Myriospora rufescens (Turner ex Ach.) Hepp ex Uloth

Flora, 44: 618, 1861. Basionym: Sagedia rufescens Ach. - Lich. Univ.: 329, 1810
Synonyms: Acarospora rufescens (Turner ex Ach.) Kremp.; Acarospora smaragdula (Wahlenb.) A. Massal. var. rufescens (Turner ex Ach.) Clauzade & Cl. Roux; Lecanora rufescens (Turner ex Ach.) Nyl.; Silobia rufescens (Turner ex Ach.) M. Westb. & Wedin; Trimmatothelopsis rufescens (Turner ex Ach.) Cl. Roux & Nav.-Ros.
Description: Thallus crustose, episubstratic, areolate, forming an extensive, smooth, even crust, dull to dark brown, becoming thinner towards the edge, the areoles contiguous, separated by cracks, angular, 0.4-1.5 mm wide, thin, flat to concave. Epicortex absent; cortex paraplectenchymatous, of isodiametric cells, without crystals; algal layer interrupted by thick anticlinal bundles of medullary hyphae; lower cortex absent. Apothecia lecanorine, 0.07-0.4 mm across, 1-2 per areole, immersed, with a brown, deeply concave disc concolorous or darker than thallus, and an entire, slightly raised, prominent thalline margin. Proper exciple colourless, but the uppermost cells with dark brown caps; epithecium brown to dark red-brown; hymenium colourless, 100-125 μm high; paraphyses simple to sparingly branched and anastomosing 1-1.5 μm thick, the apical cells cylindrical to clavate; hypothecium opaque, densely inspersed with oil droplets. Asci 100-200-spored, clavate, the apical dome K/I-. Ascospores 1-celled, hyaline, ellipsoid, 3-4 x 1-1.5 μm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: apparently a mainly western species, found on sandstone and other siliceous substrata, chiefly on monuments, gravestones, and wall tops, reported from a few localities in the Alps outside Italian territory. To be looked for in Italy.
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual

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Predictive model - CC BY-SA NC