Lacanora argentata maybe

[chrisjohnson]

Found on Alder. Thallus silver-grey, prothallus black. K+ yellow, P-. Spores (small sample) 13.5 x 8-9µm.

Any thought welcome.

Chris

[diggleken]

You know I'm not an expert Chris, but in the absence of takers, that looks spot on from Dobsons description.
Nice shot, clearly shows whats needed, incl black prothallus edging.
Cheers
Ken

[synangium]

Looks good to me too, given the prothallus.

Nigel

[JennyS]

When you measured the spores did you also check whether or not there were granules in the epithecium?

[chrisjohnson]

Hi Ken & Nigel

Thanks for the vote on this one; encouraging.

Chris

[chrisjohnson]

Originally Posted by JennyS

When you measured the spores did you also check whether or not there were granules in the epithecium?

No

I still have a sample and will have another look today.

Chris

[chrisjohnson]

Hi Jenny

No granules on or in the epithecium but large ones in the thalline margin. Got a better section today with matures spores which measure 13-13.5 x 7-9µm, so not much difference there.

Chris

[AlanS]

This is possibly L. argentata, not a bad candidate, but my money would be on L. chlarotera. If the hymenial surface genuinely had no layer of granules, then, yes, L. argentata would seem to be indicated, but these granules/crystals are much smaller and less conspicuous than in the thalline margin to the apothecium.

The black prothalli visible in the photograph most likely belong the the neighbouring Lecidella elaeochroma. When this and L. chlarotera form a mosaic, as they often do, the black prothallus of the Lecidella is often very conspicuous at the junction of the two lichens.

My gut feeliing, admittedly neither scientific nor critically reliable, is L. chlarotera for this.

Alan

[chrisjohnson]

Many thanks Alan.

I'll revisit the site for another specimen and take a closer look.

Chris