LEAF-BUDS AND BRANCHES. 97 



they do not attain a great diameter (fig. 115, 1). In other trees, 

 especially Exogens, besides the terminal bud, there are also lateral 

 ones. These, by their development, give rise to branches (ramz), from 

 which others called bmnchlets or twigs (ramuli) arise. Such buds 

 being always produced in the axils of leaves, are of course arranged 

 in the same manner as the leaves are. By the continual production 

 of lateral leaf-buds, the stem of exogenous plants acquires a great 

 diameter. 



189. Although provision is thus made for the regular formation of 

 leaf-buds, there are often great irregularities in consequence of many 

 being abortive, or remaining in a dormant state. Such buds are 

 called latent, and are capable of being developed in cases where the 

 terminal bud, or any of the branches, have been injured or destroyed. 

 In some instances, as in Firs, the latent buds follow a regular system 

 of alternation ; and in plants with opposite leaves, it frequently hap- 

 pens that the bud in the axil of one of the leaves only is developed, 

 and the different buds so produced are situated alternately on opposite 

 sides of the stem. 



190. When the terminal leaf is injured or arrested in its growth, the 

 elongation of the main axis stops, and the lateral branches often acquire 

 increased activity. By continually cutting off the terminal buds, a woody 

 plant is made to assume a bushy appearance, and thus pollard trees are 

 produced. Priming has the effect of checking the growth of terminal 

 buds, and of causing lateral Qnes to push forth. The peculiar bird-nest 

 appearance often presented by the branches of the common Birch, 

 depends on an arrestment in the terminal buds, a shortening of the 

 internodes, and a consequent clustering or fasciculation of the twigs. 

 In some plants there is a natural arrestment of the main axis after a 

 certain time, giving rise to peculiar shortened stems. Thus the crown 

 of the root (^[ 70) is a stem of this nature, forming buds and roots. 

 Such is also the case in the stem of Cyclamen, Testudinaria elephan- 

 tipes, and hi the tuber of the potato. The production of lateral in 

 place of terminal buds, sometimes gives the stem a remarkable zigzag 

 aspect. 



191. In many plants with a shortened axis, the lateral buds produce 

 long branches. Thus the Jiagellum (flagellum, a whip or twig), or 

 nmner of the Strawberry and Ranunculus, is an elongated branch, 

 developing buds as it runs along the ground ; the propagulum (pro- 

 pago, a shoot), or offset, is a short thick, branch produced laterally in 

 tleshy plants from a shortened axis, and developing a bud at its ex- 

 tremity, which is capable of living when detached, as in Houseleek. 

 Fig. 206 represents a strawberiy plant in which a' is the primary 

 axis, ending in a cluster of green leaves, r, and some rudimentary leaves, 

 f, and not elongating ; from the axil of one of the leaves proceeds a 



branch or runner, a", with a rudimentary leaf, f, about the middle, 



H 



