While in NE Scotland recently I made a couple of collections of Gnomoniaceae on fallen leaves of Betula (probably Betula pubescens). I was expecting them to be Ophiognomonia ischnostyla but the ascospores seem wrong for this species.

Details are as follows. Perithecia fully immersed; ca 600 µm diam.; with necks up to ca 1500 µm. Asci ca 45-55 x 12-16 µm; with prominent apical ring. Ascospores hyaline; fusiform; 1 -septate (septum median); constricted at septum; 22-25 x 3.5-4 µm; no appendages seen.

The ascospores seem to be too large for O. ischnostyla. For example, Sogonov et al. (2008) Studies in Mycology 62:1-79 give dimensions of (12.5–)13.5–15.5(–18.5) × (1.5–)2(–2.5) µm for O. ischnostyla. This corresponds with my experience of the species in the UK.

Monod's monograph of Gnomoniaceae contains Gnomonia betulina (synonym G. campylostyla) with ascospores 13-23 x 2.5-5 µm, which would fit with my collections. However, the spores are described as having appendages. G. betulina and/or G. campylostyla don't seem to be treated in Sogonov et al or in any other recent papers on Gnomoniaceae.

I'd be grateful for any help anyone can provide.

Thanks

Marcus