226 Mineral Nutrition of Fiingi [jan. 



of Aspergillus niger. In concentrations between 0.0002 and 0.002 

 per Cent, the maximum weight of the fungus is obtained. Higher 

 doses than 0.002 per cent. are toxic and the yield diminishes in- 

 versely with the concentration, At a concentration of 0.02 per 

 cent. cadmium practically sterihzes the medium. Spore formation 

 is normal at 0.0003 ^o 0.0002 per cent. ; higher doses retard or pre- 

 vent spore formation, though the maximum yield of the fungus is 

 obtained notwithstanding, and corresponds to that of the zinc 

 medium. 



Contrary to the Statement of Javillier and Sauton, Lepierre^^ 

 finds that glucinum can replace zinc. The maximum yield is obtained 

 in concentrations between o.ooi and o.oooooi per cent., though 

 the growth is less rapid, requiring nine or ten days. In these con- 

 centrations the spore formation is normal. By successive cultures 

 on glucinum the plant acquires a certain degree of adaptation and 

 the response is more rapid. 



Likewise uranium^^ can replace zinc as a stimulant, though the 

 same retardation occurs as in the case of glucinum. Concentrations 

 between 0.02 and 0.0000 1 per cent. give the maximum yield, though 

 not tili after ten to twelve days. No growth is obtained at o.i per 

 cent. Spores are formed if uranium does not exceed 0.0 1 per cent. ; 

 while at 0.02 per cent. the culture is sterile although it reaches the 

 maximum weight. The action of uranium is, therefore, the same 

 as, but less intense than, that of zinc. 



Lepierre^^ finds, further, that copper can replace zinc. Between 

 0.0002 and 0.000000 1 per cent. the yield is normal, but the maxi- 

 mum weight is not attained until after twelve to fifteen days. 

 Above 0.0002 per cent. the yield diminishes, until at 0.2 to o.i per 

 cent. there is no growth. Spores appear at the usual time below 

 0.0 1 per cent. ; below 0.00 1 per cent. sporulation is delayed twelve 

 to fifteen days. 



Lepierre^* concludes that zinc can not only be replaced by other 

 metals, but can be dispensed with entirely. In the latter case the 

 cultures are luxuriant, but the sporulation is very slow, requiring 



2iLepierre: Compt. rend., 156, 409-11 (1913). 

 22Lepierre: Ibid., 156, 1179-81 (1913). 

 23Lepierre: Ibid., 156, 1489-91 (1913). 

 24Lepierre: Ibid., 157, 876-9 (1913). 



