Toothed Jelly Fungus Identification Guide

The Setting You Are Standing In

Toothed Jelly Fungus belongs to old, wet, mossy conifer woodland. The setting to picture is a spruce or pine plantation past middle age, or a damp mixed wood with plenty of fallen timber: logs sunk into the moss, stumps softened into punk, and the underside of trunks lying just clear of the ground. Autumn rain has been falling for days. You crouch to look along the flank of a rotting log and see a row of translucent shapes catching the light from behind, like small pieces of frosted glass stuck to the wood.

That backlit translucency is the first impression and the most memorable one. Each fruitbody is 2 to 8 cm across and only 3 to 8 mm thick, shaped like a tongue, a spatula or an irregular fan, attached to the wood sideways by a short stubby lateral or off-centre stalk. They usually come in troops, lined along a crack in the bark or scattered over the top of a stump.

Pick one up and the second impression is textural. It is cold, wet and rubbery, elastic under the thumb, springing back after being squeezed, and it wobbles when the hand moves. Nothing else with a toothed underside behaves like this.

Reading the Upper Surface

The upper surface is smooth in outline but not in texture. Under a hand lens it is finely velvety, pruinose or minutely granular — a fine bloom of tiny pale projections that scatter light and give the surface its slightly frosted look. It is not sticky and not slimy, despite the fruitbody being gelatinous throughout.

Colour is variable and depends heavily on light and age. Fruitbodies range from near-transparent watery white through pale grey and smoky blue-grey to buff, tan or a distinct brown, with the darker forms usually being older or more exposed material. In dim woodland they often read as ghostly grey-white; against bright backlight the same fruitbody looks glassy.

The margin is entire and often gently wavy or shallowly lobed, and the whole cap frequently curls slightly, so the outline is rarely a neat fan.

The Spore-bearing Surface

Turn it over. The underside is entirely covered by soft, translucent, conical spines packed densely together, each 1 to 3 mm long, whitish to pale grey, tapering to a blunt point. Under a lens the spines look like tiny gelatinous stalactites; they are so densely set that the surface between them is hidden.

Critically, these teeth are soft. Run a fingertip across them and they flatten and spring back, giving the sensation the alternative name of the species evokes — a small, cold, rough tongue. Fleshy toothed fungi in other genera have firm, brittle spines that break when pressed. This textural difference is the fastest and most reliable field character in the whole guide.

Flesh, Structure and Colour Change

Cut a fruitbody vertically. The section is gelatinous, translucent and watery throughout, whitish to slightly greyish, with no distinct internal layers, no fibrous core and no separate skin. Sometimes a slightly denser, more opaque line marks the axis running from the attachment point out toward the margin.

The flesh is elastic rather than brittle: it bends far before it tears, and it tears with a slight rubbery resistance instead of snapping. There is no colour change on cutting or handling — no blueing, blackening or reddening — and no latex or juice beyond the water inherent in the tissue.

Two behaviours are worth knowing because they explain otherwise puzzling finds. First, the fruitbodies dry down in dry spells into hard, dark, shrivelled flakes barely recognisable as the same organism, then swell and revive within hours of rain. Second, they tolerate freezing: after a frost they thaw and continue growing, which is why they can be found late in the year when almost nothing else soft is left on the logs.

Taking a Spore Print

A gelatinous fruitbody will not sit obediently on paper, so prop it. Cut a fruitbody free with a little of the stalk, wedge it teeth-downward over a piece of dark card using a matchstick or a folded strip of paper to hold it clear of the surface, cover the arrangement with a box over a damp tissue, and leave it overnight.

The deposit is white and typically fine and sparse, so dark card is essential to see it. Spores are small, subglobose to broadly elliptical, around 5 to 7 micrometres, and smooth.

If you have a microscope, one further check is decisive for the wider group: the basidia are divided lengthwise into four cells by longitudinal septa, giving the cross-partitioned appearance typical of the jelly fungi. A squash mount from the spine tips shows them clearly, and it separates this species from every fleshy toothed fungus at a stroke.

Substrate and Season

This is a saprotroph of well-rotted wood, overwhelmingly conifer — spruce, pine, fir, hemlock and larch — with occasional records on hardwood. It prefers timber that is already soft and moss-covered, in deep shade and constant humidity, and it often fruits on the shaded underside or lower flank of a log rather than the exposed top. Stumps, fallen trunks, half-buried branches and the sawn ends of old logs are all productive.

The season is late summer through late autumn and on into early winter in mild regions, peaking after sustained wet weather. It is gregarious, so finding one usually means finding a dozen along the same length of wood, and a productive log will often fruit again in following years until the timber is fully broken down.

Separating the Look-alikes on Structure

Hedgehog fungi (Hydnum repandum and relatives) — also toothed underneath, but the whole fruitbody is firm, dry and fleshy, coloured cream to apricot, has a well-developed central stem, and grows from soil in woodland rather than from wood. Its spines are brittle and break when bent.

Sarcodon and Hydnellum species — terrestrial, tough or corky, brown, with firm spines and no gelatinous texture.

Jelly ear (Auricularia auricula-judae) — gelatinous, translucent and wood-inhabiting, so a genuine contender, but it is ear- or cup-shaped, brown to tan, and its inner surface is smoothly veined and wrinkled with no spines at all. It also favours elder and other hardwoods.

Witches' butter (Tremella mesenterica) and relatives — yellow to orange, brain-like folded lobes, no teeth, and typically growing on hardwood branches in association with crust fungi.

Black jelly fungi (Exidia glandulosa, E. nigricans) — blackish gelatinous cushions whose surface bears scattered pimple-like bumps rather than dense conical spines.

White brain fungus (Exidia thuretiana) and Ductifera species — whitish and gelatinous, but formed as spreading brain-like cushions with a smooth surface, lacking both spines and a stalked tongue shape.

A Working Checklist

1. Well-rotted mossy conifer wood in damp shade, autumn into early winter.
2. Tongue, spatula or fan shape, 2 to 8 cm, attached laterally by a stubby stalk.
3. Translucent, gelatinous, elastic flesh that springs back when squeezed.
4. Finely velvety or frosted upper surface, white to grey or brown.
5. Dense soft translucent conical spines beneath, flattening under a fingertip.
6. White spore deposit; no colour change on cutting.