Candelaria concolor (Dicks.) Stein

   Thallus typically forming small, discrete suborbicular cushions 1-3 cm diam., able to associate and form large colonies, lobules markedly divided in small straps, 0,5-1,5 long, 0.2-0.5 mm wide, more or less appressed to the substratum, tips finely incised delimiting a sorediate margin, upper surface yellow-greenish to yellow-mustard in shaded conditions, lemon yellow when sunny; almost white beneath, rhizines scattered, simple, white (N.B. The margin is consequently lace-like). Apothecia rare, 0.5-1 mm diam., disc flat, dull dark-yellow, thalline exciple ± uneven-granular with age, paler. Ascii up to 50-spored. Ascospores broadly ellipsoid, simple but sometimes appearing 1-septate owing to 2 oil microdroplets,  6-14 x 4-6 µm (7-11 x 4-5 µm according to our measures). Photobiont: Chlorococcoid. Thallus C-, K-, KC-, Pd-, UV-, K/UV+/- ochraceous. Slightly thermophilic, on nutrient-rich bark, notably of tree alignments in cities, rare on rocks or artificial substrates, but see: Candelaria concolor forme sur substrats artificiels.

N.B. Not to be confused with Xanthoria candelaria  and  some close Xanthoria species that are common on rocks, with lobes more erect and less lace-like, yellow-orange to orange (and not yellow!) and above all K+ purple.

N.B. Xanthoria ulophyllodes is very similar but is more orange and K+ purple as well as K/UV+ bright orange.