Source : Webster's Revised Unabridged Dictionary (1913)

Equisetum \Eq`ui*se"tum\, n.; pl. {Equiseta}. [L., the
   horsetail, fr. equus horse + seta a thick,, stiff hair,
   bristle.] (Bot.)
   A genus of vascular, cryptogamic, herbaceous plants; -- also
   called {horsetails}.

   Note: The {Equiseta} have hollow jointed stems and no true
         leaves. The cuticle often contains siliceous granules,
         so that one species ({E. hyemale}) is used for scouring
         and polishing, under the name of {Dutch rush} or
         {scouring rush}.