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PHYSIOLOGY 



between saprophytes in their use of offered foods — differences which 

 at present are quite inexplicable. A classification of saprophytes accord- 

 ing to the sort of food on which they thrive best has been made; but this 

 expresses only in a summary way our very imperfect knowledge of their 

 nutrition. 



Insectivorous plants. — Besides the ordinary parasites and sapro- 

 phytes, there are a few rather isolated cases of green seed plants which 



Fig. 657. — A rosette of leaves of Venus's flytrap (Dionaea muscipula) seen from 

 above. — From a photograph by G. W. Oliver. 



have special apparatus for capturing small animals and digesting them. 

 Some are submersed water plants, some grow on land. They are col- 

 lectively known as insectivorous or carnivorous plants, but the methods 

 of capture are quite diverse. 



Pitcher plants. — The pitcher plants, Sarracenia, Darlingtonia, Nepen- 

 thes (fig. 656), and Cephalotus, have part or all of the leaf trumpet-like, 

 pitcher-like, or cuplike, holding more or less water. The sides have stiff 

 downward-pointing hairs, slippery areas of treacherous footing, decep- 



