Current Literature. 547 



southern plains. It occupies about 18,000 square miles in the 

 State and its vegetation is characterized by the mesquite and 

 creosote bush. The Upper Sonoran Area of the Upper Austral 

 Zone covers most of the plains and foot-hill country, extending 

 between 4,000 feet and 8,000 feet in elevation, and it aggregates 

 92,000 square miles, two-thirds of the total area of the State. 

 The rainfall ranges from 10 inches to 15 inches and the tempera- 

 ture is mild without great extremes of heat or cold. The Great 

 Plains division of this area is mainly characterized by abundant 

 grasses and has evidently been kept tFeeless by ages of sweep- 

 ing winds and fires. The strong winds often blow the leaves off 

 and cut through the bark of planted trees. In the Great Basin 

 division, the lower, more open valleys and slopes are clothed 

 with scattered grasses, cacti, yuccas and low desert shrubs. The 

 upper ranges of both divisions support scattered trees of juniper, 

 nut pine and oak. 



The Transition Zone, extending from 7,000 feet to 8,500 feet 

 on the northeast slopes and from 8,000 feet to 9,500 feet on the 

 southwest slopes, covers 10,000 square miles within the State. 

 This is the zone of Yellow Pine. The greater portion of the 

 National Forests of the State lies within the Transition Zone. 

 The Canadian Zone occupies 2,000 square miles and occurs in ir- 

 regular strips scattered throughout the State, the largest con- 

 tinuous areas being in the northern portion. It extends on cold 

 slopes approximately from 3,500 feet to 11,000 feet and on 

 warm slopes from 9,500 feet to 12,000 feet. Its forests are 

 characterized by Engelmann Spruce, White Fir and the Aspen, 

 growing for the most part upon elevated slopes difficult of ac- 

 cess. Because of its abundant rain, its forests, and their protec- 

 tive influence, this zone is the fountain head of the agricultural 

 wealth of the surrounding country. The Hudsonian Zone and 

 the Arctic Alpine Zone occupy only 300 square miles and 100 

 square miles respectively. The mountains of the State, their 

 topography, climate and life zones, are discussed separately. Be- 

 sides the life zone map, the bulletin contains 16 plates of excel- 

 lent illustrations. 



C. D. H. 



