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 trilUum 

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



Figs. 182-187. — Petioles, and leaf attachmeut : 182, petioles of jasmine night- 

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

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

 laetuca; 186, perfoliate leaves of luoilaria; 187, peltate leaf of tropueolum. (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. 



