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Key to Eleocharis, Key C: spikerushes with cylindric spikelets about the same width as culms; fresh culms with incomplete septae not evident externally

Cyperaceae

Eleocharis

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1 Culms acutely quadrangular (with four distinct sides)
1 Culms trigonous or terete, sometimes obscurely angled.
  2 Culms 0.5-1.5 mm wide; spikelets < 3 mm wide; achene < 1.4 mm wide; plants sometimes with aquatic, submerged forms bearing vegetative, filiform, flaccid culms.
    3 Achene body 0.65-1.5 mm long, whitish, stramineous, or pale green; scales mostly ca. 3.5 mm long; culms terete when fresh; tubers absent
    3 Achene body (1.5-) 1.9-2.6 mm long, stramineous or medium brown; scales mostly ca. 5 mm long; culms acutely trigonous when fresh; tubers sometimes present
  2 Culms 1.0-7.5 (-8.5) mm wide (culms mostly > 1.5 mm); spikelets 3.5-8 mm wide; achene > 1.4 mm wide; plants without submerged, vegetative aquatic forms.
      4 Achene apex gradually narrowed into a stout spongy region, confluent with tubercle; perianth bristles smooth (or with only minutely retrorse barbs distally); [widespread in coastal areas from NC to FL, w. to TX]
      4 Achenes lacking a stout spongy region at the apex, distinctly separate from the tubercles (or achene apex slightly constricted into a hard annular thickening, but still with a distinguishable transition zone as in E. mutata); perianth bristles distinctly retrorsely barbed; [coastal areas; s. FL and s. TX].
        5 Culms terete or obscurely 3-5 angled, not conspicuously trigonous throughout; culms (2- ) 3.6-7.5 mm wide [s. TX Coastal Plain]
        5 Culms trigonous throughout; culms (1.1-) 1.5-5.1 (-8.5) mm wide [s. FL].
          6 Scales of spikelet ovate-oblong; bristles irregularly retrorse (retrorse spinules shorter and more concentrated distally), most shorter than the achene body; achenes shiny dark brown at maturity; achene apex markedly constricted into a short neck; culms primarily 1.5-3.7 mm wide; [waif, s. FL]
          6 Scales of spikelet ovate to broadly ovate; bristles coarsely retrorse, mostly exceeding achene and tubercle; achenes lustrous olive-yellow to amber at maturity, achene apex slightly constricted into hard annual thickening (not forming a "neck" between achene and tubercle); culms primarily 2.6-5.1 mm wide; [potential waif; s. TX and s. FL]