PLATE 8 
A. —a, A pot of spinach seedlings inoculated with virus-bearing aphids collected 
from blighted plants in the field. All of the plants were infected with blight. Many 
had died at the time the photograph was taken. 6, A pot of healthy seedlings which 
served as controls. (Original.) 
B. —a, Healthy spinach seedlings used as a control, b , Spinach seedlings of the 
same age as the control, inoculated by needle pricks with the blight vims. (Original.) 
