[Blastenia xanthostigma (Pers. ex Ach.) Müll. Arg., more, Caloplaca xanthostigma (Pers. ex Ach.) H. Olivier, Candelaria xanthostigma (Pers. ex Ach.) Kieff., Candelariella vitellina f. lutella (Vain.) Zahlbr., Candelariella vitellina var. xanthostigma (Pers. ex Ach.) Elenkin, Lecanora xanthostigma (Pers. ex Ach.) Röhl., Lecanora xanthostigma var. lutella Vain., Lecanora xanthostigma var. xanthostigma (Pers. ex Ach.) Röhl., Lichen xanthostigmus Pers. ex Ach.]
Thallus: crustose, composed of scattered to crowded granules, often ±evenly dispersed on the substrate, sometimes aggregated into thicker crusts granules: mostly round, 0.04-0.08 mm wide, sometimes becoming elongated surface: green yellow to yellow, smooth Apothecia: lacking to abundant, lecanorine, 0.3-0.7 mm wide margin: initially entire, later becoming granular and sometimes excluded exciple: often visible from the outside as a raised margin disc: darker yellow than the thallus, flat, becoming convex in old apothecia epihymenium: yellow-brown hymenium: hyaline, 55-70 µm tall; paraphyses: simple, ±cylindrical or somewhat swollen apically, tips to 3 µm wide; hypothecium: hyaline asci: clavate, 16-24-spored ascospores: hyaline, simple to 1-septate, ovoid to oblong, 7.5-11 x 3.5-4.5 µm Pycnidia: common, appear as darker yellow granules conidia: hyaline, ellipsoid to oblong, 2.5-3.5 x 1.5 µm Spot tests: K+ reddish, KC-, C- Secondary metabolites: calycin, pulvinic acid, pulvinic dilactone and vulpinic acid. Substrate and ecology: on the bark of broad-leaved trees and shrubs, sometimes on conifers and wood World distribution: world-wide Sonoran distribution: in coastal areas of southern California and Baja California including the Channel Islands and in open montane forests in Arizona up to the timberline. Notes: Candelariella xanthostigma is characterized by a thallus that is +entirely composed of small round granules. The likewise polysporous C. lutella has a thallus of small ±flat areoles and C. vitellina has a thallus convex areoles becoming minutely lobate.