SECTION IV. 



EFFECTS OF INJURIOUS GASES AND LIQUIDS. 



CHAPTER XVI. 



THE GASES IN SMOKE. 



SuLFUROus Acids. 



The injuries to vegetation due to tlie teases in smoke have become so 

 numerous and varied, with the constantly increasing spread of textile indus- 

 tries, that the study of them begins to form a separate branch of pathology, 

 in which chemistry and botany are equally concerned. It is thus evident 

 that this branch of science demands special attention. The subject has 

 been most extensively treated in Haselhofif and Lindau's book^ and later in 

 that of Wieler'-. Because of the abundance of material on injuries from 

 smoke we can here merely refer to these works and treat more thoroughly 

 only the points less fully taken up in them. 



For a long time, scientists were in doubt as to which element in the 

 smoke was the injurious one, until the investigations of Morren^, Stock- 

 hardf* and especially v. Schroder"' pro\cd it to be the sulfurous acid. The 

 metallic poisons, like arsenic, zinc and lead, to which especial attention was 

 formerly paid in studying the injuries due to the smoke of smelting houses, 

 have been proved experimentally to be less injurious to our cultivated plants, 

 while a very small addition of sulfurous acid to the air is able to bring about 

 the death of the plants under experimentation. How small this addition 

 need be is shown by Morren's** observations. He could perceive the charac- 

 teristic indications of destruction in the leaves even when the air contained 



1 Haselhoff, E., und Lindau, G., Die Beschadigung der Vegetation durch Rauch. 

 Berlin 1903, Borntrag-cr, 412 pages, with 217 illu.strations. 



- Wieler, A. ITntci-.suchungen iiber die Kinwirkung schwefliger Saure auf die 

 rnanzen. Berlin 1905, Gl)r. Borntrilger. 



3 Rgcherches experimentales pour dMerminer I'influence de certains gaz indus- 

 triels, specialement du gaz acide sulfureux, sur la v6g6tation. Extracted from the 

 Report of the International Horticultural Exhition, etc. London 1S66. 



* Untersuchungen iiber die schadliche Einwirkung des Hiitten- u. Steinkohlen- 

 rauches auf das Wachstum der Pflanzen. Tharandter forstl. Jahrb., Vol. 21, Part 3. 



•'■ Die Einwirkung der schwefligen Siiuro auf don I'flanzen, in Landw. Ver- 

 suchsstationen 1872. 



u IjOC. cit., page 224. 



