THE COPRINUS TYPE OF FRUIT-BODY 197 



An unripe pileus which has attained its full length is more or 

 less barrel-shaped (Plate II., Fig. 7 ; Plate IV., Figs. 21 and 22, to 

 the right). The gills are white in colour, closely packed together, 

 and with very few exceptions equal in length. 



Upon beginning to open out, the pileus alters its form from 

 that of a barrel to that of a bell (Plate IV., Figs. 21 and 22; 

 Plate I., Fig. 1). It breaks away from the stipe below and leaves 

 the latter encircled with an annulus. Whilst the gills are moving 

 radially outwards from the stipe, they become slightly separated 

 from one another. The rim of the bell-shaped pileus now turns 

 slightly outwards (Plate I., Fig. 1). This results in a further 

 separation of the . lower ends of the gills, so that the spaces which 

 have thus arisen between them are similar to those between the 

 gills throughout their' whole length in the case of a Mushroom 

 (cf. Plate IV., Figs. 23 and 25). Except at their lower ends, 

 adjacent gills at this stage in development are united by inter- 

 locking cystidia along their margin, and are just as closely packed 

 as they were when the fruit-body was barrel-shaped. The separa- 

 tion of the lower ends of the gills is accompanied by the beginning 

 of the process of " deliquescence." 



Whilst the pileus is changing from the barrel to the bell form 

 and is separating the lower ends of its gills, the basidia are rapidly 

 developing their spores. As these ripen they turn pinkish and 

 finally black. Just before "deliquescence" begins, it can clearly 

 be made out that the spores ripen on the gills from below up- 

 wards. The lower parts of the gills blacken first (Plate I., Fig. 1). 

 The black zone passes into a pink zone higher up, and this in its 

 turn, toward the top of the pileus, gradually shades into white. 



Whenever a gill has become black, a small piece of its surface, 

 when seen in face view with the microscope, has the appearance 

 shown in Plate III., Fig. 15. The pattern presented to the eye 

 is very regular and pleasing. Each basidium bears four black 

 spores, and is separated from adjacent basidia by paraphyses. 

 The four spores of a basidium are so attached to the sterigmata 

 that they are separated from one another as much as possible. 

 They are thus prevented from touching, and consequently from 

 adhering to, one another both during development and discharge. 



