154 Knight and Priestley.— The Respiration of Plants 
confined space, the heating effect of the discharge may provide a stimulus 
causing an acceleration of the katabolic processes and a consequent increase 
in the carbon dioxide production. 
The failure of the discharge itself to produce any stimulation of the 
destructive metabolism of the organism should not, however, be emphasized 
overmuch when seeking an explanation of the results of the large scale 
trials. As has been pointed out before, although these results cannot be 
interpreted in terms of katabolism, other functions of the plants may be 
accelerated as a consequence of electrification, resulting finally in earlier 
maturity. 
In view of the nature of our conclusions there is little to be said as to 
their application to field trials. 
With the current density employed in the field — io -12 to io -10 amperes 
per square centimetre — the heating effect will certainly be negligible, and 
the effect upon respiration therefore nil. In addition, were the heating 
effect, and no other, involved, there would be no economic value in applying 
electric discharge in order to obtain it, since the same result might be 
arrived at by much less elaborate methods. This, however, is a question 
upon which no final judgement can be passed until the reported acceleration 
effect in the field has been further analysed. 
Summary. 
1. Field trials upon the effect of electrical conditions upon plant 
growth have suggested that an increased crop or an earlier ripening may 
be the result of such treatment, and in the present paper an attempt has 
been made to analyse this apparent effect, by determining the effect of such 
electrical conditions upon respiration. 
2. Our experiments have shown that direct currents of a density 
io -6 to io -4 amperes have no effect upon the respiration of peas, other than 
that due to accompanying changes of temperature. The proportion of 
these currents actually traversing the peas was, however, probably very 
small, the majority being taken by the water films on the seeds. 
3. Overhead discharge, producing a current of density less than 
3 x io -6 amperes, has no effect upon respiration. When higher currents are 
employed a definite increase of the carbon dioxide output was observed. 
4. This increase can be wholly attributed to the rise of temperature 
caused by the discharge. 
5. In the field, where the currents are too small to produce any 
appreciable rise of temperature, electrification will have no effect upon 
respiration, and explanation of the acceleration of growth must be sought 
in other functions of the plant. 
6. The gaseous products of the discharge in air have no effect upon 
germinating peas, but are deleterious to young seedlings. 
