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. 
