380 Noble — Geology of the Grand Canyon, Arizona. 



soutliwestward-sloping surface of Powell Plateau, the whole 

 eastern half of which lies at an elevation of from 7000 to 7500 

 feet and is covered with the open pine forest characteristic of 

 the Kaibab. At about 7000 feet the character of the flora 

 changes, and passes into the gnarled and stunted forests of juni- 

 per and pinon characteristic of the southern plateau across the 

 canyon. 



Within the canyon itself the variation in the flora is just as 

 great, and is again an index of the elevation. 



The flora of the Esplanade platform, a thousand feet below 

 the south rim, consists of stunted bushes of juniper and pinon 

 with greasewood as the ground bush in place of the sagebrush 

 of the Coconino Plateau. The cactus, mescal, and plants of the 

 century family are present in greater abundance than on the 

 plateau, but in less abundance and in more stunted develop- 

 ment than in the bottom of the canyon. This is due to the fact 

 that the Esplanade level is within reach of the winter snows 

 and frosts. 



The flora of the Tonto platform, three thousand feet below 

 the south rim, and of all the interior of the canyon below the 

 Red Wall, is the flora of a hot and arid desert in its most 

 characteristic form. The dominant plants are the greasewood 

 bush, the mormon tea, and the cactus. The mescal and the 

 plants of the century family here attain their greatest develop- 

 ment and size. The cacti are particularly rich in species. 

 Every plant in the flora is either prickly or aromatic ; leaf sur- 

 faces are reduced to a minimum ; devices for storing water 

 attain the greatest perfection ; and the dominant color is a 

 somber gray. The somber colors and the reduction of leaf 

 surface are apt to deceive the observer, both in regard to the 

 richness of the flora in species and the abundance of plant 

 life, which is far greater than one would suspect. The only 

 tree is the screw-mesquite, which grows in the beds of those 

 washes that contain living or intermittent streams. 



The vegetation in the bottoms of those canyons of the north 

 side in the Shinumo Amphitheater which contain living streams 

 is beautiful beyond description, and in refreshing contrast to 

 the desert flora of the Tonto platform. Tall cottonwoods 

 grow in the lower canyons ; the walls are hung with maiden- 

 hair fern in the shady places ; and willow thickets border the 

 stream. Grass grows on the banks where there is soil. 

 Higher up in the canyons, oaks, maples, and other deciduous 

 trees come in, and often beds of tall rushes. The most 

 characteristic bush of these upper north-side canyons is the 

 manzanita, which does not grow on the south side of the 

 Grand Canyon. 



