204 RESEARCHES ON FUNGI 



of hymenium as is represented in Fig. 84, C (p. 199). We may 

 therefore conclude that the introduction of the phenomenon of 

 basidial dimorphism into the structure of the hymenium is a 

 distinct factor in fruit-body efficiency : it allows more spores to be 

 produced on each gill than would otherwise be possible. ^ 



We shall now discuss the manner in which the hymenium 

 develops. This matter is -not only interesting in itself, but appears 

 to throw light upon the origin of the Coprinus Type of organisa- 

 tion from the Non-Coprinus Type as represented by Panaeolus 

 carnpanulatus. 



The gills of Coprinus sterquilinus change their colour in accord- 

 ance with the rule which is common for all species of the genus 

 Coprinus : they become blackened from below upwards (Fig. 97, 

 B, C, D, p. 232), This blackening is an expression of the fact that 

 the hymenium on each gill is subjected to a wave of development 

 which progresses upwards in a zonewise manner. The first basidia 

 to begin to develop spores are those which are situated along the 

 bottom of each gill, and the last basidia to begin to develop spores 

 are those which are situated at the top of each gill ; and, since 

 the basidia all take about the same number of hours to develop 

 and ripen their spores, we find that the first basidia to ripen their 

 spores are those which are situated along the bottom of each gill 

 and that the last basidia to ripen their spores are those which are 

 situated at the top of each gill. In other words : on every gill, 

 the spores begin their development and attain maturity in suc- 

 cession from below upwards. As the spores ripen, a black pigment 

 is developed in their walls, and it is this black pigment which 

 is chiefly responsible for the blackening of the gills from below 

 upwards in the course of their development. ^ 



Some hours before the stipe begins to elongate rapidly, the gills 

 v/ithin the barrel-shaped pileus are not yet fully extended and are 

 still perfectly white (Fig. 97, A, p. 232) ; but the hymenium covering 



^ For a still more detailed analysis of the phenomenon of dimorphism, the reader 

 is referred to the previous Chapter on Coprinus comatus, pp. 152-155. 



2 The red cell-sap, which is developed in all the cells of each gill and which 

 gradually turns dull brown, is also a factor, although relatively a minor one, in the 

 darkening of the gills from below upwards. This matter was fully dealt with in 

 the preceding Section, pp. 185, 187. 



