Oct. 29.1917 
Fungus Fairy Rings 
231 
By gradual extension the mycelium develops another stimulated zone 
outside, and this in turn withers. In this way the dead zone is gradually 
increased on the outer edge. As the mycelium under this area becomes 
older it gradually dies out. Water penetration then becomes more nor¬ 
mal and the ample supply of available nitrogenous material produces 
the inner stimulated zone. 
The effect of rings of this type on cultivated plants is about the same 
as on the native plant cover. During a wet year the relative stimulation 
and depression of growth of the different areas is shown in the bisect 
(fig. 14; see also PI. 21). The wheat just beyond the mass of mycelium 
showed a slight stimulation as compared with that entirely outside the 
ring. Over the area of dense mycelium the plants ripened prematurely 
and did not produce as much straw as in the normal crop. The grain pro¬ 
duction was very low. Back of the dense area of mycelium the fungus 
filaments were evident only at greater depths in the soil, and here the 
greatest stimulation of the wheat crop occurred. The results of crop¬ 
pings made at this time are shown in Table XXII. 
Table XXII. — Yield of wheat per square meter in a ring of Agaricus tabularis 
Item. 
Inside (i). 
Bare zone 
(3). 
Outside (5). 
Ratio 3:5. 
During a wet year, Akron, Colo., Aug. 12, 
i 9 *S' 
Wheat ring— 
Number of heads. 
Height..cm,. 
Total dry matter.gm.. 
Grain.gm.. 
uring a dry year, Akron, Colo., July 6,1916: 
Wheat ring 8— 
Total dry matter.gm.. 
Wheat ring 9— 
Number of heads. 
Height.cm.. 
Total dry matter.gm.. 
Wheat ring 10— 
Number of heads. 
Height.cm.. 
Total dry matter.gm.. 
150 
50 
156 
54 
35 
57 
108 
93 
401 
63 
0 
30 
30 
34 
o 
o 
o 
190 
57 
210 
44 
500 
80 
137 
46 
108 
277 
12 
57 
53 
260 
13 
160 
50 
132 
In the same table the effect of the fairy ring on a wheat crop during 
a dry year is shown (PI. 22). The zone just above the densest area of 
mycelium (bare zone 3) was then practically free of plant growth. The 
results in the table indicate clearly the harmful effect of this fungus on 
the crop during normal or dry seasons. Only in the case of ring 9 was 
any wheat produced in the bare zone, and the yield there was partly due 
to the width of the zone (only about 1 meter' and to the slight extension 
of the cropping into the adjacent zones. 
