General Considerations 201 
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 litter- 
ing the ground is undesirable. 
6. Liability 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. 
g. 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, 
