Summary:
Features include 1) resupinate growth on conifer wood, 2) a fruitbody surface that white to grayish white, and porous-furfuraceous, 3) spores that are round, bluntly spiny, and amyloid, 4) gloeocystidia that are cylindric, with yellowish granular contents, and 5) a hyphal system that is monomitic with clamp connections. Note the different accounts of whether gloeocystidia are sulfo-positive.

Microscopic:
SPORES 4.4-6.0 in diameter, round, echinulate, amyloid, thin-walled, with a peg-like distinct apiculus; BASIDIA 4-spored, 24.0-36.0 x 4.5-6.0 microns, "suburniform, when mature cylindric and sometimes with a ventricose base, some pleurobasidiate", sterigmata up to 4.0 microns long, GLOEOCYSTIDIA numerous, 25-65 x 4-8 microns, "cylindric to slightly fusiform", "originating next to the substrate, terminating among the basidia", thin-walled, the contents colorless to yellowish, granular in KOH, sulfo-negative [note sulfo-positive in European specimens, see below]; HYPHAE monomitic, subiculum "sparse, a few strands of repent horizontally oriented hyphae"; hyphae "loosely arranged, distinct next to substrate, with a clamp connection at each septum", 1.5-3 microns wide, the walls colorless, thin; "subhymenial hyphae remaining diffuse, distinct", (Ginns(24)), SPORES 6-7 microns in diameter including ornamentation, nearly round to round, echinulate [spiny], amyloid; BASIDIA 27-35 x 4.5-5.5 microns, "tubular to subclavate, more or less sinuose, old basidia with one or more adventitious septa", normally 4-spored; GLOEOCYSTIDIA (= pseudocystidia) "tubular, more or less sinuose, often laterally borne on the bearing hyphae, 50-90 x 7-10 microns, in young specimens shorter, thinwalled, filled with oily yellowish granular contents, with positive reaction to sulfovanilline" [but note above North American specimens sulfo-negative]; hyphal structure monomitic, hyphae 2-3 microns wide, loosely interwoven, richly branched, clamp connections at all septa, (Eriksson), SPORES 5-6.5 microns in diameter excluding ornamentation, round to nearly round, echinulate, colorless, thin-walled to somewhat thick-walled, spines up to 0.5 microns long, strongly amyloid, with prominent apiculus, ornamentation instantly disappearing in 6% KOH; BASIDIA 22-35 x 4-5.5(6) microns, "terminal, rarely lateral", subcylindric "and often flexuous to clavate or urniform with a basal swelling", typically 4-spored; GLOEOCYSTIDIA 30-90 x (4)6-10 microns, terminal or more rarely lateral, cylindric, "often flexuous or somewhat swollen at the base, thin-walled, typically with yellowish contents", sulfo-positive but sometimes reaction very weak; HYPHAE monomitic, SUBICULAR HYPHAE 2-3(3.5) microns wide, loosely interwoven, colorless, thin-walled to rarely thick-walled, regular or sometimes with swellings, SUBHYMENIAL HYPHAE 1.5-3 microns wide, denser than subicular hyphae, thin-walled; all primary septa with clamp connections, (Hjortstam), SPORES 4.5-6 microns in diameter excluding ornamentation, round, bluntly verrucose-spinose, colorless, warts up to 0.7 microns long; BASIDIA 4-spored, 23-32 x 4-5.5 microns, with basal clamp connection, some with secondary septa; GLOEOCYSTIDIA 50-75 x 3.5-5 microns, sinuous, with yellowish contents, sulfo-positive; HYPHAE monomitic 1.5-3 microns wide, most septa with clamp connections, (Breitenbach), SPORES 4.5-6 microns in diameter, GLOEOCYSTIDIA sulfo-negative, (Ginns(23))

Notes:
Collections were examined from BC, OR, MB, ON, PQ, FL, MN, MS, WI, and Italy, (Ginns(24)), Sweden and Norway, (Eriksson), the Netherlands (Hjortstam), and Switzerland and Asia, (Breitenbach).