POLAR EFFECT OF ELECTRICAL CURRENT ON GROWTH.
The object of this investigation was to determine whether anode and cathode exerted similar discriminative and opposite effects on growth. For this experiment I took a specimen of Kysoor and determined the region where growth was maximum. A piece of moist cloth was wrapped round this region to serve as one of the two electrodes. The second electrode was placed in the neighbouring indifferent region where there had been a cessation of growth.
Effect of Cathode: Experiment 111.—The particular specimen of Kysoor had a normal rate of growth of 0·48 µ per second. On application of the cathode the rate was reduced to 0·14 µ per second, or to less than a third. This will be seen in record (Fig. 107), where N is the normal rate of growth and K, retarded rate under the action of the cathode.
| Fig. 107. | Fig. 108. |
Fig. 107.—Retardation of rate of growth under the action of cathode (Kysoor).
Fig. 108.—Acceleration of rate of growth under anode (Kysoor).
Effect of anode: Experiment 112.—If the cathode induced a retardation, the anode might be expected to induce an acceleration of growth. But in my first experiment on the action of anode, I could detect no perceptible variation of rate of growth. In trying to account for this failure, I found that the specimen employed for the experiment had normally a very rapid rate of growth. It appeared that an induced acceleration would be brought out more conspicuously by choosing a specimen in which the growth-rate was low, rather than in one in which it was near its maximum. Acting on this idea, I took another specimen of Kysoor in which the normal rate was as slow as 0·10 µ per second. On applying the anode to the growing region, there was an enhancement to one and half times the normal rate (Fig. 108).
TABLE XXVIII.—EFFECT OF ANODE AND CATHODE ON GROWTH (Kysoor).