Oenothera capillifolia
Oenothera sessilis
1–many, weakly decumbent to ascending or erect, unbranched to moderately branched, (10–)25–80 cm.
ascending, unbranched to few-branched, 30–65 cm.
1–9 × (0.1–)0.3–1 cm, sometimes fascicles of small leaves to 2 cm present in non-flowering axils;
petiole 0–0.6 cm;
blade linear to narrowly lanceolate or oblanceolate, often folded lengthwise, usually not much reduced distally, proximalmost leaves sometimes spatulate, base attenuate, margins subentire or serrulate or spinulose-serrate, apex acute.
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.
nodding, flowers in axils of distalmost few nodes.
opening at sunrise;
buds with free tips 0–4 mm;
floral tube 5–20 mm;
sepals 4–12 mm, midribs keeled;
petals yellow, fading orangish to purplish, 6–25 mm; antisepalous filaments 2–8 mm, antipetalous filaments 1–4 mm, anthers 2–7 mm, pollen 90–100% fertile;
style 9–30 mm, stigma sometimes blue-black, discoid to quadrangular, exserted beyond anthers.
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.
10–35 × 1–2 mm, hard, dehiscent 1/2 their length, often tardily dehiscent throughout their length.
ellipsoid, 4-angled, 8–10 × 3–4 mm, stipe 0–2 mm;
sessile.
obovoid, 1–1.8 mm, sharply angled, apex truncate.
1 × 0.5 mm.
= 56.
Oenothera capillifolia
Oenothera sessilis
Subspecies 2 (2 in the flora).
Oenothera capillifolia is self-incompatible (H. F. Towner 1977).
Oenothera berlandieri (Spach) Steudel 1841, not D. Dietrich 1840, is superfluous and cannot be used in Oenothera when transferred from Calylophus, 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.)
1. Stems 1–several, ascending to erect, 30–80 cm; leaves 2.5–9 cm. | subsp. capillifolia |
1. Stems several–many, decumbent to ascending, (10–)25–40 cm; leaves 1–4 cm. | subsp. berlandieri |
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