LETTER OF TRANSMITTAL. 



U. S. Department of Agriculture, 



Bureau of Plant Industry, 



Office of the Chief, 



Washington, D. C, July 30, 1910. 



Sir: I have the honor to transmit herewith and to recommend 

 for piibhcation as Bidletin No. 192 of the special series of this 

 Bureau the accompanying manuscript, entitled ''Drought Resistance 

 of the Olive in the Southwestern States." This paper was prepared 

 by Prof. Silas C. Mason, Arboriculturist in Crop Physiology and 

 Breeding Investigations, and has been submitted by Mr. Walter T. 

 Swingle, Physiologist in Charge, with a view to its publication. 



The data upon which the paper is based were obtained from the 

 study of olive plantations made in Arizona and California, started 

 under irrigation, but afterwards, through the failure of the water 

 supply, left to their fate. 



While most fruit trees and vines planted under similar conditions 

 soon perished, the olive trees have survived and made considerable 

 growth, showing themselves to be true desert plants having marked 

 drought-resistant characters. 



So strong is this characteristic in the case of some of the varieties 

 of olives grown for oil that it is considered desirable to investigate 

 the possibility of olive culture for oil production in those areas in 

 the Southwest having favorable conditions as to temperature and 

 soil, but with a rainfall not heretofore believed to be sufficient for 

 crop production. At the same time those who desire to experiment 

 should be warned not to plant extensively until the possibilities of 

 fruit ])roduction in an}^ particular region have been thoroughly 

 investigated. 



With the enactment and enforcement of the Pure Food Law the 

 production of olive oil in the Western States is now on a much 

 different footing from that of a few years ago. Where large ({uan- 

 tities of cheap adulterants and substitutes were then sold as pure 

 olive oil, now the olive grower has a market for his prochict on its 

 merits. With the better prices now prevailing, there seems to be 

 encouragement for a considerable extension of the oil-olive industry. 

 192 3 



