The Collaborative International Dictionary
Xyridaceous
Xyridaceous \Xyr`i*da"ceous\, a. (Bot.) Of or pertaining to a natural order ( Xyride[ae]) of endogenous plants, of which Xyris is the type.
Wiktionary
xyridaceous
a. Belonging or pertaining to the Xyridaceae, a family of flowering plants.