Synonyms: Collema bachmanianum (Fink) Degel.; Collema bachmanianum var. millegranum Degel.
Distribution: N - Lomb.
Description: Thallus foliose, homoiomerous, gelatinous when wet, 2-6 cm wide, loosely adnate, dark olive-green to black; lobes 2-4(-6) mm wide, radiating, concave to flat, 200-700 µm thick (when wet), sometimes with many isidia-like warts or lobules. Apothecia lecanorine, sessile and constricted at base, 1.5-3(-4) mm across, with a concave to flat, reddish brown disc, and a coarsely crenulate to lobulate, usually persisting thalline margin. Proper exciple thin, euthyplectenchymatous; epithecium brownish; hymenium colourless, 100-135 µm high, I+ blue; hypothecium colourless. paraphyses simple or sparingly branched, with clavate to subglobose tips; hypothecium colourless. Asci 8-spored, clavate, the apex thick, with a I+ blue apical dome and a I+ blue annulus projecting downwardly. Ascospores submuriform, mostly with 3 transverse septa and 1(-2) longitudinal septa, at first hyaline, then pale yellow or brown, ellipsoid with usually pointed ends, (20-)26-32(-36) x 8.5-15 µm. Photobiont cyanobacterial (Nostoc, the cells arranged in long chains). Spot tests: all negative. Chemistry: without lichen substances.
Note: a mainly arctic-alpine, circumpolar species found on calciferous or base-rich siliceous soil near or above treeline; restricted to the Alps in Italy. Italian samples belong to var. millegranum.
Growth form: Foliose, broad lobed
Substrata: soil, terricolous mosses, and plant debris