203 
York, and the pipe lines Styne it are so often disturbed, not 
only by fi repair work, but even by the 
ordinary heavy t traffic, the oil often becomes more or a satur- 
ated with illuminating gas, which constitutes one of the most 
toxic substances to plants. 
ew York conditions a are probably I t pl street 
planting of those of any c t i obstacl 
not found elsewhere to ae successful establishment and perma- 
roduct of coal Combustor: and o° ies T gases kee from 
great variety of ee 
hattan. The detrimental eects of atmospheric gases on street 
ad tat 
oe ali, ee ce falling a prey to saprophytic 
and parasitic enemies. ere are many instances, eeu 
in the large industrial centers, where the expectation of life of 
trees is reduced to one-half to one-third the normal, owing to the 
presence of ee atmospheric gases and no amount of soil 
renovation or tree surgery can correct such ei eiaones a 
such is the case, only the removal of t tual 
but much can be gained by care fully: selecting gas- resistant 
ti here th 
are dying from the effects of Bteorpuerc gases, and it is rarely 
that one observes a Norway sp within the vicinity 
