Xanthoria candelaria  (L.) Th. Fr.

   Thallus foliose, 2-3 cm diam., sometimes forming large mats by confluence of conspecific colonies, made of finely incised lobes, more or less erect, 1-2 mm tall, 0.2-0.5 mm wide, tips fan-shaped, covered mostly towards the margins by farinose or granulose soredia (blastids), 0.1-0.5 mm diam., concolourous to the thallus, upper surface golden yellow, orange, more yellow-greenish when shaded, potentailly fading to grey-yellowish , lower surface concolourous but usually paler and more greyish, without rhizines. Apothecia usually scarce, sessile or more or less shortly stalked, 1-2 mm diam., disc orange or brown-orange, exciple smooth, concolourous to the thallus. Ascospores hyaline, polarilocular, 12-15 x 5,5-8 µm. Pycnidia numerous, visible as dark dots. Cortex: C-, K+ purple, KC-, Pd-. Oceanic trends, on nutrient-rich substrata, on tree barks and more frequently on rocks, sometimes on cement and sawn wood. N.B. Xanthoria ucrainica, supposed to grow on old walls, is a very close taxon that we difficultly distinguish from Xanthoria candelaria. On tree barks, recall that Candelaria concolor has also lace-like lobes but less erect, more bright yellow, not fading to grey-yellowish and above all K-.*