100 A PRIMER OF BIOLOGY 



no more leaves are developed, and all further growth 

 takes the form so familiar to us on our commons 

 and moors. The white water buttercup, common 

 in wet ditches, is another illustration in point. 

 The lower leaves of this plant developed in the 

 water are much divided into numerous fine linear 

 segments, whilst those developed in the air are 

 provided with three to five obovate or rounded 

 lobes (Fig, 48). Under dry conditions all the leaves 

 have the lobed form, but if entirely submerged all 

 are filamentous. It must be understood, of course, 

 that the one type of leaf cannot, after once being 

 developed, be transformed into the other ; but leaves 

 subsequently produced will assume the aerial or 

 aquatic form according to external conditions. 



The wonderful phenomena of mimetic resemblances 



seen between animals, between plants, and between 



Mimetic plants and animals are well worthy of consideration 



bfance". m this connection, but space forbids us even to give 



instances, let alone consider any one of these in 



detail. 



