168 



BASIDIOMYCETES. 



spicuous as white patches on the bright red ground of the upper 

 surface of the pileus, and as a sheath at the base of the stalk (Fig. 

 178 r.). Another veil the velum partiale -a hyphal tissue (Figs. 

 178 a; 173) stretches from the edge of the pileus to the stalk, and 

 encloses the lamellae. This veil is ruptured as the pileus expands, 

 a portion attached to the stalk remaining as the " upper ring " 

 (annulus superus) (Figs. 173, 178 a), or a part attached to the 

 pileus hanging down as a fringe round its edge. Some genera 

 have no veil, the under side of the pileus being exposed from the 

 first (yymnoc.arpic Agaricacea?). Those which have a veil (hemi- 

 angiocarpicA.) afford a transition to the angiocarpic Grasteromycetes. 



FIG. 173. The cultivated Mushroom (Psalliota campe&tris). 



The mycelium mostly grows in soils rich in humus or dung, on 

 decaying trees and similar objects. Many species, e.g. Triclioloma 

 personatum and Marasmius oreadcs, form the so-called " fairy rings." 

 The fruit-bodies in these species are confined to a larger or smaller 

 surface on which they are very regularly arranged in a ring. The 

 reason for this is found in the radial growth of the mycelium, so 

 that the oldest portion, or the starting point, is found at the centre 

 of the ring, and the younger ones, on which the fruit-bodies are 

 formed, at the circumference. The older hypha? gradually die, and 

 at the same time, the radial growth continuing, the ring of fruit- 

 bodies becomes larger and larger. The " fairy -rings " are marked 



