Toothed Jelly Fungus

The Toothed Jelly Fungus is an oddity that combines two forms not usually seen together: the wobbling, translucent, rubbery texture of a jelly fungus and the spine-covered fertile surface of a hydnoid. Fruiting bodies are tongue-, spatula- or fan-shaped, attached to wood by a stubby lateral stalk, and are cool and gelatinous to the touch, holding their shape but flexing readily.

Despite the resemblance to Hydnum implied by its old placement, this species is a heterobasidiomycete in the Auriculariales, related to jelly ears and Exidia rather than to the true toothed fungi. Its basidia are divided by septa, a microscopic feature that separates the jelly fungi from the ordinary club-shaped basidia of gilled and pored mushrooms.

It is one of the easiest fungi in the woods to identify because nothing else shares its combination of texture and structure. Recent taxonomic work has divided the traditional broad concept into several regional species, but the general field impression of a translucent toothed jelly on conifer wood holds across all of them.

Fruiting body

Usually 2-8 cm across, spatulate, tongue-like, fan-shaped or almost bracket-like, flattened and slightly convex. The colour ranges from clear translucent white or greyish through smoky grey to brown, and the tissue is translucent enough that a specimen held up to the light glows and the outline of the spines shows through. The upper surface is finely roughened, granular or minutely hairy, giving a slightly frosted appearance.

Spines

The lower surface is covered in soft, short, conical spines 2-5 mm long, translucent white to greyish, blunt and gelatinous rather than brittle. They are yielding to the touch and quite unlike the crisp spines of Hydnum or the tough teeth of Hydnellum.

Stipe

A short, thick lateral or off-centre stalk attaches the fruiting body to wood, sometimes reduced to little more than a stub or a broad point of attachment. It is the same gelatinous texture and colour as the rest of the fungus.

Flesh and spore print

The flesh is uniformly gelatinous, translucent and rubbery, shrinking and hardening into a dark, brittle flake when it dries and reviving when rewetted. The spore print is white; spores are colourless and broadly ellipsoid to nearly round, produced on longitudinally septate basidia.

This fungus grows on well-rotted conifer wood, especially damp fallen logs, stumps and buried timber under spruce, pine, fir and hemlock, and occasionally on hardwood in some regions. It favours shaded, consistently moist situations, and is often found on the underside or shaded flanks of logs, on cut stump surfaces, and along the mossy sides of decaying trunks, appearing singly or in overlapping troops.

Fruiting runs from late summer through autumn and often continues into early winter, since the gelatinous tissue tolerates frost and can revive after freezing and thawing. The species group is widely distributed across the cool temperate and boreal Northern Hemisphere, with equivalents recorded in the Southern Hemisphere, and it is one of the more frequently encountered jelly fungi in conifer forest.

Pseudohydnum gelatinosum is a saprotroph of decaying conifer wood, colonising timber that is already well advanced in decay and contributing to the later stages of breakdown as the log softens into the forest floor. Members of the Auriculariales in general specialise in this late-stage niche, working through wood that primary decay fungi have already opened up.

The gelatinous construction is an adaptation to fluctuating moisture. The tissue absorbs water and swells rapidly during rain, exposing the toothed fertile surface and releasing spores, then dries down to a hard inconspicuous crust in dry weather without dying, ready to rehydrate at the next wetting. This cycle can repeat several times, letting a single fruiting body shed spores across weeks rather than in one short window.

Other jelly fungi in the same forests are separated by their fertile surfaces. Tremella species form lobed, brain-like or frilly masses with a smooth surface and no teeth, and Exidia species are blobby, cushion-like or button-studded with smooth fertile faces. Auricularia forms ear-shaped brackets with a veined, wrinkled underside rather than free-standing spines.

Among the toothed fungi, Hydnum species are firm and fleshy with brittle spines and grow from soil, while Hydnellum and Phellodon are corky or leathery, dry to the touch and also soil-dwelling. Nothing else is simultaneously translucent, gelatinous, toothed and attached to wood, so once the underside is checked the identification is settled.