METHODS OF TREATMENT 89 



tered over the area. These can be removed three to five 

 years after the young crop has been planted, and can be easily 

 carried away by men, or can be left on the ground if they are 

 not saleable. 



The method is, however, chiefly used when the new crop is 

 to be formed by natural regeneration. In this case a number 

 of annual cutting areas should be dealt with together, as it is 

 impossible to work with the same regularity as when the crop 

 is planted, owing to the irregularity of seed years. If, for 

 instance, it is found that ten years is the usual period for com- 

 pleting the regeneration from start to finish, ten times the 

 average cutting area should be dealt with at one and the same 

 time ; when this has been successfully regenerated, another 

 block is taken in hand. 



With natural regeneration an equal annual outturn can 

 seldom be obtained, but this inconvenience is, to a certain 

 extent, counterbalanced by the low cost of the new crop. 



By natural regeneration we mean the production of a new 

 crop by seed thrown from trees already on the ground. As 

 the new crop becomes established the existing trees are 

 gradually removed, so that the old wood, in the course of 

 a few years, is cut down and replaced by a new one. It is by 

 natural regeneration that a wood untouched by man gets re- 

 produced ; when a tree dies, from old age or other cause, an 

 opening is formed in the cover and seed falling from surround- 

 ing trees germinates and springs up. In nature this process 

 is a slow one, but in sylviculture it is hastened by the removal 

 of mature trees and by aiding the young crop. 



British foresters mainly rely on planting, but there is no 

 reason why under favourable conditions, where rabbits are 

 kept down and where weeds are not luxurious, natural re- 

 generation should not often be carried out for the reproduction 

 of beech, oak, ash, birch, sycamore, and Scotch pine. 



Natural regeneration is usually cheaper than planting, and 

 under. very favourable conditions the cost may be practically 



