POLAR EFFECTS OF MODERATE CURRENTS 229 



at the anode at break. Repetition of the experiment on 

 other specimens gave similar results. 



Table XI. — Effect of Moderate Current on Leaflets of 

 Averrhoa hilimhi 

 E.M.F. = 28 volts ; current = i6 micro-amperes 



Primary Leaf of Mimosa 



I have already described in the previous chapter the polar 

 effects of feeble currents on the pulvinus of Mimosa. In that 

 case the mono-polar method of experiment was employed. 

 The bi-polar method will now be taken up, enabling us to 

 observe the make-effect of anode and kathode in two 

 different organs simultaneously, and, in the same way, 

 the break-effect ; all these to be further corroborated by 

 reversal experiments. 



Effect of feeble current. — The bi-polar connections are 

 made either directly with, or in the close vicinity of, two 

 different pulvini, at varying heights on a single main stem 

 of Mimosa. With highly excitable specimens the polar 

 effects characteristic of Type I. may here be obtained with 

 as low an e.m.f. as 2 volts. In another case the applied 

 E.M.F. was 4 volts, and the resulting current 4 micro-amperes. 

 On going through the usual experimental cycle — with direct 

 and reverse currents — it was found that the kathode alone 

 exhibited excitation at make. There was no excitation 

 either at kathode-break or anode-make or break. Similar 

 experiments were carried out on some fifteen different plants 

 of Mimosa, the results without exception being as described. 

 The only variation seen in the case of different individuals 



