FUNCTION IN PLANT LIFE 11 



of this fruit should be high. Unfortunately it has when 

 ripe, and probably owing to its porous skin, a compara- 

 tively low insulation resistance and therefore a short life. 

 Figs. 3 and 4 will serve to illustrate the points mentioned. 



THE TOMATO. 



The tomato (Fig. 5) affords us convincing testimony of 

 the reliability of our electrodes, because during the late 

 summer we can take one grown in the open ground and 

 one from the greenhouse and test them under exactly the 

 same conditions and at the same time. That grown in the 

 open ground will be found to be negative at the stalk and 

 positive where the flower originally appeared, while that 

 from the greenhouse, where it had been deprived of its 



supply of current from the negative earth and compelled 

 to take its root-charge from the positive air, assumes an 

 opposite polarity and is positive at the stalk end, etc. 

 These remarks apply to all fruits and vegetables cultivated 

 alike in the garden and in pots in the greenhouse, such as 

 the cucumber, the orange, lemon, etc., etc. 



But if the soil in the pot is connected by a metallic 

 conductor with the earth (see illustration), no change of 

 polarity will occur. 



