Galls of various kinds are to be found on most oaks. These are excrescences caused by certain insects having laid their eggs in the soft tissues beneath the surface. More than fifty species of insects obtain their food from the oak. Some of these will be referred to in a later chapter.
Fig. 116.—The Birch.
The beech.—The beech ( [Fig. 114]) is easily recognised by the olive-grey, smooth bark, and by the shape of the base of the trunk, which usually has the appearance of being formed by the union of several separate columns. When well grown the tree is lofty, and bears a wide-spreading crown of branches which, when clothed with leaves in summer, casts a dense shade. The ground beneath the tree is generally destitute of other vegetation. The winter-buds are long and pointed; they expand in May, the new shoots at first drooping, but straightening out in a fortnight or so. The leaves ([Fig. 115]) are broad, thin, and glossy, and are fringed with fine, silky hairs. Young beeches, like young oaks, often retain their leaves through the winter.
The tree is in flower by the time the foliage has fully developed. The male flowers are borne in small, rounded catkins (a, [Fig. 115]). The female flowers (3, [Fig. 115]) are in pairs. Each pair is surrounded by prickly scales, and gives rise after fertilisation to two three-sided and pointed nuts enclosed in a woody cup or husk. The husk is covered with hard, blunt prickles, and when ripe splits into four parts.
Beeches do not harbour many insects, but squirrels frequent them for the sake of the nuts. The prickly husks protect the fruit from being eaten before it is ripe.
Fig. 117.—The Birch; leaves, flowers and fruit.
1, branch with male (b) and female (a) catkins (× ⅔);
2, bract with three male flowers (× 2);
3, bract with three female flowers (× 4);
4, ripe cone (× ⅔); 5, fruit (× ⁴⁄₃).