Ludwigia simpsonii |
Ludwigia arcuata |
|
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Simpson's primrose-willow |
Piedmont primrose-willow |
|
Habit | Herbs sometimes creeping and rooting at nodes, new shoots arising from trailing stems or main caudex, rarely forming stolons. | Herbs usually creeping and rooting at nodes, forming mats. |
Stems | erect, ascending, decumbent, or prostrate, slightly ridged, well branched, 10–60(–75) cm, glabrous, with raised lines decurrent from leaf axils. |
prostrate or decumbent and ascending at tips, slightly ridged, often well branched, 5–70 cm, glabrate to sparsely strigillose, denser on distal parts. |
Leaves | alternate or proximal pairs opposite; stipules narrowly ovate-deltate, 0.1–0.3 × 0.1–0.2 mm, succulent; petiole winged, 0.2–1 cm, blade spatulate or oblanceolate to very narrowly oblanceolate or sublinear, 0.6–1.5(–2) × (0.1–)0.3–0.7(–1.1) cm, base attenuate, margins subentire with hydathodal glands, apex acute or mucronate; bracts not much reduced. |
opposite; stipules narrowly deltate or ovate, 0.05–0.15 × 0.05–0.1 mm; submerged stems: petiole 0–0.2 cm, blade narrowly linear, 1.9–4 ×0.1–0.25 cm; emergent stems: petiole 0–0.2 cm, blade narrowly elliptic or narrowly oblanceolate-elliptic to linear, 0.6–1.8 × 0.2–0.5 cm, base narrowly cuneate, margins entire, apex acute, surfaces glabrous or sparingly strigillose on margins and abaxial midveins; bracts reduced. |
Inflorescences | open, leafy spikes or racemes, flowers solitary in leaf axils; bracteoles attached in opposite pairs near base of ovary, lanceolate-elliptic, 0.9–1.5(–2.5) × 0.4–0.9 mm, swollen at base, apex acuminate. |
in racemes or spikes, well-formed on ascending stems, not on prostrate stems; bracteoles attached at base of ovary or 1.5–8 mm proximally on pedicels, sublinear to very narrowly elliptic, 1.4–5 × 0.2–0.8 mm, apex acute, surfaces minutely strigillose. |
Flowers | sepals ascending, creamy white near base adaxially, ovate-deltate, 1.2–1.8 × 1–2 mm, margins entire, apex narrowly acute or acuminate, surfaces glabrous; petals 0 or very rare; filaments nearly translucent, 0.5–0.8 mm, anthers 0.2–0.4 × 0.3–0.4 mm; pollen shed singly; ovary obconic, subterete or scarcely 4-angled, 1.2–1.8 × 1.2–2 mm; nectary disc elevated 0.3–0.4 mm on ovary apex, green, 0.9–1.3 mm diam., distinctly 4-lobed, glabrous; style pale green, 0.4–0.6 mm, stigma pale yellow, subglobose, 0.2–0.3 × 0.2–0.3 mm, not exserted beyond anthers. |
sepals reflexed or spreading, green, lanceolate-deltate, 5.2–10 ×1.5–2.7 mm, with 3 prominent parallel veins, margins entire and minutely strigillose, apex acute or elongate-acuminate, surfaces minutely strigillose abaxially; petals rarely caducous, elliptic-obovate to spatulate-obovate, 7–11 × 4.5–8 mm, base attenuate, apex rounded; filaments initially spreading, becoming erect, yellow, 2.5–4.5 mm, anthers 1.3–2 × 0.7–1.1 mm; pollen shed in tight tetrads; ovary cylindric to funnelform, 4–5.5 × 1.5–2.8 mm; nectary disc elevated 0.6–1 mm on ovary apex, 1.5–2.6 mm diam., bright yellow, with 4 distinct domed lobes, minutely strigillose between lobes or glabrous; style yellow, 2.3–4(–4.8) mm, glabrous, stigma yellow, broadly capitate, 0.3–0.6 × 0.6–1.8 mm, as long as or exserted beyond anthers. |
Capsules | obconic, obscurely 4-angled, 1.5–2.5 × 1.5–3 mm, hard-walled, dehiscent by loculicidal slits, pedicel 0–0.4 mm. |
clavate, subterete, sometimes slightly curved, 5.5–10 × 2.3–4 mm, hard-walled, irregularly dehiscent, pedicel (12–)17–45 mm. |
Seeds | light brown or brown, ellipsoid, 0.5–0.6 × 0.3–0.4 mm, surface cells transversely elongate, glabrous, occasionally covered by minute waxy hairs. |
light to dark brown, elliptic-oblong, 0.5–0.7 × 0.3–0.4 mm, surface cells transversely elongate. |
2n | = 48. |
= 32. |
Ludwigia simpsonii |
Ludwigia arcuata |
|
Phenology | Flowering Apr–Nov (year-round). | Flowering Mar–Aug. |
Habitat | Sandy, peaty ditches, open pineland swamps, edges of cypress swamps, tidal flats and nearby marshes, limestone sinks. | Roadside ditches, edges of lakes or ponds, swampy prairies, springs, mucky or sandy beach strands. |
Elevation | 0–50 m. (0–200 ft.) | 0–150 m. (0–500 ft.) |
Distribution |
FL; MS; West Indies (Cuba, Jamaica) |
AL; FL; GA; SC |
Discussion | Ludwigia simpsonii is a hexaploid species occurring primarily in Florida, with outlier populations in southern Mississippi, western Cuba, and Jamaica. The species grows frequently in close proximity to L. curtissii; it grows mainly along roadside ditches with other weeds, whereas L. curtissii grows in less disturbed habitats, and the two seldom occur side by side (C. I. Peng 1989). Peng (1988, 1989) suggested that the hexaploid (2n = 48) L. simpsonii and the diploid (2n = 16) L. microcarpa gave rise to L. curtissii, the only octoploid (2n = 64) in sect. Isnardia. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Ludwigia arcuata is common in its range, but geographically restricted to central and western parts of peninsular Florida and adjacent Georgia, extending to southern South Carolina. Disjunct populations have been collected in Bibb County in central Georgia and Mobile County, Alabama. The tetraploid Ludwigia arcuata has the largest flowers in sect. Isnardia and is the most consistently outcrossing species; C. I. Peng (1989) reported abundant insect visitors on this species. It is morphologically most similar to the hexaploid L. brevipes, with which it shares two genomes (Peng). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 10. | FNA vol. 10. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | L. cubensis, L. curtissii var. simpsonii | Isnardia arcuata, I. pedunculosa, L. pedunculosa, Ludwigiantha arcuata |
Name authority | Chapman: Fl. South. U.S. ed. 2 repr. 2, 685. (1892) — (as simpsoni) | Walter: Fl. Carol., 89. (1788) |
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