The Collaborative International Dictionary of English v.0.48:

Legumen \Le*gu"men\ (l[-e]*g[=u]"m[e^]n), n.; pl. L. Legumina
   (-m[i^]*n[.a]), E. Legumens (-m[e^]nz). [L.]
   Same as Legume.
   [1913 Webster]