3. The birch.—Observe the graceful appearance of the tree; the slender trunk, with its bark streaked with brown, yellow, and silver; the purple-brown colour and wiriness of the young twigs; the shape and size of the dark green leaves, and the cylindrical, many-flowered catkins. The male catkins appear in the autumn, the smaller female catkins in the following spring. Examine the two kinds of flowers. Find an old birch-cone and break it open to see the winged fruits. What is the use of the wings? 4. The hazel and alder.—In what situations do these trees grow? Compare them with the birch. Notice that in both hazel and alder the male flowers are in long, dangling catkins. The groups of female flowers of the hazel look almost like leaf-buds, but can be recognised by the spreading red stigmas. The female flowers of the alder form distinct cones. Is the flowering part of the twig of this year’s or last year’s growth? Look in the autumn for the cones and catkins which will expand next spring. Trace the development of the fruit. The oak.—The student cannot better commence the study of forest trees than by selecting one as a type, and making himself thoroughly familiar with its life-history, and with its appearance at all times of the year. Other trees should then be compared and contrasted point by [Pg 143] point, is and with each other. The oak answers admirably as such a central type. It is perhaps the best-known of all British forest trees, not only from its wide distribution, but also from its historical and legendary associations. Fig. 112.—The Oak. The oak (Fig. 112) flourishes in exposed and sunny situations, especially where the soil is well drained. It can be recognised by the zig-zag and wide-spreading boughs, which often spring from the trunk almost horizontally. A very strong form of trunk is plainly necessary to support such branches, and in an old solitary oak it may often be seen that the bole is very thick at the ground line, and then rapidly narrows, until at a height about equal to the base-diameter it may be only half or one-third the thickness. Above this point it is practically cylindrical up to the origin of the boughs, where it is swollen. An oak growing in a wood, or plantation, is of very different form. Its trunk is tall and straight, and the larger boughs are not [Pg 144] given off until near the top. To secure the necessary light, the tree used its energy in growing in length, and in keeping pace with its neighbours rather than in spreading laterally. In such a crowded oak the lateral buds generally remain undeveloped, while the end of the shoot pushes onwards and upwards to the light. The opposite is the case when there is plenty of room and light on all sides. Then it is usually the terminal bud which dies, while the lateral buds grow out into branches, forming the “knee-joints” which were once so greatly valued for shipbuilding.