Stocking Webcap Identification Guide

The First Impression

Cortinarius torvus is a mushroom you almost walk past. On a damp autumn afternoon in beech or oak woodland, among deep leaf litter, you see a medium sized, dull, brownish agaric with an inrolled margin and nothing obviously distinctive about it from above. There are hundreds of such things in a European wood in October. The identification only starts when you crouch and lift the fruit body out of the litter, because the diagnosis is at the bottom of the stem: a thick white sheath ending abruptly in a rolled, upturned band, like the top of a pulled up sock. That is the stocking, and once you have seen it once you will pick this species out from three metres away.

Reading the Cap

Caps run 4 to 9 cm across, occasionally a little more. They begin convex with a strongly inrolled margin, then broaden to flat with a low broad umbo, and old caps may become slightly wavy or upturned at the edge. The surface is dry and silky fibrillose, never sticky, and it is hygrophanous, which matters more than any single colour word: soaked material is a dark date brown to greyish brown, and as it dries it pales from the centre outward to a greyish buff or clay tone, often leaving a two toned or streaky cap. Young caps commonly carry a faint lilac or violaceous flush, strongest at the margin, together with scattered white veil fibrils that wear off. Take the cap colour as a range rather than a fixed value.

Gills and the Cortina

The gills are one of the two best confirmations. They are adnate to notched at the stem, thick, broad and conspicuously distant, so that you can count them easily from the edge, and they have a slightly waxy look. In young fruit bodies they are pale violet to lilac grey; that colour is transient and is lost as the spores mature, running through clay brown to a warm rusty cinnamon. Gill edges stay paler and are minutely uneven. In buttons, look for the cortina, the fine cobwebby partial veil that stretches from the cap margin to the stem. It collapses onto the stem as the cap opens, and falling spores stain the collapsed fibres, leaving a rust coloured band rather than a proper membranous ring. Thick distant gills plus a cortina places you firmly in the subgenus Telamonia.

The Stocking: Stem and Base

Now the decisive feature. The stem is 5 to 10 cm long and 1 to 2 cm thick, firm, solid, and club shaped, thickening downward and sometimes ending in a slightly swollen but never bulbous base. Above the veil zone it is silky and distinctly pale violaceous or lilac, particularly in fresh young material, fading to whitish with age. From roughly the middle downward the stem is wrapped in a thick white layer of universal veil tissue, and the top edge of that layer does not fade out gradually: it stops in a sharply defined, rolled, outward and upward turned rim. Run a thumbnail up the stem and you will feel it catch. Below the rim the sheath continues as a white felted covering right to the base. There is no free membranous ring, no sac, and no volva; the stocking is a sheath fused to the stem.

Flesh, Colour and Odour

Split a fruit body lengthwise. The flesh is firm and whitish, but the apex of the stem is clearly tinted violaceous in fresh material, a colour that bleeds out over an hour or two and vanishes entirely in old specimens, so section a young one if you can. There is no strong bruising reaction; the base may discolour slowly brownish with handling and age. The odour is distinctive and sweetish, aromatic rather than fungal, and many recorders liken it to crushed pelargonium leaves. Cut flesh gives the strongest reading.

Taking a Spore Print

Every Cortinarius drops a rust brown print, and getting one is the fastest way to eliminate several similar looking genera. Cut a mature cap free, set it gill side down on white paper, cover it with a bowl, and leave it three to eight hours. The deposit is a strong ochre brown to rust brown and is usually heavy enough to see within a couple of hours. Under a microscope the spores are ellipsoid to almond shaped, coarsely and distinctly warted, and about 8 to 11 by 5 to 6.5 micrometres. Smooth spores would rule the genus out.

Partners, Soil and Season

This is an ectomycorrhizal species, and its root partners are broadleaved trees, principally beech, with oak and hornbeam also frequent and occasional records under birch or in mixed stands with conifers. Because of that partnership it fruits in the litter within the root zone of mature trees and is never found on wood chip beds or arable ground. It favours shaded, humus rich woodland floors and does well on richer and calcareous soils, often appearing along the edges of woodland rides where the litter is deep. The season runs from late summer to late autumn, peaking after sustained rain, and fruit bodies come scattered, in small groups, or occasionally in loose arcs following the spread of the mycelium.

Separating It from Its Relatives

• Cortinarius alboviolaceus is the closest source of error. It is silvery lilac over the whole fruit body, with a silky pale cap and a club shaped stem that carries a thin whitish veil, but the veil fades out on the stem rather than ending in a sharply rolled, upturned stocking rim, and its overall colour is far more violet.
• Cortinarius anomalus is slimmer, greyish to slightly lilac, and its stem carries several yellowish or ochre tinted girdles rather than a single thick white sheath.
• Cortinarius hemitrichus and Cortinarius flexipes are much smaller and darker, with caps covered in white fibrillose scales, thin veil bands rather than a boot, and a strong geranium odour.
• Cortinarius evernius is tall and slender with a dark date brown hygrophanous cap and white veil bands up a long stem, and it grows in wet mossy conifer and birch woodland.
• Hebeloma species have no cortina, a clay brown print, and no violet tones anywhere.
• Inocybe species share fibrillose caps and brown prints but are smaller, have a distinctly fibrous or radially split cap, and never show the white stocking.
• Lepista nuda is violet through cap, gills and stem, has no cortina and no stocking, and drops a pale pinkish buff print.

A Working Sequence

Lift the whole fruit body with a knife rather than pulling it. Check for a rolled white stocking rim on the lower stem, thick distant gills that are violet when young and rusty when old, a violaceous stem apex in section, a cobwebby cortina or a rust stained fibrous band, a dry hygrophanous fibrillose cap, and a beech or oak partner overhead. Confirm with a rust brown print.