The Collaborative International Dictionary of English v.0.48:

Tetradynamia \Tet`ra*dy*na"mi*a\, n. pl. [NL., fr. Gr. te`tra-
   (see Tetra-) + ? power.] (Bot.)
   A Linnaean class of plants having six stamens, four of which
   are longer than the others.
   [1913 Webster]