Lecania cyrtella (Ach.) Th. Fr.

    Thallus crustose, thin, film-forming, more or less smooth to minutely granulose, whitish, pale grey, pale grey-greenish, with occasionally whitish prothallus. Apothecia numerous, sessile, 0.3-0.5 mm diam., disc flat at first soon becoming convex, pale to dark brown-reddish or even almost black, exciple thin, translucent, whitish or paler than the disc, excluded when mature. Ascospores ellipsoid, 1-(3)-septate, 10-16 x 4-5 µm. Photobiont: chlorococcoid. Chemical spot tests negative. Nitrophilic, on bark of deciduous trees ((Sambuscus and Fraxinus mainly), belongs, amongst others, to the Xanthorion and rather inconspicuous due to its small size. See Lecania naegelii  of which the ascospores are 3-septate and growing on alkaline barks in areas with lower nitrates concentration. See also Lecania cyrtellina with smaller and more convex apothecia, and ascospores without septum.*