810 
Journal of Agricultural Research 
Vol. XXX, No. 9 
temperature group, R. nigricans , R. 
reflexus, and R. artocarpi. The optima 
for the high temperature group vary 
from 32° to 35° C., the maxima are 
about 42° and the minima vary from 
3.4° to 9°; the minimum for R. maydis 
has not been definitely determined. 
The optima for the low temperature 
groups vary from 18.5° to 24°, the 
maxima from 30° to 34.5°, and the 
minima from 3.4° to 12°. The extreme 
temperature limits over which the en¬ 
tire group will infect sweet potatoes 
are between 3.4° and 42°. R. tritici 
will infect over this entire range. The 
two strains of R. nigricans have a slight 
difference in their temperature re¬ 
sponse, the one having a slightly higher 
maximum than the other. The increase 
in the amount of decay with the rise in 
temperature is large, being four to 
ten times as much as one tempera¬ 
ture as at 10° below. 
LITERATURE CITED 
(1) Hanzawa, J. 
1914-15. Studien uber einige rhizopus-arten. 
Mycol. Centbl. 5: 230-246, 257-281, illus. 
(2) Harter, L. L., Weimer, J. L., and Adams, 
J. M.R. 
1918. SWEET POTATO STORAGE-ROTS. JoUr. Agr. 
Research 15: 337-368, illus. 
(3) ---and Lauritzen, J. I. 
1921. THE DECAY OF SWEET POTATOES (iPOMOEA 
batatas) produced by different species of 
rhizopus. Phytopathology 11: 279-284. 
(4) - 
1923. SOME PHYSIOLOGICAL VARIATIONS IN 
STRAINS OF RHIZOPUS NIGRICANS. JoUr. Agr. 
Research 26: 363-371. 
(5) Lauritzen, J. I. 
1919. THE RELATION OF TEMPERATURE AND 
HUMIDITY TO INFECTION BY CERTAIN FUNGI. 
Phytopathology 9: 7-35. 
(6) -and Harter, L. L. 
1923. SPECIES OF RHIZOPUS RESPONSIBLE FOR THE 
DECAY OF SWEET POTATOES IN THE STORAGE 
HOUSE AND AT DIFFERENT TEMPERATURES IN 
infection chambers. Jour. Agr. Research 
24: 441-456, illus. 
(7) Weimer, J. L., and Harter, L. L. 
1923. temperature relations of eleven 
species of rhizopus. Jour. Agr. Research 24: 
1-40, illus. 
