42 



cellar of a house, whereas in heavier soils gas is more likely to be 

 restricted to smaller areas. 



The poisonous properties of gas are undoubtedly due to coal tar 

 products, which contain such compounds as sulfates, cyanides, etc. 

 More or less of the gas and its constituents is absorbed by the water 

 in the soil, and these are taken up by the roots and translocated to 

 various parts of the tree through the sapwood, and when they come 



\ 



© 



Fig. 22. Showing methods of attaching wires to trees. A, wires attached to lagbolt 

 and protected from tree by stick. Z, section of the same. B, wire loop placed twice tightly 

 around tree, causing girdling. J, loose wire loop fastened with clamp and separated from 

 the tree by blocks. E, cross section of the same. O, section and surface views of blocks. 

 X, groove for wire. F, sliowing attachment of trolley guy wires. P, wooden sleeve for wires 

 to protect from burning. From "Woodland and Roadside." 



into contact with living tissues destroy them. The feeding roots are 

 naturally first affected, and in a brief period of time the larger roots 

 •and trunk near the surface of the ground will show the effects of 

 poisoning. 



About I or 2 per cent, of gas is absorbed by water, and the water 

 in the soil becomes saturated to a certain extent. In the course of 



