3 86 
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 
PK5. 657. A rosette of leaves of Venus's flytrap (Dionaea musciputo) 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, Sarracenla, Darlingtonia, Nepen- 
thes (fig. 656), and Ceplialotus, 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- 
