Source : Webster's Revised Unabridged Dictionary (1913)

Iridaceous \Ir`i*da"ceous\, Irideous \I*rid"e*ous\, a. [From NL.
   Iris, Iridis, the Iris.] (Bot.)
   Pertaining to, or resembling, a large natural order of
   endogenous plants ({Iridace[ae]}), which includes the genera
   {Iris}, {Ixia}, {Crocus}, {Gladiolus}, and many others.

Source : WordNet®

iridaceous
     adj : of or pertaining to or characteristic of plants of the
           family Iridaceae