1 Pedicel 2-15 mm long; capsule subglobose to spheric or cubic, about as long as wide, box-like, 4-angled, dehiscence by an apical pore (later sometimes also irregularly loculicidal); petal present, 4-15 mm long, persistent or caducous; root fascicled, fusiform, tuberous; plants lacking basal, stoloniform shoots; [section Ludwigia].

  2 Leaves cuneate at base; pedicel 2-5 mm long; nectary disc at base of style flattish, inconspicuous; [widespread in our area, in a wide variety of habitats]

  2 Leaves rounded or truncate at base; pedicel 4-15 mm long; nectary disc at base of style domed, prominent; [nearly restricted to the Coastal Plain, primarily of pinelands].

    3 Style 6-10 mm long; plants glabrous, glabrescent, or pubescent with very short hair; sepal strongly reflexed in fruit

    3 Style 1.5-3 mm long; plants glabrescent or pubescent with short to long, spreading to shaggy hair; sepal strongly reflexed, spreading, or ascending in fruit.

      4 Sepal narrowly deltoid, broadest at or near the base, 3-4× as long as wide, ascending or spreading in fruit; plants glabrescent to hirtellous with long spreading hair

      4 Sepal ovate, broadest near the middle, ca. 2× as long as wide, strongly reflexed in fruit; plants pubescent with relatively short, appressed to spreading hair

1 Pedicel 0-1 (-5) mm long; capsule subglobose, obconic, or obpyramidal, about as long as wide or longer than wide, circular to quadrangular in cross-section, dehiscence irregularly loculicidal; petal absent or present, if present (L. linearis, L. linifolia) then 0-6 mm long and caducous; root fibrous or rhizomatous; plants frequently with basal, stoloniform shoots; [section Isnardia].

        5 Capsule cylindrical, narrowly obconical, or narrowly obpyramidal, at least 2.5-5× as long as broad; petal present or absent.

          6 Primary leaves of the flowering stems narrowly elliptical, 6-12 (-20) mm wide; petal absent.

             7 Capsule 2-4 mm long; seed surface cell elongate transversely to seed length

             7 Capsule (4-) 5-8 (-9) mm long; seed surface cell elongate parallel to seed length

          6 Primary leaves of the flowering stems linear, 1.5-5 mm wide; petal present.

               8 Sepal (3.3-) 4-7 mm long; lateral and marginal veins obscure on lower leaf surface; seeds reddish brown; capsule cylindric, parallel-sided through most of their length, not grooved; anther 0.5-1.1 mm long

               8 Sepal 2.3-5 (-5.6) mm long; lateral and marginal veins distinct on lower leaf surface; seeds yellowish; capsule elongate obpyramidal, tapering through most or all of their length, with a shallow longitudinal groove on each face; anther 1.1-2 mm long.

                 9 Sepal 2.3-4 mm long, acuminate, the surfaces densely and minutely papillose, the papillae 0.02-0.05 mm long and appressed; capsule 5-8.5 (-10) mm long, 2-4 (-5) mm in diameter; pedicel 0-0.4 mm long; seed surface cell elongate parallel to the seed length (as seen at 20× or more); anther 1.1-1.6 mm long

                 9 Sepal 3-5 (-5.6) mm long, elongate-acuminate to cuspidate, the surfaces densely minutely strigillose, the hair 0.06-0.10 mm long and appressed to ascending; capsule 5-10 (-12) mm long, 3-5.5 mm in diameter; pedicel 0-3.5 (-5) mm long; seed surface cell elongate transverse to the seed length, or irregular (as seen at 20× or more); anther (1.1-) 1.3-2 mm long

        5 Capsule subglobose, obovoid, or broadly obpyramidal, 1-1.5 × as long as broad; petal absent.

                   10 Flowers in compact, headlike or elongate spike, the inflorescence lacking well-developed leaves; stems rarely branched; rhizome often present

                   10 Flowers axillary in the axil of well-developed leaves; stems usually much branched; rhizome absent.

                     11 Plants densely pubescent throughout.

                       12 Sepal apex elongate-acuminate or subcuspidate, reflexed; pubescence of stems and leaves hirtellous (the hair spreading); seed surface cell suborbicular (as seen at 20× or more); anther 0.6-0.9 (-1.3) mm long; style 1-2 mm long

                       12 Sepal apex acuminate, ascending; pubescence of stems and leaves strigillose (the hair appressed) or hirtellous (the hair spreading); seed surface cell elongate; anther 0.3-0.8 mm long; style 0.25-1 (-1.25) mm long.

                          13 Plants hirtellous; capsule oblong-obovoid; sepal greenish on the upper surface; bracteole (1.5-) 2-4.3 mm long, borne at or near the base of the capsule; seed surface cell elongate transverse to the seed length; anther 0.3-0.35 mm long; style 0.25-0.5 mm long

                          13 Plants strigillose; capsule subglobose; sepal yellowish on the upper surface; bracteole 0.5-1.5 mm long, usually borne on the short pedicel; seed surface cell in patches, some patches with cell elongate parallel to seed length, others with cell transverse to seed length, others with cell diagonal (rather resembling a badly laid-out parque floor); anther 0.5-0.8 mm long; style 0.55-1 (-1.25) mm long

                     11 Plants glabrous or subglabrous throughout.

                            14 Primary leaves of the flowering stems 4-17 mm long, 1.5-10 mm wide, mostly obovate-spatulate and 1.5-3× as long as wide; capsule 1-1.5 (-2) mm long, containing 10-20 dark reddish-brown seeds; plants typically 1-4 dm tall; nectary disc nearly flat on ovary apex

                            14 Primary leaves of the flowering stems (18-) 30-110 mm long, 2-10 (-20) mm wide, mostly elliptic, lanceolate, oblanceolate, or linear and 4-20× as long as wide; capsule 1.8- 2-7 mm long, containing 40-500 light brown, yellowish, or tan seeds; plants typically 3-10 dm tall; nectary disc distinctly raised on ovary apex.

                              15 Capsule obpyramidal, the corners narrowly winged with wings 0.3-0.9 mm wide.

                                16 Stems often distinctly ridged or winged; sepal creamy-white, nearly as long as the capsule; capsule wall bulging out longitudinally between the wings; seed surface cell elongate parallel to the seed length

                                16 Stems nearly smooth or slightly ridged; sepal greenish, about 1/2 as long as the capsule; capsule wall flat between the wings; seed surface cell suborbicular

                              15 Capsule oblong-ovoid or subglobose, the corners not winged.

                                  17 Cauline leaves lanceolate, oblong-elliptic to narrowly so, 30-110 mm long, usually about 10 × as long as wide; capsule dehiscing by irregular rupture of the outer walls; stolon present; [collectively widespread].

                                    18 Bracteole 3.5-6.5 (-8) mm long; sepal green, the apex long-acuminate, reflexed; capsule oblong-obovoid; seed surface cell elongate parallel to the seed length

                                    18 Bracteole 0.5-1.5 mm long; sepal yellowish, the apex acuminate, ascending capsule subglobose; seed surface cell in patches, some patches with cell elongate parallel to seed length, others with cell transverse to seed length, others with cell diagonal (rather resembling a badly laid-out parquet floor)

                                  17 Cauline leaves obovate-spatulate to oblanceolate, 16-30 mm long, usually < 5× as long as wide; capsule dehiscing by 4 longitudinally lenticular slits on the wall opposite the locule; stolon not common; [FL and MS].

                                       19 Capsule 1.5-2.5 mm long; sepal 1.2-1.8 mm long; vestigial petal rare; lower or seedling leaves tending to be opposite or subopposite