TYPE. UNITED STATES. South Carolina, [Berkeley County], Santee Canal, 1849, H.W. Ravenel s.n. (FH-Tuck., lectotype designated by G. Degelius 1974).
Description. Lichenized fungus.
Thallus foliose, up to 6 (-10) 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, ~0.5 mm diam., sessile; disk flat to convex, pale red, strongly white pruinose, pruina thinning in older apothecia; thalline rim pseudocorticate, well-developed. Exciple distinctly euparaplectenchymatous (cells as in main type); 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 somewhat curved, usually 6-celled (4-7-celled), (46-)50-70(-86) x (2-)3-4.5(-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. Corticolous on tree trunks.
Distribution. Eastern North America; in North Carolina found throughout.
Literature
Degelius, G. (1974) The lichen genus Collema with special reference to the extra-European species. Symbolae Botanicae Upsaliensis 20: 1-215.
Tuckerman, E. (1882) A synopsis of the North American lichens. Part. I. Comprising the Parmeliacei, Cladoniei and Coenogoniei. S.F. Cassino, Boston, 262 pp (original description as Collema nigrescens var. leucopepla).