DoRAN: ON THE GERMINATION OF FUNGOUS SPORES 321 
It is possible that in most cases the mucilaginous covering 
in which many spores are imbedded serves to prolong the life 
of the spore. For this reason, whea studying the germination 
of such spores, it is advisable that only those still adhering to- 
gether in their protective coatings be used. 
Exposure to light shortens the life of some spores, as shown 
by the results of Hoerner (15) with the urediniospores of Puccinia 
coronata. 
Some attention has beea given to the longevity of the spores 
of the Uredinales. The sporidia are the shortest-lived spores of 
this group of fungi. According to Reed and Craybill (10) the 
sporidia of Gymnosporangium Juniperi-virginianae do not live 
more than six days in dry air. Spaulding (16) reports that the 
sporidia of Cronartium ribicela live less than ten minutes at 
room temperature with the humidity at ninety. Duff (17) 
found that two weeks after the collection of the urediniospores of 
Cronartium ribicola their germination was so reduced as to be- 
come practically negligible. The life of a teliospore measured 
from the time of its formation to its death may be long, but the 
life of a teliospore if measured from the close of its normal resting 
period until its death is not long; it is apparently as short in 
some cases as the life of many non-resting spores. Melhus, 
Durrell, and Kirby (18) report that the teliospores of Puccinia 
graminis, which mature in April, cannot germinate after the end of 
June following. 
The experience of the writer is to the effect that in most cases 
aeciospores are longer lived than urediniospores. The average 
life of urediniospores is between thirty and sixty days. The 
average life of the aeciospore is about 50 per cent greater. The 
several spore forms of the Uredinales behave alike in this, that 
as they grow older their range between maximum and minimum 
conditions for germination becomes narrower. 
EXTERNAL FACTORS 
Temperature relation—One of the most important external 
factors bearing upon the germination of fungous spores is the 
temperature relation. In order to draw from the scattered data 
in the literature some more general conclusions than we now have 
as to the cardinal temperatures for the germination of fungous 
spores, TABLE I has been prepared. In it are given the cardinal 
