1	Spur 7–18 mm; viscidia ovate to oblong.		(2)
+	Spur 1–6 mm; viscidia broadly elliptic-ovate to rectangular-ovate.		(6)
2 (1)	Viscidia oblong, at least 2 times as long as wide; flowers white with green or yellow-green midvein; stem base usually thickened toward tuberoid.		(3)
+	Viscidia ovate to broadly elliptic or broadly oblong, usually less than 2 times as long as wide; flowers green; stem base uniform in diameter or attenuate toward tuberoid.		(4)
3 (2)	Spurs of most flowers straight, horizontal; stem 0.7–4.5 mm diam.; floral fragrance clovelike.		1 Piperia transversa
+	Spurs of most flowers curved, deflexed; stem (2–3)–12 mm diam.; floral fragrance musky or pleasant, not clovelike.		2a subsp. elegans
4 (2)	Seeds usually blackish brown; lip triangular-ovate; petals erect-spreading; stem attenuate toward tuberoid.		8 Piperia michaelii
+	Seeds pale brown to cinnamon brown; lip lanceolate to broadly triangular; petals usually strongly erect-recurved; stem basally attenuate or not.		(5)
5 (4)	Petals falcate, ovate-attenuate, about 2 mm wide at base and 2–3 times as long; lip less than 2 times as long as wide; spur (7–)9–15(–18) mm; widespread.		9 Piperia elongata
+	Petals straight, linear, about 1 mm wide at base and 4–5 times as long; lip about 2 times as long as wide; spur 4–9 mm; not common, California.		10 Piperia leptopetala
6 (1)	Lip strongly recurved toward spur with age; flowers white or white and green; raceme rachis usually shorter than peduncle.		(7)
+	Lip straight or upwardly curved; flowers green; raceme rachis usually at least as long as peduncle.		(9)
7 (6)	Stem bracts usually fewer than 6; raceme ± secund; lip triangular-ovate; petals straight, white or with faint green midvein; c California to se Alaska.		4 Piperia candida
+	Stem bracts usually more than 6; raceme cylindric; lip triangular-lanceolate; petals erect, curved, green with white border; California.		(8)
8 (7)	Petals falcate, outer white border much broader than inner; stem base attenuate toward tuberoid; flowers weakly fragrant, never cinnamonlike, diurnal; Monterey Bay area, California.		3 Piperia yadonii
+	Petals straight-sided, inner and outer white border subequal; stem base swollen; flowers strongly cinnamon-scented, nocturnal; Point Reyes, California.		2b subsp. decurtata
9 (6)	Spur shorter than lip, 1–2.5 mm; flowers scentless; leaves grasslike, erect, less than 1 cm wide.		5 Piperia colemanii
+	Spur at least as long as lip, 2–6 mm; flowers scented, at least at night; leaves not grasslike, prostrate to erect-spreading, usually over 1 cm wide.		(10)
10 (9)	Petals linear with slightly expanded base, about 4 times longer than wide, strongly upwardly recurved; lip narrowly lanceolate; spur attenuate, 4–9 mm; flowers with lemony scent or otherwise pleasant, not musky or honeylike.		10 Piperia leptopetala
+	Petals lanceolate to triangular-ovate, less than 3.5 times longer than wide, usually projecting to ± erect; lip triangular-ovate to lanceolate-elliptic; spur narrowly cylindric, blunt, 2–6 mm; flowers musky- or honey-scented.		(11)
11 (10)	Mature seeds blackish brown; flowers honey-scented; raceme rachis ± length of peduncle; stem attenuate toward tuberoid; Santa Monica Mountains to n Baja California, below 1500 m.		7 Piperia cooperi
+	Mature seeds tan to cinnamon brown; flowers ± musk-scented; raceme rachis usually longer than peduncle; stem diameter uniform or increasing toward tuberoid; widespread in North America but in s California occurring only above 1500 m.		6 Piperia unalascensis