THE FORMATION OF PLANTATIONS. 279 
Aspect and exposure exercise a modifying influence also on tree 
growth. One would, on first thought, naturally conclude that, for 
trees of a delicate nature, or for those that are liable to be injured 
by spring or autumn frosts, a southern exposure would be most 
congenial. This is not, however, in accordance with facts, and it 
is allowed that, if soil and elevation be favourable, a northern 
exposure answers equally as well as, if not better than, a southern. 
Although in the former case the full benefit of the sun’s rays is 
not always obtained, yet it has compensating advantages not 
possessed by the latter. It is less influenced by the violence of 
south and east winds, which frequently prevail, and are so very 
destructive to vegetation during the growing season. The north 
winds most frequently occur during the period of rest, and seldom 
prove so injurious. Hence we find that even the broad-leaved 
timber trees, which require a higher degree of heat than conifers to 
bring them to maturity, grow as freely, and attain to as great 
height, in a northerly as in a southerly exposure. 
Our British climate is proverbially variable and uncertain. This 
is more noticeable in the spring months than at any other time 
during the year. From March to June it is no uncommon 
experience to have intense heat, mild showers, frost, hail, snow, 
cold and destructive winds, all following each other in rapid suc- 
cession, and very often within the space of twenty-four hours. 
These may be said to constitute our usual spring weather. Our 
native plants are by constitution adapted to these changes, but 
the successful cultivation of exotics, accustomed to a more equable 
climate, is often a precarious undertaking. In selecting trees of 
foreign origin for plantation purposes, preference should be given to 
those which most readily adapt themselves to the variableness of 
our climate, and they should if possible be placed in exposures, 
such as north and west, where they are least likely to be damaged 
in the early part of the growing season. 
With these remarks on soil and climate, we now proceed to con- 
sider more in detail the soils and situations best adapted for some 
of the more commonly cultivated of our forest trees. 
8. Common Forest TREES. 
The Oak (Quercus Robur). The soil most suitable for the oak 
is a strong clay loam resting on a clay subsoil. But though a soil 
of this description is required to bring it to its greatest dimensions, 
