Candelariella aurella (Hoffm.) Zahlbr. forma aurella

    Thallus subsquamulose, of scattered yellow to yellow-green numerous granules, sometimes hardly visible, inconspicuous or even absent, granules to 0.5-1 mm diam., prothallus black, extensive and dominant  notably in polluted areas. Apothecia 0.2-1.2 mm diam., scattered, disc dull pale yellow, yellow-brownish, yellow, lemon-yellow, exciple entire, slightly bulging when immature and more or less crenulate when old, concolourous or paler and then potentially inconspicuous. Utriform asci with 8 spores. Ascospores simple, oblong, sometimes slightly curved, 10-18 x 5-6 µm. Photobiont: chlorococcoid. K-. Not especially maritime, on nutrient-rich calcareous rocks, the concrete, common on basic substrata in coastal polluted areas, on concrete walls, mortar, piers, jetties, etc., also common in urban areas and, in that case, with an extensive conspicuous blackish thallus. 

_ Not to be confused with some forms of Calopaca citrina agg. that are K+ purple.

N.B. This species is higly variable and different taxa may be distinguished and among them: Candelariella aurella f. smaragdula which is bright green or lemon-green, grows in the same habitats but in more shaded areas (all intermediate forms with the type may be found).

_ See Candelariella vitellina without black hypothallus and asci with 12-32 spores.