66 ELEMENTS OF SYLVICULTURE. 



elm, maple, birch, aspen, alder, and fruit trees are 

 more or less abundantly scattered about amidst a 

 crop of oak, hornbeam and beech. Although gene- 

 rally speaking, these species are of different degrees 

 of longevity, this is no obstacle against their main- 

 tenance in the forest ; on the contrary, there is an 

 advantage in retaining a certain proportion of them 

 on account of their special uses. However the 

 Ulmus diffusa must be excluded ; its wood is of very 

 inferior quality, and its presence can only be justified 

 where its extraction would leave a gap in the leaf- 

 canopy. 



BOTATION. Whenever these forests contain a suffi- 

 cient proportion of oak, the rotation must always be 

 chosen to suit this species, keeping in mind its re- 

 quirements and the uses to which it is put. 



BEGENERATION CUTTINGS. The rules laid down 

 for the trees mentioned in the preceding sections are 

 entirely applicable here. When the young oak is 

 sufficiently numerous and equally distributed over 

 the ground, the complement of the seed crop must 

 be made up with other kinds, always givingpreference 

 to those which are longest lived, notably the beech 

 and the hornbeam ; but it will suffice if there are a few 

 everywhere, the chief thing being to have the thicket 

 formed as early as possible. Of course the procedure 

 must be such that the final cutting may find a reserve 

 almost entirely composed of oak. 



IMPROVEMENT CUTTINGS. If the young crop con- 

 tains all these species of different peculiarities of 

 growth and degrees of longevity, it is very evident 

 that cleanings must begin early, in order to ensure 



