Summary:
Among Peniophora species Peniophora unica is characterized by 1) the wax-like character, 2) large cystidia and 3) minute spores, (Jackson). Other features include 4) effused growth on subalpine fir, 5) a white to cream buff fruitbody that is thin, firmly attached, and pruinose or minutely bristly, 6) spores that are smooth and inamyloid, 7) cystidia that are obclavate or cylindric, when young thin-walled, often with slight encrustation, becoming thick-walled, and 8) hyphae with clamp connections. The description is derived from Jackson(1).

Microscopic:
SPORES 3-3.5 x 2-2.5 microns, elliptic, laterally flattened with minute apiculus, smooth, inamyloid, thin-walled; BASIDIA 4-spored, 18-20 x 3-4 microns, clavate to cylindric, with slender, nearly straight sterigmata; CYSTIDIA 55-75 x 12-16 microns, broadly obclavate or subcylindric, rarely fusiform, tapering to a narrow, obtuse apex, when young thin-walled and often with slight encrustation at apex, becoming thick-walled and devoid of contents, often with 1 to 4 pseudosepta at maturity, embedded in the upper layer of the substrate or extending one third to one half of length above hymenium; "subiculum of two layers of about equal thickness, the lower layer made up of loosely interwoven, nodulose hyphae, 2-3 microns in diameter, the upper layer somewhat obscure but made up of closely compacted upright hyphae, all hyphae with clamps"

Notes:
Peniophora unica was described from BC and is known only from the type specimen.