THE SHOOT. 



73 



surface, consisting always at first of a single layer of cells. This epider- 

 mis persists as a surface covering either throughout the life of the shoot, 

 or for a long period, being replaced only upon the older surfaces of the 

 stem by subfequently formed protective layers. (See T[ iii.) 



Fig. 58. — Diagram of a section through a bud. V^ the aiiex ; i, 2, 3, 4, successively older 

 leaf rudiments ; a^ b, c, successively older branch rudiments ; d, e, vascular bundles. 

 — After Hansen, 



89. Branching. — -Branches of the shoot aiise from lateral 

 buds, which are in all respects like the terminal buds just de- 

 scribed. If, for any reason, the terminal bud of the stem is 

 destroyed, or its growth arrested, a branch, developing from 

 a lateral bud near by, may assume the position and habit of 

 the main axis. In many plants the death or arrest of the 

 terminal bud recurs at regular intervals. In such plants, 

 therefore, the main axis is really a succession of lateral 

 branches, i.e., the branching is sympodial (cf fig. 59 and 

 ^ 58). In some plants, e.g., lilac, two lateral buds standing 

 at the same level may develop, if the terminal one fails. In 

 this case the shoot divides into two equal branches. Ordi- 

 narily, however, the terminal bud develops without interrup- 

 tion. In case it is more vigorous than any of the lateral 



