Sept, i, i92i 
Transmission of Some Wilt Diseases in Seed Potatoes 825 
82.4 per cent were “browned," 13.5 per cent were “yellowed/' and only 
0.4 per cent were “not discolored." 
In still another lot of 258 Up-to-Date potato tubers grown by plants 
wilted naturally in the field with Verticillium albo-atrum during the 
season of 1916, 75 were “browned" in the vascular region. These when 
cultured gave 57.3 per cent V. albo-atrum , 9.3 per cent Fusarium 
spp., 28 per cent “miscellaneous fungi," and 5.3 per cent no organism. 
Of the 97 tubers which gave V . albo-atrum in cultures, 44.3 
per cent were “browned" in the vascular region, 41.2 per cent were 
“yellowed," and 14.4 per cent were “not discolored." 
In Table I is given a summary of practically all of the data collected 
during the course of this investigation on the relation of discoloration 
Fig. a.—Diagram prepared from the horizontal percentages given in Table I, showing the percentage 
occurrence of a given organism in tubers of different discolorations. 
of the vascular region to the occurrence of organisms in potato tubers. 
A part of the data in the table is shown graphically in figures 1 and 2. 
The results shown here are from a total of 12,136 tubers grown under a 
variety of conditions during three seasons from nine varieties and should 
therefore not be unusual but should serve as a basis for seemingly reliable 
conclusions. The table shows that Verticillium albo-atrum was isolated 
from 2.097 tubers, of which only a small percentage, 1.5, were affected 
by “jelly end" and slight dry stem-end rots. This is considered to be 
an accidental and mixed rather than a specific infection, because the 
great majoirty of the tubers affected by such rots gave other organisms 
in culture and all available data point to the fact that V. 
albo-atrum does not cause a specific rot of potato tubers. Also, only a 
small percentage, 1.1, were “blackened" in the vascular region. The 
