_Leakage of induction current._--Before completing the constant current circuit, the alternating induction current goes only through the path EE′. On completion of the constant current circuit, the alternating induction current not only passes through the shorter path EE′ but also by the circuitous path of the constant current circuit. The escaping induction current would thus excite all the leaflets directly and not by its transmitted action. This difficulty is fully overcome by the interposition of a choking coil which will be described below. A simpler, though less perfect, device may be employed to reduce and practically eliminate the leakage. This consists of a loop, L, of silver wire placed outside EE′. The leakage of induction current is thus diverted along this path of negligible resistance in preference to the longer circuit through the entire petiole, which has a resistance of several million ohms. _Polar action of current on excitability._--It is well known that an electric current induces a local depression of excitability at the point of entrance to the tissue, or at the anode, and an enhancement of excitability at the point of exit, or at the cathode. But the excitability is unaffected at a point equally distant from anode and cathode. This is known as the indifferent point. The exciting electrodes EE′ are placed at the indifferent point. But when the current enters on the right side, the terminal leaflets to the right have their excitability depressed by the proximity of anode, but the leaflets near the electrodes EE′, being at a distance from the anode are not affected by it. Moreover it will be shown that the enhanced conductivity conferred by the directive action of the current overpowers any depression of excitability in the terminal leaflets due to the proximity of the anode. I shall, for convenience, designate the transmission as ‘up-hill’, when excitation is propagated against the direction of the constant electric current, and ‘down-hill’ when transmitted with the direction of the current. _Transmission of excitation ‘Up-hill’: Experiment 38._--I shall give here an account of an experiment which may be taken as typical. I took a vigorous specimen of _Averrhoa bilimbi_, and applied a stimulus whose intensity was so adjusted that the propagated impulse brought about a fall of only two pairs of leaflets. This gave a measure of normal conduction without the passage of the current. The constant electric current was now sent from right to left. A necessary precaution is to increase the current gradually by means of a suitable potentiometer slide, to its full value. The reason for this will be given later. The intensity of the constant current employed was 1.4 micro-ampères. Now on exciting the petiole by the previous stimulus, the conducting power was found to be greatly enhanced. The excitatory impulse now reached the end of the petiole, and caused six pairs of leaflets to fall.