Exidia recisa/repanda
Willow/Birch Jelly
Names
Scientific: Exidia recisa and Exidia repanda
English: Willow Jelly and Birch Jelly
(old scientific names include Tremella recisa for E. recisa and Tremella repanda and Ulocolla repanda for E. repanda)
Exidia recisa on willow twigs
Description
Two for the price of one this month, and again without the classic umbrella shape of a mushroom or toadstool. Exidia are still a basidiomycetes (they have spores which develop on special structures called sterigmata – found on the end of a cell called a basidium) as opposed to being ascomycetes where the spores are released from inside pressurised cells but the fruit bodies are highly gelatinised. Microscopically these two Exidia species are virtually identical and they are distinguished on host preference and by the shape of the fruit body. Molecular work does seem to support there being two distinct species – certainly the rounded, button shape seems to be consistently found on birch (Exidia repanda) and the more pendulous structure almost always on willow (E. recisa). Neither species grows much more than a 2 or 3 cm fruiting structure and both are golden-brown to cinnamon in colour.
Jelly fungi are capable of drying out, shrinking and darkening so as to be virtually invisible on the substrate and then rehydrating with rainfall or high humidity. There is no point in looking for them on bright sunny days - wait for a grey, damp day in
the winter months. If you are lucky and in the right kind of habitat, it is quite possible to find both species in the same woodland – a woodland near Killiecrankie produced both in January 2011.
These ‘jellies’ are saprotrophic or ‘recycler’ fungi, breaking down dead wood. Fungi are the only group of organisms that can break down lignin and without them we would be buried under many metres of woody debris. They also play a vital role in driving the carbon cycle, releasing nutrients that they don’t require back into the habitat. Winter is the best time to see good material of many of these species fruiting, as the wetter conditions mean that the wood remains damp (and thus easier to break down) and the spores stand a good chance of being released into the air stream as surrounding ground vegetation has died down.
Exidia repanda on birch twigs
Fruiting
There are records from every month of the year for both of these species but I suspect that one of the reasons why Birch Jelly is so rarely recorded is that the vast majority fruit in the winter months when few people are looking.
Habitat
The species of tree that these Jellies appear on is crucial to any attempt to identify them. As the common names suggest, E. recisa fruits on willow twigs and branches – usually dead attached ones. Liz has tended to find E. repanda on fallen birch twigs and branches but this may not be significant. Damp broadleaved woodlands and road verges can be productive hunting grounds.
Distribution
As given in the Checklist of the British and Irish Basidiomycota Legon & Henrici 2005: Scotland and England – E. recisa ‘present but frequency unknown’ in all areas of Britain and Ireland. E. repanda ‘present but frequency unknown’ only in Scotland and N. Ireland (a single record in N. Ireland).
The total number of records for Willow Jelly on the Fungal Records Database of Britain and Ireland (2011) is 215 with 54 of those originating in Scotland. Birch Jelly has only 37 with 26 from Scotland. Is the Birch Jelly really so much rarer than the Willow Jelly? NBN distribution maps for E.recisa and E.repanda.
Please remember to submit your records to your local recording group or via the Scottish Fungi online recording form.
Liz Holden, 2011