1	"Leaves opposite or whorled"	2
1	"Leaves alternate or all basal"	25
2	"Plant aquatic, weak-stemmed; submersed, floating, or stranded on mud"	3
2	"Plant terrestrial, sometimes in damp soil, or in areas flooded at high tide"	6
3	"Leaves opposite; ovary lobed or unlobed; seeds 4--many"	4
3	"Leaves whorled; ovary unlobed; seed 1"	5
4	"Ovary unlobed, many-seeded"	"Lythraceae {Lythrum portula}"
4	"Ovary 2- or 4-lobed, 4-seeded"	"Plantaginaceae {Callitriche}"
5	"Leaves dissected into narrow lobes"	"Ceratophyllaceae {Ceratophyllum demersum}"
5	"Leaves entire"	"Plantaginaceae {Hippuris}"
6	"Ovary chambers 2 or more (doubtful cases should be keyed both ways)"	7
6	"Ovary chamber 1"	10
7	"Flowers unisexual"	8
7	"Flowers bisexual"	9
8	"Style 0, stigma sessile; leaves +- cylindric or 3-angled in ×-section, fleshy; milky latex 0; plants of coastal salt-marshes"	"Bataceae {Batis maritima}"
8	"Styles or stigmas 2--3, free; leaves thin; milky latex present or 0; plants of various habitats but not salt marsh"	Euphorbiaceae
9	"Leaves opposite, equal; fruit circumscissile --- 1/2-inferior ovary may appear superior"	"Aizoaceae {Sesuvium}"
9	"Leaves whorled, often unequal; fruit loculicidal"	Molluginaceae
10	"Ovules 2--many; fruit a capsule"	11
10	"Ovule 1; fruit an achene, 1-seeded capsule, or utricle"	14
11	"Perianth parts 6(8) --- sepals actually present in bud, but early-deciduous, 0 in open flower"	Papaveraceae
11	"Perianth parts (4)5"	12
12	"Sepals free; flowers generally in cymes"	Caryophyllaceae
12	"Sepals fused; flowers solitary in leaf axils"	13
13	"Leaves of a pair unequal; stipules present; fruit circumscissile"	Aizoaceae
13	"Leaves of a pair equal; stipules 0; fruit 5-valved"	"Myrsinaceae {Lysimachia maritima}"
14	"Style 1, undivided or stigma 1, sessile"	15
14	"Styles or style branches 2 or more"	17
15	"Sepals petal-like, fused into a tube; leaves entire or slightly lobed, stinging hairs 0"	Nyctaginaceae
15	"Sepals green, small, inconspicuous; leaves toothed or entire, sometimes with stinging hairs"	16
16	"Herbage densely covered with branched hairs"	"Amaranthaceae {Tidestromia}"
16	"Herbage glabrous or +- hairy, hairs not branched (stinging hairs present in _Hesperocnide_, _Urtica_)"	Urticaceae
17	"Leaves palmately compound or deeply lobed"	Cannabaceae
17	"Leaves simple, entire or toothed"	18
18	"Fruit a 3-angled achene; perianth parts 6 [actually in 2 whorls of 3, but this may not be evident in open flowers]"	Polygonaceae
18	"Fruit not 3-angled; perianth parts <= 5"	19
19	"Leaves with stipules"	20
19	"Leaves without stipules"	21
20	"Leaves petioled, fleshy; fruit a circumscissile capsule"	"Aizoaceae {Trianthema}"
20	"Leaves sessile, not fleshy; fruit 1-seeded, indehiscent"	Caryophyllaceae
21	"Leaves reduced to fleshy scales; inflorescence a fleshy spike"	Chenopodiaceae
21	"Leaves linear to ovate; inflorescences various or flowers solitary"	22
22	"Sepals erect, linear, fused below and hardened around ovary; stamens fused to calyx; slender annual, generally <= 15 cm; leaves narrowly linear, <= 15 mm"	"Caryophyllaceae {Scleranthus}"
22	"Sepals erect or spreading, free, not hardened around ovary (sepals generally 0 in pistillate flowers of _Atriplex_, which has a pair of +- hardened bractlets around fruit); stamens free from calyx; plants often larger, annual or perennial herb; leaves various"	23
23	"Bracts subtending flowers dry, scarious; plants neither fleshy nor with powdery or beaded surface; habitats generally not saline"	Amaranthaceae
23	"Bracts subtending flowers leaf-like or fleshy; plants often fleshy or with powdery or beaded surface; habitats often +- saline"	24
24	"Sepals pink or white, papery; plant from rhizome"	"Amaranthaceae {Nitrophila}"
24	"Sepals green or +- red-tinged, herbaceous; rhizome 0"	Chenopodiaceae
25	"Plant aquatic, raft-like, floating on water surface or stranded on shoreline --- leaves in rosettes, wedge-shaped, sessile, velvety; flowers enclosed by small, sheathing bracts"	"Araceae {Pistia}"
25	"Plant terrestrial or rooted in shallow water"	26
26	"Inflorescence a +- fleshy spike enclosed by a large, basally sheathing, often petal-like bract; petiole stout"	Araceae
26	"Inflorescence various but not a fleshy spike subtended by a sheathing bract; leaves sessile or +- slender-petioled"	27
27	"Leaves with stipules, generally well developed"	28
27	"Leaves without stipules, sometimes reduced to scale-like bracts"	35
28	"Style 1, unbranched, or stigma sessile"	29
28	"Styles or stigmas 2 or more"	30
29	"Ovule 1; fruit an achene"	Rosaceae
29	"Ovules several to many; fruit a capsule --- late season cleistogamous flowers formed in most _Viola_ species"	"Violaceae {Viola}"
30	"Leaves palmately compound"	"Cannabaceae {Cannabis}"
30	"Leaves simple, entire to lobed"	31
31	"Plant a vine, stems twining"	32
31	"Plant prostrate to erect, stems not twining"	33
32	"Leaves toothed, at least the proximal also palmately lobed"	"Cannabaceae {Humulus}"
32	"Leaves entire"	"Polygonaceae {Fallopia}"
33	"Stipules fused into a membranous sheath [ocrea] around stem, the sheath sometimes torn or shredded as branches develop"	Polygonaceae
33	"Stipules free, not fused around stem, not torn or shredded as branches develop"	34
34	"Annual; stems prostrate; stinging hairs 0; flowers bisexual"	"Caryophyllaceae {Herniaria}"
34	"Perennial herb; stems spreading to erect; stinging hairs present; flowers unisexual"	"Euphorbiaceae {Tragia}"
35	"Inflorescence flower-like with a cup-like involucre bearing 1--4(5) nectary glands that sometimes have flattened, white to +- pink, petal-like, marginal appendages --- stamens [actually staminate flowers] each with a jointed stalk [composed of a filament and a pedicel], pistillate flower 1, generally exserted from involucre, ovary 3-lobed"	Euphorbiaceae
35	"Inflorescence not flower-like or with a cup-like, nectary-gland-bearing involucre"	36
36	"Perianth parts 4 or 6, +- petal-like"	37
36	"Perianth parts <= 5, sometimes 0, generally not petal-like"	38
37	"Perianth parts 4 or 6, free; stigmas 1--many, generally sessile; fruit a capsule --- sepals actually present in bud, but early-deciduous, 0 in open flower"	Papaveraceae
37	"Perianth parts 6, proximally fused; stigmas 3, at tips of slender styles; fruit a 3-angled achene"	Polygonaceae
38	"Leaves all basal, palmately compound; leaflets 3; perianth 0"	"Berberidaceae {Achlys}"
38	"Leaves cauline, simple; perianth generally present"	39
39	"Ovule 1; inflorescences various"	40
39	"Ovules 2--many; inflorescence generally a raceme (spike, axillary cluster)"	44
40	"Herbage +- densely covered with branched hairs"	41
40	"Herbage glabrous or +- hairy, hairs not branched"	42
41	"Flowers bisexual; hairs soft, irregularly branched, branches all short; fruit indehiscent --- leaf arrangement variable, often difficult to interpret"	"Amaranthaceae {Tidestromia}"
41	"Flowers unisexual; hairs harshly stellate, central branches often long, spreading, bristle-like; fruit dehiscent"	"Euphorbiaceae {Croton setiger}"
42	"Stigma 1"	Urticaceae
42	"Stigmas 2--4"	43
43	"Bracts subtending flowers scarious-margined or dry and scarious throughout"	Amaranthaceae
43	"Bracts subtending flowers 0 or not scarious or scarious-margined"	Chenopodiaceae
44	"Flowers unisexual"	Euphorbiaceae
44	"Flowers bisexual"	45
45	"Plant red- and white-striped, non-photosynthetic, green pigment 0"	"Ericaceae {Allotropa}"
45	"Plant green and photosynthetic"	46
46	"Sepals 4"	Brassicaceae
46	"Sepals 5"	47
47	"Stems +- erect, <= 3(7) m; leaf 6--36 cm; flowers many in spike or raceme; fruit a berry, chambers 5--12; perianth radial"	"Phytolaccaceae {Phytolacca}"
47	"Stems +- decumbent, 0.5--3.5 dm; leaf <= 6 cm; flowers 1--few in raceme; fruit a capsule; chambers 2; perianth bilateral --- some flowers often +- cleistogamous"	"Polygalaceae {Polygala}"