Description: Thallus crustose, episubstratic, beige, ochre or greyish brown. greenish in shaded situations, of scattered to contiguous, irregular, 0.05-0.3 mm wide, weakly to strongly convex, frequently crenate, sorediate areoles, often delimited by a whitish prothallus; soralia irregular in outline, poorly delimited, 0.4-1 mm in diam., brown in exposed parts, whitish within, appearing greenish in shade, often coalescing into a subleprose crust. Apothecia rare, biatorine, rounded to irregular in outline, sessile and constricted at base, 0.4-1.2 mm across, with a reddish brown, flat to strongly convex, often tuberculate disc, and a concolorous or paler, weakly raised, finally often excluded proper margin. Proper exciple orange-brown in outer part, colourless or pale yellow within, with small granules, of strongly gelatinized, radiating hyphae; epithecium pale orange brown to reddish brown, granulose, the granules sometimes streaking into the hymenium; hymenium colourless, 55-85 µm high; paraphyses sparingly branched and anastomosing, c. 1 µm thick at mid-level, the apical cells to 2.5 µm wide; hypothecium colourless or pale yellowish. Asci 8-spored, cylindrical-clavate, the I+ blue tholus with a wide, I+ dark blue tube structure that expands towards the top, without a pale axial body, approaching the Micarea-type. Ascospores 1-celled, hyaline, ellipsoid, 11.5-15.5 x (5-)6-7(-8) µm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-, UV+ white. Chemistry: lobaric acid.
Note: a mainly boreal-montane, probably circumpolar lichen found especially on basal parts of trunks, on bark, sometimes on lignum, mostly in upland areas; probably more widespread in the Alps.