Summary:
Features include 1) resupinate growth on wood, 2) fruitbodies that are thin, loosely attached, cobwebby-cottony, and grayish white, 3) spores that are elliptic with the apex blunt-rounded, smooth, and inamyloid, 4) 6-spored basidia, 5) a monomitic hyphal system, the basal hyphae wide and thick-walled, the other hyphae more thin-walled, and 6) the absence of clamp connections.

Microscopic:
SPORES 7.5-12 x 3.5-5 microns, obliquely oval, apex obtuse, smooth; BASIDIA (4-)6-spored, 17-25 x 8-10 microns, "at first rounded, then obovate to subcylindrical, somewhat constricted"; HYPHAE monomitic, BASAL HYPHAE 7.5-10 microns wide, yellowish, more or less thick-walled, with sparse branching, without clamp connections, hymenial branches 5-6 microns wide, colorless, more thin-walled, without clamp connections, (Eriksson), SPORES 8-11 x 3.5-4.5 microns, elliptic, obtuse apically, smooth, inamyloid, colorless; BASIDIA 6-(7-)spored, 12-15 x 8-9 microns, cylindric to clavate, without basal clamp connection; CYSTIDIA not seen; HYPHAE monomitic: BASAL HYPHAE 6-9 microns wide, yellowish, thick-walled, somewhat branched, without clamp connections, other hyphae about the same width, thin-walled, without clamp connections, (Breitenbach)

Notes:
James Ginns collected this species from Vancouver Island in BC (J. Ginns, pers. comm.). It has also been recorded from NC and TN (Ginns(5)) and Scandinavia (Eriksson). The distribution includes Europe and Asia (Breitenbach).

Synonyms and Alternate Names:
Hypoxylon mediterraneum (De Not.) J.H. Mill.
Sphaeria mediterranea De Not.