PLATE 6 
A. —Rootrot spot, approximately 7 meters in diameter, in an alfalfa field, Sep tern - 
ber 18, 1921. 
B. —The same spot June 18, 1922, at the beginning of seasonal activity, approxi¬ 
mately 11 meters in diameter. 
C. —The same spot July 6, 1922, at the point of conjunction with another infected 
spot. . 
D. —Rootrot circle 18 meters in diameter in alfalfa field, Sacaton, Anz., 1923. 
Conidial mats several days old are shown near the periphery, and the zone of active 
disease has advanced beyond them. A whitewash solution was applied to the mats 
to facilitate photographing. The white stakes indicate the furthermost margin of 
active disease the previous year. 
