1 Leaves peltate.

  2 Leaf blades oval in shape, ca. 1.5-2× as long as wide, at maturity floating on the water’s surface; underwater portions of fresh plant coated in transparent mucilage

  2 Leaf blades orbicular in shape, ca. 1× as long as wide, at maturity floating on the water’s surface, emersed, or submersed; underwater portions of fresh plant not mucilaginous (though possibly with green algae, etc.).

    3 Leaves small, < 8 cm in diameter, at maturity emersed or submersed

    3 Leaves large, > 20 cm in diameter, at maturity floating on the water’s surface or emersed

1 Leaves not peltate, the petiole attached at a cuneate, cordate, or sagittate base.

      4 Leaf blades cuneate, rounded, or truncate at the base.

        5 Basal leaves lanceolate, 3-6 mm long

        5 Basal leaves variously shaped, > 10 mm long.

          6 Main veins palmate from the leaf base and also diverging from the midvein, the secondary and tertiary veins then reticulating; inflorescence a spike; [Eudicots]

          6 Main veins either parallel or palmate from the leaf base with cross-veins at nearly right angles to the main veins; inflorescence either a diffuse raceme or panicle of white flowers, or a linear spadix of tightly packed golden-yellow flowers; [Monocots].

             7 Inflorescence diffuse, a raceme or panicle with whorled branches or pedicels, the flowers widely spaced and white; leaves green, “wettable”

             7 Inflorescence tightly packed with flowers, an elongate, golden yellow spadix; leaves blue-green, “unwettable”

      4 Leaf blades cordate or sagittate at the base.

               8 Leaf blades sagittate, the two lobes distinctly acute; leaf apex acute; leaf blade 1.3-3× as long as wide

               8 Leaf blades cordate, the two lobes rounded or sub-acute; leaf apex rounded or apiculate; leaf blade 0.8-8× as long as wide.

                 9 Leaf blade margins serrate, dentate, and/or incised

                 9 Leaf blade margins entire or obscurely crenate.

                   10 Flowers 4-5-merous (sepals 4-5, petals 4-5, stamens 4-5); [Eudicots]

                     11 Leaves emersed or submersed, on stout, stiff petioles (the submersed and winter leaves cuneate-based and lanceolate); flowers 4-merous (sepals 4, petals 4, stamens 4); inflorescence a spike

                     11 Leaves floating, on slender, flexuous petioles (all leaves cordate-based); flowers 5-merous (sepals 5, petals 5, stamens 5); inflorescence an umbel

                   10 Flowers 3-merous or many (>5-) -merous; [Basal Angiosperms or Monocots].

                       12 Perianth parts numerous (usually showing differentiation into sepals and petals, though often with some intergradation), borne in a spiral; stamens numerous; leaves usually > 10 cm long or > 10 cm wide, or both (a few northern species of Nymphaea with leaves as small as 2.5 cm × 2.5 cm); [Basal Angiosperms]

                       12 Perianth parts 3-6 (either differentiated or not into sepals and petals); stamens either 3, or 9-12 (-18), or >20; leaves 1-10 cm long, 1-10 cm wide; [Monocots].

                          13 Perianth strongly differentiated, the 3 sepals green, leathery, and persistent, the 3 petals yellow or white, delicate, deciduous; stamens 20 or more

                          13 Perianth not strongly differentiated, the sepals petaloid and similar in texture and color to the petals; stamens 10 or fewer.

                            14 Flowers unisexual, white, the sepals and petals separate; stamens 3, 6, 9, 12, 15, or 18; leaves either with a central area of spongiform cells (most easily seen on the lower leaf surface) (Limnobium), or without spongiform cells (Ottelia)

1 Leaves compound.

  2 Plants herbaceous; leaves palmately 3-foliolate or pedately compound

  2 Plants woody; leaves either palmately divided or pinnately compound into > 20 segments

1 Leaves simple.

    3 Leaves opposite or whorled, cauline.

      4 Leaves opposite; flowers bilaterally symmetrical

      4 Leaves whorled; flowers radially or bilaterally symmetrical.

        5 Plant with 2 or more leaf-bearing nodes (all nodes whorled or some alternate).

          6 Leaves broad, < 2× as long as wide, cordate at the base; flowers unisexual and plants dioecious

          6 Leaves lanceolate, oblanceolate or narrowly elliptic, > 4× as long as wide, cuneate at the base; flowers bisexual and plants hermaphroditic

        5 Plant with a single leaf-bearing node.

             7 Leaves in whorls of 3 leaves

             7 Leaves in whorls of 5 or more leaves.

               8 Stem floccose, wiry (and at maturity with a second smaller whorl with usually 3 leaves subtending the flowers); flowers radially symmetrical

               8 Stem glabrous, fleshy, never with a second whorl; flowers bilaterally symmetrical

    3 Leaves alternate, either cauline or basal.

                 9 Inflorescence a spadix (a dense spike of hundreds of flowers, the rachis thickened and somewhat fleshy) subtended by a spathe (a green, white, orange, yellowish-green, or maroon bract) (spathe missing in Orontium)

                 9 Inflorescence otherwise, a raceme, panicle, cyme, umbel, spike, etc., the flowers arrayed in a more diffuse manner, the central rachis not thickened, the inflorescence subtended or not by green or scarious spathes.

                   10 Flowers bilaterally symmetrical or asymmetrical; fertile stamens 1 or 2 (or 5 in MUSACEAE), often with several staminodes present as well; tepals 6.

                     11 Leaf venation parallel; leaves various in size and shape, if > 3 dm long, then < 1 dm wide; perianth often differentiated into a lip and 5 petaloid tepals

                     11 Leaf venation prominently penni-parallel; leaves large, at least some on a plant with blade > 2 dm long.

                       12 Fertile stamens 5-6; leaf blades 6-30 dm long

                       12 Fertile stamen 1; leaf blades 0.5-7 dm long.

                          13 Leaves spirally arranged.

                            14 Leaves lacking ligules; ovary and fruit with warty excrescences

                            14 Leaves with 2 stipule-like ligules; ovary and fruit smooth

                          13 Leaves 2-ranked.

                              15 Leaves jointed and swollen at the summit of the petiole, forming a pulvinus.

                                16 Plants terrestrial; bracts persistent; flowers white, sepals > 5 mm long; [se. FL only]

                                16 Plants aquatic (or at least in very wet soils); bracts not persistent; flowers purple; sepals ≤ 3 mm long; [more widely distributed in southeastern coastal plain, including se. FL (T. geniculata)]

                              15 Leaves neither jointed not swollen at the summit of the petiole

                   10 Flowers radially symmetrical (weakly to strongly bilaterally symmetrical in PONTEDERIACEAE); stamens 6 (rarely 3, 4, 5, 9, 12, 15, or 18); tepals usually 6 (rarely 3 or 4), when 6, either undifferentiated (6 or 4 tepals) or differentiated into 3 petals and 3 sepals.

                                  17 Inflorescence subtended by spathes (well-developed green or scarious bracts).

                                    18 Perianth differentiated into green sepals and more brightly colored petals; flowers radially symmetrical (or weakly bilaterally symmetrical, as in some Commelina).

                                       19 Ovary superior; fruit a capsule; stamens 6; [plants mainly of uplands (Murdannia and sometimes Commelina of wetlands)]

                                       19 Ovary inferior; fruit a berry; stamens 3, 6, 9, 12, 15, or 18; [plants of wetlands]

                                  17 Inflorescence not subtended by spathes, though individual small green bracts sometimes subtending individual flowers.

                                         20 Gynoecium of 2 or more pistils (6 in Butomus); fruit achenes or follicles; inflorescence a raceme or panicle with branching in whorls of 3 OR a bracteate umbel; [wetland plants].

                                           21 Flowers consisting of white petals and green sepals, with 1-many stamens and 3-many carpels (but not consistently with 9 stamens and 6 carpels); inflorescence a raceme or panicle in whorls of 3, branched; leaf blades flat or terete

                                           21 Flowers consisting of pink petals and green-pink sepals, usually with 9 stamens and 6 carpels; inflorescence an umbel; leaf blades triquetrous in cross-section

                                         20 Gynoecium of 1 pistil; fruit simple, a capsule or berry; inflorescence various, terminal or axillary, but if a raceme or panicle, not with branching in whorls of 3; [upland (or very rarely wetland) plants].

                                             22 Leaves basal or basally disposed.

                                               23 Leaves 2 (rarely 3 in Convallaria in RUSCACEAE).

                                                 24 Inflorescence a raceme; fruit a berry; tepals united, the perianth urceolate

                                                 24 Inflorescence an umbel or a solitary flower; fruit a capsule; tepals separate or basally fused.

                                                    25 Flowers in an umbel, white; fresh plants with oniony odor

                                                    25 Flowers solitary, white or yellow; fresh plants without strong odor

                                               23 Leaves 4 or more.

                                                      26 Inflorescence a terminal umbel; fruit a blue or black berry; tepals white or yellow; flowers bisexual

                                                      26 Inflorescence a terminal raceme or panicle; fruit a capsule; tepals white, green, yellowish, or pink; flowers either bisexual (Helonias in HELONIADACEAE), or unisexual and primarily on different plants (dioecious) (Chamaelirium in CHIONOGRAPHIDACEAE), or a mix of bisexual and unisexual staminate flowers (Veratrum in MELANTHIACEAE)

                                                        27 Inflorescences bracteate, with bracts subtending individual pedicels and (if they are present) branches of the inflorescence; tepals white, greenish-white, or cream

                                                        27 Inflorescence ebracteate, lacking bracts subtending pedicels; flowers bisexual (Helonias) or predominantly unisexual and on different plants (dioecious) (Chamaelirium); tepals pink (Helonias) or white to cream (Chamaelirium).

                                                          28 Flowers white to cream; plants dioecious (individual plants either male or female, with all male flowers or all female flowers)

                                                          28 Flowers pink; plants hermaphroditic (individual flowers bisexual)

                                             22 Leaves cauline.

                                                            29 Leaves both cordate/subcordate (rarely merely rounded at the base) and obviously petiolate.

                                                              30 Inflorescence an axillary many-flowered umbel; fruit a berry; axillary tendrils often present (absent in some species)

                                                              30 Inflorescence an axillary solitary flower, a few-flowered cyme, or a panicle; fruit a capsule (winged in Dioscorea, unwinged in Croomia); axillary tendrils never present (plant not climbing, or climbing by twining).

                                                                 31 Tepals 6; stamens 6; flowers unisexual (and generally on separate plants, therefore dioecious); inflorescence of a solitary flowers or a panicle; ovary inferior; [widespread in our area]

                                                                 31 Tepals 4 (-5); stamens 4 (-5); flowers bisexual; ovary superior; [AL and adjacent GA, FL, and perhaps LA]

                                                            29 Leaves not both cordate/subcordate and petiolate (some with cordate clasping or perfoliate leaf bases).

                                                                   32 Leaves alternate and in whorls at some nodes; flowers orange; tepals > 5 cm long; inflorescence a terminal umbel or single flower

                                                                   32 Leaves strictly alternate; flowers yellow, white, pink, greenish, or maroon; tepals < 5 cm long; inflorescence either a terminal cluster, raceme, panicle or umbel, or an axillary raceme, cluster or solitary flower.

                                                                     33 Inflorescence a terminal umbel; flowers slightly zygomorphic, reddish, the tepals 3.5-4.5 cm long

                                                                     33 Inflorescence either a terminal cluster, raceme, or panicle, or an axillary raceme, cluster or solitary flower; flowers actinomorphic, variously colored (most white or yellow), the tepals < 3.5 cm long (except Uvularia grandiflora).

                                                                       34 Leaves arrayed spirally around an erect, unbranched stem; fruit a septicidal capsule; flowers a mixture of bisexual and unisexual (staminate) on a plant; perianth white, greenish white, or maroon.

                                                                         35 Leaves basally disposed; leaves not at all to slightly plicate, 1-14 cm wide; tepals glabrous, 4-9 mm long, 1-3 mm wide (3-5 mm wide in M. hybridum), with either conspicuous (M. hybridum) or diffuse (M. parviflorum and M. woodii) glands; filaments fused to the basal claw of the tepal

                                                                         35 Leaves cauline; leaves strongly plicate, 6-15 cm wide; tepals pubescent, 8-13 mm long, 3-5 mm wide, with a conspicuous pair of glands near the base of the tepal blade (these sometimes more or less fused); filaments free from the tepals

                                                                       34 Leaves arrayed distichously (2 ranked) along an arching, unbranched or dichotomously (Y-forking) branched stem; fruit a berry or loculicidal capsule; flowers all bisexual; perianth white, pink, or yellow.

                                                                           36 Stems of fertile and sterile individuals simple (never branched); inflorescence a terminal raceme or panicle (Maianthemum) or axillary racemes or clusters of 1-9 flowers (Polygonatum); fruit a berry.

                                                                              37 Inflorescence terminal, a raceme or panicle; tepals separate; leaves with 3 main parallel veins, acute to acuminate at the apex; foliage green, not glaucous

                                                                              37 Inflorescence of 1-several axillary flowers; tepals fused; leaves with > 7 main parallel veins, obtuse to acute at the apex; foliage blue-green, glaucous

                                                                           36 Stems of fertile individuals branched (always at least bifurcate), but sterile individuals in some genera characteristically unbranched; inflorescence either of 1 (-2) flower(s) borne in a leaf axil (Uvularia, Streptopus), or of (1) 2 (-3) flowers borne terminally opposite the last leaf (Prosartes); fruit a berry or capsule.

                                                                                38 Leaves perfoliate; fruit a capsule

                                                                                38 Leaves sessile (though sometimes slightly to strongly clasping); fruit a berry or capsule.

                                                                                  39 Stem brown, wiry, puberulent; last 2 leaves (near stem tip) on each branch approximate to one another (sometimes subopposite) and with noticeably oblique bases; flowers and fruits terminal on the branches

                                                                                  39 Stem green, not wiry, glabrous; last 2 leaves (near stem tip) on each branch no closer together than other leaves, with symmetrical bases; flowers (and fruits) either terminal on the branches or solitary and axillary to most leaves.

                                                                                    40 Flowers and fruits in single terminal clusters (sometimes appearing axillary, but still only one cluster per branch of the stem); tepals pale to rich yellow

                                                                                    40 Flowers and fruits 1 (-2) in the axils of many leaves; tepals white to pink