laces where it is urged that trees are
not desirable. On stretches of road where the soil is naturally wet the
heavy shade cast by certain species of trees is undoubtedly
objectionable; but there are also trees whose shade is very light. Some
trees make such a dense mass of foliage that they tend to prevent air
currents and thus keep the moisture in the road from drying out. Along
such stretches of road the method of planting may affect the matter of
light and air, and species of trees can be chosen which will be
practically unobjectionable. Most of the highway planting in the past
has been a matter of chance and there have been few definite plans for
any long stretch of roadway.

In selecting trees for planting the probable rate of growth and
appearance of the tree at maturity should be borne in mind. What might
seem entirely satisfactory in young trees may prove objectionable in the
cost of mature ones. The size and shape of the tree at maturity should
be considered as it affects the spacing of the trees. Also the amount of
care which it will be possible to give the trees should influence the
choice of species; for certain trees will produce good results with a
small amount of attention while others require a great deal of care. The
matter of interference with telephone and electric wires must also be
considered. A species should be selected which is relatively free from
the attacks of insects and fungi. It would be very difficult to find a
tree which is entirely immune but there are some trees which are more
resistant than others. The amount of shade cast by the tree is of a
great deal of importance in connection with the moisture conditions;
trees are often placed too close together which prevents their proper
development. Where quick results are desired two species are often used,
a fast growing one planted in between slower growing trees; the idea
being to cut out the fast growing tree after the slower growing ones
have reached good size. This is alright in theory but seldom works well
in practice. The fast growing trees are seldom cut at the proper time
and the result is often the stunting and injuring of the better and more
durable trees. The fast growing trees usually die before many years. The
result is seldom satisfactory.

The question of litter while of importance with city street trees does
not matter so much in the case of highway trees, but the cottony seed
from poplars is very objectionable anywhere. T