July i, 1925 Overwintering and Dissemination of Cucurbit Mosaic 
9 
Table I .—Results of trials with seed from mosaic and healthy plants of 
Micrampelis lobata 
Date of planting 
Num¬ 
ber 
of 
plants 
Condition of plants used 
as source of seed 
Num¬ 
ber of 
mosaic 
plants 
Per 
cent of 
mosaic 
plants 
Date 
observed 
Apr. 9,1919_ _ _ . 
110 
Mosaic._____ . 
13 
11 
Apr. 22,1919 
May 25,1919 
Apr. 26,1920 
May 20,1920 
May 19,1920 
June 8,1920 
Mar. 20,1921 
Apr. 18,1921 
Mar. 29,1922 
Apr. 5, 1919_ 
200 
Healthy (control). 
0 
0 
Apr. 12, 1920_ 
174 
Mosaic.__ 
10 
5 
Apr. 15', 1920_ 
219 
Healthy (control). 
0 
0 
May 10,1920_ 
211 
Mosaic.. ... 
21 
10 
May 15; 1920_ 
150 
Healthy (control). 
0 
0 
Mar. 10, 1921_ 
169 
Mosaic. .. 
22 
13 
Do.'_ 
150 
Healthy (control)_ _ 
0 
0 
Mar. 12,1922_ 
253 
Mosaic____ _ 
18 
7 
Mar. 10, 1922__ 
387 
Healthy (control)__ . . . 
0 
0 
Apr. 21,1922 
Average infection from seed from mosaic plants, 9 per cent. 
of the disease during this early period remained healthy throughout 
the experiment. This fact, together with the absence of mosaic on 
the control plants, seems to eliminate the possibility of infection 
from sources other than the seed. 
Inoculations were made from a majority of the plants supposed to 
be mosaic to healthy cucumber plants and the actual presence of the 
disease was thus established. The early symptoms of mosaic on 
infected Micrampelis seedlings are often misleading, as they may 
frequently be confused with other abnormalities of growth which 
occasionally appear on plants of the wild cucumber. The first leaf 
of mosaic plants is usually wrinkled and somewhat mottled in 
appearance, but often the mottling is not sharply defined. Infected 
seedlings are always somewhat dwarfed, however, and the cotyledons 
are considerably smaller than those of healthy plants. The suc¬ 
ceeding leaves in most cases are definitely mottled and have the 
curled and savoyed appearance which characterizes the mosaic 
disease on most cucurbits (pi. 1, B). In some instances, however, the 
leaves are a normal green, with the exception of minute yellow areas 
scattered irregularly over the surface. Such plants are somewhat 
dwarfed, but the leaves are regular in outline and show none of the 
wrinkling and curling mentioned above. In the field, where the 
plants have been attacked by insects or exposed to other unfavorable 
conditions, they often develop a similar appearance which is easily 
confused with mosaic. * The later growth of mosaic seedlings, how¬ 
ever, always shows typical mosaic symptoms. 
The consistent appearance of mosaic on a portion of the seedlings 
grown from seeds of mosaic Micrampelis, together with the fact that 
the disease did not develop on the remaining plants during their 
later growth or on plants grown from healthy seed, seems to warrant 
the conclusion that the seed of the wild cucumber acts as a carrier 
of the disease. This has been further substantiated by the field 
observations described below. 
Development op Mosaic on Wild Cucumber Seedlings in the Field 
Before definite evidence of seed transmission of Micrampelis mosaic 
was obtained it was already known that the disease was of common 
occurrence on this host (8) and that mosaic plants could be found 
in the spring before cultivated cucurbits had been planted. Since 
59836—25f—2 
