Pertusaria pseudocorallina (Lilj.) Arnold

    Thallus rather thick, often large and up to 15-20 cm across, rough to coarsely verrucose, white-greyish, although most often pale ochre-yellow, pale oche-pink, and even ochre-pink mostly in well-lit areas subjected to seaspray, ochre-pale yellowish, ochre- pale pink (and even clearly ochre-pink in seawater-splashed zones, see Pertusaria pseudocorallina pink form). Prothallus whitish, pinkish or greyish. Thallus covered with numerous small, scattered isidia, erected, digitated, pestle-shaped, constricted at their base and with a rounded dark-brown tip, 0.5-2.5 mm. Seldomly fertile, and in that case, 1-2 to 5 apothecia visible as small round blackish dots within each globose fertile wart (see Pertusaria pseudocorallina fertile for this rather different morph). Ascospores simple, very large, 120-200 x 50-80 µm. C-, K+ yellow turning red (rapid reaction), KC+ yellow turning red or in between, Pd+ golden yellow. Common species, on well-lit siliceous rocks, often recognizable from far by its pale ochre-pink colour and its brown isidia. N.B. Most often, fertile specimen have very few isidia that may render difficult their identification, especially when isidia are completely absent, increasing the probability of confusion with Pertusaria pertusa var. rupestris which is K+ yellow. Also, not to be confused with Pertusaria coccodes, very rare on rocks, with clustered isidia, these latter not constricted at base, tip greyish (and not dark-brown), and pale grey thallus instead of ochre-pink, K+ yellow, KC- and Pd+ orange. N.B. This species is extraordinarily variable and several taxa may be described under this name. Here we described one with clustered "en masse" isidia under the name of Pertusaria pseudocorallina f.  and another, with the thallus more greyish and more areolated by angular areolata, scattered with minute globose and blackish isidia, as Pertusaria pseudocorallina f. microstictica.*