GBOSS ANATOMY OF FLOWERINQ- PLANTS. XV 



others which have annual stems have liennial or perennial roots. 

 In shrubs and trees the roots are of course perennial. Many root- 

 lets, however, even in trees and shrubs die off in the autumn, and 

 new ones are produced in the spring. 



Branching. — The branching of roots is usually very irregular. 

 Where roots are branched, the main root is called the primary 

 root, while its branches are secondary roots. In examining the 

 branches of roots, notice that they spring from beneath the sur- 

 face of the main root. In this they differ from the branches of 

 stems. In stems the surface of the main stem is continuous with 

 that of its branches, but in roots the surface is broken at the 

 points where branches emerge. 



§ 3. The Leaf. 



Position on the Stem. — Leaves grow upon the stem in several 

 ways. In some cases they are scattered (or altertutte) (Fig. VII) ; 



Fia. VII. 



Fig. Vin. 



FiQ. VII.— Scattered or alternate leaves. 

 FiQ. VIII.— Opposite leaves. 



in others they are opposite (Fig. VIII) ; in others again they are 

 whorled (i.e., several occupy a circle around the stem). 



Parts. — Many leaves have three well-deflned parts: 1. A broad 

 or flattened part, the Made; 2. A leaf-stalk, upon which the blade 



