The monthly bulletin, 



241 



Interests of the other, it is easy to see how injustice might sometimes be 

 done to certain individuals. The problem of adjusting the difficulties 

 must be left to the courts, while the scientist may determine the nature 

 and extent of the injury. Thus the chemist, the botanist, the plant 

 pathologist, the horticulturist and the entomologist have played their 

 part in studying the injury and determining its relation or similarity 

 to other forms of injury. Through experiments and analyses the 

 chemists have determined that sulphur dioxide gas is the common and 

 most destructive agent liberated in the smelting of ores, and excessive 

 quantities of sulphur have been found in vegetation in areas adjacent 

 to smelters treating ores containing sulphur ; the botanist and the plant 

 pathologist, through their knowledge of plants and their structure, have 

 l)een able to list those that are susceptible to injury and to determine 

 pathological diseases which might be mistaken for sulphur dioxide 

 itijur}^; the horticulturist, because of his general knowledge of trees and 

 tlieir diseases, has through a process of elimination, been able to weed out 

 common and generally distributed troubles and thus fix in his mind a 

 type of injury which he can easily recognize, and which he knows to be 

 due to smelter fumes ; the entomologist knows of various forms of leaf 

 feeding insects and mite.s which produce a more or less whitening of the 

 foliage, but each one of which has a very characteristic appearance of 

 its own, and he, too, becomes confident in a short time that sulphur 

 dioxide injury is different from any of these, and possesses certain 

 marked characteristics Avhicli make it readily distinguishable from 

 troubles brought about by insect or mite attack. 



CAUSE AND DESCRIPTION OF INJURY. 



The cause of the most common form of smelter fumes injury is, as has 

 already been stated, sulphur dioxide gas, which is liberated in great 

 quantities during the smelt- 

 ing of heavy sulphide ores. 

 Both greenhouse and field 

 experiments w^tli varying 

 quantities of the gas have 

 been conducted with the 

 result that the typical 

 bleaching or burning effect 

 seen so commonl}^ in smelter 

 regions has been obtained. 

 Samples of over forty differ- 

 ent species of plants have 

 been collected by the writer, 

 all of which displayed the 

 common type of injury. 

 This injury may be de- 

 scribed as bleaching or 

 burning of the foliage, 

 sometimes affecting the mar- 

 gins of leaves only, and at other times producing a spotting indiscrimi- 

 nately over the surface. Certain kinds of plants always show the bleach- 



FiG. 43. — Leaves of alfalfa that have been 

 bleached by sulphur dioxide gas liberated in the 

 smelting of ores. (Original.) 



