114 



ELEMENTS OF STRUCTURAL UOTANY. 



As has already been pointed out, the leaves of Mono- 



cotyledonous plants are almost invariably straight-veined. 



170. In addition to the venation, the description of a 



Fig. 145. 



Fig. 146. 



simple leaf includes particulars concerning : (1) the gen- 

 eral outline, (2) the edge or margin, (3) the point 

 or apex, (4) the base. 



171. Outline. As to outline, it will be convenient to 

 consider first the forms assumed by leaves without lobes, 



Fig. 147. Fig. 148. 



and whose margins are therefore more or less continuous 

 Such leaves are of three sorts, viz.: those in which both 

 ends of the leaf are alike, those in which the apex is 



Fi8. 145 to 148. Various forms of foliage-leaves. 



