Cortinarius trivialis J. E. Lange - Girdled Webcap

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

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

Cortinarius trivialis is an occasional find throughout most of Britain and Ireland, where the distinctive fruitbodies appear in late summer in boggy broadleaf woodland, particularly under poplars, willows and birches. Very young fruitbodies sometimes exhibit beautiful bluish or mauve tinges, which quickly disappear from the cap surface as it becomes brown, but the blue tinge usually remains on the gills until they become stained by ripe rusty-brown spores. (Main picture courtesy Karen Horrocks)

Identification of webcaps is very difficult, and unfortunately there are many brownish species with macroscopic characteristics similar to this unremarkable member of the clan; fortunately, the 'girdled' stem is a helpful identifying feature of Cortinarius trivialis.

Distribution

An uncommon but quite widespread species in Britain and Ireland, the Girdled Webcap occurs also throughout mainland Europe, from Scandinavia right down to the Mediterranean region. Cortinarius trivialis is also recorded in North America, although it is possible that the name is being applied to a lookalike that is actually not the same species.

Taxonomic history

This striking webcap is a member of the Cortinarius sub-genus Myxacium, which contains species in which the caps, partial veils and stems are all viscid (although as is so often the case with fungi a few exceptions have crept in to this subgenus). The Girdled Webcap was described in 1940 by the Danish mycologist Jakob Emanuel Lange (1864 - 1941), who gave it the binomial name Cortinarius trivialis which remains its currently accepted scientific name.

Synonyms of Cortinarius trivialis include Myxacium collinitum var. repandum Ricken, and Cortinarius collinitus var. trivialis (J. E. Lange) A.H. Sm.

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.

Just as you might expect, the specific epithet trivialis means trivial. In this instance it is used in the sense of commonplace or ordinary. In Britain and Ireland, therefore, this is not a particularly apt adjective because the Girdled Webcap is not at all common. In May 2013 the The Fungal Records Database of Britain and Ireland contained just 170 reported finds of this species.

Toxicity

This mushroom is generally regarded as 'suspect' and may contain dangerous toxins; it should not be gathered for eating. Some reddish Cortinarius species with which the Girdled Webcap could be confused contain the toxin orellanine, which if eaten destroys human kidneys and liver.

Identification guide

	Cap 3.5 to 11cm in diameter; conico-convex at first, expanding until almost flat or occasionally with a shallow central depression but retaining a slight umbo; tawny to bay brown sometimes with a central bluish flush that is soon lost, the caps are paler towards the margin; extremely viscid.
	Gills Initially covered by a blueish glutinous cortina (a web-like partial veil), the gills are close and initially pale clay, turning ochre and then becoming stained rusty brown as the spores mature.
	Stem Stems are 1 to 2cm in diameter and 5 to 12cm tall; parallel without a basal bulb. The top of the stipe is white; below a rusty ring zone it is brown and more shaggy, belted or zoned with pale scales. The whole of the stem is covered in a thick white or clear slime.
	Spores Ellipsoidal to amygdaloid (almond shaped), coarsely verrucose, 10-14 x 6-8.5μm; inamyloid. Show larger image Spores of Cortinarius trivialis, Girdled Webcap  X  Spore print Rusty brown.
Odour/taste	Not distinctive.
Habitat & Ecological role	Ectomycorrhizal, in boggy broadleaf woodland.
Season	August to October in Britain and Ireland.
Similar species	In Funga Nordica (2008), Knudsen & Vesterholt suggest that Cortinarius trivialis is probably not a single species but a closely-related group (a 'collective species'). Other mycologists take more of a lumper approach and treat this webcap as merely a scaly-stemmed variety or form of Cortinarius collinitus. These two species certainly share similar habitats, but we are following the Kew/British Mycological Society lead in treating Cortinarius trivialis, the Girdled Webcap, as a unique species.

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.

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 Wayne Hicks and Karen Horrocks.

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