is
actually the case
Take a well-grown
straight seedling and
measure off along its
stem and along its
root, beginning from
the tip, distances
i or 2 mm. apart,
marking them with
a fine brush and
waterproof ink.
Take care not to in-
jure the plant, and
also not to make the
marks blurred or too
big. Draw the plant
showing the marks
on it as accurately as
you can, and make
the drawing exactly life-size. Grow it in damp, but
very loose sawdust, so as not to rub off the marks, and
Fig. 28. A Bean seedling : A, with divisions
marked on root and stem; B, after further
growth, showing where most of the stretching
has taken place.
CHAP. IX.
GROWTH IN SEEDLINGS
after one or two days take it out and compare it with
your original drawing.
You will find that the whole plant is bigger than when
you first drew it. Look carefully at the marks on root
and stem, and you will find that they are not all the
same distance apart, as they should be if the plant had
grown equally all over. The marks which are widest
apart are those just behind the tip of the root and below
the top of the stem, thus showing that there has been
much more growth in these two regions than in the rest
of the stem or root (see fig. 28). If you repeat this often
with many plants you will find that these are the actively
growing parts of the stems and roots ; the individual
leaves, of course, are also growing. Thus we see that
growth is not a simple stretching of the whole, but that
'there are two definite
regions where it is
specially active. That
of the stem and first
root carry on the
growth in opposite
directions, as we no-
ticed before (see p.
n), the normal stem
growing up into the
air and the root down
into the soil.
You can see how
very determined the
directions of growth
are by planting up-
side down a bean
which is just begin-
ning to sprout, so that
its root points up into
the air, As it grows
you will see the root bending over till it points vertically
downwards, while the stem bends up and grows straight
Fig. 29. A, Bean seedling
planted upside down. The root
has bent right over and is grow-
ing vertically down. B, later
stage of the same. The shoot
has bent up.
4 2 GROWTH IN SEEDLINGS CHAP. IX.
into the air (see fig. 29). The same thing happens if you
plant a seedling on its side, and even if you take quite
a big seedling, which has grown in the usual way, and
then place it upside down in moist air, you will see the
root and shoot bending in order to get into their right
positions. This very determined growth on the part of
roots and stems seems to show us that they must have
some means of " perceiving " and regulating their posi-
tion. It is not an accident that they always grow in
these very definite directions. Let us find out what we
can about this question.
Take a seedling and mark its root as you marked
the roots for the experiment on the region of growth
(see fig. 28), lay this seedling on its side on soft, damp
sawdust, so that the root can easily bend into it. Next
day you should find that the end of the root has bent,
and that the bend is in just about the same region as
that which showed the most active growth.
Is this actively growing and bending region therefore
the part of the root which " realizes " that the whole is
in a wrong position, and which therefore bends to put
it right?
To answer this question quite fully would require a
great deal of work, but there are three simple experi-
ments which you can do, and which will tell you the
most important facts about it.
(i)* Take a seedling with a fairly long root which has
been growing straight down, then very quickly and with
a sharp knife or razor, cut off the last 2 mm. of the tip
of the root. Lay the seedling on its side on damp saw-
dust and examine it next day. It will not have bent,
even though it has grown in length (see fig. 30, A).
(2) Take another like it and leave it lying on its side
for an hour, and then cut off the tip in the same way as
* It is better to have half a dozen examples for each experiment,
for the seedlings do not always act quite quickly and correctly, and
from half a dozen you can see the average result.
CHAP. IX.
GROWTH IN SEEDLINGS
43
in number one, placing it on its side once more. Next
day you will find that it has bent in the same way as one
which had not been cut (see fig. 30, B).
(3) Take a third, as like the other two as possible, and
lay it on its side all night ; do no^ cut it till next day,
when it has definitely begun to bend (see fig. 30, C),
then quickly cut off the tip, and place it in the upright
position (C '). You will find that it continues to grow in the
bent form, the root tip going on to one
side. It does not seem to know that
it is growing along instead of down.
If you keep it in this position for a few
Fig. 30. Experiments on the bending of the
root tips in Beans. (See description in text.)
days it will then get a new tip and begin to grow down-
wards in the usual way (see fig. 30, D).
Think over the results of these three experiments, and
you will see that it is only when the tip of the root is not
cut off that the plant seems to " realize " that it is not in
the right position. When the tip is removed it does not
bend down even when the whole plant is lying horizon-
tally, and in the other case (fig. 30, C 1 , D) it will keep on
bending even, after it has been put in its right position.
We noticed that it is not the very tip itself which
bends, so that we see that the very tip is the part which
"feels" what is happening, while the part iust behind it
grows and bends according to the need of the plant.
44 GROWTH IN SEEDLINGS CHAP. IX.
This is a somewhat similar case to what happens
when you realize with your brain that you are in danger
on the road, and your feet hurry you across.
When we come to consider why the root should grow
downwards in this persistent way, we find that there is
an outside influence at work on the plant. You know
when a stone is left without any support that it always
falls to the ground, and we say that it is attracted toward
the centre of the earth by the force of gravitation. It
has been proved that the strong tendency of roots to
grow down into the soil is largely the result of the same
attraction, while the stem is not attracted by it but
driven away, and therefore grows away from the centre
of the earth. To prove this, however, requires more
complicated apparatus than you are likely to be able to
use at present.
From the experiments which we have done already we
see that plants, as well as animals, are affected by their
circumstances, and can in some measure realize them,
and move to alter themselves in accordance with them.
Later on we shall find that plants have a similar power
in relation to light, supply of water, and other things.
Have we not already observed in plants nearly all the
signs of life we set out to look for ? (see p. 4).
There is one very important point about the growth
of plants which is strikingly different from the growth
of animals. A young kitten has four legs, a head, and a
tail, and as it grows to be a cat these only alter a little
in shape and get larger and stronger ; the number of its
legs remains the same. A baby plant, on the other hand,
has its little root and shoot with a few tiny leaves, but as it
gets older these increase very much in number, till it may
have many branches and thousands of leaves. In fact, the
number of its parts is much more indefinite than those
of an animal ; its body is built on quite a different plan.
Yet both plants and animals show the same important
thing in their growth, that is the increase of their living
body, which they build up out of their non-living food.
CHAPTER X.
MOVEMENT
WHILE we have been examining plants to find out
some of the facts about their other life properties, we
have at the same time seen many cases of movement
in their different parts.
For example, we found (Chapter IX.) how the tips
of roots move round to get back their vertical position
if they are placed horizontally, and how the shoots of
young plants bend over towards the light when they are
grown in a dark box where it can enter only from one
side (Chapter VIII.). Then, too, as the root tip grows
into the soil or between the crevices of rocks it bends
round the stones or other things in its way, and it is
also attracted towards water, thus showing a continual,
slow movement in its growth.
The shoot shows a parallel
kind of movement in follow-
ing the light and placing
itself as advantageously as
possible with regard to it.
You may see a still faster
movement if you carefully
examine a twining tendril.
Notice how the young ten-
drils of a sweet-pea are at
been touched- B beginning to curl fi rs t almost straight, growing
fifteen minutes after being rubbed . ,
with a twig. out into the air (see fig. 31).
Now choose such a one for
the experiment, and another like it which you do not
touch, but keep to compare with the one on which you
have experimented.
Gently rub one side of the tendril with a small rough
4 6
MOVEMENT
CHAP. X,
Fig. 32. Leaves of Wood-sorrel; A in the day
position, B " asleep " at night.
twig, and then leave it alone. You will see that in
about five or ten minutes it has begun to curve, and in
a quarter of an hour may have bent round completely.
Such movement
is more rapid
than that in the
ordinary growth,
and this power
of bending so
quickly is one
of the special
characters of
tendrils, and one
that is very im-
portant in help-
ing them to do their work for the plant and to seize on
any support within reach as quickly as possible.
Then there are other movements, one of which you
must have often observed in the " sleep " of plants.
Many flowers and leaves close up and bend down at
night, taking up their usual position again next day.
This is not the same thing as the opening of buds, for
it may occur again
and again in the
fully grown parts
of plants. For ex-
ample, you may
mark certain leaves
of wood - sorrel or
common clover,
and watch them
close up at night
and re-open in the
morning many
times. These
movements are not very fast, and you cannot see the
plant moving as you can see a kitten waving its tail,
but the difference is only one of degree.
Fig- 33-
position.
Leaf of Sensitive Plant in its usual
CHAP. X.
MOVEMENT
47
There are plants, however, which move so quickly
that you can see them close up their leaves at once at
the slightest touch.
This is the case in
the Sensitive Plant
(fig. 33), and if you
only tap one of its
tiny leaflets
with a straw,
that pair of
leaflets will
immediate-
ly fold up,
Fig. 34. Leaf of Sensitive Plant, leaflets at a
beginning to close after being gently touched.
Fig. 35. Leaf of Sensitive Plant quite
leaf ' stalk faUen ' ^ being
then the next pair, and
the next, till the whole
leaf has closed, when
it drops quickly down
(see fig. 35), this move-
ment only taking a mo-
ment. If the shock is
great, all the leaves
on the plant will close t c s c e h d e ' d and
up instantly, and they
move so quickly that you can hardly see them doing it.
Some foreign plants swing their leaflets round slowly
like the arms of a windmill, but we have not yet found out
why they do this. Also in many flowers we find move-
ment, and in flowers it is generally in relation to the
insects which visit them. For example, some orchids
shut up their big front petal with a sudden snap when
an insect alights on it and shoot the astonished fly
towards the middle of the flower.
Parts such as these, which have more power of move-
ment than the rest of the plant, are called sensitive parts,
but though in them we see it more clearly than in most
48 MOVEMENT CHAP. X.
plants, they only illustrate what is common to all, and
that is some power of movement.
The movements which you have seen so far in plants
are different from those of most animals in one way, and
that is in the fact that the whole plant remains rooted in
one place, and only parts of it can move as the circum-
stances require, while, though an animal moves its parts
separately, the result of some of those movements is to
carry its whole body about. This may appear to you a
great difference between plants and animals, but it is not
quite so great as it seems ; nor must we forget that there
are some simple slimy-looking plants which slowly crawl
along the ground, as well as many minute, green plants,
which you could only see with a microscope, which
move their whole bodies and swim about just in the
way that tiny animals swim.
SUMMARY OF PART I.
WE have now done a number of experiments with
plants, and found out many facts about their way of life,
and I think you will agree that we have collected enough
evidence to prove the statement made at the beginning
of Chapter II. that on the whole plants show the same
" signs of life " as do animals.
We have seen that like animals they breathe in a part
of the air, and that they breathe out with the air the
added carbonic acid gas, which is the characteristic
" waste product " of the out-breathing of animals.
They practically " eat " when they take in substances
as food into their bodies, even though they have no
gaping mouths which can open and close. We noticed,
too, the interesting parallel between young plants and
young animals, where both (the plants in the food in the
seed, the animals in their mothers' milk) are supplied
with ready-made food at first, and as they get older
have to find what food they require for themselves.
As regards their feeding, the plants do more work than
the animals, for they manufacture the starchy food for
themselves out of simpler elements, while the animals
require their starch to be ready made.
Then the fact that plants grow, increasing in size and
forming new structures, has been known to you ever
since you were a baby yourself. Although we noticed
here an important difference between the kind of
growth in plants and animals, yet the growth itself is
alike in the two cases, for both plants and animals build
up their living bodies out of simpler substances which
they take in as food and change till the not-living food
becomes part of themselves and is living.
(C260) 49 E
50 SUMMARY OF PART I.
Movement is not nearly so great in plants as it is in
animals, and most plants are firmly fastened in the
ground. Yet there are some plants in which we can
see very rapid movements of some of the parts, while
many simple little plants living in water can swim
actively about like animals. All plants show some form
of movement, though it is generally slow.
As a result, we find that all the signs of life we noted
in animals, viz. breathing, eating, growing, and moving,
are to be found in plants, and we must look on them
as being just as much alive as animals. We can see
that their mode of life and the work they do are
distinctly different from those of the animals, but they
are no less vital, and important for the world as a
whole.
PLATE II.
A WHOLE PLANT, TO SHOW ALL THE PARTS
FI.OWCR.
A POPPY
PART II.
THE PARTS OF A PLANT'S BODY AND
THEIR USES
CHAPTER XL
ROOTS
IF you have a garden of your own, or have even
watched another person gardening, you must have
found out that it is not always an easy thing to get rid
of the weeds, and that when one tries to " pull them up
by the roots," they often resist it very strongly indeed.
If you have never done this, try to pull up a large grass
tuft or a hedge mustard, or any fairly big common
plant, and you will find that often when it does not
look very strong it may be extremely difficult to get it
completely out of the soil, and even when it comes out
you may find that you have not got it quite whole, for
the finer branches of the root will generally break off.
Now this shows us one of the uses of its roots to a
plant ; they keep it firmly in the soil, and prevent the
wind from blowing it away, and people or animals from
overturning it too easily.
To see the form of a complete root it is wise to choose
a fairly small plant, let us say a daisy, wallflower, candy-
tuft, or young holly ; then loosen the earth all round it
and pull it very gently from the soil. Shake off the
mud and then wash it clean and spread it out on a
sheet of white paper so that you can examine it pro-
perly. Notice that there is a central chief root, with
many side branches which have again finer and finer
branchlets (see fig. 36). At the tip of the very finest
you should see a number of delicate hairs, the root
54
ROOTS
CHAP. XI.
hairs,
these
but it is very possible that you will have torn
off with the soil. To see them best, look at some
of your seedlings which
have grown in moist air,
where they are very well
developed (see fig. 8). In
any of these plants you
will notice that the main
root seems to be a down-
ward continuation of the
main stem, and that the
side roots come off all
round it, just as was the
case in your bean seed-
lings (see figs. 36 and 7).
Such a root is called a
tap root
Now dig up a small
grass plant and compare
its root with these, and
Fig. 36. Root of a young Holly : J, level
of soil ; s, stem ; c, chief root with many
side branches and finely divided rootlets.
you will see that there is no
main root, but very many roots
coming off in a tuft from the
base of the stem, just as was
the case in your corn seedlings
(see fig. 37). The difference be-
tween these roots and tap roots
is not of much importance as
regards the actual work they
Fig. 37. Grass plant, showing
the many finely divided roots.
do but is one of difference in form ; the finer branches
in both are very similar and have the same work to do.
CHAP. XI.
ROOTS
55
If you leave the plants you have pulled up lying in
the air for an hour or two, you will find that they will
wither, the leaves becoming quite limp and the whole
plant drooping. Now place them with their roots only
in water, and you will soon find that they are beginning
to revive. They will revive fully and live a long time if
their roots are kept in water. This reminds us of the
second very important use of its roots to a plant, which
we have already found out (see Chapter IV.), and shows
us again that the roots absorb water and keep the whole
plant supplied with it. Of course you know that cut
flowers can drink up water with their stems, but that is
only for a short time, and is not quite natural. The
special part of the rootlet, which does the actual absorp-
tion, is the part near the tip which is covered with root
hairs. You have already seen these root hairs in the
course of your work (see pp. 13 and 15).
There are then two chief duties of
roots, to absorb water from the soil for
the whole plant L , and to hold it firmly in
the ground. The fine fibres of the root,
which are so much divided and run in
the soil, serve both these purposes, as
they expose a large area to contact with
the soil, and so can absorb much from
it, as well as getting a good hold of it.
As well as these two chief functions,
there are many other pieces of work
which roots may do, and according
to the special work they take up, so they
become modified and look different
from usual roots.
One thing they often do is to act as
storehouses of food. For example, ex-
amine the root of a carrot. The part
we commonly call the carrot and which
we eat, you will see is really the main axis of the tap
root, and has the little side roots attached in the usual
Fig. 38. Tap root
of Carrot, swollen
with stored food,
ROOTS
CHAP. XI.
way. The unusual thickness of the main root is due to
the large quantities of food which it stores. Just in the
same way radishes
and many
plants have
Fig. 39-
with food.
Dahlia, with storage roots packed
other
their
main roots very
thick and packed
with food, while
dahlias have their
side roots thicken-
ed in a similar way
(see fig. 39). Such
modified roots,
which look quite
different from or-
dinary ones, are
called Storage
roots, and if you examine many of them you will find
them packed with starch (see p. n for iodine test).
Although it is general for the roots to hold the plant
firmly in the ground, in some cases they
grow out of the stem in the air and help
to hold it up against a tree or wall, or
some support, as in the case of ivy. If
you pull off a branch of ivy which is
climbing up a tree you will find that all
along the back of the stem there are
tufts of short thick rootlets which often
come away holding a piece of the bark
of the supporting tree. These roots,
you will see, do not come out in the
usual way from the main root or base of
the stem, but come out all along the
stem itself (see fig. 40). Such special
roots are called " Adventitious," and
they grow from the stem wherever they are needed.
Adventitious roots may also come out from a wounded
plant which has had its true roots cut away. For
example, take a piece of Forget-me-not stem without
Fig. 40. Adven-
titious roots grow-
ing out from the stem
of Ivy between the
leaf stalks.
CHAP. XI.
ROOTS
57
Fig. 41. Tufts of aii
roots of an Orchid.
any roots, and slit it at the base, and put it in a glass of
fresh water. After a week or so you
should see little white roots growing
out from the stem into the water, and
if you let them get strong you may
then plant the sprig and get a new
forget-me-not plant from it. In this
and all ''cuttings" adventitious roots
growing out from the stem do the
usual work of roots. There are many
other kinds of adventitious roots, but
we must only mention the orchids,
some of which have long tufts of
roots which grow out irregularly from
the stem and hang in the air. These
are special air-roots, and grow on
many orchids, but also on some other
plants which live attached to trees and absorb the water
out of the air instead of from the soil (see fig. 41).
There are many other curious roots, particularly in
plants which grow in
tropical countries, e.g.,
the stilt roots which come
out from the base of the
stems of many palms and
make tripod-like supports
(see fig. 42), and others
which grow from the high
branches to the ground
like pillars, and prop up
Fig. 42. supporting or stilt roots the heavy trunks. How-
fna Wi ot S utfromthebaseofasmallPalm ever, we do not need to
go so far to find very many
different kinds of roots, and if you examine carefully
those of the plants growing in our woods and lanes, you
will find what a number of extra pieces of work they can
do, in addition to their two chief duties of drawing in
water from the soil, and holding the plant in its position
in the earth.
CHAPTER XII.
STEMS
EXAMINE the stem of a sunflower ; it is tall and straight
and grows upright in the air, bearing leaves which stand
out from it.
In a young holly, and many other plants, we find
growing out from the central stem smaller side branches
which bear the leaves. As we have found already
(Chapter VI.), the leaves are the active parts of the
plant and do the food-building, so that the stem is
chiefly useful as a support, which keeps them in a
good position as regards the light and air. In general,
we do not see much of the stem because it is largely
hidden by the covering of leaves, so that if you want to
study stems you should go to the woods in the winter
when there are no leaves on the trees, and you can see
the form of the branches themselves.
In big trees, such as the oak and beech, the stems
are very important, and the chief stem or trunk becomes
very thick as it gets old. It is made of hard wood which
is tough and strong, for such high trees have to bear
great strain from the winds, as well as the weight of all
the leaves. If you go into the woods when it is very
windy, and watch the thick wooden boughs swaying,
boughs which you could not move, you will see how
much force the wind may sometimes have. The
branches need all their strength in the summer to
support the curtain of leaves which catches the wind.
In a big tree we find the few chief branches thick and
strong, but there are many hundred smaller ones, some
of them dividing to quite delicate branchlets which
58
CHAP. XII.
STEMS
59
Fig. 43. Much-branched stem of
the Oak.
bear the leaves, so that the whole tree body is very
much complicated (see fig. 43).
Each kind of tree has a way
of branching which is charac-
teristic of its species, so that
even without leaves or flowers
a woodman can tell what a
tree is. This one can learn
by practice in the woods, but
to begin with it is rather diffi-
cult. Without going into de-
tail, however, we may notice
great family differences, such
as exist between a larch or a
Christmas-tree and an oak.
In the first two there is
one straight main trunk, with side
branches at very regular intervals (see
fig. 44), and in the oak the main thick
trunk soon bears several large branches
nearly equalling the main stem ; these
divide again and again in a rather
irregular fashion (see fig. 43).
In many of the smaller plants the
stems are not strong enough to stand
up against the wind, and they simply
lie along the ground or support them-
selves by growing among other plants,
such, for (example, as the common
Stellaria, where the stem is very deli-
cate indeed (see fig. 45). Then again,
if you pull up a large water-lily, you
will notice how soft and limp the long Fig.44. The Larch,
leaf -stalks are. They cannot support showing its strong cen-
themselveS at all in the air, though delicate^ide^ranches 6
they were upright in the water. This
is because the stalks get their support from the water
which allows them to float up, so that the plant does
50
STEMS
CHAP. XII.
stemof theStellariajpartly
not build a strong stem. You will find that plants are
very economical in their use of strengthening material,
and never waste it
where it is not want-
ed. If you remember
this, and then study
all the stems you can,
and note when and
where they are streng-
thened, you will find
what good and econo-
mical architects
plants are.
As well as support-
ing the leaves, the lying on the ground
stems have another
very important duty, something like that of the roots.
Just as the roots absorb the water from the soil and
carry it up, passing it on to the stems, so the stems carry
it on to the place where it is finally used, that is, to the
leaves. In both stems and roots there are channels or
" water-pipes " which carry water about, as well as other
special " pipes " which carry the manufactured food.
So that the two chief duties of stems are to act as
supports for the leaves and flowers, and to carry the food
materials and water between the roots and leaves.
Just as we found in the case of the roots, there are
many extra duties which the stems may take over,
and as a result, we find great variety in the appearance
of stems. For example, in some plants the stem does
not grow up into the air at all, but creeps along just below
the surface of the ground. This you may see if you dig
up a Solomon's Seal or an iris, when you will find that
the stem looks very like a thick root running horizontally
in the ground. That it is really a stem you can tell from
the fact that the leaves grow out from it, and you can
see the scars of old ones as well as the present leaves,
and also some little brown scaly leaves, and a large number
CHAP. XII.
STEMS
61
Fig. 46. Underground stem of the Solomon's
Seal, called a Rhizome. It has many scaly leaves,
s and a shoot A which will come out into the air
bearing green leaves. B is the scar left by the
similar shoot of last year, r are the adventititious
roots which come out all over the stem.
of adventitious roots. The stem is rather swollen with
food materials which are stored up in it, and
it is not coloured green like many of those
growing in the air. Such a stem, creeping
under the earth,
and only sending
its green leaves
into the air, has
a special name,
and is called a
Rhizome. Many
plants have such
stems, particular-
ly ferns, as you
can see very well
if you dig up a
bracken.
Some of the un-
derground stems
which store food are still more modified, so that it is very
hard indeed to tell what they really are. This is the
case in the potato, which you would naturally think at
first is a swollen root, like those we saw in the dahlia
(fig. 39). That it is really
a stem you can see by ex-
amining the "eyes" care-
fully. The eyes (see fig.
47) are buds with scale
leaves round them, and at
the tip of the potato we
can see several such buds
together (fig. 47*). The
whole potato is a very
much swollen stem which
is packed with food and
has all its other parts so
reduced that it is difficult to recognise them,
special stems are called Tubers.
Fig. 47. A Potato : s, the stem attach-
ing it to the main stem ; , scale-leaf ; 6,
bud in its axil ; /, tip of the Potato with
several buds, some of which are sprout-
ing.
Such
STEMS
CHAP. XII.
Fig. 48. Cactus plant, showing
its fleshy stem, which is green,
and does the food building for
the plant. The tufts of spines
and hairs represent the leaves.
Certain stems take on the work of leaves, and some-
times they are so much modified for this that the plant
has no true leaves at all. This is what has happened in
the case of a cactus. If you
can get a cactus, examine it
carefully and you will see that
the whole plant consists of a
thick mass of green tissue,
which apparently is not di-
vided into stem and leaves.
But the truth is that the whole
of the thick mass of tissue is
the stem, and the little tufts of
spines and hairs are really re-
duced leaves. So that in the
cactus the green stem does all
the food building work instead
of the leaves.
In some plants this is not so
much marked, even though the stem does some of the
work for the leaves. In such cases the stem is gener-
ally green and broad or winged and the leaves small, as
in our common broom and the whortleberry, where
the leaves very soon drop off. Quite a number of
plants have stems which do this, and it is sometimes
a great advantage to the plant, for the big leaves are
often very wasteful of water, as you will see in Chapter
XVIII.
In other cases we find that the side branches of
stems may be modified to protect the plant, and so
take on the form of strong spines or thorns, as in
our blackthorn, where the sharp pointed spines are
modified side shoots.
There are many other pieces of work which stems
may do ; we must just mention the climbing and twin-
ing stems, where the stem is delicate and requires to be
supported, which we are going to examine more care-
fully in Chapter XIX.
CHAP. XII.
STEMS
Sometimes, instead of con-
tinuing to grow into the air,
the stem may bend over
into the earth again, as often
happens in big bushes of
bramble (see fig. 49), and
then from the tip of the
stem a number of adventi-
tious roots (see p. 56) grow
out and hold it firmly in
the ground. If, then, this
branch gets separated from
the rest of the plant, it
can build a complete new
individual.
In the case of the bramble
notice how the leaves get
smaller and smaller towards
the tip of this branch as it
bends down to the earth,
and of course, they do not
develop at all as true leaves
under the soil (see fig. 49).
From these examples, and
the many others you should
be able to find for yourselves,
you see that stems may take
on other duties beyond
their two chief ones, but that,
however much they change
their form and appearance,
we can always find out that
they are really stems by
g studying them with a little
care.
Fig. 49. Leafy branch of Bramble which
has bent into the earth and given rise to
a cluster of adventitious roots at the tip ;
/, level of soil ; P, point where the branch
was cut from the parent plant.
CHAPTER XIII.
LEAVES
THE late spring and summer are the best times to study
leaves, for, as you must have noticed, the woods begin
to lose their green in the autumn, and the leaves have
fallen in the winter. This tells us that the fresh green-
ness of the leaves (which you know is so important
for the plant) does not last very long, and when they are
no longer green the leaves are useless and drop away.
As you know, the chief work of leaves is to build
starchy food, for which they require their green
colour.
When you go into the woods or gardens to study the
leaves, first look at single ones,
collecting as many kinds as you
can. Though their shape varies
very much, you will find that in
almost all cases they are green,
expanded, and flat. Let us first
examine a single simple leaf, like
that of a cherry. You will see
that the expanded part (called
the leaf blade or lamina] narrows
down to a small stalk, which con-
nects the blade with the stem
from which the leaf is growing;
this stalk is called the leafstalk or
petiole. Then at the base of it,
just where it joins on to the stem,
there are two little leaf-like struc-
tures which are not true leaves, but which belong to
Fig. 50.
Cherry.
Simple leaf of the
CHAP. XIII.
LEAVES
the leaf and are called stipules; they are attached to the
base of the petiole, which spreads out to clasp the stem,
and is called the leaf base (see
fig. 50). Such a leaf shows
us all the parts of a simple
leaf ; but some leaves have no
stalks, others no stipules, and
so on.
Let us compare a rose leaf
with the simple leaf of a cherry,
oak, or beech. In the rose you
will find five or seven small
leaflets arranged on a single
main stalk, and each of these
leaflets separately is very much
like a single leaf of the beech.
Such a leaf as this we call
compound, for it is divided
up into several parts, each of
which looks like a whole leaf
(see fig. 51).
Leaves are of very many different kinds and shapes,
and special names have been given to each kind, which
you can look up in a book if you want to classify them.
Let us just notice a few of
the types. The cherry, beech,
and others which are simple
with slightly pointed ends,
we may call by the proper
term ovate. Then there are
leaves like those of the nas-
turtium, where the leaf blade
is circular and the leaf stalk
does not come in at the base
of the leaf, but is attached to
the middle of it ; such leaves as that are called peltate.
The broad or rounded leaves, which spread out like
the palm of a hand, such as the ivy (see fig. 26), are
(C2GU) Fl
Fig. 51. Compound leaf of the Rose.
Fig. 52. Peltate leaves of Nastur-
tium, showing the stalk attached in
the middle of the lamina.
66
LEAVES
CHAP. XIII.
- 53- Needle leaves of Pine grow
ing in pairs.
called cordate or lobed, and when compound, as are
those of the horse chest-
nut, palmate.
All the grasses and the
many plants belonging to
their family have very long,
narrow leaves, which we
call linear, while those of
the pine trees are sharp and
pointed, and are called
needle leaves.
As we noticed in com-
paring the leaves of the rose and cherry, some plants
have very much more complicated
leaves than others. Now such
complicated structures do not de-
velop on a plant all at once, as
you can see if you examine a very
young rose seedling. The first
pair of leaves or cotyledons do not
remain inside the seed as they do
in the bean, but grow outside into
the air and become green ; they are
quite simple leaves with smooth
edges. The next leaf which un-
folds is also simple, but it has a
deeply toothed edge (see fig. 54),
while the leaf following that is a
compound leaf, divided into three
leaflets. The other leaves gradu-
ally get five and then seven leaflets
as the seedling grows up.
This is just one example of what
usually happens in the history of
plants with compound leaves, or
leaves with any special shape ;
the young seedling's earlier leaves are much more
simple than the later ones. You should collect as many
Fig. 54. Seedling of Rose;
(c] cotyledons ; (a) next leaf,
simple, but toothed ; (b) next
older leaf divided into three
leaflets.
CHAP. XIII.
LEAVES
67
seedlings as possible and make drawings of them if you
can, to show the various stages leaves pass through
before reaching the full-grown complex form.
Now let us look again at the actual structure of leaves.
Hold up those of the rose, or lilac, or lime tree to the
light, and look at
the " veins " run-
ning in them.
There is a chief
central vein or
mid-rib, and from
it a number of
side branches
come off and di-
vide and branch
again and again
till they form a
fine net-work
throughout the
whole of the leaf
blade (see fig. 55).
If now you look
at a grass or lily
leaf, you will find
that there are very
many veins about
equally import-
ant, running from
end to end of the
Fig- 55- Skeleton of a leaf, showing the fine net-
work of the small veins.
leaf and remain-
ing nearly parallel to each other. This difference
between parallel veins and net-work (or reticulate] veins
is quite important, and is one of the characters which
help to separate two very big families of flowering plants
(see Chapter XXIII.).
Now let us see in what way the leaves are arranged on
the stem. If you pick a branch of dead nettle you will
see that the leaves are attached by their stalks to the
68
LEAVES
CHAP. XIII.
stem in pairs, two leaves coming off from the same level
at opposite sides of the stem (fig. 56) j while fig. 57 shows
that the leaves
of honey-suckle
really do the
same thing, only
they grow out
directly from the
stem as they have
no leaf stalk. Now
look once more
at the leaves of
the dead nettle,
choose one par-
ticular pair to
start with, and
then look how
the pair above it
are placed. You
will see that they
do not lie directly above the pair you chose, but are
arranged on the opposite sides of the stem, so that the
two pairs alternate. If then you look at the pair next
above them, you will see that
they are arranged in just the
same way as the first pair, and
so alternate with the second. In
this way every pair of leaves on
the stem alternates with the pair
above and below it. Now ex-
amine a pear or cherry twig, and
you will see that the leaves are
n^ n ieaf arran g ed sin gly on the stem.
Fasten a piece of thread to the
stalk of one leaf and twist it
round the base of the next, then on to the next above
and so on. You will find that the thread makes a spiral
round the stem, and finally comes to a leaf higher up it,
Fig. 56. Alternating pairs of leaves of the Dead
Nettle.
stalks.
CHAP. XIII.
LEAVES
69
Fig. 59. Leaves
arranged in a whorl
in the Horsetail.
which lies exactly above the one you started from.
Very many plants have their leaves arranged like this in
a spiral on the stem with the youngest at
the top. There are different kinds of
spirals for the arrangement of leaves in
the different plants. You can see this by
making the spiral of
thread and counting
how many leaves you
pass on your way up
the stem till you reach
the leaf which lies just
immediately above the
one you start from.
Sometimes the
leaves are arranged in
a circle all round the stem at the same
level; this is the case in the horse-
tail (see fig. 59), and such an arrange-
ment is called
a whorl, but it
is not very
common in
plants.
In the goose
grass the
leaves look
very much as
though they
were really in
a whorl (see fig.
60), but there
are only two true leaves ; the oth-
ers are the stipules, which are so
much like the leaves that it is very
difficult to tell them apart.
As we found out already, leaves require light and air,
and usually arrange themselves so as to get them ;
(C260) F2
Fig. 58. Branch of
Cherry (leaves cut off
to make it clearer), with
a string twisted from
leaf stalk to leaf stalk,
showing the spiral ar-
rangement. Note that
leaf 5 is the first to come
immediately above the
one you started from.
Fig. 60. Leaves of Goose
grass looking like a whorl.
LEAVES
CHAP. XIII.
hence, in a general way, we may observe that the
leaves all grow to face the light. If you go under a
beech tree, for example, and look up, you will find that
you can see nearly all the big branches on the inside,
while the leaves form a covering or dome on the outside.
Special cases of leaves so arranged as to get a good light
we noticed before (see pp. 36 and 37).
As well as their own particular work, leaves
may take on extra and different work, so becoming
modified to suit their different occupations, and unlike
true leaves. We already noticed in the cactus (see fig. 48)
that the leaves become
like sharp spines which
protect the fleshy stem,
and can do none of the
usual work of leaves,
because they have lost
their green colour.
In some plants leaves,
or parts of leaves, may
change into fine tendrils
whichbecome very sen-
sitive to touch, and can
twine round supports
and cling to them, and
so help the plant to
climb. Such tendrils
we saw (fig. 31) move
very quickly ; they are
quite different in their
structure from ordinary
leaves. This happens
in many plants, and you
may see it very well in
the sweet pea (see fig.
61), where only two
leaflets of the compound leaf remain leaf-like, the others
having been changed into tendrils.
Fig. 61. Leaf of Pea, showing leaflets
modified as tendrils (t] ; expanded leaflets (o).
CHAP. XIII. LEAVES 71
When we come to look at Flowers, with all their
special shapes and brightly coloured parts, we are really
looking at modified leaves. But they are so very much
modified that we have come to consider flowers as things
by themselves, and so we will study them later on.
Some plants which do not have true flowers, yet have
leaves of two kinds. For example, the " flowering fern "
has the usual green leaves and others which form rather
brownish golden spikes, and which are covered with
spore* cases. Then again, some leaves are very specially
modified and are changed from the usual structure in
order to act as traps for insects (see Chap. XXL).
Other leaves, instead of being very much developed, or
specially developed along some line, are simply reduced,
that is, are very little developed indeed. For example,
as you saw in the under-ground part of the potato and
many rhizomes growing horizontally, the leaves never
become large and green, but remain as simple brown
scales. Some scale leaves have quite a special work to
do in the way of protecting the very young green leaves
while they are in the buds, and we will look at these
carefully in the next chapter.
We have now seen that leaves, like all the other parts
of the plant, can modify themselves in a very great
number of ways, and may do many extra pieces of work
above and beyond their chief work of food manufacture.
* Spores are simple little structures which do much of the work of
seeds. See the Chapter on Ferns.
CHAPTER XIV.
BUDS
THE proper time to study buds in nature is the spring,
but then you will have to wait long to see all the different
stages of their slow unfolding. But they can be made
to open artificially, and it is really wise to study buds in
winter, when there are not so many other things to do.
You can arrange this very well if in the late autumn you
cut off fairly big branches with buds
on them (horse chestnut is particu-
larly good for this) and keep them in
a warm room. You must, of course,
keep the cut ends of their stalks in
water, which you should change every
three or four days, sometimes cut-
ting off a piece from the ends of the
branches so that they have a fresh
surface exposed to the water. In
this way they should live for months,
and may just begin to unfold and
show fresh young green leaves about
Christmas time, when the buds on the
trees out in the cold are still tightly
packed up.
Watch the buds as they unfold, and you will find that
round each bud are several dry brown scales; these
drop off, and within them are more green, leaf -like
scales enclosing the true young leaves, which are
still curled up and very small when they first come
out.
If you examine a big bud which has not yet begun to
Fig. 62. Buds of the
Horse Chestnut begin-
ning to unfold.
CHAP. XIV.
BUDS
73
Fig. 63. Bud of
the Horse Chestnut,
showing the over-
lapping of the scales.
unfold, and carefully pull off all the parts separately
with the help of a needle and knife, you will see how
the outer scales fold over one another like a coat of
mail, and where they are exposed to
the outside air they are hard and shiny,
and in many plants are covered over by
a sticky waterproof substance like tar-
paulin. These outer scales keep off
the rain and snow, and keep the inner
parts dry and unharmed. Within them
the scales are softer and often quite
green, and they, too, wrap round each
other, so that there is no crack left which
could allow the cold rains to enter to
the little leaves within. In many cases
also the young leaves are wrapped up
in soft, long hairs which look almost
like cotton wool. These hairs grow on the leaves
themselves, and you can see them after they have
opened out, but as the leaves are then much bigger,
the hairs are scattered further apart
and do not show so much.
If you cut right through the length
of a bud with a sharp knife, you will
see how all these scales and young
leaves are packed together, as in fig.
6 4 .
Take another bud and carefully pull
off all the scales one by one and lay
them in a row, beginning with those
right outside ; you will see that they
get less scale-like and more like real
leaves as you go in towards the centre
of the bud (see fig. 65). The outside
simple brown scales scarcely look like
leaves at all, but the inner ones are green and soft, and
in some plants, those right inside have quite a leaf -like
appearance.
Fig. 64. Bud cut
through lengthways,
showing the bud-
scales and young
leaves packed with-
in them.
74 BUDS CHAP. XIV.
This helps us to see that bud scales are really only
Fig. 65. A series of bud scales from a Horse Chestnut ; (a)
and \b) are entirely hard and brown ; (c) and (d) are brown at
the tips and green at the base, where the others cover them ;
(e) is quite green, soft, and leaf-like.
modified leaves, which are altered for their special work
of protection of the young leaves through the winter.
Of course, you know that the buds are already on the
trees in the late autumn after the leaves have fallen ; but
have you seen the buds already there in the summer
while the leaves are still fresh and green ? If you look
for buds you will be sure to find them, and at the same
time you will learn where they grow on the stem. You
must look right at the base of the leaf stalk, in the
angle made by the leaf stalk where it joins the main
stem ; this is called the axil of the leaf, and it is in the
axil of the leaf that you will find the small green buds
in summer-time. These buds grow out in the following
year, so that a new leaf comes in very nearly the same
place as the old one, or, what is more usual, there
grows out a new branch which may bear several new
leaves. Now examine a twig of horse chestnut or
sycamore from which the leaves have dropped ; notice
that, where the buds are to be seen on the stem,
they lie immediately above scars of a definite shape,
which are the scars left by the fallen leaf stalks, as you
can see by comparing them in the autumn with leaf
stalks which are just falling away (see fig. 66, /, b,
and s).
On the stem there are other scars, which are different
from the ordinary leaf scars, and which are like bands
of fine lines round the stem. What are these ? Now
CHAP. XIV.
BUDS
75
if the single big leaf stalk leaves its scar so clearly on
the stem, what kind of scar would a number of thin
scales lying close together be likely to leave ? Will it
not be a number of narrow scars
in a band, just such a scar as we
have here (fig. 66, a, a 1 , and
J(/ m a 2 ). If you mark a bud on a
tree or one of the branches in
your room and watch it unfold,
and keep a note of it till the
autumn, you will find at its base
where the bud scales were, that
there is then a scar just like this.
Whenever you see such a scar
you will know that it has been
left by a bud. Now you know
that, as a rule, trees have buds
only once a year, so that each
of the bud scars along the stem
must represent a past year's bud,
and if you count these scars
along the length of the stem it
will tell you the number of years
the stem has been growing. For
example, in fig. 66 the twig shows
us five years' growth if you count
the last bud which will grow out
to form a shoot;
The buds which come in the
axils of the leaves along the stem
may form new leaves, or may
develop into side shoots with new
stems and leaves. There is an-
other bud, generally bigger than
Fig. 66. Branch of Sycamore, showing leaf
stalk (/) with bud (6) in its axil. Scars of leaf stalks
(s) and large terminal bud (/) with scars (a), (a 1 ),
and (a 2 ) left by the terminal buds of past years.
7 6
BUDS
CHAP. XIV.
these, which grows at the end of the shoot (/, fig. 66).
This has just the same structure as the others, but it
will certainly grow out to form a stem and carry on the
line of growth of the main shoot, unless it is injured.
The amount that the shoot grows in one year depends
on very many things, on the light and warmth it gets,
on its food and the growth of its neighbours. Hence,
in the growth of different shoots in the same year, or
the same shoot in different years, we find very great
differences. Sometimes a number of bud scars lie very
close together, showing that for several years it had only
grown a small amount, while in the years following it
may have added very much to its length. In some
plants there are little
side shoots which ne-
ver grow much, and
always remain quite
short; for example, in
the larch each tuft of
leaves grows on a little
stunted stem which
represents several
years' growth, and
which never reaches
any length (see fig. 67).
Not only do we get leaves and stems packed away in
buds, but the flowers for next year are there also. For
example, examine several of the big horse chestnut buds
from the outer branches of the tree, and you will be sure
to find tiny sprays of young flowers packed away in the
hearts of some of them.
There are some quite special buds which we must
notice, and which at first sight appear very different
from real buds. They have been given a different name,
and are called Bulbs. Cut right through a tulip or
hyacinth bulb lengthways, and compare it with a horse
chestnut bud to which you have done the same. The
arrangement of the parts of the two things seems to be
Fig. 67. Larch, with tufts of leaves growing
from short side shoots.
CHAP. XIV.
BUDS
77
very similar. If you examine the bulb in detail, you
will find that it is protected on the outside by brown,
hard scales, and that the softer leaves within are folded
over each other very much like those in the true buds.
Now the bud of the horse chestnut is attached to the
parent stem is there nothing corresponding to the stem
in the tulip bulb ? Look carefully at the base, and you
will see a little mass of tissue
which holds the scales to-
gether (see S, fig. 68) ; this is
the stem, which is short and
very much reduced, being
unlike a usual stem. There
is also one great difference
between the scales in the
bud and the bulb. In the
bud they are rather thin and
dry, but in the bulb they are
thick and white and very
fleshy, and if you test them
with iodine, you will find
that they contain much
starchv food. They form
Fig. 68. Bulb cut through, show-
ing the overlapping scales (5) packed
with food attached to the shortened
stem S . B is the bud , which will grow
out into the air, and (ft) the bud which
will form a new bulb next year ; (r)
adventitious roots growing from the
base of the stem.
the storehouse of the tulip,
and this food will be used
by the plant when it begins to grow. In the axils of
these thick fleshy leaves you may often find small buds,
which will get large and fleshy by next year and form
the new bulbs (see fig. 686).
Sometimes little bulb-like structures grow in the
axils of ordinary leaves, for example, in the tiger lily ;
these drop off when they are ripe, and can grow into
whole new plants. They are really half-way between
bulbs and true buds.
CHAPTER XV.
FLOWERS
IF you have ever noticed a pea-flower fading, you will
have seen that from its heart there grows a little green
pea pod which ripens till there are full-grown peas in
it (see fig. 80) ; and a yellow dandelion flower turns in
the end to a white puff ball which scatters a hundred
floating fruits. In fact, almost all flowers which have
not been spoiled by the gardeners and " over-cultivated "
leave in their place when they die fruits and seeds in
some form or other. This gives us the key to the secret of
the structure of the flowers themselves. They are the
forerunners of the fruits, containing living seed, and
their structure and all their
parts are adapted in some
way to help in the forma-
tion of fruit. Now let us
examine the flowers, never
forgetting that fact.
Let us choose, for ex-
ample, a harebell. On the
outside we find five separ-
ate green parts, and if we
examine a bud which has
not yet opened we shall
find that these fold quite
tightly over the inner por-
tions " of the flower and
protect them, as they do
in the rose and in almost all flowers (see fig. 69). In
this they correspond to some extent to the bud scales,
CHAP. XV.
FLOWERS
79
and their special work is that of protection. In all hare-
bells and roses there are five of these parts, but in the
wallflower you will find only four,
and in poppies two, and so on.
There are different numbers of
them in the different kinds of
flowers. They are also of different
shapes and sizes ; sometimes each
of the five parts is free, and some-
times they are all joined up together
to form a true cup, as in the prim-
rose (see fig. 72). These outer
green protective parts have a special
name, and are called the calyx or
cup, while each of the separate
parts which makes the cup is
called a sepal.
Directly within the calyx we
come to the parts which are gener-
ally bright and prettily coloured,
and which give the chief beauty to
the flower. In the harebell which
we are examining these parts are
joined up to form a bell, but in the rose they are each
separate (see fig. 71). In both harebell and rose we find
five of these parts, and the same
number in the primrose, where
you will find that they are joined
up at the base to form a long,
narrow tube, and then spread
out separately like those of a
rose. Both in the harebell and
primrose, where they are joined
up, we can tell the number of
parts which go to make the
whole bell or tube (and this is
nearly always the case in bell flowers), while, of course,
where the parts are free it is quite easy to count them,
Fig. 70. Buds of the
Rose ; A with the calyx
covering the inner parts,
B with the petals opening
out.
Fig. 71. Flower of the Rose,
with separate petals.
8o
FLOWERS
CHAP. XV.
the tube formed by the petals.
and we find that for each kind of flower their number
is always fixed. For example, we find five in the hare-
bell, rose, primrose, and many others, four in the poppy,
wallflower, cress, and so on.
These parts are called the
petals, and in almost all
flowers you will find that
they are bright and pretty,
and stand out from the sur-
rounding green leaves, so
that they are easily seen.
When the cups or bells hang
down they may protect the
parts within from the rain,
but that is not generally
their chief work The first
duty of the petals IS to 06
attractive. You will under-
stand better why this is so after we have gone further
into the flower.
Within the petals, and, in most cases, lying at the
base of the bell, you find several yellowish dusty sacs, on
fine thread-like stalks. In most flowers they are all free
from each other and from the petals,
but in the primrose they are fastened
to the tube of the petals (see fig. 72).
In some flowers you will find a great
many of these, as you do in the wild
rose (see fig. 71) and the poppy, where
there are so many that you can hardly
count them. In other flowers there are
very few; for example, there are only
two in the blue speedwell (see fig. 73).
In most flowers the single stamens, as they are called,
are very much alike in their structure, and they all have
the same work to do. Look at these structures in a
tulip or lily, where they are very big, and carefully pull
one off and examine it (fig. 74). You will find that it
Fig. 73. Flower
of Speedwell, with
only two stamens (s).
CHAP. XV.
FLOWERS
81
A
Fig. 74. Single
stamen from Tulip
flower ; A, anthers,
or pollen sacs ; F,
filament, or stalk of
stamen.
consists of a stalk which we call the filament, with two
long sacs at the tip which hold the yellow dust, and
which we call the anthers. If you examine a fully
blown flower of the tulip or lily, you
will find that the sacs split open right
down their length and let out a fine
yellow powder. This powder is the im-
portant thing about the stamens, and is
called the pollen. In all stamens you
will find the anthers or pollen sacs,
while the stalk, which is less important,
is not always developed. Sometimes the
sacs split right open like those in the
lilies, but there are other ways of open-
ing; as for instance, in the rhododen-
dron you will see a little round hole at
the tip of each anther, which lets the
pollen shake out like pepper out of a pepper-pot.
Now we have come to the heart of the flower, and find
there the most important thing in it. Examine a sweet
pea, for example, and
you will find in the mid-
dle of the flower a tiny
green structure very like
a pea pod, with a little
sticky knob at the tip.
In the heart of a tulip
you will find a long green
box with a sticky, three-
cornered knob at the top
(fig. 75), while in a butter-
cup there are a number
of these structures in-
stead of one (see fig. 765),
each of which has very much the appearance of a little
pea-pod. Open the pea-pod, or the box of the tulip,
and you will find within it a number of very small balls
of a clear green colour. T hese are the young structures
( C 260 ) G
Fig. 75. Flower of Tulip laid open,
showing the three-cornered central green
box containing the young seeds.
FLOWERS
CHAP. XV.
which will become seeds when they are older, and they
are the most important things in the flower. The green
box which protects them
is called the carpel in the
case of the pea-pod, where
there is one space in it. In
the tulip you will find that
the box is divided into
Fig. 76. Buttercup flower laid open,
showing that there are many seed-boxes
(s) in the centre of the flower. R, the
receptacle is the swollen end of the
flower stalk.
Fig. 77. Carpels of
the Tulip cut open to
show that there are
three spaces with seeds,
each division represent-
ing a single carpel.
three compartments, and
each of these is called
a car-
pel (see
fig- 77).
You may think of the tulip carpels as
being the same thing as three pea-pods
joined very tightly together. Some
flowers have only one carpel ; others
have three or five joined up like those
of the tulip, while others like those
of the buttercup have a very large
number of single
separate carpels.
In the pea,
tulip, buttercup, and many others,
the carpels are in the centre of
the flower, above the petals, and
attached to the swollen end of the
flower stalk, which is called the
receptacle, as in fig. 76 R. Other
flowers have the receptacle hol-
lowed out like a cup or goblet,
and the carpels sunk right in it.
When this is the case, we generally
find that the sepals and petals lie
above the carpels and not below
This is also the case in the rose,
where in fig. 70 flower B shows clearly the swollen
part below the bud, which is the hollowed receptacle
Fig. 78. Flower of
Cherry cut open to show
the hollowed receptacle, R,
below the level of the
petals, and containing the
carpel, C.
them, as in fig. 78.
CHAP. XV. FLOWERS 83
containing the carpels, and the same is true of the
harebell (see fig. 69) and many flowers.
What can be the use of the sticky tip that we found
on the carpels ? Examine the tip of the carpel of a lily
which is well open, and you will very likely find some
of the yellow pollen sticking to its surface. It is a
curious fact that the little structures within the carpels
which will become seeds cannot ripen into true seeds
unless they are waked up to growth by the pollen grains.
The sticky tip of the carpels (or stigma, as it is called)
catches the pollen grains and holds them ; then they grow
down into the carpels and carry with them the nuclei (see
p. 92) that enter the undeveloped seeds. These stir the
cells to divide, and after many divisions the embryos are
formed and the seeds ripen. Sometimes the stigma has
a long stalk which places it in a good position to catch
the pollen grains. This stalk is called the style y and is
to be found in many flowers (see fig. 72).
The pollen dust is fine and light, and may be carried
by the wind on to the stigma, as it sometimes is in
poppies, and always is in pine-trees ; but this is rather
a wasteful way, because the wind blows so irregularly
that very much pollen is lost and never reaches the
stigma. In order to save some of this loss, and to make
the pollinating more certain, flowers have arranged their
parts so as to make use of the help of insects. You
know that very many flowers have sweet honey in them
which the bees like, and come to collect, going from
flower to flower to do so. When the bee settles on the
flower it gets covered with the pollen dust, and then
when it goes to the next flower and walks over it, it is
almost sure to leave behind it some of the pollen stick-
ing on the stigma. Of course, in this way also some
pollen is lost, but insects are far more reliable than the
wind. We now see the use of the bright coloured
petals ; they help to attract the bees to the flower. The
flowers have made the bees and other insects their
special carriers of pollen, and they pay the insect with
84 FLOWERS CHAP. XV.
honey, and some of the surplus pollen. Bees generally
go from flower to flower of the same kind on any one
day's journey, so that the flowers get pollen from others
of their own kind. This is important, for " foreign
pollen " (as the pollen from quite different kinds of
flowers is called) does not help the young seeds at all.
We have now found a use for all the parts of the
flower.
There are many special things about flowers which
we must leave till later on, but we may just notice now
how some are regular, like the primrose, rose, poppy,
and so on, which are after the pattern of a circle, and
appear the same from whichever side you look. Others,
like the violet, larkspur, or
sweet pea, are not regu-
lar, but have only two
sides alike. This differ-
ence is very often due to
some special structure of
the flower in relation to
the insects which visit it,
Fig. 79. A, violet, a two-sided flower, and if you examine and
B. Primrose, a circular flower. Compare the two-sided
with the circular flowers
you will generally find that the two-sided flowers are
the more complicated. Some of them become very
complicated indeed, like the orchids, which have such
strange flowers, and in which the relation between the
insects and the flower has become very special.
We must leave these more complicated cases till
Chapter XXII., and come back to the simple important
facts about the work which all flowers have to do. They
must make sure that in some way or other, seeds
are formed for the plant. If the flower does not do
this, then it is not doing the work for which it was
made.
You will find a number of flowers in gardens which
do not do their work properly, and very often have no
CHAP. XV. FLOWERS 85
seeds at all,but they are speciallycultivated by gardeners
to do other things. For the study of the true structures
of flowers, it is generally better to examine wild flowers
instead of garden ones, which are often much altered
by the rather unnatural conditions in which they are
made to live.
CHAPTER XVI.
FRUITS AND SEEDS
WITHIN the flowers we saw, protected and shut in,
the carpels or seed-box, within which are the very
young structures which will become seeds. Now let
us watch them develop. In such flowers as the sweet
pea, for example, in summer-time, this will not take
very long. Mark a special flower, and watch it each
day; you will find the little green pod will gradually
grow bigger, till it splits away the petals which are
Fig. 80. A, Pea-flower. B, the same beginning to fade, with the ripening
carpel breaking through the keel. C, the same carpel much enlarged, the
petals and stamens quite faded.
beginning to wither, and pushes out between them.
As the pod gets larger you can see the seeds within
growing too, if you look at the pod carefully against the
light. The stigma does not grow any further, as its
\vork was finished when it had caught the pollen grains.
After a time the petals and stamens drop right away,
and only the calyx remains ; it does not grow very
much, but it keeps fresh and green for some time, as it
has still to act as a cup to hold the pod. It only takes
CHAP. XVI. FRUITS AND SEEDS 87
a few days for these things to happen, then till the pea
pod is quite ripe may take a week or two more. The
pod continues to grow and turns yellowish brown and
dry, then one day when the sun is warm you may see and
hear it split
open sud-
denly down
its central
ridge, and
shoot out the brown, dry seeds. Then
the work of the flower is quite over,
and the seeds have started to make
their own way in the world.
Let us pick a nearly ripe pea-pod
and examine it; it is the ripe carpel, Fig.si. A,ripecar-
with several ripe seeds in it, and to- od.' f Bf a pd "sucu
gether they form what is called a fruit. den iy ^ and twist -
,1 f ,1 j 1 1 // e - n -A. ed U P. scattering the
In the case of the pod the " fruit it- see ds
self is a dry pea-pod husk, but in other
plants the fruits may be very different. Examine a
marrow, for example. Watch it in the course of its
trowth, if possible, and you wiii find that the marrow
ower is one of those with its seed-box below and out-
side the calyx and petals. As the marrow ripens this
swells with the food stored in it, and the many growing
seeds, till the flowers are only small shrivelled structures
at one end. If you then cut the ripe, or nearly ripe,
marrow fruit across, you will find that its wall is very
thick and fleshy, and that the many seeds are buried in
a soft pulp. The melon shows us just the same thing.
Such fruits seldom split suddenly to shoot out their
seeds (though some foreign ones do); they depend
more on animals which may eat them and so scatter the
seeds about.
In all cases it is better for the plant to have the seeds
scattered so that they do not sprout too near together,
but have room enough to grow without crowding each
other out.
88
FRUITS AND SEEDS
CHAP. XVI
Fig. 82. Cherry
fruit cut open,
showing the flesh
(/), stone (s), and
seed S.
In the pea and marrow there are many seeds, but
there are large numbers of fruits in which we find only
one. For example, in plums, cherries, and peaches we
have a fleshy outer fruit-case with a stony lining cover-
ing over one large seed. Such fruits do not open, for
there is only one seed within, and so the
fruit is scattered whole. These fruits
nearly always get scattered by animals,
for the flesh is very sweet and attractive
to eat, and then, as a rule, they get rid of
the stone (which contains the seed) at
some distance from the parent.
Sometimes we find a number of fruits
just like the cherry clustered together,
only instead of each of them being large,
they are all very small, so that the whole
cluster of fruits may be the size of a single cherry.
This is the case in the common blackberry and the
raspberry, where each of the little fruitlets really corre-
sponds to a cherry.
Then there are many fruits which belong to quite
a different class, and arrange to
scatter themselves by the help
of the wind, such as the fruits
of the dandelion, thistle, and
many others, which have light
41 parachutes," and therefore
blow away with the least puff of
wind when they are ripe and
dry (see fig. 83).
Other fruits like the sycamore
have big side-wings which catch
the wind as they fall, and get
twirled for some distance. In these cases each of the
separate parts which flies is really a fruit, only in the
case of the dandelion, thistle, and many others, each of
these fruits contains only one seed, and the fruit itself
is so small and dry that we get into the way of speaking
Fig. 83. A, head of Dandelion
fruits, with most of them scat-
tered. B, single Dandelion
fruit.
CHAP. XVI.
FRUITS AND SEEDS
89
Fig. 84. Fruit
of the whole fruit as a " seed." This is not correct,
however, because even though there is only one seed
present, yet it is surrounded by the dry
remains of the ripe carpel, and is therefore
a fruit.
Simple seeds which have wings are rather
rare, but we find them on pine seeds (see
fig. 125), and the seeds of the willow herb
are covered with a number of silky hairs,
which make them so light that they fly in
the wind. If you watch a spray of willow
herb ripening, you will find that the old
carpels, or fruits, split up into four parts
and let out a number of fluffy white seeds.
These are true flying seeds (see fig. 84).
Other seeds get scattered by the wind
although they do not fly. For example, in
the poppy the fruit is the hardened ripe
carpels which have become quite dry, and
together look like a little round box, within
which there are many tiny dry seeds.
When the box or capsule is quite ripe
openings come in it, just below the
projecting top, and then, when the
weather is dry and they are open, a
strong wind may bend the stalk of the
fruit and shake the capsule strongly.
The seeds come scattering out like
pepper from a pepper-pot, and may
get carried some distance from their
parent plant (see Plate II. and fig.
85).
Some fruits are covered with spines
and hooks, which catch on to the
wool of animals, and so get carried
quite a distance before they are
dropped. This gives the seedlings a good chance of
reaching a new spot where they can grow away from
and allowing
toesc y ape g sc
Fig. 85. Ripe Poppy
capsule, showing the
little pores at the top
which let out the ripe
seeds when the capsule
is shaken.
FRUITS AND SEEDS
CHAP. XVI.
the parent, and so not be too crowded. Well-known
fruits of this kind are the burs, which stick tightly to
one another with their dozens of little
hooks, the " bur" being really a cluster
of many fruits together.
Simple fruits of the same
kind are the bidens, each
with its two long spines,
and the small fruits of
Fig. 86. A Bur,
which is a cluster
the goose grass, which
Fig. 87
: (&
Simple
of the
of hooked fruits.
fruits
Goose grass with its
hooks ; (6) the Bidens
with its harpoon-like
spines.
are covered with the finest
hooks.
Quite a special kind of fruit is the
strawberry, which, as you know, has a thick fleshy pulp
covered with a number of small, yellow " seeds." In
reality, each of these " seeds " is a whole fruit, and the
thick flesh which we eat is the
swollen end of the flower stalk which
we call the " receptacle." Therefore
a strawberry really consists of a large
number of fruits and a piece of stalk
which is altered to form the fleshy,
attractive mass which induces birds
and people to eat the whole, and so
scatter the little dry fruits.
There are very many other kinds
of fruits which all have special de-
vices to make sure that their seeds
are scattered, and all proper fruits
have seeds in them. But, just as we
found that some garden flowers are
grown only for their beauty, and do not set any seed,
so we find that some fruits are grown specially without
any seeds, such as bananas and some oranges. Such
fruits are the result, of our liking to eat the soft, sweet
pulp without the trouble of the seeds, but such fruits
are of no use to the plant.
Now let us look at the structure of the ripe seeds
Fig. 88. Strawberry.
Each of the little " seeds "
is a whole fruit, and the
"flesh" the swollen re-
ceptacle.
CHAP. XVI.
FRUITS AND SEEDS
B.
Fig. 89. A, outside of Bean; (/) black
scar showing where the bean was attached
to the pod ; (r) ridge made by young root ;
B, bean split open ; (n) nurse leaves ; (/>)
embryo ; (a) scar where the embryo was
separated from the nurse leaf on that
side.
themselves, and see how they are fitted to go out alone
into the world prepared
to make a new plant.
Seeds are all very much
alike in the important
points of their struc-
ture, although they vary
much in the shape, size,
and colour of their
parts. We already
know what beans are
like from our careful
study of them at the
beginning of our work
(see Chapter III.), and
beans show us particu-
larly well all the important parts of a true seed, so that
we may take them as be-
ing typical of one large
family of flowering plants.
The maize embryo (see
p. 10) istypicalof the rest
of the flowering plants.
In the ripe seeds oi both of
these groups (you should
examine them again if
you have forgotten any
of the facts) w r e find that
the important thing is the
baby plant, which is sup-
plied with food and pro-
tected by two seed coats, till it is time for it to grow out
and form a new plant like its parent.
Fig. 90. A, outside of
Maize.showing the embryo
(e) on one side; B, sprout-
ing, showing the root (r)
and shoot (s) ; C, the same
further grown.
CHAPTER XVII.
THE TISSUES BUILDING UP THE PLANT BODY
IN our study of plants up to the present, we have only
looked at their structures from the outside. We have
examined the form, uses, and life of the parts of their
bodies without looking for the details which might
answer the question " How are they built up ? " Just
as a house as a whole has a definite form, with rooms,
and doors, and windows, each with their definite form
and use, and at the same time every one of these things
is built up of small separate bricks, tiles, pipes, and
pieces of wood : so we find that the whole plant is com-
posed of a number of definite parts, which are them-
selves built up of tiny individual parts, which we may
take to correspond with the bricks of a house. Of
course, they do not do this completely, for a plant is
a living thing, and is far more complicated than a house,
and each of the tiny indi-
vidual parts is also a living,
growing thing. These little
building structures are call-
ed cells both in plants and
animals, and they are so
very small that you cannot
study them fully without
a microscope, and that is
a very complicated and ex-
pensive thing, so we will
Fig. 91. Two cells from plant tissue,
(c) Living contents; () cell nucleus;
(v) spaces filled with sap ; (w) wall of
cell (much magnified).
leave it alone and only
study what we can see of the structure of plants without
it. Try, however, just to see a few cells under the
CHAR XVII.
THE TISSUES
93
microscope, so as to know what they are like. A typical
cell has a wall, within which is the actual living sub-
stance, a clear, jelly-like mass, which contains many
granules of food and stored material. Within this living
substance is a more solid mass of still more actively
living substance, which is called the nucleus. Cells like
these, or cells which were like these when they were
young, and which have become modified for special
work, build up the whole plant body (see fig. 91).
You can get a good hand magnifying-glass for several
shillings, and with this and a very sharp knife, you can
find out something of the structure of
the insides of plants, even though most
of the cells are so small as to be out of
sight except when looked at through a
microscope.
Let us first cut as thin a slice as pos-
sible across a water-lily stem, and put
it on a small piece of glass and hold it
up to the light. Examine it with the
magnifying glass, and you will see that
it is not a solid mass of tissue, but that
it is built up of a fine network like lace,
with quite large spaces between the
threads (see fig. 92). These spaces are
air spaces, and the fine lace-work threads
are meshes built up of single rows of
cells, which you may be able to see if your glass is a
good one. Cells may be packed loosely like this, or
they may be in more compact form something like a
honeycomb, as you may see in the pith of an elder twig
and many other stems. You can crush these soft cells
between your fingers, and we cannot imagine that they
could build up the hard, firm branches of trees.
Now examine the stem of a seedling sunflower, by
cutting a very thin slice across it ; you will see in it a
ring of strands where the cells are smaller than those
of the soft tissue and also much more closely packed
Fig. 92. Piece of
thin section across
Water-lily stem,
showing mesh-work
tissue seen with a
magnifying glass.
94
THE TISSUES
CHAP. XVII.
Fig- 93- P^ce ot
the stem of a seedling
Sunflower cut across,
showing strands of
"water-pipe" cells.
Fig. 94. Piece
of stem cut a-
cross and then
split lengthways,
showing the
strands of thicker
"water-pipe"
cells.
(see fig. 93). Then cut a thin slice longways down the
stem, and you will see that these more solid strands are
the cut ends of long strings of such
tissue which run through
the stem. The cells which
build up these strings are
not quite ordinary cells,
but are exceptionally long,
like water-pipes, and they
have thickened walls.
These cells do the carry-
ing of water and liquid
food up and down the
plant (see fig. 94).
You can see that the
water travels up these cells if you cut
across a stem near the root and place it in a little red
ink. After a few hours if you cut a section several
inches from the bottom of the stem you will find that
these strands are coloured red by the ink which has
passed through them, while the rest of the stem is very
little coloured, or quite colourless. This shows us that
these strands are the special water-pipes of the plant.
Large numbers of such cells
closely packed together, and
with some other hard cells be-
tween them, make up the wood
in woody stems. Cut across
a small twig of lime or oak
and examine it with your lens.
Outside is the brown bark, then
within that some green cells
and a little soft tissue, while
most of the stem is made up
of a mass of hard wood cells,
among which you can see some
of the larger water vessels distinct from the rest. All
this hard tissue really corresponds to the joined up
Fig. 95. Cross section through
a Lime twig three years old seen
with a magnifying glass.
CHAP. XVII. THE TISSUES 95
separate strands which we saw in the sunflower stem
(see fig. 95). Trees like the lime and oak, which live for
a long time, grow for a certain amount every year, and
each year they add a ring of wood to their stems. In
old stems you can see clearly the rings of wood which
have been formed by each year's growth. This is an-
other way of telling the age of the stem, and you should
compare your results from this method with those you
got from counting up the bud scars (see p. 75).
Leaves, as you know, require much water, which
comes to them up the stem through the " water-pipes."
You saw already the course of the water-pipes in leaves,
for they are the " veins" which we found sometimes
make a complete network, and sometimes run parallel
in the tissue of the leaf. If you put a leaf stalk in red
ink, you will see that the veins are connected with the
water-pipe strands in the stalk, for they will both get
coloured by the ink as it passes along them.
Just as in animals the whole body is covered over
with a skin, so in plants we find a special outside sheet
of cells, which protect the inner tissues and form a thin
skin. You can get this off very well if you break across
an iris leaf, and pull along the thin, colourless layer on
the outside. If you examine it with your lens, you may
perhaps see something of the mosaic-like pattern of the
cells which build it up. You should certainly see that
it is colourless, although the tissue of the leaf beneath
it is quite green.
On the large branches of trees and the bigger plants,
we do not find this delicate protecting layer, but instead
there is a thick brown cork. When the cork layer gets
very thick it splits irregularly as the tree grows too big
for it, and so forms a rugged bark. The cork layers
have much the same duty as the fine skin, only they are
thicker and stronger, and more suited to hold out
through the winter. You know already from daily life
the practical use of cork, for you put it into bottles to
keep the liquid in the bottle and the damp and dust
96 THE TISSUES CHAP. XVII.
in the air from entering. Just what the cork does for
the bottle, the sheets of cork wrapping round the
branches do for the plant. They prevent it from being
dried up by cold winds, and they keep out the heavy
rains of winter which would injure it. Roots have a
cork coating also when they get old. As you may
remember, it is only the tip of the root which can absorb
water for the plant, so that in the young part of the root
a cork layer would be very much out of place, and you
will never find it there. You will find instead the little
delicate root-hairs, which absorb water and pass it on to
the older parts ; these old parts do no more absorbing,
they are only the water carriers and food storers, and so
have no hairs and are protected by a layer of cork.
As we found before, plants breathe in air like animals,
and you may ask how they can do this
when they are covered with their thick air-
tight layers of cork. Examine a fairly old
elder twig, and you will see all over its
brown skin numbers of darker brown spots.
If you look at these with your magnifying
glass, you will see that they are quite
spongy and soft. They are the special
entrances for air, and are the breathing
spots or lenticels (see fig. 96). They are to
taigi De found in all corky stems, although they
showing the are not always so easy to see as in the
breathing pores ij
in the bark. elder.
On the leaves and stems of many plants
you will find a large number of hairs. In some cases
there are so many as to make the whole plant quite
woolly, like the mouse-ear leaves. These hairs are pro-
tective, and keep the leaf warm and dry, and in some
cases may shelter it from the sun. Hairs may consist
of one cell, or several in a row, or of cells which are
branched in a complicated way. Certain hair- cells
protect the plant by stinging, as you can see if you
watch a nettle-leaf with your magnifying-glass, and then
CHAP. XVII. THE TISSUES 97
rub your finger along it, only touching the hairs. You
will find that it is they which sting you, and not the
leaf itself.
Now we have found several kinds of tissues in plants,
the skin and cork covering all over and protecting the
rest ; the central vessels or watet-pipes, corresponding to
the veins and arteries of animals, the soft white ground
tissue, which in some stems may be very loosely packed,
and the soft green tissue in the leaves and young stems,
which we found was the food-manufacturing part of the
plant. There are also strands of simple strengthening
tissue^ both by the water-pipes and in separate bundles
in the soft tissue ; these we may take as representing
the bones of animals.
We have noticed (Chapter VIII.) that plants are
sensitive to light and bend towards it, that they feel
heat and cold, and that the stem and root seem to know
when they are growing in the right or wrong positions,
and bend accordingly. We know that we ourselves
and the animals recognize such things by the help of
nerves which carry messages to the brain. But where
is the brain in plants, and the nerves ? No true nerves
have been found in plants, and it seems as though
different parts of the plant were specially sensitive
without there being any <( brains." So that we cannot
speak of a central nervous system in even the highest
plants as we can in the animals. In this respect they
are built on quite a different plan from animals.
(C260)
PART III.
SPECIALISATION IN PLANTS
CHAPTER XVIII.
FOR PROTECTION AGAINST LOSS OF WATER
IF you go along the lanes and in the gardens in the
height of summer when it is hot and dry and the sun
beats on the plants all day, you may see them beginning
to wither for want of water. The roots are not able to
find enough moisture in the soil to supply the leaves,
which, being in the hot air, continue to transpire away
the water resources of the plant, so that in the end each
of its cells must suffer and the whole become limp and
droop. This happens because the ordinary green plants
of our country make no special preparation for such
dry weather. Our hot season is short, and even in the
summer we have frequent showers which keep the soil
moist enough to provide the
plants with water from day to
day, so that they have not
become accustomed to long
periods when there is no pros-
pect of rain.
Compare one of our usual
green plants, a sunflower, for
example, with such a thing as
a cactus, which you may get
growing in a pot of dry sand.
The cactus is able to withstand
the hottest sun for days, though
it gets very little water, and
sometimes apparently none at all ; yet it does not wither,
but grows, and may bear the most lovely flowers. From
99
Fig. 97. A Cactus, with needle-
like spines for leaves, and a thick
green stem.
TOO AGAINST LOSS OF WATER CHAP. XVIII.
travellers we learn how the huge cactus plants grow in
dry and stony deserts, standing every day in the blazing
sun. Such is, of course, their home, and they are used to
it ; but how is it that they are able to flourish under
conditions which would kill one of our own green
plants ?
Let us look at their structure and see in what they
differ from a usual plant. First, they have no green
leaves, for these have developed into spines (see p. 62),
while the sunflower has many large ordinary leaves.
You will remember that the surface of leaves is con-
tinually giving off water from its many pores. When a
plant has a number of big leaves this transpiring area is
large, while when it has no leaves at all, but a thick,
green stem instead, then the amount of surface from
which water vapour is being given off is very much
reduced, even though there may be about an equal
quantity of actual tissue in the two plants. You can
see that this is the case if you take a ball or thick block
of dough and roughly measure its surface, then roll it
out till it is fairly thin and measure it again ; you will
see that the thinner you roll it the more surface there
is ; all the time, of course, the amount of actual dough
remains the same. So that of two plants of the same
bulk, the one with broad, thin leaves will expose the
most surface to the air, and so lose more water than one
with very thick leaves or none at all. The latter would
therefore be better fitted to live under dry conditions.
But, you may say, leaves have a definite work to do ;
how can the plant live without them ? In the cactus
the thick stem is green and does the work of food
building ; naturally it cannot do so much for the plant
as many big leaves could, but it does enough to allow it
to live and grow slowly and surely for many years,
though it cannot grow in each year nearly at the same
rate as can the sunflower. If you cut through the stem
of a cactus you will find that its skin is very thick and
tough, and this thick coat protects the plant against the
CHAP. XVIII. AGAINST LOSS OF WATER 101
fierceness of the sun far more completely than the thin
skin of a sunflower does. At the same time, the tissues
of the two stems are different ; the sunflower is hollow
and delicate, but the cactus is very thick and juicy, and
each cell contains much gummy stuff which has the
power of holding water strongly. So that we see in
many important points the structure of a cactus is
different from that of a usual green plant, and is
specially suited to the dry conditions of the desert.
Many desert plants are built on the plan of the cactus,
but there are also others which are not at all like them,
and yet they are able to live in deserts and very dry
places. If you examine them, however, you will find
that they all have some special way of protecting them-
selves from being dried up. Some of them have hard,
dry, woody stems, well protected by corky layers, and
they only put out green leaves in the rainy season, and
lose them directly the hottest weather begins. Others,
which grow from seed every year, learn to sprout, flower,
and fruit very quickly while there is some moisture, and
they form well-protected seeds, which wait till next
rainy season. One very curious desert plant has only
two leaves, which last it the whole of its life, and which
are very hard and leathery. There are endless varieties
of things which the plants may do to protect themselves
from being dried up, and we can only look at a few
special examples.
To find plants growing in desert places we do not
not need to go out of England, because from the point
of view of the plant, one which is growing on a dry rock
or on a patch of bare dry sand, is really growing in a
little desert. For it the supply of water is the chief
problem, even though we never get hot tropical sunshine
in England. Look, for example, at the plants growing
on the sand dunes which are very like deserts in appear-
ance, and the plants on dry walls, or on the " screes " of
broken rock at a hill foot ; they are all growing in deserts.
In many cases plants growing in such positions have
102
AGAINST LOSS OF WATER CHAP. XVIII.
Fig 98. Thick fleshy
leaves of Stone-crop.
small thick leaves, nearly round, or shaped like sausages,
so that they have much water-storing
tissue in proportion to a small transpir-
ing surface. This is the case in the
stone-crop (see fig. 98) and the house-
leek, where each separate leaf has fol-
lowed the same principle as the cactus
stem, and exposes relatively little sur-
face to the air. Such
plants frequently
have very long roots,
which penetrate
deeply between the cracks of the rocks
and find hidden sources of water.
Other plants, instead of having
leaves of this type, have exceedingly
small leaves which may soon drop
off, while the stem is green and does
some of the food building. Small
leaves are assisted by the green stem
in gorse (fig. 99), which often lives in
very dry places, though it can grow
equally well under usual conditions.
Many plants roll up their leaves
when it is dry, so that the
surface with trie transpiring
pores is on the inside, and
protected by the outer side
with its hard skin (see fig.
100). In damp weather
these leaves unroll, and do
alltheworktheycan. Leaves
like this are to be seen in
many of the grasses, par-
ticularly those growing on
sand dunes and moorland ;
while a number of the heaths and heather do the same
thing to protect their transpiring surfaces.
Fig. 99. Gorse, with
green stem which does
the work of leaves.
B
Fig. loo. Leaf of the Sand-grass.
A, rolled up ; B, open, (a) and (6),
sections across the same.
CHAP. XVIII. AGAINST LOSS OF WATER 103
You will find that in nature, water is one of the most
important things in the surroundings of plants, and in
their struggles to get it and keep it they have changed
their forms in many ways, and in some cases have
become extraordinary-looking creatures as a result.
CHAPTER XIX.
SPECIALISATION FOR CLIMBING
IF you go into a wood, or even a thicket, in summer,
you can see how the leaves of the big trees make, what
is for us, a delightful shade. But look at the ground
under these tall trees, at a place where they are growing
thickly together, and you will find that there are very
few plants below them, and that the earth is almost bare
except for dead leaves, twigs, and a few mosses. In
deep pine-woods there are great patches without even
the mosses, where are only dead pine-needles and some
toadstools. You can well understand, when you re-
member how very important light is for the plants, that
it is too dark for them to grow under the heavy shadow
of thick trees. Even in gardens you may see how the
tall, quickly growing plants kill off the smaller ones
beneath them.
When many plants are growing together, it is easy to
see that the taller ones get most light, but if a plant
grows very tall it requires a strong stem to hold it up-
right, and that means the building of a large amount of
wood which takes a quantity of material, so that the
growth must be slow and costly.
Some plants, however, have learned to grow up into
the light without building a firm stem for themselves,
because they use instead the support of other plants,
and especially of trees. You must often have noticed
in a wood great sprays of honeysuckle sprawling high
up over the trees; sometimes one of the festoons of
honeysuckle may lie over the branches of several trees.,
CHAP. XIX. SPECIALISATION FOR CLIMBING 105
and so get into the best positions for the light. The
Travellers' Joy, or white clematis, grows all over the tall
hedges, and may sometimes completely smother a young
tree, so that one can see nothing but the leaves and
light green and white flowers of the clematis. Then,
too, there is the ivy, which you know may sometimes
grow up trees to a very great height, covering over the
leaves so that the whole looks like a giant ivy bush.
These plants all get their support from trees, which
have built themselves strong stems. Pull down a big
branch of honeysuckle or Travellers' Joy from the sup-
porting tree-trunks, and you will see that it cannot
remain upright but falls limply to the ground. It is
true that these plants have some wood in their stems
sometimes clematis and ivy may have woody stems
several inches thick, but they are never strong enough
to support the weight of the crown of leaves and
branches. By clinging to others in this way these
plants can economise much building material and reach
the light far quicker than they could do otherwise.
If you examine their wood, you will see that it is not
quite like that of usual plants. Cut through the stem of
a clematis which is about an inch thick, and even before
you look at it with a magnifying-glass you will see
how very loosely built the wood is, with wide rays of
soft tissue and very large water vessels. It is not built
for strength and support, but merely to carry supplies
of water up to the leaves, for although these plants use
trees as supports, they do not get anything more from
them, and must supply themselves with all else they
need. You may often see that the central part of the
wood is not in the true centre of the stem, but is pushed
to one side, and the rings of the year's growth are very
irregular, being much more to one side than to the
other. This is because they lean against the supporting
branches, and so must grow chiefly on the side away
from them. Sometimes as the ivy grows right round
the support, it will grow more, first on one and then on
io6
SPECIALISATION FOR CLIMBING CHAP. XIX.
Fig. 10 1. Adven-
titious roots growing
out from the stem of
Ivy between the leaf
stalks.
the opposite side of its stem, and so the centre does not
remain in one place, but shifts round.
The other parts of these woody climb-
ing plants are but little out of the com-
mon. They have merely learnt to econo-
mise their own stem-material, and at the
same time to reach a good position in
the light, so that it is in their stems that
we find their chief differences from usual
plants. The honeysuckle and clematis
have no special climbing organs, but the
Ivy has clusters of adventitious roots
which come out from the back of its
stem, and hold it on to the support (see
p. 56 and fig. 101).
In climbing plants in
which the above-ground
parts live only for one year and then die
down, we do not get a woody stem.
Such soft green plants as the hop and
convolvulus, for example, are entirely
dependent on others for their support.
They have specially sensitive tips to
their stems, which feel the support and
definitely twine round it in a close spiral,
which clings ever closer to the support
as they grow (see fig. 102).
Climbers of this kind have only modi-
fied their stems ; the rest of their parts
are not in any way specially altered by
this habit.
Some plants which sprawl about on
others hold themselves up by the power
of clinging and twining in their leaf-
stalks, for example, in the nasturtium
we find that the plant is held up entirely by the leaf
stalks, which catch on to anything in their way (see
fig. 103).
Fig. 102. Soft twin-
ing stem of Convol-
vulus.
CHAP. XTX. SPECIALISATION FOR CLIMBING
107
Very many plants which depend on others for support
modify their leaves, or parts of
leaves, to form sensitive ten-
drils which twine quickly
round any prop they can find,
and thus hold up the stem (see
fig. 104). The young tip of the
stem continues to grow up-
wards, the next young leaves
unfold their soft green tendrils
which twist round a support
directly they feel it, and so the
plant goes on growing higher
Fig. 103. Nasturtium stem held
up by the support given by the leaf-
stalks, which cling around any suit-
able prop.
and higher. You can see
the fate of a pea-plant
which does not find
supports, by growing
one in a big pot all by
itself. It will grow up-
right at first, but it will
soon have to creep along
the earth and fall over
the edge of the pot, for
its stem is not strong
enough to support its
own weight.
In vines and marrows
We also get tendrils, but Fig. 104. Sensitive tendrils of the Pea. (t)
they are not modified tendrilatendoffolia g eleaf ,() ordinai T leaflets
leaves, but special branches which have become sensi-
tive.
io8
SPECIALISATION FOR CLIMBING CHAP. XIX.
In some plants the sensitive tendrils do not twine,
but instead form little sticky suction pads at their tips
whenever they come in con-
tact with the support, and
these hold the tendril very
firmly on, as you can see in
the ampelopsis, which grows
right up the walls of houses.
If you look under the thick
covering of leaves, you will
find these tiny padded tendrils
clinging tightly to the wall (see
fig. 105). This is the reason
that the ampelopsis grows so
well up the walls without being
held up artificially.
There are many other things
you may find out about climb-
ing plants, but you will have
seen enough to be able to
look for more for yourself, and to understand how it is
that the climbing plants can reach such a great height
so quickly. They have learnt to avoid the trouble and
expense of building strong supporting stems for themselves,
and by getting their support from others, they are able to
grow quickly out into the good positions for the light which
they could not otherwise have reached.
Fig. 105. Ampelopsis, which
supports itself by the little suction
pads developed at the ends of the
tendrils.
CHAPTER XX.
PARASITES
WE call a plant or animal a Parasite when it does no
food-building for itself, but adapts its whole structure
to obtain and use the food made by the work of other
plants or animals. Plant parasites generally attach
themselves to a " Host " plant so closely that they suck
their food from it, and sometimes remain with it till
they have finally killed it, and so have destroyed their
only source of food and means of life.
Among plants, most of these degenerate creatures
belong to the group of Fungi. The rust and smut on
wheat, the mildew on fruit, and nearly all the thousand
spots, blemishes, and diseases of cultivated and other
plants, are the result of the parasitism of some members
of the family of fungi. Plants which prey like this on
others are without very many of the characteristics of
true plants ; they become colourless, losing their green
substance, and with it all power of building food for
themselves, so that they are quite dependent on the
host plant, without which they must ultimately die.
Fungus parasites, of which there are many thousands,
have become so specialized that they are quite a study
in themselves, and we will leave them for the present
and follow the history of a few of the higher plants which
have taken to this mode of life.
One of the most completely parasitic of the flowering
plants is the dodder, which you may often find growing
on clover. In fields of clover sometimes there are
colonies of dodder, which live together and kill the
clover in great patches so that it almost looks as though
TL09
no
PARASITES
CHAP. XX.
it had been burnt. Dodder grows on other plants, such as
gorse, as well as clover, and even
on nettles. If you find a plant
of dodder you will see that it
seems to consist of nothing
but fine, white or pinkish
threads, twisted round and
round the clover stems and
hanging in festoons over them.
Pull off these fine threads
carefully, and you will find
that at intervals along them
there are little sucker-like pads
which hold the dodder quite
firmly on to the plant on which
it is growing. If you cut
through the middle of one of
these pads and the clover-stem
while they are still attached,
and look at the cut with your
magnifying-glass, you will see
how the tissue of the dodder
Fig. 106. Dodder plants grow-
ing over Clover, (a) clusters of
Dodder flowers.
pad enters right into the
tissue of the clover stem
(see fig. 107). These pads act
as suckers for the dodder and
draw from the clover all the
ready - formed nourishment
that the dodder requires, so
that it has no work to do in
food building. It has no roots
the suckers act as roots in
Fig. 107. Section, A, across the
Clover stem, with the Dodder D at-
tached. S, suckers of the Dodder,
entering the Clover.
because it needs none
getting all the water and also the manufactured food
CHAP. XX.
PARASITES
in
the plant uses ; for the same reason it requires neither
leaves nor green chlorophyll, and its body is only a
colourless or pinkish mass of thread-like stems and
sucker pads.
There is one thing, however, that the clover plant
cannot do for the dodder, and
that is, make its seeds. When
the clover builds seeds, then
they are clover seeds and will
grow up as new clover plants.
The dodder must build its own
seeds if dodder plants are to
grow from them. That is why
we find growing out from the
simple reduced thread of a
stem, relatively large tufts of
flowers (see fig. 106), which
are very little different from
usual flowers and which form
seeds. The dodder belongs
to the same family as the con-
volvulus, and though its flow-
ers are small, if you examine
them with a magnifying-glass
you will see that they are very
much the same in structure as
those of the convolvulus.
When the young dodder
plant grows out from the seed,
it is a simple little thread with
no leaves, and it keeps on
growing at the tip, which it
moves round till it feels some
suitable host, then it quickly fastens on to it and lives
on its food.
This is the general history of all kinds of parasites, for
when any living thing ceases to use its structures and
becomes a complete parasite it loses nearly all its parts,
Fig. 108. Young Mistletoe at-
tached by its sucker-like roots S to
a twig of apple A, split open.
112
PARASITES
CHAP. XX.
as there is no longer any need for them. So that
parasites tend to sink to a lower level of development
simply as a result of their way of living.
A plant which is largely a parasite, but yet does a little
work for itself, is the mistletoe (see fig. 108). Its leaves
are greenish, but not the true healthy green of a hard-
working plant. If you can find a bough of mistletoe
growing on an oak or apple tree, you will see that it has
no root in the earth, but grows out of the bough of the
host tree. It has sucker-like roots at the base of its
stem, which go right into the stem-tissues of the host
and get much nourishment from them.
In the winter, when
the flow of food is
very slow in the
host, it is likely
that the mistletoe
does some of its own
food building in its
yellow-green leaves,
which would be ex-
posed to the full
light, as the host's
leaves would have
fallen away. The
mistletoe has soft,
white fruits which
are scattered by
birds, and as they
are very sticky, they
hold for some time
on to the branch
where they are
dropped, and there
the seedling sprouts
and fastens itself on to the tissues of the host, growing
every year with its growth.
Quite a number of plants which grow in the ground
Fig. 109. P, parasite attached to the root R of
a host plant H (which is the Ivy). A is the host
root on the other side of the parasite.
CHAP. XX. PARASITES 113
attach themselves with suckers to the roots of other
plants, from which they get all their ready-made food.
Plants which do this are generally colourless or brownish
yellow, like the broomrape, which has only whitish
leaves which cannot do the proper work of leaves (see
fig. 109).
Then there are several plants which are partly parasitic,
but which you would never guess were anything but
ordinary plants. For example, the little eyebright with
its green leaves, which do most of the food-building,
is yet partly parasitic. If you very carefully get out a
whole plant with its complete roots (this is rather diffi-
cult to do, and you must not pull it hastily, or you will
break the connections), you will find that there are tiny
suckers on them which connect them with the roots of
the plants which are growing near. So that the eye-
bright gets some of its food ready-made from the neigh-
bouring plants. The meadow cow-wheat does the same
thing, and so do the lousewort and several others;
but they are not complete parasites, for they are green
and do a lot of work for themselves, even though they
are not quite self-supporting, and tap the supplies of
other plants to some extent.
Among flowering plants, parasites are not common.
We see in plants like the eyebright and cow-wheat, which
do a little thieving, that the results are not very serious,
and they are little altered by their habit. In those
which are entirely parasitic, however, like the dodder,
the result is the loss of nearly all the organs of the
plant except the flowers, which have to be kept in order
to build seeds.
(C260)
CHAPTER XXI.
PLANTS WHICH EAT INSECTS
As a rule, plants are the sufferers and are eaten by
animals, but there are cases known in which this state
of things is reversed ; the plants catch and devour the
tinier animals and small insects such as flies. But, you
may ask, how can they do that, for the insects move so
quickly, and the plants are fastened by their roots to one
spot. Just as a spider builds a web and then waits
quietly beside it till the flies are caught, so the plants
build traps which catch the unwary insects. There are
not very many plants growing wild in England which do
this, but there are one or two that you might be able to
find.
There is the sundew, which grows among bog-moss
in wet, swampy places at the edges of lakes, or on the
wet patches on hillsides. It is fairly common in such
places, a little distance from
big towns, but it does not
like smoke, so that it will not
live within a few miles of
London, Manchester, or any
big smoky town. It is a
small plant with round, red-
dish-coloured leaves, cover-
ed over with little fingers or
tentacles each with a spark-
ling drop of sticky moisture
at the end, so that even in
the heat of the day when all the dew is dried up, the
whole plant looks as though it were spangled with tiny
Fig. no. Plant of Sundew, show-
ing the round leaves covered with
tentacles.
CHAP. XXI. PLANTS WHICH EAT INSECTS
dew-drops,
ance which
Fig. in. Single leaf
of Sundew, with the
tentacles closing over
a fly.
Perhaps it is this cool, sparkling appear-
attracts the insects to it, but when once a
fly alights on one of the leaves, its fate
is sealed. The tentacles with their
sticky tips bend over one by one till
the fly is quite covered in by them and
cannot get away. It dies, and is di-
gested by the juices given out by the
leaf, which are very much like the
digestive juices of animals.
You can watch the movement of the
tentacles very well if you drop a minute
piece of meat or white of egg on to the
leaf. They will close over it one by
one till it is quite shut in, and when the egg is all
digested, they slowly open out again. The time ( that
this takes depends a little on the
health of the plant and the time of
the year, but generally all the ten-
tacles are bent over in a few minutes.
The digestion takes longer, of course,
at least several hours and often more,
partly depending on the size and
nature of the piece of food. The sun-
dew leaves contain chlorophyll and do
some of the usual work of leaves, but
the plant gets much of its nourish-
ment from the insects it catches.
In the butter-
wort there is a dif-
ferent arrangement
for catching its
prey. You will
find its little clus-
r i j Fig. 112. Butterwort, showing the rolled leaves
ters O I broad, which catch flies and other small insects.
spoon - shaped,
yellowish-green leaves growing in marshy places and
beside streams in hilly districts. In the spring one or
u6
PLANTS WHICH EAT INSECTS CHAP. XXI.
two lilac flowers on long stalks come up from the centre
of the group of leaves. The leaves of this plant also
act as insect traps ; they are covered with little sticky
glands, and when an insect settles on them, the edge
rolls over and shuts it in, keeping it there till the juices
given out by the glands have digested all that is worth
digesting, when the leaf unrolls again, and the remains
of the feast are washed away by the rain.
There is one more animal eater which you must try
to see, which grows in the water of slow-running streams
and in ponds. It is the bladder-
wort, on which we find very many
tiny bladder -like structures on
the finely divided leaves under
the water. The
bladders are
built on some-
thing of the same
plan as a lobster
pot, with bristly
hairs pointing in-
to the entrance,
across which
there is a little
flap,which makes
it quite easy for the very minute
animals living in such abundance
in the water, to swim into the
bladder opening, but extremely difficult or almost im-
possible for them to swim out again (see fig. 114). So
there they must finally die, and their nourishing juices
are absorbed by little compound hairs, many of which
are developed on the inside of the bladder.
In the tropical countries there are many kinds of
" pitcher plants" with wonderful soup-kettle-like pitchers
which catch insects. You may be able to see these
plants in a big greenhouse, and should certainly find
them in every botanical garden. Notice how large the
Fig. 114. A single
bladder of the Blad-
derwort, much en-
larged, showing the
pointed hairs and the
flap at the opening.
Fig. 113. A piece of leaf
of a Bladderwort showing
the bladders on the branches.
CHAP. XXI. PLANTS WHICH EAT INSECTS
117
pitchers are, and that they are really modified leaves
which have become different from the other leaves of
the plant because of their special work. They gener-
ally contain
a consider-
able quantity
of water as
well as the
flies they
have caught,
and are really
"stock -pots"
which keep
the plant
supplied with
nourishing,
ready - made
food in addi-
tion to the
food which
it builds for
itself in the
green leaves.
Though
these plants
have specialised themselves to catch and use animal
food, still there are not very many plants that do so, and
the old fairy tales about trees with branches which
caught men and devoured them, as a sea-anemone
catches and devours its food, are only fairy tales, because
no such plants exist.
Fig. 115. Pitcher
penthes, which acts
kettle."
leaf of Ne-
as a "soup-
CHAPTER XXII.
FLOWER STRUCTURES IN RELATION TO INSECTS
THE relation between flowers and insects is one of
mutual help and advantage, and therefore is quite
different from that in the cases where the animals eat
the plants or vice versa. -
When we examined flowers in general, we found that
the insects do a very important work in carrying the
pollen from flower to flower, and that their structures
are arranged to attract insects and to make it easy for
them to get covered with the pollen of one flower and
leave it on the next. If we look at the details in some
of the flowers, we shall see how elaborate their structures
may be, and how carefully they are planned to make
sure that the bee gets the pollen on its body and carries
it with it to the neighbouring flowers.
In the simple circular flowers, such as roses, poppies,
and lilies, the bee can enter
freely from any side that it
chooses, and it generally goes
straight to the centre. Many of
these simple flowers, therefore,
have large numbers of stamens
which stand up in a crown in the
middle, so that the bee must
Fig.n6. circular flower of touch and stir some of them as
t R he S cen7re h **** si " mens m he dives in the centre for the
honey.
In others which are nearly circular, there is a little
difference between the back and front of the flower, and
the stamens are so placed that the visiting insect must
118
CHAP. XXII. IN RELATION TO INSECTS
119
Fig. 117. Slightly
two-sided flower of
the Foxglove, with
the petal tube cut
open to show the
four stamens bend-
ing to the front.
touch them. For example, look into the bell of a fox-
glove, where you will find only four stamens, but they
are bent so that the anthers together
form a kind of platform in the front of
the flower, over which the bees must pass
as they enter (see fig. 117). Frequently
the stamens bend in this way towards
the front of the flower, and in many
cases the whole flower becomes quite
definitely two-sided, with a front and
back, and a special place for the entrance
of the bee.
This is the
case with the
violet, pea,
monks hood,
and many
others (see
fig. 118).
When flowers have this
form, you frequently find
that the
number
of stamens is quite small, seldom
more than ten, and often less.
A plant of this kindi very inter-
esting to watch is the yellow gorse.
If you can get up and sit by a
flowering bush from about half-
past five to seven one sunny morn-
ing, you will be able to learn a great
deal about the doings of the bees
and flowers.
First examine a flower so that
you know how it is arranged. At
the back lies the big petal, or
" standard," as in the pea ; there are two side wings,
and in the front the two petals close together forming
Fig. 118. Two-sided flowers: A,
Monkshood ; B, Violet.
Fig. 119. (a) Flower of
the Gorse after the insect's
visit, showing the inner
parts exposed ; (6) young
flower nearly ready to be
visited.
120 FLOWER STRUCTURES CHAP. XXII.
the " keel." The two-sidedness of this flower is very
well marked. Inside the keel you will find ten stamens,
all joined to form a tube except the back one, which is
free, and inside them lies the carpel with its curved
style. When the stamens are ripe they are so fitted
that they lie inside the keel of the petals in a bent form,
and when they are pressed from above they fly out
with a little explosion and scatter the pollen dust about.
Now watch a bee alighting on the flowers ; he presses
the two front petals with his legs to open them to get
at the honey, and the stamen explosion covers him all
over with pollen. Then he goes to the other flowers,
but perhaps the next one he visits has already exploded
and the ripe stigma is exposed in the front of the flower,
and as he settles he touches it with his furry body all
covered with pollen, and leaves some on it. If you
watch the bees doing this yourself, you will find out
a number of things which I have not told you, while
you may notice how some of the bees are lazy and enter
the wrong side of the flower, others are stupid and go
to flowers which have already been visited several
times, and therefore are of no use, while other bees
which come late may open up buds which were not
ready for them and steal the honey before the stamens
are ripe enough to
A. T5. smother them with
pollen. I have watch-
ed them opening buds
which were still so
tightly closed that it
took them all their
Fig. 120. The two kinds of Primrose flowers, strength to get in.
A, with long style and stamens low in the petal Rnf W p rrmct not <^tnn
tube ; B, short style, with stamens at the mouth ^ Ul W mUSl
of the petal tube. too long With One
flower, for almost
every flower has some special arrangement of its own,
and all are worth study.
The primroses and cowslips are interesting, as they
CHAP. XXII. IN RELATION TO INSECTS
121
Jt.
have two kinds of flowers. If you gather a bunch of
primroses and look into them you will find that in some
you can see the little central green ball of the stigma, and
in others at
the top of
the tube are
the five
small an-
thers. These
two kinds
of flowers
make an ar-
rangement
Fig. 121. A, Flowerhead of the Daisy ; (6) a single little which en-
flower from the side with big petals fused together; (c) a c .,_- i.L_f
single little flower from the middle with very small petals.
the pollen
from the one kind of flower reaches the stigma of the
other. A big fly like the wasp-fly, and several others,
visit these flowers most frequently, and carry the pollen
from flower A (see fig. 1 20) to
the stigma of B, and the pol-
len of B to the stigma of A.
As we noticed before, the
chief duty of the petals is to
act as flags to attract the
visiting insects by their
bright colours. Now we
find that some flowers club
together, and grow cluster-
ing closely on one head, so
that it is sufficient for a few
of them to have the flag
petals which attract the in-
sect to the group, as it goes
from one to the other when once it is there. When a few
of the flowers do this, the rest can economise in petals and
have quite small ones, and yet all the same they have a
good chance of insect visits. Such an arrangement as
Fig. 122. Flowerhead of the Corn-
flower ; (a) a single flower from the
side with big petals.
122 FLOWER STRUCTURES CHAP. XXII.
this is found in the daisy (see fig. 121). A single daisy
is not one flower, but a whole bunch of flowers, in which
some of the outer flowers of the bunch (see fig. 121 (b))
form big petals, while all the inner ones (fig. 121 (c) )
are quite small and inconspicuous, and by themselves
would hardly attract any visitors. Just the same thing
happens in the cornflower, sunflower, and very many
members of the daisy family. The big outer petals
attract the insect, and once on the head of flowers it
walks about over them, and they all get the benefit.
In such cases we get a division of labour among the
flowers of a head, and this represents what is perhaps the
highest state of development that flowers have reached.
PART IV.
THE FIVE GREAT CLASSES OF PLANTS
INTRODUCTORY
IF you go out into the garden, or fields and woods in
summer, and look around you at the plants, you will
find that nearly all of them are flowering, or have flower-
buds, or have the proof of having had flowers in the
shape of fruits and seeds. Even among the few which
do not show any of these things, many will probably
be plants which you know to be the same as others of
their kind which you have seen flowering.
Generally flowers (such as roses and daisies) are easy to
see, but in some plants they are less showy, as in the oak,
for example, where the little green tails or catkins which
come out early in the spring are the flowers. On the
whole, however, if you look carefully, you will have no
difficulty in seeing proof that nearly all of the conspicu-
ous plants of our gardens and woods bear flowers.
All the same, there are very many other plants, some
of them quite easy to see, and others very small and in-
clined to hide, which do not have flowers at all, and
which are so different from the flowering plants that
even before you have studied them, you instinctively
separate them. The seaweeds or mosses, for example,
are at once recognized by any one as being of a different
family from roses and lilies.
When you have studied all the plants carefully, you
will see how true is this instinctive separation of the
chief families, and how nature seems to have made five
principal big families, so that both scientists and quite
unlearned people see more or less clearly the limits she
has set to each.
123
i2 4 INTRODUCTORY
The family which is most highly advanced is that of
the flowering plants, but the others, too, are well worth
study, and we will now notice some of the points about
their structure which are characteristic of each of the
families.
CHAPTER XXIII.
FLOWERING PLANTS
All the plants 'which have flowers are put into one
big family, about which you already know a good deal,
because nearly all the plants we have studied up to the
present have been plants which have flowers. Let us
now go systematically over the chief points about their
structure, so that we may have a clear idea of their
characters, and be able to compare other families with
them.
1 . We find that the plant body is clearly marked out
into rooty stem, leaves, and flowers. The stem may be
green and delicate, or it may be thick and strong like an
oak tree, and on the stem or its branches we find the
leaves.
2. The stem and root have definite strands of "water-
pipe " cells, and very often the stems have many rings
of wood, one of which is added every year.
3. The leaves are very various in the different plants,
but they are generally thin and big, though they are
seldom much more compound than those of the sensitive
plant.
4. The flowers are easily recognized, as a rule, and
consist of a number of parts, some of which are often
brilliantly coloured. The stamens and carpels are
generally in the same flower.
5. The seeds are always enclosed within the carpels,
and have generally two seed-coats.
6. Within the seed are always either two cotyledons, as
in the bean, or one cotyledon, as in the grasses. Thus
when the seedling grows out of the seed it may have
two first leaves or one only.
125
126 FLOWERING PLANTS CHAP. XXIII.
These are the chief characters of the whole big family
of the flowering plants, but this big family is separated
into two smaller groups according to the number of coty-
ledons in the seed. Those that have two form the group
of Di cotyledons, those with one the group of Monocoty-
ledons. This may not seem a very important point to
form the ground for separating plants with flowers so
alike as tulips and roses, but we find that, as well as the
number of cotyledons, many other differences distinguish
the two groups when we separate them in this way.
For example, the Dicotyledons have the veins of their
leaves so arranged as to form a network, as in the lime,
while the Monocotyledons have them parallel, as we
noticed in the grasses and lilies.
We also find that it is only in the Dicotyledons that
the plants have rings of wood in their stems, as is the
case in the lime, oak, and many others.
In the numbers of the parts of the flower, we also
find differences between the two groups ; for example,
the Dicotyledons have generally two, four or five, or a
multiple of these numbers such as ten, as we see in the
poppy, primrose, rose, and many others ; while the
Monocotyledons have the parts of their flowers in three
or multiples of three, as in the lily, tulip, and daffodil.
These differences between the Monocotyledons and
Dicotyledons, however, are not nearly so important as
their likenesses, for they agree in the main points (i) to
(6), and therefore belong equally to the great family of
the flowering plants, which is the most important family
now living.
CHAPTER XXIV.
THE PINE-TREE FAMILY
SINCE trees such as the oak, beech, and lime all belong to
the family of flowering plants, you may be surprised to
find that the pine-trees are separated from them. Yet
all the trees like pines, Christinas trees, larches, and
many others, form a family of their own. You will
see why this is, if you look at a pine-tree carefully, and
compare its characters with those we saw in the flower-
ing family. In the first points the two families are alike.
1. We find that the pine-tree body is clearly marked
out into rooty stem, leaves, and cones.
2. Also that the stem and root have definite strands
of " water-pipe " cells, and that the stem has rings of
wood, one of which is added every year.
3. The leaves vary a little in the different members of
the family, but the commonest kind of leaf is the fine
sharp " needle " leaf of the ordinary pine (see fig. 53). In
almost all cases the leaves remain on the tree for more
than a year ; they are evergreens (it is only the larch
among the English-growing members of the pine-tree
family which has new leaves every year), and the leaves
are simple and strong, and well protected.
4. There are no l< flowers" but the two kinds of cones
which take their place are easily recognised. The two
kinds of cone generally grow on different branches of
the tree, the small ones only live a short time and scatter
the pollen, and the larger ones often remain two or three
years on the tree, and form the seeds. The wind scatters
the pollen ; you will remember in the spring-time
before the leaves are out, how the " sulphur rain "
128
THE PINE-TREE FAMILY CHAP. XXIV.
showers down from the pine-trees; this is the yellow
pollen, which is blown in
clouds on to the seed-bear-
ing cones. There are mil-
lions of pollen grains scat-
tered in this way, and but
few of them ever reach a
cone. You will remember
that many of the flowering
plants could afford to make
small quantities of pollen, as
they had special carriers in
the insects to take it from
flower to flower.
Besides the pollen cones,
you should find two sizes
of seed-cones on the tree :
some quite small, and green
or pink, and some large ones
which are brown and ripe.
It will be easier to see their
structure at first in the big
ones ; they consist of a number of brown scales packed
Fig. 123. A branch of Pine with a
small young seed-bearing cone, and
a large ripening one.
IB
Fig. 124. Larch. A and B, young scales, showing (i) inner seed-bearing
scale, and (o) outer protective one. A, side view ; B, front view ; C and D, old
scales, C from the side, D from the front, showing how the inner scale increases
more rapidly than the outer.
neatly one over another. If you pull these apart you will
see that each of them bears two seeds on its upper side.
CHAP. XXIV. THE PINE-TREE FAMILY
129
Fig. 125.
Winged seed
of the Pine.
5. The seeds are always seen to be lying
quite openly on the upper side of the scales,
and are not covered in by closed carpels as
they are in the flowering plants. Each of
the scales (which bears its two seeds) corre-
sponds in a way to the carpel in a flower, but
there is an important difference in the fact
that it leaves the seeds open. In old pine
cones there seems to be only one scale to
each pair of seeds, but there is really a second smaller
one outside
it which is
sometimes
quite diffi-
cult to see.
It shows
betterin the
larch,where
the outside one is
much the bigger of
the two in the young
cones, and gradually
gets left behind, as
the inner scale grows
very fast(s fig. 124).
Notice, too, how the
ripe seeds have one-
sided wings, which
split off from the
inner scale, as you
can see if the cone
is not too ripe. This
wing is on the seed
itself, not on a fruit,
as is often the case
among the flower-
ing plants. Thewin^
Fig, 126. Stages in the growth of Pine seed- i i ji 11 n
lings ; (c) cotyledons. helps the SCCd to fly,
( C 260 ) K
130 THE PINE-TREE FAMILY CHAP. XXIV.
and in the late autumn (in many cases two years after it
began to grow, for some pines grow very slowly) it is
scattered with its brothers. If you are ever near pine
trees when there has been snow, you may see it sprinkled
with these winged brown seeds.
6. You may never have seen a baby pine tree. If
not, you must get some seeds and grow them. They
grow very slowly at first, and may take six weeks to
show above ground even in summer ; but they are well
worth waiting for. Notice how they come up (see fig.
126), and that at the beginning of their growth, as they
come out from the seed, they have seven or even as
many as twelve first leaves, and these leaves are really
the cotyledons, as you may see by cutting a seed across.
So that instead of the one or two cotyledons of the
flowering family, we find in the pine family that there are
manv cotyledons, and that their number may vary from
five to ten or more.
If you go back over these points, you will see that we
have found a large number of differences between the
flowering plants and the pines. Of these, the most im-
portant are the points (5) and (6), which alone would be
enough to make us place the pines and flowering plants
in separate families, though point (4) is also very im-
portant. We find, however, that the pines are more like
the flowering plants than are any of the other families,
so that they are the nearest relatives the flowering plants
have, even though they are rather far-away ones.
PLATE III.
TREE FERNS, SHOWING THEIR TALL THICK TRUNKS
AND LARGE LEAVES, WITH SMALLER FERNS GROWING
BENEATH THEM
CHAPTER XXV.
FERXS AND THEIR RELATIVES
Perhaps there is no family of plants so easy to
recognise as the ferns. It is nearly always a simple
matter to know whether or not a plant is a fern, for
although there are hundreds of different kinds, they all
have the family characters plainly marked.
We have not very many ferns growing commonly in
England, for they generally require a moister air than
is usual in this country. By far the commonest is the
bracken, which grows in all parts of the country, and
sometimes in very large masses (see Plate I.). Some
people separate the bracken fern from the others, and
speak of "bracken" and "true ferns," but this is not at
all correct, for the bracken is just as much a true fern
as the others, only as it is so much commoner, people
are apt to value it less.
In some countries, particularly in the tropics, there
are (as well as ferns like ours) very large ferns with tall,
strong, upright stems, and crowns of large spreading
leaves. Such ferns you can see in Plate III., and they
are called tree ferns. Notice how thick the stem is, and
how large the leaves are compared with it, while the
trunk seems to be all rough and hairy, which is due to
the jagged bases of the old leaves which have fallen
away. Yet even the tree ferns are easily recognised as
belonging to the fern family.
Let us examine ferns in order to find out what are the
points about them which are specially characteristic for
their family, and which help us to separate them from
the other plants.
133
FERNS AND THEIR RELATIVES CHAP. XXV.
1. We find that the fern body is clearly marked out
into roots, stem, and leaves, but there appear to be neither
flowers nor cones.
2. The stem and roots have definite " water-pipe "
cells, as you can see if you examine a thin slice with
your magnifying-glass, but there are never rings of wood
formed year by year, as in the higher families. The
stems are frequently short and stumpy, and often run
underground. They are usually covered by the rough
leaf-bases of old leaves and by dry scales.
3. The leaves are generally few in number, often only
three or four, but they are highly com-
pound, and are split up into very many
side leaflets. They are generally thin
and delicate. When they are young they
are rolled up in the bud in a close coil
(see fig. 127), and as they unfold they
bend back. This way of coiling up is
quite a special character of ferns. The
buds are generally covered with flaky,
shining scales, which stick all over the
young leaf-stalk.
4. Yon have never seen a fern with
flowers or seeds, yet there are always
plenty of new ferns every year. How
are the young ones formed ? For a long
time botanists did not know, so that
people thought there was some magic about it, but now
we know the whole story, and it is a very interesting
one.
5. There are no seeds, and
6. Therefore there are no seedlings to have cotyledons.
You must have noticed little dark brown spots on the
backs of some fern-leaves. It is in them that you must
look for the beginning of the new fern plants. The
little patches are at first hidden by green coverings,
but when they are ripe these bend back, and expose
the little brown clusters within. If vou look at one of
Fig. 127. Young
leaf of a Fern rolled
in a close coil.
CHAP. XXV. FERNS AND THEIR RELATIVES
135
Fig. 128. A small piece
of Fern leaf showing the
patches of spore-cases on
the under side.
these ripe patches with a magnifying-glass, you may be
able to see a number of little roundish boxes on stalks.
Each of these contains a number of tiny " spores "
(which are single cells with the
power to grow), and when the
spore-cases are ripe they open and
shoot out the spores, as you may
perhaps see if you look closely at
a ripe patch when it is taken into
warm, dry air.
These brown patches are not at
all like flowers, but in some way
they do the work of flowers, for
they give rise to cells which can carry on the life of the
fern to a second generation. The way in which they
do it, however, is totally different from that of the seed,
and is quite the most special character of the ferns and
their relatives.
The spores grow slowly when they come on to moist
earth, but as their develop-
ment takes a long time, you
had better get some from a
gardener which have already
grown. As the spore grows,
the one cell composing it di-
_ vides and divides again, until
^C*^? there is formed a little filmy
^j heart-shaped green structure
called a prothallium (see fig.
129), which is not in the least
like a fern plant, for it is not
more than a quarter of an inch
across. It has no stem or
leaves, and is only a thin layer
of green cells, with a few root-hairs on the under side.
Two of the cells formed on this little structure then
unite and begin to grow while still attached to it, and
finally they grow into the form of a very small, simple
Fig. 129. A Prothallium (jf>),
with a young Fern (/) growing
out from it. (Magnified).
136 FERNS AND THEIR RELATIVES CHAP. XXV.
fern plant (see fig, 129). So that between the old fern
plant and the little fern " sporeling " (for we cannot call
it a seedling) we find a whole new structure, the pro-
thallium, which is quite different from the usual fern
plant. This curious alternation of fern, prothallium,
fern, and then again prothallium, is what we call
"alternation of generations," and is very characteristic*
indeed of the fern tribe.
Some ferns take a short cut, and bear little ones
directly on their leaves without any prothallium. You
see this in the " Hundreds and Thousands " fern, where
the old plant is sometimes covered over with little ones,
which will grow if they are taken off and planted care-
fully.
Sometimes people are deceived by what is called the
"flowering fern," and expect that it will have flowers.
In this fern we find that all the spore-cases grow
together on a special leaf, which is so covered by them
that it looks quite different from a usual one, and is
called the flower, though it is not one. In all other
ways the story of the spore building and growth is like
that of usual ferns.
In our study of ferns, you see that they have many
characters which are exceedingly different from either
the flowering plants or pine-trees. In fact, they are so
different that we require to add some new points to our
list of characters for family divisions, which are :
7. Instead of flowers there are little spore-cases, which
contain a number of simple one-celled spores. These are
generally found on leaves which are otherwise like the
rest of the leaves of the plant.
8. Each spore grows out to form a small green structure,
which differs from the parent, and which we call the pro-
thallium.
9. The new fern-plant grows at first attached to the
prothallium, but soon grows out beyond it, and is quite
independent.
What we call u ferns " are not the only plants which
CHAP. XXV. FERNS AND THEIR RELATIVES 137
belong to this big family, for the club-mosses and also
the horsetails have almost the same arrangement for
their building of new plants. Our character-points (7)
(8) and (9) apply to them, even though the rest of their
structures appear to be so different from the ferns.
They are, therefore, put in the same big family with the
ferns, though they have smaller classes for themselves
apart from the true ferns.
Neither the ferns nor their near relatives are very im-
portant in the vegetation of to-day, but very long ago
they were among the chief plants in the world, and
grew to be as big as forest trees. Even then, however,
they had almost the same way of forming spores that
they have to-day, a fact which still marks them out as a
family different from all the other families of plants.
CHAPTER XXVI.
MOSSES AND THEIR RELATIVES
Mosses form another big family, the members of
which are generally easy to recognise, even when you
know little about them, because they all have a very
strong family likeness. If you look for mosses in a shady
wood, or on stones
and tree stumps
near a waterfall, you
will often find large
numbers of them
growing together,
sometimes forming
sheets of soft green,
covering the stones
and earth and tree
stumps. These
luxuriant mosses
grow, as a rule, in
moist and shady
places, but there
are others which
gro\v on dry walls
or between the
cobbles of little-
used paths, and
generally form brilliant green patches of tiny plants, like
masses of velvet. If you pick out a separate plant from
among these and look at it through a magnifying-glass,
you will see that it is very like the bigger ones of the
wood.
Fig. 130. A clump of Mosses, showing the
flower-like appearance of the tips of their branches.
CHAP. XXVI. MOSSES AND THEIR RELATIVES
I 39
For our study it is perhaps better to choose one of
the bigger ones, because all its parts show so clearly.
T. If you take a single plant, you will find that it
appears to be marked
out into root, stem, and
leaves, though all these
parts are small and
simple.
2. The stem is deli-
cate, and you will not be
able to see any " water-
pipe " cells when you
examine it with your
magnifying-glass.
3. The leaves are al-
ways very simple and
small, generally narrow,
pointed, and clustered
thickly round the stem
with no special leaf
stalks.
4. At the ends of the
stems, you will often
find little structures,
sometimes rather pink
in colour, which look
something like flowers
(see fig. 130), but they
are really quite different
in their nature from true
flowers.
5 and 6. There are
no seeds and no seed-
lings.
7. At the top of some of those plants which seem to
have flowers you will find later that a long slender stalk
grows out with a little capsule or box at the end of it
(see fig. 131 (b) )- This single box or capsule really
Fig. 131. (a) The part of the Moss corre-
sponding to the prothallium ; (b) with the
spore-capsule attached ; (c) enlarged capsule,
showing the covering: (d) naked capsule,
showing the lid which falls off at (/).
140 MOSSES AND THEIR RELATIVES CHAP. XXVI.
corresponds to the numbers of small spore-cases on the
backs of fern-leaves, for it is in this capsule that we find
the spores, which are simple and single-celled like those
of the fern.
8. When these spores grow, however, they do not
form a prothallium as they do in the ferns, but they
grow out into the leafy moss-plant.
It is very difficult really to see how this can be the
case, unless you study mosses very carefully with a
microscope, but all the same it is true that the leafy
moss-plant corresponds to the prothallium of the fern.
9. On the leafy moss-plant you find the simple stalk
and capsule which gives rise to the spores ; this spore
forming part of the plant always remains attached to
the leafy plant, so that we find the two portions of the
plant in contact all their lives, and not separated as they
are in the fern.
The only other plants which are built on anything like
this plan are the liverworts, though you might hardly
believe it, because most of
them are not marked out into
leaf and stem at all, but are
only flat, creeping, green struc-
tures, which do not look in the
least like the mosses. It is
true that they are not very
Fig. 132. A piece of Liverwort, near relatives, but because
showing the flat, creeping body, they have spore-cases rather
r e ave d s. vided int r 0t ' Stem ' and like those of the mosses in some
very important ways, the scien-
tists have put them together in the big moss family.
The true mosses have a special smaller family to them-
selves within this, a family which is quite easy for you
to recognise when you go out on your rambles into the
woods.
CHAPTER XXVII.
AND FUNGI
The last big family of plants is that containing
the simplest plants of all. They are often very
small and apparently unimportant, sometimes so small
that we cannot study them at all without magnifying
them very much with the microscope. In other cases
they are quite large and easy to see ; for example, the
big red and brown seaweeds, and the many toadstools
in the autumn woods. Sometimes they may even be
very huge indeed, as are some of the seaweeds which
grow in tropical seas. All the same, though we examine
one which is as big as can be, it is really more simple
in its detail than the mosses.
In very many of the a I gee and fungi, the whole plant
body consists only of one single cell. When this is the
case, the plant lives floating or swimming about in water,
or in very damp places. In rain-water which has stood
for a long time you may find numbers of these tiny
algae. If you put some of the water in a glass tube and
hold it against the light you may just see them, with a
magnifying-glass, as specks of green, often swimming
actively about.
The fine green " scum " which floats on many ponds
and slow-moving streams consists of masses of these
simple plants, in this case generally of forms in which
the single cells keep attached together in long rows or
chains, forming hair-like plants. Colourless plants of
this kind are the fungi, which are often built on the
same plan as the hair-like green algae, only they do no
food-building work for themselves, but live as parasites
142
AND FUNGI
CHAP. XXVII.
on other things. This is the case in many moulds and
the plants which form potato-disease, and, in fact, the
greatest number of plant-diseases are caused by such
simple parasites.
All these plants are very small and simple, and as you
can see at once, are not at all to be compared even with
the mosses, but there are others which seem to be more
complicated, as are the big seaweeds and the toadstools.
Let us see how it is they are put in the same family
as the simplest plants
of all.
You can see, even
with your magnifying-
glass, that they have
no special " water-
pipes " in what you
may call their "stem,"
(for want of a better
name), but that their
whole body is built
up of numbers of soft
cells all very much
alike, which twine in
and out, and build a
kind of soft weft ; they
have no really marked
out stem and leaves
Look at a toadstool, for example, there is just a stalk
and a cap spreading out above ground, while under the
ground there are many twining thread-like strands (see
fig- 133)-
Even in the seaweeds, which may seem to have
stems, you will find that such is not really the case. They
have generally a flat body, which is thin at the edges,
with a stronger mid-rib, and the flat edges get worn
away in the older parts of the plant, and so leave the
mid-rib looking like a stem, though it is not so really
(see fig. 134)-
Fig. 133. A Toadstool, showing the " cap "
and " stalk." Under the cap are the radiating
gills, on which the spores are formed. Thread-
like strands under the soil.
CHAP. XXVII.
ALGJE AND FUNGI
When we come to look for flowers or even spore
capsules, we see still more
clearly how simple these
plants are; they have
not nearly such a compli-
cated history as the moss.
For example, in the toad-
stools we find that there
are many spores formed
directly on its lower sur-
face, on the a gills," and
these grow out to form new
toadstool plants. You can
see the spores if you cut off
Fig. 134. A Seaweed, showing the
branched body, which is not divided
into stem and leaves.
a toadstool or mushroom head
which looks full grown and is
quite expanded, and then lay
it on a sheet of gummed paper
over-night, with the gills down-
wards, and another beside it
with the gills up. Next day you
will find that the paper under
the one where the gills were
downwards is covered with
radiating lines of spores, just
as they fell from the gills,
and repeating their pattern.
The seaweeds have the most complicated way of
Fi g- 135- Part of a Bladder-
wrack, showing the floats {/) and
special swollen tips (s).
144 ALGsE AND FUNGI CHAP. XXVII
forming spores of any of this family. There are special
little swellings at the ends of the plant, as in the
ordinary bladder-wrack, for example (fig. 135 (s)), and in
these are formed the cells which will give rise to new
plants. The other simple bladders (fig. 135 (/")) are
only full of air, and act as floats to keep the plant up in
the water.
In this the simplest family of all, we find more
variety in the appearance of its members than in any of
the others, so that it may seem to be rather difficult to
recognise the plants which belong to it. Perhaps the
easiest way of settling this, is to see if the plant fits intc
any of the other families, and if it never has flowers nor
cones, neither fern spore-capsules nor the big spore-
capsules of the moss family, then you are fairly safe in
classing it with the simplest plants.
Very many of the plants of this family are found
living in water, which is perhaps one of the reasons that
they can afford to be so simple, because the water pro-
tects them from many of the dangers land-plants have
to prepare against, such as wind, drought, or too much
sunshine. This is the simplest family of real, undoubted
plants ; but there is one class still simpler, and that is
the family of bacteria, about which you must have heard
much, as many of them cause our diseases, though
others do much valuable work for us. All the same, we
will leave these little creatures alone, and content our-
selves with the five great families of plants which we
can see with our own eyes.
( C 260 )
PLATE IV.
PART V.
PLANTS IN THEIR HOMES
CHAPTER XXVIII.
HEDGES AND DITCHES
WE do not sec plants growing under quite natural con
ditions in the hedges and ditches, because they are put
there by man in the first instance, and are continually
kept in order by him. All the same, the hedgerows,
which are so common in England, deserve a little study.
They are within the reach of every one, and there we
may often find many wild plants growing sheltered by
the actual hedge.
The principal plant is, naturally, the one which forms
the hedge, and this is very commonly the hawthorn ;
but, growing under it, and over it, and on the banks on
either side, there are many others which are generally
quite self-planted and truly wild. Of the bigger ones,
the white clematis or Travellers' Joy is very common in
the south of England, and grows climbing all over the
hedge, and often covering it with its white flow r ers.
We noticed this plant among those which are special
climbers (p. 105), and we can often see very well on the
hedges how it climbs over tree and shrub, and supports
itself on them.
A smaller plant, of somewhat similar habit, is the
goosefoot. This has long, weak stems, which grow up
amidst the other vegetation and so support themselves,
while its leaves are arranged in whorls round the stem,
and are narrow and rough, and help to keep the plant
from slipping down. Notice also its fruits, how rough
they are, and how they cling to everything. They are
beautifully adapted to catch on to every passer-by,
147
148
HEDGES AND DITCHES CHAP. XXVIII.
whether man or animal, and so to get carried to a dis-
tance where the seeds may grow.
A character of the ordinary plants growing in the hedges
is the tendency they often have to form very long, straggly
stems, which are too fine and weak to support them-
selves, but which are quite strong enough to grow up
through the hedge and
bear leaves, as they are
partly held up by the
other vegetation. You
may frequently find plants
which are usually only a
foot or so high, and able to
support themselves very
well, growing up through
the hedge to a height of
two or three feet, and hav-
ing thin, limp stems with
long spaces between the
leaves (see fig. 136). These
plants have some of the
characters both of those
grown in the dark and of
climbing plants, because
the thick-set hedge keeps
off the light from the low-
growing parts, so making
them straggly, and at the
same time gives them the
support they need if they
grow rapidly out into the light, and do not build strong
stems. Very often you may find plants of the same
species as those that grow so tall in the hedge, growing
in the shorter turf away from it, and there only reaching
their usual height.
This shows us not only that different species are
specialised to grow under different conditions, but that
even two individual plants of the same species may be
Fig. 136. Two Toadflax plants grow-
ing near together : A, on the bank by a
hedge ; B, among the plants of the actual
hedge.
CHAP.XXVUI. HEDGES AND DITCHES
149
growing within a few feet of each other, and yet have
quite a different appearance owing to the influence of
their immediate surroundings. There are many such
cases to be seen in the hedgerows.
If the hedge runs from east to west, it will cast a
shadow over the side lying to the north. Notice how
different is tJie general appearance of the plants on the
bleak side from that of tJiose on the south. You may also
find that some species which grow on the south side do
not grow on the north at all, or only in far smaller
? numbers. It is quite
fSfe worth w r hile making out
ftfj lists of all the plants you
can find on one side and
the other of the hedge if
it is a big, w T ell-established
one, and comparing the
numbers and condition of
the two sets of plants.
As we noticed before,
hedges are not entirely
natural, and as man there-
fore forms a patt of ihe
plants' environment, it is
quite interesting to see how
they respond to his influ-
ence. For example, we
may study the effect of
his trimming the hedge.
In a hedge which had
been left for some time to
itself, the plants would
have long, thin stems, bare
at the base, where no
leaves would develop, as
they would be cut off from
plants. Then comes the
Fig. 137. A, Dead Nettle which has
grown up through the hedge. B, the
same after being cut back with all the
others. Side branches have begun to
sprout now that it is well lighted and
the top has been cut off.
the
light
by all the other
hedger and ditcher," and cuts them all back, leaving
150 HEDGES AND DITCHES CHAP. XXVIII.
often only a few inches of nearly leafless stem. What
is the result ? Soon on these bare stumps leaves begin
to sprout now that the light can get at them and the
top is cut off, and many short side-branches come out,
also bearing leaves, so that where before were only long,
bare stems carrying the top tufts of leaves out to the
light, we now have short, thickly clustered plants of
bushy appearance (see fig. 137). Soon, however, the
race for light begins again, and the plants grow taller
in their attempt to overtop each other. Notice also
how the hawthorn (or whatever woody plant it may be
which makes the hedge) responds when its leafy shoots
are cut away. Many hidden and sleeping buds in the
brown woody stem now get their chance and wake to
active life. It is this continual cutting back which
makes the hedge so thick with many short branches.
/// the ditches, which often run alongside of hedges,
we find quite a different set of plants. The ditches are
generally cut out to a lower level than the surrounding
bank, and so they often contain water while the rest is
dry. In such watery ditches the plants which you will
find depend a good deal on the quantity of water in the
ditch, and whether it is always there or not. If it is
really a wet ditch, you may get many of the inhabitants
of the lakes, or if it is a dry ditch where but little
moisture collects, you will get only rushes and rank
grass. An interesting kind of ditch to watch is one
which is well supplied with water nearly all the year
round, but may dry up during the height of summer.
In such a position as this you are nearly sure to find
many pond-dwellers, such as water-cress, duckweed,
water parsnip, water buttercups, bulrushes, reeds, and
many others, which will vary with the locality. These
plants generally choose a spot where there is a per-
manent supply of water, but plants cannot foresee
the unexpected draining of the ditch, or a summer
drought, and they are sometimes left through these
causes to grow on bare mud. When this happens,
CHAP. XXVIII. HEDGES AND DITCHES
notice how they behave ; those
which were already rooted in the
mud may continue to flourish for
some time, while those which
were floating may be able to root
themselves and tide over a short
danger. If the water is perma-
nently drained off, however, they
gradually have to give in ; they
seem to draw themselves together
and the long, luxuriant branches
die off, on-
ly the short
shoots re-
maining,
which are
not so ex-
travagant
with wa-
ter. The
duckweeds,
which you
know very
well as
little float-
ing green
leaves, have long, thread-like roots
hanging from them unattached to
the soil. When the water goes, they
first root themselves in the soil with
these water-roots, but if the drought
t I /fiHjf | rnS^m the plant hides in the mud, where
li I &imr J mt Jm ^ can rema * n * or a l n S time \vait-
Eri IBW^^J mil ! ing for the return of the water.
In the ditches you will prob-
ably find a number of green,
thread-like algae ; these may also remain on the mud for
Fig. 139. Duckweed, with
simple leaves and long roots
hanging in the water.
Fig. 138. Bulrushes grow-
ing in a wet dilch.
152 HEDGES AND DITCHES CHAP. XXVIII
some time when they are dried up, and in their case
some of the cells at such times get a specially thick coat,
and remain living for long. Then, if the water returns,
it is again the home of these algae, which rapidly grow
out from their protected cells.
So that you see, even if you had no plants but those
in the hedges and ditches to study in their homes, yet
you could manage to find many examples of living plants
which are trying to fit themselves to their ever-changing
surroundings. Those that cannot succeed must die
away in that spot, and confine themselves to some other
place where the struggle is not too hard for them. All
the plants which we find anywhere living together are,
therefore, those which are suited to the conditions in
that place, and all such plants growing together in this
way form what is called a " plant association."
CHAPTER XXIX.
MOORLAND
THE word " moorland " brings at once to the mind's
eye great stretches of land which the farmer has left
practically untouched. It is not like a woodland, for
the plants are all so short that they do not shut out the
view ; hence on the moors there is a sense of space, and
Fig. 140. A moorland stream. Notice the low growth of all the plants.
one can see all around the hillsides and plateaux clothed,
though their form is not hidden, by their covering of
plants. Let us see what are the characters of the plants
which grow so lowly, and yet so thickly on these expanses
of uncultivated ground. Almost the first which rises to
J 53
154 MOORLAND CHAP. XXIX.
one's mind is the heather, with its short, bent stem and
many wiry branches. If you try to pull it up you will
find that the roots are long and fine, but strong, and
that they grow for great distances into the soil, so that
it is very difficult to get the plant out. The leaves are
small and tough, and the lower ones on the stems gener-
ally have their edges half rolled in, while the leaves on
the ends of the branches which stand further out in the
air are often so much rolled as to be almost entirely
closed. Some of the heather-plants seem to be covered
over with short hairs like soft down, while others have
shiny strong leaves. In fact, the heather has many of
the characters of plants which have to protect them-
selves from drought.
Look at the others growing with the heather ; there
is the heath, which is so like it that almost the same
description applies to it. Then there is the cranberry,
which lies close to the ground, and is somewhat pro-
tected by the other plants, and has more delicate stems,
and larger, flatter leaves, which are also rolled in at the
edges. The bilberry has certainly larger leaves than
these others, but notice in the early autumn how soon
and readily they drop off, and leave the thick, green,
ridged stem to do their work. The moorland grasses
also have protected leaves ; generally they are narrow
and pointed, and the whole leaf rolls over, so protecting
the side on which are the transpiring pores (see p. 102).
All these plants have the appearance of protecting them-
selves from loss of water; how is it? It may seem
strange when you remember that it is from our moor-
lands that so much of our water supply comes, and also
that the moors are common in the north, where there is
a large rainfall. All the same, the plants on a moor do
actually require to preserve their water, as they suffer
from " drought conditions."
Stand on a high moor on a windy day, and you will
soon feel how the force of the wind sweeps across
it. Such a day is what laundresses call " fine drying
CHAP. XXIX. MOORLAND 155
weather/' and so do the plants. Then if you go on
a bright sunny day in summer, you will soon feel how
very hot the moorland can be, for there is no shade to
be had anywhere, and the cool green glades of a wood
offer a tempting change. The moorland plants suffer
from this heat, and require to protect their transpiring
pores from the glare, so that you will find all those that
can do so, have rolled their leaves up tightly. Then
notice the soil of the moors, how springy it is, and how
black and u rich " ; very often there are traces in it of
the partly decomposed plants which form it. This is
what is called a peat}- soil, and may even be true
peat. The decomposing plants in this soil give rise to
an acid which is rather preservative, and at the same
time it acts on the living plants and makes it difficult
for them to draw in water by their root hairs. This
kind of soil adds very greatly to the " drought condi-
tions " of the moorland plants, for it makes it hard for
them to use the water which surrounds them. All these
things cause the moorland plants to be as sparing as
possible of their water, and so they have the appearance
of plants grown under dry conditions.
But why are there no trees on the moors, you may
ask ! It cannot be that they are on too high a level for
trees to grow, for some even higher hills are clothed
with them. The truth is that probably long ago there
were trees on the moors, but men cut them down fool-
ishly without having planted young ones between ithe
old ones, which would have replaced them. When
once all the trees are cut down on a hillside, it is very
difficult for young ones to get a start again, because
everything which makes it hard for ordinary small plants
to grow hinders the young trees, and the worst of all
these things is the strong wind, which can rush un-
checked over the bare moor. A strong wind is more
powerful than a young tree, and kills it.
The plantations of young trees which are to be found
on the moorland have to be started on the sheltered
156 MOORLAND CHAP. XXIX.
side, and require much care and attention. You will
notice that the trees which do grow there are those
which are specially fitted for a hard life, such as the pine,
larch, and birch.
Another feature of the moorland, and one which can-
not long escape our notice if we walk about moors at all,
is the number of patches of wet moss which shake and
tremble beneath our feet, and may form great stretches
of bog-land. Sometimes this is so soft that it gives way
altogether, and one may be knee-deep in moss and
water, where it looked firm enough to the eye. You
will find this bog moss grows in a peculiar way, the
fresh green branches growing up and up, while below
lie the half dead older stems, which are partly preserved
by the peaty acids. These layers of moss collect for
many years, till very thick masses of peat-bog may be
formed.
Among the bog-moss you will often find the sundew
and butterwort (see pp. 114-15), which are two of
our chief insect-eating plants. They love the boggy
moorland, or a damp spot beside a little moorland
stream.
There is a curious thing you may have the chance of
seeing in a wet moor. If you find a stream dripping
over a ledge some little distance on to the rocks below,
you may see how thick and beautifully green are the
patches of moss growing beneath its spray. If the
stream has passed over much limestone (and is therefore
carrying some in solution), you may see below the
living moss much dead moss just covered with a thin
coating of lime. Below this is more moss, which has
been made quite hard with the lime, and is brittle
and snaps if you try to bend it, while below this
again is a hard, compact mass of stone which is made
from the stony stems of the moss crushed together by
the weight above them and filled in with more de-
posited lime. In some places great masses of rock
are formed in this way. You have here, acted before
CHAP. XXIX. MOORLAND 157
your eyes, a piece of the history not only of the
living and dying plants of to-day, but of the building
of rocks, which may some day help in the building of
mountains.
PLATE V.
WATER PLANTS GROWING PARTLY BELOW AND PARTLY ABOVE
THE SURFACE OF THE WATER
CHAPTER XXX.
PONDS
THE \vater of a natural pond is crowded with plant-life.
Do not go to one in a London park, which is cleaned
out by the County Council at intervals, but to one
which is left to itself, and you will find it full of
interest.
Some of the plants float freely in the water, as do the
duckweeds, and others, such
as the water-lilies, are rooted
in the mud with their leaves
floating on the surface, while
yet others are rooted in the
mud at the bottom and live
almost entirely under water,
like some of the potamo-
getons, or curly pond-weeds.
The plants which are more
or less attached to the muddy
bottom, and have floating as
well as submerged leaves, are
perhaps among the most in-
teresting, for they show two
kinds of leaves. Look at a
water buttercup, for example
(fig. 141) ; on the surface of the
water, or just above it, are the flowers and leaves, which are
rather like the leaves of an ordinary buttercup. Follow
the stem a little way down under the water, and you
Avill see that the leaves are no longer simple, but are
-159
Fig. 141 . Water Buttercup, show-
ing the much-divided water-leaves,
and the simpler leaves rising into
:he air.
160 PONDS CHAP. XXX.
split up into many hair-like divisions, which sway about
easily with the water's movements. These two kinds
of leaves are each suited to their position, as you will
see if you think about them. The broad, undivided
leaves on the top of the water expose their surface to
the sunlight and do as much manufacturing of starch as
possible, while the solt much -divided leaves below the
surface are in keeping with their position, for they allow
the current to pass between their fine divisions instead
of pushing them up or tearing them, as it must do if
they had broad, flat surfaces, which would be over-
powered by the strength of the current.
Compare these leaves with those of the water-lily.
In the lily you find no divided leaves, but they all
rise to the surface and float there, spreading their
expanded blades on the water. Notice what very long
leaf-stalks they have, sometimes eight or ten feet in
length. Think how absurd the plant would look on
dry land, with its short stem and its huge leaf-stalks,
though they are so well suited for floating in the deep
water. In the air the long, soft stalks would flop about
on the ground, as they need some support, but this they
get in the water, which buoys them up and saves them
from expending too much material in the formation of
strengthening tissue.
Even those plants which, like the water marestail, can
stand up by themselves some way out of the water,
yet have softer stems than most land-plants, and far
fewer well-developed " water-pipe " cells, because they
are so surrounded by water that they can get it easily.
Both these plants and the water-lilies, as well as many
others, store air rather than water in their stems, and
often the spaces in the meshes of the stem-tissue are
filled with air, which acts both as an air reservoir and
a buoy to float the leaves. We find all through the
plant-world that the structure of a plant depends very
much on the kind of conditions under which it is living,
and in the case of those growing in the water, it is
CHAP. XXX.
PONDS
161
Fig. 142. Uuckweect, with
simple leaves, and long roots
hanging in the water.
quite clear how the soft, air-filled stems are one result
of their mode of life, and are
well adapted to it.
In the ponds you will often
find that the duckweed grows
in large masses on the surface.
Each plant seems to consist of
but one leaf and a slender root
about an inch
long, hanging
freely in the
water. Some-
times two or
more of the
leaves are at-
tached and
form a little cluster, but it is exceed-
ingly rare to find the duckweed in
flower. Simple as it is, almost sug-
gesting the algae rather than the flower-
ing plants by its general appearance,
yet the duckweed is really a flowering
plant. It is, in fact, one of the very
tiniest of flowering plants which are
known.
Floating with the duckweed are fre-
quently many fine, thread-like algae,
sometimes quite free,
and sometimes attached
to stems or rocks.
They are very delicate,
unprotected plants,
their whole body con-
sisting of simple rows
of cells. Notice how
their feathery tufts
in a
Fig. 143. Creeping rhizome of the Bulrush,
which pushes out towards the middle of the
pond.
cling
together
close mass when they are taken out of the water ;
( c 260 ) M
162
PONDS
CHAP. XXX.
they require its support and protection to enable them
to live.
There are many plants growing round the borders of
the pond, half in and half out of the water, such as the
reeds and sedges, irises and the tall marsh buttercups.
Watch how these plants gradually grow further and
Fig. 144. A water channel grown over by floating plants and the
advancing reeds and rushes.
further in towards the middle of the pond. They
advance with their creeping underground stems (see
fig. 143), and collect mud, dead leaves, and stalks around
them, gradually building up a little firm soil round their
roots. Slowly these accumulations from different plants
CHAP. XXX. PONDS 163
meet, and the whole gets more compact, till the plants
from the shore which require soil are able to grow with
them.
In this way the shore slowly advances, the floating
plants first building up some mud, and the reeds follow-
ing and bringing shore plants in their train, till in the
end the edges of the pond all meet in the middle, and
the pond, as such, no longer exists. Only a marsh
remains, till this may be gradually grown over by the
ever-increasing land-plants, and an oak-tree may grow
where once the water-lilies bloomed. If the advancing
reeds at the edge had been kept cut back, as they often
are, then the land-plants could not have taken such hold,
and the pond would have remained a pond with all its
" water-weeds."
PLATE VI,
rt J:
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12
1!
s s
I i s
o -g
Q PS
O ^ *
Z < rt
s
l-i
CHAPTER XXXI.
ALONG THE SHORE
SANDY shores with dunes are so common round Britain
that you will probably have opportunities of studying
them Did you ever notice with any care what kind of
plants grow on the sand next the sea? As you walk inland
from the sea, you will find first little hummocks of sand
with a few low, bent grasses, scattered and often far
apart. Then as you go a little further inland, the sand
mounds are higher, and a stronger grass grows first in
tufts and then thickly over them ; this grass is the useful
sand- binder, or marram grass, and grows on the shifting
sand, quite near the sea (see fig. 145). Try to pull up a
plant of this grass, and you will probably find out some
of the things which help it to hold its position in the
moving sand. It is not at all easy to pull up, and you
will have to dig rather carefully if you are to get it out
at all complete.
You will find that what you thought was a simple
tuft of grass is really connected, by an underground stem,
with other tufts. If you follow this along, you will find
that the underground stem runs for a long distance,
burrowing in the sand and sending up tufts of leaves at
intervals. The tip of the stem always remains under
the sand, prepared to grow in whatever direction is best,
and unless it is buried to a very great depth it will
always continue growing. Coming off from the stem
there are very many long roots, and at the places where
the leaf tufts arise there are generally one or two much
165
i66
ALONG THE SHORE
CHAP. XXXI
longer and stronger than the others, which run a very
great distance into the sand, and if you wish to get
them out without breaking them, you may have to dig
for several hours. It is by means of these branching
underground stems and long roots that the marram grass
gets its hold on the sand. When once this grass holds
the sand it is soon helped by a number of other plants,
Fig. 145. A Sand-dune by the sea with the Marram grass in tufts, and
the Carex tufts coming up in straight lines from their underground stems.
which come on behind it and cover the surface, and so
prevent the wind from scattering the sand-grains, and
blowing them about in clouds.
One of the first plants to follow the marram is the
sea-star grass, or carex. You have probably seen its
little tufts following in lines across bare banks of sand
(see fig. 145). This appearance is due to the under-
CHAP. XXXI.
ALONG THE SHORE
167
ground stem, which runs very great distances in nearly
straight lines, sending up groups of leaves at short
intervals as well as side-stems, which form lines crossing
the main line.
Often a bank
may be covered
with lines of this
plant. A little
piece of the
plant is shown
in fig. 146, where
you can see that
the structures
are on very much
the same plan as
those described
for the marram
grass. There
are many other
plants with this
kind of habit,
which enables
them to live on
the sandy shores
and dunes. Look
at all the plants
you can find on
the sand - hills,
and you will see
that in some way
they have their
parts adapted to
suit their
ditions.
long roots
a running
these you
dig up.
Fig. 146. A small piece of the underground stem
of Carex, \vith tufts of leaves coming above the level
of the sand; (s) stem, (r) roots (cut off) with small
side roots, (sc.) scale leaves underground.
con-
Very
and
stem are the commonest characters, and
will find on almost every plant you try to
i68
ALONG THE SHORE
CHAP. XXXI.
Sometimes the stem can grow up and up, even
though it is continually buried by
the shifting sand, as you can see
very well in the case of the sea
holly. You may dig for more than
a dozen feet before you come to
the end of the vertical stem of what
seemed to be quite a small plant
(see fig. 147).
Along the shore are other plants
of quite a different kind, which have
also special characters to help them
to conquer a region which seems to
be very inaccessible to land plants.
Many curious plants live in the
mud-flats that are frequently covered
by the tides, and which can there-
fore only get
salt water.
You re-
member
that salt
kills ordi-
nary land-
plants, so
that these
must be
specially
built to be
able to stand
it. Most of
them have
very thick,
fleshy leaves, and rather bushy
stems, while others have leath-
ery leaves covered with a kind
of wax, or with hairs, which make them look grey.
Look at the sea-daisy, and you will see that the leaves
Fig, 147. Sea Holly,
showing the plant at the
surface, and the long stem
below the level of the
sand (s).
Fig. 148. Marsh Samphire or
Glasswort, a plant with swollen
green stems which do the work
of leaves.
CHAP. XXXI. ALONG THE SHORE 169
are very thick and juicy ; so are those of the sea-blite
and salt spurry. The boldest of all these plants, the
marsh samphire, which goes furthest out to sea, and
may grow on bare mud covered by every tide, has
not leaves at all, but very thick, fleshy stems, which
are green and do the work of leaves (see fig. 148).
All these forms must remind you of the plants which
were characteristic of dry regions ; how is it that these
plants, often actually growing in the water, should yet
be specialised in the same way? It is because all the
water they get is salt, and it is very difficult for them to
live in it. They can only use a relatively small quan-
tity, otherwise the} 7 would be forced to take in too much
salt, so they must prevent their leaves from transpiring
much and using the water up. In this way they are really
in the same kind of position and so require to have the
same kind of leaves as a plant growing where very little
water of any kind is to be had. They are in the same
difficulty as the Ancient Mariner, with "Water, water
everywhere, nor any drop to drink."
Pull up a marsh samphire, and you will see that it
has a very much branched, spreading root, which gives
the plant a firm grip on the sand or mud, but it has
not long roots like the sand-dune plants, for all the
water which it can use is to be had quite easily and is
near at hand.
You may notice, too, on these mud flats the mingling
of plants from land and sea. When the marsh samphire
and sea-daisy invade the flats which are covered every
day by the tide, they are entering the region of the sea-
plants, and you may find them growing side by side
with the true seaweeds, and even in some cases we may
notice the bladderwrack seaweed further in toward the
shore than the samphire, which has ventured far out to
sea.
As you will find in everything in nature, it is always
difficult to draw a fixed line and say that on one side lies
one type of thing, and on the other side something
170 ALONG THE SHORE CHAP. XXXI.
different ; so, in dealing with different " plant associa-
tions," we find that they have their special regions, but
that they tend to cross over any limiting lines set
between them. In deep water and on high, dry land,
we find quite different kinds of plants which never
mix with each other, but on the border land between
such regions the boundary is not strictly kept, and we
sometimes find plants growing where we might expect
the conditions to be unsuited to them.
PLATE VII.
BLADDERWRACK GROWING ON THE ROCKS EXPOSED
AT LOW TIDE.
CHAPTER XXXII.
IN THE SEA
ALL the plants which grow in the sea are hastily grouped
together by most people under the name " seaweeds."
We know that there are many kinds of seaweeds, and yet
even to one who has not studied them, they do not seem
to differ so much from each other as to deserve special
classes. And this general view is quite a correct one,
for with very few exceptions, all the plants which
actually live in the sea are algae, and so belong to the
simplest family of plants (see Chapter XXVII.). Yet
they are not without interest and individuality. In the
sea these simple plants have everything to themselves;
and it is there that we get them developed in a very
special way.
You must have noticed that you never find seaweeds
actually rooted in the sand (except in protected marshes,
where the sea samphire and some flowering plants may
grow), because sand is always shifting and being churned
up by the waves, so that they cannot get a firm hold.
This is almost the same on the pebbly shores where the
stones are rolled over by the waves, and so would batter
any unfortunate plant growing on them. If you go
along a rocky coast at low water, however, you will find
countless true seaweeds, growing so thickly that the
rocks are covered by their slimy masses, while in the rock
pools are beautiful tufts of more delicate seaweeds of all
colours (see Plate VII.).
Examine a single plant of bladderwrack or fucus, and
pull it up if you can. You will find that it is very slimy
173
174 IN THE SEA CHAP. XXXII.
and slips out of your fingers, and then, that when you
have got a firm hold on it, it sticks so fast to the
rocks that it is difficult to get it off without breaking it.
Does this mean that it has roots which go right into the
rock as the roots of land-plants go into the soil ? Find a
plant growing on a small stone, if possible, and look closely
at it ; the " root " does not go into the stone at all, but
is much divided and clasps round it, bending into every
little crevice and sticking tight. Note, too, that there
are no root hairs as there are in land-plants, which is
natural enough when the whole plant is growing in
water, and can therefore absorb it through all its surface.
All that is required from the " root " is that it shall
hold firmly on to the rocks and keep the plant from
being dashed on to the shore by the waves. The " root "
is not a true root, but is really only a part of the simple
body, which is specially adapted for attachment.
The many large bladders on the plant are filled with
air, as you will see if you split them open, and they help
to buoy it up in the water. Notice, too, how flat the
whole plant is ; it is really a single sheet of tissue
or "thallus," which is much divided, but does not
branch in many directions as a land-plant does. All
these characters are those of the simple family of algae,
to which all the seaweeds belong. Though in some
cases they may form what look like very complicated
structures, yet they are always built upon these simple
lines.
Often you may find little plants growing on the bigger
ones ; sometimes a well-established weed may be almost
covered by small seaweeds of many kinds, brown, green,
or red. These attach themselves to the big plant in
much the same way as they would to a rock, but only
use it as a place of anchorage, and do not tap its food
supply, as the parasitic mistletoe does to the land-plants.
In the same way you may find numbers of seaweeds
planted on shells or growing on the backs of crabs.
As the tide goes out it gradually exposes the rocks
CHAP. XXXII.
IN THE SEA
175
and pools with their innumerable inhabitants. Now in
the case of those which are first uncovered, a long time
must pass before the water returns, while those quite
near the low water level are only uncovered for a little
while. Follow the falling tide some day, and look for
the effect \vhich this difference (in the time for which
they are exposed) has on the plants growing at different
depths.
As you go out towards the low water mark you will
Fig. 149. The Laminarias, which are only exposed at quite low water.
find first and commonest the bladderwracks, which get
more luxuriant where they are a little removed from the
region of the pounding waves at the actual shore.
Then further out you will find that the bladderwrack
gives up its place to another plant very like it, but
with more jagged margins. Beyond this you will come
to the big strap-shaped laminarias, which never grow
where they are very long exposed without water (see
149).
These different regions of seaweeds (some of which
fig.
176 IN THE SEA CHAP. XXXII.
are only laid bare by the tides which go very far out)
really depend on the fact that the different levels of
the shore are left exposed for varying lengths of time
according to their depth. If the shore is flat or gently
sloping, then the tide has a very great distance to
recede before the same depth is reached as would be
attained much nearer in where the shore slopes steeply
(see fig. 150). This explains how it is that in one place
you may have to walk out a quarter of a mile till you
come to the region of laminarias, while in another
you need walk no distance, but merely clamber down
the rather steep rocks to get to it. But as the actual
time taken by the falling tide is the same in both
H.
Fig. 150. A diagram to show how the slope of the shore influences the distance the
tide goes out, and, therefore, the distance from high-water mark at which the different
seaweeds grow. A, a gently-sloping shore ; B, a steep shore. The line H indicates
the high-tide level, and L the low-tide level.
cases, the plants at any level are left exposed for
almost the same time whatever the kind of shore
may be.
One thing that may perhaps puzzle you about the
seaweeds is their colour ; some few of them are green,
but most are blackish, brown, or even red. How then
do they build their food? It is found that true chloro-
phyll is present as well as the other colours, and that
though they hide the green tone from our eyes, they do
not hinder its activity in the plant. You can see that
the brown bladderwrack is really a green plant if you
soak some of its tissues in hot water ; the brown colour
will be washed out and will leave the plant bright green.
CHAP. XXXII. IN THE SEA 177
In almost all cases these simple algae living in the sea
are self-supporting plants, which have adapted them-
selves to the special conditions in the depths of the sea
where no flowering plants can live, and there they reign
supreme.
( C 260 )
CHAPTER XXXIII.
PLANTS OF LONG AGO
WHEN we were on the moors we noticed that we may
sometimes find plants being actually turned to stone
under our eyes (see p. 156). These are plants which are
living at the present time, but this same thing has also
happened to plants which lived long ago, and which
otherwise we could not see and study, because they are
all dead. In those cases in which they did not decom-
pose in the ordinary way after death, but were turned to
stone, we are
* sometimes
able to find
out almost as
much about
them as we
can about the
plants living
to-day.
You must
have seen in
, museums, or
even found
.j for yourself
in stones, the
remains of
leaves and
stems of plants which, too, are turned to stone, but which
yet show the shape and form of the plant with great
beauty. If you go to the north of England, where there
are many coal-mines, you will have a good chance of
Fig. 151. Plant which was living at the time coal was
made, pressed in a stone and so preserved.
CHAP. XXXIII. PLANTS OF LONG AGO
179
finding pieces of stone which have been thrown out
from the mines as refuse, and which have in them or on
them most beautiful leaves of ferns and other plants.
We know from geologists that these rocks are very old
indeed, older
than the val-
leys and downs
of the south of
England, yet
we can see to-
day what the
plants which
lived then
looked like,
because they
have been
Fig, 152. Fern which was living at the time of the turned into
coal, pressed between sheets of stone. stone and kept
for us in the
rocks till the miners dig them out when digging the
coal.
But what is coal itself ? You know that it is not at
all like an ordinary rock, for it burns as well as wood,
and has been found to be largely made of carbon. Even
directly on top of the coal, and sometimes actually in
the coal seams, we find plants preserved, and geologists
and botanists have combined to prove that coal is really
entirely composed of the crushed remains of ancient
plants.
You will remember that we found that many of the
plants in the peat bogs did not get decomposed entirely
because of the preservative peaty acids present in the
water and soil. Something of the same kind happened
to the plants of the old forests which now form our
coal. As they died they did not entirely decompose,
but got pressed tightly together, all their" living juices
being squeezed away till little but the carbon in them
remained. These masses of plants gradually sank
iSo
PLANTS OF LONG AGO CHAP. XXXIII.
beneath the sea, were covered by sandstones and
limestones, and were preserved between the beds of
rock, forming masses nearly as firm as the rocks them-
selves. These old plants, which to-day act as our fuel,
are really " as old as the hills," for they were growing in
the country before the hills were made.
As well as the many plants which were preserved in
this way, and in which we can now see little but masses
of carbon, there were others which were preserved in
stone, sometimes pressed between the layers of stone as
you press a flower between sheets of blotting-paper, in
other cases turned directly into stone without crushing,
so that they
show their
complete
form, cell by
cell. It is
from these
stone plants
that we learn
what the
plants of the
coal were
like. Some-
times we find
great trunks
of trees standing petrified together in the positions in
which they were growing, with their roots twining round
one another, and entering the muddy soil on which they
lived. Sometimes such tree-stumps stand up through
the coal-beds and rocks which must have been deposited
all round them (see fig. 153). We find also leaves and
stems, cones and seeds, in the stones, till we can build
up completely the form and life history of several of the
plants which were then living. But in all the wealth of
material which has been found, no flowers have ever
been discovered. The seeds seem to have belonged
to plants of the pine-tree family, so that these old forests
Fig. 153. The trunk, A, of a fossil tree turned into stone,
still standing in the position in which it grew. It is sur-
rounded and covered by the pressed masses of plants (coal)
C, fine mud (shales), O, and sandstones, S. Its roots, R,
are still in the clays, U, in which they grew, which are now
hardened to rock.
CHAP. XXXIII. PLANTS OF LONG AGO 181
were without any of the plants which are to-day the
most important family of all, that is, the flowering plants.
They lived so long ago that flowers had not come into
existence by that time.
Another strange thing about these forests is, that
although there were great trees in them, they were not
like those of our present forests. To-day our trees are
chiefly flowering plants, such as oaks, limes, and beeches ;
but the giants of these ancient forests \vere club-mosses
and horsetails, plants belonging to the fern tribe. Their
descendants, the club-mosses and horsetails growing
now, have degenerated, and are humble plants not
more than a few feet high at the most, and always of
little real importance in the landscape.
The true ferns then living seem to have been more
like those of the present, though perhaps a little larger
and more important. In the family of ferns then living
were some with strange histories, and among the ferns
which you may find in the stones some leaves may have
belonged to a plant which was truly a " missing link" in
the history of plants, and helps us to see the relation-
ship between ferns and pines.
Many and strange are the tales the fossil plants can
tell us of the life in the forests when the coal was made,
and just as, in the moors, only those moss-plants which
were turned to stone will still be there after centuries
have gone by, so it w r as in the old coal-forests that only
the plants which were turned to stone remain to tell us
their story to-day. For this reason our knowledge of
the forests of long ago is not complete ; but even now it
is enough to tell us something of the life of the plants
which were then doing the food-building work of the
world. Though the individual plants were so different,
the " associations " were in a general way the same as
those now living. Great trees reared their heads into
the air, and below them, or climbing round and over
them, the smaller plants found place long ago as they
do to-dav.
CHAPTER XXXIV.
PHYSICAL GEOGRAPHY AND PLANTS
IF we examine the plants of any district, we find that
a number of outside influences affect them very greatly.
The most important of these are the physical geography
and geology of the place. The form and nature of the
rocks and soil, as well as the climate, have a great effect
on the plants growing in any spot.
You can see this in an extreme case if you imagine
yourself up in a balloon looking down on England as on
a map. In certain places you see lakes, that is to say,
the rocks and soil are so arranged that they form a basin
and hold the water permanently there. Now in a lake,
as you know, only water-plants will be growing, so that
the presence of a fairly deep and constant lake makes it
quite certain what kind of plants must grow in that spot.
Imagine an earthquake or some slower earth-movement
which is strong enough to change the rocks so that the
water all runs away, and the result is that there will be
dry land in the same spot where before was the lake.
This will cause the water-plants to die sooner or later,
and land-plants will replace them.
There is continual change in the arrangement of lakes
and rivers, hills and shores, which takes place all around
us, but so slowly that we do not notice it. It is slow,
and therefore there is not a sudden killing off of any one
kind of plant, and a rapid incoming of a different set
of plants, but it causes a gradual shifting and moving of
the groups among themselves. Sometimes there may
be some swift and sudden change, as the result of a
landslip or volcano, or in a stream or lake which has
182
CHAP. XXXIV. PHYSICAL GEOGRAPHY 183
been artificially drained, which shows us a very good
object-lesson in plant geography.
The importance of the physical form of any place,
however, does not only lie in the position of its lakes and
streams and the size of its hills. The kind of rock, and
nature of the soil covering the rocks, are very important,
as well as the many other details of the land.
In England there are no very high mountains, so that
you cannot study the effect of great heights on plants,
but all the same England affords quite sufficient oppor-
tunity for the study of physical geography in its relation
to plant-distribution.
Even in the cultivated fields, where man tries to help
the plants to overcome their surroundings, you will find
the influence of the soil is very largely felt. Ask any
farmer about his land, and he may tell you that a certain
one of his fields is specially good for potatoes, another
for barley, or that in a village a few miles away they can
grow splendid crops of strawberries, while his are not
worth the planting. Then think of the different kinds
of plants for which the different counties of England
are noted. Xo one could get the produce of the cherry
orchards and hop-gardens of Kent to grow on the York-
shire moors. Nor do we find acres of heather moor on
the downs in the south of England, but instead there is
a short turf with many little flowers which love the
chalk and limestone, such as the blue ana white poly-
gala, rock roses, and several small orchids.
Now what is the difference between the north and
the south of England ? It is chiefly one of rock and
soil. On the Downs in the south you find a thin coating
of brown earth over thick masses of white chalk through
the surface of which the water supply quickly runs, so
that we get few streams or bogs. In the north the hills
are built of coarse sandstones, hard grey limestones, and
fine black shales which hold much water, so that there
are many swampy places and innumerable streams and
little waterfalls. Then, again, the land in the north of
184 PHYSICAL GEOGRAPHY CHAP. XXXIV.
Kent, which is so famous for its cherries and hops, is a
rich, fine clay, with a muddy and sandy soil, which
centuries ago was the bed of a great river, and now is
the most important factor in making Kent one of the
most fertile parts of England.
If we find that the influence of the physical nature of
the land is so strong even in the case of cultivated
plants, which are helped by man's knowledge, we shall
expect to find that it is still more felt by the wild
plants.
Let us go, for example, to the moors east of Settle, in
Yorkshire, where you find the three kinds of rock, the
hard limestone, coarse sandstone, and soft, black shales.
If you walk across the moors, you will see that the prin-
cipal plants are heather, bilberry, and several coarse
grasses, which grow in more or less irregular patches.
If you notice the grasses carefully, you will find that
they are of several different kinds, showing varieties in
their size, form of leaf, colour, and so on, and that very
frequently the different kinds grow on the different
types of rock beneath them. After a little experience,
you will almost be able to tell what is the nature of the
rock on which you are standing by the appearance of the
plants at your feet.
If you live anywhere in the south of England, walk
over some part of the downs till you see below you in
the valley a clay-pit or pottery factory, which shows
you that the chalk is no longer under the surface soil,
but that it has been replaced by clay. Walk straight
towards this place, collecting the plants you meet on the
way. On the actual downs you will find many which do
not grow near the clay-pit, since they are special chalk
lovers. In the clayey valley it is very likely that you
may find a pond ; if so, walk towards it, noting all you
pass on the way. As you get to the edge, reeds and
bulrushes, water forget-me-not, tall spikes of water
loosestrife, and many others appear which you would
have been astonished to meet with on the downs.
CHAP. XXXIV.
AND PLANTS
185
A very important factor also is the amount of rain
which the district gets. This tells particularly among
the ferns and mosses. Along the hedgerows of Kent,
for example, where it is rather dry, true ferns will
seldom grow, while in Devonshire every hedge and
bank has many hundreds of the common polypody fern
Fig. 154. A recently formed pond in Delamere with a dead forest tree
standing up in the middle.
and the hartstongue. When we come, however, to con-
sider on what it is that the rainfall depends we find that
it is the structure, size, and relations of the land masses
to the sea and the winds. In fact, it depends on the
physical geography of England as a whole. So that in
the end the plants and the physical nature of anyplace
are so much in touch that it is almost impossible to do
anything in the study of plant distribution without
considering physical geography.
Although the changes in physical geography which
i86
PHYSICAL GEOGRAPHY
CHAP. XXXIV.
made and unmake continents are slowly acting around
us all the time, it is not often that we can clearly
see them taking effect. Photos 154 and 155 are
therefore particularly interesting, for they show one of
the processes at work. Part of a forest is in the actual
course of being killed by the pond which is forming on
Fig. 155. A recently formed pond which has covered a large area of the
forest and killed many of the trees. Notice the dead trunks standing and
lying about, and the rushes growing near the edge, which would not have been
there but for the coming of the water.
sinking land. This pond and several smaller ones of
the same kind can be studied in the neighbourhood
of Delamere forest, in Cheshire. Here the under soil
gets washed out in certain places, and the surface
earth sinks and forms a hollow in which water collects.
In fig. 154 you see one tree standing in the middle of
the pond. It is dead, and has been killed by the water
(you remember that ordinary plants are drowned by
too much water) and in fig. 155 you see a large area
CHAP. XXXIV. AND PLANTS 187
entirely covered with water, and the dead trees stand-
ing up through it. This pond is spreading rapidly, and
is a good illustration of the reverse condition from that
seen in fig. 144, where the plants by their growth are
filling up a pond. The washing out of the soil and the
collecting of the water in this case was quite beyond the
control of the plants themselves, but they are supremely
affected by it.
CHAPTER XXXV.
PLANT-MAPS
IN the last chapter we noticed a few of the many facts
which show us that a close relation exists between the
plants and the nature of the land on which they grow.
We may now try to express these facts in a simple way
by making maps of the land according to the plants
growing on it.
There are maps of the whole of England, made by the
Government, which show all the roads and houses, the
chief rocks, hills, ponds, and so on. The geologists
have taken these maps and added to them details of the
kinds of rock and soil of which the land is built. If
now we take fresh copies of the u ordnance " maps, as
they are called, and put on them all the plants growing
in different associations, we can compare the resulting
" plant-maps" with the land-maps of the geologists, and
I think you will be surprised to find how much the
plant-maps and land-maps correspond.
To do this on a large scale, however, is far too big
a piece of work for one person, or a few people, to
attempt. We can only do some small piece of work on
one area which will show how the rest is done, and
yield some interesting details.
Let us suppose, for example, that the moor east of
Settle is to be mapped. First get an ordnance survey
map on a large scale 25 inches to the mile is the best,
but the 6 inches to the mile will do. On the map are
marked all the walls, streams, and even some of the
bigger trees, so that it is easy to find on it the exact
spot where you are standing. For working you should
CHAP. XXXV. PLANT-MAPS 189
cut the sheet up into at least eight pieces, of regular
size and shape, and use one of these at a time in the
field.
First get to know the part you are to work on later
in a general way, noting the chief plants and in what
way they are associated.
Be careful in working to keep your sheets in regular
order, and begin with the one at the bottom left-hand
corner of the whole map. Find the exact spot on the
ground which is represented by the point of the bottom
left-hand corner of your first sheet, and put a white
stake into it at least two feet high ; it is better if you
add a little red and white flag, so that you can see it
from a distance. Then find each of the other four
corners of your small sheet, measuring the distance from
a wall or tree if need be, and put in each a white stake
similar to that marking the first corner. If your map
is on the 25-inch scale, and you have cut it into sixteen
equal pieces, you will find that the area staked out on the
ground represented in one piece is not so large but that
you can see over it, and by walking about within it, get
all the features of the plants growing there mapped out
on to your sheet. In studying the different patches of
plants, you will find that, as a rule, in each there is one
important plant which grows in great numbers, while
there are many more scattered and less important species
growing with it. Such patches of plants growing to-
gether may be called Associations, and in mapping we
only pay attention to the chief of these. In a patch
where cotton-grass is the most conspicuous thing, there
may be also half a dozen small grasses and plants grow-
ing with it, in which case everything but the cotton
grass would be ignored in the mapping, and the associa-
tion called the "cotton grass" association. Similarly,
a patch where heather is the most important plant would
be called the heather association. Sometimes you may
find two or more plants growing together which seem
to share the area between them, so that it is impossible
190 PLANT-MAPS CHAP. XXXV.
to tell which is the chief one ; in such a case where, for
example, heather and bilberry are apparently equally
important, the association would be described as
"heather-bilberry." For the sake of reference, lists
should be kept of all the plants of less importance
growing in the associations, though they are ignored in
the mapping.
At the beginning it is wise to go over the area and
find out roughly how many chief associations there are
in it, and to make out a list of them. Then choose either
a colour or a sign to represent each of them in the map-
ping, a colour will generally be found to be clearer arid
more effective in the finished map, though a sign is very
useful for the field-work.
When all these preliminaries are finished, begin the
actual mapping by going very carefully over the different
patches in the staked-out area of one piece of the sheet.
From the details already printed in the ordnance
survey map, you will generally be able to find the exact
position of the patches of plant associations (unless they
are very small, when they must be ignored), and you
should soon be able from the help of the given details
to fill in the shape of the patches by the eye. If in any
case this is difficult, a 5-foot rule and a string of 20 feet
or 30 feet marked out into 5 feet and i foot lengths will
be found very useful. From the actual measurements
you will then get, it is easy to find how much will repre-
sent them on the map by the simple sum : 1,760 actual
yards are represented by 25 inches on the map, so that
1 6, 10, or whatever number of feet you require will
2< in. x 10 in. 2< in. x 16 in.
be represented by ^^ or- ^ x g and
so on.
Do all your field-work in pencil, and take notes in a
" field-book" as you go, so that you will be able to copy
out a neat, correct map at home in which to colour in
the associations and outline the patches with waterproof
ink. When one of the sheets is done in this way, stake
CHAP. XXXV. PLANT-MAPS 191
out the area for the next, and so on, till you have all the
sheets finished. Then paste them together again on a
piece of muslin in their proper order, and you will have
a complete " plant-map " of one definite, though small,
area. This can be easily compared with a geological
map of the same area, though the geological one will be
on a rather smaller scale (best 6 inches to the mile), and
you will see how the patches of plants frequently follow
the arrangement of the rocks. This does not show so
clearly on too small an area ; the larger the district you
can cover the better.
To work from an ordnance survey map is the easiest
way of proceeding, but if you like to combine the plant
study with a little simple survey work, it is quite possible
to make the map from the very beginning. This is not
generally worth the trouble, except in cases where you
find a rich and interesting area which would repay very
careful mapping on a larger scale than the survey have
published. For example, it would be a very good plan
to choose some small area, and in it stake out exactly
100 feet square. Along the sides plant smaller stakes
every 20 feet, and map all the details very carefully on
to mathematical paper on the scale of either 5 inches or
better, 10 inches to 100 feet. Such an area would well
repay the trouble of repeated mapping at different times
of the year. If you have a series of maps of the exact
area every two months, for example, you will be able
to see from them very well the succession of plants
throughout the year, and how the associations change
according to the seasons.
Another thing that should go with the mapping is the
plotting out of " sections" through the irregular land,
which will show clearly how frequently the plants
growing on any spot are determined by the level of the
spot and its consequent relation to the water supply.
The most striking case of this kind is that of a section
through a pond or stream and its banks. Unless you
have a boat at your service, you will have to choose a
CHAPTER XXXVI.
EXCURSIONS AND COLLECTING
WHEN you plan an excursion do not take your collecting
tin and a " Flora" in which to look up the names of all
you find, and then imagine that you are fully prepared
for a day's botanising. It is, of course, a very useful
thing to learn the names of the flowers you find, because
you cannot even speak of a plant if you do not know its
name, but the mere naming is in reality the least interest-
ing and important thing about them, as you will know
if you have followed the study of plants in the way
suggested in this book.
In arranging an excursion, or what is far better, a
series of excursions into the country, the most important
thing to have is a plan of action. Do not wander aim-
lessly in the woods, attracted from side to side by all
that comes in your way ; choose rather some special set
of things to collect and study. If there are several of
you together, then each one should have a particular
subject about which to make notes and collections; then
afterwards all the members of the excursion party should
meet together and compare their results, and show each
other any interesting specimens obtained.
Each person should be provided with : A tin collect-
ing-box, a strong knife or digger, a note-book, pencil,
and magnifying-glass, some string, and a fine knife.
In case you find it difficult to decide on special things
to do, here is a list of a few of the many suitable subjects
which may be chosen. The list is not at all complete,
but it may give you a few ideas at the beginning of
your field-\vork.
CHAP. XXXVI. EXCURSIONS AND COLLECTING 195
1. In the early spring, study particularly all the plants
which are flowering. Dig up complete specimens of all
the smaller plants, and notice how many of them have
some special means of storing food underground through
the winter, such as bulbs, tubets, and so on. This stored
food makes it possible for the flowers to bloom before
the leaves have done any work, a thing which would be
impossible in the case of ordinary young plants. Our
" early " spring flowers are really late flowerers, as they
bloom on the result of the food made in the previous
year. Make drawings, or press a series of these.
2. Collect buds and opening buds, getting series of
scales from the outer hard ones to the inner developed
leaves, and press them.
3. Notice, and make sketches of, the different ways in
which leaves are folded in buds: the fan-like beech,
the coiled fern, and so on.
4. Collect seedlings ; notice specially those of trees.
Study the form of their earlier leaves, which are gener-
ally simpler than the mature ones.
5. In summer, collect as many forms as possible of
full-grown leaves. Compare and classify them accord-
ing to their nature and shape : those which are simple
or compound, and then in more detail. Dry and mount
a series of representative ones.
6. Study very particularly flowers in relation to their
insect visitors. For this it is better to remain a long
time in one place, so that it is not so good for a general
excursion, but is splendid if you can get off for an early
excursion by yourself, or with one or two companions.
7. Make collections and lists of all climbing plants,
noting by what means they climb.
8. Keep a list for the whole year of the colours of the
flowers as they come out, noting in general which are
the most characteristic for the different seasons.
9. Collect fruits, and arrange them according to the
way they scatter the seeds.
10. When the leaves are falling, notice where thev
(C260) O2
196 EXCURSIONS AND COLLECTING CHAP. XXXVI.
break away, and what form of scars they leave. In the
case of compound leaves, whether they fall off whole or
in parts.
11. Collect series of plants which are growing together
in different places, e.g., those in a woodland glade, those
at the edge of a pond, those on a sandy hill, and so on.
Dry them by pressure between sheets of paper, and
mount them, noting how their forms correspond to their
surroundings.
12. Go to the same spot in a wood in spring, summer,
autumn, and winter ; make notes and drawings of what
you see each time. In the spring there will be a carpet
of flowers under the bare trees, note what happens in the
summer, and later on.
These suggestions are only a beginning, and special
problems will arise of their own accord in connection
with the work you are doing, till you find that the real
excursion becomes the most interesting and important
part of your work. If we go to the plants themselves
and ask them to teach us, they will never fail to give
us the chance of learning lessons of ever-increasing
interest.
INDEX
The roman numbers refer to the pages, and italicised numbers to
the figures
ABSORPTION by roots, 33, 21, 22
Adventitious roots, 56, 40, 57, 41
Alcohol, 24
Algae, 141
Algae in ditches, 151
Algae in the sea, 143, 134, 173
Ampelopsis, 108, 105
Animals eaten by plants, 114
Animals, life of, 3, 7
Anther, 80, 81
Assimilation (see Food building)
Associations of plants, 152, 189
Axil of leaf, 75, 66
BACTERIA, 144
Bean seeds, 8, 3, 9, 4
Bean seedlings, 10, 6, n, 7
Bean seedlings grown in dark,
38,27
Bean seedlings, growth of, 41,
28
Beech leaf, 65
Bees and flowers, 119
Bidens, fruits of, 90, #7
Bilberry, 154
Bladderwort, 116, 115, 114
Bladderwrack, 144, 135, 173, PL
Bog-land, 156
Bracken fern, 133, PI. 1.
Bramble, 63, 49
Bread, starch in, n
Breathing of animals, 6, 2
Breathing of plants, 5, I, 96
Breathing pores, 96, 96
Broom, 62
Broomrape, 113, 109
Buds, 72
Buds of fern, 134, 127
Buds of horse chestnut, 72, 62,
63
Buds, overlapping scales of, 73,
63,64
Bud scales, 74, 65
Bud scars, 75, 66
Buds of sycamore, 75, 66
Buds, unfolding of, 72, 62
Bulbs, 77, 68
Bulrushes, 151, 138
Bulrushes, rhizome of, 161, 143
Bur, fruit of, 90, 86
Buttercup, flower of, 82, 76
Buttercup, water-, 159, 141
Butterwort, 115, 112
CACTUS, 2, 62, 48, 99
Calcium phosphate, 15
Calcium sulphate, 15
Calyx, 79, 70
Canadian water-plant, 21, 13
Capsule of moss, 139, 131
Capsule of poppy, 89, #5
Carbon, 19, 23
Carbonic acid gas, 6, 19, 24, 27
Carex, 1 66, 146
Carpel, 82, 76, 77, 78
i 97
198
INDEX
Carrot, 55, 3$
Caustic potash, 20, 12
Cells, 92, 97
Cherry flower, 82, 78
Cherry fruit, 88, 82
Cherry leaf, 64, 50
Cherry leaf arrangement, 69, 58
Cherry stipules, 64, 50
Chlorophyll, 17, 24, 27
Circulation of water, 28
Climbing plants, 104
Climbing assisted by roots, 106,
101
Climbing by tendrils, 107, 104,
108, 105
Climbing by twining stem, 106,
102, 107, 103
Clover attacked (by dodder, no,
10(5, 107
Club-moss, 137
Coal, 153, 178
Collecting, 194
Colour of petals, 80
Cones of pine, 127, 128, 123
" Control plant," 16
Convolvulus, twining of, 106, 102
Cork, 95
Cornflower, 121, 122
Cotyledons of bean, 9, 4
Cotyledons of pine, 129, 130, 126
Cotyledons of rose, 66, 54
Cow- wheat, 113
DAHLIA, roots of, 56, 39
Daisy, flower of, 121, 121
Dandelion, fruit of, 88, #3
Darkness, effect on growth of,
38,27
Dead nettle, 68, 56, 149, 137
Deserts, 100
Dicotyledons, 126
Distilled water, 15
Ditches, 150
Dodder, no, 106, 107
Downs, 183
Duckweed, 151, 139, 161
Drowning, of trees, 185,
ELDER tree, twig of, 96, 96
Elodea, 21, 13
Embryo, 9
Excursions, 194
Eyebright, 113
FERNS, bud of, 134, 127
Ferns, family of, 133
Ferns, fossil, 179, 152 181
Ferns, prothallium of, 135, 129
Ferns, spore-cases of, 135, 128
Ferns, u sporeling " of, 136
Flowers, 78
Flowers in relation to insects,
118
Flowering family, 125
Food-building in leaves, 23
Food materials, 14, 18
Food solutions, 15
Fossils, 179, 151
Fossils, tree, 180, 153
Foxglove flower, 119, 117
Foxglove in hedges, 146, PI. IV.
Fruits, 86
Fucus, (see also Bladderwrack),
173, PL VII.
Fungi, 109
Fungi, spores of, 143
Fungi, structure of, 142, 133
GOOSE-GRASS, leaves of, 69, 60
Goose-grass, fruit of, 90, 87
Gorse, 102, 99
Gorse, flowers of, 119, 119
Grass, leaves of 66
Grass, roots of, 54, 37
Gravitation, 44
Growth, 40
INDEX
199
Growth, direction of, 41, 29, 43,
3
Growth, region of, 40, 28
H
HAIRS, 96
Harebell, 78, 69
Heather, 154
Hedges, 147, PL IV.
Holly, 54, 36
Honeysuckle, leaves of, 68, 57
Hop, 106
Horse chestnut, buds of, 72, 62
Horsetail, leaves of, 69, 59
Horsetail, family of, 137
I
INDIARUBBER tree, leaves of, 31,
20
Insects and flowers, 83
Iodine, n
Iron chloride, 16
Iron, importance of, 17
Ivy, adventitious roots of, 56, 40
Ivy, climbing of, 106, 101
Ivy as host plant, 112, 109
Ivy, leaves of, 65
Ivy, position of leaves of, 37, 26
LAKE or pond-maps, 193
Lamina of leaf, 64, 50
Laminarias, 175,149
Larch, branching of, 59, 44
Larch, family of, 127
Larch, seed-scales of, 128, 124
Larch, tufts of leaves of, 76, 67
Leaves, 64
Leaves, arrangement as regards
light, 36, 25, 37, 26
Leaves, arrangement on stem, 68
Leaves, compound, 65, 51
Leaves, form of, 64, 50
Leaves, " Mosaic," 37
Leaves, no growth without CO 2
20
Leaves, simple, 64, 50
Leaves, veins of, 67, 55
Lenticels of, 96, 96
Life, signs of, 4
Light, 35
Light from one side, 35, 23, 36,
24
Light, influence on position of
leaves, 36, 24, 25
Light, influence on size of leaves,
38, 2?
Light, influence of, in formation
of starch in leaves, 24
Lime-tree, stem of, 94, 95
Lime-water, 6, 2, 20, 12
Linear leaves, 66
Liverworts, 140, 152
Louse-wort, 113
M
MAGNESIUM sulphate, 15
Maize, seeds of, 10, 5
Maize, seedlings of, 10, 5, 13, 8
Maps of plants, 188
Marram grass (see Sandgrass),
166, 145
Marsh samphire, 1 68, 148
Mistletoe, 112, 108
Monkshood, 119, 118
Monocotyledons, 126
Moorland, 153, 140, 184
Moss, 138, 130
Moss in bogs, 156
Moss, capsule of, 139, 131
Moss, spores of, 140
Movement caused by light, 36,
24
Movement of minute plants, 48
Movement of sensitive plants, 46,
33, 34, 35
20O
INDEX
Movement of plants in sleep, 46,
32
Movement of tendrils, 45, 37
N
NASTURTIUM, movement of
leaves, 36, 24
Nasturtium, shape of leaves, 65,
52
Nasturtium, twining of petioles,
107, 103
Needle leaves, 66, 53
Nepenthes, 117, 115
Nitrogen, 19
Nucleus of cells, 92, 97
Nurse leaves (sec Cotyledons)
OAK, branching of, 59,
Orchid, roots of, 57, 41
Ovate leaves, 65
Oxygen, 19, 21, 73, 22
PALM, 57, 42
Palmate leaves, 66
Parasites, 109
Pea-flowers, 86, 80
Pea-fruits, 87, 81
Pea-pod (see Pod)
Pea-tendrils on leaf, 107, 104
Pea-tendrils t movement of, 45,31
p eat, 155, 179
Peltate leaves, 65, 52
Petals, 80, 121, 127, 122
Petiole, 64, 50
Petiole, twining of, 107, 103
Physical geography, 182
Pine-cones, 128, 123
Pine-family, 127
Pine-leaf, 66, 53
Pine-seeds, 129, 125
Pine-seedlings, 129, 126
Pitcher plants, 117, 1/5
Plantation of trees, 155
Pod of pea, 87, 81
Pollen, 81, 120, 127
Pollination, 83, 118
Pollination, arrangements to en-
sure cross-, 120, 120
Pond-maps, see Lake
Ponds, 159, PI. V. 185, 154, 155
Poppy, PL II.
Poppy capsule, 89, #5
Pores giving off water vapour, 31
Pores in stems, 96
Potassium iodide, n
Potassium nitrate, 15
Potato, starch in, n
Potato, underground stem of, 61,
P
Primrose flower, 80, 72, 84, 79,
120, 120
Prothallium, 135, 729, 139
R
RECEPTACLE of flower, 82, 7<5, 78
Reeds, 162, 144
Rhizome, 61, 46, 161, 743
Rice, starch in, n
Roots, adventitious, 56, 40, 57, 41
Roots, entrance of water into, 33,
27, 22
Roots, forms of, 54
Root-hairs, 13, #, 15, 9
Root pressure, 34
Roots of seedlings, 9
Roots, stilt-, 57, 42
Roots, storage in, 55, 38, 56, 39
Roots, uses of, 53
Rose, flowers of, 79, 70, 77, 118,
116
Rose-leaf, 65, 57
Rose-seedling, 66, 54
Runners of strawberries, 63
Rushes, 162, 144
SALTS, 14, 17, 27
Sandgrass (see Marram), 102, 700,
165, 145
INDEX
201
Sea, 174
Sea holly, 1 68, 147
Seaweeds, 143, 134, 135, 173
Seaweeds, colour in, 176
Section of pond, 192, 154
Section of stems, 93, 92
Seedlings, bean, 10, 6, 40, 2^,29
Seedlings, grass, 35, 23
Seedlings, maize, 10, 5, 13, 8
Seedlings, pine, 129, 126
Seedlings, rose, 66, 54
Seeds, 86, 125
Seeds, bean, 8, 3, 9, 4, 10, 6, 91, 89
Seeds, dodder, in
Seeds, larch, 128, 124
Seeds, maize, 10, 5, 91, 90
Seeds, mistletoe, 112
Seeds, pine, 129, 125
Sensitive plant, 47, 33, 34, 35
Sepals, 78, 69
Shore, 165, PL F/., 176, 750
Skin of leaf, 95
Skin of seed, 9, 3
Sleep of plants, 46, 32
Sodium chloride, 15
Solomon's Seal, 01, 46
Speedwell, 80, 73
Spines of cactus, 62, 99, 97
Spines of gorse, 102, 99
Spores, 135, 139, 140, 142
Stamens, 80, 72, 73, 81, 74
Starch, n, 12, 21, 23
Starch formed in leaves by sun-
light, 24
Starch stained by iodine, n
Starch stored underground, 26
Stellaria, 59, 45
Stems, 58
Stems bending again to earth, 63,
49
Stems, branching of, 59
Stems, breathing pores in, 94, 96,
96
Stems, fleshy, 62, 48
Stems, sections of, 93, 92
Stems, twining, 106, 102, no, 106
Stems, underground, 61, 46, 47
Stigma, 83
Stipules, 64, 50, 51
Stone-crop, 102, 98
Strawberry fruit, 90, 88
Strawberry runners, 63
Sundew, 114, no, 115, in
Sunflower, i, 2
Sunflower stem, 94, 93, 94
Sunlight, oxygen given off in, 21,
13
Sunlight helps to form starch in
leaves, 25
Sweet pea flower, 86, 80
Sweet pea fruit, 87, 81
Sweet pea leaf and tendrils, 45,
3i, 7, 61
Sweet pea seed, 87, 81
Sycamore, buds of, 75, 66
TENDRILS, movement of, 45, 31
Tendrils part of leaf, 70, 71
Tendrils assist climbing, 107, 104,
108, 105
Tissues, 93
Toadflax, 148, 136
Toadstool, 142, 133
Transpiration, 31
Traveller's Joy, 147
Tree ferns, 133, PL III.
Tubers, 61, 47
Tulip bulb, 77, 68
Tulip carpels, 82, 77
Tulip flower, 81, 75
Tulip stamens, 81, 74
V
VARIEGATED leaves, 26, 16
Veins of leaf, 67, 55, 95
Vine, 33
Violet, 84, 79, 119, 118
W
WATER, 12, 13
202
INDEX
Water, circulation of, in plant,
28,34
Water, entry into plant by roots,
33> 2 '> 22
Water given off by leaves, 28, 17,
30, 18, 19, 20
Water, protection against loss of,
99
Water stream in plants, 28, 34
Water vapour, 28, 17, 31
Water-buttercup, 159, 141
Water-lily leaves, 160
Water-lily, section of stem of, 93,
92
" Water-pipe " cells, 94, 97
Whorls of leaves, 69, 59
Whortleberry, 62
Willow herb, 89, 84
Wind, 154
Wood-sorrel, sleep of, 46, 32
THE NATURAL HISTORY OF PLANTS
THEIR FORMS, GROWTH, REPRODUCTION, AND DISTRIBUTION
FROM THE GERMAN OF THE LATE
ANTON KEENER VON JMARILAUN
Professor of Botany in the University of Vienna
TRANSLATED BY F. W. OLIVER, M.A., D.Sc.
Quain Professor of Botany in University College, London
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