TYPE. “Habitat in corticibus arborum, praesertim Quercus frequens.” (Wiegel 1772; JE – not found per Frisch et al. 2015).

Description. Lichenized fungus.

Thallus extensive, whitish to pale tan, continuous, rimose or evanescent, largely immersed; surface ecorticate, matt, scurfy to weakly felted-arachnoid, sometimes patchily granulose; prothallus absent. Photobiont trentepohlioid alga. Ascomata arthonioid apothecia,  rare, adnate, rounded to slightly undulate in outline, weakly to strongly convex, densely white-pruinose, 0·4–1 mm diam. and 110–200 μm tall; exciple poorly differentiated; epithecium 10–25 μm thick, greyish to brown, inspersed with pale granular crystals 1–3 μm diam.; hymenium hyaline to pale yellowish brown, 45–65 μm high, moderately gelatinized; hypothecium dark brown, 50–120 μm high; paraphysoids 1–1·5 μm diam., the apices slightly widened to ca 2 μm diam., with sparse dark brown pigment attached to the outer wall. Asci clavate to broadly clavate (arthonioid), 37–46 × 15–19 μm; ascospores obovoid, 11–19 × 4–6 μm, 2–5-septate, slightly macrocephalic. Pycnidia emergent, 0·15–0·4 mm diam., dark brown to black but covered by a thick whitish pruina; conidia bacilliform, (4–) 4·5–6 × 1–1·5 µm.

Chemistry. K−, C−, KC−, Pd−, thallus hyphae I+ pale blue, KI+ pale blue (euamyloid); byssaceum unknowns detected by HPTLC, probably 2'-O-methylperlatolic acid and one accessory compound.

Substrate and Habitat. Corticolous on trees, especially oaks, in old growth forests.

Distribution. Temperate Europe, eastern North America, Asia (Japan, Russian Far East); in North Carolina recorded from one county in the Blue Ridge ecoregion.

Literature

Cannon, P., D. Ertz, A. Frisch, A. Aptroot, S. Chambers, B. Coppins, N. Sanderson, J. Simkin & P. Woseley. (2020). Arthoniales: Arthoniaceae. Revisions to the British and Irish Lichens 1: 1-48.

Frisch, A., Y. Ohmura, D. Ertz & G. Thor, G. (2015) Inoderma and related genera in Arthoniaceae with elevated white pruinose pycnidia or sporodochia. The Lichenologist 47(4): 233-256.

Gray, S.F. (1821) A natural arrangement of British plants. 1:1-824.

Weigel, C.E. (1772) Observationes Botanicae. 51 pp. (original description as Sphaeria byssacea).