Lichen saves my bacon

Rainstorms kept me in all morning, baking bread and doing paperwork, so I was relieved when the sun broke through in mid-afternoon and I could venture out into the wet world.

But photo opps have drastically diminished with the arrival of autumn. Mammals have birthed, eggs have hatched, plants have seeded and all life is quiescent now. Even the lichen spreading over an old wooden gate looked grubby, with a sort of sooty coating. But wait, take a closer look... those black dots are something else. It wasn't till I enlarged the image (x 50% here) that I could clearly see these disc-like apothecia, the spore-containing bodies involves in the complicated process that is the sex life of lichen, evidently in full swing right now. Lichen being a combination of fungus and alga, each fungal spore has to find an algal cell with which to unite before a new lichen can be created.
I'd need a whole 'nother lifetime to be able to identify individual species of lichen of which there are estimated to be around 17,000 in the world, although only 1800 in Great Britain and Ireland. I reckon this one is some kind of Lecanora, one of the crustose forms of lichen.

Trouble with Lichen was a 1960 novel by John Wyndham about the discovery of a lichen that slowed the ageing process so as to extend human life by several hundred years. That property has not yet been recorded but lichens have been used across the world and over the centuries as medicines, food, dyes and to kill wolves. There's a good list of these uses here and an article about the amazing, mysterious, but unstable fuschia-pink colour that was obtained from a certain lichen steeped in urine here. Well worth reading for its scholarship alone.