HELIOTROPISM OF ASCI IN DISCOMYCETES 267 



the coarse one, each ascus bends toward the source of light and thus 

 causes its free end to become directed toward the source of light. 



The coarse and fine heliotropic adjustments which have just been 

 described take place not only in Aleuria re-panda but, as I have 

 observed, in other stipitate Discomycetes when grown in unilateral 

 light ; and they are analogous to the coarse and fine geotropic 



Fig. 127. — Aleuria repanda. Heliotropism of fruit-bodie3. The fruit- 

 bodies were growing on an old jute hearth-rug in a garden tool-shed 

 and, during their development, were illuminated solely by light com- 

 ing through a hole in the door. The stipes, which were positively 

 heliotropic, have turned toward the source of Hght and have thus 

 caused the upper hymenial surfaces of the cups to face the light. 

 Photographed at Tanworth-in-Arden, England, by Jessie S. Bayliss 

 Elliott. About one-lialf the natural size. 



adjustments which take place respectively in the stipe and gills of 

 many agarics, e.g. Psalliota campestris.^ In both the Discomycetes 

 and the Agaricaceae, by means of these adjustments, the fungus 

 guns (asci and basidia respectively) come to rest in positions in 

 which they point toward open spaces, from which spaces the pro- 

 jectiles (ascospores and basidiospores), immediately or shortly after 

 their discharge, can be readily carried off by the wind. 



1 These Researches, Vol. T, 1909, p. 56. 



