1 Leaves alternate (the internodes typically short and therefore the leaves apprearing nearly whorled)

1 Leaves opposite.

  2 Shrub or tree, much taller than 2 dm when mature; leaves many; [collectively widespread].

    3 Inflorescence a head, subtended by 4 showy (white, creamy, or pink) bracts.

    3 Inflorescence a compound corymb, with green, tan, or brown (non-petaloid) bracts.

      4 Inflorescence a simple umbel; fruit red when ripe; inflorescence bracts brownish, 4, 5-10 mm long, subtending the umbel and enclosing it in winter

      4 Inflorescence a compound corymb; fruit blue or white when ripe; inflorescence bracts greenish, many, < 2 mm long, subtending the primary and secondary branches of the corymb

1 Leaves tiny, bract-like, triangular, 6-14 (-17) per node

1 Leaves either needle-like, scale-like, or flattened and large, (2-) 3-4 (-6) per node.

  2 Leaves needle-like or scale-like, terete, angled, or flat in ×-section, < 2 cm long; leaves (2-) 3-4 (-6) per node

  2 Leaves flat, > 3 cm long; leaves (2-) 3 per node; [Eudicots].

    3 Plant a subshrub, < 3 dm tall, with < 10 leaves per stem.

      4 Leaves serrate, narrowly ovate or narrowly obovate; flowers (1-) 2-8 in a long-peduncled umbel or corymb, not subtended by bracts

    3 Plant a shrub or tree, > 3 dm tall, with many > 10 leaves per stem.

        5 Leaves toothed, and most leaves also lobed

        5 Leaves entire, not lobed.

          6 Leaves cordate at base, about as long as wide; medium to large tree.

             7 Flowers white to yellow; capsules linear, >10× as long as wide; leaf undersurface with curly simple hairs; nectar glands present in the main vein axils on the undersurface of the leaf (visible from the underside or the upperside in fresh leaves and herbarium specimens as a triangle 1-4 mm on a side)

             7 Flowers lavender; capsules ellipsoid, < 2× as long as wide; leaf undersurface with branched (dendritic or stellate) hairs; nectar glands absent

          6 Leaves cuneate to rounded at base; leaves > 1.5× as long as wide; shrub to small tree.

               8 Leaves rounded or retuse at the tip (at least some obviously rounded in Pittosporum).

                 9 Fruit a large, globose berry (2-8 cm in diameter), pale brown in color when mature, the surface roughened in texture; petioles with a decurrent, adaxial wing forming a groove; sepals rusty tomentose

                 9 Fruit a capsule, dehiscing alonge 1 or 5 sutures; petioles lacking a decurrent, adaxial wing forming a groove; sepals variously glabrous to pubescent, but not rusty tomentose.

                   10 Ovaries 5-10-carpellate; capsules dehiscing along 5 sutures.

                   10 Ovaries 2-carpellate; capsules dehiscing along one major adaxial suture, appearing berry-like before dehiscence, the seeds often surrounded by a glutinous material

               8 Leaves acute to acuminate at the tip.

                     11 Leaves lanceolate or oblong-elliptic to narrowly ovate (> 2.5× as long as wide), the secondary venation not prominent nor arching-parallel (except Decodon); inflorescences axillary or terminal; flowers pink or white.

                       12 Inflorescences axillary; flowers pink; leaves thin and herbaceous, with prominent secondary veins arching parallel with the margin, also with branching hairs on the abaxial leaf midvein; plants with arching stems, these often tip-rooting; [native plants of wetlands]

                       12 Inflorescences terminal or axillary; flowers pink or white; leaves thick and leathery, lacking prominent secondary veins; plants not tip-rooting nor with branching hairs on the midvein; [exotics of uplands or wetlands, persistent or weakly naturalized]

                          13 Fruit berry-like with 2-locular ovaries; flowers white-colored, smaller; inflorescence axillary or pseudo-terminal.

                          13 Fruit follicles; flowers variously colored (including white), showy and salverform; inflorescence terminal.

                            14 Plants trees, 2-60 m tall, with a single or multiple stem(s); latex milky; flowers white or cream colored, the anthers not connivent and not adhering to stigmas; [uncommon non-natives, s. FL]

                            14 Plants shrubs, 10-40 dm tall, much branched from the base; latex clear; flowers white, pink, or red, the anthers connivent and adhering to the stigmas; [commonly cultivated in our area (and sometimes persistent), particularly near the coast; NC s. to FL, w. to TX]

                     11 Leaves ovate (< 2× as long as wide), the secondary venation prominent and arching-parallel; inflorescences terminal; flowers white, greenish-yellow, red, or orange.

                              15 Flowers in a spherical or hemispherical head; corollas white or greenish-yellow; fruit a globose cluster of nutlets (dry)

                              15 Flowers in a monochasial helicoid cyme; corollas red to orange; fruit a red to black berry (fleshy)

1 Plants aerial and epiphytic, hemiparasitic shrubs (usually growing out of the branches of trees)

1 Plants terrestrial, autotrophic or hemiparasitic shrubs or subshrubs.

  2 Leaves succulent, nearly as thick as wide; [brackish to saline situations]

  2 Leaves herbaceous or leathery (succulent in Borrichia), much wider than thick; [various habitats].

    3 Creeping or short subshrubs, the stems primarily prostrate (< 2 dm tall), or spreading-ascending to decumbent and < 3 dm tall (MALPIGHIACEAE, in part; Galphimia primarily erect subshrubs to 1 m tall, of TX only in our area).

      4 Petals clawed, the bases noticeably thinned compared to the broader tips; fruit schizocarps, breaking into 2-3 nutlets or 1-seeded cocci; [in part, Aspicarpa and Galphimia]

      4 Petals not clawed, of relatively similar width from base to tip; fruit various, but never schizocarps of 2-3 nutlets or 1-seeded cocci.

        5 Well-developed leaves many per stem; inflorescence of individual flowers axillary in pairs or clusters or in terminal cymes.

          6 Flowers yellow; leaves with pellucid or dark punctate glands (use at least 10× magnification)

          6 Flowers white, pale pink, or deep pink; leaves lacking sessile, punctate glands.

             7 Leaves linear; flowers pale to deep pink, 5-merous

             7 Leaves orbicular or elliptic; flowers white to pale pink, 4-merous or 5-merous

               8 Leaves elliptic; flowers 5-merous; fruit a brownish capsule

               8 Leaves orbicular; flowers 4-merous; fruit a red berry

    3 Upright or scrambling shrubs, > 3 dm tall.

                 9 Scrambling shrubs, armed with recurved paired spines at the nodes (except Santalum, which can be a scrambling shrub and has red flowers producing drupe-like fruit bearing an apical circular rim).

                   10 Plants armed with recurved paired spines at the nodes; fruit ribbed, the ribs obviously glandular; petioles not 2-ribbed; flowers greenish-white to yellowish in color

                   10 Plants unarmed; fruit not ribbed, instead drupe-like and bearing a circular rim at the apex; petioles 2-ribbed; flowers red

                 9 Upright shrubs, unarmed.

                     11 Inflorescence a terminal head of many flowers.

                       12 Head spherical, lacking an involucre of conspicuous bracts or phyllaries

                       12 Head flattened, either subtended by 4 large white bracts or by an involucre with >5 green phyllaries.

                          13 Head subtended by 4 large white bracts; leaves with prominently parallel-arcing secondary veins; flowers 4-merous

                          13 Head subtended by an involucre of >5 green phyllaries; leaves with venation otherwise; flowers 5-merous

                     11 Inflorescence otherwise (if terminal, the flowers not arranged in heads), either of a solitary flower, or one of a wide variety of inflorescences with flowers attached at different points along branched or unbranched axes (e.g. axillary).

                            14 Inflorescence flat-topped (broader than long), terminal, a compound cyme or corymb.

                              15 Leaves distinctly 3-veined from the base, the 3 veins converging again at the leaf apex; [s. FL only in our area]

                              15 Leaves with prominently pinnate venation; [collectively widespread]

                                16 Leaves conspicuously glandular-punctate and aromatic; fruit a berry; ovary inferior; flowers with abundant stamens and a cup-shaped hypanthium; (partial; Mosiera, Myrcianthes, Syzygium).

                                16 Leaves not glandular-punctate and aromatic (only herbaceous Hypericum sometimes with black or transluscent leaf punctae, thus keyed instead in S1); flowers with 1-5 or 8-10 stamens; fruit not a berry, instead either a capsule (Hypericum), drupe (Cornus; Viburnum), follicle (APOCYNACEAE), or prominently ribbed and stipitate anthocarp (Pisonia).

                                  17 Fruit prominently ribbed (an anthocarp), the ribs with stipitate glands, the fruit thus usually sticky (this persisting on herbarium specimens)

                                  17 Fruit lacking prominent glandular ribs, the fruit not generally sticky.

                                    18 Fresh plants with white, milky juice; pistils 2, united only by the style and stigma; fruit a pair of linear or fusiform follicles, > 5-8× as long as thick, these variously shaped (terete, compressed, or prominently 3-angled)

                                    18 Fresh plants not exuding a white, milky latex (instead clear or not apparent); pistil 1 (or 2-5 in Hypericum); fruit various, but not of paired, linear follicles (see below).

                                       19 Flowers bright yellow; stamens many; leaves < 1.5 cm wide; fruit a capsule; leaves with pellucid or dark punctate glands (use at least 10× magnification)

                                       19 Flowers white or creamy; stamens 4-5; leaves > 1.5 cm wide; fruit a drupe; leaves lacking sessile, punctate glands.

                                         20 Petals 5; foliage with simple hairs

                                         20 Petals 4; foliage with T-shaped hairs

                            14 Inflorescence either terminal, axillary or leaf-opposed, if terminal elongate (not flat-topped) or flowers solitary; if axillary then variously arranged (sometimes also solitary in the axils).

                                           21 Carpels many (> 9), either separate or fused; stamens many; perianth segments either many and undifferentiated into calyx and corolla, maroon, brown, or yellow (in CALYCANTHACEAE), or differentiated into a fleshy and persistent calyx of 5-9 sepals, and a deciduous corolla of 5-9 red (or white) petals (Punica in LYTHRACEAE).

                                             22 Fruit a wrinkled, 3-7 cm long, brown to black, elliptical aggregate of nearly spherical, large achenes; flowers solitary in axils; perianth segments many and undifferentiated into calyx and corolla, maroon, brown, or yellowish; ovary superior; branches unarmed

                                             22 Fruit a leathery, 4-15 cm in diameter, reddish, spherical berry with obpyramidal seeds surrounded by a juicy sarcotesta (pomegranate); perianth differentiated, the sepals fleshy and persistent on the fruit, the petals deciduous, 5-9, bright red to white; ovary inferior; branches typically armed with axillary spines

                                           21 Carpels 1-5 (-6), fused; stamens either 1-5 or 8-10 (except 10+ in MYRTACEAE); perianth segments 4-5 or 8, variously colored; fruit a simple capsule, drupe, or berry (including berry-like fruit); flowers 2-many, in axillary or terminal inflorescences OR sometimes solitary (MYRTACEAE, SANTALACEAE, and THESIACEAE); [Eudicots].

                                               23 Ovary inferior (flowers epigynous); corolla either absent, radially symmetrical, OR bilaterally symmetrical; fruit either a berry or a 1-seeded drupe (a berry or apically dehiscent capsule in MYRTACEAE).

                                                 24 Leaves conspicuously glandular-punctate and aromatic, evergreen and usually coriaceous; fruit a berry or apically-dehiscent capsule; flowers with abundant stamens and a cup-shaped hypanthium.

                                                 24 Leaves not both conspicuously glandular-punctate nor aromatic, membranous and deciduous; fruit a drupe or berry; flowers with 1-5 or 8-10 stamens, with or without a cup-shaped hypanthium.

                                                    25 Flowers unisexual and plants dioecious; corolla absent; pistillate flowers solitary, staminate flowers in pedunculate umbels or cymes, either terminal or axillary; fruit a 1-seeded drupe; leaves acute to acuminate at the apex

                                                      26 Inflorescences terminal

                                                      26 Inflorescences axillary

                                                    25 Flowers bisexual and plants hermaphroditic; corolla present; flowers paired, terminal or axillary, or in axillary spikes; fruit a berry; leaves rounded, obtuse, to acute (or acuminate in Lonicera maackii) at the apex

                                               23 Ovary superior (flowers hypogynous); corolla primarily radially symmetrical (zygomorphic in Citharexylum in VERBENACEAE and MALPIGHIACEAE; absent in Forestiera in OLEACEAE); fruit either a 1-4-seeded drupe, or a many-seeded berry (or berry-like fruit), or a capsule.

                                                        27 Leaves with a conspicuous mix of silvery stellate hairs (upper) and rusty colored scales (lower); ovaries bearing rusty colored scales; flowers small, yellowish and inconspicuous; [nw. PA northward]

                                                        27 Leaves glabrous or nearly so, lacking a conspicuous mix of stellate hairs adaxially and rusty scales abaxially; ovaries not bearing rusty colored scales; flowers of various size and color.

                                                          28 Stamens 8-10, of 2 different lengths in each flower; petals separate, 4-5 (-7), pink purple, 10-15 mm long; stems strongly arching, rooting at the tips; [plants of flooded to saturated wetlands]

                                                          28 Stamens either (1-) 2 (-4), or 4-5, or 10, all of the same length; petals fused (separate in RHAMNACEAE and BUXACEAE, but then < 5 mm long and white or cream), white, bright-yellow, lilac, or pink; stems erect (or at least not arching and rooting at the tips); [plants of various habitats].

                                                            29 Petals separate, 4-5, white or cream; stamens 4-5.

                                                              30 Petals clawed (the bases much thinner than the broader tips); fruit a drupe; inflorescence a terminal raceme (Byrsonima) or axillary corymbs or umbels (Malpighia); [in part, Byrsonima and Malpighia; some vining species will grow shrub-like, but those keyed in J3; TX and FL only in our area]

                                                              30 Petals not clawed, the width similar throughout; fruit a drupe or capsule; inflorescence axillary and terminal.

                                                                 31 Fruit a loculicidal capsule, dehiscing into 3 valves; branches square in ×-section; leaves < 2 cm long; [exotic, cultivated and weakly established, of temperate areas]

                                                                 31 Fruit a drupe with 2-4 pyrenes; branches round or nearly so in ×-section; leaves > 2 cm long; [natives, of peninsular FL]

                                                            29 Petals fused (at least basally), 4-5, white, bright yellow, lilac, or pink; stamens either (1-) 2 (-4) or 10; fruit either a capsule or a 1-seeded drupe.

                                                                   32 Inflorescence a drooping axillary raceme (sometimes minutely so), flowers zygomorphic; fruit a drupe

                                                                   32 Inflorescence various, if a raceme then not conspicuously drooping, flowers actinomorphic; fruit a drupe or capsule.

                                                                     33 Perianth 5-merous; corolla pink; stamens 10; fruit a 5-locular capsule

                                                                     33 Perianth 4-merous; corolla white, bright yellow, or lilac; stamens (1-) 2 (-4); fruit either a 1-seeded drupe or a 2-locular capsule

1 Inflorescence an involucrate head subtended by phyllaries, the heads solitary or many and variously arrayed in secondary inflorescences, the ovary inferior, the corolla connate and tubular at least basally, the calyx absent, the stamens 5, the fruit a cypsela

1 Inflorescence, flower, and fruit structure various, but not with the combination of features as above (sometimes the flowers in a head, e.g. Pycnanthemum in LAMIACEAE, but then with other features differing, such as stamens 4, or green calyx present, or fruit a schizocarp of mericarps, etc.; Carpobrotus is superficially asteroid, but heads are composed of numerous petaloid staminodia, and receptacles lack cypselae;).

  2 Leaves scale-like, stems fleshy; flowers embedded in the fleshy stem, no perianth present; [saline environments (coastal or rarely inland)].

  2 Leaves small to large; stems not fleshy (although sometimes plants generally succulent as in Sesuvium); flowers sessile or on pedicels; [collectively of many habitats, saline and not].

    3 Ovary inferior or partially inferior.

      4 Perianth of a single whorl (petals absent) (note that in Mirabilis in NYCTAGINACEAE the petaloid calyx is subtended by a 5-lobed fused set of involucral bracts).

        5 Leaves herbaceous, suborbicular, about as long as wide or wider than long; calyx 3- or 4-merous; stamens 4, 8, or 12.

          6 Plant ascending, with a single node (2 leaves); leaves > 6 cm long and wide; calyx 3-merous, brown to yellowish; stamens 12

          6 Plant creeping, with many nodes; leaves 3-15 mm long and wide; calyx 4-merous, yellow to greenish; stamens 4 or 8

        5 Leaves fleshy, linear, lanceolate, to broadly ovate, at least slightly longer than broad; calyx 5-merous; stamens 3, 5, or 10.

             7 Flowers axillary, sessile or nearly so, solitary or a few; petaloid sepals widely spreading, separate, usually with a subapical abaxial appendage; leaves linear to oblanceolate; stamens 5 or 30-50

             7 Flowers in terminal cymose panicles; petaloid sepals connate into a narrow tube (reminiscent of the corolla of Ipomoea), lacking subapical abaxial appendages; leaves lanceolate, elliptic, ovate, or broadly ovate; stamens 3 or 5

      4 Perianth in 2 whorls (sepals and petals both present).

               8 Plants succulent, mat-forming subshrubs; flowering heads showy and consisting of numerous petaloid staminodia; [waif, FL]

               8 Plants not as above.

                 9 Petals distinct; inflorescence diffuse.

                   10 Leaves distinctly 3-veined from the base, the 3 veins converging again at the leaf apex

                   10 Leaves with prominently pinnate venation

                 9 Petals connate into a tube (at least basally); inflorescence often a head or dense terminal cyme (also axillary, or solitary on long peduncles).

                     11 Petals 5; stamens 3, 4, or 5

                       12 Creeping subshrub; flowers paired at tip of an upright peduncle

                       12 Upright herb; flowers in axils or terminal corymbs

                          13 Flowers in terminal corymbs; fruit dry

                          13 Flowers axillary; fruit fleshy

                     11 Petals 4 (or 6 or 8 in Richardia in RUBIACEAE); stamens 4, 6, or 8.

                            14 Inflorescence a head or more diffuse (see below), sometimes subtended by green bracts.

                              15 Leaves serrate; corolla bilaterally symmetrical (especially the flowers near the outer edge of the head); inflorescence a head

                              15 Leaves entire; corolla radially symmetrical; inflorescence a head or more diffuse (see below).

                                16 Petals acute; flowers in terminal panicles, cymes, or panicles, or axillary; plant habit various, not simultaneously with all the characters below

                                16 Petals broadly rounded; flowers axillary, solitary; plant a diffusely branched herb with linear leaves

    3 Ovary superior.

                                  17 Perianth of a single whorl (petals absent) or missing entirely (petals and sepals both absent).

                                    18 Inflorescence a cyathium, consisting of a single pistillate flower (reduced to a single 3-carpellate pistil) and 2 or more staminate flowers (each reduced to 1 stamen), borne in a cup-like involucre, the involucre bearing pointed or rounded glands, these sometimes brightly colored and petaloid, mimicking an individual flower (the cyathia then secondarily arranged in terminal cymes, or solitary and axillary, etc.); fresh plants with milky juice; fruit a 3-lobed, 3-locular capsule

                                    18 Inflorescence not a cyathium (and staminate or bisexual flowers with > 1 stamen, except Callitriche in PLANTAGINACEAE); fresh plants lacking milky juice; fruit various, not as above.

                                       19 Flowers 1 (or 2) in leaf axils; leaves entire.

                                         20 Flowers unisexual; sepals 0; flowers (staminate) with 1 stamen

                                         20 Flowers bisexual; sepals 4; flowers with 2, 4, or 6 stamens.

                                           21 Leaves of an opposite pair markedly different in size

                                           21 Leaves of an opposite pair essentially the same size

                                       19 Flowers many, in axillary spikes, cymes, or glomerules, or in terminal spikes, heads, cymes, or panicles; leaves entire or serrate.

                                             22 Fruit a 2-locular capsule

                                             22 Fruit single-seeded, an achene or utricle.

                                               23 Leaves serrate, regularly and sharply so; plants with stinging hairs (or not)

                                               23 Leaves entire, or with a few very obscure crenations (Iresine) or basally disposed rounded lobe-like teeth (Atriplex); plants without stinging hairs.

                                                 24 Leaves of a pair slightly to strongly different in size

                                                 24 Leaves of a pair the same size.

                                                    25 Styles 1-2 (-3); leaves 2-30 mm long, 0.5-8 mm wide, linear or narrowly elliptic

                                                    25 Style 1; leaves generally either longer than 30 mm, or wider than 8 mm (if linear and smaller than those dimensions, then fleshy).

                                                      26 Tepals scarious; inflorescence of heads, spikes, or panicles

                                                      26 Tepals herbaceous; inflorescence of glomerules, these axillary or arrayed in spikes or panicles

                                  17 Perianth in 2 whorls (sepals and petals both present).

                                                        27 Gynoecium of 4-many pistils, each 1-carpellate.

                                                          28 Pistils 4-5, in a single whorl; stamens 4, 5, 8, or 10; fruit an aggregate of follicles

                                                          28 Pistils many, spiral; stamens many; fruit an aggregate of plumose achenes

                                                        27 Gynoecium either of 1 pistil (with 1 or more carpels), or of 2 pistils, united only by the style and stigma (APOCYNACEAE).

                                                            29 Petals not at all connate, not even at their bases.

                                                              30 Leaves with pellucid punctate glands (most easily visible with transmitted light); stamens often fascicled into 3, 4, or 5 fascicles; petals yellow or pinkish

                                                              30 Leaves lacking pellucid punctate glands; stamens not fascicled; petals variously colored.

                                                                 31 Sepals 2; stamens opposite the petals

                                                                 31 Sepals 3-7; stamens opposite the sepals.

                                                                   32 Petals 3; sepals 5, dimorphic, the 2 outer sepals narrower than the 3 inner and concave sepals; stamens (3-) 5-15 (-25)

                                                                   32 Petals 4-7; sepals 4-7, normally monomorphic; stamens 4, 5, 6, 8, 10, or 12 (or sometimes rarely 2 or 3).

                                                                     33 Capsule 2-5 (-6) locular; style 1; perianth 4-7-merous; stamens 4, 6, 8, 10, or 12

                                                                     33 Capsule either 1-locular of 10-locular; styles 2-5; perianth 4-5-merous; stamens 4, 5, 8, or 10 (or rarely 2 or 3).

                                                                       34 Capsule 1-locular, dehiscent apically by teeth or valves; sepals connate into a tube or separate; styles 2-5; perianth 4-5-merous; stamens 4, 5, 8, or 10 (or rarely 2 or 3)

                                                                       34 Capsule 10-locular (each of the 5 carpels divided at maturity), septicidal; sepals distinct or nearly so; styles 5, perianth 5-merous; stamens 5

                                                            29 Petals connate at least for a short distance at their bases.

                                                                         35 Corolla radially symmetrical (or so slightly bilaterally symmetrical as to be mistakable as radially symmetrical); stamens as many as the corolla lobes (or 1 less in Ruellia in ACANTHACEAE, Buchnera in OROBANCHACEAE, Trichostema in LAMIACEAE, and Verbena in VERBENACEAE); carpels 2 or 3.

                                                                           36 Pistils 2, united only by the style and stigma; fruit a schizocarp of 2 1-carpellate follicles (often single by abortion); plant with milky juice when fresh (except Catharanthus); leaves entire

                                                                           36 Pistil 1 (of 2-5 fused carpels); fruit either a 2-5-carpellate capsule or of 2 or 4 1-seeded nutlets derived from 2 carpels; plant lacking milky juice; leaves entire or serrate.

                                                                              37 Ovary and capsule 3-5-carpellate; capsule 3- or 1-locular.

                                                                                38 Sepals 2

                                                                                38 Sepals 5.

                                                                                  39 Inflorescence a terminal cyme; corolla salverform, with an elongated and very narrow tube, pink or white; capsule 3-locular

                                                                                  39 Inflorescence various but not cymose, of terminal or axillary racemes or panicles, or of solitary axillary flowers; corolla connate only at the base, the petals appearing nearly separate (not salverform); capsule 1-locular

                                                                              37 Ovary and capsule 2-carpellate; fruit either a 2-locular capsule or of 2 or 4 1-seeded nutlets derived from 2 carpels.

                                                                                    40 Stamens 4-12, the same number as the corolla lobes; corolla (and the flower as a whole) strictly radially symmetrical.

                                                                                      41 Capsule septicidal; corolla white, pink, blue, yellowish white, or greenish white; inflorescence either a terminal or axillary cyme, or a terminal panicle or raceme, or a terminal or axillary cyme reduced to 1 or a few flowers

                                                                                      41 Capsule loculicidal and also deeply 2-lobed; corolla white, pink, or scarlet with a yellow interior; inflorescence of cymosely arranged spikes

                                                                                    40 Stamens either 4, 1 fewer than the 5 corolla lobes, or 2 (with 2 staminodes); corolla usually slightly bilaterally symmetrical (the flower as a whole made bilaterally symmetrical by the 2 or 4 stamens).

                                                                                        42 Leaves entire; corolla tube flaring for all of its length

                                                                                           43 Fruit a schizocarp of 4 1-seeded nutlets; inflorescence terminal, of cymes; corolla ca. 5 mm long; leaves prominently 3-veined

                                                                                           43 Fruit a capsule; inflorescence axillary, of cymes or clusters (often reduced to a solitary flower); corolla > 12 mm long; leaves with single primary vein

                                                                                        42 Leaves serrate; corolla salverform, the tube narrow and nearly the same diameter for most of its length; inflorescence a terminal spike, raceme, raceme of racemes, or head.

                                                                                             44 Fruit a 2-locular capsule; stamens inserted near the base of the corolla tube

                                                                                             44 Fruit a schizocarp of 4 mericarps; stamens inserted near or above the middle of the corolla tube

                                                                         35 Corolla bilaterally symmetrical (or the corolla 2-lipped but the corolla lobes twisted so as to make the flower asymmetrical); fertile stamens fewer than the corolla lobes (except Plantago in PLANTAGINACEAE, which is equal, with 4 each; a few genera have a 5th, sterile, stamen which is obviously different in form than the 4 fertile stamens) (note that many corollas are bilabiate and the number of corolla lobes, 4 or 5, may be difficult to interpret); carpels 2.

                                                                                               45 Carpels 2, each carpel slightly to deeply lobed, separating at maturity into 4 half-carpellate units (not separating in Phyla in VERBENACEAE); fruit a schizocarp of 4 mericarps (or 2 nutlets in Phyla in VERBENACEAE).

                                                                                                 46 Inflorescence a thyrse, verticillaster, or terminal cyme, the flowers borne in cymose lateral branches; corolla strongly bilaterally symmetrical (rarely nearly radially symmetrical); stems square in ×-section (or sometimes rounded, especially on older growth); fresh plants often (but not always) aromatic

                                                                                                 46 Inflorescence of spikes, racemes, or heads, the flowers or fruits single at nodes; corolla often nearly radially symmetrical; stems rounded in X-section (rarely square); fresh plants usually not aromatic

                                                                                               45 Carpels 2, unlobed; fruit a capsule (or an achene in Phryma).

                                                                                                   47 Stamens 2.

                                                                                                     48 Corolla 4 lobed, almost radially symmetrical; corolla scarious, white, or bluish

                                                                                                     48 Corolla 4-5-lobed, either strongly bilabiate or salverform (Pseuderanthemum in ACANTHACEAE); white, blue, or yellow.

                                                                                                        49 Inflorescence an axillary cluster or spike

                                                                                                        49 Inflorescence of solitary (rarely 2) axillary flower.

                                                                                                          50 Sepals 4

                                                                                                          50 Sepals 5, distinct or nearly so.

                                                                                                            51 Corolla barely bilaterally symmetrical, the lobes about as long as the tube; outer sepals ovate, much wider than the inner sepals

                                                                                                            51 Corolla distinctly bilabiate, the lobes shorter than the tube; sepals of nearly the same width.

                                                                                                              52 Sterile stamens (the lower pair) consisting of slender filaments

                                                                                                              52 Sterile stamens minute or completely absent

                                                                                                   47 Stamens 4.

                                                                                                                53 Corolla 4 lobed, nearly radially symmetrical; corolla scarious

                                                                                                                53 Corolla 5-lobed, distinctly bilabiate or in some nearly radially symmetrical; corolla colored.

                                                                                                                  54 Flowers in terminal racemes, panicles, or spikes, the inflorescence not interspersed with large, leaf-like bracts.

                                                                                                                     55 Sepals separate to the base or nearly so, not forming a tube

                                                                                                                     55 Sepals connate for at least 0.3× their length to form a tube (this cup-like and flaring in Scrophularia in SCROPHULARIACEAE).

                                                                                                                       56 Inflorescence a diffuse panicle; corolla 5-11 mm long, reddish-brown (sometimes with some yellow); fruit a septicidal capsule

                                                                                                                       56 Inflorescence of 1 or more terminal (and sometimes upper axillary) spikes or racemes; corolla 10-50 mm long (6-8 mm long in Phryma in PHRYMACEAE), white, pink, blue, purple, or yellow; fruit either a loculicidal capsule (OROBANCHACEAE) or a single seeded achene (Phryma in PHRYMACEAE).

                                                                                                                         57 Corolla 10-50 mm long, pink, blue, purple, or yellow; fruit a loculicidal capsule

                                                                                                                         57 Corolla 6-8 mm long, white to pale pink; fruit a 1-seeded achene contained in the accrescent calyx, this “lopping down” against the inflorescence axis

                                                                                                                  54 Flowers axillary and solitary, borne in the axils of normally-sized leaves or somewhat reduced but still large and leaf-like bracts [some taxa keyed here and below].

                                                                                                                           58 Sepals separate to the base or nearly so, not forming a tube.

                                                                                                                             59 Corolla distinctly bilabiate

                                                                                                                             59 Corolla not bilabiate, only slightly bilaterally symmetrical.

                                                                                                                               60 Leaves serrate, 2.0-4.5 cm long; plant usually blackening on drying

                                                                                                                               60 Leaves entire, either mostly larger or smaller [see below]; plant not blackening on drying

                                                                                                                                  61 Leaves 0.6-2.8 cm long, round, obovate, or broadly elliptic, < 1.8× as long as wide; plants creeping, ascending to 3 dm tall; [plants of wet places]

                                                                                                                                  61 Leaves 3-30 cm long, narrowly elliptic to lanceolate, > 2× as long as wide; plants erect or the stems sprawling; [plants mostly of uplands]

                                                                                                                           58 Sepals connate for at least 0.3× their length to form a tube.

                                                                                                                                    62 Corolla yellow, orange, or red.

                                                                                                                                      63 Calyx lobes longer than the tube, or as long as the tube, corolla 25-50 mm long; plants usually blackening on drying

                                                                                                                                      63 Calyx lobes shorter than the tube; corolla 14-22 mm long; plants not blackening on drying.

                                                                                                                                        64 Corolla red or orange, with a very narrow, cylindrical tube, the lobes then flaring into a limb about 1 cm across; plants blackening on drying; [rare exotic, in crop fields, a noxious hemiparasitic weed under quarantine]

                                                                                                                                        64 Corolla yellow, not narrowly cylindrical, the lower lip arched; plants not blackening on drying; [rare, in seepage wetlands]

                                                                                                                                    62 Corolla white, pale blue, lavender, or pink (sometimes with some yellow).

                                                                                                                                          65 Corolla pink (sometimes almost white), often lined with yellow inside; leaves narrowly linear, often filiform (except lanceolate in A. auriculata); plants usually blackening on drying (some species do not); corolla not strongly bilabiate

                                                                                                                                          65 Corolla white, blue, or combinations of blue and white (sometimes with some yellow markings); leaves broader, mostly lanceolate; plants not blackening on drying; corolla strongly bilabiate.

                                                                                                                                            66 Upper lip of the corolla hooded, enfolding the anthers

                                                                                                                                            66 Upper lip of the corolla not hooded and enclosing the anthers; plants not blackening on drying.

                                                                                                                                               67 Corolla blue; lower lip of the corolla arched upwards into the throat; plants perennial from rhizomes or crowns, 3-13 dm tall

                                                                                                                                               67 Corolla bicolored, the upper lip white or very pale blue, the lower lip bright blue; lower lip of the corolla folded downward into a pouch enfolding the anthers; plants annuals, 0.5-4 dm tall