744 



of sodium'. Often the phosphoric acid and chlorin also increase. In the 

 injuries due to acid gases this reaction of the plant body is shown also 

 .further by the fact that the leaves, not yet injured beyond a certain extent, 

 contain more bases than do healthy ones. 



Control Plants. 



Reference must be made to technical handbooks for technical regula- 

 tions regarding the avoidance or decrease of injuries due to smoke and 

 flying ashes. However, I would like to give here one method in clearing 

 up the question whether the injuries already perceived are connected with 

 the poisoning of the soil, or are due to the purely aerial action of gas waves 

 containing acid. This method is that of control plant cultivation and is 

 carried out as follows : Wooden cases, containing at least one cubic meter, 

 are sunk in the fields in question and are filled with soil which, before 

 witnesses, has been taken from a region free from smoke. On the other 

 hand, soil taken from the fields in question is put in similar cases which are 

 sunk in a field in a region free from smoke. Both series of cases are then 

 sown in the same way with beans {Phase olus vulgaris nanus) and harvested 

 simultaneously after a number of weeks. The harvest is examined micro- 

 scopically and chemically. 



The poisoning of the soil is proved by the fact that the plants grown 

 in the soil taken from the fields in question but kept in cases in regions free 

 from smoke become diseased with the same characteristics as those near the 

 source of smoke. If, on the other hand, the beans from the cases filled 

 with soil from a region free from smoke which had been sunk in the fields 

 in question, near the injurious industrial establishment, show the charac- 

 teristics of smoke poisoning, this then proves that the dangerous streams of 

 smoke alone are sufficient to injure vegetation. 



These comparative cultures have the advantage of giving the contesting 

 parties an insight into the kind of injury which is recognizable to the layman 

 and thereby furnish the means of an unification, of opinion, thus avoiding 

 lengthy lawsuits. It is well in regard to these to strive for the formation of 

 federal smoke commissions. We mean by this the appointed persons from 

 among botanists, chemists, agriculturalists and foresters, who would meet 

 together as a commission of specialists and would always be the same for 

 the different districts. By retaining the same persons they would have a 

 more exact insight into the special conditions of their districts and a more 

 assured judgment in these difficult cjuestions. 



Illuminating Gas and Acetylene. 

 The injurious efifect which illuminating gas exerts on plants has been 

 ascribed to the hydrogen sulfid abundantly present in it. This is, how^- 

 ever, not the only cause, for Kny- has shown that gas, carefully purified 



1 Konig (Denkschrift 1896, P. 207), found only in rye, despite a higher sodium 

 content, a smaller ash, and especially less silicic acid. It seemed to him that the 

 silicic acid was dissolved by the soda in the g-lume and then washed away. 



- Sitzungsber. d. Ges. naturforsch. Freunde zu Boilin in Bot. Zeit. 1871, p. 869. 



