SPRUCE AND BALSAM FIR TREES. 19 
The male and female flowers of the firs are produced on different 
branches of the same tree. Each sort is borne on branchlets of the 
previous year's growth, the male flowers on the lower-crown branches 
and the female flowers on the topmost branches of the same tree. 
Male flowers, which bear pollen, are elongated, cylindrical, scaly 
bodies hanging singly among the leaves from the lower side of 
branches. The female flowers, which produce cones and seeds, are 
short, spherical, rounded or elongated, scaly bodies standing erect 
and singly on branches of the uppermost part of the crown. The 
cones, whose erect or nearly erect position is unique and distinctive 
of all firs, mature in one season. (Pis. IX, XI, and XII, h.) 
During autumn their thin, closely packed, overlapping scales grad- 
ually become loosened from the central spikelike axis (PI. IX, c, 
and PL XXIII) and fall away with their winged seeds, two of 
which are borne under each scale (PL XIV, 6, and PL XVII, 
b) ; no fertile or perfect seeds are borne under scales at the two 
ends of the cones. The spikelike woody axes of the cones remain 
attached to their branches for several years. (Pis. IX, <?, and PL 
XII, h.) Morphologically these woody axes are modified twigs. The 
breaking up of mature cones on the trees is characteristic of no other 
group of our cone bearers, except the deciduous-leafed Taxodium 
("cypress") of south Atlantic forests. As the ripe cones of firs 
break up strong winds may blow the seeds several hundred feet 
from the parent trees, but as a rule the seeds fall near the mother 
tree or are wafted not more than 50 or 100 feet away. The seeds 
have peculiar resin cells, which may be seen by cutting into the seed 
coat. Under ordinary conditions the vitality of fir seeds rarely, if 
ever, endures longer than a single season, and as a rule the per- 
centage of germination is comparatively low (50 per cent or less). 
Seed-leaves (cotyledons, the first foliar organs to appear when the 
seed germinates) range from 4 to 10 in number and are flat. (PL 
XXIII, c.) 
Fir trees are of great commercial importance on account of the 
excellent saw timber the larger species produce, while some of them 
are important also because they form protection forests on steep 
slopes at high elevations where few other conifers can live. They are 
moderately long-lived trees, their age limit ranging from about 200 
to 350 years; much is yet to be learned, however, concerning their 
longevity. 
Eleven species of firs inhabit the United States. Six of them occur 
within the Rocky Mountain region (of the United States and Can- 
ada) , while four are common to both the Rocky Mountain and Pacific 
slope regions. One species ranges from the Canadian Rocky Moun- 
tain region eastward to the Atlantic coast, where it is common both in 
our northeastern States and in adjacent parts of Canada. One of 
