assistance by pointing out how some of ttie mistakes may 

 be avoided. Tlie unsatisfactory results of street-plant- 

 ing, so often met with, can generally be traced to one 

 or all of three causes : 



1. Selection of unsuitable species. 



2. The mixing of several species on the same block 

 and even in front of the same lot. 



3. Crowding the trees. 



This last-mentioned source of trouble is perhaps'.the 

 cause of more failure than the first. When trees are 



once growing, few persons have the heart to thm out 

 the specimens to the proper distance apart; finally a 

 newcomer, without personal feeling in the matter and 

 noting only that there is too much shade and too little 

 light, cutsdowu the whole row and a gap is left in what 

 may have been a fairly uniform block. Spreading 

 avenue trees of large size should not stand closer than 

 50 ft. apart; smaller trees, on narrower streets should 

 have 40 or at the very least 30 ft., unless they are slen- 

 der species such as cordylines or washingtonias, when 



