On the culture of spores and the development of the thallus of Botryocladia chiajeana (Menegh.) Kylin (Rhodymeniales, Rhodymeniaceae). - The complete development ofBotryocladia chiajeanahas been studied in culture. Spore germination and sporeling development is of thediscalis mediatustype described by Inoh(1947). The hollow vesiculous branches filled with a mucilage derive from the spacing of the erect filaments which form the stipe. The authors compare this development of the thallus with that described for other Rhodymeniales.