Source : Webster's Revised Unabridged Dictionary (1913)

Heartseed \Heart"seed`\, n. (Bot.)
   A climbing plant of the genus {Cardiospermum}, having round
   seeds which are marked with a spot like a heart. --Loudon.

Source : WordNet®

heartseed
     n : herbaceous vine of tropical America and Africa [syn: {Cardiospermum
         grandiflorum}]