1912.] PUBLIC. DOCUMENT — No. 31. 141 



however, the stem reacts one way and the root another; for 

 example, roots are positively and stems negatively geotropic. 

 It is well known that the anode and cathode behave quite diifer- 

 ently and characteristically when acting on metals, etc. Similar 

 characteristic differences might be expected in the reaction of 

 plants. Where trees have been injured by burning from direct 

 current wires the extent of the injury is about 90 per cent, 

 greater near the positive than near the negative point of contact, 

 showing that the positive electrode is more disastrous to plant 

 tissue. 



In our various experiments, where we have employed elec- 

 tricity as a stimulus, we have never observed any difference in 

 the behavior of plants in close proximity to either j^ositive or 

 negative electrodes, although in some of our previous experiments 

 with radish plants, made some years ago, in which the plants 

 were grown in soil, we found that the tops responded much more 

 freely to electrical stimulation than the roots when acted on by 

 galvanic currents. We found, however, that by substituting let- 

 tuce, which is cultivated exclusively for the leaves, the leafy 

 part responded more freely to electrical stimulation than did 

 the underground part or fleshy roots of radish. 



On the other hand we found in our experiments in growing 

 radishes in tightly closed, insulated glass cases, the atmosphere 

 of which was charged each day positively to an electrical poten- 

 tial averaging 150 volts, that the reverse was true, viz., the roots 

 or underground parts were stimulated more tban the leaves or 

 tops. The soil itself is generally negative, and the atmosphere 

 positive ; the roots therefore are accustomed to a negatively 

 charged, and the aerial parts to a positively charged, environ- 

 ment. 



In the decomposition of water by electrolysis it is assumed 

 that the oxygen is in a negatively electrical condition and is 

 attracted by the positive pole, while the hydrogen is in a posi- 

 tively electrical condition and is attracted by the negative pole, 

 Metals are described as electro-positive elements, and are usually 

 attracted to the negative pole, while the nonmetals are spoken of 

 as electro-negative elements and are attracted to the positive pole. 

 In the experiments just cited with radishes, which were grown 

 in insulated glass cases where the atmosphere was charged posi- 



