42 THE BOOK OF FORESTRY 



climates and the age must be guessed at according to 

 the size of the tree. 



During the early life of a tree height growth is quite 

 rapid, the reason being that unless it is shade-enduring 

 it must outgrow its competitors to obtain sufficient sun- 

 light. During this period the struggle for existence is 

 very keen in the young forest and many little trees 

 are crowded out and die. After the period of rapid 

 height growth has passed a tree begins to take on flesh 

 to increase in diameter and volume. In this respect 

 trees are like some fast-growing boys, quite weedy and 

 slim for a few years and then gradually becoming stout 

 and strong. 



How Trees Reproduce Themselves. About the time 

 the diameter growth is beginning to increase and a 

 surplus of starch has been stored in the roots, etc., 

 the tree is ready to produce seed, for seed produc- 

 tion is largely a matter of sufficient food. When 

 there has been a series of favorable years with 

 plenty of rain and yet sufficient warmth and sun- 

 light trees will produce large quantities of seed. These 

 seasons of bountiful seed production are known as 

 "seed years," although a little seed is produced nearly 

 every year. These seed years come at unequal in- 

 tervals depending upon the fortune of the tree three to 

 five years previous. Seed years are not uniform within 

 the species all over its range, as the white pine of the 

 Lake States may bear a heavy crop of cones while the 

 white pines of Maine will be absolutely barren. Trees 

 growing in the open produce seed in larger quantities 

 and at an earlier age than trees in the dense forest. 

 As a rule trees in the open will commence to bear 

 fertile seed at twenty-five years while those in the 

 forest are incapable of producing a crop of seed until 



