Yesterday I found some white Mollisias growing on stromata of Jackrogersella mulformis on a fallen Betula branch.

Asci 8-spored, croziers+, IKI+(b). The asci also had a little round guttule that caught my attention.

Paraphyses with a typical long VB, KOH+ strong yellow. Outer surface with short hairs. The excipulum seems a bit strange for a Mollisia ("Phialocephala piceae").

Spore OCI=0-1, measurements:

(8.2) 8.8 - 9.3 (9.5) × (2.2) 2.3 - 2.5 (2.6) µm
Q = (3.4) 3.5 - 4 (4.1) ; N = 8
Me = 9 × 2.4 µm ; Qe = 3.8

I'd assume this is Mollisia albogrisea / Phialocephala piceae, but the substrate seems a bit odd.