Oct. 29, 1917 
Fungus Fairy Rings 
237 
while sufficient moisture remained in the soil to maintain the fungus 
and the grass roots in active condition. In order to test the effect of the 
mycelium on the native vegetation, the following experiment was con¬ 
ducted during the dry season in 1916. A strip about 6 meters long and 
3 meters wide was selected on the edge of a ring of Agaricus tabularis 
where the zones were well defined. This strip extended 1 meter out 
from the border line between the withered zone (4) and the bare zone (3), 
and 2 meters inside of this line over the inner stimulated zone (2), and 
into the inside (1). The water was poured on slowly to prevent run-off 
and to give all parts of the plot approximately the same amount. The 
watering here was begun on June 12 and continued during the next four 
days. An equivalent of 2 inches of rainfall was added to the plot. On 
June 28 the plot, in contrast to the dry sod, stood out sharply because of 
the tall growth and fresh green color of the vegetation. A trench cut 
across the area just after the irrigation (PI. 24, A) showed the soil to be only 
slightly moistened under the bare zone (3) and outer stimulated zone (4), 
but much moister under the inner stimulated zone (2). The upper 3 or 
4 inches in the bare and outer stimulated zone were quite moist. By 
July 24 the grass, which had grown up rapidly on the bare zone, had 
again become dormant, owing to drouth. The plot was accordingly 
irrigated a second time with an equivalent of 3 inches of rainfall. By 
August 14 (PI. 23, B) Grindelia squarrosa, Psoralea tenniflora, Malvastrum 
coccineum , Gutierrezia sarothrae , and Artemisia frigida were all much 
more vigorous here than in the natural sod. Culms of grama grass were 
10 to 12 inches high and abundant on the plot, but out in the normal sod, 
where the grass had fruited but rarely, they were only 4 to 6 inches high. 
The few remaining plants in this bare area had revived and spread until 
it required close examination to distinguish the various zones, although 
the grass was denser and somewhat taller in the outer stimulated zone 
(4) just outside of the bare zone (3). 
It seems evident from the behavior of the vegetation under irrigation 
that the fungus does not directly attack the grasses, nor does it injure 
them by producing harmful decomposition products. It does, however, 
bring about a condition of almost certain drouth, under which even the 
grama and buffalo grasses of the Great Plains die. 
ERADICATION OF FAIRY RINGS 
Fairy rings cause bare paths and spots, ununiform growth, and unequal 
color in lawns. Since the value of a lawn is entirely dependent upon 
the uniform appearance of the turf, the presence of even a small area in¬ 
fluenced by fairy rings destroys the effect of the whole. Usually these 
dead areas are reseeded, but no good effect can be secured in this way, 
since the fungus mycelium moves on into new grass, and the follow¬ 
ing year the appearance is as bad as before. In meadows the effect is 
similar to that on lawns, while in cultivated fields the rings may cause a 
