58 



A PRIMER OF FORESTRY. 



topped and retarded trees, whicli often remain in size 

 classes which the dominant trees have lon^* since 



outgrown, tliere are 

 still many low saplings. 

 Even between the domi- 

 nant trees, in a healthy 

 forest, there are always 

 great differences. In- 

 crease in height is now 

 going on rai^idly among 

 these high saplings, and 

 either in this stage or 

 the next a point is 

 reached when the top- 

 most branches nmke 

 their longest yearly 

 growth, which is one 

 way of saying that the 

 trees make their most 

 rapid height growth as 

 large saplings or small 

 poles. (See PI. XXIX.) 

 Later on, as we shall see, 

 these upper branches lengthen much more slowly, until, 

 in standards and veterans, the growth in height gradu- 

 ally diminishes, and in very old trees finally ceases 

 altogether. 



NATURAL PRUNING. 



While the trees are i)ushing ui> most rapidly the side 

 branches are most quickly overshaded, and the process 

 of natural pruning goes on with the greatest vigor. 

 Natural pruning is the reason why old trees in a dense 

 forest have only a small crown high in the air, and why 

 their tall, straight trunks are clear of branches to such 



Fig. 56.— Standards and poles of Spruce. 

 White Mountains, New Jliiiapsbire. 



