TREES AS GOOD CITIZENS 21 



The worth of trees to a city is by no means confined to 

 beauty. The city of fine shade trees is the City Healthful 

 as well as the City Beautiful. In comfort, in health and in 

 sanitation the shade tree is an important factor in civic 

 welfare. Only a part of the benefit gained by man from 

 shade trees is reckoned as by pleasure to the eye, and relief 

 from the direct rays of the sun. Added to the welcome 

 shelter is the cooling influence produced by the trees 

 through their leaves; for trees transpire through their 

 leaves in a way that has a pronounced influence on tem- 

 perature. By absorbing moisture from the earth through 

 their roots and releasing much of it into the air through 

 their leaf-pores, the trees cool the air and freshen it. Enter 

 the woods on a hot summer day, note that the temperature 

 among the trees is several degrees lower than in the open. 

 Wherever a shade tree spreads its leafy branches, this 

 influence is constantly at work. 



By this process of evaporating and exhaling moisture, 

 the trees not only reduce the temperature, but serve a 

 further useful purpose in giving off oxygen required 

 by man in the air he breathes; and, by drinking in the 

 carbonic acid gas, perform a double function in purifying 

 the air. 



Medical authorities recognize the value of trees in 

 their influence on the health of a community. In the study 

 of human illness, and particularly of the ailments of children 

 in the crowded cities, doctors have found that trees do 

 much toward reducing the death rate. Research has shown 

 that one of the chief causes of sickness and death among 

 the children of the congested districts is the stifling heat 

 of midsummer days, intensified by reflection from heated 

 pavements and sunbaked walls. On streets where shade 

 trees are lacking, this reflected heat is given off night and 

 day, to the severe discomfort and serious harm of people 



