Ascomata perithecial, ± spherical, black, 90-110 µm diam with a very short neck, the ostiole visible from the surface as a minute black spot surrounded by a clypeus 100-150 µm diam. Peridium 6-7 µm thick, composed of 2-3 layers of flattened cells. Asci 40-60 x 7-11 µm, clavate-ellipsoidal, with a conspicuous refractive apical ring ca 2 µm diam, 8-spored. Ascospores 10.5-16 x 3.2-4.5 µm, elliptical, often slightly inaequilateral with one face ± flat, hyaline, aseptate, thin- and smooth-walled, the contents appearing granular, without a gelatinous sheath or appendages.
Anamorph: Monostichella robergei. Conidiomata acervular, inserted between the epidermis and the cuticle, 60-220 µm diam. Conidiogenous cells short, ± isodiametric, 6-9 x 5-7 µm, proliferating percurrently. Conidia 13-15 x 6.5-7.5 µm, ovoid, hyaline, aseptate.
Not formally assessed, but the small number of confirmed records indicates that the species may be in need of conservation measures. It may be under-recorded due to its inconspicuous nature and the paucity of recorders with the necessary skills for identification
Preliminary molecular analysis indicates that the genus has no close relatives, and does not belong to the Gnomoniaceae as previously assumed.
The anamorph develops in living leaves of Carpinus betulus, with the teleomorph forming in dead, overwintered tissues. Reports from other host plants need confirmation; many are likely to be the result of adopting excessively wide species concepts
In GBI: scattered, primarily in the south east. Also known from north and central Europe and eastern North America.