Thallus: foliose, medium-sized to rather large, 2-6 cm wide, rounded, ridged, loosely adnate, deeply lobate lobes: 2-4(-6) mm wide, 200-700 µm thick (moist), much swollen when moist, with a few, short to extended, radiating, ±contiguous and imbricate, flattened or slightly concave, deeply lobulate, often with ±erect accessory lobules; margin: swollen, folded and plicate upper surface: dark olive-green or black, dull, epruinose isidia: absent but isidia-like accessory lobules often present lower surface: paler than upper surface Apothecia: absent or numerous, sometimes crowded, laminal or marginal, sessile with constricted base, 1.5-3 mm wide, sometimes more disc: plane to deeply concave to sometimes slightly convex, light or dark red, usually not glossy, smooth, epruinose thalline margin: thin to thick, coarsely crenulate to finally lobulate, usually persisting, poorly developed pseudocortex sometimes present true exciple: usually thin, euthyplectenchymatous hymenium: hyaline, 100-135 µm tall asci: narrowly clavate to subcylindrical, 8-spored or less ascospores: usually pale yellow or brown when mature, ellipsoid, with acute or obtuse ends, straight, submuriform, 5-6-celled, not constricted at septa, (20-)26-32(-36) x 8.515 µm Pycnidia: common or lacking, immersed conidia: commonly lacking but with internal conidia produced from common, internal thallus hyphae, bacilliform or acicular, 10.5-13 x 2-3 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on soil among mosses World distribution: North America, Iceland, Greenland, Europe, and Siberian Far East Sonoran distribution: southern California. Notes: Collema bachmannianum was recognized only once in a H.E. Hasse collection labeled "Collema pulposum" (=C. tenax) from San Gabriel Mts. at 800 m. Collema bachmannianum is more common in northern North America. It is distinguished from the otherwise very similar Col-lema tenax by its slightly broader, submuriform ascospores that are typically pale yellow or brown. Furthermore, the apothecial margin becomes distinctly lobulate whereas in Collema tenax the apothecial margin remains smooth or becomes slightly crenate or nodulose. In Collema bachmannianum, a special type of conidia is formed: the so-called internal conidia formed from hyphae within the thallus. They are larger then common conidia produced in pycnidia in other Collemae.