318 DorAN: ON THE GERMINATION OF FUNGOUS SPORES 
of the fungus. The only spores of Sphaerotheca mors-uvae which 
Foreman (8) induced to germinate were the large spores found 
at the tips of the chains of spores. Weimer (9) observed that 
the teliospores of Gymnosporangium Juniperi-virginianae which 
are situated at the apex of the spore horn germinate best and he 
attributed this to their maturing earlier. 
As the season advanced in the autumn the writer found it 
increasingly difficult to secure good germination of the conidia 
of Venturia inaequalis even when conidia were obtained from 
fresh lesions. This is not attributed to the presence of a greater 
number of spores too old to germinate, for they would probably 
have been washed away earlier. It is believed that a larger 
number of immature conidia of this fungus were present in the 
autumn. It is not unlikely that the process of maturing of the 
spore is slower when the temperature is lower 
Very little work has been done on the relation of the viability 
of fungous spores to the conditions under which the host plant 
grew and in which the fungus developed. If certain conditions 
may retard the maturing of the spores, it is quite possible that 
other conditions during their development may entirely prevent 
their ever germinating. On the other hand, certain conditions 
during development of the spore may result in an extremely 
- vigorous spore. Spores may be mistakenly designated as mature 
and immature, on the basis of their behavior when placed under 
optimum conditions for germination, when they should properly 
be designated as spores of the same age, some vigorous and others 
without vigor. 
The inability to germinate any fungous spore under all possible 
combinations of conditions may be temporarily explained by the 
supposition that the spores are either dead, non-fu ictioning or 
in a resting condition. There are perhaps many resting spores 
not now recognized as such. Reed and Crabill (10) have ad- 
vanced the theory that a rest period is necessary for the aecio- 
spores of Gymnosporangium Juniperi-virgimianae and that these 
spores do not germinate until the spring following their dispersal. 
Longevity.—For all spores ‘there is a maximum time limit, 
variable with the environmental conditions, beyond which the 
spore cannot germinate. The spore may be alive and too old to 
germinate or it may be dead. A live spore too old to germinate 
under the range of conditions within which it formerly could 
germinate is, according to the observation of the writer, able 
