Pannaria rubiginosa (Thunb.) Bory

    Thallus foliose, composed of rosette-forming, up to 7-10 cm diam., lobes radiating, 2-5 mm wide, markedly incised, upper surface smooth, pale blue-grey and bright when dry, sometimes tinged green or olive when moist, margin paler, more or less pruinose, lower surface tomentose, hypothallus usually well-developed, fibrous, dark grey-blueish, midnight blue. Apothecia lecanorine, numerous, 0.5-1.5 mm diam., disc brown-orange, brown-red, exciple prominent, persistent, more or less crenulate, concolourous to the thallus but often white-cream. Ascii K/I-, apical cushion invisible. Ascospores simple, colourless, ellipsoid somehow like a lemon, acuminate, perispore uneven and apparently erected when observed in water, well-mature ascospores also apiculate at both tips, 15-20 x 9-10 µm without perispore and 20-24 x 10-12 µm with perispore. Photobiont: cyanobacteria. C-, K-, KC-, Pd+ red-orange. Strong oceanic trends, on mossy bark of deciduous trees in woodlands near the seashore, rare on mossy rocks (often together with Nephroma laevigatum, see pictures). N.B. For young specimen of which apothecia are not lecanorine yet, it is rather difficult to make a relevant distinction with Degelia plumbea that may grows in the same conditions and sometimes, as presented here (see pictures below), on side by side the same branch.*