8 THE OAK 
sharacters have also been described, but it is admitted 
that the forms vary much, and it is very generally con- 
ceded that these two geographical race-forms may be 
united with even less marked varieties into the one 
species Quercus Robur. 
The amount of timber produced by a sound old oak 
is very large, although the annual increment is so re- 
markably small. This increment goes on increasing 
slightly during the first hundred years or so, and 
then falls off; but considerable modifications in both 
the habit of the tree and in the amount of timber pro- 
duced annually, result from different conditions. Trees 
grown in closely-planted preserves, for instance, shoot 
up to great heights, and develop tall, straight trunks 
with few or no branches, and considerable skill in the 
forester’s art is practised in removing the proper number 
of trees at the proper time, to let in the light and air 
necessary to cause the maximum production of straight 
timber. 
Oaks growing in the open air are much shorter, 
more branched and spreading, and form the peculiar 
dense, twisted timber once so valuable for ship-building 
purposes. Such exposed trees, other things being equal, 
develop fruit and fertile seeds thirty or forty years sooner 
than those growing in closed plantations. 
The timber itself is remarkable for combining so 
many valuable properties. It is not that oak timber is 
the heaviest, the toughest, the most beautiful, &c., of 
known woods, but it is because it combines a good 
