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 flU 1 " \\} 
on these for its food. Thus, the common mush- \t \ 
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 mycelium. Indeed, every soil 
containing organic matter supports a varied if FIG ^ _ ^^ of 
minute flora, whose operations are often 'indispen- penthesMastersiana.Froma 
sable to the welfare of larger plants. photograph by G. W. OLIVER. 
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 
