Dripping Bonnet

Mycena rorida, now often placed in the segregate genus Roridomyces as Roridomyces roridus, is defined by one extraordinary feature: the stipe is enclosed in a sheath of clear, thick gluten that can be several times the diameter of the stalk it surrounds. Under a hand lens the actual stem appears as a thin dark thread suspended inside a column of glassy jelly, and in wet weather droplets gather and hang from it — hence 'dripping'.

The cap itself is unremarkable: a small whitish to pale buff or greyish disc, translucent-striate and shallowly convex to flattened, often with a slightly depressed centre. Nearly all the diagnostic weight rests on the slime sheath, which is unlike anything else at this scale in the temperate fungal flora.

The glutinous coating is thought to help the fungus retain moisture and may also play a role in spore dispersal by adhering to passing invertebrates. It survives drying poorly, so specimens collected in dry weather may show only a thin sticky film, and beginners often overlook the character entirely on shrivelled material.

Cap

The cap is 3–10 mm across, convex to flattened and often with a shallow central depression, occasionally with a slightly scalloped margin. The surface is dry to slightly moist, finely pruinose when young, and deeply translucent-striate or radially grooved almost to the centre. Colour is white to cream, pale buff or greyish-buff, usually a little darker at the disc.

Gills

Gills are adnate to shortly decurrent, distant, and white to pale cream. They are relatively few, thick-edged for the size of the mushroom, and concolorous along the edges.

Stipe

The stipe is 1–4 cm tall, but the visible column is 1–2 mm or more thick because the true stem — a thread often under 0.5 mm across — is enclosed in a thick, colourless to faintly yellowish glutinous sheath. The gluten is elastic and sticky, drips in humid conditions, and can be drawn out into strands when touched. The true stipe beneath is pale to greyish, darker at the base.

Flesh & spore print

The flesh is a thin white film with no distinct smell. The spore print is white; spores are smooth, ellipsoid and amyloid.

Dripping Bonnet fruits on fine woody and herbaceous debris: fallen twigs, small branches, bramble and rose stems, bracken rachides, dead grass culms and conifer needle clusters. It favours consistently damp, sheltered spots in woodland, hedge bottoms, scrub and heathland where debris lies close to the ground.

It appears on both broadleaf and conifer material without strong host preference. The season runs from summer through to late autumn, peaking in wet spells from August to October. The species is widespread across temperate and boreal Europe, and is recorded through northern Asia and North America, though as with many tiny fungi it is under-recorded relative to its actual frequency.

This is a saprotroph of fine plant debris, decomposing the outer tissues of twigs, canes, stems and needle litter. Its mycelium occupies small individual pieces of substrate, so fruiting is typically clustered on a single twig or cane rather than spread across the litter layer.

The glutinous sheath is a distinctive adaptation. It holds water around the fruit body, allowing the fungus to keep functioning in fluctuating humidity, and its stickiness readily traps small invertebrates and spores, which has led to suggestions that it assists in dispersal. Fruit bodies are short-lived, but repeated flushes occur on the same substrate through a wet season.

Mycena epipterygia also has a glutinous stipe, but its slime layer is a thin peelable skin rather than a thick sheath, the stipe beneath is distinctly yellow, and the cap has a separable gelatinous pellicle with a greyish-yellow colour. Mycena vulgaris has a slimy stipe too, but the cap is greyish-brown with a strongly separable elastic pellicle and it fruits in conifer needle beds.

Small white non-slimy bonnets such as Mycena stylobates are separated by the flat basal disc at the stem base and the complete absence of a gluten sheath. Marasmius and Marasmiellus species on similar twiggy substrates have dry, wiry, non-glutinous stems and often revive after drying, which M. rorida does not.