TAXONOMIC STUDIES 433 



at a depth of 2 cm and 160,000 at 8 cm. He found Zygorhynchns 

 molleri and Trichoderma koningii at the lower depths. 



Since the soil is such a complex environment, there are abun- 

 dant reasons for differences of opinion regarding kinds of soil 

 fungi in different soils. Goddard (1913) and Werkenthin (1916) 

 found a constant and characteristic fundus flora of soils, regard- 

 less of tillage, soil type, and manuring. Dale (1912, 1914) found 

 certain species common to chalky, peaty, and black earth soils in 

 England. Waksman (1916) obtained the same species from culti- 

 vated and uncultivated soils in New Jersey but concluded that 

 each soil possesses a more or less characteristic fungus flora. 

 Brown (1917) expressed a similar opinion by stating that different 

 soils have different fungus floras. Hagem (1910) isolated Alucor- 

 ales from the soil of meadows, gardens, forests, and cultivated 

 fields but observed that they are most abundant in forest soils. 

 On the other hand, Jensen (1931) found that Mucorales are most 

 abundant in field and garden soil, whereas species of Trichoderma 

 are most common in virgin soils, such as those of forests, moors, 

 and heaths. 



Cobb (1932) was led to conclude that species of Mucor and 

 Aspergillus are scarce in forest soils. She also reported differences 

 in abundance between soils under hemlock trees and under de- 

 ciduous trees, there being twice as many in the top soil under 

 hemlocks as in that under deciduous species. Other observations 

 on factors that modify the presence of specific fungi in soils in- 

 clude those of LeClerg and Smith (1928). Their evidence showed 

 that Rhizopns nigricans and Trichoderma lignornm occur most 

 abundantly in soils of low mineral and low moisture content and 

 that Fenicillium expansum is not limited by soil moisture and oc- 

 curs abundantly, as does P. lilacimim, in soils of high mineral 

 content. 



Experimentation involving the influence of each of the several 

 factors that modify the activities of soil fungi has been limited. 

 Coleman (1916) employed sterilized soils, with Aspergillus niger, 

 Trichoderma koningii, and Zygorhynchus vuilleminii among the 

 test organisms on which to study the effects of temperature, aera- 

 tion, and food supply. All grew best at approximately 30° C, 

 but the species differed in their oxygen and food requirements. At 

 any rate, there was no interaction of one species with another nor 

 with the numerous species of soil microorganisms that occur in 



