1921] 
MATSUMOTO--SPECIALIZATION IN RHIZOCTONIA 15 
these erzymes into 3 groups: (1) diastase, ete., which is found 
at least in small quantity when the fungus is grown on any med- 
ium; (2) maltoglucase, formed only when both carbohydrate 
and a nitrogen-containing salt are present; and (3), those that 
are formed only when certain substances chemically allied to the 
substratum are present; thus trehalase is formed when the cul- 
ture medium contains trehalose. 
Dox (710) believed “that enzyms not normally formed by the 
organism in demonstrable quantities" could not be developed 
by special nutrition and that the effect of a particular substra- 
tum ‘‘is, therefore, not to develop an entirely new enzym, but 
to stimulate the production of the corresponding enzym." 
Roselli (11), using Aspergillus niger, found that equal amounts 
of various carbohydrates did not affect the amount of inulase 
secreted materially, but the amount in the culture medium in- 
creased rapidly with age. Kylin (14) could not find any evi- 
dence of qualitative enzyme regulation except in the case of 
tannase formation by Aspergillus niger and Penicillium sp., 
which is conditioned by the presence of tannic or gallic acid in 
the culture medium. Quantitative regulation, however, was 
found to be pronounced, and greater in the case of Penicillium 
than in Aspergillus. 
In 1918 Young studied inulase formation in Aspergillus niger 
and concluded that under all conditions studied inulase was 
produced by the fungus in appreciable quantities, but in greater 
amount when inulin (or a related substance) was present in the 
culture medium. Within the last year Kopeloff and Byall 
(20) studied the invertase activity of the spores of Aspergillus 
niger and Penicillium expansum and reported that the maximum 
invertase activity occurred at concentrations of sucrose between 
50 and 60 per cent. 
Besides those factors mentioned above, it is also possible 
that many other chemical ‘‘stimuli,” H-ion concentration, 
temperature, etc., may influence the formation of enzymes. 
From such facts one may infer that certain forms of fungi might, 
by eonstant association with one host or certain complicated 
environmental conditions, change their nature in respect to 
enzymatie activity and ultimately become quite distinct from 
other forms of the same species. To what extent, however, 
