Ludwigia leptocarpa
Onagraceae subfam. ludwigioideae
anglestem primrose-willow, anglestem waterprimrose
usually erect or strongly ascending, rarely floating or creeping, terete to somewhat angled on young branches, 30–250 cm, well branched to sparsely branched or simple, usually villous, often also strigillose, rarely glabrous, with raised lines decurrent from leaf axils.
stipules narrowly deltate, 0.1–0.2 × 0.1–0.2 mm;
petiole 0.2–3.5 cm;
blade broadly lanceolate, 3.5–18 × 1–4 cm, base narrowly cuneate, margins subentire, apex acuminate, surfaces hirsute or villous;
bracts slightly to much reduced.
stipules present.
leafy racemes, flowers solitary in axils;
bracteoles often absent, when present, narrowly deltate, 2–3 × 1.2–2.4 mm, attached near ovary base.
sepals ovate-deltate, 5.5–11 × 1.5–3 mm, margins entire, apex acuminate, surfaces villous;
petals orange-yellow, obovate, 5–11 × 4–8 mm;
stamens (8 or)10 or 12(or 14), in 2 unequal series, longer filaments 2.5–4.5 mm, shorter ones 1.5–2.5 mm, anthers oblong, 1.2–1.6 × 0.7–1 mm, extrorse;
ovary cylindric, subterete, 10–16 × 2–3 mm, glabrate to strigillose or villous;
nectary disc slightly elevated at ovary apex, 2–4 mm diam., lobed, depressed, surrounded by densely matted white hairs;
style 3–4.5 mm, glabrous, stigma capitate-globose, 1–1.5 × 2–2.5 mm, ± 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.
obscurely [4 or]5 or 6[or 7]-angled or subterete, straight or curved, 15–50 × 2.5–4 mm, relatively thin-walled, seeds visible as bumps, tardily and irregularly loculicidal, villous, pedicel 2–20 mm.
in 1 row per locule, horizontal and loosely embedded in an easily detached horseshoe-shaped segment of firm endocarp, pale brown, obovoid, 1–1.2 mm, shiny, finely pitted, raphe much narrower than seed body.
= 32, 48.
Ludwigia leptocarpa
Onagraceae subfam. ludwigioideae
Ludwigia leptocarpa is a globally widespread and morphologically variable species; in the flora area it is distributed widely in wet areas of the southeastern United States. Both tetraploid and hexaploid plants are known, but it is not clear if or how ploidy level is related to the considerable morphological variation, especially in pubescence type and pattern.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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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