Beech Jellydisc Identification Guide

What You Are Looking At

The first sighting is usually a pale, glistening crust of small rubbery buttons packed shoulder to shoulder along the upper side of a fallen beech trunk. From a few metres away it can read as a patch of wet foam or a spill of something translucent. Close up, the colony resolves into dozens or hundreds of individual top-shaped bodies, each one to three centimetres across, flesh-pink to pale buff, sometimes with a faint lilac wash, and semi-transparent enough that you can see light through the thinner edges. Press one gently: it yields, springs back and holds its shape. That elastic, firm-jelly consistency is central to the identification.

The Setting

This is an autumn fungus of damp mature beech woodland, appearing from roughly September through November. It grows on recently fallen beech trunks and thick branches, usually where the bark is still tight or has only just started to slough, and it strongly favours wood that is freshly down rather than long rotted and crumbling. Sheltered, humid situations produce the best colonies: shaded slopes, stream-side hollows, the shaded flank of a big log. If you find a good log, note it, because the colonies often persist for weeks and reappear the following autumn while the wood still holds its substance.

Reading the Individual Fruit Body

Separate a single body from the crowd with a knife tip and look at it in isolation, because in a dense colony the shapes distort. On its own it is turbinate, meaning it narrows downward from a broad top to a short thick stalk-like base, rather like a spinning top or a squat wine cork.

The upper surface is the working part. It is flat to gently convex, smooth, even, and slightly shining, and this is the fertile face where the spore sacs sit. Colour there is pale pinkish-buff, sometimes with a lilac or faintly violet cast in fresh material, fading toward dirty cream in age.

The outer and lower surfaces are paler and duller, minutely roughened or scurfy-granular when you look with a hand lens, and they run down into a stubby base attached broadly to the wood. There is no true stipe, no ring, and nothing resembling gills, pores or spines. Where growth is very dense the bodies press against one another and become angular and irregular, so always judge shape from a marginal specimen.

Flesh and Consistency

Cut one in half vertically. The interior is uniformly gelatinous, firm, translucent and slightly rubbery, with no layering, no chambers and no colour change on exposure. It does not weep, does not go slimy on the fingers, and does not collapse. Dried out in a spell of sun it shrinks to a hard wrinkled scab and rehydrates when rain returns, which is worth knowing because half-dried colonies look completely different from fresh ones.

Getting a Spore Deposit

This is an ascomycete: the spores are shot from sacs in the flat upper surface rather than dropped from gills, so the technique differs slightly. Set a fresh fruit body upper-side-down over black glass or dark card, cover it with a bowl to trap moisture, and leave it several hours; alternatively lay a group upper-side-up under a glass slide held a few millimetres above them and let the spores fire upward onto the slide. Either way the deposit is essentially white to colourless and will only be visible against dark backing or under a lens. Microscopically the sacs each contain eight smooth, hyaline, elliptic spores of around six to nine by three to four micrometres, occasionally becoming one-septate when fully mature, and the sac apex stains blue in iodine reagent. Any blackish or brown deposit takes you elsewhere entirely.

Ecology

The fungus is a saprotroph, colonising the sapwood and inner bark of newly dead beech and drawing on the sugars and cellulose there while the wood still has structure. This is why it associates so strongly with fresh windfall: it arrives early in the decay sequence and is displaced later by tougher, longer-lived wood rotters. Colonies frequently run along the line of a split or a bark seam where moisture collects, and neighbouring bodies fuse into a continuous gelatinous ribbon several tens of centimetres long.

Separating the Look-alikes

Purple Jellydisc, Ascocoryne sarcoides. The closest confusion and often on the same beech logs. Its colour is a much stronger reddish-purple to wine-purple, and its form is far more irregular, producing lumpy, lobed, brain-like cushions alongside the neater discs. The Beech Jellydisc stays pale pinkish-buff and keeps a tidy top-shaped outline. Where colour has faded in old material, form and consistency carry the decision.

Ascocoryne cylichnium. Similar purple tones, with distinctly larger spores that become multi-septate. Again the colour separates it from the pale Beech Jellydisc.

Beech Jellybrain, Ascotremella faginea. Purple-brown and strongly convoluted into folded, brain-like lobes, so the outline is nothing like a flat-topped disc, though it shares the beech substrate.

Black Bulgar, Bulgaria inquinans. Superficially top-shaped and rubbery, but glossy black on the fertile surface, brown and roughened outside, and it grows on oak rather than beech. It also releases a copious blackish spore deposit that dirties whatever it touches.

White Brain, Exidia thuretiana. A basidiomycete jelly fungus: whitish, translucent, and folded into brain-like lobes rather than flat discs, growing on fallen branches of various broadleaves. Its spores are sausage-shaped rather than elliptic.

Crested form of the same species. Some collections develop wavy, leafy, crested margins rather than smooth discs. The colour, consistency, substrate and spores are unchanged, so treat these as variation rather than a different fungus.

Summary of the Working Characters

Dense colonies of firm, elastic, translucent, top-shaped bodies with smooth flat pale pinkish-buff upper faces and slightly scurfy paler flanks, growing on recently fallen beech in autumn, releasing colourless elliptic spores from eight-spored sacs. Read colour, form and substrate together and this fungus is straightforward.