SPRUCE AND BALSAM FIR TREES. 17 
mination and persistent vitality. Keproduction, however, is gen- 
erally scanty and confined mostly to exposed mineral soil in the 
immediate vicinity of seeding trees. Scanty reproduction elsewhere 
near mother trees probably is due to the fact that the light seed is 
prevented from coming in contact with mineral soil by the dense 
herbage and other ground cover abundant in the habitat of this 
spruce. Only seldom is abundant reproduction seen where a seed 
crop chances to fall on earth slides or on moist soil otherwise exposed. 
LONGEVITY. 
The blue spruce is apparently a very long-lived tree, some of the 
largest trees probably being not less than 400, and possibly 600 or 
more years old. Diameter growth is often extremely slow, trees 4 to 
5 inches in thickness having attained an age of from 125 to 135 years, 
while trees 18 to 22 inches in diameter are from 275 to 350 years old. 
GENERIC CHARACTERISTICS OF BALSAM FIRS. 1 
The true balsam firs are evergreen trees with conical, often sharp 
spirelike, dense crowns of heavily foliaged branches, which by side 
branching form wide, flat sprays. They are medium to very large 
size trees with very straight trunks, which gradually taper to one 
or two slender leaders. Whorls or circles of rather short small 
branches grow from the trunks at regular, distant intervals. The 
cone-shaped or arrowlike heads and straight stems of these trees 
usually distinguish them at a distance from all other associated 
conifers. Before the trunk bark is broken or furrowed by age, it is 
marked by many horizontally elongated, blisterlike resin pockets, 
which are formed just beneath the smooth surface. These resin 
pockets are often an inch or more long, and so numerous as to be 
very conspicuous. No other native trees have this characteristic so 
plainly marked. 2 It seems probable that trees of this group were 
given the popular names " balsam " and " balsam fir " because of the 
liquid resin which is obtained from the pockets of some species for 
medicinal and mechanical purposes. 3 The winter buds of our native 
1 The class and family relationship of the firs to other cone bearers is fully discussed 
by the writer in Bulletin 207, U. S. Department of Agriculture, " The Cypress and Juniper 
Trees of the Rocky Mountain Region," 1915. 
2 Small resin blisters are sometimes formed in the smooth bark, especially of the upper 
stems, of young Douglas fir (Pseudotsuga taxifolia) and Engelmann spruce. They are, 
however, rarely, if ever, as large or as numerous on these trees as the " blisters " formed 
in the bark of true balsam firs (Abies). The author is indebted to Prof. E. E. Carter for 
calling attention to the occurrence of resin blisters in the bark of Engelmann spruce he 
observed growing in Colorado. 
3 In this country the crude resin, commonly called " Canada balsam," is obtained 
entirely from one species of fir (Abies balsamea), and chiefly, if not wholly, in the eastern 
Provinces of Canada and adjacent sections of northeastern United States. A similar 
product, commercially known as " Strasburg turpentine," is collected from the European 
silver fir (Abies pectinata), and also from the Siberian fir (Abies pichta). The "blis- 
ters " of all other firs yield liquid resin of the same general character, differing, however, 
in the color and odor, due to differences in chemical composition. 
