Cortinarius uliginosus Berk. - Marsh Webcap

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

Distribution - Taxonomic History - Etymology - Toxicity - Identification - Reference Sources

Reddish webcap mushrooms are difficult to identify from their macroscopic characters alone, but the habitat in which the Marsh Webcap appears is a great help, as only a minority of mushrooms cope with very wet soil conditions.

Distribution

Scarce in Britain, the Marsh Webcap is recorded from England, Wales, Scotland and Ireland; it also occurs in many parts of northern and central Europe but rarely in Mediterranean countries.

Taxonomic history

This webcap was described in 1860 by British mycologist Miles Joseph Berkeley, who gave it the scientific binomial name Cortinarius uliginosus by which it is generally referred to today.

Synonyms of Cortinarius uliginosus include Cortinarius queletii Bataille, Cortinarius concinnus P. Karst., and Dermocybe uliginosa (Berk.) M.M. Moser, Schweiz.

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 uliginosus, which comes from Latin, means 'of marshes or bogs' and is a reference to the usual growing habitat of this webcap mushroom.

Toxicity

This mushroom is a member of the subgenus Dermocybe, which includes several deadly poisonous webcaps. It should be regarded as 'suspect' and may contain dangerous toxins, and so it should not be gathered for eating. Some reddish Cortinarius species with which the Marsh Webcap could be confused contain the toxin orellanine, which if eaten destroys human kidneys and liver.

Identification guide

	Cap Young caps often start of conical, becoming umbonate-convex 1.5 to 5cm in diameter and often developing a wavy margin. Cap colour is variable but usually tawny orange, coppery orange or occasionally brick red with the margin slightly paler than the central region; it is covered in yellowish radial fibrils most noticeably near the margin. Stem Cylindrical, 2.5-6,5cm tall and 0.3-1cm in diameter, occasionally with a slightly swollen base; surface longitudinally fibrillose and coloured as the cap; flesh yellow with a reddish tinge.
	Gills The adnate gills are close; initially bright lemon-yellow, tuning saffron to ochre-buff or tawny-buff.
	Spores Ellipsoidal, with a finely roughened surface, 8-11 x 5-6µm; inamyloid. Spore print Rusty brown.
Odour/taste	Odour, when cut or crushed, of radish. Tasting this possibly toxic toadstool is inadvisable.
Habitat & Ecological role	Ectomycorrhizal, in damp soil with deciduous woods, usually in willow or alder carr woodland. In northern Europe this webcap is found most often with willows beside lakes, rivers, bogs and marshes.
Season	August to November in Britain and Ireland.
Similar species	Cortinarius sanguineus, the Bloodred Webcap, has a blood-red cap and blood-red gills and stem. Cortinarius semisanguineus, the Surprise Webcap, has blood-red gills but otherwise it is similar macroscopically to the Marsh Webcap..

Reference Sources

Fascinated by Fungi, 2nd Edition, Pat O'Reilly 2016, reprinted by Coch-y-bonddu Books in 2022.

Funga Nordica, Henning Knudsen and Jan Vesterholt, 2008.

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

British Mycological Society, English Names for Fungi

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.

Acknowledgements

This page includes pictures kindly contributed by David Kelly.

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