NUTRITION 



385 



Saprophytes are very numerous and varied. They may be superficial, 

 or may penetrate the substratum thoroughly, showing finally at the sur- 

 face only the reproductive bodies. The very fact that they are getting 

 food from the 

 dead organism 

 indicates that 

 they are con- 

 suming it. In- 

 asmuch as they 



often must digest the food before it can enter their 

 bodies, they disintegrate the body on which they 

 feed. In the course of this digestion and disin- 

 tegration, many and varied chemical reactions 

 occur, some incited by the saprophyte, some in- 

 cidental to the changes it produces. These are 

 summed up for fluid media under the term fer- 

 mentation, and for solids under the terms decay or 

 putrefaction. Certainly in fermentation (p. 409), 

 and probably also in putrefaction and decay, some 

 of the most striking reactions are not connected 

 with food getting, though apparently they are en- 

 tirely similar thereto. 



Organic debris. — It is not necessary that the 

 dead body retain any semblance of its original 

 form. It may even be so far destroyed as to be 

 mere particles of a soil; yet the saprophyte relies 

 on these for its food. Thus, the common mush- 

 room of commerce {Agaricus campestris) is grown 

 upon a compost of soil and horse dung, the par- 

 tially digested remnants of grain and hay furnish- 

 ing the food for the mycehum. Indeed, every soil 

 containing organic matter supports a varied if 

 minute flora, whose operations are often indispen- 

 sable to the welfare of larger plants. 



Succession. — Nothing is more striking than the succession of sap- 

 rophytes that live upon a dead organism and finally dispose of all its 

 organic matter, each appropriating a suitable part and reducing that 

 to the most simple and stable compounds, until finally it " returns to the 

 dust whence it came." This emphasizes, too, the striking differences 



■S' 



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a: 



Fig. 656. — Leaf of Ne- 

 penthes Mastcrsiana. — From a 

 photograph by G. W. Oliver. 



