SOIL FUNGI 269 



genous fertilizers are added together with large quantities of manure 

 or straw, since the available energy introduced into the soil will allow 

 a rapid growth of the fungi, with the result that available nitrogen 

 compounds are used up by them, to the detriment of the growth of 

 higher plants. This action of the soil fungi has also a favorable side, 

 namely the temporary storing of the available nitrogen salts in an in- 

 soluble form, thus preventing their leaching by drainage and irrigation. 

 The favorable and unfavorable actions depend upon the presence or 

 absence of higher plants. 



The nutritive value of nitrogen compounds for fungi depends on the 

 rapidity with which they can be transformed into amino acids, according 

 to some investigators. 123 ' 124 Other investigators 125-127 are, however, of 

 the opinion that the amino acids and nitrates are reduced to ammonium 

 salts before they are assimilated by fungi. The ability of an organism 

 to assimilate ammonium salts is in direct relation to its ability to with- 

 stand the mineral acid liberated. 128 Assimilation of nitrates by fungi 

 goes through the reduction of nitrates to nitrites and ammonia. Organ- 

 isms, like certain Mucorales, that are incapable of reducing the nitrate 

 molecule cannot assimilate this source of nitrogen. 129 



123 Czapek, 1901-1902 (p. 502). 



124 Puriewitsch, K. Untersuchungen liber die Eiweisssynthese bei niederen 

 Pflanzen. Biochem. Ztschr., 38: 1-13. 1912. 



128 Raciborski, M. I. tJber die Assimilation der Stickstoffverbindungen durch 

 Pilze. Anz. Akad. Wiss. Krakau, Math. Naturw. Kl., p. 733. 1906. 



126 Hagem, 1910 (p. 237). 



127 Abderhalden, E., and Rona, P. Die Zusammensetzung des "Eiweiss" 

 von Aspergillus niger bei verschiedener Stickstoffquelle. Ztschr. physiol. 

 Chem., 46: 179-186. 1910. 



128 Ritter, G. Ammoniak und Nitrate als Stickstoffquelle fur Schimmel- 

 pilze. Ber. deut. bot. Gesell., 25: 255; 27: 582-588; 29: 570-577. 1908-1911. 



129 A detailed study of the nitrogen utilization by fungi is found in a paper 

 by Brenner, while the influence of environmental conditions on the activities of 

 soil fungi has been reviewed by Coleman. Further information on the physiol- 

 ogy of fungi including curves of growth, influence of temperature, reaction and 

 concentration is given by Mtiller. The antagonistic action of fungi to one 

 another was studied by Nadson and Zolkiewicz and Porter. Brenner, 1914 (p. 

 241); Coleman, D. A. Environmental factors influencing the activity of soil 

 fungi. Soil Sci., 2: 1-66. 1916; Mtiller, K. O. Untersuchungen zur Entwick- 

 lungsphysiologie des Pilzmycels. Beitr. Allg. Bot. 2: 276-322. 1922; Nadson, 

 G. A., and Zolkiewicz, A. I. Spicaria purporogenes n. sp. On the question of 

 antagonism among microbes. Bull. Jard. Bot. Rep. Russe., 21: suppl. 1. 1921; 

 Porter, C. L. Concerning the characters of certain fungi as exhibited by their 

 growth in the presence of other fungi. Amer. Jour. Bot., 11: 168-188. 1924. 



