Cat. Lich. Univ., 7: 387, 1931. Basionym: Lecidea patouillardii Hue - in Patouillard, Cat. Rais. Pl. Cellul. Tunisie: 149, 1897
Synonyms: Buellia zoharyi Galun
Description: Thallus crustose-placodioid, episubstratic, of radiating, white-pruinose, 1-2 cm long, 0.4-1 mm wide lobes, forming orbicular to irregular, up to 4 cm wide rosettes. Cortex c. 75 μm thick; medulla white, filled with crystals, I-; lower surface pale, attached with rhizohyphae. Apothecia not always present, lecideine, 0.5-1.7 mm across, at first immersed but soon becoming adnate, with a black, sometimes white-pruinose, flat to slightly convex disc, and a thin, black, often pruinose, persistent proper margin; a pseudothalline margin is sometimes present at the base of the proper margin. Proper exciple of radiating hyphae, dark red-brown, 50-110(-200) μm wide; hymenium colourless, not inspersed with oil droplets, 60-90 μm high, I+ blue; paraphyses 2-3.5 μm thick at mid-level, the apical cells up to 7.5 wide, with a brown cap; hypothecium greenish brown in upper part, black-brown in lower part, up to 200 μm high. Asci 8-spored, clavate to cylindrical-clavate, the apical dome K/I+ dark blue with a pale, conical-pointed apical cushion (axial mass), the wall I-, but the thin outer gel I+ blue, Bacidia-type. Ascospores 1-septate, slightly constricted at septa, brown, oblong-ellipsoid, (10-)10.5-15(-17.5) x 5.5-8.5 μm, with a microfoveate ornamentation. Pycnidia black, cylindrical to pear-shaped. Conidia bacilliform, 4-6.5 x 1-1.5 μm. Photobiont chlorococcoid. Spot tests: cortex K+ yellow (reaction sometimes faint), C-, KC-, P-; medulla K-, P-, or K+ red, P+ orange-red in spots. Chemistry: cortex with atranorin; medulla sometimes with norstictic and stictic acids.
Note: a widespread Macaronesian-Mediterranean species growing on gypsum and calciferous soil; to be looked for in the driest parts of Mediterranean Italy.