126 THE DATE PALM. 



may prove to be too cold in winter for any but hardy sorts, and, as 

 noted below (p. 132), the annual inundation with cold water will pre- 

 vent the ripening of any but the earliest sorts. At higher altitude in 

 southern Nevada the summers are hotter, and even midseason or late 

 sorts can be grown if they can withstand the winter cold. For exam- 

 ple, at St. Thomas, in the valley of the Virgin River, at an altitude of 

 1,600 feet, the summers are hotter than at Phoenix, in the Salt River 

 Valley, Arizona, but the winters are colder, the thermometer falling 

 as low as 11 F. in January, 1899 a temperature which is likely to 

 kill young palms and injure old ones. It is not impossible that there 

 may be warm situations in the Pahrump Valley and in Ash Meadows, 

 in southwestern Nevada, though in the absence of meteorological 

 records it is impossible to speak with certainty, and it is probable that 

 the winters are almost eveiy where too cold in these valleys to permit 

 dates to be grown. Hardy late sorts of dates would be very desira- 

 ble for culture in southern Nevada, and it is probable that such could 

 be found in the oases of Persia, where the winter cold is sometimes so 

 severe as to injure or even kill old date palms, although the summer 

 heat is intense. Inasmuch as such sorts would be of great value for 

 culture not only here but also in southwestern Texas and in some parts 

 of California, it would seem advisable tc make a thorough search in the 

 Persian oases as soon as possible and to secure the best varieties for 

 trial in America. 



ARIZONA. 



As has been explained above (p. 61), in treating of the drainage of 

 cold air and the inversion of temperature in relation to date culture, 

 the earlier varieties will probably succeed in some parts of Arizona 

 lying as high as 5,000 feet above sea level, and medium or late sorts 

 in most parts below an altitude of 2,000 feet, except where there is a 

 marked drainage of cold air from some higher level. This area lying 

 below 2,000 feet in altitude would include the whole of southwestern 

 Arizona, with an arm running up the Gila River, and also extending 

 up the Salt and Verde rivers, and another extending along the Colo- 

 rado river northward, passing up the tributary called Bill Williams 

 River, and reaching as far north in the Grand Canyon as the Hualapai 

 Indian Reservation. This portion of Arizona lying below the 2,000- 

 foot contour line forms on the map the shape of a capital L with a 

 very thick horizontal limb. It must not be supposed, however, that 

 any large part of the 20,000 or more square miles included in the area 

 above limited will ever be planted to date palms or to any other fruit 

 trees, since most of this area is without adequate water to carry on 

 agriculture. The irrigable areas along the Gila River and its tribu- 

 taries, especially the Salt River Valley, the Upper Gila Valley from 

 Florence westward to the Estrella Mountains, and finally the valley of 

 the lower Gila, especially about Gila Bend, are the localities best 



