ENZYMES OF WOOD -DESTROYING FUNGI 45 



Some appreciation of the scope of investigations regarding 

 enzymes produced by wood-inhabiting fungi may be gained from 

 Table 5, in which representative findings are assembled. The list 

 is not inclusive; other enzymes have been demonstrated for some 

 of the species listed, and most of the species have not been tested 

 to determine whether they are capable of producing all the en- 

 zymes mentioned. The most prominent feature shown by this 

 compilation is that nearly all species are able to produce amylase, 

 catalase, cellulase, emulsin, maltase, and sucrase. 



Whether fungi that are capable of producing many enzymes 

 attack a wide variety of woods, whereas those with restricted 

 enzyme-producing powers are limited to a single species of tree 

 or to closely related species, is as yet unknown. Studies of this 

 kind might be fruitful. Woods differ in nature, as is well known, 

 in the amount and kind of nutrients present, aside from cellulose 

 and lignin, and also in their content of toxic substances. The 

 wood of angiosperms is notably higher in pentosan content than 

 is coniferous wood. These nutritional factors may determine 

 the specificity of fungi for woods. Evidence on this point has 

 been submitted by LaFuze (1937). In cultures he found that 

 Polystictus versicolor, a generalized species, was able to oxidize 

 tannin, resorcinol, quinol, tyrosin, and guiacol, whereas Fomes 

 pinicola, a specialized species, had very little oxidizing ability. 

 Moreover, P. versicolor showed little selective ability for kinds of 

 nutrients, but F. pinicola was sensitive to differences in carbohy- 

 drates, growing poorly in the presence of pentoses, galactose, and 

 sucrose. In regard to toxic substances in woods, he suggests that 

 glucosides, alkaloids, resins, oils, terpenes, and phenolic groups 

 may be inhibitive to growth. 



The complement of enzymes produced by the assimilatory por- 

 tion of wood-attacking fungi may be different from that in the 

 sporophores, as suggested by Nutman (1929). Evidence in sup- 

 port of this contention is found in the fact that hyphal growth, 

 so far as is known, is apical, and that many fungi are able to effect 

 penetration of woody tissues not by way of the bordered pits but 

 by making boreholes. Smith (1923) noted apical growth in 

 Rhizopus nigricans, Phytophthora parasitica, Rhizoctonia solani, 

 Botrytis cinerea, Pyronema confliiens, Aspergillus niger, and Peni- 

 cillium expansum. Boreholes in wood were noted by Hartig 



