8 BULLETIN 400, IT. S. DEPARTMENT OF AGRICULTURE. 
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 light 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 
Valley, the Columbia basin, and the California valleys; and (4) the 
irrigated districts of the northern Rockv 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 locality. 
All crops have been grown by means of only the natural rainfall 
except those discussed in the fourth division, which were grown 
under irrigation. 
