Snow Fungus Identification Guide

First Impression And Setting

Snow Fungus announces itself as a splash of glassy white on dark, wet wood. You come across it in warm, humid, broadleaf forest - subtropical and tropical regions worldwide, and warm-temperate zones in a good wet season - usually within a day or two of heavy rain. It sits on fallen branches and dead standing limbs of broadleaf trees, most often on wood that has already lost its bark and gone grey.

At a glance it looks like a crumpled cluster of clear plastic ribbons, or a white sea anemone stuck to a log. The whole rosette is typically 3-8 cm across, occasionally up to 15 cm, and stands 2-5 cm proud of the wood. When it is fully hydrated it glistens and wobbles; when the sun has been on it for a day it looks like a hard yellowish scab.

Reading The Fruit Body

There is no cap, no stem, no gills and no pores. A jelly fungus of this kind produces a fruit body with no differentiated parts, so the identification is about overall architecture, texture and the way the surface behaves.

Architecture. The fruit body is built of many thin, wavy, leaf-like lobes or fronds, all radiating from a small common point of attachment on the wood. Each lobe is broad, flattened, undulating and often deeply crimped along its free edge, and the lobes overlap and curl in on one another, so the whole thing resembles a loose flower or a ruffled lettuce. This lobed, frondose construction is the single most important field character.

Colour. Pure white to translucent watery white, sometimes with the faintest ivory or pinkish tint in the thickest folds. Light passes through the lobes, so you can often see the wood grain distorted behind them. Ageing material yellows from the tips inward.

Texture. Soft, elastic and slippery to the touch, springing back when pressed, and tearing rather than snapping. Pinch a lobe and it feels like firm gelatin, not like rubber and not like flesh.

Drying and reviving. Cut off a lobe and leave it in the sun. Within hours it shrinks dramatically to a hard, horny, cream to yellowish crust glued to the wood, barely recognisable as the same organism. Wet it again and it swells back to the full ruffled rosette in under an hour. This reversible collapse is characteristic of the whole jelly-fungus group and is worth confirming, because a dried-out specimen on a log in dry weather is very easy to overlook.

Spore-Bearing Surface, Flesh And Colour Change

The fertile layer is spread over both faces of every lobe rather than being confined to one side, which is why the fungus grows a maximally crumpled surface: more folding means more spore-producing area. There is no separate flesh in the usual sense; a cross-section through a lobe shows uniform, homogeneous, translucent jelly with no rind, no core and no cavity. Cut or bruised tissue does not change colour, does not exude latex, and has no significant odour.

Getting A Spore Print

Prints are awkward from jelly fungi but perfectly possible. Take a fresh, fully turgid lobe and suspend or lay it fertile-face down over a clean glass slide or a piece of black paper, then cover the whole arrangement to keep the air still and the humidity high - an upturned tumbler with a drop of water inside works well. Leave it overnight.

The deposit is white and often sparse. Under the microscope the spores are broadly ellipsoid to nearly round, smooth, hyaline, roughly 6-9 by 5-7 micrometres. The definitive microscopic feature belongs to the basidia: in Tremella they are more or less globose and divided by longitudinal walls into four cells, giving the cross-partitioned appearance that defines the genus. Nothing in the look-alike list below shares that structure.

Substrate, Season And - The Key Point - Ecology

Here is the part that turns a probable identification into a confident one. Snow Fungus is a mycoparasite. It does not digest wood itself; it grows within the wood and parasitises the mycelium of certain black crust-forming ascomycetes, principally Annulohypoxylon and related genera. Practically speaking, that means the host fungus is almost always visible on the same branch: look for hard, black or dark brown, carbon-like crusts and hemispherical pimpled cushions on the bark or exposed wood, often within a few centimetres of the white rosette.

If you find a white jelly rosette on a broadleaf branch alongside a black carbonaceous crust, you have a strong combination. If you find the white jelly on a conifer, on soil, or on a living trunk with no black crust anywhere nearby, reconsider.

Fruiting is driven by rain and warmth rather than by season. In the tropics it appears year-round after downpours; in warm-temperate areas it is most frequent in the wet part of summer and early autumn. Fruit bodies are short-lived, dissolving or collapsing within a week or two.

Separating It From Look-alikes By Structure

Yellow Brain (Tremella mesenterica) shares the lobed jelly construction and the parasitic habit on wood-inhabiting fungi, but it is bright golden-yellow to orange. Only badly bleached, sun-faded material approaches white, and even then it keeps a yellowish core in the thickest folds.

Tremella encephala grows as a firm, brain-like whitish to pinkish cushion rather than a set of thin fronds, and cutting it reveals a distinct hard whitish core inside a softer jelly rind - the core is a reaction to its host, a Stereum. Section anything ambiguous and check for that core.

Ductifera pululahuana is white and gelatinous but forms smooth, rounded, cushion-like or pillow-like blobs that fuse into a lumpy ridge, without the thin, ruffled, leaf-like lobes.

Exidia thuretiana and Exidia nucleata are whitish to translucent-grey jellies that form irregular flattened cushions or brain-like masses pressed close to the wood; E. nucleata usually carries small hard white granules inside the jelly.

Sebacina and Tremellodendron species are whitish and gelatinous-tough but grow as branched, coral-like or fan-like uprights, and typically arise from soil or from a spreading crust on the ground.

Auricularia species are ear-shaped, brown to grey-brown, and have a velvety upper surface and a smooth, veined lower one - a differentiated fruit body, unlike the uniformly fertile fronds here.

Field Checklist

Pure white and translucent; many thin, wavy, ruffled leaf-like lobes from one attachment point; soft elastic jelly texture; dries to a hard yellowish crust and revives when wet; on dead broadleaf branches; black carbonaceous crust fungus on the same wood; white spore deposit; cross-partitioned basidia under the microscope.