156 



THE LEAVES. 



241) ; if two such ribs proceed from each side of the midi'ib, it is 

 said to be quintuple-ribhed, or quintupli-nerved. 



231 



232 



233 



234 235 



236 



279. Not unfrequently the vessels of a reticulated leaf divide at 

 the apex of the petiole into three or more portions or ribs of nearly 

 equal size, which ai'e usually divergent, each giving off veins and 

 veinlets, like the single rib of a feather-veined leaf Such leaves 

 are termed radiated-veined, or pcdmately-veined ; and, as to the 

 number of the ribs, are called three-ribbed, five-ribbed, seven-ribbed, 

 &c. (Fig. 244, 247, 253). Examples of this form are furnished by 

 the IMaple, the Gooseberry, the Mallow family, &c. Occasionally 

 the ribs of a radiated-veined leaf converge and run to the apex of the 

 blade, as in Rhexia and other plants of the same family, thus resem- 

 bling a parallel- veined or nerved leaf; from Avhich, however, it is 

 distinguished by the intermediate netted veins. But when the ribs 

 are not very strong, such leaves are frequently said to be nerved, 

 although they branch before reaching the apex. 



280. According to tlie theory of De Candolle (275), the shape 

 Avhich leaves assume may be viewed as dependent upon the dis- 

 tribution of the veins, and the quantity of parenchyma ; the gen- 

 eral outhne being determined by the division and direction of the 

 veins ; and the form of the margin, (wliether even and continuous, 

 or else interrupted by void spaces or indentations,) by the greater or 



FIG. 231-244. Various forms of simple leaves. 



