Thallus foliose, attached by adhesive discs below, to 10 cm diam., ± loosely attached, forming rosettes or irregularly spreading, often forming large patches; lobes 2-3 mm wide, ± hollow, often ascending towards the tips. Upper surface corticate, grey, smooth, ± shining, lacking isidia and pseudocyphellae, sorediate. Soralia lip-shaped, developing from the rupture of the underside tips of the lobes, becoming upturned and fan-like. Medulla white, hyphae loosely woven, arachnoid. Lower surface black, corticate, shiny, wrinkled, without rhizines. Photobiont chlorococcoid.
Anamorph: conidiomata pycnidial, minute and punctiform, immersed and blackened around the ostiole. Conidia 5-8 × 1 μm, weakly bifusiform to cylindrical.
Teleomorph: ascomata apothecia, rather rare, with short, thick stalks; disc yellow- to red-brown, shining, ± flat; thalline exciple thin, persistent. Ascospores not seen in GB&I material.
Chemistry: cortex K+ yellow; medulla and soralia C–, K–, KC+ red, Pd+ orange to red, UV+ pale violet-blue (atranorin, chloroatranorin, physodic acid, physodalic acid, ± 3-hydroxyphysodic acid and ± protocetraric acid).
BLS page: here.
Assessed as of Least Concern (Woods & Coppins, 2012).
One of the most ubiquitous macrolichens in the British Isles and absent only where mean SO2 levels exceed 100 μg/m3. Also known from Europe, Macaronesia, N. & S. America, Asia and Africa.
On siliceous rocks, trees, Calluna stems and other acidic (c. pH 4.5) substrata, supralittoral to montane.