The North American Forest 31 



throwing the aspen into shade and hindering their 

 growth ; another decade, and most of the aspens 

 have died out because, being Hght-lovers, they 

 could not thrive in the shade of the pine, which has 

 now recovered the ground it lost thirty years ago. 

 An exactly similar alternation of trees can be ob- 

 served in New York and New England, with the 

 exception that there spruces usually play the part 

 taken by pines in the Lake region. Undoubtedly 

 other sections of the country might furnish parallel 

 cases where trees have an advantage at the start 

 which they lose later on in the rivalry with other 

 species. 



Attentive readers must have observed that the 

 dangers threatening a tree are by no means over 

 when the seed has found a favorable locality and 

 developed into a seedling. Just as very few seeds 

 ever sprout at all, so very few infant trees ever 

 reach old age. A very large old tree takes up a 

 hundred times as much room as a young sapling. 

 This room must be provided by killing off the 

 weaker individuals competing for it. A wood com- 

 posed mainly of very old trees will show far fewer 

 individuals to the acre than one stocked with young 

 ones. But the crown canopy may be just as dense, 

 and the amount of timber contained in it is apt to 

 be far higher. 



It would require a volume by itself to describe 

 in detail the manifold conditions under which the 

 warfare of the forest is carried on. We have, al- 

 most at random, picked out a few of the phases 



