De I. VNER VEW D Forest Trees of the Pacific Slope

148 FOREST TREES OF THE PACIFIC SLOPE.
LIBOCEDRUS.
Trees of this group are characterized by their conical trunks. their thick
bark, and the very strong but pleasant odor of their light, soft, straightgrained,
durable wood. The small scale-like, pointed leaves (of adults) are
evergreen; those of each season's growth remain on the tree four or five years.
They overlap each other closely; much flattened on short side branchlets, but
rounded on the larger main stems. The branchlets are arranged in one plane,
forming a flat spray. Seedling leaves are scale-like, sharp-pointed, and spreading.
All of the leaves are characteristically arranged in pairs, each pair placed
on the branch at right angles to the preceding pair. The leaves are also distinguished
by their long bases, which extend down the branch. Male and female
flowers at the end of branchlets formed the preceding year are borne either on
different twigs of the same branch (native Libocedrus) or on different trees.
The small cones, which mature in one season and hang down from the branches,
are composed of 3 pairs of scales (practically of only 2)-one very short pair
and one, the largest pair, forming most of the cone's body and inclosing 1 or 2
winged seeds on each of its scales; the third pair is formed into a central flat,
thick, woody wall, upon each face of which the seed-bearing scales clasp. The
seeds are shed in early autumn, their light wings adapting them well for wide
dissemination. After shedding their seeds the cones remain on the trees at least
until the succeeding summer. All of the trees of this group are rather large,
important forest trees, and their durable woods are commercially valuable. They
are nearly all long-lived. One species only, confined to our Pacific region, inhabits
the United States. Two very important species grow in western South
America. The group is further interesting from the fact that in geologic times
species related to those now living existed in Greenland and portions of Europe.
Incense Cedar.
Libocedrus decurrens Torrey.
DISTINGUISHING CHARACTERISTICS.
The striking characteristics of old incense cedar trees are their rapidly
tapering trunks with widely buttressed bases and cinnamon-brown, deeply furrowed,
and ridged bark. The bark is from 2 to 3 or more inches thick at the
base of the trunks; higher up it is scarcely more than an inch thick. Young
trees have thin, smooth, slightly scaly, clear, reddish cinnamon colored bark.
Height, from 75 to 90 or sometimes 100 or 110 feet (very rarely more), and
from 30 to 50 inches in diameter; exceptionally large trees are from 5 to 6
feet in diameter. The crowns of large trees are very open and irregular, consisting
of a few scattered branches on the upper third of the stem, and
several large, leader-like top branches, all with dense tufts of light yellowgreen
foliage. Young trees, up to about 12 inches in diameter, carry a narrow,
open, columnar, pointed crown, reaching to the ground. At the bottom of the
crown the branches are slender and curve down and up at their ends; higher
up they gradually swing upward more and more toward the narrow pointed top.
Short, flat, drooping sprays of foliage terminate the branches. A notable feature
of the branches is that they shed numerous short side twigs, which die in
about their second year, as the main divisions of the branch enlarge. (This is
the case also with other cedars, particularly Thujas.) The scale-like leaves
(fig. 58) have been sufficiently defined under the characteristics of the genus,
as have also the cones (fig. 58). The flowers, male and female, are borne on the
ends of separate twigs of the same branch and open in midwinter. The cones