60 BRITISH FOREST TREES 



species of forest tree grown in high forest is subject to more 

 different treatment as to its economic maturity as the Scots 

 pine, the periods of rotation varying from sixty to one 

 hundred years and more. Under average conditions as to 

 soil, an eighty years' rotation frequently obtains, but where the 

 larger dimensions of timber command high prices, higher 

 rotations are fixed if the soil is not exposed to deteriorating 

 influences. Good timber for ordinary building purposes is 

 often produced by forests of seventy years of age. On 

 poorer soils a rotation of fifty to sixty years is frequently more 

 remunerative than one fixed at a later age, as increase in con- 

 tents and value of the timber on such localities is very slow. 

 From about the fortieth to fiftieth year, and on indifferent 

 soils much earlier, good seed years are frequent, six being 

 expected in every ten years, and in addition there is generally 

 some production of seed in the intervening years. The cones 

 ripen in the second October after flowering, and in the suc- 

 ceeding spring the approach of warm weather causes them 

 to open so that the seed may be wafted away by the wind. 

 The germinative power of the seed is good, experimental 

 tests generally yielding sixty to seventy per cent., although 

 of course somewhat less favourable results must be expected 

 when sowing is carried out in the open. The cones usually 

 contain from forty to forty-five seeds, and one pound of seed 

 without wings represents about 75,000 seeds, 2 which retain 

 their germinative power for between two to three years. 



1 Burckhardt, Saen und Pflanzen, 1880, p. 418, gives the following 

 comparative table for the relative number of seeds contained per unit of 

 volume : 



Scots pine 100 



Spruce 95 



Larch 93 



Austrian pine 56 



Weymouth pine 28 



Maritime pine . 15 



Silver fir . 10 



