TYPE. UNITED KINGDOM. Scotland, on the stump of a tree, 1807, Anonymous s.n. (BM BM000974981, lectotype designated by R. Santesson, 1966).

Description. Life form. Lichenized fungus.

Thallus filamentous-fruticose, dark brown to black, forming mats, often in small circular patches, decumbent or spreading on the surface, brittle, spiky branched, with outer wall undulating and irregularly corrugated. Filaments 10-20 µm thick, composed of photobiont ensheathed by mycobiont. Photobiont Trentepohlia. Mycobiont hyphae in a single layer, 3-7 µm, hyaline, contorted, nodulose, running the length of photobiont filaments, thick- and smooth-walled, forming tight sheaths around them, undulate to corrugated. Mycobiont cells immersed in the photobiont cell walls; short and barrel-shaped, with strongly thickened walls, I+ blue-black. Ascomata not reported; pycnidia not reported.

Chemistry. No lichen products detected by TLC.

Substrate and Habitat. On siliceous rockfaces, rarely on trunks, in humid environments.

Distribution. Cosmopolitan; in North Carolina found in the Piedmont and Blue Ridge ecoregions.

Notes. This lichen was originally described as an alga. Morphologically it is indistinguishable from Racodium rupestre and older specimens of R. repestre may turn out to be C. ebeneus upon further examination. Microscopically, C. ebeneus is distinguished by the contorted and narrow, nodular, shorter-celled mycobiont hyphae that appear paler than those of R. rupestre.

Literature

Dillwyn, L.W. (1809) British Confervae. W. Phillips, London (original description as Converva ebenea).

Fletcher, A. & D.H. Dalby. (2009) Cystocoleus Thwaites (1849). P. 369 in Smith, C.W., A. Aptroot, B.J. Coppins, A. Fletcher, O.L. Gilbert, P.W. James & P.A. Wolseley (eds.). The Lichens of Great Britain and Ireland. The British Lichen Society, London.

Tian, Q., P. Chomnunti, J.D. Bhat, S.A. Alias, P.E. Mortimer & K.D. Hyde. (2014). Towards a natural classification of Dothideomycetes 5: The genera Ascostratum , Chaetoscutula , Ceratocarpia , Cystocoleus, and Colensoniella (Dothideomycetes incertae sedis ). Phytotaxa 176: 42-54.

Thwaites, G.H.K. (1849) Note on Cystocoleus, a new genus of minute plants. Annals of Natural History. ser. 2, 3: 241-242.