Pear Fibrecap Identification Guide

The Setting and the First Impression

You will be in broadleaved woodland, most often on chalk or limestone, walking a path edge or a mossy bank under beech, lime, oak or hornbeam in late summer or autumn. Fibrecaps are the classic little brown mushrooms of such places, and there will usually be several unrelated species around. This one stands out for being paler than most of its relatives: a straw, cream or pale ochre cap of moderate size, three to eight centimetres across, sitting on a whitish stipe, and often with rusty or wine-red smudges where a slug has grazed it or where an earlier passer-by has touched it. Fruitbodies occur singly or in small scattered groups directly in the leaf litter, not on wood. Before you crouch down, note the tree canopy overhead, because in this genus the associated tree is part of the evidence.

Reading the Cap

The shape starts conical to bluntly bell-shaped and expands to broadly convex with a distinct, often quite prominent central umbo. The margin is incurved when young, straightening later, and frequently splits radially in older fruitbodies. The surface is dry and silky, and under a lens the whole cap is covered in fine radial fibrils lying flat along the surface, running from the umbo to the margin like brushed hair. In some fruitbodies those fibrils separate slightly into narrow appressed streaks, but the cap does not break into raised shaggy scales and it never becomes greasy or slimy. The ground colour is pale: whitish, cream, straw, or pale tan, usually a little warmer over the umbo.

The colour change is where this species declares itself. Rub the cap surface firmly with a thumb, or look at areas that have been bruised, aged or grazed, and a dull reddish, brick or wine-coloured stain develops, sometimes within a minute, sometimes over several. Older fruitbodies often colour up spontaneously so that they look pinkish brown overall, and it is worth comparing a fresh young individual with an old one from the same troop.

Odour

This is one of the few fibrecaps that can be named partly by smell. Crush a piece of cap flesh between the fingers and sniff immediately: the odour is strong, sweet and fruity, reminiscent of ripe pears or a fruit drop sweet, quite unlike the sharp, spermatic or mealy smells of most of the genus. The odour is strongest in fresh material and fades as the fruitbody dries, so check it in the field rather than at home.

The Gills

The gills are adnexed to almost free, moderately crowded, and rather narrow. Their colour sequence runs from pale greyish white or pale clay in young buttons, through dull ochre-buff, to a dull clay brown or snuff brown, sometimes with an olivaceous cast, at maturity. Look closely at the gill edge with a lens: it is finely fringed and paler than the face, appearing whitish and slightly frosted. That contrast between a brown gill face and a white flocculose edge is characteristic of the genus and helps confirm you are in the right place before you start splitting species.

Stipe, Base and Flesh

The stipe is cylindrical or slightly thickened downwards, four to nine centimetres long, solid and firm, with a silky-fibrillose surface that matches the cap. It is whitish at first and flushes pinkish red to brick, especially towards the base and especially where handled, which is a strong supporting character. There is no ring, though the very top of the stipe may look minutely powdered under a lens. The base is at most slightly clubbed; it does not form an abrupt marginate bulb and it has no sac or cup. Slice the fruitbody vertically: the flesh is white and firm, and over a few minutes it develops the same slow reddish flush, most obviously in the stipe base.

Taking a Spore Print

Sever the stipe and set the cap gills-down on white paper under a cover for four to eight hours. The print is a dull brown, described as clay brown, snuff brown or tobacco brown, without any rust-red brightness and without any purple tone. That colour matters: a bright rusty print points towards Cortinarius and its relatives, a purple-brown print towards the Psathyrella and Hypholoma end of things, and a white print rules out the genus completely. Under a microscope the spores of this species are smooth, ellipsoid to bean-shaped and lack lobes or nodules, and the gill faces carry thick-walled cystidia crowned with crystals, which is the microscopic hallmark of this part of the genus.

Substrate and Season

This is an ectomycorrhizal species, living in partnership with the roots of broadleaved trees, so it fruits from soil under its partners rather than from wood or litter heaps. Beech and lime are the most frequently cited hosts, with oak, hazel and hornbeam also recorded. It shows a marked preference for base-rich, calcareous or neutral soils, and it is often found along shaded path edges, on banks and in the disturbed ground beside woodland tracks where mineral soil is exposed. The season runs from midsummer to late autumn, with a peak in early autumn.

Separating the Look-alikes on Morphology

Within the fruity-smelling fibrecaps, the closest relative has the same sweet pear-like odour but develops distinct greenish or bluish green tones on the umbo and often on the stipe base, so any hint of green shifts the identification. Another reddening species in the genus fruits in spring and early summer under lime and hawthorn, has a whiter, more strongly rimose cap that tears into radial cracks, a stouter build, and a mealy rather than fruity odour, and it reddens far more vividly.

The large group of plain brown, strongly split-capped fibrecaps differ in three ways at once: their caps are darker brown and split conspicuously from the margin inwards, they show no reddening on handling, and their odour is spermatic or faintly earthy. The small white and lilac fibrecaps of woodland paths are far smaller, silkier and never redden.

Outside the genus, Hebeloma species are the main trap because they share the pale cap and brown gills. They differ in having a smooth, greasy to slightly slimy cap without radial fibrils, a strong odour of radish, gills that often weep droplets in humid weather leaving brown spots on the edge, and no reddening. Small Cortinarius species show remains of a cobwebby veil between cap margin and stipe and give a rust-coloured print. Pale Agaricus relatives have free gills that turn pink then chocolate and a dark brown print.

A Field Sequence

Broadleaved woodland on base-rich soil; pale straw to cream cap with flat radial fibrils and an umbo; dull red staining where bruised or aged; a strong fruity pear-like odour from crushed flesh; adnexed clay-brown gills with a white fringed edge; a solid whitish stipe reddening at the base and lacking a ring; dull brown spore print.