Fool's Webcap

Cortinarius orellanus is the broadleaf-woodland member of section Orellani, a small group of dry-capped, foxy-brown webcaps with thick distant gills and yellowish flesh. It is a solidly built mushroom of warm temperate oak and beech woods, and it is one of the more distinctive members of an enormous and notoriously difficult genus.

Cortinarius is defined by the cortina, a cobweb-like partial veil that spans the gap between cap margin and stem in young fruiting bodies, and by a rusty brown spore deposit. The genus contains more species than any other genus of gilled fungi, and most of them require microscopy and chemical spot tests to name. Section Orellani is one of the few groups that can be recognised on field characters, thanks to the combination of dry finely scurfy tawny caps, thick well-spaced gills, and pale yellowish flesh.

Compared with its close relative the Deadly Webcap, C. orellanus is stockier, its cap lacks a sharp point, and its stem is more evenly coloured. It also occupies a distinctly more southerly and warmer range, and the two species rarely occur together.

Cap

The cap is 3-9 cm across, convex when young and expanding to broadly convex or almost flat, at most with a very low broad hump but never a sharp point. The surface is dry, matt, and covered with fine appressed radial fibrils that break up into a scurfy or minutely scaly texture, particularly over the disc. Colour is a rich tawny orange, foxy red-brown, or coppery brown, fairly uniform across the cap.

Gills

The gills are adnate to emarginate, thick, broad, and conspicuously widely spaced, one of the best characters for the section. They are saffron-orange to warm ochre when young, darkening steadily to rusty cinnamon brown as the spores mature, with slightly uneven paler edges.

Stipe

The stipe is 4-9 cm long and up to 2 cm thick, more or less equal or tapering slightly downwards, solid and firm. It is pale yellow to tawny yellow-brown, silky-fibrillose along its length, and lacks conspicuous pale girdles or belts. Cortina remnants leave only a faint fibrous zone that darkens as rusty spores collect on it, and there is no membranous ring and no volva.

Flesh and spore print

The flesh is firm and pale yellow to yellowish ochre throughout, sometimes slightly more tawny in the stem base, and it does not change colour dramatically when cut. The odour is faint and slightly radish-like. The spore print is rusty brown.

Cortinarius orellanus grows in broadleaf woodland, most consistently with oak, and also with beech, birch, sweet chestnut, and hornbeam. It favours acidic to neutral, well-drained soils and warm sheltered situations, and it is characteristic of thermophilic oak woods, coppice, and wooded slopes rather than cool damp coniferous ground.

It fruits singly or in small scattered troops on the woodland floor among leaf litter from late summer into autumn. The distribution is centred on central and southern Europe, extending north patchily and becoming scarce towards the north-western fringe of the continent; it is also recorded from parts of temperate Asia. It is generally a much less frequently encountered species than the majority of common woodland webcaps.

This species is ectomycorrhizal, forming a mutually dependent partnership with the fine roots of its broadleaf hosts. The fungal mycelium wraps each rootlet in a mantle and pushes hyphae between the outer root cells to form the Hartig net, the interface across which nutrients are exchanged. The fungus delivers water, phosphorus and nitrogen drawn from a large volume of soil, and the tree returns photosynthetic sugars.

Because it depends on a living host it cannot be grown in isolation and is restricted to established woodland. Its mycelial network also links into the broader below-ground web of the forest, contributing to soil structure and nutrient cycling in oak woods. Fruiting bodies develop from that network in late summer and autumn, protecting their young gills under a cortina before expanding and releasing rusty spores into the air.

Cortinarius rubellus is the closest relative and separates on two clear structures: it has a sharply pointed umbo at the centre of the cap and its stem carries distinct pale yellow fibrous girdles, both absent in C. orellanus, which has a rounded cap and an evenly coloured stem. Their habitats differ too, C. rubellus growing with conifers among Sphagnum in cool northern woods.

Cortinarius bolaris looks superficially similar in colour but has a pale cream ground colour overlaid with distinct coppery red scales, and its flesh yellows where damaged. Species in the Cortinarius cinnamomeus group are much slimmer with crowded, brighter cinnamon to yellow gills rather than thick distant saffron ones. The Chanterelle, Cantharellus cibarius, is sometimes compared on colour but has blunt forking decurrent ridges instead of true gills, a white spore print, and never produces a cortina. Gymnopilus species share the rusty spore print but fruit in dense clusters on wood and carry a definite membranous ring.