Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Basidiomata: inducing gall-formation, convex, concolorous to the thallus, becoming orange brown at maturity, 0.2-1.5 mm in diam. hyphae: fertile hyphae: 3.5-4.5 µm in diam.; clamps: not observed haustorial branches: not observed hymenium: containing numerous probasidia; probasidial initials: subspherical, proliferations occurring through the basal clamp; hyphidia and cystidia: absent basidia,: when mature, 4-celled, with longitudinal septa, 15-20 x 10-16 µm epibasidia: subcylindrical, at least 30 µm in length, 2-4.5 µm in diam. basidiospores: ellipsoid to subspherical, with a distinct apiculus, 6-8 x 5.5-7.5 µm Anamorph: unknown. Host: thallus of Letharia vulpina World distribution: Canada (British Columbia) and U.S.A. (California) Sonoran distribution: unknown. Notes: Tremella lethariae is not yet known from the greater Sonoran Desert region. It is included here as it is known from California (Tulare Co.) and might well be found also in the flora area. As the galls are mostly concolorous to the host thallus or slightly darker, and as they are usually small, the species is probably overlooked and hence much more common.