under Various Electrical Conditions. 149 
accelerating effect of the discharge seemed to bear a definite relation to the 
current strength (Tables VII and VIII). 
Having demonstrated that the application of overhead discharge caused 
an increase in the respiration of the seeds, it became necessary to analyse 
further the cause of the increase. 
The first source investigated was the gases produced by the discharge 
in air, as it was thought these might have some effect upon the katabolic 
processes of the plant. This was investigated in the following manner : 
Two pairs of bell-jars were fitted up as respiration chambers and con- 
nected in series in the apparatus. The first was left empty except for an 
earthed piece of wire about half-way down, where the upper level of the 
mass of seeds would ordinarily be. The second chamber contained the seeds 
and had no electrodes and no turpentine, but merely delivery-tubes. 
The discharge now took place in the first chamber, and the gases were 
led into the second. In this way there was much less chance of ions from 
the discharge point reaching the peas. 
With this method the respiration was found to be unaffected by the 
discharge, and the curves show no deviation from the normal (Table IX) 
except in one reading, No. 12 1. 4, the significance of which is doubtful. 
(See note re temperature corrections, p. 145.) 
We concluded, therefore, that the gaseous products of the discharge in 
air had no effect upon the respiration of seeds, which was rather surprising in 
view of the results of Hill and Flack working with ozone. The source of the 
effect produced by the discharge must therefore be sought in another direction. 
Experiments were carried out in which the period of electrification was 
extended from half an hour to three hours (Nos. 9*5-8), and the usual 
increase in carbon dioxide output was observed, but on dismantling the appa- 
ratus at the conclusion it was noticed that the temperature of the chamber 
was very much above that of the room ; especially was this the case in No. 97, 
in which the amount of respiration was enormously increased (see Fig. 5). 
Attention was at once directed to the influence which this rise of temperature 
might have when the discharge was continued for only half an hour. 
Accordingly a trial was proceeded with (No. 98), wherein the tempera- 
ture of the seeds was taken from time to time by a thermometer inside the 
chamber. The discharge was switched on for one hour, and determinations 
of carbon dioxide were made every half-hour. By this means the curve 
(No. 98) in Figs. 5 and 6 was obtained. This curve was then subjected 
to two tests to determine to what extent temperature was the active factor 
in inducing the upward trend. The figures obtained were corrected in the 
manner indicated 4 for the direct-current experiments (p. 142) and the new 
curve (Fig. 6) compared with the normal curve and No. 98. 
The corrected curve, it will be seen, almost coincides with the normal 
curve. 
