C. H. TYLER TOWNSEND-BIO-GEOGRAPHY OF TEXAS. 
83 
tends lower on the eastern side, going down on the plain and including 
the whole region around and far to the eastward of Chihuahua City. It 
becomes diluted in southern Chihuahua State. At Santa Rosalia Hot 
Springs fine peaches and grapes are raised. Cotton is also grown, but 
the characteristics of the neighborhood are mostly Upper Sonoran. At 
Chihuahua City fine grapes and peaches are raised. Date palms can not 
grow, and orange trees left exposed through the winter perish. 
In Sonora, that portion northeast of San Ignacio is mostly Upper Sono¬ 
ran. At San Ignacio peaches yield extraordinarily, and side by side with 
them oranges grow and yield well. Pomegranates and figs yield abund¬ 
antly, but grapes do not. To the south of here six miles large date palms 
may be seen in Magdalena. This San Ignacio region is therefore distinctly 
Lower Sonoran , but it combines also the characteristics of the Upper 
Sonoran to a certain extent, and thus shows the meeting of the two zones. 
Following the line of the Mexican Central Railway south from Chi- 
hauhua State, we enter the distinct Upper Sonoran in the hilly region 
around Zacatecas; and again, much farther south, around Lena station, 
which is south of San Juan del Rio and is the highest point on the line, 
being 8133 feet elevation. 
The Upper Sonoran runs southward from northern Mexico in a long, 
ramifying, tongue-like prolongation, widened at first, continuing down 
the highest part of the plateau. Its first great narrowing is to be ob¬ 
served between Aguas Calientes and San Luis Potosi, from about La 
Honda to Solana stations. As it widens northward from here, its eastern 
boundary line goes nearly north, but its western line goes northwest. 
Southward it extends on the higher portions in branches to the lofty 
volcanic regions terminating the southeastern and southern ends of the 
plateau proper. This tongue is partially bisected by the Lower Sonoran 
in the latitude of Torreon, one of the greatest cotton producing regions 
of Mexico, as here occurs a low east and west stretch across the table¬ 
land, somewhat paralleled by the one occurring at El Paso. Saltillo is 
included in the tongue on the east, where'an inferior variety of apple is 
raised. 
Texas. —In Texas the Upper Sonoran occurs pretty well throughout 
the western portion, except for the little Transition. It extends down 
the Rio Grande to near the mouth of the Pecos, leaving a wide area of 
Lower Sonoran in the lower valley of the Pecos, which narrows rather 
rapidly northward and extends about two-thirds of the way up to Pecos 
City. The lower boundary of the Upper Sonoran then extends east from 
the Pecos about two-thirds of the way to San Antonio, when its eastern 
boundary extends irregularly north, filling out the whole Panhandle of 
Texas, otherwise called the Llano Estacado or Staked Plains. Its eastern 
boundary here is very irregular, on account of being cut into by the 
