DEVELOPMENT OF PLANTS 



263 



are several very widely distributed and familiar families of the 

 Agaricales, distinguished by the arrangement and distribution of 

 the hymenium. 



A. Thelephoraceae. These fungi form membranous, leathery 





liflli 



FIG. 171. Structure of a mushroom: A and B, cross and longitudinal 

 sections of a portion of the stipe, showing the character and arrangement 

 of the hyphae that make up the mushroom. C, tangential view of the gills 

 p, pileus; h, hymenium appearing as a dark band on the surface of the 

 gills. D, a portion of the hymenium enlarged b, basidia; pa, paraphyses; 

 s, basidiospores. 



or woody incrustations or shell-like structures or branching 

 bodies on soil or wood (Fig. 172, A, 5). The hymenium forms 

 a smooth or slightly wrinkled surface on the under side or ex- 

 posed surface of the fungus. 



