Pertusaria pertusa (Weigel) Tuck.
Thallus crustose, to 5-10 diam., rather thick, smooth to slightly rugose, greyish, grey-greenish, greenish (in continuously shaded habitats), prothallus paler, sometimes heterogeneous, covered with numerous globose warts, irregular, tips flattened and restricted at base, 1-3 mm tall, 1-2 mm diam.. Apothecia numerous at the tips of fertile warts, clustered by 1-10, punctiform, seldom well opened, disc blackish at the bottom of a minute crater. Ascii 2-spored, Ascospores narrowly fusiform, thick walls, 150-250 x 40-80 µm. C-, K+ yellow, KC+ yelow, Pd+ orange, UV+ orange. Not especially maritime species common on smooth or rough bark of tree trunks, much rarer on mossy rocks, see Pertusaria pertusa var. rupestris and Pertusaria rupestris var. rupestris forma and thus easy to confuse with fertile forms of Pertusaria usually infertile in particular with Pertusaria pseudocorallina.