8 BULLETIN 400, U. S. DEPAETMENT OP AGEICULTTJEE. 



factors. In general the precipitation decreases, the elevation in- 

 creases, and the growing season becomes shorter. The soils become 

 heavy clay loams, varying to heavy clays or gumbo on the one hand 

 and to sandy loams and sands on the other. 



West of the Rocky Mountains a new set of conditions present them- 

 selves. The precipitation usually is low, and sometimes very low. 

 The elevation in the great interior basins is high, except in the Colum- 

 bia Basin, where it seldom exceeds 2,000 feet. The soils are Hght in 

 texture. In the California valleys the elevation is low. 



In the Rocky Mountain region and westward irrigation is practiced 

 where water and topography permit. Marquis wheat has been tested 

 under irrigation as well as by dry-farming methods in the semiarid and 

 arid portions of the territory covered. 



For convenience in presenting the results obtained, the territory 

 under discussion may be separated into four divisions, according to 

 the prevailing conditions. These divisions may be called (1) the 

 northern Prairie States, or subhumid section; (2) the northern Great 

 Plains States, or semiarid section; (3) the Basin and Coast, or arid 

 areas, including the Great Basin, the Snake River basin, the Harney 

 VaUey, the Columbia basin, and the Cahfornia valleys; and (4) the 

 irrigated districts of the northern Rocky Mountain region and Great 

 Basin areas. 



RESULTS OBTAINED. 



The results of varietal experiments reported in this paper have 

 been obtained at 22 different experiment stations. At 15 of these 

 stations, in nine different States, the experiments are conducted by 

 the Office of Cereal Investigations, usually in cooperation with the 

 State agricultural experiment station or some other agency. At 

 eight different stations in four States the results given have been 

 obtained independently by the State agricultural experiment station 

 or other agency. The source of the data is explained in connection 

 with each station. 



The experimental conditions have varied somewhat at some of 

 the stations. The results obtained at one station, therefore, are not 

 necessarily directly comparable with those obtained at another station. 

 In most cases, however, they probably are directly comparable. 



In all cases the results from different varieties at the same station 

 were nearly always obtained under similar conditions and may be 

 directly compared. Any known exceptions to this fact are stated 

 in the text. 



At each station the aim has been to grow the experimental crops 

 under conditions approximating good farm practice for that locahty. 

 AU crops have been grown by means of only the natural rainfall 

 except those discussed in the fourth division, which were grown 

 under irrigation. 



