SHADE TREES. 219 



fungi will develop where the coal tar has been put on. After coal tar has 

 been on for some time it is evidently not injurious., even to delicate tissue. 



Salt. 



Salt used on sidewalks, in gutters and on trolley lines in winter has been 

 known to cause injury to the root systems of trees. In one instance we 

 noted injury to several small maples growing near a sidewalk and gutter 

 which had been treated heavily with salt. In some cases where salt had 

 been used extensively on trolley tracks, injury to trees was observed. 

 It should not be used near valuable trees. 



Other Injurious Factors. 



Arsenate of soda, potassium cyanide and other chemicals are extremely 

 poisonous to trees, and when placed in holes bored in the tree the two 

 first named will soon cause death. Since arsenate of soda is often used 

 as a weed killer, it is recommended that care be taken in applying it 

 around the feeding roots of trees. 



A quite common opinion among linemen is to the effect that copper 

 spikes driven into trees will kill them, but a small maple so treated by us 

 a few years ago showed no abnormal symptoms. 



The foliage of different trees is often injured by spraying with various 

 fungicides and insecticides. It is well known that plum and peach foliage 

 is quite susceptible to this type of injury, and even the leaves of maples 

 and other trees may be injured by arsenate of lead. The extent of the 

 injury depends not only on the nature of the spraying solution or mixture 

 used, but also on the condition of the foliage sprayed. We have observed 

 injury to maples from the use of 12 pounds of arsenate of lead to 100 gallons 

 of water; and Paris green, owing to its present-day uncertain composition, 

 often burns foliage. 



Burning insect nests with torches, although a common practice, is a 

 bad one, and invariably causes injury. Serious harm often results from 

 burning leaves and grass around trees, and the roots of forest trees, 

 which are often close to the ground, are sometimes injured by burning 

 the underbrush. 



In conclusion it may be said that in any treatment of trees one should 

 always have before him some definite object; he should leave strictly 

 alone the numerous irrational methods constantly being advocated, or 

 apply to them first the measuring stick of common sense. 



Banding Substances. 



During the past fifteen years a large number of banding substances 

 have been placed on the market, all of which with one or two exceptions 

 have proved injurious to trees. These substances usually contain some 

 oil which affects vegetation injuriously, in some cases even when applied 

 over tarred paper. The injury caused by banding substances varies 



