July i, 1925 Overwintering and Dissemination of Cucurbit Mosaic 
55 
Observations have shown that another species of pigweed, Amaran- 
thus blitoides Wats., occasionally shows symptoms which have 
somewhat the appearance of a mosaic disease, but up to the present 
the writers have not been able to demonstrate that it is transmissible. 
Cross-Inoculation Experiments with Plants of other Genera 
In the course of the studies on the overwintering of cucurbit 
mosaic, a number of plants of various families have been found to 
show symptoms of what appear to be mosaic diseases. Symptoms 
of this type have been noted on a perennial species of Helianthus 
in a number of cases, but no infection has been produced on the 
cucumber from this host, nor has the disease been transmitted to 
healthy plants of the same species. Symptoms similar to those of 
mosaic have also been found on Arctium lappa L., Abutilon theo - 
phrasti Medic., Malva rotundifolia L., Oxybaphrs nyct r gineus 
(Michx.) Sweet, Ambrosia trifida L., Bidens vulgata Greene, and on 
species of Anemone, Xanthium, and wild Rubus. A limited number 
of inoculations have been made with all of these plants, but up to 
the present the writers have no evidence which indicates that these 
are transmissible mosaic diseases. These experiments are being 
continued, however, and it may be found that certain of these hosts 
are affected with mosaic. 
Relation of Annual Host Plants to the Overwintering and Dissemi¬ 
nation of Cucurbit Mosaic 
The annual host plants of cucurbit mosaic would not appear to 
be concerned in the overwintering of the disease unless the seed of 
such plants carries the disease from year to year. Experiments 
have been conducted with seed from annual plants outside the 
Cucurbitaceae which are known to be susceptible to cucurbit mosaic— 
pepper, martynia, pigweed, and cultivated Physalis. From 300 to 
700 seedlings have been grown from seed of mosaic plants of each 
of the above hosts, but there has been no evidence that the disease 
is transmitted through the seed. For this reason, it is felt that the 
perennial wild hosts are probably the only ones concerned in the 
overwintering of the disease, with the exception of the wild cucumber. 
The annual host plants of cucurbit mosaic may be of importance, 
however, as sources of infection to the cultivated cucurbits during 
the growing season. In the course of experiments on the control 
of cucurbit mosaic through the eradication of the perennial wild 
host plants, it has been found that the disease may be contracted by 
annuals from the perennials and carried on the annual plants during 
the summer after the perennial wild hosts have been destroyed. 
Field observations have shown this to be true in the case of Amman - 
thus retrojlexus and cultivated species of Physalis, and these host 
plants have apparently acted as sources of infection to adjacent 
cucurbits throughout the season. It is evident, therefore, that 
these annual hosts are of practical importance from the standpoint 
of the control of the disease. 
Relation of Wild Host Plants to the Control of Cucurbit Mosaic 
As cucurbit mosaic is so readily transmitted by insects in the 
field, it has proved difficult to check it after it once appears in the 
fields to any appreciable extent. For this reason, the most prac- 
