21 
given; and they will perish equally if the old growth is removed too 
suddenly and the delicate leaf structure, under the influence of direct 
sunlight, is made to exercise its functions beyond its capacity. 
Left to itself, as the forest grows up and as the individual trees de- 
velop, each trying to hold its ground and struggling for light, there is 
a nataral thinning taking place, some trees lagging behind in growth 
and being shaded out, until in old age only as many trees remain as can 
occupy the ground witnout incommoding each other. 
This struggle among the individuals goes on during their entire life. 
Some few shoot ahead, perhaps because of a stronger constitution or 
some favorable external cause, and overtower their neighbors; these, 
lagging behind, fall more and more under the shading influence of their 
stronger neighbors until entirely suppressed, when they only vegetate 
until they die, while the struggle continues among the dominant class 
and is never ended in a forest that is utilized at the proper time by 
“man. 
The differentiation into dominant growth and laggards takes place in 
general earlier and more decidedly on strong soils, also in light-needing 
sooner than in shade-enduring species, which last keep up an even 
struggle much longer than the former, so that it is difficult to say 
which will finally win. 
It is to give direction and assist in this struggle, to hasten its results, 
to obviate, if possible, useless expenditure of energy by timely inter- 
ference, that the forester steps in with the ax. For the natural thinning, 
as a rule, does not progress satisfactorily for the best quantitative and 
qualitative development, and hence it is assisted by the forester, it be- 
ing well understood that there is a larger total and more valuable prod- 
uct to be had with a smaller number of individuals through better 
development of the latter. 
It is the number of trees that yield the best result, not the greatest 
number that we try to keep growing. What this ext number is de- 
pends naturally on the kind of. trees; it changes also with age, as the 
trees need more room, and with soil and situation. 
In the average we Tot not be far out of the way to require per tree 
in the twentieth year 10 square feet, in the fortieth year, 40; in the six- 
tieth year, 100; in the eightieth year, 125, and in the one hundredth 
year 160 square feet growing space, or 4,300, 1,100, 435, 350, and 270 
trees per acre, respectively, at the ages noted, would represent about the 
proper average condition of growth. There are from 50 to 75 per cent 
more shade-enduring trees possible on an acre than light-needing; 
more trees on poorer soils, sometimes two to four times as many, than 
on good soils, and more in the valley, sometimes double that of the higher 
elevations; so that while a pine growth of, say, 60 years may show 500 
trees to the acre, a beech growth may contain 750 trees under the same 
conditions. 
