Hypotrachyna revoluta (Flörke) Hale
Thalus foliose, appressed, forming rosette, 5-12 cm across, lobes narrow, indented and well separate, apices turned down, pale brown, upper surface pale glossy grey-blue, pale grey, pale cinder, with mostly marginal soralia , limited in development, not swollen, cortex visible in some places, pale grey-yellowish, greenish, with greenisg farinose soredia; lower surface more or less dark brown towards lobes, blackish towards the center, matt, with short rhizines forked or branched, extending only to lobes, soredia absent. Apothecia rare, 3-6 mm diam., exciple slightly sorediate. Ascospores ellipsoid, colourless, 10-15 x 5-9 µm. Photobiont: trebouxioid. Medulla: C+ dark pink, K-, KC+ red, Pd-. Widely distributed on bark of trunk and main upper branches of trees, also rather common on rocks. Close to Hypotrachyna afrorevoluta of which the soralia are larger, pustulate, marginal, laminal, and lower surface of lobes blackish. On rocks, see also Hypotrachyna britannica of which the soralia are well developed, dark grey with dark blue or indigo.