66 THE POLTPOBACEAE OF WISOONBIN. 



lower than those of P. pergamenus. The color of both species is the 

 same. 



P. ahietinus is a very destructive fungus in our northern woods, at- 

 tacking especially the hemlock and tamarack and producing decay. 

 These trees may become infected through wounds in the bark from 

 which infection spreads around the tree through the sapwood, produc- 

 ing a peculiar decay to a depth of about two inches. Eventually the 

 fungus kills the tree. 



Syn. Goriolus aiietinus (Dicks.) Quel. ; 19, vol. 32, p. 654. 



Polystictus planus Peck. 



Pileus thin, coriaceous, plane, suborbicular, about 2.5 cm. broad, some- 

 times confluent, dorsally attached, minutely villose or velvety, brown or 

 brownish, fawn colored, variegated with narrow darker glabrous 

 zones, margin whitish, pores minute, obtuse, short, subrotund, whitish 

 or pallid ; flesh pallid. Colors of P. scutellatus. 



This little species seems to be rare and has been collected twice. The 

 specimens were found near Madison on oak branches and twigs near the 

 ground. They are darker and thinner than P. versicolor, not sericeous 

 nor shining. On one specimen the zones are almost black. The pileus 

 is explanate, the thin margin slightly reflexed. One specimen is drawn 

 out into a sort of irregular lateral stipe, another is sessile — ^both of these 

 are gibbous behind. The color varies from brown to almost black. 

 Substance thin, coriaceous, white. The margin very thin, lighter than 

 the rest of the pileus. 



The pores are small, shallower than in P. versicolor, from whitish to 

 pale tawny. The dissepiments are at first quite obtuse ; later they be- 

 come thinner. 



§4. Stupposi. Dimidiate-sessile, pUei floccose, pirate or appressed- 

 villous, uneven, azonate; context fibrous to lignose. 

 Context white. 



Polystictus filrala Fries. 



Pileus leathery, soft, tough, velvety-hirsute, azonate, whitish, often 

 radiate-rugose, snow-white within, with entire acute margin; pores 

 small, roundish, acute, at length lacerate, yellowish. 



On fallen oak branches. Pilei variously shaped ; flabellif orm, or- 

 bicular, shield-shaped or resetted. 



