FINENESS OF GKATN. 



85 



wide and irregular zones, but as the tree gets old the annual 

 zones gradually become narrow and the wood resembles that 

 from a virgin forest. 



If, during the regeneration period, the tree serves as a 

 mother-tree, wider zones follow, as in Fig. 42. 



The Clear-cutting system, with artificial reproduction, 

 secures from the first full light to the plant, also exposure 

 to extremes of temperature and humidity. The wood is there- 



Fig, lu. Wood grown under the Shclterwood Compartment system, 

 just before a thinning. 



fore broad-zoned from the first ; zones of narrow summer- 

 wood vary with others in which the hard summer-wood is 

 broad, only in old age does the wood become uniform and 

 narrow-zoned. The clear-cutting system produces the 

 coarsest grained wood. 



If a tree is set free when old (in Fig. 4 '2 is a tree eighty 

 years old) in the clear-cutting system, under the influence 

 of the increased exposure to light and heat the annual /ones 



Fig. 11. Wood grown under the clear-rut tin 



system, 



become wider, but gradually narrow again. Such wood is also 

 coarse-grained (Fig. 42). 



The inferiority of wood produced in the open is readily 

 explained by the fact that a free position in young trees causes 

 a larger wood-increment than in trees naturally regenerated. 



It is indisputable that in old age it is not density of crop, but 

 the open crop of a selection or virgin forest that produces the 

 greatest volume of wood in a given time. Contrary to popular 

 opinion, selection or virgin forest is not dense but open and 



