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Description type:Original description 
Description:Aleurodiscus macrocystidiatus Lemke, sp. nov. (Fig. 14)
Basidiocarp corticioid, forming linear patches 0.5-3 cm long and 1-3(-5) mm wide; margins determinate, adnate. Fructification 150-250 µm thick in cross section; texture densely pruinose to subfelty. Hymenial surface continuous, drying cream to ochraceous-buff colored. Context monomitic, composed of subregular, thin-walled, simple-septate hyphae (2.5-)3-4 µm in diameter; basal hyphae with partially thickened walls, measure up to 4.5 µm in diameter, generative. Catahymenium composed of numerous acanthophyses, conspicuous pseudocystidia, and scattered basidial elements. Acanthophyses variable, basal portion cylindrical, 3.5 µm in diameter, to swollen-rectangular, and then measuring up to 45-50 x 14-15 µm, walls thin to slightly thickened, naked; aculeate-pronged portion borne laterally or at the apex, thick-walled to semisolid, cylindrical, 20-30 x 7.5-8 µm, occasionally branched. Pronged portions faintly yellowish in KOH, individual prongs measuring 1.5-2.5(-3) x 0.8 µm. Pseudocystidia (macrocystidia) clavate to ampulliform, (40-)45-60(-70) x (9-)15-18(-23) µm, generally embedded; contents conspicuously guttate and yellowish in KOH, darkening in sulphobenzaldehyde. Basidioles numerous, subclavate to clavate, (40-)50-60(-75) x (8-)13-17 µm. Single basidium observed measured 55 x 9.5 µm; with four sterigmata up to 9 µm in length. Basidiospores ellipsoid-cylindric, 14-16 x (6.5-)7-8(-9) µm, apiculate, rounded at both ends, thin-walled, smooth, amyloid in Melzer's.
Distribution: British Columbia; California.
Habitat: Effused on the lower surface of recently dead branches of Arbutus menziesii; also collected on Arctostaphylos sp.
Discussion: This species is closely related to Aleurodiscus diffissus (Sacc.) Burt, but differs from that species in having wider spores and distinctly different pseudocystidia. The prongs on the acanthophyses in this species are rather short-aculeate, whereas the prongs of A. diffissus are more linear, acicular. In gross appearance the fruiting bodies of A. macrocystidiatus are a lighter, cream-buff color, and have adnate margins. Both species occur on members of the Ericaceae.
 
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