THE LEAF 



149 



tion on the stem, the different varieties of each depending on 

 the manner in which the leaves are distributed. 



Where three or more occur at a node, as in the trillium 

 and cleavers (Galium) , they constitute a whorl, which is only 



184 



185 



186 



FIGS. 182-187. Petioles, and leaf attachment: 182, petioles of jasmine night- 

 shade (Solanum jasminoides) acting as tendrils; 183, acacia, showing petiole 

 transformed to leaf blade ; 184, sessile leaves of epilobium ; 185, clasping leaf of 

 lactuca ; 186, perfoliate leaves of uvularia ; 187, peltate leaf of tropseolum. (182 and 

 186 after GRAY.) 



a variant of the opposite arrangement. There is no limit to 

 the number of leaves that may be in a whorl except the space 

 around the stem to accommodate them. 



The phyllotaxy of alternate leaves is more complicated. 



