I wonder if you have any woods near you with oak trees growing close together, or mixed with beech and ash trees. This is the way they are grown, when they are to be cut into long planks, or poles, and most likely there will be some wood, where you can stop and look at them on your way home from school.
They will have straight, smooth trunks; some twenty, some thirty, some perhaps fifty feet high, before the branches spread out above. Yet you know that your seedling oak has buds, first on one side, then on the other, all up the stem. How is it that these buds have not grown into branches?
The reason is that in a thick wood, where the trees crowd each other, every tree wants to raise its head up to the light. So in the spring when the leaves and buds open out at the top of the little tree, and the crude sap rises up to them from the roots, the tree wants so much to use for growing up higher that only a small quantity goes down again to make new wood. So the buds lower down do not get enough food to grow, and they either die or become dormant. That is, they remain waiting for another opportunity, which often never comes. For this reason oaks in a wood grow taller and taller with only a crown of branches and leaves near the top.
But if you can find an old oak out in the open field, or at the edge of the wood, where it has plenty of room, you will see that it has grown differently. The trunk is much larger, and the branches grow out lower down. In many big oaks a man can reach the lower boughs as he stands under it. The branches are very heavy and stretch out widely all round, so that an old oak tree covers a great deal of space in open ground. If the trunk were not very strong it could not bear the weight of such huge branches. But it is very broad at the bottom and then curves in and rises like a stout pillar till it becomes broad again where the branches divide away from it.
When Smeaton, the great engineer, built the Eddystone lighthouse, he shaped it like the trunk of an oak, and the lighthouse stood firm against wind and waves for more than a hundred years.
The oak has a very thick strong root from which long ropy roots run out all round the tree. I will tell you a way by which you may know how far the roots of a tree spread underground. Look at the branches and see how far they stretch out from the trunk, for the roots will reach just as far underground as the branches do above ground.
The reason of this is very interesting. You will remember that the tips of the roots are the mouths of a plant. They drink in the water. Now when it rains, the raindrops trickle from leaf to leaf till they come to the tips of the branches, and then they drip down and sink into the ground. The roots would get very little rain-water if they stopped under the tree where you and I stand to keep out of the rain. But as the tree grows, the roots find their way farther and farther out, till they reach the place where the drip will be.
You will find it useful to know this in gardening and farming, for tree roots are often very troublesome.
When you have looked at the rugged bark of the old oak, which is so useful for tanning leather, look up at the branches. They twist and turn in all directions, and there is a very thick joint wherever a new branch starts.
You can see the reason of this, if you look at your young tree (p. 12), or at a twig of the old tree. There is not one bud at the tip of the twigs as there was in the horse-chestnut, but two, three, or sometimes more. All these buds crowd each other, and the middle one generally dies. The others go off different ways, and so make what carpenters call "knee-joints." These were used for shipbuilding in olden days, because they are very strong. But now that ships are made of iron, knee-timber is not so much wanted, and straight planks and poles are more valuable. So it is best now to plant oaks in woods, where their stems grow straight and smooth.
Oak timber has always been valuable. The beams of Westminster Hall, which was built about nine hundred years ago, are made of Durmast Oak, and are still as good as ever. Many country cottages have old chests and carved chairs in them quite as old as this. The heartwood of the oak is very firm and strong, and this is why the old song says
"Hearts of Oak are our ships,
Hearts of Oak are our men."
You can see the trunk and branches of the oak best, in winter. Then when April is nearly over, a pretty crimson colour comes on all the buds, the leaves open out, and the loose catkins hang down between them, while the tiny acorn flowers nestle between the leaf-stalk and the stem.
When the leaves are fully out, and the acorns are beginning to form, try if you can find the two kinds of English oak. Their leaves are much the same shape, long and cut into deep divisions. But the leaves of the Common Oak (1, p. 30) have very short leaf-stalks, they almost touch the stem, while the acorns stand on long stalks. In the other tree called the Durmast Oak the leaves usually have longer stalks, and the acorns have none.
The evergreen oak, which is often grown in gardens, was brought from Italy. Its leaves are something like the leaves of the holly, so it is called the holm oak or holly oak.
Get a branch of oak and notice the crowded buds. Get a log of oak and notice the dark heartwood and the rings round it. Also the rugged bark. Try to find the two kinds of English oak. Notice the scales grown together in the acorn cup.