THE CULTIVATION OF THE OAK 151 



forester also has to aim at getting as much timber as 

 possible on the ground in a given time, and in the case 

 of a tree like the oak his calculations have to be well 

 made beforehand, for the tree may have to stand for 

 from 120 to 200 years before it is cut. Left alone it 

 may live for 1,000 years, but the proportion of good 

 timber in trees after a certain age rapidly diminishes 

 a fact that has also to be reckoned with. 



It is quite different, however, when trees are re- 

 quired for seed purposes. The oak hardly bears fruit 

 at all before it is fifty to sixty years old, and seventy to 

 eighty years is a better age for the purpose ; but, as 

 with other trees, to produce really good seed the oaks 

 must be isolated, or nearly so, so that they get the maxi- 

 mum of light and air. Consequently a modification of 

 procedure has to be made when seed-trees are required. 



When the fruiting period has once been reached 

 the tree goes on producing acorns every year ; but it is 

 noticed that heavy crops of good seeds only recur every 

 five (or perhaps three) years or so, the yield in the 

 intervals being inconsiderable. This is in accordance 

 with Hartig's discovery that in the beech, for instance, 

 the tree goes on storing up nitrogenous materials and 

 salts of phosphorus and potassium during the first 

 seventy or eighty years of its life, and then suddenly 

 yields these stores to the seeds ; the drain is so exhaust- 

 ing that it requires three to five years to re-store suffi- 

 cient of these substances for another ' seed-year.' The 

 season or weather is also concerned in the matter. 



