TYPE. Not cited. Original treatment (Michaux 1803): "Hab. Arboricola in Canada et Carolina."

Description. Lichenized fungus.

Thallus foliose, uniformly pale gray; lobes 2-8 mm wide, sometimes divided into narrow lobes; marginal cilia black, scattered; vegetative diaspores absent. Lower surface black with broad brown naked zone under edges; rhizines black, simple, abundant in center, absent near lobe tips. Photobiont chlorococcoid alga. Ascomata lecanorine apothecia, flat to bowl-shaped, unperforated, up to 8 mm diam. Disk concave, brown. Pycnidia black, abundant on lobe tips; conidia hyaline, simple, straight, rod-shaped, 5.5-6.5 μm long.

Chemistry. Cortex K+ yellow (atranorin); medulla K-, KC+ pink, C-, PD+ orange-red (prorocetraric acid).

Substrate and Habitat. On exposed bark of hardwood branches, in forests and open areas.

Distribution. Eastern North America; in North Carolina common throughout.

Literature

Brodo, I.M., S. Duran Sharnoff & S. Sharnoff. (2001) Lichens of North America. Yale University Press, New Haven & London. 795 pp.

Michaux, A. (1803) Flora Boreali-Americana sistens characteres plantarum, quas in America septentrionali collegit et detexit 2: 1-340 (original description as Lobaria submarginalis).