The female gametophyte development in the fourteen investigated taxa of the Eriocaulaceae conforms to thePolygonumtype. Three circumaxial antipodal cells are organized at the chalazal pole of the embryosac. The size and form of cells vary in different taxa. The cells lose their walls prior to the fusion of polar nuclei within the embryo sac. A conspicuous antipodal cyst develops by the coalescence of the three naked protoplasts. This is followed by the enlargement and subsequent fusion of nuclei. The triploid nucleus undergoes hypertrophy. The cyst breaks down soon after the secondary nucleus is organized and when the central cell begins to elongate. A nutritive role is ascribed to the antipodal cyst. This unique behaviour of the antipodals is a consistent character of the Eriocaulaceae of the Old and the New Worlds studied.