SOIL FUNGI 263 



Cellulose decomposition by fungi. Koning 87 was the first to point out 

 the great abundance of fungi in forest soils, where colorless and brown, 

 septated and non-septated mycelia are found to penetrate the whole mass 

 of organic matter. Koning suggested that fungi play an important role 

 in the soil in decomposing the organic matter and in transforming it into 

 humus. That under favorable conditions and in the presence of avail- 

 able energy, fungi grow very rapidly in the soil and produce a greater 

 amount of C0 2 than do bacteria, 88,89 indicates a greater energy utiliza- 

 tion. This led Neller to assume that fungi exist in the soil not merely in 

 the form of spores, but are active there, since the C0 2 production by 

 pure cultures of fungi approached more that of a normal soil than the 

 C0 2 produced under similar conditions by bacteria. The decomposition 

 of celluloses and of allied compounds in the soil by fungi is of great 

 importance in soil fertility. This accounts for the abundance of fungi 

 in soils rich in organic matter and for the great increase in numbers 

 when stable manure and green manure are added to the soil. It has 

 been found, 90 for example, that the addition of 1 per cent of cellulose to 

 the soil in the form of pure filter paper resulted, in two weeks, in an 

 increase in the number of fungi from 50,000 to 1,250,000 per gram. It 

 has been further found that when a soil to which cellulose is added is 

 treated with a volatile antiseptic, in sufficient amounts to kill the fungi, 

 cellulose decomposition is greatly reduced. This process was found 

 to take place under aerobic conditions, parallel with the development 

 of fungi ; in other words, these organisms were found to be important 

 agents in the breaking down of the most abundant constituent of 

 natural organic matter. 



Students of plant diseases observed in the sixties of the nineteenth 

 century that fungus hyphae grow in plant tissues, thereby penetrating 

 cell walls. Hartig 91 found that, in trees affected by fungi, all tissues 



87 Koning, C. J. Contributions a la connaissance de la vie des champignons 

 humicoles et des ph^nomenes chimiques qui constituent l'humification. Arch, 

 neerland. Sci. Exact. Nat., Ser. II, 9: 34-107. 1904. 



88 Neller, J. R. Studies on the correlation between the production of carbon 

 dioxide and accumulation of ammonia by soil organisms. Soil Sci., 6: 225-241. 

 1918. 



89 Potter, R. S., and Snyder, R. S. The production of carbon dioxide by 

 molds inoculated into sterile soil. Soil Sci., 5: 359-377. 1918. 



90 McBeth and Scales, 1912-1915 (p. 197) ; Waksman and Starkey, 1924 (p. 770). 



91 Hartig. Untersuchungen fiber die Zersetzungserscheinungen des Holzes. 

 Berlin, 1878. 



