The Collaborative International Dictionary of English v.0.48:

Vaginant \Vag"i*nant\, a. [Cf. F. vaginant. See Vagina.]
   Serving to invest, or sheathe; sheathing.
   [1913 Webster]

   Vaginant leaf (Bot.), a leaf investing the stem or branch
      by its base, which has the form of a tube.
      [1913 Webster] Vaginate