The Collaborative International Dictionary of English v.0.48:

Jugum \Ju"gum\ (j[=u]"g[u^]m), n.; pl. L. Juga (j[=u]"g[.a]),
   E. Jugums. [L., a yoke, ridge.] (Bot.)
   (a) One of the ridges commonly found on the fruit of
       umbelliferous plants.
   (b) A pair of the opposite leaflets of a pinnate plant.
       [1913 Webster]