SPRUCE AND BALSAM FIR TREES. 25 



tree he saw there is the same as Nuttall's Abies lasioearpa. 1 A cul- 

 tivated variety of alpine fir, Abies lasioearpa caerulescens, was de- 

 scribed in 1891 by a German dendrologist. This form is distin- 

 guished by the deep silvery-blue tint of its foliage, a characteristic 

 which is, however, largely lost as the leaves become fully mature, 

 and is not as marked in older trees as in young ones. 



DISTINGUISHING CHARACTERISTICS. 



The long, narrowly conical crown, terminating in a conspicuous 

 spearlike point (PI. XII, b), at once distinguishes this fir from all 

 associated species of its kind in the region, its sharp-pointed heads 

 being recognizable at a long distance. The height attained is ordin- 

 arily from 60 to 90 feet and the diameter is from 14 to 24 inches, but 

 in exposed high situations the stems may be under 4 feet in height, 

 with very long lower branches resting on the ground. Eare old trees 

 attain heights of from 100 to 130 or, very occasionally, 160 feet and a 

 diameter of 3 to 4 feet. Still larger trees are reported, but they are 

 exceedingly rare. The trunk bark is thin, at most about 1^ inches 

 thick, hard, flinty, and but little broken even on fairly large trees, 

 except occasional shallow, narrow cracks near the base of the trunk 

 (PL XIII). The unbroken smooth areas of bark are ashy gray — 

 often chalky-white. Even on old trunks, always irregularly and 

 shallowly seamed, the flat ridges of bark are whitish, but pale- 

 brownish in the seams, while the inside of the bark is red-brown. 



In open stands the narrow crowns of both young and old trees usu- 

 ally extend down to the ground. In very close stands the trunks of 

 old trees are occasionally free from branches for from 20 to 40 feet 

 or more (PI. XIII). The dense, characteristically tough branches at 

 the base of the crown droop, and later when they die they are often 

 sharply curved or bent down upon the trunk. 2 



The foliage is deep blue-green, that of each season's growth having 

 a silvery tinge. The twigs are usually covered with minute, rusty 

 hairs for 2 to 3 years, or sometimes they are smooth. The winter buds 

 are covered with resin. The flat leaves, pointless and longer on lower- 

 crown branches (PL X) , and keenly or somewhat pointed and shorter 

 on uppermost branches (PL XI), are distinctly massed and pointing 

 upward on the top side of the branches, those below and on the sides 

 of the branches being curved so as to joint those above. This dense 



1 Dr. George Engelmann (1. c.) described and named this fir "Abies sub-alpina " in 

 1876, a name which is now a synonym of the earlier published A. lasioearpa (Hook.) 

 Nuttall. 



2 The low branches make this fir particularly subject to crown fires, which invariably 

 kill large numbers of trees, while the thin bark of the trunk is also frequently injured or 

 killed by severe ground fires. 



