THE NATURAL REGENERATION OF WOODS. 09 
also to that which is due to the laterally situated trees. Where a 
group is surrounded on all sides by a dense wood of tall trees, 
most light will be let in with the least amount of felling by 
attacking the old trees on the south and west sides rather than by 
felling on the north and east sides. 
Regeneration of a wood under this system usually takes from 
thirty to fifty years to accomplish, and the result is an uneven-aged 
wood, with the various age classes distributed throughout in groups 
of all conceivable shapes and sizes. 
Provided the management be firstclass, this system has much to 
commend it. It recognises and provides for temporal and local 
variations, and admits of parts of a wood being taken in hand at a 
time when they most require regeneration, and when the operation 
would be most likely to succeed. It preserves soil fertility from 
loss better than the two systems already considered, for the surface 
of the ground occupied by the groups is protected from the sun 
by the overhead foliage, and from the entrance of drying winds 
by the intact wood which surrounds them, or by the young 
groups which have previously been established. It is most in 
vogue in mixed woods of shade-bearing trees, especially where, 
owing to greater exposure of certain parts, soil fertility is 
being reduced, or where, owing to any cause, closeness has been 
partially interrupted and advance growth groups have established 
themselves. 
A modification of the last system is made use of in some coun- 
tries, and differs from the one we have just noticed, in so far as it 
does not deal with groups of young trees so much as with isolated 
examples. These are tended in exactly the same way as the groups 
in the former case, but here the regeneration is extended over the 
whole length of the rotation, so that all seed years are utilised, and 
one finds represented in the wood trees of all ages, from the one- 
year-old seedling up to those which are perfectly mature. 
This system ensures a constant covering for the ground, and is 
therefore most adapted for districts where violent. gales are very 
frequent, as well as for steep declivities, where the action of snow 
or water would be apt to rush away soil or rocks were the wood clear- 
felled even in part. , 
It is the system which most effectually preserves soil-fertility, for 
as the ground is constantly shaded, no opportunity for loss is ever 
presented. It can only be practised in the case of the most decidedly 
shade-bearing trees, such as the silver fir and beech, though in wood- 
