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. 



Tolerance. — 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 open and 

 in chaparral. Seedlings come up and thrive in shade of live oaks and under seed trees, 

 in open, moist, sheltered places. 



Reproduction. — Moderately 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 per- 

 sistent; 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. Reproduc- 

 tion 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 with peculiarly conical, often very spire-like, 

 dense crowns of heavily foliaged branches, which by side branching form wide, 

 flat sprays. The trunks are tall, very straight, evenly and gradually tapered to 

 one or two slender, straight leaders. Whorls of comparatively 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 an 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 " balsams," because of 

 the liquid resin obtained from the pockets for medicinal purposes. The leaves, 

 spirally arranged on the branches, persist for from five to ten years (usually 

 nine), after which those of a season'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-pointed) ; 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 somewhat 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 flowers, pollen-bearing 

 only, are elongated, cylindrical, scaly bodies hanging singly among the leaves 

 from the lower side of branches below the female flowers. The cones, whose 

 erect position is unique and distinctive of all firs, mature in one season. Dur- 



