Summary:
Features include 1) resupinate growth on wood and other substrates, 2) a fruitbody usually becoming pelliculose, the spore-bearing areas ferruginous to brown or bluish black, smooth and undulating, often becoming colliculose, the margin narrow, colored as the ferruginous brown subiculum or paler, 3) spores that are round to irregular or triangular, with bifurcate warts, the walls pale yellowish to brown, 4) basidia with median septa, and sterigmata often with septa, and 5) a monomitic hyphal system, the hyphae without clamp connections, the subicular hyphae brown (parts becoming green or blue in KOH).

Microscopic:
SPORES 7-10(11) microns in diameter, round to nearly round or irregular, when immature normally round but sometimes appearing roughly triangular, "rarely echinulate, usually warted, the warts normally bifurcate, walls pale yellowish when immature and pale to medium brown or umbrinous when mature"; BASIDIA 4-spored, 40-60(80) x 8-12 microns, often napiform [turnip-shaped] when immature, "clavate to clavipedunculate when mature, simple-septate at the base, median simple septa present", "sterigmata up to 10 microns long and often with simple septa", basidia "associated with a green, bluish green, or bluish black diffusate"; HYPHAE monomitic; SUBHYMENIAL HYPHAE 3-4 microns wide, colorless to pale brown, thin-walled or wall thickening apparent, simple-septate; SUBICULAR HYPHAE 2.5-3.5(6) microns wide, "light brown to dark ferruginous brown, parts often becoming green, bluish green, or blue due to the reaction of crystalline material with KOH", thick-walled, simple-septate, (Larsen, M.J.(8))

Notes:
Pseudotomentella tristis has been found in BC, WA, ID, AB, MB, NS, ON, AZ, CO, MA, MI, MN, MT, NJ, NM, NY, OH, PA, and SD, (Ginns). It has also been found in Austria, Czechoslovakia, Denmark, Finland, France, Germany, Netherlands, Sweden, United Kingdom, and Morocco, (Larsen, M.J.(8)).

Synonyms and Alternate Names:
Poria aurea Peck