Water pimpernel

from WordNet (r) 3.0 (2006)

water pimpernel
    n 1: a white-flowered aquatic plant of the genus Samolus

from The Collaborative International Dictionary of English v.0.48

Pimpernel \Pim"per*nel\, n. [F. pimprenelle; cf. Sp. pimpinela,
   It. pimpinella; perh. from LL. bipinnella, for bipinnula
   two-winged, equiv. to L. bipennis; bis twice + penna feather,
   wing. Cf. {Pen} a feather.] (Bot.)
   A plant of the genus {Anagallis}, of which one species
   ({Anagallis arvensis}) has small flowers, usually scarlet,
   but sometimes purple, blue, or white, which speedily close at
   the approach of bad weather.
   [1913 Webster]

   {Water pimpernel}. (Bot.) See {Brookweed}.
      [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Water pimpernel \Wa"ter pim"per*nel\ (Bot.)
   A small white-flowered shrub; brookweed.
   [1913 Webster]