33 



years until a fire that destroys all other vegetation breaks their hard seed 

 coat and calls to life the dormant germ ; the cones of some pines remain 

 closed, and release the seed only when fire, which has probably destroyed 

 all competitors, opens them. The peculiarities of the seed, then, account 

 for much in the distribution of plants. 



Next comes the peculiarity of growth. The long-leaf pine, which, for 

 the first four years, does not grow more than two or three inches above the 

 ground, is at a disadvantage in that first period, during which it has occu- 

 pied itself with forming a stout root system ; but thereafter, by virtue of 

 this root system, it may endure what a faster growing neighbor could not. 

 The thickly growing aspen covers large areas, but its reign is of short dur- 

 ation, for, as with most of the rapid growers, its life is short. The slower 

 growing spruce or pine, which could support itself under the light shade of 

 the aspen creeps in, and remains on the field, the victor by sheer persist- 

 ency. 



While rapid, persistent height-growth enables these to escape the 

 would-be suppressor, endurance of drouth or of excessive moisture, of heat 

 or cold, and of shade favors others ; windstorms and decay, in our primeval 

 forests, acting as allies now to one, now to the other side, and thus chang- 

 ing the balance of power again and again. 



In this struggle for supremacy between the different arborescent spe- 

 cies, the competition is finally less for soil than for light, the most import- 

 ant 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 at its disposal a tree has. 

 the more vigorously it will grow and spread itself. 



Now, the spreading oak or beech of the open field finds close neigh- 

 bors 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, suppressed and perhaps finally killed by more powerful, 

 densely- foliaged competitors. From the shape of the tree and of its crown 

 we can judge whether it had to wrestle with neighbors. The important 

 fact, which predicts the issue and the final result, is that the various species 

 are differently endowed as regards their ability to tolerate the shade or as 

 to the amount of light which they need for their existence. 



Go into the dense forests and see what kinds of trees you find there in 

 the deep shade, and then go into an opening recently made, an abandoned 

 field or other place where the full benefit of light is to be had by all alike, 

 and you will find a different set altogether occupying the ground. In the 

 first case, you will find, perhaps, beech and sugar-maple, or fir and spruce : 

 in the second case, you may find aspen, poplars, willow, soft maple, oaks 

 or pines, tamarack, etc. 



