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| 1 Leaves alternate, at least those on the upper stem; calyx 5-merous; stamens 4. |
| ..2 Corolla lacking a spur or pouch at the base; [tribe Digitaleae] |
| ..2 Corolla with a distinct spur or broad pouch protruding between the 2 lower calyx lobes; [tribe Antirrhineae]. |
| ....3 Corolla with a broad pouch at the base (saccate or gibbose). |
| ......4 Calyx lobes about equal, all shorter than the corolla tube; corolla 25-40 mm long; leaves to 15 mm wide |
| ......4 Calyx lobes distinctly unequal, all longer than the corolla tube; corolla 10-13 mm long; leaves to 5 mm wide |
| ....3 Corolla with a slender spur at the base. |
| ........5 Flowers in terminal racemes |
| ........5 Flowers solitary in leaf axils. |
| ..........6 Stems erect; leaves linear |
| ..........6 Stems prostrate; leaves orbicular, ovate, or triangular. |
| ............ 7 Leaves orbicular in outline, palmately lobed and veined; stems rooting at nodes |
| ............ 7 Leaves ovate or triangular, pinnately veined; stems not rooting |
| 1 Leaves either strictly basal, or opposite or whorled throughout; calyx 0-, 4-, or 5-merous; stamens 1, 2, or 4. |
| ............ ..8 Leaves strongly basally disposed, usually all the leaves basal (or with significantly reduced cauline leaves); petals 3 or 4, scarious and translucent in texture or otherwise dull-yellow and inconspicuous; inflorescence a spike; [tribe Plantagineae] |
| ............ ....9 Plants with leaves usually all basal; petals scarious and translucent in texture, not bilabiate; fruit a circumsessile dehiscent capsule (i.e. a lid-bearing pyxide); [collectively widespread] |
| ............ ....9 Plants with prominent basal leaves and reduced, sub-whorled, cauline leaves; petals yellow, bilabiate; fruit a loculicidal capsule; [s. OH w. to s. IL, northward] |
| ............ ..8 Leaves cauline, either opposite or whorled; petal 0, or 4, or 5; inflorescence various. |
| ............ ......10 Leaves whorled. |
| ............ ........11 Aquatic; leaves 5-30 mm long, lanceolate, toothed to deeply dissected into linear segments; [tribe Gratioleae] |
| ............ ........11 Terrestrial; leaves 40-15 cm long, lanceolate or elliptic, toothed; [tribe Veroniceae] |
| ............ ......10 Leaves opposite. |
| ............ ..........12 Petals 0; sepals 0, stamens 1; leaves both < 2 cm long and entire; [tribe Callitricheae] |
| ............ ..........12 Petals 4 or 5; sepals 4 or 5; stamens 2 or 4; leaves > 2 cm long, or serrate, or both. |
| ............ ............ 13 Calyx and corolla 4-merous. |
| ............ ............ ..14 Leaves punctate; stamens 4; [tribe Gratioleae] |
| ............ ............ ..14 Leaves not punctate; stamens 2; [tribe Veroniceae] |
| ............ ............ 13 Calyx and corolla 5-merous. |
| ............ ............ ....15 Plants erect, moderately robust, usually > 4 dm tall, larger leaves > 5 cm long; inflorescences terminal (the bracts subtending flowers strongly reduced in size in comparison to main leaves of the stem); [tribe Cheloneae]. |
| ............ ............ ......16 Inflorescence compact, the inflorescence axis generally hidden by the closely packed and overlapping flowers; each flower subtended by large overlapping bracts |
| ............ ............ ......16 Inflorescence more diffuse, the inflorescence axis readily visible between the flowers; flowers lacking extra subtending bracts |
| ............ ............ ....15 Plants creeping, decumbent or erect, small, usually < 4 dm tall (except Mecardonia, to 5 dm tall), larger leaves < 5 cm long; inflorescences axillary (all or most of the flowers axillary to more-or-less normally sized leaves). |
| ............ ............ ........17 Stamens 2; [section Gratioleae]. |
............ ............ ..........18 Capsule flattened, compressed in ×-section; capsule wider than long, notched; leaves dimorphic, with narrow submersed leaves on the lower stems, and broad floating leaves just subtending the aerial inflorescences; [of vernal pools on granite outcrops in Piedmont SC, GA, and AL] |
| ............ ............ ..........18 Capsule turgid, roundish in ×-section; capsule longer than wide; leaves monomorphic; [collectively of many habitats and widespread]. |
| ............ ............ ............ 19 Flowers and fruits on definite pedicels; annual or perennial; leaves not papillose |
| ............ ............ ............ 19 Flowers and fruits sessile or subsessile, the pedicels < 1 mm long; perennial; leaves papillose on the surfaces and margins |
| ............ ............ ........17 Stamens 4. |
| ............ ............ ............ ..20 Sepals evidently connate into a tube about as long as the lobes; [section Cheloneae] |
| ............ ............ ............ ..20 Sepals distinct or very nearly so. |
| ............ ............ ............ ....21 Leaves deeply pinnatifid; [tribe Stemodieae] |
| ............ ............ ............ ....21 Leaves entire or toothed; [tribe Gratioleae]. |
| ............ ............ ............ ......22 Corolla nearly radially symmetrical; corolla lobes about as long as the corolla tube; leaves palmately veined, with parallel veins diverging from the base, margins entire to crenulate; of aquatic to moist habitats, often somewhat succulent |
| ............ ............ ............ ......22 Corolla distinctly bilabiate; corolla lobes shorter than the corolla tube; leaves pinnately veined, with a single main-vein and lateral veins diverging along it, margins serrate; of moist habitats, not succulent |
1 Capsule flattened, wider than long, notched; leaves dimorphic, with narrow submersed leaves on the lower stems, and broad floating leaves just subtending the aerial inflorescences; [of vernal pools on granite outcrops in Piedmont SC, GA, and AL] |
| 1 Capsule turgid, longer than wide; leaves monomorphic; [collectively of many habitats and widespread]. |
| ..2 Flowers and fruits sessile or subsessile, the pedicels < 1 mm long; perennial. |
| ....3 Leaves linear-subulate; corolla 2-3× as long as the calyx |
| ....3 Leaves ovate; corolla 1-1.5 × as long as the calyx |
| ..2 Flowers and fruits on definite pedicels; annual or perennial. |
| ......4 Leaves clasping or subclasping-rounded at the base; perennial; [section Gratiola]. |
| ........5 Calyx subtended by 0 (-1) bractlet; corolla lobes white; corolla tube greenish yellow, conspicuously veined |
| ........5 Calyx subtended by 2 bractlets; corolla lobes white or yellow-orange; corolla tube greenish yellow and conspicuously veined, or orange and not conspicuously veined. |
| ..........6 Corolla lobes and tube yellow-orange (very rarely white), not conspicuously veined; sepals and flower stalks sparsely or not at all glandular-puberulent |
| ..........6 Corolla lobes white to lavender, corolla tube greenish yellow, usually conspicuously veined; sepals and flower stalks densely glandular-puberulent. |
| ............ 7 Leaves oblong-ovate to ovate (or linear-lanceolate in submersed forms), finely dentate; corolla veined with purple lines; sepals lanceolate to oblong-lanceolate |
| ............ 7 Leaves triangular to lanceolate, margins entire, or with a few teeth toward the tip; corolla veined with brown lines; sepals linear-lanceolate |
| ............ ..8 Leaves 3.5× as long as wide; lower leaf surface with only sunken, translucent glands |
| ............ ..8 Leaves < 3× as long as wide; lower leaf surface with large, yellow sessile glands and sunken, translucent glands |
| ......4 Leaves cuneate at the base; annual; [section Nibora]. |
| ............ ....9 Corolla yellow; [LA and TX] |
| ............ ....9 Corolla white (or with pink or purple flush); [collectively widespread]. |
| ............ ......10 Pedicels stout, erect, 1-5 (-12) mm long |
| ............ ......10 Pedicels slender, spreading, 10-45 mm long. |
| ............ ........11 Corolla 13-25 mm long; leaves oval or oblanceolate |
| ............ ........11 Corolla 5-14 mm long; leaves elliptic, rhombic-lanceolate, or lanceolate |
| ............ ..........12 Mid-stem leaves (6-) 7-13 (-18) mm long; proximal fruiting pedicels (5-) 7-17 (-22) mm long, (0.9-) 1-2 (-2.3) × as long as the subtending bracteal leaves; bracteoles shorter than to barely exceeding the sepals; [of granite outcrops in the GA Piedmont] |
| ............ ..........12 Mid-stem leaves (11-) 20-41 (-66) mm long; proximal fruiting pedicels (8-) 13-25 (-37) mm long, (0.3-) 0.5-1 (-1.6) × as long as the subtending bracteal leaves; bracteoles slightly to conspicuously longer than the sepals; [collectively of more habitats and more widespread]. |
| ............ ............ 13 Leaves narrowly elliptic or rhombic to oblanceolate, not conspicuously falcate, (2.7-) 5-11 (-18) mm wide, (2.5-) 3.5-5 (-6)× as long as wide; leaf margins with (1-) 3-5 (-7) teeth per side; primary veins 3-5 (-7); mid-stem moderately to densely glandular pubescent (rarely glabrate); seeds (0.18-) 0.22-0.26 (-0.29) mm thick; [widespread] |
| ............ ............ 13 Leaves linear, linear-lanceolate, to elliptic-lanceolate, often falcate, (1-) 2.5-4 (-4.5) mm wide, (5.5-) 6-9.5 (-11)× as long as wide; leaf margins with 0-2 (-3) teeth per side; primary veins 1 (-3); mid-stem glabrous; seeds (0.19-) 0.26-0.32 (-0.37) mm thick; [limestone cedar glades of n. AL and c. TN] |
| 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 strongle 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) |
| ............ ............ ..14 Flowers bisexual, white to blue, the perianth segments united below into a perianth tube 3-45 mm long; stamens 3; leaves lacking a central area of spongiform cells |
| 1 Leaves whorled, most nodes with 3 or more leaves. |
| ..2 Leaves strongly toothed to pectinate |
| ..2 Leaves entire or finely toothed. |
| ....3 Leaves tipped by a callus (visible at 10× magnification); leaf margins entire; flowers many, grouped in a terminal involucrate head; [Eudicots] |
| ....3 Leaves not callus-tipped; leaf margins finely toothed or at least with conical protrusions remaining from the disintegration of better-developed deciduous teeth; flowers solitary on elongate, flexuous stalks; [Monocots] |
| 1 Leaves opposite, no nodes with 3 or more leaves. |
......4 Cauline leaves in 1 pair |
| ......4 Cauline leaves in 2-many nodes. |
| ........5 Leaves in 2-3 pairs, appearing verticillate; plants of marine waters; [of FL, MS, LA and southward] |
| ........5 Leaves along stem at 2-many nodes; plants of fresh to brackish waters; [collectively widespread]. |
| ..........6 Flowers 3-merous; [Monocots]. |
| ............ 7 Leaf margins (or at least leaf sheaths) serrate or minutely spiny; fruits sessile, entire; leaves 5-15× as long as wide |
| ............ 7 Leaf margins (including sheaths) entire; fruit stalked, dentate on one side; leaves >20× as long as wide |
| ..........6 Flowers 4- or 5-merous; [Eudicots]. |
| ............ ..8 Leaves 1-12 cm long; flowers borne in axillary or terminal spikes or clusters |
| ............ ..8 Leaves 0.5-3 (-5) cm long; flowers solitary, axillary. |
| ............ ....9 Carpels 4-5, separate; fruit an aggregate of follicles; leaves succulent |
| ............ ....9 Carpels 2-5, fused; fruit capsular (variously dehiscent); leaves thin in texture or somewhat succulent (e.g. Bacopa in PLANTAGINACEAE). |
| ............ ......10 Leaves dimorphic, the terminal leaves usually spatulate (strongly expanded towards the apex); corolla absent; stamen 1 |
| ............ ......10 Leaves monomorphic, obovate, oblanceolate, or parallel-margined; corolla present (absent in Didiplis in LYTHRACEAE); stamens 2-6. |
| ............ ........11 Flower radially symmetrical, 3-4-merous; petals absent or separate |
| ............ ..........12 Stems lacking ridges running down from leaf bases |
| ............ ..........12 Stems with ridges running down from leaf bases |
| ............ ........11 Flower bilaterally symmetrical, 4-5-merous; petals present, fused at least basally, forming a tube. |
| ............ ............ 13 Corolla 4-merous |
| ............ ............ 13 Corolla 5-merous |