Dec. i, 1923 
Habits of the Cotton Rootrot Fungus 
4 i 3 
following season, but may appear elsewhere. Some observations were 
made at Sacaton during the seasons 1920 to 1922 to determine if this 
was also a characteristic behavior in the case of a perennial host plant 
such as alfalfa. The infected spots in a 9-hectare alfalfa field adjoining 
the Experiment Station at Sacaton were measured and charted on Sep¬ 
tember 30, 1921, when the disease was approaching a state of quiescence. 
In the early part of the summer of 1922 these spots were observed closely, 
so as to note the points of renewed infection. The first dead plants 
were noticed on June 11, and in nearly every instance the first plant 
Fig. 3.—Location of initial points of infection in relation to formerly occupied area at the beginning of 
the seasonal activity of rootrot fungus. The same area as shown in Plate 4, A. The new centers and 
reestablished plants are shown as actually located in the field and are drawn to approximate scale. 
showing infection was located just outside the periphery of the previous 
season and not over 70 cm. from it (fig. 3). Almost simultaneously with 
the wilting of the first plant other plants located at various intervals 
outside the old periphery, but always at the same distance from the 
center of the old infected area, showed infection (pi. 4, A, fig.3). Each 
of these plants served as a center for the infection of the plants nearest 
to them, but the many small infected areas (appearing at the same 
distance from the old periphery) soon merged into a regular band com¬ 
pletely circumscribing the old area of the previous year (pi. 4, B). The 
