COPRINUS STERQUILINUS 



185 



the cell-sap of all the cells of the gills, including the basidia and 

 the paraphyses. Its formation precedes the development of the 

 black pigment of the spore-walls. A similar formation of a red 

 pigment in the cell-sap of 



'1 



4 



all the cells of the gills 

 occurs in Coprinus comatus. 

 In that species, as one may 

 readily observe, the gills 

 turn pink from below up- 

 wards : the upward-moving 

 pink zone is followed by an 

 upward-moving blackening 

 zone, the latter owing its 

 origin to the pigmentation 

 of the spores. Under moist 

 conditions, when the stipe 

 of Cojjrinus sterquilinus has 

 attained a length of about 

 10 cm., several drops of the 

 red pigment are excreted 

 from the sides of the pileus, 

 as shown in Fig. 74. The 

 pileus, as it continues to 

 elongate, becomes dull red 

 and finally black. The 

 change in colour to black 

 is chiefly due to the fact 

 that a black pigment is 

 developed in the walls of 

 the spores, but is in part due to the fact that the red cell-sap 

 gradually changes to a dull brown. At the stage shown in Fig. 77 

 (p. 188) the pileus is so dark that it may be described as 

 black. In its final stages of development, when spore-discharge is 

 well advanced and the process of autodigestion has made consider- 

 able progress, tlie pileus is very black indeed (Fig. 98, p. 234). 



As the stipe elongates, the pileus, which is at first barrel-shaped, 

 becomes conico-cylindrical. During expansion, it first becomes 



Fig. 74. — Coprinus sterquilinus. A fruit- 

 body excreting red drops of fluid from 

 its pileus. Just removed from a horse- 

 dung culture covered by a bell-jar. 

 Natural size. 



