COPRINUS ATRAMENTARIUS 



289 



that, whenever owing to saturation of the air with water-vapour 

 evaporation was brought to a standstill, a cystidium on breaking 

 down would form a large drop which would tend to spread over 

 neighbouring basidia and prevent their spores from being liberated. 



If c. d e J g (t if c d, 



o 



Fig. 123. Coprinus atramentarius. Theautodigestionof sixcystidia. 

 a, in each drawing, is a fully turgid cystidium just before the 

 beginning of its autodigestion. b, c, d, etc., show stages in the 

 autodigestion of each cystidium. The cystidia were observed 

 stretching across the interlamellar spaces near the autodigesting 

 edges of the gills. A, B, C, and F, show cystidia which became 

 withdrawn to one of the gills. D and E show cystidia which, 

 after becoming more and more slender, snapped into two parts : 

 one part became withdrawn to one gill, and the other to the 

 other gill. C shows the autodigestion of a cystidium which has 

 been separated, whilst still turgid, from one of the gills with 

 which it was originally in contact by its rounded apical end. 

 F shows the autodigestion of a cystidium which had been 

 separated, whilst still turgid, from the gill in which it had 

 originated. Its free pointed basal end is shown in a. Magni- 

 fication, 80. 



As if to diminish the chance of the cystidial fluid interfering with 

 the spores after its liberation, there is a clear spore-free zone of 

 hymenium immediately around each cystidium (Figs. 117 and 120, 

 pp. 276 and 281). 



The disappearance of the cystidia from the gills is so well timed 

 that it seems likely that it is a regulated process. Whence comes 

 the stimulus which acts upon the protoplasm of a cystidium and thus 

 initiates its autodigestion ? Possibly, when a basidium is dis- 

 charging its spores, it sends out a stimulus in all directions which, 



VOL. III. tr 



