Paxillus involutus - Brown Rollrim

Taxonomy

Phylum: Basidiomycota

Class: Agaricomycetes

Family: Paxillaceae

From its general shape this deadly poisonous gilled fungus might be mistakenly identified as a funnel cap (Clitocybe family). It is classified as a gilled member of the order Boletales., and like the boletes themselves it forms ectomycorrhizal relationships with trees - both hardwoods and conifers.

A high-profile case of paxillus poisoning occurred in 1944, when the famous German mycologist Julius Schäffer died after eating a meal made from these milkcap lookalikes.

Identification guide

Cap	Initially convex, the ochre cap soon becomes centrally depressed, occasionally with a noticeable umbo, and gradually turns chestnut brown. The margin remains inrolled - hence the common name Brown Roll-rim - and usually has a fluted edge. Downy in dry weather, the cap surface is viscid when wet. Caps expand to between 5 and 12cm when fully mature, and the downy surface becomes smooth when the caps are very old.
Gills	Pale ochre at first, the gills gradually turn brown as the fruiting body ages. Rusty spots appear, and if the gills are bruised they very rapidly turn rusty brown, as has happened with the specimen shown here. The crowded gills are deeply decurrent.
Stem	8 to 12mm in diameter and typically 6 to 12cm long (but nearly always curved), the stem is more or less parallel sided and light ochre at first, becoming chestnut brown with age or if bruised.
Spore print	Sienna.
Odour/taste	Odour not distinctive; taste acidic. Note: the Brown Roll-rim is now known to be a poisonous species and may even be deadly.
Habitat	Under birch and other broad-leaved trees, particularly where the soil is acidic.
Season	July to October.
Occurrence	Frequent.
Similar species	Tapinella atrotomentosa (formerly Paxillus atrotomentosus), commonly referred to as the Velvet Roll-rim, is a somewhat larger species with a velvety cap and a thick short stem covered in dark brown down. It appears on and close to conifer stumps.