1. In the growing point of the root of Vicia Faba there is a daily periodicity in the rate of cell division under constant conditions of illumination, temperature and moisture. The curves indicating the variation of the rate are not always similar according as the differences in material and condition, but there is a certain definite curve for a knd of material under the same conditions, i.e. there are a primary maximum and a smaller secondary maximum during 24-hour period. 2. In the case of the elongation of the root under constant temperature, moisture and illumination, it is found to proceed in a rhythmical manner. In accordance with the material and condition, the maximum and minimum do not always occur at fixed time of day by the clock, but they have some regular length of period, i. e. the resting phase of 8 hours follows the active phase of 16 hours. 3. The primary active phase in cell division nearly coincides with the resting phase in the elongation, but the secondary maximum is accompanied by no recognizable resting phase in the elongation. However the active phase in elongation occurs several hours after the maximum point of primary active phase in cell division.