Summary:
Features include 1) resupinate growth on wood, 2) a fruitbody that is thin, chalk-white to ochraceous, the older specimens usually with abrupt margins and a tuberculate surface, 3) cylindric-curved spores, 4) obovate basidia that are longitudinally septate, 5) two types of dikaryophyses, 6) clamp connections, and 7) mineral crystals especially in the vicinity of the hymenium.

Microscopic:
SPORES 10-15(17) x 5-7(8) microns, suballantoid to ovate; PROBASIDIA 18-22 x 10-12 microns, ovate, often becoming nearly spherical, eventually cruciate-septate or sometimes 2-celled, epibasidia up to 20 microns or more long, 2-3.5 microns wide, coarse; "slender, tortuous, sparsely branched paraphyses, together with clavate and often septate paraphyses arising from the same hyphae as the basidia and with a clamp-connection at the septum, the tips of the slender paraphyses forming an agglutinated layer 20-40 microns thick above the basidia"; in section, very thin to 300(450) microns thick, consisting of a horizontal layer of interwoven hyphae parallel with the substrate, (at first colorless, then brown), an intermediate layer of gelatinized hyphae, (often calcareous), and a rather wide hymenial zone of closely aggregated basidia and paraphyses, (Martin), SPORES 10-15(17) x 5-7.5(8) microns, usually cylindric-curved, guttulate, "germinating by formation of germination tube or by repetition"; hymenium consists of fertile hyphae and two types of dikaryophyses: fertile hyphae 2-5 microns wide, toruloid, forming basidia in clusters by lateral proliferation through or near subbasidial clamp connections, probasidia arising as elongate structures becoming ovate, obovate or almost subspherical with 2 or 4 longitudinal septa, guttulate, 15-22 x 8-14 microns, epibasidia 2-4(5) microns wide, up to 75 microns long; DIKARYOPHYSES of two types: a) slender ones 1.5-4(5) microns wide, "simple to little branched, usually nodulose, becoming indistinct", forming a well defined layer 20-75 microns thick above the mature basidia, b) subcylindric septate dikaryophyses 35-70 x 3.5-10 microns, cylindric (or sometimes clavate or subfusiform), flexuous [wavy], colorless, apparently arising from the fertile hyphae; basal layer of hyphae 2.5-4 microns wide, becoming yellowish and somewhat thick-walled, with clamp connections, either parallel with substrate or interwoven and ascending, superficial to that an ascending interwoven layer of indistinct toruloid hyphae 2.5-4(6) microns wide, with clamp connections, terminating in the hymenium; mineral granules usually abundant throughout, often very abundant in vicinity of hymenium, (Wells)

Notes:
Exidiopsis macrospora has been found in BC, NS, ON, CO, FL, IA, OH, MO, NH, NY, TN, TX, and WI, (Ginns), as well as Europe (Wells).

Synonyms and Alternate Names:
Eichleriella macrospora (Ellis & Everh.) G.W. Martin
Sebacina macrospora (Ellis & Everh.) Burt
Tremella polyporina D.A. Reid Trans. Br. mycol. Soc.