98 



THE STEM. 



usually three buds at the apex of a branch ; namely, the terminal, 

 and one in the axil of each leaf; but it seldom happens that all 

 three develop at the same time. Sometimes the terminal bud con- 

 tinues the branch, the two lateral generally remaining latent, as in 

 the Plorsechestnut (Fig. 153) ; sometimes the terminal one regu- 

 lai'ly fails, and the lateral ones grow, when the stem annually be- 

 comes two-forked, as in the Lilac (Fig. 154). The undeveloped 

 buds do not necessarily perish, but are ready to be called into action 

 in case the others are checked. When the terminal buds are 

 destroyed, some of the lateral, that would else remain dormant, 

 develop in their stead, incited by the abundance of nourishment, 

 which the former would have monopolized. In this manner our 

 trees are soon reclothed with verdure, after their tender foliage and 

 branches have been kiUed by a late vernal frost, or other injury. 

 And buds which have remained latent for several years occasionally 

 shoot forth into branches from the sides of old stems. Such branch- 

 es, however, more commonly originate from irregular, accidental, or, 

 as they are named 



168. Adventitious Buds. It has been already remarked, that roots, 

 although naturally destitute of buds, do yet produce them in certain 

 plants, especially when wounded (139). So likewise do the stems 

 of some shrubs and trees, especially when surcharged witli sap, as 

 is commonly seen in Willows and Lombardy Poplars. Here buds 

 break out habitually on the sides of trunks, at least when they are 

 wounded or pollarded, or spring from the cut surface where the bark 

 and wood join. These ad\-entitious buds do not originate from 

 nodes, nor affect any order in their appearance, but are wholly 

 casual as to the point of origin. Thus the predestined symmetry of 

 the branches is obscured or interfered with in two distinct ways ; 

 first, by the failure of a part of the regular buds to develop ; and 

 secondly, by the irregular and casual development of buds from 

 other parts than the axils of the leaves : to which we may add, that 

 great numbers of branches perish and fall away after they have be- 

 gun to grow. There is still another source of irregularity, namely, 

 the production of 



169. Accessory Buds. These are, as it were, multiplications of the 

 regular axillary bud, giving rise to two, three, or more buds, instead 

 of one ; in some cases situated one above another, in others side by 

 side. In the latter case, which occurs occasionally in the Hawthorn, 

 in certain Willows, in the Maples (Fig, 158), &c., the axillary bud 



