32 A PRTMEK OF FORESTRY. 



twenty years before. The yield of the whole forest in 

 spruce for a single year may be cut each year from 

 one-twentieth of the whole area. If all the divisions 

 were cut over live times in the life of a mature tree, 

 then one-fifth of the standino- timber would be taken 



Fig. 19.— Group of spruce under beech. Germany. 



from each division at each cutting. Thus, if it took 

 one hundred years for a tree to become ripe for the ax, 

 the cutting (at intervals of twenty years) would return 

 five times during the life of the tree, at its twentieth, 

 fortieth, sixtieth, eio-htieth. and one hundredth vears. 



