Resistance changes in Laminaria bathed in solutions of NaCl, CaCl2, etc., are of importance in the theory of permeability. Such changes may be due (1) to a change in the ionic permeability of protoplasm; (2) to a change in the specific resistance of the intercellular substance, corresponding to its well-known hardening in Ca and the softening in Na salts; (3) to the specific resistance remaining constant while the cross section expands or contracts, as observed by Kotte in the walls of algae; or (4) to a change in the electrical capacitance of the cell surface which might alter the effective impedance of the whole system." Attempting to determine which of these possibilities corresponds to actuality, the author took resistance readings on Laminaria discs, using the Osterhout technique and apparatus, at the following frequencies: 1000, 13750, 45500, 115500, 375000, 1090000, and 10800000 cycles. Low frequency readings rose and fell during injury, but high frequency readings approximated a constant value. It is concluded therefore that (1) there is no change in the specific conductivity of either the inter- or intracellular material during treatment with CaCl2 or NaCl, since the high frequency value remained constant; (2) that the changes in impedance are not due to changes of capacitance, since the latter would not affect the direct current readings, which agree entirely with the 1,000 cycle values; and (3) that changes in cross section may occur, but are not sufficient to explain the results." The author concludes that the changes in resistance in Laminaria in such experiments are really changes in permeability of protoplasm to ions.