Atla alpina  

Description based on that in Savic & Tibell, Lichenologist 40: 269-282 (2008).

Thallus crustose, variably developed, in UK material partly immersed and only emerging as blackish green patches. 

Anamorph: unknown.

Teleomorph: ascomata rather large, 700-900 µm diam, shining black, almost spherical, adnate, broadly attached at the base, without a thalline cover, when old verrucose in the upper part and with an impressed to minutely papillate ostiole. Involucrellum ca 80–120 µm thick, thickened around the ostiole, in the outermost part forming a continuous, strongly carbonized, black layer with irregular extensions reaching far into the less pigmented, mottled interior of the involucrellum; in the inner and upper part fused with the excipulum; in the middle and inner part formed by a pseudoparenchyma of angular to rounded, slightly elongated cells. Excipulum 15–25 µm thick, brown, in section consisting of narrow, concentrically arranged cells, pale in the lowermost part. Interascal tissue absent except for periphyses, 55–100 µm long, numerous, slender, 1.5–2.5 µm diam, branching at wide angles; hymenial gel I+ red, KI+ blue. Asci 150–180 x 70–110 µm, broadly ellipsoidal to clavate, 8-spored, without apical thickening. Ascospores 70–83 x 39–49 µm, ellipsoidal to broadly ellipsoidal, when mature very dark brown, muriform, with 7–8 transverse and 3–4 longitudinal walls.