1	"Plant fully aquatic, submersed, floating in water, or stranded on mud"	2
1	"Plant terrestrial or parasitic on stem of woody host, or if growing in wet habitat, rooted in place and emerging well above water surface"	12
2	"Plant generally free-floating at or just below water surface, raft-like, the plant body 0.4--10 mm; leaves and stems not differentiated; roots 0--few, unbranched --- pistil located in tiny lateral, membrane-covered pouch or in minute cavity on top of plant body"	Araceae
2	"Plant rooted in bottom sediments or free-floating, generally >> 15 mm; leaves and stems clearly differentiated; roots often branched"	3
3	"Leaves alternate"	4
3	"Leaves opposite or whorled or all basal"	6
4	"Fruits borne in umbel-like clusters --- flowers actually bisexual but stamens easily overlooked and ephemeral"	"Ruppiaceae {Ruppia}"
4	"Fruits or flowers borne in spikes or heads"	5
5	"Flowers in dense, spheric heads, these solitary or in axillary or terminal clusters, not enclosed in leaf sheaths; freshwater habitats"	"Typhaceae {Sparganium}"
5	"Flowers in axillary spikes, these generally enclosed and concealed in sheaths of subtending leaves; marine habitats"	Zosteraceae
6	"Leaves all basal; flowers solitary in leaf-axils; style very elongated, generally 6--20 cm"	"Juncaginaceae {Triglochin scilloides}"
6	"Leaves cauline; flowers axillary or variously clustered; styles generally << 6 cm (except in some Hydrocharitaceae)"	7
7	"Leaf blades [at least those of submersed leaves] divided into linear or thread-like lobes"	8
7	"Leaf blades entire, toothed, or shallowly lobed"	9
8	"Blades of leaves repeatedly forked"	"Ceratophyllaceae {Ceratophyllum demersum}"
8	"Blades of leaves pinnately forked"	"Haloragaceae {Myriophyllum}"
9	"Petals and sepals both 3(4), evident; perianth and stigmas borne at water surface at end of long, tubular hypanthium; ovary inferior, sessile in leaf axil"	Hydrocharitaceae
9	"Petals and sepals both 0; stigmas submersed, borne at end of short styles; ovary or ovaries superior, sessile or short-stalked in leaf axil"	10
10	"Pistils 2--10, simple, each with a cup-like stigma; leaves entire"	"Zannichelliaceae {Zannichellia palustris}"
10	"Pistil 1, compound, bearing 2--4 slender stigmas"	11
11	"Leaves subentire to finely or coarsely toothed; ovary chamber 1, ovule 1; fruit achene-like"	"Hydrocharitaceae {Najas}"
11	"Leaves entire; ovary chambers 4, ovules 4; fruit splitting into 4 nutlets"	"Plantaginaceae {Callitriche}"
12	"Plants parasitic on stems of woody host plants"	13
12	"Plants free-living"	14
13	"Flowers of parasite borne directly on stems of host; remainder of parasite internal within tissues of host; stems and leaves not differentiated; on _Psorothamnus_"	"Apodanthaceae {Pilostyles thurberi}"
13	"Flowers borne on leafy branches of parasite; shoots of parasite external; leaves differentiated, though sometimes reduced to scales; on various woody hosts [not _Psorothamnus_]"	Viscaceae
14	"Stem fleshy, bearing spiny tubercles; leaves 0"	"Cactaceae {Mammillaria dioica}"
14	"Stem generally not fleshy, without spiny tubercles; leaves generally present"	15
15	"Leaves opposite or whorled, not all basal"	16
15	"Leaves alternate or all basal"	24
16	"Stems or leaves thick and fleshy; inflorescence a terminal spike"	17
16	"Stems and leaves of normal texture, not thick and fleshy; inflorescence various"	18
17	"Leaves +- cylindric or 3-angled in &times;-section; stigma 1, head-like, 2-lobed; ovary chambers 4; ovaries joining into a fleshy multiple fruit; perianth 0"	"Bataceae {Batis maritima}"
17	"Leaves fleshy, scale-like; stigmas 2, linear; ovary chamber 1; ovaries maturing as utricles, sometimes surrounded by fleshy bracts and perianth elements"	Chenopodiaceae
18	"Leaves compound or deeply lobed, or also some simple"	19
18	"Leaves simple, entire or toothed"	20
19	"Compound leaves palmate"	Cannabaceae
19	"Compound or deeply lobed leaves pinnate"	"Valerianaceae {Valeriana occidentalis}"
20	"Leaves whorled; ovary inferior"	"Rubiaceae {Galium}"
20	"Leaves opposite; ovary superior"	21
21	"Leaves sessile or nearly so, entire; petals free"	Caryophyllaceae
21	"Leaves conspicuously petioled, toothed; petals fused or 0"	22
22	"Corolla showy, bilateral"	Lamiaceae
22	"Corolla 0"	23
23	"Styles 2, ovary 2-chambered; stinging hairs 0"	"Euphorbiaceae {Mercurialis}"
23	"Style 0 or 1, ovary 1-chambered; stinging hairs present or 0"	Urticaceae
24	"Leaves stiff and sword-like, 0.5--1.5 m; inflorescence a large panicle; perianth parts 6"	"Ruscaceae {Nolina}"
24	"Leaves not sword-like, often smaller; inflorescences various; perianth parts mostly other than 6"	25
25	"Blades of leaves linear or narrowly lanceolate, simple and entire; veins parallel; leaf bases sheathing stem"	26
25	"Blades of leaves variously shaped, sometimes toothed, lobed, or compound; veins mostly pinnate or palmate; leaf bases often not sheathing stems --- flowers not in spikelets"	28
26	"Leaves all basal; flowers solitary in leaf axils; styles very elongated, generally 6--20 cm"	"Juncaginaceae {Triglochin scilloides}"
26	"Leaves basal and cauline or all cauline; flowers in spikes or spikelets, these generally in 2&deg; clusters; styles generally << 5 cm"	27
27	"Stem triangular; nodes not swollen; leaf blades channeled"	Cyperaceae
27	"Stem round; nodes generally swollen and knot-like; leaf blades generally flat"	Poaceae
28	"Ocreae present, persistent or not; nodes generally +- swollen"	Polygonaceae
28	"Ocreae 0; nodes generally not swollen"	29
29	"Leaves all basal"	30
29	"At least some leaves cauline"	33
30	"Leaves compound, leaflets 3; perianth parts in 5s; stolons present"	"Rosaceae {Fragaria}"
30	"Leaves simple, entire; perianth parts in 3s or 4s; stolons 0"	31
31	"Perianth parts in 4s; fruit a circumscissile capsule"	"Plantaginaceae {Plantago}"
31	"Perianth parts in 3s; fruit 1--many achenes"	32
32	"Perianth clearly differentiated into sepals and petals; pistils many; plant +- emergent aquatic, annual or perennial herb"	"Alismataceae {Sagittaria}"
32	"Perianth whorls not strongly differentiated, outer and inner similar; pistil 1; plant terrestrial matted per"	"Polygonaceae {Eriogonum}"
33	"Plants vines"	34
33	"Plants prostrate to erect herbs"	36
34	"Tendrils 0; perianth not at all corolla-like; ovary superior"	"Cannabaceae {Humulus}"
34	"Tendrils present; perianth corolla-like"	35
35	"Ovary inferior"	Cucurbitaceae
35	"Ovary superior"	"Smilacaceae {Smilax}"
36	"Pistils 2--22, simple; fruit a cluster of achenes or follicles"	37
36	"Pistil 1, simple or compound; fruit achene, utricle, capsule, or splitting into 2--13 mericarps"	39
37	"Leaves simple, fleshy"	"Crassulaceae {Rhodiola}"
37	"Leaves compound, leaflets thin"	38
38	"Leaflets coarsely crenate or shallowly lobed; sepals generally 4; petals 0; inflorescence an open panicle"	"Ranunculaceae {Thalictrum}"
38	"Leaflets 2-serrate; sepals 5; petals 5; inflorescence a panicle of dense spikes"	"Rosaceae {Aruncus}"
39	"Flowers in umbels or heads"	40
39	"Flowers solitary or in axillary clusters or in racemes or panicles"	43
40	"Inflorescence a simple or compound umbel"	Apiaceae
40	"Inflorescence of 1 or more heads"	41
41	"Head maturing as bur enclosing 1--5 fruits"	Asteraceae
41	"Head not maturing as bur"	42
42	"Corolla 0; head without involucre; ovary superior"	Chenopodiaceae
42	"Corolla tubular; head subtended by an involucre; ovary inferior"	Asteraceae
43	"Style branches 5--19; fruit splitting into 5--19 wedge-shaped mericarps at maturity"	Malvaceae
43	"Style unbranched or branches 2 or 3 (dissected into linear lobes in _Croton_); fruit unsegmented or splitting into 2--3 segments"	44
44	"Leaves palmately compound, leaflets serrate"	"Cannabaceae {Cannabis}"
44	"Leaves entire or toothed"	45
45	"Leaves densely stellate-scaly or -hairy; ovary chambers generally 3; fruit a capsule"	"Euphorbiaceae {Croton}"
45	"Leaves not stellate-hairy; ovary chamber 1; fruit an achene or utricle"	46
46	"Bractlets subtending flower 3, winged, abaxially bearing hooked hairs; stigma 1, sessile, hair-tufted; sepals 4, fused"	"Urticaceae {Soleirolia}"
46	"Bractlets subtending flower 1--2, without hooked hairs; stigmas 2, linear; sepals 0 or 3--5, free"	47
47	"Flower enclosed between a pair of bractlets; sepals generally 0; leaves generally bearing bead-like, sessile hairs or powdery scales"	"Chenopodiaceae {Atriplex}"
47	"Flower not enclosed by a pair of bractlets; sepals 3--5; leaves glabrous or glaucous"	"Amaranthaceae {Amaranthus}"