266 RESEARCHES ON FUNGI 



spaces are traversed by numerous fine cystidia which stretch between 

 and separate adjacent gills. These cystidia can be seen in the 

 field with the naked eye or with a pocket lens. The gills remain 

 connected with one another by the cystidial bridges during auto- 

 digestion, even when their upper ends have become entirely free 

 from the stipe. They are destroyed gradually from below upwards 

 by autodigestion, the destruction being just preceded by the 

 liberation of the spores. The spore-discharge period usually lasts 

 from 24 to 48 hours. The spores are oval, 10 X 5-5 /*, and deep 

 brown when seen in water under the microscope. The spore- 

 deposit on white paper is not intensely black as it is in Coprinus 

 comatus, C. sterquilinus, and C. niveus, but very dark brown. The 

 stipe, when fully elongated, varies in length from 2 to 6 inches ; 

 and it gradually increases in length as the pileus opens out and the 

 spores are shed. It is 3 to 8 lines thick at the base, tapers slightly 

 upwards, and expands again just beneath the pileus-flesh (Figs. 118 

 and 119, pp. 278 and 280). It is white, hollow, often fistulose 

 (Fig. 113, p. 269), fibrillose, rather brittle, and at its base there is 

 often a prominent encircling ridge reminding one of a volva and 

 marking the place where the unexpanded pileus was in contact with 

 the stipe (Figs. 109 and 110, pp. 264 and 265). 



The Geotropism of the Stipe. — Just before and during pilear 

 expansion the upper part of the stipe of Coprinus atramentarius, 

 like the upper part of the stipe in all other Coprini, is very sensitive 

 to the stimulus of gravity. If, during this period, the axis of the 

 stipe just beneath the pileus is not in a vertical position but is set 

 obliquely thereto, the lower side of the stipe, in response to the 

 stimulus of gravity, grows faster than the upper side, with the result 

 that the stipe curves upwards until, as shown in Fig. 111. its axis, 

 just beneath the pileus, is exactly vertical. Under natural conditions 

 in the open, the base of the stipe is always fixed in the ground, while 

 the apex, covered with the pileus, is free to move through the air; 

 and these conditions of fixation, coupled with the geotropic sensitive- 

 ness of the stipe, are sufficient to secure that the pileus, before 

 beginning to shed its spores, shall be brought into its normal upright 

 position. 



An experiment in which the normal conditions of fixation of the 



