cyathium

noun

(Gr. kyathos: cup) (pl. cyathia) A type of inflorescence characteristic of some members of Euphorbiaceae, e.g. poinsettia; consisting of a cuplike involucre bearing unisexual flowers, staminate on its inner face, pistillate from the base, surrounded by involucral bracts; i.e. consisting of a cup-shaped involucre enclosing an apetalous, pistillate flower surrounded by several staminates flowers.