Hypotrachyna laevigata (Sm.) Hale forme corticole.

    Thallus foliose, to 15 cm across, loosely attached, lobes 1-3 cm wide, 1-6 mm long, branched and more or les dichotomously divided, tips truncate, upper surface pale grey-blue, glaucous and slightly spotted, lower surface blackish with branched rhizines (in "forest of dead trees") extending to margins, grey globose soralia frequent at lobe margins, 1-2 mm. Apothecia rare, markedly constricted towards the base, stalked, 3-8 mm diam., disc concave, dark brown-red, exciple smooth and mostly sorediate, torn when old. Ascospores simple, ellipsoid, colourless, 18-21 µm. Photobiont: trebouxioid. Cortex : K+ yellow ; medullae : C+ pale orange, K-, KC+ orange, Pd-. Rare, on mossy barks of old Quercus in oceanic woodlands subjected to a high precipitation amount.

N.B. There is a saxicolous form of the rocks of the oceanic heathlands: Hypotrachyna laevigata forme saxicole which is more whitish.