Lepra corallina (L.) Hafellner =Pertusaria corallina (L.) Arnold

    Thallus crustose, 1-3 mm thick, up to 15 cm across, verrucose, white-greyish, covered with abundant coralloid isidia, 1-2 mm tall, tip rounded, concolourous to the thallus (and not brown), fragile and often broken leaving a round scar, prothallus whitish. Apothecia very rare, 0.3-0.5 mm diam., clustered by 2 to 6 at apices of fertile warts, disc brown, more or less pruinose. Ascii 2-spored. Ascospores simple, 80-150 x 40-80 µm. C-, K+ yellow to orange, KC+ yellow, Pd+ orange. Not especially maritime but able to tolerate seaspray, on dry siliceous rocks. To be compared with Pertusaria pseudocorallina of which the thallus is pale ochre-pink with less abundant isidia, with brown tips, K+ yellow > red. A K+ brown-red chemotype may be found in the center of Finistère: Lepra corallina forma *