Girdled Webcap
Cortinarius trivialis
Also called snakeskin cortinarius
A slimy webcap named for the striking series of whitish glutinous girdles that band its stem like snakeskin. It grows with willow, poplar and birch on damp, often calcareous ground.
Overview
Girdled Webcap (Cortinarius trivialis) is a member of subgenus Myxacium, the slimy-veiled webcaps. What sets it apart is the way its glutinous universal veil breaks up on the stem into a stack of overlapping whitish to ochre belts, producing a banded, almost reptilian pattern from the base up to the cortina zone.
The cap is comparatively unremarkable — smooth, glutinous, olive-ochre to warm brown — so the stem is the diagnostic surface. In wet weather the girdles are slippery and glassy; in drier conditions they contract into firm ridges and rings that are still perfectly legible.
Ecologically it is a fungus of damp lowland woodland with willow and poplar, and it is one of the more frequently reported Myxacium species in such habitats. Like all webcaps it releases rusty brown spores and shows a cobwebby cortina in youth, anchoring it firmly in Cortinarius despite its distinctive stem.
How to identify it
Cap
About 3–9 cm across, convex then expanding with a low broad umbo. The surface is smooth and strongly glutinous when moist, drying shiny and slightly sticky, coloured olive-ochre, honey-brown or clay-brown, often darker and more olive at the disc and paler towards the margin, which can retain adhering debris.
Gills
Adnate to slightly notched, moderately crowded, whitish to pale clay at first, sometimes with a faint violaceous tinge in very young specimens, then ripening through cinnamon to a strong rusty brown. The edges are paler and minutely serrate. The cortina is pale and collapses into a rusty band on the upper stem.
Stipe
The key feature: 6–12 cm tall, 1–2 cm thick, cylindrical and tapering downwards to a narrowed, often rooting base. Above the cortina zone it is whitish and dry; below, it is sheathed in the glutinous veil that separates into a series of concentric whitish, ochre or brownish girdles and belts, giving the snakeskin look.
Flesh & spore print
The flesh is whitish to pale buff, watery in the stem, with a mild and indistinct smell and no marked bruising reaction. The spore print is rusty brown; spores are almond-shaped and coarsely warted.
Where and when it grows
Cortinarius trivialis is a fungus of damp deciduous woodland and scrub, forming mycorrhizas most often with willow and poplar, and also with birch, hazel and aspen. It prefers moist, humus-rich soils and shows a marked preference for calcareous or base-rich ground, so it is frequently found in wet woodland on limestone, on dune slacks with creeping willow, and along riverside and lakeside tree belts.
Fruitbodies appear from late summer into autumn, often in scattered troops or small clusters among grass, litter and moss beneath the host trees. The species is widespread across Europe and occurs in comparable habitats in temperate North America.
Ecological role
This webcap is ectomycorrhizal, chiefly with members of the willow family. In wet woodland and dune slacks, where soils are periodically waterlogged and nutrients are patchily available, the fungal mantle around willow and poplar roots substantially improves uptake of phosphorus, nitrogen and water, while the fungus receives carbon from its host.
The thick glutinous veil is a functional adaptation as much as an identification feature, shielding the developing gills from drying and from small grazers, and its ordered breakup into girdles reflects the way the stem elongates through it. The perennial mycelium contributes to the stability of damp woodland soils and links host trees into shared underground networks.
Similar species
Cortinarius collinitus and C. mucosus are the closest relatives with glutinous stems, but both are conifer associates: C. mucosus has a richer red-brown cap and a smoother, more evenly slimy white stem, while C. collinitus shows bluish-violet tints in the stem sheath. Neither has the tapering, rooting stem base typical of C. trivialis.
Cortinarius delibutus is cleanly ochre-yellow with pale bluish-lilac young gills and grows under birch on acid soils. Outside the genus, slimy Hebeloma species lack girdles and give a clay-brown spore print, and Suillus species in damp woodland have tubes and pores instead of gills. The girdled, tapering stem plus a rusty brown spore print is the decisive combination.