light surrounds the tree, and pure air circulates all through 
the branches. In autumn the leaves fall upon the ground and 
furnish a mulch and fertilizer for the future growth oc the 
tree. The necessary city improvements have changed all this 
condition, and plunged the tree into unnatural environment. 
Our cities have been sewered, and thereby drained of the 
natural moisture upon which the. tree thrives. We have laid 
concrete sidewalks, cutting off water and air that they require. 
Instead of an ample parking space being left tnat which is 
left is so narrow that there is only about one-fourth to one- 
fifth for the normal requirements of the tree; and in the older 
portions of the city no parking space whatever has been left, 
but the entire surface covered with a brick or concrete pave- 
ment. We have built our houses so closely that light and air 
are curtailed. We sweep our streets, and take away all leaves 
that fall giving no chance for mulch or fertilizer, except as it 
is supplied in other ways. We have strung our electric wires 
to catch the branches above, and installed gas pipes to drain 
the moisture by the trencn, and to poison the roots with leak- 
ing gas. The trees not being protected, unattended horses 
with vigrous appetites gnaw the bark of the tree causing disease 
and decay. Our houses and factories give off volumes of smoke, 
and automobiles fill the air with noxious gases. We have 
bricked over or cemented up the space around the tree. Mis- 
chievous boys and thoughtless and careless people have broken 
the branches, cut the bark or bent the tree over in endeavoring to 
make swings of them. The San Jose scale is ready to attack 
trees of feeble growth as its powers of resistance are decreased, 
and so we find parastic foes of all kinds in numberless quanti- 
ties upon the older and decayed trees of the city. Not know- 
ing any better, the ice-cream man empties the salt water from 
his freezers around the tree, and that means its death. 
This gives in brief the situation that faced the Commis- 
sion at the inauguration of its work, when desiring to make the 
city more healthful and more comfortable to its citizens by the 
steady evaporation of moisture thrown off by the foilage, and 
the air made pure by the absorption of carbonic gas. 
It has been estimated that a tree with its trunk twelve 
inches in diameter and normal top, will, on a hot day, throw off 
250 gallons of water in an invisible vapor, thereby cooling the 
air to such an extent that it has been further estimated by 
scientific aboriculturists that a street lined with full grown 
trees, and having the advantage of the grateful shade and 
evaporation of this invisible vapor, will be ten degrees cooler 
than the same street with no trees or parkway area, with side- 
walks and curbs joining, bare, desolate, wind-swept, dust-laden 
and sun-beaten a terror to nee beast. 
