1	Lip subglobose, ellipsoid, or ovoid, apical margin involute, usually with a rather short basal claw		(2)
+	Lip helmet-shaped or slipper-shaped, lacking an involute apical margin and with a long basal claw		(10)
2 (1)	Lip usually ellipsoid or ovoid, longer than broad; dorsal sepal broader than petals		(3)
+	Lip usually subglobose, nearly as long as broad; dorsal sepal narrower than or ca. as broad as petals		(5)
3 (2)	Dorsal sepal and petals with a central longitudinal stripe composed of brown-red spots; staminode with caudate apex 1.5-2 mm.		9 P. wenshanense
+	Dorsal sepal and petals without a central stripe as above; staminode lacking a caudate apex as above		(4)
4 (3)	Flower yellowish to yellow; dorsal sepal and petals with maroon speckles 0.5-1 mm in diam.		7 P. concolor
+	Flower white or ivory, sometimes yellowish; dorsal sepal and petals with maroon spots 1.5-2 mm in diam.		8 P. bellatulum
5 (2)	Leaves uniformly green, very rarely obscurely tessellated with dark and light green adaxially		(6)
+	Leaves distinctly tessellated with dark and light green adaxially		(7)
6 (5)	Flower white with a yellowish lip; staminode trullate, with a deep longitudinal groove centrally, 9-10 mm wide, yellow, strongly veined with red.		5 P. emersonii
+	Flowers dull cream-colored, sometimes flushed at base with purple; staminode broadly obovate-triangular, nearly flat, 18-22 mm wide, cream-colored, heavily veined with red, and with a yellow tip.		6 P. hangianum
7 (5)	Dorsal sepal apple-green or rarely yellowish green or greenish; scape usually 30-50(-65) cm.		1 P. malipoense
+	Dorsal sepal not apple-green or yellowish green; scape usually 15-25(-30) cm		(8)
8 (7)	Plants not stoloniferous; dorsal sepal and petals white, scarcely or obscurely spotted and veined with pale pink, particularly on dorsal surface.		4 P. delenatii
+	Plants stoloniferous; dorsal sepal and petals yellow or whitish and conspicuously veined with red-purple		(9)
9 (8)	Sepals, petals, and lip yellow, lip not much larger than synsepal.		2 P. armeniacum
+	Sepals and petals white, strongly marked with purple on veins, lip much larger than synsepal, pink or rarely white.		3 P. micranthum
10 (1)	Leaves tessellated with dark and light green adaxially; lip tuberculate on incurved lateral lobes		(11)
+	Leaves uniformly green adaxially; lip not tuberculate on incurved lateral lobes		(14)
11 (10)	Petals heavily spotted with blackish maroon over whole adaxial surface.		26 P. wardii
+	Petals without or sometimes with blackish maroon speckles in basal half or a few blackish warts scattered		(12)
12 (11)	Leaves densely spotted with purple abaxially; lip and staminode distinctly green veined.		27 P. venustum
+	Leaves pale green abaxially or sometimes marked with purple at abaxial base; lip and staminode not green veined		(13)
13 (12)	Leaves usually obscurely tessellated with dark and light green adaxially, and marked with purple at abaxial base; petals spatulate, with a few warts along upper margin of basal half.		24 P. appletonianum
+	Leaves usually distinctly tessellated with green and whitish green adaxially, not marked with purple abaxially; petals suboblong or oblong-elliptic, usually with blackish maroon speckles in basal half.		25 P. purpuratum
14 (10)	Inflorescence 2-6-flowered; petals more than 2 × as long as lip		(15)
+	Inflorescence 1- or very rarely 2-flowered; petals less than 2 × as long as lip		(16)
15 (14)	Ovary glabrous; perianth persistent until fruiting.		10 P. dianthum
+	Ovary densely pubescent; perianth deciduous after pollination.		11 P. parishii
16 (14)	Leaves rigid, leathery-succulent, usually 7-10(-12.5) cm; synsepal suborbicular; flowers yellow or ochre-yellow, dorsal sepal with a white margin.		18 P. helenae
+	Leaves neither rigid nor leathery-succulent, usually (8-)10-40 cm; synsepal ovate to elliptic; flowers not as above		(17)
17 (16)	Flower with 3 irregular longitudinal maroon bars on dorsal sepal and 2 similar bars on petals.		22 P. tigrinum
+	Flower without maroon bars as above		(18)
18 (17)	Dorsal sepal white with a maroon midvein; staminode convolute on basal margin and appearing like a pair of eyes.		23 P. spicerianum
+	Dorsal sepal not colored as above; staminode without convolute basal margin as above		(19)
19 (18)	Plants with a long and stout rhizome more than 8 × 1 cm.		16 P. areeanum
+	Plants lacking a long rhizome as above		(20)
20 (19)	Staminode subsquare, with a glossy convex center, lacking a distinct umbo; petals with dense blackish maroon speckles in basal half; lip ± puberulent on outer surface.		12 P. hirsutissimum
+	Staminode obovate, with a distinct umbo centrally; petals without spots or with purple to dark maroon spots in basal half; lip glabrous on outer surface		(21)
21 (20)	Dorsal sepal very broad, 4.6-6.7 cm wide, pinkish to white, usually with reddish veins; staminode white.		13 P. charlesworthii
+	Dorsal sepal less than 4.5 cm wide, not colored as above; staminode not white		(22)
22 (21)	Leaves 8-19 × 0.7-1.8 cm; petals 3-4 cm		(23)
+	Leaves (15-)20-40 × 2-4 cm; petals 5-6 cm		(25)
23 (22)	Dorsal sepal and petals with large maroon spots; petals 14-18 mm wide.		19 P. henryanum
+	Dorsal sepal and petals without large maroon spots; petals 7-10 mm wide		(24)
24 (23)	Petals undulate at margin; staminode with a yellow umbo in central or upper part.		15 P. barbigerum
+	Petals strongly undulate at margin; staminode with a green umbo in lower part.		17 P. tranlienianum
25 (22)	Petals 1.5-2 cm wide, with same color on both sides of midvein, apical half slightly broader than or nearly as broad as basal half; dorsal sepal finely spotted with black.		14 P. insigne
+	Petals 2-4.5 cm wide, with different color on each side of midvein, apical half more than 2 × as broad as basal half; dorsal sepal unspotted or somewhat confluent-spotted with blackish maroon		(26)
26 (25)	Peduncle shortly hairy; dorsal sepal white, often tinged with pale green or pale yellow toward its base; petals 2-2.5 cm wide.		20 P. gratrixianum
+	Peduncle long hairy; dorsal sepal pale green to pale yellow, central area deep maroon and deeper striped; petals 2.2-4.5 cm wide.		21 P. villosum