7^1 



potassium salt of Orthodinitro-Cresol is more injurious to plants, according 

 to Frank's experiments^ than to leaf lice and other animal parasites. 



9. Refuse from Lactic Acid Factories. To those injuries we will add 

 a case which we owe to a report from Mr. Klitzing of Ludwigslust. He 

 noticed that the refuse from a factory which produced lactic acid from maize 

 and potatoes, for the treatment of leather, caused the death of plants. 



10. Calcium arscnitc. The arsenic solutions which are being accepted 

 more and more as a means for combating insects are used as a rule in the 

 form of Schweinfurter green, or calcium arsenite. Injuries to the leaves 

 have been observed in aqueous solutions as also in lime water or Bordeaux 

 mixtures, or sodium arsenite calcium solutions. In general we would refer 

 to the special books on the subject". 



11. Hydrocyanic acid. Fumigation with hydrocyanic acid has recently 

 been accepted as a modem method of combating animal parasites in plants 

 and has been developed especially in America. It may be said in general, in 

 opposition to individual complaints of injuries to plants, that these should 

 not prevent the use of this substance''. Townsend confirmed, for dry seeds, 

 that the germinating capacity does not suffer if the action of the hydrocyanic 

 gas is not continued longer than is necessary for killing animal life. A 

 longer treatment, however, causes considerable injury. Moist seeds suffer 

 more quickly and lose their power to germinate. 



12. Copper solutions. These come under consideration here only in 

 so far as their injuriousness is concerned. Their usefulness as fungicides, 

 which will be considered in the second volume of this book, depends, in our 

 opinion, chiefly upon the fact that the fungi give out ferments which dissolve 

 the copper salts dried on the plant parts and thus poison themselves. 

 Bordeaux mixture which, without doubt, is of great importance as a means 

 for fighting fungi, may primarily favor growth, as its enthusiastic advocates 

 would like to prove, but it cannot be acknowledged as a promotor of growth. 



Opinions as to whether the copper can penetrate through a normal 

 cuticle in all plants are not unanimous. According to Bouygues* this is not 

 the case. Rumm''' also could not prove the existence of copper in the tissue 

 of sprayed leaves and believes that the favorable action can be traced only 

 to the chemico-tactic stimulus. The electric currents, resulting from it, are 

 said to cause the favorable effect in the leaf tissue. The question whether 

 copper can react on the interior of any part of a plant and how, cannot be 

 decided universally but must be taken into consideration case by case. Old 

 cuticule, provided with a thick wax coating, will possibly not be attacked 



1 Krankheiten der Pflanzen 1S95, Vol. I, p. 329. 



2 Hollrung-, M., Jahresbericht auf dem Gebiete der Pflanzenkrankh. Berlin, Paul 

 Parey. Published since 189S. Hollrung', M., Handbuch der chemisclien Mittel gegen 

 Pflanzenkrankheiten. Berlin 1898. Paul Parey. 



3 Townsend, W. O., tJber die Wirkung- gasformiger Blausaure usw. Bot. Gaz. 

 XXXI; cit. Bot. Jahresber. 1902, I, p. 354. 



4 Bouygaies, H., La cuticule et les sels de cuivre I; cit. Centralbl. f. Bakt. nsw. 

 1905, N. 24. 



5 Rumm, C, Zur Frage nach der Wirkung der Kupferkalksalze usw. Ber. d. 

 Deutsch. Bot. Ges. 1893, p. 445. 



