Summary:
Features include 1) resupinate growth on conifer wood, 2) a wax-like fruitbody that is gray-whitish to pale buff, the surface smooth to tuberculate, under a lens appearing velvety, 3) a margin that is white and fringed, and rolls back when dried, 4) spores that are elliptic, smooth, inamyloid, and colorless, 5) cystidia that are awl-shaped to conic, projecting, becoming thick-walled, the upper half becoming encrusted, often with septa, and 6) a monomitic hyphal system, the hyphae more or less thick-walled except in the hymenium, without clamp connections except on some septa in subiculum. Phlebiopsis gigantea has been used to control Heterobasidion annosum, a polypore that infects conifers, (Lincoff).

Microscopic:
SPORES 5-7 x 3-3.5 microns, elliptic, smooth, inamyloid, colorless; BASIDIA 4-spored, 25-33 x 5-6 microns, narrowly clavate, without basal clamp connection; LAMPROCYSTIDIA up to 70-100 x 12-20 microns, subulate [awl-shaped], projecting beyond hymenium, thick-walled, upper half encrusted; HYPHAE monomitic, 2.5-5.5 microns wide, thin-walled to thick-walled, septa without clamp connections, (Breitenbach), SPORES 4.5-6(8) x 2.5-3 microns, oblong - narrowly elliptic - subcylindric, "with adaxial side mostly straight in mature spores", smooth, inamyloid, acyanophilic, thin-walled; BASIDIA 16-22 x 4-5 microns in mature fruitbodies, in young fruitbodies longer (up to 42 microns), apically dilated, 4-spored, without basal clamp connection; CYSTIDIA numerous, 60-90 x 10-20 microns, projecting 30-50 microns, conic and richly encrusted in the apical part, "basally with thickened walls, often with adventitious septa, in young state thin-walled", in the beginning bald but soon covered with crystals (in old enclosed cystidia encrustation often dissolved); HYPHAE monomitic, "2-5 microns wide, thin-walled and narrow in the hymenium, other hyphae with more or less thickened walls, clamps lacking except at some septa in the subiculum"; SUBHYMENIUM "thickening, with densely united hyphae, therefore ceraceous when wet, corneous when dried"; SUBICULUM "mostly very thick, interwoven with strands of parallel hyphae, in younger fruitbodies such strands may penetrate the hymenium and cause peg-like projections", a layer of the subiculum next to the subhymenium often ceraceous - corneous, "dark colored in dry section, while the main part of the subiculum is white", (Eriksson)

Notes:
Phlebiopsis gigantea is found in BC, OR, ID, NB, NS, ON, PQ, AK, AR, AZ, CA, CO, FL, GA, LA, MA, MD, MI, MN, MS, MT, NC, NH, NJ, NM, NY, PA, SC, SD, TX, VA, and WI, (Ginns). It is also found in Mexico (Lincoff), in Europe including Switzerland, and in Asia, (Breitenbach), and in all parts of Scandinavian forests with conifers, (Eriksson).

Synonyms and Alternate Names:
Poria romellii Donk