1 Leaves all scale-like, 1-3 (-5) mm long, appressed to the stem.

  2 Plants white or cream, lacking chlorophyll (holomycoheterotrophic); [tribe Voyrieae]

1 Leaves larger, spreading or ascending.

    3 Stem leaves whorled; plants robust, 1-3 m tall; [tribe Gentianeae, subtribe Swertiinae]

    3 Stem leaves opposite; plants generally < 1 m tall.

      4 Calyx lobes 6-8; corolla bright yellow

      4 Calyx lobes 0 (or interpretable as 2) or 4-5; corolla pink, blue, white.

        5 Calyx lobes 0 (but the flower subtended by 2 leaflike bracts that have sometimes been interpreted as sepals); stem leaves obovate, widest near the rounded tip), 0.5-1.5 cm long, crowded near the tip of the stem, basal rosette never present; [of nutrient-rich, mesic forests]; [tribe Gentianeae, subtribe Swertiinae]

        5 Calyx lobes 4-5; stem leaves lanceolate, ovate, elliptic or narrowly elliptic (widest near the middle or toward the base, the tip acute or acuminate), mostly > 1.5 cm long, distributed fairly evenly along the stem, basal rosettes sometimes present; [of various more-or-less open habitats (except some species of Gentiana, which can occur in nutrient-rich, mesic forests)].

          6 Corolla lobes 5-14, longer than the corolla tube, pink or white; [common natives]; [tribe Chironieae, subtribe Chironiinae].

             7 Stigmas shorter than the style

             7 Stigmas equaling or longer than the style

          6 Corolla lobes 4-5, shorter than the corolla tube, blue, lavender, pink or white.

               8 Corolla tube < 2 mm wide; [rare to uncommon exotics, naturalized in disturbed areas]; [tribe Chironieae, subtribe Chironiinae].

                 9 Style slightly bifid; stigma lobes reniform to shoe-shaped, fleshy; capsule linear

                 9 Style not divided or subcapitate; stigma lobes rhombic to fan-shaped, not fleshy; capsule elliptic to ovoid

               8 Corolla tube > 3 mm wide.

                   10 Corolla lobes alternating with corolla appendages (appearing as plaits or lobes, these often toothed, notched, or lacerate, sometimes as long as or longer than the true corolla lobes); main stem leaves cuneate at the base; perennial; [tribe Gentianeae, subtribe Gentianinae]

                   10 Corolla lobes not alternating with corolla appendages; main stem leaves rounded to cordate at the base; biennial or annual; [tribe Gentianeae, subtribe Swertiinae].

                     11 Corolla lobes 4, finely fringed; main stem leaves rounded at base, with lateral veins obscure; biennial

                     11 Corolla lobes 5, entire, not fringed; main stem leaves cordate (the cordate bases often overlapping the opposite leaf), with 2-3 well-developed lateral veins (prominently visible on the lower surface); annual

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. Eryngium in APIACEAE, but then with other features differing, such as stamens 4, or green calyx present, or fruit a schizocarp of mericarps, etc.).

  2 Perianth uniseriate (represented only by undifferentiated tepals or sepals; look at the front and back of the flowers for two layers) or completely absent; flowers usually unisexual, less commonly bisexual).

    3 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

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

      4 Leaf margins toothed in some manner (serrate, dentate, crenate, etc.)

        5 Leaf teeth rounded to subacute, resembling shallow lobes, irregular, few (mostly < 6 per leaf side).

          6 Fruit a single-seeded achene or utricle; [plants of various disturbed or saline, usually sunny habitats]

          6 Fruit a 3-lobed, circumscissilely dehiscent capsule; [plants native of rich moist shaded forests or exotics in suburban woodlands]

        5 Leaf teeth sharp to crenate, not lobe-like, regular, many (mostly > 10 per leaf side).

             7 Leaf bases cuneate (or strongly oblique in Begonia, with one leaf base usually being cuneate, the other variously rounded or cordate).

               8 Flowers typically with 2 or 4 (-5) showy, white-colored tepals; leaves sometimes variegated; fruit unequally or subequally 3-winged capsules; [ornamental waifs or uncommon non-natives]

               8 Flowers cyathia, not merely bearing showy tepals; leaf not variegated but sometimes bearing darkened red or black splotches; fruit capsules, but these not conspicuously winged; [natives and non-natives, usually not ornamental]

             7 Leaf bases cordate to rounded.

                 9 Styles 3; fruit a 3-lobed, 3-carpellate capsule (1 carpel sometimes aborting); inflorescence either a terminal or leaf opposed raceme, or a dense axillary condensed cyme with conspicuous toothed bracts subtending the flowers

                 9 Styles 1 or 2; fruit either an achene or a multiple of achenes; inflorescence either an axillary dense cyme (almost a head), or an axillary spike with glomerules, or a terminal or axillary panicle.

                   10 Styles 2; inflorescence a dense axillary cyme (almost a head); fruit a multiple of achenes; plant lacking stinging hairs; [exotic plant of weedy situations]

                   10 Style 1; inflorescence an axillary spikes with glomerules, or a terminal or axillary panicle; plant either with stinging hairs or not; [plant a rare exotic (Boehmeria nivea) or a native of moist forests (Boehmeria cylindrica, Laportea)]

      4 Leaf margins entire.

                     11 Ovary inferior (flowers epigynous, the ovary sitting below the perianth and androecium) or half-inferior (perigynous, the ovary sitting level with the remaining floral parts).

                       12 Leaf base cordate; calyx 3-lobed, fused into a bilaterally symmetrical, curved brown or yellowish tube; fruit a capsule

                       12 Leaf base cuneate, rounded, or truncate; calyx of 3-4-5 distinct sepals, radially symmetrical, white or yellow; fruit a dry, nutlike drupe or an achene.

                          13 Leaves subsessile or very short petiolate, elliptic or narrowly elliptic, broadest near the middle; [native]

                          13 Leaves distinctly petiolate, rhombic, widest near the base; [rarely naturalized exotics].

                            14 Inflorescence of a single axillary flower

                            14 Inflorescence terminal, spikelike

                     11 Ovary superior (flowers hypogynous, the ovary sitting above the perianth and androecium).

                              15 Inflorescence a leaf-opposed spike or raceme, the inflorescence arising opposite of stem leaves (except Saururus, whose spikelike racemes are leaf-opposed and/or terminal); flowers visually white from white petaloid sepals, white bracts, or white stamens.

                                16 Sepals present, 4 or 5; petaloid, white; carpels 1 to many (-12); stamens 4 to many (-25); fruit a berry or an apically 2-lobed achene (as in Petiveria); leaf bases cuneate or rounded (but not cordate); [Eudicots].

                                  17 Sepals 4; carpels 1; fruit subglobose berries or apically lobed achenes

                                  17 Sepals 5; carpels 5-12, distinct; fruit an oblate berry

                                16 Sepals absent; carpels 3-4; stamens 2-6 (-8); fruit a capsule, a 1-seeded drupe, or a schizocarp of 3-4 mericarps; leaf bases cordate or subcordate; [Basal Angiosperms].

                                    18 Fruit a 1-seeded drupe; stamens 2; plants terrestrial or epiphytic

                                    18 Fruit a capsule or schizocarp with 3-4 mericarps; stamens 3 or 6-8; plants terrestrial

                              15 Inflorescence not leaf opposed, instead arising with stem leaves (axillary) or terminal, the inflorescence not spikes nor racemes, instead either simpler (single axillary or glomerules of flowers) or more complexly branched (terminal or axilary panicles or terminal complex cymes); flowers white, reddish, scarious, or greenish.

                                       19 Stipules tubular, sheathing (= ocreae); flowers subtended by tubular, sheathing bracteoles (= ocreolae); nodes usually prominently swollen; perianth usually of 5-6 white to pink tepals

                                       19 Stipules not tubular or sheathing; flowers not subtended by ocreolae; nodes not swollen; perianth absent or of 3-5 sepals.

                                         20 Inflorescence a terminal involucrate cluster; flowers bisexual; stamens 9

                                         20 Inflorescence axillary, or a terminal panicle or raceme that is not involucrate; stamens 3-6.

                                           21 Ovary 3-locular; styles 3, each bifid; fruit a capsule, with 6 seeds

                                           21 Ovary 1-locular; styles 1-3, not bifid; fruit a utricle or achene (1-seeded).

                                             22 Sepals petaloid, pink and relatively conspicuous (although the sepals ca. 1-3 mm in length); plants prostrate to somewhat ascending annuals; leaves opposite or nearly whorled; achenes muricate

                                             22 Sepals not petaloid, inconspicuous, green or greyish in color; plants prostrate or erect, annual or perennial; leaves alternate OR either alternate or opposite (Amaranthaceae); achenes variously textured (smooth or textured, sometimes reticulate or verrucose, but rarely muricate).

                                               23 Styles 1, stigma 1; flowers unisexual

                                               23 Styles 1-3, if style 1, then stigmas 3; flowers bisexual or unisexual.

                                                 24 Tepals acute, scarious

                                                 24 Tepals usually blunt, herbaceous

  2 Perianth biseriate (represented by differentiated whorls of sepals and petals, the sepals usually green or drab in color, the petals often brightly colored); flowers nearly always bisexual (there are exceptions).

                                                    25 Ovary inferior (epigynous) or half-inferior (perigynous).

                                                      26 Petals connate (at least basally, often the lower half of corolla).

                                                        27 Inflorescence a leaf-opposed, dense, cylindrical spike

                                                        27 Inflorescence not a dense, leaf-opposed spike, instead a terminal head or variously axillary or terminal (the flowers solitary or not, but not in a dense spike).

                                                          28 Flowers yellow; stamens numerous (15+), monomorphic or heteromorphic (inner and outer of differing length), conspicuously exerted from the flowers, often surpassing the ovary; leaves basally lobed or unlobed (often a mix in M. floridana and M. oligosperma)

                                                          28 Flowers blue or white; stamens fewer (usually < 10), monomorphic, if exerted, the ovary usually still apparent; leaves unlobed.

                                                            29 Leaves toothed; flowers blue to white

                                                            29 Leaves entire; flowers white

                                                      26 Petals distinct.

                                                              30 Petals 5; stamens 5; inflorescence a head; fruit a schizocarp of 2 mericarps

                                                              30 Petals 4 7; stamens 6 or more; inflorescence various, not a head; fruit a capsule.

                                                                 31 Petals 4-7; stamens 1× or 2× as many as the petals, 4-7, 8, 10, 12, or14; leaves herbaceous in texture

                                                                 31 Petals 5 (or sometimes doubled in horticultural forms); stamens 6-40 (or more); leaves fleshy in texture

                                                    25 Ovary superior (hypogynous).

                                                                   32 Corolla bilaterally symmetrical (zygomorphic), petals connate, at least basally (except distinct in VIOLACEAE); fruit a capsule or legume (the capsule conspicuously spiny in Krameria).

                                                                     33 Petals distinct, 5; carpels 3; fruit a 3-loculed capsule

                                                                     33 Petals connate (at least basally), 4, 5, 6, 7, or 8; carpels 1, 2, 4, 5, or 6 (rarely 3 in Reseda in RESEDACEAE); fruit a legume or 1-, 2-, or 5-loculed capsule (except a 1-seeded indehiscent pod in Krameria in KRAMERIACEAE).

                                                                       34 Stamens 6-10 (-25), more than the number (4 or 5) of petals and the number (4 or 5) of the sepals; fruit a legume or a 1-6-carpellate capsule.

                                                                         35 Stamens fused, monadelphous or diadelphous.

                                                                           36 Stamens 10, monadelphous or diadelphous; fruit a legume

                                                                           36 Stamens 6-8, monadelphous; fruit a capsule

                                                                         35 Stamens distinct.

                                                                              37 Carpel 1; fruit a legume

                                                                              37 Carpels 3-6; fruit a capsule

                                                                       34 Stamens 4-5, less than or the same as the number (5) of the petals; fruit a 2-5-carpellate capsule.

                                                                                38 Pistil 5-carpellate; capsule 5-locular, explosively dehiscent; inflorescence of axillary, small clusters of flowers

                                                                                38 Pistil 2-carpellate; capsule 2 locular, opening gradually or not at all; inflorescence a terminal spike, raceme or panicle (or solitary, axillary flowers in Chaenorrhinum in PLANTAGINACEAE and Krameria in KRAMERIACEAE).

                                                                                  39 Fruit 1-seeded, indehiscent; sepals petaloid, red-purple; petals dimorphic, the upper 3 long-clawed, the lower 2 small, thickened, and glandlike; fruit a spiny pod

                                                                                  39 Fruit > 2-seeded, dehiscent; sepals sepaloid, green; petals not dimorphic.

                                                                                    40 Stamens 5; corolla not spurred; capsule septicidal; pubescence of the stem and leaves either gland-tipped or dendritically branched

                                                                                    40 Stamens 4; corolla with a distinct spur or sac at the base between the the 2 lower calyx lobes (except not spurred in Digitalis and Schwalbea); capsule loculicidal (only at the summit in Antirrhinum and Chaenorrhinum, and septicidal in Schwalbea); pubescence of the stem and leaves neither gland-tipped (except in Antirrhinum and Chaenorrhinum) nor dendritically branched.

                                                                                      41 Capsule septicidal; corolla not spurred

                                                                                      41 Capsule loculicidal; corolla spurred (except Digitalis)

                                                                   32 Corolla radially symmetrical (actinomorphic), petals connate or distinct; fruit various (including capsules).

                                                                                        42 Plants herbaceous vines, fleshy and mucilaginous, the leaves variously orbicular, ovate, cordate or sometimes elliptic; fruit utricles (small sacs surrounding an achene), partly to completely enclosed in the persistent, dry to somewhat fleshy perianth; sepals 2

                                                                                        42 Plants not herbaceous vines, the leaves variously shaped; fruit various, but never utricles; sepals 4 or more.

                                                                                           43 Petals distinct (flowers apopetalous); stamens 5-many (4 or 5 in Capraria).

                                                                                             44 Pistils 4-10 (each 1-carpellate) in a ring, these sometimes fused basally, each with its own style/stigma; fruit either an aggregate of achenes or follicles or a 5 (-7) locular capsule.

                                                                                               45 Pistils 5 (-7); inflorescence a compound terminal cyme.

                                                                                                 46 Fruit an aggregate of follicles; leaves fleshy in texture; inflorescence; leaves entire of sparsely and coarsely serrate, with < 12 points per leaf; [plants primarily of dry habitats]

                                                                                                 46 Fruit a 5 (-7) locular capsule; leaves membranaceous in texture; leaves serrate, with > 20 points per leaf; [plants of wet habitats]

                                                                                               45 Pistils many; inflorescence of solitary flowers, or diffuse.

                                                                                                   47 Leaves cuneate at the base; flowers in a diffuse inflorescence

                                                                                                   47 Leaves cordate at the base; flowers solitary, on long pedicels

                                                                                             44 Pistil 1, with 1-to many carpels (in many MALVACEAE, the carpels loosely united in a ring [of more than 5] around the single style/stigma); fruit either a 1-, 2-, 3-, 5-, 6-, or 10-locular capsule, or a silique/silicle, or a ring of mericarps.

                                                                                                     48 Petals 4; sepals 4; stamens 6; fruit a silique/silicle

                                                                                                     48 Petals 5 (rarely 4 or 6); sepals 5 (rarely 4 or 6); stamens 4, 5 (or multiples of 5), 6, or 12; fruit a capsule or a ring of mericarps.

                                                                                                        49 Stamens many, connate into a staminal tube; carpels 5-many; fruit a capsule or ring of mericarps; leaves usually serrate or crenate

                                                                                                        49 Stamens (4-) 5-many, distinct (not forming a staminal tube); carpels 2-5; fruit a capsule; leaves entire (serrate in Croton in EUPHORBIACEAE, distally serrate in Capraria in SCROPHULARIACEAE).

                                                                                                          50 Flowers unisexual; leaf vestiture of peltate scales and/or stellate hairs

                                                                                                          50 Flowers bisexual; leaf vestiture (if present) simple or stellate.

                                                                                                            51 Flowers 6-merous (the petals and sepals 6, the stamens 6 or 12); corolla pink or purplish (rarely white); fruit a septicidal capsule

                                                                                                            51 Flowers 5-merous (the petals and sepals 5, stamens 5 or various multiples of 5); corolla white, yellow, reddish (including pinkish), or blue; fruit a loculicidal or septicidal capsule.

                                                                                                              52 Stamens 5 ; corolla yellow or blue; capsule either 10-locular and septicidal (Linum) or 1-locular (with 3 carpels) and loculicidal.

                                                                                                                53 Capsule 10-locular (with 5 carpels) and septicidal (splitting at the septa, opening at the top)

                                                                                                                53 Capsule 1-locular (with 3 carpels) and loculicidal (splitting along outer edges, not only at the top)

                                                                                                              52 Stamens (4-) 10, 15, 20, 30 (-many); corolla white, pink, yellow, or reddish; capsule 2-, 3-, 5- (-10)-locular, loculicidal.

                                                                                                                  54 Leaf margins distally serrate, the surfaces punctate-glandular and also with internal oil-secreting cavities; corolla white (the inside sometimes with scattered purple spots); [s. FL and s. TX only in our flora area]

                                                                                                                  54 Leaf margins entire, serrate, or crenate, lacking punctate-glands and internal oil-secreting cavities; corolla white, pink, yellow, or reddish; [collectively widespread, including s. FL and s. TX].

                                                                                                                     55 Stamens (5-) 10, 15, 20, 30 (-many); corolla yellow or reddish; filaments not densely villous basally, the anthers the anthers not conspicuously tubular and lacking apical pores; capsule 3 (-10)-locular, loculicidal

                                                                                                                     55 Stamens 10; corolla white or pink; filament bases dilated basally and densely villous, the anthers tubular with conspicuous apical pore dehiscence; capsule 5-locular

                                                                                           43 Petals fused (flowers sympetalous, this includes salverform and tubular flowers); stamens (4-) 5 (-7).

                                                                                                                       56 Plants herbaceous vines, fleshy and mucilaginous, the leaves variously orbicular, ovate, cordate or sometimes elliptic; fruit utricles (small sacs surrounding an achene), partly to completely enclosed in the persistent, dry to somewhat fleshy perianth; sepals 2

                                                                                                                       56 Plants not with the above combination of characters, if herbaceous vines then fruit not utricles and sepals 4 or more.

                                                                                                                         57 Pistils 2, united only by the style and stigma; fruit a schizocarp of 2 follicles (often single by abortion); plant with milky juice when fresh; leaves entire; inflorescence an umbel

                                                                                                                         57 Pistil 1 (of 2 or 3 fused carpels); fruit a capsule, drupe, or a schizocarp splitting into 4 nutlets; plant lacking milky juice; leaves entire or serrate; inflorescence various (but not an umbel).

                                                                                                                           58 Ovary slightly to deeply 2-4-lobed (entire or shallowly lobed in Tiquilia and HELIOTROPIACEAE); fruit a schizocarp of 4 mericarps or a drupe; [BORAGINALES].

                                                                                                                             59 Ovary deeply 4-parted; style gynobasic or terminal.

                                                                                                                               60 Style gynobasic (originating from the base of the ovary's lobes); ovary slightly to deeply lobed; fruit a schizocarp of 4 mericarps

                                                                                                                               60 Style terminal (originating from the apex of the ovary), twice-cleft into 4 branches, each of which then terminates in a stigma; ovary slightly lobed; fruit a drupe with a glutinous mesocarp (or if lacking, a nut)

                                                                                                                             59 Ovary slightly 2-4-lobed, or not at all lobed; style terminal or reduced to a sessile terminal stigma.

                                                                                                                                  61 Plants usually strongly gray or white-colored and villous, growing in short, suffrutescent mounds or mats; leaves densely pubescent (hairs densely appressed adaxially, tomentose abaxially); inflorescence of solitary flowers or extra-axillary, never scirpioid; corolla lavender or whitish-lavender, the lobes 1.8-3.0 (-4.5) mm long, broadly rounded; [s. TX, westward; primarily of the Trans-Pecos region]

                                                                                                                                  61 Plants variously glabrous or pubescent (sometimes villous), usually herbaceous, occasionally suffrutescent and mound or mat-forming; inflorescence variously elongate or racemose, often scirpioid (curved or coiled on one side of the inflorescence axis; e.g., Heliotropium), occasionally solitary (e.g., Euploca, in part; although in this case the leaves of the shrubby Euploca are significantly narrower); corolla variously colored (including lavender); [plants collectively widespread, including TX]

                                                                                                                           58 Ovary not lobed; fruit a capsule or berry.

                                                                                                                                    62 Leaves larger (or only 2-8 mm long in Pyxidanthera in DIAPENSIACEAE, but then spreading); petals 5-7; stamens 5-7.

                                                                                                                                      63 Plant a creeping subshrub (keyed here as a failsafe); leaves either 0.2-0.8 cm long and acicular, or 2-10 cm long and broadly ovate or elliptic.

                                                                                                                                        64 Leaves 0.2-0.8 cm long and acicular

                                                                                                                                        64 Leaves 2-10 cm long and broadly ovate or elliptic

                                                                                                                                      63 Plant an herb, erect or sprawling; leaves > 1.5 cm long.

                                                                                                                                          65 Leaves cordate at the base; plant a twining vine

                                                                                                                                          65 Leaves cuneate to rounded at the base; plant an erect, sprawling, or reclining herb (twining in Solanum dulcamara in SOLANACEAE).

                                                                                                                                            66 Inflorescences (solitary or of several flowers) terminal on the stem.

                                                                                                                                               67 Calyces tubular, conspicuously 5-ribbed and bearing numerous stalked, capitate-glands

                                                                                                                                               67 Calyces not as above, flowers typically campanulate (not salverform), if tubular then not also 5-ribbed and capitate-glandular.

                                                                                                                                                 68 Corolla lobes longer than the fused corolla cup, blue, pink, or white; styles 2; herbage lacking stipitate glands; fresh plants not aromatic.

                                                                                                                                                   69 Flowers in axillary cymes; capsule subglobose; leaves 2-12 cm long

                                                                                                                                                   69 Flowers solitary or paired in the leaf axils; capsule cylindrical; leaves 0.5-8 cm long

                                                                                                                                                 68 Corolla lobes very short, much shorter than the corolla cup or tube, sometimes barely perceptible and represented only by teeth on the edge of the corolla limb, white or pink; style 1; herbage often with stipitate glands; fresh plants often rankly aromatic

                                                                                                                                            66 Inflorescences (of solitary or several flowers) axillary or lateral on the stem.

                                                                                                                                                     70 Flowers sessile or very-short pedicelled, solitary in the leaf axils.

                                                                                                                                                       71 Stamens alternate with the corolla lobes; flower ca. 10 mm in diameter

                                                                                                                                                       71 Stamens opposite the corolla lobes; flower ca. 1 mm in diameter

                                                                                                                                                     70 Flowers either solitary and obviously pedicelled, or several in an axillary or lateral inflorescence.

                                                                                                                                                         72 Calyces tubular, conspicuously 5-ribbed and bearing numerous stalked, capitate-glands

                                                                                                                                                         72 Calyces not as above, flowers typically campanulate (not salverform), if tubular then not also 5-ribbed and capitate-glandular.

                                                                                                                                                            73 Corolla lobes longer than the fused corolla cup, blue

                                                                                                                                                            73 Corolla lobes very short, much shorter than the corolla cup or tube, sometimes barely perceptible and represented only by teeth on the edge of the corolla limb, white, yellow, pink, various other colors (rarely including blue).

                                                                                                                                                              74 Fruit a capsule, 4-seeded

                                                                                                                                                              74 Fruit a berry or capsule, many-seeded