FUNCTION IN PLANT LIFE 9 



zinc terminal of the cell to the left-hand terminal of the 

 recording instrument. The resultant deflection is to the 

 right of zero, and we may therefore call the right side of 

 the scale from zero positive and the left side from zero 

 negative. 



Now, if we insert the needle connected to the right side 

 of the galvanometer in the stalk of the apple and the other 

 needle in the flower end, we get a constant negative deflec- 

 tion. If that deflection is due to galvanic or chemical 

 action, then so long as we do not alter the connections upon 

 the galvanometer, and reasoning upon the hypothesis that 

 the right needle is electrically negative to the left needle 

 and that chemical action is set up by their contact with the 

 malic acid of the apple, the deflection must continue to be 

 negative when the fruit is reversed and the right needle 

 is inserted in the flower end and the left needle in the stalk. 

 Also the signs of both deflections must be reversed if we 

 reverse the wires upon the terminals of the galvanometer. 

 But it is not so ; nothing of the kind ever occurs or can 

 occur. Every fruit will give a constant negative deflection 

 when the right-hand needle is inserted in the stalk, and a 

 constant positive deflection when it is inserted in the 

 flower end ; while every tree, shrub, plant, vegetable, and 

 individual leaf will yield a constant negative deflection 

 when the right-hand needle is connected with root, stalk, 

 or vein, and vice versa. The wires may be reversed upon 

 the terminals of the galvanometer as often as desired. 

 There will be no difference whatever in the phenomena 

 observed. In the case of pot-grown plants and fruits, 

 etc., polarity is reversed because the moist soil in the pot 

 receives its charge from the positive air instead of from 

 the negative earth. 



If, however, diffusion takes place by reason of injury or 

 decay, and the plant, vegetable, fruit, or leaf becomes 

 rotten, no reversal of sign will be obtained. 



