o 
Journal of Agricultural Research 
Vol. XXXI, No. 1 
type used in the earlier experiments (8) were put down at the time 
the seed was planted and 10 more were placed over other plants on 
June 29. Care was taken to see that these plants were free from 
insects before caging and the cages were lifted on]y once thereafter, 
on July 1, in order to thin the plants. The 20 cages, covering a total 
of 120 plants, were removed on August 13, when the vines had become 
so large so as to begin to tear the cloth. The caged plants were 
examined and all were found to be free from mosaic. On the same 
date approximately 95 per cent of the 2,000 uncaged plants in the 
plat were mosaic-diseased. 
EXPERIMENTS OF 1920 
A similar experiment was conducted in 1920, using the same plat 
but planting a different variety of cucumbers in each row. The cages 
were not put down until later in the season, however, owfing to the 
necessity of replanting most of the field on June 29. Eighteen 
cages were, used, seven of which were put down on July 1 and 
the remaining eleven on July 9, when the plants were just above 
ground. Many of the caged plants showed injury from the striped 
cucumber beetle, but great care was taken to exclude these insects 
from the cages. 
On August 2 some of the cages were lifted and the plants thinned 
where necessary, reducing their number from 184 to 108. At this 
time approximately 9 per cent of the uncaged plants in the plat were 
mosaic-diseased. No mosaic was found on any of the caged plants, 
although the cages put down on July 9 contained a number of plants 
affected with bacterial wilt. On August 16 the cages were finally 
lifted and the plants carefully examined for signs of mosaic infection. 
They proved healthy in all cases, while only 14 mosaic-free plants 
were found in a total of 2,100 plants left uncaged in the plat. 
These results, combined with those earlier reported ( 8 ), have 
shown that plants protected from insects may be grown year after 
year on the same soil and remain absolutely free from mosaic in¬ 
fection in all cases, although nearly all of the uncaged plants may 
become infected each season. In view of these results, it seems defi¬ 
nitely established that the soil is not an agency in overwintering 
cucurbit mosaic. 
TRIALS OFISEED FROM MOSAIC PLANTS OF THE CULTIVATED 
CUCURBITS 
CUCUMBER 
Trials made with seed from mosaic cucumber plants prior to 1919 
(6, 8) indicated that mosaic infection, through the seed of the culti¬ 
vated cucumber, occurred very rarely, if at all. Only one case of 
apparent seedling infection had occurred during trials of 10,500 
plants grown from seed from mosaic cucumber fruits, but the single 
case was so well substantiated that it assumed a possible importance, 
inasmuch as the disease is transmitted by insects so rapidly that a 
single mosaic plant may serve as a source of infection for all the 
fields in the vicinity. In order to obtain more conclusive results, 
therefore, the tests were continued both in the field and in the green¬ 
house. 
