7'^3 



Such effects may be produced if the tissue is partially poisoned but does 

 not actually die. They may also occur, however, when death actually takes 

 place in which case the dead tissue areas in many plants fall out of the leaf, 

 causing perforation. Such cases have recently been described by Schander^ . 

 In connection with this, it is mentioned that Fuschia and Oenothera secrete 

 acids which dissolve small amounts of copper hydroxid. Alkaline secretions 

 have also been found (Phaseolus multiflorus) , or the copper is dissolved not 

 by secretions of the leaf but simply by the atmospharillia, especially with 

 continued wet weather. 



Ruhland- declares, on the other hand, that the assumption of a dissolv- 

 ing of the copper by leaf secretions has no justification, and that this can be 

 ascribed only to the atmospharillia. 



Reports as to the injury to foliage from spraying with copper have 

 appeared as the process has been more generally used. In 1891 it was 

 observed in fighting Peach rot that, 

 after using Bordeaux mixture, not 

 only the leaves and blossoms fell, 

 but the young wood also was in- 

 jured''. The Amygdalaceae and 

 especially peaches have been found 

 to lie especially sensitive. Bain* 

 showed in his experiments with 

 apple, grape and peach leaves that 

 this is connected with the specific 

 sensitiveness of the protoplasm. He 

 says that the peach leaf is able to 

 dissolve copper oxid by a substance 

 secreted on its upper surface. 

 Young leaves suffer most. The in- 

 jured part of the leaf is then cut off 

 by a cork layer and thrown off 



(Shot disease, which Aderhold^ has also described for the cherry). Severely 

 diseased peach leaves fall but the apple leaf, as well as the grape, possesses 

 the ability to continue assimilation by means of the remaining lamina. 



According to Hedrick's" more recent studies, peaches, apricots, and 

 Japanese plums are the most sensitive fruit trees, while the common plum is 

 not affected more severely than the pear, apple or quince. The different 

 varieties behave differently. The most highly cultivated examples, with the 



An apple with brown spots and 

 •acks. (After Hedrick.) 



1 Loc. cit. 



~ Ruhland, W., Zur Kenntnis der Wirkung- des unloslichen basischen Kupfers 

 auf Pflanzen usw. Arbelten d. Biol. Abt. f. Forst.- u. Landwirtsch. beim Kaiser. 

 Gesundheitsamt Vol. IV, 1904, Part 2. 



3 Report of the Secretary of Agric. for 1891, "Washington 1892, p. 364. 



4 Bain, S. M., The action of copper on leaves, etc. Ag-ric. Exp. Stat, of the 

 University of Tennessee, 1902, Vol. XV. 



n Aderhold, R., tjber Clasterosporium carpophilum usw. Arh. d. Biolog-. Abt. d. 

 Kais. Gesundheitsamtes, 1902, Part 5. 



6 Hedrick, U. P., Bordeaux injury. New York, Agric. Exp. Stat. Geneva. Bull. 

 No. 287, 1907. 



