Chapter 12 

 ASSOCIATIVE EFFECTS AMONG FUNGI 



In this chapter it is proposed to consider those phenomena 

 manifest as a result of different species of fungi living together 

 in close proximity. It is essentially an ecological study of fungi 

 and corresponds in some measure to a consideration of associations 

 among seed plants. Of course, a great deal has been learned re- 

 garding the influence of one species of seed plant upon another 

 growing in close juxtaposition. Our knowledge of similar asso- 

 ciative relationships among fungi is strikingly much more meager 

 and fragmentary, and the data are rather widely dispersed in the 

 literature. Such facts regarding fungi appear none the less im- 

 portant, however, and they may be found to possess interesting 

 applications and economic potentialities. 



For convenience, the effects of interaction of fungi, one upon 

 the other, may be divided into the following categories: antibiotic, 

 symbiotic, and synergetic. The associative relationships have 

 been designated antagonism, symbiosis, and synergism, respec- 

 tively. In antibiotic effects are included those antagonistic, com- 

 petitive, or harmful effects that result to organisms from their 

 growth in close proximity. Effects resulting from parasitism are 

 among those included in this classification. In symbiotic effects 

 are included mutualistic advantages that result from the living to- 

 gether of two or more species. In synergetic effects are included 

 those in which two or more species through their combined action 

 produce effects or changes that neither could produce alone. 



It becomes apparent immediately that these categories are arbi- 

 trary, and that evidence might be found to show that they inter- 

 grade. Indeed, such evidence is at hand. Among the factors 

 studied that have to do with inter£radation and with associative 

 effects generally are competition for food, modification of food 

 supply by the metabolism of one or the other of the associated 

 species, relative availability of food constituents, changes in re- 



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