DEVELOPMENT OF PLANTS 



245 



are several very widely distributed and familiar families of the 

 Agaricales, distinguished by the arrangement and distribution of 

 their hymenium. 



A. Thelephoraceae. — These fungi form membranous, leathery 

 or woody incrustations or shell-like structures or branching bodies 

 on soil or wood (Fig. 169, A, B). The hymenium forms a 

 smooth or slightly wrinkled surface on the under side or exposed 

 surface of the fungus. 



Fig. 169. Forms of the Agaricales: A, Stereum, top view. B, underside, 

 showing the characteristic smooth hymenial surface of the Telephoraceae. 



C, a coral fungus, Clavaria, with hymenium confined to the tips of the branches. 



D, a prickly fungus, Hydnum, with the hymenium on spine-like projections. 



B. Clavariaceae or Coral Fungi. — This family includes the fairy 

 clubs and coral-like fleshy masses of various colors (Fig. 169, C). 

 The hymenium covers the branches. 



C. Hydnaceae or Prickly Fungi. — These fungi form masses of 

 widely various forms, but provided with spine-like outgrowths 

 upon which the hymenium is developed (Fig. 169, D). 



D. Polyporaceae or Pore Fungi. — This group includes largely 

 leathery, woody or corky fungi in which the hymenium is de- 

 veloped on the surface of pores. They contain some of the most 

 destructive of the timber-destroying fungi. Many of the genera 



