14 NUTRITION OF FUNGI 



produce such profound growth responses. The best evidence of 

 the quantitative essentiality of copper is offered by Wolff and 

 Emmerie (1930), who electrolytically purified the culture media 

 in which thev attempted to grow Aspergillus niger. They secured 

 no growth in the complete absence of copper. When they added 

 0.2 y of copper per 250 ml of medium, growth occurred; conidia 

 were produced only if a minimum of 0.3 y per 250 ml was added. 

 In a copper-free medium, as produced by Metz (1930), A. niger 

 was able to produce conidia, but Metz determined them to be 

 twice as numerous in copper-containing media as in copper-free 

 media. 



Wolff and Emmerie (1930) also showed that there is no pig- 

 mentation of conidia of A. niger if the amount of copper provided 

 is the minimum for conidial production, as is maintained also by 

 Steinberg (1934). In 1938 Mulder [Foster (1939)] showed that 

 maximum pigmentation in this fungus requires a minimum of 

 6.25 y of copper per 100 ml of nutrient solution. Mulder also 

 ascribed to copper an influence in the formation of acids during 

 fermentation. 



Manganese as nutrient. The status of knowledge regarding 

 manganese as a nutritive element for fungi has been reviewed by 

 Foster (1939). A series of studies by Bertrand and Javillier 

 [Foster (1939)] and by Steinberg (1936) shows that much less 

 manganese is required than either iron or zinc. In fact, manga- 

 nese in a concentration of 1 part in 10 billion is definitely stimu- 

 latory to Aspergillus niger. Bertrand believed his evidence to 

 show that iron, zinc, and manganese must have a certain balance 

 and that thev function together synergeticallv. With a certain 

 proportionality of manganese, iron, and zinc, he secured a sparse 

 production of conidia by A. niger; with a larger amount of man- 

 ganese, however, the conidia were developed in abundance. Stein- 

 berg (1935) was able to confirm these observations to an extent 

 by showing that a lack of manganese in the nutrient either sharply 

 reduces or entirely inhibits conidial production. 



Stimulation of growth, as indicated by increased dry weight, 

 followed the addition of manganese to cultures of A. flaws and 

 Rhizopus nigricans by McHargue and Calfee (1931). 



Zinc as nutrient. As has been indicated by Foster (1939), zinc 

 is the element of first choice in studies dealing with the mineral 

 nutrition of fungi. Numerous experiments involving representa- 



