assistance by pointing out liow some of tlie mistakes may 

 be avoided. The 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 blocls 

 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 thin 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, cuts down 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 washingtonia^, when 



