Generic short diagnoses:
Immersed discomycetes in leaves or needles, opening by irregular rupture of the covering layer to expose greyish to brownish discs; with ± ellipsoid to fusiform, mostly aseptate spores.
The picture originates from the MycoKey 2.0 DVD. Here you will also find a larger picture along with a detailed generic description, references and an interactive, synoptical key to genera.