I must refer to Elisabeth Stöckli's item "Nectria" with link: http://www.ascofrance.com/forum?page=1
In order not to disturb the flow of Elisabeth's item, I am launching a new item on the forum although I am convinced it is about the same species.
On 23 February 2023, I found on twigs of Sambucus nigra covered with Xanthoria parietina and Orthotrichum affine several small to very small fruiting bodies. On the rhizoids of O. affine it was Octospora affinis but on the leaves there were orange/pink perithecia singly or in small groups. They were apparently loose on the leaves (some anchor hyphae?).
Preparations were difficult to make and photography was no sinecure either. When applying a coverslip, the perithecia shot away from under the glass. To recover the fruiting bodies during a second attempt, I had to insert a piece of leaf along with the FRB's. Due to the very small size and high transparency, focusing was difficult (limitation quality microscope!).

FRB: 195 x 185 µm
Asci: 35-40 x 5-6.8 µm
Spore: 6-8.5 x 2.3-3 µm; subcylindrical with 1 septa, constricted at the septa
Melzer: negative

Following on from item by Elisabeth probably Nectria hirta ? I myself have little experience with this genus.

Many thanks for any comments,

François Bartholomeeusen