44 FOREST REGIONS AND IMPORTANT SPECIES 



until they have been thoroughly tested over a rotation under similar 

 conditions. 



(3) When employed there must be a definite justification for not using 

 local trees — 



(a) Quahty of wood (not contained in local species) required by na- 

 tional wood industries. 



(6) Rapid growth or hardiness under adverse soil or climatic conditions. 



France is poor in tree species (see p. 40) and particularly needs cabinet 

 woods and woods easy to work, like yellow poplar. She requires trees 

 hardy on unfavorable sites, but nevertheless, because of the high cost of 

 foreign tree seeds the use of exotics, even though of proven worth, is 

 rarely practicable. There are, of course, exceptions to this fundamental 

 rule — notably Scotch pine, whose range has been increased largely by 

 artificial means. Too often the forester may be tempted to use an exotic 

 which has been grown successfully in botanical gardens. This is poor 

 practice and should not be followed. Beware of exotics, because they 

 rarely succeed and are subject to insect and fungous damage! 



