92 
AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
were determined in io-cc. portions in duplicate. The results of these 
experiments are given in table I. The spores were obtained from cultures 
grown at the temperatures indicated in the table. 
It will be seen that the range of temperatures employed is somewhat 
limited. The object of these experiments was primarily to prove that a 
starch-hydrolyzing enzym was contained in the spores of Rhizopus tritici 
and R. nigricans. It was previously shown by Harter (2) that the mycelium 
produced amylase when grown at temperatures ranging from 9 0 to 40° C., 
but not uniformly so. The enzym was most active when the fungus was 
grown at 9 0 and least active when grown at 40°. Both of these fungi will 
grow and produce mycelium over a considerably wider range of temperatures 
than those at which spores are produced. As a matter of fact, R. tritici 
will grow at a much higher temperature than R. nigricans , while the latter 
will thrive better at a lower temperature than the former. The range of 
temperatures at which spores are produced is therefore limited in both 
organisms. R. tritici produced spores abundantly at temperatures ranging 
from approximately 20° to 38°, and R. nigricans from about 16 0 to 30°. 
Above and below these temperatures the quantity of spores was so small as 
to make the determination of the hydrolysis of the starch out of the question. 
Within the limits of these experiments the results indicate that amylase 
is contained in the spores at any temperature at which they are produced. 
The same was also found true with respect to the mycelium. The data at 
hand are not sufficient to justify the conclusion that the amount of amylase 
contained in the spores is correlated in any way with the temperature at 
which the organism was grown. 
Comparative tests of the hydrolyzing power of the spores and mycelium 
have shown that the enzym of the latter is more active than that of the 
former, when compared on the basis of unit weight. This holds true when 
the comparison is made between spores and mycelium grown at the same 
temperature. 
Summary 
1. An enzym capable of hydrolyzing Irish-potato starch paste to re¬ 
ducing sugars is produced in the spores of Rhizopus tritici and R. nigricans. 
2. Within the limits of these experiments the enzym is produced at any 
temperature at which spores are produced. 
U. S. Department of Agriculture, 
Washington, D. C. 
LITERATURE CITED 
1. Clark, W. B. Volumetric determination of reducing sugars. A simplification of Scales’ 
method for titrating the reduced copper without removing it from the residual 
copper solution. Jour. Amer. Chem. Soc. 40: 1759-1772. 1918. 
2. Harter, L. L. Amylase of Rhizopus tritici, with a consideration of its secretion and 
action. Jour. Agr. Res. 20: 761-786. (Literature cited, pp. 784-786.) 1921. 
3. Kopeloff, N., and Kopeloff, L. Do mold spores contain enzyms? Jour. Agr. Res. 18: 
195-209. 1919. 
