The Collaborative International Dictionary of English v.0.48:

Bractlet \Bract"let\, n. [Bract + -let] (Bot.)
   A bract on the stalk of a single flower, which is itself on a
   main stalk that support several flowers. --Gray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bractlet
    n 1: a small bract [syn: bracteole, bractlet]