Hello Gernot,
See the message of Stefan BLASER on 14/12/2013 and the comments of Zottobest regards
André LAURENT

Hello, André!

Thank you for pointing out this thread. I did read it before I posted my collection. I am mostly wondering about the host because it seems unusual for P. necans.

In the meantime I collected another specimen on Ericaceae (Calluna vulgaris) which I attach here (the last photo shows conidia). Again, the shape of the ascospores differs significantly from a previous collection of mine on Rhododendron ferrugineum: http://ascofrance.com/search_recolte/4476. It seems to me that more than one Pseudophacidium species occurs on Ericaceae.

Best wishes,
Gernot

PS:
I think that the collection linked above on Rhododendron ferrugineum might correspond to Pseudophacidium rhododendri (= Propolis rhododendri) described by Rehm from the same host with partly bent ascospores:

https://www.biodiversitylibrary.org/page/474077#page/124/mode/1up
https://www.biodiversitylibrary.org/page/1076082#page/109/mode/1up

Whereas the collection on Calluna vulgaris might fit better for Pseudophacidium callunae (= Phacidium callunae) described by Karsten from the same host with ellipsoid to oblong-ellipsoid ascospores:

https://www.biodiversitylibrary.org/page/13414700#page/256/mode/1up
https://www.biodiversitylibrary.org/item/21913#page/271/mode/1up

This group would be a good candidate for a thorough revision...

Best wishes,
Gernot

Hello, Gernot
I have recently made a collection on Calluna vulgaris which I initially labeled Pseudophacidium cf. ledi. However, this collection had differently shaped, broader spores and the cells in the marginal flaps differed from the description of P. ledi in Morphologie und Biologie von Pseudophacidium-Arten (Ascomycetes), M. C. Egger, 1968. This collection also had some paraphyses. It might have been infected with a hymenial parasite as some of the asci had aborted or deformed/discolored spores and some other asci were filled with conidia. I do know if this could have altered the shape of the “healthy” spores as well.
When I searched for other records of P. ledi to compare my specimen with I noted that photos of the marginal flaps often seemed to show somewhat different cell structure/sizes. This along with differing spore shapes in different collections could support your idea of there possibly being more than one species occurring on Ericaceae.
Here is some photos of my collection:
Best regards, Hulda

Hello, Hulda!

Thank you for sharing your collection. Every additional specimen could help us better understand this group. I will keep an eye out for these species, and who knows, maybe one day someone will actually attempt a revision using modern techniques.

Best wishes,
Gernot