hedgcock: injury by smelter smoke 71 



still continuing in the same general directions as reported by Hay- 

 wood, extending farthest to the north, 12 to 15 miles, and to the 

 west 8 to 10 miles or even more. The acute injury to the south 

 and east does not extend more than half the latter distance. No 

 accurate estimate can be made of chronic injury which apparently 

 extends much farther in all directions. Prevailing winds are the 

 deciding factors as to the directions in which acute injury extends 

 the farthest, and owing to the contour of the country all localities 

 in any direction are not equally affected. In the worst affected 

 area little herbage is found, and the hills look like a desert with a 

 greatly eroded appearance. Beyond this area grasses have been 

 able to maintain themselves owing to the greater dilution of the 

 fumes. Various flowering plants, such as asters, goldenrods, 

 and legumes begin to appear at a still greater distance than grasses, 

 and along with them certain species of trees. Garden beans 

 (Phaseolus vulgaris) are especially susceptible to the fumes, and 

 are a good index of the SO2 injury. 



Deciduous trees appear to be more resistant to smoke than 

 conifers in this region. The deciduous trees along the Ocoee 

 River to the westward appear to be resistant in the following order, 

 the most highly resistant being named first: Quercus alba, Acer 

 rubrum, Cornus florida, Nyssa sylvatica, Populus deltoides, Oxy- 

 dendrum arboreum, Liriodendron tulipifera, Robinia pseudacacia, 

 Platanus occidentalis, and Uhiius crassa. On the uplands the most 

 severe injury was found. It was most noticeable on slopes of 

 hills facing the smelters. Of the Oaks the following order of 

 resistance was noted: Quercus alba, Q. prinus, Q. coccinea, Q. 

 palustris, Q. digitata, Q. minor, Q. marylandica, Q. veluiina, and Q. 

 triloba. 



The element of the smoke that is the chief cause of injury is 

 undoubtedly SO2. Haywood ascribes the inj ury to this gas. The 

 usual form of acute injury to deciduous trees consists of irregular, 

 reddened areas of dead leaf tissue between the veins. The region 

 in the immediate vicinity of the midrib and principal veins of the 

 leaves is last to be affected. Repeated acute injury of this sort 

 kills the twigs of the trees, and finally brings about the death of 

 whole trees. Few conifers are found in the region of acute injury, 

 and no observation of these was made. 



