4 BULLETIN 879, U. S. DEPARTMENT OF AGRICULTURE. 
the losses from mosaic, many growers, especially those in certain 
sections of the Middle West, have ceased to grow cucumbers, despite 
increased prices (PL I, G). 
In the case of forcing cucumbers, growers occasionally lose an 
entire crop, because, in addition to the reduced yield and deformed 
fruit, mosaic often causes the sudden wilting and death of the plants 
under glass. An additional factor in the loss occasioned by mosaic 
is the fact that affected table stock sells for about one-fourth the 
price obtained for sound fruits, owing entirely to the effect on their 
appearance. 
Of the other cultivated cucurbits squash and muskmelon seem 
most susceptible to the mosaic, but neither of these plants is injured 
as severely as the cucumber. The muskmelon vines are stunted 
and bear only a few fruits, which are inferior in quality but only 
occasionally show mosaic symptoms. Squashes are similarly affected 
and in addition sometimes have warty and deformed fruits, the 
Summer Crookneck variety being most often and most severely 
attacked. The disease is less common and of minor importance on 
the pumpkins, gourds, and ornamental cucurbits, which are of less 
commercial value. 
CUCURBIT HOSTS. 
Most of the species of the family Cucurbitacese appear to be sus- 
ceptible to mosaic. Field observations have proved that most 
cultivated species are commonly affected, and that the disease also 
occurs on wild species. The host range has been further extended 
by cross-inoculation experiments which included most genera and 
species of cucurbits found in this country and many varieties of 
the commoner cultivated species. 
Most of the field inoculation tests were made during 1916 and 
1917. All inoculated plants were kept under insect-proof cages, 
and reciprocal inoculations were made in most cases. The various 
species were usually inoculated in stems or leaves with the expressed 
juices of mosaic cucurnb.er plants, but many successful inoculations 
were made between other species, leaving no doubt that the disease 
is identical on the various cucurbit hosts. From 10 to 50 successful 
inoculations have b^en made with all the species noted below. 
In the case of cucumber, Gucumis sativus L., 15 varieties were 
inoculated successfully, and all seemed equally susceptible. Mosaic 
was also produced on the West Indian gherkin, G anguria L., on a 
closely related variety, G grossulariaeformis Hort., and on G. metul- 
liferus Mey. 
Inoculations on 11 varieties of muskmelon, Gucumis melo L., 
have all produced the disease, including the pomegranate melon, 
G. melo var. dudaim Naudin. Seven varieties of squash and four 
varieties of pumpkin, Gucurbita pepo L., G moschata Duchesne, 
and G. maxima Duchesne, have also been infected. 
