112 



PLANT BIOLOGY 



the bud is protected by varnish (see horse-chestnut and 

 the balsam poplars). Most winter buds are more or less 

 woolly. Examine them under a lens. As we might 

 expect, bud coverings are most prominent in cold and dry 

 climates. Sprinkle water on velvet or flannel, and note 

 the result and give a reason. 



All winter buds give rise to branches, not to leaves alone; 

 that is, the leaves are borne on the lengthening axis. 

 Sometimes the axis, or branch, remains very short, so 

 short that it may not be noticed. Sometimes it grows 

 several feet long. 



Whether the branch grows large or not depends on the 

 chance it has, position on the plant, soil, rainfall, and 

 many other factors. The new shoot is the 

 unfolding and enlarging of the tiny axis 

 and leaves that we saw in the bud. If the 

 conditions are congenial, the shoot may 

 form more leaves than were tucked away 

 in the bud. The length of the shoot usu- 

 ally depends more on the lengths of the 

 internodes than on the number of leaves. 



Where Buds are. Buds are borne in the 

 axils of the leaves, in the acute angle 

 that the leaf makes with the stem. When 

 the leaf is growing in the summer, a bud 

 is forming above it. When the leaf falls, 

 the bud remains, and a scar marks the 

 place of the leaf. Fig. 139 shows the large leaf-scars of 

 ailanthus. Observe those on the horse-chestnut, maple, 

 apple, pear, basswood, or any other tree or bush. 



Sometimes two or more buds are borne in one axil ; the 

 extra ones are accessory or super nunierary buds. Observe 

 them in the Tartarian honeysuckle (common in yards), 



FIG. 139. LEAF- 

 SCARS. Ailanthus. 



