Parabagliettoa dufourii (DC) Gueidan & Cl. Roux
Verrucaria dufourii DC
Thallus crustose, more or less endolithic, slightly in relief on the substratum, smooth and not cracked, dull whitish, pale brown-greyish, pale greyish, prothallus absent but simple or double hypothalline lines frequently may be observed at the junction with other thalli, this line often is dotted due to dark brown or black pycnidia. Perithecia hemispherical to subconical, prominent, 0.3-0.5 mm in projection, apices more or less plane and sometimes concave (old volcano crater-like), ostiole hardly visible, black, broken perithecia may leave a minute well as scar on the thallus. Ascii 8-spored, 60-80 x 20-30 µm. Ascospores simple, colourless, broadly ellipsoid, sometimes with a perispore, 16-20 x 7-9 µm according to literature, 15-20 x 6-9 µm according to our measures. Pycnidia frequent, visible as black or brown minute dots, scattered all over the thallus, often arranged in lines as topstitched seams at the thallus edge. Rare in our prospection area, on hard limestone or on calcareous walls. See Verrucaria pinguicula devoid of pycnidia and Verrucaria muralis much more common on humid walls, the latter with more numerous and smaller perithecia, ostioles distinct and pycnidia absent.