70 



SHADE-TREES IN TOWNS AND CITIES 



may have two roadways separated by a planting-space 

 along its centre. The arrangement is shown in Fig. 4. 

 The central space may be used for shrubs and dwarf trees, 

 but such a street is hardly of sufficient width to permit the 

 planting of more than two rows of large trees, one row 

 along each sidewalk. Avenues or boulevards one hundred 

 and twenty or one hundred and fifty feet wide permit of 

 an arrangement of four rows of trees : two rows along the 



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FlG. 6. Streets having- buildings thirty-five feet high, on both sides, should have a 

 width of sixty-six feet. The divisions of the street and the positions of the 

 trees are shown. 



sidewalks and two rows in the central space. In the city of 

 Washington the streets having four rows of trees are about 

 one hundred and fifty feet in width. Pennsylvania Avenue 

 may be taken as a typical example, shown in Fig. 5. 



Height of Buildings. On residential streets the houses 

 are set back some distance from the sidewalk, twenty feet 

 or more. When this is the case there is more room for the 

 trees to develop. When tall buildings are close to the side- 

 walk, the conditions for growth are not so favorable. In 



