182 OUR FORESTS AND WOODLANDS 
can be utilised. Many of the trees in the Scot- 
tish highlands are thus made use of, though 
little indeed is done to improve the growth of 
the trees or to make them yield a better class 
of wood suitable for furniture, turnery, cart- 
making, and the like. 
Birch is, on land of rather a wet than a 
dry nature, very frequently found growing along 
with the Aspen or Trembling Poplar (Populus 
tremula), ‘whereof our fletchers make their 
arrowes, as Holinshed tells us; and there is so 
much that is common to both of them, as trees of 
the woodlands, that they can most conveniently 
be treated of together. They are both essenti- 
ally light-demanding trees; in fact, they make 
greater demands on light than any other kinds 
of broad-leaved trees. Like all such trees, they 
have a deep root-system,—though the direct 
connection between deep roots and a very pro- 
nounced demand for light, as in oak, larch, 
and Scots pine, is not clear. By means of this 
they are enabled to obtain a good supply of 
water from deep down in the subsoil, even 
when the surface of the ground may appear 
dry. But birch and aspen possess, in the most 
