1919] 



WEBB — SPORE GERMINATION AND H ION CONCENTRATION 219 



neutrality, favorably influence germination of the spores of 

 Aspergillus niger, Penicillium cyclopium, Botrytis cinerea, Fusa- 

 rium sp., and Lenzites saepiaria up to approximately P H 3.0. 

 However, with increase of hydrogen ion concentration above this 

 point, the germination quantities abruptly diminish. Some 

 detailed discussion is however needed to compare these results 

 with the work of others. 



It has been shown that in the case of Aspergillus niger, maxi- 

 mum germination is obtained at P H 3.1, which expressed in terms 

 of normality is N/1259. At P H 2.8, or N/631, germination is 

 considerably better than at the neutral point, so that complete 

 inhibition of germination must lie considerably higher than P H 

 2.8. Since the foregoing hydrogen ion concentrations have been 

 expressed in terms of normality, it might be well to cite the con- 

 centrations of certain acids allowing normal or almost normal 

 development of the spores of Aspergillus fiavus in beet decoction, 

 as determined by Clark ('99) : HCl, N/64; HN0 3 , N/64; H 2 S0 4 , 

 N/128; acetic, N/64; monochloracetic, N/256; dichloracetic, 

 N/128; trichloracetic, N/64; and HCN at N/8192. A mean 

 of the limiting concentrations on the alkaline side for the various 



OH ions ha\ 



N/251200, from which 



In beet decoction, Clark 



found that N/16 KOH injured the spores of Aspergillus flams, 

 while N/8 was fatal; also that N/32 NH 4 OH inhibited germina- 

 tion, while N/16 was fatal. He concludes that the hydroxyl 

 group, OH, is rather more toxic to the moulds studied than ionic 

 H. However, as previously shown, the exact concentration of 

 hydrogen ions in his cultures can not be calculated. 



Penicillium cyclopium exhibits a relation to hvdrogen ion 



concentration comparable with that of Aspergillus niger. More- 

 over, of all the forms which he studied, Clark found Penicillium 

 glaucum the most resistant to acids and alkalis as well as to 

 other poisons, the inhibiting concentrations on the whole being 

 greater than those for Aspergillus flavus. Stevens' results in- 

 dicated that Penicillium crustaceum is more resistant to poisons 

 in aqueous solution than any of the other fungi studied by him. 

 Growth occurred in N/50 HCl and H 2 S0 4 , while N/40 KOH and 

 NaOH caused death. In my study, the rise in the germination 



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