TYPE. "Habitat in America Septentrionali" (Acharius 1814), Muhlenberg s.n. (H, lectotype designated by Degelius 1974; UPS, isolectotype).
Description.Life form: Lichenized fungus.
[Modified from Degelius (1974)] Thallus foliose, membraneous, 2-4+ cm diam., thin, 65-110 μm thick when wet, ±rounded but often unilaterally developed, adnate, strongly pustulate, ±deeply and broadly lobate, dark olive-green matt or slightly glossy when dry, translucent dark greenish when wet. Lobes and lobules few, rounded or somewhat extended, ±imbricate with entire and sometimes a little ascending margin; lobules 0.3-0.5 (-1.0) cm wide. Vegetative diaspores often absent, rarely with very small isidia-like protuberances. Pustules dense, rounded or extended towards thallus center, often long and more ridge-like, radiating; lower surface with corresponding depressions. Lower surface paler than upper, often grayish. In section not stratified with a thin to disappearing pseudocortex; hyphae loose, 1-4 μm thick; photobiont Nostoc cyanobacterium; cells in chains, most abundant near upper surface, globose, 3.0-4.5(-6.5) μm diam.
Ascomata lecanorine apothecia, abundant and crowded, laminal, mostly on pustules and ridges, sessile with constricted base, 0.5-1.0(-1.5) cm diam. Disk flat to convex, pale to dark red, matte to somewhat glossy, epruinose. Margin thin, entire, smooth to finely rugose, persistent to disappearing. In section apothecia 200-300 μm tall when dry, ~600 μm when wet. Thalline exciple structurally similar to thallus; proper exciple hyaline, 50-65(-90) μm thick below hymenium, thinner laterally. Subhymenium up to 65 μm thick, pale yellow or pale brown. I+ blue. Hymenium 85-130 μm high, I+ blue. Paraphyses simple or somewhat branched, ~ 2 μm thick in K, tips sometimes thickened to 4.5 μm. Asci clavate to subcylindrical, 56-90 x 17-26 μm, wall toward s apex thickened. Ascospores usually 8 per ascus and polystichous (generally at same level in a cluster), straight or curved or flexuose in asci, acicular to subbacillar, shorter spores occasionally subfusiforrn or clavate, 6-celled with one or both end cells extended, not constricted at septa, hyaline, (32-)34-70(-84) x 3-5(-6.5). Pycnidia frequent, superficial, immersed, visible on both sides of thallus as small protuberances usually paler than thallus, with a dark center on upper side, globose or subglobose, 170-200 μm diam., pale or yellowish within. Conidia straight, slightly swollen toward ends, 4.5-6.0 x 1.2-1.5 μm.
Chemistry. Not reported.
Substrate and Habitat. Corticolous.
Distribution. Africa, Asia, North America; in North Carolina throughout.
Acharius, E. (1814) Synopsis Methodica Lichenum. Lund (original description).
Degelius, G. (1974) The lichen genus Collema with special reference to the extra-European species. - Symbolae Botanicae Upsaliensis20: 1-215.