Lecanora sulphurea (Hoffm.) Ach.
Thallus crustose, rather thick, tightly appressed to the substratum, usually smooth, but sometimes crazed to craked, uneven, granulose with scattered large granules, pale yellowish, pale yellow-greenish, grey-greenish, prothallus rather inconspicuous, greyish. Apothecia common, seldom numerous, often clustered towards thallus center, 1-1.5 mm diam., scarcely any extending above the thallus surface, at least initially, disc irregular to distorted, yellow-greenish, brown-greenish, covered with a greyish pruine and darkening with age with green or green-bluish tinges, thalline exciple concolorous, irregular, soon excluded. Ascii 40-60 x 15-20 µm according to our measures. Ascospores colourless, simple (but ascospores with apparent septa may be observed), ellipsoid, 10-13 x 4,5-5,5 µm according to literature, 10-13 (14) x 4,5-6 µm according to our measures. Pycnidia numerous, visible as minute black dots. Photobiont: Trebouxia. C-, K+ brown-yellowish, KC+ yellow, Pd-. Common, on nutrient-rich acid rocks in the seaspray zone ( xeric and aerohaline suprlittoral zone), but also inland, though far less frequent (different taxon?). This species may often start as a parasite on other crustose lichens and entirely destroy the host thalli, notably on Tephromela atra which is the preferential host subtratum (see Lecanora sulphurea parasite on Tephromela atra). It also competes with another parasitic species on Tephromela atra: Diploschistes caesioplumbeus (see Lecanora sulphurea vs. Diploschistes caesioplumbeus). N.B. This species is sometimes considered as the nonsorediate form of Lecanora orosthea of which the thallus is thinner. N.B. Apothecia frequently are infested by parasitic species and then distorted and dark brown to blackish.*