Key 1

1	Sepals 4, narrowly oblong; base of abaxial sepal appendiculate; androgynophore present		125 R. angustisepalus
+	Sepals 5, ovate or elliptic, rarely suborbicular; sepals not appendiculate; androgynophore absent.		(2)
2 (1)	Achenes tuberculate or spiny.		(3)
+	Achenes usually smooth, rarely obscurely ridged.		(8)
3 (2)	Achenes spiny.		(4)
+	Achenes tuberculate.		(5)
4 (3)	Basal leaves glabrous; stem leaves similar to basal ones, 3-lobed or undivided; achene spines 0.5--1 mm		121 R. muricatus
+	Basal leaves sparsely puberulent; stem leaves 1- or 2-ternate; achene spines up to 2 mm		122 R. arvensis
5 (3)	Basal leaves ternate or, if simple, 3-cleft; achenes flattened.		(6)
+	Basal leaves simple, undivided; achenes ± ovoid.		(7)
6 (5)	Achene tuberculate along margin only; basal leaves mostly ternate, a few simple, 3-cleft		119 R. sardous
+	Achene tuberculate on whole surface; basal leaves all ternate		120 R. trachycarpus
7 (5)	All stem leaves similar to basal ones, ovate or rhombic; petal nectary pit without a scale; style ca. 0.4 mm		93 R. ficariifolius
+	Upper stem leaves narrowly triangular or lanceolate; petal nectary pit sometimes with a scale; style ca. 0.1 mm		94 R. triangularis
8 (2)	Petals white, 3--5, oblong		95 R. cheirophyllus
+	Petals yellow, usually 5, rarely less or more, usually obovate.		(9)
9 (8)	Carpels black; style absent		92 R. melanogynus
+	Carpels greenish; style usually present (absent in R. sceleratus).		(10)
10 (9)	Achenes bilaterally compressed, flattened, marginate or winged along sutures; petal nectary pit covered by a scale.		(11)
+	Achenes ovoid or obovoid, sometimes slightly bilaterally compressed, but not flattened, neither marginate nor winged along sutures.		(44)
11 (10)	Achenes strongly bilaterally compressed, papery, winged along sutures; basal leaves pinnate.		(12)
+	Achenes thicker, not papery, narrowly marginate along sutures; basal leaves simple or 1- or 2-ternate.		(13)
12 (11)	Persistent style slightly curved		123 R. platyspermus
+	Persistent style hooked		124 R. regelianus
13 (11)	Flowers leaf-opposed; stems often prostrate.		(14)
+	Flowers terminal, solitary or 2 or more in monochasium; stems usually erect.		(15)
14 (13)	Sepals spreading; basal leaves ternate or simple		112 R. diffusus
+	Sepals reflexed; basal leaves all ternate		113 R. sieboldii
15 (13)	Basal leaves ternate.		(16)
+	Basal leaves simple, palmatipartite or palmatisect.		(23)
16 (15)	Receptacle glabrous		96 R. japonicus
+	Receptacle hairy.		(17)
17 (16)	Stolons present		117 R. repens
+	Stolons absent.		(18)
18 (17)	Aggregate fruit cylindric		118 R. chinensis
+	Aggregate fruit globose.		(19)
19 (18)	Flower solitary; carpels 10--17		111 R. sinovaginatus
+	Flowers 2--10 in monochasium; carpels many.		(20)
20 (19)	Sepals spreading		108 R. trigonus
+	Sepals reflexed.		(21)
21 (20)	Persistent style hooked		115 R. silerifolius
+	Persistent style straight or slightly curved.		(22)
22 (21)	Basal leaves 1-ternate		114 R. cantoniensis
+	Basal leaves 2-ternate		116 R. tachiroei
23 (15)	Basal leaves 3-sect.		(24)
+	Basal leaves 3-partite.		(30)
24 (23)	Receptacle glabrous.		(25)
+	Receptacle hairy.		(27)
25 (24)	Rhizomes conspicuous, terete		101 R. grandifolius
+	Rhizomes very short, inconspicuous.		(26)
26 (25)	Stems spreading hispid; stem leaves simple, 3-partite, rarely 3-sect, segments lobed; style nearly absent or very short, up to 0.2 mm		96 R. japonicus
+	Stems strigose; stem leaves ternate, or simple, 3-sect, segments dissected; style ca. 0.4 mm, recurved		111 R. sinovaginatus
27 (24)	Sepals reflexed; carpels 10--17		111 R. sinovaginatus
+	Sepals spreading; carpels many.		(28)
28 (27)	Segments of basal leaves lobed, ultimate lobes ovate or triangular		108 R. trigonus
+	Segments of basal leaves 2 or 3 × dissected, ultimate lobes linear-lanceolate, rarely ovate.		(29)
29 (28)	Persistent style straight or slightly curved		109 R. meyerianus
+	Persistent style hooked		110 R. polyanthemos
30 (23)	Receptacle hairy.		(31)
+	Receptacle glabrous.		(32)
31 (30)	Petal 9--10 × 5--9 mm		102 R. submarginatus
+	Petal 3.2--8 × 1.6--4 mm		108 R. trigonus
32 (30)	Stolons present		103 R. grandis
+	Stolons absent.		(33)
33 (32)	Basal leaf blades broadly cuneate or truncate at base.		(34)
+	Basal leaf blades cordate at base.		(36)
34 (33)	Basal leaf blades broadly rhombic, base broadly cuneate		107 R. cuneifolius
+	Basal leaf blades pentagonal, base truncate, subtruncate, or rarely broadly cuneate.		(35)
35 (34)	Stems 20--45 cm, with 2 or 3 stem leaves; basal leaves 1.8--4.5 cm wide; petal 7--10 × 4.5--6 mm		105 R. kunmingensis
+	Stems ca. 70 cm, with ca. 8 stem leaves; basal leaves ca. 10 cm wide; petal ca. 13 × 8--10 mm		106 R. changpingensis
36 (33)	Rhizomes conspicuous.		(37)
+	Rhizomes very short, inconspicuous.		(39)
37 (36)	Rhizomes tuberlike; petals 8--10 mm		98 R. smirnovii
+	Rhizomes subterete; petals up to 14 mm.		(38)
38 (37)	Basal leaves up to 7.8 cm wide; achenes ca. 2.2 mm		99 R. distans
+	Basal leaves up to 11 cm wide; achenes ca. 3.5 mm		101 R. grandifolius
39 (36)	Stems and petioles of basal leaves strigose.		(40)
+	Stems and petioles of basal leaves spreading hispid.		(41)
40 (39)	Uppermost stem leaf 3-sect, segments linear, other stem leaves not dissected, ultimate lobes ovate or triangular; nearly all carpels maturing into achenes		96 R. japonicus
+	Stem leaves 2 or 3 × dissected, ultimate lobes linear; only 1--10 carpels per flower maturing into achenes		100 R. paishanensis
41 (39)	Upper stem leaves abaxially densely silvery strigose		96 R. japonicus
+	Stem leaves abaxially sparsely white strigose.		(42)
42 (41)	Stems solid; basal leaves 2.8(--4) cm wide; flowers 5--8.5 mm in diam.; petals 2.2--5 × 1.6--2.2 mm		97 R. taisanensis
+	Stems hollow; basal leaves 5--10(--16) cm wide; flowers 14--24 mm in diam.; petals 7--12 × 5.5--8.5 mm.		(43)
43 (42)	Styles nearly absent or very short, up to 0.2 mm, straight or slightly recurved; central lobe of basal leaf obovoid-obtrapeziform, not constricted at base		96 R. japonicus
+	Styles ca. 0.5 mm, circinate at apex; central lobe of basal leaf rhombic-obovate, slightly constricted at base		104 R. borealis
44 (10)	Carpels and achenes stalked		90 R. podocarpus
+	Carpels and achenes sessile.		(45)
45 (44)	Carpel without a style, with a small stigma at top of ovary; achenes with 2 or 3 inconspicuous transverse wrinkles, somewhat turgid along sutures; aggregate fruit conspicuously elongated, more than 2 × as long as wide		91 R. sceleratus
+	Carpel ± with a style, without a stigma but with inconspicuous stigmatic tissue on ventral surface of style; achenes smooth, not turgid along sutures; aggregate fruit globose to ovoid, usually less than 2 × as long as broad.		(46)
46 (45)	Roots tuberous		89 R. ternatus
+	Roots fibrous, sometimes thickened at base, but not tuberous.		(47)
47 (46)	Basal leaves absent after anthesis or, if present, subsessile, linear, linear-lanceolate or narrowly spatulate with tapered base; stem leaves subsessile, entire, lanceolate or lanceolate-linear.		(48)
+	Basal leaves present after anthesis, clearly petiolate; stem leaves usually palmatifid.		(50)
48 (47)	Plants conspicuously stoloniferous; basal leaves present after anthesis		88 R. reptans
+	Plants ascending, not conspicuously stoloniferous; basal leaves withering at anthesis.		(49)
49 (48)	Stems ca. 10 mm thick; leaves 7--10 mm wide; flowers 3 or 4 in terminal compound monochasium, 2.7--3.8 cm in diam.; achenes 2--3 mm		86 R. lingua
+	Stems slender; stem leaves 3--5(--7) mm wide; flowers solitary, 1--2.5 cm in diam., achenes ca. 1.8 mm		87 R. amurensis
50 (47)	Herbs small, annual; stamens 4.		(51)
+	Herbs perennial, with short rhizomes; stamens usually many, rarely 4--10.		(52)
51 (50)	Stems leafless, ca. 3.5 cm; petals 3--3.8 mm, with 3 colorless veins; style longer than ovary		80 R. tetrandrus
+	Stems 1- or 2-leaved, longer; petals 1.5--2.5 mm, with 3 blue veins; style less than 1/2 as long as ovary		81 R. muscigenus
52 (52)	Blade of basal leaf divided		(52)
+	Blade of basal leaf not divided.		(53)
53 (52)	Basal leaves entire, or (in R. densiciliatus, R. yechengensis, R. nephelogenes and R. membranaceus) sometimes 1--2-dentate near apex; flowers solitary, terminal.		(54)
+	Basal leaves with 3 or more teeth at margin.		(58)
54 (53)	Leaf blade hairy.		(55)
+	Leaf blade glabrous.		(56)
55 (54)	Basal leaves ovate, elliptic, or suborbicular, abaxially glabrous, adaxially sparsely puberulent, margin densely appressed ciliate; stems and leaves drying blackish		53 R. densiciliatus
+	Basal leaves linear, oblong, or lanceolate, hairy or adaxially glabrous, margin not ciliate; stems and leaves not drying blackish		57 R. membranaceus
56 (54)	Petal apex rounded; leaf blade of basal leaf ovate, narrowly ovate, oblong, or linear-lanceolate		56 R. nephelogenes
+	Petal apex emarginate.		(57)
57 (56)	Petal 9--11 × 6.5--8.5 mm; blade of basal leaf obovate or cuneate, 5--14 × 4--11 mm, margin 1-denticulate on each side; receptacle conic, ca. 2 mm high; stems 3--5 cm		54 R. yechengensis
+	Petal 5.5--7 × 3.5--4 mm; blade of basal leaf ovate, orbicular-ovate, or elliptic, 2.5--5 × 2--3 mm, margin entire; receptacle hemispheric, ca. 0.5 mm high; stems 1.5--2 cm		55 R. humillimus
58 (53)	Carpels and achenes puberulent.		(59)
+	Carpels and achenes glabrous.		(64)
59 (58)	Basal leaves spatulate or subtrapeziform or obovate, base cuneate, 3--5-dentate at apex or 3--5-crenate on each side		(60)
+	Basal leaves suborbicular or flabellate, base broadly cuneate, rounded, subtruncate, or subcordate; flowers solitary, terminal.		(61)
60 (59)	Basal leaf margin rounded-dentate to crenate near apex; flowers 2 or 3 in a monochasium; petals 5--10 × 4--7 mm		66 R. yunnanensis
+	Basal leaf margin dentate; flower solitary; petals ca. 4 × 2.5 mm		65 R. wangianus
61 (59)	Leaf blade leathery, suborbicular, base rounded or broadly cuneate, margin 5-crenate		73 R. pseudolobatus
+	Leaf blade papery.		(62)
62 (61)	Basal leaves flabellate or oblate, margin 5--7-dentate		64 R. felixii
+	Basal leaves ovate.		(63)
63 (62)	Stems 3--10 cm; blades of basal leaves with base rounded or broadly cuneate, apex acute, margin ciliate, each side 1--3-denticulate		52 R. kunlunshanicus
+	Stems 8--36 cm; blades of basal leaves with base truncate or subcordate at base, apex obtuse or rounded, margin glabrous, each side 2--5-dentate		77 R. indivisus
64 (58)	Blades of basal leaves longer than broad, spatulate or ovate.		(65)
+	Blades of basal leaves broader than long, oblate, subreniform, orbicular-ovate, or depressed deltoid.		(68)
65 (64)	Petals 7; blades of basal leaves spatulate, cuneate, or cuneate-obovate		67 R. altaicus
+	Petals 5(or 6); blades of basal leaves broadly ovate, trapeziform-ovate, ovate, elliptic, or obovate		(66)
66 (65)	Petals narrowly oblong or oblong-oblanceolate, 8 × 2 mm		74 R. hetianensis
+	Petals obovate.		(67)
67 (66)	Stems 15--20 cm; blades of basal leaves ovate, elliptic, or obovate, base broadly cuneate or cuneate, 1--3-denticulate on each side		51 R. pulchellus
+	Stems 4--8.5 cm; blades of basal leaves broadly ovate or trapeziform-ovate, base rounded or truncate, 3--5-dentate at or near apex		76 R. lobatus
68 (64)	Basal leaves up to 1.6 cm wide; flower 0.8--1.4 cm in diam.		(69)
+	Basal leaves up to 3--3.5 cm wide, glabrous; flower 1.5--2.8 cm in diam.		(70)
69 (68)	Stems 5--11.5 cm, puberulent; basal leaves papery; stem leaves 3-lobed to 3-sect; flower 0.8--1.2 cm in diam.; carpel not winged		78 R. nyalamensis
+	Stems 1.5--5 cm, glabrous; basal leaves leathery, glabrous; stem leaves undivided; flower 1.2--1.4 cm in diam.; carpel winged along sutures		79 R. similis
70 (68)	Sepals abaxially yellowish puberulent		60 R. albertii
+	Sepals abaxially black-brown puberulent.		(71)
71 (70)	Blades of basal leaves papery, indistinctly 3-lobed, margin glabrous		61 R. transiliensis
+	Blades of basal leaves thinly leathery, unlobed, margin ciliate		62 R. fraternus