SHADE TREES. 



the evaporation of water. It may be thickened by burning in 

 an iron kettle. Coal tar does not injure the tissues to any appre- 

 ciable extent, since only the surface of the wood is cauterized by 

 it and there is no vital connection between this wood and the 

 callus which covers it. When used 

 on the elm, it is prevented from ad- 

 hering at times by water blisters pecul- 

 iar to this tree, In these cases, it should 

 be rubbed off and another coat applied. 

 Wounds made by accident may be 

 treated similarly to those made in 

 pruning, after the injured tissues have 

 been removed. Split trees should be 

 joined with a bolt instead of a band. 

 Bruised, loosened, or dead bark should 

 be entirely cut away, since it can never 

 aid in repairing the injury, but on the 

 contrary, encourages decay and pre- 

 vents the growth of new bark. 

 Decayed wood should be removed 

 and the cavity painted with coal tar, 

 then plugged with dry oak wood and 

 this smoothed on the outside even 

 with the trunk and coated with tar; 

 If the hole is too large to plug, a 

 board is sometimes nailed in it and 



painted with tar or covered with zinc to keep borers away. At 

 Wiesbaden, large holes are filled with cement, probably because 

 cement is so abundant in that region and so easily used. I 

 noticed cement also used on trees in St. James' Park, London. 

 At Bonn, they make use of a heavy tarred felt for covering 

 large cavities in the trunks of trees. Sheet iron is often 

 employed for this purpose in America, and to a limited extent in 

 Europe. If the cavity is not made thoroughly antiseptic, how- 

 ever, the use of any of these coverings is of doubtful advan- 

 tage, since the exclusion of dry air and light tends rather to 

 encourage than to prevent decay. In case the tree is hopelessly 

 diseased, anything that will strengthen the trunk or conceal an 



FIG. 25. Large elm in 

 Jthaca covered on one 

 side with sheet-iron. 



