Oct. 29, 1917 
Fungus Fairy Rings 
217 
mated yearly advance of A. tabularis. The age of the largest rings, 
which are 200 meters in diameter (PI. 24, B), would be approximately 
420 years. 
DISTRIBUTION OF THE MYCELIUM IN THE SOIL 
The distribution of the mycelium in the soil can not easily be deter¬ 
mined, except for Agaricus tabularis . On the high plains the mycelium 
-seldom penetrates deeper than the superficial soil layer, which is dark in 
color, owing to the presence of organic matter. In most cases the lower 
tabularis ring. 
limit of penetration was reached near the inside of the area when the old 
mycelium had penetrated to a depth of from 5 to 10 cm. below the level 
of the young mycelium at the front edge of the fungus development. 
In no case have the writers found the mycelium nearer to the surface 
than about 8 cm. This is probably due to the extremely dry con¬ 
dition of the surface soil during a large part of the year. Wollaston 
(1807), Molliard (1910, fig. 1), and Munch (1914) found the mycelium 
extending to the surface of the soil. This would be the case where the 
surface of the soil remained moist for a considerable time. In figures 4 
and 13 and in Plates 14, C 15, and 17 the distribution of the mycelium of 
Agaricus tabularis is shown. 
