IMPROVEMENT CUTTINGS 147 
the canopy moves upward with the height growth. 
The lower limbs die because of a lack of light. The 
amount of light varies with the climate and the spe- 
cies. In some regions there is an abundance of light. 
In tropical districts there is too much, in other regions 
not enough. Some trees grow well in the shade, while 
others do not. In dry regions, because of a lack of 
moisture, trees grow singly and seldom form close 
stands. The object of thinning, wherever it may be 
practised, is to keep the canopy dense enough so that 
the trees will shed their lower limbs, and to keep the 
population of the forest in such proportion that each 
tree may have room enough to produce the kind of 
wood desired. The most important part of the tree 
is its crown. The crown regulates the production of 
wood. The smaller the crown, the less wood pro- 
duced. . In general, the smaller the crown, until a 
minimum is reached, the better the quality of the 
wood. It grows slowly, however, and the limbs are 
shed while very small. The wood thus produced 
would be almost without blemish. Time is sacrificed 
for quality. Such a forest is not as beautiful as a 
more irregular one. Time also is a very important 
factor. It pays, therefore, to thin carefully and fre- 
quently so that the tree will free itself from branches, 
and still have crown enough to develop a good strong 
trunk, and not a long, spindling specimen which would 
