18 
Journal of Agricultural Research 
Vol. XXXI, No. 1 
cucurbits. The actual importance of the wild cucumber as a source 
of primary infection to the cultivated hosts is dependent, however, 
on the numbers of mosaic Micrampelis plants which occur in a given 
locality and their location with respect to fields of cultivated cu¬ 
curbits. The factor of the distances over which insects carry the 
infection is, of course, equally important, but, for the present at 
least, it is assumed that this distance is approximately 400 to 500 
yards. In most localities the striped beetle is always present in 
considerable numbers, so the presence of an insect carrier is assured. 
Survey of 1919 
If the wild cucumber is actually an important factor in overwinter¬ 
ing mosaic, infected wild plants would be expected to occur in con¬ 
siderable numbers in districts where the mosaic disease is severe in 
the fields. Surveys of the past three years have shown that a dis¬ 
tinct correlation of this sort exists in Wisconsin and others of the 
Central States, although the surveys have been chiefly confined to 
Wisconsin. 
In these surveys all of the fields of cucumbers and other cucurbits 
in a given area were inspected for the presence of mosaic infection 
and an effort was made to locate as many groups of wild cucumber 
plants in the vicinity as possible. The occurrence of mosaic Micram¬ 
pelis plants in different localities and the corresponding occurrence 
of mosaic on other cucurbits is shown in Table VIII. Aside from a 
few localities, however, no attempt was made to locate all of the 
mosaic wild cucumber plants in a given area. While the presence 
of the disease was noted, no attempt was made to show the number 
of cucumber fields visited or the number of these fields which were 
mosaic, because in sections visited late in the season there was natu¬ 
rally a greater amount of mosaic present than in localities visited 
when the disease had first appeared, as it had had an opportunity to 
spread from field to field during the intervening period. Under these 
circumstances the wild cucumber as a source of infection bears only 
slight relation to the extent of mosaic in the field, because only the 
early infection can safely be attributed to this source. The average 
number of fields visited in all localities was approximately 12, and 
in localities where the disease occurred mosaic was present in about 
40 per cent of the fields. 
The results of these surveys emphasized the fact that the wild 
cucumber occurs abundantly throughout the Central States. In 
many localities large groups of these plants occur along streams and 
in other moist situations and are found in smaller numbers in low 
places along roads, railway embankments, fence hedgerows, and other 
similar spots. The distribution of the plant has been greatly in- , 
creased by the fact that it is often used as an ornamental, so that 
large numbers of wild cucumber plants are found about dwellings in 
most towns and villages. It is frequently found in neglected spots 
about farm buildings as a result of having been introduced as an 
ornamental, and a thorough survey in some localities has revealed 
many more plants than would be noted by a cursory inspection. 
