78 CARBON NUTRITION 



wood (10, 31, 178), straw (143, 222), litter (117), and other materials 

 (68, 198). It is the appropriate method for the practical problem in- 

 volved in the decomposition of cellulose in nature, but suffers of course 

 from the inherent difficulty of all growth measurements in complex 

 materials, that the cellulose may not be the primary growth substrate. 



3. Determination of the loss in weight of cellulosic materials exposed 

 to the test organism (162, 233). The principal complication is that 

 the mycelial weight is included with the residual cellulose; alkali treat- 

 ment (191) can reduce but not eliminate this error. 



4. Determination of total or protein nitrogen in the insoluble mate- 

 rial left after growth of a test organism on cellulose in a medium with 

 a soluble nitrogen source (142). This is without doubt the most 

 accurate and reliable method for the measurement of real growth of a 

 fungus on an insoluble non-nitrogenous substrate such as cellulose. 

 Unfortunately, the method has been little used and cannot as yet be 

 compared to others in detail. 



The methods which have been used do not always agree; thus, 

 Aspergillus versicolor strains appear to utilize the cellulose of straw 

 (143) but apparently do not cause measurable deterioration of cotton 

 fabric (126). A complete list of the fungi reported, by various meth- 

 ods, as able to attack cellulose has been compiled (186). It is apparent 

 that certain genera of the Fungi Imperfecti and the ascomycetes are 

 particularly rich in species able to decompose cellulose. In the basi- 

 diomycetes, the wood-rotting and litter-decomposing fungi are gen- 

 erally, although not universally, able to decompose cellulose; genera 

 particularly involved include Armillaria, Clitocybe, Collybia, Corti- 

 cium, Fomes, Marasmius, Mycena, Polyporus, Polystictus, Schizophyl- 

 lum, and Stereum (31, 118, 164). It must be noted, however, that the 

 species within a given genus are not all necessarily alike in their 

 response to cellulose. This has been especially well established in 

 Aspergillus (238) and Tricholoma (142). In some species, strain dif- 

 ferences in the utilization of carboxymethylcellulose have been re- 

 ported (96). 



Among the phycomycetes, many members of the Chytridiales utilize 

 cellulose (45, 233). Limited data indicate that none of the Blasto- 

 cladiales is cellulolytic (34). In the Saprolegniales, members of sev- 

 eral genera apparently produce an enzyme hydrolyzing filter paper cel- 

 lulose (16, 173), as do species of Phytophthora in the Peronosporales 

 (128); this may be taken as prima-facie evidence for their ability to 

 grow on cellulose. None of the Mucorales so far studied is cellulolytic 

 (126, 147, 164, 236). 



