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 (Galiwm), they constitute a whorl, which is only 
Fics. 182-187.— Petioles, and leaf attachment: 182, petioles of jasmine night- 
shade (Solanum jasminoides) acting as tendrils; 183, acacia, showing petiole 
transforried to leaf blade; 184, sessile leaves of epilobium; 185, clasping leaf of 
lactuca; 186, perfoliate leaves of uvularia; 187, peltate leaf of tropzolum. (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. 
