Were I a skilful painter, What should I paint for thee? A tiny spring bud peeping out From a withered wintry tree. G. MACDONALD, BUDS AND STIPULES CHAPTER I ON BUDS EVERYONE who loves a garden knows to his cost how susceptible young leaves are to cold-how often the bright promise of spring is ruined by late frosts. Buds offer also a tempting food to insects and other animals. Moreover, their development is generally a slow process, the buds for the following year being already formed, as a rule, during the previous summer, in many cases as early as June or July, and in some even a year and a half in advance. The protection of the buds is therefore one of the most important requisites in plant lite-in cold countries against frost, in hot against the sun. During winter the young leaves lie snugly enclosed in several warm wraps, covered in many cases by furry hairs, and often still further protected from insects and browsing quadrupeds by gummy or resinous secretions. The bud is a short shoot bearing a number of young leaves closely packed together. There is generally one B at the summit of each twig and in the axil of each leaf. 6 When the year is divided into favourable and unfavourable seasons, marked either by alternations of temperature or by drought and rain, there is often a marked difference between growing' and 'resting' buds. Moreover, among our own species there is often a considerable difference between terminal and axillary buds, as, for instance, in the Black Poplar (Populus nigra). FIG. 1.-YOUNG SHOOT OF TULIP TREE (Lirioden- The following figure (fig. 1), representing a young shoot of a Tulip Tree, is an illustration of the necessity for such protection. It will be seen that the outer (lower) leaf, which had only a single covering, has been killed by frost, while the succeeding one, which had two wraps, has escaped. It is remarkable that some nearly allied genera, and even in certain cases species of the same genus, often differ in the method of the protection of the bud. This is the case, for instance, in the Willows and Poplars, the function being performed in the Poplars by stipules, in the Willows (though they possess stipules) by leaves. The bud may either be protected by older organs, or its own outer envelopes may be modified for the purpose. In some plants, especially those which are quick B FIG. 2.-BEGONIA. A, shoot seen from above. B, shoot seen from one side. Reduced. growing or natives of tropical countries, the buds are comparatively naked and unprotected. Even in the tropics, however, though protection is not needed against cold, it is required against the burning sunlight and against drought. In the Begonias (fig. 2), for instance, as Mr. Potter has pointed out (1),1 the buds are shaded from the overpowering heat of the sun by the older leaves. Plants grown under artificial conditions do not show the arrange FIG. 3. FIG. 4. B YOUNG LEAVES OF HYPERICUM CALYCINUM. Nat. size. FIG. 3, seen from the side. FIG. 4, with one leaf turned back to show the younger, enclosed pair (B). ment well, as the leaves are often drawn to one side or the other by the light. But Mr. Potter, who has had the opportunity of examining many species in a wild state, found that they were always more or less arranged as shown in fig. 2. The works referred to by these numbers (1, &c.) are given in the 'Bibliography' at the end of the book. |