Summary:
Tremella aurantia is a parasite of Stereum fruiting bodies, the unclamped hyphae of the Stereum often remaining visible amongst the clamped Tremella hyphae. Features include densely folded orange-yellow gelatinous fruitbody with white fleshy-fibrous interior core, and microscopic characters.

Microscopic:
spores 7.5-10 x 6-8 microns, broadly elliptic to elliptic, basidia "2-4 celled, 10-13 microns wide, widely clavate to subglobose or ellipsoid with a distinct stalk, most with diagonal septa"; hyphae in a gelatinous matrix, colorless, 1.5-2.5 microns wide, "thin-walled, with clamp connexions, intermixed with host hyphae, 4-6 microns wide, slightly thick-walled, without clamp connexions"; haustorial cells present and conspicuous, mostly spherical, 2-3 microns wide, giving rise to one or more thin filaments, (Roberts), spores 7-10 x 6-8.5 microns, oval-round with granular content; basidia 4-spored, ovate, 12-16.2 x 11.3-13 microns; hyphae thin-walled with sparse clamp connections, (Raitviir), spores 8-9.5 x 6.5-7.5 microns, nearly round, germinating by repetition; probasidia subglobose, metabasidia becoming ovoid to subclavate, cruciate-septate, 12.5-17.5 x 8.5-12 microns; hyphae with clamp connections, (Lowy), spores 9-10.5 x 9-10.5 microns, nearly round, slightly yellowish under lens, yellow in mass; probasidia 15-16 microns in diameter, at first clavate-elliptic, finally spherical, becoming cruciate-septate, epibasidia arising abruptly, up to 100 microns long, 2-3 microns wide except at apex where inflated to as much as 7 microns beneath sterigmata, (Martin)

Notes:
T. aurantia is found in BC, OR, CA, IA, LA, NC, NJ, SC, TX, (Ginns), Brazil (Roberts), Argentina, Brazil, (Lowy), and Armenia, Uzbekistan, (Raitviir)