an apparatus for the production of marbled articles by injecting into the injection molding die of an injection molding machine two confluent streams of plastic raw material of different hue or color which are supplied from two injection units , via separate pulsation channels which open into a common nozzle channel , just ahead of the mold cavity . the plastic raw materials flowing in the two pulsation channels are subjected to an intermittant and alternatingly pulsating advance by means of feed thrust pulsation controls which generate an intermittant advance of the plastification screws of the injection units . at the junction between the two pulsation channels may be arranged a pulsation chamber with oppositely oriented material entry ports which are alternatingly closed by a reciprocating pulsating element which moves with the pulsating plastic streams .