Summary:
Features include 1) resupinate growth on wood, 2) a spongy-membranous, tomentose fruitbody that is smooth to somewhat tuberculate and tan to pale yellow-brown, orange-brown, or lavender-brown, the margin lighter to whitish, the subiculum slightly paler than the spore-bearing surface, and fine rhizomorphs present, 3) spores that are mostly round, often appearing roughly triangular when immature, warted or spiny, the warts normally bifurcate, the walls nearly colorless to pale yellow or pale tan, 4) basidia often with median simple septa, and 5) a dimitic hyphal system, the hyphae without clamp connections.

Microscopic:
SPORES 7-11 microns in diameter, mostly round, frequently appearing roughly triangular when immature, "normally warted or sometimes echinulate, the warts normally bifurcate", walls nearly colorless to pale yellow or pale tan; BASIDIA 4-spored, 35-45(50) x 7-9 microns, spheropedunculate to napiform [turnip-shaped] when immature, clavipedunculate when mature, "simple-septate at the base, often with median simple septa", sterigmata up to 8 microns long; HYPHAE dimitic; SUBHYMENIAL HYPHAE 2-3 microns wide, pale brown to nearly colorless, thin-walled, simple-septate; SUBICULAR HYPHAE of two types 1) generative, 2-3 microns wide, pale brown, with wall thickening apparent, simple-septate, 2) skeletal, 1-2(2.5) microns wide, yellowish, thick-walled, simple septa rare; CORDONS up to 20 microns wide, yellowish brown, the individual generative hyphae 1.5-2.5 microns wide, thin-walled, simple-septate, (Larsen), SPORES 6-9 microns excluding warts, nearly round, verrucose to spinose, some warts dichotomously forked, yellow-brown; BASIDIA 4-spored, 40-60 x 7-10 microns, narrowly clavate, without basal clamp connection; CYSTIDIA not seen; HYPHAE dimitic, 1) generative hyphae 2-3 microns wide, light yellow, thin-walled, without clamp connections, 2) skeletal hyphae 2-2.5 microns wide, brown, thick-walled, without septa; HYPHAL STRANDS up to 15(20) microns wide, (Breitenbach)

Notes:
Pseudotomentella mucidula has been found in BC, WA, ID, AB, ON, AZ, NM, and NY, (Ginns), Austria, Czechoslovakia, Denmark, Finland, France, Germany, Portugal, and Sweden, (Larsen), and Switzerland and Asia, (Breitenbach).