Thallus white, bluish white, or ashy, thin, granulose to subleprose. Apothecia tiny, 0.2-0.4 mm, broadly adnate, black; disk persistently flat or becoming convex; margin thin, persistent or not; exciple dark brownish red; hypothecium hyaline or pale roseate; epihymenium intensely red; hymenium hyaline, 1+ blue then darkening; paraphyses coherent, simple or rarely branched, 1-1.5 µm, tips rarely thickened to 3-5 µm; asci clavate; spores 8, 3-5(-8)-septate, attenuate with one end commonly attenuated and the other blunt, spirally contorted or occasionally only slightly curved, 26-43 x 2-3.5 µm.

Reactions: epihymenium and exciple red parts turn violet with K in some specimens; these parts may also turn violet with HN03.

This species grows on the bark of Ulmus, Alnus, Betula, and Populus. It is known from Scandinavia and has been reported from Saskatchewan (Jonescu 1970) and Greenland (without locality) by Darbishire (1909).

Although this species has curved, vermiform spores like Scoliciosporum it is retained in Bacidia because of the simple paraphyses and general ascocarp structure and shape.

Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Thallus: crustose, discontinuous, of discrete granules or low convex areoles, or continuous and composed of contiguous granules or ±rimose surface: pale to medium gray, yellowish or greenish gray, gray-green, brown-green, rarely ±pure brown, wrinkled, warted, or tuberculate Apothecia: at first flat, eventually becoming convex, 0.3-1.2 mm in diam. disc: usually black, blue-black, or brown-black, rarely paler, purple-brown, gray-brown, brownish pink, or almost pure pink (±pigment deficient apothecia), epruinose margin: concolorous with disc or slightly paler or darker, at first distinct, level with or raised above disc, finally excluded exciple: laterally 40-75 µm wide, without crystals, orange-brown, red-brown, or black-brown (K+ purplish, N+ orange), often with a green or blue-green tinge (K-, N+ purple) in uppermost part, rim concolorous or paler than interior (to almost colorless), both slightly fading below; edge with single cell layer of enlarged cell lumina (up to 5 µm wide) epithecium: usually blue-green to olive-green, containing a blue-green (K-, N+ purple) in the hymenial gel and occasionally small amounts of a brown-gray (K+ purplish, N+ orange) pigment in some paraphyses; crystals not present hymenium: hyaline, 50-105 µm tall; paraphyses: 1.2-2.4 µm wide in mid-hymenium, apices not swollen or ±clavate, 1.6-6.5 µm wide, without distinct hoods of pigment or with diffuse brown-gray hoods hypothecium: pale to dark (often reddish) brown (K+ purplish, N+ orange), fading below asci: clavate, 8-spored ascospores: hyaline, 3-13-septate (often Pycnidia: ±immersed in thallus, bluish or black, c. 50 µm in diam. conidia: filiform, curved, non-septate, 10-20 x c. 0.8 µm Spot tests: all negative Secondary metabolites: none detected. Habitat and ecology: on bark and wood of Populus and Abies, rarely other trees, in mixed conifer forests at high elevations (22003200 m) World distribution: North America, Europe, and Asia Sonoran distribution: relatively widespread in the mountains of the eastern half of Arizona. Notes: Most specimens of Bacidia subincompta from the region have a ±granular thallus. Bacidia subincompta is similar to B. coruscans, which differs mainly in the dominance of a blue-green pigment in the exciple See also B. veneta.