Description: Thallus crustose, episubstratic and usually well-evident, granulose-verrucose to minutely squamulose, dark grey, olivaceous brown or greenish brown. Apothecia stalked, pin-like, 0.5-1.2 mm high. Stalk stout, pale to dark brown, epruinose or sometimes yellowish-pruinose in upper part, of periclinally arranged, medium brown hyphae; outer part of stalk hyaline, of strongly gelatinized hyphae. Capitulum 0.1-0.3 mm across, deep purple brown, sometimes yellowish pruinose in lower part, broadly obconical to lenticular, with a well-developed excipulum of periclinally arranged hyphae. Mazaedium well-developed, brown; hypothecium medium brown, broadly obconical, with a flat to slightly convex upper surface. Asci cylindrical to narrowly clavate, formed singly from branched ascogenous hyphae, dissolving early, with 1-2-seriate ascopores. Ascospores 1-celled, brown, globose, 6-7 µm wide, the wall with irregular cracks delimiting polygonal areas. Photobiont chlorococcoid, with globose cells. Spot tests: thallus K-, C-, KC-, P-. Chemistry: thallus without lichen substances; yellow pruina with vulpinic acid.
Note: a cool-temperate, holarctic lichen found on old oaks in open woodlands, in bark fissures seldom wetted by rain; certainly more widespread in the Alps.