Source : Webster's Revised Unabridged Dictionary (1913)

Polygonaceous \Pol`y*go*na"ceous\, a. [See {Polygonum}.] (Bot.)
   Of or pertaining to a natural order of apetalous plants
   ({Polygonace[ae]}), of which the knotweeds (species of
   {Polygonum}) are the type, and which includes also the docks
   ({Rumex}), the buckwheat, rhubarb, sea grape ({Coccoloba}),
   and several other genera.