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Title: The 'Look About You' Nature Study Books, Book 4 (of 7)
Author: Hoare, Thomas W.
Language: English
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[Illustration: Sweet Peas and Butterflies]
The
“LOOK ABOUT YOU”
Nature Study Books
BY
THOMAS W. HOARE
TEACHER OF NATURE STUDY
to the Falkirk School Board and Stirlingshire County Council
BOOK IV.
[Illustration: Publisher’s Logo]
LONDON: T. C. & E. C. JACK, Ltd.
35 PATERNOSTER ROW, E.C.
AND EDINBURGH
PRINTED IN GREAT BRITAIN BY
THOMAS NELSON AND SONS, LTD.
PREFACE.
This little book should be used as a simple guide to the practical study
of Nature rather than as a mere reader.
Every lesson herein set down has, during the author’s many years’
experience in teaching Nature Study, been taught by observation and
practice again and again; and each time with satisfactory result. The
materials required for most of the lessons—whether they be obtained from
the naturalist-dealer or from the nearest hedge, ditch, or pond—are
within everybody’s reach.
There is nothing that appeals to the heart of the ordinary child like
_living things_, be they animal or vegetable, and there is no branch of
education at the present day that bears, in the young mind, such
excellent fruit as the study of the simple, living things around us.
Your child is nothing if not curious. He wants to understand everything
that lives and moves and has its being in his bright little world.
Nature Study involves so many ingenious little deductions, that the
reasoning powers are almost constantly employed, and intelligence grows
proportionately. The child’s powers of observation are stimulated, and
his memory is cultivated in the way most pleasing to his inquiring
nature. By dissecting seeds, bulbs, buds, and flowers, his hand is
trained, and methods expeditious and exact are inculcated. By drawing
his specimens, no matter how roughly or rapidly, his eye is trained more
thoroughly than any amount of enforced copying of stiff, uninteresting
models of prisms, cones, etc., ever could train it.
The love of flowers and animals is one of the most commendable traits in
the disposition of the wondering child, and ought to be encouraged above
all others.
It is the author’s fondest and most sanguine hope that the working out
of the exercises, of which this booklet is mainly composed, may prove
much more of a joy than a task, and that the practical knowledge gained
thereby may tempt his little readers to study further the great book of
Nature, whose broad pages are ever open to us, and whose silent answers
to our manifold questions are never very difficult to read.
T. W. H.
CONTENTS
LESSON PAGE
I. Structure of Stems 7
II. Bulbs and Corms 12
III. What Goes on Inside a Plant 17
IV. Snowdrop, Crocus, and Tulip 23
V. Vegetable Fingers 29
VI. The Great Water Beetle 35
VII. Daisies 40
VIII. Chaffinch and Song-Thrush 46
IX. Plants that Arm Themselves 52
X. The Horse Pond Again 58
XI. Wasps 63
XII. Dandelions 69
XIII. The Life of a Trout 75
XIV. Silkworms 81
Appendix 88
“LOOK ABOUT YOU.”
BOOK IV.
I.—STRUCTURE OF STEMS.
“We are going to have a peep into the inside of these twigs,” said Uncle
George, as he laid some willow and horse-chestnut twigs on the table.
“First,” he said, “let us examine the outside of them.” He handed a
small willow branch to Tom and a horse-chestnut branch to Frank.
“Now, Frank, tell me all you see.”
“I see the rings of scars which mark each year’s growth,” said Frank.
“This year’s growth is at the top, above the first ring of scars. Below
this is last year’s growth. Then comes another ring of marks, and below
this again is the growth of two years ago.”[1]
“That is to say,” said his uncle, “the upper part of your twig is about
one year old, the middle part is two years old, and the lower part is
three years old. Go on, Frank.”
“The upper part is light brown, while the middle and lower parts are
dark brown.”
“Take your lens, Frank, and look at that brown covering carefully.”
“Oh, it is studded all over with little oval marks like pits,” said
Frank.
“Now, what about the buds?”
“The buds,” said Frank, putting down his lens, “are in pairs; and the
stem is swollen where each pair of buds comes off.”
“Very good,” said Uncle George. “That is exactly what I wanted you to
notice. The swollen parts of a stem are called its _nodes_. In every
stem, buds and leaves occur at the nodes. Nodes are very well seen in
grass and corn stems.”
“Then at the top of the twig there is a very large bud and a pair of
small buds, one on each side of it,” said Frank.
“You have described it very well,” said his uncle. “Now, Tom, what about
the willow twig?”
“I see some very tiny marks on it,” said Tom. “There are no rings
marking the year’s growth; and the buds are not arranged in pairs.”
[Illustration: Horse-Chestnut Twig, showing Three Years’ Growth.]
“That is quite right, Tom. Willow grows very quickly. Your twig is all
one season’s growth. It is smooth and green—not brown like the
horse-chestnut twig. The buds are arranged alternately. That is to say,
there is only one bud at each node.”
“Now, let us see what the horse-chestnut twig is made of.”
Uncle George next cut two pieces off the top part of the horse-chestnut
twig and handed one to each of the boys.
“Now, take your knives,” he said, “and carefully peel off a very small
piece of the brown covering. You will have to be very careful, as it is
very thin and rather difficult to remove. Ah, Frank, you have done that
very nicely. Now, hold it up to the light and tell us what you think it
is for.”
“It is the skin or covering of the twig,” said Frank.
“It is; and if you look with your lens you will see that the tiny
markings on it are holes. It is really a thin layer of bark or cork.
Perhaps you can tell me why the twig is covered with a thin layer of
cork?”
“To keep water from getting in,” said Frank.
“Rather to keep water from getting _out_,” said Uncle George. “You must
remember that water is continually passing up stems from the roots.
Water cannot pass through cork. If we were to remove the cork layer from
the outside of a growing twig, that twig would shrivel up and die. There
is also a layer of cork protecting the willow twig, but it is so very
thin that we can see through it. Remove as much of the cork layer as you
can, and tell me what is underneath.”
“There is a layer of green stuff beneath,” said Frank.
“Just so,” said Uncle George. “Now, if you remember, I once told you
that plants took most of their food from the air by means of the green
stuff in their leaves. This green layer in the twig does the same thing;
but how can the air get in if it is covered up by a layer of cork?”
“Oh, I see now,” said Tom, “what the tiny holes or pits are for—to let
air in to the green layer underneath.”
[Illustration: Diagram Sections of (A and B) a One-Year Old and (C and
D) Two-Year Old Stem.]
1. Bark.
2. Green Layer.
3. Bast.
4. Slippery Layer.
5. Wood.
6. Pith.
“That is what they are for, Tom,” said Uncle George. “Scrape away this
green layer. It is greenest on the outside and is rather thick. There
are really two or three layers there, but they cannot be separated with
a pen-knife. What do you come to next?”
“A white, woody layer with a very slippery surface,” said Frank.
“That slippery surface is itself a layer, and a very important one,”
said his uncle. “The wood, you can see, is a very thick layer. In the
centre you have a mass of dry, spongy stuff. This is called the pith.”
Uncle George then cut the twig straight across, and the boys saw that
each layer formed a ring. In the middle there was a round mass of pith.
Around this was a thick ring of wood with the thin slippery layer
outside. Outside this was a fairly thick ring, the outer half of which
was green in colour. And outside the whole lot was the ring of the thin
bark or cork which the boys had first examined.
“We have seen,” said Uncle George, “how a one-year-old stem is built.
Let us now make a clean cut through the two-year-old part of the twig,
and another through the three-year-old part.
“You see there are two rings of wood in the two-year-old part and three
rings of wood in the three-year-old part. What does this show us?”
“That a ring of wood is added every year,” said Frank.
“And so, three years ago, this thick branch was a tiny bud,” said Uncle
George, pointing to the lower part of the twig.
Exercises on Lesson I.
1. An apple will keep sound for months if the skin is unbroken. If we
remove a small piece of the skin, the apple soon shrivels up.
How is this?
2. Can you explain why we ought not to eat the outer skins of the
plum, grape, tomato, pear, etc.?
3. Cut a stout twig of any tree straight through. Make a rough sketch
showing the different layers, and tell how old the twig is.
4. Get stout twigs of different trees, such as ash, elm, holly,
sycamore. Take about an inch length of each. Split these down
the centre, and see if you can make out the different layers
on each side of the pith. Make an enlarged drawing of one of
these.
II.—BULBS AND CORMS.
“These,” said Uncle George, “are what we grow our snowdrops and crocuses
from.”
As he spoke he handed each of the boys a few hard, round objects. Some
of these were small, white, and almost pear-shaped. The others were
larger, rounder, and brown in colour.
“The small white ones are snowdrop _bulbs_,” he continued. “The others
are crocus _corms_. There is a great difference between a bulb and a
corm, as we shall see when we examine and compare them.”
“The corm is covered with brown, papery skins, and has white buds on the
top of it,” said Frank.
“These brown skins are leaves,” remarked Uncle George.
“Leaves?” said Tom. “I thought all leaves were green.”
“Oh no, Tom, there are other leaves besides green leaves, called
scale-leaves. Green leaves, as you know, give off the moisture which the
roots take up from the soil. They also take in plant-food from the air.
Scale-leaves protect buds, flowers, and tender stems from cold and from
insects. These thin brown leaves of the crocus corm are scale-leaves
formed underground. Please remove the brown scale-leaves from one of the
corms, Frank.”
[Illustration]
1. Snowdrop.
2. Tulip.
3. Narcissus.
4. Crocus.
When Frank had done so, it was seen that these leaves were attached in
layers all round the corm. The corm was now a white, rounded lump. The
removal of the scale-leaves had left thin rings of leaf-marks; and on
these leaf-marks, here and there a tiny bud was seen.
“Now,” said Uncle George, “we can see that a corm is a stout, swollen,
underground stem. If you could imagine a horse-chestnut stem to be
squeezed up into a lump, you would have something like a corm. These
rings of leaf-marks are the nodes, where leaves and buds are found on
all stems. The large buds on the top of the corm correspond to the large
buds at the end of your horse-chestnut stem. Now, let us take off one of
these large top buds. Notice that it is covered with many tough,
protective scale-leaves.”
[Illustration: Crocus Bud Dissected.]
1. Scales.
2, 3, 4. Parts of Flower.
5. Leaves.
6. Spathe.
7. Ovary.
8. Young Corm. A. Old Corm.
Removing these scales, Uncle George came to a round object in the
centre.
“This,” he said, “is a long sack or bag. It contains the flower of the
crocus.”
Taking a needle, he carefully opened this up.
“Now, boys,” he said, “take your magnifiers and look carefully.”
Frank and Tom looked, and saw a curious little flower, surrounded by
four or five yellow needle-shaped things which, their uncle told them,
were the young green leaves of the crocus.
“Let us now,” he said, “examine the snowdrop bulb.
“Here we have thick, fleshy scale-leaves. If we remove them one by one,
we find that they are all attached to a flat, button-shaped stem.
Between the thick scale-leaves we see, here and there, a small side bud,
and on the top the baby snowdrop flower snugly wrapped up in their sack.
This protective sack is called a _spathe_.”
Uncle George then took from his pocket a very large bulb.
“This,” he said, “is the bulb of the narcissus or ‘white lily.’ It is
almost exactly like the snowdrop bulb, but it is larger, so that we can
see things much more distinctly.”
He then split the large bulb down the centre with his knife. With a pin
he pointed out the baby flower wrapped up in its spathe. All the parts
of the flower were seen, even the little seed-vessel containing the tiny
eggs, which become seeds after the flower has grown up.
“If you remember,” said Uncle George, “in our lesson on seeds we learned
that a seed contained a baby plant and a large supply of plant-food. I
am now going to show you that both the corm and the bulb contain a large
food supply. We have seen that the protective bud-scales in the corm are
tough and thin, while the stem is swollen and hard. In the bulb, on the
other hand, the bud-scales are thick and fleshy, while the stem is flat
and very small. If we place some of our crocus corms or snowdrop bulbs
in pure water, they will grow and flower just as well as if we had
planted them in the garden. What does this show us?”
“That, like the seeds which we grew in water, bulbs and corms contain a
store of food,” said Frank.
[Illustration]
A. Narcissus Bulb split open.
s., stem;
b., side buds;
s.l., scale-leaves;
f.l., leaves.
B. Snowdrop Bulb.
C. Flower of same Dissected out.
“That is correct, Frank. Let us put a corm and a bulb in water. Let us
also plant one of each in a pot of soil. We will watch them growing and
compare them from week to week.
“Now I am going to show you a simple experiment. You know that the food
we eat is drawn largely from plants. This food which we take from the
plant world is chiefly what the chemist calls _starch_. We have it in
bread, potatoes, rice, cornflour, and in nearly all the vegetables we
eat.
“I have here in this bottle a substance, called _iodine_, dissolved in
water. Anything containing _starch_ turns blue when touched with iodine.
Now observe what happens here.”
Uncle George poured some of the iodine into a saucer. He then dipped
into the iodine a piece of crocus corm, a thick scale of the snowdrop
bulb, soaked seeds of maize and wheat, a slice of raw potato, and a
piece of bread. Each at once turned dark blue on being dipped into the
liquid.
“Now, boys,” he said, “what do you learn from this?”
“The food store in bulbs and corms is the same as that in seeds,” said
Tom.
“The food supply of the bulb is contained in the thick, fleshy
scale-leaves, while in the corm it is in the stem,” said Frank.
“Very good,” said Uncle George. “It also shows us, I think, that we
ourselves owe a great deal to the plant world.”
Exercises on Lesson II.
1. Split an onion (or tulip bulb) down the centre, and compare it with
the snowdrop bulb. Draw it, giving special attention to the
middle part.
2. Take a potato and a crocus corm. Observe them both carefully, and
find out (1) how they resemble each other, and (2) how they
differ.
3. Explain how it is that a hyacinth grows so well in water.
4. Take any underground stem (_e.g._, iris or Solomon’s seal) and
compare it with a crocus corm. Notice the marks of underground
scale-leaves on the former.
III.—WHAT GOES ON INSIDE A PLANT.
“We have seen how an ordinary twig is built up,” said Uncle George. “Let
us now try to find out what goes on inside the twig; and in order to do
this we shall have to perform one or two simple experiments.”
Uncle George took two wide-mouthed glass jars. They were both perfectly
dry, and each could be closed with a large, tight-fitting cork. He
placed some fresh green leaves inside one of the jars. The other
remained empty. Then both jars were tightly corked up, and both corks
covered outside with wax.
[Illustration: First Experiment.]
“That is experiment number one,” he said, as he placed both jars in the
window.
He next took a small plant which was growing in a pot. He wrapped the
pot up in thick, dry paper, so that the paper covered up everything but
the plant. The edges of the paper were tied tightly round the lower part
of the stem of the plant with a string. The plant was put in the window,
and over it Uncle George placed a glass bell-jar.
[Illustration: Second Experiment.]
“The third experiment is much simpler,” he said. “You see I just put one
of the willow twigs into a glass half filled with water, and into the
water I pour some red ink. Frank, place a white pansy in the coloured
water beside the willow twig.”
Uncle George’s fourth experiment was as follows:—
He placed four willow twigs in a glass of water. But from two of these
twigs he first removed a broad ring of the bark and outer layers,
leaving about an inch of the wood bare near the lower end of the twig.
“Now,” said he, “we will come back in about an hour, and I think we
shall find that some change has taken place in each of our first three
jars.
“The fourth glass one will have to be left for several weeks; and we
must take care to keep water always in the glass containing these four
twigs.”
About an hour afterwards, Uncle George and the boys came to look at the
experiments.
“Let us examine experiment one first,” said Uncle George.
“The empty jar is just the same as when we put it there,” said Tom. “The
jar containing the leaves is all dimmed, and there are tiny drops of
water on the inside of it.”
“Where did that water come from, Tom?”
“It must have come out of the leaves.”
“Exactly so! Now look at the second experiment, and you will see that
the bell-jar which covered both plant and pot is also dimmed with
moisture. Pot and soil were securely covered up, so that this moisture
on the glass must have come from the leaves of the plant. Where do you
think this water really comes from?”
“From the soil in the pot,” said Frank. “If we did not water those
plants which we keep in pots, they would die.”
“Then we have learnt that water travels up the stems of plants,” said
Uncle George, “also that it is drawn from the soil and is given off by
the leaves. The third experiment, where we placed a twig in coloured
water, will, I think, show us which part of the stem the water travels
up.”
Uncle George peeled the bark off the lower end of the willow twig which
was placed in the mixture of red ink and water. He removed all the
layers until he came to the wood. The wood was stained red. He cut slice
after slice off the twig, and it was found that the coloured water had
gone quite an inch up through the wood. None of the other layers of the
twig were stained red.
“It travels up through the wood-layer,” said Frank. “And look at the
pansy flower. It was white when we put it into the glass, now it is all
streaked with red.”
“The flower itself,” said Uncle George, “is not near the coloured
water.”
“The water must have travelled up the long stalk to the flower,” said
Frank.
[Illustration: The Fourth Experiment.]
The fourth experiment was left in the window, and two or three weeks
passed before any change was noticed in any of the four twigs which had
been placed in the water. Then roots began to grow. In the two whole
twigs these roots grew out at the bottom end. But in those twigs from
which the belt of outer layers had been removed, it was quite different.
Here the roots grew out—not at the bottom, but just where the ring of
bare wood began and at the top of it.
Frank and Tom were quite puzzled. They could not understand why the
roots should come at the bottom in two of the twigs and not in the other
two.
“First of all, then,” said Uncle George, “these new roots were made from
materials which came from inside the plant. These building materials are
carried through the plant dissolved in water—just as you dissolve sugar
in your tea. Water containing these dissolved stuffs in a plant is
called _sap_.
“We have seen, by our first three experiments, that water travels up the
wood part of the stem. This experiment shows us that sap travels _down_
the stem in the layers outside the wood. For, when I removed the outer
layers and left a bare ring of wood, the flow of the sap was stopped and
the new roots formed there.”
“And where does this sap come from first of all?” Tom asked.
“It is really formed in the leaf first of all. I think I told you that
plants take most of their food from the air by means of their green
leaves. In the great quantities of water which pass up the wood and into
the air from the leaves there is always a very little mineral matter
dissolved. This small quantity of mineral matter comes from the soil.
This, along with water and the large quantity of matter taken from the
air, are changed, inside the leaf, into a fluid which we call sap.
“Our four experiments show us that water travels up through the
wood-layer from soil to leaf; and also that sap travels down through one
of the outside layers of the stem.”
Questions on Lesson III.
1. How does water travel in a plant? How can you prove this?
2. If we enclose a leafy plant in a glass vessel, we see that water is
given off by the leaves. How is it that we do not see this
water when the plant is grown in the open air?
3. What is “sap”? Where is it first formed? How does it travel in the
twig or stem?
4. If we keep ferns growing under a glass bell—or in a glass case—we
never have to water them. Can you explain this?
IV.—SNOWDROP, CROCUS, AND TULIP.
The boys watched the growth of the crocuses in water and in soil from
day to day, and made sketches of them once a week. Fed by the food
contained in the corm, the top buds of the crocus grew longer. Then the
scales moved apart and the yellow flower was seen. Round about it were
four or five narrow green leaves, each having a pretty white stripe down
the middle. Both leaves and flower were encircled at the base by long
white sheaths.
The crocus grown in the pot did not seem to thrive much better than the
one in the water. Both flowers remained closed for a long time after
they were full grown.
At last, on one fine sunny day, they opened out wide at the top, and the
boys could see right down into them. In the evening they closed up
again. Next day was a dull day, and the crocus flowers remained closed.
The snowdrops were also watched and sketched. Their growth was somewhat
different. From the centre of the little bulb two green leaves first
appeared. These leaves were much broader and thicker than those of the
crocus. From between these leaves a little white, flat object grew up.
This the boys at once recognised as the spathe or bag containing the
flower. Then more green leaves came up. The flower-stalk grew longer.
The spathe split open, and the flower-bud appeared.
This bud grew until it became a beautiful white bell hanging downwards.
[Illustration: Crocus Flowers.]
In a large pot Uncle George had planted a few tulip bulbs. They were not
completely covered with soil, so that their growth could be watched.
Their growth was similar to that of the snowdrop. The leaves came first.
They were rolled firmly round each other. As each large, broad, green
leaf unrolled, another rolled-up leaf was seen under it. These leaves
were rolled round a thick stalk, to which they were attached. When the
last leaf unrolled, a single flower was seen at the top of the stalk.
This flower remained closed up like the crocus. When at length, however,
the warm sun shone in the window, the tulip flowers opened out very wide
indeed; in fact, they became almost saucer-shaped.
Then Uncle George dug the snowdrop and crocus out of their pots. He
washed the roots and asked the boys to compare them with those grown in
water.
“The plants grown in soil seem stronger in flower and leaves,” said
Frank. “But the greatest difference is in the corm and bulb.”
“That is right, Frank,” said Uncle George. “Look at the crocus corms.
They have both shrunk a great deal, because they have been used up to
form what has grown out of them. But the one grown in soil has formed a
new corm, which will produce new flowers next year. This new corm has
grown upon the top of the old one. The crocus grown in water has also
produced a new corm, but it is too small to produce a flower next year.
“Then, again, take the snowdrop. The one grown in the soil has produced
two or three new bulbs, while that grown in water has not. These new
bulbs were the side buds we noticed between the scales when we opened
out our snowdrop bulb. In both snowdrops the old bulb has been
completely used up to form green leaves and flower.
“But the bulb grown in soil has not only produced flowers and green
leaves. It has gathered up enough material from soil and air to form new
bulbs for next year.”
[Illustration]
1. Snowdrop Flower—_A_, the spathe.
2. Crocus Plant.
3. Old and Young Corms of Crocus.
4. Young Snowdrop Flower enclosed in its spathe.
5. Crocus Flower.
6. Tulip Flower dissected.
Uncle George then divided the crocus flower with his knife from top to
bottom.
“At the very bottom of the flower,” he said, “you see the ovary, or
seed-vessel, containing the tiny seeds. From the seed-vessel a long thin
rod or tube stretches to the very mouth of the flower. You can also see
the remains of the spathe which once enclosed the whole flower.”
“And what are those three things covered with orange-coloured dust?”
asked Tom.
“These,” said his uncle, “are the stamens or pollen-boxes; and the
orange-coloured powder is the pollen. This pollen is carried about from
flower to flower by the bees. Pollen is necessary for the production of
seeds.
“Do you know why the seed-vessel of the crocus is so far down under the
ground?
“It is because the crocus flowers in winter-time, and the frost might
kill the young seeds. Underground they are safe from frost. The snowdrop
is a hardy flower, and, besides, the walls of its seed-vessel are very
thick.
“The tulip, if grown outside, flowers much later than the other two
plants.
“Notice the difference between the flower of the tulip and those of
either crocus or snowdrop. Its petals are all separate, while those of
the others are joined to form a bell or tube. The seed-vessel of the
tulip, also, stands right up in the centre of the flower, while that of
the snowdrop (and crocus) is placed underneath the flower altogether.”
“How is it, Uncle George, that the flowers of both tulip and crocus open
out wide when the sun shines and close when the sun goes down?” asked
Frank.
“Plants can feel to a certain extent,” said Uncle George. “That is to
say, they are affected by heat and cold, by light and shade. A great
many flowers close up at night—the daisy, for instance; and have you
never noticed how clover leaves fold up long before night comes?”
“Yes, but why should the crocus and tulip open and close? The snowdrop
never closes up.”
“They do so to protect their pollen,” his uncle answered. “Rain or dew
would ruin pollen. Those flowers, like the crocus and tulip, which open
out to the sky must close up, or the precious pollen would be destroyed.
Flowers like the snowdrop and bluebell, which hang downwards, have no
need to close up, for their pollen is under a roof of joined petals.”
Exercises on Lesson IV.
1. Place an onion or daffodil bulb in the mouth of a bottle containing
water. Keep it in the dark for about ten days. Then place it
in the window. Make sketches every week.
2. Make a list of all the plants you know which close their flowers,
or fold up their leaves, at night.
3. Cut open a flower of the daffodil (or narcissus), also one of the
wallflower. Draw both, naming their parts. What points of
difference do you notice in the two flowers?
4. Examine the following flowers, and see if you can find where the
young seeds are:—Hyacinth, primrose, violet (or pansy),
chickweed, Christmas rose, shepherd’s purse.
V.—VEGETABLE FINGERS.
When the sweet-peas in the garden were nearly full grown, Uncle George
sowed some sweet-peas in a pot. In a fortnight those sown in the pot
were about four inches in height, and those in the garden were in
flower.
“Let us go into the garden, boys,” he said, “and see if we can learn
something from the sweet-pea.”
In the garden the sweet-peas were really lovely. They looked, as Frank
said, like so many beautiful butterflies on the wing; and they filled
the air with delicious perfume.
“I think,” said Frank, “that our row of sweet-peas is by far the best
thing in the garden.”
“That is quite true, Frank,” said his uncle, “but it is not so much the
flowers we are going to study at present. The sweet-pea is certainly one
of our finest flowering plants. It is also one of the most interesting.
Can you tell me why we put stakes up for our sweet-pea plants to cling
to?”
“Because they have long, slender stems—too slender and weak to grow up
by themselves,” said Frank.
“Quite right, Frank. If the sweet-pea were a wild plant, where would it
grow?”
“In the hedges,” said Tom.
“Right again,” said Uncle George. “If we grow the sweet-pea in the
garden, we must imitate its surroundings in the wild state—we must give
it a hedge of some kind to cling to, otherwise it would trail along the
ground.”
“Then it would get choked among the other plants,” said Frank.
[Illustration]
Rose Leaf.
Vetch Leaf.
Ash Leaf.
“What do you mean by ‘_choked_,’ Frank?”
“Well, it would die for want of air”——
“And light,” his uncle added. “No green plant can live without air and
sunlight; and, in order to get these, our weak-stemmed sweet-pea has to
climb. It clings to its stronger brethren just as the wild peas do in
the hedgerow. Now notice how it climbs. The end part of each leaf
consists of little gripping organs called tendrils. These twine tightly
round the smallest twigs near them.
[Illustration]
1. Ox Eye.
2. Daisy.
3. Corn Marigold.
“Here is a rose leaf. It is composed of several leaflets, and at its
base there are two small, brownish-green things called _stipules_. If we
compare this leaf with the leaf of the sweet-pea, we find that in some
points they are similar, but in others very different.
[Illustration]
Sweet-Pea.
Edible Pea.
“The rose leaf is called a compound leaf, because it is made up of many
small leaflets. The sweet-pea leaf is also a compound leaf, but it has
only two leaflets, and these are of enormous size. The rose leaf has two
small stipules. The stipules of the sweet-pea leaf are large and green.
“If I place the rose leaf beside a sweet-pea leaf, you will notice that
the latter has _no upper leaflets_.”
“It has tendrils ‘instead,’” said Frank.
“Exactly!” said Uncle George. “These tendrils correspond to leaflets.
Now, if the plant has been forced to turn all its leaflets, except two,
into gripping organs, how does it manage to make up for this loss of
green leaves?
[Illustration: Young Edible Pea.]
“We have already learned that plants take in food from the air by means
of the green substance in their leaves. The more of this green substance
a plant possesses, the more food it can take in from the air. If it
sacrifices leaves in order to climb up to the light and air, its amount
of the green material must be lessened. But the sweet-pea makes up for
this loss of leaves. Can you see how it does so?”
“The stipules are very large,” said Frank.
“And the lower part of the leaf-stalk is very flat, broad, and green,”
added Tom.
“Very good,” said Uncle George, “but look at the long, slender stem. It
has flat, green, ribbon-like outgrowths on each side throughout its
whole length. So, you see, what the plant loses in leaves, it makes up
in another way.
“Let us now look at the ordinary pea plant. Its leaf has four pairs of
leaflets and three pairs of tendrils besides the terminal tendril—seven
tendrils altogether. The stipules here are also very large—much larger
than those of the sweet-pea. But the stem is round and smooth. There are
no green outgrowths. Here is a wild pea, which I found to-day, which has
no leaves at all. All its leaflets have been turned into tendrils or
gripping organs. But look at the enormous stipules it has! They are much
bigger than ordinary pea leaves.
[Illustration]
A Wild Pea with no Leaves.
Young Sweet-Peas have no Tendrils.
“Let us now look at the tendrils of the sweet-pea, and see how they grip
their supports. Notice that they begin to twist long before they reach
the supporting twig. Then, when they have reached it, they twist round
it _in the opposite way_—just like a piece of string, if you twist it at
one end, it untwists at the other.”
“Can you see any reason for this coiling before it reaches the twig?” As
he spoke, Uncle George pulled a sweet-pea plant out from its supports,
and the boys saw that the tendril was really a spiral spring. The plant
could be pulled out a considerable length without breaking the tendril.
“You see,” Uncle George continued, “if it were not for that first
coiling of the tendril—that is to say, if the tendril grew out straight
and only began to twist when it reached the twig—the first breeze of
wind would snap the plant from its supports and it would fall to the
ground.
“Look now, at the young sweet-peas which we grew in the pot. They are
without tendrils of any kind. This shows us, I think, that the sweet-pea
was at one time a small plant, like its relative the clover. It grew in
open places and did not have to struggle for light and air. But, by and
by, when strong growing plants took up the soil, it became forced to
produce climbing organs or become choked out. And, having turned its
leaves into climbing or gripping organs, it made up for the loss of
leaves by producing large stipules and green out-growths to stem and
leaf.”
Exercises on Lesson V.
1. Draw a leaf of the wild rose and one of the sweet-pea side by side.
2. Make a list of all the climbing plants you know, and state how each
climbs.
3. Look for stipules on the apple, pansy, and bean leaves—make
sketches.
4. Those plants of the pea family which have many leaflets have smooth
round stems. Those which have few leaflets have “winged”
stems. Can you explain this?
VI.—THE GREAT WATER BEETLE.
During summer the boys paid many visits to the horse pond. Each time
they went there they saw something to interest them.
Their uncle taught them to keep perfectly still while looking into the
water. They soon came to know that this was the best way to study
pond-life, for, whenever they moved, the creatures they were watching
would dart out of sight.
One day, while they were both lying on the bank gazing into the pond, a
huge black beetle came up to the surface of the water. It remained there
for a few moments, with its head hanging downwards and its tail sticking
right out of the water. Then it dived down out of sight. In a few
minutes it came up again, and this time Frank’s net was under it before
it could escape.
Just as Frank was putting it into the glass jar, Tom whispered, “Here is
another one—quick, Frank!”
But Frank was too late; for before he could get the first beetle into
the jar, the second one had dived to the bottom of the pond. The boys
waited for a long time, hoping to see the other beetle again. At last
their patience was rewarded. The beetle came up again to the surface. As
soon as it did so, in went the net, and out came beetle number two.
“What big beauties,” said Frank. “I wonder what they are. Let us hurry
home and show them to Uncle George.”
When they got home, their uncle placed the two beetles in a glass tank
by themselves, so that they could be more easily observed.
“What do you call them, uncle?” asked Frank. “We have never seen such
large, handsome beetles before.”
[Illustration: Dyticus Beetle, male and female.]
“Have you not?” his uncle replied. “I am surprised at that, for this
beetle is found in nearly all our ponds and ditches. It has a long Latin
name,[2] which means _Bordered Diver_, but it is commonly known as the
‘great water beetle.’ There are several kinds of these diving beetles.
This is the largest. Can you give me an idea of their size?”
And Uncle George handed Frank a small measuring rule which he carried in
his pocket.
Frank looked at the beetles, and then moved his thumb nail along the
rule.
“About an inch and a half in length,” he said.
“That is about right,” said his uncle. “Are these two beetles exactly
alike?”
“They are both about the same shape and colour. One is slightly bigger
than the other. They are both greenish-black above and brown below.
There is a curious broad border of yellow all round the edge of their
bodies,” said Tom.
“But they are not both exactly alike,” said Frank, “I notice that one is
smooth on the back, while the other’s back is all grooved.”
“You are right, Frank,” said Uncle George. “The one with the grooved
wing-cases is the female. The one with the smooth cases is the male.
[Illustration: Fore Leg of Male, showing Sucker Organ.]
“Notice the long legs they have for swimming, and how they seem to oar
themselves through the water. Notice also that the male has a large flat
disc upon each of his fore legs. These are suckers, by which he can
cling to things.”
“Why do they come up to the surface so often?” Frank asked.
“They cannot live without air. They carry a supply of air under their
wing-cases. They just come up to renew it from time to time. This is
done by thrusting the end of their bodies out of the water as you see.”
“One would think they ought to thrust their heads out to get air,” said
Tom.
“That seems more natural to us, because we breathe with our mouths,”
said Uncle George. “These animals take in air with their tails. A great
many pond insects breathe in this curious way.”
“What do they feed upon?” Frank asked.
“They are fierce, greedy creatures,” his uncle replied. “They attack and
kill worms, tadpoles, and even small fishes.”
Uncle George threw a small worm into the tank. One of the beetles seized
it at once and began to devour it greedily. Presently the other beetle
seized an end of the worm. The boys watched closely, and saw that the
beetles’ jaws moved from side to side like a pair of pincers.
Next morning, when Uncle George and the boys went in to see the beetles,
they found only one in the tank. The other had escaped during the night.
After a careful search they found it, at the far end of the room, dead.
“Now, how do you think this beetle managed to get out of the tank and
travel all that way?” Uncle George asked.
“It must have crawled up the inside of the tank, then down the outside.
Then it must have fallen off the window-sill, and crawled right across
the floor,” said Frank.
Uncle George shook his head.
“It might,” he said, “have managed to crawl up to the edge of the tank
so long as its legs were wet. But as its long legs are made for
swimming, and not for crawling with, I can hardly see how it could have
crawled or walked all that distance.”
“Then how did it get there, Uncle George?”
In answer to Frank’s question, his uncle took the dead beetle, and
placed it on a piece of paper on the table. He next moved aside each of
the large black wing-cases with a pin.
Underneath these wing-cases the boys saw a pair of large wings neatly
folded up. Uncle George removed one of the wing-cases, and unfolded one
of the wings. Stretched out, it was longer than the beetle’s body, and
it seemed to be made up of thin, clear skin, stretched on a framework of
long, thin supports.
“Why, these beetles can fly,” said Tom.
[Illustration: Male and Female Beetles, showing Flying Wings.]
“Of course they can,” said his uncle. “All beetles can fly. This
creature has evidently been flying about the room all night. These
insects are furnished with wings, so that they may be able to fly to
another pool when food gets scarce, or when their pool dries up.”
Exercises on Lesson VI.
1. Would you keep water beetles, tadpoles, and stickle-backs together?
Give your reasons.
2. Water beetles cannot live without air. Explain how they get it.
3. Compare the legs of a water beetle with those of any of our garden
beetles.
4. Why are water beetles furnished with wings?
VII.—DAISIES.
While Uncle George and Frank and Tom were having a game of cricket,
Dolly was amusing herself in another way. She had pulled a bunch of
daisies and was joining them up into a daisy chain.
[Illustration: Common Daisy.]
She finished her daisy chain just as her uncle and the boys finished
their game.
“We will take some daisies home,” said Uncle George. He stooped down and
dug out a whole daisy plant with his knife, while Dolly gathered a small
bunch of the flowers. When they got home Uncle George placed his daisy
plant in a saucer of water, and told the boys to bring out their
magnifiers and sketch-books.
“First of all,” he said, “I want you to look at the daisy plant. Notice
its leaves. Each leaf is broad at the end and narrow where it joins the
plant. Notice also that the leaves all form a round green mat on the
ground. Now, can you tell me what the leaf resembles in shape.”
[Illustration]
1. Daisy Leaf.
2. Primrose Leaf.
3. Cowslip Leaf.
“It is like a spoon,” said Tom. “It is,” said his uncle; “and can you
see any reason for it being so shaped?
“You cannot? Well, I must tell you. All plants whose leaves are all at
the ground have leaves shaped something like this. The primrose and
cowslip are good examples. We have seen that plants, like the pea, climb
up so that their leaves and green parts may get as much light and air as
possible. And if you look at any tree, such as the horse-chestnut, ash,
elm, or beech, you will notice that their leaves are spread out so as to
catch as much light as possible.”
Uncle George then drew a circle.
[Illustration]
1 and 2. Diagram to show Leaf arrangement of Daisy.
3. Head of Daisy split.
4. Outer Floret.
5. Inner Floret.
“Now, boys,” he said, “I want you to try to fill that circle with leaves
so shaped that they will fill it without covering one another. The best
way to do so is to make them broad at the end. If you make them broad at
the base and narrow at the end, they overlap and rob each other of light
and air. Now you can see why the leaves of the daisy are so shaped.
“Take up a daisy and split it down the centre with your knife. You will
notice that the daisy is _not_ a flower, but a collection of tiny
flowers, or florets, all packed closely together upon a pad or disc, and
surrounded outside by many little green things like small leaves. These
little leaf-like things are called _bracts_.”
[Illustration: London Pride, showing Leaf arrangement.]
“There are two distinct kinds of florets,” said Frank, looking at the
split daisy with his lens.
“Yes,” said Uncle George, “you will see them better if you remove one of
each with a pin, and examine them separately.”
“The outer florets are very large and white,” said Frank.
“They are very flat, while the inner ones are yellow and round. They are
very like small crocus flowers. What is that small two-headed thing that
comes out in the centre of each floret?”
“That is the part which leads to the seed-vessel. Can you see the
seed-vessel at the bottom of each floret?”
“Yes,” said Tom, “it is large and round. On the top of it and all round
the petal part of the floret there are long silky hairs.”
“In flowers of this kind, when the seeds are ripe they are carried away
by the wind,” said Uncle George. “The petal part withers, but the tuft
of hairs remain. They are to the seed what sails are to a ship. They are
much better seen in some other flowers related to the daisy, such as the
thistle.
“Now cut open the seed-vessel and see how many seeds it contains.”
“There is only one, I think,” said Frank.
“You think correctly,” said his uncle. “Each seed-vessel holds a single
seed.”
“The seed-vessel in the large white floret is small and flat,” said Tom.
“It is,” said Uncle George. “In fact, the outer florets seldom produce
seeds.”
“Then what is the use of them?” Tom asked.
“I’ll show you,” said Uncle George. As he spoke he took up a fresh daisy
flower.
“Look!” he said, “what a pretty flower it is, with its golden centre and
its bright white edge tipped with red. It is like a beautiful star.”
Then he pulled off all the large white florets.
“Look at it now,” he said. “It is a dingy, ugly little flower. Without
its white florets it would not be seen at all. Now perhaps you can tell
me what the large white florets are for.”
“To help us to see them at a distance,” said Frank.
“So that bees and other flying insects may be able to see them,” said
Uncle George.
“Insects visit flowers for honey, and, in doing so, carry the yellow
dust, or pollen, from flower to flower. This pollen, as I told you
before, has to do with the making of seeds: and stronger seeds are
produced if the pollen comes from another flower.
“Now compare a white floret with a yellow one, and you will notice still
another difference between them.
“Round the _stigma_—that is the forked tube which leads to the
seed-vessel—in the yellow florets, there is a yellow ring of _stamens_,
or pollen-boxes. It is shaped like a little barrel with its ends knocked
out, and the _stigma_ grows right up through it.
“In the white florets there are no pollen-boxes of any kind.
“Thus, we see that the inner florets are _perfect_ florets which produce
seeds.
“The outer florets have all run to petal. Their business is to show the
way to the plain little florets in the middle.
“There is another thing about the daisy that I should like you to
notice,” Uncle George continued. “If you go out on a dull day, or in the
evening, you will find all the daisy flowers closed up. They only open
out in bright sunshine, when all the insects are flying about.”
Exercises on Lesson VII.
1. Daises are called “composite” flowers. Can you tell why? Cut a
large “ox-eye daisy” or corn marigold through the centre and
examine the florets carefully.
2. Using a lens, draw separately, an inside and an outside floret.
Make your drawings large, and name the various parts of each
floret.
3. Take two ox-eye daisies. Pull off all the white florets of one of
them. Then compare them. Pin both flowers up on the wall. Go
back about thirty paces and note which flower is best seen.
4. The daisy leaves form a little rosette on the ground. Make a
collection of wild plants which have similar leaves. Draw a
single leaf of each, and compare with those of the daisy.
[Illustration: Nest of Chaffinch.]
VIII.—CHAFFINCH AND SONG-THRUSH.
It was Frank who found the chaffinch’s nest in the wood. It was built in
the fork of a small tree, about eight feet from the ground.
Although not surrounded either by branches or leaves, it was completely
hidden, for the cunning little birds had matched the outside of the nest
exactly with the bark of the tree.
Uncle George got an old chaffinch’s nest from the gardener, and showed
the boys how it was constructed. Horse-hair, feathers, and moss were
neatly woven together to form the nest. The inside was lined with finer
hairs and feathers. The outside was covered with pieces of bark, lichen,
and faded moss. These were stuck on with silken threads stolen from
spider’s webs. The whole thing looked at a distance more like a part of
the tree than a bird’s nest.
[Illustration: A CHAFFINCH’S NEST]
[Illustration: THE THRUSH]
The next time the boys went to see the nest they found four tiny eggs in
it. They were bluish-green in colour, and splashed with red and brown
marks.
It was while paying a third visit to the chaffinch’s nest that Uncle
George found the nest of the song-thrush.
High up on a tall tree the cock thrush was pouring out his song, and
filling the woods with melody.
“Can you see him, boys?” Uncle George asked, and he handed Frank a pair
of field-glasses which he used for watching the birds.
“Oh, yes,” said Frank, “I can see him quite plainly. He is a brown bird,
with a white and yellow breast, all dotted over with small dark spots.”
“He is not such a beautiful bird as the chaffinch,” said Uncle George,
“but he is a much finer singer. Our prettiest birds are by no means our
best songsters. The lark, thrush, linnet, and nightingale are all plain
birds to look at, but they are by far our sweetest singers.”
“Tell us what you see through the glasses, Tom?”
“I can see him nicely,” said Tom. “He holds his head high in the air, as
if he were singing to the sky. His bill is wide open, and the feathers
of his throat are moving rapidly as he sings.”
“I think,” said Uncle George, “that his nest must be near. Let us look
for it.”
Just as Uncle George moved, a brown bird flew out of a low bush close at
hand.
“Ah, ha!” said Uncle George, “I thought we should find it. We have
disturbed the hen bird. She has been sitting on her eggs all the time.”
He moved the branches of the bush gently aside, and the boys saw a large
nest made of dried grass. It was not very high up, and the boys, by
standing on an old tree stump, could look down into it.
“Oh, what pretty eggs,” said Tom. “There are four of them, Uncle George.
They are light blue in colour, and sprinkled with black spots.
[Illustration]
Egg of Song-Thrush.
Egg of Chaffinch.
“The nest is quite smooth and hard inside. What is that queer brown
stuff all over the inside of the nest?”
“That is clay, Tom. When the thrushes have built their nest, they line
the inside of it with clay. This clay is soft at first, but it soon
dries and turns quite hard.
“But, come, let us go, boys. The cock thrush has stopped his singing. He
and his little wife are flying about in great alarm.”
When they came to the chaffinch’s neat little nest in the fork of the
tree, they got a great surprise. The four little mottled eggs were gone.
In their place were four tiny naked creatures, with little tufts of dark
coloured down upon their heads and necks. They had very large mouths,
and their eyes were closed.
“Oh, what funny little things,” said Frank.
As soon as he spoke, the baby chaffinches stretched out their slender
little necks, opened their wide, gaping mouths, and cried for food.
“_Pink, Pink, Pink!_” came from a neighbouring tree.
“Come down, Frank!” Uncle George whispered. “Let us go back from the
nest, and we will perhaps see the old birds feeding them.”
With another “_Pink, Pink, Pink_,” the cock chaffinch flew down and
stood on the edge of the nest. He had something in his bill. This he
dropped into one of the gaping little mouths, and flew away.
Next came the hen bird with something in her bill. She fed another of
the hungry little birds, and flew away also.
The boys were greatly interested. They wanted to stay the whole
afternoon and watch the chaffinches feeding their young, but their uncle
would not allow this.
“No, no, my dear boys,” he said, “we must not annoy our little feathered
friends too much, or they may forsake their beautiful nest and their
helpless young ones.
“We will come back in a fortnight and see the young birds. You will not
know them then, for they will be fully fledged.”
“What do you mean by ‘fully fledged,’ Uncle George?” Tom asked.
“It means covered all over with feathers, does it not?” said Frank.
Their uncle nodded.
“Are these little birds not cold without feathers?” asked Tom.
“Oh, dear, no,” his uncle answered. “During the day they cuddle up
together in their cosy nest. At night the mother bird folds her wings
over the nest.”
“Where does the cock bird go at night?” asked Tom.
“He sleeps on a branch quite near the nest,” his uncle answered.
[Illustration: Rooks and Nest.]
“I have just two more questions to ask, Uncle George,” said Frank. “What
do the chaffinches feed their young ones on? and what becomes of the
young birds after they are fledged?”
“They feed their young chiefly on small worms, flies, grubs, beetles,
and other insects. When the young chaffinches are fledged, their parents
lead them from the nest. They teach them to fly, and show them where to
find their food. They never lose sight of them until they are quite
grown up and able to take care of themselves.”
Exercises on Lesson VIII.
1. Describe and compare the nests of rook, thrush, and chaffinch.
Where would you look for each?
2. How does the chaffinch, in building his nest, imitate the colour of
the tree it is built on. Can you see any special reason for
this?
3. Make a list of all the British birds you know. Then divide this
list into—(1) pretty birds; (2) plain birds; (3) singing
birds.
4. Write a description of any bird’s nest you have seen, stating where
and how it was built, and also what you learned from it.
[Illustration: Holly branch.]
IX.—PLANTS THAT ARM THEMSELVES.
“Some time ago,” said Uncle George, “I promised to tell you something
about how plants arm themselves. And here, in this hedgerow, we have
some good examples of armed plants.”
“There is the stinging nettle,” said Tom, pointing to a large patch at
the roadside.
“The stinging nettle is certainly well protected,” said his uncle. “You
have only to touch any part of it lightly with your hand to find that
out. Every part of the plant is covered with small needle-shaped hairs.
These hairs are hollow and contain a poisonous juice. At the base of
each hair there is a bag filled with this juice, while the tip of each
is sharp and very brittle.
“When your hand touches a nettle—unless you grasp it tightly—the sharp
hair pierces the skin. It’s brittle point breaks off and the poisonous
juice is poured out.”
“Why is the nettle covered with these horrid stings?” asked Frank.
“To save it from being eaten up, of course. The nettle is a tender and
juicy plant, and, if it were not for its stings it would soon disappear
altogether.
“Now, here is another armed plant, the blackberry or bramble. The stem
and also the backs of the leaves are covered with large curved prickles.
These prickles not only protect the plant from grazing animals, but they
help it to climb and scramble up walls and hedges.
“If you try to pull a bramble branch down out of the hawthorn hedge, you
will find it rather difficult, for its large prickles are all turned one
way. They are really sharp hooks.”
“Here is a wild rose bush. It is also covered with large hooked
prickles,” said Frank.
“Yes, Tom, and, like the bramble, it threads its way among stronger and
taller plants.
“The wild gooseberry growing close beside it is also armed with
prickles. But the prickles of the gooseberry are for protecting its
tender leaves. It is not a climbing plant like the rose and bramble. The
raspberry also is covered with many sharp little prickles. There is a
clump of these plants growing at the other side of the road. Let us cut
off a small branch of each of these plants and take them home.”
[Illustration: Armed Plants.]
1. Thistle.
2. Blackberry.
3. Whin.
4. Barberry.
5. Raspberry.
6. Sloe.
7. Buttercup.
“This is the most prickly plant of all,” said Frank, as he halted before
a huge thistle. “You can scarcely touch it without getting severely
pricked.”
“The thistle is well armed,” said Uncle George. “There are sharp
prickles on its leaves, on its stem, and on its flowers.”
As they walked down the road they came upon a mass of whin bushes.
“Here,” said Uncle George, “we have a plant which has turned its leaves
into sharp spines.” He bent down and pulled up a tiny plant which was
growing under the larger gorse bushes. “Look at this little plant, boys.
This is a young whin plant.”
“But it is not a bit like the whin, Uncle George,” said Tom. “Its leaves
are soft and flat. They are more like clover leaves. There are no spines
or prickles on this little plant.”
“That is so, Tom; but still it is a young whin plant.
[Illustration: Young Whins.]
“There are a great many of these young whins growing under the older
bushes. Let us take a few of them home. If we grow one of them in a pot,
and supply it with plenty of water, we will find that it will _never_
produce sharp prickles.”
“That is very wonderful,” said Frank.
“It is,” said Uncle George, “and it teaches us something of the whin’s
history. Like the nettle, the whin is a juicy plant, and, if it were not
for its prickles, would be eaten by cows, sheep, and horses. In fact,
some farmers give whins to their horses. Of course the whins are passed
through a mill first. The mill crushes the whins and destroys the
prickles.
“It shows us that many, many years ago the whin was a soft-leaved plant
like the clover. It grew in moist soil. But by and by other plants
invaded the land. These plants grew more quickly than the whin, and
choked it out of the rich moist soil. Forced to grow upon bare
hill-sides and commons, the soft-leaved juicy whin would be destroyed by
grazing animals if it did not arm itself with sharp spines.
“Here is the blackthorn or sloe. It bears many hard, sharp-pointed
spines. Yet, if we grow a sloe plant in the garden, we find that its
sharp spines gradually disappear. They become branches bearing leaves
and flowers.
“But plants have other ways of protecting themselves against animals.
Look through the hedge into the meadow and you will notice that while
the grass has been eaten bare, there are other plants which have been
left to grow up untouched. Buttercups grow up all over the field, and
tall ragwort plants. How is it that the cows do not eat these plants?
They are not armed with spines or prickles.
“They protect themselves in another way. They contain bitter or
poisonous juices. No cow will eat a buttercup. If it did so it would be
ill and uncomfortable for a time.
“I want you to notice, boys, that—with the exception of those plants,
like the bramble and wild rose, which use their prickles for climbing as
well as for protection—all our armed plants grow in exposed places. The
thistle and whin are good examples of this.”
Exercises on Lesson IX.
1. Take in twigs of hawthorn, barberry, holly, bramble, and
gooseberry. Examine, and sketch them so as to show their
protective parts.
2. Grow a small whin bush in a pot and water it daily. Note that the
_new growth_ it makes is tender, and that _no spines_ are
produced.
3. Some plants are covered with dense woolly hairs. These are seldom
eaten by cattle. Can you explain why?
4. Make a list of all the armed plants you know, and tell how each is
protected.
X.—THE HORSE POND AGAIN.
Frank and Tom returned from the horse pond one day with their jars
filled with curious creatures.
“We took the water beetle back to the pond, Uncle George,” said Frank,
“and I almost felt sorry to let such a cruel and greedy monster loose
among the other creatures in the pond.”
“You have here creatures even more cruel and greedy than the diving
beetle,” said his uncle, looking into the glass jars which the boys had
brought.
“Here is the larva of the diving beetle, and a fiercer or greedier
creature is not to be found in the whole world.”
Uncle George refilled the three large tanks. He poured the contents of
one of the jars into one of the tanks. It contained, besides the larvæ
he spoke of, a number of tadpoles, some small stickle-backs, and a great
many water snails or whelks.
In addition to these, there were one or two curious insects, with a pair
of very long legs. They came to the surface every now and then, and
moved their long limbs like oars. Whenever the tank was touched, they
would suddenly dive to the bottom. Here they would remain for a short
time, then, returning to the surface, would “oar” themselves along as
usual.
“What are these queer things, Uncle George?” Tom asked. “They look
exactly like little boats.”
“They are beetles,” Uncle George replied, “and they do resemble little
row-boats—so much so that they are called ‘water boatmen.’ This beetle’s
body is shaped like a boat, and he lies on his back and moves his very
long hind legs exactly like oars. He has a large, sharp beak, which you
can see if you look closely.”
Just as Uncle George was speaking, a small fly alighted on the surface
of the water. It was immediately seized by a water boatman, who dived
with it to the bottom of the tank.
[Illustration]
1. Water Boatman.
2. Water Whelk.
3. Water Hog Louse.
“That is how the creature feeds,” said Uncle George. “When an unlucky
fly comes near, he seizes it with his two fore pairs of short legs,
drives his cruel beak deep into its body, and dives with it to the
bottom of the pool. When he has drowned his victim, he devours it at
leisure.
“But let us look at the creature I first spoke of—the larva of the
diving beetle.”
There were several in the tank. Uncle George lifted one out with a small
gauze net. He placed it in a saucer of water and asked the boys to
sketch it.
“It has six legs,” said Frank. “Its head is large and flat, and there
are two things like horns sticking out of it.”
“These are the creature’s jaws,” said his uncle.
Uncle George touched the creature’s head with the point of his pencil.
Instantly the long, curved fangs moved apart, and the creature sprang at
the pencil and closed its fangs upon the wood.
[Illustration]
1. Larva of Diving Beetle.
2, 3. Head, showing how Fangs work.
4. Larva seizing Tadpole.
“What a fierce creature,” said Tom.
“Yes,” replied his uncle. “We must remove the others from the tank, or
there will be nothing left alive in it. See, one of them has caught a
tadpole already.” And, sure enough, the creature had sunk his cruel
pincers deep into the body of a tadpole. He shook the tadpole as a dog
would shake a rat.
“Those huge fangs are hollow,” Uncle George continued. “With them he
sucks every drop of blood from his victim’s body. In this way he devours
tadpoles, whelks, little fishes, and even his own weaker brethren.
“We shall have to put these larvæ in a tank by themselves, and feed them
upon pieces of fresh raw meat, to keep them from devouring one another.
“Now, boys, I am going to describe this larva. Look closely, and see if
I am right. You can correct your drawings as we go along.
“His body, which is nearly two inches long, is narrow at each end and
broad at the middle. It is divided into twelve segments, and to each of
the first three of these segments a pair of legs are attached. His
large, flat head is almost heart-shaped. At its broad end are a pair of
large, beady eyes, three pairs of organs which look like feelers, and
the two large, curved fangs with which he seizes his prey.
“Notice how beautifully the legs are adapted for swimming. They are
edged with long, stiff hairs, which stand out flat with every down
stroke, but fold in when the legs move upwards. That is how the creature
is such a graceful swimmer.
“The last three segments of his body are thickly covered with long
hairs. His tail is divided into two long plumes. You can see what these
are for, I hope.”
“Oh yes,” said Frank. “Like the parent beetle, the larva comes often to
the surface and hangs downwards with his tail exposed to the air. So
these plumes must be his breathing organs.”
“And do these long, slender creatures actually become broad, stout
beetles like the one we returned to the pond to-day?” Tom asked.
“Yes, Tom, they do. Just as your green caterpillar became a beautiful
white butterfly. These larvæ hatched out of eggs which were laid by the
female beetle in the stem of some water weed. She first cuts a slit in
the water weed, and then places an egg in the slit.
“When the larvæ are full grown, they crawl out of the pond and bury
themselves in ground. Here they pass the winter in the pupa stage. They
come out in spring, fully-formed beetles, and pass the remainder of
their lives in the water.”
“What are these curious creatures that crawl among the water weeds?”
Frank asked. “They are very like the ‘slaters’ which we find among old
wood-work in the garden.”
“That creature is the ‘water hog.’ Its proper name is _Asellus_, and it
is very closely related to the garden ‘slater’ or wood-louse.
“These water hogs, like the whelks, are very useful in an aquarium. They
eat up all waste matter, and so help greatly to keep the water fresh.
“By the by, I want you to watch the whelks from day to day. They usually
lay their eggs in a clear, broad band on the inside of the glass tank;
and with our lenses we can watch the changes in these eggs nicely.”
Exercises on Lesson X.
1. Procure some “water boatmen” from the nearest pond (see Appendix),
feed them upon flies, and watch their habits. Notice
particularly their method of swimming and of feeding.
2. We should not keep all our pond animals in one tank. Can you
explain (giving examples) why this is?
3. Write the life-history of the diving beetle.
4. Make large sketches of the diving beetle and its larva. Compare
them.
[Illustration]
Water Beetles.
Hog Lice.
Water Whelks.
Water Boatman.
XI.—WASPS.
The wasp’s nest was found at the edge of the wood, hanging from the
branch of a small tree. It was greyish white in colour, shaped like a
pear, and about the size of a hen’s egg.
[Illustration]
Queen Wasp.
Worker Wasp.
Queen Bee.
Worker Bee.
Uncle George removed it from the branch and carried it home carefully,
for it was very light and very fragile. He took a pair of scissors and
cut through the thin walls so as to remove nearly half of the coverings.
When he had finished cutting, two thin, papery shells fell upon the
table, one a size smaller than the other.
“Examine the stuff the wasp’s nest is made of, and tell me what it is
most like, boys,” he said.
“It is more like paper than anything else,” said Tom.
“It _is_ paper,” said his uncle.
“Where did the wasps find this paper?” Frank asked.
“Not ‘_wasps_,’ Frank, but _wasp_,” his uncle answered, “for this nest
was all built by _one_ wasp. The insect did not find the paper. She made
it. It was the wasp who first taught man to make paper.
“The queen wasp awakens from her winter sleep in spring, and at once
sets about making her nest. She gathers tiny fragments of wood and bark,
chews them up, and mixes them with a fluid from her mouth. This, when it
hardens, is paper.
“First she makes a stiff rod, or pillar, of paper. This hangs down from
the branch and forms the centre of the nest. Round this are built the
walls of her house.
“Observe, boys, that there are two distinct walls of paper, one inside
the other; and there is a wide air space between them all the way round.
The entrance to the nest is at the bottom. Round the centre pillar there
is a little thing shaped like an opened umbrella. If you look underneath
this, you will see something curious, I think.”
“Oh,” said Frank, “it is divided into six cells, and in each cell there
is a small, stout maggot or grub. I can see them moving.”
“These are the young wasps,” said Uncle George. “Like your butterflies
and caddis flies, the wasp passes through egg, larva (or caterpillar),
and pupa stage before it becomes a perfect insect. These are in the
larva stage but, unlike your caterpillars, they have no legs, and they
cannot feed themselves.”
“Then the mother wasp must have laid an egg in each cell,” said Frank,
“and these grubs hatched out of them.”
“That is so,” said Uncle George. “You see what a clever and industrious
creature a wasp is. To build this beautiful nest all alone and unaided,
and to rear and feed her helpless grubs, is a task indeed.”
“What are the wasp grubs fed on?” asked Frank.
“At first,” said Uncle George, “they are fed on animal food, and this
keeps the queen wasp hunting insects all day long. As they grow older,
they are fed upon honey.
[Illustration]
Nest of Wasp in Spring.
A. Outer wall.
B. Inner wall.
C. Air space.
D. Cells with larvæ.
Same Nest in Autumn.
A. Combs of cells.
B. Supporting pillars.
C. Entrance.
DD. Inner and Outer walls.
E. Air space.
“The wasps which come from these first eggs are ‘worker’ wasps. As soon
as they are hatched out, they begin to enlarge the nest. This they do by
removing the inside wall and building a new and larger outer wall. This
is done from time to time, until at last the nest becomes as big as an
ordinary-sized turnip. While this is going on, more and more cells are
being built inside, until at last five or six large combs of cells fill
the inside of the nest. The queen wasp lays an egg in each cell as it is
formed; and the worker wasps gather food and nurse the young grubs until
they become perfect wasps.
“By and by some young queens, or female wasps, are hatched out. These
lay eggs, and soon the population the paper nest numbers many
thousands.”
“And that is why the gardener kills every wasp he sees in spring time,”
said Frank.
“Every wasp we see in spring,” said Uncle George, “is a queen wasp. If
allowed to live, each queen would become the founder of a nest and the
mother of thousands of wasps.”
“But why destroy the wasps?” asked Tom.
“Because wasps are very destructive and dangerous insects,” said Uncle
George. “They destroy our best fruit, and their sting is poisonous,
sometimes causing death.”
[Illustration: Wasp’s Nest inside Wren’s Nest.]
During the summer the boys found several wasp’s nests. One was built
under-ground at the roadside. Another was built inside a wren’s nest.
The queen wasp who built it had driven the wrens out. A third nest hung
from the branch of a gooseberry bush in the garden.
[Illustration: Humble Bees and Nest.]
The latter was watched by Uncle George and the boys as it grew larger
and larger. Soon, however, the wasps became too numerous. One day they
chased Tom and Frank out of the garden and stung them badly. Then Uncle
George removed the nest. Putting on his bee-veil and gloves, he cut off
the branch from which the nest hung. He put nest and branch inside a
large box; and, having placed a saucer containing burning sulphur inside
the box, he closed the lid.
[Illustration: Nest of Tree Wasp.]
In the morning the wasps were all dead, and the boys examined the huge
nest. Thus they were able to see queens, workers, and male wasps, eggs,
larvæ, and pupæ, and to make drawings of each.
“What becomes of the wasps in winter?” Frank asked his uncle.
“They come to a sad end, Frank,” said Uncle George. “They do not store
food like the hive bee, and so, when the cold weather comes, they starve
to death.
[Illustration]
Queen Humble Bee.
Worker Humble Bee.
“Our good-humoured and hard-working friend, the humble bee, shares the
same fate. A few young queens leave the nest before winter comes on.
These bury themselves in mossy banks and sleep the winter through.”
Exercises on Lesson XI.
1. Look under low branches of larch and spruce trees in spring for the
nest of the wasp. Make a drawing of it. Cut it open and
examine the interior.
2. Compare a piece of the wall of the nest with the torn edge of (1) a
piece of coarse brown paper and (2) a piece of ordinary
newspaper.
3. Write out the life-history of a wasp.
4. Compare the combs of the hive bee with those of the wasp. Notice
that the former are placed vertically in the nest, the latter
horizontally. Observe how the wasp’s combs are kept apart.
XII.—THE DANDELION.
Uncle George and the boys were having a stroll along a lane where briar
and hawthorn and all sorts of wild flowers grew. Although it was an
October day the sun was shining brightly, and all along the wayside the
golden flowers of the dandelion opened wide to the sunlight.
“I thought that the dandelion was an early summer flower,” said Frank.
“So it is,” said his uncle; “but this year the autumn has been so warm
that our dandelions are flowering a second time. This often happens with
many of our wild flowers during an extra mild season.
“You ought to dig up one of these dandelion plants, take it home and
grow it in a pot. It is a most interesting plant to observe, especially
the growth and ripening of its seeds. I see here dandelion flowers in
almost every stage of their growth.
“If you look you will find among the wide open flower-heads many others
which are closed. Let us split a few of these down the centre, and we
will find that they are not all alike.
“Here is one with a bright yellow tip. This one has not yet opened. If
you use your lens you will notice that, like the daisy, this is not a
single flower, but is made up of a great many small yellow florets.
These florets stand upon a flat round disc, and they are surrounded by
two rings of green things called bracts. One set of these bracts stands
up straight. These protect the florets. They open and close the flower.
The down pointing bracts protect the flower from ants and crawling
insects.
[Illustration: Dandelion.]
“Now, Frank, look at the split flower and tell me what you see with your
glass.”
“The florets are all of one kind,” said Frank. “They are all strap
shaped, and there are a great many of them. The younger florets are in
the middle.”
“If you were to pull the florets out and count them you would find about
three hundred of them in a single flower-head,” said Uncle George.
[Illustration]
1. Dandelion Flower-head not yet opened.
2. Single Floret of same.
3, 4, 5. Flower-head closed for Seed ripening.
6. Second time of opening.
“Now, take one single floret and examine it, please. It is very like the
outer (white) florets of the daisy. But it is more complete. There is a
large seed-vessel at the bottom. Just above this there are a great
number of long silky hairs. You will see what these are for by and by.
The lower part of the floret is tubular, but it opens up into a long
yellow strap-shaped petal. There are really five petals all joined
together here.”
“Oh yes,” said Frank, “at the top of the floret I can see five distinct
teeth, and five ridges run down from them. I also see the barrel-shaped
ring of stamens.”
“Let us gather some more of the closed flowers,” said Uncle George.
“Here are two other closed flowers. One of them has a yellow tip,
withered and faded almost to brown. The other has a white woolly tip.”
“Have these not opened yet?” Tom asked.
“Oh yes! they have opened and closed up again. The dandelion opens out
to the sun so that flying insects may visit it and carry pollen from
flower to flower. When it has received, in this way, enough pollen to
enable its seeds to form, it closes up completely and remains closed
until its seeds are ripened. During this time the short stalk between
the seed-vessel and petal part grows long. If you look again at a single
floret you will see that this short stout stack bears the long straight
hairs I spoke of. The flower-head closes so tightly that the yellow
strap-shaped petal parts of the florets are squeezed together into a
bunch. They soon wither. Meantime all the hair-tipped seed-stalks are
growing longer and longer. At last they push the bunch of withered
petals right out of the flower and it falls off.”
Uncle George then gathered a few more closed heads, and, by cutting them
open, showed the boys all the stages in the growth of the seeds.
“When the dandelion flower-head opens for the last time, instead of a
flat golden mass of florets, this is what appears.” As he spoke, Uncle
George pointed to a dandelion head which was one huge fluffy ball of
stalked seeds.
Frank held it up and blew his breath upon it. Immediately all the seeds
went sailing through the air.
“Why does the flower-head keep closed when the seeds are ripening?”
asked Tom.
“Because,” answered Uncle George, “not only has the seed to ripen, but a
plumed stalk has to be formed by means of which the seed is carried away
from the parent plant. These plumes have to be perfectly dry or they
would be of no use as sails to the seed. Notice that it is only on dry
days that these ‘clocks’ of the dandelion appear.”
“But, Uncle George,” said Frank, “are these seeds actually fitted with
feathery tops so that they may be carried far away from the parent
plant?”
“Certainly, my boy. You would not have them all trying to grow in the
place where the parent plant grows, would you? There would be no room
for three hundred seeds to grow there. Besides that, the parent plant
has already exhausted the soil. It is necessary that they should seek
pastures new, and therefore the seeds of most plants are furnished with
some means of travelling.”
“Are all seeds carried by the wind?” Tom asked.
“Oh dear no,” Uncle George replied, “plants have many ways of scattering
their seeds. Some plants, by suddenly bursting their seed-vessels, shoot
their seeds far out; some seeds are furnished with little hooks which
grip on to the fur of passing animals; some are carried by birds; but by
far the greater number are scattered by the wind.
“We shall learn more about these at some future time. Meantime we will
grow a dandelion plant at home, and watch the opening and closing of its
flowers, and the wonderful way in which its travelling seeds are
produced.”
Exercises on Lesson XII.
1. Gather dandelion flowers at different stages of growth. Draw, on a
large scale, a single floret from each,
2. Draw a leaf of the dandelion. Compare it with a primrose leaf. See
if you can make out, from the shape of the leaf, why the plant
is called “dandelion” (_dent de lion_ = “lion’s tooth”).
3. Take in a dandelion plant bearing young flowers. Keep the root in
well-watered soil, or in water only, and watch the growth of
its flowers.
4. Make a list of all the wind-carried seeds you know, and give a
drawing or short description of each.
[Illustration: TROUT]
XIII.—TROUT.
One day in November the postman brought Uncle George a small wooden box.
There were holes bored in the sides and top of it. The box, when opened,
seemed to be filled with damp moss; but when some of this moss was
removed there was found in the middle of the box a piece of folded
muslin.
[Illustration]
Hatching Bottle.
A. Supply pipe.
B. Exhaust pipe.
C. Trout Eggs.
Rearing Box.
C. Perforated zinc tray to fit box.
Uncle George laid the muslin on the table, and opened it out. It
contained a number of tiny pink balls, much smaller than peas.
“These are the trout eggs you promised to get for us, are they not?”
said Frank.
“They are,” said Uncle George, “and we must put them into running water
at once. I have a bottle here ready for them.”
Uncle George filled a wide-mouthed bottle with water from the tap and
placed the eggs in it. He then corked it with a cork in which he had
bored two holes.
Into each of the holes he had fitted a tube. One tube was long enough to
reach almost to the bottom of the bottle. The other was bent over the
outside of the bottle.
The straight tube was connected with the water tap by a piece of
indiarubber tubing. He then turned the tap on gently, so that the water
went in by the straight tube and came dripping out by the bent tube.
“Trout require a constant supply of fresh water,” he said. “Their eggs
are usually laid in shallow streams.
“Now, boys, I want you to watch these eggs and note down any changes you
see in them. You can remove the bottle from the tap at any time, but you
must not keep it more than fifteen minutes at a time, or your trout will
not hatch.”
At the end of a week the boys noticed two black dots and a coiled white
line in each egg.
In two weeks more some curious-looking creatures were seen wriggling
about among the eggs. As there were some empty egg-skins to be seen,
they guessed that these lively creatures must be young trout.
They were not a bit like fish. Each seemed to be made up of a long white
streak, which looked like the “backbone” of a fish, a big, clumsy yellow
bag with red veins running through it, and two large black spots that
looked like eyes.
In a few days all the eggs hatched out, and in place of the little pink
eggs there was a crowd of these wriggling creatures and a number of
empty egg-skins. The boys were puzzled, and Uncle George had to be
consulted.
[Illustration: Six Stages in Development of Trout.]
“I don’t think these were trout eggs,” said Frank. “The creatures that
came out of them are not a bit like fishes. They swim on their sides and
have a huge yellow bag attached to their bodies.”
“They _are_ young trout, I can assure you, Frank,” said his uncle
laughing. “If you remember, your tadpoles were not a bit like frogs when
they hatched out of the egg. These huge bags you talk of are called
‘yolks.’ Each trout when hatched is furnished with a huge yolk or food
supply.
“The tadpole, when hatched, has also got a yolk upon which he lives
without eating for four or five days. Our trout will require no food for
six weeks. During that time the yolk will become smaller and smaller,
and at last disappear entirely. While the yolk is shrinking, you will
notice that the creature gradually assumes the form of a fish.”
Uncle George emptied the bottle containing the young trout into a wooden
box which he had made. This box was fifteen inches long, four inches
broad, and four inches deep. The inside of it he had charred with a
red-hot iron after it was put together. It was placed under the tap, and
the water dripped into it all day and all night.
Frank made a small gauze net about the size of a dessert-spoon, and with
this they lifted troutlets out of the box whenever they wanted to
examine them.
As their uncle had said, the creatures changed from day to day. By
placing a single trout in a white saucer, the boys could note these
changes; but they were such lively little creatures that making good
sketches of them was somewhat difficult.
First the big black dots became more like eyes. Then delicate fins and
tail appeared, and mouths which opened and shut. At the top of the
yolk-sac, just under the head, the boys could see a little red thing
like a heart beating constantly. As the yolk-sac grew smaller, the
little fish’s body grew more shapely, and tiny brown spots appeared all
over it.
At last, at the end of six weeks, the yolk was completely gone, and the
young trout were now beautiful little fish, shaped and coloured exactly
like big trout.
Then Uncle George began to feed them. They were fed four times a day on
the yolk of an egg which had been boiled for half an hour. A very small
quantity of this hard yolk was squeezed through a piece of gauze into
the water, and the little fishes dashed at it and gobbled it up
greedily.
They were so rapid in their movements, swimming about and leaping out of
the water, that the boys were never tired of watching them.
“What are the brown spots on a trout for?” Frank asked his uncle one
day.
“The trout is protected by his colour,” said Uncle George. “Each trout
is coloured like the bed of the stream he lives in, and the spots
resemble grains of sand and tiny pebbles. The trout can change his
colour, like the frog, as I will show you.”
Uncle George took two trout out of the box and placed them in a glass
dish. He placed the dish in a white saucer, and so arranged it that
water was kept flowing into and out of it.
Next day he took two more trout out of the box and placed them in the
glass dish. It was then seen that the first two trout had grown quite
light in colour. They were much paler than those taken out of the box,
the inside of which was charred and black.
One day Uncle George found two of the trout dead in the box.
“I am afraid, boys,” he said, “that we cannot keep them confined any
longer. Get a large pail full of water, and we will carry them to the
brook.”
“We must come here and fish next year, Frank,” said Tom, after the trout
were transferred to the brook. “How long will it be before they become
big trout, Uncle George?”
“They are now about an inch long,” said Uncle George. “In a year they
will be four inches long. In about three years, if they are not devoured
by larger trout, they will weigh about a pound apiece.”
“I think it is a shame to kill such pretty little creatures,” said
Frank.
“I quite agree with you, Frank,” said his uncle.
Exercises on Lesson XIII.
1. Compare a newly-hatched trout with a seed (bean). How do they
resemble, and how do they differ from one another?
2. The trout is protected by its colour markings. Make a list of any
other animals you know that are “colour protected.”
3. If you put a fish (trout) into water which has been boiled and
allowed to cool, it dies. What are your reasons for this?
4. Make notes, with sketches, of the development of a young trout from
the time it is hatched until it requires food.
XIV.—SILKWORMS.
The silkworm eggs came in a very small box. They were sent by a friend
of Uncle George’s who lived in the south of England. The eggs were stuck
to pieces of paper in scattered groups. Some pieces of paper had only
one or two eggs on them, others had as many as forty. They were small,
round things, flattened on the top, and coloured light green. They
reminded the boys of small mustard seeds, but they were not so round.
In answer to Frank’s question as to why the eggs were laid in irregular
groups, Uncle George answered:
“When the silk-moth emerges from her pupa case, she lays her eggs
anywhere on the floor of her cage. As the eggs are coated with a gluey
material when newly laid, they stick firmly to the floor.
“Those people who rear silkworms always have a sheet of clean paper
covering the floor of the cage before egg-laying commences. After the
eggs are laid, they are found adhering to this sheet of paper. The paper
is taken out of the larva cage, and those parts containing eggs are cut
out with scissors.”
“How many eggs are laid by one moth,” Frank asked.
“From four to five hundred,” his uncle replied. “Let us get our larva
cage cleaned out, and we will put these eggs in the lower part of it and
await their hatching.”
“Why in the _lower_ part,” Frank asked, as he set about cleaning the
cage.
“Because its floor is a drawer which can be pulled out. If you put them
in the upper part, you must lay a sheet of paper on the floor first, for
your silkworms must not be handled on any account.”
“And how long do we have to wait for these eggs to hatch?” asked Tom.
[Illustration: Larva Case.]
“That depends altogether upon the amount of warmth they receive, Tom.
They will remain unhatched ever so long if kept in a cool place; but
whenever they are placed where they can get the necessary amount of
warmth, they begin to hatch. Let us put them in the front window, where
they can get most sunshine.”
About a week after the larva cage was placed in the window, Frank
reported to his uncle that some of the eggs had turned white.
“Take your lens and examine carefully those eggs which have lost their
colour,” said Uncle George.
Lifting out one of the small pieces of paper with eggs on it, Frank
examined it with the glass.
“Oh,” he said, “these colourless eggs are just empty shells, and there
are two small creatures crawling along the edge of the paper. How small
they are! They are no longer than the breadth of a pin-head. They are
almost black in colour, covered all over with hair, and have very large
heads.”
“Well, these are newly-hatched silkworms,” said Uncle George, “and they
are already looking for food. Run out to the garden and bring in some
fresh lettuce leaves.”
Uncle George carefully dried the lettuce leaves before putting them into
the cage. In two days all the eggs were hatched, and in their place were
as many black, hairy, crawling little creatures with clumsy heads.
Although they did not seem to eat much, they grew very rapidly. When
three days old, they were fully twice as big as when hatched.
In five days the silkworms seemed to have increased in number as well as
in size. In fact, there seemed to be twice as many grubs as there were
of eggs.
Then Uncle George explained that half of these were not grubs, but
simply empty skins.
“The silkworm, in order to grow, must cast its skin,” he said. “It does
this four times during its lifetime. Look out for another _moult_, or
skin-casting, in four days’ time.”
Four days later the grubs cast their skins again, just as Uncle George
had said. They were now about half an inch in length, and much lighter
in colour.
In six further days they moulted a third time. Instead of dingy, hairy
grubs, they were now hairless caterpillars, yellowish-white in colour,
and with round black heads. Their fourth and last moult took place in
another week. By this time they were over an inch in length. They now
began to eat the lettuce leaves ravenously, and grew very fast. For ten
days they ate much and grew rapidly. Then they seemed to get tired of
feeding, and began to crawl lazily up the sides of their cage.
[Illustration: Silk Moth.]
1. Eggs.
2. Larva.
3. Silk Cocoon.
4. Chrysalis.
“They are full grown now, boys,” said Uncle George, “and will soon begin
to spin their silken cocoons.
“They are now about three inches long, and very different from the tiny
hairy grubs which came out of the eggs over a month ago.”
“We have been comparing drawings of them with drawings we made of the
caterpillar of the white cabbage butterfly,” said Frank, “and we find
that they are very much alike.”
“That is good,” said Uncle George. “They are, indeed, very much alike.
The body is made up of thirteen segments, and they have the same number
of legs. They differ from the cabbage caterpillar, however, in size and
colour. Notice the little horn which sticks up out of the twelfth
segment. Your cabbage caterpillar did not have that. If you look closely
you will notice a long silk thread issuing from the head of one of these
silk-spinning caterpillars. This one has just begun to make his cocoon;
and, in order to prevent his threads becoming entangled with those of
the other caterpillars, I will place this small paper cone over him.”
Next day Uncle George covered several of the caterpillars with paper
cones. On the roof of the cage the boys saw one caterpillar surrounded
with a flimsy web of silk of a golden-yellow colour. As they watched the
creature turning its head round and round inside the silky veil, their
uncle told them that the creature was spinning silk at the rate of about
a foot per minute.
In three days each caterpillar had surrounded itself with a dense silken
cocoon as large as a walnut. Then Uncle George took one of the cocoons,
and, cutting it open, showed the boys the brown, shining chrysalis
inside. He took another cocoon, and, having dipped it into warm water,
began to wind the silken thread on to a piece of card.
Both Frank and Tom were amazed at the length of this silken thread. They
were more surprised when they were told that each caterpillar produces a
silk thread more than half a mile long.
“Tell us, please, Uncle George,” said Frank, “why the creature spins all
this silk, and how it makes it?”
“You are asking a difficult question,” said his uncle, “but I will tell
you something about it.
[Illustration]
S. Silk Fibres.
W. Wool.
C. Cotton.
(All highly magnified.)
“The creature spins this cocoon to protect its chrysalis, of course. The
silk is produced in two long, coiled tubes, which occupy nearly the
whole length of the creature’s body.
“Silk, before it issues from the caterpillar’s body, is a fluid.
Whenever it comes out into the air, it becomes horny. Two strands are
produced at once—one from each of the long coiled tubes. Before they
leave the caterpillar’s body they are pressed together to form one flat,
ribbon-like thread. Silk is one of the strongest fibres in the world. It
is nearly as strong as steel, and much stronger than many of our metals.
“In a fortnight your silken cocoons will produce white, fluffy moths.
‘Then you can supply your friends with hundreds of ‘silkworm’ eggs, and
still have enough over to stock your larva cage.”
[Illustration: Silk Moths—Male and Female.]
Exercises on Lesson XIV.
1. Are “silkworms” really worms? What creatures do they most resemble?
2. Many of our common caterpillars spin silk of a kind. Take in
“woolly bear” caterpillars. Feed them on the plants you find
them on. Compare the cocoons they make with those of the
“silkworm.”
3. Compare egg, larva, pupa, and perfect insect of the “silkworm” with
that of the white cabbage butterfly. Does the caterpillar of
the latter spin any silk?
4. Make a list of all the spinning insects you know, and try to
explain the use of the “silk” thread in each case.
APPENDIX.
HINTS TO TEACHERS.
STRUCTURE OF STEMS.—One- and two-year-old twigs of horse-chestnut, elm,
and willow should be cut into half-inch lengths and distributed among
the class. If cut straight across with a sharp pen-knife, the different
layers can be seen with the naked eye. Afterwards these pieces should be
slit longitudinally, and the various tissues _peeled off_ by the pupils.
BULBS AND CORMS.—Bulbs of snowdrop and tulip, and corms of crocus, can
be bought from seedsmen, from September to January, at from 6d. to 1s.
per 100. At any other season of the year the onion will make a good
substitute.
WILLOW TWIGS will root readily if placed in water and kept near the hot
pipes in school.
VEGETABLE FINGERS.—To illustrate this lesson, peas (of any kind) ought
to be grown in school. Branches of the many wild peas and vetches are to
be found in abundance in every hedgerow during spring, summer, and
autumn. Branches of Virginia creeper, clematis, tropæolum (Indian cress)
may be shown with advantage. The compound leaves of the rose, ash, or
mountain ash should be shown along with those of sweet-pea and edible
pea, and the amount of green (assimilating) area compared.
THE GREAT WATER BEETLE is found in nearly every pond. One or two should
be kept and fed upon small worms. These beetles can also be obtained
from any naturalist dealer. The larvæ of this beetle is found in ponds
in summer months.
“WATER BOATMAN” BEETLES (_notonecta_ and _corrixa_) are common to all
our ponds.
PLANT ARMOUR.—Branches of whin, bramble, hawthorn, and barberry, and
leaves of holly, thistle, and nettle will be found to illustrate this
lesson. Young whin plants are to be found plentifully in spring, growing
under the old bushes. One of these should be grown in a pot in school
and kept well watered. It will produce _no_ prickles.
TROUT EGGS are obtainable from any of the fisheries—_e.g._, Howietoun
Fisheries, Stirling, or Solway Fisheries, Dumfries, at about 1s. per
100, from October till April. They are easily hatched and reared
wherever running water can be obtained. If not hatched in a bottle, as
described in Lesson XIII., the ova ought to be placed in a shallow
trough of perforated zinc suspended in a small wooden box. The inside of
the box must be charred with a red-hot iron to prevent fungal growths.
When the yolk-sac is completely absorbed, the young trout should be fed
on yolk of hard-boiled egg, and, later on, on a mixture of this and
chopped raw beef. In each case the food should be squeezed through
perforated zinc.
“SILKWORMS.”—Eggs of the silk-bearing moth (_Bombex Mori_) can be had
from Messrs Watkins & Doncaster, 36 Strand, London, and other dealers,
at 4d. and 6d. per 100. The larva should be fed on mulberry or lettuce
leaves, and the leaves should never be given _wet_.
Caterpillars of Tiger Moth (_Arctia caja_), Emperor Moth (_Saturnia
carpini_), or Puss Moth (_Cerura vinula_) should be kept for comparison.
Footnotes
[1]See Book III. Lesson 3.
[2]_Dyticus Marginalis._
PRINTED IN GREAT BRITAIN BY THOMAS NELSON AND SONS, LTD.
The following List gives a rough idea of the main Contents in each
Volume of this Series:—
Vol. I. Jack Frost, Woods and Fields in Spring, Holly and Fir, The
Rook, Chicks, Hedgehog, Beetle, Humble Bee.
Vol. II. Sowing the Seed, Life of a Plant, A Country Walk, Harvest
Time, Gulls, Squirrels, Air, Fire, Dew, Rain, etc.
Vol. III. Birds—Seed Eaters and Insect Eaters, A Baby Plant, Uncle
George’s Tank, Tadpoles, Frogs.
Vol. IV. Snowdrop, Crocus, Tulip, Daisies, Water-beetle, Life of a
Trout, Silkworms, Chaffinch, Song Thrush.
Vol. V. Some British Forest Trees—Oak, Ash, Horse-chestnut, Elm,
Birch, Willow, Beech, The Fir Tribe.
Vol. VI. Bats, Field-mice, The Water-vole, Mole, Weasel, Reptiles,
Newts, Stickle-backs, Crayfish, etc.
Vol. VII. Butterflies and Moths, and how to collect them,
Caterpillars, Beetles, Flies, etc.
Transcriber’s Notes
--Retained publication information from the printed exemplar (this eBook
is in the public domain in the country of publication.)
--Only in the text versions, delimited italicized text with
_underscores_.
--Silently corrected several typos.
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