Distribution: N - Frl (Hinteregger 1994, Printzen 1995, in Austrian terr., near the border), Piem (TSB 33253), Lig.
Description: Thallus crustose, endo- to episubstratic, continuous to usually areolate, whitish to greenish grey, sometimes with a yellowish tinge, forming small rounded patches up to 1.5(-2) cm across, sorediate, without a distinct prothallus. Areoles discrete or contiguous, rounded to elongate, flat to convex, 0.2(-0.4) mm across. Soralia central or marginal on the areoles, pale yellow to greenish yellow, at first well-delimited, punctiform, 0.15-0.4 mm in diam., later often somewhat diffuse. Soredia 10-25 μm in diam. Apothecia rare, biatorine, 0.2-0.4(-0.6) mm across, with a pale yellowish brown to flesh-coloured, slightly convex disc and a soon excluded proper margin. Excipulum poorly developed, 25-35 μm thick, colourless, of conglutinated, outwardly radiating hyphae, without crystals; epithecium pale straw-coloured to colourless, with a minutely granular epipsamma dissolving in K; hymenium colourless, 30-50 μm high, with large crystals not soluble in K; paraphyses firmly conglutinated, simple to slightly branched in upper part, c. 2 μm thick, the apical cell sometimes slightly swollen to 3.5 μm; hypothecium colourless to pale yellow, 40-70 μm high, K/I+ blue. Asci 8-spored, clavate, with a K/I+ blue apical dome penetrated by a narrow, K/I– apical cushion surrounded by a narrow, deeply K/I+ blue zone, the wall K/I- but surrounded by an I+ red-brown, K/I+ blue outer layer, the ocular chamber relatively small, Biatora-type. Ascospores 0(-1) septate, hyaline, narrowly ellipsoid to oblong or slightly bean-shaped, 6-14 x 2.5-4(-5) μm. Photobiont chlorococcoid. Spot tests: thallus and soralia K+ yellow-orange, C+ yellowish, P-. Chemistry: atranorin (traces), usnic acid, isousnic acid, plus traces of stictic acid and other unidentified substances.
Note: a probably boreal-montane species found on twigs of subalpine shrubs, especially Rhododendron ferrugineum; certainly much more widespread in the Alps.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)