1	"Leaves generally simple, unlobed"	2
1	"Leaves deeply lobed or compound (except basal leaves of <i>Ranunculus glaberrimus</i>)"	14
2	"Petals 1--3, 1.5--2.5 mm, +- = sepals; fruit body 1--1.8 mm, beak 0 or < 0.1 mm"	3
2	"Petals 4--12, 2--14 mm, generally >= sepals; fruit body 1--4.2 mm, beak 0.1--1.4 mm."	4
3	"Bracts elliptic to ovate; sepals 3"	"Ranunculus bonariensis var. trisepalus"
3	"Bracts linear to lanceolate or oblanceolate; sepals 4--5"	"Ranunculus pusillus"
4	"Stems erect, decumbent, or prostrate, generally rooting at nodes"	5
4	"Stems erect or ascending, not rooting at nodes"	9
5	"Fruit wall papery, longitudinally ribbed; leaf tip rounded, margin crenate to crenate-serrate"	"Ranunculus cymbalaria"
5	"Fruit wall thick, smooth (occasionally hairy); leaf tip acute, acuminate, or rounded-obtuse to thread-like, margin entire or finely toothed"	6
6	"Lower cauline leaf blade lanceolate to oblanceolate or linear"	7
6	"Lower cauline leaf blade generally ovate"	8
7	"Stems erect to prostrate; sepals 3--4 mm; petals 5--7 mm, 3--4 mm wide"	"Ranunculus flammula var. flammula"
7	"Stems prostrate, occasionally ascending; sepals 2--3 mm; petals 3--5 mm, 2--3 mm wide"	"Ranunculus flammula var. ovalis"
8	"Root fusiform-thickened proximally; KR"	"Ranunculus gormanii"
8	"Root not thickened; SNE"	"Ranunculus hydrocharoides"
9	"Sepals white or pale yellow, 6--13 mm, 3--6 mm wide; petals 8--12, 2--4 mm, +- green; basal leaves shallowly lobed, cauline leaves 0--2, scale-like, unlobed"	"Ranunculus hystriculus"
9	"Sepals green, 2--6 mm, 1--4 mm wide; petals 4--6(8), 4--14 mm, yellow; basal leaves unlobed, not differentiated from cauline, cauline unlobed, at least lower large, petioled, not scale-like"	10
10	"Basal leaf bases cordate to obtuse"	"Ranunculus populago"
10	"Basal leaf bases acute"	11
11	"Leaf blade ovate or elliptic"	"Ranunculus alismifolius var. alismellus"
11	"Leaf blade lanceolate"	12
12	"Leaves minutely serrate; stem 3.5--8 mm diam"	"Ranunculus alismifolius var. alismifolius"
12	"Leaves entire; stem 1--3 mm diam"	13
13	"Petals 6--8 mm; root not or +- fusiform-thickened proximally"	"Ranunculus alismifolius var. hartwegii"
13	"Petals 10--14 mm; root generally fusiform-thickened proximally"	"Ranunculus alismifolius var. lemmonii"
14	"Stems prostrate to decumbent or creeping, rooting at nodes, or floating in water, rootless."	15
14	"Stems erect to ascending or decumbent (prostrate), generally not rooting at nodes, not floating, occasionally decumbent, rooting only at lowest nodes"	19
15	"Leaves 1-ternate; meadows, road banks, disturbed places, edges of marshes, streams"	"Ranunculus repens"
15	"Leaves lobed, parted, or dissected into thread-like segments; aquatic or on drying mud"	16
16	"Petals yellow; fruit smooth"	"Ranunculus flabellaris"
16	"Petals white, or only claws yellow; fruit strongly wrinkled"	17
17	"Receptacle glabrous; style 1--1.5 mm; achenes 2--6, bodies 2--2.4 mm; submersed leaves generally 2--3-dissected; annual"	"Ranunculus lobbii"
17	"Receptacle bristly; style 0.2--1.2 mm; achenes 15--many, bodies 1--2 mm; submersed leaves generally 3--6-dissected; perennial herb"	18
18	"Floating leaves 0 or reniform, 3-parted, segments obovate or fan-shaped, submersed leaves dissected into thread-like segments"	"Ranunculus aquatilis var. aquatilis"
18	"Floating and submersed leaves dissected into thread-like segments"	"Ranunculus aquatilis var. diffusus"
19	"Style 0; fruit margins thick, corky; plant emergent aquatic, occasionally on mud"	20
19	"Style present; fruit margins ridged to narrowly winged, or differentiated margins not evident; plant on wet or dry soil"	21
20	"Fruit faces smooth; leaves parted, generally deeply, segments lobed or parted, deeply crenate or again lobed"	"Ranunculus sceleratus var. multifidus"
20	"Fruit faces finely transversely wrinkled; leaves lobed or parted, segments undivided or lobed, crenate"	"Ranunculus sceleratus var. sceleratus"
21	"Fruit wall papery, inflated; petals +- pink-white"	"Ranunculus andersonii"
21	"Fruit wall thick, not inflated; petals yellow, occasionally +- purple abaxially"	22
22	"Cauline leaves 0; fruit beak >> body"	"Ranunculus testiculatus"
22	"Cauline leaves well developed; fruit beak generally < body"	23
23	"Fruit lenticular, width 1--2 &times; depth; stem glabrous"	24
23	"Fruit disk-like, width 3--15 &times; depth; stem hairy or glabrous"	28
24	"Basal leaves entire or with 3 wide, rounded teeth distally"	25
24	"Basal leaves 3--9-lobed or 3-parted"	26
25	"Basal leaves elliptic to very narrowly elliptic, entire (or with 3 wide, rounded teeth distally); bract lobes 3, middle >> lateral"	"Ranunculus glaberrimus var. ellipticus"
25	"Basal leaves ovate to obovate or reniform, with 3 wide, rounded, teeth distally (or entire); bract lobes 3, equal"	"Ranunculus glaberrimus var. glaberrimus"
26	"Ultimate leaf segments acute to acuminate"	"Ranunculus eschscholtzii var. suksdorfii"
26	"Ultimate leaf segments rounded, obtuse, or widely rounded-acute"	27
27	"Persistent leaf bases on caudex 0--few; basal leaves 3-parted"	"Ranunculus eschscholtzii var. eschscholtzii"
27	"Persistent leaf bases on caudex many; basal leaves shallowly 5--9-lobed or occasionally 3-parted"	"Ranunculus eschscholtzii var. oxynotus"
28	"Fruit faces papillate or spiny"	29
28	"Fruit faces smooth"	34
29	"Petals 1--2 mm; fruit faces papillate, each papilla tipped with hooked bristle"	30
29	"Petals 4--10 mm; fruit faces generally papillate or spiny, hooked bristles 0"	31
30	"Fruit ornamented on faces, margins, beaks lanceolate"	"Ranunculus hebecarpus"
30	"Fruit ornamented on faces, not margins, beaks deltate"	"Ranunculus parviflorus"
31	"Fruit spiny"	"Ranunculus arvensis"
31	"Fruit papillate or tubercled (smooth)"	32
32	"Basal leaves simple; fruit beak 2--2.5 mm"	"Ranunculus muricatus"
32	"Basal leaves 1--2 ternate; fruit beak 0.3--0.7 mm"	33
33	"Petals 7--10 mm; fruit beak 0.4--0.7 mm"	"Ranunculus sardous"
33	"Petals 4--5 mm; fruit beak +- 0.3 mm"	"Ranunculus trilobus"
34	"Petals 2--6 mm, +- = sepals"	35
34	"Petals 5--26 mm, if 5--6 mm then >> sepals"	36
35	"Petals 4--6 mm; basal leaves 1-ternate"	"Ranunculus macounii"
35	"Petals 2--4(6) mm; basal leaves 3-parted, occasionally 1-ternate"	"Ranunculus uncinatus"
36	"Sepals spreading"	"Ranunculus acris"
36	"Sepals reflexed 1--3 mm from base"	37
37	"Petals 9--17"	38
37	"Petals 5--7"	40
38	"Fruit body 3.4--4.2 mm, beak deltate"	"Ranunculus canus var. ludovicianus"
38	"Fruit body 1.8--3.2 mm, beak lanceolate"	39
39	"Stem erect to decumbent, glabrous or spreading-hairy; ultimate segments of basal leaves acute to rounded-acute"	"Ranunculus californicus var. californicus"
39	"Stem prostrate, strigose; ultimate segments of basal leaves rounded to obtuse"	"Ranunculus californicus var. cuneatus"
40	"Fruit beak straight"	41
40	"Fruit beak curved or tip hooked"	45
41	"Receptacle glabrous"	42
41	"Receptacle bristly"	43
42	"Ultimate leaf segments lanceolate to oblanceolate"	"Ranunculus occidentalis var. dissectus"
42	"Ultimate leaf segments narrowly elliptic"	"Ranunculus occidentalis var. howellii"
43	"Basal leaves simple to compound, leaflets 0 or 3, undivided, crenate; petals notched"	"Ranunculus orthorhynchus var. bloomeri"
43	"Basal leaves compound, leaflets 3--5, lobed or parted, entire, dentate, or dentate-lobed; petals rounded"	44
44	"Fruit aggregate hemispheric, occasionally spheric, 5--7 mm; petals generally red abaxially"	"Ranunculus orthorhynchus var. orthorhynchus"
44	"Fruit aggregate spheric or ovoid, 8--13 mm; petals yellow abaxially"	"Ranunculus orthorhynchus var. platyphyllus"
45	"Base of stem bulbous, corm-like"	"Ranunculus bulbosus"
45	"Base of stem not enlarged"	46
46	"Receptacle long-hairy; fruit wall coarsely papillate (smooth), beak 0.4--0.7 mm"	"Ranunculus sardous"
46	"Receptacle glabrous; fruit wall generally smooth, beak 0.2--1.4 mm"	47
47	"Fruit beak deltate, body 3.4--4.4 mm"	"Ranunculus canus var. canus"
47	"Fruit beak lanceolate, body 2.6--3.6(4) mm"	48
48	"Petals 3--6 mm wide; 0--1500 m"	"Ranunculus occidentalis var. occidentalis"
48	"Petals 1.5--2.5 mm wide; 1300--2500 m"	"Ranunculus occidentalis var. ultramontanus"