GASTROMYCETES. 7 



special arrangement for dehiscence or opening, but has to 

 decay before the spores are liberated. In species that 

 become raised above ground during their development the 

 peridium is usually differentiated into two or more layers, 

 as, for instance, in the species of Lycoperdon, where the outer 

 layer is usually resolved into warts or spines, the inner 

 layer remaining continuous, or in Geaster, where the number 

 of layers is greater, an outer portion (exoperidium) eventually 

 splitting from the apex into a variable number of pointed 

 portions, the inner, as in Lycoperdon, remaining intact and 

 dehiscing by a more or less definite aperture at the apex. 

 The entire contents of the closed peridium are collectively 

 known as the gleba, which in the immature stage, before any 

 disintegration has taken place, consists of thin plates of tissue 

 continuous with the inside of the peridium and anastomosing 

 at numerous points, thus forming an irregular labyrinthi- 

 form or cavernous structure consisting of variously- shaped 

 cavities bounded by thin plates, which are in every respect, 

 except that of arrangement, identical with the gills of 

 Agarics, and consequently bear the basidia on their free 

 surfaces, which is equivalent to saying that the walls of the 

 cavities are covered with basidia bearing spores and forming 

 the hymenium. 



The central portion of these plates consists of hyphae 

 running more or less parallel with the two surfaces and 

 constituting the trama, lateral branches of which bend 

 outwards on both sides and bear the basidia. In addition 

 to the basidia, certain tramal hyphae give origin in many 

 species to elongated, thick- walled, simple or branched hyphae 

 which collectively form the capillitium or dense mass of 

 threads mixed with the mature spores in Lycoperdon, Geaster, 

 &c., and which, in its most highly-evolved phase acts as a 

 dispersive organ. In many genera, as Bovista, Lycoperdon, 

 &c., after the spores are formed the basidia, along with the 

 tramal plates, deliquesce and totally disappear, becoming 

 partly resolved into water that saturates the gleba of im- 

 mature puff-balls ; finally, this moisture disappears, the 

 spores become mature and form a dusty mass, mixed with 

 the capillitium threads. 



In the species of Cyathus and Nidularia the tramal plates 

 do not deliquesce at maturity, but split along a central line, 



