Viability of Uredinios pores 
15 
CONCLUSIONS 
1. The influence of relative humidity on the viability of the 
urediniospores of Puccinia graminis tritici Form III is very pro- 
nounced and closely associated with temperature. 
2. At high relative humidities, depending somewhat on the 
temperature, the percentage of germination is low and the period 
over which the spores are viable is very short. 
3. The same relation exists at the low relative humidities 
except that it is not so pronounced and is more variable. 
4. The highest percentage of germination and the longest 
viable period of the spores occur at the medium relative hu- 
midities. High temperatures lower the percentage of germination 
and shorten the viable period while at low temperatures the 
opposite occurs, at the medium relative humidities. 
(3M) 
