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Page number:78 
Remarks (internal):Although not tested statistically, our observations suggest that specimens from Alnus and Salix had longer spores than specimens on other woody species.
Megalocystidium luridum is similar but differs mainly in the shape and size of the spores, which are ellipsoid to cylindric and usually less than 12 m long. Due to confusion in species concepts (see M. luridum under Excluded Names) many of the specimens examined had been misidentified as luridum.
Description type:Non-original description 
Description:Megalocystidium leucoxanthum (Bres.) Jülich. Fig. 19 Persoonia 1: 140, 1978.
? Corticium leucoxanthum Bres., Fungi Tridentini 2: 57-58, pl. CLXVI, fig. 3, 1898.
? Gloeocystidium leucoxanthum (Bres.) Höhn. & Litsch., Sitzungsber. Kaiserl. Akad. Wiss., Math.-Naturiwss. Cl. 116: 744-745, 1907.
? Gloeocystidiellum leucoxanthum (Bres.) Boidin, Compt. Rend. Hebd. Séances Acad. Sci. 233: 825, 1951.
Type specimen examined Italy: Alpes, viii.1894, G. Bresadola, s.n. (S, isotype FH).
Basidiomes effuse, up to 30 x 5 cm and up to 500 µm thick, hymenial surface ceraceous, "Pinkish Buff', "Cinnamon-Buff", to "Clay Color" when thy, smooth to strongly tuberculate, not cracked or cracked extensively exposing the nearly white subiculum; margin abrupt to slightly pruinose, whitish or concolorous, to 1 mm wide.
Hyphal system monomitic. Hyphae 2.5-5.0 (-5.5) µm diam, with clamp connections, the walls thin, distinct, forming a loosely interwoven to compact, distinct, parallel layer about 50-100 µm thick next to substrate. Marginal hyphae weakly amyloid en masse. Gloeoplerous hyphae in margin. Gloeocystidia 60-160 x 10-16 µm, numerous, cylindric to subfusoid, some with constrictions and some with a bulb at the apex, the walls thin to 0.5 µm thick, the contents yellow in KOH, granular, sulfo-negative, but many appear to be empty. Hyphidia scattered, filiform, simple, 2-2.6 µm diam, projecting to 16 µm. Basidia 45-65 x 5.0-7.5 µm, clavate, with four sterigmata, each up to 5.0 µm long. Basidiospores (12.8-) 15.2-17.6 (-21.0) x 4.5-7.0 µm, ellipsoid to suballantoid, the wall smooth, easily collapsed, amyloid, with a distinct, blunt apiculus.
Ecology and distribution. Typically on bark and wood of twigs, branches, and small stems, up to 30 mm diam, lying on the ground, associated with a white rot. Within its range the species is common and occurs predominately on amentiferous hosts, especially Alnus, Betula, Quercus, Populus, and Salix. Also reported on a variety of other angiosperm species and there is one report of it on conifer wood (Table 2). In North America restricted to Canada and northern United States, except in the cordillera where it extends south to Arizona.
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