Tree lichen- ID please.

[Hayseed]

This patch of lichen, about 2.5cm across, is on a small tree in S. Northumberland. Is it Lecanora Pulcaris? Help, please!

[chazzpott]

I don't know too much about Lichens, but I have checked my copy of Phillips (1994 edition) and this looks rather like Lecanora chlarotera.
L. pulcaris is not listed, so I can't comment on that.
Chas

[Hayseed]

Thank you for looking it up and posting a reply. I had a look in Frank Dobson's 'Lichens' and it certainly does look more like L.C hlarotera. This occurs in non-polluted areas according to Dobson, as was the tree. Thanks again!

Sorry my posting was put in twice. I thought the first one hadn't gone in.

[AlanS]

Yes, as far as one can ever tell from a photograph, this is Lecanora chlarotera.

It is quite variable. The crust always reminds me of porridge under a lens, but the porridge can be almost smooth or it can be very lumpy, the colour can be almost pure white to biscuit coloured and the discs ("jam tarts") can be pale milky brown to strongly red-brown or even quite dark. These colour differences can be shown by neighbouring patches on the same branch or trunk, which can be a little disconcerting.

However, there are several closely related species. L. pulicaris is one, usually with darker discs but this is not enough for a field or photographic ID. There are also rarer or overlooked species such as L. horiza, L. argentata and others. There is a chemical test, involving a toxic carcinogen, that separates L. chlarotera and L. pulicaris, but the only way to be certain in this group is to cut a thin vertical section of a mature disc and examine various parts of the tissue under a microscope. I have quite a few photographs of this group myself, but most await my finding a time for a "Lecanora day" that will be devoted to cutting thin sections and much use of profane language.

For all that, L. chlarotera is much the most common, especially on young trees, and I think of it as the "supermarket car-park lichen". It forms conspicuous, pale, rounded patches, often still immature, on young, smooth-barked, planted trees, often in company with Lecidella elaeochroma (small, black disks). I would be surprised if Hayseed's photograph proved to be anything else.

Alan

[Hayseed]

Thank you, Alan, for your comprehensive response. It's great news to know that an expert (yourself) is taking time and trouble to help beginners like myself.

[AlanS]

Originally Posted by Hayseed

Thank you, Alan, for your comprehensive response. It's great news to know that an expert (yourself) is taking time and trouble to help beginners like myself.

Thanks, but I'm still a long way from expert yet, though slowly learning ...

As for taking time and trouble, well, when the alternative is a pile of essays to mark, even Lecanoras are suddenly attractive!

Alan