Sept, i, 1921 Transmission of Some Wilt Diseases in Seed Potatoes 827 
Fusarium radicicola was isolated from 4.2 per cent of all the tubers 
cultured and included in the table. It occurred to a greater extent than 
Verticillium albo-atrum in the “endrot” and ‘‘blackened” tubers, the 
percentages for F. radicicola being 8.3 and 5.6, and for V. albo-atrum 1.5 
and 1.1, respectively; and much less in the “yellowed” and “not dis¬ 
colored” tubers, the percentages being 18.2 and 3.7 for the former fungus, 
and 26.2 and 6.6 for the latter, respectively. The majority, 64,2 per cent, 
of the tubers which gave this fungus were “browned” in the vascular 
region. From these figures it must be concluded that this fungus occurs 
rather frequently in potato tubers and that it causes a somewhat heavier 
discoloration than V. albo-atrum in the invaded tissues. This latter fact is 
well shown in figure 2, in which at the left of the center, where the results 
from the heavily discolored tubers appear, F. radicicola occupies a higher 
position than V. albo-atrum , and at the right of the center, where the 
results from the lightly discolored tubers are given, it occupies a lower 
position than V. albo-atrum. 
Fusarium oxysporum has not been isolated during the course of this 
investigation as frequently as either of the other two organisms already 
mentioned, having been secured from 295 tubers, or only 2.4 per cent of 
all the tubers cultured. Fifteen and two-tenths per cent of the tubers 
from which this fungus was isolated were “blackened” and only 3.4 per 
cent were “not discolored,” as compared to 5.6 per cent and 3.7 per cent, 
respectively, for F. radicicola and 1.1 per cent and 6.6 per cent, respec¬ 
tively, for Verticillium albo-atrum . A smaller percentage of the tubers 
from which F. oxysporum was isolated were “browned” than was true of 
those from which F. radicicola and V. albo-atrum were secured, the per¬ 
centages being 59.7 as compared to 64.2 and 64.6, respectively. Thus it 
appears that F. oxysporum caused even heavier discoloration in the tubers 
than either of the other two organisms. Although this is contrary to 
statements that are often made in literature (5, 7), the results secured 
during the course of this investigation have been consistent on this point 
throughout, and it is believed that they are quite representative of the 
facts. 
Several determined and undetermined species are grouped in Table I 
under “other Fusarium species,” some of which may be mentioned on 
account of their economic importance. Fusarium trichothecioides Wollenw. 
was isolated in April, 1916, from one tuber which was “browned” in the 
stem-end vascular region. There was no rot present in this tuber, 
although other tubers in the same lot were affected by “powdery dryrot” 
and presented the typical appearance of this disease. One stem-end 
seed piece from this “browned” tuber produced a normal plant, but the 
organism appeared in two tubers out of nine produced in the hill, one 
of which was affected the following spring by typical powdery dryrot, 
while the other was “blackened” in the stem-end vascular region though 
not rotted. The discoloration present in this “blackened” and the 
