Summary:
Tremella hypogymniae produces tiny fruitbodies on the lichen Hypogymnia physodes, causing pale to pinkish or brownish or darker galls with a smooth surface. The fruitbody when present is resupinate over the galls, and colored yellowish, pinkish, or pale orange. It is distinguished from related species by the induction of the formation of convex subspherical cells on the host thallus, and by the small 2-celled basidia. The description is derived from Diederich(1).

Microscopic:
spores 7-10 x 5.5-7 microns, nearly round to elliptic, colorless, with a large apiculus; basidia when mature 2-celled, 11-16(20) x 7-12 microns, "irregular in shape and septation, with one longitudinal, oblique or transverse septum, cells often unequal in size", epibasidia up to at least 30 microns long, 2-3.5 microns wide, subcylindric; hymenium colorless, "containing a few or numerous probasidia and conidiogenous cells, thickness varying according to the development of the basidioma", up to 100 microns, probasidial initials ellipsoid, proliferations occurring through the basal clamp connection; hyphidia and cystidia absent; hyphae of context 1-3 microns wide, "intermixed with the hyphae of the host lichen, not abundant, thin-walled", clamp connections present; haustorial branches not observed; anamorph poorly developed in the material examined: conidiogenous cells present, 21-35 x 5-9 microns, claviform to cylindric, colorless, immature, without apical branches, asteroconidia not observed

Notes:
Collections were seen from BC, OR, ID, ON, AK, and MT: it is apparently rare in North America though common in Europe, (Diederich(2)). It is found in Austria, Finland, France, Germany, Luxembourg, Norway, Poland, Romania, Russia, Spain, Sweden, Switzerland, United Kingdom, and Macaronesia (Canary Islands), (Diederich(1)).

Synonyms and Alternate Names:
Corticium subincarnatum Peck
Peniophora subincarnata (Peck) Litsch.