Abstract: A description of the marine alga Zhegocai (鹧鸪菜) together with its anthelmintic property first appeared in a book named Zhangpu Xianzhi (漳浦县志) in 1530. The identity of this medical seaweed has long remained a mystery. Since the beginning of this century, a widely distributed tropical alga, Digenea simplex (Wulf.) C. Ag., has been assumed by the Japanese scientists to be the Zhegocai of the Chinese literature, and this assumption has been accepted by many Chinese scientific workers for over forty years. However, from the phytogeographical point of view it is very improbable that the Zhegocai of the Zhangpu (漳浦) district, where the marine flora is subtropical in nature, could be the strongly tropical Digenea simplex. Our field investigation in Zhangpu district has revealed that there is actually a marine alga under the vernacular name Zhegocai or Huichongcai (蛔虫菜)(meaning "Ascaris vegetable") which agrees very well with the orginal description as appeared in Zhangpu Xianzhi. This is, however, not Digenea simplex of Rhodomelaceae but the Caloglossa leprieurii (Mont.) J. Ag. of Delesseriaceae. Therefore we would sugguest that the name "Zhegocai" should be returned to its actural owner, Caloglossa leprieurii, and for the better known anthelmintic seaweed Digenea simplex, the Japanese name Hairencao (海人草) is better retained. According to some Japanese work, there are several seaweeds of effective anthelmintic property other than the above mentioned, among which some, such as Codium fragile (Sur.) Harlot, Ishige okamurai Yendo and species of. Corallina and Jania are even more effective than the well-known Digenea, and some such as Sargassum thunbergii are only slightly lower in effectiveness. All of them are also common seaweeds on the Chinese coast and are note-worthy to our pharmacists in regard to their high anthelmintic value.