Thallus superficial, in small patches or wide spreading, thin to moderately thick, continuous, somewhat waxy, margin ± entire, rarely zoned; upper surface grey to yellow-green-grey or dark grey, smooth in young thalli, becoming roughened and ± tuberculate, often with deep rimose cracks. Fertile warts to 2 mm diam., often numerous and crowded, obscuring the thallus, semi-globose, often distorted (plicate-deformed), ± constricted at base, containing 1(-4) apothecia.
Anamorph: conidiomata pycnidia, immersed, the ostiole pale. Conidia 13-25 × ca 0.5 μm, straight or somewhat curved.
Teleomorph: ascomata apothecial in structure but initially appearing almost perithecial, discs (0.3-) 0.6-1 (-1.8) mm diam., rounded or rather irregular, often widening, the surface brown- or grey-black, often ± grey-white pruinose, surrounded by an uneven, often somewhat elevated thalline exciple. Epihymenium K+ violet. Interascal tissue composed of copious trabeculate pseudoparaphyses ca 1 µm diam., frequently branched and anastomosing. Asci 350-450 x 55-80 µm, clavate-ellipsoidal, very short-stalked, the apex obtuse with a broad ocular chamber, thick-walled and dehiscing with an irregular apical split, the outer gelatinous layer K/I+ blue, 8-spored. Ascospores arranged biseriately, (60-) 85-110 (-120) × (20-) 30-50 μm, ellipsoidal to fusiform-ellipsoidal, sometimes inaequilateral, distinctly narrower when immature, the wall 5-9 μm thick, to 15 µm at the apex and base, zoned, with a broad gelatinous sheath with a surface that may be minutely transversely striate.
Chemistry: thallus C+ yellow, K–, KC+ orange, Pd–, UV± pale orange (thiophaninic acid, ± O-methylmonochlornorlichexanthone and ± gyrophoric acid).
Assessed by Woods & Coppins (2012) as of Least Concern. The species is common and widespread.
Throughout the British Isles, but rare or absent in central and eastern England. BLS map here.
On bark of woodland, wayside and parkland broad-leaved trees, often in rather shaded sites, rarely on sheltered rocks in woodland.