1 Spathes absent; inflorescence open and repeatedly branched; [tribe Tradescantieae]

1 Spathes present, single or paired; inflorescence compact, unbranched.

  2 Spathes paired, terminating the stem, resembling foliage leaves in size, shape, texture, and coloration; [tribe Tradescantieae]

  2 Spathes single (or paired in Callisia), either terminal or axillary, differing from the foliage leaves (in Commelina folded, heart-shaped when spread, and usually pale-green, in Cuthbertia and Murdannia scale-like, scarious, and inconspicuous, sometimes hidden by foliage leaves in Murdannia).

    3 Spathe folded, heart-shaped when unfolded, usually pale-green, closely subtending and surrounding the flower pedicels; petals unequal, the 2 upper petals larger and usually more deeply colored than the lower petal (which is sometimes absent); [tribe Commelineae]

      4 Leaves not glaucous; spathe folded; fertile stamens 3, their filaments glabrous; [collectively widespread in our region]

      4 Leaves glaucous; spathe open; fertile stamens 6 (though of 4 disparate forms), their filaments bearded with purple or purple-and-yellow hairs; [TX only in our region]

    3 Spathe scale-like, scarious, and inconspicuous, not closely subtending and surrounding the flower pedicels; petals equal, in both size and coloration.

        5 Leaves linear, > 20× as long as wide; petals bright pink (rarely white); [tribe Tradescantieae]

        5 Leaves lanceolate, < 20× as long as wide; petals white, pink, purplish, or bluish.

          6 Fertile stamens 0-6, all fertile (no staminodes); petals white to pink; [tribe Tradescantieae]

1 Leaves broad, < 4× as long as wide.

  2 Floating leaves peltate

  2 Floating or emersed leaves cuneate to rounded at base.

    3 Floating leaves diamond-shaped, prominently serrate

    3 Floating or emersed leaves elliptic or suborbicular.

      4 Leaves emersed, lanceolate to narrowly elliptic; flowers 5-merous; [Eudicots]

      4 Leaves emersed or floating, suborbicular or elliptic (if emersed, then suborbicular; flowers 3-merous; [Monocots].

        5 Leaves emersed, suborbicular

        5 Leaves floating, elliptic

1 Leaves narrow, > 4× as long as wide.

          6 Leaves 0.3-1.4 cm long, very numerous and tightly spaced

          6 Leaves 2-35 cm long, fewer and scattered along the stem.

             7 Leaf divided into a sheath and blade, with a ligule 0.5-8 mm long at the juncture; inflorescence a spike, raceme, or panicle of spikelets

             7 Leaf not divided into a sheath and blade, but if basally sheathing lacking a ligule (though sometimes with 1-2 conspicuous stipules); inflorescence various, but not as above.

               8 Leaves terete, to 35 cm long, 0.3-2 mm wide; plants of marine habitats, growing submersed in salt water; [FL and the Gulf Coast of AL, MS, and LA]

               8 Leaves flat or terete, to 200 cm long; plants of fresh or brackish waters (if of marine waters, Zostera, the leaves obviously flat, 1.5-6 mm wide); [collectively widespread].

                 9 Leaves filiform, terete or nearly so; stipules present, adnate to the leaf base and forming a sheath around the stem > 10 mm long.

                   10 Stipule free at its tip, the sheathing portion not appearing inflated; flowers > 2, in an interrupted spike

                   10 Stipule adnate its entire length to the leaf base, appearing inflated; flowers usually 2, on a flexous, elongate peduncle

                 9 Leaves flat; stipules absent, or if present, either free or adnate to the leaf base and forming a sheath for < 10 mm.

                     11 Leaves lacking a midvein; perianth parts 6, yellow

                     11 Leaves with a midvein; perianth parts 0 or 4, variously colored (not yellow).

                       12 Plants pubescent (at least on the upper stem); leaves pinnately veined; [Eudicots]

                       12 Plants nearly or entirely glabrous; leaves with parallel venation; [Monocots].

                          13 Inflorescence a spike, terminal or axillary; with or without a spathe; perianth lacking.

                            14 Inflorescence a cylindrical, interrupted spike, lacking a spathe; leaves either parallel-margined or variously with a narrow blade differentiated from a petiole; [fresh to brackish waters]

                            14 Inflorescence either a flattened spike sheathed by a spathe-like bract, or solitary; leaves parallel-margined, to 20 dm long; [saline (marine) to brackish waters].

                              15 Leaves with a notched or tricuspidate apex; flowers solitary; [e. NC southward]

                              15 Leaves with a rounded apex; flowers in a flattened spike sheathed by a spathe-like bract; [e. NC northward]