Description: Thallus crustose, endo- to episubstratic, often forming rounded patches to c. 1 cm across, which later coalesce into several cm wide patches, sorediate. Esorediate areoles, when present, inconspicuous, greyish to greenish, mostly discrete, more or less rounded, convex, up to 0.2 mm across; soralia greyish yellow-white, pale green or pale yellowish green, bursting from the substrate or from the areoles, more or less well-delimited and punctiform when young, later diffuse, forming a sorediate, subleprose crust; soredia farinose, 12-25(-30) μm in diam. Apothecia rather rare, biatorine, 0.15-0.4 mm across, beige to ochre-brown, more or less rounded, adnate, with a flat to slightly convex disc and a thin, usually inapparent, very soon excluded proper margin. Proper exciple poorly developed, of radiating hyphae, containing crystals of gyrophoric acid; epithecium colourless, non-granular; hymenium colourless, with crystals of gyrophoric acid reacting C+ pink, 25-40 μm high, I-; paraphyses coherent, simple to sparingly branched, 1.0-2.5 μm thick at mid-level, often widening upwards, the apical cells up to 6 μm wide; hypothecium colourless, I-. Asci 8-spored, clavate, with a K/I+ blue apical dome penetrated by a narrow, K/I– apical cushion surrounded by a narrow, deeply K/I+ blue zone, the wall K/I- but surrounded by an I+ red-brown, K/I+ blue outer layer, the ocular chamber relatively small, Biatora-type. Ascospores 1-celled (rarely 1-septate), hyaline, ellipsoid or oblong, rarely slightly curved, (7.5-)9-10(-14) x 2.3-4 μm. Photobiont chlorococcoid. Spot tests: thallus and apothecial sections K-, C+ pink, KC+ pink, P-. Chemistry: gyrophoric acid and traces of lecanoric acid.
Note: on bark of various trees, mostly near the base, and on branches of dwarf shrubs, often with B. subduplex; from the Alps there are only a few scattered records, all outside the Italian territory. To be looked for in the Alps.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)