May, 1893.] SHRUBS OF THE DEATH VALLEY EXPEDITION. 293 



Paliranagat Valley. — Common, ranging up to 1,580 meters (5,200 feet) 

 on the Paliranagat Mountains. 



Pahrump Valley. — Common. 



Vegas Valley. — Enormously abundant, giving color to more than half 

 the area of the valley between Lower Cottonwood and Vegas springs. 



Fremontodendron californicum. 



This handsome small tree (6 to 7 meters or 20 to 25 feet in height), 

 which bears large and showy yellow flowers, grows in great abundance 

 and perfection on the lower slopes of the Sierra Nevada, west of the 

 divide, and on the Coast lianges, but does not occur anywhere within 

 the limits of the Great Basin. 



CALIFORNIA. 



Walker Pass. — "Reaches the summit of the pass from the west and is 

 abundant thence down into the valley of Kern Eiver, and from Kern- 

 ville north to Havilah and Walker Basin (in full flower June 20-24). 



Canada de las Uvas. — Common, and still in flower on the higher 

 mountains, June 28. 



Larrea tridentata. 



The creosote bush (Larrea tridentata) is the most characteristic, con- 

 spicuous, and widely distributed of the desert brush of the Lower 

 Sonoran Zone, covering the gravel soils, wherever of suitable altitude, 

 everywhere from the east foot of the Sierra Nevada in California to the 

 valley of the Lower Santa Clara in Utah. Its dark green leaves and 

 blackish stems render it conspicuous among all the other species with 

 which it happens to be associated, so that it is easily distinguished at 

 a distauce, and hence is the most important zone plant in tracing the 

 boundary between the upper and lower divisions of the Lower Sonoran 

 Zone. It is true that several oth er species — notably Franseria dumosa — 

 agree with it essentially in distribution, but they are so inconspicuous 

 that it would be difficult to trace the zones by their aid alone. The fol- 

 lowing notes respecting the details of its distribution were recorded: 



CALIFORNIA. 



Mohave Desert. — Universally distributed over suitable soils, reaching 

 as far west as the extreme upper limit of the lower division of the Lower 

 Sonoran Zone in Antelope Valley, which is about 0^ kilometers (4 miles) 

 east of the Liebre ranch along the middle and north part of the valley, 

 but not quite so far west on the south side. On the north side of the 

 Mohave Desert, opposite the town ol Mohave, it finds its upper limit 

 at 940 meters (3,100 feet), just reaching the mouth of the open canon 

 leading to Tehachapi Valley. On the south side of the Mohave Desert 

 near Cajon Pass it reaches its northern limit at 1,020 meters (3,350 

 feet). It does not cover the desert ranges in the Mohave Desert, and 

 falls short of the divide at Pilot Knob or Granite Mountain (altitude 

 1,400 meters or 4,000 feet). 



