The rest of pictures. On the second photo this exudate with floating spores is shown. The 3d photo shows some structures at the margin (hairs? asci?), and the 4 one is excipulum cells from the base of apothecium.

Could be something of the Pyrenopeziza subviridula aggregate to which also Mollisia dextrinospora seems to belong, but without vital characters difficult to say.

Zotto

Hi Irina,

You could also compare to Pyrenopeziza laricina f. microsperma (Le Gal & F. Mangenot), which looks similar but not identical to your species. I think it probably also belongs in the Mollisia (=Pyrenopeziza) dextrinospora group, which seems to be a clade of predominantly lignicolous Pyrenopezizas. It has similar size ascospores to your species, but they look different in shape and oil droplet content.

I've attached Le Gal & Mangenot's description in case it is of any use to you (or anyone).

Cheers,

Brian

Hi, Brian,
Thank you for the article. Although I can't read fast in french, I see that spore shape of P. laricina f. microsperma  differs from my specimen. Also a coniferous habitat doesn't fit, becouse my substrate was for sure deciduous, probably it was Sambucus.
Thank you for telling with the genus and complex within it, I'll try to recollect it and study in fresh condition.
Best regards,
Irina

Thank you, Zotto,

I didn't really hope to identify this old material to the species level, but it seemed interesting and I'm glad that now I know the genus. 
I'll look for P. subviridinula at your DVD.

With best regards,
Irina

Hi Irina, 

Pyrenopeziza subviridula is here in Zotto's amazing Cubby collection (I don't think it was on his 2005 DVD): 
https://www.cubby.com/pl/CC+Ascomycota/_1354d48ffaad4b59bd3ffdbb35915d1f#CC%20Ascomycota/7a%20Helotiales/m%20Mollisiaceae/Pyrenopeziza%20on%20woody%2Bbark

The ascospores do look very similar to your species.  The macro and micromorphology of the apothecium is (I think) also very reminiscent of Mollisia dextrinospora - I would have thought Zotto's collections were M. dextrinospora if the ascospores weren't so different.

Do you have any idea if your species was the same sort of light-dark brown when it was collected?

I wonder if the ascospores also have a very visible dextrinoid reaction in IKI, or if this is restricted to M. dextrinospora?

I don't think I've seen any host specificity in the sequences in the Mollisia dextrinospora group in GenBank: M. dextrinospora has been detected in/on Acacia, Fraxinus, Taxus and Actinidia, while the other big clades also colonise some of these substrates as well as Picea and Pinus.  I suspect they're quite good generalists, but some might be host-specific, or there might be host specific strains or subspecies, you never know!

Cheers,

Brian

Hi Brian,
Thank you for the link to very valuable resource! And of course many thanks to Zotto for this work. Yes, my spores are very similar to M.subviridicola and also the apothecial structures.
I checked spores in IKI and they don't have strong dextrinoid reaction, which is shown on the attached photo. As for the apothecia colour in fresh condition, I cannot say anything for sure, cause I didn't make a photo:(

Cheers,
Irina