pf339's picture

Lichen on flagstone

Observed: 9th July 2013 By: pf339
S159 Neighbourhood Nature - course complete
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Lichen on flagstone

Lichen with lecanorine apothecia growing on concrete flagstone. Patches, about 2cm to 3cm in size, of apothecia with brown discs and thick, white margins (like tiny white doughnut rings). C-, K-. Possibly Lecanora semipallida.


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Some fungi are very poisonous so a mistaken ID could have serious consequences.

Species interactions

No interactions present.


synan's picture

Or alternatively...

Lecanora dispersa, which has a whitish thallus rather than the grey-black 'stain' described for L. semipallida. What can be seen of the endolithic thallus in the photo seems arguably grey-white.

The apothecial margins of L. semipallida should appear yellow-orange under long-wave UV light. Apothecia I have collected from material looking like this on concrete have so far responded UV-, so I have labelled them L. dispersa.

A less easily observed difference, and one I haven't looked at, is that L. semipallida has granules in the epithecium that are soluble in K, whereas those in L. dispersa are insoluble.


pf339's picture

L. dispersa

Thanks for information and suggestion. The white margins attracted my attention but now I think that may have been the bright sunshine yesterday so L. dispersa seems probable.
I shall add a revised identification of 'Lecanora sp.' as more careful examination is likely to be needed to go further.
Many thanks.

AlanS's picture

or maybe you were right first time?

I note that the apothecia are all seated on dark patches of thallus.

This looks like what I am calling L. semipallida - apothecia are more clustered than is typical for dispersa. Strong colonies I found on concrete wall-cappings this spring actually had slightly cream apothecial margins and were quite easily separable from L. dispersa nearby. Later this summer the same (?) apothecia seem to have had their margins bleached white. Still trying to get a good photograph.