Ludwigia maritima
Onagraceae subfam. ludwigioideae
seaside primrose-willow
fibrous or fusiform, sometimes fascicled.
subterete to scarcely angled, with narrow raised lines or wings decurrent from leaf axils, 30–90 cm, simple or sparsely branched distally, strigillose to sometimes glabrate.
stipules narrowly deltate, 0.05–0.2 × 0.05–0.1 mm;
sessile;
blade ovate proximally, lanceolate to lanceolate-linear distally, (2–)3–8 × 0.3–1.5 cm, base cuneate, margins entire, apex acute, surfaces glabrate to strigillose or hirsute;
bracts usually much reduced, sublinear.
stipules present.
sparse racemes, flowers solitary in leaf axils;
bracteoles attached in subopposite pairs on distal 1/3 of pedicel, lanceolate-linear, 0.7–3.2(–5) × 0.2–0.5 mm, margins entire, apex acute, surfaces strigillose.
sepals often spreading, ovate-deltate, (4.5–)5.5–8(–9) × 3–5 mm, margins entire, apex acute to obtuse, surfaces strigillose;
petals cordate, 9–12 × 8–10 mm, base attenuate, apex emarginate;
filaments yellow, awl-shaped, 1.9–3.2 mm, anthers 1.2–2.5 × 0.4–0.7 mm;
ovary subcuboid or globose, 3–4.5 × 3–4 mm;
nectary disc elevated, domed, 0.9–1.3 mm diam., prominently 4-lobed, ringed with sparse, spreading hairs;
style 1.5–3.3 mm, glabrous, stigma capitate to hemispherical, 0.6–1.2 × 1.4–1.9 mm, shallowly 4-lobed, not exserted beyond anthers.
floral tube absent;
sepals (3 or)4 or 5(–7), persistent at ovary apex after dehiscence of other floral parts;
petals yellow or white, rarely absent.
subcuboid to squarish globose, 4–7 ×4–5 mm, 4-angled, often also 4-winged, wings 0.3–1.2 mm wide, pedicel 5–17 mm.
light brown, oblong to reniform, 0.4–0.6 ×0.2–0.4 mm, surface cells elongate transversely to seed length, except may be parallel to seed length near raphe.
= 16.
Ludwigia maritima
Onagraceae subfam. ludwigioideae
Genus 1, species 82 (31 in the flora): North America, Mexico, West Indies, Bermuda, Central America, South America, se Asia, Africa, Indian Ocean Islands, Pacific Islands, Australasia; introduced in Europe, w Asia.
Ludwigioideae were segregated as a distinct subfamily (W. L. Wagner et al. 2007) to reflect the phylogenetic relationship of Ludwigia as sister to other genera of Onagraceae in morphological and molecular analyses (see R. A. Levin et al. 2003, 2004). Ludwigia is distinguished by the absence of a floral tube, persistence of sepals on capsules after other floral parts dehisce, pollen shed in tetrads or polyads (or as monads in some sections, tetrads sometimes found elsewhere in Onagraceae), double ovule vascular supply, uniquely including a central supply (R. H. Eyde 1981), single-celled ovule archesporium (H. Tobe and P. H. Raven 1996), and a base chromosome number of x = 8.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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