FOREST TREES OF THE PACIFIC SLOPE. 27 



to Bear Lake. In timbered portions of San Jacinto Mountains, generally at elevations 

 of 5,800 to 0,000 feet, sometimes descending to 5,000 and ascending to 9,800 feet; com- 

 mon on westside trail at 6,000 feet, and also on southwest side of Tahquitz-Strawberry 

 Divide. In Cuyamaca Mountains, at from -".500 feet, on east side Cuyamaca Peak, to 

 0,500 feet on summit. 



Lower California.— Frequent in forests of San Pedro Martir Plateau at elevations 

 from 8,000 to 10,000 feet. 



OCCURREN< i :. 



Chiefly on north slopes and benches and In ravines and canyons ; occasionally on low- 

 mountain summits; found also on south and west slopes at higher altitudes. Grows on 

 variety of soils from glacial drift and volcanic ash to deep, loose sands and clays; fresh, 

 rich, well-drained, sandy loam or gravelly soils are most characteristic. 



Never in pure stands. At lower elevations, mainly with western yellow pine, incense 

 cedar, Kellogg oak, and, in northern California, also with Douglas fir; occasionally with 

 tanbark oak. At high elevations yellow pine and incense cedar decrease, and white fir, 

 and occasionally red fir, together with the big tree, become chief associates, especially on 

 east and north slopes. 



Climatic Conditions. — Atmospheric moisture is essential ; hence it prefers cool, moist 

 sites on north and oast slopes and in heads of gulches and canyons. Doubtless on account 

 of this requirement its altitudinal range of 1,000 to 3,000 feet at the north increases, 

 going southward, roughly at the rale of about 500 feet to every 200 miles, until, at its 

 southern limit. 9,000 feet is reached. 



TOLERANCE. — In early youth requires partial shade, especially on dry. south slopes; 

 when older it becomes very intolerant, even more intolerant than western yellow pine. 

 Reproduction. — Not a regular or prolific seeder. A little seed is produced locally each 

 year, but good crops occur locally at intervals of about from four to six years; regularity 

 in seed years doubtful. Trees below 20 inches in diameter seldom bear seed to any extent. 

 Ordinarily trees shed seed over ground for a distance from base of tree about equal to 

 their height ; distribution occasionally farther through increased wind, slope, or water. 



Limber Pine. 



Pin ns flcrilis James. 



DISTINGUISHING < 1 1 AKACTERISTICS. 



Comparatively little known, doubtless on account of its high, inaccessible 

 range. It is a low. thick-trunked, much-branched tree, from 25 to .°>o or some- 

 times 50 feet in height, with short trunk from 12 to 30 inches in diameter ; 

 occasionally very old trees are 3£ to -i feet in diameter. Young trees are 

 peculiar for their regular, distant whorls of short, very tough branches which 

 stand at right angles to the trunk and extend down to the ground. .Middle-aged 

 and old trees (75 to 200 years) are characterized by extremely long and 

 slender branches, especially near the ground and at the top ; the latter are 

 often 16 or 18 feet in length, falling gracefully at a sharp angle with the trunk. 

 These branches appear to develop entirely at the expense of the trunk, which 

 remains stunted. Old trunks have hark from U to nearly 2 inches thick. 

 blackish or very dark brown, with dee]) furrows between wide rectangular 

 blocks. On trunks from 8 to ll^ inches thick the bark is broken into small, thin. 

 gray-brown plates; when separated, the scales expose a dull reddish inner bark. 

 The thin, smooth bark of young pole trees and of branches is a bright whitish 

 gray, often silvery. The foliage, densely set at the ends of the branches, is 

 dark yellow-green, and the needles are 5 in a cluster (fig. 5). They are from 

 about If to nearly .". inches long. Each year's growth of leaves persists for 

 approximately live years. Cones (fig. 6), mature in late summer or early 

 autumn of the second year, shed their seed in September and early in October. 

 They are from 3£ to 10 inches long and peculiar in having their light yellowish- 

 brown scale tips greatly thickened; inner portions, of scales, pale red. 



