arrow grass

from WordNet (r) 3.0 (2006)

arrow grass
    n 1: tufted perennial found in shallow water or marshland;
         sometimes poisons livestock [syn: {arrow grass},
         {Triglochin maritima}]

from The Collaborative International Dictionary of English v.0.48

Arrow grass \Ar"row grass`\, n. (Bot.)
   An herbaceous grasslike plant ({Triglochin palustre}, and
   other species) with pods opening so as to suggest barbed
   arrowheads.
   [1913 Webster] Arrowhead