398 THE SILVEll FIR. 



foresters. The only insect which injures the Spruce Fir 

 is a kind of aphis, which in the autumn lays its eggs on 

 the under side of the buds on the side branches. When 

 these begin to burst in spring, the young leaves grow 

 together into a solid mass, composed of a nurabei- of 

 cells. Each of these contains an embryo insect, and 

 towards the end of summer opens and suffers the perfect 

 insect to escape. These galls somewhat resemble imperfect 

 cones, bearing a shoot at the summit : the part of the 

 shoot beyond the gall is often distorted in consequence, 

 and sometimes entirely killeJ. Young trees are the 

 principal sufferers from these attacks. The Laplanders, 

 it is said, eat these galls. 



THE SILVER FIR. 



PiCE.V PECTINATA. 



The Silver Fir approaches in character nearer to the Nor- 

 way Spruce than to any other of the trees yet described. 

 It may, however, be easily distinguished by the following 

 marks : The leaves, especially in young trees, are placed 

 singly, but, instead of being inserted on all sides of the 

 stems, are arranged in two opposite rows ; and thus the 

 surface of the twig is flat instead of convex : the midrib is 

 visible on the under side only, the upper side having a 

 farrow down its centre. On each side of the midrib 

 beneath is a white silvery line, from which the tree derives 

 its name ; and as the point of the leaf is always turned 

 up, these lines make a conspicuous appearance. The cones 

 are large and cylindrical, and each scale terminates in 

 a deflexed point. Their position, also, which is erect, 

 affords an infallible mark of distinction, the cones of the 

 Spruce Fir being pendent. When young they are green, 

 but as they advance towards maturity they acquire a rich 



