Myriolecis congesta (Clauzade & Vězda) M. Bertrand & Cl. Roux
in Nimis, The Lichens of Italy. A Second Annotated Catalogue: 19, 2016. Basionym: Lecanora congesta Clauzade & Vezda - Portugaliae Acta Biol, B, 9: 331, 1969.
Distribution: S - Pugl (Nimis & Tretiach 1999).
Description: Thallus crustose, episubstratic, whitish, rather thick, rimose-areolate, forming small patches 0.5-1 cm in diam. Areoles more or less convex, the peripheral ones often larger and indistinctly radiating. Apothecia lecanorine, 0.7-1.2 mm across, at first immersed, then sessile and strongly constricted at base, usually crowded and covering almost the whole thallus, with a flat, brownish grey, epruinose disc, and a smooth, prominent, more or less wavy thalline margin. Epithecium brown, K- and N-, inspersed with small brownish crystals dissolving in K; hymenium colourless, 60-70 μm high; paraphyses simple or sparingly branched in upper part, 1.5-2 μm thick at base, the apical cells slightly swollen; hypothecium colourless. Asci 8-spored, clavate, very thin-walled, with a K/I+ blue, tall tholus penetrated by a faintly amyloid apical cushion, the wall K/I-, surrounded by a blue outer layer, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid, (9.5-)10-12 x 5-7 µm. Photobiont chlorococcoid. Spot tests: thallus K- or K+ yellowish, C+ pink to red, KC+ pink to red, P-, UV-; apothecial disc K-, C-. Chemistry: thallus with gyrophoric acid.
Note: a probably Mediterranean-Atlantic species found in the adlittoral belt in sites frequently hit by waves on inclined surfaces of calciferous rocks, probably more widespread along the Mediterranean coast. The species resembles M. bandolensis, but differs in the poorly developed, sublobate thallus reacting C+ red, the numerous, crowded, prominent apothecia covering almost the whole thallus, the thick thalline margin reacting C+ red and the pale grey-brown disc reacting C-, without the bandolensis-green pigment. Like M. poeltiana, it also contains 2,7-dichlorolichexanthone (thallus and apothecia), plus gyrophoric and lecanoric acids, the latter two however limited to the thalline margin of apothecia (see Bertrand & al. 2010).