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Key to Scleria

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1 Base of achene without hypogynium (a circular, angular, lobed, or tuberculate disk differing in texture and structure from the achene body), the achene base constricted, pitted, and/or ribbed, but appearing as a continuation of the achene body.
  2 Inflorescence of 1 terminal and 1-3 axillary spikes or panicles, each spike or panicle subtended by a foliaceous bract; [subgenus Hypoporum, section Hypoporum]
  2 Inflorescence terminal only; if glomerules spike-like along an axis, then only the lowest with a (or no) bract.
    3 Inflorescence of 2-9 sessile clusters along an axis up to 13 cm long, the individual spikelets 2-5 mm long; bracts (at least above proximal cluster) setaceous; [subgenus Hypoporum, section Hypoporum].
      4 Plants perennial with rhizomes; leaf blades usually pubescent, 1.5-5 mm wide; bract and scale margins long-ciliate; spikelets 4-5 mm long; achenes smooth
      4 Plants annual with fibrous roots; leaf blades glabrous, 0.5-2 mm wide; bract and scale margins eciliate; spikelets 2-3 (-4) mm long; achenes reticulate-papillose to reticulate-verrucose
    3 Inflorescence of a single cluster, the individual spikelets 4-10 mm long; bracts foliaceous; [subgenus Trachylomia, section Trachylomia].
        5 Triangular base of achene lacking pits in the three concave sides; achene 3-4 mm long
        5 Triangular base of achene with a pair of pits on each of the three sides; achene 2-3 mm long
          6 Achene body smooth (often longitudinally ribbed); hypogynium with 0, 8, or 9 tubercles.
             7 Hypogynium with 8 or 9 tubercles, the tubercle surface minutely papillate; [subgenus Trachylomia, section Trachylomia]
             7 Hypogynium not divided into tubercles, either smooth and angled/lobed, or minutely papillate and continuous (not lobed).
                 9 Leaves 10-25 mm wide; achenes 3-4 mm long; hypogynium margin densely brown-ferruginous-ciliate
                 9 Leaves 7-11 mm wide; achenes 1-2 mm long; hypogynium margin moderately to densely white-ciliate or ciliolate
               8 Hypogynium margin eciliate; plants to 1 m long (to 1.8 m in S. lacustris of FL).
                     11 Plants perennial, rhizomatous; culms scabrous only on angles; larger leaves 3-10 mm wide, glabrous; achenes ± 2 mm long, body purplish to black, summit mucronate; hypogynium dark brown (margins paler), the 3 lobes flat, broad, and rounded apically
                     11 Plants annual, without rhizomes; culms strongly retrorsely-scabrous; larger leaves 10-25 mm wide, sparsely pubescent; achenes 3.4-3.8 mm long, body greenish to whitish, sometimes mottled gray, summit rounded; hypogynium whitish to pale brown, bluntly 3-angled; [subgenus Scleria, section Margeleia]
                   10 Hypogynium not 3-angled or 3-lobed, surface minutely papillate; [subgenus Trachylomia, section Trachylomia].
                       12 Achene 1-2 mm long; culm 1-2 mm wide at base; leaves 1-3 mm wide
                       12 Achene 2-4 mm long; culm 2.5-6 mm wide at base; leaves 5-9 mm wide.
                          13 Plants cespitose to short-rhizomatous; sheaths brown or stramineous to reddish, glabrous to glabrate on the ventral surface except for a pubescent and usually thickened summit; inflorescences terminal and lateral; achenes 2.0-3.3 mm long, (1.12-) avg. 1.25 (-1.38× as long as wide; hypogynium surface with laterally and apically rounded papillae; [of wet to mesic pinelands]
                          13 Plants long-rhizomatous or cespitose; sheaths purple to reddish, the ventral surface uniformly pubescent; inflorescences terminal only or terminal and lateral; achenes 2.5-4.0 mm long, (1.35-) avg. 1.45 (-1.54)× as long as wide; hypogynium surface with rounded or flattened papillae; habitats various.
                            14 Plants usually cespitose; inflorescence terminal and lateral (a few culms in a clump can be terminal only); hypogynium surface with laterally flattened and apically triangular-acute to acuminate papillae, often resembling shards of glass or porcelain; [of coastal hammocks, oak woods near saltwater, and blackwater swamps]
                            14 Plants usually long-rhizomatous; inflorescence terminal only; hypogynium surface with laterally and apically rounded papillae; [mostly of dry to dry-mesic pinelands and barrens]
          6 Achene reticulate or papillose, rarely smooth (most often from apparent abortion or abnormal development); hypogynium with 3 tongue-shaped lobes, or 3 or 6 tubercles.
                              15 Hypogynium of 3 tongue-shaped lobes appressed to the underside of the achene (appearing nearly bract-like); achene reticulate, the pits generally squarish or rectangular and arranged regularly in rows, rarely smooth (apparently by abortion or abnormal development); [subgenus Scleria, section Foveolidia].
                                16 Achene pubescent (occasionally becoming glabrate); lower lateral inflorescences on long, filiform, usually drooping peduncles; bract of the uppermost lateral inflorescence usually reaching from 1/3-3/4 the length of the terminal internode; terminal internode 6-30 cm long
                                16 Achene glabrous; lower lateral inflorescences sessile or on short-erect peduncles; bract of the uppermost lateral panicle usually reaching 3/4 the length of to exceeding the terminal internode; terminal internode 3-8 cm long
                              15 Hypogynium with 3 or 6 tubercles; achene papillose, sometimes reticulate (if so, the pits generally variable in shape and not forming regular rows), or rarely smooth; [subgenus Trachylomia, section Trachylomia].
                                  17 Leaves 1-2.5 mm wide; hypogynium with 6 tubercles; achene 1.0-2.5 mm long, the body papillate or roughened-reticulate.
                                  17 Leaves 1-7 mm wide; hypogynium with 3 (sometimes deeply lobed) tubercles, achene papillate or roughened-reticulate, 2.0-3.5 mm long; or hypogynium tubercles 6 and achene epapillate and smoothish, 2.5-3.4 mm long.
                                       19 Achene body smoothish with broad low rises, epapillate except for a few retrorse pappi at the very base, sometimes a faint transverse ridge near the base; achene including hypogynium 2.5- 3.2 (-3.4) mm long, 2.3-2.7 mm wide; hypogynium disk 1.4-1.8 (-2.1) mm wide, 0.1-0.2 (-0.3) mm thick; tubercles 6 (rarely 3 deeply lobed); longer cilia on terminal inflorescence primary bract 1.1-2.2 mm; longer pistillate scale keel cilia 0.5-1.0 mm; leaf blades (2.5-) 3-7 mm wide, ciliate with stiff hairs on margins and primary veins, rarely with a few stiff hairs between the veins, lacking fine puberulent hairs
                                       19 Achene body papillose throughout, often transversely ridge or reticulate (rarely papillae absent in reticulate achenes); achene including hypogynium 2.0-3.3 (-3.5) mm long, 1.7-2.4 (-2.6) mm wide; hypogynium disk (0.6-) 0.8-1.4 (-1.6) mm wide, 0.1-0.4 (-0.5) mm thick; tubercles 3, entire to deeply lobed; longer cilia on terminal inflorescence primary bract 0-1.1 (-1.3) mm; longer pistillate scale keel cilia 0-0.5 mm; leaf blades 1-6 mm wide, glabrous to ciliate on margins and primary veins to puberulent with fine hairs over entire surface, especially adaxially.
                                         20 Leaf blades 1-3 (-3.5) mm wide, adaxial surface glabrous and eciliate, or glabrous and ciliate on margins, or puberulent and ciliate; terminal inflorescence primary bract 0.4-2.2 mm wide at widest point, its longer cilia (0-) 0.1-0.7 (-0.9) mm long; hypogynium disk (0.6-) 0.8-1.3 (-1.5) mm wide, 0.1-0.2 (-0.3) mm thick.
                                         20 Leaf blades (2.5-) 3-6 mm wide, at least some adaxial surfaces puberulent throughout, often ciliate with stiff hairs on margins and primary veins; terminal inflorescence primary bract 1.2-4.1 mm wide at widest point, its longer cilia 0.7-1.1 (-1.3) mm long; hypogynium disk 1.1-1.4 (-1.6) mm wide, (0.1-) 0.2-0.4 (-0.5) mm thick