ESSENTIAL NONMETALLIC ELEMENTS 99 



references to nitrogen fixation by filamentous fungi see Wolf and Wolf 

 (1947) and Buchanan and Fulmer (1930). 



So far as we are aware, only one study of nitrogen fixation by fungi 

 using modern isotopic techniques (Tove et at., 1949) has been published. 

 Phoma causarina was grown on a sucrose-salts medium in oxygen and 

 nitrogen enriched with N^^. Growth was slow and sparse under these 

 conditions, but some N^^ was fixed. These authors state that the isotopic 

 method is about 100 times more sensitive than the Kjeldahl procedure 

 used by other investigators. 



While it is probable that only a relatively few fungi are able to fix nitro- 

 gen, the importance of biological nitrogen fixation is so great that further 

 investigations with modern techniques are desirable. Long ago Ternetz 

 (1907) reported that five species of Phoma isolated from roots of Ericaceae 

 fixed significant amounts of nitrogen. For a discussion of nitrogen fixa- 

 tion by bacteria see Wilson (1940). 



Fungi utilizing nitrate nitrogen. Nitrates occur in the soil and thus are 

 a ''natural" source of nitrogen. A fungus which utilizes nitrate nitrogen 

 (NOs") must be able to reduce the nitrogen to the oxidation level of 

 ammonia. We may assume that failure of a fungus to utilize nitrate 

 nitrogen is coupled with inability to perform this reduction. According 

 to Robbins (1937) no instances have been recorded in the literature of an 

 organism being able to utilize nitrate nitrogen and unable to utihze 

 ammonium nitrogen. This does not mean that fungi which are able to 

 utihze nitrate nitrogen will grow at the same rate on ammonium nitrogen, 

 or that all sources of organic nitrogen will be as favorable as nitrate nitro- 

 gen. Yeasts as a rule do not utilize nitrate nitrogen. 



The following is a partial list of fungi which have been reported or 

 observed to utilize nitrate nitrogen: 



Armillaria rnellea C. velutipes 



Ascobolus denudata Cordyceps militaris 



A. leveillei Dendrophoma obscurans 

 Ascochyta pisi Dothidella quercus 

 Aspergillus spp. Fusarium spp. 

 Botryotinia convoluta Glomerella cingulata 

 Botrytis allii Gyrnnoascus setosus 



B. cinerea Helminthosporium spp. 

 Cephalothecium roseum Lambertella corni-maris 

 Cercospora apii Lentinus tigrinus 



C. beticola Macrosporium sarcinaeforme 

 Chaetomiiim cochlioides Marasmius Julvobidbillosus 

 C. convolutum Neocosmopara vasinfecta 



C. globosum Ophiobolus graminis 



Colletotrichum lagenarium 0. miyabeanus 



C. lindeniuthianum Penidllium spp. 



Collybia tuberosa Phoma apiicola 



