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Key to Cyperus, Key ZC: Key to Cyperus, subgenus Pycnostachys, sections Fusci, Diffusi, and Haspani -- Spikelets in digitate clusters or glomerulate heads; scales broadly rounded or conduplicate

Cyperaceae

Cyperus

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1 Scales orbiculate or broadly obovate, to 1.1 mm long and wide, about as broad as long, minutely mucronate at the tip (“bead-like”); achenes 0.6-0.9 mm long × 0.3-0.4 mm wide, not much exceeded by the scales; plants fibrous-rooted annuals; [sect. Fusci]
  2 Heads very dense, spikelets 30-120 per head; scales 0.6-0.8 mm long × 0.6-0.8 mm wide, greenish; styles 0.1 mm long
  2 Heads looser, spikelets 3-12 per head; scales 0.9-1.1 mm long × 1 mm wide, light brown, bronze, whitish, or purplish brown; styles 0.3-0.4 mm long
1 Scales ovate to lanceolate, (1.1-) 1.6 mm long or longer, mucronate or not; achenes, if < 1.5 mm, much exceeded by (<1/2 the length of) the scales; plants perennial, often with cormose bases, stolons, or rhizomes.
    3 Leave involute; live plants viscid; scales with a mucronate to cuspidate apex at least 0.2 mm long, usually excurved; achenes with beaks 0.5-1.2 mm long or a whitish overlay and spongy stipitate base; [subgenus Cyperus, section Elegantes; keyed here as failsafes]
    3 Leaves flat or V-shaped; live plants not viscid; scales obtuse to acute (minutely mucronate in C. dentatus); achenes at most 1 mm long (longer in the obscurely spicate subg. Cyperus species keyed here as failsafes), without a beak or spongy stipitate base.
      4 Bracts large and conspicuous, 7-11, lanceolate, 5-25 mm wide, the main veins whitish-banded adaxially; inflorescence open and diffuse, often with 2nd and 3rd order rays; [cultivated, rarely naturalizing]; [section Diffusi]
      4 Bracts usually < 7, linear, < 10 mm wide, without whitish banding on the main veins, shorter than the culm.
        5 Spikelets in dense spikes, inflorescence often capitate; scales divaricate at maturity, rounded on the keel, weakly 5-13-nerved; achenes (1-) 1.4-2.5 mm long; plants mostly with hardened cormose culm bases, sometimes also rhizomatous; [dry, sandy habitats]; [subgenus Cyperus, section Laxiglumi; keyed here as failsafes].
        5 Spikelets in loose digitate clusters, rays elongate (except some forms of C. haspan); scales closely appressed, conduplicate and weakly 1-3 (-5)-ribbed; achenes 0.3-1 mm long; plants stoloniferous or rhizomatous; [mostly in wetlands]; [section Haspani]
          6 Leaf blades usually absent; bracts 2 (-4), usually much reduced; achenes 0.3-0.6 mm long, globose to obovoid.
             7 Rays 5-15; anther 1-1.2 mm long; culms hard, not much flattening in pressing; [native]
             7 Rays 200-300; anthers 0.3-0.5 mm long; culms soft, terete, flattening in pressing; [cultivated, rarely naturalizing]
          6 Leaf blades present; bracts 3-5, well-developed and often exceeding the inflorescence; achenes 0.7-1 mm long.
               8 Scales 2-2.5 mm long × 1.2-2 mm wide, ovate or broadly elliptic, 3-26 (-50) per spikelet, minutely mucronate, sometimes excurved; spikelets ovate to linear, straight, light brown to reddish-brown laterally with greenish midribs; plants with stolons terminated by tubers, and often proliferous spikelets
               8 Scales 2.5-3 mm long × 1-1.8 mm wide, relatively narrowly ovate-elliptic, 20-60 per spikelet, blunt and incurved; spikelets lanceolate to linear, often contorted, pale yellowish at maturity; plants with stolons, lacking tubers or proliferous spikelets