824 
Journal of Agricultural Research 
Vol.XXI.No. II 
Of all the tubers which were “browned,” 14.2 per cent gave no organism 
of importance, jtnd 84.3 per cent gave V. albo-atrum. Thus, if this lot 
of tubers had been sorted for seed on the basis of the presence or absence 
of discoloration in the stem-end vascular region, 38 per cent of those 
passed as fit for seed would have been infected with V. albo-atrum, while 
14 per cent of those eliminated for seed purposes would apparently have 
been entirely free from a wilt-producing organism. 
In another lot of 647 tubers of seven varieties grown in 1917 from 
disease-free seed potatoes on soil badly infested with Verticillium albo- 
atrum, nearly half of them, or 293 tubers, were “ browned ” in the vascular 
region. These when cultured gave 55.3 per cent V. albo-atrum, 21.5 per 
cent Fusarium radicicola, 14-7 percent “miscellaneous fungi,” and 7.2 per 
cent no organism. Of the 260 tubers of the entire lot which gave V. 
albo-atrum in cultures, 2.7 per cent were affected by “jelly end” or slight 
stem-end rots, 1.9 per cent were “blackened” in the stem end, 62.3 per 
cent were “browned,” 30.4 per cent were “yellowed,” and 2.7 per cent 
showed “no discoloration” in the vascular region. 
In another lot of 498 potato tubers of seven varieties grown in 1917, 
from disease-free seed potatoes inoculated at planting time with pure 
cultures of Verticillium albo-atrum, 232 tubers were “browned” in the 
vascular region. These when cultured gave 60.5 per cent V. albo-atrum, 
9.0 per cent Fusarium radicicola, 26.5 per cent “miscellaneous fungi,” 
and 2.1 per cent no organism. Of the 244 tubers which gave V. albo- 
atrum in cultures, 0.8 per cent were affected by “jelly end” or slight dry 
stem-end rots, 2.9 per cent were “blackened” in the vascular region 
