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 2 or 4-5; corolla pink, blue, white.

........5 Calyx lobes 2; 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 aliens, 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) 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 aliens in suburban woodlands]

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

............ 7 Leaf bases cuneate

............ 7 Leaf bases cordate to rounded.

............ ..8 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

............ ..8 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.

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

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

......4 Leaf margins entire.

............ ......10 Ovary inferior or half-inferior.

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

............ ........11 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.

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

............ ..........12 Leaves distinctly petiolate, rhombic, widest near the base; [rarely naturalized aliens].

............ ............ 13 Inflorescence of a single axillary flower

............ ............ 13 Inflorescence terminal, spikelike

............ ......10 Ovary superior.

............ ............ ..14 Inflorescence a leaf-opposed (sometimes apparently terminal) spike or raceme; flowers visually white from white petaloid sepals, white bracts, or white stamens.

............ ............ ....15 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].

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

............ ............ ......16 Sepals 5; carpels 6-12, distinct; fruit an oblate berry

............ ............ ....15 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].

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

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

............ ............ ..14 Inflorescence not leaf-opposed, either simpler (single axillary or glomerules of flowers) or more complexly branched (axillary or terminal panicles or complex cymes); flowers white, reddish, scarious, or greenish.

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

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

............ ............ ............ 19 Inflorescence an terminal involucrate cluster; flowers bisexual; stamens 9

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

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

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

............ ............ ............ ....21 Styles 1, stigma 1; flowers unisexual

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

............ ............ ............ ......22 Tepals acute, scarious

............ ............ ............ ......22 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).

............ ............ ............ ........23 Ovary inferior or half-inferior.

............ ............ ............ ..........24 Petals connate.

............ ............ ............ ............ 25 Inflorescence leaf-opposed, a dense, cylindrical spike

............ ............ ............ ............ 25 Inflorescence various, either a terminal head, or axillary and solitary, or variously axillary or terminal and more diffuse.

............ ............ ............ ............ ..26 Leaves toothed; flowers blue to white

............ ............ ............ ............ ..26 Leaves entire; flowers white

............ ............ ............ ..........24 Petals distinct.

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

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

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

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

............ ............ ............ ........23 Ovary superior.

............ ............ ............ ............ ........29 Corolla bilaterally symmetrical, petals connate (except distinct in VIOLACEAE); fruit a capsule or legume (except a 1-seeded indehiscent spinose pod in Krameria in KRAMERIACEAE).

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

............ ............ ............ ............ ..........30 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).

............ ............ ............ ............ ............ 31 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.

............ ............ ............ ............ ............ ..32 Stamens fused, monadelphous or diadelphous.

............ ............ ............ ............ ............ ....33 Stamens 10, monadelphous or diadelphous; fruit a legume

............ ............ ............ ............ ............ ....33 Stamens 6-8, monadelphous; fruit a capsule

............ ............ ............ ............ ............ ..32 Stamens distinct.

............ ............ ............ ............ ............ ......34 Carpel 1; fruit a legume

............ ............ ............ ............ ............ ......34 Carpels 3-6; fruit a capsule

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

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

............ ............ ............ ............ ............ ........35 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).

............ ............ ............ ............ ............ ..........36 Fruit 1-seeded, indehiscent; sepals petaloid, red-purple; petals dimorphic, the upper 3 long-clawed, the lower 2 small, thickened, and glandlike

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

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

............ ............ ............ ............ ............ ............ 37 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.

............ ............ ............ ............ ............ ............ ..38 Capsule septicidal; corolla not spurred

............ ............ ............ ............ ............ ............ ..38 Capsule loculicidal; corolla spurred (except Digitalis)

............ ............ ............ ............ ........29 Corolla radially symmetrical, petals connate or distinct; fruit various (including a capsule).

............ ............ ............ ............ ............ ............ ....39 Petals distinct; stamens 5-many.

............ ............ ............ ............ ............ ............ ......40 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.

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

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

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

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

............ ............ ............ ............ ............ ............ ............ 43 Leaves cuneate at the base; flowers in a diffuse inflorescence

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

............ ............ ............ ............ ............ ............ ......40 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.

............ ............ ............ ............ ............ ............ ............ ..44 Petals 4; sepals 4; stamens 6; fruit a silique/silicle

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

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

............ ............ ............ ............ ............ ............ ............ ....45 Stamens 5-many, distinct; carpels 2-5; fruit a capsule; leaves entire (serrate in Croton in EUPHORBIACEAE).

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

............ ............ ............ ............ ............ ............ ............ ......46 Flowers bisexual; leaf vestiture simple or stellate.

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

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

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

............ ............ ............ ............ ............ ............ ............ ............ 49 Capsule 10-locular (with 5 carpels) and septicidal

............ ............ ............ ............ ............ ............ ............ ............ 49 Capsule 1-locular (with 3 carpels) and loculicidal

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

............ ............ ............ ............ ............ ............ ............ ............ ..50 Stamens (5-) 10, 15, 20, 30 (-many); corolla yellow or reddish; capsule 3 (-10)-locular, loculicidal

............ ............ ............ ............ ............ ............ ............ ............ ..50 Stamens 10; corolla white or pink; capsule 5-locular

............ ............ ............ ............ ............ ............ ....39 Petals fused; stamens (4-) 5 (-7).

............ ............ ............ ............ ............ ............ ............ ............ ....51 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

............ ............ ............ ............ ............ ............ ............ ............ ....51 Pistil 1 (of 2 or 3 fused carpels); fruit a capsule; plant lacking milky juice; leaves entire or serrate; inflorescence various (but not an umbel).

............ ............ ............ ............ ............ ............ ............ ............ ......52 Ovary slightly to deeply 2-4-lobed; fruit a schizocarp of 4 mericarps or a drupe.

............ ............ ............ ............ ............ ............ ............ ............ ........53 Ovary deeply 4-parted; style gynobasic; fruit a schizocarp of 4 mericarps

............ ............ ............ ............ ............ ............ ............ ............ ........53 Ovary slightly 2-4-lobed, or not at all lobed; style terminal or reduced to a sessile terminal stigma; fruit a schizocarp of 4 mericarps, or a drupe

............ ............ ............ ............ ............ ............ ............ ............ ......52 Ovary not lobed; fruit a capsule or berry.

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

............ ............ ............ ............ ............ ............ ............ ............ ............ 55 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.

............ ............ ............ ............ ............ ............ ............ ............ ............ ..56 Leaves 0.2-0.8 cm long and acicular

............ ............ ............ ............ ............ ............ ............ ............ ............ ..56 Leaves 2-10 cm long and broadly ovate or elliptic

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

............ ............ ............ ............ ............ ............ ............ ............ ............ ....57 Leaves cordate at the base; plant a twining vine

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

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

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

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

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

............ ............ ............ ............ ............ ............ ............ ............ ............ ........59 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

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

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

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

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

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

............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ....63 Corolla lobes longer than the fused corolla cup, blue

............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ....63 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).

............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ......64 Fruit a capsule, 4-seeded

............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ......64 Fruit a berry or capsule, many-seeded