51 



section to which our common and widely distributed species P. 

 arcidantis belongs. It may be distinguished from that species, 

 however, by its smaller size, thinner substance, gray color and 

 slender, equal, less hairy stem. From the rare P. arcii/aric//its, 

 it differs decidedly in color and in being opaque instead of pellucid. 

 A full description of the species follows : 



Polyporus arculariformis sp. nov. 



Pileus circular, umbilicate, 0.6-0.8 cm. x 0.05— O.i cm., surface 

 regularly concentrically rugose about the white, depressed center, 

 isabelline to avellaneous, slightly imbricate-fibrillose ; margin 

 thin, acute, soon deflexed, nearly white, changing to isabelline, 

 beset with numerous long, white, pointed cilia : context mem- 

 branous, white, perfectly opaque : tubes 0.2-0.4 mm. long, 2-3 

 to a mm., radially elongated, decurrent, pallid, edges thin, 

 irregularly toothed and fimbriate : spores hyaline, smooth, thin- 

 wallcd, 2.3—2.5 //. X 7-8 fi : stipe central, stuffed, equal, concolor- 

 ous, beset with sharp bristles which partially disappear with age, 

 densely tomentose at the base, 1.5-2 cm. long, 0.5-1 mm. thick. 



Poly portis arculariformis. FiG. I. Entire plant, showing upper surface of pileus, 

 X2^. Fig. 2. Entire plant, showing lower surface of pileus, X 2^3. FiG. 3. 

 Portion of upper surface, X 8. FiG. 4. Portion of lower surface, X 8. 



Unaka Springs, East Tennessee, 1,700 ft., on dead oak and 

 chestnut sticks in deciduous woods, Murri/l, August 20, i 904, 

 nos. 702 (type) and 821. Near P. arcnlarius (Batsch) Fr. 

 New York Botanical Gardkn. 



