7(^2 



while a young leaf can suffer. In older leaves, however, injuries may also 

 occur in one case and not in another; the cuticle covering may be broken by 

 atmospheric action (late frost) and the copper solution may remain for some 

 time in these tears. Finally, the specific sensitiveness of the plant variety is 

 decisive, as will be shown in later examples. 



The first doubt as to the peculiarity of copper mixtures for favoring 

 growth arose from the results of some spraying experiments made in i89i\ 

 An arrestment in the development of potato plants could be proved as com- 

 pared with unspraycd plants which remained healthy. The considerable 

 amounts of starch and chlorophyll contained in leaves treated with copper 

 which are considered as an indication of favoring growth were traced by 

 Schander to the effect of the shade caused by the calcium copper coating'-. 

 Ewert confirms the effect of shading but calls attention to the fact that this 

 may not be the only arresting factor-'. Through the effect of the copper sub- 

 stances, especially Bordeaux mixture, stoppages occur in the transference of 

 the ass'unilates. The considerable amounts of starch and protein, here 

 observed, are not the results of increased assimilation which, as has been 

 proved, is repressed together with transpiration and respiration, but is the 

 action of arrested transpiration. This point of view which we represent 

 presupposes, at any rate, that copper actually enters the plant and this theory 

 is substantiated by the fact that scientists who do not assume a penetration 

 of the copper still find copper reactions in a number of their experiments 

 (Frank and Kriiger). Besides this, Ewert has also proved the presence of 

 copper in plants sprayed with Bordeaux mixture. Later we will quote notes 

 from Schander's work as to the way in which the copper is taken up. 



In my opinion, the copper, entering through wounds, or through the 

 epidermis of plants treated with copper mixtures, is combined at once with 

 the proteins of the protoplasm and thereby reduces cell-life. Since spraying 

 does not represent a complete wetting of all the leaf surface, certain areas 

 remain healthy, between injured ones, and these must show an increased 

 growth activity. This makes itself evident at times with an abundant 

 supply of light and moisture, in the formation of intumescences. I described 

 the first case of this kind in potatoes^. Later v. Schrenk'' observed intu- 

 mescences on cabbage plants as a result of their treatment with copper- 

 ammonium-carbonate, copper chlorid, copper acetate, copper nitrate and 

 copper sulfate. Very recently Muth" has observed a very strong formation 

 of intumescences in grape leaves after a treatment with copper. 



1 Soruuer, P., Einige Beobachtungen bei der Anwendung von Kupfermitteln 

 gegen die. Kartoffelkrankheit. Zeit.schr. I. I'flanzenkrankh. 1893, p. 32. 



- Schander* K., tjber die physiologisclic Wirkung der Kupfei-vitriolkalkbriihe. 

 Inaug'.- Diss. Berlin 1904 und Ijaindwirtsch. Jalirbiiclier 1904, Parts 4 and .^). 



3 Ewert, Der wecliselseitige Einfluss des Lichtes und der Kupferkalkbriihen 

 auT den Stoffwechsel der Pflanze. Landwirtsch. Jahrbiiclier 1905, p. 233. 



4 Zeitschr. f. Pflanzenkranldi. 1893, p. 122. 



5 Schrenk, H. v., Intumescences formed as a result of chemical stimulation. 

 Sixteentli annual report Missouri Botanical Garden. Rlay, 190."}. Special reprint. 



6 Muth, Franz, Uber d. Beschadigung d. Rebenblilltorn durch Kupfeisprilzmittel. 

 Mittel. d. Deutsch. Weinbauvereins I. Jahrg. No. 1, p. 9. 



