Jelly Tooth

Jelly Tooth (Pseudohydnum gelatinosum) is one of the most curious fungi in temperate woodland: a translucent, wobbling tongue or spatula of jelly that bears a dense pile of soft white spines on its underside. It combines the tissue of a jelly fungus with the fertile surface of a hedgehog fungus, and once seen it is essentially impossible to confuse with anything else.

The fruiting body is usually attached to a rotting conifer stump by a short, thick lateral or eccentric stalk, so that the tongue projects sideways or upwards. Held against the light it is glassy and slightly frosted, with the spines showing as a fine fringe along the lower edge.

Despite the resemblance, it is unrelated to the true toothed fungi such as Hydnum and Hericium. It belongs to the Auriculariales, the same order as Auricularia and Exidia, and the spines are simply an independent solution to the same problem of increasing fertile surface area.

Fruiting body

Tongue-, spoon- or fan-shaped, 2–8 cm across and up to about 2 cm thick, with a short thick stalk attached at one side or off-centre. The upper surface is minutely roughened or velvety, and the whole structure is soft, elastic and quivering, springing back when pressed.

Spines

The defining feature. The entire lower surface is covered in crowded, soft, blunt, conical spines 2–5 mm long, translucent white and gelatinous like the rest of the fungus, quite unlike the firm brittle teeth of a true hedgehog fungus. They yield instantly to a fingertip.

Colour

Variable: translucent white, greyish-white, smoky grey, pale brown or, in shaded and cold conditions, distinctly dark grey to brownish-grey. The spines are almost always paler than the upper surface, typically white or very pale grey.

Flesh and spore print

Flesh clear, gelatinous and watery throughout, translucent enough to read faint shapes through a thin slice, with no fibrous core, no ring and no volva. No colour change when cut or bruised. Spore print white.

Jelly Tooth grows on well-rotted conifer wood: stumps, fallen logs, large branches and buried woody debris, most often where the wood is soft, damp and mossy. Spruce and pine are the classic substrates, and it is a characteristic fungus of old plantation stumps and shaded conifer forest floors. Occasional records come from broadleaved wood.

Fruiting runs from late summer through autumn, often persisting into early winter because the gelatinous tissue tolerates frost. The species is widespread across the conifer regions of the temperate Northern Hemisphere and is also recorded from the Southern Hemisphere, including New Zealand and southern South America.

Pseudohydnum gelatinosum is a saprotroph of decaying conifer wood, fruiting from mycelium in stumps and logs that are already soft and well advanced in decay. It is therefore a late-stage member of the wood decomposition community, often appearing alongside mosses growing on the same crumbling stump.

The spines serve exactly the same purpose as gills or pores, packing a large fertile area into a small volume while presenting a downward-facing surface from which spores can fall freely. Because the tissue is gelatinous rather than fleshy, the fruiting body resists both drying and freezing far better than a soft-fleshed mushroom, which is why it can still be found in good condition after the first frosts.

Hydnum repandum (Wood Hedgehog) also has spines beneath a cap but is opaque, firm-fleshed, buff to pale orange, grows from soil in mycorrhizal association with trees, and has brittle spines that snap off; Jelly Tooth is translucent, gelatinous, grows on wood, and its spines squash rather than break. Hericium species form large branched cascades of long hanging spines and are pure white and fibrous rather than jelly-like.

Auricularia auricula-judae (Jelly Ear) shares the translucent gelatinous tissue and lateral attachment but has a smooth to veined and folded lower surface with no spines at all. Exidia thuretiana is whitish and gelatinous but forms shapeless cushions and folds with no cap, stalk or toothed underside.