284 ASSOCIATIVE EFFECTS AMONG FUNGI 



some either filterable or non-filterable. There may also exist 

 inter^radations between slight inhibition of growth and marked 

 toxic action, and in consequence it becomes practically impossible 

 to separate staling products from toxic products. Much has 

 been written regarding these toxins, since they have been em- 

 ployed to explain the proximate cause of wilting by pathogenic, 

 vascular-tissue-invading species of Fusarium. The chemical con- 

 stitution of many definitely toxic products has been determined. 

 Some appreciation of the extent of our knowledge on this matter 

 may be gained from the excellent summaries of Raistrick (1932, 

 1938). Clutterbuck, Lowell, and Raistrick (1932) isolated one 

 such toxic substance, a yellow pigment, chrysogenin, with the 

 empirical formula C 8 Ho 2 b (1 . It is formed by one of the Penicil- 

 lium chrysogemnn group on a svnthetic medium containing glu- 

 cose. Tests showed it to possess very powerful antibacterial prop- 

 erties, especially against the pyogenic cocci and the diphtheria 

 group, but it was ineffective against the colon-typhoid organisms. 

 Weindlinc; and Emerson (1936) isolated a proteinaceous toxin 

 with the formula C14H1CN2S2O4 from Gliocladium fimbriatum, 

 whereas Dutcher (1941) determined its formula to be Ci 3 Hi 4 - 

 4 N 2 S 2 . In concentration of 2.5 mg per milliliter it was bac- 

 tericidal to Staphylococcus albus, and of 1.0 mg per milliliter to 

 5. aureus and Streptococcus viridans. 



Recently Abraham and associates (1941) isolated penicillin, 

 presumably from Penicillium uotatum, finding that it was very 

 potent against several species of bacteria pathogenic to man. Peni- 

 cillin appears to have therapeutic value when used in place of sul- 

 fonamides, as is indicated in Chapter 4. In some cases the toxic 

 principles appear, from their extractability by ether or chloroform, 

 to be lipoidal in nature. 



A very different type of antagonism, in which the cause is asso- 

 ciated with sex, has been encountered among all the principal 

 groups of fungi. It has been widely studied in connection with 

 the phenomenon of heterothallism, which need not be discussed 

 at this time. Suffice it to say that, when the mycelia of mono- 

 sporic cultures are grown in the same Petri-dish culture, mutual 

 aversion may be manifest by sexual incompatibility. Cayley 

 (1923, 1931) has given special consideration to aversion, pri- 

 marily as it concerns Diaporthe permc'wsa, the cause of wilt of 

 plums in Europe. In cultures of this organism, the isolates may 



