Cortinarius

Cortinarius is a large genus of mushroom-forming fungi in the family Cortinariaceae, commonly known as webcaps. It is one of the largest genera of fleshy mushrooms, with hundreds to thousands of described species, distributed worldwide, especially in temperate forests. Most Cortinarius species are ectomycorrhizal, forming mutualistic associations with trees and contributing to nutrient exchange in forest ecosystems.

Description and identification features are highly variable. Fruiting bodies range from small to large, with caps that may be smooth, dry, or scaly and colors from brown to violet or ochre. Gills are typically adnate to adnexed and become rusty brown as the spores mature. A distinctive feature is the cortina, a cobweb-like partial veil that often leaves thread-like remnants on the stem or cap margins. The spore print is rust-brown. Many species bruise or discolor when handled, but field identification to species level is challenging and often requires microscopic examination.

Ecology and habitat: Cortinarius species grow on soil in wooded habitats, frequently in association with conifers and broadleaf trees. They fruit mainly in summer and autumn in temperate regions, reflecting their role as ectomycorrhizal partners.

Toxicity and caution: A substantial number of Cortinarius species are poisonous, and several contain orellanine, a toxin that can cause delayed kidney damage. Notable dangerous species include Cortinarius orellanus and Cortinarius rubellus. Distinguishing toxic from potentially edible species in the field is unreliable, so many authorities advise against collecting Cortinarius for consumption. Some species, such as Cortinarius caperatus (the gypsy mushroom), are considered edible by some sources, though many guides still recommend caution.

Selected notable species include Cortinarius rubescens (the blusher), Cortinarius orellanus (deadly webcap), Cortinarius violaceus (violet cort), and Cortinarius caperatus.