760 ECOLOGY 



the presence of oxgyen, finally even thriving when it is present in consider- 

 able amount. Such phenomena, as a whole, have been called accom- 

 modation, the implication being that plants have the power of adapting 

 or adjusting themselves to new situations. One of the most striking 

 features of " accommodation " is the inability of saprophytes that have 

 been grown for a long time under unusual conditions (e.g. at high tem- 

 peratures, at high concentrations, or in toxic media) to thrive when they 

 are suddenly transferred back to the ordinary media; in order to 

 flourish in the latter, they must again be grown in a series of inter- 

 mediate solutions of gradually decreasing temperature, concentration, 

 or toxicity. 



While the phenomena of '' accommodation " are not well understood, 

 no explanation is given by referring them to adaptation or adjustment 

 (see p. 947). If a fungus is transferred to a salt solution of slightly 

 higher concentration, the solute enters the plant and water passes out, 

 tending to establish an equilibrium. If a series of like transfers is made 

 to media of progressively greater concentration, similar processes take 

 place, until finally the concentration within the fungus becomes so great 

 that it can thrive in a medium which would have brought about plas- 

 molysis through sudden water withdrawal, if it had been placed therein 

 at the outset. Similarly, when a transfer is made suddenly from a strong 

 to a weak solution, water may enter so rapidly as to burst the fungus, 

 although a series of transfers to progressively weaker solutions makes 

 possible the gradual entry of water and the gradual exit of salts. Per- 

 haps the behavior of saprophytes in solutions that are subjected to pro- 

 gressive changes in temperature or in toxicity also may be capable of 

 a comparable explanation. In any event, it seems advisable to substi- 

 tute the term progressive variability for accommodation and similar 

 vitalistic expressions. 



Phosphorescence. — A few plants, chiefly saprophytes, exhibit phosphorescettce, 

 the mycelium of Agaricus melleus and of a few other fleshy fungi often being lumi- 

 nous in the dark, especially in wet weather, if there is an abundant supply of oxygen. 

 Certain bacteria associated with meat decay also are phosphorescent. The phos- 

 phorescence of decaying wood probably is due to fungi or to bacteria. Luminosity 

 is thought to be of no value to plants, although it is of possible use to certain animals. 



The distribution of saprophytes. — While light is a large factor in 

 determining the distribution of green plants, it plays almost no part in 

 the holosaprophytes, whose abundance is determined chiefly by the 

 amount of dead organic matter and by the degree of freedom from 



