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Page number:55 
Remarks (internal):The species was previously placed in Piptoporus but cultural studies have shown it to cause a white rot and thus it has been transferred to Polyporus. The presence of many unbranched vegetative hyphae in the context in addition to skeleto-ligative hyphae also makes P. pseudobetulinus a deviating species in Polyporus. 
Description type:Non-original description 
Description:Polyporus pseudobetulinus (Pilát) Thorn, Kotiranta & Niemelä Fig. 16 Mycologia 82:583, 1990. Ungulina pseudobetulina Pilát, Bull. Soc. Mycol. Fr. 48:23, 1932. Polyporus xinjiangensis? Zhao, Zu & Zhang, Acta Microbiol. Sin. 21:430, 1982.
Basidiocarps annual, attached to the substrate by a narrow base; pileus at first ungulate, then convex, dimidiate, solitary or imbricate in pairs, 6-18(24) cm broad and up to 4.5 cm thick, with a deflexed margin; upper surface yellowish-white to greyish-orange, with a thin cuticle and fine brownish to greyish-orange fibrils, becoming areolate; pore surface whitish to yellowish-orange, pores circular, 1-3 per mm, tube layer concolorous with context, up to l cm thick; context white to cream, up to 3 cm thick, fleshy, drying tough and corky.
Hyphal system dimitic; generative hyphae hyaline, thin-walled, 2.5-6 µm wide, in the pilear surface embedded in amorphous matter; skeleto-binding hyphae hyaline, thick-walled, nonseptate, up to 13 µm in diam, many vegetative hyphae unbranched in the upper context. Basidia clavate, 4-sterigmate, 18.5-40.5 x 5-7 µm, with a basal clamp at the base. Basidiospores cylindric to slightly fusiform, (6.5)7.2-10 x 2.5-3.4 µm. Cultural characteristics. See Thorn et al. 1990.
Substrata. On standing dead trunks of Populus spp., usually high above the ground, found on Salix in Japan.
Distribution. From continental areas in Finland, Russia, Japan, and Canada.

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