77° 
Journal of Agricultural Research 
Vol. XXIII, No. 9 
(4) Greater damage to potato plants occurred in the field in sclerotia- 
inoculated soil during the cool season of 1918 with a daily mean soil 
temperature for June of 20.1 0 C. than during 1919 with an average daily 
mean of 23 0 for the same growth period. This loss in 1918 was expressed 
in a greater decreased stand, a greater number and a more severe type of 
stem lesions, fewer stems per hill, decreased number of tubers per hill, 
and a total loss in yield of 50 per cent as opposed to a total loss of 15.4 
per cent in 1919. 
(5) The results in general indicate that the occurrence of an average 
daily mean temperature of 2 0 above or below the critical temperature (21 °) 
for the pathogenicity of the Corticium vagum on the growing points during 
the first six weeks of potato growth may accurately govern the damage 
done to the crop by this fungus in any one season. 
(6) Such temperature data as are here presented will go far in helping 
to explain many of the conflicting views held regarding the pathogenicity 
of Corticium vagum on the potato and other hosts. 
