Abstract: Samples of Polysiphonia scopulorum var. villum (J. Agardh) Hollenberg have been collected from Nan’ao Island, Shantou, Guangdong province during the field survey of November 2013~February 2014, and identified. We found the following combination of the characters: 1. the plants grown densely in tufts on rocks with villous mat shape; 2. the thalli composed with prostrate and erect branches in which the erect branches were less than 1 cm high; 3. the erect branches, sparsely branching out or not, with blunt apical cells; 4)the rhizoids stretching outward from the middle part of the pericentral cells with open connection; 5. the trichoblasts being sparse and short with 1~3 dichotomies, deciduous, often leaving conspicuous scar-cells; 6. mature cystocarps being ovate with a protruding ostiole; 7. the spermatangial branches arising from the entire trichoblast primordium, being arranged in a spiral manner at the tip of the branches, cylindrical without a celled sterile tip; and 8. the tetrasporangia occurring in slightly spiral series of up to 4-6-(10) successively, maturing sporangia spherical with two cover cells in a distal portion of the indeterminate lateral branches. This is the first time the species was recorded at the coast of the South China Sea. In order to observe the intimate internal structure of these filamentous thalli, a set of “dye-press” method to experimental materials was operated originally to be beneficial to the taxonomical research of those similar genera. The morphology and the tetrasporangial development of the species were observed in detail in this study. The results should enrich our knowledge of the morphology and geographical distribution of the species.

Key words: Rhodophyta, Rhodomelaceae, reproductive structure, taxonomy, geographical distribution, “Dye-press”, method