The elctron-microscopic studies on plant tissues are at present scarcely known、and a similar study on the club-root tissues of crucifers has also not yetbeen done. WORONIN,CooK and SCHWARTZ and some other investigators studied on the life cycle of the causal organism by means of the ordinal microscope,though some features of the life history remain still obscure. This article deals with the electron-microscopic observation on the club-root tissues of Chinese cabbage (Brassica chinensis L.