COPRINUS ATRAMENTARIUS 285 



spores which failed to be discharged and which have been dragged 

 down on to the hymenium by the collapse of their basidia are shown 

 at j and k in Fig. 120 (p. 281). These two spores are about to be added 

 to the other waste spores which, owing to the upward movement of 

 the liquid film at the gill-edge, have become crowded together. 

 An examination of the spores held by the liquid film reveals that, 

 while some of them are of very small size (o) and others of full size 

 but imperfectly pigmented (n), the majority have a normal appear- 

 ance (m). One and all appear to resist the action of the enzymes 

 which, we may suppose, are present in the fluid at the gill-edge. 



The Function and Fate of the Cystidia during Spore-discharge. — 

 The cystidia are so large and numerous that, if they persisted until 

 the zone of autodigestion reached them, they would form a serious 

 hindrance to the escape of the spores from between the gills : 

 they would block up so large a proportion of the interlamellar 

 spaces that a great many spores would settle upon them, adhere to 

 them, and thus never reach the outer air. But a beautiful arrange- 

 ment is provided which makes all this impossible : the cystidia do 

 not undergo autodigestion at the same time as the basidia and para- 

 physes in their immediate vicinity but a short time previously thereto ; 

 they destroy themselves in succession from below upwards on each 

 gill, and each one disappears a few minutes before the basidia in its 

 immediate neighbourhood come to be involved in the upwardly 

 progressing zone of sjjore-discharge. 



The semi-diagrammatic drawing, Fig. 122, shows what was made 

 out by a study of gill-sections cut from blocks of living gills with a 

 hand-razor. The drawing is supposed to represent a section cut 

 in a vertical plane through three gills. From above downwards, 

 the following seven zones can be distinguished : 



(rt) a zone with less ripe spores in which the cystidia are fully 

 turgid and are functioning as distance-pieces to keep the 

 gills apart, 



{b) a zone with riper spores in which the cystidia are disajjpearing 

 owing to autodigestion, 



(c) a zone of ripe spores from which the cystidia have already 

 disappeared, 



{d) a zone of spore-discharge, 



