196 



THE DESEKT 



" Grease 

 wood " 

 plains* 



Upland 

 vegetation* 



of agate and carnelian. The mesas themselves 

 are made up of sand and gravel, sometimes 

 long shelvings of horizontal rocks, sometimes 

 patches of terra-cotta, rifts of copper shale, 

 or beds of parti-colored clay. 



There is more rain in this upland country 

 and consequently more vegetation than down 

 below. Grease wood grows everywhere and is 

 the principal green thing in sight. So pre- 

 dominant is it that the term "grease wood 

 plains" is not inappropriate to the whole re- 

 gion. Groves of sahuaro stand in the valleys 

 and reach up and over the mountain-tops, 

 chollas and nopals are on the flats ; the mes- 

 quite grows in miniature forests. But besides 

 these there are bushes and trees not seen in the 

 basin. Palo fierro, palo bianco, cottonwood 

 live along the dry river-beds, white and black 

 sage on the mesas, white and black oaks in the 

 foot-hills. Then, too, there are patches of pale 

 yellow sun-dried grass covering many acres, 

 great beds of evening primrose, and fields cov- 

 ered with the purple salt-bush. It is quite an- 

 other country when you come to examine it 

 piece by piece. 



As you rise higher and higher to the Conti- 

 nental Divide the whole face of the mesa under- 



