Slime Mould (Reticularia lycoperdon)
After spending quite a while thumbing through my fungi books looking for this species I reverted to puting the photograph on to the Open University Ispot website for the experts to take a look at and in no time at all I have an identification, Reticularia lycoperdon.
So why was it not in the fungi books? Because it is not a fungus, it is a slime mould! Slime moulds were once believed to be a form of fungus and do share many properties but they are now classified as a seperate life form and they are very much a specialist subject. There are not that many common species as far as I am aware but this one is quite common on dead willows and birches.
Find out more about this slime mould here: