8 BULLETIN 879, U. S. DEPARTMENT OF AGRICULTURE. 
INOCULATIONS FROM MOSAIC PLANTS OP OTHER FAMILIES TO CUCUMBER. 
Attempts have also been made to transmit mosaic diseases found 
on plants outside the Cucurbitacese to the cucumber. A considerable 
number of inoculations have been made from tomato, tobacco, bean, 
and other plants having infectious mosaic diseases and also from 
plants which showed diseases of the mosaic type but whose infectious 
nature was not proved, such as pepper (Capsicum annuum L.), sumac 
(Rhus typhina L.), milkweed (Asclepias syriaca L.), red clover 
(Trifolium pratense L.), and others. Inoculations in most cases 
were made with the expressed juice of the mosaic plant in the manner 
already described. All the results of these inoculations have been 
negative, as shown in Table II and there is as yet no evidence that 
any of the diseases on the hosts tried are identical with the mosaic 
disease on the cucurbits. 
MOSAIC SYMPTOMS. 
The progress of the mosaic disease in the plant is characterized by 
distinct morphologic and physiologic changes, which are most marked 
in the leaves and fruits. These consist principally of an abnormal 
mosaic coloring, accompanied by certain malformations and dwarfing 
of growth. The symptoms vary somewhat according to the age of the 
plant and its vigor of growth at the time of infection, but the general 
characters are the same in all stages of growth. There is also a 
variation in the symptoms on the different species of Cucurbitaceas 
which are susceptible to the disease. The leaves of different species 
show many diverse forms of mosaic coloring, and the fruits may or 
may not be affected, although usually they show marked symptoms 
soon after the plant becomes diseased. The symptoms on the cu- 
cumber have been described in greater detail, as it is the most im- 
portant host and has been most closely studied, but the general 
characteristics wil] apply to all other hosts except for the variations 
mentioned later. 
PLANT SYMPTOMS. 
Sym.pto7hs on affected seedlings.— Seedling cucumbers are rarely 
affected with mosaic either in the field or in the greenhouse. The 
disease may appear on seedlings under certain conditions, however, 
as is shown by the fact that a very general and serious mosaic infec- 
tion occurred on the first true leaves of cucumber seedlings at Big 
Rapids, Mich., in the summer of 1918. The seed was planted late 
in August and when the plants came up the rest of the field was 
already rather badly infected with the disease. When such infection 
does occur, the first symptoms appear as a yellowing and wilting of 
the cotyledons, accompanied by a slight mottling of the young 
leaves. A sudden checking of growth soon follows and the later 
leaves remain small, wrinkled, and distorted and have a distinct 
