Oenothera riparia
Oenothera nealleyi
erect or ascending, usually many-branched throughout, proximal branches often somewhat spongy, 50–120 cm.
usually well-branched, 20–70(–100) cm.
in a basal rosette and cauline, softly succulent, 4–13.5 × 0.8–2.1 cm, petiole 0–1.5 cm, blade lanceolate to elliptic-lanceolate, margins remotely denticulate.
in a basal rosette and cauline, basal 3.5–9 × 0.5–1.5 cm, blade lyrate;
cauline 1.5–7 × 0.1–0.6 cm, blade narrowly lanceolate to linear, margins sinuate-dentate, undulate.
erect, flowers in axils of distalmost few nodes.
opening near sunrise;
buds with free tips 0.5–2(–5) mm, erect to spreading;
floral tube 14–20 mm;
sepals 20–30 mm;
petals bright yellow, fading pale pink or lavender, 16–27 mm;
filaments 10–15 mm, anthers 7–8 mm, pollen 85–100% fertile;
style 15–30 mm, stigma exserted beyond anthers at anthesis.
4-merous, zygomorphic, opening at sunset;
floral tube 10–20 mm;
sepals 11–21 mm;
petals white, fading pink to red, elliptic to elliptic-obovate, 10–15 mm;
filaments 8–13 mm, anthers 2–6 mm, pollen 90–100% fertile;
style 22–36 mm, stigma exserted beyond anthers at anthesis.
oblong-clavate to oblong-ellipsoid, 4-angled or 4-winged, and wings 0.1–0.2 mm, 7–15 × 4–6 mm, stipe 2–5 mm;
sessile.
ellipsoid or ovoid, narrowly 4-winged, furrowed between angles, 4.5–8 × 2–5 mm, stipe 0.2–2.2 mm;
sessile.
0.8 × 0.4 mm.
3 or 4 (or 5), yellowish to light brown, 2–3(–4) × 1 mm.
= 56.
= 14.
Oenothera riparia
Oenothera nealleyi
Oenothera riparia has not been accepted as a distinct species for a long time. The conservative approach used by G. B. Straley (1977) is here followed in recognizing a broadly delimited O. fruticosa, except that the very distinctive coastal tidal-freshwater semi-aquatic octoploid populations (Straley 1982) are recognized as O. riparia. Plants of these coastal populations, which occur from southern Virginia to North Carolina, are more robust, more branched, and less pubescent than those of the two subspecies of O. fruticosa, and have slightly succulent leaves and more prominent adventitious roots (Straley 1982; D. Boufford, pers. comm.). Further field studies and cytological analyses are needed to fully understand the geographical and ecological limits of O. riparia and confirm that it is strictly an octoploid species. K. N. Krakos et al. (2014) determined that Oenothera riparia is self-incompatible and is pollinated by bees (Bombus, Lassioglossum, Megachile, Parallelia, Xylocopa, and Zale).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Oenothera nealleyi is restricted to an area from trans-Pecos Texas and northern Coahuila, Mexico, north to Bernalillo and Torrance counties, New Mexico. P. H. Raven and D. P. Gregory (1972[1973]) considered O. nealleyi to represent an unevenly intergrading entity with O. suffulta based on merging of distinguishing characteristics. The known intermediates occur in Terrell County, Texas, and were previously described as Gaura suffulta var. terrellensis Munz, but until new data on its status are available, we include this name with O. nealleyi. The molecular data (K. N. Krakos, unpubl.) suggest that O. nealleyi is not as closely related to O. suffulta as suggested by Raven and Gregory, given the placement in the phylogeny and the difference in scent profiles for these two taxa. Oenothera suffulta is a member of a strongly supported clade that also includes O. patriciae and O. triangulata, while O. nealleyi is a member of a polytomy that consists of other species of subsect. Gaura, with the O. suffulta—O. triangulata—O. patriciae clade sister to it (W. L. Wagner et al. 2013). Oenothera nealleyi has a strong sweet scent, whereas O. suffulta does not have a discernible scent (Wagner et al.). Raven and Gregory determined O. nealleyi to be self-incompatible.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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