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Page number:240 
Remarks (internal):This species, commonly known as Irpex cinnamomeus, is without a modern description; the most recent is that of Murrill (1907; 3) who described it under the name Hydnoporia fuscescens, with Irpex cinnamomeus as a synonym. It is an extremely variable species in its macroscopic characters, especially in the length and shape of the teeth. It is common on hardwoods, especially Quercus, from at least as far north as the Adirondack Mountains to as far south as Mississippi. 
Description type:Non-original description 
Description:Hydnochaete olivaceum (Schw.) Banker. Mycologia 6: 234. 1914. Figs. 1, 2, 10-13.
? Sistotrema olivaceum Schw., Schr. Nat. Ges. Leipzig 1: 101. 1822.
= Sistotrema fuscescens Schw., Schr. Nat. Ges. Leipzig 1: 102. 1822.
? Irpex fuscescens (Schw.) Schw., Trans. Amer. Phil. Soc. n.s. 4: 164. 1832.
? Hydnoporia fuscescens (Schw.) Murr., N. Amer. Fl. 9: 3. 1907.
= Irpex cinnamomeus Fr., Epicr. Myc. 524. 1838.
Basidiocarp (Figs. 1 and 2) broadly effused to erumpent through lenticels, tough to woody, adherent, brown to grayish-brown, warted or hydnaceous to nearly poroid by coalescing of teeth; context 1-3 mm thick, concolorous with hymenial surface, turning black in 3% KOH; teeth up to 3(-5) mm long, flattened, rather blunt, also becoming black in 3% KOH.
Context a textura intricata; hyphae of two types; 1) 2-4 µm, broad, slightly thick-walled (walls up to 0.5 µm thick), yellow tinted, smooth, infrequently septate, lacking clamp connections, staining blue in lactophenol-aniline blue, giving rise to second type of hyphae; 2) (Fig. 12) 2-4(-5) µm broad, thick-walled (walls 0.5-1.5 µm thick), reddish-brown, smooth, infrequently septate, lacking clamp connections, not becoming blue in lactophenol-aniline blue; teeth formed by organization of hyphae into a textura porrecta perpendicular to substrate, hyphae like those of context, mostly thick-walled and reddish-brown; subhymenium not well differentiated, cells frequently septate, lacking clamp connections, frequently branched and forming a compact textura intricata; hymenium composed of setae and basidia; setae (Fig. 13) 35-80(-150) x 9-13 µm, subulate, thick-walled (walls up to 4 µm, thick), reddish-brown, usually arising as a modified tramal end cell that turns outward and penetrates the hymenium, occasionally with bifurcate or rooting base, darkening in 3% KOH; basidia (Fig. 10) 12-20 x 3-4 µm, cylindrical, hyaline, thin-walled, basal septum without clamp connection, 4 sterigmate; sterigmata 2-2.5 µm long; basidiospores (Fig. 11), 4.5-6.5 x 1.2-1.5 µm, allantoid, hyaline, thin-walled, negative in Melzer's reagent.
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