Lecanora intricata (Ach.) Ach.

   Thallus formed of slightly swollen areoles, most often contiguous but sometimes dispersed, with crenelate, indented or serrated margin, greenish-yellow, yellowish-grey, hypothallus blackish if present. Apothecia round or deformed and angular by contact, numerous to 1-2 per areole, 0.5-1 mm in diameter, most often immersed in the thallus or more rarely sessile and with an unconstricted base, disc concave at first but most often flat to slightly convex, typically emerald-green to dark green, brownish-green, but often brownish to blackish-grey in low sun areas, margin weakly emergent, flexuous may be ruled out in old age. Spores simple, elliptical, 10-14 x 5-7 µm. Photobiont: Trebouxia. Thallus: C-, K+ pale yellow barely visible, KC+ yellow, P-. Species not especially maritime and even mountainous but which can be found here and there on siliceous rocks from the xeric supralittoral zone where it seems to be a particular taxon.

N.B. To be differentiated from the more common Lecanora polytropa whose areole margins are smooth and whose apothecia are more emergent and less dark green and also from Lecanora sulphurea with a thicker thallus and apothecia that are completely included and difficult to distinguish.

N.B. Very variable species whose differential characters with Lecanora polytropa are not very clear and not very relevant (cross characters) which sometimes makes it very difficult to separate these two species, especially since there are many intermediate forms (sometimes on the same thallus!). Pending a study which will perhaps clarify the problem, we have retained here, under the name of Lecanora intricata, the often very green taxa that grow on the cliffs and large rocks of the seaside of La Pointe of Brittany.