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Page number:418 
Remarks (public):The gloeocystidia are diagnostic, showing up as light yellow bodies in microscopic preparations. O. fragilis is similar, but becomes far more brown when touched or dried and lacks cystidia. 
Description type:Non-original description 
Description:Oligoporus leucomallellus (Murrill) Gilb. & Ryvarden - Mycotaxon 22:364. 1985. - Tyromyces leucomallellus Murrill, Bull. Torrey Bot. Club 67:63, 1940. - Tyromyces gloeocystidiatus Kotl. & Pouzar, Ceska Mykol. 18:207, 1964. Basidiocarps annual, pileate, effused-reflexed to rarely resupinate, mostly with a narrow, elongated pileus along the upper edge of a decurrent tube layer, up to 1 cm wide and 5 cm long, individual pilei may fuse laterally to form a wavy, lobed or partly imbricate basidiocarp, up to 1 cm thick at the base measured vertically, soft when fresh, tough to brittle when dry; upper surface white to cream, often discoloured by drying to straw coloured or dirty brownish, often somewhat unevenly and in radial lines, at first finely velutinate to finely fibrillose, in age becoming finely scrupose to smooth, mostly azonate to weakly zonate; pore surface white to dark cream, pores angular, mostly 3-4 per mm, in parts somewhat larger when dry, dissepiments in oblique parts of the pore surface partly split, sinuous to irregular; tube layer concolourous with pore surface, up to 10 mm thick; context white, 1-2 mm thick.
Hyphal system monomitic; contextual generative hyphae with clamps, hyaline and 2-4.5 µm wide, those of the subhymenium more narrow than those of the context, thin-walled to slightly thick-walled and with conspicuous clamps.
Gloeocystidia present in the hymenium, rare to abundant, hyaline to yellow, thin-walled, cylindrical to clavate and obtuse, 10-35 x 4-8 µm, mostly embedded, rarely projecting, arising in the subhymenium.
Basidia clavate, 4-sterigmate, 12-18 x 4-6.4 µm, with a basal clamp.
Basidiospores allantoid, smooth, thin-walled, hyaline, negative in Melzer's reagent, 4.5-6 x 1-1.7 µm.
Type of rot. Causes a brown rot in dead conifers. Cultural characteristics. Unknown.
Sexuality. Unknown.
Substrata. On dead conifers, especially on Pinus, but also on Abies, Larix, and Picea, also noted a few times on Arbutus and Eucalyptus.
Distribution. Widespread in the boreal conifer zone, in Europe spread throughout the continent except in the far north. Circumboreal to North America.
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