THE GROUP SYSTEM. 



24.1 



a. Selection of Groups. 



The time when the different parts of the wood are attacked 

 depends chiefly on the following considerations : — 



i. Advance Growth. 

 In almost every mature wood groups of young growth are 

 found, which have sprung up, here and there, before the 



Fig. 78. — Elevation of a section along a 6 of Fig. 77, in four 

 successive stages. 



regeneration cuttings have been commenced ; such young 

 growth is called "advance growth." Under the uniform 

 s. H 



