86 Occurrence of Microorganisms in Soil 



The higher fungi have been divided into two general groups: 



(1) Calcofilic fungi, including Amanita ovoidea, Lepiota granulosa, 

 Clitocybe geotropa, Tricholoma album, Russula macnlata, Cortinar- 

 ius fulgens, Boletus satanas, Clavaria flava, and Lycoperdon caelatum. 



(2) Calcofugic fungi, including Ainanita virosa, Lepiota procera, 

 Clitocybe clavipes, Lactarius turpis, Russula amoena, Cortinarius 

 mucosus, and Boletus bovinus. 



Cellulose-Decomposing Fungi 



The addition of cellulose to the soil brings about an extensive de- 

 velopment of fungi, most of which possess very strong cellulose- 

 decomposing power. These include various species of Penicillium, 

 Aspergillus, Trichoderma, SporotricJuwi, Fusarium, Chaetomium, and 

 other forms. McBeth suggested that the fungi play a much more 

 important part in cellulose decomposition in moist soils, particularly 

 in humus soils, than in dry soils. Daszewska found Verticillium cel- 

 lulosae, V. glaucum, Sporotrichum olivaccum, and various other 

 sporotricha, fusaria, monosporia, alternariae, and moniliae among the 

 strongest cellulose-decomposing fungi in the soil. She also con- 

 cluded that the Hyphomycetes play a much more important part 

 than the bacteria in the decomposition of cellulose in the soil, the 

 color of the humus being due to the color of the mycelium and the 

 spores of fungi. Sugars and alcohols were formed as intermediary 

 products. 



More recent studies have fully confirmed these observations. It 

 may now be concluded that the fungi play a highly important part 

 in the decomposition of cellulose in soils and in composts. Their 

 part in the decomposition of cellulosic materials under tropical con- 

 ditions became particularly important during World War II. 



Mycorrhiza Fungi 



The mycorrhiza fungi form a special group of organisms. They 

 are capable of attacking the subterranean organs of plants, feeding 

 upon their organic constituents. The plant cells may recover, how- 

 ever, and in their turn digest the fungus mycelium. In this instance, 

 the subterranean part of the plant and the fungus mycelium form an 

 association which is frequently of benefit to both, this union being 

 known as mycorrhiza or fungus-root. 



Frank divided the mycorrhiza into two groups: (1) Ectotrophic 

 mycorrhiza, in which the fungus produces an external investment of 

 the root, in the form of a crown of hyphae, without penetrating into 



