Attack of the parasitic jelly fungus

 

This gloopy-looking stuff is Yellow brain fungus Tremella aurantia, growing on the dead branch of a tree along one of my favourite walks, in the Deerness valley, County Durham. It’s a jelly fungus with a rather sinister lifestyle, parasitising another common fungus, hairy curtain crust Stereum hirsutum, which you can just see, dying, on the underside of the branch.

The microscopically-fine hyphae of the parasite, invisible to the unaided human eye, creep through the decaying wood, find and clamp onto those of their host and eventually kill it. The damp, foggy weather we’ve had recently has been perfect for the growth of the gelatinous parasite.

There are two common species of Tremella in the British fungal flora - this one and Tremella mesenterica - which are virtually identical and can only be easily identified by the hosts they parasitise: T. mesenterica preys on another crust fungus called Peniophora, which often grows on gorse stems hereabouts.

And here, a little further down the dead branch bearing the yellow brain fungus, is some more hairy curtain crust, so there’s plenty more of its victim for it to feed on.

Mellow yellow

Yellow brain fungus Tremella mesenterica, growing on a dead branch of a large Cotoneaster in Kirkby Stephen in Cumbria. This fungus didn't kill the branch; it's a parasite on another fungus in the genus Peronospora, which had already killed the branch. The fungus is paler when young, but matures to this vibrant shade of chrome yellow.

This aspen Populus tremula, growing in upper Swaledale in North Yorkshire, is the brightest tree in the local landscape at present, beating strong competition from birches and rowans. Aspen leaf stalks are laterally flattened so each leaf flutters from side to side in the slightest breeze and the whole tree seems to shimmer.

Pictures of the winter buds of aspen here and of the fungus that attacks its leaves here.