Bonjour,
Voici un Hypoxylon (je crois) avec des spores normals ac aussi des spores angulaires.

This effused Pyrenomycete was on a log in a mixed woodland, mostly pine but with some birch and other broadleaf. The purplish-brown surface turned completely black with mostly square-angular spores with a few normal ones after a day, but within 10 days a thick matted crust of normal spores had formed, with an occasional angular spore.
The surface was rather flat, with little sign of perithecial mounds. Perithecia were oval, 0.9 x 0.3 mm. The fungus was about 1.2 mm thick, bounded by a black layer below.
Normal spores were up to 11 x 5, with a long germ slit.
Angular spores were similar in size.
Asci were about 5 -6 wide and up to 150 long, tips blueing in Lugol.
Paraphyses were thread-like.
KOH-extracted pigment was grey-brown rather than orange or red-brown.

Using a key provided by the British Mycological Society:
Stromata widely effused
Stromata with lilac tinge
Stromata not immersed, pigment olive, beige, lilac or absent, so not H. petriniae.
Could this be H. fuscopurpureum?

Cordialement,
Steve