Punctelia subrudecta
Thallus to 6 cm diam., often rosette-forming. Lobes 5-10 mm wide, closely appressed and contorted centrally, more loosely appressed, becoming overlapping and ± ascending at the apices; margins ± rounded, entire or with small indentations. Upper surface pale grey, grey or rarely tinged yellow, often uneven and pitted. Pseudocyphellae small, sparse to dense, mostly punctiform, occasionally elongating slightly and becoming sigmoid, often developing into rounded, dot-like soralia. Soredia coarse, occasionally becoming blackened or semi-corticate, also occurring along margins where they are formed from the lower cortex of the recurved lobe. Lower surface pale brown, sometimes almost white near the edges. Rhizines dense, simple or rarely clumped, often with slightly paler tips, not extending to the margin.
Anamorph: conidiomata pycnidia. Conidia 5-7 × ca 1 μm, the apices hook-shaped.
Teleomorph: ascomata apothecia, very rare, semi-stalked, to 5 mm diam. Disc red-brown, deeply concave. Thalline exciple uneven, crenate, smooth or partially sorediate. Ascospores 14-17 × 12-15 μm, subglobose to ellipsoidal.
Chemistry: cortex K+ yellow. Medulla C+ red, K–, KC+ red, Pd–, UV– (atranorin, lecanoric acid).
Assessed by Woods & Coppins (2012) as of Least Concern.
Like Punctelia borreri but the lower surface is pale brown or partly white, and marginal soralia develop from the lower cortex of recurved lobes.
Common and relatively widespread, throughout the British Isles except N Scotland and industrialized areas in C & N England. BLS map here.
On bark of broad-leaved trees, more rarely on wood, also amongst mosses on siliceous rocks, walls, roofing tiles, or standing stones in well-lit situations.