COPRINUS ATRAMENTARIUS 



267 



stipe were reversed was made as follows. A fruit-body, like that 

 shown in Fig. 109 (p. 264), was removed from its substratum and 

 turned through a right angle so that the axis of the stipe and pileus 

 came to occupy a hori- 

 zontal position instead 

 of a vertical one. The 

 pileus, along with the 

 extreme apex of the 

 stipe, was then fixed 

 with pins so that it 

 could not move, while 

 the stipe-shaft was left 

 with its basal end freely 

 projecting into the air 

 in a horizontal direc- 

 tion. On the next day, 

 it was found that the 

 stipe had curved 

 through a right angle 

 in such a way that its 

 basal end was turned 

 up into the air in the 

 manner shown in Fig; 

 112. Just as usual, in 

 response to the direc- 

 tive stimulus of gravity, 

 the under side of the 

 stipe had grown faster 

 than the upper ; but 

 since, under the condi- 

 tions of the experiment, 

 the apex of the stipe had been fixed in position instead of the base, 

 of necessity the basal end of the stipe had been turned upwards into 

 the air. An analogous experiment was made by Francis Darwin ^ 



1 Francis Darwin, " On Geotropism and the Localization of the Sensitive 

 Region," Annals of Botany, vol. xiii, 1899, pp. 567-574, Plate XXIX. In Darwin's 

 experiments the root end of the plant, after being turned upwards into the air, was 



Fig. 1 12. — Coprimes atramentarius . Tlie fruit-body 

 was fixed by its pileus so that the axis of the 

 pileus and stipe was horizontal. In response 

 to a geotropic stimulus, the stipe turned its free 

 end up into the air, as here shown. Photo- 

 graphed at Winnipeg. Natural size. 



