1	Stem erect, with elongated internodes; leaves opposite, rarely in whorls of 3; corolla brownish.		22 P. arenaria
+	Stem absent or very short; leaves usually in basal rosette, rarely densely alternate; corolla white or yellowish		(2)
2 (1)	Plant with only fibrous roots		(3)
+	Plant with a taproot		(7)
3 (2)	Leaf blade lanceolate to linear-lanceolate, 3-4 × as long as wide; corolla yellowish; anthers 1.8-2.2 mm.		7 P. fengdouensis
+	Leaf blade broadly ovate to broadly elliptic, less than 2 × as long as wide; corolla white; anthers 0.8-1.5 mm		(4)
4 (3)	Flower sessile; pyxis circumscissile at or just below middle, with (8-)12-14(-34) seeds; seeds 0.8-1.2 mm.		3 P. major
+	Flower shortly pedicellate; pyxis circumscissile near base, with (2-)5-15 seeds; seeds (1.2-)1.3-2 mm		(5)
5 (4)	Sepals acuminate at apex, keel projecting beyond apex; anthers ca. 0.8 mm.		5 P. cavaleriei
+	Sepals obtuse or acute at apex, keel not projected at apex; anthers 1-1.5 mm		(6)
6 (5)	Petiole not winged at middle; corolla lobes narrowly triangular; anthers 1-1.2 mm.		4 P. asiatica
+	Petiole broadly winged; corolla lobes ovate to broadly ovate; anthers ca. 1.5 mm.		6 P. gentianoides
7 (2)	Leaf blade broadly ovate to elliptic, veins 7-11; petiole retrorsely pubescent; stamens adnate to near base of corolla tube		(8)
+	Leaf blade obovate, elliptic, lanceolate, or linear, veins 1-5(or 7); petiole with patent, appressed upward, or rarely entangled trichomes; stamens adnate to middle of corolla tube or more apically		(9)
8 (7)	Plants turning black when dry; petiole longer than or equaling blade, not winged; bracts glabrous.		1 P. maxima
+	Plants not turning black when dry; petiole much shorter than blade, winged; bracts pubescent.		2 P. media
9 (7)	Corolla tube pubescent or lobes hirsute-villous outside		(10)
+	Corolla glabrous		(11)
10 (9)	Leaf blade papery, sparsely villous; corolla lobes densely hirsute-villous outside; stamens adnate to near apex of corolla tube.		20 P. lagocephala
+	Leaf blade leathery, sparsely strigillose or glabrous; corolla tube pubescent; stamens adnate to middle of corolla tube.		21 P. maritima
11 (9)	Lower sepals connate to near apex; stamens adnate to middle of corolla tube.		16 P. lanceolata
+	All sepals distinct; stamens adnate to or near apex of corolla tube		(12)
12 (11)	Bracts with linear to subulate apex, much longer than flower.		17 P. aristata
+	Bracts with obtuse or acute apex, shorter, equaling, or slightly longer than flower		(13)
13 (12)	Leaf blade glabrous or abaxially pubescent, vein 1; seeds 7-30 per pyxis, fusiform		(14)
+	Leaf blade hairy on both surfaces, veins (1 or)3-7; seeds 1-4 per pyxis, ellipsoid to oblong		(15)
14 (13)	Bracts broadly ovate to suborbicular; sepals broadly elliptic to orbicular; pyxis with 12-30 seeds.		14 P. polysperma
+	Bracts ovate; sepals obovate; pyxis with 7-15 seeds.		15 P. tenuiflora
15 (13)	Leaf blade elliptic, ovate-lanceolate, obovate-lanceolate, or spatulate, usually more than 1 cm wide		(16)
+	Leaf blade ± linear to narrowly lanceolate or narrowly elliptic, usually less than 1 cm wide		(18)
16 (15)	Leaf blade spatulate to obovate-lanceolate, veins (3 or)5; flowers heteromorphic; corolla yellowish, lobes erect when flowers fertile; seeds 2 per pyxis, ventral surface grooved.		8 P. virginica
+	Leaf blade elliptic to ovate-lanceolate, rarely obovate-elliptic, veins 5 or 7; flowers homomorphic; corolla white, lobes patent to reflexed; seeds 4 per pyxis, ventral surface flat or prominent but not grooved		(17)
17 (16)	Bracts triangular-ovate; corolla lobes 0.5-1 mm; anthers white; pyxis 4-5 mm.		9 P. depressa
+	Bracts ovate-elliptic; corolla lobes 1-1.5 mm; anthers reddish brown; pyxis 2.5-3 mm.		10 P. camtschatica
18 (15)	Leaf blade arachnoid or silky villous; spikes cylindric to narrowly cylindric		(19)
+	Leaf blade villous or lanate; spikes capitate or ovoid at first but later shortly cylindric		(20)
19 (18)	Leaf blade arachnoid, veins 1 or 3, margin entire or repand- crenate; spikes 1-2.5(-5) cm; flowers dense; anthers ca. 1.2 mm.		13 P. arachnoidea
+	Leaf blade sparsely silky villous, veins 3 or 5, margin remotely and retrorsely denticulate or triangular dentate; spikes 4-10 cm; flowers usually interrupted at base; anthers ca. 2 mm.		12 P. perssonii
20 (18)	Keel not extending to apex of sepals; seeds 3 or 4 per pyxis, black, (1-)1.5-2 mm, ventral face flat; cotyledons parallel to ventral side.		11 P. komarovii
+	Keel extending to apex of sepals; seeds 1 or 2 per pyxis, yellowish brown to brown, (2-)3-4 mm, ventral face with a groove; cotyledons vertical to ventral side		(21)
21 (20)	Plants with short stems, usually branched at base; corolla lobes orbicular-ovate.		18 P. ovata
+	Plants stemless; corolla lobes elliptic to narrowly ovate.		19 P. minuta