Hi Åge
Look for Melanomma.

Hi Enrique,
The spores fits with the lower range reported for Melanomma pulvis-pyrius, however, this species is only reported on broadleaved trees. In addition, the perithecia should have a more irregulary angular surface. My collect is found on Juniperus and have a smooth surface. M. juniperinum reported on conifers have somewhat lager 4-5 septate spores. Would you accept this as M. pulvis-pyrius despite the above deviations?

Regards,
Åge

Melanomma pulvis-pyrius appears to be confined to deciduous wood. 
Such 3-septate brown ascospores occur in other genera too like Teichospora and Nigrograna, see for example these papers:
Jaklitsch, W.M., I. Olariaga & H. Voglmayr (2016) Teichospora and the Teichosporaceae. Mycological Progress 15: 1-20.
Jaklitsch, W.M. & H. Voglmayr (2016) Hidden diversity in Thyridaria and a new circumscription of the Thyridariaceae. Studies in Mycology 85: 35-64.
Quote from the latter paper (page 63): "Three-septate brown ascospores are a story of success in evolution, as they are widely distributed in pyrenomycetes. Ascospore features alone seem therefore not to be very useful for classification."
Best regards, Eduard

What you said makes a lot of sense to me, Eduard.