Aspicilia leprosescens (Sandt.) Motyka

     Thallus crackled-areolate, granulose to squamulose, areoles flat to slightly convex, as soiled by greenish schizidia, pale grey, grey then turning brown when old (look like cement spots on rocks), often displaying minute branched cracks substellate on flat substrata. Prothallus more or less developed, green-grey, grey-blue, grey, delimiting. Apothecia usually scarce, sometimes absent, sometimes numerous (in case of favourable conditions), 1-2 (3) per areole, less than 1 mm diam., at first concave, later slightly erumpent; thalline margin thin, mostly paler than the thallus. Ascospores simple subglobose to broadly ellipsoid, 14-30 x 7-16 µm. C-, K-, KC- and Pd-. Photobiont : Trebouxia. Uncommon, on nutrient-rich siliceous rocks, potentially forming large conspecific colonies visible as conspicuous white films on rock pinnacles well exposed to wind and sun of the xeric supralittoral zone, in general on horizontal surfaces used as sea-bird perches, also at the top of harbour walls and enclosure walls of chapels near the sea.

N.B. This species is highly variable according to environmental conditions: grey-brownish (cement-like) and almost smooth (erosion effect) on horizontal surfaces, grey-bluish to grey-green and granulose on vertical walls.

_ See also Aspicilia caesiocinerea that may be found in the supralittoral zone, K-, but less smooth due to protruding areoles and apothecia.