TYPE. “Habitat in America Septentrionali” (Acharius 1814); G.H.E. Mühlenberg s.n. (H-ACH, lectotype, UPS, isolectotype); G.H.E. Mühlenberg 112b (PH, syntype)
Description. Lichenized fungus.
Thallus foliose, 2-4 cm diam., membraneous, thin, ± rounded, often unilaterally developed, adnate, ± deeply and broadly lobate, dark olive-green, strongly pustulate; pustules dense, rounded or extended, towards center of thallus often long and ridge-like, radiating; lower surface with corresponding depressions; lower surface paler, often greyish, matt or a slightly glossy. Lobes and lobules few, rounded or somewhat extended. ± imbricate; margin entire, slightly ascending; lobules usually 0.3-0.5(-1.0) cm broad. Vegetative diaspores absent. Photobiont Nostoc cyanobacteria; cells in chains throughout the thallus (i.e., not stratified), most abundant toward the upper surface, globose or oblong, 3-4.5(-6.5) µm; heterocysts up to 8 µm; gelatine I-. Ascomata lecanorine apothecia, numerous, often crowded, 0.5-1.0(-1.5) mm diam., sessile with constricted base; disk flat to convex, pale to dark red, epruinose; thalline rim thin, entire, disappearing; pseudocortex lacking or poorly developed. Exciple up to 90 µm thick (usually 50-65 µm), thinner marginally, euparaplectenchymatous (cells up to at least 20 µm diam; 8.5- 15 µm marginally; epithecium indistinct; hymenium hyaline, I+ blue; subhymenium and hypothecium pale yellow or pale brown, I+ blue; paraphyses simple or occasionally branched, tips somewhat expanded. Asci clavate to subcylindrical, 8-spored, wall thickened toward apex. Ascospores hyaline, acicular, straight or variously curved, 6-celled, end cells extended, smooth, (32)34-70(-8 4) x 3- 5(-6.5) µm. Pycnidia frequent, superficial, immersed, globose to subglobose, 170-200 µm diam., pale or yellowish within; conidia hyaline, straight, swollen at ends, 4.5-6 x 1.2-1.5 µm.
Chemistry. Not reported.
Substrate and Habitat. On bark and rock in moist areas.
Distribution. Cosmopolitan, primarily in eastern North America; in North Carolina found throughout.
Literature
Acharius, E. (1814) Synopsis Methodica Lichenum. Lund. 392 pp.
Degelius, G. (1974) The lichen genus Collema with special reference to the extra-European species. Symbolae Botanicae Upsaliensis20: 1-215.