ACTION AGAINST FUNGI 137 



tion. P. luteum-furpurogenum produces a thermostable substance, solu- 

 ble in ether and in chloroform, that is antagonistic to the growth and 

 acid production of A. niger (668). Coniofhora cerehella was inhibited 

 by a species of Penicillium, its mycelium being considerably modified j 

 however, in time the former organism adapted itself to the latter and 

 overgrew it, its rate of growth being eventually more rapid than that 

 of a pure culture (377). Certain fungi are able to parasitize other fungi: 

 Pi ftocef halts, for instance, attacks various species of Penicillium and As- 

 fergillus (176). The germination of the spores of one fungus may be 

 reduced by the presence of spores of another (519). 



Different fungi produce different types of fungistatic and fungicidal 

 substances, which may be stable or unstable in nature. These are formed 

 particularly by the lower fungi or the molds, with the exception of the 

 Phycomycetes that have so far not been found to produce any antibiotic 

 substances. Their action consists in modifying or killing the mycelium 

 of the other fungus, or merely in preventing spore germination. Brom- 

 melhues (88), studying the effects of H. sativum and Penicillium sp. 

 against Ofhiobolus graminis, emphasized that the inhibitory action was 

 due to a toxic substance, thermostable in nature and diffusible in agar. 

 In some cases, no relation could be observed between the acidity pro- 

 duced by one organism and its ability to influence the growth of another 

 ( lOi I ) j in other cases, as in the mutualistic effects of Sclerotium rolfsii 

 and Fusarium vasinjectum, the first overgrew completely the second at 

 ^H 6.9, whereas in alkaline ranges the reverse took place (766). 



Random isolations oi Penicillium cultur&s and of other soil-inhabiting 

 fungi were tested for their effects on the virulence of H. sativum on 

 wheat seedlings grown in steam-sterilized soil (785). Some forms ex- 

 erted a marked degree of suppression, some had no effect, and others 

 increased the virulence of the pathogeny marked variations in activity 

 were observed among the different species of Penicillium. Because 

 Hyphomycetes were found to be capable of parasitizing the oospores of 

 Pythium (184), Hyphomycetes were believed to serve as effective 

 agents in promoting soil sanitation. Various species of Torulopsis, in 

 addition to certain bacteria, are capable of inhibiting the growth of 

 Dematiaceae, fungi that cause the blue staining of wood pulp (592). 



Certain fungi may affect the reproduction of others. Melanos-pora 



