Oenothera sect. Peniophyllum
Onagraceae tribe Onagreae
erect, unbranched or branched.
in a basal rosette and cauline, cauline 1–2(–)4 cm;
blade margins subentire or remotely dentate.
alternate or basal;
stipules absent.
solitary flowers in axils of distal leaves.
opening near sunrise, nearly unscented;
buds erect, terete, without free tips;
floral tube 1–2 mm;
sepals separating in pairs;
petals bright yellow, fading pink, obcordate to obovate;
stigma shallowly 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, ellipsoid-rhombic to subglobose, 4-angled, apex rounded or obtuse, proximal part tapering to a sterile, pedicel-like base (stipe), valve midrib raised at distal end, indehiscent or tardily dehiscent distally;
sessile.
usually numerous, clustered in each locule, ovoid, surface minutely papillose.
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.
Oenothera sect. Peniophyllum
Onagraceae tribe Onagreae
Species 1.
Section Peniophyllum consists of a single diploid species. It has been treated as the sole member of subg. Kneiffia sect. Peniophyllum (P. A. Munz 1937, 1965) or sect. Kneiffia subsect. Peniophyllum (G. B. Straley 1977). It was separated from sect. Kneiffia by W. L. Wagner et al. (2007) because molecular data (R. A. Levin et al. 2004) failed to place these two groups in a single clade. Instead, Oenothera linifolia forms a very weakly supported clade with O. havardii (sect. Paradoxus), with which it shares no known morphological similarity other than characteristics of subclade B. The most distinctive characteristics of sect. Peniophyllum are the heteromorphic rosette versus cauline leaves, the cauline leaves crowded and linear, capsules ellipsoid-rhombic to subglobose, indehiscent or tardily dehiscent only at distal end, and the entire capsule falling from the plant prior to senescence. In most sections of Oenothera, the capsules are persistent on the stem, but in sect. Peniophyllum and two other sections (Gaura and Megapterium) of subclade B, the capsules often disarticulate from the plant. The flowers are self-compatible, diurnal, and autogamous or cleistogamous.
(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.)
