176 
IOWA ACADEMY OF SCIENCE 
only a single tuft of needles. Parks situated in closer proximinity to the 
industrial center do not have any conifers whatsoever. There is a con- 
trast in the pines of Jackson iand Washington Parks, those of the former 
being more abundantly supplied with needles than the latter. This is 
accounted for in the fact that the lake breeze is more of a factor, in 
Jackson Park than at Washington Park. In all surveys, and in accounts 
given, the prevailing winds serve to concentrate or disseminate the 
smoke and its effects in one general direction. Grant Park, made famous 
through the Aviation Meet, offers conditions that are met with, when 
establishing parks in the center of large cities. The elms show the 
general effect of injury, by smoke. The same is true of the elms, on the 
north edge of the park as well as those near the 12th St. station of the 
Illinois Central Railway. The trees are stunted in growth, have few 
leaves and even in the early part of August, a large portion of them 
had already fallen. The elms and oaks near the 59th St. suburban 
station of the Illinois Central show the effects to which they are sub- 
jected. The stopping and starting of the locomotives of this line cause 
a great deal of smoke to come forth. Combustion is necessarily incom- 
plete and as a result the soot includes a number of toxic substances. 
The oaks are partially dead, and the number of leaves present, are few 
in number, the elms, however, do not show as many dead branches, but 
the leaf surface is insufficient for normal photosynthetic purposes. As 
the elms and the oaks, a block away, show an entirely different color 
and tone, the conclusion is that the injury is due to the smoke emitted. 
In Des Moines the same general conditions are found to be present. 
It is rather an unusual thing to find along the railway tracks in the 
city limits, a tree like the locust, or the oak, with a full foliage. Near 
the pumping station of the city of Des Moines an interesting feature 
is met with. Around the stations there is a small park with the elm 
as the principal tree. These trees have the same general appearance 
as the elms referred to in Grant Park, Chicago. The superintendent 
informed the writer that the elms were twenty-five years old, but the 
size to which they had attained would under natural conditions, make 
one assume that they were less than one-half the aige. The superin- 
tendent said that he had spent hundreds of dollars for shrubbery and 
trees. He remarked, “We can’t grow anything here.” 
At Stony Island, Chicago, in passing from Stony Island Ave., on 
93d St., toward South Chicago, no one can but be impressed by the 
large number of oak trees that are in a pathological condition. When 
the observation was first noted (May, 1912) it was thought probably 
that other factors might enter in to influence the growth development; 
