ACTION AGAINST FUNGI 149 



Coniofhora cerehella was inhibited by a species of PenkilUumy its my- 

 celium being considerably modified j however, in time the former or- 

 ganism adapted itself to the latter and overgrew it, its rate of growth 

 being eventually more rapid than that of a pure culture (380). Certain 

 fungi are able to parasitize other fungi. The germination of the spores 

 of one fungus may be reduced by the presence of spores of another 



{SS3)- 



Different fungi produce different types of fungistatic and fungicidal 

 substances, some of which are stable, others unstable. 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 (89), studying the effects of H. sativum and Penicillium sp. 

 against Ofhiobolus graminis, emphasized that the inhibitory action was 

 due to a toxic substance that was thermostable 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 

 ( 1046) i in other cases, as in the mutualistic effects of Sderotium rolfsii 

 and Fusarium vasinfeaum, the first overgrew completely the second at 

 f¥L 6.9, whereas in alkaline ranges the reverse took place (804). 



Random isolations oi Penicillium cultures 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 (823). 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 (196), Hyphomycetes were believed to serve as effective 

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

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

 Dematiaceae, fungi that cause the blue staining of wood pulp (630). A 

 species of Penicillium (P. gladioli) was found (8ia) to produce an 

 antibiotic (gladiolic acid) which is actively fungistatic but only weakly 

 bacteriostatic. 



Certain fungi may affect the reproduction of others. Melanosfora 



