The Collaborative International Dictionary of English v.0.48:

Planogamete \Plan"o*ga*mete`\, n. [Gr. ? wandering + E. gamete.]
   (Bot.)
   One of the motile ciliated gametes, or zoogametes, found in
   isogamous plants, as many green alg[ae] (Chlorophyce[ae]).
   [Webster 1913 Suppl.]