Porina chlorotica (Ach.) Müll. Arg.

    Thallus crustose, thin, not endolithic, smooth, rimose to areolate, cracked, grey-brownish, brown-greenish, olive-brown, burgundy or with typicalnlivid-green tinge, prothallus absent or dark brownish in case of mosaics. Perithecia superficial, half immersed in the thallus, low height, hemispherical, 0.2-0.3 mm diam., apices rounded without distinct ostiole, blackish. Ascospores colourless, fusiform to narrowly ellipsoid, 3-septate, 15-22 (30) x 4-5 (6) µm according to literature, 20-26 x 5-6 µm  according to our measures. Pycnidia hemispherical, 0.1 mm diam., black. Photobiont: Trentepohlia.(directly visible on the thallus in orange spot form or in thallus rips or scratchs. Chemical spot tests negative. Not especially maritime, on damp shaded siliceous rocks, on Northern walls of chapels and churches. N.B. Near the seashore, see also Porina curnowii of which the thallus is greyer and ascospores 7-septate.