496 



lightning showing that it usuall}' is not a sini[)Ic discharge between two 

 points, but is scattered and ends in niany points. In addition to this, it 

 should be emphasized that when grapevines arc trained on wires, these 

 spread the injurious effect over a greater area. 



V. Bezold's^ statements that, according to the statistics of the Fire In- 

 surance Company in Bavaria, the danger from lightning had increased three- 

 fold between 1833 and 1882, are especially significant. The extensive 

 removal of forests and marsh drainage and the rapid increase of rails and 

 electric wire conductors are supposed to play a part in this. 



DiSAi)\ANTA(;i:s IX IClixtro-Culturf.. 



The attempts to use electricity dircctl}' in plant culti\ati()n have fol- 

 lowed three lines. In tb-e first place, it was desired to increase the assimi- 

 latory activity by illuminating with electric light ; in the second place it has 

 been attempted to let an electric current pass through the earth by sinking 

 two metal discs in the soil connected with some source of current ; in the 

 third place, an attempt was made to cause the current to pass directly 

 through the plant (or tree). 



As yet the results have been very contradictory, so that no decision 

 has been reached. Great hope is set often on the influence of a silent elec- 

 tric discharge. This takes place when, for example, a net of wires is laid 

 over a field without touching the soil and one pole of an electrifying machine 

 is connected with the wire and the other with the soil. In such cases the 

 plants act as conductors and through them, by means of the silent electric 

 discharge, the electricity will stream out from the tip of the cultivated 

 plants. Such a current must actually take place constantly in nature, since 

 the soil exhibits an electric charge differing from that in the layers of air 

 lying above it. The best known experiments are those of Lemstrom- and 

 Pringsheim^'. Older works on experiments, in which the electrical current 

 is conducted through the soil, had been collected and enlarged by Wollny'*. 



The results of Pringsheim's experiments, in which the electricity waf 

 produced by a static electric machine, sound extremely favorable, since in 

 potatoes, sugar beets, beans and strawberries a quantitatively and quali- 

 tatively better yield is obtained. Since, however, many unfavorable experi- 

 ences exist, this field, for the present, should not be considered any further, 

 as it is not sufficiently cleared up. However, Lowenherz'^ work must be 

 mentioned because it has been carried through with scientific exactness and 

 opens up new points of view. 



1 V. ]?czold. W., tthcr ziindende Blitze im Konigreich Bayern wahrend des 

 Zeitraums 1833 bis 1882. Abh. d. KrI. Bayer. Akad. d. Wiss. IT. CI.. Vol. XV. 



2 I.,emstrrim, Elektrokultur. Translated by O. Prinssheim. Berlin 1902. W. 

 Junk. 



3 Prinssheim, Otto, Neue Elektrokulturvcrsuche. Osterr. landw. Wochenbl 



1904, No. 24; cit. Centralbl. f. Agrikulturch. 190.5. Part 6. 



4 Forschungen auf dem Gebiete der Agrikulturphysik. Vol. II. 1888, p. 88. 



5 T^owonherz, Richard, Versuche liber Elektrokultur. Z. f. Pflanzenkrankh. 



1905, p. 137. 



