PLANTS FOR USE IN CONGESTED CITY DISTRICTS

The effect of dust, smoke, and gas fumes upon vegetation is wellknown and yet no considerable amount of study has been givento this subject, largely because it has not been considered an eco-nomic question. Surely the people who are compelled to live in thecongested districts of our large cities are as much entitled to shade andgreenery as any one else, and there is no question but that the health-fulness of the congested districts is lowered by the absence of shade andgrass. By the use of those plants which can survive drought, smoke,and abuse, some sort of trees or shrubbery may be had almost any-where, except perhaps in the immediate vicinity of a steel mill orsimilar factories, where not even grass will survive. The first treesone comes to on the edge of the treeless districts which surround largesteel mills are usually ailanthus or willow. The ailanthus is also thetree which most often appears in the closely built up sections of largecities, often providing the only greenery to be seen in whole sections ofa town. Ashes, locusts, European planes, European lindens, and horse-chestnuts also seem to have the ability to withstand the summerdroughts and the suffocating soot that proves disastrous to so manycity trees. No rough-leaved tree nor one which requires much watershould be used as a street tree in a congested, sooty district, becauseit is doomed beforehand to a lingering death, if it survives at all.Pin oaks and willows are useful only when they are assured of areasonable supply of water during summer droughts.