2fi 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 

 difference of onlj 3 per cent, between normal and treated. 



Conclusions. 



The foregoing experiments with lettuce and radish plants 

 show, in all instances except tAvo, a total gain by tlie use of 

 electrical stinmli. Those experiments where an attemi)t was 

 made to maintain a strength of current within narrow limits 

 showed the best results from treatment. Could an abso- 

 lutely definite strength of current be utilized throughout 

 the period of duration mucli 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 equipment was not at hand. Since the 

 variations in current strengtli depend 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 woidd undoubtedly constitute the 

 best mechanism for getting absolutely constant currents. 

 The effect 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 Jiave, 

 moreover, conclusively shown from our experiments that the 

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

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

 and 8, given in this series, should by no means be considered 

 as typical, as we have apparently failed to get the optimum 

 strength in these cases. 



The question naturally arises, in w^hat manner does elec- 

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

 ated groAvth and accelerated germination to be explained ? 

 There are numerous agencies which act as stimuli to seeds 

 and plants about which little is known in regard to hoAV 

 they stinuilate the plant. There are, to be sure, man}'^ theo- 

 ries advanced for the jmrposc of explaining the response of 

 plants to various sthnuli. 



We know perhaps as nmch about the rationale of electrical 



