Summary:
Datronia stereoides is distinguished in the field by the granulose (under a hand lens) walls of the small regular pale pinkish-buff pores, and the brown tomentum separated from the pale lower flesh by a black layer. Other features include a shelf-like form, a brown, non-zoned, upper surface that is tomentose to strigose, thin flesh, and microscopic characters.

Microscopic:
spores 10-13 x 4.5-6 microns, cylindric, smooth, inamyloid, colorless; basidia 4-spored, 25-40 x 7-8.5 microns, clavate with a narrow base, with basal clamp; cystidioles not conspicuous or abundant, not projecting, 30-40 x 5-6 microns, fusoid; dendrohyphidia abundant on dissepiment edges, 1.5-2 microns wide, much branched and contorted; hyphal system dimitic: context generative hyphae 2-2.5 microns wide, thin-walled, nodose-septate, context skeletal hyphae 2-4 microns wide, thick-walled, aseptate, with frequent branching, those in lower context pale greenish brown in KOH, those in dark upper layer dark brown in KOH, trama hyphae similar to those in lower context, (Gilbertson), spores 9.5-12 x 3.5-4.5 microns, cylindric, smooth, inamyloid, colorless, with droplets, (Breitenbach)

Notes:
Datronia stereoides has been found in BC, ID, AB, MB, AK, AZ, CA, CO, IA, IL MA, ME, MN, MO, MT, ND, NH, NY, VT, and WI, (Gilbertson). It is also known from SK (Ginns). It occurs in Europe, Asia, and Australia, (Breitenbach).

Synonyms and Alternate Names:
Albatrellus flettii Morse ex Pouzar
Coriolus planellus Murrill
Polyporus flettii Morse