MICHIGAN ACADEMY OF SCIENCE. 233 
36. Pileus large, 8 cm. or more wide (37) 
36. Pileus small, rarely exceeding 5 cm. wide: (40) 
37. Flesli of two layers, soft and spongy above, firm and woody below ; 
pileus whitish to pale tan, thick, convex to triangular; on elm, 
maple, etc.: Polyporus delectcms PK. 
( Spongipellis delectans) . 
37. Flesh at first fibrous-fleshy, rigid and friable when dry, one-layered; 
pileus applanate or convex: (38) 
38. Flesh zonate; pileus white, surface watersoaked, becoming discol- 
ored ; margin soon blackish ; odor strong ; on oak : 
Polyporus Spraguei Berk. 
( Tyromy ces Spraguei ) . 
38. Flesh not zonate; pileus attached by narrow base: (39) 
39. Tubes 8-10 mm. long; pileus rugose, whitish or tinged yellowish; on 
Tilia : Polyporus tiliopliila Murr. 
(Tyromyces tiliopliila). 
39. Tubes shorter, 3-6 mm. ; pileus 10-15 cm. broad, white or yellow- 
ish, watery-spotted ; on conifer trunks : 
Polyporus guttulatus PK. 
(Tyromyces guttulatus). 
40. Surface of pileus cartilaginous, yellowish-white; flesh horny when 
dry, very thin ; on maple, etc. : Polyporus semisupimis B. ct- C. 
(Tyromyces semisupinus) . 
40. Surface not cartilaginous: (41) 
41. Pileus effuso-reflexed : (42) 
41. Pileus dimidiate: ,...(45) 
42. Tubes large, irregular, 1-2 to a mm.; pileus white, sulate-zonate, 
slightly spongy-tomentose ; on hemlock and pine: 
Polyporus undosus PK. 
(Tyromyces undosus). 
42. Tubes much smaller, 3-6 to a mm., regular; pileus slightly villose or 
scabrous, laterally elongate : (43) 
43. On coniferous wood: (44) 
43. On branches of broad-leaved trees; pileus white to tan; tubes short, 
very minute, often blue spotted: Polyporus semipileatus PK. 
(Tyromyces semipileatus). 
44. Mouths of pores glistening; pileus subcorky, inseparable from sub- 
stratum, milk-white, not zonate : Polyporus anccps PK. 
(Tyromyces anceps). 
44. Mouths not glistening; pileus fleshy-tough, white to pale tan, often 
with reddish zones : Polyporus Ellisianus Murr. 
(Tyromyces Ellisianus). 
