Summary:
Features include 1) resupinate growth on foliage and branches near the ground at high elevations, especially near snowbanks, 2) a skin-like spore-bearing surface that is pale tan to darker brown, and wrinkled to smooth, with a narrow, white to pallid margin, 3) a thin, soft, white, floccose to arachnoid, underlying subiculum from which the spore bearing surface is easily separated, 4) spores measuring (8.5)9.9-12.0(13) x (5.0)6.3-7.7(8.8) microns, broadly elliptic, smooth, inamyloid, weakly cyanophilic, and colorless or slightly yellowish in KOH when mature, 5) cystidia that are broadly clavate, projecting slightly or embedded, and 6) a monomitic hyphal system, the hyphae with clamp connections. It is a common snowbank fungus at high elevations in western North America (Gilbertson).

Microscopic:
SPORES (8.5)9.9-12(13) x (5)6.3-7.7(8.8) microns, "mostly broadly ellipsoid or broadly obovoid, somewhat flattened on the adaxial surface, with a broad (1.1 micron wide), truncated apiculus", smooth, inamyloid, colorless, weakly cyanophilous, thin-walled, most collections lack spores and mature basidia; BASIDIA 4-spored, (32)40-55(68) x (7)9-11(13) microns, clavate, when mature the basidia projecting up to 16 microns (including sterigmata up to 8 microns) above general level of hymenium; scattered CYSTIDIA present in some specimens, arising in the subhymenium and not projecting, 55 x 14-19 microns, broadly clavate, the walls thin, colorless but sometimes 0.5 microns thick and pale yellow; HYPHAE monomitic: context hyphae 3.2-7(9) microns wide, loosely woven, "branched, sometimes with some segments crystalline encrusted, with single clamp connections and a few simple septa", the walls colorless, smooth, thin to 0.8 microns thick, (Ginns(21)), SPORES 7-10 x 5-7 microns, broadly elliptic, inamyloid, colorless or slightly yellowish in KOH when mature; BASIDIA 4-spored, up to 60 microns long and 8-12 microns wide, clavate, with basal clamp connection; CYSTIDIA projecting slightly or embedded, 40-45 microns long and up to 18 microns wide at apex, "broadly clavate with a greatly expanded apex with distinctly thickened wall", colorless; HYPHAE monomitic, SUBICULAR HYPHAE 4-6 microns wide, thin-walled, some encrusted with crystalline material, "with occasional branching, with abundant clamp connections and also simple septa", (Gilbertson), SPORES (8.5)9.9-12.0(13) x (5.0)6.3-7.7(8.8) microns, (Ginns(23))

Notes:
Cylindrobasidium corrugum has been found in BC, WA, OR, ID, AB, AK, AZ, CA, CO, NM, UT, and WY, (Ginns(5)).

Synonyms and Alternate Names:
Polyporus medulla-panis Jacq.: Fr.