1	Leaves of each pair very unequal, the larger over 5 times as long as the smaller.		(2)
+	Leaves of each pair subequal or unequal but less than 5 times in size.		(4)
2 (1)	Minor leaves of each pair strongly reduced, less than ca. 1 cm, sometimes absent, margin serrulate; male flowers borne around axis of inflorescence.		73 P. pellionioides
+	Minor leaves of each pair conspicuous, more than ca. 1 cm, margin entire or subentire; male flowers borne along side of inflorescence.		(3)
3 (2)	Leaf blade at least on upper stem base distinctly peltate, lateral veins U-shaped at base; achene verrucose.		71 P. insolens
+	Leaf blade basifixed, lateral veins spreading; achene smooth.		72 P. anisophylla
4 (1)	Plants with at least some multicellular hairs.		(5)
+	Plants with unicellular hairs or glabrous.		(9)
5 (4)	Inflorescences usually unbranched, moniliform, sometimes few branched; leaf blade elliptic or ovate-elliptic, with incurved deeply serrate acumen.		70 P. medogensis
+	Inflorescences cymose or branched; leaf blade ovate or lanceolate with entire or shallowly serrulate acumen.		(6)
6 (5)	Inflorescences dichotomously cymose or cymose-paniculate, 1-2 cm; stipules triangular, ca. 1 mm.		(7)
+	Inflorescences paniculate, 8-16 cm; stipules oblong or lanceolate, ca. 5 mm.		(8)
7 (6)	Male flowers in bud pear-shaped, ca. 1.2 mm, with a beak at apex; leaf blade ovate, cystoliths fusiform, conspicuous only along veins abaxially.		66 P. rostellata
+	Male flowers in bud globose, ca. 0.7 mm, corniculate below apex; leaf blade narrowly ovate or lanceolate, cystoliths short fusiform or subpunctate, dense on both surfaces.		67 P. salwinensis
8 (6)	Leaves unequally paired, broadly ovate or suborbicular, 3-12 × 2-9 cm; petiole 0.6-4.5 cm; achene ca. 0.6 mm.		68 P. umbrosa
+	Leaves strongly unequally paired, ovate to oblong-ovate, 6-9 × 3.5-4.5 cm; petiole 0-1.5 cm, small leaf sessile; achene ca. 1 mm.		69 P. multicellularis
9 (4)	Male flowers 2-merous; inflorescences cincinnus.		(10)
+	Male flowers 4-merous; inflorescences not cincinnus.		(11)
10 (9)	Stipules soon deciduous, ovate-oblong, 2-3 mm; female perianth lobes 3, subequal or abaxial lobe the shortest; achene with colored dots.		64 P. pumila
+	Stipules persistent, orbicular or subcordate, 2.5-4 mm; female perianth lobes 3, strongly unequal, abaxial lobe the longest, ca. 10 times as long as the lateral 2 lobes; achene without colored dots.		65 P. pauciflora
11 (9)	Leaf blade, all or some, peltate.		(12)
+	Leaf blade basifixed.		(15)
12 (11)	Leaves submembranous or thinly papery.		(13)
+	Leaves succulent, papery or thickly papery when dried.		(14)
13 (12)	Stems to 100 cm tall; leaf blade peltate, base often truncate; male inflorescences 3-11 cm.		53 P. paniculigera
+	Stems ca. 25 cm tall; leaf blade unequally paired, only major one peltate; male inflorescences 1.5-3.5 cm.		54 P. racemiformis
14 (12)	Stems 10-40 cm tall, internodes compact; leaf blade suborbicular, apex subrounded; stipule ca. 7 mm; male inflorescences 10-28 cm.		55 P. peperomioides
+	Stems 5-27 cm, internodes 1-4 cm; leaf blade broadly ovate or suborbicular, apex acute or short acuminate; stipule ca. 1 mm; male inflorescences 3-4 cm.		56 P. peltata
15 (11)	Male inflorescences capitate or subcapitate, glomerules sometimes arranged on racemose branches.		(16)
+	Male inflorescences dichotomously cymose, cymose-paniculate, or moniliform spicate, but not capitate.		(22)
16 (15)	Plants with tubers.		(17)
+	Plants without tubers.		(18)
17 (16)	Tubers globose, whitish gray, 3-20 mm in diam.; leaves on middle and upper nodes, ovate or rhombic-ovate, apex obtuse or acute.		62 P. racemosa
+	Tubers at base of stem or sometimes at rhizome nodes conic, brownish, 5-10 mm in diam.; leaves crowded at stem apex, often 4-6 in whorl, ovate to lanceolate, apex acuminate (acute in upper leaves of var. incisoserrata).		63 P. approximata
18 (16)	Leaf blade succulent, broadly ovate, rhombic, or orbicular.		(19)
+	Leaf blade not succulent, ovate or linear.		(20)
19 (18)	Herbs erect; leaf blade 8-20 × 6-18 mm, base often broadly cuneate or rounded; petiole 5-20 mm; male perianth lobes not corniculate at apex.		60 P. cavaleriei
+	Herbs prostrate; leaf blade 4-8 × 4-8.5 mm, base truncate; petiole 0.2-0.6 mm; male perianth lobes corniculate below apex.		61 P. sinocrassifolia
20 (18)	Herbs 5-10 cm tall, simple; leaf blade elliptic-lanceolate or oblong-linear, membranous, margin entire or shallowly 1-lobed in middle part.		59 P. linearifolia
+	Herbs 10-35 cm tall, much branched; leaf blade ovate or lanceolate, rarely linear, ± papery, margin serrate.		(21)
21 (20)	Leaf blade narrowly lanceolate, 2-5 × 0.4-1 cm, margin serrulate; female perianth lobes 3, abaxial lobe short corniculate below apex.		57 P. bambusifolia
+	Leaf blade ovate, 0.7-2.5 × 0.6-1 cm, margin obtusely 2-4-serrate; female perianth lobes 3, abaxial lobe strongly recurved corniculate below apex.		58 P. unciformis
22 (15)	Male inflorescences moniliform spicate of remote glomerules; stipules triangular, persistent.		(23)
+	Male inflorescences dichotomously cymose; stipules different forms, persistent or deciduous.		(26)
23 (22)	Plants 50-150 cm tall; leaf blade 5-13 × 3-7 cm, margin coarsely serrate; achene ca. 1.8 mm.		51 P. monilifera
+	Plants 3-20(-40) cm tall; leaf blade 1-6 × 0.5-3 cm, margin entire or sparsely crenate; achene 0.4-0.6 mm.		(24)
24 (23)	Leaf blade cordate, 0.6-1.5 × 0.5-1.4 cm, margin 4-6-crenate each side; male inflorescences 0.5-1.2 cm; achene with a colored dotted circle.		52 P. microcardia
+	Leaf blade 1.5-6 cm, margin entire; male inflorescences ca. 2 cm or more; achene verrucose.		(25)
25 (24)	Leaf blade broadly elliptic or rhombic-orbicular; male inflorescences 2-5 cm; female ones capitate; achene inconspicuously verrucose.		49 P. media
+	Leaf blade rhombic-elliptic or rhombic-lanceolate; male inflorescences ca. 2 cm; female ones racemose; achene spinulose-verrucose.		50 P. elegantissima
26 (22)	Female perianth lobes usually equal in size (unequal in P. hookeriana), connate 1/2 of length or to apex, often obtuse at apex.		(27)
+	Female perianth lobes unequal in size, free or connate at base, often acute at apex.		(31)
27 (26)	Stipules soon deciduous, oblong, 7-20 mm.		(28)
+	Stipules persistent, triangular, 1-2(-4) mm.		(30)
28 (27)	Stipules interpetiolar; male inflorescence unbranched, capitate or moniliform; female perianth lobes unequal.		44 P. hookeriana
+	Stipules intrapetiolar; male inflorescence cymose, branched; female perianth lobes equal.		(29)
29 (28)	Leaf blade membranous or herbaceous, margin coarsely serrate, cystoliths fusiform, 0.3-0.4 mm; achene 1.2-1.6 mm.		45 P. angulata
+	Leaf blade papery, margin serrulate, cystoliths linear, 0.5-0.6 mm; achene ca. 0.8 mm.		46 P. notata
30 (27)	Leaf blade acuminate or short caudate, margin 18-24-crenate.		16 P. verrucosa
+	Leaf blade caudate or long caudate, margin less than 15-dentate.		47 P. sinofasciata
31 (26)	Female inflorescences dichotomously cymose, sometimes compacted into clusters; male inflorescences dichotomously cymose, or cymose-paniculate; achene subglobose; basal veins on leaf blade prominent adaxially.		(32)
+	Female and male inflorescences all cymose-paniculate; achene ovoid or oblong; basal veins on leaf blade even or sunken adaxially.		(42)
32 (31)	Stipules cordate or oblong-ovate, 3-8 mm; male inflorescences solitary, cymose-paniculate.		(33)
+	Stipules triangular, 1-2(-4) mm; male inflorescences in pairs (solitary in P. matsudae), dichotomously cymose.		(37)
33 (32)	Male inflorescences often shorter or sometimes slightly longer than petioles; stipules oblong-ovate.		(34)
+	Male inflorescences often longer than petioles; stipules cordate.		(35)
34 (33)	Leaf blade membranous, oblong or elliptic, 9-15 × 5-8 cm.		23 P. elliptilimba
+	Leaf blade papery, elliptic-lanceolate, 3-7 × 1.2-2.3 cm.		24 P. chartacea
35 (33)	Leaf blade elliptic, ovate, ovate- or elliptic-lanceolate.		20 P. aquarum
+	Leaf blade obovate-oblong.		(36)
36 (35)	Stems with several sinuately membranous wings, glabrous; female cymes 1-1.5 cm.		22 P. subcoriacea
+	Stems without wings, densely pubescent; female cymes 2-5 cm.		21 P. cordistipulata
37 (32)	Leaf blade ± leathery; male cymes often longer than leaves.		25 P. lomatogramma
+	Leaf blade often membranous; male cymes or cymose panicles shorter than leaves.		(38)
38 (37)	Male inflorescences shorter than petioles; leaf blade broadly elliptic or ovate, margin coarsely serrate.		(39)
+	Male inflorescences often longer than petioles; leaf blade elliptic to lanceolate, margin serrate, crenate-serrate, or serrulate.		(40)
39 (38)	Plants densely pubescent; male cymes in compact clusters.		19 P. villicaulis
+	Plants subglabrous; male cymes in panicles.		48 P. matsudae
40 (38)	Leaf blade unequally paired, usually elliptic, base narrowly cuneate, margin serrulate or rarely subentire; achene ca. 1.8 mm.		18 P. somae
+	Leaf blade subequally paired, elliptic to lanceolate, base cuneate or subrounded, margin serrate or crenate-serrate; achene 0.7-0.8 mm.		(41)
41 (40)	Leaf blade sparsely pilose adaxially, often 3-veined, rarely triplinerved; male perianth lobes acute without corniculate appendix at apex; plants dioecious.		16 P. verrucosa
+	Leaf blade glabrous, triplinerved; male perianth lobes corniculate at apex; herbs monoecious.		17 P. rotundinucula
42 (31)	Stipules oblong or oblong-lanceolate, 4-12 mm.		(43)
+	Stipules triangular, 1-2(-3) mm (to 5 mm in P. longipedunculata).		(47)
43 (42)	Stipules brownish, 4-8 mm; leaf margin serrate; achene smooth.		(44)
+	Stipules greenish, 5-12 mm; leaf margin sharply serrulate or crenate; achene with a colored ring or smooth.		(45)
44 (43)	Upper stems and petioles glabrous or puberulent; leaf blade ovate or ovate-lanceolate, asymmetric; inflorescences longer than petioles.		26 P. martini
+	Stems and petioles densely spreading villous; leaf blade oblong-elliptic; inflorescences shorter than petioles.		27 P. menghaiensis
45 (43)	Achene with a colored ring; leaf margin shallowly but sharply serrulate, sometimes ciliate.		30 P. bracteosa
+	Achene smooth; leaf margin crenate.		(46)
46 (45)	Plants 30-80 cm tall; leaf blade 7-16 × 4-8 cm, oblique; stipules 8-12 mm.		28 P. cordifolia
+	Plants 10-25 cm tall; leaf blade 1-3 × 0.6-2.5 cm, not oblique; stipules 4-5 mm.		29 P. oxyodon
47 (42)	Male inflorescences shorter than leaves.		(48)
+	Male inflorescences longer than leaves.		(51)
48 (47)	Male inflorescences slightly longer than petioles; cystoliths linear.		(49)
+	Male inflorescences shorter than petioles; cystoliths subpunctate or very short botuliform.		(50)
49 (48)	Leaf blade subequally paired, base broadly cuneate to emarginate, margin serrulate, terminal veins interruptedly thickened; achene oblique, verrucose, often with a colored ring by margin.		31 P. scripta
+	Leaf blade unequally paired, base auriculate or cordate, margin crenate, terminal veins not thickened; achene not oblique, smooth or finely reticulate.		32 P. auricularis
50 (48)	Herbs weak or subshrubs, often climbing, glabrous; leaf apex acuminate, margin entire or shallowly serrate.		33 P. glaberrima
+	Herbs robust, covered with dense brownish squamae; leaf apex caudate-acuminate; margin crenulate.		34 P. squamosa
51 (47)	Leaf margin entire or inconspicuously 1-3-serrulate near apex.		(52)
+	Leaf margin serrate.		(54)
52 (51)	Achene strongly elevated as eyeball; leaf blade often falcate-lanceolate.		41 P. longipedunculata
+	Achene verrucose; leaf blade often ovate.		(53)
53 (52)	Leaf blade narrowly ovate to elliptic-lanceolate, 5-13 × 2-5 cm, 2-serrulate apically, lateral veins transverse, regularly reticulate.		42 P. subedentata
+	Leaf blade ovate, lanceolate, or obovate-oblong, 1-15 × 0.6-5 cm, entire, lateral veins irregularly reticulate.		43 P. plataniflora
54 (51)	Male inflorescences rather longer than leaves; achene with a colored circle or strongly elevated as eyeball.		(55)
+	Male inflorescences not or slightly longer than leaves; achene smooth or dotted but without colored circle.		(56)
55 (54)	Herbs to 2 m tall; leaf blade elliptic or elliptic-lanceolate, symmetric, 10-25 × 5-16 cm; male inflorescences 15-35 cm.		39 P. melastomoides
+	Herbs 15-35(-80) cm tall; leaf blade broadly ovate or elliptic, somewhat asymmetric, 5-12(-18) × 2.5-5(-8) cm; male inflorescences 8-14 cm.		40 P. howelliana
56 (54)	Leaf base rounded to subcordate; male perianth lobes beaked at apex; achene oblique at apex.		(57)
+	Leaf base cordate; male perianth lobes acute; achene not oblique.		(58)
57 (56)	Herbs 20-30 cm tall; leaf blade 2-6.5 × 1.5-2.5 cm; achene ca. 1 mm, smooth.		35 P. wightii
+	Herbs 30-120 cm tall; leaf blade 4-14 × 2-7 cm; achene ca. 1.5 mm, smooth, often purplish dotted.		36 P. symmeria
58 (56)	Leaf blade lanceolate, margin sinuate-crenate; female inflorescences 5-11 cm; achene ca. 2 mm, enclosed by equal perianth lobes.		37 P. macrocarpa
+	Leaf blade usually falcate-lanceolate, margin sharply serrate; female inflorescences 1.5-4 cm; achene ca. 1 mm, enclosed by unequal perianth lobes.		38 P. semisessilis