Parasola auricoma Identification Guide

The Setting and the First Impression

You almost always meet this species in the morning, and usually somewhere humanly disturbed. Fresh woodchip mulch on a shrub bed, the composted edge of a path, a scruffy corner of a garden, a park border, the gravelly margin of a car park or a lawn that has recently been dug over are all typical. What catches the eye is a scatter of small, dark, egg-shaped or thimble-shaped caps on improbably thin white stalks, standing a few centimetres above the substrate, often a dozen or more within a square metre but not truly clustered from a single point. Come back at midday and the same fruitbodies will be splayed flat like tiny parasols; come back in the evening and most will have collapsed into limp scraps. This extreme ephemerality is itself part of the identification, and it means you should do your examination on the spot rather than plan to look at the material later.

Reading the Cap

Start with the youngest, still closed fruitbody. At that stage the cap is ovoid to narrowly bell-shaped, only one to two centimetres tall, and coloured a warm reddish brown to tawny ochre, darkest over the very centre. Even at this stage the surface is not smooth: it is grooved from the margin almost to the centre by deep radial furrows that follow the gills beneath. As the cap expands, those furrows become pronounced pleats, so that the mature cap looks like a folded paper fan opened out, plane or even upturned at the rim, with a small smoother disc of darker brown retained at the middle while the pleated zone fades to grey or greyish brown. The flesh is so thin it is almost membranous, and a mature cap is translucent enough that you can see the gills through it when it is held against the light.

The character that gives this species its name needs a hand lens. Scattered over the cap surface, most easily seen on the disc of a young unexpanded cap, are stiff, thick-walled, golden brown to dark brown hairs, standing more or less erect. Under a ten times lens they read as fine dark bristles or a sparse dark stubble. They are not veil granules, not powder, and not a woolly coating; they are individual pointed hairs, and their presence in a deeply pleated little fungus of this kind is the single most useful field character.

The Gills

The gills are narrow, crowded, and attached to a collar rather than directly to the stem apex, so they appear free when you look from underneath. They pass through a clear colour sequence with age: whitish or pale greyish in a young button, then grey, then dark grey-brown, and finally blackish as the spores mature. Unlike the true inkcaps, the gills of this genus do not dissolve into a running black liquid. They may darken, shrivel and go limp, and the whole cap collapses, but there is no dripping ink. Checking that distinction on an over-mature fruitbody is worth the trouble.

Stipe, Base and Flesh

The stipe is white, hollow, brittle and glassy, three to eight centimetres long and only one or two millimetres thick, so it is very easy to snap while lifting the fruitbody. Under a lens it is finely downy or minutely fibrillose, especially towards the base, which is very slightly swollen but forms neither a bulb, a sac nor a cup. There is no ring and no trace of a ring zone. The flesh throughout is white, unchanging, and far too thin to show any bruising reaction; cutting the cap simply tears it. The odour is negligible.

Taking a Spore Print

Speed matters. Choose a cap that has just flattened out but has not yet begun to droop, sever the stipe and set the cap gills-down on white paper under a cover. Because the fruitbody is so thin it will dry out quickly, so a print is often complete within an hour or two. The deposit is black to very dark brown, and it usually reproduces the pleating as a set of fine radial lines. Under a microscope the spores are large for such a small fungus, ellipsoid to somewhat heart-shaped or bluntly angular in face view, dark reddish brown in water, with a conspicuous central germ pore.

Substrate and Season

This is a saprotroph of woody and herbaceous debris in enriched, disturbed ground. Bark mulch and woodchip are the classic substrates, along with buried twigs, compost, garden soil, rich path edges and the trampled margins of tracks. Fruiting runs from late spring through autumn and responds within a day or two to heavy rain, so a mulched bed that produced nothing all week can be covered in fruitbodies the morning after a downpour. Fruitbodies are gregarious but arise separately from the substrate rather than in tufts from one point.

Separating the Look-alikes on Morphology

The other pleated species in the same genus are the real problem. The commonest of them has a similar shape but no cap hairs at all, a paler and more clay or tan coloured central disc, a preference for grassland, lawns and mossy verges rather than mulch, and slightly different spores. Another close relative is likewise smooth-capped, with a greyer overall tone. In practice, if you cannot find dark bristles on a young cap with a lens, you should not use this name.

True inkcaps in the genera Coprinellus and Coprinopsis can look superficially similar but usually differ in several ways at once: their caps are furrowed rather than deeply pleated to the centre, their surfaces often carry a mealy, granular or shaggy veil that rubs off on the fingers, they frequently grow in dense tufts directly on stumps or buried wood, and their gills genuinely deliquesce into black fluid. The very small clustered species that carpet stumps in the hundreds have bell-shaped, finely grooved caps with a pale ochre centre, grow in tightly packed colonies, and never show erect dark cap hairs. Small brown Psathyrella species share the fragile stipe but have convex to conical, non-pleated caps, more sturdily attached gills and a dark purplish brown rather than truly black print.

A Field Sequence

A very thin, deeply pleated cap with a small dark disc; free-looking narrow gills that blacken but do not run; a fragile hollow white stipe with no ring; woodchip or disturbed enriched ground; a black spore print; and, decisively, erect dark hairs on the cap under a lens.