Anamorph: unknown in nature, a microconidial morph with cylindrical conidia 6-11 x ca 1 µm may be formed in culture according to Monod (1983).
Teleomorph: stromata absent. Ascomata 140-250 µm diam, neck central, 370-800 (-1200 µm) x 15-35 (-40) µm, very thin and straight or curved. Peridium 10-20 µm thick, composed of 2-3 layers of large dark-walled angular cells. Interascal tissue composed of rather sparse thin-walled evanescent paraphyses, much longer than the asci. Asci 21-28 x 5-8 µm, with a long tapering stalk when mature, thin-walled, evanescent at the base and sometimes eventually throughout, with a large refracive apical ring, 8-spored. Ascospores 11-15.5 x 1-1.5 µm, narrowly fusiform, straight, septum median, with variable appendages, each cell containing 2 guttules, lying in parallel within the ascus.
On dead overwintered leaves of Betula spp., Carpinus betulus and Corylus avellana. Particularly common on Betula.