Summary:
Features include 1) resupinate growth on alder and willow, 2) an orange-red to pale orange fruitbody, with a distinct gray-whitish border that is fibrillose in young specimens, 3) large elliptic spores, 4) cystidia of 2 types: thick-walled encrusted metuloids and thin-walled sulfocystidia, 5) a monomitic hyphal system, the hyphae with clamp connections.

Microscopic:
SPORES 14-17 x 7.5-10 microns, elliptic, smooth, inamyloid, with droplets, colorless, yellow-pink in deposit; BASIDIA 4-spored, 55-80 x 6-12 microns, cylindric-clavate with basal clamp connection; CYSTIDIA: 1) "lamprocystidia, thick-walled with fusiform incrusted upper part 30-50 x 7-10 microns", 2) gloeocystidia 100-130 x 5-8 microns, sulfo-positive, "thin-walled, with granular contents, arising ascuslike out of the base"; HYPHAE monomitic, 3-5 microns wide, branched, thin-walled, septa with clamp connections, (Breitenbach), SPORES elliptic, smooth, thin-walled, mostly 14-16 x 8-10 microns, colorless (but in spore print yellow or light orange depending on thickness of print); BASIDIA varying but mostly cylindric, "more or less sinuous and constricted, reaching a size of 60-90 x 10-15 microns", with 4 conic sterigmata, "in young fruitbodies some pleurobasidia seen"; CYSTIDIA of 2 types: 1) encrusted, thick-walled metuloids, the distal encrusted part 30-50 x 8-12 microns, the basal unencrusted part of varying length, often with adventitious septation, 2) thin-walled sulfocystidia, numerous especially in young specimens, "reaching a length of 100 or 150 microns and a width of 10-15, sometimes 20 microns", with granular protoplasm reacting to sulfovanillin, "elongate, obtuse, or tapering to an apex"; section showing a basal subicular layer 100-200 microns thick, of dense parallel hyphae, and a subhymenial layer "of mainly vertical hyphae and hymenial elements", at first about 100 microns thick, then increasing in thickness, HYPHAE monomitic, "with thin or slightly thickened walls", with clamp connections, the subhymenial hyphae 3-4 microns wide, richly branched, the subicular hyphae 4-5 microns long, straight, sparsely branched, (Eriksson)

Notes:
Peniophora aurantiaca has been found in BC, WA, OR, ID, AB, MB, NB, NF, NS, NT, ON, PE, YT, AK, MA, ME, MI, MS, MT, NC, NH, NY, PA, and WI, (Ginns). It also occurs in Europe including Switzerland (Breitenbach). It is common in subalpine region of central and southern Europe (Eriksson).

Synonyms and Alternate Names:
Apioporthe anomala (Peck) Hoehn.
Cryptosporella anomala (Peck) Sacc.