Sept, i, 1921 
Transmission of Some Wilt Diseases in Seed Potatoes 831 
the seed potato when planted and, being the more vigorous organism 
of the two in this locality, caused the death of the plant. The indi¬ 
cation at least is that while the great majority of tubers give only one 
organism in culture there are not uncommonly also a number which give 
two or occasionally more organisms, even two wilt-producing organisms, 
from different portions. t 
In considering the data that have been presented in Tables I and II, 
the question arises as to the accuracy of the information derived from the 
isolation cultures where only one culture is made from each tuber. It 
is quite likely that a number of the tubers recorded in Table I from which 
no organism was secured had, as a matter of fact, been invaded by some 
organism. This would seem to be particularly true of those affected by 
endrot. Yet in general the results seem to be in accord with probability. 
For instance, a very much larger percentage of all of the “not discolored ’’ 
tubers than of those that were “ yellowed “ or “browned “ gave no organ¬ 
ism, the percentages being 81.6,50.5, and 21.9, respectively. It has already 
been noted that of the lot of tubers referred to in Table II from each of 
which four cultures were made, 69 tubers, or 46 per cent, gave identical 
results from the four quarters of each tuber. Forty-eight others, or about 
32 per cent, gave identical organisms in three of the quarters of each 
tuber; and 26 tubers, or about 17 per cent, in two of the quarters of each 
tuber. From the standpoint of chance, one single culture made from each 
of these 143 tubers would have given an accurate index to the organisms 
present in a total of 118 tubers, or 82.5 per cent of the group. A single 
culture made from each of the remainder would not necessarily have 
represented the exact conditions, although even here it would have shown 
the real situation more often than not, for in many cases the fungi secured 
came from the quarter or quarters having the most discoloration, and 
where only one culture was made it was always made from the most 
heavily discolored portion. From these data it is believed that the method 
for making the cultures in this investigation, though offering some 
chance of failure in securing correct evidence as to the organisms present, 
is still at least reliable enough to give a very good indication of the facts.' 
It has seemed also to be the most practical method available where a large 
number of cultures had of necessity to be made in a comparatively short 
time and where it was desired, as in this case, to keep the tubers in as 
nearly natural condition as possible for purposes of planting for further 
records. 
RELATION BETWEEN SIZE OP POTATO TUBERS AND OCCURRENCE OF 
ORGANISMS THEREIN 
The question arises as to whether tubers of a certain general size are 
morelikely to be free from internal infection than others and might, there¬ 
fore, be selected out for planting with the expectation of getting a smaller 
amount of disease from them than from tubers of other sizes. There is 
