There is still another insect which attacks the leaf buds and causes them to grow in a curious way. Instead of opening as usual, the bud proceeds to make layers of narrow-pointed green leaves which it lays tightly one above the other, like the leaves of an artichoke or the scales of a fir cone. If you cut one of these Oak cones in half you will find many small insects inside, which have caused the bud to grow in this strange way. And there is one other oak gall you must note. When the leaves have all fallen and the twigs are brown and bare, you see clusters of hard brown balls growing on some of them. They are smooth and glossy and the colour of dried walnuts. These also have been made by an insect. Sometimes you see the tiny hole in the ball by which the grub has bored its way out. This kind of gall does great harm to the tree, as it uses up the sap that should nourish the young twigs. The wood of the Oak is very valuable. Sometimes a fine old tree will be sold for four hundred pounds, and every part of it can be used. The bark is valuable because it contains large quantities of an acid which is used in making ink; also in dyeing leather. Oak that has been lying for years in a peat bog, where there is much iron in the water, is perfectly black when dug out, black as ink, because the acid and the iron together have made the inky colour. [Illustration: PLATE II THE BEECH 1. Beech Tree in Autumn 2. Leaf Spray 3. Bud 4. Buds in Winter 5. Seed Flower 6. Stamen Flower 7. Fruit 8. Fruit when Ripe] The wood of an Oak tree lasts very long: there are Oak beams in houses which are known to be seven hundred years old, and which are as good as the day they were cut. For centuries our ships were built of Oak, the wooden walls of old England, hearts of Oak, as they have often been called, because Oak wood does not readily splinter when struck by a cannon ball. And Oak wood will not quickly rot: we know of piles which have been driven into river beds centuries ago and are still sound and strong. In pulling down an old building lately in London, which was built six hundred and fifty years ago, the workmen found many oak piles in the foundations, and these were still quite sound. PLATE II THE BEECH