[Illustration:  FIG. 154.—­Trees also Grow in Communities.]

4.  Enemies of trees:  An old stump or tree may be seen crumbling away
    under the influence of fungi and here the children may be shown the
    effects of tree diseases both as destroyers of life and as
    up-builders, because fungi turn to dust the living trees and build
    up others by furnishing them with the decomposed wood matter.

Insects too, may be invading the old dead tree, and something of their nature, habits and influences may be gone into.  They may be shown as wood borers, leaf eaters, or sap suckers, all injurious to the tree.  On the other hand they may be shown as seed disseminators and as parasites on other injurious insects; all benefactors.

Forest fires as an enemy of trees might be touched upon by noting how easily the leaves may be ignited and a surface fire started when the season is dry.  Top and ground fires emanating from surface fires can then be readily explained.

[Illustration:  FIG. 155.—­Trees Blend Together to Form a Beautiful Composition.]

5.  Expression:  The pupils have by this time been taught to feel the
    beautiful, to observe carefully and to reason intelligently and they
    may now be trained to express themselves properly.  This may be
    accomplished by asking them to remember their observations and to
    write about them in the classroom.  The lesson may be supplemented
    with effective reading about trees and forests.  Interesting reading
    matter of this sort can be found in abundance in children’s readers,
    in special books on the subject and in Arbor Day Manuals published
    by the various State Education Departments.

6.  Preparation:  In order to save time looking for objects of interest
    and for the purpose of correlating the various observations so that
    all will follow in orderly sequence, it is well for the teacher or
    leader to go over the ground beforehand and note the special
    features of interest.  The various topics can then be given some
    thought and a brief synopsis can be drawn up to serve as a
    memorandum and guide on the trip.

It is also well to be provided with a hatchet to cut into some decayed stump, a trowel to dig up the forest soil, a knife for cutting off twigs and a hand reading glass for examining the structural parts of the various objects under observation.  A camera is always a valuable asset because the photographs hung in the classroom become records of great interest to all participants.

7.  Suggestions for forming tree clubs:  A good way to interest children
    in trees and nature study is to form, among them, a Tree Club.  The
    idea has been fully developed in Brooklyn, N.Y., Newark, N.J., and
    other cities and consists of forming clubs of children in the public