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Key to Cyperaceae

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Show caption*© Paul Marcum
1 Achene enclosed in a perigynium (a sac-like structure); [subfamily Caricoideae, tribe Cariceae]
1 Achene not enclosed in a perigynium.
image of plant
Show caption*© Paul Marcum
  2 Scales obviously and strongly distichously imbricate; spikelets either aggregated into spikes or heads (Cyperus, Dulichium, Schoenus), or solitary (Abildgaardia); [subfamily Cyperoideae].
image of plant
Show caption*© Jay Horn
    3 Spikelets solitary and terminal (rarely 2-4); of FL peninsula in our area]
    3 Spikelets aggregated into terminal or axillary spikes or heads; [widespread in our area].
      4 Inflorescence axillary; leaves predominantly cauline, conspicuously 3-ranked; perianth bristles subtending the achene 6-9; [tribe Dulichieae]
      4 Inflorescence terminal, more-or-less scapose (though immediately subtended by leafy bracts); leaves predominantly basal, not 3-ranked; perianth bristles absent (Cyperus) or present (Schoenus); [tribe Cypereae].
image of plant
Show caption*© Gary P. Fleming
  2 Scales spirally imbricate; spikelets not usually aggregated.
image of plant
Show caption*© Jay Horn
          6 Achene (when ripe) bony and white; style base persistent on the summit of the achene, forming a differently-textured or differently-colored tubercle; spikelets all unisexual, the pistillate spikelets 1-flowered, the staminate spikelets several-flowered; [subfamily Sclerioideae, tribe Sclerieae]
image of plant
Show caption*© Melanie Flood
          6 Achene mostly brown, black, or tan; style base either persistent as a differentiated tubercle (Bulbostylis, Eleocharis, Rhynchospora) or not (Cladium, Eriophorum, Fuirena, Isolepis, Cyperus, Schoenoplectus, Scirpus, Trichophorum); spikelets mostly or all bisexual; [subfamily Cyperoideae].
             7 Style base persistent as a differentiated tubercle (this small and inconspicuous in Bulbostylis and some spp. of Rhynchospora).
               8 Leaves consisting of bladeless sheaths; spikelet 1 per stem, terminal (very rarely proliferating and with > 1 spikelet); [tribe Eleocharideae]
               8 Leaves with well-developed blades; spikelets few to many per stem, usually subtended by foliaceous bracts.
                 9 Perianth bristles absent; spikelets several-many-flowered; leaves capillary; [tribe Abildgaardieae]
                 9 Perianth bristles present (rarely absent in species without capillary leaves); spikelets 1-2-flowered (several-many-flowered in some species without capillary leaves); leaves capillary to broad; [tribe Schoeneae]
                   10 Achene not subtended by a modified perianth of bristles or scales (in addition to the scales of the spikelets).
                     11 Involucral bracts 1-3, the lowest erect, appearing like a continuation of the culm, the inflorescence therefore appearing lateral.
                       12 Achenes 0.5-0.7 mm long, 1.8-3× as long as wide, minutely papillose in longitudinal lines; [tribe Cypereae]
                       12 Achenes 1.2-1.5 mm long, 1-1.4× as long as wide, minutely pitted or transversely rugose.
                          13 Achenes minutely pitted in longitudinal lines; [tribe Cypereae]
                     11 Involucral bracts 2-several, spreading, the inflorescence therefore appearing terminal.
                              15 Plants diminutive, to 5 dm tall; leaves 3-15 cm long, < 1 mm wide; [tribe Abildgaardieae]
                              15 Plants moderate to very robust, (3-) 5-30 dm tall; leaves 30-150 cm long, 1.5-15 mm wide.
                   10 Achene subtended by a modified perianth of either bristles, 3 stalked paddle-like scales, or 1-2 broad-based scales (in addition to the scales of the spikelets).
                                       19 Achene lacking a perianth, but subtended by 1-2 broad-based scales; plants 0.5-3 dm tall; [tribe Cypereae]
                                       19 Achene subtended by a perianth of 3 stalked paddle-like scales; plants 2-7 dm tall; [tribe Fuireneae]
                                         20 Bristles 10-many, > 5× as long as the achene, white to tawny, straight; [tribe Scirpeae]
                                         20 Bristles 1-6, usually < 4× as long as the achene, brown, straight or conspicuously twisted (twisted if > 3× as long as the achene).
                                           21 Involucral bracts lacking, or consisting only of the slightly modified basal scales of the solitary and terminal spikelet; [of hillsides, upland forests, or cliffs; never (in our area) in marshes, bogs, or streambeds]; [tribe Scirpeae]
                                           21 Involucral bracts present, consisting either of a single, erect bract appearing as a continuation of the culm (the inflorescence thus appearing lateral) or of 2 or more spreading, foliaceous bracts (the inflorescence thus appearing terminal); [of marshes, bogs, streambeds, ditches, or (rarely) terrestrial or on rock outcrops].
                                             22 Main involucral bract 1 (rarely 2), erect, appearing as a continuation of the culm (the inflorescence thus appearing lateral, though in some species the longer inflorescence branches may overtop the bract); [tribe Fuireneae]
                                                 24 Spikelets 10-40 mm long, 6-12 mm in diameter, (1-) 2-40 (-50) per culm; [tribe Fuireneae]
                                                 24 Spikelets 2.5-19 mm long, 2-4 mm in diameter, usually > 50 per culm; [tribe Scirpeae]

Key to Schoenoplectus

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1 Main involucral bracts 2-8, spreading and foliaceous (the inflorescence thus appearing terminal); rhizomes bearing ovoid tubers; bristles persistent on the achene; achenes 2.5-5 mm long (including body and apiculus)
1 Main involucral bract 1 (rarely with an additional 1-2 lateral bracts), erect and terete or triangular, appearing as a continuation of the culm (the inflorescence thus appearing lateral, though in some species the longer inflorescence branches may overtop the bract); rhizomes not bearing tubers; bristles falling from the achene; achenes 1.0-4.5 mm long (including body and apiculus).
  2 Spikelets on stalks of varying lengths, at least some clearly not sessile.
    3 Culms distinctly triangular in cross-section, more sharply so above than below, nearly terete near the base; [section Malacogeton]
    3 Culms terete throughout, or obscurely triangular above; [section Schoenoplectus].
      4 Culms firm, not easily compressed; scales 3-4 mm long.
image of plant
Show caption*© Scott Ward, Prominently red-dotted scales
        5 Achenes biconvex (or rarely weakly trigonous), styles 2; spikelets 3-190, usually in clusters of 2-8 on pedicels, sometimes solitary, but never all solitary throughout inflorescence; bristles usually 6 (5-7), of equitant or differing lengths; scales usually with copious red-brown dots
        5 Achenes trigonous, styles 3; spikelets 5-30, mostly solitary or rarely 2 together borne on the same pedicels; bristles 4, of two conspicuous lengths; scales without copious red-brown dots (sometimes obscurely dotted)
      4 Culms soft and spongy, easily compressible; scales (2.0-) 2.5-3.0 (-3.5) mm long.
          6 Perianth bristles retrorsely barbed; spikelets obtuse; culms terete throughout their length
  2 Spikelets all sessile, in a cluster at one point (rarely with 1 or 2 short branches to 5 mm long).
             7 Spikelet solitary; leaves numerous; plant usually aquatic, the culms and leaves flaccid, supported by the water; [section Malacogeton]
             7 Spikelets (1-) 2-several; leaves 1-4; usually of wet places, but the culms stiff and erect, not floating.
               8 Cespitose annual or perennial; culms terete (or acutely triangular in Schoenoplectiella mucronata), 1-6 dm tall
               8 Rhizomatous perennial; culms triangular in cross-section, usually 5-20 dm tall.
                 9 Leaves elongate, > ½ as long as the culms; achenes trigonous; styles 3-branched; [section Malacogeton]
                 9 Leaves short, < ½ as long as the culms; achenes plano-convex; styles 2 (-3) branched; [Schoenoplectus pungens complex of section Schoenoplectus].
                   10 Sides of the culm strongly concave, wing-angled; culms 3-10 mm in diameter; main involucral bract 1-2.5 (-6) cm long; spikelet scale with apical notch 0.1-0.4 mm deep
                   10 Sides of the culm flat, slightly concave, or slightly convex; culms 1-6 mm in diameter; main involucral bract (1-) 3-20 cm long; spikelet scale with apical notch (0.3-) 0.5-1 mm deep.
                     11 Spikelets 3-35; achenes 1.9-2.6 mm long, biconvex; styles 2-fid
                     11 Spikelets 1-5 (-10); achenes (2.0-) 2.5-3.5 mm long, biconvex or trigonous; styles 2-3-fid.
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