453 
all trees, which, even if allowed to reach full maturity, would never have 
an economic value. It should also include all trees that are dead or dy- 
ing, since such trees are not only deteriorating in value but also serve as 
centers from which various diseases destructive to the forest may spread, 
and because in addition they furnish natural breeding places for many 
species of harmful insects. When such dead or dying trees are infested 
with fungus diseases cr injurious insects, they should be completely burned. 
The cleaning should also include all trees which are over-mature or for 
any cause are losing value. Trees which are undesirable in shape or from 
other causes do not promise to make a satisfactory growth should also 
be included in the cleaning. Special attention should be paid to seed bear- 
ing trees of undesirable species. ‘These should be removed whenever found 
in order to prevent their seedlings from occupying the ground at the 
expense of the more desirable forms. 
As has been suggested, these operations must not be carried on too 
vigorously since the young seedlings, which are to make the future forest, 
require shelter from the wind and from the sun during their earlier years 
and if the removal of these undesirable forms is made too completely at a 
single operation the object in view will be defeated. By the application of 
such methods not only may the condition of the wood lot be constantly 
improved so that in the end it will contain a vigorous and healthy growth 
of vaiuable forms, but at the same time much material which may be 
utilized for fuel and for other purposes will have been removed from the 
area. In almost every instance, if care is taken, these cleaning cuttings 
will more than pay for the expense required to make them. It is a con- 
servative statement to say that over one-half of the existing wood lots in 
the state would be very greatly improved in value and in productive capac- 
ity by a series of judicious cleanings. 
In addition to these cleaning cuttings, in certain regions “thinnings” 
seem to be required. Two trees of a valuable species may stand so close 
together that if both were allowed to remain, neither would develop into 
a good tree. One of them should be cut away. In almost every wood lot 
also, there are to be found clumps of trees which stand so close together 
that they have developed thin, weak stems instead of stout and sturdy 
trunks. Enough of these should be cut out to insure a healthy and vigorous 
growth on the part of the trees that remain. The thinnings differ from 
the cleanings in that, while the cleaning removes undesirable and injur- 
