BRITISH FOREST TREES 173 



groups of about twenty to twenty-four feet in diameter, it 

 is difficult to protect the oak from being overtaken and 

 suppressed by the ruling species ; with groups of larger size 

 the advantages of mixed growth become fainter and less 

 substantial, in direct proportion to the increase of area. 



As, for the production of large remunerative assortments 

 of timber, it is advisable to give the oak a much longer 

 period of rotation than would be advisable for the beech, the 

 latter can be naturally reproduced between the eightieth to 

 ninetieth year, or by means of sowing or planting should seed- 

 production prove deficient, and the role of the latter is then 

 confined to underwood until the standard oaks are harvested 

 at any convenient time during their hundred and fiftieth to 

 two-hundredth year, whenever the state of the timber-market 

 renders their fall advisable. Under such circumstances this 

 second generation of beech is not usually of the best 

 normal development ; but the loss of increment on it is 

 replaced by the greater quantitative, qualitative, and 

 financial increment of which the oak standards reap the 

 advantage. On the better classes of soil, thirty to forty 

 oak stems per acre overshadow the whole area lightly by 

 the end of the second period of rotation of the beech ; 

 on poorer classes of soil, only such number of oaks should 

 be retained as standards as will ultimately overshadow not 

 more than -J or at most -J of the area, that is to say 

 about ten to twenty per acre. Care should be taken to 

 remove the beech gradually, as, when suddenly exposed to 

 light and air, the boles of the oak are apt to become covered 

 with a flush of shoots from dormant, adventitious buds, 

 which utilise the sap during its upward flow, with the con- 

 sequence that the trees become " stag-headed " and dead in 

 the top part of the crown. For this method of treatment 

 small clumps of good sound trees, in vigorous growth, with 

 well-formed crowns, and not over a hundred years of age, 



