FOREST TREES OF THE PACIFIC SLOPE. 253 



San Joaquin River Valley, on foothills of southern Sierras, and on southern coast ranges, 

 up to 3,000 and 5,000 feet elevation. Locally noted as common on South Fork of Kern 

 River from below Canebrake ('reek to Isabella; on Kern River to Kernvllle, at a point 

 8 miles below Isabella and at Bakersfleld. East side of Sierras, only on Cottonwood 

 Creek (west side of Owens Lake), and on Cottonwood Canyon in Panaminl Mountains. 

 Probably elsewhere also on southern east side slope of Sierras and on ranges east of 

 them. Coasl ranges of southern California: Santa Lucia and San Luis Obispo mountains ; 

 abundant generally on streams at 200 to 2,600 feet elevation, including Sur, ('armelo, 

 Arroyo Seco, San Antonio. Nacimiento, ('arriso. Salinas, and Santa Margarita rivers. 

 Elsewhere, scattered throughout southern California on streams, on edges of deserts, and 

 on lowlands between the mountains and sea. Santa Barbara National Forest: All 

 watersheds, at 900 to 5,280 feet, Including Santa Maria. Santa Ynez, Santa Barbara, 

 Matilija, Piru-Sespe, Newhall, and Elizabeth fixers. In all canyons of Tehachapl Moun- 

 tains, Including Canada de las Uvas and Tejon Canyon. Hare in vicinity of Los Angeles, 

 occurring at Fernando. Not detected in Santa Ana Ramje. Lccally noted as follows: 

 San Gabriel National Forest, in Tujungn Canyon (2 miles from mouth i . at 1,600 feet; 

 Mohave desert, at Victor on Mohave River ; San Bernardino Mountains in San Ber- 

 nardino Valley, Santa Ana Canyon and Rear, Keller, and Mill creeks. Common in San 

 Die-,, County south of San Luis Rey River, extending westward nearly to sea and 

 eastward into desert to tree limit; noted at Jamul Creek, 15 miles from sea, near 

 Mexican boundary ; Mountain Spring, east side of Coast Range and just north of 

 Mexican boundary, at 2,500 feet: Salton River (Colorado Desert i . 



The detailed range of Fremont cottonwood outside of tin- Pacific region will 

 be dealt with in a future publication. 



OCCUBBENCE. 



Confined to alluvial stream bottoms and their borders, in moist sandy and humous 

 soils, or in moist gravelly ones. Very dependent upon soil moisture, of which the pres- 

 ence of this tree is always indicative. 



Forms strips and small bodies of pure growth, or is scattered in mixture with willows 

 and occasional western sycamores and white alders. 



Climatic Conditions. — Climate marked by high temperatures and small precipitation; 

 air is dry in some parts of range, but humid in others, through influence and proximity 

 of sea. 



TOLBEANCB. — Kxtremely intolerant of shade throughout life. 



Rbpbodbction. — Similar to black cottonwood. 



Family BETTJLACEJE. 



This family contains the birches and alders, well known and widely distrib- 

 uted forest trees and shrubs. They are characterized by their small, scaly fruit- 

 ing cones, which somewhat resemble in form those of the true cone-bearers. 

 The minute seeds (nuts) are produced tinder the scales of the cones, which in 

 the birches Call to pieces when ripe, scattering the seed, but which iu the aiders 

 remain intact, alter liberating the seed by a spreading of the scales. In this 

 respect the cones of these trees behave almost exactly like those of some of 

 the conifers. .Male and female flowers are each borne mi different parts of 

 the same tree, usually on different parts of the same branch. A further striking 

 analogy between the reproductive organs <>f these trees and the pines is the habil 

 of forming either partly developed male flower clusters alone, or both male 

 and female flower clusters, during the summer previous to their opening. These 

 may he seen en the leafless twigs of birches and alders in winter, during which 

 they remain in a quiescent stale until spring, when they again begin to grow 

 and the flowers open — commonly before the appearance of the leaves, which (in 

 Our species i are shed annually in antninn. The leaves are borne singly cm the 

 branches (never in pairs, one opposite another). 



The wood of these trees is dense in structure, and ils very minute, numerous 

 pores are diffused irregularly throughout the annual rings, which are very in- 

 distinctly defined. All are useful forest trees, find some are especially valuable 

 lor their timber. With few exceptions, they require moist soils. 



15188— OS IT 



