chelone glabra

from WordNet (r) 3.0 (2006)

Chelone glabra
    n 1: showy perennial of marshlands of eastern and central North
         America having waxy lanceolate leaves and flower with lower
         part creamy white and upper parts pale pink to deep purple
         [syn: {shellflower}, {shell-flower}, {turtlehead},
         {snakehead}, {snake-head}, {Chelone glabra}]

from The Collaborative International Dictionary of English v.0.48

Turtlehead \Tur"tle*head`\ (t[^u]r"t'l-h[e^]d`), n. (Bot.)
   An American perennial herb ({Chelone glabra}) having white
   flowers shaped like the head of a turtle. Called also
   {snakehead}, {shell flower}, and {balmony}.
   [1913 Webster]

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