LEAVES {6 
remains. The vein-system or venation of leaves is ex- 
ceedingly diverse, but all forms can be referred to a few 
general plans. 
In some leaves a single very prominent vein runs through 
the middle of the blade, and is called the midrib. From 
this all the minor veins arise as branches, and such a leaf is 
said to be pinnately veined (Fig. 2, A, and Fig. 9). In other 
leaves several large veins (ribs) of equal prominence enter 
the blade and diverge, each giving rise to smaller branches. 
Fic. 2.—Venation: A, pinnately veined leaf of quince, showing blade, petiole, 
and stipules; B, palmately veined leaf of geranium ; C, parallel-veined leaf of 
lily-of-the-valley.— After Gray. 
Such a leaf is said to be palmately veined (Fig. 2, B, and T'ig. 
16). In still other leaves all the visible veins run ap- 
proximately parallel from the base of the blade to its apex. 
such leaves being parallel-veined (Fig. 2, C), as distinct from 
the two preceding, which are both net-veined. 
11. Form.—The forms of leaves are exceedingly varied 
and are related to their venation. Palmately veined leaves 
2 
