Japewiella tavaresiana
Thallus immersed to superficial, thin, whitish to pale grey, sometimes appearing glossy. Prothallus black, thin. Isidia and soralia absent. Photobiont chlorococcoid.
Anamorph: not known.
Teleomorph: ascomata apothecia, 0.2-0.5 mm diam., flat, regular, pale to dark red-brown. True exciple persistent, hyaline within, composed of outwardly radiating, narrow, sparsely branched and interconnected, gelatinized hyphae; the edge and epithecium pale red-brown, K+ dull brown, N–. Hymenium 60-70 μm deep. Hypothecium 20-45 μm tall, hyaline, I+ blue. Interascal tissue of branched and anastomosed paraphyses, the apices slightly thickened with brown caps. Asci 55-65 × 15-20(-28) μm, ± Lecidella-type with a wide apical cushion, 8-spored. Ascospores 13-17 (-19) × 8.5-10 μm, ellipsoidal, hyaline, aseptate, thick-walled, the wall homogeneous, smooth, without an epispore, gelatinous sheath or appendages.
Chemistry: thallus C–, I–, K± faint yellow, KC–, Pd–, UV– (atranorin).
Locally common in the west of Britain, from the Scilly Isles and Cornwall to NW Scotland. BLS map here.
On ± smooth bark of young deciduous trees or twigs, especially on Salix spp., especially in carrs and sheltered woodland margins.