Illustration of characters
Stromata applanate to slightly convex, with low margins	A
Stromata more or less cupulate, with raised margins	B
A1- Stromata purplish brown to grey, on Tilia.	B. cinereolilacina
A1- Stromata black, host different	A2
A2- Ascospores mostly hyaline, two-celled	B. anceps
A2- Ascospores brown to dark brown, one-celled	A3
A3- Ostioles coarsely papillate, conical; ascospores 15.5-21 x 7-10 µm	B. mediterranea
A3- Ostioles discoid to slightly papillate, ascospores shorter	A4
A4- Restricted to Fagus sp.; ascospores 10-13 x 7.5-8.5 µm.	B. nummularia
A4- Restricted to Prunus sp.; ascospores 10.5-14.5 x 5-7 µm	B. granmoi

B1- Ostioles opening at the same level as the stromatal surface, discoid	B2
B1- Ostioles opening higher than the stromatal surface, coarsely papillate	B4
B2- Ascospores subglobose, dark brown, 13-16.5 x 9.5-13.5 µm, with sigmoid germ slit; mostly on Rosaceae	B. marginata
B2- Ascospores ellipsoid, brown, with straight germ slit	B3
B3- Ascospores 13-17 x 5.5-6.5 µm, with germ slit on one side; specific for Rhamnus catharticus	B. simplicior
B3- Ascospores 9-14 x 4.5-6 µm, with germ slit on both sides; mostly on Sorbus	B. repanda
B4- Stromatal surface plane to slightly convex	B. mediterranea
B4- Stromatal surface more or less concave	B5
B5- Ascospores narrowly ellipsoid with germ slit on both sides, 9-14 x 4.5-6, mostly on Rosaceae	B. repanda
B5- Ascospores broadly ellipsoid, larger	B6
B6- Ascospores 15.5-21 x 10.5-13.5 µm, with straight germ slit on one side; plurivorous, but mostly on Ulmus	B. dennisii
B6- Ascospores 17-22 x 11-14 x 9-10 µm, laterally compressed, with straight germ slit circular on narrow edges; known on Quercus	B. querna