The Collaborative International Dictionary of English v.0.48:

Primulaceous \Prim`u*la"ceous\, a. (Bot.)
   Of or pertaining to an order of herbaceous plants
   (Primulace[ae]), of which the primrose is the type, and the
   pimpernel, the cyclamen, and the water violet are other
   examples.
   [1913 Webster]