GENERAL MORPHOLOGY OF THE PLANT 29 



sides, and are thus enabled to arch over the stem. The arrange- 

 ment of the parts can be seen most easily when growth is very 

 slow, or altogether suspended, as in the winter, though the struc- 

 ture is the same at all times. The apex of the stem with its 

 covering of leaves is known as the bud. It is usual to speak of 

 terminal and lateral buds, according to their position at the apex 

 of the main stem or in the axils of the leaves. In the latter case, 

 however, the buds are the terminations of the branches and 

 are therefore really terminal. 



Fig. 40. 



Fig. 41 



Fig. 40. Erauch of Oak with alternate leaves and leaf-buds in their axils. 



a, a. Buds. 6, 6. Leaves. Fig. 41 . Vertical section through the end oi 



a twig of the Horsechestnut (jSscuIus liippocaslanam), before the bursting 

 of the bud. After Schleiden. 



The buds of temperate and cold climates, which remain 

 dormant during the winter, and which are accordingly exposed 

 to an its rigours, have generally certain protective organs de- 

 veloped on their outer surface in the form of modified leaves 

 which are commonly called scales, or cataphyllary leaves. These 

 are usually of a hardened texture, and are sometimes covered 

 with a resinous secretion, as in the Horsechestnut and several 

 species of Poplars ; or with a dense coating of soft hairs or down, 

 as in some Willows. Such scales, therefore, by interposing 

 between the tender rudimentary leaves of the bud and the air 

 a thick coating of matter which is a bad conductor of heat. 



