The Collaborative International Dictionary of English v.0.48:

Telegraph plant \Telegraph plant\ (Bot.),
   A tick trefoil (Meibomia gyrans formerly Desmodium
   gyrans), native of the East Indies; it is a leguminous plant
   whose lateral leaflets jerk up and down like the arms of a
   semaphore, and also rotate on their axes.
   [Webster 1913 Suppl.]