PLATE 141 
A. —Yield of potato tubers grown from a seed potato which had a slightly withered 
and collapsed area at the stem end from which Fusarium oxysporum and a small mite 
were secured in cultures. Three of the tubers in this yield were affected in the same 
>way as the seed tuber and gave the same results in cultures. The sunken condition 
of the stem end of these three tubers was probably due to the presence of the mite 
and is not typical of tubers invaded by F. oxysporum alone. In this latter case the 
tubers generally appear normal on the exterior. 
B. Original isolation cultures (77 days old) of wilt-producing organisms secured 
on sweet clover stems from the four quarters of the stem end of one Up-to-Date po¬ 
tato tuber: a, Verticillium albo-atrum; b, Fusarium oxysporum / c , d, no growth. At 
the top of dis shown the piece of tissue removed from the tuber for inoculating the 
clover stem. 
