154 SHADE-TREES IN TOWNS AND CITIES 



them. Very frequently an entire row of trees can be saved 

 that way. If the trees are in poor condition, however, it is 

 best to cut them down and plant new ones. With proper 

 selection, planting, and care, better trees result in a short 

 time than if an attempt is made to save poor specimens. 



When the grade of a street is raised, the filling should 

 not be brought up close to the tree, as the exclusion of air 

 will kill it. A well should be left around the tree of as large 

 a diameter as possible. In a few years the roots will come 

 to the surface, and then it will be possible to fill the well 

 and bring the soil up to grade. A grating may be placed 

 over the opening to the well so as to guard against any one's 

 falling into it. 



When the street-grade is raised it is even possible to con- 

 tinue the concrete pavement close to the tree, provided an 

 air-space is left underneath that covers as large an extent of 

 root spread as possible. The pavement should not touch the 

 trunk of the tree, but should keep clear of it, six inches or 

 more to allow for the growth of the tree and the circulation 

 of air. 



In the New York Zoological Garden, many animal cages 

 having concrete floors were built around large trees, twenty 

 inches and more in diameter. All the trees were saved by 

 raising the floor a foot or more above the ground and leav- 

 ing an air-space between them. The tree-tru,nks were 

 allowed to pass through circular openings in the floor, and 

 were protected by means of iron guards so that the animals 

 could not injure them. The work was done under the 

 direction of Hermann W. Merkel, the Forester of the Garden. 



Many cases arise in a city, involving the care and pres- 

 ervation of valuable trees. Each case should be studied 

 carefully, and the best plan followed. In cities having 



