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Sparganium

See list of 7 species in this genus

Angelo and Boufford (2000) reported Sparganium americanum ×S. fluctuans for MA. Though this collection may be accurately determined, it is not included here until further study is taken given that these two species below to different subgenera and Cook and Nichols (1986, 1987) did not mention the occurrence of this hybrid. References: Cook and Nicholls (1986, 1987).

  • 1a. All or most flowers and fruits with 2 stigmas; all or most ovaries with 2 locules; body 
of achenes truncate or abruptly tapering to the beak, with 3–7 angles (i.e., not terete in 
cross-section), not constricted near center, 4–8 mm wide
  • 1b. Flowers and fruits with 1 stigma; ovary with 1 locule; body of achenes tapering to beak, terete or weakly angled in cross-section, often slightly constricted near center, up to 4 mm wide
    • 2a. Flowering stems with 1 staminate spike; fruiting spikes 5–12 mm in diameter; beak 
of achene 0.5–1.5 mm long
    • 2b. Flowering stems with 2–20 staminate spikes; fruiting spikes 10–35 mm in diameter; beak of achene 1.5–7 mm long
      • 3a. Beak of mature fruit flattened and strongly curved; tepals adnate to fruit 
stipe for ca. ½ their length; anthers (0.5–) 0.6–0.7 (–0.9) mm long; stigmas 
(0.4–) 0.7–0.8 (–0.9) mm long
      • 3b. Beak of mature fruit ± terete, straight or only slightly curved (sometimes strongly curved in S. androcladum); tepals free from fruit stipe; anthers 0.8–1.5 mm long; stigmas (0.6–) 0.8–4 mm long
        • 4a. Both the sessile carpellate spikes of the main axis and the peduncle bases of 
the lateral branches borne directly in the axil of leaves or bracts [Fig. 306]; tepals 
± opaque, with a dark brown pad of tissue near apex, the apical margins emarginate to entire
          • 5a. Fruiting spikes 25–35 mm in diameter; achenes usually dull in basal half and lustrous in apical half, with a beak (4–) 4.5–7 mm long; anthers 1–1.6 mm long; lateral branches of inflorescence, when present, bearing only staminate spikes
          • 5b. Fruiting spikes 15–25 mm in diameter; achenes usually dull throughout, with a beak (1.5–) 3–4 (–5) mm long; anthers 0.8–1.2 mm long; lateral branches of inflorescence, when present, bearing 1–3 carpellate spikes in addition to staminate spikes [Fig. 306]
        • 4b. Some of the sessile carpellate spikes of the main axis and/or the peduncle 
bases of the lateral branches borne above the axil of leaves or bracts [Fig. 307]; tepals ± translucent, without a pad of dark tissue at the apex, the apical margins distinctly erose
          • 6a. Leaves usually erect and emergent, though sometimes flaccid and floating, 
the distal portion with a prominent abaxial keel or triangular in cross-section; 
beak of fruit 2–4.5 (–6) mm long; at least some of the staminate spikes separated by short internodes [Fig. 307]
          • 6b. Leaves flaccid and floating (or submerged), the distal portion flat, without an abaxial keel; beak of fruit 1.5–2 (–2.2) mm long; staminate spikes contiguous

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 Show photos of:   Each photo represents one species in this genus.