Synonyme: Agaricus contiguus.
English: Brown roll-rim; Common roll-rim; Poison pax.
German: Verkahlende Krempling; Kahle Krempling; Empfindlicher Krempling.
Region: widely distributed, Northern Hemisphere; introduced to Australia, New Zealand, South Africa, South America.
Habitat: deciduous and coniferous woods, grassy areas; soil acid, nitrogen rich; on conifers, oak, birch.
Use: inedible, although considered edible in the past, causing gastric upsets when eaten raw, causing potentially fatal autoimmune hemolysis, leading to renal failure, shock, acute respiratory failure, disseminated intravascular coagulation.
MycologyPaxillus involutus forms ectomycorrhizal relationships with a broad range of tree species, where the fungus reduces their heavy metals intake and increases their resistance to pathogens such as
Fusarium oxysporum. The fruit body grows up to 6 cm high. The cap is funnel-shaped, to 12 cm wide, with a distinctive inrolled rim, reddish, yellowish or olive-brown in colour, initially downy and later smooth, becoming sticky when wet. The gills are decurrent, can be pore-like close to the stipe, attached decurrently, extending down the length of the stipe, narrow brownish yellow, forked, easily peeled from the flesh, further down toward the stipe become more irregular and anastomose, and can even resemble the pores of bolete type fungi. The fungus darkens when bruised and older specimens may have darkish patches. The juicy yellowish flesh has a mild to faintly sour or sharp odor and taste, and has been described as well-flavored upon cooking. The spore print is brown. The spores are ellipsoid.
Keynotes: mutualistic, symbiotic; spores brown to yellow; flesh pale buff to yellow, coloring red on bruises; gills pale yellow, brown when older; cap brown, inrolled.
TaxonomyAlthough it has gills, it is more closely related to the pored boletes than to typical gilled mushrooms. Studies of the ecology and genetics of
Paxillus involutus indicate that it may form a complex of multiple similar-looking species.Changes in host range have occurred frequently and independently among strains within this species complex.