Most red algae with a Polysiphonia-type life history are regarded as having isomorphic phases. However, some show minor deviations in morphology, including differences in branching reported in female gametophytes and tetrasporophytes of Ceramium. By sampling populations of Ceramium codicola, an epiphyte of Codium fragile, it was possible to characterize the morphology of female and male gametophytes and tetrasporophytes. Branching pattern was characterized by the Strahler method, in which terminal branches are counted as primary branches, and higher order branches are counted where lower order branches meet. Since Ceramium shows dichotomous branching, this method can be used to characterize the degree in which branching is dichotomous. The angle of branching was also measured. Female gametophytes had a higher ratio of primary to secondary branches (3.6 to 5.1) than male gametophytes (2.5) and tetrasporophytes (2.5 to 2.6), which have a similar ratio to each other. This indicates that males and tetrasporophytes have a more dichotomous pattern of branching while female gametophytes have more proliferative primary branches. The differences in branching pattern appear to be related to the location of reproductive cells, which occur along the surface of branches in male gametophytes and tetrasporophytes, but occur near the apices in female gametophytes. The branching angle of female and male gametophytes is similar to each other, and greater than that of tetrasporophytes. Therefore, gametophytes and sporophytes differ in branching angle.

Key words: branching morphology, Ceramium codicola, life history, reproductive phase