10 INJURY BY SMELTER WASTES, 
EXPERIMENTAL INVESTIGATIONS RELATING TO THE ACTION 
OF SULPHUR DIOXID ON VEGETATION. 
ORGANS OF THE PLANT THROUGH WHICH INJURY TAKES PLACE. 
In carrying on an investigation of this kind it was first necessary 
to ascertain whether or not sulphur dioxid was injurious to plant life, 
how small a quantity was injurious, and through what organs of the 
plant such injury took place. Light is thrown on this subject by the 
work of foreign chemists. 
Freytag ® showed that sulphur dioxid and trioxid do not injure 
the plant through the roots. His experiment consisted in watering 
wheat, oats, and peas with large amounts of dilute sulphurous acid 
in one case and sulphuric acid in another. The plants neither wilted 
nor reduced their yield. Von Schroeder and Schmitz-Dumont? 
made an investigation on pines, firs, hndens, and Norway maples in 
1896, in which they treated (1) the aerial parts of the plants with 
sulphur dioxid, (2) the aerial parts of the plant and the earth with 
sulphur dioxid, and (3) the earth in which the plant was growing 
with dilute sulphurous acid. They also showed that the injury to 
vegetation by sulphur dioxid is not through the roots, but through 
the medium of the leaves, and that even extremely minute quantities 
of sulphur dioxid are injurious. : 
Wieler in his work entitled “ Untersuchungen tiber die Einwir- 
kung schwefliger Siure auf die Pflanzen,” which has been published 
since the work at Redding was done, also gives numerous experi- 
ments to show that minute amounts of sulphur dioxid injure plants 
through the leaves, but he’ also states that in the course of time the 
sulphur dioxid and trioxid present in smelter smoke injuriously 
affect the soil and so indirectly injure the plant through the roots. 
He is further of the opinion that soils subjected to the action of 
sulphur dioxid suffer from a reduction in the lower forms of animal 
and plant life which are so necessary to the series of natural changes 
taking place in normal soils. He is also of the opinion that such 
soils suffer a loss in bases, which eventually causes them to become 
acid, as not enough bases are present to form humates with the humic 
acid. In proof of the latter point, he has taken soil samples from 
the vicinity of several smelters and found that all of them contained 
free humic acid. ) 
Wieler’s conception of this additional injurious action of sulphur 
dioxid on the soil has been published so recently that the writer has 
not been able to investigate the subject sufficiently to express a defi- 
@ Mitt. d. konig). landw. Akad., Poppelsdorf, 1869. 
® Thar. forstl. Jahrb., 1896, 46: 1. 
