328 DorAN: ON THE GERMINATION OF FUNGOUS SPORES 
According to the observation of the writer, extremes of tempera- 
ture at this time, if not too long continued, have no more serious 
effect than to temporarily stop the growth of the germ tube. 
This is resumed when the temperature again approaches the 
optimum. But when the humidity of the air falls, the results 
to the spore are more serious. In the case of all spores worked — 
with, and especially with conidia of Venturia inaequalis, it was 
found that a germinating spore can live but a short time in a dry 
environment, which to an ungerminated spore would be in no 
way detrimental. A return to optimal conditions proved such 
spores to be not merely inhibited but dead. 
Wallace (37) considered the length of time apple trees remain 
wet so as to allow spore germination an important factor in 
determining whether or not a certain rain would permit infection 
by Venturia inaequalis. He found that the ascospores of this 
fungus can germinate in four hours but he believed that apple 
trees must remain wet eight or ten hours to be abundantly in- 
fected. The writer will here comment that the further the 
temperature is from the optimum for germination, the longer must 
the surface of any plant remain wet in order for the spores on 
it to germinate and infect the host. 
Duggar (3) found that after drying the germinating spores 
of Botrytis would grow no more. But the germinating spores of 
Aspergillus showed new growth after being dried several days. 
Duggar’s results with the parasitic form mentioned are in agree- 
ment with the results secured by the writer, who worked only 
with parasitic forms. 
he relation of environmental factors to the time required 
for spore germination thas occasionally been noted. The amount 
of moisture present may affect the length of time in which the 
spore germinates. Taubenhaus (38) reports that the spores of 
Glomerella rufomaculans from the sweet pea germinate in from 
six to twenty-four hours, depending on whether there is much 
or little moisture present in the atmosphere. 
The writer has noticed that spores germinating in moist air 
require a relatively longer time for the process than do the 
same spores germinating in or on precipitated moistqre. 
Anderson (11) observed that at 25° C., which is within optimal 
limits for the germination of the spores of Cylindrocladium 
scoparium, the spores of this fungus begin to germinate in two 
to three hours, but at lower temperatures a longer time is neces- 
