Lecania fructigena Zahlbr.
Thallus crustose more or less areolate, spread over the rocks without a clear and defined margin with only a blackish-brown hypothallus visible here and there, irregular areoles of 0.2-2 mm which may divide into warts or small papillae of less than 1 mm high, narrowed at the base, yellowish-gray, yellowish-brown, blackish-gray, warts or papillae are usually darker at the top, underside whitish to pale orange-brown. Apothecia sessile and even slightly stalked, 0.5-1 mm in diameter, disc flat to somewhat convex, dark brown, gray-brownish, reddish-brown, orange-brown, with blackish spots so well hydrated, concolorous margin at the thallus or more yellowish, rarely flexuous or crenate, fading in decay. Spores 1-septate, oblong, 10-15 x 4-5 µm. Numerous pycnidia immersed in the thallus. Photobiont: chlorococcoid. C-, KC-, K + dirty yellow, P-. Absence of terpenes extractable by acetone. Rare species of very exposed coastal granite rocks, where it occurs mainly on horizontal or slightly inclined surfaces.
This species which is abundant in Southern California was recently described from Brittany and Europe, it is very similar and difficult to separate from Lecania aipospila which theoretically differs from it by its darker thallus with a very clear and well defined margin, its papillae more numerous and larger, uniformly dark not narrowed at the base and its apothecia not or poorly stipulated, but the characters used to separate the two taxa are crossed and unreliable, only the different chemical composition seems to be able to be used (with all certainty relative because it is a quantitative character!): Lecania aipospila contains 2 terpenes extractable by acetone and Lecania fructigena does not contain any (which means that some authors make 2 chemotypes and not 2 different species). Pending a molecular biology study our identification should be considered provisional because there are all possible forms of passage with Lecania aipospila. Also watch out for Lecanora poliophaea with single spores, paler and more papillate thallus and larger, orange-brown apothecia with a persistent crenate margin and Lecanora praepostera with less warty thallus and blackish-brown apothecia.