Carrageenans from gametangial (male and female) and tetrasporangial plants of the red alga Iridaea cordata were isolated, fractionated, and characterized on the basis of their anhydrogalactose and sulfate content and infrared spectra. As in the case of Chondrus crispas the tetrasporangial plants yielded only λ-carrageenan while the gametangial plants produced carrageenans of the κ-type. The male plants yielded proportionately more KCl-insoluble κ-carrageenan than did the female. The infrared spectra of the various preparations from I. cordata were virtually indistinguishable from those of comparable fractions isolated from C. crispus.