Several forms of the action curve are described which might be accounted for on the ground that the outer protoplasmic surface shows no rapid electrical change. This may be due to the fact that the longitudinal flow of the outgoing current of action is in the protoplasm instead of in the cellulose wall. Hence the action curve has a short period with a single peak which does not reach zero.
On this basis we can estimate the P.D. across the inner and outer protoplasmic surfaces separately. These P.D.'s can vary independently.
In many cases there are successive action currents with incomplete recovery (with an increase or decrease or no change of magnitude).
Some of the records resemble those obtained with nerve (including bursts of action currents and after-positivity).