130 PLANT WORLD. 



lower, uncertain part of the stream with its precarious con- 

 ditions has been followed by hunter's camps and sporadic 

 ventures with small flocks, the oft-recurring seasons of ex- 

 treme drought discouraging any more serious operations. 

 F'orage, corn, wheat, melons, figs, grapes, and dates are 

 grown and with the exception of some introductions follow- 

 ing the first visit of Father Kino in 1699, the mode of life 

 of the Mexican and Indian population has changed but little 

 in two centuries. 



The heavy growth of mesquite, {Prosopis) ^ arrow-weed 

 (Pliiclicd) , batamote {Buccliaris) , palo verde and bigote 

 (Pd) kiiisouid microphylhi and /■'. torreyana) of the oasis 

 arc in sharp contrast with the desert vegetation comprising 

 the pitahaya [PUocereits thiirberi and P. sargentii) and 

 sahuaro, nopal and tuna, ocotillo and sangre de drago a few 

 feet away, the margin of the oasis being as well defined in 

 many places as the edge of a carpet. 



The length of the oasis was traversed in easy stages by 

 our expedition, a final camp being made at the end of the 

 stream of running water at Agua Dulce, below which the 

 broad channel is coated white with alkaline salts bearing 

 a characteristic vegetation Inclusive of the widespread salr- 

 grass {Disficlilis spicata). Ihe further route now carried 

 us westward across a desert of the most pronounced character 

 to Monument 180 on the international boundary and south- 

 ward to Papago Tanks on the western slopes of the Pinacate 

 mountains. 1 he water supply here and in this region is to 

 be found in a few small kettle-holes in the granite lying in 

 the streamways and filled by the rains. Most are shallow 

 and uncertain, but two beside the one mentioned being re- 

 liable so far as the information of our scout could he 

 depended upon. The topographic features presented by this 

 volcanic region afforded conditions for some unusual group- 

 ings and occurrences of plants. Over 250 cinder cones and 

 craters were counted and a tenth of this number were 

 visited. The loose but steep slopes were thickly covered with 



