866 
Journal of Agricultural Research 
Vol. XXIV, No. 10 
It was demonstrated that a macerating enzym was produced by 
Rhizopus tritici when grown on all the vegetable decoctions, with the 
possible exception of the prune, and that this enzym was quite active in 
some cases (carrot, sweet potato, and turnip). An examination of ex¬ 
periment 2, Table II, shows that loss of coherence of both sweet-potato 
and carrot disks was complete in the turnip decoction in two hours and in 
the carrot decoction in three hours, and in the suspension of hyphae 
growm on these decoctions in three and five hours respectively. The 
rate of maceration by the enzym in the sw^eet-potato decoction and 
by that in the hyphae grown on this solution was about the same as 
that obtained in many previous tests. Although there was a fair growth 
of mycelium on prune decoction, the writers were unable to demonstrate 
the presence to any extent of pectinase either in the solution or in the 
hyphae. With this exception, the vegetable media all produced a 
demonstrable amount of pectinase. There was considerable variation 
in the amount produced in the different media, the complete loss of 
coherence being showm by some solutions in less than one-half the time 
required by others. 
The production of pectinase could not be demonstrated in any of the 
synthetic solutions or in beef bouillon or the mycelium grown on them. 
From these results it seems safe to conclude that there is something in 
the composition of most of the vegetable decoctions which stimulates 
the production of pectinase, which is not present in the synthetic media 
or in beef bouillon. 
A probable explanation of the difference between the synthetic 
media and the vegetable decoctions with respect to the production of 
pectinase by the fungus growing on them may be sought in the regu¬ 
latory action of the substrate. A number of investigators have 
shown a quantitative regulation of the production of enzyms, while 
Knudson (15) demonstrated a qualitative regulation of tannase with 
Aspergillus niger and Penicillium sp. He found that these fungi pro¬ 
duced gallic acid by the fermentation of tannic acid when the latter 
was added to a modified Czapek’s nutrient solution, but if supplemented 
with glucose no tannase was formed. A number of other substances 
when used as a source of carbon failed to stimulate the secretion of 
tannase. Katz (74) studied the regulatory action of certain chemical 
substances in the substrate on the secretion of amylase by Penicillium 
glaucumy Aspergillus nigery and Bacillus megatherium and found that 
while the amylase secretion was not prohibited by the presence of sub¬ 
stances chemically allied to starch, their effect was to greatly inhibit it. 
He found that the different fungi did not act identically and cites as 
proof the results obtained with A. niger and P. glaucuiUy in which case 
sugar had a much less inhibiting effect on the production of the enzym 
with the former than with the latter. Similar conclusions were reached 
by Duclaux (d) with P. glaucum and A. glaucus, though he considered 
only the enzym excreted into the culture medium. A number of other 
investigators, among them Kylin (/6), have made similar studies. He 
worked with P. glaucumy P. hijormCy and A . nigery and found no quali¬ 
tative regulation of the enzyms (diastase, invertase, and maltase), 
though a quantitative regulation was conclusively proved. In the case 
of P. glaucum the regulatory secretion of diastase was greater than in that 
of A. niger. In this same connection the results obtained by Young 
{26) with A. niger may be cited. He showed that inulase was produced 
in greatest amount in the mycelium when inulin was used as the source 
