186 A MANUAL OF FOKESTRY. 



another and disappear. Such unremitting attention can- 

 not always be given, apart from the expense which it 

 involves. Endeavours have, therefore, been made to 

 devise a method of mixing species which is less depen- 

 dent on constant attention, and this has been found in 

 giving to the mixed species a greater difference of age. 

 Such an arrangement causes a considerable difference in 

 the ages of the component parts of the wood. Each of 

 these requires to be regenerated at its own time, so that 

 the process of regeneration is gone through several times 

 in the course of one rotation, one part of the wood being 

 regenerated on each occasion. 



Many varieties of mixed woods of uneven age have 

 been evolved, each of which corresponds, more or less, 

 with a distinct sylvicultural system. Of these the fol- 

 lowing claim attention : 



(a.) The group and selection systems. 

 (b.) High forest with standards. 

 (c.) Two-storied high forest. 

 (d.) Mixed coppice with standards. 



a. The Group and Selection Systems. 



Under the group system the regeneration of a wood 

 extends over a period ranging up to 40 and even 

 50 years. By first taking in hand the groups consisting 

 of the threatened species, they can be given a start of 

 30 to 40 years. After these have been regenerated, the 

 groups consisting of the threatening species are taken 

 in hand. Taking, for instance, a mixture of light- 

 demanding and shade-bearing species, such as Oak, 

 Larch, or Scotch Pino, with Beech, Silver Fir or Spruce, 



