The Collaborative International Dictionary of English v.0.48:

Portoir \Por"toir\, n. [OF., fr. porter to bear.]
   One who, or that which, bears; hence, one who, or that which,
   produces. [Obs.]
   [1913 Webster]

         Branches . . . which were portoirs, and bare grapes.
                                                  --Holland.
   [1913 Webster]