222 FUNDAMENTALS OF AGRICULTURE. 



SECTION XXXII. THE INJURY OF GAS AND ELEC- 

 TRICITY TO TREES. 



By DR. G. E. STONE, 

 *i Department of Botany, Massachusetts Agricuftural College. 



Causes of Gas Leakage. The greatly increased 

 death rate of trees from the effects of escaping illumi- 

 nating gas in the soil may be accounted for in part by 

 the larger amount of gas now used, and in part by the 

 different methods of laying and calking the joints, the 

 different types of connections, larger pipes, etc. Of 

 course the heavy traffic on highways, the continual ex- 

 cavation of gas conduits and the effects of frost are 

 also more or less responsible for leakage. 



Gas Leakage Injures Trees While the leakage 

 of gas may be very slight from some gas mains, pos- 

 sibly only a few cubic feet a day, even this small 

 amount will surely cause injury sooner or later, as the 

 soil becomes charged with the gas. Such leakage may 

 not cause the immediate death of the tree, but will 

 shorten its life and often results in a condition which 

 from ignorance of the true cause is sometimes called 

 " general debility," a most convenient term. 



Affected Trees Die. There is absolutely no hope 

 of recovery for a tree which has been affected with 

 gas from a large leak. There appears to be little dif- 

 ference in the susceptibility of different species to gas 

 poisoning, but trees with a large spread of roots are 

 more likely to be affected than those with a limited 

 spread. 



Symptoms. The symptoms of gas poisoning are 

 distinct to one familiar with them; one of the first ef- 

 fects being a yellowing of the foliage, followed by a 

 rapid defoliation of the tree if the poisoning is severe. 

 The trunk assumes a dark color in some cases; the sap- 

 wood is often found to be discolored and it has pecu- 

 liar, characteristic odors which assist in diagnosis; but 

 when the tree is injured in late summer, when the flow 



