THE GROT'P SYSTEM. 239 



Those wlio advocate the system sa}- that, ordinarily, the 

 breadth should not exceed the height of the trees. There 

 is no limit to the length of the strips. 



The operation should generally commence on that side of 

 the wood which is opposite to the prevailing wind direction : 

 this rule may be overridden by other considerations, for 

 instance an unfavourable distril)utibn of the age classes. 

 In some cases the wood may, if necessary, be attacked in 

 two or more places at the same time. 



For the rest, little or no difference exists between this and the 

 compartment system, except that the area under regeneration 

 is less concentrated in the former. 



3. The Group System of Xatiiml Regeneration under 

 SJielter-woods. 



If a forest is naturally regenerated under the compartment 

 system it may happen that, after the seed cutting, the area is 

 not, or only partially, stocked with a new crop. A second 

 seed year must then be awaited, and in the meantime, the 

 cover having been thinned, the soil may suffer considerably 

 under the additional admission of light, so that it may not 

 present a fit germinating bed when the second seed year 

 arrives. Extensive working of the soil or artificial forma- 

 tion has then to step in. With the view of reducing this 

 drawback to a minimum, foresters hit upon the idea of taking 

 in hand in the first place only certain limited groups, scattered 

 over the compartment ; when these have been successfully 

 regenerated, they proceed with a second set of groups, and so 

 on, until the whole compartment has passed through the 

 process of regeneration. In practice, the system has been 

 further modified : certain groups, as before, are taken first 

 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 (Figs. 77 and 78). The time 

 required for the completion of the process in each wood, or 



