POLYPORALES 445 



imbricated, tomentose, coral-pink fructifications on hard woods, often 

 accompanied by Stereum fasciatum in the Mississippi valley. 



Among the pileate genera, we have an ascending series, as in the 

 Corticiaceae and Polyporaceae. In the epixylous genera we have a 

 number of forms corresponding to genera of the higher Corticiaceae: 

 e.g., Aster odon with stellate setae in the hymenium corresponding to 

 Aster ostroma, Steccherinum, leathery with hyaline spores, as in Stereum, 

 while the perennial woody Echinodontium resembles Fomes of the Poly- 

 poraceae so much that it was originally described in the latter genus. 

 E. tinctorium was formerly used extensively as a dye and war paint by 

 the North American Indian. The tuberculiform, branched masses of 

 Hericium have long been known as wound parasites and saprophytes, 

 e.g., H. coralloides and H. caput-ursi. 



Finally, in the higher terrestrial genera they have reached the same 

 height of development attained by the fleshy Polyporaceae. Sarcodon 

 (spores colored, tuberculate) and Hydnodon (spores white, echinulate) sug- 

 gest fleshy species of Pohjporus while Hydnellum (spores colored, tuber- 

 culate) and Phellodon (spores white, echinulate) suggest Polystictus. 



Polyporaceae. — This family in the narrower sense is connected to 

 the Epithele group of the Corticiaceae, to Odontia of the Radulaceae and 

 perhaps more directly to Solenia of the Cyphellaceae. The fructifications 

 in the simpler forms, as in the Radulaceae, develop resupinate crusts or 

 brackets, while the higher forms develop laterally or centrally stipitate 

 pilei. In many species they are tough and perennial. In this case they 

 form a new layer of tubes over the surface of the old ones, either with or 

 without a layer of context separating the layers of tubes. These growth 

 zones resemble annual rings and like them may be used to determine 

 the age of the fructification. The hymenium lines the tubes but their 

 edges are always sterile, in contrast to those ofMerulius in the Radulaceae. 



The family includes several thousand species which merge into each 

 other without sharp limits, hence they have so far escaped satisfactory 

 systematic treatment. They have been classified mainly by macro- 

 scopic characters, into a few rather large genera which have been 

 differently defined by various authors. In many groups, microscopic 

 characters which are reasonably constant are available (Overholts, 1915) 

 but have been little used. 



The family may be divided into two large groups on the basis of 

 their pores. In the first, the tubes are circular or hexagonal in cross- 

 section while in the second the tubes are labyrinthiform (daedaloid) in 

 cross-section. Except in Trametes, in the first group the context (sub- 

 stance of the pileus) is distinct from the trama, usually of a different 

 color. 



Porta includes all the strictly resupinate forms with fleshy, leathery 

 or woody crusts on decaying wood. In Poria vapor aria, a cause of 



