Angel's Bonnet

Mycena arcangeliana is a characteristic fungus of the closing weeks of the mushroom season, often still fruiting on mossy trunks when most woodland species have finished. The cap combines grey, olive and yellowish tones in a way that is hard to pin to a single colour word — young specimens can look distinctly olive-grey, older ones bleach towards cream or pale yellow-buff.

The most useful confirmation is the smell. Fresh fruit bodies, and especially material left in a closed container for a few minutes, develop a clear iodine or antiseptic-like odour, sometimes described as reminiscent of iodoform. That character, combined with the late season and the tufted habit on mossy hardwood, narrows the field quickly.

The species is sometimes listed under the synonym Mycena oortiana. It sits among the wood-inhabiting bonnets with slender, smooth stipes and no coloured latex, a group that includes several superficially similar autumn species.

Cap

The cap is 1–3 cm across, conical to bell-shaped, expanding to broadly convex with a low umbo. The surface is smooth and translucent-striate when damp. Colour is variable: olive-grey to grey-brown with a faint yellowish or greenish cast when young, fading through pale ochre-yellow to cream or greyish-white with age, typically retaining a darker centre.

Gills

Gills are adnate to narrowly adnexed, moderately spaced, whitish to pale grey, and often acquiring a faint pinkish or flesh-toned flush in mature specimens. The edges are concolorous with the faces.

Stipe

The stipe is 3–7 cm tall and 1–3 mm thick, hollow, smooth and slightly shiny, pale greyish or yellowish above and darker grey-brown or olive-tinged towards the base. It is often finely white-pruinose when very young and carries fine white hairs at the point of attachment.

Flesh & spore print

The flesh is thin and pallid. The odour is the key feature: a distinct iodine-like or iodoform smell, sometimes weak in the field but strengthening when the fruit body is enclosed briefly. The spore print is white; spores are smooth, ellipsoid and amyloid.

Angel's Bonnet grows on standing and fallen hardwood — mossy trunks, stumps, fallen branches and the buried woody debris of broadleaf woodland. Beech and ash are frequent hosts, with oak, sycamore, elm and hazel also used. It has a strong association with moss-covered bark, where the moss holds the moisture the fungus needs.

Fruiting is notably late, usually starting in October and continuing through November and into December in mild conditions, sometimes persisting after the first light frosts. It is widespread and locally common in temperate Europe, especially in oceanic regions with mild, wet autumns, and is also recorded from parts of temperate Asia.

The species is a wood saprotroph, decaying the outer sapwood and bark of dead hardwood and contributing to a white rot. It typically colonises material already softened by earlier decay organisms, fruiting from crevices in bark and from the mossy surfaces of long-dead trunks.

Its late fruiting window suggests a tolerance for low temperatures and a strategy that avoids competition with the main autumn flush of wood-inhabiting fungi. Small tufts of fruit bodies emerge repeatedly from the same colonised patch through late autumn, releasing white spores into the humid air around standing deadwood.

Mycena galericulata is larger and tougher, with a plain grey-brown cap, gills that turn distinctly pink, and no iodine smell. Mycena inclinata grows in dense tufts on oak, has a strongly scalloped cap margin and an orange-brown lower stipe, and smells rancid or mealy rather than of iodine.

Mycena vitilis is more slender with a very elastic, tough stipe and a smaller grey cap, and fruits from buried twigs rather than mossy trunks. Small pale bonnets such as Mycena flavoalba are separated by their ivory-yellow colour and grassland or needle-litter habitat. The olive-yellow tint plus iodine odour plus late season is the reliable combination for M. arcangeliana.