1 Leaves not accompanied by stipules (stipules absent).

..2 Sepals fused into a toothed or lobed tube

..2 Sepals distinct, or slightly fused at their bases

1 Leaves accompanied by stipules (stipules present), these scarious or hyaline and readily apparent.

....3 Fruit a utricle; seed 1 per fruit; petals absent.

......4 Leaves alternate; staminodes petaloid, ovate to oblong; [tribe Corrigioleae]

......4 Leaves opposite (or the uppermost alternate in Herniaria); staminodes not petaloid, subulate; [tribe Paronychieae].

........5 Stipules inconspicuous; sepals green-margined, obtuse, lacking awns

........5 Stipules usually conspicuous; sepals white-scarious-margined, hooded or awned

....3 Fruit a capsule; seeds 3-many per fruit; petals present.

..........6 Floral bracts and sepals scarious throughout (thin and membranous), appearing chaffy; [non-native of disturbed, sandy habitats; c. and w. FL]

..........6 Floral bracts and sepals not scarious nor appearing chaffy (the margins hyaline, but not scarious throughout); [natives and non-natives, collectively widespread].

............ 7 Stem leaves subulate, 1-2 mm long, pectinate-fringed at the base; basal rosette leaves spatulate (usually withering quickly after overwintering; stems wiry, stiff, subdichotomously branched; [of xeric sands on the Coastal Plain from se. VA southward]

............ 7 Stem leaves larger, mostly both longer and broader, not pectinate-fringed at the base; basal rosette present or absent; stems either thicker, more flexuous, or not subdichotomously branched; [collectively more widespread].

............ ..8 Leaves opposite or in whorls of 4, linear to ovate or spatulate.

............ ....9 Leaves mostly in whorls of 4, obovate-spatulate, 2-8 mm long; [tribe Polycarpaeae]

............ ....9 Leaves opposite, linear or orbicular, 5-40 mm long.

............ ......10 Leaves orbicular-ovate; styles partly united; [tribe Polycarpaeae]

............ ......10 Leaves linear; styles separate; [tribe Spergulaeae]

1 Cauline leaves palmately compound.

..2 Cauline leaves essentially sessile, and also palmately cleft to the base, and further lacerately divided into linear or oblanceolate segments

..2 Cauline leaves petiolate, with 3-5, sessile or petiolulate, ovate, elliptic, or obovate leaflets (these serrate and sometimes with additional lobes).

....3 Inflorescence a spherical umbel of many flowers; fruit a drupe with 2-3 seeds; stem leaves 3-5

......4 Leaflets 3 (-5), sessile or subsessile, the petiolules 0-3 mm long; larger leaflets 4-8 cm long, 0.5-2.5 cm wide, averaging about 2.5× as long as wide, the apex obtuse to acute; fruit yellow-green when ripe, longitudinally winged and ribbed in ×-section; petals white (rarely tinged with pink); inflorescence nodding in bud; underground storage organ a spherical tuber

......4 Leaflets (3-) 5, petiolulate, the petiolules (7-) 10-25 mm long; larger leaflets 6-15 cm long, 3.5-7 cm wide, averaging about 1.8× as long as wide, the apex acuminate; fruit bright red when ripe, smoothly elliptical in ×-section; petals light green; inflorescence erect in bud; underground storage organ an +/- elongate root, this vertical or horizontal, and sometimes branched

....3 Inflorescence of single terminal flowers on the 1-several branches; fruit an aggregate of achenes; stem leaves 3

1 Cauline leaves simple.

........5 Inflorescence an involucrate head subtended by phyllaries, heads solitary or many, variously arrayed in secondary inflorescences; fruit a cypsela

........5 Inflorescence various, but not as above; fruit various, not as above (sometimes the flowers tightly grouped, but then with other features differing, such as stamens 4, or green calyx present, or fruit a schizocarp of mericarps, etc.).

..........6 Fruit a 3-lobed, 3-locular capsule; 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

..........6 Fruit various, not as above; inflorescence not a cyathium (and staminate or bisexual flowers almost always with > 1 stamen); fresh plants lacking milky juice.

............ 7 Leaves succulent, the terminal whorls closely juxtaposed; pistils 4-5; fruit an aggregate of follicles

............ 7 Leaves herbaceous, thin in texture, whorls separated; pistil 1, of 2-5 fused carpels; fruit a capsule, achene, or drupe.

............ ..8 Larger whorled leaves on a plant < 10 mm wide [some taxa keyed here and under the second lead].

............ ....9 Inflorescence a cymule, either axillary, or axillary and terminal; ovary inferior.

............ ......10 Leaves markedly variable in shape or size in each whorl; fruit a capsule; petals 5

............ ......10 Leaves similar in size and shape in each whorl; fruit dry or fleshy, indehiscent; petals (3-) 4

............ ....9 Inflorescence a terminal raceme, panicle, spike, cyme, corymb, or umbel; ovary superior.

............ ........11 Corolla bilaterally symmetrical, the petals connate; carpels 2; stamens 4, 6, or 8.

............ ..........12 Stamens 4; corolla blue or almost white

............ ..........12 Stamens 6 or 8; corolla pink or yellow

............ ........11 Corolla radially symmetrical, the petals separate; carpels 2, 3, or 5; stamens 5, 10, or many.

............ ............ 13 Inflorescence an axillary umbel; leaves narrowly linear and more than 10× as long as wide, > 20 mm long and < 2 mm wide; whorls of 3-6 leaves

............ ............ 13 Inflorescence a terminal cyme, raceme, panicle, or umbel; leaves as above, or broader in shape, narrower, or shorter; whorls of 3-16 leaves.

............ ............ ..14 Inflorescence a terminal cyme or umbel; corolla white; carpels 5.

............ ............ ....15 Leaves ovate or obovate, 3 (-4) in each whorl

............ ............ ..14 Inflorescence a terminal raceme or panicle; corolla reddish, maroon, or yellow.

............ ............ ......16 Corolla reddish or maroon

............ ............ ......16 Corolla yellow

............ ..8 Larger whorled leaves on a plant > 10 mm wide.

............ ............ ........17 Inflorescence a spike; perianth absent; fruit a drupe

............ ............ ........17 Inflorescence various, but not a spike; perianth present; fruit various, but not a drupe.

............ ............ ..........18 Inflorescence of terminal involucrate clusters; perianth of 6 tepals; fruit an achene; stamens 9; [plants of very dry habitats]

............ ............ ..........18 Inflorescence various, but not as above; perianth of 2 whorls (the calyx often obsolete in Galium in RUBIACEAE), 3-, 4-, 5-, 6-, or 7-merous; stamens 2-7; [plants of dry-mesic to very wet habitats].

............ ............ ............ 19 Fruit dry or fleshy, indehiscent; petals (3-) 4; ovary inferior

............ ............ ............ 19 Fruit a capsule or follicle, dehiscent; petals 4-7; ovary superior.

............ ............ ............ ..20 Inflorescence an umbel; fresh plants with milky juice

............ ............ ............ ..20 Inflorescence not an umbel; fresh plants with clear juice.

............ ............ ............ ....21 Corolla pink-purple, 6-merous, the petals separate and borne on the edge of a hypanthium; stamens 8, 10, or 12; [plants of wetlands]

............ ............ ............ ....21 Corolla white, yellow, or greenish, 4-, 5-, or 7-merous, the petals fused at least basally into a tube (falling as a unit), not on a hypanthium; stamens 2, 4, 5, or 7; [plants of mesic habitats].

............ ............ ............ ......22 Stamens 2; corolla bilaterally symmetrical

............ ............ ............ ......22 Stamens 4, 5, or 7; corolla radially symmetrical.

............ ............ ............ ........23 Petals yellowish-white, with prominent green streaks; biennial or monocarpic plant, 10-30 dm tall when fertile; leaves 15-35 cm long

............ ............ ............ ........23 Petals white or yellow; perennial plants, 1-15 dm tall; leaves 1-15 cm long.

............ ............ ............ ..........24 Leaves punctate; stem without swollen nodes

............ ............ ............ ..........24 Leaves not punctate; stem with swollen nodes