838 
Journal of Agricultural Research 
Vol. XXI, No. ii 
not highly virulent in this region. It may, however, be due in part to 
the apparent general tendency of F. oxysporum in the seed potatoes to 
fail to perpetuate itself in the plants grown therefrom, as shown by the 
work of Bisby (r) and MacMillan (6). 
Occasionally potato tubers having the stem end sunken and discolored 
gave both Fusarium oxysporum and a small mite in culture. In a few 
cases both of these organisms were evidently transmitted from the seed 
potatoes to the yields. For instance, in one hill (Pi. 141, A) grown from 
a seed tuber from which these two forms were isolated before planting, 
three out of the nine tubers produced gave the same organisms in culture 
after harvest. The presence of the mite was no doubt responsible for 
the sunken condition of the stem end of the invaded tubers, as it naturally 
would consume some of the tissues and the skin would collapse; and, 
generally, tubers containing F. oxysporum alone appeared quite if not 
entirely normal on the exterior. 
There was a slight tendency of the “other Fusarium species' * to be 
transmitted to the yields, as these organisms ran highest in the tubers 
grown from similarly infected tubers. Some of these organisms also 
were found to occur more or less indiscriminately in any lot of tubers 
cultured. 
There was no indication that any of the “miscellaneous fungi" were 
transmitted to an appreciable extent. They seemed to occur promis¬ 
cuously with no apparent relation to the condition of the seed potato at 
planting time. 
' The seed potatoes from which “no organisms" were isolated gave 
crops which frequently showed the presence of organisms, doubtless 
derived from the soil or from adjacent diseased plants, although never to 
the extent of disease-infected seed. 
In order to determine whether or not the stem-end seed piece would 
consistently transmit a higher percentage of organisms than the eye-end 
seed piece from the same tubers, a tabulation was made of the available 
data, the essential points of which are given in Table V. The kind of 
seed pieces used made no essential difference in the amount of infection 
from Verticillium albo-atrum secured either in the plants produced or in 
the yields obtained, the percentage of infection in the yields from the 
stem pieces being 22.7 and from the eyepieces 24.6. This difference is 
entirely negligible, being even less than the difference in the results 
secured from planting the two longitudinal halves of other tubers which 
presumably should have shown no difference in amounts of infection in 
the yields. However, in view of evidence later secured on the spread of 
V. albo-atrum from one plant to another in the row, the results presented 
here on the transmission of this organism in the different kinds of seed 
pieces must not be given too great weight, because the plants from the 
different kinds of seed pieces were grown in juxtaposition in the row, 
thus giving the fungus opportunity to spread from one plant to another. 
