THE MONTHLY BULLETIN. 



243 



Species of grasses are also bleached white when injury takes place. 

 Fig. 46 shows white tips of barley which have been slightly damaged 

 by the fumes. Damage such as this may take place and if later burn.i 

 do not aggravate the injury a good crop of grain may be harvested, 

 and the farmer, while he knows some daiuage has been done, can not 

 estimate how much and must be satisfied with his yield. On the other 

 hand, if several successive burns take place during a season a marked 

 diminution, if not entire failure of the crop, is the result. 



AVhile the foliage of most of the herbaceous plants is bleached as 

 described, that of trees and bushes is generally burned brown or reddish 



Fig. 46. — Barley with whitened tips from sulpliur dioxide gas liberated in the 



smelting of ores. (Original.) 



in color, the injury in every other respect being similar. Leaves of oak 

 — two species^ — and maple, typical of the appearance of the tougher 

 leaves, are shown in Figs. 47, 48 and 49. 



Sulphur dioxide injury, especially that of the herbaceous plants, which 

 assumes a white form, is sometimes mistaken by the untrained person 

 for red spider, thrips or leaf hopper damage. Each one of these insects 

 or mites causes a different and characteristic injury never mistaken for 

 smelter fumes by the entomologist or others who have observed these 

 different forms of leaf troubles at various times. Insect injury is always 

 more or less spotted; the droppings are usually plainly seen on the 



4—17154 



