13 B. E. Fernow—The Battle of the Forest. 
one, now to the other side, and thus changing the balance of 
power again and again. 
In this struggle for supremacy between the different arbores- 
cent species the competition is less for the soil than for the light, 
the most important factor of life, especially for tree-growth. It 
is under the influence of light that foliage develops and that 
leaves exercise their functions and feed the tree by assimilating 
the carbon of the air and transpiring the water from the soil. 
The more foliage and the more light a tree has at its disposal, 
the more vigorously it will grow and spread itself. 
Now the spreading oak or beech of the open field finds close 
neighbors in the forest, and is narrowed in from all sides and 
forced to lengthen its shaft, to elevate its crown, to reach up for 
light, if it would escape being overshadowed, repressed and per- 
haps finally killed by more powerful densely foliaged compet- 
itors. ; 
The various species are differently endowed as regards the 
amount of light which they need for their existence. Go into 
the dense forest and see what kinds of trees are vegetating in the 
dense shade of the older trees, and then go into an opening re- 
cently made, an abandoned field or other place, where the full 
benefit of light is to be had by all alike, and one will find a 
different set altogether occupying the ground and dominating. 
In the first case there may be found, perhaps, beech and sugar 
maple or fir and spruce; in the second case aspen, poplar, wil- 
low, soft maple, oak or pine, tamarack, ete. 
All trees thrive ultimately best in full enjoyment of light. But 
some, like those first mentioned, can at least subsist and their — 
foliage functionate with a small amount—they are shade-endur- 
ing kinds, usually having a dense foliage, many leaves, and each 
one needs to do but little work—and exert considerable shade 
when fully developed. Those last named, however, are light- 
needing kinds, and having less foliage, cannot exist long without 
a considerable amount of light. 
To offset this drawback in the constitution of these latter, 
nature has endowed them as a rule with the capacity of rapid 
height growth, to escape their would-be suppressors ; but again, 
what they have gained in the rapidity of development they lose 
in the length of life. They are mostly short lived species, while 
the shade enduring are generally slower growers, but persistent 
and long lived. Some kinds, like most of the oaks, stand be- 
