Psammina filamentosa on Punctelia?

[JennyS]

Very faint brown marks on lobe of Punctelia borreri on Dorset/Wiltshire border. Under the microscope the conidial arms were c.50-75 µm long, straight and very slightly tapered at the ends - is this Psammina filamentosa?

Some smaller clumps in the same section had conidial arms slightly more curved and much shorter, most <30 µm long - are these immature or possibly a different species?

[Paul Cannon]

Could well be, but difficult to be sure from your images. The conidial arms are supposed to be 2.5-4 um diam. and multiseptate - is that the case with your collection? Another option would be an Epithamnolia, but that doesn't seem to fit macroscopically.

Best wishes
Paul

[JennyS]

Thanks Paul - the arms were 2.5-3.5 µm wide and with septa present, but not clear enough to count how many. I emailed David Hawksworth a few days ago but haven't had a reply yet.

[JennyS]

The conidia with long arms confirmed by David Hawksworth as Psammina filamentosa.