158 SHADE-TREES IN TOWNS AND CITIES 



Trees with the bark removed are unsightly, and as long 

 as they continue their growth their deformity increases. 

 After a time they also become a source of danger. The 

 weakest part of the trunk of a tree is at a point four or five 

 feet from the ground. It is the portion of the tree that with- 

 stands the greatest strain during a storm. For example, if 

 you grasp the end of a rod with the hands and bend it suffi- 

 ciently, it will break in the middle. The resistance of the 

 roots of a tree, on the one hand, and the pressure of the 

 wind against the head, on the other, produce a like result; 

 the tree tends to break across the trunk. Sometimes during 

 storms mutilated trees snap at the points of the trunks 

 where they had been injured, and cause considerable dam- 

 age by their fall. 



When a tree is supplied with a guard, it must not be 

 allowed to remain after the tree outgrows it. The injury 

 caused by the failure to remove a guard after it becomes too 

 small, is sometimes more fatal than to expose the tree to 

 mutilation. If the guard binding a tree is weak, it yields 

 and breaks ; but before giving way under the strain of the 

 tree's growth, it usually injures the trunk. In Plate 33, Fig. 

 4, is shown the damage caused by a guard left around a tree 

 after the latter had become too large for it. The guard 

 broke ; but the tree was disfigured by an abnormal growth 

 of a ring of tissue. If the guard is very strong and the 

 increase of the diameter of the tree continues, the action of 

 the iron band around it has the effect of girdling, and the 

 tree dies. In Plate 33, Fig. 5, is shown an example of a tree, 

 the death of which was caused by the binding of the protec- 

 tor, which was cut apart before the photograph was taken. 

 The effect of its pressure on the trunk is clearly shown. 



