Oenothera sect. Oenothera
Onagraceae subfam. onagroideae
erect to ascending or decumbent, branched or unbranched.
in a basal rosette and cauline, cauline (1–)3–25 cm;
blade margins pinnately lobed to sinuate-dentate, serrate to dentate or subentire.
stipules present or absent.
solitary flowers in axils of distal leaves, usually forming a dense or lax spike.
opening near sunset, with a sweet scent or nearly unscented;
buds erect or recurved, terete or weakly quadrangular, with free tips;
floral tube 12–165(–190) mm;
sepals separating in pairs and reflexed, or splitting along only 1 suture and reflexed to one side as a unit, or separate and reflexed individually;
petals yellow, usually fading orange, reddish orange, yellow, or yellowish white, usually obcordate to obovate, sometimes rhombic, elliptic, or rhombic-ovate;
stigma deeply divided into 4 linear lobes.
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.
straight, curved, or somewhat sigmoid, becoming somewhat woody in age, cylindrical to narrowly lanceoloid or ovoid, terete to weakly 4-angled dehiscent nearly throughout their length;
sessile.
numerous, in (1 or) 2 rows per locule, prismatic and angled, narrowly to broadly ellipsoid to subglobose, rarely obovoid and obtusely angled, surface reticulate and regularly or irregularly pitted, rarely flat.
= 14.
Oenothera sect. Oenothera
Onagraceae subfam. onagroideae
Species 68 (26 in the flora).
Section Oenothera is the largest section in the genus, consisting of 68 species (79 taxa) divided into six subsections, one of which is further divided into three series. Section Oenothera has a wide geographic distribution from Canada south to Panama and throughout temperate South America, essentially encompassing the full natural distribution of the genus, although there is very sparse representation (only O. elata) from central Mexico south to Panama. Species of this section occur in a variety of habitats, often disturbed ones, from sea level to 5000 m. Most of the species are self-compatible, but with a few self-incompatible taxa and individual populations of others (W. Dietrich et al. 1997; W. L. Wagner et al. 2007). The flowers are vespertine, fading the following morning, and are pollinated by hawkmoths (in O. versicolor Lehmann perhaps by hummingbirds), or autogamous. In sect. Oenothera, as in several other sections of the genus, the diploid, bivalent-forming, usually outcrossing, species often have relatively narrow geographic and ecological ranges, whereas closely related PTH species derived from them are usually autogamous and have much wider ranges. There are 37 PTH species in sect. Oenothera, which includes the majority of species of angiosperms with this anomalous genetic system.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Genera 21, species 582 (16 genera, 246 species in the flora).
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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Floral tubes 100–165(–190) mm; herbs perennial 17p. | O. subsect. Emersonia |
1. Floral tubes (5–)12–50(–160) mm; herbs annual, biennial, or short-lived perennial. | → 2 |
2. Seeds prismatic and angled, surface irregularly pitted 17p. | O. subsect. Oenothera |
2. Seeds ellipsoid to subglobose, not angled, surface regularly pitted. | → 3 |
3. Young flower buds nodding by recurved floral tube 17p. | O. subsect. Nutantigemma |
3. Young flower buds with floral tube curved upward or straight. | → 4 |
4. Petals rhombic to elliptic or rhombic-ovate 17p. | O. subsect. Candela |
4. Petals shallowly or deeply obcordate. | → 5 |
5. Young flower buds with floral tube curved upward 17p. | O. subsect. Raimannia |
5. Young flower buds with floral tube straight 17p. | O. subsect. Munzia |
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