Oenothera sect. Hartmannia
Onagraceae tribe Onagreae
decumbent to ascending or erect, usually branched, sometimes unbranched.
in a basal rosette and cauline, cauline 1–6(–10) cm;
blade margins subentire, weakly serrate to weakly sinuate-toothed, sometimes sinuate-pinnatifid.
alternate or basal;
stipules absent.
solitary flowers in axils of distal leaves.
opening near sunrise or sunset;
buds erect, terete, without free tips or free tips minute (except to 4 mm in O. speciosa);
floral tube 4–26 mm;
sepals splitting along one suture, remaining coherent and reflexed as a unit at anthesis or, rarely, separating in pairs;
petals usually pink or rose purple, fading darker, rarely white, fading pink, obovate to obcordate;
stigma deeply divided into 4 linear lobes.
usually actinomorphic, rarely slightly zygomorphic (in Oenothera), (3 or)4-merous;
stamens 2 times as many, or rarely as many, as sepals;
pollen usually shed in monads, rarely tetrads (Chylismia sect. Lignothera).
a dry capsule, usually dehiscent, sometimes indehiscent.
hard and leathery, straight, clavate or narrowly obovoid to rhombic-ellipsoid, angled or narrowly winged (to 0.5 mm, apex attenuate to a sterile beak, proximal part tapering to a sterile, pedicel-like base (stipe), valve midrib raised (prominent in O. speciosa), dehiscent at apex or nearly throughout fertile part;
sessile.
numerous, clustered in each locule, narrowly obovoid, surface glossy, appearing granular, but minutely papillose under magnification.
few to numerous, without hairs or wings, [very rarely with asymmetrical dry wing (Xylonagra)], or with dry (Oenothera), erose or smooth wing, or with thick, papillate wings (Chylismiella).
= 14, 28, 42.
Oenothera sect. Hartmannia
Onagraceae tribe Onagreae
Species 5 (4 in the flora).
Section Hartmannia consists of five species, mostly diploid (2n = 14), but Oenothera speciosa is diploid and also has polyploid populations (2n = 28, 42). All of the species are morphologically very similar, characterized by purple to pink (or white in O. speciosa) petals, leaves often lobed toward the base or distally, capsules often straight, with the fertile portion of the capsule relatively short, angled or narrowly winged (less than 5 mm), apex attenuate, tapering to an acute beak. All species form a definite rosette, which persists at least until the onset of flowering, and ascending to decumbent stems. Most of the species occur in an area from Arizona and Texas south into Mexico, but O. speciosa extends to the Central Plains in the United States, and O. rosea also ranges farther to Central America, the Caribbean (Bermuda, Hispaniola, Jamaica), and northern South America to central Chile. Only Oenothera deserticola (Loesener) Munz occurs outside the area and is restricted to high elevations in the Trans-Volcanic Belt of Mexico. Oenothera rosea is widely naturalized worldwide in tropical and subtropical areas. Four species form bivalents in meiosis, and are self-compatible, except for O. speciosa, which is self-incompatible. Oenothera rosea is a PTH species and forms a ring of 14 chromosomes in meiosis, and is self-compatible and autogamous. Oenothera speciosa has mostly diploid (2n = 14) populations with vespertine or diurnal white flowers in the northern part of its range; many of those from central Texas southward are morning-opening, pink-flowered, and mostly tetraploid (2n = 28) or hexaploid (2n = 42). Pollinators are primarily bees, noctuids, and very few hawkmoths (in O. speciosa), and sometimes secondarily skippers and other butterflies (summarized by W. L. Wagner et al. 2007).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Genera 13, species 265 (12 genera, 199 species in the flora).
Onagreae account for more than half the total genera in Onagraceae and diversified from a center in southwestern North America (L. Katinas et al. 2004). Delimitation of the tribe by W. L. Wagner et al. (2007) differs from previous ones by the exclusion of Gongylocarpus, now in its own tribe, by the segregation of eight genera (Camissoniopsis, Chylismia, Chylismiella, Eremothera, Eulobus, Neoholmgrenia, Taraxia, and Tetrapteron) from Camissonia, and by the inclusion of three previously separate genera (Calylophus, Gaura, and Stenosiphon) in Oenothera. Within the branch of the family that lacks stipules (Gongylocarpeae, Epilobieae, and Onagreae), the last two tribes form a clade that has very strong molecular support (R. A. Levin et al. 2003, 2004), but no obvious morphological synapomorphy. The clade may be defined by a cytogenetic change from the base chromosome number of x = 11 found in Circaeeae, Gongylocarpeae, and Lopezieae, to x = 18 in Epilobieae, and x = 7 in Onagreae; however, these changes could also have occurred independently. Other than the new chromosome number x = 7, the only apparent morphological synapomorphy for Onagreae alone is pollen with prominent apertural protrusions (J. Praglowski et al. 1987, 1989), a character state also found in Circaeeae (Praglowski et al. 1994). The monophyly of Onagreae has moderate (Levin et al. 2004) to strong support (V. S. Ford and L. D. Gottlieb 2007).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Inflorescences sharply nodding; capsule stipes cylindrical. | O. speciosa |
1. Inflorescences erect; capsule stipes gradually tapering to base. | → 2 |
2. Floral tubes 4–8 mm; sepals 6–12 mm; petals 4–12 mm; pollen 35–65% fertile. | O. rosea |
2. Floral tubes 9–26 mm; sepals 7.5–23 mm; petals 8–25(–30) mm; pollen 85–100% fertile. | → 3 |
3. Floral tubes 9–14 mm; sepals 7.5–12 mm; petals 8–15 mm; styles 12–19 mm; plants strigillose, often densely so. | O. platanorum |
3. Floral tubes 15–26 mm; sepals 15–23 mm; petals 12–25(–30) mm; styles 26–36 mm; plants strigillose, also sparsely hirsute. | O. texensis |
