Hi Stefan
several features of your fungus recall Ceratosphaeria but it is clearly different from C. lampadophora.
I suggest you read Huhndoerf et al, Mycologia, 100(6), 2008, pp. 940–955. DOI: 10.3852/08-037
Best,
Jacques

Hi, Stefan,

the outer wall being composed of ± globose cells in combination with the filiform ascospores reminds me of certain Chaetosphaeria species with these characteristic features – there's a paper dedicated to them: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.522.5595&rep=rep1&type=pdf

Most (all?) of these species should have some black setae on the ascomatal wall though, maybe you overlooked them?

See also these nice images of C. ellisii that give you an overwiew of the general features of this group: http://www.discoverlife.org/mp/20q?search=Chaetosphaeria+ellisii&flags=glean:

Let's see if someone else has a better/more specific idea!

Best wishes,
Gernot

PS: Jacques beat me to it – good to see that we had similar thoughts. :-)
Edit: Oops, Jacques mentioned Ceratosphaeria, not Chaetosphaeria. Should have read it more carefully!

Dear Jacques and Gernot,

thank you very much for the suggestions, I will have a look in these directions.

Stefan

Hi everybody,

I reexamined my material mostly to search for setae.
However I was not able to observe any.

Nevertheless, I think my specimen fits well in scolecosporous Chaetosphaeria and is for example similar to Chaetosphaeria lapazina which may also lack setae. That will be my working name until better knowledge...

Stefan