4O NOTES ON FORESTRY. 



spread of valuable timbers, care must be taken to 

 perform the operation with an eye to that gradual 

 admission of light indicated in the chapters on 

 sowing. 



If we could unravel the history of any pure 

 forest of gregarious trees, we should probably find 

 that in some remote past it was a mixed forest, in 

 which many varieties struggled together for pos- 

 session of the soil, and that it became a pure 

 unmixed forest in consequence of the now domi- 

 nant variety having been endowed with special 

 qualities, such as greater rapidity of first 

 growth, greater height, greater longevity, greater 

 strength to resist snow -brook, a form which 

 did not admit of any weight of snow resting 

 on its branches, or some one quality or com- 

 bination of qualities which, specially adapting it 

 to local conditions, resulted in its final triumph 

 and the extinction of all less favoured varieties. 



This same struggle is still going on in all mixed 

 forests, and by cutting out only the more valued 

 varieties, we assist the less valued in the struggle ; 

 but, recognising Nature's mode of operations, we 

 should always study to foster the spread of those 

 species and varieties most in demand. 



