Summary: Features include 1) resupinate growth on wood, 2) a very thin, waxy fruitbody, forming a whitish-grayish bloom on the wood, under a lens finely pored, with the margin not differentiated, 3) spores that are allantoid, smooth, and inamyloid, 4) microscopic features (characterizing the genus) of the basidium which forms perpendicularly from the sparse basal hyphae by "internal repetition" from a previous basidium, forming a stem that has no septa but has clamp connections and other traces from previous basidia at intervals, 5) tube-like cystidia that are thick-walled and homogeneous, and have one or two transverse septa with clamp connections, 6) a monomitic hyphal system, the hyphae thin-walled, with short perpendicular branches, and clamp connections.
Microscopic: SPORES 8-10 x 3.5-5 microns, allantoid, smooth, inamyloid, acyanophilic, thin-walled; BASIDIA 4-spored, 8-15 x 5-7 microns, pyriform [pear-shaped], with basal clamp connection; CYSTIDIA 30-50 x 3.5-6(10) microns, "more or less tube-like, obtuse, often somewhat sinuose or constricted", "thick-walled, contents homogeneous, more or less light-refracting in phase", with one or two septa with clamp connections; HYPHAE monomitic; "hyphae thin-walled, with clamp, basal hyphae 2-3 microns wide, spreading over the substrate; short perpendicular hymenial branches, to 50 microns long", (Eriksson)
Notes: Repetobasidium macrosporum has been found in BC, (Ginns), and Germany, Norway, and Sweden, (Eriksson).