Experiments on Valonia were carried out as follows:

Stage I.—Cells in dim light accumulated 0.08 M ammonia (NH3 + NH4OH + NH4+) from sea water containing 0.0025 M ammonia (but the concentration of undissociated ammonia appeared to remain less inside than outside). Potassium came out.

Stage II.—Cells in dim light in nearly ammonia-free normal sea water lost ammonia which was replaced by sodium entering from the sea water. Potassium in the sap remained practically constant.

Stage III.—The cells were placed in stronger light where the loss of ammonia continued and potassium entered. Sodium entered more rapidly than in Stage II.

Stage IV.—Cells transferred to sea water containing 0.0025 M ammonia again accumulated ammonia up to 0.1345 M.

The results in general harmonize with the view that the direction of movement of a base M through the protoplasm depends on the difference of the activity products (M)o(OH)o and (M)i(OH)i where the subscripts o and i refer to sea water and sap respectively.

On this basis, if the entrance of ammonia raised the internal concentration of OH sufficiently in Stage I potassium should come out in Stage I, as actually happened. The behavior of sodium is in doubt.

If the internal pH in Stage II were sufficiently high sodium should enter but not potassium. This was actually found.

In Stage III, if we suppose that the effect of stronger light is to increase the external pH (by photosynthesis) more than the internal pH (as found by Crozier) we can understand why potassium entered, because such an increase in pH could readily make the external value of (K) (OH) greater than the internal. This would also explain why sodium entered more rapidly than in Stage II.

When ammonia is coming out of the cell, sodium and potassium may enter more rapidly than usual without raising the internal concentration of halide above a certain critical value at which entrance appears to be checked.

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