How Does a Tree Grow? Or, Botany for Young Australians
HOW DOES A TREE
BOTANY FOR YOUNG AUSTRALIANS.
Sub-Inspector of Denominational Schools, Victoria,
Author of “Geography of Australia and New Zealand,”
JAMES J. BLUNDELL & Co., Melbourne;
SANDS & KENNY, Sydney.
At the request of several Teachers, I have commenceda Shilling Series of School Books, chieflyto be confined to subjects of Colonial Historyand Popular Sciences.
The form of dialogue has been adopted withthe “Botany for Young Australians,” from abelief that the sympathies of our young friendswill be excited on behalf of the juvenile questioner,and their interest thus maintained in thestudy of the sciences.
A dialogue upon Astronomy will shortly follow;being a conversation between a father and hisson, coming out to Australia, from Old England.
Melbourne, April 17, 1857.
HOW A TREE GROWS
Willie was a fine rosy-faced boy of our southerncolony. Though not eight years of age, hewas as healthy and merry a lad as ever climbedup a Gum tree, picked up manna, or rode in abullock dray.
His father had once occupied a good positionin Old England; but the uncertainties and lossesof business, and the constant struggle to upholda respectable appearance with decreasing means,became so burdensome to his mind, that hisspirits failed, and his energies sunk. His attentionwas directed to Australia, the land of muttonand corn, the home of health and plenty.Gathering up the wreck of the past, he left thecountry of taxation and paupers, and establishedhimself on a small farm in Port Phillip.
The young hero of our story had been a yearor two in the colony. It so happened he had apiece of land of his own, in which he proudly[Pg 2]exhibited some rising cabbages, a few peas, anda flower or two. His father had given him arose tree, which was the reigning beauty of thebed. It was upon the occasion of his parent’svisit to the garden, that the following dialoguetook place:—
Look, father, and see how my rose tree hasgrown.
Indeed it has, Willie. Can you tell me whathas made it grow?
The sun and the rain, I suppose.
Do you remember, when we got tired of theold slab hut, and set about building this brickcottage, that you noticed it getting higher andhigher every day!
Yes, that was because more bricks and woodwere used.
Then, if your tree increases in size, theresurely must be something added on continually:do you think the sun and rain do this?
Well, I never thought about it, father; but Ishould like to know why it does grow.
Can you tell me, Willie, what a plum puddingis made of?
Yes, that I can. There is the flour, the suet,the raisins, and the cold water. All these aremixed together.
Then let us see of what our rose tree is made.
I don’t think it so easy to tell that as toreckon up the articles in a pudding.
Never mind, we will try. First, there is the[Pg 3]stalk, or woody part. When you put a piece ofstick in the fire, what becomes of it?
Oh, it smokes and blazes, and then nothing isleft 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. Butwhat do you call woody matter that will not blaze?
Charcoal, father. Then I understand nowthat wood is nothing but charcoal and the gases.What are these gases?
The gas which blazes so readily, my dear, ishydrogen: and it has a very strong smell too.The air we breathe is a mixture of two gases—oxygenand nitrogen. It is only the oxygen thatwe take into our lungs.
Well, that is curious.
I shall puzzle you more, Willie, when I tellyou that water is nothing but a mixture of oxygengas and hydrogen gas.
It certainly is funny that water, which putsout flame, should be partly composed of theburning gas.
You must also know, my lad, that hydrogenwould not burn without oxygen. You blow airinto a fire to give food for flame.
But however could the plants get hold of thegases, father?
Did it never strike you why God formedleaves?
[Pg 4]It never did, except that I thought he did itto make the trees look pretty.
That is quite true, Willie. The good Godloves beauty, and he has surrounded us withbeauty of all kinds. But he made things foruse as well as to be looked at. The leaves absorbor suck in gases from air and water.
Then I suppose the veins like that we see inleaves conduct these gases away into theplant.
Quite right, my boy. Where now shall weget the charcoal, or carbon, as the learned mencall it?
That I cannot find out at all.
You told me, Willie, that smoke came out ofburning wood. What becomes of it?
When I was a very little boy, I thought itwent up to form clouds; but now I know part ofit turns into soot in the chimney, and that lookslike our charcoal or carbon.
It really is. As to that which comes out ofthe chimney, it passes upward, and gets graduallymixed with the air. The little particles ofcarbon join the oxygen, and become a sort of gascalled carbonic acid gas, which is absorbed intothe plant.
How wonderful that the solid part of a treeshould once have been floating about in the air!
Do you think the leaves of a plant to be thesame as the stem?
Yes, I do; for when they are thrown in a fire,[Pg 5]they smoke, blaze, and leave an ash like thewood does.
Just so. You know the smoke to be carbonpassing into the air; but we must examinethe ash a little more carefully. If you take someash 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 offthe water, and allow it to evaporate in a dish,there will be found to be a sediment left, andthat is potash or pearl ash.
I have heard of people in the bush doing thatwhen they could not get soap, for they said thatthe potash got the dirt out of clothes.
It is a great pity that we in these coloniesburn away so much wood in waste when clearingland, Willie, without thinking of making potashout of the ashes, for it fetches a good price.
Then there is potash in the plant. Has anything else been found in the ash beside that andcarbon?
Yes, my lad. Sulphur or brimstone, lime,soda, flint, ammonia, phosphorus, magnesia, andiron, are contained in trees.
But how could all these things get there?
Why, if we cannot find them in the air to beabsorbed by the leaves, they must be in the soilor ground. Now, it so happens that those substancesare to be found in different quantities indifferent places.
[Pg 6]How do they get into the plant, father?
Simply by the little rootlets absorbing smallparticles of them, mixed with moisture.
But do all plants require the same amount oflime, potash, soda, and the others?
No, my dear. There are not two sorts of treesthat feed upon the same materials in exactly thesame proportions.
Is that the reason, then, why some land is somuch better fitted to grow one plant than another?
The reason is, because the one soil has moreof the right sort of food in it.
Now I see that if I wanted to grow a goodcrop of any thing, I must give it plenty of thefood it likes best.
Yes, but not too much. For like as too muchnice rich food is bad for children, so it is withvegetables: ground may be too rich, as well astoo poor.
I have heard people say that it is not wise togrow the same thing in the same soil yearafter year: why is this?
Because it would gradually consume all thefood there, and then it would starve, and lookmiserable.
Then my beautiful flower-bed will by-and-bycease to bring forth such a fine show as it hasdone this season.
Of course it will, unless you provide yourplants with fresh food.
[Pg 7]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 soadd sulphur, potash, and carbon. Sea weedmanure furnishes plenty of soda. Bone dustcontains lime and phosphorus.
It is possible, then, to apply to the ground theamount of solid matter taken out of it by theplant, so that if my radish bed had some manure,it would be as good as it was before mycrop came off.
That is perfectly correct, my boy.
But how is it that a gum-tree forest is keptup, for there must be a tremendous lot of lime,soda, flint, and the rest, removed from thesoil?
Yes, but when the trees fall, they rot, and thesolid parts return to the ground.
Oh, father, the remains are very small, comparedto the living tree.
True, because the principal part of a plantconsists 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 thebreath of animals another.
What has the breath to do with it?
Every time you respire, or breathe out, some[Pg 8]carbonic acid comes out with air, and is carriedinto the atmosphere.
Why, father, you do not mean to say that mybreath helps to make cabbages grow.
The carbon passing from your body may becomea part of a cabbage, or gum tree, or a delicatetulip.
The next time Willie and his father were outtogether, the conversation again fell upon trees.The wonder of the boy had been strongly excitedby the last lesson, and he had now lots ofquestions to ask. He knew enough to knowthat 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 besome entrances for the food to reach parts needingsupply. Then he sought to understand howthe growing process was managed, and especiallyhow seeds were formed, and how the plantsprang from them. Thus, question after questionpoured out from the boy’s lips, without even apause for a reply.
“Stop, stop, my man,” said his father; “Iam not like the Hindoo god with half-a-dozenpairs of ears, and half-a-dozen tongues. Wewill go now a little deeper into the subject; butwe must take one thing at a time. What doyou think of that gum tree yonder?
That is a noble fellow. What a barrel he has[Pg 9]got for splitting paling out of! And hasn’t hegot a fine top knot? Why, that must be almostas big as that Tasmanian tree you readabout.
Oh, no; that one was 350 feet high, and was104 feet round; while this is not above 100 feethigh, and 30 round.
Well, then, that must be a monster surely.How curious to think it was once a tiny littlething that I could pull up with my finger! Isay, father, how many cartloads of carbon thisone must have got hold of! I fancy it has gotgas enough to fill many a balloon. But how didit grow?
To answer that question, will give us sometrouble, and take some time. First, tell me allthe parts of the tree.
What I cannot see is the root; then comesthe 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 theseed?
I never thought of that. But flowers are alwayssuch pretty light things, that one wouldbe sure to see them a long way off on a gum tree.
But if instead of having fine red leaves, mylad, the flower had none, and the other part wasmuch the same colour as the leaves, do you thinkyou would notice it so readily?
[Pg 10]No, father. Won’t I give a good look out forit after this; for I am sure none of our boys atschool ever talk of gum flowers, though we oftengo to gather wattle blossoms.
To go on with our tree—we will take theroot, and there is