226 THE NORMAL AGE CLASSES. 



Class IV. 



Underwood, 16 20 } r ears old = 50 acres 



Overwood, 16 20 ,, ,, =10 



36 40 =10 



56 60 =10 



76 80 =10 



96100 , =10 



rp , i j" Underwood = 50 acres 



I Overwood = 50 



The normal state of the age classes in the case of coppice 

 with standards is of a still more ideal character than in the 

 case of the shelter-wood compartment system ; it can only 

 serve as a mathematical guide for the treatment of such woods. 

 More especially, it gives some idea of the relative number of 

 trees which should be found in each class or gradation. As 

 each should occupy about the same area, the youngest class 

 must contain a large number of trees, which is gradually 

 reduced to a comparatively small number in the oldest age 

 class. The actual proportion in these numbers depends on 

 the species and the quality of the locality. 



e. The Selection Forest. 



Here the age classes are intermixed, as in the case of the 

 overwood in coppice with standards, or even more so. The 



number of age classes will, theoretically, be equal to '! . 



t 



Let A = 1,000 acres ; r = 100 ; / = 20; then each annual 

 cutting area = - - = '- = 50 acres, and the distribution 

 would be as follows : 



