The Collaborative International Dictionary of English v.0.48:

Decagynia \Dec`a*gyn"i*a\ (d[e^]k`[.a]*j[i^]n"[i^]*[.a]), n. pl.
   [NL., fr. Gr. de`ka ten + gynh` a woman, a female.] (Bot.)
   A Linn[ae]an order of plants characterized by having ten
   styles. Decagynian