Water Requirements 135 



topic requiring some careful study in Schimper and Warming, 

 or a critical analysis of any special articles available. 



REFERENCES 



KING, F. H. Irrigation and Drainage. 502 pp., 163 figs., 1899. 

 LYON, T. L., and FIPPIN, E. O. Soils. Pp. 133-136, 1909. 

 MACDONALD, W. Dry Farming. 290 pp., 24 figs., 1909. 

 MACDOUGAL, D. T. Delta and Desert Vegetation. Bot. Gaz. 



38 : 44-63, 7 figs., 1904. 

 SHANTZ, H. L. A Study of the Vegetation of the Mesa Region 



East of Pike's Peak. Bot. Gaz. 42 : 16-47, 7 figs. ; 179-207, 



6 figs., 1906. 

 SMITH, J. W. Relation of Precipitation to Yield of Corn. 



Yearbook U. S. Dept. Agl. (1903) : 215-224. 

 VOLKENS, G. Flora der agyptisch-arabischen Wiiste. 

 WICKSON, E. J. Irrigation, in Field and Garden. U. S. Dept. of 



Agl., Farmers' Bui. 138 : 40 pp., 18 figs., 1901. (Also Off. 



Exp. Stas. U. S. Dept. Agl. Bui. 108 : , 113 : etc.) 

 WIDTSOE, J. A., and MCLAUGHLIN, W. W. The Right Way to 



Irrigate. Utah Agl. Exp. Sta. Bui. 86 : 101 pp., 12 pis., 1903. 

 WILCOX, L. M. Irrigation Farming. 494 pp., 113 figs., 1902. 

 WOLLNY, W. Untersuchungen iiber den Einfluss der Luftfeuch- 



tigkeit auf das Wachsthum der Pflanzen. Wollny's Forsch. 



a. d. Geb. d. Agrikult.-Physik. 20 : 397-437, 1898. 



TEXTS. Clements, Jost, Schimper, Sorauer, Warming. 



