Bryonora pruinosa (Th. Fr.) Holt.-Hartw.

Mycotaxon, 40: 300, 1991. Basionym: Lecanora castanea var. pruinosa Th. Fr. - Lich. Arctoi: 195, 1860
Description: Thallus crustose, indistinct or forming a thin, whitish, granulose crust. Cortex lacking internal crystals; medulla K/I+ faintly blue. Apothecia lecanorine, sessile and strongly constricted at base, 0.5-2(-3) mm across, with a pale yellowish brown to medium brown, often pruinose, usually flat disc, and a narrow, distinctly darker, blackish brown thalline margin. Proper exciple poorly developed; epithecium yellowish brown, K-, N-; hymenium colourless; paraphyses simple, coherent, the apical cells 3-5 µm wide; hypothecium pale brown to almost colourless. Asci 8-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 (rarely 1-septate), hyaline, shortly ellipsoid, (9-)11-17(-19) x (4-)4.5-5.5(-6.5) µm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC- or KC+ yellowish, P-. Chemistry: usnic acid.
Note: an arctic-alpine, circumpolar species found on plant debris and moribund lichens over siliceous substrata, often in dry sites, with a few records from the Alps outside Italian territory; to be looked for in the Italian Alps.
Growth form: Crustose
Substrata: soil, terricolous mosses, and plant debris
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual

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Predictive model

Curtis Randall Björk – CC BY-SA 4.0
British Columbia, Clearwater Valley, Edgewood West On moss over basalt boulder in open, mixed conifer-deciduous forest 2006-06-06