1913.] PUBLIC DOCUMENT — No. 31. 49 



confined to some special part of the tree or root. They are more 

 pronounced by far at the base of the tree than above, and in 

 the top are rarely to be noticed. 



We know of no remedies which can be applied to trees already 

 poisoned by gas, since the injury occurs below the surface of 

 the ground, and the effects on the tree are seldom noticeable 

 until the poisoning is more or less pronounced. If the leakage 

 of gas could be discovered quickly and the leak repaired, the 

 effects on the roots might be prevented, but this is rarely the 

 case. In some instances where only one root has been affected, 

 and the poison has not reached the trunk of the tree, amputation 

 of the root is used to prevent further harm, and we have seen 

 cases where this has proved effective. There are many cases 

 where trees have not suffered from gas poisoning although lo- 

 cated near large leaks, because in the installation of curbings 

 many of the larger roots were destroyed which grew over the 

 roadbed where the gas pipes were laid. 



When the soil is charged with gas, excavating and aerating are 

 beneficial, and in the case of severe leakage it is well to leave 

 the trench open for a few days, if possible. On the other hand, 

 boring holes in the soil and filling with water is of absolutely 

 no value. It is generally believed that if young trees are 

 planted near others which have died from gas poisoning they 

 will not live, but this is true only in part. If the soil is thor- 

 oughly saturated with gas, bad results may follow, but if young 

 trees are planted in fresh loam and the old soil aerated there is 

 little likelihood of the tree dying. It is possible, but perhaps 

 at the present time not practical in all instances, to prevent in- 

 jury to trees and asphyxiation to people in houses from gas 

 leaks, and undoubtedly in the future better methods of distrib- 

 uting gas will be employed. 



Su:mmary. 

 The symptoms of gas poisoning are best obtained from a care- 

 ful examination of the wood at the base of the tree or the roots. 

 This can be done v;hen the .poisonous principles have reached a 

 certain point in their ascent. There are many symptoms accom- 

 panying gas poisoning such as a yellowing of the leaves, drop- 



