



Produced by David E. Brown and The Online Distributed
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  HOW DOES A TREE
  GROW?

  OR

  BOTANY FOR YOUNG AUSTRALIANS.

  BY
  JAMES BONWICK,

  _Sub-Inspector of Denominational Schools, Victoria,
  Author of “Geography of Australia and New Zealand,”
  &c. &c._


  JAMES J. BLUNDELL & Co., MELBOURNE;
  SANDS & KENNY, SYDNEY.

  1857.




PREFACE.


At the request of several Teachers, I have commenced a Shilling Series
of School Books, chiefly to be confined to subjects of Colonial History
and Popular Sciences.

The form of dialogue has been adopted with the “Botany for Young
Australians,” from a belief that the sympathies of our young friends
will be excited on behalf of the juvenile questioner, and their
interest thus maintained in the study of the sciences.

A dialogue upon Astronomy will shortly follow; being a conversation
between a father and his son, coming out to Australia, from Old England.

                                                          JAMES BONWICK.

    _Melbourne, April 17, 1857._




HOW A TREE GROWS IN AUSTRALIA.


Willie was a fine rosy-faced boy of our southern colony. Though not
eight years of age, he was as healthy and merry a lad as ever climbed
up a Gum tree, picked up manna, or rode in a bullock dray.

His father had once occupied a good position in Old England; but
the uncertainties and losses of business, and the constant struggle
to uphold a respectable appearance with decreasing means, became so
burdensome to his mind, that his spirits failed, and his energies sunk.
His attention was directed to Australia, the land of mutton and corn,
the home of health and plenty. Gathering up the wreck of the past, he
left the country of taxation and paupers, and established himself on a
small farm in Port Phillip.

The young hero of our story had been a year or two in the colony. It
so happened he had a piece of land of his own, in which he proudly
exhibited some rising cabbages, a few peas, and a flower or two. His
father had given him a rose tree, which was the reigning beauty of the
bed. It was upon the occasion of his parent’s visit to the garden, that
the following dialogue took place:--

Look, father, and see how my rose tree has grown.

Indeed it has, Willie. Can you tell me what has made it grow?

The sun and the rain, I suppose.

Do you remember, when we got tired of the old slab hut, and set about
building this brick cottage, that you noticed it getting higher and
higher every day!

Yes, that was because more bricks and wood were used.

Then, if your tree increases in size, there surely must be something
added on continually: do you think the sun and rain do this?

Well, I never thought about it, father; but I should like to know why
it does grow.

Can you tell me, Willie, what a plum pudding is made of?

Yes, that I can. There is the flour, the suet, the raisins, and the
cold water. All these are mixed together.

Then let us see of what our rose tree is made.

I don’t think it so easy to tell that as to reckon up the articles in a
pudding.

Never mind, we will try. First, there is the stalk, or woody part.
When you put a piece of stick in the fire, what becomes of it?

Oh, it smokes and blazes, and then nothing is left but some ashes.

What is it which burns away?

That I cannot tell.

It is the gaseous part which burns in a flame, like what you have seen
come out of coal. But what do you call woody matter that will not blaze?

Charcoal, father. Then I understand now that wood is nothing but
charcoal and the gases. What are these gases?

The gas which blazes so readily, my dear, is hydrogen: and it has
a very strong smell too. The air we breathe is a mixture of two
gases--oxygen and nitrogen. It is only the oxygen that we take into our
lungs.

Well, that is curious.

I shall puzzle you more, Willie, when I tell you that water is nothing
but a mixture of oxygen gas and hydrogen gas.

It certainly is funny that water, which puts out flame, should be
partly composed of the burning gas.

You must also know, my lad, that hydrogen would not burn without
oxygen. You blow air into a fire to give food for flame.

But however could the plants get hold of the gases, father?

Did it never strike you why God formed leaves?

It never did, except that I thought he did it to make the trees look
pretty.

That is quite true, Willie. The good God loves beauty, and he has
surrounded us with beauty of all kinds. But he made things for use as
well as to be looked at. The leaves absorb or suck in gases from air
and water.

Then I suppose the veins like that we see in leaves conduct these gases
away into the plant.

Quite right, my boy. Where now shall we get the charcoal, or carbon, as
the learned men call it?

That I cannot find out at all.

You told me, Willie, that smoke came out of burning wood. What becomes
of it?

When I was a very little boy, I thought it went up to form clouds; but
now I know part of it turns into soot in the chimney, and that looks
like our charcoal or carbon.

It really is. As to that which comes out of the chimney, it passes
upward, and gets gradually mixed with the air. The little particles of
carbon join the oxygen, and become a sort of gas called carbonic acid
gas, which is absorbed into the plant.

How wonderful that the solid part of a tree should once have been
floating about in the air!

Do you think the leaves of a plant to be the same as the stem?

Yes, I do; for when they are thrown in a fire, they smoke, blaze, and
leave an ash like the wood does.

Just so. You know the smoke to be carbon passing into the air; but we
must examine the ash a little more carefully. If you take some ash from
the fireplace, and put it into hot water, the solid part will of course
fall to the bottom.

Will no part mix with the water?

There will be something; for if we pour off the water, and allow it to
evaporate in a dish, there will be found to be a sediment left, and
that is potash or pearl ash.

I have heard of people in the bush doing that when they could not get
soap, for they said that the potash got the dirt out of clothes.

It is a great pity that we in these colonies burn away so much wood in
waste when clearing land, Willie, without thinking of making potash out
of the ashes, for it fetches a good price.

Then there is potash in the plant. Has any thing else been found in the
ash beside that and carbon?

Yes, my lad. Sulphur or brimstone, lime, soda, flint, ammonia,
phosphorus, magnesia, and iron, are contained in trees.

But how could all these things get there?

Why, if we cannot find them in the air to be absorbed by the leaves,
they must be in the soil or ground. Now, it so happens that those
substances are to be found in different quantities in different places.

How do they get into the plant, father?

Simply by the little rootlets absorbing small particles of them, mixed
with moisture.

But do all plants require the same amount of lime, potash, soda, and
the others?

No, my dear. There are not two sorts of trees that feed upon the same
materials in exactly the same proportions.

Is that the reason, then, why some land is so much better fitted to
grow one plant than another?

The reason is, because the one soil has more of the right sort of food
in it.

Now I see that if I wanted to grow a good crop of any thing, I must
give it plenty of the food it likes best.

Yes, but not too much. For like as too much nice rich food is bad for
children, so it is with vegetables: ground may be too rich, as well as
too poor.

I have heard people say that it is not wise to grow the same thing in
the same soil year after year: why is this?

Because it would gradually consume all the food there, and then it
would starve, and look miserable.

Then my beautiful flower-bed will by-and-by cease to bring forth such a
fine show as it has done this season.

Of course it will, unless you provide your plants with fresh food.

Fresh food, father; I do not understand you.

I mean, manure must be mixed with the soil.

How is manure food for plants?

Because it contains the materials they require. You throw wood ashes
over the ground, and so add sulphur, potash, and carbon. Sea weed
manure furnishes plenty of soda. Bone dust contains lime and phosphorus.

It is possible, then, to apply to the ground the amount of solid matter
taken out of it by the plant, so that if my radish bed had some manure,
it would be as good as it was before my crop came off.

That is perfectly correct, my boy.

But how is it that a gum-tree forest is kept up, for there must be a
tremendous lot of lime, soda, flint, and the rest, removed from the
soil?

Yes, but when the trees fall, they rot, and the solid parts return to
the ground.

Oh, father, the remains are very small, compared to the living tree.

True, because the principal part of a plant consists of the gases,
which fly off, and of carbon, which unites with the oxygen of the air.

How does God bring fresh carbon to the forest?

Several ways: smoke is one source, and the breath of animals another.

What has the breath to do with it?

Every time you respire, or breathe out, some carbonic acid comes out
with air, and is carried into the atmosphere.

Why, father, you do not mean to say that my breath helps to make
cabbages grow.

The carbon passing from your body may become a part of a cabbage, or
gum tree, or a delicate tulip.

       *       *       *       *       *

The next time Willie and his father were out together, the conversation
again fell upon trees. The wonder of the boy had been strongly excited
by the last lesson, and he had now lots of questions to ask. He knew
enough to know that there must be a great deal more to learn. He had
been told that trees fed the same as animals, and he felt sure that
inside there must be some entrances for the food to reach parts needing
supply. Then he sought to understand how the growing process was
managed, and especially how seeds were formed, and how the plant sprang
from them. Thus, question after question poured out from the boy’s
lips, without even a pause for a reply.

“Stop, stop, my man,” said his father; “I am not like the Hindoo
god with half-a-dozen pairs of ears, and half-a-dozen tongues. We will
go now a little deeper into the subject; but we must take one thing at
a time. What do you think of that gum tree yonder?

That is a noble fellow. What a barrel he has got for splitting paling
out of! And hasn’t he got a fine top knot? Why, that must be almost as
big as that Tasmanian tree you read about.

Oh, no; that one was 350 feet high, and was 104 feet round; while this
is not above 100 feet high, and 30 round.

Well, then, that must be a monster surely. How curious to think it was
once a tiny little thing that I could pull up with my finger! I say,
father, how many cartloads of carbon this one must have got hold of! I
fancy it has got gas enough to fill many a balloon. But how did it grow?

To answer that question, will give us some trouble, and take some time.
First, tell me all the parts of the tree.

What I cannot see is the root; then comes the stem, then the branches,
and then the leaves.

You forget the flower.

Flower! whoever heard tell of a gum flower? How funny the word sounds!

If there be no flower, how are you to get the seed?

I never thought of that. But flowers are always such pretty light
things, that one would be sure to see them a long way off on a gum tree.

But if instead of having fine red leaves, my lad, the flower had none,
and the other part was much the same colour as the leaves, do you think
you would notice it so readily?

No, father. Won’t I give a good look out for it after this; for I am
sure none of our boys at school ever talk of gum flowers, though we
often go to gather wattle blossoms.

To go on with our tree--we will take the root, and there is a Stringy
Bark blown over in the last storm.

And a strong root it has, too. How the wind must have puffed to
overcome the weight of all the gravel and clay resting on that lot of
roots, especially as they held the gravel like so many fingers. So
these are the suckers of moisture and food out of the soil.

Yes, but you do not see the real suckers. They are very small, and were
broken off and left behind. Those are called _spongioles_, because
they suck up like a sponge. They are situated at the ends of the small
fibres of roots, and have their mouths always open.

Yet I don’t see why the moisture rises. If I put my mouth into the rain
cask, the water will not rush up into it.

Your mouth is too big. Supposing you put a lump of salt near a little
water, so as to be touched, what will be the result?

The salt will gradually absorb the water, until there be none left.

After dipping the corner of a towel in the basin, and hanging it up by
the opposite corner, does not the dampness run down when drying?

No, the moisture ascends and wets the dry part of the towel.

So you see, then, that the water in small particles can arise in the
pores, or narrow openings of substances. This is because the sides
attract it, and the process is called _capillary_, or hairlike,
_attraction_. On this principle the moisture rises into the rootlets
through the spongioles.

Is that all the work they do?

Sometimes these fibres reject things not wanted in the tree, and that
often prove poisonous to its growth. Such important little workmen as
the spongioles ought not to be disturbed in their labour, and this is
what makes the difficulty in moving trees.

I know that most of those I move are sure to die. But gardeners are
more lucky.

The reason is, because they do it at a proper time.

What, father, can we catch the spongioles asleep?

Not exactly; but they only live a year, and you must take up the
tree between the time of the death of one set, and the production of
another, which is the winter season. Even then you should get up as
many fine roots as possible, for at the end of these the spongioles
grow.

All roots are not alike, father.

That is true: some are creeping, or fibrous, or bulbous, or knobbed, or
taprooted. Can you give me instances of each?

Let me see. The mint spreads underground by its creeping roots. The
potatoe is knobbed, and the onion and tulip are bulbous. The grass is
fibrous, and the parsnip has a tap root.”

       *       *       *       *       *

So much for the root. Now let us look at the bark. I suppose you have
noticed the difference of the bark of our forest trees.

I know that they shed their bark, though not in the same way. The
stringy bark peels off in strings. The gum throws out fine long
ribands, waving in the wind. The iron bark sheds its thick coat in
great lumps.

But does the whole of the bark thus fall off?

Oh, no: it is only the rough, worn-out stuff. There is always bark
left. It puts me in mind of _my_ hand, that got so horny after sawing a
whole day at a big tree; for days after the rough skin got peeling off
as if it was not wanted.

Then you have more skins than one. You are just like a tree, for that
has several coats to its bark. Which is the softer, the outer or inner
bark?

The outer is hard, and the inner soft. But there is a fresh gum tree
just cut down: that will show us the barks.--Yes, now I peel off the
outside, there is a very soft, juicy stuff, a thing I feel--a soft coat
of bark close to the ring of white-looking wood.

Mind, Willie, the outside is the _cuticle_ or _epidermis_, having
pores or openings through which moisture issues at one time, and is
absorbed at another. These _Stomates_ or openings are very small; in
our Bush Pigfaces, that the Blacks eat, there are 70,000 Stomates to
every square inch of skin.

Then the tree perspires in the same manner that we do: that is odd. But
what is the middle pulpy bark, with its green colour and sticky feeling?

Botanists call that the _Chlorophyll_ or colouring matter. The inner
bark is the _liber_, which you see to be soft and fibrous like, being
full of sap.

Why, this is something like our skin, as there is a watery stuff
between our cuticle and the skin that has the blood in it. I have heard
of people writing on bark: that must have been on the liber.

It was so. The English wrote on the bok or bark, and thus we have the
word _book_; while with _liber_ we connect the word _library_. But we
shall return to the liber in another lesson.

