AQ PRACTICAL FORESTRY 
and yields more certain and even in quantity. There 
is a qualitative as well as quantitative increment. Of 
the two, qualitative increment is often the more im- 
portant, because good wood sometimes sells at a rate 
out of all proportion to its bulk. We should strive 
to produce, therefore, not only a large quantity of 
wood, but the largest possible quantity of the choicest 
grade of wood. This can be done only by the closest 
attention to the rules of silviculture; but, as has been 
already stated in a previous chapter, practical limita- 
tions often hinder the merest approximation to our 
cherished ideals. 
The function of the woody trunk of a tree is 
mainly support. It forms an axis which supports the 
branches and branchlets, which, in turn, hold the 
working parts in the best positions in reference to 
light. In the open, it is irregular in form, short in 
stature, and often fortified by heavy buttresses. It 
is thus able to withstand heavy gales. In the forest, 
it is often a slender column bearing at its top a 
bouquet of foliage. It has no individuality. If left 
alone, without the support of its neighbors, it bends 
over, helpless, of its own weight. 
The trunks vary, of course, in size and form with 
every species, from the stunted Alpine spruce to the 
big trees of California and the karri (Hucalyptus 
diversicolor) of Australia. 
