This is a very small and difficult to find lichen. You really need to know what you are looking for to come across this little fellow. Yet, I wasn’t looking for it! Firstly, it occurs on trees, I believe on mature or old trees in undisturbed places. Its though to be indicative of a woodland that has a long undisturbed history, one that has not been felled for trees or to make way for farming any time in its history. I found it in West Cork on an old oak tree. I had stopped by the old oak to have a break and figure out where I would go next. While thinking on the difficulty of identifying lichens (especially in the field) I started admiring the lushness of mosses on the trunk of the oak when I spotted the tiny emerald green squamules. Sandwich was promptly put aside and out came the hand lens. Yes, that looked like an Agonimia okay. Eventually I decided it must be octospora. Much photographing (and how difficult it was) and a small sample bagged, it was time to set off again with renewed energy.
Work at home lead to the conclusion that it was indeed the rare and difficult to find Agnoimia octospora (8 spores in the ascus). Will I every find it again? Probably not. This will be a nice one for the 2nd edition of my book!
Books used to confirm my identification:
Lichens – Frank Dobson – then on to The Lichens of Great Britain and Ireland and lastly some Googling.