620 SCIENCE PROGRESS 



show the same lack of realisation ( i ) of the necessity for quanti- 

 tative measurement of the electric discharge, (2) that a stimulus 

 may act differently on the plant at different stages of its life, 



(3) that the effect of the stimulus depends on its intensity, 



(4) that the effect of the stimulus depends on the time for 

 which it is applied, and (5) that the effect of the stimulus may 

 appear a considerable time after it is applied. Numerous 

 examples of this can be quoted. 



That in the electric discharge we possess a means which 

 can be used as a stimulus at most periods of plant life seems 

 clear from the greater number of experiments, but how in- 

 different, or even hostile, plant physiologists have been to the 

 general conception of stimuli is perhaps best illustrated from 

 some experiments of Gassner on electroculture published in 

 1907. First of all he finds that with Pisum and Helianthus 

 the electric discharge has no influence on germination and 

 growth, the electrical treatment lasting eight to fourteen days, 

 and being used for fourteen hours daily. The electric discharge 

 was so strong that light phenomena appeared round the plants 

 and the plants were black on account of precipitated dust. 

 But with barley he concludes that the discharge has a favour- 

 able influence. We may quote in detail one of his experiments 

 on this plant. The electrified series consisted of three pots 

 where the distances between the discharging points and the 

 plants were respectively 10 cms., 21 cms., and 35 cms. On 

 March 12 thirty barley grains were sown in each pot. On 

 March 16 the seedlings began to appear, and on the same day 

 the discharge was started. On March 1 7 all the seedlings had 

 appeared ; no difference was visible between any of the experi- 

 mental pots, nor between experimental and control. On 

 March 1 8 the electrified were visibly in advance of the control 

 and more in advance the smaller the distance between the 

 discharging point and the plant. On that day the first leaf 

 had appeared in 16 plants in the pots 10 cms. from the dis- 

 charging point, 12 in the pot 21 cms. from the point, and 4 

 in the pot 3 5 cms. away ; the numbers for the two controls 

 were 1 and 3. In the further course of the experiment the 

 electrified developed quicker than the control, but soon the 

 plants farther away from the discharging point were ahead of 

 the others. On March 27 the experiment was stopped. 



Consideration of Molisch's experiments will render these 



