258 BOTANICAL GAZETTE [APRIL 
and with the lamellae radiating in all directions from the center 
(jig. 3): 
In the highly differentiated Coprinus no formative influence of 
gravity could be observed. It is evident that here the organization 
of the fruit-body depends largely upon internal causes or upon stimuli 
not yet sufficiently analyzed. 
In conclusion, it follows from the foregoing observations, on three 
widely separated forms of the Basidiomycetes, that although gravity 
has no apparent effect on the organization of the hymenophore,? it 
has a marked influence on determining the configuration of the fruit- 
body of some forms. This effect is most marked in the more primi- 
tive forms, which are thereby shown to be the more plastic. In the 
more highly differentiated forms this effect of gravity disappears. 
The effect of gravity on the configuration of Polystictus is due partly 
to the positive geotropic property of the hymenophore, and partly to 
the fact that the differentiation of the fruit-body into sterile and fertile 
tissue depends on the action of gravity. When this force is removed, 
the fruit-body assumes the resupinate or a pulvinate form char- 
acteristic of the simplest types of the Basidiomycetes. 
THE UNIVERSITY OF CHICAGO 
9 This term applies only to the parts immediately bearing the hymenium, 7. ¢., 
the gills, spines, etc., and not, as it is sometimes used, to the whole fruit-body. 
