Verrucaria elaeina Borrer
Thallus crustose, relatively thin, rimose and cracked, smooth surface but a bit rough in places where epinecral (dead cells) layer and medulla do not bear algae, pale grey-greenish, grey-whitish slightly brownish in places, sometimes with a thin prothallus, cream. Numerous perithecia, 1/4 to 3/4 burried in the thallus (but rarely completely), 0.2-0.4 mm diam. at their base, blackish, sometimes covered by the thallus at base, often reduced to a blackish ring with a grey-whitish center. Colorless ascospores, ellipsoid, without perispore, 16-22 x 7-9 µm according to the literature, 14-21 x 7-9 (10) µm according to our measurements. No significant chemical reactions. Rare (or unperceived?), growing on rocks a bit chalky or siliceous but not much acid, wet and shady, in oceanic forests particularly along seashore, also on old moisty walls, in the shed. Cf. Verrucaria praetermissa more aquatic and coming on more acid rocks.