364 
Journal of Agricultural Research 
Vol. XXVI, No. 8 
Table I.— Isolation , key number , the host , the locality , and the name of the person who 
isolated each of the 18 strains of Rhizopus nigricans studied 
Number. 
Host. 
Locality. 
Isolated by— 
5061 
5053 
5063 
505 1 
5054 
5056 
5057 
5055 
4652 
5052 
5060 
5058 
4682 
4684 
4887 
5062 
5059 
5050 
Artocarpus integrifolia. . . 
Cabbage. 
Unknown. 
Bean. 
Strawberry. 
Pepper. 
Strawberry. 
Anona reticulata . 
Sweet potato. 
Unknown. 
Artocarpus integrifolia. .. 
A nona squamosa . 
Raspberry. 
Strawberry. 
Psidium guajava L. 
Musa paradisiaca . 
Tomato. 
Peach. 
Soledad, Cuba. 
Chicago, Ill. 
Amsterdam, Holland.... 
Michigan.. 
Lewiston, Me. 
Chicago, Ill. 
Plant City, Fla. 
Santiago de las Vegas, 
Cuba. 
Washington, D. C. 
Amsterdam, Holland. .. 
Santiago de las Vegas, 
Cuba. 
.do. 
New York, N. Y. 
El Monte, Calif.. 
Santiago de las Vegas, 
Cuba. 
Havana, Cuba. 
Chicago, Ill..... 
Washington, D. C. 
L. L. Harter. 
G. B. Ramsey. 
Unknown. 
E. A. Bessey. 
Neil E. Stevens. 
G. B. Ramsey. 
Neil E. Stevens. 
S. C. Bruner. 
L. L. Harter. 
Unknown. 
S. C. Bruner. 
S. C. Bruner. 
E. D. Eddy. 
Neil E. Stevens. 
S. C. Bruner. 
S. C. Bruner. 
G. B. Ramsey. 
J. S. Cooley. 
Numbers 5063 and 5052 are plus and minus strains respectively, and 
were obtained through the Centraalbureau voor Schimmelcultures, 
Amsterdam, Holland. 
Before these strains were employed in these investigations each was 
studied (not critically) and found to conform to what the writers have 
identified as Rhizopus nigricans. No difference morphologically was 
detected between any of them. 
In view of the fact that more than one species of Rhizopus is frequently 
isolated from a host, each of the strains employed in these investigations 
was “pure lined,” that is, a culture was obtained from a single spore. 
The fungi were kept in a vigorous state of growth by frequent trans¬ 
fers to some medium on which they grew well. Sweet potato agar in 
100 cc. Erlenmeyer flasks was generally employed. The cultures were 
held at a temperature of from 20° to 22 0 C. 
PARASITISM 
The parasitism of the eighteen strains was tested on sweet potatoes 
according to the method usually employed by the authors, which is 
briefly as follows: The potatoes were carefully washed but not disin¬ 
fected. The inoculations were made by the “well” method (5). The 
potatoes were confined in moist chambers with filter paper in the bottom, 
and incubated in the dark at a temperature of from 20° to 22 0 C. The 
cultures used in making the inoculations were grown in sweet potato 
decoction, in one experiment for two days and in another for three 
days. The above temperatures were employed because it had been 
shown that the strains of R . nigricans previously studied grew well at 
about 20 0 to 22 0 C. 
