Oenothera capillifolia |
Oenothera rhombipetala |
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fourpoint evening primrose |
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Habit | Herbs perennial (short-lived or, sometimes, suffrutescent) or annual, glabrous or strigillose; from a stout taproot. | Herbs biennial, densely to sparsely strigillose, sometimes also sparsely glandular puberulent distally. | ||||
Stems | 1–many, weakly decumbent to ascending or erect, unbranched to moderately branched, (10–)25–80 cm. |
sometimes with lateral branches arising obliquely from rosette, 30–100(–150) cm. |
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Leaves | 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 6–20 × 0.6–2 cm, cauline 3–15 × 0.8–2.5 cm; blade narrowly oblanceolate, gradually narrowly elliptic to narrowly lanceolate, oblanceolate, or ovate distally, margins lobed to remotely dentate or subentire; bracts slightly longer than capsule they subtend. |
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Inflorescences | dense, usually without lateral branches, mature buds usually not overtopping spike apex. |
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Flowers | 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. |
2–several per spike opening per day near sunset; buds erect, with free tips erect, 0.5–3 mm; floral tube slightly curved upward to ± straight, 30–45 mm; sepals 15–30 mm; petals yellow, broadly elliptic to rhombic-elliptic, 15–35 mm; filaments 13–25 mm, anthers 3–8 mm, pollen 85–100% fertile; style 25–50 mm, stigma exserted beyond anthers at anthesis. |
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Capsules | 10–35 × 1–2 mm, hard, dehiscent 1/2 their length, often tardily dehiscent throughout their length. |
narrowly lanceoloid, 13–25 × 2.5–3 mm. |
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Seeds | obovoid, 1–1.8 mm, sharply angled, apex truncate. |
brown, sometimes flecked with dark red spots, ellipsoid, 1–1.7 × 0.4–0.7 mm. |
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2n | = 14. |
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Oenothera capillifolia |
Oenothera rhombipetala |
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Phenology | Flowering May–Oct. | |||||
Habitat | Fields, prairies, sandy soil. | |||||
Elevation | 60–600(–1300) m. (200–2000(–4300) ft.) | |||||
Distribution | c United States; sc United States; n Mexico |
AR; CO; IL; KS; MI; MN; MO; NE; NM; OK; SD; TX; WI
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Discussion | 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 rhombipetala is primarily a central plains species that has scattered localities in the Midwest to Illinois, Michigan, and Wisconsin, and barely entering the easternmost parts of Colorado and New Mexico. Oenothera rhombipetala had a broader delimitation (P. A. Munz 1965) until W. Dietrich and W. L. Wagner (1988) divided it into three species (O. clelandii, O. curtissii, and O. rhombipetala), with both of the split-off species being PTH. Evidence gathered by Dietrich and Wagner showed that these PTH species are geographically separated populations of small-flowered plants, and although they are very close morphologically, their distributions and morphological differences suggest that they were each derived independently from O. rhombipetala. Oenothera rhombipetala is self-incompatible. Oenothera pyramidalis H. Léveillé is a superfluous name and pertains here. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 10. | FNA vol. 10. | ||||
Parent taxa | Onagraceae > subfam. Onagroideae > tribe Onagreae > Oenothera > sect. Calylophus > subsect. Calylophus | Onagraceae > subfam. Onagroideae > tribe Onagreae > Oenothera > sect. Oenothera > subsect. Candela | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Meriolix capillifolia | O. heterophylla var. rhombipetala, O. leona, Raimannia rhombipetala | ||||
Name authority | Scheele: Linnaea 21: 576. (1848) | Nuttall ex Torrey & A. Gray: Fl. N. Amer. 1: 493. (1840) | ||||
Web links |