Anamorph: rarely observed; conidiomata scattered on pale areas of living or dead twigs, preceding and accompanying the ascomata; inconspicuous and at most only slightly darker than the twig, 100-200 µm diam., circular, with a central ostiole and sometimes a thin black or dark brown perimeter line, the ostiole no more than a crack in the overlying cuticle, surrounded by a small area of blackened fungal cells.
Teleomorph: ascomata scattered on pale areas of dead or living twigs, 350-600 (-900) x 300-500 µm, broadly elliptical from above, markedly raising the surface of the twig, dark grey to black, surrounded by a thin black perimeter line, opening in humid conditions (but not widely) with a straight longitudinal split in the covering layer revealing the greyish disc, without clearly distinguishable lip cells; located beneath the twig cuticle and above strongly tanned twig cells. Upper wall to 40 µm thick, composed of ± globose to angular cells 5-7 µm diam. with pigmented walls, much thicker nearer lhe split where the thicker portion is bent upwards and outwards. Lower wall similar to and continuous with the upper wall. Interascal tissue of simple paraphyses, thin-walled, smooth, filiform, sometimes irregularly branched at the apex, longer than the asci, enveloped in a mucous sheath. Asci arising from croziers, maturing sequentially, 80-125 x 6-9 µm, cylindrical, with an obtuse to rounded apex, uniformly thin-walled, not bluing in iodine, with no obvious apical ring, 8-spored. Ascospores in a fascicle, (65-) 75-90 x 1-2 µm, filiform, slightly tapering towards each end, hyaline, thin-walled, smooth, aseptate, without a mucous sheath or appendages.
Not formally assessed, but this is a quite common and widespread species that would almost certainly be assessed as of Least Concern.
Information useful for identification includes the short and tall coffee-bean shaped ascomata that lack lip cells lining the slit in the upper wall, which develop on bleached areas of the host tissues.
Found on noticeably paler areas of twigs of Vaccinium myrtillus, either as a weak parasite of living tissues or a saprotroph colonising died-back branches.
Present throughout western areas of Great Britain, ranging from Cornwall to Sutherland, the Outer Hebrides and Shetland; also known from the North York Moors.