Summary:
The distinctly reniform [kidney-shaped] spore is the principal distinguishing character of this rare fungus. Features include 1) resupinate growth on conifers, 2) thin, delicate, waxy fruitbodies that are grayish white to pale ochraceous, and smooth to granulose, the margin not especially differentiated, 3) spores that are kidney-shaped, warted, and amyloid, 4) basidia that are suburniform, 5) gloeocystidia that are numerous, obclavate, clavate, and cylindric, the apex rounded, sometimes with 1-2 small papillate apical appendages, the contents pale yellow and granular in KOH and sulfo-positive or sulfo-negative, and 6) a monomitic hyphal system, the hyphae richly branched, with clamp connections. The placement of this species is uncertain: Julich suggested Boidinia in 1982, but Eriksson(3) calls it Gloeocystidiellum subasperisporum (mentioning the anomalous suburniform basidia) and Stalpers(3) appears to favor the latter tentatively, based in part on similarity to Gloeocystidiellum porosum.

Microscopic:
SPORES 4.0-5.0 x 2.5-3.5 microns, reniform, ornamented with rather distinct warts, amyloid, thin-walled, "with a small, rounded, distinct apiculus"; BASIDIA 4-spored, (16)20-24(30) x 3-5 microns, cylindric, suburniform, some with a ventricose base, sterigmata up to 4.5 microns long; GLOEOCYSTIDIA numerous, 18-38 x 3.5-5.5 microns, "obclavate, clavate, cylindric, apex rounded, sometimes with a small papillate tip, thin-walled, the contents pale yellow in KOH under bright field, granular", sulfo-negative (in herbarium collections stored for more than 20 years, but at least one had been reported sulfo-positive when less old, and European collections have been reported to have sulfo-positive gloeocystidia); HYPHAE monomitic; subiculum compact, indistinct, lacking a layer of parallel hyphae next to the substrate; hyphae 1.5-2.5 microns wide, colorless, thin-walled, with a clamp connection at each septum, (Ginns), SPORES 3.5-4.5 x 2-2.5 microns, reniform, finely verrucose, amyloid, thin-walled; BASIDIA subcylindric, in the middle constricted, suburniform, sometimes with adventitious septa, normally 4-spored and with basal clamp connection; GLOEOCYSTIDIA (= pseudocystidia) small, 20-30 x 3-5 microns, very often with 1 or 2 apical appendices, contents in KOH granular, oily, yellowish, with positive reaction to sulfovanillin; HYPHAE monomitic, 1.5-2.5 microns wide, densely intertwined, richly branched, thin-walled, with clamp connections; "subhymenial trama very little developed in the specimens studied", (Eriksson), SPORES 3.5-5 x 2-3.5 microns, reniform, warted; BASIDIA 20-30 x 3-5 microns, urniform to subcylindric; GLOEOCYSTIDIA 18-38 x 3-5.5 microns, often with 1 or 2 apical constrictions, sulfo-positive; HYPHAE 1.5-2.5 microns wide, thin-walled, (Stalpers)

Notes:
Collections were examined from BC, ON, PQ, and Sweden, (Ginns).

Synonyms and Alternate Names:
Hypoxylon punctatum (L.) Grev.
Poronia truncata (Bolton) Fr.