DORAN: ON THE GERMINATION OF FUNGOUS SPORES 319 
to germinate when all conditions approach the optimum. There 
comes a time when even this is not stimulative and the spore is 
then dead so far as we can tell. Neglect of the age factor may 
render any study of spore germination undependable. 
In studying the relation of the age of spores to their viability, 
points to be considered are the date of collection, the conditions 
in which the spores are placed after collecting, and the length 
of time spores remain viable after their collection. Aeciospores 
of Cronartium ribicola were found to germinate with diminishing 
vigor as the season advanced. The aeciospores of this fungus 
were collected on May 25th, June 4th and June 12th from the 
same sorus. On the first date, the relative number of spores 
germinating was one hundred, on the second date forty-nine 
and on the third date twenty-nine. Observations with this. 
and other fungi indicate that although there is at first a sharp 
falling-off in viability, it is retained for a comparatively long 
time and only gradually lost. In any spore germination studies 
which involve comparisons, spores should be used which are 
known to be of the same age. 
Among the factors bearing upon the retention of viability 
after the collection of spores are moisture, temperature, and 
freedom from or connection with the parent. Detachment 
from the parent was not found to have any effect on the length 
of life of the aeciospores of Cronartium ribicola, viability de- 
creasing the same in both cases. When collected, the relative 
number of these spores germinating was one hundred, after 
having been collected thirty days the germination fell to seventy- 
three, after fifty days to five, and after a days no spores 
germinated. 
Freshly collected aeciospores of apenas ribicola were 
stored indoors at temperatures of 7° C., 15° C., ae These 
various temperatures had no effect upoa the peer of the 
spores. But aeciospores stored in moist air retained their 
: viability longer than those stored in dryer air. At least in the 
case of this fungus moisture is of more importance than tempera- 
ture in its effect on the length of life of the spore. This effect of 
moisture is to be expected; for all spores lose water in dry and 
moist air, and if other conditions are equal they should live 
longer in moist air than ia dry air. These results agree with 
those of Anderson (11) who found that in a humid atmosphere 
