Summary:
Features include 1) resupinate growth on pine, 2) a fruitbody that is cream to pinkish or brownish or brownish purple, lighter and fringed / radially fingered toward the margin, the surface with umbos at various points, 3) spores that are cylindric to almost kidney-shaped, 4) cystidia of 2 types: thick-walled encrusted and thin-walled, and 5) often individual brown-walled hyphae traversing a colored area. The description is derived from Weresub(2).

Microscopic:
SPORES (5.5)6-7.2(7.7) x (1.7)2.2(2.5) microns, cylindric, straight to almost kidney-shaped; BASIDIA about 4.5-5.5 microns broad at apex, flexuous-clavate; CYSTIDIA of 2 types: 1) "abundant to rare, projecting or not; when mature, wall of stalk thin, emphasized, or thickened, swollen sometimes to the point of capillarity of the lumen; where brown hyphae frequent, sometimes arising from these with brown stalks; full length as much as 60 microns though frequently shorter, particularly in the hymenium; apex sometimes capped only with a scatter of crystals but characteristically heavily encrusted, from 8 x 5.5 microns to as much as 40 x 15 microns", 2) gloeocystidia generally abundant, but varying from rare, "observed throughout the context and in the hymenium, but typically and most regularly in the upper subicular, transition, and lower subhymenial areas", variable in shape, "most typically strongly vesiculose to globoid", on narrowed stem, "with or without a hyphal rostrum", variable also in size of expanded part: up to 50 microns long (averaging 25 microns), up to 20 microns or more wide but generally 10-15 microns wide; IN SECTION, either colorless or browned "in zones (a) in the basal part of the subiculum or (b) from the transition area halfway or fully into the hymenium or in patches throughout the context, brownish due either to a deposit between hyphae or an impregnation of the walls or cytoplasmic content of the hyphae", context depth (less hymenium) typically 175-350 microns, subiculum "typically looking as if hyphae embedded in a matrix, composed of clearly parallel and mainly horizontal hyphae" (in radial section), transition area more or less gradual, HYPHAE 3.5-7 microns wide (occasionally up to 9.5 microns), "with walls only slightly thickened or swollen to as much as 3 microns in width", subhymenial hyphae "usually with walls considerably narrower than those of the subiculum" "where hyphal outlines may become indefinite through gelatinization, erosion, or cross-striation", most hyphae with colorless walls except in darker-colored patches, but individual brown-walled hyphae traversing a predominantly colorless area, with swollen, attenuate, or contorted or dichotomously branched tips in subhymenium or hymenium, when present, are strongly diagnostic of this taxon

Notes:
Peniophora pseudopini has been found in BC, OR, AB, MB, NT, ON, PQ, MA, ME, NH, NY, PA, and WI, (Ginns).