THE THEORY AND PRACTICE OF WORKING PLANS 



19 



normal age classes being equal-sized and placed next to the 

 unequal blocks showing the actual size of the various age 

 classes. 



It is always of advantage to compare the real and the normal 

 age-class distribution; for it is a criterion of a sustained yield 



Diagram D 



and, in conjunction with the increment, determines the degree 

 of approach toward a normal forest. 



Note. — For a consideration of the value of the growing stock of a normal 

 forest, see Roth: " Forest Valuation," Ann Arbor, Mich., 1916, pp. 65-70. See 

 also, by the same author, " Normal Forest and Actual Forest, Normal Growing 

 Stock and Actual Growing Stock, Normal Stand and Actual Stand," Forestry- 

 Quarterly, Vol. XIII, No. 2, pp. 154-162. 



