Micarea lignaria (Ach.) Hedl. var. lignaria
Thallus crustose, granulose, granules to 0.1-0.3 mm diam., pale grey when dry, grey-brownish tinged olivaceous when moist. Apothecia numerous, sessile or shortly stipitate, globose, 0.2-0.8 mm diam., black, usually inmarginate. Ascospores colourless, narrowly ellipsoid to fusiform, sometimes slightly curved, 3-7-septate, 16-36 x 4-6 µm. Photobiont: micareoid. Thallus: C-, K-, KC-, Pd+ red; apothecia (in section) C-. Rather common, on various acid substrata: mosses, plant debris, humid rocks in shaded areas, old walls, etc.
N.B. There is a rarer oceanic variety with a thallus sometimes tinged with yellowish: Micarea lignaria var. endoleuca which is: C + orange, KC + red-orange, K-, P-.