Verrucaria polysticta Borrer ss. auct. brit.

      Thallus crustose 0.3-1 mm thick, formed of areoles arising on a black prothallus, areoles 0.3-1 mm, angular and bordered with blackish, flat to slightly convex, gray, grayish, brownish-gray, more or less streaked with black lines. Perithecia arranged over the entire surface of the areoles and not only at their margins, generally immersed in the thallus and rarely slightly protruding, 1-14 per areole according to the literature, 2-8 according to our observations. These perithecia appear in the form of more or less regular black dots of 100-250 µm. Ascospores long elliptical, hyaline, simple without perispore, 12.5-15.5 x 5.5-7 µm. Rare taxon found on moist limestone or slightly acidic rocks, walls, etc.

N.B. Taxon variously interpreted by the authors, we have retained here the interpretation of the British authors.

N.B. Would be the host of Verrucaria cernaensis, which is the case here.