Cicuta virosa

from The Collaborative International Dictionary of English v.0.48

Hemlock \Hem"lock\, n. [OE. hemeluc, humloc, AS. hemlic,
   hymlic.]
   1. (Bot.) The name of several poisonous umbelliferous herbs
      having finely cut leaves and small white flowers, as the
      {Cicuta maculata}, {Cicuta bulbifera}, and {Cicuta
      virosa}, and the {Conium maculatum}. See {Conium}.
      [1913 Webster]

   Note: The potion of hemlock administered to Socrates is by
         some thought to have been a decoction of {Cicuta
         virosa}, or water hemlock, by others, of {Conium
         maculatum}.
         [1913 Webster]

   2. (Bot.) An evergreen tree common in North America ({Abies
      Canadensis} or {Tsuga Canadensis}); hemlock spruce.
      [1913 Webster]

            The murmuring pines and the hemlocks. --Longfellow.
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   3. The wood or timber of the hemlock tree.
      [1913 Webster]

   {Ground hemlock}, or {Dwarf hemlock}. See under {Ground}.
      [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Water hemlock \Wa"ter hem"lock\ (Bot)
   (a) A poisonous umbelliferous plant ({Cicuta virosa}) of
       Europe; also, any one of several plants of that genus.
   (b) A poisonous plant ({[OE]nanthe crocata}) resembling the
       above.
       [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Cowbane \Cow"bane`\ (kou"b[=a]n`), n. (Bot.)
   A poisonous umbelliferous plant; in England, the {Cicuta
   virosa}; in the United States, the {Cicuta maculata} and the
   {Archemora rigida}. See {Water hemlock}.
   [1913 Webster]