80 THE POLYPORACEAE OF WISCONSIN. 



ing somewhat indistinct. The tubes in this specimen are about 1 cm. 

 long, smaller than in F. fomentarius and with thinner dissepiments; 

 their color like that of the flesh, is a yellowish ferruginous, and there 

 is a layer of hymenophore separating each stratum. The pilei are di- 

 midiate and frequently imbricated. The older part of the surface is 

 blackened, and opaque, rimose ; the margin is yellowish-rust color, even, 

 tomentose. Specimens of this large type are not common. The usual 

 form is ungulate, about 10 cm. wide, 8 cm. long and 7 cm. thick. The 

 tubes stratified but continuous, each layer about 5 to 7 mm. in length 

 and like the hymenophore of a rich ferruginous color. The substance 

 of the pileus is distinctly zonate. Young nodular specimens appear to 

 be made of concentric shell-like layers which are often partially separ- 

 able. 



A few specimens of this smaller type were sent to Peck. He identi- 

 fied them as F. igniarius, but not typical. They seem in fact to ap- 

 proach in appearance the variety of F. nigricans which is found so 

 commonly on poplar in this region. The resemblance is so close that it 

 is often difficult to keep the two separate. F. nigricans, however, is 

 much darker in color and harder ; the sulcations are also more numerous 

 and narrower. Its pileus is more triangular in cross-section and the 

 margin in young plants is not so much rounded as in F. igniarius, nor 

 has it ever the yellow tomentum. F. salicinus is also closely related 

 but this is always distinguishable by its harder substance and the re- 

 supinate form. 



Syn. : Pyropolyporus igniarius (L.) Murr. ; 19, 30, p. 110. 

 Polyporus igniarius (L.) Winter; 28, p. 424. 



Fomes nigricans Fries (Plate VIII, fig. 29). 



Hoof -shaped or pulvinate, very thick, pileus densely and concentric- 

 ally sulcate, cuticle very hard, with a crusty varnished surface layer, 

 black, smooth, shining, margin very obtuse, ferruginous; flesh very 

 hard, ferruginous; tubes elongated, distinctly stratose ferruginous; 

 pores 0.3 mm. across, obsoletely angular, naked from the first ; spores 

 elliptical, both ends rounded, brown, 5 by 3 microns. 



Fries describes a form of this species with the "pileus triangular, 

 rugose, opaque, which approaches Fomes igniarius." He might have 

 added ' ' and radially rimose, ' ' to complete the description for our spec- 

 imens. 



Very common on poplar, birch, maple and elm. Localities : Horicon, 

 Bangor, Sparta, Madison, Hazelhurst, Crandon, Star Lake, Shana- 

 golden and Ladysmith. 



