408 
Journal of Agricultural Research 
Vol. XXVI, No. 9 
the spore mats frequently appeared at the mouths of holes in the ground 
(PI. i, B), and desiring to ascertain if the fruiting bodies advanced in a 
centrifugal manner with the spread of the disease, the writer made a 
circle of 50 holes with a one-inch soil tube on July 27, 1921, just 15 cm. 
outside the circle of dying plants, and not closer than 15 cm. to the 
nearest spore mats. Conditions continued favorable for the fruiting of 
the fungus and within 10 days spore mats had made their appearance, 
lining the mouths of 23 of the holes. 
On August 25,1921, a count was made of all the spore mats in an irregu¬ 
lar rootrot spot of approximately 500 square meters in area in an alfalfa 
field at the Cooperative Testing Station, Sacaton, Ariz. The surface 
and are drawn approximately to scale. 
area of each mat was measured and its location with reference to the 
perimeter of the spot was charted. Of the 98 mats charted 80 were 
within 60 cm. of the rim of recently wilted plants, and all but one of the 
other 18 were old powdered masses of a former crop. The total surface 
area occupied by the mats was 2.5 square meters. 
On September 6, 1922, a circular spot 10 meters in diameter in an 
alfalfa field on the Indian School farm at Sacaton was charted in the same 
manner. (See fig. 2 and pi. 2, A.) All of the 71 freshly formed spore 
bodies were within 40 cm. of the ring of recently wilted plants, and the 
total surface area occupied by the mats was 1.86 square meters. 
