Cobweb-like

What is a cortina?

In the "Key to the Fungi of Ukraine," M.Ya. Zerova explains: in a young fruiting body, instead of a continuous leathery membrane, the cap margin is joined to the stem by a dense network of fine, silky threads that look exactly like a spider's web.

As the cap opens, these threads tear. Some of them stick to the cap margin, while the rest settle on the stem, forming a barely visible fibrous band — the "cobweb-like ring."

The hallmark of webcaps

In "Mushrooms Demystified," David Arora stresses that the cortina is an absolute diagnostic feature of the largest genus of macrofungi in the world — the webcaps (Cortinarius). This genus has thousands of species and includes some of the most deadly poisonous mushrooms on the planet (for example, the fool's webcap — Cortinarius orellanus, which contains the toxin orellanine).

Roger Phillips describes how to recognize a cobweb-like ring on mature mushrooms, once the web itself has already torn:

- The spores of all webcaps are an intense rusty brown or brick color.

- When the spores ripen and fall from the gills, they get caught in the remains of the cobweb-like ring on the stem.

- That's why the stem of a mature webcap always has a characteristic rusty-brown fibrous band or stripe. These are the remains of the cortina, colored by the spores.

Other mushrooms with a cobweb-like ring

A cobweb-like veil isn't found only in the genus Cortinarius. You can also find it, for example, in some poisonous fibrecaps (Inocybe) and in the slimy spike (Gomphidius glutinosus), but in the slimy spike the web is thickly coated in slime and its spores are black, so the band on the stem turns charcoal black.