2 BULLETIN 327, U. S. DEPARTMENT OF AGRICULTURE. 
The class and family relationship of the spruces and balsam firs 
to other cone-bearing trees of the Kocky Mountain region is fully 
explained in the above-mentioned publication, to which the reader 
is referred for this general information. 
Keys are provided on pp. 42 and 43 for the identification of genera 
and species. 
GENERIC CHARACTERISTICS OF SPRUCES. 1 
The spruces are evergreen trees with sharp-pointed, pyramid- 
shaped crowns and conspicuously straight, tapering trunks. The 
branches grow from the trunks in regularly distant circles or whorls. 
Their stiff, acute, often very keenly pointed, single leaves have a 
characteristic spiral arrangement on the twigs and branches which 
they clothe on all sides. The leaves of each season's growth adhere 
to the branches for from about 7 to 10 years. When the leaves die 
and fall from the branches they leave a basal portion which gives 
the branches a rough appearance. 2 All but two of the North Ameri- 
can spruces have more or less distinctly 4- angled leaves, all sides 
of which are provided with minute stomata or pores. Leaves of 
the other two species are flat, being very indistinctly 4-angled, or 
flat triangular in cross section, and with minute pores only on the 
upper surface. In cross section the leaves of spruces usually show 
one or two resin ducts situated very near the lower surface ; in some 
cases the leaves have no resin ducts. The winter b.uds of the spruces 
are made up of overlapping scales and, unlike those of the fir trees, 
have no resinous covering. 
Male and female flowers of spruces are borne on the same tree 
and on twigs of the previous year's growth. The male or pollen- 
bearing flowers are upright or drooping, yellow, bright purple, 
or rose-red, long or short, cylindrical bodies, about three-fourths 
inch to 1 inch by one-fourth to one-half inch. The female flowers, 
which produce cones and seed, are erect, yellowish-green or bright 
1 Considerable confusion still exists, especially among nurserymen, regarding the trees 
that are properly included in the genus Picea, which in 1830 the German botanist Link 
technically adopted as a generic name for the true spruces as we now know them. It 
seems probable, but this can not be established, that Pliny first used Picea as a classical 
name for a fir and Abies for a spruce tree. Later writers used Picea for the spruces and 
Abies for the firs, while in 1719 Tournefort consigned the firs, spruces, and our hemlock 
to the genus Abies. In 1754 Linnaeus went still farther by combining under Pinus the 
firs, spruces, hemlock, and larch. This gave rise to such peculiarly anomalous technical 
names as " Pinus abies " for the Norway spruce, " Pinus picea " for the European silver 
fir, and " Pinus larix " for the European larch. As late even as 1836 Endlicher main- 
tained Link's use of Picea for the spruces, but made it a subgenus of Pinus. From 1837 
to 1858, however, such eminent authors as D. Don, Loudon, and Gordon used Abies for the 
spruces and Picea for the balsam firs. Notwithstanding the fact that properly all Euro- 
pean and American botanists maintain Picea as the only legitimate generic name for the 
spruces and Abies for the firs, many European and American nurserymen and horticul- 
turists continue to use Picea for the firs and Abies for the spruces, some even including 
the hemlocks (Tsuga) in the latter genus. 
2 See p. 18 for statement regarding the characteristic leaf-scars of firs. 
