VENATION OF LEAVES. 



157 



120 



438. Parallel venation is of two 

 principal kinds : (1) that in wliich. 

 large nerves run in long curves 

 from the base to the apex of the 

 leaf; (2) that in which smaller 

 nerves run generally at right an- 

 gles from a main nerve (or midrib) 

 to the edges of the leaf. In both 

 these kinds of parallel venation 

 the veins are more or less con- 

 nected bj' means of inconspicuous 

 cross-veinlets and b^- the anasto- 

 mosing extremities, but some of 

 the veins may be free. 



439. Eeticulated venation is 

 likewise of two principal kinds : 



(1) palmate (Fig. 120), in which 

 relatively large veins diverge from 

 each other at the base of the leaf ; 



(2) pinnate (Fig. 121), in which 



Fig. 120. Venation of the le^f of Asarum Europseum. (Ettingshansen.) 

 Fig. 121. Venation of the leaf of Salix graiidifolia. (EttinesliauBcn.) 



