24 BOTANY OF CROP PLANTS 



buds by their external appearance. In some cases, however, 

 they have a different shape. In the apple, for example, 

 fruit buds (here, really mixed buds) are rather thick and 

 rounded, while leaf buds are smaller and more pointed. 

 In all plums, the flower buds are lateral, and usually stand 

 out at an angle of about 30°, while leaf buds are more ap- 

 pressed to the stem. 



Buds may be classified as to their position on the stem into : 

 (a) terminal, (b) lateral or axillary, (c) accessory or super- 

 numerary, (d) adventitious, and (e) dormant. 



Most stems end in a bud. Such a terminal bud is almost 

 always a leaf bud; occasionally it bears flowers, too, as in the 

 apple. The terminal bud is normally the most vigorous of 

 all on the stem, as is evidenced by the fact that it elongates 

 into a shoot which exceeds in length those from the lateral 

 buds. Lateral (side) buds arise in the leaf axils. They give 

 rise to side branches or to flowers. Accessory or supernumer- 

 ary buds are extra ones coming out in the leaf axils. They 

 are best shown in the maples and box elder. Adventitious 

 buds arise out of order, in unusual places, not in leaf 

 axils or at the end of a stem. They are usually stimu- 

 lated by injury. For example, when a branch is cut back, 

 numerous adventitious buds develop about the edge of the 

 cut surface. Dormant buds are ones that have arisen in a 

 regular fashion in the leaf axil, but which, for some reason, 

 do not develop. Hence, they may be grown over with the 

 succeeding layers of wood and lie buried within the tissue in 

 a latent condition. Such a bud may be called into activity 

 later in the life of the plant and come to the surface. It 

 would appear to be endogenous in its origin, while in reality 

 it is exogenous. Irregular branching may result from the 

 development of dormant buds, or as is more commonly the 

 case, from the development of adventitious buds. 



