1 Perianth with tepals campanulate basally, flaring distally; annual; plants usually < 2 dm tall; tepals 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) nodes; tepals with maroon blaze near base; mature capsules globose, tan with purple sutures; [widespread]

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

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

    3 Inflorescences paired (each inflorescence composed of 1-several flowers, their pedicels emanating from within 2 chartaceous scales; thus, there are 2 pairs of scales within the 2 outer, leaflike, green spathe bracts); 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 bracts there is only one pair of chartaceous scales); outer spathe bract connate 2-6 mm (except 0-1 mm in S. campestre).

               8 Stems simple, unbranched (rarely branched).

                 9 Spathe bracts connate 0-1 mm

                 9 Spathe bracts connate > 1 mm.

                   10 Base of plant with fibrous remains of leaves

                   10 Base of plant without fibrous remains of leaves.

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

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

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

                          13 Margins of outer spathe connate basally 1-3.5 mm; plants drying green or olive; [ne. WV northward]

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

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

               8 Stems branched, with 1-5 nodes.

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

                              15 Plant bases 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 bracts 15-20 (-25) mm long

                                  17 Stems 0.5-1.2 mm wide, not scabrous; plants drying pale brown or greenish brown; spathe bracts 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 capsules mostly 5.5-8 mm long; [of FL and sw. GA]

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

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

                                       19 Stems and branches scabrous on margins 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 capsules 4-6 mm long; [of e. MD northward to sw. Nova Scotia]

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

                              15 Plant bases 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 margins of inner spathe bract acute (contra S. atlanticum)

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

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

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

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

                                                 24 Spathe bracts and stems with abundant white spicules or papillae, sometimes these +/- flattened like lenticels; outer spathe bract usually > inner by 2.5-5.5 mm; spathe bracts 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 margins, 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 capsules 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, bogs, and marshes

                                                      26 Stem body as wide or narrower than the margins (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 capsules 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); capsules usually drying tan to brown; hyaline margin of inner spathe broadly acute, obtuse, or truncate apically, and often projecting as lobes; 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; nodes not geniculate, nodes purplish; mature capsules dark brown to black

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

                                                            29 Surface of leaves, stems and peduncles distinctly granular (like grains of white sand); leaves and spathes scabrous on surface and margins 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 prairies, fields, open post oak woodlands, and adjacent roadsides and lawns

                                                            29 Surface of leaves, stems and peduncles glabrous, margins sometimes scabrous or denticulate (character often lost on dried plants); outer spathe shorter on average and spathes 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; spathes 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; spathes green, not turgid and narrower, with purple coloration mostly confined to base of spathe.

                                                                 31 Plants typically sprawling; majority of spathes with the inner spathe longer than the outer (character unique to this species), some spathes equal or with outer slightly longer than inner; endemic to prairies 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); spathes 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); peduncles 2 to 3 (x̅ = 2.5); endemic from southcentral Texas, rarely eastward to Brazoria County historically; on calcareous substrates in prairies, 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); peduncles 2 to 5 (x̅ = 3.1); endemic to deep sandy substrates in southern Texas