BASIDIA AND PARAPHYSES 7 



In the Coprini, the hymenium, when seen in face view, presents 

 to the eye a remarkably regular pattern (Plate III., Fig. 15). 

 The basidia, bearing black spores, are evenly spaced between the 

 paraphyses. Adjacent basidia, in a zone proceeding from below 

 upwards on each gill, ripen their spores simultaneously. Hence, 

 on any small portion of a gill, all the basidia are practically in 

 the same stage of development. It appears to be the chief 

 function of the paraphyses to act as spacing agents, so that by 

 their presence they prevent the spores belonging to adjacent 

 basidia from coming into contact. The large, unicellular cystidia 

 which are so prominent on the swollen edges of the gills in rnany 

 species, e.g. Coprinus conwtus, seem to be significant in that they 

 form suitable surfaces of contact where the gills touch one another 

 and the stipe. The swollen gill-margins serve to keep the gills 

 sufficiently separated from one another, during the development 

 of the basidia and spores (Plate I., Fig. 5; Plate III., Fig. 14). 

 If the gills were not kept apart, the spores of opposing gills would 

 touch one another, and, owing to their great adhesiveness, would 

 stick together. The proper spacing of the gills during develop- 

 ment, therefore, is essential in securing the efficiency of a fruit- 

 body as a spore-producing organ. 



Excluding the highly specialised Coprini, we find that in the 

 Agaricinea3 generally, as well as in the other groups of Hymeno- 

 mycetes, the basidia do not all ripen on any part of the hymenium 

 simultaneously. Adjacent basidia on the gill of a Mushroom, 

 in the hymenial tube of Polyporus squamosus, &e., are at any 

 one time in the most diverse stages of development (Plate I., 

 Fig. 3). A basidinm, bearing ripe spores, may thus have 

 adjacent to it one basidium which has shed its spores some 

 hours or days previously; a second which has spores in the most 

 rudimentary condition ; and, possibly, yet a third upon which not 

 even the sterigmata have appeared. Neighbouring basidia with 

 ripe spores are often very closely situated, but never near enough 

 to touch one another. To what extent this spacing is brought 

 about by the paraphyses, or by other basidia, is difficult to deter- 

 mine. Possibly, the fact that, in a Mushroom, adjacent basidia 

 ripen and shed their spores successively, instead of simultaneously, 



