TYPE. Amer. bor. [North America]. G.H.E. Mühlenberg 1410 (H-ACH, holotype).
Description. Life form: lichenized fungus.
[Modified from Hinds & Hinds (2007)] Thallus foliose, adnate, 3-6 cm diam.; lobes short, irregularly branched, sublinear, truncate, 1-2 mm wide, contiguous with sparse, short (0.3 mm), black cilia, mostly in axils. Upper surface gray, densely isidiate. Isidia short-cylindrical, occasionally branched. Photobiont chlorococcoid alga. Medulla white or yellowish to pale orange. Lower surface black; rhizines short, simple, near margins. Ascomata lecanorine apothecia, rare.
Chemistry. Cortex K+ pale yellow (atronorin); medulla K+ yellow, PD+ orange (galbinic acid, secalonic acid A, salazinic acid).
Substrate and Habitat. Saxicolous on noncalcareous rocks in forests.
Distribution. Eastern North America; in North Carolina found in the Blue Ridge and Piedmont ecoregions.
Acharius, E. (1814) Synopsis Methodica Lichenum. Lund. 392 pp (original description as Parmelia obsessa).
Hinds, J.W. & P.L. Hinds (2007) The Macrolichens of New England. Memoirs of the New York Botanical Garden No. 96. New York Botanical Garden Press, Bronx, New York. 584 pp.