1 Achene enclosed in a perigynium (a sac-like structure); [subfamily Caricoideae, tribe Cariceae]

1 Achene not enclosed in a perigynium.

  2 Scales obviously and strongly distichously imbricate; spikelets either aggregated into spikes or heads (Cyperus, Dulichium, Schoenus), or solitary (Abildgaardia); [subfamily Cyperoideae].

    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].

        5 Perianth bristles present

        5 Perianth bristles absent

  2 Scales spirally imbricate; spikelets not usually aggregated.

          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]

          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]

             7 Style base not persistent as a differentiated tubercle.

                   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 transversely rugose; [tribe Fuireneae]

                          13 Achenes minutely pitted in longitudinal lines; [tribe Cypereae]

                            14 Spikelets aggregated into spherical glomerules

                     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.

                                16 Flowers 1-2 per spikelet; [tribe Schoeneae]

                                16 Flowers several-many per spikelet.

                                  17 Style fimbriate; leaves 0.5-5 mm wide; [tribe Abildgaardieae]

                                  17 Style smooth; leaves (2-) 5-18 mm wide; [tribe Scirpeae]

                   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).

                                    18 Achene subtended by stalked paddle-like scales or broad-based scales.

                                       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]

                                    18 Achene subtended by bristles.

                                         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]

                                               23 Achenes rugulose; plants annual

                                               23 Achenes smooth; plants perennial

                                             22 Main involucral bracts 2-8, spreading and foliaceous (the inflorescence thus appearing terminal).

                                                 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]