ARBORETUMS AND BOTANIC GARDENS 283 



localities and dates of planting would be very 

 useful. 



In an arboretum, the space allotted to each plant 

 or group of plants should be large enough to allow 

 full development for each individual or group and 

 also open surrounding space so that trees and shrubs 

 can be seen to advantage even when they have reached 

 old age and attained their greatest size. The land 

 selected for an arboretum should, if possible, have 

 a varied topography with slopes to the north, south, 

 east and west and each plant should be placed in its 

 most appropriate location in regard to slope, soil, 

 and moisture. For example, birches and hemlocks 

 should be on the north slope. Most trees and shrubs 

 noted for their blossoms should have a south or at 

 least a sunny exposure. Some trees prefer sand or 

 gravel and others a clay soil. 



The roads and walks in the arboretum should be 

 planned with easy lines and grades with the plants 

 to be seen from them so placed that they can be ob- 

 served conveniently. To save space and expense, 

 there should be comparatively few roads. Those 

 who are studying plants can do so best when walking 

 or standing. 



Even though an arboretum is primarily a museum, 



