80 UNIVERSALITY OF DEGENERATIVE EVOLUTION 



tion of the leaflet, is by no means uncommon. Vicia 

 Pyrenaica (fig. 44) furnishes a good example of 

 this change, of which the degeneration of the blade 

 is the necessary consequence. 



In Gucumis sativus (the cucumber) some of the 

 leaves are the shape of ordinary assimilative leaves, 

 while others are entirely modified into tendrils ; in 

 the case of the latter the blade has completely 

 degenerated. 



2, Adaptation to carnivorous nutrition. Some 

 plants, instead of obtaining nutriment exclusively 

 from minerals and carbon dioxide, are capable of 

 assimilating animal matter from insects and other 

 small organisms, which they capture by means of a 

 special function exercised by the leaves. 



(a) Utricularia. In the aquatic Utricularia the 

 leaves are minutely sub-divided like many other 

 submerged plants. The leaves of Utricularia 

 vulgaris exhibit leaves of this type. Some of 

 their ramifications carry pouches, which serve for 

 the capture of minute organisms. These pouches 

 are formed by the modification of part of the 

 blade, and have almost completely lost their 

 chlorophyll. 



Utricularia intermedia (fig. 45) exhibits two 

 kinds of branches ; the one kind stretches out 

 horizontally and carries green leaves ; the others 

 are devoid of chlorophyll, and the leaves are 

 purely carnivorous. 



(1) Nepenthe. The distal extremity of the leaf 



