INJURIOUS AMOUNTS OF SULPHUR DIOXID. H 



nite opinion in regard to its merits. It would appear, however, from 

 the work done that Wieler lays too much stress on the sulphur dioxid 

 injury to the soil, as compared with the injury caused by the sulphur 

 dioxid acting on the foliage. In support of this opinion several soils 

 from the vicinity of a smelter were tested by the author. These 

 soils Avere taken from forest land where certain trees were practically 

 annihilated by smelter fumes, as proved by chemical 'analysis, and 

 yet all of the soils gave an alkaline reaction, showing that there had 

 evidently not been such a loss of bases as to give rise to free humic 

 acid. 



On the whole, then, the work done undoubtedly points to the fact 

 that sulphur dioxid injures vegetation through the leaves, but whether 

 it injures the soil, and so indirectly injures the plant through the 

 roots, is a problem which must be studied further before a definite 

 conclusion can be reached. 



AMOUNT OF SULPHUR DIOXID THAT MAY CAUSE INJURY. 



In regard to the amounts of sulphur dioxid in the atmosphere that 

 may injure vegetation, Stockhardt" showed that 1 part of sulphur 

 dioxid to 1,000,000 parts of air injured potted pines seriously after 

 865 fumigations. Freyag« cast doubt on Stockhardt's data by his 

 investigations, and Stockhardt's Avork was repeated by Yon Schroeder 

 and Schmitz-Dumont," who showed that great injury was inflicted by 

 fumigating pines 109 times with 1 part of sulphur dioxid to 100,000 

 parts of air and that injury was to be noted on fumigating pines 583 

 times with 1 part of sulphur dioxid to 1,000,000 parts of air. 



The details of the work done by the writer in relation to injury to 

 pines and young cowpeas ^ by sulphur dioxid show the following 

 results : 



(1) Pine trees fumigated^ 6 times with 1 part of sulphur dioxid 

 to 100 parts of air shoAved marked injury. All of the needles Avere 

 drooping, and nearly all had turned yelloAV or broAvn. 



(2) Pine trees fumigated 9 times with 1 part of sulphur dioxid to 

 1,000 parts of air Avere greatly injured in the same manner as the 

 plants just described. 



(3) Pine trees fumigated 50 times Avith 1 part of sulphur dioxid to 

 10,000 parts of air were badly injured. 



(4) Cow^peas fumigated 18 times Avith 1 jDart of sulphur dioxid to 

 10,000 parts of air lost all their leaves and could not be revived, al- 

 though carefully watered and tended outside the fumigation chamber. 



''Haselhoft" and Lindau, Die Beschadigung der Vegetation dnrch Raucli, pp. 

 58-66. 



* U. S. Dept. Agr., Bureau of Cliemistry, Bui. 89. 

 '^ Each fumigation lasted for one hour. 



