741 



but also the soil which has been rich in copper salts. Even in the latter 

 place, which is free from smoke, the plants. {Phase olus vulgaris) became 

 diseased while those sown in the same region in soil which had always been 

 there remained healthy and developed vigorously. 



An analysis of potatoes, of which the plants themselves were covered 

 by the metallic dust from a nickel factory, shows how much of the metal 

 may be taken up by the plants during one period of growth. The healthy 

 foliage contained (in percentages of substances free from water and from 

 sand) : 



Copper oxid 0.19S 



Zinc oxid 0.169 



Nickel oxid 



The diseased foliage contained (in percentages of substances free from 

 water and sand) : 



Copper oxid 0.0713 



Zinc oxid 0.1712 



Nickel oxid 0.0251 



Analyses of the tubers from these plants, however, did not give any 

 zinc and nickel oxid, and only 0.0043 P^r cent, of copper oxid as contrasted 

 with healthy tubers which contained 0.0041 per cent^ 



Besides copper as a poison the arsenic compounds are important because 

 of their injuriousness. According to v. Schroder these impair vegetation 

 even if present in the soil in amounts of less than o.i per cent. 



Nevertheless, the improved technique of manufacture takes care that 

 more and more of the arsenic, as well as the soluble metal salts, is kept back 

 from the smoke in the flying dust flues, so that at present a fresh metallic 

 poisoning of the soil is less to be feared. 



And yet the throwing off of flying ashes requires increased attention. A 

 number of my own experiments have shown that with many flying ashes 

 which become mixed with the soil a visible increase of growth may be 

 obtained, while those from other industries have caused poisoning. This is 

 less often a direct injury to the aerial parts of the plants, but more fre- 

 quently an indirect one, manifesting itself by its effects on certain heavy 

 kinds of soil, rich in water. In aerial injuries, sodium sulfid and calcium 

 sulfid can produce corrosion in some, more tender plants. The course of 

 the action in the indirect injuries has not yet been sufficiently explained. 

 In my opinion, reduction phenomena in the soil are partially concerned in it 

 by which hydrogen sulfid is developed. 



In heavy soils deeply covered by flying ashes, especially if they have 

 been heavily fertilized with lime, a phenomenon of disease appears to such 

 an extent in barley (I have called it "spotted necrosis") that the harvest is 

 greatly reduced. All parts of the plants, even the beards of the glumes, 

 appear closely stippled with brown. The brown points represent centers of 



1 Konig-, J. Denkschrift der Landwirtschat'tl. Versuchsstation Munster i. W. 

 1S96, p. 204. 



