MAMMALS OF THE MEXICAN BOUNDARY. 35 



Grande peak; altitude, 2,545 meters, or 8,350 feet. Agave sonorw 

 (Torrey) Mearns" covers the foothills of the Pajaritos and Guada- 

 lupe mountains like a carpet, making travel difficult; and Agave 

 deserti Engelmann is likewise troublesome on portions of the east 

 slope of the Coast Range mountains of California. 



Several species of Ephedra, greenish, wide-spreading bushes re- 

 lated to the conifers, occur in greater or less abundance throughout 

 the boundary strip. i 



Vines and climbing plants are not abundant. Grapes, however, are 

 numerous in the Texan Tract, and also occur in moist canyons in the 

 mountains of the Eelevated Central and Pacific Coast tracts. Forms 

 of the Virginia creeper {Partlienoclssus quinqnefolia) and trumpet 

 flower are found in similar places in Texas and the Elevated Cen- 

 tral Tract. Several species of Convolvulus and Ipomoia, and legu- 

 minous climbers occur in abundance in moist places. The Texas 

 matrimony vine {Lycium torreyi Gray) grows luxuriantly along the 

 Rio Grande, a pale species {Lyeiuvi pallidum Miers) occurs in the 

 Elevated Central Tract, and still another species of Lycium was 

 found in great abundance along the Sonoyta River, in Sonora. 

 Climbing milkweeds of the genus Philihertella are of common occur- 

 rence along the streams, often ascending to the tops of bushes and 

 small trees. With them clematis or virgin's bower is not infre- 

 quently associated, -and several species of gourds of the genera 

 Cucurbita, Apodanthera, and lierrillea cover otherwise bare spaces 

 of ground or entwine themselves in the edges of thickets. 



Canes and coarse rushes are mostly confined to the edges of the 

 Rio Grande, Yaqui, and Colorado rivers, and other water-loving 

 plants are likewise of rare occurrence. Anemopsis, or " yerba mansa " 

 of the Mexicans, grows wherever there is permanent water with 

 marshy banks, and is the commonest paludose plant of the inte- 

 rior. On the coasts of the ocean and Gulf of California are numerous 

 pulpy-leaved plants said to have been derived from the Asiatic side 

 of the Pacific, among them a bush ranging from the Gulf of Califor- 

 nia up the alluvial bottom lands of the Colorado and Gila rivers as 

 far as Adonde. A very rank growth of wild hemp and amaranth 

 also extends up the Colorado bottom nearly to the mouth of the Gila 

 River. The cocklebur (Xanthium) and Datura are also character- 

 istic plants along streams. 



The greasewood {Atriplex) , of which there are several species, is 

 a very characteristic plant of the Lower Sonoran life zone, and so 

 is the creosote bush {Covillea tridentata). 



The region is famed for its spiny shrubs. Of such, the leguminous 

 genera Acacia, Prosopis, Rohinia, Mimosa, and ParoseJa are usually 



<^Agave f/emiiiiflnra sonorw Torrey, Bot. Jlex. Bound., 1859, p. 214. Agave 

 sohottii Engelmann, Trans. St. Louis Acad., Ill, 1873, p. 305. 



