150 Pflanzenkrankheiten. 



Jones, L. R. and W. W. Gilbert. Lightning injury to 

 potato and cotton plant s. (Phytopathology. V. p. 94—102. 1915.) 



During the last two years the authors have been observing 

 injury of two field crops by lightning, the one (Jones) on potatoes 

 in Wisconsin, the other (Gilbert) on cotton in South Caro- 

 lina. The phenomena observed are described in detail in this 

 paper; the evidence as to the nature ot the lightning injury to 

 these herbaceous plants is too fragmentary to furnish ground of 

 why it is more serious upon some crops than others. Some plants, 

 e. g. cotton, potatoes and beets seem more liable to injury than 

 others, e. g. grass, grains and corn. With the potato and cotton 

 the injury occurs chiefly at or near the ground line. It seems clear 

 that the lightning does not strike the individual plants generally 

 over the injured area or at least that the main force of the electric 

 current does not pass through the lenght of the stem. Instead the 

 evidence indicates that the discharge is from the surface of the soil. 

 The authors propose this explanation: „VVhen an electric storm- 

 breaks suddenly following a period of dry weather and the first 

 rain wets the top soil, there remains a layer of dry earth between 

 this wet surface and the moist soil underneath , which is a poor 

 conductor of electricity. When the lightning strikes the wet surface 

 soil, it desperses in all directions, horizontally and then down ward 

 into the earth, following lines of least resistance. The plant stems 

 and roots with their abundant water contents are better conductors 

 than the layer of dry soil just mentioned and so the electrical cur- 

 rent passes through them. The tissues may thus be variously injured 

 or killed depending upon the amount of current passing through 

 them. With the cotton, it seems that the higher water content of 

 the bark and cambium may make these regions the especial paths 

 thus explaining why the injurj'' appears greater in these." 



M. J. Sirks (Haarlem). 



Krüger, W. und G. Wimmer. lieber die Anwendung von 

 Saatschutzmitteln bei Rübensaat zur Bekämpfung des 

 Wurzelbrandes. (Mitt. herz, anhält. Versuchsstat. Bernburg. p. 

 95—97. 1914.) 



Es wurden die früher nur zur Fernhaltung von Vögeln (Krä- 

 hen, Tauben), neuerdings auch für die Behandlung des Rübensaat- 

 gutes zur Bekämpfung des Wurzelbrandes angepriesenen Mittel 

 Corbin, Cuprocorbin und Antimycel im Vergleich zu der erfahrungs- 

 gemäss gut wirkenden Behandlung mit V2'Vo Carbolsäure im Keim- 

 versuch geprüft. Drei Rübensaalproben verschiedener Herkunft lie- 

 ferten nach der Aussaat in Sandtorf kranke Keime in Prozenten: 



Die Carbolsäure-Beizung vermochte demnach das verwendete 

 Saatgut vor Befall durch Wurzelbrand fast vollständig zu schützen, 

 dagegen versagten die übrigen Mittel vollkommen. 



Simon (Dresden). 



