FORMATION OF MIXED WOODS. 187 



operations commence with the groups of the former, and 

 are brought to a close by a regeneration of the latter. 



Again, in a mixture of shade-bearers only, such as 

 Beech, Silver Fir and Spruce, the last mentioned is 

 likely to outgrow the Beech and also the Silver Fir ; 

 hence a sufficient number of groups of Beech and Silver 

 Fir are first established, and then the groups of the Spruce. 



In the case of selection forests the differences in age 

 are still greater, and much can be done on the lines 

 indicated above, to protect the threatened against the 

 threatening species. 



b. High Forest with Standards. 



If such woods are mixed, the threatened species are 

 selected for standards, if otherwise suitable for the pur- 

 pose ; it is essential that the rotation should not be very 

 high, otherwise the future standards may suffer before 

 the end of the first rotation has been reached. 



c. Two-storied High Forest. 



It has been explained in Volume I., page 220, that 

 when a high forest has run through part of the normal 

 rotation, a portion of the trees are removed, and a new 

 crop is introduced, which grows up between the trees 

 remaining of the first crop, the two being allowed to run 

 through an additional whole rotation. The difference 

 between the two crops ranges from 20 to 60 years. Here 

 then is an excellent opportunity of protecting a threatened 

 against a threatening species, the first crop consisting of 

 the former, and the second of the latter. In Europe the 



