SPRUCE AND i.AI.SAA! FIB TREES. 23 



varies from elevations near sea level to over 5,000 feet. Only low, 

 almost prostrate forms occur, however, at high elevations. The 

 largest trees of this species occur in eastern Canada and in our North- 

 eastern States. In the Canadian Rocky Mountain region balsam fir 

 is a much smaller tree, often closely associated with white spruce, 

 while jack pine, tamarack, black spruce, balm of Gilead, aspen, and 

 paper and mountain birches occur more or less within the same 

 region and are often interspersed with it. Small groups and pure 

 stands of very limited extent occur frequently in deep, rich moist 

 soils of depressions, coves, along streams, and about lakes and ponds. 



During the first or 8 years of its life balsam fir is able to grow 

 thriftily in the dense shade of other trees, but during the remainder 

 of its life it requires nearly full top light for the best delevopment. 

 It is much more tolerant of shade in moist soil than in dry situa- 

 tions. Trees continue to live under deep shade for a very long 

 period, but with extremely slow growth. If overhead light is 

 admitted during the period of suppression, the trees recover quickly 

 and resume their normal rapid growth. 



Seed is borne abundantly at intervals of 2 and 3 years, and 

 sometimes of 4 years, while considerable seed is produced every 

 year. Trees growing in full enjoyment of the light bear much 

 heavier crops of cones than do those in close stands. Trees long 

 suppressed by shade do not produce seed, doubtless because of the 

 practically arrested growth of the " leader " and upper crown, the 

 only part of the tree that normally produces cones. Pole-size trees 

 (20 to 25 years old) bear a small number of cones, the amount of 

 seed produced increasing as the trees grow older. 



The seed has a low rate of germination (15 to 30 per cent) and 

 very transient vitality. Germination occurs plentifully in openings 

 and under the deep shade of the mother trees, where dense groups 

 and thickets of seedlings are frequent as a result of a copious fall 

 of seed. Seedlings are also often thinly scattered. The seed 

 germinates readily in moist exposed soil and humus, but most 

 abundantly on moss-covered decayed logs, in sphagnum, and among 

 other dense herbage, where the even supply of moisture affords the 

 most favorable conditions. Reproduction is always scanty in drier 

 situations. Branches of balsam fir layered in moist soil sometimes 

 strike root, occasionally producing new plants by this vegetative 

 method. 



LONGEVITY. 



Balsam fir is comparatively short-lived, the largest trees probably 

 not attaining a greater age than 150 years. Dominant trees in a 

 close or open stand grow much more rapidly in diameter than do 

 trees in a close even-aged stand. Diameter growth is still slower in 



