Tricholoma fracticum

First described as Agaricus fracticus by German mycologist Max Britzelmayr in 1893,[3] it was transferred to the genus Tricholoma in 1984 by Hanns Kreisel.[4] Though it has been occasionally listed as a synonym of Tricholoma batschii, a European species, T. fracticum possesses larger spores and 2-spored basidia in contrast with T. batschii's 4-spored basidia,[5] and they are currently considered separate species.[1]

Tricholoma fracticum is distinguishable with relative ease by noting the combination of a red-brown cap that becomes viscid (slimy) when wet, and a quickly disappearing partial veil that leaves a flimsy ring or sometimes only a delineation in stipe color up towards the gills. No other Tricholoma in California has both of these features.[5] Also worth noting is its sharp, bitter taste, which is always present in this species and distinguishes it from lookalikes such as Tricholoma aurantium, which has a blander, mealy taste. The cap is more or less smooth, with an initially inrolled margin, 3-10cm in diameter, broadly convex and flattening slightly in maturity. Gills are whitish, attached, and notched to subdecurrent. Stem sturdy, 2-8cm long, 1-2.5cm thick, whitish near apex, orange-brown below, with a flimsy but usually present ring. Flesh white, not bruising or changing upon exposure. Odor indistinct. Spore print white.[2]

• List of North American Tricholoma
• List of Tricholoma species