THE LEAF CONSIDERED AS AN ELECTRIC ORGAN 257 



excitation already described, it is found that a very strong 

 responsive current is obtained, whose direction is, as in the 

 last case, from the glanduloid to the non-glanduloid surface. 



The effect of the serial arrangement, again, in enhancing 

 the electro-motive force as seen in the pile- like arrangement 

 of the electrical organ of fishes may be exemplified, in 

 the parallel instance of the plant-organ, by means of the 

 superposed scales of the bulb, as found in nature. The bulb 

 may be divided longitudinally into halves, of which the 

 right-hand half is mounted, for experiment, with the scales 

 vertical. It will be understood that all the glanduloid 

 surfaces here face the left, while the non-glanduloid are 

 turned to the right. Thus the left aspect of this pile 

 corresponds to the head aspect of the organ of Malepterurus. 

 The latter, on excitation, responds by a current in the 

 direction of head to tail that is to say, from glandular to 

 non-glandular ; and similarly, in the pile-like half-bulb of 

 Uriclis lily, the responsive current is from glanduloid to non- 

 glanduloid that is to say, from left to right. 



Another interesting way to perform the same experi- 

 ment is without making any section of the bulb. We 

 take a bulb of Uriclis, with the peduncle rising out of the 

 middle. When this hollow peduncle is cut across, it allows of 

 an electrical connection being made with the centre of the 

 interior of the bulb. An equatorial belt makes the second, 

 or outer, connection. On subjecting this to equi-alternating 

 shocks, the resulting response will be found to be from the 

 inner surface to the outer, through the numerous intermediate 

 scales, the individual effect in each being concordant and 

 additive. 



We have thus seen how the response of a leaf gives us an 

 insight into the action of a plate of an electrical organ ; how 

 the differential excitabilities of the two surfaces give rise on 

 stimulation to an induced E.M.F. as between the two ; how 

 a nervous and indifferent-tissued surface will give rise to a 

 response in one direction, and a glandular and s non-glandular 



S 



