General Considerations 20i 



3. Rate, persistence (longevity), and mode of growth, 

 the branching being either spreading or upright; points 

 which are of importance, especially in the grouping of trees 

 and in the selection for certain special situations, such as 

 small places, narrow streets, etc. 



4. Relative water and light requirements are essential 

 considerations in grouping trees; the latter quality especially 

 in connection with the rate of height growth, fitting or unfit- 

 ting them for grouping and underplanting. 



5. Cleanliness of habit; a consideration which deserves 

 attention especially in street-tree planting, where continu- 

 ous shedding of foliage, flowers, fruit, or other parts htter- 

 ing the ground is undesirable. 



6. LiabiHty to insect pests; which is closely related to the 

 requirements of cleanliness, and increases the need of care. 



7. Liability to fungus and other diseases. 



8. Endurance and recuperative powers; which enable 

 the trees to repair damage readily and to respond to pruning 

 and other restorative treatment. 



9. Special requirements or habits which give additional 

 point or else exclude the use of some trees in given situa- 

 tions. Such requirements or objects to be attained may 

 consist in proper grouping, in fitting special locations of 

 valley, slope, or hill as to foliage, color, or outline, in 

 furnishing shelter, in withstanding special hardships, such 

 as winds, untoward soil conditions, deleterious gases, etc. 



In the choice of street trees in particular, endurance and 

 recuperative power are most essential; cleanliness of habit 

 coming next. Being planted for shade, the degree of such 

 shade is a matter of consideration, and thus the length of 

 leaf period forms an important part in this consideration. 



Rapidity of growth usually means short life, hence where 

 the planting is to be of permanent character, as in streets, 



