THE PLANT AND ITS ENVIRONMENT 



173 



of normal roots, u reduction in size of the leaves, and a partial or 

 complete loss of chlorophyll. Some parasites, particularly 

 those whose roots attack the roots of other plants, may be only 

 partially parasitic, whereas others derive their entire food supply 

 from their hosts and can live only as parasites. 



The small but interesting group of insectivorous plants have 

 gone a step further and reversed the ordinary relation between 

 animals and plants by becoming parasites upon insects. These 

 plants capture their prey either by a closing trap, as in the 



Fig. 92. — An insectivorous plant, the sundew (Drosera). In the sticky tentacles 

 of its leaves, insects become entangled. 



Venus's Fly Trap; a pouch of hquid, as in the Pitcher Plants, or a 

 mass of sticky tentacles, as in the Sundews (Fig. 92). Once 

 caught, the bodies of the insects are apparently digested by 

 enzymes secreted by the plant, and may thus furnish a small 

 supply of nitrogenous food. Parasitism is comparatively rare 

 among seed plants but is very common in the fungi, many of 

 which attack the tissues of both plant and animal hosts, pro- 

 ducing serious bacterial and fungous diseases. 



Saprophytes. — Similar in certain respects to parasites are a 

 group of plants which also depend upon other organisms for 

 food instead of manufacturing it independently from raw mate- 

 rials. This group, however, does not attack living animals and 

 plants but lives instead upon their dead bodies, drawing there- 

 from the already combined organic compounds and using them 

 directly as food. Such plants are known as saprophytes. Here 

 belong the bacteria of decay and all bacteria and other fungi 

 which are not parasites. There are a few saprophytes among 

 seed plants, of which the Indian Pipe (Fig. 93) is perhaps the 



