9 
to do, while the ground would be kept moist and in a state 
favourable to the decomposition of vegetable matter. It 
is desirable therefore to frame regulations regarding such 
forests, deciding the minimum to be preserved of the 
number of trees per acre, due regard being ot course paid 
to age, species, altitude, and locality. For these reasons 
it is highly important that a// such forests, whether private 
property, commons, or belonging to the State, should be 
placed under the control of the State. 
The different trees have naturally a different effect as 
regards conservation of water and production of food and 
shelter for fish, as I will here briefly point out. To simplify 
matters we may divide all forest trees into two large groups, 
the deciduous and the evergreen trees. The deciduous 
trees, of which, as far as Great Britain is concerned, the oak, 
elm, beech, plane, larch, willow, and poplar are the most 
prominent, have a decided advantage over the evergreens. 
I need not here enlarge upon the fact that the full 
shady foliage during the summer is far more effective in 
preventing a large evaporation, and that the branches of 
the trees of this group are more spreading than those of the 
other. The energy of life seems to be far greater in these 
trees towards effecting our objects, and for direct border 
trees to a watercourse they are undoubtedly the best suited. 
The great amount of foliage and branchlets yearly thrown 
by these trees forms a very prominent factor in the economy 
of nature, and their decaying vegetation is full of teeming 
life and food for fish. 
That this group is eminently suited for water conserva- 
tion, was illustrated in a forest in Denmark, where an area 
of firs and pines was cultivated with beech and oak. After 
a lapse of about fifteen years a millstream, which during 
the time of the evergreen trees had dwindled down con- 
