130 FOEESTS, WOODS, AND TEEES 



On Deeside, according to Mr. Crozier, " the common 

 silver fir, formerly one of the most reliable trees, is now 

 hopelessly unreliable as a timber crop owing to its 

 susceptibility to Chermes. Old trees are immune ; but the 

 difficulty of raising young stock is likely to lead to its 

 extinction altogether as an economic species." This 

 difficulty exists elsewhere, but can be overcome. Young 

 plants should be raised under shade in nurseries situated in 

 woodlands, and when planted out ought to be always 

 mixed with beech. In Wicklow natural seedlings of silver 

 fir keep free from Chermes, while planted seedlings close 

 by are liable to attack. The attack occurs not long after 

 they are planted out, the period when their growth and 

 vigour are checked by the act of transplantation. 



Abies grandis. — This is the fastest in growth of all the 

 silver firs ; and isolated trees in different parts of the 

 British Isles often equal and sometimes excel the Douglas 

 fir in vigour. Associated with this vigour is good health, 

 as, unlike the common silver fir, it is not attacked by 

 Chermes, and is not liable to injury from frost in the young 

 stage. An acre of this tree in Sussex, which was planted 

 in 1900, had attained in 1917 an average height of 35 

 feet and a girth of 21 inches. The seedlings are easily 

 reared, grow much faster than those of the common silver 

 fir, and may be put out when three years old after being 

 transplanted once. Abies grandis may be tried as a main- 

 crop tree in localities where the common silver fir is 

 difficult to establish on account of Chermes and late frosts. 

 It is not known whether it will resist wind as well as the 

 common silver fir, and it does not bear so much shade as 

 the latter. 



The timber in western North America is little known 

 commercially ; but is probably better than any of the 

 other American silver firs except Ahies nolilis. It is 

 white and soft, yet firm enough to be useful. 



Abies nobilis. — This species is a mountain tree in western 

 North America, and differs from Abies grandis in its 



