26 HATCH EXPERIMENT STATION. [Jan. 



the lettuce treatment where the normal plants have excelled, 

 in growth the treated ones, although in No. 21 there is a 

 diflerence of only 3 per cent, between normal and treated. 



Conclusions. 



The foregoing experiments with lettuce and radish plants 

 show, in all instances except two, a total gain by the use of 

 electrical stinuili. Those experiments where an attempt was 

 made to maintain a strenoth of current within narrow limits 

 showed the best results from treatment. Could an abso- 

 lutely definite strength of current be utilized tlu-oughout 

 the period of duration nmch closer results could be obtained, 

 and the optinuun current be more closely determined. Such 

 an arrangement suggested itself to us quite early in our work, 

 but the necessary ecpipment was not at hand. Since the 

 variations in current strength de})end largely upon the varia- 

 tions in soil moisture, tolerably constant currents might be 

 obtained by regulating the water supply ; but some auto- 

 matic resistance appliance would undoubtedly constitute the 

 best mechanism for getting absolutely constant currents. 

 The efl'ect which electricity has in accelerating the growth 

 of plants and on the germination of seeds is positive ; and 

 in hundreds of experiments, conducted in a different manner, 

 we have seldom obtained any negative results. We have, 

 moreover, conclusively shown from our experiments that the 

 alternating current is much superior to the direct as a stimu- 

 lator ; therefore the alternating-current experiments, Nos. 3 

 and 8, given in this series, should l)y no means be considered 

 as tj^pical, as we have apparently failed to get the optimum 

 strength in these cases. 



The questicjn naturally arises, in what manner does elec- 

 tricity stimulate plants ; or, in other words, how are acceler- 

 ated growth and accelerated germination to be explained? 

 There arc mnnerous agencies which act as stimuli to seeds 

 and plants about which little is known in regard to how 

 they stinmlate the plant. There are, to be sure, many theo- 

 ries advanced for the purpose of explaining the response of 

 plants to various stinuili. 



We know perhaps as much about the rationale of electrical 



