How a Tree Starts

We saw in Book III. that some plants live much longer than others. Some live for one year only, make their seeds and die. These we call annuals. Others live two years. They grow their roots and leaves one year, and flower and make their seeds the next year. These we call biennials, because bi means two. Others live for many years, and are called perennials. Trees are perennials, for they live for very many years. There are some oak trees more than a thousand years old.

Yet all these old trees began their lives as little seedlings, like the bean you grew on the top of the earth in the flower-pot. How, then, have they managed to live so long? We shall learn this best by looking at a young seedling.

If you poke about in a wood, you will easily find some small plant, either of oak, or beech, or hazel, which has grown up from a nut, or an acorn trodden into the ground. I am going to take an oak tree, because I have one close to my door and can give you a picture of it. If you get an acorn and stick it in the neck of a bottle, the same way up as it sits in its cup, and keep the bottle full of water, you can grow a small oak for yourself, and see if yours is like mine.

First the acorn puts out some roots downwards. Then the husk splits, and you can see the two thick seed-leaves open, with the growing tip between them. This tip now grows steadily upwards and soon puts forth leaves. There may be one, or even two, one above the other, on the sides of the stem. But there will certainly be two or three close together at the top of the little tree by the time autumn comes. At the foot of each leaf, nestling up to the stem, will be a little bud, and at the end of the stem will be a stout bud, bigger than all the rest.

The difference between the oak-plant and the bean which we grew in Book III. is that the stem is woody. If you get another oak-plant of the same age from the wood, and cut off its head this is what you will see (Fig. 1, p. 13). In the middle there is a round white patch, p. This is the pith, or soft part, which you scoop out of the branch of an elder-tree when you make a popgun. Next comes a ring of soft whitish wood, w. Outside this again is the bark, b.

Now you know that water, with earthy matter in it, has to rise up from the roots and go to the leaves, to be made into food. It travels up through this ring of living wood, and when it comes back it makes new wood and new bark just where the wood and the bark meet. You know how easy it is to peel the bark off wood. That is because the tender new part is between them, and gives way easily.

But as soon as autumn comes, the roots leave off taking in water; and the crude sap, as it is called, does not rise up any more. The stalks of the leaves dry up where they join the stem, and they fall off. The tree rests for the winter.

Now watch your little plant next sprung. You will see the big bud at the tip, and often two other buds close to it, begin to grow into branches and have leaves of their own. But in a very young tree the smaller ones usually die away and the trunk grows straight up. However, you can always tell where the new growth began in the spring, because there is a ring (r, p. 12) left by the scales of the buds. The wood of the new piece will be just like the wood of the lower piece was last year. But that lower piece will be growing some fresh wood and getting bigger (Fig. 2, p. 13). The sap will go up and down as before, and a new ring of wood (w 2) will form outside the old wood, and a very thin new ring of bark inside the old bark. So at the end of the second year, while the new piece will have only one ring of wood, the old piece below the scales will have two rings (w and w 2), with a mark between the rings, showing where the tree rested in the winter.

All this is rather difficult to see in such small trees, and you must look at the diagrams. But if you go into the wood when they are cutting down timber, you will see the rings much more distinctly in the older trees, and you will like to look at the trunks, and try to make out how old the trees are. You cannot be quite sure that you count all the years, because as the new wood grows, the old is squeezed together, and makes a very hard wood, called "heart-wood," in the middle of the trunk. But you can be sure that the tree is not younger, and most likely much older, than the rings you can count.

Now to come back to our question, how trees live to be so old. Year after year they make a new ring of wood, narrower and narrower its they grow older. Through the younger rings the crude sap goes up to the leaves, and the food-sap comes down to feed the parts of the tree. Buds are formed every spring on the stems at the foot of each leaf, and these buds are like new plants. They start with fresh strength, making new food for the tree, which carries them up on its trunk and branches into the light and air.

The heart-wood of the tree is really dead, and sometimes decays away while the outer part of the tree is still flourishing. But many of the rings of wood far inside the trunk still want food, and if you look at a felled tree you can see how they get it. Besides the rings, you will see some lines (m), like the spokes of a wheel, starting from the centre of the trunk and spreading out to the bark. These lines are made of pith, like that we saw in the middle of the young seedling oak. Until they are squeezed away the sap passes along them all through the tree.

There are some trees, such as the palms, which you see in hot-houses, which do not grow in rings. But these are not English, and do not concern us here.

Get several pieces of tree-branches and try to see the bark, the inner bark, the rings of wood and the heart-wood—Lilac, Lime, and Elder show the parts well. Oak and Pine show heart-wood best.