Lecania baeomma (Nyl.) P. James & J. R. Laudon

    Thallus crustose, 1-3 cm diam., thick and roughly verrucose, sometimes indeterminate or not well defined, irregular, rimose to areolate, dull whitish, grey-yellowish, covered with indigo pustular soralia, becoming paler and greyish when old or by erosion. Apothecia irregular, more or less sessile, scarce and scattered, 1-1.5 mm diam., disc flat, dark brown, brown to brown-blackish, typically covered, at least when young, with a pale lilac, grey-mauve or grey-bluish pruine, exciple persistent, more or less sorediate, paler to whitish. Ascospores ellipsoid, 1-septate, 12-18 x 4-5.5 µm. Photobiont: Chlorococcoid. Chemical spot tests negative. Rare, one of the few species growing on the walls exposed to the North or below overhangs of siliceous rocks in the aerohaline zone. N.B. Often sterile and in that case difficult to identify. N.B. Not to be confused with Lecanora actophila whose thallus is smoother and growing in well-lit areas.*