|Major Groups > Gilled Mushrooms > Dark-Spored > Paxillus > Paxillus involutus|
by Michael Kuo
Paxillus involutus is a widely distributed, variable species found under a variety of trees. Its gills are its most distinctive feature: they stain brown when damaged, and they are separable as a layer (push with a fingertip just above the apex of the stem). In northern and montane areas of North America, Paxillus involutus should be compared with Paxillus vernalis, which is nearly identical but features a somewhat wider stem (2-4 cm) and grows under quaking aspen and paper birch.
The Paxillus involutus group has been subjected to both mating studies (Fries, 1985) and DNA analysis (Jarosch & Bresinski, 1999), along with traditional morphological analyses--and results have upheld the idea that Paxillus involutus and Paxillus vernalis are biologically and genetically distinct, though they are difficult to separate on the basis of physical features.
Ecology: Mycorrhizal with a wide variety of hardwoods and conifers; apparently also capable of existing as a saprobe on wood; found in woods and in urban settings; growing alone, scattered, or gregariously; summer and fall; widely distributed in North America.
Cap: 4-15 cm; convex to broadly convex with a strongly inrolled, cottony margin; becoming planoconvex or centrally depressed; sticky or dry; smooth or finely hairy; brown to yellow-brown, olive brown, or grayish brown.
Gills: Separable as a layer; running down the stem; close or crowded; often becoming convoluted or pore-like near the stem; yellowish to pale cinnamon or pale olive; bruising brown to reddish brown.
Stem: 2-8 cm long; up to 2 cm thick; often tapered to base; dry; smooth or finely hairy; colored like the cap or paler; bruising brownish to reddish brown.
Flesh: Thick and firm; yellowish; discoloring brown when exposed.
Odor and Taste: Taste acidic or not distinctive; odor not distinctive or somewhat fragrant.
Chemical Reactions: KOH on cap surface gray.
Spore Print: Purplish brown to yellow-brown.
Microscopic Features: Spores 6.5-10 x 5-7 µ; smooth; elliptical. Pleuro- and cheilocystidia more or less fusoid; 40-90 µ long; with brown contents. Pileipellis a cutis of elements 3-6 µ wide,with brownish contents. Clamp connections present.
REFERENCES: (Batsch, 1786) Fries, 1838. (Fries, 1821; Saccardo, 1887; Kauffman, 1918; Smith, Smith & Weber, 1979; Fries, 1985; Thiers, 1985; Arora, 1986; Breitenbach & Kränzlin, 1991; Phillips, 1991/2005; Lincoff, 1992; Barron, 1999; Jarosch & Bresinski, 1999; Roody, 2003; McNeil, 2006; Miller & Miller, 2006.) Herb. Kuo 09120701, 09130703, 10031202.
Further Online Information:
Cite this page as:
Kuo, M. (2008, February). Paxillus involutus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/paxillus_involutus.html