A genus of about 30 species (once segregates are removed), mostly neotropical, with a few species in s. Africa. Circumscription follows Gasper et al. (2016, 2017) and PPG I (2016).
Ref: Cranfill (1993b) In Flora of North America Editorial Committee (1993b); Gasper et al. (2016); Gasper et al. (2017); Kramer, Chambers, & Hennipman In Kramer & Green (1990); Mickel & Smith (2004); Perrie et al. (2014); PPG I (2016). Show full citations.