no 



BOTANY AND PHARMACOGNOSY, 



moreover be noticed that the distribution of the veins in this 

 manner produces a lamina with an even, or entire margin, and 

 such a system of venation is known as a closed system of 

 venation (Fig. 72, A). The leaves of Veratrum (Fig. 129) and 

 Zea Mays, furnish other examples of parallel-nerved leaves. 



In palms (Fig. 251) the venation is somewhat different. The 

 veins instead of converging toward the apex as they do in the 

 more or less lanceolate leaf of lily-of-the valley, radiate from the 

 base to the margin of the more or less round leaf, and a leaf of 

 this type is said to be palmi-nerved. 



Fig. 72. Leaf venation: A. parallel-veined leaf of Solomon's seal {Vagnera race- 

 mosa); B, pinnately-reticulate leaf of chestnut; C, palmately-veined leaf of Menispermum 

 canadense. 



There is still a third type of venation in Monocotyledons. 

 In this instance one principal vein runs from the base to the apex 

 of the leaf, and from this branches run parallel to the margin. 

 The banana furnishes an example of this type, and is said to be 



PINNT-NERVED. 



Venation in Dicotyledons. Here the veins are charac- 

 terized by their habit of repeatedly branching and anastomosing. 



