23 
of favorable soii conditions, which requires dense shading, while large 
yield in quantity requires room and loose position, and trunk develop- 
ment in quality requires rfoderate crowding. 
A study of crown development is necessary to form a judgment as to 
what is required. Here we have the predominant few, with an excep- 
tionally full crown, while the majority of the trees have only a moder- 
ately developed head. We next discern quite a number which have 
still a normally developed crown, yet form only a subordinate part in 
the main crown canopy. These three classes form the dominant growth 
and the active crown cover. Underneath these we find trees with small 
undeveloped crowns, suppressed, dying, dead. These last classes are, 
to be sure, out of the struggle, and their removal means nothing to the 
superior or dominant growth; they may be taken or left as their wood 
can be made useful or not. The question can only be which of the other 
three classes to favor and how. much to open the crown canopy. 
As to the latter question, soil conditions are to be consulted first. On 
poorer soils less opening is preferable; the same rule is good on steep 
hills, southern exposures, and where windfalls may be invited by too 
severe thinning. The age of the growth also has a bearing. lLateron, 
when the principal height growth has been attained and the trunks are 
clear of branches to a sufficient height, and the formation of clean 
boles is not any more to be considered, the thinnings may be made 
severer. As arule the crown cover should not be interrupted more 
than the remaining growth is capable of closing up again within 3 to5 
years; this would take rarely more than one-fifth to one-third of the 
growth if the crown cover was normal at the time of thinning. As to 
which class to favor and which to remove opinions are at variance just 
now. The old conservative school permitted the removal of the first or 
second class only, when either a more valuable kind was threatened to 
be overgrown and killed out by a less valuable, or when the latter had 
an abnormally spreading crown, overpowering more neighbors than it 
could possibly supplant in amount and quality of growth, or when mal- 
formed or diseased, or else when a growth showed too large a number 
of individuals developed equally, in which case the natural differentia- 
tion into dominant and overgrown takes too long a time to be accom- 
plished naturally. 
The new, more radical school argues that when the time for severer 
thinning has arrived the foremost trees should be utilized first, because 
they yield the most valuable material and the next two classes are thus 
given opportunity to develop still into superior material, which they 
will do under the increased light influence, and that with more profit, 
than if the stoutest trees had been given further advantages. 
In the opinion of the writer this question can not be decided for all 
cases alike, but species, age, and soil conditions may require one or the 
other principle to prevail. 
In mixed growths it should especially not be overlooked that the 
