Added: 30th January 2013 Description:
Growing on a sheltered wall. I'm not sure if these are lichens - lots of moss and very moist patches. But I keep thinking I've seen something like this before.
ADDED a third picture - "cobwebby" or just out of focus? Thanks to AlanS.
Identifications Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
Confidence: It might be this. Notes: May not be a lichen - a very confusing mixture of green and white matter; difficult to describe.
Confidence: It's likely to be this, but I can't be certain. Notes: This is a parasitic fungus, or one could think of it more as an aggressive predator, attacking and killing 'chlorococcoid' green algae, including those inside lichens, and then also killing the lichens themselves. Its ring-like growth is often seen on urban trunks and walls. I have not shown 100% certainty as Athelia is a difficult genus, and while lichenologists happily call this A. arachnoidea, this is not quite so clear cut in Athelia literature. "arachnoidea" is a reference, I assume, to a cobweb-like appearance, which it often has when freshly growing. (As/when/if I get back to my website I'll probably put up a page on this species - time I added some more lichenicolous fungi.)
No interactions present.
Other observations of