BASIDIOMYCETES 



107 



body, and radiate from the central stalk. Those which are first 

 formed extend from the edge of the pileus to the stalk; those 

 formed later reach only a longer or shorter portion of this distance, 

 according to their age. In structure the lamellae (Fig. 174) con- 

 sist of a central mass of hyphas, the trama, continuous with the 

 hyphae of the pileus ; these terminate in a layer of shorter cells, 

 the subtly menial layer, immediately beneath the hymenium which 

 is composed of basidia and paraphyses. In a few species, but not 

 in the majority, the lamellae are branched, and in some they are 

 decurrent. A few have the stalk placed excentrically, or it may 

 be entirely absent. 



FIG. 172. Development of Psalliota campestris : a, b, c, d show the various stages of 

 the development of the fruit-bodies and the mycelium (in) (nat. size); the fruit-body 

 in a somewhat later stage, slightly magnified ; / longitudinal section of e ; n first forma- 

 tion of the hymenium ; g longitudinal section of a more advanced fruit-body (nat. size) ; 

 n the hymenium ; o velum partiale (see Fig. 133.) 



In the early stages of its development the fruit-body is more or 

 less enclosed in a hyphal tissue the " veil " (velum universale, or 

 volva). The veil at first completely encloses the young fruit-body, 

 but is afterwards ruptured as the latter grows, part remaining 

 at the base of the stalk as the "sheath" (annulus inferiis), and 

 part on the pileus as scales or warts. In the " Fly Mushroom " 

 (Amanita muscaria) the remains of the veil are especially con- 



