COPRINUS STERQUILINUS 221 



germ-tubes may take place. Were the spores of any wood- 

 destroying fungus as large as those of Coprinus sterquilinus, they 

 would be ill-suited as organs of dispersion for the species on 

 account of their relatively rapid rate of fall and tendency to reach 

 the ground quickly. 



According to Fa3^od, in the majority of Agarics having coloured 

 spores as well as in some having colourless spores {Lepiota procera), 

 the wall of the spore consists of an outer colourless exospore, which 

 previously had been overlooked, and an inner pigmented ejidospore} 

 Furthermore, Hansen * has demonstrated the presence of an outer 

 colourless layer for the spore-wall of Coprinus stercorarius. He 

 placed the spores in chlor-zinc iodine and observed that in a few 

 minutes the outer colourless spore-wall became much swollen, 

 whereas the inner pigmented wall remained unchanged ; and I 

 have repeated this experiment with the same result. The wall 

 of the spore of Coprinus sterquilinus, when the spore is mounted in 

 water, also appears to be double, i.e. to have a colourless exospore 

 and a pigmented endospore ; for, if a spore is exposed to view in 

 profile in such a way that its hilum projects freely on its flatter 

 dorsal side, one can readily perceive that, on its more rounded 

 ventral side, there is a colourless layer of wall-substance covering 

 the pigmented layer and somewhat resembling in form a median 

 section taken through a concavo-convex lens {vide three of the 

 five top spores in Fig. 92, p. 219).^ However, when one attempts 

 to trace this colourless layer all around the spore, a difficulty arises : 

 one perceives a thin white layer extending along the flatter dorsal 

 edge of the spore, but here there is the possibility that this layer 

 is apparent and not real ; for tiny air-bubbles the size of spores, 

 seen in water, also appear to be enveloped by a thin sharp white 

 layer, i.e. by a layer which, of course, is due to diffraction and 

 therefore insubstantial. The outer wall of a spore of Coprinus 



^ V. Fayod, " Prodrome d'une histoire naturelle des Agaricin^s," An7i. de sc. 

 nat., T. 9, 1889, p. 269. 



2 E. C. Hansen, " Biologische Untersuchungen iiber mist-bewohnende Pilze," 

 Bot. Zeit., 1897, pp. 111-132, Taf. II. 



^ The original photograph showed the colourless layer more clearly than does 

 its reproduction in Fig. 92. 



