Lecanora polytropa (Hoffm.) Rabenh.
Thallus crustose, seldom continuous, most often composed of dispersed areoles, notably in depressions and cracks of the substratum, areoles round, smooth and flat, grey-yellowish, grey-brownish, prothallus black more or less effuse. Apothecia numerous, scattered or clustered sometimes crowded and slightly distorted due to compression, sessile, 0.3-1 mm diam., disc smooth, flat at first then slightly convex, pale yellow, brown-greenish, yellow-greenish, jade, exciple thin, paler than the discs, determinate at first then either excluded or wavy or crenulate. Ascospores simple, ellipsoid, 0-14 x 5-6.5 µm. Photobiont: Trebouxia. Thallus: C-, K+ faint yellow, KC+ yellow, Pd-. Not especially maritime but very common on acid rocks from the xeric zone, also common on walls of maritime works. N.B. Lecanora stenotropa is very similar but with a darker thallus and apothecia discs more brownish and above all, narrower ascospores: 8-12 x 3-4 µm. Some forms with disc colour almost green may be confused with Lecanora intricata of which the discs are dark emerald, but this species, although present in our prospection area is rather montane.*