24 NUTRITION OF FUNGI 



The studies of Duggar and Davis (1916) on fixation of atmos- 

 pheric nitrogen showed gains in cultures of Fhoma betae on 

 manqel-wurzel decoction and on suqar-beet decoction of 3.022 

 mg and 7.752 mg of nitrogen, respectively. Under the same 

 conditions there were no gains in cultures of Aspergillus niger, 

 Macrosporium commune, Penicillium digitatum, P. expansum, 

 and Glomerella gossypii. 



Aspergillus niger was employed in experiments involving fixa- 

 tion of atmospheric nitrogen by Schober (1930), but no evidence 

 of any increase in nitrogen in the culture flasks was obtained. 

 Roberg (1931) got negative results of fixation not only with 13 

 strains of A. niger but also with 13 other species of Aspergillus. 

 Further confirmation of the inability of A. niger to fix atmos- 

 pheric nitroq-en was supplied by Allison, Hoover, and Morris 

 (1934). 



Certain symbiotic fungi, however, are able to fix nitrogen, as is 

 shown by the work of Ternetz (1904). She isolated varieties of 

 mycorrhizal fungi belonging to fhoma radicis from ericaceous 

 plants and compared their nitrogen-fixing capabilities with those 

 of Azotobacter chroococcum and Clostridium pastorianum. The 

 strains of P. radicis gave yields of 18 to 22 mg of nitrogen per 

 gram of dextrose used. 



The nitrogen requirements of fungi appear worthy of further 

 study. Techniques patterned after those employed by the bac- 

 teriologist should prove most serviceable. Sources of error in 

 the interpretation of results of such studies should include those 

 which have been mentioned valid in the interpretation of data 

 involving carbon sources. 



GROWTH FACTORS 



The discovery by Wildiers (1901) in 1901 of the need of a 

 growth factor for the cultivation of yeast on synthetic media 

 marked the beginning of studies on accessory growth substances 

 for fungi. Wilders attempted without success to use a medium 

 which Pasteur maintained was adequate. When he employed as 

 inoculum a few yeast cells, no growth occurred with this medium; 

 but when he added a sizable mass of inoculum, the yeast grew. 

 He interpreted these results as showing the need for a sufficient 

 amount of a substance that he called "bios." As a result of this 



