38 PRACTICAL FORESTRY IN THE ADIRONDACKS. 
-has been cleared by wind, fire, or otherwise, the succeeding growth is 
of a comparatively even age. Seed is distributed over the clearing, 
and the whole area stocked with some kind of tree growth in a com- 
paratively short time. After a windfall there are usually a few saplings 
which have escaped being blown down, but aside from these few speci- 
mens the second growth often will not vary more than 10 to 20 years 
in age. This new growth frequently comes up very dense, aS many as 
4,000 or 5,000 plants often springing up on 1 acre. As these small 
trees grow larger and require more light and space for their develop- 
ment, the more thrifty plants take the lead and overtop the weak speci- 
mens, which die on account of the shade. As the trees grow older their 
number falls off, but because of the great ability of the Spruce to 
tolerate shade there is always a large number of trees per acreina 
pure forest. On account of the mutual crowding of the trees the lower 
branches die and break off early in life, and as a result long, clear 
shafts are produced. 
From a large number of measurements in the heavy Spruce forests in 
the White Mountains of New Hampshire, it was found that from 200 to 
250 trees often grow on 1 acre at maturity. 
SPRUCE IN MIXTURE. 
_In a virgin forest of mixed species, like that in the Adirondacks, the 
life history of the Spruce is entirely different from that in pure stands. 
Here large tracts are seldom cleared by destructive natural agencies, 
but individual trees are continually dying and being replaced by others, 
so that the forest is composed of trees of all sizes and ages. In the tech- 
nical parlance of forestry such a stand is called a “selection” forest. 
It is obvious that the young trees which germinate in openings made 
‘by the death of one or two trees will have comparatively little light 
for their development. The consequence is that the young Spruce 
which comes up under such conditions is very backward in its growth 
and survives only through its marvelous capacity to live in deep shade. 
If the crowns of the larger trees close together above the small trees, 
the growth in height is frequently so checked that the terminal shoots 
add but a fraction of an inch each year. In such cases the growth goes 
chiefly to the side branches, with the result that the trees are shaped 
like mushrooms. (PI. X, fig. 2.) When the cover is removed from over- 
head the young trees shoot up with new vigor and attain a normal 
development; but where the side branches are large the timber is apt 
to becoarse. Ithas been observed also that trees which have been sup- 
pressed in this way are apt to become rotten at the place where the 
branches are clustered. 
In a pure forest, where the trees are of about the same age, the timber 
grows more rapidly than in a mixed forest, because the competition is 
between trees of approximately the same height, and in consequence 
there is no shade from above, as is the case in mixed hardwood forests. 
