354 BRITISH FUNGI 



central stem, resembling an agaric in general appearance, but 

 differing in having tubes on the under surface of the cap, instead of 

 gills. In Polyporiis we meet with species having a lateral stem; 

 in Fomes the stem is altogether absent ; whereas in Poria and 

 Meruliiis the entire fungus is reduced to a thin layer, adhering by- 

 its entire under surface to the substratum, and the upper or free 

 surface, consisting entirely of the porous hymenium. In general 

 consistency there is equal diversity, some being soft and fleshy, 

 others hard and woody. Some are perennial. Practically all the 

 species grow on wood. 



Key to the Genera 



Cap regular, fleshy, hymenium on the under surface, the tubes 

 easily removed from the flesh of the cap ; stem central, stout. 

 Spores elongated. Boletus. 



General structure as in Boletus, but the cap is covered with large, 

 shaggy scales, and the spores are globose. Styobilomyces. 



Cap very fleshy, soft, sessile, and attached by the edge, tubes 

 crowded side by side, but distinct from each other. Fistulina. 



Stratum of tubes sharply defined from the flesh of the cap, but 

 not separable from it ; fleshy and tough ; stem central, lateral or 

 absent altogether, and attached by a broad base. Polyporus. 



Perennial. Woody, sessile, horizontal, and attached by a broad 

 base ; tubes stratified, or consisting of two or more superposed 

 layers. Fomes. 



Cap quite thin, limp, velvety or downy ; tubes quite short. 



Polystictus. 



Entirely adnate to the substratum, thin, pores uppermost. Poria. 



Tubes immersed at various depths into the flesh of the cap ; cap 

 corky, sessile and attached by a broad base. Often fragrant. 



Trametes. 



Cap tough and corky, attached by a Inroad base ; pores often long 

 and irregularly wavy, dissepiments or walls of the tubes thick, 

 corky, elastic. DcBdalea. 



Subgelatinous. Thin and adnate to the substratum ; pores 

 very shallow, often wavy. Merulius. 



NOTES ON the GENERA 



Boletus 

 The cap is always symmetrical, and usually very fleshy, and 

 bears the porous hymenium on its under surface. Stem central, 

 stout. The colours are often very bright, the cap is sometimes 

 minutely velvety, but never scaly. In some species the white or 

 yellow flesh changes to a deep blue colour when broken and exposed 

 to the air. All the species grow on the ground, and many appear 

 during the summer season. Some are edible. 



