knot·grass /ˈnɑtˌgræs/
  軟花屬植物
  Knot·grass n. Bot. (a) a common weed with jointed stems (Polygonum aviculare); knotweed. (b) The dog grass. See under Dog.
  Note: ☞ An infusion of Polygonum aviculare was once supposed to have the effect of stopping the growth of an animal, and hence it was called, as by Shakespeare, “hindering knotgrass.”
  We want a boy extremely for this function,
  Kept under for a year with milk and knotgrass.   --Beau. &  Fl.
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  knotgrass
       n : low-growing weedy grass with spikelets along the leaf stems
           [syn: Paspalum distichum]