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DescriptionBasidiomata: subspherical, convex, with a constricted base, waxy-cartilaginous, pale pink, brown or black, 0.3; context hyphae: thick-walled, 2.5-3.5 µm in diam., with clamp connections; fertile hyphae: thick-walled, 2.5-3 µm in diam.; haustorial branches: unknown; hymenium: gelatinous, containing numerous probasidia; probasidial initials: claviform, thick-walled, with a basal clamp connection; hyphidia and cystidia: absent; basidia: when mature, composed of an elongate, claviform, thick-walled probasidium, 20-35 x 5.5-6 µm, and a cylindrical, often bent or irregular, thin-walled, 3septate, upper part (meiosporangium), up to 80 µm long and 3.5-4.5 µm in diam., with 4 epibasidia; epibasidia: +perpendicular to the basidium, subulate, 1.5-2 µm thick, 4-7 µm long, distinctively refractive at the apex; basidiospores: ellipsoid to fusiform, +symmetrical, rarely a little bent, with a distinct refractive apiculus at the lower end, 8.5-10 x 4-5 µm.; Hosts: thallus of Usnea species, inducing the formation of typical, +round galls; World distribution: North, Central and South America; Sonoran distribution: once collected in Sinaloa; also known from central, coastal California (Mendocino County).; Notes: Cystobasidium usneicola can easily be confused with Biatoropsis usnearum, as they grow on the same host genus, and induce the formation of similar galls. The two species are distinguished by different kinds of basidia and basidiospores, but examination of these elements, especially in immature specimens, is extremely difficult for nonspecialists. An undescribed Tremella species with similar basidiomata is also known from Usnea thalli in Arizona.