Tremella mesenterica Retz.

Yellow Brain (Tremella mesenterica) is a bright golden jelly fungus that looks like a small, wobbly heap of folded yellow lobes on a dead twig. When wet it is soft, translucent and glistening, deepening to orange with age. In dry weather it shrinks to a hard, dull orange crust, then swells back into life after the next rain.

It grows on dead branches of broadleaf trees, often still attached to the tree, and is common on gorse. It can be found all year, but is most obvious in wet winter weather. It is not really feeding on the wood: it is a parasite of crust fungi (Peniophora) growing on the same branch.

Naematelia aurantia is very similar but more orange, and grows on Hairy Curtain Crust (Stereum hirsutum). Leafy Brain (Phaeotremella foliacea) is brown. Yellow Brain is not poisonous, but it is tasteless and insubstantial, so it is not worth collecting.