Apr. 7.1923 Temperature Relations of Eleven Species of Rhizopus 33 
CERTAIN ENVIRONMENTAL FACTORS INFLUENCING GERMINATION 
AND GROWTH 
TEMPERATURE AT WHICH THE SPORES ARE PRODUCED 
Wiesner {22) found that the temperature at which the mycelium of 
Penicillium glaucum Link developed influenced the time required for 
the germination of the spores. For example, he showed that spores 
which matured at 14° C. germinated more quickly at 3° than those which 
had developed at 3^, while the spores that were produced at 22^^ germi¬ 
nated more slowly than those produced at 14®. The influence which the 
growing temperature of Rhizopus nigricans has on the germination of 
its spores has been studied to some extent by the writers. Stock cul- 
tiu-es were grown for 7 days on Irish potato agar in Erlenmeyer flasks 
at 16®, 24°, and 27^. Spore suspensions were prepared in portions of 
the same solution. The hanging drops were prepared as previously 
described and incubated at 26®. The spores grown at 16^, 24^, and 27° 
formed germ tubes as long as the spores in 2 hours, in 2 hours and 5 
minutes, and in 2 hours and 25 minutes, respectively. Similar tests 
were made with delemar with the following results: Spores produced at 
20.5"^, 27.5"^, 31.5^ and 36.5° germinated at 36.5^ after 3 hours and 45 
minutes, 3 hours and 50 minutes, 4 hours and 45 minutes, and 7 hours -f 
(no germination within 7 hours but some later), respectively. Tests 
with some of the other species showed a similar tendency—that is, 
spores which were produced at the lower temperatures germinated more 
quickly than those from cultures grown at higher temperatures. It was 
thought that possibly the difference in the rate of germination of the 
spores produced at different temperatures was due to a difference in age. 
The physiological activities of the organism are admittedly more rapid 
at the higher temperatures, the spores therefore being produced more 
quickly and probably aging more rapidly. In order to determine 
whether the difference in the rate of germination of spores produced at 
different temperatures might have been due to the age of the spores in 
the foregoing experiments, another test was made in the following 
manner: Fifteen loo-cc. Erlenmeyer flasks, each containing 30 cc. of 
Irish potato agar, were inoculated with a loop of a suspension of nigricans 
spores. Five of these flasks were then held at each of the following 
temperatures: io°, 20°, and 26°. The time required for the develop¬ 
ment of the sporangia was noted in each case, and germination tests 
were made from time to time. The tests were conducted at 25.5®. 
The spores from cultures which had been fruiting for 3, 5, 8, and 12 
days at 20° and 26° germinated in 3^^ hours. One flask held at 26° 
became contaminated and was discarded. The final test for the spores 
produced at 20^ was made after 20 days, and the time required for 
germination was the same as when the other tests had been made. 
The spores produced at 10° when 3, 5, and 15 days old required only 
2^4 hours for germination to start. The other two cultures failed to 
fruit. These experiments show first that spores produced at the lowest 
temperature (10°) germinated 30 minutes earlier than those formed at 
20° and 26^, and second that the age of the spores, at least up to 20 
days, did not influence the time necessary for the beginning of germi¬ 
nation. It is quite evident from these results that it is important to 
grow the stock cultures used in comparative experiments at the same 
temperature. 
30615—23-3 
