Oenothera glaucifolia
Oenothera sessilis
false gaura
erect, branched or unbranched, 30–300 cm.
ascending, unbranched to few-branched, 30–65 cm.
in a basal rosette and cauline, basal 3–7 × 0.5–2 cm, sessile, blade oblong to oblong-lanceolate, base usually ± auriculate, margins entire;
cauline 3–8(–10) × 0.4–1.8 cm, blade lanceolate to oblong-lanceolate, gradually smaller, becoming linear-subulate distally.
in a basal rosette and cauline, basal 2.5–7 ×0.7–2.3 cm, petiole 1–1.5 cm, blade oblanceolate, margins subentire, undulate;
cauline (3–)6–7(–9) ×(0.3–)0.6–0.8(–1.1) cm, sessile, blade lanceolate to narrowly lanceolate, margins subentire.
long, wandlike, unbranched or branched.
nodding, flowers in axils of distalmost few nodes.
4-merous, nearly actinomorphic, opening near sunrise;
floral tube 6–17 mm;
sepals 4–6 mm;
petals white, fading off-white or tinged pink, slightly unequal, rhombic, 4–6 mm, abruptly clawed;
filaments 5–8 mm, anthers 1.5–2 mm, pollen 85–100% fertile;
style 6–10, stigma exserted beyond anthers at anthesis.
opening near sunrise;
buds with free tips 1–2 mm, connivent to spreading;
floral tube 10–15(–20) mm;
sepals 10–18 mm;
petals bright yellow, fading pale pink, 15–25 mm;
filaments 7–9 mm, anthers 5–8 mm, pollen 85–100% fertile;
style 10–12 mm, stigma exserted beyond anthers at anthesis.
ovoid, 4-angled, somewhat flattened, 3–4 × 1.5–2.3 mm, valves with raised midrib and conspicuous lateral veins;
sessile.
ellipsoid, 4-angled, 8–10 × 3–4 mm, stipe 0–2 mm;
sessile.
1, pale yellow, oblanceoloid, 2.4–2.6 × 1–1.5 mm.
1 × 0.5 mm.
= 14.
= 56.
Oenothera glaucifolia
Oenothera sessilis
Oenothera glaucifolia is self-incompatible, the flowers diurnal, pollinated primarily by wasps (R. Clinebell, unpubl.), as well as bees, flies, butterflies, and occasionally beetles (summarized by W. L. Wagner et al. 2007). It was collected once in 1988 in Indiana at Miller Woods Visitor Center (Lake County), Dritz 596 (MOR); it seems likely that it was introduced, and has not been collected there since.
Stenosiphon virgatus Spach is a superfluous name and pertains here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Oenothera sessilis is relatively rare within its range and has a narrow overall distribution, occurring in Ashley, Phillips, Prairie, and St. Francis counties in Arkansas, Allen, Claiborne, and Tensas parishes in Louisiana, and Galveston County in Texas. Oenothera sessilis appears to be relatively rare and may no longer occur in Texas; it was last collected there in the 1840s by Lindheimer on Galveston Island. It is also rare in Louisiana but has been collected in recent decades. It is currently most common in Arkansas. P. A. Munz (1937, 1965) treated this taxon as O. sessilis, but G. B. Straley (1977) in his revision of sect. Kneiffia placed it as a subspecies of O. pilosella based on a common octoploid (2n = 56) chromosome number, morphology, and field studies. K. N. Krakos et al. (2014), based on new field studies, controlled greenhouse breeding experiments, and phylogenetic data found that this taxon differs morphologically from O. pilosella by having consistently shorter stature and smaller flowers, is self-compatible, and does not form a monophyletic group with O. pilosella in molecular analyses, and is here reinstated as a distinct species.
Oenothera sessilis is in the Center for Plant Conservation’s National Collection of Endangered Plants as O. pilosella subsp. sessilis.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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