1	Tepals yellow to orange; seeds usually hemispherical with depression on flattened side, or globose with or without obvious depression; filaments distinct or connate only basally.		(2)
+	Tepals purple to light blue, white, lavender, pink, or magenta, occasionally yellow; seeds globose to obconic, depression absent or occasionally slight; filaments connate ± full length (only basally in S. rosulatum).		(6)
2 (1)	Stems 2–8 mm wide; capsules 6–19 mm; tepals usually 12+ mm.		(3)
+	Stems 0.5–2(–2.3) mm wide; capsules 3–9 mm; tepals usually less than 12 mm.		(4)
3 (2)	Stems simple; seeds 0.7–1.5 mm, hemispherical with shallow depression.		1 Sisyrinchium californicum
+	Stems branched; seeds 1.5–2.2 mm, globose, lacking depression.		2 Sisyrinchium arizonicum
4 (2)	Plants annual; tepals 2.6–5 mm; seeds 0.9–1.1 mm, with deep depression.		5 Sisyrinchium cernuum
+	Plants perennial; tepals 7.5–11 mm; seeds 1–1.7 mm, with shallow depression.		(5)
5 (4)	Fruiting pedicels recurved to spreading; capsules globose or turbinate to broadly fusiform.		3 Sisyrinchium elmeri
+	Fruiting pedicels ascending to erect; capsules slightly turbinate to ± globose.		4 Sisyrinchium longipes
6 (1)	Perianth campanulate basally, flaring distally; plants annual or occasionally short-lived perennial; tepals lavender, pink, magenta, yellow, or occasionally white.		(7)
+	Perianth widely flaring or reflexed from base, not campanulate; plants perennial; tepals purple to violet, blue, or white.		(8)
7 (6)	Stems with 3–6 nodes; filaments connate ± full length, tapering evenly, stipitate-glandular on proximal 0.8–1.2 mm; capsule turbinate to broadly fusiform, uniformly light brown.		6 Sisyrinchium minus
+	Stems with 1–2(–3) nodes; filaments connate basally or occasionally to 1/2 length, inflated basally, stipitate-glandular on proximal 0.5–0.8 mm; capsule ± globose, bicolored, sutures and sometimes apex purplish, intrasuture surface tan.		7 Sisyrinchium rosulatum
8 (6)	Rhipidia usually paired, rarely borne singly, sessile or rarely outer with branch to 7 mm; rhipidia and associated spathes closely subtended by enveloping bractlike leaf (because the 2 rhipidia are nearly enveloped by the leaf, these species can be mistaken as having a single rhipidium).		(9)
+	Rhipidia borne singly, terminating stem or branch; rhipidium and associated spathes not subtended by leaf.		(10)
9 (8)	Stems 1.5–3.4 mm wide, obviously winged, not wiry.		8 Sisyrinchium albidum
+	Stems 0.5–1 mm wide, hardly or not winged, wiry.		9 Sisyrinchium capillare
10 (8)	Stems branched or populations predominantly with branched individuals (see discussion).		(11)
+	Stems simple or populations predominantly with simple-stemmed individuals.		(33)
11 (10)	Stems with 2–5 nodes; spathes ± equaling branches in width.		10 Sisyrinchium dichotomum
+	Stems with 1–3 nodes; spathes much wider than branches.		(12)
12 (11)	Main stems usually more than 2 mm wide.		(13)
+	Main stems usually 2 mm or less wide.		(21)
13 (12)	First internode equaling or shorter than longest leaf, if equaling leaves then apex of hyaline margins of inner spathe acute to acuminate.		(14)
+	First internode equaling or longer than longest leaf, if equaling leaves then hyaline margins of inner spathe broadly obtuse or acute apically.		(16)
14 (13)	Stems and leaves glabrous; hyaline margins of inner spathe broadly acute to obtuse or truncate apically, sometimes projecting as lobes.		11 Sisyrinchium ensigerum
+	Stems and leaves usually scabrous, at least apically on margins; hyaline margins of inner spathe tapering to acute to acuminate apex, never projecting as lobes.		(15)
15 (14)	Leaf bases persistent as fibrous tufts; outer spathe 0.5–1.8 mm longer than inner.		12 Sisyrinchium xerophyllum
+	Leaf bases not persistent or fibrous; outer spathe 2.5–5.5 mm longer than inner.		13 Sisyrinchium pruinosum
16 (13)	Leaf bases persistent as fibrous tufts.		14 Sisyrinchium nashii
+	Leaf bases not persistent or fibrous.		(17)
17 (16)	Hyaline margins of inner spathe 0.1–0.3 mm wide; e of the Rocky Mountains.		(18)
+	Hyaline margins of inner spathe (0.1–)0.4–1.1 mm wide; w of the Rocky Mountains.		(19)
18 (17)	Capsules dark brown or black; plants usually drying dark olive green, bronze, or blackish.		15 Sisyrinchium angustifolium
+	Capsules tan to nearly white; plants drying light green to yellowish green.		16 Sisyrinchium strictum
19 (17)	Hyaline margins of inner spathe usually equaling or longer than green apex; foliage strongly glaucous; tepals pale blue.		17 Sisyrinchium funereum
+	Hyaline margins of inner spathe usually shorter than green apex; foliage various but usually not strongly glaucous; tepals usually bluish violet to violet-purple.		(20)
20 (19)	Outer tepals elliptic to oblanceolate; stem margins white or translucent cartilaginous; filament column usually stipitate-glandular.		18 Sisyrinchium radicatum
+	Outer tepals often broadly cuneate; stem margins same color and texture as stem body; filament column usually not stipitate-glandular.		19 Sisyrinchium bellum
21 (12)	Margins of outer spathe connate basally (1.5–)2–4 mm (–5 mm in S. langloisii).		(22)
+	Margins of outer spathe connate basally 3.5–9 mm.		(26)
22 (21)	Outer spathe 2.5–5.5 mm longer than inner; spathes usually scabrous.		13 Sisyrinchium pruinosum
+	Outer spathe shorter or no more than 2.7 mm longer than inner; spathe usually glabrous.		(23)
23 (22)	Leaf bases persistent as thick, fibrous tufts.		20 Sisyrinchium fuscatum
+	Leaf bases not persistent as fibrous tufts.		(24)
24 (23)	Ovary and capsule black, contrasting with much lighter foliage; hyaline margins of inner spathe broadly rounded or truncate apically.		21 Sisyrinchium atlanticum
+	Ovary and capsule not contrasting with foliage; hyaline margins of inner spathe usually acuminate to acute or sometimes obtuse apically.		22 Sisyrinchium langloisii
26 (21)	Ovaries and capsules black, contrasting with much lighter foliage.		21 Sisyrinchium atlanticum
+	Ovaries and capsules not contrasting with foliage.		(27)
27 (26)	Hyaline margins of inner spathe broadly rounded or truncate apically.		(28)
+	Hyaline margins of inner spathe usually acute or acuminate apically.		(30)
28 (27)	Hyaline margins of inner spathe usually equaling or longer than green apex; foliage strongly glaucous; tepals pale blue.		17 Sisyrinchium funereum
+	Hyaline margins of inner spathe usually shorter than green apex; foliage various, not strongly glaucous; tepals bluish violet to violet-purple.		(29)
29 (28)	Outer tepals elliptic to oblanceolate; stem margins white or translucent-cartilaginous; filament column usually stipitate-glandular.		18 Sisyrinchium radicatum
+	Outer tepals often broadly cuneate; stem margins similar to stem body; filament column usually not stipitate-glandular.		19 Sisyrinchium bellum
30 (27)	First internode equaling or shorter than leaves.		(31)
+	First internode longer than leaves.		(32)
31 (30)	Plants drying brownish olive to bronze; rhizomes obvious.		23 Sisyrinchium miamiense
+	Plants drying yellowish green to olive, occasionally bronze; rhizomes scarcely discernable.		24 Sisyrinchium biforme
32 (30)	Capsules 4–7.5+; sw United States.		25 Sisyrinchium demissum
+	Capsules 3.5–4.9 mm; Great Lakes region.		16 Sisyrinchium strictum
33 (10)	Margins of outer spathe distinct basally or rarely connate to 1 mm, and then stems greater than 1.5 mm wide, glabrous or scabrous.		26 Sisyrinchium campestre
+	Margins of outer spathe obviously connate basally 1 mm or more (rarely connate less than 1 mm and then spathes tinged strongly purple), usually glabrous or rarely slightly scabrous.		(34)
34 (33)	Leaf bases persisting in fibrous tufts.		35 Sisyrinchium sagittiferum
+	Leaf bases not persisting in fibrous tufts.		(35)
35 (34)	Rhizomes obvious and elongate; tepals purple to dark reddish purple or very rarely bluish violet, base purple.		30 Sisyrinchium hitchcockii
+	Rhizomes scarcely discernable; tepals bluish violet, occasionally purple or purplish blue, to light blue or white, base yellow.		(36)
36 (35)	Spathes subequal, or outer up to 4.5 mm longer than inner.		(37)
+	Spathes distinctly unequal, outer at least 6 mm longer than inner.		(38)
37 (36)	Capsules 2.2–4 mm; hyaline margins of inner spathe broadly rounded to truncate apically, often extending as 2 lobes beyond green apex; w United States.		31 Sisyrinchium halophilum
+	Capsules 5–7 mm; hyaline margins of inner spathe acute to acuminate or occasionally lobed and slightly exceeding green apex; s United States and n Mexico.		24 Sisyrinchium biforme
38 (36)	Tepals pale blue; outer tepals usually rounded apically to slightly emarginate.		(39)
+	Tepals blue-violet to purplish blue, occasionally purple; outer tepals emarginate, truncate or occasionally rounded apically.		(42)
39 (38)	Outer tepals greater than 10 mm; Columbia River Gorge.		33 Sisyrinchium sarmentosum
+	Outer tepals 10 mm or less; elsewhere.		(40)
40 (39)	Outer spathes usually connate more than 2.6 mm; outer tepals slightly emarginate to rounded apically; Colorado, Wyoming.		28 Sisyrinchium pallidum
+	Outer spathes connate less than 2.6 mm; outer tepals rounded apically, never emarginate; elsewhere.		(41)
41 (40)	Capsules dark brown to black; Greenland.		36 Sisyrinchium groenlandicum
+	Capsules beige to light brown; w Canada, Washington.		37 Sisyrinchium septentrionale
42 (38)	Stems with very narrow or scarcely discernable wings, almost wiry, 0.9–2 mm wide.		29 Sisyrinchium mucronatum
+	Stems obviously winged, 1–3.7 mm wide.		(43)
43 (42)	Capsules 6.2–8.1 mm; outer tepals usually rounded to slightly truncate apically.		32 Sisyrinchium littorale
+	Capsules 3–6.8 mm; outer tepals usually emarginate or truncate apically (rarely rounded and capsules shorter than 6 mm).		(44)
44 (43)	Outer spathes usually at least (12–)16 mm longer than inner; stems usually (1.5–)2–3.7 mm wide; keel of inner spathe ± gibbous basally; seed coat rugulose.		27 Sisyrinchium montanum
+	Outer spathes no more than 16 mm longer than inner; stems 1–2.5 mm wide; keel of inner spathe not gibbous; seed coat usually granular.		34 Sisyrinchium idahoense