1 Leaves opposite, reduced to scale a few mm long, clasping and appressed against the succulent stem; flowers in groups of 3, sunken into the stem; [subfamily Salicornioideae].

1 Leaves alternate, not reduced to scale; flowers not sunken into the stem.

  2 Fruit enclosed and concealed by paired accrescent bracteole (these usually deltoid, diamond-shaped, or ovoid); [subfamily Chenopodioideae].

    3 Leaves bright to dark green; stigma 4-5; plants with basal leaves, the flowering stems erect, strict or with ascending branches in the inflorescence; [introduced, frequently cultivated as a garden vegetable, rarely escaped]; [tribe Spinacieae]

  2 Fruit enclosed by the persistent calyx.

      4 Leaves sessile, linear (linear to lanceolate in Corispermum), entire, succulent or not.

        5 Leaves spine-tipped with a sharp spine > (0.5) 1 mm long; [subfamily Salsoloideae]

        5 Leaves not spine-tipped.

          6 Leaves glabrous; [subfamily Suaedoideae]

          6 Leaves pubescent to villous; [subfamily Camphorosmoideae].

             7 Calyx segment (all 5) bearing a horizontal wing or hooked spine

             7 Calyx segment (1 lower and 2 upper) bearing stout knobs

      4 Leaves petiolate, lanceolate or wider, the larger leaves generally toothed, not succulent or only slightly so.

               8 Fruit dehiscent; ovary half-inferior; root usually enlarged; [subfamily Betioideae]

               8 Fruit indehiscent; ovary superior; root not enlarged; [subfamily Chenopodioideae].

                 9 Fruiting calyx winged horizontally

                 9 Fruiting calyx not winged, the lobe flat, keeled, or hooded.

                   10 Plants aromatic, leaves and perianth with stalked glandular hair and/or subsessile gland

                   10 Plants non-aromatic (but sometimes fetid), vesicular hairy (farinose) or glabrous.

                     11 Inflorescence in dichasial or monochasial loose cyme; plants glabrous or glabrescent

                     11 Inflorescence spicately or paniculately arranged dense glomerule with few to many flowers; plants either farinose (at least when young) or glabrous.

                       12 Stems unbranched or sparingly branched; basal leaves often forming a rosette; perianth often changed to succulent or hardened in fruit, sometimes reduced to 1 lobe; stigma 2-4; seeds vertical in the fruit

                       12 Stem usually branched; basal leaves not in a rosette; perianth unchanged in fruit, not reduced; stigma 2 (-3), seeds vertical and/or horizontal in the fruit.

                          13 Flowers often dimorphic, in lateral flowers perianth segment 3 (-5), seeds either vertical or horizontal in the fruit; stamen 1-3

                          13 Flowers not dimorphic, perianth segment 5, seeds exclusively horizontal in the fruit; stamen almost always 5.

                            14 Young stems and leaves not farinose (with vesicular trichome that become totally collapsed when dry, and are caducous and therefore rarely present at maturity); perianth segment with prominent midvein visible inside; seeds distinctly pitted to sometimes rugulose or almost smooth

                            14 Young stems and leaves densely farinose (covered with vesicular globose trichome that become cup-shaped when dry and are mostly persistent at maturity); perianth segment without prominent midvein visible inside; seeds smooth or striate and somewhat rugulose, sometimes pitted

1 Inflorescence an involucrate head subtended by phyllaries, the heads solitary or many and variously arrayed in secondary inflorescence, the ovary inferior, the corolla connate and tubular at least basally, the calyx absent, the stamen 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 stamen 4, or green calyx present, or fruit a schizocarp of mericarp, etc.; Carpobrotus is superficially asteroid, but heads are composed of numerous petaloid staminodia, and receptacle 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 pedicel; [collectively of many habitats, saline and not].

    3 Ovary inferior or partially inferior.

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

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

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

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

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

             7 Flowers in terminal cymose panicle; petaloid sepal connate into a narrow tube (reminiscent of the corolla of Ipomoea), lacking subapical abaxial appendage; leaves lanceolate, elliptic, ovate, or broadly ovate; stamen 3 or 5

      4 Perianth in 2 whorl (sepal and petal both present).

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

               8 Plants not as above.

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

                     11 Petal 5; stamen 3, 4, or 5

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

                       12 Upright herb; flowers in axil or terminal corymb

                          13 Flowers in terminal corymb; fruit dry

                          13 Flowers axillary; fruit fleshy

                     11 Petal 4 (or 6 or 8 in Richardia in RUBIACEAE); stamen 4, 6, or 8.

                            14 Inflorescence a head, subtended by 4 large bright white bract

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

                              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 Petal acute; flowers in terminal panicle, cyme, or panicle, or axillary; plant habit various, not simultaneously with all the characters below

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

    3 Ovary superior.

                                  17 Perianth of a single whorl (petal absent) or missing entirely (petal and sepal 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 gland, these sometimes brightly colored and petaloid, mimicking an individual flower (the cyathia then secondarily arranged in terminal cyme, 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 axil; leaves entire.

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

                                         20 Flowers bisexual; sepal 4; flowers with 2, 4, or 6 stamen.

                                           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 spike, cyme, or glomerule, or in terminal spike, heads, cyme, or panicle; 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 hair (or not)

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

                                                 24 Leaves of a pair slightly to strongly different in size

                                                 24 Leaves of a pair the same size.

                                                    25 Style 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 Tepal scarious; inflorescence of heads, spike, or panicle

                                  17 Perianth in 2 whorl (sepal and petal both present).

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

                                                          28 Pistil 4-5, in a single whorl; stamen 4, 5, 8, or 10; fruit an aggregate of follicle

                                                          28 Pistil many, spiral; stamen many; fruit an aggregate of plumose achene

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

                                                            29 Petal not at all connate, not even at their base.

                                                              30 Leaves with pellucid punctate gland (most easily visible with transmitted light); stamen often fascicled into 3, 4, or 5 fascicle; petal yellow or pinkish

                                                              30 Leaves lacking pellucid punctate gland; stamen not fascicled; petal variously colored.

                                                                 31 Sepal 2; stamen opposite the petal

                                                                 31 Sepal 3-7; stamen opposite the sepal.

                                                                   32 Petal 3; sepal 5, dimorphic, the 2 outer sepal narrower than the 3 inner and concave sepal; stamen (3-) 5-15 (-25)

                                                                   32 Petal 4-7; sepal 4-7, normally monomorphic; stamen 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; stamen 4, 6, 8, 10, or 12

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

                                                                       34 Capsule 1-locular, dehiscent apically by teeth or valve; sepal connate into a tube or separate; style 2-5; perianth 4-5-merous; stamen 4, 5, 8, or 10 (or rarely 2 or 3)

                                                                       34 Capsule 10-locular (each of the 5 carpel divided at maturity), septicidal; sepal distinct or nearly so; style 5, perianth 5-merous; stamen 5

                                                            29 Petal connate at least for a short distance at their base.

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

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

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

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

                                                                                38 Sepal 2

                                                                                38 Sepal 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 raceme or panicle, or of solitary axillary flowers; corolla connate only at the base, the petal 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 nutlet derived from 2 carpel.

                                                                                    40 Stamen 4-12, the same number as the corolla lobe; 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 spike

                                                                                    40 Stamen either 4, 1 fewer than the 5 corolla lobe, or 2 (with 2 staminode); corolla usually slightly bilaterally symmetrical (the flower as a whole made bilaterally symmetrical by the 2 or 4 stamen).

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

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

                                                                                           43 Fruit a capsule; inflorescence axillary, of cyme 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 raceme, or head.

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

                                                                                             44 Fruit a schizocarp of 4 mericarp; stamen inserted near or above the middle of the corolla tube

                                                                         35 Corolla bilaterally symmetrical (or the corolla 2-lipped but the corolla lobe twisted so as to make the flower asymmetrical); fertile stamen fewer than the corolla lobe (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 stamen) (note that many corolla are bilabiate and the number of corolla lobe, 4 or 5, may be difficult to interpret); carpel 2.

                                                                                               45 Carpel 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 mericarp (or 2 nutlet 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 spike, raceme, or heads, the flowers or fruits single at node; corolla often nearly radially symmetrical; stems rounded in X-section (rarely square); fresh plants usually not aromatic

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

                                                                                                   47 Stamen 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 Sepal 4

                                                                                                          50 Sepal 5, distinct or nearly so.

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

                                                                                                            51 Corolla distinctly bilabiate, the lobe shorter than the tube; sepal of nearly the same width.

                                                                                                              52 Sterile stamen (the lower pair) consisting of slender filament

                                                                                                              52 Sterile stamen minute or completely absent

                                                                                                   47 Stamen 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 raceme, panicle, or spike, the inflorescence not interspersed with large, leaf-like bract.

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

                                                                                                                     55 Sepal 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) spike or raceme; 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 axil of normally-sized leaves or somewhat reduced but still large and leaf-like bract [some taxa keyed here and below].

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

                                                                                                                                    62 Corolla yellow, orange, or red.

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

                                                                                                                                      63 Calyx lobe 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 lobe 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 anther

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

                                                                                                                                               67 Corolla blue; lower lip of the corolla arched upwards into the throat; plants perennial from rhizome or crown, 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 anther; plants annuals, 0.5-4 dm tall

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

1 Inflorescence, flower, and fruit structure various, but not with the combination of features as above (sometimes the flowers tightly grouped, but then with other features differing, such as stamen 4, or green calyx present, or fruit a schizocarp of mericarp, etc.).

  2 Flowers larger, individually conspicuous; perianth present, the petal or sepal brightly colored; fruit a capsule (or aggregate of achene in Clematis in RANUNCULACEAE or schizocarp of 4 mericarp in Glandularia in VERBENACEAE).

    3 Flowers radially symmetrical; stamen 5 or many; fruit a capsule or aggregate of achene.

      4 Stamen 5; fruit a capsule

      4 Stamen many; fruit an aggregate of plumose achene

    3 Flowers bilaterally symmetrical (sometimes only slightly so); stamen 4 (or 2 in Veronica in PLANTAGINACEAE); fruit a capsule or schizocarp of mericarp.

        5 Inflorescence of cymosely arranged spike or heads; fruit a schizocarp of 4 nutlet

        5 Inflorescence of solitary axillary flowers or terminal raceme.

          6 Corolla yellow, orange, or red; plants often drying black (but not Striga); sepal connate into a tube at least 1/3 as long as the corolla lobe; calyx 5-merous

          6 Corolla white, pink, lavender, or blue; plants not drying black; sepal distinct or only shortly connate into a short tube, the calyx lobe much longer than the tube; calyx 5- or 4-merous