ARID REGION OF WESTERN TEXAS 3 



Tucson, Arizona. Here they remained February 2 and 3, examining 

 the desert flora of the plain and adjacent mountain slopes. On Feb- 

 ruary 4 they proceeded by rail to Nogales, on the boundary line 

 between Arizona and Mexico, where they stayed February 5, making 

 observations on the vegetation in that vicinity. On the morning of 

 February 6 they arrived by rail at Torres, Sonora, Mexico. February 

 7 to 10 was spent on a saddle trip into the desert west of Torres, 

 toward the Gulf of California. February ii a journey was made by 

 rail to Guaymas and return which afforded an opportunity to observe 

 both the desert and the seacoast flora of Guaymas harbor. February 

 12 and 13 were passed on the desert in the immediate vicinity of 

 Torres. On February 14 the Board returned to Tucson where they 

 remained during the two following days. On the morning of February 

 17 they arrived by rail at Salton, in the Colorado desert of southern 

 California, and remained during the day examining the vegetation of 

 the salt and alkali lands. On the morning of February 18 they pro- 

 ceeded to Indio, also in the Colorado desert, and in the afternoon drove 

 to Thousand Palm canyon and return. February 19 they went by 

 rail to Los Angeles and the next morning took a train east, passing 

 through Cajon pass and across the Mohave desert, arriving on the 

 evening of February 21 at the Grand Canyon of the Colorado river, 

 in Arizona. February 22 and 23 were spent in a trip to the river by 

 the Bright Angel trail. On the morning of February 24 they left the 

 canyon and on February 28 arrived in Washington. 



THE ARID REGION OF WESTERN TEXAS. 



Eastern Texas has the characteristic humid subtropical flora of the 

 Gulf region, with longleaf pine (^Pinus palustris)^ cane (^Arundi- 

 narid)^ bald cypress {^Taxodium dtsticktim) ^ and their associates, but 

 this flora gradually merges into the wholly different one of arid 

 western Texas. Beginning east of San Antonio the ground is covered 

 with an open growth of mesquite trees {Prosopis)^ 10 to 20 feet 

 high, resembling a vast peach orchard. Scattered through it are larger 

 trees, some deciduous, others evergreen oaks. The mesquites them- 

 selves are nearly leafless in late winter and are much infested with a 

 mistletoe. Scattered among them are various shrubs 4 to 8 feet 

 high, and as the most conspicuous feature of the undergrowth a 

 prickly pear with large flat orbicular vertical joints, the whole plant 

 rising i to 3 feet from the ground. Another occasional feature of the 

 undergrowth is a small Tucca with long and broad leaves, commonly 

 without a trunk but occasionally reaching a height of 6 to 8 feet. 

 Some of the oaks have their branches clothed with a gray epiphyte 



