68 
Journal of Agricultural Research 
Vol. XXI, No. I 
An examination of Table VIII discloses that net-necrosis was inherited 
only in three Green Mountain lots (n, V-138, and V-139). That is, 
the sublot which was selected as showing net-necrosis in 1919 developed 
as much disease in 1920 as was shown by any other sublot, or more. 
However, in the majority of such sublots (in lots V-134, V-142, V-143, 
V-144, V-148, V-155, and V-156) there was no net-necrosis in 1920, 
although in three lots (V-134, V-148, and V-156) varietal susceptibility 
was shown by the fact that some tubers were net-necrosis that were 
produced by plants becoming infected with leaf roll in 1919. This 
difference between lots in the inheritability of net-necrosis, apparently 
varietal, might, however, seem to be due possibly to a difference in the 
weights of the tubers harvested. This question is considered, for the 
sublots just previously mentioned, in Table IX. It is seen in Table IX 
that by far the greater number of tubers in all lots were small. Therefore 
the tendency to inherit net-necrosis was varietal rather than due to any 
tuber weight. 
Table IX .—Relation between tuber weight and net-necrosis at the time of planting in 
sublots selected for net-necrosis a year previously 
The effect of recency of infection is revealed in Table VIII in lot V-148. 
No net-necrosis was shown by the 1920 generation of the sublots selected 
in 1919 on account of the presence of net-necrosis or of leafroll, while 
the second generation of the sublot selected in 1919 as healthy hills next 
in the row to leafroll hills contained many net-necrosis tubers of which 
about three-fourths were affected severely (PI. 12, A). Apparently in 
this stock and variety, net-necrosis was dependent upon leafroll inocu¬ 
lation that occurred not earlier than during the preceding season. The 
possibility of the differences between sublots 2, 3, and 4 of lot V-148 
being due also to a difference in tuber weight is considered in Table X. 
