Summary:
Features include 1) resupinate growth on hardwood and conifer wood, 2) pale to bright yellow fruitbodies that fade to more ochraceous when old or dried, the surface waxy, and smooth to tuberculate, the margin white and fibrillose, 3) spores that are round to nearly round, smooth, weakly amyloid, and colorless, 4) numerous thin-walled gloeocystidia that are bladder-like and apically tapering, the basal ones usually very wide, but those in hymenium narrow (ventricose-rostrate, lageniform, fusiform), the gloeocystidia generally considered sulfo-negative, but found to be sulfo-positive in fresh culture, 5) scattered hyphidia, and 6) a monomitic hyphal system, the hyphae without clamp connections.

Microscopic:
SPORES 5.5-6.5 microns wide, round to nearly round, smooth, weakly amyloid (weakly mottled on the interior surface in Melzer''s reagent), wall thin up to 0.4 microns thick, spore with a distinct apiculus; BASIDIA 4-spored, 35-60 x 4.0-7.5 microns, clavate or cylindric, sterigmata up to 5.0 microns long; GLOEOCYSTIDIA numerous, 40-105 x 7-20 microns, "ventricose, ventricose-rostrate, and lageniform, thin-walled, the contents not refringent, sulfo-negative in herbarium specimens" (but said by Boidin & Lanquetin 1983 to be sulfo-positive in living cultures); HYPHIDIA "scattered, uncommon", 2-3 microns wide, "filiform, some weakly branched at the apex"; HYPHAE monomitic; subiculum "a loosely arranged layer about 25-50 microns thick of distinct, parallel hyphae"; hyphae 2.0-4.0(5.6) microns wide, without clamp connections; subhymenial hyphae 2.5-5.6 microns, compact, distinct, colorless, thin-walled; gloeoplerous hyphae "adjoining the substrate, unbranched with scattered septa", 5 microns wide, the contents oily, (Ginns), SPORES round to nearly round, smooth, amyloid, thin-walled, containing one or more oil droplets, with prominent apiculus, mostly 4-5 microns in diameter; BASIDIA narrowly clavate, containing a number of oil droplets of varying sizes, mostly 30-50 x 5-7 microns, without basal clamp connection, normally 4-spored; GLOEOCYSTIDIA vesicular [bladder-like], apically tapering, mostly 50-70 x 10-20 microns, thin-walled with watery contents, without reaction to sulfo-vanillin; basal gloeocystidia usually very wide, vesicular, while in the hymenium very narrow gloeocystidia can be found; in thicker fruitbodies "prolonged gloeocystidia can be seen, reaching a length of 150 microns"; the hymenial gloeocystidia contain a number of oil droplets, while such droplets are usually absent in the basal gloeocystidia; HYPHAE monomitic, 1.5-2.5 microns wide, acyanophilic, very thin-walled, without clamp connections; "next to the substrate a layer of varying thickness of more or less parallel hyphae"; texture when young loose, denser when mature, especially in the subhymenial trama, (Eriksson), SPORES 4.5-6 microns in diameter, nearly round, smooth, amyloid, colorless, with 1 droplet; BASIDIA 1-4-spored, 35-45 x 5-7 microns, narrowly clavate; GLOEOCYSTIDIA 40-60 x 15-20 microns, ventricose-rostrate to narrowly fusiform, without visible contents, sulfo-negative; HYPHAE monomitic, 2-3 microns wide, acyanophilic, without clamp connections, (Breitenbach), SPORES (4) 5-6.5(7) microns; BASIDIA, 30-60 x 4-7.5 microns, clavate; GLOEOCYSTIDIA vesicular to fusiform or flexuous-cylindric, 40-100(150) x 7-20 microns, usually sulfo-negative; GENERATIVE HYPHAE 1.5-4(5.5) microns wide, (Stalpers)

Notes:
Collections were examined from BC, OR, ID, AB, ON, PQ, AZ, CA, CO, CT, MA, MI, MT, NC, NJ, NM, NY, PA, TN, UT, VT, WI, WY, and France: the species is also reported from WA, NB, NS, AK, AL, AR, FL, LA, MO, MS, and WV, (Ginns). It is a fairly common species in most parts of Scandinavia, (Eriksson). It is also occurs in Switzerland and Asia, (Breitenbach).

Synonyms and Alternate Names:
Polyporus latemarginatus Durieu & Mont.
Poria ambigua Bres.