SPRUCE AND BALSAM FIR TREES. 23 
varies from elevations near sea level to over 5,600 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 6 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 
