ORGANS OF NUTRITION. 1 63 



it is emarginate, as in some kinds of Senna (Cassia obovata) (Jig. 

 313a), and common Box (Buxus semper vireris) ; when the 

 leaf terminates very abruptly, as if it had been cut across in a 



Fig. 313a. Fig. 3l3b. 



Fig. 313a. Leaflet of Cassia obovata. It 13 obovate in form, oblique at the 



base, and emarginate at its apex. Fig. 3136. Branch of Tulip-tree 



( Liriodendron tiiUpifera) with flower and leaves. The latter terminate ab- 

 ruptly, hence they are said to be truncate. 



Straight line, it is truncate, as in the leaf of the Tulip-tree (Lirio- 

 dendron tulipifera) (Jig. 3136) ; if under the same circum- 

 stances the termination is ragged and irregular, as if it had been 

 bitten otF, it is prcemorse, as in the leaf of Caryota wens. When 

 the apex is sharp, so that the two margins form an acute angle 

 with each other (Jig. 320 and 322), it is acute or .sharp pointed, 

 as in the leaf of the Lady's Shpper (Cypripedium Calceolus) and 

 most lanceolate leaves ; when the point is very long, and taper- 

 ing (Jigs. 317 and 320), it is acuminate or taper-pointed, as in the 

 leaf of the White Willow (Salix alba) and common B.eed(Phrag- 

 mites communis); when it tapers gradually into a rigid point, it is 

 cuspidate, as in many Rubi ; when the apex is rounded, and has 

 a short hard or softened point standing on it, it is mvcronate, 

 (Jig. 319), as in the leaf of Statice mucronata, and Lathyrus 

 prateiisis. 



4. General Outline. — By the general outline of the leaf we 

 understand the superficial aspect or figure which is described by 

 its margins. This is subject to great variations depending as 

 we have seen, according to DeCandoUe (p. 157), upon the 

 direction and length of the veins. The development of veins 

 and parenchyma is usually nearly equal on the two sides of 

 the midrib, or petiole, so that the leaf in most instances is 

 nearly symmetrical and of some regular figure ; in which case 

 it is said to be equal (Jigs. 320 — 323). When, as occasion- 

 ally happens, the leaf i.s more developed on one side than 

 on the other, it is termed uyiequal or oblique (fig. 313a); 

 this is remarkably the case in the Begonias (Jig. 315). 

 M 2 



