1b. Onagraceae Jussieu subfam. Onagroideae W. L. Wagner & Hoch, Syst. Bot. Monogr. 83: 41. 2007.
Leaves: stipules present or absent. Flowers: floral tube present or, rarely, absent; sepals 2 or 4 (very rarely 3), deciduous with floral tube, petals, and stamens; petals yellow, white, pink, red, rarely in combination. x = 7, 10, 11, 15, 18.
Genera 21, species 582 (16 genera, 246 species in the flora): North America, Mexico, West Indies, Central America, South America, Eurasia, Pacific Islands (New Zealand, Society Islands), Australia.
Onagroideae encompass the main lineage of the family, after the early branching of Ludwigia (R. A. Levin et al. 2003, 2004). This large and diverse lineage is distinguished by the presence of a floral tube beyond the apex of the ovary; sepals deciduous with the floral tube, petals, and stamens; pollen shed in monads (or tetrads in Chylismia sect. Lignothera and all but one species of Epilobium); ovular vascular system exclusively transseptal (R. H. Eyde 1981); ovule archesporium multicellular (H. Tobe and P. H. Raven 1996); and change in base chromosome number from x = 8 in Ludwigia to x = 10 or x = 11 at the base of Onagroideae (Raven 1979; Levin et al. 2003). Molecular work (Levin et al. 2003, 2004) substantially supports the traditional tribal classification (P. A. Munz 1965; Raven 1979, 1988); tribes are recognized to delimit major branches within the phylogeny of Onagroideae, where the branches comprise strongly supported monophyletic groups of one or more genera.
