This fantastic mushroom is a brown brain fungus – Tremella steidleri.
You can find it growing on oak trees. It is related to the yellow brain fungus that is often seen growing on gorse bushes hereabouts:
Both species are parasites on other fungi – the brown brain fungus feeds on hairy stereum: an apricot orange, crinkly bracket fungus that is very common on oaks.
Brown brain fungi do vary greatly in size, the largest are somewhat larger than a sheep’s brain, but I have not yet seen one that would adequately fill out an adult human cranium.
It is a master of disguise, with a number of different looks:
when fresh, it has a distinctive light grey bloom on an ochre background;
in dry weather it can shrivel and blacken;
but the jelly dissolves in rain, to make a slimy, translucent glob.
This can then dry again to a formless, tan mass.
It has a soft, rubbery texture and a fine, branching internal structure – rather like a cauliflower floret.
A First in Scotland
This fungus is nationally and internationally scarce, and recent reports of it growing in Glenan, posted on iNaturalist, turned out to be the first time the fungus has been recorded in Scotland.
I went back to collect a specimen so that its DNA can be sequenced. The specimen was sliced up; dried in a dehydrator at 40C; sealed; and sent by mail to the Grampian Fungus Group who have gene sequencing equipment and very kindly agreed to process this sample despite how far away we are from their part of the country.
Sequencing doesn’t always work, but if we’re lucky, Glenan might be able to provide the information required to put the brown brains in their proper place.
You can track observations of this fungus on iNaturalist: https://www.inaturalist.org/observations?subview=map&taxon_id=517556
And see what else has been discovered living in and around Glenan: https://www.inaturalist.org/projects/friends-of-glenan-wood?tab=observations
[Submitted by Ben Mitchell, member and volunteer at Glenan Wood]
