pillwort

/ˈpɪlwɜːrt/
noun
  1. A small aquatic fern (Pilularia globulifera) that grows in shallow water or wet soil, with leaves that look like tiny green pills.
    • The pond was full of pillwort, its round leaves floating on the surface.
    • Pillwort is often found in muddy areas near lakes and streams.
    • We learned about pillwort during our biology field trip to the wetlands.
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