ELECTRO CULTURE 201 



and other crops show the beneficial action of overhead electric 

 discharge.* In the year 191 5 the increase in grain and in 

 straw was 30 and 50 per cent, respectively greater than the 

 control, and in 191 6 the corresponding figures were 49 and 88 

 per cent. The effect of the discharge also showed itself in 

 the year subsequent to its application ; thus in the clover and 

 grass crop there was a marked increase in 191 6, the year 

 following the treatment. Continued observation confirms this 

 earlier work : of eighteen field experiments f with various 

 crops, fourteen gave increased yields ; of these three only 

 gave increases of less than 10 per cent, and the rest gave 

 increases of over 30 per cent., sometimes of over 50 per cent. 

 Four experimental plots showed a decreased yield of less than 

 10 per cent., compared with the controls. 



Like results were obtained with pot cultures, J thus the 

 percentage increase in the dry weight of maize grown under 

 glass was 27 ± 5"8, whilst barley under the same conditions 

 gave a percentage increase of 18 ± 2-4. 



The effect of these minute electric currents is not always 

 the same ; in one experiment with barley the increase in the 

 yield of grain was greater than the increase in the total dry 

 weight. This was due not to an increase in the number of 

 ears but to an increase in the percentage of fertile flowers per 

 ear.§ The effect of electro-culture is stimulative, for the 

 energy supplied is out of all proportion to the energy value of 

 the additional plant material produced ; to take one example, 

 the additional energy supplied by the electric discharge to a 

 culture of maize at most was 15 calories; the calorific value of 

 the extra material produced, calculated on dry weight, was 

 of the order of 9000 calories. The results obtained from field 

 experiments, pot cultures and laboratory experiment, || leave 

 no doubt about the beneficial action of electric discharge ; 

 but the reasons for this are still unknown. 



* Blackman and Jorgensen : " Journ. Board Agric," 1916, 23, 671 ; 



1917. 24» 45- 



f Blackman : " Journ. Agric. Sci.," 1924, 14, 240. 



t Blackman and Legg : id., 1924, 14, 268. 



§ Private communication from the authors. 



|| Blackman, Legg and Gregory : " Proc. Roy. Soc," B, 1923, 95, 

 214. Gregory and Batten: id., 1926, 99, 122. 



