PLATE 139 
A.—Up-to-Date potato tuber with surface of stem end cut off to show discolored 
vascular tissue from which Verlicillium albo-atrum was isolated in culture. 
Karly Rose tuber from which Fusarium oxysporum was isolated. 
On the average F. oxysporum caused heavier discoloration than did V. albo-atrum 
in the invaded tubers, though the appearance of the tubers could not be depended on 
for differentiating between the two organisms. 
C.-— Early Rose potato tuber from the discolored portion of which F. oxysporum 
was isolated in culture. The two plants grown from the two stem-end seed pieces 
became diseased, did not grow more than 9 inches in height, and died without pro¬ 
ducing any yield. The two plants from the two eye-end seed pieces remained healthy 
throughout the season and produced an average yield of 45 ounces. This difference 
in results from the stem-end and eye-end seed pieces is unusual, however, for on the 
average the former performed almost as well as the latter. 
