Lecania fructigena Zahlbr.
Thallus crustose, more or less areolate, spread over the rocks without clear margin and only a more or less distinct brown-blackish prothallus, areoles irregular, 0.2-2 mm, potentially dividing into minute warts or papillae, to 1 mm across, narrowed towards the base, grey-yellowish, brown-yellowish, grey-brownish, warts or papillae usually darker towards apices, lower surface whitish to pale orange. Apothecia sessile or shortly stalked, 0.5-1 mm diam., disc flat to slightly convex, dark brown, grey-brownish, brown-reddish, brown-orange with black dots when moist, exciple concolourous to the thallus or more yellowish, seldom wavy or crenulate, excluded when old. Ascospores 1-septate, oblong, 10-15 x 4-5 µm. Pycnidia numerous, immersed in the thallus. Photobiont: chlorococcoid. C-, KC-, K+ dull yellow, Pd-. No extractable terpene with acetone. Rare, on granitic coastal rocks, common in Southern California and recently described in Brittany and Europe. N.B. Very close to Lecania aipospila but the latter differs by its darker thallus with a conspicuous and distinct prothallus, its more abundant papillae evenly darker and not constricted towards the base and its unstalked apothecia. However, in many cases, chemical spot tests are required to obtain a non-ambiguous identification. Lecania aipospila contains 2 extractible terpenes with acetone whereas Lecania fructigena has none (explaining why some authors restrict their classification to chemotypes). Here only morphological characteristics have been considered and our identification is provisional until full chemical analyses are completed. Not to be confused with Lecanora poliophaea of which the papillate thallus is paler, apothecia larger, brown-orange, exciple permanent and crenulate and spores simple. See also Lecanora praepostera with a less verrucose thallus and brown-black apothecia.