Lecanora rupicola subsp. subplanata (Nyl.) Leuchert & Poelt
Thallus crustose well defined reaching 8 cm across, cracked surface, more or less rough and bumpy, chalky, limestone-white, greyish-white, black hypothallus, thin, almost visible in case of mosaïc of several individuals, or through contact with other crustose species. Abundant apothecia, immerged in the thallus, seldomly prominent by their margin, 1 to 2 mm diam., flat disc, whitish to cream-coloured but can appear greyish-pale by the marked bloom covering, sinuous margin being prominent and appearing in relief on the thallus, whitish or lighter, entire to crenate. Simple spores, elliptic, 9-15 x 5,5-7 µm according to literature, 12-15 (18) x 5-8 µm according to our measurements. Photobiont: green algae. Thallus: C- or C+ orange, K+ yellow, P- or P+/- yellow ; apothecia disc : C- or C+ orange (because the usual bleach solution contains NaOH), KC+ orange. Species coming on siliceous rocks, with strong shore affinities, common in the xeric supra-littoral zone where it can form large colonies, occurs also in the aerohaline zone, even farer inlands.
N.B. Parasitism by Arthonia varians is very frequent, if it is easy to determine Lecanora rupicola subsp. subplanata in case of partial parasitism by its black parasitized apothecia melted with non-parasitized KC+ orange apothecia, it is harder and harder to distinguish this species in case of a thallus totally sterile because of its parasite, mostly if it is an isolated thallus far from a colony, in this case only the thallus K+ yellow reaction will orientate towards Lecanora rupicola s.l.
N.B. Colored chemical reactions here signaled are diversely interpreted by authors and this point is quite confused, conerning for instance the specimens tested in oour prospected area (marine siliceous rocks), all were C+ orange and KC+ orange in apothecia disc, that does not exactly match with the indications given by the literature (a particular chemotype?).*