TORRES 17 



rior mentality of mankind ; this I described in ' The Beginning of Agriculture ' 

 {American AnfkroJ>ologcst,Yo\. VIII, pp. 350-375); and the lesson I learned 

 from the Papago experimentalists themselves as their ancestors learned it from 

 Nature long ago. They were prominent among the aboriginal makers of corn, 

 as well as the bean and other native crop plants." 



NOGALES. 



The region immediatel}' about Nogales, on the border between Ari- 

 zona and Sonora, lies at an elevation of about 4,000 feet, just below 

 the oak belt. The characteristic vegetation of the hills is of yucca-like 

 plants, including species of Tucca^ Nolina^ Dasylirion^ and Agave. 

 Shrubs of the ordinary desert character are few and form no part of the 

 vegetative landscape. Scattered oak trees of small dimensions appear 

 here and there among the yuccas (Plate XIV). 



TORRES. 



The plain in which lies the railroad station Torres is at an elevation 

 of about Soo feet above the sea. Its most characteristic vegetation is 

 a growth of small leguminous trees, notably palo fierro ( Olneya tesota) 

 and palo verde (Parkinsonia)^ two species of Cercus of large dimen- 

 sions {Cereus tJmrberi and C. sckotiti) (Plate XV), and two cylin- 

 drical stemmed species of Opuntia. The palo fierro, meaning iron- 

 wood, produces a very hard wood, which with the lighter but 

 still hard mesquite {Prosopis) and the zygophyllaceous guaiacan, 

 or lignum vitae ( Guaiacum coulteri) , constitutes the greater part 

 of the fuel used on the railroad locomotives. Palo fierro is con- 

 sidered by the railroad oflicials a better fuel, by about 25 per cent, 

 than mesquite, and guaiacan about 10 per cent better than palo fierro. 

 A metric cord (that is, a pile 3 meters long by i meter high and 0.75 

 meter In length of stick) of mixed palo fierro and guaiacan was con- 

 sidered by an engineer of experience as the equivalent, for fuel, of a ton 

 and a half of the ordinary soft coal available in the Southwest. The palo 

 verde, of which the region contains two species and perhaps more, is 

 an especially abundant tree. It is in use everywhere for household 

 fuel, and one of the species {Parktnsonia tnicrophylla) is commonly 

 employed as green forage for horses in winter, the branches being cut 

 and thrown into the corrals, where the horses eat the twigs to the 

 diameter of nearly half an inch. It is probable that at this season the 

 twigs contain a large amount of stored food. Cercus schottii as well 

 as another smaller species of the same genus are known as sina. 

 Cereus thurberi is called pitahaya. One of the common species of 

 Opuntia., known as siviri, forms a small tree 8 to 15 feet high, with 

 cylindrical joints about half an inch in diameter. It possesses a sour 



