Description: Thallus fruticose, more or less filamentous and shrubby, greenish grey to yellowish green, the apices concolour or blackened, matt. Branches to 13 cm long 1-2(-3) mm thick, stiff, elongate, prostrate to ascending, sparingly anisotomic-dichotomously divided, the apices sometimes drooping. Pseudocyphellae numerous, linear, raised, longitudinally oriented, to c. 1 mm long. Medulla white, compact. Apothecia extremely rare (not seen in Italian material), lecanorine. Epithecium brown; hymenium and hypothecium colourless. Asci 2-4-spored, clavate, the K/I+ blue tholus penetrated by a faintly amyloid apical cushion with parallel or diverging flanks, the wall K/I-, surrounded by a K/I+ blue outer layer, Lecanora-type. Ascospores 1-celled, broadly ellipsoid, pigmented when old. Pycnidia dark, semi-immersed, mainly apical. Conidia bacilliform. Photobiont chlorococcoid. Spot tests: K-, C-, KC+ pale yellow, P-, UV-; medulla K-, C-, KC-, P-, UV-;. Chemistry: cortex with usnic acid, medulla with diffractaic acid.
Note: an arctic-alpine, circumpolar species found on windy ridges in moss-lichens heaths, more frequent on siliceous substrata, but sometimes also occurring in areas with dolomite, with optimum above treeline. Restricted to the Alps and the northern Apennines in Italy.
Growth form: Fruticose filamentous
Substrata: soil, terricolous mosses, and plant debris
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by thallus fragmentation