Ludwigia simpsonii
Ludwigia ravenii
Simpson's primrose-willow
Raven's primrose-willow
erect, ascending, decumbent, or prostrate, slightly ridged, well branched, 10–60(–75) cm, glabrous, with raised lines decurrent from leaf axils.
erect, slightly ridged, usually well branched, (15–)35–90 cm, densely hirtellous.
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.
alternate;
stipules lanceolate to broadly deltate, 0.2–0.5 × 0.1–0.3 mm;
stolons: petiole 0.1–0.3 cm, blade elliptic to orbiculate, 1–1.8 × 0.6–1.4 cm, base attenuate, apex rounded to acute;
stems: petiole narrowly winged, 0.1–0.8 cm, blade narrowly lanceolate-elliptic, 1.3–6.5 × 0.4–1.5 cm, base attenuate, margins entire with minute hydathodal glands, apex acute, surfaces densely hirtellous;
bracts not much reduced.
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.
leafy racemes, flowers solitary in leaf axils;
bracteoles attached near base of ovary, lanceolate or elliptic to narrowly so, (1.5–)2–4.3 ×0.3–0.9 mm, apex acuminate, surfaces hirtellous.
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 ascending-spreading, green, broadly ovate-deltate, 1.5–3 × 1.4–2.1 mm, margins entire, apex acuminate, surfaces densely hirtellous;
petals 0;
filaments light green, 0.7–1.1 mm, anthers 0.3–0.4 × 0.4–0.5 mm;
pollen shed in tetrads;
ovary obovoid to obconic, 2.8–3.5 × 2–3 mm;
nectary disc elevated 0.3–0.4 mm on ovary apex, light green, 1.4–2.5 mm diam., 4-lobed, glabrous;
style light green, 0.3–0.5 mm, glabrous, stigma clavate to subcapitate, 0.4–0.6 × 0.3–0.5 mm, not exserted beyond anthers.
obconic, obscurely 4-angled, 1.5–2.5 × 1.5–3 mm, hard-walled, dehiscent by loculicidal slits, pedicel 0–0.4 mm.
oblong-obovoid, subterete to scarcely 4-angled, (3–)4–5(–5.3) × 2.5–3.5(–4) mm, hard-walled, irregularly dehiscent, pedicel 0.2–0.5 mm.
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 brown, elliptic-oblong with slightly curved ends, 0.5–0.7 ×0.3–0.4 mm, surface cells elongate transversely to seed length.
= 48.
= 32.
Ludwigia simpsonii
Ludwigia ravenii
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 ravenii is an uncommon species occurring in scattered populations in coastal southeastern Virginia and eastern North Carolina, with single disjunct populations in southeastern South Carolina and northeastern Florida. C. I. Peng (1989) observed its similarity to L. pilosa by virtue of its dense, hirtellous pubescence, but noted its smaller, more consistently autogamous flowers. It is in the Center for Plant Conservation’s National Collection of Endangered Plants.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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