MANAGEMENT OF SCOTS FIR FORESTS IN NORTH GERMANY. 199 
greater importance than where the trees are deriving a plentiful 
supply of mineral matter from the soil, because in the former case 
a larger proportion of water must be taken up in order to get an 
equivalent quantity of inorganic constituents, and consequently the 
former element must be again evaporated from the leaves. This 
necessitates a larger leaf surface and a freer circulation of air, which 
the crowded condition is not calculated to provide, and in conse- 
quence the vigour of the trees gradually declines, and their chances 
of development are small. This is more easily seen when the 
stocking of such ground is considered, and the large number of 
undersized trees which are present examined. It is then seen that 
the struggle for supremacy has not resulted in the survival of the 
fittest, but in the gradual weakening of the whole; and instead 
of the stronger trees making room for themselves by smothering 
their smaller neighbours, they have only been injured in the 
attempt. Schwappach gives 1600 trees per hectare as the average 
for soils of the fifth quality at the age of eighty years, which is 
equivalent to 647 per acre. The average diameter of these 647 is 
only 5} inches, and the height 35 feet, so that timber dimensions 
are not reached, and quality need not be considered, as in the case 
of the better qualities. Without actual proofs one cannot say 
whether such trees would have reached a much greater size had 
they been duly thinned or not, but there is every reason to suppose 
that want of space has had as much to do with their small size as 
inferiority of soil. Thinning is a subject upon which no two men 
can be found to agree in every detail, and in spite of all experiments, 
no hard and fast rules can be laid down for its guidance, so that it 
is possible for errors to be committed under the most careful and 
scientific management, although the general results may be good. 
