Measurements have been made of the "osmotic" water permeability (Pos) of internodal cells of Ohara australis using the method of transcellular osmosis. The mean value was 5�6 /1-3//1-2 ? min. atm, which is close to that obtained by Kamiya and Tazawa (1956) with cells of Nitella. A small difference between rates of water movement into and out of the cell is ascribed to an assymetry of the driving forces in the system and not to a real difference in permeability.