Cortinarius alboviolaceus (Pers.) Fr. - Pearly Webcap

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Agaricales - Family: Cortinariaceae

Cortinarius alboviolaceus - Pearly Webcap, Scotland

Cortinarius alboviolaceus, the Pearly Webcap, is found in summer and autumn mainly in beech woods but also occasionally under conifers. The pale lilac or mauve tinted cap is quite distinctive.

The genus Cortinarius is sometimes subdivided, and the Pearly Webcap is a very typical member of the subgenus Sericeocybe, meaning 'silky head'. The silky lilac-flushed cap is paler towards the centre making this species very distinctive, unlike most webcaps.

Cortinarius alboviolaceus - Pearly Webcap, Wales

Distribution

An occasional species in Britain, most often reported from Scotland, the Pearly Webcap is found also throughout much of mainland Europe and is reported from many parts of North America.

Taxonomic history

When in 1801 Christiaan Hendrik Persoon described this webcap he gave it the name Agaricus alboviolaceus. (Vast numbers of gilled fungi were dumped into the Agaricus genus in the early days of fungal taxonomy; most have since been moved to other genera leaving in the present-day Agaricus genus a much smaller number of gilled mushrooms that are sometimes referred to as the 'true mushrooms'.) It was the great Swedish mycologist Elias Magnus Fries who, in 1838, transferred this species to the genus Cortinarius, whereupon it acquired its currently-accepted scientific name Cortinarius alboviolaceus.

Agaricus alboviolaceus Pers., is thus a synonym of Cortinarius alboviolaceus.

Etymology

The generic name Cortinarius is a reference to the partial veil or cortina (meaning a curtain) that covers the gills when caps are immature. In the genus Cortinarius most species produce partial veils in the form of a fine web of radial fibres connecting the stem to the rim of the cap rather than a solid membrane.

The specific epithet alboviolaceus come from the prefix albo- meaning white and violaceus indicating that it is tinted or flushed with violet. Perfectly appropriate!

Toxicity

This mushroom is generally regarded as inedible or suspect and we recommend that it should not be gathered for eating. Some Cortinarius species contain the toxin orellanine, which if eaten destroys human kidneys and liver.

In prolonged dry weather, cap margins of the Pearly Webcap tend to split, producing starry displays like the example pictured above; such patterns are more commonly associated with the Torn Fibrecap Inocybe rimosa (synonym Inocybe fastigiata).

Identification guide

Cap of Cortinarius alboviolaceus - Pearly Webcap

Cap

At first domed and then shallowly convex with a broad umbo, the dry, silky caps vary in colour from almost white through pale lilac to pale mauve.

Cap diameter varies from 3 to 9cm at maturity.

Gills and stem of Cortinarius alboviolaceus - Pearly Webcap

Gills

The notched gills are violaceous at first. As the spores mature, the gills turn clay brown and eventually they are stained rust brown by the spores.

Stem

The stipe, which is often bowed rather than straight, is pale and fibrous with a slightly clavate (club-shaped) base. Typically 6 to 15mm in diameter the stems are often clavate and 8 to 12 cm tall.

The remains of the white cortina that adhere to the stem are soon marked by a reddish-brown stain from falling spores.

Spores of Cortinarius alboviolaceus

Spores

Broadly ellipsoidal, 7.5-9 x 4.5-6µm; with fine warty ornamentation; inamyloid.

Spore print

Rusty brown.

Odour/taste

Not strong, but detectable odour and taste of radish.

Habitat & Ecological role

Under beech and less frequently other hardwood trees in areas where the soil is acidic; occasionally also under conifers.

Season

July to November in Britain and Ireland.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2016.

Funga Nordica, Henning Knudsen and Jan Vesterholt, 2008.

Fungi of Switzerland Agarics, part 3: Cortinariaceae, Breitenbach, J., Kränzlin, F.

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.

Other web authorities on this species

Roger Phillips (UK)

Michael Kuo (USA)

Marek Snowarski (Poland)

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