Mycena chlorophos Identification Guide

What You Are Looking At, and Where

Almost everyone meets Mycena chlorophos twice: once in daylight, when it is easy to walk past, and once at night, when a patch of decaying bamboo appears to be lit from inside with a soft green light. The daylight version is a scatter of tiny, pale, glassy caps on damp wood, each one no wider than a thumbnail and mounted on a hair-thin stem. The night version is unmistakable, and it is the reason the species is chased across subtropical East Asia by photographers every rainy season.

The setting is humid, shaded, low-elevation subtropical or tropical forest: the Ogasawara and Ryukyu islands of Japan, Taiwan, southern China, mainland Southeast Asia, and scattered records south to Australia and across to Brazil. Stand in a gully where bamboo has fallen and rotted, where palm fronds lie in wet mats, where the air does not dry out between showers. That is the habitat. If the litter crackles underfoot, you are in the wrong place.

First Impression and Growth Habit

Fruit bodies come up in troops, sometimes dozens on a single length of bamboo culm or a single sodden petiole. They are gregarious but not fused: each stem is separate, and each is anchored by a tiny flat disc glued to the wood. The whole colony looks fragile, translucent and slightly wet, as though moulded from candle wax. Individual mushrooms last only a day or two, so a colony you photograph on Tuesday can be gone by Thursday.

Reading the Cap

Measure first. The cap runs roughly 6 to 30 mm across, usually toward the smaller end. It begins hemispherical, almost a bead on a wire, then opens to convex and finally nearly flat, sometimes with a shallow central depression in age.

Colour is pale and thin: greyish brown when very young and freshly emerged, with a slightly darker centre, then fading rapidly toward greyish white or almost pure whitish as the cap expands and thins. Colour is a weak character here because it drains so quickly.

Two surface features matter far more. First, the cap is viscid, coated in a thin sticky film when moist, so litter fragments and grit stick to it. Second, the cap is deeply and regularly grooved from the margin toward the disc, so that the ridges correspond to the gills beneath. Hold the cap against the sky and it is translucent enough that the gill lines show through. A striate, sticky, translucent, greyish cap on a hair-like stem is already most of the identification.

The Gills

Turn the cap over with the tip of a knife rather than your fingers, which will crush it. The gills are adnate, sometimes with a short decurrent tooth running onto the stipe apex, and they are relatively few: roughly 17 to 32 reach the stem, with shorter intermediate gills between them. They are whitish to pale grey, with even, concolorous edges, and they are broad relative to the tiny cap.

In darkness, the gills are the brightest part of the fungus. Light output is greenish, strongest in freshly expanded fruit bodies, and it fades as the cap ages and flattens.

Stipe, Base and Flesh

The stipe is 6 to 30 mm long and only 0.3 to 1 mm thick, filiform, hollow, more or less equal, translucent greyish and often slightly viscid. Under a lens the surface may look finely powdery near the apex.

The base is the character worth training your eye on. It ends in a small, flat, whitish basal disc, a tiny adhesive pad pressed against the substrate. Lift a fruit body cleanly and the disc usually comes with it, sometimes with a few coarse hairs. Many small litter agarics simply run into the wood; this one sits on a discrete plate.

Flesh is essentially nonexistent, a membrane a fraction of a millimetre thick. There is no colour change when you cut or bruise it. Any reported change is almost always drying, not a chemical reaction.

Taking a Spore Print

The mushroom is small, so use a small target. Snap the stipe just under the cap and lay the cap gills down on a piece of glass or a microscope slide, not on paper, which absorbs the few spores that fall. Cover with a shot glass or a film canister to hold humidity and leave it three to six hours in a cool place. Hold the glass against black card to read the deposit.

The print is white. Under the microscope the spores are ellipsoid, smooth, roughly 7 to 8.5 by 5 to 6 micrometres, and they turn blue-grey in Melzer reagent, that is, they are amyloid. Amyloid spores plus a white print place the fungus comfortably in Mycena and rule out the rusty-spored litter agarics that fruit in the same conditions.

Substrate, Season and the Glow

Substrate is a genuine identification character. Look on dead bamboo culms and bamboo litter, fallen palm petioles, rotting twigs, and packed leaf litter in wet forest. The species is a litter and small-wood decomposer; it does not fruit on living trees or on soil without a woody base.

Season is the wet season, and fruiting follows rain by a day or two in warm conditions. Luminescence is temperature dependent and is reported to peak near 27 degrees Celsius, dropping off sharply when the air is cool. To confirm the glow, sit in complete darkness for at least fifteen to twenty minutes without looking at any screen or torch. The light is faint, steady and green, and it appears strongest along the gill edges and the cap margin.

Separating the Look-Alikes on Morphology

Mycena illuminans also glows and also grows on woody litter in the same region, but it is a larger, sturdier fungus with more strongly ochre to yellow-brown tones, a proportionally thicker stipe and more numerous gills. Mycena lux-coeli, from Japan, is likewise luminous but has a more brownish, less translucent cap and typically a longer stipe with a differently shaped basal attachment.

Filoboletus manipularis is the trap for photographers. It glows, it grows in troops on rotting wood in the same forests, and from above it looks like a small white Mycena. Turn it over: the underside is poroid, a fine sheet of tiny pores, not gills. That single check settles it.

Panellus species and other luminous pleurotoid fungi are attached laterally or sessile, shell-shaped or kidney-shaped, and lack a slender central stipe with a basal disc.

Finally, there is a long list of non-luminous small Mycena species with striate caps that grow in the same litter. Separate them on the combination of a sticky cap surface, a discrete flat basal disc, few gills, and the amyloid white spore print. If none of those line up, and the fungus does not glow after proper dark adaptation, it is one of the many other litter mycenas rather than M. chlorophos.