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Oenothera

See list of 15 species in this genus

The circumscription of Oenothera has broadened in recent years by the inclusion of Calylophus and Gaura (in our area) due to phylogenetic evidence that shows these genera to be nested within Oenothera (Levin et al. 2004). References: Raven and Gregory (1972), Straley (1977), Dietrich et al. (1997).

  • 1a. Flowers zygomorphic, the petals all oriented toward one side of the flower [Fig. 744]; fruit indehiscent, with 2–6 seeds 1.25–3.5 mm long
  • 1b. Flowers actinomorphic [Fig. 745]; fruit dehiscent, with many seeds 0.3–2 mm long
    • 4a. Ovary quadrangular in cross-section (at least in the apical portion); capsules sharply quadrangular to 4-winged, tapering to the base
      • 5a. Petals 3–10 mm long; style 3–10 mm long; anthers 1.5–2.5 mm long; inflorescence of scattered flowers, the axis and apex commonly drooping in bud
      • 5b. Petals 10–25 mm long; style 10–20 mm long; anthers 4–8 mm long; inflorescence relatively more compact, the axis and apex commonly erect in bud
        • 6a. Sepal appendages mostly shorter than 1 (–1.4) mm and erect; capsules clavate to obpyramidal in outline, stipitate; plants subglabrous to sparsely pubescent with hairs mostly shorter than 1 (–1.5) mm; hypanthium 5–15 (–17) mm long
        • 6b. Sepal appendages mostly 1–4 mm long and divergent; capsules linear-elliptic, elliptic, to narrow-clavate in outline, sessile or short-stipitate; plants conspicuously pubescent with hairs mostly 1–3 mm long; hypanthium 15–25 mm long
    • 4b. Ovary ± terete in cross-section; capsules terete to bluntly quadrangular, abruptly rounded to truncate at the base
      • 7a. Stigmas peltate with 4 short, rounded lobes, stigmatic on the upper and inside surfaces; hypanthium funnel-shaped, quadrangular in cross-section; calyx lobes prominently keeled; stamens alternately of different size
      • 7b. Stigmas with 4 linear lobes [Fig. 745], stigmatic all around; hypanthium 
tubular terete in cross-section; calyx lobes scarcely or not at all keeled; stamens all 
of similar size
        • 8a. Leaf and bract blades prominently dentate to pinnatifid; capsules not tapering to the apex, essentially of uniform width; ovules and seeds vertically oriented in the locules, the seeds without angular faces, conspicuously pitted; plants annual
        • 8b. Leaf and bract blades entire to dentate; capsules slightly tapering to the apex, widest at the base; ovules and seeds horizontally oriented in the locules, the seeds with angular faces, not pitted; plants biennial or short-lived perennial
          • 9a. Petals (25–) 30–45 mm long; sepal appendages (2–) 5–9 mm long; anthers 10–15 mm long; stigmas exserted beyond the anthers [Fig. 745]
            • 10a. Apical half of stem, hypanthium, sepals, and ovary conspicuously pubescent, some of the hairs red and pustulose-based; bracts of inflorescence green and persistent into fruit; sepals yellow-green and usually tinged with red or striped with red (sometimes entirely dark red)
            • 10b. Apical half of stem, hypanthium, sepals, and ovary glabrous or appearing so without magnification, pustulose hairs (when rarely present) translucent; bracts of inflorescence sometimes pale green and deciduous; sepals yellow-green or sometimes tinged with red
          • 9b. Petals 7–25 mm long; sepal appendages 0.5–6 mm long; anthers 3–10 mm long; stigmas surrounded by or shorter than the anthers

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