42 BULLETIN 33, U. S. DEPARTMENT OF AGRICULTURE. 
grains. In the F, generation the plants are covered with a light 
straw mulch to prevent winterkilling. In the F, generation they are 
planted in the regular nursery row at the usual rate and tested for 
winter resistance. The parent strains are planted as checks. This 
work was retarded by the hailstorm in July, 1912, when practically 
all of the crosses made in that year were destroyed. No conclusions 
can be drawn from the work already done, although there are now in 
existence several apparently hardy strains. 
In this connection it is of interest to note that Nilsson-Ehle?* has 
concluded that the winter-resistant character is transmitted as are 
other characters, that crossing results in segregation of gradations 
of this character, and that it seems to be the result of a variety of 
combinations of many Mendelian factors. 
MISCELLANEOUS TESTS. 
Several cultural tests have been under way in the nursery with the 
different varieties of cereals, but the results of these tests are not 
germane to the purposes of this bulletin. 
SUMMARY. 
Cooperative experiments with cereals have been conducted at the 
Dickinson (N. Dak.) substation since 1907. The testing and im- 
provement of cereal varieties have constituted the major part of the 
work. 
The substation is located near the center of Stark County, in south- 
western North Dakota, at an elevation of approximately 2,500 feet. 
The average annual rainfall at Dickinson for the 22 years from 
1892 to 1913, inclusive, was 15.46 inches, of which 70.1 per cent fell 
during the months from Apri] to August, inclusive, the growing sea- 
son at Dickinson. The average precipitation for the growing season 
for the years 1907 to 1918, the period during which cooperative ex- 
periments with cereals have been conducted, was 11.04 inches. The 
average evaporation from a free water surface during the same period 
was 29.524 inches. 
The average wind velocity per hour during the months from May 
to August, inclusive, for the 6 years from 1908 to 1913 was 7 miles. 
The average mean temperature for these months was 57° F.; the av- 
erage length of the frost-free period, 99 days. The maximum frost- 
free period was in 1909, from May 17 to September 14, 120 days. 
The latest date at which frost has occurred in the spring in the seven 
years was June 5; the earliest frost in the fall was on August 19. 
1Nilsson-Ehle, Herman. Zur Kenntnis der Erblichkeitsverhiiltnisse der Eigenschaft 
Winterfestigkeit beim Weizen. Jn Ztschr. Pflanzenzucht., Bd. 1, Heft 1, p. 5-12, 1912. 
