280 ASSOCIATIVE EFFECTS AMONG FUNGI 



action of the medium, production of inhibitory toxic products, 

 production of stimulatory or growth-controlling substances, such 

 as vitamins, auxins and hormones, and variation in temperature 

 and in 2 tension. These matters, as they apply to associative 

 effects, have been capablv reviewed bv Waksman (1937), Porter 

 and Carter (1938), Weindling (1938), D'Aeth (1939), and 

 Waksman (1941), each of whose summaries should be carefully 

 perused. 



ANTAGONISM 



In our social organization the human race may be spoken of as 

 constituted of two groups, producers and consumers, and if this 

 analogy is applied to fungi, all of them, by virtue of their lack of 

 chlorophyll, are perforce in the consumer grouping. They not 

 only are largely dependent upon other organisms, living or dead, 

 as sources of food, but also the "struggle for existence" is just as 

 acute among them, with resultant "survival of the fittest," as it is 

 among a nv other tvpe of organism. This associative interaction 

 exists not only among the fungi themselves but between bacteria 

 and fungi, slime molds and fungi, actinomycetes and fungi, proto- 

 zoa and fungi, and also various other organisms and fungi. In fact, 

 it is doubtful if anv chlorophyll-bearing species of plant is free 

 from attack bv fungi, and, moreover, records of hyperparasitism 

 among fungi are not infrequent. 



Evidence of antagonism from cultures. One of the essential 

 techniques in the study of fungi is their isolation in pure culture. 

 These procedures are based upon the use of semisolid media, first 

 utilized by Koch to isolate bacteria in pure culture. All mycolo- 

 gists have come to place enormous importance upon the use of 

 pure cultures, although they know full well that in nature pure 

 cultures are either non-existent or else occur as miraculous oddi- 

 ties. In consequence of insistence upon use of pure cultures, too 

 little attention has been given to studies of known mixtures of 

 fungi [Fawcett (1931)]. 



It has long been known that microorganisms in culture produce 

 substances that limit their own period of growth. As evidence 

 the production of alcohol by yeasts, of citric acid by Aspergillus 

 niger, and of lactic acid by Rhizopus sp. may be cited. These 

 growth-inhibiting substances have been regarded as aids in the 

 struggle for existence of microorganisms. 



