Oenothera psammophila |
Oenothera riparia |
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St. Anthony dunes evening primrose |
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Habit | Herbs perennial, caulescent, glabrous, also with resinous exudate, especially on younger leaves; from woody taproot. | Herbs perennial, sparsely strigillose, becoming glabrate distally, usually also glandular puberulent distally; from a somewhat fleshy rootstock, forming adventitious roots where submerged. |
Stems | decumbent, usually branched, 10–30 cm, becoming woody and buried in sand. |
erect or ascending, usually many-branched throughout, proximal branches often somewhat spongy, 50–120 cm. |
Leaves | (6–)8–9(–14.2) × (0.7–)1.5–2(–3.1) cm; petiole 3–9 cm; blade narrowly oblanceolate to oblanceolate, margins usually subentire or repand or remotely dentate, rarely serrate, apex acute. |
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. |
Inflorescences | erect, flowers in axils of distalmost few nodes. |
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Flowers | 1–3 per stem opening per day near sunset, with sweet scent; buds erect; floral tube 42–60 mm; sepals 22–28 mm; petals white, fading rose pink to rose, 23–40 mm; filaments 17–19 mm, anthers 13–16 mm; style 60–72(–88) mm, stigma exserted beyond anthers at anthesis. |
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. |
Capsules | somewhat curved and often somewhat twisted, lanceoloid-cylindrical, nearly cylindrical, (20–)30–47 × 7–8 mm, gradually tapering to apex, 6–8 mm, dehiscent nearly throughout their length, valve margins with a conspicuous, irregular, wavy ridge; pedicel 1–5 mm. |
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. |
Seeds | numerous, in 2 distinct rows per locule, narrowly obovoid, 2.5–3 × 1.2–1.4 mm, embryo 7/8 of seed volume, surface finely reticulate; seed collar with a broad membrane sealing cavity, margin entire. |
0.8 × 0.4 mm. |
2n | = 14. |
= 56. |
Oenothera psammophila |
Oenothera riparia |
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Phenology | Flowering May–Jul. | Flowering May–Jul. |
Habitat | On barren areas of drifting sand at interface between outcrops of lava and sand dunes. | Isolated colonies in or at edge of water in marshes or slow-running rivers, apparently with at least some tidal influence. |
Elevation | 1500–1700 m. (4900–5600 ft.) | 0–10 m. (0–0 ft.) |
Distribution |
ID |
GA; NC; SC; VA |
Discussion | Oenothera psammophila is known only from the dune area north and west of St. Anthony, Fremont County. It is unique in Oenothera because of the exudate produced on the leaves to which sand particles adhere, forming a sand sheath, presumably for protection from the constantly blowing sand particles. It is self-incompatible (W. L. Wagner et al. 1985; Wagner 2005). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 10. | FNA vol. 10. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Pachylophus psammophilusa., O. cespitosa var. psammophila | Kneiffia riparia, O. tetragona var. riparia |
Name authority | (A. Nelson & J. F. Macbride) W. L. Wagner, Stockhouse & W. M. Klein: Monogr. Syst. Bot. Missouri Bot. Gard. 12: 84. (1985) | Nuttall: Gen. N. Amer. Pl. 1: 247. (1818) |
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