50 
GERTRUDE E. DOUGLAS 
for Other exogenous forms. Except for the fact that these gills 
develop on the exposed under surface of the pileus and not within 
a gill cavity, their method of origin is the same as that of the endoge- 
nous forms of the Agaricus type recently studied (i, 2, 3, 4, 5, 6, 7, 8, 
15, 20, 21). 
In conclusion I wish to express my sincere appreciation to Professor 
Atkinson for his unfailing interest and helpfulness in the preparation 
of this paper. 
Department of Botany, 
Cornell University 
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