12 
Journal of Agricultural Research 
Vol. XIV, No. i 
plants in a field cage was pricked, and the juice from the blighted plants 
then sprayed on them with an atomizer. The wet leaves were again 
pricked with a flamed needle to insure the entrance of the virus into the 
tissues. An adjoining row of plants in the same cage was pricked with a 
flamed needle to serve as controls. Sixty-two days after inoculation 
blighted plants were observed in row i, while the row of control plants 
appeared healthy. 
Eighty-nine days after inoculation a mottled leaf was removed from a 
blighted plant in row i, and six plants in one pot in the greenhouse were 
inoculated with it by mashing the blighted tissues into the healthy leaves 
of the seedlings. Several pots of plants similar to the above were pricked 
with a flamed needle to serve as controls. Thirty-one days after inocu¬ 
lation the six plants were in the advanced stages of blight, but the con¬ 
trol plants remained healthy. These results indicate that the disease is 
due to a specific virus which is capable of producing the characteristic 
symptoms of blight both in the greenhouse and the field plants. 
One typical blighted plant from a large area was selected for inoculation 
purposes. This plant was mashed, and the juice strained through a 
cloth and used to inoculate one large potted plant in the greenhouse by 
needle pricks. A similar plant in another pot was pricked with a flamed 
needle and served as a control. Thirty days later the inoculated plant 
had developed typical symptoms of blight, while the control plant 
remained healthy. Nine days later individuals of R . persicae , which 
were known to be free from infection were placed on the diseased plant. 
Twenty-five days later aphids were removed from the above plant and 
placed on leaves of three large spinach plants growing in a field cage. 
Similar plants in the same field cage were used as controls. Twenty-one 
days later the control plants appeared healthy, but the three inoculated 
plants had developed typical symptoms of blight. These results indicate 
that the plants in the large area had typical spinach-blight, and that the 
virus from these plants produced the disease in greenhouse plants; 
further, that when aphids free from infection were allowed to feed on 
blighted greenhouse plants they were able to transfer the infectious 
entity to plants in field cages. 
INOCULATIONS WITH A WATER SUSPENSION OF VIRUS FROM BLIGHTED 
PLANTS 
A water suspension of blighted plants was made by mashing the 
mottled leaves in tap water. This suspension was strained through a 
cloth into an atomizer. With a flamed needle a row of plants in a field 
cage were pricked, and then sprayed with the contents of the atomizer. 
The wet leaves were again pricked with a flamed needle to insure the 
virus entering the tissues. Another row of plants in the same cage was 
pricked with a flamed needle and served as a control. Twenty days 
