1 Perianth with tepal campanulate basally, flaring distally; annual; plants usually < 2 dm tall; tepal lavender, pink, white, magenta, or yellow, with a maroon blaze near the base (S. micranthum) or the base wholly yellow (S. minus).

  2 Stems with 1-2 (-3) node; tepal with maroon blaze near base; mature capsule globose, tan with purple suture; [widespread]

  2 Stems with 3-6 node; tepal yellow basally; mature capsule broadly fusiform, elliptical, or barrel-shaped, uniformly light brown; [of MS to TX]

1 Perianth with tepal abruptly spreading in a plane; perennial, plants usually > 2 dm tall; tepal blue, violet, or white.

    3 Inflorescence paired (each inflorescence composed of 1-several flowers, their pedicel emanating from within 2 chartaceous scale; thus, there are 2 pairs of scale within the 2 outer, leaflike, green spathe bract); outer spathe bract connate 0-1 mm.

      4 Stems not winged or scarcely so, each wing narrower than the diameter of the stem core; outer spathe pair about equal in length to the inner pair

      4 Stems obviously winged, each wing wider than the diameter of the stem core; outer spathe pair longer than the inner by 2.3 mm (average) or more.

        5 Stems mostly 0.7-1.3 mm wide; corolla medium blue; [calcareous glades, n. AL and sc. TN]

        5 Stems mostly 1.0-2.5 mm wide; corolla pale blue to whitish; [of various habitats and collectively widespread].

          6 Stems (20) 30-48 cm tall, stems (2.5) 3.7-6.0 mm wide, leaves (2) 3.1-5.5 mm wide, outer spathe of outer rhipidium (15) 22-40 (48) mm long (x̅= 24.7 mm), ovaries drying tan to brown; [deep sandy soils, endemic to e. TX and nw. LA]

          6 Stems (16) 20-40 (42) cm tall, stems 2.0-3.5 (4.1) mm wide, leaves 1.8-3.5 mm wide, outer spathe of outer rhipidium (12) 15-22 (35) mm long, ovaries drying either brown to black or tan or light brown; [collectively various habitats and widespread]

             7 Ovaries drying brown to black; [various habitats, widespread]

             7 Ovaries drying tan to light brown; [calcareous glades of c. TN, sc. KY, and ne. MS]

    3 Inflorescence solitary, not paired (within the 2 green spathe bract there is only one pair of chartaceous scale); outer spathe bract connate 2-6 mm (except 0-1 mm in S. campestre).

               8 Stems simple, unbranched (rarely branched).

                 9 Spathe bract connate > 1 mm.

                   10 Base of plant with fibrous remains of leaves

                   10 Base of plant without fibrous remains of leaves.

                     11 Spathe bract equal or subequal, outer bract up to 4.2 mm longer than inner; [of coastal LA and s. TX]

                     11 Spathe bract distinctly unequal, outer usually > 6 mm longer than inner; [of southern Appalachians and northward].

                       12 Stems 1-2 mm wide, narrowly winged; spathe bract purple on margin at least (often throughout); capsule 3.2-5.5 mm long; [northern, extending south to nw. GA and c. AL]

                       12 Stems (1.5-) 2-4 mm wide, obviously winged; spathe bract green, rarely purplish; capsule 4-6.8 mm long; [northern, extending south to n. VA]

                          13 Margin of outer spathe connate basally 1-3.5 mm; plants drying green or olive; [sw. NS northward]

                          13 Margin of outer spathe connate basally 4-5.7 mm; plants drying dark brown or bronze; [NJ(?), NY northward]

               8 Stems branched, with 1-5 node.

                            14 Stems with 2-5 node, the branching dichotomous; tepal white, recurved at maturity; [of escarpment region of sw. NC and nw. SC]

                            14 Stems with 1-3 node, the branching uneven; tepal blue to violet, oriented in a plane; collectively widespread.

                              15 Plant base with fibrous remains of leaves (usually abundant).

                                16 Main stems 0.5-2.1 mm wide (usually < 2 mm wide).

                                  17 Stems mostly 1.5-2.1 mm wide, scabrous; plants drying dark brown or blackish; spathe bract 15-20 (-25) mm long

                                  17 Stems 0.5-1.2 mm wide, not scabrous; plants drying pale brown or greenish brown; spathe bract 12-14 (-15) mm long

                                16 Main stems 1.5-6 mm wide (usually >2 mm wide).

                                    18 Stems and leaves shiny, especially in life; stems mostly 3-6 mm wide; mature capsule mostly 5.5-8 mm long; [of FL and sw. GA]

                                    18 Stems and leaves dull; stems 1.5-4.5 mm wide; mature capsule 2.5-6 mm long; [collectively widespread].

                                       19 Stems and branches smooth on margin; stems mostly 2.3-4.5 mm wide; plants dry dull green or brownish green; [widespread]

                                       19 Stems and branches scabrous on margin at least distally; stems 1.5-3.0 (-3.5) mm wide; plants dry dark brown or blackish; [of the Coastal Plain].

                                         20 Stems mostly 2.0-3.0(-3.5) mm wide; mature capsule 4-6 mm long; [of e. MD northward to sw. Nova Scotia]

                                         20 Stems mostly 1.5-2.1 mm wide; mature capsule 2.5-4 mm long; [of se. VA to se. LA]

                              15 Plant base without fibrous remains of leaves

                                           21 Main stems usually < 2 mm wide.

                                             22 Rhizome present and obvious (although not longer than about 3 cm), about 2 mm thick, hard, blackish; hyaline margin of inner spathe bract acute (contra S. atlanticum)

                                             22 Rhizome absent or at least not evident; hyaline margin of inner spathe bract various.

                                               23 Ovaries and capsule black, strongly contrasting with foliage (which dries pale yellowish or tan); hyaline margin of inner spathe bract obtuse or truncate apically, sometimes projecting as lobe

                                               23 Ovaries and capsule pale to medium brown; foliage drying dull green or brownish; hyaline margin of inner spathe bract acute, never projecting as lobe.

                                                 24 Spathe bract and stems without spicule or papillae; outer spathe bract usually > inner by 1-2.7 mm; spathe bract purple tinged basally and sometimes also on margin; plants usually densely cespitose

                                                 24 Spathe bract and stems with abundant white spicule or papillae, sometimes these +/- flattened like lenticel; outer spathe bract usually > inner by 2.5-5.5 mm; spathe bract green; plants usually with few-several stems, not densely cespitose

                                           21 Main stems usually > 3 mm wide.

                                                    25 Plants light green when fresh and drying yellowish, light green, green or olive; relatively fewer stems from base, rarely to 32 stems, but averaging 5.5 stems or less; blooming from early April through October

                                                      26 Stem body mostly broader than the margin, thus whole stem appears somewhat rounded with sides tapering to scarcely discernable wings; plants drying yellowish or light olive-green; stem and wings drying about the same color; ovaries and capsule dark brown or black and contrasting with the much lighter dried foliage; stems averaging 3.3 from base; blooming early April through May; occurring in moist to wet sandy or silty soils in open areas, bog, and marsh

                                                      26 Stem body as wide or narrower than the margin (body looks more like a midvein), stems appear flattened with easily discernible wings, plants drying olive or green; stem body often drying slightly lighter than wings, forming a pale “stripe” down the center; ovaries and capsule not strongly contrasting with dried foliage.

                                                        27 Live plants green, not glaucous, drying olive; wide stems (2.9-7.4 mm, x̅ = 5.0) and leaves (3.9-7.8, x̅ = 5.4); stems appearing flat with prominent wings; blooming from late March through May; flowers blue or often white on clayey substrates; in rich calcareous forests, bottomland hardwood forests, and shady roadsides

                                                        27 Outer spathe (18.7-42.8 mm, x̅ = 25.4), to 13.5 mm longer than inner (x̅ = 2.5); capsule usually drying tan to brown; hyaline margin of inner spathe broadly acute, obtuse, or truncate apically, and often projecting as lobe; blooming from late March through July; usually over limestone substrates in a wide variety of habitats

                                                    25 Plants dark green when fresh, drying olive to dark brown; mature plants with numerous stems from base (to 55), averaging 7.3 or more; blooming from late February through April, rarely into May.

                                                          28 Plant 30-70 cm tall; node not geniculate, node purplish; mature capsule dark brown to black

                                                          28 Plant <45 cm tall; node usually geniculate and green (occasionally purplish); mature capsule tan to brown.

                                                            29 Surface of leaves, stems and peduncle distinctly granular (like grain of white sand); leaves and spathe scabrous on surface and margin of fresh plants (this character often lost in drying); outer spathe 18.6-34.1 mm (x̅ = 25.8) ; 0.4-12.4 mm longer than inner spathe (x̅ = 4.7); occurring in northcentral Texas on calcareous soils in remnant prairie, fields, open post oak woodlands, and adjacent roadsides and lawns

                                                            29 Surface of leaves, stems and peduncle glabrous, margin sometimes scabrous or denticulate (character often lost on dried plants); outer spathe shorter on average and spathe equal or outer spathe averaging much less than 4.7 mm longer than inner; occurring east and south of northcentral Texas.

                                                              30 Most stems branched, but often with one to a few unbranched stems from base; spathe turgid usually tan or brown and strongly tinged with purple to 6.2 mm wide (x̅ = 4.9); occurring on sandy to loamy soils in prairie remnants, fields, adjacent roadsides, and along grassy bayous in southeastern Texas

                                                              30 All stems branched with numerous stems on mature plants; spathe green, not turgid and narrower, with purple coloration mostly confined to base of spathe.

                                                                 31 Plants typically sprawling; majority of spathe with the inner spathe longer than the outer (character unique to this species), some spathe equal or with outer slightly longer than inner; endemic to prairie and adjacent disturbed habitats primarily in Coastal Bend of Texas, rarely south and west, on calcareous substrates

                                                                 31 Plants typically ascending to erect (S. varians sprawling); spathe equal or with the outer slightly longer than inner (rarely with inner longer than outer).

                                                                   32 Stems 1.8-5.2 mm wide (x̅ = 3.2); leaves 2-4.9 mm (x̅ = 3.9); in a wide variety of open habitats typically on or in close proximity to calcareous substrates (abundant along roadsides)

                                                                   32 Stems 2.3-7.4 mm wide (x̅ = 4.2); leaves 3.6-8.4 mm wide (x̅ = 5.4); occurring in southeastern and southern Texas.

                                                                     33 Plants usually sprawling; stems 2.6-5.6 mm wide (x̅ = 3.9); stems 2 to 18 (x̅ = 8); leaves 3.6-8.4 mm wide (x̅ = 5); peduncle 2 to 3 (x̅ = 2.5); endemic from southcentral Texas, rarely eastward to Brazoria County historically; on calcareous substrates in prairie, open woodlands, and adjacent roadsides and typically on or in close proximity to rocky or gravelly outcroppings

                                                                     33 Plants ascending to erect; stems 2.3-7.4 mm wide (x̅ = 4.5); stems 2 to 55 (x̅ = 10.8) (most of any species observed); leaves 3.7-8 mm wide (x̅ = 5.8); peduncle 2 to 5 (x̅ = 3.1); endemic to deep sandy substrates in southern Texas