1	Glomerules all axillary on normal leaf branches; male flowers 4-merous; leaves alternate.		1 B. glomerulifera
+	Glomerules all or partly arranged on specialized slender flowering branches; male flowers (3-)4-5-merous; leaves alternate or opposite.		(2)
2 (1)	Male glomerules in axils of foliage leaves, female glomerules on specialized long spikelike shoots in terminal and subterminal axils; male flowers 4-5-merous, pedicel 2-5 mm.		3 B. zollingeriana
+	Glomerules all arranged on specialized slender flowering shoots, rarely simply axillary; male flowers 4-merous, pedicel very short to absent.		(3)
3 (2)	Flowering shoots with tuft of foliage leaves at apex.		(4)
+	Flowering shoots without tuft of leaves at apex (except rarely in B. silvestrii).		(5)
4 (3)	Leaves not lobed, apex acuminate or caudate.		4 B. clidemioides
+	Leaves lobed, apex cuspidate.		5 B. umbrosa
5 (3)	Flowering shoots branched; leaves alternate or opposite.		(6)
+	Flowering shoots usually unbranched, sometimes loosely branched at base; leaves opposite, seldom alternate in distal part of stem (only in B. allophylla and B. tricuspis).		(8)
6 (5)	Flowering shoots in pairs; leaves alternate, abaxially often white tomentose (or strigose in var. tenacissima); achene long stipitate at base.		2 B. nivea
+	Flowering shoots solitary; leaves opposite, glabrous or sparsely strigillose abaxially; achene base obtuse or cuneate.		(7)
7 (6)	Leaf blade elliptic ovate, apex acuminate; flowering shoots with irregular second order branching; achene base narrowly cuneate.		20 B. polystachya
+	Leaf blade ovate-orbicular to suborbicular, apex abruptly caudate; flowering shoots with simple, spikelike branches only; achene base rounded.		21 B. conica
8 (5)	Leaf blade often 3-cusped or 3-lobed, rarely 5-lobed at apex.		(9)
+	Leaf blade not divided at apex.		(12)
9 (8)	Leaf blade often papery, 7-15(-22) cm wide, teeth 10-20 mm.		(10)
+	Leaf blade herbaceous, 1-8(-13) cm wide, teeth less than 10 mm.		(11)
10 (9)	Leaf blade ovate or broadly ovate, apex sometimes inconspicuously tricuspidate, base often broadly cuneate; spikes or rarely few branched at base.		15 B. japonica
+	Leaf blade oblate to 5-angled or oblate to orbicular-ovate, apex often 3-lobed, base often truncate or subcordate; spikes well branched into subpanicle.		16 B. tricuspis
11 (9)	Leaves all opposite, apex 3- or 5-cuspidate, base broadly cuneate to subtruncate, teeth 2-10 mm, sparsely strigose or subglabrous on both surfaces.		17 B. silvestrii
+	Leaves alternate on upper stems, opposite on lower stems, apex tricuspidate, base broadly cuneate, teeth 1-2.5 mm, long appressed hirsute adaxially, pubescent abaxially.		19 B. allophylla
12 (8)	Leaf blade lanceolate or linear-lanceolate.		(13)
+	Leaf blade ovate or suborbicular, rarely sublanceolate (in B. hamiltoniana).		(16)
13 (12)	Leaf blade herbaceous, lanceolate, smooth adaxially, apex caudate or acuminate; female spikes of usually distant glomerules, often branched at base, straight; achene stipitate or very shortly so.		(14)
+	Leaf blade thickly papery, linear-lanceolate, often strongly rugose adaxially, apex tapering to acuminate; female spikes of congested glomerules, simple, nodding; achene long stipitate.		(15)
14 (13)	Leaf blade apex entire, margin dentate; flowering shoots unbranched or with a few short irregular branches near base; achene almost without stipe.		10 B. formosana
+	Leaf blade apex serrulate, margin finely serrulate; female flowering shoot dichotomously forked at lowermost glomerule; achene stipitate.		23 B. ingjiangensis
15 (13)	Leaf blade 14-29 × 2.2-5.5 cm, glabrous or glabrescent adaxially, teeth revolute; female spikes 6-32 cm; perianth tube of female flower 1.6-2.2 mm, apex rounded.		24 B. penduliflora
+	Leaf blade 5-24 × 2-6.4 cm, densely appressed strigillose adaxially, teeth flattened; female spikes 4-18 cm; perianth tube of female flower 1-1.5 mm, apex attenuate.		25 B. densiflora
16 (12)	Flowering shoots branched at base.		(17)
+	Flowering shoots unbranched.		(27)
17 (16)	Shrubs.		(18)
+	Herbs perennial or subshrubs.		(21)
18 (17)	Leaf blade elliptic ovate; flowering shoots with irregular second order branching.		20 B. polystachya
+	Leaf blade oblong, narrowly ovate or oblanceolate; flowering shoots with simple, spikelike branches only.		(19)
19 (18)	Branches glabrous; spikes very slender, to 26 cm.		11 B. hamiltoniana
+	Branches strigose; spikes straight, 4-10 cm.		(20)
20 (19)	Branches dark purplish brown; leaf blade oblong or oblong-lanceolate, apex acuminate, tip denticulate; inflorescence unbranched.		8 B. lanceolata
+	Branches light brown; leaf blade elliptic, apex acuminate, tip entire; inflorescence with shorter branches from base.		9 B. lohuiensis
21 (17)	Leaf margin coarsely 7-14-dentate, teeth gradually larger distally.		15 B. japonica
+	Leaf margin dentate, denticulate, or serrulate, all regular.		(22)
22 (21)	Leaf blade herbaceous or rarely membranous, suborbicular or orbicular-ovate.		(23)
+	Leaf blade usually herbaceous or papery, ovate or oblong.		(25)
23 (22)	Leaf base rounded, patent pubescent abaxially.		6 B. macrophylla
+	Leaf base truncate or cordate, appressed strigose abaxially.		(24)
24 (23)	Leaf blade 6.5-19 × 6-17.5 cm; spikes of distant glomerules to 40 cm.		13 B. dolichostachya
+	Leaf blade 5-9.4 × 5-8 cm; spikes of congested glomerules to 5.5 cm.		14 B. densiglomerata
25 (22)	Leaf blade papery, oblong, apex denticulate.		8 B. lanceolata
+	Leaf blade usually herbaceous, ovate or narrowly ovate, apex entire.		(26)
26 (25)	Leaf margin dentate; achene verrucose.		10 B. formosana
+	Leaf margin denticulate or serrulate; achene smooth.		6 B. macrophylla
27 (16)	Leaf blade ovate-rhombic or rhombic, margin coarsely 3-9-dentate.		18 B. spicata
+	Leaf blade ovate or suborbicular, margin serrulate, crenulate, or denticulate.		(28)
28 (27)	Leaf blade suborbicular.		(29)
+	Leaf blade ovate, rarely also lanceolate (in B. hamiltoniana).		(34)
29 (28)	Leaf margin coarsely 9-14-dentate, teeth gradually larger distally.		15 B. japonica
+	Leaf margin subregularly dentate, denticulate, or serrulate.		(30)
30 (29)	Branchlets densely yellowish tomentose; leaf blade tomentose to densely pubescent on both surfaces.		12 B. tomentosa
+	Branchlets strigose; leaf blade strigose adaxially.		(31)
31 (30)	Leaf blade patent pubescent abaxially.		(32)
+	Leaf blade strigillose abaxially.		(33)
32 (31)	Leaf blade sparsely puberulent abaxially.		6 B. macrophylla
+	Leaf blade densely pubescent abaxially.		13 B. dolichostachya
33 (31)	Herbs perennial to 0.5 m tall; leaf blade 5-9.4 × 5-8 cm; female or bisexual spikes of congested glomerules 2-5 cm.		14 B. densiglomerata
+	Subshrubs or shrubs to 3 m tall; leaf blade 6.5-19 × 6-17.5 cm; female spikes of distant glomerules 9-40 cm.		13 B. dolichostachya
34 (28)	Branches glabrous; leaf blade narrowly ovate to lanceolate, margin finely crenulate throughout; spikes very slender, to 26 cm.		11 B. hamiltoniana
+	Branches strigose; leaf blade ovate or narrowly ovate, margin dentate, denticulate, or serrulate, with entire tip; spikes usually less than 26 cm.		(35)
35 (34)	Female spikes 0.8-2 cm; plants 0.4-0.6 m tall.		7 B. pilosiuscula
+	Female spikes 4-20 cm; plants 0.7-3.5 m tall.		(36)
36 (35)	Shrubs or small trees; petiole to 1.2 cm; female inflorescences often in groups of 2-4; female perianth tube patent-puberulent all over.		22 B. siamensis
+	Herbs perennial or subshrubs; petiole to 6 or 13 cm; female inflorescences solitary; female perianth tube strigillose on shoulder.		(37)
37 (36)	Leaf teeth 6-20 mm, gradually larger distally.		15 B. japonica
+	Leaf teeth 2-5 mm, regular.		(38)
38 (37)	Leaf narrowly ovate or oblong-ovate, glabrous or subglabrous adaxially; achene verrucose.		10 B. formosana
+	Leaf ovate, often rugose, strigose adaxially; achene smooth.		6 B. macrophylla