368 
Journal of Agricultural Research 
Vol. XXVI, No. fr 
examination of Table II that it is the lowest temperature form of the iS 
strains of Rhizopus nigricans studied, its optimum temperature being 
26.7° C. If intermediate temperatures had been employed, the optimum 
would doubtless be somewhat higher. This organism germinated in a 
shorter length of time (5 days) at i.8° C. than any of the others tried. 
As a matter of fact, the spores of this organism germinated in a shorter 
length of time at all temperatures, except at 31 0 C., than any of the 
others. Quite contrary to the results obtained with the other organ¬ 
isms, the spores of 4652 did not germinate at 32.5 0 and 33.5 0 C., showing 
that a temperature much above 31 0 C. is fatal to them. 
Table III .—Diameter (in mms.) of the mycelial disks formed by 18 different strains of 
Rhizopus nigricans at different temperatures 
Organism No. 
7° C. 
18 days. 
»;c. 
7 days. 
22.5 0 C. 
1 day. 
26.2° c. 
i day. 
27° C. 
1 day. 
3 o* e. 
i day. 
31° C. 
5 days. 
35° c 
S days. 
S061 . 
O 
45 
29-5 
37-5 
39 -o 
17.1 
0 
O' 
S°S 3 . 
O 
70 
32.O 
38.0 
39 -o 
17.9 
0 
O 
5° 6 3 . 
0 
25.0 
35 -° 
35 -° 
17.8 
10 
O 
50 S 1 . 
O 
70 
19-5 
24-5 
26.0 
18.2 
0 
O 
5054 . 
O 
27-5 
38.5 
44.0 
16.3 
4 
O 
S°S6 . 
O 
70 
30.0 
35-5 
38.0 
13.8 
0 
O 
S°S 7 . 
O 
60 
20.0 
34 *o 
36.0 
12 .3 
0 
O 
5055 . 
O 
30 
3 i -5 
38.5 
39 -o 
20.1 
II .2 
O 
4652 . 
40 
25 
19.0 
26.5 
22.0 
0 
O 
O 
5052 . 
IO 
70 
24.5 
36.5 
39 *o 
I4.O 
O 
O 
5060. 
O 
O 
29-5 
39 -o 
39 -o 
18.4 
4.2 
O 
S°S8. 
O 
6 
30.0 
38.0. 
41.0 
16.O 
17.6 
O 
4682 . 
32 
67 
22.5 
29-5 
32.5 
II.O 
8.5 
O 
4684 . 
O 
45 
3i-5 
41.0 
42.0 
I4.6 
O 
O 
4887 . 
0 
50 
23.0 
37 -o 
39 -o 
21. I 
O 
O 
5062 . 
O 
55 
30.0 
43 -o 
43-5 
22.6 
O 
O 
5059. 
O 
8 
29.0 
38.0 
37*5 
19-5 
8 
O 
An examination of Table III shows that the average optimum tempera¬ 
ture for the growth of the mycelium of the different strains of R. nigricans 
is about 2 7 0 C. There is a considerable falling off in the diameter of 
the disks at 30° C., only three degrees above the optimum, and at 31 0 C. 
only a part of the organisms grew. A reference to Table II will show that 
this was the optimum temperature for the germination of the spores. 
The growth curve is in general very similar to the curve of spore germina¬ 
tion, the optimum and maximum temperatures for growth, however, 
being somewhat lower than those for spore germination. In these experi¬ 
ments the spores often germinated at temperatures at which further 
growth did not take place. 
It is interesting to note the results obtained with the organism 4652 
with which so much previous work in other connections has been done. 
It was found in the spore germination tests that this fungus had a lower 
optimum and maximum than any of the other strains studied. From 
Table III it is seen that the optimum for its growth is somewhat lower 
than that for the other fungi, being approximately 26.2° C. At 30° C. 
and above it made no growth though the spores germinated very well 
at 31 0 C. This organism also made a fair growth at a temperature of 
7 0 C., while most of the other strains made no growth at the same tem¬ 
perature. 
