Description: Thallus foliose, heteromerous, dorsiventral, forming rosettes to 15 cm in diam. Lobes large, to 30 mm wide (usually less), rounded, flat to concave with up-turned, wavy margins. Upper surface smooth to roughened. ashy to reddish brown when dry, olive-green when wet, sometimes densely white-reticulated. Lower surface bright orange, with brownish-orange, branched veins and yellow to orange interspaces, more or less tomentose, with black rhizines. Upper cortex paraplectenchymatous; photobiont layer divided into an upper part with green algae and a lower part (intenernal cephalodia) with Nostoc; .medulla bright orange; lower cortex absent. Apothecia frequent, rounded, without a thalline margin, semi-immersed in the thallus, up to 12 mm across, with a brown to black disc. Epithecium brownish, hymenium and hypothecium colourless; paraphyses not anastomosing, simple, not apically thickened, adglutinated. Asci (6-)8-spored, clavate, fissitunicate, the thickened apex with a K/I+ blue ring, Peltigera-type. Ascospores 1-septate, not constricted at septa, brown, oblong-ellipsoid, 30-55 x 10-14 μm, the wall ornamented with rounded papillae. Photobiont chlorococcoid (Coccomyxa) in thallus, Nostoc in the internal cephalodia. Spot tests: upper cortex K-, C-, KC-, P-, UV-; medulla and lower surface K+ purple. Chemistry: medulla with solorinic acid.
Note: an arctic-alpine, circumpolar lichen found on acid mineral soil with a long snow-lie, mostly above treeline, reaching the nival belt in the Alps; restricted to the Alps and the northern Apennines in Italy.
Growth form: Foliose, broad lobed
Substrata: soil, terricolous mosses, and plant debris