Pot-culture experiments carried out during a period of four years with Wheat, Barley and Maize show that these plants exhibit increase of dry weight when subjected to minute electric currents (of an intensity as low as 0·1 × 10–10 amp. per plant) from wire networks charged to a high voltage suspended above them. Of 28 sets in which the cultural conditions were satisfactory 23 showed an increased yield.

A percentage increase in dry weight of 27 ± 5·8 was shown by Maize plants grown under glass and little more than a month old. With Barley the largest percentage increase was 18 ± 2·4.

Direct currents were mostly studied, but increased growth was obtained with both direct and alternating current, the alternating current being apparently as effective or even more effective than the direct; the plants themselves, however, are able to bring about a slight rectification of the current.

Electrification of Barley for the first month of the growing season appears to be as effective as electrification during the whole growing season.

The discharging networks were usually charged positively, but a similar stimulating effect on dry weight production was obtained with a negative charge on the network.

Currents of the order of 1 × 10–8 amp. per plant and higher are injurious, causing a reduction of dry weight.

In one experiment plants screened from the normal atmospheric current by a series of parallel “earthed” wires (0·35 mm. diameter) showed, by comparison with the controls, a percentage decrease of 4·7 ± 2·3, which is hardly significant. It indicates however that though a favourable effect may be exerted by the normal atmospheric (air-earth) current, yet the effect can be but slight.

In one experiment with Barley indications of a differential effect of the discharge were obtained, for the increase in grain yield brought about by the discharge was greater than the increase in total dry weight.

The effect is to be.classed as of the nature of a stimulation since the energy-value of the additional plant material produced is out of all proportion to the energy supplied by the electric discharge.

These experiments with pot-cultures fall into line with those from the field (1) and from the laboratory(2); they leave no uncertainty as to the favourable action of the electric discharge.