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

106 FOREST TREES OF THE PACIFIC SLOPE.
slopes. Large part of precipitation and moisture from fogs never enters soil, but is
quickly evaporated, only temporarily reducing general evaporation and transpiration.
Summers long, hot, and dry; occasional thunderstorms, hailstorms, or cloudbursts on
higher mountains. Dew generally unknown. July to October, inclusive, is dry or
" danger " season, when there is great risk of forest fires, which are there very destructive
and hard to control unless they burn out or meet some barrier. Once destroyed, forest
cover is hard to replace.
ToLERANcz.-Intolerant of shade except in early seedling stage; throughout later life
requires full overhead light for best growth ; mature stands usually open, stems clear of
branches for one-third or more of length, but occasionally limbed to ground in cpen and
in chaparral. Seedlings come up and thrive in shade of live oaks and under seed trees,
in open, moist, sheltered places.
REPRODUcTioN.-Aloderately abundant seeder, but cones are produced at rather long
and infrequent intervals, though small amounts of seed are borne locally about every
year. Seed of low germination, owing to large number usually imperfect; vitality persistent.
Much seed eaten by rodents and birds. Reproduction generally very scanty, due
probably to poor seed, loss by animals, and destruction by repeated past fires. Mature
trees are protected by thick bark, but young growth is easily killed by fire. Reproduction
commonly in leaf litter under shade and in vicinity of seed trees and under live
oaks. Seedlings grow slowly at first, but, once well established, they increase rapidly
in height, requiring more light.
ABIES. FIRS.
The firs are evergreen trees wvith peculiarly conical, often very spire-like,
dense crowns of heavily foliaged branches, which by side branching form wide,
fiat sprays. The trunks are tall, very straight, evenly and gradually tapered to
one or two slender, straight leaders. Whorls of cilpuparatively small branches
grow from the trunks at regular distant intervals. Their sharply defined heads
of dense, often very dark foliage and arrow-like stems distinguish them among
all other trees. The trunk bark, before it is broken or furrowed by age, is
marked by many blister-like resin pockets, formed within and just beneath the
smooth surface. These are often atn inch or more long, and so numerous as to
be very conspicuous. This character, which no other native trees possess so
markedly, may have given them their popular name of " balsamns," because of
the liquid resin obtalined from the pockets for niedicinal purposes. The leaves.
spirally arranged on the branches, persist for from five to ten years (usually
niine), after which those of a seasoi's growth gradually disappear. Leaves on
the lower branches of our native firs are mostly flat (in one species triangular),
rounded, or blunt, not prickly at the end (in one species needle-poliuted); they
appear to grow more or less distinctly from two opposite sides, or from the top,
of the branch. Those of the extreme upper branches, particularly on the stout
leaders, are stouter, crowded and curved toward the upper side of the hori-
zontal twigs, and often keenly pointed or soinewhlat sharp-pointed. It is exceed-
ingly important to note the very dissimilar form, habit, and character of leaves
from the two parts of the crown. Leaves from the middle branches of the
crown are sometimes different in form from those of either the lower or upper
branches. In cross section the leaves of firs show 2 resin ducts near the lower
surface of the leaves and commonly close to the edges of the leaves, but in
some of our firs these ducts are in the interior of the leaf's tissue, about the
same distance from the upper as from the lower surface. Flowers of two sexes.
male and female, are borne on branchlets of the previous year's growth in dif-
ferent parts of the same tree. Female flowers, producing cones and seeds, are
short, spherical, rounded or elongated scaly bodies standing erect and singly
on branches of the uppermost part of the crown. Male flowvers, pollen-bearing
only, are elongated, cylindrical, scaly bodies hanging singly among the leaves
from the lower side of brandles below the female flowers. Time cones, whose
erect position is unique and distinctive of all firs, mature in one season. Dur-