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DRY FARMING CONGRESS. 



conditions as to soil moisture may be real or only apparent. In most cases 

 the desert receives only the scant supply of moisture, which falls from the 

 clouds. This may, as in the case of the region along the Colorado about 

 Yuma and Needles, not average more than 2 1-2 inches annually, or in the 

 region about Casa Grande and Phoenix in southwest Arizona may rise 

 to an average of 7 or 8 1-2 inches. Still more favored zones may receive 

 a precipitation of 12 to 15 inches, like the western portion of Kansas, 

 eastern Colorado and the Panhandle country of Texas, and so on up 

 to the section where general farming becomes possible. 



Can any kind of vegetation maintain a permanent existence in a re- 

 gion of 2 1-2 inches of rainfall? The traveler on any of the mesa or 

 upland regions of southwestern California or Arizona must at once an- 

 swer yes, because he knows that the desert is clothed with herbage of its 

 own kind, and that among this herbage is a considerable community of 

 animal life which subsists upon it. These are the true desert or dry-land 

 plants, having their tops and root systems so constructed as to enable 

 them to maintain an existence upon the minimum of moisture. Another 

 class of plants not less truly of the desert will be found along the washes 

 where the occasional rainfall from the mountains discharges a sheet of 

 water over the sand toward the desert for a brief time. Here tiny plants 

 of great beauty will spring up, produce perhaps a single blossom on 

 the top of a stalk of not more than two inches in height, perfect their 

 seed, and die as the moisture evaporates, but in their brief day they have 

 performed the important function of all plant life — produced seed for an- 

 other generation. During more favorable seasons when the rainfall and 

 scant flow of water is increased these same plants may grow to great size 

 and luxuriance, producing myriads of blossoms and seed. Such is the 

 wonderful adaptation of desert plant life to conditions. 



Submerged Rivers (Underground.) 



But every desert traveler knows that there are limited stretches of 

 country clothed with vegetation of a much more permanent character, 

 whose growth seems to be out of proportion to the recorded rainfall of 

 the district. For instance, along the so-called "Santa Cruz River," from 

 the Mexican boundary line down past Tucson, and then through a gap 

 in the mountains out into the wide plain in the neighborhood of Casa 

 Grande there are more or less continuous groves of mesquite. A careful 

 survey of this so-called river course shows that at times the floods from 

 the mountains cut deep channels into the loose friable soil, making veritable 

 river courses of a primitive character, but that as the grade is reduced 

 farther along, this channel entirely disappears, and the flood waters simply 

 spread out over a wide area scarcely defined by any channel at all. 

 Where these channels are cut, as in the Indian Reservation at Mission San 

 Xavier del Bac, springs may be found oozing out of these banks in suffi- 

 cient numbers to furnish a flow of water for small irrigation canals. This 

 water may be all taken out leaving the main channel simply a dry bed of 

 gravel, as is found along the main wagon road between the Mission and 



