216 



TEXTBOOK OF BOTANY 



find how many different things have been wrapped up in so 

 small a space. Thus the flower bud of the lilac contains the 

 beginnings of many leaves and of a whole flower cluster, in- 

 cluding perhaps a hundred or more flowers. 



As a rule, a single bud is borne in the axil of each of the 

 leaves on a stem or branch. There are exceptions to this 

 rule, such as the asparagus, which has a cluster of short 

 branches (each developed from a bud) 

 in the axil of each scale leaf. In 

 general, the upper axillary buds, that 

 is, those nearest the terminal bud of 

 the stem or branch, are larger and 

 more likely to develop than the lower 

 ones. The difference in size between 

 upper and lower buds is very marked 

 in the lilac. The buds of an annual 

 plant, like the cucumber, must develop 

 very soon after they are formed, if 

 they are to develop at all. Such buds 

 have no covering for the young leaves, 

 branches, and flowers that they con- 

 tain. But perennial plants in tem- 

 perate and cold countries form buds 

 which must rest through the winter, 

 and so require protection against the 

 cold. Such buds are covered by scale-like leaves that 

 never become foliage leaves but that usually fall off in the 

 spring when the buds open. The grape and some other 

 perennials form some naked axillary buds that develop at 

 once, and other scaly axillary buds that rest throughout the 

 remainder of the year in which they were formed and develop 

 the next spring. But many perennials, including the lilac, 

 the apple, and most trees, bear only scaly buds in their axils, 

 which rest without further growth until the next spring. 

 As a rule, the terminal buds of a perennial plant grow con- 



FIG. 133. A, portion 

 of a lilac stem, with a 

 terminal bud and the 

 four uppermost axillary 

 buds. B, portion of an 

 Ailanthus stem with ac- 

 cessory buds at a, only 

 one of which will de- 

 velop. Notice the con- 

 spicuous bundle traces in 

 the leaf scar at b. 



