LEAF-VARIATION 97 



I have alluded to the considerable morphological 

 variations which are observed in Ranunculus aquatilis, 

 Godron, who, in 1839, published an important mono- 

 graph/ of the Ranunculus group, has studied these 

 variations with great detail. When the plant develops 

 wholly under the surface of water, all its leaves are 

 delicately laciniated. If the plant is able to send 

 some of its leaves to the surface, they float and assume 

 a very different form, being kidneyvshaped and lobed. 

 The same plant when growing entirely out of water 

 presents a very different appearance : the stem is 

 short, much divided into branches, which bear a large 

 number of small leaves, cylindrical, much divided, 

 and somewhat thick. If it were not for the floral 

 organs, one would certainly believe in two or three 

 species. There is but one, however, which varies 

 greatly according to external circumstances, and this 

 is shown by the fact that the same individual plant 

 under different circumstances presents the different 

 appearances which have been mentioned. Lamarck 

 believed that Ranunculus aquatilis might be trans- 

 formed into R. hederaceus through changes in the 

 environment, but Godron denies the fact. Rubus 

 fruticosus seems also to vary considerably. Sagittaria 

 sagittcefolia, when growing in deep water has also 

 ribbon-shaped leaves, while in shallow water it has 

 also arrow-shaped leaves, which rise vertically instead 



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