8 THE OAK. 



have also been described, but it is admitted that the 

 forms vary much, and it is very generally conceded 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 produced 

 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 forest- 

 er's art is practiced 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, etc., of 

 known woods, but it is because it combines a good pro- 



