INJURIOUS AMOUNTS OF SULPHUR DIOXID. Th 
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 were 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 St6ckhardt’s work was repeated by Von 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 
pimes 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 showed marked injury. All of the needles were 
drooping, and nearly all had turned yellow or brown. 
(2) Pine trees fumigated 9 times with 1 part of sulphur dioxid to 
1,000 parts of air were greatly injured in the same manner as the 
plants just described. 
(3) Pine trees fumigated 50 times with 1 part of sulphur dioxid to 
10,000 parts of air were badly injured. 
(4) Cowpeas fumigated 18 times with 1 part 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 Beschidigung der Vegetation durch Rauch, pp. 
58-66. 
®U. S. Dept. Agr., Bureau of Chemistry, Bul. 89. 
© Each fumigation lasted for one hour. 
