Pixie's Parasol Identification Guide

First impressions and the setting

Nothing else looks like this. You are in a wet gully in cool temperate rainforest, among tree ferns, mosses and myrtle beech, on the shaded side of a fallen log after several days of rain. Down at log level a scatter of tiny caps glows a startling sky to cobalt blue, each one 5-20 mm across on a translucent stalk barely a millimetre thick. In dim gully light they read as blue beads or drops of ink sitting on the moss.

The species is a southern-hemisphere speciality of Australia, Tasmania, New Zealand and southern South America, and its habitat is narrow: cool, permanently damp, densely shaded forest with abundant rotting wood. If you are standing in dry sclerophyll or open woodland, you are in the wrong place.

Reading the cap

Get down to log level and look at the cap in profile before touching it. Young caps are hemispherical to almost spherical, like small blue balloons; with age they expand to broadly convex or shallowly bell-shaped, and only the oldest flatten. Deep radial striations run in from the margin, reflecting the gills beneath, and the flesh is thin enough to be translucent, so the outline of the gills shows through the cap skin.

Colour is the headline. The centre is usually the deepest, a strong blue to blue-grey, sometimes with a slightly paler or greyish umbo, while the margin fades to pale blue, milky blue-white or nearly white. Colour intensity varies with age and hydration, and old, weathered or sun-touched specimens bleach markedly, so a pale, tired specimen may show blue only as a wash near the disc.

Touch the surface with a fingertip. It is distinctly viscid to gelatinous when moist, and there is a separable elastic pellicle: with a fine blade you can peel a thin, rubbery, transparent skin off the cap. That gelatinous layer is a good confirming character and is why the caps look glazed and slightly wet even in still air.

Gills and the spore-bearing surface

Gills are moderately distant, fairly broad for the size of the cap, and attached to the stem as adnate to slightly adnexed, sometimes with a tiny decurrent tooth. They are white to very pale blue-grey, always paler than the cap, and in fresh specimens the gill edges can carry a faint blue tint that shows best against a dark background under a lens.

Count the full-length gills. There are relatively few, typically in the mid-teens, with shorter gills interspersed between them. The gills are soft and thin and tear easily.

Stipe, base and the basal disc

The stipe is 10-30 mm long and under 1.5 mm thick, cylindrical, smooth, hollow and glassy-translucent. It is pale blue near the apex, often intensifying to a stronger blue at the very top just under the cap, and fading to whitish or greyish downward. It is viscid when wet, so it can look varnished, and it is fragile: a careless pull snaps it.

The base is the character to chase. Slide a blade under the attachment rather than pulling the mushroom, because the stipe arises from a small, flattened, circular basal disc that grips the wood like a tiny suction pad, sometimes fringed with fine white hairs. In a good specimen the disc is 1-2 mm across and clearly demarcated from the stipe. That disc is a defining structural feature and is easy to destroy by pulling, so extract specimens with a knife tip and a fragment of the wood.

There is no ring and no volva, and no rooting extension into the wood.

Flesh, odour and colour change

The flesh is extremely thin, watery, pale blue in the cap and whitish in the stipe. It does not exude latex or coloured juice when broken, and it does not stain when bruised, though rough handling smears the blue pigment and can leave a faint bluish trace on your fingers. That is transferred surface pigment, not a bruising reaction, and the distinction is worth noting when you write the specimen up. There is no distinctive odour.

Taking a spore print

With a cap this small the technique matters. Cut the cap free with a razor blade, place it gill-side down on a glass slide or a small square of black card, and cover it with a small upturned container with a damp scrap of paper inside to stop the cap desiccating. A thin, gelatinous cap dries out and stops dropping spores within an hour or two in open air.

Leave it three to six hours, or overnight. The print is white, and against black card it shows as a faint pale halo of gill-line rays. A white print keeps you inside Mycena and rules out the pink-spored and rusty-spored blue mushrooms that share the region.

Substrate, season and ecology

Mycena interrupta is a wood-rotting saprotroph. It fruits on damp, well-decayed fallen wood: logs, branches, stumps, bark, sometimes on tree fern trunks and on wood buried under moss. It is strongly associated with myrtle beech and other rainforest hardwoods but is not restricted to a single host. It needs high, sustained humidity, which is why it concentrates in gullies, on the shaded south or south-east faces of logs, and under dense canopy.

Fruiting peaks in autumn and early winter in southern Australia and Tasmania, extending later where conditions stay wet, and it appears in troops of dozens over a single well-rotted log. Fruit bodies are short-lived, collapsing within a few days, so a flush is worth photographing on the spot.

Separating it from look-alikes on morphology alone

Werewere-kokako (Entoloma hochstetteri). The other famous blue fungus of the region and the one most often confused in photographs. It is far larger, with a conical to umbonate cap 20-40 mm across on a stout blue stem, it grows from soil and litter rather than from wood, it has no basal disc, its gills flush salmon-pink with maturity, and its spore print is pink. Any pink in the gills ends the comparison instantly.

Cortinarius rotundisporus and blue-capped webcaps. Much larger and fleshier, with a slimy blue-green cap, a stout solid stipe with a bulbous base, cobwebby cortinal fibres between margin and stem in young specimens, and a rust-brown spore print. They grow on soil with living trees rather than on rotten wood.

Other small Mycena on the same logs. Grey, brown, pink and white species abound in the same habitat. Separate them on two characters: the blue pigment, and the flattened basal disc. Most Mycena species have a stipe base that is either bare, slightly swollen, or fringed with coarse basal fibrils, not a discrete circular pad.

Blue-green wood stain fungi (Chlorociboria species). These turn the wood itself blue-green and produce small stalked cups with no gills at all. If the wood beneath is stained turquoise and the fruit bodies are cups, you are looking at a different organism entirely.

Panellus and small bracket-like species. These attach laterally with an eccentric or absent stem and lack the central stipe with a basal disc.

A quick field sequence

Wet rainforest gully, well-rotted log. Cap 5-20 mm, blue, striate, gelatinous with a peelable skin. Gills distant, whitish to pale blue, adnate, sometimes blue-edged. Stipe thread-thin, translucent, blue at apex, arising from a small circular basal disc. No ring, no volva, no colour change on cutting. White spore print. That sequence confirms Pixie's Parasol.