SOIL FUNGI 237 



tions, particularly in uncultivated soils and below the layer containing 

 humus, fungi may be as abundant as, if not more so than, bacteria. 

 The earlier workers 2 emphasized the fact that fungi predominate in 

 acid soils, and bacteria in neutral soils. This is true only to a certain 

 extent. Fungi can, as a rule, withstand greater concentrations of 

 acidity than bacteria and actinomyces, so that, at a pH of 4.0, the 

 soil may contain only small numbers of the last two groups of organisms, 

 while the fungi may still be present in abundance. Such a reaction is 

 also inhibitive to the growth of most higher plants. At less acid reac- 

 tions, when conditions are favorable for cultivated plants (pH 4.6 to 

 6.5), bacteria occur most abundantly, whereas the numbers of fungi will 

 depend on the soil reaction, on the amount of organic matter, and on the 

 abundance of water in the soil. 



As far back as 1886, 3 attempts were made to isolate fungi from the 

 soil and to give them names and descriptions; it is only since 1902, 

 however, that the subject began to be treated in a systematic manner. 

 Oudemans and Koning 4 published a paper in 1902, which was the first 

 real attempt made at a systematic study of the occurrence of fungi in 

 the soil and their proper classification. In 1908 appeared the excellent 

 contributions of Hagem 5 and Lendner 6 , on the Mucorales of the soil. 

 These contributions were soon followed by those of other investigators 7-9 

 who made extensive studies of the occurrence of fungi in various types 

 of soil, under different climatic and other environmental conditions. 

 In addition to these, a number of other contributions have been made 

 dealing in one way or another with one or more groups of soil fungi. 



2 Ramann, E. Bodenkunde. Berlin, Springer. 1920. 



3 Adametz, L. Untersuchungen iiber die niederen Pilze der Ackerkrume. 

 Inaug. Diss. Leipzig, 1886, 78 p., 2 pi. 



4 Oudemans, C. A. J. A., and Koning, C. J. Prodrome d'une flore mycolo- 

 gique, obtenue par la culture sur gelatin preparee de la terre humeuse du Span- 

 derswoud pres de Russum. Arch. Neerland. Sci. Exact, et Nat. (2), 7: 266-298. 

 1902. 



5 Hagem, O. Untersuchungen iiber norwegische Mucorineen, Vidensk. Selsk., 

 I Math. Naturw. Klasse, 7: 1-50. 1907; 10: 1-52. 1910; Ann. Mycol. 8: 265- 

 286. 1910. 



6 Lendner, A. Les Mucorinees de la Suisse. Bern, 1908. 



7 Jensen, C. N. Fungus flora of the soil. Cornell Univ. Agr. Exp. Sta. Bui. 

 315, 1912. 



8 Dale, E. On the fungi of the soil. Ann. Mycol. 10: 452-477. 1912; 12: 

 33-62. 1914. 



9 Waksman, S. A. Soil fungi and their activities. Soil Sci. 2: 103-155. 1916; 

 3: 565-589. 1917. 



