PLATE 20 
Agaricus tabulans: 
A ring caused by A . tabularis and distinguished by a uniform growth of Plantago 
purshii. This plant is almost as abundant outside of the ring as inside, but outside 
it is very small and therefore not as noticeable. This is a relatively small ring, and 
the stimulation extends to the center. Akron, Colo., June 14, 1915. 
