Dear George,

your find certainly belongs to the Octospora humosa complex. O. humosa s.str. grows on Polytrichum piliferum but I also know related collections on Atrichum undulatum, Polytrichum formosum, P. longisetum, Pogonatum aloides,P. urnigerum, Oligotrichum hercynicum and even Pogonatum pensylvanicum in North America. Preliminary DNA-studies group the collections according to their host species suggesting a different taxon for each host. Unfortunately, the apothecia can grow with the moss still in protonemal stage, making the identification of the host sometimes impossible. The whole O. humosa complex has a unique infection structure of large globose galls on the rhizoids, whereas the gall surface is free of hyphae (see image). When you find these galls you can be certain it belongs to this group.

With best wishes

Jan