THE MOSAIC DISEASE OF CUCURBITS. 61 
The fact that the micrampelis plant is so common, coupled with 
the presence of occasional mosaic infection, made it seem possible 
that it might be a source of spring infection to cucumber. During 
1917 a close inspection was made of all plants which could be found 
in the western portion of Madison, Wis., and in the country adjoining 
the fields where the cucumber plats were located. A particularly large 
number of micrampelis plants were found in the sand pit already 
referred to near the main experimental field. On July 9 eight 
plants in two groups were found at this point, all of them showing 
typical mosaic symptoms. No mosaic was found on any other 
cucurbit host until at least 10 days later. 
Mr. I. C. Hoffman, working at Plymouth, Ind., found several wild 
micrampelis plants which showed s} T mptoms of mosaic as early as 
June 30. The plants in both cases were proved to be truly mosaic 
by successful inoculations on cucumber. 
No other cases were found prior to the appearance of the mosaic 
disease on the cultivated host in the spring of 1917, but during the 
summer 10 different centers of mosaic micrampelis were found in the 
vicinity of Madison at rather widely separated points. In the fall of 
1917 the disease was also reported by Mr. W. W. Gilbert as occurring 
at Big Rapids, Mich., and Brighton, Colo., and by Mr. I. C. Hoffman 
at Fort Collins, Colo. 
Observations were again made about Madison during the spring 
of 1918, particularly in localities where the disease had appeared on 
micrampelis in 1917. In two such locations the disease was again found 
on June 15. In one case 4 out of 18 plants were infected with mosaic 
and in the other case 6 out of 27 showed it. In all cases the plants 
were about 5 weeks old. Cultivated cucurbits were being planted at 
that time, and none of the adjacent gardens contained any cucurbits 
of other species. Several mosaic micrampelis vines were also found 
by Mr. W. W. Gilbert at Big Rapids, Mich., on June 23, 1918. These 
plants were being grown as ornamentals near a garden where the 
disease had been found the previous season on cucumbers. They 
were 4 to 6 feet tall when seen, while the cucumbers in near-by gar- 
dens were only a few inches high and in the adjacent fields few were 
up. A considerable number of striped beetles were observed feeding 
on the micrampelis vines. 
There is no doubt, therefore, that the disease occurs on wild plants 
some time before its appearance on cultivated hosts, since most 
cucumber fields had just been planted at the time the disease ap- 
peared on the micrampelis vines. The source of infection on the 
micrampelis plants in these cases was undetermined. To test the 
possibility of seed overwintering, about 150 plants were grown from 
seed collected in each of the Madison localities in 1917. The plants 
were grown in the greenhouse for six weeks during January and Feb- 
