SOIL FUNGI 259 



Occurrence of specific fungi in the soil. Of the various genera of 

 fungi found in the soil, the most common, both in number of species 

 and in frequency of occurrence, are Zygorhynchus, Penicillium, Tri- 

 choderma, Fusarium, Mucor, Aspergillus and Rhizopus. This is 

 clearly demonstrated in table 16, where an asterisk designates that a 

 particular genus is represented by one or more species in one or more 

 soils. Brierly 67 tabulated systematically all the fungi which have been 

 recorded and described in soil investigations and found 56 species of 

 Phycomycetes belonging to 11 genera; 12 species of Ascomycetes 

 belonging to 8 genera; 197 species of Fungi imperfecti including Actino- 

 myces, but not sterile mycelia, belonging to 62 genera. 



Fungi are not limited in the soil to any particular depth, but occur 

 at all depths, at least to a depth of four feet or more even in soils in 

 humid regions. The numbers usually drop below the surface (upper 

 six inches) , but in the subsoil there does not seem to be a rapid diminu- 

 tion with greater depth. Some genera, like Zygorhynchus, occur abun- 

 dantly in the subsurface soils. The distribution of fungi in the soil is be- 

 lieved to depend upon the amount of moisture and the character of the 

 soil. 77 The distribution of certain organisms in the soil, like Fusarium, 

 has been ascribed to earthworms. 78 Various fungi are found in the soil 

 at a depth of 1 to 44 inches (Trichoderma koningi most abundantly); 

 practically the same species were isolated from the intestinal canals 

 of grubs and worms picked out from the soil and properly washed; 



67 Brierly, W. B. The occurrence of fungi in the soil. In The microorganisms 

 of the soil, by Sir John Russell. 1923, 118-130. 

 e8 Oudemans and Koning, 1902 (p. 237). 



69 Dale, 1912 (p. 237). 



70 Jensen, 1912 (p. 237). 



71 Goddard, H. M. Can fungi living in agricultural soil assimilate free nitro- 

 gen? Bot. Gaz., 66: 249-305. 1913. 



72 McLean, H. C., and Wilson, G. W. Ammonification studies with soil fungi. 

 N. J. Agr. Exp. Sta. Bui., 270: 39. 1914. 



"Waksman, 1916 (p. 240). 



74 Rathbun, A. E. The fungus flora of pine seed beds. Phytopathol., 8: 

 469-483. 1918. 



76 Pratt, 1918 (p. 257). 



76 Takahashi, R. On the fungus flora of the soil. Ann. Phytopathol. Soc. 

 Japan, 12: 17-22. 1919 (Bot. Abstr. 6: 92. 1920). 



77 Beckwith, T. D. Foot and culm infections of wheat by soil fungi in North 

 Dakota. Phytopathol., 1: 169-176. 1911. 



78 Taylor, M. W. Preliminary note on the vertical distribution of Fusarium. 

 Phytopathol., 7: 374-378. 1917. 



