#duckweed  any small or minute aquatic plant of the family Lemnaceae that float on or near the surface of shallow ponds
  supertype:  aquatic_plant__aquaticplant__water_plant__waterplant__hydrophyte__hydrophytic_plant__hydrophyticplant  a plant that grows partly or wholly in water whether rooted in the mud, as a lotus, or floating without anchorage, as the water hyacinth
  member of:  family_Lemnaceae
  subtype:  common_duckweed__lesser_duckweed__Lemna_minor  of temperate regions except eastern Asia and Australia
  subtype:  star-duckweed__Lemna_trisulca  cosmopolitan in temperate regions except North America
  subtype:  great_duckweed__greatduckweed__water_flaxseed__waterflaxseed__Spirodela_polyrrhiza  cosmopolitan except South America and New Zealand and some oceanic islands
  subtype:  watermeal  any of various aquatic plants of the genus Wolffia; throughout warmer regions of the world
     subtype:  common_wolffia__Wolffia_columbiana  smallest flowering plants known; of the Americas
  subtype:  mud_midget__mudmidget__bogmat__Wolffiella_gladiata  having narrow flat sickle-shaped submerged fronds; North America

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