Horsehair Parachute
Gymnopus androsaceus
Also called horsehair fungus, horse hair mushroom
A pinhead-sized brown parachute perched on a stiff black hair, often accompanied by tangles of black horsehair-like cords running through the needle litter.
Overview
Long placed in Marasmius and also treated in the genus Setulipes, the Horsehair Parachute is now most often called Gymnopus androsaceus. Whatever the name, it is one of the most abundant small fungi of conifer plantations, heathland and acid woodland across the temperate Northern Hemisphere.
The fruit bodies are so small that the species is usually noticed first by its black, wiry rhizomorphs: shining strands, exactly like horsehair, that spread over and through the litter and often knit fallen needles into loose mats. The caps then appear along these strands like miniature parasols.
It is a classic example of a marcescent fungus, drying to a scrap of tissue in warm weather and swelling back to a functional mushroom within an hour of rain.
How to identify it
Cap
The cap is 3-10 mm across, convex then flattening and often centrally dimpled, membrane-thin, and radially wrinkled or grooved. Colours run from pale tan and pinkish buff to reddish brown, becoming much paler and duller as it dries.
Gills
There are relatively few gills, widely spaced and rather thick for such a small mushroom, whitish to pale pinkish buff, attached to the stem.
Stipe
The stem is 2-6 cm long and only about 0.2 mm thick, perfectly smooth, shining, and black or blackish brown for its whole length, so stiff and springy that it holds the cap upright well above the litter. It springs directly from a needle, leaf or twig, without a basal pad of white mycelium.
Rhizomorphs, flesh and spore print
The black, branching, hair-like rhizomorphs in the surrounding litter are diagnostic and can persist long after the caps have gone. Flesh is tough and pliant; the spore print is white.
Where and when it grows
The Horsehair Parachute grows on fallen conifer needles, especially pine and spruce, on heather (Calluna) stems and litter, and on the leaves, petioles and fine twigs of broadleaved trees. It is at home in acid soils: plantations, heaths, moorland and bilberry-rich woodland.
Fruiting runs from summer through late autumn, with the biggest flushes after prolonged rain. The species is widespread across Europe, northern Asia and North America, and is often the commonest agaric in a stand of conifers by sheer number of fruit bodies.
Ecological role
This is a needle- and litter-decomposing saprotroph and, in some coniferous and heathland systems, one of the dominant organisms of the litter layer. Its rhizomorph network transports water and nutrients between scattered patches of substrate, letting the fungus exploit patchy litter and colonise newly fallen needles quickly.
By binding needles into mats, the mycelium also affects the physical structure of the forest floor and the rate at which the litter layer breaks down and is incorporated into soil.
Similar species
Marasmius rotula has a whitish, deeply pleated cap and its gills are joined to a distinct collar around a black stem; it also grows on woody debris rather than needle litter, and lacks the abundant free rhizomorphs. Marasmius bulliardii is comparably tiny with a collar as well. Marasmius epiphyllus is white-capped and grows on leaf veins and petioles.
Gymnopus perforans fruits on conifer needles too and has a similarly slender dark stem, but the stem is velvety rather than smooth and shining, and the fungus has a strong unpleasant smell. Small Mycena species have brittle flesh, paler stems and do not revive after drying.