Synonyms: Bacidina delicata auct. p.p. non (Leight.) V. Wirth & Vězda
Distribution: N - Emil (Nascimbene & al. 2021).
Description: Thallus crustose to subleprose, bright yellow-green, turning grey-green or brown-green in the herbarium, often forming very large patches, entirely or partly disintegrating into loosely arranged, 30-50 μm wide goniocysts, which are at first gathered into 0.1-0.2 mm wide, discrete and punctiform soralia-like patches, but soon cover the whole thallus, forming an up to 1 mm thick, more or less cracked layer. Apothecia rare, biatorine, sessile, constricted at base, (0.2-)0.4-0.7 mm across, with a flat, pale pink to dark blue-black, often only partly coloured disc, the darkened parts with an aeruginose-blue pigment in section; proper margin conspicuous, 0.1-0.2 mm wide, pinkish with aeruginose-blue or dark brown flecks. Proper exciple well-developed, 25–35 μm thick, the cells with isodiametric to slightly ellipsoid lumina, colourless but often aeruginose-blue or orange-brown in upper parts, without crystals; epithecium colourless to aeruginose-blue or orange-brown, 5-10 μm thick, K- or the coloured parts K+ intensifying; hymenium colourless or orange-brown, K+ intensifying brown-purplish, 60-70 μm high; paraphyses c. 1 μm thick at base, the apical cells up to c. 5 μm wide; hypothecium colourless or very pale straw-coloured, 40-60 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) never penetrating through the entire d-layer, the wall K/I-, but the thin outer gel K/I+ blue, Bacidia-type. Ascospores 2-10-septate, hyaline, acicular, straight or slightly curved, 40-50 x 0.9-1.2 μm. Pycnidia rare, white, immersed, c. 0.1 mm across. Conidia thread-like, 35-50 x 1-1.2 μm, with 4-6 indistinct septa. Photobiont chlorococcoid. Spot tests: K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: described from the Netherlands and known from Belgium, England and Germany (Sparrius & Aptroot 2003), bound to anthropized environments where it usually grows on acid or neutral, eutrophicated bark.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)