Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Basidiomata: brownish, resupinate, forming a thin subgelatinous film over galls of the host lichen galls: initially simple, with a constricted base, often irregular in form, 0.6-3 mm in diam., later bullate and reaching up to 17 mm in diam., initially concolourous with the thallus, becoming brown in the upper part context hyphae: difficult to study, 1-1.5 µm in diam.; clamp connections: not observed; fertile hyphae: thick-walled, 2-5-4 µm in diam. haustorial branches: unknown hymenium: containing numerous probasidia, intermixed with some fertile hyphae, embedded in a dense gel, 30-40 µm tall probasidial initials: subspherical to ellipsoid, thick-walled, with a basal clamp connection basidia: when mature, composed of an ellipsoid, thick-walled probasidium, 11-19 x 7-11 µm, and a cylindrical, generally bent, thin-walled, often deciduous, upper part (meiosporangium), 29-38 x 3.5-5 µm, with 3 transverse septa, individual cells collapsing after spore production, with 4 epibasidia epibasidia: +perpendicular to the basidium, subulate, 1-2 µm thick, 3.5-8.5 µm long, distinctively refractive at the apex basidiospores: ellipsoid to fusiform, +symmetrical, with a distinct refractive apiculus at the lower end, 8.5-12 x 4.5-6 µm. Hosts: thallus of Hypogymnia species; in the Sonoran area, on H. physodes, in California also on H. imshaugii; the fungus is inducing the formation of typical, often irregular and bullate galls World distribution: Europe (Finland) and North America (Canada, U.S.A.) Sonoran distribution: once collected in Arizona; also known from California (Lake and Sierra Counties). Notes: Cystobasidium hypogymniicola can easily be confused with Tremella hypogymniae, as they grow on the same host genus. Tremella hypogymniae differs by having more regular, subspherical galls, and tremelloid basidia and basidiospores.