Abstract
1. The potential difference (P. D.) between the two ends of one and the same internodial cell of Nitella was measured when water enters the cell at one end and goes out at the other under the osmotic gradient of 0.2M sucrose.
2. When the cell is in contact with the KCl solution in the concentration range of 0.05M-0.01M, the potential at the part where water comes out of the cell becomes always higher than that where water enters.
3. This phenomenon is explained by the uneven distribution of KCI in the cell sap in terms of diffusion potential.
4. When very diluted KCl solutions (0.001M-0.0001M) are applied to the external medium, the P. D. between the two parts of the cell shows discrepancies which are not apprehensible on the basis of diffusion potential unless changes in the mobility of K+ in the protoplasmic layer are postulated in the cell part where water flows out.
The author wishes to express his most cordial thanks to Professor N. Kamiya for his helpful advice and directions throughout this work.
