A genus of about 180 species, herbs, nearly cosmopolitan (at least now), most diverse in Europe. The genus appears to be paraphyletic as currently circumscribed (Albach & Chase 2001). Subgeneric classification (shown in the key) follows Albach in FNA (2019).
Ref: Albach (2019) In Flora of North America Editorial Committee (2019); Albach & Chase (2001); Atha et al. (2021b); Bardy et al. (2010); Crow & Hellquist (2000a); Pennell (1935); Stace (2010); Walters & Webb (1972) In Tutin et al. (1972). Show full citations.