Arabella B. Buckley.

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pure sulphuric acid can be secured from any chemist. Great care
must be taken in using it, as it burns everything it touches.) You
see, then, that from the whitest substance in plants we can get
this black carbon; and in truth, one-half of the dry part of every
plant is composed of it.

Now look at my plant again, and tell me if we have not already
found a curious history? Fancy that you see the water creeping
in at the roots, oozing up from cell to cell till it reaches the
leaves, and there meeting the carbon which has just come out of
the air, and being worked up with it by the sun-waves into
starch, or sugar, or oils.

But meanwhile, how is new protoplasm to be formed? for without
this active substance none of the work can go on. Here comes
into use a lazy gas we spoke of in Lecture III. There we thought
that nitrogen was of no use except to float oxygen in the air,
but here we shall find it very useful. So far, as we know,
plants cannot take up nitrogen out of the air, but they can get
it out of the ammonia which the water brings in at their roots.

Ammonia, you will remember, is a strong-smelling gas, made of
hydrogen and nitrogen, and which is often almost stifling near a
manure-heap. When you manure a plant you help it to get this
ammonia, but at any time it gets some from the soil and also
from the rain-drops which bring it down in the air. Out of this
ammonia the plant takes the nitrogen and works it up with the
three elements, carbon, oxygen, and hydrogen, to make the
substances called albuminoids, which form a large part of the
food of the plant, and it is these albuminoids which go to make
protoplasm. You will notice that while the starch and other
substances are only made of three elements, the active protoplasm
is made of these three added to a fourth, nitrogen, and it also
contains phosphorus and sulphur.

And so hour after hour and day after day our primrose goes on
pumping up water and ammonia from its roots to its leaves,
drinking in carbonic acid from the air, and using the sun-waves
to work them all up into food to be sent to all parts of its
body. In this way these leaves act, you see, as the stomach of
the plant, and digest its food.

Sometimes more water is drawn up into the leaves than can be
used, and then the leaf opens thousands of little mouths in the
skin of its under surface, which let the drops out just as drops
of perspiration ooze through our skin when we are overheated.
These little mouths, which are called stomates (a, Fig. 42) are
made of two flattened cells, fitting against each other. When
the air is damp and the plant has too much water these lie open
and let it out, but when the air is dry, and the plant wants to
keep as much water as it can, then they are closely shut. There
are as many as a hundred thousand of these mouths under one
apple-leaf, so you may imagine how small they often are.

Plants which only live one year, such as mignonette, the sweet
pea, and the poppy, take in just enough food to supply their
daily wants and to make the seeds we shall speak of presently.
Then, as soon as their seeds are ripe their roots begin to
shrivel, and water is no longer carried up. The green cells can
no longer get food to digest, and they themselves are broken up by
the sunbeams and turn yellow, and the plant dies.

But many plants are more industrious than the stock and
mignonette, and lay by store for another year, and our primrose
is one of these. Look at this thick solid mass below the primrose
leaves, out of which the roots spring. (See the plant in the
foreground of the heading of the lecture.) This is really the
stem of the primrose hidden underground, and all the starch,
albuminoids, &c., which the plant can spare as it grows, are
sent down into this underground stem and stored up there, to lie
quietly in the ground through the long winter, and then when the
warm spring comes this stem begins to send out leaves for a new
plant.



Week 21

We have now seen how a plant springs up, feeds itself, grows,
stores up food, withers, and dies; but we have said nothing yet
about its beautiful flowers or how it forms its seeds. If we
look down close to the bottom of the leaves in a primrose root
in spring-time, we shall always find three or four little green
buds nestling in among the leaves, and day by day we may see the
stalk of these buds lengthening till they reach up into the open
sunshine, and then the flower opens and shows its beautiful pale-
yellow crown.

We all know that seeds are formed in the flower, and that the
seeds are necessary to grow into new plants. But do we know the
history of how they are formed, or what is the use of the
different parts of the bud? Let us examine them all, and then I
think you will agree with me that this is not the least wonderful
part of the plant.

Remember that the seed is the one important thing and then notice
how the flower protects it. First, look at the outside green
covering, which we call the calyx. See how closely it fits in
the bud, so that no insects can creep in to gnaw the flower, nor
any harm come to it from cold or blight. Then, when the calyx
opens, notice that the yellow leaves which form the crown or
corolla, are each alternate with one of the calyx leaves, so that
anything which got past the first covering would be stopped by
the second. Lastly, when the delicate corolla has opened out,
look at those curious yellow bags just at the top of the tube
(b,2, Fig. 43). What is their use?

But I fancy I see two or three little questioning faces which
seem to say, "I see no yellow bags at the top of the tube." Well,
I cannot tell whether you can or not in the specimen you have in
your hand; for one of the most curious things about primrose
flowers is, that some of them have these yellow bags at the top of
the tube and some of them hidden down right in the middle. But
this I can tell you:those of you who have got no yellow bags at
the top will have a round knob there (I a, Fig. 43), and will find
the yellow bags (b) buried in the tube. Those, on the other hand,
who have the yellow bags (2 b, Fig. 43) at the top will find the
knob (a) half-way down the tube.

Now for the use of these yellow bags, which are called the
anthers of the stamens, the stalk on which they grow being
called the filament or thread. If you can manage to split them
open you will find that they have a yellow powder in them,
called pollen, the same as the powder which sticks to your nose
when you put it into a lily; and if you look with a magnifying
glass at the little green knob in the centre of the flower, you
will probably see some of this yellow dust sticking on it (A,
Fig. 43). We will leave it there for a time, and examine the
body called the pistil, to which the knob belongs. Pull off the
yellow corolla (which will come off quite easily), and turn back
the green leaves. You will then see that the knob stands on the
top of a column, and at the bottom of this column there is a
round ball (s v), which is a vessel for holding the seeds. In
this diagram (A, Fig. 43) I have drawn the whole of this curious
ball and column as if cut in half, so that we may see what is in
it. In the middle of the ball, in a cluster, there are a number of
round transparent little bodies, looking something like round
green orange-cells full of juice. They are really cells full of
protoplasm, with one little dark spot in each of them, which
by-and-by is to make our little plantlet that we found in the
seed.

"These, then, are seeds," you will say. Not yet; they are only
ovules, or little bodies which may become seeds. If they were
left as they are they would all wither and die. But those little
grains of pollen, which we saw sticking to the knob at the top,
are coming down to help them. As soon as these yellow grains
touch the sticky knob or stigma, as it is called, they throw out
tubes, which grow down the column until they reach the ovules. In
each one of these they find a tiny hole, and into this they
creep, and then they pour into the ovule all the protoplasm from
the pollen-grain which is sticking above, and this enables it to
grow into a real seed, with a tiny plantlet inside.

This is how the plant forms its seed to bring up new little ones
next year, while the leaves and the roots are at work preparing
the necessary food. Think sometimes when you walk in the woods,
how hard at work the little plants and big trees are, all around
you. You breathe in the nice fresh oxygen they have been
throwing out, and little think that it is they who are making
the country so fresh and pleasant, and that while they look as if
they were doing nothing but enjoying the bright sunshine, they
are really fulfilling their part in the world by the help of
this sunshine; earning their food from the ground working it up;
turning their leaves where they can best get light (and in this it
is chiefly the violet sun-waves that help them), growing, even at
night, by making new cells out of the food they have taken in the
day; storing up for the winter; putting out their flowers and
making their seeds, and all the while smiling so pleasantly in
quiet nooks and sunny dells that it makes us glad to see them.

But why should the primroses have such golden crowns? plain green
ones would protect the seed quite as well. Ah! now we come to a
secret well worth knowing. Look at the two primrose flowers, 1
and 2, Fig. 43, p. 163, and tell me how you think the dust gets
on to the top of the sticky knob or stigma. No. 2 seems easy
enough to explain, for it looks as if the pollen could fall down
easily from the stamens on to the knob, but it cannot fall up,
as it would have to do in No. 1. Now the curious truth is, as Mr.
Darwin has shown, that neither of these flowers can get the dust
easily for themselves, but of the two No. 1 has the least
difficulty.

Look at a withered primrose, and see how it holds its head down,
and after a little while the yellow crown falls off. It is just
about as it is falling that the anthers or bags of stamens burst
open, and then, in No. 1 (Fig. 44), they are dragged over the
knob and some of the grains stick there. But in the other form
of primrose, No. 2, when the flower falls off, the stamens do
not come near the knob, so it has no chance of getting any
pollen; and while the primrose is upright the tube is so narrow
that the dust does not easily fall. But, as I have said, neither
kind gets it very easily, nor is it good for them if they do. The
seeds are much stronger and better if the dust or pollen of one
flower is carried away and left on the knob or stigma of another
flower; and the only way this can be done is by insects flying
from one flower to another and carrying the dust on their legs and
bodies.

If you suck the end of the tube of the primrose flower you will
find it tastes sweet, because a drop of honey has been lying
there. When the insects go in to get this honey, they brush
themselves against the yellow dust-bags, and some of the dust
sticks to them, and then when they go to the next flower they
rub it off on to its sticky knob.

Look at No. 1 and No. 2 (Fig. 43) and you will see at once that
if an insect goes into No. 1 and the pollen sticks to him, when
he goes into No. 2 just that part of his body on which the
pollen is will touch the knob; and so the flowers become what we
call "crossed," that is, the pollen-dust of the one feeds the
ovule of the other. And just the same thing will happen if he
flies from No. 2 to No. 1. There the dust will be just in the
position to touch the knob which sticks out of the flower.

Therefore, we can see clearly that it is good for the primrose
that bees and other insects should come to it, and anything it
can do to entice them will be useful. Now, do you not think that
when an insect once knew that the pale-yellow crown showed where
honey was to be found, he would soon spy these crowns out as he
flew along? or if they were behind a hedge, and he could not see
them, would not the sweet scent tell him where to come and look
for them? And so we see that the pretty sweet-scented corolla is
not only delightful for us to look at and to smell, but it is
really very useful in helping the primrose to make strong
healthy seeds out of which the young plants are to grow next
year.

And now let us see what we have learnt. We began with a tiny
seed, though we did not then know how this seed had been made.
We saw the plantlet buried in it, and learnt how it fed at first
on prepared food, but soon began to make living matter for
itself out of gases taken from the water through the cells to
its stomach - the leaves! And how marvellously the sun-waves
entering there formed the little green granules, and then helped
them to make food and living protoplasm! At this point we might
have gone further, and studied how the fibres and all the
different vessels of the plant are formed, and a wondrous history
it would have been. But it was too long for one hour's lecture,
and you must read it for yourselves in books on botany. We had to
pass on to the flower, and learn the use of the covering leaves,
the gaily coloured crown attracting the insects, the dust-bags
holding the pollen, the little ovules each with the germ of a new
plantlet, lying hidden in the seed- vessel, waiting for the
pollen-grains to grow down to them. Lastly, when the pollen crept
in at the tiny opening we learnt that the ovule had now all it
wanted to grow into a perfect seed.

And so we came back to a primrose seed, the point from which we
started; and we have a history of our primrose from its birth to
the day when its leaves and flowers wither away and it dies down
for the winter.

But what fairies are they which have been at work here? First,
the busy little fairy Life in the active protoplasm; and
secondly, the sun-waves. We have seen that it was by the help of
the sunbeams that the green granules were made, and the water,
carbonic acid, and nitrogen worked up into the living plant. And
in doing this work the sun-waves were caught and their strength
used up, so that they could no longer quiver back into space. But
are they gone for ever? So long as the leaves or the stem or the
root of the plant remain they are gone, but when those are
destroyed we can get them back again. Take a handful of dry
withered plants and light them with a match, then as the leaves
burn and are turned back again to carbonic acid, nitrogen, and
water, our sunbeams come back again in the flame and heat.

And the life of the plant? What is it, and why is this protoplasm
always active and busy? I cannot tell you. Study as we may, the
life of the tiny plant is as much a mystery as your life and
mine. It came, like all things, from the bosom of the Great
Father, but we cannot tell how it came nor what it is. We can
see the active grains moving under the microscope, but we cannot
see the power that moves them. We only know it is a power given
to the plant, as to you and to me, to enable it to live its
life, and to do its useful work in the world.




Week 22

LECTURE VIII

THE HISTORY OF A PIECE OF COAL

I have here a piece of coal (Fig. 45), which, though it has been
cut with some care so as to have a smooth face, is really in no
other way different from any ordinary lump which you can pick for
yourself out of the coal-scuttle. Our work to-day is to relate
the history of this black lump; to learn what it is, what it has
been, and what it will be.

It looks uninteresting enough at first sight, and yet if we
examine it closely we shall find some questions to ask even about
its appearance. Look at the smooth face of this specimen and see
if you can explain those fine lines which run across so close
together as to look like the edges of the leaves of a book. Try
to break a piece of coal, and you will find that it will split
much more easily along those lines than across the other way of
the lump; and if you wish to light a fire quickly you should
always put this lined face downwards so that the heat can force
its way up through these cracks and gradually split up the block.
Then again if you break the coal carefully along one of these
lines you will find a fine film of charcoal lying in the crack,
and you will begin to suspect that this black coal must have been
built up in very thin layers, with a kind of black dust between
them.

The next thing you will call to mind is that this coal burns and
gives flame and heat, and that this means that in some way
sunbeams are imprisoned in it; lastly, this will lead you to
think of plants, and how they work up the strength of the
sunbeams into their leaves, and hide black carbon in even the
purest and whitest substance they contain.

Is coal made of burnt plants, then? Not burnt ones, for if so it
would not burn again; but you may have read how the makers of
charcoal take wood and bake it without letting it burn, and then
it turns black and will afterwards make a very good fire; and so
you will see that it is probable that our piece of coal is made
of plants which have been baked and altered, but which have still
much sunbeam strength bottled up in them, which can be set free
as they burn.

If you will take an imaginary journey with me to a coal-pit near
Newcastle, which I visited many years ago, you will see that we
have very good evidence that coal is made of plants, for in all
coal-mines we find remains of them at every step we take.

Let us imagine that we have put on old clothes which will not
spoil, and have stepped into the iron basket (see Fig. 46) called
by the miners a cage, and are being let down the shaft to the
gallery where the miners are at work. Most of them will probably
be in the gallery b, because a great deal of the coal in a has
been already taken out. But we will stop in a because there we
can see a great deal of the roof and the floor. When we land on
the floor of the gallery we shall find ourselves in a kind of
tunnel with railway lines laid along it and trucks laden with
coal coming towards the cage to be drawn up, while empty ones are
running back to be loaded where the miners are at work. Taking
lamps in our hands and keeping out of the way of the trucks, we
will first throw the light on the roof, which is made of shale or
hardened clay. We shall not have gone many yards before we see
impressions of plants in the shale, like those in this specimen
(Fig. 47), which was taken out of a coal-mine at Neath in
Glamorganshire, a few days ago, and sent up for this lecture.
You will recognize at once the marks of ferns (a), for they look
like those you gather in the hedges of an ordinary country lane,
and that long striped branch (b) does not look unlike a reed, and
indeed it is something of this kind, as we shall see by-and-by.
You will find plenty of these impressions of plants as you go
along the gallery and look up at the roof, and with them there
will be others with spotted stems, or with stems having a curious
diamond pattern upon them, and many ferns of various kinds.

Next look down at your feet and examine the floor. You will not
have to search long before you will almost certainly find a piece
of stone like that represented in Fig. 48, which has also come
from Neath Colliery. This fossil, which is the cast of a piece
of a plant, puzzled those who found it for a very long time. At
last, however, Mr. Binney found the specimen growing to the
bottom of the trunk of one of the fossil trees with spotted
stems, called Sigillaria; and so proved that this curious pitted
stone is a piece of fossil root, or rather underground stem, like
that which we found in the primrose, and that the little pits or
dents in it are scars where the rootlets once were given off.

Whole masses of these root-stems, with ribbon-like roots lying
scattered near them, are found buried in the layer of clay called
the underclay which makes the floor of the coal, and they prove
to us that this underclay must have been once the ground in which
the roots of the coal-plants grew. You will feel still more sure
of this when you find that there is not only one straight gallery
of coal, but that galleries branch out right and left, and that
everywhere you find the coal lying like a sandwich between the
floor and the roof, showing that quite a large piece of country
must be covered by these remains of plants all rooted in the
underclay.

But how about the coal itself? It seems likely, when we find
roots below and leaves and stems above, that the middle is made
of plants, but can we prove it? We shall see presently that it
has been so crushed and altered by being buried deep in the
ground that the traces of leaves have almost been destroyed,
though people who are used to examining with the microscope, can
see the crushed remains of plants in thin slices of coal.

But fortunately for us, perfect pieces of plants have been
preserved even in the coal-bed itself. Do you remember our
learning in Lecture IV, that water with lime in it petrifies
things, that is, leaves carbonate of lime to fill up grain by
grain the fibres of an animal or plant as the living matter
decays, and so keeps an exact representation of the object?

Now, it so happens that in a coal-bed at South Ouram, near
Halifax, as well as in some other places, carbonate of lime
trickled in before the plants were turned into coal, and made
some round nodules in the plant-bed, which look like cannon-
balls. Afterwards, when all the rest of the bed was turned into
coal, these round balls remained crystallized, and by cutting
thin transparent slices across the nodule we can distinctly see
the leaves and stems and curious little round bodies which make
up the coal. Several such sections may be seen at the British
Museum, and when we compare these fragments of plants with those
which we find above and below the coal-bed, we find that they
agree, thus proving that coal is made of plants, and of those
plants whose roots grew in the clay floor, while their heads
reached up far above where the roof now is.

The next question is, what kind of plants were these? Have we
anything like them living in the world now? You might perhaps
think that it would be impossible to decide this question from
mere petrified pieces of plants. But many men have spent their
whole lives in deciphering all the fragments that could be found,
and though the section given in Fig. 49 may look to you quite
incomprehensible, yet a botanist can reed it as we read a book.
For example, at S and L, where stems are cut across, he can learn
exactly how they were build up inside, and compare them with the
stems of living plants, while the fruits cc and the little round
spores lying near them, tell him their history as well as if he
had gathered them from the tree. In this way we have learnt to
know very fairly what the plants of the coal were like, and you
will be surprised when I tell you that the huge trees of the
coal-forests, of which we sometimes find trunks in the coal-mines
from ten to fifty feet long, are only represented on the earth
now by small insignificant plants, scarcely ever more than two
feet, and often not many inches high.

Have you ever seen the little club moss or Lycopodium which grows
all over England, but chiefly in the north, on heaths and
mountains? At the end of each of its branches it bears a cone
made of scaly leaves; and fixed to the inside of each of these
leaves is a case called a sporangium, full of little spores or
moss-seeds, as we may call them, though they are not exactly like
true seeds. In one of these club-mosses called Selaginella, the
cases near the bottom of the cone contain large spores, while
those near the top contain a powdery dust. These spores are full
of resin, and they are collected on the Continent for making
artificial lightning in the theatres, because they flare when
lighted.

Now this little Selaginella is of all living plants the one most
like some of the gigantic trees of the coal-forests. If you look
at this picture of a coal-forest (Fig. 51), you will find it
difficult perhaps to believe that those great trees, with diamond
markings all up the trunk, hanging over from the right to the
left of the picture, and covering all the top with their boughs,
could be in any way relations of the little Selaginella; yet we
find branches of them in the beds above the coal, bearing cones
larger but just like Selaginella cones; and what is most curious,
the spores in these cones are of exactly the same kind and not
any larger than those of the club-mosses.


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