THE FUNGI : ASCOMYCETES AND BASIDIOMYCETES 323 



the region of the gill cavity, bursting the veil and carrying up the cap or 

 pileus on its top. The veil, thus broken, remains partly as a vestigial structure 

 on the top of the pileus and partly as a ragged fringe of tissue attached to the 

 stipe, called the annulus. In the case of Amanita, the universal veil is 



Trama 



Subhymenium 



Basidium 



Basidiospores 



^Hymenium 



Fig. 316. — Psalliota campestris. Section through a portion of a gill 

 to show the hymenial layer and the basidia with basidiospores. 



ruptured in two places, one above and the other below the annulus so that a 

 cup-shaped volva is left around the base of the stipe. 



In the mature fruiting body of Psalliota the gills radiate out as a series 

 of flat, thin plates which are not joined to the stipe, though in other genera 

 they may not only join but run for some distance down it. These gills exhibit 

 a complex structure (Fig. 316). There is a central core of tissue or trama, 

 composed of anastomosing, irregularly interwoven hyphae which give ofi^ 

 short branches running obliquely outwards and forming a more compact 

 tissue known as the subhymenium. From this layer the hymenium 



