The Collaborative International Dictionary of English v.0.48:

Dutchman's breeches \Dutchman's breeches\, Dutchman's-breeches
\Dutchman's-breeches\n. (Bot.),
   a delicate perennial spring-flowering herb (Dicentra
   cucullaria) of eastern U.S., having peculiar double-spurred
   white flowers. See Illust. of Dicentra

   Syn: Dicentra cucullaria.
        [1913 Webster + WordNet 1.5]

WordNet (r) 3.0 (2006):

Dicentra cucullaria
    n 1: delicate spring-flowering plant of the eastern United
         States having white flowers with double spurs [syn:
         Dutchman's breeches, Dicentra cucullaria]