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See list of 3 genera in this family

The leaf sheaths in this family are usually separate from the blade and appear as stipules. For circumscription of the family, see Lindquist et al. (2006). References: Hellquist and Crow (1980), Wiegleb and Kaplan (1998).

  • 1a. Leaves opposite; flowers unisexual; staminate flowers with 1 stamen; stigma funnelform
  • 1b. Leaves alternate; flowers bisexual, with 2 or 4 stamens; stigma slender to capitate
    • 2a. Leaf blades narrow-linear, 0.2–1.5 mm wide, all submersed, cross-septate throughout; stipules connate to the blade for a distance of 4–30 mm, commonly more than 10 mm; spikes submersed or sometimes floating, with well-separated lower whorls of flowers, on thin, flexuous peduncles; drupes not compressed, with an indistinctly coiled embryo
    • 2b. Leaf blades filiform to orbicular, 0.1–75 mm wide, all submersed or some floating, cross-septate only in the central lacunar bands (if present); stipules distinct from the blade or connate for a distance of less than 10 mm (long-connate in P. robbinsii); spikes usually with contiguous whorls of flowers, on thick, stiff peduncles, usually emersed; drupes compressed, with a distinctly coiled embryo (indistinctly coiled in P. robbinsii)

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