THE SHAPES OF LEAVES. 



141 



mixed symmetry occurs under conditions that are interme 

 diate. A more marked degree of the same relation is pre 

 sented in the leaf of the Lady s Mantle, Fig. 215. And 



then in the Sycamore and the Vine, we have a cleft type of 

 leaf in which a decided bilateralness of form co- exists with 

 a decided bilateralness of conditions. 



The quite simple leaves to which we now descend, exhibit, 

 very distinctly, a parallel series of facts. Where they grow 

 up on long and completely-independent foot- stalks, without 

 definite subordination to some central vertical axis, the 

 leaves of water-plants are symmetrically peltate. Of this 

 the sacred Indian-bean, Fig. 216, furnishes an example. Here 

 there is only a trace of bilateralness in the venation of the 

 leaf, corresponding to the very small difference of the con 

 ditions on the proximal and distal sides. In the Victoria 

 regia, Fig. 217, the foot-stalks, though radiating almost 

 horizontally from a centre, are so long as to keep the leaves 

 quite remote from one another ; and in it each leaf is almost 

 symmetrically peltate, with a bilateralness indicated only by 

 a seam over the line of the foot-stalk. The leaves of the 

 Nymphxa, Fig. 218, more closely clustered, and having less 



3J0- 



room transversely than longitudinally, exhibit a marked 

 advance to the two-sided form ; not only in the excess of 

 the length over the breadth, but in the existence of a cleft, 



