NATURAL REGENERATION. 



153 



in hand, and when these have been regenerated, they 

 are gradually enlarged by regenerating successive 

 narrow bands around them, and this process is continued 

 until the several groups merge into each other (Fig. 71). 

 The time required for the completion of the process in 



Fig. 70. 



a, a, a, a. Groups regenerated first. 

 b, b, b, b. ,, second. 



c, c, c, c. Groups regenerated third. 

 d, d, d, d. ,, ,, fourth. 



each wood, or compartment, is considerably longer than 

 under the compartment system, and it extends generally 

 over a period of 20 to 50 years, according to species and 

 local conditions. 



A wood, while being regenerated under this system, 

 presents a varying picture ; some parts of it have been 

 completely regenerated, others are more or less advanced 

 in the process, and others again are as yet untouched, 



